diff --git a/.cargo/config.toml b/.cargo/config.toml
index 4e54d1d3b18..79a36b71742 100644
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -10,9 +10,12 @@ rustflags = ["--cfg=getrandom_backend=\"wasm_js\""]
 # Enforce a 1 MB stack limit for WASI targets.
 # (Runaway heap growth is fixed by the smaller DataStack chunk
 # and the size‑optimized wasm‑release profile.)
+
 [target.wasm32-wasip1]
 rustflags = [
     "-C", "link-arg=-zstack-size=1048576",
+    "-L", "crates/host_env/vendor/wasm32-wasip1",
+    "-l", "wasi-emulated-signal",
 ]
 
 [target.wasm32-wasip2]
diff --git a/.claude/scripts/setup-env.sh b/.claude/scripts/setup-env.sh
index f5d28a3f14c..97e38f22976 100755
--- a/.claude/scripts/setup-env.sh
+++ b/.claude/scripts/setup-env.sh
@@ -16,7 +16,7 @@ if [ "$(printf '%s\n' "3.13" "$CURRENT_PY" | sort -V | head -1)" != "3.13" ]; th
     echo "Upgrading python3 default to 3.13..."
     # Find best available Python >= 3.13
     TARGET=""
-    for ver in python3.14 python3.13; do
+    for ver in python3.15 python3.14 python3.13; do
         if command -v "$ver" &>/dev/null; then
             TARGET=$(command -v "$ver")
             break
@@ -38,13 +38,17 @@ else
     echo "python3 already >= 3.13: $(python3 --version)"
 fi
 
-# 2. Clone CPython source if not present (needed for scripts/update_lib)
-if [ ! -d "cpython" ]; then
-    echo "Cloning CPython v3.14.3 (shallow)..."
-    git clone --depth 1 --branch v3.14.3 https://github.com/python/cpython.git cpython
-    echo "CPython source ready."
+# 2. Ensure the CPython source matches the target (needed for scripts/update_lib)
+PYTHON_VERSION="v3.15.0"
+if [ ! -e "cpython" ]; then
+    git clone --depth 1 --branch "$PYTHON_VERSION" https://github.com/python/cpython.git cpython
+elif [ ! -d "cpython/.git" ] || [ ! -d "cpython/Lib" ] ||
+    [ "$(git -C cpython rev-parse HEAD)" != "$(git -C cpython rev-parse --verify "$PYTHON_VERSION^{commit}" 2>/dev/null)" ] ||
+    [ -n "$(git -C cpython status --porcelain)" ]; then
+    echo "ERROR: cpython must be a clean checkout of $PYTHON_VERSION. Move the existing directory aside and rerun." >&2
+    exit 1
 else
-    echo "CPython source already present."
+    echo "CPython $PYTHON_VERSION source already present."
 fi
 
 echo "=== Setup complete ==="
diff --git a/.cspell.dict/cpython.txt b/.cspell.dict/cpython.txt
index a00cd9e2584..7fc991670d2 100644
--- a/.cspell.dict/cpython.txt
+++ b/.cspell.dict/cpython.txt
@@ -222,6 +222,7 @@ pylifecycle
 pymain
 pymem
 pyrepl
+pyrun
 pystate
 pystrcmp
 PYTHONTRACEMALLOC
diff --git a/.cspell.dict/python-more.txt b/.cspell.dict/python-more.txt
index 7ea660a5d1f..f2383f15f97 100644
--- a/.cspell.dict/python-more.txt
+++ b/.cspell.dict/python-more.txt
@@ -127,6 +127,7 @@ isabstractmethod
 isbytes
 iscased
 isfinal
+issubnormal
 istext
 itemiterator
 itemsize
diff --git a/.cspell.dict/rustpython.txt b/.cspell.dict/rustpython.txt
index b4170d20da4..563b58c248a 100644
--- a/.cspell.dict/rustpython.txt
+++ b/.cspell.dict/rustpython.txt
@@ -12,6 +12,7 @@ pyast
 pyattr
 pyclass
 pyclassmethod
+pycode
 pyexception
 pyfunction
 pygetset
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index cd0b1349c09..5762703b146 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -19,8 +19,8 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  CARGO_ARGS: --no-default-features --features stdlib,importlib,stdio,encodings,sqlite,ssl-rustls-aws-lc,host_env,doc
-  CARGO_ARGS_NO_SSL: --no-default-features --features stdlib,importlib,stdio,encodings,sqlite,host_env,doc
+  CARGO_ARGS: --no-default-features --features stdlib,importlib,stdio,encodings,sqlite,ssl-rustls-aws-lc,host_env,doc,ucd_3_2_0
+  CARGO_ARGS_NO_SSL: --no-default-features --features stdlib,importlib,stdio,encodings,sqlite,host_env,doc,ucd_3_2_0
   CARGO_ARGS_MOST_FEATS: --features capi,encodings,jit,sqlite,threading
   # Crates excluded from workspace builds:
   # - rustpython_wasm: requires wasm target
@@ -43,6 +43,7 @@ jobs:
     outputs:
       # Flag that is raised when any rust code is changed.
       rust_code: ${{ steps.check_rust_code.outputs.changed }}
+      update_lib: ${{ steps.check_update_lib.outputs.changed }}
       # WASM demo / notebook / example_projects, independent of rust_code.
       wasm_code: ${{ steps.check_wasm_code.outputs.changed }}
       # Cross-target cargo check is skipped unless the diff can change
@@ -77,6 +78,7 @@ jobs:
             ':examples/**' \
             ':benches/**' \
             ':example_projects/**' \
+            ':extra_tests/snippets/**' \
             ':.github/workflows/ci.yaml' \
           ; then
               echo "changed=false" >> "$GITHUB_OUTPUT"
@@ -86,6 +88,17 @@ jobs:
         env:
           MERGE_BASE: ${{ steps.merge_base.outputs.sha }}
 
+      - name: Check if update_lib changed
+        id: check_update_lib
+        run: |
+          if git diff --quiet "${MERGE_BASE}...HEAD" -- ':scripts/update_lib/**' ':.python-version'; then
+              echo "changed=false" >> "$GITHUB_OUTPUT"
+          else
+              echo "changed=true" >> "$GITHUB_OUTPUT"
+          fi
+        env:
+          MERGE_BASE: ${{ steps.merge_base.outputs.sha }}
+
       - name: Check if WASM package or demo sources changed
         id: check_wasm_code
         run: |
@@ -208,6 +221,7 @@ jobs:
     env:
       RUST_BACKTRACE: full
       RUN_RUST_TESTS: ${{ needs.determine_changes.outputs.rust_code == 'true' || github.ref == 'refs/heads/main' }}
+      RUN_UPDATE_LIB_TESTS: ${{ needs.determine_changes.outputs.update_lib == 'true' }}
     # Named after the matrix entry rather than left to be named for it: a
     # generated name lists every value in the entry, so adding or removing one
     # renames the check and drops it from the required list.
@@ -221,10 +235,10 @@ jobs:
     steps:
       - name: Skip rust tests when sources did not change
         if: env.RUN_RUST_TESTS != 'true'
-        run: echo "No rust source changes; required check is green without rebuilding."
+        run: echo "No rust source changes; skipping Rust build and tests."
 
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        if: env.RUN_RUST_TESTS == 'true'
+        if: env.RUN_RUST_TESTS == 'true' || (env.RUN_UPDATE_LIB_TESTS == 'true' && runner.os == 'Linux')
         with:
           persist-credentials: false
 
@@ -295,6 +309,10 @@ jobs:
         working-directory: crates/capi
         run: cargo test --doc --locked
 
+      - name: Check host_env without ctypes
+        if: env.RUN_RUST_TESTS == 'true' && runner.os == 'Windows'
+        run: cargo check --locked -p rustpython-host_env --no-default-features --lib
+
       - name: check compilation without host_env (sandbox mode)
         if: env.RUN_RUST_TESTS == 'true' && runner.os == 'Linux'
         run: |
@@ -310,7 +328,12 @@ jobs:
 
       - name: Test openssl build
         if: env.RUN_RUST_TESTS == 'true' && runner.os == 'Linux'
-        run: cargo build --locked --no-default-features --features ssl-openssl
+        run: |
+          cargo build --locked --no-default-features --features ssl-openssl
+          cargo build --locked --release --features threading,jit,ssl-openssl ${{ env.CARGO_ARGS_NO_SSL }}
+          target/release/rustpython -B extra_tests/snippets/stdlib_ssl.py
+          target/release/rustpython -B -m test -v --single-process --timeout=300 test_ssl
+        timeout-minutes: 30
 
       - name: Test vendored OpenSSL build
         if: env.RUN_RUST_TESTS == 'true' && runner.os == 'Linux'
@@ -340,9 +363,19 @@ jobs:
         if: env.RUN_RUST_TESTS == 'true' && runner.os == 'Linux'
         run: cargo build --locked
 
+      - uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+        if: env.RUN_RUST_TESTS != 'true' && env.RUN_UPDATE_LIB_TESTS == 'true' && runner.os == 'Linux'
+        with:
+          python-version-file: .python-version
+
       - name: run update_lib tests
-        if: env.RUN_RUST_TESTS == 'true' && runner.os == 'Linux'
-        run: target/debug/rustpython -m unittest discover -s scripts/update_lib/tests -v
+        if: (env.RUN_RUST_TESTS == 'true' || env.RUN_UPDATE_LIB_TESTS == 'true') && runner.os == 'Linux'
+        run: |
+          if [ "$RUN_RUST_TESTS" = "true" ]; then
+            target/debug/rustpython -m unittest discover -s scripts/update_lib/tests -v
+          else
+            python -m unittest update_lib.tests.test_patch_spec update_lib.tests.test_migrate -v
+          fi
         env:
           PYTHONPATH: scripts
 
@@ -498,6 +531,9 @@ jobs:
             - '-u all'
             - '--timeout 600'
             - '--dont-add-python-opts'
+            # CPython's installed py.exe reports its own version, not RustPython's.
+            # Keep the remaining launcher integration tests and runtime version checks.
+            - '--ignore test.test_launcher.TestLauncher.test_version'
           env_polluting_tests: []
           skips: []
           timeout: 50
@@ -559,6 +595,7 @@ jobs:
 
       - name: Run CPython tests
         run: |
+          # shellcheck disable=SC2086
           target/release/rustpython -u -m test --slow-ci -j "$CORES" $EXTRA_TEST_ARGS $SKIPS
         timeout-minutes: ${{ matrix.timeout }}
         shell: bash
@@ -725,7 +762,7 @@ jobs:
 
       - uses: dtolnay/rust-toolchain@stable
 
-      - uses: taiki-e/install-action@94c31af3204a9f15ab40b35ad084410b905bbc73 # v2.87.17
+      - uses: taiki-e/install-action@f7e5d7c961414b23f5b25b2da9294395d08513ad # v2.87.26
         with:
           tool: cargo-shear
           fallback: none
@@ -754,7 +791,7 @@ jobs:
           components: rustfmt
 
       - name: actionlint
-        uses: reviewdog/action-actionlint@320fcdd9c860767cf17fab3b20e22e739d5d02b8 # v1.76.0
+        uses: reviewdog/action-actionlint@1758727be30241166609dad4c97588b6ad411f32 # v1.79.1
 
       - name: zizmor
         uses: zizmorcore/zizmor-action@cc914d7f3750a2d13d75c7f184a1060aa0e9d482 # v0.6.4
@@ -767,7 +804,7 @@ jobs:
 
       - name: install prek
         id: prek
-        uses: j178/prek-action@4e14d07f9231acabce116ccfca13b13dd9755ece # v3.0.0
+        uses: j178/prek-action@1382ad72dea72f9d53832f2bcb65b3e87a947204 # v3.0.1
         with:
           cache: false
           show-verbose-logs: false
@@ -776,18 +813,12 @@ jobs:
       - name: prek run
         run: prek run --show-diff-on-failure --color=always --all-files
 
-      - name: Get target CPython version
-        id: cpython-version
-        run: |
-          version=$(cat .python-version)
-          echo "version=${version}" >> "$GITHUB_OUTPUT"
-
-      - name: Clone CPython
+      - name: Clone CPython opcode metadata source
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           repository: python/cpython
           path: cpython
-          ref: "v${{ steps.cpython-version.outputs.version }}"
+          ref: "v3.15.0"
           persist-credentials: false
 
       - name: prek run (manual stage)
@@ -1005,10 +1036,71 @@ jobs:
     env:
       FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
       RUN_WASM_WASI: ${{ needs.determine_changes.outputs.rust_code == 'true' || github.ref == 'refs/heads/main' }}
-      # Passing snippets under wasm32-wasip1.
-      WASM_WASI_SNIPPETS: >-
-        stdlib_random
-        stdlib_time
+      # extra_tests/snippets files that still fail or hang under wasm32-wasip1;
+      # every other snippet is discovered and run automatically.
+      WASM_WASI_SNIPPET_EXCLUDE: >-
+        builtin_bytearray
+        builtin_bytes
+        builtin_hash
+        builtin_int
+        builtin_iter
+        builtin_list
+        builtin_map
+        builtin_memoryview
+        builtin_open
+        builtin_posixshmem
+        builtin_slice
+        builtin_str
+        builtin_thread
+        cli_int_max_str_digits
+        protocol_index_argument
+        recursion
+        stdlib_ast
+        stdlib_asyncio
+        stdlib_collections_deque
+        stdlib_contextvars
+        stdlib_ctypes
+        stdlib_ctypes_byvalue
+        stdlib_ctypes_calls
+        stdlib_ctypes_from_buffer
+        stdlib_genericalias
+        stdlib_io
+        stdlib_io_blocking_buffer
+        stdlib_itertools
+        stdlib_json
+        stdlib_mmap
+        stdlib_multiprocessing_condition
+        stdlib_multiprocessing_fork_sharer
+        stdlib_multiprocessing_sharedctypes
+        stdlib_os
+        stdlib_pwd
+        stdlib_queue_signal
+        stdlib_select
+        stdlib_socket
+        stdlib_sqlite
+        stdlib_ssl
+        stdlib_ssl_short_recv
+        stdlib_struct
+        stdlib_subinterpreters
+        stdlib_subprocess
+        stdlib_sys
+        stdlib_sys_audit
+        stdlib_threading_current_frames
+        stdlib_threading_gc_frame_race
+        stdlib_threading_gc_import
+        stdlib_threading_generator
+        stdlib_threading_set_repr
+        stdlib_threading_type_cache
+        stdlib_thread_native_id
+        stdlib_types
+        stdlib_typing
+        stdlib_urllib_https_misaligned_recv
+        stdlib_zoneinfo_cache
+        syntax_async
+        syntax_async_comprehension
+        syntax_deep_nesting
+        vm_frame_locals
+        xfail_assert
       # Passing Lib/test files under wasm32-wasip1
       WASM_WASI_TEST_FILES: >-
         test_int
@@ -1026,7 +1118,7 @@ jobs:
     steps:
       - name: Skip wasm-wasi when rust sources did not change
         if: env.RUN_WASM_WASI != 'true'
-        run: echo "No rust source changes; required check is green without rebuilding."
+        run: echo "No rust source changes; skipping Rust build and tests."
 
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         if: env.RUN_WASM_WASI == 'true'
@@ -1067,13 +1159,18 @@ jobs:
 
       - name: build rustpython
         if: env.RUN_WASM_WASI == 'true'
-        run: cargo build --locked --profile wasm-release --target wasm32-wasip1 --no-default-features --features freeze-stdlib,stdlib,stdio,importlib,host_env,doc --verbose
+        run: cargo build --locked --profile wasm-release --target wasm32-wasip1 --no-default-features --features freeze-stdlib,stdlib,stdio,importlib,host_env,doc,ucd_3_2_0 --verbose
       - name: run snippets
         if: env.RUN_WASM_WASI == 'true'
         run: |
-          for name in $WASM_WASI_SNIPPETS; do
-            echo "::group::extra_tests/snippets/${name}.py"
-            wasmer run --volume "$(pwd)" target/wasm32-wasip1/wasm-release/rustpython.wasm -- "$(pwd)/extra_tests/snippets/${name}.py"
+          exclude=" $WASM_WASI_SNIPPET_EXCLUDE "
+          for path in extra_tests/snippets/*.py; do
+            name=$(basename "$path" .py)
+            case "$exclude" in
+              *" $name "*) continue ;;
+            esac
+            echo "::group::${path}"
+            wasmer run --volume "$(pwd)" target/wasm32-wasip1/wasm-release/rustpython.wasm -- "$(pwd)/${path}"
             echo "::endgroup::"
           done
       - name: run cpython unittest
diff --git a/.github/workflows/cron-ci.yaml b/.github/workflows/cron-ci.yaml
index 16c74bdc43a..115458ae940 100644
--- a/.github/workflows/cron-ci.yaml
+++ b/.github/workflows/cron-ci.yaml
@@ -14,7 +14,7 @@ on:
       - .github/workflows/cron-ci.yaml
 
 env:
-  CARGO_ARGS: --no-default-features --features stdlib,importlib,stdio,encodings,ssl-rustls-aws-lc,jit,host_env,doc
+  CARGO_ARGS: --no-default-features --features stdlib,importlib,stdio,encodings,ssl-rustls-aws-lc,jit,host_env,doc,ucd_3_2_0
 
 jobs:
   # codecov collects code coverage data from the rust tests, python snippets and python test suite.
@@ -33,7 +33,7 @@ jobs:
 
       - uses: dtolnay/rust-toolchain@stable
 
-      - uses: taiki-e/install-action@94c31af3204a9f15ab40b35ad084410b905bbc73 # v2.87.17
+      - uses: taiki-e/install-action@f7e5d7c961414b23f5b25b2da9294395d08513ad # v2.87.26
         with:
           tool: cargo-llvm-cov
 
@@ -42,7 +42,7 @@ jobs:
       - run: sudo apt-get update && sudo apt-get -y install lcov
 
       - name: Run cargo-llvm-cov with Rust tests.
-        run: cargo llvm-cov --no-report --workspace --exclude rustpython_wasm --exclude rustpython-venvlauncher --exclude rustpython-capi --verbose --no-default-features --features stdlib,importlib,stdio,encodings,ssl-rustls-aws-lc,jit,host_env,doc
+        run: cargo llvm-cov --no-report --workspace --exclude rustpython_wasm --exclude rustpython-venvlauncher --exclude rustpython-capi --verbose --no-default-features --features stdlib,importlib,stdio,encodings,ssl-rustls-aws-lc,jit,host_env,doc,ucd_3_2_0
 
       - name: Run cargo-llvm-cov with Python snippets.
         run: python scripts/cargo-llvm-cov.py
diff --git a/.github/workflows/pyperformance.yaml b/.github/workflows/pyperformance.yaml
index 1d304582ce2..05f76266e26 100644
--- a/.github/workflows/pyperformance.yaml
+++ b/.github/workflows/pyperformance.yaml
@@ -63,7 +63,7 @@ jobs:
       - uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
         id: cpython
         with:
-          python-version: "3.14"
+          python-version: "3.15.0"
 
       - name: Restore cache
         uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
diff --git a/.github/workflows/update-doc-db.yml b/.github/workflows/update-doc-db.yml
index 8874c3aeac8..3abdf27de72 100644
--- a/.github/workflows/update-doc-db.yml
+++ b/.github/workflows/update-doc-db.yml
@@ -8,7 +8,7 @@ on:
       python-version:
         description: Target python version to generate doc db for
         type: string
-        default: "3.14.7"
+        default: "3.15.0"
       base-ref:
         description: Base branch to create the update branch from
         type: string
diff --git a/.github/workflows/upgrade-pylib.lock.yml b/.github/workflows/upgrade-pylib.lock.yml
index 23c1aeec47c..dfdc331c8a1 100644
--- a/.github/workflows/upgrade-pylib.lock.yml
+++ b/.github/workflows/upgrade-pylib.lock.yml
@@ -24,7 +24,7 @@
 # Pick an out-of-sync Python library from the todo list and upgrade it
 # by running `scripts/update_lib quick`, then open a pull request.
 #
-# frontmatter-hash: 3129480d6628afe028911bb8b31b6bb3b5eb251e395f00ed0677922cd21727cb
+# frontmatter-hash: bf5b6c1bf4e49141df567a8ff69cce1fc96faa991e1cc353ed6a77aa7c2ba719
 
 name: "Upgrade Python Library"
 "on":
@@ -44,7 +44,7 @@ run-name: "Upgrade Python Library"
 
 env:
   ISSUE_ID: "6839"
-  PYTHON_VERSION: v3.14.3
+  PYTHON_VERSION: v3.15.0
 
 # Cache configuration from frontmatter was processed and added to the main job steps
 
@@ -58,7 +58,7 @@ jobs:
       comment_repo: ""
     steps:
       - name: Setup Scripts
-        uses: github/gh-aw/actions/setup@00457477720387bcc7d7baaf841dedb22ad06617 # v0.89.17
+        uses: github/gh-aw/actions/setup@382f4b025fefaa7d6b2492c3608f098340bf6536 # v0.91.3
         with:
           destination: /opt/gh-aw/actions
       - name: Check workflow file timestamps
@@ -99,7 +99,7 @@ jobs:
       secret_verification_result: ${{ steps.validate-secret.outputs.verification_result }}
     steps:
       - name: Setup Scripts
-        uses: github/gh-aw/actions/setup@00457477720387bcc7d7baaf841dedb22ad06617 # v0.89.17
+        uses: github/gh-aw/actions/setup@382f4b025fefaa7d6b2492c3608f098340bf6536 # v0.91.3
         with:
           destination: /opt/gh-aw/actions
       - name: Checkout repository
@@ -109,7 +109,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
         with:
-          python-version: '3.14'
+          python-version: '3.15'
       - name: Create gh-aw temp directory
         run: bash /opt/gh-aw/actions/create_gh_aw_tmp_dir.sh
       # Cache configuration from frontmatter processed below
@@ -118,8 +118,6 @@ jobs:
         with:
           key: cpython-lib-${{ env.PYTHON_VERSION }}
           path: cpython
-          restore-keys: |
-            cpython-lib-
       - name: Configure Git credentials
         env:
           REPO_NAME: ${{ github.repository }}
@@ -806,7 +804,7 @@ jobs:
       total_count: ${{ steps.missing_tool.outputs.total_count }}
     steps:
       - name: Setup Scripts
-        uses: github/gh-aw/actions/setup@00457477720387bcc7d7baaf841dedb22ad06617 # v0.89.17
+        uses: github/gh-aw/actions/setup@382f4b025fefaa7d6b2492c3608f098340bf6536 # v0.91.3
         with:
           destination: /opt/gh-aw/actions
       - name: Download agent output artifact
@@ -927,7 +925,7 @@ jobs:
       success: ${{ steps.parse_results.outputs.success }}
     steps:
       - name: Setup Scripts
-        uses: github/gh-aw/actions/setup@00457477720387bcc7d7baaf841dedb22ad06617 # v0.89.17
+        uses: github/gh-aw/actions/setup@382f4b025fefaa7d6b2492c3608f098340bf6536 # v0.91.3
         with:
           destination: /opt/gh-aw/actions
       - name: Download agent artifacts
@@ -1039,7 +1037,7 @@ jobs:
       process_safe_outputs_temporary_id_map: ${{ steps.process_safe_outputs.outputs.temporary_id_map }}
     steps:
       - name: Setup Scripts
-        uses: github/gh-aw/actions/setup@00457477720387bcc7d7baaf841dedb22ad06617 # v0.89.17
+        uses: github/gh-aw/actions/setup@382f4b025fefaa7d6b2492c3608f098340bf6536 # v0.91.3
         with:
           destination: /opt/gh-aw/actions
       - name: Download agent output artifact
diff --git a/.github/workflows/upgrade-pylib.md b/.github/workflows/upgrade-pylib.md
index cd05eb77734..238c0d43bef 100644
--- a/.github/workflows/upgrade-pylib.md
+++ b/.github/workflows/upgrade-pylib.md
@@ -28,7 +28,7 @@ engine: copilot
 
 runtimes:
   python:
-    version: "3.14"
+    version: "3.15"
 
 tools:
   bash:
@@ -48,11 +48,9 @@ safe-outputs:
 cache:
   key: cpython-lib-${{ env.PYTHON_VERSION }}
   path: cpython
-  restore-keys:
-    - cpython-lib-
 
 env:
-  PYTHON_VERSION: "v3.14.7"
+  PYTHON_VERSION: "v3.15.0"
   ISSUE_ID: "6839"
 ---
 
@@ -65,10 +63,15 @@ You are an automated maintenance agent for RustPython, a Python 3 interpreter wr
 The CPython source may already be cached. Check if the `cpython` directory exists and has the correct version:
 
 ```bash
-if [ -d "cpython/Lib" ]; then
-    echo "CPython cache hit, skipping clone"
-else
+if [ ! -e "cpython" ]; then
     git clone --depth 1 --branch "$PYTHON_VERSION" https://github.com/python/cpython.git cpython
+elif [ ! -d "cpython/.git" ] || [ ! -d "cpython/Lib" ] ||
+    [ "$(git -C cpython rev-parse HEAD)" != "$(git -C cpython rev-parse --verify "$PYTHON_VERSION^{commit}" 2>/dev/null)" ] ||
+    [ -n "$(git -C cpython status --porcelain)" ]; then
+    echo "ERROR: cpython must be a clean checkout of $PYTHON_VERSION. Move the existing directory aside and rerun." >&2
+    exit 1
+else
+    echo "CPython $PYTHON_VERSION source already present."
 fi
 ```
 
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index aeef06ed6a6..a78da8d2e6a 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -10,7 +10,7 @@ repos:
         priority: 0
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.16.8
+    rev: v0.16.10
     hooks:
       - id: ruff-format
         priority: 0
@@ -63,7 +63,7 @@ repos:
           - manual
 
   - repo: https://github.com/streetsidesoftware/cspell-cli
-    rev: v10.2.0
+    rev: v10.3.0
     hooks:
       - id: cspell
         types: [rust]
@@ -77,7 +77,7 @@ repos:
         priority: 0
 
   - repo: https://github.com/rbubley/mirrors-prettier
-    rev: v3.9.8
+    rev: v3.9.9
     hooks:
       - id: prettier
         files: '^wasm/.*$'
diff --git a/.python-version b/.python-version
index a128d5c0d97..f02113fe87c 100644
--- a/.python-version
+++ b/.python-version
@@ -1 +1 @@
-3.14.7
+3.15.0
diff --git a/AGENTS.md b/AGENTS.md
index ae24d41671d..c814ce52040 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -4,7 +4,7 @@ This document provides guidelines for AI coding agents (GitHub Copilot, Claude C
 
 ## Project Overview
 
-RustPython is a Python 3 interpreter written in Rust, implementing Python 3.14.0+ compatibility. The project aims to provide:
+RustPython is a Python 3 interpreter written in Rust, targeting Python 3.15 with compatibility work in progress. The project aims to provide:
 
 - A complete Python-3 environment entirely in Rust (not CPython bindings)
 - A clean implementation without compatibility hacks
@@ -116,6 +116,9 @@ rm -r target/debug/build/rustpython-* && find . | grep -E "\.pyc$" | xargs rm -r
 
 ### Testing
 
+- Never add tests to `extra_tests/snippets` that duplicate coverage in `Lib/test`.
+- Prefer adding tests to the most closely related existing file in `extra_tests/snippets` rather than creating a new snippet file.
+
 ```bash
 # Run Rust unit tests
 cargo test --workspace --exclude rustpython_wasm --exclude rustpython-venvlauncher --exclude rustpython-capi
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 637ecf0993a..710bb2cafd3 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -49,7 +49,7 @@ RustPython requires the following:
       stable version: `rustup update stable`
     - If you do not have Rust installed, use [rustup](https://rustup.rs/) to
       do so.
-- CPython version 3.14 or higher
+- CPython version 3.15 or higher
     - CPython can be installed by your operating system's package manager,
       from the [Python website](https://www.python.org/downloads/), or
       using a third-party distribution, such as 
diff --git a/Cargo.lock b/Cargo.lock
index 3f3a54435c0..01c2bc8d576 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -277,9 +277,9 @@ checksum = "f2032f911046de80f0a198e0901378627c33f59ea0ac00e363d481118bd70a53"
 
 [[package]]
 name = "aws-lc-fips-sys"
-version = "0.13.15"
+version = "0.14.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6c0e6249c249b8916c98ebae7bc06216c8dcab3002f32872b4abe642d17063b1"
+checksum = "03367707e92796b190a4207d4d39b0a4271d574503d2969c2b0cfbf5c87658ee"
 dependencies = [
  "bindgen 0.72.1",
  "cc",
@@ -292,9 +292,9 @@ dependencies = [
 
 [[package]]
 name = "aws-lc-rs"
-version = "1.17.1"
+version = "1.18.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4342d8937fc7e5dd9b1c60292261c0670c882a2cd1719cfc11b1af41731e32ad"
+checksum = "b281d307588d634de920874890732659e2e7672f72b5e10e81badc1a8a83621e"
 dependencies = [
  "aws-lc-fips-sys",
  "aws-lc-sys",
@@ -303,9 +303,9 @@ dependencies = [
 
 [[package]]
 name = "aws-lc-sys"
-version = "0.42.0"
+version = "0.45.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6d9ceb1da931507a12f4fccea479dccd00da1943e1b4ae72d8e502d707361444"
+checksum = "9bff6c3b54fad79a2e60b8102caf565819711497c1f5f092f49508e2f5c31b27"
 dependencies = [
  "cc",
  "cmake",
@@ -320,12 +320,6 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4c7f02d4ea65f2c1853089ffd8d2787bdbc63de2f0d29dedbcf8ccdfa0ccd4cf"
 
-[[package]]
-name = "base64"
-version = "0.23.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ac07cdecf99051d9a5238b80f35af32cdeba5b336e55d957b318b50137e18da5"
-
 [[package]]
 name = "base64ct"
 version = "1.8.3"
@@ -338,7 +332,7 @@ version = "0.71.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5f58bf3d7db68cfbac37cfc485a8d711e87e064c3d0fe0435b92f7a407f9d6b3"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "cexpr",
  "clang-sys",
  "itertools 0.10.5",
@@ -358,7 +352,7 @@ version = "0.72.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "993776b509cfb49c750f11b8f07a46fa23e0a1386ffc01fb1e7d343efc387895"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "cexpr",
  "clang-sys",
  "itertools 0.10.5",
@@ -380,9 +374,9 @@ checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
 [[package]]
 name = "bitflags"
-version = "2.13.1"
+version = "2.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b588b76d00fde79687d7646a9b5bdf3cc0f655e0bbd080335a95d7e96f3587da"
+checksum = "3ded4057c258ba199e2d26386d3af3780957ecaee6c4ef4041c6b4b8b97c0b06"
 
 [[package]]
 name = "bitflagset"
@@ -445,9 +439,9 @@ dependencies = [
 
 [[package]]
 name = "bstr"
-version = "1.13.0"
+version = "1.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1f7dc094d718f2e1c1559ad110e27eeaae14a5465d3d56dd6dbd793079fbd530"
+checksum = "6bb31b46c14244e20ee9984b11bf5c992b91fb6939fea616e3512c8baecdbe5f"
 dependencies = [
  "memchr",
  "regex-automata",
@@ -504,9 +498,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.2.66"
+version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f5d6cac793997bd970000024b2934968efe83b382de4fdcf4fcb46b6ee4ad996"
+checksum = "f360145194ee8e21db5ee7f3fcd4fe52210864c75c985dae33218202c8bbe040"
 dependencies = [
  "find-msvc-tools",
  "jobserver",
@@ -572,9 +566,9 @@ dependencies = [
 
 [[package]]
 name = "char_str"
-version = "0.0.2"
+version = "0.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "576ba56f6ca18ebb069d0d07260407171712aff4dfe15ee3f8982dc16a455bcf"
+checksum = "c9cba78a5abb515610e10af297615434b019755b5d7be14e559ff5340dff50c4"
 dependencies = [
  "castaway",
  "get-size2",
@@ -703,7 +697,7 @@ dependencies = [
  "getrandom 0.4.3",
  "glob",
  "libc",
- "nix 0.31.3",
+ "nix",
  "serde",
  "serde_json",
  "statrs",
@@ -1302,9 +1296,9 @@ dependencies = [
 
 [[package]]
 name = "dirs"
-version = "6.0.0"
+version = "7.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c3e8aa94d75141228480295a7d0e7feb620b1a5ad9f12bc40be62411e38cce4e"
+checksum = "8d57d423b3c82e89b9a24ca3091fee61f456a26edbd28d26c65906f4bc1dcd8f"
 dependencies = [
  "dirs-sys",
 ]
@@ -1334,9 +1328,9 @@ dependencies = [
 
 [[package]]
 name = "dns-lookup"
-version = "4.0.1"
+version = "4.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6120e7e5dcd1c90098e349def389e2797377cdbe6b465ad8fdd115c0c99d5cf2"
+checksum = "263c0ccfc6b3b6a93e959edad4f985779e76c0b36dbb2e13e3d27c690974adf1"
 dependencies = [
  "cfg-if",
  "libc",
@@ -1502,9 +1496,9 @@ checksum = "28dea519a9695b9977216879a3ebfddf92f1c08c05d984f8996aecd6ecdc811d"
 
 [[package]]
 name = "find-msvc-tools"
-version = "0.1.9"
+version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5baebc0774151f905a1a2cc41989300b1e6fbb29aff0ceffa1064fdd3088d582"
+checksum = "aedcfb3409746eddb02b9e19ebda1c3394f759a152e48ee875a0844d1b955484"
 
 [[package]]
 name = "flame"
@@ -1612,9 +1606,9 @@ dependencies = [
 
 [[package]]
 name = "get-size-derive2"
-version = "0.10.3"
+version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c736d226c32e496b8377813b52269e11ad3a48d8373b68862d0364f04fd1229d"
+checksum = "7efe46d2adb529015748742f1a38594039ce357dbb21e6d178de342cfce468d4"
 dependencies = [
  "attribute-derive",
  "quote",
@@ -1623,9 +1617,9 @@ dependencies = [
 
 [[package]]
 name = "get-size2"
-version = "0.10.3"
+version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b411f34418305908ab15a82ff78958c2a9aee9a272b2a2e663836b20a4e4b9d3"
+checksum = "d4d338de392104417fe6fdbe588c52383b9236956d8afe5654f0077176edc632"
 dependencies = [
  "compact_str",
  "get-size-derive2",
@@ -1726,9 +1720,9 @@ dependencies = [
 
 [[package]]
 name = "glob"
-version = "0.3.3"
+version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0cc23270f6e1808e30a928bdc84dea0b9b4136a8bc82338574f23baf47bbd280"
+checksum = "e4eba85ea1d0a966a983acd07deee566e67395d2d96b6fb39e62b5a833f1eb0b"
 
 [[package]]
 name = "graviola"
@@ -1983,9 +1977,9 @@ dependencies = [
 
 [[package]]
 name = "indexmap"
-version = "2.14.0"
+version = "2.14.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d466e9454f08e4a911e14806c24e16fba1b4c121d1ea474396f396069cf949d9"
+checksum = "cc4e190f5d26ca7051642629da2c52fc03bde85a03197c99408dcd291734c855"
 dependencies = [
  "equivalent",
  "hashbrown 0.17.1",
@@ -2092,9 +2086,9 @@ checksum = "8f42a60cbdf9a97f5d2305f08a87dc4e09308d1276d28c869c684d7777685682"
 
 [[package]]
 name = "jiff"
-version = "0.2.37"
+version = "0.2.38"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0ab1baf72f08796de0260609515130699b890ac25f30e610ad894bc5856cafdb"
+checksum = "b2b005715dcbeb0089a3c0dab99f2ff1cc3b2525323552703d648585d342a383"
 dependencies = [
  "defmt",
  "jiff-core",
@@ -2120,9 +2114,9 @@ dependencies = [
 
 [[package]]
 name = "jiff-static"
-version = "0.2.37"
+version = "0.2.38"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "378268a1116ad67ae6228701118ac9f491d78fda38a40a1f1a9e1348de6f7212"
+checksum = "2cc9817253cf7c7ee4684451bd327e88d6f3658014e54a29198625590650695c"
 dependencies = [
  "jiff-core",
  "proc-macro2",
@@ -2132,9 +2126,9 @@ dependencies = [
 
 [[package]]
 name = "jiff-tzdb"
-version = "0.1.8"
+version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "142bd39932ad231f10513df9ab62661fead8719872150b7ad02a2df79f4e141e"
+checksum = "fa8377070c6bae868759445e5a77f66d84f0b72f3a054bfb00e6d038b8282da7"
 
 [[package]]
 name = "jiff-tzdb-platform"
@@ -2365,12 +2359,12 @@ dependencies = [
 
 [[package]]
 name = "mac_address"
-version = "1.1.8"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c0aeb26bf5e836cc1c341c8106051b573f1766dfa05aa87f0b98be5e51b02303"
+checksum = "f3d0581a75c45969c63afd2bb87b1d8b25cfcc556c7a918cf9bb13b0fe8d2381"
 dependencies = [
- "nix 0.29.0",
- "winapi",
+ "nix",
+ "windows-sys 0.61.2",
 ]
 
 [[package]]
@@ -2384,9 +2378,9 @@ dependencies = [
 
 [[package]]
 name = "malachite-base"
-version = "0.12.0"
+version = "0.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f368e032195e6f046f237a982cd541cac7d4e17d5c680cac5534dfa71cd8879e"
+checksum = "d5399d024a5e8fd066c158d208a02fb2dabb737c401ab03954f27d170fd49ffc"
 dependencies = [
  "hashbrown 0.16.1",
  "itertools 0.14.0",
@@ -2396,9 +2390,9 @@ dependencies = [
 
 [[package]]
 name = "malachite-bigint"
-version = "0.12.0"
+version = "0.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "47d673b71d4521ba5ca045cd23d62eda6b321474ff231d6a1698cc9b892851f2"
+checksum = "2ba82fa23fb2f63fcebd9ca012d885d41d4e95c9f14904df6cdcad9232646b2a"
 dependencies = [
  "malachite-base",
  "malachite-nz",
@@ -2409,10 +2403,11 @@ dependencies = [
 
 [[package]]
 name = "malachite-nz"
-version = "0.12.0"
+version = "0.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ec0b3ad1a8d2a722fbfad2e1fc7c5044f7ab38e027240cfbcb086a62ca95c9c2"
+checksum = "7ac55a9e8426447c374668b93c35b7b6ab43a21dc7ba97ad0e852be2305a5900"
 dependencies = [
+ "bytemuck",
  "itertools 0.14.0",
  "libm",
  "malachite-base",
@@ -2421,9 +2416,9 @@ dependencies = [
 
 [[package]]
 name = "malachite-q"
-version = "0.12.0"
+version = "0.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7841d36b3f5d39f1c65d4bcc45cb104fde66cf7eafc10da3922483fa2847cb94"
+checksum = "070267491ad6c23e504a71368542a2376d62f6622286be47870d7dcd56f24fce"
 dependencies = [
  "itertools 0.14.0",
  "libm",
@@ -2521,26 +2516,13 @@ dependencies = [
  "smallvec",
 ]
 
-[[package]]
-name = "nix"
-version = "0.29.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "71e2746dc3a24dd78b3cfcb7be93368c6de9963d30f43a6a73998a9cf4b17b46"
-dependencies = [
- "bitflags 2.13.1",
- "cfg-if",
- "cfg_aliases",
- "libc",
- "memoffset",
-]
-
 [[package]]
 name = "nix"
 version = "0.31.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf20d2fde8ff38632c426f1165ed7436270b44f199fc55284c38276f9db47c3d"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "cfg-if",
  "cfg_aliases",
  "libc",
@@ -2706,7 +2688,7 @@ version = "0.10.81"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77823a27f0babb03091cb9ed9ef80af3b39dbc82f97e8fa530374b7dafd87a45"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "cfg-if",
  "foreign-types",
  "libc",
@@ -2975,7 +2957,7 @@ dependencies = [
  "pbkdf2",
  "rand_core 0.10.1",
  "scrypt",
- "sha2 0.11.0",
+ "sha2 0.11.1",
  "spki 0.8.0",
 ]
 
@@ -3174,8 +3156,7 @@ dependencies = [
 [[package]]
 name = "pymath"
 version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bc10e50b7a1f2cc3887e983721cb51fc7574be0066c84bff3ef9e5c096e8d6d5"
+source = "git+https://github.com/RustPython/pymath.git?rev=dd1e9a4cf26d68caf3b549c09476f52e356e16a3#dd1e9a4cf26d68caf3b549c09476f52e356e16a3"
 dependencies = [
  "libc",
  "libm",
@@ -3187,9 +3168,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3"
-version = "0.29.3"
+version = "0.30.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "700d18fa267b73b9b521fd7e13580e2f446916f176cacee1ab63fcc8191f1655"
+checksum = "229ca13b8a15bb0d1487b81ab975bfcd97513416499a8312011b6036e42e0de4"
 dependencies = [
  "libc",
  "once_cell",
@@ -3201,18 +3182,18 @@ dependencies = [
 
 [[package]]
 name = "pyo3-build-config"
-version = "0.29.3"
+version = "0.30.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7b3fc0c4d08f6bb10e71fe39dfb9e2f59c6eb6854e22ec8092f50c69a4499adb"
+checksum = "70130e2b6dd1ee589a8788026a429561ca5c40fa7a2fa7914c2282eddae24700"
 dependencies = [
  "target-lexicon",
 ]
 
 [[package]]
 name = "pyo3-ffi"
-version = "0.29.3"
+version = "0.30.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dfc0b8e19df29aad7086cf977bb0c2a2f143e30567eb113e9cf72b62ca698330"
+checksum = "5e7ff73c555c286d212d4ce7e5fbda845a973c4f61bd5f160f5f2c3c2a04d1c4"
 dependencies = [
  "libc",
  "pyo3-build-config",
@@ -3220,26 +3201,26 @@ dependencies = [
 
 [[package]]
 name = "pyo3-macros"
-version = "0.29.3"
+version = "0.30.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6100e8a4b5eba53afaa5ed078364851a0b2499c553a44c31026b929049b49dc6"
+checksum = "c46d2e5862c7bb8207e3b639f713dda3c499933444784154c11d013c5a691b60"
 dependencies = [
  "proc-macro2",
  "pyo3-macros-backend",
  "quote",
- "syn 2.0.119",
+ "syn 3.0.3",
 ]
 
 [[package]]
 name = "pyo3-macros-backend"
-version = "0.29.3"
+version = "0.30.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6143877a16e82b5a727b7127ff4cd86858a24a28d745d72f43e6f227c7b1bdb3"
+checksum = "38b89f066f2ae72a2aef52d1537ca2fcd104440ebfadee06e97aa90738a25b9b"
 dependencies = [
  "heck",
  "proc-macro2",
  "quote",
- "syn 2.0.119",
+ "syn 3.0.3",
 ]
 
 [[package]]
@@ -3392,7 +3373,7 @@ version = "0.5.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed2bf2547551a7053d6fdfafda3f938979645c44812fbfcda098faae3f1a362d"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
 ]
 
 [[package]]
@@ -3573,11 +3554,11 @@ dependencies = [
 
 [[package]]
 name = "rustix"
-version = "1.1.4"
+version = "1.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b6fe4565b9518b83ef4f91bb47ce29620ca828bd32cb7e408f0062e9930ba190"
+checksum = "891efababe418670775f199f0d233d84843c227a0949a883ce15b37c78d6629d"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "errno",
  "libc",
  "linux-raw-sys",
@@ -3586,14 +3567,14 @@ dependencies = [
 
 [[package]]
 name = "rustls"
-version = "0.23.43"
+version = "0.23.45"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0283386ce02abc0151e1761d08802dfe86c173b0b494af5cbc086574e453da06"
+checksum = "0d41d731c7d2f962d1ccc364cec258de3c0e93b38c2fb3ba97ac74513048d634"
 dependencies = [
  "aws-lc-rs",
  "once_cell",
  "rustls-pki-types",
- "rustls-webpki 0.103.13",
+ "rustls-webpki 0.103.15",
  "subtle",
  "zeroize",
 ]
@@ -3631,9 +3612,9 @@ dependencies = [
 
 [[package]]
 name = "rustls-pki-types"
-version = "1.15.0"
+version = "1.15.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "764899a24af3980067ee14bc143654f297b22eaebfe3c7b6b211920a5a59b046"
+checksum = "2f4925028c7eb5d1fcdaf196971378ed9d2c1c4efc7dc5d011256f76c99c0a96"
 dependencies = [
  "web-time",
  "zeroize",
@@ -3682,9 +3663,9 @@ dependencies = [
 
 [[package]]
 name = "rustls-webpki"
-version = "0.103.13"
+version = "0.103.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "61c429a8649f110dddef65e2a5ad240f747e85f7758a6bccc7e5777bd33f756e"
+checksum = "f3c3cf1d8b1e7d4927e2d154c3fcb02979afb9939629c62cd9048d4f07b60ac2"
 dependencies = [
  "aws-lc-rs",
  "ring",
@@ -3722,7 +3703,7 @@ dependencies = [
 name = "rustpython-capi"
 version = "0.6.1"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "itertools 0.15.0",
  "libc",
  "malachite-bigint",
@@ -3731,13 +3712,14 @@ dependencies = [
  "rustpython-pylib",
  "rustpython-stdlib",
  "rustpython-vm",
+ "static_assertions",
 ]
 
 [[package]]
 name = "rustpython-codegen"
 version = "0.6.1"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "indexmap",
  "itertools 0.15.0",
  "log",
@@ -3761,8 +3743,7 @@ name = "rustpython-common"
 version = "0.6.1"
 dependencies = [
  "ascii",
- "base64",
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "blake2b_simd",
  "blake2s_simd",
  "bzip2",
@@ -3786,7 +3767,7 @@ dependencies = [
  "rustpython-wtf8",
  "scrypt",
  "sha1",
- "sha2 0.11.0",
+ "sha2 0.11.1",
  "sha3",
  "shake",
  "siphasher",
@@ -3812,7 +3793,7 @@ dependencies = [
 name = "rustpython-compiler-core"
 version = "0.6.1"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "bitflagset",
  "itertools 0.15.0",
  "lz4_flex",
@@ -3857,7 +3838,7 @@ dependencies = [
 name = "rustpython-host_env"
 version = "0.6.1"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "bitflagset",
  "cc",
  "der 0.8.2",
@@ -3871,7 +3852,7 @@ dependencies = [
  "mac_address",
  "memchr",
  "memmap2",
- "nix 0.31.3",
+ "nix",
  "num-traits",
  "num_cpus",
  "parking_lot",
@@ -3881,11 +3862,11 @@ dependencies = [
  "rustls",
  "rustls-native-certs",
  "rustls-pemfile",
- "rustls-webpki 0.103.13",
+ "rustls-webpki 0.103.15",
  "rustpython-wtf8",
  "rustyline",
  "schannel",
- "sha2 0.11.0",
+ "sha2 0.11.1",
  "socket2",
  "system-configuration",
  "termios",
@@ -3935,13 +3916,13 @@ dependencies = [
 
 [[package]]
 name = "rustpython-ruff_python_ast"
-version = "0.16.5"
+version = "0.16.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bc19eeb4cfa2c35428143693eadf85ee78816f22a829298593581a56700c0a21"
+checksum = "5b7ffeb85f9a68c461d538839c79548584768df08f2d68cb1ee693be697e0355"
 dependencies = [
  "aho-corasick",
  "arrayvec",
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "char_str",
  "compact_str",
  "get-size2",
@@ -3957,14 +3938,16 @@ dependencies = [
 
 [[package]]
 name = "rustpython-ruff_python_parser"
-version = "0.16.5"
+version = "0.16.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "480eec9ac4dda77b6724f0c9a54a81d3c57868d6a707c3d7c5133fd83c933f66"
+checksum = "7c9729e35cac02839c7a67aaccfea3eba32032f7aeacca2e82ad79e8d7b7fd95"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "bstr",
  "drop_bomb",
  "get-size2",
+ "hashbrown 0.17.1",
+ "icu_properties",
  "memchr",
  "rustc-hash",
  "rustpython-ruff_python_ast",
@@ -3980,22 +3963,24 @@ dependencies = [
 
 [[package]]
 name = "rustpython-ruff_python_trivia"
-version = "0.16.5"
+version = "0.16.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6d69a5d9bb610a76bee05d23adce0de55f0fa06f251c0e1c7f7a0c625a366a58"
+checksum = "764f43ea060f888164fbd360b0e1a36f2a35f5c03def85407bab7039fc62a645"
 dependencies = [
  "itertools 0.15.0",
+ "memchr",
  "rustc-hash",
  "rustpython-ruff_source_file",
  "rustpython-ruff_text_size",
  "unicode-ident",
+ "unicode-normalization",
 ]
 
 [[package]]
 name = "rustpython-ruff_source_file"
-version = "0.16.5"
+version = "0.16.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d3aa9c91c8a4e86bf0fa8a67aec284fa6c0c533cdefb900b08584be15748c606"
+checksum = "cfe26430c3f2eadb40524b6df7ac9a3970dd2b58f921b01ed75df0121e332fad"
 dependencies = [
  "memchr",
  "rustpython-ruff_text_size",
@@ -4003,9 +3988,9 @@ dependencies = [
 
 [[package]]
 name = "rustpython-ruff_text_size"
-version = "0.16.5"
+version = "0.16.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8fedbd1af4f91cd828185123d95119662db9c4a0b21c02b695783d74360d4f46"
+checksum = "5e5377a04f2855030600b93a05754242950ea9b070507ef9aef67965a52eeb09"
 dependencies = [
  "get-size2",
 ]
@@ -4014,7 +3999,7 @@ dependencies = [
 name = "rustpython-sre_engine"
 version = "0.6.1"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "codspeed-criterion-compat",
  "num_enum",
  "optional",
@@ -4085,7 +4070,7 @@ dependencies = [
  "icu_normalizer",
  "icu_properties",
  "rustpython-wtf8",
- "unicode_names2 3.1.0",
+ "unicode_names2 4.0.0",
  "writeable",
  "zlib-rs",
 ]
@@ -4099,7 +4084,7 @@ name = "rustpython-vm"
 version = "0.6.1"
 dependencies = [
  "ascii",
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "bitflagset",
  "bstr",
  "constant_time_eq 0.6.0",
@@ -4200,14 +4185,14 @@ version = "18.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "53f6a737db68eb1a8ccff86b584b2fc13eca6a7bb6f78ebc7c529547e3ab9684"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "cfg-if",
  "clipboard-win",
  "home",
  "libc",
  "log",
  "memchr",
- "nix 0.31.3",
+ "nix",
  "radix_trie",
  "unicode-segmentation",
  "unicode-width",
@@ -4223,9 +4208,9 @@ checksum = "9774ba4a74de5f7b1c1451ed6cd5285a32eddb5cccb8cc655a4e50009e06477f"
 
 [[package]]
 name = "safe_arch"
-version = "1.0.0"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1f7caad094bd561859bcd467734a720c3c1f5d1f338995351fefe2190c45efed"
+checksum = "42c6efa15875e6ecb39ca61fb0b0c1a40b84fac5a5ffe71eef7d1000c8eb3f5f"
 dependencies = [
  "bytemuck",
 ]
@@ -4273,7 +4258,7 @@ dependencies = [
  "cfg-if",
  "pbkdf2",
  "salsa20",
- "sha2 0.11.0",
+ "sha2 0.11.1",
 ]
 
 [[package]]
@@ -4296,7 +4281,7 @@ version = "3.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b7f4bc775c73d9a02cde8bf7b2ec4c9d12743edf609006c7facc23998404cd1d"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "core-foundation",
  "core-foundation-sys",
  "libc",
@@ -4406,9 +4391,9 @@ dependencies = [
 
 [[package]]
 name = "sha2"
-version = "0.11.0"
+version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "446ba717509524cb3f22f17ecc096f10f4822d76ab5c0b9822c5f9c284e825f4"
+checksum = "47d7069beb7d6ac7b9acd1039986e73443f24234f41074da099d6f994ac9ad19"
 dependencies = [
  "cfg-if",
  "cpufeatures 0.3.0",
@@ -4475,9 +4460,9 @@ checksum = "bbbb5d9659141646ae647b42fe094daf6c6192d1620870b449d9557f748b2daa"
 
 [[package]]
 name = "siphasher"
-version = "1.0.3"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8ee5873ec9cce0195efcb7a4e9507a04cd49aec9c83d0389df45b1ef7ba2e649"
+checksum = "33f4fe9184a62d842c9ef383018f3306d8ba224fd9d836f56d7288308847c256"
 
 [[package]]
 name = "slab"
@@ -4642,7 +4627,7 @@ version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "501336eb7ba9e417300a6a0fa985721065467aa83a6dcf0422a8e43e4c0328fa"
 dependencies = [
- "bitflags 2.13.1",
+ "bitflags 2.13.2",
  "core-foundation",
  "system-configuration-sys",
 ]
@@ -4679,7 +4664,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
 dependencies = [
  "fastrand",
- "getrandom 0.3.4",
+ "getrandom 0.4.3",
  "once_cell",
  "rustix",
  "windows-sys 0.61.2",
@@ -4702,9 +4687,9 @@ checksum = "6ecfad6c3abc80a577f2b91c1e412ee57e7a060d430b553c1b0c940974ebcd49"
 
 [[package]]
 name = "thin-vec"
-version = "0.2.19"
+version = "0.2.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "79def32ffcd477db1ff26f76dab9e3a91f0bd42a85ca96577089b24623056f9d"
+checksum = "4568d7e143ec86d2021c338bae2afa88699e84b8e0af523626654fe6f03a1748"
 
 [[package]]
 name = "thiserror"
@@ -4902,12 +4887,12 @@ dependencies = [
 
 [[package]]
 name = "unicode_names2"
-version = "3.1.0"
+version = "4.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "82c3e18d850bb6ebd57735e5654f0af65e572b05c2397e7b2b1a7c6a792cc29c"
+checksum = "8ba646312acace3c9ec35d7404b58214b6fbf17cbb0d040f35a88407c424447f"
 dependencies = [
  "phf 0.11.3",
- "unicode_names2_generator 3.1.0",
+ "unicode_names2_generator 4.0.0",
 ]
 
 [[package]]
@@ -4924,9 +4909,9 @@ dependencies = [
 
 [[package]]
 name = "unicode_names2_generator"
-version = "3.1.0"
+version = "4.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "849744a58c479122ff24910d7ca57f312b62613ef0412dc327776ae6b235d16a"
+checksum = "3afbb72a8cff40859641ae4e56679215a15764e5c155a46f0f534611bdc08e0e"
 dependencies = [
  "phf_codegen",
  "rand 0.8.6",
@@ -5131,18 +5116,18 @@ dependencies = [
 
 [[package]]
 name = "which"
-version = "8.0.5"
+version = "8.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8f3ef584124b911bcc3875c2f1472e80f24361ceb789bd1c62b3e9a3df9ff43c"
+checksum = "bae2f2b2b816647a1cab1acc91f5bd20812d53cb344382635ec2181940c8034f"
 dependencies = [
  "libc",
 ]
 
 [[package]]
 name = "wide"
-version = "1.5.0"
+version = "1.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dfdfe6a32973f2d1b268b8895845a8a96cac2f0191e72c27cc929036060dbf89"
+checksum = "d920ac99c3c8edce110cb8d07dbb324d6d026011dce85b1e9355b70f0adacc4f"
 dependencies = [
  "bytemuck",
  "safe_arch",
diff --git a/Cargo.toml b/Cargo.toml
index 74565c4b09e..0b9c6af8d60 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,7 +11,7 @@ license.workspace = true
 
 [features]
 capi = ["dep:rustpython-capi", "threading"]
-default = ["threading", "stdlib", "stdio", "importlib", "ssl-rustls-aws-lc", "host_env", "mimalloc", "doc"]
+default = ["threading", "stdlib", "stdio", "importlib", "ssl-rustls-aws-lc", "host_env", "mimalloc", "doc", "ucd_3_2_0"]
 doc = ["rustpython-vm/doc", "rustpython-stdlib?/doc"]
 mimalloc = ["dep:mimalloc"]
 host_env = ["rustpython-vm/host_env", "rustpython-stdlib?/host_env"]
@@ -32,13 +32,13 @@ ssl-rustls-aws-lc-fips = ["ssl-rustls-aws-lc", "rustls/fips"]
 ssl-openssl = ["ssl", "rustpython-stdlib/ssl-openssl"]
 ssl-openssl-vendor = ["ssl-openssl", "rustpython-stdlib/ssl-openssl-vendor"]
 tkinter = ["rustpython-stdlib/tkinter"]
+ucd_3_2_0 = ["rustpython-stdlib?/ucd_3_2_0"]
 
 [build-dependencies]
 winresource = "0.1"
 
 [dependencies]
 rustpython-capi = { workspace = true, optional = true }
-rustpython-compiler = { workspace = true }
 rustpython-pylib = { workspace = true, optional = true }
 rustpython-stdlib = { workspace = true, optional = true, default-features = false, features = ["compiler"] }
 rustpython-vm = { workspace = true, features = ["compiler", "gc"] }
@@ -47,7 +47,7 @@ log = { workspace = true }
 flame = { workspace = true, optional = true }
 
 lexopt = "0.3"
-dirs = "6"
+dirs = "7"
 env_logger = "0.11"
 flamescope = { version = "0.1.2", optional = true }
 
@@ -61,12 +61,20 @@ rustyline = { workspace = true }
 mimalloc = { version = "0.1", optional = true, default-features = false }
 
 [dev-dependencies]
+rustpython-compiler = { workspace = true }
 criterion = { workspace = true }
 pyo3 = { workspace = true, features = ["auto-initialize"] }
 rustls-graviola = { workspace = true }
 rustpython-stdlib = { workspace = true }
 ruff_python_parser = { workspace = true }
 
+# Only the criterion benchmarks below are measured. Without `bench = false`,
+# `cargo bench` (and `cargo codspeed build`) also builds the library and binary
+# unit-test harnesses with the LTO bench profile, adding a full extra link of
+# the interpreter that is never run.
+[lib]
+bench = false
+
 [[bench]]
 name = "execution"
 harness = false
@@ -78,6 +86,7 @@ harness = false
 [[bin]]
 name = "rustpython"
 path = "src/main.rs"
+bench = false
 
 [[example]]
 name = "custom_tls_providers"
@@ -183,22 +192,21 @@ rustpython-vm = { path = "crates/vm", default-features = false, version = "0.6.1
 rustpython-pylib = { path = "crates/pylib", version = "0.6.1" }
 rustpython-stdlib = { path = "crates/stdlib", default-features = false, version = "0.6.1" }
 rustpython-sre_engine = { path = "crates/sre_engine", version = "0.6.1" }
-rustpython-unicode = { path = "crates/unicode", version = "0.6.1" }
+rustpython-unicode = { path = "crates/unicode", default-features = false, version = "0.6.1" }
 rustpython-wtf8 = { path = "crates/wtf8", version = "0.6.1" }
 rustpython-doc = { path = "crates/doc", version = "0.6.1" }
 
 # Use the RustPython Ruff fork for RustPython public `_ast` metadata.
-ruff_python_parser = { package = "rustpython-ruff_python_parser", version = "0.16.5" }
-ruff_python_ast = { package = "rustpython-ruff_python_ast", version = "0.16.5" }
-ruff_text_size = { package = "rustpython-ruff_text_size", version = "0.16.5" }
-ruff_source_file = { package = "rustpython-ruff_source_file", version = "0.16.5" }
+ruff_python_parser = { package = "rustpython-ruff_python_parser", version = "0.16.10" }
+ruff_python_ast = { package = "rustpython-ruff_python_ast", version = "0.16.10" }
+ruff_text_size = { package = "rustpython-ruff_text_size", version = "0.16.10" }
+ruff_source_file = { package = "rustpython-ruff_source_file", version = "0.16.10" }
 
 der = { version = "0.8", features = ["alloc", "oid", "pem", "zeroize"] }
 phf = { version = "0.14.0", default-features = false, features = ["macros"]}
 adler32 = "1.2.0"
 approx = "0.5.1"
 ascii = { version = "1.1", default-features = false }
-base64 = "0.23"
 blake2b_simd = "1.0.4"
 blake2s_simd = "1.0.4"
 bitflags = "2.11.0"
@@ -246,9 +254,9 @@ log = "0.4.30"
 lz4_flex = "0.14"
 nix = { version = "0.31", features = ["fs", "user", "process", "term", "time", "signal", "ioctl", "socket", "sched", "zerocopy", "dir", "hostname", "net", "poll"] }
 mac_address = "1.1.3"
-malachite-bigint = "0.12.0"
-malachite-q = "0.12.0"
-malachite-base = "0.12.0"
+malachite-bigint = "0.14.0"
+malachite-q = "0.14.0"
+malachite-base = "0.14.0"
 md-5 = "0.11"
 memchr = { version = "2.8.1", default-features = false, features = ["alloc"] }
 memmap2 = "0.9.10"
@@ -267,8 +275,8 @@ pem-rfc7468 = "1.0"
 pkcs8 = "0.11"
 proc-macro2 = "1.0.105"
 psm = "0.1"
-pymath = { version = "0.2.0", features = ["mul_add", "malachite-bigint", "complex"] }
-pyo3 = "0.29"
+pymath = { git = "https://github.com/RustPython/pymath.git", rev = "dd1e9a4cf26d68caf3b549c09476f52e356e16a3", features = ["mul_add", "malachite-bigint", "complex"] }
+pyo3 = "0.30"
 quote = "1.0.45"
 radium = "1.1.1"
 rand = "0.10"
@@ -309,7 +317,7 @@ icu_locale = "2"
 icu_properties = "2"
 icu_normalizer = "2"
 uuid = "1.23.2"
-unicode_names2 = { version = "3", default-features = false, features = ["no_std"] }
+unicode_names2 = { version = "4", default-features = false, features = ["no_std"] }
 widestring = "1.2.0"
 windows-sys = "0.61.2"
 wasm-bindgen = "0.2.106"
diff --git a/Lib/_ast_unparse.py b/Lib/_ast_unparse.py
index 1c8741b5a55..916bb25d74d 100644
--- a/Lib/_ast_unparse.py
+++ b/Lib/_ast_unparse.py
@@ -239,11 +239,11 @@ def visit_NamedExpr(self, node):
             self.traverse(node.value)
 
     def visit_Import(self, node):
-        self.fill("import ")
+        self.fill("lazy import " if node.is_lazy else "import ")
         self.interleave(lambda: self.write(", "), self.traverse, node.names)
 
     def visit_ImportFrom(self, node):
-        self.fill("from ")
+        self.fill("lazy from " if node.is_lazy else "from ")
         self.write("." * (node.level or 0))
         if node.module:
             self.write(node.module)
@@ -738,9 +738,13 @@ def visit_SetComp(self, node):
 
     def visit_DictComp(self, node):
         with self.delimit("{", "}"):
-            self.traverse(node.key)
-            self.write(": ")
-            self.traverse(node.value)
+            if node.value:
+                self.traverse(node.key)
+                self.write(": ")
+                self.traverse(node.value)
+            else:
+                self.write("**")
+                self.traverse(node.key)
             for gen in node.generators:
                 self.traverse(gen)
 
diff --git a/Lib/_colorize.py b/Lib/_colorize.py
index d6673f6692f..27eb7f13bac 100644
--- a/Lib/_colorize.py
+++ b/Lib/_colorize.py
@@ -1,21 +1,19 @@
+import builtins
 import os
 import sys
 
 from collections.abc import Callable, Iterator, Mapping
 from dataclasses import dataclass, field, Field
+lazy from typing import IO, Literal, Self, ClassVar
 
 COLORIZE = True
 
-
-# types
-if False:
-    from typing import IO, Self, ClassVar
-    _theme: Theme
+_theme: Theme
+type BackgroundStyle = Literal["dark", "light"]
 
 
 class ANSIColors:
     RESET = "\x1b[0m"
-
     BLACK = "\x1b[30m"
     BLUE = "\x1b[34m"
     CYAN = "\x1b[36m"
@@ -74,6 +72,19 @@ class ANSIColors:
         setattr(NoColors, attr, "")
 
 
+class CursesColors:
+    """Curses color constants for terminal UI theming."""
+    BLACK = 0
+    RED = 1
+    GREEN = 2
+    YELLOW = 3
+    BLUE = 4
+    MAGENTA = 5
+    CYAN = 6
+    WHITE = 7
+    DEFAULT = -1
+
+
 #
 # Experimental theming support (see gh-133346)
 #
@@ -168,10 +179,227 @@ class Argparse(ThemeSection):
     short_option: str = ANSIColors.BOLD_GREEN
     label: str = ANSIColors.BOLD_YELLOW
     action: str = ANSIColors.BOLD_GREEN
+    default: str = ANSIColors.GREY
+    interpolated_value: str = ANSIColors.YELLOW
+    reset: str = ANSIColors.RESET
+    error: str = ANSIColors.BOLD_MAGENTA
+    warning: str = ANSIColors.BOLD_YELLOW
+    message: str = ANSIColors.MAGENTA
+
+
+@dataclass(frozen=True, kw_only=True)
+class Ast(ThemeSection):
+    node: str = ANSIColors.CYAN
+    field: str = ANSIColors.BLUE
+    attribute: str = ANSIColors.GREY
+    string: str = ANSIColors.GREEN
+    number: str = ANSIColors.YELLOW
+    keyword: str = ANSIColors.BOLD_BLUE
+    reset: str = ANSIColors.RESET
+
+
+@dataclass(frozen=True, kw_only=True)
+class Calendar(ThemeSection):
+    header: str = ANSIColors.BOLD
+    highlight: str = ANSIColors.BLACK + ANSIColors.BACKGROUND_YELLOW
+    weekday: str = ANSIColors.CYAN
+    reset: str = ANSIColors.RESET
+
+
+@dataclass(frozen=True, kw_only=True)
+class Difflib(ThemeSection):
+    """A 'git diff'-like theme for `difflib.unified_diff`."""
+    added: str = ANSIColors.GREEN
+    context: str = ANSIColors.RESET  # context lines
+    header: str = ANSIColors.BOLD  # eg "---" and "+++" lines
+    hunk: str = ANSIColors.CYAN  # the "@@" lines
+    removed: str = ANSIColors.RED
+    reset: str = ANSIColors.RESET
+
+
+@dataclass(frozen=True, kw_only=True)
+class FancyCompleter(ThemeSection):
+    # functions and methods
+    function: builtins.str = ANSIColors.BOLD_BLUE
+    builtin_function_or_method: builtins.str = ANSIColors.BOLD_BLUE
+    method: builtins.str = ANSIColors.BOLD_CYAN
+    method_wrapper: builtins.str = ANSIColors.BOLD_CYAN
+    wrapper_descriptor: builtins.str = ANSIColors.BOLD_CYAN
+    method_descriptor: builtins.str = ANSIColors.BOLD_CYAN
+
+    # numbers
+    int: builtins.str = ANSIColors.BOLD_YELLOW
+    float: builtins.str = ANSIColors.BOLD_YELLOW
+    complex: builtins.str = ANSIColors.BOLD_YELLOW
+    bool: builtins.str = ANSIColors.BOLD_YELLOW
+
+    # others
+    type: builtins.str = ANSIColors.BOLD_MAGENTA
+    module: builtins.str = ANSIColors.CYAN
+    NoneType: builtins.str = ANSIColors.GREY
+    bytes: builtins.str = ANSIColors.BOLD_GREEN
+    str: builtins.str = ANSIColors.BOLD_GREEN
+
+
+@dataclass(frozen=True, kw_only=True)
+class HttpServer(ThemeSection):
+    error: str = ANSIColors.YELLOW
+    path: str = ANSIColors.CYAN
+    serving: str = ANSIColors.GREEN
+    size: str = ANSIColors.GREY
+    status_informational: str = ANSIColors.RESET
+    status_ok: str = ANSIColors.GREEN
+    status_redirect: str = ANSIColors.INTENSE_CYAN
+    status_client_error: str = ANSIColors.YELLOW
+    status_server_error: str = ANSIColors.RED
+    timestamp: str = ANSIColors.GREY
+    url: str = ANSIColors.CYAN
+    reset: str = ANSIColors.RESET
+
+
+@dataclass(frozen=True, kw_only=True)
+class LiveProfiler(ThemeSection):
+    """Theme section for the live profiling TUI (Tachyon profiler).
+
+    Colors use CursesColors constants (BLACK, RED, GREEN, YELLOW,
+    BLUE, MAGENTA, CYAN, WHITE, DEFAULT).
+    """
+    # Header colors
+    title_fg: int = CursesColors.CYAN
+    title_bg: int = CursesColors.DEFAULT
+
+    # Status display colors
+    pid_fg: int = CursesColors.CYAN
+    uptime_fg: int = CursesColors.GREEN
+    time_fg: int = CursesColors.YELLOW
+    interval_fg: int = CursesColors.MAGENTA
+
+    # Thread view colors
+    thread_all_fg: int = CursesColors.GREEN
+    thread_single_fg: int = CursesColors.MAGENTA
+
+    # Progress bar colors
+    bar_good_fg: int = CursesColors.GREEN
+    bar_bad_fg: int = CursesColors.RED
+
+    # Stats colors
+    on_gil_fg: int = CursesColors.GREEN
+    off_gil_fg: int = CursesColors.RED
+    waiting_gil_fg: int = CursesColors.YELLOW
+    gc_fg: int = CursesColors.MAGENTA
+
+    # Function display colors
+    func_total_fg: int = CursesColors.CYAN
+    func_exec_fg: int = CursesColors.GREEN
+    func_stack_fg: int = CursesColors.YELLOW
+    func_shown_fg: int = CursesColors.MAGENTA
+
+    # Table header colors (for sorted column highlight)
+    sorted_header_fg: int = CursesColors.BLACK
+    sorted_header_bg: int = CursesColors.CYAN
+
+    # Normal header colors (non-sorted columns) - use reverse video style
+    normal_header_fg: int = CursesColors.BLACK
+    normal_header_bg: int = CursesColors.WHITE
+
+    # Data row colors
+    samples_fg: int = CursesColors.CYAN
+    file_fg: int = CursesColors.GREEN
+    func_fg: int = CursesColors.YELLOW
+
+    # Trend indicator colors
+    trend_up_fg: int = CursesColors.GREEN
+    trend_down_fg: int = CursesColors.RED
+
+    # Medal colors for top functions
+    medal_gold_fg: int = CursesColors.RED
+    medal_silver_fg: int = CursesColors.YELLOW
+    medal_bronze_fg: int = CursesColors.GREEN
+
+    # Background style: 'dark' or 'light'
+    background_style: BackgroundStyle = "dark"
+
+
+LiveProfilerLight = LiveProfiler(
+    # Header colors
+    title_fg=CursesColors.BLUE,  # Blue is more readable than cyan on light bg
+
+    # Status display colors - darker colors for light backgrounds
+    pid_fg=CursesColors.BLUE,
+    uptime_fg=CursesColors.BLACK,
+    time_fg=CursesColors.BLACK,
+    interval_fg=CursesColors.BLUE,
+
+    # Thread view colors
+    thread_all_fg=CursesColors.BLACK,
+    thread_single_fg=CursesColors.BLUE,
+
+    # Stats colors
+    waiting_gil_fg=CursesColors.RED,
+    gc_fg=CursesColors.BLUE,
+
+    # Function display colors
+    func_total_fg=CursesColors.BLUE,
+    func_exec_fg=CursesColors.BLACK,
+    func_stack_fg=CursesColors.BLACK,
+    func_shown_fg=CursesColors.BLUE,
+
+    # Table header colors (for sorted column highlight)
+    sorted_header_fg=CursesColors.WHITE,
+    sorted_header_bg=CursesColors.BLUE,
+
+    # Normal header colors (non-sorted columns)
+    normal_header_fg=CursesColors.WHITE,
+    normal_header_bg=CursesColors.BLACK,
+
+    # Data row colors - use dark colors readable on white
+    samples_fg=CursesColors.BLACK,
+    file_fg=CursesColors.BLACK,
+    func_fg=CursesColors.BLUE,  # Blue is more readable than magenta on light bg
+
+    # Medal colors for top functions
+    medal_silver_fg=CursesColors.BLUE,
+
+    # Background style
+    background_style="light",
+)
+
+
+@dataclass(frozen=True, kw_only=True)
+class ProfilerDump(ThemeSection):
+    header: str = ANSIColors.BOLD_BLUE
+    interpreter: str = ANSIColors.GREY
+    thread: str = ANSIColors.BOLD_CYAN
+    status: str = ANSIColors.YELLOW
+    frame_index: str = ANSIColors.GREY
+    frame: str = ANSIColors.BOLD_GREEN
+    filename: str = ANSIColors.CYAN
+    line_no: str = ANSIColors.YELLOW
+    source: str = ANSIColors.WHITE
+    source_highlight: str = ANSIColors.BOLD_YELLOW
+    opcode: str = ANSIColors.GREY
+    warning: str = ANSIColors.YELLOW
+    reset: str = ANSIColors.RESET
+
+
+@dataclass(frozen=True, kw_only=True)
+class Pickletools(ThemeSection):
+    annotation: str = ANSIColors.GREY
+    arg_number: str = ANSIColors.YELLOW
+    arg_string: str = ANSIColors.GREEN
+    mark: str = ANSIColors.GREY
+    op_call: str = ANSIColors.GREEN
+    op_container: str = ANSIColors.INTENSE_BLUE
+    op_memo: str = ANSIColors.MAGENTA
+    op_meta: str = ANSIColors.GREY
+    op_stack: str = ANSIColors.BOLD_RED
+    opcode_code: str = ANSIColors.CYAN
+    position: str = ANSIColors.GREY
+    proto: str = ANSIColors.YELLOW
     reset: str = ANSIColors.RESET
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, kw_only=True)
 class Syntax(ThemeSection):
     prompt: str = ANSIColors.BOLD_MAGENTA
     keyword: str = ANSIColors.BOLD_BLUE
@@ -186,10 +414,31 @@ class Syntax(ThemeSection):
     reset: str = ANSIColors.RESET
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, kw_only=True)
+class Timeit(ThemeSection):
+    timing: str = ANSIColors.CYAN
+    best: str = ANSIColors.BOLD_GREEN
+    per_loop: str = ANSIColors.GREEN
+    punctuation: str = ANSIColors.GREY
+    warning: str = ANSIColors.YELLOW
+    warning_worst: str = ANSIColors.MAGENTA
+    warning_best: str = ANSIColors.GREEN
+    reset: str = ANSIColors.RESET
+
+
+@dataclass(frozen=True, kw_only=True)
+class Tokenize(ThemeSection):
+    whitespace: str = ANSIColors.GREY
+    error: str = ANSIColors.BOLD_RED
+    position: str = ANSIColors.GREY
+    delimiter: str = ANSIColors.RESET
+
+
+@dataclass(frozen=True, kw_only=True)
 class Traceback(ThemeSection):
     type: str = ANSIColors.BOLD_MAGENTA
     message: str = ANSIColors.MAGENTA
+    note: str = ANSIColors.CYAN
     filename: str = ANSIColors.MAGENTA
     line_no: str = ANSIColors.MAGENTA
     frame: str = ANSIColors.MAGENTA
@@ -198,7 +447,7 @@ class Traceback(ThemeSection):
     reset: str = ANSIColors.RESET
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, kw_only=True)
 class Unittest(ThemeSection):
     passed: str = ANSIColors.GREEN
     warn: str = ANSIColors.YELLOW
@@ -207,7 +456,7 @@ class Unittest(ThemeSection):
     reset: str = ANSIColors.RESET
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, kw_only=True)
 class Theme:
     """A suite of themes for all sections of Python.
 
@@ -215,7 +464,17 @@ class Theme:
     below.
     """
     argparse: Argparse = field(default_factory=Argparse)
+    ast: Ast = field(default_factory=Ast)
+    calendar: Calendar = field(default_factory=Calendar)
+    difflib: Difflib = field(default_factory=Difflib)
+    fancycompleter: FancyCompleter = field(default_factory=FancyCompleter)
+    http_server: HttpServer = field(default_factory=HttpServer)
+    live_profiler: LiveProfiler = field(default_factory=LiveProfiler)
+    pickletools: Pickletools = field(default_factory=Pickletools)
+    profiler_dump: ProfilerDump = field(default_factory=ProfilerDump)
     syntax: Syntax = field(default_factory=Syntax)
+    timeit: Timeit = field(default_factory=Timeit)
+    tokenize: Tokenize = field(default_factory=Tokenize)
     traceback: Traceback = field(default_factory=Traceback)
     unittest: Unittest = field(default_factory=Unittest)
 
@@ -223,7 +482,17 @@ def copy_with(
         self,
         *,
         argparse: Argparse | None = None,
+        ast: Ast | None = None,
+        calendar: Calendar | None = None,
+        difflib: Difflib | None = None,
+        fancycompleter: FancyCompleter | None = None,
+        http_server: HttpServer | None = None,
+        live_profiler: LiveProfiler | None = None,
+        pickletools: Pickletools | None = None,
+        profiler_dump: ProfilerDump | None = None,
         syntax: Syntax | None = None,
+        timeit: Timeit | None = None,
+        tokenize: Tokenize | None = None,
         traceback: Traceback | None = None,
         unittest: Unittest | None = None,
     ) -> Self:
@@ -234,7 +503,17 @@ def copy_with(
         """
         return type(self)(
             argparse=argparse or self.argparse,
+            ast=ast or self.ast,
+            calendar=calendar or self.calendar,
+            difflib=difflib or self.difflib,
+            fancycompleter=fancycompleter or self.fancycompleter,
+            http_server=http_server or self.http_server,
+            live_profiler=live_profiler or self.live_profiler,
+            pickletools=pickletools or self.pickletools,
+            profiler_dump=profiler_dump or self.profiler_dump,
             syntax=syntax or self.syntax,
+            timeit=timeit or self.timeit,
+            tokenize=tokenize or self.tokenize,
             traceback=traceback or self.traceback,
             unittest=unittest or self.unittest,
         )
@@ -249,7 +528,17 @@ def no_colors(cls) -> Self:
         """
         return cls(
             argparse=Argparse.no_colors(),
+            ast=Ast.no_colors(),
+            calendar=Calendar.no_colors(),
+            difflib=Difflib.no_colors(),
+            fancycompleter=FancyCompleter.no_colors(),
+            http_server=HttpServer.no_colors(),
+            live_profiler=LiveProfiler.no_colors(),
+            pickletools=Pickletools.no_colors(),
+            profiler_dump=ProfilerDump.no_colors(),
             syntax=Syntax.no_colors(),
+            timeit=Timeit.no_colors(),
+            tokenize=Tokenize.no_colors(),
             traceback=Traceback.no_colors(),
             unittest=Unittest.no_colors(),
         )
@@ -318,6 +607,9 @@ def _safe_getenv(k: str, fallback: str | None = None) -> str | None:
 default_theme = Theme()
 theme_no_color = default_theme.no_colors()
 
+# Convenience theme with light profiler colors (for white/light terminal backgrounds)
+light_profiler_theme = default_theme.copy_with(live_profiler=LiveProfilerLight)
+
 
 def get_theme(
     *,
diff --git a/Lib/_compat_pickle.py b/Lib/_compat_pickle.py
index 60793c391ae..64db87d4fff 100644
--- a/Lib/_compat_pickle.py
+++ b/Lib/_compat_pickle.py
@@ -183,7 +183,6 @@
     'SimpleDialog': 'tkinter.simpledialog',
     'DocXMLRPCServer': 'xmlrpc.server',
     'SimpleHTTPServer': 'http.server',
-    'CGIHTTPServer': 'http.server',
     # For compatibility with broken pickles saved in old Python 3 versions
     'UserDict': 'collections',
     'UserList': 'collections',
@@ -225,8 +224,6 @@
         ('DocXMLRPCServer', 'DocCGIXMLRPCRequestHandler'),
     ('http.server', 'SimpleHTTPRequestHandler'):
         ('SimpleHTTPServer', 'SimpleHTTPRequestHandler'),
-    ('http.server', 'CGIHTTPRequestHandler'):
-        ('CGIHTTPServer', 'CGIHTTPRequestHandler'),
     ('_socket', 'socket'): ('socket', '_socketobject'),
 })
 
@@ -251,6 +248,7 @@
     REVERSE_NAME_MAPPING[('builtins', excname)] = ('exceptions', 'OSError')
 
 PYTHON3_IMPORTERROR_EXCEPTIONS = (
+    'ImportCycleError',
     'ModuleNotFoundError',
 )
 
diff --git a/Lib/_opcode_metadata.py b/Lib/_opcode_metadata.py
index 001a016621c..5415356e502 100644
--- a/Lib/_opcode_metadata.py
+++ b/Lib/_opcode_metadata.py
@@ -1,371 +1,387 @@
 # This file is generated by tools/opcode_metadata/generate_py_opcode_metadata.py
-# for RustPython bytecode format (CPython 3.14 compatible opcode numbers).
+# for RustPython bytecode format.
 # Do not edit!
+_specializations = frozendict(
+    RESUME=(
+            "RESUME_CHECK",
+            "RESUME_CHECK_JIT",
+    ),
+    TO_BOOL=(
+            "TO_BOOL_ALWAYS_TRUE",
+            "TO_BOOL_BOOL",
+            "TO_BOOL_INT",
+            "TO_BOOL_LIST",
+            "TO_BOOL_NONE",
+            "TO_BOOL_STR",
+    ),
+    BINARY_OP=(
+            "BINARY_OP_MULTIPLY_INT",
+            "BINARY_OP_ADD_INT",
+            "BINARY_OP_SUBTRACT_INT",
+            "BINARY_OP_MULTIPLY_FLOAT",
+            "BINARY_OP_ADD_FLOAT",
+            "BINARY_OP_SUBTRACT_FLOAT",
+            "BINARY_OP_ADD_UNICODE",
+            "BINARY_OP_SUBSCR_LIST_INT",
+            "BINARY_OP_SUBSCR_LIST_SLICE",
+            "BINARY_OP_SUBSCR_TUPLE_INT",
+            "BINARY_OP_SUBSCR_STR_INT",
+            "BINARY_OP_SUBSCR_USTR_INT",
+            "BINARY_OP_SUBSCR_DICT",
+            "BINARY_OP_SUBSCR_GETITEM",
+            "BINARY_OP_INPLACE_ADD_UNICODE",
+            "BINARY_OP_EXTEND",
+    ),
+    STORE_SUBSCR=(
+            "STORE_SUBSCR_DICT",
+            "STORE_SUBSCR_LIST_INT",
+    ),
+    SEND=(
+            "SEND_GEN",
+            "SEND_VIRTUAL",
+            "SEND_ASYNC_GEN",
+    ),
+    UNPACK_SEQUENCE=(
+            "UNPACK_SEQUENCE_TWO_TUPLE",
+            "UNPACK_SEQUENCE_TUPLE",
+            "UNPACK_SEQUENCE_LIST",
+    ),
+    STORE_ATTR=(
+            "STORE_ATTR_INSTANCE_VALUE",
+            "STORE_ATTR_SLOT",
+            "STORE_ATTR_WITH_HINT",
+    ),
+    LOAD_GLOBAL=(
+            "LOAD_GLOBAL_MODULE",
+            "LOAD_GLOBAL_BUILTIN",
+    ),
+    LOAD_SUPER_ATTR=(
+            "LOAD_SUPER_ATTR_ATTR",
+            "LOAD_SUPER_ATTR_METHOD",
+    ),
+    LOAD_ATTR=(
+            "LOAD_ATTR_INSTANCE_VALUE",
+            "LOAD_ATTR_MODULE",
+            "LOAD_ATTR_WITH_HINT",
+            "LOAD_ATTR_SLOT",
+            "LOAD_ATTR_CLASS",
+            "LOAD_ATTR_CLASS_WITH_METACLASS_CHECK",
+            "LOAD_ATTR_PROPERTY",
+            "LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN",
+            "LOAD_ATTR_METHOD_WITH_VALUES",
+            "LOAD_ATTR_METHOD_NO_DICT",
+            "LOAD_ATTR_METHOD_LAZY_DICT",
+            "LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES",
+            "LOAD_ATTR_NONDESCRIPTOR_NO_DICT",
+    ),
+    COMPARE_OP=(
+            "COMPARE_OP_FLOAT",
+            "COMPARE_OP_INT",
+            "COMPARE_OP_STR",
+    ),
+    CONTAINS_OP=(
+            "CONTAINS_OP_SET",
+            "CONTAINS_OP_DICT",
+    ),
+    JUMP_BACKWARD=(
+            "JUMP_BACKWARD_NO_JIT",
+            "JUMP_BACKWARD_JIT",
+    ),
+    GET_ITER=(
+            "GET_ITER_SELF",
+            "GET_ITER_VIRTUAL",
+    ),
+    FOR_ITER=(
+            "FOR_ITER_LIST",
+            "FOR_ITER_TUPLE",
+            "FOR_ITER_RANGE",
+            "FOR_ITER_GEN",
+            "FOR_ITER_VIRTUAL",
+    ),
+    CALL=(
+            "CALL_BOUND_METHOD_EXACT_ARGS",
+            "CALL_PY_EXACT_ARGS",
+            "CALL_TYPE_1",
+            "CALL_STR_1",
+            "CALL_TUPLE_1",
+            "CALL_BUILTIN_CLASS",
+            "CALL_BUILTIN_O",
+            "CALL_BUILTIN_FAST",
+            "CALL_BUILTIN_FAST_WITH_KEYWORDS",
+            "CALL_LEN",
+            "CALL_ISINSTANCE",
+            "CALL_LIST_APPEND",
+            "CALL_METHOD_DESCRIPTOR_O",
+            "CALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS",
+            "CALL_METHOD_DESCRIPTOR_NOARGS",
+            "CALL_METHOD_DESCRIPTOR_FAST",
+            "CALL_ALLOC_AND_ENTER_INIT",
+            "CALL_PY_GENERAL",
+            "CALL_BOUND_METHOD_GENERAL",
+            "CALL_NON_PY_GENERAL",
+    ),
+    CALL_KW=(
+            "CALL_KW_BOUND_METHOD",
+            "CALL_KW_PY",
+            "CALL_KW_NON_PY",
+    ),
+    CALL_FUNCTION_EX=(
+            "CALL_EX_PY",
+            "CALL_EX_NON_PY_GENERAL",
+    ),
+)
 
-_specializations = {
-    "RESUME": [
-        "RESUME_CHECK",
-    ],
-    "LOAD_CONST": [
-        "LOAD_CONST_MORTAL",
-        "LOAD_CONST_IMMORTAL",
-    ],
-    "TO_BOOL": [
-        "TO_BOOL_ALWAYS_TRUE",
-        "TO_BOOL_BOOL",
-        "TO_BOOL_INT",
-        "TO_BOOL_LIST",
-        "TO_BOOL_NONE",
-        "TO_BOOL_STR",
-    ],
-    "BINARY_OP": [
-        "BINARY_OP_MULTIPLY_INT",
-        "BINARY_OP_ADD_INT",
-        "BINARY_OP_SUBTRACT_INT",
-        "BINARY_OP_MULTIPLY_FLOAT",
-        "BINARY_OP_ADD_FLOAT",
-        "BINARY_OP_SUBTRACT_FLOAT",
-        "BINARY_OP_ADD_UNICODE",
-        "BINARY_OP_SUBSCR_LIST_INT",
-        "BINARY_OP_SUBSCR_LIST_SLICE",
-        "BINARY_OP_SUBSCR_TUPLE_INT",
-        "BINARY_OP_SUBSCR_STR_INT",
-        "BINARY_OP_SUBSCR_DICT",
-        "BINARY_OP_SUBSCR_GETITEM",
-        "BINARY_OP_EXTEND",
-        "BINARY_OP_INPLACE_ADD_UNICODE",
-    ],
-    "STORE_SUBSCR": [
-        "STORE_SUBSCR_DICT",
-        "STORE_SUBSCR_LIST_INT",
-    ],
-    "SEND": [
-        "SEND_GEN",
-    ],
-    "UNPACK_SEQUENCE": [
-        "UNPACK_SEQUENCE_TWO_TUPLE",
-        "UNPACK_SEQUENCE_TUPLE",
-        "UNPACK_SEQUENCE_LIST",
-    ],
-    "STORE_ATTR": [
-        "STORE_ATTR_INSTANCE_VALUE",
-        "STORE_ATTR_SLOT",
-        "STORE_ATTR_WITH_HINT",
-    ],
-    "LOAD_GLOBAL": [
-        "LOAD_GLOBAL_MODULE",
-        "LOAD_GLOBAL_BUILTIN",
-    ],
-    "LOAD_SUPER_ATTR": [
-        "LOAD_SUPER_ATTR_ATTR",
-        "LOAD_SUPER_ATTR_METHOD",
-    ],
-    "LOAD_ATTR": [
-        "LOAD_ATTR_INSTANCE_VALUE",
-        "LOAD_ATTR_MODULE",
-        "LOAD_ATTR_WITH_HINT",
-        "LOAD_ATTR_SLOT",
-        "LOAD_ATTR_CLASS",
-        "LOAD_ATTR_CLASS_WITH_METACLASS_CHECK",
-        "LOAD_ATTR_PROPERTY",
-        "LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN",
-        "LOAD_ATTR_METHOD_WITH_VALUES",
-        "LOAD_ATTR_METHOD_NO_DICT",
-        "LOAD_ATTR_METHOD_LAZY_DICT",
-        "LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES",
-        "LOAD_ATTR_NONDESCRIPTOR_NO_DICT",
-    ],
-    "COMPARE_OP": [
-        "COMPARE_OP_FLOAT",
-        "COMPARE_OP_INT",
-        "COMPARE_OP_STR",
-    ],
-    "CONTAINS_OP": [
-        "CONTAINS_OP_SET",
-        "CONTAINS_OP_DICT",
-    ],
-    "JUMP_BACKWARD": [
-        "JUMP_BACKWARD_NO_JIT",
-        "JUMP_BACKWARD_JIT",
-    ],
-    "FOR_ITER": [
-        "FOR_ITER_LIST",
-        "FOR_ITER_TUPLE",
-        "FOR_ITER_RANGE",
-        "FOR_ITER_GEN",
-    ],
-    "CALL": [
-        "CALL_BOUND_METHOD_EXACT_ARGS",
-        "CALL_PY_EXACT_ARGS",
-        "CALL_TYPE_1",
-        "CALL_STR_1",
-        "CALL_TUPLE_1",
-        "CALL_BUILTIN_CLASS",
-        "CALL_BUILTIN_O",
-        "CALL_BUILTIN_FAST",
-        "CALL_BUILTIN_FAST_WITH_KEYWORDS",
-        "CALL_LEN",
-        "CALL_ISINSTANCE",
-        "CALL_LIST_APPEND",
-        "CALL_METHOD_DESCRIPTOR_O",
-        "CALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS",
-        "CALL_METHOD_DESCRIPTOR_NOARGS",
-        "CALL_METHOD_DESCRIPTOR_FAST",
-        "CALL_ALLOC_AND_ENTER_INIT",
-        "CALL_PY_GENERAL",
-        "CALL_BOUND_METHOD_GENERAL",
-        "CALL_NON_PY_GENERAL",
-    ],
-    "CALL_KW": [
-        "CALL_KW_BOUND_METHOD",
-        "CALL_KW_PY",
-        "CALL_KW_NON_PY",
-    ],
-}
+_specialized_opmap = frozendict(
+    BINARY_OP_ADD_FLOAT=129,
+    BINARY_OP_ADD_INT=130,
+    BINARY_OP_ADD_UNICODE=131,
+    BINARY_OP_EXTEND=132,
+    BINARY_OP_INPLACE_ADD_UNICODE=3,
+    BINARY_OP_MULTIPLY_FLOAT=133,
+    BINARY_OP_MULTIPLY_INT=134,
+    BINARY_OP_SUBSCR_DICT=135,
+    BINARY_OP_SUBSCR_GETITEM=136,
+    BINARY_OP_SUBSCR_LIST_INT=137,
+    BINARY_OP_SUBSCR_LIST_SLICE=138,
+    BINARY_OP_SUBSCR_STR_INT=139,
+    BINARY_OP_SUBSCR_TUPLE_INT=140,
+    BINARY_OP_SUBSCR_USTR_INT=141,
+    BINARY_OP_SUBTRACT_FLOAT=142,
+    BINARY_OP_SUBTRACT_INT=143,
+    CALL_ALLOC_AND_ENTER_INIT=144,
+    CALL_BOUND_METHOD_EXACT_ARGS=145,
+    CALL_BOUND_METHOD_GENERAL=146,
+    CALL_BUILTIN_CLASS=147,
+    CALL_BUILTIN_FAST=148,
+    CALL_BUILTIN_FAST_WITH_KEYWORDS=149,
+    CALL_BUILTIN_O=150,
+    CALL_EX_NON_PY_GENERAL=151,
+    CALL_EX_PY=152,
+    CALL_ISINSTANCE=153,
+    CALL_KW_BOUND_METHOD=154,
+    CALL_KW_NON_PY=155,
+    CALL_KW_PY=156,
+    CALL_LEN=157,
+    CALL_LIST_APPEND=158,
+    CALL_METHOD_DESCRIPTOR_FAST=159,
+    CALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS=160,
+    CALL_METHOD_DESCRIPTOR_NOARGS=161,
+    CALL_METHOD_DESCRIPTOR_O=162,
+    CALL_NON_PY_GENERAL=163,
+    CALL_PY_EXACT_ARGS=164,
+    CALL_PY_GENERAL=165,
+    CALL_STR_1=166,
+    CALL_TUPLE_1=167,
+    CALL_TYPE_1=168,
+    COMPARE_OP_FLOAT=169,
+    COMPARE_OP_INT=170,
+    COMPARE_OP_STR=171,
+    CONTAINS_OP_DICT=172,
+    CONTAINS_OP_SET=173,
+    FOR_ITER_GEN=174,
+    FOR_ITER_LIST=175,
+    FOR_ITER_RANGE=176,
+    FOR_ITER_TUPLE=177,
+    FOR_ITER_VIRTUAL=178,
+    GET_ITER_SELF=179,
+    GET_ITER_VIRTUAL=180,
+    JUMP_BACKWARD_JIT=181,
+    JUMP_BACKWARD_NO_JIT=182,
+    LOAD_ATTR_CLASS=183,
+    LOAD_ATTR_CLASS_WITH_METACLASS_CHECK=184,
+    LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN=185,
+    LOAD_ATTR_INSTANCE_VALUE=186,
+    LOAD_ATTR_METHOD_LAZY_DICT=187,
+    LOAD_ATTR_METHOD_NO_DICT=188,
+    LOAD_ATTR_METHOD_WITH_VALUES=189,
+    LOAD_ATTR_MODULE=190,
+    LOAD_ATTR_NONDESCRIPTOR_NO_DICT=191,
+    LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES=192,
+    LOAD_ATTR_PROPERTY=193,
+    LOAD_ATTR_SLOT=194,
+    LOAD_ATTR_WITH_HINT=195,
+    LOAD_GLOBAL_BUILTIN=196,
+    LOAD_GLOBAL_MODULE=197,
+    LOAD_SUPER_ATTR_ATTR=198,
+    LOAD_SUPER_ATTR_METHOD=199,
+    RESUME_CHECK=200,
+    RESUME_CHECK_JIT=201,
+    SEND_ASYNC_GEN=202,
+    SEND_GEN=203,
+    SEND_VIRTUAL=204,
+    STORE_ATTR_INSTANCE_VALUE=205,
+    STORE_ATTR_SLOT=206,
+    STORE_ATTR_WITH_HINT=207,
+    STORE_SUBSCR_DICT=208,
+    STORE_SUBSCR_LIST_INT=209,
+    TO_BOOL_ALWAYS_TRUE=210,
+    TO_BOOL_BOOL=211,
+    TO_BOOL_INT=212,
+    TO_BOOL_LIST=213,
+    TO_BOOL_NONE=214,
+    TO_BOOL_STR=215,
+    UNPACK_SEQUENCE_LIST=216,
+    UNPACK_SEQUENCE_TUPLE=217,
+    UNPACK_SEQUENCE_TWO_TUPLE=218,
+)
 
-_specialized_opmap = {
-    'BINARY_OP_ADD_FLOAT': 129,
-    'BINARY_OP_ADD_INT': 130,
-    'BINARY_OP_ADD_UNICODE': 131,
-    'BINARY_OP_EXTEND': 132,
-    'BINARY_OP_INPLACE_ADD_UNICODE': 3,
-    'BINARY_OP_MULTIPLY_FLOAT': 133,
-    'BINARY_OP_MULTIPLY_INT': 134,
-    'BINARY_OP_SUBSCR_DICT': 135,
-    'BINARY_OP_SUBSCR_GETITEM': 136,
-    'BINARY_OP_SUBSCR_LIST_INT': 137,
-    'BINARY_OP_SUBSCR_LIST_SLICE': 138,
-    'BINARY_OP_SUBSCR_STR_INT': 139,
-    'BINARY_OP_SUBSCR_TUPLE_INT': 140,
-    'BINARY_OP_SUBTRACT_FLOAT': 141,
-    'BINARY_OP_SUBTRACT_INT': 142,
-    'CALL_ALLOC_AND_ENTER_INIT': 143,
-    'CALL_BOUND_METHOD_EXACT_ARGS': 144,
-    'CALL_BOUND_METHOD_GENERAL': 145,
-    'CALL_BUILTIN_CLASS': 146,
-    'CALL_BUILTIN_FAST': 147,
-    'CALL_BUILTIN_FAST_WITH_KEYWORDS': 148,
-    'CALL_BUILTIN_O': 149,
-    'CALL_ISINSTANCE': 150,
-    'CALL_KW_BOUND_METHOD': 151,
-    'CALL_KW_NON_PY': 152,
-    'CALL_KW_PY': 153,
-    'CALL_LEN': 154,
-    'CALL_LIST_APPEND': 155,
-    'CALL_METHOD_DESCRIPTOR_FAST': 156,
-    'CALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS': 157,
-    'CALL_METHOD_DESCRIPTOR_NOARGS': 158,
-    'CALL_METHOD_DESCRIPTOR_O': 159,
-    'CALL_NON_PY_GENERAL': 160,
-    'CALL_PY_EXACT_ARGS': 161,
-    'CALL_PY_GENERAL': 162,
-    'CALL_STR_1': 163,
-    'CALL_TUPLE_1': 164,
-    'CALL_TYPE_1': 165,
-    'COMPARE_OP_FLOAT': 166,
-    'COMPARE_OP_INT': 167,
-    'COMPARE_OP_STR': 168,
-    'CONTAINS_OP_DICT': 169,
-    'CONTAINS_OP_SET': 170,
-    'FOR_ITER_GEN': 171,
-    'FOR_ITER_LIST': 172,
-    'FOR_ITER_RANGE': 173,
-    'FOR_ITER_TUPLE': 174,
-    'JUMP_BACKWARD_JIT': 175,
-    'JUMP_BACKWARD_NO_JIT': 176,
-    'LOAD_ATTR_CLASS': 177,
-    'LOAD_ATTR_CLASS_WITH_METACLASS_CHECK': 178,
-    'LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN': 179,
-    'LOAD_ATTR_INSTANCE_VALUE': 180,
-    'LOAD_ATTR_METHOD_LAZY_DICT': 181,
-    'LOAD_ATTR_METHOD_NO_DICT': 182,
-    'LOAD_ATTR_METHOD_WITH_VALUES': 183,
-    'LOAD_ATTR_MODULE': 184,
-    'LOAD_ATTR_NONDESCRIPTOR_NO_DICT': 185,
-    'LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES': 186,
-    'LOAD_ATTR_PROPERTY': 187,
-    'LOAD_ATTR_SLOT': 188,
-    'LOAD_ATTR_WITH_HINT': 189,
-    'LOAD_CONST_IMMORTAL': 190,
-    'LOAD_CONST_MORTAL': 191,
-    'LOAD_GLOBAL_BUILTIN': 192,
-    'LOAD_GLOBAL_MODULE': 193,
-    'LOAD_SUPER_ATTR_ATTR': 194,
-    'LOAD_SUPER_ATTR_METHOD': 195,
-    'RESUME_CHECK': 196,
-    'SEND_GEN': 197,
-    'STORE_ATTR_INSTANCE_VALUE': 198,
-    'STORE_ATTR_SLOT': 199,
-    'STORE_ATTR_WITH_HINT': 200,
-    'STORE_SUBSCR_DICT': 201,
-    'STORE_SUBSCR_LIST_INT': 202,
-    'TO_BOOL_ALWAYS_TRUE': 203,
-    'TO_BOOL_BOOL': 204,
-    'TO_BOOL_INT': 205,
-    'TO_BOOL_LIST': 206,
-    'TO_BOOL_NONE': 207,
-    'TO_BOOL_STR': 208,
-    'UNPACK_SEQUENCE_LIST': 209,
-    'UNPACK_SEQUENCE_TUPLE': 210,
-    'UNPACK_SEQUENCE_TWO_TUPLE': 211,
-}
+opmap = frozendict(
+    CACHE=0,
+    RESERVED=17,
+    RESUME=128,
+    INSTRUMENTED_LINE=253,
+    ENTER_EXECUTOR=254,
+    TRACE_RECORD=255,
+    BINARY_SLICE=1,
+    BUILD_TEMPLATE=2,
+    CALL_FUNCTION_EX=4,
+    CHECK_EG_MATCH=5,
+    CHECK_EXC_MATCH=6,
+    CLEANUP_THROW=7,
+    DELETE_SUBSCR=8,
+    END_FOR=9,
+    END_SEND=10,
+    EXIT_INIT_CHECK=11,
+    FORMAT_SIMPLE=12,
+    FORMAT_WITH_SPEC=13,
+    GET_AITER=14,
+    GET_ANEXT=15,
+    GET_LEN=16,
+    INTERPRETER_EXIT=18,
+    LOAD_BUILD_CLASS=19,
+    LOAD_LOCALS=20,
+    MAKE_FUNCTION=21,
+    MATCH_KEYS=22,
+    MATCH_MAPPING=23,
+    MATCH_SEQUENCE=24,
+    NOP=25,
+    NOT_TAKEN=26,
+    POP_EXCEPT=27,
+    POP_ITER=28,
+    POP_TOP=29,
+    PUSH_EXC_INFO=30,
+    PUSH_NULL=31,
+    RETURN_GENERATOR=32,
+    RETURN_VALUE=33,
+    SETUP_ANNOTATIONS=34,
+    STORE_SLICE=35,
+    STORE_SUBSCR=36,
+    TO_BOOL=37,
+    UNARY_INVERT=38,
+    UNARY_NEGATIVE=39,
+    UNARY_NOT=40,
+    WITH_EXCEPT_START=41,
+    BINARY_OP=42,
+    BUILD_INTERPOLATION=43,
+    BUILD_LIST=44,
+    BUILD_MAP=45,
+    BUILD_SET=46,
+    BUILD_SLICE=47,
+    BUILD_STRING=48,
+    BUILD_TUPLE=49,
+    CALL=50,
+    CALL_INTRINSIC_1=51,
+    CALL_INTRINSIC_2=52,
+    CALL_KW=53,
+    COMPARE_OP=54,
+    CONTAINS_OP=55,
+    CONVERT_VALUE=56,
+    COPY=57,
+    COPY_FREE_VARS=58,
+    DELETE_ATTR=59,
+    DELETE_DEREF=60,
+    DELETE_FAST=61,
+    DELETE_GLOBAL=62,
+    DELETE_NAME=63,
+    DICT_MERGE=64,
+    DICT_UPDATE=65,
+    END_ASYNC_FOR=66,
+    EXTENDED_ARG=67,
+    FOR_ITER=68,
+    GET_AWAITABLE=69,
+    GET_ITER=70,
+    IMPORT_FROM=71,
+    IMPORT_NAME=72,
+    IS_OP=73,
+    JUMP_BACKWARD=74,
+    JUMP_BACKWARD_NO_INTERRUPT=75,
+    JUMP_FORWARD=76,
+    LIST_APPEND=77,
+    LIST_EXTEND=78,
+    LOAD_ATTR=79,
+    LOAD_COMMON_CONSTANT=80,
+    LOAD_CONST=81,
+    LOAD_DEREF=82,
+    LOAD_FAST=83,
+    LOAD_FAST_AND_CLEAR=84,
+    LOAD_FAST_BORROW=85,
+    LOAD_FAST_BORROW_LOAD_FAST_BORROW=86,
+    LOAD_FAST_CHECK=87,
+    LOAD_FAST_LOAD_FAST=88,
+    LOAD_FROM_DICT_OR_DEREF=89,
+    LOAD_FROM_DICT_OR_GLOBALS=90,
+    LOAD_GLOBAL=91,
+    LOAD_NAME=92,
+    LOAD_SMALL_INT=93,
+    LOAD_SPECIAL=94,
+    LOAD_SUPER_ATTR=95,
+    MAKE_CELL=96,
+    MAP_ADD=97,
+    MATCH_CLASS=98,
+    POP_JUMP_IF_FALSE=99,
+    POP_JUMP_IF_NONE=100,
+    POP_JUMP_IF_NOT_NONE=101,
+    POP_JUMP_IF_TRUE=102,
+    RAISE_VARARGS=103,
+    RERAISE=104,
+    SEND=105,
+    SET_ADD=106,
+    SET_FUNCTION_ATTRIBUTE=107,
+    SET_UPDATE=108,
+    STORE_ATTR=109,
+    STORE_DEREF=110,
+    STORE_FAST=111,
+    STORE_FAST_LOAD_FAST=112,
+    STORE_FAST_STORE_FAST=113,
+    STORE_GLOBAL=114,
+    STORE_NAME=115,
+    SWAP=116,
+    UNPACK_EX=117,
+    UNPACK_SEQUENCE=118,
+    YIELD_VALUE=119,
+    BUILD_LIST_FROM_ARG=219,
+    INSTRUMENTED_END_FOR=233,
+    INSTRUMENTED_POP_ITER=234,
+    INSTRUMENTED_END_SEND=235,
+    INSTRUMENTED_FOR_ITER=236,
+    INSTRUMENTED_INSTRUCTION=237,
+    INSTRUMENTED_JUMP_FORWARD=238,
+    INSTRUMENTED_NOT_TAKEN=239,
+    INSTRUMENTED_POP_JUMP_IF_TRUE=240,
+    INSTRUMENTED_POP_JUMP_IF_FALSE=241,
+    INSTRUMENTED_POP_JUMP_IF_NONE=242,
+    INSTRUMENTED_POP_JUMP_IF_NOT_NONE=243,
+    INSTRUMENTED_RESUME=244,
+    INSTRUMENTED_RETURN_VALUE=245,
+    INSTRUMENTED_YIELD_VALUE=246,
+    INSTRUMENTED_END_ASYNC_FOR=247,
+    INSTRUMENTED_LOAD_SUPER_ATTR=248,
+    INSTRUMENTED_CALL=249,
+    INSTRUMENTED_CALL_KW=250,
+    INSTRUMENTED_CALL_FUNCTION_EX=251,
+    INSTRUMENTED_JUMP_BACKWARD=252,
+    ANNOTATIONS_PLACEHOLDER=256,
+    JUMP=257,
+    JUMP_IF_FALSE=258,
+    JUMP_IF_TRUE=259,
+    JUMP_NO_INTERRUPT=260,
+    LOAD_CLOSURE=261,
+    POP_BLOCK=262,
+    SETUP_CLEANUP=263,
+    SETUP_FINALLY=264,
+    SETUP_WITH=265,
+    STORE_FAST_MAYBE_NULL=266,
+)
 
-opmap = {
-    'CACHE': 0,
-    'RESERVED': 17,
-    'RESUME': 128,
-    'INSTRUMENTED_LINE': 254,
-    'ENTER_EXECUTOR': 255,
-    'BINARY_SLICE': 1,
-    'BUILD_TEMPLATE': 2,
-    'CALL_FUNCTION_EX': 4,
-    'CHECK_EG_MATCH': 5,
-    'CHECK_EXC_MATCH': 6,
-    'CLEANUP_THROW': 7,
-    'DELETE_SUBSCR': 8,
-    'END_FOR': 9,
-    'END_SEND': 10,
-    'EXIT_INIT_CHECK': 11,
-    'FORMAT_SIMPLE': 12,
-    'FORMAT_WITH_SPEC': 13,
-    'GET_AITER': 14,
-    'GET_ANEXT': 15,
-    'GET_ITER': 16,
-    'GET_LEN': 18,
-    'GET_YIELD_FROM_ITER': 19,
-    'INTERPRETER_EXIT': 20,
-    'LOAD_BUILD_CLASS': 21,
-    'LOAD_LOCALS': 22,
-    'MAKE_FUNCTION': 23,
-    'MATCH_KEYS': 24,
-    'MATCH_MAPPING': 25,
-    'MATCH_SEQUENCE': 26,
-    'NOP': 27,
-    'NOT_TAKEN': 28,
-    'POP_EXCEPT': 29,
-    'POP_ITER': 30,
-    'POP_TOP': 31,
-    'PUSH_EXC_INFO': 32,
-    'PUSH_NULL': 33,
-    'RETURN_GENERATOR': 34,
-    'RETURN_VALUE': 35,
-    'SETUP_ANNOTATIONS': 36,
-    'STORE_SLICE': 37,
-    'STORE_SUBSCR': 38,
-    'TO_BOOL': 39,
-    'UNARY_INVERT': 40,
-    'UNARY_NEGATIVE': 41,
-    'UNARY_NOT': 42,
-    'WITH_EXCEPT_START': 43,
-    'BINARY_OP': 44,
-    'BUILD_INTERPOLATION': 45,
-    'BUILD_LIST': 46,
-    'BUILD_MAP': 47,
-    'BUILD_SET': 48,
-    'BUILD_SLICE': 49,
-    'BUILD_STRING': 50,
-    'BUILD_TUPLE': 51,
-    'CALL': 52,
-    'CALL_INTRINSIC_1': 53,
-    'CALL_INTRINSIC_2': 54,
-    'CALL_KW': 55,
-    'COMPARE_OP': 56,
-    'CONTAINS_OP': 57,
-    'CONVERT_VALUE': 58,
-    'COPY': 59,
-    'COPY_FREE_VARS': 60,
-    'DELETE_ATTR': 61,
-    'DELETE_DEREF': 62,
-    'DELETE_FAST': 63,
-    'DELETE_GLOBAL': 64,
-    'DELETE_NAME': 65,
-    'DICT_MERGE': 66,
-    'DICT_UPDATE': 67,
-    'END_ASYNC_FOR': 68,
-    'EXTENDED_ARG': 69,
-    'FOR_ITER': 70,
-    'GET_AWAITABLE': 71,
-    'IMPORT_FROM': 72,
-    'IMPORT_NAME': 73,
-    'IS_OP': 74,
-    'JUMP_BACKWARD': 75,
-    'JUMP_BACKWARD_NO_INTERRUPT': 76,
-    'JUMP_FORWARD': 77,
-    'LIST_APPEND': 78,
-    'LIST_EXTEND': 79,
-    'LOAD_ATTR': 80,
-    'LOAD_COMMON_CONSTANT': 81,
-    'LOAD_CONST': 82,
-    'LOAD_DEREF': 83,
-    'LOAD_FAST': 84,
-    'LOAD_FAST_AND_CLEAR': 85,
-    'LOAD_FAST_BORROW': 86,
-    'LOAD_FAST_BORROW_LOAD_FAST_BORROW': 87,
-    'LOAD_FAST_CHECK': 88,
-    'LOAD_FAST_LOAD_FAST': 89,
-    'LOAD_FROM_DICT_OR_DEREF': 90,
-    'LOAD_FROM_DICT_OR_GLOBALS': 91,
-    'LOAD_GLOBAL': 92,
-    'LOAD_NAME': 93,
-    'LOAD_SMALL_INT': 94,
-    'LOAD_SPECIAL': 95,
-    'LOAD_SUPER_ATTR': 96,
-    'MAKE_CELL': 97,
-    'MAP_ADD': 98,
-    'MATCH_CLASS': 99,
-    'POP_JUMP_IF_FALSE': 100,
-    'POP_JUMP_IF_NONE': 101,
-    'POP_JUMP_IF_NOT_NONE': 102,
-    'POP_JUMP_IF_TRUE': 103,
-    'RAISE_VARARGS': 104,
-    'RERAISE': 105,
-    'SEND': 106,
-    'SET_ADD': 107,
-    'SET_FUNCTION_ATTRIBUTE': 108,
-    'SET_UPDATE': 109,
-    'STORE_ATTR': 110,
-    'STORE_DEREF': 111,
-    'STORE_FAST': 112,
-    'STORE_FAST_LOAD_FAST': 113,
-    'STORE_FAST_STORE_FAST': 114,
-    'STORE_GLOBAL': 115,
-    'STORE_NAME': 116,
-    'SWAP': 117,
-    'UNPACK_EX': 118,
-    'UNPACK_SEQUENCE': 119,
-    'YIELD_VALUE': 120,
-    'INSTRUMENTED_END_FOR': 234,
-    'INSTRUMENTED_POP_ITER': 235,
-    'INSTRUMENTED_END_SEND': 236,
-    'INSTRUMENTED_FOR_ITER': 237,
-    'INSTRUMENTED_INSTRUCTION': 238,
-    'INSTRUMENTED_JUMP_FORWARD': 239,
-    'INSTRUMENTED_NOT_TAKEN': 240,
-    'INSTRUMENTED_POP_JUMP_IF_TRUE': 241,
-    'INSTRUMENTED_POP_JUMP_IF_FALSE': 242,
-    'INSTRUMENTED_POP_JUMP_IF_NONE': 243,
-    'INSTRUMENTED_POP_JUMP_IF_NOT_NONE': 244,
-    'INSTRUMENTED_RESUME': 245,
-    'INSTRUMENTED_RETURN_VALUE': 246,
-    'INSTRUMENTED_YIELD_VALUE': 247,
-    'INSTRUMENTED_END_ASYNC_FOR': 248,
-    'INSTRUMENTED_LOAD_SUPER_ATTR': 249,
-    'INSTRUMENTED_CALL': 250,
-    'INSTRUMENTED_CALL_KW': 251,
-    'INSTRUMENTED_CALL_FUNCTION_EX': 252,
-    'INSTRUMENTED_JUMP_BACKWARD': 253,
-    'ANNOTATIONS_PLACEHOLDER': 256,
-    'JUMP': 257,
-    'JUMP_IF_FALSE': 258,
-    'JUMP_IF_TRUE': 259,
-    'JUMP_NO_INTERRUPT': 260,
-    'LOAD_CLOSURE': 261,
-    'POP_BLOCK': 262,
-    'SETUP_CLEANUP': 263,
-    'SETUP_FINALLY': 264,
-    'SETUP_WITH': 265,
-    'STORE_FAST_MAYBE_NULL': 266,
-}
-
-HAVE_ARGUMENT = 43
-MIN_INSTRUMENTED_OPCODE = 234
+HAVE_ARGUMENT = 41
+MIN_INSTRUMENTED_OPCODE = 233
diff --git a/Lib/_osx_support.py b/Lib/_osx_support.py
index 0cb064fcd79..29b89e311cb 100644
--- a/Lib/_osx_support.py
+++ b/Lib/_osx_support.py
@@ -17,7 +17,8 @@
 _UNIVERSAL_CONFIG_VARS = ('CFLAGS', 'LDFLAGS', 'CPPFLAGS', 'BASECFLAGS',
                             'BLDSHARED', 'LDSHARED', 'CC', 'CXX',
                             'PY_CFLAGS', 'PY_LDFLAGS', 'PY_CPPFLAGS',
-                            'PY_CORE_CFLAGS', 'PY_CORE_LDFLAGS')
+                            'PY_CORE_CFLAGS', 'PY_CORE_LDFLAGS',
+                            'PY_CORE_EXE_LDFLAGS')
 
 # configuration variables that may contain compiler calls
 _COMPILER_CONFIG_VARS = ('BLDSHARED', 'LDSHARED', 'CC', 'CXX')
diff --git a/Lib/_py_abc.py b/Lib/_py_abc.py
index c870ae9048b..2bfb9489a7a 100644
--- a/Lib/_py_abc.py
+++ b/Lib/_py_abc.py
@@ -92,7 +92,12 @@ def _abc_caches_clear(cls):
     def __instancecheck__(cls, instance):
         """Override for isinstance(instance, cls)."""
         # Inline the cache checking
-        subclass = instance.__class__
+        try:
+            subclass = instance.__class__
+        except AttributeError:
+            # Fall back to the type when the instance has no __class__,
+            # matching the behaviour of the built-in isinstance() (gh-153772).
+            subclass = type(instance)
         if subclass in cls._abc_cache:
             return True
         subtype = type(instance)
diff --git a/Lib/_py_warnings.py b/Lib/_py_warnings.py
index 55f8c069591..ab09913de68 100644
--- a/Lib/_py_warnings.py
+++ b/Lib/_py_warnings.py
@@ -369,9 +369,15 @@ def _setoption(arg):
     if message or module:
         import re
     if message:
-        message = re.escape(message)
+        if len(message) >= 2 and message[0] == message[-1] == '/':
+            message = message[1:-1]
+        else:
+            message = re.escape(message)
     if module:
-        module = re.escape(module) + r'\z'
+        if len(module) >= 2 and module[0] == module[-1] == '/':
+            module = module[1:-1]
+        else:
+            module = re.escape(module) + r'\z'
     if lineno:
         try:
             lineno = int(lineno)
@@ -381,7 +387,23 @@ def _setoption(arg):
             raise _wm._OptionError("invalid lineno %r" % (lineno,)) from None
     else:
         lineno = 0
-    _wm.filterwarnings(action, message, category, module, lineno)
+    try:
+        _wm.filterwarnings(action, message, category, module, lineno)
+    except re.PatternError if message or module else ():
+        if message:
+            try:
+                re.compile(message)
+            except re.PatternError:
+                raise _wm._OptionError(f"invalid regular expression for "
+                                       f"message: {message!r}") from None
+        if module:
+            try:
+                re.compile(module)
+            except re.PatternError:
+                raise _wm._OptionError(f"invalid regular expression for "
+                                       f"module: {module!r}") from None
+        # Should never happen.
+        raise
 
 
 # Helper for _setoption()
@@ -449,9 +471,12 @@ def warn(message, category=None, stacklevel=1, source=None,
     # Check category argument
     if category is None:
         category = UserWarning
-    if not (isinstance(category, type) and issubclass(category, Warning)):
-        raise TypeError("category must be a Warning subclass, "
-                        "not '{:s}'".format(type(category).__name__))
+    elif not isinstance(category, type):
+        raise TypeError(f"category must be a Warning subclass, not "
+                        f"'{type(category).__name__}'")
+    elif not issubclass(category, Warning):
+        raise TypeError(f"category must be a Warning subclass, not "
+                        f"class '{category.__name__}'")
     if not isinstance(skip_file_prefixes, tuple):
         # The C version demands a tuple for implementation performance.
         raise TypeError('skip_file_prefixes must be a tuple of strs.')
@@ -495,14 +520,43 @@ def warn(message, category=None, stacklevel=1, source=None,
     )
 
 
+def _match_filename(pattern, filename, *, MS_WINDOWS=(sys.platform == 'win32')):
+    if not filename:
+        return pattern.match('<unknown>') is not None
+    if filename[0] == '<' and filename[-1] == '>':
+        return pattern.match(filename) is not None
+
+    is_py = (filename[-3:].lower() == '.py'
+             if MS_WINDOWS else
+             filename.endswith('.py'))
+    if is_py:
+        filename = filename[:-3]
+    if pattern.match(filename):  # for backward compatibility
+        return True
+    if MS_WINDOWS:
+        if not is_py and filename[-4:].lower() == '.pyw':
+            filename = filename[:-4]
+            is_py = True
+        if is_py and filename[-9:].lower() in (r'\__init__', '/__init__'):
+            filename = filename[:-9]
+        filename = filename.replace('\\', '/')
+    else:
+        if is_py and filename.endswith('/__init__'):
+            filename = filename[:-9]
+    filename = filename.replace('/', '.')
+    i = 0
+    while True:
+        if pattern.match(filename, i):
+            return True
+        i = filename.find('.', i) + 1
+        if not i:
+            return False
+
+
 def warn_explicit(message, category, filename, lineno,
                   module=None, registry=None, module_globals=None,
                   source=None):
     lineno = int(lineno)
-    if module is None:
-        module = filename or "<unknown>"
-        if module[-3:].lower() == ".py":
-            module = module[:-3] # XXX What about leading pathname?
     if isinstance(message, Warning):
         text = str(message)
         category = message.__class__
@@ -524,9 +578,11 @@ def warn_explicit(message, category, filename, lineno,
             action, msg, cat, mod, ln = item
             if ((msg is None or msg.match(text)) and
                 issubclass(category, cat) and
-                (mod is None or mod.match(module)) and
-                (ln == 0 or lineno == ln)):
-                break
+                (ln == 0 or lineno == ln) and
+                (mod is None or (_match_filename(mod, filename)
+                                 if module is None else
+                                 mod.match(module)))):
+                    break
         else:
             action = _wm.defaultaction
         # Early exit actions
@@ -564,17 +620,18 @@ def warn_explicit(message, category, filename, lineno,
     linecache.getlines(filename, module_globals)
 
     # Print message and context
-    msg = _wm.WarningMessage(message, category, filename, lineno, source=source)
+    msg = _wm.WarningMessage(message, category, filename, lineno,
+                             module=module, source=source)
     _wm._showwarnmsg(msg)
 
 
 class WarningMessage(object):
 
     _WARNING_DETAILS = ("message", "category", "filename", "lineno", "file",
-                        "line", "source")
+                        "line", "source", "module")
 
     def __init__(self, message, category, filename, lineno, file=None,
-                 line=None, source=None):
+                 line=None, source=None, module=None):
         self.message = message
         self.category = category
         self.filename = filename
@@ -582,12 +639,14 @@ def __init__(self, message, category, filename, lineno, file=None,
         self.file = file
         self.line = line
         self.source = source
+        self.module = module
         self._category_name = category.__name__ if category else None
 
     def __str__(self):
-        return ("{message : %r, category : %r, filename : %r, lineno : %s, "
-                    "line : %r}" % (self.message, self._category_name,
-                                    self.filename, self.lineno, self.line))
+        return ("{message : %r, category : %r, module : %r, "
+                "filename : %r, lineno : %s, line : %r}" % (
+                    self.message, self._category_name, self.module,
+                    self.filename, self.lineno, self.line))
 
     def __repr__(self):
         return f'<{type(self).__qualname__} {self}>'
@@ -647,8 +706,8 @@ def __enter__(self):
                 context = None
                 self._filters = self._module.filters
                 self._module.filters = self._filters[:]
-                self._showwarning = self._module.showwarning
                 self._showwarnmsg_impl = self._module._showwarnmsg_impl
+            self._showwarning = self._module.showwarning
             self._module._filters_mutated_lock_held()
             if self._record:
                 if _use_context:
@@ -656,9 +715,9 @@ def __enter__(self):
                 else:
                     log = []
                     self._module._showwarnmsg_impl = log.append
-                    # Reset showwarning() to the default implementation to make sure
-                    # that _showwarnmsg() calls _showwarnmsg_impl()
-                    self._module.showwarning = self._module._showwarning_orig
+                # Reset showwarning() to the default implementation to make sure
+                # that _showwarnmsg() calls _showwarnmsg_impl()
+                self._module.showwarning = self._module._showwarning_orig
             else:
                 log = None
         if self._filter is not None:
@@ -673,8 +732,8 @@ def __exit__(self, *exc_info):
                 self._module._warnings_context.set(self._saved_context)
             else:
                 self._module.filters = self._filters
-                self._module.showwarning = self._showwarning
                 self._module._showwarnmsg_impl = self._showwarnmsg_impl
+            self._module.showwarning = self._showwarning
             self._module._filters_mutated_lock_held()
 
 
diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index 0f95a575084..c47f4e671b3 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -457,6 +457,7 @@ def _parse_isoformat_time(tstr):
     hour, minute, second, microsecond = time_comps
     became_next_day = False
     error_from_components = False
+    error_from_tz = None
     if (hour == 24):
         if all(time_comp == 0 for time_comp in time_comps[1:]):
             hour = 0
@@ -490,14 +491,22 @@ def _parse_isoformat_time(tstr):
         else:
             tzsign = -1 if tstr[tz_pos - 1] == '-' else 1
 
-            td = timedelta(hours=tz_comps[0], minutes=tz_comps[1],
-                           seconds=tz_comps[2], microseconds=tz_comps[3])
-
-            tzi = timezone(tzsign * td)
+            try:
+                # This function is intended to validate datetimes, but because
+                # we restrict time zones to ±24h, it serves here as well.
+                _check_time_fields(hour=tz_comps[0], minute=tz_comps[1],
+                                   second=tz_comps[2], microsecond=tz_comps[3],
+                                   fold=0)
+            except ValueError as e:
+                error_from_tz = e
+            else:
+                td = timedelta(hours=tz_comps[0], minutes=tz_comps[1],
+                               seconds=tz_comps[2], microseconds=tz_comps[3])
+                tzi = timezone(tzsign * td)
 
     time_comps.append(tzi)
 
-    return time_comps, became_next_day, error_from_components
+    return time_comps, became_next_day, error_from_components, error_from_tz
 
 # tuple[int, int, int] -> tuple[int, int, int] version of date.fromisocalendar
 def _isoweek_to_gregorian(year, week, day):
@@ -1064,7 +1073,11 @@ def fromisocalendar(cls, year, week, day):
 
     @classmethod
     def strptime(cls, date_string, format):
-        """Parse a date string according to the given format (like time.strptime())."""
+        """Parse string according to the given date format (like time.strptime()).
+
+        For a list of supported format codes, see the documentation:
+            https://docs.python.org/3/library/datetime.html#format-codes
+        """
         import _strptime
         return _strptime._strptime_datetime_date(cls, date_string, format)
 
@@ -1101,6 +1114,8 @@ def strftime(self, format):
         Format using strftime().
 
         Example: "%d/%m/%Y, %H:%M:%S"
+        For a list of supported format codes, see the documentation:
+            https://docs.python.org/3/library/datetime.html#format-codes
         """
         return _wrap_strftime(self, format, self.timetuple())
 
@@ -1291,7 +1306,7 @@ def __reduce__(self):
 
 
 class tzinfo:
-    """Abstract base class for time zone info classes.
+    """Abstract base class for time zone info objects.
 
     Subclasses must override the tzname(), utcoffset() and dst() methods.
     """
@@ -1448,8 +1463,13 @@ def __new__(cls, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold
         return self
 
     @classmethod
+
     def strptime(cls, date_string, format):
-        """string, format -> new time parsed from a string (like time.strptime())."""
+        """Parse string according to the given time format (like time.strptime()).
+
+        For a list of supported format codes, see the documentation:
+            https://docs.python.org/3/library/datetime.html#format-codes
+        """
         import _strptime
         return _strptime._strptime_datetime_time(cls, date_string, format)
 
@@ -1623,13 +1643,28 @@ def fromisoformat(cls, time_string):
         time_string = time_string.removeprefix('T')
 
         try:
-            return cls(*_parse_isoformat_time(time_string)[0])
-        except Exception:
-            raise ValueError(f'Invalid isoformat string: {time_string!r}')
+            time_components, _, error_from_components, error_from_tz = (
+                _parse_isoformat_time(time_string)
+            )
+        except ValueError:
+            raise ValueError(
+                f'Invalid isoformat string: {time_string!r}') from None
+        else:
+            if error_from_tz:
+                raise error_from_tz
+            if error_from_components:
+                raise ValueError(
+                    "Minute, second, and microsecond must be 0 when hour is 24"
+                )
+
+            return cls(*time_components)
 
     def strftime(self, format):
         """Format using strftime().  The date part of the timestamp passed
         to underlying strftime should not be used.
+
+        For a list of supported format codes, see the documentation:
+            https://docs.python.org/3/library/datetime.html#format-codes
         """
         # The year must be >= 1000 else Python's strftime implementation
         # can raise a bogus exception.
@@ -1745,7 +1780,7 @@ def __reduce__(self):
 
 
 class datetime(date):
-    """datetime(year, month, day[, hour[, minute[, second[, microsecond[,tzinfo]]]]])
+    """A combination of a date and a time.
 
     The year, month and day arguments are required. tzinfo may be None, or an
     instance of a tzinfo subclass. The remaining arguments may be ints.
@@ -1937,11 +1972,16 @@ def fromisoformat(cls, date_string):
 
         if tstr:
             try:
-                time_components, became_next_day, error_from_components = _parse_isoformat_time(tstr)
+                (time_components,
+                 became_next_day,
+                 error_from_components,
+                 error_from_tz) = _parse_isoformat_time(tstr)
             except ValueError:
                 raise ValueError(
                     f'Invalid isoformat string: {date_string!r}') from None
             else:
+                if error_from_tz:
+                    raise error_from_tz
                 if error_from_components:
                     raise ValueError("minute, second, and microsecond must be 0 when hour is 24")
 
@@ -2079,7 +2119,6 @@ def _local_timezone(self):
         else:
             ts = (self - _EPOCH) // timedelta(seconds=1)
         localtm = _time.localtime(ts)
-        local = datetime(*localtm[:6])
         # Extract TZ data
         gmtoff = localtm.tm_gmtoff
         zone = localtm.tm_zone
@@ -2174,7 +2213,11 @@ def __str__(self):
 
     @classmethod
     def strptime(cls, date_string, format):
-        'string, format -> new datetime parsed from a string (like time.strptime()).'
+        """Parse string according to the given time format (like time.strptime()).
+
+        For a list of supported format codes, see the documentation:
+            https://docs.python.org/3/library/datetime.html#format-codes
+        """
         import _strptime
         return _strptime._strptime_datetime_datetime(cls, date_string, format)
 
@@ -2400,6 +2443,8 @@ def _isoweek1monday(year):
 
 
 class timezone(tzinfo):
+    """Fixed offset from UTC implementation of tzinfo."""
+
     __slots__ = '_offset', '_name'
 
     # Sentinel value to disallow None
diff --git a/Lib/_pydecimal.py b/Lib/_pydecimal.py
index 2277578df54..8c0afd14d61 100644
--- a/Lib/_pydecimal.py
+++ b/Lib/_pydecimal.py
@@ -47,13 +47,16 @@
     'HAVE_THREADS',
 
     # C version: compile time choice that enables the coroutine local context
-    'HAVE_CONTEXTVAR'
+    'HAVE_CONTEXTVAR',
+
+    # Highest version of the spec this module complies with
+    'SPEC_VERSION',
 ]
 
 __xname__ = __name__    # sys.modules lookup (--without-threads)
 __name__ = 'decimal'    # For pickling
-__version__ = '1.70'    # Highest version of the spec this complies with
-                        # See http://speleotrove.com/decimal/
+SPEC_VERSION = '1.70'   # Highest version of the spec this complies with
+                        # See https://speleotrove.com/decimal/decarith.html
 __libmpdec_version__ = "2.4.2" # compatible libmpdec version
 
 import math as _math
@@ -6404,3 +6407,11 @@ def _format_number(is_negative, intpart, fracpart, exp, spec):
 # _PyHASH_10INV is the inverse of 10 modulo the prime _PyHASH_MODULUS
 _PyHASH_10INV = pow(10, _PyHASH_MODULUS - 2, _PyHASH_MODULUS)
 del sys
+
+def __getattr__(name):
+    if name == "__version__":
+        from warnings import _deprecated
+
+        _deprecated("__version__", remove=(3, 20))
+        return SPEC_VERSION
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index cc336d29394..342a50724d4 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -550,7 +550,7 @@ def nreadahead():
             res += b
             if res.endswith(b"\n"):
                 break
-        return bytes(res)
+        return res.take_bytes()
 
     def __iter__(self):
         self._checkClosed()
@@ -624,7 +624,7 @@ def read(self, size=-1):
         if n < 0 or n > len(b):
             raise ValueError(f"readinto returned {n} outside buffer size {len(b)}")
         del b[n:]
-        return bytes(b)
+        return b.take_bytes()
 
     def readall(self):
         """Read until EOF, using multiple read() call."""
@@ -632,7 +632,7 @@ def readall(self):
         while data := self.read(DEFAULT_BUFFER_SIZE):
             res += data
         if res:
-            return bytes(res)
+            return res.take_bytes()
         else:
             # b'' or None
             return data
@@ -882,16 +882,28 @@ class BytesIO(BufferedIOBase):
     _buffer = None
 
     def __init__(self, initial_bytes=None):
+        # Use to keep self._buffer and self._pos consistent.
+        self._lock = Lock()
+
         buf = bytearray()
         if initial_bytes is not None:
             buf += initial_bytes
-        self._buffer = buf
-        self._pos = 0
+
+        with self._lock:
+            self._buffer = buf
+            self._pos = 0
 
     def __getstate__(self):
         if self.closed:
             raise ValueError("__getstate__ on closed file")
-        return self.__dict__.copy()
+        with self._lock:
+            state = self.__dict__.copy()
+        del state['_lock']
+        return state
+
+    def __setstate__(self, state):
+        self.__dict__.update(state)
+        self._lock = Lock()
 
     def getvalue(self):
         """Return the bytes value (contents) of the buffer
@@ -924,14 +936,16 @@ def read(self, size=-1):
                 raise TypeError(f"{size!r} is not an integer")
             else:
                 size = size_index()
-        if size < 0:
-            size = len(self._buffer)
-        if len(self._buffer) <= self._pos:
-            return b""
-        newpos = min(len(self._buffer), self._pos + size)
-        b = self._buffer[self._pos : newpos]
-        self._pos = newpos
-        return bytes(b)
+
+        with self._lock:
+            if size < 0:
+                size = len(self._buffer)
+            if len(self._buffer) <= self._pos:
+                return b""
+            newpos = min(len(self._buffer), self._pos + size)
+            b = self._buffer[self._pos : newpos]
+            self._pos = newpos
+            return bytes(b)
 
     def read1(self, size=-1):
         """This is the same as read.
@@ -949,13 +963,14 @@ def write(self, b):
             if n == 0:
                 return 0
 
-            pos = self._pos
-            if pos > len(self._buffer):
-                # Pad buffer to pos with null bytes.
-                self._buffer.resize(pos)
-            self._buffer[pos:pos + n] = view
-            self._pos += n
-        return n
+            with self._lock:
+                pos = self._pos
+                if pos > len(self._buffer):
+                    # Pad buffer to pos with null bytes.
+                    self._buffer.resize(pos)
+                self._buffer[pos:pos + n] = view
+                self._pos += n
+            return n
 
     def seek(self, pos, whence=0):
         if self.closed:
@@ -971,9 +986,11 @@ def seek(self, pos, whence=0):
                 raise ValueError("negative seek position %r" % (pos,))
             self._pos = pos
         elif whence == 1:
-            self._pos = max(0, self._pos + pos)
+            with self._lock:
+                self._pos = max(0, self._pos + pos)
         elif whence == 2:
-            self._pos = max(0, len(self._buffer) + pos)
+            with self._lock:
+                self._pos = max(0, len(self._buffer) + pos)
         else:
             raise ValueError("unsupported whence value")
         return self._pos
@@ -986,18 +1003,20 @@ def tell(self):
     def truncate(self, pos=None):
         if self.closed:
             raise ValueError("truncate on closed file")
-        if pos is None:
-            pos = self._pos
-        else:
-            try:
-                pos_index = pos.__index__
-            except AttributeError:
-                raise TypeError(f"{pos!r} is not an integer")
+
+        with self._lock:
+            if pos is None:
+                pos = self._pos
             else:
-                pos = pos_index()
-            if pos < 0:
-                raise ValueError("negative truncate position %r" % (pos,))
-        del self._buffer[pos:]
+                try:
+                    pos_index = pos.__index__
+                except AttributeError:
+                    raise TypeError(f"{pos!r} is not an integer")
+                else:
+                    pos = pos_index()
+                if pos < 0:
+                    raise ValueError("negative truncate position %r" % (pos,))
+            del self._buffer[pos:]
         return pos
 
     def readable(self):
@@ -1486,6 +1505,7 @@ class FileIO(RawIOBase):
     _writable = False
     _appending = False
     _seekable = None
+    _truncate = False
     _closefd = True
 
     def __init__(self, file, mode='r', closefd=True, opener=None):
@@ -1546,6 +1566,7 @@ def __init__(self, file, mode='r', closefd=True, opener=None):
             flags = 0
         elif 'w' in mode:
             self._writable = True
+            self._truncate = True
             flags = os.O_CREAT | os.O_TRUNC
         elif 'a' in mode:
             self._writable = True
@@ -1727,7 +1748,7 @@ def readall(self):
         assert len(result) - bytes_read >= 1, \
             "os.readinto buffer size 0 will result in erroneous EOF / returns 0"
         result.resize(bytes_read)
-        return bytes(result)
+        return result.take_bytes()
 
     def readinto(self, buffer):
         """Same as RawIOBase.readinto()."""
@@ -1871,7 +1892,10 @@ def mode(self):
                 return 'ab'
         elif self._readable:
             if self._writable:
-                return 'rb+'
+                if self._truncate:
+                    return 'wb+'
+                else:
+                    return 'rb+'
             else:
                 return 'rb'
         else:
diff --git a/Lib/_sitebuiltins.py b/Lib/_sitebuiltins.py
index c66269a5719..84551e3546e 100644
--- a/Lib/_sitebuiltins.py
+++ b/Lib/_sitebuiltins.py
@@ -36,7 +36,7 @@ def __init__(self, name, data, files=(), dirs=()):
         import os
         self.__name = name
         self.__data = data
-        self.__lines = None
+        self.__lines = []
         self.__filenames = [os.path.join(dir, filename)
                             for dir in dirs
                             for filename in files]
@@ -65,24 +65,22 @@ def __repr__(self):
             return "Type %s() to see the full %s text" % ((self.__name,)*2)
 
     def __call__(self):
-        self.__setup()
-        prompt = 'Hit Return for more, or q (and Return) to quit: '
-        lineno = 0
-        while 1:
+        try:
+            from _pyrepl.pager import get_pager
+        except ModuleNotFoundError:
             try:
-                for i in range(lineno, lineno + self.MAXLINES):
-                    print(self.__lines[i])
-            except IndexError:
-                break
-            else:
-                lineno += self.MAXLINES
-                key = None
-                while key is None:
-                    key = input(prompt)
-                    if key not in ('', 'q'):
-                        key = None
-                if key == 'q':
-                    break
+                from pydoc import get_pager
+            except ModuleNotFoundError:
+                def get_pager():
+                    def _print(text, title=None):
+                        print(text)
+                    return _print
+
+        self.__setup()
+
+        pager = get_pager()
+        text = "\n".join(self.__lines)
+        pager(text, title=self.__name)
 
 
 class _Helper(object):
diff --git a/Lib/_strptime.py b/Lib/_strptime.py
index fc7e369c3d1..746b0907c1d 100644
--- a/Lib/_strptime.py
+++ b/Lib/_strptime.py
@@ -7,7 +7,7 @@
 
 FUNCTIONS:
     _getlang -- Figure out what language is being used for the locale
-    strptime -- Calculates the time struct represented by the passed-in string
+    _strptime -- Calculates the time struct represented by the passed-in string
 
 """
 import os
@@ -371,7 +371,9 @@ def __init__(self, locale_time=None):
             # W is set below by using 'U'
             'y': r"(?P<y>\d\d)",
             'Y': r"(?P<Y>\d\d\d\d)",
-            'z': r"(?P<z>[+-]\d\d:?[0-5]\d(:?[0-5]\d(\.\d{1,6})?)?|(?-i:Z))",
+            # See gh-121237: "z" must support colons for backwards compatibility.
+            'z': r"(?P<z>([+-]\d\d:?[0-5]\d(:?[0-5]\d(\.\d{1,6})?)?)|(?-i:Z))?",
+            ':z': r"(?P<colon_z>([+-]\d\d:[0-5]\d(:[0-5]\d(\.\d{1,6})?)?)|(?-i:Z))?",
             'A': self.__seqToRE(self.locale_time.f_weekday, 'A'),
             'a': self.__seqToRE(self.locale_time.a_weekday, 'a'),
             'B': self.__seqToRE(_fixmonths(self.locale_time.f_month[1:]), 'B'),
@@ -380,7 +382,10 @@ def __init__(self, locale_time=None):
             'Z': self.__seqToRE((tz for tz_names in self.locale_time.timezone
                                         for tz in tz_names),
                                 'Z'),
-            '%': '%'}
+            'n': r'\s*',
+            't': r'\s*',
+            '%': '%',
+        }
         if self.locale_time.LC_alt_digits is None:
             for d in 'dmyCHIMS':
                 mapping['O' + d] = r'(?P<%s>\d\d|\d| \d)' % d
@@ -416,6 +421,8 @@ def __init__(self, locale_time=None):
         mapping['W'] = mapping['U'].replace('U', 'W')
 
         base.__init__(mapping)
+        base.__setitem__('D', self.pattern('%m/%d/%y'))
+        base.__setitem__('F', self.pattern('%Y-%m-%d'))
         base.__setitem__('T', self.pattern('%H:%M:%S'))
         base.__setitem__('R', self.pattern('%H:%M'))
         base.__setitem__('r', self.pattern(self.locale_time.LC_time_ampm))
@@ -457,28 +464,39 @@ def pattern(self, format):
         format = re_sub(r'\s+', r'\\s+', format)
         format = re_sub(r"'", "['\u02bc]", format)  # needed for br_FR
         year_in_format = False
-        day_of_month_in_format = False
+        day_d_in_format = False
+        day_e_in_format = False
         def repl(m):
-            format_char = m[1]
-            match format_char:
+            directive = m.group()[1:] # exclude `%` symbol
+            match directive:
                 case 'Y' | 'y' | 'G':
                     nonlocal year_in_format
                     year_in_format = True
                 case 'd':
-                    nonlocal day_of_month_in_format
-                    day_of_month_in_format = True
-            return self[format_char]
-        format = re_sub(r'%[-_0^#]*[0-9]*([OE]?\\?.?)', repl, format)
-        if day_of_month_in_format and not year_in_format:
-            import warnings
-            warnings.warn("""\
+                    nonlocal day_d_in_format
+                    day_d_in_format = True
+                case 'e':
+                    nonlocal day_e_in_format
+                    day_e_in_format = True
+            return self[directive]
+        format = re_sub(r'%[-_0^#]*[0-9]*([OE]?[:\\]?.?)', repl, format)
+        if not year_in_format:
+            if day_d_in_format:
+                raise ValueError(
+                    "Day of month directive '%d' may not be used without "
+                    "a year directive. Parsing dates involving a day of "
+                    "month without a year is ambiguous and fails to parse "
+                    "leap day. Add a year to the input and format. "
+                    "See https://github.com/python/cpython/issues/70647.")
+            if day_e_in_format:
+                import warnings
+                warnings.warn("""\
 Parsing dates involving a day of month without a year specified is ambiguous
-and fails to parse leap day. The default behavior will change in Python 3.15
-to either always raise an exception or to use a different default year (TBD).
-To avoid trouble, add a specific year to the input & format.
+and fails to parse leap day. '%e' without a year will become an error in Python 3.17.
+To avoid trouble, add a specific year to the input and format.
 See https://github.com/python/cpython/issues/70647.""",
-                          DeprecationWarning,
-                          skip_file_prefixes=(os.path.dirname(__file__),))
+                              DeprecationWarning,
+                              skip_file_prefixes=(os.path.dirname(__file__),))
         return format
 
     def compile(self, format):
@@ -514,9 +532,10 @@ def _calc_julian_from_U_or_W(year, week_of_year, day_of_week, week_starts_Mon):
 
 
 def _strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
-    """Return a 2-tuple consisting of a time struct and an int containing
-    the number of microseconds based on the input string and the
-    format string."""
+    """Return a 3-tuple consisting of a tuple with time components,
+    an int containing the number of microseconds, and an int
+    containing the microseconds part of the GMT offset, based on the
+    input string and the format string."""
 
     for index, arg in enumerate([data_string, format]):
         if not isinstance(arg, str):
@@ -555,8 +574,17 @@ def _strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
         raise ValueError("time data %r does not match format %r" %
                          (data_string, format))
     if len(data_string) != found.end():
-        raise ValueError("unconverted data remains: %s" %
-                          data_string[found.end():])
+        rest = data_string[found.end():]
+        # Specific check for '%:z' directive
+        if (
+            "colon_z" in found.re.groupindex
+            and found.group("colon_z") is not None
+            and rest[0] != ":"
+        ):
+            raise ValueError(
+                f"Missing colon in %:z before '{rest}', got '{data_string}'"
+            )
+        raise ValueError("unconverted data remains: %s" % rest)
 
     iso_year = year = None
     month = day = 1
@@ -616,18 +644,18 @@ def parse_int(s):
             hour = parse_int(found_dict['I'])
             ampm = found_dict.get('p', '').lower()
             # If there was no AM/PM indicator, we'll treat this like AM
-            if ampm in ('', locale_time.am_pm[0]):
-                # We're in AM so the hour is correct unless we're
-                # looking at 12 midnight.
-                # 12 midnight == 12 AM == hour 0
-                if hour == 12:
-                    hour = 0
-            elif ampm == locale_time.am_pm[1]:
+            if ampm == locale_time.am_pm[1]:
                 # We're in PM so we need to add 12 to the hour unless
                 # we're looking at 12 noon.
                 # 12 noon == 12 PM == hour 12
                 if hour != 12:
                     hour += 12
+            else:
+                # We're in AM so the hour is correct unless we're
+                # looking at 12 midnight.
+                # 12 midnight == 12 AM == hour 0
+                if hour == 12:
+                    hour = 0
         elif group_key == 'M':
             minute = parse_int(found_dict['M'])
         elif group_key == 'S':
@@ -662,29 +690,30 @@ def parse_int(s):
                 week_of_year_start = 0
         elif group_key == 'V':
             iso_week = int(found_dict['V'])
-        elif group_key == 'z':
-            z = found_dict['z']
-            if z == 'Z':
-                gmtoff = 0
-            else:
-                if z[3] == ':':
-                    z = z[:3] + z[4:]
-                    if len(z) > 5:
-                        if z[5] != ':':
-                            msg = f"Inconsistent use of : in {found_dict['z']}"
-                            raise ValueError(msg)
-                        z = z[:5] + z[6:]
-                hours = int(z[1:3])
-                minutes = int(z[3:5])
-                seconds = int(z[5:7] or 0)
-                gmtoff = (hours * 60 * 60) + (minutes * 60) + seconds
-                gmtoff_remainder = z[8:]
-                # Pad to always return microseconds.
-                gmtoff_remainder_padding = "0" * (6 - len(gmtoff_remainder))
-                gmtoff_fraction = int(gmtoff_remainder + gmtoff_remainder_padding)
-                if z.startswith("-"):
-                    gmtoff = -gmtoff
-                    gmtoff_fraction = -gmtoff_fraction
+        elif group_key in ('z', 'colon_z'):
+            z = found_dict[group_key]
+            if z:
+                if z == 'Z':
+                    gmtoff = 0
+                else:
+                    if z[3] == ':':
+                        z = z[:3] + z[4:]
+                        if len(z) > 5:
+                            if z[5] != ':':
+                                msg = f"Inconsistent use of : in {found_dict[group_key]}"
+                                raise ValueError(msg)
+                            z = z[:5] + z[6:]
+                    hours = int(z[1:3])
+                    minutes = int(z[3:5])
+                    seconds = int(z[5:7] or 0)
+                    gmtoff = (hours * 60 * 60) + (minutes * 60) + seconds
+                    gmtoff_remainder = z[8:]
+                    # Pad to always return microseconds.
+                    gmtoff_remainder_padding = "0" * (6 - len(gmtoff_remainder))
+                    gmtoff_fraction = int(gmtoff_remainder + gmtoff_remainder_padding)
+                    if z.startswith("-"):
+                        gmtoff = -gmtoff
+                        gmtoff_fraction = -gmtoff_fraction
         elif group_key == 'Z':
             # Since -1 is default value only need to worry about setting tz if
             # it can be something other than -1.
diff --git a/Lib/_threading_local.py b/Lib/_threading_local.py
index 0b9e5d3bbf6..2af3885458b 100644
--- a/Lib/_threading_local.py
+++ b/Lib/_threading_local.py
@@ -57,7 +57,7 @@ def thread_deleted(_, idt=idt):
             # as soon as the OS-level thread ends instead.
             local = wrlocal()
             if local is not None:
-                dct = local.dicts.pop(idt)
+                local.dicts.pop(idt)
         wrlocal = ref(self, local_deleted)
         wrthread = ref(thread, thread_deleted)
         thread.__dict__[key] = wrlocal
diff --git a/Lib/annotationlib.py b/Lib/annotationlib.py
index 5c9a0812646..9ae1e3a06e9 100644
--- a/Lib/annotationlib.py
+++ b/Lib/annotationlib.py
@@ -191,12 +191,27 @@ def evaluate(
 
         arg = self.__forward_arg__
         if arg.isidentifier() and not keyword.iskeyword(arg):
+            resolved = _sentinel
             if arg in locals:
-                return locals[arg]
+                resolved = locals[arg]
             elif arg in globals:
-                return globals[arg]
+                resolved = globals[arg]
             elif hasattr(builtins, arg):
-                return getattr(builtins, arg)
+                resolved = getattr(builtins, arg)
+
+            if resolved is not _sentinel:
+                if isinstance(resolved, types.LazyImportType):
+                    # We try reifying the lazy object. If this fails, we propagate
+                    # the error in the VALUE format and leave the
+                    # ForwardRef unresolved in the FORWARDREF format.
+                    try:
+                        return resolved.resolve()
+                    except Exception:
+                        if not is_forwardref_format:
+                            raise
+                        return self
+                else:
+                    return resolved
             elif is_forwardref_format:
                 return self
             else:
diff --git a/Lib/ast.py b/Lib/ast.py
index 2f11683ecf7..4f88a554344 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -24,7 +24,7 @@
 
 
 def parse(source, filename='<unknown>', mode='exec', *,
-          type_comments=False, feature_version=None, optimize=-1):
+          type_comments=False, feature_version=None, optimize=-1, module=None):
     """
     Parse the source into an AST node.
     Equivalent to compile(source, filename, mode, PyCF_ONLY_AST).
@@ -44,7 +44,8 @@ def parse(source, filename='<unknown>', mode='exec', *,
         feature_version = minor
     # Else it should be an int giving the minor version for 3.x.
     return compile(source, filename, mode, flags,
-                   _feature_version=feature_version, optimize=optimize)
+                   _feature_version=feature_version, optimize=optimize,
+                   module=module)
 
 
 def literal_eval(node_or_string):
@@ -57,73 +58,93 @@ def literal_eval(node_or_string):
     Caution: A complex expression can overflow the C stack and cause a crash.
     """
     if isinstance(node_or_string, str):
-        node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval')
-    if isinstance(node_or_string, Expression):
+        node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval').body
+    elif isinstance(node_or_string, Expression):
         node_or_string = node_or_string.body
-    def _raise_malformed_node(node):
-        msg = "malformed node or string"
-        if lno := getattr(node, 'lineno', None):
-            msg += f' on line {lno}'
-        raise ValueError(msg + f': {node!r}')
-    def _convert_num(node):
-        if not isinstance(node, Constant) or type(node.value) not in (int, float, complex):
-            _raise_malformed_node(node)
+    return _convert_literal(node_or_string)
+
+
+def _convert_literal(node):
+    """
+    Used by `literal_eval` to convert an AST node into a value.
+    """
+    if isinstance(node, Constant):
         return node.value
-    def _convert_signed_num(node):
-        if isinstance(node, UnaryOp) and isinstance(node.op, (UAdd, USub)):
-            operand = _convert_num(node.operand)
-            if isinstance(node.op, UAdd):
-                return + operand
-            else:
-                return - operand
-        return _convert_num(node)
-    def _convert(node):
-        if isinstance(node, Constant):
-            return node.value
-        elif isinstance(node, Tuple):
-            return tuple(map(_convert, node.elts))
-        elif isinstance(node, List):
-            return list(map(_convert, node.elts))
-        elif isinstance(node, Set):
-            return set(map(_convert, node.elts))
-        elif (isinstance(node, Call) and isinstance(node.func, Name) and
-              node.func.id == 'set' and node.args == node.keywords == []):
-            return set()
-        elif isinstance(node, Dict):
-            if len(node.keys) != len(node.values):
-                _raise_malformed_node(node)
-            return dict(zip(map(_convert, node.keys),
-                            map(_convert, node.values)))
-        elif isinstance(node, BinOp) and isinstance(node.op, (Add, Sub)):
-            left = _convert_signed_num(node.left)
-            right = _convert_num(node.right)
-            if isinstance(left, (int, float)) and isinstance(right, complex):
-                if isinstance(node.op, Add):
-                    return left + right
-                else:
-                    return left - right
-        return _convert_signed_num(node)
-    return _convert(node_or_string)
+    if isinstance(node, Dict) and len(node.keys) == len(node.values):
+        return dict(zip(
+            map(_convert_literal, node.keys),
+            map(_convert_literal, node.values),
+        ))
+    if isinstance(node, Tuple):
+        return tuple(map(_convert_literal, node.elts))
+    if isinstance(node, List):
+        return list(map(_convert_literal, node.elts))
+    if isinstance(node, Set):
+        return set(map(_convert_literal, node.elts))
+    if (
+        isinstance(node, Call) and isinstance(node.func, Name)
+        and node.func.id == 'set' and node.args == node.keywords == []
+    ):
+        return set()
+    if (
+        isinstance(node, UnaryOp)
+        and isinstance(node.op, (UAdd, USub))
+        and isinstance(node.operand, Constant)
+        and type(operand := node.operand.value) in (int, float, complex)
+    ):
+        if isinstance(node.op, UAdd):
+            return + operand
+        else:
+            return - operand
+    if (
+        isinstance(node, BinOp)
+        and isinstance(node.op, (Add, Sub))
+        and isinstance(node.left, (Constant, UnaryOp))
+        and isinstance(node.right, Constant)
+        and type(left := _convert_literal(node.left)) in (int, float)
+        and type(right := _convert_literal(node.right)) is complex
+    ):
+        if isinstance(node.op, Add):
+            return left + right
+        else:
+            return left - right
+    msg = "malformed node or string"
+    if lno := getattr(node, 'lineno', None):
+        msg += f' on line {lno}'
+    raise ValueError(msg + f': {node!r}')
 
 
 def dump(
     node, annotate_fields=True, include_attributes=False,
     *,
-    indent=None, show_empty=False,
+    color=False, indent=None, show_empty=False,
 ):
     """
     Return a formatted dump of the tree in node.  This is mainly useful for
-    debugging purposes.  If annotate_fields is true (by default),
-    the returned string will show the names and the values for fields.
-    If annotate_fields is false, the result string will be more compact by
-    omitting unambiguous field names.  Attributes such as line
-    numbers and column offsets are not dumped by default.  If this is wanted,
-    include_attributes can be set to true.  If indent is a non-negative
-    integer or string, then the tree will be pretty-printed with that indent
-    level. None (the default) selects the single line representation.
+    debugging purposes.
+
+    If annotate_fields is true (by default), the returned string will show the
+    names and the values for fields. If annotate_fields is false, the result
+    string will be more compact by omitting unambiguous field names.
+
+    Attributes such as line numbers and column offsets are not dumped by default.
+    If this is wanted, include_attributes can be set to true.
+
+    If color is true, the returned string is syntax highlighted using ANSI
+    escape sequences. If color is false (the default), colored output is always
+    disabled.
+
+    If indent is a non-negative integer or string, then the tree will be
+    pretty-printed with that indent level. If indent is None (the default),
+    the tree is dumped on a single line.
+
     If show_empty is False, then empty lists and fields that are None
     will be omitted from the output for better readability.
     """
+    from _colorize import get_theme
+
+    t = get_theme(force_color=color, force_no_color=not color).ast
+
     def _format(node, level=0):
         if indent is not None:
             level += 1
@@ -154,13 +175,21 @@ def _format(node, level=0):
                             if not keywords:
                                 args_buffer.append(repr(value))
                             continue
+                    elif isinstance(value, Load):
+                        field_type = cls._field_types.get(name, object)
+                        if field_type is expr_context:
+                            if not keywords:
+                                args_buffer.append(
+                                    f'{t.node}{type(value).__name__}'
+                                    f'{t.reset}()')
+                            continue
                     if not keywords:
                         args.extend(args_buffer)
                         args_buffer = []
                 value, simple = _format(value, level)
                 allsimple = allsimple and simple
                 if keywords:
-                    args.append('%s=%s' % (name, value))
+                    args.append(f'{t.field}{name}{t.reset}={value}')
                 else:
                     args.append(value)
             if include_attributes and node._attributes:
@@ -173,14 +202,21 @@ def _format(node, level=0):
                         continue
                     value, simple = _format(value, level)
                     allsimple = allsimple and simple
-                    args.append('%s=%s' % (name, value))
+                    args.append(f'{t.attribute}{name}{t.reset}={value}')
+            cls_name = f'{t.node}{cls.__name__}{t.reset}'
             if allsimple and len(args) <= 3:
-                return '%s(%s)' % (node.__class__.__name__, ', '.join(args)), not args
-            return '%s(%s%s)' % (node.__class__.__name__, prefix, sep.join(args)), False
+                return f'{cls_name}({", ".join(args)})', not args
+            return f'{cls_name}({prefix}{sep.join(args)})', False
         elif isinstance(node, list):
             if not node:
                 return '[]', True
             return '[%s%s]' % (prefix, sep.join(_format(x, level)[0] for x in node)), False
+        if isinstance(node, bool) or node is None or node is Ellipsis:
+            return f'{t.keyword}{node!r}{t.reset}', True
+        if isinstance(node, (int, float, complex)):
+            return f'{t.number}{node!r}{t.reset}', True
+        if isinstance(node, (str, bytes)):
+            return f'{t.string}{node!r}{t.reset}', True
         return repr(node), True
 
     if not isinstance(node, AST):
@@ -628,9 +664,9 @@ def main(args=None):
     import argparse
     import sys
 
-    parser = argparse.ArgumentParser(color=True)
+    parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter)
     parser.add_argument('infile', nargs='?', default='-',
-                        help='the file to parse; defaults to stdin')
+                        help='the file to parse; defaults to `stdin`')
     parser.add_argument('-m', '--mode', default='exec',
                         choices=('exec', 'single', 'eval', 'func_type'),
                         help='specify what kind of code must be parsed')
@@ -643,11 +679,11 @@ def main(args=None):
                         help='indentation of nodes (number of spaces)')
     parser.add_argument('--feature-version',
                         type=str, default=None, metavar='VERSION',
-                        help='Python version in the format 3.x '
-                             '(for example, 3.10)')
+                        help='Python version in the format `3.x` '
+                             '(for example, `3.10`)')
     parser.add_argument('-O', '--optimize',
                         type=int, default=-1, metavar='LEVEL',
-                        help='optimization level for parser (default -1)')
+                        help='optimization level for parser')
     parser.add_argument('--show-empty', default=False, action='store_true',
                         help='show empty lists and fields in dump output')
     args = parser.parse_args(args)
@@ -673,7 +709,9 @@ def main(args=None):
 
     tree = parse(source, name, args.mode, type_comments=args.no_type_comments,
                  feature_version=feature_version, optimize=args.optimize)
+    from _colorize import can_colorize
     print(dump(tree, include_attributes=args.include_attributes,
+               color=can_colorize(file=sys.stdout),
                indent=args.indent, show_empty=args.show_empty))
 
 if __name__ == '__main__':
diff --git a/Lib/asyncio/futures.py b/Lib/asyncio/futures.py
index e8a99556b18..11858a0274a 100644
--- a/Lib/asyncio/futures.py
+++ b/Lib/asyncio/futures.py
@@ -79,6 +79,10 @@ def __init__(self, *, loop=None):
         loop object used by the future. If it's not provided, the future uses
         the default event loop.
         """
+        if self._loop is not None:
+            raise RuntimeError(f"{self.__class__.__name__} object is already "
+                                "initialized")
+
         if loop is None:
             self._loop = events.get_event_loop()
         else:
@@ -351,22 +355,19 @@ def _set_concurrent_future_state(concurrent, source):
 def _copy_future_state(source, dest):
     """Internal helper to copy state from another Future.
 
-    The other Future may be a concurrent.futures.Future.
+    The other Future must be a concurrent.futures.Future.
     """
-    assert source.done()
     if dest.cancelled():
         return
     assert not dest.done()
-    if source.cancelled():
+    done, cancelled, result, exception = source._get_snapshot()
+    assert done
+    if cancelled:
         dest.cancel()
+    elif exception is not None:
+        dest.set_exception(_convert_future_exc(exception))
     else:
-        exception = source.exception()
-        if exception is not None:
-            dest.set_exception(_convert_future_exc(exception))
-        else:
-            result = source.result()
-            dest.set_result(result)
-
+        dest.set_result(result)
 
 def _chain_future(source, destination):
     """Chain two futures so that when one completes, so does the other.
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index 14d3c1ceb58..bdc577319c2 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -103,11 +103,20 @@ def __init__(self, coro, *, loop=None, name=None, context=None,
         self._coro = coro
         if context is None:
             self._context = contextvars.copy_context()
+        elif not isinstance(context, contextvars.Context):
+            # gh-157301: the passed value must be a contextvars.Context
+            self._log_destroy_pending = False
+            raise TypeError('a contextvars.Context was expected, '
+                            f'got {type(context).__name__}')
         else:
             self._context = context
 
         if eager_start and self._loop.is_running():
-            self.__eager_start()
+            try:
+                self.__eager_start()
+            except:
+                self._log_destroy_pending = False
+                raise
         else:
             self._loop.call_soon(self.__step, context=self._context)
             _py_register_task(self)
@@ -440,15 +449,13 @@ def _release_waiter(waiter, *args):
 async def wait_for(fut, timeout):
     """Wait for the single Future or coroutine to complete, with timeout.
 
-    Coroutine will be wrapped in Task.
-
     Returns result of the Future or coroutine.  When a timeout occurs,
-    it cancels the task and raises TimeoutError.  To avoid the task
-    cancellation, wrap it in shield().
+    it cancels fut and raises TimeoutError.  To prevent fut from being
+    cancelled, wrap it in shield().
 
-    If the wait is cancelled, the task is also cancelled.
+    If the wait is cancelled, fut is also cancelled.
 
-    If the task suppresses the cancellation and returns a value instead,
+    If fut suppresses the cancellation and returns a value instead,
     that value is returned.
 
     This function is a coroutine.
@@ -524,6 +531,7 @@ def _on_completion(f):
             timeout_handle.cancel()
         for f in fs:
             f.remove_done_callback(_on_completion)
+            futures.future_discard_from_awaited_by(f, cur_task)
 
     done, pending = set(), set()
     for f in fs:
@@ -542,6 +550,10 @@ async def _cancel_and_wait(fut):
     cb = functools.partial(_release_waiter, waiter)
     fut.add_done_callback(cb)
 
+    # gh-157058: awaiting the waiter leaves no edge on fut, add it here
+    cur_task = current_task()
+    futures.future_add_to_awaited_by(fut, cur_task)
+
     try:
         fut.cancel()
         # We cannot wait on *fut* directly to make
@@ -549,6 +561,7 @@ async def _cancel_and_wait(fut):
         await waiter
     finally:
         fut.remove_done_callback(cb)
+        futures.future_discard_from_awaited_by(fut, cur_task)
 
 
 class _AsCompletedIterator:
@@ -563,9 +576,11 @@ def __init__(self, aws, timeout):
         self._timeout_handle = None
 
         loop = events.get_event_loop()
+        self._cur_task = current_task()
         todo = {ensure_future(aw, loop=loop) for aw in set(aws)}
         for f in todo:
             f.add_done_callback(self._handle_completion)
+            futures.future_add_to_awaited_by(f, self._cur_task)
         if todo and timeout is not None:
             self._timeout_handle = (
                 loop.call_later(timeout, self._handle_timeout)
@@ -596,6 +611,7 @@ def __next__(self):
     def _handle_timeout(self):
         for f in self._todo:
             f.remove_done_callback(self._handle_completion)
+            futures.future_discard_from_awaited_by(f, self._cur_task)
             self._done.put_nowait(None)  # Sentinel for _wait_for_one().
         self._todo.clear()  # Can't do todo.remove(f) in the loop.
 
@@ -603,6 +619,7 @@ def _handle_completion(self, f):
         if not self._todo:
             return  # _handle_timeout() was here first.
         self._todo.remove(f)
+        futures.future_discard_from_awaited_by(f, self._cur_task)
         self._done.put_nowait(f)
         if not self._todo and self._timeout_handle is not None:
             self._timeout_handle.cancel()
@@ -767,6 +784,11 @@ def cancel(self, msg=None):
         return ret
 
 
+def _discard_awaited_by(children, waiter, outer):
+    for fut in children:
+        futures.future_discard_from_awaited_by(fut, waiter)
+
+
 def gather(*coros_or_futures, return_exceptions=False):
     """Return a future aggregating results from the given coroutines/futures.
 
@@ -900,6 +922,10 @@ def _done_callback(fut, cur_task=cur_task):
         children.append(fut)
 
     outer = _GatheringFuture(children, loop=loop)
+    if cur_task is not None:
+        # gh-157213: a child outliving gather() must lose the awaited-by edge
+        outer.add_done_callback(
+            functools.partial(_discard_awaited_by, children, cur_task))
     # Run done callbacks after GatheringFuture created so any post-processing
     # can be performed at this point
     # optimization: in the special case that *all* futures finished eagerly,
@@ -996,6 +1022,9 @@ def _outer_done_callback(outer):
             # Keep only one callback to log on cancel
             inner.remove_done_callback(_log_on_exception)
             inner.add_done_callback(_log_on_exception)
+            if cur_task is not None:
+                inner.remove_done_callback(_clear_awaited_by_callback)
+                futures.future_discard_from_awaited_by(inner, cur_task)
 
     if cur_task is not None:
         inner.add_done_callback(_clear_awaited_by_callback)
diff --git a/Lib/base64.py b/Lib/base64.py
index 0f84420d7a2..fa562f74a81 100644
--- a/Lib/base64.py
+++ b/Lib/base64.py
@@ -4,7 +4,6 @@
 # Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support
 # Modified 22-May-2007 by Guido van Rossum to use bytes everywhere
 
-import struct
 import binascii
 
 
@@ -26,6 +25,8 @@
     ]
 
 
+_NOT_SPECIFIED = ['NOT SPECIFIED']
+
 bytes_types = (bytes, bytearray)  # Types acceptable as binary data
 
 def _bytes_from_decode_data(s):
@@ -45,44 +46,90 @@ def _bytes_from_decode_data(s):
 
 # Base64 encoding/decoding uses binascii
 
-def b64encode(s, altchars=None):
+def b64encode(s, altchars=None, *, padded=True, wrapcol=0):
     """Encode the bytes-like object s using Base64 and return a bytes object.
 
     Optional altchars should be a byte string of length 2 which specifies an
     alternative alphabet for the '+' and '/' characters.  This allows an
     application to e.g. generate url or filesystem safe Base64 strings.
+
+    If padded is false, omit padding in the output.
+
+    If wrapcol is non-zero, insert a newline (b'\\n') character after at most
+    every wrapcol characters.
     """
-    encoded = binascii.b2a_base64(s, newline=False)
     if altchars is not None:
-        assert len(altchars) == 2, repr(altchars)
-        return encoded.translate(bytes.maketrans(b'+/', altchars))
-    return encoded
+        if len(altchars) != 2:
+            raise ValueError(f'invalid altchars: {altchars!r}')
+        alphabet = binascii.BASE64_ALPHABET[:-2] + altchars
+        return binascii.b2a_base64(s, padded=padded, wrapcol=wrapcol, newline=False,
+                                   alphabet=alphabet)
+    return binascii.b2a_base64(s, padded=padded, wrapcol=wrapcol, newline=False)
 
 
-def b64decode(s, altchars=None, validate=False):
+def b64decode(s, altchars=None, validate=_NOT_SPECIFIED,
+              *, padded=True, ignorechars=_NOT_SPECIFIED, canonical=False):
     """Decode the Base64 encoded bytes-like object or ASCII string s.
 
     Optional altchars must be a bytes-like object or ASCII string of length 2
     which specifies the alternative alphabet used instead of the '+' and '/'
     characters.
 
+    If padded is false, padding in input is not required.
+
     The result is returned as a bytes object.  A binascii.Error is raised if
     s is incorrectly padded.
 
-    If validate is False (the default), characters that are neither in the
-    normal base-64 alphabet nor the alternative alphabet are discarded prior
-    to the padding check.  If validate is True, these non-alphabet characters
-    in the input result in a binascii.Error.
+    If ignorechars is specified, it should be a byte string containing
+    characters to ignore from the input.  The default value of validate is
+    True if ignorechars is specified, False otherwise.
+
+    If validate is false, characters that are neither in the normal base-64
+    alphabet nor the alternative alphabet are discarded prior to the
+    padding check.  If validate is true, these non-alphabet characters in
+    the input result in a binascii.Error if they are not in ignorechars.
     For more information about the strict base64 check, see:
 
     https://docs.python.org/3.11/library/binascii.html#binascii.a2b_base64
     """
     s = _bytes_from_decode_data(s)
+    if validate is _NOT_SPECIFIED:
+        validate = ignorechars is not _NOT_SPECIFIED
+    badchar = None
     if altchars is not None:
         altchars = _bytes_from_decode_data(altchars)
-        assert len(altchars) == 2, repr(altchars)
-        s = s.translate(bytes.maketrans(altchars, b'+/'))
-    return binascii.a2b_base64(s, strict_mode=validate)
+        if len(altchars) != 2:
+            raise ValueError(f'invalid altchars: {altchars!r}')
+        if ignorechars is _NOT_SPECIFIED:
+            for b in b'+/':
+                if b not in altchars and b in s:
+                    badchar = b
+                    break
+            s = s.translate(bytes.maketrans(altchars, b'+/'))
+        else:
+            alphabet = binascii.BASE64_ALPHABET[:-2] + altchars
+            return binascii.a2b_base64(s, strict_mode=validate,
+                                       alphabet=alphabet,
+                                       padded=padded, ignorechars=ignorechars,
+                                       canonical=canonical)
+    if ignorechars is _NOT_SPECIFIED:
+        ignorechars = b''
+    result = binascii.a2b_base64(s, strict_mode=validate,
+                                 padded=padded, ignorechars=ignorechars,
+                                 canonical=canonical)
+    if badchar is not None:
+        import warnings
+        if validate:
+            warnings.warn(f'invalid character {chr(badchar)!a} in Base64 data '
+                          f'with altchars={altchars!r} and validate=True '
+                          f'will be an error in future Python versions',
+                          DeprecationWarning, stacklevel=2)
+        else:
+            warnings.warn(f'invalid character {chr(badchar)!a} in Base64 data '
+                          f'with altchars={altchars!r} and validate=False '
+                          f'will be discarded in future Python versions',
+                          FutureWarning, stacklevel=2)
+    return result
 
 
 def standard_b64encode(s):
@@ -103,19 +150,21 @@ def standard_b64decode(s):
     return b64decode(s)
 
 
-_urlsafe_encode_translation = bytes.maketrans(b'+/', b'-_')
 _urlsafe_decode_translation = bytes.maketrans(b'-_', b'+/')
 
-def urlsafe_b64encode(s):
+def urlsafe_b64encode(s, *, padded=True):
     """Encode bytes using the URL- and filesystem-safe Base64 alphabet.
 
     Argument s is a bytes-like object to encode.  The result is returned as a
     bytes object.  The alphabet uses '-' instead of '+' and '_' instead of
     '/'.
+
+    If padded is false, omit padding in the output.
     """
-    return b64encode(s).translate(_urlsafe_encode_translation)
+    return binascii.b2a_base64(s, padded=padded, newline=False,
+                               alphabet=binascii.URLSAFE_BASE64_ALPHABET)
 
-def urlsafe_b64decode(s):
+def urlsafe_b64decode(s, *, padded=False):
     """Decode bytes using the URL- and filesystem-safe Base64 alphabet.
 
     Argument s is a bytes-like object or ASCII string to decode.  The result
@@ -124,23 +173,46 @@ def urlsafe_b64decode(s):
     alphabet, and are not a plus '+' or slash '/', are discarded prior to the
     padding check.
 
+    If padded is false, padding in input is not required.
+
     The alphabet uses '-' instead of '+' and '_' instead of '/'.
     """
     s = _bytes_from_decode_data(s)
+    badchar = None
+    for b in b'+/':
+        if b in s:
+            badchar = b
+            break
     s = s.translate(_urlsafe_decode_translation)
-    return b64decode(s)
+    result = binascii.a2b_base64(s, strict_mode=False, padded=padded)
+    if badchar is not None:
+        import warnings
+        warnings.warn(f'invalid character {chr(badchar)!a} in URL-safe Base64 data '
+                      f'will be discarded in future Python versions',
+                      FutureWarning, stacklevel=2)
+    return result
 
 
 
 # Base32 encoding/decoding must be done in Python
 _B32_ENCODE_DOCSTRING = '''
 Encode the bytes-like objects using {encoding} and return a bytes object.
+
+If padded is false, omit padding in the output.
+
+If wrapcol is non-zero, insert a newline (b'\\n') character after at most
+every wrapcol characters.
 '''
 _B32_DECODE_DOCSTRING = '''
 Decode the {encoding} encoded bytes-like object or ASCII string s.
 
 Optional casefold is a flag specifying whether a lowercase alphabet is
 acceptable as input.  For security purposes, the default is False.
+
+If padded is false, padding in input is not required.
+
+ignorechars should be a byte string containing characters to ignore
+from the input.
 {extra_args}
 The result is returned as a bytes object.  A binascii.Error is raised if
 the input is incorrectly padded or if there are non-alphabet
@@ -155,108 +227,41 @@ def urlsafe_b64decode(s):
 the letter O).  For security purposes the default is None, so that
 0 and 1 are not allowed in the input.
 '''
-_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
-_b32hexalphabet = b'0123456789ABCDEFGHIJKLMNOPQRSTUV'
-_b32tab2 = {}
-_b32rev = {}
-
-def _b32encode(alphabet, s):
-    # Delay the initialization of the table to not waste memory
-    # if the function is never called
-    if alphabet not in _b32tab2:
-        b32tab = [bytes((i,)) for i in alphabet]
-        _b32tab2[alphabet] = [a + b for a in b32tab for b in b32tab]
-        b32tab = None
-
-    if not isinstance(s, bytes_types):
-        s = memoryview(s).tobytes()
-    leftover = len(s) % 5
-    # Pad the last quantum with zero bits if necessary
-    if leftover:
-        s = s + b'\0' * (5 - leftover)  # Don't use += !
-    encoded = bytearray()
-    from_bytes = int.from_bytes
-    b32tab2 = _b32tab2[alphabet]
-    for i in range(0, len(s), 5):
-        c = from_bytes(s[i: i + 5])              # big endian
-        encoded += (b32tab2[c >> 30] +           # bits 1 - 10
-                    b32tab2[(c >> 20) & 0x3ff] + # bits 11 - 20
-                    b32tab2[(c >> 10) & 0x3ff] + # bits 21 - 30
-                    b32tab2[c & 0x3ff]           # bits 31 - 40
-                   )
-    # Adjust for any leftover partial quanta
-    if leftover == 1:
-        encoded[-6:] = b'======'
-    elif leftover == 2:
-        encoded[-4:] = b'===='
-    elif leftover == 3:
-        encoded[-3:] = b'==='
-    elif leftover == 4:
-        encoded[-1:] = b'='
-    return bytes(encoded)
-
-def _b32decode(alphabet, s, casefold=False, map01=None):
-    # Delay the initialization of the table to not waste memory
-    # if the function is never called
-    if alphabet not in _b32rev:
-        _b32rev[alphabet] = {v: k for k, v in enumerate(alphabet)}
+
+def b32encode(s, *, padded=True, wrapcol=0):
+    return binascii.b2a_base32(s, padded=padded, wrapcol=wrapcol)
+b32encode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32')
+
+def b32decode(s, casefold=False, map01=None, *, padded=True, ignorechars=b'',
+              canonical=False):
     s = _bytes_from_decode_data(s)
-    if len(s) % 8:
-        raise binascii.Error('Incorrect padding')
     # Handle section 2.4 zero and one mapping.  The flag map01 will be either
     # False, or the character to map the digit 1 (one) to.  It should be
     # either L (el) or I (eye).
     if map01 is not None:
         map01 = _bytes_from_decode_data(map01)
-        assert len(map01) == 1, repr(map01)
         s = s.translate(bytes.maketrans(b'01', b'O' + map01))
     if casefold:
         s = s.upper()
-    # Strip off pad characters from the right.  We need to count the pad
-    # characters because this will tell us how many null bytes to remove from
-    # the end of the decoded string.
-    l = len(s)
-    s = s.rstrip(b'=')
-    padchars = l - len(s)
-    # Now decode the full quanta
-    decoded = bytearray()
-    b32rev = _b32rev[alphabet]
-    for i in range(0, len(s), 8):
-        quanta = s[i: i + 8]
-        acc = 0
-        try:
-            for c in quanta:
-                acc = (acc << 5) + b32rev[c]
-        except KeyError:
-            raise binascii.Error('Non-base32 digit found') from None
-        decoded += acc.to_bytes(5)  # big endian
-    # Process the last, partial quanta
-    if l % 8 or padchars not in {0, 1, 3, 4, 6}:
-        raise binascii.Error('Incorrect padding')
-    if padchars and decoded:
-        acc <<= 5 * padchars
-        last = acc.to_bytes(5)  # big endian
-        leftover = (43 - 5 * padchars) // 8  # 1: 4, 3: 3, 4: 2, 6: 1
-        decoded[-5:] = last[:leftover]
-    return bytes(decoded)
-
-
-def b32encode(s):
-    return _b32encode(_b32alphabet, s)
-b32encode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32')
-
-def b32decode(s, casefold=False, map01=None):
-    return _b32decode(_b32alphabet, s, casefold, map01)
+    return binascii.a2b_base32(s, padded=padded, ignorechars=ignorechars,
+                               canonical=canonical)
 b32decode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32',
                                         extra_args=_B32_DECODE_MAP01_DOCSTRING)
 
-def b32hexencode(s):
-    return _b32encode(_b32hexalphabet, s)
+def b32hexencode(s, *, padded=True, wrapcol=0):
+    return binascii.b2a_base32(s, padded=padded, wrapcol=wrapcol,
+                               alphabet=binascii.BASE32HEX_ALPHABET)
 b32hexencode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32hex')
 
-def b32hexdecode(s, casefold=False):
+def b32hexdecode(s, casefold=False, *, padded=True, ignorechars=b'',
+                 canonical=False):
+    s = _bytes_from_decode_data(s)
     # base32hex does not have the 01 mapping
-    return _b32decode(_b32hexalphabet, s, casefold)
+    if casefold:
+        s = s.upper()
+    return binascii.a2b_base32(s, alphabet=binascii.BASE32HEX_ALPHABET,
+                               padded=padded, ignorechars=ignorechars,
+                               canonical=canonical)
 b32hexdecode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32hex',
                                                     extra_args='')
 
@@ -264,62 +269,47 @@ def b32hexdecode(s, casefold=False):
 # RFC 4648, Base 16 Alphabet specifies uppercase, but hexlify() returns
 # lowercase.  The RFC also recommends against accepting input case
 # insensitively.
-def b16encode(s):
+def b16encode(s, *, wrapcol=0):
     """Encode the bytes-like object s using Base16 and return a bytes object.
+
+    If wrapcol is non-zero, insert a newline (b'\\n') character after at most
+    every wrapcol characters.
     """
-    return binascii.hexlify(s).upper()
+    if not wrapcol:
+        return binascii.hexlify(s).upper()
+    if wrapcol < 0:
+        raise ValueError('Negative wrapcol')
+    if wrapcol < 2:
+        wrapcol = 2
+    return binascii.hexlify(s, bytes_per_sep=-(wrapcol//2), sep=b'\n').upper()
 
 
-def b16decode(s, casefold=False):
+def b16decode(s, casefold=False, *, ignorechars=b''):
     """Decode the Base16 encoded bytes-like object or ASCII string s.
 
     Optional casefold is a flag specifying whether a lowercase alphabet is
     acceptable as input.  For security purposes, the default is False.
 
+    ignorechars should be a byte string containing characters to ignore
+    from the input.
+
     The result is returned as a bytes object.  A binascii.Error is raised if
     s is incorrectly padded or if there are non-alphabet characters present
     in the input.
     """
-    s = _bytes_from_decode_data(s)
-    if casefold:
-        s = s.upper()
-    if s.translate(None, delete=b'0123456789ABCDEF'):
-        raise binascii.Error('Non-base16 digit found')
-    return binascii.unhexlify(s)
+    if not casefold:
+        s = _bytes_from_decode_data(s)
+        if not isinstance(ignorechars, bytes):
+            ignorechars = bytes(memoryview(ignorechars))
+        for b in b'abcdef':
+            if b in s and b not in ignorechars:
+                raise binascii.Error('Non-base16 digit found')
+        s = s.translate(None, delete=b'abcdef')
+    return binascii.unhexlify(s, ignorechars=ignorechars)
 
 #
 # Ascii85 encoding/decoding
 #
-
-_a85chars = None
-_a85chars2 = None
-_A85START = b"<~"
-_A85END = b"~>"
-
-def _85encode(b, chars, chars2, pad=False, foldnuls=False, foldspaces=False):
-    # Helper function for a85encode and b85encode
-    if not isinstance(b, bytes_types):
-        b = memoryview(b).tobytes()
-
-    padding = (-len(b)) % 4
-    if padding:
-        b = b + b'\0' * padding
-    words = struct.Struct('!%dI' % (len(b) // 4)).unpack(b)
-
-    chunks = [b'z' if foldnuls and not word else
-              b'y' if foldspaces and word == 0x20202020 else
-              (chars2[word // 614125] +
-               chars2[word // 85 % 7225] +
-               chars[word % 85])
-              for word in words]
-
-    if padding and not pad:
-        if chunks[-1] == b'z':
-            chunks[-1] = chars[0] * 5
-        chunks[-1] = chunks[-1][:-padding]
-
-    return b''.join(chunks)
-
 def a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False):
     """Encode bytes-like object b using Ascii85 and return a bytes object.
 
@@ -340,31 +330,11 @@ def a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False):
     with ~>, they must not use a leading <~.
 
     """
-    global _a85chars, _a85chars2
-    # Delay the initialization of tables to not waste memory
-    # if the function is never called
-    if _a85chars2 is None:
-        _a85chars = [bytes((i,)) for i in range(33, 118)]
-        _a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]
-
-    result = _85encode(b, _a85chars, _a85chars2, pad, True, foldspaces)
-
-    if adobe:
-        result = _A85START + result
-    if wrapcol:
-        wrapcol = max(2 if adobe else 1, wrapcol)
-        chunks = [result[i: i + wrapcol]
-                  for i in range(0, len(result), wrapcol)]
-        if adobe:
-            if len(chunks[-1]) + 2 > wrapcol:
-                chunks.append(b'')
-        result = b'\n'.join(chunks)
-    if adobe:
-        result += _A85END
+    return binascii.b2a_ascii85(b, foldspaces=foldspaces,
+                                adobe=adobe, wrapcol=wrapcol, pad=pad)
 
-    return result
-
-def a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v'):
+def a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v',
+              canonical=False):
     """Decode the Ascii85 encoded bytes-like object or ASCII string b.
 
     foldspaces is a flag that specifies whether the 'y' short sequence
@@ -380,156 +350,60 @@ def a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v'):
     input. This should only contain whitespace characters, and by default
     contains all whitespace characters in ASCII.
 
+    If canonical is true, non-canonical encodings are rejected.
+
     The result is returned as a bytes object.
     """
-    b = _bytes_from_decode_data(b)
-    if adobe:
-        if not b.endswith(_A85END):
-            raise ValueError(
-                "Ascii85 encoded byte sequences must end "
-                "with {!r}".format(_A85END)
-                )
-        if b.startswith(_A85START):
-            b = b[2:-2]  # Strip off start/end markers
-        else:
-            b = b[:-2]
-    #
-    # We have to go through this stepwise, so as to ignore spaces and handle
-    # special short sequences
-    #
-    packI = struct.Struct('!I').pack
-    decoded = []
-    decoded_append = decoded.append
-    curr = []
-    curr_append = curr.append
-    curr_clear = curr.clear
-    for x in b + b'u' * 4:
-        if b'!'[0] <= x <= b'u'[0]:
-            curr_append(x)
-            if len(curr) == 5:
-                acc = 0
-                for x in curr:
-                    acc = 85 * acc + (x - 33)
-                try:
-                    decoded_append(packI(acc))
-                except struct.error:
-                    raise ValueError('Ascii85 overflow') from None
-                curr_clear()
-        elif x == b'z'[0]:
-            if curr:
-                raise ValueError('z inside Ascii85 5-tuple')
-            decoded_append(b'\0\0\0\0')
-        elif foldspaces and x == b'y'[0]:
-            if curr:
-                raise ValueError('y inside Ascii85 5-tuple')
-            decoded_append(b'\x20\x20\x20\x20')
-        elif x in ignorechars:
-            # Skip whitespace
-            continue
-        else:
-            raise ValueError('Non-Ascii85 digit found: %c' % x)
-
-    result = b''.join(decoded)
-    padding = 4 - len(curr)
-    if padding:
-        # Throw away the extra padding
-        result = result[:-padding]
-    return result
+    return binascii.a2b_ascii85(b, foldspaces=foldspaces,
+                                adobe=adobe, ignorechars=ignorechars,
+                                canonical=canonical)
 
-# The following code is originally taken (with permission) from Mercurial
-
-_b85alphabet = (b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-                b"abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~")
-_b85chars = None
-_b85chars2 = None
-_b85dec = None
-
-def b85encode(b, pad=False):
+def b85encode(b, pad=False, *, wrapcol=0):
     """Encode bytes-like object b in base85 format and return a bytes object.
 
+    If wrapcol is non-zero, insert a newline (b'\\n') character after at most
+    every wrapcol characters.
+
     The input is padded with b'\0' so its length is a multiple of 4
     bytes before encoding.  If pad is true, all the resulting
     characters are retained in the output, which will always be a
     multiple of 5 bytes.
     """
-    global _b85chars, _b85chars2
-    # Delay the initialization of tables to not waste memory
-    # if the function is never called
-    if _b85chars2 is None:
-        _b85chars = [bytes((i,)) for i in _b85alphabet]
-        _b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]
-    return _85encode(b, _b85chars, _b85chars2, pad)
-
-def b85decode(b):
+    return binascii.b2a_base85(b, wrapcol=wrapcol, pad=pad)
+
+def b85decode(b, *, ignorechars=b'', canonical=False):
     """Decode the base85-encoded bytes-like object or ASCII string b
 
+    If canonical is true, non-canonical encodings are rejected.
+
     The result is returned as a bytes object.
     """
-    global _b85dec
-    # Delay the initialization of tables to not waste memory
-    # if the function is never called
-    if _b85dec is None:
-        # we don't assign to _b85dec directly to avoid issues when
-        # multiple threads call this function simultaneously
-        b85dec_tmp = [None] * 256
-        for i, c in enumerate(_b85alphabet):
-            b85dec_tmp[c] = i
-        _b85dec = b85dec_tmp
-
-    b = _bytes_from_decode_data(b)
-    padding = (-len(b)) % 5
-    b = b + b'~' * padding
-    out = []
-    packI = struct.Struct('!I').pack
-    for i in range(0, len(b), 5):
-        chunk = b[i:i + 5]
-        acc = 0
-        try:
-            for c in chunk:
-                acc = acc * 85 + _b85dec[c]
-        except TypeError:
-            for j, c in enumerate(chunk):
-                if _b85dec[c] is None:
-                    raise ValueError('bad base85 character at position %d'
-                                    % (i + j)) from None
-            raise
-        try:
-            out.append(packI(acc))
-        except struct.error:
-            raise ValueError('base85 overflow in hunk starting at byte %d'
-                             % i) from None
-
-    result = b''.join(out)
-    if padding:
-        result = result[:-padding]
-    return result
+    return binascii.a2b_base85(b, ignorechars=ignorechars,
+                               canonical=canonical)
+
+def z85encode(s, pad=False, *, wrapcol=0):
+    """Encode bytes-like object b in z85 format and return a bytes object.
+
+    If wrapcol is non-zero, insert a newline (b'\\n') character after at most
+    every wrapcol characters.
+
+    The input is padded with b'\0' so its length is a multiple of
+    bytes before encoding.  If pad is true, all the resulting
+    characters are retained in the output, which will always be a
+    multiple of 5 bytes, as required by the ZeroMQ standard.
+    """
+    return binascii.b2a_base85(s, wrapcol=wrapcol, pad=pad,
+                               alphabet=binascii.Z85_ALPHABET)
 
-_z85alphabet = (b'0123456789abcdefghijklmnopqrstuvwxyz'
-                b'ABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#')
-# Translating b85 valid but z85 invalid chars to b'\x00' is required
-# to prevent them from being decoded as b85 valid chars.
-_z85_b85_decode_diff = b';_`|~'
-_z85_decode_translation = bytes.maketrans(
-    _z85alphabet + _z85_b85_decode_diff,
-    _b85alphabet + b'\x00' * len(_z85_b85_decode_diff)
-)
-_z85_encode_translation = bytes.maketrans(_b85alphabet, _z85alphabet)
-
-def z85encode(s):
-    """Encode bytes-like object b in z85 format and return a bytes object."""
-    return b85encode(s).translate(_z85_encode_translation)
-
-def z85decode(s):
+def z85decode(s, *, ignorechars=b'', canonical=False):
     """Decode the z85-encoded bytes-like object or ASCII string b
 
+    If canonical is true, non-canonical encodings are rejected.
+
     The result is returned as a bytes object.
     """
-    s = _bytes_from_decode_data(s)
-    s = s.translate(_z85_decode_translation)
-    try:
-        return b85decode(s)
-    except ValueError as e:
-        raise ValueError(e.args[0].replace('base85', 'z85')) from None
+    return binascii.a2b_base85(s, alphabet=binascii.Z85_ALPHABET,
+                               ignorechars=ignorechars, canonical=canonical)
 
 # Legacy interface.  This code could be cleaned up since I don't believe
 # binascii has any line length limitations.  It just doesn't seem worth it
@@ -573,11 +447,10 @@ def encodebytes(s):
     """Encode a bytestring into a bytes object containing multiple lines
     of base-64 data."""
     _input_type_check(s)
-    pieces = []
-    for i in range(0, len(s), MAXBINSIZE):
-        chunk = s[i : i + MAXBINSIZE]
-        pieces.append(binascii.b2a_base64(chunk))
-    return b"".join(pieces)
+    result = binascii.b2a_base64(s, wrapcol=MAXLINESIZE)
+    if result == b'\n':
+        return b''
+    return result
 
 
 def decodebytes(s):
diff --git a/Lib/compileall.py b/Lib/compileall.py
index 67fe370451e..812a496611e 100644
--- a/Lib/compileall.py
+++ b/Lib/compileall.py
@@ -165,6 +165,14 @@ def compile_file(fullname, ddir=None, force=False, rx=None, quiet=0,
     stripdir = os.fspath(stripdir) if stripdir is not None else None
     name = os.path.basename(fullname)
 
+    # Without a cache_tag, we can only create legacy .pyc files. None of our
+    # callers seem to expect this, so the best we can do is fail without raising
+    if not legacy and sys.implementation.cache_tag is None:
+        if not quiet:
+            print("No cache tag is available to generate .pyc path for",
+                  repr(fullname))
+        return False
+
     dfile = None
 
     if ddir is not None:
@@ -223,7 +231,7 @@ def compile_file(fullname, ddir=None, force=False, rx=None, quiet=0,
                     cfile = importlib.util.cache_from_source(fullname)
                     opt_cfiles[opt_level] = cfile
 
-        head, tail = name[:-3], name[-3:]
+        tail = name[-3:]
         if tail == '.py':
             if not force:
                 try:
@@ -318,7 +326,6 @@ def main():
 
     parser = argparse.ArgumentParser(
         description='Utilities to support installing Python libraries.',
-        color=True,
     )
     parser.add_argument('-l', action='store_const', const=0,
                         default=None, dest='maxlevels',
@@ -330,10 +337,10 @@ def main():
     parser.add_argument('-f', action='store_true', dest='force',
                         help='force rebuild even if timestamps are up to date')
     parser.add_argument('-q', action='count', dest='quiet', default=0,
-                        help='output only error messages; -qq will suppress '
+                        help='output only error messages; `-qq` will suppress '
                              'the error messages as well.')
     parser.add_argument('-b', action='store_true', dest='legacy',
-                        help='use legacy (pre-PEP3147) compiled file locations')
+                        help='use legacy (pre-PEP 3147) compiled file locations')
     parser.add_argument('-d', metavar='DESTDIR',  dest='ddir', default=None,
                         help=('directory to prepend to file paths for use in '
                               'compile-time tracebacks and in runtime '
@@ -359,28 +366,28 @@ def main():
                               'of each file considered for compilation'))
     parser.add_argument('-i', metavar='FILE', dest='flist',
                         help=('add all the files and directories listed in '
-                              'FILE to the list considered for compilation; '
-                              'if "-", names are read from stdin'))
+                              '`FILE` to the list considered for compilation; '
+                              'if `"-"`, names are read from `stdin`'))
     parser.add_argument('compile_dest', metavar='FILE|DIR', nargs='*',
                         help=('zero or more file and directory names '
                               'to compile; if no arguments given, defaults '
-                              'to the equivalent of -l sys.path'))
+                              'to the equivalent of `-l` `sys.path`'))
     parser.add_argument('-j', '--workers', default=1,
                         type=int, help='Run compileall concurrently')
     invalidation_modes = [mode.name.lower().replace('_', '-')
                           for mode in py_compile.PycInvalidationMode]
     parser.add_argument('--invalidation-mode',
                         choices=sorted(invalidation_modes),
-                        help=('set .pyc invalidation mode; defaults to '
-                              '"checked-hash" if the SOURCE_DATE_EPOCH '
+                        help=('set `.pyc` invalidation mode; defaults to '
+                              '`"checked-hash"` if the `SOURCE_DATE_EPOCH` '
                               'environment variable is set, and '
-                              '"timestamp" otherwise.'))
+                              '`"timestamp"` otherwise.'))
     parser.add_argument('-o', action='append', type=int, dest='opt_levels',
                         help=('Optimization levels to run compilation with. '
-                              'Default is -1 which uses the optimization level '
-                              'of the Python interpreter itself (see -O).'))
+                              'Default is `-1` which uses the optimization level '
+                              'of the Python interpreter itself (see `-O`).'))
     parser.add_argument('-e', metavar='DIR', dest='limit_sl_dest',
-                        help='Ignore symlinks pointing outsite of the DIR')
+                        help='Ignore symlinks pointing outsite of the `DIR`')
     parser.add_argument('--hardlink-dupes', action='store_true',
                         dest='hardlink_dupes',
                         help='Hardlink duplicated pyc files')
diff --git a/Lib/concurrent/futures/_base.py b/Lib/concurrent/futures/_base.py
index 96156f47acc..43774066c5a 100644
--- a/Lib/concurrent/futures/_base.py
+++ b/Lib/concurrent/futures/_base.py
@@ -563,6 +563,33 @@ def set_exception(self, exception):
             self._condition.notify_all()
         self._invoke_callbacks()
 
+    def _get_snapshot(self):
+        """Get a snapshot of the future's current state.
+
+        This method atomically retrieves the state in one lock acquisition,
+        which is significantly faster than multiple method calls.
+
+        Returns:
+            Tuple of (done, cancelled, result, exception)
+            - done: True if the future is done (cancelled or finished)
+            - cancelled: True if the future was cancelled
+            - result: The result if available and not cancelled
+            - exception: The exception if available and not cancelled
+        """
+        # Fast path: check if already finished without lock
+        if self._state == FINISHED:
+            return True, False, self._result, self._exception
+
+        # Need lock for other states since they can change
+        with self._condition:
+            # We have to check the state again after acquiring the lock
+            # because it may have changed in the meantime.
+            if self._state == FINISHED:
+                return True, False, self._result, self._exception
+            if self._state in {CANCELLED, CANCELLED_AND_NOTIFIED}:
+                return True, True, None, None
+            return False, False, None, None
+
     __class_getitem__ = classmethod(types.GenericAlias)
 
 class Executor(object):
@@ -676,5 +703,5 @@ def __exit__(self, exc_type, exc_val, exc_tb):
 
 class BrokenExecutor(RuntimeError):
     """
-    Raised when a executor has become non-functional after a severe failure.
+    Raised when an executor has become non-functional after a severe failure.
     """
diff --git a/Lib/configparser.py b/Lib/configparser.py
index 3c452afe8ad..88015ef6086 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -618,7 +618,8 @@ class RawConfigParser(MutableMapping):
     _OPT_TMPL = r"""
         (?P<option>                        # very permissive!
             (?:(?!{delim})\S)*             # non-delimiter non-whitespace
-            (?:\s+(?:(?!{delim})\S)+)*)    # optionally more words
+            (?:(?:(?!{delim})\s)+          # optionally more
+             (?:(?!{delim})\S)+)*)         #   space-separated words
         \s*(?P<vi>{delim})\s*              # any number of space/tab,
                                            # followed by any of the
                                            # allowed delimiters,
@@ -628,7 +629,8 @@ class RawConfigParser(MutableMapping):
     _OPT_NV_TMPL = r"""
         (?P<option>                        # very permissive!
             (?:(?!{delim})\S)*             # non-delimiter non-whitespace
-            (?:\s+(?:(?!{delim})\S)+)*)    # optionally more words
+            (?:(?:(?!{delim})\s)+          # optionally more
+             (?:(?!{delim})\S)+)*)         #   space-separated words
         \s*(?:                             # any number of space/tab,
         (?P<vi>{delim})\s*                 # optionally followed by
                                            # any of the allowed
diff --git a/Lib/copy.py b/Lib/copy.py
index c64fc076179..6149301ad13 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -100,14 +100,14 @@ def copy(x):
     return _reconstruct(x, None, *rv)
 
 
-_copy_atomic_types = {types.NoneType, int, float, bool, complex, str, tuple,
-          bytes, frozenset, type, range, slice, property,
+_copy_atomic_types = frozenset({types.NoneType, int, float, bool, complex, str, tuple,
+          bytes, frozendict, frozenset, type, range, slice, property,
           types.BuiltinFunctionType, types.EllipsisType,
           types.NotImplementedType, types.FunctionType, types.CodeType,
-          weakref.ref, super}
-_copy_builtin_containers = {list, dict, set, bytearray}
+          weakref.ref, super})
+_copy_builtin_containers = frozenset({list, dict, set, bytearray})
 
-def deepcopy(x, memo=None, _nil=[]):
+def deepcopy(x, memo=None):
     """Deep copy operation on arbitrary Python objects.
 
     See the module's __doc__ string for more info.
@@ -122,8 +122,8 @@ def deepcopy(x, memo=None, _nil=[]):
     if memo is None:
         memo = {}
     else:
-        y = memo.get(d, _nil)
-        if y is not _nil:
+        y = memo.get(d, None)
+        if y is not None:
             return y
 
     copier = _deepcopy_dispatch.get(cls)
@@ -162,9 +162,9 @@ def deepcopy(x, memo=None, _nil=[]):
         _keep_alive(x, memo) # Make sure x lives at least as long as d
     return y
 
-_atomic_types =  {types.NoneType, types.EllipsisType, types.NotImplementedType,
+_atomic_types = frozenset({types.NoneType, types.EllipsisType, types.NotImplementedType,
           int, float, bool, complex, bytes, str, types.CodeType, type, range,
-          types.BuiltinFunctionType, types.FunctionType, weakref.ref, property}
+          types.BuiltinFunctionType, types.FunctionType, weakref.ref, property})
 
 _deepcopy_dispatch = d = {}
 
@@ -203,6 +203,21 @@ def _deepcopy_dict(x, memo, deepcopy=deepcopy):
     return y
 d[dict] = _deepcopy_dict
 
+def _deepcopy_frozendict(x, memo, deepcopy=deepcopy):
+    y = {}
+    for key, value in x.items():
+        y[deepcopy(key, memo)] = deepcopy(value, memo)
+
+    # We're not going to put the frozendict in the memo, but it's still
+    # important we check for it, in case the frozendict contains recursive
+    # mutable structures.
+    try:
+        return memo[id(x)]
+    except KeyError:
+        pass
+    return frozendict(y)
+d[frozendict] = _deepcopy_frozendict
+
 def _deepcopy_method(x, memo): # Copy instance methods
     return type(x)(x.__func__, deepcopy(x.__self__, memo))
 d[types.MethodType] = _deepcopy_method
@@ -230,7 +245,7 @@ def _reconstruct(x, memo, func, args,
                  *, deepcopy=deepcopy):
     deep = memo is not None
     if deep and args:
-        args = (deepcopy(arg, memo) for arg in args)
+        args = [deepcopy(arg, memo) for arg in args]
     y = func(*args)
     if deep:
         memo[id(x)] = y
diff --git a/Lib/csv.py b/Lib/csv.py
index 5d15344ea24..4940aa28dcd 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -81,8 +81,6 @@ class excel:
            "unregister_dialect", "DictReader", "DictWriter",
            "unix_dialect"]
 
-__version__ = "1.0"
-
 
 class Dialect:
     """Describe a CSV dialect.
@@ -378,31 +376,33 @@ def _guess_delimiter(self, data, delimiters):
         try and evaluate the smallest portion of the data possible, evaluating
         additional chunks as necessary.
         """
+        from collections import Counter, defaultdict
 
         data = list(filter(None, data.split('\n')))
 
-        ascii = [chr(c) for c in range(127)] # 7-bit ASCII
-
         # build frequency tables
         chunkLength = min(10, len(data))
         iteration = 0
-        charFrequency = {}
+        num_lines = 0
+        # {char -> {count_per_line -> num_lines_with_that_count}}
+        char_frequency = defaultdict(Counter)
         modes = {}
         delims = {}
         start, end = 0, chunkLength
         while start < len(data):
             iteration += 1
             for line in data[start:end]:
-                for char in ascii:
-                    metaFrequency = charFrequency.get(char, {})
-                    # must count even if frequency is 0
-                    freq = line.count(char)
-                    # value is the mode
-                    metaFrequency[freq] = metaFrequency.get(freq, 0) + 1
-                    charFrequency[char] = metaFrequency
-
-            for char in charFrequency.keys():
-                items = list(charFrequency[char].items())
+                num_lines += 1
+                for char, count in Counter(line).items():
+                    if char.isascii():
+                        char_frequency[char][count] += 1
+
+            for char, counts in char_frequency.items():
+                items = list(counts.items())
+                missed_lines = num_lines - sum(counts.values())
+                if missed_lines:
+                    # Store the number of lines 'char' was missing from.
+                    items.append((0, missed_lines))
                 if len(items) == 1 and items[0][0] == 0:
                     continue
                 # get the mode of the frequencies
@@ -525,3 +525,12 @@ def has_header(self, sample):
                     hasHeader -= 1
 
         return hasHeader > 0
+
+
+def __getattr__(name):
+    if name == "__version__":
+        from warnings import _deprecated
+
+        _deprecated("__version__", remove=(3, 20))
+        return "1.0"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 242a6d2ffc2..863e4101f98 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -1,13 +1,12 @@
-import re
 import sys
-import copy
 import types
-import inspect
 import keyword
 import itertools
 import annotationlib
 import abc
 from reprlib import recursive_repr
+lazy import copy
+lazy import re
 
 
 __all__ = ['dataclass',
@@ -178,21 +177,16 @@ def __repr__(self):
         return '<factory>'
 _HAS_DEFAULT_FACTORY = _HAS_DEFAULT_FACTORY_CLASS()
 
-# A sentinel object to detect if a parameter is supplied or not.  Use
-# a class to give it a better repr.
-class _MISSING_TYPE:
-    pass
-MISSING = _MISSING_TYPE()
+# A sentinel object to detect if a parameter is supplied or not.
+MISSING = sentinel("MISSING")
 
 # A sentinel object to indicate that following fields are keyword-only by
-# default.  Use a class to give it a better repr.
-class _KW_ONLY_TYPE:
-    pass
-KW_ONLY = _KW_ONLY_TYPE()
+# default.
+KW_ONLY = sentinel("KW_ONLY")
 
 # Since most per-field metadata will be unused, create an empty
-# read-only proxy that can be shared among all fields.
-_EMPTY_METADATA = types.MappingProxyType({})
+# read-only dictionary that can be shared among all fields.
+_EMPTY_METADATA = frozendict()
 
 # Markers for the various kinds of fields and pseudo-fields.
 class _FIELD_BASE:
@@ -217,9 +211,8 @@ def __repr__(self):
 _POST_INIT_NAME = '__post_init__'
 
 # String regex that string annotations for ClassVar or InitVar must match.
-# Allows "identifier.identifier[" or "identifier[".
-# https://bugs.python.org/issue33453 for details.
-_MODULE_IDENTIFIER_RE = re.compile(r'^(?:\s*(\w+)\s*\.)?\s*(\w+)')
+# This regular expression is compiled on demand so that 're' module can be imported lazily
+_MODULE_IDENTIFIER_RE = None
 
 # Atomic immutable types which don't require any recursive handling and for which deepcopy
 # returns the same object. We can provide a fast-path for these types in asdict and astuple.
@@ -763,22 +756,16 @@ def _is_kw_only(a_type, dataclasses):
     return a_type is dataclasses.KW_ONLY
 
 
-def _is_type(annotation, cls, a_module, a_type, is_type_predicate):
-    # Given a type annotation string, does it refer to a_type in
-    # a_module?  For example, when checking that annotation denotes a
-    # ClassVar, then a_module is typing, and a_type is
-    # typing.ClassVar.
+def _get_type_from_annotation(annotation, cls):
+    # Loosely parse a string annotation and return its type.
 
-    # It's possible to look up a_module given a_type, but it involves
-    # looking in sys.modules (again!), and seems like a waste since
-    # the caller already knows a_module.
+    # We can't perform a full type hint evaluation at the point where @dataclass
+    # was invoked because class's module is not fully initialized yet. So we resort
+    # to parsing string annotation using regexp, and extracting a type before
+    # the first square bracket.
 
     # - annotation is a string type annotation
     # - cls is the class that this annotation was found in
-    # - a_module is the module we want to match
-    # - a_type is the type in that module we want to match
-    # - is_type_predicate is a function called with (obj, a_module)
-    #   that determines if obj is of the desired type.
 
     # Since this test does not do a local namespace lookup (and
     # instead only a module (global) lookup), there are some things it
@@ -804,22 +791,26 @@ def _is_type(annotation, cls, a_module, a_type, is_type_predicate):
     # a eval() penalty for every single field of every dataclass
     # that's defined.  It was judged not worth it.
 
-    match = _MODULE_IDENTIFIER_RE.match(annotation)
-    if match:
-        ns = None
-        module_name = match.group(1)
-        if not module_name:
-            # No module name, assume the class's module did
-            # "from dataclasses import InitVar".
-            ns = sys.modules.get(cls.__module__).__dict__
-        else:
-            # Look up module_name in the class's module.
-            module = sys.modules.get(cls.__module__)
-            if module and module.__dict__.get(module_name) is a_module:
-                ns = sys.modules.get(a_type.__module__).__dict__
-        if ns and is_type_predicate(ns.get(match.group(2)), a_module):
-            return True
-    return False
+    # String regex that string annotations for ClassVar or InitVar must match.
+    # Allows "identifier.identifier[" or "identifier[".
+    # https://github.com/python/cpython/issues/77634 for details.
+    global _MODULE_IDENTIFIER_RE
+    if _MODULE_IDENTIFIER_RE is None:
+        _MODULE_IDENTIFIER_RE = re.compile(r'^\s*(\w+(?:\s*\.\s*\w+)*)')
+
+    match = _MODULE_IDENTIFIER_RE.prefixmatch(annotation)
+    if not match:
+        return None
+
+    # Note: _MODULE_IDENTIFIER_RE guarantees that path is non-empty
+    path = match[1].split(".")
+    root = sys.modules.get(cls.__module__)
+    for path_item in path:
+        root = getattr(root, path_item.strip(), None)
+        if root is None:
+            return None
+
+    return root
 
 
 def _get_field(cls, a_name, a_type, default_kw_only):
@@ -857,6 +848,10 @@ def _get_field(cls, a_name, a_type, default_kw_only):
     # is actually of the correct type.
 
     # For the complete discussion, see https://bugs.python.org/issue33453
+    if isinstance(a_type, str):
+        a_type_annotation = _get_type_from_annotation(a_type, cls)
+    else:
+        a_type_annotation = a_type
 
     # If typing has not been imported, then it's impossible for any
     # annotation to be a ClassVar.  So, only look for ClassVar if
@@ -864,10 +859,7 @@ def _get_field(cls, a_name, a_type, default_kw_only):
     # module).
     typing = sys.modules.get('typing')
     if typing:
-        if (_is_classvar(a_type, typing)
-            or (isinstance(f.type, str)
-                and _is_type(f.type, cls, typing, typing.ClassVar,
-                             _is_classvar))):
+        if _is_classvar(a_type_annotation, typing):
             f._field_type = _FIELD_CLASSVAR
 
     # If the type is InitVar, or if it's a matching string annotation,
@@ -876,10 +868,7 @@ def _get_field(cls, a_name, a_type, default_kw_only):
         # The module we're checking against is the module we're
         # currently in (dataclasses.py).
         dataclasses = sys.modules[__name__]
-        if (_is_initvar(a_type, dataclasses)
-            or (isinstance(f.type, str)
-                and _is_type(f.type, cls, dataclasses, dataclasses.InitVar,
-                             _is_initvar))):
+        if _is_initvar(a_type_annotation, dataclasses):
             f._field_type = _FIELD_INITVAR
 
     # Validations for individual fields.  This is delayed until now,
@@ -982,6 +971,29 @@ def _hash_exception(cls, fields, func_builder):
 # See https://bugs.python.org/issue32929#msg312829 for an if-statement
 # version of this table.
 
+# A non-data descriptor to autogenerate class docstring
+# from the signature of its __init__ method on demand.
+# The primary reason is to be able to lazy import `inspect` module.
+class _AutoDocstring:
+
+    def __get__(self, _obj, cls):
+        try:
+            # In some cases fetching a signature is not possible.
+            # But, we surely should not fail in this case.
+            import inspect
+            text_sig = str(inspect.signature(
+                 cls,
+                 annotation_format=annotationlib.Format.FORWARDREF,
+            )).replace(' -> None', '')
+        except TypeError, ValueError:
+            text_sig = ''
+
+        doc = cls.__name__ + text_sig
+        setattr(cls, '__doc__', doc)
+        return doc
+
+_auto_docstring = _AutoDocstring()
+
 
 def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen,
                    match_args, kw_only, slots, weakref_slot):
@@ -1050,10 +1062,11 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen,
     dataclasses = sys.modules[__name__]
     for name, type in cls_annotations.items():
         # See if this is a marker to change the value of kw_only.
-        if (_is_kw_only(type, dataclasses)
-            or (isinstance(type, str)
-                and _is_type(type, cls, dataclasses, dataclasses.KW_ONLY,
-                             _is_kw_only))):
+        if isinstance(type, str):
+            a_type_annotation = _get_type_from_annotation(type, cls)
+        else:
+            a_type_annotation = type
+        if _is_kw_only(a_type_annotation, dataclasses):
             # Switch the default to kw_only=True, and ignore this
             # annotation: it's not a real field.
             if KW_ONLY_seen:
@@ -1209,23 +1222,13 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen,
     if hash_action:
         cls.__hash__ = hash_action(cls, field_list, func_builder)
 
-    # Generate the methods and add them to the class.  This needs to be done
-    # before the __doc__ logic below, since inspect will look at the __init__
-    # signature.
+    # Generate the methods and add them to the class.
     func_builder.add_fns_to_class(cls)
 
     if not getattr(cls, '__doc__'):
-        # Create a class doc-string.
-        try:
-            # In some cases fetching a signature is not possible.
-            # But, we surely should not fail in this case.
-            text_sig = str(inspect.signature(
-                cls,
-                annotation_format=annotationlib.Format.FORWARDREF,
-            )).replace(' -> None', '')
-        except (TypeError, ValueError):
-            text_sig = ''
-        cls.__doc__ = (cls.__name__ + text_sig)
+        # Create a class doc-string lazily via descriptor protocol
+        # to avoid importing `inspect` module.
+        cls.__doc__ = _auto_docstring
 
     if match_args:
         # I could probably compute this once.
@@ -1344,10 +1347,6 @@ def _add_slots(cls, is_frozen, weakref_slot, defined_fields):
     if '__slots__' in cls.__dict__:
         raise TypeError(f'{cls.__name__} already specifies __slots__')
 
-    # gh-102069: Remove existing __weakref__ descriptor.
-    # gh-135228: Make sure the original class can be garbage collected.
-    sys._clear_type_descriptors(cls)
-
     # Create a new dict for our new class.
     cls_dict = dict(cls.__dict__)
     field_names = tuple(f.name for f in fields(cls))
@@ -1365,6 +1364,11 @@ def _add_slots(cls, is_frozen, weakref_slot, defined_fields):
         #  available in _MARKER.
         cls_dict.pop(field_name, None)
 
+    # Remove __dict__ and `__weakref__` descriptors.
+    # They'll be added back if applicable.
+    cls_dict.pop('__dict__', None)
+    cls_dict.pop('__weakref__', None)  # gh-102069
+
     # And finally create the class.
     qualname = getattr(cls, '__qualname__', None)
     newcls = type(cls)(cls.__name__, cls.__bases__, cls_dict)
@@ -1385,8 +1389,11 @@ def _add_slots(cls, is_frozen, weakref_slot, defined_fields):
     # make an update, since all closures for a class will share a
     # given cell.
     for member in newcls.__dict__.values():
+
         # If this is a wrapped function, unwrap it.
-        member = inspect.unwrap(member)
+        if not isinstance(member, type) and hasattr(member, '__wrapped__'):
+            import inspect
+            member = inspect.unwrap(member)
 
         if isinstance(member, types.FunctionType):
             if _update_func_cell_for__class__(member, cls, newcls):
@@ -1498,7 +1505,8 @@ class C:
     If given, 'dict_factory' will be used instead of built-in dict.
     The function applies recursively to field values that are
     dataclass instances. This will also look into built-in containers:
-    tuples, lists, and dicts. Other objects are copied with 'copy.deepcopy()'.
+    tuples, lists, dicts, and frozendicts. Other objects are copied
+    with 'copy.deepcopy()'.
     """
     if not _is_dataclass_instance(obj):
         raise TypeError("asdict() should be called on dataclass instances")
@@ -1554,7 +1562,7 @@ def _asdict_inner(obj, dict_factory):
             return obj_type(*[_asdict_inner(v, dict_factory) for v in obj])
         else:
             return obj_type(_asdict_inner(v, dict_factory) for v in obj)
-    elif issubclass(obj_type, dict):
+    elif issubclass(obj_type, (dict, frozendict)):
         if hasattr(obj_type, 'default_factory'):
             # obj is a defaultdict, which has a different constructor from
             # dict as it requires the default_factory as its first arg.
@@ -1589,7 +1597,8 @@ class C:
     If given, 'tuple_factory' will be used instead of built-in tuple.
     The function applies recursively to field values that are
     dataclass instances. This will also look into built-in containers:
-    tuples, lists, and dicts. Other objects are copied with 'copy.deepcopy()'.
+    tuples, lists, dicts, and frozendicts. Other objects are copied
+    with 'copy.deepcopy()'.
     """
 
     if not _is_dataclass_instance(obj):
@@ -1618,7 +1627,7 @@ def _astuple_inner(obj, tuple_factory):
         # generator (which is not true for namedtuples, handled
         # above).
         return type(obj)(_astuple_inner(v, tuple_factory) for v in obj)
-    elif isinstance(obj, dict):
+    elif isinstance(obj, (dict, frozendict)):
         obj_type = type(obj)
         if hasattr(obj_type, 'default_factory'):
             # obj is a defaultdict, which has a different constructor from
diff --git a/Lib/decimal.py b/Lib/decimal.py
index 530bdfb3895..cf13050bfef 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -100,8 +100,8 @@
 
 try:
     from _decimal import *
-    from _decimal import __version__  # noqa: F401
     from _decimal import __libmpdec_version__  # noqa: F401
+    from _decimal import __getattr__  # noqa: F401
 except ImportError:
     import _pydecimal
     import sys
diff --git a/Lib/dis.py b/Lib/dis.py
index d6d2c1386dd..d60507ae473 100644
--- a/Lib/dis.py
+++ b/Lib/dis.py
@@ -35,6 +35,7 @@
 FUNCTION_ATTR_FLAGS = ('defaults', 'kwdefaults', 'annotations', 'closure', 'annotate')
 
 ENTER_EXECUTOR = opmap['ENTER_EXECUTOR']
+IMPORT_NAME = opmap['IMPORT_NAME']
 LOAD_GLOBAL = opmap['LOAD_GLOBAL']
 LOAD_SMALL_INT = opmap['LOAD_SMALL_INT']
 BINARY_OP = opmap['BINARY_OP']
@@ -530,7 +531,6 @@ def print_instruction_line(self, instr, mark_as_current):
         fields.append(instr.opname.ljust(_OPNAME_WIDTH))
         # Column: Opcode argument
         if instr.arg is not None:
-            arg = repr(instr.arg)
             # If opname is longer than _OPNAME_WIDTH, we allow it to overflow into
             # the space reserved for oparg. This results in fewer misaligned opargs
             # in the disassembly output.
@@ -601,6 +601,12 @@ def get_argval_argrepr(self, op, arg, offset):
                     argval, argrepr = _get_name_info(arg//4, get_name)
                     if (arg & 1) and argrepr:
                         argrepr = f"{argrepr} + NULL|self"
+                elif deop == IMPORT_NAME:
+                    argval, argrepr = _get_name_info(arg//4, get_name)
+                    if (arg & 1) and argrepr:
+                        argrepr = f"{argrepr} + lazy"
+                    elif (arg & 2) and argrepr:
+                        argrepr = f"{argrepr} + eager"
                 else:
                     argval, argrepr = _get_name_info(arg, get_name)
             elif deop in hasjump or deop in hasexc:
@@ -637,6 +643,7 @@ def get_argval_argrepr(self, op, arg, offset):
                 argrepr = _intrinsic_2_descs[arg]
             elif deop == LOAD_COMMON_CONSTANT:
                 obj = _common_constants[arg]
+                argval = obj
                 if isinstance(obj, type):
                     argrepr = obj.__name__
                 else:
@@ -686,10 +693,15 @@ def _get_const_value(op, arg, co_consts):
        Otherwise (if it is a LOAD_CONST and co_consts is not
        provided) returns the dis.UNKNOWN sentinel.
     """
-    assert op in hasconst or op == LOAD_SMALL_INT
+    assert op in hasconst or op == LOAD_SMALL_INT or op == LOAD_COMMON_CONSTANT
 
     if op == LOAD_SMALL_INT:
         return arg
+    if op == LOAD_COMMON_CONSTANT:
+        # Opargs 0-6 are callables; 7-11 are literal values.
+        if 7 <= arg <= 11:
+            return _common_constants[arg]
+        return UNKNOWN
     argval = UNKNOWN
     if co_consts is not None:
         argval = co_consts[arg]
@@ -1009,11 +1021,14 @@ def _find_imports(co):
         if op == IMPORT_NAME and i >= 2:
             from_op = opargs[i-1]
             level_op = opargs[i-2]
-            if (from_op[0] in hasconst and
-                (level_op[0] in hasconst or level_op[0] == LOAD_SMALL_INT)):
+            if ((from_op[0] in hasconst or from_op[0] == LOAD_COMMON_CONSTANT) and
+                (level_op[0] in hasconst or level_op[0] == LOAD_SMALL_INT or
+                 level_op[0] == LOAD_COMMON_CONSTANT)):
                 level = _get_const_value(level_op[0], level_op[1], consts)
                 fromlist = _get_const_value(from_op[0], from_op[1], consts)
-                yield (names[oparg], level, fromlist)
+                # IMPORT_NAME encodes lazy/eager flags in bits 0-1,
+                # name index in bits 2+.
+                yield (names[oparg >> 2], level, fromlist)
 
 def _find_store_names(co):
     """Find names of variables which are written in the code
@@ -1131,7 +1146,7 @@ def dis(self):
 def main(args=None):
     import argparse
 
-    parser = argparse.ArgumentParser(color=True)
+    parser = argparse.ArgumentParser()
     parser.add_argument('-C', '--show-caches', action='store_true',
                         help='show inline caches')
     parser.add_argument('-O', '--show-offsets', action='store_true',
diff --git a/Lib/email/_encoded_words.py b/Lib/email/_encoded_words.py
index 05a34a4c105..ecbaecb7a68 100644
--- a/Lib/email/_encoded_words.py
+++ b/Lib/email/_encoded_words.py
@@ -161,10 +161,10 @@ def decode(ew):
     This function expects exactly such a string (that is, it does not check the
     syntax and may raise errors if the string is not well formed), and returns
     the encoded_string decoded first from its Content Transfer Encoding and
-    then from the resulting bytes into unicode using the specified charset.  If
-    the cte-decoded string does not successfully decode using the specified
+    then from the resulting bytes into a string using the specified charset.
+    If the cte-decoded string does not successfully decode using the specified
     character set, a defect is added to the defects list and the unknown octets
-    are replaced by the unicode 'unknown' character \\uFDFF.
+    are replaced by the Unicode 'unknown' character \\uFDFF.
 
     The specified charset and language are returned.  The default for language,
     which is rarely if ever encountered, is the empty string.
@@ -176,7 +176,7 @@ def decode(ew):
     # Recover the original bytes and do CTE decoding.
     bstring = cte_string.encode('ascii', 'surrogateescape')
     bstring, defects = _cte_decoders[cte](bstring)
-    # Turn the CTE decoded bytes into unicode.
+    # Turn the CTE decoded bytes into a string.
     try:
         string = bstring.decode(charset)
     except UnicodeDecodeError:
diff --git a/Lib/email/_header_value_parser.py b/Lib/email/_header_value_parser.py
index c02175e24e0..792072ab9f6 100644
--- a/Lib/email/_header_value_parser.py
+++ b/Lib/email/_header_value_parser.py
@@ -157,10 +157,7 @@ def all_defects(self):
     def startswith_fws(self):
         return self[0].startswith_fws()
 
-    @property
-    def as_ew_allowed(self):
-        """True if all top level tokens of this part may be RFC2047 encoded."""
-        return all(part.as_ew_allowed for part in self)
+    as_ew_allowed = True
 
     @property
     def comments(self):
@@ -429,6 +426,7 @@ def addr_spec(self):
 class AngleAddr(TokenList):
 
     token_type = 'angle-addr'
+    as_ew_allowed = False
 
     @property
     def local_part(self):
@@ -803,6 +801,10 @@ def params(self):
                         value = urllib.parse.unquote(value, encoding='latin-1')
                     else:
                         try:
+                            # Explicitly look up the codec for warning generation, see gh-140030
+                            # Can be removed in 3.17
+                            import codecs
+                            codecs.lookup(charset)
                             value = value.decode(charset, 'surrogateescape')
                         except (LookupError, UnicodeEncodeError):
                             # XXX: there should really be a custom defect for
@@ -843,26 +845,22 @@ def params(self):
 
 class ContentType(ParameterizedHeaderValue):
     token_type = 'content-type'
-    as_ew_allowed = False
     maintype = 'text'
     subtype = 'plain'
 
 
 class ContentDisposition(ParameterizedHeaderValue):
     token_type = 'content-disposition'
-    as_ew_allowed = False
     content_disposition = None
 
 
 class ContentTransferEncoding(TokenList):
     token_type = 'content-transfer-encoding'
-    as_ew_allowed = False
     cte = '7bit'
 
 
 class HeaderLabel(TokenList):
     token_type = 'header-label'
-    as_ew_allowed = False
 
 
 class MsgID(TokenList):
@@ -1515,11 +1513,6 @@ def get_local_part(value):
             local_part.defects.append(errors.ObsoleteHeaderDefect(
                 "local-part is not a dot-atom (contains CFWS)"))
         local_part[0] = obs_local_part
-    try:
-        local_part.value.encode('ascii')
-    except UnicodeEncodeError:
-        local_part.defects.append(errors.NonASCIILocalPartDefect(
-                "local-part contains non-ASCII characters)"))
     return local_part, value
 
 def get_obs_local_part(value):
@@ -2841,13 +2834,68 @@ def _steal_trailing_WSP_if_exists(lines):
 
 
 def _refold_parse_tree(parse_tree, *, policy):
-    """Return string of contents of parse_tree folded according to RFC rules.
-
-    """
     # max_line_length 0/None means no limit, ie: infinitely long.
     maxlen = policy.max_line_length or sys.maxsize
     encoding = 'utf-8' if policy.utf8 else 'us-ascii'
     lines = ['']  # Folded lines to be output
+    if parse_tree.as_ew_allowed:
+        _refold_with_ew(parse_tree, lines, maxlen, encoding, policy=policy)
+    else:
+        _refold_without_ew(parse_tree, lines, maxlen, encoding, policy=policy)
+    return policy.linesep.join(lines) + policy.linesep
+
+def _refold_without_ew(parse_tree, lines, maxlen, encoding, *, policy):
+    parts = list(parse_tree)
+    while parts:
+        part = parts.pop(0)
+        tstr = str(part)
+        try:
+            tstr.encode(encoding)
+        except UnicodeEncodeError:
+            if any(isinstance(x, errors.UndecodableBytesDefect)
+                   for x in part.all_defects):
+                # There is garbage data from parsing a message in binary mode,
+                # just pass it through.  Not good, but the best we can do.
+                pass
+            elif policy.utf8:
+                # If this happens, it's a programmer error.
+                raise
+            else:
+                raise errors.HeaderWriteError(
+                    f"Non-ASCII {part.token_type} '{part}' is invalid"
+                    " under current policy setting (utf8=False)"
+                )
+        if len(tstr) <= maxlen - len(lines[-1]):
+            lines[-1] += tstr
+            continue
+        # This part is too long to fit.  The RFC wants us to break at
+        # "major syntactic breaks", so unless we don't consider this
+        # to be one, check if it will fit on the next line by itself.
+        if (part.syntactic_break and
+                len(tstr) + 1 <= maxlen):
+            newline = _steal_trailing_WSP_if_exists(lines)
+            if newline or part.startswith_fws():
+                lines.append(newline + tstr)
+                continue
+        if not hasattr(part, 'encode'):
+            # It's not a terminal, try folding the subparts.
+            newparts = list(part)
+            parts = newparts + parts
+            continue
+        # We can't figure out how to wrap, it, so give up.
+        newline = _steal_trailing_WSP_if_exists(lines)
+        if newline or part.startswith_fws():
+            lines.append(newline + tstr)
+        else:
+            # We can't fold it onto the next line either...
+            lines[-1] += tstr
+    return
+
+
+def _refold_with_ew(parse_tree, lines, maxlen, encoding, *, policy):
+    """Return string of contents of parse_tree folded according to RFC rules.
+
+    """
     last_word_is_ew = False
     last_ew = None  # if there is an encoded word in the last line of lines,
                     # points to the encoded word's first character
@@ -2861,6 +2909,11 @@ def _refold_parse_tree(parse_tree, *, policy):
         if part is end_ew_not_allowed:
             wrap_as_ew_blocked -= 1
             continue
+        if part.token_type == 'mime-parameters':
+            # Mime parameter folding (using RFC2231) is extra special.
+            _fold_mime_parameters(part, lines, maxlen, encoding)
+            last_word_is_ew = False
+            continue
         tstr = str(part)
         if not want_encoding:
             if part.token_type in ('ptext', 'vtext'):
@@ -2882,14 +2935,11 @@ def _refold_parse_tree(parse_tree, *, policy):
                 charset = 'utf-8'
             want_encoding = True
 
-        if part.token_type == 'mime-parameters':
-            # Mime parameter folding (using RFC2231) is extra special.
-            _fold_mime_parameters(part, lines, maxlen, encoding)
-            last_word_is_ew = False
-            continue
-
         if want_encoding and not wrap_as_ew_blocked:
-            if not part.as_ew_allowed:
+            if any(
+                    not x.as_ew_allowed for x in part
+                    if hasattr(x, 'as_ew_allowed')
+                ):
                 want_encoding = False
                 last_ew = None
                 if part.syntactic_break:
@@ -2970,6 +3020,8 @@ def _refold_parse_tree(parse_tree, *, policy):
                     [ValueTerminal(make_quoted_pairs(p), 'ptext')
                      for p in newparts] +
                     [ValueTerminal('"', 'ptext')])
+                _refold_without_ew(newparts, lines, maxlen, encoding, policy=policy)
+                continue
             if part.token_type == 'comment':
                 newparts = (
                     [ValueTerminal('(', 'ptext')] +
@@ -2997,7 +3049,7 @@ def _refold_parse_tree(parse_tree, *, policy):
             lines[-1] += tstr
         last_word_is_ew = last_word_is_ew and not bool(tstr.strip(_WSP))
 
-    return policy.linesep.join(lines) + policy.linesep
+    return
 
 def _fold_as_ew(to_encode, lines, maxlen, last_ew, ew_combine_allowed, charset, last_word_is_ew):
     """Fold string to_encode into lines as encoded word, combining if allowed.
diff --git a/Lib/email/_policybase.py b/Lib/email/_policybase.py
index e23843df448..ab40be6b920 100644
--- a/Lib/email/_policybase.py
+++ b/Lib/email/_policybase.py
@@ -365,7 +365,7 @@ def _fold(self, name, value, sanitize):
                                       charset=_charset.UNKNOWN8BIT,
                                       header_name=name)
                 else:
-                    # If we have raw 8bit data in a byte string, we have no idea
+                    # If we have raw 8bit data in a string, we have no idea
                     # what the encoding is.  There is no safe way to split this
                     # string.  If it's ascii-subset, then we could do a normal
                     # ascii split, but if it's multibyte then we could break the
diff --git a/Lib/email/base64mime.py b/Lib/email/base64mime.py
index a5a3f737a97..5766f9ad655 100644
--- a/Lib/email/base64mime.py
+++ b/Lib/email/base64mime.py
@@ -83,16 +83,15 @@ def body_encode(s, maxlinelen=76, eol=NL):
     if not s:
         return ""
 
-    encvec = []
-    max_unencoded = maxlinelen * 3 // 4
-    for i in range(0, len(s), max_unencoded):
-        # BAW: should encode() inherit b2a_base64()'s dubious behavior in
-        # adding a newline to the encoded string?
-        enc = b2a_base64(s[i:i + max_unencoded]).decode("ascii")
-        if enc.endswith(NL) and eol != NL:
-            enc = enc[:-1] + eol
-        encvec.append(enc)
-    return EMPTYSTRING.join(encvec)
+    if not eol:
+        return b2a_base64(s, newline=False).decode("ascii")
+
+    # BAW: should encode() inherit b2a_base64()'s dubious behavior in
+    # adding a newline to the encoded string?
+    enc = b2a_base64(s, wrapcol=maxlinelen).decode("ascii")
+    if eol != NL:
+        enc = enc.replace(NL, eol)
+    return enc
 
 
 def decode(string):
diff --git a/Lib/email/charset.py b/Lib/email/charset.py
index c4b246455f8..44fe0794bb7 100644
--- a/Lib/email/charset.py
+++ b/Lib/email/charset.py
@@ -9,6 +9,7 @@
     'add_codec',
     ]
 
+import codecs
 from functools import partial
 
 import email.base64mime
@@ -58,37 +59,71 @@
     'shift_jis':   (BASE64,    None,    'iso-2022-jp'),
     'iso-2022-jp': (BASE64,    None,    None),
     'koi8-r':      (BASE64,    BASE64,  None),
-    'utf-8':       (SHORTEST,  BASE64, 'utf-8'),
     }
 
-# Aliases for other commonly-used names for character sets.  Map
-# them to the real ones used in email.
+# Map Python codec names to their corresponding MIME/IANA names.
 ALIASES = {
-    'latin_1': 'iso-8859-1',
-    'latin-1': 'iso-8859-1',
-    'latin_2': 'iso-8859-2',
-    'latin-2': 'iso-8859-2',
-    'latin_3': 'iso-8859-3',
-    'latin-3': 'iso-8859-3',
-    'latin_4': 'iso-8859-4',
-    'latin-4': 'iso-8859-4',
-    'latin_5': 'iso-8859-9',
-    'latin-5': 'iso-8859-9',
-    'latin_6': 'iso-8859-10',
-    'latin-6': 'iso-8859-10',
-    'latin_7': 'iso-8859-13',
-    'latin-7': 'iso-8859-13',
-    'latin_8': 'iso-8859-14',
-    'latin-8': 'iso-8859-14',
-    'latin_9': 'iso-8859-15',
-    'latin-9': 'iso-8859-15',
-    'latin_10':'iso-8859-16',
-    'latin-10':'iso-8859-16',
-    'cp949':   'ks_c_5601-1987',
-    'euc_jp':  'euc-jp',
-    'euc_kr':  'euc-kr',
-    'ascii':   'us-ascii',
-    }
+    'ascii': 'us-ascii',
+    'big5hkscs': 'big5-hkscs',
+    'cp037': 'ibm037',
+    'cp1026': 'ibm1026',
+    'cp1140': 'ibm01140',
+    'cp1250': 'windows-1250',
+    'cp1251': 'windows-1251',
+    'cp1252': 'windows-1252',
+    'cp1253': 'windows-1253',
+    'cp1254': 'windows-1254',
+    'cp1255': 'windows-1255',
+    'cp1256': 'windows-1256',
+    'cp1257': 'windows-1257',
+    'cp1258': 'windows-1258',
+    'cp273': 'ibm273',
+    'cp424': 'ibm424',
+    'cp437': 'ibm437',
+    'cp500': 'ibm500',
+    'cp775': 'ibm775',
+    'cp850': 'ibm850',
+    'cp852': 'ibm852',
+    'cp855': 'ibm855',
+    'cp857': 'ibm857',
+    'cp858': 'ibm00858',
+    'cp860': 'ibm860',
+    'cp861': 'ibm861',
+    'cp862': 'ibm862',
+    'cp863': 'ibm863',
+    'cp864': 'ibm864',
+    'cp865': 'ibm865',
+    'cp866': 'ibm866',
+    'cp869': 'ibm869',
+    'cp874': 'windows-874',
+    'euc_jp': 'euc-jp',
+    'euc_kr': 'euc-kr',
+    'hz': 'hz-gb-2312',
+    'iso2022_jp': 'iso-2022-jp',
+    'iso2022_jp_2': 'iso-2022-jp-2',
+    'iso2022_kr': 'iso-2022-kr',
+    'iso8859-1': 'iso-8859-1',
+    'iso8859-10': 'iso-8859-10',
+    'iso8859-11': 'iso-8859-11',
+    'iso8859-13': 'iso-8859-13',
+    'iso8859-14': 'iso-8859-14',
+    'iso8859-15': 'iso-8859-15',
+    'iso8859-16': 'iso-8859-16',
+    'iso8859-2': 'iso-8859-2',
+    'iso8859-3': 'iso-8859-3',
+    'iso8859-4': 'iso-8859-4',
+    'iso8859-5': 'iso-8859-5',
+    'iso8859-6': 'iso-8859-6',
+    'iso8859-7': 'iso-8859-7',
+    'iso8859-8': 'iso-8859-8-i',
+    'iso8859-9': 'iso-8859-9',
+    'kz1048': 'kz-1048',
+    'mac-roman': 'macintosh',
+
+    # CP949 is not registered in IANA. KS_C_5601-1987 is not the same,
+    # but the closest registered option.
+    'cp949': 'ks_c_5601-1987',
+}
 
 
 # Map charsets to their Unicode codec strings.
@@ -142,8 +177,8 @@ def add_codec(charset, codecname):
     """Add a codec that map characters in the given charset to/from Unicode.
 
     charset is the canonical name of a character set.  codecname is the name
-    of a Python codec, as appropriate for the second argument to the unicode()
-    built-in, or to the encode() method of a Unicode string.
+    of a Python codec, as appropriate for the second argument to the str()
+    built-in, or to the encode() method of a string.
     """
     CODEC_MAP[charset] = codecname
 
@@ -203,8 +238,8 @@ class Charset:
     """
     def __init__(self, input_charset=DEFAULT_CHARSET):
         # RFC 2046, $4.1.2 says charsets are not case sensitive.  We coerce to
-        # unicode because its .lower() is locale insensitive.  If the argument
-        # is already a unicode, we leave it at that, but ensure that the
+        # str because its .lower() is locale insensitive.  If the argument
+        # is already a str, we leave it at that, but ensure that the
         # charset is ASCII, as the standard (RFC XXX) requires.
         try:
             if isinstance(input_charset, str):
@@ -215,7 +250,18 @@ def __init__(self, input_charset=DEFAULT_CHARSET):
             raise errors.CharsetError(input_charset)
         input_charset = input_charset.lower()
         # Set the input charset after filtering through the aliases
-        self.input_charset = ALIASES.get(input_charset, input_charset)
+        # For backward compatibility, try ALIASES first to let the user
+        # override it.
+        if input_charset in ALIASES:
+            input_charset = ALIASES[input_charset]
+        else:
+            try:
+                input_codec = codecs.lookup(input_charset).name
+            except LookupError:
+                pass
+            else:
+                input_charset = ALIASES.get(input_codec, input_codec)
+        self.input_charset = input_charset
         # We can try to guess which encoding and conversion to use by the
         # charset_map dictionary.  Try that first, but let the user override
         # it.
@@ -319,7 +365,7 @@ def header_encode_lines(self, string, maxlengths):
         # encoded word must stand on its own.  So the problem is you have to
         # encode to bytes to figure out this word's length, but you must split
         # on characters.  This causes two problems: first, we don't know how
-        # many octets a specific substring of unicode characters will get
+        # many octets a specific substring of characters will get
         # encoded to, and second, we don't know how many ASCII characters
         # those octets will get encoded to.  Unless we try it.  Which seems
         # inefficient.  In the interest of being correct rather than fast (and
diff --git a/Lib/email/contentmanager.py b/Lib/email/contentmanager.py
index 11d1536db27..c0090af7165 100644
--- a/Lib/email/contentmanager.py
+++ b/Lib/email/contentmanager.py
@@ -129,19 +129,6 @@ def _finalize_set(msg, disposition, filename, cid, params):
             msg.set_param(key, value)
 
 
-# XXX: This is a cleaned-up version of base64mime.body_encode (including a bug
-# fix in the calculation of unencoded_bytes_per_line).  It would be nice to
-# drop both this and quoprimime.body_encode in favor of enhanced binascii
-# routines that accepted a max_line_length parameter.
-def _encode_base64(data, max_line_length):
-    encoded_lines = []
-    unencoded_bytes_per_line = max_line_length // 4 * 3
-    for i in range(0, len(data), unencoded_bytes_per_line):
-        thisline = data[i:i+unencoded_bytes_per_line]
-        encoded_lines.append(binascii.b2a_base64(thisline).decode('ascii'))
-    return ''.join(encoded_lines)
-
-
 def _encode_text(string, charset, cte, policy):
     # If max_line_length is 0 or None, there is no limit.
     maxlen = policy.max_line_length or sys.maxsize
@@ -176,7 +163,7 @@ def normal_body(lines): return b'\n'.join(lines) + b'\n'
         data = quoprimime.body_encode(normal_body(lines).decode('latin-1'),
                                       maxlen)
     elif cte == 'base64':
-        data = _encode_base64(embedded_body(lines), maxlen)
+        data = binascii.b2a_base64(embedded_body(lines), wrapcol=maxlen).decode('ascii')
     else:
         raise ValueError("Unknown content transfer encoding {}".format(cte))
     return cte, data
@@ -186,11 +173,12 @@ def set_text_content(msg, string, subtype="plain", charset='utf-8', cte=None,
                      disposition=None, filename=None, cid=None,
                      params=None, headers=None):
     _prepare_set(msg, 'text', subtype, headers)
+
+    cs = email.charset.Charset(charset)
+    charset = cs.output_charset
     cte, payload = _encode_text(string, charset, cte, msg.policy)
     msg.set_payload(payload)
-    msg.set_param('charset',
-                  email.charset.ALIASES.get(charset, charset),
-                  replace=True)
+    msg.set_param('charset', charset, replace=True)
     msg['Content-Transfer-Encoding'] = cte
     _finalize_set(msg, disposition, filename, cid, params)
 raw_data_manager.add_set_handler(str, set_text_content)
@@ -234,7 +222,8 @@ def set_bytes_content(msg, data, maintype, subtype, cte='base64',
                      params=None, headers=None):
     _prepare_set(msg, maintype, subtype, headers)
     if cte == 'base64':
-        data = _encode_base64(data, max_line_length=msg.policy.max_line_length)
+        data = binascii.b2a_base64(data, wrapcol=msg.policy.max_line_length)
+        data = data.decode('ascii')
     elif cte == 'quoted-printable':
         # XXX: quoprimime.body_encode won't encode newline characters in data,
         # so we can't use it.  This means max_line_length is ignored.  Another
diff --git a/Lib/email/errors.py b/Lib/email/errors.py
index 6bc744bd59c..859307dd85b 100644
--- a/Lib/email/errors.py
+++ b/Lib/email/errors.py
@@ -109,9 +109,9 @@ class ObsoleteHeaderDefect(HeaderDefect):
     """Header uses syntax declared obsolete by RFC 5322"""
 
 class NonASCIILocalPartDefect(HeaderDefect):
-    """local_part contains non-ASCII characters"""
-    # This defect only occurs during unicode parsing, not when
-    # parsing messages decoded from binary.
+    """Unused. Note: this error is deprecated and may be removed in the future."""
+    # RFC 6532 permits a non-ASCII local-part. _header_value_parser previously
+    # treated this as a parse-time defect (when parsing Unicode, but not bytes).
 
 class InvalidDateDefect(HeaderDefect):
     """Header has unparsable or invalid date"""
diff --git a/Lib/email/header.py b/Lib/email/header.py
index 220a84a7454..ea1f84ea964 100644
--- a/Lib/email/header.py
+++ b/Lib/email/header.py
@@ -189,7 +189,7 @@ def __init__(self, s=None, charset=None,
 
         Optional s is the initial header value.  If None, the initial header
         value is not set.  You can later append to the header with .append()
-        method calls.  s may be a byte string or a Unicode string, but see the
+        method calls.  s may be a byte string or a string, but see the
         .append() documentation for semantics.
 
         Optional charset serves two purposes: it has the same meaning as the
@@ -263,7 +263,7 @@ def __str__(self):
     # have or explicitly disable <, <=, >, >= operators?
     def __eq__(self, other):
         # other may be a Header or a string.  Both are fine so coerce
-        # ourselves to a unicode (of the unencoded header value), swap the
+        # ourselves to a str (of the unencoded header value), swap the
         # args and do another comparison.
         return other == str(self)
 
@@ -275,10 +275,10 @@ def append(self, s, charset=None, errors='strict'):
         value of None (the default) means that the charset given in the
         constructor is used.
 
-        s may be a byte string or a Unicode string.  If it is a byte string
+        s may be a byte string or a string.  If it is a byte string
         (i.e. isinstance(s, str) is false), then charset is the encoding of
         that byte string, and a UnicodeError will be raised if the string
-        cannot be decoded with that charset.  If s is a Unicode string, then
+        cannot be decoded with that charset.  If s is a string, then
         charset is a hint specifying the character set of the characters in
         the string.  In either case, when producing an RFC 2822 compliant
         header using RFC 2047 rules, the string will be encoded using the
@@ -397,7 +397,7 @@ def encode(self, splitchars=';, \t', maxlinelen=None, linesep='\n'):
 
     def _normalize(self):
         # Step 1: Normalize the chunks so that all runs of identical charsets
-        # get collapsed into a single unicode string.
+        # get collapsed into a single string.
         chunks = []
         last_charset = None
         last_chunk = []
diff --git a/Lib/email/headerregistry.py b/Lib/email/headerregistry.py
index 0e8698efc0b..48cd85a65ba 100644
--- a/Lib/email/headerregistry.py
+++ b/Lib/email/headerregistry.py
@@ -3,8 +3,6 @@
 This module provides an implementation of the HeaderRegistry API.
 The implementation is designed to flexibly follow RFC5322 rules.
 """
-from types import MappingProxyType
-
 from email import utils
 from email import errors
 from email import _header_value_parser as parser
@@ -462,7 +460,7 @@ def init(self, *args, **kw):
 
     @property
     def params(self):
-        return MappingProxyType(self._params)
+        return frozendict(self._params)
 
 
 class ContentTypeHeader(ParameterizedMIMEHeader):
diff --git a/Lib/email/message.py b/Lib/email/message.py
index 641fb2e944d..64e6c1e23cf 100644
--- a/Lib/email/message.py
+++ b/Lib/email/message.py
@@ -98,7 +98,7 @@ def _parseparam(s):
 
 def _unquotevalue(value):
     # This is different than utils.collapse_rfc2231_value() because it doesn't
-    # try to convert the value to a unicode.  Message.get_param() and
+    # try to convert the value to a str.  Message.get_param() and
     # Message.get_params() are both currently defined to return the tuple in
     # the face of RFC 2231 parameters.
     if isinstance(value, tuple):
@@ -182,7 +182,7 @@ def as_string(self, unixfrom=False, maxheaderlen=0, policy=None):
 
         If the message object contains binary data that is not encoded
         according to RFC standards, the non-compliant data will be replaced by
-        unicode "unknown character" code points.
+        Unicode "unknown character" code points.
         """
         from email.generator import Generator
         policy = self.policy if policy is None else policy
@@ -315,7 +315,7 @@ def get_payload(self, i=None, decode=False):
                 bpayload = payload.encode('ascii', 'surrogateescape')
             except UnicodeEncodeError:
                 # This won't happen for RFC compliant messages (messages
-                # containing only ASCII code points in the unicode input).
+                # containing only ASCII code points in the string input).
                 # If it does happen, turn the string into bytes in a way
                 # guaranteed not to fail.
                 bpayload = payload.encode('raw-unicode-escape')
@@ -395,7 +395,7 @@ def set_charset(self, charset):
             try:
                 cte(self)
             except TypeError:
-                # This 'if' is for backward compatibility, it allows unicode
+                # This 'if' is for backward compatibility, it allows str
                 # through even though that won't work correctly if the
                 # message is serialized.
                 payload = self._payload
diff --git a/Lib/email/policy.py b/Lib/email/policy.py
index 4169150101a..d09d2f5238d 100644
--- a/Lib/email/policy.py
+++ b/Lib/email/policy.py
@@ -160,7 +160,7 @@ def header_fetch_parse(self, name, value):
         Otherwise the name and the value with any linesep characters removed
         are passed to the header_factory method, and the resulting custom
         header object is returned.  Any surrogateescaped bytes get turned
-        into the unicode unknown-character glyph.
+        into the Unicode unknown-character glyph.
 
         """
         if hasattr(value, 'name'):
@@ -201,7 +201,7 @@ def fold_binary(self, name, value):
         data consists of single byte characters or multibyte characters.
 
         If utf8 is true, headers are encoded to utf8, otherwise to ascii with
-        non-ASCII unicode rendered as encoded words.
+        non-ASCII characters rendered as encoded words.
 
         """
         folded = self._fold(name, value, refold_binary=self.cte_type=='7bit')
diff --git a/Lib/email/utils.py b/Lib/email/utils.py
index 5838a808568..cea21b856d4 100644
--- a/Lib/email/utils.py
+++ b/Lib/email/utils.py
@@ -58,7 +58,7 @@ def _has_surrogates(s):
 # How to deal with a string containing bytes before handing it to the
 # application through the 'normal' interface.
 def _sanitize(string):
-    # Turn any escaped bytes into unicode 'unknown' char.  If the escaped
+    # Turn any escaped bytes into the Unicode 'unknown' char.  If the escaped
     # bytes happen to be utf-8 they will instead get decoded, even if they
     # were invalid in the charset the source was supposed to be in.  This
     # seems like it is not a bad thing; a defect was still registered.
@@ -453,7 +453,7 @@ def collapse_rfc2231_value(value, errors='replace',
                            fallback_charset='us-ascii'):
     if not isinstance(value, tuple) or len(value) != 3:
         return unquote(value)
-    # While value comes to us as a unicode string, we need it to be a bytes
+    # While value comes to us as a string, we need it to be a bytes
     # object.  We do not want bytes() normal utf-8 decoder, we want a straight
     # interpretation of the string as character bytes.
     charset, language, text = value
@@ -463,6 +463,10 @@ def collapse_rfc2231_value(value, errors='replace',
         charset = fallback_charset
     rawbytes = bytes(text, 'raw-unicode-escape')
     try:
+        # Explicitly look up the codec for warning generation, see gh-140030
+        # Can be removed in 3.17
+        import codecs
+        codecs.lookup(charset)
         return str(rawbytes, charset, errors)
     except LookupError:
         # charset is not a known codec.
diff --git a/Lib/encodings/__init__.py b/Lib/encodings/__init__.py
index 8548bbe04ad..169c48324f2 100644
--- a/Lib/encodings/__init__.py
+++ b/Lib/encodings/__init__.py
@@ -26,10 +26,11 @@
 
 (c) Copyright CNRI, All Rights Reserved. NO WARRANTY.
 
-"""#"
+"""
 
 import codecs
 import sys
+from _codecs import _normalize_encoding
 from . import aliases
 
 _cache = {}
@@ -56,18 +57,13 @@ def normalize_encoding(encoding):
     if isinstance(encoding, bytes):
         encoding = str(encoding, "ascii")
 
-    chars = []
-    punct = False
-    for c in encoding:
-        if c.isalnum() or c == '.':
-            if punct and chars:
-                chars.append('_')
-            if c.isascii():
-                chars.append(c)
-            punct = False
-        else:
-            punct = True
-    return ''.join(chars)
+    if not encoding.isascii():
+        import warnings
+        warnings.warn(
+            "Support for non-ascii encoding names will be removed in 3.17",
+            DeprecationWarning, stacklevel=2)
+
+    return _normalize_encoding(encoding)
 
 def search_function(encoding):
 
diff --git a/Lib/encodings/aliases.py b/Lib/encodings/aliases.py
index 8b175772c58..ef51168d755 100644
--- a/Lib/encodings/aliases.py
+++ b/Lib/encodings/aliases.py
@@ -17,7 +17,7 @@
 """
 aliases = {
 
-    # Please keep this list sorted alphabetically by value !
+    # Please keep this list sorted alphabetically by value!
 
     # ascii codec
     '646'                : 'ascii',
@@ -43,6 +43,7 @@
 
     # big5hkscs codec
     'big5_hkscs'         : 'big5hkscs',
+    'csbig5hkscs'        : 'big5hkscs',
     'hkscs'              : 'big5hkscs',
 
     # bz2_codec codec
@@ -71,6 +72,7 @@
 
     # cp1140 codec
     '1140'               : 'cp1140',
+    'ccsid01140'         : 'cp1140',
     'cp01140'            : 'cp1140',
     'csibm01140'         : 'cp1140',
     'ebcdic_us_37_euro'  : 'cp1140',
@@ -79,38 +81,47 @@
 
     # cp1250 codec
     '1250'               : 'cp1250',
+    'cswindows1250'      : 'cp1250',
     'windows_1250'       : 'cp1250',
 
     # cp1251 codec
     '1251'               : 'cp1251',
+    'cswindows1251'      : 'cp1251',
     'windows_1251'       : 'cp1251',
 
     # cp1252 codec
     '1252'               : 'cp1252',
+    'cswindows1252'      : 'cp1252',
     'windows_1252'       : 'cp1252',
 
     # cp1253 codec
     '1253'               : 'cp1253',
+    'cswindows1253'      : 'cp1253',
     'windows_1253'       : 'cp1253',
 
     # cp1254 codec
     '1254'               : 'cp1254',
+    'cswindows1254'      : 'cp1254',
     'windows_1254'       : 'cp1254',
 
     # cp1255 codec
     '1255'               : 'cp1255',
+    'cswindows1255'      : 'cp1255',
     'windows_1255'       : 'cp1255',
 
     # cp1256 codec
     '1256'               : 'cp1256',
+    'cswindows1256'      : 'cp1256',
     'windows_1256'       : 'cp1256',
 
     # cp1257 codec
     '1257'               : 'cp1257',
+    'cswindows1257'      : 'cp1257',
     'windows_1257'       : 'cp1257',
 
     # cp1258 codec
     '1258'               : 'cp1258',
+    'cswindows1258'      : 'cp1258',
     'windows_1258'       : 'cp1258',
 
     # cp273 codec
@@ -163,6 +174,7 @@
 
     # cp858 codec
     '858'                : 'cp858',
+    'ccsid00858'         : 'cp858',
     'cp00858'            : 'cp858',
     'csibm00858'         : 'cp858',
     'csibm858'           : 'cp858',
@@ -214,11 +226,13 @@
 
     # cp874 codec
     '874'                : 'cp874',
+    'cswindows874'       : 'cp874',
     'ms874'              : 'cp874',
     'windows_874'        : 'cp874',
 
     # cp932 codec
     '932'                : 'cp932',
+    'cswindows31j'       : 'cp932',
     'ms932'              : 'cp932',
     'mskanji'            : 'cp932',
     'ms_kanji'           : 'cp932',
@@ -226,6 +240,16 @@
 
     # cp949 codec
     '949'                : 'cp949',
+    'csksc56011987'      : 'cp949',
+    'iso_ir_149'         : 'cp949',
+    'korean'             : 'cp949',
+    'ks_c_5601_1987'     : 'cp949',
+    'ks_c_5601_1989'     : 'cp949',
+    'ksc5601'            : 'cp949',
+    'ks_c_5601'          : 'cp949',
+    'ksc_5601'           : 'cp949',
+    'ksx1001'            : 'cp949',
+    'ks_x_1001'          : 'cp949',
     'ms949'              : 'cp949',
     'uhc'                : 'cp949',
 
@@ -242,47 +266,47 @@
     'eucjisx0213'        : 'euc_jisx0213',
 
     # euc_jp codec
+    'cseucpkdfmtjapanese' : 'euc_jp',
     'eucjp'              : 'euc_jp',
     'ujis'               : 'euc_jp',
     'u_jis'              : 'euc_jp',
 
     # euc_kr codec
-    'euckr'              : 'euc_kr',
-    'korean'             : 'euc_kr',
-    'ksc5601'            : 'euc_kr',
-    'ks_c_5601'          : 'euc_kr',
-    'ks_c_5601_1987'     : 'euc_kr',
-    'ksx1001'            : 'euc_kr',
-    'ks_x_1001'          : 'euc_kr',
     'cseuckr'            : 'euc_kr',
+    'euckr'              : 'euc_kr',
 
     # gb18030 codec
+    'csgb18030'          : 'gb18030',
     'gb18030_2000'       : 'gb18030',
 
     # gb2312 codec
     'chinese'            : 'gb2312',
+    'csgb2312'           : 'gb2312',
     'csiso58gb231280'    : 'gb2312',
     'euc_cn'             : 'gb2312',
     'euccn'              : 'gb2312',
     'eucgb2312_cn'       : 'gb2312',
     'gb2312_1980'        : 'gb2312',
     'gb2312_80'          : 'gb2312',
+    'gb_2312_80'         : 'gb2312',
     'iso_ir_58'          : 'gb2312',
 
     # gbk codec
     '936'                : 'gbk',
     'cp936'              : 'gbk',
+    'csgbk'              : 'gbk',
     'ms936'              : 'gbk',
+    'windows_936'        : 'gbk',
 
     # hex_codec codec
     'hex'                : 'hex_codec',
 
     # hp_roman8 codec
-    'roman8'             : 'hp_roman8',
-    'r8'                 : 'hp_roman8',
-    'csHPRoman8'         : 'hp_roman8',
     'cp1051'             : 'hp_roman8',
+    'cshproman8'         : 'hp_roman8',
     'ibm1051'            : 'hp_roman8',
+    'r8'                 : 'hp_roman8',
+    'roman8'             : 'hp_roman8',
 
     # hz codec
     'hzgb'               : 'hz',
@@ -299,6 +323,7 @@
     'iso_2022_jp_1'      : 'iso2022_jp_1',
 
     # iso2022_jp_2 codec
+    'csiso2022jp2'       : 'iso2022_jp_2',
     'iso2022jp_2'        : 'iso2022_jp_2',
     'iso_2022_jp_2'      : 'iso2022_jp_2',
 
@@ -326,6 +351,7 @@
     'iso_ir_157'         : 'iso8859_10',
     'l6'                 : 'iso8859_10',
     'latin6'             : 'iso8859_10',
+    'latin_6'            : 'iso8859_10',
 
     # iso8859_11 codec
     'thai'               : 'iso8859_11',
@@ -333,29 +359,37 @@
     'iso_8859_11_2001'   : 'iso8859_11',
 
     # iso8859_13 codec
+    'csiso885913'        : 'iso8859_13',
     'iso_8859_13'        : 'iso8859_13',
     'l7'                 : 'iso8859_13',
     'latin7'             : 'iso8859_13',
+    'latin_7'            : 'iso8859_13',
 
     # iso8859_14 codec
+    'csiso885914'        : 'iso8859_14',
     'iso_8859_14'        : 'iso8859_14',
     'iso_8859_14_1998'   : 'iso8859_14',
     'iso_celtic'         : 'iso8859_14',
     'iso_ir_199'         : 'iso8859_14',
     'l8'                 : 'iso8859_14',
     'latin8'             : 'iso8859_14',
+    'latin_8'            : 'iso8859_14',
 
     # iso8859_15 codec
+    'csiso885915'        : 'iso8859_15',
     'iso_8859_15'        : 'iso8859_15',
     'l9'                 : 'iso8859_15',
     'latin9'             : 'iso8859_15',
+    'latin_9'            : 'iso8859_15',
 
     # iso8859_16 codec
+    'csiso885916'        : 'iso8859_16',
     'iso_8859_16'        : 'iso8859_16',
     'iso_8859_16_2001'   : 'iso8859_16',
     'iso_ir_226'         : 'iso8859_16',
     'l10'                : 'iso8859_16',
     'latin10'            : 'iso8859_16',
+    'latin_10'           : 'iso8859_16',
 
     # iso8859_2 codec
     'csisolatin2'        : 'iso8859_2',
@@ -364,6 +398,7 @@
     'iso_ir_101'         : 'iso8859_2',
     'l2'                 : 'iso8859_2',
     'latin2'             : 'iso8859_2',
+    'latin_2'            : 'iso8859_2',
 
     # iso8859_3 codec
     'csisolatin3'        : 'iso8859_3',
@@ -372,6 +407,7 @@
     'iso_ir_109'         : 'iso8859_3',
     'l3'                 : 'iso8859_3',
     'latin3'             : 'iso8859_3',
+    'latin_3'            : 'iso8859_3',
 
     # iso8859_4 codec
     'csisolatin4'        : 'iso8859_4',
@@ -380,6 +416,7 @@
     'iso_ir_110'         : 'iso8859_4',
     'l4'                 : 'iso8859_4',
     'latin4'             : 'iso8859_4',
+    'latin_4'            : 'iso8859_4',
 
     # iso8859_5 codec
     'csisolatincyrillic' : 'iso8859_5',
@@ -408,6 +445,8 @@
     'iso_ir_126'         : 'iso8859_7',
 
     # iso8859_8 codec
+    'csiso88598e'        : 'iso8859_8',
+    'csiso88598i'        : 'iso8859_8',
     'csisolatinhebrew'   : 'iso8859_8',
     'hebrew'             : 'iso8859_8',
     'iso_8859_8'         : 'iso8859_8',
@@ -423,6 +462,7 @@
     'iso_ir_148'         : 'iso8859_9',
     'l5'                 : 'iso8859_9',
     'latin5'             : 'iso8859_9',
+    'latin_5'            : 'iso8859_9',
 
     # johab codec
     'cp1361'             : 'johab',
@@ -431,7 +471,11 @@
     # koi8_r codec
     'cskoi8r'            : 'koi8_r',
 
+    # koi8_u codec
+    'cskoi8u'            : 'koi8_u',
+
     # kz1048 codec
+    'cskz1048'          : 'kz1048',
     'kz_1048'           : 'kz1048',
     'rk1048'            : 'kz1048',
     'strk1048_2002'     : 'kz1048',
@@ -471,7 +515,9 @@
     'maclatin2'          : 'mac_latin2',
 
     # mac_roman codec
+    'csmacintosh'        : 'mac_roman',
     'macintosh'          : 'mac_roman',
+    'mac'                : 'mac_roman',
     'macroman'           : 'mac_roman',
 
     # mac_turkish codec
@@ -512,6 +558,7 @@
     's_jisx0213'         : 'shift_jisx0213',
 
     # tis_620 codec
+    'cstis620'           : 'tis_620',
     'tis620'             : 'tis_620',
     'tis_620_0'          : 'tis_620',
     'tis_620_2529_0'     : 'tis_620',
@@ -519,33 +566,42 @@
     'iso_ir_166'         : 'tis_620',
 
     # utf_16 codec
+    'csutf16'            : 'utf_16',
     'u16'                : 'utf_16',
     'utf16'              : 'utf_16',
 
     # utf_16_be codec
+    'csutf16be'          : 'utf_16_be',
     'unicodebigunmarked' : 'utf_16_be',
     'utf_16be'           : 'utf_16_be',
 
     # utf_16_le codec
+    'csutf16le'          : 'utf_16_le',
     'unicodelittleunmarked' : 'utf_16_le',
     'utf_16le'           : 'utf_16_le',
 
     # utf_32 codec
+    'csutf32'            : 'utf_32',
     'u32'                : 'utf_32',
     'utf32'              : 'utf_32',
 
     # utf_32_be codec
+    'csutf32be'          : 'utf_32_be',
     'utf_32be'           : 'utf_32_be',
 
     # utf_32_le codec
+    'csutf32le'          : 'utf_32_le',
     'utf_32le'           : 'utf_32_le',
 
     # utf_7 codec
+    'csunicode11utf7'    : 'utf_7',
+    'csutf7'             : 'utf_7',
     'u7'                 : 'utf_7',
     'utf7'               : 'utf_7',
     'unicode_1_1_utf_7'  : 'utf_7',
 
     # utf_8 codec
+    'csutf8'             : 'utf_8',
     'u8'                 : 'utf_8',
     'utf'                : 'utf_8',
     'utf8'               : 'utf_8',
@@ -553,6 +609,9 @@
     'utf8_ucs4'          : 'utf_8',
     'cp65001'            : 'utf_8',
 
+    # utf_8_sig codec
+    'utf8_sig'           : 'utf_8_sig',
+
     # uu_codec codec
     'uu'                 : 'uu_codec',
 
diff --git a/Lib/encodings/idna.py b/Lib/encodings/idna.py
index 0c90b4c9fe1..d31ee07ab45 100644
--- a/Lib/encodings/idna.py
+++ b/Lib/encodings/idna.py
@@ -226,7 +226,8 @@ def encode(self, input, errors='strict'):
                     offset + exc.end,
                     exc.reason,
                 )
-        return bytes(result+trailing_dot), len(input)
+        result += trailing_dot
+        return result.take_bytes(), len(input)
 
     def decode(self, input, errors='strict'):
 
@@ -311,7 +312,7 @@ def _buffer_encode(self, input, errors, final):
 
         result += trailing_dot
         size += len(trailing_dot)
-        return (bytes(result), size)
+        return (result.take_bytes(), size)
 
 class IncrementalDecoder(codecs.BufferedIncrementalDecoder):
     def _buffer_decode(self, input, errors, final):
diff --git a/Lib/encodings/punycode.py b/Lib/encodings/punycode.py
index 4622fc8c920..268fccbd539 100644
--- a/Lib/encodings/punycode.py
+++ b/Lib/encodings/punycode.py
@@ -17,7 +17,7 @@ def segregate(str):
         else:
             extended.add(c)
     extended = sorted(extended)
-    return bytes(base), extended
+    return base.take_bytes(), extended
 
 def selective_len(str, max):
     """Return the length of str, considering only characters below max."""
@@ -83,7 +83,7 @@ def generate_generalized_integer(N, bias):
         t = T(j, bias)
         if N < t:
             result.append(digits[N])
-            return bytes(result)
+            return result.take_bytes()
         result.append(digits[t + ((N - t) % (36 - t))])
         N = (N - t) // (36 - t)
         j += 1
@@ -112,7 +112,7 @@ def generate_integers(baselen, deltas):
         s = generate_generalized_integer(delta, bias)
         result.extend(s)
         bias = adapt(delta, points==0, baselen+points+1)
-    return bytes(result)
+    return result.take_bytes()
 
 def punycode_encode(text):
     base, extended = segregate(text)
diff --git a/Lib/encodings/uu_codec.py b/Lib/encodings/uu_codec.py
index 4e58c62fe9e..4f8704016e2 100644
--- a/Lib/encodings/uu_codec.py
+++ b/Lib/encodings/uu_codec.py
@@ -56,7 +56,7 @@ def uu_decode(input, errors='strict'):
             break
         try:
             data = binascii.a2b_uu(s)
-        except binascii.Error as v:
+        except binascii.Error:
             # Workaround for broken uuencoders by /Fredrik Lundh
             nbytes = (((s[0]-32) & 63) * 4 + 5) // 3
             data = binascii.a2b_uu(s[:nbytes])
diff --git a/Lib/enum.py b/Lib/enum.py
index 87b2f2ab7eb..f536a3eae2b 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -10,14 +10,15 @@
         'FlagBoundary', 'STRICT', 'CONFORM', 'EJECT', 'KEEP',
         'global_flag_repr', 'global_enum_repr', 'global_str', 'global_enum',
         'EnumCheck', 'CONTINUOUS', 'NAMED_FLAGS', 'UNIQUE',
-        'pickle_by_global_name', 'pickle_by_enum_name',
+        'pickle_by_global_name', 'pickle_by_enum_name', 'show_flag_values',
+        'bin',
         ]
 
 
 # Dummy value for Enum and Flag as there are explicit checks for them
 # before they have been created.
 # This is also why there are checks in EnumType like `if Enum is not None`
-Enum = Flag = EJECT = _stdlib_enums = ReprEnum = None
+Enum = Flag = EJECT = ReprEnum = None
 
 class nonmember(object):
     """
@@ -536,7 +537,7 @@ def __new__(metacls, cls, bases, classdict, *, boundary=None, _simple=False, **k
         # now set the __repr__ for the value
         classdict['_value_repr_'] = metacls._find_data_repr_(cls, bases)
         #
-        # Flag structures (will be removed if final class is not a Flag
+        # Flag structures (will be removed if final class is not a Flag)
         classdict['_boundary_'] = (
                 boundary
                 or getattr(first_enum, '_boundary_', None)
@@ -545,6 +546,29 @@ def __new__(metacls, cls, bases, classdict, *, boundary=None, _simple=False, **k
         classdict['_singles_mask_'] = 0
         classdict['_all_bits_'] = 0
         classdict['_inverted_'] = None
+        # check for negative flag values and invert if found (using _proto_members)
+        if Flag is not None and bases and issubclass(bases[-1], Flag):
+            bits = 0
+            inverted = []
+            for n in member_names:
+                p = classdict[n]
+                if isinstance(p.value, int):
+                    if p.value < 0:
+                        inverted.append(p)
+                    else:
+                        bits |= p.value
+                elif p.value is None:
+                    pass
+                elif isinstance(p.value, tuple) and p.value and isinstance(p.value[0], int):
+                    if p.value[0] < 0:
+                        inverted.append(p)
+                    else:
+                        bits |= p.value[0]
+            for p in inverted:
+                if isinstance(p.value, int):
+                    p.value = bits & p.value
+                else:
+                    p.value = (bits & p.value[0], ) + p.value[1:]
         try:
             classdict['_%s__in_progress' % cls] = True
             enum_class = super().__new__(metacls, cls, bases, classdict, **kwds)
@@ -752,12 +776,16 @@ def __delattr__(cls, attr):
         super().__delattr__(attr)
 
     def __dir__(cls):
+        if issubclass(cls, Flag):
+            members = list(cls._member_map_.keys())
+        else:
+            members = cls._member_names_
         interesting = set([
                 '__class__', '__contains__', '__doc__', '__getitem__',
                 '__iter__', '__len__', '__members__', '__module__',
                 '__name__', '__qualname__',
                 ]
-                + cls._member_names_
+                + members
                 )
         if cls._new_member_ is not object.__new__:
             interesting.add('__new__')
@@ -1489,7 +1517,10 @@ def _missing_(cls, value):
                         )
         if value < 0:
             neg_value = value
-            value = all_bits + 1 + value
+            if cls._boundary_ in (EJECT, KEEP):
+                value = all_bits + 1 + value
+            else:
+                value = singles_mask & value
         # get members and unknown
         unknown = value & ~flag_mask
         aliases = value & ~singles_mask
@@ -2165,5 +2196,3 @@ def _old_convert_(etype, name, module, filter, source=None, *, boundary=None):
         members.sort(key=lambda t: t[0])
     cls = etype(name, members, module=module, boundary=boundary or KEEP)
     return cls
-
-_stdlib_enums = IntEnum, StrEnum, IntFlag
diff --git a/Lib/fractions.py b/Lib/fractions.py
index a497ee19935..c1b12e7a1c0 100644
--- a/Lib/fractions.py
+++ b/Lib/fractions.py
@@ -242,11 +242,6 @@ def __new__(cls, numerator=0, denominator=None):
                 self._denominator = 1
                 return self
 
-            elif isinstance(numerator, numbers.Rational):
-                self._numerator = numerator.numerator
-                self._denominator = numerator.denominator
-                return self
-
             elif (isinstance(numerator, float) or
                   (not isinstance(numerator, type) and
                    hasattr(numerator, 'as_integer_ratio'))):
@@ -282,6 +277,11 @@ def __new__(cls, numerator=0, denominator=None):
                 if m.group('sign') == '-':
                     numerator = -numerator
 
+            elif isinstance(numerator, numbers.Rational):
+                self._numerator = numerator.numerator
+                self._denominator = numerator.denominator
+                return self
+
             else:
                 raise TypeError("argument should be a string or a Rational "
                                 "instance or have the as_integer_ratio() method")
diff --git a/Lib/functools.py b/Lib/functools.py
index e8ccc2795d2..c5aaa15f3d5 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -19,7 +19,7 @@
 # import weakref  # Deferred to single_dispatch()
 from operator import itemgetter
 from reprlib import recursive_repr
-from types import GenericAlias, MethodType, MappingProxyType, UnionType
+from types import FunctionType, GenericAlias, MethodType, MappingProxyType, UnionType
 from _thread import RLock
 
 ################################################################################
@@ -170,7 +170,7 @@ def _lt_from_ge(self, other):
         return op_result
     return not op_result
 
-_convert = {
+_convert = frozendict({
     '__lt__': [('__gt__', _gt_from_lt),
                ('__le__', _le_from_lt),
                ('__ge__', _ge_from_lt)],
@@ -183,7 +183,7 @@ def _lt_from_ge(self, other):
     '__ge__': [('__le__', _le_from_ge),
                ('__gt__', _gt_from_ge),
                ('__lt__', _lt_from_ge)]
-}
+})
 
 def total_ordering(cls):
     """Class decorator that fills in missing ordering methods"""
@@ -232,7 +232,7 @@ def __ge__(self, other):
 ### reduce() sequence to a single item
 ################################################################################
 
-_initial_missing = object()
+_initial_missing = sentinel('_initial_missing')
 
 def reduce(function, sequence, initial=_initial_missing):
     """
@@ -517,7 +517,7 @@ def _unwrap_partialmethod(func):
 ### LRU Cache function decorator
 ################################################################################
 
-_CacheInfo = namedtuple("CacheInfo", ["hits", "misses", "maxsize", "currsize"])
+_CacheInfo = namedtuple("CacheInfo", ("hits", "misses", "maxsize", "currsize"))
 
 def _make_key(args, kwds, typed,
              kwd_mark = (object(),),
@@ -539,13 +539,15 @@ def _make_key(args, kwds, typed,
     # distinct call from f(y=2, x=1) which will be cached separately.
     key = args
     if kwds:
+        key = list(key)
         key += kwd_mark
         for item in kwds.items():
             key += item
+        key = tuple(key)
     if typed:
-        key += tuple(type(v) for v in args)
+        key += tuple([type(v) for v in args])
         if kwds:
-            key += tuple(type(v) for v in kwds.values())
+            key += tuple([type(v) for v in kwds.values()])
     elif len(key) == 1 and type(key[0]) in fasttypes:
         return key[0]
     return key
@@ -580,12 +582,14 @@ def lru_cache(maxsize=128, typed=False):
         # Negative maxsize is treated as 0
         if maxsize < 0:
             maxsize = 0
+
     elif callable(maxsize) and isinstance(typed, bool):
         # The user_function was passed in directly via the maxsize argument
         user_function, maxsize = maxsize, 128
         wrapper = _lru_cache_wrapper(user_function, maxsize, typed, _CacheInfo)
         wrapper.cache_parameters = lambda : {'maxsize': maxsize, 'typed': typed}
         return update_wrapper(wrapper, user_function)
+
     elif maxsize is not None:
         raise TypeError(
             'Expected first argument to be an integer, a callable, or None')
@@ -598,6 +602,9 @@ def decorating_function(user_function):
     return decorating_function
 
 def _lru_cache_wrapper(user_function, maxsize, typed, _CacheInfo):
+    if not callable(user_function):
+        raise TypeError("the first argument must be callable")
+
     # Constants shared by all lru cache instances:
     sentinel = object()          # unique object used to signal cache misses
     make_key = _make_key         # build a key from the function arguments
@@ -617,6 +624,7 @@ def _lru_cache_wrapper(user_function, maxsize, typed, _CacheInfo):
         def wrapper(*args, **kwds):
             # No caching -- just a statistics update
             nonlocal misses
+
             misses += 1
             result = user_function(*args, **kwds)
             return result
@@ -626,6 +634,7 @@ def wrapper(*args, **kwds):
         def wrapper(*args, **kwds):
             # Simple caching without ordering or size limit
             nonlocal hits, misses
+
             key = make_key(args, kwds, typed)
             result = cache_get(key, sentinel)
             if result is not sentinel:
@@ -641,7 +650,9 @@ def wrapper(*args, **kwds):
         def wrapper(*args, **kwds):
             # Size limited caching that tracks accesses by recency
             nonlocal root, hits, misses, full
+
             key = make_key(args, kwds, typed)
+
             with lock:
                 link = cache_get(key)
                 if link is not None:
@@ -656,7 +667,9 @@ def wrapper(*args, **kwds):
                     hits += 1
                     return result
                 misses += 1
+
             result = user_function(*args, **kwds)
+
             with lock:
                 if key in cache:
                     # Getting here means that this same key was added to the
@@ -664,11 +677,13 @@ def wrapper(*args, **kwds):
                     # update is already done, we need only return the
                     # computed result and update the count of misses.
                     pass
+
                 elif full:
                     # Use the old root to store the new key and result.
                     oldroot = root
                     oldroot[KEY] = key
                     oldroot[RESULT] = result
+
                     # Empty the oldest link and make it the new root.
                     # Keep a reference to the old key and old result to
                     # prevent their ref counts from going to zero during the
@@ -677,22 +692,27 @@ def wrapper(*args, **kwds):
                     # still adjusting the links.
                     root = oldroot[NEXT]
                     oldkey = root[KEY]
-                    oldresult = root[RESULT]
+                    oldresult = root[RESULT]  # noqa: F841
                     root[KEY] = root[RESULT] = None
+
                     # Now update the cache dictionary.
                     del cache[oldkey]
+
                     # Save the potentially reentrant cache[key] assignment
                     # for last, after the root and links have been put in
                     # a consistent state.
                     cache[key] = oldroot
+
                 else:
                     # Put result in a new link at the front of the queue.
                     last = root[PREV]
                     link = [last, root, key, result]
                     last[NEXT] = root[PREV] = cache[key] = link
+
                     # Use the cache_len bound method instead of the len() function
                     # which could potentially be wrapped in an lru_cache itself.
                     full = (cache_len() >= maxsize)
+
             return result
 
     def cache_info():
@@ -703,6 +723,7 @@ def cache_info():
     def cache_clear():
         """Clear the cache and cache statistics"""
         nonlocal hits, misses, full
+
         with lock:
             cache.clear()
             root[:] = [root, root, None, None]
@@ -995,7 +1016,8 @@ def wrapper(*args, **kw):
 class singledispatchmethod:
     """Single-dispatch generic method descriptor.
 
-    Supports wrapping existing descriptors.
+    Supports wrapping existing descriptors and handles non-descriptor
+    callables as instance methods.
     """
 
     def __init__(self, func):
@@ -1038,6 +1060,11 @@ def __init__(self, unbound, obj, cls):
         # Set instance attributes which cannot be handled in __getattr__()
         # because they conflict with type descriptors.
         func = unbound.func
+
+        # Dispatch on the second argument if a generic method turns into
+        # a bound method on instance-level access. See GH-143535.
+        self._dispatch_arg_index = 1 if obj is None and isinstance(func, FunctionType) else 0
+
         try:
             self.__module__ = func.__module__
         except AttributeError:
@@ -1066,7 +1093,23 @@ def __call__(self, /, *args, **kwargs):
                                'singledispatchmethod method')
             raise TypeError(f'{funcname} requires at least '
                             '1 positional argument')
-        return self._dispatch(args[0].__class__).__get__(self._obj, self._cls)(*args, **kwargs)
+        method = self._dispatch(args[self._dispatch_arg_index].__class__)
+
+        if hasattr(method, "__get__"):
+            # If the method is a descriptor, it might be necessary
+            # to drop the first argument before calling
+            # as it can be no longer expected after descriptor access.
+            skip_bound_arg = False
+            if isinstance(method, staticmethod):
+                skip_bound_arg = self._dispatch_arg_index == 1
+
+            method = method.__get__(self._obj, self._cls)
+            if isinstance(method, MethodType):
+                skip_bound_arg = self._dispatch_arg_index == 1
+
+            if skip_bound_arg:
+                return method(*args[1:], **kwargs)
+        return method(*args, **kwargs)
 
     def __getattr__(self, name):
         # Resolve these attributes lazily to speed up creation of
diff --git a/Lib/genericpath.py b/Lib/genericpath.py
index 9363f564aab..71ae1919083 100644
--- a/Lib/genericpath.py
+++ b/Lib/genericpath.py
@@ -8,7 +8,8 @@
 
 __all__ = ['commonprefix', 'exists', 'getatime', 'getctime', 'getmtime',
            'getsize', 'isdevdrive', 'isdir', 'isfile', 'isjunction', 'islink',
-           'lexists', 'samefile', 'sameopenfile', 'samestat', 'ALLOW_MISSING']
+           'lexists', 'samefile', 'sameopenfile', 'samestat',
+           'ALL_BUT_LAST', 'ALLOW_MISSING']
 
 
 # Does a path exist?
@@ -81,29 +82,38 @@ def isdevdrive(path):
     return False
 
 
-def getsize(filename):
+def getsize(filename, /):
     """Return the size of a file, reported by os.stat()."""
     return os.stat(filename).st_size
 
 
-def getmtime(filename):
+def getmtime(filename, /):
     """Return the last modification time of a file, reported by os.stat()."""
     return os.stat(filename).st_mtime
 
 
-def getatime(filename):
+def getatime(filename, /):
     """Return the last access time of a file, reported by os.stat()."""
     return os.stat(filename).st_atime
 
 
-def getctime(filename):
+def getctime(filename, /):
     """Return the metadata change time of a file, reported by os.stat()."""
     return os.stat(filename).st_ctime
 
 
 # Return the longest prefix of all list elements.
-def commonprefix(m):
+def commonprefix(m, /):
     "Given a list of pathnames, returns the longest common leading component"
+    import warnings
+    warnings.warn('os.path.commonprefix() is deprecated. Use '
+                  'os.path.commonpath() for longest path prefix.',
+                  category=DeprecationWarning,
+                  stacklevel=2)
+    return _commonprefix(m)
+
+def _commonprefix(m, /):
+    "Internal implementation of commonprefix()"
     if not m: return ''
     # Some people pass in a list of pathname parts to operate in an OS-agnostic
     # fashion; don't try to translate in that case as that's an abuse of the
@@ -120,14 +130,14 @@ def commonprefix(m):
 
 # Are two stat buffers (obtained from stat, fstat or lstat)
 # describing the same file?
-def samestat(s1, s2):
+def samestat(s1, s2, /):
     """Test whether two stat buffers reference the same file"""
     return (s1.st_ino == s2.st_ino and
             s1.st_dev == s2.st_dev)
 
 
 # Are two filenames really pointing to the same file?
-def samefile(f1, f2):
+def samefile(f1, f2, /):
     """Test whether two pathnames reference the same actual file or directory
 
     This is determined by the device number and i-node number and
@@ -190,7 +200,17 @@ def _check_arg_types(funcname, *args):
     if hasstr and hasbytes:
         raise TypeError("Can't mix strings and bytes in path components") from None
 
-# A singleton with a true boolean value.
+
+# Singletons with a true boolean value.
+
+@object.__new__
+class ALL_BUT_LAST:
+    """Special value for use in realpath()."""
+    def __repr__(self):
+        return 'os.path.ALL_BUT_LAST'
+    def __reduce__(self):
+        return self.__class__.__name__
+
 @object.__new__
 class ALLOW_MISSING:
     """Special value for use in realpath()."""
diff --git a/Lib/gettext.py b/Lib/gettext.py
index 6c11ab2b1eb..2f77f0e849e 100644
--- a/Lib/gettext.py
+++ b/Lib/gettext.py
@@ -111,8 +111,9 @@ def _error(value):
     ('+', '-'),
     ('*', '/', '%'),
 )
-_binary_ops = {op: i for i, ops in enumerate(_binary_ops, 1) for op in ops}
-_c2py_ops = {'||': 'or', '&&': 'and', '/': '//'}
+_binary_ops = frozendict({op: i for i, ops in enumerate(_binary_ops, 1)
+                          for op in ops})
+_c2py_ops = frozendict({'||': 'or', '&&': 'and', '/': '//'})
 
 
 def _parse(tokens, priority=-1):
diff --git a/Lib/glob.py b/Lib/glob.py
index 173272ba38f..07b9d3eb952 100644
--- a/Lib/glob.py
+++ b/Lib/glob.py
@@ -149,21 +149,6 @@ def _glob0(dirname, basename, dir_fd, dironly, include_hidden=False):
             return [basename]
     return []
 
-_deprecated_function_message = (
-    "{name} is deprecated and will be removed in Python {remove}. Use "
-    "glob.glob and pass a directory to its root_dir argument instead."
-)
-
-def glob0(dirname, pattern):
-    import warnings
-    warnings._deprecated("glob.glob0", _deprecated_function_message, remove=(3, 15))
-    return _glob0(dirname, pattern, None, False)
-
-def glob1(dirname, pattern):
-    import warnings
-    warnings._deprecated("glob.glob1", _deprecated_function_message, remove=(3, 15))
-    return _glob1(dirname, pattern, None, False)
-
 # This helper function recursively yields relative pathnames inside a literal
 # directory.
 
@@ -385,6 +370,12 @@ def concat_path(path, text):
         """
         raise NotImplementedError
 
+    @staticmethod
+    def stringify_path(path):
+        """Converts the path to a string object
+        """
+        raise NotImplementedError
+
     # High-level methods
 
     def compile(self, pat, altsep=None):
@@ -493,8 +484,9 @@ def recursive_selector(self, part, parts):
         select_next = self.selector(parts)
 
         def select_recursive(path, exists=False):
-            match_pos = len(str(path))
-            if match is None or match(str(path), match_pos):
+            path_str = self.stringify_path(path)
+            match_pos = len(path_str)
+            if match is None or match(path_str, match_pos):
                 yield from select_next(path, exists)
             stack = [path]
             while stack:
@@ -516,7 +508,7 @@ def select_recursive_step(stack, match_pos):
                         pass
 
                     if is_dir or not dir_only:
-                        entry_path_str = str(entry_path)
+                        entry_path_str = self.stringify_path(entry_path)
                         if dir_only:
                             entry_path = self.concat_path(entry_path, self.sep)
                         if match is None or match(entry_path_str, match_pos):
@@ -556,19 +548,6 @@ def scandir(path):
             entries = list(scandir_it)
         return ((entry, entry.name, entry.path) for entry in entries)
 
-
-class _PathGlobber(_GlobberBase):
-    """Provides shell-style pattern matching and globbing for pathlib paths.
-    """
-
-    @staticmethod
-    def lexists(path):
-        return path.info.exists(follow_symlinks=False)
-
     @staticmethod
-    def scandir(path):
-        return ((child.info, child.name, child) for child in path.iterdir())
-
-    @staticmethod
-    def concat_path(path, text):
-        return path.with_segments(str(path) + text)
+    def stringify_path(path):
+        return path  # Already a string.
diff --git a/Lib/graphlib.py b/Lib/graphlib.py
index 7961c9c5cac..af5245ccbcd 100644
--- a/Lib/graphlib.py
+++ b/Lib/graphlib.py
@@ -199,6 +199,7 @@ def done(self, *nodes):
                     self._ready_nodes.append(successor)
             self._nfinished += 1
 
+    # See note "On Finding Cycles" at the bottom.
     def _find_cycle(self):
         n2i = self._node2info
         stack = []
@@ -212,8 +213,6 @@ def _find_cycle(self):
 
             while True:
                 if node in seen:
-                    # If we have seen already the node and is in the
-                    # current stack we have found a cycle.
                     if node in node2stacki:
                         return stack[node2stacki[node] :] + [node]
                     # else go on to get next successor
@@ -228,11 +227,15 @@ def _find_cycle(self):
                 while stack:
                     try:
                         node = itstack[-1]()
-                        break
+                        break # resume at top of "while True:"
                     except StopIteration:
+                        # no more successors; pop the stack
+                        # and continue looking up
                         del node2stacki[stack.pop()]
                         itstack.pop()
                 else:
+                    # stack is empty; look for a fresh node to
+                    # start over from (a node not yet in seen)
                     break
         return None
 
@@ -252,3 +255,55 @@ def static_order(self):
             self.done(*node_group)
 
     __class_getitem__ = classmethod(GenericAlias)
+
+
+# On Finding Cycles
+# -----------------
+# There is a (at least one) total order if and only if the graph is
+# acyclic.
+#
+# When it is cyclic, "there's a cycle - somewhere!" isn't very helpful.
+# In theory, it would be most helpful to partition the graph into
+# strongly connected components (SCCs) and display those with more than
+# one node. Then all cycles could easily be identified "by eyeball".
+#
+# That's a lot of work, though, and we can get most of the benefit much
+# more easily just by showing a single specific cycle.
+#
+# Approaches to that are based on breadth first or depth first search
+# (BFS or DFS). BFS is most natural, which can easily be arranged to
+# find a shortest-possible cycle. But memory burden can be high, because
+# every path-in-progress has to keep its own idea of what "the path" is
+# so far.
+#
+# DFS is much easier on RAM, only requiring keeping track of _the_ path
+# from the starting node to the current node at the current recursion
+# level. But there may be any number of nodes, and so there's no bound
+# on recursion depth short of the total number of nodes.
+#
+# So we use an iterative version of DFS, keeping an exploit list
+# (`stack`) of the path so far. A parallel stack (`itstack`) holds the
+# `__next__` method of an iterator over the current level's node's
+# successors, so when backtracking to a shallower level we can just call
+# that to get the node's next successor. This is state that a recursive
+# version would implicitly store in a `for` loop's internals.
+#
+# `seen()` is a set recording which nodes have already been, at some
+# time, pushed on the stack. If a node has been pushed on the stack, DFS
+# will find any cycle it's part of, so there's no need to ever look at
+# it again.
+#
+# Finally, `node2stacki` maps a node to its index on the current stack,
+# for and only for nodes currently _on_ the stack. If a successor to be
+# pushed on the stack is in that dict, the node is already on the path,
+# at that index. The cycle is then `stack[that_index :] + [node]`.
+#
+# As is often the case when removing recursion, the control flow looks a
+# bit off. The "while True:" loop here rarely actually loops - it's only
+# looking to go "up the stack" until finding a level that has another
+# successor to consider, emulating a chain of returns in a recursive
+# version.
+#
+# Worst cases: O(V+E) for time, and O(V) for memory, where V is the
+# number of nodes and E the number of edges (which may be quadratic in
+# V!). It requires care to ensure these bounds are met.
diff --git a/Lib/gzip.py b/Lib/gzip.py
index f3f9fa91c81..c7b4563fdfe 100644
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -30,7 +30,7 @@
 _WRITE_BUFFER_SIZE = 4 * io.DEFAULT_BUFFER_SIZE
 
 
-def open(filename, mode="rb", compresslevel=_COMPRESS_LEVEL_BEST,
+def open(filename, mode="rb", compresslevel=_COMPRESS_LEVEL_TRADEOFF,
          encoding=None, errors=None, newline=None):
     """Open a gzip-compressed file in binary or text mode.
 
@@ -158,7 +158,7 @@ class GzipFile(_streams.BaseStream):
     myfileobj = None
 
     def __init__(self, filename=None, mode=None,
-                 compresslevel=_COMPRESS_LEVEL_BEST, fileobj=None, mtime=None):
+                 compresslevel=_COMPRESS_LEVEL_TRADEOFF, fileobj=None, mtime=None):
         """Constructor for the GzipFile class.
 
         At least one of fileobj and filename must be given a
@@ -189,9 +189,10 @@ def __init__(self, filename=None, mode=None,
 
         The optional mtime argument is the timestamp requested by gzip.
         The time is in Unix format, i.e., seconds since 00:00:00 UTC,
-        January 1, 1970.  If mtime is omitted or None, the current time
-        is used.  Use mtime = 0 to generate a compressed stream that does
-        not depend on creation time.
+        January 1, 1970.  Set mtime to 0 to generate a compressed stream
+        that does not depend on creation time.  If mtime is omitted or None,
+        the current time is used.  If the resulting mtime is outside the
+        range 0 to 2**32-1, then the value 0 is used instead.
 
         """
 
@@ -270,8 +271,6 @@ def _init_write(self, filename):
         self.name = filename
         self.crc = zlib.crc32(b"")
         self.size = 0
-        self.writebuf = []
-        self.bufsize = 0
         self.offset = 0  # Current file offset for seek(), tell(), etc
 
     def tell(self):
@@ -299,6 +298,8 @@ def _write_gzip_header(self, compresslevel):
         mtime = self._write_mtime
         if mtime is None:
             mtime = time.time()
+        if not 0 <= mtime < 2**32:
+            mtime = 0
         write32u(self.fileobj, int(mtime))
         if compresslevel == _COMPRESS_LEVEL_BEST:
             xfl = b'\002'
@@ -488,40 +489,73 @@ def _read_exact(fp, n):
     return data
 
 
+def _read_until_null(fp, crc=None):
+    '''Read until the first encountered null byte in fp.
+    If crc is not None, update and return the CRC.
+    '''
+    if crc is None:
+        while True:
+            s = fp.read(1)
+            if not s or s == b'\000':
+                break
+    else:
+        while True:
+            s = fp.read(1)
+            crc = zlib.crc32(s, crc)
+            if not s or s == b'\000':
+                break
+    return crc
+
+
 def _read_gzip_header(fp):
     '''Read a gzip header from `fp` and progress to the end of the header.
 
     Returns last mtime if header was present or None otherwise.
     '''
     magic = fp.read(2)
-    if magic == b'':
+    if not magic:
         return None
 
     if magic != b'\037\213':
         raise BadGzipFile('Not a gzipped file (%r)' % magic)
-
-    (method, flag, last_mtime) = struct.unpack("<BBIxx", _read_exact(fp, 8))
+    base_header = _read_exact(fp, 8)
+    (method, flag, last_mtime) = struct.unpack("<BBIxx", base_header)
     if method != 8:
         raise BadGzipFile('Unknown compression method')
 
+    # Most common cases are no flags (gzip.compress, zlib.compress) or only
+    # FNAME set (GzipFile, gzip command line application). Exit early
+    # in those cases.
+    if not flag:
+        return last_mtime
+    if flag == FNAME:
+        # Read and discard a null-terminated string containing the filename
+        _read_until_null(fp)
+        return last_mtime
+
+    # Processing for more complex flags. Save header parts for FHCRC checking.
+    if flag & FHCRC:
+        crc = zlib.crc32(magic + base_header)
+    else:
+        crc = None
     if flag & FEXTRA:
-        # Read & discard the extra field, if present
-        extra_len, = struct.unpack("<H", _read_exact(fp, 2))
-        _read_exact(fp, extra_len)
+        extra_len_bytes = _read_exact(fp, 2)
+        extra_len, = struct.unpack("<H", extra_len_bytes)
+        extra = _read_exact(fp, extra_len)
+        if crc is not None:
+            crc = zlib.crc32(extra_len_bytes, crc)
+            crc = zlib.crc32(extra, crc)
     if flag & FNAME:
-        # Read and discard a null-terminated string containing the filename
-        while True:
-            s = fp.read(1)
-            if not s or s==b'\000':
-                break
+        crc = _read_until_null(fp, crc)
     if flag & FCOMMENT:
-        # Read and discard a null-terminated string containing a comment
-        while True:
-            s = fp.read(1)
-            if not s or s==b'\000':
-                break
-    if flag & FHCRC:
-        _read_exact(fp, 2)     # Read & discard the 16-bit header CRC
+        crc = _read_until_null(fp, crc)
+    if crc is not None:
+        # Header CRC is the last 16 bits of a crc32.
+        header_crc, = struct.unpack("<H", _read_exact(fp, 2))
+        crc = crc & 0xFFFF
+        if header_crc != crc:
+            raise BadGzipFile(f"Corrupted gzip header. Checksums do not "
+                              f"match: {crc:04x} != {header_crc:04x}")
     return last_mtime
 
 
@@ -623,7 +657,7 @@ def _rewind(self):
         self._new_member = True
 
 
-def compress(data, compresslevel=_COMPRESS_LEVEL_BEST, *, mtime=0):
+def compress(data, compresslevel=_COMPRESS_LEVEL_TRADEOFF, *, mtime=0):
     """Compress data in one shot and return the compressed string.
 
     compresslevel sets the compression level in range of 0-9.
@@ -634,6 +668,8 @@ def compress(data, compresslevel=_COMPRESS_LEVEL_BEST, *, mtime=0):
     gzip_data = zlib.compress(data, level=compresslevel, wbits=31)
     if mtime is None:
         mtime = time.time()
+    if not 0 <= mtime < 2**32:
+        mtime = 0
     # Reuse gzip header created by zlib, replace mtime and OS byte for
     # consistency.
     header = struct.pack("<4sLBB", gzip_data, int(mtime), gzip_data[8], 255)
@@ -668,15 +704,14 @@ def decompress(data):
 def main():
     from argparse import ArgumentParser
     parser = ArgumentParser(description=
-        "A simple command line interface for the gzip module: act like gzip, "
+        "A simple command line interface for the `gzip` module: act like `gzip`, "
         "but do not delete the input file.",
-        color=True,
     )
     group = parser.add_mutually_exclusive_group()
     group.add_argument('--fast', action='store_true', help='compress faster')
     group.add_argument('--best', action='store_true', help='compress better')
     group.add_argument("-d", "--decompress", action="store_true",
-                        help="act like gunzip instead of gzip")
+                        help="act like `gunzip` instead of `gzip`")
 
     parser.add_argument("args", nargs="*", default=["-"], metavar='file')
     args = parser.parse_args()
diff --git a/Lib/hashlib.py b/Lib/hashlib.py
index 0e9bd98aa1f..c1e2d07c435 100644
--- a/Lib/hashlib.py
+++ b/Lib/hashlib.py
@@ -2,7 +2,7 @@
 #  Licensed to PSF under a Contributor Agreement.
 #
 
-__doc__ = """hashlib module - A common interface to many hash functions.
+__doc__ = r"""hashlib module - A common interface to many hash functions.
 
 new(name, data=b'', **kwargs) - returns a new hash object implementing the
                                 given hash function; initializing the hash
@@ -12,7 +12,7 @@
 than using new(name):
 
 md5(), sha1(), sha224(), sha256(), sha384(), sha512(), blake2b(), blake2s(),
-sha3_224, sha3_256, sha3_384, sha3_512, shake_128, and shake_256.
+sha3_224(), sha3_256(), sha3_384(), sha3_512(), shake_128(), and shake_256().
 
 More algorithms may be available on your platform but the above are guaranteed
 to exist.  See the algorithms_guaranteed and algorithms_available attributes
@@ -21,8 +21,8 @@
 NOTE: If you want the adler32 or crc32 hash functions they are available in
 the zlib module.
 
-Choose your hash function wisely.  Some have known collision weaknesses.
-sha384 and sha512 will be slow on 32 bit platforms.
+Choose your hash function wisely.  Some have known collision weaknesses,
+while others may be slower depending on the CPU architecture.
 
 Hash objects have these methods:
  - update(data): Update the hash object with the bytes in data. Repeated calls
@@ -36,21 +36,21 @@
                  efficiently compute the digests of data that share a common
                  initial substring.
 
-For example, to obtain the digest of the byte string 'Nobody inspects the
-spammish repetition':
+Assuming that Python has been built with SHA-2 support, the SHA-256 digest
+of the byte string b'Nobody inspects the spammish repetition' is computed
+as follows:
 
     >>> import hashlib
-    >>> m = hashlib.md5()
+    >>> m = hashlib.sha256()
     >>> m.update(b"Nobody inspects")
     >>> m.update(b" the spammish repetition")
-    >>> m.digest()
-    b'\\xbbd\\x9c\\x83\\xdd\\x1e\\xa5\\xc9\\xd9\\xde\\xc9\\xa1\\x8d\\xf0\\xff\\xe9'
+    >>> m.digest()  # doctest: +ELLIPSIS
+    b'\x03\x1e\xdd}Ae\x15\x93\xc5\xfe\\\x00o\xa5u+7...'
 
 More condensed:
 
-    >>> hashlib.sha224(b"Nobody inspects the spammish repetition").hexdigest()
-    'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'
-
+    >>> hashlib.sha256(b"Nobody inspects the spammish repetition").hexdigest()
+    '031edd7d41651593c5fe5c006fa5752b37fddff7bc4e843aa6af0c950f4b9406'
 """
 
 # This tuple and __get_builtin_constructor() must be modified if a new
@@ -80,6 +80,11 @@
 }
 
 def __get_builtin_constructor(name):
+    if not isinstance(name, str):
+        # Since this function is only used by new(), we use the same
+        # exception as _hashlib.new() when 'name' is of incorrect type.
+        err = f"new() argument 'name' must be str, not {type(name).__name__}"
+        raise TypeError(err)
     cache = __builtin_constructor_cache
     constructor = cache.get(name)
     if constructor is not None:
@@ -120,20 +125,33 @@ def __get_builtin_constructor(name):
     if constructor is not None:
         return constructor
 
-    raise ValueError('unsupported hash type ' + name)
+    # Keep the message in sync with hashlib.h::HASHLIB_UNSUPPORTED_ALGORITHM.
+    raise ValueError(f'unsupported hash algorithm {name}')
 
 
 def __get_openssl_constructor(name):
+    # This function is only used until the module has been initialized.
+    assert isinstance(name, str), "invalid call to __get_openssl_constructor()"
     if name in __block_openssl_constructor:
         # Prefer our builtin blake2 implementation.
         return __get_builtin_constructor(name)
     try:
-        # MD5, SHA1, and SHA2 are in all supported OpenSSL versions
-        # SHA3/shake are available in OpenSSL 1.1.1+
+        # Fetch the OpenSSL hash function if it exists,
+        # independently of the context security policy.
         f = getattr(_hashlib, 'openssl_' + name)
-        # Allow the C module to raise ValueError.  The function will be
-        # defined but the hash not actually available.  Don't fall back to
-        # builtin if the current security policy blocks a digest, bpo#40695.
+        # Check if the context security policy blocks the digest or not
+        # by allowing the C module to raise a ValueError. The function
+        # will be defined but the hash will not be available at runtime.
+        #
+        # We use "usedforsecurity=False" to prevent falling back to the
+        # built-in function in case the security policy does not allow it.
+        #
+        # Note that this only affects the explicit named constructors,
+        # and not the algorithms exposed through hashlib.new() which
+        # can still be resolved to a built-in function even if the
+        # current security policy does not allow it.
+        #
+        # See https://github.com/python/cpython/issues/84872.
         f(usedforsecurity=False)
         # Use the C function directly (very fast)
         return f
@@ -154,6 +172,8 @@ def __hash_new(name, *args, **kwargs):
     optionally initialized with data (which must be a bytes-like object).
     """
     if name in __block_openssl_constructor:
+        # __block_openssl_constructor is expected to contain strings only
+        assert isinstance(name, str), f"unexpected name: {name}"
         # Prefer our builtin blake2 implementation.
         return __get_builtin_constructor(name)(*args, **kwargs)
     try:
@@ -187,7 +207,8 @@ def __hash_new(name, *args, **kwargs):
 
 try:
     # OpenSSL's scrypt requires OpenSSL 1.1+
-    from _hashlib import scrypt  # noqa: F401
+    from _hashlib import scrypt
+    __all__ += ('scrypt',)
 except ImportError:
     pass
 
@@ -203,7 +224,7 @@ def file_digest(fileobj, digest, /, *, _bufsize=2**18):
     *digest* must either be a hash algorithm name as a *str*, a hash
     constructor, or a callable that returns a hash object.
     """
-    # On Linux we could use AF_ALG sockets and sendfile() to archive zero-copy
+    # On Linux we could use AF_ALG sockets and sendfile() to achieve zero-copy
     # hashing with hardware acceleration.
     if isinstance(digest, str):
         digestobj = new(digest)
@@ -246,9 +267,30 @@ def file_digest(fileobj, digest, /, *, _bufsize=2**18):
     try:
         globals()[__func_name] = __get_hash(__func_name)
     except ValueError:
-        import logging
-        logging.exception('code for hash %s was not found.', __func_name)
-
+        # Don't log here: logging at import time has global side effects and
+        # would tell the wrong audience; code that uses a missing algorithm
+        # gets a ValueError from the stub installed below.
+        # The following code can be simplified in Python 3.19
+        # once "string" is removed from the signature.
+        __code = f'''\
+def {__func_name}(data=__UNSET, *, usedforsecurity=True, string=__UNSET):
+    if data is __UNSET and string is not __UNSET:
+        import warnings
+        warnings.warn(
+            "the 'string' keyword parameter is deprecated since "
+            "Python 3.15 and slated for removal in Python 3.19; "
+            "use the 'data' keyword parameter or pass the data "
+            "to hash as a positional argument instead",
+            DeprecationWarning, stacklevel=2)
+    if data is not __UNSET and string is not __UNSET:
+        raise TypeError("'data' and 'string' are mutually exclusive "
+                        "and support for 'string' keyword parameter "
+                        "is slated for removal in a future version.")
+    raise ValueError("unsupported hash algorithm {__func_name}")
+'''
+        exec(__code, {"__UNSET": object()}, __locals := {})
+        globals()[__func_name] = __locals[__func_name]
+        del __code, __locals
 
 # Cleanup locals()
 del __always_supported, __func_name, __get_hash
diff --git a/Lib/heapq.py b/Lib/heapq.py
index 17f62dd2d58..a3af6dc05bf 100644
--- a/Lib/heapq.py
+++ b/Lib/heapq.py
@@ -494,7 +494,7 @@ def nsmallest(n, iterable, key=None):
         pass
     else:
         if n >= size:
-            return sorted(iterable, key=key)[:n]
+            return sorted(iterable, key=key)
 
     # When key is none, use simpler decoration
     if key is None:
@@ -511,7 +511,7 @@ def nsmallest(n, iterable, key=None):
         for elem in it:
             if elem < top:
                 _heapreplace(result, (elem, order))
-                top, _order = result[0]
+                top = result[0][0]
                 order += 1
         result.sort()
         return [elem for (elem, order) in result]
@@ -529,7 +529,7 @@ def nsmallest(n, iterable, key=None):
         k = key(elem)
         if k < top:
             _heapreplace(result, (k, order, elem))
-            top, _order, _elem = result[0]
+            top = result[0][0]
             order += 1
     result.sort()
     return [elem for (k, order, elem) in result]
@@ -554,7 +554,7 @@ def nlargest(n, iterable, key=None):
         pass
     else:
         if n >= size:
-            return sorted(iterable, key=key, reverse=True)[:n]
+            return sorted(iterable, key=key, reverse=True)
 
     # When key is none, use simpler decoration
     if key is None:
@@ -569,7 +569,7 @@ def nlargest(n, iterable, key=None):
         for elem in it:
             if top < elem:
                 _heapreplace(result, (elem, order))
-                top, _order = result[0]
+                top = result[0][0]
                 order -= 1
         result.sort(reverse=True)
         return [elem for (elem, order) in result]
@@ -587,7 +587,7 @@ def nlargest(n, iterable, key=None):
         k = key(elem)
         if top < k:
             _heapreplace(result, (k, order, elem))
-            top, _order, _elem = result[0]
+            top = result[0][0]
             order -= 1
     result.sort(reverse=True)
     return [elem for (k, order, elem) in result]
diff --git a/Lib/hmac.py b/Lib/hmac.py
index 2d6016cda11..e0c040bcd5f 100644
--- a/Lib/hmac.py
+++ b/Lib/hmac.py
@@ -26,6 +26,16 @@
 digest_size = None
 
 
+def _is_shake_constructor(digest_like):
+    if isinstance(digest_like, str):
+        name = digest_like
+    else:
+        h = digest_like() if callable(digest_like) else digest_like.new()
+        if not isinstance(name := getattr(h, "name", None), str):
+            return False
+    return name.startswith(("shake", "SHAKE"))
+
+
 def _get_digest_constructor(digest_like):
     if callable(digest_like):
         return digest_like
@@ -109,6 +119,8 @@ def _init_old(self, key, msg, digestmod):
         import warnings
 
         digest_cons = _get_digest_constructor(digestmod)
+        if _is_shake_constructor(digest_cons):
+            raise ValueError(f"unsupported hash algorithm {digestmod}")
 
         self._hmac = None
         self._outer = digest_cons()
@@ -256,6 +268,8 @@ def digest(key, msg, digest):
 
 def _compute_digest_fallback(key, msg, digest):
     digest_cons = _get_digest_constructor(digest)
+    if _is_shake_constructor(digest_cons):
+        raise ValueError(f"unsupported hash algorithm {digest}")
     inner = digest_cons()
     outer = digest_cons()
     blocksize = getattr(inner, 'block_size', 64)
diff --git a/Lib/importlib/_abc.py b/Lib/importlib/_abc.py
index 693b4661126..2598036dac4 100644
--- a/Lib/importlib/_abc.py
+++ b/Lib/importlib/_abc.py
@@ -19,21 +19,3 @@ def create_module(self, spec):
 
     # We don't define exec_module() here since that would break
     # hasattr checks we do to support backward compatibility.
-
-    def load_module(self, fullname):
-        """Return the loaded module.
-
-        The module must be added to sys.modules and have import-related
-        attributes set properly.  The fullname is a str.
-
-        ImportError is raised on failure.
-
-        This method is deprecated in favor of loader.exec_module(). If
-        exec_module() exists then it is used to provide a backwards-compatible
-        functionality for this method.
-
-        """
-        if not hasattr(self, 'exec_module'):
-            raise ImportError
-        # Warning implemented in _load_module_shim().
-        return _bootstrap._load_module_shim(self, fullname)
diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
index 9d911e1dcab..75bc901e238 100644
--- a/Lib/importlib/_bootstrap.py
+++ b/Lib/importlib/_bootstrap.py
@@ -424,6 +424,64 @@ def __exit__(self, *args, **kwargs):
         self._lock.release()
 
 
+def _get_module_chain(name):
+    """Return the chain of dotted-name prefixes from root to leaf.
+
+    For example: 'a.b.c' -> ['a', 'a.b', 'a.b.c']
+    """
+    parts = name.split('.')
+    return ['.'.join(parts[:i+1]) for i in range(len(parts))]
+
+
+class _HierarchicalLockManager:
+    """Manages acquisition of multiple module locks in hierarchical order.
+
+    This prevents deadlocks by ensuring all threads acquire locks in the
+    same order (parent modules before child modules).
+    """
+
+    def __init__(self, name):
+        self._name = name
+        self._module_chain = _get_module_chain(name)
+        self._locks = []
+
+    def __enter__(self):
+        try:
+            for module_name in self._module_chain:
+                # Only acquire lock if module is not already fully loaded
+                module = sys.modules.get(module_name)
+                if (module is None or
+                    getattr(getattr(module, "__spec__", None),
+                            "_initializing", False)):
+                    lock = _get_module_lock(module_name)
+                    try:
+                        lock.acquire()
+                    except _DeadlockError:
+                        if module_name == self._name:
+                            raise
+                        # The parent is being initialised by a thread that
+                        # is (transitively) waiting on a lock we hold.
+                        # Apply the same policy as _lock_unlock_module():
+                        # accept a partially-initialised parent for circular
+                        # imports rather than failing the whole chain.
+                        continue
+                    self._locks.append((module_name, lock))
+        except:
+            # __exit__ is not called when __enter__ raises (e.g. _DeadlockError
+            # on the leaf lock, or KeyboardInterrupt), so release whatever we
+            # already hold to avoid permanently leaking held module locks.
+            for module_name, lock in reversed(self._locks):
+                lock.release()
+            self._locks.clear()
+            raise
+        return self
+
+    def __exit__(self, *args, **kwargs):
+        for module_name, lock in reversed(self._locks):
+            lock.release()
+        self._locks.clear()
+
+
 # The following two functions are for consumption by Python/import.c.
 
 def _get_module_lock(name):
@@ -521,24 +579,6 @@ def _requires_frozen_wrapper(self, fullname):
     return _requires_frozen_wrapper
 
 
-# Typically used by loader classes as a method replacement.
-def _load_module_shim(self, fullname):
-    """Load the specified module into sys.modules and return it.
-
-    This method is deprecated.  Use loader.exec_module() instead.
-
-    """
-    msg = ("the load_module() method is deprecated and slated for removal in "
-           "Python 3.15; use exec_module() instead")
-    _warnings.warn(msg, DeprecationWarning)
-    spec = spec_from_loader(fullname, self)
-    if fullname in sys.modules:
-        module = sys.modules[fullname]
-        _exec(spec, module)
-        return sys.modules[fullname]
-    else:
-        return _load(spec)
-
 # Module specifications #######################################################
 
 def _module_repr(module):
@@ -583,8 +623,7 @@ class ModuleSpec:
     `has_location` indicates that a spec's "origin" reflects a location.
     When this is True, `__file__` attribute of the module is set.
 
-    `cached` is the location of the cached bytecode file, if any.  It
-    corresponds to the `__cached__` attribute.
+    `cached` is the location of the cached bytecode file, if any.
 
     `submodule_search_locations` is the sequence of path entries to
     search when importing submodules.  If set, is_package should be
@@ -717,10 +756,6 @@ def _spec_from_module(module, loader=None, origin=None):
             origin = getattr(loader, '_ORIGIN', None)
         if not origin and location is not None:
             origin = location
-    try:
-        cached = module.__cached__
-    except AttributeError:
-        cached = None
     try:
         submodule_search_locations = list(module.__path__)
     except AttributeError:
@@ -728,7 +763,7 @@ def _spec_from_module(module, loader=None, origin=None):
 
     spec = ModuleSpec(name, loader, origin=origin)
     spec._set_fileattr = False if location is None else (origin == location)
-    spec.cached = cached
+    spec.cached = None
     spec.submodule_search_locations = submodule_search_locations
     return spec
 
@@ -763,8 +798,7 @@ def _init_module_attrs(spec, module, *, override=False):
                 # should also be None for consistency.  While a bit of a hack,
                 # this is the best place to ensure this consistency.
                 #
-                # See # https://docs.python.org/3/library/importlib.html#importlib.abc.Loader.load_module
-                # and bpo-32305
+                # See bpo-32305
                 module.__file__ = None
         try:
             module.__loader__ = loader
@@ -789,7 +823,7 @@ def _init_module_attrs(spec, module, *, override=False):
                 module.__path__ = spec.submodule_search_locations
             except AttributeError:
                 pass
-    # __file__/__cached__
+    # __file__
     if spec.has_location:
         if override or getattr(module, '__file__', None) is None:
             try:
@@ -797,12 +831,6 @@ def _init_module_attrs(spec, module, *, override=False):
             except AttributeError:
                 pass
 
-        if override or getattr(module, '__cached__', None) is None:
-            if spec.cached is not None:
-                try:
-                    module.__cached__ = spec.cached
-                except AttributeError:
-                    pass
     return module
 
 
@@ -844,7 +872,7 @@ def _module_repr_from_spec(spec):
             return f'<module {spec.name!r} ({spec.origin})>'
 
 
-# Used by importlib.reload() and _load_module_shim().
+# Used by importlib.reload().
 def _exec(spec, module):
     """Execute the spec's specified module in an existing module's namespace."""
     name = spec.name
@@ -860,13 +888,7 @@ def _exec(spec, module):
                 _init_module_attrs(spec, module, override=True)
             else:
                 _init_module_attrs(spec, module, override=True)
-                if not hasattr(spec.loader, 'exec_module'):
-                    msg = (f"{_object_name(spec.loader)}.exec_module() not found; "
-                           "falling back to load_module()")
-                    _warnings.warn(msg, ImportWarning)
-                    spec.loader.load_module(name)
-                else:
-                    spec.loader.exec_module(module)
+                spec.loader.exec_module(module)
         finally:
             # Update the order of insertion into sys.modules for module
             # clean-up at shutdown.
@@ -874,53 +896,8 @@ def _exec(spec, module):
             sys.modules[spec.name] = module
     return module
 
-
-def _load_backward_compatible(spec):
-    # It is assumed that all callers have been warned about using load_module()
-    # appropriately before calling this function.
-    try:
-        spec.loader.load_module(spec.name)
-    except:
-        if spec.name in sys.modules:
-            module = sys.modules.pop(spec.name)
-            sys.modules[spec.name] = module
-        raise
-    # The module must be in sys.modules at this point!
-    # Move it to the end of sys.modules.
-    module = sys.modules.pop(spec.name)
-    sys.modules[spec.name] = module
-    if getattr(module, '__loader__', None) is None:
-        try:
-            module.__loader__ = spec.loader
-        except AttributeError:
-            pass
-    if getattr(module, '__package__', None) is None:
-        try:
-            # Since module.__path__ may not line up with
-            # spec.submodule_search_paths, we can't necessarily rely
-            # on spec.parent here.
-            module.__package__ = module.__name__
-            if not hasattr(module, '__path__'):
-                module.__package__ = spec.name.rpartition('.')[0]
-        except AttributeError:
-            pass
-    if getattr(module, '__spec__', None) is None:
-        try:
-            module.__spec__ = spec
-        except AttributeError:
-            pass
-    return module
-
 def _load_unlocked(spec):
     # A helper for direct use by the import system.
-    if spec.loader is not None:
-        # Not a namespace package.
-        if not hasattr(spec.loader, 'exec_module'):
-            msg = (f"{_object_name(spec.loader)}.exec_module() not found; "
-                    "falling back to load_module()")
-            _warnings.warn(msg, ImportWarning)
-            return _load_backward_compatible(spec)
-
     module = module_from_spec(spec)
 
     # This must be done before putting the module in sys.modules
@@ -954,8 +931,7 @@ def _load_unlocked(spec):
 
     return module
 
-# A method used during testing of _load_unlocked() and by
-# _load_module_shim().
+# A method used during testing of _load_unlocked().
 def _load(spec):
     """Return a new module object, loaded by the spec's loader.
 
@@ -1020,8 +996,6 @@ def is_package(cls, fullname):
         """Return False as built-in modules are never packages."""
         return False
 
-    load_module = classmethod(_load_module_shim)
-
 
 class FrozenImporter:
 
@@ -1178,25 +1152,6 @@ def exec_module(module):
         code = _call_with_frames_removed(_imp.get_frozen_object, name)
         exec(code, module.__dict__)
 
-    @classmethod
-    def load_module(cls, fullname):
-        """Load a frozen module.
-
-        This method is deprecated.  Use exec_module() instead.
-
-        """
-        # Warning about deprecation implemented in _load_module_shim().
-        module = _load_module_shim(cls, fullname)
-        info = _imp.find_frozen(fullname)
-        assert info is not None
-        _, ispkg, origname = info
-        module.__origname__ = origname
-        vars(module).pop('__file__', None)
-        if ispkg:
-            module.__path__ = []
-        cls._fix_up_module(module)
-        return module
-
     @classmethod
     @_requires_frozen
     def get_code(cls, fullname):
@@ -1305,8 +1260,16 @@ def _sanity_check(name, package, level):
 
 _ERR_MSG_PREFIX = 'No module named '
 
-def _find_and_load_unlocked(name, import_):
+def _find_and_load_unlocked(name, import_, *, lazy_submodule=False):
     path = None
+    sys.audit(
+        "import",
+        name,
+        path,
+        getattr(sys, "path", None),
+        getattr(sys, "meta_path", None),
+        getattr(sys, "path_hooks", None)
+    )
     parent = name.rpartition('.')[0]
     parent_spec = None
     if parent:
@@ -1320,6 +1283,8 @@ def _find_and_load_unlocked(name, import_):
         try:
             path = parent_module.__path__
         except AttributeError:
+            if lazy_submodule:
+                return None
             msg = f'{_ERR_MSG_PREFIX}{name!r}; {parent!r} is not a package'
             raise ModuleNotFoundError(msg, name=name) from None
         parent_spec = parent_module.__spec__
@@ -1332,6 +1297,8 @@ def _find_and_load_unlocked(name, import_):
         child = name.rpartition('.')[2]
     spec = _find_spec(name, path)
     if spec is None:
+        if lazy_submodule:
+            return None
         raise ModuleNotFoundError(f'{_ERR_MSG_PREFIX}{name!r}', name=name)
     else:
         if parent_spec:
@@ -1351,13 +1318,19 @@ def _find_and_load_unlocked(name, import_):
         except AttributeError:
             msg = f"Cannot set an attribute on {parent!r} for child module {child!r}"
             _warnings.warn(msg, ImportWarning)
+    # Set attributes to lazy submodules on the module.
+    try:
+        _imp._set_lazy_attributes(module, name)
+    except Exception as e:
+        msg = f"Cannot set lazy attributes on {name!r}: {e!r}"
+        _warnings.warn(msg, ImportWarning)
     return module
 
 
 _NEEDS_LOADING = object()
 
 
-def _find_and_load(name, import_):
+def _find_and_load(name, import_, *, lazy_submodule=False):
     """Find and load the module."""
 
     # Optimization: we avoid unneeded module locking if the module
@@ -1365,10 +1338,17 @@ def _find_and_load(name, import_):
     module = sys.modules.get(name, _NEEDS_LOADING)
     if (module is _NEEDS_LOADING or
         getattr(getattr(module, "__spec__", None), "_initializing", False)):
-        with _ModuleLockManager(name):
+
+        if '.' in name:
+            lock_manager = _HierarchicalLockManager(name)
+        else:
+            lock_manager = _ModuleLockManager(name)
+
+        with lock_manager:
             module = sys.modules.get(name, _NEEDS_LOADING)
             if module is _NEEDS_LOADING:
-                return _find_and_load_unlocked(name, import_)
+                return _find_and_load_unlocked(
+                    name, import_, lazy_submodule=lazy_submodule)
 
         # Optimization: only call _bootstrap._lock_unlock_module() if
         # module.__spec__._initializing is True.
@@ -1382,7 +1362,7 @@ def _find_and_load(name, import_):
         # to preserve normal semantics: the caller gets the exception from
         # the actual import failure rather than a synthetic error.
         if sys.modules.get(name) is not module:
-            return _find_and_load(name, import_)
+            return _find_and_load(name, import_, lazy_submodule=lazy_submodule)
 
     if module is None:
         message = f'import of {name} halted; None in sys.modules'
@@ -1391,6 +1371,10 @@ def _find_and_load(name, import_):
     return module
 
 
+def _find_and_load_lazy_submodule(name, import_):
+    return _find_and_load(name, import_, lazy_submodule=True)
+
+
 def _gcd_import(name, package=None, level=0):
     """Import and return the module based on its name, the package the call is
     being made from, and the level adjustment.
diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index 6a828ae75ed..a1cb729efb7 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -236,7 +236,7 @@ def _write_atomic(path, data, mode=0o666):
 # Deprecated.
 DEBUG_BYTECODE_SUFFIXES = OPTIMIZED_BYTECODE_SUFFIXES = BYTECODE_SUFFIXES
 
-def cache_from_source(path, debug_override=None, *, optimization=None):
+def cache_from_source(path, *, optimization=None):
     """Given the path to a .py file, return the path to its .pyc file.
 
     The .py file does not need to exist; this simply returns the path to the
@@ -247,20 +247,9 @@ def cache_from_source(path, debug_override=None, *, optimization=None):
     of the argument is taken and verified to be alphanumeric (else ValueError
     is raised).
 
-    The debug_override parameter is deprecated. If debug_override is not None,
-    a True value is the same as setting 'optimization' to the empty string
-    while a False value is equivalent to setting 'optimization' to '1'.
-
     If sys.implementation.cache_tag is None then NotImplementedError is raised.
 
     """
-    if debug_override is not None:
-        _warnings.warn('the debug_override parameter is deprecated; use '
-                       "'optimization' instead", DeprecationWarning)
-        if optimization is not None:
-            message = 'debug_override or optimization must be set to None'
-            raise TypeError(message)
-        optimization = '' if debug_override else 1
     path = _os.fspath(path)
     head, tail = _path_split(path)
     base, sep, rest = tail.rpartition('.')
@@ -548,8 +537,7 @@ def decode_source(source_bytes):
     import tokenize  # To avoid bootstrap issues.
     source_bytes_readline = _io.BytesIO(source_bytes).readline
     encoding = tokenize.detect_encoding(source_bytes_readline)
-    newline_decoder = _io.IncrementalNewlineDecoder(None, True)
-    return newline_decoder.decode(source_bytes.decode(encoding[0]))
+    return _io.TextIOWrapper(_io.BytesIO(source_bytes), encoding=encoding[0], newline=None).read()
 
 
 # Module specifications #######################################################
@@ -758,11 +746,6 @@ def exec_module(self, module):
                               'get_code() returns None')
         _bootstrap._call_with_frames_removed(exec, code, module.__dict__)
 
-    def load_module(self, fullname):
-        """This method is deprecated."""
-        # Warning implemented in _load_module_shim().
-        return _bootstrap._load_module_shim(self, fullname)
-
 
 class SourceLoader(_LoaderBasics):
 
@@ -815,13 +798,14 @@ def get_source(self, fullname):
                               name=fullname) from exc
         return decode_source(source_bytes)
 
-    def source_to_code(self, data, path, *, _optimize=-1):
+    def source_to_code(self, data, path, fullname=None, *, _optimize=-1):
         """Return the code object compiled from source.
 
         The 'data' argument can be any object type that compile() supports.
         """
         return _bootstrap._call_with_frames_removed(compile, data, path, 'exec',
-                                        dont_inherit=True, optimize=_optimize)
+                                        dont_inherit=True, optimize=_optimize,
+                                        module=fullname)
 
     def get_code(self, fullname):
         """Concrete implementation of InspectLoader.get_code.
@@ -890,7 +874,7 @@ def get_code(self, fullname):
                                                  source_path=source_path)
         if source_bytes is None:
             source_bytes = self.get_data(source_path)
-        code_object = self.source_to_code(source_bytes, source_path)
+        code_object = self.source_to_code(source_bytes, source_path, fullname)
         _bootstrap._verbose_message('code object from {}', source_path)
         if (not sys.dont_write_bytecode and bytecode_path is not None and
                 source_mtime is not None):
@@ -927,18 +911,6 @@ def __eq__(self, other):
     def __hash__(self):
         return hash(self.name) ^ hash(self.path)
 
-    @_check_name
-    def load_module(self, fullname):
-        """Load a module from a file.
-
-        This method is deprecated.  Use exec_module() instead.
-
-        """
-        # The only reason for this method is for the name check.
-        # Issue #14857: Avoid the zero-argument form of super so the implementation
-        # of that form can be updated without breaking the frozen module.
-        return super(FileLoader, self).load_module(fullname)
-
     @_check_name
     def get_filename(self, fullname):
         """Return the path to the source file as found by the finder."""
@@ -1082,12 +1054,18 @@ def get_filename(self, fullname):
         return self.path
 
 
-class _NamespacePath:
-    """Represents a namespace package's path.  It uses the module name
-    to find its parent module, and from there it looks up the parent's
-    __path__.  When this changes, the module's own path is recomputed,
-    using path_finder.  For top-level modules, the parent module's path
-    is sys.path."""
+class NamespacePath:
+    """Represents a namespace package's path.
+
+    It uses the module *name* to find its parent module, and from there it looks
+    up the parent's __path__. When this changes, the module's own path is
+    recomputed, using *path_finder*. The initial value is set to *path*.
+
+    For top-level modules, the parent module's path is sys.path.
+
+    *path_finder* should be a callable with the same signature as
+    MetaPathFinder.find_spec((fullname, path, target=None) -> spec).
+    """
 
     # When invalidate_caches() is called, this epoch is incremented
     # https://bugs.python.org/issue45703
@@ -1112,7 +1090,15 @@ def _find_parent_path_names(self):
 
     def _get_parent_path(self):
         parent_module_name, path_attr_name = self._find_parent_path_names()
-        return getattr(sys.modules[parent_module_name], path_attr_name)
+        try:
+            module = sys.modules[parent_module_name]
+        except KeyError as e:
+            raise ModuleNotFoundError(
+                f"{parent_module_name!r} must be imported before finding {self._name!r}.",
+                name=parent_module_name,
+            ) from e
+        else:
+            return getattr(module, path_attr_name)
 
     def _recalculate(self):
         # If the parent's path has changed, recalculate _path
@@ -1141,7 +1127,7 @@ def __len__(self):
         return len(self._recalculate())
 
     def __repr__(self):
-        return f'_NamespacePath({self._path!r})'
+        return f'NamespacePath({self._path!r})'
 
     def __contains__(self, item):
         return item in self._recalculate()
@@ -1150,12 +1136,16 @@ def append(self, item):
         self._path.append(item)
 
 
+# For backwards-compatibility for anyone desperate enough to get at the class back in the day.
+_NamespacePath = NamespacePath
+
+
 # This class is actually exposed publicly in a namespace package's __loader__
 # attribute, so it should be available through a non-private name.
 # https://github.com/python/cpython/issues/92054
 class NamespaceLoader:
     def __init__(self, name, path, path_finder):
-        self._path = _NamespacePath(name, path, path_finder)
+        self._path = NamespacePath(name, path, path_finder)
 
     def is_package(self, fullname):
         return True
@@ -1164,7 +1154,7 @@ def get_source(self, fullname):
         return ''
 
     def get_code(self, fullname):
-        return compile('', '<string>', 'exec', dont_inherit=True)
+        return compile('', '<string>', 'exec', dont_inherit=True, module=fullname)
 
     def create_module(self, spec):
         """Use default semantics for module creation."""
@@ -1172,18 +1162,6 @@ def create_module(self, spec):
     def exec_module(self, module):
         pass
 
-    def load_module(self, fullname):
-        """Load a namespace module.
-
-        This method is deprecated.  Use exec_module() instead.
-
-        """
-        # The import system never calls this method.
-        _bootstrap._verbose_message('namespace module loaded with path {!r}',
-                                    self._path)
-        # Warning implemented in _load_module_shim().
-        return _bootstrap._load_module_shim(self, fullname)
-
     def get_resource_reader(self, module):
         from importlib.readers import NamespaceReader
         return NamespaceReader(self._path)
@@ -1210,9 +1188,9 @@ def invalidate_caches():
                 del sys.path_importer_cache[name]
             elif hasattr(finder, 'invalidate_caches'):
                 finder.invalidate_caches()
-        # Also invalidate the caches of _NamespacePaths
+        # Also invalidate the caches of NamespacePaths
         # https://bugs.python.org/issue45703
-        _NamespacePath._epoch += 1
+        NamespacePath._epoch += 1
 
         from importlib.metadata import MetadataPathFinder
         MetadataPathFinder.invalidate_caches()
@@ -1298,13 +1276,30 @@ def find_spec(cls, fullname, path=None, target=None):
                 # We found at least one namespace path.  Return a spec which
                 # can create the namespace package.
                 spec.origin = None
-                spec.submodule_search_locations = _NamespacePath(fullname, namespace_path, cls._get_spec)
+                spec.submodule_search_locations = NamespacePath(fullname, namespace_path, cls._get_spec)
                 return spec
             else:
                 return None
         else:
             return spec
 
+    @classmethod
+    def discover(cls, parent=None):
+        if parent is None:
+            path = sys.path
+        elif parent.submodule_search_locations is None:
+            raise ValueError(f'{parent} is not a package module')
+        else:
+            path = parent.submodule_search_locations
+
+        for entry in set(path):
+            if not isinstance(entry, str):
+                continue
+            if (finder := cls._path_importer_cache(entry)) is None:
+                continue
+            if discover := getattr(finder, 'discover', None):
+                yield from discover(parent)
+
     @staticmethod
     def find_distributions(*args, **kwargs):
         """
@@ -1454,6 +1449,37 @@ def path_hook_for_FileFinder(path):
 
         return path_hook_for_FileFinder
 
+    def _find_children(self):
+        with _os.scandir(self.path) as scan_iterator:
+            while True:
+                try:
+                    entry = next(scan_iterator)
+                    if entry.name == _PYCACHE:
+                        continue
+                    # packages
+                    if entry.is_dir() and '.' not in entry.name:
+                        yield entry.name
+                    # files
+                    if entry.is_file():
+                        yield from {
+                            entry.name.removesuffix(suffix)
+                            for suffix, _ in self._loaders
+                            if entry.name.endswith(suffix)
+                        }
+                except OSError:
+                    pass  # ignore exceptions from next(scan_iterator) and os.DirEntry
+                except StopIteration:
+                    break
+
+    def discover(self, parent=None):
+        if parent and parent.submodule_search_locations is None:
+            raise ValueError(f'{parent} is not a package module')
+
+        module_prefix = f'{parent.name}.' if parent else ''
+        for child_name in self._find_children():
+            if spec := self.find_spec(module_prefix + child_name):
+                yield spec
+
     def __repr__(self):
         return f'FileFinder({self.path!r})'
 
@@ -1525,7 +1551,6 @@ def _fix_up_module(ns, name, pathname, cpathname=None):
         ns['__spec__'] = spec
         ns['__loader__'] = loader
         ns['__file__'] = pathname
-        ns['__cached__'] = cpathname
     except Exception:
         # Not important enough to report.
         pass
diff --git a/Lib/importlib/abc.py b/Lib/importlib/abc.py
index 1e47495f65f..9ca127ad9c7 100644
--- a/Lib/importlib/abc.py
+++ b/Lib/importlib/abc.py
@@ -45,6 +45,16 @@ def invalidate_caches(self):
         This method is used by importlib.invalidate_caches().
         """
 
+    def discover(self, parent=None):
+        """An optional method which searches for possible specs with given *parent*
+        module spec. If *parent* is *None*, MetaPathFinder.discover will search
+        for top-level modules.
+
+        Returns an iterable of possible specs.
+        """
+        return ()
+
+
 _register(MetaPathFinder, machinery.BuiltinImporter, machinery.FrozenImporter,
           machinery.PathFinder, machinery.WindowsRegistryFinder)
 
@@ -58,6 +68,15 @@ def invalidate_caches(self):
         This method is used by PathFinder.invalidate_caches().
         """
 
+    def discover(self, parent=None):
+        """An optional method which searches for possible specs with given
+        *parent* module spec. If *parent* is *None*, PathEntryFinder.discover
+        will search for top-level modules.
+
+        Returns an iterable of possible specs.
+        """
+        return ()
+
 _register(PathEntryFinder, machinery.FileFinder)
 
 
@@ -108,7 +127,7 @@ def get_code(self, fullname):
         source = self.get_source(fullname)
         if source is None:
             return None
-        return self.source_to_code(source)
+        return self.source_to_code(source, '<string>', fullname)
 
     @abc.abstractmethod
     def get_source(self, fullname):
@@ -120,15 +139,14 @@ def get_source(self, fullname):
         raise ImportError
 
     @staticmethod
-    def source_to_code(data, path='<string>'):
+    def source_to_code(data, path='<string>', fullname=None):
         """Compile 'data' into a code object.
 
         The 'data' argument can be anything that compile() can handle. The'path'
         argument should be where the data was retrieved (when applicable)."""
-        return compile(data, path, 'exec', dont_inherit=True)
+        return compile(data, path, 'exec', dont_inherit=True, module=fullname)
 
     exec_module = _bootstrap_external._LoaderBasics.exec_module
-    load_module = _bootstrap_external._LoaderBasics.load_module
 
 _register(InspectLoader, machinery.BuiltinImporter, machinery.FrozenImporter, machinery.NamespaceLoader)
 
@@ -163,9 +181,8 @@ def get_code(self, fullname):
         try:
             path = self.get_filename(fullname)
         except ImportError:
-            return self.source_to_code(source)
-        else:
-            return self.source_to_code(source, path)
+            path = '<string>'
+        return self.source_to_code(source, path, fullname)
 
 _register(
     ExecutionLoader,
diff --git a/Lib/importlib/machinery.py b/Lib/importlib/machinery.py
index 63d726445c3..023f77d750f 100644
--- a/Lib/importlib/machinery.py
+++ b/Lib/importlib/machinery.py
@@ -16,6 +16,7 @@
 from ._bootstrap_external import ExtensionFileLoader
 from ._bootstrap_external import AppleFrameworkLoader
 from ._bootstrap_external import NamespaceLoader
+from ._bootstrap_external import NamespacePath
 
 
 def all_suffixes():
diff --git a/Lib/importlib/metadata/__init__.py b/Lib/importlib/metadata/__init__.py
index 8ce62dd864f..32f4b7d2d6e 100644
--- a/Lib/importlib/metadata/__init__.py
+++ b/Lib/importlib/metadata/__init__.py
@@ -1,40 +1,50 @@
+"""
+APIs exposing metadata from third-party Python packages.
+
+This codebase is shared between importlib.metadata in the stdlib
+and importlib_metadata in PyPI. See
+https://github.com/python/importlib_metadata/wiki/Development-Methodology
+for more detail.
+"""
+
 from __future__ import annotations
 
-import os
-import re
 import abc
-import sys
-import json
+import collections
 import email
-import types
-import inspect
-import pathlib
-import zipfile
-import operator
-import textwrap
-import warnings
 import functools
 import itertools
+import operator
+import os
+import pathlib
 import posixpath
-import collections
-
-from . import _meta
-from ._collections import FreezableDefaultDict, Pair
-from ._functools import method_cache, pass_none
-from ._itertools import always_iterable, unique_everseen
-from ._meta import PackageMetadata, SimplePath
-
+import re
+import sys
+import textwrap
+import types
+from collections.abc import Iterable, Mapping
 from contextlib import suppress
 from importlib import import_module
 from importlib.abc import MetaPathFinder
 from itertools import starmap
-from typing import Any, Iterable, List, Mapping, Match, Optional, Set, cast
+from typing import Any
+
+from . import _meta
+from ._collections import FreezableDefaultDict, Pair
+from ._context import ExceptionTrap
+from ._functools import method_cache, noop, pass_none, passthrough
+from ._itertools import always_iterable, bucket, unique_everseen
+from ._meta import PackageMetadata, SimplePath
+from ._typing import md_none
 
 __all__ = [
     'Distribution',
     'DistributionFinder',
     'PackageMetadata',
     'PackageNotFoundError',
+    'PackagePath',
+    'MetadataNotFound',
+    'SimplePath',
     'distribution',
     'distributions',
     'entry_points',
@@ -53,11 +63,15 @@ def __str__(self) -> str:
         return f"No package metadata was found for {self.name}"
 
     @property
-    def name(self) -> str:  # type: ignore[override]
+    def name(self) -> str:  # type: ignore[override] # make readonly
         (name,) = self.args
         return name
 
 
+class MetadataNotFound(FileNotFoundError):
+    """No metadata file is present in the distribution."""
+
+
 class Sectioned:
     """
     A simple entry point config parser for performance
@@ -123,6 +137,12 @@ def valid(line: str):
         return line and not line.startswith('#')
 
 
+class _EntryPointMatch(types.SimpleNamespace):
+    module: str
+    attr: str
+    extras: str
+
+
 class EntryPoint:
     """An entry point as defined by Python packaging conventions.
 
@@ -138,6 +158,30 @@ class EntryPoint:
     'attr'
     >>> ep.extras
     ['extra1', 'extra2']
+
+    If the value package or module are not valid identifiers, a
+    ValueError is raised on access.
+
+    >>> EntryPoint(name=None, group=None, value='invalid-name').module
+    Traceback (most recent call last):
+    ...
+    ValueError: ('Invalid object reference...invalid-name...
+    >>> EntryPoint(name=None, group=None, value='invalid-name').attr
+    Traceback (most recent call last):
+    ...
+    ValueError: ('Invalid object reference...invalid-name...
+    >>> EntryPoint(name=None, group=None, value='invalid-name').extras
+    Traceback (most recent call last):
+    ...
+    ValueError: ('Invalid object reference...invalid-name...
+
+    The same thing happens on construction.
+
+    >>> EntryPoint(name=None, group=None, value='invalid-name')
+    Traceback (most recent call last):
+    ...
+    ValueError: ('Invalid object reference...invalid-name...
+
     """
 
     pattern = re.compile(
@@ -165,38 +209,44 @@ class EntryPoint:
     value: str
     group: str
 
-    dist: Optional[Distribution] = None
+    dist: Distribution | None = None
 
     def __init__(self, name: str, value: str, group: str) -> None:
         vars(self).update(name=name, value=value, group=group)
+        self.module
 
     def load(self) -> Any:
         """Load the entry point from its definition. If only a module
         is indicated by the value, return that module. Otherwise,
         return the named object.
         """
-        match = cast(Match, self.pattern.match(self.value))
-        module = import_module(match.group('module'))
-        attrs = filter(None, (match.group('attr') or '').split('.'))
+        module = import_module(self.module)
+        attrs = filter(None, (self.attr or '').split('.'))
         return functools.reduce(getattr, attrs, module)
 
     @property
     def module(self) -> str:
-        match = self.pattern.match(self.value)
-        assert match is not None
-        return match.group('module')
+        return self._match.module
 
     @property
     def attr(self) -> str:
-        match = self.pattern.match(self.value)
-        assert match is not None
-        return match.group('attr')
+        return self._match.attr
 
     @property
-    def extras(self) -> List[str]:
+    def extras(self) -> list[str]:
+        return re.findall(r'\w+', self._match.extras or '')
+
+    @functools.cached_property
+    def _match(self) -> _EntryPointMatch:
         match = self.pattern.match(self.value)
-        assert match is not None
-        return re.findall(r'\w+', match.group('extras') or '')
+        if not match:
+            raise ValueError(
+                'Invalid object reference. '
+                'See https://packaging.python.org'
+                '/en/latest/specifications/entry-points/#data-model',
+                self.value,
+            )
+        return _EntryPointMatch(**match.groupdict())
 
     def _for(self, dist):
         vars(self).update(dist=dist)
@@ -222,9 +272,26 @@ def matches(self, **params):
         >>> ep.matches(attr='bong')
         True
         """
+        self._disallow_dist(params)
         attrs = (getattr(self, param) for param in params)
         return all(map(operator.eq, params.values(), attrs))
 
+    @staticmethod
+    def _disallow_dist(params):
+        """
+        Querying by dist is not allowed (dist objects are not comparable).
+        >>> EntryPoint(name='fan', value='fav', group='fag').matches(dist='foo')
+        Traceback (most recent call last):
+        ...
+        ValueError: "dist" is not suitable for matching...
+        """
+        if "dist" in params:
+            raise ValueError(
+                '"dist" is not suitable for matching. '
+                "Instead, use Distribution.entry_points.select() on a "
+                "located distribution."
+            )
+
     def _key(self):
         return self.name, self.value, self.group
 
@@ -254,7 +321,7 @@ class EntryPoints(tuple):
 
     __slots__ = ()
 
-    def __getitem__(self, name: str) -> EntryPoint:  # type: ignore[override]
+    def __getitem__(self, name: str) -> EntryPoint:  # type: ignore[override] # Work with str instead of int
         """
         Get the EntryPoint in self matching name.
         """
@@ -278,14 +345,14 @@ def select(self, **params) -> EntryPoints:
         return EntryPoints(ep for ep in self if ep.matches(**params))
 
     @property
-    def names(self) -> Set[str]:
+    def names(self) -> set[str]:
         """
         Return the set of all names of all entry points.
         """
         return {ep.name for ep in self}
 
     @property
-    def groups(self) -> Set[str]:
+    def groups(self) -> set[str]:
         """
         Return the set of all groups of all entry points.
         """
@@ -306,11 +373,11 @@ def _from_text(text):
 class PackagePath(pathlib.PurePosixPath):
     """A reference to a path in a package"""
 
-    hash: Optional[FileHash]
+    hash: FileHash | None
     size: int
     dist: Distribution
 
-    def read_text(self, encoding: str = 'utf-8') -> str:  # type: ignore[override]
+    def read_text(self, encoding: str = 'utf-8') -> str:
         return self.locate().read_text(encoding=encoding)
 
     def read_binary(self) -> bytes:
@@ -329,27 +396,7 @@ def __repr__(self) -> str:
         return f'<FileHash mode: {self.mode} value: {self.value}>'
 
 
-class DeprecatedNonAbstract:
-    # Required until Python 3.14
-    def __new__(cls, *args, **kwargs):
-        all_names = {
-            name for subclass in inspect.getmro(cls) for name in vars(subclass)
-        }
-        abstract = {
-            name
-            for name in all_names
-            if getattr(getattr(cls, name), '__isabstractmethod__', False)
-        }
-        if abstract:
-            warnings.warn(
-                f"Unimplemented abstract methods {abstract}",
-                DeprecationWarning,
-                stacklevel=2,
-            )
-        return super().__new__(cls)
-
-
-class Distribution(DeprecatedNonAbstract):
+class Distribution(metaclass=abc.ABCMeta):
     """
     An abstract Python distribution package.
 
@@ -361,7 +408,7 @@ class Distribution(DeprecatedNonAbstract):
     """
 
     @abc.abstractmethod
-    def read_text(self, filename) -> Optional[str]:
+    def read_text(self, filename) -> str | None:
         """Attempt to load metadata file given by the name.
 
         Python distribution metadata is organized by blobs of text
@@ -388,6 +435,17 @@ def locate_file(self, path: str | os.PathLike[str]) -> SimplePath:
         """
         Given a path to a file in this distribution, return a SimplePath
         to it.
+
+        This method is used by callers of ``Distribution.files()`` to
+        locate files within the distribution. If it's possible for a
+        Distribution to represent files in the distribution as
+        ``SimplePath`` objects, it should implement this method
+        to resolve such objects.
+
+        Some Distribution providers may elect not to resolve SimplePath
+        objects within the distribution by raising a
+        NotImplementedError, but consumers of such a Distribution would
+        be unable to invoke ``Distribution.files()``.
         """
 
     @classmethod
@@ -404,13 +462,13 @@ def from_name(cls, name: str) -> Distribution:
         if not name:
             raise ValueError("A distribution name is required.")
         try:
-            return next(iter(cls.discover(name=name)))
+            return next(iter(cls._prefer_valid(cls.discover(name=name))))
         except StopIteration:
-            raise PackageNotFoundError(name)
+            raise PackageNotFoundError(name) from None
 
     @classmethod
     def discover(
-        cls, *, context: Optional[DistributionFinder.Context] = None, **kwargs
+        cls, *, context: DistributionFinder.Context | None = None, **kwargs
     ) -> Iterable[Distribution]:
         """Return an iterable of Distribution objects for all packages.
 
@@ -428,6 +486,21 @@ def discover(
             resolver(context) for resolver in cls._discover_resolvers()
         )
 
+    @staticmethod
+    def _prefer_valid(dists: Iterable[Distribution]) -> Iterable[Distribution]:
+        """
+        Prefer (move to the front) distributions that have metadata.
+
+        Ref python/importlib_resources#489.
+        """
+
+        has_metadata = ExceptionTrap(MetadataNotFound).passes(
+            operator.attrgetter('metadata')
+        )
+
+        buckets = bucket(dists, has_metadata)
+        return itertools.chain(buckets[True], buckets[False])
+
     @staticmethod
     def at(path: str | os.PathLike[str]) -> Distribution:
         """Return a Distribution for the indicated metadata path.
@@ -455,11 +528,11 @@ def metadata(self) -> _meta.PackageMetadata:
 
         Custom providers may provide the METADATA file or override this
         property.
+
+        :raises MetadataNotFound: If no metadata file is present.
         """
-        # deferred for performance (python/cpython#109829)
-        from . import _adapters
 
-        opt_text = (
+        text = (
             self.read_text('METADATA')
             or self.read_text('PKG-INFO')
             # This last clause is here to support old egg-info files.  Its
@@ -467,9 +540,21 @@ def metadata(self) -> _meta.PackageMetadata:
             # (which points to the egg-info file) attribute unchanged.
             or self.read_text('')
         )
-        text = cast(str, opt_text)
+        return self._assemble_message(self._ensure_metadata_present(text))
+
+    @staticmethod
+    def _assemble_message(text: str) -> _meta.PackageMetadata:
+        # deferred for performance (python/cpython#109829)
+        from . import _adapters
+
         return _adapters.Message(email.message_from_string(text))
 
+    def _ensure_metadata_present(self, text: str | None) -> str:
+        if text is not None:
+            return text
+
+        raise MetadataNotFound('No package metadata was found.')
+
     @property
     def name(self) -> str:
         """Return the 'Name' metadata for the distribution package."""
@@ -496,7 +581,7 @@ def entry_points(self) -> EntryPoints:
         return EntryPoints._from_text_for(self.read_text('entry_points.txt'), self)
 
     @property
-    def files(self) -> Optional[List[PackagePath]]:
+    def files(self) -> list[PackagePath] | None:
         """Files in this distribution.
 
         :return: List of PackagePath for this distribution or None
@@ -589,7 +674,7 @@ def _read_files_egginfo_sources(self):
         return text and map('"{}"'.format, text.splitlines())
 
     @property
-    def requires(self) -> Optional[List[str]]:
+    def requires(self) -> list[str] | None:
         """Generated requirements specified for this Distribution"""
         reqs = self._read_dist_info_reqs() or self._read_egg_info_reqs()
         return reqs and list(reqs)
@@ -645,6 +730,9 @@ def origin(self):
         return self._load_json('direct_url.json')
 
     def _load_json(self, filename):
+        # Deferred for performance (python/importlib_metadata#503)
+        import json
+
         return pass_none(json.loads)(
             self.read_text(filename),
             object_hook=lambda data: types.SimpleNamespace(**data),
@@ -692,7 +780,7 @@ def __init__(self, **kwargs):
             vars(self).update(kwargs)
 
         @property
-        def path(self) -> List[str]:
+        def path(self) -> list[str]:
             """
             The sequence of directory path that a distribution finder
             should search.
@@ -713,6 +801,20 @@ def find_distributions(self, context=Context()) -> Iterable[Distribution]:
         """
 
 
+@passthrough
+def _clear_after_fork(cached):
+    """Ensure ``func`` clears cached state after ``fork`` when supported.
+
+    ``FastPath`` caches zip-backed ``pathlib.Path`` objects that retain a
+    reference to the parent's open ``ZipFile`` handle. Re-using a cached
+    instance in a forked child can therefore resurrect invalid file pointers
+    and trigger ``BadZipFile``/``OSError`` failures (python/importlib_metadata#520).
+    Registering ``cache_clear`` with ``os.register_at_fork`` keeps each process
+    on its own cache.
+    """
+    getattr(os, 'register_at_fork', noop)(after_in_child=cached.cache_clear)
+
+
 class FastPath:
     """
     Micro-optimized class for searching a root for children.
@@ -729,7 +831,8 @@ class FastPath:
     True
     """
 
-    @functools.lru_cache()  # type: ignore
+    @_clear_after_fork  # type: ignore[misc]
+    @functools.lru_cache()
     def __new__(cls, root):
         return super().__new__(cls)
 
@@ -747,6 +850,9 @@ def children(self):
         return []
 
     def zip_children(self):
+        # deferred for performance (python/importlib_metadata#502)
+        import zipfile
+
         zip_path = zipfile.Path(self.root)
         names = zip_path.root.namelist()
         self.joinpath = zip_path.joinpath
@@ -841,7 +947,7 @@ class Prepared:
     normalized = None
     legacy_normalized = None
 
-    def __init__(self, name: Optional[str]):
+    def __init__(self, name: str | None):
         self.name = name
         if name is None:
             return
@@ -852,8 +958,15 @@ def __init__(self, name: Optional[str]):
     def normalize(name):
         """
         PEP 503 normalization plus dashes as underscores.
+
+        Specifically avoids ``re.sub`` as prescribed for performance
+        benefits (see python/cpython#143658).
         """
-        return re.sub(r"[-_.]+", "-", name).lower().replace('-', '_')
+        value = name.lower().replace("-", "_").replace(".", "_")
+        # Condense repeats
+        while "__" in value:
+            value = value.replace("__", "_")
+        return value
 
     @staticmethod
     def legacy_normalize(name):
@@ -904,7 +1017,7 @@ def __init__(self, path: SimplePath) -> None:
         """
         self._path = path
 
-    def read_text(self, filename: str | os.PathLike[str]) -> Optional[str]:
+    def read_text(self, filename: str | os.PathLike[str]) -> str | None:
         with suppress(
             FileNotFoundError,
             IsADirectoryError,
@@ -973,6 +1086,7 @@ def metadata(distribution_name: str) -> _meta.PackageMetadata:
 
     :param distribution_name: The name of the distribution package to query.
     :return: A PackageMetadata containing the parsed metadata.
+    :raises MetadataNotFound: If no metadata file is present in the distribution.
     """
     return Distribution.from_name(distribution_name).metadata
 
@@ -1011,7 +1125,7 @@ def entry_points(**params) -> EntryPoints:
     return EntryPoints(eps).select(**params)
 
 
-def files(distribution_name: str) -> Optional[List[PackagePath]]:
+def files(distribution_name: str) -> list[PackagePath] | None:
     """Return a list of files for the named package.
 
     :param distribution_name: The name of the distribution package to query.
@@ -1020,7 +1134,7 @@ def files(distribution_name: str) -> Optional[List[PackagePath]]:
     return distribution(distribution_name).files
 
 
-def requires(distribution_name: str) -> Optional[List[str]]:
+def requires(distribution_name: str) -> list[str] | None:
     """
     Return a list of requirements for the named package.
 
@@ -1030,7 +1144,7 @@ def requires(distribution_name: str) -> Optional[List[str]]:
     return distribution(distribution_name).requires
 
 
-def packages_distributions() -> Mapping[str, List[str]]:
+def packages_distributions() -> Mapping[str, list[str]]:
     """
     Return a mapping of top-level packages to their
     distributions.
@@ -1051,7 +1165,7 @@ def _top_level_declared(dist):
     return (dist.read_text('top_level.txt') or '').split()
 
 
-def _topmost(name: PackagePath) -> Optional[str]:
+def _topmost(name: PackagePath) -> str | None:
     """
     Return the top-most parent as long as there is a parent.
     """
@@ -1077,11 +1191,10 @@ def _get_toplevel_name(name: PackagePath) -> str:
     >>> _get_toplevel_name(PackagePath('foo.dist-info'))
     'foo.dist-info'
     """
-    return _topmost(name) or (
-        # python/typeshed#10328
-        inspect.getmodulename(name)  # type: ignore
-        or str(name)
-    )
+    # Defer import of inspect for performance (python/cpython#118761)
+    import inspect
+
+    return _topmost(name) or inspect.getmodulename(name) or str(name)
 
 
 def _top_level_inferred(dist):
diff --git a/Lib/importlib/metadata/_adapters.py b/Lib/importlib/metadata/_adapters.py
index 59116880895..dede395d79a 100644
--- a/Lib/importlib/metadata/_adapters.py
+++ b/Lib/importlib/metadata/_adapters.py
@@ -1,22 +1,59 @@
-import functools
-import warnings
+import email.message
+import email.policy
 import re
 import textwrap
-import email.message
 
 from ._text import FoldedCase
 
 
-# Do not remove prior to 2024-01-01 or Python 3.14
-_warn = functools.partial(
-    warnings.warn,
-    "Implicit None on return values is deprecated and will raise KeyErrors.",
-    DeprecationWarning,
-    stacklevel=2,
-)
+class RawPolicy(email.policy.EmailPolicy):
+    def fold(self, name, value):
+        folded = self.linesep.join(
+            textwrap
+            .indent(value, prefix=' ' * 8, predicate=lambda line: True)
+            .lstrip()
+            .splitlines()
+        )
+        return f'{name}: {folded}{self.linesep}'
 
 
 class Message(email.message.Message):
+    r"""
+    Specialized Message subclass to handle metadata naturally.
+
+    Reads values that may have newlines in them and converts the
+    payload to the Description.
+
+    >>> msg_text = textwrap.dedent('''
+    ...     Name: Foo
+    ...     Version: 3.0
+    ...     License: blah
+    ...             de-blah
+    ...     <BLANKLINE>
+    ...     First line of description.
+    ...     Second line of description.
+    ...     <BLANKLINE>
+    ...     Fourth line!
+    ...     ''').lstrip().replace('<BLANKLINE>', '')
+    >>> msg = Message(email.message_from_string(msg_text))
+    >>> msg['Description']
+    'First line of description.\nSecond line of description.\n\nFourth line!\n'
+
+    Message should render even if values contain newlines.
+
+    >>> print(msg)
+    Name: Foo
+    Version: 3.0
+    License: blah
+            de-blah
+    Description: First line of description.
+            Second line of description.
+    <BLANKLINE>
+            Fourth line!
+    <BLANKLINE>
+    <BLANKLINE>
+    """
+
     multiple_use_keys = set(
         map(
             FoldedCase,
@@ -52,26 +89,36 @@ def __iter__(self):
 
     def __getitem__(self, item):
         """
-        Warn users that a ``KeyError`` can be expected when a
-        missing key is supplied. Ref python/importlib_metadata#371.
+        Override parent behavior to typical dict behavior.
+
+        ``email.message.Message`` will emit None values for missing
+        keys. Typical mappings, including this ``Message``, will raise
+        a key error for missing keys.
+
+        Ref python/importlib_metadata#371.
         """
         res = super().__getitem__(item)
         if res is None:
-            _warn()
+            raise KeyError(item)
         return res
 
     def _repair_headers(self):
         def redent(value):
             "Correct for RFC822 indentation"
-            if not value or '\n' not in value:
+            indent = ' ' * 8
+            if not value or '\n' + indent not in value:
                 return value
-            return textwrap.dedent(' ' * 8 + value)
+            return textwrap.dedent(indent + value)
 
         headers = [(key, redent(value)) for key, value in vars(self)['_headers']]
         if self._payload:
             headers.append(('Description', self.get_payload()))
+            self.set_payload('')
         return headers
 
+    def as_string(self):
+        return super().as_string(policy=RawPolicy())
+
     @property
     def json(self):
         """
diff --git a/Lib/importlib/metadata/_collections.py b/Lib/importlib/metadata/_collections.py
index cf0954e1a30..fc5045d36be 100644
--- a/Lib/importlib/metadata/_collections.py
+++ b/Lib/importlib/metadata/_collections.py
@@ -1,4 +1,5 @@
 import collections
+import typing
 
 
 # from jaraco.collections 3.3
@@ -24,7 +25,10 @@ def freeze(self):
         self._frozen = lambda key: self.default_factory()
 
 
-class Pair(collections.namedtuple('Pair', 'name value')):
+class Pair(typing.NamedTuple):
+    name: str
+    value: str
+
     @classmethod
     def parse(cls, text):
         return cls(*map(str.strip, text.split("=", 1)))
diff --git a/Lib/importlib/metadata/_context.py b/Lib/importlib/metadata/_context.py
new file mode 100644
index 00000000000..2635b164ce8
--- /dev/null
+++ b/Lib/importlib/metadata/_context.py
@@ -0,0 +1,118 @@
+from __future__ import annotations
+
+import functools
+import operator
+
+
+# from jaraco.context 6.1
+class ExceptionTrap:
+    """
+    A context manager that will catch certain exceptions and provide an
+    indication they occurred.
+
+    >>> with ExceptionTrap() as trap:
+    ...     raise Exception()
+    >>> bool(trap)
+    True
+
+    >>> with ExceptionTrap() as trap:
+    ...     pass
+    >>> bool(trap)
+    False
+
+    >>> with ExceptionTrap(ValueError) as trap:
+    ...     raise ValueError("1 + 1 is not 3")
+    >>> bool(trap)
+    True
+    >>> trap.value
+    ValueError('1 + 1 is not 3')
+    >>> trap.tb
+    <traceback object at ...>
+
+    >>> with ExceptionTrap(ValueError) as trap:
+    ...     raise Exception()
+    Traceback (most recent call last):
+    ...
+    Exception
+
+    >>> bool(trap)
+    False
+    """
+
+    exc_info = None, None, None
+
+    def __init__(self, exceptions=(Exception,)):
+        self.exceptions = exceptions
+
+    def __enter__(self):
+        return self
+
+    @property
+    def type(self):
+        return self.exc_info[0]
+
+    @property
+    def value(self):
+        return self.exc_info[1]
+
+    @property
+    def tb(self):
+        return self.exc_info[2]
+
+    def __exit__(self, *exc_info):
+        type = exc_info[0]
+        matches = type and issubclass(type, self.exceptions)
+        if matches:
+            self.exc_info = exc_info
+        return matches
+
+    def __bool__(self):
+        return bool(self.type)
+
+    def raises(self, func, *, _test=bool):
+        """
+        Wrap func and replace the result with the truth
+        value of the trap (True if an exception occurred).
+
+        First, give the decorator an alias to support Python 3.8
+        Syntax.
+
+        >>> raises = ExceptionTrap(ValueError).raises
+
+        Now decorate a function that always fails.
+
+        >>> @raises
+        ... def fail():
+        ...     raise ValueError('failed')
+        >>> fail()
+        True
+        """
+
+        @functools.wraps(func)
+        def wrapper(*args, **kwargs):
+            with ExceptionTrap(self.exceptions) as trap:
+                func(*args, **kwargs)
+            return _test(trap)
+
+        return wrapper
+
+    def passes(self, func):
+        """
+        Wrap func and replace the result with the truth
+        value of the trap (True if no exception).
+
+        First, give the decorator an alias to support Python 3.8
+        Syntax.
+
+        >>> passes = ExceptionTrap(ValueError).passes
+
+        Now decorate a function that always fails.
+
+        >>> @passes
+        ... def fail():
+        ...     raise ValueError('failed')
+
+        >>> fail()
+        False
+        """
+        return self.raises(func, _test=operator.not_)
diff --git a/Lib/importlib/metadata/_functools.py b/Lib/importlib/metadata/_functools.py
index 71f66bd03cb..c159b46e489 100644
--- a/Lib/importlib/metadata/_functools.py
+++ b/Lib/importlib/metadata/_functools.py
@@ -1,5 +1,7 @@
-import types
 import functools
+import types
+from collections.abc import Callable
+from typing import TypeVar
 
 
 # from jaraco.functools 3.3
@@ -102,3 +104,33 @@ def wrapper(param, *args, **kwargs):
             return func(param, *args, **kwargs)
 
     return wrapper
+
+
+# From jaraco.functools 4.4
+def noop(*args, **kwargs):
+    """
+    A no-operation function that does nothing.
+
+    >>> noop(1, 2, three=3)
+    """
+
+
+_T = TypeVar('_T')
+
+
+# From jaraco.functools 4.4
+def passthrough(func: Callable[..., object]) -> Callable[[_T], _T]:
+    """
+    Wrap the function to always return the first parameter.
+
+    >>> passthrough(print)('3')
+    3
+    '3'
+    """
+
+    @functools.wraps(func)
+    def wrapper(first: _T, *args, **kwargs) -> _T:
+        func(first, *args, **kwargs)
+        return first
+
+    return wrapper  # type: ignore[return-value]
diff --git a/Lib/importlib/metadata/_itertools.py b/Lib/importlib/metadata/_itertools.py
index d4ca9b9140e..79d37198ce7 100644
--- a/Lib/importlib/metadata/_itertools.py
+++ b/Lib/importlib/metadata/_itertools.py
@@ -1,3 +1,4 @@
+from collections import defaultdict, deque
 from itertools import filterfalse
 
 
@@ -71,3 +72,100 @@ def always_iterable(obj, base_type=(str, bytes)):
         return iter(obj)
     except TypeError:
         return iter((obj,))
+
+
+# Copied from more_itertools 10.3
+class bucket:
+    """Wrap *iterable* and return an object that buckets the iterable into
+    child iterables based on a *key* function.
+
+        >>> iterable = ['a1', 'b1', 'c1', 'a2', 'b2', 'c2', 'b3']
+        >>> s = bucket(iterable, key=lambda x: x[0])  # Bucket by 1st character
+        >>> sorted(list(s))  # Get the keys
+        ['a', 'b', 'c']
+        >>> a_iterable = s['a']
+        >>> next(a_iterable)
+        'a1'
+        >>> next(a_iterable)
+        'a2'
+        >>> list(s['b'])
+        ['b1', 'b2', 'b3']
+
+    The original iterable will be advanced and its items will be cached until
+    they are used by the child iterables. This may require significant storage.
+
+    By default, attempting to select a bucket to which no items belong  will
+    exhaust the iterable and cache all values.
+    If you specify a *validator* function, selected buckets will instead be
+    checked against it.
+
+        >>> from itertools import count
+        >>> it = count(1, 2)  # Infinite sequence of odd numbers
+        >>> key = lambda x: x % 10  # Bucket by last digit
+        >>> validator = lambda x: x in {1, 3, 5, 7, 9}  # Odd digits only
+        >>> s = bucket(it, key=key, validator=validator)
+        >>> 2 in s
+        False
+        >>> list(s[2])
+        []
+
+    """
+
+    def __init__(self, iterable, key, validator=None):
+        self._it = iter(iterable)
+        self._key = key
+        self._cache = defaultdict(deque)
+        self._validator = validator or (lambda x: True)
+
+    def __contains__(self, value):
+        if not self._validator(value):
+            return False
+
+        try:
+            item = next(self[value])
+        except StopIteration:
+            return False
+        else:
+            self._cache[value].appendleft(item)
+
+        return True
+
+    def _get_values(self, value):
+        """
+        Helper to yield items from the parent iterator that match *value*.
+        Items that don't match are stored in the local cache as they
+        are encountered.
+        """
+        while True:
+            # If we've cached some items that match the target value, emit
+            # the first one and evict it from the cache.
+            if self._cache[value]:
+                yield self._cache[value].popleft()
+            # Otherwise we need to advance the parent iterator to search for
+            # a matching item, caching the rest.
+            else:
+                while True:
+                    try:
+                        item = next(self._it)
+                    except StopIteration:
+                        return
+                    item_value = self._key(item)
+                    if item_value == value:
+                        yield item
+                        break
+                    elif self._validator(item_value):
+                        self._cache[item_value].append(item)
+
+    def __iter__(self):
+        for item in self._it:
+            item_value = self._key(item)
+            if self._validator(item_value):
+                self._cache[item_value].append(item)
+
+        yield from self._cache.keys()
+
+    def __getitem__(self, value):
+        if not self._validator(value):
+            return iter(())
+
+        return self._get_values(value)
diff --git a/Lib/importlib/metadata/_meta.py b/Lib/importlib/metadata/_meta.py
index 1927d0f624d..0c20eff3da7 100644
--- a/Lib/importlib/metadata/_meta.py
+++ b/Lib/importlib/metadata/_meta.py
@@ -1,9 +1,13 @@
 from __future__ import annotations
 
 import os
-from typing import Protocol
-from typing import Any, Dict, Iterator, List, Optional, TypeVar, Union, overload
-
+from collections.abc import Iterator
+from typing import (
+    Any,
+    Protocol,
+    TypeVar,
+    overload,
+)
 
 _T = TypeVar("_T")
 
@@ -20,25 +24,25 @@ def __iter__(self) -> Iterator[str]: ...  # pragma: no cover
     @overload
     def get(
         self, name: str, failobj: None = None
-    ) -> Optional[str]: ...  # pragma: no cover
+    ) -> str | None: ...  # pragma: no cover
 
     @overload
-    def get(self, name: str, failobj: _T) -> Union[str, _T]: ...  # pragma: no cover
+    def get(self, name: str, failobj: _T) -> str | _T: ...  # pragma: no cover
 
     # overload per python/importlib_metadata#435
     @overload
     def get_all(
         self, name: str, failobj: None = None
-    ) -> Optional[List[Any]]: ...  # pragma: no cover
+    ) -> list[Any] | None: ...  # pragma: no cover
 
     @overload
-    def get_all(self, name: str, failobj: _T) -> Union[List[Any], _T]:
+    def get_all(self, name: str, failobj: _T) -> list[Any] | _T:
         """
         Return all values associated with a possibly multi-valued key.
         """
 
     @property
-    def json(self) -> Dict[str, Union[str, List[str]]]:
+    def json(self) -> dict[str, str | list[str]]:
         """
         A JSON-compatible form of the metadata.
         """
@@ -50,11 +54,11 @@ class SimplePath(Protocol):
     """
 
     def joinpath(
-        self, other: Union[str, os.PathLike[str]]
+        self, other: str | os.PathLike[str]
     ) -> SimplePath: ...  # pragma: no cover
 
     def __truediv__(
-        self, other: Union[str, os.PathLike[str]]
+        self, other: str | os.PathLike[str]
     ) -> SimplePath: ...  # pragma: no cover
 
     @property
diff --git a/Lib/importlib/metadata/_typing.py b/Lib/importlib/metadata/_typing.py
new file mode 100644
index 00000000000..32b1d2b98ac
--- /dev/null
+++ b/Lib/importlib/metadata/_typing.py
@@ -0,0 +1,15 @@
+import functools
+import typing
+
+from ._meta import PackageMetadata
+
+md_none = functools.partial(typing.cast, PackageMetadata)
+"""
+Suppress type errors for optional metadata.
+
+Although Distribution.metadata can return None when metadata is corrupt
+and thus None, allow callers to assume it's not None and crash if
+that's the case.
+
+# python/importlib_metadata#493
+"""
diff --git a/Lib/importlib/resources/__init__.py b/Lib/importlib/resources/__init__.py
index 723c9f9eb33..27d6c7f8930 100644
--- a/Lib/importlib/resources/__init__.py
+++ b/Lib/importlib/resources/__init__.py
@@ -8,12 +8,11 @@
 """
 
 from ._common import (
+    Anchor,
+    Package,
     as_file,
     files,
-    Package,
-    Anchor,
 )
-
 from ._functional import (
     contents,
     is_resource,
@@ -23,10 +22,8 @@
     read_binary,
     read_text,
 )
-
 from .abc import ResourceReader
 
-
 __all__ = [
     'Package',
     'Anchor',
diff --git a/Lib/importlib/resources/_common.py b/Lib/importlib/resources/_common.py
index 4e9014c45a0..6f87d77492f 100644
--- a/Lib/importlib/resources/_common.py
+++ b/Lib/importlib/resources/_common.py
@@ -1,54 +1,20 @@
-import os
-import pathlib
-import tempfile
-import functools
 import contextlib
-import types
+import functools
 import importlib
 import inspect
-import warnings
 import itertools
+import os
+import pathlib
+import tempfile
+import types
+from typing import Optional, cast
 
-from typing import Union, Optional, cast
 from .abc import ResourceReader, Traversable
 
-Package = Union[types.ModuleType, str]
+Package = types.ModuleType | str
 Anchor = Package
 
 
-def package_to_anchor(func):
-    """
-    Replace 'package' parameter as 'anchor' and warn about the change.
-
-    Other errors should fall through.
-
-    >>> files('a', 'b')
-    Traceback (most recent call last):
-    TypeError: files() takes from 0 to 1 positional arguments but 2 were given
-
-    Remove this compatibility in Python 3.14.
-    """
-    undefined = object()
-
-    @functools.wraps(func)
-    def wrapper(anchor=undefined, package=undefined):
-        if package is not undefined:
-            if anchor is not undefined:
-                return func(anchor, package)
-            warnings.warn(
-                "First parameter to files is renamed to 'anchor'",
-                DeprecationWarning,
-                stacklevel=2,
-            )
-            return func(package)
-        elif anchor is undefined:
-            return func()
-        return func(anchor)
-
-    return wrapper
-
-
-@package_to_anchor
 def files(anchor: Optional[Anchor] = None) -> Traversable:
     """
     Get a Traversable resource for an anchor.
@@ -105,6 +71,19 @@ def is_wrapper(frame_info):
     return next(callers).frame
 
 
+def _assert_spec(package: types.ModuleType) -> None:
+    """
+    Provide a nicer error message when package is ``__main__``
+    and its ``__spec__`` is ``None``
+    (https://docs.python.org/3/reference/import.html#main-spec).
+    """
+    if package.__spec__ is None:
+        raise TypeError(
+            f"Cannot access resources for '{package.__name__}' "
+            "as it does not appear to correspond to an importable module (its __spec__ is None)."
+        )
+
+
 def from_package(package: types.ModuleType):
     """
     Return a Traversable object for the given package.
@@ -113,6 +92,7 @@ def from_package(package: types.ModuleType):
     # deferred for performance (python/cpython#109829)
     from ._adapters import wrap_spec
 
+    _assert_spec(package)
     spec = wrap_spec(package)
     reader = spec.loader.get_resource_reader(spec.name)
     return reader.files()
diff --git a/Lib/importlib/resources/_functional.py b/Lib/importlib/resources/_functional.py
index f59416f2dd6..b08a5c6efe2 100644
--- a/Lib/importlib/resources/_functional.py
+++ b/Lib/importlib/resources/_functional.py
@@ -2,8 +2,8 @@
 
 import warnings
 
-from ._common import files, as_file
-
+from ._common import as_file, files
+from .abc import TraversalError
 
 _MISSING = object()
 
@@ -42,7 +42,10 @@ def is_resource(anchor, *path_names):
 
     Otherwise returns ``False``.
     """
-    return _get_resource(anchor, path_names).is_file()
+    try:
+        return _get_resource(anchor, path_names).is_file()
+    except TraversalError:
+        return False
 
 
 def contents(anchor, *path_names):
diff --git a/Lib/importlib/resources/abc.py b/Lib/importlib/resources/abc.py
index 6750a7aaf14..0b5fdee80e8 100644
--- a/Lib/importlib/resources/abc.py
+++ b/Lib/importlib/resources/abc.py
@@ -1,14 +1,22 @@
 import abc
-import io
 import itertools
 import os
 import pathlib
-from typing import Any, BinaryIO, Iterable, Iterator, NoReturn, Text, Optional
-from typing import runtime_checkable, Protocol
-from typing import Union
-
-
-StrPath = Union[str, os.PathLike[str]]
+from collections.abc import Iterable, Iterator
+from typing import (
+    Any,
+    BinaryIO,
+    Literal,
+    NoReturn,
+    Optional,
+    Protocol,
+    Text,
+    TextIO,
+    overload,
+    runtime_checkable,
+)
+
+StrPath = str | os.PathLike[str]
 
 __all__ = ["ResourceReader", "Traversable", "TraversableResources"]
 
@@ -82,11 +90,13 @@ def read_bytes(self) -> bytes:
         with self.open('rb') as strm:
             return strm.read()
 
-    def read_text(self, encoding: Optional[str] = None) -> str:
+    def read_text(
+        self, encoding: Optional[str] = None, errors: Optional[str] = None
+    ) -> str:
         """
         Read contents of self as text
         """
-        with self.open(encoding=encoding) as strm:
+        with self.open(encoding=encoding, errors=errors) as strm:
             return strm.read()
 
     @abc.abstractmethod
@@ -132,8 +142,14 @@ def __truediv__(self, child: StrPath) -> "Traversable":
         """
         return self.joinpath(child)
 
+    @overload
+    def open(self, mode: Literal['r'] = 'r', *args: Any, **kwargs: Any) -> TextIO: ...
+
+    @overload
+    def open(self, mode: Literal['rb'], *args: Any, **kwargs: Any) -> BinaryIO: ...
+
     @abc.abstractmethod
-    def open(self, mode='r', *args, **kwargs):
+    def open(self, mode: str = 'r', *args: Any, **kwargs: Any) -> TextIO | BinaryIO:
         """
         mode may be 'r' or 'rb' to open as text or binary. Return a handle
         suitable for reading (same as pathlib.Path.open).
@@ -160,7 +176,7 @@ class TraversableResources(ResourceReader):
     def files(self) -> "Traversable":
         """Return a Traversable object for the loaded package."""
 
-    def open_resource(self, resource: StrPath) -> io.BufferedReader:
+    def open_resource(self, resource: StrPath) -> BinaryIO:
         return self.files().joinpath(resource).open('rb')
 
     def resource_path(self, resource: Any) -> NoReturn:
diff --git a/Lib/importlib/resources/readers.py b/Lib/importlib/resources/readers.py
index 70fc7e2b9c0..5d0ae46d672 100644
--- a/Lib/importlib/resources/readers.py
+++ b/Lib/importlib/resources/readers.py
@@ -3,15 +3,14 @@
 import collections
 import contextlib
 import itertools
-import pathlib
 import operator
+import pathlib
 import re
 import warnings
 import zipfile
 from collections.abc import Iterator
 
 from . import abc
-
 from ._itertools import only
 
 
diff --git a/Lib/importlib/resources/simple.py b/Lib/importlib/resources/simple.py
index 2e75299b13a..5e182d12607 100644
--- a/Lib/importlib/resources/simple.py
+++ b/Lib/importlib/resources/simple.py
@@ -5,7 +5,7 @@
 import abc
 import io
 import itertools
-from typing import BinaryIO, List
+from typing import BinaryIO
 
 from .abc import Traversable, TraversableResources
 
@@ -24,14 +24,14 @@ def package(self) -> str:
         """
 
     @abc.abstractmethod
-    def children(self) -> List['SimpleReader']:
+    def children(self) -> list['SimpleReader']:
         """
         Obtain an iterable of SimpleReader for available
         child containers (e.g. directories).
         """
 
     @abc.abstractmethod
-    def resources(self) -> List[str]:
+    def resources(self) -> list[str]:
         """
         Obtain available named resources for this virtual package.
         """
diff --git a/Lib/inspect.py b/Lib/inspect.py
index cf61ae943b1..92664f46d35 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -153,9 +153,9 @@
 import itertools
 import linecache
 import os
-import re
+lazy import re
 import sys
-import tokenize
+lazy import tokenize
 import token
 import types
 import functools
@@ -163,9 +163,9 @@
 from keyword import iskeyword
 from operator import attrgetter
 from collections import namedtuple, OrderedDict
-from weakref import ref as make_weakref
+from _weakref import ref as make_weakref
 
-# Create constants for the compiler flags in Include/code.h
+# Create constants for the compiler flags in Include/cpython/code.h
 # We try to get them from dis to avoid duplication
 mod_dict = globals()
 for k, v in dis.COMPILER_FLAG_NAMES.items():
@@ -421,7 +421,6 @@ def iscode(object):
         co_freevars         tuple of names of free variables
         co_posonlyargcount  number of positional only arguments
         co_kwonlyargcount   number of keyword only arguments (not including ** arg)
-        co_lnotab           encoded mapping of line numbers to bytecode indices
         co_name             name with which this code object was defined
         co_names            tuple of names other than arguments and function locals
         co_nlocals          number of local variables
@@ -712,8 +711,8 @@ def _findclass(func):
         return None
     return cls
 
-def _finddoc(obj):
-    if isclass(obj):
+def _finddoc(obj, *, search_in_class=True):
+    if search_in_class and isclass(obj):
         for base in obj.__mro__:
             if base is not object:
                 try:
@@ -753,6 +752,12 @@ def _finddoc(obj):
         cls = _findclass(obj.fget)
         if cls is None or getattr(cls, name) is not obj:
             return None
+    # Should be tested before ismethoddescriptor()
+    elif isinstance(obj, functools.cached_property):
+        name = obj.attrname
+        cls = _findclass(obj.func)
+        if cls is None or getattr(cls, name) is not obj:
+            return None
     elif ismethoddescriptor(obj) or isdatadescriptor(obj):
         name = obj.__name__
         cls = obj.__objclass__
@@ -773,19 +778,37 @@ def _finddoc(obj):
             return doc
     return None
 
-def getdoc(object):
+def _getowndoc(obj):
+    """Get the documentation string for an object if it is not
+    inherited from its class."""
+    try:
+        doc = object.__getattribute__(obj, '__doc__')
+        if doc is None:
+            return None
+        if obj is not type:
+            typedoc = type(obj).__doc__
+            if isinstance(typedoc, str) and typedoc == doc:
+                return None
+        return doc
+    except AttributeError:
+        return None
+
+def getdoc(object, *, fallback_to_class_doc=True, inherit_class_doc=True):
     """Get the documentation string for an object.
 
     All tabs are expanded to spaces.  To clean up docstrings that are
     indented to line up with blocks of code, any whitespace than can be
     uniformly removed from the second line onwards is removed."""
-    try:
-        doc = object.__doc__
-    except AttributeError:
-        return None
+    if fallback_to_class_doc:
+        try:
+            doc = object.__doc__
+        except AttributeError:
+            return None
+    else:
+        doc = _getowndoc(object)
     if doc is None:
         try:
-            doc = _finddoc(object)
+            doc = _finddoc(object, search_in_class=inherit_class_doc)
         except (AttributeError, TypeError):
             return None
     if not isinstance(doc, str):
@@ -1236,11 +1259,10 @@ def getargs(co):
 FullArgSpec = namedtuple('FullArgSpec',
     'args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, annotations')
 
-def getfullargspec(func):
+def getfullargspec(func, *, annotation_format=Format.VALUE):
     """Get the names and default values of a callable object's parameters.
 
-    A tuple of seven things is returned:
-    (args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, annotations).
+    A FullArgSpec namedtuple is returned, which has the following attributes:
     'args' is a list of the parameter names.
     'varargs' and 'varkw' are the names of the * and ** parameters or None.
     'defaults' is an n-tuple of the default values of the last n parameters.
@@ -1248,6 +1270,9 @@ def getfullargspec(func):
     'kwonlydefaults' is a dictionary mapping names from kwonlyargs to defaults.
     'annotations' is a dictionary mapping parameter names to annotations.
 
+    The *annotation_format* parameter controls the format of the annotations.
+    See the annotationlib documentation for details.
+
     Notable differences from inspect.signature():
       - the "self" parameter is always reported, even for bound methods
       - wrapper chains defined by __wrapped__ *not* unwrapped automatically
@@ -1273,7 +1298,8 @@ def getfullargspec(func):
                                        follow_wrapper_chains=False,
                                        skip_bound_arg=False,
                                        sigcls=Signature,
-                                       eval_str=False)
+                                       eval_str=False,
+                                       annotation_format=annotation_format)
     except Exception as ex:
         # Most of the times 'signature' will raise ValueError.
         # But, it can also raise AttributeError, and, maybe something
@@ -1615,7 +1641,6 @@ def getframeinfo(frame, context=1):
 
 def getlineno(frame):
     """Get the line number from a frame object, allowing for optimization."""
-    # FrameType.f_lineno is now a descriptor that grovels co_lnotab
     return frame.f_lineno
 
 _FrameInfo = namedtuple('_FrameInfo', ('frame',) + Traceback._fields)
@@ -1709,7 +1734,8 @@ def _shadowed_dict_from_weakref_mro_tuple(*weakref_mro):
             class_dict = dunder_dict['__dict__']
             if not (type(class_dict) is types.GetSetDescriptorType and
                     class_dict.__name__ == "__dict__" and
-                    class_dict.__objclass__ is entry):
+                    (class_dict.__objclass__ is object or
+                     class_dict.__objclass__ is entry)):
                 return class_dict
     return _sentinel
 
@@ -1793,13 +1819,7 @@ def getgeneratorstate(generator):
       GEN_SUSPENDED: Currently suspended at a yield expression.
       GEN_CLOSED: Execution has completed.
     """
-    if generator.gi_running:
-        return GEN_RUNNING
-    if generator.gi_suspended:
-        return GEN_SUSPENDED
-    if generator.gi_frame is None:
-        return GEN_CLOSED
-    return GEN_CREATED
+    return generator.gi_state
 
 
 def getgeneratorlocals(generator):
@@ -1835,13 +1855,7 @@ def getcoroutinestate(coroutine):
       CORO_SUSPENDED: Currently suspended at an await expression.
       CORO_CLOSED: Execution has completed.
     """
-    if coroutine.cr_running:
-        return CORO_RUNNING
-    if coroutine.cr_suspended:
-        return CORO_SUSPENDED
-    if coroutine.cr_frame is None:
-        return CORO_CLOSED
-    return CORO_CREATED
+    return coroutine.cr_state
 
 
 def getcoroutinelocals(coroutine):
@@ -1874,13 +1888,7 @@ def getasyncgenstate(agen):
       AGEN_SUSPENDED: Currently suspended at a yield expression.
       AGEN_CLOSED: Execution has completed.
     """
-    if agen.ag_running:
-        return AGEN_RUNNING
-    if agen.ag_suspended:
-        return AGEN_SUSPENDED
-    if agen.ag_frame is None:
-        return AGEN_CLOSED
-    return AGEN_CREATED
+    return agen.ag_state
 
 
 def getasyncgenlocals(agen):
@@ -2121,7 +2129,6 @@ def _signature_strip_non_python_syntax(signature):
 
     current_parameter = 0
     OP = token.OP
-    ERRORTOKEN = token.ERRORTOKEN
 
     # token stream always starts with ENCODING token, skip it
     t = next(token_stream)
@@ -2198,7 +2205,8 @@ def wrap_value(s):
             except NameError:
                 raise ValueError
 
-        if isinstance(value, (str, int, float, bytes, bool, type(None))):
+        if isinstance(value, (str, int, float, bytes, bool, type(None),
+                              sentinel)):
             return ast.Constant(value)
         raise ValueError
 
@@ -3356,22 +3364,113 @@ class BufferFlags(enum.IntFlag):
     WRITE = 0x200
 
 
+def _get_details_for_cli(module, nominal_target, resolved_target):
+    # Determine if the given module name is an alias for another module,
+    # or if it is reexporting a name that is actually defined elsewhere
+    resolved_module = getmodule(resolved_target)
+    if resolved_module is not None and resolved_module is not module:
+        # Referenced target indicates it was defined somewhere else,
+        # so report the details of that module rather than the lookup module
+        module = resolved_module
+    reported_module_name = module.__name__
+    # Ensure the reported source file reflects the actual defining location
+    try:
+        source_file = getsourcefile(resolved_target)
+    except Exception:
+        try:
+            source_file = getsourcefile(module)
+        except Exception:
+            source_file = None
+    # Determine if the nominal target location is its defining location
+    if resolved_target is module:
+        reported_target = reported_module_name
+    else:
+        reported_qualname = getattr(resolved_target, "__qualname__", None)
+        if not reported_qualname:
+            reported_qualname = nominal_target.partition(":")[2]
+        reported_target = f"{reported_module_name}:{reported_qualname}"
+        # Special case for looking up functions in frozen modules
+        if source_file == f"<frozen {reported_module_name}>":
+            source_file = module.__file__
+    # Populate the actual details to be reported
+    details = {
+        "target": reported_target,
+        "origin": module.__spec__.origin,
+        "cached": module.__spec__.cached,
+        "source": source_file,
+    }
+    if reported_target != nominal_target:
+        details["alias"] = nominal_target
+    error = None
+    if not source_file:
+        if module.__name__ in sys.builtin_module_names:
+            error = "No source code available for builtin module"
+        else:
+            error = "No source code available for defining module"
+    if resolved_target is module:
+        details["loader"] = repr(module.__spec__.loader)
+        if hasattr(module, '__path__'):
+            details["submodule_paths"] = str(module.__path__)
+    elif source_file:
+            try:
+                __, lineno = findsource(resolved_target)
+            except Exception:
+                error = "Failed to retrieve source code for given target"
+            else:
+                details["lineno"] = lineno
+    if error:
+        details["error"] = error
+    return details
+
+def _render_details_for_cli(details):
+    resolved_target = details["target"]
+    alias = details.get("alias")
+    if alias:
+        rendered_target = f'{resolved_target} (looked up as "{alias}")'
+    else:
+        rendered_target = resolved_target
+    lines = [
+        f'Target: {rendered_target}',
+        f'Origin: {details["origin"]}',
+        f'Source: {details["source"]}',
+        f'Cached: {details["cached"]}',
+    ]
+    loader = details.get("loader")
+    if loader:
+        lines.append(f'Loader: {loader}')
+        submodule_paths = details.get("submodule_paths")
+        if submodule_paths:
+            lines.append(f'Submodule search paths: {submodule_paths}')
+    else:
+        error = details.get("error")
+        if error:
+            # The error is only informational when retrieving object details
+            lines.append(error)
+        else:
+            lines.append(f'Line: {details["lineno"]}')
+
+    lines.append("")
+    return "\n".join(lines)
+
+
 def _main():
     """ Logic for inspecting an object given at command line """
     import argparse
     import importlib
 
-    parser = argparse.ArgumentParser(color=True)
+    parser = argparse.ArgumentParser()
     parser.add_argument(
         'object',
          help="The object to be analysed. "
-              "It supports the 'module:qualname' syntax")
+              "It supports the `module:qualname` syntax")
     parser.add_argument(
         '-d', '--details', action='store_true',
         help='Display info about the module rather than its source code')
 
     args = parser.parse_args()
 
+    # We don't use `pkgutil.resolve_name` here because we want to obtain
+    # references to both the module *and* the fully resolved target object
     target = args.object
     mod_name, has_attrs, attrs = target.partition(":")
     try:
@@ -3389,29 +3488,16 @@ def _main():
         for part in parts:
             obj = getattr(obj, part)
 
-    if module.__name__ in sys.builtin_module_names:
-        print("Can't get info for builtin modules.", file=sys.stderr)
-        sys.exit(1)
-
+    details = _get_details_for_cli(module, target, obj)
     if args.details:
-        print('Target: {}'.format(target))
-        print('Origin: {}'.format(getsourcefile(module)))
-        print('Cached: {}'.format(module.__cached__))
-        if obj is module:
-            print('Loader: {}'.format(repr(module.__loader__)))
-            if hasattr(module, '__path__'):
-                print('Submodule search path: {}'.format(module.__path__))
-        else:
-            try:
-                __, lineno = findsource(obj)
-            except Exception:
-                pass
-            else:
-                print('Line: {}'.format(lineno))
-
-        print('\n')
+        print(_render_details_for_cli(details))
     else:
-        print(getsource(obj))
+        # Attempt to render target source details
+        error = details.get("error")
+        if error:
+            sys.exit(error)
+        else:
+            print(getsource(obj))
 
 
 if __name__ == "__main__":
diff --git a/Lib/ipaddress.py b/Lib/ipaddress.py
index ca732e4f2e8..f1062a8cd05 100644
--- a/Lib/ipaddress.py
+++ b/Lib/ipaddress.py
@@ -8,9 +8,6 @@
 
 """
 
-__version__ = '1.0'
-
-
 import functools
 
 IPV4LENGTH = 32
@@ -1479,6 +1476,10 @@ def with_hostmask(self):
         return '%s/%s' % (self._string_from_ip_int(self._ip),
                           self.hostmask)
 
+    @property
+    def is_unspecified(self):
+        return self._ip == 0 and self.network.is_unspecified
+
 
 class IPv4Network(_BaseV4, _BaseNetwork):
 
@@ -2415,3 +2416,12 @@ class _IPv6Constants:
 
 IPv6Address._constants = _IPv6Constants
 IPv6Network._constants = _IPv6Constants
+
+
+def __getattr__(name):
+    if name == "__version__":
+        from warnings import _deprecated
+
+        _deprecated("__version__", remove=(3, 20))
+        return "1.0"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/json/__init__.py b/Lib/json/__init__.py
index 800cc37f6af..37a86831ff9 100644
--- a/Lib/json/__init__.py
+++ b/Lib/json/__init__.py
@@ -95,7 +95,6 @@
     $ echo '{ 1.2:3.4}' | python -m json
     Expecting property name enclosed in double quotes: line 1 column 3 (char 2)
 """
-__version__ = '2.0.9'
 __all__ = [
     'dump', 'dumps', 'load', 'loads',
     'JSONDecoder', 'JSONDecodeError', 'JSONEncoder',
@@ -242,7 +241,7 @@ def dumps(obj, *, skipkeys=False, ensure_ascii=True, check_circular=True,
         **kw).encode(obj)
 
 
-_default_decoder = JSONDecoder(object_hook=None, object_pairs_hook=None)
+_default_decoder = JSONDecoder()
 
 
 def detect_encoding(b):
@@ -276,7 +275,8 @@ def detect_encoding(b):
 
 
 def load(fp, *, cls=None, object_hook=None, parse_float=None,
-        parse_int=None, parse_constant=None, object_pairs_hook=None, **kw):
+         parse_int=None, parse_constant=None, object_pairs_hook=None,
+         array_hook=None, **kw):
     """Deserialize ``fp`` (a ``.read()``-supporting file-like object containing
     a JSON document) to a Python object.
 
@@ -292,17 +292,27 @@ def load(fp, *, cls=None, object_hook=None, parse_float=None,
     ``object_hook`` is also defined, the ``object_pairs_hook`` takes
     priority.
 
+    ``array_hook`` is an optional function that will be called with the
+    result of any literal array decode (a ``list``).  The return value of
+    this function will be used instead of the ``list``.  This feature can
+    be used along ``object_pairs_hook`` to customize the resulting data
+    structure - for example, by setting that to ``frozendict`` and
+    ``array_hook`` to ``tuple``, one can get a deep immutable data structure
+    from any JSON data.
+
     To use a custom ``JSONDecoder`` subclass, specify it with the ``cls``
     kwarg; otherwise ``JSONDecoder`` is used.
     """
     return loads(fp.read(),
         cls=cls, object_hook=object_hook,
         parse_float=parse_float, parse_int=parse_int,
-        parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
+        parse_constant=parse_constant, object_pairs_hook=object_pairs_hook,
+        array_hook=array_hook, **kw)
 
 
 def loads(s, *, cls=None, object_hook=None, parse_float=None,
-        parse_int=None, parse_constant=None, object_pairs_hook=None, **kw):
+          parse_int=None, parse_constant=None, object_pairs_hook=None,
+          array_hook=None, **kw):
     """Deserialize ``s`` (a ``str``, ``bytes`` or ``bytearray`` instance
     containing a JSON document) to a Python object.
 
@@ -318,6 +328,14 @@ def loads(s, *, cls=None, object_hook=None, parse_float=None,
     ``object_hook`` is also defined, the ``object_pairs_hook`` takes
     priority.
 
+    ``array_hook`` is an optional function that will be called with the
+    result of any literal array decode (a ``list``).  The return value of
+    this function will be used instead of the ``list``.  This feature can
+    be used along ``object_pairs_hook`` to customize the resulting data
+    structure - for example, by setting that to ``frozendict`` and
+    ``array_hook`` to ``tuple``, one can get a deep immutable data structure
+    from any JSON data.
+
     ``parse_float``, if specified, will be called with the string
     of every JSON float to be decoded. By default this is equivalent to
     float(num_str). This can be used to use another datatype or parser
@@ -348,7 +366,8 @@ def loads(s, *, cls=None, object_hook=None, parse_float=None,
 
     if (cls is None and object_hook is None and
             parse_int is None and parse_float is None and
-            parse_constant is None and object_pairs_hook is None and not kw):
+            parse_constant is None and object_pairs_hook is None
+            and array_hook is None and not kw):
         return _default_decoder.decode(s)
     if cls is None:
         cls = JSONDecoder
@@ -356,6 +375,8 @@ def loads(s, *, cls=None, object_hook=None, parse_float=None,
         kw['object_hook'] = object_hook
     if object_pairs_hook is not None:
         kw['object_pairs_hook'] = object_pairs_hook
+    if array_hook is not None:
+        kw['array_hook'] = array_hook
     if parse_float is not None:
         kw['parse_float'] = parse_float
     if parse_int is not None:
@@ -363,3 +384,12 @@ def loads(s, *, cls=None, object_hook=None, parse_float=None,
     if parse_constant is not None:
         kw['parse_constant'] = parse_constant
     return cls(**kw).decode(s)
+
+
+def __getattr__(name):
+    if name == "__version__":
+        from warnings import _deprecated
+
+        _deprecated("__version__", remove=(3, 20))
+        return "2.0.9"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/json/decoder.py b/Lib/json/decoder.py
index 04e000e0760..3150a29405f 100644
--- a/Lib/json/decoder.py
+++ b/Lib/json/decoder.py
@@ -27,20 +27,6 @@ class JSONDecodeError(ValueError):
     colno: The column corresponding to pos
 
     """
-    # RUSTPYTHON SPECIFIC
-    @classmethod
-    def _from_serde(cls, msg, doc, line, col):
-        pos = 0
-        # 0-indexed
-        line -= 1
-        col -= 1
-        while line > 0:
-            i = doc.index('\n', pos)
-            line -= 1
-            pos = i
-        pos += col
-        return cls(msg, doc, pos)
-
     # Note that this exception is used from _json
     def __init__(self, msg, doc, pos):
         lineno = doc.count('\n', 0, pos) + 1
@@ -57,11 +43,11 @@ def __reduce__(self):
         return self.__class__, (self.msg, self.doc, self.pos)
 
 
-_CONSTANTS = {
+_CONSTANTS = frozendict({
     '-Infinity': NegInf,
     'Infinity': PosInf,
     'NaN': NaN,
-}
+})
 
 
 HEXDIGITS = re.compile(r'[0-9A-Fa-f]{4}', FLAGS)
@@ -232,7 +218,7 @@ def JSONObject(s_and_end, strict, scan_once, object_hook, object_pairs_hook,
         pairs = object_hook(pairs)
     return pairs, end
 
-def JSONArray(s_and_end, scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
+def JSONArray(s_and_end, scan_once, array_hook, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
     s, end = s_and_end
     values = []
     nextchar = s[end:end + 1]
@@ -241,6 +227,8 @@ def JSONArray(s_and_end, scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
         nextchar = s[end:end + 1]
     # Look-ahead for trivial empty array
     if nextchar == ']':
+        if array_hook is not None:
+            values = array_hook(values)
         return values, end + 1
     _append = values.append
     while True:
@@ -270,6 +258,8 @@ def JSONArray(s_and_end, scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
         if nextchar == ']':
             raise JSONDecodeError("Illegal trailing comma before end of array", s, comma_idx)
 
+    if array_hook is not None:
+        values = array_hook(values)
     return values, end
 
 
@@ -305,7 +295,7 @@ class JSONDecoder(object):
 
     def __init__(self, *, object_hook=None, parse_float=None,
             parse_int=None, parse_constant=None, strict=True,
-            object_pairs_hook=None):
+            object_pairs_hook=None, array_hook=None):
         """``object_hook``, if specified, will be called with the result
         of every JSON object decoded and its return value will be used in
         place of the given ``dict``.  This can be used to provide custom
@@ -318,6 +308,14 @@ def __init__(self, *, object_hook=None, parse_float=None,
         If ``object_hook`` is also defined, the ``object_pairs_hook`` takes
         priority.
 
+        ``array_hook`` is an optional function that will be called with the
+        result of any literal array decode (a ``list``). The return value of
+        this function will be used instead of the ``list``. This feature can
+        be used along ``object_pairs_hook`` to customize the resulting data
+        structure - for example, by setting that to ``frozendict`` and
+        ``array_hook`` to ``tuple``, one can get a deep immutable data
+        structute from any JSON data.
+
         ``parse_float``, if specified, will be called with the string
         of every JSON float to be decoded. By default this is equivalent to
         float(num_str). This can be used to use another datatype or parser
@@ -344,6 +342,7 @@ def __init__(self, *, object_hook=None, parse_float=None,
         self.parse_constant = parse_constant or _CONSTANTS.__getitem__
         self.strict = strict
         self.object_pairs_hook = object_pairs_hook
+        self.array_hook = array_hook
         self.parse_object = JSONObject
         self.parse_array = JSONArray
         self.parse_string = scanstring
diff --git a/Lib/json/encoder.py b/Lib/json/encoder.py
index 5cf6d64f3ea..718b3254241 100644
--- a/Lib/json/encoder.py
+++ b/Lib/json/encoder.py
@@ -79,7 +79,7 @@ class JSONEncoder(object):
     +-------------------+---------------+
     | Python            | JSON          |
     +===================+===============+
-    | dict              | object        |
+    | dict, frozendict  | object        |
     +-------------------+---------------+
     | list, tuple       | array         |
     +-------------------+---------------+
@@ -264,17 +264,6 @@ def floatstr(o, allow_nan=self.allow_nan,
 
 def _make_iterencode(markers, _default, _encoder, _indent, _floatstr,
         _key_separator, _item_separator, _sort_keys, _skipkeys, _one_shot,
-        ## HACK: hand-optimized bytecode; turn globals into locals
-        ValueError=ValueError,
-        dict=dict,
-        float=float,
-        id=id,
-        int=int,
-        isinstance=isinstance,
-        list=list,
-        str=str,
-        tuple=tuple,
-        _intstr=int.__repr__,
     ):
 
     def _iterencode_list(lst, _current_indent_level):
@@ -311,7 +300,7 @@ def _iterencode_list(lst, _current_indent_level):
                     # Subclasses of int/float may override __repr__, but we still
                     # want to encode them as integers/floats in JSON. One example
                     # within the standard library is IntEnum.
-                    yield buf + _intstr(value)
+                    yield buf + int.__repr__(value)
                 elif isinstance(value, float):
                     # see comment above for int
                     yield buf + _floatstr(value)
@@ -319,7 +308,7 @@ def _iterencode_list(lst, _current_indent_level):
                     yield buf
                     if isinstance(value, (list, tuple)):
                         chunks = _iterencode_list(value, _current_indent_level)
-                    elif isinstance(value, dict):
+                    elif isinstance(value, (dict, frozendict)):
                         chunks = _iterencode_dict(value, _current_indent_level)
                     else:
                         chunks = _iterencode(value, _current_indent_level)
@@ -374,7 +363,7 @@ def _iterencode_dict(dct, _current_indent_level):
                 key = 'null'
             elif isinstance(key, int):
                 # see comment for int/float in _make_iterencode
-                key = _intstr(key)
+                key = int.__repr__(key)
             elif _skipkeys:
                 continue
             else:
@@ -399,14 +388,14 @@ def _iterencode_dict(dct, _current_indent_level):
                     yield 'false'
                 elif isinstance(value, int):
                     # see comment for int/float in _make_iterencode
-                    yield _intstr(value)
+                    yield int.__repr__(value)
                 elif isinstance(value, float):
                     # see comment for int/float in _make_iterencode
                     yield _floatstr(value)
                 else:
                     if isinstance(value, (list, tuple)):
                         chunks = _iterencode_list(value, _current_indent_level)
-                    elif isinstance(value, dict):
+                    elif isinstance(value, (dict, frozendict)):
                         chunks = _iterencode_dict(value, _current_indent_level)
                     else:
                         chunks = _iterencode(value, _current_indent_level)
@@ -434,13 +423,13 @@ def _iterencode(o, _current_indent_level):
             yield 'false'
         elif isinstance(o, int):
             # see comment for int/float in _make_iterencode
-            yield _intstr(o)
+            yield int.__repr__(o)
         elif isinstance(o, float):
             # see comment for int/float in _make_iterencode
             yield _floatstr(o)
         elif isinstance(o, (list, tuple)):
             yield from _iterencode_list(o, _current_indent_level)
-        elif isinstance(o, dict):
+        elif isinstance(o, (dict, frozendict)):
             yield from _iterencode_dict(o, _current_indent_level)
         else:
             if markers is not None:
@@ -458,4 +447,13 @@ def _iterencode(o, _current_indent_level):
                 raise
             if markers is not None:
                 del markers[markerid]
-    return _iterencode
+
+    def _iterencode_once(o, _current_indent_level):
+        nonlocal _iterencode, _iterencode_dict, _iterencode_list
+        try:
+            yield from _iterencode(o, _current_indent_level)
+        finally:
+            # Break reference cycles due to mutually recursive closures:
+            del _iterencode, _iterencode_dict, _iterencode_list
+
+    return _iterencode_once
diff --git a/Lib/json/scanner.py b/Lib/json/scanner.py
index 090897515fe..b484e00be0f 100644
--- a/Lib/json/scanner.py
+++ b/Lib/json/scanner.py
@@ -23,6 +23,7 @@ def py_make_scanner(context):
     parse_constant = context.parse_constant
     object_hook = context.object_hook
     object_pairs_hook = context.object_pairs_hook
+    array_hook = context.array_hook
     memo = context.memo
 
     def _scan_once(string, idx):
@@ -37,7 +38,7 @@ def _scan_once(string, idx):
             return parse_object((string, idx + 1), strict,
                 _scan_once, object_hook, object_pairs_hook, memo)
         elif nextchar == '[':
-            return parse_array((string, idx + 1), _scan_once)
+            return parse_array((string, idx + 1), _scan_once, array_hook)
         elif nextchar == 'n' and string[idx:idx + 4] == 'null':
             return None, idx + 4
         elif nextchar == 't' and string[idx:idx + 4] == 'true':
diff --git a/Lib/json/tool.py b/Lib/json/tool.py
index 0cabbdba85a..6385d971f73 100644
--- a/Lib/json/tool.py
+++ b/Lib/json/tool.py
@@ -22,13 +22,13 @@
     (?P<null>null)
 ''', re.VERBOSE)
 
-_group_to_theme_color = {
+_group_to_theme_color = frozendict({
     "key": "definition",
     "string": "string",
     "number": "number",
     "boolean": "keyword",
     "null": "keyword",
-}
+})
 
 
 def _colorize_json(json_str, theme):
@@ -44,12 +44,13 @@ def _replace_match_callback(match):
 def main():
     description = ('A simple command line interface for json module '
                    'to validate and pretty-print JSON objects.')
-    parser = argparse.ArgumentParser(description=description, color=True)
+    parser = argparse.ArgumentParser(description=description)
     parser.add_argument('infile', nargs='?',
-                        help='a JSON file to be validated or pretty-printed',
+                        help='a JSON file to be validated or pretty-printed; '
+                             'defaults to `stdin`',
                         default='-')
     parser.add_argument('outfile', nargs='?',
-                        help='write the output of infile to outfile',
+                        help='write the output of `infile` to `outfile`',
                         default=None)
     parser.add_argument('--sort-keys', action='store_true', default=False,
                         help='sort the output of dictionaries alphabetically by key')
@@ -57,7 +58,7 @@ def main():
                         help='disable escaping of non-ASCII characters')
     parser.add_argument('--json-lines', action='store_true', default=False,
                         help='parse input using the JSON Lines format. '
-                        'Use with --no-indent or --compact to produce valid JSON Lines output.')
+                        'Use with `--no-indent` or `--compact` to produce valid JSON Lines output.')
     group = parser.add_mutually_exclusive_group()
     group.add_argument('--indent', default=4, type=int,
                        help='separate items with newlines and use this number '
diff --git a/Lib/linecache.py b/Lib/linecache.py
index ef3b2d9136b..b5bf9dbdd3c 100644
--- a/Lib/linecache.py
+++ b/Lib/linecache.py
@@ -224,21 +224,58 @@ def lazycache(filename, module_globals):
 def _make_lazycache_entry(filename, module_globals):
     if not filename or (filename.startswith('<') and filename.endswith('>')):
         return None
-    # Try for a __loader__, if available
-    if module_globals and '__name__' in module_globals:
-        spec = module_globals.get('__spec__')
-        name = getattr(spec, 'name', None) or module_globals['__name__']
-        loader = getattr(spec, 'loader', None)
-        if loader is None:
-            loader = module_globals.get('__loader__')
-        get_source = getattr(loader, 'get_source', None)
-
-        if name and get_source:
-            def get_lines(name=name, *args, **kwargs):
-                return get_source(name, *args, **kwargs)
-            return (get_lines,)
-    return None
 
+    if module_globals is not None and not isinstance(module_globals, dict):
+        raise TypeError(f'module_globals must be a dict, not {type(module_globals).__qualname__}')
+    if not module_globals or '__name__' not in module_globals:
+        return None
+
+    spec = module_globals.get('__spec__')
+    name = getattr(spec, 'name', None) or module_globals['__name__']
+    if name is None:
+        return None
+
+    loader = _bless_my_loader(module_globals)
+    if loader is None:
+        return None
+
+    get_source = getattr(loader, 'get_source', None)
+    if get_source is None:
+        return None
+
+    def get_lines(name=name, *args, **kwargs):
+        return get_source(name, *args, **kwargs)
+    return (get_lines,)
+
+def _bless_my_loader(module_globals):
+    # Similar to _bless_my_loader() in importlib._bootstrap_external,
+    # but always emits warnings instead of errors.
+    loader = module_globals.get('__loader__')
+    if loader is None and '__spec__' not in module_globals:
+        return None
+    spec = module_globals.get('__spec__')
+
+    # The __main__ module has __spec__ = None.
+    if spec is None and module_globals.get('__name__') == '__main__':
+        return loader
+
+    spec_loader = getattr(spec, 'loader', None)
+    if spec_loader is None:
+        import warnings
+        warnings.warn(
+            'Module globals is missing a __spec__.loader',
+            DeprecationWarning)
+        return loader
+
+    assert spec_loader is not None
+    if loader is not None and loader != spec_loader:
+        import warnings
+        warnings.warn(
+            'Module globals; __loader__ != __spec__.loader',
+            DeprecationWarning)
+        return loader
+
+    return spec_loader
 
 
 def _register_code(code, string, name):
diff --git a/Lib/locale.py b/Lib/locale.py
index 6984a6a5e2b..4ff6f8c0f0a 100644
--- a/Lib/locale.py
+++ b/Lib/locale.py
@@ -214,7 +214,7 @@ def format_string(f, val, grouping=False, monetary=False):
 
     Grouping is applied if the third parameter is true.
     Conversion uses monetary thousands separator and grouping strings if
-    forth parameter monetary is true."""
+    fourth parameter monetary is true."""
     global _percent_re
     if _percent_re is None:
         import re
@@ -375,12 +375,14 @@ def _replace_encoding(code, encoding):
 def _append_modifier(code, modifier):
     if modifier == 'euro':
         if '.' not in code:
-            return code + '.ISO8859-15'
+            # Linux appears to require keeping the "@euro" modifier in place,
+            # even when using the ".ISO8859-15" encoding.
+            return code + '.ISO8859-15@euro'
         _, _, encoding = code.partition('.')
-        if encoding in ('ISO8859-15', 'UTF-8'):
+        if encoding == 'UTF-8':
             return code
         if encoding == 'ISO8859-1':
-            return _replace_encoding(code, 'ISO8859-15')
+            code = _replace_encoding(code, 'ISO8859-15')
     return code + '@' + modifier
 
 def normalize(localename):
@@ -485,13 +487,18 @@ def _parse_localename(localename):
         # Deal with locale modifiers
         code, modifier = code.split('@', 1)
         if modifier == 'euro' and '.' not in code:
-            # Assume Latin-9 for @euro locales. This is bogus,
-            # since some systems may use other encodings for these
-            # locales. Also, we ignore other modifiers.
-            return code, 'iso-8859-15'
+            # Assume ISO8859-15 for @euro locales. Do note that some systems
+            # may use other encodings for these locales, so this may not always
+            # be correct.
+            return code + '@euro', 'ISO8859-15'
+    else:
+        modifier = ''
 
     if '.' in code:
-        return tuple(code.split('.')[:2])
+        code, encoding = code.split('.')[:2]
+        if modifier:
+            code += '@' + modifier
+        return code, encoding
     elif code == 'C':
         return None, None
     elif code == 'UTF-8':
@@ -516,7 +523,14 @@ def _build_localename(localetuple):
         if encoding is None:
             return language
         else:
-            return language + '.' + encoding
+            if '@' in language:
+                language, modifier = language.split('@', 1)
+            else:
+                modifier = ''
+            localename = language + '.' + encoding
+            if modifier:
+                localename += '@' + modifier
+            return localename
     except (TypeError, ValueError):
         raise TypeError('Locale must be None, a string, or an iterable of '
                         'two strings -- language code, encoding.') from None
@@ -556,10 +570,6 @@ def _getdefaultlocale(envvars=('LC_ALL', 'LC_CTYPE', 'LANG', 'LANGUAGE')):
     except (ImportError, AttributeError):
         pass
     else:
-        # make sure the code/encoding values are valid
-        if sys.platform == "win32" and code and code[:2] == "0x":
-            # map windows language identifier to language name
-            code = windows_locale.get(int(code, 0))
         # ...add other platform-specific processing here, if
         # necessary...
         return code, encoding
@@ -645,7 +655,8 @@ def getpreferredencoding(do_setlocale=True):
         if sys.flags.warn_default_encoding:
             import warnings
             warnings.warn(
-                "UTF-8 Mode affects locale.getpreferredencoding(). Consider locale.getencoding() instead.",
+                "UTF-8 Mode affects locale.getpreferredencoding(). "
+                "Consider locale.getencoding() instead.",
                 EncodingWarning, 2)
         if sys.flags.utf8_mode:
             return 'utf-8'
@@ -881,6 +892,12 @@ def getpreferredencoding(do_setlocale=True):
 # SS 2025-06-10:
 # Remove 'c.utf8' -> 'en_US.UTF-8' because 'en_US.UTF-8' does not exist
 # on all platforms.
+#
+# SS 2025-07-30:
+# Remove conflicts with GNU libc.
+#
+#    removed 'el_gr@euro'
+#    removed 'uz_uz@cyrillic'
 
 locale_alias = {
     'a3':                                   'az_AZ.KOI8-C',
@@ -1014,7 +1031,6 @@ def getpreferredencoding(do_setlocale=True):
     'el':                                   'el_GR.ISO8859-7',
     'el_cy':                                'el_CY.ISO8859-7',
     'el_gr':                                'el_GR.ISO8859-7',
-    'el_gr@euro':                           'el_GR.ISO8859-15',
     'en':                                   'en_US.ISO8859-1',
     'en_ag':                                'en_AG.UTF-8',
     'en_au':                                'en_AU.ISO8859-1',
@@ -1449,7 +1465,6 @@ def getpreferredencoding(do_setlocale=True):
     'ur_pk':                                'ur_PK.CP1256',
     'uz':                                   'uz_UZ.UTF-8',
     'uz_uz':                                'uz_UZ.UTF-8',
-    'uz_uz@cyrillic':                       'uz_UZ.UTF-8',
     've':                                   've_ZA.UTF-8',
     've_za':                                've_ZA.UTF-8',
     'vi':                                   'vi_VN.TCVN',
diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 9005f1ef865..80ce896a780 100644
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -45,9 +45,6 @@
 
 __author__  = "Vinay Sajip <vinay_sajip@red-dove.com>"
 __status__  = "production"
-# The following module attributes are no longer updated.
-__version__ = "0.5.1.2"
-__date__    = "07 February 2010"
 
 #---------------------------------------------------------------------------
 #   Miscellaneous module data
@@ -625,6 +622,9 @@ def __init__(self, fmt=None, datefmt=None, style='%', validate=True, *,
         self._fmt = self._style._fmt
         self.datefmt = datefmt
 
+    def __repr__(self):
+        return '<%s (%s)>' % (self.__class__.__name__, self._fmt)
+
     default_time_format = '%Y-%m-%d %H:%M:%S'
     default_msec_format = '%s,%03d'
 
@@ -797,6 +797,9 @@ def __init__(self, name=''):
         self.name = name
         self.nlen = len(name)
 
+    def __repr__(self):
+        return '<%s (%s)>' % (self.__class__.__name__, self.name)
+
     def filter(self, record):
         """
         Determine if the specified record is to be logged.
@@ -1694,7 +1697,11 @@ def removeHandler(self, hdlr):
         """
         with _lock:
             if hdlr in self.handlers:
-                self.handlers.remove(hdlr)
+                # Replace the list instead of mutating it in place, so that
+                # callHandlers() can iterate it without a lock (gh-79366).
+                handlers = self.handlers.copy()
+                handlers.remove(hdlr)
+                self.handlers = handlers
 
     def hasHandlers(self):
         """
@@ -2047,6 +2054,15 @@ def basicConfig(**kwargs):
               created FileHandler, causing it to be used when the file is
               opened in text mode. If not specified, the default value is
               `backslashreplace`.
+    formatter If specified, set this formatter instance for all involved
+              handlers.
+              If not specified, the default is to create and use an instance of
+              `logging.Formatter` based on arguments 'format', 'datefmt' and
+              'style'.
+              When 'formatter' is specified together with any of the three
+              arguments 'format', 'datefmt' and 'style', a `ValueError`
+              is raised to signal that these arguments would lose meaning
+              otherwise.
 
     Note that you could specify a stream created using open(filename, mode)
     rather than passing the filename and mode in. However, it should be
@@ -2069,6 +2085,9 @@ def basicConfig(**kwargs):
 
     .. versionchanged:: 3.9
        Added the ``encoding`` and ``errors`` parameters.
+
+    .. versionchanged:: 3.15
+       Added the ``formatter`` parameter.
     """
     # Add thread safety in case someone mistakenly calls
     # basicConfig() from multiple threads
@@ -2104,13 +2123,19 @@ def basicConfig(**kwargs):
                     stream = kwargs.pop("stream", None)
                     h = StreamHandler(stream)
                 handlers = [h]
-            dfs = kwargs.pop("datefmt", None)
-            style = kwargs.pop("style", '%')
-            if style not in _STYLES:
-                raise ValueError('Style must be one of: %s' % ','.join(
-                                 _STYLES.keys()))
-            fs = kwargs.pop("format", _STYLES[style][1])
-            fmt = Formatter(fs, dfs, style)
+            fmt = kwargs.pop("formatter", None)
+            if fmt is None:
+                dfs = kwargs.pop("datefmt", None)
+                style = kwargs.pop("style", '%')
+                if style not in _STYLES:
+                    raise ValueError('Style must be one of: %s' % ','.join(
+                                    _STYLES.keys()))
+                fs = kwargs.pop("format", _STYLES[style][1])
+                fmt = Formatter(fs, dfs, style)
+            else:
+                for forbidden_key in ("datefmt", "format", "style"):
+                    if forbidden_key in kwargs:
+                        raise ValueError(f"{forbidden_key!r} should not be specified together with 'formatter'")
             for h in handlers:
                 if h.formatter is None:
                     h.setFormatter(fmt)
@@ -2324,3 +2349,16 @@ def captureWarnings(capture):
         if _warnings_showwarning is not None:
             warnings.showwarning = _warnings_showwarning
             _warnings_showwarning = None
+
+
+def __getattr__(name):
+    if name in ("__version__", "__date__"):
+        from warnings import _deprecated
+
+        _deprecated(name, remove=(3, 20))
+        return {  # Do not change
+            "__version__": "0.5.1.2",
+            "__date__": "07 February 2010",
+        }[name]
+
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/logging/config.py b/Lib/logging/config.py
index 3d9aa00fa52..e0524eb5e3d 100644
--- a/Lib/logging/config.py
+++ b/Lib/logging/config.py
@@ -32,6 +32,7 @@
 import os
 import queue
 import re
+import socket
 import struct
 import threading
 import traceback
@@ -1022,6 +1023,15 @@ class ConfigSocketReceiver(ThreadingTCPServer):
 
         def __init__(self, host='localhost', port=DEFAULT_LOGGING_CONFIG_PORT,
                      handler=None, ready=None, verify=None):
+            # The host can have no IPv4 address, for example if "localhost"
+            # is only aliased to ::1.  Leave resolution errors to the server.
+            try:
+                infos = socket.getaddrinfo(host, port, type=socket.SOCK_STREAM)
+            except OSError:
+                pass
+            else:
+                if not any(info[0] == socket.AF_INET for info in infos):
+                    self.address_family = infos[0][0]
             ThreadingTCPServer.__init__(self, (host, port), handler)
             with logging._lock:
                 self.abort = 0
@@ -1053,9 +1063,14 @@ def __init__(self, rcvr, hdlr, port, verify):
             self.ready = threading.Event()
 
         def run(self):
-            server = self.rcvr(port=self.port, handler=self.hdlr,
-                               ready=self.ready,
-                               verify=self.verify)
+            try:
+                server = self.rcvr(port=self.port, handler=self.hdlr,
+                                   ready=self.ready,
+                                   verify=self.verify)
+            except BaseException:
+                # Do not leave the caller waiting for ready forever.
+                self.ready.set()
+                raise
             if self.port == 0:
                 self.port = server.server_address[1]
             self.ready.set()
diff --git a/Lib/logging/handlers.py b/Lib/logging/handlers.py
index 4a07258f8d6..575f2babbc4 100644
--- a/Lib/logging/handlers.py
+++ b/Lib/logging/handlers.py
@@ -1129,7 +1129,7 @@ class NTEventLogHandler(logging.Handler):
     """
     A handler class which sends events to the NT Event Log. Adds a
     registry entry for the specified application name. If no dllname is
-    provided, win32service.pyd (which contains some basic message
+    provided and pywin32 installed, win32service.pyd (which contains some basic message
     placeholders) is used. Note that use of these placeholders will make
     your event logs big, as the entire message source is held in the log.
     If you want slimmer logs, you have to pass in the name of your own DLL
@@ -1137,38 +1137,46 @@ class NTEventLogHandler(logging.Handler):
     """
     def __init__(self, appname, dllname=None, logtype="Application"):
         logging.Handler.__init__(self)
-        try:
-            import win32evtlogutil, win32evtlog
-            self.appname = appname
-            self._welu = win32evtlogutil
-            if not dllname:
-                dllname = os.path.split(self._welu.__file__)
+        import _winapi
+        self._winapi = _winapi
+        self.appname = appname
+        if not dllname:
+            # backward compatibility
+            try:
+                import win32evtlogutil
+                dllname = os.path.split(win32evtlogutil.__file__)
                 dllname = os.path.split(dllname[0])
                 dllname = os.path.join(dllname[0], r'win32service.pyd')
-            self.dllname = dllname
-            self.logtype = logtype
-            # Administrative privileges are required to add a source to the registry.
-            # This may not be available for a user that just wants to add to an
-            # existing source - handle this specific case.
-            try:
-                self._welu.AddSourceToRegistry(appname, dllname, logtype)
-            except Exception as e:
-                # This will probably be a pywintypes.error. Only raise if it's not
-                # an "access denied" error, else let it pass
-                if getattr(e, 'winerror', None) != 5:  # not access denied
-                    raise
-            self.deftype = win32evtlog.EVENTLOG_ERROR_TYPE
-            self.typemap = {
-                logging.DEBUG   : win32evtlog.EVENTLOG_INFORMATION_TYPE,
-                logging.INFO    : win32evtlog.EVENTLOG_INFORMATION_TYPE,
-                logging.WARNING : win32evtlog.EVENTLOG_WARNING_TYPE,
-                logging.ERROR   : win32evtlog.EVENTLOG_ERROR_TYPE,
-                logging.CRITICAL: win32evtlog.EVENTLOG_ERROR_TYPE,
-         }
-        except ImportError:
-            print("The Python Win32 extensions for NT (service, event "\
-                        "logging) appear not to be available.")
-            self._welu = None
+            except ImportError:
+                pass
+        self.dllname = dllname
+        self.logtype = logtype
+        # Administrative privileges are required to add a source to the registry.
+        # This may not be available for a user that just wants to add to an
+        # existing source - handle this specific case.
+        try:
+            self._add_source_to_registry(appname, dllname, logtype)
+        except PermissionError:
+            pass
+        self.deftype = _winapi.EVENTLOG_ERROR_TYPE
+        self.typemap = {
+            logging.DEBUG: _winapi.EVENTLOG_INFORMATION_TYPE,
+            logging.INFO: _winapi.EVENTLOG_INFORMATION_TYPE,
+            logging.WARNING: _winapi.EVENTLOG_WARNING_TYPE,
+            logging.ERROR: _winapi.EVENTLOG_ERROR_TYPE,
+            logging.CRITICAL: _winapi.EVENTLOG_ERROR_TYPE,
+        }
+
+    @staticmethod
+    def _add_source_to_registry(appname, dllname, logtype):
+        import winreg
+
+        key_path = f"SYSTEM\\CurrentControlSet\\Services\\EventLog\\{logtype}\\{appname}"
+
+        with winreg.CreateKey(winreg.HKEY_LOCAL_MACHINE, key_path) as key:
+            if dllname:
+                winreg.SetValueEx(key, "EventMessageFile", 0, winreg.REG_EXPAND_SZ, dllname)
+            winreg.SetValueEx(key, "TypesSupported", 0, winreg.REG_DWORD, 7)  # All types are supported
 
     def getMessageID(self, record):
         """
@@ -1209,15 +1217,20 @@ def emit(self, record):
         Determine the message ID, event category and event type. Then
         log the message in the NT event log.
         """
-        if self._welu:
+        try:
+            id = self.getMessageID(record)
+            cat = self.getEventCategory(record)
+            type = self.getEventType(record)
+            msg = self.format(record)
+
+            # Get a handle to the event log
+            handle = self._winapi.RegisterEventSource(None, self.appname)
             try:
-                id = self.getMessageID(record)
-                cat = self.getEventCategory(record)
-                type = self.getEventType(record)
-                msg = self.format(record)
-                self._welu.ReportEvent(self.appname, id, cat, type, [msg])
-            except Exception:
-                self.handleError(record)
+                self._winapi.ReportEvent(handle, type, cat, id, msg)
+            finally:
+                self._winapi.DeregisterEventSource(handle)
+        except Exception:
+            self.handleError(record)
 
     def close(self):
         """
diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
index e7581d2ae0a..6d9278bccf9 100644
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -244,7 +244,7 @@ def read(self, filename, strict=True):
         list of standard types, else to the list of non-standard
         types.
         """
-        with open(filename, encoding='utf-8', errors='surrogateescape') as fp:
+        with open(filename, encoding='utf-8') as fp:
             self.readfp(fp, strict)
 
     def readfp(self, fp, strict=True):
@@ -435,7 +435,7 @@ def init(files=None):
 
 def read_mime_types(file):
     try:
-        f = open(file, encoding='utf-8', errors='surrogateescape')
+        f = open(file, encoding='utf-8')
     except OSError:
         return None
     with f:
@@ -477,6 +477,8 @@ def _default_mime_types():
     types_map = _types_map_default = {
         '.js'     : 'text/javascript',
         '.mjs'    : 'text/javascript',
+        '.dcm'    : 'application/dicom',
+        '.efi'    : 'application/efi',
         '.epub'   : 'application/epub+zip',
         '.gz'     : 'application/gzip',
         '.json'   : 'application/json',
@@ -486,26 +488,35 @@ def _default_mime_types():
         '.wiz'    : 'application/msword',
         '.nq'     : 'application/n-quads',
         '.nt'     : 'application/n-triples',
+        '.cjs'    : 'application/node',
         '.bin'    : 'application/octet-stream',
         '.a'      : 'application/octet-stream',
-        '.dll'    : 'application/octet-stream',
-        '.exe'    : 'application/octet-stream',
         '.o'      : 'application/octet-stream',
         '.obj'    : 'application/octet-stream',
         '.so'     : 'application/octet-stream',
         '.oda'    : 'application/oda',
         '.ogx'    : 'application/ogg',
         '.pdf'    : 'application/pdf',
+        '.ai'     : 'application/pdf',
         '.p7c'    : 'application/pkcs7-mime',
         '.ps'     : 'application/postscript',
-        '.ai'     : 'application/postscript',
         '.eps'    : 'application/postscript',
+        '.rtf'    : 'application/rtf',
+        '.sql'    : 'application/sql',
+        '.texi'   : 'application/texinfo',
+        '.texinfo': 'application/texinfo',
+        '.toml'   : 'application/toml',
         '.trig'   : 'application/trig',
         '.m3u'    : 'application/vnd.apple.mpegurl',
         '.m3u8'   : 'application/vnd.apple.mpegurl',
+        '.dll'    : 'application/vnd.microsoft.portable-executable',
+        '.exe'    : 'application/vnd.microsoft.portable-executable',
+        '.cab'    : 'application/vnd.ms-cab-compressed',
         '.xls'    : 'application/vnd.ms-excel',
         '.xlb'    : 'application/vnd.ms-excel',
         '.eot'    : 'application/vnd.ms-fontobject',
+        '.chm'    : 'application/vnd.ms-htmlhelp',
+        '.thmx'   : 'application/vnd.ms-officetheme',
         '.ppt'    : 'application/vnd.ms-powerpoint',
         '.pot'    : 'application/vnd.ms-powerpoint',
         '.ppa'    : 'application/vnd.ms-powerpoint',
@@ -519,6 +530,8 @@ def _default_mime_types():
         '.xlsx'   : 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
         '.docx'   : 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
         '.rar'    : 'application/vnd.rar',
+        '.sqlite3': 'application/vnd.sqlite3',
+        '.sqlite' : 'application/vnd.sqlite3',
         '.wasm'   : 'application/wasm',
         '.7z'     : 'application/x-7z-compressed',
         '.bcpio'  : 'application/x-bcpio',
@@ -548,8 +561,6 @@ def _default_mime_types():
         '.tar'    : 'application/x-tar',
         '.tcl'    : 'application/x-tcl',
         '.tex'    : 'application/x-tex',
-        '.texi'   : 'application/x-texinfo',
-        '.texinfo': 'application/x-texinfo',
         '.roff'   : 'application/x-troff',
         '.t'      : 'application/x-troff',
         '.tr'     : 'application/x-troff',
@@ -587,11 +598,15 @@ def _default_mime_types():
         '.aiff'   : 'audio/x-aiff',
         '.ra'     : 'audio/x-pn-realaudio',
         '.wav'    : 'audio/vnd.wave',
+        '.weba'   : 'audio/webm',
+        '.ttc'    : 'font/collection',
         '.otf'    : 'font/otf',
         '.ttf'    : 'font/ttf',
-        '.weba'   : 'audio/webm',
         '.woff'   : 'font/woff',
         '.woff2'  : 'font/woff2',
+        '.hjif'   : 'haptics/hjif',
+        '.hmpg'   : 'haptics/hmpg',
+        '.ivs'    : 'haptics/ivs',
         '.avif'   : 'image/avif',
         '.bmp'    : 'image/bmp',
         '.emf'    : 'image/emf',
@@ -605,6 +620,7 @@ def _default_mime_types():
         '.jpeg'   : 'image/jpeg',
         '.jpm'    : 'image/jpm',
         '.jpx'    : 'image/jpx',
+        '.jxl'    : 'image/jxl',
         '.heic'   : 'image/heic',
         '.heif'   : 'image/heif',
         '.png'    : 'image/png',
@@ -647,7 +663,6 @@ def _default_mime_types():
         '.pl'     : 'text/plain',
         '.srt'    : 'text/plain',
         '.rtx'    : 'text/richtext',
-        '.rtf'    : 'text/rtf',
         '.tsv'    : 'text/tab-separated-values',
         '.vtt'    : 'text/vtt',
         '.py'     : 'text/x-python',
@@ -680,11 +695,9 @@ def _default_mime_types():
 
     # Please sort these too
     common_types = _common_types_default = {
-        '.rtf' : 'application/rtf',
         '.apk' : 'application/vnd.android.package-archive',
         '.midi': 'audio/midi',
         '.mid' : 'audio/midi',
-        '.jpg' : 'image/jpg',
         '.pict': 'image/pict',
         '.pct' : 'image/pict',
         '.pic' : 'image/pict',
@@ -699,7 +712,7 @@ def _parse_args(args):
     from argparse import ArgumentParser
 
     parser = ArgumentParser(
-        description='map filename extensions to MIME types', color=True
+        description='map filename extensions to MIME types',
     )
     parser.add_argument(
         '-e', '--extension',
diff --git a/Lib/netrc.py b/Lib/netrc.py
index bd003e80a48..cb1e3782a01 100644
--- a/Lib/netrc.py
+++ b/Lib/netrc.py
@@ -48,11 +48,12 @@ def _read_char(self):
     def get_token(self):
         if self.pushback:
             return self.pushback.pop(0)
-        token = ""
+        token = None
         fiter = iter(self._read_char, "")
         for ch in fiter:
             if ch in self.whitespace:
                 continue
+            token = ""
             if ch == '"':
                 for ch in fiter:
                     if ch == '"':
@@ -95,10 +96,10 @@ def _parse(self, file, fp, default_netrc):
         while 1:
             # Look for a machine, default, or macdef top-level keyword
             saved_lineno = lexer.lineno
-            toplevel = tt = lexer.get_token()
-            if not tt:
+            tt = lexer.get_token()
+            if tt is None:
                 break
-            elif tt[0] == '#':
+            elif tt.startswith('#'):
                 if lexer.lineno == saved_lineno and len(tt) == 1:
                     lexer.instream.readline()
                 continue
@@ -135,40 +136,45 @@ def _parse(self, file, fp, default_netrc):
             while 1:
                 prev_lineno = lexer.lineno
                 tt = lexer.get_token()
-                if tt.startswith('#'):
+                if tt is not None and tt.startswith('#'):
                     if lexer.lineno == prev_lineno:
                         lexer.instream.readline()
                     continue
-                if tt in {'', 'machine', 'default', 'macdef'}:
+                if tt in {None, 'machine', 'default', 'macdef'}:
                     self.hosts[entryname] = (login, account, password)
                     lexer.push_token(tt)
                     break
                 elif tt == 'login' or tt == 'user':
-                    login = lexer.get_token()
+                    login = lexer.get_token() or ''
                 elif tt == 'account':
-                    account = lexer.get_token()
+                    account = lexer.get_token() or ''
                 elif tt == 'password':
-                    password = lexer.get_token()
+                    password = lexer.get_token() or ''
                 else:
                     raise NetrcParseError("bad follower token %r" % tt,
                                           file, lexer.lineno)
-            self._security_check(fp, default_netrc, self.hosts[entryname][0])
-
-    def _security_check(self, fp, default_netrc, login):
-        if _can_security_check() and default_netrc and login != "anonymous":
-            prop = os.fstat(fp.fileno())
-            current_user_id = os.getuid()
-            if prop.st_uid != current_user_id:
-                fowner = _getpwuid(prop.st_uid)
-                user = _getpwuid(current_user_id)
-                raise NetrcParseError(
-                    (f"~/.netrc file owner ({fowner}, {user}) does not match"
-                     " current user"))
-            if (prop.st_mode & (stat.S_IRWXG | stat.S_IRWXO)):
-                raise NetrcParseError(
-                    "~/.netrc access too permissive: access"
-                    " permissions must restrict access to only"
-                    " the owner")
+
+        if _can_security_check() and default_netrc:
+            for entry in self.hosts.values():
+                if entry[0] != "anonymous":
+                    # Raises on security issue; once passed once can exit.
+                    self._security_check(fp)
+                    return
+
+    def _security_check(self, fp):
+        prop = os.fstat(fp.fileno())
+        current_user_id = os.getuid()
+        if prop.st_uid != current_user_id:
+            fowner = _getpwuid(prop.st_uid)
+            user = _getpwuid(current_user_id)
+            raise NetrcParseError(
+                f"~/.netrc file owner ({fowner}) does not match"
+                f" current user ({user})")
+        if (prop.st_mode & (stat.S_IRWXG | stat.S_IRWXO)):
+            raise NetrcParseError(
+                "~/.netrc access too permissive: access"
+                " permissions must restrict access to only"
+                " the owner")
 
     def authenticators(self, host):
         """Return a (user, account, password) tuple for given host."""
diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index 36da5b7cb0f..b3c23f0abc2 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -29,7 +29,7 @@
            "abspath","curdir","pardir","sep","pathsep","defpath","altsep",
            "extsep","devnull","realpath","supports_unicode_filenames","relpath",
            "samefile", "sameopenfile", "samestat", "commonpath", "isjunction",
-           "isdevdrive", "ALLOW_MISSING"]
+           "isdevdrive", "ALL_BUT_LAST", "ALLOW_MISSING"]
 
 def _get_bothseps(path):
     if isinstance(path, bytes):
@@ -47,7 +47,7 @@ def _get_bothseps(path):
         LOCALE_NAME_INVARIANT as _LOCALE_NAME_INVARIANT,
         LCMAP_LOWERCASE as _LCMAP_LOWERCASE)
 
-    def normcase(s):
+    def normcase(s, /):
         """Normalize case of pathname.
 
         Makes all characters lowercase and all slashes into backslashes.
@@ -66,7 +66,7 @@ def normcase(s):
                                   _LCMAP_LOWERCASE,
                                   s.replace('/', '\\'))
 except ImportError:
-    def normcase(s):
+    def normcase(s, /):
         """Normalize case of pathname.
 
         Makes all characters lowercase and all slashes into backslashes.
@@ -77,7 +77,7 @@ def normcase(s):
         return s.replace('/', '\\').lower()
 
 
-def isabs(s):
+def isabs(s, /):
     """Test whether a path is absolute"""
     s = os.fspath(s)
     if isinstance(s, bytes):
@@ -96,7 +96,7 @@ def isabs(s):
 
 
 # Join two (or more) paths.
-def join(path, *paths):
+def join(path, /, *paths):
     path = os.fspath(path)
     if isinstance(path, bytes):
         sep = b'\\'
@@ -143,7 +143,7 @@ def join(path, *paths):
 # Split a path in a drive specification (a drive letter followed by a
 # colon) and the path specification.
 # It is always true that drivespec + pathspec == p
-def splitdrive(p):
+def splitdrive(p, /):
     """Split a pathname into drive/UNC sharepoint and relative path specifiers.
     Returns a 2-tuple (drive_or_unc, path); either part may be empty.
 
@@ -171,7 +171,7 @@ def splitdrive(p):
 try:
     from nt import _path_splitroot_ex as splitroot
 except ImportError:
-    def splitroot(p):
+    def splitroot(p, /):
         """Split a pathname into drive, root and tail.
 
         The tail contains anything after the root."""
@@ -221,7 +221,7 @@ def splitroot(p):
 # join(head, tail) == p holds.
 # The resulting head won't end in '/' unless it is the root.
 
-def split(p):
+def split(p, /):
     """Split a pathname.
 
     Return tuple (head, tail) where tail is everything after the final
@@ -242,7 +242,7 @@ def split(p):
 # pathname component; the root is everything before that.
 # It is always true that root + ext == p.
 
-def splitext(p):
+def splitext(p, /):
     p = os.fspath(p)
     if isinstance(p, bytes):
         return genericpath._splitext(p, b'\\', b'/', b'.')
@@ -253,14 +253,14 @@ def splitext(p):
 
 # Return the tail (basename) part of a path.
 
-def basename(p):
+def basename(p, /):
     """Returns the final component of a pathname"""
     return split(p)[1]
 
 
 # Return the head (dirname) part of a path.
 
-def dirname(p):
+def dirname(p, /):
     """Returns the directory component of a pathname"""
     return split(p)[0]
 
@@ -559,7 +559,7 @@ def abspath(path):
     from nt import _findfirstfile, _getfinalpathname, readlink as _nt_readlink
 except ImportError:
     # realpath is a no-op on systems without _getfinalpathname support.
-    def realpath(path, *, strict=False):
+    def realpath(path, /, *, strict=False):
         return abspath(path)
 else:
     def _readlink_deep(path, ignored_error=OSError):
@@ -660,7 +660,7 @@ def _getfinalpathname_nonstrict(path, ignored_error=OSError):
                 tail = join(name, tail) if tail else name
         return tail
 
-    def realpath(path, *, strict=False):
+    def realpath(path, /, *, strict=False):
         path = normpath(path)
         if isinstance(path, bytes):
             prefix = b'\\\\?\\'
@@ -684,7 +684,8 @@ def realpath(path, *, strict=False):
 
         if strict is ALLOW_MISSING:
             ignored_error = FileNotFoundError
-            strict = True
+        elif strict is ALL_BUT_LAST:
+            ignored_error = FileNotFoundError
         elif strict:
             ignored_error = ()
         else:
@@ -704,6 +705,12 @@ def realpath(path, *, strict=False):
                 raise OSError(str(ex)) from None
             path = normpath(path)
         except ignored_error as ex:
+            if strict is ALL_BUT_LAST:
+                dirname, basename = split(path)
+                if not basename:
+                    dirname, basename = split(path)
+                if not isdir(dirname):
+                    raise
             initial_winerror = ex.winerror
             path = _getfinalpathname_nonstrict(path,
                                                ignored_error=ignored_error)
@@ -721,7 +728,7 @@ def realpath(path, *, strict=False):
             try:
                 if _getfinalpathname(spath) == path:
                     path = spath
-            except ValueError as ex:
+            except ValueError:
                 # Unexpected, as an invalid path should not have gained a prefix
                 # at any point, but we ignore this error just in case.
                 pass
diff --git a/Lib/opcode.py b/Lib/opcode.py
index 0e9520b6832..4e60fb5af34 100644
--- a/Lib/opcode.py
+++ b/Lib/opcode.py
@@ -40,83 +40,96 @@
 _intrinsic_2_descs = _opcode.get_intrinsic2_descs()
 _special_method_names = _opcode.get_special_method_names()
 _common_constants = [builtins.AssertionError, builtins.NotImplementedError,
-                     builtins.tuple, builtins.all, builtins.any]
+                     builtins.tuple, builtins.all, builtins.any, builtins.list,
+                     builtins.set,
+                     # Append-only — must match CONSTANT_* in
+                     # Include/internal/pycore_opcode_utils.h.
+                     None, "", True, False, -1]
 _nb_ops = _opcode.get_nb_ops()
 
 hascompare = [opmap["COMPARE_OP"]]
 
-_cache_format = {
-    "LOAD_GLOBAL": {
-        "counter": 1,
-        "index": 1,
-        "module_keys_version": 1,
-        "builtin_keys_version": 1,
-    },
-    "BINARY_OP": {
-        "counter": 1,
-        "descr": 4,
-    },
-    "UNPACK_SEQUENCE": {
-        "counter": 1,
-    },
-    "COMPARE_OP": {
-        "counter": 1,
-    },
-    "CONTAINS_OP": {
-        "counter": 1,
-    },
-    "FOR_ITER": {
-        "counter": 1,
-    },
-    "LOAD_SUPER_ATTR": {
-        "counter": 1,
-    },
-    "LOAD_ATTR": {
-        "counter": 1,
-        "version": 2,
-        "keys_version": 2,
-        "descr": 4,
-    },
-    "STORE_ATTR": {
-        "counter": 1,
-        "version": 2,
-        "index": 1,
-    },
-    "CALL": {
-        "counter": 1,
-        "func_version": 2,
-    },
-    "CALL_KW": {
-        "counter": 1,
-        "func_version": 2,
-    },
-    "STORE_SUBSCR": {
-        "counter": 1,
-    },
-    "SEND": {
-        "counter": 1,
-    },
-    "JUMP_BACKWARD": {
-        "counter": 1,
-    },
-    "TO_BOOL": {
-        "counter": 1,
-        "version": 2,
-    },
-    "POP_JUMP_IF_TRUE": {
-        "counter": 1,
-    },
-    "POP_JUMP_IF_FALSE": {
-        "counter": 1,
-    },
-    "POP_JUMP_IF_NONE": {
-        "counter": 1,
-    },
-    "POP_JUMP_IF_NOT_NONE": {
-        "counter": 1,
-    },
-}
+_cache_format = frozendict(
+    LOAD_GLOBAL=frozendict(
+        counter=1,
+        index=1,
+        module_keys_version=1,
+        builtin_keys_version=1,
+    ),
+    BINARY_OP=frozendict(
+        counter=1,
+        descr=4,
+    ),
+    UNPACK_SEQUENCE=frozendict(
+        counter=1,
+    ),
+    COMPARE_OP=frozendict(
+        counter=1,
+    ),
+    CONTAINS_OP=frozendict(
+        counter=1,
+    ),
+    FOR_ITER=frozendict(
+        counter=1,
+    ),
+    GET_ITER=frozendict(
+        counter=1,
+    ),
+    LOAD_SUPER_ATTR=frozendict(
+        counter=1,
+    ),
+    LOAD_ATTR=frozendict(
+        counter=1,
+        version=2,
+        keys_version=2,
+        descr=4,
+    ),
+    STORE_ATTR=frozendict(
+        counter=1,
+        version=2,
+        index=1,
+    ),
+    CALL=frozendict(
+        counter=1,
+        func_version=2,
+    ),
+    CALL_KW=frozendict(
+        counter=1,
+        func_version=2,
+    ),
+    CALL_FUNCTION_EX=frozendict(
+        counter=1,
+    ),
+    STORE_SUBSCR=frozendict(
+        counter=1,
+    ),
+    SEND=frozendict(
+        counter=1,
+    ),
+    JUMP_BACKWARD=frozendict(
+        counter=1,
+    ),
+    TO_BOOL=frozendict(
+        counter=1,
+        version=2,
+    ),
+    POP_JUMP_IF_TRUE=frozendict(
+        counter=1,
+    ),
+    POP_JUMP_IF_FALSE=frozendict(
+        counter=1,
+    ),
+    POP_JUMP_IF_NONE=frozendict(
+        counter=1,
+    ),
+    POP_JUMP_IF_NOT_NONE=frozendict(
+        counter=1,
+    ),
+    RESUME=frozendict(
+        counter=1,
+    ),
+)
 
-_inline_cache_entries = {
+_inline_cache_entries = frozendict({
     name : sum(value.values()) for (name, value) in _cache_format.items()
-}
+})
diff --git a/Lib/optparse.py b/Lib/optparse.py
index 38cf16d21ef..2928f8d7774 100644
--- a/Lib/optparse.py
+++ b/Lib/optparse.py
@@ -1,12 +1,5 @@
 """A powerful, extensible, and easy-to-use option parser.
 
-By Greg Ward <gward@python.net>
-
-Originally distributed as Optik.
-
-For support, use the optik-users@lists.sourceforge.net mailing list
-(http://lists.sourceforge.net/lists/listinfo/optik-users).
-
 Simple usage example:
 
    from optparse import OptionParser
@@ -21,8 +14,6 @@
    (options, args) = parser.parse_args()
 """
 
-__version__ = "1.5.3"
-
 __all__ = ['Option',
            'make_option',
            'SUPPRESS_HELP',
@@ -409,10 +400,12 @@ def _parse_num(val, type):
 def _parse_int(val):
     return _parse_num(val, int)
 
-_builtin_cvt = { "int" : (_parse_int, _("integer")),
-                 "long" : (_parse_int, _("integer")),
-                 "float" : (float, _("floating-point")),
-                 "complex" : (complex, _("complex")) }
+_builtin_cvt = frozendict({
+    "int": (_parse_int, _("integer")),
+    "long": (_parse_int, _("integer")),
+    "float": (float, _("floating-point")),
+    "complex": (complex, _("complex")),
+})
 
 def check_builtin(option, opt, value):
     (cvt, what) = _builtin_cvt[option.type]
@@ -1374,7 +1367,7 @@ def parse_args(self, args=None, values=None):
         self.values = values
 
         try:
-            stop = self._process_args(largs, rargs, values)
+            self._process_args(largs, rargs, values)
         except (BadOptionError, OptionValueError) as err:
             self.error(str(err))
 
@@ -1669,3 +1662,12 @@ def _match_abbrev(s, wordmap):
 # which will become a factory function when there are many Option
 # classes.
 make_option = Option
+
+
+def __getattr__(name):
+    if name == "__version__":
+        from warnings import _deprecated
+
+        _deprecated("__version__", remove=(3, 20))
+        return "1.5.3"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/os.py b/Lib/os.py
index 9bb00f45f01..a5e1d805556 100644
--- a/Lib/os.py
+++ b/Lib/os.py
@@ -58,6 +58,11 @@ def _get_exports_list(module):
         __all__.append('_exit')
     except ImportError:
         pass
+    try:
+        from posix import _clearenv
+        __all__.append('_clearenv')
+    except ImportError:
+        pass
     import posixpath as path
 
     try:
@@ -131,6 +136,8 @@ def _add(str, fn):
     _add("HAVE_UNLINKAT",   "unlink")
     _add("HAVE_UNLINKAT",   "rmdir")
     _add("HAVE_UTIMENSAT",  "utime")
+    if _exists("statx"):
+        _set.add(statx)
     supports_dir_fd = _set
 
     _set = set()
@@ -152,6 +159,8 @@ def _add(str, fn):
     _add("HAVE_FPATHCONF",  "pathconf")
     if _exists("statvfs") and _exists("fstatvfs"): # mac os x10.3
         _add("HAVE_FSTATVFS", "statvfs")
+    if _exists("statx"):
+        _set.add(statx)
     supports_fd = _set
 
     _set = set()
@@ -190,6 +199,8 @@ def _add(str, fn):
     _add("HAVE_FSTATAT",    "stat")
     _add("HAVE_UTIMENSAT",  "utime")
     _add("MS_WINDOWS",      "stat")
+    if _exists("statx"):
+        _set.add(statx)
     supports_follow_symlinks = _set
 
     del _set
@@ -208,14 +219,17 @@ def _add(str, fn):
 # Super directory utilities.
 # (Inspired by Eric Raymond; the doc strings are mostly his)
 
-def makedirs(name, mode=0o777, exist_ok=False):
-    """makedirs(name [, mode=0o777][, exist_ok=False])
+def makedirs(name, mode=0o777, exist_ok=False, *, parent_mode=None):
+    """makedirs(name [, mode=0o777][, exist_ok=False][, parent_mode=None])
 
     Super-mkdir; create a leaf directory and all intermediate ones.  Works
     like mkdir, except that any intermediate path segment (not just the
     rightmost) will be created if it does not exist.  If the target
     directory already exists, raise an OSError if exist_ok is False.
-    Otherwise no exception is raised.  This is recursive.
+    Otherwise no exception is raised.  If parent_mode is not None, it will
+    be used as the mode for any newly-created, intermediate-level
+    directories. Otherwise, intermediate directories are created with the
+    default permissions (respecting umask).  This is recursive.
 
     """
     head, tail = path.split(name)
@@ -223,7 +237,11 @@ def makedirs(name, mode=0o777, exist_ok=False):
         head, tail = path.split(head)
     if head and tail and not path.exists(head):
         try:
-            makedirs(head, exist_ok=exist_ok)
+            if parent_mode is not None:
+                makedirs(head, mode=parent_mode, exist_ok=exist_ok,
+                         parent_mode=parent_mode)
+            else:
+                makedirs(head, exist_ok=exist_ok)
         except FileExistsError:
             # Defeats race condition when another thread created the path
             pass
@@ -417,14 +435,16 @@ def walk(top, topdown=True, onerror=None, followlinks=False):
             # Yield before sub-directory traversal if going top down
             yield top, dirs, nondirs
             # Traverse into sub-directories
-            for dirname in reversed(dirs):
-                new_path = join(top, dirname)
-                # bpo-23605: os.path.islink() is used instead of caching
-                # entry.is_symlink() result during the loop on os.scandir() because
-                # the caller can replace the directory entry during the "yield"
-                # above.
-                if followlinks or not islink(new_path):
-                    stack.append(new_path)
+            if dirs:
+                prefix = join(top, top[:0])  # Add trailing slash
+                for dirname in reversed(dirs):
+                    new_path = prefix + dirname
+                    # bpo-23605: os.path.islink() is used instead of caching
+                    # entry.is_symlink() result during the loop on os.scandir() because
+                    # the caller can replace the directory entry during the "yield"
+                    # above.
+                    if followlinks or not islink(new_path):
+                        stack.append(new_path)
         else:
             # Yield after sub-directory traversal if going bottom up
             stack.append((top, dirs, nondirs))
@@ -766,6 +786,12 @@ def __ror__(self, other):
         new.update(self)
         return new
 
+    if _exists("_clearenv"):
+        def clear(self):
+            _clearenv()
+            self._data.clear()
+
+
 def _create_environ_mapping():
     if name == 'nt':
         # Where Env Var Names Must Be UPPERCASE
diff --git a/Lib/pathlib/__init__.py b/Lib/pathlib/__init__.py
index 0d763d1f0dc..8dd16c6225b 100644
--- a/Lib/pathlib/__init__.py
+++ b/Lib/pathlib/__init__.py
@@ -12,10 +12,13 @@
 import posixpath
 import sys
 from errno import *
-from glob import _StringGlobber, _no_recurse_symlinks
 from itertools import chain
-from stat import S_ISDIR, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
+from stat import (
+    S_IMODE, S_ISDIR, S_ISREG, S_ISLNK, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO,
+)
 from _collections_abc import Sequence
+lazy import shutil
+lazy from glob import _StringGlobber, _no_recurse_symlinks
 
 try:
     import pwd
@@ -27,9 +30,9 @@
     grp = None
 
 from pathlib._os import (
-    PathInfo, DirEntryInfo,
+    vfsopen, vfspath,
     ensure_different_files, ensure_distinct_paths,
-    copyfile2, copyfileobj, magic_open, copy_info,
+    copyfile2, copyfileobj,
 )
 
 
@@ -187,9 +190,6 @@ def __reduce__(self):
     def __repr__(self):
         return "{}({!r})".format(self.__class__.__name__, self.as_posix())
 
-    def __fspath__(self):
-        return str(self)
-
     def __bytes__(self):
         """Return the bytes representation of the path.  This is only
         recommended to use under Unix."""
@@ -258,6 +258,9 @@ def __str__(self):
                                                   self._tail) or '.'
             return self._str
 
+    __fspath__ = __str__
+    __vfspath__ = __str__
+
     @classmethod
     def _format_parsed_parts(cls, drv, root, tail):
         if drv or root:
@@ -483,16 +486,19 @@ def relative_to(self, other, *, walk_up=False):
         """
         if not hasattr(other, 'with_segments'):
             other = self.with_segments(other)
-        for step, path in enumerate(chain([other], other.parents)):
+        parts = []
+        for path in chain([other], other.parents):
             if path == self or path in self.parents:
                 break
             elif not walk_up:
                 raise ValueError(f"{str(self)!r} is not in the subpath of {str(other)!r}")
             elif path.name == '..':
                 raise ValueError(f"'..' segment in {str(other)!r} cannot be walked")
+            else:
+                parts.append('..')
         else:
             raise ValueError(f"{str(self)!r} and {str(other)!r} have different anchors")
-        parts = ['..'] * step + self._tail[len(path._tail):]
+        parts.extend(self._tail[len(path._tail):])
         return self._from_parsed_parts('', '', parts)
 
     def is_relative_to(self, other):
@@ -513,18 +519,6 @@ def is_absolute(self):
             return False
         return self.parser.isabs(self)
 
-    def is_reserved(self):
-        """Return True if the path contains one of the special names reserved
-        by the system, if any."""
-        import warnings
-        msg = ("pathlib.PurePath.is_reserved() is deprecated and scheduled "
-               "for removal in Python 3.15. Use os.path.isreserved() to "
-               "detect reserved paths on Windows.")
-        warnings._deprecated("pathlib.PurePath.is_reserved", msg, remove=(3, 15))
-        if self.parser is ntpath:
-            return self.parser.isreserved(self)
-        return False
-
     def as_uri(self):
         """Return the path as a URI."""
         import warnings
@@ -618,6 +612,211 @@ class PureWindowsPath(PurePath):
     __slots__ = ()
 
 
+_STAT_RESULT_ERROR = []  # falsy sentinel indicating stat() failed.
+
+
+class _Info:
+    """Implementation of pathlib.types.PathInfo that provides status
+    information by querying a wrapped os.stat_result object. Don't try to
+    construct it yourself."""
+    __slots__ = ('_path', '_entry', '_stat_result', '_lstat_result')
+
+    def __init__(self, path, entry=None):
+        self._path = path
+        self._entry = entry
+        self._stat_result = None
+        self._lstat_result = None
+
+    def __repr__(self):
+        path_type = "WindowsPath" if os.name == "nt" else "PosixPath"
+        return f"<{path_type}.info>"
+
+    def _stat(self, *, follow_symlinks=True):
+        """Return the status as an os.stat_result."""
+        if self._entry:
+            return self._entry.stat(follow_symlinks=follow_symlinks)
+        if follow_symlinks:
+            if not self._stat_result:
+                try:
+                    self._stat_result = os.stat(self._path)
+                except (OSError, ValueError):
+                    self._stat_result = _STAT_RESULT_ERROR
+                    raise
+            return self._stat_result
+        else:
+            if not self._lstat_result:
+                try:
+                    self._lstat_result = os.lstat(self._path)
+                except (OSError, ValueError):
+                    self._lstat_result = _STAT_RESULT_ERROR
+                    raise
+            return self._lstat_result
+
+    def exists(self, *, follow_symlinks=True):
+        """Whether this path exists."""
+        if self._entry:
+            if not follow_symlinks:
+                return True
+        if follow_symlinks:
+            if self._stat_result is _STAT_RESULT_ERROR:
+                return False
+        else:
+            if self._lstat_result is _STAT_RESULT_ERROR:
+                return False
+        try:
+            self._stat(follow_symlinks=follow_symlinks)
+        except (OSError, ValueError):
+            return False
+        return True
+
+    def is_dir(self, *, follow_symlinks=True):
+        """Whether this path is a directory."""
+        if self._entry:
+            try:
+                return self._entry.is_dir(follow_symlinks=follow_symlinks)
+            except OSError:
+                return False
+        if follow_symlinks:
+            if self._stat_result is _STAT_RESULT_ERROR:
+                return False
+        else:
+            if self._lstat_result is _STAT_RESULT_ERROR:
+                return False
+        try:
+            st = self._stat(follow_symlinks=follow_symlinks)
+        except (OSError, ValueError):
+            return False
+        return S_ISDIR(st.st_mode)
+
+    def is_file(self, *, follow_symlinks=True):
+        """Whether this path is a regular file."""
+        if self._entry:
+            try:
+                return self._entry.is_file(follow_symlinks=follow_symlinks)
+            except OSError:
+                return False
+        if follow_symlinks:
+            if self._stat_result is _STAT_RESULT_ERROR:
+                return False
+        else:
+            if self._lstat_result is _STAT_RESULT_ERROR:
+                return False
+        try:
+            st = self._stat(follow_symlinks=follow_symlinks)
+        except (OSError, ValueError):
+            return False
+        return S_ISREG(st.st_mode)
+
+    def is_symlink(self):
+        """Whether this path is a symbolic link."""
+        if self._entry:
+            try:
+                return self._entry.is_symlink()
+            except OSError:
+                return False
+        if self._lstat_result is _STAT_RESULT_ERROR:
+            return False
+        try:
+            st = self._stat(follow_symlinks=False)
+        except (OSError, ValueError):
+            return False
+        return S_ISLNK(st.st_mode)
+
+    def _posix_permissions(self, *, follow_symlinks=True):
+        """Return the POSIX file permissions."""
+        return S_IMODE(self._stat(follow_symlinks=follow_symlinks).st_mode)
+
+    def _file_id(self, *, follow_symlinks=True):
+        """Returns the identifier of the file."""
+        st = self._stat(follow_symlinks=follow_symlinks)
+        return st.st_dev, st.st_ino
+
+    def _access_time_ns(self, *, follow_symlinks=True):
+        """Return the access time in nanoseconds."""
+        return self._stat(follow_symlinks=follow_symlinks).st_atime_ns
+
+    def _mod_time_ns(self, *, follow_symlinks=True):
+        """Return the modify time in nanoseconds."""
+        return self._stat(follow_symlinks=follow_symlinks).st_mtime_ns
+
+    if hasattr(os.stat_result, 'st_flags'):
+        def _bsd_flags(self, *, follow_symlinks=True):
+            """Return the flags."""
+            return self._stat(follow_symlinks=follow_symlinks).st_flags
+
+    if hasattr(os, 'listxattr'):
+        def _xattrs(self, *, follow_symlinks=True):
+            """Return the xattrs as a list of (attr, value) pairs, or an empty
+            list if extended attributes aren't supported."""
+            try:
+                return [
+                    (attr, os.getxattr(self._path, attr, follow_symlinks=follow_symlinks))
+                    for attr in os.listxattr(self._path, follow_symlinks=follow_symlinks)]
+            except OSError as err:
+                if err.errno not in (EPERM, ENOTSUP, ENODATA, EINVAL, EACCES):
+                    raise
+                return []
+
+
+def _copy_info(info, target, follow_symlinks=True):
+    """Copy metadata from the given PathInfo to the given local path."""
+    copy_times_ns = (
+        hasattr(info, '_access_time_ns') and
+        hasattr(info, '_mod_time_ns') and
+        (follow_symlinks or os.utime in os.supports_follow_symlinks))
+    if copy_times_ns:
+        t0 = info._access_time_ns(follow_symlinks=follow_symlinks)
+        t1 = info._mod_time_ns(follow_symlinks=follow_symlinks)
+        os.utime(target, ns=(t0, t1), follow_symlinks=follow_symlinks)
+
+    # We must copy extended attributes before the file is (potentially)
+    # chmod()'ed read-only, otherwise setxattr() will error with -EACCES.
+    copy_xattrs = (
+        hasattr(info, '_xattrs') and
+        hasattr(os, 'setxattr') and
+        (follow_symlinks or os.setxattr in os.supports_follow_symlinks))
+    if copy_xattrs:
+        xattrs = info._xattrs(follow_symlinks=follow_symlinks)
+        for attr, value in xattrs:
+            try:
+                os.setxattr(target, attr, value, follow_symlinks=follow_symlinks)
+            except OSError as e:
+                if e.errno not in (EPERM, ENOTSUP, ENODATA, EINVAL, EACCES):
+                    raise
+
+    copy_posix_permissions = (
+        hasattr(info, '_posix_permissions') and
+        (follow_symlinks or os.chmod in os.supports_follow_symlinks))
+    if copy_posix_permissions:
+        posix_permissions = info._posix_permissions(follow_symlinks=follow_symlinks)
+        try:
+            os.chmod(target, posix_permissions, follow_symlinks=follow_symlinks)
+        except NotImplementedError:
+            # if we got a NotImplementedError, it's because
+            #   * follow_symlinks=False,
+            #   * lchown() is unavailable, and
+            #   * either
+            #       * fchownat() is unavailable or
+            #       * fchownat() doesn't implement AT_SYMLINK_NOFOLLOW.
+            #         (it returned ENOSUP.)
+            # therefore we're out of options--we simply cannot chown the
+            # symlink.  give up, suppress the error.
+            # (which is what shutil always did in this circumstance.)
+            pass
+
+    copy_bsd_flags = (
+        hasattr(info, '_bsd_flags') and
+        hasattr(os, 'chflags') and
+        (follow_symlinks or os.chflags in os.supports_follow_symlinks))
+    if copy_bsd_flags:
+        bsd_flags = info._bsd_flags(follow_symlinks=follow_symlinks)
+        try:
+            os.chflags(target, bsd_flags, follow_symlinks=follow_symlinks)
+        except OSError as why:
+            if why.errno not in (EOPNOTSUPP, ENOTSUP):
+                raise
+
+
 class Path(PurePath):
     """PurePath subclass that can make system calls.
 
@@ -643,7 +842,7 @@ def info(self):
         try:
             return self._info
         except AttributeError:
-            self._info = PathInfo(self)
+            self._info = _Info(str(self))
             return self._info
 
     def stat(self, *, follow_symlinks=True):
@@ -823,7 +1022,7 @@ def _filter_trailing_slash(self, paths):
     def _from_dir_entry(self, dir_entry, path_str):
         path = self.with_segments(path_str)
         path._str = path_str
-        path._info = DirEntryInfo(dir_entry)
+        path._info = _Info(dir_entry.path, dir_entry)
         return path
 
     def iterdir(self):
@@ -1003,7 +1202,7 @@ def touch(self, mode=0o666, exist_ok=True):
         fd = os.open(self, flags, mode)
         os.close(fd)
 
-    def mkdir(self, mode=0o777, parents=False, exist_ok=False):
+    def mkdir(self, mode=0o777, parents=False, exist_ok=False, *, parent_mode=None):
         """
         Create a new directory at this given path.
         """
@@ -1012,7 +1211,11 @@ def mkdir(self, mode=0o777, parents=False, exist_ok=False):
         except FileNotFoundError:
             if not parents or self.parent == self:
                 raise
-            self.parent.mkdir(parents=True, exist_ok=True)
+            if parent_mode is not None:
+                self.parent.mkdir(mode=parent_mode, parents=True, exist_ok=True,
+                                  parent_mode=parent_mode)
+            else:
+                self.parent.mkdir(parents=True, exist_ok=True)
             self.mkdir(mode, parents=False, exist_ok=exist_ok)
         except OSError:
             # Cannot rely on checking for EEXIST, since the operating system
@@ -1057,8 +1260,6 @@ def _delete(self):
         if self.is_symlink() or self.is_junction():
             self.unlink()
         elif self.is_dir():
-            # Lazy import to improve module import time
-            import shutil
             shutil.rmtree(self)
         else:
             self.unlink()
@@ -1129,17 +1330,17 @@ def _copy_from(self, source, follow_symlinks=True, preserve_metadata=False):
                 self.joinpath(child.name)._copy_from(
                     child, follow_symlinks, preserve_metadata)
             if preserve_metadata:
-                copy_info(source.info, self)
+                _copy_info(source.info, self)
         else:
             self._copy_from_file(source, preserve_metadata)
 
     def _copy_from_file(self, source, preserve_metadata=False):
         ensure_different_files(source, self)
-        with magic_open(source, 'rb') as source_f:
+        with vfsopen(source, 'rb') as source_f:
             with open(self, 'wb') as target_f:
                 copyfileobj(source_f, target_f)
         if preserve_metadata:
-            copy_info(source.info, self)
+            _copy_info(source.info, self)
 
     if copyfile2:
         # Use fast OS routine for local file copying where available.
@@ -1159,14 +1360,14 @@ def _copy_from_file(self, source, preserve_metadata=False):
         # os.symlink() incorrectly creates a file-symlink on Windows. Avoid
         # this by passing *target_is_dir* to os.symlink() on Windows.
         def _copy_from_symlink(self, source, preserve_metadata=False):
-            os.symlink(str(source.readlink()), self, source.info.is_dir())
+            os.symlink(vfspath(source.readlink()), self, source.info.is_dir())
             if preserve_metadata:
-                copy_info(source.info, self, follow_symlinks=False)
+                _copy_info(source.info, self, follow_symlinks=False)
     else:
         def _copy_from_symlink(self, source, preserve_metadata=False):
-            os.symlink(str(source.readlink()), self)
+            os.symlink(vfspath(source.readlink()), self)
             if preserve_metadata:
-                copy_info(source.info, self, follow_symlinks=False)
+                _copy_info(source.info, self, follow_symlinks=False)
 
     def move(self, target):
         """
diff --git a/Lib/pathlib/_os.py b/Lib/pathlib/_os.py
index 039836941dd..79a1969d5f8 100644
--- a/Lib/pathlib/_os.py
+++ b/Lib/pathlib/_os.py
@@ -4,7 +4,6 @@
 
 from errno import *
 from io import TextIOWrapper, text_encoding
-from stat import S_ISDIR, S_ISREG, S_ISLNK, S_IMODE
 import os
 import sys
 try:
@@ -166,48 +165,100 @@ def copyfileobj(source_f, target_f):
         write_target(buf)
 
 
-def magic_open(path, mode='r', buffering=-1, encoding=None, errors=None,
-               newline=None):
+def _open_reader(obj):
+    cls = type(obj)
+    try:
+        open_reader = cls.__open_reader__
+    except AttributeError:
+        cls_name = cls.__name__
+        raise TypeError(f"{cls_name} can't be opened for reading") from None
+    else:
+        return open_reader(obj)
+
+
+def _open_writer(obj, mode):
+    cls = type(obj)
+    try:
+        open_writer = cls.__open_writer__
+    except AttributeError:
+        cls_name = cls.__name__
+        raise TypeError(f"{cls_name} can't be opened for writing") from None
+    else:
+        return open_writer(obj, mode)
+
+
+def _open_updater(obj, mode):
+    cls = type(obj)
+    try:
+        open_updater = cls.__open_updater__
+    except AttributeError:
+        cls_name = cls.__name__
+        raise TypeError(f"{cls_name} can't be opened for updating") from None
+    else:
+        return open_updater(obj, mode)
+
+
+def vfsopen(obj, mode='r', buffering=-1, encoding=None, errors=None,
+            newline=None):
     """
     Open the file pointed to by this path and return a file object, as
     the built-in open() function does.
+
+    Unlike the built-in open() function, this function additionally accepts
+    'openable' objects, which are objects with any of these special methods:
+
+        __open_reader__()
+        __open_writer__(mode)
+        __open_updater__(mode)
+
+    '__open_reader__' is called for 'r' mode; '__open_writer__' for 'a', 'w'
+    and 'x' modes; and '__open_updater__' for 'r+' and 'w+' modes. If text
+    mode is requested, the result is wrapped in an io.TextIOWrapper object.
     """
+    if buffering != -1:
+        raise ValueError("buffer size can't be customized")
     text = 'b' not in mode
     if text:
         # Call io.text_encoding() here to ensure any warning is raised at an
         # appropriate stack level.
         encoding = text_encoding(encoding)
     try:
-        return open(path, mode, buffering, encoding, errors, newline)
+        return open(obj, mode, buffering, encoding, errors, newline)
     except TypeError:
         pass
-    cls = type(path)
+    if not text:
+        if encoding is not None:
+            raise ValueError("binary mode doesn't take an encoding argument")
+        if errors is not None:
+            raise ValueError("binary mode doesn't take an errors argument")
+        if newline is not None:
+            raise ValueError("binary mode doesn't take a newline argument")
     mode = ''.join(sorted(c for c in mode if c not in 'bt'))
+    if mode == 'r':
+        stream = _open_reader(obj)
+    elif mode in ('a', 'w', 'x'):
+        stream = _open_writer(obj, mode)
+    elif mode in ('+r', '+w'):
+        stream = _open_updater(obj, mode[1])
+    else:
+        raise ValueError(f'invalid mode: {mode}')
     if text:
-        try:
-            attr = getattr(cls, f'__open_{mode}__')
-        except AttributeError:
-            pass
-        else:
-            return attr(path, buffering, encoding, errors, newline)
-    elif encoding is not None:
-        raise ValueError("binary mode doesn't take an encoding argument")
-    elif errors is not None:
-        raise ValueError("binary mode doesn't take an errors argument")
-    elif newline is not None:
-        raise ValueError("binary mode doesn't take a newline argument")
+        stream = TextIOWrapper(stream, encoding, errors, newline)
+    return stream
 
+
+def vfspath(obj):
+    """
+    Return the string representation of a virtual path object.
+    """
+    cls = type(obj)
     try:
-        attr = getattr(cls, f'__open_{mode}b__')
+        vfspath_method = cls.__vfspath__
     except AttributeError:
-        pass
+        cls_name = cls.__name__
+        raise TypeError(f"expected JoinablePath object, not {cls_name}") from None
     else:
-        stream = attr(path, buffering)
-        if text:
-            stream = TextIOWrapper(stream, encoding, errors, newline)
-        return stream
-
-    raise TypeError(f"{cls.__name__} can't be opened with mode {mode!r}")
+        return vfspath_method(obj)
 
 
 def ensure_distinct_paths(source, target):
@@ -225,8 +276,8 @@ def ensure_distinct_paths(source, target):
         err = OSError(EINVAL, "Source path is a parent of target path")
     else:
         return
-    err.filename = str(source)
-    err.filename2 = str(target)
+    err.filename = vfspath(source)
+    err.filename2 = vfspath(target)
     raise err
 
 
@@ -247,284 +298,6 @@ def ensure_different_files(source, target):
         except (OSError, ValueError):
             return
     err = OSError(EINVAL, "Source and target are the same file")
-    err.filename = str(source)
-    err.filename2 = str(target)
+    err.filename = vfspath(source)
+    err.filename2 = vfspath(target)
     raise err
-
-
-def copy_info(info, target, follow_symlinks=True):
-    """Copy metadata from the given PathInfo to the given local path."""
-    copy_times_ns = (
-        hasattr(info, '_access_time_ns') and
-        hasattr(info, '_mod_time_ns') and
-        (follow_symlinks or os.utime in os.supports_follow_symlinks))
-    if copy_times_ns:
-        t0 = info._access_time_ns(follow_symlinks=follow_symlinks)
-        t1 = info._mod_time_ns(follow_symlinks=follow_symlinks)
-        os.utime(target, ns=(t0, t1), follow_symlinks=follow_symlinks)
-
-    # We must copy extended attributes before the file is (potentially)
-    # chmod()'ed read-only, otherwise setxattr() will error with -EACCES.
-    copy_xattrs = (
-        hasattr(info, '_xattrs') and
-        hasattr(os, 'setxattr') and
-        (follow_symlinks or os.setxattr in os.supports_follow_symlinks))
-    if copy_xattrs:
-        xattrs = info._xattrs(follow_symlinks=follow_symlinks)
-        for attr, value in xattrs:
-            try:
-                os.setxattr(target, attr, value, follow_symlinks=follow_symlinks)
-            except OSError as e:
-                if e.errno not in (EPERM, ENOTSUP, ENODATA, EINVAL, EACCES):
-                    raise
-
-    copy_posix_permissions = (
-        hasattr(info, '_posix_permissions') and
-        (follow_symlinks or os.chmod in os.supports_follow_symlinks))
-    if copy_posix_permissions:
-        posix_permissions = info._posix_permissions(follow_symlinks=follow_symlinks)
-        try:
-            os.chmod(target, posix_permissions, follow_symlinks=follow_symlinks)
-        except NotImplementedError:
-            # if we got a NotImplementedError, it's because
-            #   * follow_symlinks=False,
-            #   * lchown() is unavailable, and
-            #   * either
-            #       * fchownat() is unavailable or
-            #       * fchownat() doesn't implement AT_SYMLINK_NOFOLLOW.
-            #         (it returned ENOSUP.)
-            # therefore we're out of options--we simply cannot chown the
-            # symlink.  give up, suppress the error.
-            # (which is what shutil always did in this circumstance.)
-            pass
-
-    copy_bsd_flags = (
-        hasattr(info, '_bsd_flags') and
-        hasattr(os, 'chflags') and
-        (follow_symlinks or os.chflags in os.supports_follow_symlinks))
-    if copy_bsd_flags:
-        bsd_flags = info._bsd_flags(follow_symlinks=follow_symlinks)
-        try:
-            os.chflags(target, bsd_flags, follow_symlinks=follow_symlinks)
-        except OSError as why:
-            if why.errno not in (EOPNOTSUPP, ENOTSUP):
-                raise
-
-
-class _PathInfoBase:
-    __slots__ = ('_path', '_stat_result', '_lstat_result')
-
-    def __init__(self, path):
-        self._path = str(path)
-
-    def __repr__(self):
-        path_type = "WindowsPath" if os.name == "nt" else "PosixPath"
-        return f"<{path_type}.info>"
-
-    def _stat(self, *, follow_symlinks=True, ignore_errors=False):
-        """Return the status as an os.stat_result, or None if stat() fails and
-        ignore_errors is true."""
-        if follow_symlinks:
-            try:
-                result = self._stat_result
-            except AttributeError:
-                pass
-            else:
-                if ignore_errors or result is not None:
-                    return result
-            try:
-                self._stat_result = os.stat(self._path)
-            except (OSError, ValueError):
-                self._stat_result = None
-                if not ignore_errors:
-                    raise
-            return self._stat_result
-        else:
-            try:
-                result = self._lstat_result
-            except AttributeError:
-                pass
-            else:
-                if ignore_errors or result is not None:
-                    return result
-            try:
-                self._lstat_result = os.lstat(self._path)
-            except (OSError, ValueError):
-                self._lstat_result = None
-                if not ignore_errors:
-                    raise
-            return self._lstat_result
-
-    def _posix_permissions(self, *, follow_symlinks=True):
-        """Return the POSIX file permissions."""
-        return S_IMODE(self._stat(follow_symlinks=follow_symlinks).st_mode)
-
-    def _file_id(self, *, follow_symlinks=True):
-        """Returns the identifier of the file."""
-        st = self._stat(follow_symlinks=follow_symlinks)
-        return st.st_dev, st.st_ino
-
-    def _access_time_ns(self, *, follow_symlinks=True):
-        """Return the access time in nanoseconds."""
-        return self._stat(follow_symlinks=follow_symlinks).st_atime_ns
-
-    def _mod_time_ns(self, *, follow_symlinks=True):
-        """Return the modify time in nanoseconds."""
-        return self._stat(follow_symlinks=follow_symlinks).st_mtime_ns
-
-    if hasattr(os.stat_result, 'st_flags'):
-        def _bsd_flags(self, *, follow_symlinks=True):
-            """Return the flags."""
-            return self._stat(follow_symlinks=follow_symlinks).st_flags
-
-    if hasattr(os, 'listxattr'):
-        def _xattrs(self, *, follow_symlinks=True):
-            """Return the xattrs as a list of (attr, value) pairs, or an empty
-            list if extended attributes aren't supported."""
-            try:
-                return [
-                    (attr, os.getxattr(self._path, attr, follow_symlinks=follow_symlinks))
-                    for attr in os.listxattr(self._path, follow_symlinks=follow_symlinks)]
-            except OSError as err:
-                if err.errno not in (EPERM, ENOTSUP, ENODATA, EINVAL, EACCES):
-                    raise
-                return []
-
-
-class _WindowsPathInfo(_PathInfoBase):
-    """Implementation of pathlib.types.PathInfo that provides status
-    information for Windows paths. Don't try to construct it yourself."""
-    __slots__ = ('_exists', '_is_dir', '_is_file', '_is_symlink')
-
-    def exists(self, *, follow_symlinks=True):
-        """Whether this path exists."""
-        if not follow_symlinks and self.is_symlink():
-            return True
-        try:
-            return self._exists
-        except AttributeError:
-            if os.path.exists(self._path):
-                self._exists = True
-                return True
-            else:
-                self._exists = self._is_dir = self._is_file = False
-                return False
-
-    def is_dir(self, *, follow_symlinks=True):
-        """Whether this path is a directory."""
-        if not follow_symlinks and self.is_symlink():
-            return False
-        try:
-            return self._is_dir
-        except AttributeError:
-            if os.path.isdir(self._path):
-                self._is_dir = self._exists = True
-                return True
-            else:
-                self._is_dir = False
-                return False
-
-    def is_file(self, *, follow_symlinks=True):
-        """Whether this path is a regular file."""
-        if not follow_symlinks and self.is_symlink():
-            return False
-        try:
-            return self._is_file
-        except AttributeError:
-            if os.path.isfile(self._path):
-                self._is_file = self._exists = True
-                return True
-            else:
-                self._is_file = False
-                return False
-
-    def is_symlink(self):
-        """Whether this path is a symbolic link."""
-        try:
-            return self._is_symlink
-        except AttributeError:
-            self._is_symlink = os.path.islink(self._path)
-            return self._is_symlink
-
-
-class _PosixPathInfo(_PathInfoBase):
-    """Implementation of pathlib.types.PathInfo that provides status
-    information for POSIX paths. Don't try to construct it yourself."""
-    __slots__ = ()
-
-    def exists(self, *, follow_symlinks=True):
-        """Whether this path exists."""
-        st = self._stat(follow_symlinks=follow_symlinks, ignore_errors=True)
-        if st is None:
-            return False
-        return True
-
-    def is_dir(self, *, follow_symlinks=True):
-        """Whether this path is a directory."""
-        st = self._stat(follow_symlinks=follow_symlinks, ignore_errors=True)
-        if st is None:
-            return False
-        return S_ISDIR(st.st_mode)
-
-    def is_file(self, *, follow_symlinks=True):
-        """Whether this path is a regular file."""
-        st = self._stat(follow_symlinks=follow_symlinks, ignore_errors=True)
-        if st is None:
-            return False
-        return S_ISREG(st.st_mode)
-
-    def is_symlink(self):
-        """Whether this path is a symbolic link."""
-        st = self._stat(follow_symlinks=False, ignore_errors=True)
-        if st is None:
-            return False
-        return S_ISLNK(st.st_mode)
-
-
-PathInfo = _WindowsPathInfo if os.name == 'nt' else _PosixPathInfo
-
-
-class DirEntryInfo(_PathInfoBase):
-    """Implementation of pathlib.types.PathInfo that provides status
-    information by querying a wrapped os.DirEntry object. Don't try to
-    construct it yourself."""
-    __slots__ = ('_entry',)
-
-    def __init__(self, entry):
-        super().__init__(entry.path)
-        self._entry = entry
-
-    def _stat(self, *, follow_symlinks=True, ignore_errors=False):
-        try:
-            return self._entry.stat(follow_symlinks=follow_symlinks)
-        except OSError:
-            if not ignore_errors:
-                raise
-            return None
-
-    def exists(self, *, follow_symlinks=True):
-        """Whether this path exists."""
-        if not follow_symlinks:
-            return True
-        return self._stat(ignore_errors=True) is not None
-
-    def is_dir(self, *, follow_symlinks=True):
-        """Whether this path is a directory."""
-        try:
-            return self._entry.is_dir(follow_symlinks=follow_symlinks)
-        except OSError:
-            return False
-
-    def is_file(self, *, follow_symlinks=True):
-        """Whether this path is a regular file."""
-        try:
-            return self._entry.is_file(follow_symlinks=follow_symlinks)
-        except OSError:
-            return False
-
-    def is_symlink(self):
-        """Whether this path is a symbolic link."""
-        try:
-            return self._entry.is_symlink()
-        except OSError:
-            return False
diff --git a/Lib/pathlib/types.py b/Lib/pathlib/types.py
index d8f5c34a1a7..f21ce077454 100644
--- a/Lib/pathlib/types.py
+++ b/Lib/pathlib/types.py
@@ -11,9 +11,10 @@
 
 
 from abc import ABC, abstractmethod
-from glob import _PathGlobber
+from glob import _GlobberBase
 from io import text_encoding
-from pathlib._os import magic_open, ensure_distinct_paths, ensure_different_files, copyfileobj
+from pathlib._os import (vfsopen, vfspath, ensure_distinct_paths,
+                         ensure_different_files, copyfileobj)
 from pathlib import PurePath, Path
 from typing import Optional, Protocol, runtime_checkable
 
@@ -60,6 +61,25 @@ def is_file(self, *, follow_symlinks: bool = True) -> bool: ...
     def is_symlink(self) -> bool: ...
 
 
+class _PathGlobber(_GlobberBase):
+    """Provides shell-style pattern matching and globbing for ReadablePath.
+    """
+
+    @staticmethod
+    def lexists(path):
+        return path.info.exists(follow_symlinks=False)
+
+    @staticmethod
+    def scandir(path):
+        return ((child.info, child.name, child) for child in path.iterdir())
+
+    @staticmethod
+    def concat_path(path, text):
+        return path.with_segments(vfspath(path) + text)
+
+    stringify_path = staticmethod(vfspath)
+
+
 class _JoinablePath(ABC):
     """Abstract base class for pure path objects.
 
@@ -86,20 +106,19 @@ def with_segments(self, *pathsegments):
         raise NotImplementedError
 
     @abstractmethod
-    def __str__(self):
-        """Return the string representation of the path, suitable for
-        passing to system calls."""
+    def __vfspath__(self):
+        """Return the string representation of the path."""
         raise NotImplementedError
 
     @property
     def anchor(self):
         """The concatenation of the drive and root, or ''."""
-        return _explode_path(str(self), self.parser.split)[0]
+        return _explode_path(vfspath(self), self.parser.split)[0]
 
     @property
     def name(self):
         """The final path component, if any."""
-        return self.parser.split(str(self))[1]
+        return self.parser.split(vfspath(self))[1]
 
     @property
     def suffix(self):
@@ -135,7 +154,7 @@ def with_name(self, name):
         split = self.parser.split
         if split(name)[0]:
             raise ValueError(f"Invalid name {name!r}")
-        path = str(self)
+        path = vfspath(self)
         path = path.removesuffix(split(path)[1]) + name
         return self.with_segments(path)
 
@@ -168,7 +187,7 @@ def with_suffix(self, suffix):
     def parts(self):
         """An object providing sequence-like access to the
         components in the filesystem path."""
-        anchor, parts = _explode_path(str(self), self.parser.split)
+        anchor, parts = _explode_path(vfspath(self), self.parser.split)
         if anchor:
             parts.append(anchor)
         return tuple(reversed(parts))
@@ -179,24 +198,24 @@ def joinpath(self, *pathsegments):
         paths) or a totally different path (if one of the arguments is
         anchored).
         """
-        return self.with_segments(str(self), *pathsegments)
+        return self.with_segments(vfspath(self), *pathsegments)
 
     def __truediv__(self, key):
         try:
-            return self.with_segments(str(self), key)
+            return self.with_segments(vfspath(self), key)
         except TypeError:
             return NotImplemented
 
     def __rtruediv__(self, key):
         try:
-            return self.with_segments(key, str(self))
+            return self.with_segments(key, vfspath(self))
         except TypeError:
             return NotImplemented
 
     @property
     def parent(self):
         """The logical parent of the path."""
-        path = str(self)
+        path = vfspath(self)
         parent = self.parser.split(path)[0]
         if path != parent:
             return self.with_segments(parent)
@@ -206,7 +225,7 @@ def parent(self):
     def parents(self):
         """A sequence of this path's logical parents."""
         split = self.parser.split
-        path = str(self)
+        path = vfspath(self)
         parent = split(path)[0]
         parents = []
         while path != parent:
@@ -215,6 +234,33 @@ def parents(self):
             parent = split(path)[0]
         return tuple(parents)
 
+    def relative_to(self, other, *, walk_up=False):
+        """Return the relative path to another path identified by the passed
+        arguments.  If the operation is not possible (because this is not
+        related to the other path), raise ValueError.
+
+        The *walk_up* parameter controls whether `..` may be used to resolve
+        the path.
+        """
+        parts = []
+        for path in (other,) + other.parents:
+            if self.is_relative_to(path):
+                break
+            elif not walk_up:
+                raise ValueError(f"{self!r} is not in the subpath of {other!r}")
+            elif path.name == '..':
+                raise ValueError(f"'..' segment in {other!r} cannot be walked")
+            else:
+                parts.append('..')
+        else:
+            raise ValueError(f"{self!r} and {other!r} have different anchors")
+        return self.with_segments(*parts, *self.parts[len(path.parts):])
+
+    def is_relative_to(self, other):
+        """Return True if the path is relative to another path or False.
+        """
+        return other == self or other in self.parents
+
     def full_match(self, pattern):
         """
         Return True if this path matches the given glob-style pattern. The
@@ -223,7 +269,7 @@ def full_match(self, pattern):
         case_sensitive = self.parser.normcase('Aa') == 'Aa'
         globber = _PathGlobber(self.parser.sep, case_sensitive, recursive=True)
         match = globber.compile(pattern, altsep=self.parser.altsep)
-        return match(str(self)) is not None
+        return match(vfspath(self)) is not None
 
 
 class _ReadablePath(_JoinablePath):
@@ -245,10 +291,10 @@ def info(self):
         raise NotImplementedError
 
     @abstractmethod
-    def __open_rb__(self, buffering=-1):
+    def __open_reader__(self):
         """
         Open the file pointed to by this path for reading in binary mode and
-        return a file object, like open(mode='rb').
+        return a file object.
         """
         raise NotImplementedError
 
@@ -256,7 +302,7 @@ def read_bytes(self):
         """
         Open the file in bytes mode, read it, and close the file.
         """
-        with magic_open(self, mode='rb', buffering=0) as f:
+        with vfsopen(self, mode='rb') as f:
             return f.read()
 
     def read_text(self, encoding=None, errors=None, newline=None):
@@ -266,7 +312,7 @@ def read_text(self, encoding=None, errors=None, newline=None):
         # Call io.text_encoding() here to ensure any warning is raised at an
         # appropriate stack level.
         encoding = text_encoding(encoding)
-        with magic_open(self, mode='r', encoding=encoding, errors=errors, newline=newline) as f:
+        with vfsopen(self, mode='r', encoding=encoding, errors=errors, newline=newline) as f:
             return f.read()
 
     @abstractmethod
@@ -375,10 +421,10 @@ def mkdir(self):
         raise NotImplementedError
 
     @abstractmethod
-    def __open_wb__(self, buffering=-1):
+    def __open_writer__(self, mode):
         """
         Open the file pointed to by this path for writing in binary mode and
-        return a file object, like open(mode='wb').
+        return a file object.
         """
         raise NotImplementedError
 
@@ -388,7 +434,7 @@ def write_bytes(self, data):
         """
         # type-check for the buffer interface before truncating the file
         view = memoryview(data)
-        with magic_open(self, mode='wb') as f:
+        with vfsopen(self, mode='wb') as f:
             return f.write(view)
 
     def write_text(self, data, encoding=None, errors=None, newline=None):
@@ -401,7 +447,7 @@ def write_text(self, data, encoding=None, errors=None, newline=None):
         if not isinstance(data, str):
             raise TypeError('data must be str, not %s' %
                             data.__class__.__name__)
-        with magic_open(self, mode='w', encoding=encoding, errors=errors, newline=newline) as f:
+        with vfsopen(self, mode='w', encoding=encoding, errors=errors, newline=newline) as f:
             return f.write(data)
 
     def _copy_from(self, source, follow_symlinks=True):
@@ -412,7 +458,7 @@ def _copy_from(self, source, follow_symlinks=True):
         while stack:
             src, dst = stack.pop()
             if not follow_symlinks and src.info.is_symlink():
-                dst.symlink_to(str(src.readlink()), src.info.is_dir())
+                dst.symlink_to(vfspath(src.readlink()), src.info.is_dir())
             elif src.info.is_dir():
                 children = src.iterdir()
                 dst.mkdir()
@@ -420,8 +466,8 @@ def _copy_from(self, source, follow_symlinks=True):
                     stack.append((child, dst.joinpath(child.name)))
             else:
                 ensure_different_files(src, dst)
-                with magic_open(src, 'rb') as source_f:
-                    with magic_open(dst, 'wb') as target_f:
+                with vfsopen(src, 'rb') as source_f:
+                    with vfsopen(dst, 'wb') as target_f:
                         copyfileobj(source_f, target_f)
 
 
diff --git a/Lib/plistlib.py b/Lib/plistlib.py
index c3aee1e15c7..93f3ef5e38a 100644
--- a/Lib/plistlib.py
+++ b/Lib/plistlib.py
@@ -2,7 +2,7 @@
 
 The property list (.plist) file format is a simple XML pickle supporting
 basic object types, like dictionaries, lists, numbers and strings.
-Usually the top level object is a dictionary.
+Usually the top level object is a dictionary or a frozen dictionary.
 
 To write out a plist file, use the dump(value, file)
 function. 'value' is the top level object, 'file' is
@@ -122,13 +122,7 @@ def __hash__(self):
     r"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f]")
 
 def _encode_base64(s, maxlinelength=76):
-    # copied from base64.encodebytes(), with added maxlinelength argument
-    maxbinsize = (maxlinelength//4)*3
-    pieces = []
-    for i in range(0, len(s), maxbinsize):
-        chunk = s[i : i + maxbinsize]
-        pieces.append(binascii.b2a_base64(chunk))
-    return b''.join(pieces)
+    return binascii.b2a_base64(s, wrapcol=maxlinelength, newline=False)
 
 def _decode_base64(s):
     if isinstance(s, str):
@@ -363,7 +357,7 @@ def write_value(self, value):
         elif isinstance(value, float):
             self.simple_element("real", repr(value))
 
-        elif isinstance(value, dict):
+        elif isinstance(value, (dict, frozendict)):
             self.write_dict(value)
 
         elif isinstance(value, (bytes, bytearray)):
@@ -382,11 +376,10 @@ def write_value(self, value):
     def write_bytes(self, data):
         self.begin_element("data")
         self._indent_level -= 1
-        maxlinelength = max(
-            16,
-            76 - len((self.indent * self._indent_level).expandtabs()))
-
-        for line in _encode_base64(data, maxlinelength).split(b"\n"):
+        wrapcol = 76 - len((self.indent * self._indent_level).expandtabs())
+        wrapcol = max(16, wrapcol)
+        encoded = binascii.b2a_base64(data, wrapcol=wrapcol, newline=False)
+        for line in encoded.split(b"\n"):
             if line:
                 self.writeln(line)
         self._indent_level += 1
@@ -460,7 +453,7 @@ class InvalidFileException (ValueError):
     def __init__(self, message="Invalid file"):
         ValueError.__init__(self, message)
 
-_BINARY_FORMAT = {1: 'B', 2: 'H', 4: 'L', 8: 'Q'}
+_BINARY_FORMAT = frozendict({1: 'B', 2: 'H', 4: 'L', 8: 'Q'})
 
 _undefined = object()
 
@@ -722,7 +715,7 @@ def _flatten(self, value):
             self._objidtable[id(value)] = refnum
 
         # And finally recurse into containers
-        if isinstance(value, dict):
+        if isinstance(value, (dict, frozendict)):
             keys = []
             values = []
             items = value.items()
@@ -843,7 +836,7 @@ def _write_object(self, value):
             self._write_size(0xA0, s)
             self._fp.write(struct.pack('>' + self._ref_format * s, *refs))
 
-        elif isinstance(value, dict):
+        elif isinstance(value, (dict, frozendict)):
             keyRefs, valRefs = [], []
 
             if self._sort_keys:
@@ -876,18 +869,18 @@ def _is_fmt_binary(header):
 # Generic bits
 #
 
-_FORMATS={
-    FMT_XML: dict(
+_FORMATS=frozendict({
+    FMT_XML: frozendict(
         detect=_is_fmt_xml,
         parser=_PlistParser,
         writer=_PlistWriter,
     ),
-    FMT_BINARY: dict(
+    FMT_BINARY: frozendict(
         detect=_is_fmt_binary,
         parser=_BinaryPlistParser,
         writer=_BinaryPlistWriter,
     )
-}
+})
 
 
 def load(fp, *, fmt=None, dict_type=dict, aware_datetime=False):
diff --git a/Lib/poplib.py b/Lib/poplib.py
index 4469bff44b4..b97274c5c32 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -122,6 +122,8 @@ def _putline(self, line):
     def _putcmd(self, line):
         if self._debugging: print('*cmd*', repr(line))
         line = bytes(line, self.encoding)
+        if re.search(b'[\x00-\x1F\x7F]', line):
+            raise ValueError('Control characters not allowed in commands')
         self._putline(line)
 
 
diff --git a/Lib/posixpath.py b/Lib/posixpath.py
index ad86cc06c01..8025b063397 100644
--- a/Lib/posixpath.py
+++ b/Lib/posixpath.py
@@ -36,7 +36,8 @@
            "samefile","sameopenfile","samestat",
            "curdir","pardir","sep","pathsep","defpath","altsep","extsep",
            "devnull","realpath","supports_unicode_filenames","relpath",
-           "commonpath", "isjunction","isdevdrive","ALLOW_MISSING"]
+           "commonpath","isjunction","isdevdrive",
+           "ALL_BUT_LAST","ALLOW_MISSING"]
 
 
 def _get_sep(path):
@@ -50,7 +51,7 @@ def _get_sep(path):
 # normalizations (such as optimizing '../' away) are not allowed
 # (another function should be defined to do that).
 
-def normcase(s):
+def normcase(s, /):
     """Normalize case of pathname.  Has no effect under Posix"""
     return os.fspath(s)
 
@@ -58,7 +59,7 @@ def normcase(s):
 # Return whether a path is absolute.
 # Trivial in Posix, harder on the Mac or MS-DOS.
 
-def isabs(s):
+def isabs(s, /):
     """Test whether a path is absolute"""
     s = os.fspath(s)
     sep = _get_sep(s)
@@ -69,7 +70,7 @@ def isabs(s):
 # Ignore the previous parts if a part is absolute.
 # Insert a '/' unless the first part is empty or already ends in '/'.
 
-def join(a, *p):
+def join(a, /, *p):
     """Join two or more pathname components, inserting '/' as needed.
     If any component is an absolute path, all previous path components
     will be discarded.  An empty last part will result in a path that
@@ -97,7 +98,7 @@ def join(a, *p):
 # '/' in the path, head  will be empty.
 # Trailing '/'es are stripped from head unless it is the root.
 
-def split(p):
+def split(p, /):
     """Split a pathname.  Returns tuple "(head, tail)" where "tail" is
     everything after the final slash.  Either part may be empty."""
     p = os.fspath(p)
@@ -114,7 +115,7 @@ def split(p):
 # pathname component; the root is everything before that.
 # It is always true that root + ext == p.
 
-def splitext(p):
+def splitext(p, /):
     p = os.fspath(p)
     if isinstance(p, bytes):
         sep = b'/'
@@ -128,7 +129,7 @@ def splitext(p):
 # Split a pathname into a drive specification and the rest of the
 # path.  Useful on DOS/Windows/NT; on Unix, the drive is always empty.
 
-def splitdrive(p):
+def splitdrive(p, /):
     """Split a pathname into drive and path. On Posix, drive is always
     empty."""
     p = os.fspath(p)
@@ -138,7 +139,7 @@ def splitdrive(p):
 try:
     from posix import _path_splitroot_ex as splitroot
 except ImportError:
-    def splitroot(p):
+    def splitroot(p, /):
         """Split a pathname into drive, root and tail.
 
         The tail contains anything after the root."""
@@ -163,7 +164,7 @@ def splitroot(p):
 
 # Return the tail (basename) part of a path, same as split(path)[1].
 
-def basename(p):
+def basename(p, /):
     """Returns the final component of a pathname"""
     p = os.fspath(p)
     sep = _get_sep(p)
@@ -173,7 +174,7 @@ def basename(p):
 
 # Return the head (dirname) part of a path, same as split(path)[0].
 
-def dirname(p):
+def dirname(p, /):
     """Returns the directory component of a pathname"""
     p = os.fspath(p)
     sep = _get_sep(p)
@@ -385,7 +386,7 @@ def abspath(path):
 # Return a canonical path (i.e. the absolute location of a file on the
 # filesystem).
 
-def realpath(filename, *, strict=False):
+def realpath(filename, /, *, strict=False):
     """Return the canonical path of the specified filename, eliminating any
 symbolic links encountered in the path."""
     filename = os.fspath(filename)
@@ -401,7 +402,8 @@ def realpath(filename, *, strict=False):
         getcwd = os.getcwd
     if strict is ALLOW_MISSING:
         ignored_error = FileNotFoundError
-        strict = True
+    elif strict is ALL_BUT_LAST:
+        ignored_error = FileNotFoundError
     elif strict:
         ignored_error = ()
     else:
@@ -415,7 +417,7 @@ def realpath(filename, *, strict=False):
     # indicates that a symlink target has been resolved, and that the original
     # symlink path can be retrieved by popping again. The [::-1] slice is a
     # very fast way of spelling list(reversed(...)).
-    rest = filename.split(sep)[::-1]
+    rest = filename.rstrip(sep).split(sep)[::-1]
 
     # Number of unprocessed parts in 'rest'. This can differ from len(rest)
     # later, because 'rest' might contain markers for unresolved symlinks.
@@ -424,6 +426,7 @@ def realpath(filename, *, strict=False):
     # The resolved path, which is absolute throughout this function.
     # Note: getcwd() returns a normalized and symlink-free path.
     path = sep if filename.startswith(sep) else getcwd()
+    trailing_sep = filename.endswith(sep)
 
     # Mapping from symlink paths to *fully resolved* symlink targets. If a
     # symlink is encountered but not yet resolved, the value is None. This is
@@ -456,7 +459,8 @@ def realpath(filename, *, strict=False):
         try:
             st_mode = lstat(newpath).st_mode
             if not stat.S_ISLNK(st_mode):
-                if strict and part_count and not stat.S_ISDIR(st_mode):
+                if (strict and (part_count or trailing_sep)
+                    and not stat.S_ISDIR(st_mode)):
                     raise OSError(errno.ENOTDIR, os.strerror(errno.ENOTDIR),
                                   newpath)
                 path = newpath
@@ -483,7 +487,8 @@ def realpath(filename, *, strict=False):
                 continue
             target = readlink(newpath)
         except ignored_error:
-            pass
+            if strict is ALL_BUT_LAST and part_count:
+                raise
         else:
             # Resolve the symbolic link
             if target.startswith(sep):
@@ -537,7 +542,7 @@ def relpath(path, start=None):
         start_list = start_tail.split(sep) if start_tail else []
         path_list = path_tail.split(sep) if path_tail else []
         # Work out how much of the filepath is shared by start and path.
-        i = len(commonprefix([start_list, path_list]))
+        i = len(genericpath._commonprefix([start_list, path_list]))
 
         rel_list = [pardir] * (len(start_list)-i) + path_list[i:]
         if not rel_list:
diff --git a/Lib/pprint.py b/Lib/pprint.py
index dc0953cec67..6b574218277 100644
--- a/Lib/pprint.py
+++ b/Lib/pprint.py
@@ -44,20 +44,22 @@
 
 
 def pprint(object, stream=None, indent=1, width=80, depth=None, *,
-           compact=False, sort_dicts=True, underscore_numbers=False):
+           compact=False, expand=False, sort_dicts=True,
+           underscore_numbers=False):
     """Pretty-print a Python object to a stream [default is sys.stdout]."""
     printer = PrettyPrinter(
         stream=stream, indent=indent, width=width, depth=depth,
-        compact=compact, sort_dicts=sort_dicts,
+        compact=compact, expand=expand, sort_dicts=sort_dicts,
         underscore_numbers=underscore_numbers)
     printer.pprint(object)
 
 
 def pformat(object, indent=1, width=80, depth=None, *,
-            compact=False, sort_dicts=True, underscore_numbers=False):
+            compact=False, expand=False, sort_dicts=True,
+            underscore_numbers=False):
     """Format a Python object into a pretty-printed representation."""
     return PrettyPrinter(indent=indent, width=width, depth=depth,
-                         compact=compact, sort_dicts=sort_dicts,
+                         compact=compact, expand=expand, sort_dicts=sort_dicts,
                          underscore_numbers=underscore_numbers).pformat(object)
 
 
@@ -111,7 +113,8 @@ def _safe_tuple(t):
 
 class PrettyPrinter:
     def __init__(self, indent=1, width=80, depth=None, stream=None, *,
-                 compact=False, sort_dicts=True, underscore_numbers=False):
+                 compact=False, expand=False, sort_dicts=True,
+                 underscore_numbers=False):
         """Handle pretty printing operations onto a stream using a set of
         configured parameters.
 
@@ -130,6 +133,12 @@ def __init__(self, indent=1, width=80, depth=None, stream=None, *,
 
         compact
             If true, several items will be combined in one line.
+            Incompatible with expand mode.
+
+        expand
+            If true, the output will be formatted similar to
+            pretty-printed json.dumps() when ``indent`` is supplied.
+            Incompatible with compact mode.
 
         sort_dicts
             If true, dict keys are sorted.
@@ -146,6 +155,8 @@ def __init__(self, indent=1, width=80, depth=None, stream=None, *,
             raise ValueError('depth must be > 0')
         if not width:
             raise ValueError('width must be != 0')
+        if compact and expand:
+            raise ValueError('compact and expand are incompatible')
         self._depth = depth
         self._indent_per_level = indent
         self._width = width
@@ -154,6 +165,7 @@ def __init__(self, indent=1, width=80, depth=None, stream=None, *,
         else:
             self._stream = _sys.stdout
         self._compact = bool(compact)
+        self._expand = bool(expand)
         self._sort_dicts = sort_dicts
         self._underscore_numbers = underscore_numbers
 
@@ -175,6 +187,11 @@ def isreadable(self, object):
         return readable and not recursive
 
     def _format(self, object, stream, indent, allowance, context, level):
+        # Width of any "key: " prefix already written on the current line by
+        # _format_child().  In expand mode `indent` is the block indent and so
+        # does not include it, but it still consumes width here.
+        prefix_len = self._pending_prefix_len
+        self._pending_prefix_len = 0
         objid = id(object)
         if objid in context:
             stream.write(_recursion(object))
@@ -182,7 +199,7 @@ def _format(self, object, stream, indent, allowance, context, level):
             self._readable = False
             return
         rep = self._repr(object, context, level)
-        max_width = self._width - indent - allowance
+        max_width = self._width - indent - prefix_len - allowance
         if len(rep) > max_width:
             p = self._dispatch.get(type(object).__repr__, None)
             # Lazy import to improve module import time
@@ -205,24 +222,64 @@ def _format(self, object, stream, indent, allowance, context, level):
                 return
         stream.write(rep)
 
+    def _format_block_start(self, start_str, indent):
+        if self._expand:
+            return f"{start_str}\n{' ' * indent}"
+        return start_str
+
+    def _format_block_end(self, end_str, indent):
+        if self._expand:
+            return f"\n{' ' * indent}{end_str}"
+        return end_str
+
+    def _child_indent(self, indent, prefix_len):
+        if self._expand:
+            return indent
+        return indent + prefix_len
+
+    # Set by _format_child() immediately before it calls _format(), and
+    # consumed there.  Passing it out of band keeps _format()'s signature
+    # unchanged for third-party subclasses that override it.
+    _pending_prefix_len = 0
+
+    def _format_child(self, object, stream, indent, allowance, context, level,
+                      prefix_len):
+        if self._expand:
+            # Aligned mode folds the prefix into the indent (see
+            # _child_indent), so only expand mode needs to report it.
+            self._pending_prefix_len = prefix_len
+        try:
+            self._format(object, stream, indent, allowance, context, level)
+        finally:
+            self._pending_prefix_len = 0
+
+    def _write_indent_padding(self, write):
+        if self._expand:
+            if self._indent_per_level > 0:
+                write(self._indent_per_level * " ")
+        elif self._indent_per_level > 1:
+            write((self._indent_per_level - 1) * " ")
+
     def _pprint_dataclass(self, object, stream, indent, allowance, context, level):
         # Lazy import to improve module import time
         from dataclasses import fields as dataclass_fields
 
         cls_name = object.__class__.__name__
-        indent += len(cls_name) + 1
+        if self._expand:
+            indent += self._indent_per_level
+        else:
+            indent += len(cls_name) + 1
         items = [(f.name, getattr(object, f.name)) for f in dataclass_fields(object) if f.repr]
-        stream.write(cls_name + '(')
+        stream.write(self._format_block_start(cls_name + '(', indent))
         self._format_namespace_items(items, stream, indent, allowance, context, level)
-        stream.write(')')
+        stream.write(self._format_block_end(')', indent - self._indent_per_level))
 
     _dispatch = {}
 
     def _pprint_dict(self, object, stream, indent, allowance, context, level):
         write = stream.write
-        write('{')
-        if self._indent_per_level > 1:
-            write((self._indent_per_level - 1) * ' ')
+        write(self._format_block_start('{', indent))
+        self._write_indent_padding(write)
         length = len(object)
         if length:
             if self._sort_dicts:
@@ -231,37 +288,117 @@ def _pprint_dict(self, object, stream, indent, allowance, context, level):
                 items = object.items()
             self._format_dict_items(items, stream, indent, allowance + 1,
                                     context, level)
-        write('}')
+        write(self._format_block_end('}', indent))
 
     _dispatch[dict.__repr__] = _pprint_dict
 
+    def _pprint_frozendict(self, object, stream, indent, allowance, context, level):
+        write = stream.write
+        cls = object.__class__
+        if not len(object):
+            write(repr(object))
+            return
+
+        write(self._format_block_start(cls.__name__ + "({", indent))
+        self._write_indent_padding(write)
+
+        if self._sort_dicts:
+            items = sorted(object.items(), key=_safe_tuple)
+        else:
+            items = object.items()
+        self._format_dict_items(
+            items,
+            stream,
+            self._child_indent(indent, len(cls.__name__) + 1),
+            allowance + 2,
+            context,
+            level,
+        )
+        write(self._format_block_end("})", indent))
+
+    _dispatch[frozendict.__repr__] = _pprint_frozendict
+
     def _pprint_ordered_dict(self, object, stream, indent, allowance, context, level):
         if not len(object):
             stream.write(repr(object))
             return
         cls = object.__class__
         stream.write(cls.__name__ + '(')
-        self._format(list(object.items()), stream,
-                     indent + len(cls.__name__) + 1, allowance + 1,
-                     context, level)
+        self._format_child(
+            list(object.items()),
+            stream,
+            self._child_indent(indent, len(cls.__name__) + 1),
+            allowance + 1,
+            context,
+            level,
+            len(cls.__name__) + 1,
+        )
         stream.write(')')
 
     _dispatch[_collections.OrderedDict.__repr__] = _pprint_ordered_dict
 
+    def _pprint_dict_view(self, object, stream, indent, allowance, context, level):
+        """Pretty print dict views (keys, values, items)."""
+        if isinstance(object, self._dict_items_view):
+            key = _safe_tuple
+        else:
+            key = _safe_key
+
+        write = stream.write
+        write(
+            self._format_block_start(object.__class__.__name__ + "([", indent)
+        )
+
+        if len(object):
+            if self._sort_dicts:
+                entries = sorted(object, key=key)
+            else:
+                entries = object
+            self._format_items(
+                entries, stream, indent, allowance + 2, context, level
+            )
+        write(self._format_block_end("])", indent))
+
+    def _pprint_mapping_abc_view(self, object, stream, indent, allowance, context, level):
+        """Pretty print mapping views from collections.abc."""
+        write = stream.write
+        write(object.__class__.__name__ + '(')
+        # Dispatch formatting to the view's _mapping
+        self._format(object._mapping, stream, indent, allowance, context, level)
+        write(')')
+
+    _dict_keys_view = type({}.keys())
+    _dispatch[_dict_keys_view.__repr__] = _pprint_dict_view
+
+    _dict_values_view = type({}.values())
+    _dispatch[_dict_values_view.__repr__] = _pprint_dict_view
+
+    _dict_items_view = type({}.items())
+    _dispatch[_dict_items_view.__repr__] = _pprint_dict_view
+
+    _dispatch[_collections.abc.MappingView.__repr__] = _pprint_mapping_abc_view
+
+    _view_reprs = {cls.__repr__ for cls in
+                   (_dict_keys_view, _dict_values_view, _dict_items_view,
+                    _collections.abc.MappingView)}
+
     def _pprint_list(self, object, stream, indent, allowance, context, level):
-        stream.write('[')
+        stream.write(self._format_block_start('[', indent))
         self._format_items(object, stream, indent, allowance + 1,
                            context, level)
-        stream.write(']')
+        stream.write(self._format_block_end(']', indent))
 
     _dispatch[list.__repr__] = _pprint_list
 
     def _pprint_tuple(self, object, stream, indent, allowance, context, level):
-        stream.write('(')
-        endchar = ',)' if len(object) == 1 else ')'
+        stream.write(self._format_block_start('(', indent))
+        if len(object) == 1 and not self._expand:
+            endchar = ',)'
+        else:
+            endchar = ')'
         self._format_items(object, stream, indent, allowance + len(endchar),
                            context, level)
-        stream.write(endchar)
+        stream.write(self._format_block_end(endchar, indent))
 
     _dispatch[tuple.__repr__] = _pprint_tuple
 
@@ -271,16 +408,17 @@ def _pprint_set(self, object, stream, indent, allowance, context, level):
             return
         typ = object.__class__
         if typ is set:
-            stream.write('{')
+            stream.write(self._format_block_start('{', indent))
             endchar = '}'
         else:
-            stream.write(typ.__name__ + '({')
+            stream.write(self._format_block_start(typ.__name__ + '({', indent))
             endchar = '})'
-            indent += len(typ.__name__) + 1
+            if not self._expand:
+                indent += len(typ.__name__) + 1
         object = sorted(object, key=_safe_key)
         self._format_items(object, stream, indent, allowance + len(endchar),
                            context, level)
-        stream.write(endchar)
+        stream.write(self._format_block_end(endchar, indent))
 
     _dispatch[set.__repr__] = _pprint_set
     _dispatch[frozenset.__repr__] = _pprint_set
@@ -293,7 +431,10 @@ def _pprint_str(self, object, stream, indent, allowance, context, level):
         chunks = []
         lines = object.splitlines(True)
         if level == 1:
-            indent += 1
+            if self._expand:
+                indent += self._indent_per_level
+            else:
+                indent += 1
             allowance += 1
         max_width1 = max_width = self._width - indent
         for i, line in enumerate(lines):
@@ -329,13 +470,13 @@ def _pprint_str(self, object, stream, indent, allowance, context, level):
             write(rep)
             return
         if level == 1:
-            write('(')
+            write(self._format_block_start("(", indent))
         for i, rep in enumerate(chunks):
             if i > 0:
                 write('\n' + ' '*indent)
             write(rep)
         if level == 1:
-            write(')')
+            write(self._format_block_end(")", indent - self._indent_per_level))
 
     _dispatch[str.__repr__] = _pprint_str
 
@@ -346,9 +487,12 @@ def _pprint_bytes(self, object, stream, indent, allowance, context, level):
             return
         parens = level == 1
         if parens:
-            indent += 1
+            if self._expand:
+                indent += self._indent_per_level
+            else:
+                indent += 1
             allowance += 1
-            write('(')
+            write(self._format_block_start('(', indent))
         delim = ''
         for rep in _wrap_bytes_repr(object, self._width - indent, allowance):
             write(delim)
@@ -356,23 +500,35 @@ def _pprint_bytes(self, object, stream, indent, allowance, context, level):
             if not delim:
                 delim = '\n' + ' '*indent
         if parens:
-            write(')')
+            write(self._format_block_end(')', indent - self._indent_per_level))
 
     _dispatch[bytes.__repr__] = _pprint_bytes
 
     def _pprint_bytearray(self, object, stream, indent, allowance, context, level):
         write = stream.write
-        write('bytearray(')
-        self._pprint_bytes(bytes(object), stream, indent + 10,
+        write(self._format_block_start('bytearray(', indent))
+        if self._expand:
+            write(' ' * self._indent_per_level)
+            recursive_indent = indent + self._indent_per_level
+        else:
+            recursive_indent = indent + 10
+        self._pprint_bytes(bytes(object), stream, recursive_indent,
                            allowance + 1, context, level + 1)
-        write(')')
+        write(self._format_block_end(')', indent))
 
     _dispatch[bytearray.__repr__] = _pprint_bytearray
 
     def _pprint_mappingproxy(self, object, stream, indent, allowance, context, level):
         stream.write('mappingproxy(')
-        self._format(object.copy(), stream, indent + 13, allowance + 1,
-                     context, level)
+        self._format_child(
+            object.copy(),
+            stream,
+            self._child_indent(indent, 13),
+            allowance + 1,
+            context,
+            level,
+            13,
+        )
         stream.write(')')
 
     _dispatch[_types.MappingProxyType.__repr__] = _pprint_mappingproxy
@@ -384,11 +540,15 @@ def _pprint_simplenamespace(self, object, stream, indent, allowance, context, le
             cls_name = 'namespace'
         else:
             cls_name = object.__class__.__name__
-        indent += len(cls_name) + 1
+        if self._expand:
+            indent += self._indent_per_level
+        else:
+            indent += len(cls_name) + 1
         items = object.__dict__.items()
-        stream.write(cls_name + '(')
-        self._format_namespace_items(items, stream, indent, allowance, context, level)
-        stream.write(')')
+        stream.write(self._format_block_start(cls_name + '(', indent))
+        self._format_namespace_items(items, stream, indent, allowance, context,
+                                     level)
+        stream.write(self._format_block_end(')', indent - self._indent_per_level))
 
     _dispatch[_types.SimpleNamespace.__repr__] = _pprint_simplenamespace
 
@@ -403,11 +563,19 @@ def _format_dict_items(self, items, stream, indent, allowance, context,
             rep = self._repr(key, context, level)
             write(rep)
             write(': ')
-            self._format(ent, stream, indent + len(rep) + 2,
-                         allowance if last else 1,
-                         context, level)
+            self._format_child(
+                ent,
+                stream,
+                self._child_indent(indent, len(rep) + 2),
+                allowance if last else 1,
+                context,
+                level,
+                len(rep) + 2,
+            )
             if not last:
                 write(delimnl)
+            elif self._expand:
+                write(',')
 
     def _format_namespace_items(self, items, stream, indent, allowance, context, level):
         write = stream.write
@@ -422,17 +590,24 @@ def _format_namespace_items(self, items, stream, indent, allowance, context, lev
                 # recursive dataclass repr.
                 write("...")
             else:
-                self._format(ent, stream, indent + len(key) + 1,
-                             allowance if last else 1,
-                             context, level)
+                self._format_child(
+                    ent,
+                    stream,
+                    self._child_indent(indent, len(key) + 1),
+                    allowance if last else 1,
+                    context,
+                    level,
+                    len(key) + 1,
+                )
             if not last:
                 write(delimnl)
+            elif self._expand:
+                write(',')
 
     def _format_items(self, items, stream, indent, allowance, context, level):
         write = stream.write
         indent += self._indent_per_level
-        if self._indent_per_level > 1:
-            write((self._indent_per_level - 1) * ' ')
+        self._write_indent_padding(write)
         delimnl = ',\n' + ' ' * indent
         delim = ''
         width = max_width = self._width - indent + 1
@@ -468,6 +643,8 @@ def _format_items(self, items, stream, indent, allowance, context, level):
             self._format(ent, stream, indent,
                          allowance if last else 1,
                          context, level)
+            if last and self._expand:
+                write(',')
 
     def _repr(self, object, context, level):
         repr, readable, recursive = self.format(object, context.copy(),
@@ -491,9 +668,13 @@ def _pprint_default_dict(self, object, stream, indent, allowance, context, level
             return
         rdf = self._repr(object.default_factory, context, level)
         cls = object.__class__
-        indent += len(cls.__name__) + 1
-        stream.write('%s(%s,\n%s' % (cls.__name__, rdf, ' ' * indent))
-        self._pprint_dict(object, stream, indent, allowance + 1, context, level)
+        if self._expand:
+            stream.write('%s(%s, ' % (cls.__name__, rdf))
+        else:
+            indent += len(cls.__name__) + 1
+            stream.write('%s(%s,\n%s' % (cls.__name__, rdf, ' ' * indent))
+        self._pprint_dict(object, stream, indent, allowance + 1, context,
+                          level)
         stream.write(')')
 
     _dispatch[_collections.defaultdict.__repr__] = _pprint_default_dict
@@ -503,14 +684,18 @@ def _pprint_counter(self, object, stream, indent, allowance, context, level):
             stream.write(repr(object))
             return
         cls = object.__class__
-        stream.write(cls.__name__ + '({')
-        if self._indent_per_level > 1:
-            stream.write((self._indent_per_level - 1) * ' ')
+        stream.write(self._format_block_start(cls.__name__ + '({', indent))
+        self._write_indent_padding(stream.write)
         items = object.most_common()
-        self._format_dict_items(items, stream,
-                                indent + len(cls.__name__) + 1, allowance + 2,
-                                context, level)
-        stream.write('})')
+        self._format_dict_items(
+            items,
+            stream,
+            self._child_indent(indent, len(cls.__name__) + 1),
+            allowance + 2,
+            context,
+            level,
+        )
+        stream.write(self._format_block_end('})', indent))
 
     _dispatch[_collections.Counter.__repr__] = _pprint_counter
 
@@ -519,12 +704,18 @@ def _pprint_chain_map(self, object, stream, indent, allowance, context, level):
             stream.write(repr(object))
             return
         cls = object.__class__
-        stream.write(cls.__name__ + '(')
-        indent += len(cls.__name__) + 1
+        stream.write(self._format_block_start(cls.__name__ + '(',
+                                              indent + self._indent_per_level))
+        if self._expand:
+            indent += self._indent_per_level
+        else:
+            indent += len(cls.__name__) + 1
         for i, m in enumerate(object.maps):
             if i == len(object.maps) - 1:
                 self._format(m, stream, indent, allowance + 1, context, level)
-                stream.write(')')
+                if self._expand:
+                    stream.write(',')
+                stream.write(self._format_block_end(')', indent - self._indent_per_level))
             else:
                 self._format(m, stream, indent, 1, context, level)
                 stream.write(',\n' + ' ' * indent)
@@ -536,18 +727,21 @@ def _pprint_deque(self, object, stream, indent, allowance, context, level):
             stream.write(repr(object))
             return
         cls = object.__class__
-        stream.write(cls.__name__ + '(')
-        indent += len(cls.__name__) + 1
-        stream.write('[')
+        stream.write(self._format_block_start(cls.__name__ + '([', indent))
+        if not self._expand:
+            indent += len(cls.__name__) + 1
         if object.maxlen is None:
             self._format_items(object, stream, indent, allowance + 2,
                                context, level)
-            stream.write('])')
+            stream.write(self._format_block_end('])', indent))
         else:
             self._format_items(object, stream, indent, 2,
                                context, level)
             rml = self._repr(object.maxlen, context, level)
-            stream.write('],\n%smaxlen=%s)' % (' ' * indent, rml))
+            if self._expand:
+                stream.write('%s], maxlen=%s)' % ('\n' + ' ' * indent, rml))
+            else:
+                stream.write('],\n%smaxlen=%s)' % (' ' * indent, rml))
 
     _dispatch[_collections.deque.__repr__] = _pprint_deque
 
@@ -566,6 +760,61 @@ def _pprint_user_string(self, object, stream, indent, allowance, context, level)
 
     _dispatch[_collections.UserString.__repr__] = _pprint_user_string
 
+    def _pprint_template(self, object, stream, indent, allowance, context, level):
+        cls_name = object.__class__.__name__
+        if self._expand:
+            indent += self._indent_per_level
+        else:
+            indent += len(cls_name) + 1
+
+        items = (
+            ("strings", object.strings),
+            ("interpolations", object.interpolations),
+        )
+        stream.write(self._format_block_start(cls_name + "(", indent))
+        self._format_namespace_items(
+            items, stream, indent, allowance, context, level
+        )
+        stream.write(
+            self._format_block_end(")", indent - self._indent_per_level)
+        )
+
+    def _pprint_interpolation(self, object, stream, indent, allowance, context, level):
+        cls_name = object.__class__.__name__
+        if self._expand:
+            indent += self._indent_per_level
+            items = (
+                ("value", object.value),
+                ("expression", object.expression),
+                ("conversion", object.conversion),
+                ("format_spec", object.format_spec),
+            )
+            stream.write(self._format_block_start(cls_name + "(", indent))
+            self._format_namespace_items(
+                items, stream, indent, allowance, context, level
+            )
+            stream.write(
+                self._format_block_end(")", indent - self._indent_per_level)
+            )
+        else:
+            indent += len(cls_name)
+            items = (
+                object.value,
+                object.expression,
+                object.conversion,
+                object.format_spec,
+            )
+            stream.write(cls_name + "(")
+            self._format_items(
+                items, stream, indent, allowance, context, level
+            )
+            stream.write(")")
+
+    t = t"{0}"
+    _dispatch[type(t).__repr__] = _pprint_template
+    _dispatch[type(t.interpolations[0]).__repr__] = _pprint_interpolation
+    del t
+
     def _safe_repr(self, object, context, maxlevels, level):
         # Return triple (repr_string, isreadable, isrecursive).
         typ = type(object)
@@ -580,12 +829,21 @@ def _safe_repr(self, object, context, maxlevels, level):
             else:
                 return repr(object), True, False
 
-        if issubclass(typ, dict) and r is dict.__repr__:
+        if ((issubclass(typ, dict) and r is dict.__repr__)
+            or (issubclass(typ, frozendict) and r is frozendict.__repr__)):
+            is_frozendict = issubclass(typ, frozendict)
             if not object:
-                return "{}", True, False
+                if is_frozendict:
+                    rep = f"{object.__class__.__name__}()"
+                else:
+                    rep = "{}"
+                return rep, True, False
             objid = id(object)
             if maxlevels and level >= maxlevels:
-                return "{...}", False, objid in context
+                rep = "{...}"
+                if is_frozendict:
+                    rep = f"{object.__class__.__name__}({rep})"
+                return rep, False, objid in context
             if objid in context:
                 return _recursion(object), False, True
             context[objid] = 1
@@ -608,7 +866,10 @@ def _safe_repr(self, object, context, maxlevels, level):
                 if krecur or vrecur:
                     recursive = True
             del context[objid]
-            return "{%s}" % ", ".join(components), readable, recursive
+            rep = "{%s}" % ", ".join(components)
+            if is_frozendict:
+                rep = f"{object.__class__.__name__}({rep})"
+            return rep, readable, recursive
 
         if (issubclass(typ, list) and r is list.__repr__) or \
            (issubclass(typ, tuple) and r is tuple.__repr__):
@@ -644,6 +905,42 @@ def _safe_repr(self, object, context, maxlevels, level):
             del context[objid]
             return format % ", ".join(components), readable, recursive
 
+        if issubclass(typ, _collections.abc.MappingView) and r in self._view_reprs:
+            objid = id(object)
+            if maxlevels and level >= maxlevels:
+                return "{...}", False, objid in context
+            if objid in context:
+                return _recursion(object), False, True
+            key = _safe_key
+            if issubclass(typ, (self._dict_items_view, _collections.abc.ItemsView)):
+                key = _safe_tuple
+            if hasattr(object, "_mapping"):
+                # Dispatch formatting to the view's _mapping
+                mapping_repr, readable, recursive = self.format(
+                    object._mapping, context, maxlevels, level)
+                return (typ.__name__ + '(%s)' % mapping_repr), readable, recursive
+            elif hasattr(typ, "_mapping"):
+                #  We have a view that somehow has lost its type's _mapping, raise
+                #  an error by calling repr() instead of failing cryptically later
+                return repr(object), True, False
+            if self._sort_dicts:
+                object = sorted(object, key=key)
+            context[objid] = 1
+            readable = True
+            recursive = False
+            components = []
+            append = components.append
+            level += 1
+            for val in object:
+                vrepr, vreadable, vrecur = self.format(
+                    val, context, maxlevels, level)
+                append(vrepr)
+                readable = readable and vreadable
+                if vrecur:
+                    recursive = True
+            del context[objid]
+            return typ.__name__ + '([%s])' % ", ".join(components), readable, recursive
+
         rep = repr(object)
         return rep, (rep and not rep.startswith('<')), False
 
diff --git a/Lib/py_compile.py b/Lib/py_compile.py
index 43d8ec90ffb..7ca479141e0 100644
--- a/Lib/py_compile.py
+++ b/Lib/py_compile.py
@@ -177,7 +177,7 @@ def main():
     import argparse
 
     description = 'A simple command-line interface for py_compile module.'
-    parser = argparse.ArgumentParser(description=description, color=True)
+    parser = argparse.ArgumentParser(description=description)
     parser.add_argument(
         '-q', '--quiet',
         action='store_true',
@@ -194,8 +194,10 @@ def main():
     else:
         filenames = args.filenames
     for filename in filenames:
+        cfilename = (None if sys.implementation.cache_tag
+                     else f"{filename.rpartition('.')[0]}.pyc")
         try:
-            compile(filename, doraise=True)
+            compile(filename, cfilename, doraise=True)
         except PyCompileError as error:
             if args.quiet:
                 parser.exit(1)
diff --git a/Lib/random.py b/Lib/random.py
index 0e6a183d179..7db76103450 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -1020,26 +1020,26 @@ def _test(N=10_000):
 def _parse_args(arg_list: list[str] | None):
     import argparse
     parser = argparse.ArgumentParser(
-        formatter_class=argparse.RawTextHelpFormatter, color=True)
+        formatter_class=argparse.RawTextHelpFormatter)
     group = parser.add_mutually_exclusive_group()
     group.add_argument(
         "-c", "--choice", nargs="+",
         help="print a random choice")
     group.add_argument(
         "-i", "--integer", type=int, metavar="N",
-        help="print a random integer between 1 and N inclusive")
+        help="print a random integer between 1 and `N` inclusive")
     group.add_argument(
         "-f", "--float", type=float, metavar="N",
-        help="print a random floating-point number between 0 and N inclusive")
+        help="print a random floating-point number between 0 and `N` inclusive")
     group.add_argument(
         "--test", type=int, const=10_000, nargs="?",
         help=argparse.SUPPRESS)
     parser.add_argument("input", nargs="*",
                         help="""\
 if no options given, output depends on the input
-    string or multiple: same as --choice
-    integer: same as --integer
-    float: same as --float""")
+    string or multiple: same as `--choice`
+    integer: same as `--integer`
+    float: same as `--float`""")
     args = parser.parse_args(arg_list)
     return args, parser.format_help()
 
diff --git a/Lib/re/__init__.py b/Lib/re/__init__.py
index af2808a77da..e6d29fd7a40 100644
--- a/Lib/re/__init__.py
+++ b/Lib/re/__init__.py
@@ -85,17 +85,18 @@
     \\       Matches a literal backslash.
 
 This module exports the following functions:
-    match     Match a regular expression pattern to the beginning of a string.
-    fullmatch Match a regular expression pattern to all of a string.
-    search    Search a string for the presence of a pattern.
-    sub       Substitute occurrences of a pattern found in a string.
-    subn      Same as sub, but also return the number of substitutions made.
-    split     Split a string by the occurrences of a pattern.
-    findall   Find all occurrences of a pattern in a string.
-    finditer  Return an iterator yielding a Match object for each match.
-    compile   Compile a pattern into a Pattern object.
-    purge     Clear the regular expression cache.
-    escape    Backslash all non-alphanumerics in a string.
+    prefixmatch Match a regular expression pattern to the beginning of a str.
+    match       The original name of prefixmatch prior to 3.15.
+    fullmatch   Match a regular expression pattern to all of a string.
+    search      Search a string for the presence of a pattern.
+    sub         Substitute occurrences of a pattern found in a string.
+    subn        Same as sub, but also return the number of substitutions made.
+    split       Split a string by the occurrences of a pattern.
+    findall     Find all occurrences of a pattern in a string.
+    finditer    Return an iterator yielding a Match object for each match.
+    compile     Compile a pattern into a Pattern object.
+    purge       Clear the regular expression cache.
+    escape      Backslash all non-alphanumerics in a string.
 
 Each function other than purge and escape can take an optional 'flags' argument
 consisting of one or more of the following module constants, joined by "|".
@@ -130,15 +131,13 @@
 
 # public symbols
 __all__ = [
-    "match", "fullmatch", "search", "sub", "subn", "split",
+    "prefixmatch", "match", "fullmatch", "search", "sub", "subn", "split",
     "findall", "finditer", "compile", "purge", "escape",
     "error", "Pattern", "Match", "A", "I", "L", "M", "S", "X", "U",
     "ASCII", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE",
     "UNICODE", "NOFLAG", "RegexFlag", "PatternError"
 ]
 
-__version__ = "2.2.1"
-
 @enum.global_enum
 @enum._simple_enum(enum.IntFlag, boundary=enum.KEEP)
 class RegexFlag:
@@ -161,10 +160,13 @@ class RegexFlag:
 # --------------------------------------------------------------------
 # public interface
 
-def match(pattern, string, flags=0):
+def prefixmatch(pattern, string, flags=0):
     """Try to apply the pattern at the start of the string, returning
     a Match object, or None if no match was found."""
-    return _compile(pattern, flags).match(string)
+    return _compile(pattern, flags).prefixmatch(string)
+
+# Our original name which was less explicitly clear about the behavior for prefixmatch.
+match = prefixmatch
 
 def fullmatch(pattern, string, flags=0):
     """Try to apply the pattern to all of the string, returning
@@ -313,7 +315,7 @@ def escape(pattern):
         return pattern.translate(_special_chars_map).encode('latin1')
 
 Pattern = type(_compiler.compile('', 0))
-Match = type(_compiler.compile('', 0).match(''))
+Match = type(_compiler.compile('', 0).prefixmatch(''))
 
 # --------------------------------------------------------------------
 # internals
@@ -399,9 +401,12 @@ def __init__(self, lexicon, flags=0):
         s = _parser.State()
         s.flags = flags
         for phrase, action in lexicon:
+            sub_pattern = _parser.parse(phrase, flags)
+            if sub_pattern.state.groups != 1:
+                raise ValueError("Cannot use capturing groups in re.Scanner")
             gid = s.opengroup()
             p.append(_parser.SubPattern(s, [
-                (SUBPATTERN, (gid, 0, 0, _parser.parse(phrase, flags))),
+                (SUBPATTERN, (gid, 0, 0, sub_pattern)),
                 ]))
             s.closegroup(gid, p[-1])
         p = _parser.SubPattern(s, [(BRANCH, (None, p))])
@@ -409,10 +414,10 @@ def __init__(self, lexicon, flags=0):
     def scan(self, string):
         result = []
         append = result.append
-        match = self.scanner.scanner(string).match
+        _match = self.scanner.scanner(string).prefixmatch
         i = 0
         while True:
-            m = match()
+            m = _match()
             if not m:
                 break
             j = m.end()
@@ -426,3 +431,12 @@ def scan(self, string):
                 append(action)
             i = j
         return result, string[i:]
+
+
+def __getattr__(name):
+    if name == "__version__":
+        from warnings import _deprecated
+
+        _deprecated("__version__", remove=(3, 20))
+        return "2.2.1"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/re/_compiler.py b/Lib/re/_compiler.py
index 20dd561d1c1..c2ca8e25abe 100644
--- a/Lib/re/_compiler.py
+++ b/Lib/re/_compiler.py
@@ -375,7 +375,7 @@ def _optimize_charset(charset, iscased=None, fixup=None, fixes=None):
     # less significant byte is a bit index in the chunk (just like the
     # CHARSET matching).
 
-    charmap = bytes(charmap) # should be hashable
+    charmap = charmap.take_bytes() # should be hashable
     comps = {}
     mapping = bytearray(256)
     block = 0
diff --git a/Lib/re/_parser.py b/Lib/re/_parser.py
index 35ab7ede2a7..bd189fe0695 100644
--- a/Lib/re/_parser.py
+++ b/Lib/re/_parser.py
@@ -455,7 +455,6 @@ def _parse_sub(source, state, verbose, nested):
     items = []
     itemsappend = items.append
     sourcematch = source.match
-    start = source.tell()
     while True:
         itemsappend(_parse(source, state, verbose, nested + 1,
                            not nested and not items))
diff --git a/Lib/runpy.py b/Lib/runpy.py
index 1d5ecf0cf15..a535b4f651a 100644
--- a/Lib/runpy.py
+++ b/Lib/runpy.py
@@ -80,7 +80,6 @@ def _run_code(code, run_globals, init_globals=None,
             pkg_name = mod_spec.parent
     run_globals.update(__name__ = mod_name,
                        __file__ = fname,
-                       __cached__ = cached,
                        __doc__ = None,
                        __loader__ = loader,
                        __package__ = pkg_name,
@@ -185,7 +184,6 @@ def _run_module_as_main(mod_name, alter_argv=True):
        At the very least, these variables in __main__ will be overwritten:
            __name__
            __file__
-           __cached__
            __loader__
            __package__
     """
@@ -254,7 +252,7 @@ def _get_main_module_details(error=ImportError):
         sys.modules[main_name] = saved_main
 
 
-def _get_code_from_file(fname):
+def _get_code_from_file(fname, module):
     # Check for a compiled file first
     from pkgutil import read_code
     code_path = os.path.abspath(fname)
@@ -263,7 +261,7 @@ def _get_code_from_file(fname):
     if code is None:
         # That didn't work, so try it as normal source code
         with io.open_code(code_path) as f:
-            code = compile(f.read(), fname, 'exec')
+            code = compile(f.read(), fname, 'exec', module=module)
     return code
 
 def run_path(path_name, init_globals=None, run_name=None):
@@ -290,7 +288,7 @@ def run_path(path_name, init_globals=None, run_name=None):
     if isinstance(importer, type(None)):
         # Not a valid sys.path entry, so run the code directly
         # execfile() doesn't help as we want to allow compiled files
-        code = _get_code_from_file(path_name)
+        code = _get_code_from_file(path_name, run_name)
         return _run_module_code(code, init_globals, run_name,
                                 pkg_name=pkg_name, script_name=path_name)
     else:
diff --git a/Lib/shutil.py b/Lib/shutil.py
index a3a112f6954..0086c1c96c1 100644
--- a/Lib/shutil.py
+++ b/Lib/shutil.py
@@ -745,6 +745,7 @@ def _rmtree_safe_fd_step(stack, onexc):
     #   save a call to os.lstat() when walking subdirectories.
     func, dirfd, path, orig_entry = stack.pop()
     name = path if orig_entry is None else orig_entry.name
+    parent_fd = None if func is os.close else dirfd
     try:
         if func is os.close:
             os.close(dirfd)
@@ -792,14 +793,14 @@ def _rmtree_safe_fd_step(stack, onexc):
             except FileNotFoundError:
                 continue
             except OSError as err:
-                onexc(os.unlink, fullname, err)
+                onexc(os.unlink, fullname, err, direntry=entry, dir_fd=topfd)
     except FileNotFoundError as err:
         if orig_entry is None or func is os.close:
             err.filename = path
-            onexc(func, path, err)
+            onexc(func, path, err, direntry=orig_entry, dir_fd=parent_fd)
     except OSError as err:
         err.filename = path
-        onexc(func, path, err)
+        onexc(func, path, err, direntry=orig_entry, dir_fd=parent_fd)
 
 _use_fd_functions = ({os.open, os.stat, os.unlink, os.rmdir} <=
                      os.supports_dir_fd and
@@ -807,7 +808,8 @@ def _rmtree_safe_fd_step(stack, onexc):
                      os.stat in os.supports_follow_symlinks)
 _rmtree_impl = _rmtree_safe_fd if _use_fd_functions else _rmtree_unsafe
 
-def rmtree(path, ignore_errors=False, onerror=None, *, onexc=None, dir_fd=None):
+def rmtree(path, ignore_errors=False, onerror=None, *, onexc=None, dir_fd=None,
+           _onexc_kwargs=False):
     """Recursively delete a directory tree.
 
     If dir_fd is not None, it should be a file descriptor open to a directory;
@@ -830,24 +832,29 @@ def rmtree(path, ignore_errors=False, onerror=None, *, onexc=None, dir_fd=None):
 
     sys.audit("shutil.rmtree", path, dir_fd)
     if ignore_errors:
-        def onexc(*args):
+        def onexc(*args, **kwargs):
             pass
     elif onerror is None and onexc is None:
-        def onexc(*args):
+        def onexc(*args, **kwargs):
             raise
     elif onexc is None:
         if onerror is None:
-            def onexc(*args):
+            def onexc(*args, **kwargs):
                 raise
         else:
             # delegate to onerror
-            def onexc(*args):
+            def onexc(*args, **kwargs):
                 func, path, exc = args
                 if exc is None:
                     exc_info = None, None, None
                 else:
                     exc_info = type(exc), exc, exc.__traceback__
                 return onerror(func, path, exc_info)
+    elif not _onexc_kwargs:
+        # Only the internal caller in tempfile asks for the extra arguments.
+        _onexc = onexc
+        def onexc(func, path, err, **kwargs):
+            return _onexc(func, path, err)
 
     _rmtree_impl(path, dir_fd, onexc)
 
@@ -1216,19 +1223,22 @@ def make_archive(base_name, format, root_dir=None, base_dir=None, verbose=0,
     for arg, val in format_info[1]:
         kwargs[arg] = val
 
+    base_name = os.fspath(base_name)
+
     if base_dir is None:
         base_dir = os.curdir
+    else:
+        base_dir = os.fspath(base_dir)
 
     supports_root_dir = getattr(func, 'supports_root_dir', False)
     save_cwd = None
     if root_dir is not None:
+        root_dir = os.fspath(root_dir)
         stmd = os.stat(root_dir).st_mode
         if not stat.S_ISDIR(stmd):
             raise NotADirectoryError(errno.ENOTDIR, 'Not a directory', root_dir)
 
         if supports_root_dir:
-            # Support path-like base_name here for backwards-compatibility.
-            base_name = os.fspath(base_name)
             kwargs['root_dir'] = root_dir
         else:
             save_cwd = os.getcwd()
diff --git a/Lib/socket.py b/Lib/socket.py
index 9ac0badc660..2a4f875f76b 100644
--- a/Lib/socket.py
+++ b/Lib/socket.py
@@ -56,6 +56,7 @@
 import os
 import sys
 from enum import IntEnum, IntFlag
+from functools import partial
 
 try:
     import errno
@@ -122,7 +123,7 @@ def _intenum_converter(value, enum_klass):
         10004: "The operation was interrupted.",
         10009: "A bad file handle was passed.",
         10013: "Permission denied.",
-        10014: "A fault occurred on the network??",
+        10014: "An invalid pointer was passed.",
         10022: "An invalid operation was attempted.",
         10024: "Too many open files.",
         10035: "The socket operation would block.",
@@ -180,7 +181,7 @@ def _intenum_converter(value, enum_klass):
         11001: "Host not found.",
         11002: "Nonauthoritative host not found.",
         11003: "This is a nonrecoverable error.",
-        11004: "Valid name, no data record requested type.",
+        11004: "Valid name, no data record of requested type.",
         11005: "QoS receivers.",
         11006: "QoS senders.",
         11007: "No QoS senders.",
@@ -196,7 +197,7 @@ def _intenum_converter(value, enum_klass):
         11017: "QoS flowspec error.",
         11018: "Invalid QoS provider buffer.",
         11019: "Invalid QoS filter style.",
-        11020: "Invalid QoS filter style.",
+        11020: "Invalid QoS filter type.",
         11021: "Incorrect QoS filter count.",
         11022: "Invalid QoS object length.",
         11023: "Incorrect QoS flow count.",
@@ -348,75 +349,83 @@ def makefile(self, mode="r", buffering=None, *,
         text.mode = mode
         return text
 
-    if hasattr(os, 'sendfile'):
+    def _sendfile_zerocopy(self, zerocopy_func, giveup_exc_type, file,
+                           offset=0, count=None):
+        """
+        Send a file using a zero-copy function.
+        """
+        import selectors
 
-        def _sendfile_use_sendfile(self, file, offset=0, count=None):
-            # Lazy import to improve module import time
-            import selectors
+        self._check_sendfile_params(file, offset, count)
+        sockno = self.fileno()
+        try:
+            fileno = file.fileno()
+        except (AttributeError, io.UnsupportedOperation) as err:
+            raise giveup_exc_type(err)  # not a regular file
+        try:
+            fsize = os.fstat(fileno).st_size
+        except OSError as err:
+            raise giveup_exc_type(err)  # not a regular file
+        if not fsize:
+            return 0  # empty file
+        # Truncate to 1GiB to avoid OverflowError, see bpo-38319.
+        blocksize = min(count or fsize, 2 ** 30)
+        timeout = self.gettimeout()
+        if timeout == 0:
+            raise ValueError("non-blocking sockets are not supported")
+        # poll/select have the advantage of not requiring any
+        # extra file descriptor, contrarily to epoll/kqueue
+        # (also, they require a single syscall).
+        if hasattr(selectors, 'PollSelector'):
+            selector = selectors.PollSelector()
+        else:
+            selector = selectors.SelectSelector()
+        selector.register(sockno, selectors.EVENT_WRITE)
 
-            self._check_sendfile_params(file, offset, count)
-            sockno = self.fileno()
-            try:
-                fileno = file.fileno()
-            except (AttributeError, io.UnsupportedOperation) as err:
-                raise _GiveupOnSendfile(err)  # not a regular file
-            try:
-                fsize = os.fstat(fileno).st_size
-            except OSError as err:
-                raise _GiveupOnSendfile(err)  # not a regular file
-            if not fsize:
-                return 0  # empty file
-            # Truncate to 1GiB to avoid OverflowError, see bpo-38319.
-            blocksize = min(count or fsize, 2 ** 30)
-            timeout = self.gettimeout()
-            if timeout == 0:
-                raise ValueError("non-blocking sockets are not supported")
-            # poll/select have the advantage of not requiring any
-            # extra file descriptor, contrarily to epoll/kqueue
-            # (also, they require a single syscall).
-            if hasattr(selectors, 'PollSelector'):
-                selector = selectors.PollSelector()
-            else:
-                selector = selectors.SelectSelector()
-            selector.register(sockno, selectors.EVENT_WRITE)
-
-            total_sent = 0
-            # localize variable access to minimize overhead
-            selector_select = selector.select
-            os_sendfile = os.sendfile
-            try:
-                while True:
-                    if timeout and not selector_select(timeout):
-                        raise TimeoutError('timed out')
-                    if count:
-                        blocksize = min(count - total_sent, blocksize)
-                        if blocksize <= 0:
-                            break
-                    try:
-                        sent = os_sendfile(sockno, fileno, offset, blocksize)
-                    except BlockingIOError:
-                        if not timeout:
-                            # Block until the socket is ready to send some
-                            # data; avoids hogging CPU resources.
-                            selector_select()
-                        continue
-                    except OSError as err:
-                        if total_sent == 0:
-                            # We can get here for different reasons, the main
-                            # one being 'file' is not a regular mmap(2)-like
-                            # file, in which case we'll fall back on using
-                            # plain send().
-                            raise _GiveupOnSendfile(err)
-                        raise err from None
-                    else:
-                        if sent == 0:
-                            break  # EOF
-                        offset += sent
-                        total_sent += sent
-                return total_sent
-            finally:
-                if total_sent > 0 and hasattr(file, 'seek'):
-                    file.seek(offset)
+        total_sent = 0
+        # localize variable access to minimize overhead
+        selector_select = selector.select
+        try:
+            while True:
+                if timeout and not selector_select(timeout):
+                    raise TimeoutError('timed out')
+                if count:
+                    blocksize = min(count - total_sent, blocksize)
+                    if blocksize <= 0:
+                        break
+                try:
+                    sent = zerocopy_func(fileno, offset, blocksize)
+                except BlockingIOError:
+                    if not timeout:
+                        # Block until the socket is ready to send some
+                        # data; avoids hogging CPU resources.
+                        selector_select()
+                    continue
+                except OSError as err:
+                    if total_sent == 0:
+                        # We can get here for different reasons, the main
+                        # one being 'file' is not a regular mmap(2)-like
+                        # file, in which case we'll fall back on using
+                        # plain send().
+                        raise giveup_exc_type(err)
+                    raise err from None
+                else:
+                    if sent == 0:
+                        break  # EOF
+                    offset += sent
+                    total_sent += sent
+            return total_sent
+        finally:
+            if total_sent > 0 and hasattr(file, 'seek'):
+                file.seek(offset)
+
+    if hasattr(os, 'sendfile'):
+        def _sendfile_use_sendfile(self, file, offset=0, count=None):
+            return self._sendfile_zerocopy(
+                partial(os.sendfile, self.fileno()),
+                _GiveupOnSendfile,
+                file, offset, count,
+            )
     else:
         def _sendfile_use_sendfile(self, file, offset=0, count=None):
             raise _GiveupOnSendfile(
diff --git a/Lib/socketserver.py b/Lib/socketserver.py
index 35b2723de3b..ec389457ef5 100644
--- a/Lib/socketserver.py
+++ b/Lib/socketserver.py
@@ -120,9 +120,6 @@ class will essentially render the service "deaf" while one request is
 
 # Author of the BaseServer patch: Luke Kenneth Casson Leighton
 
-__version__ = "0.4"
-
-
 import socket
 import selectors
 import os
@@ -441,7 +438,7 @@ class TCPServer(BaseServer):
 
     socket_type = socket.SOCK_STREAM
 
-    request_queue_size = 5
+    request_queue_size = getattr(socket, "SOMAXCONN", 5)
 
     allow_reuse_address = False
 
@@ -861,3 +858,12 @@ def setup(self):
 
     def finish(self):
         self.socket.sendto(self.wfile.getvalue(), self.client_address)
+
+
+def __getattr__(name):
+    if name == "__version__":
+        from warnings import _deprecated
+
+        _deprecated("__version__", remove=(3, 20))
+        return "0.4"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/ssl.py b/Lib/ssl.py
index 8889aff92fa..6929951b414 100644
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -13,6 +13,9 @@
 
 Functions:
 
+  get_sigalgs          -- return a list of all available TLS signature
+                          algorithms (requires OpenSSL 3.4 or later)
+
   cert_time_to_seconds -- convert time string used for certificate
                           notBefore and notAfter functions to integer
                           seconds past the Epoch (the time values
@@ -107,16 +110,12 @@
     )
 from _ssl import txt2obj as _txt2obj, nid2obj as _nid2obj
 from _ssl import RAND_status, RAND_add, RAND_bytes
-try:
-    from _ssl import RAND_egd
-except ImportError:
-    # RAND_egd is not supported on some platforms
-    pass
+from _ssl import get_sigalgs
 
 
 from _ssl import (
     HAS_SNI, HAS_ECDH, HAS_NPN, HAS_ALPN, HAS_SSLv2, HAS_SSLv3, HAS_TLSv1,
-    HAS_TLSv1_1, HAS_TLSv1_2, HAS_TLSv1_3, HAS_PSK, HAS_PHA
+    HAS_TLSv1_1, HAS_TLSv1_2, HAS_TLSv1_3, HAS_PSK, HAS_PSK_TLS13, HAS_PHA
 )
 from _ssl import _DEFAULT_CIPHERS, _OPENSSL_API_VERSION
 
@@ -151,7 +150,8 @@
     source=_ssl)
 
 PROTOCOL_SSLv23 = _SSLMethod.PROTOCOL_SSLv23 = _SSLMethod.PROTOCOL_TLS
-_PROTOCOL_NAMES = {value: name for name, value in _SSLMethod.__members__.items()}
+_PROTOCOL_NAMES = frozendict({
+    value: name for name, value in _SSLMethod.__members__.items()})
 
 _SSLv2_IF_EXISTS = getattr(_SSLMethod, 'PROTOCOL_SSLv2', None)
 
@@ -373,6 +373,20 @@ def _ipaddress_match(cert_ipaddress, host_ip):
     return ip == host_ip
 
 
+def _check_sslobject_params(server_side, context=None, server_hostname=None, session=None):
+    """Raises a ValueError if SSLObject._create() parameters aren't valid.
+    """
+    if server_side:
+        if server_hostname:
+            raise ValueError("server_hostname can only be specified "
+                             "in client mode")
+        if session is not None:
+            raise ValueError("session can only be specified in "
+                             "client mode")
+    if context.check_hostname and not server_hostname:
+        raise ValueError("check_hostname requires server_hostname")
+
+
 DefaultVerifyPaths = namedtuple("DefaultVerifyPaths",
     "cafile capath openssl_cafile_env openssl_cafile openssl_capath_env "
     "openssl_capath")
@@ -813,6 +827,8 @@ def __init__(self, *args, **kwargs):
     @classmethod
     def _create(cls, incoming, outgoing, server_side=False,
                  server_hostname=None, session=None, context=None):
+        _check_sslobject_params(server_side=server_side, context=context,
+                                server_hostname=server_hostname, session=session)
         self = cls.__new__(cls)
         sslobj = context._wrap_bio(
             incoming, outgoing, server_side=server_side,
@@ -931,6 +947,18 @@ def cipher(self):
         ssl_version, secret_bits)``."""
         return self._sslobj.cipher()
 
+    def group(self):
+        """Return the currently selected key agreement group name."""
+        return self._sslobj.group()
+
+    def client_sigalg(self):
+        """Return the selected client authentication signature algorithm."""
+        return self._sslobj.client_sigalg()
+
+    def server_sigalg(self):
+        """Return the selected server handshake signature algorithm."""
+        return self._sslobj.server_sigalg()
+
     def shared_ciphers(self):
         """Return a list of ciphers shared by the client during the handshake or
         None if this is not a valid server connection.
@@ -975,6 +1003,10 @@ def _sslcopydoc(func):
     return func
 
 
+class _GiveupOnSSLSendfile(Exception):
+    pass
+
+
 class SSLSocket(socket):
     """This class implements a subtype of socket.socket that wraps
     the underlying OS socket in an SSL context when necessary, and
@@ -993,15 +1025,8 @@ def _create(cls, sock, server_side=False, do_handshake_on_connect=True,
                 context=None, session=None):
         if sock.getsockopt(SOL_SOCKET, SO_TYPE) != SOCK_STREAM:
             raise NotImplementedError("only stream sockets are supported")
-        if server_side:
-            if server_hostname:
-                raise ValueError("server_hostname can only be specified "
-                                 "in client mode")
-            if session is not None:
-                raise ValueError("session can only be specified in "
-                                 "client mode")
-        if context.check_hostname and not server_hostname:
-            raise ValueError("check_hostname requires server_hostname")
+        _check_sslobject_params(server_side=server_side, context=context,
+                                server_hostname=server_hostname, session=session)
 
         sock_timeout = sock.gettimeout()
         kwargs = dict(
@@ -1206,6 +1231,30 @@ def cipher(self):
         else:
             return self._sslobj.cipher()
 
+    @_sslcopydoc
+    def group(self):
+        self._checkClosed()
+        if self._sslobj is None:
+            return None
+        else:
+            return self._sslobj.group()
+
+    @_sslcopydoc
+    def client_sigalg(self):
+        self._checkClosed()
+        if self._sslobj is None:
+            return None
+        else:
+            return self._sslobj.client_sigalg()
+
+    @_sslcopydoc
+    def server_sigalg(self):
+        self._checkClosed()
+        if self._sslobj is None:
+            return None
+        else:
+            return self._sslobj.server_sigalg()
+
     @_sslcopydoc
     def shared_ciphers(self):
         self._checkClosed()
@@ -1266,15 +1315,26 @@ def sendall(self, data, flags=0):
             return super().sendall(data, flags)
 
     def sendfile(self, file, offset=0, count=None):
-        """Send a file, possibly by using os.sendfile() if this is a
-        clear-text socket.  Return the total number of bytes sent.
+        """Send a file, possibly by using an efficient sendfile() call if
+        the system supports it.  Return the total number of bytes sent.
         """
-        if self._sslobj is not None:
-            return self._sendfile_use_send(file, offset, count)
-        else:
-            # os.sendfile() works with plain sockets only
+        if self._sslobj is None:
             return super().sendfile(file, offset, count)
 
+        if not self._sslobj.uses_ktls_for_send():
+            return self._sendfile_use_send(file, offset, count)
+
+        sendfile = getattr(self._sslobj, "sendfile", None)
+        if sendfile is None:
+            return self._sendfile_use_send(file, offset, count)
+
+        try:
+            return self._sendfile_zerocopy(
+                sendfile, _GiveupOnSSLSendfile, file, offset, count,
+            )
+        except _GiveupOnSSLSendfile:
+            return self._sendfile_use_send(file, offset, count)
+
     def recv(self, buflen=1024, flags=0):
         self._checkClosed()
         if self._sslobj is not None:
@@ -1484,11 +1544,8 @@ def DER_cert_to_PEM_cert(der_cert_bytes):
     """Takes a certificate in binary DER format and returns the
     PEM version of it as a string."""
 
-    f = str(base64.standard_b64encode(der_cert_bytes), 'ASCII', 'strict')
-    ss = [PEM_HEADER]
-    ss += [f[i:i+64] for i in range(0, len(f), 64)]
-    ss.append(PEM_FOOTER + '\n')
-    return '\n'.join(ss)
+    f = str(base64.b64encode(der_cert_bytes, wrapcol=64), 'ASCII')
+    return f'{PEM_HEADER}\n{f}\n{PEM_FOOTER}\n'
 
 def PEM_cert_to_DER_cert(pem_cert_string):
     """Takes a certificate in ASCII PEM format and returns the
diff --git a/Lib/stat.py b/Lib/stat.py
index 81f694329bf..214c7917b5e 100644
--- a/Lib/stat.py
+++ b/Lib/stat.py
@@ -205,6 +205,21 @@ def filemode(mode):
 FILE_ATTRIBUTE_VIRTUAL = 65536
 
 
+# Linux STATX_ATTR constants for interpreting os.statx()'s
+# "stx_attributes" and "stx_attributes_mask" members
+
+STATX_ATTR_COMPRESSED = 0x00000004
+STATX_ATTR_IMMUTABLE = 0x00000010
+STATX_ATTR_APPEND = 0x00000020
+STATX_ATTR_NODUMP = 0x00000040
+STATX_ATTR_ENCRYPTED = 0x00000800
+STATX_ATTR_AUTOMOUNT = 0x00001000
+STATX_ATTR_MOUNT_ROOT = 0x00002000
+STATX_ATTR_VERITY = 0x00100000
+STATX_ATTR_DAX = 0x00200000
+STATX_ATTR_WRITE_ATOMIC = 0x00400000
+
+
 # If available, use C implementation
 try:
     from _stat import *
diff --git a/Lib/statistics.py b/Lib/statistics.py
index 26cf925529e..01ca6c51daf 100644
--- a/Lib/statistics.py
+++ b/Lib/statistics.py
@@ -136,7 +136,7 @@
 
 from fractions import Fraction
 from decimal import Decimal
-from itertools import count, groupby, repeat
+from itertools import compress, count, groupby, repeat
 from bisect import bisect_left, bisect_right
 from math import hypot, sqrt, fabs, exp, erfc, tau, log, fsum, sumprod
 from math import isfinite, isinf, pi, cos, sin, tan, cosh, asin, atan, acos
@@ -145,6 +145,7 @@
 from collections import Counter, namedtuple, defaultdict
 
 _SQRT2 = sqrt(2.0)
+_SQRT2PI = sqrt(tau)
 _random = random
 
 ## Exceptions ##############################################################
@@ -194,9 +195,9 @@ def fmean(data, weights=None):
             n = len(data)
         except TypeError:
             # Handle iterators that do not define __len__().
-            counter = count()
-            total = fsum(map(itemgetter(0), zip(data, counter)))
-            n = next(counter)
+            counter = count(1)
+            total = fsum(compress(data, counter))
+            n = next(counter) - 1
         else:
             total = fsum(data)
 
@@ -247,7 +248,7 @@ def count_positive(iterable):
             elif x == 0.0:
                 found_zero = True
             else:
-                raise StatisticsError('No negative inputs allowed', x)
+                raise StatisticsError(f'No negative inputs allowed: {x!r}')
 
     total = fsum(map(log, count_positive(data)))
 
@@ -1257,11 +1258,11 @@ def samples(self, n, *, seed=None):
 
     def pdf(self, x):
         "Probability density function.  P(x <= X < x+dx) / dx"
-        variance = self._sigma * self._sigma
-        if not variance:
+        sigma = self._sigma
+        if not sigma:
             raise StatisticsError('pdf() not defined when sigma is zero')
-        diff = x - self._mu
-        return exp(diff * diff / (-2.0 * variance)) / sqrt(tau * variance)
+        z = (x - self._mu) / sigma
+        return exp(-0.5 * z * z) / (_SQRT2PI * sigma)
 
     def cdf(self, x):
         "Cumulative distribution function.  P(X <= x)"
diff --git a/Lib/string/__init__.py b/Lib/string/__init__.py
index b2c369ef9d1..88f1ae1b9b0 100644
--- a/Lib/string/__init__.py
+++ b/Lib/string/__init__.py
@@ -198,16 +198,14 @@ def get_identifiers(self):
 
 
 ########################################################################
-# the Formatter class
-# see PEP 3101 for details and purpose of this class
-
-# The hard parts are reused from the C implementation.  They're exposed as "_"
-# prefixed methods of str.
-
+# The Formatter class (PEP 3101).
+#
 # The overall parser is implemented in _string.formatter_parser.
-# The field name parser is implemented in _string.formatter_field_name_split
+# The field name parser is implemented in _string.formatter_field_name_split.
 
 class Formatter:
+    """See PEP 3101 for details and purpose of this class."""
+
     def format(self, format_string, /, *args, **kwargs):
         return self.vformat(format_string, args, kwargs)
 
@@ -271,22 +269,18 @@ def _vformat(self, format_string, args, kwargs, used_args, recursion_depth,
 
         return ''.join(result), auto_arg_index
 
-
     def get_value(self, key, args, kwargs):
         if isinstance(key, int):
             return args[key]
         else:
             return kwargs[key]
 
-
     def check_unused_args(self, used_args, args, kwargs):
         pass
 
-
     def format_field(self, value, format_spec):
         return format(value, format_spec)
 
-
     def convert_field(self, value, conversion):
         # do any conversion on the resulting object
         if conversion is None:
@@ -299,28 +293,26 @@ def convert_field(self, value, conversion):
             return ascii(value)
         raise ValueError("Unknown conversion specifier {0!s}".format(conversion))
 
-
-    # returns an iterable that contains tuples of the form:
-    # (literal_text, field_name, format_spec, conversion)
-    # literal_text can be zero length
-    # field_name can be None, in which case there's no
-    #  object to format and output
-    # if field_name is not None, it is looked up, formatted
-    #  with format_spec and conversion and then used
     def parse(self, format_string):
+        """
+        Return an iterable that contains tuples of the form
+        (literal_text, field_name, format_spec, conversion).
+
+        *field_name* can be None, in which case there's no object
+        to format and output; otherwise, it is looked up and
+        formatted with *format_spec* and *conversion*.
+        """
         return _string.formatter_parser(format_string)
 
-
-    # given a field_name, find the object it references.
-    #  field_name:   the field being looked up, e.g. "0.name"
-    #                 or "lookup[3]"
-    #  used_args:    a set of which args have been used
-    #  args, kwargs: as passed in to vformat
     def get_field(self, field_name, args, kwargs):
-        first, rest = _string.formatter_field_name_split(field_name)
+        """Find the object referenced by a given field name.
 
+        The field name *field_name* can be for instance "0.name"
+        or "lookup[3]". The *args* and *kwargs* arguments are
+        passed to get_value().
+        """
+        first, rest = _string.formatter_field_name_split(field_name)
         obj = self.get_value(first, args, kwargs)
-
         # loop through the rest of the field_name, doing
         #  getattr or getitem as needed
         for is_attr, i in rest:
@@ -328,5 +320,4 @@ def get_field(self, field_name, args, kwargs):
                 obj = getattr(obj, i)
             else:
                 obj = obj[i]
-
         return obj, first
diff --git a/Lib/stringprep.py b/Lib/stringprep.py
index 44ecdb266ce..abad847830c 100644
--- a/Lib/stringprep.py
+++ b/Lib/stringprep.py
@@ -5,12 +5,18 @@
 and mappings, for which a mapping function is provided.
 """
 
-from unicodedata import ucd_3_2_0 as unicodedata
+# This check asserts that mkstringprep.py has been run
+# when unicodedata is modified to ensure conformant behavior.
+import unicodedata
 
-assert unicodedata.unidata_version == '3.2.0'
+assert unicodedata.unidata_version == '17.0.0'
+
+from unicodedata import ucd_3_2_0 as unicodedata_320
+
+assert unicodedata_320.unidata_version == '3.2.0'
 
 def in_table_a1(code):
-    if unicodedata.category(code) != 'Cn': return False
+    if unicodedata_320.category(code) != 'Cn': return False
     c = ord(code)
     if 0xFDD0 <= c < 0xFDF0: return False
     return (c & 0xFFFF) not in (0xFFFE, 0xFFFF)
@@ -22,57 +28,233 @@ def in_table_b1(code):
 
 
 b3_exceptions = {
-0xb5:'\u03bc', 0xdf:'ss', 0x130:'i\u0307', 0x149:'\u02bcn',
-0x17f:'s', 0x1f0:'j\u030c', 0x345:'\u03b9', 0x37a:' \u03b9',
-0x390:'\u03b9\u0308\u0301', 0x3b0:'\u03c5\u0308\u0301', 0x3c2:'\u03c3', 0x3d0:'\u03b2',
-0x3d1:'\u03b8', 0x3d2:'\u03c5', 0x3d3:'\u03cd', 0x3d4:'\u03cb',
-0x3d5:'\u03c6', 0x3d6:'\u03c0', 0x3f0:'\u03ba', 0x3f1:'\u03c1',
-0x3f2:'\u03c3', 0x3f5:'\u03b5', 0x587:'\u0565\u0582', 0x1e96:'h\u0331',
-0x1e97:'t\u0308', 0x1e98:'w\u030a', 0x1e99:'y\u030a', 0x1e9a:'a\u02be',
-0x1e9b:'\u1e61', 0x1f50:'\u03c5\u0313', 0x1f52:'\u03c5\u0313\u0300', 0x1f54:'\u03c5\u0313\u0301',
-0x1f56:'\u03c5\u0313\u0342', 0x1f80:'\u1f00\u03b9', 0x1f81:'\u1f01\u03b9', 0x1f82:'\u1f02\u03b9',
-0x1f83:'\u1f03\u03b9', 0x1f84:'\u1f04\u03b9', 0x1f85:'\u1f05\u03b9', 0x1f86:'\u1f06\u03b9',
-0x1f87:'\u1f07\u03b9', 0x1f88:'\u1f00\u03b9', 0x1f89:'\u1f01\u03b9', 0x1f8a:'\u1f02\u03b9',
-0x1f8b:'\u1f03\u03b9', 0x1f8c:'\u1f04\u03b9', 0x1f8d:'\u1f05\u03b9', 0x1f8e:'\u1f06\u03b9',
-0x1f8f:'\u1f07\u03b9', 0x1f90:'\u1f20\u03b9', 0x1f91:'\u1f21\u03b9', 0x1f92:'\u1f22\u03b9',
-0x1f93:'\u1f23\u03b9', 0x1f94:'\u1f24\u03b9', 0x1f95:'\u1f25\u03b9', 0x1f96:'\u1f26\u03b9',
-0x1f97:'\u1f27\u03b9', 0x1f98:'\u1f20\u03b9', 0x1f99:'\u1f21\u03b9', 0x1f9a:'\u1f22\u03b9',
-0x1f9b:'\u1f23\u03b9', 0x1f9c:'\u1f24\u03b9', 0x1f9d:'\u1f25\u03b9', 0x1f9e:'\u1f26\u03b9',
-0x1f9f:'\u1f27\u03b9', 0x1fa0:'\u1f60\u03b9', 0x1fa1:'\u1f61\u03b9', 0x1fa2:'\u1f62\u03b9',
-0x1fa3:'\u1f63\u03b9', 0x1fa4:'\u1f64\u03b9', 0x1fa5:'\u1f65\u03b9', 0x1fa6:'\u1f66\u03b9',
-0x1fa7:'\u1f67\u03b9', 0x1fa8:'\u1f60\u03b9', 0x1fa9:'\u1f61\u03b9', 0x1faa:'\u1f62\u03b9',
-0x1fab:'\u1f63\u03b9', 0x1fac:'\u1f64\u03b9', 0x1fad:'\u1f65\u03b9', 0x1fae:'\u1f66\u03b9',
-0x1faf:'\u1f67\u03b9', 0x1fb2:'\u1f70\u03b9', 0x1fb3:'\u03b1\u03b9', 0x1fb4:'\u03ac\u03b9',
-0x1fb6:'\u03b1\u0342', 0x1fb7:'\u03b1\u0342\u03b9', 0x1fbc:'\u03b1\u03b9', 0x1fbe:'\u03b9',
-0x1fc2:'\u1f74\u03b9', 0x1fc3:'\u03b7\u03b9', 0x1fc4:'\u03ae\u03b9', 0x1fc6:'\u03b7\u0342',
-0x1fc7:'\u03b7\u0342\u03b9', 0x1fcc:'\u03b7\u03b9', 0x1fd2:'\u03b9\u0308\u0300', 0x1fd3:'\u03b9\u0308\u0301',
-0x1fd6:'\u03b9\u0342', 0x1fd7:'\u03b9\u0308\u0342', 0x1fe2:'\u03c5\u0308\u0300', 0x1fe3:'\u03c5\u0308\u0301',
-0x1fe4:'\u03c1\u0313', 0x1fe6:'\u03c5\u0342', 0x1fe7:'\u03c5\u0308\u0342', 0x1ff2:'\u1f7c\u03b9',
-0x1ff3:'\u03c9\u03b9', 0x1ff4:'\u03ce\u03b9', 0x1ff6:'\u03c9\u0342', 0x1ff7:'\u03c9\u0342\u03b9',
-0x1ffc:'\u03c9\u03b9', 0x20a8:'rs', 0x2102:'c', 0x2103:'\xb0c',
-0x2107:'\u025b', 0x2109:'\xb0f', 0x210b:'h', 0x210c:'h',
-0x210d:'h', 0x2110:'i', 0x2111:'i', 0x2112:'l',
-0x2115:'n', 0x2116:'no', 0x2119:'p', 0x211a:'q',
-0x211b:'r', 0x211c:'r', 0x211d:'r', 0x2120:'sm',
-0x2121:'tel', 0x2122:'tm', 0x2124:'z', 0x2128:'z',
-0x212c:'b', 0x212d:'c', 0x2130:'e', 0x2131:'f',
-0x2133:'m', 0x213e:'\u03b3', 0x213f:'\u03c0', 0x2145:'d',
-0x3371:'hpa', 0x3373:'au', 0x3375:'ov', 0x3380:'pa',
-0x3381:'na', 0x3382:'\u03bca', 0x3383:'ma', 0x3384:'ka',
-0x3385:'kb', 0x3386:'mb', 0x3387:'gb', 0x338a:'pf',
-0x338b:'nf', 0x338c:'\u03bcf', 0x3390:'hz', 0x3391:'khz',
-0x3392:'mhz', 0x3393:'ghz', 0x3394:'thz', 0x33a9:'pa',
-0x33aa:'kpa', 0x33ab:'mpa', 0x33ac:'gpa', 0x33b4:'pv',
-0x33b5:'nv', 0x33b6:'\u03bcv', 0x33b7:'mv', 0x33b8:'kv',
-0x33b9:'mv', 0x33ba:'pw', 0x33bb:'nw', 0x33bc:'\u03bcw',
-0x33bd:'mw', 0x33be:'kw', 0x33bf:'mw', 0x33c0:'k\u03c9',
-0x33c1:'m\u03c9', 0x33c3:'bq', 0x33c6:'c\u2215kg', 0x33c7:'co.',
-0x33c8:'db', 0x33c9:'gy', 0x33cb:'hp', 0x33cd:'kk',
-0x33ce:'km', 0x33d7:'ph', 0x33d9:'ppm', 0x33da:'pr',
-0x33dc:'sv', 0x33dd:'wb', 0xfb00:'ff', 0xfb01:'fi',
-0xfb02:'fl', 0xfb03:'ffi', 0xfb04:'ffl', 0xfb05:'st',
-0xfb06:'st', 0xfb13:'\u0574\u0576', 0xfb14:'\u0574\u0565', 0xfb15:'\u0574\u056b',
-0xfb16:'\u057e\u0576', 0xfb17:'\u0574\u056d', 0x1d400:'a', 0x1d401:'b',
+0xb5:'\u03bc', 0xdf:'ss', 0x149:'\u02bcn', 0x17f:'s',
+0x1f0:'j\u030c', 0x23a:'\u023a', 0x23b:'\u023b', 0x23d:'\u023d',
+0x23e:'\u023e', 0x241:'\u0241', 0x243:'\u0243', 0x244:'\u0244',
+0x245:'\u0245', 0x246:'\u0246', 0x248:'\u0248', 0x24a:'\u024a',
+0x24c:'\u024c', 0x24e:'\u024e', 0x345:'\u03b9', 0x370:'\u0370',
+0x372:'\u0372', 0x376:'\u0376', 0x37a:' \u03b9', 0x37f:'\u037f',
+0x390:'\u03b9\u0308\u0301', 0x3b0:'\u03c5\u0308\u0301', 0x3c2:'\u03c3', 0x3cf:'\u03cf',
+0x3d0:'\u03b2', 0x3d1:'\u03b8', 0x3d2:'\u03c5', 0x3d3:'\u03cd',
+0x3d4:'\u03cb', 0x3d5:'\u03c6', 0x3d6:'\u03c0', 0x3f0:'\u03ba',
+0x3f1:'\u03c1', 0x3f2:'\u03c3', 0x3f5:'\u03b5', 0x3f7:'\u03f7',
+0x3f9:'\u03f9', 0x3fa:'\u03fa', 0x3fd:'\u03fd', 0x3fe:'\u03fe',
+0x3ff:'\u03ff', 0x4c0:'\u04c0', 0x4f6:'\u04f6', 0x4fa:'\u04fa',
+0x4fc:'\u04fc', 0x4fe:'\u04fe', 0x510:'\u0510', 0x512:'\u0512',
+0x514:'\u0514', 0x516:'\u0516', 0x518:'\u0518', 0x51a:'\u051a',
+0x51c:'\u051c', 0x51e:'\u051e', 0x520:'\u0520', 0x522:'\u0522',
+0x524:'\u0524', 0x526:'\u0526', 0x528:'\u0528', 0x52a:'\u052a',
+0x52c:'\u052c', 0x52e:'\u052e', 0x587:'\u0565\u0582', 0x10a0:'\u10a0',
+0x10a1:'\u10a1', 0x10a2:'\u10a2', 0x10a3:'\u10a3', 0x10a4:'\u10a4',
+0x10a5:'\u10a5', 0x10a6:'\u10a6', 0x10a7:'\u10a7', 0x10a8:'\u10a8',
+0x10a9:'\u10a9', 0x10aa:'\u10aa', 0x10ab:'\u10ab', 0x10ac:'\u10ac',
+0x10ad:'\u10ad', 0x10ae:'\u10ae', 0x10af:'\u10af', 0x10b0:'\u10b0',
+0x10b1:'\u10b1', 0x10b2:'\u10b2', 0x10b3:'\u10b3', 0x10b4:'\u10b4',
+0x10b5:'\u10b5', 0x10b6:'\u10b6', 0x10b7:'\u10b7', 0x10b8:'\u10b8',
+0x10b9:'\u10b9', 0x10ba:'\u10ba', 0x10bb:'\u10bb', 0x10bc:'\u10bc',
+0x10bd:'\u10bd', 0x10be:'\u10be', 0x10bf:'\u10bf', 0x10c0:'\u10c0',
+0x10c1:'\u10c1', 0x10c2:'\u10c2', 0x10c3:'\u10c3', 0x10c4:'\u10c4',
+0x10c5:'\u10c5', 0x10c7:'\u10c7', 0x10cd:'\u10cd', 0x13a0:'\u13a0',
+0x13a1:'\u13a1', 0x13a2:'\u13a2', 0x13a3:'\u13a3', 0x13a4:'\u13a4',
+0x13a5:'\u13a5', 0x13a6:'\u13a6', 0x13a7:'\u13a7', 0x13a8:'\u13a8',
+0x13a9:'\u13a9', 0x13aa:'\u13aa', 0x13ab:'\u13ab', 0x13ac:'\u13ac',
+0x13ad:'\u13ad', 0x13ae:'\u13ae', 0x13af:'\u13af', 0x13b0:'\u13b0',
+0x13b1:'\u13b1', 0x13b2:'\u13b2', 0x13b3:'\u13b3', 0x13b4:'\u13b4',
+0x13b5:'\u13b5', 0x13b6:'\u13b6', 0x13b7:'\u13b7', 0x13b8:'\u13b8',
+0x13b9:'\u13b9', 0x13ba:'\u13ba', 0x13bb:'\u13bb', 0x13bc:'\u13bc',
+0x13bd:'\u13bd', 0x13be:'\u13be', 0x13bf:'\u13bf', 0x13c0:'\u13c0',
+0x13c1:'\u13c1', 0x13c2:'\u13c2', 0x13c3:'\u13c3', 0x13c4:'\u13c4',
+0x13c5:'\u13c5', 0x13c6:'\u13c6', 0x13c7:'\u13c7', 0x13c8:'\u13c8',
+0x13c9:'\u13c9', 0x13ca:'\u13ca', 0x13cb:'\u13cb', 0x13cc:'\u13cc',
+0x13cd:'\u13cd', 0x13ce:'\u13ce', 0x13cf:'\u13cf', 0x13d0:'\u13d0',
+0x13d1:'\u13d1', 0x13d2:'\u13d2', 0x13d3:'\u13d3', 0x13d4:'\u13d4',
+0x13d5:'\u13d5', 0x13d6:'\u13d6', 0x13d7:'\u13d7', 0x13d8:'\u13d8',
+0x13d9:'\u13d9', 0x13da:'\u13da', 0x13db:'\u13db', 0x13dc:'\u13dc',
+0x13dd:'\u13dd', 0x13de:'\u13de', 0x13df:'\u13df', 0x13e0:'\u13e0',
+0x13e1:'\u13e1', 0x13e2:'\u13e2', 0x13e3:'\u13e3', 0x13e4:'\u13e4',
+0x13e5:'\u13e5', 0x13e6:'\u13e6', 0x13e7:'\u13e7', 0x13e8:'\u13e8',
+0x13e9:'\u13e9', 0x13ea:'\u13ea', 0x13eb:'\u13eb', 0x13ec:'\u13ec',
+0x13ed:'\u13ed', 0x13ee:'\u13ee', 0x13ef:'\u13ef', 0x13f0:'\u13f0',
+0x13f1:'\u13f1', 0x13f2:'\u13f2', 0x13f3:'\u13f3', 0x13f4:'\u13f4',
+0x13f5:'\u13f5', 0x1c89:'\u1c89', 0x1c90:'\u1c90', 0x1c91:'\u1c91',
+0x1c92:'\u1c92', 0x1c93:'\u1c93', 0x1c94:'\u1c94', 0x1c95:'\u1c95',
+0x1c96:'\u1c96', 0x1c97:'\u1c97', 0x1c98:'\u1c98', 0x1c99:'\u1c99',
+0x1c9a:'\u1c9a', 0x1c9b:'\u1c9b', 0x1c9c:'\u1c9c', 0x1c9d:'\u1c9d',
+0x1c9e:'\u1c9e', 0x1c9f:'\u1c9f', 0x1ca0:'\u1ca0', 0x1ca1:'\u1ca1',
+0x1ca2:'\u1ca2', 0x1ca3:'\u1ca3', 0x1ca4:'\u1ca4', 0x1ca5:'\u1ca5',
+0x1ca6:'\u1ca6', 0x1ca7:'\u1ca7', 0x1ca8:'\u1ca8', 0x1ca9:'\u1ca9',
+0x1caa:'\u1caa', 0x1cab:'\u1cab', 0x1cac:'\u1cac', 0x1cad:'\u1cad',
+0x1cae:'\u1cae', 0x1caf:'\u1caf', 0x1cb0:'\u1cb0', 0x1cb1:'\u1cb1',
+0x1cb2:'\u1cb2', 0x1cb3:'\u1cb3', 0x1cb4:'\u1cb4', 0x1cb5:'\u1cb5',
+0x1cb6:'\u1cb6', 0x1cb7:'\u1cb7', 0x1cb8:'\u1cb8', 0x1cb9:'\u1cb9',
+0x1cba:'\u1cba', 0x1cbd:'\u1cbd', 0x1cbe:'\u1cbe', 0x1cbf:'\u1cbf',
+0x1e96:'h\u0331', 0x1e97:'t\u0308', 0x1e98:'w\u030a', 0x1e99:'y\u030a',
+0x1e9a:'a\u02be', 0x1e9b:'\u1e61', 0x1e9e:'\u1e9e', 0x1efa:'\u1efa',
+0x1efc:'\u1efc', 0x1efe:'\u1efe', 0x1f50:'\u03c5\u0313', 0x1f52:'\u03c5\u0313\u0300',
+0x1f54:'\u03c5\u0313\u0301', 0x1f56:'\u03c5\u0313\u0342', 0x1f80:'\u1f00\u03b9', 0x1f81:'\u1f01\u03b9',
+0x1f82:'\u1f02\u03b9', 0x1f83:'\u1f03\u03b9', 0x1f84:'\u1f04\u03b9', 0x1f85:'\u1f05\u03b9',
+0x1f86:'\u1f06\u03b9', 0x1f87:'\u1f07\u03b9', 0x1f88:'\u1f00\u03b9', 0x1f89:'\u1f01\u03b9',
+0x1f8a:'\u1f02\u03b9', 0x1f8b:'\u1f03\u03b9', 0x1f8c:'\u1f04\u03b9', 0x1f8d:'\u1f05\u03b9',
+0x1f8e:'\u1f06\u03b9', 0x1f8f:'\u1f07\u03b9', 0x1f90:'\u1f20\u03b9', 0x1f91:'\u1f21\u03b9',
+0x1f92:'\u1f22\u03b9', 0x1f93:'\u1f23\u03b9', 0x1f94:'\u1f24\u03b9', 0x1f95:'\u1f25\u03b9',
+0x1f96:'\u1f26\u03b9', 0x1f97:'\u1f27\u03b9', 0x1f98:'\u1f20\u03b9', 0x1f99:'\u1f21\u03b9',
+0x1f9a:'\u1f22\u03b9', 0x1f9b:'\u1f23\u03b9', 0x1f9c:'\u1f24\u03b9', 0x1f9d:'\u1f25\u03b9',
+0x1f9e:'\u1f26\u03b9', 0x1f9f:'\u1f27\u03b9', 0x1fa0:'\u1f60\u03b9', 0x1fa1:'\u1f61\u03b9',
+0x1fa2:'\u1f62\u03b9', 0x1fa3:'\u1f63\u03b9', 0x1fa4:'\u1f64\u03b9', 0x1fa5:'\u1f65\u03b9',
+0x1fa6:'\u1f66\u03b9', 0x1fa7:'\u1f67\u03b9', 0x1fa8:'\u1f60\u03b9', 0x1fa9:'\u1f61\u03b9',
+0x1faa:'\u1f62\u03b9', 0x1fab:'\u1f63\u03b9', 0x1fac:'\u1f64\u03b9', 0x1fad:'\u1f65\u03b9',
+0x1fae:'\u1f66\u03b9', 0x1faf:'\u1f67\u03b9', 0x1fb2:'\u1f70\u03b9', 0x1fb3:'\u03b1\u03b9',
+0x1fb4:'\u03ac\u03b9', 0x1fb6:'\u03b1\u0342', 0x1fb7:'\u03b1\u0342\u03b9', 0x1fbc:'\u03b1\u03b9',
+0x1fbe:'\u03b9', 0x1fc2:'\u1f74\u03b9', 0x1fc3:'\u03b7\u03b9', 0x1fc4:'\u03ae\u03b9',
+0x1fc6:'\u03b7\u0342', 0x1fc7:'\u03b7\u0342\u03b9', 0x1fcc:'\u03b7\u03b9', 0x1fd2:'\u03b9\u0308\u0300',
+0x1fd3:'\u03b9\u0308\u0301', 0x1fd6:'\u03b9\u0342', 0x1fd7:'\u03b9\u0308\u0342', 0x1fe2:'\u03c5\u0308\u0300',
+0x1fe3:'\u03c5\u0308\u0301', 0x1fe4:'\u03c1\u0313', 0x1fe6:'\u03c5\u0342', 0x1fe7:'\u03c5\u0308\u0342',
+0x1ff2:'\u1f7c\u03b9', 0x1ff3:'\u03c9\u03b9', 0x1ff4:'\u03ce\u03b9', 0x1ff6:'\u03c9\u0342',
+0x1ff7:'\u03c9\u0342\u03b9', 0x1ffc:'\u03c9\u03b9', 0x20a8:'rs', 0x2102:'c',
+0x2103:'\xb0c', 0x2107:'\u025b', 0x2109:'\xb0f', 0x210b:'h',
+0x210c:'h', 0x210d:'h', 0x2110:'i', 0x2111:'i',
+0x2112:'l', 0x2115:'n', 0x2116:'no', 0x2119:'p',
+0x211a:'q', 0x211b:'r', 0x211c:'r', 0x211d:'r',
+0x2120:'sm', 0x2121:'tel', 0x2122:'tm', 0x2124:'z',
+0x2128:'z', 0x212c:'b', 0x212d:'c', 0x2130:'e',
+0x2131:'f', 0x2132:'\u2132', 0x2133:'m', 0x213e:'\u03b3',
+0x213f:'\u03c0', 0x2145:'d', 0x2183:'\u2183', 0x2c00:'\u2c00',
+0x2c01:'\u2c01', 0x2c02:'\u2c02', 0x2c03:'\u2c03', 0x2c04:'\u2c04',
+0x2c05:'\u2c05', 0x2c06:'\u2c06', 0x2c07:'\u2c07', 0x2c08:'\u2c08',
+0x2c09:'\u2c09', 0x2c0a:'\u2c0a', 0x2c0b:'\u2c0b', 0x2c0c:'\u2c0c',
+0x2c0d:'\u2c0d', 0x2c0e:'\u2c0e', 0x2c0f:'\u2c0f', 0x2c10:'\u2c10',
+0x2c11:'\u2c11', 0x2c12:'\u2c12', 0x2c13:'\u2c13', 0x2c14:'\u2c14',
+0x2c15:'\u2c15', 0x2c16:'\u2c16', 0x2c17:'\u2c17', 0x2c18:'\u2c18',
+0x2c19:'\u2c19', 0x2c1a:'\u2c1a', 0x2c1b:'\u2c1b', 0x2c1c:'\u2c1c',
+0x2c1d:'\u2c1d', 0x2c1e:'\u2c1e', 0x2c1f:'\u2c1f', 0x2c20:'\u2c20',
+0x2c21:'\u2c21', 0x2c22:'\u2c22', 0x2c23:'\u2c23', 0x2c24:'\u2c24',
+0x2c25:'\u2c25', 0x2c26:'\u2c26', 0x2c27:'\u2c27', 0x2c28:'\u2c28',
+0x2c29:'\u2c29', 0x2c2a:'\u2c2a', 0x2c2b:'\u2c2b', 0x2c2c:'\u2c2c',
+0x2c2d:'\u2c2d', 0x2c2e:'\u2c2e', 0x2c2f:'\u2c2f', 0x2c60:'\u2c60',
+0x2c62:'\u2c62', 0x2c63:'\u2c63', 0x2c64:'\u2c64', 0x2c67:'\u2c67',
+0x2c69:'\u2c69', 0x2c6b:'\u2c6b', 0x2c6d:'\u2c6d', 0x2c6e:'\u2c6e',
+0x2c6f:'\u2c6f', 0x2c70:'\u2c70', 0x2c72:'\u2c72', 0x2c75:'\u2c75',
+0x2c7e:'\u2c7e', 0x2c7f:'\u2c7f', 0x2c80:'\u2c80', 0x2c82:'\u2c82',
+0x2c84:'\u2c84', 0x2c86:'\u2c86', 0x2c88:'\u2c88', 0x2c8a:'\u2c8a',
+0x2c8c:'\u2c8c', 0x2c8e:'\u2c8e', 0x2c90:'\u2c90', 0x2c92:'\u2c92',
+0x2c94:'\u2c94', 0x2c96:'\u2c96', 0x2c98:'\u2c98', 0x2c9a:'\u2c9a',
+0x2c9c:'\u2c9c', 0x2c9e:'\u2c9e', 0x2ca0:'\u2ca0', 0x2ca2:'\u2ca2',
+0x2ca4:'\u2ca4', 0x2ca6:'\u2ca6', 0x2ca8:'\u2ca8', 0x2caa:'\u2caa',
+0x2cac:'\u2cac', 0x2cae:'\u2cae', 0x2cb0:'\u2cb0', 0x2cb2:'\u2cb2',
+0x2cb4:'\u2cb4', 0x2cb6:'\u2cb6', 0x2cb8:'\u2cb8', 0x2cba:'\u2cba',
+0x2cbc:'\u2cbc', 0x2cbe:'\u2cbe', 0x2cc0:'\u2cc0', 0x2cc2:'\u2cc2',
+0x2cc4:'\u2cc4', 0x2cc6:'\u2cc6', 0x2cc8:'\u2cc8', 0x2cca:'\u2cca',
+0x2ccc:'\u2ccc', 0x2cce:'\u2cce', 0x2cd0:'\u2cd0', 0x2cd2:'\u2cd2',
+0x2cd4:'\u2cd4', 0x2cd6:'\u2cd6', 0x2cd8:'\u2cd8', 0x2cda:'\u2cda',
+0x2cdc:'\u2cdc', 0x2cde:'\u2cde', 0x2ce0:'\u2ce0', 0x2ce2:'\u2ce2',
+0x2ceb:'\u2ceb', 0x2ced:'\u2ced', 0x2cf2:'\u2cf2', 0x3371:'hpa',
+0x3373:'au', 0x3375:'ov', 0x3380:'pa', 0x3381:'na',
+0x3382:'\u03bca', 0x3383:'ma', 0x3384:'ka', 0x3385:'kb',
+0x3386:'mb', 0x3387:'gb', 0x338a:'pf', 0x338b:'nf',
+0x338c:'\u03bcf', 0x3390:'hz', 0x3391:'khz', 0x3392:'mhz',
+0x3393:'ghz', 0x3394:'thz', 0x33a9:'pa', 0x33aa:'kpa',
+0x33ab:'mpa', 0x33ac:'gpa', 0x33b4:'pv', 0x33b5:'nv',
+0x33b6:'\u03bcv', 0x33b7:'mv', 0x33b8:'kv', 0x33b9:'mv',
+0x33ba:'pw', 0x33bb:'nw', 0x33bc:'\u03bcw', 0x33bd:'mw',
+0x33be:'kw', 0x33bf:'mw', 0x33c0:'k\u03c9', 0x33c1:'m\u03c9',
+0x33c3:'bq', 0x33c6:'c\u2215kg', 0x33c7:'co.', 0x33c8:'db',
+0x33c9:'gy', 0x33cb:'hp', 0x33cd:'kk', 0x33ce:'km',
+0x33d7:'ph', 0x33d9:'ppm', 0x33da:'pr', 0x33dc:'sv',
+0x33dd:'wb', 0xa640:'\ua640', 0xa642:'\ua642', 0xa644:'\ua644',
+0xa646:'\ua646', 0xa648:'\ua648', 0xa64a:'\ua64a', 0xa64c:'\ua64c',
+0xa64e:'\ua64e', 0xa650:'\ua650', 0xa652:'\ua652', 0xa654:'\ua654',
+0xa656:'\ua656', 0xa658:'\ua658', 0xa65a:'\ua65a', 0xa65c:'\ua65c',
+0xa65e:'\ua65e', 0xa660:'\ua660', 0xa662:'\ua662', 0xa664:'\ua664',
+0xa666:'\ua666', 0xa668:'\ua668', 0xa66a:'\ua66a', 0xa66c:'\ua66c',
+0xa680:'\ua680', 0xa682:'\ua682', 0xa684:'\ua684', 0xa686:'\ua686',
+0xa688:'\ua688', 0xa68a:'\ua68a', 0xa68c:'\ua68c', 0xa68e:'\ua68e',
+0xa690:'\ua690', 0xa692:'\ua692', 0xa694:'\ua694', 0xa696:'\ua696',
+0xa698:'\ua698', 0xa69a:'\ua69a', 0xa722:'\ua722', 0xa724:'\ua724',
+0xa726:'\ua726', 0xa728:'\ua728', 0xa72a:'\ua72a', 0xa72c:'\ua72c',
+0xa72e:'\ua72e', 0xa732:'\ua732', 0xa734:'\ua734', 0xa736:'\ua736',
+0xa738:'\ua738', 0xa73a:'\ua73a', 0xa73c:'\ua73c', 0xa73e:'\ua73e',
+0xa740:'\ua740', 0xa742:'\ua742', 0xa744:'\ua744', 0xa746:'\ua746',
+0xa748:'\ua748', 0xa74a:'\ua74a', 0xa74c:'\ua74c', 0xa74e:'\ua74e',
+0xa750:'\ua750', 0xa752:'\ua752', 0xa754:'\ua754', 0xa756:'\ua756',
+0xa758:'\ua758', 0xa75a:'\ua75a', 0xa75c:'\ua75c', 0xa75e:'\ua75e',
+0xa760:'\ua760', 0xa762:'\ua762', 0xa764:'\ua764', 0xa766:'\ua766',
+0xa768:'\ua768', 0xa76a:'\ua76a', 0xa76c:'\ua76c', 0xa76e:'\ua76e',
+0xa779:'\ua779', 0xa77b:'\ua77b', 0xa77d:'\ua77d', 0xa77e:'\ua77e',
+0xa780:'\ua780', 0xa782:'\ua782', 0xa784:'\ua784', 0xa786:'\ua786',
+0xa78b:'\ua78b', 0xa78d:'\ua78d', 0xa790:'\ua790', 0xa792:'\ua792',
+0xa796:'\ua796', 0xa798:'\ua798', 0xa79a:'\ua79a', 0xa79c:'\ua79c',
+0xa79e:'\ua79e', 0xa7a0:'\ua7a0', 0xa7a2:'\ua7a2', 0xa7a4:'\ua7a4',
+0xa7a6:'\ua7a6', 0xa7a8:'\ua7a8', 0xa7aa:'\ua7aa', 0xa7ab:'\ua7ab',
+0xa7ac:'\ua7ac', 0xa7ad:'\ua7ad', 0xa7ae:'\ua7ae', 0xa7b0:'\ua7b0',
+0xa7b1:'\ua7b1', 0xa7b2:'\ua7b2', 0xa7b3:'\ua7b3', 0xa7b4:'\ua7b4',
+0xa7b6:'\ua7b6', 0xa7b8:'\ua7b8', 0xa7ba:'\ua7ba', 0xa7bc:'\ua7bc',
+0xa7be:'\ua7be', 0xa7c0:'\ua7c0', 0xa7c2:'\ua7c2', 0xa7c4:'\ua7c4',
+0xa7c5:'\ua7c5', 0xa7c6:'\ua7c6', 0xa7c7:'\ua7c7', 0xa7c9:'\ua7c9',
+0xa7cb:'\ua7cb', 0xa7cc:'\ua7cc', 0xa7ce:'\ua7ce', 0xa7d0:'\ua7d0',
+0xa7d2:'\ua7d2', 0xa7d4:'\ua7d4', 0xa7d6:'\ua7d6', 0xa7d8:'\ua7d8',
+0xa7da:'\ua7da', 0xa7dc:'\ua7dc', 0xa7f5:'\ua7f5', 0xfb00:'ff',
+0xfb01:'fi', 0xfb02:'fl', 0xfb03:'ffi', 0xfb04:'ffl',
+0xfb05:'st', 0xfb06:'st', 0xfb13:'\u0574\u0576', 0xfb14:'\u0574\u0565',
+0xfb15:'\u0574\u056b', 0xfb16:'\u057e\u0576', 0xfb17:'\u0574\u056d', 0x10426:'\U00010426',
+0x10427:'\U00010427', 0x104b0:'\U000104b0', 0x104b1:'\U000104b1', 0x104b2:'\U000104b2',
+0x104b3:'\U000104b3', 0x104b4:'\U000104b4', 0x104b5:'\U000104b5', 0x104b6:'\U000104b6',
+0x104b7:'\U000104b7', 0x104b8:'\U000104b8', 0x104b9:'\U000104b9', 0x104ba:'\U000104ba',
+0x104bb:'\U000104bb', 0x104bc:'\U000104bc', 0x104bd:'\U000104bd', 0x104be:'\U000104be',
+0x104bf:'\U000104bf', 0x104c0:'\U000104c0', 0x104c1:'\U000104c1', 0x104c2:'\U000104c2',
+0x104c3:'\U000104c3', 0x104c4:'\U000104c4', 0x104c5:'\U000104c5', 0x104c6:'\U000104c6',
+0x104c7:'\U000104c7', 0x104c8:'\U000104c8', 0x104c9:'\U000104c9', 0x104ca:'\U000104ca',
+0x104cb:'\U000104cb', 0x104cc:'\U000104cc', 0x104cd:'\U000104cd', 0x104ce:'\U000104ce',
+0x104cf:'\U000104cf', 0x104d0:'\U000104d0', 0x104d1:'\U000104d1', 0x104d2:'\U000104d2',
+0x104d3:'\U000104d3', 0x10570:'\U00010570', 0x10571:'\U00010571', 0x10572:'\U00010572',
+0x10573:'\U00010573', 0x10574:'\U00010574', 0x10575:'\U00010575', 0x10576:'\U00010576',
+0x10577:'\U00010577', 0x10578:'\U00010578', 0x10579:'\U00010579', 0x1057a:'\U0001057a',
+0x1057c:'\U0001057c', 0x1057d:'\U0001057d', 0x1057e:'\U0001057e', 0x1057f:'\U0001057f',
+0x10580:'\U00010580', 0x10581:'\U00010581', 0x10582:'\U00010582', 0x10583:'\U00010583',
+0x10584:'\U00010584', 0x10585:'\U00010585', 0x10586:'\U00010586', 0x10587:'\U00010587',
+0x10588:'\U00010588', 0x10589:'\U00010589', 0x1058a:'\U0001058a', 0x1058c:'\U0001058c',
+0x1058d:'\U0001058d', 0x1058e:'\U0001058e', 0x1058f:'\U0001058f', 0x10590:'\U00010590',
+0x10591:'\U00010591', 0x10592:'\U00010592', 0x10594:'\U00010594', 0x10595:'\U00010595',
+0x10c80:'\U00010c80', 0x10c81:'\U00010c81', 0x10c82:'\U00010c82', 0x10c83:'\U00010c83',
+0x10c84:'\U00010c84', 0x10c85:'\U00010c85', 0x10c86:'\U00010c86', 0x10c87:'\U00010c87',
+0x10c88:'\U00010c88', 0x10c89:'\U00010c89', 0x10c8a:'\U00010c8a', 0x10c8b:'\U00010c8b',
+0x10c8c:'\U00010c8c', 0x10c8d:'\U00010c8d', 0x10c8e:'\U00010c8e', 0x10c8f:'\U00010c8f',
+0x10c90:'\U00010c90', 0x10c91:'\U00010c91', 0x10c92:'\U00010c92', 0x10c93:'\U00010c93',
+0x10c94:'\U00010c94', 0x10c95:'\U00010c95', 0x10c96:'\U00010c96', 0x10c97:'\U00010c97',
+0x10c98:'\U00010c98', 0x10c99:'\U00010c99', 0x10c9a:'\U00010c9a', 0x10c9b:'\U00010c9b',
+0x10c9c:'\U00010c9c', 0x10c9d:'\U00010c9d', 0x10c9e:'\U00010c9e', 0x10c9f:'\U00010c9f',
+0x10ca0:'\U00010ca0', 0x10ca1:'\U00010ca1', 0x10ca2:'\U00010ca2', 0x10ca3:'\U00010ca3',
+0x10ca4:'\U00010ca4', 0x10ca5:'\U00010ca5', 0x10ca6:'\U00010ca6', 0x10ca7:'\U00010ca7',
+0x10ca8:'\U00010ca8', 0x10ca9:'\U00010ca9', 0x10caa:'\U00010caa', 0x10cab:'\U00010cab',
+0x10cac:'\U00010cac', 0x10cad:'\U00010cad', 0x10cae:'\U00010cae', 0x10caf:'\U00010caf',
+0x10cb0:'\U00010cb0', 0x10cb1:'\U00010cb1', 0x10cb2:'\U00010cb2', 0x10d50:'\U00010d50',
+0x10d51:'\U00010d51', 0x10d52:'\U00010d52', 0x10d53:'\U00010d53', 0x10d54:'\U00010d54',
+0x10d55:'\U00010d55', 0x10d56:'\U00010d56', 0x10d57:'\U00010d57', 0x10d58:'\U00010d58',
+0x10d59:'\U00010d59', 0x10d5a:'\U00010d5a', 0x10d5b:'\U00010d5b', 0x10d5c:'\U00010d5c',
+0x10d5d:'\U00010d5d', 0x10d5e:'\U00010d5e', 0x10d5f:'\U00010d5f', 0x10d60:'\U00010d60',
+0x10d61:'\U00010d61', 0x10d62:'\U00010d62', 0x10d63:'\U00010d63', 0x10d64:'\U00010d64',
+0x10d65:'\U00010d65', 0x118a0:'\U000118a0', 0x118a1:'\U000118a1', 0x118a2:'\U000118a2',
+0x118a3:'\U000118a3', 0x118a4:'\U000118a4', 0x118a5:'\U000118a5', 0x118a6:'\U000118a6',
+0x118a7:'\U000118a7', 0x118a8:'\U000118a8', 0x118a9:'\U000118a9', 0x118aa:'\U000118aa',
+0x118ab:'\U000118ab', 0x118ac:'\U000118ac', 0x118ad:'\U000118ad', 0x118ae:'\U000118ae',
+0x118af:'\U000118af', 0x118b0:'\U000118b0', 0x118b1:'\U000118b1', 0x118b2:'\U000118b2',
+0x118b3:'\U000118b3', 0x118b4:'\U000118b4', 0x118b5:'\U000118b5', 0x118b6:'\U000118b6',
+0x118b7:'\U000118b7', 0x118b8:'\U000118b8', 0x118b9:'\U000118b9', 0x118ba:'\U000118ba',
+0x118bb:'\U000118bb', 0x118bc:'\U000118bc', 0x118bd:'\U000118bd', 0x118be:'\U000118be',
+0x118bf:'\U000118bf', 0x16e40:'\U00016e40', 0x16e41:'\U00016e41', 0x16e42:'\U00016e42',
+0x16e43:'\U00016e43', 0x16e44:'\U00016e44', 0x16e45:'\U00016e45', 0x16e46:'\U00016e46',
+0x16e47:'\U00016e47', 0x16e48:'\U00016e48', 0x16e49:'\U00016e49', 0x16e4a:'\U00016e4a',
+0x16e4b:'\U00016e4b', 0x16e4c:'\U00016e4c', 0x16e4d:'\U00016e4d', 0x16e4e:'\U00016e4e',
+0x16e4f:'\U00016e4f', 0x16e50:'\U00016e50', 0x16e51:'\U00016e51', 0x16e52:'\U00016e52',
+0x16e53:'\U00016e53', 0x16e54:'\U00016e54', 0x16e55:'\U00016e55', 0x16e56:'\U00016e56',
+0x16e57:'\U00016e57', 0x16e58:'\U00016e58', 0x16e59:'\U00016e59', 0x16e5a:'\U00016e5a',
+0x16e5b:'\U00016e5b', 0x16e5c:'\U00016e5c', 0x16e5d:'\U00016e5d', 0x16e5e:'\U00016e5e',
+0x16e5f:'\U00016e5f', 0x16ea0:'\U00016ea0', 0x16ea1:'\U00016ea1', 0x16ea2:'\U00016ea2',
+0x16ea3:'\U00016ea3', 0x16ea4:'\U00016ea4', 0x16ea5:'\U00016ea5', 0x16ea6:'\U00016ea6',
+0x16ea7:'\U00016ea7', 0x16ea8:'\U00016ea8', 0x16ea9:'\U00016ea9', 0x16eaa:'\U00016eaa',
+0x16eab:'\U00016eab', 0x16eac:'\U00016eac', 0x16ead:'\U00016ead', 0x16eae:'\U00016eae',
+0x16eaf:'\U00016eaf', 0x16eb0:'\U00016eb0', 0x16eb1:'\U00016eb1', 0x16eb2:'\U00016eb2',
+0x16eb3:'\U00016eb3', 0x16eb4:'\U00016eb4', 0x16eb5:'\U00016eb5', 0x16eb6:'\U00016eb6',
+0x16eb7:'\U00016eb7', 0x16eb8:'\U00016eb8', 0x1d400:'a', 0x1d401:'b',
 0x1d402:'c', 0x1d403:'d', 0x1d404:'e', 0x1d405:'f',
 0x1d406:'g', 0x1d407:'h', 0x1d408:'i', 0x1d409:'j',
 0x1d40a:'k', 0x1d40b:'l', 0x1d40c:'m', 0x1d40d:'n',
@@ -184,7 +366,16 @@ def in_table_b1(code):
 0x1d79c:'\u03bd', 0x1d79d:'\u03be', 0x1d79e:'\u03bf', 0x1d79f:'\u03c0',
 0x1d7a0:'\u03c1', 0x1d7a1:'\u03b8', 0x1d7a2:'\u03c3', 0x1d7a3:'\u03c4',
 0x1d7a4:'\u03c5', 0x1d7a5:'\u03c6', 0x1d7a6:'\u03c7', 0x1d7a7:'\u03c8',
-0x1d7a8:'\u03c9', 0x1d7bb:'\u03c3', }
+0x1d7a8:'\u03c9', 0x1d7bb:'\u03c3', 0x1e900:'\U0001e900', 0x1e901:'\U0001e901',
+0x1e902:'\U0001e902', 0x1e903:'\U0001e903', 0x1e904:'\U0001e904', 0x1e905:'\U0001e905',
+0x1e906:'\U0001e906', 0x1e907:'\U0001e907', 0x1e908:'\U0001e908', 0x1e909:'\U0001e909',
+0x1e90a:'\U0001e90a', 0x1e90b:'\U0001e90b', 0x1e90c:'\U0001e90c', 0x1e90d:'\U0001e90d',
+0x1e90e:'\U0001e90e', 0x1e90f:'\U0001e90f', 0x1e910:'\U0001e910', 0x1e911:'\U0001e911',
+0x1e912:'\U0001e912', 0x1e913:'\U0001e913', 0x1e914:'\U0001e914', 0x1e915:'\U0001e915',
+0x1e916:'\U0001e916', 0x1e917:'\U0001e917', 0x1e918:'\U0001e918', 0x1e919:'\U0001e919',
+0x1e91a:'\U0001e91a', 0x1e91b:'\U0001e91b', 0x1e91c:'\U0001e91c', 0x1e91d:'\U0001e91d',
+0x1e91e:'\U0001e91e', 0x1e91f:'\U0001e91f', 0x1e920:'\U0001e920', 0x1e921:'\U0001e921',
+}
 
 def map_table_b3(code):
     r = b3_exceptions.get(ord(code))
@@ -194,9 +385,9 @@ def map_table_b3(code):
 
 def map_table_b2(a):
     al = map_table_b3(a)
-    b = unicodedata.normalize("NFKC", al)
+    b = unicodedata_320.normalize("NFKC", al)
     bl = "".join([map_table_b3(ch) for ch in b])
-    c = unicodedata.normalize("NFKC", bl)
+    c = unicodedata_320.normalize("NFKC", bl)
     if b != c:
         return c
     else:
@@ -208,29 +399,29 @@ def in_table_c11(code):
 
 
 def in_table_c12(code):
-    return unicodedata.category(code) == "Zs" and code != " "
+    return unicodedata_320.category(code) == "Zs" and code != " "
 
 def in_table_c11_c12(code):
-    return unicodedata.category(code) == "Zs"
+    return unicodedata_320.category(code) == "Zs"
 
 
 def in_table_c21(code):
-    return ord(code) < 128 and unicodedata.category(code) == "Cc"
+    return ord(code) < 128 and unicodedata_320.category(code) == "Cc"
 
 c22_specials = set([1757, 1807, 6158, 8204, 8205, 8232, 8233, 65279] + list(range(8288,8292)) + list(range(8298,8304)) + list(range(65529,65533)) + list(range(119155,119163)))
 def in_table_c22(code):
     c = ord(code)
     if c < 128: return False
-    if unicodedata.category(code) == "Cc": return True
+    if unicodedata_320.category(code) == "Cc": return True
     return c in c22_specials
 
 def in_table_c21_c22(code):
-    return unicodedata.category(code) == "Cc" or \
+    return unicodedata_320.category(code) == "Cc" or \
            ord(code) in c22_specials
 
 
 def in_table_c3(code):
-    return unicodedata.category(code) == "Co"
+    return unicodedata_320.category(code) == "Co"
 
 
 def in_table_c4(code):
@@ -241,7 +432,7 @@ def in_table_c4(code):
 
 
 def in_table_c5(code):
-    return unicodedata.category(code) == "Cs"
+    return unicodedata_320.category(code) == "Cs"
 
 
 c6_set = set(range(65529,65534))
@@ -265,8 +456,8 @@ def in_table_c9(code):
 
 
 def in_table_d1(code):
-    return unicodedata.bidirectional(code) in ("R","AL")
+    return unicodedata_320.bidirectional(code) in ("R","AL")
 
 
 def in_table_d2(code):
-    return unicodedata.bidirectional(code) == "L"
+    return unicodedata_320.bidirectional(code) == "L"
diff --git a/Lib/sysconfig/__init__.py b/Lib/sysconfig/__init__.py
index 029d5bcfcbe..be1a9ae3b1f 100644
--- a/Lib/sysconfig/__init__.py
+++ b/Lib/sysconfig/__init__.py
@@ -219,18 +219,7 @@ def _safe_realpath(path):
 if "_PYTHON_PROJECT_BASE" in os.environ:
     _PROJECT_BASE = _safe_realpath(os.environ["_PYTHON_PROJECT_BASE"])
 
-def is_python_build(check_home=None):
-    if check_home is not None:
-        import warnings
-        warnings.warn(
-            (
-                'The check_home argument of sysconfig.is_python_build is '
-                'deprecated and its value is ignored. '
-                'It will be removed in Python 3.15.'
-            ),
-            DeprecationWarning,
-            stacklevel=2,
-        )
+def is_python_build():
     for fn in ("Setup", "Setup.local"):
         if os.path.isfile(os.path.join(_PROJECT_BASE, "Modules", fn)):
             return True
@@ -423,7 +412,13 @@ def _init_non_posix(vars):
     vars['EXE'] = '.exe'
     vars['VERSION'] = _PY_VERSION_SHORT_NO_DOT
     vars['BINDIR'] = os.path.dirname(_safe_realpath(sys.executable))
-    vars['TZPATH'] = ''
+    # No standard path exists on Windows for this, but we'll check
+    # whether someone is imitating a POSIX-like layout
+    check_tzpath = os.path.join(vars['prefix'], 'share', 'zoneinfo')
+    if os.path.exists(check_tzpath):
+        vars['TZPATH'] = check_tzpath
+    else:
+        vars['TZPATH'] = ''
 
 #
 # public APIs
@@ -442,6 +437,7 @@ def parse_config_h(fp, vars=None):
     import re
     define_rx = re.compile("#define ([A-Z][A-Za-z0-9_]+) (.*)\n")
     undef_rx = re.compile("/[*] #undef ([A-Z][A-Za-z0-9_]+) [*]/\n")
+    quoted_re = re.compile('^"(.*)"$')
 
     while True:
         line = fp.readline()
@@ -450,6 +446,8 @@ def parse_config_h(fp, vars=None):
         m = define_rx.match(line)
         if m:
             n, v = m.group(1, 2)
+            if mq := quoted_re.match(v):
+                v = mq.group(1)
             try:
                 if n in _ALWAYS_STR:
                     raise ValueError
@@ -650,6 +648,9 @@ def get_platform():
     isn't particularly important.
 
     Examples of returned values:
+       linux-x86_64
+       linux-aarch64
+       solaris-2.6-sun4u
 
 
     Windows:
@@ -667,12 +668,10 @@ def get_platform():
 
     For other non-POSIX platforms, currently just returns :data:`sys.platform`."""
     if os.name == 'nt':
-        if 'amd64' in sys.version.lower():
-            return 'win-amd64'
-        if '(arm)' in sys.version.lower():
-            return 'win-arm32'
-        if '(arm64)' in sys.version.lower():
-            return 'win-arm64'
+        import _sysconfig
+        platform = _sysconfig.get_platform()
+        if platform:
+            return platform
         return sys.platform
 
     if os.name != "posix" or not hasattr(os, 'uname'):
diff --git a/Lib/sysconfig/__main__.py b/Lib/sysconfig/__main__.py
index bc2197cfe79..0cf0cf4dbb9 100644
--- a/Lib/sysconfig/__main__.py
+++ b/Lib/sysconfig/__main__.py
@@ -21,8 +21,9 @@
 # Regexes needed for parsing Makefile (and similar syntaxes,
 # like old-style Setup files).
 _variable_rx = r"([a-zA-Z][a-zA-Z0-9_]+)\s*=\s*(.*)"
-_findvar1_rx = r"\$\(([A-Za-z][A-Za-z0-9_]*)\)"
-_findvar2_rx = r"\${([A-Za-z][A-Za-z0-9_]*)}"
+_findvar_rx = (r"\$(\([A-Za-z][A-Za-z0-9_]*\)"
+                 r"|\{[A-Za-z][A-Za-z0-9_]*\}"
+                 r"|\$?)")
 
 
 def _parse_makefile(filename, vars=None, keep_unresolved=True):
@@ -49,26 +50,7 @@ def _parse_makefile(filename, vars=None, keep_unresolved=True):
         m = re.match(_variable_rx, line)
         if m:
             n, v = m.group(1, 2)
-            v = v.strip()
-            # `$$' is a literal `$' in make
-            tmpv = v.replace('$$', '')
-
-            if "$" in tmpv:
-                notdone[n] = v
-            else:
-                try:
-                    if n in _ALWAYS_STR:
-                        raise ValueError
-
-                    v = int(v)
-                except ValueError:
-                    # insert literal `$'
-                    done[n] = v.replace('$$', '$')
-                else:
-                    done[n] = v
-
-    # do variable interpolation here
-    variables = list(notdone.keys())
+            notdone[n] = v.strip()
 
     # Variables with a 'PY_' prefix in the makefile. These need to
     # be made available without that prefix through sysconfig.
@@ -76,72 +58,64 @@ def _parse_makefile(filename, vars=None, keep_unresolved=True):
     # if the expansion uses the name without a prefix.
     renamed_variables = ('CFLAGS', 'LDFLAGS', 'CPPFLAGS')
 
-    while len(variables) > 0:
-        for name in tuple(variables):
-            value = notdone[name]
-            m1 = re.search(_findvar1_rx, value)
-            m2 = re.search(_findvar2_rx, value)
-            if m1 and m2:
-                m = m1 if m1.start() < m2.start() else m2
-            else:
-                m = m1 if m1 else m2
-            if m is not None:
-                n = m.group(1)
-                found = True
-                if n in done:
-                    item = str(done[n])
-                elif n in notdone:
-                    # get it on a subsequent round
-                    found = False
-                elif n in os.environ:
-                    # do it like make: fall back to environment
-                    item = os.environ[n]
-
-                elif n in renamed_variables:
-                    if (name.startswith('PY_') and
-                        name[3:] in renamed_variables):
-                        item = ""
-
-                    elif 'PY_' + n in notdone:
-                        found = False
-
-                    else:
-                        item = str(done['PY_' + n])
-
+    def resolve_var(name):
+        def repl(m):
+            n = m[1]
+            if n == '$':
+                return '$'
+            elif n == '':
+                # bogus variable reference (e.g. "prefix=$/opt/python")
+                if keep_unresolved:
+                    return m[0]
+                raise ValueError
+            elif n[0] == '(' and n[-1] == ')':
+                n = n[1:-1]
+            elif n[0] == '{' and n[-1] == '}':
+                n = n[1:-1]
+
+            if n in done:
+                return str(done[n])
+            elif n in notdone:
+                return str(resolve_var(n))
+            elif n in os.environ:
+                # do it like make: fall back to environment
+                return os.environ[n]
+            elif n in renamed_variables:
+                if name.startswith('PY_') and name[3:] in renamed_variables:
+                    return ""
+                n = 'PY_' + n
+                if n in notdone:
+                    return str(resolve_var(n))
                 else:
-                    done[n] = item = ""
-
-                if found:
-                    after = value[m.end():]
-                    value = value[:m.start()] + item + after
-                    if "$" in after:
-                        notdone[name] = value
-                    else:
-                        try:
-                            if name in _ALWAYS_STR:
-                                raise ValueError
-                            value = int(value)
-                        except ValueError:
-                            done[name] = value.strip()
-                        else:
-                            done[name] = value
-                        variables.remove(name)
-
-                        if name.startswith('PY_') \
-                        and name[3:] in renamed_variables:
-
-                            name = name[3:]
-                            if name not in done:
-                                done[name] = value
-
+                    assert n not in done
+                    return ""
             else:
-                # Adds unresolved variables to the done dict.
-                # This is disabled when called from distutils.sysconfig
-                if keep_unresolved:
-                    done[name] = value
-                # bogus variable reference (e.g. "prefix=$/opt/python");
-                # just drop it since we can't deal
-                variables.remove(name)
+                done[n] = ""
+                return ""
+
+        assert name not in done
+        done[name] = ""
+        try:
+            value = re.sub(_findvar_rx, repl, notdone[name])
+        except ValueError:
+            del done[name]
+            return ""
+        value = value.strip()
+        if name not in _ALWAYS_STR:
+            try:
+                value = int(value)
+            except ValueError:
+                pass
+        done[name] = value
+        if name.startswith('PY_') and name[3:] in renamed_variables:
+            name = name[3:]
+            if name not in done:
+                done[name] = value
+        return value
+
+    for n in notdone:
+        if n not in done:
+            resolve_var(n)
 
     # strip spurious spaces
     for k, v in done.items():
diff --git a/Lib/tabnanny.py b/Lib/tabnanny.py
index c0097351b26..04c5baf7b52 100644
--- a/Lib/tabnanny.py
+++ b/Lib/tabnanny.py
@@ -16,8 +16,6 @@
 # XXX The API needs to undergo changes however; the current code is too
 # XXX script-like.  This will be addressed later.
 
-__version__ = "6"
-
 import os
 import sys
 import tokenize
@@ -49,7 +47,7 @@ def main():
         if o == '-v':
             verbose = verbose + 1
     if not args:
-        errprint("Usage:", sys.argv[0], "[-v] file_or_directory ...")
+        errprint(f"Usage: {sys.executable} -m tabnanny [-v] file_or_directory ...")
     for arg in args:
         check(arg)
 
@@ -334,5 +332,14 @@ def _process_tokens(tokens):
                 raise NannyNag(start[0], msg, line)
 
 
+def __getattr__(name):
+    if name == "__version__":
+        from warnings import _deprecated
+
+        _deprecated("__version__", remove=(3, 20))
+        return "6"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+
+
 if __name__ == '__main__':
     main()
diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index d3c48999700..e36e4c30300 100644
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -28,7 +28,6 @@
 """Read from and write to tar format archives.
 """
 
-version     = "0.9.0"
 __author__  = "Lars Gust\u00e4bel (lars@gustaebel.de)"
 __credits__ = "Gustavo Niemeyer, Niels Gust\u00e4bel, Richard Townsend."
 
@@ -201,7 +200,6 @@ def itn(n, digits=8, format=DEFAULT_FORMAT):
     # base-256 representation. This allows values up to (256**(digits-1))-1.
     # A 0o200 byte indicates a positive number, a 0o377 byte a negative
     # number.
-    original_n = n
     n = int(n)
     if 0 <= n < 8 ** (digits - 1):
         s = bytes("%0*o" % (digits - 1, n), "ascii") + NUL
@@ -365,7 +363,7 @@ class _Stream:
     """
 
     def __init__(self, name, mode, comptype, fileobj, bufsize,
-                 compresslevel, preset):
+                 compresslevel, preset, mtime):
         """Construct a _Stream object.
         """
         self._extfileobj = True
@@ -400,7 +398,7 @@ def __init__(self, name, mode, comptype, fileobj, bufsize,
                     self.exception = zlib.error
                     self._init_read_gz()
                 else:
-                    self._init_write_gz(compresslevel)
+                    self._init_write_gz(compresslevel, mtime)
 
             elif comptype == "bz2":
                 try:
@@ -408,7 +406,6 @@ def __init__(self, name, mode, comptype, fileobj, bufsize,
                 except ImportError:
                     raise CompressionError("bz2 module is not available") from None
                 if mode == "r":
-                    self.dbuf = b""
                     self.cmp = bz2.BZ2Decompressor()
                     self.exception = OSError
                 else:
@@ -420,7 +417,6 @@ def __init__(self, name, mode, comptype, fileobj, bufsize,
                 except ImportError:
                     raise CompressionError("lzma module is not available") from None
                 if mode == "r":
-                    self.dbuf = b""
                     self.cmp = lzma.LZMADecompressor()
                     self.exception = lzma.LZMAError
                 else:
@@ -431,7 +427,6 @@ def __init__(self, name, mode, comptype, fileobj, bufsize,
                 except ImportError:
                     raise CompressionError("compression.zstd module is not available") from None
                 if mode == "r":
-                    self.dbuf = b""
                     self.cmp = zstd.ZstdDecompressor()
                     self.exception = zstd.ZstdError
                 else:
@@ -449,7 +444,7 @@ def __del__(self):
         if hasattr(self, "closed") and not self.closed:
             self.close()
 
-    def _init_write_gz(self, compresslevel):
+    def _init_write_gz(self, compresslevel, mtime):
         """Initialize for writing with gzip compression.
         """
         self.cmp = self.zlib.compressobj(compresslevel,
@@ -457,7 +452,9 @@ def _init_write_gz(self, compresslevel):
                                          -self.zlib.MAX_WBITS,
                                          self.zlib.DEF_MEM_LEVEL,
                                          0)
-        timestamp = struct.pack("<L", int(time.time()))
+        if mtime is None:
+            mtime = int(time.time())
+        timestamp = struct.pack("<L", mtime)
         self.__write(b"\037\213\010\010" + timestamp + b"\002\377")
         if self.name.endswith(".gz"):
             self.name = self.name[:-3]
@@ -511,7 +508,6 @@ def _init_read_gz(self):
         """Initialize for reading a gzip compressed fileobj.
         """
         self.cmp = self.zlib.decompressobj(-self.zlib.MAX_WBITS)
-        self.dbuf = b""
 
         # taken from gzip.GzipFile with some alterations
         if self.__read(2) != b"\037\213":
@@ -571,26 +567,44 @@ def _read(self, size):
         if self.comptype == "tar":
             return self.__read(size)
 
-        c = len(self.dbuf)
-        t = [self.dbuf]
+        c = 0
+        t = []
         while c < size:
-            # Skip underlying buffer to avoid unaligned double buffering.
-            if self.buf:
-                buf = self.buf
-                self.buf = b""
+            if self.comptype == "gz":
+                # zlib interface is different than others.
+                # It returns data in unconsumed_tail.
+                if self.buf:
+                    cbuf = self.buf
+                    self.buf = b""
+                else:
+                    cbuf = self.fileobj.read(self.bufsize)
+                    if not cbuf:
+                        break
+
+                try:
+                    dbuf = self.cmp.decompress(cbuf, size - c)
+                    self.buf = self.cmp.unconsumed_tail
+                except self.exception as e:
+                    raise ReadError("invalid compressed data") from e
             else:
-                buf = self.fileobj.read(self.bufsize)
-                if not buf:
-                    break
-            try:
-                buf = self.cmp.decompress(buf)
-            except self.exception as e:
-                raise ReadError("invalid compressed data") from e
-            t.append(buf)
-            c += len(buf)
-        t = b"".join(t)
-        self.dbuf = t[size:]
-        return t[:size]
+                # Other decompressors have needs_input.
+                # decompress() can buffer data internally.
+                if self.cmp.needs_input:
+                    cbuf = self.fileobj.read(self.bufsize)
+                    if not cbuf:
+                        break
+                else:
+                    cbuf = b""
+
+                try:
+                    dbuf = self.cmp.decompress(cbuf, size - c)
+                except self.exception as e:
+                    raise ReadError("invalid compressed data") from e
+
+            t.append(dbuf)
+            c += len(dbuf)
+
+        return b"".join(t)
 
     def __read(self, size):
         """Return size bytes from stream. If internal buffer is empty,
@@ -819,6 +833,13 @@ def _get_filtered_attrs(member, dest_path, for_data=True):
         # For example, 'C:/foo' on Windows.
         raise AbsolutePathError(member)
     # Ensure we stay in the destination
+    if '..' in name.replace(os.sep, '/').split('/'):
+        # Directories are created from the name as given, so a name that
+        # leaves the destination part-way through would create them
+        # outside it even if the resolved path stays inside.
+        normalized = os.path.normpath(name)
+        if normalized != name:
+            name = new_attrs['name'] = normalized
     target_path = os.path.realpath(os.path.join(dest_path, name),
                                    strict=os.path.ALLOW_MISSING)
     if os.path.commonpath([target_path, dest_path]) != dest_path:
@@ -895,11 +916,11 @@ def data_filter(member, dest_path):
         return member.replace(**new_attrs, deep=False)
     return member
 
-_NAMED_FILTERS = {
+_NAMED_FILTERS = frozendict({
     "fully_trusted": fully_trusted_filter,
     "tar": tar_filter,
     "data": data_filter,
-}
+})
 
 #------------------
 # Exported Classes
@@ -1785,7 +1806,7 @@ class TarFile(object):
     def __init__(self, name=None, mode="r", fileobj=None, format=None,
             tarinfo=None, dereference=None, ignore_zeros=None, encoding=None,
             errors="surrogateescape", pax_headers=None, debug=None,
-            errorlevel=None, copybufsize=None, stream=False):
+            errorlevel=None, copybufsize=None, stream=False, mtime=None):
         """Open an (uncompressed) tar archive 'name'. 'mode' is either 'r' to
            read from an existing archive, 'a' to append data to an existing
            file or 'w' to create a new file overwriting an existing one. 'mode'
@@ -1989,10 +2010,11 @@ def not_compressed(comptype):
             if "preset" in kwargs and comptype not in ("xz",):
                 raise ValueError("preset is only valid for w|xz mode")
 
-            compresslevel = kwargs.pop("compresslevel", 9)
+            compresslevel = kwargs.pop("compresslevel", 6)
             preset = kwargs.pop("preset", None)
+            mtime = kwargs.pop("mtime", None)
             stream = _Stream(name, filemode, comptype, fileobj, bufsize,
-                             compresslevel, preset)
+                             compresslevel, preset, mtime)
             try:
                 t = cls(name, filemode, stream, **kwargs)
             except:
@@ -2015,7 +2037,7 @@ def taropen(cls, name, mode="r", fileobj=None, **kwargs):
         return cls(name, mode, fileobj, **kwargs)
 
     @classmethod
-    def gzopen(cls, name, mode="r", fileobj=None, compresslevel=9, **kwargs):
+    def gzopen(cls, name, mode="r", fileobj=None, compresslevel=6, **kwargs):
         """Open gzip compressed tar archive name for reading or writing.
            Appending is not allowed.
         """
@@ -2028,7 +2050,8 @@ def gzopen(cls, name, mode="r", fileobj=None, compresslevel=9, **kwargs):
             raise CompressionError("gzip module is not available") from None
 
         try:
-            fileobj = GzipFile(name, mode + "b", compresslevel, fileobj)
+            mtime = kwargs.pop("mtime", None)
+            fileobj = GzipFile(name, mode + "b", compresslevel, fileobj, mtime=mtime)
         except OSError as e:
             if fileobj is not None and mode == 'r':
                 raise ReadError("not a gzip file") from e
@@ -2259,7 +2282,7 @@ def gettarinfo(self, name=None, arcname=None, fileobj=None):
             type = FIFOTYPE
         elif stat.S_ISLNK(stmd):
             type = SYMTYPE
-            linkname = os.readlink(name)
+            linkname = os.readlink(name).replace(os.sep, "/")
         elif stat.S_ISCHR(stmd):
             type = CHRTYPE
         elif stat.S_ISBLK(stmd):
@@ -2782,7 +2805,13 @@ def makelink_with_filter(self, tarinfo, targetpath,
                 if os.path.lexists(targetpath):
                     # Avoid FileExistsError on following os.symlink.
                     os.unlink(targetpath)
-                os.symlink(tarinfo.linkname, targetpath)
+                link_target = tarinfo.linkname
+                if os.name == "nt":
+                    # gh-57911: Posix-flavoured forward-slash path separators in
+                    # symlink targets aren't acknowledged by Windows, resulting
+                    # in corrupted links.
+                    link_target = link_target.replace("/", os.path.sep)
+                os.symlink(link_target, targetpath)
                 return
             else:
                 if os.path.exists(tarinfo._link_target):
@@ -2811,9 +2840,11 @@ def makelink_with_filter(self, tarinfo, targetpath,
                     "makelink_with_filter: if filter_function is not None, "
                     + "extraction_root must also not be None")
             try:
-                filter_function(
+                filtered = filter_function(
                     unfiltered.replace(name=tarinfo.name, deep=False),
                     extraction_root)
+                if filtered is None:
+                    return
                 filtered = filter_function(unfiltered, extraction_root)
             except _FILTER_ERRORS as cause:
                 raise LinkFallbackError(tarinfo, unfiltered.name) from cause
@@ -3104,7 +3135,7 @@ def main():
     import argparse
 
     description = 'A simple command-line interface for tarfile module.'
-    parser = argparse.ArgumentParser(description=description, color=True)
+    parser = argparse.ArgumentParser(description=description)
     parser.add_argument('-v', '--verbose', action='store_true', default=False,
                         help='Verbose output')
     parser.add_argument('--filter', metavar='<filtername>',
@@ -3198,5 +3229,15 @@ def main():
         if args.verbose:
             print('{!r} file created.'.format(tar_name))
 
+
+def __getattr__(name):
+    if name == "version":
+        from warnings import _deprecated
+
+        _deprecated("version", remove=(3, 20))
+        return "0.9.0"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+
+
 if __name__ == '__main__':
     main()
diff --git a/Lib/tempfile.py b/Lib/tempfile.py
index 6c036d2fd51..d14c187a275 100644
--- a/Lib/tempfile.py
+++ b/Lib/tempfile.py
@@ -43,6 +43,7 @@
 import shutil as _shutil
 import errno as _errno
 from random import Random as _Random
+import stat as _stat
 import sys as _sys
 import types as _types
 import weakref as _weakref
@@ -273,15 +274,68 @@ def _dont_follow_symlinks(func, path, *args):
     elif not _os.path.islink(path):
         func(path, *args)
 
-def _resetperms(path):
+def _resetflags(path):
     try:
         chflags = _os.chflags
     except AttributeError:
         pass
     else:
         _dont_follow_symlinks(chflags, path, 0)
+
+def _resetperms(path):
+    _resetflags(path)
     _dont_follow_symlinks(_os.chmod, path, 0o700)
 
+# True if TemporaryDirectory._rmtree() can work relative to open directories
+# instead of resolving paths again.
+_rmtree_use_dir_fd = (
+    {_os.chmod, _os.unlink, _os.lstat} <= _os.supports_dir_fd
+    and _os.chmod in _os.supports_fd
+)
+
+def _resetperms_fd(dir_fd, path):
+    # Same as _resetperms(), but for the directory referred to by dir_fd.
+    if dir_fd is None:
+        _resetperms(path)
+        return
+    _resetflags(path)
+    _os.chmod(dir_fd, 0o700)
+
+try:
+    _nofollow_mode = _os.O_RDONLY | _os.O_NONBLOCK | _os.O_NOFOLLOW
+except AttributeError:
+    _nofollow_mode = None
+
+def _resetperms_at(name, dir_fd, path):
+    # Same as _resetperms(), but name is resolved relative to the directory
+    # file descriptor dir_fd. path is only used for os.chflags(), which
+    # doesn't support dir_fd or file descriptors.
+    if dir_fd is None:
+        _resetperms(path)
+        return
+    _resetflags(path)
+    if _os.chmod in _os.supports_follow_symlinks:
+        _os.chmod(name, 0o700, dir_fd=dir_fd, follow_symlinks=False)
+    else:
+        # dir_fd & follow_symlinks is not supported on this platform.
+        # Try chmod opening the file with O_NOFOLLOW.
+        if _nofollow_mode is not None:
+            try:
+                fd = _os.open(name, _nofollow_mode, dir_fd=dir_fd)
+            except OSError:
+                pass
+            else:
+                try:
+                    _os.chmod(fd, 0o700)
+                finally:
+                    _os.close(fd)
+                return
+        # If that did not work, we change by name, which is subject to a race
+        # condition.
+        stat = _os.lstat(name, dir_fd=dir_fd)
+        if not _stat.S_ISLNK(stat.st_mode):
+            _os.chmod(name, 0o700, dir_fd=dir_fd)
+
 
 # User visible interfaces.
 
@@ -656,7 +710,7 @@ def TemporaryFile(mode='w+b', buffering=-1, encoding=None,
             fd = None
             def opener(*args):
                 nonlocal fd
-                flags2 = (flags | _os.O_TMPFILE) & ~_os.O_CREAT
+                flags2 = (flags | _os.O_TMPFILE) & ~_os.O_CREAT & ~_os.O_EXCL
                 fd = _os.open(dir, flags2, 0o600)
                 return fd
             try:
@@ -691,7 +745,7 @@ def opener(*args):
             fd, name = _mkstemp_inner(dir, prefix, suffix, flags, output_type)
             try:
                 _os.unlink(name)
-            except BaseException as e:
+            except BaseException:
                 _os.close(fd)
                 raise
             return fd
@@ -913,8 +967,12 @@ def __init__(self, suffix=None, prefix=None, dir=None,
             ignore_errors=self._ignore_cleanup_errors, delete=self._delete)
 
     @classmethod
-    def _rmtree(cls, name, ignore_errors=False, repeated=False):
-        def onexc(func, path, exc):
+    def _rmtree(cls, name, ignore_errors=False, repeated=False, dir_fd=None,
+                fullname=None):
+        if fullname is None:
+            fullname = name
+
+        def onexc(func, path, exc, direntry=None, dir_fd=None):
             # On DragonFly BSD, UF_NOUNLINK removal fails with EISDIR, not EPERM.
             if isinstance(exc, (PermissionError, IsADirectoryError)):
                 if repeated and path == name:
@@ -922,15 +980,30 @@ def onexc(func, path, exc):
                         return
                     raise
 
+                # fullpath is path as seen from the working directory
+                fullpath = fullname + path[len(name):]
+                # base is path relative to dir_fd, the directory rmtree()
+                # reached it through, or the whole path when there is none
+                if dir_fd is None or not _rmtree_use_dir_fd:
+                    base, dir_fd = path, None
+                elif direntry is None:
+                    base = path
+                else:
+                    base = direntry.name
+
                 try:
                     if path != name:
-                        _resetperms(_os.path.dirname(path))
-                    _resetperms(path)
+                        # The parent directory of path is the one referred to
+                        # by dir_fd.
+                        _resetperms_fd(dir_fd, _os.path.dirname(fullpath))
+                    _resetperms_at(base, dir_fd, fullpath)
 
                     try:
-                        _os.unlink(path)
+                        _os.unlink(base, dir_fd=dir_fd)
                     except IsADirectoryError:
-                        cls._rmtree(path, ignore_errors=ignore_errors)
+                        cls._rmtree(base, ignore_errors=ignore_errors,
+                                    repeated=(path == name),
+                                    dir_fd=dir_fd, fullname=fullpath)
                     except PermissionError:
                         # The PermissionError handler was originally added for
                         # FreeBSD in directories, but it seems that it is raised
@@ -939,21 +1012,27 @@ def onexc(func, path, exc):
                         # raise NotADirectoryError and mask the PermissionError.
                         # So we must re-raise the current PermissionError if
                         # path is not a directory.
-                        if not _os.path.isdir(path) or _os.path.isjunction(path):
+                        if (not _os.path.isdir(fullpath)
+                                or _os.path.isjunction(fullpath)):
                             if ignore_errors:
                                 return
                             raise
-                        cls._rmtree(path, ignore_errors=ignore_errors,
-                                    repeated=(path == name))
+                        cls._rmtree(base, ignore_errors=ignore_errors,
+                                    repeated=(path == name),
+                                    dir_fd=dir_fd, fullname=fullpath)
                 except FileNotFoundError:
                     pass
+                except OSError:
+                    if ignore_errors:
+                        return
+                    raise
             elif isinstance(exc, FileNotFoundError):
                 pass
             else:
                 if not ignore_errors:
                     raise
 
-        _shutil.rmtree(name, onexc=onexc)
+        _shutil.rmtree(name, onexc=onexc, dir_fd=dir_fd, _onexc_kwargs=True)
 
     @classmethod
     def _cleanup(cls, name, warn_message, ignore_errors=False, delete=True):
diff --git a/Lib/test/_test_monitoring_shutdown.py b/Lib/test/_test_monitoring_shutdown.py
new file mode 100644
index 00000000000..3d0fbec029d
--- /dev/null
+++ b/Lib/test/_test_monitoring_shutdown.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+
+# gh-115832: An object destructor running during the final GC of interpreter
+# shutdown triggered an infinite loop in the instrumentation code.
+
+import sys
+
+class CallableCycle:
+    def __init__(self):
+        self._cycle = self
+
+    def __del__(self):
+        pass
+
+    def __call__(self, code, instruction_offset):
+        pass
+
+def tracefunc(frame, event, arg):
+    pass
+
+def main():
+    tool_id = sys.monitoring.PROFILER_ID
+    event_id = sys.monitoring.events.PY_START
+
+    sys.monitoring.use_tool_id(tool_id, "test profiler")
+    sys.monitoring.set_events(tool_id, event_id)
+    sys.monitoring.register_callback(tool_id, event_id, CallableCycle())
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/Lib/test/audiodata/pluck-float32.wav b/Lib/test/audiodata/pluck-float32.wav
new file mode 100644
index 00000000000..2030fb16d6e
Binary files /dev/null and b/Lib/test/audiodata/pluck-float32.wav differ
diff --git a/Lib/test/audiotests.py b/Lib/test/audiotests.py
index 9d6c4cc2b4b..394097df17d 100644
--- a/Lib/test/audiotests.py
+++ b/Lib/test/audiotests.py
@@ -27,17 +27,18 @@ def tearDown(self):
         unlink(TESTFN)
 
     def check_params(self, f, nchannels, sampwidth, framerate, nframes,
-                     comptype, compname):
+                     comptype, compname, format):
         self.assertEqual(f.getnchannels(), nchannels)
         self.assertEqual(f.getsampwidth(), sampwidth)
         self.assertEqual(f.getframerate(), framerate)
         self.assertEqual(f.getnframes(), nframes)
         self.assertEqual(f.getcomptype(), comptype)
         self.assertEqual(f.getcompname(), compname)
+        self.assertEqual(f.getformat(), format)
 
         params = f.getparams()
         self.assertEqual(params,
-                (nchannels, sampwidth, framerate, nframes, comptype, compname))
+            (nchannels, sampwidth, framerate, nframes, comptype, compname))
         self.assertEqual(params.nchannels, nchannels)
         self.assertEqual(params.sampwidth, sampwidth)
         self.assertEqual(params.framerate, framerate)
@@ -51,13 +52,17 @@ def check_params(self, f, nchannels, sampwidth, framerate, nframes,
 
 
 class AudioWriteTests(AudioTests):
+    readonly = False
 
     def create_file(self, testfile):
+        if self.readonly:
+            self.skipTest('Read only file format')
         f = self.fout = self.module.open(testfile, 'wb')
         f.setnchannels(self.nchannels)
         f.setsampwidth(self.sampwidth)
         f.setframerate(self.framerate)
         f.setcomptype(self.comptype, self.compname)
+        f.setformat(self.format)
         return f
 
     def check_file(self, testfile, nframes, frames):
@@ -67,13 +72,14 @@ def check_file(self, testfile, nframes, frames):
             self.assertEqual(f.getframerate(), self.framerate)
             self.assertEqual(f.getnframes(), nframes)
             self.assertEqual(f.readframes(nframes), frames)
+            self.assertEqual(f.getformat(), self.format)
 
     def test_write_params(self):
         f = self.create_file(TESTFN)
         f.setnframes(self.nframes)
         f.writeframes(self.frames)
         self.check_params(f, self.nchannels, self.sampwidth, self.framerate,
-                          self.nframes, self.comptype, self.compname)
+                          self.nframes, self.comptype, self.compname, self.format)
         f.close()
 
     def test_write_context_manager_calls_close(self):
@@ -257,7 +263,7 @@ def test_read_params(self):
         f = self.f = self.module.open(self.sndfilepath)
         #self.assertEqual(f.getfp().name, self.sndfilepath)
         self.check_params(f, self.nchannels, self.sampwidth, self.framerate,
-                          self.sndfilenframes, self.comptype, self.compname)
+                          self.sndfilenframes, self.comptype, self.compname, self.format)
 
     def test_close(self):
         with open(self.sndfilepath, 'rb') as testfile:
@@ -298,6 +304,8 @@ def test_read(self):
             f.setpos(f.getnframes() + 1)
 
     def test_copy(self):
+        if self.readonly:
+            self.skipTest('Read only file format')
         f = self.f = self.module.open(self.sndfilepath)
         fout = self.fout = self.module.open(TESTFN, 'wb')
         fout.setparams(f.getparams())
diff --git a/Lib/test/audit-tests.py b/Lib/test/audit-tests.py
index 6884ac0dbe6..8be5bf8aa4f 100644
--- a/Lib/test/audit-tests.py
+++ b/Lib/test/audit-tests.py
@@ -8,6 +8,8 @@
 import contextlib
 import os
 import sys
+import unittest.mock
+from test.support import swap_item
 
 
 class TestHook:
@@ -206,6 +208,16 @@ def rl(name):
         else:
             return None
 
+    try:
+        import _remote_debugging
+    except ImportError:
+        _remote_debugging = None
+
+    def rd(name):
+        if _remote_debugging:
+            return getattr(_remote_debugging, name, None)
+        return None
+
     # Try a range of "open" functions.
     # All of them should fail
     with TestHook(raise_on_events={"open"}) as hook:
@@ -223,6 +235,8 @@ def rl(name):
             (rl("append_history_file"), 0, None),
             (rl("read_init_file"), testfn),
             (rl("read_init_file"), None),
+            (rd("BinaryWriter"), testfn, 1000, 0),
+            (rd("BinaryReader"), testfn),
         ]:
             if not fn:
                 continue
@@ -256,6 +270,8 @@ def rl(name):
                 ("~/.history", "a") if rl("append_history_file") else None,
                 (testfn, "r") if readline else None,
                 ("<readline_init_file>", "r") if readline else None,
+                (testfn, "wb") if rd("BinaryWriter") else None,
+                (testfn, "rb") if rd("BinaryReader") else None,
             ]
             if i is not None
         ],
@@ -672,6 +688,84 @@ def hook(event, args):
         assertEqual(event_script_path, tmp_file.name)
         assertEqual(remote_event_script_path, tmp_file.name)
 
+def test_import_module():
+    import importlib
+
+    with TestHook() as hook:
+        importlib.import_module("importlib")  # already imported, won't get logged
+        importlib.import_module("email") # standard library module
+        importlib.import_module("pythoninfo")  # random module
+        importlib.import_module(".audit_test_data.submodule", "test")  # relative import
+        importlib.import_module("test.audit_test_data.submodule2")  # absolute import
+        importlib.import_module("_testcapi")  # extension module
+
+    actual = [a for e, a in hook.seen if e == "import"]
+    assertSequenceEqual(
+        [
+            ("email", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("pythoninfo", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data.submodule", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data.submodule2", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("_testcapi", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("_testcapi", unittest.mock.ANY, None, None, None)
+        ],
+        actual,
+    )
+
+def test_builtin__import__():
+    import importlib # noqa: F401
+
+    with TestHook() as hook:
+        __import__("importlib")
+        __import__("email")
+        __import__("pythoninfo")
+        __import__("audit_test_data.submodule", level=1, globals={"__package__": "test"})
+        __import__("test.audit_test_data.submodule2")
+        __import__("_testcapi")
+
+    actual = [a for e, a in hook.seen if e == "import"]
+    assertSequenceEqual(
+        [
+            ("email", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("pythoninfo", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data.submodule", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data.submodule2", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("_testcapi", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("_testcapi", unittest.mock.ANY, None, None, None)
+        ],
+        actual,
+    )
+
+def test_import_statement():
+    import importlib # noqa: F401
+    # Set __package__ so relative imports work
+    with swap_item(globals(), "__package__", "test"):
+        with TestHook() as hook:
+            import importlib # noqa: F401
+            import email # noqa: F401
+            import pythoninfo # noqa: F401
+            from .audit_test_data import submodule # noqa: F401
+            import test.audit_test_data.submodule2 # noqa: F401
+            import _testcapi # noqa: F401
+
+    actual = [a for e, a in hook.seen if e == "import"]
+    # Import statement ordering is different because the package is
+    # loaded first and then the submodule
+    assertSequenceEqual(
+        [
+            ("email", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("pythoninfo", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data.submodule", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("test.audit_test_data.submodule2", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("_testcapi", None, sys.path, sys.meta_path, sys.path_hooks),
+            ("_testcapi", unittest.mock.ANY, None, None, None)
+        ],
+        actual,
+    )
+
 if __name__ == "__main__":
     from test.support import suppress_msvcrt_asserts
 
diff --git a/Lib/test/test_importlib/data/__init__.py b/Lib/test/audit_test_data/__init__.py
similarity index 100%
rename from Lib/test/test_importlib/data/__init__.py
rename to Lib/test/audit_test_data/__init__.py
diff --git a/Lib/test/test_importlib/resources/data01/__init__.py b/Lib/test/audit_test_data/submodule.py
similarity index 100%
rename from Lib/test/test_importlib/resources/data01/__init__.py
rename to Lib/test/audit_test_data/submodule.py
diff --git a/Lib/test/test_importlib/resources/data01/subdirectory/__init__.py b/Lib/test/audit_test_data/submodule2.py
similarity index 100%
rename from Lib/test/test_importlib/resources/data01/subdirectory/__init__.py
rename to Lib/test/audit_test_data/submodule2.py
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 1b71b71c544..c11e9c068be 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -3,6 +3,7 @@
 import contextlib
 import copy
 import decimal
+import fractions
 import io
 import itertools
 import os
@@ -21,7 +22,7 @@
 
 from test import support
 from test.support import is_resource_enabled, ALWAYS_EQ, LARGEST, SMALLEST
-from test.support import os_helper, script_helper, warnings_helper
+from test.support import os_helper, script_helper
 
 import datetime as datetime_module
 from datetime import MINYEAR, MAXYEAR
@@ -1205,15 +1206,20 @@ def test_strptime_single_digit(self):
                 newdate = strptime(string, format)
                 self.assertEqual(newdate, target, msg=reason)
 
-    @warnings_helper.ignore_warnings(category=DeprecationWarning)
     def test_strptime_leap_year(self):
-        # GH-70647: warns if parsing a format with a day and no year.
+        # GH-70647: %d errors if parsing a format with a day and no year.
         with self.assertRaises(ValueError):
             # The existing behavior that GH-70647 seeks to change.
             date.strptime('02-29', '%m-%d')
+        # %e without a year is deprecated, scheduled for removal in 3.17.
+        _strptime._regex_cache.clear()
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'.*day of month without a year.*'):
+            date.strptime('02-01', '%m-%e')
         with self._assertNotWarns(DeprecationWarning):
             date.strptime('20-03-14', '%y-%m-%d')
             date.strptime('02-29,2024', '%m-%d,%Y')
+            date.strptime('02-29,2024', '%m-%e,%Y')
 
 class SubclassDate(date):
     sub_var = 1
@@ -2157,14 +2163,20 @@ def test_fromisocalendar_value_errors(self):
             (10000, 1, 1),
             (0, 1, 1),
             (9999999, 1, 1),
+        ]
+        for isocal in isocals:
+            with self.subTest(isocal=isocal):
+                with self.assertRaises(ValueError):
+                    self.theclass.fromisocalendar(*isocal)
+
+        isocals = [
             (2<<32, 1, 1),
             (2019, 2<<32, 1),
             (2019, 1, 2<<32),
         ]
-
         for isocal in isocals:
             with self.subTest(isocal=isocal):
-                with self.assertRaises(ValueError):
+                with self.assertRaises((ValueError, OverflowError)):
                     self.theclass.fromisocalendar(*isocal)
 
     def test_fromisocalendar_type_errors(self):
@@ -2190,6 +2202,34 @@ def test_fromisocalendar_type_errors(self):
                 with self.assertRaises(TypeError):
                     self.theclass.fromisocalendar(*isocal)
 
+    def test_strptime_F_format(self):
+        test_date = "2025-10-26"
+        self.assertEqual(
+            self.theclass.strptime(test_date, "%F"),
+            self.theclass.strptime(test_date, "%Y-%m-%d")
+        )
+
+    def test_strptime_D_format(self):
+        test_date = "11/28/25"
+        self.assertEqual(
+            self.theclass.strptime(test_date, "%D"),
+            self.theclass.strptime(test_date, "%m/%d/%y")
+        )
+
+    def test_strptime_n_and_t_format(self):
+        format_directives = ('%n', '%t', '%n%t', '%t%n')
+        whitespaces = ('', ' ', '\t', '\r', '\v', '\n', '\f')
+        for fd in format_directives:
+            for ws in (*whitespaces, ''.join(whitespaces)):
+                with self.subTest(format_directive=fd, whitespace=ws):
+                    self.assertEqual(
+                        self.theclass.strptime(
+                            f"2026{ws}02{ws}03",
+                            f"%Y{fd}%m{fd}%d",
+                        ),
+                        self.theclass(2026, 2, 3),
+                    )
+
 
 #############################################################################
 # datetime tests
@@ -2311,7 +2351,7 @@ def test_isoformat_timezone(self):
             dt = dt_base.replace(tzinfo=tzi)
             exp = exp_base + exp_tz
             with self.subTest(tzi=tzi):
-                assert dt.isoformat() == exp
+                self.assertEqual(dt.isoformat(), exp)
 
     def test_format(self):
         dt = self.theclass(2007, 9, 10, 4, 5, 1, 123)
@@ -2624,6 +2664,10 @@ def test_fromtimestamp(self):
         expected = time.localtime(ts)
         got = self.theclass.fromtimestamp(ts)
         self.verify_field_equality(expected, got)
+        got = self.theclass.fromtimestamp(decimal.Decimal(ts))
+        self.verify_field_equality(expected, got)
+        got = self.theclass.fromtimestamp(fractions.Fraction(ts))
+        self.verify_field_equality(expected, got)
 
     def test_fromtimestamp_keyword_arg(self):
         import time
@@ -2639,6 +2683,12 @@ def test_utcfromtimestamp(self):
         with self.assertWarns(DeprecationWarning):
             got = self.theclass.utcfromtimestamp(ts)
         self.verify_field_equality(expected, got)
+        with self.assertWarns(DeprecationWarning):
+            got = self.theclass.utcfromtimestamp(decimal.Decimal(ts))
+        self.verify_field_equality(expected, got)
+        with self.assertWarns(DeprecationWarning):
+            got = self.theclass.utcfromtimestamp(fractions.Fraction(ts))
+        self.verify_field_equality(expected, got)
 
     # Run with US-style DST rules: DST begins 2 a.m. on second Sunday in
     # March (M3.2.0) and ends 2 a.m. on first Sunday in November (M11.1.0).
@@ -2693,24 +2743,20 @@ def utcfromtimestamp(*args, **kwargs):
             self.assertEqual(zero.second, 0)
             self.assertEqual(zero.microsecond, 0)
             one = fts(1e-6)
-            try:
-                minus_one = fts(-1e-6)
-            except OSError:
-                # localtime(-1) and gmtime(-1) is not supported on Windows
-                pass
-            else:
-                self.assertEqual(minus_one.second, 59)
-                self.assertEqual(minus_one.microsecond, 999999)
-
-                t = fts(-1e-8)
-                self.assertEqual(t, zero)
-                t = fts(-9e-7)
-                self.assertEqual(t, minus_one)
-                t = fts(-1e-7)
-                self.assertEqual(t, zero)
-                t = fts(-1/2**7)
-                self.assertEqual(t.second, 59)
-                self.assertEqual(t.microsecond, 992188)
+            minus_one = fts(-1e-6)
+
+            self.assertEqual(minus_one.second, 59)
+            self.assertEqual(minus_one.microsecond, 999999)
+
+            t = fts(-1e-8)
+            self.assertEqual(t, zero)
+            t = fts(-9e-7)
+            self.assertEqual(t, minus_one)
+            t = fts(-1e-7)
+            self.assertEqual(t, zero)
+            t = fts(-1/2**7)
+            self.assertEqual(t.second, 59)
+            self.assertEqual(t.microsecond, 992188)
 
             t = fts(1e-7)
             self.assertEqual(t, zero)
@@ -2726,6 +2772,100 @@ def utcfromtimestamp(*args, **kwargs):
             self.assertEqual(t.second, 0)
             self.assertEqual(t.microsecond, 7812)
 
+    @support.run_with_tz('MSK-03')  # Something east of Greenwich
+    def test_microsecond_rounding_decimal(self):
+        D = decimal.Decimal
+        def utcfromtimestamp(*args, **kwargs):
+            with self.assertWarns(DeprecationWarning):
+                return self.theclass.utcfromtimestamp(*args, **kwargs)
+
+        for fts in [self.theclass.fromtimestamp,
+                    utcfromtimestamp]:
+            zero = fts(D(0))
+            self.assertEqual(zero.second, 0)
+            self.assertEqual(zero.microsecond, 0)
+            one = fts(D('0.000_001'))
+            minus_one = fts(D('-0.000_001'))
+
+            self.assertEqual(minus_one.second, 59)
+            self.assertEqual(minus_one.microsecond, 999_999)
+
+            t = fts(D('-0.000_000_1'))
+            self.assertEqual(t, zero)
+            t = fts(D('-0.000_000_9'))
+            self.assertEqual(t, minus_one)
+            t = fts(D(-1)/2**7)
+            self.assertEqual(t.second, 59)
+            self.assertEqual(t.microsecond, 992188)
+
+            t = fts(D('0.000_000_1'))
+            self.assertEqual(t, zero)
+            t = fts(D('0.000_000_5'))
+            self.assertEqual(t, zero)
+            t = fts(D('0.000_000_500_000_000_000_000_1'))
+            self.assertEqual(t, one)
+            t = fts(D('0.000_000_9'))
+            self.assertEqual(t, one)
+            t = fts(D('0.999_999_499_999_999_9'))
+            self.assertEqual(t.second, 0)
+            self.assertEqual(t.microsecond, 999_999)
+            t = fts(D('0.999_999_5'))
+            self.assertEqual(t.second, 1)
+            self.assertEqual(t.microsecond, 0)
+            t = fts(D('0.999_999_9'))
+            self.assertEqual(t.second, 1)
+            self.assertEqual(t.microsecond, 0)
+            t = fts(D(1)/2**7)
+            self.assertEqual(t.second, 0)
+            self.assertEqual(t.microsecond, 7812)
+
+    @support.run_with_tz('MSK-03')  # Something east of Greenwich
+    def test_microsecond_rounding_fraction(self):
+        F = fractions.Fraction
+        def utcfromtimestamp(*args, **kwargs):
+            with self.assertWarns(DeprecationWarning):
+                return self.theclass.utcfromtimestamp(*args, **kwargs)
+
+        for fts in [self.theclass.fromtimestamp,
+                    utcfromtimestamp]:
+            zero = fts(F(0))
+            self.assertEqual(zero.second, 0)
+            self.assertEqual(zero.microsecond, 0)
+            one = fts(F(1, 1_000_000))
+            minus_one = fts(F(-1, 1_000_000))
+
+            self.assertEqual(minus_one.second, 59)
+            self.assertEqual(minus_one.microsecond, 999_999)
+
+            t = fts(F(-1, 10_000_000))
+            self.assertEqual(t, zero)
+            t = fts(F(-9, 10_000_000))
+            self.assertEqual(t, minus_one)
+            t = fts(F(-1, 2**7))
+            self.assertEqual(t.second, 59)
+            self.assertEqual(t.microsecond, 992188)
+
+            t = fts(F(1, 10_000_000))
+            self.assertEqual(t, zero)
+            t = fts(F(5, 10_000_000))
+            self.assertEqual(t, zero)
+            t = fts(F(5_000_000_000, 9_999_999_999_999_999))
+            self.assertEqual(t, one)
+            t = fts(F(9, 10_000_000))
+            self.assertEqual(t, one)
+            t = fts(F(9_999_995_000_000_000, 10_000_000_000_000_001))
+            self.assertEqual(t.second, 0)
+            self.assertEqual(t.microsecond, 999_999)
+            t = fts(F(9_999_995, 10_000_000))
+            self.assertEqual(t.second, 1)
+            self.assertEqual(t.microsecond, 0)
+            t = fts(F(9_999_999, 10_000_000))
+            self.assertEqual(t.second, 1)
+            self.assertEqual(t.microsecond, 0)
+            t = fts(F(1, 2**7))
+            self.assertEqual(t.second, 0)
+            self.assertEqual(t.microsecond, 7812)
+
     def test_timestamp_limits(self):
         with self.subTest("minimum UTC"):
             min_dt = self.theclass.min.replace(tzinfo=timezone.utc)
@@ -2745,6 +2885,7 @@ def test_timestamp_limits(self):
             # If that assumption changes, this value can change as well
             self.assertEqual(max_ts, 253402300799.0)
 
+    @unittest.skipIf(sys.platform == "win32", "Windows doesn't support min timestamp")
     def test_fromtimestamp_limits(self):
         try:
             self.theclass.fromtimestamp(-2**32 - 1)
@@ -2784,6 +2925,7 @@ def test_fromtimestamp_limits(self):
                     # OverflowError, especially on 32-bit platforms.
                     self.theclass.fromtimestamp(ts)
 
+    @unittest.skipIf(sys.platform == "win32", "Windows doesn't support min timestamp")
     def test_utcfromtimestamp_limits(self):
         with self.assertWarns(DeprecationWarning):
             try:
@@ -2845,13 +2987,11 @@ def test_insane_utcfromtimestamp(self):
                 self.assertRaises(OverflowError, self.theclass.utcfromtimestamp,
                                   insane)
 
-    @unittest.skipIf(sys.platform == "win32", "Windows doesn't accept negative timestamps")
     def test_negative_float_fromtimestamp(self):
         # The result is tz-dependent; at least test that this doesn't
         # fail (like it did before bug 1646728 was fixed).
         self.theclass.fromtimestamp(-1.05)
 
-    @unittest.skipIf(sys.platform == "win32", "Windows doesn't accept negative timestamps")
     def test_negative_float_utcfromtimestamp(self):
         with self.assertWarns(DeprecationWarning):
             d = self.theclass.utcfromtimestamp(-1.05)
@@ -2905,6 +3045,12 @@ def test_strptime(self):
             strptime("-00:02:01.000003", "%z").utcoffset(),
             -timedelta(minutes=2, seconds=1, microseconds=3)
         )
+        self.assertEqual(strptime("+01:07", "%:z").utcoffset(),
+                         1 * HOUR + 7 * MINUTE)
+        self.assertEqual(strptime("-10:02", "%:z").utcoffset(),
+                         -(10 * HOUR + 2 * MINUTE))
+        self.assertEqual(strptime("-00:00:01.00001", "%:z").utcoffset(),
+                         -timedelta(seconds=1, microseconds=10))
         # Only local timezone and UTC are supported
         for tzseconds, tzname in ((0, 'UTC'), (0, 'GMT'),
                                  (-_time.timezone, _time.tzname[0])):
@@ -2934,6 +3080,16 @@ def test_strptime(self):
         with self.assertRaises(ValueError): strptime("-000", "%z")
         with self.assertRaises(ValueError): strptime("z", "%z")
 
+    def test_strptime_ampm(self):
+        dt = datetime(1999, 3, 17, 0, 44, 55, 2)
+        for hour in range(0, 24):
+            with self.subTest(hour=hour):
+                new_dt = dt.replace(hour=hour)
+                dt_str = new_dt.strftime("%I %p")
+
+                self.assertEqual(self.theclass.strptime(dt_str, "%I %p").hour,
+                                 hour)
+
     def test_strptime_single_digit(self):
         # bpo-34903: Check that single digit dates and times are allowed.
 
@@ -2968,19 +3124,35 @@ def test_strptime_single_digit(self):
                 newdate = strptime(string, format)
                 self.assertEqual(newdate, target, msg=reason)
 
-    @warnings_helper.ignore_warnings(category=DeprecationWarning)
     def test_strptime_leap_year(self):
-        # GH-70647: warns if parsing a format with a day and no year.
+        # GH-70647: %d errors if parsing a format with a day and no year.
         with self.assertRaises(ValueError):
             # The existing behavior that GH-70647 seeks to change.
             self.theclass.strptime('02-29', '%m-%d')
+        with self.assertRaises(ValueError):
+            self.theclass.strptime('03-14.159265', '%m-%d.%f')
+        # %e without a year is deprecated, scheduled for removal in 3.17.
+        _strptime._regex_cache.clear()
         with self.assertWarnsRegex(DeprecationWarning,
                                    r'.*day of month without a year.*'):
-            self.theclass.strptime('03-14.159265', '%m-%d.%f')
+            self.theclass.strptime('03-14.159265', '%m-%e.%f')
         with self._assertNotWarns(DeprecationWarning):
             self.theclass.strptime('20-03-14.159265', '%y-%m-%d.%f')
         with self._assertNotWarns(DeprecationWarning):
             self.theclass.strptime('02-29,2024', '%m-%d,%Y')
+        with self._assertNotWarns(DeprecationWarning):
+            self.theclass.strptime('02-29,2024', '%m-%e,%Y')
+
+    def test_strptime_z_empty(self):
+        for directive in ('z', ':z'):
+            string = '2025-04-25 11:42:47'
+            format = f'%Y-%m-%d %H:%M:%S%{directive}'
+            target = self.theclass(2025, 4, 25, 11, 42, 47)
+            with self.subTest(string=string,
+                              format=format,
+                              target=target):
+                result = self.theclass.strptime(string, format)
+                self.assertEqual(result, target)
 
     def test_more_timetuple(self):
         # This tests fields beyond those tested by the TestDate.test_timetuple.
@@ -3348,7 +3520,7 @@ def test_fromisoformat_timezone(self):
 
             with self.subTest(tstr=dtstr):
                 dt_rt = self.theclass.fromisoformat(dtstr)
-                assert dt == dt_rt, dt_rt
+                self.assertEqual(dt_rt, dt)
 
     def test_fromisoformat_separators(self):
         separators = [
@@ -3581,11 +3753,15 @@ def test_fromisoformat_fails_datetime(self):
             '2009-04-19T12:30:45.400 +02:30',  # Space between ms and timezone (gh-130959)
             '2009-04-19T12:30:45.400 ',        # Trailing space (gh-130959)
             '2009-04-19T12:30:45. 400',        # Space before fraction (gh-130959)
-            '2020-2020',                       # Ambiguous 9-char date portion
-            '2009-04-19T12:30:45.+05:00',      # Empty fraction before offset
-            '2009-04-19T12:30:45.-05:00',      # Empty fraction before offset
-            '2009-04-19T12:30:45.Z',           # Empty fraction before Z
-            '2009-04-19T12:30:45,+05:00',      # Empty fraction (comma) before offset
+            '2009-04-19T12:30:45+00:90:00', # Time zone field out from range
+            '2009-04-19T12:30:45+00:00:90', # Time zone field out from range
+            '2009-04-19T12:30:45-00:90:00', # Time zone field out from range
+            '2009-04-19T12:30:45-00:00:90', # Time zone field out from range
+            '2020-2020',                    # Ambiguous 9-char date portion
+            '2009-04-19T12:30:45.+05:00',   # Empty fraction before offset
+            '2009-04-19T12:30:45.-05:00',   # Empty fraction before offset
+            '2009-04-19T12:30:45.Z',        # Empty fraction before Z
+            '2009-04-19T12:30:45,+05:00',   # Empty fraction (comma) before offset
         ]
 
         for bad_str in bad_strs:
@@ -3678,6 +3854,13 @@ def test_repr_subclass(self):
         td = SubclassDatetime(2010, 10, 2, second=3)
         self.assertEqual(repr(td), "SubclassDatetime(2010, 10, 2, 0, 0, 3)")
 
+    def test_strptime_T_format(self):
+        test_time = "15:00:00"
+        self.assertEqual(
+            self.theclass.strptime(test_time, "%T"),
+            self.theclass.strptime(test_time, "%H:%M:%S")
+        )
+
 
 class TestSubclassDateTime(TestDateTime):
     theclass = SubclassDatetime
@@ -3892,7 +4075,7 @@ def test_isoformat_timezone(self):
             t = t_base.replace(tzinfo=tzi)
             exp = exp_base + exp_tz
             with self.subTest(tzi=tzi):
-                assert t.isoformat() == exp
+                self.assertEqual(t.isoformat(), exp)
 
     def test_1653736(self):
         # verify it doesn't accept extra keyword arguments
@@ -4073,6 +4256,12 @@ def test_strptime_tz(self):
             strptime("-00:02:01.000003", "%z").utcoffset(),
             -timedelta(minutes=2, seconds=1, microseconds=3)
         )
+        self.assertEqual(strptime("+01:07", "%:z").utcoffset(),
+                         1 * HOUR + 7 * MINUTE)
+        self.assertEqual(strptime("-10:02", "%:z").utcoffset(),
+                         -(10 * HOUR + 2 * MINUTE))
+        self.assertEqual(strptime("-00:00:01.00001", "%:z").utcoffset(),
+                         -timedelta(seconds=1, microseconds=10))
         # Only local timezone and UTC are supported
         for tzseconds, tzname in ((0, 'UTC'), (0, 'GMT'),
                                  (-_time.timezone, _time.tzname[0])):
@@ -4102,9 +4291,11 @@ def test_strptime_tz(self):
         self.assertEqual(strptime("UTC", "%Z").tzinfo, None)
 
     def test_strptime_errors(self):
-        for tzstr in ("-2400", "-000", "z"):
+        for tzstr in ("-2400", "-000", "z", "24:00"):
             with self.assertRaises(ValueError):
                 self.theclass.strptime(tzstr, "%z")
+            with self.assertRaises(ValueError):
+                self.theclass.strptime(tzstr, "%:z")
 
     def test_strptime_single_digit(self):
         # bpo-34903: Check that single digit times are allowed.
@@ -4382,7 +4573,7 @@ def utcoffset(self, t):
                     elif x is d2:
                         expected = -1
                     else:
-                        assert y is d2
+                        self.assertIs(y, d2)
                         expected = 1
                     self.assertEqual(got, expected)
 
@@ -4710,7 +4901,7 @@ def test_fromisoformat_timezone(self):
 
             with self.subTest(tstr=tstr):
                 t_rt = self.theclass.fromisoformat(tstr)
-                assert t == t_rt
+                self.assertEqual(t_rt, t)
 
     def test_fromisoformat_timespecs(self):
         time_bases = [
@@ -4842,6 +5033,11 @@ def test_fromisoformat_fails(self):
             '12:30:45.400 +02:30',      # Space between ms and timezone (gh-130959)
             '12:30:45.400 ',            # Trailing space (gh-130959)
             '12:30:45. 400',            # Space before fraction (gh-130959)
+            '24:00:00.000001',          # Has non-zero microseconds on 24:00
+            '24:00:01.000000',          # Has non-zero seconds on 24:00
+            '24:01:00.000000',          # Has non-zero minutes on 24:00
+            '12:30:45+00:90:00',        # Time zone field out from range
+            '12:30:45+00:00:90',        # Time zone field out from range
             '12:30:45.+05:00',          # Empty fraction before offset
             '12:30:45.-05:00',          # Empty fraction before offset
             '12:30:45.Z',               # Empty fraction before Z
@@ -5546,7 +5742,7 @@ def utcoffset(self, t):
                 elif x is d2:
                     expected = timedelta(minutes=(11-59)-0)
                 else:
-                    assert y is d2
+                    self.assertIs(y, d2)
                     expected = timedelta(minutes=0-(11-59))
                 self.assertEqual(got, expected)
 
diff --git a/Lib/test/exception_hierarchy.txt b/Lib/test/exception_hierarchy.txt
index f2649aa2d41..98a5e950602 100644
--- a/Lib/test/exception_hierarchy.txt
+++ b/Lib/test/exception_hierarchy.txt
@@ -14,6 +14,7 @@ BaseException
       ├── EOFError
       ├── ExceptionGroup [BaseExceptionGroup]
       ├── ImportError
+      │    └── ImportCycleError
       │    └── ModuleNotFoundError
       ├── LookupError
       │    ├── IndexError
diff --git a/Lib/test/lock_tests.py b/Lib/test/lock_tests.py
index fb11f482895..691029a1a54 100644
--- a/Lib/test/lock_tests.py
+++ b/Lib/test/lock_tests.py
@@ -124,6 +124,11 @@ def test_constructor(self):
         lock = self.locktype()
         del lock
 
+    def test_constructor_noargs(self):
+        self.assertRaises(TypeError, self.locktype, 1)
+        self.assertRaises(TypeError, self.locktype, x=1)
+        self.assertRaises(TypeError, self.locktype, 1, x=2)
+
     def test_repr(self):
         lock = self.locktype()
         self.assertRegex(repr(lock), "<unlocked .* object (.*)?at .*>")
diff --git a/Lib/test/mapping_tests.py b/Lib/test/mapping_tests.py
index 1358200add5..ae2fb3f5f44 100644
--- a/Lib/test/mapping_tests.py
+++ b/Lib/test/mapping_tests.py
@@ -4,7 +4,7 @@
 from test import support
 
 
-class BasicTestMappingProtocol(unittest.TestCase):
+class BasicTestImmutableMappingProtocol(unittest.TestCase):
     # This base class can be used to check that an object conforms to the
     # mapping protocol
 
@@ -20,12 +20,9 @@ def _empty_mapping(self):
         """Return an empty mapping object"""
         return self.type2test()
     def _full_mapping(self, data):
-        """Return a mapping object with the value contained in data
+        """Return a mapping object with the values contained in data
         dictionary"""
-        x = self._empty_mapping()
-        for key, value in data.items():
-            x[key] = value
-        return x
+        return self.type2test(data)
 
     def __init__(self, *args, **kw):
         unittest.TestCase.__init__(self, *args, **kw)
@@ -88,6 +85,72 @@ def check_iterandlist(iter, lst, ref):
         self.assertEqual(d.get(knownkey, knownvalue), knownvalue)
         self.assertNotIn(knownkey, d)
 
+    def test_constructor(self):
+        self.assertEqual(self._empty_mapping(), self._empty_mapping())
+
+    def test_bool(self):
+        self.assertTrue(not self._empty_mapping())
+        self.assertTrue(self.reference)
+        self.assertFalse(bool(self._empty_mapping()))
+        self.assertTrue(bool(self.reference))
+
+    def test_keys(self):
+        d = self._empty_mapping()
+        self.assertEqual(list(d.keys()), [])
+        d = self.reference
+        self.assertIn(list(self.inmapping.keys())[0], d.keys())
+        self.assertNotIn(list(self.other.keys())[0], d.keys())
+        self.assertRaises(TypeError, d.keys, None)
+
+    def test_values(self):
+        d = self._empty_mapping()
+        self.assertEqual(list(d.values()), [])
+
+        self.assertRaises(TypeError, d.values, None)
+
+    def test_items(self):
+        d = self._empty_mapping()
+        self.assertEqual(list(d.items()), [])
+
+        self.assertRaises(TypeError, d.items, None)
+
+    def test_len(self):
+        d = self._empty_mapping()
+        self.assertEqual(len(d), 0)
+
+    def test_getitem(self):
+        d = self.reference
+        self.assertEqual(d[list(self.inmapping.keys())[0]],
+                         list(self.inmapping.values())[0])
+
+        self.assertRaises(TypeError, d.__getitem__)
+
+    # no test_fromkeys or test_copy as both os.environ and selves don't support it
+
+    def test_get(self):
+        d = self._empty_mapping()
+        self.assertIsNone(d.get(list(self.other.keys())[0]))
+        self.assertEqual(d.get(list(self.other.keys())[0], 3), 3)
+        d = self.reference
+        self.assertIsNone(d.get(list(self.other.keys())[0]))
+        self.assertEqual(d.get(list(self.other.keys())[0], 3), 3)
+        self.assertEqual(d.get(list(self.inmapping.keys())[0]),
+                         list(self.inmapping.values())[0])
+        self.assertEqual(d.get(list(self.inmapping.keys())[0], 3),
+                         list(self.inmapping.values())[0])
+        self.assertRaises(TypeError, d.get)
+        self.assertRaises(TypeError, d.get, None, None, None)
+
+
+class BasicTestMappingProtocol(BasicTestImmutableMappingProtocol):
+    def _full_mapping(self, data):
+        """Return a mapping object with the values contained in data
+        dictionary"""
+        x = self._empty_mapping()
+        for key, value in data.items():
+            x[key] = value
+        return x
+
     def test_write(self):
         # Test for write operations on mapping
         p = self._empty_mapping()
@@ -130,46 +193,6 @@ def test_write(self):
         p=self._empty_mapping()
         self.assertRaises(KeyError, p.popitem)
 
-    def test_constructor(self):
-        self.assertEqual(self._empty_mapping(), self._empty_mapping())
-
-    def test_bool(self):
-        self.assertTrue(not self._empty_mapping())
-        self.assertTrue(self.reference)
-        self.assertTrue(bool(self._empty_mapping()) is False)
-        self.assertTrue(bool(self.reference) is True)
-
-    def test_keys(self):
-        d = self._empty_mapping()
-        self.assertEqual(list(d.keys()), [])
-        d = self.reference
-        self.assertIn(list(self.inmapping.keys())[0], d.keys())
-        self.assertNotIn(list(self.other.keys())[0], d.keys())
-        self.assertRaises(TypeError, d.keys, None)
-
-    def test_values(self):
-        d = self._empty_mapping()
-        self.assertEqual(list(d.values()), [])
-
-        self.assertRaises(TypeError, d.values, None)
-
-    def test_items(self):
-        d = self._empty_mapping()
-        self.assertEqual(list(d.items()), [])
-
-        self.assertRaises(TypeError, d.items, None)
-
-    def test_len(self):
-        d = self._empty_mapping()
-        self.assertEqual(len(d), 0)
-
-    def test_getitem(self):
-        d = self.reference
-        self.assertEqual(d[list(self.inmapping.keys())[0]],
-                         list(self.inmapping.values())[0])
-
-        self.assertRaises(TypeError, d.__getitem__)
-
     def test_update(self):
         # mapping argument
         d = self._empty_mapping()
@@ -265,22 +288,6 @@ def __next__(self):
 
         self.assertRaises(ValueError, d.update, [(1, 2, 3)])
 
-    # no test_fromkeys or test_copy as both os.environ and selves don't support it
-
-    def test_get(self):
-        d = self._empty_mapping()
-        self.assertTrue(d.get(list(self.other.keys())[0]) is None)
-        self.assertEqual(d.get(list(self.other.keys())[0], 3), 3)
-        d = self.reference
-        self.assertTrue(d.get(list(self.other.keys())[0]) is None)
-        self.assertEqual(d.get(list(self.other.keys())[0], 3), 3)
-        self.assertEqual(d.get(list(self.inmapping.keys())[0]),
-                         list(self.inmapping.values())[0])
-        self.assertEqual(d.get(list(self.inmapping.keys())[0], 3),
-                         list(self.inmapping.values())[0])
-        self.assertRaises(TypeError, d.get)
-        self.assertRaises(TypeError, d.get, None, None, None)
-
     def test_setdefault(self):
         d = self._empty_mapping()
         self.assertRaises(TypeError, d.setdefault)
@@ -622,7 +629,7 @@ def __repr__(self):
         d = self._full_mapping({1: BadRepr()})
         self.assertRaises(Exc, repr, d)
 
-    @support.run_with_limited_c_stack()
+    @support.skip_if_huge_c_stack()
     @support.skip_wasi_stack_overflow()
     @support.skip_emscripten_stack_overflow()
     @support.skip_if_sanitizer("requires deep stack", ub=True)
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 504a0ffb401..9a7d416797b 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -22,6 +22,7 @@
 
 
 __all__ = [
+    "requires_root_user", "requires_non_root_user",
     # globals
     "PIPE_MAX_SIZE", "verbose", "max_memuse", "use_resources", "failfast",
     # exceptions
@@ -1651,8 +1652,12 @@ def _platform_specific(self):
                 ))
 
             self._env = {k.upper(): os.getenv(k) for k in os.environ}
-            self._env["PYTHONHOME"] = os.path.dirname(self.real)
+            home = os.path.dirname(self.real)
             if sysconfig.is_python_build():
+                home = os.path.join(home, sysconfig.get_config_var('VPATH'))
+            self._env["PYTHONHOME"] = home
+            # TODO: RUSTPYTHON; Cargo builds do not use CPython's Modules/Setup.
+            if sys.implementation.name == 'rustpython':
                 self._env["PYTHONPATH"] = STDLIB_DIR
     else:
         def _platform_specific(self):
@@ -3336,6 +3341,11 @@ def control_characters_c0() -> list[str]:
     return [chr(c) for c in range(0x00, 0x20)] + ["\x7F"]
 
 
+_ROOT_IN_POSIX = hasattr(os, 'geteuid') and os.geteuid() == 0
+requires_root_user = unittest.skipUnless(_ROOT_IN_POSIX, "test needs root privilege")
+requires_non_root_user = unittest.skipIf(_ROOT_IN_POSIX, "test needs non-root account")
+
+
 STATUS_DLL_INIT_FAILED = 0xC0000142
 def skip_on_low_desktop_heap_memory_subprocess(returncode):
     if sys.platform not in ('win32', 'cygwin'):
diff --git a/Lib/test/support/_hypothesis_stubs/__init__.py b/Lib/test/support/_hypothesis_stubs/__init__.py
index 6ba5bb814b9..6fa013b55b2 100644
--- a/Lib/test/support/_hypothesis_stubs/__init__.py
+++ b/Lib/test/support/_hypothesis_stubs/__init__.py
@@ -24,7 +24,13 @@ def decorator(f):
             @functools.wraps(f)
             def test_function(self):
                 for example_args, example_kwargs in examples:
-                    with self.subTest(*example_args, **example_kwargs):
+                    if len(example_args) < 2:
+                        subtest_args = example_args
+                    else:
+                        # subTest takes up to one positional argument.
+                        # When there are more, display them as a tuple
+                        subtest_args = [example_args]
+                    with self.subTest(*subtest_args, **example_kwargs):
                         f(self, *example_args, **example_kwargs)
 
         else:
diff --git a/Lib/test/support/hashlib_helper.py b/Lib/test/support/hashlib_helper.py
index 7032257b068..818f99d0023 100644
--- a/Lib/test/support/hashlib_helper.py
+++ b/Lib/test/support/hashlib_helper.py
@@ -1,45 +1,515 @@
+import contextlib
+import enum
 import functools
-import hashlib
 import importlib
+import inspect
 import unittest
-from test.support.import_helper import import_module
+import unittest.mock
+from test.support import import_helper
 
-try:
-    import _hashlib
-except ImportError:
-    _hashlib = None
 
-try:
-    import _hmac
-except ImportError:
-    _hmac = None
+def _parse_fullname(fullname, *, strict=False):
+    """Parse a fully-qualified name ``<module_name>.<member_name>``.
 
+    The ``module_name`` component contains one or more dots.
+    The ``member_name`` component does not contain any dot.
 
-def requires_hashlib():
-    return unittest.skipIf(_hashlib is None, "requires _hashlib")
+    If *strict* is true, *fullname* must be a string. Otherwise,
+    it can be None, and, ``module_name`` and ``member_name`` will
+    also be None.
+    """
+    if fullname is None:
+        assert not strict
+        return None, None
+    assert isinstance(fullname, str), fullname
+    assert fullname.count(".") >= 1, fullname
+    module_name, member_name = fullname.rsplit(".", maxsplit=1)
+    return module_name, member_name
 
 
-def requires_builtin_hmac():
-    return unittest.skipIf(_hmac is None, "requires _hmac")
+def _import_module(module_name, *, strict=False):
+    """Import a module from its fully-qualified name.
 
+    If *strict* is false, import failures are suppressed and None is returned.
+    """
+    if module_name is None:
+        # To prevent a TypeError in importlib.import_module
+        if strict:
+            raise ImportError("no module to import")
+        return None
+    try:
+        return importlib.import_module(module_name)
+    except ImportError as exc:
+        if strict:
+            raise exc
+        return None
 
-def _missing_hash(digestname, implementation=None, *, exc=None):
-    parts = ["missing", implementation, f"hash algorithm: {digestname!r}"]
-    msg = " ".join(filter(None, parts))
-    raise unittest.SkipTest(msg) from exc
 
+def _import_member(module_name, member_name, *, strict=False):
+    """Import a member from a module.
+
+    If *strict* is false, import failures are suppressed and None is returned.
+    """
+    if member_name is None:
+        if strict:
+            raise ImportError(f"no member to import from {module_name}")
+        return None
+    module = _import_module(module_name, strict=strict)
+    if strict:
+        return getattr(module, member_name)
+    return getattr(module, member_name, None)
+
+
+class Implementation(enum.StrEnum):
+    # Indicate that the hash function is implemented by a built-in module.
+    builtin = enum.auto()
+    # Indicate that the hash function is implemented by OpenSSL.
+    openssl = enum.auto()
+    # Indicate that the hash function is provided through the public API.
+    hashlib = enum.auto()
+
+
+class _HashId(enum.StrEnum):
+    """Enumeration containing the canonical digest names.
+
+    Those names should only be used by hashlib.new() or hmac.new().
+    Their support by _hashlib.new() is not necessarily guaranteed.
+    """
+
+    md5 = enum.auto()
+    sha1 = enum.auto()
+
+    sha224 = enum.auto()
+    sha256 = enum.auto()
+    sha384 = enum.auto()
+    sha512 = enum.auto()
+
+    sha3_224 = enum.auto()
+    sha3_256 = enum.auto()
+    sha3_384 = enum.auto()
+    sha3_512 = enum.auto()
+
+    shake_128 = enum.auto()
+    shake_256 = enum.auto()
+
+    blake2s = enum.auto()
+    blake2b = enum.auto()
+
+    def __repr__(self):
+        return str(self)
+
+    @property
+    def is_xof(self):
+        """Indicate whether the hash is an extendable-output hash function."""
+        return self.startswith("shake_")
+
+    @property
+    def is_keyed(self):
+        """Indicate whether the hash is a keyed hash function."""
+        return self.startswith("blake2")
+
+
+CANONICAL_DIGEST_NAMES = frozenset(map(str, _HashId.__members__))
+NON_HMAC_DIGEST_NAMES = frozenset((
+    _HashId.shake_128, _HashId.shake_256,
+    _HashId.blake2s, _HashId.blake2b,
+))
+
+
+class _HashInfoItem:
+    """Interface for interacting with a named object.
+
+    The object is entirely described by its fully-qualified *fullname*.
+
+    *fullname* must be None or a string "<module_name>.<member_name>".
+    """
+
+    def __init__(self, fullname=None, *, strict=False):
+        module_name, member_name = _parse_fullname(fullname, strict=strict)
+        self.fullname = fullname
+        self.module_name = module_name
+        self.member_name = member_name
+
+    def import_module(self, *, strict=False):
+        """Import the described module.
+
+        If *strict* is true, an ImportError may be raised if importing fails,
+        otherwise, None is returned on error.
+        """
+        return _import_module(self.module_name, strict=strict)
+
+    def import_member(self, *, strict=False):
+        """Import the described member.
+
+        If *strict* is true, an AttributeError or an ImportError may be
+        raised if importing fails; otherwise, None is returned on error.
+        """
+        return _import_member(
+            self.module_name, self.member_name, strict=strict
+        )
 
-def _openssl_availabillity(digestname, *, usedforsecurity):
-    try:
-        _hashlib.new(digestname, usedforsecurity=usedforsecurity)
-    except AttributeError:
-        assert _hashlib is None
-        _missing_hash(digestname, "OpenSSL")
-    except ValueError as exc:
-        _missing_hash(digestname, "OpenSSL", exc=exc)
 
+class _HashInfoBase:
+    """Base dataclass containing "backend" information.
+
+    Subclasses may define an attribute named after one of the known
+    implementations ("builtin", "openssl" or "hashlib") which stores
+    an _HashInfoItem object.
+
+    Those attributes can be retrieved through __getitem__(), e.g.,
+    ``info["builtin"]`` returns the _HashInfoItem corresponding to
+    the builtin implementation.
+    """
+
+    def __init__(self, canonical_name):
+        assert isinstance(canonical_name, _HashId), canonical_name
+        self.canonical_name = canonical_name
+
+    def __getitem__(self, implementation):
+        try:
+            attrname = Implementation(implementation)
+        except ValueError:
+            raise self.invalid_implementation_error(implementation) from None
+
+        try:
+            provider = getattr(self, attrname)
+        except AttributeError:
+            raise self.invalid_implementation_error(implementation) from None
+
+        if not isinstance(provider, _HashInfoItem):
+            raise KeyError(implementation)
+        return provider
+
+    def invalid_implementation_error(self, implementation):
+        msg = f"no implementation {implementation} for {self.canonical_name}"
+        return AssertionError(msg)
+
+
+class _HashTypeInfo(_HashInfoBase):
+    """Dataclass containing information for hash functions types.
+
+    - *canonical_name* must be a _HashId.
+
+    - *builtin* is the fully-qualified name for the builtin HACL* type,
+      e.g., "_md5.MD5Type".
+
+    - *openssl* is the fully-qualified name for the OpenSSL wrapper type,
+      e.g., "_hashlib.HASH".
+    """
+
+    def __init__(self, canonical_name, builtin, openssl):
+        super().__init__(canonical_name)
+        self.builtin = _HashInfoItem(builtin, strict=True)
+        self.openssl = _HashInfoItem(openssl, strict=True)
+
+    def fullname(self, implementation):
+        """Get the fully qualified name of a given implementation.
+
+        This returns a string of the form "MODULE_NAME.OBJECT_NAME" or None
+        if the hash function does not have a corresponding implementation.
+
+        *implementation* must be "builtin" or "openssl".
+        """
+        return self[implementation].fullname
+
+    def module_name(self, implementation):
+        """Get the name of the module containing the hash object type."""
+        return self[implementation].module_name
+
+    def object_type_name(self, implementation):
+        """Get the name of the hash object class name."""
+        return self[implementation].member_name
+
+    def import_module(self, implementation, *, allow_skip=False):
+        """Import the module containing the hash object type.
+
+        On error, return None if *allow_skip* is false, or raise SkipNoHash.
+        """
+        target = self[implementation]
+        module = target.import_module()
+        if allow_skip and module is None:
+            reason = f"cannot import module {target.module_name}"
+            raise SkipNoHash(self.canonical_name, implementation, reason)
+        return module
+
+    def import_object_type(self, implementation, *, allow_skip=False):
+        """Get the runtime hash object type.
+
+        On error, return None if *allow_skip* is false, or raise SkipNoHash.
+        """
+        target = self[implementation]
+        member = target.import_member()
+        if allow_skip and member is None:
+            reason = f"cannot import class {target.fullname}"
+            raise SkipNoHash(self.canonical_name, implementation, reason)
+        return member
+
+
+class _HashFuncInfo(_HashInfoBase):
+    """Dataclass containing information for hash functions constructors.
+
+    - *canonical_name* must be a _HashId.
+
+    - *builtin* is the fully-qualified name of the HACL*
+      hash constructor function, e.g., "_md5.md5".
+
+    - *openssl* is the fully-qualified name of the "_hashlib" method
+      for the OpenSSL named constructor, e.g., "_hashlib.openssl_md5".
+
+    - *hashlib* is the fully-qualified name of the "hashlib" method
+      for the explicit named hash constructor, e.g., "hashlib.md5".
+    """
 
-def _decorate_func_or_class(func_or_class, decorator_func):
+    def __init__(self, canonical_name, builtin, openssl=None, hashlib=None):
+        super().__init__(canonical_name)
+        self.builtin = _HashInfoItem(builtin, strict=True)
+        self.openssl = _HashInfoItem(openssl, strict=False)
+        self.hashlib = _HashInfoItem(hashlib, strict=False)
+
+    def fullname(self, implementation):
+        """Get the fully qualified name of a given implementation.
+
+        This returns a string of the form "MODULE_NAME.METHOD_NAME" or None
+        if the hash function does not have a corresponding implementation.
+
+        *implementation* must be "builtin", "openssl" or "hashlib".
+        """
+        return self[implementation].fullname
+
+    def module_name(self, implementation):
+        """Get the name of the constructor function module.
+
+        The *implementation* must be "builtin", "openssl" or "hashlib".
+        """
+        return self[implementation].module_name
+
+    def method_name(self, implementation):
+        """Get the name of the constructor function module method.
+
+        Use fullname() to get the constructor function fully-qualified name.
+
+        The *implementation* must be "builtin", "openssl" or "hashlib".
+        """
+        return self[implementation].member_name
+
+
+class _HashInfo:
+    """Dataclass containing information for supported hash functions.
+
+    Attributes
+    ----------
+    canonical_name : _HashId
+        The hash function canonical name.
+    type : _HashTypeInfo
+        The hash object types information.
+    func : _HashTypeInfo
+        The hash object constructors information.
+    """
+
+    def __init__(
+        self,
+        canonical_name,
+        builtin_object_type_fullname,
+        openssl_object_type_fullname,
+        builtin_method_fullname,
+        openssl_method_fullname=None,
+        hashlib_method_fullname=None,
+    ):
+        """
+        - *canonical_name* must be a _HashId.
+
+        - *builtin_object_type_fullname* is the fully-qualified name
+          for the builtin HACL* type, e.g., "_md5.MD5Type".
+
+        - *openssl_object_type_fullname* is the fully-qualified name
+          for the OpenSSL wrapper type, e.g., "_hashlib.HASH".
+
+        - *builtin_method_fullname* is the fully-qualified name
+          of the HACL* hash constructor function, e.g., "_md5.md5".
+
+        - *openssl_method_fullname* is the fully-qualified name
+          of the "_hashlib" module method for the explicit OpenSSL
+          hash constructor function, e.g., "_hashlib.openssl_md5".
+
+        - *hashlib_method_fullname* is the fully-qualified name
+          of the "hashlib"  module method for the explicit hash
+          constructor function, e.g., "hashlib.md5".
+        """
+        assert isinstance(canonical_name, _HashId), canonical_name
+        self.canonical_name = canonical_name
+        self.type = _HashTypeInfo(
+            canonical_name,
+            builtin_object_type_fullname,
+            openssl_object_type_fullname,
+        )
+        self.func = _HashFuncInfo(
+            canonical_name,
+            builtin_method_fullname,
+            openssl_method_fullname,
+            hashlib_method_fullname,
+        )
+
+
+_HASHINFO_DATABASE = frozendict({
+    _HashId.md5: _HashInfo(
+        _HashId.md5,
+        "_md5.MD5Type",
+        "_hashlib.HASH",
+        "_md5.md5",
+        "_hashlib.openssl_md5",
+        "hashlib.md5",
+    ),
+    _HashId.sha1: _HashInfo(
+        _HashId.sha1,
+        "_sha1.SHA1Type",
+        "_hashlib.HASH",
+        "_sha1.sha1",
+        "_hashlib.openssl_sha1",
+        "hashlib.sha1",
+    ),
+    _HashId.sha224: _HashInfo(
+        _HashId.sha224,
+        "_sha2.SHA224Type",
+        "_hashlib.HASH",
+        "_sha2.sha224",
+        "_hashlib.openssl_sha224",
+        "hashlib.sha224",
+    ),
+    _HashId.sha256: _HashInfo(
+        _HashId.sha256,
+        "_sha2.SHA256Type",
+        "_hashlib.HASH",
+        "_sha2.sha256",
+        "_hashlib.openssl_sha256",
+        "hashlib.sha256",
+    ),
+    _HashId.sha384: _HashInfo(
+        _HashId.sha384,
+        "_sha2.SHA384Type",
+        "_hashlib.HASH",
+        "_sha2.sha384",
+        "_hashlib.openssl_sha384",
+        "hashlib.sha384",
+    ),
+    _HashId.sha512: _HashInfo(
+        _HashId.sha512,
+        "_sha2.SHA512Type",
+        "_hashlib.HASH",
+        "_sha2.sha512",
+        "_hashlib.openssl_sha512",
+        "hashlib.sha512",
+    ),
+    _HashId.sha3_224: _HashInfo(
+        _HashId.sha3_224,
+        "_sha3.sha3_224",
+        "_hashlib.HASH",
+        "_sha3.sha3_224",
+        "_hashlib.openssl_sha3_224",
+        "hashlib.sha3_224",
+    ),
+    _HashId.sha3_256: _HashInfo(
+        _HashId.sha3_256,
+        "_sha3.sha3_256",
+        "_hashlib.HASH",
+        "_sha3.sha3_256",
+        "_hashlib.openssl_sha3_256",
+        "hashlib.sha3_256",
+    ),
+    _HashId.sha3_384: _HashInfo(
+        _HashId.sha3_384,
+        "_sha3.sha3_384",
+        "_hashlib.HASH",
+        "_sha3.sha3_384",
+        "_hashlib.openssl_sha3_384",
+        "hashlib.sha3_384",
+    ),
+    _HashId.sha3_512: _HashInfo(
+        _HashId.sha3_512,
+        "_sha3.sha3_512",
+        "_hashlib.HASH",
+        "_sha3.sha3_512",
+        "_hashlib.openssl_sha3_512",
+        "hashlib.sha3_512",
+    ),
+    _HashId.shake_128: _HashInfo(
+        _HashId.shake_128,
+        "_sha3.shake_128",
+        "_hashlib.HASHXOF",
+        "_sha3.shake_128",
+        "_hashlib.openssl_shake_128",
+        "hashlib.shake_128",
+    ),
+    _HashId.shake_256: _HashInfo(
+        _HashId.shake_256,
+        "_sha3.shake_256",
+        "_hashlib.HASHXOF",
+        "_sha3.shake_256",
+        "_hashlib.openssl_shake_256",
+        "hashlib.shake_256",
+    ),
+    _HashId.blake2s: _HashInfo(
+        _HashId.blake2s,
+        "_blake2.blake2s",
+        "_hashlib.HASH",
+        "_blake2.blake2s",
+        None,
+        "hashlib.blake2s",
+    ),
+    _HashId.blake2b: _HashInfo(
+        _HashId.blake2b,
+        "_blake2.blake2b",
+        "_hashlib.HASH",
+        "_blake2.blake2b",
+        None,
+        "hashlib.blake2b",
+    ),
+})
+assert _HASHINFO_DATABASE.keys() == CANONICAL_DIGEST_NAMES
+
+
+def get_hash_type_info(name):
+    info = _HASHINFO_DATABASE[name]
+    assert isinstance(info, _HashInfo), info
+    return info.type
+
+
+def get_hash_func_info(name):
+    info = _HASHINFO_DATABASE[name]
+    assert isinstance(info, _HashInfo), info
+    return info.func
+
+
+def _iter_hash_func_info(excluded):
+    for name, info in _HASHINFO_DATABASE.items():
+        if name not in excluded:
+            yield info.func
+
+
+# Mapping from canonical hash names to their explicit HACL* HMAC constructor.
+# There is currently no OpenSSL one-shot named function and there will likely
+# be none in the future.
+_HMACINFO_DATABASE = {
+    _HashId(canonical_name): _HashInfoItem(f"_hmac.compute_{canonical_name}")
+    for canonical_name in CANONICAL_DIGEST_NAMES
+}
+# Neither HACL* nor OpenSSL supports HMAC over XOFs.
+_HMACINFO_DATABASE[_HashId.shake_128] = _HashInfoItem()
+_HMACINFO_DATABASE[_HashId.shake_256] = _HashInfoItem()
+# Strictly speaking, HMAC-BLAKE is meaningless as BLAKE2 is already a
+# keyed hash function. However, as it's exposed by HACL*, we test it.
+_HMACINFO_DATABASE[_HashId.blake2s] = _HashInfoItem('_hmac.compute_blake2s_32')
+_HMACINFO_DATABASE[_HashId.blake2b] = _HashInfoItem('_hmac.compute_blake2b_32')
+_HMACINFO_DATABASE = frozendict(_HMACINFO_DATABASE)
+assert _HMACINFO_DATABASE.keys() == CANONICAL_DIGEST_NAMES
+
+
+def get_hmac_item_info(name):
+    info = _HMACINFO_DATABASE[name]
+    assert isinstance(info, _HashInfoItem), info
+    return info
+
+
+def _decorate_func_or_class(decorator_func, func_or_class):
     if not isinstance(func_or_class, type):
         return decorator_func(func_or_class)
 
@@ -57,114 +527,225 @@ def setUpClass(cls):
     return decorated_class
 
 
-def requires_hashdigest(digestname, openssl=None, usedforsecurity=True):
-    """Decorator raising SkipTest if a hashing algorithm is not available.
+def _chain_decorators(decorators):
+    """Obtain a decorator by chaining multiple decorators.
 
-    The hashing algorithm may be missing, blocked by a strict crypto policy,
-    or Python may be configured with `--with-builtin-hashlib-hashes=no`.
+    The decorators are applied in the order they are given.
+    """
+    def decorator_func(func):
+        return functools.reduce(lambda w, deco: deco(w), decorators, func)
+    return functools.partial(_decorate_func_or_class, decorator_func)
 
-    If 'openssl' is True, then the decorator checks that OpenSSL provides
-    the algorithm. Otherwise the check falls back to (optional) built-in
-    HACL* implementations.
 
-    The usedforsecurity flag is passed to the constructor but has no effect
-    on HACL* implementations.
+def _ensure_wrapper_signature(wrapper, wrapped):
+    """Ensure that a wrapper has the same signature as the wrapped function.
 
-    Examples of exceptions being suppressed:
-    ValueError: [digital envelope routines: EVP_DigestInit_ex] disabled for FIPS
-    ValueError: unsupported hash type md4
+    This is used to guarantee that a TypeError raised due to a bad API call
+    is raised consistently (using variadic signatures would hide such errors).
     """
-    if openssl and _hashlib is not None:
-        def test_availability():
-            _hashlib.new(digestname, usedforsecurity=usedforsecurity)
-    else:
-        def test_availability():
-            hashlib.new(digestname, usedforsecurity=usedforsecurity)
+    try:
+        wrapped_sig = inspect.signature(wrapped)
+    except ValueError:  # built-in signature cannot be found
+        return
+
+    wrapper_sig = inspect.signature(wrapper)
+    if wrapped_sig != wrapper_sig:
+        fullname = f"{wrapped.__module__}.{wrapped.__qualname__}"
+        raise AssertionError(
+            f"signature for {fullname}() is incorrect:\n"
+            f"  expect: {wrapped_sig}\n"
+            f"  actual: {wrapper_sig}"
+        )
 
+
+def _make_conditional_decorator(test, /, *test_args, **test_kwargs):
     def decorator_func(func):
         @functools.wraps(func)
         def wrapper(*args, **kwargs):
-            try:
-                test_availability()
-            except ValueError as exc:
-                _missing_hash(digestname, exc=exc)
+            test(*test_args, **test_kwargs)
             return func(*args, **kwargs)
         return wrapper
+    return functools.partial(_decorate_func_or_class, decorator_func)
 
-    def decorator(func_or_class):
-        return _decorate_func_or_class(func_or_class, decorator_func)
-    return decorator
 
+def requires_openssl_hashlib():
+    _hashlib = _import_module("_hashlib")
+    return unittest.skipIf(_hashlib is None, "requires _hashlib")
 
-def requires_openssl_hashdigest(digestname, *, usedforsecurity=True):
-    """Decorator raising SkipTest if an OpenSSL hashing algorithm is missing.
 
-    The hashing algorithm may be missing or blocked by a strict crypto policy.
-    """
-    def decorator_func(func):
-        @requires_hashlib()  # avoid checking at each call
-        @functools.wraps(func)
-        def wrapper(*args, **kwargs):
-            _openssl_availabillity(digestname, usedforsecurity=usedforsecurity)
-            return func(*args, **kwargs)
-        return wrapper
+def requires_builtin_hmac():
+    _hmac = _import_module("_hmac")
+    return unittest.skipIf(_hmac is None, "requires _hmac")
+
+
+class SkipNoHash(unittest.SkipTest):
+    """A SkipTest exception raised when a hash is not available."""
+
+    def __init__(self, digestname, implementation=None, reason=None):
+        parts = ["missing", implementation, f"hash algorithm {digestname!r}"]
+        if reason is not None:
+            parts.insert(0, f"{reason}: ")
+        super().__init__(" ".join(filter(None, parts)))
+
 
-    def decorator(func_or_class):
-        return _decorate_func_or_class(func_or_class, decorator_func)
-    return decorator
+class SkipNoHashInCall(SkipNoHash):
 
+    def __init__(self, func, digestname, implementation=None):
+        super().__init__(digestname, implementation, f"cannot use {func}")
 
-def find_openssl_hashdigest_constructor(digestname, *, usedforsecurity=True):
-    """Find the OpenSSL hash function constructor by its name."""
+
+def _hashlib_new(digestname, openssl, /, **kwargs):
+    """Check availability of [hashlib|_hashlib].new(digestname, **kwargs).
+
+    If *openssl* is True, module is "_hashlib" (C extension module),
+    otherwise it is "hashlib" (pure Python interface).
+
+    The constructor function is returned (without binding **kwargs),
+    or SkipTest is raised if none exists.
+    """
     assert isinstance(digestname, str), digestname
-    _openssl_availabillity(digestname, usedforsecurity=usedforsecurity)
-    # This returns a function of the form _hashlib.openssl_<name> and
-    # not a lambda function as it is rejected by _hashlib.hmac_new().
-    return getattr(_hashlib, f"openssl_{digestname}")
+    # Re-import 'hashlib' in case it was mocked, but propagate
+    # exceptions as it should be unconditionally available.
+    hashlib = importlib.import_module("hashlib")
+    # re-import '_hashlib' in case it was mocked
+    _hashlib = _import_module("_hashlib")
+    module = _hashlib if openssl and _hashlib is not None else hashlib
+    try:
+        module.new(digestname, **kwargs)
+    except ValueError as exc:
+        raise SkipNoHashInCall(f"{module.__name__}.new", digestname) from exc
+    return functools.partial(module.new, digestname)
 
 
-def requires_builtin_hashdigest(
-    module_name, digestname, *, usedforsecurity=True
-):
-    """Decorator raising SkipTest if a HACL* hashing algorithm is missing.
+def _builtin_hash(module_name, digestname, /, **kwargs):
+    """Check availability of <module_name>.<digestname>(**kwargs).
 
     - The *module_name* is the C extension module name based on HACL*.
     - The *digestname* is one of its member, e.g., 'md5'.
+
+    The constructor function is returned, or SkipTest is raised if none exists.
     """
-    def decorator_func(func):
-        @functools.wraps(func)
-        def wrapper(*args, **kwargs):
-            module = import_module(module_name)
-            try:
-                getattr(module, digestname)
-            except AttributeError:
-                fullname = f'{module_name}.{digestname}'
-                _missing_hash(fullname, implementation="HACL")
-            return func(*args, **kwargs)
-        return wrapper
+    assert isinstance(module_name, str), module_name
+    assert isinstance(digestname, str), digestname
+    fullname = f'{module_name}.{digestname}'
+    try:
+        builtin_module = importlib.import_module(module_name)
+    except ImportError as exc:
+        raise SkipNoHash(fullname, "builtin") from exc
+    try:
+        constructor = getattr(builtin_module, digestname)
+    except AttributeError as exc:
+        raise SkipNoHash(fullname, "builtin") from exc
+    try:
+        constructor(**kwargs)
+    except ValueError as exc:
+        raise SkipNoHash(fullname, "builtin") from exc
+    return constructor
 
-    def decorator(func_or_class):
-        return _decorate_func_or_class(func_or_class, decorator_func)
-    return decorator
 
+def _openssl_new(digestname, /, **kwargs):
+    """Check availability of _hashlib.new(digestname, **kwargs).
 
-def find_builtin_hashdigest_constructor(
-    module_name, digestname, *, usedforsecurity=True
-):
-    """Find the HACL* hash function constructor.
+    The constructor function is returned (without binding **kwargs),
+    or SkipTest is raised if none exists.
+    """
+    assert isinstance(digestname, str), digestname
+    try:
+        # re-import '_hashlib' in case it was mocked
+        _hashlib = importlib.import_module("_hashlib")
+    except ImportError as exc:
+        raise SkipNoHash(digestname, "openssl") from exc
+    try:
+        _hashlib.new(digestname, **kwargs)
+    except ValueError as exc:
+        raise SkipNoHashInCall("_hashlib.new", digestname) from exc
+    return functools.partial(_hashlib.new, digestname)
 
-    - The *module_name* is the C extension module name based on HACL*.
-    - The *digestname* is one of its member, e.g., 'md5'.
+
+def _openssl_hash(digestname, /, **kwargs):
+    """Check availability of _hashlib.openssl_<digestname>(**kwargs).
+
+    The constructor function is returned (without binding **kwargs),
+    or SkipTest is raised if none exists.
     """
-    module = import_module(module_name)
+    assert isinstance(digestname, str), digestname
+    method_name = f"openssl_{digestname}"
+    fullname = f"_hashlib.{method_name}"
+    try:
+        # re-import '_hashlib' in case it was mocked
+        _hashlib = importlib.import_module("_hashlib")
+    except ImportError as exc:
+        raise SkipNoHash(fullname, "openssl") from exc
     try:
-        constructor = getattr(module, digestname)
-        constructor(b'', usedforsecurity=usedforsecurity)
-    except (AttributeError, TypeError, ValueError):
-        _missing_hash(f'{module_name}.{digestname}', implementation="HACL")
+        constructor = getattr(_hashlib, method_name)
+    except AttributeError as exc:
+        raise SkipNoHash(fullname, "openssl") from exc
+    try:
+        constructor(**kwargs)
+    except ValueError as exc:
+        raise SkipNoHash(fullname, "openssl") from exc
     return constructor
 
 
+def requires_hashdigest(digestname, openssl=None, *, usedforsecurity=True):
+    """Decorator raising SkipTest if a hashing algorithm is not available.
+
+    The hashing algorithm may be missing, blocked by a strict crypto policy,
+    or Python may be configured with `--with-builtin-hashlib-hashes=no`.
+
+    If 'openssl' is True, then the decorator checks that OpenSSL provides
+    the algorithm. Otherwise the check falls back to (optional) built-in
+    HACL* implementations.
+
+    The usedforsecurity flag is passed to the constructor but has no effect
+    on HACL* implementations.
+
+    Examples of exceptions being suppressed:
+    ValueError: [digital envelope routines: EVP_DigestInit_ex] disabled for FIPS
+    ValueError: unsupported hash type md4
+    """
+    return _make_conditional_decorator(
+        _hashlib_new, digestname, openssl, usedforsecurity=usedforsecurity
+    )
+
+
+def requires_openssl_hashdigest(digestname, *, usedforsecurity=True):
+    """Decorator raising SkipTest if an OpenSSL hashing algorithm is missing.
+
+    The hashing algorithm may be missing or blocked by a strict crypto policy.
+    """
+    return _make_conditional_decorator(
+        _openssl_new, digestname, usedforsecurity=usedforsecurity
+    )
+
+
+def _make_requires_builtin_hashdigest_decorator(item, *, usedforsecurity=True):
+    assert isinstance(item, _HashInfoItem), item
+    return _make_conditional_decorator(
+        _builtin_hash,
+        item.module_name,
+        item.member_name,
+        usedforsecurity=usedforsecurity,
+    )
+
+
+def requires_builtin_hashdigest(canonical_name, *, usedforsecurity=True):
+    """Decorator raising SkipTest if a HACL* hashing algorithm is missing."""
+    info = get_hash_func_info(canonical_name)
+    return _make_requires_builtin_hashdigest_decorator(
+        info.builtin, usedforsecurity=usedforsecurity
+    )
+
+
+def requires_builtin_hashes(*, exclude=(), usedforsecurity=True):
+    """Decorator raising SkipTest if one HACL* hashing algorithm is missing."""
+    return _chain_decorators((
+        _make_requires_builtin_hashdigest_decorator(
+            info.builtin, usedforsecurity=usedforsecurity
+        ) for info in _iter_hash_func_info(exclude)
+    ))
+
+
 class HashFunctionsTrait:
     """Mixin trait class containing hash functions.
 
@@ -178,59 +759,31 @@ class HashFunctionsTrait:
     implementation of HMAC).
     """
 
-    ALGORITHMS = [
-        'md5', 'sha1',
-        'sha224', 'sha256', 'sha384', 'sha512',
-        'sha3_224', 'sha3_256', 'sha3_384', 'sha3_512',
-    ]
-
-    # Default 'usedforsecurity' to use when looking up a hash function.
+    # Default 'usedforsecurity' to use when checking a hash function.
+    # When the trait properties are callables (e.g., _md5.md5) and
+    # not strings, they must be called with the same 'usedforsecurity'.
     usedforsecurity = True
 
-    def _find_constructor(self, name):
-        # By default, a missing algorithm skips the test that uses it.
-        self.assertIn(name, self.ALGORITHMS)
-        self.skipTest(f"missing hash function: {name}")
-
-    @property
-    def md5(self):
-        return self._find_constructor("md5")
+    def is_valid_digest_name(self, digestname):
+        self.assertIn(digestname, _HashId)
 
-    @property
-    def sha1(self):
-        return self._find_constructor("sha1")
-
-    @property
-    def sha224(self):
-        return self._find_constructor("sha224")
-
-    @property
-    def sha256(self):
-        return self._find_constructor("sha256")
-
-    @property
-    def sha384(self):
-        return self._find_constructor("sha384")
-
-    @property
-    def sha512(self):
-        return self._find_constructor("sha512")
-
-    @property
-    def sha3_224(self):
-        return self._find_constructor("sha3_224")
+    def _find_constructor(self, digestname):
+        # By default, a missing algorithm skips the test that uses it.
+        self.is_valid_digest_name(digestname)
+        self.skipTest(f"missing hash function: {digestname}")
 
-    @property
-    def sha3_256(self):
-        return self._find_constructor("sha3_256")
+    md5 = property(lambda self: self._find_constructor("md5"))
+    sha1 = property(lambda self: self._find_constructor("sha1"))
 
-    @property
-    def sha3_384(self):
-        return self._find_constructor("sha3_384")
+    sha224 = property(lambda self: self._find_constructor("sha224"))
+    sha256 = property(lambda self: self._find_constructor("sha256"))
+    sha384 = property(lambda self: self._find_constructor("sha384"))
+    sha512 = property(lambda self: self._find_constructor("sha512"))
 
-    @property
-    def sha3_512(self):
-        return self._find_constructor("sha3_512")
+    sha3_224 = property(lambda self: self._find_constructor("sha3_224"))
+    sha3_256 = property(lambda self: self._find_constructor("sha3_256"))
+    sha3_384 = property(lambda self: self._find_constructor("sha3_384"))
+    sha3_512 = property(lambda self: self._find_constructor("sha3_512"))
 
 
 class NamedHashFunctionsTrait(HashFunctionsTrait):
@@ -239,9 +792,9 @@ class NamedHashFunctionsTrait(HashFunctionsTrait):
     Hash functions are available if and only if they are available in hashlib.
     """
 
-    def _find_constructor(self, name):
-        self.assertIn(name, self.ALGORITHMS)
-        return name
+    def _find_constructor(self, digestname):
+        self.is_valid_digest_name(digestname)
+        return str(digestname)  # ensure that we are an exact string
 
 
 class OpenSSLHashFunctionsTrait(HashFunctionsTrait):
@@ -250,11 +803,11 @@ class OpenSSLHashFunctionsTrait(HashFunctionsTrait):
     Hash functions are available if and only if they are available in _hashlib.
     """
 
-    def _find_constructor(self, name):
-        self.assertIn(name, self.ALGORITHMS)
-        return find_openssl_hashdigest_constructor(
-            name, usedforsecurity=self.usedforsecurity
-        )
+    def _find_constructor(self, digestname):
+        self.is_valid_digest_name(digestname)
+        # This returns a function of the form _hashlib.openssl_<name> and
+        # not a lambda function as it is rejected by _hashlib.hmac_new().
+        return _openssl_hash(digestname, usedforsecurity=self.usedforsecurity)
 
 
 class BuiltinHashFunctionsTrait(HashFunctionsTrait):
@@ -265,65 +818,278 @@ class BuiltinHashFunctionsTrait(HashFunctionsTrait):
     is not since the former is unconditionally built.
     """
 
-    def _find_constructor_in(self, module, name):
-        self.assertIn(name, self.ALGORITHMS)
-        return find_builtin_hashdigest_constructor(module, name)
+    def _find_constructor(self, digestname):
+        self.is_valid_digest_name(digestname)
+        info = get_hash_func_info(digestname)
+        return _builtin_hash(
+            info.builtin.module_name,
+            info.builtin.member_name,
+            usedforsecurity=self.usedforsecurity,
+        )
 
-    @property
-    def md5(self):
-        return self._find_constructor_in("_md5", "md5")
 
-    @property
-    def sha1(self):
-        return self._find_constructor_in("_sha1", "sha1")
+def find_gil_minsize(modules_names, default=2048):
+    """Get the largest GIL_MINSIZE value for the given cryptographic modules.
 
-    @property
-    def sha224(self):
-        return self._find_constructor_in("_sha2", "sha224")
+    The valid module names are the following:
 
-    @property
-    def sha256(self):
-        return self._find_constructor_in("_sha2", "sha256")
+    - _hashlib
+    - _md5, _sha1, _sha2, _sha3, _blake2
+    - _hmac
+    """
+    sizes = []
+    for module_name in modules_names:
+        module = _import_module(module_name)
+        if module is not None:
+            sizes.append(getattr(module, '_GIL_MINSIZE', default))
+    return max(sizes, default=default)
 
-    @property
-    def sha384(self):
-        return self._find_constructor_in("_sha2", "sha384")
 
-    @property
-    def sha512(self):
-        return self._find_constructor_in("_sha2", "sha512")
+def _block_openssl_hash_new(blocked_name):
+    """Block OpenSSL implementation of _hashlib.new()."""
+    assert isinstance(blocked_name, str), blocked_name
 
-    @property
-    def sha3_224(self):
-        return self._find_constructor_in("_sha3", "sha3_224")
+    # re-import '_hashlib' in case it was mocked
+    if (_hashlib := _import_module("_hashlib")) is None:
+        return contextlib.nullcontext()
 
-    @property
-    def sha3_256(self):
-        return self._find_constructor_in("_sha3","sha3_256")
+    @functools.wraps(wrapped := _hashlib.new)
+    def _hashlib_new(name, data=b'', *, usedforsecurity=True, string=None):
+        if name == blocked_name:
+            raise _hashlib.UnsupportedDigestmodError(blocked_name)
+        return wrapped(name, data,
+                       usedforsecurity=usedforsecurity, string=string)
 
-    @property
-    def sha3_384(self):
-        return self._find_constructor_in("_sha3","sha3_384")
+    _ensure_wrapper_signature(_hashlib_new, wrapped)
+    return unittest.mock.patch('_hashlib.new', _hashlib_new)
 
-    @property
-    def sha3_512(self):
-        return self._find_constructor_in("_sha3","sha3_512")
 
+def _block_openssl_hmac_new(blocked_name):
+    """Block OpenSSL HMAC-HASH implementation."""
+    assert isinstance(blocked_name, str), blocked_name
 
-def find_gil_minsize(modules_names, default=2048):
-    """Get the largest GIL_MINSIZE value for the given cryptographic modules.
+    # re-import '_hashlib' in case it was mocked
+    if (_hashlib := _import_module("_hashlib")) is None:
+        return contextlib.nullcontext()
 
-    The valid module names are the following:
+    @functools.wraps(wrapped := _hashlib.hmac_new)
+    def wrapper(key, msg=b'', digestmod=None):
+        if digestmod == blocked_name:
+            raise _hashlib.UnsupportedDigestmodError(blocked_name)
+        return wrapped(key, msg, digestmod)
 
-    - _hashlib
-    - _md5, _sha1, _sha2, _sha3, _blake2
-    - _hmac
+    _ensure_wrapper_signature(wrapper, wrapped)
+    return unittest.mock.patch('_hashlib.hmac_new', wrapper)
+
+
+def _block_openssl_hmac_digest(blocked_name):
+    """Block OpenSSL HMAC-HASH one-shot digest implementation."""
+    assert isinstance(blocked_name, str), blocked_name
+
+    # re-import '_hashlib' in case it was mocked
+    if (_hashlib := _import_module("_hashlib")) is None:
+        return contextlib.nullcontext()
+
+    @functools.wraps(wrapped := _hashlib.hmac_digest)
+    def _hashlib_hmac_digest(key, msg, digest):
+        if digest == blocked_name:
+            raise _hashlib.UnsupportedDigestmodError(blocked_name)
+        return wrapped(key, msg, digest)
+
+    _ensure_wrapper_signature(_hashlib_hmac_digest, wrapped)
+    return unittest.mock.patch('_hashlib.hmac_digest', _hashlib_hmac_digest)
+
+
+def _block_builtin_hash_new(name):
+    """Block a buitin-in hash name from the hashlib.new() interface."""
+    assert isinstance(name, str), name
+    assert name.lower() == name, f"invalid name: {name}"
+    assert name in _HashId, f"invalid hash: {name}"
+
+    # Re-import 'hashlib' in case it was mocked
+    hashlib = importlib.import_module('hashlib')
+    builtin_constructor_cache = getattr(hashlib, '__builtin_constructor_cache')
+    builtin_constructor_cache_mock = builtin_constructor_cache.copy()
+    builtin_constructor_cache_mock.pop(name, None)
+    builtin_constructor_cache_mock.pop(name.upper(), None)
+
+    # __get_builtin_constructor() imports the HACL* modules on demand,
+    # so we need to block the possibility of importing it, but only
+    # during the call to __get_builtin_constructor().
+    get_builtin_constructor = getattr(hashlib, '__get_builtin_constructor')
+    builtin_module_name = get_hash_func_info(name).builtin.module_name
+
+    @functools.wraps(get_builtin_constructor)
+    def get_builtin_constructor_mock(name):
+        with import_helper.isolated_modules():
+            sys = importlib.import_module("sys")
+            sys.modules[builtin_module_name] = None  # block module's import
+            return get_builtin_constructor(name)
+
+    return unittest.mock.patch.multiple(
+        hashlib,
+        __get_builtin_constructor=get_builtin_constructor_mock,
+        __builtin_constructor_cache=builtin_constructor_cache_mock,
+    )
+
+
+def _block_builtin_hmac_new(blocked_name):
+    assert isinstance(blocked_name, str), blocked_name
+
+    # re-import '_hmac' in case it was mocked
+    if (_hmac := _import_module("_hmac")) is None:
+        return contextlib.nullcontext()
+
+    @functools.wraps(wrapped := _hmac.new)
+    def _hmac_new(key, msg=None, digestmod=None):
+        if digestmod == blocked_name:
+            raise _hmac.UnknownHashError(blocked_name)
+        return wrapped(key, msg, digestmod)
+
+    _ensure_wrapper_signature(_hmac_new, wrapped)
+    return unittest.mock.patch('_hmac.new', _hmac_new)
+
+
+def _block_builtin_hmac_digest(blocked_name):
+    assert isinstance(blocked_name, str), blocked_name
+
+    # re-import '_hmac' in case it was mocked
+    if (_hmac := _import_module("_hmac")) is None:
+        return contextlib.nullcontext()
+
+    @functools.wraps(wrapped := _hmac.compute_digest)
+    def _hmac_compute_digest(key, msg, digest):
+        if digest == blocked_name:
+            raise _hmac.UnknownHashError(blocked_name)
+        return wrapped(key, msg, digest)
+
+    _ensure_wrapper_signature(_hmac_compute_digest, wrapped)
+    return unittest.mock.patch('_hmac.compute_digest', _hmac_compute_digest)
+
+
+def _make_hash_constructor_blocker(name, dummy, implementation):
+    info = get_hash_func_info(name)[implementation]
+    if (wrapped := info.import_member()) is None:
+        # function shouldn't exist for this implementation
+        return contextlib.nullcontext()
+    wrapper = functools.wraps(wrapped)(dummy)
+    _ensure_wrapper_signature(wrapper, wrapped)
+    return unittest.mock.patch(info.fullname, wrapper)
+
+
+def _block_hashlib_hash_constructor(name):
+    """Block explicit public constructors."""
+    def dummy(data=b'', *, usedforsecurity=True, string=None):
+        raise ValueError(f"blocked explicit public hash name: {name}")
+    return _make_hash_constructor_blocker(name, dummy, 'hashlib')
+
+
+def _block_openssl_hash_constructor(name):
+    """Block explicit OpenSSL constructors."""
+    def dummy(data=b'', *, usedforsecurity=True, string=None):
+        raise ValueError(f"blocked explicit OpenSSL hash name: {name}")
+    return _make_hash_constructor_blocker(name, dummy, 'openssl')
+
+
+def _block_builtin_hash_constructor(name):
+    """Block explicit HACL* constructors."""
+    def dummy(data=b'', *, usedforsecurity=True, string=b''):
+        raise ValueError(f"blocked explicit builtin hash name: {name}")
+    return _make_hash_constructor_blocker(name, dummy, 'builtin')
+
+
+def _block_builtin_hmac_constructor(name):
+    """Block explicit HACL* HMAC constructors."""
+    info = get_hmac_item_info(name)
+    assert info.module_name is None or info.module_name == "_hmac", info
+    if (wrapped := info.import_member()) is None:
+        # function shouldn't exist for this implementation
+        return contextlib.nullcontext()
+
+    @functools.wraps(wrapped)
+    def wrapper(key, obj):
+        raise ValueError(f"blocked hash name: {name}")
+
+    _ensure_wrapper_signature(wrapper, wrapped)
+    return unittest.mock.patch(info.fullname, wrapper)
+
+
+@contextlib.contextmanager
+def block_algorithm(name, *, allow_openssl=False, allow_builtin=False):
+    """Block a hash algorithm for both hashing and HMAC.
+
+    Be careful with this helper as a function may be allowed, but can
+    still raise a ValueError at runtime if the OpenSSL security policy
+    disables it, e.g., if allow_openssl=True and FIPS mode is on.
     """
-    sizes = []
-    for module_name in modules_names:
-        try:
-            module = importlib.import_module(module_name)
-        except ImportError:
-            continue
-        sizes.append(getattr(module, '_GIL_MINSIZE', default))
-    return max(sizes, default=default)
+    with contextlib.ExitStack() as stack:
+        if not (allow_openssl or allow_builtin):
+            # Named constructors have a different behavior in the sense
+            # that they are either built-ins or OpenSSL ones, but not
+            # "agile" ones (namely once "hashlib" has been imported,
+            # they are fixed).
+            #
+            # If OpenSSL is not available, hashes fall back to built-in ones,
+            # in which case we don't need to block the explicit public hashes
+            # as they will call a mocked one.
+            #
+            # If OpenSSL is available, hashes fall back to "openssl_*" ones,
+            # except for BLAKE2b and BLAKE2s.
+            stack.enter_context(_block_hashlib_hash_constructor(name))
+        elif (
+            # In FIPS mode, hashlib.<name>() functions may raise if they use
+            # the OpenSSL implementation, except with usedforsecurity=False.
+            # However, blocking such functions also means blocking them
+            # so we again need to block them if we want to.
+            (_hashlib := _import_module("_hashlib"))
+            and _hashlib.get_fips_mode()
+            and not allow_openssl
+        ) or (
+            # Without OpenSSL, hashlib.<name>() functions are aliases
+            # to built-in functions, so both of them must be blocked
+            # as the module may have been imported before the HACL ones.
+            not (_hashlib := _import_module("_hashlib"))
+            and not allow_builtin
+        ):
+            stack.enter_context(_block_hashlib_hash_constructor(name))
+
+        if not allow_openssl:
+            # _hashlib.new()
+            stack.enter_context(_block_openssl_hash_new(name))
+            # _hashlib.openssl_*()
+            stack.enter_context(_block_openssl_hash_constructor(name))
+            # _hashlib.hmac_new()
+            stack.enter_context(_block_openssl_hmac_new(name))
+            # _hashlib.hmac_digest()
+            stack.enter_context(_block_openssl_hmac_digest(name))
+
+        if not allow_builtin:
+            # __get_builtin_constructor(name)
+            stack.enter_context(_block_builtin_hash_new(name))
+            # <built-in module>.<built-in name>()
+            stack.enter_context(_block_builtin_hash_constructor(name))
+            # _hmac.new(..., name)
+            stack.enter_context(_block_builtin_hmac_new(name))
+            # _hmac.compute_<name>()
+            stack.enter_context(_block_builtin_hmac_constructor(name))
+            # _hmac.compute_digest(..., name)
+            stack.enter_context(_block_builtin_hmac_digest(name))
+        yield
+
+
+@contextlib.contextmanager
+def block_openssl_algorithms(*, exclude=()):
+    """Block OpenSSL implementations, except those given in *exclude*."""
+    with contextlib.ExitStack() as stack:
+        for name in CANONICAL_DIGEST_NAMES.difference(exclude):
+            stack.enter_context(block_algorithm(name, allow_builtin=True))
+        yield
+
+
+@contextlib.contextmanager
+def block_builtin_algorithms(*, exclude=()):
+    """Block HACL* implementations, except those given in *exclude*."""
+    with contextlib.ExitStack() as stack:
+        for name in CANONICAL_DIGEST_NAMES.difference(exclude):
+            stack.enter_context(block_algorithm(name, allow_openssl=True))
+        yield
diff --git a/Lib/test/support/import_helper.py b/Lib/test/support/import_helper.py
index 4c7eac0b7eb..e8a3d176ad6 100644
--- a/Lib/test/support/import_helper.py
+++ b/Lib/test/support/import_helper.py
@@ -4,6 +4,7 @@
 import importlib.machinery
 import importlib.util
 import os
+import py_compile
 import shutil
 import sys
 import textwrap
@@ -49,20 +50,31 @@ def forget(modname):
         # combinations of PEP 3147/488 and legacy pyc files.
         unlink(source + 'c')
         for opt in ('', 1, 2):
-            unlink(importlib.util.cache_from_source(source, optimization=opt))
+            try:
+                unlink(importlib.util.cache_from_source(source, optimization=opt))
+            except NotImplementedError:
+                pass
 
 
-def make_legacy_pyc(source):
+def make_legacy_pyc(source, allow_compile=False):
     """Move a PEP 3147/488 pyc file to its legacy pyc location.
 
     :param source: The file system path to the source file.  The source file
-        does not need to exist, however the PEP 3147/488 pyc file must exist.
+        does not need to exist, however the PEP 3147/488 pyc file must exist or
+        allow_compile must be set.
+    :param allow_compile: If True, uses py_compile to create a .pyc if it does
+        not exist. This should be passed as True if cache_tag may be None.
     :return: The file system path to the legacy pyc file.
     """
-    pyc_file = importlib.util.cache_from_source(source)
     assert source.endswith('.py')
     legacy_pyc = source + 'c'
-    shutil.move(pyc_file, legacy_pyc)
+    try:
+        pyc_file = importlib.util.cache_from_source(source)
+        shutil.move(pyc_file, legacy_pyc)
+    except FileNotFoundError, NotImplementedError:
+        if not allow_compile:
+            raise
+        py_compile.compile(source, legacy_pyc, doraise=True)
     return legacy_pyc
 
 
@@ -313,7 +325,7 @@ def ready_to_import(name=None, source=""):
                 sys.modules.pop(name, None)
 
 
-def ensure_lazy_imports(imported_module, modules_to_block):
+def ensure_lazy_imports(imported_module, modules_to_block, *, additional_code=None):
     """Test that when imported_module is imported, none of the modules in
     modules_to_block are imported as a side effect."""
     modules_to_block = frozenset(modules_to_block)
@@ -331,6 +343,16 @@ def ensure_lazy_imports(imported_module, modules_to_block):
             raise AssertionError(f'unexpectedly imported after importing {imported_module}: {{after}}')
         """
     )
+    if additional_code:
+        script += additional_code
+        script += textwrap.dedent(
+            f"""
+            if unexpected := modules_to_block & sys.modules.keys():
+                after = ", ".join(unexpected)
+                raise AssertionError(f'unexpectedly imported after additional code: {{after}}')
+            """
+        )
+
     from .script_helper import assert_python_ok
     assert_python_ok("-S", "-c", script)
 
diff --git a/Lib/test/support/os_helper.py b/Lib/test/support/os_helper.py
index daf6060940e..12d34dedfe1 100644
--- a/Lib/test/support/os_helper.py
+++ b/Lib/test/support/os_helper.py
@@ -1,6 +1,7 @@
 import collections.abc
 import contextlib
 import errno
+import functools
 import logging
 import os
 import re
@@ -433,7 +434,10 @@ def _rmtree_inner(path):
                           file=sys.__stderr__)
                     mode = 0
                 if stat.S_ISDIR(mode):
-                    _waitfor(_rmtree_inner, fullname, waitall=True)
+                    # Do not follow junctions, which os.lstat() reports
+                    # as directories.
+                    if not os.path.isjunction(fullname):
+                        _waitfor(_rmtree_inner, fullname, waitall=True)
                     _force_run(fullname, os.rmdir, fullname)
                 else:
                     _force_run(fullname, os.unlink, fullname)
@@ -806,6 +810,48 @@ def __exit__(self, *ignore_exc):
         os.environ = self._environ
 
 
+def without_source_date_epoch(fxn):
+    """Runs function with SOURCE_DATE_EPOCH unset."""
+    @functools.wraps(fxn)
+    def wrapper(*args, **kwargs):
+        with EnvironmentVarGuard() as env:
+            env.unset('SOURCE_DATE_EPOCH')
+            return fxn(*args, **kwargs)
+    return wrapper
+
+
+_MISSING = sentinel("MISSING")
+
+def with_source_date_epoch(fxn=_MISSING, *, epoch=123456789):
+    """Runs function with SOURCE_DATE_EPOCH set to *epoch*."""
+    if fxn is _MISSING:
+        return functools.partial(with_source_date_epoch, epoch=epoch)
+
+    @functools.wraps(fxn)
+    def wrapper(*args, **kwargs):
+        with EnvironmentVarGuard() as env:
+            env['SOURCE_DATE_EPOCH'] = str(epoch)
+            return fxn(*args, **kwargs)
+    return wrapper
+
+
+# Run tests with SOURCE_DATE_EPOCH set or unset explicitly.
+class SourceDateEpochTestMeta(type(unittest.TestCase)):
+    def __new__(mcls, name, bases, dct, *, source_date_epoch):
+        cls = super().__new__(mcls, name, bases, dct)
+
+        for attr in dir(cls):
+            if attr.startswith('test_'):
+                meth = getattr(cls, attr)
+                if source_date_epoch:
+                    wrapper = with_source_date_epoch(meth)
+                else:
+                    wrapper = without_source_date_epoch(meth)
+                setattr(cls, attr, wrapper)
+
+        return cls
+
+
 try:
     if support.MS_WINDOWS:
         import ctypes
diff --git a/Lib/test/support/warnings_helper.py b/Lib/test/support/warnings_helper.py
index 5f6f14afd74..c046f39fbff 100644
--- a/Lib/test/support/warnings_helper.py
+++ b/Lib/test/support/warnings_helper.py
@@ -1,11 +1,11 @@
 import contextlib
-import functools
 import importlib
 import re
 import sys
 import warnings
 
 
+
 def import_deprecated(name):
     """Import *name* while suppressing DeprecationWarning."""
     with warnings.catch_warnings():
@@ -42,20 +42,32 @@ def check_syntax_warning(testcase, statement, errtext='',
     testcase.assertEqual(warns, [])
 
 
-def ignore_warnings(*, category):
+@contextlib.contextmanager
+def ignore_warnings(*, category, message=''):
     """Decorator to suppress warnings.
 
-    Use of context managers to hide warnings make diffs
-    more noisy and tools like 'git blame' less useful.
+    Can also be used as a context manager. This is not preferred,
+    because it makes diffs more noisy and tools like 'git blame' less useful.
+    But, it's useful for async functions.
     """
-    def decorator(test):
-        @functools.wraps(test)
-        def wrapper(self, *args, **kwargs):
-            with warnings.catch_warnings():
-                warnings.simplefilter('ignore', category=category)
-                return test(self, *args, **kwargs)
-        return wrapper
-    return decorator
+    with warnings.catch_warnings():
+        warnings.filterwarnings('ignore', category=category, message=message)
+        yield
+
+
+@contextlib.contextmanager
+def ignore_fork_in_thread_deprecation_warnings():
+    """Suppress deprecation warnings related to forking in multi-threaded code.
+
+    See gh-135427
+
+    Can be used as decorator (preferred) or context manager.
+    """
+    with ignore_warnings(
+        message=".*fork.*may lead to deadlocks in the child.*",
+        category=DeprecationWarning,
+    ):
+        yield
 
 
 class WarningsRecorder(object):
diff --git a/Lib/test/test__osx_support.py b/Lib/test/test__osx_support.py
index 0813c4804c1..b92ce6796b5 100644
--- a/Lib/test/test__osx_support.py
+++ b/Lib/test/test__osx_support.py
@@ -25,7 +25,7 @@ def setUp(self):
             'CFLAGS', 'LDFLAGS', 'CPPFLAGS',
             'BASECFLAGS', 'BLDSHARED', 'LDSHARED', 'CC',
             'CXX', 'PY_CFLAGS', 'PY_LDFLAGS', 'PY_CPPFLAGS',
-            'PY_CORE_CFLAGS', 'PY_CORE_LDFLAGS'
+            'PY_CORE_CFLAGS', 'PY_CORE_LDFLAGS', 'PY_CORE_EXE_LDFLAGS'
         )
 
     def add_expected_saved_initial_values(self, config_vars, expected_vars):
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
index 80ee9e0ba56..bdfad263db6 100644
--- a/Lib/test/test_abc.py
+++ b/Lib/test/test_abc.py
@@ -349,6 +349,25 @@ class C(str): pass
             self.assertIsSubclass(C, A)
             self.assertIsSubclass(C, (A,))
 
+        def test_instancecheck_no_class(self):
+            # gh-153772: __instancecheck__ must fall back to type(instance)
+            # when the instance has no __class__, matching isinstance().
+            class NoClass:
+                def __getattribute__(self, name):
+                    if name == "__class__":
+                        raise AttributeError(name)
+                    return super().__getattribute__(name)
+
+            class A(metaclass=abc_ABCMeta):
+                pass
+
+            obj = NoClass()
+            # Must return False rather than propagating the AttributeError.
+            self.assertNotIsInstance(obj, A)
+            # Registering the actual type makes the fallback report a match.
+            A.register(NoClass)
+            self.assertIsInstance(obj, A)
+
         def test_registration_edge_cases(self):
             class A(metaclass=abc_ABCMeta):
                 pass
diff --git a/Lib/test/test_annotationlib.py b/Lib/test/test_annotationlib.py
index 5087c3ca425..a7d3bca7402 100644
--- a/Lib/test/test_annotationlib.py
+++ b/Lib/test/test_annotationlib.py
@@ -654,6 +654,13 @@ def f(x: 'int') -> 'str': ...
         result = get_annotations(f, eval_str=True)
         self.assertEqual(result, {'x': int, 'return': str})
 
+    def test_eval_str_wrapped_partial_cycle_self(self):
+        def f(x: 'int') -> 'str': ...
+        f.__wrapped__ = functools.partial(f, 0)
+        # Cycle is detected and broken; globals from f itself are used.
+        result = get_annotations(f, eval_str=True)
+        self.assertEqual(result, {'x': int, 'return': str})
+
     def test_eval_str_wrapped_cycle_mutual(self):
         # gh-146556: mutual __wrapped__ cycle (a -> b -> a) must not hang.
         def a(x: 'int'): ...
@@ -1862,7 +1869,7 @@ def nested():
         self.assertEqual(type_repr(t'''{ 0
             & 1
             | 2
-        }'''), 't"""{ 0\n            & 1\n            | 2}"""')
+        }'''), 't"""{ 0\n            & 1\n            | 2\n        }"""')
         self.assertEqual(
             type_repr(Template("hi", Interpolation(42, "42"))), "t'hi{42}'"
         )
@@ -1874,6 +1881,10 @@ def nested():
             type_repr(Template("hi", Interpolation(42, "   "))),
             "Template('hi', Interpolation(42, '   ', None, ''))",
         )
+        self.assertEqual(
+            type_repr(Template("hi", Interpolation(42, "4!2"))),
+            "Template('hi', Interpolation(42, '4!2', None, ''))",
+        )
         # gh138558: perhaps in the future, we can improve this behavior:
         self.assertEqual(type_repr(Template(Interpolation(42, "99"))), "t'{99}'")
 
@@ -2133,8 +2144,13 @@ def f(a: unknown | str | int | list[str] | tuple[int, ...]): ...
         self.assertIsNone(fr.__resolved_str_cache__)
 
         self.assertEqual(fr.evaluate(format=Format.STRING), "unknown | str | int | list[str] | tuple[int, ...]")
+
+        # Test that the cache is now set correctly
         self.assertEqual(fr.__resolved_str_cache__, "unknown | str | int | list[str] | tuple[int, ...]")
 
+        # Test that future evaluations return the same cache
+        self.assertIs(fr.evaluate(format=Format.STRING), fr.__resolved_str_cache__)
+
     def test_evaluate_forwardref_format(self):
         fr = ForwardRef("undef")
         evaluated = fr.evaluate(format=Format.FORWARDREF)
@@ -2163,6 +2179,118 @@ def test_evaluate_forwardref_format(self):
             support.EqualToForwardRef('"a" + 1'),
         )
 
+    def test_evaluate_lazy_import(self):
+        ns = {}
+        exec(
+            textwrap.dedent(
+                """
+                lazy from test.test_lazy_import.data.basic2 import x
+                lazy from test.test_lazy_import.data.broken_module import y
+
+                class A:
+                    a: x
+
+                class B:
+                    b: y
+                """
+            ),
+            ns,
+        )
+        self.addCleanup(
+            import_helper.unload, "test.test_lazy_import.data.basic2"
+        )
+        self.addCleanup(
+            import_helper.unload, "test.test_lazy_import.data.broken_module"
+        )
+        self.assertIs(type(ns["x"]), types.LazyImportType)
+        self.assertIs(type(ns["y"]), types.LazyImportType)
+
+        # The lazy import resolves successfully:
+        for format in (Format.VALUE, Format.FORWARDREF):
+            with self.subTest(format=format):
+                self.assertEqual(
+                    ForwardRef("x").evaluate(globals=ns, format=format), 42
+                )
+                self.assertEqual(
+                    ForwardRef("x").evaluate(locals=ns, format=format), 42
+                )
+        self.assertEqual(
+            get_annotations(ns["A"], format=Format.FORWARDREF), {"a": 42}
+        )
+
+        # The lazy import fails to resolve:
+        fr = ForwardRef("y")
+        with self.assertRaisesRegex(ValueError, "always fails to import"):
+            fr.evaluate(globals=ns, format=Format.VALUE)
+        with self.assertRaisesRegex(ValueError, "always fails to import"):
+            fr.evaluate(locals=ns, format=Format.VALUE)
+        self.assertIs(fr.evaluate(globals=ns, format=Format.FORWARDREF), fr)
+        self.assertIs(fr.evaluate(locals=ns, format=Format.FORWARDREF), fr)
+
+        annos = get_annotations(ns["B"], format=Format.FORWARDREF)
+        self.assertEqual(
+            annos,
+            {"b": support.EqualToForwardRef("y", is_class=True, owner=ns["B"])},
+        )
+        with self.assertRaisesRegex(ValueError, "always fails to import"):
+            annos["b"].evaluate(format=Format.VALUE)
+        with self.assertRaisesRegex(ValueError, "always fails to import"):
+            get_annotations(ns["B"], format=Format.VALUE)
+
+    def test_get_annotations_lazy_import(self):
+        ns = {}
+        exec(
+            textwrap.dedent(
+                """
+                lazy from test.test_lazy_import.data.basic2 import x
+                lazy from test.test_lazy_import.data.broken_module import y
+
+                class A:
+                    a: object.fail
+                    b: x
+
+                class B:
+                    a: object.fail
+                    b: y
+                """
+            ),
+            ns,
+        )
+        self.addCleanup(
+            import_helper.unload, "test.test_lazy_import.data.basic2"
+        )
+        self.addCleanup(
+            import_helper.unload, "test.test_lazy_import.data.broken_module"
+        )
+        self.assertIs(type(ns["x"]), types.LazyImportType)
+        self.assertIs(type(ns["y"]), types.LazyImportType)
+
+        annos = get_annotations(ns["A"], format=Format.FORWARDREF)
+        self.assertEqual(
+            annos,
+            {
+                "a": support.EqualToForwardRef(
+                    "object.fail", is_class=True, owner=ns["A"]
+                ),
+                "b": 42,
+            },
+        )
+
+        annos = get_annotations(ns["B"], format=Format.FORWARDREF)
+        self.assertEqual(
+            annos,
+            {
+                "a": support.EqualToForwardRef(
+                    "object.fail", is_class=True, owner=ns["B"]
+                ),
+                "b": support.EqualToForwardRef(
+                    "y", is_class=True, owner=ns["B"]
+                ),
+            },
+        )
+        with self.assertRaisesRegex(ValueError, "always fails to import"):
+            annos["b"].evaluate(format=Format.VALUE)
+
     def test_evaluate_notimplemented_format(self):
         class C:
             x: alias
diff --git a/Lib/test/test_ast/data/ast_repr.txt b/Lib/test/test_ast/data/ast_repr.txt
index 1c1985519cd..cc6accd766b 100644
--- a/Lib/test/test_ast/data/ast_repr.txt
+++ b/Lib/test/test_ast/data/ast_repr.txt
@@ -69,10 +69,14 @@ Module(body=[Try(body=[Pass()], handlers=[ExceptHandler(type=Name(...), name='ex
 Module(body=[TryStar(body=[Pass()], handlers=[ExceptHandler(type=Name(...), name='exc', body=[Pass(...)])], orelse=[Pass()], finalbody=[Pass()])], type_ignores=[])
 Module(body=[Assert(test=Name(id='v', ctx=Load(...)), msg=None)], type_ignores=[])
 Module(body=[Assert(test=Name(id='v', ctx=Load(...)), msg=Constant(value='message', kind=None))], type_ignores=[])
-Module(body=[Import(names=[alias(name='sys', asname=None)])], type_ignores=[])
-Module(body=[Import(names=[alias(name='foo', asname='bar')])], type_ignores=[])
-Module(body=[ImportFrom(module='sys', names=[alias(name='x', asname='y')], level=0)], type_ignores=[])
-Module(body=[ImportFrom(module='sys', names=[alias(name='v', asname=None)], level=0)], type_ignores=[])
+Module(body=[Import(names=[alias(name='sys', asname=None)], is_lazy=0)], type_ignores=[])
+Module(body=[Import(names=[alias(name='foo', asname='bar')], is_lazy=0)], type_ignores=[])
+Module(body=[ImportFrom(module='sys', names=[alias(name='x', asname='y')], level=0, is_lazy=0)], type_ignores=[])
+Module(body=[ImportFrom(module='sys', names=[alias(name='v', asname=None)], level=0, is_lazy=0)], type_ignores=[])
+Module(body=[Import(names=[alias(name='sys', asname=None)], is_lazy=1)], type_ignores=[])
+Module(body=[Import(names=[alias(name='foo', asname='bar')], is_lazy=1)], type_ignores=[])
+Module(body=[ImportFrom(module='sys', names=[alias(name='x', asname='y')], level=0, is_lazy=1)], type_ignores=[])
+Module(body=[ImportFrom(module='sys', names=[alias(name='v', asname=None)], level=0, is_lazy=1)], type_ignores=[])
 Module(body=[Global(names=['v'])], type_ignores=[])
 Module(body=[Expr(value=Constant(value=1, kind=None))], type_ignores=[])
 Module(body=[Pass()], type_ignores=[])
diff --git a/Lib/test/test_ast/snippets.py b/Lib/test/test_ast/snippets.py
index b76f98901d2..a565ed10f8b 100644
--- a/Lib/test/test_ast/snippets.py
+++ b/Lib/test/test_ast/snippets.py
@@ -118,6 +118,12 @@
     # ImportFrom
     "from sys import x as y",
     "from sys import v",
+    # Lazy Import
+    "lazy import sys",
+    "lazy import foo as bar",
+    # Lazy ImportFrom
+    "lazy from sys import x as y",
+    "lazy from sys import v",
     # Global
     "global v",
     # Expr
@@ -460,10 +466,14 @@ def main():
 ('Module', [('TryStar', (1, 0, 7, 6), [('Pass', (2, 2, 2, 6))], [('ExceptHandler', (3, 0, 4, 6), ('Name', (3, 8, 3, 17), 'Exception', ('Load',)), 'exc', [('Pass', (4, 2, 4, 6))])], [('Pass', (5, 7, 5, 11))], [('Pass', (7, 2, 7, 6))])], []),
 ('Module', [('Assert', (1, 0, 1, 8), ('Name', (1, 7, 1, 8), 'v', ('Load',)), None)], []),
 ('Module', [('Assert', (1, 0, 1, 19), ('Name', (1, 7, 1, 8), 'v', ('Load',)), ('Constant', (1, 10, 1, 19), 'message', None))], []),
-('Module', [('Import', (1, 0, 1, 10), [('alias', (1, 7, 1, 10), 'sys', None)])], []),
-('Module', [('Import', (1, 0, 1, 17), [('alias', (1, 7, 1, 17), 'foo', 'bar')])], []),
-('Module', [('ImportFrom', (1, 0, 1, 22), 'sys', [('alias', (1, 16, 1, 22), 'x', 'y')], 0)], []),
-('Module', [('ImportFrom', (1, 0, 1, 17), 'sys', [('alias', (1, 16, 1, 17), 'v', None)], 0)], []),
+('Module', [('Import', (1, 0, 1, 10), [('alias', (1, 7, 1, 10), 'sys', None)], 0)], []),
+('Module', [('Import', (1, 0, 1, 17), [('alias', (1, 7, 1, 17), 'foo', 'bar')], 0)], []),
+('Module', [('ImportFrom', (1, 0, 1, 22), 'sys', [('alias', (1, 16, 1, 22), 'x', 'y')], 0, 0)], []),
+('Module', [('ImportFrom', (1, 0, 1, 17), 'sys', [('alias', (1, 16, 1, 17), 'v', None)], 0, 0)], []),
+('Module', [('Import', (1, 0, 1, 15), [('alias', (1, 12, 1, 15), 'sys', None)], 1)], []),
+('Module', [('Import', (1, 0, 1, 22), [('alias', (1, 12, 1, 22), 'foo', 'bar')], 1)], []),
+('Module', [('ImportFrom', (1, 0, 1, 27), 'sys', [('alias', (1, 21, 1, 27), 'x', 'y')], 0, 1)], []),
+('Module', [('ImportFrom', (1, 0, 1, 22), 'sys', [('alias', (1, 21, 1, 22), 'v', None)], 0, 1)], []),
 ('Module', [('Global', (1, 0, 1, 8), ['v'])], []),
 ('Module', [('Expr', (1, 0, 1, 1), ('Constant', (1, 0, 1, 1), 1, None))], []),
 ('Module', [('Pass', (1, 0, 1, 4))], []),
diff --git a/Lib/test/test_ast/test_ast.py b/Lib/test/test_ast/test_ast.py
index aeaa4872e28..68255d17932 100644
--- a/Lib/test/test_ast/test_ast.py
+++ b/Lib/test/test_ast/test_ast.py
@@ -1,4 +1,5 @@
 import _ast_unparse
+import _ast
 import ast
 import builtins
 import contextlib
@@ -13,6 +14,7 @@
 import textwrap
 import types
 import unittest
+import warnings
 import weakref
 from io import StringIO
 from pathlib import Path
@@ -86,7 +88,9 @@ def _assertTrueorder(self, ast_node, parent_pos):
         self.assertEqual(ast_node._fields, ast_node.__match_args__)
 
     def test_AST_objects(self):
-        x = ast.AST()
+        # Directly instantiating abstract node class AST is allowed (but deprecated)
+        with self.assertWarns(DeprecationWarning):
+            x = ast.AST()
         self.assertEqual(x._fields, ())
         x.foobar = 42
         self.assertEqual(x.foobar, 42)
@@ -95,7 +99,7 @@ def test_AST_objects(self):
         with self.assertRaises(AttributeError):
             x.vararg
 
-        with self.assertRaises(TypeError):
+        with self.assertRaises(TypeError), self.assertWarns(DeprecationWarning):
             # "ast.AST constructor takes 0 positional arguments"
             ast.AST(2)
 
@@ -111,15 +115,21 @@ def cleanup():
 
         msg = "type object 'ast.AST' has no attribute '_fields'"
         # Both examples used to crash:
-        with self.assertRaisesRegex(AttributeError, msg):
+        with (
+            self.assertRaisesRegex(AttributeError, msg),
+            self.assertWarns(DeprecationWarning),
+        ):
             ast.AST(arg1=123)
-        with self.assertRaisesRegex(AttributeError, msg):
+        with (
+            self.assertRaisesRegex(AttributeError, msg),
+            self.assertWarns(DeprecationWarning),
+        ):
             ast.AST()
 
-    def test_AST_garbage_collection(self):
+    def test_node_garbage_collection(self):
         class X:
             pass
-        a = ast.AST()
+        a = ast.Module()
         a.x = X()
         a.x.a = a
         ref = weakref.ref(a.x)
@@ -133,7 +143,7 @@ def test_snippets(self):
                                     (eval_tests, eval_results, "eval")):
             for i, o in zip(input, output):
                 with self.subTest(action="parsing", input=i):
-                    ast_tree = compile(i, "?", kind, ast.PyCF_ONLY_AST)
+                    ast_tree = compile(i, "?", kind, ast.PyCF_ONLY_AST, optimize=False)
                     self.assertEqual(to_tuple(ast_tree), o)
                     self._assertTrueorder(ast_tree, (0, 0))
                 with self.subTest(action="compiling", input=i, kind=kind):
@@ -143,7 +153,7 @@ def test_ast_validation(self):
         # compile() is the only function that calls PyAST_Validate
         snippets_to_validate = exec_tests + single_tests + eval_tests
         for snippet in snippets_to_validate:
-            tree = ast.parse(snippet)
+            tree = ast.parse(snippet, optimize=False)
             compile(tree, '<string>', 'exec')
 
     def test_parse_invalid_ast(self):
@@ -152,6 +162,15 @@ def test_parse_invalid_ast(self):
             self.assertRaises(TypeError, ast.parse, ast.Constant(42),
                               optimize=optval)
 
+    def test_parse_ast_func_type(self):
+        # see gh-156689
+        tree = ast.parse('(int, str) -> bool', mode='func_type')
+        self.assertEqual(ast.dump(ast.parse(tree, mode='func_type')),
+                         ast.dump(tree))
+        self.assertRaises(TypeError, ast.parse, ast.Constant(42),
+                          mode='func_type')
+        self.assertRaises(TypeError, ast.parse, tree, mode='exec')
+
     def test_optimization_levels__debug__(self):
         cases = [(-1, '__debug__'), (0, '__debug__'), (1, False), (2, False)]
         for (optval, expected) in cases:
@@ -419,6 +438,17 @@ def test_field_attr_existence(self):
                 if isinstance(x, ast.AST):
                     self.assertIs(type(x._fields), tuple)
 
+    def test_dynamic_attr(self):
+        for name, item in ast.__dict__.items():
+            # constructor has a different signature
+            if name == 'Index':
+                continue
+            if self._is_ast_node(name, item):
+                x = self._construct_ast_class(item)
+                # Custom attribute assignment is allowed
+                x.foo = 5
+                self.assertEqual(x.foo, 5)
+
     def _construct_ast_class(self, cls):
         kwargs = {}
         for name, typ in cls.__annotations__.items():
@@ -429,7 +459,15 @@ def _construct_ast_class(self, cls):
             elif typ is object:
                 kwargs[name] = b'capybara'
             elif isinstance(typ, type) and issubclass(typ, ast.AST):
-                kwargs[name] = self._construct_ast_class(typ)
+                if _ast._is_abstract(typ):
+                    # Use an arbitrary concrete subclass
+                    concrete = next((sub for sub in typ.__subclasses__()
+                                     if not _ast._is_abstract(sub)), None)
+                    msg = f"abstract node class {typ} has no concrete subclasses"
+                    self.assertIsNotNone(concrete, msg)
+                else:
+                    concrete = typ
+                kwargs[name] = self._construct_ast_class(concrete)
         return cls(**kwargs)
 
     def test_arguments(self):
@@ -460,14 +498,9 @@ def test_field_attr_writable(self):
         self.assertEqual(x._fields, 666)
 
     def test_classattrs(self):
-        with self.assertWarns(DeprecationWarning):
-            x = ast.Constant()
+        x = ast.Constant(42)
         self.assertEqual(x._fields, ('value', 'kind'))
 
-        with self.assertRaises(AttributeError):
-            x.value
-
-        x = ast.Constant(42)
         self.assertEqual(x.value, 42)
 
         with self.assertRaises(AttributeError):
@@ -487,11 +520,8 @@ def test_classattrs(self):
         self.assertRaises(TypeError, ast.Constant, 1, None, 2)
         self.assertRaises(TypeError, ast.Constant, 1, None, 2, lineno=0)
 
-        # Arbitrary keyword arguments are supported (but deprecated)
-        with self.assertWarns(DeprecationWarning):
-            self.assertEqual(ast.Constant(1, foo='bar').foo, 'bar')
-
-        with self.assertRaisesRegex(TypeError, "Constant got multiple values for argument 'value'"):
+        msg = "ast.Constant got multiple values for argument 'value'"
+        with self.assertRaisesRegex(TypeError, re.escape(msg)):
             ast.Constant(1, value=2)
 
         self.assertEqual(ast.Constant(42).value, 42)
@@ -530,23 +560,24 @@ def test_module(self):
         self.assertEqual(x.body, body)
 
     def test_nodeclasses(self):
-        # Zero arguments constructor explicitly allowed (but deprecated)
-        with self.assertWarns(DeprecationWarning):
-            x = ast.BinOp()
-        self.assertEqual(x._fields, ('left', 'op', 'right'))
-
-        # Random attribute allowed too
-        x.foobarbaz = 5
-        self.assertEqual(x.foobarbaz, 5)
+        # Zero arguments constructor is not allowed
+        msg = "ast.BinOp.__init__ missing 3 required positional arguments: 'left', 'op', and 'right'"
+        self.assertRaisesRegex(TypeError, re.escape(msg), ast.BinOp)
 
         n1 = ast.Constant(1)
         n3 = ast.Constant(3)
         addop = ast.Add()
         x = ast.BinOp(n1, addop, n3)
+        self.assertEqual(x._fields, ('left', 'op', 'right'))
         self.assertEqual(x.left, n1)
         self.assertEqual(x.op, addop)
         self.assertEqual(x.right, n3)
 
+        # Arbitrary attributes are allowed
+        x.foobarbaz = 5
+        self.assertEqual(x.foobarbaz, 5)
+        self.assertEqual(x._fields, ('left', 'op', 'right'))
+
         x = ast.BinOp(1, 2, 3)
         self.assertEqual(x.left, 1)
         self.assertEqual(x.op, 2)
@@ -570,10 +601,14 @@ def test_nodeclasses(self):
         self.assertEqual(x.right, 3)
         self.assertEqual(x.lineno, 0)
 
-        # Random kwargs also allowed (but deprecated)
-        with self.assertWarns(DeprecationWarning):
-            x = ast.BinOp(1, 2, 3, foobarbaz=42)
-        self.assertEqual(x.foobarbaz, 42)
+        # Arbitrary keyword arguments are not allowed
+        msg = "ast.BinOp.__init__ got an unexpected keyword argument 'foobarbaz'"
+        with self.assertRaisesRegex(TypeError, re.escape(msg)):
+            ast.BinOp(1, 2, 3, foobarbaz=42)
+
+        # Directly instantiating abstract node types is allowed (but deprecated)
+        self.assertWarns(DeprecationWarning, ast.stmt)
+        self.assertWarns(DeprecationWarning, ast.expr_context)
 
     def test_no_fields(self):
         # this used to fail because Sub._fields was None
@@ -582,7 +617,10 @@ def test_no_fields(self):
 
     def test_invalid_sum(self):
         pos = dict(lineno=2, col_offset=3)
-        m = ast.Module([ast.Expr(ast.expr(**pos), **pos)], [])
+        with self.assertWarns(DeprecationWarning):
+            # Creating instances of ast.expr is deprecated
+            e = ast.expr(**pos)
+        m = ast.Module([ast.Expr(e, **pos)], [])
         with self.assertRaises(TypeError) as cm:
             compile(m, "<test>", "exec")
         self.assertIn("but got expr()", str(cm.exception))
@@ -949,6 +987,34 @@ def test_constant_as_name(self):
             with self.assertRaisesRegex(ValueError, f"identifier field can't represent '{constant}' constant"):
                 compile(expr, "<test>", "eval")
 
+    def test_constant_in_identifier_fields(self):
+        # gh-85260: an identifier field holding a constant name used to
+        # crash the compiler
+        for statement in [
+            "def x(): pass",
+            "async def x(): pass",
+            "class x: pass",
+            "from a import x",
+            "from a import b as x",
+            "from a import b, c, d as x",
+            "import x",
+            "import a, b, x",
+            "try: pass\nexcept A as x: pass",
+            "try: pass\nexcept A as b: pass\nexcept B as x: pass\n",
+        ]:
+            for constant in "True", "False", "None":
+                with self.subTest(statement=statement, constant=constant):
+                    tree = ast.parse(statement)
+                    for node in ast.walk(tree):
+                        for field, value in ast.iter_fields(node):
+                            if value == "x":
+                                setattr(node, field, constant)
+                    with self.assertRaisesRegex(
+                            ValueError,
+                            f"identifier field can't represent "
+                            f"'{constant}' constant"):
+                        compile(tree, "<test>", "exec")
+
     @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError not raised
     def test_constant_as_unicode_name(self):
         constants = [
@@ -992,8 +1058,7 @@ def next(self):
         enum._test_simple_enum(_Precedence, _ast_unparse._Precedence)
 
     @support.cpython_only
-    @support.run_with_limited_c_stack(
-        100_000 if sys.platform == "android" else 500_000)
+    @support.skip_if_huge_c_stack(100_000 if sys.platform == "android" else 500_000)
     @skip_wasi_stack_overflow()
     @skip_emscripten_stack_overflow()
     def test_ast_recursion_limit(self):
@@ -1055,7 +1120,7 @@ def test_repr(self) -> None:
         snapshots = AST_REPR_DATA_FILE.read_text().split("\n")
         for test, snapshot in zip(ast_repr_get_test_cases(), snapshots, strict=True):
             with self.subTest(test_input=test):
-                self.assertEqual(repr(ast.parse(test)), snapshot)
+                self.assertEqual(repr(ast.parse(test, optimize=False)), snapshot)
 
     def test_repr_large_input_crash(self):
         # gh-125010: Fix use-after-free in ast repr()
@@ -1076,13 +1141,28 @@ def test_tstring(self):
         self.assertIsInstance(tree.body[0].value.values[0], ast.Constant)
         self.assertIsInstance(tree.body[0].value.values[1], ast.Interpolation)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_optimization_levels_const_folding(self):
-        return super().test_optimization_levels_const_folding()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; will be removed in Python 3.14
-    def test_constant_subclasses_deprecated(self):
-        return super().test_constant_subclasses_deprecated()
+    def test_filter_syntax_warnings_by_module(self):
+        filename = support.findfile('test_import/data/syntax_warnings.py')
+        with open(filename, 'rb') as f:
+            source = f.read()
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=r'<unknown>\z')
+            ast.parse(source)
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10])
+        for wm in wlog:
+            self.assertEqual(wm.filename, '<unknown>')
+            self.assertIs(wm.category, SyntaxWarning)
+
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=r'package\.module\z')
+            warnings.filterwarnings('error', module=r'<unknown>')
+            ast.parse(source, filename, module='package.module')
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10])
+        for wm in wlog:
+            self.assertEqual(wm.filename, filename)
+            self.assertIs(wm.category, SyntaxWarning)
 
 
 class CopyTests(unittest.TestCase):
@@ -1092,14 +1172,19 @@ class CopyTests(unittest.TestCase):
     def iter_ast_classes():
         """Iterate over the (native) subclasses of ast.AST recursively.
 
-        This excludes the special class ast.Index since its constructor
-        returns an integer.
+        This excludes:
+          * abstract AST nodes
+          * the special class ast.Index, since its constructor returns
+            an integer.
         """
         def do(cls):
             if cls.__module__ != 'ast':
                 return
             if cls is ast.Index:
                 return
+            # Don't attempt to create instances of abstract AST nodes
+            if _ast._is_abstract(cls):
+                return
 
             yield cls
             for sub in cls.__subclasses__():
@@ -1366,14 +1451,14 @@ def test_replace_ignore_known_custom_instance_fields(self):
         self.assertRaises(AttributeError, getattr, repl, 'extra')
 
     def test_replace_reject_missing_field(self):
-        # case: warn if deleted field is not replaced
+        # case: raise if deleted field is not replaced
         node = ast.parse('x').body[0].value
         context = node.ctx
         del node.id
 
         self.assertRaises(AttributeError, getattr, node, 'id')
         self.assertIs(node.ctx, context)
-        msg = "Name.__replace__ missing 1 keyword argument: 'id'."
+        msg = "ast.Name.__init__ missing 1 required positional argument: 'id'"
         with self.assertRaisesRegex(TypeError, re.escape(msg)):
             copy.replace(node)
         # assert that there is no side-effect
@@ -1410,7 +1495,7 @@ def test_replace_reject_known_custom_instance_fields_commits(self):
 
         # explicit rejection of known instance fields
         self.assertHasAttr(node, 'extra')
-        msg = "Name.__replace__ got an unexpected keyword argument 'extra'."
+        msg = "ast.Name.__init__ got an unexpected keyword argument 'extra'"
         with self.assertRaisesRegex(TypeError, re.escape(msg)):
             copy.replace(node, extra=1)
         # assert that there is no side-effect
@@ -1424,7 +1509,7 @@ def test_replace_reject_unknown_instance_fields(self):
 
         # explicit rejection of unknown extra fields
         self.assertRaises(AttributeError, getattr, node, 'unknown')
-        msg = "Name.__replace__ got an unexpected keyword argument 'unknown'."
+        msg = "ast.Name.__init__ got an unexpected keyword argument 'unknown'"
         with self.assertRaisesRegex(TypeError, re.escape(msg)):
             copy.replace(node, unknown=1)
         # assert that there is no side-effect
@@ -1459,17 +1544,17 @@ def test_parse_in_error(self):
     def test_dump(self):
         node = ast.parse('spam(eggs, "and cheese")')
         self.assertEqual(ast.dump(node),
-            "Module(body=[Expr(value=Call(func=Name(id='spam', ctx=Load()), "
-            "args=[Name(id='eggs', ctx=Load()), Constant(value='and cheese')]))])"
+            "Module(body=[Expr(value=Call(func=Name(id='spam'), "
+            "args=[Name(id='eggs'), Constant(value='and cheese')]))])"
         )
         self.assertEqual(ast.dump(node, annotate_fields=False),
-            "Module([Expr(Call(Name('spam', Load()), [Name('eggs', Load()), "
+            "Module([Expr(Call(Name('spam'), [Name('eggs'), "
             "Constant('and cheese')]))])"
         )
         self.assertEqual(ast.dump(node, include_attributes=True),
-            "Module(body=[Expr(value=Call(func=Name(id='spam', ctx=Load(), "
+            "Module(body=[Expr(value=Call(func=Name(id='spam', "
             "lineno=1, col_offset=0, end_lineno=1, end_col_offset=4), "
-            "args=[Name(id='eggs', ctx=Load(), lineno=1, col_offset=5, "
+            "args=[Name(id='eggs', lineno=1, col_offset=5, "
             "end_lineno=1, end_col_offset=9), Constant(value='and cheese', "
             "lineno=1, col_offset=11, end_lineno=1, end_col_offset=23)], "
             "lineno=1, col_offset=0, end_lineno=1, end_col_offset=24), "
@@ -1483,18 +1568,18 @@ def test_dump_indent(self):
    body=[
       Expr(
          value=Call(
-            func=Name(id='spam', ctx=Load()),
+            func=Name(id='spam'),
             args=[
-               Name(id='eggs', ctx=Load()),
+               Name(id='eggs'),
                Constant(value='and cheese')]))])""")
         self.assertEqual(ast.dump(node, annotate_fields=False, indent='\t'), """\
 Module(
 \t[
 \t\tExpr(
 \t\t\tCall(
-\t\t\t\tName('spam', Load()),
+\t\t\t\tName('spam'),
 \t\t\t\t[
-\t\t\t\t\tName('eggs', Load()),
+\t\t\t\t\tName('eggs'),
 \t\t\t\t\tConstant('and cheese')]))])""")
         self.assertEqual(ast.dump(node, include_attributes=True, indent=3), """\
 Module(
@@ -1503,7 +1588,6 @@ def test_dump_indent(self):
          value=Call(
             func=Name(
                id='spam',
-               ctx=Load(),
                lineno=1,
                col_offset=0,
                end_lineno=1,
@@ -1511,7 +1595,6 @@ def test_dump_indent(self):
             args=[
                Name(
                   id='eggs',
-                  ctx=Load(),
                   lineno=1,
                   col_offset=5,
                   end_lineno=1,
@@ -1541,23 +1624,23 @@ def test_dump_incomplete(self):
         )
         node = ast.Raise(exc=ast.Name(id='e', ctx=ast.Load()), lineno=3, col_offset=4)
         self.assertEqual(ast.dump(node),
-            "Raise(exc=Name(id='e', ctx=Load()))"
+            "Raise(exc=Name(id='e'))"
         )
         self.assertEqual(ast.dump(node, annotate_fields=False),
-            "Raise(Name('e', Load()))"
+            "Raise(Name('e'))"
         )
         self.assertEqual(ast.dump(node, include_attributes=True),
-            "Raise(exc=Name(id='e', ctx=Load()), lineno=3, col_offset=4)"
+            "Raise(exc=Name(id='e'), lineno=3, col_offset=4)"
         )
         self.assertEqual(ast.dump(node, annotate_fields=False, include_attributes=True),
-            "Raise(Name('e', Load()), lineno=3, col_offset=4)"
+            "Raise(Name('e'), lineno=3, col_offset=4)"
         )
         node = ast.Raise(cause=ast.Name(id='e', ctx=ast.Load()))
         self.assertEqual(ast.dump(node),
-            "Raise(cause=Name(id='e', ctx=Load()))"
+            "Raise(cause=Name(id='e'))"
         )
         self.assertEqual(ast.dump(node, annotate_fields=False),
-            "Raise(cause=Name('e', Load()))"
+            "Raise(cause=Name('e'))"
         )
         # Arguments:
         node = ast.arguments(args=[ast.arg("x")])
@@ -1589,10 +1672,10 @@ def test_dump_incomplete(self):
             [ast.Name('dataclass', ctx=ast.Load())],
         )
         self.assertEqual(ast.dump(node),
-            "ClassDef(name='T', keywords=[keyword(arg='a', value=Constant(value=None))], decorator_list=[Name(id='dataclass', ctx=Load())])",
+            "ClassDef(name='T', keywords=[keyword(arg='a', value=Constant(value=None))], decorator_list=[Name(id='dataclass')])",
         )
         self.assertEqual(ast.dump(node, annotate_fields=False),
-            "ClassDef('T', [], [keyword('a', Constant(None))], [], [Name('dataclass', Load())])",
+            "ClassDef('T', [], [keyword('a', Constant(None))], [], [Name('dataclass')])",
         )
 
     def test_dump_show_empty(self):
@@ -1620,7 +1703,7 @@ def check_text(code, empty, full, **kwargs):
         check_node(
             # Corner case: there are no real `Name` instances with `id=''`:
             ast.Name(id='', ctx=ast.Load()),
-            empty="Name(id='', ctx=Load())",
+            empty="Name(id='')",
             full="Name(id='', ctx=Load())",
         )
 
@@ -1668,35 +1751,45 @@ def check_text(code, empty, full, **kwargs):
 
         check_text(
             "def a(b: int = 0, *, c): ...",
-            empty="Module(body=[FunctionDef(name='a', args=arguments(args=[arg(arg='b', annotation=Name(id='int', ctx=Load()))], kwonlyargs=[arg(arg='c')], kw_defaults=[None], defaults=[Constant(value=0)]), body=[Expr(value=Constant(value=Ellipsis))])])",
+            empty="Module(body=[FunctionDef(name='a', args=arguments(args=[arg(arg='b', annotation=Name(id='int'))], kwonlyargs=[arg(arg='c')], kw_defaults=[None], defaults=[Constant(value=0)]), body=[Expr(value=Constant(value=Ellipsis))])])",
             full="Module(body=[FunctionDef(name='a', args=arguments(posonlyargs=[], args=[arg(arg='b', annotation=Name(id='int', ctx=Load()))], kwonlyargs=[arg(arg='c')], kw_defaults=[None], defaults=[Constant(value=0)]), body=[Expr(value=Constant(value=Ellipsis))], decorator_list=[], type_params=[])], type_ignores=[])",
         )
 
         check_text(
             "def a(b: int = 0, *, c): ...",
-            empty="Module(body=[FunctionDef(name='a', args=arguments(args=[arg(arg='b', annotation=Name(id='int', ctx=Load(), lineno=1, col_offset=9, end_lineno=1, end_col_offset=12), lineno=1, col_offset=6, end_lineno=1, end_col_offset=12)], kwonlyargs=[arg(arg='c', lineno=1, col_offset=21, end_lineno=1, end_col_offset=22)], kw_defaults=[None], defaults=[Constant(value=0, lineno=1, col_offset=15, end_lineno=1, end_col_offset=16)]), body=[Expr(value=Constant(value=Ellipsis, lineno=1, col_offset=25, end_lineno=1, end_col_offset=28), lineno=1, col_offset=25, end_lineno=1, end_col_offset=28)], lineno=1, col_offset=0, end_lineno=1, end_col_offset=28)])",
+            empty="Module(body=[FunctionDef(name='a', args=arguments(args=[arg(arg='b', annotation=Name(id='int', lineno=1, col_offset=9, end_lineno=1, end_col_offset=12), lineno=1, col_offset=6, end_lineno=1, end_col_offset=12)], kwonlyargs=[arg(arg='c', lineno=1, col_offset=21, end_lineno=1, end_col_offset=22)], kw_defaults=[None], defaults=[Constant(value=0, lineno=1, col_offset=15, end_lineno=1, end_col_offset=16)]), body=[Expr(value=Constant(value=Ellipsis, lineno=1, col_offset=25, end_lineno=1, end_col_offset=28), lineno=1, col_offset=25, end_lineno=1, end_col_offset=28)], lineno=1, col_offset=0, end_lineno=1, end_col_offset=28)])",
             full="Module(body=[FunctionDef(name='a', args=arguments(posonlyargs=[], args=[arg(arg='b', annotation=Name(id='int', ctx=Load(), lineno=1, col_offset=9, end_lineno=1, end_col_offset=12), lineno=1, col_offset=6, end_lineno=1, end_col_offset=12)], kwonlyargs=[arg(arg='c', lineno=1, col_offset=21, end_lineno=1, end_col_offset=22)], kw_defaults=[None], defaults=[Constant(value=0, lineno=1, col_offset=15, end_lineno=1, end_col_offset=16)]), body=[Expr(value=Constant(value=Ellipsis, lineno=1, col_offset=25, end_lineno=1, end_col_offset=28), lineno=1, col_offset=25, end_lineno=1, end_col_offset=28)], decorator_list=[], type_params=[], lineno=1, col_offset=0, end_lineno=1, end_col_offset=28)], type_ignores=[])",
             include_attributes=True,
         )
 
         check_text(
             'spam(eggs, "and cheese")',
-            empty="Module(body=[Expr(value=Call(func=Name(id='spam', ctx=Load()), args=[Name(id='eggs', ctx=Load()), Constant(value='and cheese')]))])",
+            empty="Module(body=[Expr(value=Call(func=Name(id='spam'), args=[Name(id='eggs'), Constant(value='and cheese')]))])",
             full="Module(body=[Expr(value=Call(func=Name(id='spam', ctx=Load()), args=[Name(id='eggs', ctx=Load()), Constant(value='and cheese')], keywords=[]))], type_ignores=[])",
         )
 
         check_text(
             'spam(eggs, text="and cheese")',
-            empty="Module(body=[Expr(value=Call(func=Name(id='spam', ctx=Load()), args=[Name(id='eggs', ctx=Load())], keywords=[keyword(arg='text', value=Constant(value='and cheese'))]))])",
+            empty="Module(body=[Expr(value=Call(func=Name(id='spam'), args=[Name(id='eggs')], keywords=[keyword(arg='text', value=Constant(value='and cheese'))]))])",
             full="Module(body=[Expr(value=Call(func=Name(id='spam', ctx=Load()), args=[Name(id='eggs', ctx=Load())], keywords=[keyword(arg='text', value=Constant(value='and cheese'))]))], type_ignores=[])",
         )
 
         check_text(
             "import _ast as ast; from module import sub",
-            empty="Module(body=[Import(names=[alias(name='_ast', asname='ast')]), ImportFrom(module='module', names=[alias(name='sub')], level=0)])",
-            full="Module(body=[Import(names=[alias(name='_ast', asname='ast')]), ImportFrom(module='module', names=[alias(name='sub')], level=0)], type_ignores=[])",
+            empty="Module(body=[Import(names=[alias(name='_ast', asname='ast')], is_lazy=0), ImportFrom(module='module', names=[alias(name='sub')], level=0, is_lazy=0)])",
+            full="Module(body=[Import(names=[alias(name='_ast', asname='ast')], is_lazy=0), ImportFrom(module='module', names=[alias(name='sub')], level=0, is_lazy=0)], type_ignores=[])",
         )
 
+    def test_dump_with_color(self):
+        node = ast.parse("x = 1")
+        self.assertNotIn("\x1b[", ast.dump(node))
+        self.assertNotIn("\x1b[", ast.dump(node, color=False))
+        self.assertIn("\x1b[", ast.dump(node, color=True))
+
+        node = ast.Constant(value="\x1b[31m")
+        self.assertEqual(ast.dump(node), "Constant(value='\\x1b[31m')")
+        self.assertIn("'\\x1b[31m'", ast.dump(node, color=True))
+
     def test_copy_location(self):
         src = ast.parse('1 + 1', mode='eval')
         src.body.right = ast.copy_location(ast.Constant(2), src.body.right)
@@ -1721,12 +1814,12 @@ def test_fix_missing_locations(self):
         self.assertEqual(src, ast.fix_missing_locations(src))
         self.maxDiff = None
         self.assertEqual(ast.dump(src, include_attributes=True),
-            "Module(body=[Expr(value=Call(func=Name(id='write', ctx=Load(), "
+            "Module(body=[Expr(value=Call(func=Name(id='write', "
             "lineno=1, col_offset=0, end_lineno=1, end_col_offset=5), "
             "args=[Constant(value='spam', lineno=1, col_offset=6, end_lineno=1, "
             "end_col_offset=12)], lineno=1, col_offset=0, end_lineno=1, "
             "end_col_offset=13), lineno=1, col_offset=0, end_lineno=1, "
-            "end_col_offset=13), Expr(value=Call(func=Name(id='spam', ctx=Load(), "
+            "end_col_offset=13), Expr(value=Call(func=Name(id='spam', "
             "lineno=1, col_offset=0, end_lineno=1, end_col_offset=0), "
             "args=[Constant(value='eggs', lineno=1, col_offset=0, end_lineno=1, "
             "end_col_offset=0)], lineno=1, col_offset=0, end_lineno=1, "
@@ -1787,22 +1880,22 @@ def test_iter_child_nodes(self):
         )
 
     def test_get_docstring(self):
-        node = ast.parse('"""line one\n  line two"""')
+        node = ast.parse('"""line one\n  line two"""', optimize=False)
         self.assertEqual(ast.get_docstring(node),
                          'line one\nline two')
 
-        node = ast.parse('class foo:\n  """line one\n  line two"""')
+        node = ast.parse('class foo:\n  """line one\n  line two"""', optimize=False)
         self.assertEqual(ast.get_docstring(node.body[0]),
                          'line one\nline two')
 
-        node = ast.parse('def foo():\n  """line one\n  line two"""')
+        node = ast.parse('def foo():\n  """line one\n  line two"""', optimize=False)
         self.assertEqual(ast.get_docstring(node.body[0]),
                          'line one\nline two')
 
-        node = ast.parse('async def foo():\n  """spam\n  ham"""')
+        node = ast.parse('async def foo():\n  """spam\n  ham"""', optimize=False)
         self.assertEqual(ast.get_docstring(node.body[0]), 'spam\nham')
 
-        node = ast.parse('async def foo():\n  """spam\n  ham"""')
+        node = ast.parse('async def foo():\n  """spam\n  ham"""', optimize=False)
         self.assertEqual(ast.get_docstring(node.body[0], clean=False), 'spam\n  ham')
 
         node = ast.parse('x')
@@ -1841,7 +1934,8 @@ def test_multi_line_docstring_col_offset_and_lineno_issue16806(self):
             'def foo():\n  """line one\n  line two"""\n\n'
             '  def bar():\n    """line one\n    line two"""\n'
             '  """line one\n  line two"""\n'
-            '"""line one\nline two"""\n\n'
+            '"""line one\nline two"""\n\n',
+            optimize=False
         )
         self.assertEqual(node.body[0].col_offset, 0)
         self.assertEqual(node.body[0].lineno, 1)
@@ -2414,9 +2508,9 @@ def test_stdlib_validates(self):
                 fn = os.path.join(STDLIB, module)
                 with open(fn, "r", encoding="utf-8") as fp:
                     source = fp.read()
-                mod = ast.parse(source, fn)
+                mod = ast.parse(source, fn, optimize=False)
                 compile(mod, fn, "exec")
-                mod2 = ast.parse(source, fn)
+                mod2 = ast.parse(source, fn, optimize=False)
                 self.assertTrue(ast.compare(mod, mod2))
 
     constant_1 = ast.Constant(1)
@@ -2630,16 +2724,17 @@ def test_assign_to_constant(self):
                          "to in Store context")
 
     def test_get_docstring(self):
-        tree = ast.parse("'docstring'\nx = 1")
+        tree = ast.parse("'docstring'\nx = 1", optimize=False)
         self.assertEqual(ast.get_docstring(tree), 'docstring')
 
     def get_load_const(self, tree):
         # Compile to bytecode, disassemble and get parameter of LOAD_CONST
-        # instructions
+        # and LOAD_COMMON_CONSTANT instructions
         co = compile(tree, '<string>', 'exec')
         consts = []
         for instr in dis.get_instructions(co):
-            if instr.opcode in dis.hasconst:
+            if instr.opcode in dis.hasconst or \
+                    instr.opname == 'LOAD_COMMON_CONSTANT':
                 consts.append(instr.argval)
         return consts
 
@@ -3062,8 +3157,8 @@ def test_source_segment_missing_info(self):
 
 class NodeTransformerTests(ASTTestMixin, unittest.TestCase):
     def assertASTTransformation(self, transformer_class,
-                                initial_code, expected_code):
-        initial_ast = ast.parse(dedent(initial_code))
+                                code, expected_code):
+        initial_ast = ast.parse(dedent(code))
         expected_ast = ast.parse(dedent(expected_code))
 
         transformer = transformer_class()
@@ -3183,11 +3278,10 @@ def test_FunctionDef(self):
         args = ast.arguments()
         self.assertEqual(args.args, [])
         self.assertEqual(args.posonlyargs, [])
-        with self.assertWarnsRegex(DeprecationWarning,
-                                   r"FunctionDef\.__init__ missing 1 required positional argument: 'name'"):
-            node = ast.FunctionDef(args=args)
-        self.assertNotHasAttr(node, "name")
-        self.assertEqual(node.decorator_list, [])
+        msg = "ast.FunctionDef.__init__ missing 1 required positional argument: 'name'"
+        with self.assertRaisesRegex(TypeError, re.escape(msg)):
+            ast.FunctionDef(args=args)
+
         node = ast.FunctionDef(name='foo', args=args)
         self.assertEqual(node.name, 'foo')
         self.assertEqual(node.decorator_list, [])
@@ -3205,9 +3299,8 @@ def test_expr_context(self):
         self.assertEqual(name3.id, "x")
         self.assertIsInstance(name3.ctx, ast.Del)
 
-        with self.assertWarnsRegex(DeprecationWarning,
-                                   r"Name\.__init__ missing 1 required positional argument: 'id'"):
-            name3 = ast.Name()
+        msg = "ast.Name.__init__ missing 1 required positional argument: 'id'"
+        self.assertRaisesRegex(TypeError, re.escape(msg), ast.Name)
 
     def test_custom_subclass_with_no_fields(self):
         class NoInit(ast.AST):
@@ -3246,20 +3339,18 @@ class MyAttrs(ast.AST):
         self.assertEqual(obj.a, 1)
         self.assertEqual(obj.b, 2)
 
-        with self.assertWarnsRegex(DeprecationWarning,
-                                   r"MyAttrs.__init__ got an unexpected keyword argument 'c'."):
-            obj = MyAttrs(c=3)
+        msg = "MyAttrs.__init__ got an unexpected keyword argument 'c'"
+        with self.assertRaisesRegex(TypeError, re.escape(msg)):
+            MyAttrs(c=3)
 
     def test_fields_and_types_no_default(self):
         class FieldsAndTypesNoDefault(ast.AST):
             _fields = ('a',)
             _field_types = {'a': int}
 
-        with self.assertWarnsRegex(DeprecationWarning,
-                                   r"FieldsAndTypesNoDefault\.__init__ missing 1 required positional argument: 'a'\."):
-            obj = FieldsAndTypesNoDefault()
-        with self.assertRaises(AttributeError):
-            obj.a
+        msg = "FieldsAndTypesNoDefault.__init__ missing 1 required positional argument: 'a'"
+        self.assertRaisesRegex(TypeError, re.escape(msg), FieldsAndTypesNoDefault)
+
         obj = FieldsAndTypesNoDefault(a=1)
         self.assertEqual(obj.a, 1)
 
@@ -3270,13 +3361,8 @@ class MoreFieldsThanTypes(ast.AST):
             a: int | None = None
             b: int | None = None
 
-        with self.assertWarnsRegex(
-            DeprecationWarning,
-            r"Field 'b' is missing from MoreFieldsThanTypes\._field_types"
-        ):
-            obj = MoreFieldsThanTypes()
-        self.assertIs(obj.a, None)
-        self.assertIs(obj.b, None)
+        msg = r"Field 'b' is missing from .*\.MoreFieldsThanTypes\._field_types"
+        self.assertRaisesRegex(TypeError, msg, MoreFieldsThanTypes)
 
         obj = MoreFieldsThanTypes(a=1, b=2)
         self.assertEqual(obj.a, 1)
@@ -3288,8 +3374,7 @@ class BadFields(ast.AST):
             _field_types = {'a': int}
 
         # This should not crash
-        with self.assertWarnsRegex(DeprecationWarning, r"Field b'\\xff\\xff.*' .*"):
-            obj = BadFields()
+        self.assertRaisesRegex(TypeError, r"Field b'\\xff\\xff.*' .*", BadFields)
 
     def test_complete_field_types(self):
         class _AllFieldTypes(ast.AST):
@@ -3409,6 +3494,7 @@ def test_subinterpreter(self):
         self.assertEqual(res, 0)
 
 
+@support.force_not_colorized_test_class
 class CommandLineTests(unittest.TestCase):
     def setUp(self):
         self.filename = tempfile.mktemp()
@@ -3481,7 +3567,7 @@ def test_exec_mode_flag(self):
                body=[
                   AnnAssign(
                      target=Name(id='x', ctx=Store()),
-                     annotation=Name(id='bool', ctx=Load()),
+                     annotation=Name(id='bool'),
                      value=Constant(value=1),
                      simple=1)],
                type_ignores=[
@@ -3509,7 +3595,7 @@ def test_eval_mode_flag(self):
         expect = '''
             Expression(
                body=Call(
-                  func=Name(id='print', ctx=Load()),
+                  func=Name(id='print'),
                   args=[
                      Constant(value=1),
                      Constant(value=2),
@@ -3525,12 +3611,11 @@ def test_func_type_mode_flag(self):
         expect = '''
             FunctionType(
                argtypes=[
-                  Name(id='int', ctx=Load()),
-                  Name(id='str', ctx=Load())],
+                  Name(id='int'),
+                  Name(id='str')],
                returns=Subscript(
-                  value=Name(id='list', ctx=Load()),
-                  slice=Name(id='int', ctx=Load()),
-                  ctx=Load()))
+                  value=Name(id='list'),
+                  slice=Name(id='int')))
         '''
         for flag in ('-m=func_type', '--mode=func_type'):
             with self.subTest(flag=flag):
@@ -3544,7 +3629,7 @@ def test_no_type_comments_flag(self):
                body=[
                   AnnAssign(
                      target=Name(id='x', ctx=Store()),
-                     annotation=Name(id='bool', ctx=Load()),
+                     annotation=Name(id='bool'),
                      value=Constant(value=1),
                      simple=1)])
         '''
@@ -3589,7 +3674,7 @@ def test_feature_version_flag(self):
             Module(
                body=[
                   Match(
-                     subject=Name(id='x', ctx=Load()),
+                     subject=Name(id='x'),
                      cases=[
                         match_case(
                            pattern=MatchValue(
@@ -3612,7 +3697,7 @@ def test_no_optimize_flag(self):
             Module(
                body=[
                   Match(
-                     subject=Name(id='a', ctx=Load()),
+                     subject=Name(id='a'),
                      cases=[
                         match_case(
                            pattern=MatchValue(
@@ -3638,7 +3723,7 @@ def test_optimize_flag(self):
             Module(
                body=[
                   Match(
-                     subject=Name(id='a', ctx=Load()),
+                     subject=Name(id='a'),
                      cases=[
                         match_case(
                            pattern=MatchValue(
@@ -3793,46 +3878,6 @@ def test_match_case_not_folded_in_unoptimized_ast(self):
         for optval in (0, 1, 2):
             self.assertIn(folded if optval else unfolded, ast.dump(ast.parse(src, optimize=optval)))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_binop(self):
-        return super().test_folding_binop()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_comparator(self):
-        return super().test_folding_comparator()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_iter(self):
-        return super().test_folding_iter()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_not(self):
-        return super().test_folding_not()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_subscript(self):
-        return super().test_folding_subscript()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_tuple(self):
-        return super().test_folding_tuple()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_type_param_in_class_def(self):
-        return super().test_folding_type_param_in_class_def()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_type_param_in_function_def(self):
-        return super().test_folding_type_param_in_function_def()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_type_param_in_type_alias(self):
-        return super().test_folding_type_param_in_type_alias()
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ValueError: compile() unrecognized flags
-    def test_folding_unaryop(self):
-        return super().test_folding_unaryop()
-
 
 if __name__ == '__main__':
     if len(sys.argv) > 1 and sys.argv[1] == '--snapshot-update':
diff --git a/Lib/test/test_asyncio/test_futures.py b/Lib/test/test_asyncio/test_futures.py
index 785258a2749..9385a65e528 100644
--- a/Lib/test/test_asyncio/test_futures.py
+++ b/Lib/test/test_asyncio/test_futures.py
@@ -413,7 +413,7 @@ def func_repr(func):
     def test_copy_state(self):
         from asyncio.futures import _copy_future_state
 
-        f = self._new_future(loop=self.loop)
+        f = concurrent.futures.Future()
         f.set_result(10)
 
         newf = self._new_future(loop=self.loop)
@@ -421,7 +421,7 @@ def test_copy_state(self):
         self.assertTrue(newf.done())
         self.assertEqual(newf.result(), 10)
 
-        f_exception = self._new_future(loop=self.loop)
+        f_exception = concurrent.futures.Future()
         f_exception.set_exception(RuntimeError())
 
         newf_exception = self._new_future(loop=self.loop)
@@ -429,7 +429,7 @@ def test_copy_state(self):
         self.assertTrue(newf_exception.done())
         self.assertRaises(RuntimeError, newf_exception.result)
 
-        f_cancelled = self._new_future(loop=self.loop)
+        f_cancelled = concurrent.futures.Future()
         f_cancelled.cancel()
 
         newf_cancelled = self._new_future(loop=self.loop)
@@ -441,7 +441,7 @@ def test_copy_state(self):
         except BaseException as e:
             f_exc = e
 
-        f_conexc = self._new_future(loop=self.loop)
+        f_conexc = concurrent.futures.Future()
         f_conexc.set_exception(f_exc)
 
         newf_conexc = self._new_future(loop=self.loop)
@@ -454,6 +454,56 @@ def test_copy_state(self):
         newf_tb = ''.join(traceback.format_tb(newf_exc.__traceback__))
         self.assertEqual(newf_tb.count('raise concurrent.futures.InvalidStateError'), 1)
 
+    def test_copy_state_from_concurrent_futures(self):
+        """Test _copy_future_state from concurrent.futures.Future.
+
+        This tests the optimized path using _get_snapshot when available.
+        """
+        from asyncio.futures import _copy_future_state
+
+        # Test with a result
+        f_concurrent = concurrent.futures.Future()
+        f_concurrent.set_result(42)
+        f_asyncio = self._new_future(loop=self.loop)
+        _copy_future_state(f_concurrent, f_asyncio)
+        self.assertTrue(f_asyncio.done())
+        self.assertEqual(f_asyncio.result(), 42)
+
+        # Test with an exception
+        f_concurrent_exc = concurrent.futures.Future()
+        f_concurrent_exc.set_exception(ValueError("test exception"))
+        f_asyncio_exc = self._new_future(loop=self.loop)
+        _copy_future_state(f_concurrent_exc, f_asyncio_exc)
+        self.assertTrue(f_asyncio_exc.done())
+        with self.assertRaises(ValueError) as cm:
+            f_asyncio_exc.result()
+        self.assertEqual(str(cm.exception), "test exception")
+
+        # Test with cancelled state
+        f_concurrent_cancelled = concurrent.futures.Future()
+        f_concurrent_cancelled.cancel()
+        f_asyncio_cancelled = self._new_future(loop=self.loop)
+        _copy_future_state(f_concurrent_cancelled, f_asyncio_cancelled)
+        self.assertTrue(f_asyncio_cancelled.cancelled())
+
+        # Test that destination already cancelled prevents copy
+        f_concurrent_result = concurrent.futures.Future()
+        f_concurrent_result.set_result(10)
+        f_asyncio_precancelled = self._new_future(loop=self.loop)
+        f_asyncio_precancelled.cancel()
+        _copy_future_state(f_concurrent_result, f_asyncio_precancelled)
+        self.assertTrue(f_asyncio_precancelled.cancelled())
+
+        # Test exception type conversion
+        f_concurrent_invalid = concurrent.futures.Future()
+        f_concurrent_invalid.set_exception(concurrent.futures.InvalidStateError("invalid"))
+        f_asyncio_invalid = self._new_future(loop=self.loop)
+        _copy_future_state(f_concurrent_invalid, f_asyncio_invalid)
+        self.assertTrue(f_asyncio_invalid.done())
+        with self.assertRaises(asyncio.exceptions.InvalidStateError) as cm:
+            f_asyncio_invalid.result()
+        self.assertEqual(str(cm.exception), "invalid")
+
     def test_iter(self):
         fut = self._new_future(loop=self.loop)
 
@@ -700,6 +750,10 @@ def test_future_cancelled_exception_refcycles(self):
         self.assertIsNotNone(exc)
         self.assertListEqual(gc.get_referrers(exc), [])
 
+    def test_future_disallow_multiple_initialization(self):
+        f = self._new_future(loop=self.loop)
+        with self.assertRaises(RuntimeError, msg="is already initialized"):
+            f.__init__(loop=self.loop)
 
 @unittest.skipUnless(hasattr(futures, '_CFuture'),
                      'requires the C _asyncio module')
@@ -1041,33 +1095,6 @@ def __getattribute__(self, name):
             fut.add_done_callback(fut_callback_0)
             self.assertRaises(ReachableCode, fut.set_result, "boom")
 
-    def test_use_after_free_on_fut_context_0_with_evil__getattribute__(self):
-        # see: https://github.com/python/cpython/issues/125984
-
-        class EvilEventLoop(SimpleEvilEventLoop):
-            def call_soon(self, *args, **kwargs):
-                super().call_soon(*args, **kwargs)
-                raise ReachableCode
-
-            def __getattribute__(self, name):
-                if name == 'call_soon':
-                    # resets the future's event loop
-                    fut.__init__(loop=SimpleEvilEventLoop())
-                return object.__getattribute__(self, name)
-
-        evil_loop = EvilEventLoop()
-        with mock.patch.object(self, 'loop', evil_loop):
-            fut = self._new_future()
-            self.assertIs(fut.get_loop(), evil_loop)
-
-            fut_callback_0 = mock.Mock()
-            fut_context_0 = mock.Mock()
-            fut.add_done_callback(fut_callback_0, context=fut_context_0)
-            del fut_context_0
-            del fut_callback_0
-            self.assertRaises(ReachableCode, fut.set_result, "boom")
-
-
 @unittest.skipUnless(hasattr(futures, '_CFuture'),
                      'requires the C _asyncio module')
 class CFutureDoneCallbackTests(BaseFutureDoneCallbackTests,
diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py
index a3c5351fed0..a2f80edeb1d 100644
--- a/Lib/test/test_asyncio/test_tasks.py
+++ b/Lib/test/test_asyncio/test_tasks.py
@@ -1218,6 +1218,38 @@ def gen():
         loop.advance_time(10)
         loop.run_until_complete(asyncio.wait([a, b]))
 
+    def test_wait_discards_awaited_by_for_pending(self):
+        # gh-152569: wait() must remove itself from the await-graph of every
+        # future once it returns, including futures that never resolved.
+        async def coro():
+            immortal = self.loop.create_future()
+            done = self.new_task(self.loop, asyncio.sleep(0))
+            await asyncio.wait({done, immortal},
+                               return_when=asyncio.FIRST_COMPLETED)
+            self.assertFalse(immortal._asyncio_awaited_by)
+            immortal.cancel()
+
+        self.loop.run_until_complete(self.new_task(self.loop, coro()))
+
+    def test_gather_discards_awaited_by_for_pending(self):
+        # gh-157213: a child outliving gather() must lose the awaited-by edge
+        async def fail():
+            raise ValueError
+
+        async def survivor():
+            await asyncio.Future()
+
+        async def coro():
+            t = self.new_task(self.loop, survivor())
+            with self.assertRaises(ValueError):
+                await asyncio.gather(t, fail())
+            self.assertFalse(t._asyncio_awaited_by)
+            t.cancel()
+            with self.assertRaises(asyncio.CancelledError):
+                await t
+
+        self.loop.run_until_complete(self.new_task(self.loop, coro()))
+
     def test_wait_really_done(self):
         # there is possibility that some tasks in the pending list
         # became done but their callbacks haven't all been called yet
@@ -2115,6 +2147,8 @@ def test_shield_cancel_outer(self):
         test_utils.run_briefly(self.loop)
         self.assertTrue(outer.cancelled())
         self.assertEqual(0, 0 if outer._callbacks is None else len(outer._callbacks))
+        self.assertFalse(inner._asyncio_awaited_by)
+        self.assertTrue({f for f, _ctx in inner._callbacks or []} <= {asyncio.tasks._log_on_exception})
 
     def test_shield_cancel_outer_result(self):
         mock_handler = mock.Mock()
@@ -2140,6 +2174,21 @@ def test_shield_cancel_outer_exception(self):
         test_utils.run_briefly(self.loop)
         mock_handler.assert_called_once()
 
+    def test_shield_cancel_outer_in_task(self):
+        inner = self.new_future(self.loop)
+
+        async def coro():
+            outer = asyncio.shield(inner)
+            self.assertNotEqual(0, len(inner._callbacks))
+            outer.cancel()
+            await asyncio.sleep(0)
+            self.assertTrue(outer.cancelled())
+
+        task = self.new_task(self.loop, coro())
+        self.loop.run_until_complete(task)
+        self.assertFalse(inner._asyncio_awaited_by)
+        self.assertTrue({f for f, _ctx in inner._callbacks or []} <= {asyncio.tasks._log_on_exception})
+
     def test_shield_duplicate_log_once(self):
         mock_handler = mock.Mock()
         self.loop.set_exception_handler(mock_handler)
@@ -2581,6 +2630,68 @@ async def main():
         finally:
             loop.close()
 
+    def test_context_not_a_context(self):
+        # gh-157301
+        async def coro():
+            pass
+
+        loop = asyncio.new_event_loop()
+        c = coro()
+        try:
+            with self.assertRaises(TypeError):
+                self.new_task(loop, c, context='not a context')
+        finally:
+            c.close()
+            loop.close()
+
+    def test_context_not_a_context_leaves_loop_usable(self):
+        # gh-157301
+        async def coro():
+            pass
+
+        async def main():
+            c = coro()
+            try:
+                with self.assertRaises(TypeError):
+                    self.new_task(loop, c, context='not a context',
+                                  eager_start=True)
+            finally:
+                c.close()
+            await asyncio.sleep(0)
+
+        loop = asyncio.new_event_loop()
+        loop.call_later(support.SHORT_TIMEOUT, loop.stop)
+        try:
+            loop.run_until_complete(self.new_task(loop, main()))
+        finally:
+            loop.close()
+
+    def test_context_already_entered_leaves_loop_usable(self):
+        # gh-157301
+        async def coro():
+            pass
+
+        async def main():
+            ctx = contextvars.copy_context()
+
+            def inside():
+                c = coro()
+                try:
+                    with self.assertRaises(RuntimeError):
+                        self.new_task(loop, c, context=ctx, eager_start=True)
+                finally:
+                    c.close()
+
+            ctx.run(inside)
+            await asyncio.sleep(0)
+
+        loop = asyncio.new_event_loop()
+        loop.call_later(support.SHORT_TIMEOUT, loop.stop)
+        try:
+            loop.run_until_complete(self.new_task(loop, main()))
+        finally:
+            loop.close()
+
     def test_context_2(self):
         cvar = contextvars.ContextVar('cvar', default='nope')
 
@@ -2739,6 +2850,18 @@ async def main():
             self.assertEqual(name, "example")
             await t
 
+    def test_eager_start_true_no_loop(self):
+        # gh-154695: eager_start must use the resolved loop, not loop=None.
+        async def asyncfn():
+            return 42
+
+        async def main():
+            t = self.__class__.Task(asyncfn(), eager_start=True)
+            self.assertTrue(t.done())
+            self.assertEqual(await t, 42)
+
+        asyncio.run(main(), loop_factory=asyncio.EventLoop)
+
     def test_eager_start_false(self):
         name = None
 
@@ -2776,28 +2899,17 @@ def test_get_context(self):
         finally:
             loop.close()
 
-    def test_proper_refcounts(self):
-        # see: https://github.com/python/cpython/issues/126083
-        class Break:
-            def __str__(self):
-                raise RuntimeError("break")
-
-        obj = object()
-        initial_refcount = sys.getrefcount(obj)
-
-        coro = coroutine_function()
-        with contextlib.closing(asyncio.EventLoop()) as loop:
-            task = asyncio.Task.__new__(asyncio.Task)
-            for _ in range(5):
-                with self.assertRaisesRegex(RuntimeError, 'break'):
-                    task.__init__(coro, loop=loop, context=obj, name=Break())
-
-            coro.close()
-            task._log_destroy_pending = False
-            del task
+    def test_task_disallow_multiple_initialization(self):
+        async def foo():
+            pass
 
-            self.assertEqual(sys.getrefcount(obj), initial_refcount)
+        coro = foo()
+        self.addCleanup(coro.close)
+        task = self.new_task(self.loop, coro)
+        task._log_destroy_pending = False
 
+        with self.assertRaises(RuntimeError, msg="is already initialized"):
+            task.__init__(coro, loop=self.loop)
 
 def add_subclass_tests(cls):
     BaseTask = cls.Task
@@ -2921,19 +3033,6 @@ class CTask_CFuture_Tests(BaseTaskTests, SetMethodsTest,
     all_tasks = getattr(tasks, '_c_all_tasks', None)
     current_task = staticmethod(getattr(tasks, '_c_current_task', None))
 
-    @support.refcount_test
-    def test_refleaks_in_task___init__(self):
-        gettotalrefcount = support.get_attribute(sys, 'gettotalrefcount')
-        async def coro():
-            pass
-        task = self.new_task(self.loop, coro())
-        self.loop.run_until_complete(task)
-        refs_before = gettotalrefcount()
-        for i in range(100):
-            task.__init__(coro(), loop=self.loop)
-            self.loop.run_until_complete(task)
-        self.assertAlmostEqual(gettotalrefcount() - refs_before, 0, delta=10)
-
     def test_del__log_destroy_pending_segfault(self):
         async def coro():
             pass
@@ -2942,6 +3041,16 @@ async def coro():
         with self.assertRaises(AttributeError):
             del task._log_destroy_pending
 
+    def test_get_context_uninitialized_segfault(self):
+        # https://github.com/python/cpython/issues/154871
+
+        class UninitializedTask(self.Task):
+            def __init__(self, *args, **kwargs):
+                pass
+
+        task = UninitializedTask()
+        self.assertIsNone(task.get_context())
+
 
 @unittest.skipUnless(hasattr(futures, '_CFuture') and
                      hasattr(tasks, '_CTask'),
diff --git a/Lib/test/test_audit.py b/Lib/test/test_audit.py
index 690a6e7434e..8c1658ca604 100644
--- a/Lib/test/test_audit.py
+++ b/Lib/test/test_audit.py
@@ -94,7 +94,6 @@ def test_posixsubprocess(self):
         import_helper.import_module("_posixsubprocess")
         self.do_test("test_posixsubprocess")
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_excepthook(self):
         returncode, events, stderr = self.run_python("test_excepthook")
         if not returncode:
@@ -345,5 +344,17 @@ def test_sys_remote_exec(self):
         if returncode:
             self.fail(stderr)
 
+    @unittest.expectedFailureIf(__import__("importlib.util", fromlist=["find_spec"]).find_spec("_testcapi") is None, "TODO: RUSTPYTHON; requires the absent _testcapi module for extension import audit events; recheck when discoverable")
+    def test_import_module(self):
+        self.do_test("test_import_module")
+
+    @unittest.expectedFailureIf(__import__("importlib.util", fromlist=["find_spec"]).find_spec("_testcapi") is None, "TODO: RUSTPYTHON; requires the absent _testcapi module for extension import audit events; recheck when discoverable")
+    def test_builtin__import__(self):
+        self.do_test("test_builtin__import__")
+
+    @unittest.expectedFailureIf(__import__("importlib.util", fromlist=["find_spec"]).find_spec("_testcapi") is None, "TODO: RUSTPYTHON; requires the absent _testcapi module for extension import audit events; recheck when discoverable")
+    def test_import_statement(self):
+        self.do_test("test_import_statement")
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_base64.py b/Lib/test/test_base64.py
index 9fe69f4f692..868abcfee24 100644
--- a/Lib/test/test_base64.py
+++ b/Lib/test/test_base64.py
@@ -1,9 +1,11 @@
 import unittest
 import base64
 import binascii
+import string
+import sys
 import os
 from array import array
-from test.support import cpython_only
+from test.support import cpython_only, check_impl_detail
 from test.support import os_helper
 from test.support import script_helper
 from test.support.import_helper import ensure_lazy_imports
@@ -14,6 +16,8 @@ class LazyImportTest(unittest.TestCase):
     def test_lazy_import(self):
         ensure_lazy_imports("base64", {"re", "getopt"})
 
+from test.support.hypothesis_helper import hypothesis
+
 
 class LegacyBase64TestCase(unittest.TestCase):
 
@@ -68,6 +72,13 @@ def test_decodebytes(self):
         eq(base64.decodebytes(array('B', b'YWJj\n')), b'abc')
         self.check_type_errors(base64.decodebytes)
 
+    @hypothesis.given(payload=hypothesis.strategies.binary())
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz')
+    def test_bytes_encode_decode_round_trip(self, payload):
+        encoded = base64.encodebytes(payload)
+        decoded = base64.decodebytes(encoded)
+        self.assertEqual(payload, decoded)
+
     def test_encode(self):
         eq = self.assertEqual
         from io import BytesIO, StringIO
@@ -96,6 +107,19 @@ def test_decode(self):
         self.assertRaises(TypeError, base64.encode, BytesIO(b'YWJj\n'), StringIO())
         self.assertRaises(TypeError, base64.encode, StringIO('YWJj\n'), StringIO())
 
+    @hypothesis.given(payload=hypothesis.strategies.binary())
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz')
+    def test_legacy_encode_decode_round_trip(self, payload):
+        from io import BytesIO
+        payload_file_r = BytesIO(payload)
+        encoded_file_w = BytesIO()
+        base64.encode(payload_file_r, encoded_file_w)
+        encoded_file_r = BytesIO(encoded_file_w.getvalue())
+        decoded_file_w = BytesIO()
+        base64.decode(encoded_file_r, decoded_file_w)
+        decoded = decoded_file_w.getvalue()
+        self.assertEqual(payload, decoded)
+
 
 class BaseXYTestCase(unittest.TestCase):
 
@@ -149,6 +173,7 @@ def test_b64encode(self):
            b"YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXpBQkNE"
            b"RUZHSElKS0xNTk9QUVJTVFVWV1hZWjAxMjM0NT"
            b"Y3ODkhQCMwXiYqKCk7Ojw+LC4gW117fQ==")
+
         # Test with arbitrary alternative characters
         eq(base64.b64encode(b'\xd3V\xbeo\xf7\x1d', altchars=b'*$'), b'01a*b$cd')
         eq(base64.b64encode(b'\xd3V\xbeo\xf7\x1d', altchars=bytearray(b'*$')),
@@ -184,6 +209,55 @@ def test_b64encode(self):
                                b'\xd3V\xbeo\xf7\x1d', b'01a-b_cd')
         self.check_encode_type_errors(base64.urlsafe_b64encode)
 
+    def test_b64encode_padded(self):
+        b64encode = base64.b64encode
+        self.assertEqual(b64encode(b'', padded=False), b'')
+        self.assertEqual(b64encode(b'a', padded=False), b'YQ')
+        self.assertEqual(b64encode(b'ab', padded=False), b'YWI')
+        self.assertEqual(b64encode(b'abc', padded=False), b'YWJj')
+        self.assertEqual(b64encode(b'\xfb', padded=False, altchars=b'-_'), b'-w')
+        self.assertEqual(b64encode(b'\xfb\xff', padded=False, altchars=b'-_'),
+                         b'-_8')
+        self.assertEqual(b64encode(b'\xfb\xff\xbf', padded=False, altchars=b'-_'),
+                         b'-_-_')
+
+        urlsafe_b64encode = base64.urlsafe_b64encode
+        self.assertEqual(urlsafe_b64encode(b'', padded=False), b'')
+        self.assertEqual(urlsafe_b64encode(b'\xfb', padded=False), b'-w')
+        self.assertEqual(urlsafe_b64encode(b'\xfb\xff', padded=False), b'-_8')
+        self.assertEqual(urlsafe_b64encode(b'\xfb\xff\xbf', padded=False),
+                         b'-_-_')
+
+    def _common_test_wrapcol(self, func, data):
+        eq = self.assertEqual
+        expected = func(data)
+        eq(func(data, wrapcol=0), expected)
+        eq(func(data, wrapcol=80), expected)
+        eq(func(b'', wrapcol=0), func(b''))
+        eq(func(b'', wrapcol=1), func(b''))
+        eq(func(data, wrapcol=sys.maxsize), expected)
+        if check_impl_detail():
+            eq(func(data, wrapcol=sys.maxsize*2), expected)
+            with self.assertRaises(OverflowError):
+                func(data, wrapcol=2**1000)
+        with self.assertRaises(ValueError):
+            func(data, wrapcol=-80)
+        with self.assertRaises(TypeError):
+            func(data, wrapcol=80.0)
+        with self.assertRaises(TypeError):
+            func(data, wrapcol='80')
+        if func is not base64.b16encode:
+            with self.assertRaises(TypeError):
+                func(data, wrapcol=None)
+
+    def test_b64encode_wrapcol(self):
+        eq = self.assertEqual
+        b = b'www.python.org'
+        self._common_test_wrapcol(base64.b64encode, b)
+        eq(base64.b64encode(b, wrapcol=8), b'd3d3LnB5\ndGhvbi5v\ncmc=')
+        eq(base64.b64encode(b, wrapcol=11), b'd3d3LnB5\ndGhvbi5v\ncmc=')
+        eq(base64.b64encode(b, wrapcol=1), b'd3d3\nLnB5\ndGhv\nbi5v\ncmc=')
+
     def test_b64decode(self):
         eq = self.assertEqual
 
@@ -241,29 +315,100 @@ def test_b64decode_altchars(self):
             eq(base64.b64decode(data_str, altchars=altchars), res)
             eq(base64.b64decode(data, altchars=altchars_str), res)
             eq(base64.b64decode(data_str, altchars=altchars_str), res)
+            eq(base64.b64decode(data, altchars=altchars, ignorechars=b'\n'), res)
+
+        eq(base64.b64decode(b'/----', altchars=b'-+', ignorechars=b'/'), b'\xfb\xef\xbe')
+        eq(base64.b64decode(b'/----', altchars=b'+-', ignorechars=b'/'), b'\xff\xff\xff')
+        eq(base64.b64decode(b'+----', altchars=b'-/', ignorechars=b'+'), b'\xfb\xef\xbe')
+        eq(base64.b64decode(b'+----', altchars=b'/-', ignorechars=b'+'), b'\xff\xff\xff')
+        eq(base64.b64decode(b'+/+/', altchars=b'/+', ignorechars=b''), b'\xff\xef\xfe')
+        eq(base64.b64decode(b'/+/+', altchars=b'+/', ignorechars=b''), b'\xff\xef\xfe')
+
+        self.assertRaises(ValueError, base64.b64decode, b'', altchars=b'+')
+        self.assertRaises(ValueError, base64.b64decode, b'', altchars=b'+/-')
+        self.assertRaises(ValueError, base64.b64decode, '', altchars='+')
+        self.assertRaises(ValueError, base64.b64decode, '', altchars='+/-')
 
     def test_b64decode_padding_error(self):
         self.assertRaises(binascii.Error, base64.b64decode, b'abc')
         self.assertRaises(binascii.Error, base64.b64decode, 'abc')
 
+    def test_b64decode_padded(self):
+        b64decode = base64.b64decode
+        urlsafe_b64decode = base64.urlsafe_b64decode
+        def check(data, expected, padded=0):
+            if b'=' in data:
+                with self.assertRaisesRegex(binascii.Error, 'Padding not allowed'):
+                    b64decode(data, padded=False, validate=True)
+            self.assertEqual(b64decode(data, padded=False, ignorechars=b'='),
+                             expected)
+            self.assertEqual(urlsafe_b64decode(data, padded=True), expected)
+            self.assertEqual(urlsafe_b64decode(data, padded=False), expected)
+            data = data.replace(b'=', b'')
+            self.assertEqual(b64decode(data, padded=False), expected)
+            self.assertEqual(b64decode(data, padded=False, validate=True),
+                             expected)
+            self.assertEqual(urlsafe_b64decode(data), expected)
+
+        check(b'', b'')
+        check(b'YQ==', b'a')
+        check(b'YWI=', b'ab')
+        check(b'YWJj', b'abc')
+        check(b'Y=WJj', b'abc')
+        check(b'YW=Jj', b'abc')
+        check(b'YWJ=j', b'abc')
+
+        with self.assertRaisesRegex(binascii.Error, 'Incorrect padding'):
+            urlsafe_b64decode(b'YQ', padded=True)
+        with self.assertRaisesRegex(binascii.Error, 'Incorrect padding'):
+            urlsafe_b64decode(b'YWI', padded=True)
+
+    def _common_test_ignorechars(self, func):
+        eq = self.assertEqual
+        eq(func(b'', ignorechars=b' \n'), b'')
+        eq(func(b'', ignorechars=b''), b'')
+        eq(func(b' \n', ignorechars=b' \n'), b'')
+        with self.assertRaises(binascii.Error):
+            func(b' \n', ignorechars=b'')
+        with self.assertRaises(binascii.Error):
+            func(b' \n', ignorechars=b' ')
+        with self.assertRaises(binascii.Error):
+            func(b' \n', ignorechars=b'\n')
+        with self.assertRaises(TypeError):
+            func(b'', ignorechars='')
+        with self.assertRaises(TypeError):
+            func(b'', ignorechars=[])
+        with self.assertRaises(TypeError):
+            func(b'', ignorechars=None)
+
     def test_b64decode_invalid_chars(self):
         # issue 1466065: Test some invalid characters.
-        tests = ((b'%3d==', b'\xdd'),
-                 (b'$3d==', b'\xdd'),
-                 (b'[==', b''),
-                 (b'YW]3=', b'am'),
-                 (b'3{d==', b'\xdd'),
-                 (b'3d}==', b'\xdd'),
-                 (b'@@', b''),
-                 (b'!', b''),
-                 (b"YWJj\n", b"abc"),
-                 (b'YWJj\nYWI=', b'abcab'))
+        tests = ((b'%3d==', b'\xdd', b'%$'),
+                 (b'$3d==', b'\xdd', b'%$'),
+                 (b'[==', b'', b'[='),
+                 (b'YW]3=', b'am', b']'),
+                 (b'3{d==', b'\xdd', b'{}'),
+                 (b'3d}==', b'\xdd', b'{}'),
+                 (b'@@', b'', b'@!'),
+                 (b'!', b'', b'@!'),
+                 (b"YWJj\n", b"abc", b'\n'),
+                 (b'YWJj\nYWI=', b'abcab', b'\n'),
+                 (b'=YWJj', b'abc', b'='),
+                 (b'Y=WJj', b'abc', b'='),
+                 (b'Y==WJj', b'abc', b'='),
+                 (b'Y===WJj', b'abc', b'='),
+                 (b'YW=Jj', b'abc', b'='),
+                 (b'YWJj=', b'abc', b'='),
+                 (b'YW\nJj', b'abc', b'\n'),
+                 (b'YW\nJj', b'abc', bytearray(b'\n')),
+                 (b'YW\nJj', b'abc', memoryview(b'\n')),
+        )
         funcs = (
             base64.b64decode,
             base64.standard_b64decode,
             base64.urlsafe_b64decode,
         )
-        for bstr, res in tests:
+        for bstr, res, ignorechars in tests:
             for func in funcs:
                 with self.subTest(bstr=bstr, func=func):
                     self.assertEqual(func(bstr), res)
@@ -272,14 +417,111 @@ def test_b64decode_invalid_chars(self):
                 base64.b64decode(bstr, validate=True)
             with self.assertRaises(binascii.Error):
                 base64.b64decode(bstr.decode('ascii'), validate=True)
-
-        # Normal alphabet characters not discarded when alternative given
-        res = b'\xfb\xef\xff'
-        self.assertEqual(base64.b64decode(b'++//', validate=True), res)
-        self.assertEqual(base64.b64decode(b'++//', '-_', validate=True), res)
-        self.assertEqual(base64.b64decode(b'--__', '-_', validate=True), res)
-        self.assertEqual(base64.urlsafe_b64decode(b'++//'), res)
-        self.assertEqual(base64.urlsafe_b64decode(b'--__'), res)
+            with self.assertRaises(binascii.Error):
+                # Even empty ignorechars enables the strict mode.
+                base64.b64decode(bstr, ignorechars=b'')
+            r = base64.b64decode(bstr, ignorechars=ignorechars)
+            self.assertEqual(r, res)
+
+        self._common_test_ignorechars(base64.b64decode)
+
+        # Normal alphabet characters will be discarded when alternative given
+        discarded = ("invalid character %a in Base64 data with %s "
+                     "will be discarded in future Python versions")
+        error = ("invalid character %a in Base64 data with %s "
+                 "will be an error in future Python versions")
+        with self.assertWarns(FutureWarning) as cm:
+            r = base64.b64decode(b'++++', altchars=b'-_')
+        self.assertEqual(r, b'\xfb\xef\xbe')
+        self.assertEqual(str(cm.warning),
+                         discarded % ('+', "altchars=b'-_' and validate=False"))
+        with self.assertWarns(FutureWarning) as cm:
+            r = base64.b64decode(b'////', altchars=b'-_')
+        self.assertEqual(r, b'\xff\xff\xff')
+        self.assertEqual(str(cm.warning),
+                         discarded % ('/', "altchars=b'-_' and validate=False"))
+        with self.assertWarns(DeprecationWarning) as cm:
+            r = base64.b64decode(b'++++', altchars=b'-_', validate=True)
+        self.assertEqual(r, b'\xfb\xef\xbe')
+        self.assertEqual(str(cm.warning),
+                         error % ('+', "altchars=b'-_' and validate=True"))
+        with self.assertWarns(DeprecationWarning) as cm:
+            r = base64.b64decode(b'////', altchars=b'-_', validate=True)
+        self.assertEqual(r, b'\xff\xff\xff')
+        self.assertEqual(str(cm.warning),
+                         error % ('/', "altchars=b'-_' and validate=True"))
+        r = base64.b64decode(b'++++', altchars=b'-_', ignorechars=b'+')
+        self.assertEqual(r, b'')
+        r = base64.b64decode(b'////', altchars=b'-_', ignorechars=b'/')
+        self.assertEqual(r, b'')
+        r = base64.b64decode(b'++++////', altchars=b'-_', validate=False, ignorechars=b'')
+        self.assertEqual(r, b'')
+        with self.assertRaisesRegex(binascii.Error, 'Only base64 data is allowed'):
+            base64.b64decode(b'////', altchars=b'-_', ignorechars=b'')
+        with self.assertRaisesRegex(binascii.Error, 'Only base64 data is allowed'):
+            base64.b64decode(b'++++', altchars=b'-_', ignorechars=b'')
+        r = base64.b64decode(b'++++YWJj----____', altchars=b'-_', ignorechars=b'+')
+        self.assertEqual(r, b'abc\xfb\xef\xbe\xff\xff\xff')
+        r = base64.b64decode(b'////YWJj----____', altchars=b'-_', ignorechars=b'/')
+        self.assertEqual(r, b'abc\xfb\xef\xbe\xff\xff\xff')
+        r = base64.b64decode(b'++++,,,,', altchars=b'+,', ignorechars=b'+')
+        self.assertEqual(r, b'\xfb\xef\xbe\xff\xff\xff')
+        r = base64.b64decode(b'////YWJj++++,,,,', altchars=b'+,', ignorechars=b'/')
+        self.assertEqual(r, b'abc\xfb\xef\xbe\xff\xff\xff')
+        r = base64.b64decode(b'----////', altchars=b'-/', ignorechars=b'/')
+        self.assertEqual(r, b'\xfb\xef\xbe\xff\xff\xff')
+        r = base64.b64decode(b'++++YWJj----////', altchars=b'-/', ignorechars=b'+')
+        self.assertEqual(r, b'abc\xfb\xef\xbe\xff\xff\xff')
+
+        with self.assertWarns(FutureWarning) as cm:
+            self.assertEqual(base64.urlsafe_b64decode(b'++++'), b'\xfb\xef\xbe')
+        self.assertEqual(str(cm.warning),
+                         "invalid character '+' in URL-safe Base64 data "
+                         "will be discarded in future Python versions")
+        with self.assertWarns(FutureWarning) as cm:
+            self.assertEqual(base64.urlsafe_b64decode(b'////'), b'\xff\xff\xff')
+        self.assertEqual(str(cm.warning),
+                         "invalid character '/' in URL-safe Base64 data "
+                         "will be discarded in future Python versions")
+        with self.assertRaises(binascii.Error):
+            base64.b64decode(b'+/!', altchars=b'-_')
+
+    def _altchars_strategy():
+        """Generate 'altchars' for base64 encoding."""
+        reserved_chars = (string.digits + string.ascii_letters + "=").encode()
+        allowed_chars = hypothesis.strategies.sampled_from(
+            [n for n in range(256) if n not in reserved_chars])
+        two_bytes_strategy = hypothesis.strategies.lists(
+            allowed_chars, min_size=2, max_size=2, unique=True).map(bytes)
+        return (hypothesis.strategies.none()
+                | hypothesis.strategies.just(b"_-")
+                | two_bytes_strategy)
+
+    @hypothesis.given(
+        payload=hypothesis.strategies.binary(),
+        altchars=_altchars_strategy(),
+        validate=hypothesis.strategies.booleans())
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', b"_-", True)
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', b"_-", False)
+    def test_b64_encode_decode_round_trip(self, payload, altchars, validate):
+        encoded = base64.b64encode(payload, altchars=altchars)
+        decoded = base64.b64decode(encoded, altchars=altchars,
+                                   validate=validate)
+        self.assertEqual(payload, decoded)
+
+    @hypothesis.given(payload=hypothesis.strategies.binary())
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz')
+    def test_standard_b64_encode_decode_round_trip(self, payload):
+        encoded = base64.standard_b64encode(payload)
+        decoded = base64.standard_b64decode(encoded)
+        self.assertEqual(payload, decoded)
+
+    @hypothesis.given(payload=hypothesis.strategies.binary())
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz')
+    def test_urlsafe_b64_encode_decode_round_trip(self, payload):
+        encoded = base64.urlsafe_b64encode(payload)
+        decoded = base64.urlsafe_b64decode(encoded)
+        self.assertEqual(payload, decoded)
 
     def test_b32encode(self):
         eq = self.assertEqual
@@ -294,6 +536,23 @@ def test_b32encode(self):
         self.check_other_types(base64.b32encode, b'abcd', b'MFRGGZA=')
         self.check_encode_type_errors(base64.b32encode)
 
+    def test_b32encode_padded(self):
+        b32encode = base64.b32encode
+        self.assertEqual(b32encode(b'', padded=False), b'')
+        self.assertEqual(b32encode(b'a', padded=False), b'ME')
+        self.assertEqual(b32encode(b'ab', padded=False), b'MFRA')
+        self.assertEqual(b32encode(b'abc', padded=False), b'MFRGG')
+        self.assertEqual(b32encode(b'abcd', padded=False), b'MFRGGZA')
+        self.assertEqual(b32encode(b'abcde', padded=False), b'MFRGGZDF')
+
+    def test_b32encode_wrapcol(self):
+        eq = self.assertEqual
+        b = b'www.python.org'
+        self._common_test_wrapcol(base64.b32encode, b)
+        eq(base64.b32encode(b, wrapcol=16), b'O53XOLTQPF2GQ33O\nFZXXEZY=')
+        eq(base64.b32encode(b, wrapcol=23), b'O53XOLTQPF2GQ33O\nFZXXEZY=')
+        eq(base64.b32encode(b, wrapcol=1), b'O53XOLTQ\nPF2GQ33O\nFZXXEZY=')
+
     def test_b32decode(self):
         eq = self.assertEqual
         tests = {b'': b'',
@@ -329,6 +588,7 @@ def test_b32decode_casefold(self):
 
         for data, res in tests.items():
             eq(base64.b32decode(data, True), res)
+            eq(base64.b32decode(data, casefold=True), res)
             eq(base64.b32decode(data.decode('ascii'), True), res)
 
         self.assertRaises(binascii.Error, base64.b32decode, b'me======')
@@ -347,6 +607,11 @@ def test_b32decode_map01(self):
         self.assertRaises(binascii.Error, base64.b32decode, b'M1O23456')
         self.assertRaises(binascii.Error, base64.b32decode, b'ML023456')
         self.assertRaises(binascii.Error, base64.b32decode, b'MI023456')
+        self.assertRaises(ValueError, base64.b32decode, b'', map01=b'')
+        self.assertRaises(ValueError, base64.b32decode, b'', map01=b'LI')
+        self.assertRaises(TypeError, base64.b32decode, b'', map01=0)
+        eq(base64.b32decode(b'MLO23456', map01=None), res_L)
+        self.assertRaises(binascii.Error, base64.b32decode, b'M1023456', map01=None)
 
         data = b'M1023456'
         data_str = data.decode('ascii')
@@ -362,6 +627,56 @@ def test_b32decode_map01(self):
             eq(base64.b32decode(b'M%c023456' % map01, map01=map01), res)
             eq(base64.b32decode(b'M%cO23456' % map01, map01=map01), res)
 
+    def test_b32decode_padded(self):
+        b32decode = base64.b32decode
+        def check(data, expected):
+            if b'=' in data:
+                with self.assertRaisesRegex(binascii.Error, 'Padding not allowed'):
+                    b32decode(data, padded=False)
+            self.assertEqual(b32decode(data, padded=False, ignorechars=b'='),
+                             expected)
+            data = data.replace(b'=', b'')
+            self.assertEqual(b32decode(data, padded=False), expected)
+
+        check(b'', b'')
+        check(b'ME======', b'a')
+        check(b'MFRA====', b'ab')
+        check(b'MFRGG===', b'abc')
+        check(b'MFRGGZA=', b'abcd')
+        check(b'MFRGGZDF', b'abcde')
+        check(b'M=FRGGZDF', b'abcde')
+        check(b'MF=RGGZDF', b'abcde')
+        check(b'MFR=GGZDF', b'abcde')
+        check(b'MFRG=GZDF', b'abcde')
+        check(b'MFRGG=ZDF', b'abcde')
+        check(b'MFRGGZ=DF', b'abcde')
+        check(b'MFRGGZD=F', b'abcde')
+
+    def test_b32decode_ignorechars(self):
+        self._common_test_ignorechars(base64.b32decode)
+        eq = self.assertEqual
+        eq(base64.b32decode(b'MFRG\n GZDF\n', ignorechars=b' \n'), b'abcde')
+        eq(base64.b32decode(b'MFRG\n GZDF\n', ignorechars=bytearray(b' \n')), b'abcde')
+        eq(base64.b32decode(b'M=======FRGGZDF', ignorechars=b'='), b'abcde')
+        eq(base64.b32decode(b'MF======RGGZDF', ignorechars=b'='), b'abcde')
+        eq(base64.b32decode(b'MFR=====GGZDF', ignorechars=b'='), b'abcde')
+        eq(base64.b32decode(b'MFRG====GZDF', ignorechars=b'='), b'abcde')
+        eq(base64.b32decode(b'MFRGG===ZDF', ignorechars=b'='), b'abcde')
+        eq(base64.b32decode(b'MFRGGZ==DF', ignorechars=b'='), b'abcde')
+        eq(base64.b32decode(b'MFRGGZD=F', ignorechars=b'='), b'abcde')
+        eq(base64.b32decode(b'MFRGGZDF=', ignorechars=b'='), b'abcde')
+        eq(base64.b32decode(b'MFRA======', ignorechars=b'='), b'ab')
+
+        eq(base64.b32decode(b'mfRggzDfmzTQ====', ignorechars=b'mfgz'),
+           b'\x88\xe7')
+        eq(base64.b32decode(b'mfRggzDfmzTQ====', casefold=True, ignorechars=b'mfgz'),
+           b'abcdefg')
+        eq(base64.b32decode(b'M0F1R0G1G0Z1D0F1', ignorechars=b'01'), b'abcde')
+        eq(base64.b32decode(b'M0F1R0G1G0Z1D0F1', map01=b'L', ignorechars=b'01'),
+           b'c\x8a\xb8\xb8\xcb3\xb2\xb1\xb8\xab')
+        eq(base64.b32decode(b'M0F1R0G1G0Z1D0F1', map01=b'I', ignorechars=b'01'),
+           b'c\x8a\x88\xb8\xc83\xb2\x81\xb8\xa8')
+
     def test_b32decode_error(self):
         tests = [b'abc', b'ABCDEF==', b'==ABCDEF']
         prefixes = [b'M', b'ME', b'MFRA', b'MFRGG', b'MFRGGZA', b'MFRGGZDF']
@@ -378,6 +693,19 @@ def test_b32decode_error(self):
                 with self.assertRaises(binascii.Error):
                     base64.b32decode(data.decode('ascii'))
 
+    @hypothesis.given(
+        payload=hypothesis.strategies.binary(),
+        casefold=hypothesis.strategies.booleans(),
+        map01=(
+            hypothesis.strategies.none()
+            | hypothesis.strategies.binary(min_size=1, max_size=1)))
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', True, None)
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', False, None)
+    def test_b32_encode_decode_round_trip(self, payload, casefold, map01):
+        encoded = base64.b32encode(payload)
+        decoded = base64.b32decode(encoded, casefold=casefold, map01=map01)
+        self.assertEqual(payload, decoded)
+
     def test_b32hexencode(self):
         test_cases = [
             # to_encode, expected
@@ -392,11 +720,21 @@ def test_b32hexencode(self):
         for to_encode, expected in test_cases:
             with self.subTest(to_decode=to_encode):
                 self.assertEqual(base64.b32hexencode(to_encode), expected)
+                self.assertEqual(base64.b32hexencode(to_encode, padded=False),
+                                 expected.rstrip(b'='))
 
     def test_b32hexencode_other_types(self):
         self.check_other_types(base64.b32hexencode, b'abcd', b'C5H66P0=')
         self.check_encode_type_errors(base64.b32hexencode)
 
+    def test_b32hexencode_wrapcol(self):
+        eq = self.assertEqual
+        b = b'www.python.org'
+        self._common_test_wrapcol(base64.b32hexencode, b)
+        eq(base64.b32hexencode(b, wrapcol=16), b'ETRNEBJGF5Q6GRRE\n5PNN4PO=')
+        eq(base64.b32hexencode(b, wrapcol=23), b'ETRNEBJGF5Q6GRRE\n5PNN4PO=')
+        eq(base64.b32hexencode(b, wrapcol=1), b'ETRNEBJG\nF5Q6GRRE\n5PNN4PO=')
+
     def test_b32hexdecode(self):
         test_cases = [
             # to_decode, expected, casefold
@@ -431,6 +769,53 @@ def test_b32hexdecode_other_types(self):
         self.check_other_types(base64.b32hexdecode, b'C5H66===', b'abc')
         self.check_decode_type_errors(base64.b32hexdecode)
 
+    def test_b32hexdecode_padded(self):
+        b32hexdecode = base64.b32hexdecode
+        def check(data, expected):
+            if b'=' in data:
+                with self.assertRaisesRegex(binascii.Error, 'Padding not allowed'):
+                    b32hexdecode(data, padded=False)
+            self.assertEqual(b32hexdecode(data, padded=False, ignorechars=b'='),
+                             expected)
+            data = data.replace(b'=', b'')
+            self.assertEqual(b32hexdecode(data, padded=False), expected)
+
+        check(b'', b'')
+        check(b'C4======', b'a')
+        check(b'C5H0====', b'ab')
+        check(b'C5H66===', b'abc')
+        check(b'C5H66P0=', b'abcd')
+        check(b'C5H66P35', b'abcde')
+        check(b'C=5H66P35', b'abcde')
+        check(b'C5=H66P35', b'abcde')
+        check(b'C5H=66P35', b'abcde')
+        check(b'C5H6=6P35', b'abcde')
+        check(b'C5H66=P35', b'abcde')
+        check(b'C5H66P=35', b'abcde')
+        check(b'C5H66P3=5', b'abcde')
+
+    def test_b32hexdecode_ignorechars(self):
+        self._common_test_ignorechars(base64.b32hexdecode)
+        eq = self.assertEqual
+        eq(base64.b32hexdecode(b'C5H6\n 6P35\n', ignorechars=b' \n'), b'abcde')
+        eq(base64.b32hexdecode(b'C5H6\n 6P35\n', ignorechars=bytearray(b' \n')), b'abcde')
+        eq(base64.b32hexdecode(b'========C5H66P35', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C=======5H66P35', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C5======H66P35', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C5H=====66P35', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C5H6====6P35', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C5H66===P35', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C5H66P==35', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C5H66P3=5', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C5H66P35=', ignorechars=b'='), b'abcde')
+        eq(base64.b32hexdecode(b'C5H0======', ignorechars=b'='), b'ab')
+
+        eq(base64.b32hexdecode(b'c5h66p35cpjmg===', ignorechars=b'cghjmp'),
+           b')\x8c2')
+        eq(base64.b32hexdecode(b'c5h66p35cpjmg===', casefold=True,
+                               ignorechars=b'cghjmp'),
+           b'abcdefgh')
+
     def test_b32hexdecode_error(self):
         tests = [b'abc', b'ABCDEF==', b'==ABCDEF', b'c4======']
         prefixes = [b'M', b'ME', b'MFRA', b'MFRGG', b'MFRGGZA', b'MFRGGZDF']
@@ -447,6 +832,15 @@ def test_b32hexdecode_error(self):
                 with self.assertRaises(binascii.Error):
                     base64.b32hexdecode(data.decode('ascii'))
 
+    @hypothesis.given(
+        payload=hypothesis.strategies.binary(),
+        casefold=hypothesis.strategies.booleans())
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', True)
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', False)
+    def test_b32_hexencode_decode_round_trip(self, payload, casefold):
+        encoded = base64.b32hexencode(payload)
+        decoded = base64.b32hexdecode(encoded, casefold=casefold)
+        self.assertEqual(payload, decoded)
 
     def test_b16encode(self):
         eq = self.assertEqual
@@ -457,6 +851,14 @@ def test_b16encode(self):
                                b'0102ABCDEF')
         self.check_encode_type_errors(base64.b16encode)
 
+    def test_b16encode_wrapcol(self):
+        eq = self.assertEqual
+        b = b'\x01\x02\xab\xcd\xef'
+        self._common_test_wrapcol(base64.b16encode, b)
+        eq(base64.b16encode(b, wrapcol=4), b'0102\nABCD\nEF')
+        eq(base64.b16encode(b, wrapcol=5), b'0102\nABCD\nEF')
+        eq(base64.b16encode(b, wrapcol=1), b'01\n02\nAB\nCD\nEF')
+
     def test_b16decode(self):
         eq = self.assertEqual
         eq(base64.b16decode(b'0102ABCDEF'), b'\x01\x02\xab\xcd\xef')
@@ -484,6 +886,24 @@ def test_b16decode(self):
         # Incorrect "padding"
         self.assertRaises(binascii.Error, base64.b16decode, '010')
 
+    def test_b16decode_ignorechars(self):
+        self._common_test_ignorechars(base64.b16decode)
+        eq = self.assertEqual
+        eq(base64.b16decode(b'A B\nC D\n', ignorechars=b' \n'), b'\xab\xcd')
+        eq(base64.b16decode(b'A B\nC D\n', ignorechars=bytearray(b' \n')), b'\xab\xcd')
+        eq(base64.b16decode(b'aBcD', ignorechars=b'ac'), b'\xbd')
+        eq(base64.b16decode(b'aBcD', casefold=True, ignorechars=b'ac'), b'\xab\xcd')
+
+    @hypothesis.given(
+        payload=hypothesis.strategies.binary(),
+        casefold=hypothesis.strategies.booleans())
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', True)
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', False)
+    def test_b16_encode_decode_round_trip(self, payload, casefold):
+        endoded = base64.b16encode(payload)
+        decoded = base64.b16decode(endoded, casefold=casefold)
+        self.assertEqual(payload, decoded)
+
     def test_a85encode(self):
         eq = self.assertEqual
 
@@ -522,18 +942,33 @@ def test_a85encode(self):
 
         self.assertRaises(TypeError, base64.a85encode, "")
 
-        eq(base64.a85encode(b"www.python.org", wrapcol=7, adobe=False),
-           b'GB\\6`E-\nZP=Df.1\nGEb>')
-        eq(base64.a85encode(b"\0\0\0\0www.python.org", wrapcol=7, adobe=False),
-           b'zGB\\6`E\n-ZP=Df.\n1GEb>')
-        eq(base64.a85encode(b"www.python.org", wrapcol=7, adobe=True),
-           b'<~GB\\6`\nE-ZP=Df\n.1GEb>\n~>')
-
         eq(base64.a85encode(b' '*8, foldspaces=True, adobe=False), b'yy')
         eq(base64.a85encode(b' '*7, foldspaces=True, adobe=False), b'y+<Vd')
         eq(base64.a85encode(b' '*6, foldspaces=True, adobe=False), b'y+<U')
         eq(base64.a85encode(b' '*5, foldspaces=True, adobe=False), b'y+9')
 
+    def test_a85encode_wrapcol(self):
+        eq = self.assertEqual
+        b = b'www.python.org'
+        self._common_test_wrapcol(base64.a85encode, b)
+        eq(base64.a85encode(b, wrapcol=7), b'GB\\6`E-\nZP=Df.1\nGEb>')
+        eq(base64.a85encode(b"\0\0\0\0www.python.org", wrapcol=7),
+           b'zGB\\6`E\n-ZP=Df.\n1GEb>')
+        eq(base64.a85encode(b, wrapcol=75), b'GB\\6`E-ZP=Df.1GEb>')
+        eq(base64.a85encode(b, wrapcol=1),
+           b'G\nB\n\\\n6\n`\nE\n-\nZ\nP\n=\nD\nf\n.\n1\nG\nE\nb\n>')
+        eq(base64.a85encode(b, wrapcol=7, adobe=True),
+           b'<~GB\\6`\nE-ZP=Df\n.1GEb>\n~>')
+        eq(base64.a85encode(b, wrapcol=1),
+           b'G\nB\n\\\n6\n`\nE\n-\nZ\nP\n=\nD\nf\n.\n1\nG\nE\nb\n>')
+        eq(base64.a85encode(b, wrapcol=1, adobe=True),
+           b'<~\nGB\n\\6\n`E\n-Z\nP=\nDf\n.1\nGE\nb>\n~>')
+        with self.assertRaises(ValueError):
+            base64.a85encode(b, wrapcol=-7, adobe=True)
+        eq(base64.a85encode(b'', wrapcol=1, adobe=True), b'<~\n~>')
+        eq(base64.a85encode(b'', wrapcol=3, adobe=True), b'<~\n~>')
+        eq(base64.a85encode(b'', wrapcol=4, adobe=True), b'<~~>')
+
     def test_b85encode(self):
         eq = self.assertEqual
 
@@ -568,11 +1003,20 @@ def test_b85encode(self):
         self.check_other_types(base64.b85encode, b"www.python.org",
                                b'cXxL#aCvlSZ*DGca%T')
 
+    def test_b85encode_wrapcol(self):
+        eq = self.assertEqual
+        b = b'www.python.org'
+        self._common_test_wrapcol(base64.b85encode, b)
+        eq(base64.b85encode(b, wrapcol=10), b'cXxL#aCvlS\nZ*DGca%T')
+        eq(base64.b85encode(b, wrapcol=14), b'cXxL#aCvlS\nZ*DGca%T')
+        eq(base64.b85encode(b, wrapcol=1), b'cXxL#\naCvlS\nZ*DGc\na%T')
+
     def test_z85encode(self):
         eq = self.assertEqual
 
         tests = {
             b'': b'',
+            b'\x86\x4F\xD2\x6F\xB5\x59\xF7\x5B': b'HelloWorld',
             b'www.python.org': b'CxXl-AcVLsz/dgCA+t',
             bytes(range(255)): b"""009c61o!#m2NH?C3>iWS5d]J*6CRx17-skh9337x"""
                 b"""ar.{NbQB=+c[cR@eg&FcfFLssg=mfIi5%2YjuU>)kTv.7l}6Nnnj=AD"""
@@ -602,6 +1046,14 @@ def test_z85encode(self):
         self.check_other_types(base64.z85encode, b"www.python.org",
                                b'CxXl-AcVLsz/dgCA+t')
 
+    def test_z85encode_wrapcol(self):
+        eq = self.assertEqual
+        b = b'www.python.org'
+        self._common_test_wrapcol(base64.z85encode, b)
+        eq(base64.z85encode(b, wrapcol=10), b'CxXl-AcVLs\nz/dgCA+t')
+        eq(base64.z85encode(b, wrapcol=14), b'CxXl-AcVLs\nz/dgCA+t')
+        eq(base64.z85encode(b, wrapcol=1), b'CxXl-\nAcVLs\nz/dgC\nA+t')
+
     def test_a85decode(self):
         eq = self.assertEqual
 
@@ -733,6 +1185,12 @@ def test_a85_padding(self):
         eq(base64.a85decode(b'G^+IX'), b"xxxx")
         eq(base64.a85decode(b'G^+IXGQ7^D'), b"xxxxx\x00\x00\x00")
 
+        eq(base64.a85encode(b"\x00", pad=True), b'z')
+        eq(base64.a85encode(b"\x00"*2, pad=True), b'z')
+        eq(base64.a85encode(b"\x00"*3, pad=True), b'z')
+        eq(base64.a85encode(b"\x00"*4, pad=True), b'z')
+        eq(base64.a85encode(b"\x00"*5, pad=True), b'zz')
+
     def test_b85_padding(self):
         eq = self.assertEqual
 
@@ -748,6 +1206,21 @@ def test_b85_padding(self):
         eq(base64.b85decode(b'czAet'), b"xxxx")
         eq(base64.b85decode(b'czAetcmMzZ'), b"xxxxx\x00\x00\x00")
 
+    def test_z85_padding(self):
+        eq = self.assertEqual
+
+        eq(base64.z85encode(b"x", pad=True), b'CMmZz')
+        eq(base64.z85encode(b"xx", pad=True), b'CZ6h*')
+        eq(base64.z85encode(b"xxx", pad=True), b'CZaDk')
+        eq(base64.z85encode(b"xxxx", pad=True), b'CZaET')
+        eq(base64.z85encode(b"xxxxx", pad=True), b'CZaETCMmZz')
+
+        eq(base64.z85decode(b'CMmZz'), b"x\x00\x00\x00")
+        eq(base64.z85decode(b'CZ6h*'), b"xx\x00\x00")
+        eq(base64.z85decode(b'CZaDk'), b"xxx\x00")
+        eq(base64.z85decode(b'CZaET'), b"xxxx")
+        eq(base64.z85decode(b'CZaETCMmZz'), b"xxxxx\x00\x00\x00")
+
     def test_a85decode_errors(self):
         illegal = (set(range(32)) | set(range(118, 256))) - set(b' \t\n\r\v')
         for c in illegal:
@@ -787,24 +1260,20 @@ def test_a85decode_errors(self):
 
         self.assertEqual(base64.a85decode(b"a b\nc", ignorechars=b" \n"),
                          b'\xc9\x89')
-        with self.assertRaises(ValueError):
-            base64.a85decode(b"a b\nc", ignorechars=b"")
-        with self.assertRaises(ValueError):
-            base64.a85decode(b"a b\nc", ignorechars=b" ")
-        with self.assertRaises(ValueError):
-            base64.a85decode(b"a b\nc", ignorechars=b"\n")
-        with self.assertRaises(TypeError):
-            base64.a85decode(b"a b\nc", ignorechars=" \n")
-        with self.assertRaises(TypeError):
-            base64.a85decode(b"a b\nc", ignorechars=None)
+        self._common_test_ignorechars(base64.a85decode)
 
     def test_b85decode_errors(self):
         illegal = list(range(33)) + \
                   list(b'"\',./:[\\]') + \
                   list(range(128, 256))
         for c in illegal:
-            with self.assertRaises(ValueError, msg=bytes([c])):
-                base64.b85decode(b'0000' + bytes([c]))
+            b = bytes([c])
+            with self.assertRaises(ValueError, msg=b):
+                base64.b85decode(b'0000' + b)
+            self.assertEqual(base64.b85decode(b'0000' + b, ignorechars=b),
+                             b'\x00\x00\x00')
+
+        self._common_test_ignorechars(base64.b85decode)
 
         self.assertRaises(ValueError, base64.b85decode, b'|')
         self.assertRaises(ValueError, base64.b85decode, b'|N')
@@ -817,8 +1286,13 @@ def test_z85decode_errors(self):
                   list(b'"\',;_`|\\~') + \
                   list(range(128, 256))
         for c in illegal:
-            with self.assertRaises(ValueError, msg=bytes([c])):
-                base64.z85decode(b'0000' + bytes([c]))
+            b = bytes([c])
+            with self.assertRaises(ValueError, msg=b):
+                base64.z85decode(b'0000' + b)
+            self.assertEqual(base64.z85decode(b'0000' + b, ignorechars=b),
+                             b'\x00\x00\x00')
+
+        self._common_test_ignorechars(base64.z85decode)
 
         # b'\xff\xff\xff\xff' encodes to b'%nSc0', the following will overflow:
         self.assertRaises(ValueError, base64.z85decode, b'%')
@@ -827,6 +1301,61 @@ def test_z85decode_errors(self):
         self.assertRaises(ValueError, base64.z85decode, b'%nSc')
         self.assertRaises(ValueError, base64.z85decode, b'%nSc1')
 
+    def add_padding(self, payload):
+        """Add the expected padding for test_?85_encode_decode_round_trip."""
+        if len(payload) % 4 != 0:
+            padding = b"\0" * ((-len(payload)) % 4)
+            payload = payload + padding
+        return payload
+
+    @hypothesis.given(
+        payload=hypothesis.strategies.binary(),
+        foldspaces=hypothesis.strategies.booleans(),
+        wrapcol=(
+            hypothesis.strategies.just(0)
+            | hypothesis.strategies.integers(1, 1000)),
+        pad=hypothesis.strategies.booleans(),
+        adobe=hypothesis.strategies.booleans(),
+    )
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', False, 0, False, False)
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', False, 20, True, True)
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', True, 0, False, True)
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', True, 20, True, False)
+    def test_a85_encode_decode_round_trip(
+        self, payload, foldspaces, wrapcol, pad, adobe
+    ):
+        encoded = base64.a85encode(
+            payload, foldspaces=foldspaces, wrapcol=wrapcol,
+            pad=pad, adobe=adobe,
+        )
+        if wrapcol:
+            if adobe and wrapcol == 1:
+                # "adobe" needs wrapcol to be at least 2.
+                # a85decode quietly uses 2 if 1 is given; it's not worth
+                # loudly deprecating this behavior.
+                wrapcol = 2
+            for line in encoded.splitlines(keepends=False):
+                self.assertLessEqual(len(line), wrapcol)
+        if adobe:
+            self.assertTrue(encoded.startswith(b'<~'))
+            self.assertTrue(encoded.endswith(b'~>'))
+        decoded = base64.a85decode(encoded, foldspaces=foldspaces, adobe=adobe)
+        if pad:
+            payload = self.add_padding(payload)
+        self.assertEqual(payload, decoded)
+
+    @hypothesis.given(
+        payload=hypothesis.strategies.binary(),
+        pad=hypothesis.strategies.booleans())
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', True)
+    @hypothesis.example(b'abcdefghijklmnopqrstuvwxyz', False)
+    def test_b85_encode_decode_round_trip(self, payload, pad):
+        encoded = base64.b85encode(payload, pad=pad)
+        if pad:
+            payload = self.add_padding(payload)
+        decoded = base64.b85decode(encoded)
+        self.assertEqual(payload, decoded)
+
     def test_decode_nonascii_str(self):
         decode_funcs = (base64.b64decode,
                         base64.standard_b64decode,
diff --git a/Lib/test/test_binascii.py b/Lib/test/test_binascii.py
index 82eabf4bb06..cedbdc61f18 100644
--- a/Lib/test/test_binascii.py
+++ b/Lib/test/test_binascii.py
@@ -4,14 +4,17 @@
 import binascii
 import array
 import re
-from test.support import bigmemtest, _1G, _4G
+import sys
+from test.support import bigmemtest, _1G, _4G, check_impl_detail
 from test.support.hypothesis_helper import hypothesis
 
 
 # Note: "*_hex" functions are aliases for "(un)hexlify"
-b2a_functions = ['b2a_base64', 'b2a_hex', 'b2a_qp', 'b2a_uu',
+b2a_functions = ['b2a_ascii85', 'b2a_base32', 'b2a_base64', 'b2a_base85',
+                 'b2a_hex', 'b2a_qp', 'b2a_uu',
                  'hexlify']
-a2b_functions = ['a2b_base64', 'a2b_hex', 'a2b_qp', 'a2b_uu',
+a2b_functions = ['a2b_ascii85', 'a2b_base32', 'a2b_base64', 'a2b_base85',
+                 'a2b_hex', 'a2b_qp', 'a2b_uu',
                  'unhexlify']
 all_functions = a2b_functions + b2a_functions + ['crc32', 'crc_hqx']
 
@@ -23,6 +26,8 @@ class BinASCIITest(unittest.TestCase):
     rawdata = b"The quick brown fox jumps over the lazy dog.\r\n"
     # Be slow so we don't depend on other modules
     rawdata += bytes(range(256))
+    rawdata += b'\0'*32
+    rawdata += b' '*32
     rawdata += b"\r\nHello world.\n"
 
     def setUp(self):
@@ -41,6 +46,40 @@ def test_exceptions(self):
         self.assertIsSubclass(binascii.Error, Exception)
         self.assertIsSubclass(binascii.Incomplete, Exception)
 
+    def test_constants(self):
+        self.assertEqual(binascii.BASE64_ALPHABET,
+                         b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+                         b'abcdefghijklmnopqrstuvwxyz'
+                         b'0123456789+/')
+        self.assertEqual(binascii.URLSAFE_BASE64_ALPHABET,
+                         binascii.BASE64_ALPHABET[:-2] + b'-_')
+        self.assertEqual(binascii.UU_ALPHABET, bytes(range(32, 32+64)))
+        self.assertEqual(binascii.CRYPT_ALPHABET,
+                         b'./0123456789'
+                         b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+                         b'abcdefghijklmnopqrstuvwxyz')
+        self.assertEqual(binascii.BINHEX_ALPHABET,
+                         b'!"#$%&\'()*+,-012345689'
+                         b'@ABCDEFGHIJKLMNPQRSTUVXYZ['
+                         b'`abcdefhijklmpqr')
+
+        self.assertEqual(binascii.BASE85_ALPHABET,
+                         b'0123456789'
+                         b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+                         b'abcdefghijklmnopqrstuvwxyz'
+                         b'!#$%&()*+-;<=>?@^_`{|}~')
+        self.assertEqual(binascii.ASCII85_ALPHABET, bytes(range(33, 33+85)))
+        self.assertEqual(binascii.Z85_ALPHABET,
+                         b'0123456789'
+                         b'abcdefghijklmnopqrstuvwxyz'
+                         b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+                         b'.-:+=^!/*?&<>()[]{}@%$#')
+
+        self.assertEqual(binascii.BASE32_ALPHABET,
+                         b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567')
+        self.assertEqual(binascii.BASE32HEX_ALPHABET,
+                         b'0123456789ABCDEFGHIJKLMNOPQRSTUV')
+
     def test_functions(self):
         # Check presence of all functions
         for name in all_functions:
@@ -117,62 +156,170 @@ def addnoise(line):
         # empty strings. TBD: shouldn't it raise an exception instead ?
         self.assertEqual(binascii.a2b_base64(self.type2test(fillers)), b'')
 
-    def test_base64_strict_mode(self):
-        # Test base64 with strict mode on
-        def _assertRegexTemplate(assert_regex: str, data: bytes, non_strict_mode_expected_result: bytes):
+    def test_base64_bad_padding(self):
+        # Test malformed padding
+        def _assertRegexTemplate(assert_regex, data,
+                                 non_strict_mode_expected_result, **kwargs):
+            data = self.type2test(data)
             with self.assertRaisesRegex(binascii.Error, assert_regex):
-                binascii.a2b_base64(self.type2test(data), strict_mode=True)
-            self.assertEqual(binascii.a2b_base64(self.type2test(data), strict_mode=False),
+                binascii.a2b_base64(data, strict_mode=True, **kwargs)
+            self.assertEqual(binascii.a2b_base64(data, strict_mode=False),
                              non_strict_mode_expected_result)
-            self.assertEqual(binascii.a2b_base64(self.type2test(data)),
+            self.assertEqual(binascii.a2b_base64(data, strict_mode=True,
+                                                 ignorechars=b' ='),
+                             non_strict_mode_expected_result)
+            self.assertEqual(binascii.a2b_base64(data),
                              non_strict_mode_expected_result)
 
-        def assertExcessData(data, non_strict_mode_expected_result: bytes):
-            _assertRegexTemplate(r'(?i)Excess data', data, non_strict_mode_expected_result)
-
-        def assertNonBase64Data(data, non_strict_mode_expected_result: bytes):
-            _assertRegexTemplate(r'(?i)Only base64 data', data, non_strict_mode_expected_result)
+        def assertLeadingPadding(*args, **kwargs):
+            _assertRegexTemplate(r'(?i)Leading padding', *args, **kwargs)
 
-        def assertLeadingPadding(data, non_strict_mode_expected_result: bytes):
-            _assertRegexTemplate(r'(?i)Leading padding', data, non_strict_mode_expected_result)
+        def assertDiscontinuousPadding(*args):
+            _assertRegexTemplate(r'(?i)Discontinuous padding', *args)
 
-        def assertDiscontinuousPadding(data, non_strict_mode_expected_result: bytes):
-            _assertRegexTemplate(r'(?i)Discontinuous padding', data, non_strict_mode_expected_result)
+        def assertExcessPadding(*args):
+            _assertRegexTemplate(r'(?i)Excess padding', *args)
 
-        def assertExcessPadding(data, non_strict_mode_expected_result: bytes):
-            _assertRegexTemplate(r'(?i)Excess padding', data, non_strict_mode_expected_result)
+        def assertInvalidLength(data, *args, length=None, **kwargs):
+            if length is None:
+                length = len(data.split(b'=', 1)[0].replace(b' ', b''))
+            assert_regex = fr"(?i)Invalid.+number of data characters \({length}\)"
+            _assertRegexTemplate(assert_regex, data, *args, **kwargs)
 
-        # Test excess data exceptions
         assertExcessPadding(b'ab===', b'i')
         assertExcessPadding(b'ab====', b'i')
-        assertNonBase64Data(b'ab==:', b'i')
-        assertExcessData(b'abc=a', b'i\xb7\x1a')
-        assertNonBase64Data(b'abc=:', b'i\xb7')
-        assertNonBase64Data(b'ab==\n', b'i')
         assertExcessPadding(b'abc==', b'i\xb7')
         assertExcessPadding(b'abc===', b'i\xb7')
         assertExcessPadding(b'abc====', b'i\xb7')
         assertExcessPadding(b'abc=====', b'i\xb7')
 
-        # Test non-base64 data exceptions
-        assertNonBase64Data(b'\nab==', b'i')
-        assertNonBase64Data(b'ab:(){:|:&};:==', b'i')
-        assertNonBase64Data(b'a\nb==', b'i')
-        assertNonBase64Data(b'a\x00b==', b'i')
-
-        # Test malformed padding
         assertLeadingPadding(b'=', b'')
         assertLeadingPadding(b'==', b'')
         assertLeadingPadding(b'===', b'')
         assertLeadingPadding(b'====', b'')
         assertLeadingPadding(b'=====', b'')
+        assertLeadingPadding(b'=abcd', b'i\xb7\x1d')
+        assertLeadingPadding(b'==abcd', b'i\xb7\x1d')
+        assertLeadingPadding(b'===abcd', b'i\xb7\x1d')
+        assertLeadingPadding(b'====abcd', b'i\xb7\x1d')
+        assertLeadingPadding(b'=====abcd', b'i\xb7\x1d')
+        assertLeadingPadding(b' =abcd', b'i\xb7\x1d', ignorechars=b' ')
+
+        assertInvalidLength(b'a=b==', b'i')
+        assertInvalidLength(b'a=bc=', b'i\xb7')
+        assertInvalidLength(b'a=bc==', b'i\xb7')
+        assertInvalidLength(b'a=bcd', b'i\xb7\x1d')
+        assertInvalidLength(b'a=bcd=', b'i\xb7\x1d')
+        assertInvalidLength(b' a=b==', b'i', ignorechars=b' ')
+        assertInvalidLength(b'abcde=f==', b'i\xb7\x1dy')
+        assertInvalidLength(b' abcde=f==', b'i\xb7\x1dy', ignorechars=b' ')
+
         assertDiscontinuousPadding(b'ab=c=', b'i\xb7')
-        assertDiscontinuousPadding(b'ab=ab==', b'i\xb6\x9b')
+        assertDiscontinuousPadding(b'ab=cd', b'i\xb7\x1d')
+        assertDiscontinuousPadding(b'ab=cd==', b'i\xb7\x1d')
+
         assertExcessPadding(b'abcd=', b'i\xb7\x1d')
         assertExcessPadding(b'abcd==', b'i\xb7\x1d')
         assertExcessPadding(b'abcd===', b'i\xb7\x1d')
         assertExcessPadding(b'abcd====', b'i\xb7\x1d')
         assertExcessPadding(b'abcd=====', b'i\xb7\x1d')
+        assertExcessPadding(b'abcd==', b'i\xb7\x1d')
+        assertExcessPadding(b'abcd===', b'i\xb7\x1d')
+        assertExcessPadding(b'abcd====', b'i\xb7\x1d')
+        assertExcessPadding(b'abcd=====', b'i\xb7\x1d')
+        assertExcessPadding(b'abcd=efgh', b'i\xb7\x1dy\xf8!')
+        assertExcessPadding(b'abcd==efgh', b'i\xb7\x1dy\xf8!')
+        assertExcessPadding(b'abcd===efgh', b'i\xb7\x1dy\xf8!')
+        assertExcessPadding(b'abcd====efgh', b'i\xb7\x1dy\xf8!')
+        assertExcessPadding(b'abcd=====efgh', b'i\xb7\x1dy\xf8!')
+
+    def test_a2b_base64_padded(self):
+        a2b_base64 = binascii.a2b_base64
+        t = self.type2test
+        def check(data, expected):
+            if b'=' in data:
+                with self.assertRaisesRegex(binascii.Error, 'Padding not allowed'):
+                    a2b_base64(t(data), padded=False, strict_mode=True)
+            self.assertEqual(a2b_base64(t(data), padded=False, ignorechars=b'='),
+                             expected)
+            data = data.replace(b'=', b'')
+            self.assertEqual(a2b_base64(t(data), padded=False), expected)
+            self.assertEqual(a2b_base64(t(data), padded=False, strict_mode=True),
+                             expected)
+
+        check(b'', b'')
+        check(b'YQ==', b'a')
+        check(b'YWI=', b'ab')
+        check(b'YWJj', b'abc')
+        check(b'Y=WJj', b'abc')
+        check(b'YW=Jj', b'abc')
+        check(b'YWJ=j', b'abc')
+
+    def _common_test_ignorechars(self, func):
+        eq = self.assertEqual
+        empty = self.type2test(b'')
+        data = self.type2test(b'\n \n')
+        ignorechars = self.type2test(b' \n')
+        eq(func(empty, ignorechars=ignorechars), b'')
+        eq(func(empty, ignorechars=empty), b'')
+        eq(func(data, ignorechars=ignorechars), b'')
+        with self.assertRaises(binascii.Error):
+            func(data, ignorechars=empty)
+        with self.assertRaises(binascii.Error):
+            func(data, ignorechars=ignorechars[1:])
+        with self.assertRaises(binascii.Error):
+            func(data, ignorechars=ignorechars[:-1])
+        with self.assertRaises(TypeError):
+            func(empty, ignorechars='')
+        with self.assertRaises(TypeError):
+            func(empty, ignorechars=[])
+        with self.assertRaises(TypeError):
+            func(empty, ignorechars=None)
+
+    def test_base64_invalidchars(self):
+        # Test non-base64 data exceptions
+        self._common_test_ignorechars(binascii.a2b_base64)
+        def assertNonBase64Data(data, expected, ignorechars):
+            data = self.type2test(data)
+            assert_regex = r'(?i)Only base64 data'
+            self.assertEqual(binascii.a2b_base64(data), expected)
+            with self.assertRaisesRegex(binascii.Error, assert_regex):
+                binascii.a2b_base64(data, strict_mode=True)
+            with self.assertRaisesRegex(binascii.Error, assert_regex):
+                binascii.a2b_base64(data, ignorechars=b'')
+            self.assertEqual(binascii.a2b_base64(data, ignorechars=ignorechars),
+                             expected)
+            self.assertEqual(binascii.a2b_base64(data, strict_mode=False, ignorechars=b''),
+                             expected)
+
+        assertNonBase64Data(b'\nab==', b'i', ignorechars=b'\n')
+        assertNonBase64Data(b'ab:(){:|:&};:==', b'i', ignorechars=b':;(){}|&')
+        assertNonBase64Data(b'a\nb==', b'i', ignorechars=b'\n')
+        assertNonBase64Data(b'a\x00b==', b'i', ignorechars=b'\x00')
+        assertNonBase64Data(b'ab:==', b'i', ignorechars=b':')
+        assertNonBase64Data(b'ab=:=', b'i', ignorechars=b':')
+        assertNonBase64Data(b'ab==:', b'i', ignorechars=b':')
+        assertNonBase64Data(b'abc=:', b'i\xb7', ignorechars=b':')
+        assertNonBase64Data(b'ab==\n', b'i', ignorechars=b'\n')
+        assertNonBase64Data(b'a\nb==', b'i', ignorechars=bytearray(b'\n'))
+        assertNonBase64Data(b'a\nb==', b'i', ignorechars=memoryview(b'\n'))
+
+        self.assertEqual(binascii.a2b_base64(b'+A-/B_', ignorechars=b'+/-_'),
+                         b'\xf8\x0f\xc1')
+        self.assertEqual(binascii.a2b_base64(b'+A-/B_', ignorechars=b'+/-_',
+                                alphabet=binascii.URLSAFE_BASE64_ALPHABET),
+                         b'\x03\xe0\x7f')
+
+        # Same cell in the cache: '\r' >> 3 == '\n' >> 3.
+        data = self.type2test(b'\r\n')
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base64(data, ignorechars=b'\r')
+        self.assertEqual(binascii.a2b_base64(data, ignorechars=b'\r\n'), b'')
+        # Same bit mask in the cache: '*' & 31 == '\n' & 31.
+        data = self.type2test(b'*\n')
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base64(data, ignorechars=b'*')
+        self.assertEqual(binascii.a2b_base64(data, ignorechars=b'*\n'), b'')
 
     def test_base64_excess_data(self):
         # Test excess data exceptions
@@ -183,6 +330,9 @@ def assertExcessData(data, expected):
                 binascii.a2b_base64(data, strict_mode=True)
             self.assertEqual(binascii.a2b_base64(data, strict_mode=False),
                              expected)
+            self.assertEqual(binascii.a2b_base64(data, strict_mode=True,
+                                                 ignorechars=b'='),
+                             expected)
             self.assertEqual(binascii.a2b_base64(data), expected)
 
         assertExcessData(b'ab==c=', b'i\xb7')
@@ -191,9 +341,15 @@ def assertExcessData(data, expected):
 
     def test_base64errors(self):
         # Test base64 with invalid padding
-        def assertIncorrectPadding(data):
+        def assertIncorrectPadding(data, strict_mode=True):
+            data = self.type2test(data)
+            with self.assertRaisesRegex(binascii.Error, r'(?i)Incorrect padding'):
+                binascii.a2b_base64(data)
             with self.assertRaisesRegex(binascii.Error, r'(?i)Incorrect padding'):
-                binascii.a2b_base64(self.type2test(data))
+                binascii.a2b_base64(data, strict_mode=False)
+            if strict_mode:
+                with self.assertRaisesRegex(binascii.Error, r'(?i)Incorrect padding'):
+                    binascii.a2b_base64(data, strict_mode=True)
 
         assertIncorrectPadding(b'ab')
         assertIncorrectPadding(b'ab=')
@@ -201,16 +357,22 @@ def assertIncorrectPadding(data):
         assertIncorrectPadding(b'abcdef')
         assertIncorrectPadding(b'abcdef=')
         assertIncorrectPadding(b'abcdefg')
-        assertIncorrectPadding(b'a=b=')
-        assertIncorrectPadding(b'a\nb=')
+        assertIncorrectPadding(b'a=b=', strict_mode=False)
+        assertIncorrectPadding(b'a\nb=', strict_mode=False)
 
         # Test base64 with invalid number of valid characters (1 mod 4)
-        def assertInvalidLength(data):
+        def assertInvalidLength(data, strict_mode=True):
             n_data_chars = len(re.sub(br'[^A-Za-z0-9/+]', br'', data))
+            data = self.type2test(data)
             expected_errmsg_re = \
                 r'(?i)Invalid.+number of data characters.+' + str(n_data_chars)
             with self.assertRaisesRegex(binascii.Error, expected_errmsg_re):
-                binascii.a2b_base64(self.type2test(data))
+                binascii.a2b_base64(data)
+            with self.assertRaisesRegex(binascii.Error, expected_errmsg_re):
+                binascii.a2b_base64(data, strict_mode=False)
+            if strict_mode:
+                with self.assertRaisesRegex(binascii.Error, expected_errmsg_re):
+                    binascii.a2b_base64(data, strict_mode=True)
 
         assertInvalidLength(b'a')
         assertInvalidLength(b'a=')
@@ -218,7 +380,911 @@ def assertInvalidLength(data):
         assertInvalidLength(b'a===')
         assertInvalidLength(b'a' * 5)
         assertInvalidLength(b'a' * (4 * 87 + 1))
-        assertInvalidLength(b'A\tB\nC ??DE')  # only 5 valid characters
+        assertInvalidLength(b'A\tB\nC ??DE', # only 5 valid characters
+                            strict_mode=False)
+
+    def test_base64_canonical(self):
+        # https://datatracker.ietf.org/doc/html/rfc4648.html#section-3.5
+        # Decoders MAY reject encoded data if the pad bits are not zero.
+
+        # Without canonical=True, non-zero padding bits are accepted
+        self.assertEqual(binascii.a2b_base64(self.type2test(b'AB==')), b'\x00')
+        self.assertEqual(binascii.a2b_base64(self.type2test(b'AB=='),
+                                             strict_mode=True), b'\x00')
+
+        # 2 data chars + "==": last char has 4 padding bits
+        # 'A' = 0, 'B' = 1 -> leftover 0001 (non-zero)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base64(self.type2test(b'AB=='), canonical=True)
+        # 'A' = 0, 'P' = 15 -> leftover 1111 (non-zero)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base64(self.type2test(b'AP=='), canonical=True)
+
+        # 3 data chars + "=": last char has 2 padding bits
+        # 'A' = 0, 'A' = 0, 'B' = 1 -> leftover 01 (non-zero)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base64(self.type2test(b'AAB='), canonical=True)
+        # 'A' = 0, 'A' = 0, 'D' = 3 -> leftover 11 (non-zero)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base64(self.type2test(b'AAD='), canonical=True)
+
+        # Verify that zero padding bits are accepted
+        binascii.a2b_base64(self.type2test(b'AA=='), canonical=True)
+        binascii.a2b_base64(self.type2test(b'AAA='), canonical=True)
+
+        # Full quads with no padding have no leftover bits -- always valid
+        binascii.a2b_base64(self.type2test(b'AAAA'), canonical=True)
+
+    @hypothesis.given(payload=hypothesis.strategies.binary())
+    @hypothesis.example(b'')
+    @hypothesis.example(b'\x00')
+    @hypothesis.example(b'\xff\xff')
+    @hypothesis.example(b'abc')
+    def test_base64_canonical_roundtrip(self, payload):
+        # The encoder must always produce canonical output.
+        encoded = binascii.b2a_base64(payload, newline=False)
+        decoded = binascii.a2b_base64(encoded, canonical=True)
+        self.assertEqual(decoded, payload)
+
+    def test_base64_alphabet(self):
+        alphabet = (b'!"#$%&\'()*+,-012345689@'
+                    b'ABCDEFGHIJKLMNPQRSTUVXYZ[`abcdefhijklmpqr')
+        data = self.type2test(self.rawdata)
+        encoded = binascii.b2a_base64(data, alphabet=alphabet)
+        trans = bytes.maketrans(binascii.BASE64_ALPHABET, alphabet)
+        expected = binascii.b2a_base64(data).translate(trans)
+        self.assertEqual(encoded, expected)
+        self.assertEqual(binascii.a2b_base64(encoded, alphabet=alphabet), self.rawdata)
+        self.assertEqual(binascii.b2a_base64(data, alphabet=self.type2test(alphabet)), expected)
+
+        data = self.type2test(b'')
+        self.assertEqual(binascii.b2a_base64(data, alphabet=alphabet), b'\n')
+        self.assertEqual(binascii.a2b_base64(data, alphabet=alphabet), b'')
+
+        for func in binascii.b2a_base64, binascii.a2b_base64:
+            with self.assertRaises(TypeError):
+                func(data, alphabet=None)
+            with self.assertRaises(TypeError):
+                func(data, alphabet=alphabet.decode())
+            with self.assertRaises(ValueError):
+                func(data, alphabet=alphabet[:-1])
+            with self.assertRaises(ValueError):
+                func(data, alphabet=alphabet+b'?')
+        with self.assertRaises(TypeError):
+            binascii.a2b_base64(data, alphabet=bytearray(alphabet))
+
+    def test_ascii85_valid(self):
+        # Test Ascii85 with valid data
+        ASCII85_PREFIX = b"<~"
+        ASCII85_SUFFIX = b"~>"
+
+        # Interleave blocks of 4 null bytes and 4 spaces into test data
+        rawdata = bytearray()
+        rawlines, i = [], 0
+        for k in range(1, len(self.rawdata) + 1):
+            b = b"\0\0\0\0" if k & 1 else b"    "
+            b = b + self.rawdata[i:i + k]
+            b = b"    " if k & 1 else b"\0\0\0\0"
+            rawdata += b
+            rawlines.append(b)
+            i += k
+            if i >= len(self.rawdata):
+                break
+
+        # Test core parameter combinations
+        params = (False, False), (False, True), (True, False), (True, True)
+        for foldspaces, adobe in params:
+            lines = []
+            for rawline in rawlines:
+                b = self.type2test(rawline)
+                a = binascii.b2a_ascii85(b, foldspaces=foldspaces, adobe=adobe)
+                lines.append(a)
+            res = bytearray()
+            for line in lines:
+                a = self.type2test(line)
+                b = binascii.a2b_ascii85(a, foldspaces=foldspaces, adobe=adobe)
+                res += b
+            self.assertEqual(res, rawdata)
+
+        # Inputs with length 1 mod 5 end with a 1-char group, which is
+        # an encoding violation per the PLRM spec.
+        error_params = [
+            (b"a", False, False, b""),
+            (b"xbw", False, False, b"wx"),
+            (b"<~c~>", False, True, b""),
+            (b"{d ~>", False, True, b" {"),
+            (b"ye", True, False, b""),
+            (b"z\x01y\x00f", True, False, b"\x00\x01"),
+            (b"<~FCfN8yg~>", True, True, b""),
+            (b"FE;\x03#8zFCf\x02N8yh~>", True, True, b"\x02\x03"),
+        ]
+        for a, foldspaces, adobe, ignorechars in error_params:
+            kwargs = {"foldspaces": foldspaces, "adobe": adobe, "ignorechars": ignorechars}
+            with self.assertRaises(binascii.Error):
+                binascii.a2b_ascii85(self.type2test(a), **kwargs)
+
+    def test_ascii85_invalid(self):
+        # Test Ascii85 with invalid characters interleaved
+        lines, i = [], 0
+        for k in range(1, len(self.rawdata) + 1):
+            b = self.type2test(self.rawdata[i:i + k])
+            a = binascii.b2a_ascii85(b)
+            lines.append(a)
+            i += k
+            if i >= len(self.rawdata):
+                break
+
+        fillers = bytearray()
+        valid = b"!\"#$%&'()*+,-./0123456789:;<=>?@" \
+                b"ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstu" + b"z"
+        for i in range(256):
+            if i not in valid:
+                fillers.append(i)
+        def addnoise(line):
+            res = bytearray()
+            for i in range(len(line)):
+                res.append(line[i])
+                for j in range(i, len(fillers), len(line)):
+                    res.append(fillers[j])
+            return res
+        res = bytearray()
+        for line in map(addnoise, lines):
+            a = self.type2test(line)
+            b = binascii.a2b_ascii85(a, ignorechars=fillers)
+            res += b
+        self.assertEqual(res, self.rawdata)
+
+        # Test Ascii85 with only invalid characters
+        fillers = self.type2test(fillers)
+        b = binascii.a2b_ascii85(fillers, ignorechars=fillers)
+        self.assertEqual(b, b"")
+
+    def test_ascii85_errors(self):
+        def _assertRegexTemplate(assert_regex, data, **kwargs):
+            with self.assertRaisesRegex(binascii.Error, assert_regex):
+                binascii.a2b_ascii85(self.type2test(data), **kwargs)
+
+        def assertMissingDelimiter(data):
+            _assertRegexTemplate(r"(?i)end with b'~>'", data, adobe=True)
+
+        def assertOverflow(data):
+            _assertRegexTemplate(r"(?i)Ascii85 overflow", data)
+
+        def assertInvalidSpecial(data):
+            _assertRegexTemplate(r"(?i)'[yz]'.+5-tuple", data, foldspaces=True)
+
+        def assertInvalidChar(data, **kwargs):
+            _assertRegexTemplate(r"(?i)Non-Ascii85 digit", data, **kwargs)
+
+        # Test Ascii85 with missing delimiters
+        assertMissingDelimiter(b"")
+        assertMissingDelimiter(b"a")
+        assertMissingDelimiter(b"<~")
+        assertMissingDelimiter(b"<~!~")
+        assertMissingDelimiter(b"<~abc>")
+        assertMissingDelimiter(b"<~has delimiter but not terminal~>  !")
+
+        # Test Ascii85 with out-of-range encoded value
+        assertOverflow(b"t")
+        assertOverflow(b"s9")
+        assertOverflow(b"s8X")
+        assertOverflow(b"s8W.")
+        assertOverflow(b's8W-"')
+        assertOverflow(b"s8W-!u")
+        assertOverflow(b"s8W-!s8W-!zs8X")
+
+        # Test Ascii85 with misplaced short form groups
+        assertInvalidSpecial(b"ay")
+        assertInvalidSpecial(b"az")
+        assertInvalidSpecial(b"aby")
+        assertInvalidSpecial(b"ayz")
+        assertInvalidSpecial(b"abcz")
+        assertInvalidSpecial(b"abcdy")
+        assertInvalidSpecial(b"y!and!z!then!!y")
+
+        # Test Ascii85 with non-ignored invalid characters
+        assertInvalidChar(b"j\n")
+        assertInvalidChar(b" ", ignorechars=b"")
+        assertInvalidChar(b" valid\x02until\x03", ignorechars=b"\x00\x01\x02\x04")
+        assertInvalidChar(b"\tFCb", ignorechars=b"\n")
+        assertInvalidChar(b"xxxB\nP\thU'D v/F+", ignorechars=b" \n\tv")
+
+    def _common_test_wrapcol(self, func):
+        eq = self.assertEqual
+        data = self.data
+        expected = func(data)
+        eq(func(data, wrapcol=0), expected)
+        eq(func(data, wrapcol=8000), expected)
+        eq(func(b'', wrapcol=0), func(b''))
+        eq(func(b'', wrapcol=1), func(b''))
+        eq(func(data, wrapcol=sys.maxsize), expected)
+        if check_impl_detail():
+            eq(func(data, wrapcol=sys.maxsize*2), expected)
+            with self.assertRaises(OverflowError):
+                func(data, wrapcol=2**1000)
+        with self.assertRaises(ValueError):
+            func(data, wrapcol=-80)
+        with self.assertRaises(TypeError):
+            func(data, wrapcol=80.0)
+        with self.assertRaises(TypeError):
+            func(data, wrapcol='80')
+        with self.assertRaises(TypeError):
+            func(data, wrapcol=None)
+
+    def test_ascii85_wrapcol(self):
+        # Test Ascii85 splitting lines
+        self._common_test_wrapcol(binascii.b2a_ascii85)
+
+        def assertEncode(a_expected, data, n, adobe=False):
+            b = self.type2test(data)
+            a = binascii.b2a_ascii85(b, adobe=adobe, wrapcol=n)
+            self.assertEqual(a, a_expected)
+
+        def assertDecode(data, b_expected, adobe=False):
+            a = self.type2test(data)
+            b = binascii.a2b_ascii85(a, adobe=adobe, ignorechars=b"\n")
+            self.assertEqual(b, b_expected)
+
+        tests = [
+            (b"", 0, b"", b"<~~>"),
+            (b"", 1, b"", b"<~\n~>"),
+            (b"a", 0, b"@/", b"<~@/~>"),
+            (b"a", 1, b"@\n/", b"<~\n@/\n~>"),
+            (b"a", 2, b"@/", b"<~\n@/\n~>"),
+            (b"a", 3, b"@/", b"<~@\n/~>"),
+            (b"a", 4, b"@/", b"<~@/\n~>"),
+            (b"a", 5, b"@/", b"<~@/\n~>"),
+            (b"a", 6, b"@/", b"<~@/~>"),
+            (b"a", 7, b"@/", b"<~@/~>"),
+            (b"a", 123, b"@/", b"<~@/~>"),
+            (b"this is a test", 7, b"FD,B0+D\nGm>@3BZ\n'F*%",
+                                   b"<~FD,B0\n+DGm>@3\nBZ'F*%\n~>"),
+            (b"a test!!!!!!!    ", 11, b"@3BZ'F*&QK+\nX&!P+WqmM+9",
+                                       b"<~@3BZ'F*&Q\nK+X&!P+WqmM\n+9~>"),
+            (b"\0" * 56, 7, b"zzzzzzz\nzzzzzzz", b"<~zzzzz\nzzzzzzz\nzz~>"),
+        ]
+        for b, n, a, a_wrap in tests:
+            assertEncode(a, b, n)
+            assertEncode(a_wrap, b, n, adobe=True)
+            assertDecode(a, b)
+            assertDecode(a_wrap, b, adobe=True)
+
+    def test_ascii85_pad(self):
+        # Test Ascii85 with encode padding
+        rawdata = b"n1n3tee\n ch@rAcTer$"
+        for i in range(1, len(rawdata) + 1):
+            padding = -i % 4
+            b = rawdata[:i]
+            a_pad = binascii.b2a_ascii85(self.type2test(b), pad=True)
+            b_pad = binascii.a2b_ascii85(self.type2test(a_pad))
+            b_pad_expected = b + b"\0" * padding
+            self.assertEqual(b_pad, b_pad_expected)
+
+        # Test Ascii85 short form groups with encode padding
+        def assertShortPad(data, expected, **kwargs):
+            data = self.type2test(data)
+            res = binascii.b2a_ascii85(data, **kwargs)
+            self.assertEqual(res, expected)
+
+        assertShortPad(b"\0", b"!!", pad=False)
+        assertShortPad(b"\0", b"z", pad=True)
+        assertShortPad(b"\0" * 2, b"z", pad=True)
+        assertShortPad(b"\0" * 3, b"z", pad=True)
+        assertShortPad(b"\0" * 4, b"z", pad=True)
+        assertShortPad(b"\0" * 5, b"zz", pad=True)
+        assertShortPad(b"\0" * 6, b"z!!!")
+        assertShortPad(b" " * 7, b"y+<Vd,", foldspaces=True, pad=True)
+        assertShortPad(b"\0" * 8, b"<~zz~>",
+                       foldspaces=True, adobe=True, pad=True)
+        assertShortPad(b"\0\0\0\0abcd    \0\0", b"<~z@:E_Wy\nz~>",
+                       foldspaces=True, adobe=True, wrapcol=9, pad=True)
+
+    def test_ascii85_ignorechars(self):
+        # Test Ascii85 with ignored characters
+        def assertIgnore(data, expected, ignorechars=b"", **kwargs):
+            data = self.type2test(data)
+            ignore = self.type2test(ignorechars)
+            with self.assertRaisesRegex(binascii.Error, r"(?i)Non-Ascii85 digit"):
+                binascii.a2b_ascii85(data, **kwargs)
+            res = binascii.a2b_ascii85(data, ignorechars=ignorechars, **kwargs)
+            self.assertEqual(res, expected)
+
+        assertIgnore(b"\n", b"", ignorechars=b"\n")
+        assertIgnore(b"<~ ~>", b"", ignorechars=b" ", adobe=True)
+        assertIgnore(b"z|z", b"\0" * 8, ignorechars=b"|||")    # repeats don't matter
+        assertIgnore(b"zz!!|", b"\0" * 9, ignorechars=b"|!z")  # ignore only if invalid
+        assertIgnore(b"<~B P~@~>", b"hi", ignorechars=b" <~>", adobe=True)
+        assertIgnore(b"zy}", b"\0\0\0\0", ignorechars=b"zy}")
+        assertIgnore(b"zy}", b"\0\0\0\0    ", ignorechars=b"zy}", foldspaces=True)
+
+    def test_base85_valid(self):
+        # Test base85 with valid data
+        lines, i = [], 0
+        for k in range(1, len(self.rawdata) + 1):
+            b = self.type2test(self.rawdata[i:i + k])
+            a = binascii.b2a_base85(b)
+            lines.append(a)
+            i += k
+            if i >= len(self.rawdata):
+                break
+        res = bytes()
+        for line in lines:
+            a = self.type2test(line)
+            b = binascii.a2b_base85(a)
+            res += b
+        self.assertEqual(res, self.rawdata)
+
+        # Test decoding inputs with different length
+        # 1-char groups are rejected (encoding violation)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base85(self.type2test(b'a'))
+        self.assertEqual(binascii.a2b_base85(self.type2test(b'ab')), b'q')
+        self.assertEqual(binascii.a2b_base85(self.type2test(b'abc')), b'qa')
+        self.assertEqual(binascii.a2b_base85(self.type2test(b'abcd')),
+                         b'qa\x9e')
+        self.assertEqual(binascii.a2b_base85(self.type2test(b'abcde')),
+                         b'qa\x9e\xb6')
+        # 6-char input = full 5-char group + trailing 1-char group (rejected)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base85(self.type2test(b'abcdef'))
+        self.assertEqual(binascii.a2b_base85(self.type2test(b'abcdefg')),
+                         b'qa\x9e\xb6\x81')
+
+    def test_base85_errors(self):
+        def _assertRegexTemplate(assert_regex, data, **kwargs):
+            with self.assertRaisesRegex(binascii.Error, assert_regex):
+                binascii.a2b_base85(self.type2test(data), **kwargs)
+
+        def assertNonBase85Data(data):
+            _assertRegexTemplate(r"(?i)bad base85 character", data)
+
+        def assertOverflow(data):
+            _assertRegexTemplate(r"(?i)base85 overflow", data)
+
+        assertNonBase85Data(b"\xda")
+        assertNonBase85Data(b"00\0\0")
+        assertNonBase85Data(b"Z )*")
+        assertNonBase85Data(b"bY*jNb0Hyq\n")
+
+        # Test base85 with out-of-range encoded value
+        assertOverflow(b"}")
+        assertOverflow(b"|O")
+        assertOverflow(b"|Nt")
+        assertOverflow(b"|NsD")
+        assertOverflow(b"|NsC1")
+        assertOverflow(b"|NsC0~")
+        assertOverflow(b"|NsC0|NsC0|NsD0")
+
+    def test_base85_wrapcol(self):
+        self._common_test_wrapcol(binascii.b2a_base85)
+        b = self.type2test(b'www.python.org')
+        self.assertEqual(binascii.b2a_base85(b, wrapcol=10),
+                         b'cXxL#aCvlS\nZ*DGca%T')
+        self.assertEqual(binascii.b2a_base85(b, wrapcol=14),
+                         b'cXxL#aCvlS\nZ*DGca%T')
+        self.assertEqual(binascii.b2a_base85(b, wrapcol=1),
+                         b'cXxL#\naCvlS\nZ*DGc\na%T')
+
+    def test_base85_pad(self):
+        # Test base85 with encode padding
+        rawdata = b"n1n3Tee\n ch@rAc\te\r$"
+        for i in range(1, len(rawdata) + 1):
+            padding = -i % 4
+            b = rawdata[:i]
+            a_pad = binascii.b2a_base85(self.type2test(b), pad=True)
+            b_pad = binascii.a2b_base85(self.type2test(a_pad))
+            b_pad_expected = b + b"\0" * padding
+            self.assertEqual(b_pad, b_pad_expected)
+
+    def test_base85_ignorechars(self):
+        a2b_base85 = binascii.a2b_base85
+        self._common_test_ignorechars(a2b_base85)
+        eq = self.assertEqual
+        eq(a2b_base85(b'VPa\n !s\n', ignorechars=b' \n'), b'abcd')
+        eq(a2b_base85(b'VPa\n !s\n', ignorechars=bytearray(b' \n')), b'abcd')
+
+        eq(a2b_base85(b'A~[B];C', ignorechars=b';[]~'), b'"1\xa3\x15')
+        eq(a2b_base85(b'A~[B];C', ignorechars=b';[]~',
+                      alphabet=binascii.Z85_ALPHABET), b'r\xd8dv')
+
+    def test_base85_alphabet(self):
+        alphabet = (b'0123456789abcdefghijklmnopqrstuvwxyz'
+                    b'ABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#')
+        data = self.type2test(self.rawdata)
+        encoded = binascii.b2a_base85(data, alphabet=alphabet)
+        trans = bytes.maketrans(binascii.BASE85_ALPHABET, alphabet)
+        expected = binascii.b2a_base85(data).translate(trans)
+        self.assertEqual(encoded, expected)
+        self.assertEqual(binascii.a2b_base85(encoded, alphabet=alphabet), self.rawdata)
+        self.assertEqual(binascii.b2a_base85(data, alphabet=self.type2test(alphabet)), expected)
+
+        data = self.type2test(b'')
+        self.assertEqual(binascii.b2a_base85(data, alphabet=alphabet), b'')
+        self.assertEqual(binascii.a2b_base85(data, alphabet=alphabet), b'')
+
+        for func in binascii.b2a_base85, binascii.a2b_base85:
+            with self.assertRaises(TypeError):
+                func(data, alphabet=None)
+            with self.assertRaises(TypeError):
+                func(data, alphabet=alphabet.decode())
+            with self.assertRaises(ValueError):
+                func(data, alphabet=alphabet[:-1])
+            with self.assertRaises(ValueError):
+                func(data, alphabet=alphabet+b'?')
+        with self.assertRaises(TypeError):
+            binascii.a2b_base64(data, alphabet=bytearray(alphabet))
+
+    def test_base85_canonical(self):
+        # Non-canonical encodings are accepted without canonical=True
+        self.assertEqual(binascii.a2b_base85(b'VF'), b'a')
+
+        # 1-char partial groups are always rejected (encoding violation:
+        # no conforming encoder produces them)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base85(b'V')
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base85(b'0')
+
+        # Verify round-trip: encode then decode with canonical=True works
+        for data in [b'a', b'ab', b'abc', b'abcd', b'abcde',
+                     b'\x00', b'\xff', b'\x00\x00', b'\xff\xff\xff']:
+            encoded = binascii.b2a_base85(data)
+            decoded = binascii.a2b_base85(encoded, canonical=True)
+            self.assertEqual(decoded, data)
+
+        # Test non-canonical rejection for each partial group size
+        # (2-char/1-byte, 3-char/2-byte, 4-char/3-byte).
+        # Incrementing the last digit by 1 produces a non-canonical
+        # encoding.  For 4-char groups (n_pad=1) a +1 can change the
+        # output byte, so we use b'ab\x00' whose canonical form allows
+        # a +1 that still decodes to the same 3 bytes.
+        for data in [b'a', b'ab', b'ab\x00']:
+            canonical_enc = binascii.b2a_base85(data)
+            non_canonical = (canonical_enc[:-1]
+                             + bytes([canonical_enc[-1] + 1]))
+            # Same decoded output without canonical check
+            self.assertEqual(binascii.a2b_base85(non_canonical), data)
+            # Rejected with canonical=True
+            with self.assertRaises(binascii.Error):
+                binascii.a2b_base85(non_canonical, canonical=True)
+
+        # Boundary bytes: \x00 and \xff for each partial group size
+        for data in [b'\x00', b'\x00\x00', b'\x00\x00\x00',
+                     b'\xff', b'\xff\xff', b'\xff\xff\xff']:
+            canonical_enc = binascii.b2a_base85(data)
+            binascii.a2b_base85(canonical_enc, canonical=True)
+
+        # Full 5-char groups are always canonical (no padding bits)
+        self.assertEqual(
+            binascii.a2b_base85(b'VPa!s', canonical=True), b'abcd')
+
+        # Empty input is valid
+        self.assertEqual(binascii.a2b_base85(b'', canonical=True), b'')
+
+    @hypothesis.given(payload=hypothesis.strategies.binary())
+    @hypothesis.example(b'')
+    @hypothesis.example(b'\x00')
+    @hypothesis.example(b'\xff\xff')
+    @hypothesis.example(b'abc')
+    def test_base85_canonical_roundtrip(self, payload):
+        encoded = binascii.b2a_base85(payload)
+        decoded = binascii.a2b_base85(encoded, canonical=True)
+        self.assertEqual(decoded, payload)
+
+    @hypothesis.given(payload=hypothesis.strategies.binary(min_size=1, max_size=3))
+    @hypothesis.example(b'\x00')
+    @hypothesis.example(b'\xff')
+    @hypothesis.example(b'ab\x00')
+    def test_base85_canonical_unique(self, payload):
+        # For a partial group, sweeping all 85 last-digit values should
+        # yield exactly one encoding that both decodes to the original
+        # payload AND passes canonical=True.
+        hypothesis.assume(len(payload) % 4 != 0)
+        canonical_enc = binascii.b2a_base85(payload)
+        table = binascii.BASE85_ALPHABET
+        accepted = []
+        for digit in table:
+            candidate = canonical_enc[:-1] + bytes([digit])
+            try:
+                result = binascii.a2b_base85(candidate, canonical=True)
+                if result == payload:
+                    accepted.append(candidate)
+            except binascii.Error:
+                pass
+        self.assertEqual(accepted, [canonical_enc])
+
+    def test_ascii85_canonical(self):
+        # Non-canonical encodings are accepted without canonical=True
+        self.assertEqual(binascii.a2b_ascii85(b'@0'), b'a')
+
+        # 1-char partial groups are always rejected (PLRM encoding violation)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_ascii85(b'@')
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_ascii85(b'!')
+
+        # Verify round-trip: encode then decode with canonical=True works
+        for data in [b'a', b'ab', b'abc', b'abcd', b'abcde',
+                     b'\x00', b'\xff', b'\x00\x00', b'\xff\xff\xff']:
+            encoded = binascii.b2a_ascii85(data)
+            decoded = binascii.a2b_ascii85(encoded, canonical=True)
+            self.assertEqual(decoded, data)
+
+        # Test non-canonical rejection for each partial group size.
+        # See test_base85_canonical for why b'ab\x00' is used for 3 bytes.
+        for data in [b'a', b'ab', b'ab\x00']:
+            canonical_enc = binascii.b2a_ascii85(data)
+            non_canonical = (canonical_enc[:-1]
+                             + bytes([canonical_enc[-1] + 1]))
+            self.assertEqual(binascii.a2b_ascii85(non_canonical), data)
+            with self.assertRaises(binascii.Error):
+                binascii.a2b_ascii85(non_canonical, canonical=True)
+
+        # Full 5-char groups are always canonical
+        self.assertEqual(
+            binascii.a2b_ascii85(b'@:E_W', canonical=True), b'abcd')
+
+        # 'z' is the canonical form for all-zero groups per the PLRM.
+        # '!!!!!' decodes identically but is non-canonical.
+        self.assertEqual(binascii.a2b_ascii85(b'!!!!!'), b'\x00' * 4)
+        self.assertEqual(binascii.a2b_ascii85(b'z'), b'\x00' * 4)
+        self.assertEqual(
+            binascii.a2b_ascii85(b'z', canonical=True), b'\x00' * 4)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_ascii85(b'!!!!!', canonical=True)
+        # Multiple groups: z + !!!!! should fail
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_ascii85(b'z!!!!!', canonical=True)
+        # Multiple z groups are fine
+        self.assertEqual(
+            binascii.a2b_ascii85(b'zz', canonical=True), b'\x00' * 8)
+
+        # Empty input is valid
+        self.assertEqual(binascii.a2b_ascii85(b'', canonical=True), b'')
+
+        # Adobe-wrapped with canonical
+        self.assertEqual(
+            binascii.a2b_ascii85(b'<~@:E_W~>', canonical=True, adobe=True),
+            b'abcd')
+
+    @hypothesis.given(payload=hypothesis.strategies.binary())
+    @hypothesis.example(b'')
+    @hypothesis.example(b'\x00')
+    @hypothesis.example(b'\x00\x00\x00\x00')  # triggers z abbreviation
+    @hypothesis.example(b'\xff\xff')
+    @hypothesis.example(b'abc')
+    def test_ascii85_canonical_roundtrip(self, payload):
+        encoded = binascii.b2a_ascii85(payload)
+        decoded = binascii.a2b_ascii85(encoded, canonical=True)
+        self.assertEqual(decoded, payload)
+
+    @hypothesis.given(payload=hypothesis.strategies.binary(min_size=1, max_size=3))
+    @hypothesis.example(b'\x00')
+    @hypothesis.example(b'\xff')
+    @hypothesis.example(b'ab\x00')
+    def test_ascii85_canonical_unique(self, payload):
+        hypothesis.assume(len(payload) % 4 != 0)
+        canonical_enc = binascii.b2a_ascii85(payload)
+        # Ascii85 alphabet: '!' (33) through 'u' (117)
+        accepted = []
+        for digit in range(33, 118):
+            candidate = canonical_enc[:-1] + bytes([digit])
+            try:
+                result = binascii.a2b_ascii85(candidate, canonical=True)
+                if result == payload:
+                    accepted.append(candidate)
+            except binascii.Error:
+                pass
+        self.assertEqual(accepted, [canonical_enc])
+
+    def test_base32_valid(self):
+        # Test base32 with valid data
+        lines = []
+        step = 0
+        i = 0
+        while i < len(self.rawdata):
+            b = self.type2test(self.rawdata[i:i + step])
+            a = binascii.b2a_base32(b)
+            lines.append(a)
+            i += step
+            step += 1
+        res = bytes()
+        for line in lines:
+            a = self.type2test(line)
+            b = binascii.a2b_base32(a)
+            res += b
+        self.assertEqual(res, self.rawdata)
+
+    def test_base32_errors(self):
+        def _fixPadding(data):
+            fixed = data.replace(b"=", b"")
+            len_8 = len(fixed) % 8
+            p = 8 - len_8 if len_8 else 0
+            return fixed + b"=" * p
+
+        def _assertRegexTemplate(assert_regex, data, good_padding_result=None, **kwargs):
+            with self.assertRaisesRegex(binascii.Error, assert_regex):
+                binascii.a2b_base32(self.type2test(data), **kwargs)
+            if good_padding_result:
+                fixed = self.type2test(_fixPadding(data))
+                self.assertEqual(binascii.a2b_base32(fixed), good_padding_result)
+
+        def assertNonBase32Data(*args):
+            _assertRegexTemplate(r"(?i)Only base32 data", *args)
+
+        def assertExcessData(*args):
+            _assertRegexTemplate(r"(?i)Excess data", *args)
+
+        def assertExcessPadding(*args):
+            _assertRegexTemplate(r"(?i)Excess padding", *args)
+
+        def assertLeadingPadding(*args, **kwargs):
+            _assertRegexTemplate(r"(?i)Leading padding", *args, **kwargs)
+
+        def assertIncorrectPadding(*args):
+            _assertRegexTemplate(r"(?i)Incorrect padding", *args)
+
+        def assertDiscontinuousPadding(*args):
+            _assertRegexTemplate(r"(?i)Discontinuous padding", *args)
+
+        def assertInvalidLength(data, *args, length=None, **kwargs):
+            if length is None:
+                length = len(data.split(b'=', 1)[0].replace(b' ', b''))
+            assert_regex = fr"(?i)Invalid.+number of data characters \({length}\)"
+            _assertRegexTemplate(assert_regex, data, *args, **kwargs)
+
+        assertNonBase32Data(b"a")
+        assertNonBase32Data(b"AA-")
+        assertNonBase32Data(b"ABCDE==!")
+        assertNonBase32Data(b"ab:(){:|:&};:==")
+
+        assertExcessData(b"AB======C")
+        assertExcessData(b"AB======CD")
+        assertExcessData(b"ABCD====E")
+        assertExcessData(b"ABCDE===FGH")
+        assertExcessData(b"ABCDEFG=H")
+        assertExcessData(b"432Z====55555555")
+
+        assertExcessData(b"BE======EF", b"\t\x08")
+        assertExcessData(b"BEEF====C", b"\t\x08Q")
+        assertExcessData(b"BEEFC===AK", b"\t\x08Q\x01")
+        assertExcessData(b"BEEFCAK=E", b"\t\x08Q\x01D")
+
+        assertExcessPadding(b"BE=======", b"\t")
+        assertExcessPadding(b"BE========", b"\t")
+        assertExcessPadding(b"BEEF=====", b"\t\x08")
+        assertExcessPadding(b"BEEF======", b"\t\x08")
+        assertExcessPadding(b"BEEFC====", b"\t\x08Q")
+        assertExcessPadding(b"BEEFC=====", b"\t\x08Q")
+        assertExcessPadding(b"BEEFCAK==", b"\t\x08Q\x01")
+        assertExcessPadding(b"BEEFCAK===", b"\t\x08Q\x01")
+        assertExcessPadding(b"BEEFCAKE=", b"\t\x08Q\x01D")
+        assertExcessPadding(b"BEEFCAKE==", b"\t\x08Q\x01D")
+        assertExcessPadding(b"BEEFCAKE===", b"\t\x08Q\x01D")
+        assertExcessPadding(b"BEEFCAKE====", b"\t\x08Q\x01D")
+        assertExcessPadding(b"BEEFCAKE=====", b"\t\x08Q\x01D")
+        assertExcessPadding(b"BEEFCAKE======", b"\t\x08Q\x01D")
+        assertExcessPadding(b"BEEFCAKE=======", b"\t\x08Q\x01D")
+        assertExcessPadding(b"BEEFCAKE========", b"\t\x08Q\x01D")
+        assertExcessPadding(b"BEEFCAKE=========", b"\t\x08Q\x01D")
+
+        assertLeadingPadding(b"=", b"")
+        assertLeadingPadding(b"==", b"")
+        assertLeadingPadding(b"===", b"")
+        assertLeadingPadding(b"====", b"")
+        assertLeadingPadding(b"=====", b"")
+        assertLeadingPadding(b"======", b"")
+        assertLeadingPadding(b"=======", b"")
+        assertLeadingPadding(b"========", b"")
+        assertLeadingPadding(b"=========", b"")
+        assertLeadingPadding(b"=BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b"==BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b"===BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b"====BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b"=====BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b"======BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b"=======BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b"========BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b"=========BEEFCAKE", b"\t\x08Q\x01D")
+        assertLeadingPadding(b" =BEEFCAKE", ignorechars=b' ')
+
+        assertIncorrectPadding(b"AB")
+        assertIncorrectPadding(b"ABCD")
+        assertIncorrectPadding(b"ABCDE")
+        assertIncorrectPadding(b"ABCDEFG")
+
+        assertIncorrectPadding(b"BE=", b"\t")
+        assertIncorrectPadding(b"BE==", b"\t")
+        assertIncorrectPadding(b"BE===", b"\t")
+        assertIncorrectPadding(b"BE====", b"\t")
+        assertIncorrectPadding(b"BE=====", b"\t")
+        assertIncorrectPadding(b"BEEF=", b"\t\x08")
+        assertIncorrectPadding(b"BEEF==", b"\t\x08")
+        assertIncorrectPadding(b"BEEF===", b"\t\x08")
+        assertIncorrectPadding(b"BEEFC=", b"\t\x08Q")
+        assertIncorrectPadding(b"BEEFC==", b"\t\x08Q")
+
+        assertDiscontinuousPadding(b"BE=EF===", b"\t\x08")
+        assertDiscontinuousPadding(b"BE==EF==", b"\t\x08")
+        assertDiscontinuousPadding(b"BEEF=C==", b"\t\x08Q")
+        assertDiscontinuousPadding(b"BEEFC=AK", b"\t\x08Q\x01")
+
+        assertInvalidLength(b"A")
+        assertInvalidLength(b"ABC")
+        assertInvalidLength(b"ABCDEF")
+        assertInvalidLength(b"ABCDEFGHI")
+        assertInvalidLength(b"ABCDEFGHIJK")
+        assertInvalidLength(b"ABCDEFGHIJKLMN")
+
+        assertInvalidLength(b"A=")
+        assertInvalidLength(b"A==")
+        assertInvalidLength(b"A===")
+        assertInvalidLength(b"A====")
+        assertInvalidLength(b"A=====")
+        assertInvalidLength(b"A======")
+        assertInvalidLength(b"ABC=")
+        assertInvalidLength(b"ABC==")
+        assertInvalidLength(b"ABC===")
+        assertInvalidLength(b"ABC====")
+        assertInvalidLength(b"ABCDEF=")
+
+        assertInvalidLength(b"B=E=====", b"\t")
+        assertInvalidLength(b"B==E====", b"\t")
+        assertInvalidLength(b"BEE=F===", b"\t\x08")
+        assertInvalidLength(b"BEE==F==", b"\t\x08")
+        assertInvalidLength(b"BEEFCA=K", b"\t\x08Q\x01")
+        assertInvalidLength(b"BEEFCA=====K", b"\t\x08Q\x01")
+
+        assertInvalidLength(b" A", ignorechars=b' ')
+        assertInvalidLength(b" ABC", ignorechars=b' ')
+        assertInvalidLength(b" ABCDEF", ignorechars=b' ')
+        assertInvalidLength(b" ABCDEFGHI", ignorechars=b' ')
+        assertInvalidLength(b" ABCDEFGHIJK", ignorechars=b' ')
+        assertInvalidLength(b" ABCDEFGHIJKLMN", ignorechars=b' ')
+        assertInvalidLength(b" A=======", ignorechars=b' ')
+        assertInvalidLength(b" ABC=====", ignorechars=b' ')
+        assertInvalidLength(b" ABCDEF==", ignorechars=b' ')
+
+    def test_base32_canonical(self):
+        # https://datatracker.ietf.org/doc/html/rfc4648.html#section-3.5
+        # Decoders MAY reject encoded data if the pad bits are not zero.
+
+        # Without canonical=True, non-zero padding bits are accepted
+        self.assertEqual(binascii.a2b_base32(self.type2test(b'AB======')),
+                         b'\x00')
+
+        # 2 data chars + "======": last char has 2 padding bits
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base32(self.type2test(b'AB======'), canonical=True)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base32(self.type2test(b'AD======'), canonical=True)
+
+        # 4 data chars + "====": last char has 4 padding bits
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base32(self.type2test(b'AAAB===='), canonical=True)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base32(self.type2test(b'AAAP===='), canonical=True)
+
+        # 5 data chars + "===": last char has 1 padding bit
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base32(self.type2test(b'AAAAB==='), canonical=True)
+
+        # 7 data chars + "=": last char has 3 padding bits
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base32(self.type2test(b'AAAAAAB='), canonical=True)
+        with self.assertRaises(binascii.Error):
+            binascii.a2b_base32(self.type2test(b'AAAAAAH='), canonical=True)
+
+        # Verify that zero padding bits are accepted
+        binascii.a2b_base32(self.type2test(b'AA======'), canonical=True)
+        binascii.a2b_base32(self.type2test(b'AAAA===='), canonical=True)
+        binascii.a2b_base32(self.type2test(b'AAAAA==='), canonical=True)
+        binascii.a2b_base32(self.type2test(b'AAAAAAA='), canonical=True)
+
+        # Full octet with no padding -- always valid
+        binascii.a2b_base32(self.type2test(b'AAAAAAAA'), canonical=True)
+
+    @hypothesis.given(payload=hypothesis.strategies.binary())
+    @hypothesis.example(b'')
+    @hypothesis.example(b'\x00')
+    @hypothesis.example(b'\xff\xff')
+    @hypothesis.example(b'abc')
+    def test_base32_canonical_roundtrip(self, payload):
+        encoded = binascii.b2a_base32(payload)
+        decoded = binascii.a2b_base32(encoded, canonical=True)
+        self.assertEqual(decoded, payload)
+
+    def test_a2b_base32_padded(self):
+        a2b_base32 = binascii.a2b_base32
+        t = self.type2test
+        def check(data, expected):
+            if b'=' in data:
+                with self.assertRaisesRegex(binascii.Error, 'Padding not allowed'):
+                    a2b_base32(t(data), padded=False)
+            self.assertEqual(a2b_base32(t(data), padded=False, ignorechars=b'='),
+                             expected)
+            data = data.replace(b'=', b'')
+            self.assertEqual(a2b_base32(t(data), padded=False), expected)
+
+        check(b'', b'')
+        check(b'ME======', b'a')
+        check(b'MFRA====', b'ab')
+        check(b'MFRGG===', b'abc')
+        check(b'MFRGGZA=', b'abcd')
+        check(b'MFRGGZDF', b'abcde')
+        check(b'M=FRGGZDF', b'abcde')
+        check(b'MF=RGGZDF', b'abcde')
+        check(b'MFR=GGZDF', b'abcde')
+        check(b'MFRG=GZDF', b'abcde')
+        check(b'MFRGG=ZDF', b'abcde')
+        check(b'MFRGGZ=DF', b'abcde')
+        check(b'MFRGGZD=F', b'abcde')
+
+    def test_b2a_base32_padded(self):
+        b2a_base32 = binascii.b2a_base32
+        t = self.type2test
+        self.assertEqual(b2a_base32(t(b''), padded=False), b'')
+        self.assertEqual(b2a_base32(t(b'a'), padded=False), b'ME')
+        self.assertEqual(b2a_base32(t(b'ab'), padded=False), b'MFRA')
+        self.assertEqual(b2a_base32(t(b'abc'), padded=False), b'MFRGG')
+        self.assertEqual(b2a_base32(t(b'abcd'), padded=False), b'MFRGGZA')
+        self.assertEqual(b2a_base32(t(b'abcde'), padded=False), b'MFRGGZDF')
+
+    def test_base32_wrapcol(self):
+        self._common_test_wrapcol(binascii.b2a_base32)
+        b = self.type2test(b'www.python.org')
+        self.assertEqual(binascii.b2a_base32(b, wrapcol=16),
+                         b'O53XOLTQPF2GQ33O\nFZXXEZY=')
+        self.assertEqual(binascii.b2a_base32(b, wrapcol=23),
+                         b'O53XOLTQPF2GQ33O\nFZXXEZY=')
+        self.assertEqual(binascii.b2a_base32(b, wrapcol=1),
+                         b'O53XOLTQ\nPF2GQ33O\nFZXXEZY=')
+
+    def test_base32_ignorechars(self):
+        a2b_base32 = binascii.a2b_base32
+        self._common_test_ignorechars(a2b_base32)
+        eq = self.assertEqual
+        eq(a2b_base32(b'MFRG\n GZDF\n', ignorechars=b' \n'), b'abcde')
+        eq(a2b_base32(b'MFRG\n GZDF\n', ignorechars=bytearray(b' \n')), b'abcde')
+        eq(a2b_base32(b'M=======FRGGZDF', ignorechars=b'='), b'abcde')
+        eq(a2b_base32(b'MF======RGGZDF', ignorechars=b'='), b'abcde')
+        eq(a2b_base32(b'MFR=====GGZDF', ignorechars=b'='), b'abcde')
+        eq(a2b_base32(b'MFRG====GZDF', ignorechars=b'='), b'abcde')
+        eq(a2b_base32(b'MFRGG===ZDF', ignorechars=b'='), b'abcde')
+        eq(a2b_base32(b'MFRGGZ==DF', ignorechars=b'='), b'abcde')
+        eq(a2b_base32(b'MFRGGZD=F', ignorechars=b'='), b'abcde')
+        eq(a2b_base32(b'MFRGGZDF=', ignorechars=b'='), b'abcde')
+        eq(a2b_base32(b'MFRA======', ignorechars=b'='), b'ab')
+
+        eq(a2b_base32(b'A1B3C5W7Z9', ignorechars=b'19WZ'), b'\x00v.\xdb\xf9')
+        eq(a2b_base32(b'A1B3C5W7Z9', ignorechars=b'19WZ',
+                      alphabet=binascii.BASE32HEX_ALPHABET), b'PV6\x14\xe9')
+
+    def test_base32_alphabet(self):
+        alphabet = b'0Aa1Bb2Cc3Dd4Ee5Ff6Gg7Hh8Ii9JjKk'
+        data = self.type2test(self.rawdata)
+        encoded = binascii.b2a_base32(data, alphabet=alphabet)
+        trans = bytes.maketrans(binascii.BASE32_ALPHABET, alphabet)
+        expected = binascii.b2a_base32(data).translate(trans)
+        self.assertEqual(encoded, expected)
+        self.assertEqual(binascii.a2b_base32(encoded, alphabet=alphabet), self.rawdata)
+        self.assertEqual(binascii.b2a_base32(data, alphabet=self.type2test(alphabet)), expected)
+
+        data = self.type2test(b'')
+        self.assertEqual(binascii.b2a_base32(data, alphabet=alphabet), b'')
+        self.assertEqual(binascii.a2b_base32(data, alphabet=alphabet), b'')
+
+        for func in binascii.b2a_base32, binascii.a2b_base32:
+            with self.assertRaises(TypeError):
+                func(data, alphabet=None)
+            with self.assertRaises(TypeError):
+                func(data, alphabet=alphabet.decode())
+            with self.assertRaises(ValueError):
+                func(data, alphabet=alphabet[:-1])
+            with self.assertRaises(ValueError):
+                func(data, alphabet=alphabet+b'?')
+        with self.assertRaises(TypeError):
+            binascii.a2b_base32(data, alphabet=bytearray(alphabet))
 
     def test_uu(self):
         MAX_UU = 45
@@ -325,6 +1391,15 @@ def test_hex_separator(self):
         expected1 = s.hex(':').encode('ascii')
         self.assertEqual(binascii.b2a_hex(self.type2test(s), ':'), expected1)
 
+    def test_hex_ignorechars(self):
+        a2b_hex = binascii.a2b_hex
+        self._common_test_ignorechars(a2b_hex)
+        self._common_test_ignorechars(binascii.unhexlify)
+        eq = self.assertEqual
+        eq(a2b_hex(b'A B\nC D\n', ignorechars=b' \n'), b'\xab\xcd')
+        eq(a2b_hex(b'A B\nC D\n', ignorechars=bytearray(b' \n')), b'\xab\xcd')
+        eq(a2b_hex(b'aBcD', ignorechars=b'ac'), b'\xab\xcd')
+
     def test_qp(self):
         type2test = self.type2test
         a2b_qp = binascii.a2b_qp
@@ -499,6 +1574,32 @@ def test_b2a_base64_newline(self):
                          b'aGVsbG8=\n')
         self.assertEqual(binascii.b2a_base64(b, newline=False),
                          b'aGVsbG8=')
+        b = self.type2test(b'')
+        self.assertEqual(binascii.b2a_base64(b), b'\n')
+        self.assertEqual(binascii.b2a_base64(b, newline=True), b'\n')
+        self.assertEqual(binascii.b2a_base64(b, newline=False), b'')
+
+    def test_b2a_base64_padded(self):
+        b2a_base64 = binascii.b2a_base64
+        t = self.type2test
+        self.assertEqual(b2a_base64(t(b''), padded=False), b'\n')
+        self.assertEqual(b2a_base64(t(b'a'), padded=False), b'YQ\n')
+        self.assertEqual(b2a_base64(t(b'ab'), padded=False), b'YWI\n')
+        self.assertEqual(b2a_base64(t(b'abc'), padded=False), b'YWJj\n')
+
+    def test_b2a_base64_wrapcol(self):
+        self._common_test_wrapcol(binascii.b2a_base64)
+        b = self.type2test(b'www.python.org')
+        self.assertEqual(binascii.b2a_base64(b, wrapcol=8),
+                         b'd3d3LnB5\ndGhvbi5v\ncmc=\n')
+        self.assertEqual(binascii.b2a_base64(b, wrapcol=11),
+                         b'd3d3LnB5\ndGhvbi5v\ncmc=\n')
+        self.assertEqual(binascii.b2a_base64(b, wrapcol=8, newline=False),
+                         b'd3d3LnB5\ndGhvbi5v\ncmc=')
+        self.assertEqual(binascii.b2a_base64(b, wrapcol=1),
+                         b'd3d3\nLnB5\ndGhv\nbi5v\ncmc=\n')
+        b = self.type2test(b'')
+        self.assertEqual(binascii.b2a_base64(b, wrapcol=8, newline=False), b'')
 
     @hypothesis.given(
         binary=hypothesis.strategies.binary(),
diff --git a/Lib/test/test_bufio.py b/Lib/test/test_bufio.py
deleted file mode 100644
index cb9cb4d0bc7..00000000000
--- a/Lib/test/test_bufio.py
+++ /dev/null
@@ -1,73 +0,0 @@
-import unittest
-from test.support import os_helper
-
-import io # C implementation.
-import _pyio as pyio # Python implementation.
-
-# Simple test to ensure that optimizations in the IO library deliver the
-# expected results.  For best testing, run this under a debug-build Python too
-# (to exercise asserts in the C code).
-
-lengths = list(range(1, 257)) + [512, 1000, 1024, 2048, 4096, 8192, 10000,
-                                 16384, 32768, 65536, 1000000]
-
-class BufferSizeTest:
-    def try_one(self, s):
-        # Write s + "\n" + s to file, then open it and ensure that successive
-        # .readline()s deliver what we wrote.
-
-        # Ensure we can open TESTFN for writing.
-        os_helper.unlink(os_helper.TESTFN)
-
-        # Since C doesn't guarantee we can write/read arbitrary bytes in text
-        # files, use binary mode.
-        f = self.open(os_helper.TESTFN, "wb")
-        try:
-            # write once with \n and once without
-            f.write(s)
-            f.write(b"\n")
-            f.write(s)
-            f.close()
-            f = self.open(os_helper.TESTFN, "rb")
-            line = f.readline()
-            self.assertEqual(line, s + b"\n")
-            line = f.readline()
-            self.assertEqual(line, s)
-            line = f.readline()
-            self.assertFalse(line) # Must be at EOF
-            f.close()
-        finally:
-            os_helper.unlink(os_helper.TESTFN)
-
-    def drive_one(self, pattern):
-        for length in lengths:
-            # Repeat string 'pattern' as often as needed to reach total length
-            # 'length'.  Then call try_one with that string, a string one larger
-            # than that, and a string one smaller than that.  Try this with all
-            # small sizes and various powers of 2, so we exercise all likely
-            # stdio buffer sizes, and "off by one" errors on both sides.
-            q, r = divmod(length, len(pattern))
-            teststring = pattern * q + pattern[:r]
-            self.assertEqual(len(teststring), length)
-            self.try_one(teststring)
-            self.try_one(teststring + b"x")
-            self.try_one(teststring[:-1])
-
-    def test_primepat(self):
-        # A pattern with prime length, to avoid simple relationships with
-        # stdio buffer sizes.
-        self.drive_one(b"1234567890\00\01\02\03\04\05\06")
-
-    def test_nullpat(self):
-        self.drive_one(b'\0' * 1000)
-
-
-class CBufferSizeTest(BufferSizeTest, unittest.TestCase):
-    open = io.open
-
-class PyBufferSizeTest(BufferSizeTest, unittest.TestCase):
-    open = staticmethod(pyio.open)
-
-
-if __name__ == "__main__":
-    unittest.main()
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index 8fdee358acf..2a1a876660e 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -4,6 +4,7 @@
 import builtins
 import collections
 import contextlib
+import copy
 import decimal
 import fractions
 import gc
@@ -21,6 +22,7 @@
 import typing
 import unittest
 import warnings
+import weakref
 from contextlib import ExitStack
 from functools import partial
 from inspect import CO_COROUTINE
@@ -31,6 +33,7 @@
 from test import support
 from test.support import cpython_only, swap_attr
 from test.support import async_yield, run_yielding_async_fn
+from test.support import warnings_helper
 from test.support.import_helper import import_module
 from test.support.os_helper import (EnvironmentVarGuard, TESTFN, unlink)
 from test.support.script_helper import assert_python_ok
@@ -51,6 +54,10 @@
 
 # used as proof of globals being used
 A_GLOBAL_VALUE = 123
+A_SENTINEL = sentinel("A_SENTINEL")
+
+class SentinelContainer:
+    CLASS_SENTINEL = sentinel("SentinelContainer.CLASS_SENTINEL")
 
 class Squares:
 
@@ -245,7 +252,7 @@ def test_any(self):
         S = [10, 20, 30]
         self.assertEqual(any(x > 42 for x in S), False)
 
-    def test_all_any_tuple_optimization(self):
+    def test_all_any_tuple_list_set_optimization(self):
         def f_all():
             return all(x-2 for x in [1,2,3])
 
@@ -255,7 +262,13 @@ def f_any():
         def f_tuple():
             return tuple(2*x for x in [1,2,3])
 
-        funcs = [f_all, f_any, f_tuple]
+        def f_list():
+            return list(2*x for x in [1,2,3])
+
+        def f_set():
+            return set(2*x for x in [1,2,3])
+
+        funcs = [f_all, f_any, f_tuple, f_list, f_set]
 
         for f in funcs:
             # check that generator code object is not duplicated
@@ -265,33 +278,35 @@ def f_tuple():
 
         # check the overriding the builtins works
 
-        global all, any, tuple
-        saved = all, any, tuple
+        global all, any, tuple, list, set
+        saved = all, any, tuple, list, set
         try:
             all = lambda x : "all"
             any = lambda x : "any"
             tuple = lambda x : "tuple"
+            list = lambda x : "list"
+            set = lambda x : "set"
 
             overridden_outputs = [f() for f in funcs]
         finally:
-            all, any, tuple = saved
-
-        self.assertEqual(overridden_outputs, ['all', 'any', 'tuple'])
+            all, any, tuple, list, set = saved
 
+        self.assertEqual(overridden_outputs, ['all', 'any', 'tuple', 'list', 'set'])
         # Now repeat, overriding the builtins module as well
-        saved = all, any, tuple
+        saved = all, any, tuple, list, set
         try:
             builtins.all = all = lambda x : "all"
             builtins.any = any = lambda x : "any"
             builtins.tuple = tuple = lambda x : "tuple"
+            builtins.list = list = lambda x : "list"
+            builtins.set = set = lambda x : "set"
 
             overridden_outputs = [f() for f in funcs]
         finally:
-            all, any, tuple = saved
-            builtins.all, builtins.any, builtins.tuple = saved
-
-        self.assertEqual(overridden_outputs, ['all', 'any', 'tuple'])
+            all, any, tuple, list, set = saved
+            builtins.all, builtins.any, builtins.tuple, builtins.list, builtins.set = saved
 
+        self.assertEqual(overridden_outputs, ['all', 'any', 'tuple', 'list', 'set'])
 
     def test_builtin_call_async_genexpr_no_crash(self):
         async def f_all():
@@ -527,6 +542,10 @@ async def sleep(delay, result=None):
             '''a = [x async for x in (x async for x in arange(5))][1]''',
             '''a, = [1 for x in {x async for x in arange(1)}]''',
             '''a = [await sleep(0, x) async for x in arange(2)][1]''',
+            '''a = [await sleep(0, 1) for _ in [0]][0]''',
+            '''a = {await sleep(0, 1) for _ in [0]}.pop()''',
+            '''a = {0: await sleep(0, 1) for _ in [0]}[0]''',
+            '''a = (lambda x=[await sleep(0, 1) for _ in [0]]: x)()[0]''',
             # gh-121637: Make sure we correctly handle the case where the
             # async code is optimized away
             '''assert not await sleep(0); a = 1''',
@@ -595,7 +614,26 @@ async def __aexit__(self, *exc_info):
             '''def f():
                    async with Lock() as l:
                        a = 1
-            '''
+            ''',
+            '''class C:
+                   [await x for x in y]
+            ''',
+            '''class C:
+                   [x async for x in arange(10)]
+            ''',
+            '''async def f():
+                   class C:
+                       [await x for x in y]
+            ''',
+            '''lambda: [await x for x in y]''',
+            '''class C:
+                   def f(self, x=[await y for y in z]):
+                       pass
+            ''',
+            '''type T = [await x for x in y]''',
+            '''async def f[T=[await x for x in y]]():
+                   pass
+            ''',
         ]
         for mode, code_sample in product(modes, code_samples):
             source = dedent(code_sample)
@@ -796,6 +834,16 @@ def __getitem__(self, key):
                 raise ValueError
         self.assertRaises(ValueError, eval, "foo", {}, X())
 
+    def test_eval_frozendict(self):
+        ns = frozendict(x=1, data=[], __builtins__=__builtins__)
+        eval("data.append(x)", ns, ns)
+        self.assertEqual(ns['data'], [1])
+
+        ns = frozendict()
+        errmsg = "cannot assign __builtins__ to frozendict globals"
+        with self.assertRaisesRegex(TypeError, errmsg):
+            eval("", ns, ns)
+
     def test_eval_kwargs(self):
         data = {"A_GLOBAL_VALUE": 456}
         self.assertEqual(eval("globals()['A_GLOBAL_VALUE']", globals=data), 456)
@@ -894,6 +942,21 @@ def test_exec(self):
             del l['__builtins__']
         self.assertEqual((g, l), ({'a': 1}, {'b': 2}))
 
+    def test_exec_frozendict(self):
+        ns = frozendict(x=1, data=[], __builtins__=__builtins__)
+        exec("data.append(x)", ns, ns)
+        self.assertEqual(ns['data'], [1])
+
+        ns = frozendict(__builtins__=__builtins__)
+        errmsg = "'frozendict' object does not support item assignment"
+        with self.assertRaisesRegex(TypeError, errmsg):
+            exec("x = 1", ns, ns)
+
+        ns = frozendict()
+        errmsg = "cannot assign __builtins__ to frozendict globals"
+        with self.assertRaisesRegex(TypeError, errmsg):
+            exec("", ns, ns)
+
     def test_exec_kwargs(self):
         g = {}
         exec('global z\nz = 1', globals=g)
@@ -1108,6 +1171,30 @@ def four_freevars():
             three_freevars.__globals__,
             closure=my_closure)
 
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; SyntaxError: invalid decimal literal
+    def test_exec_filter_syntax_warnings_by_module(self):
+        filename = support.findfile('test_import/data/syntax_warnings.py')
+        with open(filename, 'rb') as f:
+            source = f.read()
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=r'<string>\z')
+            exec(source, {})
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10, 13, 14, 21])
+        for wm in wlog:
+            self.assertEqual(wm.filename, '<string>')
+            self.assertIs(wm.category, SyntaxWarning)
+
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=r'package.module\z')
+            warnings.filterwarnings('error', module=r'<string>')
+            exec(source, {'__name__': 'package.module', '__file__': filename})
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10, 13, 14, 21])
+        for wm in wlog:
+            self.assertEqual(wm.filename, '<string>')
+            self.assertIs(wm.category, SyntaxWarning)
+
 
     def test_filter(self):
         self.assertEqual(list(filter(lambda c: 'a' <= c <= 'z', 'Hello World')), list('elloorld'))
@@ -1868,6 +1955,115 @@ class C:
             __repr__ = None
         self.assertRaises(TypeError, repr, C())
 
+    def test_sentinel(self):
+        missing = sentinel("MISSING")
+        other = sentinel("MISSING")
+
+        self.assertIsInstance(missing, sentinel)
+        self.assertIs(type(missing), sentinel)
+        self.assertEqual(missing.__name__, "MISSING")
+        self.assertEqual(missing.__module__, __name__)
+        self.assertIsNot(missing, other)
+        self.assertEqual(repr(missing), "MISSING")
+        self.assertTrue(missing)
+        self.assertIs(copy.copy(missing), missing)
+        self.assertIs(copy.deepcopy(missing), missing)
+        self.assertEqual(missing, missing)
+        self.assertNotEqual(missing, other)
+        self.assertRaises(TypeError, sentinel)
+        self.assertRaises(TypeError, sentinel, "MISSING", "EXTRA")
+        self.assertRaises(TypeError, sentinel, name="MISSING")
+        with self.assertRaisesRegex(TypeError, "must be str"):
+            sentinel(1)
+        self.assertTrue(sentinel.__flags__ & support._TPFLAGS_IMMUTABLETYPE)
+        self.assertTrue(sentinel.__flags__ & support._TPFLAGS_HAVE_GC)
+        self.assertFalse(sentinel.__flags__ & support._TPFLAGS_BASETYPE)
+        with self.assertRaises(TypeError):
+            class SubSentinel(sentinel):
+                pass
+
+    def test_sentinel_attributes(self):
+        missing = sentinel("MISSING")
+        with self.assertRaises(TypeError):
+            sentinel.attribute = "value"
+        with self.assertRaises(AttributeError):
+            missing.attribute = "value"
+        with self.assertRaises(AttributeError):
+            missing.__name__ = "CHANGED"
+        missing.__module__ = "changed"
+        self.assertEqual(missing.__module__, "changed")
+        with self.assertRaises(AttributeError):
+            del missing.__name__
+        del missing.__module__
+        with self.assertRaises(AttributeError):
+            missing.__module__
+
+    def test_sentinel_repr(self):
+        with_repr = sentinel("WITH_REPR", repr="custom")
+        without_repr = sentinel("WITHOUT_REPR", repr=None)
+        self.assertEqual(repr(with_repr), "custom")
+        self.assertEqual(repr(without_repr), "WITHOUT_REPR")
+        self.assertEqual(str(with_repr), "custom")
+        self.assertEqual(str(without_repr), "WITHOUT_REPR")
+
+        with self.assertRaisesRegex(TypeError, "repr.*str or None"):
+            sentinel("BAD_REPR", repr=42)
+
+    def test_sentinel_pickle(self):
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(protocol=proto):
+                self.assertIs(
+                    pickle.loads(pickle.dumps(A_SENTINEL, protocol=proto)),
+                    A_SENTINEL)
+                self.assertIs(
+                    pickle.loads(pickle.dumps(
+                        SentinelContainer.CLASS_SENTINEL, protocol=proto)),
+                    SentinelContainer.CLASS_SENTINEL)
+
+        missing = sentinel("MISSING")
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(protocol=proto):
+                with self.assertRaises(pickle.PicklingError):
+                    pickle.dumps(missing, protocol=proto)
+
+    def test_sentinel_str_subclass_name_cycle(self):
+        class Name(str):
+            pass
+
+        name = Name("MISSING")
+        missing = sentinel(name)
+        self.assertIs(missing.__name__, name)
+        self.assertTrue(gc.is_tracked(missing))
+
+        name.missing = missing
+        ref = weakref.ref(name)
+        del name, missing
+        support.gc_collect()
+        self.assertIsNone(ref())
+
+    def test_sentinel_union(self):
+        missing = sentinel("MISSING")
+
+        self.assertIsInstance(missing | int, typing.Union)
+        self.assertEqual((missing | int).__args__, (missing, int))
+        self.assertIsInstance(int | missing, typing.Union)
+        self.assertEqual((int | missing).__args__, (int, missing))
+        self.assertIs(missing | missing, missing)
+        self.assertEqual(repr(int | missing), "int | MISSING")
+        self.assertIsInstance(missing | None, typing.Union)
+        self.assertEqual((missing | None).__args__, (missing, type(None)))
+        self.assertIsInstance(None | missing, typing.Union)
+        self.assertEqual((None | missing).__args__, (type(None), missing))
+        self.assertIsInstance(missing | list[int], typing.Union)
+        self.assertEqual((missing | list[int]).__args__, (missing, list[int]))
+        self.assertIsInstance(missing | (int | str), typing.Union)
+        self.assertEqual((missing | (int | str)).__args__, (missing, int, str))
+
+        with self.assertRaises(TypeError):
+            missing | 1
+        with self.assertRaises(TypeError):
+            1 | missing
+
     def test_round(self):
         self.assertEqual(round(0.0), 0.0)
         self.assertEqual(type(round(0.0)), int)
@@ -2594,6 +2790,7 @@ def run_child(self, child, terminal_input):
         finally:
             signal.signal(signal.SIGHUP, old_sighup)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     def _run_child(self, child, terminal_input):
         r, w = os.pipe()  # Pipe test results from child back to parent
         try:
@@ -2983,6 +3180,12 @@ def test_type_doc(self):
             A.__doc__ = doc
             self.assertEqual(A.__doc__, doc)
 
+    def test_type_frozendict(self):
+        A = type('A', (), frozendict({'x': 4, 'y': 2}))
+        self.assertEqual(A.x, 4)
+        self.assertEqual(A.y, 2)
+        self.assertEqual(A.__name__, 'A')
+
     def test_bad_args(self):
         with self.assertRaises(TypeError):
             type()
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 57dec4e04a8..ea1e2d4cb34 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -553,10 +553,10 @@ def test_hex_separator_basics(self):
         self.assertEqual(three_bytes.hex('*', -2), 'b901*ef')
         self.assertEqual(three_bytes.hex(sep=':', bytes_per_sep=2), 'b9:01ef')
         self.assertEqual(three_bytes.hex(sep='*', bytes_per_sep=-2), 'b901*ef')
-        for bytes_per_sep in 3, -3, 2**31-1, -(2**31-1):
+        for bytes_per_sep in 3, -3, sys.maxsize, -sys.maxsize:
             with self.subTest(bytes_per_sep=bytes_per_sep):
                 self.assertEqual(three_bytes.hex(':', bytes_per_sep), 'b901ef')
-        for bytes_per_sep in 2**31, -2**31, 2**1000, -2**1000:
+        for bytes_per_sep in sys.maxsize+1, -sys.maxsize-1, 2**1000, -2**1000:
             with self.subTest(bytes_per_sep=bytes_per_sep):
                 try:
                     self.assertEqual(three_bytes.hex(':', bytes_per_sep), 'b901ef')
@@ -586,6 +586,37 @@ def test_hex_separator_six_bytes(self):
         self.assertEqual(six_bytes.hex(':', -6), '0306090c0f12')
         self.assertEqual(six_bytes.hex(' ', -95), '0306090c0f12')
 
+    def test_hex_simd_boundaries(self):
+        # Test lengths around the SIMD threshold (16 bytes).
+        # SIMD processes 16 bytes at a time; smaller inputs use scalar code.
+        for length in (14, 15, 16, 17, 31, 32, 33, 64, 65):
+            data = self.type2test(bytes(range(length)))
+            expected = ''.join(f'{b:02x}' for b in range(length))
+            with self.subTest(length=length):
+                self.assertEqual(data.hex(), expected)
+
+    def test_hex_nibble_boundaries(self):
+        # Test the nibble value boundary at 9/10 (where '9' becomes 'a').
+        # SIMD uses signed comparison for efficiency; verify correctness
+        # at this boundary for various nibble combinations.
+        boundary_bytes = self.type2test(bytes([
+            0x09,  # both nibbles: 0, 9
+            0x0a,  # both nibbles: 0, 10
+            0x90,  # both nibbles: 9, 0
+            0x99,  # both nibbles: 9, 9 (max all-digit)
+            0x9a,  # both nibbles: 9, 10
+            0xa0,  # both nibbles: 10, 0
+            0xa9,  # both nibbles: 10, 9
+            0xaa,  # both nibbles: 10, 10 (min all-letter)
+            0x00,  # min value
+            0xff,  # max value
+        ]))
+        self.assertEqual(boundary_bytes.hex(), '090a90999aa0a9aa00ff')
+
+        # Repeat with 16+ bytes to exercise SIMD path
+        simd_boundary = self.type2test(boundary_bytes * 2)
+        self.assertEqual(simd_boundary.hex(), '090a90999aa0a9aa00ff' * 2)
+
     def test_join(self):
         self.assertEqual(self.type2test(b"").join([]), b"")
         self.assertEqual(self.type2test(b"").join([b""]), b"")
@@ -616,6 +647,32 @@ def test_join(self):
         with self.assertRaises(TypeError):
             dot_join([memoryview(b"ab"), "cd", b"ef"])
 
+    def test_join_concurrent_buffer_mutation(self):
+        # __buffer__() can release the GIL, letting another thread concurrently
+        # mutate the joined sequence (simulated here by mutating in __buffer__).
+        # See: https://github.com/python/cpython/issues/151295
+        def make_seq(mutate):
+            # Item is only referenced from the list slot, so mutate() frees it.
+            class Item:
+                def __buffer__(self, flags):
+                    mutate(seq)
+                    return memoryview(b'x')
+            seq = [b'a', Item(), b'c']
+            return seq
+
+        for sep in (self.type2test(b''), self.type2test(b'::')):
+            with self.subTest(sep=sep):
+                # Changing the list length is reported as a RuntimeError.
+                seq = make_seq(lambda seq: seq.clear())
+                self.assertRaises(RuntimeError, sep.join, seq)
+
+                # The list length is unchanged, so the size-change recheck
+                # cannot fire: only keeping the item alive avoids the crash.
+                def replace(seq):
+                    seq[1] = b'z'
+                seq = make_seq(replace)
+                self.assertEqual(sep.join(seq), sep.join([b'a', b'x', b'c']))
+
     def test_count(self):
         b = self.type2test(b'mississippi')
         i = 105
@@ -794,16 +851,16 @@ def __int__(self):
         pi = PseudoFloat(3.1415)
 
         exceptions_params = [
-            ('%x format: an integer is required, not float', b'%x', 3.14),
-            ('%X format: an integer is required, not float', b'%X', 2.11),
-            ('%o format: an integer is required, not float', b'%o', 1.79),
-            ('%x format: an integer is required, not PseudoFloat', b'%x', pi),
-            ('%x format: an integer is required, not complex', b'%x', 3j),
-            ('%X format: an integer is required, not complex', b'%X', 2j),
-            ('%o format: an integer is required, not complex', b'%o', 1j),
-            ('%u format: a real number is required, not complex', b'%u', 3j),
-            ('%i format: a real number is required, not complex', b'%i', 2j),
-            ('%d format: a real number is required, not complex', b'%d', 2j),
+            ('%x requires an integer, not float', b'%x', 3.14),
+            ('%X requires an integer, not float', b'%X', 2.11),
+            ('%o requires an integer, not float', b'%o', 1.79),
+            (r'%x requires an integer, not .*\.PseudoFloat', b'%x', pi),
+            ('%x requires an integer, not complex', b'%x', 3j),
+            ('%X requires an integer, not complex', b'%X', 2j),
+            ('%o requires an integer, not complex', b'%o', 1j),
+            ('%u requires a real number, not complex', b'%u', 3j),
+            ('%i requires a real number, not complex', b'%i', 2j),
+            ('%d requires a real number, not complex', b'%d', 2j),
             (
                 r'%c requires an integer in range\(256\)'
                 r' or a single byte, not .*\.PseudoFloat',
@@ -812,7 +869,7 @@ def __int__(self):
         ]
 
         for msg, format_bytes, value in exceptions_params:
-            with self.assertRaisesRegex(TypeError, msg):
+            with self.assertRaisesRegex(TypeError, 'format argument: ' + msg):
                 operator.mod(format_bytes, value)
 
     def test_memory_leak_gh_140939(self):
@@ -849,6 +906,13 @@ def test_replace(self):
         self.assertEqual(b.replace(b'i', b'a'), b'massassappa')
         self.assertEqual(b.replace(b'ss', b'x'), b'mixixippi')
 
+    def test_replace_count_keyword(self):
+        b = self.type2test(b'aa')
+        self.assertEqual(b.replace(b'a', b'b', count=0), b'aa')
+        self.assertEqual(b.replace(b'a', b'b', count=1), b'ba')
+        self.assertEqual(b.replace(b'a', b'b', count=2), b'bb')
+        self.assertEqual(b.replace(b'a', b'b', count=3), b'bb')
+
     def test_replace_int_error(self):
         self.assertRaises(TypeError, self.type2test(b'a b').replace, 32, b'')
 
@@ -1337,10 +1401,6 @@ class SubBytes(bytes):
         self.assertNotEqual(id(s), id(1 * s))
         self.assertNotEqual(id(s), id(s * 2))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
-    def test_mod(self):
-        return super().test_mod()
-
 
 class ByteArrayTest(BaseBytesTest, unittest.TestCase):
     type2test = bytearray
@@ -1393,7 +1453,6 @@ def test_bytearray_api(self):
             except OSError:
                 pass
 
-    @unittest.skip("TODO: RUSTPYTHON; segfault")
     def test_mod_concurrent_mutation(self):
         # Prevent crash in __mod__ when formatting mutates the bytearray.
         # Regression test for https://github.com/python/cpython/issues/142557.
@@ -1432,6 +1491,16 @@ def test_clear(self):
         b.append(ord('p'))
         self.assertEqual(b, b'p')
 
+        # Cleared object should be empty.
+        b = bytearray(b'abc')
+        b.clear()
+        self.assertEqual(b.__alloc__(), 0)
+        base_size = sys.getsizeof(bytearray())
+        self.assertEqual(sys.getsizeof(b), base_size)
+        c = b.copy()
+        self.assertEqual(c.__alloc__(), 0)
+        self.assertEqual(sys.getsizeof(c), base_size)
+
     def test_copy(self):
         b = bytearray(b'abc')
         bb = b.copy()
@@ -1494,6 +1563,124 @@ def test_resize(self):
         self.assertRaises(MemoryError, bytearray().resize, sys.maxsize)
         self.assertRaises(MemoryError, bytearray(1000).resize, sys.maxsize)
 
+    def test_take_bytes(self):
+        ba = bytearray(b'ab')
+        self.assertEqual(ba.take_bytes(), b'ab')
+        self.assertEqual(len(ba), 0)
+        self.assertEqual(ba, bytearray(b''))
+        self.assertEqual(ba.__alloc__(), 0)
+        base_size = sys.getsizeof(bytearray())
+        self.assertEqual(sys.getsizeof(ba), base_size)
+
+        # Positive and negative slicing.
+        ba = bytearray(b'abcdef')
+        self.assertEqual(ba.take_bytes(1), b'a')
+        self.assertEqual(ba, bytearray(b'bcdef'))
+        self.assertEqual(len(ba), 5)
+        self.assertEqual(ba.take_bytes(-5), b'')
+        self.assertEqual(ba, bytearray(b'bcdef'))
+        self.assertEqual(len(ba), 5)
+        self.assertEqual(ba.take_bytes(-3), b'bc')
+        self.assertEqual(ba, bytearray(b'def'))
+        self.assertEqual(len(ba), 3)
+        self.assertEqual(ba.take_bytes(3), b'def')
+        self.assertEqual(ba, bytearray(b''))
+        self.assertEqual(len(ba), 0)
+
+        # Take nothing from emptiness.
+        self.assertEqual(ba.take_bytes(0), b'')
+        self.assertEqual(ba.take_bytes(), b'')
+        self.assertEqual(ba.take_bytes(None), b'')
+
+        # Out of bounds, bad take value.
+        self.assertRaises(IndexError, ba.take_bytes, -1)
+        self.assertRaises(TypeError, ba.take_bytes, 3.14)
+        ba = bytearray(b'abcdef')
+        self.assertRaises(IndexError, ba.take_bytes, 7)
+
+        # Offset between physical and logical start (ob_bytes != ob_start).
+        ba = bytearray(b'abcde')
+        del ba[:2]
+        self.assertEqual(ba, bytearray(b'cde'))
+        self.assertEqual(ba.take_bytes(), b'cde')
+
+        # Overallocation at end.
+        ba = bytearray(b'abcde')
+        del ba[-2:]
+        self.assertEqual(ba, bytearray(b'abc'))
+        self.assertEqual(ba.take_bytes(), b'abc')
+        ba = bytearray(b'abcde')
+        ba.resize(4)
+        self.assertEqual(ba.take_bytes(), b'abcd')
+
+        # Take of a bytearray with references should fail.
+        ba = bytearray(b'abc')
+        with memoryview(ba) as mv:
+            self.assertRaises(BufferError, ba.take_bytes)
+        self.assertEqual(ba.take_bytes(), b'abc')
+
+        # Leaving one byte must not adopt the shared single-byte bytes object
+        # as the buffer.
+        ba = bytearray(b'abc')
+        self.assertEqual(ba.take_bytes(2), b'ab')
+        ba[0] = ord('A')
+        self.assertEqual(ba, bytearray(b'A'))
+        self.assertEqual(ord(b'c'), ord('c'))
+
+    @support.cpython_only  # tests an implementation detail
+    def test_take_bytes_optimization(self):
+        # Validate optimization around taking lots of little chunks out of a
+        # much bigger buffer. Save work by only copying a little rather than
+        # moving a lot.
+        ba = bytearray(b'abcdef' + b'0' * 1000)
+        start_alloc = ba.__alloc__()
+
+        # Take two bytes at a time, checking alloc doesn't change.
+        self.assertEqual(ba.take_bytes(2), b'ab')
+        self.assertEqual(ba.__alloc__(), start_alloc)
+        self.assertEqual(len(ba), 4 + 1000)
+        self.assertEqual(ba.take_bytes(2), b'cd')
+        self.assertEqual(ba.__alloc__(), start_alloc)
+        self.assertEqual(len(ba), 2 + 1000)
+        self.assertEqual(ba.take_bytes(2), b'ef')
+        self.assertEqual(ba.__alloc__(), start_alloc)
+        self.assertEqual(len(ba), 0 + 1000)
+        self.assertEqual(ba.__alloc__(), start_alloc)
+
+        # Take over half, alloc shrinks to exact size.
+        self.assertEqual(ba.take_bytes(501), b'0' * 501)
+        self.assertEqual(len(ba), 499)
+        bytes_header_size = sys.getsizeof(b'')
+        self.assertEqual(ba.__alloc__(), 499 + bytes_header_size)
+
+    def test_take_bytes_reentrant_resize(self):
+        # gh-153570: n.__index__() can resize the bytearray, so take_bytes()
+        # must re-read the size afterwards.  It cached the size before the
+        # call and used it for the bounds check and the buffer reads, so a
+        # reentrant clear() returned freed memory (a use-after-free read).
+        def take(target, resize, n):
+            class Evil:
+                def __index__(self):
+                    resize(target)
+                    return n
+            return target.take_bytes(Evil())
+
+        # clear() during __index__: nothing is left to take.
+        ba = bytearray(b'abcdefgh')
+        with self.assertRaises(IndexError):
+            take(ba, lambda b: b.clear(), 8)
+        self.assertEqual(ba, b'')
+
+        # shrink during __index__: n past the new size is out of range.
+        ba = bytearray(b'abcdefgh')
+        with self.assertRaises(IndexError):
+            take(ba, lambda b: b.__delitem__(slice(4, None)), 8)
+        self.assertEqual(ba, b'abcd')
+
+        # grow during __index__: the take runs against the new, larger size.
+        ba = bytearray(b'abcd')
+        self.assertEqual(take(ba, lambda b: b.extend(b'efgh'), 8), b'abcdefgh')
+        self.assertEqual(ba, b'')
 
     @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_setitem(self):
@@ -2013,7 +2200,6 @@ def __index__(self):
             self.assertEqual(instance.ba[0], ord("?"), "Assigned bytearray not altered")
             self.assertEqual(instance.new_ba, bytearray(0x180), "Wrong object altered")
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; TypeError: unexpected type Evil
     def test_search_methods_reentrancy_raises_buffererror(self):
         # gh-142560: Raise BufferError if buffer mutates during search arg conversion.
         class Evil:
@@ -2063,7 +2249,6 @@ def __length_hint__(self):
 
         self.assertRaises(ValueError, float, bytearray())
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: BufferError not raised by hex
     def test_hex_use_after_free(self):
         # Prevent UAF in bytearray.hex(sep) with re-entrant sep.__len__.
         # Regression test for https://github.com/python/cpython/issues/143195.
@@ -2076,9 +2261,45 @@ def __len__(self):
 
         self.assertRaises(BufferError, ba.hex, S(b':'))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
-    def test_mod(self):
-        return super().test_mod()
+    def test_no_init_called(self):
+        # A bytearray created without calling bytearray.__init__
+        # should not crash the interpreter (see gh-153419).
+        def bytearray_new():
+            return bytearray.__new__(bytearray)
+
+        bytearray_new().insert(0, 1)
+        bytearray_new().extend(b"x")
+        bytearray_new().extend([1, 2, 3])
+        bytearray_new().resize(4)
+        bytearray_new().__init__(5)
+        bytearray_new().__init__(b"xyz")
+        bytearray_new().take_bytes()
+        bytearray_new().take_bytes(0)
+
+        a = bytearray_new()
+        a.append(1)
+
+        a = bytearray_new()
+        a += b"x"
+
+        a = bytearray_new()
+        a[:] = b"xyz"
+
+    def test_reinit_length(self):
+        # There is a shortcut taken when resizing, where alloc/2 < newsize.
+        # In this case, the existing buffer is reused, rather than reset.
+        # If this happens when newsize == 0 and alloc == 1, then various
+        # code assumptions can be violated.  This test should catch those
+        # in debug builds. (see gh-153419)
+        a = bytearray(1)
+        a.__init__()
+        self.assertEqual(a, b"")
+
+    def test_reinit_with_view(self):
+        a = bytearray()
+        with memoryview(a):
+            self.assertRaises(BufferError, a.__init__, "x", "ascii")
+        self.assertEqual(a, b"")
 
 
 class AssortedBytesTest(unittest.TestCase):
@@ -2108,7 +2329,7 @@ def test_bytearray_repr(self, f=repr):
         self.assertEqual(f(bytearray([7, 8, 9, 10, 11, 12, 13])),
                             r"bytearray(b'\x07\x08\t\n\x0b\x0c\r')")
         self.assertEqual(f(bytearray(b'"')), """bytearray(b'"')""") # '"'
-        self.assertEqual(f(bytearray(b"'")), r'''bytearray(b"\'")''') # "\'"
+        self.assertEqual(f(bytearray(b"'")), '''bytearray(b"'")''') # "'"
         self.assertEqual(f(bytearray(b"'\"")), r"""bytearray(b'\'"')""") # '\'"'
         self.assertEqual(f(bytearray(b"\"'\"")), r"""bytearray(b'"\'"')""") # '"\'"'
         self.assertEqual(f(bytearray(b'\'"\'')), r"""bytearray(b'\'"\'')""") # '\'"\''
@@ -2701,6 +2922,18 @@ def resize(b, a):  # MODIFIES!
             b.wait()
             a.resize(10)
 
+        def take_bytes(b, a):  # MODIFIES!
+            b.wait()
+            c = a.take_bytes()
+            assert not c or c[0] == 48  # '0'
+
+        def take_bytes_n(b, a):  # MODIFIES!
+            b.wait()
+            try:
+                c = a.take_bytes(10)
+                assert c == b'0123456789'
+            except IndexError: pass
+
         def check(funcs, a=None, *args):
             if a is None:
                 a = bytearray(b'0' * 0x400000)
@@ -2765,6 +2998,10 @@ def check(funcs, a=None, *args):
 
         check([clear] + [resize] * 10)
 
+        check([clear] + [take_bytes] * 10)
+        check([take_bytes_n] * 10, bytearray(b'0123456789' * 0x400))
+        check([take_bytes_n] * 10, bytearray(b'0123456789' * 5))
+
         check([clear] + [contains] * 10)
         check([clear] + [subscript] * 10)
         check([clear2] + [ass_subscript2] * 10, None, bytearray(b'0' * 0x400000))
@@ -2837,5 +3074,18 @@ def resize_stress(ba):
         with threading_helper.start_threads(threads):
             pass
 
+    @threading_helper.reap_threads
+    @threading_helper.requires_working_threading()
+    def test_free_threading_bytearray_resize_other_thread(self):
+        # Shrinking a bytearray whose buffer another thread owns must not
+        # adopt the immortal single-byte bytes object a the buffer.
+        ba = bytearray(b'abc')
+        thread = threading.Thread(target=ba.resize, args=(1,))
+        with threading_helper.start_threads([thread]):
+            pass
+        ba[0] = ord('X')
+        self.assertEqual(ba, bytearray(b'X'))
+        self.assertEqual(ord(b'a'), ord('a'))
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
index d6fcfa3b471..b9d1b9493a7 100644
--- a/Lib/test/test_cmd_line.py
+++ b/Lib/test/test_cmd_line.py
@@ -2,6 +2,7 @@
 # Most tests are executed with environment variables ignored
 # See test_cmd_line_script.py for testing of script execution
 
+import locale
 import os
 import re
 import subprocess
@@ -32,6 +33,17 @@ def _kill_python_and_exit_code(p):
     return data, returncode
 
 
+def presite_func():
+    print("presite func")
+
+class Namespace:
+    pass
+
+presite = Namespace()
+presite.attr = Namespace()
+presite.attr.func = presite_func
+
+
 class CmdLineTest(unittest.TestCase):
     def test_directories(self):
         assert_python_failure('.')
@@ -46,6 +58,7 @@ def verify_valid_flag(self, cmd_line):
         return out
 
     @support.cpython_only
+    @support.force_not_colorized
     def test_help(self):
         self.verify_valid_flag('-h')
         self.verify_valid_flag('-?')
@@ -57,6 +70,7 @@ def test_help(self):
         self.assertLess(len(lines), 50)
 
     @support.cpython_only
+    @support.force_not_colorized
     def test_help_env(self):
         out = self.verify_valid_flag('--help-env')
         self.assertIn(b'PYTHONHOME', out)
@@ -70,6 +84,7 @@ def test_help_env(self):
                              "env vars should be sorted alphabetically")
 
     @support.cpython_only
+    @support.force_not_colorized
     def test_help_xoptions(self):
         out = self.verify_valid_flag('--help-xoptions')
         self.assertIn(b'-X dev', out)
@@ -78,6 +93,7 @@ def test_help_xoptions(self):
                          "options should be sorted alphabetically")
 
     @support.cpython_only
+    @support.force_not_colorized
     def test_help_all(self):
         out = self.verify_valid_flag('--help-all')
         lines = out.splitlines()
@@ -89,6 +105,25 @@ def test_help_all(self):
         # but the rest should be ASCII-only
         b''.join(lines[1:]).decode('ascii')
 
+    @support.cpython_only
+    @support.force_colorized
+    def test_help_colorized(self):
+        rc, out, err = assert_python_ok("--help", FORCE_COLOR="1")
+        # Check ANSI color codes are present
+        self.assertIn(b"\x1b[", out)
+        # Check that key text elements are still present
+        self.assertIn(b"usage:", out)
+        self.assertIn(b"-h", out)
+        self.assertIn(b"--help-all", out)
+        self.assertIn(b"cmd", out)
+        self.assertIn(b"Arguments:", out)
+
+    @support.cpython_only
+    @support.force_not_colorized
+    def test_help_not_colorized(self):
+        rc, out, err = assert_python_ok("--help")
+        self.assertNotIn(b"\x1b[", out)
+
     def test_optimize(self):
         self.verify_valid_flag('-O')
         self.verify_valid_flag('-OO')
@@ -322,6 +357,10 @@ def run_utf8_mode(arg):
             cmd = [sys.executable, '-X', 'utf8', '-c', code, arg]
             return subprocess.run(cmd, stdout=subprocess.PIPE, text=True)
 
+        def run_no_utf8_mode(arg):
+            cmd = [sys.executable, '-X', 'utf8=0', '-c', code, arg]
+            return subprocess.run(cmd, stdout=subprocess.PIPE, text=True)
+
         valid_utf8 = 'e:\xe9, euro:\u20ac, non-bmp:\U0010ffff'.encode('utf-8')
         # invalid UTF-8 byte sequences with a valid UTF-8 sequence
         # in the middle.
@@ -334,8 +373,27 @@ def run_utf8_mode(arg):
         )
         test_args = [valid_utf8, invalid_utf8]
 
-        for run_cmd in (run_default, run_c_locale, run_utf8_mode):
-            with self.subTest(run_cmd=run_cmd):
+        for run_cmd, encoding in (
+            (run_default, sys.getfilesystemencoding()),
+            (run_c_locale, None),
+            (run_utf8_mode, None),
+            (run_no_utf8_mode, locale.getencoding())
+        ):
+            with self.subTest(run_cmd=run_cmd.__name__):
+                # Arbitrary bytes round-trip through surrogateescape only in
+                # UTF-8 and single-byte encodings, not in a multibyte encoding
+                # such as EUC-JP.
+                if encoding is not None:
+                    try:
+                        lossless = len(bytes(range(256)).decode(
+                            encoding, 'surrogateescape')) == 256
+                    except UnicodeError:
+                        lossless = False
+                else:
+                    lossless = True
+                if not lossless:
+                    self.skipTest(f'{encoding} cannot losslessly '
+                                  f'round-trip arbitrary bytes')
                 for arg in test_args:
                     proc = run_cmd(arg)
                     self.assertEqual(proc.stdout.rstrip(), ascii(arg))
@@ -433,7 +491,6 @@ def test_empty_PYTHONPATH_issue16309(self):
             path = ":".join(sys.path)
             path = path.encode("ascii", "backslashreplace")
             sys.stdout.buffer.write(path)"""
-        # TODO: RUSTPYTHON we must unset RUSTPYTHONPATH as well
         rc1, out1, err1 = assert_python_ok('-c', code, PYTHONPATH="", RUSTPYTHONPATH="")
         rc2, out2, err2 = assert_python_ok('-c', code, __isolated=False)
         # regarding to Posix specification, outputs should be equal
@@ -509,6 +566,7 @@ def test_unmached_quote(self):
         self.assertEqual(b'', out)
 
     @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @force_not_colorized
     def test_stdout_flush_at_shutdown(self):
         # Issue #5319: if stdout.flush() fails at shutdown, an error should
         # be printed out.
@@ -1066,6 +1124,7 @@ def test_argv0_normalization(self):
         self.assertEqual(proc.stdout.strip(), b'0')
 
     @support.cpython_only
+    @support.force_not_colorized
     def test_parsing_error(self):
         args = [sys.executable, '-I', '--unknown-option']
         proc = subprocess.run(args,
@@ -1207,7 +1266,6 @@ def test_cpu_count_default(self):
         res = assert_python_ok('-c', code, PYTHON_CPU_COUNT='default')
         self.assertEqual(self.res2int(res), (os.cpu_count(), os.process_cpu_count()))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_import_time(self):
         # os is not imported at startup
         code = 'import os; import os'
@@ -1226,6 +1284,25 @@ def test_import_time(self):
         assert_python_failure('-X', 'importtime=-1', '-c', code)
         assert_python_failure('-X', 'importtime=3', '-c', code)
 
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; -X importtime=2 timing output and surrogate module import exception semantics are not implemented correctly
+    def test_import_time_unencodable_module_name(self):
+        code = textwrap.dedent("""
+            import sys, types
+            name = 'mod\\ud800'
+            sys.modules[name] = types.ModuleType(name)
+            __import__(name)
+            try:
+                __import__('nonexistent\\ud800')
+            except ModuleNotFoundError:
+                pass
+        """)
+        res = assert_python_ok('-X', 'importtime=2', '-c', code)
+        res_err = res.err.decode('utf-8')
+        self.assertRegex(res_err,
+                         r'import time: cached\s* \| cached\s* \| mod\\ud800')
+        self.assertRegex(res_err,
+                         r'import time: \s*\d+ \| \s*\d+ \| \s*nonexistent\\ud800')
+
     def res2int(self, res):
         out = res.out.strip().decode("utf-8")
         return tuple(int(i) for i in out.split())
@@ -1282,6 +1359,29 @@ def test_invalid_thread_local_bytecode(self):
         rc, out, err = assert_python_failure(PYTHON_TLBC="2")
         self.assertIn(b"PYTHON_TLBC=N: N is missing or invalid", err)
 
+    @unittest.skipUnless(support.Py_DEBUG,
+                         '-X presite requires a Python debug build')
+    def test_presite(self):
+        entrypoint = "test.test_cmd_line:presite_func"
+        proc = assert_python_ok("-X", f"presite={entrypoint}", "-c", "pass")
+        self.assertEqual(proc.out.rstrip(), b"presite func")
+
+        entrypoint = "test.test_cmd_line:presite.attr.func"
+        proc = assert_python_ok("-X", f"presite={entrypoint}", "-c", "pass")
+        self.assertEqual(proc.out.rstrip(), b"presite func")
+
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; explicit PYTHONHOME startup path configuration and fatal encodings failure reporting are not implemented
+    def test_dump_path_config(self):
+        # gh-151253: At the first import (import encodings) during Python
+        # startup, if the import fails, dump the Python path configuration.
+        nonexistent = '/nonexistent-python-path'
+        # Use -X frozen_modules=off to disable frozen encodings module
+        # on release build.
+        cmd = ["-X", "frozen_modules=off", "-c", "pass"]
+        proc = assert_python_failure(*cmd, PYTHONHOME=nonexistent)
+        self.assertIn(b'Python path configuration:', proc.err)
+        self.assertIn(f"PYTHONHOME = '{nonexistent}'".encode(), proc.err)
+
 
 @unittest.skipIf(interpreter_requires_environment(),
                  'Cannot run -I tests when PYTHON env vars are required.')
@@ -1330,11 +1430,9 @@ def check_string(self, code):
         self.assertNotEqual(proc.stderr, None)
         self.assertIn(b"\nSyntaxError", proc.stderr)
 
-    @unittest.expectedFailureIf(not support.is_android, "TODO: RUSTPYTHON")
     def test_tokenizer_error_with_stdin(self):
         self.check_string(b"(1+2+3")
 
-    @unittest.expectedFailureIf(not support.is_android, "TODO: RUSTPYTHON")
     def test_decoding_error_at_the_end_of_the_line(self):
         self.check_string(br"'\u1f'")
 
diff --git a/Lib/test/test_cmd_line_script.py b/Lib/test/test_cmd_line_script.py
index 8dd64afcc00..a2ea0535389 100644
--- a/Lib/test/test_cmd_line_script.py
+++ b/Lib/test/test_cmd_line_script.py
@@ -44,7 +44,6 @@ def f():
 _loader = __loader__ if __loader__ is BuiltinImporter else type(__loader__)
 print('__loader__==%a' % _loader)
 print('__file__==%a' % __file__)
-print('__cached__==%a' % __cached__)
 print('__package__==%r' % __package__)
 # Check PEP 451 details
 import os.path
@@ -58,8 +57,6 @@ def f():
     assertEqual(__spec__.parent, __package__)
     assertIdentical(__spec__.submodule_search_locations, None)
     assertEqual(__spec__.origin, __file__)
-    if __spec__.cached is not None:
-        assertEqual(__spec__.cached, __cached__)
 # Check the sys module
 import sys
 assertIdentical(globals(), sys.modules[__name__].__dict__)
diff --git a/Lib/test/test_code.py b/Lib/test/test_code.py
index 6c26259cf15..0af191cb5df 100644
--- a/Lib/test/test_code.py
+++ b/Lib/test/test_code.py
@@ -87,7 +87,7 @@
 freevars: ()
 nlocals: 0
 flags: 67108867
-consts: ("'doc string'", 'None')
+consts: ("'doc string'",)
 
 >>> def keywordonly_args(a,b,*,k1):
 ...     return a,b,k1
@@ -161,7 +161,7 @@
 freevars: ()
 nlocals: 3
 flags: 67108995
-consts: ("'This is a docstring from async function'", 'None')
+consts: ("'This is a docstring from async function'",)
 
 >>> def no_docstring(x, y, z):
 ...     return x + "hello" + y + z + "world"
@@ -423,14 +423,6 @@ def func():
         new_code = code = func.__code__.replace(co_linetable=b'')
         self.assertEqual(list(new_code.co_lines()), [])
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; co_lnotab intentionally not implemented (deprecated since 3.12)
-    def test_co_lnotab_is_deprecated(self):  # TODO: remove in 3.14
-        def func():
-            pass
-
-        with self.assertWarns(DeprecationWarning):
-            func.__code__.co_lnotab
-
     @unittest.skipIf(_testinternalcapi is None, '_testinternalcapi is missing')
     def test_returns_only_none(self):
         value = True
@@ -540,7 +532,7 @@ def test_co_positions_artificial_instructions(self):
             ],
             [
                 ("PUSH_EXC_INFO", None),
-                ("LOAD_CONST", None), # artificial 'None'
+                ("LOAD_COMMON_CONSTANT", None), # artificial 'None'
                 ("STORE_NAME", "e"),  # XX: we know the location for this
                 ("DELETE_NAME", "e"),
                 ("RERAISE", 1),
@@ -1165,6 +1157,18 @@ def test_stateless(self):
                     with self.assertRaises(Exception):
                         _testinternalcapi.verify_stateless_code(func)
 
+    def test_code_richcompare_raise_exception(self):
+        class BadStr(str):
+            def __eq__(self, _):
+                raise RuntimeError("Poison!")
+
+            __hash__ = str.__hash__
+
+        c1 = compile("pass", "test", "exec")
+        c2 = c1.replace(co_name=BadStr("poison"))
+        c3 = compile("pass", "poison", "exec")
+        with self.assertRaises(RuntimeError):
+            c2 == c3
 
 def isinterned(s):
     return s is sys.intern(('_' + s + '_')[1:-1])
@@ -1438,6 +1442,7 @@ def f():
             co_code=bytes(
                 [
                     dis.opmap["RESUME"], 0,
+                    dis.opmap["CACHE"], 0,
                     dis.opmap["LOAD_COMMON_CONSTANT"], 0,
                     dis.opmap["RAISE_VARARGS"], 1,
                 ]
@@ -1446,7 +1451,7 @@ def f():
                 [
                     (1 << 7)
                     | (PY_CODE_LOCATION_INFO_NO_COLUMNS << 3)
-                    | (3 - 1),
+                    | (4 - 1),
                     0,
                 ]
             ),
@@ -1454,7 +1459,7 @@ def f():
         self.assertRaises(AssertionError, f)
         self.assertEqual(
             list(f.__code__.co_positions()),
-            3 * [(42, 42, None, None)],
+            4 * [(42, 42, None, None)],
         )
 
     @cpython_only
diff --git a/Lib/test/test_code_module.py b/Lib/test/test_code_module.py
index fb519878cd8..3642b47c2c1 100644
--- a/Lib/test/test_code_module.py
+++ b/Lib/test/test_code_module.py
@@ -111,7 +111,6 @@ def test_syntax_error(self):
         self.assertIsNone(self.sysmod.last_value.__traceback__)
         self.assertIs(self.sysmod.last_exc, self.sysmod.last_value)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; -  'IndentationError: unexpected indentation']
     def test_indentation_error(self):
         self.infunc.side_effect = ["  1", EOFError('Finished')]
         self.console.interact()
@@ -187,7 +186,6 @@ def test_sysexcepthook_syntax_error(self):
             '        ^\n',
             'SyntaxError: invalid syntax\n'])
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; +  'IndentationError: unexpected indent\n']
     def test_sysexcepthook_indentation_error(self):
         self.infunc.side_effect = ["  1", EOFError('Finished')]
         hook = mock.Mock()
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index fd21c7b05b0..3189fe7f6c6 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -13,6 +13,7 @@
 
 from test import support
 from test.support import os_helper
+from test.support import warnings_helper
 
 try:
     import _testlimitedcapi
@@ -1622,6 +1623,15 @@ def test_builtin_encode(self):
         self.assertEqual("pyth\xf6n.org".encode("idna"), b"xn--pythn-mua.org")
         self.assertEqual("pyth\xf6n.org.".encode("idna"), b"xn--pythn-mua.org.")
 
+    @support.subTests(['unicode', 'encoded'], [
+        ('\N{CHEROKEE LETTER A}\N{CHEROKEE LETTER A}', b"xn--58da"),
+        ('\N{GEORGIAN CAPITAL LETTER AN}.', b"xn--7md."),
+        ('\N{CYRILLIC LETTER PALOCHKA}.example', b"xn--d5a.example"),
+        ('\N{ROMAN NUMERAL REVERSED ONE HUNDRED}.example.', b"xn--q5g.example."),
+    ])
+    def test_new_unicode_case_folding(self, unicode, encoded):
+        self.assertEqual(unicode.encode("idna"), encoded)
+
     def test_builtin_encode_invalid(self):
         for case, expected in self.invalid_encode_testcases:
             with self.subTest(case=case, expected=expected):
@@ -2768,7 +2778,6 @@ def test_partial(self):
             ]
         )
 
-
 class RawUnicodeEscapeTest(ReadTest, unittest.TestCase):
     encoding = "raw-unicode-escape"
 
@@ -3875,32 +3884,27 @@ def test_rot13_func(self):
 class CodecNameNormalizationTest(unittest.TestCase):
     """Test codec name normalization"""
     def test_codecs_lookup(self):
-        FOUND = (1, 2, 3, 4)
-        NOT_FOUND = (None, None, None, None)
         def search_function(encoding):
-            if encoding == "aaa_8":
-                return FOUND
+            if encoding.startswith("test."):
+                return (encoding, 2, 3, 4)
             else:
-                return NOT_FOUND
+                return None
 
         codecs.register(search_function)
         self.addCleanup(codecs.unregister, search_function)
-        self.assertEqual(FOUND, codecs.lookup('aaa_8'))
-        self.assertEqual(FOUND, codecs.lookup('AAA-8'))
-        self.assertEqual(FOUND, codecs.lookup('AAA---8'))
-        self.assertEqual(FOUND, codecs.lookup('AAA   8'))
-        self.assertEqual(FOUND, codecs.lookup('aaa\xe9\u20ac-8'))
-        self.assertEqual(NOT_FOUND, codecs.lookup('AAA.8'))
-        self.assertEqual(NOT_FOUND, codecs.lookup('AAA...8'))
-        self.assertEqual(NOT_FOUND, codecs.lookup('BBB-8'))
-        self.assertEqual(NOT_FOUND, codecs.lookup('BBB.8'))
-        self.assertEqual(NOT_FOUND, codecs.lookup('a\xe9\u20ac-8'))
+        self.assertEqual(codecs.lookup('test.aaa_8'), ('test.aaa_8', 2, 3, 4))
+        self.assertEqual(codecs.lookup('TEST.AAA-8'), ('test.aaa-8', 2, 3, 4))
+        self.assertEqual(codecs.lookup('TEST.AAA 8'), ('test.aaa-8', 2, 3, 4))
+        self.assertEqual(codecs.lookup('TEST.AAA---8'), ('test.aaa---8', 2, 3, 4))
+        self.assertEqual(codecs.lookup('TEST.AAA   8'), ('test.aaa---8', 2, 3, 4))
+        self.assertEqual(codecs.lookup('TEST.AAA.8'), ('test.aaa.8', 2, 3, 4))
+        self.assertEqual(codecs.lookup('TEST.AAA...8'), ('test.aaa...8', 2, 3, 4))
+        with self.assertWarns(DeprecationWarning):
+            self.assertEqual(codecs.lookup('TEST.AAA\xe9\u20ac-8'), ('test.aaa\xe9\u20ac-8', 2, 3, 4))
 
     def test_encodings_normalize_encoding(self):
-        # encodings.normalize_encoding() ignores non-ASCII characters.
         normalize = encodings.normalize_encoding
         self.assertEqual(normalize('utf_8'), 'utf_8')
-        self.assertEqual(normalize('utf\xE9\u20AC\U0010ffff-8'), 'utf_8')
         self.assertEqual(normalize('utf   8'), 'utf_8')
         # encodings.normalize_encoding() doesn't convert
         # characters to lower case.
@@ -3908,6 +3912,11 @@ def test_encodings_normalize_encoding(self):
         self.assertEqual(normalize('utf.8'), 'utf.8')
         self.assertEqual(normalize('utf...8'), 'utf...8')
 
+        # Non-ASCII *encoding* is deprecated.
+        msg = "Support for non-ascii encoding names will be removed in 3.17"
+        with warnings_helper.check_warnings((msg, DeprecationWarning)):
+            self.assertEqual(normalize('utf\xE9\u20AC\U0010ffff-8'), 'utf_8')
+
 
 class CodecCacheTest(unittest.TestCase):
     def test_cache_bounded(self):
diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index 021c3622566..d279851e7b7 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -724,8 +724,7 @@ def test_yet_more_evil_still_undecodable(self):
 
     @support.cpython_only
     @unittest.skipIf(support.is_wasi, "exhausts limited stack on WASI")
-    @support.run_with_limited_c_stack(
-        100_000 if sys.platform == "android" else 500_000)
+    @support.skip_if_huge_c_stack(100_000 if sys.platform == "android" else 500_000)
     @support.skip_emscripten_stack_overflow()
     def test_compiler_recursion_limit(self):
         # Compiler frames are small
@@ -841,8 +840,10 @@ def f():
             else:
                 return "unused"
 
-        self.assertEqual(f.__code__.co_consts,
-                         (f.__doc__, "used"))
+        if f.__doc__ is None:
+            self.assertEqual(f.__code__.co_consts, (True, "used"))
+        else:
+            self.assertEqual(f.__code__.co_consts, (f.__doc__, "used"))
 
     @support.cpython_only
     def test_remove_unused_consts_no_docstring(self):
@@ -887,7 +888,11 @@ def test_strip_unused_None(self):
         def f1():
             "docstring"
             return 42
-        self.assertEqual(f1.__code__.co_consts, (f1.__doc__,))
+
+        if f1.__doc__ is None:
+            self.assertEqual(f1.__code__.co_consts, (42,))
+        else:
+            self.assertEqual(f1.__code__.co_consts, (f1.__doc__,))
 
     # This is a regression test for a CPython specific peephole optimizer
     # implementation bug present in a few releases.  It's assertion verifies
@@ -1294,7 +1299,7 @@ def return_genexp():
                     x
                     in
                     y)
-        genexp_lines = [0, 4, 2, 0, 4]
+        genexp_lines = [4, 0, 4, 2, 0, 4]
 
         genexp_code = return_genexp.__code__.co_consts[0]
         code_lines = self.get_code_lines(genexp_code)
@@ -1629,6 +1634,17 @@ def test_remove_redundant_nop_edge_case(self):
         def f():
             a if (1 if b else c) else d
 
+    def test_lineno_propagation_empty_blocks(self):
+        # Smoke test. See gh-138714.
+        def f():
+            while name:
+                try:
+                    break
+                except:
+                    pass
+            else:
+                1 if 1 else 1
+
     def test_global_declaration_in_except_used_in_else(self):
         # See gh-111123
         code = textwrap.dedent("""\
@@ -1733,6 +1749,30 @@ def test_compile_warning_in_finally(self):
             self.assertEqual(wm.category, SyntaxWarning)
             self.assertIn("\"is\" with 'int' literal", str(wm.message))
 
+    def test_filter_syntax_warnings_by_module(self):
+        filename = support.findfile('test_import/data/syntax_warnings.py')
+        with open(filename, 'rb') as f:
+            source = f.read()
+        module_re = r'test\.test_import\.data\.syntax_warnings\z'
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=module_re)
+            compile(source, filename, 'exec')
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10, 13, 14, 21])
+        for wm in wlog:
+            self.assertEqual(wm.filename, filename)
+            self.assertIs(wm.category, SyntaxWarning)
+
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=r'package\.module\z')
+            warnings.filterwarnings('error', module=module_re)
+            compile(source, filename, 'exec', module='package.module')
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10, 13, 14, 21])
+        for wm in wlog:
+            self.assertEqual(wm.filename, filename)
+            self.assertIs(wm.category, SyntaxWarning)
+
     @support.subTests('src', [
         textwrap.dedent("""
             def f():
@@ -2419,8 +2459,8 @@ def test_lambda_return_position(self):
                 for i, pos in enumerate(positions):
                     with self.subTest(i=i, pos=pos):
                         start_line, end_line, start_col, end_col = pos
-                        if i == 0 and start_col == end_col == 0:
-                            # ignore the RESUME in the beginning
+                        if i <= 1:
+                            # ignore the RESUME and CACHE in the beginning
                             continue
                         self.assertEqual(start_line, 1)
                         self.assertEqual(end_line, 1)
@@ -2446,12 +2486,13 @@ def f():
             start_line, end_line, _, _ = instr.positions
             self.assertEqual(start_line, end_line)
 
-        # Expect four `LOAD_CONST None` instructions:
+        # Expect four `None`-loading instructions:
         # three for the no-exception __exit__ call, and one for the return.
         # They should all have the locations of the context manager ('xyz').
 
         load_none = [instr for instr in dis.get_instructions(f) if
-                     instr.opname == 'LOAD_CONST' and instr.argval is None]
+                     instr.opname in ('LOAD_CONST', 'LOAD_COMMON_CONSTANT')
+                     and instr.argval is None]
         return_value = [instr for instr in dis.get_instructions(f) if
                         instr.opname == 'RETURN_VALUE']
 
diff --git a/Lib/test/test_compileall.py b/Lib/test/test_compileall.py
index be5e7d7feee..a612a729014 100644
--- a/Lib/test/test_compileall.py
+++ b/Lib/test/test_compileall.py
@@ -28,11 +28,15 @@
 from test import support
 from test.support import os_helper
 from test.support import script_helper
-from test.test_py_compile import without_source_date_epoch
-from test.test_py_compile import SourceDateEpochTestMeta
+from test.support.os_helper import without_source_date_epoch
+from test.support.os_helper import SourceDateEpochTestMeta
 from test.support.os_helper import FakePath
 
 
+if sys.implementation.cache_tag is None:
+    raise unittest.SkipTest('requires sys.implementation.cache_tag is not None')
+
+
 def get_pyc(script, opt):
     if not opt:
         # Replace None and 0 with ''
diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
index 6dc27ff07a3..91b37a8fb00 100644
--- a/Lib/test/test_complex.py
+++ b/Lib/test/test_complex.py
@@ -244,7 +244,6 @@ def test_richcompare(self):
         self.assertIs(operator.ne(1+1j, 2+2j), True)
         self.assertIs(operator.eq(1+1j, 2.0), False)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: True is not False
     def test_richcompare_boundaries(self):
         def check(n, deltas, is_equal, imag = 0.0):
             for delta in deltas:
diff --git a/Lib/test/test_concurrent_futures/test_future.py b/Lib/test/test_concurrent_futures/test_future.py
index 4066ea1ee4b..06b11a3bacf 100644
--- a/Lib/test/test_concurrent_futures/test_future.py
+++ b/Lib/test/test_concurrent_futures/test_future.py
@@ -6,6 +6,7 @@
     PENDING, RUNNING, CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED, Future)
 
 from test import support
+from test.support import threading_helper
 
 from .util import (
     PENDING_FUTURE, RUNNING_FUTURE, CANCELLED_FUTURE,
@@ -282,6 +283,62 @@ def test_multiple_set_exception(self):
 
         self.assertEqual(f.exception(), e)
 
+    def test_get_snapshot(self):
+        """Test the _get_snapshot method for atomic state retrieval."""
+        # Test with a pending future
+        f = Future()
+        done, cancelled, result, exception = f._get_snapshot()
+        self.assertFalse(done)
+        self.assertFalse(cancelled)
+        self.assertIsNone(result)
+        self.assertIsNone(exception)
+
+        # Test with a finished future (successful result)
+        f = Future()
+        f.set_result(42)
+        done, cancelled, result, exception = f._get_snapshot()
+        self.assertTrue(done)
+        self.assertFalse(cancelled)
+        self.assertEqual(result, 42)
+        self.assertIsNone(exception)
+
+        # Test with a finished future (exception)
+        f = Future()
+        exc = ValueError("test error")
+        f.set_exception(exc)
+        done, cancelled, result, exception = f._get_snapshot()
+        self.assertTrue(done)
+        self.assertFalse(cancelled)
+        self.assertIsNone(result)
+        self.assertIs(exception, exc)
+
+        # Test with a cancelled future
+        f = Future()
+        f.cancel()
+        done, cancelled, result, exception = f._get_snapshot()
+        self.assertTrue(done)
+        self.assertTrue(cancelled)
+        self.assertIsNone(result)
+        self.assertIsNone(exception)
+
+        # Test concurrent access (basic thread safety check)
+        f = Future()
+        f.set_result(100)
+        results = []
+
+        def get_snapshot():
+            for _ in range(1000):
+                snapshot = f._get_snapshot()
+                results.append(snapshot)
+
+        threads = [threading.Thread(target=get_snapshot) for _ in range(4)]
+        with threading_helper.start_threads(threads):
+            pass
+        # All snapshots should be identical for a finished future
+        expected = (True, False, 100, None)
+        for result in results:
+            self.assertEqual(result, expected)
+
 
 def setUpModule():
     setup_module()
diff --git a/Lib/test/test_configparser.py b/Lib/test/test_configparser.py
index 4783943f71a..7d1e68fe381 100644
--- a/Lib/test/test_configparser.py
+++ b/Lib/test/test_configparser.py
@@ -43,7 +43,7 @@ class CfgParserTestCaseClass:
     default_section = configparser.DEFAULTSECT
     interpolation = configparser._UNSET
 
-    def newconfig(self, defaults=None):
+    def newconfig(self, defaults=None, **kwargs):
         arguments = dict(
             defaults=defaults,
             allow_no_value=self.allow_no_value,
@@ -56,6 +56,7 @@ def newconfig(self, defaults=None):
             default_section=self.default_section,
             interpolation=self.interpolation,
         )
+        arguments.update(kwargs)
         instance = self.config_class(**arguments)
         return instance
 
@@ -358,6 +359,32 @@ def test_basic(self):
                 the larch {0[1]} 1
             """.format(self.delimiters)))
 
+    @support.subTests('data', [
+        'foo bar=baz',
+        'foo   bar=baz',
+        'foo=bar=baz',
+        'foo = bar=baz',
+        'foo\t \t=\t \tbar=baz',
+    ])
+    def test_space_delimiter(self, data):
+        # gh-156353: Space should be accepted as a delimiter
+        cf = self.newconfig(delimiters=(' ', '='))
+        cf.read_string(f"[all]\n{data}")
+        self.assertEqual(cf.options('all'), ['foo'])
+        self.assertEqual(cf.get('all', 'foo'), 'bar=baz')
+
+    @support.subTests('delimiter', ' =:;#x\t\0\N{RS}\N{CEDILLA}\N{CAT}')
+    @support.subTests('space_before', ['', ' ', '\t', ' \t'])
+    @support.subTests('space_after', ['', ' ', '\t', ' \t'])
+    def test_any_delimiter(self, delimiter, space_before, space_after):
+        cf = self.newconfig(
+            delimiters=(delimiter,),
+            inline_comment_prefixes=None,
+        )
+        cf.read_string(f"[all]\nfoo{space_before}{delimiter}{space_after}bar=baz")
+        self.assertEqual(cf.options('all'), ['foo'])
+        self.assertEqual(cf.get('all', 'foo'), 'bar=baz')
+
     def test_basic_from_dict(self):
         config = {
             "Foo Bar": {
@@ -1991,8 +2018,8 @@ class ConvertersTestCase(BasicTestCase, unittest.TestCase):
 
     config_class = configparser.ConfigParser
 
-    def newconfig(self, defaults=None):
-        instance = super().newconfig(defaults=defaults)
+    def newconfig(self, defaults=None, **kwargs):
+        instance = super().newconfig(defaults=defaults, **kwargs)
         instance.converters['list'] = lambda v: [e.strip() for e in v.split()
                                                  if e.strip()]
         return instance
diff --git a/Lib/test/test_copy.py b/Lib/test/test_copy.py
index b452ddbef5c..13b7ce29565 100644
--- a/Lib/test/test_copy.py
+++ b/Lib/test/test_copy.py
@@ -60,7 +60,7 @@ class C(object):
             def __reduce_ex__(self, proto):
                 c.append(1)
                 return ""
-            def __reduce__(self):
+            def __reduce__(*args):
                 self.fail("shouldn't call this")
         c = []
         x = C()
@@ -70,9 +70,15 @@ def __reduce__(self):
 
     def test_copy_reduce(self):
         class C(object):
+            def __reduce_ex__(*args):
+                self.fail("shouldn't call this")
             def __reduce__(self):
                 c.append(1)
                 return ""
+            def __getattribute__(self, name):
+                if name == "__reduce_ex__":
+                    raise AttributeError(name)
+                return object.__getattribute__(self, name)
         c = []
         x = C()
         y = copy.copy(x)
@@ -133,6 +139,12 @@ def test_copy_dict(self):
         self.assertEqual(y, x)
         self.assertIsNot(y, x)
 
+    def test_copy_frozendict(self):
+        x = frozendict(x=1, y=2)
+        self.assertIs(copy.copy(x), x)
+        x = frozendict()
+        self.assertIs(copy.copy(x), x)
+
     def test_copy_set(self):
         x = {1, 2, 3}
         y = copy.copy(x)
@@ -323,7 +335,7 @@ class C(object):
             def __reduce_ex__(self, proto):
                 c.append(1)
                 return ""
-            def __reduce__(self):
+            def __reduce__(*args):
                 self.fail("shouldn't call this")
         c = []
         x = C()
@@ -333,9 +345,15 @@ def __reduce__(self):
 
     def test_deepcopy_reduce(self):
         class C(object):
+            def __reduce_ex__(*args):
+                self.fail("shouldn't call this")
             def __reduce__(self):
                 c.append(1)
                 return ""
+            def __getattribute__(self, name):
+                if name == "__reduce_ex__":
+                    raise AttributeError(name)
+                return object.__getattribute__(self, name)
         c = []
         x = C()
         y = copy.deepcopy(x)
@@ -421,6 +439,30 @@ def test_deepcopy_dict(self):
         self.assertIsNot(x, y)
         self.assertIsNot(x["foo"], y["foo"])
 
+    def test_deepcopy_frozendict(self):
+        x = frozendict({"foo": [1, 2], "bar": 3})
+        y = copy.deepcopy(x)
+        self.assertEqual(y, x)
+        self.assertIsNot(x, y)
+        self.assertIsNot(x["foo"], y["foo"])
+
+        # recursive frozendict
+        x = frozendict(foo=[])
+        x['foo'].append(x)
+        y = copy.deepcopy(x)
+        self.assertEqual(y.keys(), x.keys())
+        self.assertIsNot(x, y)
+        self.assertIsNot(x["foo"], y["foo"])
+        self.assertIs(y['foo'][0], y)
+
+        x = frozendict(foo=[])
+        x['foo'].append(x)
+        x = x['foo']
+        y = copy.deepcopy(x)
+        self.assertIsNot(x, y)
+        self.assertIsNot(x[0], y[0])
+        self.assertIs(y[0]['foo'], y)
+
     @support.skip_if_huge_c_stack()
     @support.skip_emscripten_stack_overflow()
     @support.skip_wasi_stack_overflow()
diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 7e76f4bc1cb..a055aeb7b61 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -228,7 +228,6 @@ def test_write_quoting(self):
         self._write_test(['a','',None,1], '"a","",,"1"',
                          quoting = csv.QUOTE_NOTNULL)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_write_escape(self):
         self._write_test(['a',1,'p,q'], 'a,1,"p,q"',
                          escapechar='\\')
@@ -1309,6 +1308,19 @@ class mydialect(csv.Dialect):
                     self.assertRaises(ValueError, create_invalid, field_name, " ",
                                       skipinitialspace=True)
 
+    def test_dialect_getattr_non_attribute_error_propagates(self):
+        # gh-145966: non-AttributeError exceptions raised by __getattr__
+        # during dialect attribute lookup must propagate, not be silenced.
+        class BadDialect:
+            def __getattr__(self, name):
+                raise RuntimeError("boom")
+
+        with self.assertRaises(RuntimeError):
+            csv.reader([], dialect=BadDialect())
+
+        with self.assertRaises(RuntimeError):
+            csv.writer(StringIO(), dialect=BadDialect())
+
 
 class TestSniffer(unittest.TestCase):
     sample1 = """\
@@ -1503,6 +1515,56 @@ def test_doublequote(self):
         dialect = sniffer.sniff(self.sample9)
         self.assertTrue(dialect.doublequote)
 
+    def test_guess_delimiter_crlf_not_chosen(self):
+        # Ensure that we pick the real delimiter ("|") over "\r" in a tie.
+        sniffer = csv.Sniffer()
+        sample = "a|b\r\nc|d\r\ne|f\r\n"
+        self.assertEqual(sniffer.sniff(sample).delimiter, "|")
+        self.assertNotEqual(sniffer.sniff(sample).delimiter, "\r")
+
+    def test_zero_mode_tie_order_independence(self):
+        sniffer = csv.Sniffer()
+        # ":" appears in half the rows (1, 0, 1, 0) - a tie between
+        #     0 and 1 per line.
+        # "," appears once every row (true delimiter).
+        #
+        # Even if the zero-frequency bucket is appended vs. inserted, the tie
+        # yields an adjusted score of 0, so ":" should not be promoted and
+        # "," must be selected.
+        sample = (
+            "a,b:c\n"
+            "d,e\n"
+            "f,g:c\n"
+            "h,i\n"
+        )
+        dialect = sniffer.sniff(sample)
+        self.assertEqual(dialect.delimiter, ",")
+
+    def test_zero_mode_tie_order_comma_first(self):
+        sniffer = csv.Sniffer()
+        pattern = (
+            "a,b\n"
+            "c:d\n"
+            "e,f\n"
+            "g:h\n"
+        )
+        sample = pattern * 10
+        with self.assertRaisesRegex(csv.Error, "Could not determine delimiter"):
+            sniffer.sniff(sample)
+
+    def test_zero_mode_tie_order_colon_first(self):
+        sniffer = csv.Sniffer()
+        pattern = (
+            "a:b\n"
+            "c,d\n"
+            "e:f\n"
+            "g,h\n"
+        )
+        sample = pattern * 10
+        with self.assertRaisesRegex(csv.Error, "Could not determine delimiter"):
+            sniffer.sniff(sample)
+
+
     def test_sniff_regex_backtracking(self):
         # gh-109638: this artificial sample used to take minutes.
         sniffer = csv.Sniffer()
@@ -1720,5 +1782,16 @@ def test_disallow_instantiation(self):
             with self.subTest(tp=tp):
                 check_disallow_instantiation(self, tp)
 
+
+class TestModule(unittest.TestCase):
+    def test_deprecated__version__(self):
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            "'__version__' is deprecated and slated for removal in Python 3.20",
+        ) as cm:
+            getattr(csv, "__version__")
+        self.assertEqual(cm.filename, __file__)
+
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/Lib/test/test_dataclasses/__init__.py b/Lib/test/test_dataclasses/__init__.py
index acbbf60ef37..17dee875991 100644
--- a/Lib/test/test_dataclasses/__init__.py
+++ b/Lib/test/test_dataclasses/__init__.py
@@ -27,11 +27,21 @@
 import dataclasses  # Needed for the string "dataclasses.InitVar[int]" to work as an annotation.
 
 from test import support
-from test.support import import_helper
+from test.support import cpython_only, import_helper
 
 # Just any custom exception we can catch.
 class CustomError(Exception): pass
 
+
+class TestImportTime(unittest.TestCase):
+
+    @cpython_only
+    def test_lazy_import(self):
+        import_helper.ensure_lazy_imports(
+            "dataclasses", {"inspect", "re", "copy"}
+        )
+
+
 class TestCase(unittest.TestCase):
     def test_no_fields(self):
         @dataclass
@@ -71,7 +81,7 @@ def test_field_repr(self):
         expected_output = "Field(name='id',type=None," \
                            f"default=1,default_factory={MISSING!r}," \
                            "init=True,repr=False,hash=None," \
-                           "compare=True,metadata=mappingproxy({})," \
+                           "compare=True,metadata=frozendict()," \
                            f"kw_only={MISSING!r}," \
                            "doc='Docstring'," \
                            "_field_type=None)"
@@ -985,7 +995,7 @@ class D:
         self.assertNotIn('x', D.__dict__)
 
     def test_missing_repr(self):
-        self.assertIn('MISSING_TYPE object', repr(MISSING))
+        self.assertEqual(repr(MISSING), 'MISSING')
 
     def test_dont_include_other_annotations(self):
         @dataclass
@@ -1693,17 +1703,24 @@ class GroupTuple:
         class GroupDict:
             id: int
             users: Dict[str, User]
+        @dataclass
+        class GroupFrozenDict:
+            id: int
+            users: frozendict[str, User]
         a = User('Alice', 1)
         b = User('Bob', 2)
         gl = GroupList(0, [a, b])
         gt = GroupTuple(0, (a, b))
         gd = GroupDict(0, {'first': a, 'second': b})
+        gfd = GroupFrozenDict(0, frozendict({'first': a, 'second': b}))
         self.assertEqual(asdict(gl), {'id': 0, 'users': [{'name': 'Alice', 'id': 1},
                                                          {'name': 'Bob', 'id': 2}]})
         self.assertEqual(asdict(gt), {'id': 0, 'users': ({'name': 'Alice', 'id': 1},
                                                          {'name': 'Bob', 'id': 2})})
-        self.assertEqual(asdict(gd), {'id': 0, 'users': {'first': {'name': 'Alice', 'id': 1},
-                                                         'second': {'name': 'Bob', 'id': 2}}})
+        expected_dict = {'id': 0, 'users': {'first': {'name': 'Alice', 'id': 1},
+                                            'second': {'name': 'Bob', 'id': 2}}}
+        self.assertEqual(asdict(gd), expected_dict)
+        self.assertEqual(asdict(gfd), expected_dict)
 
     def test_helper_asdict_builtin_object_containers(self):
         @dataclass
@@ -1884,14 +1901,21 @@ class GroupTuple:
         class GroupDict:
             id: int
             users: Dict[str, User]
+        @dataclass
+        class GroupFrozenDict:
+            id: int
+            users: frozendict[str, User]
         a = User('Alice', 1)
         b = User('Bob', 2)
         gl = GroupList(0, [a, b])
         gt = GroupTuple(0, (a, b))
         gd = GroupDict(0, {'first': a, 'second': b})
+        gfd = GroupFrozenDict(0, frozendict({'first': a, 'second': b}))
         self.assertEqual(astuple(gl), (0, [('Alice', 1), ('Bob', 2)]))
         self.assertEqual(astuple(gt), (0, (('Alice', 1), ('Bob', 2))))
-        self.assertEqual(astuple(gd), (0, {'first': ('Alice', 1), 'second': ('Bob', 2)}))
+        d = {'first': ('Alice', 1), 'second': ('Bob', 2)}
+        self.assertEqual(astuple(gd), (0, d))
+        self.assertEqual(astuple(gfd), (0, frozendict(d)))
 
     def test_helper_astuple_builtin_object_containers(self):
         @dataclass
@@ -2295,6 +2319,20 @@ class C:
 
         self.assertDocStrEqual(C.__doc__, "C()")
 
+    def test_docstring_slotted(self):
+        @dataclass(slots=True)
+        class C:
+            x: int
+
+        self.assertDocStrEqual(C.__doc__, "C(x:int)")
+
+    def test_docstring_recursive(self):
+        @dataclass()
+        class C:
+            x: list[C]
+
+        self.assertDocStrEqual(C.__doc__, "C(x:list[test.test_dataclasses.TestDocString.test_docstring_recursive.<locals>.C])")
+
     def test_docstring_one_field(self):
         @dataclass
         class C:
@@ -4444,10 +4482,17 @@ def test_classvar_module_level_import(self):
         from test.test_dataclasses import dataclass_module_1_str
         from test.test_dataclasses import dataclass_module_2
         from test.test_dataclasses import dataclass_module_2_str
-
-        for m in (dataclass_module_1, dataclass_module_1_str,
-                  dataclass_module_2, dataclass_module_2_str,
-                  ):
+        from test.test_dataclasses import dataclass_module_3
+        from test.test_dataclasses import dataclass_module_3_str
+        from test.test_dataclasses import dataclass_module_4
+        from test.test_dataclasses import dataclass_module_4_str
+
+        for m in (
+            dataclass_module_1, dataclass_module_1_str,
+            dataclass_module_2, dataclass_module_2_str,
+            dataclass_module_3, dataclass_module_3_str,
+            dataclass_module_4, dataclass_module_4_str,
+        ):
             with self.subTest(m=m):
                 # There's a difference in how the ClassVars are
                 # interpreted when using string annotations or
@@ -4751,6 +4796,14 @@ def custom_dataclass(cls, *args, **kwargs):
         self.assertEqual(c.x, 10)
         self.assertEqual(c.__custom__, True)
 
+    def test_empty_annotation_string(self):
+        @dataclass
+        class DataclassWithEmptyTypeAnnotation:
+            x: ""
+
+        c = DataclassWithEmptyTypeAnnotation(10)
+        self.assertEqual(c.x, 10)
+
 
 class TestReplace(unittest.TestCase):
     def test(self):
diff --git a/Lib/test/test_dataclasses/_types_proxy.py b/Lib/test/test_dataclasses/_types_proxy.py
new file mode 100644
index 00000000000..f4aaeef7aec
--- /dev/null
+++ b/Lib/test/test_dataclasses/_types_proxy.py
@@ -0,0 +1,8 @@
+# We need this to test a case when a type
+# is imported via some other package,
+# like ClassVar from typing_extensions instead of typing.
+# https://github.com/python/cpython/issues/133956
+from typing import ClassVar
+from dataclasses import InitVar
+
+__all__ = ["ClassVar", "InitVar"]
diff --git a/Lib/test/test_dataclasses/dataclass_module_3.py b/Lib/test/test_dataclasses/dataclass_module_3.py
new file mode 100644
index 00000000000..74abc091f35
--- /dev/null
+++ b/Lib/test/test_dataclasses/dataclass_module_3.py
@@ -0,0 +1,32 @@
+#from __future__ import annotations
+USING_STRINGS = False
+
+# dataclass_module_3.py and dataclass_module_3_str.py are identical
+# except only the latter uses string annotations.
+
+from dataclasses import dataclass
+import test.test_dataclasses._types_proxy as tp
+
+T_CV2 = tp.ClassVar[int]
+T_CV3 = tp.ClassVar
+
+T_IV2 = tp.InitVar[int]
+T_IV3 = tp.InitVar
+
+@dataclass
+class CV:
+    T_CV4 = tp.ClassVar
+    cv0: tp.ClassVar[int] = 20
+    cv1: tp.ClassVar = 30
+    cv2: T_CV2
+    cv3: T_CV3
+    not_cv4: T_CV4  # When using string annotations, this field is not recognized as a ClassVar.
+
+@dataclass
+class IV:
+    T_IV4 = tp.InitVar
+    iv0: tp.InitVar[int]
+    iv1: tp.InitVar
+    iv2: T_IV2
+    iv3: T_IV3
+    not_iv4: T_IV4  # When using string annotations, this field is not recognized as an InitVar.
diff --git a/Lib/test/test_dataclasses/dataclass_module_3_str.py b/Lib/test/test_dataclasses/dataclass_module_3_str.py
new file mode 100644
index 00000000000..49e5fca6183
--- /dev/null
+++ b/Lib/test/test_dataclasses/dataclass_module_3_str.py
@@ -0,0 +1,32 @@
+from __future__ import annotations
+USING_STRINGS = True
+
+# dataclass_module_3.py and dataclass_module_3_str.py are identical
+# except only the latter uses string annotations.
+
+from dataclasses import dataclass
+import test.test_dataclasses._types_proxy as tp
+
+T_CV2 = tp.ClassVar[int]
+T_CV3 = tp.ClassVar
+
+T_IV2 = tp.InitVar[int]
+T_IV3 = tp.InitVar
+
+@dataclass
+class CV:
+    T_CV4 = tp.ClassVar
+    cv0: tp.ClassVar[int] = 20
+    cv1: tp.ClassVar = 30
+    cv2: T_CV2
+    cv3: T_CV3
+    not_cv4: T_CV4  # When using string annotations, this field is not recognized as a ClassVar.
+
+@dataclass
+class IV:
+    T_IV4 = tp.InitVar
+    iv0: tp.InitVar[int]
+    iv1: tp.InitVar
+    iv2: T_IV2
+    iv3: T_IV3
+    not_iv4: T_IV4  # When using string annotations, this field is not recognized as an InitVar.
diff --git a/Lib/test/test_dataclasses/dataclass_module_4.py b/Lib/test/test_dataclasses/dataclass_module_4.py
new file mode 100644
index 00000000000..7e0c8a18356
--- /dev/null
+++ b/Lib/test/test_dataclasses/dataclass_module_4.py
@@ -0,0 +1,38 @@
+#from __future__ import annotations
+USING_STRINGS = False
+
+# dataclass_module_4.py and dataclass_module_4_str.py are identical
+# except only the latter uses string annotations.
+
+from dataclasses import dataclass
+import dataclasses
+import typing
+
+class TypingProxy:
+    class Nested:
+        ClassVar = typing.ClassVar
+        InitVar = dataclasses.InitVar
+
+T_CV2 = TypingProxy.Nested.ClassVar[int]
+T_CV3 = TypingProxy.Nested.ClassVar
+
+T_IV2 = TypingProxy.Nested.InitVar[int]
+T_IV3 = TypingProxy.Nested.InitVar
+
+@dataclass
+class CV:
+    T_CV4 = TypingProxy.Nested.ClassVar
+    cv0: TypingProxy.Nested.ClassVar[int] = 20
+    cv1: TypingProxy.Nested.ClassVar = 30
+    cv2: T_CV2
+    cv3: T_CV3
+    not_cv4: T_CV4  # When using string annotations, this field is not recognized as a ClassVar.
+
+@dataclass
+class IV:
+    T_IV4 = TypingProxy.Nested.InitVar
+    iv0: TypingProxy.Nested.InitVar[int]
+    iv1: TypingProxy.Nested.InitVar
+    iv2: T_IV2
+    iv3: T_IV3
+    not_iv4: T_IV4  # When using string annotations, this field is not recognized as an InitVar.
diff --git a/Lib/test/test_dataclasses/dataclass_module_4_str.py b/Lib/test/test_dataclasses/dataclass_module_4_str.py
new file mode 100644
index 00000000000..876f3dcf7c8
--- /dev/null
+++ b/Lib/test/test_dataclasses/dataclass_module_4_str.py
@@ -0,0 +1,38 @@
+from __future__ import annotations
+USING_STRINGS = True
+
+# dataclass_module_4.py and dataclass_module_4_str.py are identical
+# except only the latter uses string annotations.
+
+from dataclasses import dataclass
+import dataclasses
+import typing
+
+class TypingProxy:
+    class Nested:
+        ClassVar = typing.ClassVar
+        InitVar = dataclasses.InitVar
+
+T_CV2 = TypingProxy.Nested.ClassVar[int]
+T_CV3 = TypingProxy.Nested.ClassVar
+
+T_IV2 = TypingProxy.Nested.InitVar[int]
+T_IV3 = TypingProxy.Nested.InitVar
+
+@dataclass
+class CV:
+    T_CV4 = TypingProxy.Nested.ClassVar
+    cv0: TypingProxy.Nested.ClassVar[int] = 20
+    cv1: TypingProxy.Nested.ClassVar = 30
+    cv2: T_CV2
+    cv3: T_CV3
+    not_cv4: T_CV4  # When using string annotations, this field is not recognized as a ClassVar.
+
+@dataclass
+class IV:
+    T_IV4 = TypingProxy.Nested.InitVar
+    iv0: TypingProxy.Nested.InitVar[int]
+    iv1: TypingProxy.Nested.InitVar
+    iv2: T_IV2
+    iv3: T_IV3
+    not_iv4: T_IV4  # When using string annotations, this field is not recognized as an InitVar.
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index c621b7ac08c..1c723b25784 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -28,7 +28,6 @@
 import math
 import os, sys
 import operator
-import warnings
 import pickle, copy
 import unittest
 import numbers
@@ -3964,15 +3963,21 @@ def test_flag_comparisons(self):
         d.update(c.flags)
         self.assertEqual(d, c.flags)
         self.assertEqual(c.flags, d)
+        self.assertEqual(frozendict(d), c.flags)
+        self.assertEqual(c.flags, frozendict(d))
 
         d[Inexact] = True
         self.assertNotEqual(d, c.flags)
         self.assertNotEqual(c.flags, d)
+        self.assertNotEqual(frozendict(d), c.flags)
+        self.assertNotEqual(c.flags, frozendict(d))
 
         # Invalid SignalDict
         d = {Inexact:False}
         self.assertNotEqual(d, c.flags)
         self.assertNotEqual(c.flags, d)
+        self.assertNotEqual(frozendict(d), c.flags)
+        self.assertNotEqual(c.flags, frozendict(d))
 
         d = ["xyz"]
         self.assertNotEqual(d, c.flags)
@@ -4142,6 +4147,15 @@ def test_float_operation_default(self):
 @requires_cdecimal
 class CContextFlags(ContextFlags, unittest.TestCase):
     decimal = C
+
+    def test_signaldict_repr(self):
+        Context = self.decimal.Context
+        ctx = Context(prec=7)
+        mapping = ctx.flags
+        del ctx
+        with self.assertRaisesRegex(ValueError, 'invalid signal dict'):
+            repr(mapping)
+
 class PyContextFlags(ContextFlags, unittest.TestCase):
     decimal = P
 
@@ -4475,7 +4489,7 @@ def test_module_attributes(self):
         self.assertTrue(C.HAVE_THREADS is True or C.HAVE_THREADS is False)
         self.assertTrue(P.HAVE_THREADS is True or P.HAVE_THREADS is False)
 
-        self.assertEqual(C.__version__, P.__version__)
+        self.assertEqual(C.SPEC_VERSION, P.SPEC_VERSION)
 
         self.assertLessEqual(set(dir(C)), set(dir(P)))
         self.assertEqual([n for n in dir(C) if n[:2] != '__'], sorted(P.__all__))
@@ -4962,6 +4976,14 @@ def test_c_context(self):
         self.assertEqual(c._flags, C.DecClamped)
         self.assertEqual(c._traps, C.DecRounded)
 
+    @requires_extra_functionality
+    def test_c_context_apply(self):
+        c = C.Context(prec=3)
+        self.assertEqual(c.apply(C.Decimal('1.23456')), C.Decimal('1.23'))
+        # A higher precision won't see them as equal.
+        c = C.Context(prec=5)
+        self.assertNotEqual(c.apply(C.Decimal('1.23456')), C.Decimal('1.23'))
+
     @requires_extra_functionality
     def test_constants(self):
         # Condition flags
@@ -5930,6 +5952,23 @@ def doit(ty):
         doit('Context')
 
 
+class TestModule:
+    def test_deprecated__version__(self):
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            "'__version__' is deprecated and slated for removal in Python 3.20",
+        ) as cm:
+            getattr(self.decimal, "__version__")
+        self.assertEqual(cm.filename, __file__)
+
+
+@requires_cdecimal
+class CTestModule(TestModule, unittest.TestCase):
+    decimal = C
+class PyTestModule(TestModule, unittest.TestCase):
+    decimal = P
+
+
 def load_tests(loader, tests, pattern):
     if TODO_TESTS is not None:
         # Run only Arithmetic tests
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index a27eb7399dc..ca9861e1994 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1329,6 +1329,18 @@ class X(object):
         with self.assertRaisesRegex(AttributeError, "'X' object has no attribute 'a'"):
             X().a
 
+    def test_slots_after_items(self):
+        class C(tuple):
+            __slots__ = ['a']
+        x = C((1, 2, 3))
+        self.assertNotHasAttr(x, "__dict__")
+        self.assertNotHasAttr(x, "a")
+        x.a = 42
+        self.assertEqual(x.a, 42)
+        del x.a
+        self.assertNotHasAttr(x, "a")
+        self.assertEqual(x, (1, 2, 3))
+
     def test_slots_special(self):
         # Testing __dict__ and __weakref__ in __slots__...
         class D(object):
@@ -1338,18 +1350,17 @@ class D(object):
         self.assertNotHasAttr(a, "__weakref__")
         a.foo = 42
         self.assertEqual(a.__dict__, {"foo": 42})
+        with self.assertRaises(TypeError):
+            weakref.ref(a)
 
         class W(object):
             __slots__ = ["__weakref__"]
         a = W()
         self.assertHasAttr(a, "__weakref__")
         self.assertNotHasAttr(a, "__dict__")
-        try:
+        with self.assertRaises(AttributeError):
             a.foo = 42
-        except AttributeError:
-            pass
-        else:
-            self.fail("shouldn't be allowed to set a.foo")
+        self.assertIs(weakref.ref(a)(), a)
 
         class C1(W, D):
             __slots__ = []
@@ -1358,6 +1369,7 @@ class C1(W, D):
         self.assertHasAttr(a, "__weakref__")
         a.foo = 42
         self.assertEqual(a.__dict__, {"foo": 42})
+        self.assertIs(weakref.ref(a)(), a)
 
         class C2(D, W):
             __slots__ = []
@@ -1366,6 +1378,80 @@ class C2(D, W):
         self.assertHasAttr(a, "__weakref__")
         a.foo = 42
         self.assertEqual(a.__dict__, {"foo": 42})
+        self.assertIs(weakref.ref(a)(), a)
+
+    @unittest.skipIf(_testcapi is None, 'need the _testcapi module')
+    def test_slots_special_before_items(self):
+        class D(_testcapi.HeapCCollection):
+            __slots__ = ["__dict__"]
+        a = D(1, 2, 3)
+        self.assertHasAttr(a, "__dict__")
+        self.assertNotHasAttr(a, "__weakref__")
+        a.foo = 42
+        self.assertEqual(a.__dict__, {"foo": 42})
+        with self.assertRaises(TypeError):
+            weakref.ref(a)
+        del a.__dict__
+        self.assertNotHasAttr(a, "foo")
+        self.assertEqual(a.__dict__, {})
+        self.assertEqual(list(a), [1, 2, 3])
+
+        class W(_testcapi.HeapCCollection):
+            __slots__ = ["__weakref__"]
+        a = W(1, 2, 3)
+        self.assertHasAttr(a, "__weakref__")
+        self.assertNotHasAttr(a, "__dict__")
+        with self.assertRaises(AttributeError):
+            a.foo = 42
+        self.assertIs(weakref.ref(a)(), a)
+
+        with self.assertRaises(TypeError):
+            class X(_testcapi.HeapCCollection):
+                __slots__ = ['x']
+
+        with self.assertRaises(TypeError):
+            class X(_testcapi.HeapCCollection):
+                __slots__ = ['__dict__', 'x']
+
+    @support.subTests(('base', 'arg'), [
+        (tuple, (1, 2, 3)),
+        (int, 9876543210**2),
+        (bytes, b'ab'),
+    ])
+    def test_slots_special_after_items(self, base, arg):
+        class D(base):
+            __slots__ = ["__dict__"]
+        a = D(arg)
+        self.assertHasAttr(a, "__dict__")
+        self.assertNotHasAttr(a, "__weakref__")
+        a.foo = 42
+        self.assertEqual(a.__dict__, {"foo": 42})
+        with self.assertRaises(TypeError):
+            weakref.ref(a)
+        del a.__dict__
+        self.assertNotHasAttr(a, "foo")
+        self.assertEqual(a.__dict__, {})
+        self.assertEqual(a, base(arg))
+
+        class W(base):
+            __slots__ = ["__weakref__"]
+        a = W(arg)
+        self.assertHasAttr(a, "__weakref__")
+        self.assertNotHasAttr(a, "__dict__")
+        with self.assertRaises(AttributeError):
+            a.foo = 42
+        self.assertIs(weakref.ref(a)(), a)
+        self.assertEqual(a, base(arg))
+
+    @support.subTests('base', [int, bytes] +
+                      ([_testcapi.HeapCCollection] if _testcapi else []))
+    def test_unsupported_slots(self, base):
+        with self.assertRaises(TypeError):
+            class X(base):
+                __slots__ = ['x']
+        with self.assertRaises(TypeError):
+            class X(base):
+                __slots__ = ['__dict__', 'x']
 
     def test_slots_special2(self):
         # Testing __qualname__ and __classcell__ in __slots__
@@ -1650,6 +1736,18 @@ def annotated(cls) -> int: pass
                     del method.__annotate__
                     self.assertIs(method.__annotate__, original_annotate)
 
+    def test_classmethod_without_dict_access(self):
+        class Spam:
+            @classmethod
+            def method(cls, x, y):
+                pass
+
+        obj = Spam.__dict__['method']
+        self.assertIsInstance(obj, classmethod)
+        self.assertEqual(obj.__annotations__, {})
+        self.assertEqual(obj.__name__, 'method')
+        self.assertEqual(obj.__module__, __name__)
+
     def test_staticmethod_annotations_without_dict_access(self):
         # gh-125017: this used to crash
         class Spam:
@@ -1660,15 +1758,8 @@ def __new__(cls, x, y):
         obj = Spam.__dict__['__new__']
         self.assertIsInstance(obj, staticmethod)
         self.assertEqual(obj.__annotations__, {})
-
-    @support.refcount_test
-    def test_refleaks_in_classmethod___init__(self):
-        gettotalrefcount = support.get_attribute(sys, 'gettotalrefcount')
-        cm = classmethod(None)
-        refs_before = gettotalrefcount()
-        for i in range(100):
-            cm.__init__(None)
-        self.assertAlmostEqual(gettotalrefcount() - refs_before, 0, delta=10)
+        self.assertEqual(obj.__name__, '__new__')
+        self.assertEqual(obj.__module__, __name__)
 
     @support.impl_detail("the module 'xxsubtype' is internal")
     @unittest.skipIf(xxsubtype is None, "requires xxsubtype module")
@@ -1767,15 +1858,6 @@ class D(C):
         del sm.x
         self.assertNotHasAttr(sm, "x")
 
-    @support.refcount_test
-    def test_refleaks_in_staticmethod___init__(self):
-        gettotalrefcount = support.get_attribute(sys, 'gettotalrefcount')
-        sm = staticmethod(None)
-        refs_before = gettotalrefcount()
-        for i in range(100):
-            sm.__init__(None)
-        self.assertAlmostEqual(gettotalrefcount() - refs_before, 0, delta=10)
-
     @support.impl_detail("the module 'xxsubtype' is internal")
     @unittest.skipIf(xxsubtype is None, "requires xxsubtype module")
     def test_staticmethods_in_c(self):
@@ -4111,42 +4193,195 @@ class E(D):
         self.assertEqual(e.a, 2)
         self.assertEqual(C2.__subclasses__(), [D])
 
-        try:
+        with self.assertRaisesRegex(TypeError,
+                    "cannot delete '__bases__' attribute of type 'D'"):
             del D.__bases__
-        except (TypeError, AttributeError):
-            pass
-        else:
-            self.fail("shouldn't be able to delete .__bases__")
-
-        try:
+        with self.assertRaisesRegex(TypeError, 'can only assign non-empty tuple'):
             D.__bases__ = ()
-        except TypeError as msg:
-            if str(msg) == "a new-style class can't have only classic bases":
-                self.fail("wrong error message for .__bases__ = ()")
-        else:
-            self.fail("shouldn't be able to set .__bases__ to ()")
-
-        try:
+        with self.assertRaisesRegex(TypeError, 'can only assign tuple'):
+            D.__bases__ = [C]
+        with self.assertRaisesRegex(TypeError, 'duplicate base class'):
+            D.__bases__ = (C, C)
+        with self.assertRaisesRegex(TypeError, 'inheritance cycle'):
             D.__bases__ = (D,)
-        except TypeError:
-            pass
-        else:
-            # actually, we'll have crashed by here...
-            self.fail("shouldn't be able to create inheritance cycles")
+        with self.assertRaisesRegex(TypeError, 'inheritance cycle'):
+            D.__bases__ = (E,)
 
-        try:
-            D.__bases__ = (C, C)
-        except TypeError:
-            pass
-        else:
-            self.fail("didn't detect repeated base classes")
+        class A:
+            __slots__ = ()
+            def __repr__(self):
+                return '<A>'
+        class A_with_dict:
+            __slots__ = ('__dict__',)
+            def __repr__(self):
+                return '<A_with_dict>'
+        class A_with_dict_weakref:
+            def __repr__(self):
+                return '<A_with_dict_weakref>'
+        class A_with_slots:
+            __slots__ = ('x',)
+            def __repr__(self):
+                return '<A_with_slots>'
+        class A_with_slots_dict:
+            __slots__ = ('x', '__dict__')
+            def __repr__(self):
+                return '<A_with_slots_dict>'
 
-        try:
-            D.__bases__ = (E,)
-        except TypeError:
+        class B:
+            __slots__ = ()
+        b = B()
+        r = repr(b)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B.__bases__ = (int,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B.__bases__ = (A_with_dict_weakref,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B.__bases__ = (A_with_dict,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B.__bases__ = (A_with_slots,)
+        B.__bases__ = (A,)
+        self.assertNotHasAttr(b, '__dict__')
+        self.assertNotHasAttr(b, '__weakref__')
+        self.assertEqual(repr(b), '<A>')
+        B.__bases__ = (object,)
+        self.assertEqual(repr(b), r)
+
+        class B_with_dict_weakref:
+            pass
+        b = B_with_dict_weakref()
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B.__bases__ = (A_with_slots,)
+        B_with_dict_weakref.__bases__ = (A_with_dict_weakref,)
+        self.assertEqual(repr(b), '<A_with_dict_weakref>')
+        B_with_dict_weakref.__bases__ = (A_with_dict,)
+        self.assertEqual(repr(b), '<A_with_dict>')
+        B_with_dict_weakref.__bases__ = (A,)
+        self.assertEqual(repr(b), '<A>')
+        B_with_dict_weakref.__bases__ = (object,)
+
+        class B_with_slots:
+            __slots__ = ('x',)
+        b = B_with_slots()
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_with_slots.__bases__ = (A_with_dict_weakref,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_with_slots.__bases__ = (A_with_dict,)
+        B_with_slots.__bases__ = (A,)
+        self.assertEqual(repr(b), '<A>')
+
+        class B_with_slots_dict:
+            __slots__ = ('x', '__dict__')
+        b = B_with_slots_dict()
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_with_slots_dict.__bases__ = (A_with_dict_weakref,)
+        B_with_slots_dict.__bases__ = (A_with_dict,)
+        self.assertEqual(repr(b), '<A_with_dict>')
+        B_with_slots_dict.__bases__ = (A,)
+        self.assertEqual(repr(b), '<A>')
+
+        class B_with_slots_dict_weakref:
+            __slots__ = ('x', '__dict__', '__weakref__')
+        b = B_with_slots_dict_weakref()
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_with_slots_dict_weakref.__bases__ = (A_with_slots_dict,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_with_slots_dict_weakref.__bases__ = (A_with_slots,)
+        B_with_slots_dict_weakref.__bases__ = (A_with_dict_weakref,)
+        self.assertEqual(repr(b), '<A_with_dict_weakref>')
+        B_with_slots_dict_weakref.__bases__ = (A_with_dict,)
+        self.assertEqual(repr(b), '<A_with_dict>')
+        B_with_slots_dict_weakref.__bases__ = (A,)
+        self.assertEqual(repr(b), '<A>')
+
+        class C_with_slots(A_with_slots):
+            __slots__ = ()
+        c = C_with_slots()
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            C_with_slots.__bases__ = (A_with_slots_dict,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            C_with_slots.__bases__ = (A_with_dict_weakref,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            C_with_slots.__bases__ = (A_with_dict,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            C_with_slots.__bases__ = (A,)
+        C_with_slots.__bases__ = (A_with_slots,)
+        self.assertEqual(repr(c), '<A_with_slots>')
+
+        class C_with_slots_dict(A_with_slots):
+            pass
+        c = C_with_slots_dict()
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            C_with_slots_dict.__bases__ = (A_with_dict_weakref,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            C_with_slots_dict.__bases__ = (A_with_dict,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            C_with_slots_dict.__bases__ = (A,)
+        C_with_slots_dict.__bases__ = (A_with_slots_dict,)
+        self.assertEqual(repr(c), '<A_with_slots_dict>')
+        C_with_slots_dict.__bases__ = (A_with_slots,)
+        self.assertEqual(repr(c), '<A_with_slots>')
+
+        class A_int(int):
+            __slots__ = ()
+            def __repr__(self):
+                return '<A_int>'
+        class B_int(int):
+            __slots__ = ()
+        b = B_int(42)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_int.__bases__ = (object,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_int.__bases__ = (tuple,)
+        with self.assertRaisesRegex(TypeError, 'is not an acceptable base type'):
+            B_int.__bases__ = (bool,)
+        B_int.__bases__ = (A_int,)
+        self.assertEqual(repr(b), '<A_int>')
+        B_int.__bases__ = (int,)
+        self.assertEqual(repr(b), '42')
+
+        class A_tuple(tuple):
+            __slots__ = ()
+            def __repr__(self):
+                return '<A_tuple>'
+        class B_tuple(tuple):
+            __slots__ = ()
+        b = B_tuple((1, 2))
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_tuple.__bases__ = (object,)
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
+            B_tuple.__bases__ = (int,)
+        B_tuple.__bases__ = (A_tuple,)
+        self.assertEqual(repr(b), '<A_tuple>')
+        B_tuple.__bases__ = (tuple,)
+        self.assertEqual(repr(b), '(1, 2)')
+
+    def test_assign_bases_many_subclasses(self):
+        # This is intended to check that typeobject.c:queue_slot_update() can
+        # handle updating many subclasses when a slot method is re-assigned.
+        class A:
+            x = 'hello'
+            def __call__(self):
+                return 123
+            def __getitem__(self, index):
+                return None
+
+        class X:
+            x = 'bye'
+
+        class B(A):
             pass
-        else:
-            self.fail("shouldn't be able to create inheritance cycles")
+
+        subclasses = []
+        for i in range(1000):
+            sc = type(f'Sub{i}', (B,), {})
+            subclasses.append(sc)
+
+        self.assertEqual(subclasses[0]()(), 123)
+        self.assertEqual(subclasses[0]().x, 'hello')
+        B.__bases__ = (X,)
+        with self.assertRaises(TypeError):
+            subclasses[0]()()
+        self.assertEqual(subclasses[0]().x, 'bye')
 
     def test_builtin_bases(self):
         # Make sure all the builtin types can have their base queried without
@@ -4171,26 +4406,14 @@ class C(object):
         class D(C):
             pass
 
-        try:
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
             L.__bases__ = (dict,)
-        except TypeError:
-            pass
-        else:
-            self.fail("shouldn't turn list subclass into dict subclass")
 
-        try:
+        with self.assertRaisesRegex(TypeError, 'immutable type'):
             list.__bases__ = (dict,)
-        except TypeError:
-            pass
-        else:
-            self.fail("shouldn't be able to assign to list.__bases__")
 
-        try:
+        with self.assertRaisesRegex(TypeError, 'layout differs'):
             D.__bases__ = (C, list)
-        except TypeError:
-            pass
-        else:
-            self.fail("best_base calculation found wanting")
 
     def test_unsubclassable_types(self):
         with self.assertRaises(TypeError):
@@ -4956,7 +5179,7 @@ class X:
 
         with self.assertRaises(TypeError) as cm:
             type(X).__dict__["__doc__"].__delete__(X)
-        self.assertIn("cannot delete '__doc__' attribute of immutable type 'X'", str(cm.exception))
+        self.assertIn("cannot delete '__doc__' attribute of type 'X'", str(cm.exception))
         self.assertEqual(X.__doc__, "banana")
 
     def test_qualname(self):
@@ -5173,25 +5396,30 @@ def foo(self):
         with self.assertRaisesRegex(NotImplementedError, "BAR"):
             B().foo
 
-    def test_staticmethod_new(self):
-        class MyStaticMethod(staticmethod):
-            def __init__(self, func):
-                pass
-        def func(): pass
-        sm = MyStaticMethod(func)
-        self.assertEqual(repr(sm), '<staticmethod(None)>')
-        self.assertIsNone(sm.__func__)
-        self.assertIsNone(sm.__wrapped__)
-
-    def test_classmethod_new(self):
-        class MyClassMethod(classmethod):
-            def __init__(self, func):
-                pass
-        def func(): pass
-        cm = MyClassMethod(func)
-        self.assertEqual(repr(cm), '<classmethod(None)>')
-        self.assertIsNone(cm.__func__)
-        self.assertIsNone(cm.__wrapped__)
+    def test_gh146587(self):
+        # See https://github.com/python/cpython/issues/146587
+
+        class A:
+            def __radd__(self, other): ...
+
+        class B(tuple): ...
+
+        self.assertIsNone(() + A())
+        self.assertIsNone(B() + A())
+
+        from typing import NamedTuple
+
+        class T(NamedTuple):
+            x: int
+
+        class A:
+            def __init__(self, *args):
+                self.lst = list(args)
+            def __radd__(self, other):
+                return A(*self.lst, other)
+
+        self.assertEqual(((1,)+A()).lst, [(1,)])
+        self.assertEqual((T(x=1)+A()).lst, [T(x=1)])
 
 
 class DictProxyTests(unittest.TestCase):
@@ -5742,7 +5970,6 @@ def __repr__(self):
                     objcopy2 = deepcopy(objcopy)
                     self._assert_is_copy(obj, objcopy2)
 
-    @unittest.skip("TODO: RUSTPYTHON")
     def test_issue24097(self):
         # Slot name is freed inside __getattr__ and is later used.
         class S(str):  # Not interned
@@ -6041,5 +6268,69 @@ class A(metaclass=M):
                 pass
 
 
+class TestGenericDescriptors(unittest.TestCase):
+    def test___dict__(self):
+        class CustomClass:
+            pass
+        class SlotClass:
+            __slots__ = ['foo']
+        class SlotSubClass(SlotClass):
+            pass
+        class IntSubclass(int):
+            pass
+
+        dict_descriptor = CustomClass.__dict__['__dict__']
+        self.assertEqual(dict_descriptor.__objclass__, object)
+
+        for cls in CustomClass, SlotSubClass, IntSubclass:
+            with self.subTest(cls=cls):
+                self.assertIs(cls.__dict__['__dict__'], dict_descriptor)
+                instance = cls()
+                instance.attr = 123
+                self.assertEqual(
+                    dict_descriptor.__get__(instance, cls),
+                    {'attr': 123},
+                )
+        with self.assertRaises(AttributeError):
+            print(dict_descriptor.__get__(True, bool))
+        with self.assertRaises(AttributeError):
+            print(dict_descriptor.__get__(SlotClass(), SlotClass))
+
+        # delegation to type.__dict__
+        self.assertIsInstance(
+            dict_descriptor.__get__(type, type),
+            types.MappingProxyType,
+        )
+
+    def test___weakref__(self):
+        class CustomClass:
+            pass
+        class SlotClass:
+            __slots__ = ['foo']
+        class SlotSubClass(SlotClass):
+            pass
+        class IntSubclass(int):
+            pass
+
+        weakref_descriptor = CustomClass.__dict__['__weakref__']
+        self.assertEqual(weakref_descriptor.__objclass__, object)
+
+        for cls in CustomClass, SlotSubClass:
+            with self.subTest(cls=cls):
+                self.assertIs(cls.__dict__['__weakref__'], weakref_descriptor)
+                instance = cls()
+                instance.attr = 123
+                self.assertEqual(
+                    weakref_descriptor.__get__(instance, cls),
+                    None,
+                )
+        with self.assertRaises(AttributeError):
+            weakref_descriptor.__get__(True, bool)
+        with self.assertRaises(AttributeError):
+            weakref_descriptor.__get__(SlotClass(), SlotClass)
+        with self.assertRaises(AttributeError):
+            weakref_descriptor.__get__(IntSubclass(), IntSubclass)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index e11dd17f1d9..e0d2dbb92b3 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -678,7 +678,7 @@ def __repr__(self):
         d = {1: BadRepr()}
         self.assertRaises(Exc, repr, d)
 
-    @support.run_with_limited_c_stack()
+    @support.skip_if_huge_c_stack()
     @support.skip_wasi_stack_overflow()
     @support.skip_emscripten_stack_overflow()
     def test_repr_deep(self):
@@ -951,7 +951,6 @@ def test_empty_presized_dict_in_freelist(self):
                  'f': None, 'g': None, 'h': None}
         d = {}
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_container_iterator(self):
         # Bug #3680: tp_traverse was not implemented for dictiter and
         # dictview objects.
@@ -1264,7 +1263,6 @@ def test_free_after_iterating(self):
         support.check_free_after_iterating(self, lambda d: iter(d.values()), dict)
         support.check_free_after_iterating(self, lambda d: iter(d.items()), dict)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_equal_operator_modifying_operand(self):
         # test fix for seg fault reported in bpo-27945 part 3.
         class X():
@@ -1405,7 +1403,6 @@ def __init__(self, x, y):
         self.assertEqual(list(reversed(A(1, 0).__dict__)), ['x'])
         self.assertEqual(list(reversed(A(0, 1).__dict__)), ['y'])
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; RuntimeError: dictionary changed size during iteration
     def test_reversed_dict_after_clear_and_restore(self):
         d = {}
         for i in range(1000):
@@ -1427,6 +1424,32 @@ def test_reversed_dict_after_clear_and_restore(self):
         for it in iterators:
             self.assertEqual(list(it), [])
 
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: RuntimeError not raised
+    def test_reversed_dict_keys_changed_during_iteration(self):
+        d = dict.fromkeys(range(10))
+        for i in range(7):
+            del d[i]
+
+        iterators = (
+            reversed(d),
+            reversed(d.keys()),
+            reversed(d.values()),
+            reversed(d.items()),
+        )
+        for it in iterators:
+            next(it)
+
+        # Same size as before, but with different keys below
+        # the iterators' current position.
+        d.clear()
+        d.update(dict.fromkeys(range(10)))
+        for i in range(3, 10):
+            del d[i]
+
+        for it in iterators:
+            with self.assertRaisesRegex(RuntimeError, 'keys changed'):
+                list(it)
+
     def test_dict_copy_order(self):
         # bpo-34320
         od = collections.OrderedDict([('a', 1), ('b', 2)])
@@ -1614,7 +1637,6 @@ class Shenanigans:
         self.assertEqual(holds_reference.ref['data'], 42)
         self.assertEqual(holds_reference.attr, "whatever")
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_unhashable_key(self):
         d = {'a': 1}
         key = [1, 2, 3]
@@ -1636,7 +1658,7 @@ def check_unhashable_key():
         with check_unhashable_key():
             d.get(key)
 
-        # Only TypeError exception is overriden,
+        # Only TypeError exception is overridden,
         # other exceptions are left unchanged.
         class HashError:
             def __hash__(self):
@@ -1832,6 +1854,250 @@ class Dict(dict):
 class SubclassMappingTests(mapping_tests.BasicTestMappingProtocol):
     type2test = Dict
 
+class FrozenDictMappingTests(mapping_tests.BasicTestImmutableMappingProtocol):
+    type2test = frozendict
+
+
+class FrozenDict(frozendict):
+    pass
+
+
+class FrozenDictSlots(frozendict):
+    __slots__ = ('slot_attr',)
+
+
+class FrozenDictTests(unittest.TestCase):
+    def test_constructor(self):
+        # frozendict.__init__() has no effect
+        d = frozendict(a=1, b=2, c=3)
+        d.__init__(x=1)
+        self.assertEqual(d, frozendict(a=1, b=2, c=3))
+
+        # dict constructor cannot be used on frozendict
+        with self.assertRaises(TypeError):
+            dict.__init__(d, x=1)
+
+        # Avoid copy if it's frozendict type
+        d2 = frozendict(d)
+        self.assertIs(d2, d)
+        d2 = FrozenDict(d)
+        self.assertIsNot(d2, d)
+        self.assertEqual(d2, d)
+
+    def test_copy(self):
+        d = frozendict(x=1, y=2)
+        d2 = d.copy()
+        self.assertIs(d2, d)
+
+        d = FrozenDict(x=1, y=2)
+        d2 = d.copy()
+        self.assertIsNot(d2, d)
+        self.assertEqual(d2, frozendict(x=1, y=2))
+        self.assertEqual(type(d2), frozendict)
+
+    def test_merge(self):
+        # test "a | b" operator
+        self.assertEqual(frozendict(x=1) | frozendict(y=2),
+                         frozendict({'x': 1, 'y': 2}))
+        self.assertEqual(frozendict(x=1) | dict(y=2),
+                         frozendict({'x': 1, 'y': 2}))
+        self.assertEqual(frozendict(x=1, y=2) | frozendict(y=5),
+                         frozendict({'x': 1, 'y': 5}))
+        self.assertEqual(FrozenDict(x=1, y=2) | FrozenDict(y=5),
+                         frozendict({'x': 1, 'y': 5}))
+
+        fd = frozendict(x=1, y=2)
+        self.assertIs(fd | frozendict(), fd)
+        self.assertIs(fd | {}, fd)
+        self.assertIs(frozendict() | fd, fd)
+
+        fd = FrozenDict(x=1, y=2)
+        self.assertEqual(fd | frozendict(), fd)
+        self.assertEqual(fd | {}, fd)
+        self.assertEqual(frozendict() | fd, fd)
+
+        # gh-149676: Test hash(frozendict | frozendict)
+        a = frozendict({"a": 1})
+        b = frozendict({"b": 2})
+        self.assertEqual(hash(a | b), hash(frozendict({"a": 1, "b": 2})))
+
+    def test_update(self):
+        # test "a |= b" operator
+        d = frozendict(x=1)
+        copy = d
+        self.assertIs(copy, d)
+        d |= frozendict(y=2)
+        self.assertIsNot(copy, d)
+        self.assertEqual(d, frozendict({'x': 1, 'y': 2}))
+        self.assertEqual(copy, frozendict({'x': 1}))
+
+    def test_items_xor(self):
+        # test "a ^ b" operator on items views
+        res = frozendict(a=1, b=2).items() ^ frozendict(b=2, c=3).items()
+        self.assertEqual(res, {('a', 1), ('c', 3)})
+
+    def test_repr(self):
+        d = frozendict()
+        self.assertEqual(repr(d), "frozendict()")
+
+        d = frozendict(x=1, y=2)
+        self.assertEqual(repr(d), "frozendict({'x': 1, 'y': 2})")
+
+        d = FrozenDict(x=1, y=2)
+        self.assertEqual(repr(d), "FrozenDict({'x': 1, 'y': 2})")
+
+    def test_hash(self):
+        # hash() doesn't rely on the items order
+        self.assertEqual(hash(frozendict(x=1, y=2)),
+                         hash(frozendict(y=2, x=1)))
+
+        # Check that hash() computes the hash of (key, value) pairs
+        cases = [
+            frozendict(a=False, b=True, c=True),
+            frozendict(a=True, b=False, c=True),
+            frozendict(a=True, b=True, c=False),
+            frozendict({False: "a", "b": True, "c": True}),
+            frozendict({"a": "b", False: True, True: "c"}),
+        ]
+        hashes = {hash(fd) for fd in cases}
+        self.assertEqual(len(hashes), len(cases))
+
+        fd = frozendict(x=[1], y=[2])
+        with self.assertRaisesRegex(TypeError, "unhashable type: 'list'"):
+            hash(fd)
+
+    @support.cpython_only
+    def test_hash_cpython(self):
+        # Check that hash(frozendict) implementation is:
+        # hash(frozenset(fd.items()))
+        for fd in (
+            frozendict(),
+            frozendict(x=1, y=2),
+            frozendict(y=2, x=1),
+            frozendict(a=False, b=True, c=True),
+            frozendict.fromkeys('abc'),
+        ):
+            with self.subTest(fd=fd):
+                self.assertEqual(hash(fd), hash(frozenset(fd.items())))
+
+    def test_fromkeys(self):
+        self.assertEqual(frozendict.fromkeys('abc'),
+                         frozendict(a=None, b=None, c=None))
+
+        # Subclass which overrides the constructor
+        created = frozendict(x=1)
+        class FrozenDictSubclass(frozendict):
+            def __new__(cls, *args, **kwargs):
+                if args or kwargs:
+                    return super().__new__(cls, *args, **kwargs)
+                else:
+                    return created
+
+        fd = FrozenDictSubclass.fromkeys("abc")
+        self.assertEqual(fd, frozendict(x=1, a=None, b=None, c=None))
+        self.assertEqual(type(fd), FrozenDictSubclass)
+        self.assertEqual(created, frozendict(x=1))
+
+        fd = FrozenDictSubclass.fromkeys(frozendict(y=2))
+        self.assertEqual(fd, frozendict(x=1, y=None))
+        self.assertEqual(type(fd), FrozenDictSubclass)
+        self.assertEqual(created, frozendict(x=1))
+
+        # Dict subclass with a constructor which returns a frozendict
+        # by default
+        class DictSubclass(dict):
+            def __new__(cls, *args, **kwargs):
+                if args or kwargs:
+                    return super().__new__(cls, *args, **kwargs)
+                else:
+                    return created
+
+        fd = DictSubclass.fromkeys("abc")
+        self.assertEqual(fd, frozendict(x=1, a=None, b=None, c=None))
+        self.assertEqual(type(fd), DictSubclass)
+        self.assertEqual(created, frozendict(x=1))
+
+        # Subclass which doesn't override the constructor
+        class FrozenDictSubclass2(frozendict):
+            pass
+
+        fd = FrozenDictSubclass2.fromkeys("abc")
+        self.assertEqual(fd, frozendict(a=None, b=None, c=None))
+        self.assertEqual(type(fd), FrozenDictSubclass2)
+
+    def test_pickle(self):
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            for fd in (
+                frozendict(),
+                frozendict(x=1, y=2),
+                FrozenDict(x=1, y=2),
+                FrozenDictSlots(x=1, y=2),
+            ):
+                if type(fd) == FrozenDict:
+                    fd.attr = 123
+                if type(fd) == FrozenDictSlots:
+                    fd.slot_attr = 456
+                with self.subTest(fd=fd, proto=proto):
+                    if proto >= 2:
+                        p = pickle.dumps(fd, proto)
+                        fd2 = pickle.loads(p)
+                        self.assertEqual(fd2, fd)
+                        self.assertEqual(type(fd2), type(fd))
+                        if type(fd) == FrozenDict:
+                            self.assertEqual(fd2.attr, 123)
+                        if type(fd) == FrozenDictSlots:
+                            self.assertEqual(fd2.slot_attr, 456)
+                    else:
+                        # protocol 0 and 1 don't support frozendict
+                        with self.assertRaises(TypeError):
+                            pickle.dumps(fd, proto)
+
+    def test_pickle_iter(self):
+        fd = frozendict(c=1, b=2, a=3, d=4, e=5, f=6)
+        for method_name in (None, 'keys', 'values', 'items'):
+            if method_name is not None:
+                meth = getattr(fd, method_name)
+            else:
+                meth = lambda: fd
+            expected = list(meth())[1:]
+            for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+                with self.subTest(method_name=method_name, protocol=proto):
+                    it = iter(meth())
+                    next(it)
+                    p = pickle.dumps(it, proto)
+                    unpickled = pickle.loads(p)
+                    self.assertEqual(list(unpickled), expected)
+                    self.assertEqual(list(it), expected)
+
+    def test_unhashable_key(self):
+        d = frozendict(a=1)
+        key = [1, 2, 3]
+
+        def check_unhashable_key():
+            msg = "cannot use 'list' as a frozendict key (unhashable type: 'list')"
+            return self.assertRaisesRegex(TypeError, re.escape(msg))
+
+        with check_unhashable_key():
+            key in d
+        with check_unhashable_key():
+            d[key]
+        with check_unhashable_key():
+            d.get(key)
+
+        # Only TypeError exception is overridden,
+        # other exceptions are left unchanged.
+        class HashError:
+            def __hash__(self):
+                raise KeyError('error')
+
+        key2 = HashError()
+        with self.assertRaises(KeyError):
+            key2 in d
+        with self.assertRaises(KeyError):
+            d[key2]
+        with self.assertRaises(KeyError):
+            d.get(key2)
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_dictcomps.py b/Lib/test/test_dictcomps.py
index fc7ebb0f5a6..26b56dac503 100644
--- a/Lib/test/test_dictcomps.py
+++ b/Lib/test/test_dictcomps.py
@@ -75,7 +75,6 @@ def test_local_visibility(self):
         self.assertEqual(actual, expected)
         self.assertEqual(v, "Local variable")
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_illegal_assignment(self):
         with self.assertRaisesRegex(SyntaxError, "cannot assign"):
             compile("{x: y for y, x in ((1, 2), (3, 4))} = 5", "<test>",
diff --git a/Lib/test/test_dis.py b/Lib/test/test_dis.py
index 190374fba8c..a103601a23a 100644
--- a/Lib/test/test_dis.py
+++ b/Lib/test/test_dis.py
@@ -56,7 +56,7 @@ def cm(cls, x):
               COMPARE_OP              72 (==)
               LOAD_FAST_BORROW         0 (self)
               STORE_ATTR               0 (x)
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """ % (_C.__init__.__code__.co_firstlineno, _C.__init__.__code__.co_firstlineno + 1,)
 
@@ -67,7 +67,7 @@ def cm(cls, x):
           COMPARE_OP              72 (==)
           LOAD_FAST_BORROW         0
           STORE_ATTR               0
-          LOAD_CONST               1
+          LOAD_COMMON_CONSTANT     7 (None)
           RETURN_VALUE
 """
 
@@ -79,7 +79,7 @@ def cm(cls, x):
               COMPARE_OP              72 (==)
               LOAD_FAST_BORROW         0 (cls)
               STORE_ATTR               0 (x)
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """ % (_C.cm.__code__.co_firstlineno, _C.cm.__code__.co_firstlineno + 2,)
 
@@ -90,7 +90,7 @@ def cm(cls, x):
               LOAD_SMALL_INT           1
               COMPARE_OP              72 (==)
               STORE_FAST               0 (x)
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """ % (_C.sm.__code__.co_firstlineno, _C.sm.__code__.co_firstlineno + 2,)
 
@@ -127,13 +127,13 @@ def _f(a):
 dis_f_with_offsets = """\
 %3d          0       RESUME                   0
 
-%3d          2       LOAD_GLOBAL              1 (print + NULL)
-            12       LOAD_FAST_BORROW         0 (a)
-            14       CALL                     1
-            22       POP_TOP
+%3d          4       LOAD_GLOBAL              1 (print + NULL)
+            14       LOAD_FAST_BORROW         0 (a)
+            16       CALL                     1
+            24       POP_TOP
 
-%3d         24       LOAD_SMALL_INT           1
-            26       RETURN_VALUE
+%3d         26       LOAD_SMALL_INT           1
+            28       RETURN_VALUE
 """ % (_f.__code__.co_firstlineno,
        _f.__code__.co_firstlineno + 1,
        _f.__code__.co_firstlineno + 2)
@@ -174,7 +174,7 @@ def bug708901():
 %3d           LOAD_SMALL_INT          10
 
 %3d           CALL                     2
-              GET_ITER
+              GET_ITER                 0
       L1:     FOR_ITER                 3 (to L2)
               STORE_FAST               0 (res)
 
@@ -182,7 +182,7 @@ def bug708901():
 
 %3d   L2:     END_FOR
               POP_ITER
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """ % (bug708901.__code__.co_firstlineno,
        bug708901.__code__.co_firstlineno + 1,
@@ -204,7 +204,6 @@ def bug1333982(x=[]):
               LOAD_CONST               1 (<code object <genexpr> at 0x..., file "%s", line %d>)
               MAKE_FUNCTION
               LOAD_FAST_BORROW         0 (x)
-              GET_ITER
               CALL                     0
 
 %3d           LOAD_SMALL_INT           1
@@ -230,7 +229,7 @@ def bug42562():
 
 dis_bug42562 = """\
           RESUME                   0
-          LOAD_CONST               0 (None)
+          LOAD_COMMON_CONSTANT     7 (None)
           RETURN_VALUE
 """
 
@@ -283,7 +282,7 @@ def wrap_func_w_kwargs():
               LOAD_CONST               1 (('c',))
               CALL_KW                  3
               POP_TOP
-              LOAD_CONST               2 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """ % (wrap_func_w_kwargs.__code__.co_firstlineno,
        wrap_func_w_kwargs.__code__.co_firstlineno + 1)
@@ -293,10 +292,10 @@ def wrap_func_w_kwargs():
 
   1           LOAD_SMALL_INT           0
               LOAD_CONST               1 (('*',))
-              IMPORT_NAME              0 (math)
+              IMPORT_NAME              2 (math + eager)
               CALL_INTRINSIC_1         2 (INTRINSIC_IMPORT_STAR)
               POP_TOP
-              LOAD_CONST               2 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """
 
@@ -323,7 +322,7 @@ def wrap_func_w_kwargs():
 
 %3d           LOAD_GLOBAL              0 (spam)
               POP_TOP
-              LOAD_CONST               0 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """
 
@@ -332,19 +331,19 @@ def wrap_func_w_kwargs():
 
 %4d           LOAD_GLOBAL              0 (spam)
                POP_TOP
-               LOAD_CONST               0 (None)
+               LOAD_COMMON_CONSTANT     7 (None)
                RETURN_VALUE
 """
 
 dis_module_expected_results = """\
 Disassembly of f:
   4           RESUME                   0
-              LOAD_CONST               0 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 
 Disassembly of g:
   5           RESUME                   0
-              LOAD_CONST               0 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 
 """
@@ -369,7 +368,7 @@ def wrap_func_w_kwargs():
               LOAD_SMALL_INT           1
               BINARY_OP                0 (+)
               STORE_NAME               0 (x)
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """
 
@@ -410,7 +409,7 @@ def wrap_func_w_kwargs():
                LOAD_SMALL_INT           0
                CALL                     1
                STORE_SUBSCR
-               LOAD_CONST               2 (None)
+               LOAD_COMMON_CONSTANT     7 (None)
                RETURN_VALUE
 """
 
@@ -428,7 +427,7 @@ def foo(a: int, b: str) -> str:
               MAKE_FUNCTION
               SET_FUNCTION_ATTRIBUTE  16 (annotate)
               STORE_NAME               0 (foo)
-              LOAD_CONST               2 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """
 
@@ -454,52 +453,53 @@ def foo(a: int, b: str) -> str:
 """
 
 dis_traceback = """\
-%4d           RESUME                   0
+%4d            RESUME                   0
 
-%4d           NOP
+%4d            NOP
 
-%4d   L1:     LOAD_SMALL_INT           1
-               LOAD_SMALL_INT           0
-           --> BINARY_OP               11 (/)
-               POP_TOP
+%4d    L1:     LOAD_SMALL_INT           1
+                LOAD_SMALL_INT           0
+            --> BINARY_OP               11 (/)
+                POP_TOP
 
-%4d   L2:     LOAD_FAST_CHECK          1 (tb)
-               RETURN_VALUE
+%4d    L2:     LOAD_FAST_CHECK          1 (tb)
+                RETURN_VALUE
 
-  --   L3:     PUSH_EXC_INFO
+  --    L3:     PUSH_EXC_INFO
 
-%4d           LOAD_GLOBAL              0 (Exception)
-               CHECK_EXC_MATCH
-               POP_JUMP_IF_FALSE       24 (to L7)
-               NOT_TAKEN
-               STORE_FAST               0 (e)
+%4d            LOAD_GLOBAL              0 (Exception)
+                CHECK_EXC_MATCH
+                POP_JUMP_IF_FALSE       24 (to L9)
+        L4:     NOT_TAKEN
+        L5:     STORE_FAST               0 (e)
 
-%4d   L4:     LOAD_FAST                0 (e)
-               LOAD_ATTR                2 (__traceback__)
-               STORE_FAST               1 (tb)
-       L5:     POP_EXCEPT
-               LOAD_CONST               1 (None)
-               STORE_FAST               0 (e)
-               DELETE_FAST              0 (e)
+%4d    L6:     LOAD_FAST                0 (e)
+                LOAD_ATTR                2 (__traceback__)
+                STORE_FAST               1 (tb)
+        L7:     POP_EXCEPT
+                LOAD_COMMON_CONSTANT     7 (None)
+                STORE_FAST               0 (e)
+                DELETE_FAST              0 (e)
 
-%4d           LOAD_FAST                1 (tb)
-               RETURN_VALUE
+%4d            LOAD_FAST                1 (tb)
+                RETURN_VALUE
 
-  --   L6:     LOAD_CONST               1 (None)
-               STORE_FAST               0 (e)
-               DELETE_FAST              0 (e)
-               RERAISE                  1
+  --    L8:     LOAD_COMMON_CONSTANT     7 (None)
+                STORE_FAST               0 (e)
+                DELETE_FAST              0 (e)
+                RERAISE                  1
 
-%4d   L7:     RERAISE                  0
+%4d    L9:     RERAISE                  0
 
-  --   L8:     COPY                     3
-               POP_EXCEPT
-               RERAISE                  1
+  --   L10:     COPY                     3
+                POP_EXCEPT
+                RERAISE                  1
 ExceptionTable:
   L1 to L2 -> L3 [0]
-  L3 to L4 -> L8 [1] lasti
-  L4 to L5 -> L6 [1] lasti
-  L6 to L8 -> L8 [1] lasti
+  L3 to L4 -> L10 [1] lasti
+  L5 to L6 -> L10 [1] lasti
+  L6 to L7 -> L8 [1] lasti
+  L8 to L10 -> L10 [1] lasti
 """ % (TRACEBACK_CODE.co_firstlineno,
        TRACEBACK_CODE.co_firstlineno + 1,
        TRACEBACK_CODE.co_firstlineno + 2,
@@ -554,40 +554,41 @@ def _with(c):
 %4d           LOAD_SMALL_INT           1
                STORE_FAST               1 (x)
 
-%4d   L2:     LOAD_CONST               1 (None)
-               LOAD_CONST               1 (None)
-               LOAD_CONST               1 (None)
+%4d   L2:     LOAD_COMMON_CONSTANT     7 (None)
+               LOAD_COMMON_CONSTANT     7 (None)
+               LOAD_COMMON_CONSTANT     7 (None)
                CALL                     3
                POP_TOP
 
 %4d           LOAD_SMALL_INT           2
                STORE_FAST               2 (y)
-               LOAD_CONST               1 (None)
+               LOAD_COMMON_CONSTANT     7 (None)
                RETURN_VALUE
 
 %4d   L3:     PUSH_EXC_INFO
                WITH_EXCEPT_START
                TO_BOOL
-               POP_JUMP_IF_TRUE         2 (to L4)
-               NOT_TAKEN
-               RERAISE                  2
-       L4:     POP_TOP
-       L5:     POP_EXCEPT
+               POP_JUMP_IF_TRUE         2 (to L6)
+       L4:     NOT_TAKEN
+       L5:     RERAISE                  2
+       L6:     POP_TOP
+       L7:     POP_EXCEPT
                POP_TOP
                POP_TOP
                POP_TOP
 
 %4d           LOAD_SMALL_INT           2
                STORE_FAST               2 (y)
-               LOAD_CONST               1 (None)
+               LOAD_COMMON_CONSTANT     7 (None)
                RETURN_VALUE
 
-  --   L6:     COPY                     3
+  --   L8:     COPY                     3
                POP_EXCEPT
                RERAISE                  1
 ExceptionTable:
   L1 to L2 -> L3 [2] lasti
-  L3 to L5 -> L6 [4] lasti
+  L3 to L4 -> L8 [4] lasti
+  L5 to L7 -> L8 [4] lasti
 """ % (_with.__code__.co_firstlineno,
        _with.__code__.co_firstlineno + 1,
        _with.__code__.co_firstlineno + 2,
@@ -615,47 +616,50 @@ async def _asyncwith(c):
                 LOAD_SPECIAL             2 (__aenter__)
                 CALL                     0
                 GET_AWAITABLE            1
-                LOAD_CONST               0 (None)
-        L2:     SEND                     3 (to L5)
+                PUSH_NULL
+                LOAD_COMMON_CONSTANT     7 (None)
+        L2:     SEND                     4 (to L5)
         L3:     YIELD_VALUE              1
         L4:     RESUME                   3
-                JUMP_BACKWARD_NO_INTERRUPT 5 (to L2)
+                JUMP_BACKWARD_NO_INTERRUPT 6 (to L2)
         L5:     END_SEND
         L6:     POP_TOP
 
 %4d            LOAD_SMALL_INT           1
                 STORE_FAST               1 (x)
 
-%4d    L7:     LOAD_CONST               0 (None)
-                LOAD_CONST               0 (None)
-                LOAD_CONST               0 (None)
+%4d    L7:     LOAD_COMMON_CONSTANT     7 (None)
+                LOAD_COMMON_CONSTANT     7 (None)
+                LOAD_COMMON_CONSTANT     7 (None)
                 CALL                     3
                 GET_AWAITABLE            2
-                LOAD_CONST               0 (None)
-        L8:     SEND                     3 (to L11)
+                PUSH_NULL
+                LOAD_COMMON_CONSTANT     7 (None)
+        L8:     SEND                     4 (to L11)
         L9:     YIELD_VALUE              1
        L10:     RESUME                   3
-                JUMP_BACKWARD_NO_INTERRUPT 5 (to L8)
+                JUMP_BACKWARD_NO_INTERRUPT 6 (to L8)
        L11:     END_SEND
                 POP_TOP
 
 %4d            LOAD_SMALL_INT           2
                 STORE_FAST               2 (y)
-                LOAD_CONST               0 (None)
+                LOAD_COMMON_CONSTANT     7 (None)
                 RETURN_VALUE
 
 %4d   L12:     CLEANUP_THROW
-       L13:     JUMP_BACKWARD_NO_INTERRUPT 26 (to L5)
+       L13:     JUMP_BACKWARD_NO_INTERRUPT 28 (to L5)
        L14:     CLEANUP_THROW
        L15:     JUMP_BACKWARD_NO_INTERRUPT 10 (to L11)
        L16:     PUSH_EXC_INFO
                 WITH_EXCEPT_START
                 GET_AWAITABLE            2
-                LOAD_CONST               0 (None)
-       L17:     SEND                     4 (to L21)
+                PUSH_NULL
+                LOAD_COMMON_CONSTANT     7 (None)
+       L17:     SEND                     5 (to L21)
        L18:     YIELD_VALUE              1
        L19:     RESUME                   3
-                JUMP_BACKWARD_NO_INTERRUPT 5 (to L17)
+                JUMP_BACKWARD_NO_INTERRUPT 6 (to L17)
        L20:     CLEANUP_THROW
        L21:     END_SEND
                 TO_BOOL
@@ -670,7 +674,7 @@ async def _asyncwith(c):
 
 %4d            LOAD_SMALL_INT           2
                 STORE_FAST               2 (y)
-                LOAD_CONST               0 (None)
+                LOAD_COMMON_CONSTANT     7 (None)
                 RETURN_VALUE
 
   --   L26:     COPY                     3
@@ -680,15 +684,15 @@ async def _asyncwith(c):
                 RERAISE                  1
 ExceptionTable:
   L1 to L3 -> L27 [0] lasti
-  L3 to L4 -> L12 [4]
+  L3 to L4 -> L12 [5]
   L4 to L6 -> L27 [0] lasti
   L6 to L7 -> L16 [2] lasti
   L7 to L9 -> L27 [0] lasti
-  L9 to L10 -> L14 [2]
+  L9 to L10 -> L14 [3]
   L10 to L13 -> L27 [0] lasti
   L14 to L15 -> L27 [0] lasti
   L16 to L18 -> L26 [4] lasti
-  L18 to L19 -> L20 [7]
+  L18 to L19 -> L20 [8]
   L19 to L22 -> L26 [4] lasti
   L23 to L25 -> L26 [4] lasti
   L25 to L27 -> L27 [0] lasti
@@ -826,14 +830,35 @@ def foo(x):
 
 %4d           RESUME                   0
 
-%4d           LOAD_GLOBAL              1 (list + NULL)
+%4d           LOAD_GLOBAL              0 (list)
+               COPY                     1
+               LOAD_COMMON_CONSTANT     5 (list)
+               IS_OP                    0 (is)
+               POP_JUMP_IF_FALSE       22 (to L3)
+               NOT_TAKEN
+               POP_TOP
+               BUILD_LIST               0
+               LOAD_FAST_BORROW         0 (x)
+               BUILD_TUPLE              1
+               LOAD_CONST               %d (<code object <genexpr> at 0x..., file "%s", line %d>)
+               MAKE_FUNCTION
+               SET_FUNCTION_ATTRIBUTE   8 (closure)
+               LOAD_DEREF               1 (y)
+               CALL                     0
+               PUSH_NULL
+       L1:     FOR_ITER                 3 (to L2)
+               LIST_APPEND              3
+               JUMP_BACKWARD            5 (to L1)
+       L2:     END_FOR
+               POP_ITER
+               RETURN_VALUE
+       L3:     PUSH_NULL
                LOAD_FAST_BORROW         0 (x)
                BUILD_TUPLE              1
                LOAD_CONST               1 (<code object <genexpr> at 0x..., file "%s", line %d>)
                MAKE_FUNCTION
                SET_FUNCTION_ATTRIBUTE   8 (closure)
                LOAD_DEREF               1 (y)
-               GET_ITER
                CALL                     0
                CALL                     1
                RETURN_VALUE
@@ -842,6 +867,9 @@ def foo(x):
        _h.__code__.co_firstlineno + 1,
        _h.__code__.co_firstlineno + 1,
        _h.__code__.co_firstlineno + 3,
+       1 if __debug__ else 0,
+       __file__,
+       _h.__code__.co_firstlineno + 3,
        __file__,
        _h.__code__.co_firstlineno + 3,
 )
@@ -849,29 +877,31 @@ def foo(x):
 dis_nested_2 = """%s
 Disassembly of <code object <genexpr> at 0x..., file "%s", line %d>:
   --           COPY_FREE_VARS           1
+               RESUME                   4
 
-%4d           RETURN_GENERATOR
+%4d           LOAD_FAST                0 (.0)
+               GET_ITER                 0
+               RETURN_GENERATOR
                POP_TOP
        L1:     RESUME                   0
-               LOAD_FAST                0 (.0)
-       L2:     FOR_ITER                14 (to L3)
+       L2:     FOR_ITER                15 (to L3)
                STORE_FAST               1 (z)
                LOAD_DEREF               2 (x)
                LOAD_FAST_BORROW         1 (z)
                BINARY_OP                0 (+)
                YIELD_VALUE              0
-               RESUME                   5
+               RESUME                   9
                POP_TOP
-               JUMP_BACKWARD           16 (to L2)
+               JUMP_BACKWARD           17 (to L2)
        L3:     END_FOR
                POP_ITER
-               LOAD_CONST               0 (None)
+               LOAD_COMMON_CONSTANT     7 (None)
                RETURN_VALUE
 
   --   L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
                RERAISE                  1
 ExceptionTable:
-  L1 to L4 -> L4 [0] lasti
+  L1 to L4 -> L4 [2] lasti
 """ % (dis_nested_1,
        __file__,
        _h.__code__.co_firstlineno + 3,
@@ -883,7 +913,7 @@ def load_test(x, y=0):
     return a, b
 
 dis_load_test_quickened_code = """\
-%3d           RESUME_CHECK             0
+%3d           RESUME_CHECK{: <6}       0
 
 %3d           LOAD_FAST_LOAD_FAST      1 (x, y)
               STORE_FAST_STORE_FAST   50 (b, a)
@@ -900,14 +930,14 @@ def loop_test():
         load_test(i)
 
 dis_loop_test_quickened_code = """\
-%3d           RESUME_CHECK             0
+%3d           RESUME_CHECK{: <6}       0
 
 %3d           BUILD_LIST               0
-              LOAD_CONST_MORTAL        2 ((1, 2, 3))
+              LOAD_CONST               1 ((1, 2, 3))
               LIST_EXTEND              1
               LOAD_SMALL_INT           3
               BINARY_OP                5 (*)
-              GET_ITER
+              GET_ITER_VIRTUAL         0
       L1:     FOR_ITER_LIST           14 (to L2)
               STORE_FAST               0 (i)
 
@@ -919,7 +949,7 @@ def loop_test():
 
 %3d   L2:     END_FOR
               POP_ITER
-              LOAD_CONST_IMMORTAL      1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """ % (loop_test.__code__.co_firstlineno,
        loop_test.__code__.co_firstlineno + 1,
@@ -937,7 +967,7 @@ def extended_arg_quick():
               UNPACK_EX              256
               POP_TOP
               STORE_FAST               0 (_)
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 """% (extended_arg_quick.__code__.co_firstlineno,
       extended_arg_quick.__code__.co_firstlineno + 1,)
@@ -1009,6 +1039,7 @@ def test_widths(self):
         long_opcodes = set(['JUMP_BACKWARD_NO_INTERRUPT',
                             'LOAD_FAST_BORROW_LOAD_FAST_BORROW',
                             'INSTRUMENTED_CALL_FUNCTION_EX',
+                            'YIELD_FROM_CORO_CHECK',
                             'ANNOTATIONS_PLACEHOLDER'])
         for op, opname in enumerate(dis.opname):
             if opname in long_opcodes or opname.startswith("INSTRUMENTED"):
@@ -1053,7 +1084,7 @@ def test_dis_with_some_positions(self):
             '',
             '2:3-3:15             NOP',
             '',
-            '3:11-3:15            LOAD_CONST               0 (None)',
+            '3:11-3:15            LOAD_COMMON_CONSTANT     7 (None)',
             '3:11-3:15            RETURN_VALUE',
             '',
             '  --         L1:     PUSH_EXC_INFO',
@@ -1084,7 +1115,7 @@ def test_dis_with_linenos_but_no_columns(self):
             '',
             '2:5-2:6            LOAD_SMALL_INT           1',
             '2:?-2:?            STORE_FAST               0 (x)',
-            '2:?-2:?            LOAD_CONST               1 (None)',
+            '2:?-2:?            LOAD_COMMON_CONSTANT     7 (None)',
             '2:?-2:?            RETURN_VALUE',
             '',
         ])
@@ -1097,7 +1128,7 @@ def f():
         f.__code__ = f.__code__.replace(co_linetable=b'')
         expect = '\n'.join([
             '          RESUME                   0',
-            '          LOAD_CONST               0 (None)',
+            '          LOAD_COMMON_CONSTANT     7 (None)',
             '          RETURN_VALUE',
             '',
         ])
@@ -1297,28 +1328,32 @@ def code_quicken(f):
     def test_super_instructions(self):
         self.code_quicken(lambda: load_test(0, 0))
         got = self.get_disassembly(load_test, adaptive=True)
-        self.do_disassembly_compare(got, dis_load_test_quickened_code)
+        jit = sys._jit.is_enabled()
+        expected = dis_load_test_quickened_code.format("_JIT" if jit else "")
+        self.do_disassembly_compare(got, expected)
 
     @cpython_only
     @requires_specialization
     def test_load_attr_specialize(self):
         load_attr_quicken = """\
-  0           RESUME_CHECK             0
+  0           RESUME_CHECK{: <6}       0
 
-  1           LOAD_CONST_IMMORTAL      0 ('a')
+  1           LOAD_CONST               0 ('a')
               LOAD_ATTR_SLOT           0 (__class__)
               RETURN_VALUE
 """
         co = compile("'a'.__class__", "", "eval")
         self.code_quicken(lambda: exec(co, {}, {}))
         got = self.get_disassembly(co, adaptive=True)
-        self.do_disassembly_compare(got, load_attr_quicken)
+        jit = sys._jit.is_enabled()
+        expected = load_attr_quicken.format("_JIT" if jit else "")
+        self.do_disassembly_compare(got, expected)
 
     @cpython_only
     @requires_specialization
     def test_call_specialize(self):
         call_quicken = """\
-  0           RESUME_CHECK             0
+  0           RESUME_CHECK{: <6}       0
 
   1           LOAD_NAME                0 (str)
               PUSH_NULL
@@ -1329,7 +1364,9 @@ def test_call_specialize(self):
         co = compile("str(1)", "", "eval")
         self.code_quicken(lambda: exec(co, {}, {}))
         got = self.get_disassembly(co, adaptive=True)
-        self.do_disassembly_compare(got, call_quicken)
+        jit = sys._jit.is_enabled()
+        expected = call_quicken.format("_JIT" if jit else "")
+        self.do_disassembly_compare(got, expected)
 
     @cpython_only
     @requires_specialization
@@ -1338,7 +1375,9 @@ def test_loop_quicken(self):
         self.code_quicken(loop_test)
         got = self.get_disassembly(loop_test, adaptive=True)
         jit = sys._jit.is_enabled()
-        expected = dis_loop_test_quickened_code.format("JIT" if jit else "NO_JIT")
+        resume_str = "_JIT" if jit else ""
+        jit_str = "JIT " if jit else "NO_JIT"
+        expected = dis_loop_test_quickened_code.format(resume_str, jit_str)
         self.do_disassembly_compare(got, expected)
 
     @cpython_only
@@ -1405,7 +1444,7 @@ def test_show_caches(self):
                     caches = list(self.get_cached_values(quickened, adaptive))
                     for cache in caches:
                         self.assertRegex(cache, pattern)
-                    total_caches = 21
+                    total_caches = 23
                     empty_caches = 7
                     self.assertEqual(caches.count(""), empty_caches)
                     self.assertEqual(len(caches), total_caches)
@@ -1467,7 +1506,7 @@ def get_disassembly(self, func, lasti=-1, wrapper=True, **kwargs):
 Kw-only arguments: 0
 Number of locals:  1
 Stack size:        \\d+
-Flags:             OPTIMIZED, NEWLOCALS, HAS_DOCSTRING
+Flags:             OPTIMIZED, NEWLOCALS(, HAS_DOCSTRING)?
 Constants:
    {code_info_consts}
 Names:
@@ -1494,7 +1533,6 @@ def f(c=c):
 Flags:             OPTIMIZED, NEWLOCALS, VARARGS, VARKEYWORDS, GENERATOR
 Constants:
    0: <code object f at (.*), file "(.*)", line (.*)>
-   1: None
 Variable names:
    0: a
    1: b
@@ -1566,7 +1604,6 @@ def f(c=c):
 Flags:             0x0
 Constants:
    0: 1
-   1: None
 Names:
    0: x"""
 
@@ -1601,7 +1638,6 @@ async def async_def():
 Flags:             OPTIMIZED, NEWLOCALS, COROUTINE
 Constants:
    0: 1
-   1: None
 Names:
    0: b
    1: c
@@ -1750,209 +1786,210 @@ def _prepare_test_cases():
 expected_opinfo_outer = [
   make_inst(opname='MAKE_CELL', arg=0, argval='a', argrepr='a', offset=0, start_offset=0, starts_line=True, line_number=None),
   make_inst(opname='MAKE_CELL', arg=1, argval='b', argrepr='b', offset=2, start_offset=2, starts_line=False, line_number=None),
-  make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=4, start_offset=4, starts_line=True, line_number=1),
-  make_inst(opname='LOAD_CONST', arg=4, argval=(3, 4), argrepr='(3, 4)', offset=6, start_offset=6, starts_line=True, line_number=2),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='a', argrepr='a', offset=8, start_offset=8, starts_line=False, line_number=2),
-  make_inst(opname='LOAD_FAST_BORROW', arg=1, argval='b', argrepr='b', offset=10, start_offset=10, starts_line=False, line_number=2),
-  make_inst(opname='BUILD_TUPLE', arg=2, argval=2, argrepr='', offset=12, start_offset=12, starts_line=False, line_number=2),
-  make_inst(opname='LOAD_CONST', arg=1, argval=code_object_f, argrepr=repr(code_object_f), offset=14, start_offset=14, starts_line=False, line_number=2),
-  make_inst(opname='MAKE_FUNCTION', arg=None, argval=None, argrepr='', offset=16, start_offset=16, starts_line=False, line_number=2),
-  make_inst(opname='SET_FUNCTION_ATTRIBUTE', arg=8, argval=8, argrepr='closure', offset=18, start_offset=18, starts_line=False, line_number=2),
-  make_inst(opname='SET_FUNCTION_ATTRIBUTE', arg=1, argval=1, argrepr='defaults', offset=20, start_offset=20, starts_line=False, line_number=2),
-  make_inst(opname='STORE_FAST', arg=2, argval='f', argrepr='f', offset=22, start_offset=22, starts_line=False, line_number=2),
-  make_inst(opname='LOAD_GLOBAL', arg=1, argval='print', argrepr='print + NULL', offset=24, start_offset=24, starts_line=True, line_number=7, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_DEREF', arg=0, argval='a', argrepr='a', offset=34, start_offset=34, starts_line=False, line_number=7),
-  make_inst(opname='LOAD_DEREF', arg=1, argval='b', argrepr='b', offset=36, start_offset=36, starts_line=False, line_number=7),
-  make_inst(opname='LOAD_CONST', arg=2, argval='', argrepr="''", offset=38, start_offset=38, starts_line=False, line_number=7),
-  make_inst(opname='LOAD_SMALL_INT', arg=1, argval=1, argrepr='', offset=40, start_offset=40, starts_line=False, line_number=7),
-  make_inst(opname='BUILD_LIST', arg=0, argval=0, argrepr='', offset=42, start_offset=42, starts_line=False, line_number=7),
-  make_inst(opname='BUILD_MAP', arg=0, argval=0, argrepr='', offset=44, start_offset=44, starts_line=False, line_number=7),
-  make_inst(opname='LOAD_CONST', arg=3, argval='Hello world!', argrepr="'Hello world!'", offset=46, start_offset=46, starts_line=False, line_number=7),
-  make_inst(opname='CALL', arg=7, argval=7, argrepr='', offset=48, start_offset=48, starts_line=False, line_number=7, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=56, start_offset=56, starts_line=False, line_number=7),
-  make_inst(opname='LOAD_FAST_BORROW', arg=2, argval='f', argrepr='f', offset=58, start_offset=58, starts_line=True, line_number=8),
-  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=60, start_offset=60, starts_line=False, line_number=8),
+  make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=4, start_offset=4, starts_line=True, line_number=1, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_CONST', arg=3, argval=(3, 4), argrepr='(3, 4)', offset=8, start_offset=8, starts_line=True, line_number=2),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='a', argrepr='a', offset=10, start_offset=10, starts_line=False, line_number=2),
+  make_inst(opname='LOAD_FAST_BORROW', arg=1, argval='b', argrepr='b', offset=12, start_offset=12, starts_line=False, line_number=2),
+  make_inst(opname='BUILD_TUPLE', arg=2, argval=2, argrepr='', offset=14, start_offset=14, starts_line=False, line_number=2),
+  make_inst(opname='LOAD_CONST', arg=1, argval=code_object_f, argrepr=repr(code_object_f), offset=16, start_offset=16, starts_line=False, line_number=2),
+  make_inst(opname='MAKE_FUNCTION', arg=None, argval=None, argrepr='', offset=18, start_offset=18, starts_line=False, line_number=2),
+  make_inst(opname='SET_FUNCTION_ATTRIBUTE', arg=8, argval=8, argrepr='closure', offset=20, start_offset=20, starts_line=False, line_number=2),
+  make_inst(opname='SET_FUNCTION_ATTRIBUTE', arg=1, argval=1, argrepr='defaults', offset=22, start_offset=22, starts_line=False, line_number=2),
+  make_inst(opname='STORE_FAST', arg=2, argval='f', argrepr='f', offset=24, start_offset=24, starts_line=False, line_number=2),
+  make_inst(opname='LOAD_GLOBAL', arg=1, argval='print', argrepr='print + NULL', offset=26, start_offset=26, starts_line=True, line_number=7, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_DEREF', arg=0, argval='a', argrepr='a', offset=36, start_offset=36, starts_line=False, line_number=7),
+  make_inst(opname='LOAD_DEREF', arg=1, argval='b', argrepr='b', offset=38, start_offset=38, starts_line=False, line_number=7),
+  make_inst(opname='LOAD_COMMON_CONSTANT', arg=8, argval='', argrepr="''", offset=40, start_offset=40, starts_line=False, line_number=7),
+  make_inst(opname='LOAD_SMALL_INT', arg=1, argval=1, argrepr='', offset=42, start_offset=42, starts_line=False, line_number=7),
+  make_inst(opname='BUILD_LIST', arg=0, argval=0, argrepr='', offset=44, start_offset=44, starts_line=False, line_number=7),
+  make_inst(opname='BUILD_MAP', arg=0, argval=0, argrepr='', offset=46, start_offset=46, starts_line=False, line_number=7),
+  make_inst(opname='LOAD_CONST', arg=2, argval='Hello world!', argrepr="'Hello world!'", offset=48, start_offset=48, starts_line=False, line_number=7),
+  make_inst(opname='CALL', arg=7, argval=7, argrepr='', offset=50, start_offset=50, starts_line=False, line_number=7, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=58, start_offset=58, starts_line=False, line_number=7),
+  make_inst(opname='LOAD_FAST_BORROW', arg=2, argval='f', argrepr='f', offset=60, start_offset=60, starts_line=True, line_number=8),
+  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=62, start_offset=62, starts_line=False, line_number=8),
 ]
 
 expected_opinfo_f = [
   make_inst(opname='COPY_FREE_VARS', arg=2, argval=2, argrepr='', offset=0, start_offset=0, starts_line=True, line_number=None),
   make_inst(opname='MAKE_CELL', arg=0, argval='c', argrepr='c', offset=2, start_offset=2, starts_line=False, line_number=None),
   make_inst(opname='MAKE_CELL', arg=1, argval='d', argrepr='d', offset=4, start_offset=4, starts_line=False, line_number=None),
-  make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=6, start_offset=6, starts_line=True, line_number=2),
-  make_inst(opname='LOAD_CONST', arg=2, argval=(5, 6), argrepr='(5, 6)', offset=8, start_offset=8, starts_line=True, line_number=3),
-  make_inst(opname='LOAD_FAST_BORROW', arg=3, argval='a', argrepr='a', offset=10, start_offset=10, starts_line=False, line_number=3),
-  make_inst(opname='LOAD_FAST_BORROW', arg=4, argval='b', argrepr='b', offset=12, start_offset=12, starts_line=False, line_number=3),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='c', argrepr='c', offset=14, start_offset=14, starts_line=False, line_number=3),
-  make_inst(opname='LOAD_FAST_BORROW', arg=1, argval='d', argrepr='d', offset=16, start_offset=16, starts_line=False, line_number=3),
-  make_inst(opname='BUILD_TUPLE', arg=4, argval=4, argrepr='', offset=18, start_offset=18, starts_line=False, line_number=3),
-  make_inst(opname='LOAD_CONST', arg=1, argval=code_object_inner, argrepr=repr(code_object_inner), offset=20, start_offset=20, starts_line=False, line_number=3),
-  make_inst(opname='MAKE_FUNCTION', arg=None, argval=None, argrepr='', offset=22, start_offset=22, starts_line=False, line_number=3),
-  make_inst(opname='SET_FUNCTION_ATTRIBUTE', arg=8, argval=8, argrepr='closure', offset=24, start_offset=24, starts_line=False, line_number=3),
-  make_inst(opname='SET_FUNCTION_ATTRIBUTE', arg=1, argval=1, argrepr='defaults', offset=26, start_offset=26, starts_line=False, line_number=3),
-  make_inst(opname='STORE_FAST', arg=2, argval='inner', argrepr='inner', offset=28, start_offset=28, starts_line=False, line_number=3),
-  make_inst(opname='LOAD_GLOBAL', arg=1, argval='print', argrepr='print + NULL', offset=30, start_offset=30, starts_line=True, line_number=5, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_DEREF', arg=3, argval='a', argrepr='a', offset=40, start_offset=40, starts_line=False, line_number=5),
-  make_inst(opname='LOAD_DEREF', arg=4, argval='b', argrepr='b', offset=42, start_offset=42, starts_line=False, line_number=5),
-  make_inst(opname='LOAD_DEREF', arg=0, argval='c', argrepr='c', offset=44, start_offset=44, starts_line=False, line_number=5),
-  make_inst(opname='LOAD_DEREF', arg=1, argval='d', argrepr='d', offset=46, start_offset=46, starts_line=False, line_number=5),
-  make_inst(opname='CALL', arg=4, argval=4, argrepr='', offset=48, start_offset=48, starts_line=False, line_number=5, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=56, start_offset=56, starts_line=False, line_number=5),
-  make_inst(opname='LOAD_FAST_BORROW', arg=2, argval='inner', argrepr='inner', offset=58, start_offset=58, starts_line=True, line_number=6),
-  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=60, start_offset=60, starts_line=False, line_number=6),
+  make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=6, start_offset=6, starts_line=True, line_number=2, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_CONST', arg=2, argval=(5, 6), argrepr='(5, 6)', offset=10, start_offset=10, starts_line=True, line_number=3),
+  make_inst(opname='LOAD_FAST_BORROW', arg=3, argval='a', argrepr='a', offset=12, start_offset=12, starts_line=False, line_number=3),
+  make_inst(opname='LOAD_FAST_BORROW', arg=4, argval='b', argrepr='b', offset=14, start_offset=14, starts_line=False, line_number=3),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='c', argrepr='c', offset=16, start_offset=16, starts_line=False, line_number=3),
+  make_inst(opname='LOAD_FAST_BORROW', arg=1, argval='d', argrepr='d', offset=18, start_offset=18, starts_line=False, line_number=3),
+  make_inst(opname='BUILD_TUPLE', arg=4, argval=4, argrepr='', offset=20, start_offset=20, starts_line=False, line_number=3),
+  make_inst(opname='LOAD_CONST', arg=1, argval=code_object_inner, argrepr=repr(code_object_inner), offset=22, start_offset=22, starts_line=False, line_number=3),
+  make_inst(opname='MAKE_FUNCTION', arg=None, argval=None, argrepr='', offset=24, start_offset=24, starts_line=False, line_number=3),
+  make_inst(opname='SET_FUNCTION_ATTRIBUTE', arg=8, argval=8, argrepr='closure', offset=26, start_offset=26, starts_line=False, line_number=3),
+  make_inst(opname='SET_FUNCTION_ATTRIBUTE', arg=1, argval=1, argrepr='defaults', offset=28, start_offset=28, starts_line=False, line_number=3),
+  make_inst(opname='STORE_FAST', arg=2, argval='inner', argrepr='inner', offset=30, start_offset=30, starts_line=False, line_number=3),
+  make_inst(opname='LOAD_GLOBAL', arg=1, argval='print', argrepr='print + NULL', offset=32, start_offset=32, starts_line=True, line_number=5, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_DEREF', arg=3, argval='a', argrepr='a', offset=42, start_offset=42, starts_line=False, line_number=5),
+  make_inst(opname='LOAD_DEREF', arg=4, argval='b', argrepr='b', offset=44, start_offset=44, starts_line=False, line_number=5),
+  make_inst(opname='LOAD_DEREF', arg=0, argval='c', argrepr='c', offset=46, start_offset=46, starts_line=False, line_number=5),
+  make_inst(opname='LOAD_DEREF', arg=1, argval='d', argrepr='d', offset=48, start_offset=48, starts_line=False, line_number=5),
+  make_inst(opname='CALL', arg=4, argval=4, argrepr='', offset=50, start_offset=50, starts_line=False, line_number=5, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=58, start_offset=58, starts_line=False, line_number=5),
+  make_inst(opname='LOAD_FAST_BORROW', arg=2, argval='inner', argrepr='inner', offset=60, start_offset=60, starts_line=True, line_number=6),
+  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=62, start_offset=62, starts_line=False, line_number=6),
 ]
 
 expected_opinfo_inner = [
   make_inst(opname='COPY_FREE_VARS', arg=4, argval=4, argrepr='', offset=0, start_offset=0, starts_line=True, line_number=None),
-  make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=2, start_offset=2, starts_line=True, line_number=3),
-  make_inst(opname='LOAD_GLOBAL', arg=1, argval='print', argrepr='print + NULL', offset=4, start_offset=4, starts_line=True, line_number=4, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_DEREF', arg=2, argval='a', argrepr='a', offset=14, start_offset=14, starts_line=False, line_number=4),
-  make_inst(opname='LOAD_DEREF', arg=3, argval='b', argrepr='b', offset=16, start_offset=16, starts_line=False, line_number=4),
-  make_inst(opname='LOAD_DEREF', arg=4, argval='c', argrepr='c', offset=18, start_offset=18, starts_line=False, line_number=4),
-  make_inst(opname='LOAD_DEREF', arg=5, argval='d', argrepr='d', offset=20, start_offset=20, starts_line=False, line_number=4),
-  make_inst(opname='LOAD_FAST_BORROW_LOAD_FAST_BORROW', arg=1, argval=('e', 'f'), argrepr='e, f', offset=22, start_offset=22, starts_line=False, line_number=4),
-  make_inst(opname='CALL', arg=6, argval=6, argrepr='', offset=24, start_offset=24, starts_line=False, line_number=4, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=32, start_offset=32, starts_line=False, line_number=4),
-  make_inst(opname='LOAD_CONST', arg=0, argval=None, argrepr='None', offset=34, start_offset=34, starts_line=False, line_number=4),
-  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=36, start_offset=36, starts_line=False, line_number=4),
+  make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=2, start_offset=2, starts_line=True, line_number=3, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_GLOBAL', arg=1, argval='print', argrepr='print + NULL', offset=6, start_offset=6, starts_line=True, line_number=4, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_DEREF', arg=2, argval='a', argrepr='a', offset=16, start_offset=16, starts_line=False, line_number=4),
+  make_inst(opname='LOAD_DEREF', arg=3, argval='b', argrepr='b', offset=18, start_offset=18, starts_line=False, line_number=4),
+  make_inst(opname='LOAD_DEREF', arg=4, argval='c', argrepr='c', offset=20, start_offset=20, starts_line=False, line_number=4),
+  make_inst(opname='LOAD_DEREF', arg=5, argval='d', argrepr='d', offset=22, start_offset=22, starts_line=False, line_number=4),
+  make_inst(opname='LOAD_FAST_BORROW_LOAD_FAST_BORROW', arg=1, argval=('e', 'f'), argrepr='e, f', offset=24, start_offset=24, starts_line=False, line_number=4),
+  make_inst(opname='CALL', arg=6, argval=6, argrepr='', offset=26, start_offset=26, starts_line=False, line_number=4, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=34, start_offset=34, starts_line=False, line_number=4),
+  make_inst(opname='LOAD_COMMON_CONSTANT', arg=7, argval=None, argrepr='None', offset=36, start_offset=36, starts_line=False, line_number=4),
+  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=38, start_offset=38, starts_line=False, line_number=4),
 ]
 
 expected_opinfo_jumpy = [
-  make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=0, start_offset=0, starts_line=True, line_number=1),
-  make_inst(opname='LOAD_GLOBAL', arg=1, argval='range', argrepr='range + NULL', offset=2, start_offset=2, starts_line=True, line_number=3, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_SMALL_INT', arg=10, argval=10, argrepr='', offset=12, start_offset=12, starts_line=False, line_number=3),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=14, start_offset=14, starts_line=False, line_number=3, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='GET_ITER', arg=None, argval=None, argrepr='', offset=22, start_offset=22, starts_line=False, line_number=3),
-  make_inst(opname='FOR_ITER', arg=32, argval=92, argrepr='to L4', offset=24, start_offset=24, starts_line=False, line_number=3, label=1, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='STORE_FAST', arg=0, argval='i', argrepr='i', offset=28, start_offset=28, starts_line=False, line_number=3),
-  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=30, start_offset=30, starts_line=True, line_number=4, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=40, start_offset=40, starts_line=False, line_number=4),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=42, start_offset=42, starts_line=False, line_number=4, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=50, start_offset=50, starts_line=False, line_number=4),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=52, start_offset=52, starts_line=True, line_number=5),
-  make_inst(opname='LOAD_SMALL_INT', arg=4, argval=4, argrepr='', offset=54, start_offset=54, starts_line=False, line_number=5),
-  make_inst(opname='COMPARE_OP', arg=18, argval='<', argrepr='bool(<)', offset=56, start_offset=56, starts_line=False, line_number=5, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='POP_JUMP_IF_FALSE', arg=3, argval=70, argrepr='to L2', offset=60, start_offset=60, starts_line=False, line_number=5, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=64, start_offset=64, starts_line=False, line_number=5),
-  make_inst(opname='JUMP_BACKWARD', arg=23, argval=24, argrepr='to L1', offset=66, start_offset=66, starts_line=True, line_number=6, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=70, start_offset=70, starts_line=True, line_number=7, label=2),
-  make_inst(opname='LOAD_SMALL_INT', arg=6, argval=6, argrepr='', offset=72, start_offset=72, starts_line=False, line_number=7),
-  make_inst(opname='COMPARE_OP', arg=148, argval='>', argrepr='bool(>)', offset=74, start_offset=74, starts_line=False, line_number=7, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='POP_JUMP_IF_TRUE', arg=3, argval=88, argrepr='to L3', offset=78, start_offset=78, starts_line=False, line_number=7, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=82, start_offset=82, starts_line=False, line_number=7),
-  make_inst(opname='JUMP_BACKWARD', arg=32, argval=24, argrepr='to L1', offset=84, start_offset=84, starts_line=False, line_number=7, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=88, start_offset=88, starts_line=True, line_number=8, label=3),
-  make_inst(opname='JUMP_FORWARD', arg=13, argval=118, argrepr='to L5', offset=90, start_offset=90, starts_line=False, line_number=8),
-  make_inst(opname='END_FOR', arg=None, argval=None, argrepr='', offset=92, start_offset=92, starts_line=True, line_number=3, label=4),
-  make_inst(opname='POP_ITER', arg=None, argval=None, argrepr='', offset=94, start_offset=94, starts_line=False, line_number=3),
-  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=96, start_offset=96, starts_line=True, line_number=10, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_CONST', arg=1, argval='I can haz else clause?', argrepr="'I can haz else clause?'", offset=106, start_offset=106, starts_line=False, line_number=10),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=108, start_offset=108, starts_line=False, line_number=10, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=116, start_offset=116, starts_line=False, line_number=10),
-  make_inst(opname='LOAD_FAST_CHECK', arg=0, argval='i', argrepr='i', offset=118, start_offset=118, starts_line=True, line_number=11, label=5),
-  make_inst(opname='TO_BOOL', arg=None, argval=None, argrepr='', offset=120, start_offset=120, starts_line=False, line_number=11, cache_info=[('counter', 1, b'\x00\x00'), ('version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_JUMP_IF_FALSE', arg=40, argval=212, argrepr='to L8', offset=128, start_offset=128, starts_line=False, line_number=11, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=132, start_offset=132, starts_line=False, line_number=11),
-  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=134, start_offset=134, starts_line=True, line_number=12, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=144, start_offset=144, starts_line=False, line_number=12),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=146, start_offset=146, starts_line=False, line_number=12, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=154, start_offset=154, starts_line=False, line_number=12),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=156, start_offset=156, starts_line=True, line_number=13),
-  make_inst(opname='LOAD_SMALL_INT', arg=1, argval=1, argrepr='', offset=158, start_offset=158, starts_line=False, line_number=13),
-  make_inst(opname='BINARY_OP', arg=23, argval=23, argrepr='-=', offset=160, start_offset=160, starts_line=False, line_number=13, cache_info=[('counter', 1, b'\x00\x00'), ('descr', 4, b'\x00\x00\x00\x00\x00\x00\x00\x00')]),
-  make_inst(opname='STORE_FAST', arg=0, argval='i', argrepr='i', offset=172, start_offset=172, starts_line=False, line_number=13),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=174, start_offset=174, starts_line=True, line_number=14),
-  make_inst(opname='LOAD_SMALL_INT', arg=6, argval=6, argrepr='', offset=176, start_offset=176, starts_line=False, line_number=14),
-  make_inst(opname='COMPARE_OP', arg=148, argval='>', argrepr='bool(>)', offset=178, start_offset=178, starts_line=False, line_number=14, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='POP_JUMP_IF_FALSE', arg=3, argval=192, argrepr='to L6', offset=182, start_offset=182, starts_line=False, line_number=14, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=186, start_offset=186, starts_line=False, line_number=14),
-  make_inst(opname='JUMP_BACKWARD', arg=37, argval=118, argrepr='to L5', offset=188, start_offset=188, starts_line=True, line_number=15, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=192, start_offset=192, starts_line=True, line_number=16, label=6),
-  make_inst(opname='LOAD_SMALL_INT', arg=4, argval=4, argrepr='', offset=194, start_offset=194, starts_line=False, line_number=16),
-  make_inst(opname='COMPARE_OP', arg=18, argval='<', argrepr='bool(<)', offset=196, start_offset=196, starts_line=False, line_number=16, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='POP_JUMP_IF_TRUE', arg=3, argval=210, argrepr='to L7', offset=200, start_offset=200, starts_line=False, line_number=16, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=204, start_offset=204, starts_line=False, line_number=16),
-  make_inst(opname='JUMP_BACKWARD', arg=46, argval=118, argrepr='to L5', offset=206, start_offset=206, starts_line=False, line_number=16, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='JUMP_FORWARD', arg=11, argval=234, argrepr='to L9', offset=210, start_offset=210, starts_line=True, line_number=17, label=7),
-  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=212, start_offset=212, starts_line=True, line_number=19, label=8, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_CONST', arg=2, argval='Who let lolcatz into this test suite?', argrepr="'Who let lolcatz into this test suite?'", offset=222, start_offset=222, starts_line=False, line_number=19),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=224, start_offset=224, starts_line=False, line_number=19, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=232, start_offset=232, starts_line=False, line_number=19),
-  make_inst(opname='NOP', arg=None, argval=None, argrepr='', offset=234, start_offset=234, starts_line=True, line_number=20, label=9),
-  make_inst(opname='LOAD_SMALL_INT', arg=1, argval=1, argrepr='', offset=236, start_offset=236, starts_line=True, line_number=21),
-  make_inst(opname='LOAD_SMALL_INT', arg=0, argval=0, argrepr='', offset=238, start_offset=238, starts_line=False, line_number=21),
-  make_inst(opname='BINARY_OP', arg=11, argval=11, argrepr='/', offset=240, start_offset=240, starts_line=False, line_number=21, cache_info=[('counter', 1, b'\x00\x00'), ('descr', 4, b'\x00\x00\x00\x00\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=252, start_offset=252, starts_line=False, line_number=21),
-  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=254, start_offset=254, starts_line=True, line_number=25),
-  make_inst(opname='COPY', arg=1, argval=1, argrepr='', offset=256, start_offset=256, starts_line=False, line_number=25),
-  make_inst(opname='LOAD_SPECIAL', arg=1, argval=1, argrepr='__exit__', offset=258, start_offset=258, starts_line=False, line_number=25),
-  make_inst(opname='SWAP', arg=2, argval=2, argrepr='', offset=260, start_offset=260, starts_line=False, line_number=25),
-  make_inst(opname='SWAP', arg=3, argval=3, argrepr='', offset=262, start_offset=262, starts_line=False, line_number=25),
-  make_inst(opname='LOAD_SPECIAL', arg=0, argval=0, argrepr='__enter__', offset=264, start_offset=264, starts_line=False, line_number=25),
-  make_inst(opname='CALL', arg=0, argval=0, argrepr='', offset=266, start_offset=266, starts_line=False, line_number=25, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='STORE_FAST', arg=1, argval='dodgy', argrepr='dodgy', offset=274, start_offset=274, starts_line=False, line_number=25),
-  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=276, start_offset=276, starts_line=True, line_number=26, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_CONST', arg=3, argval='Never reach this', argrepr="'Never reach this'", offset=286, start_offset=286, starts_line=False, line_number=26),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=288, start_offset=288, starts_line=False, line_number=26, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=296, start_offset=296, starts_line=False, line_number=26),
-  make_inst(opname='LOAD_CONST', arg=4, argval=None, argrepr='None', offset=298, start_offset=298, starts_line=True, line_number=25),
-  make_inst(opname='LOAD_CONST', arg=4, argval=None, argrepr='None', offset=300, start_offset=300, starts_line=False, line_number=25),
-  make_inst(opname='LOAD_CONST', arg=4, argval=None, argrepr='None', offset=302, start_offset=302, starts_line=False, line_number=25),
-  make_inst(opname='CALL', arg=3, argval=3, argrepr='', offset=304, start_offset=304, starts_line=False, line_number=25, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=312, start_offset=312, starts_line=False, line_number=25),
-  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=314, start_offset=314, starts_line=True, line_number=28, label=10, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_CONST', arg=6, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=324, start_offset=324, starts_line=False, line_number=28),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=326, start_offset=326, starts_line=False, line_number=28, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=334, start_offset=334, starts_line=False, line_number=28),
-  make_inst(opname='LOAD_CONST', arg=4, argval=None, argrepr='None', offset=336, start_offset=336, starts_line=False, line_number=28),
-  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=338, start_offset=338, starts_line=False, line_number=28),
-  make_inst(opname='PUSH_EXC_INFO', arg=None, argval=None, argrepr='', offset=340, start_offset=340, starts_line=True, line_number=25),
-  make_inst(opname='WITH_EXCEPT_START', arg=None, argval=None, argrepr='', offset=342, start_offset=342, starts_line=False, line_number=25),
-  make_inst(opname='TO_BOOL', arg=None, argval=None, argrepr='', offset=344, start_offset=344, starts_line=False, line_number=25, cache_info=[('counter', 1, b'\x00\x00'), ('version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_JUMP_IF_TRUE', arg=2, argval=360, argrepr='to L11', offset=352, start_offset=352, starts_line=False, line_number=25, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=356, start_offset=356, starts_line=False, line_number=25),
-  make_inst(opname='RERAISE', arg=2, argval=2, argrepr='', offset=358, start_offset=358, starts_line=False, line_number=25),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=360, start_offset=360, starts_line=False, line_number=25, label=11),
-  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=362, start_offset=362, starts_line=False, line_number=25),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=364, start_offset=364, starts_line=False, line_number=25),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=366, start_offset=366, starts_line=False, line_number=25),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=368, start_offset=368, starts_line=False, line_number=25),
-  make_inst(opname='JUMP_BACKWARD_NO_INTERRUPT', arg=29, argval=314, argrepr='to L10', offset=370, start_offset=370, starts_line=False, line_number=25),
-  make_inst(opname='COPY', arg=3, argval=3, argrepr='', offset=372, start_offset=372, starts_line=True, line_number=None),
-  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=374, start_offset=374, starts_line=False, line_number=None),
-  make_inst(opname='RERAISE', arg=1, argval=1, argrepr='', offset=376, start_offset=376, starts_line=False, line_number=None),
-  make_inst(opname='PUSH_EXC_INFO', arg=None, argval=None, argrepr='', offset=378, start_offset=378, starts_line=False, line_number=None),
-  make_inst(opname='LOAD_GLOBAL', arg=4, argval='ZeroDivisionError', argrepr='ZeroDivisionError', offset=380, start_offset=380, starts_line=True, line_number=22, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='CHECK_EXC_MATCH', arg=None, argval=None, argrepr='', offset=390, start_offset=390, starts_line=False, line_number=22),
-  make_inst(opname='POP_JUMP_IF_FALSE', arg=15, argval=426, argrepr='to L12', offset=392, start_offset=392, starts_line=False, line_number=22, cache_info=[('counter', 1, b'\x00\x00')]),
-  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=396, start_offset=396, starts_line=False, line_number=22),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=398, start_offset=398, starts_line=False, line_number=22),
-  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=400, start_offset=400, starts_line=True, line_number=23, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_CONST', arg=5, argval='Here we go, here we go, here we go...', argrepr="'Here we go, here we go, here we go...'", offset=410, start_offset=410, starts_line=False, line_number=23),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=412, start_offset=412, starts_line=False, line_number=23, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=420, start_offset=420, starts_line=False, line_number=23),
-  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=422, start_offset=422, starts_line=False, line_number=23),
-  make_inst(opname='JUMP_BACKWARD_NO_INTERRUPT', arg=56, argval=314, argrepr='to L10', offset=424, start_offset=424, starts_line=False, line_number=23),
-  make_inst(opname='RERAISE', arg=0, argval=0, argrepr='', offset=426, start_offset=426, starts_line=True, line_number=22, label=12),
-  make_inst(opname='COPY', arg=3, argval=3, argrepr='', offset=428, start_offset=428, starts_line=True, line_number=None),
-  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=430, start_offset=430, starts_line=False, line_number=None),
-  make_inst(opname='RERAISE', arg=1, argval=1, argrepr='', offset=432, start_offset=432, starts_line=False, line_number=None),
-  make_inst(opname='PUSH_EXC_INFO', arg=None, argval=None, argrepr='', offset=434, start_offset=434, starts_line=False, line_number=None),
-  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=436, start_offset=436, starts_line=True, line_number=28, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
-  make_inst(opname='LOAD_CONST', arg=6, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=446, start_offset=446, starts_line=False, line_number=28),
-  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=448, start_offset=448, starts_line=False, line_number=28, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
-  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=456, start_offset=456, starts_line=False, line_number=28),
-  make_inst(opname='RERAISE', arg=0, argval=0, argrepr='', offset=458, start_offset=458, starts_line=False, line_number=28),
-  make_inst(opname='COPY', arg=3, argval=3, argrepr='', offset=460, start_offset=460, starts_line=True, line_number=None),
-  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=462, start_offset=462, starts_line=False, line_number=None),
-  make_inst(opname='RERAISE', arg=1, argval=1, argrepr='', offset=464, start_offset=464, starts_line=False, line_number=None),
+  make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=0, start_offset=0, starts_line=True, line_number=1, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_GLOBAL', arg=1, argval='range', argrepr='range + NULL', offset=4, start_offset=4, starts_line=True, line_number=3, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_SMALL_INT', arg=10, argval=10, argrepr='', offset=14, start_offset=14, starts_line=False, line_number=3),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=16, start_offset=16, starts_line=False, line_number=3, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='GET_ITER', arg=0, argval=0, argrepr='', offset=24, start_offset=24, starts_line=False, line_number=3, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='FOR_ITER', arg=33, argval=98, argrepr='to L4', offset=28, start_offset=28, starts_line=False, line_number=3, label=1, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='STORE_FAST', arg=0, argval='i', argrepr='i', offset=32, start_offset=32, starts_line=False, line_number=3),
+  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=34, start_offset=34, starts_line=True, line_number=4, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=44, start_offset=44, starts_line=False, line_number=4),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=46, start_offset=46, starts_line=False, line_number=4, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=54, start_offset=54, starts_line=False, line_number=4),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=56, start_offset=56, starts_line=True, line_number=5),
+  make_inst(opname='LOAD_SMALL_INT', arg=4, argval=4, argrepr='', offset=58, start_offset=58, starts_line=False, line_number=5),
+  make_inst(opname='COMPARE_OP', arg=18, argval='<', argrepr='bool(<)', offset=60, start_offset=60, starts_line=False, line_number=5, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='POP_JUMP_IF_FALSE', arg=3, argval=74, argrepr='to L2', offset=64, start_offset=64, starts_line=False, line_number=5, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=68, start_offset=68, starts_line=False, line_number=5),
+  make_inst(opname='JUMP_BACKWARD', arg=23, argval=28, argrepr='to L1', offset=70, start_offset=70, starts_line=True, line_number=6, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=74, start_offset=74, starts_line=True, line_number=7, label=2),
+  make_inst(opname='LOAD_SMALL_INT', arg=6, argval=6, argrepr='', offset=76, start_offset=76, starts_line=False, line_number=7),
+  make_inst(opname='COMPARE_OP', arg=148, argval='>', argrepr='bool(>)', offset=78, start_offset=78, starts_line=False, line_number=7, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='POP_JUMP_IF_TRUE', arg=3, argval=92, argrepr='to L3', offset=82, start_offset=82, starts_line=False, line_number=7, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=86, start_offset=86, starts_line=False, line_number=7),
+  make_inst(opname='JUMP_BACKWARD', arg=32, argval=28, argrepr='to L1', offset=88, start_offset=88, starts_line=False, line_number=7, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=92, start_offset=92, starts_line=True, line_number=8, label=3),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=94, start_offset=94, starts_line=False, line_number=8),
+  make_inst(opname='JUMP_FORWARD', arg=13, argval=124, argrepr='to L5', offset=96, start_offset=96, starts_line=False, line_number=8),
+  make_inst(opname='END_FOR', arg=None, argval=None, argrepr='', offset=98, start_offset=98, starts_line=True, line_number=3, label=4),
+  make_inst(opname='POP_ITER', arg=None, argval=None, argrepr='', offset=100, start_offset=100, starts_line=False, line_number=3),
+  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=102, start_offset=102, starts_line=True, line_number=10, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_CONST', arg=1, argval='I can haz else clause?', argrepr="'I can haz else clause?'", offset=112, start_offset=112, starts_line=False, line_number=10),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=114, start_offset=114, starts_line=False, line_number=10, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=122, start_offset=122, starts_line=False, line_number=10),
+  make_inst(opname='LOAD_FAST_CHECK', arg=0, argval='i', argrepr='i', offset=124, start_offset=124, starts_line=True, line_number=11, label=5),
+  make_inst(opname='TO_BOOL', arg=None, argval=None, argrepr='', offset=126, start_offset=126, starts_line=False, line_number=11, cache_info=[('counter', 1, b'\x00\x00'), ('version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_JUMP_IF_FALSE', arg=40, argval=218, argrepr='to L8', offset=134, start_offset=134, starts_line=False, line_number=11, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=138, start_offset=138, starts_line=False, line_number=11),
+  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=140, start_offset=140, starts_line=True, line_number=12, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=150, start_offset=150, starts_line=False, line_number=12),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=152, start_offset=152, starts_line=False, line_number=12, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=160, start_offset=160, starts_line=False, line_number=12),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=162, start_offset=162, starts_line=True, line_number=13),
+  make_inst(opname='LOAD_SMALL_INT', arg=1, argval=1, argrepr='', offset=164, start_offset=164, starts_line=False, line_number=13),
+  make_inst(opname='BINARY_OP', arg=23, argval=23, argrepr='-=', offset=166, start_offset=166, starts_line=False, line_number=13, cache_info=[('counter', 1, b'\x00\x00'), ('descr', 4, b'\x00\x00\x00\x00\x00\x00\x00\x00')]),
+  make_inst(opname='STORE_FAST', arg=0, argval='i', argrepr='i', offset=178, start_offset=178, starts_line=False, line_number=13),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=180, start_offset=180, starts_line=True, line_number=14),
+  make_inst(opname='LOAD_SMALL_INT', arg=6, argval=6, argrepr='', offset=182, start_offset=182, starts_line=False, line_number=14),
+  make_inst(opname='COMPARE_OP', arg=148, argval='>', argrepr='bool(>)', offset=184, start_offset=184, starts_line=False, line_number=14, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='POP_JUMP_IF_FALSE', arg=3, argval=198, argrepr='to L6', offset=188, start_offset=188, starts_line=False, line_number=14, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=192, start_offset=192, starts_line=False, line_number=14),
+  make_inst(opname='JUMP_BACKWARD', arg=37, argval=124, argrepr='to L5', offset=194, start_offset=194, starts_line=True, line_number=15, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=198, start_offset=198, starts_line=True, line_number=16, label=6),
+  make_inst(opname='LOAD_SMALL_INT', arg=4, argval=4, argrepr='', offset=200, start_offset=200, starts_line=False, line_number=16),
+  make_inst(opname='COMPARE_OP', arg=18, argval='<', argrepr='bool(<)', offset=202, start_offset=202, starts_line=False, line_number=16, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='POP_JUMP_IF_TRUE', arg=3, argval=216, argrepr='to L7', offset=206, start_offset=206, starts_line=False, line_number=16, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=210, start_offset=210, starts_line=False, line_number=16),
+  make_inst(opname='JUMP_BACKWARD', arg=46, argval=124, argrepr='to L5', offset=212, start_offset=212, starts_line=False, line_number=16, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='JUMP_FORWARD', arg=11, argval=240, argrepr='to L9', offset=216, start_offset=216, starts_line=True, line_number=17, label=7),
+  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=218, start_offset=218, starts_line=True, line_number=19, label=8, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_CONST', arg=2, argval='Who let lolcatz into this test suite?', argrepr="'Who let lolcatz into this test suite?'", offset=228, start_offset=228, starts_line=False, line_number=19),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=230, start_offset=230, starts_line=False, line_number=19, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=238, start_offset=238, starts_line=False, line_number=19),
+  make_inst(opname='NOP', arg=None, argval=None, argrepr='', offset=240, start_offset=240, starts_line=True, line_number=20, label=9),
+  make_inst(opname='LOAD_SMALL_INT', arg=1, argval=1, argrepr='', offset=242, start_offset=242, starts_line=True, line_number=21),
+  make_inst(opname='LOAD_SMALL_INT', arg=0, argval=0, argrepr='', offset=244, start_offset=244, starts_line=False, line_number=21),
+  make_inst(opname='BINARY_OP', arg=11, argval=11, argrepr='/', offset=246, start_offset=246, starts_line=False, line_number=21, cache_info=[('counter', 1, b'\x00\x00'), ('descr', 4, b'\x00\x00\x00\x00\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=258, start_offset=258, starts_line=False, line_number=21),
+  make_inst(opname='LOAD_FAST_BORROW', arg=0, argval='i', argrepr='i', offset=260, start_offset=260, starts_line=True, line_number=25),
+  make_inst(opname='COPY', arg=1, argval=1, argrepr='', offset=262, start_offset=262, starts_line=False, line_number=25),
+  make_inst(opname='LOAD_SPECIAL', arg=1, argval=1, argrepr='__exit__', offset=264, start_offset=264, starts_line=False, line_number=25),
+  make_inst(opname='SWAP', arg=2, argval=2, argrepr='', offset=266, start_offset=266, starts_line=False, line_number=25),
+  make_inst(opname='SWAP', arg=3, argval=3, argrepr='', offset=268, start_offset=268, starts_line=False, line_number=25),
+  make_inst(opname='LOAD_SPECIAL', arg=0, argval=0, argrepr='__enter__', offset=270, start_offset=270, starts_line=False, line_number=25),
+  make_inst(opname='CALL', arg=0, argval=0, argrepr='', offset=272, start_offset=272, starts_line=False, line_number=25, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='STORE_FAST', arg=1, argval='dodgy', argrepr='dodgy', offset=280, start_offset=280, starts_line=False, line_number=25),
+  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=282, start_offset=282, starts_line=True, line_number=26, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_CONST', arg=3, argval='Never reach this', argrepr="'Never reach this'", offset=292, start_offset=292, starts_line=False, line_number=26),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=294, start_offset=294, starts_line=False, line_number=26, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=302, start_offset=302, starts_line=False, line_number=26),
+  make_inst(opname='LOAD_COMMON_CONSTANT', arg=7, argval=None, argrepr='None', offset=304, start_offset=304, starts_line=True, line_number=25),
+  make_inst(opname='LOAD_COMMON_CONSTANT', arg=7, argval=None, argrepr='None', offset=306, start_offset=306, starts_line=False, line_number=25),
+  make_inst(opname='LOAD_COMMON_CONSTANT', arg=7, argval=None, argrepr='None', offset=308, start_offset=308, starts_line=False, line_number=25),
+  make_inst(opname='CALL', arg=3, argval=3, argrepr='', offset=310, start_offset=310, starts_line=False, line_number=25, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=318, start_offset=318, starts_line=False, line_number=25),
+  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=320, start_offset=320, starts_line=True, line_number=28, label=10, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_CONST', arg=5, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=330, start_offset=330, starts_line=False, line_number=28),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=332, start_offset=332, starts_line=False, line_number=28, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=340, start_offset=340, starts_line=False, line_number=28),
+  make_inst(opname='LOAD_COMMON_CONSTANT', arg=7, argval=None, argrepr='None', offset=342, start_offset=342, starts_line=False, line_number=28),
+  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=344, start_offset=344, starts_line=False, line_number=28),
+  make_inst(opname='PUSH_EXC_INFO', arg=None, argval=None, argrepr='', offset=346, start_offset=346, starts_line=True, line_number=25),
+  make_inst(opname='WITH_EXCEPT_START', arg=None, argval=None, argrepr='', offset=348, start_offset=348, starts_line=False, line_number=25),
+  make_inst(opname='TO_BOOL', arg=None, argval=None, argrepr='', offset=350, start_offset=350, starts_line=False, line_number=25, cache_info=[('counter', 1, b'\x00\x00'), ('version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_JUMP_IF_TRUE', arg=2, argval=366, argrepr='to L11', offset=358, start_offset=358, starts_line=False, line_number=25, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=362, start_offset=362, starts_line=False, line_number=25),
+  make_inst(opname='RERAISE', arg=2, argval=2, argrepr='', offset=364, start_offset=364, starts_line=False, line_number=25),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=366, start_offset=366, starts_line=False, line_number=25, label=11),
+  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=368, start_offset=368, starts_line=False, line_number=25),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=370, start_offset=370, starts_line=False, line_number=25),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=372, start_offset=372, starts_line=False, line_number=25),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=374, start_offset=374, starts_line=False, line_number=25),
+  make_inst(opname='JUMP_BACKWARD_NO_INTERRUPT', arg=29, argval=320, argrepr='to L10', offset=376, start_offset=376, starts_line=False, line_number=25),
+  make_inst(opname='COPY', arg=3, argval=3, argrepr='', offset=378, start_offset=378, starts_line=True, line_number=None),
+  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=380, start_offset=380, starts_line=False, line_number=None),
+  make_inst(opname='RERAISE', arg=1, argval=1, argrepr='', offset=382, start_offset=382, starts_line=False, line_number=None),
+  make_inst(opname='PUSH_EXC_INFO', arg=None, argval=None, argrepr='', offset=384, start_offset=384, starts_line=False, line_number=None),
+  make_inst(opname='LOAD_GLOBAL', arg=4, argval='ZeroDivisionError', argrepr='ZeroDivisionError', offset=386, start_offset=386, starts_line=True, line_number=22, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='CHECK_EXC_MATCH', arg=None, argval=None, argrepr='', offset=396, start_offset=396, starts_line=False, line_number=22),
+  make_inst(opname='POP_JUMP_IF_FALSE', arg=15, argval=432, argrepr='to L12', offset=398, start_offset=398, starts_line=False, line_number=22, cache_info=[('counter', 1, b'\x00\x00')]),
+  make_inst(opname='NOT_TAKEN', arg=None, argval=None, argrepr='', offset=402, start_offset=402, starts_line=False, line_number=22),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=404, start_offset=404, starts_line=False, line_number=22),
+  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=406, start_offset=406, starts_line=True, line_number=23, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_CONST', arg=4, argval='Here we go, here we go, here we go...', argrepr="'Here we go, here we go, here we go...'", offset=416, start_offset=416, starts_line=False, line_number=23),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=418, start_offset=418, starts_line=False, line_number=23, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=426, start_offset=426, starts_line=False, line_number=23),
+  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=428, start_offset=428, starts_line=False, line_number=23),
+  make_inst(opname='JUMP_BACKWARD_NO_INTERRUPT', arg=56, argval=320, argrepr='to L10', offset=430, start_offset=430, starts_line=False, line_number=23),
+  make_inst(opname='RERAISE', arg=0, argval=0, argrepr='', offset=432, start_offset=432, starts_line=True, line_number=22, label=12),
+  make_inst(opname='COPY', arg=3, argval=3, argrepr='', offset=434, start_offset=434, starts_line=True, line_number=None),
+  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=436, start_offset=436, starts_line=False, line_number=None),
+  make_inst(opname='RERAISE', arg=1, argval=1, argrepr='', offset=438, start_offset=438, starts_line=False, line_number=None),
+  make_inst(opname='PUSH_EXC_INFO', arg=None, argval=None, argrepr='', offset=440, start_offset=440, starts_line=False, line_number=None),
+  make_inst(opname='LOAD_GLOBAL', arg=3, argval='print', argrepr='print + NULL', offset=442, start_offset=442, starts_line=True, line_number=28, cache_info=[('counter', 1, b'\x00\x00'), ('index', 1, b'\x00\x00'), ('module_keys_version', 1, b'\x00\x00'), ('builtin_keys_version', 1, b'\x00\x00')]),
+  make_inst(opname='LOAD_CONST', arg=5, argval="OK, now we're done", argrepr='"OK, now we\'re done"', offset=452, start_offset=452, starts_line=False, line_number=28),
+  make_inst(opname='CALL', arg=1, argval=1, argrepr='', offset=454, start_offset=454, starts_line=False, line_number=28, cache_info=[('counter', 1, b'\x00\x00'), ('func_version', 2, b'\x00\x00\x00\x00')]),
+  make_inst(opname='POP_TOP', arg=None, argval=None, argrepr='', offset=462, start_offset=462, starts_line=False, line_number=28),
+  make_inst(opname='RERAISE', arg=0, argval=0, argrepr='', offset=464, start_offset=464, starts_line=False, line_number=28),
+  make_inst(opname='COPY', arg=3, argval=3, argrepr='', offset=466, start_offset=466, starts_line=True, line_number=None),
+  make_inst(opname='POP_EXCEPT', arg=None, argval=None, argrepr='', offset=468, start_offset=468, starts_line=False, line_number=None),
+  make_inst(opname='RERAISE', arg=1, argval=1, argrepr='', offset=470, start_offset=470, starts_line=False, line_number=None),
 ]
 
 # One last piece of inspect fodder to check the default line number handling
 def simple(): pass
 expected_opinfo_simple = [
   make_inst(opname='RESUME', arg=0, argval=0, argrepr='', offset=0, start_offset=0, starts_line=True, line_number=simple.__code__.co_firstlineno),
-  make_inst(opname='LOAD_CONST', arg=0, argval=None, argrepr='None', offset=2, start_offset=2, starts_line=False, line_number=simple.__code__.co_firstlineno),
-  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=4, start_offset=4, starts_line=False, line_number=simple.__code__.co_firstlineno),
+  make_inst(opname='LOAD_COMMON_CONSTANT', arg=7, argval=None, argrepr='None', offset=4, start_offset=4, starts_line=False, line_number=simple.__code__.co_firstlineno),
+  make_inst(opname='RETURN_VALUE', arg=None, argval=None, argrepr='', offset=6, start_offset=6, starts_line=False, line_number=simple.__code__.co_firstlineno),
 ]
 
 
@@ -2343,8 +2380,10 @@ def test_from_traceback_dis(self):
     @requires_debug_ranges()
     def test_bytecode_co_positions(self):
         bytecode = dis.Bytecode("a=1")
-        for instr, positions in zip(bytecode, bytecode.codeobj.co_positions()):
-            assert instr.positions == positions
+        it = bytecode.codeobj.co_positions()
+        next(it) # Ignore the CACHE for the RESUME
+        for instr, positions in zip(bytecode, it):
+            self.assertEqual(instr.positions, positions)
 
 class TestBytecodeTestCase(BytecodeTestCase):
     def test_assert_not_in_with_op_not_in_bytecode(self):
@@ -2412,7 +2451,7 @@ def func():
 
         code = func.__code__
         offsets = [linestart[0] for linestart in dis.findlinestarts(code)]
-        self.assertEqual(offsets, [0, 2])
+        self.assertEqual(offsets, [0, 4])
 
 
 class TestDisTraceback(DisTestBase):
@@ -2550,6 +2589,7 @@ def test_show_cache(self):
         source = 'print()'
         expect = '''
             0           RESUME                   0
+                        CACHE                    0 (counter: 0)
 
             1           LOAD_NAME                0 (print)
                         PUSH_NULL
@@ -2558,7 +2598,7 @@ def test_show_cache(self):
                         CACHE                    0 (func_version: 0)
                         CACHE                    0
                         POP_TOP
-                        LOAD_CONST               0 (None)
+                        LOAD_COMMON_CONSTANT     7 (None)
                         RETURN_VALUE
         '''
         for flag in ['-C', '--show-caches']:
@@ -2570,8 +2610,8 @@ def test_show_offsets(self):
         expect = '''
             0          0       RESUME                   0
 
-            1          2       LOAD_CONST               0 (None)
-                       4       RETURN_VALUE
+            1          4       LOAD_COMMON_CONSTANT     7 (None)
+                       6       RETURN_VALUE
         '''
         for flag in ['-O', '--show-offsets']:
             self.check_output(source, expect, flag)
@@ -2582,7 +2622,7 @@ def test_show_positions(self):
         expect = '''
             0:0-1:0            RESUME                   0
 
-            1:0-1:4            LOAD_CONST               0 (None)
+            1:0-1:4            LOAD_COMMON_CONSTANT     7 (None)
             1:0-1:4            RETURN_VALUE
         '''
         for flag in ['-P', '--show-positions']:
@@ -2594,7 +2634,7 @@ def test_specialized_code(self):
         expect = '''
             0           RESUME                   0
 
-            1           LOAD_CONST               0 (None)
+            1           LOAD_COMMON_CONSTANT     7 (None)
                         RETURN_VALUE
         '''
         for flag in ['-S', '--specialized']:
diff --git a/Lib/test/test_doctest/test_doctest.py b/Lib/test/test_doctest/test_doctest.py
index 1945cd3f0dd..b9f67f07ebc 100644
--- a/Lib/test/test_doctest/test_doctest.py
+++ b/Lib/test/test_doctest/test_doctest.py
@@ -742,7 +742,7 @@ def non_Python_modules(): r"""
 
     >>> import builtins
     >>> tests = doctest.DocTestFinder().find(builtins)
-    >>> 750 < len(tests) < 800 # approximate number of objects with docstrings
+    >>> 750 < len(tests) < 850 # approximate number of objects with docstrings
     True
     >>> real_tests = [t for t in tests if len(t.examples) > 0]
     >>> len(real_tests) # objects that actually have doctests
diff --git a/Lib/test/test_dynamic.py b/Lib/test/test_dynamic.py
index 948a2029f1e..1df010732c1 100644
--- a/Lib/test/test_dynamic.py
+++ b/Lib/test/test_dynamic.py
@@ -135,7 +135,7 @@ def test_eval_gives_lambda_custom_globals(self):
         self.assertEqual(foo(), 7)
 
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @unittest.expectedFailureIf(sys.getrecursionlimit() == 256, "TODO: RUSTPYTHON; default debug recursion limit is 256")
     @skip_wasi_stack_overflow()
     def test_load_global_specialization_failure_keeps_oparg(self):
         # https://github.com/python/cpython/issues/91625
diff --git a/Lib/test/test_email/test__header_value_parser.py b/Lib/test/test_email/test__header_value_parser.py
index 8c9601288da..9d9fe418ee4 100644
--- a/Lib/test/test_email/test__header_value_parser.py
+++ b/Lib/test/test_email/test__header_value_parser.py
@@ -1307,17 +1307,6 @@ def test_get_local_part_valid_and_invalid_qp_in_atom_list(self):
             '@example.com')
         self.assertEqual(local_part.local_part, r'\example\\ example')
 
-    def test_get_local_part_unicode_defect(self):
-        # Currently this only happens when parsing unicode, not when parsing
-        # stuff that was originally binary.
-        local_part = self._test_get_x(parser.get_local_part,
-            'exámple@example.com',
-            'exámple',
-            'exámple',
-            [errors.NonASCIILocalPartDefect],
-            '@example.com')
-        self.assertEqual(local_part.local_part, 'exámple')
-
     # get_dtext
 
     def test_get_dtext_only(self):
@@ -3462,10 +3451,12 @@ def test_fold_unfoldable_element_stealing_whitespace(self):
         self._test(token, expected, policy=policy)
 
     def test_encoded_word_with_undecodable_bytes(self):
-        self._test(parser.get_address_list(
-            ' =?utf-8?Q?=E5=AE=A2=E6=88=B6=E6=AD=A3=E8=A6=8F=E4=BA=A4=E7?='
+        self._test(
+            parser.get_address_list(
+                ' =?utf-8?Q?=E5=AE=A2=E6=88=B6=E6=AD=A3=E8=A6=8F=E4=BA=A4=E7?='
+                ' <xyz@abc.com>'
                 )[0],
-            ' =?unknown-8bit?b?5a6i5oi25q2j6KaP5Lqk5w==?=\n',
+            ' =?unknown-8bit?b?5a6i5oi25q2j6KaP5Lqk5w==?= <xyz@abc.com>\n',
             )
 
 
diff --git a/Lib/test/test_email/test_asian_codecs.py b/Lib/test/test_email/test_asian_codecs.py
index 85979ffd816..59013f08719 100644
--- a/Lib/test/test_email/test_asian_codecs.py
+++ b/Lib/test/test_email/test_asian_codecs.py
@@ -83,15 +83,15 @@ def test_chinese_codecs(self):
         h.append(s, Charset('big5hkscs'))
         eq(h.encode(), """\
 Chinese =?gb2312?b?1tDOxA==?= =?gbk?b?1tDOxA==?= =?gb18030?b?1tDOxA==?=
- =?hz?b?fntWUE5Efn0=?= =?big5?b?pKSk5Q==?= =?big5hkscs?b?pKSk5Q==?=""")
+ =?hz-gb-2312?b?fntWUE5Efn0=?= =?big5?b?pKSk5Q==?= =?big5-hkscs?b?pKSk5Q==?=""")
         eq(decode_header(h.encode()),
            [(b'Chinese ', None),
             (b'\xd6\xd0\xce\xc4', 'gb2312'),
             (b'\xd6\xd0\xce\xc4', 'gbk'),
             (b'\xd6\xd0\xce\xc4', 'gb18030'),
-            (b'~{VPND~}', 'hz'),
+            (b'~{VPND~}', 'hz-gb-2312'),
             (b'\xa4\xa4\xa4\xe5', 'big5'),
-            (b'\xa4\xa4\xa4\xe5', 'big5hkscs'),
+            (b'\xa4\xa4\xa4\xe5', 'big5-hkscs'),
            ])
 
     def test_korean_codecs(self):
diff --git a/Lib/test/test_email/test_contentmanager.py b/Lib/test/test_email/test_contentmanager.py
index dceb54f15e4..3115941f870 100644
--- a/Lib/test/test_email/test_contentmanager.py
+++ b/Lib/test/test_email/test_contentmanager.py
@@ -342,6 +342,66 @@ def test_set_text_charset_latin_1(self):
         self.assertEqual(m.get_payload(decode=True).decode('utf-8'), content)
         self.assertEqual(m.get_content(), content)
 
+    def test_set_text_charset_cp949(self):
+        m = self._make_message()
+        content = "\ud55c\uad6d\uc5b4\n\uac02\n"
+        raw_data_manager.set_content(m, content, charset='cp949')
+        self.assertEqual(str(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="ks_c_5601-1987"
+            Content-Transfer-Encoding: base64
+
+            x9Gxub7uCoFBCg==
+            """))
+        self.assertEqual(bytes(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="ks_c_5601-1987"
+            Content-Transfer-Encoding: 8bit
+
+            \ud55c\uad6d\uc5b4
+            \uac02
+            """).encode('ks_c_5601-1987'))
+        self.assertEqual(m.get_payload(decode=True), content.encode('ks_c_5601-1987'))
+        self.assertEqual(m.get_content(), content)
+
+    def test_set_text_charset_shift_jis(self):
+        m = self._make_message()
+        content = "\u65e5\u672c\u8a9e\n"
+        raw_data_manager.set_content(m, content, charset='shift_jis')
+        self.assertEqual(m['Content-Type'], 'text/plain; charset="iso-2022-jp"')
+        self.assertEqual(m.get_payload(decode=True), content.encode('iso-2022-jp'))
+        self.assertEqual(m.get_content(), content)
+        self.assertEqual(str(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-2022-jp"
+            Content-Transfer-Encoding: 7bit
+
+            \x1b$BF|K\\8l\x1b(B
+            """))
+        self.assertEqual(bytes(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-2022-jp"
+            Content-Transfer-Encoding: 7bit
+
+            \u65e5\u672c\u8a9e
+            """).encode('iso-2022-jp'))
+
+    def test_set_text_charset_euc_jp(self):
+        m = self._make_message()
+        content = "\u65e5\u672c\u8a9e\n"
+        raw_data_manager.set_content(m, content, charset='euc-jp')
+        self.assertEqual(m['Content-Type'], 'text/plain; charset="iso-2022-jp"')
+        self.assertEqual(m.get_payload(decode=True), content.encode('iso-2022-jp'))
+        self.assertEqual(m.get_content(), content)
+        self.assertEqual(str(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-2022-jp"
+            Content-Transfer-Encoding: 7bit
+
+            \x1b$BF|K\\8l\x1b(B
+            """))
+        self.assertEqual(bytes(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="iso-2022-jp"
+            Content-Transfer-Encoding: 7bit
+
+            \u65e5\u672c\u8a9e
+            """).encode('iso-2022-jp'))
+
     def test_set_text_plain_long_line_heuristics(self):
         m = self._make_message()
         content = ("Simple but long message that is over 78 characters"
diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py
index ec0fb2fc2d9..cab641496b9 100644
--- a/Lib/test/test_email/test_email.py
+++ b/Lib/test/test_email/test_email.py
@@ -41,6 +41,7 @@
 
 from test import support
 from test.support import threading_helper
+from test.support import warnings_helper
 from test.support.os_helper import unlink
 from test.test_email import openfile, TestEmailBase
 
@@ -4970,6 +4971,128 @@ def tearDown(self):
         except KeyError:
             pass
 
+    def test_attributes(self):
+        from email import charset
+        c = Charset()
+        self.assertEqual(c.input_charset, 'us-ascii')
+        self.assertEqual(c.header_encoding, None)
+        self.assertEqual(c.body_encoding, None)
+        self.assertEqual(c.output_charset, 'us-ascii')
+        self.assertEqual(c.input_codec, None)
+        self.assertEqual(c.output_codec, None)
+
+        c = Charset('us-ascii')
+        self.assertEqual(c.input_charset, 'us-ascii')
+        self.assertEqual(c.header_encoding, None)
+        self.assertEqual(c.body_encoding, None)
+        self.assertEqual(c.output_charset, 'us-ascii')
+        self.assertEqual(c.input_codec, None)
+        self.assertEqual(c.output_codec, None)
+
+        c = Charset('utf8')
+        self.assertEqual(c.input_charset, 'utf-8')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'utf-8')
+        self.assertEqual(c.input_codec, 'utf-8')
+        self.assertEqual(c.output_codec, 'utf-8')
+
+        c = Charset('latin1')
+        self.assertEqual(c.input_charset, 'iso-8859-1')
+        self.assertEqual(c.header_encoding, charset.QP)
+        self.assertEqual(c.body_encoding, charset.QP)
+        self.assertEqual(c.output_charset, 'iso-8859-1')
+        self.assertEqual(c.input_codec, 'iso-8859-1')
+        self.assertEqual(c.output_codec, 'iso-8859-1')
+
+        c = Charset('latin9')
+        self.assertEqual(c.input_charset, 'iso-8859-15')
+        self.assertEqual(c.header_encoding, charset.QP)
+        self.assertEqual(c.body_encoding, charset.QP)
+        self.assertEqual(c.output_charset, 'iso-8859-15')
+        self.assertEqual(c.input_codec, 'iso-8859-15')
+        self.assertEqual(c.output_codec, 'iso-8859-15')
+
+        c = Charset('cyrillic')
+        self.assertEqual(c.input_charset, 'iso-8859-5')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'iso-8859-5')
+        self.assertEqual(c.input_codec, 'iso-8859-5')
+        self.assertEqual(c.output_codec, 'iso-8859-5')
+
+        c = Charset('cp1251')
+        self.assertEqual(c.input_charset, 'windows-1251')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'windows-1251')
+        self.assertEqual(c.input_codec, 'windows-1251')
+        self.assertEqual(c.output_codec, 'windows-1251')
+
+        c = Charset('cp1252')
+        self.assertEqual(c.input_charset, 'windows-1252')
+        self.assertEqual(c.header_encoding, charset.QP)
+        self.assertEqual(c.body_encoding, charset.QP)
+        self.assertEqual(c.output_charset, 'windows-1252')
+        self.assertEqual(c.input_codec, 'windows-1252')
+        self.assertEqual(c.output_codec, 'windows-1252')
+
+        c = Charset('eucjp')
+        self.assertEqual(c.input_charset, 'euc-jp')
+        self.assertEqual(c.header_encoding, charset.BASE64)
+        self.assertEqual(c.body_encoding, None)
+        self.assertEqual(c.output_charset, 'iso-2022-jp')
+        self.assertEqual(c.input_codec, 'euc-jp')
+        self.assertEqual(c.output_codec, 'iso-2022-jp')
+
+        c = Charset('cp949')
+        self.assertEqual(c.input_charset, 'ks_c_5601-1987')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'ks_c_5601-1987')
+        self.assertEqual(c.input_codec, 'ks_c_5601-1987')
+        self.assertEqual(c.output_codec, 'ks_c_5601-1987')
+
+        c = Charset('gb2312')
+        self.assertEqual(c.input_charset, 'gb2312')
+        self.assertEqual(c.header_encoding, charset.BASE64)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'gb2312')
+        self.assertEqual(c.input_codec, 'gb2312')
+        self.assertEqual(c.output_codec, 'gb2312')
+
+        c = Charset('big5')
+        self.assertEqual(c.input_charset, 'big5')
+        self.assertEqual(c.header_encoding, charset.BASE64)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'big5')
+        self.assertEqual(c.input_codec, 'big5')
+        self.assertEqual(c.output_codec, 'big5')
+
+    def test_user_charsets(self):
+        from email import charset
+        c = Charset('fake0')
+        self.assertEqual(c.input_charset, 'fake0')
+        self.assertEqual(c.header_encoding, charset.SHORTEST)
+        self.assertEqual(c.body_encoding, charset.BASE64)
+        self.assertEqual(c.output_charset, 'fake0')
+        self.assertEqual(c.input_codec, 'fake0')
+        self.assertEqual(c.output_codec, 'fake0')
+
+        charset.add_alias('fake1', 'mime-fake')
+        charset.add_alias('output-mime-fake', 'output-mime-fake-alias')
+        charset.add_codec('mime-fake', 'fakecodec')
+        charset.add_codec('output-mime-fake-alias', 'outputfakecodec')
+        charset.add_charset('mime-fake', charset.QP, None, 'output-mime-fake')
+
+        c = Charset('fake1')
+        self.assertEqual(c.input_charset, 'mime-fake')
+        self.assertEqual(c.header_encoding, charset.QP)
+        self.assertEqual(c.body_encoding, None)
+        self.assertEqual(c.output_charset, 'output-mime-fake-alias')
+        self.assertEqual(c.input_codec, 'fakecodec')
+        self.assertEqual(c.output_codec, 'outputfakecodec')
+
     def test_codec_encodeable(self):
         eq = self.assertEqual
         # Make sure us-ascii = no Unicode conversion
@@ -5010,6 +5133,11 @@ def test_unicode_charset_name(self):
         self.assertEqual(str(charset), 'us-ascii')
         self.assertRaises(errors.CharsetError, Charset, 'asc\xffii')
 
+    def test_bytes_charset_name(self):
+        charset = Charset(b'us-ascii')
+        self.assertEqual(str(charset), 'us-ascii')
+        self.assertRaises(errors.CharsetError, Charset, b'asc\xffii')
+
 
 
 # Test multilingual MIME headers.
@@ -5653,7 +5781,8 @@ def test_rfc2231_bad_character_in_encoding(self):
 
 """
         msg = email.message_from_string(m)
-        self.assertEqual(msg.get_filename(), 'myfile.txt')
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.assertEqual(msg.get_filename(), 'myfile.txt')
 
     def test_rfc2231_single_tick_in_filename_extended(self):
         eq = self.assertEqual
diff --git a/Lib/test/test_email/test_generator.py b/Lib/test/test_email/test_generator.py
index 3c9a86f3e8c..8d912738029 100644
--- a/Lib/test/test_email/test_generator.py
+++ b/Lib/test/test_email/test_generator.py
@@ -1,4 +1,5 @@
 import io
+import re
 import textwrap
 import unittest
 import random
@@ -295,6 +296,69 @@ def test_keep_long_encoded_newlines(self):
         g.flatten(msg)
         self.assertEqual(s.getvalue(), self.typ(expected))
 
+    def test_non_ascii_addr_spec_raises(self):
+        # non-ascii is not permitted in any part of an addr-spec.  If the
+        # programmer generated it, it's an error.  (See also
+        # test_non_ascii_addr_spec_preserved below.)
+        p = self.policy.clone(utf8=False, max_line_length=20)
+        g = self.genclass(self.ioclass(), policy=p)
+        # XXX The particular part detected here isn't part of a behavioral
+        # spec and may change in the future.
+        cases = [
+            ('wők@example.com', 'wők', 'local-part'),
+            ('wok@exàmple.com', 'exàmple.com', 'domain'),
+            ('wők@exàmple.com', 'wők', 'local-part'),
+            (
+                '"Name, for display" <wők@example.com>',
+                'wők@example.com',
+                'addr-spec',
+                ),
+            (
+                'Näyttönimi <wők@example.com>',
+                'wők@example.com',
+                'addr-spec',
+                ),
+            (
+                '"a lőng quoted string as the local part"@example.com',
+                'a lőng quoted string as the local part',
+                'local-part',
+                ),
+
+        ]
+        for address, badtoken, partname in cases:
+            with self.subTest(address=address):
+                msg = EmailMessage()
+                msg['To'] = address
+                expected_error = (
+                    fr"(?i)(?=.*non-ascii)"
+                    fr"(?=.*{re.escape(badtoken)})"
+                    fr"(?=.*{partname})"
+                    fr"(?=.*policy.*utf8)"
+                )
+                with self.assertRaisesRegex(
+                    email.errors.HeaderWriteError, expected_error
+                ):
+                    g.flatten(msg)
+
+    def test_local_part_quoted_string_wrapped_correctly(self):
+        msg = self.msgmaker(self.typ(textwrap.dedent("""\
+            To: <"a long local part in a quoted string"@example.com>
+            Subject: test
+
+            None
+            """)), policy=self.policy.clone(max_line_length=20))
+        expected = textwrap.dedent("""\
+            To: <"a long local part in a
+             quoted string"@example.com>
+            Subject: test
+
+            None
+            """)
+        s = self.ioclass()
+        g = self.genclass(s, policy=self.policy.clone(max_line_length=30))
+        g.flatten(msg)
+        self.assertEqual(s.getvalue(), self.typ(expected))
+
     def _test_boundary_detection(self, linesep):
         # Generate a boundary token in the same way as _make_boundary
         token = random.randrange(sys.maxsize)
@@ -515,12 +579,12 @@ def test_cte_type_7bit_transforms_8bit_cte(self):
 
     def test_smtputf8_policy(self):
         msg = EmailMessage()
-        msg['From'] = "Páolo <főo@bar.com>"
+        msg['From'] = "Páolo <főo@bàr.com>"
         msg['To'] = 'Dinsdale'
         msg['Subject'] = 'Nudge nudge, wink, wink \u1F609'
         msg.set_content("oh là là, know what I mean, know what I mean?")
         expected = textwrap.dedent("""\
-            From: Páolo <főo@bar.com>
+            From: Páolo <főo@bàr.com>
             To: Dinsdale
             Subject: Nudge nudge, wink, wink \u1F609
             Content-Type: text/plain; charset="utf-8"
@@ -555,6 +619,37 @@ def test_smtp_policy(self):
         g.flatten(msg)
         self.assertEqual(s.getvalue(), expected)
 
+    def test_non_ascii_addr_spec_preserved(self):
+        # A defective non-ASCII addr-spec parsed from the original
+        # message is left unchanged when flattening.
+        # (See also test_non_ascii_addr_spec_raises above.)
+        source = (
+            'To: jörg@example.com, "But a long name still works with refold_source" <jörg@example.com>'
+        ).encode()
+        expected = (
+            b'To: j\xc3\xb6rg@example.com,\n'
+            b' "But a long name still works with refold_source" <j\xc3\xb6rg@example.com>\n'
+            b'\n'
+        )
+        msg = message_from_bytes(source, policy=policy.default)
+        s = io.BytesIO()
+        g = BytesGenerator(s, policy=policy.default)
+        g.flatten(msg)
+        self.assertEqual(s.getvalue(), expected)
+
+    def test_idna_encoding_preserved(self):
+        # Nothing tries to decode a pre-encoded IDNA domain.
+        msg = EmailMessage()
+        msg["To"] = Address(
+            username='jörg',
+            domain='☕.example'.encode('idna').decode()  # IDNA 2003
+        )
+        expected = 'To: jörg@xn--53h.example\n\n'.encode()
+        s = io.BytesIO()
+        g = BytesGenerator(s, policy=policy.default.clone(utf8=True))
+        g.flatten(msg)
+        self.assertEqual(s.getvalue(), expected)
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/Lib/test/test_email/test_headerregistry.py b/Lib/test/test_email/test_headerregistry.py
index a173b8b2512..c118fd5e20d 100644
--- a/Lib/test/test_email/test_headerregistry.py
+++ b/Lib/test/test_email/test_headerregistry.py
@@ -8,6 +8,7 @@
 from email import headerregistry
 from email.headerregistry import Address, Group
 from test.support import ALWAYS_EQ
+from test.support import warnings_helper
 
 
 DITTO = object()
@@ -165,6 +166,7 @@ def string_as_value(self,
 
     }
 
+
 @parameterize
 class TestDateHeader(TestHeaderBase):
 
@@ -254,7 +256,15 @@ def content_type_as_value(self,
         decoded =  args[2] if l>2 and args[2] is not DITTO else source
         header = 'Content-Type:' + ' ' if source else ''
         folded = args[3] if l>3 else header + decoded + '\n'
-        h = self.make_header('Content-Type', source)
+        # Both rfc2231 test cases with utf-8%E2%80%9D raise warnings,
+        # clear encoding cache to ensure test isolation.
+        if 'utf-8%E2%80%9D' in source and 'ascii' not in source:
+            import encodings
+            encodings._cache.clear()
+            with warnings_helper.check_warnings(('', DeprecationWarning)):
+                h = self.make_header('Content-Type', source)
+        else:
+            h = self.make_header('Content-Type', source)
         self.assertEqual(h.content_type, content_type)
         self.assertEqual(h.maintype, maintype)
         self.assertEqual(h.subtype, subtype)
@@ -1541,17 +1551,19 @@ def test_quoting(self):
         self.assertEqual(str(a), '"Sara J." <"bad name"@example.com>')
 
     def test_il8n(self):
-        a = Address('Éric', 'wok', 'exàmple.com')
+        a = Address('Éric', 'wők', 'exàmple.com')
         self.assertEqual(a.display_name, 'Éric')
-        self.assertEqual(a.username, 'wok')
+        self.assertEqual(a.username, 'wők')
         self.assertEqual(a.domain, 'exàmple.com')
-        self.assertEqual(a.addr_spec, 'wok@exàmple.com')
-        self.assertEqual(str(a), 'Éric <wok@exàmple.com>')
+        self.assertEqual(a.addr_spec, 'wők@exàmple.com')
+        self.assertEqual(str(a), 'Éric <wők@exàmple.com>')
 
-    # XXX: there is an API design issue that needs to be solved here.
-    #def test_non_ascii_username_raises(self):
-    #    with self.assertRaises(ValueError):
-    #        Address('foo', 'wők', 'example.com')
+    def test_i18n_in_addr_spec(self):
+        a = Address(addr_spec='wők@exàmple.com')
+        self.assertEqual(a.username, 'wők')
+        self.assertEqual(a.domain, 'exàmple.com')
+        self.assertEqual(a.addr_spec, 'wők@exàmple.com')
+        self.assertEqual(str(a), 'wők@exàmple.com')
 
     def test_crlf_in_constructor_args_raises(self):
         cases = (
@@ -1572,10 +1584,6 @@ def test_crlf_in_constructor_args_raises(self):
             with self.subTest(kwargs=kwargs), self.assertRaisesRegex(ValueError, "invalid arguments"):
                 Address(**kwargs)
 
-    def test_non_ascii_username_in_addr_spec_raises(self):
-        with self.assertRaises(ValueError):
-            Address('foo', addr_spec='wők@example.com')
-
     def test_address_addr_spec_and_username_raises(self):
         with self.assertRaises(TypeError):
             Address('foo', username='bing', addr_spec='bar@baz')
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index 57981ccc71b..7bc8b4c6ede 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -1002,12 +1002,18 @@ class OpenAB(self.enum_type):
             self.assertIs(~(A|B), OpenAB(252))
             self.assertIs(~AB_MASK, OpenAB(0))
             self.assertIs(~OpenAB(0), AB_MASK)
+            self.assertIs(OpenAB(~4), OpenAB(251))
         else:
             self.assertIs(~A, B)
             self.assertIs(~B, A)
+            self.assertIs(OpenAB(~1), B)
+            self.assertIs(OpenAB(~2), A)
             self.assertIs(~(A|B), OpenAB(0))
             self.assertIs(~AB_MASK, OpenAB(0))
             self.assertIs(~OpenAB(0), (A|B))
+            self.assertIs(OpenAB(~3), OpenAB(0))
+            self.assertIs(OpenAB(~4), OpenAB(3))
+            self.assertIs(OpenAB(~33), B)
         #
         class OpenXYZ(self.enum_type):
             X = 4
@@ -1031,6 +1037,9 @@ class OpenXYZ(self.enum_type):
             self.assertIs(~X, Y|Z)
             self.assertIs(~Y, X|Z)
             self.assertIs(~Z, X|Y)
+            self.assertIs(OpenXYZ(~4), Y|Z)
+            self.assertIs(OpenXYZ(~2), X|Z)
+            self.assertIs(OpenXYZ(~1), X|Y)
             self.assertIs(~(X|Y), Z)
             self.assertIs(~(X|Z), Y)
             self.assertIs(~(Y|Z), X)
@@ -1038,6 +1047,28 @@ class OpenXYZ(self.enum_type):
             self.assertIs(~XYZ_MASK, OpenXYZ(0))
             self.assertTrue(~OpenXYZ(0), (X|Y|Z))
 
+    def test_assigned_negative_value(self):
+        class X(self.enum_type):
+            A = auto()
+            B = auto()
+            C = A | B
+            D = ~A
+        self.assertEqual(list(X), [X.A, X.B])
+        self.assertIs(~X.A, X.B)
+        self.assertIs(X.D, X.B)
+        self.assertEqual(X.D.value, 2)
+        #
+        class Y(self.enum_type):
+            A = auto()
+            B = auto()
+            C = A | B
+            D = ~A
+            E = auto()
+        self.assertEqual(list(Y), [Y.A, Y.B, Y.E])
+        self.assertIs(~Y.A, Y.B|Y.E)
+        self.assertIs(Y.D, Y.B|Y.E)
+        self.assertEqual(Y.D.value, 6)
+
 
 class TestPlainEnumClass(_EnumTests, _PlainOutputTests, unittest.TestCase):
     enum_type = Enum
@@ -3036,7 +3067,6 @@ class ThirdFailedStrEnum(StrEnum):
                 one = '1'
                 two = b'2', 'ascii', 9
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; fails on encoding testing : TypeError: Expected type 'str' but 'builtin_function_or_method' found
     def test_custom_strenum(self):
         class CustomStrEnum(str, Enum):
             pass
@@ -3682,6 +3712,8 @@ class SkipFlag(enum.Flag):
             C = 4 | B
         #
         self.assertTrue(SkipFlag.C in (SkipFlag.A|SkipFlag.C))
+        self.assertTrue(SkipFlag.B in SkipFlag.C)
+        self.assertIs(SkipFlag(~1), SkipFlag.B)
         self.assertRaisesRegex(ValueError, 'SkipFlag.. invalid value 42', SkipFlag, 42)
         #
         class SkipIntFlag(enum.IntFlag):
@@ -3690,6 +3722,8 @@ class SkipIntFlag(enum.IntFlag):
             C = 4 | B
         #
         self.assertTrue(SkipIntFlag.C in (SkipIntFlag.A|SkipIntFlag.C))
+        self.assertTrue(SkipIntFlag.B in SkipIntFlag.C)
+        self.assertIs(SkipIntFlag(~1), SkipIntFlag.B|SkipIntFlag.C)
         self.assertEqual(SkipIntFlag(42).value, 42)
         #
         class MethodHint(Flag):
@@ -4729,6 +4763,8 @@ class Color(Flag):
             BLUE = 4
             WHITE = -1
         # no error means success
+        self.assertEqual(list(Color.WHITE), [Color.RED, Color.GREEN, Color.BLUE])
+        self.assertEqual(Color.WHITE.value, 7)
 
 
 class TestInternals(unittest.TestCase):
@@ -4852,7 +4888,7 @@ class Color(Enum):
                 def _generate_next_value_(name, start, count, last):
                     return name
 
-    def test_auto_order_wierd(self):
+    def test_auto_order_weird(self):
         weird_auto = auto()
         weird_auto.value = 'pathological case'
         class Color(Enum):
@@ -5289,7 +5325,7 @@ def __new__(cls, value, label):
 class MiscTestCase(unittest.TestCase):
 
     def test__all__(self):
-        support.check__all__(self, enum, not_exported={'bin', 'show_flag_values'})
+        support.check__all__(self, enum)
 
     @cpython_only
     def test_lazy_import(self):
@@ -5494,12 +5530,16 @@ def test_enum_dict_standalone(self):
 # helpers
 
 def enum_dir(cls):
+    if issubclass(cls, Flag):
+        members = list(cls._member_map_.keys())
+    else:
+        members = cls._member_names_
     interesting = set([
             '__class__', '__contains__', '__doc__', '__getitem__',
             '__iter__', '__len__', '__members__', '__module__',
             '__name__', '__qualname__',
             ]
-            + cls._member_names_
+            + members
             )
     if cls._new_member_ is not object.__new__:
         interesting.add('__new__')
diff --git a/Lib/test/test_extcall.py b/Lib/test/test_extcall.py
index 483d5ad5f2b..c816d0135a1 100644
--- a/Lib/test/test_extcall.py
+++ b/Lib/test/test_extcall.py
@@ -442,7 +442,7 @@
     ...     False
     True
 
-    >>> id(1, **{'foo': 1}) # TODO: RUSTPYTHON # doctest:+EXPECTED_FAILURE
+    >>> id(1, **{'foo': 1})
     Traceback (most recent call last):
       ...
     TypeError: id() takes no keyword arguments
diff --git a/Lib/test/test_finalization.py b/Lib/test/test_finalization.py
index 42871f8a09b..9dd68cf8d57 100644
--- a/Lib/test/test_finalization.py
+++ b/Lib/test/test_finalization.py
@@ -174,7 +174,7 @@ def test_simple(self):
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors([])
-            self.assertIs(wr(), None)
+            self.assertIsNone(wr())
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors([])
@@ -188,12 +188,12 @@ def test_simple_resurrect(self):
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors(ids)
-            self.assertIsNot(wr(), None)
+            self.assertIsNotNone(wr())
             self.clear_survivors()
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors([])
-        self.assertIs(wr(), None)
+        self.assertIsNone(wr())
 
     @support.cpython_only
     def test_non_gc(self):
@@ -265,7 +265,7 @@ def test_simple(self):
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors([])
-            self.assertIs(wr(), None)
+            self.assertIsNone(wr())
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors([])
@@ -276,19 +276,24 @@ def test_simple_resurrect(self):
             s = SelfCycleResurrector()
             ids = [id(s)]
             wr = weakref.ref(s)
+            wrc = weakref.ref(s, lambda x: None)
             del s
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors(ids)
-            # XXX is this desirable?
-            self.assertIs(wr(), None)
+            # This used to be None because weakrefs were cleared before
+            # calling finalizers.  Now they are cleared after.
+            self.assertIsNotNone(wr())
+            # A weakref with a callback is still cleared before calling
+            # finalizers.
+            self.assertIsNone(wrc())
             # When trying to destroy the object a second time, __del__
             # isn't called anymore (and the object isn't resurrected).
             self.clear_survivors()
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors([])
-            self.assertIs(wr(), None)
+            self.assertIsNone(wr())
 
     def test_simple_suicide(self):
         # Test the GC is able to deal with an object that kills its last
@@ -301,11 +306,11 @@ def test_simple_suicide(self):
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors([])
-            self.assertIs(wr(), None)
+            self.assertIsNone(wr())
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors([])
-            self.assertIs(wr(), None)
+            self.assertIsNone(wr())
 
 
 class ChainedBase:
@@ -378,18 +383,27 @@ def check_non_resurrecting_chain(self, classes):
 
     def check_resurrecting_chain(self, classes):
         N = len(classes)
+        def dummy_callback(ref):
+            pass
         with SimpleBase.test():
             nodes = self.build_chain(classes)
             N = len(nodes)
             ids = [id(s) for s in nodes]
             survivor_ids = [id(s) for s in nodes if isinstance(s, SimpleResurrector)]
             wrs = [weakref.ref(s) for s in nodes]
+            wrcs = [weakref.ref(s, dummy_callback) for s in nodes]
             del nodes
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_survivors(survivor_ids)
-            # XXX desirable?
-            self.assertEqual([wr() for wr in wrs], [None] * N)
+            for wr in wrs:
+                # These values used to be None because weakrefs were cleared
+                # before calling finalizers.  Now they are cleared after.
+                self.assertIsNotNone(wr())
+            for wr in wrcs:
+                # Weakrefs with callbacks are still cleared before calling
+                # finalizers.
+                self.assertIsNone(wr())
             self.clear_survivors()
             gc.collect()
             self.assert_del_calls(ids)
@@ -491,7 +505,7 @@ def test_legacy(self):
             self.assert_del_calls(ids)
             self.assert_tp_del_calls(ids)
             self.assert_survivors([])
-            self.assertIs(wr(), None)
+            self.assertIsNone(wr())
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_tp_del_calls(ids)
@@ -507,13 +521,13 @@ def test_legacy_resurrect(self):
             self.assert_tp_del_calls(ids)
             self.assert_survivors(ids)
             # weakrefs are cleared before tp_del is called.
-            self.assertIs(wr(), None)
+            self.assertIsNone(wr())
             self.clear_survivors()
             gc.collect()
             self.assert_del_calls(ids)
             self.assert_tp_del_calls(ids * 2)
             self.assert_survivors(ids)
-        self.assertIs(wr(), None)
+        self.assertIsNone(wr())
 
     def test_legacy_self_cycle(self):
         # Self-cycles with legacy finalizers end up in gc.garbage.
@@ -527,11 +541,11 @@ def test_legacy_self_cycle(self):
             self.assert_tp_del_calls([])
             self.assert_survivors([])
             self.assert_garbage(ids)
-            self.assertIsNot(wr(), None)
+            self.assertIsNotNone(wr())
             # Break the cycle to allow collection
             gc.garbage[0].ref = None
         self.assert_garbage([])
-        self.assertIs(wr(), None)
+        self.assertIsNone(wr())
 
 
 if __name__ == "__main__":
diff --git a/Lib/test/test_format.py b/Lib/test/test_format.py
index aa28108312e..a4bf797aab1 100644
--- a/Lib/test/test_format.py
+++ b/Lib/test/test_format.py
@@ -529,7 +529,6 @@ def test_with_an_underscore_and_a_comma_in_format_specifier(self):
         with self.assertRaisesRegex(ValueError, error_msg):
             '{:._,f}'.format(1.1)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_better_error_message_format(self):
         # https://bugs.python.org/issue20524
         for value in [12j, 12, 12.0, "12"]:
@@ -551,7 +550,6 @@ def test_better_error_message_format(self):
                 with self.assertRaisesRegex(ValueError, err):
                     eval("f'xx{value:{bad_format_spec}}yy'")
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_unicode_in_error_message(self):
         str_err = re.escape(
             "Invalid format specifier '%ЫйЯЧ' for object of type 'str'")
@@ -615,7 +613,6 @@ def test_negative_zero(self):
         self.assertEqual(f"{-0.:x>z6.1f}", "xxx0.0")
         self.assertEqual(f"{-0.:🖤>z6.1f}", "🖤🖤🖤0.0")  # multi-byte fill char
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_specifier_z_error(self):
         error_msg = re.compile("Invalid format specifier '.*z.*'")
         with self.assertRaisesRegex(ValueError, error_msg):
@@ -629,7 +626,7 @@ def test_specifier_z_error(self):
         with self.assertRaisesRegex(ValueError, error_msg):
             f"{'x':zs}"  # can't apply to string
 
-        error_msg = re.escape("unsupported format character 'z'")
+        error_msg = re.escape("unsupported format %z at position 0")
         with self.assertRaisesRegex(ValueError, error_msg):
             "%z.1f" % 0  # not allowed in old style string interpolation
         with self.assertRaisesRegex(ValueError, error_msg):
diff --git a/Lib/test/test_fstring.py b/Lib/test/test_fstring.py
index b68e356e04d..baa638e07fa 100644
--- a/Lib/test/test_fstring.py
+++ b/Lib/test/test_fstring.py
@@ -865,7 +865,6 @@ def __format__(self, spec):
         x = X()
         self.assertEqual(f'{x} {x}', '1 2')
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_missing_expression(self):
         self.assertAllRaise(SyntaxError,
                             "f-string: valid expression required before '}'",
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index c06140dbd58..9887fc74c23 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -438,7 +438,7 @@ def test_setstate_subclasses(self):
         self.assertIs(type(r[0]), tuple)
 
     @support.skip_if_sanitizer("thread sanitizer crashes in __tsan::FuncEntry", thread=True)
-    @support.skip_if_unlimited_stack_size
+    @support.skip_if_huge_c_stack()
     @support.skip_emscripten_stack_overflow()
     def test_recursive_pickle(self):
         with replaced_module('functools', self.module):
@@ -565,7 +565,53 @@ def __repr__(self):
         g_partial = functools.partial(func, trigger, None, None, None, None, arg=None)
         self.assertEqual(repr(g_partial),"functools.partial(Function(old_function), EvilObject, None, None, None, None, arg=None)")
 
+    def test_str_subclass_error(self):
+        class BadStr(str):
+            def __eq__(self, other):
+                raise RuntimeError
+            def __hash__(self):
+                return str.__hash__(self)
+
+        def f(**kwargs):
+            return kwargs
+
+        p = functools.partial(f, poison="")
+        with self.assertRaises(RuntimeError):
+            result = p(**{BadStr("poison"): "new_value"})
+
+    def test_call_safety_against_reentrant_mutation(self):
+        def old_function(*args, **kwargs):
+            return "old_function", args, kwargs
+
+        def new_function(*args, **kwargs):
+            return "new_function", args, kwargs
+
+        g_partial = None
+
+        class EvilKey(str):
+            armed = False
+            def __hash__(self):
+                if EvilKey.armed and g_partial is not None:
+                    EvilKey.armed = False
+                    new_args_tuple = ("new_arg",)
+                    new_keywords_dict = {"new_keyword": None}
+                    new_tuple_state = (new_function, new_args_tuple, new_keywords_dict, None)
+                    g_partial.__setstate__(new_tuple_state)
+                    gc.collect()
+                return str.__hash__(self)
+
+        g_partial = functools.partial(old_function, "old_arg", old_keyword=None)
+
+        kwargs = {EvilKey("evil_key"): None}
+        EvilKey.armed = True
+
+        result = g_partial(**kwargs)
+        expected = ("old_function", ("old_arg",), {"old_keyword": None, "evil_key": None})
+        self.assertEqual(result, expected)
 
+        result = g_partial()
+        expected = ("new_function", ("new_arg",), {"new_keyword": None})
+        self.assertEqual(result, expected)
 
 @unittest.skipUnless(c_functools, 'requires the C _functools module')
 class TestPartialC(TestPartial, unittest.TestCase):
@@ -2209,6 +2255,13 @@ def fib(n):
                 with self.assertRaises(RecursionError):
                     fib(support.exceeds_recursion_limit())
 
+    def test_lru_checks_arg_is_callable(self):
+        with self.assertRaisesRegex(
+            TypeError,
+            "the first argument must be callable",
+        ):
+            self.module.lru_cache(1)('hello')
+
 
 @py_functools.lru_cache()
 def py_cached_func(x, y):
@@ -2843,7 +2896,7 @@ class Slot:
             @functools.singledispatchmethod
             @classmethod
             def go(cls, item, arg):
-                pass
+                return item - arg
 
             @go.register
             @classmethod
@@ -2852,7 +2905,9 @@ def _(cls, item: int, arg):
 
         s = Slot()
         self.assertEqual(s.go(1, 1), 2)
+        self.assertEqual(s.go(1.5, 1), 0.5)
         self.assertEqual(Slot.go(1, 1), 2)
+        self.assertEqual(Slot.go(1.5, 1), 0.5)
 
     def test_staticmethod_slotted_class(self):
         class A:
@@ -3052,6 +3107,57 @@ def static_func(arg: int) -> str:
         self.assertEqual(A.static_func.__name__, 'static_func')
         self.assertEqual(A().static_func.__name__, 'static_func')
 
+    def test_method_classlevel_calls(self):
+        """Regression test for GH-143535."""
+        class C:
+            @functools.singledispatchmethod
+            def generic(self, x: object):
+                return "generic"
+
+            @generic.register
+            def special1(self, x: int):
+                return "special1"
+
+            @generic.register
+            @classmethod
+            def special2(self, x: float):
+                return "special2"
+
+            @generic.register
+            @staticmethod
+            def special3(x: complex):
+                return "special3"
+
+            def special4(self, x):
+                return "special4"
+
+            class D1:
+                def __get__(self, _, owner):
+                    return lambda inst, x: owner.special4(inst, x)
+
+            generic.register(D1, D1())
+
+            def special5(self, x):
+                return "special5"
+
+            class D2:
+                def __get__(self, inst, owner):
+                    # Different instance bound to the returned method
+                    # doesn't cause it to receive the original instance
+                    # as a separate argument.
+                    # To work around this, wrap the returned bound method
+                    # with `functools.partial`.
+                    return C().special5
+
+            generic.register(D2, D2())
+
+        self.assertEqual(C.generic(C(), "foo"), "generic")
+        self.assertEqual(C.generic(C(), 1), "special1")
+        self.assertEqual(C.generic(C(), 2.0), "special2")
+        self.assertEqual(C.generic(C(), 3j), "special3")
+        self.assertEqual(C.generic(C(), C.D1()), "special4")
+        self.assertEqual(C.generic(C(), C.D2()), "special5")
+
     def test_method_repr(self):
         class Callable:
             def __call__(self, *args):
@@ -3290,6 +3396,21 @@ def t(self, *args, **kwargs):
         with self.assertRaisesRegex(TypeError, msg):
             A().t(a=1)
 
+    def test_positional_only_argument(self):
+        @functools.singledispatch
+        def f(arg, /, extra):
+            return "base"
+        @f.register
+        def f_int(arg: int, /, extra: str):
+            return "int"
+        @f.register
+        def f_str(arg: str, /, extra: int):
+            return "str"
+
+        self.assertEqual(f(None, "extra"), "base")
+        self.assertEqual(f(1, "extra"), "int")
+        self.assertEqual(f("s", "extra"), "str")
+
     def test_union(self):
         @functools.singledispatch
         def f(arg):
@@ -3538,6 +3659,37 @@ def _(item: int, arg: bytes) -> str:
         self.assertEqual(str(Signature.from_callable(A.static_func)),
                          '(item, arg: int) -> str')
 
+    def test_method_non_descriptor(self):
+        class Callable:
+            def __init__(self, value):
+                self.value = value
+            def __call__(self, arg):
+                return self.value, arg
+
+        class A:
+            t = functools.singledispatchmethod(Callable('general'))
+            t.register(int, Callable('special'))
+
+            @functools.singledispatchmethod
+            def u(self, arg):
+                return 'general', arg
+            u.register(int, Callable('special'))
+
+            v = functools.singledispatchmethod(Callable('general'))
+            @v.register(int)
+            def _(self, arg):
+                return 'special', arg
+
+        a = A()
+        self.assertEqual(a.t(0), ('special', 0))
+        self.assertEqual(a.t(2.5), ('general', 2.5))
+        self.assertEqual(A.t(0), ('special', 0))
+        self.assertEqual(A.t(2.5), ('general', 2.5))
+        self.assertEqual(a.u(0), ('special', 0))
+        self.assertEqual(a.u(2.5), ('general', 2.5))
+        self.assertEqual(a.v(0), ('special', 0))
+        self.assertEqual(a.v(2.5), ('general', 2.5))
+
 
 class CachedCostItem:
     _cost = 1
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index 3ed2aabafcb..c477006c9cc 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -236,7 +236,6 @@ def test_function(self):
         # is 3 because it includes f's code object.
         self.assertIn(gc.collect(), (2, 3))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; - weakref clear ordering differs from 3.15+
     def test_function_tp_clear_leaves_consistent_state(self):
         # https://github.com/python/cpython/issues/91636
         code = """if 1:
@@ -310,6 +309,26 @@ def func():
         self.assertRegex(stdout, rb"""\A\s*func=None""")
         self.assertFalse(stderr)
 
+    def test_datetime_weakref_cycle(self):
+        # https://github.com/python/cpython/issues/132413
+        # If the weakref used by the datetime extension gets cleared by the GC (due to being
+        # in an unreachable cycle) then datetime functions would crash (get_module_state()
+        # was returning a NULL pointer).  This bug is fixed by clearing weakrefs without
+        # callbacks *after* running finalizers.
+        code = """if 1:
+        import _datetime
+        class C:
+            def __del__(self):
+                print('__del__ called')
+                _datetime.timedelta(days=1)  # crash?
+
+        l = [C()]
+        l.append(l)
+        """
+        rc, stdout, stderr = assert_python_ok("-c", code)
+        self.assertEqual(rc, 0)
+        self.assertEqual(stdout.strip(), b'__del__ called')
+
     @refcount_test
     def test_frame(self):
         def f():
@@ -667,9 +686,8 @@ def callback(ignored):
         gc.collect()
         self.assertEqual(len(ouch), 2)  # else the callbacks didn't run
         for x in ouch:
-            # If the callback resurrected one of these guys, the instance
-            # would be damaged, with an empty __dict__.
-            self.assertEqual(x, None)
+            # The weakref should be cleared before executing the callback.
+            self.assertIsNone(x)
 
     def test_bug21435(self):
         # This is a poor test - its only virtue is that it happened to
@@ -831,17 +849,20 @@ def __del__(self):
         rc, out, err = assert_python_ok(TESTFN)
         self.assertEqual(out.strip(), b'__del__ called')
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_get_stats(self):
         stats = gc.get_stats()
         self.assertEqual(len(stats), 3)
         for st in stats:
             self.assertIsInstance(st, dict)
-            self.assertEqual(set(st),
-                             {"collected", "collections", "uncollectable"})
+            self.assertEqual(
+                set(st),
+                {"collected", "collections", "uncollectable", "candidates", "duration"}
+            )
             self.assertGreaterEqual(st["collected"], 0)
             self.assertGreaterEqual(st["collections"], 0)
             self.assertGreaterEqual(st["uncollectable"], 0)
+            self.assertGreaterEqual(st["candidates"], 0)
+            self.assertGreaterEqual(st["duration"], 0)
         # Check that collection counts are incremented correctly
         if gc.isenabled():
             self.addCleanup(gc.enable)
@@ -852,11 +873,25 @@ def test_get_stats(self):
         self.assertEqual(new[0]["collections"], old[0]["collections"] + 1)
         self.assertEqual(new[1]["collections"], old[1]["collections"])
         self.assertEqual(new[2]["collections"], old[2]["collections"])
+        self.assertGreater(new[0]["duration"], old[0]["duration"])
+        self.assertEqual(new[1]["duration"], old[1]["duration"])
+        self.assertEqual(new[2]["duration"], old[2]["duration"])
+        for stat in ["collected", "uncollectable", "candidates"]:
+            self.assertGreaterEqual(new[0][stat], old[0][stat])
+            self.assertEqual(new[1][stat], old[1][stat])
+            self.assertEqual(new[2][stat], old[2][stat])
         gc.collect(2)
-        new = gc.get_stats()
-        self.assertEqual(new[0]["collections"], old[0]["collections"] + 1)
+        old, new = new, gc.get_stats()
+        self.assertEqual(new[0]["collections"], old[0]["collections"])
         self.assertEqual(new[1]["collections"], old[1]["collections"])
         self.assertEqual(new[2]["collections"], old[2]["collections"] + 1)
+        self.assertEqual(new[0]["duration"], old[0]["duration"])
+        self.assertEqual(new[1]["duration"], old[1]["duration"])
+        self.assertGreater(new[2]["duration"], old[2]["duration"])
+        for stat in ["collected", "uncollectable", "candidates"]:
+            self.assertEqual(new[0][stat], old[0][stat])
+            self.assertEqual(new[1][stat], old[1][stat])
+            self.assertGreaterEqual(new[2][stat], old[2][stat])
 
     def test_freeze(self):
         gc.freeze()
@@ -1204,6 +1239,37 @@ def test_something(self):
         """)
         assert_python_ok("-c", source)
 
+    def test_do_not_cleanup_type_subclasses_before_finalization(self):
+        #  See https://github.com/python/cpython/issues/135552
+        # If we cleanup weakrefs for tp_subclasses before calling
+        # the finalizer (__del__) then the line `fail = BaseNode.next.next`
+        # should fail because we are trying to access a subclass
+        # attribute. But subclass type cache was not properly invalidated.
+        code = """
+            class BaseNode:
+                def __del__(self):
+                    BaseNode.next = BaseNode.next.next
+                    fail = BaseNode.next.next
+
+            class Node(BaseNode):
+                pass
+
+            BaseNode.next = Node()
+            BaseNode.next.next = Node()
+        """
+        # this test checks garbage collection while interp
+        # finalization
+        assert_python_ok("-c", textwrap.dedent(code))
+
+        code_inside_function = textwrap.dedent(F"""
+            def test():
+                {textwrap.indent(code, '    ')}
+
+            test()
+        """)
+        # this test checks regular garbage collection
+        assert_python_ok("-c", code_inside_function)
+
 
     @unittest.expectedFailure  # TODO: RUSTPYTHON; long_lived_total does not count untracked tuples
     @unittest.skipUnless(Py_GIL_DISABLED, "requires free-threaded GC")
@@ -1308,9 +1374,11 @@ def test_collect(self):
         # Check that we got the right info dict for all callbacks
         for v in self.visit:
             info = v[2]
-            self.assertTrue("generation" in info)
-            self.assertTrue("collected" in info)
-            self.assertTrue("uncollectable" in info)
+            self.assertIn("generation", info)
+            self.assertIn("collected", info)
+            self.assertIn("uncollectable", info)
+            self.assertIn("candidates", info)
+            self.assertIn("duration", info)
 
     def test_collect_generation(self):
         self.preclean()
@@ -1498,6 +1566,7 @@ def callback(ignored):
             self.assertEqual(x, None)
 
     @gc_threshold(1000, 0, 0)
+    @unittest.skipIf(Py_GIL_DISABLED, "requires GC generations or increments")
     def test_bug1055820d(self):
         # Corresponds to temp2d.py in the bug report.  This is very much like
         # test_bug1055820c, but uses a __del__ method instead of a weakref
@@ -1595,6 +1664,25 @@ def test_indirect_calls_with_gc_disabled(self):
         finally:
             gc.enable()
 
+    def test_get_count_nonnegative(self):
+        xs = [[] for _ in range(1500)]
+        gc.collect()
+        del xs[:1000]
+        self.assertGreaterEqual(gc.get_count()[0], 0)
+
+    @gc_threshold(1000, 0, 0)
+    def test_get_count_does_not_prevent_collection(self):
+        junk = []
+        gc.collect()
+        detector = GC_Detector()
+        for _ in range(10000):
+            junk.append([])
+            gc.get_count()
+            if detector.gc_happened:
+                break
+        else:
+            self.fail("gc didn't happen after 10000 iterations")
+
     # Ensure that setting *threshold0* to zero disables collection.
     @gc_threshold(0)
     def test_threshold_zero(self):
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 037c1bed5fe..6eb25960101 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -300,7 +300,7 @@ class C:
             def __iter__(self):
                 return Iterator()
 
-        self.assertEqual([1, 2], list(i for i in C()))
+        self.assertEqual([1,2], list(i for i in C()))
 
     def test_close_clears_frame(self):
         # gh-142766: Test that closing a generator clears its frame
@@ -357,26 +357,25 @@ def gen(it):
                 yield x
         return gen(range(10))
 
-    def process_tests(self, get_generator, is_expr):
-        err_iterator = "'.*' object is not an iterator"
-        err_iterable = "'.*' object is not iterable"
-        for obj in self.iterables:
-            g_obj = get_generator(obj)
-            with self.subTest(g_obj=g_obj, obj=obj):
-                if is_expr:
-                    self.assertRaisesRegex(TypeError, err_iterator, list, g_obj)
-                else:
+    def process_tests(self, get_generator, changes_iterable):
+        if changes_iterable:
+            for obj in self.iterables:
+                g_obj = get_generator(obj)
+                with self.subTest(g_obj=g_obj, obj=obj):
                     self.assertListEqual(list(g_obj), list(obj))
 
-            g_iter = get_generator(iter(obj))
-            with self.subTest(g_iter=g_iter, obj=obj):
-                self.assertListEqual(list(g_iter), list(obj))
+                g_iter = get_generator(iter(obj))
+                with self.subTest(g_iter=g_iter, obj=obj):
+                    self.assertListEqual(list(g_iter), list(obj))
 
+        err_regex = "'.*' object is not iterable"
         for obj in self.non_iterables:
             g_obj = get_generator(obj)
             with self.subTest(g_obj=g_obj):
-                err = err_iterator if is_expr else err_iterable
-                self.assertRaisesRegex(TypeError, err, list, g_obj)
+                if changes_iterable:
+                    self.assertRaisesRegex(TypeError, err_regex, list, g_obj)
+                else:
+                    next(g_obj)
 
     def test_modify_f_locals(self):
         def modify_f_locals(g, local, obj):
@@ -389,22 +388,22 @@ def get_generator_genexpr(obj):
         def get_generator_genfunc(obj):
             return modify_f_locals(self.genfunc(), 'it', obj)
 
-        self.process_tests(get_generator_genexpr, True)
-        self.process_tests(get_generator_genfunc, False)
+        self.process_tests(get_generator_genexpr, False)
+        self.process_tests(get_generator_genfunc, True)
 
     def test_new_gen_from_gi_code(self):
         def new_gen_from_gi_code(g, obj):
             generator_func = types.FunctionType(g.gi_code, {})
             return generator_func(obj)
 
-        def get_generator_genexpr(obj):
-            return new_gen_from_gi_code(self.genexpr(), obj)
+        for obj in self.non_iterables:
+            with self.assertRaises(TypeError):
+                new_gen_from_gi_code(self.genexpr(), obj)
 
         def get_generator_genfunc(obj):
             return new_gen_from_gi_code(self.genfunc(), obj)
 
-        self.process_tests(get_generator_genexpr, True)
-        self.process_tests(get_generator_genfunc, False)
+        self.process_tests(get_generator_genfunc, True)
 
 
 class ExceptionTest(unittest.TestCase):
@@ -1367,7 +1366,7 @@ def b():
 >>> type(i)
 <class 'generator'>
 >>> [s for s in dir(i) if not s.startswith('_')]
-['close', 'gi_code', 'gi_frame', 'gi_running', 'gi_suspended', 'gi_yieldfrom', 'send', 'throw']
+['close', 'gi_code', 'gi_frame', 'gi_running', 'gi_state', 'gi_suspended', 'gi_yieldfrom', 'send', 'throw']
 >>> from test.support import HAVE_DOCSTRINGS
 >>> print(i.__next__.__doc__ if HAVE_DOCSTRINGS else 'Implement next(self).')
 Implement next(self).
@@ -2878,8 +2877,7 @@ def printsolution(self, x):
             }
 
 def load_tests(loader, tests, pattern):
-    from test.support.rustpython import DocTestChecker  # TODO: RUSTPYTHON
-    tests.addTest(doctest.DocTestSuite(checker=DocTestChecker()))  # TODO: RUSTPYTHON
+    tests.addTest(doctest.DocTestSuite())
     return tests
 
 
diff --git a/Lib/test/test_genericalias.py b/Lib/test/test_genericalias.py
index 121d169dd07..7816775620b 100644
--- a/Lib/test/test_genericalias.py
+++ b/Lib/test/test_genericalias.py
@@ -17,7 +17,7 @@
 from functools import partial, partialmethod, cached_property
 from graphlib import TopologicalSorter
 from logging import LoggerAdapter, StreamHandler
-from mailbox import Mailbox, _PartialFile
+from mailbox import Mailbox
 try:
     import ctypes
 except ImportError:
@@ -100,7 +100,9 @@
 
 class BaseTest(unittest.TestCase):
     """Test basics."""
-    generic_types = [type, tuple, list, dict, set, frozenset, enumerate, memoryview,
+    generic_types = [type, tuple, list, dict, frozendict,
+                     set, frozenset, enumerate, memoryview,
+                     slice,
                      defaultdict, deque,
                      SequenceMatcher,
                      dircmp,
@@ -116,7 +118,7 @@ class BaseTest(unittest.TestCase):
                      Iterable, Iterator,
                      Reversible,
                      Container, Collection,
-                     Mailbox, _PartialFile,
+                     Mailbox,
                      ContextVar, Token,
                      Field,
                      Set, MutableSet,
diff --git a/Lib/test/test_genericpath.py b/Lib/test/test_genericpath.py
index 1a44cedcd36..10d3f409d88 100644
--- a/Lib/test/test_genericpath.py
+++ b/Lib/test/test_genericpath.py
@@ -2,8 +2,10 @@
 Tests common to genericpath, ntpath and posixpath
 """
 
+import copy
 import genericpath
 import os
+import pickle
 import sys
 import unittest
 import warnings
@@ -32,6 +34,10 @@ def test_no_argument(self):
                                 .format(self.pathmodule.__name__, attr))
 
     def test_commonprefix(self):
+        with warnings_helper.check_warnings((".*commonpath().*", DeprecationWarning)):
+            self.do_test_commonprefix()
+
+    def do_test_commonprefix(self):
         commonprefix = self.pathmodule.commonprefix
         self.assertEqual(
             commonprefix([]),
@@ -320,6 +326,21 @@ def test_sameopenfile(self):
                 fd2 = fp2.fileno()
                 self.assertTrue(self.pathmodule.sameopenfile(fd1, fd2))
 
+    def test_realpath_mode_values(self):
+        for name in 'ALL_BUT_LAST', 'ALLOW_MISSING':
+            with self.subTest(name):
+                mode = getattr(self.pathmodule, name)
+                self.assertEqual(repr(mode), 'os.path.' + name)
+                self.assertEqual(str(mode), 'os.path.' + name)
+                self.assertTrue(mode)
+                self.assertIs(copy.copy(mode), mode)
+                self.assertIs(copy.deepcopy(mode), mode)
+                for proto in range(pickle.HIGHEST_PROTOCOL+1):
+                    with self.subTest(protocol=proto):
+                        pickled = pickle.dumps(mode, proto)
+                        unpickled = pickle.loads(pickled)
+                        self.assertIs(unpickled, mode)
+
 
 class TestGenericTest(GenericTest, unittest.TestCase):
     # Issue 16852: GenericTest can't inherit from unittest.TestCase
@@ -589,8 +610,9 @@ def test_path_isdir(self):
         self.assertPathEqual(os.path.isdir)
 
     def test_path_commonprefix(self):
-        self.assertEqual(os.path.commonprefix([self.file_path, self.file_name]),
-                         self.file_name)
+        with warnings_helper.check_warnings((".*commonpath().*", DeprecationWarning)):
+            self.assertEqual(os.path.commonprefix([self.file_path, self.file_name]),
+                             self.file_name)
 
     def test_path_getsize(self):
         self.assertPathEqual(os.path.getsize)
diff --git a/Lib/test/test_glob.py b/Lib/test/test_glob.py
index d0ed5129253..9e4e82b2542 100644
--- a/Lib/test/test_glob.py
+++ b/Lib/test/test_glob.py
@@ -4,7 +4,6 @@
 import shutil
 import sys
 import unittest
-import warnings
 
 from test.support import is_wasi, Py_DEBUG
 from test.support.os_helper import (TESTFN, skip_unless_symlink,
@@ -393,36 +392,6 @@ def test_glob_many_open_files(self):
             for it in iters:
                 self.assertEqual(next(it), p)
 
-    def test_glob0(self):
-        with self.assertWarns(DeprecationWarning):
-            glob.glob0(self.tempdir, 'a')
-
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore')
-            eq = self.assertSequencesEqual_noorder
-            eq(glob.glob0(self.tempdir, 'a'), ['a'])
-            eq(glob.glob0(self.tempdir, '.bb'), ['.bb'])
-            eq(glob.glob0(self.tempdir, '.b*'), [])
-            eq(glob.glob0(self.tempdir, 'b'), [])
-            eq(glob.glob0(self.tempdir, '?'), [])
-            eq(glob.glob0(self.tempdir, '*a'), [])
-            eq(glob.glob0(self.tempdir, 'a*'), [])
-
-    def test_glob1(self):
-        with self.assertWarns(DeprecationWarning):
-            glob.glob1(self.tempdir, 'a')
-
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore')
-            eq = self.assertSequencesEqual_noorder
-            eq(glob.glob1(self.tempdir, 'a'), ['a'])
-            eq(glob.glob1(self.tempdir, '.bb'), ['.bb'])
-            eq(glob.glob1(self.tempdir, '.b*'), ['.bb'])
-            eq(glob.glob1(self.tempdir, 'b'), [])
-            eq(glob.glob1(self.tempdir, '?'), ['a'])
-            eq(glob.glob1(self.tempdir, '*a'), ['a', 'aaa'])
-            eq(glob.glob1(self.tempdir, 'a*'), ['a', 'aaa', 'aab'])
-
     def test_translate_matching(self):
         match = re.compile(glob.translate('*')).match
         self.assertIsNotNone(match('foo'))
diff --git a/Lib/test/test_gzip.py b/Lib/test/test_gzip.py
index ccbacc7c19b..cafac9d3c8b 100644
--- a/Lib/test/test_gzip.py
+++ b/Lib/test/test_gzip.py
@@ -9,10 +9,10 @@
 import struct
 import sys
 import unittest
-import warnings
 from subprocess import PIPE, Popen
+from unittest import mock
 from test.support import catch_unraisable_exception
-from test.support import import_helper
+from test.support import force_not_colorized_test_class, import_helper
 from test.support import os_helper
 from test.support import _4G, bigmemtest, requires_subprocess
 from test.support.script_helper import assert_python_ok, assert_python_failure
@@ -351,10 +351,30 @@ def test_mtime(self):
             self.assertEqual(dataRead, data1)
             self.assertEqual(fRead.mtime, mtime)
 
+    def test_mtime_out_of_range(self):
+        for mtime in (-1, 2**32):
+            with gzip.GzipFile(self.filename, 'w', mtime=mtime) as fWrite:
+                fWrite.write(data1)
+            with gzip.GzipFile(self.filename) as fRead:
+                fRead.read(1)
+                self.assertEqual(fRead.mtime, 0)
+            datac = gzip.compress(data1, mtime=mtime)
+            with gzip.GzipFile(fileobj=io.BytesIO(datac)) as fRead:
+                fRead.read(1)
+                self.assertEqual(fRead.mtime, 0)
+
+        for mtime in (-1, 2**32):
+            with mock.patch('time.time', return_value=float(mtime)):
+                with gzip.GzipFile(self.filename, 'w') as fWrite:
+                    fWrite.write(data1)
+                with gzip.GzipFile(self.filename) as fRead:
+                    fRead.read(1)
+                    self.assertEqual(fRead.mtime, 0)
+
     def test_metadata(self):
         mtime = 123456789
 
-        with gzip.GzipFile(self.filename, 'w', mtime = mtime) as fWrite:
+        with gzip.GzipFile(self.filename, 'w', mtime = mtime, compresslevel = 9) as fWrite:
             fWrite.write(data1)
 
         with open(self.filename, 'rb') as fRead:
@@ -640,7 +660,7 @@ def test_fileobj_mode(self):
             with open(self.filename, mode) as f:
                 with gzip.GzipFile(fileobj=f) as g:
                     self.assertEqual(g.mode, gzip.READ)
-        for mode in "wb", "ab", "xb":
+        for mode in "wb", "ab", "xb", "wb+", "ab+", "xb+":
             if "x" in mode:
                 os_helper.unlink(self.filename)
             with open(self.filename, mode) as f:
@@ -796,6 +816,35 @@ def test_decompress_missing_trailer(self):
         compressed_data = gzip.compress(data1)
         self.assertRaises(EOFError, gzip.decompress, compressed_data[:-8])
 
+    def test_truncated_header(self):
+        truncated_headers = [
+            b"\x1f\x8b\x08\x00\x00\x00\x00\x00\x00",             # Missing OS byte
+            b"\x1f\x8b\x08\x02\x00\x00\x00\x00\x00\xff",         # FHRC, but no checksum
+            b"\x1f\x8b\x08\x04\x00\x00\x00\x00\x00\xff",         # FEXTRA, but no xlen
+            b"\x1f\x8b\x08\x04\x00\x00\x00\x00\x00\xff\xaa\x00", # FEXTRA, xlen, but no data
+            b"\x1f\x8b\x08\x08\x00\x00\x00\x00\x00\xff",         # FNAME but no fname
+            b"\x1f\x8b\x08\x10\x00\x00\x00\x00\x00\xff",         # FCOMMENT, but no fcomment
+        ]
+        for header in truncated_headers:
+            with self.subTest(header=header):
+                with self.assertRaises(EOFError):
+                    gzip.decompress(header)
+
+    def test_corrupted_gzip_header(self):
+        header = (b"\x1f\x8b\x08\x1f\x00\x00\x00\x00\x00\xff"  # All flags set
+                  b"\x05\x00"  # Xlen = 5
+                  b"extra"
+                  b"name\x00"
+                  b"comment\x00")
+        true_crc = zlib.crc32(header) & 0xFFFF
+        corrupted_crc = true_crc ^ 0xFFFF
+        corrupted_header = header + corrupted_crc.to_bytes(2, "little")
+        with self.assertRaises(gzip.BadGzipFile) as err:
+            gzip.decompress(corrupted_header)
+        self.assertEqual(str(err.exception),
+                         f"Corrupted gzip header. Checksums do not "
+                         f"match: {true_crc:04x} != {corrupted_crc:04x}")
+
     def test_read_truncated(self):
         data = data1*50
         # Drop the CRC (4 bytes) and file size (4 bytes).
@@ -1058,6 +1107,7 @@ def wrapper(*args, **kwargs):
     return decorator
 
 
+@force_not_colorized_test_class
 class TestCommandLine(unittest.TestCase):
     data = b'This is a simple test with gzip'
 
diff --git a/Lib/test/test_hashlib.py b/Lib/test/test_hashlib.py
index 6652b829b5a..253a8f45585 100644
--- a/Lib/test/test_hashlib.py
+++ b/Lib/test/test_hashlib.py
@@ -18,7 +18,6 @@
 import tempfile
 import threading
 import unittest
-import warnings
 from test import support
 from test.support import _4G, bigmemtest
 from test.support import hashlib_helper
@@ -95,6 +94,14 @@ def read_vectors(hash_name):
             yield parts
 
 
+DEPRECATED_STRING_PARAMETER = re.escape(
+    "the 'string' keyword parameter is deprecated since "
+    "Python 3.15 and slated for removal in Python 3.19; "
+    "use the 'data' keyword parameter or pass the data "
+    "to hash as a positional argument instead"
+)
+
+
 class HashLibTestCase(unittest.TestCase):
     supported_hash_names = ( 'md5', 'MD5', 'sha1', 'SHA1',
                              'sha224', 'SHA224', 'sha256', 'SHA256',
@@ -199,6 +206,11 @@ def hash_constructors(self):
         constructors = self.constructors_to_test.values()
         return itertools.chain.from_iterable(constructors)
 
+    @property
+    def shake_constructors(self):
+        for shake_name in self.shakes:
+            yield from self.constructors_to_test.get(shake_name, ())
+
     @property
     def is_fips_mode(self):
         return get_fips_mode()
@@ -260,22 +272,27 @@ def test_clinic_signature(self):
             with self.subTest(constructor.__name__):
                 constructor(b'')
                 constructor(data=b'')
-                constructor(string=b'')  # should be deprecated in the future
+                with self.assertWarnsRegex(DeprecationWarning,
+                                           DEPRECATED_STRING_PARAMETER):
+                    constructor(string=b'')
 
             digest_name = constructor(b'').name
             with self.subTest(digest_name):
                 hashlib.new(digest_name, b'')
                 hashlib.new(digest_name, data=b'')
-                hashlib.new(digest_name, string=b'')
+                with self.assertWarnsRegex(DeprecationWarning,
+                                           DEPRECATED_STRING_PARAMETER):
+                    hashlib.new(digest_name, string=b'')
                 # Make sure that _hashlib contains the constructor
                 # to test when using a combination of libcrypto and
                 # interned hash implementations.
                 if self._hashlib and digest_name in self._hashlib._constructors:
                     self._hashlib.new(digest_name, b'')
                     self._hashlib.new(digest_name, data=b'')
-                    self._hashlib.new(digest_name, string=b'')
+                    with self.assertWarnsRegex(DeprecationWarning,
+                                               DEPRECATED_STRING_PARAMETER):
+                        self._hashlib.new(digest_name, string=b'')
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; duplicate positional/keyword arg error message differs
     @unittest.skipIf(get_fips_mode(), "skip in FIPS mode")
     def test_clinic_signature_errors(self):
         nomsg = b''
@@ -330,7 +347,9 @@ def test_clinic_signature_errors(self):
 
     def test_unknown_hash(self):
         self.assertRaises(ValueError, hashlib.new, 'spam spam spam spam spam')
-        self.assertRaises(TypeError, hashlib.new, 1)
+        # ensure that the exception message remains consistent
+        err = re.escape("new() argument 'name' must be str, not int")
+        self.assertRaisesRegex(TypeError, err, hashlib.new, 1)
 
     def test_new_upper_to_lower(self):
         self.assertEqual(hashlib.new("SHA256").name, "sha256")
@@ -357,11 +376,23 @@ def test_get_builtin_constructor(self):
                 sys.modules['_md5'] = _md5
             else:
                 del sys.modules['_md5']
-        self.assertRaises(TypeError, get_builtin_constructor, 3)
+        # ensure that the exception message remains consistent
+        err = re.escape("new() argument 'name' must be str, not int")
+        self.assertRaises(TypeError, err, get_builtin_constructor, 3)
         constructor = get_builtin_constructor('md5')
         self.assertIs(constructor, _md5.md5)
         self.assertEqual(sorted(builtin_constructor_cache), ['MD5', 'md5'])
 
+    def test_copy(self):
+        for cons in self.hash_constructors:
+            h1 = cons(os.urandom(16), usedforsecurity=False)
+            h2 = h1.copy()
+            self.assertIs(type(h1), type(h2))
+            self.assertEqual(h1.name, h2.name)
+            size = (16,) if h1.name in self.shakes else ()
+            self.assertEqual(h1.digest(*size), h2.digest(*size))
+            self.assertEqual(h1.hexdigest(*size), h2.hexdigest(*size))
+
     def test_hexdigest(self):
         for cons in self.hash_constructors:
             h = cons(usedforsecurity=False)
@@ -372,21 +403,50 @@ def test_hexdigest(self):
                 self.assertIsInstance(h.digest(), bytes)
                 self.assertEqual(hexstr(h.digest()), h.hexdigest())
 
-    def test_digest_length_overflow(self):
-        # See issue #34922
-        large_sizes = (2**29, 2**32-10, 2**32+10, 2**61, 2**64-10, 2**64+10)
-        for cons in self.hash_constructors:
-            h = cons(usedforsecurity=False)
-            if h.name not in self.shakes:
-                continue
-            if HASH is not None and isinstance(h, HASH):
-                # _hashopenssl's take a size_t
-                continue
-            for digest in h.digest, h.hexdigest:
-                self.assertRaises(ValueError, digest, -10)
-                for length in large_sizes:
-                    with self.assertRaises((ValueError, OverflowError)):
-                        digest(length)
+    def test_shakes_zero_digest_length(self):
+        for constructor in self.shake_constructors:
+            with self.subTest(constructor=constructor):
+                h = constructor(b'abcdef', usedforsecurity=False)
+                self.assertEqual(h.digest(0), b'')
+                self.assertEqual(h.hexdigest(0), '')
+
+    def test_shakes_invalid_digest_length(self):
+        # See https://github.com/python/cpython/issues/79103.
+        for constructor in self.shake_constructors:
+            with self.subTest(constructor=constructor):
+                h = constructor(usedforsecurity=False)
+                # Note: digest() and hexdigest() take a signed input and
+                # raise if it is negative; the rationale is that we use
+                # internally PyBytes_FromStringAndSize() and _Py_strhex()
+                # which both take a Py_ssize_t.
+                for negative_size in (-1, -10, -(1 << 31), -sys.maxsize):
+                    self.assertRaises(ValueError, h.digest, negative_size)
+                    self.assertRaises(ValueError, h.hexdigest, negative_size)
+
+    def test_shakes_overflow_digest_length(self):
+        # See https://github.com/python/cpython/issues/135759.
+
+        exc_types = (OverflowError, ValueError)
+        # HACL* accepts an 'uint32_t' while OpenSSL accepts a 'size_t'.
+        openssl_overflown_sizes = (sys.maxsize + 1, 2 * sys.maxsize)
+        # https://github.com/python/cpython/issues/79103 restricts
+        # the accepted built-in lengths to 2 ** 29, even if OpenSSL
+        # accepts such lengths.
+        builtin_overflown_sizes = openssl_overflown_sizes + (
+            2 ** 29, 2 ** 32 - 10, 2 ** 32, 2 ** 32 + 10,
+            2 ** 61, 2 ** 64 - 10, 2 ** 64, 2 ** 64 + 10,
+        )
+
+        for constructor in self.shake_constructors:
+            with self.subTest(constructor=constructor):
+                h = constructor(usedforsecurity=False)
+                if HASH is not None and isinstance(h, HASH):
+                    overflown_sizes = openssl_overflown_sizes
+                else:
+                    overflown_sizes = builtin_overflown_sizes
+                for invalid_size in overflown_sizes:
+                    self.assertRaises(exc_types, h.digest, invalid_size)
+                    self.assertRaises(exc_types, h.hexdigest, invalid_size)
 
     def test_name_attribute(self):
         for cons in self.hash_constructors:
@@ -490,13 +550,17 @@ def check(self, name, data, hexdigest, shake=False, **kwargs):
 
     def check_file_digest(self, name, data, hexdigest):
         hexdigest = hexdigest.lower()
-        try:
-            hashlib.new(name)
-        except ValueError:
-            # skip, algorithm is blocked by security policy.
-            return
-        digests = [name]
-        digests.extend(self.constructors_to_test[name])
+        digests = []
+        for digest in [name, *self.constructors_to_test[name]]:
+            try:
+                if callable(digest):
+                    digest(b"")
+                else:
+                    hashlib.new(digest)
+            except ValueError:
+                # skip, algorithm is blocked by security policy.
+                continue
+            digests.append(digest)
 
         with tempfile.TemporaryFile() as f:
             f.write(data)
@@ -627,12 +691,12 @@ def test_case_md5_2(self):
         )
 
     @unittest.skipIf(sys.maxsize < _4G + 5, 'test cannot run on 32-bit systems')
-    @bigmemtest(size=_4G + 5, memuse=1, dry_run=False)
+    @bigmemtest(size=_4G + 5, memuse=2, dry_run=False)
     def test_case_md5_huge(self, size):
         self.check('md5', b'A'*size, 'c9af2dff37468ce5dfee8f2cfc0a9c6d')
 
     @unittest.skipIf(sys.maxsize < _4G - 1, 'test cannot run on 32-bit systems')
-    @bigmemtest(size=_4G - 1, memuse=1, dry_run=False)
+    @bigmemtest(size=_4G - 1, memuse=2, dry_run=False)
     def test_case_md5_uintmax(self, size):
         self.check('md5', b'A'*size, '28138d306ff1b8281f1a9067e1a1a2b3')
 
@@ -1017,49 +1081,73 @@ def test_gil(self):
 
     def test_sha256_gil(self):
         gil_minsize = hashlib_helper.find_gil_minsize(['_sha2', '_hashlib'])
+        data = b'1' + b'#' * gil_minsize + b'1'
+        expected = hashlib.sha256(data).hexdigest()
+
         m = hashlib.sha256()
         m.update(b'1')
         m.update(b'#' * gil_minsize)
         m.update(b'1')
-        self.assertEqual(
-            m.hexdigest(),
-            '1cfceca95989f51f658e3f3ffe7f1cd43726c9e088c13ee10b46f57cef135b94'
-        )
+        self.assertEqual(m.hexdigest(), expected)
 
-        m = hashlib.sha256(b'1' + b'#' * gil_minsize + b'1')
-        self.assertEqual(
-            m.hexdigest(),
-            '1cfceca95989f51f658e3f3ffe7f1cd43726c9e088c13ee10b46f57cef135b94'
-        )
+    @threading_helper.reap_threads
+    @threading_helper.requires_working_threading()
+    def test_threaded_hashing_fast(self):
+        # Same as test_threaded_hashing_slow() but only tests some functions
+        # since otherwise test_hashlib.py becomes too slow during development.
+        algos = ['md5', 'sha1', 'sha256', 'sha3_256', 'blake2s']
+        for name in algos:
+            if constructor := getattr(hashlib, name, None):
+                with self.subTest(name):
+                    try:
+                        self.do_test_threaded_hashing(constructor, is_shake=False)
+                    except ValueError as exc:
+                        self.skip_if_blake2_not_builtin(name, exc)
+                        raise
 
+        if shake_128 := getattr(hashlib, 'shake_128', None):
+            self.do_test_threaded_hashing(shake_128, is_shake=True)
+
+    @requires_resource('cpu')
     @threading_helper.reap_threads
     @threading_helper.requires_working_threading()
-    def test_threaded_hashing(self):
+    def test_threaded_hashing_slow(self):
+        for algorithm, constructors in self.constructors_to_test.items():
+            is_shake = algorithm in self.shakes
+            for constructor in constructors:
+                with self.subTest(constructor.__name__, is_shake=is_shake):
+                    self.do_test_threaded_hashing(constructor, is_shake)
+
+    def do_test_threaded_hashing(self, constructor, is_shake):
         # Updating the same hash object from several threads at once
         # using data chunk sizes containing the same byte sequences.
         #
         # If the internal locks are working to prevent multiple
         # updates on the same object from running at once, the resulting
         # hash will be the same as doing it single threaded upfront.
-        hasher = hashlib.sha1()
-        num_threads = 5
-        smallest_data = b'swineflu'
-        data = smallest_data * 200000
-        expected_hash = hashlib.sha1(data*num_threads).hexdigest()
-
-        def hash_in_chunks(chunk_size):
-            index = 0
-            while index < len(data):
-                hasher.update(data[index:index + chunk_size])
-                index += chunk_size
+
+        # The data to hash has length s|M|q^N and the chunk size for the i-th
+        # thread is s|M|q^(N-i), where N is the number of threads, M is a fixed
+        # message of small length, and s >= 1 and q >= 2 are small integers.
+        smallest_size, num_threads, s, q = 8, 5, 2, 10
+
+        smallest_data = os.urandom(smallest_size)
+        data = s * smallest_data * (q ** num_threads)
+
+        h1 = constructor(usedforsecurity=False)
+        h2 = constructor(data * num_threads, usedforsecurity=False)
+
+        def update(chunk_size):
+            for index in range(0, len(data), chunk_size):
+                h1.update(data[index:index + chunk_size])
 
         threads = []
-        for threadnum in range(num_threads):
-            chunk_size = len(data) // (10 ** threadnum)
+        for thread_num in range(num_threads):
+            # chunk_size = len(data) // (q ** thread_num)
+            chunk_size = s * smallest_size * q ** (num_threads - thread_num)
             self.assertGreater(chunk_size, 0)
-            self.assertEqual(chunk_size % len(smallest_data), 0)
-            thread = threading.Thread(target=hash_in_chunks,
-                                      args=(chunk_size,))
+            self.assertEqual(chunk_size % smallest_size, 0)
+            thread = threading.Thread(target=update, args=(chunk_size,))
             threads.append(thread)
 
         for thread in threads:
@@ -1067,7 +1155,10 @@ def hash_in_chunks(chunk_size):
         for thread in threads:
             thread.join()
 
-        self.assertEqual(expected_hash, hasher.hexdigest())
+        if is_shake:
+            self.assertEqual(h1.hexdigest(16), h2.hexdigest(16))
+        else:
+            self.assertEqual(h1.hexdigest(), h2.hexdigest())
 
     def test_get_fips_mode(self):
         fips_mode = self.is_fips_mode
@@ -1124,12 +1215,6 @@ class KDFTests(unittest.TestCase):
         (b'pass\0word', b'sa\0lt', 4096, 16),
     ]
 
-    scrypt_test_vectors = [
-        (b'', b'', 16, 1, 1, unhexlify('77d6576238657b203b19ca42c18a0497f16b4844e3074ae8dfdffa3fede21442fcd0069ded0948f8326a753a0fc81f17e8d3e0fb2e0d3628cf35e20c38d18906')),
-        (b'password', b'NaCl', 1024, 8, 16, unhexlify('fdbabe1c9d3472007856e7190d01e9fe7c6ad7cbc8237830e77376634b3731622eaf30d92e22a3886ff109279d9830dac727afb94a83ee6d8360cbdfa2cc0640')),
-        (b'pleaseletmein', b'SodiumChloride', 16384, 8, 1, unhexlify('7023bdcb3afd7348461c06cd81fd38ebfda8fbba904f8e3ea9b543f6545da1f2d5432955613f0fcf62d49705242a9af9e61e85dc0d651e40dfcf017b45575887')),
-   ]
-
     pbkdf2_results = {
         "sha1": [
             # official test vectors from RFC 6070
@@ -1221,46 +1306,6 @@ def _test_pbkdf2_hmac(self, pbkdf2, supported):
     def test_pbkdf2_hmac_c(self):
         self._test_pbkdf2_hmac(openssl_hashlib.pbkdf2_hmac, openssl_md_meth_names)
 
-    @unittest.skipUnless(hasattr(hashlib, 'scrypt'),
-                     '   test requires OpenSSL > 1.1')
-    @unittest.skipIf(get_fips_mode(), reason="scrypt is blocked in FIPS mode")
-    def test_scrypt(self):
-        for password, salt, n, r, p, expected in self.scrypt_test_vectors:
-            result = hashlib.scrypt(password, salt=salt, n=n, r=r, p=p)
-            self.assertEqual(result, expected)
-
-        # this values should work
-        hashlib.scrypt(b'password', salt=b'salt', n=2, r=8, p=1)
-        # password and salt must be bytes-like
-        with self.assertRaises(TypeError):
-            hashlib.scrypt('password', salt=b'salt', n=2, r=8, p=1)
-        with self.assertRaises(TypeError):
-            hashlib.scrypt(b'password', salt='salt', n=2, r=8, p=1)
-        # require keyword args
-        with self.assertRaises(TypeError):
-            hashlib.scrypt(b'password')
-        with self.assertRaises(TypeError):
-            hashlib.scrypt(b'password', b'salt')
-        with self.assertRaises(TypeError):
-            hashlib.scrypt(b'password', 2, 8, 1, salt=b'salt')
-        for n in [-1, 0, 1, None]:
-            with self.assertRaises((ValueError, OverflowError, TypeError)):
-                hashlib.scrypt(b'password', salt=b'salt', n=n, r=8, p=1)
-        for r in [-1, 0, None]:
-            with self.assertRaises((ValueError, OverflowError, TypeError)):
-                hashlib.scrypt(b'password', salt=b'salt', n=2, r=r, p=1)
-        for p in [-1, 0, None]:
-            with self.assertRaises((ValueError, OverflowError, TypeError)):
-                hashlib.scrypt(b'password', salt=b'salt', n=2, r=8, p=p)
-        for maxmem in [-1, None]:
-            with self.assertRaises((ValueError, OverflowError, TypeError)):
-                hashlib.scrypt(b'password', salt=b'salt', n=2, r=8, p=1,
-                               maxmem=maxmem)
-        for dklen in [-1, None]:
-            with self.assertRaises((ValueError, OverflowError, TypeError)):
-                hashlib.scrypt(b'password', salt=b'salt', n=2, r=8, p=1,
-                               dklen=dklen)
-
     def test_normalized_name(self):
         self.assertNotIn("blake2b512", hashlib.algorithms_available)
         self.assertNotIn("sha3-512", hashlib.algorithms_available)
@@ -1302,5 +1347,76 @@ def readable(self):
             hashlib.file_digest(NonBlocking(), hashlib.sha256)
 
 
+@unittest.skipUnless(hasattr(hashlib, 'scrypt'), 'requires OpenSSL 1.1+')
+@unittest.skipIf(get_fips_mode(), reason="scrypt is blocked in FIPS mode")
+class TestScrypt(unittest.TestCase):
+
+    scrypt_test_vectors = [
+        (b'', b'', 16, 1, 1, unhexlify('77d6576238657b203b19ca42c18a0497f16b4844e3074ae8dfdffa3fede21442fcd0069ded0948f8326a753a0fc81f17e8d3e0fb2e0d3628cf35e20c38d18906')),
+        (b'password', b'NaCl', 1024, 8, 16, unhexlify('fdbabe1c9d3472007856e7190d01e9fe7c6ad7cbc8237830e77376634b3731622eaf30d92e22a3886ff109279d9830dac727afb94a83ee6d8360cbdfa2cc0640')),
+        (b'pleaseletmein', b'SodiumChloride', 16384, 8, 1, unhexlify('7023bdcb3afd7348461c06cd81fd38ebfda8fbba904f8e3ea9b543f6545da1f2d5432955613f0fcf62d49705242a9af9e61e85dc0d651e40dfcf017b45575887')),
+   ]
+
+    def test_scrypt(self):
+        for password, salt, n, r, p, expected in self.scrypt_test_vectors:
+            result = hashlib.scrypt(password, salt=salt, n=n, r=r, p=p)
+            self.assertEqual(result, expected)
+
+        # these parameters must be valid
+        hashlib.scrypt(b'password', salt=b'salt', n=2, r=8, p=1)
+        hashlib.scrypt(b'password', salt=b'salt', n=2, r=8, p=1, maxmem=0)
+        hashlib.scrypt(b'password', salt=b'salt', n=2, r=8, p=1, dklen=1)
+
+    def test_scrypt_types(self):
+        # password and salt must be bytes-like
+        with self.assertRaises(TypeError):
+            hashlib.scrypt('password', salt=b'salt', n=2, r=8, p=1)
+        with self.assertRaises(TypeError):
+            hashlib.scrypt(b'password', salt='salt', n=2, r=8, p=1)
+        # require keyword args
+        with self.assertRaises(TypeError):
+            hashlib.scrypt(b'password')
+        with self.assertRaises(TypeError):
+            hashlib.scrypt(b'password', b'salt')
+        with self.assertRaises(TypeError):
+            hashlib.scrypt(b'password', 2, 8, 1, salt=b'salt')
+
+    def test_scrypt_validate(self):
+        def scrypt(password=b"password", /, **kwargs):
+            # overwrite well-defined parameters with bad ones
+            kwargs = dict(salt=b'salt', n=2, r=8, p=1) | kwargs
+            return hashlib.scrypt(password, **kwargs)
+
+        for param_name in ('n', 'r', 'p', 'maxmem', 'dklen'):
+            param = {param_name: None}
+            with self.subTest(**param):
+                self.assertRaises(TypeError, scrypt, **param)
+
+        self.assertRaises(ValueError, scrypt, n=0)
+        self.assertRaises(ValueError, scrypt, n=-1)
+        self.assertRaises(ValueError, scrypt, n=1)
+
+        self.assertRaises(ValueError, scrypt, r=0)
+        self.assertRaises(ValueError, scrypt, r=-1)
+
+        self.assertRaises(ValueError, scrypt, p=-1)
+        self.assertRaises(ValueError, scrypt, p=0)
+
+        self.assertRaises(ValueError, scrypt, maxmem=-1)
+        # OpenSSL hard limit for 'maxmem' is an 'uint64_t' but for now,
+        # we do not use the 'uint64' Clinic converter but the 'long' one.
+        self.assertRaises(OverflowError, scrypt, maxmem=(1 << 64))
+        # Historically, Python allowed 'maxmem' to be at most INT_MAX,
+        # which is at most 2**32-1 (on Windows, sizeof(long) == 4, so
+        # an OverflowError will be raised instead of a ValueError).
+        numeric_exc_types = (OverflowError, ValueError)
+        self.assertRaises(numeric_exc_types, scrypt, maxmem=(1 << 32))
+
+        self.assertRaises(ValueError, scrypt, dklen=-1)
+        self.assertRaises(ValueError, scrypt, dklen=0)
+        MAX_DKLEN = ((1 << 32) - 1) * 32  # see RFC 7914
+        self.assertRaises(numeric_exc_types, scrypt, dklen=MAX_DKLEN + 1)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_hmac.py b/Lib/test/test_hmac.py
index 1d270b2a43c..c43188cc333 100644
--- a/Lib/test/test_hmac.py
+++ b/Lib/test/test_hmac.py
@@ -21,10 +21,10 @@
 import hmac
 import hashlib
 import random
-import types
 import unittest
 import warnings
 from _operator import _compare_digest as operator_compare_digest
+from test import support
 from test.support import _4G, bigmemtest
 from test.support import check_disallow_instantiation
 from test.support import hashlib_helper, import_helper
@@ -161,7 +161,7 @@ def hmac_digest(self, key, msg=None, digestmod=DIGESTMOD_SENTINEL):
         return _call_digest_func(self.hmac.digest, key, msg, digestmod)
 
 
-@hashlib_helper.requires_hashlib()
+@hashlib_helper.requires_openssl_hashlib()
 class ThroughOpenSSLAPIMixin(CreatorMixin, DigestMixin):
     """Mixin delegating to _hashlib.hmac_new() and _hashlib.hmac_digest()."""
 
@@ -303,7 +303,7 @@ def assert_hmac_new_by_name(
 
     def check_hmac_new(
         self, key, msg, hexdigest, hashname, digest_size, block_size,
-        hmac_new_func, hmac_new_kwds=types.MappingProxyType({}),
+        hmac_new_func, hmac_new_kwds=frozendict(),
     ):
         """Check that HMAC(key, msg) == digest.
 
@@ -349,7 +349,7 @@ def assert_hmac_hexdigest_by_name(
 
     def check_hmac_hexdigest(
         self, key, msg, hexdigest, digest_size,
-        hmac_digest_func, hmac_digest_kwds=types.MappingProxyType({}),
+        hmac_digest_func, hmac_digest_kwds=frozendict(),
     ):
         """Check and return a HMAC digest computed by hmac_digest_func().
 
@@ -965,7 +965,7 @@ def raiser():
         with self.assertRaisesRegex(RuntimeError, "custom exception"):
             func(b'key', b'msg', raiser)
 
-        with self.assertRaisesRegex(ValueError, 'hash type'):
+        with self.assertRaisesRegex(ValueError, 'unsupported hash algorithm'):
             func(b'key', b'msg', 'unknown')
 
         with self.assertRaisesRegex(AttributeError, 'new'):
@@ -1025,6 +1025,13 @@ def test_hmac_digest_digestmod_parameter(self):
             ):
                 self.hmac_digest(b'key', b'msg', value)
 
+    @support.subTests("xof_name", ("shake_128", "shake_256"))
+    def test_hmac_new_xof_digestmod(self, xof_name):
+        # gh-145200: XOF digests (SHAKE) are not supported by HMAC.
+        # Verify that the error path does not leak the EVP_MAC_CTX.
+        with self.assertRaises(_hashlib.UnsupportedDigestmodError):
+            self.hmac_new(b'key', digestmod=xof_name)
+
 
 class BuiltinConstructorTestCase(ThroughBuiltinAPIMixin,
                                  ExtensionConstructorTestCaseMixin,
@@ -1440,7 +1447,7 @@ def test_compare_digest_func(self):
             self.assertIs(self.compare_digest, operator_compare_digest)
 
 
-@hashlib_helper.requires_hashlib()
+@hashlib_helper.requires_openssl_hashlib()
 class OpenSSLCompareDigestTestCase(CompareDigestMixin, unittest.TestCase):
     compare_digest = openssl_compare_digest
 
@@ -1452,19 +1459,25 @@ class OperatorCompareDigestTestCase(CompareDigestMixin, unittest.TestCase):
 class PyMiscellaneousTests(unittest.TestCase):
     """Miscellaneous tests for the pure Python HMAC module."""
 
+    @staticmethod
+    def mock__compute_digest_fallback(hmac):
+        fn = getattr(hmac, meth := "_compute_digest_fallback")
+        return patch.object(hmac, meth, wraps=fn)
+
+    @staticmethod
+    def mock_HMAC_method(hmac, method):
+        fn = getattr(hmac.HMAC, method)
+        return patch.object(hmac.HMAC, method, autospec=True, wraps=fn)
+
     @hashlib_helper.requires_builtin_hmac()
     def test_hmac_constructor_uses_builtin(self):
         # Block the OpenSSL implementation and check that
         # HMAC() uses the built-in implementation instead.
         hmac = import_fresh_module("hmac", blocked=["_hashlib"])
 
-        def watch_method(cls, name):
-            wraps = getattr(cls, name)
-            return patch.object(cls, name, autospec=True, wraps=wraps)
-
         with (
-            watch_method(hmac.HMAC, '_init_openssl_hmac') as f,
-            watch_method(hmac.HMAC, '_init_builtin_hmac') as g,
+            self.mock_HMAC_method(hmac, '_init_openssl_hmac') as f,
+            self.mock_HMAC_method(hmac, '_init_builtin_hmac') as g,
         ):
             _ = hmac.HMAC(b'key', b'msg', digestmod="sha256")
             f.assert_not_called()
@@ -1518,7 +1531,7 @@ def test_hmac_digest_overflow_error_openssl_only(self, size):
         hmac = import_fresh_module("hmac", blocked=["_hmac"])
         self.do_test_hmac_digest_overflow_error_switch_to_slow(hmac, size)
 
-    @hashlib_helper.requires_builtin_hashdigest("_md5", "md5")
+    @hashlib_helper.requires_builtin_hashdigest("md5")
     @bigmemtest(size=_4G + 5, memuse=2, dry_run=False)
     def test_hmac_digest_overflow_error_builtin_only(self, size):
         hmac = import_fresh_module("hmac", blocked=["_hashlib"])
@@ -1535,11 +1548,11 @@ def do_test_hmac_digest_overflow_error_switch_to_slow(self, hmac, size):
         bigkey = b'K' * size
         bigmsg = b'M' * size
 
-        with patch.object(hmac, "_compute_digest_fallback") as slow:
+        with self.mock__compute_digest_fallback(hmac) as slow:
             hmac.digest(bigkey, b'm', "md5")
             slow.assert_called_once()
 
-        with patch.object(hmac, "_compute_digest_fallback") as slow:
+        with self.mock__compute_digest_fallback(hmac) as slow:
             hmac.digest(b'k', bigmsg, "md5")
             slow.assert_called_once()
 
@@ -1550,7 +1563,7 @@ def test_hmac_digest_no_overflow_error_in_fallback(self, size):
 
         for key, msg in [(b'K' * size, b'm'), (b'k', b'M' * size)]:
             with self.subTest(keysize=len(key), msgsize=len(msg)):
-                with patch.object(hmac, "_compute_digest_fallback") as slow:
+                with self.mock__compute_digest_fallback(hmac) as slow:
                     hmac.digest(key, msg, "md5")
                     slow.assert_called_once()
 
diff --git a/Lib/test/test_import/__init__.py b/Lib/test/test_import/__init__.py
index 3233a72750b..5d8e764b569 100644
--- a/Lib/test/test_import/__init__.py
+++ b/Lib/test/test_import/__init__.py
@@ -15,6 +15,7 @@
 import os
 import py_compile
 import random
+import re
 import shutil
 import stat
 import subprocess
@@ -23,6 +24,7 @@
 import threading
 import time
 import types
+import warnings
 import unittest
 from unittest import mock
 import _imp
@@ -52,7 +54,7 @@
     TESTFN, rmtree, temp_umask, TESTFN_UNENCODABLE)
 from test.support import script_helper
 from test.support import threading_helper
-from test.test_importlib.util import uncache
+from test.test_importlib.util import uncache, temporary_pycache_prefix
 from types import ModuleType
 try:
     import _testsinglephase
@@ -64,8 +66,10 @@
     _testmultiphase = None
 try:
     import _interpreters
+    import concurrent.interpreters
 except ModuleNotFoundError:
     _interpreters = None
+    concurrent = None
 try:
     import _testinternalcapi
 except ImportError:
@@ -73,7 +77,7 @@
 
 
 skip_if_dont_write_bytecode = unittest.skipIf(
-        sys.dont_write_bytecode,
+        sys.dont_write_bytecode or sys.implementation.cache_tag is None,
         "test meaningful only when writing bytecode")
 
 
@@ -363,11 +367,11 @@ def test_import_raises_ModuleNotFoundError(self):
     def test_import_null_byte_in_name_raises_ModuleNotFoundError(self):
         # gh-150633: module names containing null bytes should not
         # lead to duplicates in sys.modules
-        before = set(sys.modules.keys())
+        before = set(sys.modules)
         with self.assertRaises(ModuleNotFoundError):
             __import__('zipimport\x00junk')
 
-        self.assertEqual(set(sys.modules.keys()), before)
+        self.assertEqual(set(sys.modules), before)
 
     def test_from_import_missing_module_raises_ModuleNotFoundError(self):
         with self.assertRaises(ModuleNotFoundError):
@@ -422,7 +426,6 @@ def test_from_import_missing_attr_path_is_canonical(self):
         self.assertIsNotNone(cm.exception)
 
     def test_from_import_star_invalid_type(self):
-        import re
         with ready_to_import() as (name, path):
             with open(path, 'w', encoding='utf-8') as f:
                 f.write("__all__ = [b'invalid_type']")
@@ -511,7 +514,7 @@ def test_module_with_large_stack(self, module='longlist'):
         try:
             # Compile & remove .py file; we only need .pyc.
             # Bytecode must be relocated from the PEP 3147 bytecode-only location.
-            py_compile.compile(filename)
+            make_legacy_pyc(filename, allow_compile=True)
         finally:
             unlink(filename)
 
@@ -521,7 +524,6 @@ def test_module_with_large_stack(self, module='longlist'):
 
         namespace = {}
         try:
-            make_legacy_pyc(filename)
             # This used to crash.
             exec('import ' + module, None, namespace)
         finally:
@@ -786,7 +788,7 @@ def test_dll_dependency_import(self):
         pydname = importlib.util.find_spec("_sqlite3").origin
         depname = os.path.join(
             os.path.dirname(pydname),
-            "sqlite3{}.dll".format("_d" if "_d" in pydname else ""))
+            "sqlite3{}.dll".format("_d" if "_d" in os.path.basename(pydname) else ""))
 
         with os_helper.temp_dir() as tmp:
             tmp2 = os.path.join(tmp, "DLLs")
@@ -1261,6 +1263,44 @@ class Spec2:
                 origin = "a\x00b"
             _imp.create_dynamic(Spec2())
 
+    def test_create_builtin(self):
+        class Spec:
+            pass
+        spec = Spec()
+
+        spec.name = "sys"
+        self.assertIs(_imp.create_builtin(spec), sys)
+
+        spec.name = None
+        with self.assertRaisesRegex(TypeError, 'name must be string, not NoneType'):
+            _imp.create_builtin(spec)
+
+        # gh-142029
+        spec.name = "nonexistent_lib"
+        with self.assertRaises(ModuleNotFoundError):
+            _imp.create_builtin(spec)
+
+        # gh-142029
+        spec.name = ""
+        with self.assertRaisesRegex(ValueError, 'name must not be empty'):
+            _imp.create_builtin(spec)
+
+    def test_filter_syntax_warnings_by_module(self):
+        module_re = r'test\.test_import\.data\.syntax_warnings\z'
+        unload('test.test_import.data.syntax_warnings')
+        with (os_helper.temp_dir() as tmpdir,
+              temporary_pycache_prefix(tmpdir),
+              warnings.catch_warnings(record=True) as wlog):
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=module_re)
+            warnings.filterwarnings('error', module='syntax_warnings')
+            import test.test_import.data.syntax_warnings
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10, 13, 14, 21])
+        filename = test.test_import.data.syntax_warnings.__file__
+        for wm in wlog:
+            self.assertEqual(wm.filename, filename)
+            self.assertIs(wm.category, SyntaxWarning)
+
 
 @skip_if_dont_write_bytecode
 class FilePermissionTests(unittest.TestCase):
@@ -1369,7 +1409,10 @@ def func():
 """
     dir_name = os.path.abspath(TESTFN)
     file_name = os.path.join(dir_name, module_name) + os.extsep + "py"
-    compiled_name = importlib.util.cache_from_source(file_name)
+    try:
+        compiled_name = importlib.util.cache_from_source(file_name)
+    except NotImplementedError:
+        compiled_name = None
 
     def setUp(self):
         self.sys_path = sys.path[:]
@@ -1387,7 +1430,8 @@ def tearDown(self):
         else:
             unload(self.module_name)
         unlink(self.file_name)
-        unlink(self.compiled_name)
+        if self.compiled_name:
+            unlink(self.compiled_name)
         rmtree(self.dir_name)
 
     def import_module(self):
@@ -1406,6 +1450,8 @@ def test_basics(self):
         self.assertEqual(mod.code_filename, self.file_name)
         self.assertEqual(mod.func_filename, self.file_name)
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag is not None')
     def test_incorrect_code_name(self):
         py_compile.compile(self.file_name, dfile="another_module.py")
         mod = self.import_module()
@@ -1415,9 +1461,9 @@ def test_incorrect_code_name(self):
 
     def test_module_without_source(self):
         target = "another_module.py"
-        py_compile.compile(self.file_name, dfile=target)
+        pyc_file = self.file_name + 'c'
+        py_compile.compile(self.file_name, pyc_file, dfile=target)
         os.remove(self.file_name)
-        pyc_file = make_legacy_pyc(self.file_name)
         importlib.invalidate_caches()
         mod = self.import_module()
         self.assertEqual(mod.module_filename, pyc_file)
@@ -1425,8 +1471,9 @@ def test_module_without_source(self):
         self.assertEqual(mod.func_filename, target)
 
     def test_foreign_code(self):
-        py_compile.compile(self.file_name)
-        with open(self.compiled_name, "rb") as f:
+        compiled_name = self.compiled_name or (self.file_name + 'c')
+        py_compile.compile(self.file_name, compiled_name)
+        with open(compiled_name, "rb") as f:
             header = f.read(16)
             code = marshal.load(f)
         constants = list(code.co_consts)
@@ -1434,9 +1481,11 @@ def test_foreign_code(self):
         pos = constants.index(1000)
         constants[pos] = foreign_code
         code = code.replace(co_consts=tuple(constants))
-        with open(self.compiled_name, "wb") as f:
+        with open(compiled_name, "wb") as f:
             f.write(header)
             marshal.dump(code, f)
+        if not self.compiled_name:
+            os.remove(self.file_name)
         mod = self.import_module()
         self.assertEqual(mod.constant.co_filename, foreign_code.co_filename)
 
@@ -1621,6 +1670,11 @@ def _clean(self):
         unlink(self.source)
 
     def setUp(self):
+        # These tests assume bytecode is written next to the source in a
+        # local __pycache__ directory, so neutralize any pycache prefix (e.g.
+        # when the test suite is run with PYTHONPYCACHEPREFIX set).
+        self._orig_pycache_prefix = sys.pycache_prefix
+        sys.pycache_prefix = None
         self.source = TESTFN + '.py'
         self._clean()
         with open(self.source, 'w', encoding='utf-8') as fp:
@@ -1632,6 +1686,7 @@ def tearDown(self):
         assert sys.path[0] == os.curdir, 'Unexpected sys.path[0]'
         del sys.path[0]
         self._clean()
+        sys.pycache_prefix = self._orig_pycache_prefix
 
     @skip_if_dont_write_bytecode
     def test_import_pyc_path(self):
@@ -1691,78 +1746,6 @@ def test_missing_source_legacy(self):
         finally:
             os.remove(pyc_file)
 
-    def test___cached__(self):
-        # Modules now also have an __cached__ that points to the pyc file.
-        m = __import__(TESTFN)
-        pyc_file = importlib.util.cache_from_source(TESTFN + '.py')
-        self.assertEqual(m.__cached__, os.path.join(os.getcwd(), pyc_file))
-
-    @skip_if_dont_write_bytecode
-    def test___cached___legacy_pyc(self):
-        # Like test___cached__() except that for backward compatibility,
-        # when the pyc file lives where the py file would have been (and named
-        # without the tag), it is importable.  The __cached__ of the imported
-        # module is the pyc location.
-        __import__(TESTFN)
-        # pyc_file gets removed in _clean() via tearDown().
-        pyc_file = make_legacy_pyc(self.source)
-        os.remove(self.source)
-        unload(TESTFN)
-        importlib.invalidate_caches()
-        m = __import__(TESTFN)
-        self.assertEqual(m.__cached__,
-                         os.path.join(os.getcwd(), os.path.relpath(pyc_file)))
-
-    @skip_if_dont_write_bytecode
-    def test_package___cached__(self):
-        # Like test___cached__ but for packages.
-        def cleanup():
-            rmtree('pep3147')
-            unload('pep3147.foo')
-            unload('pep3147')
-        os.mkdir('pep3147')
-        self.addCleanup(cleanup)
-        # Touch the __init__.py
-        with open(os.path.join('pep3147', '__init__.py'), 'wb'):
-            pass
-        with open(os.path.join('pep3147', 'foo.py'), 'wb'):
-            pass
-        importlib.invalidate_caches()
-        m = __import__('pep3147.foo')
-        init_pyc = importlib.util.cache_from_source(
-            os.path.join('pep3147', '__init__.py'))
-        self.assertEqual(m.__cached__, os.path.join(os.getcwd(), init_pyc))
-        foo_pyc = importlib.util.cache_from_source(os.path.join('pep3147', 'foo.py'))
-        self.assertEqual(sys.modules['pep3147.foo'].__cached__,
-                         os.path.join(os.getcwd(), foo_pyc))
-
-    def test_package___cached___from_pyc(self):
-        # Like test___cached__ but ensuring __cached__ when imported from a
-        # PEP 3147 pyc file.
-        def cleanup():
-            rmtree('pep3147')
-            unload('pep3147.foo')
-            unload('pep3147')
-        os.mkdir('pep3147')
-        self.addCleanup(cleanup)
-        # Touch the __init__.py
-        with open(os.path.join('pep3147', '__init__.py'), 'wb'):
-            pass
-        with open(os.path.join('pep3147', 'foo.py'), 'wb'):
-            pass
-        importlib.invalidate_caches()
-        m = __import__('pep3147.foo')
-        unload('pep3147.foo')
-        unload('pep3147')
-        importlib.invalidate_caches()
-        m = __import__('pep3147.foo')
-        init_pyc = importlib.util.cache_from_source(
-            os.path.join('pep3147', '__init__.py'))
-        self.assertEqual(m.__cached__, os.path.join(os.getcwd(), init_pyc))
-        foo_pyc = importlib.util.cache_from_source(os.path.join('pep3147', 'foo.py'))
-        self.assertEqual(sys.modules['pep3147.foo'].__cached__,
-                         os.path.join(os.getcwd(), foo_pyc))
-
     def test_recompute_pyc_same_second(self):
         # Even when the source file doesn't change timestamp, a change in
         # source size is enough to trigger recomputation of the pyc file.
@@ -2031,10 +2014,6 @@ def test_import_bug(self):
         # away from the traceback.
         self.create_module("foo", "")
         importlib = sys.modules['_frozen_importlib_external']
-        if 'load_module' in vars(importlib.SourceLoader):
-            old_exec_module = importlib.SourceLoader.exec_module
-        else:
-            old_exec_module = None
         try:
             def exec_module(*args):
                 1/0
@@ -2047,10 +2026,7 @@ def exec_module(*args):
                 self.fail("ZeroDivisionError should have been raised")
             self.assert_traceback(tb, [__file__, '<frozen importlib', __file__])
         finally:
-            if old_exec_module is None:
-                del importlib.SourceLoader.exec_module
-            else:
-                importlib.SourceLoader.exec_module = old_exec_module
+            del importlib.SourceLoader.exec_module
 
     @unittest.expectedFailure  # TODO: RUSTPYTHON; subprocess fails on Windows
     @unittest.skipUnless(TESTFN_UNENCODABLE, 'need TESTFN_UNENCODABLE')
@@ -2479,6 +2455,21 @@ def test_multi_init_extension_per_interpreter_gil_compat(self):
                         self.check_compatible_here(
                             modname, filename, strict=False, isolated=False)
 
+    @unittest.skipIf(_testmultiphase is None, "test requires _testmultiphase module")
+    def test_testmultiphase_exec_multiple(self):
+        modname = '_testmultiphase_exec_multiple'
+        filename = _testmultiphase.__file__
+        module = import_extension_from_file(modname, filename,
+                                            put_in_sys_modules=False)
+        # All three exec's were called.
+        self.assertEqual(module.a, 1)
+        self.assertEqual(module.b, 2)
+        self.assertEqual(module.c, 3)
+        # They were called in order.
+        keys = list(module.__dict__)
+        self.assertLess(keys.index('a'), keys.index('b'))
+        self.assertLess(keys.index('b'), keys.index('c'))
+
     @unittest.skipIf(_testinternalcapi is None, "requires _testinternalcapi")
     def test_python_compat(self):
         module = 'threading'
@@ -2552,8 +2543,9 @@ def test_disallowed_reimport(self):
         excsnap = _interpreters.run_string(interpid, script)
         self.assertIsNot(excsnap, None)
 
-    @requires_subinterpreters
     @unittest.skip("TODO: RUSTPYTHON; test requires _testsinglephase module")
+    @cpython_only
+    @requires_subinterpreters
     def test_pyinit_function_raises_exception(self):
         # gh-144601: PyInit functions that raised exceptions would cause a
         # crash when imported from a subinterpreter.
@@ -2783,9 +2775,6 @@ def _load_dynamic(self, name, path):
         # This is essentially copied from the old imp module.
         from importlib._bootstrap import _load
         loader = self.LOADER(name, path)
-
-        # Issue bpo-24748: Skip the sys.modules check in _load_module_shim;
-        # always load new extension.
         spec = importlib.util.spec_from_file_location(name, path,
                                                       loader=loader)
         return _load(spec)
@@ -3268,6 +3257,7 @@ def test_basic_multiple_interpreters_main_no_reset(self):
         #  * m_copy was copied from interp2 (was from interp1)
         #  * module's global state was updated, not reset
 
+    @unittest.skip("gh-131229: This is suddenly very flaky")
     @no_rerun(reason="rerun not possible; module state is never cleared (see gh-102251)")
     @requires_subinterpreters
     def test_basic_multiple_interpreters_deleted_no_reset(self):
@@ -3403,6 +3393,158 @@ def test_basic_multiple_interpreters_reset_each(self):
         #  * module's global state was initialized, not reset
 
 
+@unittest.skipIf(_testmultiphase is None, "test requires _testmultiphase module")
+class ModexportTests(unittest.TestCase):
+    def test_from_modexport(self):
+        modname = '_test_from_modexport'
+        filename = _testmultiphase.__file__
+        module = import_extension_from_file(modname, filename,
+                                            put_in_sys_modules=False)
+
+        self.assertEqual(module.__name__, modname)
+
+    @requires_subinterpreters
+    def test_from_modexport_gil_used(self):
+        # Test that a module with Py_MOD_GIL_USED (re-)enables the GIL.
+        # Do this in a new interpreter to avoid interfering with global state.
+        modname = '_test_from_modexport_gil_used'
+        filename = _testmultiphase.__file__
+        interp = concurrent.interpreters.create()
+        self.addCleanup(interp.close)
+        queue = concurrent.interpreters.create_queue()
+        interp.prepare_main(
+            modname=modname,
+            filename=filename,
+            queue=queue,
+        )
+        enabled_before = sys._is_gil_enabled()
+        interp.exec(f"""if True:
+            import sys
+            from test.support.warnings_helper import check_warnings
+            from {__name__} import import_extension_from_file
+            with check_warnings((".*GIL..has been enabled.*", RuntimeWarning),
+                                quiet=True):
+                module = import_extension_from_file(modname, filename,
+                                                    put_in_sys_modules=False)
+            queue.put(module.__name__)
+            queue.put(sys._is_gil_enabled())
+        """)
+
+        self.assertEqual(queue.get(), modname)
+        self.assertEqual(queue.get(), True)
+        self.assertTrue(queue.empty())
+
+        self.assertEqual(enabled_before, sys._is_gil_enabled())
+
+    def test_from_modexport_null(self):
+        modname = '_test_from_modexport_null'
+        filename = _testmultiphase.__file__
+        with self.assertRaises(SystemError):
+            import_extension_from_file(modname, filename,
+                                       put_in_sys_modules=False)
+
+    def test_from_modexport_exception(self):
+        modname = '_test_from_modexport_exception'
+        filename = _testmultiphase.__file__
+        with self.assertRaises(ValueError):
+            import_extension_from_file(modname, filename,
+                                       put_in_sys_modules=False)
+
+    def test_from_modexport_create_nonmodule(self):
+        modname = '_test_from_modexport_create_nonmodule'
+        filename = _testmultiphase.__file__
+        module = import_extension_from_file(modname, filename,
+                                            put_in_sys_modules=False)
+        self.assertIsInstance(module, str)
+
+    @requires_subinterpreters
+    def test_from_modexport_create_nonmodule_gil_used(self):
+        # Test that a module with Py_MOD_GIL_USED (re-)enables the GIL.
+        # Do this in a new interpreter to avoid interfering with global state.
+        modname = '_test_from_modexport_create_nonmodule_gil_used'
+        filename = _testmultiphase.__file__
+        interp = concurrent.interpreters.create()
+        self.addCleanup(interp.close)
+        queue = concurrent.interpreters.create_queue()
+        interp.prepare_main(
+            modname=modname,
+            filename=filename,
+            queue=queue,
+        )
+        enabled_before = sys._is_gil_enabled()
+        interp.exec(f"""if True:
+            import sys
+            from test.support.warnings_helper import check_warnings
+            from {__name__} import import_extension_from_file
+            with check_warnings((".*GIL..has been enabled.*", RuntimeWarning),
+                                quiet=True):
+                module = import_extension_from_file(modname, filename,
+                                                    put_in_sys_modules=False)
+            queue.put(module)
+            queue.put(sys._is_gil_enabled())
+        """)
+
+        self.assertIsInstance(queue.get(), str)
+        self.assertEqual(queue.get(), True)
+        self.assertTrue(queue.empty())
+
+        self.assertEqual(enabled_before, sys._is_gil_enabled())
+
+    def test_from_modexport_smoke(self):
+        # General positive test for sundry features
+        # (PyModule_FromSlotsAndSpec tests exercise these more carefully)
+        modname = '_test_from_modexport_smoke'
+        filename = _testmultiphase.__file__
+        module = import_extension_from_file(modname, filename,
+                                            put_in_sys_modules=False)
+        self.assertEqual(module.__doc__, "the expected docstring")
+        self.assertEqual(module.number, 147)
+        self.assertEqual(module.get_state_int(), 258)
+        self.assertGreater(module.get_test_token(), 0)
+
+    def test_from_modexport_smoke_token(self):
+        _testcapi = import_module("_testcapi")
+
+        modname = '_test_from_modexport_smoke'
+        filename = _testmultiphase.__file__
+        module = import_extension_from_file(modname, filename,
+                                            put_in_sys_modules=False)
+        token = module.get_test_token()
+        self.assertEqual(_testcapi.pymodule_get_token(module), token)
+
+        tp = module.Example
+        self.assertEqual(_testcapi.pytype_getmodulebytoken(tp, token), module)
+        class Sub(tp):
+            pass
+        self.assertEqual(_testcapi.pytype_getmodulebytoken(Sub, token), module)
+
+    def test_from_modexport_empty_slots(self):
+        # Module to test that Py_mod_abi is mandatory for PyModExport
+        modname = '_test_from_modexport_empty_slots'
+        filename = _testmultiphase.__file__
+        with self.assertRaises(SystemError):
+            import_extension_from_file(
+                modname, filename, put_in_sys_modules=False)
+
+    @requires_gil_enabled("this module re-enables GIL")
+    def test_from_modexport_minimal_slots(self):
+        # Module to test that:
+        # - no slots except Py_mod_abi is mandatory for PyModExport
+        # - the slots array is used as the default token
+        modname = '_test_from_modexport_minimal_slots'
+        filename = _testmultiphase.__file__
+        module = import_extension_from_file(
+            modname, filename, put_in_sys_modules=False)
+
+        self.assertEqual(module.__name__, modname)
+        self.assertEqual(module.__doc__, None)
+
+        _testcapi = import_module("_testcapi")
+        smoke_mod = import_extension_from_file(
+            '_test_from_modexport_smoke', filename, put_in_sys_modules=False)
+        self.assertEqual(_testcapi.pymodule_get_token(module),
+                         smoke_mod.get_modexport_minimal_slots())
+
 @cpython_only
 class TestMagicNumber(unittest.TestCase):
     def test_magic_number_endianness(self):
diff --git a/Lib/test/test_import/data/syntax_warnings.py b/Lib/test/test_import/data/syntax_warnings.py
new file mode 100644
index 00000000000..103f07b6187
--- /dev/null
+++ b/Lib/test/test_import/data/syntax_warnings.py
@@ -0,0 +1,21 @@
+# Syntax warnings emitted in different parts of the Python compiler.
+
+# Parser/lexer/lexer.c
+x = 1or 0  # line 4
+
+# Parser/tokenizer/helpers.c
+'\z'  # line 7
+
+# Parser/string_parser.c
+'\400'  # line 10
+
+# _PyCompile_Warn() in Python/codegen.c
+assert(x, 'message')  # line 13
+x is 1  # line 14
+
+# _PyErr_EmitSyntaxWarning() in Python/ast_preprocess.c
+def f():
+    try:
+        pass
+    finally:
+        return 42  # line 21
diff --git a/Lib/test/test_import/data/unwritable/__init__.py b/Lib/test/test_import/data/unwritable/__init__.py
index da4ddb3d027..1d61ff348d8 100644
--- a/Lib/test/test_import/data/unwritable/__init__.py
+++ b/Lib/test/test_import/data/unwritable/__init__.py
@@ -1,9 +1,9 @@
 import sys
 
 class MyMod(object):
-    __slots__ = ['__builtins__', '__cached__', '__doc__',
-                 '__file__', '__loader__', '__name__',
-                 '__package__', '__path__', '__spec__']
+    __slots__ = ['__builtins__', '__doc__', '__file__',
+                 '__loader__', '__name__', '__package__',
+                 '__path__', '__spec__']
     def __init__(self):
         for attr in self.__slots__:
             setattr(self, attr, globals()[attr])
diff --git a/Lib/test/test_importlib/_context.py b/Lib/test/test_importlib/_context.py
deleted file mode 100644
index 8a53eb55d15..00000000000
--- a/Lib/test/test_importlib/_context.py
+++ /dev/null
@@ -1,13 +0,0 @@
-import contextlib
-
-
-# from jaraco.context 4.3
-class suppress(contextlib.suppress, contextlib.ContextDecorator):
-    """
-    A version of contextlib.suppress with decorator support.
-
-    >>> @suppress(KeyError)
-    ... def key_error():
-    ...     {}['']
-    >>> key_error()
-    """
diff --git a/Lib/test/test_importlib/_path.py b/Lib/test/test_importlib/_path.py
deleted file mode 100644
index 71a704389b9..00000000000
--- a/Lib/test/test_importlib/_path.py
+++ /dev/null
@@ -1,109 +0,0 @@
-# from jaraco.path 3.5
-
-import functools
-import pathlib
-from typing import Dict, Union
-
-try:
-    from typing import Protocol, runtime_checkable
-except ImportError:  # pragma: no cover
-    # Python 3.7
-    from typing_extensions import Protocol, runtime_checkable  # type: ignore
-
-
-FilesSpec = Dict[str, Union[str, bytes, 'FilesSpec']]  # type: ignore
-
-
-@runtime_checkable
-class TreeMaker(Protocol):
-    def __truediv__(self, *args, **kwargs):
-        ...  # pragma: no cover
-
-    def mkdir(self, **kwargs):
-        ...  # pragma: no cover
-
-    def write_text(self, content, **kwargs):
-        ...  # pragma: no cover
-
-    def write_bytes(self, content):
-        ...  # pragma: no cover
-
-
-def _ensure_tree_maker(obj: Union[str, TreeMaker]) -> TreeMaker:
-    return obj if isinstance(obj, TreeMaker) else pathlib.Path(obj)  # type: ignore
-
-
-def build(
-    spec: FilesSpec,
-    prefix: Union[str, TreeMaker] = pathlib.Path(),  # type: ignore
-):
-    """
-    Build a set of files/directories, as described by the spec.
-
-    Each key represents a pathname, and the value represents
-    the content. Content may be a nested directory.
-
-    >>> spec = {
-    ...     'README.txt': "A README file",
-    ...     "foo": {
-    ...         "__init__.py": "",
-    ...         "bar": {
-    ...             "__init__.py": "",
-    ...         },
-    ...         "baz.py": "# Some code",
-    ...     }
-    ... }
-    >>> target = getfixture('tmp_path')
-    >>> build(spec, target)
-    >>> target.joinpath('foo/baz.py').read_text(encoding='utf-8')
-    '# Some code'
-    """
-    for name, contents in spec.items():
-        create(contents, _ensure_tree_maker(prefix) / name)
-
-
-@functools.singledispatch
-def create(content: Union[str, bytes, FilesSpec], path):
-    path.mkdir(exist_ok=True)
-    build(content, prefix=path)  # type: ignore
-
-
-@create.register
-def _(content: bytes, path):
-    path.write_bytes(content)
-
-
-@create.register
-def _(content: str, path):
-    path.write_text(content, encoding='utf-8')
-
-
-@create.register
-def _(content: str, path):
-    path.write_text(content, encoding='utf-8')
-
-
-class Recording:
-    """
-    A TreeMaker object that records everything that would be written.
-
-    >>> r = Recording()
-    >>> build({'foo': {'foo1.txt': 'yes'}, 'bar.txt': 'abc'}, r)
-    >>> r.record
-    ['foo/foo1.txt', 'bar.txt']
-    """
-
-    def __init__(self, loc=pathlib.PurePosixPath(), record=None):
-        self.loc = loc
-        self.record = record if record is not None else []
-
-    def __truediv__(self, other):
-        return Recording(self.loc / other, self.record)
-
-    def write_text(self, content, **kwargs):
-        self.record.append(str(self.loc))
-
-    write_bytes = write_text
-
-    def mkdir(self, **kwargs):
-        return
diff --git a/Lib/test/test_importlib/abc.py b/Lib/test/test_importlib/abc.py
index 5d4b9587676..0da98e0c99e 100644
--- a/Lib/test/test_importlib/abc.py
+++ b/Lib/test/test_importlib/abc.py
@@ -40,22 +40,6 @@ def test_failure(self):
 
 class LoaderTests(metaclass=abc.ABCMeta):
 
-    @abc.abstractmethod
-    def test_module(self):
-        """A module should load without issue.
-
-        After the loader returns the module should be in sys.modules.
-
-        Attributes to verify:
-
-            * __file__
-            * __loader__
-            * __name__
-            * No __path__
-
-        """
-        pass
-
     @abc.abstractmethod
     def test_package(self):
         """Loading a package should work.
diff --git a/Lib/test/test_importlib/builtin/test_loader.py b/Lib/test/test_importlib/builtin/test_loader.py
index 7e9d1b1960f..2a5c2a8f39e 100644
--- a/Lib/test/test_importlib/builtin/test_loader.py
+++ b/Lib/test/test_importlib/builtin/test_loader.py
@@ -7,70 +7,6 @@
 import unittest
 import warnings
 
-@unittest.skipIf(util.BUILTINS.good_name is None, 'no reasonable builtin module')
-class LoaderTests(abc.LoaderTests):
-
-    """Test load_module() for built-in modules."""
-
-    def setUp(self):
-        self.verification = {'__name__': 'errno', '__package__': '',
-                             '__loader__': self.machinery.BuiltinImporter}
-
-    def verify(self, module):
-        """Verify that the module matches against what it should have."""
-        self.assertIsInstance(module, types.ModuleType)
-        for attr, value in self.verification.items():
-            self.assertEqual(getattr(module, attr), value)
-        self.assertIn(module.__name__, sys.modules)
-
-    def load_module(self, name):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            return self.machinery.BuiltinImporter.load_module(name)
-
-    def test_module(self):
-        # Common case.
-        with util.uncache(util.BUILTINS.good_name):
-            module = self.load_module(util.BUILTINS.good_name)
-            self.verify(module)
-
-    # Built-in modules cannot be a package.
-    test_package = test_lacking_parent = None
-
-    # No way to force an import failure.
-    test_state_after_failure = None
-
-    def test_module_reuse(self):
-        # Test that the same module is used in a reload.
-        with util.uncache(util.BUILTINS.good_name):
-            module1 = self.load_module(util.BUILTINS.good_name)
-            module2 = self.load_module(util.BUILTINS.good_name)
-            self.assertIs(module1, module2)
-
-    def test_unloadable(self):
-        name = 'dssdsdfff'
-        assert name not in sys.builtin_module_names
-        with self.assertRaises(ImportError) as cm:
-            self.load_module(name)
-        self.assertEqual(cm.exception.name, name)
-
-    def test_already_imported(self):
-        # Using the name of a module already imported but not a built-in should
-        # still fail.
-        module_name = 'builtin_reload_test'
-        assert module_name not in sys.builtin_module_names
-        with util.uncache(module_name):
-            module = types.ModuleType(module_name)
-            sys.modules[module_name] = module
-        with self.assertRaises(ImportError) as cm:
-            self.load_module(module_name)
-        self.assertEqual(cm.exception.name, module_name)
-
-
-(Frozen_LoaderTests,
- Source_LoaderTests
- ) = util.test_both(LoaderTests, machinery=machinery)
-
 
 @unittest.skipIf(util.BUILTINS.good_name is None, 'no reasonable builtin module')
 class InspectLoaderTests:
diff --git a/Lib/test/test_importlib/data/example-21.12-py3-none-any.whl b/Lib/test/test_importlib/data/example-21.12-py3-none-any.whl
deleted file mode 100644
index 641ab07f7aa..00000000000
Binary files a/Lib/test/test_importlib/data/example-21.12-py3-none-any.whl and /dev/null differ
diff --git a/Lib/test/test_importlib/data/example-21.12-py3.6.egg b/Lib/test/test_importlib/data/example-21.12-py3.6.egg
deleted file mode 100644
index cdb298a19b0..00000000000
Binary files a/Lib/test/test_importlib/data/example-21.12-py3.6.egg and /dev/null differ
diff --git a/Lib/test/test_importlib/data/example2-1.0.0-py3-none-any.whl b/Lib/test/test_importlib/data/example2-1.0.0-py3-none-any.whl
deleted file mode 100644
index 5ca93657f81..00000000000
Binary files a/Lib/test/test_importlib/data/example2-1.0.0-py3-none-any.whl and /dev/null differ
diff --git a/Lib/test/test_importlib/data01/binary.file b/Lib/test/test_importlib/data01/binary.file
deleted file mode 100644
index eaf36c1dacc..00000000000
Binary files a/Lib/test/test_importlib/data01/binary.file and /dev/null differ
diff --git a/Lib/test/test_importlib/data01/subdirectory/binary.file b/Lib/test/test_importlib/data01/subdirectory/binary.file
deleted file mode 100644
index eaf36c1dacc..00000000000
Binary files a/Lib/test/test_importlib/data01/subdirectory/binary.file and /dev/null differ
diff --git a/Lib/test/test_importlib/data01/utf-16.file b/Lib/test/test_importlib/data01/utf-16.file
deleted file mode 100644
index 2cb772295ef..00000000000
Binary files a/Lib/test/test_importlib/data01/utf-16.file and /dev/null differ
diff --git a/Lib/test/test_importlib/extension/test_finder.py b/Lib/test/test_importlib/extension/test_finder.py
index cdc8884d668..e33c0465654 100644
--- a/Lib/test/test_importlib/extension/test_finder.py
+++ b/Lib/test/test_importlib/extension/test_finder.py
@@ -1,10 +1,11 @@
-from test.support import is_apple_mobile
+from test.support import is_apple_mobile, Py_GIL_DISABLED
 from test.test_importlib import abc, util
 
 machinery = util.import_importlib('importlib.machinery')
 
 import unittest
 import sys
+import sysconfig
 
 
 class FinderTests(abc.FinderTests):
@@ -59,6 +60,28 @@ def test_module(self):
     def test_failure(self):
         self.assertIsNone(self.find_spec('asdfjkl;'))
 
+    def test_abi3_extension_suffixes(self):
+        suffixes = self.machinery.EXTENSION_SUFFIXES
+        platform = sysconfig.get_config_var("SOABI_PLATFORM")
+        if 'win32' in sys.platform:
+            # Either "_d.pyd" or ".pyd" must be in suffixes
+            self.assertTrue({"_d.pyd", ".pyd"}.intersection(suffixes))
+        elif 'cygwin' in sys.platform:
+            pass
+        else:
+            if Py_GIL_DISABLED:
+                self.assertNotIn(".abi3.so", suffixes)
+            else:
+                self.assertIn(".abi3.so", suffixes)
+            self.assertIn(".abi3t.so", suffixes)
+
+            if platform:
+                if Py_GIL_DISABLED:
+                    self.assertNotIn(f".abi3-{platform}.so", suffixes)
+                else:
+                    self.assertIn(f".abi3-{platform}.so", suffixes)
+                self.assertIn(f".abi3t-{platform}.so", suffixes)
+
 
 (Frozen_FinderTests,
  Source_FinderTests
diff --git a/Lib/test/test_importlib/extension/test_loader.py b/Lib/test/test_importlib/extension/test_loader.py
index 0dd21e079eb..15d5a7d4752 100644
--- a/Lib/test/test_importlib/extension/test_loader.py
+++ b/Lib/test/test_importlib/extension/test_loader.py
@@ -35,11 +35,6 @@ def setUp(self):
 
         self.loader = self.LoaderClass(util.EXTENSIONS.name, util.EXTENSIONS.file_path)
 
-    def load_module(self, fullname):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            return self.loader.load_module(fullname)
-
     def test_equality(self):
         other = self.LoaderClass(util.EXTENSIONS.name, util.EXTENSIONS.file_path)
         self.assertEqual(self.loader, other)
@@ -48,25 +43,6 @@ def test_inequality(self):
         other = self.LoaderClass('_' + util.EXTENSIONS.name, util.EXTENSIONS.file_path)
         self.assertNotEqual(self.loader, other)
 
-    def test_load_module_API(self):
-        # Test the default argument for load_module().
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            self.loader.load_module()
-            self.loader.load_module(None)
-            with self.assertRaises(ImportError):
-                self.load_module('XXX')
-
-    def test_module(self):
-        with util.uncache(util.EXTENSIONS.name):
-            module = self.load_module(util.EXTENSIONS.name)
-            for attr, value in [('__name__', util.EXTENSIONS.name),
-                                ('__file__', util.EXTENSIONS.file_path),
-                                ('__package__', '')]:
-                self.assertEqual(getattr(module, attr), value)
-            self.assertIn(util.EXTENSIONS.name, sys.modules)
-            self.assertIsInstance(module.__loader__, self.LoaderClass)
-
     # No extension module as __init__ available for testing.
     test_package = None
 
@@ -76,18 +52,6 @@ def test_module(self):
     # No easy way to trigger a failure after a successful import.
     test_state_after_failure = None
 
-    def test_unloadable(self):
-        name = 'asdfjkl;'
-        with self.assertRaises(ImportError) as cm:
-            self.load_module(name)
-        self.assertEqual(cm.exception.name, name)
-
-    def test_module_reuse(self):
-        with util.uncache(util.EXTENSIONS.name):
-            module1 = self.load_module(util.EXTENSIONS.name)
-            module2 = self.load_module(util.EXTENSIONS.name)
-            self.assertIs(module1, module2)
-
     def test_is_package(self):
         self.assertFalse(self.loader.is_package(util.EXTENSIONS.name))
         for suffix in self.machinery.EXTENSION_SUFFIXES:
@@ -126,11 +90,6 @@ def setUp(self):
 
         self.loader = self.LoaderClass(self.name, self.spec.origin)
 
-    def load_module(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            return self.loader.load_module(self.name)
-
     def load_module_by_name(self, fullname):
         # Load a module from the test extension by name.
         origin = self.spec.origin
@@ -140,19 +99,6 @@ def load_module_by_name(self, fullname):
         loader.exec_module(module)
         return module
 
-    def test_module(self):
-        # Test loading an extension module.
-        with util.uncache(self.name):
-            module = self.load_module()
-            for attr, value in [('__name__', self.name),
-                                ('__file__', self.spec.origin),
-                                ('__package__', '')]:
-                self.assertEqual(getattr(module, attr), value)
-            with self.assertRaises(AttributeError):
-                module.__path__
-            self.assertIs(module, sys.modules[self.name])
-            self.assertIsInstance(module.__loader__, self.LoaderClass)
-
     # No extension module as __init__ available for testing.
     test_package = None
 
@@ -213,12 +159,6 @@ def setUp(self):
         assert self.spec
         self.loader = self.LoaderClass(self.name, self.spec.origin)
 
-    def load_module(self):
-        # Load the module from the test extension.
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            return self.loader.load_module(self.name)
-
     def load_module_by_name(self, fullname):
         # Load a module from the test extension by name.
         origin = self.spec.origin
@@ -237,60 +177,6 @@ def load_module_by_name(self, fullname):
     # Handling failure on reload is the up to the module.
     test_state_after_failure = None
 
-    def test_module(self):
-        # Test loading an extension module.
-        with util.uncache(self.name):
-            module = self.load_module()
-            for attr, value in [('__name__', self.name),
-                                ('__file__', self.spec.origin),
-                                ('__package__', '')]:
-                self.assertEqual(getattr(module, attr), value)
-            with self.assertRaises(AttributeError):
-                module.__path__
-            self.assertIs(module, sys.modules[self.name])
-            self.assertIsInstance(module.__loader__, self.LoaderClass)
-
-    def test_functionality(self):
-        # Test basic functionality of stuff defined in an extension module.
-        with util.uncache(self.name):
-            module = self.load_module()
-            self.assertIsInstance(module, types.ModuleType)
-            ex = module.Example()
-            self.assertEqual(ex.demo('abcd'), 'abcd')
-            self.assertEqual(ex.demo(), None)
-            with self.assertRaises(AttributeError):
-                ex.abc
-            ex.abc = 0
-            self.assertEqual(ex.abc, 0)
-            self.assertEqual(module.foo(9, 9), 18)
-            self.assertIsInstance(module.Str(), str)
-            self.assertEqual(module.Str(1) + '23', '123')
-            with self.assertRaises(module.error):
-                raise module.error()
-            self.assertEqual(module.int_const, 1969)
-            self.assertEqual(module.str_const, 'something different')
-
-    def test_reload(self):
-        # Test that reload didn't re-set the module's attributes.
-        with util.uncache(self.name):
-            module = self.load_module()
-            ex_class = module.Example
-            importlib.reload(module)
-            self.assertIs(ex_class, module.Example)
-
-    def test_try_registration(self):
-        # Assert that the PyState_{Find,Add,Remove}Module C API doesn't work.
-        with util.uncache(self.name):
-            module = self.load_module()
-            with self.subTest('PyState_FindModule'):
-                self.assertEqual(module.call_state_registration_func(0), None)
-            with self.subTest('PyState_AddModule'):
-                with self.assertRaises(SystemError):
-                    module.call_state_registration_func(1)
-            with self.subTest('PyState_RemoveModule'):
-                with self.assertRaises(SystemError):
-                    module.call_state_registration_func(2)
-
     def test_load_submodule(self):
         # Test loading a simulated submodule.
         module = self.load_module_by_name('pkg.' + self.name)
diff --git a/Lib/test/test_importlib/fixtures.py b/Lib/test/test_importlib/fixtures.py
deleted file mode 100644
index 73e5da2ba92..00000000000
--- a/Lib/test/test_importlib/fixtures.py
+++ /dev/null
@@ -1,382 +0,0 @@
-import os
-import sys
-import copy
-import shutil
-import pathlib
-import tempfile
-import textwrap
-import functools
-import contextlib
-
-from test.support.os_helper import FS_NONASCII
-from test.support import requires_zlib
-
-from . import _path
-from ._path import FilesSpec
-
-
-try:
-    from importlib import resources  # type: ignore
-
-    getattr(resources, 'files')
-    getattr(resources, 'as_file')
-except (ImportError, AttributeError):
-    import importlib_resources as resources  # type: ignore
-
-
-@contextlib.contextmanager
-def tempdir():
-    tmpdir = tempfile.mkdtemp()
-    try:
-        yield pathlib.Path(tmpdir)
-    finally:
-        shutil.rmtree(tmpdir)
-
-
-@contextlib.contextmanager
-def save_cwd():
-    orig = os.getcwd()
-    try:
-        yield
-    finally:
-        os.chdir(orig)
-
-
-@contextlib.contextmanager
-def tempdir_as_cwd():
-    with tempdir() as tmp:
-        with save_cwd():
-            os.chdir(str(tmp))
-            yield tmp
-
-
-@contextlib.contextmanager
-def install_finder(finder):
-    sys.meta_path.append(finder)
-    try:
-        yield
-    finally:
-        sys.meta_path.remove(finder)
-
-
-class Fixtures:
-    def setUp(self):
-        self.fixtures = contextlib.ExitStack()
-        self.addCleanup(self.fixtures.close)
-
-
-class SiteDir(Fixtures):
-    def setUp(self):
-        super().setUp()
-        self.site_dir = self.fixtures.enter_context(tempdir())
-
-
-class OnSysPath(Fixtures):
-    @staticmethod
-    @contextlib.contextmanager
-    def add_sys_path(dir):
-        sys.path[:0] = [str(dir)]
-        try:
-            yield
-        finally:
-            sys.path.remove(str(dir))
-
-    def setUp(self):
-        super().setUp()
-        self.fixtures.enter_context(self.add_sys_path(self.site_dir))
-
-
-class DistInfoPkg(OnSysPath, SiteDir):
-    files: FilesSpec = {
-        "distinfo_pkg-1.0.0.dist-info": {
-            "METADATA": """
-                Name: distinfo-pkg
-                Author: Steven Ma
-                Version: 1.0.0
-                Requires-Dist: wheel >= 1.0
-                Requires-Dist: pytest; extra == 'test'
-                Keywords: sample package
-
-                Once upon a time
-                There was a distinfo pkg
-                """,
-            "RECORD": "mod.py,sha256=abc,20\n",
-            "entry_points.txt": """
-                [entries]
-                main = mod:main
-                ns:sub = mod:main
-            """,
-        },
-        "mod.py": """
-            def main():
-                print("hello world")
-            """,
-    }
-
-    def setUp(self):
-        super().setUp()
-        build_files(DistInfoPkg.files, self.site_dir)
-
-    def make_uppercase(self):
-        """
-        Rewrite metadata with everything uppercase.
-        """
-        shutil.rmtree(self.site_dir / "distinfo_pkg-1.0.0.dist-info")
-        files = copy.deepcopy(DistInfoPkg.files)
-        info = files["distinfo_pkg-1.0.0.dist-info"]
-        info["METADATA"] = info["METADATA"].upper()
-        build_files(files, self.site_dir)
-
-
-class DistInfoPkgWithDot(OnSysPath, SiteDir):
-    files: FilesSpec = {
-        "pkg_dot-1.0.0.dist-info": {
-            "METADATA": """
-                Name: pkg.dot
-                Version: 1.0.0
-                """,
-        },
-    }
-
-    def setUp(self):
-        super().setUp()
-        build_files(DistInfoPkgWithDot.files, self.site_dir)
-
-
-class DistInfoPkgWithDotLegacy(OnSysPath, SiteDir):
-    files: FilesSpec = {
-        "pkg.dot-1.0.0.dist-info": {
-            "METADATA": """
-                Name: pkg.dot
-                Version: 1.0.0
-                """,
-        },
-        "pkg.lot.egg-info": {
-            "METADATA": """
-                Name: pkg.lot
-                Version: 1.0.0
-                """,
-        },
-    }
-
-    def setUp(self):
-        super().setUp()
-        build_files(DistInfoPkgWithDotLegacy.files, self.site_dir)
-
-
-class DistInfoPkgOffPath(SiteDir):
-    def setUp(self):
-        super().setUp()
-        build_files(DistInfoPkg.files, self.site_dir)
-
-
-class EggInfoPkg(OnSysPath, SiteDir):
-    files: FilesSpec = {
-        "egginfo_pkg.egg-info": {
-            "PKG-INFO": """
-                Name: egginfo-pkg
-                Author: Steven Ma
-                License: Unknown
-                Version: 1.0.0
-                Classifier: Intended Audience :: Developers
-                Classifier: Topic :: Software Development :: Libraries
-                Keywords: sample package
-                Description: Once upon a time
-                        There was an egginfo package
-                """,
-            "SOURCES.txt": """
-                mod.py
-                egginfo_pkg.egg-info/top_level.txt
-            """,
-            "entry_points.txt": """
-                [entries]
-                main = mod:main
-            """,
-            "requires.txt": """
-                wheel >= 1.0; python_version >= "2.7"
-                [test]
-                pytest
-            """,
-            "top_level.txt": "mod\n",
-        },
-        "mod.py": """
-            def main():
-                print("hello world")
-            """,
-    }
-
-    def setUp(self):
-        super().setUp()
-        build_files(EggInfoPkg.files, prefix=self.site_dir)
-
-
-class EggInfoPkgPipInstalledNoToplevel(OnSysPath, SiteDir):
-    files: FilesSpec = {
-        "egg_with_module_pkg.egg-info": {
-            "PKG-INFO": "Name: egg_with_module-pkg",
-            # SOURCES.txt is made from the source archive, and contains files
-            # (setup.py) that are not present after installation.
-            "SOURCES.txt": """
-                egg_with_module.py
-                setup.py
-                egg_with_module_pkg.egg-info/PKG-INFO
-                egg_with_module_pkg.egg-info/SOURCES.txt
-                egg_with_module_pkg.egg-info/top_level.txt
-            """,
-            # installed-files.txt is written by pip, and is a strictly more
-            # accurate source than SOURCES.txt as to the installed contents of
-            # the package.
-            "installed-files.txt": """
-                ../egg_with_module.py
-                PKG-INFO
-                SOURCES.txt
-                top_level.txt
-            """,
-            # missing top_level.txt (to trigger fallback to installed-files.txt)
-        },
-        "egg_with_module.py": """
-            def main():
-                print("hello world")
-            """,
-    }
-
-    def setUp(self):
-        super().setUp()
-        build_files(EggInfoPkgPipInstalledNoToplevel.files, prefix=self.site_dir)
-
-
-class EggInfoPkgPipInstalledNoModules(OnSysPath, SiteDir):
-    files: FilesSpec = {
-        "egg_with_no_modules_pkg.egg-info": {
-            "PKG-INFO": "Name: egg_with_no_modules-pkg",
-            # SOURCES.txt is made from the source archive, and contains files
-            # (setup.py) that are not present after installation.
-            "SOURCES.txt": """
-                setup.py
-                egg_with_no_modules_pkg.egg-info/PKG-INFO
-                egg_with_no_modules_pkg.egg-info/SOURCES.txt
-                egg_with_no_modules_pkg.egg-info/top_level.txt
-            """,
-            # installed-files.txt is written by pip, and is a strictly more
-            # accurate source than SOURCES.txt as to the installed contents of
-            # the package.
-            "installed-files.txt": """
-                PKG-INFO
-                SOURCES.txt
-                top_level.txt
-            """,
-            # top_level.txt correctly reflects that no modules are installed
-            "top_level.txt": b"\n",
-        },
-    }
-
-    def setUp(self):
-        super().setUp()
-        build_files(EggInfoPkgPipInstalledNoModules.files, prefix=self.site_dir)
-
-
-class EggInfoPkgSourcesFallback(OnSysPath, SiteDir):
-    files: FilesSpec = {
-        "sources_fallback_pkg.egg-info": {
-            "PKG-INFO": "Name: sources_fallback-pkg",
-            # SOURCES.txt is made from the source archive, and contains files
-            # (setup.py) that are not present after installation.
-            "SOURCES.txt": """
-                sources_fallback.py
-                setup.py
-                sources_fallback_pkg.egg-info/PKG-INFO
-                sources_fallback_pkg.egg-info/SOURCES.txt
-            """,
-            # missing installed-files.txt (i.e. not installed by pip) and
-            # missing top_level.txt (to trigger fallback to SOURCES.txt)
-        },
-        "sources_fallback.py": """
-            def main():
-                print("hello world")
-            """,
-    }
-
-    def setUp(self):
-        super().setUp()
-        build_files(EggInfoPkgSourcesFallback.files, prefix=self.site_dir)
-
-
-class EggInfoFile(OnSysPath, SiteDir):
-    files: FilesSpec = {
-        "egginfo_file.egg-info": """
-            Metadata-Version: 1.0
-            Name: egginfo_file
-            Version: 0.1
-            Summary: An example package
-            Home-page: www.example.com
-            Author: Eric Haffa-Vee
-            Author-email: eric@example.coms
-            License: UNKNOWN
-            Description: UNKNOWN
-            Platform: UNKNOWN
-            """,
-    }
-
-    def setUp(self):
-        super().setUp()
-        build_files(EggInfoFile.files, prefix=self.site_dir)
-
-
-# dedent all text strings before writing
-orig = _path.create.registry[str]
-_path.create.register(str, lambda content, path: orig(DALS(content), path))
-
-
-build_files = _path.build
-
-
-def build_record(file_defs):
-    return ''.join(f'{name},,\n' for name in record_names(file_defs))
-
-
-def record_names(file_defs):
-    recording = _path.Recording()
-    _path.build(file_defs, recording)
-    return recording.record
-
-
-class FileBuilder:
-    def unicode_filename(self):
-        return FS_NONASCII or self.skip("File system does not support non-ascii.")
-
-
-def DALS(str):
-    "Dedent and left-strip"
-    return textwrap.dedent(str).lstrip()
-
-
-@requires_zlib()
-class ZipFixtures:
-    root = 'test.test_importlib.data'
-
-    def _fixture_on_path(self, filename):
-        pkg_file = resources.files(self.root).joinpath(filename)
-        file = self.resources.enter_context(resources.as_file(pkg_file))
-        assert file.name.startswith('example'), file.name
-        sys.path.insert(0, str(file))
-        self.resources.callback(sys.path.pop, 0)
-
-    def setUp(self):
-        # Add self.zip_name to the front of sys.path.
-        self.resources = contextlib.ExitStack()
-        self.addCleanup(self.resources.close)
-
-
-def parameterize(*args_set):
-    """Run test method with a series of parameters."""
-
-    def wrapper(func):
-        @functools.wraps(func)
-        def _inner(self):
-            for args in args_set:
-                with self.subTest(**args):
-                    func(self, **args)
-
-        return _inner
-
-    return wrapper
diff --git a/Lib/test/test_importlib/import_/test_api.py b/Lib/test/test_importlib/import_/test_api.py
index d6ad590b3d4..ea1e29a4e5f 100644
--- a/Lib/test/test_importlib/import_/test_api.py
+++ b/Lib/test/test_importlib/import_/test_api.py
@@ -27,13 +27,6 @@ def exec_module(module):
             raise ImportError('I cannot be loaded!')
 
 
-class BadLoaderFinder:
-    @classmethod
-    def load_module(cls, fullname):
-        if fullname == SUBMOD_NAME:
-            raise ImportError('I cannot be loaded!')
-
-
 class APITest:
 
     """Test API-specific details for __import__ (e.g. raising the right
@@ -93,45 +86,6 @@ def test_blocked_fromlist(self):
                 self.assertEqual(cm.exception.name, SUBMOD_NAME)
 
 
-class OldAPITests(APITest):
-    bad_finder_loader = BadLoaderFinder
-
-    def test_raises_ModuleNotFoundError(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            super().test_raises_ModuleNotFoundError()
-
-    def test_name_requires_rparition(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            super().test_name_requires_rparition()
-
-    def test_negative_level(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            super().test_negative_level()
-
-    def test_nonexistent_fromlist_entry(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            super().test_nonexistent_fromlist_entry()
-
-    def test_fromlist_load_error_propagates(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            super().test_fromlist_load_error_propagates
-
-    def test_blocked_fromlist(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            super().test_blocked_fromlist()
-
-
-(Frozen_OldAPITests,
- Source_OldAPITests
- ) = util.test_both(OldAPITests, __import__=util.__import__)
-
-
 class SpecAPITests(APITest):
     bad_finder_loader = BadSpecFinderLoader
 
diff --git a/Lib/test/test_importlib/import_/test_helpers.py b/Lib/test/test_importlib/import_/test_helpers.py
index 550f88d1d7a..7587276a41e 100644
--- a/Lib/test/test_importlib/import_/test_helpers.py
+++ b/Lib/test/test_importlib/import_/test_helpers.py
@@ -19,8 +19,7 @@ def test_no_loader_but_spec(self):
         ns = {"__spec__": spec}
         _bootstrap_external._fix_up_module(ns, name, path)
 
-        expected = {"__spec__": spec, "__loader__": loader, "__file__": path,
-                    "__cached__": None}
+        expected = {"__spec__": spec, "__loader__": loader, "__file__": path}
         self.assertEqual(ns, expected)
 
     def test_no_loader_no_spec_but_sourceless(self):
@@ -29,7 +28,7 @@ def test_no_loader_no_spec_but_sourceless(self):
         ns = {}
         _bootstrap_external._fix_up_module(ns, name, path, path)
 
-        expected = {"__file__": path, "__cached__": path}
+        expected = {"__file__": path}
 
         for key, val in expected.items():
             with self.subTest(f"{key}: {val}"):
@@ -51,7 +50,7 @@ def test_no_loader_no_spec_but_source(self):
         ns = {}
         _bootstrap_external._fix_up_module(ns, name, path)
 
-        expected = {"__file__": path, "__cached__": None}
+        expected = {"__file__": path}
 
         for key, val in expected.items():
             with self.subTest(f"{key}: {val}"):
diff --git a/Lib/test/test_importlib/metadata/__init__.py b/Lib/test/test_importlib/metadata/__init__.py
index 8b137891791..e69de29bb2d 100644
--- a/Lib/test/test_importlib/metadata/__init__.py
+++ b/Lib/test/test_importlib/metadata/__init__.py
@@ -1 +0,0 @@
-
diff --git a/Lib/test/test_importlib/metadata/_path.py b/Lib/test/test_importlib/metadata/_path.py
index b3cfb9cd549..e63d889f96b 100644
--- a/Lib/test/test_importlib/metadata/_path.py
+++ b/Lib/test/test_importlib/metadata/_path.py
@@ -1,9 +1,14 @@
-# from jaraco.path 3.7
+# from jaraco.path 3.7.2
+
+from __future__ import annotations
 
 import functools
 import pathlib
-from typing import Dict, Protocol, Union
-from typing import runtime_checkable
+from collections.abc import Mapping
+from typing import TYPE_CHECKING, Protocol, Union, runtime_checkable
+
+if TYPE_CHECKING:
+    from typing_extensions import Self
 
 
 class Symlink(str):
@@ -12,29 +17,25 @@ class Symlink(str):
     """
 
 
-FilesSpec = Dict[str, Union[str, bytes, Symlink, 'FilesSpec']]  # type: ignore
+FilesSpec = Mapping[str, Union[str, bytes, Symlink, 'FilesSpec']]
 
 
 @runtime_checkable
 class TreeMaker(Protocol):
-    def __truediv__(self, *args, **kwargs): ...  # pragma: no cover
-
-    def mkdir(self, **kwargs): ...  # pragma: no cover
-
-    def write_text(self, content, **kwargs): ...  # pragma: no cover
-
-    def write_bytes(self, content): ...  # pragma: no cover
-
-    def symlink_to(self, target): ...  # pragma: no cover
+    def __truediv__(self, other, /) -> Self: ...
+    def mkdir(self, *, exist_ok) -> object: ...
+    def write_text(self, content, /, *, encoding) -> object: ...
+    def write_bytes(self, content, /) -> object: ...
+    def symlink_to(self, target, /) -> object: ...
 
 
-def _ensure_tree_maker(obj: Union[str, TreeMaker]) -> TreeMaker:
-    return obj if isinstance(obj, TreeMaker) else pathlib.Path(obj)  # type: ignore
+def _ensure_tree_maker(obj: str | TreeMaker) -> TreeMaker:
+    return obj if isinstance(obj, TreeMaker) else pathlib.Path(obj)
 
 
 def build(
     spec: FilesSpec,
-    prefix: Union[str, TreeMaker] = pathlib.Path(),  # type: ignore
+    prefix: str | TreeMaker = pathlib.Path(),
 ):
     """
     Build a set of files/directories, as described by the spec.
@@ -66,23 +67,24 @@ def build(
 
 
 @functools.singledispatch
-def create(content: Union[str, bytes, FilesSpec], path):
+def create(content: str | bytes | FilesSpec, path: TreeMaker) -> None:
     path.mkdir(exist_ok=True)
-    build(content, prefix=path)  # type: ignore
+    # Mypy only looks at the signature of the main singledispatch method. So it must contain the complete Union
+    build(content, prefix=path)  # type: ignore[arg-type] # python/mypy#11727
 
 
 @create.register
-def _(content: bytes, path):
+def _(content: bytes, path: TreeMaker) -> None:
     path.write_bytes(content)
 
 
 @create.register
-def _(content: str, path):
+def _(content: str, path: TreeMaker) -> None:
     path.write_text(content, encoding='utf-8')
 
 
 @create.register
-def _(content: Symlink, path):
+def _(content: Symlink, path: TreeMaker) -> None:
     path.symlink_to(content)
 
 
diff --git a/Lib/test/test_importlib/metadata/data/__init__.py b/Lib/test/test_importlib/metadata/data/__init__.py
index 8b137891791..e69de29bb2d 100644
--- a/Lib/test/test_importlib/metadata/data/__init__.py
+++ b/Lib/test/test_importlib/metadata/data/__init__.py
@@ -1 +0,0 @@
-
diff --git a/Lib/test/test_importlib/metadata/fixtures.py b/Lib/test/test_importlib/metadata/fixtures.py
index 826b1b3259b..3283697d418 100644
--- a/Lib/test/test_importlib/metadata/fixtures.py
+++ b/Lib/test/test_importlib/metadata/fixtures.py
@@ -1,11 +1,12 @@
-import sys
+import contextlib
 import copy
+import functools
 import json
-import shutil
 import pathlib
+import shutil
+import sys
 import textwrap
-import functools
-import contextlib
+from importlib import resources
 
 from test.support import import_helper
 from test.support import os_helper
@@ -15,15 +16,6 @@
 from ._path import FilesSpec
 
 
-try:
-    from importlib import resources  # type: ignore
-
-    getattr(resources, 'files')
-    getattr(resources, 'as_file')
-except (ImportError, AttributeError):
-    import importlib_resources as resources  # type: ignore
-
-
 @contextlib.contextmanager
 def tmp_path():
     """
diff --git a/Lib/test/test_importlib/metadata/test_api.py b/Lib/test/test_importlib/metadata/test_api.py
index 2256e0c502e..5449f048449 100644
--- a/Lib/test/test_importlib/metadata/test_api.py
+++ b/Lib/test/test_importlib/metadata/test_api.py
@@ -1,14 +1,12 @@
+import importlib
 import re
 import textwrap
 import unittest
-import warnings
-import importlib
-import contextlib
 
-from . import fixtures
 from importlib.metadata import (
     Distribution,
     PackageNotFoundError,
+    Prepared,
     distribution,
     entry_points,
     files,
@@ -17,12 +15,7 @@
     version,
 )
 
-
-@contextlib.contextmanager
-def suppress_known_deprecation():
-    with warnings.catch_warnings(record=True) as ctx:
-        warnings.simplefilter('default', category=DeprecationWarning)
-        yield ctx
+from . import fixtures
 
 
 class APITests(
@@ -153,13 +146,13 @@ def test_metadata_for_this_package(self):
         classifiers = md.get_all('Classifier')
         assert 'Topic :: Software Development :: Libraries' in classifiers
 
-    def test_missing_key_legacy(self):
+    def test_missing_key(self):
         """
-        Requesting a missing key will still return None, but warn.
+        Requesting a missing key raises KeyError.
         """
         md = metadata('distinfo-pkg')
-        with suppress_known_deprecation():
-            assert md['does-not-exist'] is None
+        with self.assertRaises(KeyError):
+            md['does-not-exist']
 
     def test_get_key(self):
         """
@@ -321,3 +314,34 @@ class InvalidateCache(unittest.TestCase):
     def test_invalidate_cache(self):
         # No externally observable behavior, but ensures test coverage...
         importlib.invalidate_caches()
+
+
+class PreparedTests(unittest.TestCase):
+    @fixtures.parameterize(
+        # Simple
+        dict(input='sample', expected='sample'),
+        # Mixed case
+        dict(input='Sample', expected='sample'),
+        dict(input='SAMPLE', expected='sample'),
+        dict(input='SaMpLe', expected='sample'),
+        # Separator conversions
+        dict(input='sample-pkg', expected='sample_pkg'),
+        dict(input='sample.pkg', expected='sample_pkg'),
+        dict(input='sample_pkg', expected='sample_pkg'),
+        # Multiple separators
+        dict(input='sample---pkg', expected='sample_pkg'),
+        dict(input='sample___pkg', expected='sample_pkg'),
+        dict(input='sample...pkg', expected='sample_pkg'),
+        # Mixed separators
+        dict(input='sample-._pkg', expected='sample_pkg'),
+        dict(input='sample_.-pkg', expected='sample_pkg'),
+        # Complex
+        dict(input='Sample__Pkg-name.foo', expected='sample_pkg_name_foo'),
+        dict(input='Sample__Pkg.name__foo', expected='sample_pkg_name_foo'),
+        # Uppercase with separators
+        dict(input='SAMPLE-PKG', expected='sample_pkg'),
+        dict(input='Sample.Pkg', expected='sample_pkg'),
+        dict(input='SAMPLE_PKG', expected='sample_pkg'),
+    )
+    def test_normalize(self, input, expected):
+        self.assertEqual(Prepared.normalize(input), expected)
diff --git a/Lib/test/test_importlib/metadata/test_main.py b/Lib/test/test_importlib/metadata/test_main.py
index e4218076f8c..aae052160d9 100644
--- a/Lib/test/test_importlib/metadata/test_main.py
+++ b/Lib/test/test_importlib/metadata/test_main.py
@@ -1,23 +1,18 @@
-import re
+import importlib
 import pickle
+import re
 import unittest
-import warnings
-import importlib
-import importlib.metadata
-import contextlib
-from test.support import os_helper
 
 try:
     import pyfakefs.fake_filesystem_unittest as ffs
 except ImportError:
     from .stubs import fake_filesystem_unittest as ffs
+from test.support import os_helper
 
-from . import fixtures
-from ._context import suppress
-from ._path import Symlink
 from importlib.metadata import (
     Distribution,
     EntryPoint,
+    MetadataNotFound,
     PackageNotFoundError,
     _unique,
     distributions,
@@ -27,12 +22,8 @@
     version,
 )
 
-
-@contextlib.contextmanager
-def suppress_known_deprecation():
-    with warnings.catch_warnings(record=True) as ctx:
-        warnings.simplefilter('default', category=DeprecationWarning)
-        yield ctx
+from . import fixtures
+from ._path import Symlink
 
 
 class BasicTests(fixtures.DistInfoPkg, unittest.TestCase):
@@ -59,9 +50,6 @@ def test_package_not_found_mentions_metadata(self):
 
         assert "metadata" in str(ctx.exception)
 
-    # expected to fail until ABC is enforced
-    @suppress(AssertionError)
-    @suppress_known_deprecation()
     def test_abc_enforced(self):
         with self.assertRaises(TypeError):
             type('DistributionSubclass', (Distribution,), {})()
@@ -146,6 +134,43 @@ def test_unique_distributions(self):
         assert len(after) == len(before)
 
 
+class InvalidMetadataTests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
+    @staticmethod
+    def make_pkg(name, files=dict(METADATA="VERSION: 1.0")):
+        """
+        Create metadata for a dist-info package with name and files.
+        """
+        return {
+            f'{name}.dist-info': files,
+        }
+
+    def test_valid_dists_preferred(self):
+        """
+        Dists with metadata should be preferred when discovered by name.
+
+        Ref python/importlib_metadata#489.
+        """
+        # create three dists with the valid one in the middle (lexicographically)
+        # such that on most file systems, the valid one is never naturally first.
+        fixtures.build_files(self.make_pkg('foo-4.0', files={}), self.site_dir)
+        fixtures.build_files(self.make_pkg('foo-4.1'), self.site_dir)
+        fixtures.build_files(self.make_pkg('foo-4.2', files={}), self.site_dir)
+        dist = Distribution.from_name('foo')
+        assert dist.version == "1.0"
+
+    def test_missing_metadata(self):
+        """
+        Dists with a missing metadata file should raise ``MetadataNotFound``.
+
+        Ref python/importlib_metadata#493 and python/cpython#143387.
+        """
+        fixtures.build_files(self.make_pkg('foo-4.3', files={}), self.site_dir)
+        with self.assertRaises(MetadataNotFound):
+            Distribution.from_name('foo').metadata
+        with self.assertRaises(MetadataNotFound):
+            metadata('foo')
+
+
 class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
     @staticmethod
     def pkg_with_non_ascii_description(site_dir):
diff --git a/Lib/test/test_importlib/metadata/test_zip.py b/Lib/test/test_importlib/metadata/test_zip.py
index 276f6288c91..97168549667 100644
--- a/Lib/test/test_importlib/metadata/test_zip.py
+++ b/Lib/test/test_importlib/metadata/test_zip.py
@@ -1,8 +1,12 @@
+import multiprocessing
+import os
 import sys
 import unittest
 
-from . import fixtures
+from test.support import requires_fork, warnings_helper
+
 from importlib.metadata import (
+    FastPath,
     PackageNotFoundError,
     distribution,
     distributions,
@@ -11,6 +15,8 @@
     version,
 )
 
+from . import fixtures
+
 
 class TestZip(fixtures.ZipFixtures, unittest.TestCase):
     def setUp(self):
@@ -46,6 +52,39 @@ def test_one_distribution(self):
         dists = list(distributions(path=sys.path[:1]))
         assert len(dists) == 1
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
+    @requires_fork()
+    @unittest.skipUnless(
+        hasattr(os, 'register_at_fork')
+        and 'fork' in multiprocessing.get_all_start_methods(),
+        'requires fork-based multiprocessing support',
+    )
+    def test_fastpath_cache_cleared_in_forked_child(self):
+        zip_path = sys.path[0]
+
+        FastPath(zip_path)
+        assert FastPath.__new__.cache_info().currsize >= 1
+
+        ctx = multiprocessing.get_context('fork')
+        parent_conn, child_conn = ctx.Pipe()
+
+        def child(conn, root):
+            try:
+                before = FastPath.__new__.cache_info().currsize
+                FastPath(root)
+                after = FastPath.__new__.cache_info().currsize
+                conn.send((before, after))
+            finally:
+                conn.close()
+
+        proc = ctx.Process(target=child, args=(child_conn, zip_path))
+        proc.start()
+        child_conn.close()
+        cache_sizes = parent_conn.recv()
+        proc.join()
+
+        self.assertEqual(cache_sizes, (0, 1))
+
 
 class TestEgg(TestZip):
     def setUp(self):
diff --git a/Lib/test/test_importlib/namespace_pkgs/foo/README.md b/Lib/test/test_importlib/namespace_pkgs/foo/README.md
new file mode 100644
index 00000000000..9f6bc74941d
--- /dev/null
+++ b/Lib/test/test_importlib/namespace_pkgs/foo/README.md
@@ -0,0 +1,2 @@
+This directory should not be a package, but should share a name with an
+unrelated subpackage.
diff --git a/Lib/test/test_importlib/namespace_pkgs/not_a_namespace_pkg/foo/__init__.py b/Lib/test/test_importlib/namespace_pkgs/not_a_namespace_pkg/foo/__init__.py
index 8b137891791..e69de29bb2d 100644
--- a/Lib/test/test_importlib/namespace_pkgs/not_a_namespace_pkg/foo/__init__.py
+++ b/Lib/test/test_importlib/namespace_pkgs/not_a_namespace_pkg/foo/__init__.py
@@ -1 +0,0 @@
-
diff --git a/Lib/test/test_importlib/namespacedata01/binary.file b/Lib/test/test_importlib/namespacedata01/binary.file
deleted file mode 100644
index eaf36c1dacc..00000000000
Binary files a/Lib/test/test_importlib/namespacedata01/binary.file and /dev/null differ
diff --git a/Lib/test/test_importlib/namespacedata01/utf-16.file b/Lib/test/test_importlib/namespacedata01/utf-16.file
deleted file mode 100644
index 2cb772295ef..00000000000
Binary files a/Lib/test/test_importlib/namespacedata01/utf-16.file and /dev/null differ
diff --git a/Lib/test/test_importlib/resources/__init__.py b/Lib/test/test_importlib/resources/__init__.py
index 8b137891791..e69de29bb2d 100644
--- a/Lib/test/test_importlib/resources/__init__.py
+++ b/Lib/test/test_importlib/resources/__init__.py
@@ -1 +0,0 @@
-
diff --git a/Lib/test/test_importlib/resources/_path.py b/Lib/test/test_importlib/resources/_path.py
index b144628cb73..3720af7c508 100644
--- a/Lib/test/test_importlib/resources/_path.py
+++ b/Lib/test/test_importlib/resources/_path.py
@@ -1,10 +1,6 @@
-import pathlib
 import functools
-
-from typing import Dict, Union
-from typing import runtime_checkable
-from typing import Protocol
-
+import pathlib
+from typing import Protocol, Union, runtime_checkable
 
 ####
 # from jaraco.path 3.7.1
@@ -16,7 +12,7 @@ class Symlink(str):
     """
 
 
-FilesSpec = Dict[str, Union[str, bytes, Symlink, 'FilesSpec']]
+FilesSpec = dict[str, Union[str, bytes, Symlink, 'FilesSpec']]
 
 
 @runtime_checkable
@@ -32,13 +28,13 @@ def write_bytes(self, content): ...  # pragma: no cover
     def symlink_to(self, target): ...  # pragma: no cover
 
 
-def _ensure_tree_maker(obj: Union[str, TreeMaker]) -> TreeMaker:
+def _ensure_tree_maker(obj: str | TreeMaker) -> TreeMaker:
     return obj if isinstance(obj, TreeMaker) else pathlib.Path(obj)  # type: ignore[return-value]
 
 
 def build(
     spec: FilesSpec,
-    prefix: Union[str, TreeMaker] = pathlib.Path(),  # type: ignore[assignment]
+    prefix: str | TreeMaker = pathlib.Path(),  # type: ignore[assignment]
 ):
     """
     Build a set of files/directories, as described by the spec.
@@ -70,7 +66,7 @@ def build(
 
 
 @functools.singledispatch
-def create(content: Union[str, bytes, FilesSpec], path):
+def create(content: str | bytes | FilesSpec, path):
     path.mkdir(exist_ok=True)
     build(content, prefix=path)  # type: ignore[arg-type]
 
diff --git a/Lib/test/test_importlib/resources/data01/binary.file b/Lib/test/test_importlib/resources/data01/binary.file
deleted file mode 100644
index eaf36c1dacc..00000000000
Binary files a/Lib/test/test_importlib/resources/data01/binary.file and /dev/null differ
diff --git a/Lib/test/test_importlib/resources/data01/subdirectory/binary.file b/Lib/test/test_importlib/resources/data01/subdirectory/binary.file
deleted file mode 100644
index eaf36c1dacc..00000000000
Binary files a/Lib/test/test_importlib/resources/data01/subdirectory/binary.file and /dev/null differ
diff --git a/Lib/test/test_importlib/resources/data01/utf-16.file b/Lib/test/test_importlib/resources/data01/utf-16.file
deleted file mode 100644
index 2cb772295ef..00000000000
Binary files a/Lib/test/test_importlib/resources/data01/utf-16.file and /dev/null differ
diff --git a/Lib/test/test_importlib/resources/data01/utf-8.file b/Lib/test/test_importlib/resources/data01/utf-8.file
deleted file mode 100644
index 1c0132ad90a..00000000000
--- a/Lib/test/test_importlib/resources/data01/utf-8.file
+++ /dev/null
@@ -1 +0,0 @@
-Hello, UTF-8 world!
diff --git a/Lib/test/test_importlib/resources/data02/one/resource1.txt b/Lib/test/test_importlib/resources/data02/one/resource1.txt
deleted file mode 100644
index 61a813e4017..00000000000
--- a/Lib/test/test_importlib/resources/data02/one/resource1.txt
+++ /dev/null
@@ -1 +0,0 @@
-one resource
diff --git a/Lib/test/test_importlib/resources/data02/subdirectory/subsubdir/resource.txt b/Lib/test/test_importlib/resources/data02/subdirectory/subsubdir/resource.txt
deleted file mode 100644
index 48f587a2d0a..00000000000
--- a/Lib/test/test_importlib/resources/data02/subdirectory/subsubdir/resource.txt
+++ /dev/null
@@ -1 +0,0 @@
-a resource
\ No newline at end of file
diff --git a/Lib/test/test_importlib/resources/data02/two/__init__.py b/Lib/test/test_importlib/resources/data02/two/__init__.py
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/Lib/test/test_importlib/resources/data02/two/resource2.txt b/Lib/test/test_importlib/resources/data02/two/resource2.txt
deleted file mode 100644
index a80ce46ea36..00000000000
--- a/Lib/test/test_importlib/resources/data02/two/resource2.txt
+++ /dev/null
@@ -1 +0,0 @@
-two resource
diff --git a/Lib/test/test_importlib/resources/data03/__init__.py b/Lib/test/test_importlib/resources/data03/__init__.py
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/Lib/test/test_importlib/resources/data03/namespace/portion1/__init__.py b/Lib/test/test_importlib/resources/data03/namespace/portion1/__init__.py
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/Lib/test/test_importlib/resources/data03/namespace/portion2/__init__.py b/Lib/test/test_importlib/resources/data03/namespace/portion2/__init__.py
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/Lib/test/test_importlib/resources/data03/namespace/resource1.txt b/Lib/test/test_importlib/resources/data03/namespace/resource1.txt
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/Lib/test/test_importlib/resources/namespacedata01/binary.file b/Lib/test/test_importlib/resources/namespacedata01/binary.file
deleted file mode 100644
index eaf36c1dacc..00000000000
Binary files a/Lib/test/test_importlib/resources/namespacedata01/binary.file and /dev/null differ
diff --git a/Lib/test/test_importlib/resources/namespacedata01/utf-16.file b/Lib/test/test_importlib/resources/namespacedata01/utf-16.file
deleted file mode 100644
index 2cb772295ef..00000000000
Binary files a/Lib/test/test_importlib/resources/namespacedata01/utf-16.file and /dev/null differ
diff --git a/Lib/test/test_importlib/resources/namespacedata01/utf-8.file b/Lib/test/test_importlib/resources/namespacedata01/utf-8.file
deleted file mode 100644
index 1c0132ad90a..00000000000
--- a/Lib/test/test_importlib/resources/namespacedata01/utf-8.file
+++ /dev/null
@@ -1 +0,0 @@
-Hello, UTF-8 world!
diff --git a/Lib/test/test_importlib/resources/test_compatibilty_files.py b/Lib/test/test_importlib/resources/test_compatibilty_files.py
index bcf608d9e2c..2fd39bedf25 100644
--- a/Lib/test/test_importlib/resources/test_compatibilty_files.py
+++ b/Lib/test/test_importlib/resources/test_compatibilty_files.py
@@ -1,8 +1,6 @@
+import importlib.resources as resources
 import io
 import unittest
-
-from importlib import resources
-
 from importlib.resources._adapters import (
     CompatibilityFiles,
     wrap_spec,
@@ -26,51 +24,46 @@ def files(self):
         return resources.files(self.package)
 
     def test_spec_path_iter(self):
-        self.assertEqual(
-            sorted(path.name for path in self.files.iterdir()),
-            ['a', 'b', 'c'],
-        )
+        assert sorted(path.name for path in self.files.iterdir()) == ['a', 'b', 'c']
 
     def test_child_path_iter(self):
-        self.assertEqual(list((self.files / 'a').iterdir()), [])
+        assert list((self.files / 'a').iterdir()) == []
 
     def test_orphan_path_iter(self):
-        self.assertEqual(list((self.files / 'a' / 'a').iterdir()), [])
-        self.assertEqual(list((self.files / 'a' / 'a' / 'a').iterdir()), [])
+        assert list((self.files / 'a' / 'a').iterdir()) == []
+        assert list((self.files / 'a' / 'a' / 'a').iterdir()) == []
 
     def test_spec_path_is(self):
-        self.assertFalse(self.files.is_file())
-        self.assertFalse(self.files.is_dir())
+        assert not self.files.is_file()
+        assert not self.files.is_dir()
 
     def test_child_path_is(self):
-        self.assertTrue((self.files / 'a').is_file())
-        self.assertFalse((self.files / 'a').is_dir())
+        assert (self.files / 'a').is_file()
+        assert not (self.files / 'a').is_dir()
 
     def test_orphan_path_is(self):
-        self.assertFalse((self.files / 'a' / 'a').is_file())
-        self.assertFalse((self.files / 'a' / 'a').is_dir())
-        self.assertFalse((self.files / 'a' / 'a' / 'a').is_file())
-        self.assertFalse((self.files / 'a' / 'a' / 'a').is_dir())
+        assert not (self.files / 'a' / 'a').is_file()
+        assert not (self.files / 'a' / 'a').is_dir()
+        assert not (self.files / 'a' / 'a' / 'a').is_file()
+        assert not (self.files / 'a' / 'a' / 'a').is_dir()
 
     def test_spec_path_name(self):
-        self.assertEqual(self.files.name, 'testingpackage')
+        assert self.files.name == 'testingpackage'
 
     def test_child_path_name(self):
-        self.assertEqual((self.files / 'a').name, 'a')
+        assert (self.files / 'a').name == 'a'
 
     def test_orphan_path_name(self):
-        self.assertEqual((self.files / 'a' / 'b').name, 'b')
-        self.assertEqual((self.files / 'a' / 'b' / 'c').name, 'c')
+        assert (self.files / 'a' / 'b').name == 'b'
+        assert (self.files / 'a' / 'b' / 'c').name == 'c'
 
     def test_spec_path_open(self):
-        self.assertEqual(self.files.read_bytes(), b'Hello, world!')
-        self.assertEqual(self.files.read_text(encoding='utf-8'), 'Hello, world!')
+        assert self.files.read_bytes() == b'Hello, world!'
+        assert self.files.read_text(encoding='utf-8') == 'Hello, world!'
 
     def test_child_path_open(self):
-        self.assertEqual((self.files / 'a').read_bytes(), b'Hello, world!')
-        self.assertEqual(
-            (self.files / 'a').read_text(encoding='utf-8'), 'Hello, world!'
-        )
+        assert (self.files / 'a').read_bytes() == b'Hello, world!'
+        assert (self.files / 'a').read_text(encoding='utf-8') == 'Hello, world!'
 
     def test_orphan_path_open(self):
         with self.assertRaises(FileNotFoundError):
@@ -88,7 +81,7 @@ def test_orphan_path_invalid(self):
 
     def test_wrap_spec(self):
         spec = wrap_spec(self.package)
-        self.assertIsInstance(spec.loader.get_resource_reader(None), CompatibilityFiles)
+        assert isinstance(spec.loader.get_resource_reader(None), CompatibilityFiles)
 
 
 class CompatibilityFilesNoReaderTests(unittest.TestCase):
@@ -101,4 +94,4 @@ def files(self):
         return resources.files(self.package)
 
     def test_spec_path_joinpath(self):
-        self.assertIsInstance(self.files / 'a', CompatibilityFiles.OrphanPath)
+        assert isinstance(self.files / 'a', CompatibilityFiles.OrphanPath)
diff --git a/Lib/test/test_importlib/resources/test_contents.py b/Lib/test/test_importlib/resources/test_contents.py
index 4e4e0e9c337..bdc158d85a2 100644
--- a/Lib/test/test_importlib/resources/test_contents.py
+++ b/Lib/test/test_importlib/resources/test_contents.py
@@ -1,5 +1,5 @@
+import importlib.resources as resources
 import unittest
-from importlib import resources
 
 from . import util
 
diff --git a/Lib/test/test_importlib/resources/test_custom.py b/Lib/test/test_importlib/resources/test_custom.py
index 640f90fc0dd..a7fc6bc35c5 100644
--- a/Lib/test/test_importlib/resources/test_custom.py
+++ b/Lib/test/test_importlib/resources/test_custom.py
@@ -1,12 +1,12 @@
-import unittest
 import contextlib
+import importlib.resources as resources
 import pathlib
+import unittest
+from importlib.resources import abc
+from importlib.resources.abc import ResourceReader, TraversableResources
 
 from test.support import os_helper
 
-from importlib import resources
-from importlib.resources import abc
-from importlib.resources.abc import TraversableResources, ResourceReader
 from . import util
 
 
diff --git a/Lib/test/test_importlib/resources/test_files.py b/Lib/test/test_importlib/resources/test_files.py
index 3ce44999f98..c922d32cedc 100644
--- a/Lib/test/test_importlib/resources/test_files.py
+++ b/Lib/test/test_importlib/resources/test_files.py
@@ -1,15 +1,16 @@
+import contextlib
+import importlib
+import importlib.resources as resources
 import pathlib
 import py_compile
 import textwrap
 import unittest
 import warnings
-import importlib
-import contextlib
-
-from importlib import resources
 from importlib.resources.abc import Traversable
+
+from test.support import import_helper, os_helper
+
 from . import util
-from test.support import os_helper, import_helper
 
 
 @contextlib.contextmanager
@@ -36,15 +37,7 @@ def test_traversable(self):
     def test_joinpath_with_multiple_args(self):
         files = resources.files(self.data)
         binfile = files.joinpath('subdirectory', 'binary.file')
-        self.assertTrue(binfile.is_file())
-
-    def test_old_parameter(self):
-        """
-        Files used to take a 'package' parameter. Make sure anyone
-        passing by name is still supported.
-        """
-        with suppress_known_deprecation():
-            resources.files(package=self.data)
+        assert binfile.is_file()
 
 
 class OpenDiskTests(FilesTests, util.DiskSetup, unittest.TestCase):
@@ -70,7 +63,7 @@ def test_non_paths_in_dunder_path(self):
         to cause the ``PathEntryFinder`` to be called when searching
         for packages. In that case, resources should still be loadable.
         """
-        import namespacedata01
+        import namespacedata01  # type: ignore[import-not-found]
 
         namespacedata01.__path__.append(
             '__editable__.sample_namespace-1.0.finder.__path_hook__'
@@ -161,7 +154,9 @@ def _compile_importlib(self):
         sources = pathlib.Path(resources.__file__).parent
 
         for source_path in sources.glob('**/*.py'):
-            c_path = c_resources.joinpath(source_path.relative_to(sources)).with_suffix('.pyc')
+            c_path = c_resources.joinpath(source_path.relative_to(sources)).with_suffix(
+                '.pyc'
+            )
             py_compile.compile(source_path, c_path)
         self.fixtures.enter_context(import_helper.DirsOnSysPath(bin_site))
 
diff --git a/Lib/test/test_importlib/resources/test_functional.py b/Lib/test/test_importlib/resources/test_functional.py
index e8d25fa4d9f..9cec6af9a5d 100644
--- a/Lib/test/test_importlib/resources/test_functional.py
+++ b/Lib/test/test_importlib/resources/test_functional.py
@@ -1,17 +1,12 @@
-import unittest
-import os
 import importlib
+import importlib.resources as resources
+import os
+import unittest
 
 from test.support import warnings_helper
 
-from importlib import resources
-
 from . import util
 
-# Since the functional API forwards to Traversable, we only test
-# filesystem resources here -- not zip files, namespace packages etc.
-# We do test for two kinds of Anchor, though.
-
 
 class StringAnchorMixin:
     anchor01 = 'data01'
@@ -28,7 +23,7 @@ def anchor02(self):
         return importlib.import_module('data02')
 
 
-class FunctionalAPIBase(util.DiskSetup):
+class FunctionalAPIBase:
     def setUp(self):
         super().setUp()
         self.load_fixture('data02')
@@ -43,83 +38,90 @@ def _gen_resourcetxt_path_parts(self):
             with self.subTest(path_parts=path_parts):
                 yield path_parts
 
+    @staticmethod
+    def remove_utf16_bom(string):
+        """Remove an architecture-specific UTF-16 BOM prefix when present.
+
+        Some platforms surface UTF-16 BOM bytes as escaped text when the
+        fixture is intentionally decoded as UTF-8 with ``errors='backslashreplace'``.
+        Strip that prefix so assertions validate content consistently."""
+        for bom in ('\\xff\\xfe', '\\xfe\\xff', '\ufeff'):
+            if string.startswith(bom):
+                return string[len(bom) :]
+        return string
+
     def test_read_text(self):
-        self.assertEqual(
-            resources.read_text(self.anchor01, 'utf-8.file'),
-            'Hello, UTF-8 world!\n',
+        assert (
+            resources.read_text(self.anchor01, 'utf-8.file') == 'Hello, UTF-8 world!\n'
         )
-        self.assertEqual(
+        assert (
             resources.read_text(
                 self.anchor02,
                 'subdirectory',
                 'subsubdir',
                 'resource.txt',
                 encoding='utf-8',
-            ),
-            'a resource',
+            )
+            == 'a resource'
         )
         for path_parts in self._gen_resourcetxt_path_parts():
-            self.assertEqual(
+            assert (
                 resources.read_text(
                     self.anchor02,
                     *path_parts,
                     encoding='utf-8',
-                ),
-                'a resource',
+                )
+                == 'a resource'
             )
         # Use generic OSError, since e.g. attempting to read a directory can
         # fail with PermissionError rather than IsADirectoryError
         with self.assertRaises(OSError):
             resources.read_text(self.anchor01)
-        with self.assertRaises(OSError):
+        with self.assertRaises((OSError, resources.abc.TraversalError)):
             resources.read_text(self.anchor01, 'no-such-file')
         with self.assertRaises(UnicodeDecodeError):
             resources.read_text(self.anchor01, 'utf-16.file')
-        self.assertEqual(
+        assert (
             resources.read_text(
                 self.anchor01,
                 'binary.file',
                 encoding='latin1',
-            ),
-            '\x00\x01\x02\x03',
+            )
+            == '\x00\x01\x02\x03'
         )
-        self.assertEndsWith(  # ignore the BOM
+        assert self.remove_utf16_bom(
             resources.read_text(
                 self.anchor01,
                 'utf-16.file',
                 errors='backslashreplace',
             ),
-            'Hello, UTF-16 world!\n'.encode('utf-16-le').decode(
-                errors='backslashreplace',
-            ),
+        ) == 'Hello, UTF-16 world!\n'.encode('utf-16-le').decode(
+            errors='backslashreplace',
         )
 
     def test_read_binary(self):
-        self.assertEqual(
-            resources.read_binary(self.anchor01, 'utf-8.file'),
-            b'Hello, UTF-8 world!\n',
+        assert (
+            resources.read_binary(self.anchor01, 'utf-8.file')
+            == b'Hello, UTF-8 world!\n'
         )
         for path_parts in self._gen_resourcetxt_path_parts():
-            self.assertEqual(
-                resources.read_binary(self.anchor02, *path_parts),
-                b'a resource',
-            )
+            assert resources.read_binary(self.anchor02, *path_parts) == b'a resource'
 
     def test_open_text(self):
         with resources.open_text(self.anchor01, 'utf-8.file') as f:
-            self.assertEqual(f.read(), 'Hello, UTF-8 world!\n')
+            assert f.read() == 'Hello, UTF-8 world!\n'
         for path_parts in self._gen_resourcetxt_path_parts():
             with resources.open_text(
                 self.anchor02,
                 *path_parts,
                 encoding='utf-8',
             ) as f:
-                self.assertEqual(f.read(), 'a resource')
+                assert f.read() == 'a resource'
         # Use generic OSError, since e.g. attempting to read a directory can
         # fail with PermissionError rather than IsADirectoryError
         with self.assertRaises(OSError):
             resources.open_text(self.anchor01)
-        with self.assertRaises(OSError):
+        with self.assertRaises((OSError, resources.abc.TraversalError)):
             resources.open_text(self.anchor01, 'no-such-file')
         with resources.open_text(self.anchor01, 'utf-16.file') as f:
             with self.assertRaises(UnicodeDecodeError):
@@ -129,71 +131,70 @@ def test_open_text(self):
             'binary.file',
             encoding='latin1',
         ) as f:
-            self.assertEqual(f.read(), '\x00\x01\x02\x03')
+            assert f.read() == '\x00\x01\x02\x03'
         with resources.open_text(
             self.anchor01,
             'utf-16.file',
             errors='backslashreplace',
         ) as f:
-            self.assertEndsWith(  # ignore the BOM
-                f.read(),
-                'Hello, UTF-16 world!\n'.encode('utf-16-le').decode(
-                    errors='backslashreplace',
-                ),
+            assert self.remove_utf16_bom(f.read()) == 'Hello, UTF-16 world!\n'.encode(
+                'utf-16-le'
+            ).decode(
+                errors='backslashreplace',
             )
 
     def test_open_binary(self):
         with resources.open_binary(self.anchor01, 'utf-8.file') as f:
-            self.assertEqual(f.read(), b'Hello, UTF-8 world!\n')
+            assert f.read() == b'Hello, UTF-8 world!\n'
         for path_parts in self._gen_resourcetxt_path_parts():
             with resources.open_binary(
                 self.anchor02,
                 *path_parts,
             ) as f:
-                self.assertEqual(f.read(), b'a resource')
+                assert f.read() == b'a resource'
 
     def test_path(self):
         with resources.path(self.anchor01, 'utf-8.file') as path:
             with open(str(path), encoding='utf-8') as f:
-                self.assertEqual(f.read(), 'Hello, UTF-8 world!\n')
+                assert f.read() == 'Hello, UTF-8 world!\n'
         with resources.path(self.anchor01) as path:
             with open(os.path.join(path, 'utf-8.file'), encoding='utf-8') as f:
-                self.assertEqual(f.read(), 'Hello, UTF-8 world!\n')
+                assert f.read() == 'Hello, UTF-8 world!\n'
 
     def test_is_resource(self):
         is_resource = resources.is_resource
-        self.assertTrue(is_resource(self.anchor01, 'utf-8.file'))
-        self.assertFalse(is_resource(self.anchor01, 'no_such_file'))
-        self.assertFalse(is_resource(self.anchor01))
-        self.assertFalse(is_resource(self.anchor01, 'subdirectory'))
+        assert is_resource(self.anchor01, 'utf-8.file')
+        assert not is_resource(self.anchor01, 'no_such_file')
+        assert not is_resource(self.anchor01)
+        assert not is_resource(self.anchor01, 'subdirectory')
         for path_parts in self._gen_resourcetxt_path_parts():
-            self.assertTrue(is_resource(self.anchor02, *path_parts))
+            assert is_resource(self.anchor02, *path_parts)
 
     def test_contents(self):
         with warnings_helper.check_warnings((".*contents.*", DeprecationWarning)):
             c = resources.contents(self.anchor01)
-        self.assertGreaterEqual(
-            set(c),
-            {'utf-8.file', 'utf-16.file', 'binary.file', 'subdirectory'},
-        )
-        with self.assertRaises(OSError), warnings_helper.check_warnings((
-            ".*contents.*",
-            DeprecationWarning,
-        )):
+        assert set(c) >= {'utf-8.file', 'utf-16.file', 'binary.file', 'subdirectory'}
+        with (
+            self.assertRaises(OSError),
+            warnings_helper.check_warnings((
+                ".*contents.*",
+                DeprecationWarning,
+            )),
+        ):
             list(resources.contents(self.anchor01, 'utf-8.file'))
 
         for path_parts in self._gen_resourcetxt_path_parts():
-            with self.assertRaises(OSError), warnings_helper.check_warnings((
-                ".*contents.*",
-                DeprecationWarning,
-            )):
+            with (
+                self.assertRaises((OSError, resources.abc.TraversalError)),
+                warnings_helper.check_warnings((
+                    ".*contents.*",
+                    DeprecationWarning,
+                )),
+            ):
                 list(resources.contents(self.anchor01, *path_parts))
         with warnings_helper.check_warnings((".*contents.*", DeprecationWarning)):
             c = resources.contents(self.anchor01, 'subdirectory')
-        self.assertGreaterEqual(
-            set(c),
-            {'binary.file'},
-        )
+        assert set(c) >= {'binary.file'}
 
     @warnings_helper.ignore_warnings(category=DeprecationWarning)
     def test_common_errors(self):
@@ -233,17 +234,28 @@ def test_text_errors(self):
                     )
 
 
-class FunctionalAPITest_StringAnchor(
+class FunctionalAPITest_StringAnchor_Disk(
     StringAnchorMixin,
     FunctionalAPIBase,
+    util.DiskSetup,
     unittest.TestCase,
 ):
     pass
 
 
-class FunctionalAPITest_ModuleAnchor(
+class FunctionalAPITest_ModuleAnchor_Disk(
     ModuleAnchorMixin,
     FunctionalAPIBase,
+    util.DiskSetup,
+    unittest.TestCase,
+):
+    pass
+
+
+class FunctionalAPITest_StringAnchor_Memory(
+    StringAnchorMixin,
+    FunctionalAPIBase,
+    util.MemorySetup,
     unittest.TestCase,
 ):
     pass
diff --git a/Lib/test/test_importlib/resources/test_open.py b/Lib/test/test_importlib/resources/test_open.py
index 8c00378ad3c..950f71db05a 100644
--- a/Lib/test/test_importlib/resources/test_open.py
+++ b/Lib/test/test_importlib/resources/test_open.py
@@ -1,6 +1,6 @@
+import importlib.resources as resources
 import unittest
 
-from importlib import resources
 from . import util
 
 
@@ -23,19 +23,19 @@ def test_open_binary(self):
         target = resources.files(self.data) / 'binary.file'
         with target.open('rb') as fp:
             result = fp.read()
-            self.assertEqual(result, bytes(range(4)))
+            assert result == bytes(range(4))
 
     def test_open_text_default_encoding(self):
         target = resources.files(self.data) / 'utf-8.file'
         with target.open(encoding='utf-8') as fp:
             result = fp.read()
-            self.assertEqual(result, 'Hello, UTF-8 world!\n')
+            assert result == 'Hello, UTF-8 world!\n'
 
     def test_open_text_given_encoding(self):
         target = resources.files(self.data) / 'utf-16.file'
         with target.open(encoding='utf-16', errors='strict') as fp:
             result = fp.read()
-        self.assertEqual(result, 'Hello, UTF-16 world!\n')
+        assert result == 'Hello, UTF-16 world!\n'
 
     def test_open_text_with_errors(self):
         """
@@ -46,11 +46,10 @@ def test_open_text_with_errors(self):
             self.assertRaises(UnicodeError, fp.read)
         with target.open(encoding='utf-8', errors='ignore') as fp:
             result = fp.read()
-        self.assertEqual(
-            result,
+        assert result == (
             'H\x00e\x00l\x00l\x00o\x00,\x00 '
             '\x00U\x00T\x00F\x00-\x001\x006\x00 '
-            '\x00w\x00o\x00r\x00l\x00d\x00!\x00\n\x00',
+            '\x00w\x00o\x00r\x00l\x00d\x00!\x00\n\x00'
         )
 
     def test_open_binary_FileNotFoundError(self):
diff --git a/Lib/test/test_importlib/resources/test_path.py b/Lib/test/test_importlib/resources/test_path.py
index 903911f57b3..162344e5d83 100644
--- a/Lib/test/test_importlib/resources/test_path.py
+++ b/Lib/test/test_importlib/resources/test_path.py
@@ -1,8 +1,8 @@
+import importlib.resources as resources
 import io
 import pathlib
 import unittest
 
-from importlib import resources
 from . import util
 
 
@@ -19,9 +19,9 @@ def test_reading(self):
         """
         target = resources.files(self.data) / 'utf-8.file'
         with resources.as_file(target) as path:
-            self.assertIsInstance(path, pathlib.Path)
-            self.assertEndsWith(path.name, "utf-8.file")
-            self.assertEqual('Hello, UTF-8 world!\n', path.read_text(encoding='utf-8'))
+            assert isinstance(path, pathlib.Path)
+            assert path.name.endswith("utf-8.file"), repr(path)
+            assert 'Hello, UTF-8 world!\n' == path.read_text(encoding='utf-8')
 
 
 class PathDiskTests(PathTests, util.DiskSetup, unittest.TestCase):
diff --git a/Lib/test/test_importlib/resources/test_read.py b/Lib/test/test_importlib/resources/test_read.py
index 59c237d9641..4085a64b0ee 100644
--- a/Lib/test/test_importlib/resources/test_read.py
+++ b/Lib/test/test_importlib/resources/test_read.py
@@ -1,6 +1,6 @@
+import importlib.resources as resources
 import unittest
-
-from importlib import import_module, resources
+from importlib import import_module
 
 from . import util
 
@@ -18,23 +18,25 @@ def execute(self, package, path):
 class ReadTests:
     def test_read_bytes(self):
         result = resources.files(self.data).joinpath('binary.file').read_bytes()
-        self.assertEqual(result, bytes(range(4)))
+        assert result == bytes(range(4))
 
     def test_read_text_default_encoding(self):
         result = (
-            resources.files(self.data)
+            resources
+            .files(self.data)
             .joinpath('utf-8.file')
             .read_text(encoding='utf-8')
         )
-        self.assertEqual(result, 'Hello, UTF-8 world!\n')
+        assert result == 'Hello, UTF-8 world!\n'
 
     def test_read_text_given_encoding(self):
         result = (
-            resources.files(self.data)
+            resources
+            .files(self.data)
             .joinpath('utf-16.file')
             .read_text(encoding='utf-16')
         )
-        self.assertEqual(result, 'Hello, UTF-16 world!\n')
+        assert result == 'Hello, UTF-16 world!\n'
 
     def test_read_text_with_errors(self):
         """
@@ -43,11 +45,10 @@ def test_read_text_with_errors(self):
         target = resources.files(self.data) / 'utf-16.file'
         self.assertRaises(UnicodeError, target.read_text, encoding='utf-8')
         result = target.read_text(encoding='utf-8', errors='ignore')
-        self.assertEqual(
-            result,
+        assert result == (
             'H\x00e\x00l\x00l\x00o\x00,\x00 '
             '\x00U\x00T\x00F\x00-\x001\x006\x00 '
-            '\x00w\x00o\x00r\x00l\x00d\x00!\x00\n\x00',
+            '\x00w\x00o\x00r\x00l\x00d\x00!\x00\n\x00'
         )
 
 
@@ -59,13 +60,13 @@ class ReadZipTests(ReadTests, util.ZipSetup, unittest.TestCase):
     def test_read_submodule_resource(self):
         submodule = import_module('data01.subdirectory')
         result = resources.files(submodule).joinpath('binary.file').read_bytes()
-        self.assertEqual(result, bytes(range(4, 8)))
+        assert result == bytes(range(4, 8))
 
     def test_read_submodule_resource_by_name(self):
         result = (
             resources.files('data01.subdirectory').joinpath('binary.file').read_bytes()
         )
-        self.assertEqual(result, bytes(range(4, 8)))
+        assert result == bytes(range(4, 8))
 
 
 class ReadNamespaceTests(ReadTests, util.DiskSetup, unittest.TestCase):
@@ -78,15 +79,16 @@ class ReadNamespaceZipTests(ReadTests, util.ZipSetup, unittest.TestCase):
     def test_read_submodule_resource(self):
         submodule = import_module('namespacedata01.subdirectory')
         result = resources.files(submodule).joinpath('binary.file').read_bytes()
-        self.assertEqual(result, bytes(range(12, 16)))
+        assert result == bytes(range(12, 16))
 
     def test_read_submodule_resource_by_name(self):
         result = (
-            resources.files('namespacedata01.subdirectory')
+            resources
+            .files('namespacedata01.subdirectory')
             .joinpath('binary.file')
             .read_bytes()
         )
-        self.assertEqual(result, bytes(range(12, 16)))
+        assert result == bytes(range(12, 16))
 
 
 if __name__ == '__main__':
diff --git a/Lib/test/test_importlib/resources/test_reader.py b/Lib/test/test_importlib/resources/test_reader.py
index ed5693ab416..691a78bb060 100644
--- a/Lib/test/test_importlib/resources/test_reader.py
+++ b/Lib/test/test_importlib/resources/test_reader.py
@@ -1,9 +1,8 @@
 import os.path
 import pathlib
 import unittest
-
 from importlib import import_module
-from importlib.readers import MultiplexedPath, NamespaceReader
+from importlib.resources.readers import MultiplexedPath, NamespaceReader
 
 from . import util
 
@@ -31,9 +30,7 @@ def test_iterdir(self):
             contents.remove('__pycache__')
         except (KeyError, ValueError):
             pass
-        self.assertEqual(
-            contents, {'subdirectory', 'binary.file', 'utf-16.file', 'utf-8.file'}
-        )
+        assert contents == {'subdirectory', 'binary.file', 'utf-16.file', 'utf-8.file'}
 
     def test_iterdir_duplicate(self):
         contents = {
@@ -44,16 +41,19 @@ def test_iterdir_duplicate(self):
                 contents.remove(remove)
             except (KeyError, ValueError):
                 pass
-        self.assertEqual(
-            contents,
-            {'__init__.py', 'binary.file', 'subdirectory', 'utf-16.file', 'utf-8.file'},
-        )
+        assert contents == {
+            '__init__.py',
+            'binary.file',
+            'subdirectory',
+            'utf-16.file',
+            'utf-8.file',
+        }
 
     def test_is_dir(self):
-        self.assertEqual(MultiplexedPath(self.folder).is_dir(), True)
+        assert MultiplexedPath(self.folder).is_dir()
 
     def test_is_file(self):
-        self.assertEqual(MultiplexedPath(self.folder).is_file(), False)
+        assert not MultiplexedPath(self.folder).is_file()
 
     def test_open_file(self):
         path = MultiplexedPath(self.folder)
@@ -67,19 +67,17 @@ def test_open_file(self):
     def test_join_path(self):
         prefix = str(self.folder.parent)
         path = MultiplexedPath(self.folder, self.data01)
-        self.assertEqual(
-            str(path.joinpath('binary.file'))[len(prefix) + 1 :],
-            os.path.join('namespacedata01', 'binary.file'),
+        assert str(path.joinpath('binary.file'))[len(prefix) + 1 :] == os.path.join(
+            'namespacedata01', 'binary.file'
         )
         sub = path.joinpath('subdirectory')
         assert isinstance(sub, MultiplexedPath)
         assert 'namespacedata01' in str(sub)
         assert 'data01' in str(sub)
-        self.assertEqual(
-            str(path.joinpath('imaginary'))[len(prefix) + 1 :],
-            os.path.join('namespacedata01', 'imaginary'),
+        assert str(path.joinpath('imaginary'))[len(prefix) + 1 :] == os.path.join(
+            'namespacedata01', 'imaginary'
         )
-        self.assertEqual(path.joinpath(), path)
+        assert path.joinpath() == path
 
     def test_join_path_compound(self):
         path = MultiplexedPath(self.folder)
@@ -88,23 +86,16 @@ def test_join_path_compound(self):
     def test_join_path_common_subdir(self):
         prefix = str(self.data02.parent)
         path = MultiplexedPath(self.data01, self.data02)
-        self.assertIsInstance(path.joinpath('subdirectory'), MultiplexedPath)
-        self.assertEqual(
-            str(path.joinpath('subdirectory', 'subsubdir'))[len(prefix) + 1 :],
-            os.path.join('data02', 'subdirectory', 'subsubdir'),
+        assert isinstance(path.joinpath('subdirectory'), MultiplexedPath)
+        assert str(path.joinpath('subdirectory', 'subsubdir'))[len(prefix) + 1 :] == (
+            os.path.join('data02', 'subdirectory', 'subsubdir')
         )
 
     def test_repr(self):
-        self.assertEqual(
-            repr(MultiplexedPath(self.folder)),
-            f"MultiplexedPath('{self.folder}')",
-        )
+        assert repr(MultiplexedPath(self.folder)) == f"MultiplexedPath('{self.folder}')"
 
     def test_name(self):
-        self.assertEqual(
-            MultiplexedPath(self.folder).name,
-            os.path.basename(self.folder),
-        )
+        assert MultiplexedPath(self.folder).name == os.path.basename(self.folder)
 
 
 class NamespaceReaderTest(util.DiskSetup, unittest.TestCase):
@@ -119,18 +110,14 @@ def test_resource_path(self):
         reader = NamespaceReader(namespacedata01.__spec__.submodule_search_locations)
 
         root = self.data.__path__[0]
-        self.assertEqual(
-            reader.resource_path('binary.file'), os.path.join(root, 'binary.file')
-        )
-        self.assertEqual(
-            reader.resource_path('imaginary'), os.path.join(root, 'imaginary')
-        )
+        assert reader.resource_path('binary.file') == os.path.join(root, 'binary.file')
+        assert reader.resource_path('imaginary') == os.path.join(root, 'imaginary')
 
     def test_files(self):
         reader = NamespaceReader(self.data.__spec__.submodule_search_locations)
         root = self.data.__path__[0]
-        self.assertIsInstance(reader.files(), MultiplexedPath)
-        self.assertEqual(repr(reader.files()), f"MultiplexedPath('{root}')")
+        assert isinstance(reader.files(), MultiplexedPath)
+        assert repr(reader.files()) == f"MultiplexedPath('{root}')"
 
 
 if __name__ == '__main__':
diff --git a/Lib/test/test_importlib/resources/test_resource.py b/Lib/test/test_importlib/resources/test_resource.py
index fcede14b891..b114b1f0d80 100644
--- a/Lib/test/test_importlib/resources/test_resource.py
+++ b/Lib/test/test_importlib/resources/test_resource.py
@@ -1,7 +1,9 @@
+import importlib.resources as resources
+import types
 import unittest
+from importlib import import_module
 
 from . import util
-from importlib import resources, import_module
 
 
 class ResourceTests:
@@ -9,16 +11,16 @@ class ResourceTests:
 
     def test_is_file_exists(self):
         target = resources.files(self.data) / 'binary.file'
-        self.assertTrue(target.is_file())
+        assert target.is_file()
 
     def test_is_file_missing(self):
         target = resources.files(self.data) / 'not-a-file'
-        self.assertFalse(target.is_file())
+        assert not target.is_file()
 
     def test_is_dir(self):
         target = resources.files(self.data) / 'subdirectory'
-        self.assertFalse(target.is_file())
-        self.assertTrue(target.is_dir())
+        assert not target.is_file()
+        assert target.is_dir()
 
 
 class ResourceDiskTests(ResourceTests, util.DiskSetup, unittest.TestCase):
@@ -38,7 +40,7 @@ def test_resource_contents(self):
         package = util.create_package(
             file=self.data, path=self.data.__file__, contents=['A', 'B', 'C']
         )
-        self.assertEqual(names(resources.files(package)), {'A', 'B', 'C'})
+        assert names(resources.files(package)) == {'A', 'B', 'C'}
 
     def test_is_file(self):
         package = util.create_package(
@@ -46,7 +48,7 @@ def test_is_file(self):
             path=self.data.__file__,
             contents=['A', 'B', 'C', 'D/E', 'D/F'],
         )
-        self.assertTrue(resources.files(package).joinpath('B').is_file())
+        assert resources.files(package).joinpath('B').is_file()
 
     def test_is_dir(self):
         package = util.create_package(
@@ -54,7 +56,7 @@ def test_is_dir(self):
             path=self.data.__file__,
             contents=['A', 'B', 'C', 'D/E', 'D/F'],
         )
-        self.assertTrue(resources.files(package).joinpath('D').is_dir())
+        assert resources.files(package).joinpath('D').is_dir()
 
     def test_resource_missing(self):
         package = util.create_package(
@@ -62,7 +64,7 @@ def test_resource_missing(self):
             path=self.data.__file__,
             contents=['A', 'B', 'C', 'D/E', 'D/F'],
         )
-        self.assertFalse(resources.files(package).joinpath('Z').is_file())
+        assert not resources.files(package).joinpath('Z').is_file()
 
 
 class ResourceCornerCaseTests(util.DiskSetup, unittest.TestCase):
@@ -82,30 +84,26 @@ def test_package_has_no_reader_fallback(self):
         module.__file__ = '/path/which/shall/not/be/named'
         module.__spec__.loader = module.__loader__
         module.__spec__.origin = module.__file__
-        self.assertFalse(resources.files(module).joinpath('A').is_file())
+        assert not resources.files(module).joinpath('A').is_file()
 
 
 class ResourceFromZipsTest01(util.ZipSetup, unittest.TestCase):
     def test_is_submodule_resource(self):
         submodule = import_module('data01.subdirectory')
-        self.assertTrue(resources.files(submodule).joinpath('binary.file').is_file())
+        assert resources.files(submodule).joinpath('binary.file').is_file()
 
     def test_read_submodule_resource_by_name(self):
-        self.assertTrue(
-            resources.files('data01.subdirectory').joinpath('binary.file').is_file()
-        )
+        assert resources.files('data01.subdirectory').joinpath('binary.file').is_file()
 
     def test_submodule_contents(self):
         submodule = import_module('data01.subdirectory')
-        self.assertEqual(
-            names(resources.files(submodule)), {'__init__.py', 'binary.file'}
-        )
+        assert names(resources.files(submodule)) == {'__init__.py', 'binary.file'}
 
     def test_submodule_contents_by_name(self):
-        self.assertEqual(
-            names(resources.files('data01.subdirectory')),
-            {'__init__.py', 'binary.file'},
-        )
+        assert names(resources.files('data01.subdirectory')) == {
+            '__init__.py',
+            'binary.file',
+        }
 
     def test_as_file_directory(self):
         with resources.as_file(resources.files('data01')) as data:
@@ -124,14 +122,8 @@ def test_unrelated_contents(self):
         Test thata zip with two unrelated subpackages return
         distinct resources. Ref python/importlib_resources#44.
         """
-        self.assertEqual(
-            names(resources.files('data02.one')),
-            {'__init__.py', 'resource1.txt'},
-        )
-        self.assertEqual(
-            names(resources.files('data02.two')),
-            {'__init__.py', 'resource2.txt'},
-        )
+        assert names(resources.files('data02.one')) == {'__init__.py', 'resource1.txt'}
+        assert names(resources.files('data02.two')) == {'__init__.py', 'resource2.txt'}
 
 
 class DeletingZipsTest(util.ZipSetup, unittest.TestCase):
@@ -168,16 +160,15 @@ def test_read_text_does_not_keep_open(self):
 
 class ResourceFromNamespaceTests:
     def test_is_submodule_resource(self):
-        self.assertTrue(
-            resources.files(import_module('namespacedata01'))
+        assert (
+            resources
+            .files(import_module('namespacedata01'))
             .joinpath('binary.file')
             .is_file()
         )
 
     def test_read_submodule_resource_by_name(self):
-        self.assertTrue(
-            resources.files('namespacedata01').joinpath('binary.file').is_file()
-        )
+        assert resources.files('namespacedata01').joinpath('binary.file').is_file()
 
     def test_submodule_contents(self):
         contents = names(resources.files(import_module('namespacedata01')))
@@ -185,9 +176,7 @@ def test_submodule_contents(self):
             contents.remove('__pycache__')
         except KeyError:
             pass
-        self.assertEqual(
-            contents, {'subdirectory', 'binary.file', 'utf-8.file', 'utf-16.file'}
-        )
+        assert contents == {'subdirectory', 'binary.file', 'utf-8.file', 'utf-16.file'}
 
     def test_submodule_contents_by_name(self):
         contents = names(resources.files('namespacedata01'))
@@ -195,9 +184,7 @@ def test_submodule_contents_by_name(self):
             contents.remove('__pycache__')
         except KeyError:
             pass
-        self.assertEqual(
-            contents, {'subdirectory', 'binary.file', 'utf-8.file', 'utf-16.file'}
-        )
+        assert contents == {'subdirectory', 'binary.file', 'utf-8.file', 'utf-16.file'}
 
     def test_submodule_sub_contents(self):
         contents = names(resources.files(import_module('namespacedata01.subdirectory')))
@@ -205,7 +192,7 @@ def test_submodule_sub_contents(self):
             contents.remove('__pycache__')
         except KeyError:
             pass
-        self.assertEqual(contents, {'binary.file'})
+        assert contents == {'binary.file'}
 
     def test_submodule_sub_contents_by_name(self):
         contents = names(resources.files('namespacedata01.subdirectory'))
@@ -213,7 +200,7 @@ def test_submodule_sub_contents_by_name(self):
             contents.remove('__pycache__')
         except KeyError:
             pass
-        self.assertEqual(contents, {'binary.file'})
+        assert contents == {'binary.file'}
 
 
 class ResourceFromNamespaceDiskTests(
@@ -232,5 +219,24 @@ class ResourceFromNamespaceZipTests(
     MODULE = 'namespacedata01'
 
 
+class MainModuleTests(unittest.TestCase):
+    def test_main_module_with_none_spec(self):
+        """
+        __main__ module with no spec should raise TypeError (for clarity).
+
+        See python/cpython#138531 for details.
+        """
+        # construct a __main__ module with no __spec__.
+        mainmodule = types.ModuleType("__main__")
+
+        assert mainmodule.__spec__ is None
+
+        with self.assertRaises(
+            TypeError,
+            msg="Cannot access resources for '__main__' as it does not appear to correspond to an importable module (its __spec__ is None).",
+        ):
+            resources.files(mainmodule)
+
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/Lib/test/test_importlib/resources/test_util.py b/Lib/test/test_importlib/resources/test_util.py
new file mode 100644
index 00000000000..de304b6f351
--- /dev/null
+++ b/Lib/test/test_importlib/resources/test_util.py
@@ -0,0 +1,29 @@
+import unittest
+
+from .util import MemorySetup, Traversable
+
+
+class TestMemoryTraversableImplementation(unittest.TestCase):
+    def test_concrete_methods_are_not_overridden(self):
+        """`MemoryTraversable` must not override `Traversable` concrete methods.
+
+        This test is not an attempt to enforce a particular `Traversable` protocol;
+        it merely catches changes in the `Traversable` abstract/concrete methods
+        that have not been mirrored in the `MemoryTraversable` subclass.
+        """
+
+        traversable_concrete_methods = {
+            method
+            for method, value in Traversable.__dict__.items()
+            if callable(value) and method not in Traversable.__abstractmethods__
+        }
+        memory_traversable_concrete_methods = {
+            method
+            for method, value in MemorySetup.MemoryTraversable.__dict__.items()
+            if callable(value) and not method.startswith("__")
+        }
+        overridden_methods = (
+            memory_traversable_concrete_methods & traversable_concrete_methods
+        )
+
+        assert not overridden_methods
diff --git a/Lib/test/test_importlib/resources/update-zips.py b/Lib/test/test_importlib/resources/update-zips.py
deleted file mode 100755
index 231334aa7e3..00000000000
--- a/Lib/test/test_importlib/resources/update-zips.py
+++ /dev/null
@@ -1,53 +0,0 @@
-"""
-Generate the zip test data files.
-
-Run to build the tests/zipdataNN/ziptestdata.zip files from
-files in tests/dataNN.
-
-Replaces the file with the working copy, but does commit anything
-to the source repo.
-"""
-
-import contextlib
-import os
-import pathlib
-import zipfile
-
-
-def main():
-    """
-    >>> from unittest import mock
-    >>> monkeypatch = getfixture('monkeypatch')
-    >>> monkeypatch.setattr(zipfile, 'ZipFile', mock.MagicMock())
-    >>> print(); main()  # print workaround for bpo-32509
-    <BLANKLINE>
-    ...data01... -> ziptestdata/...
-    ...
-    ...data02... -> ziptestdata/...
-    ...
-    """
-    suffixes = '01', '02'
-    tuple(map(generate, suffixes))
-
-
-def generate(suffix):
-    root = pathlib.Path(__file__).parent.relative_to(os.getcwd())
-    zfpath = root / f'zipdata{suffix}/ziptestdata.zip'
-    with zipfile.ZipFile(zfpath, 'w') as zf:
-        for src, rel in walk(root / f'data{suffix}'):
-            dst = 'ziptestdata' / pathlib.PurePosixPath(rel.as_posix())
-            print(src, '->', dst)
-            zf.write(src, dst)
-
-
-def walk(datapath):
-    for dirpath, dirnames, filenames in os.walk(datapath):
-        with contextlib.suppress(ValueError):
-            dirnames.remove('__pycache__')
-        for filename in filenames:
-            res = pathlib.Path(dirpath) / filename
-            rel = res.relative_to(datapath)
-            yield res, rel
-
-
-__name__ == '__main__' and main()
diff --git a/Lib/test/test_importlib/resources/util.py b/Lib/test/test_importlib/resources/util.py
index e2d995f5963..85b5c61518d 100644
--- a/Lib/test/test_importlib/resources/util.py
+++ b/Lib/test/test_importlib/resources/util.py
@@ -1,18 +1,18 @@
 import abc
+import contextlib
+import functools
 import importlib
 import io
+import pathlib
 import sys
 import types
-import pathlib
-import contextlib
+from importlib.machinery import ModuleSpec
+from importlib.resources.abc import ResourceReader, Traversable, TraversableResources
 
-from importlib.resources.abc import ResourceReader
 from test.support import import_helper, os_helper
-from . import zip as zip_
-from . import _path
-
 
-from importlib.machinery import ModuleSpec
+from . import _path
+from . import zip as zip_
 
 
 class Reader(ResourceReader):
@@ -122,7 +122,7 @@ def test_missing_path(self):
         bytes_data = io.BytesIO(b'Hello, world!')
         package = create_package(file=bytes_data, path=FileNotFoundError())
         self.execute(package, 'utf-8.file')
-        self.assertEqual(package.__loader__._path, 'utf-8.file')
+        assert package.__loader__._path == 'utf-8.file'
 
     def test_extant_path(self):
         # Attempting to open or read or request the path when the
@@ -133,7 +133,7 @@ def test_extant_path(self):
         path = __file__
         package = create_package(file=bytes_data, path=path)
         self.execute(package, 'utf-8.file')
-        self.assertEqual(package.__loader__._path, 'utf-8.file')
+        assert package.__loader__._path == 'utf-8.file'
 
     def test_useless_loader(self):
         package = create_package(file=FileNotFoundError(), path=FileNotFoundError())
@@ -202,5 +202,108 @@ def tree_on_path(self, spec):
         self.fixtures.enter_context(import_helper.DirsOnSysPath(temp_dir))
 
 
+class MemorySetup(ModuleSetup):
+    """Support loading a module in memory."""
+
+    MODULE = 'data01'
+
+    def load_fixture(self, module):
+        self.fixtures.enter_context(self.augment_sys_metapath(module))
+        return importlib.import_module(module)
+
+    @contextlib.contextmanager
+    def augment_sys_metapath(self, module):
+        finder_instance = self.MemoryFinder(module)
+        sys.meta_path.append(finder_instance)
+        yield
+        sys.meta_path.remove(finder_instance)
+
+    class MemoryFinder(importlib.abc.MetaPathFinder):
+        def __init__(self, module):
+            self._module = module
+
+        def find_spec(self, fullname, path, target=None):
+            if fullname != self._module:
+                return None
+
+            return importlib.machinery.ModuleSpec(
+                name=fullname,
+                loader=MemorySetup.MemoryLoader(self._module),
+                is_package=True,
+            )
+
+    class MemoryLoader(importlib.abc.Loader):
+        def __init__(self, module):
+            self._module = module
+
+        def exec_module(self, module):
+            pass
+
+        def get_resource_reader(self, fullname):
+            return MemorySetup.MemoryTraversableResources(self._module, fullname)
+
+    class MemoryTraversableResources(TraversableResources):
+        def __init__(self, module, fullname):
+            self._module = module
+            self._fullname = fullname
+
+        def files(self):
+            return MemorySetup.MemoryTraversable(self._module, self._fullname)
+
+    class MemoryTraversable(Traversable):
+        """Implement only the abstract methods of `Traversable`.
+
+        Besides `.__init__()`, no other methods may be implemented or overridden.
+        This is critical for validating the concrete `Traversable` implementations.
+        """
+
+        def __init__(self, module, fullname):
+            self._module = module
+            self._fullname = fullname
+
+        def _resolve(self):
+            """
+            Fully traverse the `fixtures` dictionary.
+
+            This should be wrapped in a `try/except KeyError`
+            but it is not currently needed and lowers the code coverage numbers.
+            """
+            path = pathlib.PurePosixPath(self._fullname)
+            return functools.reduce(lambda d, p: d[p], path.parts, fixtures)
+
+        def iterdir(self):
+            directory = self._resolve()
+            if not isinstance(directory, dict):
+                # Filesystem openers raise OSError, and that exception is mirrored here.
+                raise OSError(f"{self._fullname} is not a directory")
+            for path in directory:
+                yield MemorySetup.MemoryTraversable(
+                    self._module, f"{self._fullname}/{path}"
+                )
+
+        def is_dir(self) -> bool:
+            return isinstance(self._resolve(), dict)
+
+        def is_file(self) -> bool:
+            return not self.is_dir()
+
+        def open(self, mode='r', encoding=None, errors=None, *_, **__):
+            contents = self._resolve()
+            if isinstance(contents, dict):
+                # Filesystem openers raise OSError when attempting to open a directory,
+                # and that exception is mirrored here.
+                raise OSError(f"{self._fullname} is a directory")
+            if isinstance(contents, str):
+                contents = contents.encode("utf-8")
+            result = io.BytesIO(contents)
+            if "b" in mode:
+                return result
+            return io.TextIOWrapper(result, encoding=encoding, errors=errors)
+
+        @property
+        def name(self):
+            return pathlib.PurePosixPath(self._fullname).name
+
+
 class CommonTests(DiskSetup, CommonTestsBase):
     pass
diff --git a/Lib/test/test_importlib/resources/zipdata01/__init__.py b/Lib/test/test_importlib/resources/zipdata01/__init__.py
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/Lib/test/test_importlib/resources/zipdata01/ziptestdata.zip b/Lib/test/test_importlib/resources/zipdata01/ziptestdata.zip
deleted file mode 100644
index 9a3bb0739f8..00000000000
Binary files a/Lib/test/test_importlib/resources/zipdata01/ziptestdata.zip and /dev/null differ
diff --git a/Lib/test/test_importlib/resources/zipdata02/__init__.py b/Lib/test/test_importlib/resources/zipdata02/__init__.py
deleted file mode 100644
index e69de29bb2d..00000000000
diff --git a/Lib/test/test_importlib/resources/zipdata02/ziptestdata.zip b/Lib/test/test_importlib/resources/zipdata02/ziptestdata.zip
deleted file mode 100644
index d63ff512d28..00000000000
Binary files a/Lib/test/test_importlib/resources/zipdata02/ziptestdata.zip and /dev/null differ
diff --git a/Lib/test/test_importlib/source/test_file_loader.py b/Lib/test/test_importlib/source/test_file_loader.py
index f35adec1a8e..ca2cc045fa6 100644
--- a/Lib/test/test_importlib/source/test_file_loader.py
+++ b/Lib/test/test_importlib/source/test_file_loader.py
@@ -5,24 +5,21 @@
 machinery = util.import_importlib('importlib.machinery')
 importlib_util = util.import_importlib('importlib.util')
 
-import errno
 import marshal
 import os
 import py_compile
-import shutil
 import stat
 import sys
 import types
 import unittest
-import warnings
 
-from test.support.import_helper import make_legacy_pyc, unload
+from test.support.import_helper import make_legacy_pyc
 
-from test.test_py_compile import without_source_date_epoch
-from test.test_py_compile import SourceDateEpochTestMeta
+from test.support.os_helper import without_source_date_epoch
+from test.support.os_helper import SourceDateEpochTestMeta
 
 
-class SimpleTest(abc.LoaderTests):
+class SimpleTest:
 
     """Should have no issue importing a source module [basic]. And if there is
     a syntax error, it should raise a SyntaxError [syntax error].
@@ -34,17 +31,6 @@ def setUp(self):
         self.filepath = os.path.join('ham', self.name + '.py')
         self.loader = self.machinery.SourceFileLoader(self.name, self.filepath)
 
-    def test_load_module_API(self):
-        class Tester(self.abc.FileLoader):
-            def get_source(self, _): return 'attr = 42'
-            def is_package(self, _): return False
-
-        loader = Tester('blah', 'blah.py')
-        self.addCleanup(unload, 'blah')
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore', DeprecationWarning)
-            module = loader.load_module()  # Should not raise an exception.
-
     def test_get_filename_API(self):
         # If fullname is not set then assume self.path is desired.
         class Tester(self.abc.FileLoader):
@@ -69,173 +55,11 @@ def test_inequality(self):
         other = self.machinery.SourceFileLoader('_' + self.name, self.filepath)
         self.assertNotEqual(self.loader, other)
 
-    # [basic]
-    def test_module(self):
-        with util.create_modules('_temp') as mapping:
-            loader = self.machinery.SourceFileLoader('_temp', mapping['_temp'])
-            with warnings.catch_warnings():
-                warnings.simplefilter('ignore', DeprecationWarning)
-                module = loader.load_module('_temp')
-            self.assertIn('_temp', sys.modules)
-            check = {'__name__': '_temp', '__file__': mapping['_temp'],
-                     '__package__': ''}
-            for attr, value in check.items():
-                self.assertEqual(getattr(module, attr), value)
-
-    def test_package(self):
-        with util.create_modules('_pkg.__init__') as mapping:
-            loader = self.machinery.SourceFileLoader('_pkg',
-                                                 mapping['_pkg.__init__'])
-            with warnings.catch_warnings():
-                warnings.simplefilter('ignore', DeprecationWarning)
-                module = loader.load_module('_pkg')
-            self.assertIn('_pkg', sys.modules)
-            check = {'__name__': '_pkg', '__file__': mapping['_pkg.__init__'],
-                     '__path__': [os.path.dirname(mapping['_pkg.__init__'])],
-                     '__package__': '_pkg'}
-            for attr, value in check.items():
-                self.assertEqual(getattr(module, attr), value)
-
-
-    def test_lacking_parent(self):
-        with util.create_modules('_pkg.__init__', '_pkg.mod')as mapping:
-            loader = self.machinery.SourceFileLoader('_pkg.mod',
-                                                    mapping['_pkg.mod'])
-            with warnings.catch_warnings():
-                warnings.simplefilter('ignore', DeprecationWarning)
-                module = loader.load_module('_pkg.mod')
-            self.assertIn('_pkg.mod', sys.modules)
-            check = {'__name__': '_pkg.mod', '__file__': mapping['_pkg.mod'],
-                     '__package__': '_pkg'}
-            for attr, value in check.items():
-                self.assertEqual(getattr(module, attr), value)
 
     def fake_mtime(self, fxn):
         """Fake mtime to always be higher than expected."""
         return lambda name: fxn(name) + 1
 
-    def test_module_reuse(self):
-        with util.create_modules('_temp') as mapping:
-            loader = self.machinery.SourceFileLoader('_temp', mapping['_temp'])
-            with warnings.catch_warnings():
-                warnings.simplefilter('ignore', DeprecationWarning)
-                module = loader.load_module('_temp')
-            module_id = id(module)
-            module_dict_id = id(module.__dict__)
-            with open(mapping['_temp'], 'w', encoding='utf-8') as file:
-                file.write("testing_var = 42\n")
-            with warnings.catch_warnings():
-                warnings.simplefilter('ignore', DeprecationWarning)
-                module = loader.load_module('_temp')
-            self.assertIn('testing_var', module.__dict__,
-                         "'testing_var' not in "
-                            "{0}".format(list(module.__dict__.keys())))
-            self.assertEqual(module, sys.modules['_temp'])
-            self.assertEqual(id(module), module_id)
-            self.assertEqual(id(module.__dict__), module_dict_id)
-
-    def test_state_after_failure(self):
-        # A failed reload should leave the original module intact.
-        attributes = ('__file__', '__path__', '__package__')
-        value = '<test>'
-        name = '_temp'
-        with util.create_modules(name) as mapping:
-            orig_module = types.ModuleType(name)
-            for attr in attributes:
-                setattr(orig_module, attr, value)
-            with open(mapping[name], 'w', encoding='utf-8') as file:
-                file.write('+++ bad syntax +++')
-            loader = self.machinery.SourceFileLoader('_temp', mapping['_temp'])
-            with self.assertRaises(SyntaxError):
-                loader.exec_module(orig_module)
-            for attr in attributes:
-                self.assertEqual(getattr(orig_module, attr), value)
-            with self.assertRaises(SyntaxError):
-                with warnings.catch_warnings():
-                    warnings.simplefilter('ignore', DeprecationWarning)
-                    loader.load_module(name)
-            for attr in attributes:
-                self.assertEqual(getattr(orig_module, attr), value)
-
-    # [syntax error]
-    def test_bad_syntax(self):
-        with util.create_modules('_temp') as mapping:
-            with open(mapping['_temp'], 'w', encoding='utf-8') as file:
-                file.write('=')
-            loader = self.machinery.SourceFileLoader('_temp', mapping['_temp'])
-            with self.assertRaises(SyntaxError):
-                with warnings.catch_warnings():
-                    warnings.simplefilter('ignore', DeprecationWarning)
-                    loader.load_module('_temp')
-            self.assertNotIn('_temp', sys.modules)
-
-    def test_file_from_empty_string_dir(self):
-        # Loading a module found from an empty string entry on sys.path should
-        # not only work, but keep all attributes relative.
-        file_path = '_temp.py'
-        with open(file_path, 'w', encoding='utf-8') as file:
-            file.write("# test file for importlib")
-        try:
-            with util.uncache('_temp'):
-                loader = self.machinery.SourceFileLoader('_temp', file_path)
-                with warnings.catch_warnings():
-                    warnings.simplefilter('ignore', DeprecationWarning)
-                    mod = loader.load_module('_temp')
-                self.assertEqual(file_path, mod.__file__)
-                self.assertEqual(self.util.cache_from_source(file_path),
-                                 mod.__cached__)
-        finally:
-            os.unlink(file_path)
-            pycache = os.path.dirname(self.util.cache_from_source(file_path))
-            if os.path.exists(pycache):
-                shutil.rmtree(pycache)
-
-    @util.writes_bytecode_files
-    def test_timestamp_overflow(self):
-        # When a modification timestamp is larger than 2**32, it should be
-        # truncated rather than raise an OverflowError.
-        with util.create_modules('_temp') as mapping:
-            source = mapping['_temp']
-            compiled = self.util.cache_from_source(source)
-            with open(source, 'w', encoding='utf-8') as f:
-                f.write("x = 5")
-            try:
-                os.utime(source, (2 ** 33 - 5, 2 ** 33 - 5))
-            except OverflowError:
-                self.skipTest("cannot set modification time to large integer")
-            except OSError as e:
-                if e.errno != getattr(errno, 'EOVERFLOW', None):
-                    raise
-                self.skipTest("cannot set modification time to large integer ({})".format(e))
-            loader = self.machinery.SourceFileLoader('_temp', mapping['_temp'])
-            # PEP 451
-            module = types.ModuleType('_temp')
-            module.__spec__ = self.util.spec_from_loader('_temp', loader)
-            loader.exec_module(module)
-            self.assertEqual(module.x, 5)
-            self.assertTrue(os.path.exists(compiled))
-            os.unlink(compiled)
-            # PEP 302
-            with warnings.catch_warnings():
-                warnings.simplefilter('ignore', DeprecationWarning)
-                mod = loader.load_module('_temp')
-            # Sanity checks.
-            self.assertEqual(mod.__cached__, compiled)
-            self.assertEqual(mod.x, 5)
-            # The pyc file was created.
-            self.assertTrue(os.path.exists(compiled))
-
-    def test_unloadable(self):
-        loader = self.machinery.SourceFileLoader('good name', {})
-        module = types.ModuleType('bad name')
-        module.__spec__ = self.machinery.ModuleSpec('bad name', loader)
-        with self.assertRaises(ImportError):
-            loader.exec_module(module)
-        with self.assertRaises(ImportError):
-            with warnings.catch_warnings():
-                warnings.simplefilter('ignore', DeprecationWarning)
-                loader.load_module('bad name')
-
     @util.writes_bytecode_files
     def test_checked_hash_based_pyc(self):
         with util.create_modules('_temp') as mapping:
@@ -386,12 +210,21 @@ def manipulate_bytecode(self,
             del sys.modules['_temp']
         except KeyError:
             pass
-        py_compile.compile(mapping[name], invalidation_mode=invalidation_mode)
-        if not del_source:
-            bytecode_path = self.util.cache_from_source(mapping[name])
+        if sys.implementation.cache_tag is None:
+            if del_source:
+                bytecode_path = mapping[name] + 'c'
+                py_compile.compile(mapping[name], bytecode_path,
+                                   invalidation_mode=invalidation_mode)
+                os.unlink(mapping[name])
+            else:
+                raise unittest.SkipTest('requires sys.implementation.cache_tag')
         else:
-            os.unlink(mapping[name])
-            bytecode_path = make_legacy_pyc(mapping[name])
+            py_compile.compile(mapping[name], invalidation_mode=invalidation_mode)
+            if not del_source:
+                bytecode_path = self.util.cache_from_source(mapping[name])
+            else:
+                os.unlink(mapping[name])
+                bytecode_path = make_legacy_pyc(mapping[name])
         if manipulator:
             with open(bytecode_path, 'rb') as file:
                 bc = file.read()
@@ -511,16 +344,6 @@ def import_(self, file, module_name):
         loader.exec_module(module)
 
 
-class BadBytecodeTestPEP302(BadBytecodeTest):
-
-    def import_(self, file, module_name):
-        loader = self.loader(module_name, file)
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore', DeprecationWarning)
-            module = loader.load_module(module_name)
-        self.assertIn(module_name, sys.modules)
-
-
 class SourceLoaderBadBytecodeTest:
 
     @classmethod
@@ -681,18 +504,6 @@ class SourceLoaderBadBytecodeTestPEP451(
                     util=importlib_util)
 
 
-class SourceLoaderBadBytecodeTestPEP302(
-        SourceLoaderBadBytecodeTest, BadBytecodeTestPEP302):
-    pass
-
-
-(Frozen_SourceBadBytecodePEP302,
- Source_SourceBadBytecodePEP302
- ) = util.test_both(SourceLoaderBadBytecodeTestPEP302, importlib=importlib,
-                    machinery=machinery, abc=importlib_abc,
-                    util=importlib_util)
-
-
 class SourcelessLoaderBadBytecodeTest:
 
     @classmethod
@@ -779,17 +590,5 @@ class SourcelessLoaderBadBytecodeTestPEP451(SourcelessLoaderBadBytecodeTest,
                     util=importlib_util)
 
 
-class SourcelessLoaderBadBytecodeTestPEP302(SourcelessLoaderBadBytecodeTest,
-        BadBytecodeTestPEP302):
-    pass
-
-
-(Frozen_SourcelessBadBytecodePEP302,
- Source_SourcelessBadBytecodePEP302
- ) = util.test_both(SourcelessLoaderBadBytecodeTestPEP302, importlib=importlib,
-                    machinery=machinery, abc=importlib_abc,
-                    util=importlib_util)
-
-
 if __name__ == '__main__':
     unittest.main()
diff --git a/Lib/test/test_importlib/source/test_finder.py b/Lib/test/test_importlib/source/test_finder.py
index 4de736a6bf3..91865b997ad 100644
--- a/Lib/test/test_importlib/source/test_finder.py
+++ b/Lib/test/test_importlib/source/test_finder.py
@@ -57,6 +57,8 @@ def run_test(self, test, create=None, *, compile_=None, unlink=None):
         """
         if create is None:
             create = {test}
+        if (compile_ or unlink) and sys.implementation.cache_tag is None:
+            raise unittest.SkipTest('requires sys.implementation.cache_tag')
         with util.create_modules(*create) as mapping:
             if compile_:
                 for name in compile_:
@@ -73,7 +75,7 @@ def run_test(self, test, create=None, *, compile_=None, unlink=None):
                         if error.errno != errno.ENOENT:
                             raise
             loader = self.import_(mapping['.root'], test)
-            self.assertHasAttr(loader, 'load_module')
+            self.assertHasAttr(loader, 'exec_module')
             return loader
 
     def test_module(self):
@@ -100,7 +102,7 @@ def test_module_in_package(self):
         with util.create_modules('pkg.__init__', 'pkg.sub') as mapping:
             pkg_dir = os.path.dirname(mapping['pkg.__init__'])
             loader = self.import_(pkg_dir, 'pkg.sub')
-            self.assertHasAttr(loader, 'load_module')
+            self.assertHasAttr(loader, 'exec_module')
 
     # [sub package]
     def test_package_in_package(self):
@@ -108,7 +110,7 @@ def test_package_in_package(self):
         with context as mapping:
             pkg_dir = os.path.dirname(mapping['pkg.__init__'])
             loader = self.import_(pkg_dir, 'pkg.sub')
-            self.assertHasAttr(loader, 'load_module')
+            self.assertHasAttr(loader, 'exec_module')
 
     # [package over modules]
     def test_package_over_module(self):
@@ -129,7 +131,7 @@ def test_empty_string_for_dir(self):
             file.write("# test file for importlib")
         try:
             loader = self._find(finder, 'mod', loader_only=True)
-            self.assertHasAttr(loader, 'load_module')
+            self.assertHasAttr(loader, 'exec_module')
         finally:
             os.unlink('mod.py')
 
diff --git a/Lib/test/test_importlib/source/test_source_encoding.py b/Lib/test/test_importlib/source/test_source_encoding.py
index c09c9aa12b8..fada07877fc 100644
--- a/Lib/test/test_importlib/source/test_source_encoding.py
+++ b/Lib/test/test_importlib/source/test_source_encoding.py
@@ -102,19 +102,6 @@ def load(self, loader):
  ) = util.test_both(EncodingTestPEP451, machinery=machinery)
 
 
-class EncodingTestPEP302(EncodingTest):
-
-    def load(self, loader):
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore', DeprecationWarning)
-            return loader.load_module(self.module_name)
-
-
-(Frozen_EncodingTestPEP302,
- Source_EncodingTestPEP302
- ) = util.test_both(EncodingTestPEP302, machinery=machinery)
-
-
 class LineEndingTest:
 
     r"""Source written with the three types of line endings (\n, \r\n, \r)
@@ -158,18 +145,5 @@ def load(self, loader, module_name):
  ) = util.test_both(LineEndingTestPEP451, machinery=machinery)
 
 
-class LineEndingTestPEP302(LineEndingTest):
-
-    def load(self, loader, module_name):
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore', DeprecationWarning)
-            return loader.load_module(module_name)
-
-
-(Frozen_LineEndingTestPEP302,
- Source_LineEndingTestPEP302
- ) = util.test_both(LineEndingTestPEP302, machinery=machinery)
-
-
 if __name__ == '__main__':
     unittest.main()
diff --git a/Lib/test/test_importlib/stubs.py b/Lib/test/test_importlib/stubs.py
deleted file mode 100644
index e5b011c399f..00000000000
--- a/Lib/test/test_importlib/stubs.py
+++ /dev/null
@@ -1,10 +0,0 @@
-import unittest
-
-
-class fake_filesystem_unittest:
-    """
-    Stubbed version of the pyfakefs module
-    """
-    class TestCase(unittest.TestCase):
-        def setUpPyfakefs(self):
-            self.skipTest("pyfakefs not available")
diff --git a/Lib/test/test_importlib/test_abc.py b/Lib/test/test_importlib/test_abc.py
index dd943210ffc..b24c5766468 100644
--- a/Lib/test/test_importlib/test_abc.py
+++ b/Lib/test/test_importlib/test_abc.py
@@ -194,10 +194,6 @@ def test_create_module(self):
         spec = 'a spec'
         self.assertIsNone(self.ins.create_module(spec))
 
-    def test_load_module(self):
-        with self.assertRaises(ImportError):
-            self.ins.load_module('something')
-
     def test_module_repr(self):
         mod = types.ModuleType('blah')
         with warnings.catch_warnings():
@@ -358,38 +354,6 @@ def is_package(self, fullname):
 
         return SpecLoader()
 
-    def test_fresh(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            loader = self.loader()
-            name = 'blah'
-            with test_util.uncache(name):
-                loader.load_module(name)
-                module = loader.found
-                self.assertIs(sys.modules[name], module)
-            self.assertEqual(loader, module.__loader__)
-            self.assertEqual(loader, module.__spec__.loader)
-            self.assertEqual(name, module.__name__)
-            self.assertEqual(name, module.__spec__.name)
-            self.assertIsNotNone(module.__path__)
-            self.assertIsNotNone(module.__path__,
-                                module.__spec__.submodule_search_locations)
-
-    def test_reload(self):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            name = 'blah'
-            loader = self.loader()
-            module = types.ModuleType(name)
-            module.__spec__ = self.util.spec_from_loader(name, loader)
-            module.__loader__ = loader
-            with test_util.uncache(name):
-                sys.modules[name] = module
-                loader.load_module(name)
-                found = loader.found
-                self.assertIs(found, sys.modules[name])
-                self.assertIs(module, sys.modules[name])
-
 
 (Frozen_LoaderLoadModuleTests,
  Source_LoaderLoadModuleTests
@@ -478,59 +442,6 @@ def test_get_code_source_not_found(self):
                          InspectLoaderSubclass=SPLIT_IL)
 
 
-class InspectLoaderLoadModuleTests:
-
-    """Test InspectLoader.load_module()."""
-
-    module_name = 'blah'
-
-    def setUp(self):
-        import_helper.unload(self.module_name)
-        self.addCleanup(import_helper.unload, self.module_name)
-
-    def load(self, loader):
-        spec = self.util.spec_from_loader(self.module_name, loader)
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore', DeprecationWarning)
-            return self.init._bootstrap._load_unlocked(spec)
-
-    def mock_get_code(self):
-        return mock.patch.object(self.InspectLoaderSubclass, 'get_code')
-
-    def test_get_code_ImportError(self):
-        # If get_code() raises ImportError, it should propagate.
-        with self.mock_get_code() as mocked_get_code:
-            mocked_get_code.side_effect = ImportError
-            with self.assertRaises(ImportError):
-                loader = self.InspectLoaderSubclass()
-                self.load(loader)
-
-    def test_get_code_None(self):
-        # If get_code() returns None, raise ImportError.
-        with self.mock_get_code() as mocked_get_code:
-            mocked_get_code.return_value = None
-            with self.assertRaises(ImportError):
-                loader = self.InspectLoaderSubclass()
-                self.load(loader)
-
-    def test_module_returned(self):
-        # The loaded module should be returned.
-        code = compile('attr = 42', '<string>', 'exec')
-        with self.mock_get_code() as mocked_get_code:
-            mocked_get_code.return_value = code
-            loader = self.InspectLoaderSubclass()
-            module = self.load(loader)
-            self.assertEqual(module, sys.modules[self.module_name])
-
-
-(Frozen_ILLoadModuleTests,
- Source_ILLoadModuleTests
- ) = test_util.test_both(InspectLoaderLoadModuleTests,
-                         InspectLoaderSubclass=SPLIT_IL,
-                         init=init,
-                         util=util)
-
-
 ##### ExecutionLoader concrete methods #########################################
 class ExecutionLoaderGetCodeTests:
 
@@ -599,8 +510,7 @@ def test_get_code_no_path(self):
 class SourceOnlyLoader:
 
     # Globals that should be defined for all modules.
-    source = (b"_ = '::'.join([__name__, __file__, __cached__, __package__, "
-              b"repr(__loader__)])")
+    source = (b"_ = '::'.join([__name__, __file__, __package__, repr(__loader__)])")
 
     def __init__(self, path):
         self.path = path
@@ -623,7 +533,10 @@ class SourceLoader(SourceOnlyLoader):
 
     def __init__(self, path, magic=None):
         super().__init__(path)
-        self.bytecode_path = self.util.cache_from_source(self.path)
+        try:
+            self.bytecode_path = self.util.cache_from_source(self.path)
+        except NotImplementedError:
+            self.bytecode_path = None
         self.source_size = len(self.source)
         if magic is None:
             magic = self.util.MAGIC_NUMBER
@@ -669,26 +582,26 @@ def setUp(self, *, is_package=True, **kwargs):
             module_name = 'mod'
             self.path = os.path.join(self.package, '.'.join(['mod', 'py']))
             self.name = '.'.join([self.package, module_name])
-        self.cached = self.util.cache_from_source(self.path)
+        try:
+            self.cached = self.util.cache_from_source(self.path)
+        except NotImplementedError:
+            self.cached = None
         self.loader = self.loader_mock(self.path, **kwargs)
 
     def verify_module(self, module):
         self.assertEqual(module.__name__, self.name)
         self.assertEqual(module.__file__, self.path)
-        self.assertEqual(module.__cached__, self.cached)
         self.assertEqual(module.__package__, self.package)
         self.assertEqual(module.__loader__, self.loader)
         values = module._.split('::')
         self.assertEqual(values[0], self.name)
         self.assertEqual(values[1], self.path)
-        self.assertEqual(values[2], self.cached)
-        self.assertEqual(values[3], self.package)
-        self.assertEqual(values[4], repr(self.loader))
+        self.assertEqual(values[2], self.package)
+        self.assertEqual(values[3], repr(self.loader))
 
     def verify_code(self, code_object):
         module = types.ModuleType(self.name)
         module.__file__ = self.path
-        module.__cached__ = self.cached
         module.__package__ = self.package
         module.__loader__ = self.loader
         module.__path__ = []
@@ -729,34 +642,6 @@ def test_source_to_code(self):
         code = self.loader.source_to_code(self.loader.source, self.path)
         self.verify_code(code)
 
-    def test_load_module(self):
-        # Loading a module should set __name__, __loader__, __package__,
-        # __path__ (for packages), __file__, and __cached__.
-        # The module should also be put into sys.modules.
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            with test_util.uncache(self.name):
-                with warnings.catch_warnings():
-                    warnings.simplefilter('ignore', DeprecationWarning)
-                    module = self.loader.load_module(self.name)
-                self.verify_module(module)
-                self.assertEqual(module.__path__, [os.path.dirname(self.path)])
-                self.assertIn(self.name, sys.modules)
-
-    def test_package_settings(self):
-        # __package__ needs to be set, while __path__ is set on if the module
-        # is a package.
-        # Testing the values for a package are covered by test_load_module.
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            self.setUp(is_package=False)
-            with test_util.uncache(self.name):
-                with warnings.catch_warnings():
-                    warnings.simplefilter('ignore', DeprecationWarning)
-                    module = self.loader.load_module(self.name)
-                self.verify_module(module)
-                self.assertNotHasAttr(module, '__path__')
-
     def test_get_source_encoding(self):
         # Source is considered encoded in UTF-8 by default unless otherwise
         # specified by an encoding line.
@@ -777,6 +662,8 @@ def test_get_source_encoding(self):
 
 
 @unittest.skipIf(sys.dont_write_bytecode, "sys.dont_write_bytecode is true")
+@unittest.skipIf(sys.implementation.cache_tag is None,
+                 "sys.implementation.cache_tag is None")
 class SourceLoaderBytecodeTests(SourceLoaderTestHarness):
 
     """Test importlib.abc.SourceLoader's use of bytecode.
@@ -904,7 +791,7 @@ def test_universal_newlines(self):
         mock = self.SourceOnlyLoaderMock('mod.file')
         source = "x = 42\r\ny = -13\r\n"
         mock.source = source.encode('utf-8')
-        expect = io.IncrementalNewlineDecoder(None, True).decode(source)
+        expect = io.StringIO(source, newline=None).getvalue()
         self.assertEqual(mock.get_source(name), expect)
 
 
diff --git a/Lib/test/test_importlib/test_api.py b/Lib/test/test_importlib/test_api.py
index 1bc531a2fe3..70d93d693ae 100644
--- a/Lib/test/test_importlib/test_api.py
+++ b/Lib/test/test_importlib/test_api.py
@@ -231,11 +231,9 @@ def test_reload_location_changed(self):
                     # Start as a plain module.
                     self.init.invalidate_caches()
                     path = os.path.join(cwd, name + '.py')
-                    cached = self.util.cache_from_source(path)
                     expected = {'__name__': name,
                                 '__package__': '',
                                 '__file__': path,
-                                '__cached__': cached,
                                 '__doc__': None,
                                 }
                     os_helper.create_empty_file(path)
@@ -252,11 +250,9 @@ def test_reload_location_changed(self):
                     # Change to a package.
                     self.init.invalidate_caches()
                     init_path = os.path.join(cwd, name, '__init__.py')
-                    cached = self.util.cache_from_source(init_path)
                     expected = {'__name__': name,
                                 '__package__': name,
                                 '__file__': init_path,
-                                '__cached__': cached,
                                 '__path__': [os.path.dirname(init_path)],
                                 '__doc__': None,
                                 }
@@ -283,7 +279,6 @@ def test_reload_namespace_changed(self):
                     # Start as a namespace package.
                     self.init.invalidate_caches()
                     bad_path = os.path.join(cwd, name, '__init.py')
-                    cached = self.util.cache_from_source(bad_path)
                     expected = {'__name__': name,
                                 '__package__': name,
                                 '__doc__': None,
@@ -312,11 +307,9 @@ def test_reload_namespace_changed(self):
                     # Change to a regular package.
                     self.init.invalidate_caches()
                     init_path = os.path.join(cwd, name, '__init__.py')
-                    cached = self.util.cache_from_source(init_path)
                     expected = {'__name__': name,
                                 '__package__': name,
                                 '__file__': init_path,
-                                '__cached__': cached,
                                 '__path__': [os.path.dirname(init_path)],
                                 '__doc__': None,
                                 'eggs': None,
diff --git a/Lib/test/test_importlib/test_discover.py b/Lib/test/test_importlib/test_discover.py
new file mode 100644
index 00000000000..c4ab7b6982e
--- /dev/null
+++ b/Lib/test/test_importlib/test_discover.py
@@ -0,0 +1,121 @@
+from unittest.mock import Mock
+
+from test.test_importlib import util
+
+importlib = util.import_importlib('importlib')
+machinery = util.import_importlib('importlib.machinery')
+
+
+class DiscoverableFinder:
+    def __init__(self, discover=[]):
+        self._discovered_values = discover
+
+    def find_spec(self, fullname, path=None, target=None):
+        raise NotImplementedError
+
+    def discover(self, parent=None):
+        yield from self._discovered_values
+
+
+class TestPathFinder:
+    """PathFinder implements MetaPathFinder, which uses the PathEntryFinder(s)
+    registered in sys.path_hooks (and sys.path_importer_cache) to search
+    sys.path or the parent's __path__.
+
+    PathFinder.discover() should redirect to the .discover() method of the
+    PathEntryFinder for each path entry.
+    """
+
+    def test_search_path_hooks_top_level(self):
+        modules = [
+            self.machinery.ModuleSpec(name='example1', loader=None),
+            self.machinery.ModuleSpec(name='example2', loader=None),
+            self.machinery.ModuleSpec(name='example3', loader=None),
+        ]
+
+        with util.import_state(
+            path_importer_cache={
+                'discoverable': DiscoverableFinder(discover=modules),
+            },
+            path=['discoverable'],
+        ):
+            discovered = list(self.machinery.PathFinder.discover())
+
+        self.assertEqual(discovered, modules)
+
+
+    def test_search_path_hooks_parent(self):
+        parent = self.machinery.ModuleSpec(name='example', loader=None, is_package=True)
+        parent.submodule_search_locations.append('discoverable')
+
+        children = [
+            self.machinery.ModuleSpec(name='example.child1', loader=None),
+            self.machinery.ModuleSpec(name='example.child2', loader=None),
+            self.machinery.ModuleSpec(name='example.child3', loader=None),
+        ]
+
+        with util.import_state(
+            path_importer_cache={
+                'discoverable': DiscoverableFinder(discover=children)
+            },
+            path=[],
+        ):
+            discovered = list(self.machinery.PathFinder.discover(parent))
+
+        self.assertEqual(discovered, children)
+
+    def test_invalid_parent(self):
+        parent = self.machinery.ModuleSpec(name='example', loader=None)
+        with self.assertRaises(ValueError):
+            list(self.machinery.PathFinder.discover(parent))
+
+
+(
+    Frozen_TestPathFinder,
+    Source_TestPathFinder,
+) = util.test_both(TestPathFinder, importlib=importlib, machinery=machinery)
+
+
+class TestFileFinder:
+    """FileFinder implements PathEntryFinder and provides the base finder
+    implementation to search the file system.
+    """
+
+    def get_finder(self, path):
+        loader_details = [
+            (self.machinery.SourceFileLoader, self.machinery.SOURCE_SUFFIXES),
+            (self.machinery.SourcelessFileLoader, self.machinery.BYTECODE_SUFFIXES),
+        ]
+        return self.machinery.FileFinder(path, *loader_details)
+
+    def test_discover_top_level(self):
+        modules = {'example1', 'example2', 'example3'}
+        with util.create_modules(*modules) as mapping:
+            finder = self.get_finder(mapping['.root'])
+            discovered = list(finder.discover())
+        self.assertEqual({spec.name for spec in discovered}, modules)
+
+    def test_discover_parent(self):
+        modules = {
+            'example.child1',
+            'example.child2',
+            'example.child3',
+        }
+        with util.create_modules(*modules) as mapping:
+            example = self.get_finder(mapping['.root']).find_spec('example')
+            finder = self.get_finder(example.submodule_search_locations[0])
+            discovered = list(finder.discover(example))
+        self.assertEqual({spec.name for spec in discovered}, modules)
+
+    def test_invalid_parent(self):
+        with util.create_modules('example') as mapping:
+            finder = self.get_finder(mapping['.root'])
+            example = finder.find_spec('example')
+            with self.assertRaises(ValueError):
+                list(finder.discover(example))
+
+
+(
+    Frozen_TestFileFinder,
+    Source_TestFileFinder,
+) = util.test_both(TestFileFinder, importlib=importlib, machinery=machinery)
diff --git a/Lib/test/test_importlib/test_main.py b/Lib/test/test_importlib/test_main.py
deleted file mode 100644
index 81f683799cb..00000000000
--- a/Lib/test/test_importlib/test_main.py
+++ /dev/null
@@ -1,427 +0,0 @@
-import re
-import pickle
-import unittest
-import warnings
-import importlib.metadata
-import contextlib
-import itertools
-
-try:
-    import pyfakefs.fake_filesystem_unittest as ffs
-except ImportError:
-    from .stubs import fake_filesystem_unittest as ffs
-
-from . import fixtures
-from ._context import suppress
-from importlib.metadata import (
-    Distribution,
-    EntryPoint,
-    PackageNotFoundError,
-    _unique,
-    distributions,
-    entry_points,
-    metadata,
-    packages_distributions,
-    version,
-)
-
-
-@contextlib.contextmanager
-def suppress_known_deprecation():
-    with warnings.catch_warnings(record=True) as ctx:
-        warnings.simplefilter('default', category=DeprecationWarning)
-        yield ctx
-
-
-class BasicTests(fixtures.DistInfoPkg, unittest.TestCase):
-    version_pattern = r'\d+\.\d+(\.\d)?'
-
-    def test_retrieves_version_of_self(self):
-        dist = Distribution.from_name('distinfo-pkg')
-        assert isinstance(dist.version, str)
-        assert re.match(self.version_pattern, dist.version)
-
-    def test_for_name_does_not_exist(self):
-        with self.assertRaises(PackageNotFoundError):
-            Distribution.from_name('does-not-exist')
-
-    def test_package_not_found_mentions_metadata(self):
-        """
-        When a package is not found, that could indicate that the
-        package is not installed or that it is installed without
-        metadata. Ensure the exception mentions metadata to help
-        guide users toward the cause. See #124.
-        """
-        with self.assertRaises(PackageNotFoundError) as ctx:
-            Distribution.from_name('does-not-exist')
-
-        assert "metadata" in str(ctx.exception)
-
-    # expected to fail until ABC is enforced
-    @suppress(AssertionError)
-    @suppress_known_deprecation()
-    def test_abc_enforced(self):
-        with self.assertRaises(TypeError):
-            type('DistributionSubclass', (Distribution,), {})()
-
-    @fixtures.parameterize(
-        dict(name=None),
-        dict(name=''),
-    )
-    def test_invalid_inputs_to_from_name(self, name):
-        with self.assertRaises(ValueError):
-            Distribution.from_name(name)
-
-
-class ImportTests(fixtures.DistInfoPkg, unittest.TestCase):
-    def test_import_nonexistent_module(self):
-        # Ensure that the MetadataPathFinder does not crash an import of a
-        # non-existent module.
-        with self.assertRaises(ImportError):
-            importlib.import_module('does_not_exist')
-
-    def test_resolve(self):
-        ep = entry_points(group='entries')['main']
-        self.assertEqual(ep.load().__name__, "main")
-
-    def test_entrypoint_with_colon_in_name(self):
-        ep = entry_points(group='entries')['ns:sub']
-        self.assertEqual(ep.value, 'mod:main')
-
-    def test_resolve_without_attr(self):
-        ep = EntryPoint(
-            name='ep',
-            value='importlib.metadata',
-            group='grp',
-        )
-        assert ep.load() is importlib.metadata
-
-
-class NameNormalizationTests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
-    @staticmethod
-    def make_pkg(name):
-        """
-        Create minimal metadata for a dist-info package with
-        the indicated name on the file system.
-        """
-        return {
-            f'{name}.dist-info': {
-                'METADATA': 'VERSION: 1.0\n',
-            },
-        }
-
-    def test_dashes_in_dist_name_found_as_underscores(self):
-        """
-        For a package with a dash in the name, the dist-info metadata
-        uses underscores in the name. Ensure the metadata loads.
-        """
-        fixtures.build_files(self.make_pkg('my_pkg'), self.site_dir)
-        assert version('my-pkg') == '1.0'
-
-    def test_dist_name_found_as_any_case(self):
-        """
-        Ensure the metadata loads when queried with any case.
-        """
-        pkg_name = 'CherryPy'
-        fixtures.build_files(self.make_pkg(pkg_name), self.site_dir)
-        assert version(pkg_name) == '1.0'
-        assert version(pkg_name.lower()) == '1.0'
-        assert version(pkg_name.upper()) == '1.0'
-
-    def test_unique_distributions(self):
-        """
-        Two distributions varying only by non-normalized name on
-        the file system should resolve as the same.
-        """
-        fixtures.build_files(self.make_pkg('abc'), self.site_dir)
-        before = list(_unique(distributions()))
-
-        alt_site_dir = self.fixtures.enter_context(fixtures.tempdir())
-        self.fixtures.enter_context(self.add_sys_path(alt_site_dir))
-        fixtures.build_files(self.make_pkg('ABC'), alt_site_dir)
-        after = list(_unique(distributions()))
-
-        assert len(after) == len(before)
-
-
-class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
-    @staticmethod
-    def pkg_with_non_ascii_description(site_dir):
-        """
-        Create minimal metadata for a package with non-ASCII in
-        the description.
-        """
-        contents = {
-            'portend.dist-info': {
-                'METADATA': 'Description: pôrˈtend',
-            },
-        }
-        fixtures.build_files(contents, site_dir)
-        return 'portend'
-
-    @staticmethod
-    def pkg_with_non_ascii_description_egg_info(site_dir):
-        """
-        Create minimal metadata for an egg-info package with
-        non-ASCII in the description.
-        """
-        contents = {
-            'portend.dist-info': {
-                'METADATA': """
-                Name: portend
-
-                pôrˈtend""",
-            },
-        }
-        fixtures.build_files(contents, site_dir)
-        return 'portend'
-
-    def test_metadata_loads(self):
-        pkg_name = self.pkg_with_non_ascii_description(self.site_dir)
-        meta = metadata(pkg_name)
-        assert meta['Description'] == 'pôrˈtend'
-
-    def test_metadata_loads_egg_info(self):
-        pkg_name = self.pkg_with_non_ascii_description_egg_info(self.site_dir)
-        meta = metadata(pkg_name)
-        assert meta['Description'] == 'pôrˈtend'
-
-
-class DiscoveryTests(
-    fixtures.EggInfoPkg,
-    fixtures.EggInfoPkgPipInstalledNoToplevel,
-    fixtures.EggInfoPkgPipInstalledNoModules,
-    fixtures.EggInfoPkgSourcesFallback,
-    fixtures.DistInfoPkg,
-    unittest.TestCase,
-):
-    def test_package_discovery(self):
-        dists = list(distributions())
-        assert all(isinstance(dist, Distribution) for dist in dists)
-        assert any(dist.metadata['Name'] == 'egginfo-pkg' for dist in dists)
-        assert any(dist.metadata['Name'] == 'egg_with_module-pkg' for dist in dists)
-        assert any(dist.metadata['Name'] == 'egg_with_no_modules-pkg' for dist in dists)
-        assert any(dist.metadata['Name'] == 'sources_fallback-pkg' for dist in dists)
-        assert any(dist.metadata['Name'] == 'distinfo-pkg' for dist in dists)
-
-    def test_invalid_usage(self):
-        with self.assertRaises(ValueError):
-            list(distributions(context='something', name='else'))
-
-
-class DirectoryTest(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
-    def test_egg_info(self):
-        # make an `EGG-INFO` directory that's unrelated
-        self.site_dir.joinpath('EGG-INFO').mkdir()
-        # used to crash with `IsADirectoryError`
-        with self.assertRaises(PackageNotFoundError):
-            version('unknown-package')
-
-    def test_egg(self):
-        egg = self.site_dir.joinpath('foo-3.6.egg')
-        egg.mkdir()
-        with self.add_sys_path(egg):
-            with self.assertRaises(PackageNotFoundError):
-                version('foo')
-
-
-class MissingSysPath(fixtures.OnSysPath, unittest.TestCase):
-    site_dir = '/does-not-exist'
-
-    def test_discovery(self):
-        """
-        Discovering distributions should succeed even if
-        there is an invalid path on sys.path.
-        """
-        importlib.metadata.distributions()
-
-
-class InaccessibleSysPath(fixtures.OnSysPath, ffs.TestCase):
-    site_dir = '/access-denied'
-
-    def setUp(self):
-        super().setUp()
-        self.setUpPyfakefs()
-        self.fs.create_dir(self.site_dir, perm_bits=000)
-
-    def test_discovery(self):
-        """
-        Discovering distributions should succeed even if
-        there is an invalid path on sys.path.
-        """
-        list(importlib.metadata.distributions())
-
-
-class TestEntryPoints(unittest.TestCase):
-    def __init__(self, *args):
-        super().__init__(*args)
-        self.ep = importlib.metadata.EntryPoint(
-            name='name', value='value', group='group'
-        )
-
-    def test_entry_point_pickleable(self):
-        revived = pickle.loads(pickle.dumps(self.ep))
-        assert revived == self.ep
-
-    def test_positional_args(self):
-        """
-        Capture legacy (namedtuple) construction, discouraged.
-        """
-        EntryPoint('name', 'value', 'group')
-
-    def test_immutable(self):
-        """EntryPoints should be immutable"""
-        with self.assertRaises(AttributeError):
-            self.ep.name = 'badactor'
-
-    def test_repr(self):
-        assert 'EntryPoint' in repr(self.ep)
-        assert 'name=' in repr(self.ep)
-        assert "'name'" in repr(self.ep)
-
-    def test_hashable(self):
-        """EntryPoints should be hashable"""
-        hash(self.ep)
-
-    def test_module(self):
-        assert self.ep.module == 'value'
-
-    def test_attr(self):
-        assert self.ep.attr is None
-
-    def test_sortable(self):
-        """
-        EntryPoint objects are sortable, but result is undefined.
-        """
-        sorted(
-            [
-                EntryPoint(name='b', value='val', group='group'),
-                EntryPoint(name='a', value='val', group='group'),
-            ]
-        )
-
-
-class FileSystem(
-    fixtures.OnSysPath, fixtures.SiteDir, fixtures.FileBuilder, unittest.TestCase
-):
-    def test_unicode_dir_on_sys_path(self):
-        """
-        Ensure a Unicode subdirectory of a directory on sys.path
-        does not crash.
-        """
-        fixtures.build_files(
-            {self.unicode_filename(): {}},
-            prefix=self.site_dir,
-        )
-        list(distributions())
-
-
-class PackagesDistributionsPrebuiltTest(fixtures.ZipFixtures, unittest.TestCase):
-    def test_packages_distributions_example(self):
-        self._fixture_on_path('example-21.12-py3-none-any.whl')
-        assert packages_distributions()['example'] == ['example']
-
-    def test_packages_distributions_example2(self):
-        """
-        Test packages_distributions on a wheel built
-        by trampolim.
-        """
-        self._fixture_on_path('example2-1.0.0-py3-none-any.whl')
-        assert packages_distributions()['example2'] == ['example2']
-
-
-class PackagesDistributionsTest(
-    fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase
-):
-    def test_packages_distributions_neither_toplevel_nor_files(self):
-        """
-        Test a package built without 'top-level.txt' or a file list.
-        """
-        fixtures.build_files(
-            {
-                'trim_example-1.0.0.dist-info': {
-                    'METADATA': """
-                Name: trim_example
-                Version: 1.0.0
-                """,
-                }
-            },
-            prefix=self.site_dir,
-        )
-        packages_distributions()
-
-    def test_packages_distributions_all_module_types(self):
-        """
-        Test top-level modules detected on a package without 'top-level.txt'.
-        """
-        suffixes = importlib.machinery.all_suffixes()
-        metadata = dict(
-            METADATA="""
-                Name: all_distributions
-                Version: 1.0.0
-                """,
-        )
-        files = {
-            'all_distributions-1.0.0.dist-info': metadata,
-        }
-        for i, suffix in enumerate(suffixes):
-            files.update(
-                {
-                    f'importable-name {i}{suffix}': '',
-                    f'in_namespace_{i}': {
-                        f'mod{suffix}': '',
-                    },
-                    f'in_package_{i}': {
-                        '__init__.py': '',
-                        f'mod{suffix}': '',
-                    },
-                }
-            )
-        metadata.update(RECORD=fixtures.build_record(files))
-        fixtures.build_files(files, prefix=self.site_dir)
-
-        distributions = packages_distributions()
-
-        for i in range(len(suffixes)):
-            assert distributions[f'importable-name {i}'] == ['all_distributions']
-            assert distributions[f'in_namespace_{i}'] == ['all_distributions']
-            assert distributions[f'in_package_{i}'] == ['all_distributions']
-
-        assert not any(name.endswith('.dist-info') for name in distributions)
-
-
-class PackagesDistributionsEggTest(
-    fixtures.EggInfoPkg,
-    fixtures.EggInfoPkgPipInstalledNoToplevel,
-    fixtures.EggInfoPkgPipInstalledNoModules,
-    fixtures.EggInfoPkgSourcesFallback,
-    unittest.TestCase,
-):
-    def test_packages_distributions_on_eggs(self):
-        """
-        Test old-style egg packages with a variation of 'top_level.txt',
-        'SOURCES.txt', and 'installed-files.txt', available.
-        """
-        distributions = packages_distributions()
-
-        def import_names_from_package(package_name):
-            return {
-                import_name
-                for import_name, package_names in distributions.items()
-                if package_name in package_names
-            }
-
-        # egginfo-pkg declares one import ('mod') via top_level.txt
-        assert import_names_from_package('egginfo-pkg') == {'mod'}
-
-        # egg_with_module-pkg has one import ('egg_with_module') inferred from
-        # installed-files.txt (top_level.txt is missing)
-        assert import_names_from_package('egg_with_module-pkg') == {'egg_with_module'}
-
-        # egg_with_no_modules-pkg should not be associated with any import names
-        # (top_level.txt is empty, and installed-files.txt has no .py files)
-        assert import_names_from_package('egg_with_no_modules-pkg') == set()
-
-        # sources_fallback-pkg has one import ('sources_fallback') inferred from
-        # SOURCES.txt (top_level.txt and installed-files.txt is missing)
-        assert import_names_from_package('sources_fallback-pkg') == {'sources_fallback'}
diff --git a/Lib/test/test_importlib/test_metadata_api.py b/Lib/test/test_importlib/test_metadata_api.py
deleted file mode 100644
index 33c6e85ee94..00000000000
--- a/Lib/test/test_importlib/test_metadata_api.py
+++ /dev/null
@@ -1,322 +0,0 @@
-import re
-import textwrap
-import unittest
-import warnings
-import importlib
-import contextlib
-
-from . import fixtures
-from importlib.metadata import (
-    Distribution,
-    PackageNotFoundError,
-    distribution,
-    entry_points,
-    files,
-    metadata,
-    requires,
-    version,
-)
-
-
-@contextlib.contextmanager
-def suppress_known_deprecation():
-    with warnings.catch_warnings(record=True) as ctx:
-        warnings.simplefilter('default', category=DeprecationWarning)
-        yield ctx
-
-
-class APITests(
-    fixtures.EggInfoPkg,
-    fixtures.EggInfoPkgPipInstalledNoToplevel,
-    fixtures.EggInfoPkgPipInstalledNoModules,
-    fixtures.EggInfoPkgSourcesFallback,
-    fixtures.DistInfoPkg,
-    fixtures.DistInfoPkgWithDot,
-    fixtures.EggInfoFile,
-    unittest.TestCase,
-):
-    version_pattern = r'\d+\.\d+(\.\d)?'
-
-    def test_retrieves_version_of_self(self):
-        pkg_version = version('egginfo-pkg')
-        assert isinstance(pkg_version, str)
-        assert re.match(self.version_pattern, pkg_version)
-
-    def test_retrieves_version_of_distinfo_pkg(self):
-        pkg_version = version('distinfo-pkg')
-        assert isinstance(pkg_version, str)
-        assert re.match(self.version_pattern, pkg_version)
-
-    def test_for_name_does_not_exist(self):
-        with self.assertRaises(PackageNotFoundError):
-            distribution('does-not-exist')
-
-    def test_name_normalization(self):
-        names = 'pkg.dot', 'pkg_dot', 'pkg-dot', 'pkg..dot', 'Pkg.Dot'
-        for name in names:
-            with self.subTest(name):
-                assert distribution(name).metadata['Name'] == 'pkg.dot'
-
-    def test_prefix_not_matched(self):
-        prefixes = 'p', 'pkg', 'pkg.'
-        for prefix in prefixes:
-            with self.subTest(prefix):
-                with self.assertRaises(PackageNotFoundError):
-                    distribution(prefix)
-
-    def test_for_top_level(self):
-        tests = [
-            ('egginfo-pkg', 'mod'),
-            ('egg_with_no_modules-pkg', ''),
-        ]
-        for pkg_name, expect_content in tests:
-            with self.subTest(pkg_name):
-                self.assertEqual(
-                    distribution(pkg_name).read_text('top_level.txt').strip(),
-                    expect_content,
-                )
-
-    def test_read_text(self):
-        tests = [
-            ('egginfo-pkg', 'mod\n'),
-            ('egg_with_no_modules-pkg', '\n'),
-        ]
-        for pkg_name, expect_content in tests:
-            with self.subTest(pkg_name):
-                top_level = [
-                    path for path in files(pkg_name) if path.name == 'top_level.txt'
-                ][0]
-                self.assertEqual(top_level.read_text(), expect_content)
-
-    def test_entry_points(self):
-        eps = entry_points()
-        assert 'entries' in eps.groups
-        entries = eps.select(group='entries')
-        assert 'main' in entries.names
-        ep = entries['main']
-        self.assertEqual(ep.value, 'mod:main')
-        self.assertEqual(ep.extras, [])
-
-    def test_entry_points_distribution(self):
-        entries = entry_points(group='entries')
-        for entry in ("main", "ns:sub"):
-            ep = entries[entry]
-            self.assertIn(ep.dist.name, ('distinfo-pkg', 'egginfo-pkg'))
-            self.assertEqual(ep.dist.version, "1.0.0")
-
-    def test_entry_points_unique_packages_normalized(self):
-        """
-        Entry points should only be exposed for the first package
-        on sys.path with a given name (even when normalized).
-        """
-        alt_site_dir = self.fixtures.enter_context(fixtures.tempdir())
-        self.fixtures.enter_context(self.add_sys_path(alt_site_dir))
-        alt_pkg = {
-            "DistInfo_pkg-1.1.0.dist-info": {
-                "METADATA": """
-                Name: distinfo-pkg
-                Version: 1.1.0
-                """,
-                "entry_points.txt": """
-                [entries]
-                main = mod:altmain
-            """,
-            },
-        }
-        fixtures.build_files(alt_pkg, alt_site_dir)
-        entries = entry_points(group='entries')
-        assert not any(
-            ep.dist.name == 'distinfo-pkg' and ep.dist.version == '1.0.0'
-            for ep in entries
-        )
-        # ns:sub doesn't exist in alt_pkg
-        assert 'ns:sub' not in entries.names
-
-    def test_entry_points_missing_name(self):
-        with self.assertRaises(KeyError):
-            entry_points(group='entries')['missing']
-
-    def test_entry_points_missing_group(self):
-        assert entry_points(group='missing') == ()
-
-    def test_entry_points_allows_no_attributes(self):
-        ep = entry_points().select(group='entries', name='main')
-        with self.assertRaises(AttributeError):
-            ep.foo = 4
-
-    def test_metadata_for_this_package(self):
-        md = metadata('egginfo-pkg')
-        assert md['author'] == 'Steven Ma'
-        assert md['LICENSE'] == 'Unknown'
-        assert md['Name'] == 'egginfo-pkg'
-        classifiers = md.get_all('Classifier')
-        assert 'Topic :: Software Development :: Libraries' in classifiers
-
-    def test_missing_key_legacy(self):
-        """
-        Requesting a missing key will still return None, but warn.
-        """
-        md = metadata('distinfo-pkg')
-        with suppress_known_deprecation():
-            assert md['does-not-exist'] is None
-
-    def test_get_key(self):
-        """
-        Getting a key gets the key.
-        """
-        md = metadata('egginfo-pkg')
-        assert md.get('Name') == 'egginfo-pkg'
-
-    def test_get_missing_key(self):
-        """
-        Requesting a missing key will return None.
-        """
-        md = metadata('distinfo-pkg')
-        assert md.get('does-not-exist') is None
-
-    @staticmethod
-    def _test_files(files):
-        root = files[0].root
-        for file in files:
-            assert file.root == root
-            assert not file.hash or file.hash.value
-            assert not file.hash or file.hash.mode == 'sha256'
-            assert not file.size or file.size >= 0
-            assert file.locate().exists()
-            assert isinstance(file.read_binary(), bytes)
-            if file.name.endswith('.py'):
-                file.read_text()
-
-    def test_file_hash_repr(self):
-        util = [p for p in files('distinfo-pkg') if p.name == 'mod.py'][0]
-        self.assertRegex(repr(util.hash), '<FileHash mode: sha256 value: .*>')
-
-    def test_files_dist_info(self):
-        self._test_files(files('distinfo-pkg'))
-
-    def test_files_egg_info(self):
-        self._test_files(files('egginfo-pkg'))
-        self._test_files(files('egg_with_module-pkg'))
-        self._test_files(files('egg_with_no_modules-pkg'))
-        self._test_files(files('sources_fallback-pkg'))
-
-    def test_version_egg_info_file(self):
-        self.assertEqual(version('egginfo-file'), '0.1')
-
-    def test_requires_egg_info_file(self):
-        requirements = requires('egginfo-file')
-        self.assertIsNone(requirements)
-
-    def test_requires_egg_info(self):
-        deps = requires('egginfo-pkg')
-        assert len(deps) == 2
-        assert any(dep == 'wheel >= 1.0; python_version >= "2.7"' for dep in deps)
-
-    def test_requires_egg_info_empty(self):
-        fixtures.build_files(
-            {
-                'requires.txt': '',
-            },
-            self.site_dir.joinpath('egginfo_pkg.egg-info'),
-        )
-        deps = requires('egginfo-pkg')
-        assert deps == []
-
-    def test_requires_dist_info(self):
-        deps = requires('distinfo-pkg')
-        assert len(deps) == 2
-        assert all(deps)
-        assert 'wheel >= 1.0' in deps
-        assert "pytest; extra == 'test'" in deps
-
-    def test_more_complex_deps_requires_text(self):
-        requires = textwrap.dedent(
-            """
-            dep1
-            dep2
-
-            [:python_version < "3"]
-            dep3
-
-            [extra1]
-            dep4
-            dep6@ git+https://example.com/python/dep.git@v1.0.0
-
-            [extra2:python_version < "3"]
-            dep5
-            """
-        )
-        deps = sorted(Distribution._deps_from_requires_text(requires))
-        expected = [
-            'dep1',
-            'dep2',
-            'dep3; python_version < "3"',
-            'dep4; extra == "extra1"',
-            'dep5; (python_version < "3") and extra == "extra2"',
-            'dep6@ git+https://example.com/python/dep.git@v1.0.0 ; extra == "extra1"',
-        ]
-        # It's important that the environment marker expression be
-        # wrapped in parentheses to avoid the following 'and' binding more
-        # tightly than some other part of the environment expression.
-
-        assert deps == expected
-
-    def test_as_json(self):
-        md = metadata('distinfo-pkg').json
-        assert 'name' in md
-        assert md['keywords'] == ['sample', 'package']
-        desc = md['description']
-        assert desc.startswith('Once upon a time\nThere was')
-        assert len(md['requires_dist']) == 2
-
-    def test_as_json_egg_info(self):
-        md = metadata('egginfo-pkg').json
-        assert 'name' in md
-        assert md['keywords'] == ['sample', 'package']
-        desc = md['description']
-        assert desc.startswith('Once upon a time\nThere was')
-        assert len(md['classifier']) == 2
-
-    def test_as_json_odd_case(self):
-        self.make_uppercase()
-        md = metadata('distinfo-pkg').json
-        assert 'name' in md
-        assert len(md['requires_dist']) == 2
-        assert md['keywords'] == ['SAMPLE', 'PACKAGE']
-
-
-class LegacyDots(fixtures.DistInfoPkgWithDotLegacy, unittest.TestCase):
-    def test_name_normalization(self):
-        names = 'pkg.dot', 'pkg_dot', 'pkg-dot', 'pkg..dot', 'Pkg.Dot'
-        for name in names:
-            with self.subTest(name):
-                assert distribution(name).metadata['Name'] == 'pkg.dot'
-
-    def test_name_normalization_versionless_egg_info(self):
-        names = 'pkg.lot', 'pkg_lot', 'pkg-lot', 'pkg..lot', 'Pkg.Lot'
-        for name in names:
-            with self.subTest(name):
-                assert distribution(name).metadata['Name'] == 'pkg.lot'
-
-
-class OffSysPathTests(fixtures.DistInfoPkgOffPath, unittest.TestCase):
-    def test_find_distributions_specified_path(self):
-        dists = Distribution.discover(path=[str(self.site_dir)])
-        assert any(dist.metadata['Name'] == 'distinfo-pkg' for dist in dists)
-
-    def test_distribution_at_pathlib(self):
-        """Demonstrate how to load metadata direct from a directory."""
-        dist_info_path = self.site_dir / 'distinfo_pkg-1.0.0.dist-info'
-        dist = Distribution.at(dist_info_path)
-        assert dist.version == '1.0.0'
-
-    def test_distribution_at_str(self):
-        dist_info_path = self.site_dir / 'distinfo_pkg-1.0.0.dist-info'
-        dist = Distribution.at(str(dist_info_path))
-        assert dist.version == '1.0.0'
-
-
-class InvalidateCache(unittest.TestCase):
-    def test_invalidate_cache(self):
-        # No externally observable behavior, but ensures test coverage...
-        importlib.invalidate_caches()
diff --git a/Lib/test/test_importlib/test_namespace_pkgs.py b/Lib/test/test_importlib/test_namespace_pkgs.py
index 6ca0978f9bc..522ed9fa43f 100644
--- a/Lib/test/test_importlib/test_namespace_pkgs.py
+++ b/Lib/test/test_importlib/test_namespace_pkgs.py
@@ -318,6 +318,17 @@ def test_module_before_namespace_package(self):
         self.assertEqual(a_test.attr, 'in module')
 
 
+class NamespaceSubpackageSameName(NamespacePackageTest):
+    paths = ['']
+
+    def test_namespace_subpackage_shares_name_with_directory(self):
+        submodule_path = 'project4.foo'
+        with self.assertRaises(ModuleNotFoundError) as cm:
+            importlib.machinery.PathFinder.find_spec(submodule_path)
+
+        self.assertEqual(cm.exception.name, 'project4')
+
+
 class ReloadTests(NamespacePackageTest):
     paths = ['portion1']
 
diff --git a/Lib/test/test_importlib/test_pkg_import.py b/Lib/test/test_importlib/test_pkg_import.py
index 5ffae6222ba..287684efc85 100644
--- a/Lib/test/test_importlib/test_pkg_import.py
+++ b/Lib/test/test_importlib/test_pkg_import.py
@@ -39,9 +39,12 @@ def tearDown(self):
         self.remove_modules()
 
     def rewrite_file(self, contents):
-        compiled_path = cache_from_source(self.module_path)
-        if os.path.exists(compiled_path):
-            os.remove(compiled_path)
+        try:
+            compiled_path = cache_from_source(self.module_path)
+            if os.path.exists(compiled_path):
+                os.remove(compiled_path)
+        except NotImplementedError:
+            pass
         with open(self.module_path, 'w', encoding='utf-8') as f:
             f.write(contents)
 
diff --git a/Lib/test/test_importlib/test_spec.py b/Lib/test/test_importlib/test_spec.py
index aebeabaf83f..77b6228940c 100644
--- a/Lib/test/test_importlib/test_spec.py
+++ b/Lib/test/test_importlib/test_spec.py
@@ -52,7 +52,10 @@ class ModuleSpecTests:
     def setUp(self):
         self.name = 'spam'
         self.path = 'spam.py'
-        self.cached = self.util.cache_from_source(self.path)
+        try:
+            self.cached = self.util.cache_from_source(self.path)
+        except NotImplementedError:
+            self.cached = None
         self.loader = TestLoader()
         self.spec = self.machinery.ModuleSpec(self.name, self.loader)
         self.loc_spec = self.machinery.ModuleSpec(self.name, self.loader,
@@ -184,6 +187,8 @@ def test_cached_with_origin_not_location(self):
 
         self.assertIs(spec.cached, None)
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     "sys.implementation.cache_tag is None")
     def test_cached_source(self):
         expected = self.util.cache_from_source(self.path)
 
@@ -224,7 +229,10 @@ def bootstrap(self):
     def setUp(self):
         self.name = 'spam'
         self.path = 'spam.py'
-        self.cached = self.util.cache_from_source(self.path)
+        try:
+            self.cached = self.util.cache_from_source(self.path)
+        except NotImplementedError:
+            self.cached = None
         self.loader = TestLoader()
         self.spec = self.machinery.ModuleSpec(self.name, self.loader)
         self.loc_spec = self.machinery.ModuleSpec(self.name, self.loader,
@@ -287,20 +295,6 @@ def exec_module(self, module):
                 loaded = self.bootstrap._load(self.spec)
             self.assertNotIn(self.spec.name, sys.modules)
 
-    def test_load_legacy_attributes_immutable(self):
-        module = object()
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", ImportWarning)
-            class ImmutableLoader(TestLoader):
-                def load_module(self, name):
-                    sys.modules[name] = module
-                    return module
-            self.spec.loader = ImmutableLoader()
-            with CleanImport(self.spec.name):
-                loaded = self.bootstrap._load(self.spec)
-
-                self.assertIs(sys.modules[self.spec.name], module)
-
     # reload()
 
     def test_reload(self):
@@ -350,7 +344,6 @@ def test_reload_init_module_attrs(self):
         self.assertIs(loaded.__spec__, self.spec)
         self.assertNotHasAttr(loaded, '__path__')
         self.assertNotHasAttr(loaded, '__file__')
-        self.assertNotHasAttr(loaded, '__cached__')
 
 
 (Frozen_ModuleSpecMethodsTests,
@@ -364,7 +357,10 @@ class FactoryTests:
     def setUp(self):
         self.name = 'spam'
         self.path = os.path.abspath('spam.py')
-        self.cached = self.util.cache_from_source(self.path)
+        try:
+            self.cached = self.util.cache_from_source(self.path)
+        except NotImplementedError:
+            self.cached = None
         self.loader = TestLoader()
         self.fileloader = TestLoader(self.path)
         self.pkgloader = TestLoader(self.path, True)
diff --git a/Lib/test/test_importlib/test_threaded_import.py b/Lib/test/test_importlib/test_threaded_import.py
index 0e0d0721eb5..f68f1d83af7 100644
--- a/Lib/test/test_importlib/test_threaded_import.py
+++ b/Lib/test/test_importlib/test_threaded_import.py
@@ -326,6 +326,143 @@ def do_import(delay=0):
             # Neither thread should have errors about stale modules
             self.assertEqual(errors, [], f"Race condition detected: {errors}")
 
+    def test_hierarchical_import_deadlock(self):
+        # Regression test for bpo-38884 / gh-83065
+        # Tests that concurrent imports at different hierarchy levels
+        # don't deadlock when parent imports child in __init__.py
+
+        # Create package structure:
+        # package/__init__.py: from package import subpackage
+        # package/subpackage/__init__.py: from package.subpackage.module import *
+        # package/subpackage/module.py: class SomeClass: pass
+
+        pkg_dir = os.path.join(TESTFN, 'hier_deadlock_pkg')
+        os.makedirs(pkg_dir)
+        self.addCleanup(shutil.rmtree, TESTFN)
+
+        subpkg_dir = os.path.join(pkg_dir, 'subpackage')
+        os.makedirs(subpkg_dir)
+
+        with open(os.path.join(pkg_dir, "__init__.py"), "w") as f:
+            f.write("from hier_deadlock_pkg import subpackage\n")
+
+        with open(os.path.join(subpkg_dir, "__init__.py"), "w") as f:
+            f.write("from hier_deadlock_pkg.subpackage.module import *\n")
+
+        with open(os.path.join(subpkg_dir, "module.py"), "w") as f:
+            f.write("class SomeClass:\n    pass\n")
+
+        sys.path.insert(0, TESTFN)
+        self.addCleanup(sys.path.remove, TESTFN)
+        self.addCleanup(forget, 'hier_deadlock_pkg')
+        self.addCleanup(forget, 'hier_deadlock_pkg.subpackage')
+        self.addCleanup(forget, 'hier_deadlock_pkg.subpackage.module')
+
+        importlib.invalidate_caches()
+
+        errors = []
+        results = []
+        barrier = threading.Barrier(2)
+
+        def t1():
+            barrier.wait()
+            try:
+                import hier_deadlock_pkg.subpackage
+                results.append('t1_success')
+            except Exception as e:
+                errors.append(('t1', type(e).__name__, str(e)))
+
+        def t2():
+            barrier.wait()
+            try:
+                import hier_deadlock_pkg.subpackage.module
+                results.append('t2_success')
+            except Exception as e:
+                errors.append(('t2', type(e).__name__, str(e)))
+
+        # Run multiple times to increase chance of hitting race condition
+        for i in range(10):
+            for mod in ['hier_deadlock_pkg', 'hier_deadlock_pkg.subpackage',
+                       'hier_deadlock_pkg.subpackage.module']:
+                sys.modules.pop(mod, None)
+
+            errors.clear()
+            results.clear()
+            barrier.reset()
+
+            thread1 = threading.Thread(target=t1)
+            thread2 = threading.Thread(target=t2)
+
+            thread1.start()
+            thread2.start()
+
+            thread1.join(timeout=5)
+            thread2.join(timeout=5)
+
+            if thread1.is_alive() or thread2.is_alive():
+                self.fail(f"Threads deadlocked on iteration {i}")
+
+            self.assertEqual(
+                errors, [],
+                f"Import(s) failed on iteration {i}: {errors}")
+            self.assertEqual(
+                sorted(results), ['t1_success', 't2_success'],
+                f"Not all imports succeeded on iteration {i}: {results}")
+
+    def test_cross_package_circular_import(self):
+        # Two packages whose __init__.py each import a submodule of the
+        # other. Concurrent imports of submodules of each must not raise
+        # _DeadlockError; the import system accepts a partially-initialised
+        # parent in this case (see _lock_unlock_module).
+        os.makedirs(os.path.join(TESTFN, "circ_a"))
+        os.makedirs(os.path.join(TESTFN, "circ_b"))
+        self.addCleanup(shutil.rmtree, TESTFN)
+        with open(os.path.join(TESTFN, "circ_a", "__init__.py"), "w") as f:
+            f.write("import time; time.sleep(0.03)\nimport circ_b.other\n")
+        with open(os.path.join(TESTFN, "circ_b", "__init__.py"), "w") as f:
+            f.write("import time; time.sleep(0.03)\nimport circ_a.other\n")
+        for pkg in ("circ_a", "circ_b"):
+            for mod in ("sub.py", "other.py"):
+                with open(os.path.join(TESTFN, pkg, mod), "w") as f:
+                    f.write("X = 1\n")
+
+        sys.path.insert(0, TESTFN)
+        self.addCleanup(sys.path.remove, TESTFN)
+        for mod in ("circ_a", "circ_a.sub", "circ_a.other",
+                    "circ_b", "circ_b.sub", "circ_b.other"):
+            self.addCleanup(forget, mod)
+        importlib.invalidate_caches()
+
+        errors = []
+        barrier = threading.Barrier(2)
+
+        def do_import(name):
+            barrier.wait()
+            try:
+                importlib.import_module(name)
+            except Exception as e:
+                errors.append((name, type(e).__name__, str(e)))
+
+        for i in range(10):
+            for mod in ("circ_a", "circ_a.sub", "circ_a.other",
+                        "circ_b", "circ_b.sub", "circ_b.other"):
+                sys.modules.pop(mod, None)
+            errors.clear()
+            barrier.reset()
+
+            thread1 = threading.Thread(target=do_import, args=("circ_a.sub",))
+            thread2 = threading.Thread(target=do_import, args=("circ_b.sub",))
+            thread1.start()
+            thread2.start()
+            thread1.join(timeout=5)
+            thread2.join(timeout=5)
+
+            if thread1.is_alive() or thread2.is_alive():
+                self.fail(f"Threads deadlocked on iteration {i}")
+            self.assertEqual(
+                errors, [],
+                f"Import(s) failed on iteration {i}: {errors}")
+
 
 def setUpModule():
     thread_info = threading_helper.threading_setup()
diff --git a/Lib/test/test_importlib/test_util.py b/Lib/test/test_importlib/test_util.py
index 8c14b96271a..8a911c1b751 100644
--- a/Lib/test/test_importlib/test_util.py
+++ b/Lib/test/test_importlib/test_util.py
@@ -124,12 +124,6 @@ def test___file__(self):
         module = self.util.module_from_spec(spec)
         self.assertEqual(module.__file__, spec.origin)
 
-    def test___cached__(self):
-        spec = self.machinery.ModuleSpec('test', object())
-        spec.cached = 'some/path'
-        spec.has_location = True
-        module = self.util.module_from_spec(spec)
-        self.assertEqual(module.__cached__, spec.cached)
 
 (Frozen_ModuleFromSpecTests,
  Source_ModuleFromSpecTests
@@ -334,6 +328,17 @@ class PEP3147Tests:
 
     tag = sys.implementation.cache_tag
 
+    def setUp(self):
+        # Most of these tests assume the default (unset) pycache prefix, so
+        # clear it for the duration of the test (e.g. when the test suite is
+        # run with PYTHONPYCACHEPREFIX set).  Tests that need a specific prefix
+        # set their own via util.temporary_pycache_prefix().
+        self._orig_pycache_prefix = sys.pycache_prefix
+        sys.pycache_prefix = None
+
+    def tearDown(self):
+        sys.pycache_prefix = self._orig_pycache_prefix
+
     @unittest.skipIf(sys.implementation.cache_tag is None,
                      'requires sys.implementation.cache_tag not be None')
     def test_cache_from_source(self):
@@ -351,6 +356,8 @@ def test_cache_from_source_no_cache_tag(self):
             with self.assertRaises(NotImplementedError):
                 self.util.cache_from_source('whatever.py')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_cache_from_source_no_dot(self):
         # Directory with a dot, filename without dot.
         path = os.path.join('foo.bar', 'file')
@@ -359,47 +366,16 @@ def test_cache_from_source_no_dot(self):
         self.assertEqual(self.util.cache_from_source(path, optimization=''),
                          expect)
 
-    def test_cache_from_source_debug_override(self):
-        # Given the path to a .py file, return the path to its PEP 3147/PEP 488
-        # defined .pyc file (i.e. under __pycache__).
-        path = os.path.join('foo', 'bar', 'baz', 'qux.py')
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore')
-            self.assertEqual(self.util.cache_from_source(path, False),
-                             self.util.cache_from_source(path, optimization=1))
-            self.assertEqual(self.util.cache_from_source(path, True),
-                             self.util.cache_from_source(path, optimization=''))
-        with warnings.catch_warnings():
-            warnings.simplefilter('error')
-            with self.assertRaises(DeprecationWarning):
-                self.util.cache_from_source(path, False)
-            with self.assertRaises(DeprecationWarning):
-                self.util.cache_from_source(path, True)
-
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_cache_from_source_cwd(self):
         path = 'foo.py'
         expect = os.path.join('__pycache__', 'foo.{}.pyc'.format(self.tag))
         self.assertEqual(self.util.cache_from_source(path, optimization=''),
                          expect)
 
-    def test_cache_from_source_override(self):
-        # When debug_override is not None, it can be any true-ish or false-ish
-        # value.
-        path = os.path.join('foo', 'bar', 'baz.py')
-        # However if the bool-ishness can't be determined, the exception
-        # propagates.
-        class Bearish:
-            def __bool__(self): raise RuntimeError
-        with warnings.catch_warnings():
-            warnings.simplefilter('ignore')
-            self.assertEqual(self.util.cache_from_source(path, []),
-                             self.util.cache_from_source(path, optimization=1))
-            self.assertEqual(self.util.cache_from_source(path, [17]),
-                             self.util.cache_from_source(path, optimization=''))
-            with self.assertRaises(RuntimeError):
-                self.util.cache_from_source('/foo/bar/baz.py', Bearish())
-
-
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_cache_from_source_optimization_empty_string(self):
         # Setting 'optimization' to '' leads to no optimization tag (PEP 488).
         path = 'foo.py'
@@ -407,6 +383,8 @@ def test_cache_from_source_optimization_empty_string(self):
         self.assertEqual(self.util.cache_from_source(path, optimization=''),
                          expect)
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_cache_from_source_optimization_None(self):
         # Setting 'optimization' to None uses the interpreter's optimization.
         # (PEP 488)
@@ -423,6 +401,8 @@ def test_cache_from_source_optimization_None(self):
         self.assertEqual(self.util.cache_from_source(path, optimization=None),
                          expect)
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_cache_from_source_optimization_set(self):
         # The 'optimization' parameter accepts anything that has a string repr
         # that passes str.alnum().
@@ -440,6 +420,8 @@ def test_cache_from_source_optimization_set(self):
         with self.assertRaises(ValueError):
             self.util.cache_from_source(path, optimization='path/is/bad')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_cache_from_source_debug_override_optimization_both_set(self):
         # Can only set one of the optimization-related parameters.
         with warnings.catch_warnings():
@@ -449,6 +431,8 @@ def test_cache_from_source_debug_override_optimization_both_set(self):
 
     @unittest.skipUnless(os.sep == '\\' and os.altsep == '/',
                      'test meaningful only where os.altsep is defined')
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_sep_altsep_and_sep_cache_from_source(self):
         # Windows path and PEP 3147 where sep is right of altsep.
         self.assertEqual(
@@ -481,44 +465,60 @@ def test_source_from_cache_no_cache_tag(self):
             with self.assertRaises(NotImplementedError):
                 self.util.source_from_cache(path)
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_source_from_cache_bad_path(self):
         # When the path to a pyc file is not in PEP 3147 format, a ValueError
         # is raised.
         self.assertRaises(
             ValueError, self.util.source_from_cache, '/foo/bar/bazqux.pyc')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_source_from_cache_no_slash(self):
         # No slashes at all in path -> ValueError
         self.assertRaises(
             ValueError, self.util.source_from_cache, 'foo.cpython-32.pyc')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_source_from_cache_too_few_dots(self):
         # Too few dots in final path component -> ValueError
         self.assertRaises(
             ValueError, self.util.source_from_cache, '__pycache__/foo.pyc')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_source_from_cache_too_many_dots(self):
         with self.assertRaises(ValueError):
             self.util.source_from_cache(
                     '__pycache__/foo.cpython-32.opt-1.foo.pyc')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_source_from_cache_not_opt(self):
         # Non-`opt-` path component -> ValueError
         self.assertRaises(
             ValueError, self.util.source_from_cache,
             '__pycache__/foo.cpython-32.foo.pyc')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_source_from_cache_no__pycache__(self):
         # Another problem with the path -> ValueError
         self.assertRaises(
             ValueError, self.util.source_from_cache,
             '/foo/bar/foo.cpython-32.foo.pyc')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_source_from_cache_optimized_bytecode(self):
         # Optimized bytecode is not an issue.
         path = os.path.join('__pycache__', 'foo.{}.opt-1.pyc'.format(self.tag))
         self.assertEqual(self.util.source_from_cache(path), 'foo.py')
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag to not be None')
     def test_source_from_cache_missing_optimization(self):
         # An empty optimization level is a no-no.
         path = os.path.join('__pycache__', 'foo.{}.opt-.pyc'.format(self.tag))
@@ -633,7 +633,7 @@ class MagicNumberTests(unittest.TestCase):
         'only applies to candidate or final python release levels'
     )
     def test_magic_number(self):
-        # Each python minor release should generally have a MAGIC_NUMBER
+        # Each Python feature release should generally have a MAGIC_NUMBER
         # that does not change once the release reaches candidate status.
 
         # Once a release reaches candidate status, the value of the constant
@@ -643,11 +643,11 @@ def test_magic_number(self):
 
         # In exceptional cases, it may be required to change the MAGIC_NUMBER
         # for a maintenance release. In this case the change should be
-        # discussed in python-dev. If a change is required, community
+        # discussed in on Discourse. If a change is required, community
         # stakeholders such as OS package maintainers must be notified
         # in advance. Such exceptional releases will then require an
         # adjustment to this test case.
-        EXPECTED_MAGIC_NUMBER = 3627
+        EXPECTED_MAGIC_NUMBER = 3666
         actual = int.from_bytes(importlib.util.MAGIC_NUMBER[:2], 'little')
 
         msg = (
@@ -659,7 +659,7 @@ def test_magic_number(self):
             "magic number in this test to the current MAGIC_NUMBER to "
             "continue with the release.\n\n"
             "Changing the MAGIC_NUMBER for a maintenance release "
-            "requires discussion in python-dev and notification of "
+            "requires discussion on Discourse and notification of "
             "community stakeholders."
         )
         self.assertEqual(EXPECTED_MAGIC_NUMBER, actual, msg)
diff --git a/Lib/test/test_importlib/test_zip.py b/Lib/test/test_importlib/test_zip.py
deleted file mode 100644
index 276f6288c91..00000000000
--- a/Lib/test/test_importlib/test_zip.py
+++ /dev/null
@@ -1,62 +0,0 @@
-import sys
-import unittest
-
-from . import fixtures
-from importlib.metadata import (
-    PackageNotFoundError,
-    distribution,
-    distributions,
-    entry_points,
-    files,
-    version,
-)
-
-
-class TestZip(fixtures.ZipFixtures, unittest.TestCase):
-    def setUp(self):
-        super().setUp()
-        self._fixture_on_path('example-21.12-py3-none-any.whl')
-
-    def test_zip_version(self):
-        self.assertEqual(version('example'), '21.12')
-
-    def test_zip_version_does_not_match(self):
-        with self.assertRaises(PackageNotFoundError):
-            version('definitely-not-installed')
-
-    def test_zip_entry_points(self):
-        scripts = entry_points(group='console_scripts')
-        entry_point = scripts['example']
-        self.assertEqual(entry_point.value, 'example:main')
-        entry_point = scripts['Example']
-        self.assertEqual(entry_point.value, 'example:main')
-
-    def test_missing_metadata(self):
-        self.assertIsNone(distribution('example').read_text('does not exist'))
-
-    def test_case_insensitive(self):
-        self.assertEqual(version('Example'), '21.12')
-
-    def test_files(self):
-        for file in files('example'):
-            path = str(file.dist.locate_file(file))
-            assert '.whl/' in path, path
-
-    def test_one_distribution(self):
-        dists = list(distributions(path=sys.path[:1]))
-        assert len(dists) == 1
-
-
-class TestEgg(TestZip):
-    def setUp(self):
-        super().setUp()
-        self._fixture_on_path('example-21.12-py3.6.egg')
-
-    def test_files(self):
-        for file in files('example'):
-            path = str(file.dist.locate_file(file))
-            assert '.egg/' in path, path
-
-    def test_normalized_name(self):
-        dist = distribution('example')
-        assert dist._normalized_name == 'example'
diff --git a/Lib/test/test_importlib/util.py b/Lib/test/test_importlib/util.py
index 2eaefd68747..33f82e77396 100644
--- a/Lib/test/test_importlib/util.py
+++ b/Lib/test/test_importlib/util.py
@@ -294,6 +294,9 @@ def writes_bytecode_files(fxn):
     tests that require it to be set to False."""
     if sys.dont_write_bytecode:
         return unittest.skip("relies on writing bytecode")(fxn)
+    if sys.implementation.cache_tag is None:
+        return unittest.skip("requires sys.implementation.cache_tag to not be None")(fxn)
+
     @functools.wraps(fxn)
     def wrapper(*args, **kwargs):
         original = sys.dont_write_bytecode
diff --git a/Lib/test/test_importlib/zipdata01/ziptestdata.zip b/Lib/test/test_importlib/zipdata01/ziptestdata.zip
deleted file mode 100644
index 9a3bb0739f8..00000000000
Binary files a/Lib/test/test_importlib/zipdata01/ziptestdata.zip and /dev/null differ
diff --git a/Lib/test/test_importlib/zipdata02/ziptestdata.zip b/Lib/test/test_importlib/zipdata02/ziptestdata.zip
deleted file mode 100644
index d63ff512d28..00000000000
Binary files a/Lib/test/test_importlib/zipdata02/ziptestdata.zip and /dev/null differ
diff --git a/Lib/test/test_inspect/inspect_fodder3.py b/Lib/test/test_inspect/inspect_fodder3.py
new file mode 100644
index 00000000000..ea2481edf93
--- /dev/null
+++ b/Lib/test/test_inspect/inspect_fodder3.py
@@ -0,0 +1,39 @@
+from functools import cached_property
+
+# docstring in parent, inherited in child
+class ParentInheritDoc:
+    @cached_property
+    def foo(self):
+        """docstring for foo defined in parent"""
+
+class ChildInheritDoc(ParentInheritDoc):
+    pass
+
+class ChildInheritDefineDoc(ParentInheritDoc):
+    @cached_property
+    def foo(self):
+        pass
+
+# Redefine foo as something other than cached_property
+class ChildPropertyFoo(ParentInheritDoc):
+    @property
+    def foo(self):
+        """docstring for the property foo"""
+
+class ChildMethodFoo(ParentInheritDoc):
+    def foo(self):
+        """docstring for the method foo"""
+
+# docstring in child but not parent
+class ParentNoDoc:
+    @cached_property
+    def foo(self):
+        pass
+
+class ChildNoDoc(ParentNoDoc):
+    pass
+
+class ChildDefineDoc(ParentNoDoc):
+    @cached_property
+    def foo(self):
+        """docstring for foo defined in child"""
diff --git a/Lib/test/test_inspect/test_inspect.py b/Lib/test/test_inspect/test_inspect.py
index c7c9a2930ad..41fc33b7c89 100644
--- a/Lib/test/test_inspect/test_inspect.py
+++ b/Lib/test/test_inspect/test_inspect.py
@@ -47,6 +47,7 @@
 
 from test.test_inspect import inspect_fodder as mod
 from test.test_inspect import inspect_fodder2 as mod2
+from test.test_inspect import inspect_fodder3 as mod3
 from test.test_inspect import inspect_stringized_annotations
 from test.test_inspect import inspect_deferred_annotations
 
@@ -173,6 +174,15 @@ def __get__(self, instance, owner):
         return self.func.__get__(instance, owner)
 
 
+class TestImportTime(unittest.TestCase):
+
+    @cpython_only
+    def test_lazy_import(self):
+        import_helper.ensure_lazy_imports(
+            "inspect", {"re", "tokenize"}
+        )
+
+
 class TestPredicates(IsTestBase):
 
     def test_excluding_predicates(self):
@@ -689,10 +699,56 @@ def test_getdoc_inherited(self):
         self.assertEqual(inspect.getdoc(mod.FesteringGob.contradiction),
                          'The automatic gainsaying.')
 
+    @unittest.skipIf(sys.flags.optimize >= 2,
+                     "Docstrings are omitted with -O2 and above")
+    def test_getdoc_inherited_class_doc(self):
+        class A:
+            """Common base class"""
+        class B(A):
+            pass
+
+        a = A()
+        self.assertEqual(inspect.getdoc(A), 'Common base class')
+        self.assertEqual(inspect.getdoc(A, inherit_class_doc=False),
+                         'Common base class')
+        self.assertEqual(inspect.getdoc(a), 'Common base class')
+        self.assertIsNone(inspect.getdoc(a, fallback_to_class_doc=False))
+        a.__doc__ = 'Instance'
+        self.assertEqual(inspect.getdoc(a, fallback_to_class_doc=False),
+                          'Instance')
+
+        b = B()
+        self.assertEqual(inspect.getdoc(B), 'Common base class')
+        self.assertIsNone(inspect.getdoc(B, inherit_class_doc=False))
+        self.assertIsNone(inspect.getdoc(b))
+        self.assertIsNone(inspect.getdoc(b, fallback_to_class_doc=False))
+        b.__doc__ = 'Instance'
+        self.assertEqual(inspect.getdoc(b, fallback_to_class_doc=False), 'Instance')
+
+    def test_getdoc_inherited_cached_property(self):
+        doc = inspect.getdoc(mod3.ParentInheritDoc.foo)
+        self.assertEqual(doc, 'docstring for foo defined in parent')
+        self.assertEqual(inspect.getdoc(mod3.ChildInheritDoc.foo), doc)
+        self.assertEqual(inspect.getdoc(mod3.ChildInheritDefineDoc.foo), doc)
+
+    def test_getdoc_redefine_cached_property_as_other(self):
+        self.assertEqual(inspect.getdoc(mod3.ChildPropertyFoo.foo),
+                         'docstring for the property foo')
+        self.assertEqual(inspect.getdoc(mod3.ChildMethodFoo.foo),
+                         'docstring for the method foo')
+
+    def test_getdoc_define_cached_property(self):
+        self.assertEqual(inspect.getdoc(mod3.ChildDefineDoc.foo),
+                         'docstring for foo defined in child')
+
+    def test_getdoc_nodoc_inherited(self):
+        self.assertIsNone(inspect.getdoc(mod3.ChildNoDoc.foo))
+
     @unittest.skipIf(MISSING_C_DOCSTRINGS, "test requires docstrings")
     def test_finddoc(self):
         finddoc = inspect._finddoc
         self.assertEqual(finddoc(int), int.__doc__)
+        self.assertIsNone(finddoc(int, search_in_class=False))
         self.assertEqual(finddoc(int.to_bytes), int.to_bytes.__doc__)
         self.assertEqual(finddoc(int().to_bytes), int.to_bytes.__doc__)
         self.assertEqual(finddoc(int.from_bytes), int.from_bytes.__doc__)
@@ -1300,9 +1356,10 @@ def assertFullArgSpecEquals(self, routine, args_e, varargs_e=None,
                                     varkw_e=None, defaults_e=None,
                                     posonlyargs_e=[], kwonlyargs_e=[],
                                     kwonlydefaults_e=None,
-                                    ann_e={}):
+                                    ann_e={},
+                                    annotation_format=Format.VALUE):
         args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, ann = \
-            inspect.getfullargspec(routine)
+            inspect.getfullargspec(routine, annotation_format=annotation_format)
         self.assertEqual(args, args_e)
         self.assertEqual(varargs, varargs_e)
         self.assertEqual(varkw, varkw_e)
@@ -1335,6 +1392,19 @@ def test_getfullargspec(self):
                                      kwonlyargs_e=['e', 'f'],
                                      kwonlydefaults_e={'e': 4, 'f': 5})
 
+    def get_getfullargspec_with_undefined_names_in_annotations(self):
+        def my_func(a: undefined_name):
+            pass
+
+        with self.assertRaises(NameError):
+            inspect.getfullargspec(my_func)
+
+        self.assertFullArgSpecEquals(my_func, ['a'], ann_e={'a': 'undefined_name'},
+                                     annotation_format=Format.STRING)
+
+        arg_spec = inspect.getfullargspec(my_func, annotation_format=Format.FORWARDREF)
+        self.assertIsInstance(arg_spec.annotations['a'], ForwardRef)
+
     def test_argspec_api_ignores_wrapped(self):
         # Issue 20684: low level introspection API must ignore __wrapped__
         @functools.wraps(mod.spam)
@@ -6081,7 +6151,8 @@ def _test_builtin_methods_have_signatures(self, cls, no_signature, unsupported_s
                 self.assertRaises(ValueError, inspect.signature, getattr(cls, name))
 
     def test_builtins_have_signatures(self):
-        no_signature = {'type', 'super', 'bytearray', 'bytes', 'dict', 'int', 'str'}
+        no_signature = {'type', 'super', 'bytearray', 'bytes',
+                        'dict', 'frozendict', 'int', 'str'}
         # These need PEP 457 groups
         needs_groups = {"range", "slice", "dir", "getattr",
                         "next", "iter", "vars"}
@@ -6113,6 +6184,7 @@ def test_types_module_has_signatures(self):
             'AsyncGeneratorType': {'athrow'},
             'CoroutineType': {'throw'},
             'GeneratorType': {'throw'},
+            'FrameLocalsProxyType': {'setdefault', 'pop', 'get'},
         }
         self._test_module_has_signatures(types,
                 unsupported_signature=unsupported_signature,
@@ -6157,6 +6229,21 @@ def test_collections_abc_module_has_signatures(self):
         import collections.abc
         self._test_module_has_signatures(collections.abc)
 
+    def test_datetime_module_has_signatures(self):
+        # Only test if the C implementation is available.
+        import_helper.import_module('_datetime')
+        import datetime
+        no_signature = {'tzinfo'}
+        unsupported_signature = {'timezone'}
+        methods_unsupported_signature = {
+            'date': {'replace'},
+            'time': {'replace'},
+            'datetime': {'replace', 'combine'},
+        }
+        self._test_module_has_signatures(datetime,
+                no_signature, unsupported_signature,
+                methods_unsupported_signature=methods_unsupported_signature)
+
     def test_errno_module_has_signatures(self):
         import errno
         self._test_module_has_signatures(errno)
@@ -6169,8 +6256,7 @@ def test_faulthandler_module_has_signatures(self):
         self._test_module_has_signatures(faulthandler, unsupported_signature=unsupported_signature)
 
     def test_functools_module_has_signatures(self):
-        unsupported_signature = {"reduce"}
-        self._test_module_has_signatures(functools, unsupported_signature=unsupported_signature)
+        self._test_module_has_signatures(functools)
 
     def test_gc_module_has_signatures(self):
         import gc
@@ -6214,7 +6300,10 @@ def test_pwd_module_has_signatures(self):
 
     def test_re_module_has_signatures(self):
         import re
-        methods_no_signature = {'Match': {'group'}}
+        methods_no_signature = {
+                'Match': {'group'},
+                'Pattern': {'match'},  # It is now an alias for prefixmatch
+        }
         self._test_module_has_signatures(re,
                 methods_no_signature=methods_no_signature,
                 good_exceptions={'error', 'PatternError'})
@@ -6227,6 +6316,10 @@ def test_stat_module_has_signatures(self):
         import stat
         self._test_module_has_signatures(stat)
 
+    def test_struct_module_has_signatures(self):
+        import struct
+        self._test_module_has_signatures(struct)
+
     def test_string_module_has_signatures(self):
         import string
         self._test_module_has_signatures(string)
@@ -6284,7 +6377,7 @@ def test_typing_module_has_signatures(self):
                 methods_unsupported_signature=methods_unsupported_signature)
 
     def test_warnings_module_has_signatures(self):
-        unsupported_signature = {'warn', 'warn_explicit'}
+        unsupported_signature = {'warn_explicit'}
         self._test_module_has_signatures(warnings, unsupported_signature=unsupported_signature)
 
     def test_weakref_module_has_signatures(self):
@@ -6415,8 +6508,19 @@ def test_wrapped_descriptor(self):
         self.assertIs(inspect.unwrap(staticmethod(classmethod)), classmethod)
         self.assertIs(inspect.unwrap(classmethod(staticmethod)), staticmethod)
 
+def _clean_object_ids(text):
+    # Helper to handle "<obj at 0x...>" details in CLI output checks
+    import re
+    detect = r"object at 0x([0-9A-Fa-f]+)>"
+    replace = "object at 0x...>"
+    return re.sub(detect, replace, text)
+
+class TestModuleCLI(unittest.TestCase):
+
+    BUILTIN_ERROR = "No source code available for builtin module"
+    NO_SOURCE_ERROR = "No source code available for defining module"
+    NO_SOURCE_TARGET_ERROR = "Failed to retrieve source code for given target"
 
-class TestMain(unittest.TestCase):
     @staticmethod
     def _expected_cached(module):
         # assert_python_ok() runs the subprocess in isolated mode (-I), which
@@ -6457,27 +6561,228 @@ def test_qualname_source(self):
                          inspect.getsource(ThreadPoolExecutor).splitlines())
         self.assertEqual(err, b'')
 
-    def test_builtins(self):
+    def test_error_builtins(self):
         _, out, err = assert_python_failure('-m', 'inspect',
                                             'sys')
         lines = err.decode().splitlines()
-        self.assertEqual(lines, ["Can't get info for builtin modules."])
+        self.assertEqual(lines, [self.BUILTIN_ERROR])
+
+    @unittest.skipIf(importlib.util.find_spec("_testcapi") is None, "TODO: RUSTPYTHON; _testcapi extension fixture is unavailable")
+    def test_error_extension(self):
+        module_name = "_testcapi"
+        if module_name in sys.builtin_module_names:
+            # WASI test environment has even _testcapi as a builtin module
+            expected_error = self.BUILTIN_ERROR
+        else:
+            expected_error = self.NO_SOURCE_ERROR
+        _, out, err = assert_python_failure('-m', 'inspect',
+                                            module_name)
+        lines = err.decode().splitlines()
+        self.assertEqual(lines, [expected_error])
 
-    def test_details(self):
-        module = importlib.import_module('unittest')
+    def test_error_data(self):
+        _, out, err = assert_python_failure('-m', 'inspect',
+                                            'importlib.machinery:SOURCE_SUFFIXES')
+        lines = err.decode().splitlines()
+        self.assertEqual(lines, [self.NO_SOURCE_TARGET_ERROR])
+
+    def test_details_option_with_package(self):
+        module_name = 'unittest'
+        module = importlib.import_module(module_name)
         args = support.optim_args_from_interpreter_flags()
         rc, out, err = assert_python_ok(*args, '-m', 'inspect',
-                                        'unittest', '--details')
-        output = out.decode()
+                                        module_name, '--details')
         cached = self._expected_cached(module)
-        # Just a quick sanity check on the output
-        self.assertIn(module.__spec__.name, output)
-        self.assertIn(module.__name__, output)
-        self.assertIn(module.__spec__.origin, output)
-        self.assertIn(module.__file__, output)
-        self.assertIn(cached, output)
+        # Full rendering check on the expected output
+        expected_lines = [
+            f"Target: {module.__name__}",  # No aliasing
+            f"Origin: {module.__spec__.origin}",
+            f"Source: {module.__file__}",
+            f"Cached: {cached}",  # None is still displayed
+            f"Loader: {_clean_object_ids(repr(module.__spec__.loader))}",
+            f"Submodule search paths: {module.__path__}",
+            "",
+        ]
+        output_lines = _clean_object_ids(out.decode()).splitlines()
+        self.assertEqual(output_lines, expected_lines)
         self.assertEqual(err, b'')
 
+    def test_details_option_with_builtin_module(self):
+        # Also an end-to-end test of non-package lookups
+        module_name = 'sys'
+        module = importlib.import_module(module_name)
+        args = support.optim_args_from_interpreter_flags()
+        rc, out, err = assert_python_ok(*args, '-m', 'inspect',
+                                        module_name, '--details')
+        # Full rendering check on the expected output
+        # No error is reported when just fetching the module details
+        expected_lines = [
+            f"Target: {module.__name__}",  # No aliasing
+            f"Origin: {module.__spec__.origin}",
+            "Source: None",
+            "Cached: None",
+            f"Loader: {_clean_object_ids(repr(module.__spec__.loader))}",
+            "",
+        ]
+        output_lines = _clean_object_ids(out.decode()).splitlines()
+        self.assertEqual(output_lines, expected_lines)
+        self.assertEqual(err, b'')
+
+    def test_details_option_with_data_target(self):
+        # Also an end-to-end test of non-module lookups without aliasing
+        module_name = 'importlib.machinery'
+        cli_target = f"{module_name}:SOURCE_SUFFIXES"
+        module = importlib.import_module(module_name)
+        args = support.optim_args_from_interpreter_flags()
+        rc, out, err = assert_python_ok(*args, '-m', 'inspect',
+                                        cli_target, '--details')
+        cached = self._expected_cached(module)
+        # Full rendering check on the expected output
+        # The error is only informational when reading source details
+        expected_lines = [
+            f"Target: {cli_target}",  # No aliasing
+            f"Origin: {module.__spec__.origin}",
+            f"Source: {module.__file__}",
+            f"Cached: {cached}",  # None is still displayed
+            self.NO_SOURCE_TARGET_ERROR,
+            "",
+        ]
+        output_lines = out.decode().splitlines()
+        self.assertEqual(output_lines, expected_lines)
+        self.assertEqual(err, b'')
+
+    @unittest.skipIf(not os.path.exists(os.path.__file__), "Needs frozen source file")
+    def test_details_option_with_aliased_target(self):
+        # Also an end-to-end test of successful non-module lookups
+        module = importlib.import_module("os.path")
+        target = module.join
+        cli_target = "os:path.join"  # Defining module is os.path, not os
+        defining_target = f"{target.__module__}:{target.__qualname__}"
+
+        args = support.optim_args_from_interpreter_flags()
+        rc, out, err = assert_python_ok(*args, '-m', 'inspect',
+                                        cli_target, '--details')
+        cached = self._expected_cached(module)
+        # Full rendering check on the expected output
+        expected_lines = [
+            f'Target: {defining_target} (looked up as "{cli_target}")',
+            f"Origin: {module.__spec__.origin}",
+            f"Source: {module.__file__}",
+            f"Cached: {cached}",  # None is still displayed
+            f"Line: {inspect.findsource(target)[1]}",
+            "",
+        ]
+        output_lines = out.decode().splitlines()
+        self.assertEqual(output_lines, expected_lines)
+        self.assertEqual(err, b'')
+
+    def _check_details(self, module, details, other_expected_keys=(), *, alias=None, error=None):
+        expected_keys = {"target", "origin", "source", "cached"}
+        if other_expected_keys:
+            expected_keys |= other_expected_keys
+        if alias is not None:
+            expected_keys.add("alias")
+        if error is not None:
+            expected_keys.add("error")
+        self.assertEqual(set(details.keys()), expected_keys)
+        self.assertEqual(module.__spec__.origin, details["origin"])
+        try:
+            expected_source = inspect.getsourcefile(module)
+        except Exception:
+            expected_source = None
+        if expected_source and expected_source.startswith("<frozen"):
+            # Check special case for frozen modules
+            expected_source = module.__file__
+        self.assertEqual(expected_source, details["source"])
+        self.assertEqual(module.__spec__.cached, details["cached"])
+        if "loader" in other_expected_keys:
+            self.assertEqual(repr(module.__spec__.loader), details["loader"])
+        if "submodule_paths" in other_expected_keys:
+            self.assertEqual(repr(module.__path__), details["submodule_paths"])
+        if alias is not None:
+            self.assertEqual(details["alias"], alias)
+            self.assertNotEqual(details["target"], alias)
+        if error is not None:
+            self.assertEqual(details["error"], error)
+
+    def test_get_cli_details_for_source_module(self):
+        module_name = "inspect"
+        module = importlib.import_module(module_name)
+        details = inspect._get_details_for_cli(module, module_name, module)
+        self._check_details(module, details, {"loader"})
+        target = module.signature
+        nominal_target = f"{module_name}:{target.__qualname__}"
+        details = inspect._get_details_for_cli(module, nominal_target, target)
+        self._check_details(module, details, {"lineno"})
+        self.assertEqual(inspect.findsource(target)[1], details["lineno"])
+
+    def test_get_cli_details_for_source_package(self):
+        module_name = "importlib"
+        module = importlib.import_module(module_name)
+        details = inspect._get_details_for_cli(module, module_name, module)
+        self._check_details(module, details, {"loader", "submodule_paths"})
+        target = module.import_module  # Assumes this is not re-exported
+        nominal_target = f"{module_name}:{target.__qualname__}"
+        details = inspect._get_details_for_cli(module, nominal_target, target)
+        self._check_details(module, details, {"lineno"})
+        self.assertEqual(inspect.findsource(target)[1], details["lineno"])
+
+    def test_get_cli_details_for_builtin_module(self):
+        expected_error = self.BUILTIN_ERROR
+        module_name = "sys"
+        module = importlib.import_module(module_name)
+        details = inspect._get_details_for_cli(module, module_name, module)
+        self._check_details(module, details, {"loader"}, error=expected_error)
+        target = module.exit
+        nominal_target = f"{module_name}:{target.__qualname__}"
+        details = inspect._get_details_for_cli(module, nominal_target, target)
+        self._check_details(module, details, error=expected_error)
+
+    def test_get_cli_details_for_frozen_module(self):
+        # Source is actually available for this frozen module, as
+        # __file__ refers to the location of importlib._bootstrap
+        module_name = "_frozen_importlib"
+        module = importlib.import_module(module_name)
+        details = inspect._get_details_for_cli(module, module_name, module)
+        self._check_details(module, details, {"loader"}, alias=module_name)
+        target = module.__import__
+        nominal_target = f"{module_name}:{target.__qualname__}"
+        details = inspect._get_details_for_cli(module, nominal_target, target)
+        self._check_details(module, details, {"lineno"}, alias=nominal_target)
+        self.assertEqual(inspect.findsource(target)[1], details["lineno"])
+
+    @unittest.skipIf(importlib.util.find_spec("_testcapi") is None, "TODO: RUSTPYTHON; _testcapi extension fixture is unavailable")
+    def test_get_cli_details_for_extension_module(self):
+        module_name = "_testcapi"
+        if module_name in sys.builtin_module_names:
+            # WASI test environment has even _testcapi as a builtin module
+            expected_error = self.BUILTIN_ERROR
+        else:
+            expected_error = self.NO_SOURCE_ERROR
+        module = importlib.import_module(module_name)
+        details = inspect._get_details_for_cli(module, module_name, module)
+        self._check_details(module, details, {"loader"}, error=expected_error)
+        target = module.fatal_error
+        nominal_target = f"{module_name}:{target.__qualname__}"
+        details = inspect._get_details_for_cli(module, nominal_target, target)
+        self._check_details(module, details, error=expected_error)
+
+    @unittest.skipIf(not os.path.exists(os.path.__file__), "Needs frozen source file")
+    def test_get_cli_details_for_aliased_module(self):
+        # os.path is an alias for a platform dependent implementation module
+        # Test is skipped if the source file is missing (as the output changes),
+        # which may happen if running the test suite after deployment.
+        module_name = "os.path"
+        module = importlib.import_module(module_name)
+        details = inspect._get_details_for_cli(module, module_name, module)
+        self._check_details(module, details, {"loader"}, alias=module_name)
+        nominal_module = importlib.import_module("os")
+        nominal_target = "os:path.join"
+        target = module.join
+        details = inspect._get_details_for_cli(nominal_module, nominal_target, target)
+        self._check_details(module, details, {"lineno"}, alias=nominal_target)
+        self.assertEqual(inspect.findsource(target)[1], details["lineno"])
+
 
 class TestReload(unittest.TestCase):
 
@@ -6518,12 +6823,14 @@ def spawn_repl(self, *args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **
         object.
         """
 
+        # TODO(picnixz): refactor this as it's used by test_repl.py
+
         # To run the REPL without using a terminal, spawn python with the command
         # line option '-i' and the process name set to '<stdin>'.
         # The directory of argv[0] must match the directory of the Python
         # executable for the Popen() call to python to succeed as the directory
-        # path may be used by Py_GetPath() to build the default module search
-        # path.
+        # path may be used by PyConfig_Get("module_search_paths") to build the
+        # default module search path.
         stdin_fname = os.path.join(os.path.dirname(sys.executable), "<stdin>")
         cmd_line = [stdin_fname, '-E', '-i']
         cmd_line.extend(args)
@@ -6568,7 +6875,5 @@ def f():
         self.assertIn(expected, output)
 
 
-
-
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
deleted file mode 100644
index 212cbaa324f..00000000000
--- a/Lib/test/test_io.py
+++ /dev/null
@@ -1,5129 +0,0 @@
-"""Unit tests for the io module."""
-
-# Tests of io are scattered over the test suite:
-# * test_bufio - tests file buffering
-# * test_memoryio - tests BytesIO and StringIO
-# * test_fileio - tests FileIO
-# * test_file - tests the file interface
-# * test_io - tests everything else in the io module
-# * test_univnewlines - tests universal newline support
-# * test_largefile - tests operations on a file greater than 2**32 bytes
-#     (only enabled with -ulargefile)
-
-################################################################################
-# ATTENTION TEST WRITERS!!!
-################################################################################
-# When writing tests for io, it's important to test both the C and Python
-# implementations. This is usually done by writing a base test that refers to
-# the type it is testing as an attribute. Then it provides custom subclasses to
-# test both implementations. This file has lots of examples.
-################################################################################
-
-import abc
-import array
-import errno
-import locale
-import os
-import pickle
-import random
-import signal
-import sys
-import textwrap
-import threading
-import time
-import unittest
-import warnings
-import weakref
-from collections import deque, UserList
-from itertools import cycle, count
-from test import support
-from test.support.script_helper import (
-    assert_python_ok, assert_python_failure, run_python_until_end)
-from test.support import (
-    import_helper, is_apple, os_helper, threading_helper, warnings_helper,
-)
-from test.support.os_helper import FakePath
-
-import codecs
-import io  # C implementation of io
-import _pyio as pyio # Python implementation of io
-
-try:
-    import ctypes
-except ImportError:
-    def byteslike(*pos, **kw):
-        return array.array("b", bytes(*pos, **kw))
-else:
-    def byteslike(*pos, **kw):
-        """Create a bytes-like object having no string or sequence methods"""
-        data = bytes(*pos, **kw)
-        obj = EmptyStruct()
-        ctypes.resize(obj, len(data))
-        memoryview(obj).cast("B")[:] = data
-        return obj
-    class EmptyStruct(ctypes.Structure):
-        pass
-
-
-def _default_chunk_size():
-    """Get the default TextIOWrapper chunk size"""
-    with open(__file__, "r", encoding="latin-1") as f:
-        return f._CHUNK_SIZE
-
-requires_alarm = unittest.skipUnless(
-    hasattr(signal, "alarm"), "test requires signal.alarm()"
-)
-
-
-class BadIndex:
-    def __index__(self):
-        1/0
-
-class MockRawIOWithoutRead:
-    """A RawIO implementation without read(), so as to exercise the default
-    RawIO.read() which calls readinto()."""
-
-    def __init__(self, read_stack=()):
-        self._read_stack = list(read_stack)
-        self._write_stack = []
-        self._reads = 0
-        self._extraneous_reads = 0
-
-    def write(self, b):
-        self._write_stack.append(bytes(b))
-        return len(b)
-
-    def writable(self):
-        return True
-
-    def fileno(self):
-        return 42
-
-    def readable(self):
-        return True
-
-    def seekable(self):
-        return True
-
-    def seek(self, pos, whence):
-        return 0   # wrong but we gotta return something
-
-    def tell(self):
-        return 0   # same comment as above
-
-    def readinto(self, buf):
-        self._reads += 1
-        max_len = len(buf)
-        try:
-            data = self._read_stack[0]
-        except IndexError:
-            self._extraneous_reads += 1
-            return 0
-        if data is None:
-            del self._read_stack[0]
-            return None
-        n = len(data)
-        if len(data) <= max_len:
-            del self._read_stack[0]
-            buf[:n] = data
-            return n
-        else:
-            buf[:] = data[:max_len]
-            self._read_stack[0] = data[max_len:]
-            return max_len
-
-    def truncate(self, pos=None):
-        return pos
-
-class CMockRawIOWithoutRead(MockRawIOWithoutRead, io.RawIOBase):
-    pass
-
-class PyMockRawIOWithoutRead(MockRawIOWithoutRead, pyio.RawIOBase):
-    pass
-
-
-class MockRawIO(MockRawIOWithoutRead):
-
-    def read(self, n=None):
-        self._reads += 1
-        try:
-            return self._read_stack.pop(0)
-        except:
-            self._extraneous_reads += 1
-            return b""
-
-class CMockRawIO(MockRawIO, io.RawIOBase):
-    pass
-
-class PyMockRawIO(MockRawIO, pyio.RawIOBase):
-    pass
-
-
-class MisbehavedRawIO(MockRawIO):
-    def write(self, b):
-        return super().write(b) * 2
-
-    def read(self, n=None):
-        return super().read(n) * 2
-
-    def seek(self, pos, whence):
-        return -123
-
-    def tell(self):
-        return -456
-
-    def readinto(self, buf):
-        super().readinto(buf)
-        return len(buf) * 5
-
-class CMisbehavedRawIO(MisbehavedRawIO, io.RawIOBase):
-    pass
-
-class PyMisbehavedRawIO(MisbehavedRawIO, pyio.RawIOBase):
-    pass
-
-
-class SlowFlushRawIO(MockRawIO):
-    def __init__(self):
-        super().__init__()
-        self.in_flush = threading.Event()
-
-    def flush(self):
-        self.in_flush.set()
-        time.sleep(0.25)
-
-class CSlowFlushRawIO(SlowFlushRawIO, io.RawIOBase):
-    pass
-
-class PySlowFlushRawIO(SlowFlushRawIO, pyio.RawIOBase):
-    pass
-
-
-class CloseFailureIO(MockRawIO):
-    closed = 0
-
-    def close(self):
-        if not self.closed:
-            self.closed = 1
-            raise OSError
-
-class CCloseFailureIO(CloseFailureIO, io.RawIOBase):
-    pass
-
-class PyCloseFailureIO(CloseFailureIO, pyio.RawIOBase):
-    pass
-
-
-class MockFileIO:
-
-    def __init__(self, data):
-        self.read_history = []
-        super().__init__(data)
-
-    def read(self, n=None):
-        res = super().read(n)
-        self.read_history.append(None if res is None else len(res))
-        return res
-
-    def readinto(self, b):
-        res = super().readinto(b)
-        self.read_history.append(res)
-        return res
-
-class CMockFileIO(MockFileIO, io.BytesIO):
-    pass
-
-class PyMockFileIO(MockFileIO, pyio.BytesIO):
-    pass
-
-
-class MockUnseekableIO:
-    def seekable(self):
-        return False
-
-    def seek(self, *args):
-        raise self.UnsupportedOperation("not seekable")
-
-    def tell(self, *args):
-        raise self.UnsupportedOperation("not seekable")
-
-    def truncate(self, *args):
-        raise self.UnsupportedOperation("not seekable")
-
-class CMockUnseekableIO(MockUnseekableIO, io.BytesIO):
-    UnsupportedOperation = io.UnsupportedOperation
-
-class PyMockUnseekableIO(MockUnseekableIO, pyio.BytesIO):
-    UnsupportedOperation = pyio.UnsupportedOperation
-
-
-class MockCharPseudoDevFileIO(MockFileIO):
-    # GH-95782
-    # ftruncate() does not work on these special files (and CPython then raises
-    # appropriate exceptions), so truncate() does not have to be accounted for
-    # here.
-    def __init__(self, data):
-        super().__init__(data)
-
-    def seek(self, *args):
-        return 0
-
-    def tell(self, *args):
-        return 0
-
-class CMockCharPseudoDevFileIO(MockCharPseudoDevFileIO, io.BytesIO):
-    pass
-
-class PyMockCharPseudoDevFileIO(MockCharPseudoDevFileIO, pyio.BytesIO):
-    pass
-
-
-class MockNonBlockWriterIO:
-
-    def __init__(self):
-        self._write_stack = []
-        self._blocker_char = None
-
-    def pop_written(self):
-        s = b"".join(self._write_stack)
-        self._write_stack[:] = []
-        return s
-
-    def block_on(self, char):
-        """Block when a given char is encountered."""
-        self._blocker_char = char
-
-    def readable(self):
-        return True
-
-    def seekable(self):
-        return True
-
-    def seek(self, pos, whence=0):
-        # naive implementation, enough for tests
-        return 0
-
-    def writable(self):
-        return True
-
-    def write(self, b):
-        b = bytes(b)
-        n = -1
-        if self._blocker_char:
-            try:
-                n = b.index(self._blocker_char)
-            except ValueError:
-                pass
-            else:
-                if n > 0:
-                    # write data up to the first blocker
-                    self._write_stack.append(b[:n])
-                    return n
-                else:
-                    # cancel blocker and indicate would block
-                    self._blocker_char = None
-                    return None
-        self._write_stack.append(b)
-        return len(b)
-
-class CMockNonBlockWriterIO(MockNonBlockWriterIO, io.RawIOBase):
-    BlockingIOError = io.BlockingIOError
-
-class PyMockNonBlockWriterIO(MockNonBlockWriterIO, pyio.RawIOBase):
-    BlockingIOError = pyio.BlockingIOError
-
-
-class IOTest(unittest.TestCase):
-
-    def setUp(self):
-        os_helper.unlink(os_helper.TESTFN)
-
-    def tearDown(self):
-        os_helper.unlink(os_helper.TESTFN)
-
-    def write_ops(self, f):
-        self.assertEqual(f.write(b"blah."), 5)
-        f.truncate(0)
-        self.assertEqual(f.tell(), 5)
-        f.seek(0)
-
-        self.assertEqual(f.write(b"blah."), 5)
-        self.assertEqual(f.seek(0), 0)
-        self.assertEqual(f.write(b"Hello."), 6)
-        self.assertEqual(f.tell(), 6)
-        self.assertEqual(f.seek(-1, 1), 5)
-        self.assertEqual(f.tell(), 5)
-        buffer = bytearray(b" world\n\n\n")
-        self.assertEqual(f.write(buffer), 9)
-        buffer[:] = b"*" * 9  # Overwrite our copy of the data
-        self.assertEqual(f.seek(0), 0)
-        self.assertEqual(f.write(b"h"), 1)
-        self.assertEqual(f.seek(-1, 2), 13)
-        self.assertEqual(f.tell(), 13)
-
-        self.assertEqual(f.truncate(12), 12)
-        self.assertEqual(f.tell(), 13)
-        self.assertRaises(TypeError, f.seek, 0.0)
-
-    def read_ops(self, f, buffered=False):
-        data = f.read(5)
-        self.assertEqual(data, b"hello")
-        data = byteslike(data)
-        self.assertEqual(f.readinto(data), 5)
-        self.assertEqual(bytes(data), b" worl")
-        data = bytearray(5)
-        self.assertEqual(f.readinto(data), 2)
-        self.assertEqual(len(data), 5)
-        self.assertEqual(data[:2], b"d\n")
-        self.assertEqual(f.seek(0), 0)
-        self.assertEqual(f.read(20), b"hello world\n")
-        self.assertEqual(f.read(1), b"")
-        self.assertEqual(f.readinto(byteslike(b"x")), 0)
-        self.assertEqual(f.seek(-6, 2), 6)
-        self.assertEqual(f.read(5), b"world")
-        self.assertEqual(f.read(0), b"")
-        self.assertEqual(f.readinto(byteslike()), 0)
-        self.assertEqual(f.seek(-6, 1), 5)
-        self.assertEqual(f.read(5), b" worl")
-        self.assertEqual(f.tell(), 10)
-        self.assertRaises(TypeError, f.seek, 0.0)
-        if buffered:
-            f.seek(0)
-            self.assertEqual(f.read(), b"hello world\n")
-            f.seek(6)
-            self.assertEqual(f.read(), b"world\n")
-            self.assertEqual(f.read(), b"")
-            f.seek(0)
-            data = byteslike(5)
-            self.assertEqual(f.readinto1(data), 5)
-            self.assertEqual(bytes(data), b"hello")
-
-    LARGE = 2**31
-
-    def large_file_ops(self, f):
-        assert f.readable()
-        assert f.writable()
-        try:
-            self.assertEqual(f.seek(self.LARGE), self.LARGE)
-        except (OverflowError, ValueError):
-            self.skipTest("no largefile support")
-        self.assertEqual(f.tell(), self.LARGE)
-        self.assertEqual(f.write(b"xxx"), 3)
-        self.assertEqual(f.tell(), self.LARGE + 3)
-        self.assertEqual(f.seek(-1, 1), self.LARGE + 2)
-        self.assertEqual(f.truncate(), self.LARGE + 2)
-        self.assertEqual(f.tell(), self.LARGE + 2)
-        self.assertEqual(f.seek(0, 2), self.LARGE + 2)
-        self.assertEqual(f.truncate(self.LARGE + 1), self.LARGE + 1)
-        self.assertEqual(f.tell(), self.LARGE + 2)
-        self.assertEqual(f.seek(0, 2), self.LARGE + 1)
-        self.assertEqual(f.seek(-1, 2), self.LARGE)
-        self.assertEqual(f.read(2), b"x")
-
-    def test_invalid_operations(self):
-        # Try writing on a file opened in read mode and vice-versa.
-        exc = self.UnsupportedOperation
-        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as fp:
-            self.assertRaises(exc, fp.read)
-            self.assertRaises(exc, fp.readline)
-        with self.open(os_helper.TESTFN, "wb") as fp:
-            self.assertRaises(exc, fp.read)
-            self.assertRaises(exc, fp.readline)
-        with self.open(os_helper.TESTFN, "wb", buffering=0) as fp:
-            self.assertRaises(exc, fp.read)
-            self.assertRaises(exc, fp.readline)
-        with self.open(os_helper.TESTFN, "rb", buffering=0) as fp:
-            self.assertRaises(exc, fp.write, b"blah")
-            self.assertRaises(exc, fp.writelines, [b"blah\n"])
-        with self.open(os_helper.TESTFN, "rb") as fp:
-            self.assertRaises(exc, fp.write, b"blah")
-            self.assertRaises(exc, fp.writelines, [b"blah\n"])
-        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as fp:
-            self.assertRaises(exc, fp.write, "blah")
-            self.assertRaises(exc, fp.writelines, ["blah\n"])
-            # Non-zero seeking from current or end pos
-            self.assertRaises(exc, fp.seek, 1, self.SEEK_CUR)
-            self.assertRaises(exc, fp.seek, -1, self.SEEK_END)
-
-    @support.cpython_only
-    def test_startup_optimization(self):
-        # gh-132952: Test that `io` is not imported at startup and that the
-        # __module__ of UnsupportedOperation is set to "io".
-        assert_python_ok("-S", "-c", textwrap.dedent(
-            """
-            import sys
-            assert "io" not in sys.modules
-            try:
-                sys.stdin.truncate()
-            except Exception as e:
-                typ = type(e)
-                assert typ.__module__ == "io", (typ, typ.__module__)
-                assert typ.__name__ == "UnsupportedOperation", (typ, typ.__name__)
-            else:
-                raise AssertionError("Expected UnsupportedOperation")
-            """
-        ))
-
-    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
-    def test_optional_abilities(self):
-        # Test for OSError when optional APIs are not supported
-        # The purpose of this test is to try fileno(), reading, writing and
-        # seeking operations with various objects that indicate they do not
-        # support these operations.
-
-        def pipe_reader():
-            [r, w] = os.pipe()
-            os.close(w)  # So that read() is harmless
-            return self.FileIO(r, "r")
-
-        def pipe_writer():
-            [r, w] = os.pipe()
-            self.addCleanup(os.close, r)
-            # Guarantee that we can write into the pipe without blocking
-            thread = threading.Thread(target=os.read, args=(r, 100))
-            thread.start()
-            self.addCleanup(thread.join)
-            return self.FileIO(w, "w")
-
-        def buffered_reader():
-            return self.BufferedReader(self.MockUnseekableIO())
-
-        def buffered_writer():
-            return self.BufferedWriter(self.MockUnseekableIO())
-
-        def buffered_random():
-            return self.BufferedRandom(self.BytesIO())
-
-        def buffered_rw_pair():
-            return self.BufferedRWPair(self.MockUnseekableIO(),
-                self.MockUnseekableIO())
-
-        def text_reader():
-            class UnseekableReader(self.MockUnseekableIO):
-                writable = self.BufferedIOBase.writable
-                write = self.BufferedIOBase.write
-            return self.TextIOWrapper(UnseekableReader(), "ascii")
-
-        def text_writer():
-            class UnseekableWriter(self.MockUnseekableIO):
-                readable = self.BufferedIOBase.readable
-                read = self.BufferedIOBase.read
-            return self.TextIOWrapper(UnseekableWriter(), "ascii")
-
-        tests = (
-            (pipe_reader, "fr"), (pipe_writer, "fw"),
-            (buffered_reader, "r"), (buffered_writer, "w"),
-            (buffered_random, "rws"), (buffered_rw_pair, "rw"),
-            (text_reader, "r"), (text_writer, "w"),
-            (self.BytesIO, "rws"), (self.StringIO, "rws"),
-        )
-
-        def do_test(test, obj, abilities):
-            readable = "r" in abilities
-            self.assertEqual(obj.readable(), readable)
-            writable = "w" in abilities
-            self.assertEqual(obj.writable(), writable)
-
-            if isinstance(obj, self.TextIOBase):
-                data = "3"
-            elif isinstance(obj, (self.BufferedIOBase, self.RawIOBase)):
-                data = b"3"
-            else:
-                self.fail("Unknown base class")
-
-            if "f" in abilities:
-                obj.fileno()
-            else:
-                self.assertRaises(OSError, obj.fileno)
-
-            if readable:
-                obj.read(1)
-                obj.read()
-            else:
-                self.assertRaises(OSError, obj.read, 1)
-                self.assertRaises(OSError, obj.read)
-
-            if writable:
-                obj.write(data)
-            else:
-                self.assertRaises(OSError, obj.write, data)
-
-            if sys.platform.startswith("win") and test in (
-                    pipe_reader, pipe_writer):
-                # Pipes seem to appear as seekable on Windows
-                return
-            seekable = "s" in abilities
-            self.assertEqual(obj.seekable(), seekable)
-
-            if seekable:
-                obj.tell()
-                obj.seek(0)
-            else:
-                self.assertRaises(OSError, obj.tell)
-                self.assertRaises(OSError, obj.seek, 0)
-
-            if writable and seekable:
-                obj.truncate()
-                obj.truncate(0)
-            else:
-                self.assertRaises(OSError, obj.truncate)
-                self.assertRaises(OSError, obj.truncate, 0)
-
-        for [test, abilities] in tests:
-            with self.subTest(test):
-                if test == pipe_writer and not threading_helper.can_start_thread:
-                    self.skipTest("Need threads")
-                with test() as obj:
-                    do_test(test, obj, abilities)
-
-
-    def test_open_handles_NUL_chars(self):
-        fn_with_NUL = 'foo\0bar'
-        self.assertRaises(ValueError, self.open, fn_with_NUL, 'w', encoding="utf-8")
-
-        bytes_fn = bytes(fn_with_NUL, 'ascii')
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            self.assertRaises(ValueError, self.open, bytes_fn, 'w', encoding="utf-8")
-
-    def test_raw_file_io(self):
-        with self.open(os_helper.TESTFN, "wb", buffering=0) as f:
-            self.assertEqual(f.readable(), False)
-            self.assertEqual(f.writable(), True)
-            self.assertEqual(f.seekable(), True)
-            self.write_ops(f)
-        with self.open(os_helper.TESTFN, "rb", buffering=0) as f:
-            self.assertEqual(f.readable(), True)
-            self.assertEqual(f.writable(), False)
-            self.assertEqual(f.seekable(), True)
-            self.read_ops(f)
-
-    def test_buffered_file_io(self):
-        with self.open(os_helper.TESTFN, "wb") as f:
-            self.assertEqual(f.readable(), False)
-            self.assertEqual(f.writable(), True)
-            self.assertEqual(f.seekable(), True)
-            self.write_ops(f)
-        with self.open(os_helper.TESTFN, "rb") as f:
-            self.assertEqual(f.readable(), True)
-            self.assertEqual(f.writable(), False)
-            self.assertEqual(f.seekable(), True)
-            self.read_ops(f, True)
-
-    def test_readline(self):
-        with self.open(os_helper.TESTFN, "wb") as f:
-            f.write(b"abc\ndef\nxyzzy\nfoo\x00bar\nanother line")
-        with self.open(os_helper.TESTFN, "rb") as f:
-            self.assertEqual(f.readline(), b"abc\n")
-            self.assertEqual(f.readline(10), b"def\n")
-            self.assertEqual(f.readline(2), b"xy")
-            self.assertEqual(f.readline(4), b"zzy\n")
-            self.assertEqual(f.readline(), b"foo\x00bar\n")
-            self.assertEqual(f.readline(None), b"another line")
-            self.assertRaises(TypeError, f.readline, 5.3)
-        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
-            self.assertRaises(TypeError, f.readline, 5.3)
-
-    def test_readline_nonsizeable(self):
-        # Issue #30061
-        # Crash when readline() returns an object without __len__
-        class R(self.IOBase):
-            def readline(self):
-                return None
-        self.assertRaises((TypeError, StopIteration), next, R())
-
-    def test_next_nonsizeable(self):
-        # Issue #30061
-        # Crash when __next__() returns an object without __len__
-        class R(self.IOBase):
-            def __next__(self):
-                return None
-        self.assertRaises(TypeError, R().readlines, 1)
-
-    def test_raw_bytes_io(self):
-        f = self.BytesIO()
-        self.write_ops(f)
-        data = f.getvalue()
-        self.assertEqual(data, b"hello world\n")
-        f = self.BytesIO(data)
-        self.read_ops(f, True)
-
-    def test_large_file_ops(self):
-        # On Windows and Apple platforms this test consumes large resources; It
-        # takes a long time to build the >2 GiB file and takes >2 GiB of disk
-        # space therefore the resource must be enabled to run this test.
-        if sys.platform[:3] == 'win' or is_apple:
-            support.requires(
-                'largefile',
-                'test requires %s bytes and a long time to run' % self.LARGE)
-        with self.open(os_helper.TESTFN, "w+b", 0) as f:
-            self.large_file_ops(f)
-        with self.open(os_helper.TESTFN, "w+b") as f:
-            self.large_file_ops(f)
-
-    def test_with_open(self):
-        for bufsize in (0, 100):
-            with self.open(os_helper.TESTFN, "wb", bufsize) as f:
-                f.write(b"xxx")
-            self.assertEqual(f.closed, True)
-            try:
-                with self.open(os_helper.TESTFN, "wb", bufsize) as f:
-                    1/0
-            except ZeroDivisionError:
-                self.assertEqual(f.closed, True)
-            else:
-                self.fail("1/0 didn't raise an exception")
-
-    # issue 5008
-    def test_append_mode_tell(self):
-        with self.open(os_helper.TESTFN, "wb") as f:
-            f.write(b"xxx")
-        with self.open(os_helper.TESTFN, "ab", buffering=0) as f:
-            self.assertEqual(f.tell(), 3)
-        with self.open(os_helper.TESTFN, "ab") as f:
-            self.assertEqual(f.tell(), 3)
-        with self.open(os_helper.TESTFN, "a", encoding="utf-8") as f:
-            self.assertGreater(f.tell(), 0)
-
-    def test_destructor(self):
-        record = []
-        class MyFileIO(self.FileIO):
-            def __del__(self):
-                record.append(1)
-                try:
-                    f = super().__del__
-                except AttributeError:
-                    pass
-                else:
-                    f()
-            def close(self):
-                record.append(2)
-                super().close()
-            def flush(self):
-                record.append(3)
-                super().flush()
-        with warnings_helper.check_warnings(('', ResourceWarning)):
-            f = MyFileIO(os_helper.TESTFN, "wb")
-            f.write(b"xxx")
-            del f
-            support.gc_collect()
-            self.assertEqual(record, [1, 2, 3])
-            with self.open(os_helper.TESTFN, "rb") as f:
-                self.assertEqual(f.read(), b"xxx")
-
-    def _check_base_destructor(self, base):
-        record = []
-        class MyIO(base):
-            def __init__(self):
-                # This exercises the availability of attributes on object
-                # destruction.
-                # (in the C version, close() is called by the tp_dealloc
-                # function, not by __del__)
-                self.on_del = 1
-                self.on_close = 2
-                self.on_flush = 3
-            def __del__(self):
-                record.append(self.on_del)
-                try:
-                    f = super().__del__
-                except AttributeError:
-                    pass
-                else:
-                    f()
-            def close(self):
-                record.append(self.on_close)
-                super().close()
-            def flush(self):
-                record.append(self.on_flush)
-                super().flush()
-        f = MyIO()
-        del f
-        support.gc_collect()
-        self.assertEqual(record, [1, 2, 3])
-
-    def test_IOBase_destructor(self):
-        self._check_base_destructor(self.IOBase)
-
-    def test_RawIOBase_destructor(self):
-        self._check_base_destructor(self.RawIOBase)
-
-    def test_BufferedIOBase_destructor(self):
-        self._check_base_destructor(self.BufferedIOBase)
-
-    def test_TextIOBase_destructor(self):
-        self._check_base_destructor(self.TextIOBase)
-
-    def test_close_flushes(self):
-        with self.open(os_helper.TESTFN, "wb") as f:
-            f.write(b"xxx")
-        with self.open(os_helper.TESTFN, "rb") as f:
-            self.assertEqual(f.read(), b"xxx")
-
-    def test_array_writes(self):
-        a = array.array('i', range(10))
-        n = len(a.tobytes())
-        def check(f):
-            with f:
-                self.assertEqual(f.write(a), n)
-                f.writelines((a,))
-        check(self.BytesIO())
-        check(self.FileIO(os_helper.TESTFN, "w"))
-        check(self.BufferedWriter(self.MockRawIO()))
-        check(self.BufferedRandom(self.MockRawIO()))
-        check(self.BufferedRWPair(self.MockRawIO(), self.MockRawIO()))
-
-    def test_closefd(self):
-        self.assertRaises(ValueError, self.open, os_helper.TESTFN, 'w',
-                          encoding="utf-8", closefd=False)
-
-    def test_read_closed(self):
-        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
-            f.write("egg\n")
-        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
-            file = self.open(f.fileno(), "r", encoding="utf-8", closefd=False)
-            self.assertEqual(file.read(), "egg\n")
-            file.seek(0)
-            file.close()
-            self.assertRaises(ValueError, file.read)
-        with self.open(os_helper.TESTFN, "rb") as f:
-            file = self.open(f.fileno(), "rb", closefd=False)
-            self.assertEqual(file.read()[:3], b"egg")
-            file.close()
-            self.assertRaises(ValueError, file.readinto, bytearray(1))
-
-    def test_no_closefd_with_filename(self):
-        # can't use closefd in combination with a file name
-        self.assertRaises(ValueError, self.open, os_helper.TESTFN, "r",
-                          encoding="utf-8", closefd=False)
-
-    def test_closefd_attr(self):
-        with self.open(os_helper.TESTFN, "wb") as f:
-            f.write(b"egg\n")
-        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
-            self.assertEqual(f.buffer.raw.closefd, True)
-            file = self.open(f.fileno(), "r", encoding="utf-8", closefd=False)
-            self.assertEqual(file.buffer.raw.closefd, False)
-
-    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
-    def test_garbage_collection(self):
-        # FileIO objects are collected, and collecting them flushes
-        # all data to disk.
-        with warnings_helper.check_warnings(('', ResourceWarning)):
-            f = self.FileIO(os_helper.TESTFN, "wb")
-            f.write(b"abcxxx")
-            f.f = f
-            wr = weakref.ref(f)
-            del f
-            support.gc_collect()
-        self.assertIsNone(wr(), wr)
-        with self.open(os_helper.TESTFN, "rb") as f:
-            self.assertEqual(f.read(), b"abcxxx")
-
-    def test_unbounded_file(self):
-        # Issue #1174606: reading from an unbounded stream such as /dev/zero.
-        zero = "/dev/zero"
-        if not os.path.exists(zero):
-            self.skipTest("{0} does not exist".format(zero))
-        if sys.maxsize > 0x7FFFFFFF:
-            self.skipTest("test can only run in a 32-bit address space")
-        if support.real_max_memuse < support._2G:
-            self.skipTest("test requires at least 2 GiB of memory")
-        with self.open(zero, "rb", buffering=0) as f:
-            self.assertRaises(OverflowError, f.read)
-        with self.open(zero, "rb") as f:
-            self.assertRaises(OverflowError, f.read)
-        with self.open(zero, "r") as f:
-            self.assertRaises(OverflowError, f.read)
-
-    def check_flush_error_on_close(self, *args, **kwargs):
-        # Test that the file is closed despite failed flush
-        # and that flush() is called before file closed.
-        f = self.open(*args, **kwargs)
-        closed = []
-        def bad_flush():
-            closed[:] = [f.closed]
-            raise OSError()
-        f.flush = bad_flush
-        self.assertRaises(OSError, f.close) # exception not swallowed
-        self.assertTrue(f.closed)
-        self.assertTrue(closed)      # flush() called
-        self.assertFalse(closed[0])  # flush() called before file closed
-        f.flush = lambda: None  # break reference loop
-
-    def test_flush_error_on_close(self):
-        # raw file
-        # Issue #5700: io.FileIO calls flush() after file closed
-        self.check_flush_error_on_close(os_helper.TESTFN, 'wb', buffering=0)
-        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
-        self.check_flush_error_on_close(fd, 'wb', buffering=0)
-        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
-        self.check_flush_error_on_close(fd, 'wb', buffering=0, closefd=False)
-        os.close(fd)
-        # buffered io
-        self.check_flush_error_on_close(os_helper.TESTFN, 'wb')
-        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
-        self.check_flush_error_on_close(fd, 'wb')
-        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
-        self.check_flush_error_on_close(fd, 'wb', closefd=False)
-        os.close(fd)
-        # text io
-        self.check_flush_error_on_close(os_helper.TESTFN, 'w', encoding="utf-8")
-        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
-        self.check_flush_error_on_close(fd, 'w', encoding="utf-8")
-        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
-        self.check_flush_error_on_close(fd, 'w', encoding="utf-8", closefd=False)
-        os.close(fd)
-
-    def test_multi_close(self):
-        f = self.open(os_helper.TESTFN, "wb", buffering=0)
-        f.close()
-        f.close()
-        f.close()
-        self.assertRaises(ValueError, f.flush)
-
-    def test_RawIOBase_read(self):
-        # Exercise the default limited RawIOBase.read(n) implementation (which
-        # calls readinto() internally).
-        rawio = self.MockRawIOWithoutRead((b"abc", b"d", None, b"efg", None))
-        self.assertEqual(rawio.read(2), b"ab")
-        self.assertEqual(rawio.read(2), b"c")
-        self.assertEqual(rawio.read(2), b"d")
-        self.assertEqual(rawio.read(2), None)
-        self.assertEqual(rawio.read(2), b"ef")
-        self.assertEqual(rawio.read(2), b"g")
-        self.assertEqual(rawio.read(2), None)
-        self.assertEqual(rawio.read(2), b"")
-
-    def test_RawIOBase_read_bounds_checking(self):
-        # Make sure a `.readinto` call which returns a value outside
-        # (0, len(buffer)) raises.
-        class Misbehaved(self.RawIOBase):
-            def __init__(self, readinto_return) -> None:
-                self._readinto_return = readinto_return
-            def readinto(self, b):
-                return self._readinto_return
-
-        with self.assertRaises(ValueError) as cm:
-            Misbehaved(2).read(1)
-        self.assertEqual(str(cm.exception), "readinto returned 2 outside buffer size 1")
-        for bad_size in (2147483647, sys.maxsize, -1, -1000):
-            with self.assertRaises(ValueError):
-                Misbehaved(bad_size).read()
-
-    def test_types_have_dict(self):
-        test = (
-            self.IOBase(),
-            self.RawIOBase(),
-            self.TextIOBase(),
-            self.StringIO(),
-            self.BytesIO()
-        )
-        for obj in test:
-            self.assertHasAttr(obj, "__dict__")
-
-    def test_opener(self):
-        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
-            f.write("egg\n")
-        fd = os.open(os_helper.TESTFN, os.O_RDONLY)
-        def opener(path, flags):
-            return fd
-        with self.open("non-existent", "r", encoding="utf-8", opener=opener) as f:
-            self.assertEqual(f.read(), "egg\n")
-
-    def test_bad_opener_negative_1(self):
-        # Issue #27066.
-        def badopener(fname, flags):
-            return -1
-        with self.assertRaises(ValueError) as cm:
-            self.open('non-existent', 'r', opener=badopener)
-        self.assertEqual(str(cm.exception), 'opener returned -1')
-
-    def test_bad_opener_other_negative(self):
-        # Issue #27066.
-        def badopener(fname, flags):
-            return -2
-        with self.assertRaises(ValueError) as cm:
-            self.open('non-existent', 'r', opener=badopener)
-        self.assertEqual(str(cm.exception), 'opener returned -2')
-
-    def test_opener_invalid_fd(self):
-        # Check that OSError is raised with error code EBADF if the
-        # opener returns an invalid file descriptor (see gh-82212).
-        fd = os_helper.make_bad_fd()
-        with self.assertRaises(OSError) as cm:
-            self.open('foo', opener=lambda name, flags: fd)
-        self.assertEqual(cm.exception.errno, errno.EBADF)
-
-    def test_fileio_closefd(self):
-        # Issue #4841
-        with self.open(__file__, 'rb') as f1, \
-             self.open(__file__, 'rb') as f2:
-            fileio = self.FileIO(f1.fileno(), closefd=False)
-            # .__init__() must not close f1
-            fileio.__init__(f2.fileno(), closefd=False)
-            f1.readline()
-            # .close() must not close f2
-            fileio.close()
-            f2.readline()
-
-    def test_nonbuffered_textio(self):
-        with warnings_helper.check_no_resource_warning(self):
-            with self.assertRaises(ValueError):
-                self.open(os_helper.TESTFN, 'w', encoding="utf-8", buffering=0)
-
-    def test_invalid_newline(self):
-        with warnings_helper.check_no_resource_warning(self):
-            with self.assertRaises(ValueError):
-                self.open(os_helper.TESTFN, 'w', encoding="utf-8", newline='invalid')
-
-    def test_buffered_readinto_mixin(self):
-        # Test the implementation provided by BufferedIOBase
-        class Stream(self.BufferedIOBase):
-            def read(self, size):
-                return b"12345"
-            read1 = read
-        stream = Stream()
-        for method in ("readinto", "readinto1"):
-            with self.subTest(method):
-                buffer = byteslike(5)
-                self.assertEqual(getattr(stream, method)(buffer), 5)
-                self.assertEqual(bytes(buffer), b"12345")
-
-    def test_fspath_support(self):
-        def check_path_succeeds(path):
-            with self.open(path, "w", encoding="utf-8") as f:
-                f.write("egg\n")
-
-            with self.open(path, "r", encoding="utf-8") as f:
-                self.assertEqual(f.read(), "egg\n")
-
-        check_path_succeeds(FakePath(os_helper.TESTFN))
-        check_path_succeeds(FakePath(os.fsencode(os_helper.TESTFN)))
-
-        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
-            bad_path = FakePath(f.fileno())
-            with self.assertRaises(TypeError):
-                self.open(bad_path, 'w', encoding="utf-8")
-
-        bad_path = FakePath(None)
-        with self.assertRaises(TypeError):
-            self.open(bad_path, 'w', encoding="utf-8")
-
-        bad_path = FakePath(FloatingPointError)
-        with self.assertRaises(FloatingPointError):
-            self.open(bad_path, 'w', encoding="utf-8")
-
-        # ensure that refcounting is correct with some error conditions
-        with self.assertRaisesRegex(ValueError, 'read/write/append mode'):
-            self.open(FakePath(os_helper.TESTFN), 'rwxa', encoding="utf-8")
-
-    def test_RawIOBase_readall(self):
-        # Exercise the default unlimited RawIOBase.read() and readall()
-        # implementations.
-        rawio = self.MockRawIOWithoutRead((b"abc", b"d", b"efg"))
-        self.assertEqual(rawio.read(), b"abcdefg")
-        rawio = self.MockRawIOWithoutRead((b"abc", b"d", b"efg"))
-        self.assertEqual(rawio.readall(), b"abcdefg")
-
-    def test_BufferedIOBase_readinto(self):
-        # Exercise the default BufferedIOBase.readinto() and readinto1()
-        # implementations (which call read() or read1() internally).
-        class Reader(self.BufferedIOBase):
-            def __init__(self, avail):
-                self.avail = avail
-            def read(self, size):
-                result = self.avail[:size]
-                self.avail = self.avail[size:]
-                return result
-            def read1(self, size):
-                """Returns no more than 5 bytes at once"""
-                return self.read(min(size, 5))
-        tests = (
-            # (test method, total data available, read buffer size, expected
-            #     read size)
-            ("readinto", 10, 5, 5),
-            ("readinto", 10, 6, 6),  # More than read1() can return
-            ("readinto", 5, 6, 5),  # Buffer larger than total available
-            ("readinto", 6, 7, 6),
-            ("readinto", 10, 0, 0),  # Empty buffer
-            ("readinto1", 10, 5, 5),  # Result limited to single read1() call
-            ("readinto1", 10, 6, 5),  # Buffer larger than read1() can return
-            ("readinto1", 5, 6, 5),  # Buffer larger than total available
-            ("readinto1", 6, 7, 5),
-            ("readinto1", 10, 0, 0),  # Empty buffer
-        )
-        UNUSED_BYTE = 0x81
-        for test in tests:
-            with self.subTest(test):
-                method, avail, request, result = test
-                reader = Reader(bytes(range(avail)))
-                buffer = bytearray((UNUSED_BYTE,) * request)
-                method = getattr(reader, method)
-                self.assertEqual(method(buffer), result)
-                self.assertEqual(len(buffer), request)
-                self.assertSequenceEqual(buffer[:result], range(result))
-                unused = (UNUSED_BYTE,) * (request - result)
-                self.assertSequenceEqual(buffer[result:], unused)
-                self.assertEqual(len(reader.avail), avail - result)
-
-    def test_close_assert(self):
-        class R(self.IOBase):
-            def __setattr__(self, name, value):
-                pass
-            def flush(self):
-                raise OSError()
-        f = R()
-        # This would cause an assertion failure.
-        self.assertRaises(OSError, f.close)
-
-        # Silence destructor error
-        R.flush = lambda self: None
-
-    @threading_helper.requires_working_threading()
-    def test_write_readline_races(self):
-        # gh-134908: Concurrent iteration over a file caused races
-        thread_count = 2
-        write_count = 100
-        read_count = 100
-
-        def writer(file, barrier):
-            barrier.wait()
-            for _ in range(write_count):
-                file.write("x")
-
-        def reader(file, barrier):
-            barrier.wait()
-            for _ in range(read_count):
-                for line in file:
-                    self.assertEqual(line, "")
-
-        with self.open(os_helper.TESTFN, "w+") as f:
-            barrier = threading.Barrier(thread_count + 1)
-            reader = threading.Thread(target=reader, args=(f, barrier))
-            writers = [threading.Thread(target=writer, args=(f, barrier))
-                       for _ in range(thread_count)]
-            with threading_helper.catch_threading_exception() as cm:
-                with threading_helper.start_threads(writers + [reader]):
-                    pass
-                self.assertIsNone(cm.exc_type)
-
-        self.assertEqual(os.stat(os_helper.TESTFN).st_size,
-                         write_count * thread_count)
-
-
-class CIOTest(IOTest):
-
-    def test_IOBase_finalize(self):
-        # Issue #12149: segmentation fault on _PyIOBase_finalize when both a
-        # class which inherits IOBase and an object of this class are caught
-        # in a reference cycle and close() is already in the method cache.
-        class MyIO(self.IOBase):
-            def close(self):
-                pass
-
-        # create an instance to populate the method cache
-        MyIO()
-        obj = MyIO()
-        obj.obj = obj
-        wr = weakref.ref(obj)
-        del MyIO
-        del obj
-        support.gc_collect()
-        self.assertIsNone(wr(), wr)
-
-@support.cpython_only
-class TestIOCTypes(unittest.TestCase):
-    def setUp(self):
-        _io = import_helper.import_module("_io")
-        self.types = [
-            _io.BufferedRWPair,
-            _io.BufferedRandom,
-            _io.BufferedReader,
-            _io.BufferedWriter,
-            _io.BytesIO,
-            _io.FileIO,
-            _io.IncrementalNewlineDecoder,
-            _io.StringIO,
-            _io.TextIOWrapper,
-            _io._BufferedIOBase,
-            _io._BytesIOBuffer,
-            _io._IOBase,
-            _io._RawIOBase,
-            _io._TextIOBase,
-        ]
-        if sys.platform == "win32":
-            self.types.append(_io._WindowsConsoleIO)
-        self._io = _io
-
-    def test_immutable_types(self):
-        for tp in self.types:
-            with self.subTest(tp=tp):
-                with self.assertRaisesRegex(TypeError, "immutable"):
-                    tp.foo = "bar"
-
-    def test_class_hierarchy(self):
-        def check_subs(types, base):
-            for tp in types:
-                with self.subTest(tp=tp, base=base):
-                    self.assertIsSubclass(tp, base)
-
-        def recursive_check(d):
-            for k, v in d.items():
-                if isinstance(v, dict):
-                    recursive_check(v)
-                elif isinstance(v, set):
-                    check_subs(v, k)
-                else:
-                    self.fail("corrupt test dataset")
-
-        _io = self._io
-        hierarchy = {
-            _io._IOBase: {
-                _io._BufferedIOBase: {
-                    _io.BufferedRWPair,
-                    _io.BufferedRandom,
-                    _io.BufferedReader,
-                    _io.BufferedWriter,
-                    _io.BytesIO,
-                },
-                _io._RawIOBase: {
-                    _io.FileIO,
-                },
-                _io._TextIOBase: {
-                    _io.StringIO,
-                    _io.TextIOWrapper,
-                },
-            },
-        }
-        if sys.platform == "win32":
-            hierarchy[_io._IOBase][_io._RawIOBase].add(_io._WindowsConsoleIO)
-
-        recursive_check(hierarchy)
-
-    def test_subclassing(self):
-        _io = self._io
-        dataset = {k: True for k in self.types}
-        dataset[_io._BytesIOBuffer] = False
-
-        for tp, is_basetype in dataset.items():
-            with self.subTest(tp=tp, is_basetype=is_basetype):
-                name = f"{tp.__name__}_subclass"
-                bases = (tp,)
-                if is_basetype:
-                    _ = type(name, bases, {})
-                else:
-                    msg = "not an acceptable base type"
-                    with self.assertRaisesRegex(TypeError, msg):
-                        _ = type(name, bases, {})
-
-    def test_disallow_instantiation(self):
-        _io = self._io
-        support.check_disallow_instantiation(self, _io._BytesIOBuffer)
-
-    def test_stringio_setstate(self):
-        # gh-127182: Calling __setstate__() with invalid arguments must not crash
-        obj = self._io.StringIO()
-        with self.assertRaisesRegex(
-            TypeError,
-            'initial_value must be str or None, not int',
-        ):
-            obj.__setstate__((1, '', 0, {}))
-
-        obj.__setstate__((None, '', 0, {}))  # should not crash
-        self.assertEqual(obj.getvalue(), '')
-
-        obj.__setstate__(('', '', 0, {}))
-        self.assertEqual(obj.getvalue(), '')
-
-class PyIOTest(IOTest):
-    pass
-
-
-@support.cpython_only
-class APIMismatchTest(unittest.TestCase):
-
-    def test_RawIOBase_io_in_pyio_match(self):
-        """Test that pyio RawIOBase class has all c RawIOBase methods"""
-        mismatch = support.detect_api_mismatch(pyio.RawIOBase, io.RawIOBase,
-                                               ignore=('__weakref__', '__static_attributes__'))
-        self.assertEqual(mismatch, set(), msg='Python RawIOBase does not have all C RawIOBase methods')
-
-    def test_RawIOBase_pyio_in_io_match(self):
-        """Test that c RawIOBase class has all pyio RawIOBase methods"""
-        mismatch = support.detect_api_mismatch(io.RawIOBase, pyio.RawIOBase)
-        self.assertEqual(mismatch, set(), msg='C RawIOBase does not have all Python RawIOBase methods')
-
-
-class CommonBufferedTests:
-    # Tests common to BufferedReader, BufferedWriter and BufferedRandom
-
-    def test_detach(self):
-        raw = self.MockRawIO()
-        buf = self.tp(raw)
-        self.assertIs(buf.detach(), raw)
-        self.assertRaises(ValueError, buf.detach)
-
-        repr(buf)  # Should still work
-
-    def test_fileno(self):
-        rawio = self.MockRawIO()
-        bufio = self.tp(rawio)
-
-        self.assertEqual(42, bufio.fileno())
-
-    def test_invalid_args(self):
-        rawio = self.MockRawIO()
-        bufio = self.tp(rawio)
-        # Invalid whence
-        self.assertRaises(ValueError, bufio.seek, 0, -1)
-        self.assertRaises(ValueError, bufio.seek, 0, 9)
-
-    def test_override_destructor(self):
-        tp = self.tp
-        record = []
-        class MyBufferedIO(tp):
-            def __del__(self):
-                record.append(1)
-                try:
-                    f = super().__del__
-                except AttributeError:
-                    pass
-                else:
-                    f()
-            def close(self):
-                record.append(2)
-                super().close()
-            def flush(self):
-                record.append(3)
-                super().flush()
-        rawio = self.MockRawIO()
-        bufio = MyBufferedIO(rawio)
-        del bufio
-        support.gc_collect()
-        self.assertEqual(record, [1, 2, 3])
-
-    def test_context_manager(self):
-        # Test usability as a context manager
-        rawio = self.MockRawIO()
-        bufio = self.tp(rawio)
-        def _with():
-            with bufio:
-                pass
-        _with()
-        # bufio should now be closed, and using it a second time should raise
-        # a ValueError.
-        self.assertRaises(ValueError, _with)
-
-    def test_error_through_destructor(self):
-        # Test that the exception state is not modified by a destructor,
-        # even if close() fails.
-        rawio = self.CloseFailureIO()
-        with support.catch_unraisable_exception() as cm:
-            with self.assertRaises(AttributeError):
-                self.tp(rawio).xyzzy
-
-            self.assertEqual(cm.unraisable.exc_type, OSError)
-
-    def test_repr(self):
-        raw = self.MockRawIO()
-        b = self.tp(raw)
-        clsname = r"(%s\.)?%s" % (self.tp.__module__, self.tp.__qualname__)
-        self.assertRegex(repr(b), "<%s>" % clsname)
-        raw.name = "dummy"
-        self.assertRegex(repr(b), "<%s name='dummy'>" % clsname)
-        raw.name = b"dummy"
-        self.assertRegex(repr(b), "<%s name=b'dummy'>" % clsname)
-
-    def test_recursive_repr(self):
-        # Issue #25455
-        raw = self.MockRawIO()
-        b = self.tp(raw)
-        with support.swap_attr(raw, 'name', b), support.infinite_recursion(25):
-            with self.assertRaises(RuntimeError):
-                repr(b)  # Should not crash
-
-    def test_flush_error_on_close(self):
-        # Test that buffered file is closed despite failed flush
-        # and that flush() is called before file closed.
-        raw = self.MockRawIO()
-        closed = []
-        def bad_flush():
-            closed[:] = [b.closed, raw.closed]
-            raise OSError()
-        raw.flush = bad_flush
-        b = self.tp(raw)
-        self.assertRaises(OSError, b.close) # exception not swallowed
-        self.assertTrue(b.closed)
-        self.assertTrue(raw.closed)
-        self.assertTrue(closed)      # flush() called
-        self.assertFalse(closed[0])  # flush() called before file closed
-        self.assertFalse(closed[1])
-        raw.flush = lambda: None  # break reference loop
-
-    def test_close_error_on_close(self):
-        raw = self.MockRawIO()
-        def bad_flush():
-            raise OSError('flush')
-        def bad_close():
-            raise OSError('close')
-        raw.close = bad_close
-        b = self.tp(raw)
-        b.flush = bad_flush
-        with self.assertRaises(OSError) as err: # exception not swallowed
-            b.close()
-        self.assertEqual(err.exception.args, ('close',))
-        self.assertIsInstance(err.exception.__context__, OSError)
-        self.assertEqual(err.exception.__context__.args, ('flush',))
-        self.assertFalse(b.closed)
-
-        # Silence destructor error
-        raw.close = lambda: None
-        b.flush = lambda: None
-
-    def test_nonnormalized_close_error_on_close(self):
-        # Issue #21677
-        raw = self.MockRawIO()
-        def bad_flush():
-            raise non_existing_flush
-        def bad_close():
-            raise non_existing_close
-        raw.close = bad_close
-        b = self.tp(raw)
-        b.flush = bad_flush
-        with self.assertRaises(NameError) as err: # exception not swallowed
-            b.close()
-        self.assertIn('non_existing_close', str(err.exception))
-        self.assertIsInstance(err.exception.__context__, NameError)
-        self.assertIn('non_existing_flush', str(err.exception.__context__))
-        self.assertFalse(b.closed)
-
-        # Silence destructor error
-        b.flush = lambda: None
-        raw.close = lambda: None
-
-    def test_multi_close(self):
-        raw = self.MockRawIO()
-        b = self.tp(raw)
-        b.close()
-        b.close()
-        b.close()
-        self.assertRaises(ValueError, b.flush)
-
-    def test_unseekable(self):
-        bufio = self.tp(self.MockUnseekableIO(b"A" * 10))
-        self.assertRaises(self.UnsupportedOperation, bufio.tell)
-        self.assertRaises(self.UnsupportedOperation, bufio.seek, 0)
-
-    def test_readonly_attributes(self):
-        raw = self.MockRawIO()
-        buf = self.tp(raw)
-        x = self.MockRawIO()
-        with self.assertRaises(AttributeError):
-            buf.raw = x
-
-    def test_pickling_subclass(self):
-        global MyBufferedIO
-        class MyBufferedIO(self.tp):
-            def __init__(self, raw, tag):
-                super().__init__(raw)
-                self.tag = tag
-            def __getstate__(self):
-                return self.tag, self.raw.getvalue()
-            def __setstate__(slf, state):
-                tag, value = state
-                slf.__init__(self.BytesIO(value), tag)
-
-        raw = self.BytesIO(b'data')
-        buf = MyBufferedIO(raw, tag='ham')
-        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
-            with self.subTest(protocol=proto):
-                pickled = pickle.dumps(buf, proto)
-                newbuf = pickle.loads(pickled)
-                self.assertEqual(newbuf.raw.getvalue(), b'data')
-                self.assertEqual(newbuf.tag, 'ham')
-        del MyBufferedIO
-
-
-class SizeofTest:
-
-    @support.cpython_only
-    def test_sizeof(self):
-        bufsize1 = 4096
-        bufsize2 = 8192
-        rawio = self.MockRawIO()
-        bufio = self.tp(rawio, buffer_size=bufsize1)
-        size = sys.getsizeof(bufio) - bufsize1
-        rawio = self.MockRawIO()
-        bufio = self.tp(rawio, buffer_size=bufsize2)
-        self.assertEqual(sys.getsizeof(bufio), size + bufsize2)
-
-    @support.cpython_only
-    def test_buffer_freeing(self) :
-        bufsize = 4096
-        rawio = self.MockRawIO()
-        bufio = self.tp(rawio, buffer_size=bufsize)
-        size = sys.getsizeof(bufio) - bufsize
-        bufio.close()
-        self.assertEqual(sys.getsizeof(bufio), size)
-
-class BufferedReaderTest(unittest.TestCase, CommonBufferedTests):
-    read_mode = "rb"
-
-    def test_constructor(self):
-        rawio = self.MockRawIO([b"abc"])
-        bufio = self.tp(rawio)
-        bufio.__init__(rawio)
-        bufio.__init__(rawio, buffer_size=1024)
-        bufio.__init__(rawio, buffer_size=16)
-        self.assertEqual(b"abc", bufio.read())
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
-        rawio = self.MockRawIO([b"abc"])
-        bufio.__init__(rawio)
-        self.assertEqual(b"abc", bufio.read())
-
-    def test_uninitialized(self):
-        bufio = self.tp.__new__(self.tp)
-        del bufio
-        bufio = self.tp.__new__(self.tp)
-        self.assertRaisesRegex((ValueError, AttributeError),
-                               'uninitialized|has no attribute',
-                               bufio.read, 0)
-        bufio.__init__(self.MockRawIO())
-        self.assertEqual(bufio.read(0), b'')
-
-    def test_read(self):
-        for arg in (None, 7):
-            rawio = self.MockRawIO((b"abc", b"d", b"efg"))
-            bufio = self.tp(rawio)
-            self.assertEqual(b"abcdefg", bufio.read(arg))
-        # Invalid args
-        self.assertRaises(ValueError, bufio.read, -2)
-
-    def test_read1(self):
-        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
-        bufio = self.tp(rawio)
-        self.assertEqual(b"a", bufio.read(1))
-        self.assertEqual(b"b", bufio.read1(1))
-        self.assertEqual(rawio._reads, 1)
-        self.assertEqual(b"", bufio.read1(0))
-        self.assertEqual(b"c", bufio.read1(100))
-        self.assertEqual(rawio._reads, 1)
-        self.assertEqual(b"d", bufio.read1(100))
-        self.assertEqual(rawio._reads, 2)
-        self.assertEqual(b"efg", bufio.read1(100))
-        self.assertEqual(rawio._reads, 3)
-        self.assertEqual(b"", bufio.read1(100))
-        self.assertEqual(rawio._reads, 4)
-
-    def test_read1_arbitrary(self):
-        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
-        bufio = self.tp(rawio)
-        self.assertEqual(b"a", bufio.read(1))
-        self.assertEqual(b"bc", bufio.read1())
-        self.assertEqual(b"d", bufio.read1())
-        self.assertEqual(b"efg", bufio.read1(-1))
-        self.assertEqual(rawio._reads, 3)
-        self.assertEqual(b"", bufio.read1())
-        self.assertEqual(rawio._reads, 4)
-
-    def test_readinto(self):
-        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
-        bufio = self.tp(rawio)
-        b = bytearray(2)
-        self.assertEqual(bufio.readinto(b), 2)
-        self.assertEqual(b, b"ab")
-        self.assertEqual(bufio.readinto(b), 2)
-        self.assertEqual(b, b"cd")
-        self.assertEqual(bufio.readinto(b), 2)
-        self.assertEqual(b, b"ef")
-        self.assertEqual(bufio.readinto(b), 1)
-        self.assertEqual(b, b"gf")
-        self.assertEqual(bufio.readinto(b), 0)
-        self.assertEqual(b, b"gf")
-        rawio = self.MockRawIO((b"abc", None))
-        bufio = self.tp(rawio)
-        self.assertEqual(bufio.readinto(b), 2)
-        self.assertEqual(b, b"ab")
-        self.assertEqual(bufio.readinto(b), 1)
-        self.assertEqual(b, b"cb")
-
-    def test_readinto1(self):
-        buffer_size = 10
-        rawio = self.MockRawIO((b"abc", b"de", b"fgh", b"jkl"))
-        bufio = self.tp(rawio, buffer_size=buffer_size)
-        b = bytearray(2)
-        self.assertEqual(bufio.peek(3), b'abc')
-        self.assertEqual(rawio._reads, 1)
-        self.assertEqual(bufio.readinto1(b), 2)
-        self.assertEqual(b, b"ab")
-        self.assertEqual(rawio._reads, 1)
-        self.assertEqual(bufio.readinto1(b), 1)
-        self.assertEqual(b[:1], b"c")
-        self.assertEqual(rawio._reads, 1)
-        self.assertEqual(bufio.readinto1(b), 2)
-        self.assertEqual(b, b"de")
-        self.assertEqual(rawio._reads, 2)
-        b = bytearray(2*buffer_size)
-        self.assertEqual(bufio.peek(3), b'fgh')
-        self.assertEqual(rawio._reads, 3)
-        self.assertEqual(bufio.readinto1(b), 6)
-        self.assertEqual(b[:6], b"fghjkl")
-        self.assertEqual(rawio._reads, 4)
-
-    def test_readinto_array(self):
-        buffer_size = 60
-        data = b"a" * 26
-        rawio = self.MockRawIO((data,))
-        bufio = self.tp(rawio, buffer_size=buffer_size)
-
-        # Create an array with element size > 1 byte
-        b = array.array('i', b'x' * 32)
-        assert len(b) != 16
-
-        # Read into it. We should get as many *bytes* as we can fit into b
-        # (which is more than the number of elements)
-        n = bufio.readinto(b)
-        self.assertGreater(n, len(b))
-
-        # Check that old contents of b are preserved
-        bm = memoryview(b).cast('B')
-        self.assertLess(n, len(bm))
-        self.assertEqual(bm[:n], data[:n])
-        self.assertEqual(bm[n:], b'x' * (len(bm[n:])))
-
-    def test_readinto1_array(self):
-        buffer_size = 60
-        data = b"a" * 26
-        rawio = self.MockRawIO((data,))
-        bufio = self.tp(rawio, buffer_size=buffer_size)
-
-        # Create an array with element size > 1 byte
-        b = array.array('i', b'x' * 32)
-        assert len(b) != 16
-
-        # Read into it. We should get as many *bytes* as we can fit into b
-        # (which is more than the number of elements)
-        n = bufio.readinto1(b)
-        self.assertGreater(n, len(b))
-
-        # Check that old contents of b are preserved
-        bm = memoryview(b).cast('B')
-        self.assertLess(n, len(bm))
-        self.assertEqual(bm[:n], data[:n])
-        self.assertEqual(bm[n:], b'x' * (len(bm[n:])))
-
-    def test_readlines(self):
-        def bufio():
-            rawio = self.MockRawIO((b"abc\n", b"d\n", b"ef"))
-            return self.tp(rawio)
-        self.assertEqual(bufio().readlines(), [b"abc\n", b"d\n", b"ef"])
-        self.assertEqual(bufio().readlines(5), [b"abc\n", b"d\n"])
-        self.assertEqual(bufio().readlines(None), [b"abc\n", b"d\n", b"ef"])
-
-    def test_buffering(self):
-        data = b"abcdefghi"
-        dlen = len(data)
-
-        tests = [
-            [ 100, [ 3, 1, 4, 8 ], [ dlen, 0 ] ],
-            [ 100, [ 3, 3, 3],     [ dlen ]    ],
-            [   4, [ 1, 2, 4, 2 ], [ 4, 4, 1 ] ],
-        ]
-
-        for bufsize, buf_read_sizes, raw_read_sizes in tests:
-            rawio = self.MockFileIO(data)
-            bufio = self.tp(rawio, buffer_size=bufsize)
-            pos = 0
-            for nbytes in buf_read_sizes:
-                self.assertEqual(bufio.read(nbytes), data[pos:pos+nbytes])
-                pos += nbytes
-            # this is mildly implementation-dependent
-            self.assertEqual(rawio.read_history, raw_read_sizes)
-
-    def test_read_non_blocking(self):
-        # Inject some None's in there to simulate EWOULDBLOCK
-        rawio = self.MockRawIO((b"abc", b"d", None, b"efg", None, None, None))
-        bufio = self.tp(rawio)
-        self.assertEqual(b"abcd", bufio.read(6))
-        self.assertEqual(b"e", bufio.read(1))
-        self.assertEqual(b"fg", bufio.read())
-        self.assertEqual(b"", bufio.peek(1))
-        self.assertIsNone(bufio.read())
-        self.assertEqual(b"", bufio.read())
-
-        rawio = self.MockRawIO((b"a", None, None))
-        self.assertEqual(b"a", rawio.readall())
-        self.assertIsNone(rawio.readall())
-
-    def test_read_past_eof(self):
-        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
-        bufio = self.tp(rawio)
-
-        self.assertEqual(b"abcdefg", bufio.read(9000))
-
-    def test_read_all(self):
-        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
-        bufio = self.tp(rawio)
-
-        self.assertEqual(b"abcdefg", bufio.read())
-
-    @threading_helper.requires_working_threading()
-    @support.requires_resource('cpu')
-    def test_threads(self):
-        try:
-            # Write out many bytes with exactly the same number of 0's,
-            # 1's... 255's. This will help us check that concurrent reading
-            # doesn't duplicate or forget contents.
-            N = 1000
-            l = list(range(256)) * N
-            random.shuffle(l)
-            s = bytes(bytearray(l))
-            with self.open(os_helper.TESTFN, "wb") as f:
-                f.write(s)
-            with self.open(os_helper.TESTFN, self.read_mode, buffering=0) as raw:
-                bufio = self.tp(raw, 8)
-                errors = []
-                results = []
-                def f():
-                    try:
-                        # Intra-buffer read then buffer-flushing read
-                        for n in cycle([1, 19]):
-                            s = bufio.read(n)
-                            if not s:
-                                break
-                            # list.append() is atomic
-                            results.append(s)
-                    except Exception as e:
-                        errors.append(e)
-                        raise
-                threads = [threading.Thread(target=f) for x in range(20)]
-                with threading_helper.start_threads(threads):
-                    time.sleep(0.02) # yield
-                self.assertFalse(errors,
-                    "the following exceptions were caught: %r" % errors)
-                s = b''.join(results)
-                for i in range(256):
-                    c = bytes(bytearray([i]))
-                    self.assertEqual(s.count(c), N)
-        finally:
-            os_helper.unlink(os_helper.TESTFN)
-
-    def test_unseekable(self):
-        bufio = self.tp(self.MockUnseekableIO(b"A" * 10))
-        self.assertRaises(self.UnsupportedOperation, bufio.tell)
-        self.assertRaises(self.UnsupportedOperation, bufio.seek, 0)
-        bufio.read(1)
-        self.assertRaises(self.UnsupportedOperation, bufio.seek, 0)
-        self.assertRaises(self.UnsupportedOperation, bufio.tell)
-
-    def test_misbehaved_io(self):
-        rawio = self.MisbehavedRawIO((b"abc", b"d", b"efg"))
-        bufio = self.tp(rawio)
-        self.assertRaises(OSError, bufio.seek, 0)
-        self.assertRaises(OSError, bufio.tell)
-
-        # Silence destructor error
-        bufio.close = lambda: None
-
-    def test_no_extraneous_read(self):
-        # Issue #9550; when the raw IO object has satisfied the read request,
-        # we should not issue any additional reads, otherwise it may block
-        # (e.g. socket).
-        bufsize = 16
-        for n in (2, bufsize - 1, bufsize, bufsize + 1, bufsize * 2):
-            rawio = self.MockRawIO([b"x" * n])
-            bufio = self.tp(rawio, bufsize)
-            self.assertEqual(bufio.read(n), b"x" * n)
-            # Simple case: one raw read is enough to satisfy the request.
-            self.assertEqual(rawio._extraneous_reads, 0,
-                             "failed for {}: {} != 0".format(n, rawio._extraneous_reads))
-            # A more complex case where two raw reads are needed to satisfy
-            # the request.
-            rawio = self.MockRawIO([b"x" * (n - 1), b"x"])
-            bufio = self.tp(rawio, bufsize)
-            self.assertEqual(bufio.read(n), b"x" * n)
-            self.assertEqual(rawio._extraneous_reads, 0,
-                             "failed for {}: {} != 0".format(n, rawio._extraneous_reads))
-
-    def test_read_on_closed(self):
-        # Issue #23796
-        b = self.BufferedReader(self.BytesIO(b"12"))
-        b.read(1)
-        b.close()
-        with self.subTest('peek'):
-            self.assertRaises(ValueError, b.peek)
-        with self.subTest('read1'):
-            self.assertRaises(ValueError, b.read1, 1)
-        with self.subTest('read'):
-            self.assertRaises(ValueError, b.read)
-        with self.subTest('readinto'):
-            self.assertRaises(ValueError, b.readinto, bytearray())
-        with self.subTest('readinto1'):
-            self.assertRaises(ValueError, b.readinto1, bytearray())
-        with self.subTest('flush'):
-            self.assertRaises(ValueError, b.flush)
-        with self.subTest('truncate'):
-            self.assertRaises(ValueError, b.truncate)
-        with self.subTest('seek'):
-            self.assertRaises(ValueError, b.seek, 0)
-
-    def test_truncate_on_read_only(self):
-        rawio = self.MockFileIO(b"abc")
-        bufio = self.tp(rawio)
-        self.assertFalse(bufio.writable())
-        self.assertRaises(self.UnsupportedOperation, bufio.truncate)
-        self.assertRaises(self.UnsupportedOperation, bufio.truncate, 0)
-
-    def test_tell_character_device_file(self):
-        # GH-95782
-        # For the (former) bug in BufferedIO to manifest, the wrapped IO obj
-        # must be able to produce at least 2 bytes.
-        raw = self.MockCharPseudoDevFileIO(b"12")
-        buf = self.tp(raw)
-        self.assertEqual(buf.tell(), 0)
-        self.assertEqual(buf.read(1), b"1")
-        self.assertEqual(buf.tell(), 0)
-
-    def test_seek_character_device_file(self):
-        raw = self.MockCharPseudoDevFileIO(b"12")
-        buf = self.tp(raw)
-        self.assertEqual(buf.seek(0, io.SEEK_CUR), 0)
-        self.assertEqual(buf.seek(1, io.SEEK_SET), 0)
-        self.assertEqual(buf.seek(0, io.SEEK_CUR), 0)
-        self.assertEqual(buf.read(1), b"1")
-
-        # In the C implementation, tell() sets the BufferedIO's abs_pos to 0,
-        # which means that the next seek() could return a negative offset if it
-        # does not sanity-check:
-        self.assertEqual(buf.tell(), 0)
-        self.assertEqual(buf.seek(0, io.SEEK_CUR), 0)
-
-
-class CBufferedReaderTest(BufferedReaderTest, SizeofTest):
-    tp = io.BufferedReader
-
-    def test_initialization(self):
-        rawio = self.MockRawIO([b"abc"])
-        bufio = self.tp(rawio)
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
-        self.assertRaises(ValueError, bufio.read)
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
-        self.assertRaises(ValueError, bufio.read)
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
-        self.assertRaises(ValueError, bufio.read)
-
-    def test_misbehaved_io_read(self):
-        rawio = self.MisbehavedRawIO((b"abc", b"d", b"efg"))
-        bufio = self.tp(rawio)
-        # _pyio.BufferedReader seems to implement reading different, so that
-        # checking this is not so easy.
-        self.assertRaises(OSError, bufio.read, 10)
-
-    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
-    def test_garbage_collection(self):
-        # C BufferedReader objects are collected.
-        # The Python version has __del__, so it ends into gc.garbage instead
-        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
-        with warnings_helper.check_warnings(('', ResourceWarning)):
-            rawio = self.FileIO(os_helper.TESTFN, "w+b")
-            f = self.tp(rawio)
-            f.f = f
-            wr = weakref.ref(f)
-            del f
-            support.gc_collect()
-        self.assertIsNone(wr(), wr)
-
-    def test_args_error(self):
-        # Issue #17275
-        with self.assertRaisesRegex(TypeError, "BufferedReader"):
-            self.tp(self.BytesIO(), 1024, 1024, 1024)
-
-    def test_bad_readinto_value(self):
-        rawio = self.tp(self.BytesIO(b"12"))
-        rawio.readinto = lambda buf: -1
-        bufio = self.tp(rawio)
-        with self.assertRaises(OSError) as cm:
-            bufio.readline()
-        self.assertIsNone(cm.exception.__cause__)
-
-    def test_bad_readinto_type(self):
-        rawio = self.tp(self.BytesIO(b"12"))
-        rawio.readinto = lambda buf: b''
-        bufio = self.tp(rawio)
-        with self.assertRaises(OSError) as cm:
-            bufio.readline()
-        self.assertIsInstance(cm.exception.__cause__, TypeError)
-
-
-class PyBufferedReaderTest(BufferedReaderTest):
-    tp = pyio.BufferedReader
-
-
-class BufferedWriterTest(unittest.TestCase, CommonBufferedTests):
-    write_mode = "wb"
-
-    def test_constructor(self):
-        rawio = self.MockRawIO()
-        bufio = self.tp(rawio)
-        bufio.__init__(rawio)
-        bufio.__init__(rawio, buffer_size=1024)
-        bufio.__init__(rawio, buffer_size=16)
-        self.assertEqual(3, bufio.write(b"abc"))
-        bufio.flush()
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
-        bufio.__init__(rawio)
-        self.assertEqual(3, bufio.write(b"ghi"))
-        bufio.flush()
-        self.assertEqual(b"".join(rawio._write_stack), b"abcghi")
-
-    def test_uninitialized(self):
-        bufio = self.tp.__new__(self.tp)
-        del bufio
-        bufio = self.tp.__new__(self.tp)
-        self.assertRaisesRegex((ValueError, AttributeError),
-                               'uninitialized|has no attribute',
-                               bufio.write, b'')
-        bufio.__init__(self.MockRawIO())
-        self.assertEqual(bufio.write(b''), 0)
-
-    def test_detach_flush(self):
-        raw = self.MockRawIO()
-        buf = self.tp(raw)
-        buf.write(b"howdy!")
-        self.assertFalse(raw._write_stack)
-        buf.detach()
-        self.assertEqual(raw._write_stack, [b"howdy!"])
-
-    def test_write(self):
-        # Write to the buffered IO but don't overflow the buffer.
-        writer = self.MockRawIO()
-        bufio = self.tp(writer, 8)
-        bufio.write(b"abc")
-        self.assertFalse(writer._write_stack)
-        buffer = bytearray(b"def")
-        bufio.write(buffer)
-        buffer[:] = b"***"  # Overwrite our copy of the data
-        bufio.flush()
-        self.assertEqual(b"".join(writer._write_stack), b"abcdef")
-
-    def test_write_overflow(self):
-        writer = self.MockRawIO()
-        bufio = self.tp(writer, 8)
-        contents = b"abcdefghijklmnop"
-        for n in range(0, len(contents), 3):
-            bufio.write(contents[n:n+3])
-        flushed = b"".join(writer._write_stack)
-        # At least (total - 8) bytes were implicitly flushed, perhaps more
-        # depending on the implementation.
-        self.assertStartsWith(flushed, contents[:-8])
-
-    def check_writes(self, intermediate_func):
-        # Lots of writes, test the flushed output is as expected.
-        contents = bytes(range(256)) * 1000
-        n = 0
-        writer = self.MockRawIO()
-        bufio = self.tp(writer, 13)
-        # Generator of write sizes: repeat each N 15 times then proceed to N+1
-        def gen_sizes():
-            for size in count(1):
-                for i in range(15):
-                    yield size
-        sizes = gen_sizes()
-        while n < len(contents):
-            size = min(next(sizes), len(contents) - n)
-            self.assertEqual(bufio.write(contents[n:n+size]), size)
-            intermediate_func(bufio)
-            n += size
-        bufio.flush()
-        self.assertEqual(contents, b"".join(writer._write_stack))
-
-    def test_writes(self):
-        self.check_writes(lambda bufio: None)
-
-    def test_writes_and_flushes(self):
-        self.check_writes(lambda bufio: bufio.flush())
-
-    def test_writes_and_seeks(self):
-        def _seekabs(bufio):
-            pos = bufio.tell()
-            bufio.seek(pos + 1, 0)
-            bufio.seek(pos - 1, 0)
-            bufio.seek(pos, 0)
-        self.check_writes(_seekabs)
-        def _seekrel(bufio):
-            pos = bufio.seek(0, 1)
-            bufio.seek(+1, 1)
-            bufio.seek(-1, 1)
-            bufio.seek(pos, 0)
-        self.check_writes(_seekrel)
-
-    def test_writes_and_truncates(self):
-        self.check_writes(lambda bufio: bufio.truncate(bufio.tell()))
-
-    def test_write_non_blocking(self):
-        raw = self.MockNonBlockWriterIO()
-        bufio = self.tp(raw, 8)
-
-        self.assertEqual(bufio.write(b"abcd"), 4)
-        self.assertEqual(bufio.write(b"efghi"), 5)
-        # 1 byte will be written, the rest will be buffered
-        raw.block_on(b"k")
-        self.assertEqual(bufio.write(b"jklmn"), 5)
-
-        # 8 bytes will be written, 8 will be buffered and the rest will be lost
-        raw.block_on(b"0")
-        try:
-            bufio.write(b"opqrwxyz0123456789")
-        except self.BlockingIOError as e:
-            written = e.characters_written
-        else:
-            self.fail("BlockingIOError should have been raised")
-        self.assertEqual(written, 16)
-        self.assertEqual(raw.pop_written(),
-            b"abcdefghijklmnopqrwxyz")
-
-        self.assertEqual(bufio.write(b"ABCDEFGHI"), 9)
-        s = raw.pop_written()
-        # Previously buffered bytes were flushed
-        self.assertStartsWith(s, b"01234567A")
-
-    def test_write_and_rewind(self):
-        raw = self.BytesIO()
-        bufio = self.tp(raw, 4)
-        self.assertEqual(bufio.write(b"abcdef"), 6)
-        self.assertEqual(bufio.tell(), 6)
-        bufio.seek(0, 0)
-        self.assertEqual(bufio.write(b"XY"), 2)
-        bufio.seek(6, 0)
-        self.assertEqual(raw.getvalue(), b"XYcdef")
-        self.assertEqual(bufio.write(b"123456"), 6)
-        bufio.flush()
-        self.assertEqual(raw.getvalue(), b"XYcdef123456")
-
-    def test_flush(self):
-        writer = self.MockRawIO()
-        bufio = self.tp(writer, 8)
-        bufio.write(b"abc")
-        bufio.flush()
-        self.assertEqual(b"abc", writer._write_stack[0])
-
-    def test_writelines(self):
-        l = [b'ab', b'cd', b'ef']
-        writer = self.MockRawIO()
-        bufio = self.tp(writer, 8)
-        bufio.writelines(l)
-        bufio.flush()
-        self.assertEqual(b''.join(writer._write_stack), b'abcdef')
-
-    def test_writelines_userlist(self):
-        l = UserList([b'ab', b'cd', b'ef'])
-        writer = self.MockRawIO()
-        bufio = self.tp(writer, 8)
-        bufio.writelines(l)
-        bufio.flush()
-        self.assertEqual(b''.join(writer._write_stack), b'abcdef')
-
-    def test_writelines_error(self):
-        writer = self.MockRawIO()
-        bufio = self.tp(writer, 8)
-        self.assertRaises(TypeError, bufio.writelines, [1, 2, 3])
-        self.assertRaises(TypeError, bufio.writelines, None)
-        self.assertRaises(TypeError, bufio.writelines, 'abc')
-
-    def test_destructor(self):
-        writer = self.MockRawIO()
-        bufio = self.tp(writer, 8)
-        bufio.write(b"abc")
-        del bufio
-        support.gc_collect()
-        self.assertEqual(b"abc", writer._write_stack[0])
-
-    def test_truncate(self):
-        # Truncate implicitly flushes the buffer.
-        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
-        with self.open(os_helper.TESTFN, self.write_mode, buffering=0) as raw:
-            bufio = self.tp(raw, 8)
-            bufio.write(b"abcdef")
-            self.assertEqual(bufio.truncate(3), 3)
-            self.assertEqual(bufio.tell(), 6)
-        with self.open(os_helper.TESTFN, "rb", buffering=0) as f:
-            self.assertEqual(f.read(), b"abc")
-
-    def test_truncate_after_write(self):
-        # Ensure that truncate preserves the file position after
-        # writes longer than the buffer size.
-        # Issue: https://bugs.python.org/issue32228
-        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
-        with self.open(os_helper.TESTFN, "wb") as f:
-            # Fill with some buffer
-            f.write(b'\x00' * 10000)
-        buffer_sizes = [8192, 4096, 200]
-        for buffer_size in buffer_sizes:
-            with self.open(os_helper.TESTFN, "r+b", buffering=buffer_size) as f:
-                f.write(b'\x00' * (buffer_size + 1))
-                # After write write_pos and write_end are set to 0
-                f.read(1)
-                # read operation makes sure that pos != raw_pos
-                f.truncate()
-                self.assertEqual(f.tell(), buffer_size + 2)
-
-    @threading_helper.requires_working_threading()
-    @support.requires_resource('cpu')
-    def test_threads(self):
-        try:
-            # Write out many bytes from many threads and test they were
-            # all flushed.
-            N = 1000
-            contents = bytes(range(256)) * N
-            sizes = cycle([1, 19])
-            n = 0
-            queue = deque()
-            while n < len(contents):
-                size = next(sizes)
-                queue.append(contents[n:n+size])
-                n += size
-            del contents
-            # We use a real file object because it allows us to
-            # exercise situations where the GIL is released before
-            # writing the buffer to the raw streams. This is in addition
-            # to concurrency issues due to switching threads in the middle
-            # of Python code.
-            with self.open(os_helper.TESTFN, self.write_mode, buffering=0) as raw:
-                bufio = self.tp(raw, 8)
-                errors = []
-                def f():
-                    try:
-                        while True:
-                            try:
-                                s = queue.popleft()
-                            except IndexError:
-                                return
-                            bufio.write(s)
-                    except Exception as e:
-                        errors.append(e)
-                        raise
-                threads = [threading.Thread(target=f) for x in range(20)]
-                with threading_helper.start_threads(threads):
-                    time.sleep(0.02) # yield
-                self.assertFalse(errors,
-                    "the following exceptions were caught: %r" % errors)
-                bufio.close()
-            with self.open(os_helper.TESTFN, "rb") as f:
-                s = f.read()
-            for i in range(256):
-                self.assertEqual(s.count(bytes([i])), N)
-        finally:
-            os_helper.unlink(os_helper.TESTFN)
-
-    def test_misbehaved_io(self):
-        rawio = self.MisbehavedRawIO()
-        bufio = self.tp(rawio, 5)
-        self.assertRaises(OSError, bufio.seek, 0)
-        self.assertRaises(OSError, bufio.tell)
-        self.assertRaises(OSError, bufio.write, b"abcdef")
-
-        # Silence destructor error
-        bufio.close = lambda: None
-
-    def test_max_buffer_size_removal(self):
-        with self.assertRaises(TypeError):
-            self.tp(self.MockRawIO(), 8, 12)
-
-    def test_write_error_on_close(self):
-        raw = self.MockRawIO()
-        def bad_write(b):
-            raise OSError()
-        raw.write = bad_write
-        b = self.tp(raw)
-        b.write(b'spam')
-        self.assertRaises(OSError, b.close) # exception not swallowed
-        self.assertTrue(b.closed)
-
-    @threading_helper.requires_working_threading()
-    def test_slow_close_from_thread(self):
-        # Issue #31976
-        rawio = self.SlowFlushRawIO()
-        bufio = self.tp(rawio, 8)
-        t = threading.Thread(target=bufio.close)
-        t.start()
-        rawio.in_flush.wait()
-        self.assertRaises(ValueError, bufio.write, b'spam')
-        self.assertTrue(bufio.closed)
-        t.join()
-
-
-
-class CBufferedWriterTest(BufferedWriterTest, SizeofTest):
-    tp = io.BufferedWriter
-
-    def test_initialization(self):
-        rawio = self.MockRawIO()
-        bufio = self.tp(rawio)
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
-        self.assertRaises(ValueError, bufio.write, b"def")
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
-        self.assertRaises(ValueError, bufio.write, b"def")
-        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
-        self.assertRaises(ValueError, bufio.write, b"def")
-
-    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
-    def test_garbage_collection(self):
-        # C BufferedWriter objects are collected, and collecting them flushes
-        # all data to disk.
-        # The Python version has __del__, so it ends into gc.garbage instead
-        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
-        with warnings_helper.check_warnings(('', ResourceWarning)):
-            rawio = self.FileIO(os_helper.TESTFN, "w+b")
-            f = self.tp(rawio)
-            f.write(b"123xxx")
-            f.x = f
-            wr = weakref.ref(f)
-            del f
-            support.gc_collect()
-        self.assertIsNone(wr(), wr)
-        with self.open(os_helper.TESTFN, "rb") as f:
-            self.assertEqual(f.read(), b"123xxx")
-
-    def test_args_error(self):
-        # Issue #17275
-        with self.assertRaisesRegex(TypeError, "BufferedWriter"):
-            self.tp(self.BytesIO(), 1024, 1024, 1024)
-
-
-class PyBufferedWriterTest(BufferedWriterTest):
-    tp = pyio.BufferedWriter
-
-class BufferedRWPairTest(unittest.TestCase):
-
-    def test_constructor(self):
-        pair = self.tp(self.MockRawIO(), self.MockRawIO())
-        self.assertFalse(pair.closed)
-
-    def test_uninitialized(self):
-        pair = self.tp.__new__(self.tp)
-        del pair
-        pair = self.tp.__new__(self.tp)
-        self.assertRaisesRegex((ValueError, AttributeError),
-                               'uninitialized|has no attribute',
-                               pair.read, 0)
-        self.assertRaisesRegex((ValueError, AttributeError),
-                               'uninitialized|has no attribute',
-                               pair.write, b'')
-        pair.__init__(self.MockRawIO(), self.MockRawIO())
-        self.assertEqual(pair.read(0), b'')
-        self.assertEqual(pair.write(b''), 0)
-
-    def test_detach(self):
-        pair = self.tp(self.MockRawIO(), self.MockRawIO())
-        self.assertRaises(self.UnsupportedOperation, pair.detach)
-
-    def test_constructor_max_buffer_size_removal(self):
-        with self.assertRaises(TypeError):
-            self.tp(self.MockRawIO(), self.MockRawIO(), 8, 12)
-
-    def test_constructor_with_not_readable(self):
-        class NotReadable(MockRawIO):
-            def readable(self):
-                return False
-
-        self.assertRaises(OSError, self.tp, NotReadable(), self.MockRawIO())
-
-    def test_constructor_with_not_writeable(self):
-        class NotWriteable(MockRawIO):
-            def writable(self):
-                return False
-
-        self.assertRaises(OSError, self.tp, self.MockRawIO(), NotWriteable())
-
-    def test_read(self):
-        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
-
-        self.assertEqual(pair.read(3), b"abc")
-        self.assertEqual(pair.read(1), b"d")
-        self.assertEqual(pair.read(), b"ef")
-        pair = self.tp(self.BytesIO(b"abc"), self.MockRawIO())
-        self.assertEqual(pair.read(None), b"abc")
-
-    def test_readlines(self):
-        pair = lambda: self.tp(self.BytesIO(b"abc\ndef\nh"), self.MockRawIO())
-        self.assertEqual(pair().readlines(), [b"abc\n", b"def\n", b"h"])
-        self.assertEqual(pair().readlines(), [b"abc\n", b"def\n", b"h"])
-        self.assertEqual(pair().readlines(5), [b"abc\n", b"def\n"])
-
-    def test_read1(self):
-        # .read1() is delegated to the underlying reader object, so this test
-        # can be shallow.
-        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
-
-        self.assertEqual(pair.read1(3), b"abc")
-        self.assertEqual(pair.read1(), b"def")
-
-    def test_readinto(self):
-        for method in ("readinto", "readinto1"):
-            with self.subTest(method):
-                pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
-
-                data = byteslike(b'\0' * 5)
-                self.assertEqual(getattr(pair, method)(data), 5)
-                self.assertEqual(bytes(data), b"abcde")
-
-    def test_write(self):
-        w = self.MockRawIO()
-        pair = self.tp(self.MockRawIO(), w)
-
-        pair.write(b"abc")
-        pair.flush()
-        buffer = bytearray(b"def")
-        pair.write(buffer)
-        buffer[:] = b"***"  # Overwrite our copy of the data
-        pair.flush()
-        self.assertEqual(w._write_stack, [b"abc", b"def"])
-
-    def test_peek(self):
-        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
-
-        self.assertStartsWith(pair.peek(3), b"abc")
-        self.assertEqual(pair.read(3), b"abc")
-
-    def test_readable(self):
-        pair = self.tp(self.MockRawIO(), self.MockRawIO())
-        self.assertTrue(pair.readable())
-
-    def test_writeable(self):
-        pair = self.tp(self.MockRawIO(), self.MockRawIO())
-        self.assertTrue(pair.writable())
-
-    def test_seekable(self):
-        # BufferedRWPairs are never seekable, even if their readers and writers
-        # are.
-        pair = self.tp(self.MockRawIO(), self.MockRawIO())
-        self.assertFalse(pair.seekable())
-
-    # .flush() is delegated to the underlying writer object and has been
-    # tested in the test_write method.
-
-    def test_close_and_closed(self):
-        pair = self.tp(self.MockRawIO(), self.MockRawIO())
-        self.assertFalse(pair.closed)
-        pair.close()
-        self.assertTrue(pair.closed)
-
-    def test_reader_close_error_on_close(self):
-        def reader_close():
-            reader_non_existing
-        reader = self.MockRawIO()
-        reader.close = reader_close
-        writer = self.MockRawIO()
-        pair = self.tp(reader, writer)
-        with self.assertRaises(NameError) as err:
-            pair.close()
-        self.assertIn('reader_non_existing', str(err.exception))
-        self.assertTrue(pair.closed)
-        self.assertFalse(reader.closed)
-        self.assertTrue(writer.closed)
-
-        # Silence destructor error
-        reader.close = lambda: None
-
-    def test_writer_close_error_on_close(self):
-        def writer_close():
-            writer_non_existing
-        reader = self.MockRawIO()
-        writer = self.MockRawIO()
-        writer.close = writer_close
-        pair = self.tp(reader, writer)
-        with self.assertRaises(NameError) as err:
-            pair.close()
-        self.assertIn('writer_non_existing', str(err.exception))
-        self.assertFalse(pair.closed)
-        self.assertTrue(reader.closed)
-        self.assertFalse(writer.closed)
-
-        # Silence destructor error
-        writer.close = lambda: None
-        writer = None
-
-        # Ignore BufferedWriter (of the BufferedRWPair) unraisable exception
-        with support.catch_unraisable_exception():
-            # Ignore BufferedRWPair unraisable exception
-            with support.catch_unraisable_exception():
-                pair = None
-                support.gc_collect()
-            support.gc_collect()
-
-    def test_reader_writer_close_error_on_close(self):
-        def reader_close():
-            reader_non_existing
-        def writer_close():
-            writer_non_existing
-        reader = self.MockRawIO()
-        reader.close = reader_close
-        writer = self.MockRawIO()
-        writer.close = writer_close
-        pair = self.tp(reader, writer)
-        with self.assertRaises(NameError) as err:
-            pair.close()
-        self.assertIn('reader_non_existing', str(err.exception))
-        self.assertIsInstance(err.exception.__context__, NameError)
-        self.assertIn('writer_non_existing', str(err.exception.__context__))
-        self.assertFalse(pair.closed)
-        self.assertFalse(reader.closed)
-        self.assertFalse(writer.closed)
-
-        # Silence destructor error
-        reader.close = lambda: None
-        writer.close = lambda: None
-
-    def test_isatty(self):
-        class SelectableIsAtty(MockRawIO):
-            def __init__(self, isatty):
-                MockRawIO.__init__(self)
-                self._isatty = isatty
-
-            def isatty(self):
-                return self._isatty
-
-        pair = self.tp(SelectableIsAtty(False), SelectableIsAtty(False))
-        self.assertFalse(pair.isatty())
-
-        pair = self.tp(SelectableIsAtty(True), SelectableIsAtty(False))
-        self.assertTrue(pair.isatty())
-
-        pair = self.tp(SelectableIsAtty(False), SelectableIsAtty(True))
-        self.assertTrue(pair.isatty())
-
-        pair = self.tp(SelectableIsAtty(True), SelectableIsAtty(True))
-        self.assertTrue(pair.isatty())
-
-    def test_weakref_clearing(self):
-        brw = self.tp(self.MockRawIO(), self.MockRawIO())
-        ref = weakref.ref(brw)
-        brw = None
-        ref = None # Shouldn't segfault.
-
-class CBufferedRWPairTest(BufferedRWPairTest):
-    tp = io.BufferedRWPair
-
-class PyBufferedRWPairTest(BufferedRWPairTest):
-    tp = pyio.BufferedRWPair
-
-
-class BufferedRandomTest(BufferedReaderTest, BufferedWriterTest):
-    read_mode = "rb+"
-    write_mode = "wb+"
-
-    def test_constructor(self):
-        BufferedReaderTest.test_constructor(self)
-        BufferedWriterTest.test_constructor(self)
-
-    def test_uninitialized(self):
-        BufferedReaderTest.test_uninitialized(self)
-        BufferedWriterTest.test_uninitialized(self)
-
-    def test_read_and_write(self):
-        raw = self.MockRawIO((b"asdf", b"ghjk"))
-        rw = self.tp(raw, 8)
-
-        self.assertEqual(b"as", rw.read(2))
-        rw.write(b"ddd")
-        rw.write(b"eee")
-        self.assertFalse(raw._write_stack) # Buffer writes
-        self.assertEqual(b"ghjk", rw.read())
-        self.assertEqual(b"dddeee", raw._write_stack[0])
-
-    def test_seek_and_tell(self):
-        raw = self.BytesIO(b"asdfghjkl")
-        rw = self.tp(raw)
-
-        self.assertEqual(b"as", rw.read(2))
-        self.assertEqual(2, rw.tell())
-        rw.seek(0, 0)
-        self.assertEqual(b"asdf", rw.read(4))
-
-        rw.write(b"123f")
-        rw.seek(0, 0)
-        self.assertEqual(b"asdf123fl", rw.read())
-        self.assertEqual(9, rw.tell())
-        rw.seek(-4, 2)
-        self.assertEqual(5, rw.tell())
-        rw.seek(2, 1)
-        self.assertEqual(7, rw.tell())
-        self.assertEqual(b"fl", rw.read(11))
-        rw.flush()
-        self.assertEqual(b"asdf123fl", raw.getvalue())
-
-        self.assertRaises(TypeError, rw.seek, 0.0)
-
-    def check_flush_and_read(self, read_func):
-        raw = self.BytesIO(b"abcdefghi")
-        bufio = self.tp(raw)
-
-        self.assertEqual(b"ab", read_func(bufio, 2))
-        bufio.write(b"12")
-        self.assertEqual(b"ef", read_func(bufio, 2))
-        self.assertEqual(6, bufio.tell())
-        bufio.flush()
-        self.assertEqual(6, bufio.tell())
-        self.assertEqual(b"ghi", read_func(bufio))
-        raw.seek(0, 0)
-        raw.write(b"XYZ")
-        # flush() resets the read buffer
-        bufio.flush()
-        bufio.seek(0, 0)
-        self.assertEqual(b"XYZ", read_func(bufio, 3))
-
-    def test_flush_and_read(self):
-        self.check_flush_and_read(lambda bufio, *args: bufio.read(*args))
-
-    def test_flush_and_readinto(self):
-        def _readinto(bufio, n=-1):
-            b = bytearray(n if n >= 0 else 9999)
-            n = bufio.readinto(b)
-            return bytes(b[:n])
-        self.check_flush_and_read(_readinto)
-
-    def test_flush_and_peek(self):
-        def _peek(bufio, n=-1):
-            # This relies on the fact that the buffer can contain the whole
-            # raw stream, otherwise peek() can return less.
-            b = bufio.peek(n)
-            if n != -1:
-                b = b[:n]
-            bufio.seek(len(b), 1)
-            return b
-        self.check_flush_and_read(_peek)
-
-    def test_flush_and_write(self):
-        raw = self.BytesIO(b"abcdefghi")
-        bufio = self.tp(raw)
-
-        bufio.write(b"123")
-        bufio.flush()
-        bufio.write(b"45")
-        bufio.flush()
-        bufio.seek(0, 0)
-        self.assertEqual(b"12345fghi", raw.getvalue())
-        self.assertEqual(b"12345fghi", bufio.read())
-
-    def test_threads(self):
-        BufferedReaderTest.test_threads(self)
-        BufferedWriterTest.test_threads(self)
-
-    def test_writes_and_peek(self):
-        def _peek(bufio):
-            bufio.peek(1)
-        self.check_writes(_peek)
-        def _peek(bufio):
-            pos = bufio.tell()
-            bufio.seek(-1, 1)
-            bufio.peek(1)
-            bufio.seek(pos, 0)
-        self.check_writes(_peek)
-
-    def test_writes_and_reads(self):
-        def _read(bufio):
-            bufio.seek(-1, 1)
-            bufio.read(1)
-        self.check_writes(_read)
-
-    def test_writes_and_read1s(self):
-        def _read1(bufio):
-            bufio.seek(-1, 1)
-            bufio.read1(1)
-        self.check_writes(_read1)
-
-    def test_writes_and_readintos(self):
-        def _read(bufio):
-            bufio.seek(-1, 1)
-            bufio.readinto(bytearray(1))
-        self.check_writes(_read)
-
-    def test_write_after_readahead(self):
-        # Issue #6629: writing after the buffer was filled by readahead should
-        # first rewind the raw stream.
-        for overwrite_size in [1, 5]:
-            raw = self.BytesIO(b"A" * 10)
-            bufio = self.tp(raw, 4)
-            # Trigger readahead
-            self.assertEqual(bufio.read(1), b"A")
-            self.assertEqual(bufio.tell(), 1)
-            # Overwriting should rewind the raw stream if it needs so
-            bufio.write(b"B" * overwrite_size)
-            self.assertEqual(bufio.tell(), overwrite_size + 1)
-            # If the write size was smaller than the buffer size, flush() and
-            # check that rewind happens.
-            bufio.flush()
-            self.assertEqual(bufio.tell(), overwrite_size + 1)
-            s = raw.getvalue()
-            self.assertEqual(s,
-                b"A" + b"B" * overwrite_size + b"A" * (9 - overwrite_size))
-
-    def test_write_rewind_write(self):
-        # Various combinations of reading / writing / seeking backwards / writing again
-        def mutate(bufio, pos1, pos2):
-            assert pos2 >= pos1
-            # Fill the buffer
-            bufio.seek(pos1)
-            bufio.read(pos2 - pos1)
-            bufio.write(b'\x02')
-            # This writes earlier than the previous write, but still inside
-            # the buffer.
-            bufio.seek(pos1)
-            bufio.write(b'\x01')
-
-        b = b"\x80\x81\x82\x83\x84"
-        for i in range(0, len(b)):
-            for j in range(i, len(b)):
-                raw = self.BytesIO(b)
-                bufio = self.tp(raw, 100)
-                mutate(bufio, i, j)
-                bufio.flush()
-                expected = bytearray(b)
-                expected[j] = 2
-                expected[i] = 1
-                self.assertEqual(raw.getvalue(), expected,
-                                 "failed result for i=%d, j=%d" % (i, j))
-
-    def test_truncate_after_read_or_write(self):
-        raw = self.BytesIO(b"A" * 10)
-        bufio = self.tp(raw, 100)
-        self.assertEqual(bufio.read(2), b"AA") # the read buffer gets filled
-        self.assertEqual(bufio.truncate(), 2)
-        self.assertEqual(bufio.write(b"BB"), 2) # the write buffer increases
-        self.assertEqual(bufio.truncate(), 4)
-
-    def test_misbehaved_io(self):
-        BufferedReaderTest.test_misbehaved_io(self)
-        BufferedWriterTest.test_misbehaved_io(self)
-
-    def test_interleaved_read_write(self):
-        # Test for issue #12213
-        with self.BytesIO(b'abcdefgh') as raw:
-            with self.tp(raw, 100) as f:
-                f.write(b"1")
-                self.assertEqual(f.read(1), b'b')
-                f.write(b'2')
-                self.assertEqual(f.read1(1), b'd')
-                f.write(b'3')
-                buf = bytearray(1)
-                f.readinto(buf)
-                self.assertEqual(buf, b'f')
-                f.write(b'4')
-                self.assertEqual(f.peek(1), b'h')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'1b2d3f4h')
-
-        with self.BytesIO(b'abc') as raw:
-            with self.tp(raw, 100) as f:
-                self.assertEqual(f.read(1), b'a')
-                f.write(b"2")
-                self.assertEqual(f.read(1), b'c')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'a2c')
-
-    def test_read1_after_write(self):
-        with self.BytesIO(b'abcdef') as raw:
-            with self.tp(raw, 3) as f:
-                f.write(b"1")
-                self.assertEqual(f.read1(1), b'b')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'1bcdef')
-        with self.BytesIO(b'abcdef') as raw:
-            with self.tp(raw, 3) as f:
-                f.write(b"1")
-                self.assertEqual(f.read1(), b'bcd')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'1bcdef')
-        with self.BytesIO(b'abcdef') as raw:
-            with self.tp(raw, 3) as f:
-                f.write(b"1")
-                # XXX: read(100) returns different numbers of bytes
-                # in Python and C implementations.
-                self.assertEqual(f.read1(100)[:3], b'bcd')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'1bcdef')
-
-    def test_interleaved_readline_write(self):
-        with self.BytesIO(b'ab\ncdef\ng\n') as raw:
-            with self.tp(raw) as f:
-                f.write(b'1')
-                self.assertEqual(f.readline(), b'b\n')
-                f.write(b'2')
-                self.assertEqual(f.readline(), b'def\n')
-                f.write(b'3')
-                self.assertEqual(f.readline(), b'\n')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'1b\n2def\n3\n')
-
-    # You can't construct a BufferedRandom over a non-seekable stream.
-    test_unseekable = None
-
-    # writable() returns True, so there's no point to test it over
-    # a writable stream.
-    test_truncate_on_read_only = None
-
-
-class CBufferedRandomTest(BufferedRandomTest, SizeofTest):
-    tp = io.BufferedRandom
-
-    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
-    def test_garbage_collection(self):
-        CBufferedReaderTest.test_garbage_collection(self)
-        CBufferedWriterTest.test_garbage_collection(self)
-
-    def test_args_error(self):
-        # Issue #17275
-        with self.assertRaisesRegex(TypeError, "BufferedRandom"):
-            self.tp(self.BytesIO(), 1024, 1024, 1024)
-
-
-class PyBufferedRandomTest(BufferedRandomTest):
-    tp = pyio.BufferedRandom
-
-
-# To fully exercise seek/tell, the StatefulIncrementalDecoder has these
-# properties:
-#   - A single output character can correspond to many bytes of input.
-#   - The number of input bytes to complete the character can be
-#     undetermined until the last input byte is received.
-#   - The number of input bytes can vary depending on previous input.
-#   - A single input byte can correspond to many characters of output.
-#   - The number of output characters can be undetermined until the
-#     last input byte is received.
-#   - The number of output characters can vary depending on previous input.
-
-class StatefulIncrementalDecoder(codecs.IncrementalDecoder):
-    """
-    For testing seek/tell behavior with a stateful, buffering decoder.
-
-    Input is a sequence of words.  Words may be fixed-length (length set
-    by input) or variable-length (period-terminated).  In variable-length
-    mode, extra periods are ignored.  Possible words are:
-      - 'i' followed by a number sets the input length, I (maximum 99).
-        When I is set to 0, words are space-terminated.
-      - 'o' followed by a number sets the output length, O (maximum 99).
-      - Any other word is converted into a word followed by a period on
-        the output.  The output word consists of the input word truncated
-        or padded out with hyphens to make its length equal to O.  If O
-        is 0, the word is output verbatim without truncating or padding.
-    I and O are initially set to 1.  When I changes, any buffered input is
-    re-scanned according to the new I.  EOF also terminates the last word.
-    """
-
-    def __init__(self, errors='strict'):
-        codecs.IncrementalDecoder.__init__(self, errors)
-        self.reset()
-
-    def __repr__(self):
-        return '<SID %x>' % id(self)
-
-    def reset(self):
-        self.i = 1
-        self.o = 1
-        self.buffer = bytearray()
-
-    def getstate(self):
-        i, o = self.i ^ 1, self.o ^ 1 # so that flags = 0 after reset()
-        return bytes(self.buffer), i*100 + o
-
-    def setstate(self, state):
-        buffer, io = state
-        self.buffer = bytearray(buffer)
-        i, o = divmod(io, 100)
-        self.i, self.o = i ^ 1, o ^ 1
-
-    def decode(self, input, final=False):
-        output = ''
-        for b in input:
-            if self.i == 0: # variable-length, terminated with period
-                if b == ord('.'):
-                    if self.buffer:
-                        output += self.process_word()
-                else:
-                    self.buffer.append(b)
-            else: # fixed-length, terminate after self.i bytes
-                self.buffer.append(b)
-                if len(self.buffer) == self.i:
-                    output += self.process_word()
-        if final and self.buffer: # EOF terminates the last word
-            output += self.process_word()
-        return output
-
-    def process_word(self):
-        output = ''
-        if self.buffer[0] == ord('i'):
-            self.i = min(99, int(self.buffer[1:] or 0)) # set input length
-        elif self.buffer[0] == ord('o'):
-            self.o = min(99, int(self.buffer[1:] or 0)) # set output length
-        else:
-            output = self.buffer.decode('ascii')
-            if len(output) < self.o:
-                output += '-'*self.o # pad out with hyphens
-            if self.o:
-                output = output[:self.o] # truncate to output length
-            output += '.'
-        self.buffer = bytearray()
-        return output
-
-    codecEnabled = False
-
-
-# bpo-41919: This method is separated from StatefulIncrementalDecoder to avoid a resource leak
-# when registering codecs and cleanup functions.
-def lookupTestDecoder(name):
-    if StatefulIncrementalDecoder.codecEnabled and name == 'test_decoder':
-        latin1 = codecs.lookup('latin-1')
-        return codecs.CodecInfo(
-            name='test_decoder', encode=latin1.encode, decode=None,
-            incrementalencoder=None,
-            streamreader=None, streamwriter=None,
-            incrementaldecoder=StatefulIncrementalDecoder)
-
-
-class StatefulIncrementalDecoderTest(unittest.TestCase):
-    """
-    Make sure the StatefulIncrementalDecoder actually works.
-    """
-
-    test_cases = [
-        # I=1, O=1 (fixed-length input == fixed-length output)
-        (b'abcd', False, 'a.b.c.d.'),
-        # I=0, O=0 (variable-length input, variable-length output)
-        (b'oiabcd', True, 'abcd.'),
-        # I=0, O=0 (should ignore extra periods)
-        (b'oi...abcd...', True, 'abcd.'),
-        # I=0, O=6 (variable-length input, fixed-length output)
-        (b'i.o6.x.xyz.toolongtofit.', False, 'x-----.xyz---.toolon.'),
-        # I=2, O=6 (fixed-length input < fixed-length output)
-        (b'i.i2.o6xyz', True, 'xy----.z-----.'),
-        # I=6, O=3 (fixed-length input > fixed-length output)
-        (b'i.o3.i6.abcdefghijklmnop', True, 'abc.ghi.mno.'),
-        # I=0, then 3; O=29, then 15 (with longer output)
-        (b'i.o29.a.b.cde.o15.abcdefghijabcdefghij.i3.a.b.c.d.ei00k.l.m', True,
-         'a----------------------------.' +
-         'b----------------------------.' +
-         'cde--------------------------.' +
-         'abcdefghijabcde.' +
-         'a.b------------.' +
-         '.c.------------.' +
-         'd.e------------.' +
-         'k--------------.' +
-         'l--------------.' +
-         'm--------------.')
-    ]
-
-    def test_decoder(self):
-        # Try a few one-shot test cases.
-        for input, eof, output in self.test_cases:
-            d = StatefulIncrementalDecoder()
-            self.assertEqual(d.decode(input, eof), output)
-
-        # Also test an unfinished decode, followed by forcing EOF.
-        d = StatefulIncrementalDecoder()
-        self.assertEqual(d.decode(b'oiabcd'), '')
-        self.assertEqual(d.decode(b'', 1), 'abcd.')
-
-class TextIOWrapperTest(unittest.TestCase):
-
-    def setUp(self):
-        self.testdata = b"AAA\r\nBBB\rCCC\r\nDDD\nEEE\r\n"
-        self.normalized = b"AAA\nBBB\nCCC\nDDD\nEEE\n".decode("ascii")
-        os_helper.unlink(os_helper.TESTFN)
-        codecs.register(lookupTestDecoder)
-        self.addCleanup(codecs.unregister, lookupTestDecoder)
-
-    def tearDown(self):
-        os_helper.unlink(os_helper.TESTFN)
-
-    def test_constructor(self):
-        r = self.BytesIO(b"\xc3\xa9\n\n")
-        b = self.BufferedReader(r, 1000)
-        t = self.TextIOWrapper(b, encoding="utf-8")
-        t.__init__(b, encoding="latin-1", newline="\r\n")
-        self.assertEqual(t.encoding, "latin-1")
-        self.assertEqual(t.line_buffering, False)
-        t.__init__(b, encoding="utf-8", line_buffering=True)
-        self.assertEqual(t.encoding, "utf-8")
-        self.assertEqual(t.line_buffering, True)
-        self.assertEqual("\xe9\n", t.readline())
-        invalid_type = TypeError if self.is_C else ValueError
-        with self.assertRaises(invalid_type):
-            t.__init__(b, encoding=42)
-        with self.assertRaises(UnicodeEncodeError):
-            t.__init__(b, encoding='\udcfe')
-        with self.assertRaises(ValueError):
-            t.__init__(b, encoding='utf-8\0')
-        with self.assertRaises(invalid_type):
-            t.__init__(b, encoding="utf-8", errors=42)
-        if support.Py_DEBUG or sys.flags.dev_mode or self.is_C:
-            with self.assertRaises(UnicodeEncodeError):
-                t.__init__(b, encoding="utf-8", errors='\udcfe')
-        if support.Py_DEBUG or sys.flags.dev_mode or self.is_C:
-            with self.assertRaises(ValueError):
-                t.__init__(b, encoding="utf-8", errors='replace\0')
-        with self.assertRaises(TypeError):
-            t.__init__(b, encoding="utf-8", newline=42)
-        with self.assertRaises(ValueError):
-            t.__init__(b, encoding="utf-8", newline='\udcfe')
-        with self.assertRaises(ValueError):
-            t.__init__(b, encoding="utf-8", newline='\n\0')
-        with self.assertRaises(ValueError):
-            t.__init__(b, encoding="utf-8", newline='xyzzy')
-
-    def test_uninitialized(self):
-        t = self.TextIOWrapper.__new__(self.TextIOWrapper)
-        del t
-        t = self.TextIOWrapper.__new__(self.TextIOWrapper)
-        self.assertRaises(Exception, repr, t)
-        self.assertRaisesRegex((ValueError, AttributeError),
-                               'uninitialized|has no attribute',
-                               t.read, 0)
-        t.__init__(self.MockRawIO(), encoding="utf-8")
-        self.assertEqual(t.read(0), '')
-
-    def test_non_text_encoding_codecs_are_rejected(self):
-        # Ensure the constructor complains if passed a codec that isn't
-        # marked as a text encoding
-        # http://bugs.python.org/issue20404
-        r = self.BytesIO()
-        b = self.BufferedWriter(r)
-        with self.assertRaisesRegex(LookupError, "is not a text encoding"):
-            self.TextIOWrapper(b, encoding="hex")
-
-    def test_detach(self):
-        r = self.BytesIO()
-        b = self.BufferedWriter(r)
-        t = self.TextIOWrapper(b, encoding="ascii")
-        self.assertIs(t.detach(), b)
-
-        t = self.TextIOWrapper(b, encoding="ascii")
-        t.write("howdy")
-        self.assertFalse(r.getvalue())
-        t.detach()
-        self.assertEqual(r.getvalue(), b"howdy")
-        self.assertRaises(ValueError, t.detach)
-
-        # Operations independent of the detached stream should still work
-        repr(t)
-        self.assertEqual(t.encoding, "ascii")
-        self.assertEqual(t.errors, "strict")
-        self.assertFalse(t.line_buffering)
-        self.assertFalse(t.write_through)
-
-    def test_repr(self):
-        raw = self.BytesIO("hello".encode("utf-8"))
-        b = self.BufferedReader(raw)
-        t = self.TextIOWrapper(b, encoding="utf-8")
-        modname = self.TextIOWrapper.__module__
-        self.assertRegex(repr(t),
-                         r"<(%s\.)?TextIOWrapper encoding='utf-8'>" % modname)
-        raw.name = "dummy"
-        self.assertRegex(repr(t),
-                         r"<(%s\.)?TextIOWrapper name='dummy' encoding='utf-8'>" % modname)
-        t.mode = "r"
-        self.assertRegex(repr(t),
-                         r"<(%s\.)?TextIOWrapper name='dummy' mode='r' encoding='utf-8'>" % modname)
-        raw.name = b"dummy"
-        self.assertRegex(repr(t),
-                         r"<(%s\.)?TextIOWrapper name=b'dummy' mode='r' encoding='utf-8'>" % modname)
-
-        t.buffer.detach()
-        repr(t)  # Should not raise an exception
-
-    def test_recursive_repr(self):
-        # Issue #25455
-        raw = self.BytesIO()
-        t = self.TextIOWrapper(raw, encoding="utf-8")
-        with support.swap_attr(raw, 'name', t), support.infinite_recursion(25):
-            with self.assertRaises(RuntimeError):
-                repr(t)  # Should not crash
-
-    def test_subclass_repr(self):
-        class TestSubclass(self.TextIOWrapper):
-            pass
-
-        f = TestSubclass(self.StringIO())
-        self.assertIn(TestSubclass.__name__, repr(f))
-
-    def test_line_buffering(self):
-        r = self.BytesIO()
-        b = self.BufferedWriter(r, 1000)
-        t = self.TextIOWrapper(b, encoding="utf-8", newline="\n", line_buffering=True)
-        t.write("X")
-        self.assertEqual(r.getvalue(), b"")  # No flush happened
-        t.write("Y\nZ")
-        self.assertEqual(r.getvalue(), b"XY\nZ")  # All got flushed
-        t.write("A\rB")
-        self.assertEqual(r.getvalue(), b"XY\nZA\rB")
-
-    def test_reconfigure_line_buffering(self):
-        r = self.BytesIO()
-        b = self.BufferedWriter(r, 1000)
-        t = self.TextIOWrapper(b, encoding="utf-8", newline="\n", line_buffering=False)
-        t.write("AB\nC")
-        self.assertEqual(r.getvalue(), b"")
-
-        t.reconfigure(line_buffering=True)   # implicit flush
-        self.assertEqual(r.getvalue(), b"AB\nC")
-        t.write("DEF\nG")
-        self.assertEqual(r.getvalue(), b"AB\nCDEF\nG")
-        t.write("H")
-        self.assertEqual(r.getvalue(), b"AB\nCDEF\nG")
-        t.reconfigure(line_buffering=False)   # implicit flush
-        self.assertEqual(r.getvalue(), b"AB\nCDEF\nGH")
-        t.write("IJ")
-        self.assertEqual(r.getvalue(), b"AB\nCDEF\nGH")
-
-        # Keeping default value
-        t.reconfigure()
-        t.reconfigure(line_buffering=None)
-        self.assertEqual(t.line_buffering, False)
-        t.reconfigure(line_buffering=True)
-        t.reconfigure()
-        t.reconfigure(line_buffering=None)
-        self.assertEqual(t.line_buffering, True)
-
-    @unittest.skipIf(sys.flags.utf8_mode, "utf-8 mode is enabled")
-    def test_default_encoding(self):
-        with os_helper.EnvironmentVarGuard() as env:
-            # try to get a user preferred encoding different than the current
-            # locale encoding to check that TextIOWrapper() uses the current
-            # locale encoding and not the user preferred encoding
-            env.unset('LC_ALL', 'LANG', 'LC_CTYPE')
-
-            current_locale_encoding = locale.getencoding()
-            b = self.BytesIO()
-            with warnings.catch_warnings():
-                warnings.simplefilter("ignore", EncodingWarning)
-                t = self.TextIOWrapper(b)
-            self.assertEqual(t.encoding, current_locale_encoding)
-
-    def test_encoding(self):
-        # Check the encoding attribute is always set, and valid
-        b = self.BytesIO()
-        t = self.TextIOWrapper(b, encoding="utf-8")
-        self.assertEqual(t.encoding, "utf-8")
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", EncodingWarning)
-            t = self.TextIOWrapper(b)
-        self.assertIsNotNone(t.encoding)
-        codecs.lookup(t.encoding)
-
-    def test_encoding_errors_reading(self):
-        # (1) default
-        b = self.BytesIO(b"abc\n\xff\n")
-        t = self.TextIOWrapper(b, encoding="ascii")
-        self.assertRaises(UnicodeError, t.read)
-        # (2) explicit strict
-        b = self.BytesIO(b"abc\n\xff\n")
-        t = self.TextIOWrapper(b, encoding="ascii", errors="strict")
-        self.assertRaises(UnicodeError, t.read)
-        # (3) ignore
-        b = self.BytesIO(b"abc\n\xff\n")
-        t = self.TextIOWrapper(b, encoding="ascii", errors="ignore")
-        self.assertEqual(t.read(), "abc\n\n")
-        # (4) replace
-        b = self.BytesIO(b"abc\n\xff\n")
-        t = self.TextIOWrapper(b, encoding="ascii", errors="replace")
-        self.assertEqual(t.read(), "abc\n\ufffd\n")
-
-    def test_encoding_errors_writing(self):
-        # (1) default
-        b = self.BytesIO()
-        t = self.TextIOWrapper(b, encoding="ascii")
-        self.assertRaises(UnicodeError, t.write, "\xff")
-        # (2) explicit strict
-        b = self.BytesIO()
-        t = self.TextIOWrapper(b, encoding="ascii", errors="strict")
-        self.assertRaises(UnicodeError, t.write, "\xff")
-        # (3) ignore
-        b = self.BytesIO()
-        t = self.TextIOWrapper(b, encoding="ascii", errors="ignore",
-                             newline="\n")
-        t.write("abc\xffdef\n")
-        t.flush()
-        self.assertEqual(b.getvalue(), b"abcdef\n")
-        # (4) replace
-        b = self.BytesIO()
-        t = self.TextIOWrapper(b, encoding="ascii", errors="replace",
-                             newline="\n")
-        t.write("abc\xffdef\n")
-        t.flush()
-        self.assertEqual(b.getvalue(), b"abc?def\n")
-
-    def test_newlines(self):
-        input_lines = [ "unix\n", "windows\r\n", "os9\r", "last\n", "nonl" ]
-
-        tests = [
-            [ None, [ 'unix\n', 'windows\n', 'os9\n', 'last\n', 'nonl' ] ],
-            [ '', input_lines ],
-            [ '\n', [ "unix\n", "windows\r\n", "os9\rlast\n", "nonl" ] ],
-            [ '\r\n', [ "unix\nwindows\r\n", "os9\rlast\nnonl" ] ],
-            [ '\r', [ "unix\nwindows\r", "\nos9\r", "last\nnonl" ] ],
-        ]
-        encodings = (
-            'utf-8', 'latin-1',
-            'utf-16', 'utf-16-le', 'utf-16-be',
-            'utf-32', 'utf-32-le', 'utf-32-be',
-        )
-
-        # Try a range of buffer sizes to test the case where \r is the last
-        # character in TextIOWrapper._pending_line.
-        for encoding in encodings:
-            # XXX: str.encode() should return bytes
-            data = bytes(''.join(input_lines).encode(encoding))
-            for do_reads in (False, True):
-                for bufsize in range(1, 10):
-                    for newline, exp_lines in tests:
-                        bufio = self.BufferedReader(self.BytesIO(data), bufsize)
-                        textio = self.TextIOWrapper(bufio, newline=newline,
-                                                  encoding=encoding)
-                        if do_reads:
-                            got_lines = []
-                            while True:
-                                c2 = textio.read(2)
-                                if c2 == '':
-                                    break
-                                self.assertEqual(len(c2), 2)
-                                got_lines.append(c2 + textio.readline())
-                        else:
-                            got_lines = list(textio)
-
-                        for got_line, exp_line in zip(got_lines, exp_lines):
-                            self.assertEqual(got_line, exp_line)
-                        self.assertEqual(len(got_lines), len(exp_lines))
-
-    def test_newlines_input(self):
-        testdata = b"AAA\nBB\x00B\nCCC\rDDD\rEEE\r\nFFF\r\nGGG"
-        normalized = testdata.replace(b"\r\n", b"\n").replace(b"\r", b"\n")
-        for newline, expected in [
-            (None, normalized.decode("ascii").splitlines(keepends=True)),
-            ("", testdata.decode("ascii").splitlines(keepends=True)),
-            ("\n", ["AAA\n", "BB\x00B\n", "CCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
-            ("\r\n", ["AAA\nBB\x00B\nCCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
-            ("\r",  ["AAA\nBB\x00B\nCCC\r", "DDD\r", "EEE\r", "\nFFF\r", "\nGGG"]),
-            ]:
-            buf = self.BytesIO(testdata)
-            txt = self.TextIOWrapper(buf, encoding="ascii", newline=newline)
-            self.assertEqual(txt.readlines(), expected)
-            txt.seek(0)
-            self.assertEqual(txt.read(), "".join(expected))
-
-    def test_newlines_output(self):
-        testdict = {
-            "": b"AAA\nBBB\nCCC\nX\rY\r\nZ",
-            "\n": b"AAA\nBBB\nCCC\nX\rY\r\nZ",
-            "\r": b"AAA\rBBB\rCCC\rX\rY\r\rZ",
-            "\r\n": b"AAA\r\nBBB\r\nCCC\r\nX\rY\r\r\nZ",
-            }
-        tests = [(None, testdict[os.linesep])] + sorted(testdict.items())
-        for newline, expected in tests:
-            buf = self.BytesIO()
-            txt = self.TextIOWrapper(buf, encoding="ascii", newline=newline)
-            txt.write("AAA\nB")
-            txt.write("BB\nCCC\n")
-            txt.write("X\rY\r\nZ")
-            txt.flush()
-            self.assertEqual(buf.closed, False)
-            self.assertEqual(buf.getvalue(), expected)
-
-    def test_destructor(self):
-        l = []
-        base = self.BytesIO
-        class MyBytesIO(base):
-            def close(self):
-                l.append(self.getvalue())
-                base.close(self)
-        b = MyBytesIO()
-        t = self.TextIOWrapper(b, encoding="ascii")
-        t.write("abc")
-        del t
-        support.gc_collect()
-        self.assertEqual([b"abc"], l)
-
-    def test_override_destructor(self):
-        record = []
-        class MyTextIO(self.TextIOWrapper):
-            def __del__(self):
-                record.append(1)
-                try:
-                    f = super().__del__
-                except AttributeError:
-                    pass
-                else:
-                    f()
-            def close(self):
-                record.append(2)
-                super().close()
-            def flush(self):
-                record.append(3)
-                super().flush()
-        b = self.BytesIO()
-        t = MyTextIO(b, encoding="ascii")
-        del t
-        support.gc_collect()
-        self.assertEqual(record, [1, 2, 3])
-
-    def test_error_through_destructor(self):
-        # Test that the exception state is not modified by a destructor,
-        # even if close() fails.
-        rawio = self.CloseFailureIO()
-        with support.catch_unraisable_exception() as cm:
-            with self.assertRaises(AttributeError):
-                self.TextIOWrapper(rawio, encoding="utf-8").xyzzy
-
-            self.assertEqual(cm.unraisable.exc_type, OSError)
-
-    # Systematic tests of the text I/O API
-
-    def test_basic_io(self):
-        for chunksize in (1, 2, 3, 4, 5, 15, 16, 17, 31, 32, 33, 63, 64, 65):
-            for enc in "ascii", "latin-1", "utf-8" :# , "utf-16-be", "utf-16-le":
-                f = self.open(os_helper.TESTFN, "w+", encoding=enc)
-                f._CHUNK_SIZE = chunksize
-                self.assertEqual(f.write("abc"), 3)
-                f.close()
-                f = self.open(os_helper.TESTFN, "r+", encoding=enc)
-                f._CHUNK_SIZE = chunksize
-                self.assertEqual(f.tell(), 0)
-                self.assertEqual(f.read(), "abc")
-                cookie = f.tell()
-                self.assertEqual(f.seek(0), 0)
-                self.assertEqual(f.read(None), "abc")
-                f.seek(0)
-                self.assertEqual(f.read(2), "ab")
-                self.assertEqual(f.read(1), "c")
-                self.assertEqual(f.read(1), "")
-                self.assertEqual(f.read(), "")
-                self.assertEqual(f.tell(), cookie)
-                self.assertEqual(f.seek(0), 0)
-                self.assertEqual(f.seek(0, 2), cookie)
-                self.assertEqual(f.write("def"), 3)
-                self.assertEqual(f.seek(cookie), cookie)
-                self.assertEqual(f.read(), "def")
-                if enc.startswith("utf"):
-                    self.multi_line_test(f, enc)
-                f.close()
-
-    def multi_line_test(self, f, enc):
-        f.seek(0)
-        f.truncate()
-        sample = "s\xff\u0fff\uffff"
-        wlines = []
-        for size in (0, 1, 2, 3, 4, 5, 30, 31, 32, 33, 62, 63, 64, 65, 1000):
-            chars = []
-            for i in range(size):
-                chars.append(sample[i % len(sample)])
-            line = "".join(chars) + "\n"
-            wlines.append((f.tell(), line))
-            f.write(line)
-        f.seek(0)
-        rlines = []
-        while True:
-            pos = f.tell()
-            line = f.readline()
-            if not line:
-                break
-            rlines.append((pos, line))
-        self.assertEqual(rlines, wlines)
-
-    def test_telling(self):
-        f = self.open(os_helper.TESTFN, "w+", encoding="utf-8")
-        p0 = f.tell()
-        f.write("\xff\n")
-        p1 = f.tell()
-        f.write("\xff\n")
-        p2 = f.tell()
-        f.seek(0)
-        self.assertEqual(f.tell(), p0)
-        self.assertEqual(f.readline(), "\xff\n")
-        self.assertEqual(f.tell(), p1)
-        self.assertEqual(f.readline(), "\xff\n")
-        self.assertEqual(f.tell(), p2)
-        f.seek(0)
-        for line in f:
-            self.assertEqual(line, "\xff\n")
-            self.assertRaises(OSError, f.tell)
-        self.assertEqual(f.tell(), p2)
-        f.close()
-
-    def test_seeking(self):
-        chunk_size = _default_chunk_size()
-        prefix_size = chunk_size - 2
-        u_prefix = "a" * prefix_size
-        prefix = bytes(u_prefix.encode("utf-8"))
-        self.assertEqual(len(u_prefix), len(prefix))
-        u_suffix = "\u8888\n"
-        suffix = bytes(u_suffix.encode("utf-8"))
-        line = prefix + suffix
-        with self.open(os_helper.TESTFN, "wb") as f:
-            f.write(line*2)
-        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
-            s = f.read(prefix_size)
-            self.assertEqual(s, str(prefix, "ascii"))
-            self.assertEqual(f.tell(), prefix_size)
-            self.assertEqual(f.readline(), u_suffix)
-
-    def test_seeking_too(self):
-        # Regression test for a specific bug
-        data = b'\xe0\xbf\xbf\n'
-        with self.open(os_helper.TESTFN, "wb") as f:
-            f.write(data)
-        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
-            f._CHUNK_SIZE  # Just test that it exists
-            f._CHUNK_SIZE = 2
-            f.readline()
-            f.tell()
-
-    def test_seek_and_tell(self):
-        #Test seek/tell using the StatefulIncrementalDecoder.
-        # Make test faster by doing smaller seeks
-        CHUNK_SIZE = 128
-
-        def test_seek_and_tell_with_data(data, min_pos=0):
-            """Tell/seek to various points within a data stream and ensure
-            that the decoded data returned by read() is consistent."""
-            f = self.open(os_helper.TESTFN, 'wb')
-            f.write(data)
-            f.close()
-            f = self.open(os_helper.TESTFN, encoding='test_decoder')
-            f._CHUNK_SIZE = CHUNK_SIZE
-            decoded = f.read()
-            f.close()
-
-            for i in range(min_pos, len(decoded) + 1): # seek positions
-                for j in [1, 5, len(decoded) - i]: # read lengths
-                    f = self.open(os_helper.TESTFN, encoding='test_decoder')
-                    self.assertEqual(f.read(i), decoded[:i])
-                    cookie = f.tell()
-                    self.assertEqual(f.read(j), decoded[i:i + j])
-                    f.seek(cookie)
-                    self.assertEqual(f.read(), decoded[i:])
-                    f.close()
-
-        # Enable the test decoder.
-        StatefulIncrementalDecoder.codecEnabled = 1
-
-        # Run the tests.
-        try:
-            # Try each test case.
-            for input, _, _ in StatefulIncrementalDecoderTest.test_cases:
-                test_seek_and_tell_with_data(input)
-
-            # Position each test case so that it crosses a chunk boundary.
-            for input, _, _ in StatefulIncrementalDecoderTest.test_cases:
-                offset = CHUNK_SIZE - len(input)//2
-                prefix = b'.'*offset
-                # Don't bother seeking into the prefix (takes too long).
-                min_pos = offset*2
-                test_seek_and_tell_with_data(prefix + input, min_pos)
-
-        # Ensure our test decoder won't interfere with subsequent tests.
-        finally:
-            StatefulIncrementalDecoder.codecEnabled = 0
-
-    def test_multibyte_seek_and_tell(self):
-        f = self.open(os_helper.TESTFN, "w", encoding="euc_jp")
-        f.write("AB\n\u3046\u3048\n")
-        f.close()
-
-        f = self.open(os_helper.TESTFN, "r", encoding="euc_jp")
-        self.assertEqual(f.readline(), "AB\n")
-        p0 = f.tell()
-        self.assertEqual(f.readline(), "\u3046\u3048\n")
-        p1 = f.tell()
-        f.seek(p0)
-        self.assertEqual(f.readline(), "\u3046\u3048\n")
-        self.assertEqual(f.tell(), p1)
-        f.close()
-
-    def test_tell_after_readline_with_cr(self):
-        # Test for gh-141314: TextIOWrapper.tell() assertion failure
-        # when dealing with standalone carriage returns
-        data = b'line1\r'
-        with self.open(os_helper.TESTFN, "wb") as f:
-            f.write(data)
-
-        with self.open(os_helper.TESTFN, "r") as f:
-            # Read line that ends with \r
-            line = f.readline()
-            self.assertEqual(line, "line1\n")
-            # This should not cause an assertion failure
-            pos = f.tell()
-            # Verify we can seek back to this position
-            f.seek(pos)
-            remaining = f.read()
-            self.assertEqual(remaining, "")
-
-    def test_seek_with_encoder_state(self):
-        f = self.open(os_helper.TESTFN, "w", encoding="euc_jis_2004")
-        f.write("\u00e6\u0300")
-        p0 = f.tell()
-        f.write("\u00e6")
-        f.seek(p0)
-        f.write("\u0300")
-        f.close()
-
-        f = self.open(os_helper.TESTFN, "r", encoding="euc_jis_2004")
-        self.assertEqual(f.readline(), "\u00e6\u0300\u0300")
-        f.close()
-
-    def test_encoded_writes(self):
-        data = "1234567890"
-        tests = ("utf-16",
-                 "utf-16-le",
-                 "utf-16-be",
-                 "utf-32",
-                 "utf-32-le",
-                 "utf-32-be")
-        for encoding in tests:
-            buf = self.BytesIO()
-            f = self.TextIOWrapper(buf, encoding=encoding)
-            # Check if the BOM is written only once (see issue1753).
-            f.write(data)
-            f.write(data)
-            f.seek(0)
-            self.assertEqual(f.read(), data * 2)
-            f.seek(0)
-            self.assertEqual(f.read(), data * 2)
-            self.assertEqual(buf.getvalue(), (data * 2).encode(encoding))
-
-    def test_unreadable(self):
-        class UnReadable(self.BytesIO):
-            def readable(self):
-                return False
-        txt = self.TextIOWrapper(UnReadable(), encoding="utf-8")
-        self.assertRaises(OSError, txt.read)
-
-    def test_read_one_by_one(self):
-        txt = self.TextIOWrapper(self.BytesIO(b"AA\r\nBB"), encoding="utf-8")
-        reads = ""
-        while True:
-            c = txt.read(1)
-            if not c:
-                break
-            reads += c
-        self.assertEqual(reads, "AA\nBB")
-
-    def test_readlines(self):
-        txt = self.TextIOWrapper(self.BytesIO(b"AA\nBB\nCC"), encoding="utf-8")
-        self.assertEqual(txt.readlines(), ["AA\n", "BB\n", "CC"])
-        txt.seek(0)
-        self.assertEqual(txt.readlines(None), ["AA\n", "BB\n", "CC"])
-        txt.seek(0)
-        self.assertEqual(txt.readlines(5), ["AA\n", "BB\n"])
-
-    # read in amounts equal to TextIOWrapper._CHUNK_SIZE which is 128.
-    def test_read_by_chunk(self):
-        # make sure "\r\n" straddles 128 char boundary.
-        txt = self.TextIOWrapper(self.BytesIO(b"A" * 127 + b"\r\nB"), encoding="utf-8")
-        reads = ""
-        while True:
-            c = txt.read(128)
-            if not c:
-                break
-            reads += c
-        self.assertEqual(reads, "A"*127+"\nB")
-
-    def test_writelines(self):
-        l = ['ab', 'cd', 'ef']
-        buf = self.BytesIO()
-        txt = self.TextIOWrapper(buf, encoding="utf-8")
-        txt.writelines(l)
-        txt.flush()
-        self.assertEqual(buf.getvalue(), b'abcdef')
-
-    def test_writelines_userlist(self):
-        l = UserList(['ab', 'cd', 'ef'])
-        buf = self.BytesIO()
-        txt = self.TextIOWrapper(buf, encoding="utf-8")
-        txt.writelines(l)
-        txt.flush()
-        self.assertEqual(buf.getvalue(), b'abcdef')
-
-    def test_writelines_error(self):
-        txt = self.TextIOWrapper(self.BytesIO(), encoding="utf-8")
-        self.assertRaises(TypeError, txt.writelines, [1, 2, 3])
-        self.assertRaises(TypeError, txt.writelines, None)
-        self.assertRaises(TypeError, txt.writelines, b'abc')
-
-    def test_issue1395_1(self):
-        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
-
-        # read one char at a time
-        reads = ""
-        while True:
-            c = txt.read(1)
-            if not c:
-                break
-            reads += c
-        self.assertEqual(reads, self.normalized)
-
-    def test_issue1395_2(self):
-        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
-        txt._CHUNK_SIZE = 4
-
-        reads = ""
-        while True:
-            c = txt.read(4)
-            if not c:
-                break
-            reads += c
-        self.assertEqual(reads, self.normalized)
-
-    def test_issue1395_3(self):
-        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
-        txt._CHUNK_SIZE = 4
-
-        reads = txt.read(4)
-        reads += txt.read(4)
-        reads += txt.readline()
-        reads += txt.readline()
-        reads += txt.readline()
-        self.assertEqual(reads, self.normalized)
-
-    def test_issue1395_4(self):
-        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
-        txt._CHUNK_SIZE = 4
-
-        reads = txt.read(4)
-        reads += txt.read()
-        self.assertEqual(reads, self.normalized)
-
-    def test_issue1395_5(self):
-        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
-        txt._CHUNK_SIZE = 4
-
-        reads = txt.read(4)
-        pos = txt.tell()
-        txt.seek(0)
-        txt.seek(pos)
-        self.assertEqual(txt.read(4), "BBB\n")
-
-    def test_issue2282(self):
-        buffer = self.BytesIO(self.testdata)
-        txt = self.TextIOWrapper(buffer, encoding="ascii")
-
-        self.assertEqual(buffer.seekable(), txt.seekable())
-
-    def test_append_bom(self):
-        # The BOM is not written again when appending to a non-empty file
-        filename = os_helper.TESTFN
-        for charset in ('utf-8-sig', 'utf-16', 'utf-32'):
-            with self.open(filename, 'w', encoding=charset) as f:
-                f.write('aaa')
-                pos = f.tell()
-            with self.open(filename, 'rb') as f:
-                self.assertEqual(f.read(), 'aaa'.encode(charset))
-
-            with self.open(filename, 'a', encoding=charset) as f:
-                f.write('xxx')
-            with self.open(filename, 'rb') as f:
-                self.assertEqual(f.read(), 'aaaxxx'.encode(charset))
-
-    def test_seek_bom(self):
-        # Same test, but when seeking manually
-        filename = os_helper.TESTFN
-        for charset in ('utf-8-sig', 'utf-16', 'utf-32'):
-            with self.open(filename, 'w', encoding=charset) as f:
-                f.write('aaa')
-                pos = f.tell()
-            with self.open(filename, 'r+', encoding=charset) as f:
-                f.seek(pos)
-                f.write('zzz')
-                f.seek(0)
-                f.write('bbb')
-            with self.open(filename, 'rb') as f:
-                self.assertEqual(f.read(), 'bbbzzz'.encode(charset))
-
-    def test_seek_append_bom(self):
-        # Same test, but first seek to the start and then to the end
-        filename = os_helper.TESTFN
-        for charset in ('utf-8-sig', 'utf-16', 'utf-32'):
-            with self.open(filename, 'w', encoding=charset) as f:
-                f.write('aaa')
-            with self.open(filename, 'a', encoding=charset) as f:
-                f.seek(0)
-                f.seek(0, self.SEEK_END)
-                f.write('xxx')
-            with self.open(filename, 'rb') as f:
-                self.assertEqual(f.read(), 'aaaxxx'.encode(charset))
-
-    def test_errors_property(self):
-        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
-            self.assertEqual(f.errors, "strict")
-        with self.open(os_helper.TESTFN, "w", encoding="utf-8", errors="replace") as f:
-            self.assertEqual(f.errors, "replace")
-
-    @support.no_tracing
-    @threading_helper.requires_working_threading()
-    def test_threads_write(self):
-        # Issue6750: concurrent writes could duplicate data
-        event = threading.Event()
-        with self.open(os_helper.TESTFN, "w", encoding="utf-8", buffering=1) as f:
-            def run(n):
-                text = "Thread%03d\n" % n
-                event.wait()
-                f.write(text)
-            threads = [threading.Thread(target=run, args=(x,))
-                       for x in range(20)]
-            with threading_helper.start_threads(threads, event.set):
-                time.sleep(0.02)
-        with self.open(os_helper.TESTFN, encoding="utf-8") as f:
-            content = f.read()
-            for n in range(20):
-                self.assertEqual(content.count("Thread%03d\n" % n), 1)
-
-    def test_flush_error_on_close(self):
-        # Test that text file is closed despite failed flush
-        # and that flush() is called before file closed.
-        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
-        closed = []
-        def bad_flush():
-            closed[:] = [txt.closed, txt.buffer.closed]
-            raise OSError()
-        txt.flush = bad_flush
-        self.assertRaises(OSError, txt.close) # exception not swallowed
-        self.assertTrue(txt.closed)
-        self.assertTrue(txt.buffer.closed)
-        self.assertTrue(closed)      # flush() called
-        self.assertFalse(closed[0])  # flush() called before file closed
-        self.assertFalse(closed[1])
-        txt.flush = lambda: None  # break reference loop
-
-    def test_close_error_on_close(self):
-        buffer = self.BytesIO(self.testdata)
-        def bad_flush():
-            raise OSError('flush')
-        def bad_close():
-            raise OSError('close')
-        buffer.close = bad_close
-        txt = self.TextIOWrapper(buffer, encoding="ascii")
-        txt.flush = bad_flush
-        with self.assertRaises(OSError) as err: # exception not swallowed
-            txt.close()
-        self.assertEqual(err.exception.args, ('close',))
-        self.assertIsInstance(err.exception.__context__, OSError)
-        self.assertEqual(err.exception.__context__.args, ('flush',))
-        self.assertFalse(txt.closed)
-
-        # Silence destructor error
-        buffer.close = lambda: None
-        txt.flush = lambda: None
-
-    def test_nonnormalized_close_error_on_close(self):
-        # Issue #21677
-        buffer = self.BytesIO(self.testdata)
-        def bad_flush():
-            raise non_existing_flush
-        def bad_close():
-            raise non_existing_close
-        buffer.close = bad_close
-        txt = self.TextIOWrapper(buffer, encoding="ascii")
-        txt.flush = bad_flush
-        with self.assertRaises(NameError) as err: # exception not swallowed
-            txt.close()
-        self.assertIn('non_existing_close', str(err.exception))
-        self.assertIsInstance(err.exception.__context__, NameError)
-        self.assertIn('non_existing_flush', str(err.exception.__context__))
-        self.assertFalse(txt.closed)
-
-        # Silence destructor error
-        buffer.close = lambda: None
-        txt.flush = lambda: None
-
-    def test_multi_close(self):
-        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
-        txt.close()
-        txt.close()
-        txt.close()
-        self.assertRaises(ValueError, txt.flush)
-
-    def test_unseekable(self):
-        txt = self.TextIOWrapper(self.MockUnseekableIO(self.testdata), encoding="utf-8")
-        self.assertRaises(self.UnsupportedOperation, txt.tell)
-        self.assertRaises(self.UnsupportedOperation, txt.seek, 0)
-
-    def test_readonly_attributes(self):
-        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
-        buf = self.BytesIO(self.testdata)
-        with self.assertRaises(AttributeError):
-            txt.buffer = buf
-
-    def test_rawio(self):
-        # Issue #12591: TextIOWrapper must work with raw I/O objects, so
-        # that subprocess.Popen() can have the required unbuffered
-        # semantics with universal_newlines=True.
-        raw = self.MockRawIO([b'abc', b'def', b'ghi\njkl\nopq\n'])
-        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
-        # Reads
-        self.assertEqual(txt.read(4), 'abcd')
-        self.assertEqual(txt.readline(), 'efghi\n')
-        self.assertEqual(list(txt), ['jkl\n', 'opq\n'])
-
-    def test_rawio_write_through(self):
-        # Issue #12591: with write_through=True, writes don't need a flush
-        raw = self.MockRawIO([b'abc', b'def', b'ghi\njkl\nopq\n'])
-        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n',
-                                 write_through=True)
-        txt.write('1')
-        txt.write('23\n4')
-        txt.write('5')
-        self.assertEqual(b''.join(raw._write_stack), b'123\n45')
-
-    def test_bufio_write_through(self):
-        # Issue #21396: write_through=True doesn't force a flush()
-        # on the underlying binary buffered object.
-        flush_called, write_called = [], []
-        class BufferedWriter(self.BufferedWriter):
-            def flush(self, *args, **kwargs):
-                flush_called.append(True)
-                return super().flush(*args, **kwargs)
-            def write(self, *args, **kwargs):
-                write_called.append(True)
-                return super().write(*args, **kwargs)
-
-        rawio = self.BytesIO()
-        data = b"a"
-        bufio = BufferedWriter(rawio, len(data)*2)
-        textio = self.TextIOWrapper(bufio, encoding='ascii',
-                                    write_through=True)
-        # write to the buffered io but don't overflow the buffer
-        text = data.decode('ascii')
-        textio.write(text)
-
-        # buffer.flush is not called with write_through=True
-        self.assertFalse(flush_called)
-        # buffer.write *is* called with write_through=True
-        self.assertTrue(write_called)
-        self.assertEqual(rawio.getvalue(), b"") # no flush
-
-        write_called = [] # reset
-        textio.write(text * 10) # total content is larger than bufio buffer
-        self.assertTrue(write_called)
-        self.assertEqual(rawio.getvalue(), data * 11) # all flushed
-
-    def test_reconfigure_write_through(self):
-        raw = self.MockRawIO([])
-        t = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
-        t.write('1')
-        t.reconfigure(write_through=True)  # implied flush
-        self.assertEqual(t.write_through, True)
-        self.assertEqual(b''.join(raw._write_stack), b'1')
-        t.write('23')
-        self.assertEqual(b''.join(raw._write_stack), b'123')
-        t.reconfigure(write_through=False)
-        self.assertEqual(t.write_through, False)
-        t.write('45')
-        t.flush()
-        self.assertEqual(b''.join(raw._write_stack), b'12345')
-        # Keeping default value
-        t.reconfigure()
-        t.reconfigure(write_through=None)
-        self.assertEqual(t.write_through, False)
-        t.reconfigure(write_through=True)
-        t.reconfigure()
-        t.reconfigure(write_through=None)
-        self.assertEqual(t.write_through, True)
-
-    def test_read_nonbytes(self):
-        # Issue #17106
-        # Crash when underlying read() returns non-bytes
-        t = self.TextIOWrapper(self.StringIO('a'), encoding="utf-8")
-        self.assertRaises(TypeError, t.read, 1)
-        t = self.TextIOWrapper(self.StringIO('a'), encoding="utf-8")
-        self.assertRaises(TypeError, t.readline)
-        t = self.TextIOWrapper(self.StringIO('a'), encoding="utf-8")
-        self.assertRaises(TypeError, t.read)
-
-    def test_illegal_encoder(self):
-        # Issue 31271: Calling write() while the return value of encoder's
-        # encode() is invalid shouldn't cause an assertion failure.
-        rot13 = codecs.lookup("rot13")
-        with support.swap_attr(rot13, '_is_text_encoding', True):
-            t = self.TextIOWrapper(self.BytesIO(b'foo'), encoding="rot13")
-        self.assertRaises(TypeError, t.write, 'bar')
-
-    def test_illegal_decoder(self):
-        # Issue #17106
-        # Bypass the early encoding check added in issue 20404
-        def _make_illegal_wrapper():
-            quopri = codecs.lookup("quopri")
-            quopri._is_text_encoding = True
-            try:
-                t = self.TextIOWrapper(self.BytesIO(b'aaaaaa'),
-                                       newline='\n', encoding="quopri")
-            finally:
-                quopri._is_text_encoding = False
-            return t
-        # Crash when decoder returns non-string
-        t = _make_illegal_wrapper()
-        self.assertRaises(TypeError, t.read, 1)
-        t = _make_illegal_wrapper()
-        self.assertRaises(TypeError, t.readline)
-        t = _make_illegal_wrapper()
-        self.assertRaises(TypeError, t.read)
-
-        # Issue 31243: calling read() while the return value of decoder's
-        # getstate() is invalid should neither crash the interpreter nor
-        # raise a SystemError.
-        def _make_very_illegal_wrapper(getstate_ret_val):
-            class BadDecoder:
-                def getstate(self):
-                    return getstate_ret_val
-            def _get_bad_decoder(dummy):
-                return BadDecoder()
-            quopri = codecs.lookup("quopri")
-            with support.swap_attr(quopri, 'incrementaldecoder',
-                                   _get_bad_decoder):
-                return _make_illegal_wrapper()
-        t = _make_very_illegal_wrapper(42)
-        self.assertRaises(TypeError, t.read, 42)
-        t = _make_very_illegal_wrapper(())
-        self.assertRaises(TypeError, t.read, 42)
-        t = _make_very_illegal_wrapper((1, 2))
-        self.assertRaises(TypeError, t.read, 42)
-
-    def _check_create_at_shutdown(self, **kwargs):
-        # Issue #20037: creating a TextIOWrapper at shutdown
-        # shouldn't crash the interpreter.
-        iomod = self.io.__name__
-        code = """if 1:
-            import codecs
-            import {iomod} as io
-
-            # Avoid looking up codecs at shutdown
-            codecs.lookup('utf-8')
-
-            class C:
-                def __del__(self):
-                    io.TextIOWrapper(io.BytesIO(), **{kwargs})
-                    print("ok")
-            c = C()
-            """.format(iomod=iomod, kwargs=kwargs)
-        return assert_python_ok("-c", code)
-
-    def test_create_at_shutdown_without_encoding(self):
-        rc, out, err = self._check_create_at_shutdown()
-        if err:
-            # Can error out with a RuntimeError if the module state
-            # isn't found.
-            self.assertIn(self.shutdown_error, err.decode())
-        else:
-            self.assertEqual("ok", out.decode().strip())
-
-    def test_create_at_shutdown_with_encoding(self):
-        rc, out, err = self._check_create_at_shutdown(encoding='utf-8',
-                                                      errors='strict')
-        self.assertFalse(err)
-        self.assertEqual("ok", out.decode().strip())
-
-    def test_read_byteslike(self):
-        r = MemviewBytesIO(b'Just some random string\n')
-        t = self.TextIOWrapper(r, 'utf-8')
-
-        # TextIOwrapper will not read the full string, because
-        # we truncate it to a multiple of the native int size
-        # so that we can construct a more complex memoryview.
-        bytes_val =  _to_memoryview(r.getvalue()).tobytes()
-
-        self.assertEqual(t.read(200), bytes_val.decode('utf-8'))
-
-    def test_issue22849(self):
-        class F(object):
-            def readable(self): return True
-            def writable(self): return True
-            def seekable(self): return True
-
-        for i in range(10):
-            try:
-                self.TextIOWrapper(F(), encoding='utf-8')
-            except Exception:
-                pass
-
-        F.tell = lambda x: 0
-        t = self.TextIOWrapper(F(), encoding='utf-8')
-
-    def test_reconfigure_locale(self):
-        wrapper = self.TextIOWrapper(self.BytesIO(b"test"))
-        wrapper.reconfigure(encoding="locale")
-
-    def test_reconfigure_encoding_read(self):
-        # latin1 -> utf8
-        # (latin1 can decode utf-8 encoded string)
-        data = 'abc\xe9\n'.encode('latin1') + 'd\xe9f\n'.encode('utf8')
-        raw = self.BytesIO(data)
-        txt = self.TextIOWrapper(raw, encoding='latin1', newline='\n')
-        self.assertEqual(txt.readline(), 'abc\xe9\n')
-        with self.assertRaises(self.UnsupportedOperation):
-            txt.reconfigure(encoding='utf-8')
-        with self.assertRaises(self.UnsupportedOperation):
-            txt.reconfigure(newline=None)
-
-    def test_reconfigure_write_fromascii(self):
-        # ascii has a specific encodefunc in the C implementation,
-        # but utf-8-sig has not. Make sure that we get rid of the
-        # cached encodefunc when we switch encoders.
-        raw = self.BytesIO()
-        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
-        txt.write('foo\n')
-        txt.reconfigure(encoding='utf-8-sig')
-        txt.write('\xe9\n')
-        txt.flush()
-        self.assertEqual(raw.getvalue(), b'foo\n\xc3\xa9\n')
-
-    def test_reconfigure_write(self):
-        # latin -> utf8
-        raw = self.BytesIO()
-        txt = self.TextIOWrapper(raw, encoding='latin1', newline='\n')
-        txt.write('abc\xe9\n')
-        txt.reconfigure(encoding='utf-8')
-        self.assertEqual(raw.getvalue(), b'abc\xe9\n')
-        txt.write('d\xe9f\n')
-        txt.flush()
-        self.assertEqual(raw.getvalue(), b'abc\xe9\nd\xc3\xa9f\n')
-
-        # ascii -> utf-8-sig: ensure that no BOM is written in the middle of
-        # the file
-        raw = self.BytesIO()
-        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
-        txt.write('abc\n')
-        txt.reconfigure(encoding='utf-8-sig')
-        txt.write('d\xe9f\n')
-        txt.flush()
-        self.assertEqual(raw.getvalue(), b'abc\nd\xc3\xa9f\n')
-
-    def test_reconfigure_write_non_seekable(self):
-        raw = self.BytesIO()
-        raw.seekable = lambda: False
-        raw.seek = None
-        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
-        txt.write('abc\n')
-        txt.reconfigure(encoding='utf-8-sig')
-        txt.write('d\xe9f\n')
-        txt.flush()
-
-        # If the raw stream is not seekable, there'll be a BOM
-        self.assertEqual(raw.getvalue(),  b'abc\n\xef\xbb\xbfd\xc3\xa9f\n')
-
-    def test_reconfigure_defaults(self):
-        txt = self.TextIOWrapper(self.BytesIO(), 'ascii', 'replace', '\n')
-        txt.reconfigure(encoding=None)
-        self.assertEqual(txt.encoding, 'ascii')
-        self.assertEqual(txt.errors, 'replace')
-        txt.write('LF\n')
-
-        txt.reconfigure(newline='\r\n')
-        self.assertEqual(txt.encoding, 'ascii')
-        self.assertEqual(txt.errors, 'replace')
-
-        txt.reconfigure(errors='ignore')
-        self.assertEqual(txt.encoding, 'ascii')
-        self.assertEqual(txt.errors, 'ignore')
-        txt.write('CRLF\n')
-
-        txt.reconfigure(encoding='utf-8', newline=None)
-        self.assertEqual(txt.errors, 'strict')
-        txt.seek(0)
-        self.assertEqual(txt.read(), 'LF\nCRLF\n')
-
-        self.assertEqual(txt.detach().getvalue(), b'LF\nCRLF\r\n')
-
-    def test_reconfigure_errors(self):
-        txt = self.TextIOWrapper(self.BytesIO(), 'ascii', 'replace', '\r')
-        with self.assertRaises(TypeError):  # there was a crash
-            txt.reconfigure(encoding=42)
-        if self.is_C:
-            with self.assertRaises(UnicodeEncodeError):
-                txt.reconfigure(encoding='\udcfe')
-            with self.assertRaises(LookupError):
-                txt.reconfigure(encoding='locale\0')
-        # TODO: txt.reconfigure(encoding='utf-8\0')
-        # TODO: txt.reconfigure(encoding='nonexisting')
-        with self.assertRaises(TypeError):
-            txt.reconfigure(errors=42)
-        if self.is_C:
-            with self.assertRaises(UnicodeEncodeError):
-                txt.reconfigure(errors='\udcfe')
-        # TODO: txt.reconfigure(errors='ignore\0')
-        # TODO: txt.reconfigure(errors='nonexisting')
-        with self.assertRaises(TypeError):
-            txt.reconfigure(newline=42)
-        with self.assertRaises(ValueError):
-            txt.reconfigure(newline='\udcfe')
-        with self.assertRaises(ValueError):
-            txt.reconfigure(newline='xyz')
-        if not self.is_C:
-            # TODO: Should fail in C too.
-            with self.assertRaises(ValueError):
-                txt.reconfigure(newline='\n\0')
-        if self.is_C:
-            # TODO: Use __bool__(), not __index__().
-            with self.assertRaises(ZeroDivisionError):
-                txt.reconfigure(line_buffering=BadIndex())
-            with self.assertRaises(OverflowError):
-                txt.reconfigure(line_buffering=2**1000)
-            with self.assertRaises(ZeroDivisionError):
-                txt.reconfigure(write_through=BadIndex())
-            with self.assertRaises(OverflowError):
-                txt.reconfigure(write_through=2**1000)
-            with self.assertRaises(ZeroDivisionError):  # there was a crash
-                txt.reconfigure(line_buffering=BadIndex(),
-                                write_through=BadIndex())
-        self.assertEqual(txt.encoding, 'ascii')
-        self.assertEqual(txt.errors, 'replace')
-        self.assertIs(txt.line_buffering, False)
-        self.assertIs(txt.write_through, False)
-
-        txt.reconfigure(encoding='latin1', errors='ignore', newline='\r\n',
-                        line_buffering=True, write_through=True)
-        self.assertEqual(txt.encoding, 'latin1')
-        self.assertEqual(txt.errors, 'ignore')
-        self.assertIs(txt.line_buffering, True)
-        self.assertIs(txt.write_through, True)
-
-    def test_reconfigure_newline(self):
-        raw = self.BytesIO(b'CR\rEOF')
-        txt = self.TextIOWrapper(raw, 'ascii', newline='\n')
-        txt.reconfigure(newline=None)
-        self.assertEqual(txt.readline(), 'CR\n')
-        raw = self.BytesIO(b'CR\rEOF')
-        txt = self.TextIOWrapper(raw, 'ascii', newline='\n')
-        txt.reconfigure(newline='')
-        self.assertEqual(txt.readline(), 'CR\r')
-        raw = self.BytesIO(b'CR\rLF\nEOF')
-        txt = self.TextIOWrapper(raw, 'ascii', newline='\r')
-        txt.reconfigure(newline='\n')
-        self.assertEqual(txt.readline(), 'CR\rLF\n')
-        raw = self.BytesIO(b'LF\nCR\rEOF')
-        txt = self.TextIOWrapper(raw, 'ascii', newline='\n')
-        txt.reconfigure(newline='\r')
-        self.assertEqual(txt.readline(), 'LF\nCR\r')
-        raw = self.BytesIO(b'CR\rCRLF\r\nEOF')
-        txt = self.TextIOWrapper(raw, 'ascii', newline='\r')
-        txt.reconfigure(newline='\r\n')
-        self.assertEqual(txt.readline(), 'CR\rCRLF\r\n')
-
-        txt = self.TextIOWrapper(self.BytesIO(), 'ascii', newline='\r')
-        txt.reconfigure(newline=None)
-        txt.write('linesep\n')
-        txt.reconfigure(newline='')
-        txt.write('LF\n')
-        txt.reconfigure(newline='\n')
-        txt.write('LF\n')
-        txt.reconfigure(newline='\r')
-        txt.write('CR\n')
-        txt.reconfigure(newline='\r\n')
-        txt.write('CRLF\n')
-        expected = 'linesep' + os.linesep + 'LF\nLF\nCR\rCRLF\r\n'
-        self.assertEqual(txt.detach().getvalue().decode('ascii'), expected)
-
-    def test_issue25862(self):
-        # Assertion failures occurred in tell() after read() and write().
-        t = self.TextIOWrapper(self.BytesIO(b'test'), encoding='ascii')
-        t.read(1)
-        t.read()
-        t.tell()
-        t = self.TextIOWrapper(self.BytesIO(b'test'), encoding='ascii')
-        t.read(1)
-        t.write('x')
-        t.tell()
-
-    def test_issue35928(self):
-        p = self.BufferedRWPair(self.BytesIO(b'foo\nbar\n'), self.BytesIO())
-        f = self.TextIOWrapper(p)
-        res = f.readline()
-        self.assertEqual(res, 'foo\n')
-        f.write(res)
-        self.assertEqual(res + f.readline(), 'foo\nbar\n')
-
-    def test_pickling_subclass(self):
-        global MyTextIO
-        class MyTextIO(self.TextIOWrapper):
-            def __init__(self, raw, tag):
-                super().__init__(raw)
-                self.tag = tag
-            def __getstate__(self):
-                return self.tag, self.buffer.getvalue()
-            def __setstate__(slf, state):
-                tag, value = state
-                slf.__init__(self.BytesIO(value), tag)
-
-        raw = self.BytesIO(b'data')
-        txt = MyTextIO(raw, 'ham')
-        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
-            with self.subTest(protocol=proto):
-                pickled = pickle.dumps(txt, proto)
-                newtxt = pickle.loads(pickled)
-                self.assertEqual(newtxt.buffer.getvalue(), b'data')
-                self.assertEqual(newtxt.tag, 'ham')
-        del MyTextIO
-
-    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
-    def test_read_non_blocking(self):
-        import os
-        r, w = os.pipe()
-        try:
-            os.set_blocking(r, False)
-            with self.io.open(r, 'rt') as textfile:
-                r = None
-                # Nothing has been written so a non-blocking read raises a BlockingIOError exception.
-                with self.assertRaises(BlockingIOError):
-                    textfile.read()
-        finally:
-            if r is not None:
-                os.close(r)
-            os.close(w)
-
-
-class MemviewBytesIO(io.BytesIO):
-    '''A BytesIO object whose read method returns memoryviews
-       rather than bytes'''
-
-    def read1(self, len_):
-        return _to_memoryview(super().read1(len_))
-
-    def read(self, len_):
-        return _to_memoryview(super().read(len_))
-
-def _to_memoryview(buf):
-    '''Convert bytes-object *buf* to a non-trivial memoryview'''
-
-    arr = array.array('i')
-    idx = len(buf) - len(buf) % arr.itemsize
-    arr.frombytes(buf[:idx])
-    return memoryview(arr)
-
-
-class CTextIOWrapperTest(TextIOWrapperTest):
-    io = io
-    shutdown_error = "LookupError: unknown encoding: ascii"
-
-    def test_initialization(self):
-        r = self.BytesIO(b"\xc3\xa9\n\n")
-        b = self.BufferedReader(r, 1000)
-        t = self.TextIOWrapper(b, encoding="utf-8")
-        self.assertRaises(ValueError, t.__init__, b, encoding="utf-8", newline='xyzzy')
-        self.assertRaises(ValueError, t.read)
-
-        t = self.TextIOWrapper.__new__(self.TextIOWrapper)
-        self.assertRaises(Exception, repr, t)
-
-    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
-    def test_garbage_collection(self):
-        # C TextIOWrapper objects are collected, and collecting them flushes
-        # all data to disk.
-        # The Python version has __del__, so it ends in gc.garbage instead.
-        with warnings_helper.check_warnings(('', ResourceWarning)):
-            rawio = self.FileIO(os_helper.TESTFN, "wb")
-            b = self.BufferedWriter(rawio)
-            t = self.TextIOWrapper(b, encoding="ascii")
-            t.write("456def")
-            t.x = t
-            wr = weakref.ref(t)
-            del t
-            support.gc_collect()
-        self.assertIsNone(wr(), wr)
-        with self.open(os_helper.TESTFN, "rb") as f:
-            self.assertEqual(f.read(), b"456def")
-
-    def test_rwpair_cleared_before_textio(self):
-        # Issue 13070: TextIOWrapper's finalization would crash when called
-        # after the reference to the underlying BufferedRWPair's writer got
-        # cleared by the GC.
-        for i in range(1000):
-            b1 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
-            t1 = self.TextIOWrapper(b1, encoding="ascii")
-            b2 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
-            t2 = self.TextIOWrapper(b2, encoding="ascii")
-            # circular references
-            t1.buddy = t2
-            t2.buddy = t1
-        support.gc_collect()
-
-    def test_del__CHUNK_SIZE_SystemError(self):
-        t = self.TextIOWrapper(self.BytesIO(), encoding='ascii')
-        with self.assertRaises(AttributeError):
-            del t._CHUNK_SIZE
-
-    def test_internal_buffer_size(self):
-        # bpo-43260: TextIOWrapper's internal buffer should not store
-        # data larger than chunk size.
-        chunk_size = 8192  # default chunk size, updated later
-
-        class MockIO(self.MockRawIO):
-            def write(self, data):
-                if len(data) > chunk_size:
-                    raise RuntimeError
-                return super().write(data)
-
-        buf = MockIO()
-        t = self.TextIOWrapper(buf, encoding="ascii")
-        chunk_size = t._CHUNK_SIZE
-        t.write("abc")
-        t.write("def")
-        # default chunk size is 8192 bytes so t don't write data to buf.
-        self.assertEqual([], buf._write_stack)
-
-        with self.assertRaises(RuntimeError):
-            t.write("x"*(chunk_size+1))
-
-        self.assertEqual([b"abcdef"], buf._write_stack)
-        t.write("ghi")
-        t.write("x"*chunk_size)
-        self.assertEqual([b"abcdef", b"ghi", b"x"*chunk_size], buf._write_stack)
-
-    def test_issue119506(self):
-        chunk_size = 8192
-
-        class MockIO(self.MockRawIO):
-            written = False
-            def write(self, data):
-                if not self.written:
-                    self.written = True
-                    t.write("middle")
-                return super().write(data)
-
-        buf = MockIO()
-        t = self.TextIOWrapper(buf)
-        t.write("abc")
-        t.write("def")
-        # writing data which size >= chunk_size cause flushing buffer before write.
-        t.write("g" * chunk_size)
-        t.flush()
-
-        self.assertEqual([b"abcdef", b"middle", b"g"*chunk_size],
-                         buf._write_stack)
-
-    def test_issue142594(self):
-        wrapper = None
-        detached = False
-        class ReentrantRawIO(self.RawIOBase):
-            @property
-            def closed(self):
-                nonlocal detached
-                if wrapper is not None and not detached:
-                    detached = True
-                    wrapper.detach()
-                return False
-
-        raw = ReentrantRawIO()
-        wrapper = self.TextIOWrapper(raw)
-        wrapper.close()  # should not crash
-
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; TypeError: a bytes-like object is required, not 'NoneType'
-    def test_read_non_blocking(self):
-        return super().test_read_non_blocking()
-
-
-class PyTextIOWrapperTest(TextIOWrapperTest):
-    io = pyio
-    shutdown_error = "LookupError: unknown encoding: ascii"
-
-    @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON; os.set_blocking not available on Windows")
-    def test_read_non_blocking(self):
-        return super().test_read_non_blocking()
-
-
-class IncrementalNewlineDecoderTest(unittest.TestCase):
-
-    def check_newline_decoding_utf8(self, decoder):
-        # UTF-8 specific tests for a newline decoder
-        def _check_decode(b, s, **kwargs):
-            # We exercise getstate() / setstate() as well as decode()
-            state = decoder.getstate()
-            self.assertEqual(decoder.decode(b, **kwargs), s)
-            decoder.setstate(state)
-            self.assertEqual(decoder.decode(b, **kwargs), s)
-
-        _check_decode(b'\xe8\xa2\x88', "\u8888")
-
-        _check_decode(b'\xe8', "")
-        _check_decode(b'\xa2', "")
-        _check_decode(b'\x88', "\u8888")
-
-        _check_decode(b'\xe8', "")
-        _check_decode(b'\xa2', "")
-        _check_decode(b'\x88', "\u8888")
-
-        _check_decode(b'\xe8', "")
-        self.assertRaises(UnicodeDecodeError, decoder.decode, b'', final=True)
-
-        decoder.reset()
-        _check_decode(b'\n', "\n")
-        _check_decode(b'\r', "")
-        _check_decode(b'', "\n", final=True)
-        _check_decode(b'\r', "\n", final=True)
-
-        _check_decode(b'\r', "")
-        _check_decode(b'a', "\na")
-
-        _check_decode(b'\r\r\n', "\n\n")
-        _check_decode(b'\r', "")
-        _check_decode(b'\r', "\n")
-        _check_decode(b'\na', "\na")
-
-        _check_decode(b'\xe8\xa2\x88\r\n', "\u8888\n")
-        _check_decode(b'\xe8\xa2\x88', "\u8888")
-        _check_decode(b'\n', "\n")
-        _check_decode(b'\xe8\xa2\x88\r', "\u8888")
-        _check_decode(b'\n', "\n")
-
-    def check_newline_decoding(self, decoder, encoding):
-        result = []
-        if encoding is not None:
-            encoder = codecs.getincrementalencoder(encoding)()
-            def _decode_bytewise(s):
-                # Decode one byte at a time
-                for b in encoder.encode(s):
-                    result.append(decoder.decode(bytes([b])))
-        else:
-            encoder = None
-            def _decode_bytewise(s):
-                # Decode one char at a time
-                for c in s:
-                    result.append(decoder.decode(c))
-        self.assertEqual(decoder.newlines, None)
-        _decode_bytewise("abc\n\r")
-        self.assertEqual(decoder.newlines, '\n')
-        _decode_bytewise("\nabc")
-        self.assertEqual(decoder.newlines, ('\n', '\r\n'))
-        _decode_bytewise("abc\r")
-        self.assertEqual(decoder.newlines, ('\n', '\r\n'))
-        _decode_bytewise("abc")
-        self.assertEqual(decoder.newlines, ('\r', '\n', '\r\n'))
-        _decode_bytewise("abc\r")
-        self.assertEqual("".join(result), "abc\n\nabcabc\nabcabc")
-        decoder.reset()
-        input = "abc"
-        if encoder is not None:
-            encoder.reset()
-            input = encoder.encode(input)
-        self.assertEqual(decoder.decode(input), "abc")
-        self.assertEqual(decoder.newlines, None)
-
-    def test_newline_decoder(self):
-        encodings = (
-            # None meaning the IncrementalNewlineDecoder takes unicode input
-            # rather than bytes input
-            None, 'utf-8', 'latin-1',
-            'utf-16', 'utf-16-le', 'utf-16-be',
-            'utf-32', 'utf-32-le', 'utf-32-be',
-        )
-        for enc in encodings:
-            decoder = enc and codecs.getincrementaldecoder(enc)()
-            decoder = self.IncrementalNewlineDecoder(decoder, translate=True)
-            self.check_newline_decoding(decoder, enc)
-        decoder = codecs.getincrementaldecoder("utf-8")()
-        decoder = self.IncrementalNewlineDecoder(decoder, translate=True)
-        self.check_newline_decoding_utf8(decoder)
-        self.assertRaises(TypeError, decoder.setstate, 42)
-
-    def test_newline_bytes(self):
-        # Issue 5433: Excessive optimization in IncrementalNewlineDecoder
-        def _check(dec):
-            self.assertEqual(dec.newlines, None)
-            self.assertEqual(dec.decode("\u0D00"), "\u0D00")
-            self.assertEqual(dec.newlines, None)
-            self.assertEqual(dec.decode("\u0A00"), "\u0A00")
-            self.assertEqual(dec.newlines, None)
-        dec = self.IncrementalNewlineDecoder(None, translate=False)
-        _check(dec)
-        dec = self.IncrementalNewlineDecoder(None, translate=True)
-        _check(dec)
-
-    def test_translate(self):
-        # issue 35062
-        for translate in (-2, -1, 1, 2):
-            decoder = codecs.getincrementaldecoder("utf-8")()
-            decoder = self.IncrementalNewlineDecoder(decoder, translate)
-            self.check_newline_decoding_utf8(decoder)
-        decoder = codecs.getincrementaldecoder("utf-8")()
-        decoder = self.IncrementalNewlineDecoder(decoder, translate=0)
-        self.assertEqual(decoder.decode(b"\r\r\n"), "\r\r\n")
-
-class CIncrementalNewlineDecoderTest(IncrementalNewlineDecoderTest):
-    @support.cpython_only
-    def test_uninitialized(self):
-        uninitialized = self.IncrementalNewlineDecoder.__new__(
-            self.IncrementalNewlineDecoder)
-        self.assertRaises(ValueError, uninitialized.decode, b'bar')
-        self.assertRaises(ValueError, uninitialized.getstate)
-        self.assertRaises(ValueError, uninitialized.setstate, (b'foo', 0))
-        self.assertRaises(ValueError, uninitialized.reset)
-
-
-class PyIncrementalNewlineDecoderTest(IncrementalNewlineDecoderTest):
-    pass
-
-
-# XXX Tests for open()
-
-class MiscIOTest(unittest.TestCase):
-
-    # for test__all__, actual values are set in subclasses
-    name_of_module = None
-    extra_exported = ()
-    not_exported = ()
-
-    def tearDown(self):
-        os_helper.unlink(os_helper.TESTFN)
-
-    def test___all__(self):
-        support.check__all__(self, self.io, self.name_of_module,
-                             extra=self.extra_exported,
-                             not_exported=self.not_exported)
-
-    def test_attributes(self):
-        f = self.open(os_helper.TESTFN, "wb", buffering=0)
-        self.assertEqual(f.mode, "wb")
-        f.close()
-
-        f = self.open(os_helper.TESTFN, "w+", encoding="utf-8")
-        self.assertEqual(f.mode,            "w+")
-        self.assertEqual(f.buffer.mode,     "rb+") # Does it really matter?
-        self.assertEqual(f.buffer.raw.mode, "rb+")
-
-        g = self.open(f.fileno(), "wb", closefd=False)
-        self.assertEqual(g.mode,     "wb")
-        self.assertEqual(g.raw.mode, "wb")
-        self.assertEqual(g.name,     f.fileno())
-        self.assertEqual(g.raw.name, f.fileno())
-        f.close()
-        g.close()
-
-    def test_removed_u_mode(self):
-        # bpo-37330: The "U" mode has been removed in Python 3.11
-        for mode in ("U", "rU", "r+U"):
-            with self.assertRaises(ValueError) as cm:
-                self.open(os_helper.TESTFN, mode)
-            self.assertIn('invalid mode', str(cm.exception))
-
-    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
-    def test_open_pipe_with_append(self):
-        # bpo-27805: Ignore ESPIPE from lseek() in open().
-        r, w = os.pipe()
-        self.addCleanup(os.close, r)
-        f = self.open(w, 'a', encoding="utf-8")
-        self.addCleanup(f.close)
-        # Check that the file is marked non-seekable. On Windows, however, lseek
-        # somehow succeeds on pipes.
-        if sys.platform != 'win32':
-            self.assertFalse(f.seekable())
-
-    def test_io_after_close(self):
-        for kwargs in [
-                {"mode": "w"},
-                {"mode": "wb"},
-                {"mode": "w", "buffering": 1},
-                {"mode": "w", "buffering": 2},
-                {"mode": "wb", "buffering": 0},
-                {"mode": "r"},
-                {"mode": "rb"},
-                {"mode": "r", "buffering": 1},
-                {"mode": "r", "buffering": 2},
-                {"mode": "rb", "buffering": 0},
-                {"mode": "w+"},
-                {"mode": "w+b"},
-                {"mode": "w+", "buffering": 1},
-                {"mode": "w+", "buffering": 2},
-                {"mode": "w+b", "buffering": 0},
-            ]:
-            if "b" not in kwargs["mode"]:
-                kwargs["encoding"] = "utf-8"
-            f = self.open(os_helper.TESTFN, **kwargs)
-            f.close()
-            self.assertRaises(ValueError, f.flush)
-            self.assertRaises(ValueError, f.fileno)
-            self.assertRaises(ValueError, f.isatty)
-            self.assertRaises(ValueError, f.__iter__)
-            if hasattr(f, "peek"):
-                self.assertRaises(ValueError, f.peek, 1)
-            self.assertRaises(ValueError, f.read)
-            if hasattr(f, "read1"):
-                self.assertRaises(ValueError, f.read1, 1024)
-                self.assertRaises(ValueError, f.read1)
-            if hasattr(f, "readall"):
-                self.assertRaises(ValueError, f.readall)
-            if hasattr(f, "readinto"):
-                self.assertRaises(ValueError, f.readinto, bytearray(1024))
-            if hasattr(f, "readinto1"):
-                self.assertRaises(ValueError, f.readinto1, bytearray(1024))
-            self.assertRaises(ValueError, f.readline)
-            self.assertRaises(ValueError, f.readlines)
-            self.assertRaises(ValueError, f.readlines, 1)
-            self.assertRaises(ValueError, f.seek, 0)
-            self.assertRaises(ValueError, f.tell)
-            self.assertRaises(ValueError, f.truncate)
-            self.assertRaises(ValueError, f.write,
-                              b"" if "b" in kwargs['mode'] else "")
-            self.assertRaises(ValueError, f.writelines, [])
-            self.assertRaises(ValueError, next, f)
-
-    def test_blockingioerror(self):
-        # Various BlockingIOError issues
-        class C(str):
-            pass
-        c = C("")
-        b = self.BlockingIOError(1, c)
-        c.b = b
-        b.c = c
-        wr = weakref.ref(c)
-        del c, b
-        support.gc_collect()
-        self.assertIsNone(wr(), wr)
-
-    def test_abcs(self):
-        # Test the visible base classes are ABCs.
-        self.assertIsInstance(self.IOBase, abc.ABCMeta)
-        self.assertIsInstance(self.RawIOBase, abc.ABCMeta)
-        self.assertIsInstance(self.BufferedIOBase, abc.ABCMeta)
-        self.assertIsInstance(self.TextIOBase, abc.ABCMeta)
-
-    def _check_abc_inheritance(self, abcmodule):
-        with self.open(os_helper.TESTFN, "wb", buffering=0) as f:
-            self.assertIsInstance(f, abcmodule.IOBase)
-            self.assertIsInstance(f, abcmodule.RawIOBase)
-            self.assertNotIsInstance(f, abcmodule.BufferedIOBase)
-            self.assertNotIsInstance(f, abcmodule.TextIOBase)
-        with self.open(os_helper.TESTFN, "wb") as f:
-            self.assertIsInstance(f, abcmodule.IOBase)
-            self.assertNotIsInstance(f, abcmodule.RawIOBase)
-            self.assertIsInstance(f, abcmodule.BufferedIOBase)
-            self.assertNotIsInstance(f, abcmodule.TextIOBase)
-        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
-            self.assertIsInstance(f, abcmodule.IOBase)
-            self.assertNotIsInstance(f, abcmodule.RawIOBase)
-            self.assertNotIsInstance(f, abcmodule.BufferedIOBase)
-            self.assertIsInstance(f, abcmodule.TextIOBase)
-
-    def test_abc_inheritance(self):
-        # Test implementations inherit from their respective ABCs
-        self._check_abc_inheritance(self)
-
-    def test_abc_inheritance_official(self):
-        # Test implementations inherit from the official ABCs of the
-        # baseline "io" module.
-        self._check_abc_inheritance(io)
-
-    def _check_warn_on_dealloc(self, *args, **kwargs):
-        f = self.open(*args, **kwargs)
-        r = repr(f)
-        with self.assertWarns(ResourceWarning) as cm:
-            f = None
-            support.gc_collect()
-        self.assertIn(r, str(cm.warning.args[0]))
-
-    def test_warn_on_dealloc(self):
-        self._check_warn_on_dealloc(os_helper.TESTFN, "wb", buffering=0)
-        self._check_warn_on_dealloc(os_helper.TESTFN, "wb")
-        self._check_warn_on_dealloc(os_helper.TESTFN, "w", encoding="utf-8")
-
-    def _check_warn_on_dealloc_fd(self, *args, **kwargs):
-        fds = []
-        def cleanup_fds():
-            for fd in fds:
-                try:
-                    os.close(fd)
-                except OSError as e:
-                    if e.errno != errno.EBADF:
-                        raise
-        self.addCleanup(cleanup_fds)
-        r, w = os.pipe()
-        fds += r, w
-        self._check_warn_on_dealloc(r, *args, **kwargs)
-        # When using closefd=False, there's no warning
-        r, w = os.pipe()
-        fds += r, w
-        with warnings_helper.check_no_resource_warning(self):
-            self.open(r, *args, closefd=False, **kwargs)
-
-    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
-    def test_warn_on_dealloc_fd(self):
-        self._check_warn_on_dealloc_fd("rb", buffering=0)
-        self._check_warn_on_dealloc_fd("rb")
-        self._check_warn_on_dealloc_fd("r", encoding="utf-8")
-
-
-    def test_pickling(self):
-        # Pickling file objects is forbidden
-        msg = "cannot pickle"
-        for kwargs in [
-                {"mode": "w"},
-                {"mode": "wb"},
-                {"mode": "wb", "buffering": 0},
-                {"mode": "r"},
-                {"mode": "rb"},
-                {"mode": "rb", "buffering": 0},
-                {"mode": "w+"},
-                {"mode": "w+b"},
-                {"mode": "w+b", "buffering": 0},
-            ]:
-            if "b" not in kwargs["mode"]:
-                kwargs["encoding"] = "utf-8"
-            for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
-                with self.subTest(protocol=protocol, kwargs=kwargs):
-                    with self.open(os_helper.TESTFN, **kwargs) as f:
-                        with self.assertRaisesRegex(TypeError, msg):
-                            pickle.dumps(f, protocol)
-
-    @unittest.skipIf(support.is_emscripten, "Emscripten corrupts memory when writing to nonblocking fd")
-    def test_nonblock_pipe_write_bigbuf(self):
-        self._test_nonblock_pipe_write(16*1024)
-
-    @unittest.skipIf(support.is_emscripten, "Emscripten corrupts memory when writing to nonblocking fd")
-    def test_nonblock_pipe_write_smallbuf(self):
-        self._test_nonblock_pipe_write(1024)
-
-    @unittest.skipUnless(hasattr(os, 'set_blocking'),
-                         'os.set_blocking() required for this test')
-    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
-    def _test_nonblock_pipe_write(self, bufsize):
-        sent = []
-        received = []
-        r, w = os.pipe()
-        os.set_blocking(r, False)
-        os.set_blocking(w, False)
-
-        # To exercise all code paths in the C implementation we need
-        # to play with buffer sizes.  For instance, if we choose a
-        # buffer size less than or equal to _PIPE_BUF (4096 on Linux)
-        # then we will never get a partial write of the buffer.
-        rf = self.open(r, mode='rb', closefd=True, buffering=bufsize)
-        wf = self.open(w, mode='wb', closefd=True, buffering=bufsize)
-
-        with rf, wf:
-            for N in 9999, 73, 7574:
-                try:
-                    i = 0
-                    while True:
-                        msg = bytes([i % 26 + 97]) * N
-                        sent.append(msg)
-                        wf.write(msg)
-                        i += 1
-
-                except self.BlockingIOError as e:
-                    self.assertEqual(e.args[0], errno.EAGAIN)
-                    self.assertEqual(e.args[2], e.characters_written)
-                    sent[-1] = sent[-1][:e.characters_written]
-                    received.append(rf.read())
-                    msg = b'BLOCKED'
-                    wf.write(msg)
-                    sent.append(msg)
-
-            while True:
-                try:
-                    wf.flush()
-                    break
-                except self.BlockingIOError as e:
-                    self.assertEqual(e.args[0], errno.EAGAIN)
-                    self.assertEqual(e.args[2], e.characters_written)
-                    self.assertEqual(e.characters_written, 0)
-                    received.append(rf.read())
-
-            received += iter(rf.read, None)
-
-        sent, received = b''.join(sent), b''.join(received)
-        self.assertEqual(sent, received)
-        self.assertTrue(wf.closed)
-        self.assertTrue(rf.closed)
-
-    def test_create_fail(self):
-        # 'x' mode fails if file is existing
-        with self.open(os_helper.TESTFN, 'w', encoding="utf-8"):
-            pass
-        self.assertRaises(FileExistsError, self.open, os_helper.TESTFN, 'x', encoding="utf-8")
-
-    def test_create_writes(self):
-        # 'x' mode opens for writing
-        with self.open(os_helper.TESTFN, 'xb') as f:
-            f.write(b"spam")
-        with self.open(os_helper.TESTFN, 'rb') as f:
-            self.assertEqual(b"spam", f.read())
-
-    def test_open_allargs(self):
-        # there used to be a buffer overflow in the parser for rawmode
-        self.assertRaises(ValueError, self.open, os_helper.TESTFN, 'rwax+', encoding="utf-8")
-
-    def test_check_encoding_errors(self):
-        # bpo-37388: open() and TextIOWrapper must check encoding and errors
-        # arguments in dev mode
-        mod = self.io.__name__
-        filename = __file__
-        invalid = 'Boom, Shaka Laka, Boom!'
-        code = textwrap.dedent(f'''
-            import sys
-            from {mod} import open, TextIOWrapper
-
-            try:
-                open({filename!r}, encoding={invalid!r})
-            except LookupError:
-                pass
-            else:
-                sys.exit(21)
-
-            try:
-                open({filename!r}, errors={invalid!r})
-            except LookupError:
-                pass
-            else:
-                sys.exit(22)
-
-            fp = open({filename!r}, "rb")
-            with fp:
-                try:
-                    TextIOWrapper(fp, encoding={invalid!r})
-                except LookupError:
-                    pass
-                else:
-                    sys.exit(23)
-
-                try:
-                    TextIOWrapper(fp, errors={invalid!r})
-                except LookupError:
-                    pass
-                else:
-                    sys.exit(24)
-
-            sys.exit(10)
-        ''')
-        proc = assert_python_failure('-X', 'dev', '-c', code)
-        self.assertEqual(proc.rc, 10, proc)
-
-    def test_check_encoding_warning(self):
-        # PEP 597: Raise warning when encoding is not specified
-        # and sys.flags.warn_default_encoding is set.
-        mod = self.io.__name__
-        filename = __file__
-        code = textwrap.dedent(f'''\
-            import sys
-            from {mod} import open, TextIOWrapper
-            import pathlib
-
-            with open({filename!r}) as f:           # line 5
-                pass
-
-            pathlib.Path({filename!r}).read_text()  # line 8
-        ''')
-        proc = assert_python_ok('-X', 'warn_default_encoding', '-c', code)
-        warnings = proc.err.splitlines()
-        self.assertEqual(len(warnings), 2)
-        self.assertStartsWith(warnings[0], b"<string>:5: EncodingWarning: ")
-        self.assertStartsWith(warnings[1], b"<string>:8: EncodingWarning: ")
-
-    def test_text_encoding(self):
-        # PEP 597, bpo-47000. io.text_encoding() returns "locale" or "utf-8"
-        # based on sys.flags.utf8_mode
-        code = "import io; print(io.text_encoding(None))"
-
-        proc = assert_python_ok('-X', 'utf8=0', '-c', code)
-        self.assertEqual(b"locale", proc.out.strip())
-
-        proc = assert_python_ok('-X', 'utf8=1', '-c', code)
-        self.assertEqual(b"utf-8", proc.out.strip())
-
-
-class CMiscIOTest(MiscIOTest):
-    io = io
-    name_of_module = "io", "_io"
-    extra_exported = "BlockingIOError",
-
-    def test_readinto_buffer_overflow(self):
-        # Issue #18025
-        class BadReader(self.io.BufferedIOBase):
-            def read(self, n=-1):
-                return b'x' * 10**6
-        bufio = BadReader()
-        b = bytearray(2)
-        self.assertRaises(ValueError, bufio.readinto, b)
-
-    def check_daemon_threads_shutdown_deadlock(self, stream_name):
-        # Issue #23309: deadlocks at shutdown should be avoided when a
-        # daemon thread and the main thread both write to a file.
-        code = """if 1:
-            import sys
-            import time
-            import threading
-            from test.support import SuppressCrashReport
-
-            file = sys.{stream_name}
-
-            def run():
-                while True:
-                    file.write('.')
-                    file.flush()
-
-            crash = SuppressCrashReport()
-            crash.__enter__()
-            # don't call __exit__(): the crash occurs at Python shutdown
-
-            thread = threading.Thread(target=run)
-            thread.daemon = True
-            thread.start()
-
-            time.sleep(0.5)
-            file.write('!')
-            file.flush()
-            """.format_map(locals())
-        res, _ = run_python_until_end("-c", code)
-        err = res.err.decode()
-        if res.rc != 0:
-            # Failure: should be a fatal error
-            pattern = (r"Fatal Python error: _enter_buffered_busy: "
-                       r"could not acquire lock "
-                       r"for <(_io\.)?BufferedWriter name='<{stream_name}>'> "
-                       r"at interpreter shutdown, possibly due to "
-                       r"daemon threads".format_map(locals()))
-            self.assertRegex(err, pattern)
-        else:
-            self.assertFalse(err.strip('.!'))
-
-    @threading_helper.requires_working_threading()
-    @support.requires_resource('walltime')
-    def test_daemon_threads_shutdown_stdout_deadlock(self):
-        self.check_daemon_threads_shutdown_deadlock('stdout')
-
-    @threading_helper.requires_working_threading()
-    @support.requires_resource('walltime')
-    def test_daemon_threads_shutdown_stderr_deadlock(self):
-        self.check_daemon_threads_shutdown_deadlock('stderr')
-
-
-class PyMiscIOTest(MiscIOTest):
-    io = pyio
-    name_of_module = "_pyio", "io"
-    extra_exported = "BlockingIOError", "open_code",
-    not_exported = "valid_seek_flags",
-
-
-@unittest.skipIf(os.name == 'nt', 'POSIX signals required for this test.')
-class SignalsTest(unittest.TestCase):
-
-    def setUp(self):
-        self.oldalrm = signal.signal(signal.SIGALRM, self.alarm_interrupt)
-
-    def tearDown(self):
-        signal.signal(signal.SIGALRM, self.oldalrm)
-
-    def alarm_interrupt(self, sig, frame):
-        1/0
-
-    def check_interrupted_write(self, item, bytes, **fdopen_kwargs):
-        """Check that a partial write, when it gets interrupted, properly
-        invokes the signal handler, and bubbles up the exception raised
-        in the latter."""
-
-        # XXX This test has three flaws that appear when objects are
-        # XXX not reference counted.
-
-        # - if wio.write() happens to trigger a garbage collection,
-        #   the signal exception may be raised when some __del__
-        #   method is running; it will not reach the assertRaises()
-        #   call.
-
-        # - more subtle, if the wio object is not destroyed at once
-        #   and survives this function, the next opened file is likely
-        #   to have the same fileno (since the file descriptor was
-        #   actively closed).  When wio.__del__ is finally called, it
-        #   will close the other's test file...  To trigger this with
-        #   CPython, try adding "global wio" in this function.
-
-        # - This happens only for streams created by the _pyio module,
-        #   because a wio.close() that fails still consider that the
-        #   file needs to be closed again.  You can try adding an
-        #   "assert wio.closed" at the end of the function.
-
-        # Fortunately, a little gc.collect() seems to be enough to
-        # work around all these issues.
-        support.gc_collect()  # For PyPy or other GCs.
-
-        read_results = []
-        def _read():
-            s = os.read(r, 1)
-            read_results.append(s)
-
-        t = threading.Thread(target=_read)
-        t.daemon = True
-        r, w = os.pipe()
-        fdopen_kwargs["closefd"] = False
-        large_data = item * (support.PIPE_MAX_SIZE // len(item) + 1)
-        try:
-            wio = self.io.open(w, **fdopen_kwargs)
-            if hasattr(signal, 'pthread_sigmask'):
-                # create the thread with SIGALRM signal blocked
-                signal.pthread_sigmask(signal.SIG_BLOCK, [signal.SIGALRM])
-                t.start()
-                signal.pthread_sigmask(signal.SIG_UNBLOCK, [signal.SIGALRM])
-            else:
-                t.start()
-
-            # Fill the pipe enough that the write will be blocking.
-            # It will be interrupted by the timer armed above.  Since the
-            # other thread has read one byte, the low-level write will
-            # return with a successful (partial) result rather than an EINTR.
-            # The buffered IO layer must check for pending signal
-            # handlers, which in this case will invoke alarm_interrupt().
-            signal.alarm(1)
-            try:
-                self.assertRaises(ZeroDivisionError, wio.write, large_data)
-            finally:
-                signal.alarm(0)
-                t.join()
-            # We got one byte, get another one and check that it isn't a
-            # repeat of the first one.
-            read_results.append(os.read(r, 1))
-            self.assertEqual(read_results, [bytes[0:1], bytes[1:2]])
-        finally:
-            os.close(w)
-            os.close(r)
-            # This is deliberate. If we didn't close the file descriptor
-            # before closing wio, wio would try to flush its internal
-            # buffer, and block again.
-            try:
-                wio.close()
-            except OSError as e:
-                if e.errno != errno.EBADF:
-                    raise
-
-    @requires_alarm
-    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
-    def test_interrupted_write_unbuffered(self):
-        self.check_interrupted_write(b"xy", b"xy", mode="wb", buffering=0)
-
-    @requires_alarm
-    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
-    def test_interrupted_write_buffered(self):
-        self.check_interrupted_write(b"xy", b"xy", mode="wb")
-
-    @requires_alarm
-    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
-    def test_interrupted_write_text(self):
-        self.check_interrupted_write("xy", b"xy", mode="w", encoding="ascii")
-
-    @support.no_tracing
-    def check_reentrant_write(self, data, **fdopen_kwargs):
-        def on_alarm(*args):
-            # Will be called reentrantly from the same thread
-            wio.write(data)
-            1/0
-        signal.signal(signal.SIGALRM, on_alarm)
-        r, w = os.pipe()
-        wio = self.io.open(w, **fdopen_kwargs)
-        try:
-            signal.alarm(1)
-            # Either the reentrant call to wio.write() fails with RuntimeError,
-            # or the signal handler raises ZeroDivisionError.
-            with self.assertRaises((ZeroDivisionError, RuntimeError)) as cm:
-                while 1:
-                    for i in range(100):
-                        wio.write(data)
-                        wio.flush()
-                    # Make sure the buffer doesn't fill up and block further writes
-                    os.read(r, len(data) * 100)
-            exc = cm.exception
-            if isinstance(exc, RuntimeError):
-                self.assertStartsWith(str(exc), "reentrant call")
-        finally:
-            signal.alarm(0)
-            wio.close()
-            os.close(r)
-
-    @requires_alarm
-    def test_reentrant_write_buffered(self):
-        self.check_reentrant_write(b"xy", mode="wb")
-
-    @requires_alarm
-    def test_reentrant_write_text(self):
-        self.check_reentrant_write("xy", mode="w", encoding="ascii")
-
-    def check_interrupted_read_retry(self, decode, **fdopen_kwargs):
-        """Check that a buffered read, when it gets interrupted (either
-        returning a partial result or EINTR), properly invokes the signal
-        handler and retries if the latter returned successfully."""
-        r, w = os.pipe()
-        fdopen_kwargs["closefd"] = False
-        def alarm_handler(sig, frame):
-            os.write(w, b"bar")
-        signal.signal(signal.SIGALRM, alarm_handler)
-        try:
-            rio = self.io.open(r, **fdopen_kwargs)
-            os.write(w, b"foo")
-            signal.alarm(1)
-            # Expected behaviour:
-            # - first raw read() returns partial b"foo"
-            # - second raw read() returns EINTR
-            # - third raw read() returns b"bar"
-            self.assertEqual(decode(rio.read(6)), "foobar")
-        finally:
-            signal.alarm(0)
-            rio.close()
-            os.close(w)
-            os.close(r)
-
-    @requires_alarm
-    @support.requires_resource('walltime')
-    def test_interrupted_read_retry_buffered(self):
-        self.check_interrupted_read_retry(lambda x: x.decode('latin1'),
-                                          mode="rb")
-
-    @requires_alarm
-    @support.requires_resource('walltime')
-    def test_interrupted_read_retry_text(self):
-        self.check_interrupted_read_retry(lambda x: x,
-                                          mode="r", encoding="latin1")
-
-    def check_interrupted_write_retry(self, item, **fdopen_kwargs):
-        """Check that a buffered write, when it gets interrupted (either
-        returning a partial result or EINTR), properly invokes the signal
-        handler and retries if the latter returned successfully."""
-        select = import_helper.import_module("select")
-
-        # A quantity that exceeds the buffer size of an anonymous pipe's
-        # write end.
-        N = support.PIPE_MAX_SIZE
-        r, w = os.pipe()
-        fdopen_kwargs["closefd"] = False
-
-        # We need a separate thread to read from the pipe and allow the
-        # write() to finish.  This thread is started after the SIGALRM is
-        # received (forcing a first EINTR in write()).
-        read_results = []
-        write_finished = False
-        error = None
-        def _read():
-            try:
-                while not write_finished:
-                    while r in select.select([r], [], [], 1.0)[0]:
-                        s = os.read(r, 1024)
-                        read_results.append(s)
-            except BaseException as exc:
-                nonlocal error
-                error = exc
-        t = threading.Thread(target=_read)
-        t.daemon = True
-        def alarm1(sig, frame):
-            signal.signal(signal.SIGALRM, alarm2)
-            signal.alarm(1)
-        def alarm2(sig, frame):
-            t.start()
-
-        large_data = item * N
-        signal.signal(signal.SIGALRM, alarm1)
-        try:
-            wio = self.io.open(w, **fdopen_kwargs)
-            signal.alarm(1)
-            # Expected behaviour:
-            # - first raw write() is partial (because of the limited pipe buffer
-            #   and the first alarm)
-            # - second raw write() returns EINTR (because of the second alarm)
-            # - subsequent write()s are successful (either partial or complete)
-            written = wio.write(large_data)
-            self.assertEqual(N, written)
-
-            wio.flush()
-            write_finished = True
-            t.join()
-
-            self.assertIsNone(error)
-            self.assertEqual(N, sum(len(x) for x in read_results))
-        finally:
-            signal.alarm(0)
-            write_finished = True
-            os.close(w)
-            os.close(r)
-            # This is deliberate. If we didn't close the file descriptor
-            # before closing wio, wio would try to flush its internal
-            # buffer, and could block (in case of failure).
-            try:
-                wio.close()
-            except OSError as e:
-                if e.errno != errno.EBADF:
-                    raise
-
-    @requires_alarm
-    @support.requires_resource('walltime')
-    def test_interrupted_write_retry_buffered(self):
-        self.check_interrupted_write_retry(b"x", mode="wb")
-
-    @requires_alarm
-    @support.requires_resource('walltime')
-    def test_interrupted_write_retry_text(self):
-        self.check_interrupted_write_retry("x", mode="w", encoding="latin1")
-
-
-class CSignalsTest(SignalsTest):
-    io = io
-
-class PySignalsTest(SignalsTest):
-    io = pyio
-
-    # Handling reentrancy issues would slow down _pyio even more, so the
-    # tests are disabled.
-    test_reentrant_write_buffered = None
-    test_reentrant_write_text = None
-
-
-class ProtocolsTest(unittest.TestCase):
-    class MyReader:
-        def read(self, sz=-1):
-            return b""
-
-    class MyWriter:
-        def write(self, b: bytes):
-            pass
-
-    def test_reader_subclass(self):
-        self.assertIsSubclass(self.MyReader, io.Reader)
-        self.assertNotIsSubclass(str, io.Reader)
-
-    def test_writer_subclass(self):
-        self.assertIsSubclass(self.MyWriter, io.Writer)
-        self.assertNotIsSubclass(str, io.Writer)
-
-
-def load_tests(loader, tests, pattern):
-    tests = (CIOTest, PyIOTest, APIMismatchTest,
-             CBufferedReaderTest, PyBufferedReaderTest,
-             CBufferedWriterTest, PyBufferedWriterTest,
-             CBufferedRWPairTest, PyBufferedRWPairTest,
-             CBufferedRandomTest, PyBufferedRandomTest,
-             StatefulIncrementalDecoderTest,
-             CIncrementalNewlineDecoderTest, PyIncrementalNewlineDecoderTest,
-             CTextIOWrapperTest, PyTextIOWrapperTest,
-             CMiscIOTest, PyMiscIOTest,
-             CSignalsTest, PySignalsTest, TestIOCTypes,
-             ProtocolsTest,
-             )
-
-    # Put the namespaces of the IO module we are testing and some useful mock
-    # classes in the __dict__ of each test.
-    mocks = (MockRawIO, MisbehavedRawIO, MockFileIO, CloseFailureIO,
-             MockNonBlockWriterIO, MockUnseekableIO, MockRawIOWithoutRead,
-             SlowFlushRawIO, MockCharPseudoDevFileIO)
-    all_members = io.__all__
-    c_io_ns = {name : getattr(io, name) for name in all_members}
-    py_io_ns = {name : getattr(pyio, name) for name in all_members}
-    globs = globals()
-    c_io_ns.update((x.__name__, globs["C" + x.__name__]) for x in mocks)
-    py_io_ns.update((x.__name__, globs["Py" + x.__name__]) for x in mocks)
-    for test in tests:
-        if test.__name__.startswith("C"):
-            for name, obj in c_io_ns.items():
-                setattr(test, name, obj)
-            test.is_C = True
-        elif test.__name__.startswith("Py"):
-            for name, obj in py_io_ns.items():
-                setattr(test, name, obj)
-            test.is_C = False
-
-    suite = loader.suiteClass()
-    for test in tests:
-        suite.addTest(loader.loadTestsFromTestCase(test))
-    return suite
-
-if __name__ == "__main__":
-    unittest.main()
diff --git a/Lib/test/test_io/__init__.py b/Lib/test/test_io/__init__.py
new file mode 100644
index 00000000000..c94fad3e779
--- /dev/null
+++ b/Lib/test/test_io/__init__.py
@@ -0,0 +1,28 @@
+"""Tests for the io module and its implementations (_io and _pyio)
+
+Tests are split across multiple files to increase
+parallelism and focus on specific implementation pieces.
+
+* test_io
+  * test_bufferedio - tests file buffering
+  * test_memoryio - tests BytesIO and StringIO
+  * test_fileio - tests FileIO
+  * test_file - tests the file interface
+  * test_general - tests everything else in the io module
+  * test_univnewlines - tests universal newline support
+  * test_largefile - tests operations on a file greater than 2**32 bytes
+    (only enabled with -ulargefile)
+* test_free_threading/test_io - tests thread safety of io objects
+
+.. attention::
+   When writing tests for io, it's important to test both the C and Python
+   implementations. This is usually done by writing a base test that refers to
+   the type it is testing as an attribute. Then it provides custom subclasses to
+   test both implementations. This directory contains lots of examples.
+"""
+
+import os
+from test.support import load_package_tests
+
+def load_tests(*args):
+    return load_package_tests(os.path.dirname(__file__), *args)
diff --git a/Lib/test/test_io/__main__.py b/Lib/test/test_io/__main__.py
new file mode 100644
index 00000000000..40a23a297ec
--- /dev/null
+++ b/Lib/test/test_io/__main__.py
@@ -0,0 +1,4 @@
+from . import load_tests
+import unittest
+
+unittest.main()
diff --git a/Lib/test/test_io/test_bufferedio.py b/Lib/test/test_io/test_bufferedio.py
new file mode 100644
index 00000000000..5aaaf13a3d4
--- /dev/null
+++ b/Lib/test/test_io/test_bufferedio.py
@@ -0,0 +1,1570 @@
+import array
+import pickle
+import random
+import sys
+import threading
+import time
+import unittest
+import warnings
+import weakref
+from collections import deque, UserList
+from itertools import cycle, count
+from test import support
+from test.support import check_sanitizer, os_helper, threading_helper
+from .utils import byteslike, CTestCase, PyTestCase
+
+
+import io # C implementation.
+import _pyio as pyio # Python implementation.
+
+
+class CommonBufferedTests:
+    # Tests common to BufferedReader, BufferedWriter and BufferedRandom
+
+    def test_detach(self):
+        raw = self.MockRawIO()
+        buf = self.tp(raw)
+        self.assertIs(buf.detach(), raw)
+        self.assertRaises(ValueError, buf.detach)
+
+        repr(buf)  # Should still work
+
+    def test_fileno(self):
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+
+        self.assertEqual(42, bufio.fileno())
+
+    def test_invalid_args(self):
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+        # Invalid whence
+        self.assertRaises(ValueError, bufio.seek, 0, -1)
+        self.assertRaises(ValueError, bufio.seek, 0, 9)
+
+    def test_override_destructor(self):
+        tp = self.tp
+        record = []
+        class MyBufferedIO(tp):
+            def __del__(self):
+                record.append(1)
+                try:
+                    f = super().__del__
+                except AttributeError:
+                    pass
+                else:
+                    f()
+            def close(self):
+                record.append(2)
+                super().close()
+            def flush(self):
+                record.append(3)
+                super().flush()
+        rawio = self.MockRawIO()
+        bufio = MyBufferedIO(rawio)
+        del bufio
+        support.gc_collect()
+        self.assertEqual(record, [1, 2, 3])
+
+    def test_context_manager(self):
+        # Test usability as a context manager
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+        def _with():
+            with bufio:
+                pass
+        _with()
+        # bufio should now be closed, and using it a second time should raise
+        # a ValueError.
+        self.assertRaises(ValueError, _with)
+
+    def test_error_through_destructor(self):
+        # Test that the exception state is not modified by a destructor,
+        # even if close() fails.
+        rawio = self.CloseFailureIO()
+        with support.catch_unraisable_exception() as cm:
+            with self.assertRaises(AttributeError):
+                self.tp(rawio).xyzzy
+
+            self.assertEqual(cm.unraisable.exc_type, OSError)
+
+    def test_repr(self):
+        raw = self.MockRawIO()
+        b = self.tp(raw)
+        clsname = r"(%s\.)?%s" % (self.tp.__module__, self.tp.__qualname__)
+        self.assertRegex(repr(b), "<%s>" % clsname)
+        raw.name = "dummy"
+        self.assertRegex(repr(b), "<%s name='dummy'>" % clsname)
+        raw.name = b"dummy"
+        self.assertRegex(repr(b), "<%s name=b'dummy'>" % clsname)
+
+    def test_recursive_repr(self):
+        # Issue #25455
+        raw = self.MockRawIO()
+        b = self.tp(raw)
+        with support.swap_attr(raw, 'name', b), support.infinite_recursion(25):
+            with self.assertRaises(RuntimeError):
+                repr(b)  # Should not crash
+
+    def test_flush_error_on_close(self):
+        # Test that buffered file is closed despite failed flush
+        # and that flush() is called before file closed.
+        raw = self.MockRawIO()
+        closed = []
+        def bad_flush():
+            closed[:] = [b.closed, raw.closed]
+            raise OSError()
+        raw.flush = bad_flush
+        b = self.tp(raw)
+        self.assertRaises(OSError, b.close) # exception not swallowed
+        self.assertTrue(b.closed)
+        self.assertTrue(raw.closed)
+        self.assertTrue(closed)      # flush() called
+        self.assertFalse(closed[0])  # flush() called before file closed
+        self.assertFalse(closed[1])
+        raw.flush = lambda: None  # break reference loop
+
+    def test_close_error_on_close(self):
+        raw = self.MockRawIO()
+        def bad_flush():
+            raise OSError('flush')
+        def bad_close():
+            raise OSError('close')
+        raw.close = bad_close
+        b = self.tp(raw)
+        b.flush = bad_flush
+        with self.assertRaises(OSError) as err: # exception not swallowed
+            b.close()
+        self.assertEqual(err.exception.args, ('close',))
+        self.assertIsInstance(err.exception.__context__, OSError)
+        self.assertEqual(err.exception.__context__.args, ('flush',))
+        self.assertFalse(b.closed)
+
+        # Silence destructor error
+        raw.close = lambda: None
+        b.flush = lambda: None
+
+    def test_nonnormalized_close_error_on_close(self):
+        # Issue #21677
+        raw = self.MockRawIO()
+        def bad_flush():
+            raise non_existing_flush
+        def bad_close():
+            raise non_existing_close
+        raw.close = bad_close
+        b = self.tp(raw)
+        b.flush = bad_flush
+        with self.assertRaises(NameError) as err: # exception not swallowed
+            b.close()
+        self.assertIn('non_existing_close', str(err.exception))
+        self.assertIsInstance(err.exception.__context__, NameError)
+        self.assertIn('non_existing_flush', str(err.exception.__context__))
+        self.assertFalse(b.closed)
+
+        # Silence destructor error
+        b.flush = lambda: None
+        raw.close = lambda: None
+
+    def test_multi_close(self):
+        raw = self.MockRawIO()
+        b = self.tp(raw)
+        b.close()
+        b.close()
+        b.close()
+        self.assertRaises(ValueError, b.flush)
+
+    def test_unseekable(self):
+        bufio = self.tp(self.MockUnseekableIO(b"A" * 10))
+        self.assertRaises(self.UnsupportedOperation, bufio.tell)
+        self.assertRaises(self.UnsupportedOperation, bufio.seek, 0)
+
+    def test_readonly_attributes(self):
+        raw = self.MockRawIO()
+        buf = self.tp(raw)
+        x = self.MockRawIO()
+        with self.assertRaises(AttributeError):
+            buf.raw = x
+
+    def test_pickling_subclass(self):
+        global MyBufferedIO
+        class MyBufferedIO(self.tp):
+            def __init__(self, raw, tag):
+                super().__init__(raw)
+                self.tag = tag
+            def __getstate__(self):
+                return self.tag, self.raw.getvalue()
+            def __setstate__(slf, state):
+                tag, value = state
+                slf.__init__(self.BytesIO(value), tag)
+
+        raw = self.BytesIO(b'data')
+        buf = MyBufferedIO(raw, tag='ham')
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(protocol=proto):
+                pickled = pickle.dumps(buf, proto)
+                newbuf = pickle.loads(pickled)
+                self.assertEqual(newbuf.raw.getvalue(), b'data')
+                self.assertEqual(newbuf.tag, 'ham')
+        del MyBufferedIO
+
+
+class SizeofTest:
+
+    @support.cpython_only
+    def test_sizeof(self):
+        bufsize1 = 4096
+        bufsize2 = 8192
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio, buffer_size=bufsize1)
+        size = sys.getsizeof(bufio) - bufsize1
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio, buffer_size=bufsize2)
+        self.assertEqual(sys.getsizeof(bufio), size + bufsize2)
+
+    @support.cpython_only
+    def test_buffer_freeing(self) :
+        bufsize = 4096
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio, buffer_size=bufsize)
+        size = sys.getsizeof(bufio) - bufsize
+        bufio.close()
+        self.assertEqual(sys.getsizeof(bufio), size)
+
+class BufferedReaderTest(CommonBufferedTests):
+    read_mode = "rb"
+
+    def test_constructor(self):
+        rawio = self.MockRawIO([b"abc"])
+        bufio = self.tp(rawio)
+        bufio.__init__(rawio)
+        bufio.__init__(rawio, buffer_size=1024)
+        bufio.__init__(rawio, buffer_size=16)
+        self.assertEqual(b"abc", bufio.read())
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
+        rawio = self.MockRawIO([b"abc"])
+        bufio.__init__(rawio)
+        self.assertEqual(b"abc", bufio.read())
+
+    def test_uninitialized(self):
+        bufio = self.tp.__new__(self.tp)
+        del bufio
+        bufio = self.tp.__new__(self.tp)
+        self.assertRaisesRegex((ValueError, AttributeError),
+                               'uninitialized|has no attribute',
+                               bufio.read, 0)
+        bufio.__init__(self.MockRawIO())
+        self.assertEqual(bufio.read(0), b'')
+
+    def test_read(self):
+        for arg in (None, 7):
+            rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+            bufio = self.tp(rawio)
+            self.assertEqual(b"abcdefg", bufio.read(arg))
+        # Invalid args
+        self.assertRaises(ValueError, bufio.read, -2)
+
+    def test_read1(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        self.assertEqual(b"a", bufio.read(1))
+        self.assertEqual(b"b", bufio.read1(1))
+        self.assertEqual(rawio._reads, 1)
+        self.assertEqual(b"", bufio.read1(0))
+        self.assertEqual(b"c", bufio.read1(100))
+        self.assertEqual(rawio._reads, 1)
+        self.assertEqual(b"d", bufio.read1(100))
+        self.assertEqual(rawio._reads, 2)
+        self.assertEqual(b"efg", bufio.read1(100))
+        self.assertEqual(rawio._reads, 3)
+        self.assertEqual(b"", bufio.read1(100))
+        self.assertEqual(rawio._reads, 4)
+
+    def test_read1_arbitrary(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        self.assertEqual(b"a", bufio.read(1))
+        self.assertEqual(b"bc", bufio.read1())
+        self.assertEqual(b"d", bufio.read1())
+        self.assertEqual(b"efg", bufio.read1(-1))
+        self.assertEqual(rawio._reads, 3)
+        self.assertEqual(b"", bufio.read1())
+        self.assertEqual(rawio._reads, 4)
+
+    def test_readinto(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        b = bytearray(2)
+        self.assertEqual(bufio.readinto(b), 2)
+        self.assertEqual(b, b"ab")
+        self.assertEqual(bufio.readinto(b), 2)
+        self.assertEqual(b, b"cd")
+        self.assertEqual(bufio.readinto(b), 2)
+        self.assertEqual(b, b"ef")
+        self.assertEqual(bufio.readinto(b), 1)
+        self.assertEqual(b, b"gf")
+        self.assertEqual(bufio.readinto(b), 0)
+        self.assertEqual(b, b"gf")
+        rawio = self.MockRawIO((b"abc", None))
+        bufio = self.tp(rawio)
+        self.assertEqual(bufio.readinto(b), 2)
+        self.assertEqual(b, b"ab")
+        self.assertEqual(bufio.readinto(b), 1)
+        self.assertEqual(b, b"cb")
+
+    def test_readinto1(self):
+        buffer_size = 10
+        rawio = self.MockRawIO((b"abc", b"de", b"fgh", b"jkl"))
+        bufio = self.tp(rawio, buffer_size=buffer_size)
+        b = bytearray(2)
+        self.assertEqual(bufio.peek(3), b'abc')
+        self.assertEqual(rawio._reads, 1)
+        self.assertEqual(bufio.readinto1(b), 2)
+        self.assertEqual(b, b"ab")
+        self.assertEqual(rawio._reads, 1)
+        self.assertEqual(bufio.readinto1(b), 1)
+        self.assertEqual(b[:1], b"c")
+        self.assertEqual(rawio._reads, 1)
+        self.assertEqual(bufio.readinto1(b), 2)
+        self.assertEqual(b, b"de")
+        self.assertEqual(rawio._reads, 2)
+        b = bytearray(2*buffer_size)
+        self.assertEqual(bufio.peek(3), b'fgh')
+        self.assertEqual(rawio._reads, 3)
+        self.assertEqual(bufio.readinto1(b), 6)
+        self.assertEqual(b[:6], b"fghjkl")
+        self.assertEqual(rawio._reads, 4)
+
+    def test_readinto_array(self):
+        buffer_size = 60
+        data = b"a" * 26
+        rawio = self.MockRawIO((data,))
+        bufio = self.tp(rawio, buffer_size=buffer_size)
+
+        # Create an array with element size > 1 byte
+        b = array.array('i', b'x' * 32)
+        assert len(b) != 16
+
+        # Read into it. We should get as many *bytes* as we can fit into b
+        # (which is more than the number of elements)
+        n = bufio.readinto(b)
+        self.assertGreater(n, len(b))
+
+        # Check that old contents of b are preserved
+        bm = memoryview(b).cast('B')
+        self.assertLess(n, len(bm))
+        self.assertEqual(bm[:n], data[:n])
+        self.assertEqual(bm[n:], b'x' * (len(bm[n:])))
+
+    def test_readinto1_array(self):
+        buffer_size = 60
+        data = b"a" * 26
+        rawio = self.MockRawIO((data,))
+        bufio = self.tp(rawio, buffer_size=buffer_size)
+
+        # Create an array with element size > 1 byte
+        b = array.array('i', b'x' * 32)
+        assert len(b) != 16
+
+        # Read into it. We should get as many *bytes* as we can fit into b
+        # (which is more than the number of elements)
+        n = bufio.readinto1(b)
+        self.assertGreater(n, len(b))
+
+        # Check that old contents of b are preserved
+        bm = memoryview(b).cast('B')
+        self.assertLess(n, len(bm))
+        self.assertEqual(bm[:n], data[:n])
+        self.assertEqual(bm[n:], b'x' * (len(bm[n:])))
+
+    def test_readlines(self):
+        def bufio():
+            rawio = self.MockRawIO((b"abc\n", b"d\n", b"ef"))
+            return self.tp(rawio)
+        self.assertEqual(bufio().readlines(), [b"abc\n", b"d\n", b"ef"])
+        self.assertEqual(bufio().readlines(5), [b"abc\n", b"d\n"])
+        self.assertEqual(bufio().readlines(None), [b"abc\n", b"d\n", b"ef"])
+
+    def test_buffering(self):
+        data = b"abcdefghi"
+        dlen = len(data)
+
+        tests = [
+            [ 100, [ 3, 1, 4, 8 ], [ dlen, 0 ] ],
+            [ 100, [ 3, 3, 3],     [ dlen ]    ],
+            [   4, [ 1, 2, 4, 2 ], [ 4, 4, 1 ] ],
+        ]
+
+        for bufsize, buf_read_sizes, raw_read_sizes in tests:
+            rawio = self.MockFileIO(data)
+            bufio = self.tp(rawio, buffer_size=bufsize)
+            pos = 0
+            for nbytes in buf_read_sizes:
+                self.assertEqual(bufio.read(nbytes), data[pos:pos+nbytes])
+                pos += nbytes
+            # this is mildly implementation-dependent
+            self.assertEqual(rawio.read_history, raw_read_sizes)
+
+    def test_read_non_blocking(self):
+        # Inject some None's in there to simulate EWOULDBLOCK
+        rawio = self.MockRawIO((b"abc", b"d", None, b"efg", None, None, None))
+        bufio = self.tp(rawio)
+        self.assertEqual(b"abcd", bufio.read(6))
+        self.assertEqual(b"e", bufio.read(1))
+        self.assertEqual(b"fg", bufio.read())
+        self.assertEqual(b"", bufio.peek(1))
+        self.assertIsNone(bufio.read())
+        self.assertEqual(b"", bufio.read())
+
+        rawio = self.MockRawIO((b"a", None, None))
+        self.assertEqual(b"a", rawio.readall())
+        self.assertIsNone(rawio.readall())
+
+    def test_read_past_eof(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+
+        self.assertEqual(b"abcdefg", bufio.read(9000))
+
+    def test_read_all(self):
+        rawio = self.MockRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+
+        self.assertEqual(b"abcdefg", bufio.read())
+
+    @threading_helper.requires_working_threading()
+    @support.requires_resource('cpu')
+    def test_threads(self):
+        try:
+            # Write out many bytes with exactly the same number of 0's,
+            # 1's... 255's. This will help us check that concurrent reading
+            # doesn't duplicate or forget contents.
+            N = 1000
+            l = list(range(256)) * N
+            random.shuffle(l)
+            s = bytes(bytearray(l))
+            with self.open(os_helper.TESTFN, "wb") as f:
+                f.write(s)
+            with self.open(os_helper.TESTFN, self.read_mode, buffering=0) as raw:
+                bufio = self.tp(raw, 8)
+                errors = []
+                results = []
+                def f():
+                    try:
+                        # Intra-buffer read then buffer-flushing read
+                        for n in cycle([1, 19]):
+                            s = bufio.read(n)
+                            if not s:
+                                break
+                            # list.append() is atomic
+                            results.append(s)
+                    except Exception as e:
+                        errors.append(e)
+                        raise
+                threads = [threading.Thread(target=f) for x in range(20)]
+                with threading_helper.start_threads(threads):
+                    time.sleep(0.02) # yield
+                self.assertFalse(errors,
+                    "the following exceptions were caught: %r" % errors)
+                s = b''.join(results)
+                for i in range(256):
+                    c = bytes(bytearray([i]))
+                    self.assertEqual(s.count(c), N)
+        finally:
+            os_helper.unlink(os_helper.TESTFN)
+
+    def test_unseekable(self):
+        bufio = self.tp(self.MockUnseekableIO(b"A" * 10))
+        self.assertRaises(self.UnsupportedOperation, bufio.tell)
+        self.assertRaises(self.UnsupportedOperation, bufio.seek, 0)
+        bufio.read(1)
+        self.assertRaises(self.UnsupportedOperation, bufio.seek, 0)
+        self.assertRaises(self.UnsupportedOperation, bufio.tell)
+
+    def test_misbehaved_io(self):
+        rawio = self.MisbehavedRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        self.assertRaises(OSError, bufio.seek, 0)
+        self.assertRaises(OSError, bufio.tell)
+
+        # Silence destructor error
+        bufio.close = lambda: None
+
+    def test_no_extraneous_read(self):
+        # Issue #9550; when the raw IO object has satisfied the read request,
+        # we should not issue any additional reads, otherwise it may block
+        # (e.g. socket).
+        bufsize = 16
+        for n in (2, bufsize - 1, bufsize, bufsize + 1, bufsize * 2):
+            rawio = self.MockRawIO([b"x" * n])
+            bufio = self.tp(rawio, bufsize)
+            self.assertEqual(bufio.read(n), b"x" * n)
+            # Simple case: one raw read is enough to satisfy the request.
+            self.assertEqual(rawio._extraneous_reads, 0,
+                             "failed for {}: {} != 0".format(n, rawio._extraneous_reads))
+            # A more complex case where two raw reads are needed to satisfy
+            # the request.
+            rawio = self.MockRawIO([b"x" * (n - 1), b"x"])
+            bufio = self.tp(rawio, bufsize)
+            self.assertEqual(bufio.read(n), b"x" * n)
+            self.assertEqual(rawio._extraneous_reads, 0,
+                             "failed for {}: {} != 0".format(n, rawio._extraneous_reads))
+
+    def test_read_on_closed(self):
+        # Issue #23796
+        b = self.BufferedReader(self.BytesIO(b"12"))
+        b.read(1)
+        b.close()
+        with self.subTest('peek'):
+            self.assertRaises(ValueError, b.peek)
+        with self.subTest('read1'):
+            self.assertRaises(ValueError, b.read1, 1)
+        with self.subTest('read'):
+            self.assertRaises(ValueError, b.read)
+        with self.subTest('readinto'):
+            self.assertRaises(ValueError, b.readinto, bytearray())
+        with self.subTest('readinto1'):
+            self.assertRaises(ValueError, b.readinto1, bytearray())
+        with self.subTest('flush'):
+            self.assertRaises(ValueError, b.flush)
+        with self.subTest('truncate'):
+            self.assertRaises(ValueError, b.truncate)
+        with self.subTest('seek'):
+            self.assertRaises(ValueError, b.seek, 0)
+
+    def test_truncate_on_read_only(self):
+        rawio = self.MockFileIO(b"abc")
+        bufio = self.tp(rawio)
+        self.assertFalse(bufio.writable())
+        self.assertRaises(self.UnsupportedOperation, bufio.truncate)
+        self.assertRaises(self.UnsupportedOperation, bufio.truncate, 0)
+
+    def test_tell_character_device_file(self):
+        # GH-95782
+        # For the (former) bug in BufferedIO to manifest, the wrapped IO obj
+        # must be able to produce at least 2 bytes.
+        raw = self.MockCharPseudoDevFileIO(b"12")
+        buf = self.tp(raw)
+        self.assertEqual(buf.tell(), 0)
+        self.assertEqual(buf.read(1), b"1")
+        self.assertEqual(buf.tell(), 0)
+
+    def test_seek_character_device_file(self):
+        raw = self.MockCharPseudoDevFileIO(b"12")
+        buf = self.tp(raw)
+        self.assertEqual(buf.seek(0, io.SEEK_CUR), 0)
+        self.assertEqual(buf.seek(1, io.SEEK_SET), 0)
+        self.assertEqual(buf.seek(0, io.SEEK_CUR), 0)
+        self.assertEqual(buf.read(1), b"1")
+
+        # In the C implementation, tell() sets the BufferedIO's abs_pos to 0,
+        # which means that the next seek() could return a negative offset if it
+        # does not sanity-check:
+        self.assertEqual(buf.tell(), 0)
+        self.assertEqual(buf.seek(0, io.SEEK_CUR), 0)
+
+
+class CBufferedReaderTest(BufferedReaderTest, SizeofTest, CTestCase):
+    tp = io.BufferedReader
+
+    def test_initialization(self):
+        rawio = self.MockRawIO([b"abc"])
+        bufio = self.tp(rawio)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
+        self.assertRaises(ValueError, bufio.read)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
+        self.assertRaises(ValueError, bufio.read)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
+        self.assertRaises(ValueError, bufio.read)
+
+    def test_misbehaved_io_read(self):
+        rawio = self.MisbehavedRawIO((b"abc", b"d", b"efg"))
+        bufio = self.tp(rawio)
+        # _pyio.BufferedReader seems to implement reading different, so that
+        # checking this is not so easy.
+        self.assertRaises(OSError, bufio.read, 10)
+
+    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
+    def test_garbage_collection(self):
+        # C BufferedReader objects are collected.
+        # The Python version has __del__, so it ends into gc.garbage instead
+        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
+        # Note that using warnings_helper.check_warnings() will keep the
+        # file alive due to the `source` argument to warn().  So, use
+        # catch_warnings() instead.
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", ResourceWarning)
+            rawio = self.FileIO(os_helper.TESTFN, "w+b")
+            f = self.tp(rawio)
+            f.f = f
+            wr = weakref.ref(f)
+            del f
+            support.gc_collect()
+        self.assertIsNone(wr(), wr)
+
+    def test_args_error(self):
+        # Issue #17275
+        with self.assertRaisesRegex(TypeError, "BufferedReader"):
+            self.tp(self.BytesIO(), 1024, 1024, 1024)
+
+    def test_bad_readinto_value(self):
+        rawio = self.tp(self.BytesIO(b"12"))
+        rawio.readinto = lambda buf: -1
+        bufio = self.tp(rawio)
+        with self.assertRaises(OSError) as cm:
+            bufio.readline()
+        self.assertIsNone(cm.exception.__cause__)
+
+    def test_bad_readinto_type(self):
+        rawio = self.tp(self.BytesIO(b"12"))
+        rawio.readinto = lambda buf: b''
+        bufio = self.tp(rawio)
+        with self.assertRaises(OSError) as cm:
+            bufio.readline()
+        self.assertIsInstance(cm.exception.__cause__, TypeError)
+
+    @unittest.skipUnless(sys.maxsize > 2**32, 'requires 64bit platform')
+    @unittest.skipIf(check_sanitizer(thread=True),
+                     'ThreadSanitizer aborts on huge allocations (exit code 66).')
+    def test_read1_error_does_not_cause_reentrant_failure(self):
+        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
+        with self.open(os_helper.TESTFN, "wb") as f:
+            f.write(b"hello")
+
+        with self.open(os_helper.TESTFN, "rb", buffering=0) as raw:
+            bufio = self.tp(raw, buffer_size=8)
+            # To request a size that is far too huge to ever be satisfied,
+            # so that the internal buffer allocation reliably fails with MemoryError.
+            huge = sys.maxsize // 2 + 1
+            with self.assertRaises(MemoryError):
+                bufio.read1(huge)
+
+            # Used to crash before gh-143689:
+            self.assertEqual(bufio.read1(1), b"h")
+
+
+class PyBufferedReaderTest(BufferedReaderTest, PyTestCase):
+    tp = pyio.BufferedReader
+
+
+class BufferedWriterTest(CommonBufferedTests):
+    write_mode = "wb"
+
+    def test_constructor(self):
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+        bufio.__init__(rawio)
+        bufio.__init__(rawio, buffer_size=1024)
+        bufio.__init__(rawio, buffer_size=16)
+        self.assertEqual(3, bufio.write(b"abc"))
+        bufio.flush()
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
+        bufio.__init__(rawio)
+        self.assertEqual(3, bufio.write(b"ghi"))
+        bufio.flush()
+        self.assertEqual(b"".join(rawio._write_stack), b"abcghi")
+
+    def test_uninitialized(self):
+        bufio = self.tp.__new__(self.tp)
+        del bufio
+        bufio = self.tp.__new__(self.tp)
+        self.assertRaisesRegex((ValueError, AttributeError),
+                               'uninitialized|has no attribute',
+                               bufio.write, b'')
+        bufio.__init__(self.MockRawIO())
+        self.assertEqual(bufio.write(b''), 0)
+
+    def test_detach_flush(self):
+        raw = self.MockRawIO()
+        buf = self.tp(raw)
+        buf.write(b"howdy!")
+        self.assertFalse(raw._write_stack)
+        buf.detach()
+        self.assertEqual(raw._write_stack, [b"howdy!"])
+
+    def test_write(self):
+        # Write to the buffered IO but don't overflow the buffer.
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        bufio.write(b"abc")
+        self.assertFalse(writer._write_stack)
+        buffer = bytearray(b"def")
+        bufio.write(buffer)
+        buffer[:] = b"***"  # Overwrite our copy of the data
+        bufio.flush()
+        self.assertEqual(b"".join(writer._write_stack), b"abcdef")
+
+    def test_write_overflow(self):
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        contents = b"abcdefghijklmnop"
+        for n in range(0, len(contents), 3):
+            bufio.write(contents[n:n+3])
+        flushed = b"".join(writer._write_stack)
+        # At least (total - 8) bytes were implicitly flushed, perhaps more
+        # depending on the implementation.
+        self.assertStartsWith(flushed, contents[:-8])
+
+    def check_writes(self, intermediate_func):
+        # Lots of writes, test the flushed output is as expected.
+        contents = bytes(range(256)) * 1000
+        n = 0
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 13)
+        # Generator of write sizes: repeat each N 15 times then proceed to N+1
+        def gen_sizes():
+            for size in count(1):
+                for i in range(15):
+                    yield size
+        sizes = gen_sizes()
+        while n < len(contents):
+            size = min(next(sizes), len(contents) - n)
+            self.assertEqual(bufio.write(contents[n:n+size]), size)
+            intermediate_func(bufio)
+            n += size
+        bufio.flush()
+        self.assertEqual(contents, b"".join(writer._write_stack))
+
+    def test_writes(self):
+        self.check_writes(lambda bufio: None)
+
+    def test_writes_and_flushes(self):
+        self.check_writes(lambda bufio: bufio.flush())
+
+    def test_writes_and_seeks(self):
+        def _seekabs(bufio):
+            pos = bufio.tell()
+            bufio.seek(pos + 1, 0)
+            bufio.seek(pos - 1, 0)
+            bufio.seek(pos, 0)
+        self.check_writes(_seekabs)
+        def _seekrel(bufio):
+            pos = bufio.seek(0, 1)
+            bufio.seek(+1, 1)
+            bufio.seek(-1, 1)
+            bufio.seek(pos, 0)
+        self.check_writes(_seekrel)
+
+    def test_writes_and_truncates(self):
+        self.check_writes(lambda bufio: bufio.truncate(bufio.tell()))
+
+    def test_write_non_blocking(self):
+        raw = self.MockNonBlockWriterIO()
+        bufio = self.tp(raw, 8)
+
+        self.assertEqual(bufio.write(b"abcd"), 4)
+        self.assertEqual(bufio.write(b"efghi"), 5)
+        # 1 byte will be written, the rest will be buffered
+        raw.block_on(b"k")
+        self.assertEqual(bufio.write(b"jklmn"), 5)
+
+        # 8 bytes will be written, 8 will be buffered and the rest will be lost
+        raw.block_on(b"0")
+        try:
+            bufio.write(b"opqrwxyz0123456789")
+        except self.BlockingIOError as e:
+            written = e.characters_written
+        else:
+            self.fail("BlockingIOError should have been raised")
+        self.assertEqual(written, 16)
+        self.assertEqual(raw.pop_written(),
+            b"abcdefghijklmnopqrwxyz")
+
+        self.assertEqual(bufio.write(b"ABCDEFGHI"), 9)
+        s = raw.pop_written()
+        # Previously buffered bytes were flushed
+        self.assertStartsWith(s, b"01234567A")
+
+    def test_write_and_rewind(self):
+        raw = self.BytesIO()
+        bufio = self.tp(raw, 4)
+        self.assertEqual(bufio.write(b"abcdef"), 6)
+        self.assertEqual(bufio.tell(), 6)
+        bufio.seek(0, 0)
+        self.assertEqual(bufio.write(b"XY"), 2)
+        bufio.seek(6, 0)
+        self.assertEqual(raw.getvalue(), b"XYcdef")
+        self.assertEqual(bufio.write(b"123456"), 6)
+        bufio.flush()
+        self.assertEqual(raw.getvalue(), b"XYcdef123456")
+
+    def test_flush(self):
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        bufio.write(b"abc")
+        bufio.flush()
+        self.assertEqual(b"abc", writer._write_stack[0])
+
+    def test_writelines(self):
+        l = [b'ab', b'cd', b'ef']
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        bufio.writelines(l)
+        bufio.flush()
+        self.assertEqual(b''.join(writer._write_stack), b'abcdef')
+
+    def test_writelines_userlist(self):
+        l = UserList([b'ab', b'cd', b'ef'])
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        bufio.writelines(l)
+        bufio.flush()
+        self.assertEqual(b''.join(writer._write_stack), b'abcdef')
+
+    def test_writelines_error(self):
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        self.assertRaises(TypeError, bufio.writelines, [1, 2, 3])
+        self.assertRaises(TypeError, bufio.writelines, None)
+        self.assertRaises(TypeError, bufio.writelines, 'abc')
+
+    def test_destructor(self):
+        writer = self.MockRawIO()
+        bufio = self.tp(writer, 8)
+        bufio.write(b"abc")
+        del bufio
+        support.gc_collect()
+        self.assertEqual(b"abc", writer._write_stack[0])
+
+    def test_truncate(self):
+        # Truncate implicitly flushes the buffer.
+        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
+        with self.open(os_helper.TESTFN, self.write_mode, buffering=0) as raw:
+            bufio = self.tp(raw, 8)
+            bufio.write(b"abcdef")
+            self.assertEqual(bufio.truncate(3), 3)
+            self.assertEqual(bufio.tell(), 6)
+        with self.open(os_helper.TESTFN, "rb", buffering=0) as f:
+            self.assertEqual(f.read(), b"abc")
+
+    def test_truncate_after_write(self):
+        # Ensure that truncate preserves the file position after
+        # writes longer than the buffer size.
+        # Issue: https://bugs.python.org/issue32228
+        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
+        with self.open(os_helper.TESTFN, "wb") as f:
+            # Fill with some buffer
+            f.write(b'\x00' * 10000)
+        buffer_sizes = [8192, 4096, 200]
+        for buffer_size in buffer_sizes:
+            with self.open(os_helper.TESTFN, "r+b", buffering=buffer_size) as f:
+                f.write(b'\x00' * (buffer_size + 1))
+                # After write write_pos and write_end are set to 0
+                f.read(1)
+                # read operation makes sure that pos != raw_pos
+                f.truncate()
+                self.assertEqual(f.tell(), buffer_size + 2)
+
+    @threading_helper.requires_working_threading()
+    @support.requires_resource('cpu')
+    def test_threads(self):
+        try:
+            # Write out many bytes from many threads and test they were
+            # all flushed.
+            N = 1000
+            contents = bytes(range(256)) * N
+            sizes = cycle([1, 19])
+            n = 0
+            queue = deque()
+            while n < len(contents):
+                size = next(sizes)
+                queue.append(contents[n:n+size])
+                n += size
+            del contents
+            # We use a real file object because it allows us to
+            # exercise situations where the GIL is released before
+            # writing the buffer to the raw streams. This is in addition
+            # to concurrency issues due to switching threads in the middle
+            # of Python code.
+            with self.open(os_helper.TESTFN, self.write_mode, buffering=0) as raw:
+                bufio = self.tp(raw, 8)
+                errors = []
+                def f():
+                    try:
+                        while True:
+                            try:
+                                s = queue.popleft()
+                            except IndexError:
+                                return
+                            bufio.write(s)
+                    except Exception as e:
+                        errors.append(e)
+                        raise
+                threads = [threading.Thread(target=f) for x in range(20)]
+                with threading_helper.start_threads(threads):
+                    time.sleep(0.02) # yield
+                self.assertFalse(errors,
+                    "the following exceptions were caught: %r" % errors)
+                bufio.close()
+            with self.open(os_helper.TESTFN, "rb") as f:
+                s = f.read()
+            for i in range(256):
+                self.assertEqual(s.count(bytes([i])), N)
+        finally:
+            os_helper.unlink(os_helper.TESTFN)
+
+    def test_misbehaved_io(self):
+        rawio = self.MisbehavedRawIO()
+        bufio = self.tp(rawio, 5)
+        self.assertRaises(OSError, bufio.seek, 0)
+        self.assertRaises(OSError, bufio.tell)
+        self.assertRaises(OSError, bufio.write, b"abcdef")
+
+        # Silence destructor error
+        bufio.close = lambda: None
+
+    def test_max_buffer_size_removal(self):
+        with self.assertRaises(TypeError):
+            self.tp(self.MockRawIO(), 8, 12)
+
+    def test_write_error_on_close(self):
+        raw = self.MockRawIO()
+        def bad_write(b):
+            raise OSError()
+        raw.write = bad_write
+        b = self.tp(raw)
+        b.write(b'spam')
+        self.assertRaises(OSError, b.close) # exception not swallowed
+        self.assertTrue(b.closed)
+
+    @threading_helper.requires_working_threading()
+    def test_slow_close_from_thread(self):
+        # Issue #31976
+        rawio = self.SlowFlushRawIO()
+        bufio = self.tp(rawio, 8)
+        t = threading.Thread(target=bufio.close)
+        t.start()
+        rawio.in_flush.wait()
+        self.assertRaises(ValueError, bufio.write, b'spam')
+        self.assertTrue(bufio.closed)
+        t.join()
+
+
+class CBufferedWriterTest(BufferedWriterTest, SizeofTest, CTestCase):
+    tp = io.BufferedWriter
+
+    def test_initialization(self):
+        rawio = self.MockRawIO()
+        bufio = self.tp(rawio)
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=0)
+        self.assertRaises(ValueError, bufio.write, b"def")
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-16)
+        self.assertRaises(ValueError, bufio.write, b"def")
+        self.assertRaises(ValueError, bufio.__init__, rawio, buffer_size=-1)
+        self.assertRaises(ValueError, bufio.write, b"def")
+
+    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
+    def test_garbage_collection(self):
+        # C BufferedWriter objects are collected, and collecting them flushes
+        # all data to disk.
+        # The Python version has __del__, so it ends into gc.garbage instead
+        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
+        # Note that using warnings_helper.check_warnings() will keep the
+        # file alive due to the `source` argument to warn().  So, use
+        # catch_warnings() instead.
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", ResourceWarning)
+            rawio = self.FileIO(os_helper.TESTFN, "w+b")
+            f = self.tp(rawio)
+            f.write(b"123xxx")
+            f.x = f
+            wr = weakref.ref(f)
+            del f
+            support.gc_collect()
+        self.assertIsNone(wr(), wr)
+        with self.open(os_helper.TESTFN, "rb") as f:
+            self.assertEqual(f.read(), b"123xxx")
+
+    def test_args_error(self):
+        # Issue #17275
+        with self.assertRaisesRegex(TypeError, "BufferedWriter"):
+            self.tp(self.BytesIO(), 1024, 1024, 1024)
+
+    def test_non_boolean_closed_attr(self):
+        # gh-140650: check TypeError is raised
+        class MockRawIOWithoutClosed(self.MockRawIO):
+            closed = NotImplemented
+
+        bufio = self.tp(MockRawIOWithoutClosed())
+        self.assertRaises(TypeError, bufio.write, b"")
+        self.assertRaises(TypeError, bufio.flush)
+        self.assertRaises(TypeError, bufio.close)
+
+    def test_closed_attr_raises(self):
+        class MockRawIOClosedRaises(self.MockRawIO):
+            @property
+            def closed(self):
+                raise ValueError("test")
+
+        bufio = self.tp(MockRawIOClosedRaises())
+        self.assertRaisesRegex(ValueError, "test", bufio.write, b"")
+        self.assertRaisesRegex(ValueError, "test", bufio.flush)
+        self.assertRaisesRegex(ValueError, "test", bufio.close)
+
+
+class PyBufferedWriterTest(BufferedWriterTest, PyTestCase):
+    tp = pyio.BufferedWriter
+
+class BufferedRWPairTest:
+
+    def test_constructor(self):
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertFalse(pair.closed)
+
+    def test_uninitialized(self):
+        pair = self.tp.__new__(self.tp)
+        del pair
+        pair = self.tp.__new__(self.tp)
+        self.assertRaisesRegex((ValueError, AttributeError),
+                               'uninitialized|has no attribute',
+                               pair.read, 0)
+        self.assertRaisesRegex((ValueError, AttributeError),
+                               'uninitialized|has no attribute',
+                               pair.write, b'')
+        pair.__init__(self.MockRawIO(), self.MockRawIO())
+        self.assertEqual(pair.read(0), b'')
+        self.assertEqual(pair.write(b''), 0)
+
+    def test_detach(self):
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertRaises(self.UnsupportedOperation, pair.detach)
+
+    def test_constructor_max_buffer_size_removal(self):
+        with self.assertRaises(TypeError):
+            self.tp(self.MockRawIO(), self.MockRawIO(), 8, 12)
+
+    def test_constructor_with_not_readable(self):
+        class NotReadable(self.MockRawIO):
+            def readable(self):
+                return False
+
+        self.assertRaises(OSError, self.tp, NotReadable(), self.MockRawIO())
+
+    def test_constructor_with_not_writeable(self):
+        class NotWriteable(self.MockRawIO):
+            def writable(self):
+                return False
+
+        self.assertRaises(OSError, self.tp, self.MockRawIO(), NotWriteable())
+
+    def test_read(self):
+        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
+
+        self.assertEqual(pair.read(3), b"abc")
+        self.assertEqual(pair.read(1), b"d")
+        self.assertEqual(pair.read(), b"ef")
+        pair = self.tp(self.BytesIO(b"abc"), self.MockRawIO())
+        self.assertEqual(pair.read(None), b"abc")
+
+    def test_readlines(self):
+        pair = lambda: self.tp(self.BytesIO(b"abc\ndef\nh"), self.MockRawIO())
+        self.assertEqual(pair().readlines(), [b"abc\n", b"def\n", b"h"])
+        self.assertEqual(pair().readlines(), [b"abc\n", b"def\n", b"h"])
+        self.assertEqual(pair().readlines(5), [b"abc\n", b"def\n"])
+
+    def test_read1(self):
+        # .read1() is delegated to the underlying reader object, so this test
+        # can be shallow.
+        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
+
+        self.assertEqual(pair.read1(3), b"abc")
+        self.assertEqual(pair.read1(), b"def")
+
+    def test_readinto(self):
+        for method in ("readinto", "readinto1"):
+            with self.subTest(method):
+                pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
+
+                data = byteslike(b'\0' * 5)
+                self.assertEqual(getattr(pair, method)(data), 5)
+                self.assertEqual(bytes(data), b"abcde")
+
+        # gh-138720: C BufferedRWPair would destruct in a bad order resulting in
+        # an unraisable exception.
+        support.gc_collect()
+
+    def test_write(self):
+        w = self.MockRawIO()
+        pair = self.tp(self.MockRawIO(), w)
+
+        pair.write(b"abc")
+        pair.flush()
+        buffer = bytearray(b"def")
+        pair.write(buffer)
+        buffer[:] = b"***"  # Overwrite our copy of the data
+        pair.flush()
+        self.assertEqual(w._write_stack, [b"abc", b"def"])
+
+    def test_peek(self):
+        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
+
+        self.assertStartsWith(pair.peek(3), b"abc")
+        self.assertEqual(pair.read(3), b"abc")
+
+    def test_readable(self):
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertTrue(pair.readable())
+
+    def test_writeable(self):
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertTrue(pair.writable())
+
+    def test_seekable(self):
+        # BufferedRWPairs are never seekable, even if their readers and writers
+        # are.
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertFalse(pair.seekable())
+
+    # .flush() is delegated to the underlying writer object and has been
+    # tested in the test_write method.
+
+    def test_close_and_closed(self):
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertFalse(pair.closed)
+        pair.close()
+        self.assertTrue(pair.closed)
+
+    def test_reader_close_error_on_close(self):
+        def reader_close():
+            reader_non_existing
+        reader = self.MockRawIO()
+        reader.close = reader_close
+        writer = self.MockRawIO()
+        pair = self.tp(reader, writer)
+        with self.assertRaises(NameError) as err:
+            pair.close()
+        self.assertIn('reader_non_existing', str(err.exception))
+        self.assertTrue(pair.closed)
+        self.assertFalse(reader.closed)
+        self.assertTrue(writer.closed)
+
+        # Silence destructor error
+        reader.close = lambda: None
+
+    def test_writer_close_error_on_close(self):
+        def writer_close():
+            writer_non_existing
+        reader = self.MockRawIO()
+        writer = self.MockRawIO()
+        writer.close = writer_close
+        pair = self.tp(reader, writer)
+        with self.assertRaises(NameError) as err:
+            pair.close()
+        self.assertIn('writer_non_existing', str(err.exception))
+        self.assertFalse(pair.closed)
+        self.assertTrue(reader.closed)
+        self.assertFalse(writer.closed)
+
+        # Silence destructor error
+        writer.close = lambda: None
+        writer = None
+
+        # Ignore BufferedWriter (of the BufferedRWPair) unraisable exception
+        with support.catch_unraisable_exception():
+            # Ignore BufferedRWPair unraisable exception
+            with support.catch_unraisable_exception():
+                pair = None
+                support.gc_collect()
+            support.gc_collect()
+
+    def test_reader_writer_close_error_on_close(self):
+        def reader_close():
+            reader_non_existing
+        def writer_close():
+            writer_non_existing
+        reader = self.MockRawIO()
+        reader.close = reader_close
+        writer = self.MockRawIO()
+        writer.close = writer_close
+        pair = self.tp(reader, writer)
+        with self.assertRaises(NameError) as err:
+            pair.close()
+        self.assertIn('reader_non_existing', str(err.exception))
+        self.assertIsInstance(err.exception.__context__, NameError)
+        self.assertIn('writer_non_existing', str(err.exception.__context__))
+        self.assertFalse(pair.closed)
+        self.assertFalse(reader.closed)
+        self.assertFalse(writer.closed)
+
+        # Silence destructor error
+        reader.close = lambda: None
+        writer.close = lambda: None
+
+    def test_isatty(self):
+        class SelectableIsAtty(self.MockRawIO):
+            def __init__(self, isatty):
+                super().__init__()
+                self._isatty = isatty
+
+            def isatty(self):
+                return self._isatty
+
+        pair = self.tp(SelectableIsAtty(False), SelectableIsAtty(False))
+        self.assertFalse(pair.isatty())
+
+        pair = self.tp(SelectableIsAtty(True), SelectableIsAtty(False))
+        self.assertTrue(pair.isatty())
+
+        pair = self.tp(SelectableIsAtty(False), SelectableIsAtty(True))
+        self.assertTrue(pair.isatty())
+
+        pair = self.tp(SelectableIsAtty(True), SelectableIsAtty(True))
+        self.assertTrue(pair.isatty())
+
+    def test_weakref_clearing(self):
+        brw = self.tp(self.MockRawIO(), self.MockRawIO())
+        ref = weakref.ref(brw)
+        brw = None
+        ref = None # Shouldn't segfault.
+
+class CBufferedRWPairTest(BufferedRWPairTest, CTestCase):
+    tp = io.BufferedRWPair
+
+class PyBufferedRWPairTest(BufferedRWPairTest, PyTestCase):
+    tp = pyio.BufferedRWPair
+
+
+class BufferedRandomTest(BufferedReaderTest, BufferedWriterTest):
+    read_mode = "rb+"
+    write_mode = "wb+"
+
+    def test_constructor(self):
+        BufferedReaderTest.test_constructor(self)
+        BufferedWriterTest.test_constructor(self)
+
+    def test_uninitialized(self):
+        BufferedReaderTest.test_uninitialized(self)
+        BufferedWriterTest.test_uninitialized(self)
+
+    def test_read_and_write(self):
+        raw = self.MockRawIO((b"asdf", b"ghjk"))
+        rw = self.tp(raw, 8)
+
+        self.assertEqual(b"as", rw.read(2))
+        rw.write(b"ddd")
+        rw.write(b"eee")
+        self.assertFalse(raw._write_stack) # Buffer writes
+        self.assertEqual(b"ghjk", rw.read())
+        self.assertEqual(b"dddeee", raw._write_stack[0])
+
+    def test_seek_and_tell(self):
+        raw = self.BytesIO(b"asdfghjkl")
+        rw = self.tp(raw)
+
+        self.assertEqual(b"as", rw.read(2))
+        self.assertEqual(2, rw.tell())
+        rw.seek(0, 0)
+        self.assertEqual(b"asdf", rw.read(4))
+
+        rw.write(b"123f")
+        rw.seek(0, 0)
+        self.assertEqual(b"asdf123fl", rw.read())
+        self.assertEqual(9, rw.tell())
+        rw.seek(-4, 2)
+        self.assertEqual(5, rw.tell())
+        rw.seek(2, 1)
+        self.assertEqual(7, rw.tell())
+        self.assertEqual(b"fl", rw.read(11))
+        rw.flush()
+        self.assertEqual(b"asdf123fl", raw.getvalue())
+
+        self.assertRaises(TypeError, rw.seek, 0.0)
+
+    def check_flush_and_read(self, read_func):
+        raw = self.BytesIO(b"abcdefghi")
+        bufio = self.tp(raw)
+
+        self.assertEqual(b"ab", read_func(bufio, 2))
+        bufio.write(b"12")
+        self.assertEqual(b"ef", read_func(bufio, 2))
+        self.assertEqual(6, bufio.tell())
+        bufio.flush()
+        self.assertEqual(6, bufio.tell())
+        self.assertEqual(b"ghi", read_func(bufio))
+        raw.seek(0, 0)
+        raw.write(b"XYZ")
+        # flush() resets the read buffer
+        bufio.flush()
+        bufio.seek(0, 0)
+        self.assertEqual(b"XYZ", read_func(bufio, 3))
+
+    def test_flush_and_read(self):
+        self.check_flush_and_read(lambda bufio, *args: bufio.read(*args))
+
+    def test_flush_and_readinto(self):
+        def _readinto(bufio, n=-1):
+            b = bytearray(n if n >= 0 else 9999)
+            n = bufio.readinto(b)
+            b.resize(n)
+            return b.take_bytes()
+        self.check_flush_and_read(_readinto)
+
+    def test_flush_and_peek(self):
+        def _peek(bufio, n=-1):
+            # This relies on the fact that the buffer can contain the whole
+            # raw stream, otherwise peek() can return less.
+            b = bufio.peek(n)
+            if n != -1:
+                b = b[:n]
+            bufio.seek(len(b), 1)
+            return b
+        self.check_flush_and_read(_peek)
+
+    def test_flush_and_write(self):
+        raw = self.BytesIO(b"abcdefghi")
+        bufio = self.tp(raw)
+
+        bufio.write(b"123")
+        bufio.flush()
+        bufio.write(b"45")
+        bufio.flush()
+        bufio.seek(0, 0)
+        self.assertEqual(b"12345fghi", raw.getvalue())
+        self.assertEqual(b"12345fghi", bufio.read())
+
+    def test_threads(self):
+        BufferedReaderTest.test_threads(self)
+        BufferedWriterTest.test_threads(self)
+
+    def test_writes_and_peek(self):
+        def _peek(bufio):
+            bufio.peek(1)
+        self.check_writes(_peek)
+        def _peek(bufio):
+            pos = bufio.tell()
+            bufio.seek(-1, 1)
+            bufio.peek(1)
+            bufio.seek(pos, 0)
+        self.check_writes(_peek)
+
+    def test_writes_and_reads(self):
+        def _read(bufio):
+            bufio.seek(-1, 1)
+            bufio.read(1)
+        self.check_writes(_read)
+
+    def test_writes_and_read1s(self):
+        def _read1(bufio):
+            bufio.seek(-1, 1)
+            bufio.read1(1)
+        self.check_writes(_read1)
+
+    def test_writes_and_readintos(self):
+        def _read(bufio):
+            bufio.seek(-1, 1)
+            bufio.readinto(bytearray(1))
+        self.check_writes(_read)
+
+    def test_write_after_readahead(self):
+        # Issue #6629: writing after the buffer was filled by readahead should
+        # first rewind the raw stream.
+        for overwrite_size in [1, 5]:
+            raw = self.BytesIO(b"A" * 10)
+            bufio = self.tp(raw, 4)
+            # Trigger readahead
+            self.assertEqual(bufio.read(1), b"A")
+            self.assertEqual(bufio.tell(), 1)
+            # Overwriting should rewind the raw stream if it needs so
+            bufio.write(b"B" * overwrite_size)
+            self.assertEqual(bufio.tell(), overwrite_size + 1)
+            # If the write size was smaller than the buffer size, flush() and
+            # check that rewind happens.
+            bufio.flush()
+            self.assertEqual(bufio.tell(), overwrite_size + 1)
+            s = raw.getvalue()
+            self.assertEqual(s,
+                b"A" + b"B" * overwrite_size + b"A" * (9 - overwrite_size))
+
+    def test_write_rewind_write(self):
+        # Various combinations of reading / writing / seeking backwards / writing again
+        def mutate(bufio, pos1, pos2):
+            assert pos2 >= pos1
+            # Fill the buffer
+            bufio.seek(pos1)
+            bufio.read(pos2 - pos1)
+            bufio.write(b'\x02')
+            # This writes earlier than the previous write, but still inside
+            # the buffer.
+            bufio.seek(pos1)
+            bufio.write(b'\x01')
+
+        b = b"\x80\x81\x82\x83\x84"
+        for i in range(0, len(b)):
+            for j in range(i, len(b)):
+                raw = self.BytesIO(b)
+                bufio = self.tp(raw, 100)
+                mutate(bufio, i, j)
+                bufio.flush()
+                expected = bytearray(b)
+                expected[j] = 2
+                expected[i] = 1
+                self.assertEqual(raw.getvalue(), expected,
+                                 "failed result for i=%d, j=%d" % (i, j))
+
+    def test_truncate_after_read_or_write(self):
+        raw = self.BytesIO(b"A" * 10)
+        bufio = self.tp(raw, 100)
+        self.assertEqual(bufio.read(2), b"AA") # the read buffer gets filled
+        self.assertEqual(bufio.truncate(), 2)
+        self.assertEqual(bufio.write(b"BB"), 2) # the write buffer increases
+        self.assertEqual(bufio.truncate(), 4)
+
+    def test_misbehaved_io(self):
+        BufferedReaderTest.test_misbehaved_io(self)
+        BufferedWriterTest.test_misbehaved_io(self)
+
+    def test_interleaved_read_write(self):
+        # Test for issue #12213
+        with self.BytesIO(b'abcdefgh') as raw:
+            with self.tp(raw, 100) as f:
+                f.write(b"1")
+                self.assertEqual(f.read(1), b'b')
+                f.write(b'2')
+                self.assertEqual(f.read1(1), b'd')
+                f.write(b'3')
+                buf = bytearray(1)
+                f.readinto(buf)
+                self.assertEqual(buf, b'f')
+                f.write(b'4')
+                self.assertEqual(f.peek(1), b'h')
+                f.flush()
+                self.assertEqual(raw.getvalue(), b'1b2d3f4h')
+
+        with self.BytesIO(b'abc') as raw:
+            with self.tp(raw, 100) as f:
+                self.assertEqual(f.read(1), b'a')
+                f.write(b"2")
+                self.assertEqual(f.read(1), b'c')
+                f.flush()
+                self.assertEqual(raw.getvalue(), b'a2c')
+
+    def test_read1_after_write(self):
+        with self.BytesIO(b'abcdef') as raw:
+            with self.tp(raw, 3) as f:
+                f.write(b"1")
+                self.assertEqual(f.read1(1), b'b')
+                f.flush()
+                self.assertEqual(raw.getvalue(), b'1bcdef')
+        with self.BytesIO(b'abcdef') as raw:
+            with self.tp(raw, 3) as f:
+                f.write(b"1")
+                self.assertEqual(f.read1(), b'bcd')
+                f.flush()
+                self.assertEqual(raw.getvalue(), b'1bcdef')
+        with self.BytesIO(b'abcdef') as raw:
+            with self.tp(raw, 3) as f:
+                f.write(b"1")
+                # XXX: read(100) returns different numbers of bytes
+                # in Python and C implementations.
+                self.assertEqual(f.read1(100)[:3], b'bcd')
+                f.flush()
+                self.assertEqual(raw.getvalue(), b'1bcdef')
+
+    def test_interleaved_readline_write(self):
+        with self.BytesIO(b'ab\ncdef\ng\n') as raw:
+            with self.tp(raw) as f:
+                f.write(b'1')
+                self.assertEqual(f.readline(), b'b\n')
+                f.write(b'2')
+                self.assertEqual(f.readline(), b'def\n')
+                f.write(b'3')
+                self.assertEqual(f.readline(), b'\n')
+                f.flush()
+                self.assertEqual(raw.getvalue(), b'1b\n2def\n3\n')
+
+    # You can't construct a BufferedRandom over a non-seekable stream.
+    test_unseekable = None
+
+    # writable() returns True, so there's no point to test it over
+    # a writable stream.
+    test_truncate_on_read_only = None
+
+
+class CBufferedRandomTest(BufferedRandomTest, SizeofTest, CTestCase):
+    tp = io.BufferedRandom
+
+    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
+    def test_garbage_collection(self):
+        CBufferedReaderTest.test_garbage_collection(self)
+        CBufferedWriterTest.test_garbage_collection(self)
+
+    def test_args_error(self):
+        # Issue #17275
+        with self.assertRaisesRegex(TypeError, "BufferedRandom"):
+            self.tp(self.BytesIO(), 1024, 1024, 1024)
+
+
+class PyBufferedRandomTest(BufferedRandomTest, PyTestCase):
+    tp = pyio.BufferedRandom
+
+
+# Simple test to ensure that optimizations in the IO library deliver the
+# expected results.  For best testing, run this under a debug-build Python too
+# (to exercise asserts in the C code).
+
+lengths = list(range(1, 257)) + [512, 1000, 1024, 2048, 4096, 8192, 10000,
+                                 16384, 32768, 65536, 1000000]
+
+class BufferSizeTest:
+    def try_one(self, s):
+        # Write s + "\n" + s to file, then open it and ensure that successive
+        # .readline()s deliver what we wrote.
+
+        # Ensure we can open TESTFN for writing.
+        os_helper.unlink(os_helper.TESTFN)
+
+        # Since C doesn't guarantee we can write/read arbitrary bytes in text
+        # files, use binary mode.
+        f = self.open(os_helper.TESTFN, "wb")
+        try:
+            # write once with \n and once without
+            f.write(s)
+            f.write(b"\n")
+            f.write(s)
+            f.close()
+            f = self.open(os_helper.TESTFN, "rb")
+            line = f.readline()
+            self.assertEqual(line, s + b"\n")
+            line = f.readline()
+            self.assertEqual(line, s)
+            line = f.readline()
+            self.assertFalse(line) # Must be at EOF
+            f.close()
+        finally:
+            os_helper.unlink(os_helper.TESTFN)
+
+    def drive_one(self, pattern):
+        for length in lengths:
+            # Repeat string 'pattern' as often as needed to reach total length
+            # 'length'.  Then call try_one with that string, a string one larger
+            # than that, and a string one smaller than that.  Try this with all
+            # small sizes and various powers of 2, so we exercise all likely
+            # stdio buffer sizes, and "off by one" errors on both sides.
+            q, r = divmod(length, len(pattern))
+            teststring = pattern * q + pattern[:r]
+            self.assertEqual(len(teststring), length)
+            self.try_one(teststring)
+            self.try_one(teststring + b"x")
+            self.try_one(teststring[:-1])
+
+    def test_primepat(self):
+        # A pattern with prime length, to avoid simple relationships with
+        # stdio buffer sizes.
+        self.drive_one(b"1234567890\00\01\02\03\04\05\06")
+
+    def test_nullpat(self):
+        self.drive_one(b'\0' * 1000)
+
+
+class CBufferSizeTest(BufferSizeTest, unittest.TestCase):
+    open = io.open
+
+class PyBufferSizeTest(BufferSizeTest, unittest.TestCase):
+    open = staticmethod(pyio.open)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_file.py b/Lib/test/test_io/test_file.py
similarity index 100%
rename from Lib/test/test_file.py
rename to Lib/test/test_io/test_file.py
diff --git a/Lib/test/test_fileio.py b/Lib/test/test_io/test_fileio.py
similarity index 99%
rename from Lib/test/test_fileio.py
rename to Lib/test/test_io/test_fileio.py
index 4f195cf045c..b65848f9d77 100644
--- a/Lib/test/test_fileio.py
+++ b/Lib/test/test_io/test_fileio.py
@@ -568,8 +568,8 @@ def testModeStrings(self):
         # test that the mode attribute is correct for various mode strings
         # given as init args
         try:
-            for modes in [('w', 'wb'), ('wb', 'wb'), ('wb+', 'rb+'),
-                          ('w+b', 'rb+'), ('a', 'ab'), ('ab', 'ab'),
+            for modes in [('w', 'wb'), ('wb', 'wb'), ('wb+', 'wb+'),
+                          ('w+b', 'wb+'), ('a', 'ab'), ('ab', 'ab'),
                           ('ab+', 'ab+'), ('a+b', 'ab+'), ('r', 'rb'),
                           ('rb', 'rb'), ('rb+', 'rb+'), ('r+b', 'rb+')]:
                 # read modes are last so that TESTFN will exist first
diff --git a/Lib/test/test_io/test_general.py b/Lib/test/test_io/test_general.py
new file mode 100644
index 00000000000..6a6671186ba
--- /dev/null
+++ b/Lib/test/test_io/test_general.py
@@ -0,0 +1,1432 @@
+"""General tests for the io module.
+
+New tests should go in more specific modules; see test_io/__init__.py
+"""
+
+import abc
+import array
+import errno
+import os
+import pickle
+import sys
+import textwrap
+import threading
+import unittest
+import warnings
+import weakref
+from test import support
+from test.support.script_helper import (
+    assert_python_ok, assert_python_failure, run_python_until_end)
+from test.support import (
+    import_helper, is_apple, os_helper, threading_helper, warnings_helper,
+)
+from test.support.os_helper import FakePath
+from .utils import byteslike, CTestCase, PyTestCase
+
+import io  # C implementation of io
+import _pyio as pyio # Python implementation of io
+
+
+class IOTest:
+
+    def setUp(self):
+        os_helper.unlink(os_helper.TESTFN)
+
+    def tearDown(self):
+        os_helper.unlink(os_helper.TESTFN)
+
+    def write_ops(self, f):
+        self.assertEqual(f.write(b"blah."), 5)
+        f.truncate(0)
+        self.assertEqual(f.tell(), 5)
+        f.seek(0)
+
+        self.assertEqual(f.write(b"blah."), 5)
+        self.assertEqual(f.seek(0), 0)
+        self.assertEqual(f.write(b"Hello."), 6)
+        self.assertEqual(f.tell(), 6)
+        self.assertEqual(f.seek(-1, 1), 5)
+        self.assertEqual(f.tell(), 5)
+        buffer = bytearray(b" world\n\n\n")
+        self.assertEqual(f.write(buffer), 9)
+        buffer[:] = b"*" * 9  # Overwrite our copy of the data
+        self.assertEqual(f.seek(0), 0)
+        self.assertEqual(f.write(b"h"), 1)
+        self.assertEqual(f.seek(-1, 2), 13)
+        self.assertEqual(f.tell(), 13)
+
+        self.assertEqual(f.truncate(12), 12)
+        self.assertEqual(f.tell(), 13)
+        self.assertRaises(TypeError, f.seek, 0.0)
+
+    def read_ops(self, f, buffered=False):
+        data = f.read(5)
+        self.assertEqual(data, b"hello")
+        data = byteslike(data)
+        self.assertEqual(f.readinto(data), 5)
+        self.assertEqual(bytes(data), b" worl")
+        data = bytearray(5)
+        self.assertEqual(f.readinto(data), 2)
+        self.assertEqual(len(data), 5)
+        self.assertEqual(data[:2], b"d\n")
+        self.assertEqual(f.seek(0), 0)
+        self.assertEqual(f.read(20), b"hello world\n")
+        self.assertEqual(f.read(1), b"")
+        self.assertEqual(f.readinto(byteslike(b"x")), 0)
+        self.assertEqual(f.seek(-6, 2), 6)
+        self.assertEqual(f.read(5), b"world")
+        self.assertEqual(f.read(0), b"")
+        self.assertEqual(f.readinto(byteslike()), 0)
+        self.assertEqual(f.seek(-6, 1), 5)
+        self.assertEqual(f.read(5), b" worl")
+        self.assertEqual(f.tell(), 10)
+        self.assertRaises(TypeError, f.seek, 0.0)
+        if buffered:
+            f.seek(0)
+            self.assertEqual(f.read(), b"hello world\n")
+            f.seek(6)
+            self.assertEqual(f.read(), b"world\n")
+            self.assertEqual(f.read(), b"")
+            f.seek(0)
+            data = byteslike(5)
+            self.assertEqual(f.readinto1(data), 5)
+            self.assertEqual(bytes(data), b"hello")
+
+    LARGE = 2**31
+
+    def large_file_ops(self, f):
+        assert f.readable()
+        assert f.writable()
+        try:
+            self.assertEqual(f.seek(self.LARGE), self.LARGE)
+        except (OverflowError, ValueError):
+            self.skipTest("no largefile support")
+        self.assertEqual(f.tell(), self.LARGE)
+        self.assertEqual(f.write(b"xxx"), 3)
+        self.assertEqual(f.tell(), self.LARGE + 3)
+        self.assertEqual(f.seek(-1, 1), self.LARGE + 2)
+        self.assertEqual(f.truncate(), self.LARGE + 2)
+        self.assertEqual(f.tell(), self.LARGE + 2)
+        self.assertEqual(f.seek(0, 2), self.LARGE + 2)
+        self.assertEqual(f.truncate(self.LARGE + 1), self.LARGE + 1)
+        self.assertEqual(f.tell(), self.LARGE + 2)
+        self.assertEqual(f.seek(0, 2), self.LARGE + 1)
+        self.assertEqual(f.seek(-1, 2), self.LARGE)
+        self.assertEqual(f.read(2), b"x")
+
+    def test_invalid_operations(self):
+        # Try writing on a file opened in read mode and vice-versa.
+        exc = self.UnsupportedOperation
+        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as fp:
+            self.assertRaises(exc, fp.read)
+            self.assertRaises(exc, fp.readline)
+        with self.open(os_helper.TESTFN, "wb") as fp:
+            self.assertRaises(exc, fp.read)
+            self.assertRaises(exc, fp.readline)
+        with self.open(os_helper.TESTFN, "wb", buffering=0) as fp:
+            self.assertRaises(exc, fp.read)
+            self.assertRaises(exc, fp.readall)
+            self.assertRaises(exc, fp.readline)
+        with self.open(os_helper.TESTFN, "rb", buffering=0) as fp:
+            self.assertRaises(exc, fp.write, b"blah")
+            self.assertRaises(exc, fp.writelines, [b"blah\n"])
+        with self.open(os_helper.TESTFN, "rb") as fp:
+            self.assertRaises(exc, fp.write, b"blah")
+            self.assertRaises(exc, fp.writelines, [b"blah\n"])
+        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as fp:
+            self.assertRaises(exc, fp.write, "blah")
+            self.assertRaises(exc, fp.writelines, ["blah\n"])
+            # Non-zero seeking from current or end pos
+            self.assertRaises(exc, fp.seek, 1, self.SEEK_CUR)
+            self.assertRaises(exc, fp.seek, -1, self.SEEK_END)
+
+    @support.cpython_only
+    def test_startup_optimization(self):
+        # gh-132952: Test that `io` is not imported at startup and that the
+        # __module__ of UnsupportedOperation is set to "io".
+        assert_python_ok("-S", "-c", textwrap.dedent(
+            """
+            import sys
+            assert "io" not in sys.modules
+            try:
+                sys.stdin.truncate()
+            except Exception as e:
+                typ = type(e)
+                assert typ.__module__ == "io", (typ, typ.__module__)
+                assert typ.__name__ == "UnsupportedOperation", (typ, typ.__name__)
+            else:
+                raise AssertionError("Expected UnsupportedOperation")
+            """
+        ))
+
+    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    def test_optional_abilities(self):
+        # Test for OSError when optional APIs are not supported
+        # The purpose of this test is to try fileno(), reading, writing and
+        # seeking operations with various objects that indicate they do not
+        # support these operations.
+
+        def pipe_reader():
+            [r, w] = os.pipe()
+            os.close(w)  # So that read() is harmless
+            return self.FileIO(r, "r")
+
+        def pipe_writer():
+            [r, w] = os.pipe()
+            self.addCleanup(os.close, r)
+            # Guarantee that we can write into the pipe without blocking
+            thread = threading.Thread(target=os.read, args=(r, 100))
+            thread.start()
+            self.addCleanup(thread.join)
+            return self.FileIO(w, "w")
+
+        def buffered_reader():
+            return self.BufferedReader(self.MockUnseekableIO())
+
+        def buffered_writer():
+            return self.BufferedWriter(self.MockUnseekableIO())
+
+        def buffered_random():
+            return self.BufferedRandom(self.BytesIO())
+
+        def buffered_rw_pair():
+            return self.BufferedRWPair(self.MockUnseekableIO(),
+                self.MockUnseekableIO())
+
+        def text_reader():
+            class UnseekableReader(self.MockUnseekableIO):
+                writable = self.BufferedIOBase.writable
+                write = self.BufferedIOBase.write
+            return self.TextIOWrapper(UnseekableReader(), "ascii")
+
+        def text_writer():
+            class UnseekableWriter(self.MockUnseekableIO):
+                readable = self.BufferedIOBase.readable
+                read = self.BufferedIOBase.read
+            return self.TextIOWrapper(UnseekableWriter(), "ascii")
+
+        tests = (
+            (pipe_reader, "fr"), (pipe_writer, "fw"),
+            (buffered_reader, "r"), (buffered_writer, "w"),
+            (buffered_random, "rws"), (buffered_rw_pair, "rw"),
+            (text_reader, "r"), (text_writer, "w"),
+            (self.BytesIO, "rws"), (self.StringIO, "rws"),
+        )
+
+        def do_test(test, obj, abilities):
+            readable = "r" in abilities
+            self.assertEqual(obj.readable(), readable)
+            writable = "w" in abilities
+            self.assertEqual(obj.writable(), writable)
+
+            if isinstance(obj, self.TextIOBase):
+                data = "3"
+            elif isinstance(obj, (self.BufferedIOBase, self.RawIOBase)):
+                data = b"3"
+            else:
+                self.fail("Unknown base class")
+
+            if "f" in abilities:
+                obj.fileno()
+            else:
+                self.assertRaises(OSError, obj.fileno)
+
+            if readable:
+                obj.read(1)
+                obj.read()
+            else:
+                self.assertRaises(OSError, obj.read, 1)
+                self.assertRaises(OSError, obj.read)
+
+            if writable:
+                obj.write(data)
+            else:
+                self.assertRaises(OSError, obj.write, data)
+
+            if sys.platform.startswith("win") and test in (
+                    pipe_reader, pipe_writer):
+                # Pipes seem to appear as seekable on Windows
+                return
+            seekable = "s" in abilities
+            self.assertEqual(obj.seekable(), seekable)
+
+            if seekable:
+                obj.tell()
+                obj.seek(0)
+            else:
+                self.assertRaises(OSError, obj.tell)
+                self.assertRaises(OSError, obj.seek, 0)
+
+            if writable and seekable:
+                obj.truncate()
+                obj.truncate(0)
+            else:
+                self.assertRaises(OSError, obj.truncate)
+                self.assertRaises(OSError, obj.truncate, 0)
+
+        for [test, abilities] in tests:
+            with self.subTest(test):
+                if test == pipe_writer and not threading_helper.can_start_thread:
+                    self.skipTest("Need threads")
+                with test() as obj:
+                    do_test(test, obj, abilities)
+
+
+    def test_open_handles_NUL_chars(self):
+        fn_with_NUL = 'foo\0bar'
+        self.assertRaises(ValueError, self.open, fn_with_NUL, 'w', encoding="utf-8")
+
+        bytes_fn = bytes(fn_with_NUL, 'ascii')
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
+            self.assertRaises(ValueError, self.open, bytes_fn, 'w', encoding="utf-8")
+
+    def test_raw_file_io(self):
+        with self.open(os_helper.TESTFN, "wb", buffering=0) as f:
+            self.assertEqual(f.readable(), False)
+            self.assertEqual(f.writable(), True)
+            self.assertEqual(f.seekable(), True)
+            self.write_ops(f)
+        with self.open(os_helper.TESTFN, "rb", buffering=0) as f:
+            self.assertEqual(f.readable(), True)
+            self.assertEqual(f.writable(), False)
+            self.assertEqual(f.seekable(), True)
+            self.read_ops(f)
+
+    def test_buffered_file_io(self):
+        with self.open(os_helper.TESTFN, "wb") as f:
+            self.assertEqual(f.readable(), False)
+            self.assertEqual(f.writable(), True)
+            self.assertEqual(f.seekable(), True)
+            self.write_ops(f)
+        with self.open(os_helper.TESTFN, "rb") as f:
+            self.assertEqual(f.readable(), True)
+            self.assertEqual(f.writable(), False)
+            self.assertEqual(f.seekable(), True)
+            self.read_ops(f, True)
+
+    def test_readline(self):
+        with self.open(os_helper.TESTFN, "wb") as f:
+            f.write(b"abc\ndef\nxyzzy\nfoo\x00bar\nanother line")
+        with self.open(os_helper.TESTFN, "rb") as f:
+            self.assertEqual(f.readline(), b"abc\n")
+            self.assertEqual(f.readline(10), b"def\n")
+            self.assertEqual(f.readline(2), b"xy")
+            self.assertEqual(f.readline(4), b"zzy\n")
+            self.assertEqual(f.readline(), b"foo\x00bar\n")
+            self.assertEqual(f.readline(None), b"another line")
+            self.assertRaises(TypeError, f.readline, 5.3)
+        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
+            self.assertRaises(TypeError, f.readline, 5.3)
+
+    def test_readline_nonsizeable(self):
+        # Issue #30061
+        # Crash when readline() returns an object without __len__
+        class R(self.IOBase):
+            def readline(self):
+                return None
+        self.assertRaises((TypeError, StopIteration), next, R())
+
+    def test_next_nonsizeable(self):
+        # Issue #30061
+        # Crash when __next__() returns an object without __len__
+        class R(self.IOBase):
+            def __next__(self):
+                return None
+        self.assertRaises(TypeError, R().readlines, 1)
+
+    def test_raw_bytes_io(self):
+        f = self.BytesIO()
+        self.write_ops(f)
+        data = f.getvalue()
+        self.assertEqual(data, b"hello world\n")
+        f = self.BytesIO(data)
+        self.read_ops(f, True)
+
+    def test_large_file_ops(self):
+        # On Windows and Apple platforms this test consumes large resources; It
+        # takes a long time to build the >2 GiB file and takes >2 GiB of disk
+        # space therefore the resource must be enabled to run this test.
+        if sys.platform[:3] == 'win' or is_apple:
+            support.requires(
+                'largefile',
+                'test requires %s bytes and a long time to run' % self.LARGE)
+        with self.open(os_helper.TESTFN, "w+b", 0) as f:
+            self.large_file_ops(f)
+        with self.open(os_helper.TESTFN, "w+b") as f:
+            self.large_file_ops(f)
+
+    def test_with_open(self):
+        for bufsize in (0, 100):
+            with self.open(os_helper.TESTFN, "wb", bufsize) as f:
+                f.write(b"xxx")
+            self.assertEqual(f.closed, True)
+            try:
+                with self.open(os_helper.TESTFN, "wb", bufsize) as f:
+                    1/0
+            except ZeroDivisionError:
+                self.assertEqual(f.closed, True)
+            else:
+                self.fail("1/0 didn't raise an exception")
+
+    # issue 5008
+    def test_append_mode_tell(self):
+        with self.open(os_helper.TESTFN, "wb") as f:
+            f.write(b"xxx")
+        with self.open(os_helper.TESTFN, "ab", buffering=0) as f:
+            self.assertEqual(f.tell(), 3)
+        with self.open(os_helper.TESTFN, "ab") as f:
+            self.assertEqual(f.tell(), 3)
+        with self.open(os_helper.TESTFN, "a", encoding="utf-8") as f:
+            self.assertGreater(f.tell(), 0)
+
+    def test_destructor(self):
+        record = []
+        class MyFileIO(self.FileIO):
+            def __del__(self):
+                record.append(1)
+                try:
+                    f = super().__del__
+                except AttributeError:
+                    pass
+                else:
+                    f()
+            def close(self):
+                record.append(2)
+                super().close()
+            def flush(self):
+                record.append(3)
+                super().flush()
+        with warnings_helper.check_warnings(('', ResourceWarning)):
+            f = MyFileIO(os_helper.TESTFN, "wb")
+            f.write(b"xxx")
+            del f
+            support.gc_collect()
+            self.assertEqual(record, [1, 2, 3])
+            with self.open(os_helper.TESTFN, "rb") as f:
+                self.assertEqual(f.read(), b"xxx")
+
+    def _check_base_destructor(self, base):
+        record = []
+        class MyIO(base):
+            def __init__(self):
+                # This exercises the availability of attributes on object
+                # destruction.
+                # (in the C version, close() is called by the tp_dealloc
+                # function, not by __del__)
+                self.on_del = 1
+                self.on_close = 2
+                self.on_flush = 3
+            def __del__(self):
+                record.append(self.on_del)
+                try:
+                    f = super().__del__
+                except AttributeError:
+                    pass
+                else:
+                    f()
+            def close(self):
+                record.append(self.on_close)
+                super().close()
+            def flush(self):
+                record.append(self.on_flush)
+                super().flush()
+        f = MyIO()
+        del f
+        support.gc_collect()
+        self.assertEqual(record, [1, 2, 3])
+
+    def test_IOBase_destructor(self):
+        self._check_base_destructor(self.IOBase)
+
+    def test_RawIOBase_destructor(self):
+        self._check_base_destructor(self.RawIOBase)
+
+    def test_BufferedIOBase_destructor(self):
+        self._check_base_destructor(self.BufferedIOBase)
+
+    def test_TextIOBase_destructor(self):
+        self._check_base_destructor(self.TextIOBase)
+
+    def test_close_flushes(self):
+        with self.open(os_helper.TESTFN, "wb") as f:
+            f.write(b"xxx")
+        with self.open(os_helper.TESTFN, "rb") as f:
+            self.assertEqual(f.read(), b"xxx")
+
+    def test_array_writes(self):
+        a = array.array('i', range(10))
+        n = len(a.tobytes())
+        def check(f):
+            with f:
+                self.assertEqual(f.write(a), n)
+                f.writelines((a,))
+        check(self.BytesIO())
+        check(self.FileIO(os_helper.TESTFN, "w"))
+        check(self.BufferedWriter(self.MockRawIO()))
+        check(self.BufferedRandom(self.MockRawIO()))
+        check(self.BufferedRWPair(self.MockRawIO(), self.MockRawIO()))
+
+    def test_closefd(self):
+        self.assertRaises(ValueError, self.open, os_helper.TESTFN, 'w',
+                          encoding="utf-8", closefd=False)
+
+    def test_read_closed(self):
+        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
+            f.write("egg\n")
+        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
+            file = self.open(f.fileno(), "r", encoding="utf-8", closefd=False)
+            self.assertEqual(file.read(), "egg\n")
+            file.seek(0)
+            file.close()
+            self.assertRaises(ValueError, file.read)
+        with self.open(os_helper.TESTFN, "rb") as f:
+            file = self.open(f.fileno(), "rb", closefd=False)
+            self.assertEqual(file.read()[:3], b"egg")
+            file.close()
+            self.assertRaises(ValueError, file.readinto, bytearray(1))
+
+    def test_no_closefd_with_filename(self):
+        # can't use closefd in combination with a file name
+        self.assertRaises(ValueError, self.open, os_helper.TESTFN, "r",
+                          encoding="utf-8", closefd=False)
+
+    def test_closefd_attr(self):
+        with self.open(os_helper.TESTFN, "wb") as f:
+            f.write(b"egg\n")
+        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
+            self.assertEqual(f.buffer.raw.closefd, True)
+            file = self.open(f.fileno(), "r", encoding="utf-8", closefd=False)
+            self.assertEqual(file.buffer.raw.closefd, False)
+
+    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
+    def test_garbage_collection(self):
+        # FileIO objects are collected, and collecting them flushes
+        # all data to disk.
+        #
+        # Note that using warnings_helper.check_warnings() will keep the
+        # file alive due to the `source` argument to warn().  So, use
+        # catch_warnings() instead.
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", ResourceWarning)
+            f = self.FileIO(os_helper.TESTFN, "wb")
+            f.write(b"abcxxx")
+            f.f = f
+            wr = weakref.ref(f)
+            del f
+            support.gc_collect()
+        self.assertIsNone(wr(), wr)
+        with self.open(os_helper.TESTFN, "rb") as f:
+            self.assertEqual(f.read(), b"abcxxx")
+
+    def test_unbounded_file(self):
+        # Issue #1174606: reading from an unbounded stream such as /dev/zero.
+        zero = "/dev/zero"
+        if not os.path.exists(zero):
+            self.skipTest("{0} does not exist".format(zero))
+        if sys.maxsize > 0x7FFFFFFF:
+            self.skipTest("test can only run in a 32-bit address space")
+        if support.real_max_memuse < support._2G:
+            self.skipTest("test requires at least 2 GiB of memory")
+        with self.open(zero, "rb", buffering=0) as f:
+            self.assertRaises(OverflowError, f.read)
+        with self.open(zero, "rb") as f:
+            self.assertRaises(OverflowError, f.read)
+        with self.open(zero, "r") as f:
+            self.assertRaises(OverflowError, f.read)
+
+    def check_flush_error_on_close(self, *args, **kwargs):
+        # Test that the file is closed despite failed flush
+        # and that flush() is called before file closed.
+        f = self.open(*args, **kwargs)
+        closed = []
+        def bad_flush():
+            closed[:] = [f.closed]
+            raise OSError()
+        f.flush = bad_flush
+        self.assertRaises(OSError, f.close) # exception not swallowed
+        self.assertTrue(f.closed)
+        self.assertTrue(closed)      # flush() called
+        self.assertFalse(closed[0])  # flush() called before file closed
+        f.flush = lambda: None  # break reference loop
+
+    def test_flush_error_on_close(self):
+        # raw file
+        # Issue #5700: io.FileIO calls flush() after file closed
+        self.check_flush_error_on_close(os_helper.TESTFN, 'wb', buffering=0)
+        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
+        self.check_flush_error_on_close(fd, 'wb', buffering=0)
+        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
+        self.check_flush_error_on_close(fd, 'wb', buffering=0, closefd=False)
+        os.close(fd)
+        # buffered io
+        self.check_flush_error_on_close(os_helper.TESTFN, 'wb')
+        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
+        self.check_flush_error_on_close(fd, 'wb')
+        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
+        self.check_flush_error_on_close(fd, 'wb', closefd=False)
+        os.close(fd)
+        # text io
+        self.check_flush_error_on_close(os_helper.TESTFN, 'w', encoding="utf-8")
+        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
+        self.check_flush_error_on_close(fd, 'w', encoding="utf-8")
+        fd = os.open(os_helper.TESTFN, os.O_WRONLY|os.O_CREAT)
+        self.check_flush_error_on_close(fd, 'w', encoding="utf-8", closefd=False)
+        os.close(fd)
+
+    def test_multi_close(self):
+        f = self.open(os_helper.TESTFN, "wb", buffering=0)
+        f.close()
+        f.close()
+        f.close()
+        self.assertRaises(ValueError, f.flush)
+
+    def test_RawIOBase_read(self):
+        # Exercise the default limited RawIOBase.read(n) implementation (which
+        # calls readinto() internally).
+        rawio = self.MockRawIOWithoutRead((b"abc", b"d", None, b"efg", None))
+        self.assertEqual(rawio.read(2), b"ab")
+        self.assertEqual(rawio.read(2), b"c")
+        self.assertEqual(rawio.read(2), b"d")
+        self.assertEqual(rawio.read(2), None)
+        self.assertEqual(rawio.read(2), b"ef")
+        self.assertEqual(rawio.read(2), b"g")
+        self.assertEqual(rawio.read(2), None)
+        self.assertEqual(rawio.read(2), b"")
+
+    def test_RawIOBase_read_bounds_checking(self):
+        # Make sure a `.readinto` call which returns a value outside
+        # (0, len(buffer)) raises.
+        class Misbehaved(self.io.RawIOBase):
+            def __init__(self, readinto_return) -> None:
+                self._readinto_return = readinto_return
+            def readinto(self, b):
+                return self._readinto_return
+
+        with self.assertRaises(ValueError) as cm:
+            Misbehaved(2).read(1)
+        self.assertEqual(str(cm.exception), "readinto returned 2 outside buffer size 1")
+        for bad_size in (2147483647, sys.maxsize, -1, -1000):
+            with self.assertRaises(ValueError):
+                Misbehaved(bad_size).read()
+
+    def test_RawIOBase_read_gh60107(self):
+        # gh-60107: Ensure a "Raw I/O" which keeps a reference to the
+        # mutable memory doesn't allow making a mutable bytes.
+        class RawIOKeepsReference(self.MockRawIOWithoutRead):
+            def __init__(self, *args, **kwargs):
+                self.buf = None
+                super().__init__(*args, **kwargs)
+
+            def readinto(self, buf):
+                # buf is the bytearray so keeping a reference to it doesn't keep
+                # the memory alive; a memoryview does.
+                self.buf = memoryview(buf)
+                buf[0:4] = self._read_stack.pop()
+                return 3
+
+        with self.assertRaises(BufferError):
+            rawio = RawIOKeepsReference([b"1234"])
+            rawio.read(4)
+
+    def test_types_have_dict(self):
+        test = (
+            self.IOBase(),
+            self.RawIOBase(),
+            self.TextIOBase(),
+            self.StringIO(),
+            self.BytesIO()
+        )
+        for obj in test:
+            self.assertHasAttr(obj, "__dict__")
+
+    def test_opener(self):
+        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
+            f.write("egg\n")
+        fd = os.open(os_helper.TESTFN, os.O_RDONLY)
+        def opener(path, flags):
+            return fd
+        with self.open("non-existent", "r", encoding="utf-8", opener=opener) as f:
+            self.assertEqual(f.read(), "egg\n")
+
+    def test_bad_opener_negative_1(self):
+        # Issue #27066.
+        def badopener(fname, flags):
+            return -1
+        with self.assertRaises(ValueError) as cm:
+            self.open('non-existent', 'r', opener=badopener)
+        self.assertEqual(str(cm.exception), 'opener returned -1')
+
+    def test_bad_opener_other_negative(self):
+        # Issue #27066.
+        def badopener(fname, flags):
+            return -2
+        with self.assertRaises(ValueError) as cm:
+            self.open('non-existent', 'r', opener=badopener)
+        self.assertEqual(str(cm.exception), 'opener returned -2')
+
+    def test_opener_invalid_fd(self):
+        # Check that OSError is raised with error code EBADF if the
+        # opener returns an invalid file descriptor (see gh-82212).
+        fd = os_helper.make_bad_fd()
+        with self.assertRaises(OSError) as cm:
+            self.open('foo', opener=lambda name, flags: fd)
+        self.assertEqual(cm.exception.errno, errno.EBADF)
+
+    def test_fileio_closefd(self):
+        # Issue #4841
+        with self.open(__file__, 'rb') as f1, \
+             self.open(__file__, 'rb') as f2:
+            fileio = self.FileIO(f1.fileno(), closefd=False)
+            # .__init__() must not close f1
+            fileio.__init__(f2.fileno(), closefd=False)
+            f1.readline()
+            # .close() must not close f2
+            fileio.close()
+            f2.readline()
+
+    def test_nonbuffered_textio(self):
+        with warnings_helper.check_no_resource_warning(self):
+            with self.assertRaises(ValueError):
+                self.open(os_helper.TESTFN, 'w', encoding="utf-8", buffering=0)
+
+    def test_invalid_newline(self):
+        with warnings_helper.check_no_resource_warning(self):
+            with self.assertRaises(ValueError):
+                self.open(os_helper.TESTFN, 'w', encoding="utf-8", newline='invalid')
+
+    def test_buffered_readinto_mixin(self):
+        # Test the implementation provided by BufferedIOBase
+        class Stream(self.BufferedIOBase):
+            def read(self, size):
+                return b"12345"
+            read1 = read
+        stream = Stream()
+        for method in ("readinto", "readinto1"):
+            with self.subTest(method):
+                buffer = byteslike(5)
+                self.assertEqual(getattr(stream, method)(buffer), 5)
+                self.assertEqual(bytes(buffer), b"12345")
+
+    def test_fspath_support(self):
+        def check_path_succeeds(path):
+            with self.open(path, "w", encoding="utf-8") as f:
+                f.write("egg\n")
+
+            with self.open(path, "r", encoding="utf-8") as f:
+                self.assertEqual(f.read(), "egg\n")
+
+        check_path_succeeds(FakePath(os_helper.TESTFN))
+        check_path_succeeds(FakePath(os.fsencode(os_helper.TESTFN)))
+
+        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
+            bad_path = FakePath(f.fileno())
+            with self.assertRaises(TypeError):
+                self.open(bad_path, 'w', encoding="utf-8")
+
+        bad_path = FakePath(None)
+        with self.assertRaises(TypeError):
+            self.open(bad_path, 'w', encoding="utf-8")
+
+        bad_path = FakePath(FloatingPointError)
+        with self.assertRaises(FloatingPointError):
+            self.open(bad_path, 'w', encoding="utf-8")
+
+        # ensure that refcounting is correct with some error conditions
+        with self.assertRaisesRegex(ValueError, 'read/write/append mode'):
+            self.open(FakePath(os_helper.TESTFN), 'rwxa', encoding="utf-8")
+
+    def test_RawIOBase_readall(self):
+        # Exercise the default unlimited RawIOBase.read() and readall()
+        # implementations.
+        rawio = self.MockRawIOWithoutRead((b"abc", b"d", b"efg"))
+        self.assertEqual(rawio.read(), b"abcdefg")
+        rawio = self.MockRawIOWithoutRead((b"abc", b"d", b"efg"))
+        self.assertEqual(rawio.readall(), b"abcdefg")
+
+    def test_BufferedIOBase_readinto(self):
+        # Exercise the default BufferedIOBase.readinto() and readinto1()
+        # implementations (which call read() or read1() internally).
+        class Reader(self.BufferedIOBase):
+            def __init__(self, avail):
+                self.avail = avail
+            def read(self, size):
+                result = self.avail[:size]
+                self.avail = self.avail[size:]
+                return result
+            def read1(self, size):
+                """Returns no more than 5 bytes at once"""
+                return self.read(min(size, 5))
+        tests = (
+            # (test method, total data available, read buffer size, expected
+            #     read size)
+            ("readinto", 10, 5, 5),
+            ("readinto", 10, 6, 6),  # More than read1() can return
+            ("readinto", 5, 6, 5),  # Buffer larger than total available
+            ("readinto", 6, 7, 6),
+            ("readinto", 10, 0, 0),  # Empty buffer
+            ("readinto1", 10, 5, 5),  # Result limited to single read1() call
+            ("readinto1", 10, 6, 5),  # Buffer larger than read1() can return
+            ("readinto1", 5, 6, 5),  # Buffer larger than total available
+            ("readinto1", 6, 7, 5),
+            ("readinto1", 10, 0, 0),  # Empty buffer
+        )
+        UNUSED_BYTE = 0x81
+        for test in tests:
+            with self.subTest(test):
+                method, avail, request, result = test
+                reader = Reader(bytes(range(avail)))
+                buffer = bytearray((UNUSED_BYTE,) * request)
+                method = getattr(reader, method)
+                self.assertEqual(method(buffer), result)
+                self.assertEqual(len(buffer), request)
+                self.assertSequenceEqual(buffer[:result], range(result))
+                unused = (UNUSED_BYTE,) * (request - result)
+                self.assertSequenceEqual(buffer[result:], unused)
+                self.assertEqual(len(reader.avail), avail - result)
+
+    def test_close_assert(self):
+        class R(self.IOBase):
+            def __setattr__(self, name, value):
+                pass
+            def flush(self):
+                raise OSError()
+        f = R()
+        # This would cause an assertion failure.
+        self.assertRaises(OSError, f.close)
+
+        # Silence destructor error
+        R.flush = lambda self: None
+
+    @threading_helper.requires_working_threading()
+    def test_write_readline_races(self):
+        # gh-134908: Concurrent iteration over a file caused races
+        thread_count = 2
+        write_count = 100
+        read_count = 100
+
+        def writer(file, barrier):
+            barrier.wait()
+            for _ in range(write_count):
+                file.write("x")
+
+        def reader(file, barrier):
+            barrier.wait()
+            for _ in range(read_count):
+                for line in file:
+                    self.assertEqual(line, "")
+
+        with self.open(os_helper.TESTFN, "w+") as f:
+            barrier = threading.Barrier(thread_count + 1)
+            reader = threading.Thread(target=reader, args=(f, barrier))
+            writers = [threading.Thread(target=writer, args=(f, barrier))
+                       for _ in range(thread_count)]
+            with threading_helper.catch_threading_exception() as cm:
+                with threading_helper.start_threads(writers + [reader]):
+                    pass
+                self.assertIsNone(cm.exc_type)
+
+        self.assertEqual(os.stat(os_helper.TESTFN).st_size,
+                         write_count * thread_count)
+
+
+class CIOTest(IOTest, CTestCase):
+
+    def test_IOBase_finalize(self):
+        # Issue #12149: segmentation fault on _PyIOBase_finalize when both a
+        # class which inherits IOBase and an object of this class are caught
+        # in a reference cycle and close() is already in the method cache.
+        class MyIO(self.IOBase):
+            def close(self):
+                pass
+
+        # create an instance to populate the method cache
+        MyIO()
+        obj = MyIO()
+        obj.obj = obj
+        wr = weakref.ref(obj)
+        del MyIO
+        del obj
+        support.gc_collect()
+        self.assertIsNone(wr(), wr)
+
+@support.cpython_only
+class TestIOCTypes(unittest.TestCase):
+    def setUp(self):
+        _io = import_helper.import_module("_io")
+        self.types = [
+            _io.BufferedRWPair,
+            _io.BufferedRandom,
+            _io.BufferedReader,
+            _io.BufferedWriter,
+            _io.BytesIO,
+            _io.FileIO,
+            _io.IncrementalNewlineDecoder,
+            _io.StringIO,
+            _io.TextIOWrapper,
+            _io._BufferedIOBase,
+            _io._BytesIOBuffer,
+            _io._IOBase,
+            _io._RawIOBase,
+            _io._TextIOBase,
+        ]
+        if sys.platform == "win32":
+            self.types.append(_io._WindowsConsoleIO)
+        self._io = _io
+
+    def test_immutable_types(self):
+        for tp in self.types:
+            with self.subTest(tp=tp):
+                with self.assertRaisesRegex(TypeError, "immutable"):
+                    tp.foo = "bar"
+
+    def test_class_hierarchy(self):
+        def check_subs(types, base):
+            for tp in types:
+                with self.subTest(tp=tp, base=base):
+                    self.assertIsSubclass(tp, base)
+
+        def recursive_check(d):
+            for k, v in d.items():
+                if isinstance(v, dict):
+                    recursive_check(v)
+                elif isinstance(v, set):
+                    check_subs(v, k)
+                else:
+                    self.fail("corrupt test dataset")
+
+        _io = self._io
+        hierarchy = {
+            _io._IOBase: {
+                _io._BufferedIOBase: {
+                    _io.BufferedRWPair,
+                    _io.BufferedRandom,
+                    _io.BufferedReader,
+                    _io.BufferedWriter,
+                    _io.BytesIO,
+                },
+                _io._RawIOBase: {
+                    _io.FileIO,
+                },
+                _io._TextIOBase: {
+                    _io.StringIO,
+                    _io.TextIOWrapper,
+                },
+            },
+        }
+        if sys.platform == "win32":
+            hierarchy[_io._IOBase][_io._RawIOBase].add(_io._WindowsConsoleIO)
+
+        recursive_check(hierarchy)
+
+    def test_subclassing(self):
+        _io = self._io
+        dataset = {k: True for k in self.types}
+        dataset[_io._BytesIOBuffer] = False
+
+        for tp, is_basetype in dataset.items():
+            with self.subTest(tp=tp, is_basetype=is_basetype):
+                name = f"{tp.__name__}_subclass"
+                bases = (tp,)
+                if is_basetype:
+                    _ = type(name, bases, {})
+                else:
+                    msg = "not an acceptable base type"
+                    with self.assertRaisesRegex(TypeError, msg):
+                        _ = type(name, bases, {})
+
+    def test_disallow_instantiation(self):
+        _io = self._io
+        support.check_disallow_instantiation(self, _io._BytesIOBuffer)
+
+    def test_stringio_setstate(self):
+        # gh-127182: Calling __setstate__() with invalid arguments must not crash
+        obj = self._io.StringIO()
+        with self.assertRaisesRegex(
+            TypeError,
+            'initial_value must be str or None, not int',
+        ):
+            obj.__setstate__((1, '', 0, {}))
+
+        obj.__setstate__((None, '', 0, {}))  # should not crash
+        self.assertEqual(obj.getvalue(), '')
+
+        obj.__setstate__(('', '', 0, {}))
+        self.assertEqual(obj.getvalue(), '')
+
+class PyIOTest(IOTest, PyTestCase):
+    pass
+
+
+@support.cpython_only
+class APIMismatchTest(unittest.TestCase):
+
+    def test_RawIOBase_io_in_pyio_match(self):
+        """Test that pyio RawIOBase class has all c RawIOBase methods"""
+        mismatch = support.detect_api_mismatch(pyio.RawIOBase, io.RawIOBase,
+                                               ignore=('__weakref__', '__static_attributes__'))
+        self.assertEqual(mismatch, set(), msg='Python RawIOBase does not have all C RawIOBase methods')
+
+    def test_RawIOBase_pyio_in_io_match(self):
+        """Test that c RawIOBase class has all pyio RawIOBase methods"""
+        mismatch = support.detect_api_mismatch(io.RawIOBase, pyio.RawIOBase)
+        self.assertEqual(mismatch, set(), msg='C RawIOBase does not have all Python RawIOBase methods')
+
+
+# XXX Tests for open()
+
+class MiscIOTest:
+
+    # for test__all__, actual values are set in subclasses
+    name_of_module = None
+    extra_exported = ()
+    not_exported = ()
+
+    def tearDown(self):
+        os_helper.unlink(os_helper.TESTFN)
+
+    def test___all__(self):
+        support.check__all__(self, self.io, self.name_of_module,
+                             extra=self.extra_exported,
+                             not_exported=self.not_exported)
+
+    def test_attributes(self):
+        f = self.open(os_helper.TESTFN, "wb", buffering=0)
+        self.assertEqual(f.mode, "wb")
+        f.close()
+
+        f = self.open(os_helper.TESTFN, "w+", encoding="utf-8")
+        self.assertEqual(f.mode,            "w+")
+        self.assertEqual(f.buffer.mode,     "wb+")
+        self.assertEqual(f.buffer.raw.mode, "wb+")
+
+        g = self.open(f.fileno(), "wb", closefd=False)
+        self.assertEqual(g.mode,     "wb")
+        self.assertEqual(g.raw.mode, "wb")
+        self.assertEqual(g.name,     f.fileno())
+        self.assertEqual(g.raw.name, f.fileno())
+        f.close()
+        g.close()
+
+    def test_removed_u_mode(self):
+        # bpo-37330: The "U" mode has been removed in Python 3.11
+        for mode in ("U", "rU", "r+U"):
+            with self.assertRaises(ValueError) as cm:
+                self.open(os_helper.TESTFN, mode)
+            self.assertIn('invalid mode', str(cm.exception))
+
+    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    def test_open_pipe_with_append(self):
+        # bpo-27805: Ignore ESPIPE from lseek() in open().
+        r, w = os.pipe()
+        self.addCleanup(os.close, r)
+        f = self.open(w, 'a', encoding="utf-8")
+        self.addCleanup(f.close)
+        # Check that the file is marked non-seekable. On Windows, however, lseek
+        # somehow succeeds on pipes.
+        if sys.platform != 'win32':
+            self.assertFalse(f.seekable())
+
+    def test_io_after_close(self):
+        for kwargs in [
+                {"mode": "w"},
+                {"mode": "wb"},
+                {"mode": "w", "buffering": 1},
+                {"mode": "w", "buffering": 2},
+                {"mode": "wb", "buffering": 0},
+                {"mode": "r"},
+                {"mode": "rb"},
+                {"mode": "r", "buffering": 1},
+                {"mode": "r", "buffering": 2},
+                {"mode": "rb", "buffering": 0},
+                {"mode": "w+"},
+                {"mode": "w+b"},
+                {"mode": "w+", "buffering": 1},
+                {"mode": "w+", "buffering": 2},
+                {"mode": "w+b", "buffering": 0},
+            ]:
+            if "b" not in kwargs["mode"]:
+                kwargs["encoding"] = "utf-8"
+            f = self.open(os_helper.TESTFN, **kwargs)
+            f.close()
+            self.assertRaises(ValueError, f.flush)
+            self.assertRaises(ValueError, f.fileno)
+            self.assertRaises(ValueError, f.isatty)
+            self.assertRaises(ValueError, f.__iter__)
+            if hasattr(f, "peek"):
+                self.assertRaises(ValueError, f.peek, 1)
+            self.assertRaises(ValueError, f.read)
+            if hasattr(f, "read1"):
+                self.assertRaises(ValueError, f.read1, 1024)
+                self.assertRaises(ValueError, f.read1)
+            if hasattr(f, "readall"):
+                self.assertRaises(ValueError, f.readall)
+            if hasattr(f, "readinto"):
+                self.assertRaises(ValueError, f.readinto, bytearray(1024))
+            if hasattr(f, "readinto1"):
+                self.assertRaises(ValueError, f.readinto1, bytearray(1024))
+            self.assertRaises(ValueError, f.readline)
+            self.assertRaises(ValueError, f.readlines)
+            self.assertRaises(ValueError, f.readlines, 1)
+            self.assertRaises(ValueError, f.seek, 0)
+            self.assertRaises(ValueError, f.tell)
+            self.assertRaises(ValueError, f.truncate)
+            self.assertRaises(ValueError, f.write,
+                              b"" if "b" in kwargs['mode'] else "")
+            self.assertRaises(ValueError, f.writelines, [])
+            self.assertRaises(ValueError, next, f)
+
+    def test_blockingioerror(self):
+        # Various BlockingIOError issues
+        class C(str):
+            pass
+        c = C("")
+        b = self.BlockingIOError(1, c)
+        c.b = b
+        b.c = c
+        wr = weakref.ref(c)
+        del c, b
+        support.gc_collect()
+        self.assertIsNone(wr(), wr)
+
+    def test_abcs(self):
+        # Test the visible base classes are ABCs.
+        self.assertIsInstance(self.IOBase, abc.ABCMeta)
+        self.assertIsInstance(self.RawIOBase, abc.ABCMeta)
+        self.assertIsInstance(self.BufferedIOBase, abc.ABCMeta)
+        self.assertIsInstance(self.TextIOBase, abc.ABCMeta)
+
+    def _check_abc_inheritance(self, abcmodule):
+        with self.open(os_helper.TESTFN, "wb", buffering=0) as f:
+            self.assertIsInstance(f, abcmodule.IOBase)
+            self.assertIsInstance(f, abcmodule.RawIOBase)
+            self.assertNotIsInstance(f, abcmodule.BufferedIOBase)
+            self.assertNotIsInstance(f, abcmodule.TextIOBase)
+        with self.open(os_helper.TESTFN, "wb") as f:
+            self.assertIsInstance(f, abcmodule.IOBase)
+            self.assertNotIsInstance(f, abcmodule.RawIOBase)
+            self.assertIsInstance(f, abcmodule.BufferedIOBase)
+            self.assertNotIsInstance(f, abcmodule.TextIOBase)
+        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
+            self.assertIsInstance(f, abcmodule.IOBase)
+            self.assertNotIsInstance(f, abcmodule.RawIOBase)
+            self.assertNotIsInstance(f, abcmodule.BufferedIOBase)
+            self.assertIsInstance(f, abcmodule.TextIOBase)
+
+    def test_abc_inheritance(self):
+        # Test implementations inherit from their respective ABCs
+        self._check_abc_inheritance(self)
+
+    def test_abc_inheritance_official(self):
+        # Test implementations inherit from the official ABCs of the
+        # baseline "io" module.
+        self._check_abc_inheritance(io)
+
+    def _check_warn_on_dealloc(self, *args, **kwargs):
+        f = self.open(*args, **kwargs)
+        r = repr(f)
+        with self.assertWarns(ResourceWarning) as cm:
+            f = None
+            support.gc_collect()
+        self.assertIn(r, str(cm.warning.args[0]))
+
+    def test_warn_on_dealloc(self):
+        self._check_warn_on_dealloc(os_helper.TESTFN, "wb", buffering=0)
+        self._check_warn_on_dealloc(os_helper.TESTFN, "wb")
+        self._check_warn_on_dealloc(os_helper.TESTFN, "w", encoding="utf-8")
+
+    def _check_warn_on_dealloc_fd(self, *args, **kwargs):
+        fds = []
+        def cleanup_fds():
+            for fd in fds:
+                try:
+                    os.close(fd)
+                except OSError as e:
+                    if e.errno != errno.EBADF:
+                        raise
+        self.addCleanup(cleanup_fds)
+        r, w = os.pipe()
+        fds += r, w
+        self._check_warn_on_dealloc(r, *args, **kwargs)
+        # When using closefd=False, there's no warning
+        r, w = os.pipe()
+        fds += r, w
+        with warnings_helper.check_no_resource_warning(self):
+            self.open(r, *args, closefd=False, **kwargs)
+
+    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    def test_warn_on_dealloc_fd(self):
+        self._check_warn_on_dealloc_fd("rb", buffering=0)
+        self._check_warn_on_dealloc_fd("rb")
+        self._check_warn_on_dealloc_fd("r", encoding="utf-8")
+
+
+    def test_pickling(self):
+        # Pickling file objects is forbidden
+        msg = "cannot pickle"
+        for kwargs in [
+                {"mode": "w"},
+                {"mode": "wb"},
+                {"mode": "wb", "buffering": 0},
+                {"mode": "r"},
+                {"mode": "rb"},
+                {"mode": "rb", "buffering": 0},
+                {"mode": "w+"},
+                {"mode": "w+b"},
+                {"mode": "w+b", "buffering": 0},
+            ]:
+            if "b" not in kwargs["mode"]:
+                kwargs["encoding"] = "utf-8"
+            for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
+                with self.subTest(protocol=protocol, kwargs=kwargs):
+                    with self.open(os_helper.TESTFN, **kwargs) as f:
+                        with self.assertRaisesRegex(TypeError, msg):
+                            pickle.dumps(f, protocol)
+
+    @unittest.skipIf(support.is_emscripten, "Emscripten corrupts memory when writing to nonblocking fd")
+    def test_nonblock_pipe_write_bigbuf(self):
+        self._test_nonblock_pipe_write(16*1024)
+
+    @unittest.skipIf(support.is_emscripten, "Emscripten corrupts memory when writing to nonblocking fd")
+    def test_nonblock_pipe_write_smallbuf(self):
+        self._test_nonblock_pipe_write(1024)
+
+    @unittest.skipUnless(hasattr(os, 'set_blocking'),
+                         'os.set_blocking() required for this test')
+    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    def _test_nonblock_pipe_write(self, bufsize):
+        sent = []
+        received = []
+        r, w = os.pipe()
+        os.set_blocking(r, False)
+        os.set_blocking(w, False)
+
+        # To exercise all code paths in the C implementation we need
+        # to play with buffer sizes.  For instance, if we choose a
+        # buffer size less than or equal to _PIPE_BUF (4096 on Linux)
+        # then we will never get a partial write of the buffer.
+        rf = self.open(r, mode='rb', closefd=True, buffering=bufsize)
+        wf = self.open(w, mode='wb', closefd=True, buffering=bufsize)
+
+        with rf, wf:
+            for N in 9999, 73, 7574:
+                try:
+                    i = 0
+                    while True:
+                        msg = bytes([i % 26 + 97]) * N
+                        sent.append(msg)
+                        wf.write(msg)
+                        i += 1
+
+                except self.BlockingIOError as e:
+                    self.assertEqual(e.args[0], errno.EAGAIN)
+                    self.assertEqual(e.args[2], e.characters_written)
+                    sent[-1] = sent[-1][:e.characters_written]
+                    received.append(rf.read())
+                    msg = b'BLOCKED'
+                    wf.write(msg)
+                    sent.append(msg)
+
+            while True:
+                try:
+                    wf.flush()
+                    break
+                except self.BlockingIOError as e:
+                    self.assertEqual(e.args[0], errno.EAGAIN)
+                    self.assertEqual(e.args[2], e.characters_written)
+                    self.assertEqual(e.characters_written, 0)
+                    received.append(rf.read())
+
+            received += iter(rf.read, None)
+
+        sent, received = b''.join(sent), b''.join(received)
+        self.assertEqual(sent, received)
+        self.assertTrue(wf.closed)
+        self.assertTrue(rf.closed)
+
+    def test_create_fail(self):
+        # 'x' mode fails if file is existing
+        with self.open(os_helper.TESTFN, 'w', encoding="utf-8"):
+            pass
+        self.assertRaises(FileExistsError, self.open, os_helper.TESTFN, 'x', encoding="utf-8")
+
+    def test_create_writes(self):
+        # 'x' mode opens for writing
+        with self.open(os_helper.TESTFN, 'xb') as f:
+            f.write(b"spam")
+        with self.open(os_helper.TESTFN, 'rb') as f:
+            self.assertEqual(b"spam", f.read())
+
+    def test_open_allargs(self):
+        # there used to be a buffer overflow in the parser for rawmode
+        self.assertRaises(ValueError, self.open, os_helper.TESTFN, 'rwax+', encoding="utf-8")
+
+    def test_check_encoding_errors(self):
+        # bpo-37388: open() and TextIOWrapper must check encoding and errors
+        # arguments in dev mode
+        mod = self.io.__name__
+        filename = __file__
+        invalid = 'Boom, Shaka Laka, Boom!'
+        code = textwrap.dedent(f'''
+            import sys
+            from {mod} import open, TextIOWrapper
+
+            try:
+                open({filename!r}, encoding={invalid!r})
+            except LookupError:
+                pass
+            else:
+                sys.exit(21)
+
+            try:
+                open({filename!r}, errors={invalid!r})
+            except LookupError:
+                pass
+            else:
+                sys.exit(22)
+
+            fp = open({filename!r}, "rb")
+            with fp:
+                try:
+                    TextIOWrapper(fp, encoding={invalid!r})
+                except LookupError:
+                    pass
+                else:
+                    sys.exit(23)
+
+                try:
+                    TextIOWrapper(fp, errors={invalid!r})
+                except LookupError:
+                    pass
+                else:
+                    sys.exit(24)
+
+            sys.exit(10)
+        ''')
+        proc = assert_python_failure('-X', 'dev', '-c', code)
+        self.assertEqual(proc.rc, 10, proc)
+
+    def test_check_encoding_warning(self):
+        # PEP 597: Raise warning when encoding is not specified
+        # and sys.flags.warn_default_encoding is set.
+        mod = self.io.__name__
+        filename = __file__
+        code = textwrap.dedent(f'''\
+            import sys
+            from {mod} import open, TextIOWrapper
+            import pathlib
+
+            with open({filename!r}) as f:           # line 5
+                pass
+
+            pathlib.Path({filename!r}).read_text()  # line 8
+        ''')
+        proc = assert_python_ok('-X', 'warn_default_encoding', '-c', code)
+        warnings = proc.err.splitlines()
+        self.assertEqual(len(warnings), 2)
+        self.assertStartsWith(warnings[0], b"<string>:5: EncodingWarning: ")
+        self.assertStartsWith(warnings[1], b"<string>:8: EncodingWarning: ")
+
+    def test_text_encoding(self):
+        # PEP 597, bpo-47000. io.text_encoding() returns "locale" or "utf-8"
+        # based on sys.flags.utf8_mode
+        code = "import io; print(io.text_encoding(None))"
+
+        proc = assert_python_ok('-X', 'utf8=0', '-c', code)
+        self.assertEqual(b"locale", proc.out.strip())
+
+        proc = assert_python_ok('-X', 'utf8=1', '-c', code)
+        self.assertEqual(b"utf-8", proc.out.strip())
+
+
+class CMiscIOTest(MiscIOTest, CTestCase):
+    name_of_module = "io", "_io"
+    extra_exported = "BlockingIOError",
+
+    def test_readinto_buffer_overflow(self):
+        # Issue #18025
+        class BadReader(self.io.BufferedIOBase):
+            def read(self, n=-1):
+                return b'x' * 10**6
+        bufio = BadReader()
+        b = bytearray(2)
+        self.assertRaises(ValueError, bufio.readinto, b)
+
+    def check_daemon_threads_shutdown_deadlock(self, stream_name):
+        # Issue #23309: deadlocks at shutdown should be avoided when a
+        # daemon thread and the main thread both write to a file.
+        code = """if 1:
+            import sys
+            import time
+            import threading
+            from test.support import SuppressCrashReport
+
+            file = sys.{stream_name}
+
+            def run():
+                while True:
+                    file.write('.')
+                    file.flush()
+
+            crash = SuppressCrashReport()
+            crash.__enter__()
+            # don't call __exit__(): the crash occurs at Python shutdown
+
+            thread = threading.Thread(target=run)
+            thread.daemon = True
+            thread.start()
+
+            time.sleep(0.5)
+            file.write('!')
+            file.flush()
+            """.format_map(locals())
+        res, _ = run_python_until_end("-c", code)
+        err = res.err.decode()
+        if res.rc != 0:
+            # Failure: should be a fatal error
+            pattern = (r"Fatal Python error: _enter_buffered_busy: "
+                       r"could not acquire lock "
+                       r"for <(_io\.)?BufferedWriter name='<{stream_name}>'> "
+                       r"at interpreter shutdown, possibly due to "
+                       r"daemon threads".format_map(locals()))
+            self.assertRegex(err, pattern)
+        else:
+            self.assertFalse(err.strip('.!'))
+
+    @threading_helper.requires_working_threading()
+    @support.requires_resource('walltime')
+    def test_daemon_threads_shutdown_stdout_deadlock(self):
+        self.check_daemon_threads_shutdown_deadlock('stdout')
+
+    @threading_helper.requires_working_threading()
+    @support.requires_resource('walltime')
+    def test_daemon_threads_shutdown_stderr_deadlock(self):
+        self.check_daemon_threads_shutdown_deadlock('stderr')
+
+
+class PyMiscIOTest(MiscIOTest, PyTestCase):
+    name_of_module = "_pyio", "io"
+    extra_exported = "BlockingIOError", "open_code",
+    not_exported = "valid_seek_flags",
+
+
+class ProtocolsTest(unittest.TestCase):
+    class MyReader:
+        def read(self, sz=-1):
+            return b""
+
+    class MyWriter:
+        def write(self, b: bytes):
+            pass
+
+    def test_reader_subclass(self):
+        self.assertIsSubclass(self.MyReader, io.Reader)
+        self.assertNotIsSubclass(str, io.Reader)
+
+    def test_writer_subclass(self):
+        self.assertIsSubclass(self.MyWriter, io.Writer)
+        self.assertNotIsSubclass(str, io.Writer)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_largefile.py b/Lib/test/test_io/test_largefile.py
similarity index 98%
rename from Lib/test/test_largefile.py
rename to Lib/test/test_io/test_largefile.py
index 41f7b70e5cf..438a90a92ed 100644
--- a/Lib/test/test_largefile.py
+++ b/Lib/test/test_io/test_largefile.py
@@ -56,9 +56,7 @@ class TestFileMethods(LargeFileTest):
     (i.e. > 2 GiB) files.
     """
 
-    # _pyio.FileIO.readall() uses a temporary bytearray then casted to bytes,
-    # so memuse=2 is needed
-    @bigmemtest(size=size, memuse=2, dry_run=False)
+    @bigmemtest(size=size, memuse=1, dry_run=False)
     def test_large_read(self, _size):
         # bpo-24658: Test that a read greater than 2GB does not fail.
         with self.open(TESTFN, "rb") as f:
@@ -154,7 +152,7 @@ def test_seekable(self):
                 f.seek(pos)
                 self.assertTrue(f.seekable())
 
-    @bigmemtest(size=size, memuse=2, dry_run=False)
+    @bigmemtest(size=size, memuse=1, dry_run=False)
     def test_seek_readall(self, _size):
         # Seek which doesn't change position should readall successfully.
         with self.open(TESTFN, 'rb') as f:
diff --git a/Lib/test/test_memoryio.py b/Lib/test/test_io/test_memoryio.py
similarity index 100%
rename from Lib/test/test_memoryio.py
rename to Lib/test/test_io/test_memoryio.py
diff --git a/Lib/test/test_io/test_signals.py b/Lib/test/test_io/test_signals.py
new file mode 100644
index 00000000000..03f1da1eb1c
--- /dev/null
+++ b/Lib/test/test_io/test_signals.py
@@ -0,0 +1,280 @@
+import errno
+import os
+import signal
+import threading
+import unittest
+from test import support
+from test.support import import_helper
+from .utils import PyTestCase, CTestCase
+
+
+requires_alarm = unittest.skipUnless(
+    hasattr(signal, "alarm"), "test requires signal.alarm()"
+)
+
+
+@unittest.skipIf(os.name == 'nt', 'POSIX signals required for this test.')
+class SignalsTest:
+
+    def setUp(self):
+        self.oldalrm = signal.signal(signal.SIGALRM, self.alarm_interrupt)
+
+    def tearDown(self):
+        signal.signal(signal.SIGALRM, self.oldalrm)
+
+    def alarm_interrupt(self, sig, frame):
+        1/0
+
+    def check_interrupted_write(self, item, bytes, **fdopen_kwargs):
+        """Check that a partial write, when it gets interrupted, properly
+        invokes the signal handler, and bubbles up the exception raised
+        in the latter."""
+
+        # XXX This test has three flaws that appear when objects are
+        # XXX not reference counted.
+
+        # - if wio.write() happens to trigger a garbage collection,
+        #   the signal exception may be raised when some __del__
+        #   method is running; it will not reach the assertRaises()
+        #   call.
+
+        # - more subtle, if the wio object is not destroyed at once
+        #   and survives this function, the next opened file is likely
+        #   to have the same fileno (since the file descriptor was
+        #   actively closed).  When wio.__del__ is finally called, it
+        #   will close the other's test file...  To trigger this with
+        #   CPython, try adding "global wio" in this function.
+
+        # - This happens only for streams created by the _pyio module,
+        #   because a wio.close() that fails still consider that the
+        #   file needs to be closed again.  You can try adding an
+        #   "assert wio.closed" at the end of the function.
+
+        # Fortunately, a little gc.collect() seems to be enough to
+        # work around all these issues.
+        support.gc_collect()  # For PyPy or other GCs.
+
+        read_results = []
+        def _read():
+            s = os.read(r, 1)
+            read_results.append(s)
+
+        t = threading.Thread(target=_read)
+        t.daemon = True
+        r, w = os.pipe()
+        fdopen_kwargs["closefd"] = False
+        large_data = item * (support.PIPE_MAX_SIZE // len(item) + 1)
+        try:
+            wio = self.io.open(w, **fdopen_kwargs)
+            if hasattr(signal, 'pthread_sigmask'):
+                # create the thread with SIGALRM signal blocked
+                signal.pthread_sigmask(signal.SIG_BLOCK, [signal.SIGALRM])
+                t.start()
+                signal.pthread_sigmask(signal.SIG_UNBLOCK, [signal.SIGALRM])
+            else:
+                t.start()
+
+            # Fill the pipe enough that the write will be blocking.
+            # It will be interrupted by the timer armed above.  Since the
+            # other thread has read one byte, the low-level write will
+            # return with a successful (partial) result rather than an EINTR.
+            # The buffered IO layer must check for pending signal
+            # handlers, which in this case will invoke alarm_interrupt().
+            signal.alarm(1)
+            try:
+                self.assertRaises(ZeroDivisionError, wio.write, large_data)
+            finally:
+                signal.alarm(0)
+                t.join()
+            # We got one byte, get another one and check that it isn't a
+            # repeat of the first one.
+            read_results.append(os.read(r, 1))
+            self.assertEqual(read_results, [bytes[0:1], bytes[1:2]])
+        finally:
+            os.close(w)
+            os.close(r)
+            # This is deliberate. If we didn't close the file descriptor
+            # before closing wio, wio would try to flush its internal
+            # buffer, and block again.
+            try:
+                wio.close()
+            except OSError as e:
+                if e.errno != errno.EBADF:
+                    raise
+
+    @requires_alarm
+    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    def test_interrupted_write_unbuffered(self):
+        self.check_interrupted_write(b"xy", b"xy", mode="wb", buffering=0)
+
+    @requires_alarm
+    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    def test_interrupted_write_buffered(self):
+        self.check_interrupted_write(b"xy", b"xy", mode="wb")
+
+    @requires_alarm
+    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    def test_interrupted_write_text(self):
+        self.check_interrupted_write("xy", b"xy", mode="w", encoding="ascii")
+
+    @support.no_tracing
+    def check_reentrant_write(self, data, **fdopen_kwargs):
+        def on_alarm(*args):
+            # Will be called reentrantly from the same thread
+            wio.write(data)
+            1/0
+        signal.signal(signal.SIGALRM, on_alarm)
+        r, w = os.pipe()
+        wio = self.io.open(w, **fdopen_kwargs)
+        try:
+            signal.alarm(1)
+            # Either the reentrant call to wio.write() fails with RuntimeError,
+            # or the signal handler raises ZeroDivisionError.
+            with self.assertRaises((ZeroDivisionError, RuntimeError)) as cm:
+                while 1:
+                    for i in range(100):
+                        wio.write(data)
+                        wio.flush()
+                    # Make sure the buffer doesn't fill up and block further writes
+                    os.read(r, len(data) * 100)
+            exc = cm.exception
+            if isinstance(exc, RuntimeError):
+                self.assertStartsWith(str(exc), "reentrant call")
+        finally:
+            signal.alarm(0)
+            wio.close()
+            os.close(r)
+
+    @requires_alarm
+    def test_reentrant_write_buffered(self):
+        self.check_reentrant_write(b"xy", mode="wb")
+
+    @requires_alarm
+    def test_reentrant_write_text(self):
+        self.check_reentrant_write("xy", mode="w", encoding="ascii")
+
+    def check_interrupted_read_retry(self, decode, **fdopen_kwargs):
+        """Check that a buffered read, when it gets interrupted (either
+        returning a partial result or EINTR), properly invokes the signal
+        handler and retries if the latter returned successfully."""
+        r, w = os.pipe()
+        fdopen_kwargs["closefd"] = False
+        def alarm_handler(sig, frame):
+            os.write(w, b"bar")
+        signal.signal(signal.SIGALRM, alarm_handler)
+        try:
+            rio = self.io.open(r, **fdopen_kwargs)
+            os.write(w, b"foo")
+            signal.alarm(1)
+            # Expected behaviour:
+            # - first raw read() returns partial b"foo"
+            # - second raw read() returns EINTR
+            # - third raw read() returns b"bar"
+            self.assertEqual(decode(rio.read(6)), "foobar")
+        finally:
+            signal.alarm(0)
+            rio.close()
+            os.close(w)
+            os.close(r)
+
+    @requires_alarm
+    @support.requires_resource('walltime')
+    def test_interrupted_read_retry_buffered(self):
+        self.check_interrupted_read_retry(lambda x: x.decode('latin1'),
+                                          mode="rb")
+
+    @requires_alarm
+    @support.requires_resource('walltime')
+    def test_interrupted_read_retry_text(self):
+        self.check_interrupted_read_retry(lambda x: x,
+                                          mode="r", encoding="latin1")
+
+    def check_interrupted_write_retry(self, item, **fdopen_kwargs):
+        """Check that a buffered write, when it gets interrupted (either
+        returning a partial result or EINTR), properly invokes the signal
+        handler and retries if the latter returned successfully."""
+        select = import_helper.import_module("select")
+
+        # A quantity that exceeds the buffer size of an anonymous pipe's
+        # write end.
+        N = support.PIPE_MAX_SIZE
+        r, w = os.pipe()
+        fdopen_kwargs["closefd"] = False
+
+        # We need a separate thread to read from the pipe and allow the
+        # write() to finish.  This thread is started after the SIGALRM is
+        # received (forcing a first EINTR in write()).
+        read_results = []
+        write_finished = False
+        error = None
+        def _read():
+            try:
+                while not write_finished:
+                    while r in select.select([r], [], [], 1.0)[0]:
+                        s = os.read(r, 1024)
+                        read_results.append(s)
+            except BaseException as exc:
+                nonlocal error
+                error = exc
+        t = threading.Thread(target=_read)
+        t.daemon = True
+        def alarm1(sig, frame):
+            signal.signal(signal.SIGALRM, alarm2)
+            signal.alarm(1)
+        def alarm2(sig, frame):
+            t.start()
+
+        large_data = item * N
+        signal.signal(signal.SIGALRM, alarm1)
+        try:
+            wio = self.io.open(w, **fdopen_kwargs)
+            signal.alarm(1)
+            # Expected behaviour:
+            # - first raw write() is partial (because of the limited pipe buffer
+            #   and the first alarm)
+            # - second raw write() returns EINTR (because of the second alarm)
+            # - subsequent write()s are successful (either partial or complete)
+            written = wio.write(large_data)
+            self.assertEqual(N, written)
+
+            wio.flush()
+            write_finished = True
+            t.join()
+
+            self.assertIsNone(error)
+            self.assertEqual(N, sum(len(x) for x in read_results))
+        finally:
+            signal.alarm(0)
+            write_finished = True
+            os.close(w)
+            os.close(r)
+            # This is deliberate. If we didn't close the file descriptor
+            # before closing wio, wio would try to flush its internal
+            # buffer, and could block (in case of failure).
+            try:
+                wio.close()
+            except OSError as e:
+                if e.errno != errno.EBADF:
+                    raise
+
+    @requires_alarm
+    @support.requires_resource('walltime')
+    def test_interrupted_write_retry_buffered(self):
+        self.check_interrupted_write_retry(b"x", mode="wb")
+
+    @requires_alarm
+    @support.requires_resource('walltime')
+    def test_interrupted_write_retry_text(self):
+        self.check_interrupted_write_retry("x", mode="w", encoding="latin1")
+
+
+class CSignalsTest(SignalsTest, CTestCase):
+    pass
+
+class PySignalsTest(SignalsTest, PyTestCase):
+    pass
+
+    # Handling reentrancy issues would slow down _pyio even more, so the
+    # tests are disabled.
+    test_reentrant_write_buffered = None
+    test_reentrant_write_text = None
diff --git a/Lib/test/test_io/test_textio.py b/Lib/test/test_io/test_textio.py
new file mode 100644
index 00000000000..dfa77ea23b3
--- /dev/null
+++ b/Lib/test/test_io/test_textio.py
@@ -0,0 +1,1704 @@
+import array
+import codecs
+import locale
+import os
+import pickle
+import sys
+import threading
+import time
+import unittest
+import warnings
+import weakref
+from collections import UserList
+from test import support
+from test.support import os_helper, threading_helper
+from test.support.script_helper import assert_python_ok
+from .utils import CTestCase, PyTestCase
+
+import io  # C implementation of io
+import _pyio as pyio # Python implementation of io
+
+
+def _default_chunk_size():
+    """Get the default TextIOWrapper chunk size"""
+    with open(__file__, "r", encoding="latin-1") as f:
+        return f._CHUNK_SIZE
+
+
+class BadIndex:
+    def __index__(self):
+        1/0
+
+
+# To fully exercise seek/tell, the StatefulIncrementalDecoder has these
+# properties:
+#   - A single output character can correspond to many bytes of input.
+#   - The number of input bytes to complete the character can be
+#     undetermined until the last input byte is received.
+#   - The number of input bytes can vary depending on previous input.
+#   - A single input byte can correspond to many characters of output.
+#   - The number of output characters can be undetermined until the
+#     last input byte is received.
+#   - The number of output characters can vary depending on previous input.
+
+class StatefulIncrementalDecoder(codecs.IncrementalDecoder):
+    """
+    For testing seek/tell behavior with a stateful, buffering decoder.
+
+    Input is a sequence of words.  Words may be fixed-length (length set
+    by input) or variable-length (period-terminated).  In variable-length
+    mode, extra periods are ignored.  Possible words are:
+      - 'i' followed by a number sets the input length, I (maximum 99).
+        When I is set to 0, words are space-terminated.
+      - 'o' followed by a number sets the output length, O (maximum 99).
+      - Any other word is converted into a word followed by a period on
+        the output.  The output word consists of the input word truncated
+        or padded out with hyphens to make its length equal to O.  If O
+        is 0, the word is output verbatim without truncating or padding.
+    I and O are initially set to 1.  When I changes, any buffered input is
+    re-scanned according to the new I.  EOF also terminates the last word.
+    """
+
+    def __init__(self, errors='strict'):
+        codecs.IncrementalDecoder.__init__(self, errors)
+        self.reset()
+
+    def __repr__(self):
+        return '<SID %x>' % id(self)
+
+    def reset(self):
+        self.i = 1
+        self.o = 1
+        self.buffer = bytearray()
+
+    def getstate(self):
+        i, o = self.i ^ 1, self.o ^ 1 # so that flags = 0 after reset()
+        return bytes(self.buffer), i*100 + o
+
+    def setstate(self, state):
+        buffer, io = state
+        self.buffer = bytearray(buffer)
+        i, o = divmod(io, 100)
+        self.i, self.o = i ^ 1, o ^ 1
+
+    def decode(self, input, final=False):
+        output = ''
+        for b in input:
+            if self.i == 0: # variable-length, terminated with period
+                if b == ord('.'):
+                    if self.buffer:
+                        output += self.process_word()
+                else:
+                    self.buffer.append(b)
+            else: # fixed-length, terminate after self.i bytes
+                self.buffer.append(b)
+                if len(self.buffer) == self.i:
+                    output += self.process_word()
+        if final and self.buffer: # EOF terminates the last word
+            output += self.process_word()
+        return output
+
+    def process_word(self):
+        output = ''
+        if self.buffer[0] == ord('i'):
+            self.i = min(99, int(self.buffer[1:] or 0)) # set input length
+        elif self.buffer[0] == ord('o'):
+            self.o = min(99, int(self.buffer[1:] or 0)) # set output length
+        else:
+            output = self.buffer.decode('ascii')
+            if len(output) < self.o:
+                output += '-'*self.o # pad out with hyphens
+            if self.o:
+                output = output[:self.o] # truncate to output length
+            output += '.'
+        self.buffer = bytearray()
+        return output
+
+    codecEnabled = False
+
+
+# bpo-41919: This method is separated from StatefulIncrementalDecoder to avoid a resource leak
+# when registering codecs and cleanup functions.
+def lookupTestDecoder(name):
+    if StatefulIncrementalDecoder.codecEnabled and name == 'test_decoder':
+        latin1 = codecs.lookup('latin-1')
+        return codecs.CodecInfo(
+            name='test_decoder', encode=latin1.encode, decode=None,
+            incrementalencoder=None,
+            streamreader=None, streamwriter=None,
+            incrementaldecoder=StatefulIncrementalDecoder)
+
+
+class StatefulIncrementalDecoderTest(unittest.TestCase):
+    """
+    Make sure the StatefulIncrementalDecoder actually works.
+    """
+
+    test_cases = [
+        # I=1, O=1 (fixed-length input == fixed-length output)
+        (b'abcd', False, 'a.b.c.d.'),
+        # I=0, O=0 (variable-length input, variable-length output)
+        (b'oiabcd', True, 'abcd.'),
+        # I=0, O=0 (should ignore extra periods)
+        (b'oi...abcd...', True, 'abcd.'),
+        # I=0, O=6 (variable-length input, fixed-length output)
+        (b'i.o6.x.xyz.toolongtofit.', False, 'x-----.xyz---.toolon.'),
+        # I=2, O=6 (fixed-length input < fixed-length output)
+        (b'i.i2.o6xyz', True, 'xy----.z-----.'),
+        # I=6, O=3 (fixed-length input > fixed-length output)
+        (b'i.o3.i6.abcdefghijklmnop', True, 'abc.ghi.mno.'),
+        # I=0, then 3; O=29, then 15 (with longer output)
+        (b'i.o29.a.b.cde.o15.abcdefghijabcdefghij.i3.a.b.c.d.ei00k.l.m', True,
+         'a----------------------------.' +
+         'b----------------------------.' +
+         'cde--------------------------.' +
+         'abcdefghijabcde.' +
+         'a.b------------.' +
+         '.c.------------.' +
+         'd.e------------.' +
+         'k--------------.' +
+         'l--------------.' +
+         'm--------------.')
+    ]
+
+    def test_decoder(self):
+        # Try a few one-shot test cases.
+        for input, eof, output in self.test_cases:
+            d = StatefulIncrementalDecoder()
+            self.assertEqual(d.decode(input, eof), output)
+
+        # Also test an unfinished decode, followed by forcing EOF.
+        d = StatefulIncrementalDecoder()
+        self.assertEqual(d.decode(b'oiabcd'), '')
+        self.assertEqual(d.decode(b'', 1), 'abcd.')
+
+class TextIOWrapperTest:
+
+    def setUp(self):
+        self.testdata = b"AAA\r\nBBB\rCCC\r\nDDD\nEEE\r\n"
+        self.normalized = b"AAA\nBBB\nCCC\nDDD\nEEE\n".decode("ascii")
+        os_helper.unlink(os_helper.TESTFN)
+        codecs.register(lookupTestDecoder)
+        self.addCleanup(codecs.unregister, lookupTestDecoder)
+
+    def tearDown(self):
+        os_helper.unlink(os_helper.TESTFN)
+
+    def test_constructor(self):
+        r = self.BytesIO(b"\xc3\xa9\n\n")
+        b = self.BufferedReader(r, 1000)
+        t = self.TextIOWrapper(b, encoding="utf-8")
+        t.__init__(b, encoding="latin-1", newline="\r\n")
+        self.assertEqual(t.encoding, "latin-1")
+        self.assertEqual(t.line_buffering, False)
+        t.__init__(b, encoding="utf-8", line_buffering=True)
+        self.assertEqual(t.encoding, "utf-8")
+        self.assertEqual(t.line_buffering, True)
+        self.assertEqual("\xe9\n", t.readline())
+        invalid_type = TypeError if self.is_C else ValueError
+        with self.assertRaises(invalid_type):
+            t.__init__(b, encoding=42)
+        with self.assertRaises(UnicodeEncodeError):
+            t.__init__(b, encoding='\udcfe')
+        with self.assertRaises(ValueError):
+            t.__init__(b, encoding='utf-8\0')
+        with self.assertRaises(invalid_type):
+            t.__init__(b, encoding="utf-8", errors=42)
+        if support.Py_DEBUG or sys.flags.dev_mode or self.is_C:
+            with self.assertRaises(UnicodeEncodeError):
+                t.__init__(b, encoding="utf-8", errors='\udcfe')
+        if support.Py_DEBUG or sys.flags.dev_mode or self.is_C:
+            with self.assertRaises(ValueError):
+                t.__init__(b, encoding="utf-8", errors='replace\0')
+        with self.assertRaises(TypeError):
+            t.__init__(b, encoding="utf-8", newline=42)
+        with self.assertRaises(ValueError):
+            t.__init__(b, encoding="utf-8", newline='\udcfe')
+        with self.assertRaises(ValueError):
+            t.__init__(b, encoding="utf-8", newline='\n\0')
+        with self.assertRaises(ValueError):
+            t.__init__(b, encoding="utf-8", newline='xyzzy')
+
+    def test_uninitialized(self):
+        t = self.TextIOWrapper.__new__(self.TextIOWrapper)
+        del t
+        t = self.TextIOWrapper.__new__(self.TextIOWrapper)
+        self.assertRaises(Exception, repr, t)
+        self.assertRaisesRegex((ValueError, AttributeError),
+                               'uninitialized|has no attribute',
+                               t.read, 0)
+        t.__init__(self.MockRawIO(), encoding="utf-8")
+        self.assertEqual(t.read(0), '')
+
+    def test_non_text_encoding_codecs_are_rejected(self):
+        # Ensure the constructor complains if passed a codec that isn't
+        # marked as a text encoding
+        # http://bugs.python.org/issue20404
+        r = self.BytesIO()
+        b = self.BufferedWriter(r)
+        with self.assertRaisesRegex(LookupError, "is not a text encoding"):
+            self.TextIOWrapper(b, encoding="hex")
+
+    def test_detach(self):
+        r = self.BytesIO()
+        b = self.BufferedWriter(r)
+        t = self.TextIOWrapper(b, encoding="ascii")
+        self.assertIs(t.detach(), b)
+
+        t = self.TextIOWrapper(b, encoding="ascii")
+        t.write("howdy")
+        self.assertFalse(r.getvalue())
+        t.detach()
+        self.assertEqual(r.getvalue(), b"howdy")
+        self.assertRaises(ValueError, t.detach)
+
+        # Operations independent of the detached stream should still work
+        repr(t)
+        self.assertEqual(t.encoding, "ascii")
+        self.assertEqual(t.errors, "strict")
+        self.assertFalse(t.line_buffering)
+        self.assertFalse(t.write_through)
+
+    def test_repr(self):
+        raw = self.BytesIO("hello".encode("utf-8"))
+        b = self.BufferedReader(raw)
+        t = self.TextIOWrapper(b, encoding="utf-8")
+        modname = self.TextIOWrapper.__module__
+        self.assertRegex(repr(t),
+                         r"<(%s\.)?TextIOWrapper encoding='utf-8'>" % modname)
+        raw.name = "dummy"
+        self.assertRegex(repr(t),
+                         r"<(%s\.)?TextIOWrapper name='dummy' encoding='utf-8'>" % modname)
+        t.mode = "r"
+        self.assertRegex(repr(t),
+                         r"<(%s\.)?TextIOWrapper name='dummy' mode='r' encoding='utf-8'>" % modname)
+        raw.name = b"dummy"
+        self.assertRegex(repr(t),
+                         r"<(%s\.)?TextIOWrapper name=b'dummy' mode='r' encoding='utf-8'>" % modname)
+
+        t.buffer.detach()
+        repr(t)  # Should not raise an exception
+
+    def test_recursive_repr(self):
+        # Issue #25455
+        raw = self.BytesIO()
+        t = self.TextIOWrapper(raw, encoding="utf-8")
+        with support.swap_attr(raw, 'name', t), support.infinite_recursion(25):
+            with self.assertRaises(RuntimeError):
+                repr(t)  # Should not crash
+
+    def test_subclass_repr(self):
+        class TestSubclass(self.TextIOWrapper):
+            pass
+
+        f = TestSubclass(self.StringIO())
+        self.assertIn(TestSubclass.__name__, repr(f))
+
+    def test_line_buffering(self):
+        r = self.BytesIO()
+        b = self.BufferedWriter(r, 1000)
+        t = self.TextIOWrapper(b, encoding="utf-8", newline="\n", line_buffering=True)
+        t.write("X")
+        self.assertEqual(r.getvalue(), b"")  # No flush happened
+        t.write("Y\nZ")
+        self.assertEqual(r.getvalue(), b"XY\nZ")  # All got flushed
+        t.write("A\rB")
+        self.assertEqual(r.getvalue(), b"XY\nZA\rB")
+
+    def test_reconfigure_line_buffering(self):
+        r = self.BytesIO()
+        b = self.BufferedWriter(r, 1000)
+        t = self.TextIOWrapper(b, encoding="utf-8", newline="\n", line_buffering=False)
+        t.write("AB\nC")
+        self.assertEqual(r.getvalue(), b"")
+
+        t.reconfigure(line_buffering=True)   # implicit flush
+        self.assertEqual(r.getvalue(), b"AB\nC")
+        t.write("DEF\nG")
+        self.assertEqual(r.getvalue(), b"AB\nCDEF\nG")
+        t.write("H")
+        self.assertEqual(r.getvalue(), b"AB\nCDEF\nG")
+        t.reconfigure(line_buffering=False)   # implicit flush
+        self.assertEqual(r.getvalue(), b"AB\nCDEF\nGH")
+        t.write("IJ")
+        self.assertEqual(r.getvalue(), b"AB\nCDEF\nGH")
+
+        # Keeping default value
+        t.reconfigure()
+        t.reconfigure(line_buffering=None)
+        self.assertEqual(t.line_buffering, False)
+        t.reconfigure(line_buffering=True)
+        t.reconfigure()
+        t.reconfigure(line_buffering=None)
+        self.assertEqual(t.line_buffering, True)
+
+    @unittest.skipIf(sys.flags.utf8_mode, "utf-8 mode is enabled")
+    def test_default_encoding(self):
+        with os_helper.EnvironmentVarGuard() as env:
+            # try to get a user preferred encoding different than the current
+            # locale encoding to check that TextIOWrapper() uses the current
+            # locale encoding and not the user preferred encoding
+            env.unset('LC_ALL', 'LANG', 'LC_CTYPE')
+
+            current_locale_encoding = locale.getencoding()
+            b = self.BytesIO()
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore", EncodingWarning)
+                t = self.TextIOWrapper(b)
+            self.assertEqual(t.encoding, current_locale_encoding)
+
+    def test_encoding(self):
+        # Check the encoding attribute is always set, and valid
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="utf-8")
+        self.assertEqual(t.encoding, "utf-8")
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", EncodingWarning)
+            t = self.TextIOWrapper(b)
+        self.assertIsNotNone(t.encoding)
+        codecs.lookup(t.encoding)
+
+    def test_encoding_errors_reading(self):
+        # (1) default
+        b = self.BytesIO(b"abc\n\xff\n")
+        t = self.TextIOWrapper(b, encoding="ascii")
+        self.assertRaises(UnicodeError, t.read)
+        # (2) explicit strict
+        b = self.BytesIO(b"abc\n\xff\n")
+        t = self.TextIOWrapper(b, encoding="ascii", errors="strict")
+        self.assertRaises(UnicodeError, t.read)
+        # (3) ignore
+        b = self.BytesIO(b"abc\n\xff\n")
+        t = self.TextIOWrapper(b, encoding="ascii", errors="ignore")
+        self.assertEqual(t.read(), "abc\n\n")
+        # (4) replace
+        b = self.BytesIO(b"abc\n\xff\n")
+        t = self.TextIOWrapper(b, encoding="ascii", errors="replace")
+        self.assertEqual(t.read(), "abc\n\ufffd\n")
+
+    def test_encoding_errors_writing(self):
+        # (1) default
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii")
+        self.assertRaises(UnicodeError, t.write, "\xff")
+        # (2) explicit strict
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii", errors="strict")
+        self.assertRaises(UnicodeError, t.write, "\xff")
+        # (3) ignore
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii", errors="ignore",
+                             newline="\n")
+        t.write("abc\xffdef\n")
+        t.flush()
+        self.assertEqual(b.getvalue(), b"abcdef\n")
+        # (4) replace
+        b = self.BytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii", errors="replace",
+                             newline="\n")
+        t.write("abc\xffdef\n")
+        t.flush()
+        self.assertEqual(b.getvalue(), b"abc?def\n")
+
+    def test_newlines(self):
+        input_lines = [ "unix\n", "windows\r\n", "os9\r", "last\n", "nonl" ]
+
+        tests = [
+            [ None, [ 'unix\n', 'windows\n', 'os9\n', 'last\n', 'nonl' ] ],
+            [ '', input_lines ],
+            [ '\n', [ "unix\n", "windows\r\n", "os9\rlast\n", "nonl" ] ],
+            [ '\r\n', [ "unix\nwindows\r\n", "os9\rlast\nnonl" ] ],
+            [ '\r', [ "unix\nwindows\r", "\nos9\r", "last\nnonl" ] ],
+        ]
+        encodings = (
+            'utf-8', 'latin-1',
+            'utf-16', 'utf-16-le', 'utf-16-be',
+            'utf-32', 'utf-32-le', 'utf-32-be',
+        )
+
+        # Try a range of buffer sizes to test the case where \r is the last
+        # character in TextIOWrapper._pending_line.
+        for encoding in encodings:
+            # XXX: str.encode() should return bytes
+            data = bytes(''.join(input_lines).encode(encoding))
+            for do_reads in (False, True):
+                for bufsize in range(1, 10):
+                    for newline, exp_lines in tests:
+                        bufio = self.BufferedReader(self.BytesIO(data), bufsize)
+                        textio = self.TextIOWrapper(bufio, newline=newline,
+                                                  encoding=encoding)
+                        if do_reads:
+                            got_lines = []
+                            while True:
+                                c2 = textio.read(2)
+                                if c2 == '':
+                                    break
+                                self.assertEqual(len(c2), 2)
+                                got_lines.append(c2 + textio.readline())
+                        else:
+                            got_lines = list(textio)
+
+                        for got_line, exp_line in zip(got_lines, exp_lines):
+                            self.assertEqual(got_line, exp_line)
+                        self.assertEqual(len(got_lines), len(exp_lines))
+
+    def test_newlines_input(self):
+        testdata = b"AAA\nBB\x00B\nCCC\rDDD\rEEE\r\nFFF\r\nGGG"
+        normalized = testdata.replace(b"\r\n", b"\n").replace(b"\r", b"\n")
+        for newline, expected in [
+            (None, normalized.decode("ascii").splitlines(keepends=True)),
+            ("", testdata.decode("ascii").splitlines(keepends=True)),
+            ("\n", ["AAA\n", "BB\x00B\n", "CCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
+            ("\r\n", ["AAA\nBB\x00B\nCCC\rDDD\rEEE\r\n", "FFF\r\n", "GGG"]),
+            ("\r",  ["AAA\nBB\x00B\nCCC\r", "DDD\r", "EEE\r", "\nFFF\r", "\nGGG"]),
+            ]:
+            buf = self.BytesIO(testdata)
+            txt = self.TextIOWrapper(buf, encoding="ascii", newline=newline)
+            self.assertEqual(txt.readlines(), expected)
+            txt.seek(0)
+            self.assertEqual(txt.read(), "".join(expected))
+
+    def test_newlines_output(self):
+        testdict = {
+            "": b"AAA\nBBB\nCCC\nX\rY\r\nZ",
+            "\n": b"AAA\nBBB\nCCC\nX\rY\r\nZ",
+            "\r": b"AAA\rBBB\rCCC\rX\rY\r\rZ",
+            "\r\n": b"AAA\r\nBBB\r\nCCC\r\nX\rY\r\r\nZ",
+            }
+        tests = [(None, testdict[os.linesep])] + sorted(testdict.items())
+        for newline, expected in tests:
+            buf = self.BytesIO()
+            txt = self.TextIOWrapper(buf, encoding="ascii", newline=newline)
+            txt.write("AAA\nB")
+            txt.write("BB\nCCC\n")
+            txt.write("X\rY\r\nZ")
+            txt.flush()
+            self.assertEqual(buf.closed, False)
+            self.assertEqual(buf.getvalue(), expected)
+
+    def test_destructor(self):
+        l = []
+        base = self.BytesIO
+        class MyBytesIO(base):
+            def close(self):
+                l.append(self.getvalue())
+                base.close(self)
+        b = MyBytesIO()
+        t = self.TextIOWrapper(b, encoding="ascii")
+        t.write("abc")
+        del t
+        support.gc_collect()
+        self.assertEqual([b"abc"], l)
+
+    def test_override_destructor(self):
+        record = []
+        class MyTextIO(self.TextIOWrapper):
+            def __del__(self):
+                record.append(1)
+                try:
+                    f = super().__del__
+                except AttributeError:
+                    pass
+                else:
+                    f()
+            def close(self):
+                record.append(2)
+                super().close()
+            def flush(self):
+                record.append(3)
+                super().flush()
+        b = self.BytesIO()
+        t = MyTextIO(b, encoding="ascii")
+        del t
+        support.gc_collect()
+        self.assertEqual(record, [1, 2, 3])
+
+    def test_error_through_destructor(self):
+        # Test that the exception state is not modified by a destructor,
+        # even if close() fails.
+        rawio = self.CloseFailureIO()
+        with support.catch_unraisable_exception() as cm:
+            with self.assertRaises(AttributeError):
+                self.TextIOWrapper(rawio, encoding="utf-8").xyzzy
+
+            self.assertEqual(cm.unraisable.exc_type, OSError)
+
+    # Systematic tests of the text I/O API
+
+    def test_basic_io(self):
+        for chunksize in (1, 2, 3, 4, 5, 15, 16, 17, 31, 32, 33, 63, 64, 65):
+            for enc in "ascii", "latin-1", "utf-8" :# , "utf-16-be", "utf-16-le":
+                f = self.open(os_helper.TESTFN, "w+", encoding=enc)
+                f._CHUNK_SIZE = chunksize
+                self.assertEqual(f.write("abc"), 3)
+                f.close()
+                f = self.open(os_helper.TESTFN, "r+", encoding=enc)
+                f._CHUNK_SIZE = chunksize
+                self.assertEqual(f.tell(), 0)
+                self.assertEqual(f.read(), "abc")
+                cookie = f.tell()
+                self.assertEqual(f.seek(0), 0)
+                self.assertEqual(f.read(None), "abc")
+                f.seek(0)
+                self.assertEqual(f.read(2), "ab")
+                self.assertEqual(f.read(1), "c")
+                self.assertEqual(f.read(1), "")
+                self.assertEqual(f.read(), "")
+                self.assertEqual(f.tell(), cookie)
+                self.assertEqual(f.seek(0), 0)
+                self.assertEqual(f.seek(0, 2), cookie)
+                self.assertEqual(f.write("def"), 3)
+                self.assertEqual(f.seek(cookie), cookie)
+                self.assertEqual(f.read(), "def")
+                if enc.startswith("utf"):
+                    self.multi_line_test(f, enc)
+                f.close()
+
+    def multi_line_test(self, f, enc):
+        f.seek(0)
+        f.truncate()
+        sample = "s\xff\u0fff\uffff"
+        wlines = []
+        for size in (0, 1, 2, 3, 4, 5, 30, 31, 32, 33, 62, 63, 64, 65, 1000):
+            chars = []
+            for i in range(size):
+                chars.append(sample[i % len(sample)])
+            line = "".join(chars) + "\n"
+            wlines.append((f.tell(), line))
+            f.write(line)
+        f.seek(0)
+        rlines = []
+        while True:
+            pos = f.tell()
+            line = f.readline()
+            if not line:
+                break
+            rlines.append((pos, line))
+        self.assertEqual(rlines, wlines)
+
+    def test_telling(self):
+        f = self.open(os_helper.TESTFN, "w+", encoding="utf-8")
+        p0 = f.tell()
+        f.write("\xff\n")
+        p1 = f.tell()
+        f.write("\xff\n")
+        p2 = f.tell()
+        f.seek(0)
+        self.assertEqual(f.tell(), p0)
+        self.assertEqual(f.readline(), "\xff\n")
+        self.assertEqual(f.tell(), p1)
+        self.assertEqual(f.readline(), "\xff\n")
+        self.assertEqual(f.tell(), p2)
+        f.seek(0)
+        for line in f:
+            self.assertEqual(line, "\xff\n")
+            self.assertRaises(OSError, f.tell)
+        self.assertEqual(f.tell(), p2)
+        f.close()
+
+    def test_seeking(self):
+        chunk_size = _default_chunk_size()
+        prefix_size = chunk_size - 2
+        u_prefix = "a" * prefix_size
+        prefix = bytes(u_prefix.encode("utf-8"))
+        self.assertEqual(len(u_prefix), len(prefix))
+        u_suffix = "\u8888\n"
+        suffix = bytes(u_suffix.encode("utf-8"))
+        line = prefix + suffix
+        with self.open(os_helper.TESTFN, "wb") as f:
+            f.write(line*2)
+        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
+            s = f.read(prefix_size)
+            self.assertEqual(s, str(prefix, "ascii"))
+            self.assertEqual(f.tell(), prefix_size)
+            self.assertEqual(f.readline(), u_suffix)
+
+    def test_seeking_too(self):
+        # Regression test for a specific bug
+        data = b'\xe0\xbf\xbf\n'
+        with self.open(os_helper.TESTFN, "wb") as f:
+            f.write(data)
+        with self.open(os_helper.TESTFN, "r", encoding="utf-8") as f:
+            f._CHUNK_SIZE  # Just test that it exists
+            f._CHUNK_SIZE = 2
+            f.readline()
+            f.tell()
+
+    def test_seek_and_tell(self):
+        #Test seek/tell using the StatefulIncrementalDecoder.
+        # Make test faster by doing smaller seeks
+        CHUNK_SIZE = 128
+
+        def test_seek_and_tell_with_data(data, min_pos=0):
+            """Tell/seek to various points within a data stream and ensure
+            that the decoded data returned by read() is consistent."""
+            f = self.open(os_helper.TESTFN, 'wb')
+            f.write(data)
+            f.close()
+            f = self.open(os_helper.TESTFN, encoding='test_decoder')
+            f._CHUNK_SIZE = CHUNK_SIZE
+            decoded = f.read()
+            f.close()
+
+            for i in range(min_pos, len(decoded) + 1): # seek positions
+                for j in [1, 5, len(decoded) - i]: # read lengths
+                    f = self.open(os_helper.TESTFN, encoding='test_decoder')
+                    self.assertEqual(f.read(i), decoded[:i])
+                    cookie = f.tell()
+                    self.assertEqual(f.read(j), decoded[i:i + j])
+                    f.seek(cookie)
+                    self.assertEqual(f.read(), decoded[i:])
+                    f.close()
+
+        # Enable the test decoder.
+        StatefulIncrementalDecoder.codecEnabled = 1
+
+        # Run the tests.
+        try:
+            # Try each test case.
+            for input, _, _ in StatefulIncrementalDecoderTest.test_cases:
+                test_seek_and_tell_with_data(input)
+
+            # Position each test case so that it crosses a chunk boundary.
+            for input, _, _ in StatefulIncrementalDecoderTest.test_cases:
+                offset = CHUNK_SIZE - len(input)//2
+                prefix = b'.'*offset
+                # Don't bother seeking into the prefix (takes too long).
+                min_pos = offset*2
+                test_seek_and_tell_with_data(prefix + input, min_pos)
+
+        # Ensure our test decoder won't interfere with subsequent tests.
+        finally:
+            StatefulIncrementalDecoder.codecEnabled = 0
+
+    def test_multibyte_seek_and_tell(self):
+        f = self.open(os_helper.TESTFN, "w", encoding="euc_jp")
+        f.write("AB\n\u3046\u3048\n")
+        f.close()
+
+        f = self.open(os_helper.TESTFN, "r", encoding="euc_jp")
+        self.assertEqual(f.readline(), "AB\n")
+        p0 = f.tell()
+        self.assertEqual(f.readline(), "\u3046\u3048\n")
+        p1 = f.tell()
+        f.seek(p0)
+        self.assertEqual(f.readline(), "\u3046\u3048\n")
+        self.assertEqual(f.tell(), p1)
+        f.close()
+
+    def test_tell_after_readline_with_cr(self):
+        # Test for gh-141314: TextIOWrapper.tell() assertion failure
+        # when dealing with standalone carriage returns
+        data = b'line1\r'
+        with self.open(os_helper.TESTFN, "wb") as f:
+            f.write(data)
+
+        with self.open(os_helper.TESTFN, "r") as f:
+            # Read line that ends with \r
+            line = f.readline()
+            self.assertEqual(line, "line1\n")
+            # This should not cause an assertion failure
+            pos = f.tell()
+            # Verify we can seek back to this position
+            f.seek(pos)
+            remaining = f.read()
+            self.assertEqual(remaining, "")
+
+
+    def test_seek_with_encoder_state(self):
+        f = self.open(os_helper.TESTFN, "w", encoding="euc_jis_2004")
+        f.write("\u00e6\u0300")
+        p0 = f.tell()
+        f.write("\u00e6")
+        f.seek(p0)
+        f.write("\u0300")
+        f.close()
+
+        f = self.open(os_helper.TESTFN, "r", encoding="euc_jis_2004")
+        self.assertEqual(f.readline(), "\u00e6\u0300\u0300")
+        f.close()
+
+    def test_encoded_writes(self):
+        data = "1234567890"
+        tests = ("utf-16",
+                 "utf-16-le",
+                 "utf-16-be",
+                 "utf-32",
+                 "utf-32-le",
+                 "utf-32-be")
+        for encoding in tests:
+            buf = self.BytesIO()
+            f = self.TextIOWrapper(buf, encoding=encoding)
+            # Check if the BOM is written only once (see issue1753).
+            f.write(data)
+            f.write(data)
+            f.seek(0)
+            self.assertEqual(f.read(), data * 2)
+            f.seek(0)
+            self.assertEqual(f.read(), data * 2)
+            self.assertEqual(buf.getvalue(), (data * 2).encode(encoding))
+
+    def test_unreadable(self):
+        class UnReadable(self.BytesIO):
+            def readable(self):
+                return False
+        txt = self.TextIOWrapper(UnReadable(), encoding="utf-8")
+        self.assertRaises(OSError, txt.read)
+
+    def test_read_one_by_one(self):
+        txt = self.TextIOWrapper(self.BytesIO(b"AA\r\nBB"), encoding="utf-8")
+        reads = ""
+        while True:
+            c = txt.read(1)
+            if not c:
+                break
+            reads += c
+        self.assertEqual(reads, "AA\nBB")
+
+    def test_readlines(self):
+        txt = self.TextIOWrapper(self.BytesIO(b"AA\nBB\nCC"), encoding="utf-8")
+        self.assertEqual(txt.readlines(), ["AA\n", "BB\n", "CC"])
+        txt.seek(0)
+        self.assertEqual(txt.readlines(None), ["AA\n", "BB\n", "CC"])
+        txt.seek(0)
+        self.assertEqual(txt.readlines(5), ["AA\n", "BB\n"])
+
+    # read in amounts equal to TextIOWrapper._CHUNK_SIZE which is 128.
+    def test_read_by_chunk(self):
+        # make sure "\r\n" straddles 128 char boundary.
+        txt = self.TextIOWrapper(self.BytesIO(b"A" * 127 + b"\r\nB"), encoding="utf-8")
+        reads = ""
+        while True:
+            c = txt.read(128)
+            if not c:
+                break
+            reads += c
+        self.assertEqual(reads, "A"*127+"\nB")
+
+    def test_writelines(self):
+        l = ['ab', 'cd', 'ef']
+        buf = self.BytesIO()
+        txt = self.TextIOWrapper(buf, encoding="utf-8")
+        txt.writelines(l)
+        txt.flush()
+        self.assertEqual(buf.getvalue(), b'abcdef')
+
+    def test_writelines_userlist(self):
+        l = UserList(['ab', 'cd', 'ef'])
+        buf = self.BytesIO()
+        txt = self.TextIOWrapper(buf, encoding="utf-8")
+        txt.writelines(l)
+        txt.flush()
+        self.assertEqual(buf.getvalue(), b'abcdef')
+
+    def test_writelines_error(self):
+        txt = self.TextIOWrapper(self.BytesIO(), encoding="utf-8")
+        self.assertRaises(TypeError, txt.writelines, [1, 2, 3])
+        self.assertRaises(TypeError, txt.writelines, None)
+        self.assertRaises(TypeError, txt.writelines, b'abc')
+
+    def test_issue1395_1(self):
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
+
+        # read one char at a time
+        reads = ""
+        while True:
+            c = txt.read(1)
+            if not c:
+                break
+            reads += c
+        self.assertEqual(reads, self.normalized)
+
+    def test_issue1395_2(self):
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
+        txt._CHUNK_SIZE = 4
+
+        reads = ""
+        while True:
+            c = txt.read(4)
+            if not c:
+                break
+            reads += c
+        self.assertEqual(reads, self.normalized)
+
+    def test_issue1395_3(self):
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
+        txt._CHUNK_SIZE = 4
+
+        reads = txt.read(4)
+        reads += txt.read(4)
+        reads += txt.readline()
+        reads += txt.readline()
+        reads += txt.readline()
+        self.assertEqual(reads, self.normalized)
+
+    def test_issue1395_4(self):
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
+        txt._CHUNK_SIZE = 4
+
+        reads = txt.read(4)
+        reads += txt.read()
+        self.assertEqual(reads, self.normalized)
+
+    def test_issue1395_5(self):
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
+        txt._CHUNK_SIZE = 4
+
+        reads = txt.read(4)
+        pos = txt.tell()
+        txt.seek(0)
+        txt.seek(pos)
+        self.assertEqual(txt.read(4), "BBB\n")
+
+    def test_issue2282(self):
+        buffer = self.BytesIO(self.testdata)
+        txt = self.TextIOWrapper(buffer, encoding="ascii")
+
+        self.assertEqual(buffer.seekable(), txt.seekable())
+
+    def test_append_bom(self):
+        # The BOM is not written again when appending to a non-empty file
+        filename = os_helper.TESTFN
+        for charset in ('utf-8-sig', 'utf-16', 'utf-32'):
+            with self.open(filename, 'w', encoding=charset) as f:
+                f.write('aaa')
+                pos = f.tell()
+            with self.open(filename, 'rb') as f:
+                self.assertEqual(f.read(), 'aaa'.encode(charset))
+
+            with self.open(filename, 'a', encoding=charset) as f:
+                f.write('xxx')
+            with self.open(filename, 'rb') as f:
+                self.assertEqual(f.read(), 'aaaxxx'.encode(charset))
+
+    def test_seek_bom(self):
+        # Same test, but when seeking manually
+        filename = os_helper.TESTFN
+        for charset in ('utf-8-sig', 'utf-16', 'utf-32'):
+            with self.open(filename, 'w', encoding=charset) as f:
+                f.write('aaa')
+                pos = f.tell()
+            with self.open(filename, 'r+', encoding=charset) as f:
+                f.seek(pos)
+                f.write('zzz')
+                f.seek(0)
+                f.write('bbb')
+            with self.open(filename, 'rb') as f:
+                self.assertEqual(f.read(), 'bbbzzz'.encode(charset))
+
+    def test_seek_append_bom(self):
+        # Same test, but first seek to the start and then to the end
+        filename = os_helper.TESTFN
+        for charset in ('utf-8-sig', 'utf-16', 'utf-32'):
+            with self.open(filename, 'w', encoding=charset) as f:
+                f.write('aaa')
+            with self.open(filename, 'a', encoding=charset) as f:
+                f.seek(0)
+                f.seek(0, self.SEEK_END)
+                f.write('xxx')
+            with self.open(filename, 'rb') as f:
+                self.assertEqual(f.read(), 'aaaxxx'.encode(charset))
+
+    def test_errors_property(self):
+        with self.open(os_helper.TESTFN, "w", encoding="utf-8") as f:
+            self.assertEqual(f.errors, "strict")
+        with self.open(os_helper.TESTFN, "w", encoding="utf-8", errors="replace") as f:
+            self.assertEqual(f.errors, "replace")
+
+    @support.no_tracing
+    @threading_helper.requires_working_threading()
+    def test_threads_write(self):
+        # Issue6750: concurrent writes could duplicate data
+        event = threading.Event()
+        with self.open(os_helper.TESTFN, "w", encoding="utf-8", buffering=1) as f:
+            def run(n):
+                text = "Thread%03d\n" % n
+                event.wait()
+                f.write(text)
+            threads = [threading.Thread(target=run, args=(x,))
+                       for x in range(20)]
+            with threading_helper.start_threads(threads, event.set):
+                time.sleep(0.02)
+        with self.open(os_helper.TESTFN, encoding="utf-8") as f:
+            content = f.read()
+            for n in range(20):
+                self.assertEqual(content.count("Thread%03d\n" % n), 1)
+
+    def test_flush_error_on_close(self):
+        # Test that text file is closed despite failed flush
+        # and that flush() is called before file closed.
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
+        closed = []
+        def bad_flush():
+            closed[:] = [txt.closed, txt.buffer.closed]
+            raise OSError()
+        txt.flush = bad_flush
+        self.assertRaises(OSError, txt.close) # exception not swallowed
+        self.assertTrue(txt.closed)
+        self.assertTrue(txt.buffer.closed)
+        self.assertTrue(closed)      # flush() called
+        self.assertFalse(closed[0])  # flush() called before file closed
+        self.assertFalse(closed[1])
+        txt.flush = lambda: None  # break reference loop
+
+    def test_close_error_on_close(self):
+        buffer = self.BytesIO(self.testdata)
+        def bad_flush():
+            raise OSError('flush')
+        def bad_close():
+            raise OSError('close')
+        buffer.close = bad_close
+        txt = self.TextIOWrapper(buffer, encoding="ascii")
+        txt.flush = bad_flush
+        with self.assertRaises(OSError) as err: # exception not swallowed
+            txt.close()
+        self.assertEqual(err.exception.args, ('close',))
+        self.assertIsInstance(err.exception.__context__, OSError)
+        self.assertEqual(err.exception.__context__.args, ('flush',))
+        self.assertFalse(txt.closed)
+
+        # Silence destructor error
+        buffer.close = lambda: None
+        txt.flush = lambda: None
+
+    def test_nonnormalized_close_error_on_close(self):
+        # Issue #21677
+        buffer = self.BytesIO(self.testdata)
+        def bad_flush():
+            raise non_existing_flush
+        def bad_close():
+            raise non_existing_close
+        buffer.close = bad_close
+        txt = self.TextIOWrapper(buffer, encoding="ascii")
+        txt.flush = bad_flush
+        with self.assertRaises(NameError) as err: # exception not swallowed
+            txt.close()
+        self.assertIn('non_existing_close', str(err.exception))
+        self.assertIsInstance(err.exception.__context__, NameError)
+        self.assertIn('non_existing_flush', str(err.exception.__context__))
+        self.assertFalse(txt.closed)
+
+        # Silence destructor error
+        buffer.close = lambda: None
+        txt.flush = lambda: None
+
+    def test_multi_close(self):
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
+        txt.close()
+        txt.close()
+        txt.close()
+        self.assertRaises(ValueError, txt.flush)
+
+    def test_unseekable(self):
+        txt = self.TextIOWrapper(self.MockUnseekableIO(self.testdata), encoding="utf-8")
+        self.assertRaises(self.UnsupportedOperation, txt.tell)
+        self.assertRaises(self.UnsupportedOperation, txt.seek, 0)
+
+    def test_readonly_attributes(self):
+        txt = self.TextIOWrapper(self.BytesIO(self.testdata), encoding="ascii")
+        buf = self.BytesIO(self.testdata)
+        with self.assertRaises(AttributeError):
+            txt.buffer = buf
+
+    def test_rawio(self):
+        # Issue #12591: TextIOWrapper must work with raw I/O objects, so
+        # that subprocess.Popen() can have the required unbuffered
+        # semantics with universal_newlines=True.
+        raw = self.MockRawIO([b'abc', b'def', b'ghi\njkl\nopq\n'])
+        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
+        # Reads
+        self.assertEqual(txt.read(4), 'abcd')
+        self.assertEqual(txt.readline(), 'efghi\n')
+        self.assertEqual(list(txt), ['jkl\n', 'opq\n'])
+
+    def test_rawio_write_through(self):
+        # Issue #12591: with write_through=True, writes don't need a flush
+        raw = self.MockRawIO([b'abc', b'def', b'ghi\njkl\nopq\n'])
+        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n',
+                                 write_through=True)
+        txt.write('1')
+        txt.write('23\n4')
+        txt.write('5')
+        self.assertEqual(b''.join(raw._write_stack), b'123\n45')
+
+    def test_bufio_write_through(self):
+        # Issue #21396: write_through=True doesn't force a flush()
+        # on the underlying binary buffered object.
+        flush_called, write_called = [], []
+        class BufferedWriter(self.BufferedWriter):
+            def flush(self, *args, **kwargs):
+                flush_called.append(True)
+                return super().flush(*args, **kwargs)
+            def write(self, *args, **kwargs):
+                write_called.append(True)
+                return super().write(*args, **kwargs)
+
+        rawio = self.BytesIO()
+        data = b"a"
+        bufio = BufferedWriter(rawio, len(data)*2)
+        textio = self.TextIOWrapper(bufio, encoding='ascii',
+                                    write_through=True)
+        # write to the buffered io but don't overflow the buffer
+        text = data.decode('ascii')
+        textio.write(text)
+
+        # buffer.flush is not called with write_through=True
+        self.assertFalse(flush_called)
+        # buffer.write *is* called with write_through=True
+        self.assertTrue(write_called)
+        self.assertEqual(rawio.getvalue(), b"") # no flush
+
+        write_called = [] # reset
+        textio.write(text * 10) # total content is larger than bufio buffer
+        self.assertTrue(write_called)
+        self.assertEqual(rawio.getvalue(), data * 11) # all flushed
+
+    def test_reconfigure_write_through(self):
+        raw = self.MockRawIO([])
+        t = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
+        t.write('1')
+        t.reconfigure(write_through=True)  # implied flush
+        self.assertEqual(t.write_through, True)
+        self.assertEqual(b''.join(raw._write_stack), b'1')
+        t.write('23')
+        self.assertEqual(b''.join(raw._write_stack), b'123')
+        t.reconfigure(write_through=False)
+        self.assertEqual(t.write_through, False)
+        t.write('45')
+        t.flush()
+        self.assertEqual(b''.join(raw._write_stack), b'12345')
+        # Keeping default value
+        t.reconfigure()
+        t.reconfigure(write_through=None)
+        self.assertEqual(t.write_through, False)
+        t.reconfigure(write_through=True)
+        t.reconfigure()
+        t.reconfigure(write_through=None)
+        self.assertEqual(t.write_through, True)
+
+    def test_read_nonbytes(self):
+        # Issue #17106
+        # Crash when underlying read() returns non-bytes
+        t = self.TextIOWrapper(self.StringIO('a'), encoding="utf-8")
+        self.assertRaises(TypeError, t.read, 1)
+        t = self.TextIOWrapper(self.StringIO('a'), encoding="utf-8")
+        self.assertRaises(TypeError, t.readline)
+        t = self.TextIOWrapper(self.StringIO('a'), encoding="utf-8")
+        self.assertRaises(TypeError, t.read)
+
+    def test_illegal_encoder(self):
+        # Issue 31271: Calling write() while the return value of encoder's
+        # encode() is invalid shouldn't cause an assertion failure.
+        rot13 = codecs.lookup("rot13")
+        with support.swap_attr(rot13, '_is_text_encoding', True):
+            t = self.TextIOWrapper(self.BytesIO(b'foo'), encoding="rot13")
+        self.assertRaises(TypeError, t.write, 'bar')
+
+    def test_illegal_decoder(self):
+        # Issue #17106
+        # Bypass the early encoding check added in issue 20404
+        def _make_illegal_wrapper():
+            quopri = codecs.lookup("quopri")
+            quopri._is_text_encoding = True
+            try:
+                t = self.TextIOWrapper(self.BytesIO(b'aaaaaa'),
+                                       newline='\n', encoding="quopri")
+            finally:
+                quopri._is_text_encoding = False
+            return t
+        # Crash when decoder returns non-string
+        t = _make_illegal_wrapper()
+        self.assertRaises(TypeError, t.read, 1)
+        t = _make_illegal_wrapper()
+        self.assertRaises(TypeError, t.readline)
+        t = _make_illegal_wrapper()
+        self.assertRaises(TypeError, t.read)
+
+        # Issue 31243: calling read() while the return value of decoder's
+        # getstate() is invalid should neither crash the interpreter nor
+        # raise a SystemError.
+        def _make_very_illegal_wrapper(getstate_ret_val):
+            class BadDecoder:
+                def getstate(self):
+                    return getstate_ret_val
+            def _get_bad_decoder(dummy):
+                return BadDecoder()
+            quopri = codecs.lookup("quopri")
+            with support.swap_attr(quopri, 'incrementaldecoder',
+                                   _get_bad_decoder):
+                return _make_illegal_wrapper()
+        t = _make_very_illegal_wrapper(42)
+        self.assertRaises(TypeError, t.read, 42)
+        t = _make_very_illegal_wrapper(())
+        self.assertRaises(TypeError, t.read, 42)
+        t = _make_very_illegal_wrapper((1, 2))
+        self.assertRaises(TypeError, t.read, 42)
+
+    def _check_create_at_shutdown(self, **kwargs):
+        # Issue #20037: creating a TextIOWrapper at shutdown
+        # shouldn't crash the interpreter.
+        iomod = self.io.__name__
+        code = """if 1:
+            import codecs
+            import {iomod} as io
+
+            # Avoid looking up codecs at shutdown
+            codecs.lookup('utf-8')
+
+            class C:
+                def __del__(self):
+                    io.TextIOWrapper(io.BytesIO(), **{kwargs})
+                    print("ok")
+            c = C()
+            """.format(iomod=iomod, kwargs=kwargs)
+        return assert_python_ok("-c", code)
+
+    def test_create_at_shutdown_without_encoding(self):
+        rc, out, err = self._check_create_at_shutdown()
+        if err:
+            # Can error out with a RuntimeError if the module state
+            # isn't found.
+            self.assertIn(self.shutdown_error, err.decode())
+        else:
+            self.assertEqual("ok", out.decode().strip())
+
+    def test_create_at_shutdown_with_encoding(self):
+        rc, out, err = self._check_create_at_shutdown(encoding='utf-8',
+                                                      errors='strict')
+        self.assertFalse(err)
+        self.assertEqual("ok", out.decode().strip())
+
+    def test_read_byteslike(self):
+        r = MemviewBytesIO(b'Just some random string\n')
+        t = self.TextIOWrapper(r, 'utf-8')
+
+        # TextIOwrapper will not read the full string, because
+        # we truncate it to a multiple of the native int size
+        # so that we can construct a more complex memoryview.
+        bytes_val =  _to_memoryview(r.getvalue()).tobytes()
+
+        self.assertEqual(t.read(200), bytes_val.decode('utf-8'))
+
+    def test_issue22849(self):
+        class F(object):
+            def readable(self): return True
+            def writable(self): return True
+            def seekable(self): return True
+
+        for i in range(10):
+            try:
+                self.TextIOWrapper(F(), encoding='utf-8')
+            except Exception:
+                pass
+
+        F.tell = lambda x: 0
+        t = self.TextIOWrapper(F(), encoding='utf-8')
+
+    def test_reconfigure_locale(self):
+        wrapper = self.TextIOWrapper(self.BytesIO(b"test"))
+        wrapper.reconfigure(encoding="locale")
+
+    def test_reconfigure_encoding_read(self):
+        # latin1 -> utf8
+        # (latin1 can decode utf-8 encoded string)
+        data = 'abc\xe9\n'.encode('latin1') + 'd\xe9f\n'.encode('utf8')
+        raw = self.BytesIO(data)
+        txt = self.TextIOWrapper(raw, encoding='latin1', newline='\n')
+        self.assertEqual(txt.readline(), 'abc\xe9\n')
+        with self.assertRaises(self.UnsupportedOperation):
+            txt.reconfigure(encoding='utf-8')
+        with self.assertRaises(self.UnsupportedOperation):
+            txt.reconfigure(newline=None)
+
+    def test_reconfigure_write_fromascii(self):
+        # ascii has a specific encodefunc in the C implementation,
+        # but utf-8-sig has not. Make sure that we get rid of the
+        # cached encodefunc when we switch encoders.
+        raw = self.BytesIO()
+        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
+        txt.write('foo\n')
+        txt.reconfigure(encoding='utf-8-sig')
+        txt.write('\xe9\n')
+        txt.flush()
+        self.assertEqual(raw.getvalue(), b'foo\n\xc3\xa9\n')
+
+    def test_reconfigure_write(self):
+        # latin -> utf8
+        raw = self.BytesIO()
+        txt = self.TextIOWrapper(raw, encoding='latin1', newline='\n')
+        txt.write('abc\xe9\n')
+        txt.reconfigure(encoding='utf-8')
+        self.assertEqual(raw.getvalue(), b'abc\xe9\n')
+        txt.write('d\xe9f\n')
+        txt.flush()
+        self.assertEqual(raw.getvalue(), b'abc\xe9\nd\xc3\xa9f\n')
+
+        # ascii -> utf-8-sig: ensure that no BOM is written in the middle of
+        # the file
+        raw = self.BytesIO()
+        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
+        txt.write('abc\n')
+        txt.reconfigure(encoding='utf-8-sig')
+        txt.write('d\xe9f\n')
+        txt.flush()
+        self.assertEqual(raw.getvalue(), b'abc\nd\xc3\xa9f\n')
+
+    def test_reconfigure_write_non_seekable(self):
+        raw = self.BytesIO()
+        raw.seekable = lambda: False
+        raw.seek = None
+        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
+        txt.write('abc\n')
+        txt.reconfigure(encoding='utf-8-sig')
+        txt.write('d\xe9f\n')
+        txt.flush()
+
+        # If the raw stream is not seekable, there'll be a BOM
+        self.assertEqual(raw.getvalue(),  b'abc\n\xef\xbb\xbfd\xc3\xa9f\n')
+
+    def test_reconfigure_defaults(self):
+        txt = self.TextIOWrapper(self.BytesIO(), 'ascii', 'replace', '\n')
+        txt.reconfigure(encoding=None)
+        self.assertEqual(txt.encoding, 'ascii')
+        self.assertEqual(txt.errors, 'replace')
+        txt.write('LF\n')
+
+        txt.reconfigure(newline='\r\n')
+        self.assertEqual(txt.encoding, 'ascii')
+        self.assertEqual(txt.errors, 'replace')
+
+        txt.reconfigure(errors='ignore')
+        self.assertEqual(txt.encoding, 'ascii')
+        self.assertEqual(txt.errors, 'ignore')
+        txt.write('CRLF\n')
+
+        txt.reconfigure(encoding='utf-8', newline=None)
+        self.assertEqual(txt.errors, 'strict')
+        txt.seek(0)
+        self.assertEqual(txt.read(), 'LF\nCRLF\n')
+
+        self.assertEqual(txt.detach().getvalue(), b'LF\nCRLF\r\n')
+
+    def test_reconfigure_errors(self):
+        txt = self.TextIOWrapper(self.BytesIO(), 'ascii', 'replace', '\r')
+        with self.assertRaises(TypeError):  # there was a crash
+            txt.reconfigure(encoding=42)
+        if self.is_C:
+            with self.assertRaises(UnicodeEncodeError):
+                txt.reconfigure(encoding='\udcfe')
+            with self.assertRaises(LookupError):
+                txt.reconfigure(encoding='locale\0')
+        # TODO: txt.reconfigure(encoding='utf-8\0')
+        # TODO: txt.reconfigure(encoding='nonexisting')
+        with self.assertRaises(TypeError):
+            txt.reconfigure(errors=42)
+        if self.is_C:
+            with self.assertRaises(UnicodeEncodeError):
+                txt.reconfigure(errors='\udcfe')
+        # TODO: txt.reconfigure(errors='ignore\0')
+        # TODO: txt.reconfigure(errors='nonexisting')
+        with self.assertRaises(TypeError):
+            txt.reconfigure(newline=42)
+        with self.assertRaises(ValueError):
+            txt.reconfigure(newline='\udcfe')
+        with self.assertRaises(ValueError):
+            txt.reconfigure(newline='xyz')
+        if not self.is_C:
+            # TODO: Should fail in C too.
+            with self.assertRaises(ValueError):
+                txt.reconfigure(newline='\n\0')
+        if self.is_C:
+            # TODO: Use __bool__(), not __index__().
+            with self.assertRaises(ZeroDivisionError):
+                txt.reconfigure(line_buffering=BadIndex())
+            with self.assertRaises(OverflowError):
+                txt.reconfigure(line_buffering=2**1000)
+            with self.assertRaises(ZeroDivisionError):
+                txt.reconfigure(write_through=BadIndex())
+            with self.assertRaises(OverflowError):
+                txt.reconfigure(write_through=2**1000)
+            with self.assertRaises(ZeroDivisionError):  # there was a crash
+                txt.reconfigure(line_buffering=BadIndex(),
+                                write_through=BadIndex())
+        self.assertEqual(txt.encoding, 'ascii')
+        self.assertEqual(txt.errors, 'replace')
+        self.assertIs(txt.line_buffering, False)
+        self.assertIs(txt.write_through, False)
+
+        txt.reconfigure(encoding='latin1', errors='ignore', newline='\r\n',
+                        line_buffering=True, write_through=True)
+        self.assertEqual(txt.encoding, 'latin1')
+        self.assertEqual(txt.errors, 'ignore')
+        self.assertIs(txt.line_buffering, True)
+        self.assertIs(txt.write_through, True)
+
+    def test_reconfigure_newline(self):
+        raw = self.BytesIO(b'CR\rEOF')
+        txt = self.TextIOWrapper(raw, 'ascii', newline='\n')
+        txt.reconfigure(newline=None)
+        self.assertEqual(txt.readline(), 'CR\n')
+        raw = self.BytesIO(b'CR\rEOF')
+        txt = self.TextIOWrapper(raw, 'ascii', newline='\n')
+        txt.reconfigure(newline='')
+        self.assertEqual(txt.readline(), 'CR\r')
+        raw = self.BytesIO(b'CR\rLF\nEOF')
+        txt = self.TextIOWrapper(raw, 'ascii', newline='\r')
+        txt.reconfigure(newline='\n')
+        self.assertEqual(txt.readline(), 'CR\rLF\n')
+        raw = self.BytesIO(b'LF\nCR\rEOF')
+        txt = self.TextIOWrapper(raw, 'ascii', newline='\n')
+        txt.reconfigure(newline='\r')
+        self.assertEqual(txt.readline(), 'LF\nCR\r')
+        raw = self.BytesIO(b'CR\rCRLF\r\nEOF')
+        txt = self.TextIOWrapper(raw, 'ascii', newline='\r')
+        txt.reconfigure(newline='\r\n')
+        self.assertEqual(txt.readline(), 'CR\rCRLF\r\n')
+
+        txt = self.TextIOWrapper(self.BytesIO(), 'ascii', newline='\r')
+        txt.reconfigure(newline=None)
+        txt.write('linesep\n')
+        txt.reconfigure(newline='')
+        txt.write('LF\n')
+        txt.reconfigure(newline='\n')
+        txt.write('LF\n')
+        txt.reconfigure(newline='\r')
+        txt.write('CR\n')
+        txt.reconfigure(newline='\r\n')
+        txt.write('CRLF\n')
+        expected = 'linesep' + os.linesep + 'LF\nLF\nCR\rCRLF\r\n'
+        self.assertEqual(txt.detach().getvalue().decode('ascii'), expected)
+
+    def test_issue25862(self):
+        # Assertion failures occurred in tell() after read() and write().
+        t = self.TextIOWrapper(self.BytesIO(b'test'), encoding='ascii')
+        t.read(1)
+        t.read()
+        t.tell()
+        t = self.TextIOWrapper(self.BytesIO(b'test'), encoding='ascii')
+        t.read(1)
+        t.write('x')
+        t.tell()
+
+    def test_issue35928(self):
+        p = self.BufferedRWPair(self.BytesIO(b'foo\nbar\n'), self.BytesIO())
+        f = self.TextIOWrapper(p)
+        res = f.readline()
+        self.assertEqual(res, 'foo\n')
+        f.write(res)
+        self.assertEqual(res + f.readline(), 'foo\nbar\n')
+
+    def test_pickling_subclass(self):
+        global MyTextIO
+        class MyTextIO(self.TextIOWrapper):
+            def __init__(self, raw, tag):
+                super().__init__(raw)
+                self.tag = tag
+            def __getstate__(self):
+                return self.tag, self.buffer.getvalue()
+            def __setstate__(slf, state):
+                tag, value = state
+                slf.__init__(self.BytesIO(value), tag)
+
+        raw = self.BytesIO(b'data')
+        txt = MyTextIO(raw, 'ham')
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(protocol=proto):
+                pickled = pickle.dumps(txt, proto)
+                newtxt = pickle.loads(pickled)
+                self.assertEqual(newtxt.buffer.getvalue(), b'data')
+                self.assertEqual(newtxt.tag, 'ham')
+        del MyTextIO
+
+    @unittest.skipUnless(hasattr(os, "pipe"), "requires os.pipe()")
+    def test_read_non_blocking(self):
+        import os
+        r, w = os.pipe()
+        try:
+            os.set_blocking(r, False)
+            with self.io.open(r, 'rt') as textfile:
+                r = None
+                # Nothing has been written so a non-blocking read raises a BlockingIOError exception.
+                with self.assertRaises(BlockingIOError):
+                    textfile.read()
+        finally:
+            if r is not None:
+                os.close(r)
+            os.close(w)
+
+
+class MemviewBytesIO(io.BytesIO):
+    '''A BytesIO object whose read method returns memoryviews
+       rather than bytes'''
+
+    def read1(self, len_):
+        return _to_memoryview(super().read1(len_))
+
+    def read(self, len_):
+        return _to_memoryview(super().read(len_))
+
+def _to_memoryview(buf):
+    '''Convert bytes-object *buf* to a non-trivial memoryview'''
+
+    arr = array.array('i')
+    idx = len(buf) - len(buf) % arr.itemsize
+    arr.frombytes(buf[:idx])
+    return memoryview(arr)
+
+
+class CTextIOWrapperTest(TextIOWrapperTest, CTestCase):
+    shutdown_error = "LookupError: unknown encoding: ascii"
+
+    def test_initialization(self):
+        r = self.BytesIO(b"\xc3\xa9\n\n")
+        b = self.BufferedReader(r, 1000)
+        t = self.TextIOWrapper(b, encoding="utf-8")
+        self.assertRaises(ValueError, t.__init__, b, encoding="utf-8", newline='xyzzy')
+        self.assertRaises(ValueError, t.read)
+
+        t = self.TextIOWrapper.__new__(self.TextIOWrapper)
+        self.assertRaises(Exception, repr, t)
+
+    @unittest.skipIf(sys.platform == "win32", "TODO: RUSTPYTHON; cyclic GC not supported, causes file locking")
+    def test_garbage_collection(self):
+        # C TextIOWrapper objects are collected, and collecting them flushes
+        # all data to disk.
+        # The Python version has __del__, so it ends in gc.garbage instead.
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", ResourceWarning)
+            rawio = self.FileIO(os_helper.TESTFN, "wb")
+            b = self.BufferedWriter(rawio)
+            t = self.TextIOWrapper(b, encoding="ascii")
+            t.write("456def")
+            t.x = t
+            wr = weakref.ref(t)
+            del t
+            support.gc_collect()
+        self.assertIsNone(wr(), wr)
+        with self.open(os_helper.TESTFN, "rb") as f:
+            self.assertEqual(f.read(), b"456def")
+
+    def test_rwpair_cleared_before_textio(self):
+        # Issue 13070: TextIOWrapper's finalization would crash when called
+        # after the reference to the underlying BufferedRWPair's writer got
+        # cleared by the GC.
+        for i in range(1000):
+            b1 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
+            t1 = self.TextIOWrapper(b1, encoding="ascii")
+            b2 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
+            t2 = self.TextIOWrapper(b2, encoding="ascii")
+            # circular references
+            t1.buddy = t2
+            t2.buddy = t1
+        support.gc_collect()
+
+    def test_del__CHUNK_SIZE_SystemError(self):
+        t = self.TextIOWrapper(self.BytesIO(), encoding='ascii')
+        with self.assertRaises(AttributeError):
+            del t._CHUNK_SIZE
+
+    def test_internal_buffer_size(self):
+        # bpo-43260: TextIOWrapper's internal buffer should not store
+        # data larger than chunk size.
+        chunk_size = 8192  # default chunk size, updated later
+
+        class MockIO(self.MockRawIO):
+            def write(self, data):
+                if len(data) > chunk_size:
+                    raise RuntimeError
+                return super().write(data)
+
+        buf = MockIO()
+        t = self.TextIOWrapper(buf, encoding="ascii")
+        chunk_size = t._CHUNK_SIZE
+        t.write("abc")
+        t.write("def")
+        # default chunk size is 8192 bytes so t don't write data to buf.
+        self.assertEqual([], buf._write_stack)
+
+        with self.assertRaises(RuntimeError):
+            t.write("x"*(chunk_size+1))
+
+        self.assertEqual([b"abcdef"], buf._write_stack)
+        t.write("ghi")
+        t.write("x"*chunk_size)
+        self.assertEqual([b"abcdef", b"ghi", b"x"*chunk_size], buf._write_stack)
+
+    def test_issue119506(self):
+        chunk_size = 8192
+
+        class MockIO(self.MockRawIO):
+            written = False
+            def write(self, data):
+                if not self.written:
+                    self.written = True
+                    t.write("middle")
+                return super().write(data)
+
+        buf = MockIO()
+        t = self.TextIOWrapper(buf)
+        t.write("abc")
+        t.write("def")
+        # writing data which size >= chunk_size cause flushing buffer before write.
+        t.write("g" * chunk_size)
+        t.flush()
+
+        self.assertEqual([b"abcdef", b"middle", b"g"*chunk_size],
+                         buf._write_stack)
+
+    def test_issue142594(self):
+        wrapper = None
+        detached = False
+        class ReentrantRawIO(self.RawIOBase):
+            @property
+            def closed(self):
+                nonlocal detached
+                if wrapper is not None and not detached:
+                    detached = True
+                    wrapper.detach()
+                return False
+
+        raw = ReentrantRawIO()
+        wrapper = self.TextIOWrapper(raw)
+        wrapper.close()  # should not crash
+
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; TypeError: a bytes-like object is required, not 'NoneType'
+    def test_read_non_blocking(self):
+        return super().test_read_non_blocking()
+
+
+class PyTextIOWrapperTest(TextIOWrapperTest, PyTestCase):
+    shutdown_error = "LookupError: unknown encoding: ascii"
+
+
+class IncrementalNewlineDecoderTest:
+
+    def check_newline_decoding_utf8(self, decoder):
+        # UTF-8 specific tests for a newline decoder
+        def _check_decode(b, s, **kwargs):
+            # We exercise getstate() / setstate() as well as decode()
+            state = decoder.getstate()
+            self.assertEqual(decoder.decode(b, **kwargs), s)
+            decoder.setstate(state)
+            self.assertEqual(decoder.decode(b, **kwargs), s)
+
+        _check_decode(b'\xe8\xa2\x88', "\u8888")
+
+        _check_decode(b'\xe8', "")
+        _check_decode(b'\xa2', "")
+        _check_decode(b'\x88', "\u8888")
+
+        _check_decode(b'\xe8', "")
+        _check_decode(b'\xa2', "")
+        _check_decode(b'\x88', "\u8888")
+
+        _check_decode(b'\xe8', "")
+        self.assertRaises(UnicodeDecodeError, decoder.decode, b'', final=True)
+
+        decoder.reset()
+        _check_decode(b'\n', "\n")
+        _check_decode(b'\r', "")
+        _check_decode(b'', "\n", final=True)
+        _check_decode(b'\r', "\n", final=True)
+
+        _check_decode(b'\r', "")
+        _check_decode(b'a', "\na")
+
+        _check_decode(b'\r\r\n', "\n\n")
+        _check_decode(b'\r', "")
+        _check_decode(b'\r', "\n")
+        _check_decode(b'\na', "\na")
+
+        _check_decode(b'\xe8\xa2\x88\r\n', "\u8888\n")
+        _check_decode(b'\xe8\xa2\x88', "\u8888")
+        _check_decode(b'\n', "\n")
+        _check_decode(b'\xe8\xa2\x88\r', "\u8888")
+        _check_decode(b'\n', "\n")
+
+    def check_newline_decoding(self, decoder, encoding):
+        result = []
+        if encoding is not None:
+            encoder = codecs.getincrementalencoder(encoding)()
+            def _decode_bytewise(s):
+                # Decode one byte at a time
+                for b in encoder.encode(s):
+                    result.append(decoder.decode(bytes([b])))
+        else:
+            encoder = None
+            def _decode_bytewise(s):
+                # Decode one char at a time
+                for c in s:
+                    result.append(decoder.decode(c))
+        self.assertEqual(decoder.newlines, None)
+        _decode_bytewise("abc\n\r")
+        self.assertEqual(decoder.newlines, '\n')
+        _decode_bytewise("\nabc")
+        self.assertEqual(decoder.newlines, ('\n', '\r\n'))
+        _decode_bytewise("abc\r")
+        self.assertEqual(decoder.newlines, ('\n', '\r\n'))
+        _decode_bytewise("abc")
+        self.assertEqual(decoder.newlines, ('\r', '\n', '\r\n'))
+        _decode_bytewise("abc\r")
+        self.assertEqual("".join(result), "abc\n\nabcabc\nabcabc")
+        decoder.reset()
+        input = "abc"
+        if encoder is not None:
+            encoder.reset()
+            input = encoder.encode(input)
+        self.assertEqual(decoder.decode(input), "abc")
+        self.assertEqual(decoder.newlines, None)
+
+    def test_newline_decoder(self):
+        encodings = (
+            # None meaning the IncrementalNewlineDecoder takes unicode input
+            # rather than bytes input
+            None, 'utf-8', 'latin-1',
+            'utf-16', 'utf-16-le', 'utf-16-be',
+            'utf-32', 'utf-32-le', 'utf-32-be',
+        )
+        for enc in encodings:
+            decoder = enc and codecs.getincrementaldecoder(enc)()
+            decoder = self.IncrementalNewlineDecoder(decoder, translate=True)
+            self.check_newline_decoding(decoder, enc)
+        decoder = codecs.getincrementaldecoder("utf-8")()
+        decoder = self.IncrementalNewlineDecoder(decoder, translate=True)
+        self.check_newline_decoding_utf8(decoder)
+        self.assertRaises(TypeError, decoder.setstate, 42)
+
+    def test_newline_bytes(self):
+        # Issue 5433: Excessive optimization in IncrementalNewlineDecoder
+        def _check(dec):
+            self.assertEqual(dec.newlines, None)
+            self.assertEqual(dec.decode("\u0D00"), "\u0D00")
+            self.assertEqual(dec.newlines, None)
+            self.assertEqual(dec.decode("\u0A00"), "\u0A00")
+            self.assertEqual(dec.newlines, None)
+        dec = self.IncrementalNewlineDecoder(None, translate=False)
+        _check(dec)
+        dec = self.IncrementalNewlineDecoder(None, translate=True)
+        _check(dec)
+
+    def test_translate(self):
+        # issue 35062
+        for translate in (-2, -1, 1, 2):
+            decoder = codecs.getincrementaldecoder("utf-8")()
+            decoder = self.IncrementalNewlineDecoder(decoder, translate)
+            self.check_newline_decoding_utf8(decoder)
+        decoder = codecs.getincrementaldecoder("utf-8")()
+        decoder = self.IncrementalNewlineDecoder(decoder, translate=0)
+        self.assertEqual(decoder.decode(b"\r\r\n"), "\r\r\n")
+
+class CIncrementalNewlineDecoderTest(IncrementalNewlineDecoderTest, unittest.TestCase):
+    IncrementalNewlineDecoder = io.IncrementalNewlineDecoder
+
+    @support.cpython_only
+    def test_uninitialized(self):
+        uninitialized = self.IncrementalNewlineDecoder.__new__(
+            self.IncrementalNewlineDecoder)
+        self.assertRaises(ValueError, uninitialized.decode, b'bar')
+        self.assertRaises(ValueError, uninitialized.getstate)
+        self.assertRaises(ValueError, uninitialized.setstate, (b'foo', 0))
+        self.assertRaises(ValueError, uninitialized.reset)
+
+
+class PyIncrementalNewlineDecoderTest(IncrementalNewlineDecoderTest, unittest.TestCase):
+    IncrementalNewlineDecoder = pyio.IncrementalNewlineDecoder
diff --git a/Lib/test/test_univnewlines.py b/Lib/test/test_io/test_univnewlines.py
similarity index 100%
rename from Lib/test/test_univnewlines.py
rename to Lib/test/test_io/test_univnewlines.py
diff --git a/Lib/test/test_io/utils.py b/Lib/test/test_io/utils.py
new file mode 100644
index 00000000000..3b1faec2140
--- /dev/null
+++ b/Lib/test/test_io/utils.py
@@ -0,0 +1,318 @@
+import array
+import threading
+import time
+import unittest
+
+import io  # C implementation of io
+import _pyio as pyio # Python implementation of io
+
+
+try:
+    import ctypes
+except ImportError:
+    def byteslike(*pos, **kw):
+        return array.array("b", bytes(*pos, **kw))
+else:
+    class EmptyStruct(ctypes.Structure):
+        pass
+
+    def byteslike(*pos, **kw):
+        """Create a bytes-like object having no string or sequence methods"""
+        data = bytes(*pos, **kw)
+        obj = EmptyStruct()
+        ctypes.resize(obj, len(data))
+        memoryview(obj).cast("B")[:] = data
+        return obj
+
+
+class MockRawIOWithoutRead:
+    """A RawIO implementation without read(), so as to exercise the default
+    RawIO.read() which calls readinto()."""
+
+    def __init__(self, read_stack=()):
+        self._read_stack = list(read_stack)
+        self._write_stack = []
+        self._reads = 0
+        self._extraneous_reads = 0
+
+    def write(self, b):
+        self._write_stack.append(bytes(b))
+        return len(b)
+
+    def writable(self):
+        return True
+
+    def fileno(self):
+        return 42
+
+    def readable(self):
+        return True
+
+    def seekable(self):
+        return True
+
+    def seek(self, pos, whence):
+        return 0   # wrong but we gotta return something
+
+    def tell(self):
+        return 0   # same comment as above
+
+    def readinto(self, buf):
+        self._reads += 1
+        max_len = len(buf)
+        try:
+            data = self._read_stack[0]
+        except IndexError:
+            self._extraneous_reads += 1
+            return 0
+        if data is None:
+            del self._read_stack[0]
+            return None
+        n = len(data)
+        if len(data) <= max_len:
+            del self._read_stack[0]
+            buf[:n] = data
+            return n
+        else:
+            buf[:] = data[:max_len]
+            self._read_stack[0] = data[max_len:]
+            return max_len
+
+    def truncate(self, pos=None):
+        return pos
+
+class CMockRawIOWithoutRead(MockRawIOWithoutRead, io.RawIOBase):
+    pass
+
+class PyMockRawIOWithoutRead(MockRawIOWithoutRead, pyio.RawIOBase):
+    pass
+
+
+class MockRawIO(MockRawIOWithoutRead):
+
+    def read(self, n=None):
+        self._reads += 1
+        try:
+            return self._read_stack.pop(0)
+        except:
+            self._extraneous_reads += 1
+            return b""
+
+class CMockRawIO(MockRawIO, io.RawIOBase):
+    pass
+
+class PyMockRawIO(MockRawIO, pyio.RawIOBase):
+    pass
+
+
+class MisbehavedRawIO(MockRawIO):
+    def write(self, b):
+        return super().write(b) * 2
+
+    def read(self, n=None):
+        return super().read(n) * 2
+
+    def seek(self, pos, whence):
+        return -123
+
+    def tell(self):
+        return -456
+
+    def readinto(self, buf):
+        super().readinto(buf)
+        return len(buf) * 5
+
+class CMisbehavedRawIO(MisbehavedRawIO, io.RawIOBase):
+    pass
+
+class PyMisbehavedRawIO(MisbehavedRawIO, pyio.RawIOBase):
+    pass
+
+
+class SlowFlushRawIO(MockRawIO):
+    def __init__(self):
+        super().__init__()
+        self.in_flush = threading.Event()
+
+    def flush(self):
+        self.in_flush.set()
+        time.sleep(0.25)
+
+class CSlowFlushRawIO(SlowFlushRawIO, io.RawIOBase):
+    pass
+
+class PySlowFlushRawIO(SlowFlushRawIO, pyio.RawIOBase):
+    pass
+
+
+class CloseFailureIO(MockRawIO):
+    closed = 0
+
+    def close(self):
+        if not self.closed:
+            self.closed = 1
+            raise OSError
+
+class CCloseFailureIO(CloseFailureIO, io.RawIOBase):
+    pass
+
+class PyCloseFailureIO(CloseFailureIO, pyio.RawIOBase):
+    pass
+
+
+class MockFileIO:
+
+    def __init__(self, data):
+        self.read_history = []
+        super().__init__(data)
+
+    def read(self, n=None):
+        res = super().read(n)
+        self.read_history.append(None if res is None else len(res))
+        return res
+
+    def readinto(self, b):
+        res = super().readinto(b)
+        self.read_history.append(res)
+        return res
+
+class CMockFileIO(MockFileIO, io.BytesIO):
+    pass
+
+class PyMockFileIO(MockFileIO, pyio.BytesIO):
+    pass
+
+
+class MockUnseekableIO:
+    def seekable(self):
+        return False
+
+    def seek(self, *args):
+        raise self.UnsupportedOperation("not seekable")
+
+    def tell(self, *args):
+        raise self.UnsupportedOperation("not seekable")
+
+    def truncate(self, *args):
+        raise self.UnsupportedOperation("not seekable")
+
+class CMockUnseekableIO(MockUnseekableIO, io.BytesIO):
+    UnsupportedOperation = io.UnsupportedOperation
+
+class PyMockUnseekableIO(MockUnseekableIO, pyio.BytesIO):
+    UnsupportedOperation = pyio.UnsupportedOperation
+
+
+class MockCharPseudoDevFileIO(MockFileIO):
+    # GH-95782
+    # ftruncate() does not work on these special files (and CPython then raises
+    # appropriate exceptions), so truncate() does not have to be accounted for
+    # here.
+    def __init__(self, data):
+        super().__init__(data)
+
+    def seek(self, *args):
+        return 0
+
+    def tell(self, *args):
+        return 0
+
+class CMockCharPseudoDevFileIO(MockCharPseudoDevFileIO, io.BytesIO):
+    pass
+
+class PyMockCharPseudoDevFileIO(MockCharPseudoDevFileIO, pyio.BytesIO):
+    pass
+
+
+class MockNonBlockWriterIO:
+
+    def __init__(self):
+        self._write_stack = []
+        self._blocker_char = None
+
+    def pop_written(self):
+        s = b"".join(self._write_stack)
+        self._write_stack[:] = []
+        return s
+
+    def block_on(self, char):
+        """Block when a given char is encountered."""
+        self._blocker_char = char
+
+    def readable(self):
+        return True
+
+    def seekable(self):
+        return True
+
+    def seek(self, pos, whence=0):
+        # naive implementation, enough for tests
+        return 0
+
+    def writable(self):
+        return True
+
+    def write(self, b):
+        b = bytes(b)
+        n = -1
+        if self._blocker_char:
+            try:
+                n = b.index(self._blocker_char)
+            except ValueError:
+                pass
+            else:
+                if n > 0:
+                    # write data up to the first blocker
+                    self._write_stack.append(b[:n])
+                    return n
+                else:
+                    # cancel blocker and indicate would block
+                    self._blocker_char = None
+                    return None
+        self._write_stack.append(b)
+        return len(b)
+
+class CMockNonBlockWriterIO(MockNonBlockWriterIO, io.RawIOBase):
+    BlockingIOError = io.BlockingIOError
+
+class PyMockNonBlockWriterIO(MockNonBlockWriterIO, pyio.RawIOBase):
+    BlockingIOError = pyio.BlockingIOError
+
+
+# Build classes which point to all the right mocks per io implementation
+class CTestCase(unittest.TestCase):
+    io = io
+    is_C = True
+
+    MockRawIO = CMockRawIO
+    MisbehavedRawIO = CMisbehavedRawIO
+    MockFileIO = CMockFileIO
+    CloseFailureIO = CCloseFailureIO
+    MockNonBlockWriterIO = CMockNonBlockWriterIO
+    MockUnseekableIO = CMockUnseekableIO
+    MockRawIOWithoutRead = CMockRawIOWithoutRead
+    SlowFlushRawIO = CSlowFlushRawIO
+    MockCharPseudoDevFileIO = CMockCharPseudoDevFileIO
+
+    # Use the class as a proxy to the io module members.
+    def __getattr__(self, name):
+        return getattr(io, name)
+
+
+class PyTestCase(unittest.TestCase):
+    io = pyio
+    is_C = False
+
+    MockRawIO = PyMockRawIO
+    MisbehavedRawIO = PyMisbehavedRawIO
+    MockFileIO = PyMockFileIO
+    CloseFailureIO = PyCloseFailureIO
+    MockNonBlockWriterIO = PyMockNonBlockWriterIO
+    MockUnseekableIO = PyMockUnseekableIO
+    MockRawIOWithoutRead = PyMockRawIOWithoutRead
+    SlowFlushRawIO = PySlowFlushRawIO
+    MockCharPseudoDevFileIO = PyMockCharPseudoDevFileIO
+
+    # Use the class as a proxy to the _pyio module members.
+    def __getattr__(self, name):
+        return getattr(pyio, name)
diff --git a/Lib/test/test_ipaddress.py b/Lib/test/test_ipaddress.py
index 8af91e857d8..3f017b97dc2 100644
--- a/Lib/test/test_ipaddress.py
+++ b/Lib/test/test_ipaddress.py
@@ -2303,6 +2303,10 @@ def testReservedIpv4(self):
         self.assertEqual(False, ipaddress.ip_network('240.0.0.0').is_multicast)
         self.assertEqual(True, ipaddress.ip_network('240.0.0.0').is_reserved)
 
+        self.assertTrue(ipaddress.ip_interface('0.0.0.0/32').is_unspecified)
+        self.assertFalse(ipaddress.ip_interface('0.0.0.0/31').is_unspecified)
+        self.assertFalse(ipaddress.ip_interface('1.2.3.4/32').is_unspecified)
+
         self.assertEqual(True, ipaddress.ip_interface(
                 '192.168.1.1/17').is_private)
         self.assertEqual(False, ipaddress.ip_network('192.169.0.0').is_private)
@@ -2851,5 +2855,15 @@ def testNetworkV6HashCollisions(self):
         )
 
 
+class TestModule(unittest.TestCase):
+    def test_deprecated__version__(self):
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            "'__version__' is deprecated and slated for removal in Python 3.20",
+        ) as cm:
+            getattr(ipaddress, "__version__")
+        self.assertEqual(cm.filename, __file__)
+
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/Lib/test/test_json/test_decode.py b/Lib/test/test_json/test_decode.py
index 6d6ca11f673..13938ed3316 100644
--- a/Lib/test/test_json/test_decode.py
+++ b/Lib/test/test_json/test_decode.py
@@ -1,4 +1,5 @@
 import decimal
+import unittest.mock
 from io import StringIO
 from collections import OrderedDict
 from test.test_json import PyTest, CTest
@@ -49,6 +50,26 @@ def test_empty_objects(self):
         self.assertEqual(self.loads('[]'), [])
         self.assertEqual(self.loads('""'), "")
 
+    def test_object_hook(self):
+        s = '{"a":{"b":{}}}'
+
+        expected_result = {"a":{"b":{"x":1}, "x":1}, "x":1}
+        expected_hook_arguments = [
+            {}, {"b": {"x":1}}, {"a": {"b": {"x":1}, "x":1}}
+        ]
+
+        hook_arguments = []
+
+        def hook(x):
+            hook_arguments.append(x)
+            return {**x, "x":1}
+
+        result = self.loads(s, object_hook=hook)
+
+        self.assertEqual(result, expected_result)
+        self.assertEqual(hook_arguments, expected_hook_arguments)
+
+
     def test_object_pairs_hook(self):
         s = '{"xkd":1, "kcw":2, "art":3, "hxm":4, "qrt":5, "pad":6, "hoy":7}'
         p = [("xkd", 1), ("kcw", 2), ("art", 3), ("hxm", 4),
@@ -71,6 +92,31 @@ def test_object_pairs_hook(self):
                                     object_pairs_hook=OrderedDict),
                          OrderedDict([('empty', OrderedDict())]))
 
+    def test_array_hook(self):
+        s = '[1, 2, 3]'
+        t = self.loads(s, array_hook=tuple)
+        self.assertEqual(t, (1, 2, 3))
+        self.assertEqual(type(t), tuple)
+
+        # Nested array in inner structure with object_hook
+        s = '{"xkd": [[1], [2], [3]]}'
+        p = frozendict(xkd=((1,), (2,), (3,)))
+        data = self.loads(s, object_hook=frozendict, array_hook=tuple)
+        self.assertEqual(data, p)
+        self.assertEqual(type(data), frozendict)
+        self.assertEqual(type(data["xkd"]), tuple)
+        for item in data["xkd"]:
+            self.assertEqual(type(item), tuple)
+
+        self.assertEqual(self.loads('[]', array_hook=tuple), ())
+
+    def test_load_array_hook(self):
+        # json.load must forward array_hook to loads
+        fp = StringIO('[10, 20, 30]')
+        result = self.json.load(fp, array_hook=tuple)
+        self.assertEqual(result, (10, 20, 30))
+        self.assertEqual(type(result), tuple)
+
     def test_decoder_optimizations(self):
         # Several optimizations were made that skip over calls to
         # the whitespace regex, so this test is designed to try and
@@ -125,6 +171,10 @@ def test_negative_index(self):
         d = self.json.JSONDecoder()
         self.assertRaises(ValueError, d.raw_decode, 'a'*42, -50000)
 
+    def test_unterminated_string(self):
+        d = self.json.JSONDecoder()
+        self.assertRaises(self.JSONDecodeError, d.raw_decode, '"\\')
+
     def test_limit_int(self):
         maxdigits = 5000
         with support.adjust_int_max_str_digits(maxdigits):
@@ -132,9 +182,20 @@ def test_limit_int(self):
             with self.assertRaises(ValueError):
                 self.loads('1' * (maxdigits + 1))
 
+    def test_explicit_cls_skips_json_decoder_default(self):
+        class CustomDecoder:
+            pass
+
+        with unittest.mock.patch.object(
+                CustomDecoder, 'decode', create=True) as mock_decode:
+            self.loads('{}', cls=CustomDecoder)
+        mock_decode.assert_called_once()
+
 
 class TestPyDecode(TestDecode, PyTest): pass
 class TestCDecode(TestDecode, CTest):
+    pass
+
     @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_limit_int(self):
         return super().test_limit_int()
diff --git a/Lib/test/test_json/test_dump.py b/Lib/test/test_json/test_dump.py
index 39470754003..5bc03085e60 100644
--- a/Lib/test/test_json/test_dump.py
+++ b/Lib/test/test_json/test_dump.py
@@ -12,6 +12,18 @@ def test_dump(self):
     def test_dumps(self):
         self.assertEqual(self.dumps({}), '{}')
 
+    def test_dumps_dict(self):
+        self.assertEqual(self.dumps({'x': 1, 'y': 2}),
+                         '{"x": 1, "y": 2}')
+        self.assertEqual(self.dumps(frozendict({'x': 1, 'y': 2})),
+                         '{"x": 1, "y": 2}')
+        lst = [{'x': 1}, frozendict(y=2)]
+        self.assertEqual(self.dumps(lst),
+                         '[{"x": 1}, {"y": 2}]')
+        data = {'x': dict(a=1), 'y': frozendict(b=2)}
+        self.assertEqual(self.dumps(data),
+                         '{"x": {"a": 1}, "y": {"b": 2}}')
+
     def test_dump_skipkeys(self):
         v = {b'invalid_key': False, 'valid_key': True}
         with self.assertRaises(TypeError):
@@ -65,6 +77,59 @@ def __lt__(self, o):
         d[1337] = "true.dat"
         self.assertEqual(self.dumps(d, sort_keys=True), '{"1337": "true.dat"}')
 
+    # gh-145244: UAF on borrowed key when default callback mutates dict
+    def test_default_clears_dict_key_uaf(self):
+        class Evil:
+            pass
+
+        class AlsoEvil:
+            pass
+
+        # Use a non-interned string key so it can actually be freed
+        key = "A" * 100
+        target = {key: Evil()}
+        del key
+
+        def evil_default(obj):
+            if isinstance(obj, Evil):
+                target.clear()
+                return AlsoEvil()
+            raise TypeError("not serializable")
+
+        with self.assertRaises(TypeError):
+            self.json.dumps(target, default=evil_default,
+                            check_circular=False)
+
+    def test_dumps_str_subclass(self):
+        # Don't call obj.__str__() on str subclasses
+
+        # str subclass which returns a different string on str(obj)
+        class StrSubclass(str):
+            def __str__(self):
+                return "StrSubclass"
+
+        obj = StrSubclass('ascii')
+        self.assertEqual(self.dumps(obj), '"ascii"')
+        self.assertEqual(self.dumps([obj]), '["ascii"]')
+        self.assertEqual(self.dumps({'key': obj}), '{"key": "ascii"}')
+
+        obj = StrSubclass('escape\n')
+        self.assertEqual(self.dumps(obj), '"escape\\n"')
+        self.assertEqual(self.dumps([obj]), '["escape\\n"]')
+        self.assertEqual(self.dumps({'key': obj}), '{"key": "escape\\n"}')
+
+        obj = StrSubclass('nonascii:é')
+        self.assertEqual(self.dumps(obj, ensure_ascii=False),
+                         '"nonascii:é"')
+        self.assertEqual(self.dumps([obj], ensure_ascii=False),
+                         '["nonascii:é"]')
+        self.assertEqual(self.dumps({'key': obj}, ensure_ascii=False),
+                         '{"key": "nonascii:é"}')
+        self.assertEqual(self.dumps(obj), '"nonascii:\\u00e9"')
+        self.assertEqual(self.dumps([obj]), '["nonascii:\\u00e9"]')
+        self.assertEqual(self.dumps({'key': obj}),
+                         '{"key": "nonascii:\\u00e9"}')
+
 
 class TestPyDump(TestDump, PyTest): pass
 
diff --git a/Lib/test/test_json/test_encode_basestring_ascii.py b/Lib/test/test_json/test_encode_basestring_ascii.py
index c90d3e968e5..1b5dfcfde01 100644
--- a/Lib/test/test_json/test_encode_basestring_ascii.py
+++ b/Lib/test/test_json/test_encode_basestring_ascii.py
@@ -3,6 +3,11 @@
 from test.support import bigaddrspacetest
 
 
+# str subclass which returns a different string on str(obj)
+class StrSubclass(str):
+    def __str__(self):
+        return "StrSubclass"
+
 CASES = [
     ('/\\"\ucafe\ubabe\uab98\ufcde\ubcda\uef4a\x08\x0c\n\r\t`1~!@#$%^&*()_+-=[]{}|;:\',./<>?', '"/\\\\\\"\\ucafe\\ubabe\\uab98\\ufcde\\ubcda\\uef4a\\b\\f\\n\\r\\t`1~!@#$%^&*()_+-=[]{}|;:\',./<>?"'),
     ('\u0123\u4567\u89ab\ucdef\uabcd\uef4a', '"\\u0123\\u4567\\u89ab\\ucdef\\uabcd\\uef4a"'),
@@ -14,6 +19,8 @@
     ('\U0001d120', '"\\ud834\\udd20"'),
     ('\u03b1\u03a9', '"\\u03b1\\u03a9"'),
     ("`1~!@#$%^&*()_+-={':[,]}|;.</>?", '"`1~!@#$%^&*()_+-={\':[,]}|;.</>?"'),
+    # Don't call obj.__str__() on str subclasses
+    (StrSubclass('ascii'), '"ascii"'),
 ]
 
 class TestEncodeBasestringAscii:
diff --git a/Lib/test/test_json/test_enum.py b/Lib/test/test_json/test_enum.py
index 10f414898b8..518c3e11200 100644
--- a/Lib/test/test_json/test_enum.py
+++ b/Lib/test/test_json/test_enum.py
@@ -26,11 +26,14 @@ class FloatNum(float, Enum):
 NEG_INF = float('-inf')
 NAN = float('nan')
 
-class WierdNum(float, Enum):
+class WeirdNum(float, Enum):
     inf = INF
     neg_inf = NEG_INF
     nan = NAN
 
+class StringEnum(str, Enum):
+    COLOR = "color"
+
 class TestEnum:
 
     def test_floats(self):
@@ -40,7 +43,7 @@ def test_floats(self):
             self.assertEqual(self.loads(self.dumps(enum)), enum)
 
     def test_weird_floats(self):
-        for enum, expected in zip(WierdNum, ('Infinity', '-Infinity', 'NaN')):
+        for enum, expected in zip(WeirdNum, ('Infinity', '-Infinity', 'NaN')):
             self.assertEqual(self.dumps(enum), expected)
             if not isnan(enum):
                 self.assertEqual(float(self.dumps(enum)), enum)
@@ -64,16 +67,16 @@ def test_list(self):
                          str([E, PI, TAU]))
         self.assertEqual(self.loads(self.dumps(list(FloatNum))),
                          list(FloatNum))
-        self.assertEqual(self.dumps(list(WierdNum)),
+        self.assertEqual(self.dumps(list(WeirdNum)),
                         '[Infinity, -Infinity, NaN]')
-        self.assertEqual(self.loads(self.dumps(list(WierdNum)))[:2],
-                         list(WierdNum)[:2])
-        self.assertTrue(isnan(self.loads(self.dumps(list(WierdNum)))[2]))
+        self.assertEqual(self.loads(self.dumps(list(WeirdNum)))[:2],
+                         list(WeirdNum)[:2])
+        self.assertTrue(isnan(self.loads(self.dumps(list(WeirdNum)))[2]))
 
     def test_dict_keys(self):
         s, b, h, r = BigNum
         e, p, t = FloatNum
-        i, j, n = WierdNum
+        i, j, n = WeirdNum
         d = {
             s:'tiny', b:'large', h:'larger', r:'largest',
             e:"Euler's number", p:'pi', t:'tau',
@@ -100,9 +103,9 @@ def test_dict_values(self):
                 e=FloatNum.e,
                 pi=FloatNum.pi,
                 tau=FloatNum.tau,
-                i=WierdNum.inf,
-                j=WierdNum.neg_inf,
-                n=WierdNum.nan,
+                i=WeirdNum.inf,
+                j=WeirdNum.neg_inf,
+                n=WeirdNum.nan,
                 )
         nd = self.loads(self.dumps(d))
         self.assertEqual(nd['tiny'], SMALL)
@@ -116,5 +119,11 @@ def test_dict_values(self):
         self.assertEqual(nd['j'], NEG_INF)
         self.assertTrue(isnan(nd['n']))
 
+    def test_str_enum(self):
+        obj = StringEnum.COLOR
+        self.assertEqual(self.dumps(obj), '"color"')
+        self.assertEqual(self.dumps([obj]), '["color"]')
+        self.assertEqual(self.dumps({'key': obj}), '{"key": "color"}')
+
 class TestPyEnum(TestEnum, PyTest): pass
 class TestCEnum(TestEnum, CTest): pass
diff --git a/Lib/test/test_json/test_pickleable.py b/Lib/test/test_json/test_pickleable.py
new file mode 100644
index 00000000000..517cfcdd41a
--- /dev/null
+++ b/Lib/test/test_json/test_pickleable.py
@@ -0,0 +1,14 @@
+import json
+import pickle
+import unittest
+
+class TestPickleable(unittest.TestCase):
+    def test_json_decode_error_is_pickleable(self):
+        e = json.JSONDecodeError(msg="abc", doc="def", pos=7)
+
+        pickled = pickle.dumps(e)
+        unpickled = pickle.loads(pickled)
+
+        self.assertEqual(unpickled.msg, e.msg)
+        self.assertEqual(unpickled.doc, e.doc)
+        self.assertEqual(unpickled.pos, e.pos)
diff --git a/Lib/test/test_json/test_scanstring.py b/Lib/test/test_json/test_scanstring.py
index e77ec152280..baa43f93624 100644
--- a/Lib/test/test_json/test_scanstring.py
+++ b/Lib/test/test_json/test_scanstring.py
@@ -144,7 +144,6 @@ def test_bad_escapes(self):
             with self.assertRaises(self.JSONDecodeError, msg=s):
                 scanstring(s, 1, True)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_overflow(self):
         with self.assertRaises(OverflowError):
             self.json.decoder.scanstring("xxx", sys.maxsize+1)
diff --git a/Lib/test/test_json/test_unicode.py b/Lib/test/test_json/test_unicode.py
index 1aa9546dc46..291580cb047 100644
--- a/Lib/test/test_json/test_unicode.py
+++ b/Lib/test/test_json/test_unicode.py
@@ -44,7 +44,13 @@ def test_ascii_non_printable_decode(self):
                          '\b\t\n\f\r')
         s = ''.join(map(chr, range(32)))
         for c in s:
-            self.assertRaises(self.JSONDecodeError, self.loads, f'"{c}"')
+            with self.subTest(control_character=ord(c)):
+                with self.assertRaises(self.JSONDecodeError) as cm:
+                    self.loads(f'"a{c}b"')
+                error = cm.exception
+                self.assertEqual(error.pos, 2)
+                self.assertEqual(error.lineno, 1)
+                self.assertEqual(error.colno, 3)
         self.assertEqual(self.loads(f'"{s}"', strict=False), s)
         self.assertEqual(self.loads('"\x7f"'), '\x7f')
 
diff --git a/Lib/test/test_lazy_import/__init__.py b/Lib/test/test_lazy_import/__init__.py
new file mode 100644
index 00000000000..4c116ca0c0a
--- /dev/null
+++ b/Lib/test/test_lazy_import/__init__.py
@@ -0,0 +1,2826 @@
+"""Tests for PEP 810 lazy imports."""
+
+import io
+import dis
+import subprocess
+import sys
+import textwrap
+import threading
+import types
+import unittest
+import tempfile
+import os
+import contextlib
+
+from test import support
+from test.support.script_helper import assert_python_ok, assert_python_failure
+
+try:
+    import _testcapi
+except ImportError:
+    _testcapi = None
+
+
+class LazyImportTestCase(unittest.TestCase):
+    def setUp(self):
+        self.lazy_imports_filter = sys.get_lazy_imports_filter()
+        self.lazy_imports = sys.get_lazy_imports()
+
+    def tearDown(self):
+        """Clean up any test modules from sys.modules."""
+        for key in list(sys.modules.keys()):
+            if key.startswith('test.test_lazy_import.data'):
+                del sys.modules[key]
+
+        sys.set_lazy_imports_filter(self.lazy_imports_filter)
+        sys.set_lazy_imports(self.lazy_imports)
+        sys.lazy_modules.clear()
+
+
+class LazyImportTests(LazyImportTestCase):
+    """Tests for basic lazy import functionality."""
+
+    def test_basic_unused(self):
+        """Lazy imported module should not be loaded if never accessed."""
+        import test.test_lazy_import.data.basic_unused
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+        self.assertIn("test.test_lazy_import.data.basic2", sys.lazy_modules)
+
+    def test_sys_lazy_modules(self):
+        try:
+            import test.test_lazy_import.data.basic_from_unused
+        except ImportError as e:
+            self.fail('lazy import failed')
+
+        self.assertFalse("test.test_lazy_import.data.basic2" in sys.modules)
+        # The package is already loaded, so it is not a pending import.
+        self.assertNotIn("test.test_lazy_import.data", sys.lazy_modules)
+        self.assertIn("test.test_lazy_import.data.basic2", sys.lazy_modules)
+        test.test_lazy_import.data.basic_from_unused.basic2
+        self.assertNotIn("test.test_import.data", sys.lazy_modules)
+
+    def test_basic_unused_use_externally(self):
+        """Lazy import should load module when accessed from outside."""
+        from test.test_lazy_import.data import basic_unused
+
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+        x = basic_unused.test.test_lazy_import.data.basic2
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_basic_from_unused_use_externally(self):
+        """Lazy 'from' import should load when accessed from outside."""
+        from test.test_lazy_import.data import basic_from_unused
+
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+        x = basic_from_unused.basic2
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_basic_unused_dir(self):
+        """dir() on module should not trigger lazy import reification."""
+        import test.test_lazy_import.data.basic_unused
+
+        x = dir(test.test_lazy_import.data.basic_unused)
+        self.assertIn("test", x)
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_basic_dir(self):
+        """dir() at module scope should not trigger lazy import reification."""
+        from test.test_lazy_import.data import basic_dir
+
+        self.assertIn("test", basic_dir.x)
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_basic_used(self):
+        """Lazy import should load when accessed within the module."""
+        import test.test_lazy_import.data.basic_used
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    @support.requires_subprocess()
+    def test_from_import_with_module_getattr(self):
+        """Lazy from import should respect module-level __getattr__."""
+        code = textwrap.dedent("""
+            lazy from test.test_lazy_import.data.module_with_getattr import dynamic_attr
+            assert dynamic_attr == "from_getattr"
+        """)
+        assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_from_import_with_module_getattr_raising(self):
+        """Lazy from import should respect module-level __getattr__."""
+        code = textwrap.dedent("""
+            lazy from test.test_lazy_import.data.module_with_getattr import raising_attr
+
+            try:
+                raising_attr
+            except ValueError as exc:
+                assert str(exc) == 'from_getattr', exc
+            else:
+                assert False, f'ValueError is not raised: {raising_attr}'
+        """)
+        assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_from_import_with_module_getattr_missing(self):
+        """Lazy from import should respect module-level __getattr__."""
+        for attr in ("missing_attr", "import_error_attr"):
+            with self.subTest(attr=attr):
+                code = textwrap.dedent(f"""
+                    lazy from test.test_lazy_import.data.module_with_getattr import {attr}
+
+                    try:
+                        {attr}
+                    except ImportError as exc:
+                        assert '{attr}' in str(exc), exc
+                        assert exc.__cause__ is not None
+                    else:
+                        assert False, ('ImportError is not raised', {attr})
+                """)
+                assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_from_import_with_module_getattr_warning(self):
+        """Lazy from import should respect module-level __getattr__."""
+        code = textwrap.dedent("""
+            import warnings
+
+            with warnings.catch_warnings(record=True) as log:
+                lazy from test.test_lazy_import.data.module_with_getattr import warning_attr
+
+            assert log == []
+
+            with warnings.catch_warnings(record=True) as log:
+                warning_attr
+            assert warning_attr == 'from_warning_attr', warning_attr
+            assert len(log) == 1, log
+            assert isinstance(log[0].message, UserWarning), log
+            assert str(log[0].message) == 'from_getattr', log
+        """)
+        assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_from_import_with_imported_module_getattr(self):
+        """Lazy from import should not shadow an imported module's __getattr__."""
+        code = textwrap.dedent("""
+            import test.test_lazy_import.data.module_with_getattr as mod
+            lazy from test.test_lazy_import.data.module_with_getattr import dynamic_attr
+            assert dynamic_attr == "from_getattr"
+            assert mod.dynamic_attr == "from_getattr"
+        """)
+        assert_python_ok("-c", code)
+
+
+class GlobalLazyImportModeTests(LazyImportTestCase):
+    """Tests for sys.set_lazy_imports() global mode control."""
+
+    def tearDown(self):
+        for key in list(sys.modules.keys()):
+            if key.startswith('test.test_lazy_import.data'):
+                del sys.modules[key]
+
+        sys.set_lazy_imports_filter(None)
+        sys.set_lazy_imports("normal")
+
+    def test_global_off_rejected(self):
+        """Mode 'none' is not supported."""
+        with self.assertRaises(ValueError):
+            sys.set_lazy_imports("none")
+
+    def test_global_on(self):
+        """Mode 'all' should make regular imports lazy."""
+        import test.test_lazy_import.data.global_on
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_global_filter(self):
+        """Filter returning False should prevent lazy loading."""
+        import test.test_lazy_import.data.global_filter
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_global_filter_true(self):
+        """Filter returning True should allow lazy loading."""
+        import test.test_lazy_import.data.global_filter_true
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_global_filter_from(self):
+        """Filter should work with 'from' imports."""
+        import test.test_lazy_import.data.global_filter_from
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_global_filter_from_true(self):
+        """Filter returning True should allow lazy 'from' imports."""
+        import test.test_lazy_import.data.global_filter_from_true
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+
+class CompatibilityModeTests(LazyImportTestCase):
+    """Tests for __lazy_modules__ compatibility mode."""
+
+    def test_compatibility_mode(self):
+        """__lazy_modules__ should enable lazy imports for listed modules."""
+        import test.test_lazy_import.data.basic_compatibility_mode
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_compatibility_mode_used(self):
+        """Using a lazy import from __lazy_modules__ should load the module."""
+        import test.test_lazy_import.data.basic_compatibility_mode_used
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_compatibility_mode_func(self):
+        """Imports inside functions should be eager even in compatibility mode."""
+        import test.test_lazy_import.data.compatibility_mode_func
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_compatibility_mode_try_except(self):
+        """Imports in try/except should be eager even in compatibility mode."""
+        import test.test_lazy_import.data.compatibility_mode_try_except
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_compatibility_mode_relative(self):
+        """__lazy_modules__ should work with relative imports."""
+        import test.test_lazy_import.data.basic_compatibility_mode_relative
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+
+class ModuleIntrospectionTests(LazyImportTestCase):
+    """Tests for module dict and getattr behavior with lazy imports."""
+
+    def test_modules_dict(self):
+        """Accessing module.__dict__ should not trigger reification."""
+        import test.test_lazy_import.data.modules_dict
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_modules_getattr(self):
+        """Module __getattr__ for lazy import name should trigger reification."""
+        import test.test_lazy_import.data.modules_getattr
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_modules_getattr_other(self):
+        """Module __getattr__ for other names should not trigger reification."""
+        import test.test_lazy_import.data.modules_getattr_other
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+
+class LazyImportTypeTests(LazyImportTestCase):
+    """Tests for the LazyImportType and its resolve() method."""
+
+    def test_lazy_value_resolve(self):
+        """resolve() method should force the lazy import to load."""
+        import test.test_lazy_import.data.lazy_get_value
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_lazy_import_type_exposed(self):
+        """LazyImportType should be exposed in types module."""
+        self.assertHasAttr(types, 'LazyImportType')
+        self.assertEqual(types.LazyImportType.__name__, 'lazy_import')
+
+    def test_lazy_import_type_cant_construct(self):
+        """LazyImportType should not be directly constructible."""
+        self.assertRaises(TypeError, types.LazyImportType, {}, "module")
+
+    @support.requires_subprocess()
+    def test_lazy_import_type_attributes_accessible(self):
+        """Check that static PyLazyImport_Type is initialized at startup."""
+        code = textwrap.dedent("""
+            lazy import json
+            print(globals()["json"].resolve)
+        """)
+        proc = assert_python_ok("-c", code)
+        self.assertIn(b"<built-in method resolve of lazy_import object at", proc.out)
+
+    @support.requires_subprocess()
+    def test_lazy_import_type_attribute_error_message(self):
+        """Check that LazyImportType attribute error message is helpful."""
+        code = textwrap.dedent("""
+            lazy import asyncio
+            try:
+                globals()["asyncio"].Task
+            except AttributeError as exc:
+                assert str(exc) == (
+                    "cannot access attribute 'Task' "
+                    "on unresolved lazy import 'asyncio'"
+                ), repr(str(exc))
+            else:
+                assert False, 'AttributeError is not raised'
+        """)
+        assert_python_ok("-c", code)
+
+
+class SyntaxRestrictionTests(LazyImportTestCase):
+    """Tests for syntax restrictions on lazy imports."""
+
+    def test_lazy_try_except(self):
+        """lazy import inside try/except should raise SyntaxError."""
+        with self.assertRaises(SyntaxError):
+            import test.test_lazy_import.data.badsyntax.lazy_try_except
+
+    def test_lazy_try_except_from(self):
+        """lazy from import inside try/except should raise SyntaxError."""
+        with self.assertRaises(SyntaxError):
+            import test.test_lazy_import.data.badsyntax.lazy_try_except_from
+
+    def test_lazy_try_except_from_star(self):
+        """lazy from import * should raise SyntaxError."""
+        with self.assertRaises(SyntaxError):
+            import test.test_lazy_import.data.badsyntax.lazy_try_except_from_star
+
+    def test_lazy_future_import(self):
+        """lazy from __future__ import should raise SyntaxError."""
+        with self.assertRaises(SyntaxError) as cm:
+            import test.test_lazy_import.data.badsyntax.lazy_future_import
+        # Check we highlight 'lazy' (column offset 0, end offset 4)
+        self.assertEqual(cm.exception.offset, 1)
+        self.assertEqual(cm.exception.end_offset, 5)
+
+    def test_lazy_import_func(self):
+        """lazy import inside function should raise SyntaxError."""
+        with self.assertRaises(SyntaxError):
+            import test.test_lazy_import.data.badsyntax.lazy_import_func
+
+    def test_lazy_import_exec_in_function(self):
+        """lazy import via exec() inside a function should raise SyntaxError."""
+        # exec() inside a function creates a non-module-level context
+        # where lazy imports are not allowed
+        def f():
+            exec("lazy import json")
+
+        with self.assertRaises(SyntaxError) as cm:
+            f()
+        self.assertIn("only allowed at module level", str(cm.exception))
+
+    def test_lazy_import_exec_in_class(self):
+        """lazy import via exec() inside a class should raise SyntaxError."""
+        # exec() inside a class body also has non-module-level locals.
+        with self.assertRaises(SyntaxError) as cm:
+            class C:
+                exec("lazy import json")
+
+        self.assertIn("only allowed at module level", str(cm.exception))
+
+    @support.requires_subprocess()
+    def test_lazy_import_exec_at_module_level(self):
+        """lazy import via exec() at module level should work."""
+        # exec() at module level (globals == locals) should allow lazy imports
+        code = textwrap.dedent("""
+            import sys
+            exec("lazy import json")
+            # Should be lazy - not loaded yet
+            assert 'json' not in sys.modules
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+
+class EagerImportInLazyModeTests(LazyImportTestCase):
+    """Tests for imports that should remain eager even in lazy mode."""
+
+    def test_try_except_eager(self):
+        """Imports in try/except should be eager even with mode='all'."""
+        sys.set_lazy_imports("all")
+        import test.test_lazy_import.data.try_except_eager
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_try_except_eager_from(self):
+        """From imports in try/except should be eager even with mode='all'."""
+        sys.set_lazy_imports("all")
+        import test.test_lazy_import.data.try_except_eager_from
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_eager_import_func(self):
+        """Imports inside functions should return modules, not proxies."""
+        sys.set_lazy_imports("all")
+        import test.test_lazy_import.data.eager_import_func
+
+        f = test.test_lazy_import.data.eager_import_func.f
+        self.assertEqual(type(f()), type(sys))
+
+    def test_exec_import_func(self):
+        """Implicit lazy imports via exec() inside functions should be eager."""
+        sys.set_lazy_imports("all")
+
+        def f():
+            exec("import test.test_lazy_import.data.basic2")
+
+        f()
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_exec_import_func_with_lazy_modules(self):
+        """__lazy_modules__ should not make exec() imports lazy inside functions."""
+        globals()["__lazy_modules__"] = ["test.test_lazy_import.data.basic2"]
+        try:
+            def f():
+                exec("import test.test_lazy_import.data.basic2")
+
+            f()
+            self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+        finally:
+            del globals()["__lazy_modules__"]
+
+    def test_exec_import_class(self):
+        """Implicit lazy imports via exec() inside classes should be eager."""
+        sys.set_lazy_imports("all")
+
+        class C:
+            exec("import test.test_lazy_import.data.basic2")
+
+        self.assertIsNotNone(C)
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_exec_import_class_with_lazy_modules(self):
+        """__lazy_modules__ should not make exec() imports lazy inside classes."""
+        globals()["__lazy_modules__"] = ["test.test_lazy_import.data.basic2"]
+        try:
+            class C:
+                exec("import test.test_lazy_import.data.basic2")
+
+            self.assertIsNotNone(C)
+            self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+        finally:
+            del globals()["__lazy_modules__"]
+
+
+class WithStatementTests(LazyImportTestCase):
+    """Tests for lazy imports in with statement context."""
+
+    def test_lazy_with(self):
+        """lazy import with 'with' statement should work."""
+        import test.test_lazy_import.data.lazy_with
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_lazy_with_from(self):
+        """lazy from import with 'with' statement should work."""
+        import test.test_lazy_import.data.lazy_with_from
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+
+@support.requires_subprocess()
+class IndependentSubmoduleTests(LazyImportTestCase):
+    def check(self, code):
+        assert_python_ok('-c', textwrap.dedent(code))
+
+    def test_siblings(self):
+        for package, children in (
+            ('test.test_lazy_import.data.pkg', ('b', 'bar')),
+            ('test.test_lazy_import.data.metasyntactic.foo', ('ack', 'bar')),
+        ):
+            for first, second in (children, children[::-1]):
+                with self.subTest(package=package, first=first):
+                    self.check(f"""
+                        import sys
+                        lazy import {package}.{first}
+                        lazy import {package}.{second}
+                        assert {package}.{first} is sys.modules['{package}.{first}']
+                        assert '{package}.{second}' not in sys.modules
+                        assert {package}.{second} is sys.modules['{package}.{second}']
+                    """)
+
+    def test_star_import(self):
+        self.check("""
+            lazy import urllib.nonexistent
+            lazy import urllib
+            assert urllib.__name__ == 'urllib'
+            from urllib import *
+        """)
+
+    def test_deleted_child(self):
+        self.check("""
+            lazy from xml import dom
+            assert dom.__name__ == 'xml.dom'
+            import xml
+            del xml.dom
+            assert not hasattr(xml, 'dom')
+            lazy from xml import dom
+            assert hasattr(xml, 'dom')
+        """)
+
+    def test_cached_import_releases_builtins(self):
+        for statement in ('lazy from xml.dom import Node',
+                          'lazy import xml.dom.minidom'):
+            with self.subTest(statement=statement):
+                self.check(f"""
+                    import builtins, gc, weakref
+                    import xml.dom.minidom
+                    class Payload:
+                        pass
+                    payload = Payload()
+                    reference = weakref.ref(payload)
+                    namespace = {{'__builtins__': dict(vars(builtins), payload=payload)}}
+                    exec({statement!r}, namespace)
+                    exec('Node' if 'from' in {statement!r} else 'xml.dom.minidom', namespace)
+                    del namespace, payload
+                    gc.collect()
+                    assert reference() is None
+                """)
+
+    def test_invalid_descendant_retries(self):
+        self.check("""
+            lazy import test.test_lazy_import.data.pkg.b.foo
+            for _ in range(2):
+                try:
+                    test.test_lazy_import.data.pkg.b.foo
+                except ModuleNotFoundError:
+                    pass
+                else:
+                    raise AssertionError('imported an attribute as a module')
+            import test.test_lazy_import.data.pkg.b
+            assert callable(test.test_lazy_import.data.pkg.b.foo)
+        """)
+
+    def test_namespace_import_hooks(self):
+        self.check("""
+            import builtins
+            first = {'__builtins__': vars(builtins).copy()}
+            second = {'__builtins__': vars(builtins).copy()}
+            exec('lazy import xml.dom', first)
+            exec('lazy import xml.dom', second)
+            def denied(*args):
+                raise AssertionError('used another namespace import hook')
+            second['__builtins__']['__import__'] = denied
+            exec('assert xml.dom.__name__ == "xml.dom"', first)
+        """)
+
+    def test_retry_after_recursive_access(self):
+        self.check("""
+            import sys, xml
+            from importlib.machinery import ModuleSpec
+            class Loader:
+                calls = 0
+                def find_spec(self, name, path=None, target=None):
+                    if name == 'xml.broken':
+                        return ModuleSpec(name, self)
+                def create_module(self, spec):
+                    return None
+                def exec_module(self, module):
+                    self.calls += 1
+                    xml.broken
+                    raise RuntimeError('failed initialization')
+            loader = Loader()
+            sys.meta_path.insert(0, loader)
+            lazy import xml.broken
+            for _ in range(2):
+                try:
+                    xml.broken
+                except RuntimeError as exc:
+                    assert str(exc) == 'failed initialization'
+                else:
+                    raise AssertionError('returned a failed partial module')
+            assert loader.calls == 2
+        """)
+
+
+class PackageTests(LazyImportTestCase):
+    """Tests for lazy imports with packages."""
+
+    def test_lazy_import_pkg(self):
+        """lazy import of package submodule should load the package."""
+        out = io.StringIO()
+
+        with contextlib.redirect_stdout(out):
+            import test.test_lazy_import.data.lazy_import_pkg
+
+        self.assertIn("test.test_lazy_import.data.pkg", sys.modules)
+        self.assertIn("test.test_lazy_import.data.pkg.bar", sys.modules)
+        self.assertIn("BAR_MODULE_LOADED", out.getvalue())
+
+    def test_lazy_submodule_stored_in_parent_dict(self):
+        """Accessing a lazy submodule should store it in the parent's __dict__."""
+        out = io.StringIO()
+
+        with contextlib.redirect_stdout(out):
+            import test.test_lazy_import.data.lazy_import_pkg
+
+        pkg = sys.modules["test.test_lazy_import.data.pkg"]
+        self.assertIn("bar", pkg.__dict__)
+        self.assertIs(pkg.__dict__["bar"], sys.modules["test.test_lazy_import.data.pkg.bar"])
+        self.assertIn("BAR_MODULE_LOADED", out.getvalue())
+
+    def test_lazy_import_pkg_cross_import(self):
+        """Cross-imports within package should preserve lazy imports."""
+        import test.test_lazy_import.data.pkg.c
+
+        self.assertIn("test.test_lazy_import.data.pkg", sys.modules)
+        self.assertIn("test.test_lazy_import.data.pkg.c", sys.modules)
+        self.assertNotIn("test.test_lazy_import.data.pkg.b", sys.modules)
+
+        g = test.test_lazy_import.data.pkg.c.get_globals()
+        self.assertEqual(type(g["x"]), int)
+        self.assertEqual(type(g["b"]), types.LazyImportType)
+
+    @support.requires_subprocess()
+    def test_lazy_from_import_does_not_pollute_parent(self):
+        """Lazy from import should not add the name to the parent module's dict."""
+        code = textwrap.dedent("""
+            lazy from json import nonexistent_attr
+            import json
+            assert "nonexistent_attr" not in json.__dict__, (
+                "lazy from import should not publish attributes on the parent module"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_package_from_import_with_module_getattr_raising(self):
+        """Lazy from import should respect a package's __getattr__."""
+        code = textwrap.dedent("""
+            lazy from test.test_lazy_import.data.pkg import raising_attr
+
+            try:
+                raising_attr
+            except ValueError as exc:
+                assert str(exc) == 'from_getattr', exc
+            else:
+                assert False, f'ValueError is not raised: {raising_attr}'
+        """)
+        assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_package_from_import_with_module_getattr_missing(self):
+        """Lazy from import should respect package's __getattr__."""
+        for attr in ("missing_attr", "import_error_attr"):
+            with self.subTest(attr=attr):
+                code = textwrap.dedent(f"""
+                    lazy from test.test_lazy_import.data.pkg import {attr}
+
+                    try:
+                        {attr}
+                    except ImportError as exc:
+                        assert '{attr}' in str(exc), exc
+                        assert exc.__cause__ is not None
+                    else:
+                        assert False, ('ImportError is not raised', {attr})
+                """)
+                assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_from_import_with_module_getattr_warning(self):
+        """Lazy from import should respect package's __getattr__."""
+        code = textwrap.dedent("""
+            import warnings
+
+            with warnings.catch_warnings(record=True) as log:
+                lazy from test.test_lazy_import.data.pkg import warning_attr
+
+            assert log == []
+
+            with warnings.catch_warnings(record=True) as log:
+                warning_attr
+            assert warning_attr == 'from_warning_attr', warning_attr
+            assert len(log) == 1, log
+            assert isinstance(log[0].message, UserWarning), log
+            assert str(log[0].message) == 'from_getattr', log
+        """)
+        assert_python_ok("-c", code)
+
+    @support.requires_subprocess()
+    def test_package_from_import_with_module_getattr(self):
+        """Lazy from import should respect a package's __getattr__."""
+        code = textwrap.dedent("""
+            import test.test_lazy_import.data.pkg as pkg
+            lazy from test.test_lazy_import.data.pkg import dynamic_attr
+            assert dynamic_attr == "from_getattr"
+            assert pkg.dynamic_attr == "from_getattr"
+        """)
+        assert_python_ok("-c", code)
+
+
+class DunderLazyImportTests(LazyImportTestCase):
+    """Tests for __lazy_import__ builtin function."""
+
+    def test_dunder_lazy_import(self):
+        """__lazy_import__ should create lazy import proxy."""
+        import test.test_lazy_import.data.dunder_lazy_import
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_dunder_lazy_import_with_custom_filter(self):
+        sys.set_lazy_imports_filter(lambda importer, imported, fromlist: False)
+        import test.test_lazy_import.data.dunder_lazy_import
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_dunder_lazy_import_used(self):
+        """Using __lazy_import__ result should trigger module load."""
+        import test.test_lazy_import.data.dunder_lazy_import_used
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    @support.requires_subprocess()
+    def test_dunder_lazy_import_fromlist_resolves_to_module(self):
+        for fromlist in ["basic2", ("basic2",)]:
+            with self.subTest(fromlist=fromlist):
+                code = textwrap.dedent(f"""
+                    import sys
+                    import types
+
+                    lazy = __lazy_import__("test.test_lazy_import.data", fromlist={fromlist!r})
+
+                    def check():
+                        lazy_obj = globals()["lazy"]
+                        assert type(lazy_obj) is types.LazyImportType, lazy_obj
+                        assert "test.test_lazy_import.data.basic2" not in sys.modules
+
+                        resolved = lazy_obj.resolve()
+                        assert type(resolved) is types.ModuleType, resolved
+                        assert "test.test_lazy_import.data.basic2" in sys.modules
+                        assert resolved.__name__ == "test.test_lazy_import.data"
+                        assert resolved.basic2.x == 42
+
+                    check()
+                """)
+                assert_python_ok("-c", code)
+
+    def test_dunder_lazy_import_invalid_arguments(self):
+        """__lazy_import__ should reject invalid arguments."""
+        for invalid_name in (b"", 123, None):
+            with self.assertRaises(TypeError):
+                __lazy_import__(invalid_name)
+
+        with self.assertRaises(ValueError):
+            __lazy_import__("sys", level=-1)
+        with self.assertRaises(TypeError):
+            __lazy_import__("sys", globals=1)
+
+        code = textwrap.dedent("""
+            __lazy_import__("sys", fromlist=(1, 2, 3))
+        """)
+        result = assert_python_failure("-c", code, NO_COLOR='y')
+        self.assertIn(
+            b"TypeError: Item in ``from list'' must be str, not int",
+            result.err)
+
+    def test_dunder_lazy_import_builtins(self):
+        """__lazy_import__ should use module's __builtins__ for __import__."""
+        from test.test_lazy_import.data import dunder_lazy_import_builtins
+
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+        self.assertEqual(dunder_lazy_import_builtins.basic.basic2, 42)
+
+
+class SysLazyImportsAPITests(LazyImportTestCase):
+    """Tests for sys lazy imports API functions."""
+
+    def test_set_lazy_imports_requires_string(self):
+        """set_lazy_imports should reject non-string arguments."""
+        with self.assertRaises(TypeError):
+            sys.set_lazy_imports(True)
+        with self.assertRaises(TypeError):
+            sys.set_lazy_imports(None)
+        with self.assertRaises(TypeError):
+            sys.set_lazy_imports(1)
+
+    def test_set_lazy_imports_rejects_invalid_mode(self):
+        """set_lazy_imports should reject invalid mode strings."""
+        with self.assertRaises(ValueError):
+            sys.set_lazy_imports("invalid")
+        with self.assertRaises(ValueError):
+            sys.set_lazy_imports("on")
+        with self.assertRaises(ValueError):
+            sys.set_lazy_imports("off")
+
+    def test_get_lazy_imports_returns_string(self):
+        """get_lazy_imports should return string modes."""
+        sys.set_lazy_imports("normal")
+        self.assertEqual(sys.get_lazy_imports(), "normal")
+
+        sys.set_lazy_imports("all")
+        self.assertEqual(sys.get_lazy_imports(), "all")
+
+    def test_get_lazy_imports_filter_default(self):
+        """get_lazy_imports_filter should return None by default."""
+        sys.set_lazy_imports_filter(None)
+        self.assertIsNone(sys.get_lazy_imports_filter())
+
+    def test_set_and_get_lazy_imports_filter(self):
+        """set/get_lazy_imports_filter should round-trip filter function."""
+        def my_filter(name):
+            return name.startswith("test.")
+
+        sys.set_lazy_imports_filter(my_filter)
+        self.assertIs(sys.get_lazy_imports_filter(), my_filter)
+
+    def test_lazy_modules_attribute_is_dict(self):
+        """sys.lazy_modules should be a set per PEP 810."""
+        self.assertIsInstance(sys.lazy_modules, set)
+
+    @support.requires_subprocess()
+    def test_lazy_modules_tracks_lazy_imports(self):
+        """sys.lazy_modules should track lazily imported module names."""
+        code = textwrap.dedent("""
+            import sys
+            initial_count = len(sys.lazy_modules)
+            import test.test_lazy_import.data.basic_unused
+            assert "test.test_lazy_import.data.basic2" in sys.lazy_modules
+            assert len(sys.lazy_modules) > initial_count
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+
+@support.requires_subprocess()
+class ErrorHandlingTests(LazyImportTestCase):
+    """Tests for error handling during lazy import reification."""
+
+    def test_missing_lazy_submodule_raises_module_not_found_error(self):
+        """Accessing a nonexistent lazy submodule via parent attr raises ModuleNotFoundError."""
+        code = textwrap.dedent("""
+            lazy import test.test_lazy_import.data.nonexistent_module
+
+            try:
+                _ = test.test_lazy_import.data.nonexistent_module
+            except ModuleNotFoundError:
+                pass
+            else:
+                raise AssertionError("ModuleNotFoundError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_non_package_lazily_imported(self):
+        """Accessing a nonexistent lazy name via parent attr raises ModuleNotFoundError."""
+        code = textwrap.dedent("""
+            lazy import math.pi
+
+            try:
+                _ = math.pi
+            except ModuleNotFoundError:
+                pass
+            else:
+                raise AssertionError("ModuleNotFoundError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_non_package_lazily_imported_as(self):
+        """A dotted lazy import as raises when the name is not a module."""
+        # gh-157757: the eager statement raises, so the lazy one raises too.
+        code = textwrap.dedent("""
+            lazy import math.pi as pi
+
+            try:
+                pi
+            except ModuleNotFoundError:
+                pass
+            else:
+                raise AssertionError("ModuleNotFoundError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_missing_attribute_raises_import_error(self):
+        """Accessing a nonexistent lazy name via from import raises ImportError."""
+        code = textwrap.dedent("""
+            lazy from sys import doesnotexist
+
+            try:
+                _ = doesnotexist
+            except ImportError:
+                pass
+            else:
+                raise AssertionError("ImportError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_missing_lazy_from_import_shows_chained_traceback(self):
+        """Accessing missing attribute from lazy from-import should chain errors."""
+        code = textwrap.dedent("""
+            lazy from test.test_lazy_import.data.basic2 import nonexistent_name
+
+            try:
+                _ = nonexistent_name
+            except ImportError as e:
+                assert e.__cause__ is not None, "Expected chained exception"
+            else:
+                raise AssertionError("ImportError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    @support.subTests('name', (
+        'test.test_lazy_import.data.broken_module_chained_cause',
+        'test.test_lazy_import.data.broken_module_chained_context',
+        'test.test_lazy_import.data.broken_module_chained_suppressed',
+    ))
+    def test_chained_exception_import_shows_notes(self, name):
+        """Accessing missing attribute from lazy from-import should chain errors."""
+        code = textwrap.dedent(f"""
+            lazy import {name}
+
+            try:
+                _ = {name}
+            except ValueError as e:
+                assert any(
+                    note.startswith("lazy import of '{name}' declared in ")
+                    for note in e.__notes__
+                ), e.__notes__
+            else:
+                raise AssertionError("ImportError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_reification_retries_on_failure(self):
+        """Failed reification should allow retry on subsequent access.
+
+        PEP 810: "If reification fails, the lazy object is not reified or replaced.
+        Subsequent uses of the lazy object will re-try the reification."
+        """
+        code = textwrap.dedent("""
+            import sys
+
+            lazy import test.test_lazy_import.data.broken_module
+
+            try:
+                _ = test.test_lazy_import.data.broken_module
+            except ValueError as exc:
+                assert str(exc) == "This module always fails to import", exc
+            else:
+                raise AssertionError("ValueError was not raised")
+
+            assert "test.test_lazy_import.data.broken_module" not in sys.modules
+
+            try:
+                _ = test.test_lazy_import.data.broken_module
+            except ValueError as exc:
+                assert str(exc) == "This module always fails to import", exc
+            else:
+                raise AssertionError("ValueError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_lazy_submodule_traceback_hides_importlib_frames(self):
+        code = textwrap.dedent("""
+            import traceback
+
+            lazy import test.test_lazy_import.data.broken_module
+
+            try:
+                _ = test.test_lazy_import.data.broken_module
+            except ValueError as exc:
+                frames = traceback.extract_tb(exc.__traceback__)
+                assert [frame.name for frame in frames] == ["<module>", "<module>"], frames
+                assert frames[0].filename == "<string>", frames
+                assert frames[1].filename.endswith("broken_module.py"), frames
+            else:
+                raise AssertionError("ValueError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_module_not_found_during_module_execution_propagates(self):
+        code = textwrap.dedent("""
+            lazy import test.test_lazy_import.data.missing_dependency
+
+            try:
+                _ = test.test_lazy_import.data.missing_dependency
+            except ModuleNotFoundError as exc:
+                assert exc.name == "missing_dependency_for_lazy_import_test", exc.name
+                assert str(exc) == "No module named 'missing_dependency_for_lazy_import_test'", exc
+            else:
+                raise AssertionError("ModuleNotFoundError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_self_named_module_not_found_during_module_execution_propagates(self):
+        code = textwrap.dedent("""
+            lazy import test.test_lazy_import.data.self_named_module_not_found
+
+            try:
+                _ = test.test_lazy_import.data.self_named_module_not_found
+            except ModuleNotFoundError as exc:
+                assert exc.name == "test.test_lazy_import.data.self_named_module_not_found", exc.name
+                assert str(exc) == "boom", exc
+            else:
+                raise AssertionError("ModuleNotFoundError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_none_in_sys_modules_during_submodule_resolution_propagates(self):
+        code = textwrap.dedent("""
+            import sys
+
+            sys.modules["test.test_lazy_import.data.blocked_module"] = None
+            lazy import test.test_lazy_import.data.blocked_module
+
+            try:
+                _ = test.test_lazy_import.data.blocked_module
+            except ModuleNotFoundError as exc:
+                assert exc.name == "test.test_lazy_import.data.blocked_module", exc.name
+                assert str(exc) == (
+                    "import of test.test_lazy_import.data.blocked_module "
+                    "halted; None in sys.modules"
+                ), exc
+            else:
+                raise AssertionError("ModuleNotFoundError was not raised")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_circular_lazy_import_does_not_crash_for_gh_144727(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            a_path = os.path.join(tmpdir, "a.py")
+            b_path = os.path.join(tmpdir, "b.py")
+
+            with open(a_path, "w") as f:
+                f.write(textwrap.dedent("""\
+                    lazy import b
+
+                    def something():
+                        b.hello()
+
+                    something()
+                """))
+
+            with open(b_path, "w") as f:
+                f.write(textwrap.dedent("""\
+                    lazy import a
+
+                    def hello():
+                        print(a)
+                """))
+
+            result = subprocess.run(
+                [sys.executable, a_path],
+                capture_output=True,
+                text=True,
+                cwd=tmpdir,
+            )
+            # Should get a proper Python error, not a crash
+            self.assertEqual(result.returncode, 1)
+            self.assertIn("Error", result.stderr)
+
+
+@support.requires_subprocess()
+class GlobalsAndDictTests(LazyImportTestCase):
+    """Tests for globals() and __dict__ behavior with lazy imports.
+
+    PEP 810: "Calling globals() or accessing a module's __dict__ does not trigger
+    reification – they return the module's dictionary, and accessing lazy objects
+    through that dictionary still returns lazy proxy objects."
+    """
+
+    def test_globals_returns_lazy_proxy_when_accessed_from_function(self):
+        """globals() accessed from a function should return lazy proxy without reification.
+
+        Note: At module level, accessing globals()['name'] triggers LOAD_NAME which
+        automatically resolves lazy imports. Inside a function, accessing globals()['name']
+        uses BINARY_SUBSCR which returns the lazy proxy without resolution.
+        """
+        code = textwrap.dedent("""
+            import sys
+            import types
+
+            lazy from test.test_lazy_import.data.basic2 import x
+
+            # Check that module is not yet loaded
+            assert 'test.test_lazy_import.data.basic2' not in sys.modules
+
+            def check_lazy():
+                # Access through globals() from inside a function
+                g = globals()
+                lazy_obj = g['x']
+                return type(lazy_obj) is types.LazyImportType
+
+            # Inside function, should get lazy proxy
+            is_lazy = check_lazy()
+            assert is_lazy, "Expected LazyImportType from function scope"
+
+            # Module should STILL not be loaded
+            assert 'test.test_lazy_import.data.basic2' not in sys.modules
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_globals_dict_access_returns_lazy_proxy_inline(self):
+        """Accessing globals()['name'] inline should return lazy proxy.
+
+        Note: Assigning g['name'] to a local variable at module level triggers
+        reification due to STORE_NAME bytecode. Inline access preserves laziness.
+        """
+        code = textwrap.dedent("""
+            import sys
+            import types
+            lazy import json
+            # Inline access without assignment to local variable preserves lazy proxy
+            assert type(globals()['json']) is types.LazyImportType
+            assert 'json' not in sys.modules
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_module_dict_returns_lazy_proxy_without_reifying(self):
+        """module.__dict__ access should not trigger reification."""
+        import test.test_lazy_import.data.globals_access
+
+        # Module not loaded yet via direct dict access
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+        # Access via get_from_globals should return lazy proxy
+        lazy_obj = test.test_lazy_import.data.globals_access.get_from_globals()
+        self.assertEqual(type(lazy_obj), types.LazyImportType)
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_direct_access_triggers_reification(self):
+        """Direct name access (not through globals()) should trigger reification."""
+        import test.test_lazy_import.data.globals_access
+
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+        # Direct access should reify
+        result = test.test_lazy_import.data.globals_access.get_direct()
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_resolve_method_forces_reification(self):
+        """Calling resolve() on lazy proxy should force reification.
+
+        Note: Must access lazy proxy from within a function to avoid automatic
+        reification by LOAD_NAME at module level.
+        """
+        code = textwrap.dedent("""
+            import sys
+            import types
+
+            lazy from test.test_lazy_import.data.basic2 import x
+
+            assert 'test.test_lazy_import.data.basic2' not in sys.modules
+
+            def test_resolve():
+                g = globals()
+                lazy_obj = g['x']
+                assert type(lazy_obj) is types.LazyImportType, f"Expected lazy proxy, got {type(lazy_obj)}"
+
+                resolved = lazy_obj.resolve()
+
+                # Now module should be loaded
+                assert 'test.test_lazy_import.data.basic2' in sys.modules
+                assert resolved == 42  # x is 42 in basic2.py
+                return True
+
+            assert test_resolve()
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_add_lazy_to_globals(self):
+        code = textwrap.dedent("""
+            import sys
+            import types
+
+            lazy from test.test_lazy_import.data import basic2
+
+            assert 'test.test_lazy_import.data.basic2' not in sys.modules
+
+            class C: pass
+            sneaky = C()
+            sneaky.x = 1
+
+            def f():
+                t = 0
+                for _ in range(5):
+                    t += sneaky.x
+                return t
+
+            f()
+            globals()["sneaky"] = globals()["basic2"]
+            assert f() == 210
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_add_lazy_to_exec_globals_after_specialization(self):
+        code = textwrap.dedent("""
+            source = '''
+            import sys
+            import types
+
+            lazy from test.test_lazy_import.data import basic2
+
+            assert 'test.test_lazy_import.data.basic2' not in sys.modules
+
+            class C: pass
+            sneaky = C()
+            sneaky.x = 1
+
+            def f():
+                t = 0
+                for _ in range(5):
+                    t += sneaky.x
+                return t
+
+            f()
+            globals()["sneaky"] = globals()["basic2"]
+            assert f() == 210
+            print("OK")
+            '''
+            ns = {"__name__": "lazy_exec_globals"}
+            exec(source, ns)
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_add_lazy_to_exec_builtins_after_specialization(self):
+        code = textwrap.dedent("""
+            import builtins
+            source = '''
+            import sys
+            import types
+
+            lazy from test.test_lazy_import.data import basic2
+
+            assert 'test.test_lazy_import.data.basic2' not in sys.modules
+
+            class C: pass
+            sneaky = C()
+            sneaky.x = 1
+            __builtins__["sneaky"] = sneaky
+            del sneaky
+
+            def f():
+                t = 0
+                for _ in range(5):
+                    t += sneaky.x
+                return t
+
+            f()
+            __builtins__["sneaky"] = globals()["basic2"]
+            assert f() == 210
+            print("OK")
+            '''
+            ns = {"__name__": "lazy_exec_builtins", "__builtins__": builtins.__dict__.copy()}
+            exec(source, ns)
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+
+@support.requires_subprocess()
+class MultipleNameFromImportTests(LazyImportTestCase):
+    """Tests for lazy from ... import with multiple names.
+
+    PEP 810: "When using lazy from ... import, each imported name is bound to a
+    lazy proxy object. The first access to any of these names triggers loading
+    of the entire module and reifies only that specific name to its actual value.
+    Other names remain as lazy proxies until they are accessed."
+    """
+
+    def test_accessing_one_name_leaves_others_as_proxies(self):
+        """Accessing one name from multi-name import should leave others lazy."""
+        code = textwrap.dedent("""
+            import sys
+            import types
+
+            lazy from test.test_lazy_import.data.basic2 import f, x
+
+            # Neither should be loaded yet
+            assert 'test.test_lazy_import.data.basic2' not in sys.modules
+
+            g = globals()
+            assert type(g['f']) is types.LazyImportType
+            assert type(g['x']) is types.LazyImportType
+
+            # Access 'x' - this loads the module and reifies only 'x'
+            value = x
+            assert value == 42
+
+            # Module is now loaded
+            assert 'test.test_lazy_import.data.basic2' in sys.modules
+
+            # 'x' should be reified (int), 'f' should still be lazy proxy
+            assert type(g['x']) is int, f"Expected int, got {type(g['x'])}"
+            assert type(g['f']) is types.LazyImportType, f"Expected LazyImportType, got {type(g['f'])}"
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_accessing_one_name_imports_only_its_submodule(self):
+        """Accessing one name should not import the other names' submodules."""
+        code = textwrap.dedent("""
+            import sys
+
+            lazy from test.test_lazy_import.data.pkg import b, bar, broken
+
+            # Importing bar prints, and importing broken raises.
+            b.foo()
+
+            assert "test.test_lazy_import.data.pkg.bar" not in sys.modules
+            assert "test.test_lazy_import.data.pkg.broken" not in sys.modules
+        """)
+        rc, out, err = assert_python_ok("-c", code)
+        self.assertEqual(out, b"")
+
+    def test_all_names_reified_after_all_accessed(self):
+        """All names should be reified after each is accessed."""
+        code = textwrap.dedent("""
+            import sys
+            import types
+
+            lazy from test.test_lazy_import.data.basic2 import f, x
+
+            g = globals()
+
+            # Access both
+            _ = x
+            _ = f
+
+            # Both should be reified now
+            assert type(g['x']) is int
+            assert callable(g['f'])
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+
+@support.requires_subprocess()
+class SysLazyModulesTrackingTests(LazyImportTestCase):
+    """Tests for sys.lazy_modules tracking behavior.
+
+    PEP 810: "When the module is reified, it's removed from sys.lazy_modules"
+    """
+
+    def test_module_added_to_lazy_modules_on_lazy_import(self):
+        """Module should be added to sys.lazy_modules when lazily imported."""
+        # PEP 810 states lazy_modules tracks modules that have been lazily imported
+        # Note: The current implementation keeps modules in lazy_modules even after
+        # reification (primarily for diagnostics and introspection)
+        code = textwrap.dedent("""
+            import sys
+
+            initial_count = len(sys.lazy_modules)
+
+            lazy import test.test_lazy_import.data.basic2
+
+            # Should be in lazy_modules after lazy import
+            assert "test.test_lazy_import.data.basic2" in sys.lazy_modules
+            assert len(sys.lazy_modules) > initial_count
+
+            # Trigger reification
+            _ = test.test_lazy_import.data.basic2.x
+
+            # Module should still be tracked (for diagnostics per PEP 810)
+            assert "test.test_lazy_import.data.basic2" not in sys.lazy_modules
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_lazy_modules_is_per_interpreter(self):
+        """Each interpreter should have independent sys.lazy_modules."""
+        # Basic test that sys.lazy_modules exists and is a set
+        self.assertIsInstance(sys.lazy_modules, set)
+
+    def test_lazy_module_without_children_is_tracked(self):
+        code = textwrap.dedent("""
+            import sys
+            lazy import json
+            assert "json" in sys.lazy_modules, (
+                f"expected 'json' in sys.lazy_modules, got {set(sys.lazy_modules)}"
+            )
+            print("OK")
+        """)
+        assert_python_ok("-c", code)
+
+    def test_already_loaded_module_is_not_tracked(self):
+        """A lazy import of an already loaded module should not be tracked."""
+        code = textwrap.dedent("""
+            import sys
+
+            # Loaded by a regular import.
+            import json
+            lazy import json as lazy_json
+            assert "json" not in sys.lazy_modules, (
+                f"expected 'json' not in sys.lazy_modules, got {sys.lazy_modules}"
+            )
+
+            # Loaded by reifying an earlier lazy import.
+            lazy import base64
+            _ = base64.b64encode
+            lazy import base64 as lazy_base64
+            assert "base64" not in sys.lazy_modules, (
+                f"expected 'base64' not in sys.lazy_modules, got {sys.lazy_modules}"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+    def test_already_loaded_submodule_is_not_tracked(self):
+        """`lazy from` a loaded submodule should not be tracked either."""
+        code = textwrap.dedent("""
+            import sys
+            import test.test_lazy_import.data.pkg.b
+            lazy from test.test_lazy_import.data.pkg import b
+            assert "test.test_lazy_import.data.pkg.b" not in sys.lazy_modules, (
+                f"expected 'pkg.b' untracked, got {sys.lazy_modules}"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+    def test_attribute_entry_removed_on_reification(self):
+        """`lazy from x import attr` should untrack "x.attr" once resolved."""
+        code = textwrap.dedent("""
+            import sys
+            lazy from test.test_lazy_import.data.basic2 import x
+            assert "test.test_lazy_import.data.basic2.x" in sys.lazy_modules, (
+                f"expected 'basic2.x' tracked, got {sys.lazy_modules}"
+            )
+            _ = x
+            assert "test.test_lazy_import.data.basic2.x" not in sys.lazy_modules, (
+                f"expected 'basic2.x' untracked, got {sys.lazy_modules}"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+    def test_already_loaded_attribute_is_not_tracked(self):
+        code = textwrap.dedent("""
+            import sys
+            import math
+
+            lazy from math import pi
+            assert "math.pi" not in sys.lazy_modules, sys.lazy_modules
+            assert pi == math.pi
+        """)
+        assert_python_ok("-c", code)
+
+    def test_cached_lazy_attribute_tracks_its_target(self):
+        code = textwrap.dedent("""
+            import sys
+            import test.test_lazy_import.data.basic_from_unused
+
+            holder = "test.test_lazy_import.data.basic_from_unused"
+            target = "test.test_lazy_import.data.basic2"
+
+            namespace = {"__name__": "cached_import_test"}
+            exec(f"lazy from {holder} import basic2", namespace)
+            assert holder + ".basic2" not in sys.lazy_modules, sys.lazy_modules
+            assert target in sys.lazy_modules, sys.lazy_modules
+            exec("assert basic2.x == 42", namespace)
+            assert target not in sys.lazy_modules, sys.lazy_modules
+        """)
+        assert_python_ok("-c", code)
+
+    def test_cached_attribute_keeps_pending_module_tracked(self):
+        code = textwrap.dedent("""
+            import sys
+            import test.test_lazy_import.data.pkg as pkg
+            pkg.b = 42
+
+            lazy import test.test_lazy_import.data.pkg.b as pending
+            lazy from test.test_lazy_import.data.pkg import b
+            name = "test.test_lazy_import.data.pkg.b"
+            assert b == 42, b
+            assert name not in sys.modules, sys.modules
+            assert name in sys.lazy_modules, sys.lazy_modules
+            assert pending.foo() == "foo"
+            assert name not in sys.lazy_modules, sys.lazy_modules
+        """)
+        assert_python_ok("-c", code)
+
+    def test_failed_reification_stays_tracked(self):
+        """A lazy import that fails to resolve must stay tracked."""
+        code = textwrap.dedent("""
+            import sys
+            lazy import test.test_lazy_import.data.broken_module
+            try:
+                _ = test.test_lazy_import.data.broken_module
+            except ValueError:
+                pass
+            else:
+                raise AssertionError("ValueError was not raised")
+            assert "test.test_lazy_import.data.broken_module" in sys.lazy_modules, (
+                f"failed reification must stay tracked, got {sys.lazy_modules}"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+    def test_blocked_module_is_still_tracked(self):
+        """A ``None`` entry in sys.modules must not count as loaded."""
+        code = textwrap.dedent("""
+            import sys
+            sys.modules['test.test_lazy_import.data.basic2'] = None
+            lazy import test.test_lazy_import.data.basic2
+            assert "test.test_lazy_import.data.basic2" in sys.lazy_modules, (
+                f"blocked module must stay tracked, got {sys.lazy_modules}"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+    def test_initializing_module_is_still_tracked(self):
+        """A module that is still executing must not count as loaded."""
+        code = textwrap.dedent("""
+            import sys
+            name = "test.test_lazy_import.data.init_fails"
+            try:
+                import test.test_lazy_import.data.init_fails
+            except ValueError:
+                pass
+            else:
+                raise AssertionError("ValueError was not raised")
+            assert name not in sys.modules, "failed import left a module behind"
+            assert name in sys.lazy_modules, (
+                f"expected {name!r} tracked, got {sys.lazy_modules}"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+    def test_module_spec_descriptor_is_not_run(self):
+        """Checking whether a module is loaded must not run its descriptors."""
+        code = textwrap.dedent("""
+            import sys
+            import types
+
+            class RaisingSpec(types.ModuleType):
+                @property
+                def __spec__(self):
+                    raise RuntimeError("__spec__ descriptor was run")
+
+            sys.modules["raising_spec"] = RaisingSpec("raising_spec")
+            lazy import raising_spec
+            assert "raising_spec" not in sys.lazy_modules, (
+                f"expected 'raising_spec' untracked, got {sys.lazy_modules}"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+    def test_spec_initializing_descriptor_is_not_run(self):
+        code = textwrap.dedent("""
+            import sys
+            import types
+
+            class Spec:
+                @property
+                def _initializing(self):
+                    raise RuntimeError("_initializing descriptor was run")
+
+                @property
+                def __dict__(self):
+                    raise RuntimeError("__dict__ descriptor was run")
+
+            class SlottedSpec:
+                __slots__ = ()
+
+                @property
+                def _initializing(self):
+                    raise RuntimeError("_initializing descriptor was run")
+
+            for spec in (Spec(), SlottedSpec()):
+                module = types.ModuleType("custom_spec")
+                module.__spec__ = spec
+                sys.modules["custom_spec"] = module
+                lazy import custom_spec
+        """)
+        assert_python_ok("-c", code)
+
+    def test_cached_attribute_does_not_check_spec_twice(self):
+        code = textwrap.dedent("""
+            import sys
+            import types
+
+            class Spec:
+                def __init__(self):
+                    self.calls = 0
+
+                @property
+                def _initializing(self):
+                    self.calls += 1
+                    if self.calls == 2:
+                        raise RuntimeError("_initializing was read twice")
+                    return False
+
+            module = types.ModuleType("cached_spec")
+            module.__spec__ = Spec()
+            module.attr = 1
+            sys.modules["cached_spec"] = module
+            lazy from cached_spec import attr
+            assert attr == 1, attr
+        """)
+        assert_python_ok("-c", code)
+
+    def test_spec_initializing_truth_conversion_is_not_run(self):
+        code = textwrap.dedent("""
+            import sys
+            import types
+            from importlib.machinery import ModuleSpec
+
+            class Flag:
+                def __bool__(self):
+                    raise RuntimeError("_initializing truth conversion was run")
+
+            released = memoryview(b"")
+            released.release()
+            for flag in (Flag(), released):
+                sys.lazy_modules.discard("custom_spec")
+                module = types.ModuleType("custom_spec")
+                module.__spec__ = ModuleSpec("custom_spec", None)
+                module.__spec__._initializing = flag
+                sys.modules["custom_spec"] = module
+                lazy import custom_spec
+                assert "custom_spec" in sys.lazy_modules, sys.lazy_modules
+        """)
+        assert_python_ok("-c", code)
+
+    def test_pending_submodule_is_still_tracked(self):
+        """`lazy from` a submodule that is not loaded must stay tracked."""
+        code = textwrap.dedent("""
+            import sys
+            lazy from test.test_lazy_import.data.pkg import b
+            assert "test.test_lazy_import.data.pkg.b" in sys.lazy_modules, (
+                f"expected 'pkg.b' tracked, got {sys.lazy_modules}"
+            )
+            import test.test_lazy_import.data.pkg
+            assert "test.test_lazy_import.data.pkg.b" not in sys.modules, (
+                "loading the package must not load the submodule"
+            )
+            assert "test.test_lazy_import.data.pkg.b" in sys.lazy_modules, (
+                f"loading the package must not untrack the submodule, "
+                f"got {sys.lazy_modules}"
+            )
+        """)
+        assert_python_ok("-c", code)
+
+
+@support.requires_subprocess()
+class CommandLineAndEnvVarTests(unittest.TestCase):
+    """Tests for command-line and environment variable control.
+
+    PEP 810: The global lazy imports flag can be controlled through:
+    - The -X lazy_imports=<mode> command-line option
+    - The PYTHON_LAZY_IMPORTS=<mode> environment variable
+    """
+
+    def test_cli_lazy_imports_all_makes_regular_imports_lazy(self):
+        """-X lazy_imports=all should make all imports potentially lazy."""
+        code = textwrap.dedent("""
+            import sys
+            # In 'all' mode, regular imports become lazy
+            import json
+            # json should not be in sys.modules yet (lazy)
+            # Actually accessing it triggers reification
+            if 'json' not in sys.modules:
+                print("LAZY")
+            else:
+                print("EAGER")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-X", "lazy_imports=all", "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stderr: {result.stderr}")
+        self.assertIn("LAZY", result.stdout)
+
+    def test_cli_lazy_imports_none_is_rejected(self):
+        """-X lazy_imports=none should be rejected."""
+        result = subprocess.run(
+            [sys.executable, "-X", "lazy_imports=none", "-c", "pass"],
+            capture_output=True,
+            text=True
+        )
+        self.assertNotEqual(result.returncode, 0)
+        self.assertIn("-X lazy_imports: invalid value", result.stderr)
+        self.assertIn("expected 'all' or 'normal'", result.stderr)
+
+    def test_cli_lazy_imports_normal_respects_lazy_keyword_only(self):
+        """-X lazy_imports=normal should respect lazy keyword only."""
+        # Note: Use test modules instead of stdlib modules to avoid
+        # modules already loaded by the interpreter startup
+        code = textwrap.dedent("""
+            import sys
+            import test.test_lazy_import.data.basic2  # Should be eager
+            lazy import test.test_lazy_import.data.pkg.b  # Should be lazy
+
+            eager_loaded = 'test.test_lazy_import.data.basic2' in sys.modules
+            lazy_loaded = 'test.test_lazy_import.data.pkg.b' in sys.modules
+
+            if eager_loaded and not lazy_loaded:
+                print("OK")
+            else:
+                print(f"FAIL: eager={eager_loaded}, lazy={lazy_loaded}")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-X", "lazy_imports=normal", "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_env_var_lazy_imports_all_enables_global_lazy(self):
+        """PYTHON_LAZY_IMPORTS=all should enable global lazy imports."""
+        code = textwrap.dedent("""
+            import sys
+            import json
+            if 'json' not in sys.modules:
+                print("LAZY")
+            else:
+                print("EAGER")
+        """)
+        import os
+        env = os.environ.copy()
+        env["PYTHON_LAZY_IMPORTS"] = "all"
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True,
+            env=env
+        )
+        self.assertEqual(result.returncode, 0, f"stderr: {result.stderr}")
+        self.assertIn("LAZY", result.stdout)
+
+    def test_env_var_lazy_imports_none_is_rejected(self):
+        """PYTHON_LAZY_IMPORTS=none should be rejected."""
+        import os
+        env = os.environ.copy()
+        env["PYTHON_LAZY_IMPORTS"] = "none"
+        result = subprocess.run(
+            [sys.executable, "-c", "pass"],
+            capture_output=True,
+            text=True,
+            env=env
+        )
+        self.assertNotEqual(result.returncode, 0)
+        self.assertIn("PYTHON_LAZY_IMPORTS: invalid value", result.stderr)
+        self.assertIn("expected 'all' or 'normal'", result.stderr)
+
+    def test_cli_overrides_env_var(self):
+        """Command-line option should take precedence over environment variable."""
+        # PEP 810: -X lazy_imports takes precedence over PYTHON_LAZY_IMPORTS
+        code = textwrap.dedent("""
+            import sys
+            import json
+            if 'json' in sys.modules:
+                print("EAGER")
+            else:
+                print("LAZY")
+        """)
+        import os
+        env = os.environ.copy()
+        env["PYTHON_LAZY_IMPORTS"] = "all"  # env says all imports are lazy
+        result = subprocess.run(
+            [sys.executable, "-X", "lazy_imports=normal", "-c", code],
+            capture_output=True,
+            text=True,
+            env=env
+        )
+        self.assertEqual(result.returncode, 0, f"stderr: {result.stderr}")
+        # CLI should win, so a regular import should stay eager.
+        self.assertIn("EAGER", result.stdout)
+
+    def test_sys_set_lazy_imports_overrides_cli(self):
+        """sys.set_lazy_imports() should take precedence over CLI option."""
+        code = textwrap.dedent("""
+            import sys
+            sys.set_lazy_imports("normal")  # Override CLI
+            import json
+            if 'json' in sys.modules:
+                print("EAGER")
+            else:
+                print("LAZY")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-X", "lazy_imports=all", "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stderr: {result.stderr}")
+        self.assertIn("EAGER", result.stdout)
+
+
+@support.requires_subprocess()
+class FilterFunctionSignatureTests(LazyImportTestCase):
+    """Tests for the filter function signature per PEP 810.
+
+    PEP 810: func(importer: str, name: str, fromlist: tuple[str, ...] | None) -> bool
+    """
+
+    def _run_subprocess_with_modules(self, code, files):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            for relpath, contents in files.items():
+                path = os.path.join(tmpdir, relpath)
+                os.makedirs(os.path.dirname(path), exist_ok=True)
+                with open(path, "w", encoding="utf-8") as file:
+                    file.write(textwrap.dedent(contents))
+
+            env = os.environ.copy()
+            env["PYTHONPATH"] = os.pathsep.join(
+                entry for entry in (tmpdir, env.get("PYTHONPATH")) if entry
+            )
+            env["PYTHON_LAZY_IMPORTS"] = "normal"
+
+            result = subprocess.run(
+                [sys.executable, "-c", textwrap.dedent(code)],
+                capture_output=True,
+                cwd=tmpdir,
+                env=env,
+                text=True,
+            )
+        return result
+
+    def _assert_subprocess_ok(self, code, files):
+        result = self._run_subprocess_with_modules(code, files)
+        self.assertEqual(
+            result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}"
+        )
+        return result
+
+    def test_filter_receives_correct_arguments_for_import(self):
+        """Filter should receive (importer, name, fromlist=None) for 'import x'."""
+        code = textwrap.dedent("""
+            import sys
+
+            received_args = []
+
+            def my_filter(importer, name, fromlist):
+                received_args.append((importer, name, fromlist))
+                return True
+
+            sys.set_lazy_imports_filter(my_filter)
+
+            lazy import json
+
+            assert len(received_args) == 1, f"Expected 1 call, got {len(received_args)}"
+            importer, name, fromlist = received_args[0]
+            assert name == "json", f"Expected name='json', got {name!r}"
+            assert fromlist is None, f"Expected fromlist=None, got {fromlist!r}"
+            assert isinstance(importer, str), f"Expected str importer, got {type(importer)}"
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_filter_receives_fromlist_for_from_import(self):
+        """Filter should receive fromlist tuple for 'from x import y, z'."""
+        code = textwrap.dedent("""
+            import sys
+
+            received_args = []
+
+            def my_filter(importer, name, fromlist):
+                received_args.append((importer, name, fromlist))
+                return True
+
+            sys.set_lazy_imports_filter(my_filter)
+
+            lazy from json import dumps, loads
+
+            assert len(received_args) == 1, f"Expected 1 call, got {len(received_args)}"
+            importer, name, fromlist = received_args[0]
+            assert name == "json", f"Expected name='json', got {name!r}"
+            assert fromlist == ("dumps", "loads"), f"Expected ('dumps', 'loads'), got {fromlist!r}"
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_filter_returning_false_forces_eager_import(self):
+        """Filter returning False should make import eager."""
+        code = textwrap.dedent("""
+            import sys
+
+            def deny_filter(importer, name, fromlist):
+                return False
+
+            sys.set_lazy_imports_filter(deny_filter)
+
+            lazy import json
+
+            # Should be eager due to filter
+            if 'json' in sys.modules:
+                print("EAGER")
+            else:
+                print("LAZY")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stderr: {result.stderr}")
+        self.assertIn("EAGER", result.stdout)
+
+    def test_filter_distinguishes_absolute_and_relative_from_imports(self):
+        """Relative imports should pass resolved module names to the filter."""
+        files = {
+            "target.py": """
+                VALUE = "absolute"
+            """,
+            "pkg/__init__.py": "",
+            "pkg/target.py": """
+                VALUE = "relative"
+            """,
+            "pkg/runner.py": """
+                import sys
+
+                seen = []
+
+                def my_filter(importer, name, fromlist):
+                    seen.append((importer, name, fromlist))
+                    return True
+
+                sys.set_lazy_imports_filter(my_filter)
+
+                lazy from target import VALUE as absolute_value
+                lazy from .target import VALUE as relative_value
+
+                assert seen == [
+                    (__name__, "target", ("VALUE",)),
+                    (__name__, "pkg.target", ("VALUE",)),
+                ], seen
+            """,
+        }
+
+        result = self._assert_subprocess_ok(
+            """
+            import pkg.runner
+            print("OK")
+            """,
+            files,
+        )
+        self.assertIn("OK", result.stdout)
+
+    def test_filter_receives_resolved_name_for_relative_package_import(self):
+        """'lazy from . import x' should report the resolved package name."""
+        files = {
+            "pkg/__init__.py": "",
+            "pkg/sibling.py": """
+                VALUE = 1
+            """,
+            "pkg/runner.py": """
+                import sys
+
+                seen = []
+
+                def my_filter(importer, name, fromlist):
+                    seen.append((importer, name, fromlist))
+                    return True
+
+                sys.set_lazy_imports_filter(my_filter)
+
+                lazy from . import sibling
+
+                assert seen == [
+                    (__name__, "pkg", ("sibling",)),
+                ], seen
+            """,
+        }
+
+        result = self._assert_subprocess_ok(
+            """
+            import pkg.runner
+            print("OK")
+            """,
+            files,
+        )
+        self.assertIn("OK", result.stdout)
+
+    def test_filter_receives_resolved_name_for_parent_relative_import(self):
+        """Parent relative imports should also use the resolved module name."""
+        files = {
+            "pkg/__init__.py": "",
+            "pkg/target.py": """
+                VALUE = 1
+            """,
+            "pkg/sub/__init__.py": "",
+            "pkg/sub/runner.py": """
+                import sys
+
+                seen = []
+
+                def my_filter(importer, name, fromlist):
+                    seen.append((importer, name, fromlist))
+                    return True
+
+                sys.set_lazy_imports_filter(my_filter)
+
+                lazy from ..target import VALUE
+
+                assert seen == [
+                    (__name__, "pkg.target", ("VALUE",)),
+                ], seen
+            """,
+        }
+
+        result = self._assert_subprocess_ok(
+            """
+            import pkg.sub.runner
+            print("OK")
+            """,
+            files,
+        )
+        self.assertIn("OK", result.stdout)
+
+    def test_filter_can_force_eager_only_for_resolved_relative_target(self):
+        """Resolved names should let filters treat relative and absolute imports differently."""
+        files = {
+            "target.py": """
+                VALUE = "absolute"
+            """,
+            "pkg/__init__.py": "",
+            "pkg/target.py": """
+                VALUE = "relative"
+            """,
+            "pkg/runner.py": """
+                import sys
+
+                def my_filter(importer, name, fromlist):
+                    return name != "pkg.target"
+
+                sys.set_lazy_imports_filter(my_filter)
+
+                lazy from target import VALUE as absolute_value
+                lazy from .target import VALUE as relative_value
+
+                assert "pkg.target" in sys.modules, sorted(
+                    name for name in sys.modules
+                    if name in {"target", "pkg.target"}
+                )
+                assert "target" not in sys.modules, sorted(
+                    name for name in sys.modules
+                    if name in {"target", "pkg.target"}
+                )
+                assert relative_value == "relative", relative_value
+            """,
+        }
+
+        result = self._assert_subprocess_ok(
+            """
+            import pkg.runner
+            print("OK")
+            """,
+            files,
+        )
+        self.assertIn("OK", result.stdout)
+
+
+class AdditionalSyntaxRestrictionTests(LazyImportTestCase):
+    """Additional syntax restriction tests per PEP 810."""
+
+    def test_lazy_import_inside_class_raises_syntax_error(self):
+        """lazy import inside class body should raise SyntaxError."""
+        # PEP 810: "The soft keyword is only allowed at the global (module) level,
+        # not inside functions, class bodies, try blocks, or import *"
+        with self.assertRaises(SyntaxError):
+            import test.test_lazy_import.data.badsyntax.lazy_class_body
+
+
+@support.requires_subprocess()
+class MixedLazyEagerImportTests(LazyImportTestCase):
+    """Tests for mixing lazy and eager imports of the same module.
+
+    PEP 810: "If module foo is imported both lazily and eagerly in the same
+    program, the eager import takes precedence and both bindings resolve to
+    the same module object."
+    """
+
+    def test_eager_import_before_lazy_resolves_to_same_module(self):
+        """Eager import before lazy should make lazy resolve to same module."""
+        code = textwrap.dedent("""
+            import sys
+            import json  # Eager import first
+
+            lazy import json as lazy_json  # Lazy import same module
+
+            # lazy_json should resolve to the same object
+            assert json is lazy_json, "Lazy and eager imports should resolve to same module"
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_lazy_import_before_eager_resolves_to_same_module(self):
+        """Lazy import followed by eager should both point to same module."""
+        code = textwrap.dedent("""
+            import sys
+
+            lazy import json as lazy_json
+
+            # Lazy not loaded yet
+            assert 'json' not in sys.modules
+
+            import json  # Eager import triggers load
+
+            # Both should be the same object
+            assert json is lazy_json
+            print("OK")
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+
+class RelativeImportTests(LazyImportTestCase):
+    """Tests for relative imports with lazy keyword."""
+
+    def test_relative_lazy_import(self):
+        """lazy from . import submodule should work."""
+        from test.test_lazy_import.data import relative_lazy
+
+        # basic2 should not be loaded yet
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+        # Access triggers reification
+        result = relative_lazy.get_basic2()
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+    def test_relative_lazy_from_import(self):
+        """lazy from .module import name should work."""
+        from test.test_lazy_import.data import relative_lazy_from
+
+        # basic2 should not be loaded yet
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+        # Access triggers reification
+        result = relative_lazy_from.get_x()
+        self.assertEqual(result, 42)
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+
+class LazyModulesCompatibilityFromImportTests(LazyImportTestCase):
+    """Tests for __lazy_modules__ with from imports.
+
+    PEP 810: "When a module is made lazy this way, from-imports using that
+    module are also lazy"
+    """
+
+    def test_lazy_modules_makes_from_imports_lazy(self):
+        """__lazy_modules__ should make from imports of listed modules lazy."""
+        from test.test_lazy_import.data import lazy_compat_from
+
+        # basic2 should not be loaded yet because it's in __lazy_modules__
+        self.assertNotIn("test.test_lazy_import.data.basic2", sys.modules)
+
+        # Access triggers reification
+        result = lazy_compat_from.get_x()
+        self.assertEqual(result, 42)
+        self.assertIn("test.test_lazy_import.data.basic2", sys.modules)
+
+
+@support.requires_subprocess()
+class ImportStateAtReificationTests(LazyImportTestCase):
+    """Tests for import system state at reification time.
+
+    PEP 810: "Reification still calls __import__ to resolve the import, which uses
+    the state of the import system (e.g. sys.path, sys.meta_path, sys.path_hooks
+    and __import__) at reification time, not the state when the lazy import
+    statement was evaluated."
+    """
+
+    def test_sys_path_at_reification_time_is_used(self):
+        """sys.path changes after lazy import should affect reification."""
+        code = textwrap.dedent("""
+            import sys
+            import tempfile
+            import os
+
+            # Create a temporary module
+            with tempfile.TemporaryDirectory() as tmpdir:
+                mod_path = os.path.join(tmpdir, "dynamic_test_module.py")
+                with open(mod_path, "w") as f:
+                    f.write("VALUE = 'from_temp_dir'\\n")
+
+                # Lazy import before adding to path
+                lazy import dynamic_test_module
+
+                # Module cannot be found yet
+                try:
+                    _ = dynamic_test_module
+                    print("FAIL - should not find module")
+                except ModuleNotFoundError:
+                    pass
+
+                # Now add temp dir to path
+                sys.path.insert(0, tmpdir)
+
+                # Now reification should succeed using current sys.path
+                assert dynamic_test_module.VALUE == 'from_temp_dir'
+                print("OK")
+
+                sys.path.remove(tmpdir)
+        """)
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+
+@support.requires_subprocess()
+class ThreadSafetyTests(LazyImportTestCase):
+    """Tests for thread-safety of lazy imports."""
+
+    def test_concurrent_lazy_import_reification(self):
+        """Multiple threads racing to reify the same lazy import should succeed."""
+        from test.test_lazy_import.data import basic_unused
+
+        num_threads = 10
+        results = [None] * num_threads
+        errors = []
+        barrier = threading.Barrier(num_threads)
+
+        def access_lazy_import(idx):
+            try:
+                barrier.wait()
+                module = basic_unused.test.test_lazy_import.data.basic2
+                results[idx] = module
+            except Exception as e:
+                errors.append((idx, e))
+
+        threads = [
+            threading.Thread(target=access_lazy_import, args=(i,))
+            for i in range(num_threads)
+        ]
+
+        for t in threads:
+            t.start()
+        for t in threads:
+            t.join()
+
+        self.assertEqual(errors, [], f"Errors occurred: {errors}")
+        self.assertTrue(all(r is not None for r in results))
+        first_module = results[0]
+        for r in results[1:]:
+            self.assertIs(r, first_module)
+
+    def test_concurrent_reification_multiple_modules(self):
+        """Multiple threads reifying different lazy imports concurrently."""
+        code = textwrap.dedent("""
+            import sys
+            import threading
+
+            sys.set_lazy_imports("all")
+
+            lazy import json
+            lazy import os
+            lazy import io
+            lazy import re
+
+            num_threads = 8
+            results = {}
+            errors = []
+            barrier = threading.Barrier(num_threads)
+
+            def access_modules(idx):
+                try:
+                    barrier.wait()
+                    mods = [json, os, io, re]
+                    results[idx] = [type(m).__name__ for m in mods]
+                except Exception as e:
+                    errors.append((idx, e))
+
+            threads = [
+                threading.Thread(target=access_modules, args=(i,))
+                for i in range(num_threads)
+            ]
+
+            for t in threads:
+                t.start()
+            for t in threads:
+                t.join()
+
+            assert not errors, f"Errors: {errors}"
+            for idx, mods in results.items():
+                assert all(m == 'module' for m in mods), f"Thread {idx} got: {mods}"
+
+            print("OK")
+        """)
+
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_concurrent_lazy_modules_dict_updates(self):
+        """Multiple threads creating lazy imports should safely update sys.lazy_modules."""
+        code = textwrap.dedent("""
+            import sys
+            import threading
+
+            num_threads = 16
+            iterations = 50
+            errors = []
+            barrier = threading.Barrier(num_threads)
+
+            def create_lazy_imports(idx):
+                try:
+                    barrier.wait()
+                    for i in range(iterations):
+                        exec(f"lazy import json as json_{idx}_{i}", globals())
+                        exec(f"lazy import os as os_{idx}_{i}", globals())
+                except Exception as e:
+                    errors.append((idx, e))
+
+            threads = [
+                threading.Thread(target=create_lazy_imports, args=(i,))
+                for i in range(num_threads)
+            ]
+
+            for t in threads:
+                t.start()
+            for t in threads:
+                t.join()
+
+            assert not errors, f"Errors: {errors}"
+            assert isinstance(sys.lazy_modules, set), "sys.lazy_modules is not a dict"
+            print("OK")
+        """)
+
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_concurrent_reification_same_module_high_contention(self):
+        """High contention: many threads reifying the exact same lazy import."""
+        code = textwrap.dedent("""
+            import sys
+            import threading
+            import types
+
+            sys.set_lazy_imports("all")
+
+            lazy import json
+
+            num_threads = 20
+            results = [None] * num_threads
+            errors = []
+            barrier = threading.Barrier(num_threads)
+
+            def access_json(idx):
+                try:
+                    barrier.wait()
+                    for _ in range(100):
+                        _ = json.dumps
+                        _ = json.loads
+                    results[idx] = json
+                except Exception as e:
+                    errors.append((idx, e))
+
+            threads = [
+                threading.Thread(target=access_json, args=(i,))
+                for i in range(num_threads)
+            ]
+
+            for t in threads:
+                t.start()
+            for t in threads:
+                t.join()
+
+            assert not errors, f"Errors: {errors}"
+            assert all(r is not None for r in results), "Some threads got None"
+            first = results[0]
+            assert all(r is first for r in results), "Inconsistent module objects"
+            assert not isinstance(first, types.LazyImportType), "Got lazy import instead of module"
+            print("OK")
+        """)
+
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+    def test_concurrent_reification_with_module_attribute_access(self):
+        """Threads racing to reify and immediately access module attributes."""
+        code = textwrap.dedent("""
+            import sys
+            import threading
+
+            sys.set_lazy_imports("all")
+
+            lazy import collections
+            lazy import functools
+            lazy import itertools
+
+            num_threads = 12
+            results = {}
+            errors = []
+            barrier = threading.Barrier(num_threads)
+
+            def stress_lazy_imports(idx):
+                try:
+                    barrier.wait()
+                    for _ in range(50):
+                        _ = collections.OrderedDict
+                        _ = functools.partial
+                        _ = itertools.chain
+                        _ = collections.defaultdict
+                        _ = functools.lru_cache
+                        _ = itertools.islice
+                    results[idx] = (
+                        type(collections).__name__,
+                        type(functools).__name__,
+                        type(itertools).__name__,
+                    )
+                except Exception as e:
+                    errors.append((idx, e))
+
+            threads = [
+                threading.Thread(target=stress_lazy_imports, args=(i,))
+                for i in range(num_threads)
+            ]
+
+            for t in threads:
+                t.start()
+            for t in threads:
+                t.join()
+
+            assert not errors, f"Errors: {errors}"
+            for idx, types_tuple in results.items():
+                assert all(t == 'module' for t in types_tuple), f"Thread {idx}: {types_tuple}"
+            print("OK")
+        """)
+
+        result = subprocess.run(
+            [sys.executable, "-c", code],
+            capture_output=True,
+            text=True
+        )
+        self.assertEqual(result.returncode, 0, f"stdout: {result.stdout}, stderr: {result.stderr}")
+        self.assertIn("OK", result.stdout)
+
+
+class LazyImportDisTests(unittest.TestCase):
+    def test_lazy_import_dis(self):
+        """dis should properly show lazy import"""
+        code = compile("lazy import foo", "exec", "exec")
+        f = io.StringIO()
+        dis.dis(code, file=f)
+        self.assertIn("foo + lazy", f.getvalue())
+
+    def test_normal_import_dis(self):
+        """non lazy imports should just show the name"""
+        code = compile("import foo", "exec", "exec")
+        f = io.StringIO()
+        dis.dis(code, file=f)
+        for line in f.getvalue().split('\n'):
+            if "IMPORT_NAME" in line:
+                self.assertIn("(foo)", line)
+                break
+        else:
+            self.assertFail("IMPORT_NAME not found")
+
+
+@unittest.skipIf(_testcapi is None, 'need the _testcapi module')
+class LazyCApiTests(LazyImportTestCase):
+    def test_set_matches_sys(self):
+        self.assertEqual(_testcapi.PyImport_GetLazyImportsMode(), sys.get_lazy_imports())
+        for mode in ("normal", "all"):
+            _testcapi.PyImport_SetLazyImportsMode(mode)
+            self.assertEqual(_testcapi.PyImport_GetLazyImportsMode(), sys.get_lazy_imports())
+        self.assertRaises(ValueError, _testcapi.PyImport_SetLazyImportsMode, "none")
+
+    def test_filter_matches_sys(self):
+        self.assertEqual(_testcapi.PyImport_GetLazyImportsFilter(), sys.get_lazy_imports_filter())
+
+        def filter(*args):
+            pass
+
+        _testcapi.PyImport_SetLazyImportsFilter(filter)
+        self.assertEqual(_testcapi.PyImport_GetLazyImportsFilter(), sys.get_lazy_imports_filter())
+
+    def test_set_bad_filter(self):
+        self.assertRaises(ValueError, _testcapi.PyImport_SetLazyImportsFilter, 42)
+
+    def test_dunder_lazy_import_without_frame(self):
+        # gh-151510: __lazy_import__() called with no globals and no running
+        # Python frame must raise TypeError instead of crashing.
+        with self.assertRaisesRegex(
+            TypeError,
+            r"__lazy_import__\(\) missing globals when called without a frame",
+        ):
+            _testcapi.lazy_import_without_frame(
+                "test.test_lazy_import.data.basic2"
+            )
+
+
+class DottedLazyImportTests(unittest.TestCase):
+
+    def test_lazy_import_as_wins_over_variable(self):
+        """A dotted lazy import as imports the submodule the variable hides."""
+        # gh-157757: importing pkg.b rebinds pkg.b from the variable to the
+        # module, eagerly and lazily alike.
+        code = textwrap.dedent("""
+            import sys
+            import test.test_lazy_import.data.pkg as pkg
+            pkg.b = "hides the b submodule"
+
+            lazy import test.test_lazy_import.data.pkg.b as b
+            lazy import xml.dom.minidom as minidom
+
+            assert b is sys.modules["test.test_lazy_import.data.pkg.b"], b
+            assert minidom is sys.modules["xml.dom.minidom"], minidom
+        """)
+        assert_python_ok("-c", code)
+
+
+    def test_dotted_as_of_loaded_module(self):
+        """A dotted lazy import as binds the module, not a same-named attribute."""
+        # importlib.metadata is already loaded and has a `metadata` attribute.
+        code = textwrap.dedent("""
+            import importlib.metadata
+            import importlib.metadata as eager
+
+            lazy import importlib.metadata as lazily
+
+            assert lazily is eager, lazily
+        """)
+        assert_python_ok("-c", code)
+
+
+    def test_dotted_as_replays_lookups_on_custom_placeholder(self):
+        """A dotted lazy import as looks up its names on what the hook returned."""
+        code = textwrap.dedent("""
+            import builtins
+            import xml.dom
+
+            # In a list, so the hook reading it does not resolve it.
+            placeholder = [__lazy_import__("xml")]
+            default = builtins.__lazy_import__
+            builtins.__lazy_import__ = lambda *args: placeholder[0]
+            lazy import fake.dom as dom
+            builtins.__lazy_import__ = default
+
+            assert dom is xml.dom, dom
+        """)
+        assert_python_ok("-c", code)
+
+
+    def test_empty_fromlist_placeholder_matches_no_fromlist(self):
+        """An empty fromlist behaves like None."""
+        code = textwrap.dedent("""
+            expected = "<lazy_import 'xml.dom'>"
+            # In lists, so reading them does not resolve them.
+            for fromlist in (None, ()):
+                same = [__lazy_import__("xml.dom", fromlist=fromlist)]
+                assert repr(same[0]) == expected, (fromlist, repr(same[0]))
+            bare = [__lazy_import__("xml.dom")]
+            assert repr(bare[0]) == expected, repr(bare[0])
+        """)
+        assert_python_ok("-c", code)
+
+
+    def test_empty_fromlist_preserved_for_custom_import(self):
+        code = textwrap.dedent("""
+            import builtins
+            import types
+
+            value = object()
+            module = types.SimpleNamespace(dom=value)
+            placeholder = [__lazy_import__("xml.dom", fromlist=())]
+            default_import = builtins.__import__
+            default_lazy_import = builtins.__lazy_import__
+            calls = []
+
+            def import_hook(name, globals, locals, fromlist, level):
+                assert name == "xml.dom", name
+                assert fromlist == (), fromlist
+                calls.append(fromlist)
+                return module
+
+            builtins.__import__ = import_hook
+            assert placeholder[0].resolve() is module
+            builtins.__lazy_import__ = lambda *args: placeholder[0]
+            lazy import fake.dom as dom
+            assert dom is value
+            builtins.__import__ = default_import
+            builtins.__lazy_import__ = default_lazy_import
+
+            assert calls == [(), ()], calls
+        """)
+        assert_python_ok("-c", code)
+
+
+    def test_dotted_as_replays_lookups_on_dotted_placeholder(self):
+        """A dotted lazy import as replays its names on the hook's package."""
+        # importlib.metadata has a `metadata` attribute of its own, which the
+        # placeholder for importlib must not answer with.
+        for target in ("xml.dom", "importlib.metadata"):
+            with self.subTest(target=target):
+                leaf = target.rpartition(".")[2]
+                code = textwrap.dedent(f"""
+                    import builtins
+                    import sys
+                    import {target}
+
+                    # In a list, so the hook reading it does not resolve it.
+                    placeholder = [__lazy_import__("{target}", fromlist=())]
+                    default = builtins.__lazy_import__
+                    builtins.__lazy_import__ = lambda *args: placeholder[0]
+                    lazy import fake.{leaf} as {leaf}
+                    builtins.__lazy_import__ = default
+
+                    name = repr(globals()["{leaf}"])
+                    assert name == "<lazy_import '{target}'>", name
+                    assert {leaf} is sys.modules["{target}"], {leaf}
+                """)
+                assert_python_ok("-c", code)
+
+
+class SubmoduleLazinessTests(unittest.TestCase):
+    """Tests that module-level lazy imports remain lazy until accessed."""
+
+    def tearDown(self):
+        for key in list(sys.modules.keys()):
+            if key.startswith('test.test_lazy_import.data'):
+                del sys.modules[key]
+        sys.set_lazy_imports_filter(None)
+        sys.set_lazy_imports("normal")
+
+    def test_unaccessed_imports_stay_lazy(self):
+        """Imports in 'all' mode should stay lazy until accessed."""
+        sys.set_lazy_imports("all")
+        from test.test_lazy_import.data.metasyntactic import names
+        self.assertIsInstance(names.__dict__["Foo"], types.LazyImportType)
+        self.assertNotIn(
+            "test.test_lazy_import.data.metasyntactic.foo", sys.modules
+        )
+        _ = names.Foo
+        self.assertEqual(names.Foo, "Foo")
+        self.assertIn(
+            "test.test_lazy_import.data.metasyntactic.foo", sys.modules
+        )
+        self.assertIsInstance(names.__dict__["Ack"], types.LazyImportType)
+        self.assertNotIn(
+            "test.test_lazy_import.data.metasyntactic.foo.ack", sys.modules
+        )
+
+
+class AttributeSideEffectTests(unittest.TestCase):
+    """Tests that submodule imports don't overwrite parent attributes."""
+
+    def tearDown(self):
+        for key in list(sys.modules.keys()):
+            if key.startswith('test.test_lazy_import.data'):
+                del sys.modules[key]
+        sys.set_lazy_imports_filter(None)
+        sys.set_lazy_imports("normal")
+
+    def test_version_submodule_does_not_overwrite(self):
+        """A __version__ submodule should not overwrite the parent's
+        __version__ attribute imported in __init__.py."""
+        import test.test_lazy_import.data.versioned as versioned
+        self.assertEqual(versioned.__version__, "1.0")
+        self.assertEqual(
+            versioned.__copyright__,
+            "Copyright (c) 2001-2022 Python Software Foundation.",
+        )
+
+
+class ModuleVariableNameCollisionTests(unittest.TestCase):
+    """Tests for name collision between a submodule and a variable."""
+
+    def tearDown(self):
+        for key in list(sys.modules.keys()):
+            if key.startswith('test.test_lazy_import.data'):
+                del sys.modules[key]
+        sys.set_lazy_imports_filter(None)
+        sys.set_lazy_imports("normal")
+
+    def test_variable_after_import_wins(self):
+        """Variable assigned after import should overwrite the submodule."""
+        from test.test_lazy_import.data import module_same_name_var_order1
+        self.assertEqual(module_same_name_var_order1.bar, "Blah")
+
+    def test_import_after_variable_wins(self):
+        """Import after variable assignment should overwrite the variable."""
+        from test.test_lazy_import.data import module_same_name_var_order2
+        bar_mod = sys.modules[
+            "test.test_lazy_import.data.module_same_name_var_order2.bar"
+        ]
+        self.assertIs(module_same_name_var_order2.bar, bar_mod)
+
+
+class DeletedModuleReimportTests(unittest.TestCase):
+    """Tests for reimporting after module deletion from sys.modules."""
+
+    def tearDown(self):
+        for key in list(sys.modules.keys()):
+            if key.startswith('test.test_lazy_import.data'):
+                del sys.modules[key]
+        sys.set_lazy_imports_filter(None)
+        sys.set_lazy_imports("normal")
+
+    def test_reimport_creates_new_module(self):
+        """Deleting and reimporting should create a new module object."""
+        import test.test_lazy_import.data.metasyntactic.foo
+        import test.test_lazy_import.data.metasyntactic.foo.bar.baz
+
+        first_bar = test.test_lazy_import.data.metasyntactic.foo.bar
+
+        del sys.modules[
+            "test.test_lazy_import.data.metasyntactic.foo.bar"
+        ]
+
+        import test.test_lazy_import.data.metasyntactic.foo.bar.thud
+
+        second_bar = test.test_lazy_import.data.metasyntactic.foo.bar
+
+        self.assertIsNot(first_bar, second_bar)
+        self.assertIn("baz", dir(first_bar))
+        self.assertNotIn("thud", dir(first_bar))
+        self.assertIn("thud", dir(second_bar))
+        self.assertNotIn("baz", dir(second_bar))
+
+
+@support.requires_subprocess()
+class CircularImportLazyTests(unittest.TestCase):
+    """Tests that lazy imports can break circular import patterns."""
+
+    def test_succeeds_with_lazy(self):
+        """Same-level circular imports should succeed with lazy mode."""
+        proc = assert_python_ok(
+            "-X", "lazy_imports=all", "-c",
+            "import test.test_lazy_import.data.circular_import_pkg.main;"
+            "print('OK')",
+        )
+        self.assertIn(b"OK", proc.out)
+
+    def test_fails_without_lazy(self):
+        """Same-level circular imports should fail without lazy mode."""
+        result = subprocess.run(
+            [sys.executable, "-c",
+             "import test.test_lazy_import.data.circular_import_pkg.main"],
+            capture_output=True, text=True,
+        )
+        self.assertNotEqual(result.returncode, 0)
+        self.assertIn("ImportError", result.stderr)
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/Lib/test/test_lazy_import/__main__.py b/Lib/test/test_lazy_import/__main__.py
new file mode 100644
index 00000000000..d6c94efaf30
--- /dev/null
+++ b/Lib/test/test_lazy_import/__main__.py
@@ -0,0 +1,3 @@
+import unittest
+
+unittest.main('test.test_lazy_import')
diff --git a/Lib/test/test_lazy_import/data/badsyntax/lazy_class_body.py b/Lib/test/test_lazy_import/data/badsyntax/lazy_class_body.py
new file mode 100644
index 00000000000..e154b78f6cd
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/badsyntax/lazy_class_body.py
@@ -0,0 +1,3 @@
+# SyntaxError: lazy import inside class body is not allowed
+class Foo:
+    lazy import json
diff --git a/Lib/test/test_lazy_import/data/badsyntax/lazy_future_import.py b/Lib/test/test_lazy_import/data/badsyntax/lazy_future_import.py
new file mode 100644
index 00000000000..8bd258b76b4
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/badsyntax/lazy_future_import.py
@@ -0,0 +1 @@
+lazy from __future__ import annotations
diff --git a/Lib/test/test_lazy_import/data/badsyntax/lazy_import_func.py b/Lib/test/test_lazy_import/data/badsyntax/lazy_import_func.py
new file mode 100644
index 00000000000..af758b51127
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/badsyntax/lazy_import_func.py
@@ -0,0 +1,2 @@
+def f():
+    lazy import foo
diff --git a/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except.py b/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except.py
new file mode 100644
index 00000000000..e58d1f929ca
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except.py
@@ -0,0 +1,4 @@
+try:
+    lazy import foo
+except:
+    pass
diff --git a/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except_from.py b/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except_from.py
new file mode 100644
index 00000000000..8c97553f486
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except_from.py
@@ -0,0 +1,4 @@
+try:
+    lazy from foo import bar
+except:
+    pass
diff --git a/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except_from_star.py b/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except_from_star.py
new file mode 100644
index 00000000000..b2370eaae77
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/badsyntax/lazy_try_except_from_star.py
@@ -0,0 +1 @@
+lazy from foo import *
diff --git a/Lib/test/test_lazy_import/data/basic2.py b/Lib/test/test_lazy_import/data/basic2.py
new file mode 100644
index 00000000000..f93ec89d5ab
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/basic2.py
@@ -0,0 +1,4 @@
+def f():
+   pass
+
+x = 42
diff --git a/Lib/test/test_lazy_import/data/basic_compatibility_mode.py b/Lib/test/test_lazy_import/data/basic_compatibility_mode.py
new file mode 100644
index 00000000000..33eeab8879c
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/basic_compatibility_mode.py
@@ -0,0 +1,2 @@
+__lazy_modules__ = ['test.test_lazy_import.data.basic2']
+import test.test_lazy_import.data.basic2
diff --git a/Lib/test/test_lazy_import/data/basic_compatibility_mode_relative.py b/Lib/test/test_lazy_import/data/basic_compatibility_mode_relative.py
new file mode 100644
index 00000000000..15c1ea77630
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/basic_compatibility_mode_relative.py
@@ -0,0 +1,2 @@
+__lazy_modules__ = ['test.test_lazy_import.data.basic2']
+lazy from .basic2 import f
diff --git a/Lib/test/test_lazy_import/data/basic_compatibility_mode_used.py b/Lib/test/test_lazy_import/data/basic_compatibility_mode_used.py
new file mode 100644
index 00000000000..78bb4ffa523
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/basic_compatibility_mode_used.py
@@ -0,0 +1,3 @@
+__lazy_modules__ = ['test.test_lazy_import.data.basic2']
+import test.test_lazy_import.data.basic2
+test.test_lazy_import.data.basic2.f()
diff --git a/Lib/test/test_lazy_import/data/basic_dir.py b/Lib/test/test_lazy_import/data/basic_dir.py
new file mode 100644
index 00000000000..a88c8ed80a1
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/basic_dir.py
@@ -0,0 +1,2 @@
+lazy import test.test_lazy_import.data.basic2
+x = dir()
diff --git a/Lib/test/test_lazy_import/data/basic_from_unused.py b/Lib/test/test_lazy_import/data/basic_from_unused.py
new file mode 100644
index 00000000000..62fa04bc8fa
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/basic_from_unused.py
@@ -0,0 +1 @@
+lazy from test.test_lazy_import.data import basic2
diff --git a/Lib/test/test_lazy_import/data/basic_unused.py b/Lib/test/test_lazy_import/data/basic_unused.py
new file mode 100644
index 00000000000..f3e502c59e7
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/basic_unused.py
@@ -0,0 +1 @@
+lazy import test.test_lazy_import.data.basic2
diff --git a/Lib/test/test_lazy_import/data/basic_used.py b/Lib/test/test_lazy_import/data/basic_used.py
new file mode 100644
index 00000000000..7234bd2fe02
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/basic_used.py
@@ -0,0 +1,3 @@
+lazy import test.test_lazy_import.data.basic2 as basic2
+
+basic2.f()
diff --git a/Lib/test/test_lazy_import/data/broken_attr_module.py b/Lib/test/test_lazy_import/data/broken_attr_module.py
new file mode 100644
index 00000000000..a60bca2bad0
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/broken_attr_module.py
@@ -0,0 +1,3 @@
+# Module that exists but doesn't have expected attributes
+x = 42
+# No 'nonexistent_attr' here
diff --git a/Lib/test/test_lazy_import/data/broken_module.py b/Lib/test/test_lazy_import/data/broken_module.py
new file mode 100644
index 00000000000..b49d4a4a15f
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/broken_module.py
@@ -0,0 +1,2 @@
+# Module that raises an error during import
+raise ValueError("This module always fails to import")
diff --git a/Lib/test/test_lazy_import/data/broken_module_chained_cause.py b/Lib/test/test_lazy_import/data/broken_module_chained_cause.py
new file mode 100644
index 00000000000..786607b7bb5
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/broken_module_chained_cause.py
@@ -0,0 +1,3 @@
+# Module that raises an exception with explicit cause during import
+cause = ValueError("Cause of failure")
+raise ValueError("This module always fails to import") from cause
diff --git a/Lib/test/test_lazy_import/data/broken_module_chained_context.py b/Lib/test/test_lazy_import/data/broken_module_chained_context.py
new file mode 100644
index 00000000000..82640856e3e
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/broken_module_chained_context.py
@@ -0,0 +1,5 @@
+# Module that raises an exception with context during import
+try:
+    raise ValueError("Cause of failure")
+except:
+    raise ValueError("This module always fails to import")
diff --git a/Lib/test/test_lazy_import/data/broken_module_chained_suppressed.py b/Lib/test/test_lazy_import/data/broken_module_chained_suppressed.py
new file mode 100644
index 00000000000..5c34654afc1
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/broken_module_chained_suppressed.py
@@ -0,0 +1,2 @@
+# Module that raises an exception with suppressed context during import
+raise ValueError("This module always fails to import") from None
diff --git a/Lib/test/test_importlib/resources/data02/__init__.py b/Lib/test/test_lazy_import/data/circular_import_pkg/__init__.py
similarity index 100%
rename from Lib/test/test_importlib/resources/data02/__init__.py
rename to Lib/test/test_lazy_import/data/circular_import_pkg/__init__.py
diff --git a/Lib/test/test_lazy_import/data/circular_import_pkg/main.py b/Lib/test/test_lazy_import/data/circular_import_pkg/main.py
new file mode 100644
index 00000000000..0b897b377e2
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/circular_import_pkg/main.py
@@ -0,0 +1,2 @@
+from .x import X2
+X2()
diff --git a/Lib/test/test_lazy_import/data/circular_import_pkg/x.py b/Lib/test/test_lazy_import/data/circular_import_pkg/x.py
new file mode 100644
index 00000000000..b44d5185c9e
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/circular_import_pkg/x.py
@@ -0,0 +1,7 @@
+def X1():
+    return "X"
+
+from .y import Y1
+
+def X2():
+    return Y1()
diff --git a/Lib/test/test_lazy_import/data/circular_import_pkg/y.py b/Lib/test/test_lazy_import/data/circular_import_pkg/y.py
new file mode 100644
index 00000000000..d2385f7e67c
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/circular_import_pkg/y.py
@@ -0,0 +1,7 @@
+def Y1():
+    return "Y"
+
+from .x import X2
+
+def Y2():
+    return X2()
diff --git a/Lib/test/test_lazy_import/data/compatibility_mode_func.py b/Lib/test/test_lazy_import/data/compatibility_mode_func.py
new file mode 100644
index 00000000000..9405d2f832b
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/compatibility_mode_func.py
@@ -0,0 +1,5 @@
+__lazy_modules__ = ['test.test_lazy_import.data.basic2']
+def f():
+    import test.test_lazy_import.data.basic2
+
+f()
diff --git a/Lib/test/test_lazy_import/data/compatibility_mode_try_except.py b/Lib/test/test_lazy_import/data/compatibility_mode_try_except.py
new file mode 100644
index 00000000000..a746c4a34a5
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/compatibility_mode_try_except.py
@@ -0,0 +1,5 @@
+__lazy_modules__ = ['test.test_lazy_import.data.basic2']
+try:
+    import test.test_lazy_import.data.basic2
+except:
+    pass
diff --git a/Lib/test/test_lazy_import/data/dunder_lazy_import.py b/Lib/test/test_lazy_import/data/dunder_lazy_import.py
new file mode 100644
index 00000000000..c4f4d61623f
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/dunder_lazy_import.py
@@ -0,0 +1 @@
+basic = __lazy_import__('test.test_lazy_import.data.basic2')
diff --git a/Lib/test/test_lazy_import/data/dunder_lazy_import_builtins.py b/Lib/test/test_lazy_import/data/dunder_lazy_import_builtins.py
new file mode 100644
index 00000000000..8b6dbd7e3f6
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/dunder_lazy_import_builtins.py
@@ -0,0 +1,14 @@
+import sys
+
+def myimport(*args):
+    return sys.modules[__name__]
+
+
+new_globals = dict(globals())
+new_globals["__builtins__"] = {
+    "__import__": myimport,
+}
+basic2 = 42
+basic = __lazy_import__("test.test_lazy_import.data.basic2",
+                        globals=new_globals)
+basic
diff --git a/Lib/test/test_lazy_import/data/dunder_lazy_import_used.py b/Lib/test/test_lazy_import/data/dunder_lazy_import_used.py
new file mode 100644
index 00000000000..42c026994b1
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/dunder_lazy_import_used.py
@@ -0,0 +1,3 @@
+basic = __lazy_import__('test.test_lazy_import.data',
+                        fromlist=("basic2", ))
+basic
diff --git a/Lib/test/test_lazy_import/data/eager_import_func.py b/Lib/test/test_lazy_import/data/eager_import_func.py
new file mode 100644
index 00000000000..1f7130209d4
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/eager_import_func.py
@@ -0,0 +1,3 @@
+def f():
+    import test.test_lazy_import.data.basic2 as basic2
+    return basic2
diff --git a/Lib/test/test_lazy_import/data/global_filter.py b/Lib/test/test_lazy_import/data/global_filter.py
new file mode 100644
index 00000000000..0e2311842df
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/global_filter.py
@@ -0,0 +1,10 @@
+import sys
+
+def filter(module_name, imported_name, from_list):
+    assert module_name == __name__
+    assert imported_name == "test.test_lazy_import.data.basic2"
+    return False
+
+sys.set_lazy_imports_filter(filter)
+
+lazy import test.test_lazy_import.data.basic2 as basic2
diff --git a/Lib/test/test_lazy_import/data/global_filter_from.py b/Lib/test/test_lazy_import/data/global_filter_from.py
new file mode 100644
index 00000000000..da9d22e8727
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/global_filter_from.py
@@ -0,0 +1,11 @@
+import sys
+
+def filter(module_name, imported_name, from_list):
+    assert module_name == __name__
+    assert imported_name == "test.test_lazy_import.data.basic2"
+    assert from_list == ('f',)
+    return False
+
+sys.set_lazy_imports_filter(filter)
+
+lazy from test.test_lazy_import.data.basic2 import f
diff --git a/Lib/test/test_lazy_import/data/global_filter_from_true.py b/Lib/test/test_lazy_import/data/global_filter_from_true.py
new file mode 100644
index 00000000000..2d8b1de4c7c
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/global_filter_from_true.py
@@ -0,0 +1,12 @@
+import sys
+
+def filter(module_name, imported_name, from_list):
+    assert module_name == __name__
+    assert imported_name == "test.test_lazy_import.data.basic2"
+    assert from_list == ('f',)
+    return True
+
+sys.set_lazy_imports("normal")
+sys.set_lazy_imports_filter(filter)
+
+lazy from test.test_lazy_import.data.basic2 import f
diff --git a/Lib/test/test_lazy_import/data/global_filter_true.py b/Lib/test/test_lazy_import/data/global_filter_true.py
new file mode 100644
index 00000000000..da4abeacf87
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/global_filter_true.py
@@ -0,0 +1,11 @@
+import sys
+
+def filter(module_name, imported_name, from_list):
+    assert module_name == __name__
+    assert imported_name == "test.test_lazy_import.data.basic2"
+    return True
+
+sys.set_lazy_imports("normal")
+sys.set_lazy_imports_filter(filter)
+
+lazy import test.test_lazy_import.data.basic2 as basic2
diff --git a/Lib/test/test_lazy_import/data/global_on.py b/Lib/test/test_lazy_import/data/global_on.py
new file mode 100644
index 00000000000..ddacab5468b
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/global_on.py
@@ -0,0 +1,5 @@
+import sys
+
+sys.set_lazy_imports("all")
+
+import test.test_lazy_import.data.basic2 as basic2
diff --git a/Lib/test/test_lazy_import/data/globals_access.py b/Lib/test/test_lazy_import/data/globals_access.py
new file mode 100644
index 00000000000..af6fc40115b
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/globals_access.py
@@ -0,0 +1,9 @@
+# Test that globals() returns lazy proxy objects without reifying
+lazy import test.test_lazy_import.data.basic2 as basic2
+
+def get_from_globals():
+    g = globals()
+    return g['basic2']
+
+def get_direct():
+    return basic2
diff --git a/Lib/test/test_lazy_import/data/init_fails.py b/Lib/test/test_lazy_import/data/init_fails.py
new file mode 100644
index 00000000000..16e7ad363b0
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/init_fails.py
@@ -0,0 +1,4 @@
+# Imported by test_initializing_module_is_still_tracked.  The module it imports
+# lazily imports this one back while this one is still initializing.
+import test.test_lazy_import.data.lazy_on_init_fails
+raise ValueError("initialization failed")
diff --git a/Lib/test/test_lazy_import/data/lazy_compat_from.py b/Lib/test/test_lazy_import/data/lazy_compat_from.py
new file mode 100644
index 00000000000..d6f7ed9a785
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/lazy_compat_from.py
@@ -0,0 +1,6 @@
+# Test __lazy_modules__ with from imports
+__lazy_modules__ = ['test.test_lazy_import.data.basic2']
+from test.test_lazy_import.data.basic2 import x, f
+
+def get_x():
+    return x
diff --git a/Lib/test/test_lazy_import/data/lazy_get_value.py b/Lib/test/test_lazy_import/data/lazy_get_value.py
new file mode 100644
index 00000000000..f216dc52f29
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/lazy_get_value.py
@@ -0,0 +1,7 @@
+lazy import test.test_lazy_import.data.basic2 as basic2
+
+def f():
+    x = globals()
+    return x['basic2'].resolve()
+
+f()
diff --git a/Lib/test/test_lazy_import/data/lazy_import_pkg.py b/Lib/test/test_lazy_import/data/lazy_import_pkg.py
new file mode 100644
index 00000000000..f237b50fd42
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/lazy_import_pkg.py
@@ -0,0 +1,2 @@
+lazy import test.test_lazy_import.data.pkg.bar
+x = test.test_lazy_import.data.pkg.bar.f
diff --git a/Lib/test/test_lazy_import/data/lazy_on_init_fails.py b/Lib/test/test_lazy_import/data/lazy_on_init_fails.py
new file mode 100644
index 00000000000..7203fcbb4aa
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/lazy_on_init_fails.py
@@ -0,0 +1 @@
+lazy import test.test_lazy_import.data.init_fails
diff --git a/Lib/test/test_lazy_import/data/lazy_with.py b/Lib/test/test_lazy_import/data/lazy_with.py
new file mode 100644
index 00000000000..30cf9d37762
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/lazy_with.py
@@ -0,0 +1,3 @@
+import contextlib
+with contextlib.nullcontext():
+    lazy import test.test_lazy_import.data.basic2
diff --git a/Lib/test/test_lazy_import/data/lazy_with_from.py b/Lib/test/test_lazy_import/data/lazy_with_from.py
new file mode 100644
index 00000000000..794ba33f828
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/lazy_with_from.py
@@ -0,0 +1,3 @@
+import contextlib
+with contextlib.nullcontext():
+    lazy import test.test_lazy_import.data.basic2 as basic2
diff --git a/Lib/test/test_lazy_import/data/lazypkg/__init__.py b/Lib/test/test_lazy_import/data/lazypkg/__init__.py
new file mode 100644
index 00000000000..276b51823fe
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/lazypkg/__init__.py
@@ -0,0 +1 @@
+lazy from . import bar
diff --git a/Lib/test/test_lazy_import/data/lazypkg/bar.py b/Lib/test/test_lazy_import/data/lazypkg/bar.py
new file mode 100644
index 00000000000..b8d8b60b886
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/lazypkg/bar.py
@@ -0,0 +1,2 @@
+print("BAR_MODULE_LOADED")
+def f(): pass
diff --git a/Lib/test/test_importlib/resources/data02/one/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/__init__.py
similarity index 100%
rename from Lib/test/test_importlib/resources/data02/one/__init__.py
rename to Lib/test/test_lazy_import/data/metasyntactic/__init__.py
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/foo/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/foo/__init__.py
new file mode 100644
index 00000000000..632a9fb87ac
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/foo/__init__.py
@@ -0,0 +1 @@
+Foo = "Foo"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/foo/ack/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/foo/ack/__init__.py
new file mode 100644
index 00000000000..c4c249f3b65
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/foo/ack/__init__.py
@@ -0,0 +1 @@
+Ack = "Ack"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/__init__.py
new file mode 100644
index 00000000000..03faa550258
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/__init__.py
@@ -0,0 +1 @@
+Bar = "Bar"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/baz/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/baz/__init__.py
new file mode 100644
index 00000000000..62d8366b440
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/baz/__init__.py
@@ -0,0 +1 @@
+Baz = "Baz"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/baz/qux/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/baz/qux/__init__.py
new file mode 100644
index 00000000000..12389d76a28
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/baz/qux/__init__.py
@@ -0,0 +1 @@
+Qux = "Qux"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/thud/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/thud/__init__.py
new file mode 100644
index 00000000000..a4dd8ab0fae
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/foo/bar/thud/__init__.py
@@ -0,0 +1 @@
+Thud = "Thud"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/names.py b/Lib/test/test_lazy_import/data/metasyntactic/names.py
new file mode 100644
index 00000000000..b2edf13e850
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/names.py
@@ -0,0 +1,9 @@
+from .foo import Foo
+from .foo.ack import Ack
+from .foo.bar import Bar
+from .foo.bar.baz import Baz
+from .foo.bar.thud import Thud
+from .waldo import Waldo
+from .waldo.fred import Fred
+from .plugh import Plugh
+Metasyntactic = "Metasyntactic"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/plugh/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/plugh/__init__.py
new file mode 100644
index 00000000000..5db053204fc
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/plugh/__init__.py
@@ -0,0 +1 @@
+Plugh = "Plugh"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/waldo/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/waldo/__init__.py
new file mode 100644
index 00000000000..39f5a1b1838
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/waldo/__init__.py
@@ -0,0 +1 @@
+Waldo = "Waldo"
diff --git a/Lib/test/test_lazy_import/data/metasyntactic/waldo/fred/__init__.py b/Lib/test/test_lazy_import/data/metasyntactic/waldo/fred/__init__.py
new file mode 100644
index 00000000000..8c9dce1b3cf
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/metasyntactic/waldo/fred/__init__.py
@@ -0,0 +1 @@
+Fred = "Fred"
diff --git a/Lib/test/test_lazy_import/data/missing_dependency.py b/Lib/test/test_lazy_import/data/missing_dependency.py
new file mode 100644
index 00000000000..aa2f2d0f65f
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/missing_dependency.py
@@ -0,0 +1 @@
+import missing_dependency_for_lazy_import_test
diff --git a/Lib/test/test_lazy_import/data/module_same_name_var_order1/__init__.py b/Lib/test/test_lazy_import/data/module_same_name_var_order1/__init__.py
new file mode 100644
index 00000000000..b815b2a7d6f
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/module_same_name_var_order1/__init__.py
@@ -0,0 +1,3 @@
+from .bar import Bar
+bar = "Blah"
+Bar
diff --git a/Lib/test/test_lazy_import/data/module_same_name_var_order1/bar.py b/Lib/test/test_lazy_import/data/module_same_name_var_order1/bar.py
new file mode 100644
index 00000000000..03faa550258
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/module_same_name_var_order1/bar.py
@@ -0,0 +1 @@
+Bar = "Bar"
diff --git a/Lib/test/test_lazy_import/data/module_same_name_var_order2/__init__.py b/Lib/test/test_lazy_import/data/module_same_name_var_order2/__init__.py
new file mode 100644
index 00000000000..008d199c73e
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/module_same_name_var_order2/__init__.py
@@ -0,0 +1,3 @@
+bar = "Blah"
+from .bar import Bar
+Bar
diff --git a/Lib/test/test_lazy_import/data/module_same_name_var_order2/bar.py b/Lib/test/test_lazy_import/data/module_same_name_var_order2/bar.py
new file mode 100644
index 00000000000..03faa550258
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/module_same_name_var_order2/bar.py
@@ -0,0 +1 @@
+Bar = "Bar"
diff --git a/Lib/test/test_lazy_import/data/module_with_getattr.py b/Lib/test/test_lazy_import/data/module_with_getattr.py
new file mode 100644
index 00000000000..db3a2301075
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/module_with_getattr.py
@@ -0,0 +1,12 @@
+def __getattr__(name):
+    if name == "dynamic_attr":
+        return "from_getattr"
+    elif name == "raising_attr":
+        raise ValueError("from_getattr")
+    elif name == "import_error_attr":
+        raise ImportError(name)
+    elif name == "warning_attr":
+        import warnings
+        warnings.warn("from_getattr", category=UserWarning)
+        return "from_warning_attr"
+    raise AttributeError(name)
diff --git a/Lib/test/test_lazy_import/data/modules_dict.py b/Lib/test/test_lazy_import/data/modules_dict.py
new file mode 100644
index 00000000000..562a3b9a62f
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/modules_dict.py
@@ -0,0 +1,5 @@
+lazy import test.test_lazy_import.data.basic2 as basic2
+
+import sys
+mod = sys.modules[__name__]
+x = mod.__dict__
diff --git a/Lib/test/test_lazy_import/data/modules_getattr.py b/Lib/test/test_lazy_import/data/modules_getattr.py
new file mode 100644
index 00000000000..f0b8e2bd061
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/modules_getattr.py
@@ -0,0 +1,5 @@
+lazy import test.test_lazy_import.data.basic2 as basic2
+
+import sys
+mod = sys.modules[__name__]
+x = mod.basic2
diff --git a/Lib/test/test_lazy_import/data/modules_getattr_other.py b/Lib/test/test_lazy_import/data/modules_getattr_other.py
new file mode 100644
index 00000000000..642840c2872
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/modules_getattr_other.py
@@ -0,0 +1,5 @@
+lazy import test.test_lazy_import.data.basic2 as basic2
+
+import sys
+mod = sys.modules[__name__]
+x = mod.__name__
diff --git a/Lib/test/test_lazy_import/data/multi_from_import.py b/Lib/test/test_lazy_import/data/multi_from_import.py
new file mode 100644
index 00000000000..dfd875975dd
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/multi_from_import.py
@@ -0,0 +1,5 @@
+# Test that lazy from import with multiple names only reifies accessed names
+lazy from test.test_lazy_import.data.basic2 import f, x
+
+def get_globals():
+    return globals()
diff --git a/Lib/test/test_lazy_import/data/pkg/__init__.py b/Lib/test/test_lazy_import/data/pkg/__init__.py
new file mode 100644
index 00000000000..5f7b8662596
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/pkg/__init__.py
@@ -0,0 +1,14 @@
+x = 42
+
+def __getattr__(name):
+    if name == "dynamic_attr":
+        return "from_getattr"
+    elif name == "raising_attr":
+        raise ValueError("from_getattr")
+    elif name == "import_error_attr":
+        raise ImportError(name)
+    elif name == "warning_attr":
+        import warnings
+        warnings.warn("from_getattr", category=UserWarning)
+        return "from_warning_attr"
+    raise AttributeError(name)
diff --git a/Lib/test/test_lazy_import/data/pkg/b.py b/Lib/test/test_lazy_import/data/pkg/b.py
new file mode 100644
index 00000000000..a266b7c7c0d
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/pkg/b.py
@@ -0,0 +1,2 @@
+def foo():
+    return 'foo'
diff --git a/Lib/test/test_lazy_import/data/pkg/bar.py b/Lib/test/test_lazy_import/data/pkg/bar.py
new file mode 100644
index 00000000000..b8d8b60b886
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/pkg/bar.py
@@ -0,0 +1,2 @@
+print("BAR_MODULE_LOADED")
+def f(): pass
diff --git a/Lib/test/test_lazy_import/data/pkg/broken.py b/Lib/test/test_lazy_import/data/pkg/broken.py
new file mode 100644
index 00000000000..6499aa9e150
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/pkg/broken.py
@@ -0,0 +1,2 @@
+# Submodule that raises an error during import
+raise ValueError("This module always fails to import")
diff --git a/Lib/test/test_lazy_import/data/pkg/c.py b/Lib/test/test_lazy_import/data/pkg/c.py
new file mode 100644
index 00000000000..0bb03119864
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/pkg/c.py
@@ -0,0 +1,4 @@
+lazy from . import b, x
+
+def get_globals():
+    return globals()
diff --git a/Lib/test/test_lazy_import/data/relative_lazy.py b/Lib/test/test_lazy_import/data/relative_lazy.py
new file mode 100644
index 00000000000..6273d3883ab
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/relative_lazy.py
@@ -0,0 +1,5 @@
+# Test relative imports with lazy keyword
+lazy from . import basic2
+
+def get_basic2():
+    return basic2
diff --git a/Lib/test/test_lazy_import/data/relative_lazy_from.py b/Lib/test/test_lazy_import/data/relative_lazy_from.py
new file mode 100644
index 00000000000..1bae2d6853d
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/relative_lazy_from.py
@@ -0,0 +1,8 @@
+# Test relative from imports with lazy keyword
+lazy from .basic2 import x, f
+
+def get_x():
+    return x
+
+def get_f():
+    return f
diff --git a/Lib/test/test_lazy_import/data/self_named_module_not_found.py b/Lib/test/test_lazy_import/data/self_named_module_not_found.py
new file mode 100644
index 00000000000..941230d5da2
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/self_named_module_not_found.py
@@ -0,0 +1 @@
+raise ModuleNotFoundError("boom", name=__name__)
diff --git a/Lib/test/test_lazy_import/data/try_except_eager.py b/Lib/test/test_lazy_import/data/try_except_eager.py
new file mode 100644
index 00000000000..90b4bc62898
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/try_except_eager.py
@@ -0,0 +1,4 @@
+try:
+    import test.test_lazy_import.data.basic2
+except:
+    pass
diff --git a/Lib/test/test_lazy_import/data/try_except_eager_from.py b/Lib/test/test_lazy_import/data/try_except_eager_from.py
new file mode 100644
index 00000000000..1e6c650d0d1
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/try_except_eager_from.py
@@ -0,0 +1,4 @@
+try:
+    from test.test_lazy_import.data.basic2 import f
+except:
+    pass
diff --git a/Lib/test/test_lazy_import/data/versioned/__init__.py b/Lib/test/test_lazy_import/data/versioned/__init__.py
new file mode 100644
index 00000000000..be5bb3f8e60
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/versioned/__init__.py
@@ -0,0 +1,2 @@
+from .__version__ import __version__
+from .__version__ import __copyright__
diff --git a/Lib/test/test_lazy_import/data/versioned/__version__.py b/Lib/test/test_lazy_import/data/versioned/__version__.py
new file mode 100644
index 00000000000..37a10438735
--- /dev/null
+++ b/Lib/test/test_lazy_import/data/versioned/__version__.py
@@ -0,0 +1,2 @@
+__version__ = "1.0"
+__copyright__ = "Copyright (c) 2001-2022 Python Software Foundation."
diff --git a/Lib/test/test_linecache.py b/Lib/test/test_linecache.py
index 02f65338428..fcd94edc611 100644
--- a/Lib/test/test_linecache.py
+++ b/Lib/test/test_linecache.py
@@ -259,22 +259,44 @@ def raise_memoryerror(*args, **kwargs):
     def test_loader(self):
         filename = 'scheme://path'
 
-        for loader in (None, object(), NoSourceLoader()):
+        linecache.clearcache()
+        module_globals = {'__name__': 'a.b.c', '__loader__': None}
+        self.assertEqual(linecache.getlines(filename, module_globals), [])
+
+        for loader in object(), NoSourceLoader():
             linecache.clearcache()
             module_globals = {'__name__': 'a.b.c', '__loader__': loader}
-            self.assertEqual(linecache.getlines(filename, module_globals), [])
+            with self.assertWarns(DeprecationWarning) as w:
+                self.assertEqual(linecache.getlines(filename, module_globals), [])
+            self.assertEqual(str(w.warning),
+                             'Module globals is missing a __spec__.loader')
 
         linecache.clearcache()
         module_globals = {'__name__': 'a.b.c', '__loader__': FakeLoader()}
-        self.assertEqual(linecache.getlines(filename, module_globals),
-                         ['source for a.b.c\n'])
+        with self.assertWarns(DeprecationWarning) as w:
+            self.assertEqual(linecache.getlines(filename, module_globals),
+                             ['source for a.b.c\n'])
+        self.assertEqual(str(w.warning),
+                         'Module globals is missing a __spec__.loader')
 
-        for spec in (None, object(), ModuleSpec('', FakeLoader())):
+        for spec in None, object():
             linecache.clearcache()
             module_globals = {'__name__': 'a.b.c', '__loader__': FakeLoader(),
                               '__spec__': spec}
+            with self.assertWarns(DeprecationWarning) as w:
+                self.assertEqual(linecache.getlines(filename, module_globals),
+                                 ['source for a.b.c\n'])
+            self.assertEqual(str(w.warning),
+                             'Module globals is missing a __spec__.loader')
+
+        linecache.clearcache()
+        module_globals = {'__name__': 'a.b.c', '__loader__': FakeLoader(),
+                          '__spec__': ModuleSpec('', FakeLoader())}
+        with self.assertWarns(DeprecationWarning) as w:
             self.assertEqual(linecache.getlines(filename, module_globals),
                              ['source for a.b.c\n'])
+        self.assertEqual(str(w.warning),
+                         'Module globals; __loader__ != __spec__.loader')
 
         linecache.clearcache()
         spec = ModuleSpec('x.y.z', FakeLoader())
diff --git a/Lib/test/test_locale.py b/Lib/test/test_locale.py
index f91843562c3..a06c600cf56 100644
--- a/Lib/test/test_locale.py
+++ b/Lib/test/test_locale.py
@@ -1,4 +1,5 @@
 from decimal import Decimal
+from test import support
 from test.support import cpython_only, verbose, is_android, linked_to_musl, os_helper
 from test.support.import_helper import ensure_lazy_imports, import_fresh_module
 from unittest import mock
@@ -423,8 +424,8 @@ def test_hyphenated_encoding(self):
         self.check('cs_CZ.ISO8859-2', 'cs_CZ.ISO8859-2')
 
     def test_euro_modifier(self):
-        self.check('de_DE@euro', 'de_DE.ISO8859-15')
-        self.check('en_US.ISO8859-15@euro', 'en_US.ISO8859-15')
+        self.check('de_DE@euro', 'de_DE.ISO8859-15@euro')
+        self.check('en_US.ISO8859-15@euro', 'en_US.ISO8859-15@euro')
         self.check('de_DE.utf8@euro', 'de_DE.UTF-8')
 
     def test_latin_modifier(self):
@@ -532,6 +533,105 @@ def test_setlocale_long_encoding(self):
         with self.assertRaises(locale.Error):
             locale.setlocale(locale.LC_ALL, loc2)
 
+    @support.subTests('localename,localetuple', [
+        ('fr_FR.ISO8859-15@euro', ('fr_FR@euro', 'iso885915')),
+        ('fr_FR.ISO8859-15@euro', ('fr_FR@euro', 'iso88591')),
+        ('fr_FR.ISO8859-15@euro', ('fr_FR@euro', 'ISO8859-15')),
+        ('fr_FR.ISO8859-15@euro', ('fr_FR@euro', 'ISO8859-1')),
+        ('fr_FR.ISO8859-15@euro', ('fr_FR@euro', None)),
+        ('de_DE.ISO8859-15@euro', ('de_DE@euro', 'iso885915')),
+        ('de_DE.ISO8859-15@euro', ('de_DE@euro', 'iso88591')),
+        ('de_DE.ISO8859-15@euro', ('de_DE@euro', 'ISO8859-15')),
+        ('de_DE.ISO8859-15@euro', ('de_DE@euro', 'ISO8859-1')),
+        ('de_DE.ISO8859-15@euro', ('de_DE@euro', None)),
+        ('el_GR.ISO8859-7@euro', ('el_GR@euro', 'iso88597')),
+        ('el_GR.ISO8859-7@euro', ('el_GR@euro', 'ISO8859-7')),
+        ('el_GR.ISO8859-7@euro', ('el_GR@euro', None)),
+        ('ca_ES.ISO8859-15@euro', ('ca_ES@euro', 'iso885915')),
+        ('ca_ES.ISO8859-15@euro', ('ca_ES@euro', 'iso88591')),
+        ('ca_ES.ISO8859-15@euro', ('ca_ES@euro', 'ISO8859-15')),
+        ('ca_ES.ISO8859-15@euro', ('ca_ES@euro', 'ISO8859-1')),
+        ('ca_ES.ISO8859-15@euro', ('ca_ES@euro', None)),
+        ('ca_ES.UTF-8@valencia', ('ca_ES@valencia', 'utf8')),
+        ('ca_ES.UTF-8@valencia', ('ca_ES@valencia', 'UTF-8')),
+        ('ca_ES.UTF-8@valencia', ('ca_ES@valencia', None)),
+        ('ks_IN.UTF-8@devanagari', ('ks_IN@devanagari', 'utf8')),
+        ('ks_IN.UTF-8@devanagari', ('ks_IN@devanagari', 'UTF-8')),
+        ('ks_IN.UTF-8@devanagari', ('ks_IN@devanagari', None)),
+        ('sd_IN.UTF-8@devanagari', ('sd_IN@devanagari', 'utf8')),
+        ('sd_IN.UTF-8@devanagari', ('sd_IN@devanagari', 'UTF-8')),
+        ('sd_IN.UTF-8@devanagari', ('sd_IN@devanagari', None)),
+        ('be_BY.UTF-8@latin', ('be_BY@latin', 'utf8')),
+        ('be_BY.UTF-8@latin', ('be_BY@latin', 'UTF-8')),
+        ('be_BY.UTF-8@latin', ('be_BY@latin', None)),
+        ('sr_RS.UTF-8@latin', ('sr_RS@latin', 'utf8')),
+        ('sr_RS.UTF-8@latin', ('sr_RS@latin', 'UTF-8')),
+        ('sr_RS.UTF-8@latin', ('sr_RS@latin', None)),
+        ('ug_CN.UTF-8@latin', ('ug_CN@latin', 'utf8')),
+        ('ug_CN.UTF-8@latin', ('ug_CN@latin', 'UTF-8')),
+        ('ug_CN.UTF-8@latin', ('ug_CN@latin', None)),
+        ('uz_UZ.UTF-8@cyrillic', ('uz_UZ@cyrillic', 'utf8')),
+        ('uz_UZ.UTF-8@cyrillic', ('uz_UZ@cyrillic', 'UTF-8')),
+        ('uz_UZ.UTF-8@cyrillic', ('uz_UZ@cyrillic', None)),
+    ])
+    def test_setlocale_with_modifier(self, localename, localetuple):
+        try:
+            locale.setlocale(locale.LC_CTYPE, localename)
+        except locale.Error as exc:
+            self.skipTest(str(exc))
+        loc = locale.setlocale(locale.LC_CTYPE, localetuple)
+        self.assertEqual(loc, localename)
+
+        loctuple = locale.getlocale(locale.LC_CTYPE)
+        loc = locale.setlocale(locale.LC_CTYPE, loctuple)
+        self.assertEqual(loc, localename)
+
+    @support.subTests('localename,localetuple', [
+        ('fr_FR.iso885915@euro', ('fr_FR@euro', 'ISO8859-15')),
+        ('fr_FR.ISO8859-15@euro', ('fr_FR@euro', 'ISO8859-15')),
+        ('fr_FR@euro', ('fr_FR@euro', 'ISO8859-15')),
+        ('de_DE.iso885915@euro', ('de_DE@euro', 'ISO8859-15')),
+        ('de_DE.ISO8859-15@euro', ('de_DE@euro', 'ISO8859-15')),
+        ('de_DE@euro', ('de_DE@euro', 'ISO8859-15')),
+        ('el_GR.iso88597@euro', ('el_GR@euro', 'ISO8859-7')),
+        ('el_GR.ISO8859-7@euro', ('el_GR@euro', 'ISO8859-7')),
+        ('el_GR@euro', ('el_GR@euro', 'ISO8859-7')),
+        ('ca_ES.iso885915@euro', ('ca_ES@euro', 'ISO8859-15')),
+        ('ca_ES.ISO8859-15@euro', ('ca_ES@euro', 'ISO8859-15')),
+        ('ca_ES@euro', ('ca_ES@euro', 'ISO8859-15')),
+        ('ca_ES.utf8@valencia', ('ca_ES@valencia', 'UTF-8')),
+        ('ca_ES.UTF-8@valencia', ('ca_ES@valencia', 'UTF-8')),
+        ('ca_ES@valencia', ('ca_ES@valencia', 'UTF-8')),
+        ('ks_IN.utf8@devanagari', ('ks_IN@devanagari', 'UTF-8')),
+        ('ks_IN.UTF-8@devanagari', ('ks_IN@devanagari', 'UTF-8')),
+        ('ks_IN@devanagari', ('ks_IN@devanagari', 'UTF-8')),
+        ('sd_IN.utf8@devanagari', ('sd_IN@devanagari', 'UTF-8')),
+        ('sd_IN.UTF-8@devanagari', ('sd_IN@devanagari', 'UTF-8')),
+        ('sd_IN@devanagari', ('sd_IN@devanagari', 'UTF-8')),
+        ('be_BY.utf8@latin', ('be_BY@latin', 'UTF-8')),
+        ('be_BY.UTF-8@latin', ('be_BY@latin', 'UTF-8')),
+        ('be_BY@latin', ('be_BY@latin', 'UTF-8')),
+        ('sr_RS.utf8@latin', ('sr_RS@latin', 'UTF-8')),
+        ('sr_RS.UTF-8@latin', ('sr_RS@latin', 'UTF-8')),
+        ('sr_RS@latin', ('sr_RS@latin', 'UTF-8')),
+        ('ug_CN.utf8@latin', ('ug_CN@latin', 'UTF-8')),
+        ('ug_CN.UTF-8@latin', ('ug_CN@latin', 'UTF-8')),
+        ('ug_CN@latin', ('ug_CN@latin', 'UTF-8')),
+        ('uz_UZ.utf8@cyrillic', ('uz_UZ@cyrillic', 'UTF-8')),
+        ('uz_UZ.UTF-8@cyrillic', ('uz_UZ@cyrillic', 'UTF-8')),
+        ('uz_UZ@cyrillic', ('uz_UZ@cyrillic', 'UTF-8')),
+    ])
+    def test_getlocale_with_modifier(self, localename, localetuple):
+        try:
+            locale.setlocale(locale.LC_CTYPE, localename)
+        except locale.Error as exc:
+            self.skipTest(str(exc))
+        loctuple = locale.getlocale(locale.LC_CTYPE)
+        self.assertEqual(loctuple, localetuple)
+
+        locale.setlocale(locale.LC_CTYPE, loctuple)
+        self.assertEqual(locale.getlocale(locale.LC_CTYPE), localetuple)
+
 
 class TestMiscellaneous(unittest.TestCase):
     def test_defaults_UTF8(self):
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index 69364b0575d..9effc375851 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -62,7 +62,7 @@
 import weakref
 
 from http.server import HTTPServer, BaseHTTPRequestHandler
-from unittest.mock import patch
+from unittest.mock import call, Mock, patch
 from urllib.parse import urlparse, parse_qs
 from socketserver import (ThreadingUDPServer, DatagramRequestHandler,
                           ThreadingTCPServer, StreamRequestHandler)
@@ -404,6 +404,20 @@ def test_empty_filter(self):
         r = logging.makeLogRecord({'name': 'spam.eggs'})
         self.assertTrue(f.filter(r))
 
+    def test_filter_repr(self):
+        f = logging.Filter('myapp')
+        self.assertEqual(repr(f), '<Filter (myapp)>')
+
+    def test_filter_repr_empty(self):
+        f = logging.Filter()
+        self.assertEqual(repr(f), '<Filter ()>')
+
+    def test_filter_repr_subclass(self):
+        class MyFilter(logging.Filter):
+            pass
+        f = MyFilter('myapp')
+        self.assertEqual(repr(f), '<MyFilter (myapp)>')
+
 #
 #   First, we define our levels. There can be as many as you want - the only
 #     limitations are that they should be integers, the lowest should be > 0 and
@@ -731,6 +745,7 @@ def remove_loop(fname, tries):
     # based on os.fork existing because that is what users and this test use.
     # This helps ensure that when fork exists (the important concept) that the
     # register_at_fork mechanism is also present and used.
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @support.requires_fork()
     @threading_helper.requires_working_threading()
     @skip_if_asan_fork
@@ -799,6 +814,23 @@ def lock_holder_thread_fn():
 
             support.wait_process(pid, exitcode=0)
 
+    def test_remove_handler_while_emitting(self):
+        # Removing a handler while callHandlers() iterates over the handlers
+        # should not cause the following handlers to be skipped (gh-79366).
+        logger = logging.Logger('test_remove_handler_while_emitting')
+        calls = []
+        class RemovingHandler(logging.Handler):
+            def emit(self, record):
+                calls.append('removing')
+                logger.removeHandler(self)
+        class CountingHandler(logging.Handler):
+            def emit(self, record):
+                calls.append('counting')
+        logger.addHandler(RemovingHandler())
+        logger.addHandler(CountingHandler())
+        logger.error('spam')
+        self.assertEqual(calls, ['removing', 'counting'])
+
 
 class BadStream(object):
     def write(self, data):
@@ -3634,14 +3666,14 @@ def setup_via_listener(self, text, verify=None):
         # Ask for a randomly assigned port (by using port 0)
         t = logging.config.listen(0, verify)
         t.start()
-        t.ready.wait()
+        self.assertTrue(t.ready.wait(support.LONG_TIMEOUT),
+                        msg='the listener did not start')
         # Now get the port allocated
         port = t.port
         t.ready.clear()
         try:
-            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-            sock.settimeout(2.0)
-            sock.connect(('localhost', port))
+            # The server can listen on IPv6, so do not force a family.
+            sock = socket.create_connection(('localhost', port), timeout=2.0)
 
             slen = struct.pack('>L', len(text))
             s = slen + text
@@ -3756,6 +3788,18 @@ def verify_reverse(stuff):
             ('ERROR', '2'),
         ], pat=r"^[\w.]+ -> (\w+): (\d+)$")
 
+    @support.requires_working_socket()
+    def test_listen_server_error(self):
+        # The "ready" event should be set even if the server fails to start.
+        t = logging.config.listen(-1)
+        t.daemon = True
+        with threading_helper.catch_threading_exception() as cm:
+            t.start()
+            self.assertTrue(t.ready.wait(support.SHORT_TIMEOUT),
+                            msg='the listener did not report the failure')
+            threading_helper.join_thread(t)
+            self.assertIs(cm.exc_type, OverflowError)
+
     def test_bad_format(self):
         self.assertRaises(ValueError, self.apply_config, self.bad_format)
 
@@ -4046,6 +4090,7 @@ def test_config_queue_handler_invalid_config_does_not_create_multiprocessing_man
                 self._apply_simple_queue_listener_configuration(qspec)
                 manager.assert_not_called()
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @skip_if_tsan_fork
     @support.requires_subprocess()
     @unittest.skipUnless(support.Py_DEBUG, "requires a debug build for testing"
@@ -4068,6 +4113,7 @@ def test_config_reject_simple_queue_handler_multiprocessing_context(self):
                 with self.assertRaises(ValueError):
                     self._apply_simple_queue_listener_configuration(qspec)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @skip_if_tsan_fork
     @support.requires_subprocess()
     @unittest.skipUnless(support.Py_DEBUG, "requires a debug build for testing"
@@ -4108,6 +4154,7 @@ def _mpinit_issue121723(qspec, message_to_log):
         # log a message (this creates a record put in the queue)
         logging.getLogger().info(message_to_log)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @skip_if_tsan_fork
     @support.requires_subprocess()
     def test_multiprocessing_queues(self):
@@ -4911,6 +4958,20 @@ def test_relativeCreated_has_higher_precision(self):
                 # After PR gh-102412, precision (places) increases from 3 to 7
                 self.assertAlmostEqual(relativeCreated, offset_ns / 1e6, places=7)
 
+    def test_formatter_repr(self):
+        f = logging.Formatter('%(message)s')
+        self.assertEqual(repr(f), '<Formatter (%(message)s)>')
+
+    def test_formatter_repr_default(self):
+        f = logging.Formatter()
+        self.assertEqual(repr(f), '<Formatter (%(message)s)>')
+
+    def test_formatter_repr_subclass(self):
+        class MyFormatter(logging.Formatter):
+            pass
+        f = MyFormatter('%(message)s')
+        self.assertEqual(repr(f), '<MyFormatter (%(message)s)>')
+
 
 class TestBufferingFormatter(logging.BufferingFormatter):
     def formatHeader(self, records):
@@ -5339,6 +5400,7 @@ def _extract_logrecord_process_name(key, logMultiprocessing, conn=None):
         else:
             return results
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @skip_if_tsan_fork
     def test_multiprocessing(self):
         support.skip_if_broken_multiprocessing_synchronize()
@@ -5574,12 +5636,19 @@ def test_incompatible(self):
         assertRaises = self.assertRaises
         handlers = [logging.StreamHandler()]
         stream = sys.stderr
+        formatter = logging.Formatter()
         assertRaises(ValueError, logging.basicConfig, filename='test.log',
                                                       stream=stream)
         assertRaises(ValueError, logging.basicConfig, filename='test.log',
                                                       handlers=handlers)
         assertRaises(ValueError, logging.basicConfig, stream=stream,
                                                       handlers=handlers)
+        assertRaises(ValueError, logging.basicConfig, formatter=formatter,
+                                                      format='%(message)s')
+        assertRaises(ValueError, logging.basicConfig, formatter=formatter,
+                                                      datefmt='%H:%M:%S')
+        assertRaises(ValueError, logging.basicConfig, formatter=formatter,
+                                                      style='%')
         # Issue 23207: test for invalid kwargs
         assertRaises(ValueError, logging.basicConfig, loglevel=logging.INFO)
         # Should pop both filename and filemode even if filename is None
@@ -5714,6 +5783,20 @@ def dummy_handle_error(record):
             # didn't write anything due to the encoding error
             self.assertEqual(data, r'')
 
+    def test_formatter_given(self):
+        mock_formatter = Mock()
+        mock_handler = Mock(formatter=None)
+        with patch("logging.Formatter") as mock_formatter_init:
+            logging.basicConfig(formatter=mock_formatter, handlers=[mock_handler])
+        self.assertEqual(mock_handler.setFormatter.call_args_list, [call(mock_formatter)])
+        self.assertEqual(mock_formatter_init.call_count, 0)
+
+    def test_formatter_not_given(self):
+        mock_handler = Mock(formatter=None)
+        with patch("logging.Formatter") as mock_formatter_init:
+            logging.basicConfig(handlers=[mock_handler])
+        self.assertEqual(mock_formatter_init.call_count, 1)
+
     @support.requires_working_socket()
     def test_log_taskName(self):
         async def log_record():
@@ -6276,11 +6359,12 @@ def setUp(self):
         self.rmfiles = []
 
     def tearDown(self):
-        for fn in self.rmfiles:
-            os.unlink(fn)
-        if os.path.exists(self.fn):
-            os.unlink(self.fn)
-        BaseTest.tearDown(self)
+        try:
+            for fn in self.rmfiles:
+                os_helper.unlink(fn)
+            os_helper.unlink(self.fn)
+        finally:
+            BaseTest.tearDown(self)
 
     def assertLogFile(self, filename):
         "Assert a log file is there and register it for deletion"
@@ -7223,8 +7307,8 @@ def test_compute_rollover(self, when=when, interval=interval, exp=exp):
         setattr(TimedRotatingFileHandlerTest, name, test_compute_rollover)
 
 
-@unittest.skipUnless(win32evtlog, 'win32evtlog/win32evtlogutil/pywintypes required for this test.')
 class NTEventLogHandlerTest(BaseTest):
+    @unittest.skipUnless(win32evtlog, 'win32evtlog/win32evtlogutil/pywintypes required for this test.')
     def test_basic(self):
         logtype = 'Application'
         elh = win32evtlog.OpenEventLog(None, logtype)
@@ -7258,6 +7342,17 @@ def test_basic(self):
         msg = 'Record not found in event log, went back %d records' % GO_BACK
         self.assertTrue(found, msg=msg)
 
+    @unittest.skipUnless(sys.platform == "win32", "Windows required for this test")
+    def test_without_pywin32(self):
+        h = logging.handlers.NTEventLogHandler('python_test')
+        self.addCleanup(h.close)
+
+        # Verify that the handler uses _winapi module
+        self.assertIsNotNone(h._winapi, "_winapi module should be available")
+
+        r = logging.makeLogRecord({'msg': 'Hello!'})
+        h.emit(r)
+
 
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
@@ -7269,6 +7364,16 @@ def test__all__(self):
         support.check__all__(self, logging, not_exported=not_exported)
 
 
+class TestModule(unittest.TestCase):
+    def test_deprecated__version__and__date__(self):
+        msg = "is deprecated and slated for removal in Python 3.20"
+        for attr in ("__version__", "__date__"):
+            with self.subTest(attr=attr):
+                with self.assertWarnsRegex(DeprecationWarning, msg) as cm:
+                    getattr(logging, attr)
+                self.assertEqual(cm.filename, __file__)
+
+
 # Set the locale to the platform-dependent default.  I have no idea
 # why the test does this, but in any case we save the current locale
 # first and restore it at the end.
diff --git a/Lib/test/test_lzma.py b/Lib/test/test_lzma.py
index c7f2662ab0b..90556525dc9 100644
--- a/Lib/test/test_lzma.py
+++ b/Lib/test/test_lzma.py
@@ -63,7 +63,6 @@ def test_simple_bad_args(self):
         lzd.decompress(empty)
         self.assertRaises(EOFError, lzd.decompress, b"quux")
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; lzma.LZMAError: Failed to initialize encoder
     def test_bad_filter_spec(self):
         self.assertRaises(TypeError, LZMACompressor, filters=[b"wobsite"])
         self.assertRaises(ValueError, LZMACompressor, filters=[{"xyzzy": 3}])
@@ -674,7 +673,6 @@ def test_init_bad_preset(self):
         with self.assertRaises(ValueError):
             LZMAFile(BytesIO(COMPRESSED_XZ), preset=3)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; lzma.LZMAError: Failed to initialize encoder
     def test_init_bad_filter_spec(self):
         with self.assertRaises(TypeError):
             LZMAFile(BytesIO(), "w", filters=[b"wobsite"])
diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index 943448d69ca..c16c25970bc 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -17,6 +17,7 @@
 
 eps = 1E-05
 NAN = float('nan')
+NNAN = float('-nan')
 INF = float('inf')
 NINF = float('-inf')
 FLOAT_MAX = sys.float_info.max
@@ -54,56 +55,6 @@ def to_ulps(x):
     return n
 
 
-# Here's a pure Python version of the math.factorial algorithm, for
-# documentation and comparison purposes.
-#
-# Formula:
-#
-#   factorial(n) = factorial_odd_part(n) << (n - count_set_bits(n))
-#
-# where
-#
-#   factorial_odd_part(n) = product_{i >= 0} product_{0 < j <= n >> i; j odd} j
-#
-# The outer product above is an infinite product, but once i >= n.bit_length,
-# (n >> i) < 1 and the corresponding term of the product is empty.  So only the
-# finitely many terms for 0 <= i < n.bit_length() contribute anything.
-#
-# We iterate downwards from i == n.bit_length() - 1 to i == 0.  The inner
-# product in the formula above starts at 1 for i == n.bit_length(); for each i
-# < n.bit_length() we get the inner product for i from that for i + 1 by
-# multiplying by all j in {n >> i+1 < j <= n >> i; j odd}.  In Python terms,
-# this set is range((n >> i+1) + 1 | 1, (n >> i) + 1 | 1, 2).
-
-def count_set_bits(n):
-    """Number of '1' bits in binary expansion of a nonnnegative integer."""
-    return 1 + count_set_bits(n & n - 1) if n else 0
-
-def partial_product(start, stop):
-    """Product of integers in range(start, stop, 2), computed recursively.
-    start and stop should both be odd, with start <= stop.
-
-    """
-    numfactors = (stop - start) >> 1
-    if not numfactors:
-        return 1
-    elif numfactors == 1:
-        return start
-    else:
-        mid = (start + numfactors) | 1
-        return partial_product(start, mid) * partial_product(mid, stop)
-
-def py_factorial(n):
-    """Factorial of nonnegative integer n, via "Binary Split Factorial Formula"
-    described at http://www.luschny.de/math/factorial/binarysplitfact.html
-
-    """
-    inner = outer = 1
-    for i in reversed(range(n.bit_length())):
-        inner *= partial_product((n >> i + 1) + 1 | 1, (n >> i) + 1 | 1)
-        outer *= inner
-    return outer << (n - count_set_bits(n))
-
 def ulp_abs_check(expected, got, ulp_tol, abs_tol):
     """Given finite floats `expected` and `got`, check that they're
     approximately equal to within the given number of ulps or the
@@ -238,18 +189,21 @@ def __init__(self, value):
     def __index__(self):
         return self.value
 
-# int subclass with broken arithmetic operators; implementations must
-# convert their arguments to exact ints instead of using these.
-class BadIntSubclass(int):
-    def _binop(self, other='ignored', mod=None):
-        return 42
-    __add__ = __radd__ = __sub__ = __rsub__ = _binop
-    __mul__ = __rmul__ = __mod__ = __rmod__ = _binop
-    __divmod__ = __rdivmod__ = __pow__ = __rpow__ = _binop
-    __floordiv__ = __rfloordiv__ = _binop
-    __lshift__ = __rlshift__ = __rshift__ = __rrshift__ = _binop
-    __and__ = __rand__ = __or__ = __ror__ = __xor__ = __rxor__ = _binop
-    __lt__ = __le__ = __gt__ = __ge__ = _binop
+class IndexableFloatLike:
+    def __init__(self, float_value, index_value):
+        self.float_value = float_value
+        self.index_value = index_value
+
+    def __float__(self):
+        if isinstance(self.float_value, BaseException):
+            raise self.float_value
+        return self.float_value
+
+    def __index__(self):
+        if isinstance(self.index_value, BaseException):
+            raise self.index_value
+        return self.index_value
+
 
 class BadDescr:
     def __get__(self, obj, objtype=None):
@@ -490,6 +444,19 @@ def testCopysign(self):
         # similarly, copysign(2., NAN) could be 2. or -2.
         self.assertEqual(abs(math.copysign(2., NAN)), 2.)
 
+    def test_signbit(self):
+        self.assertRaises(TypeError, math.signbit)
+        self.assertRaises(TypeError, math.signbit, '1.0')
+
+        # C11, §7.12.3.6 requires signbit() to return a nonzero value
+        # if and only if the sign of its argument value is negative,
+        # but in practice, we are only interested in a boolean value.
+        self.assertIsInstance(math.signbit(1.0), bool)
+
+        for arg in [0., 1., INF, NAN]:
+            self.assertFalse(math.signbit(arg))
+            self.assertTrue(math.signbit(-arg))
+
     def testCos(self):
         self.assertRaises(TypeError, math.cos)
         self.ftest('cos(-pi/2)', math.cos(-math.pi/2), 0, abs_tol=math.ulp(1))
@@ -548,33 +515,6 @@ def testFabs(self):
         self.ftest('fabs(0)', math.fabs(0), 0)
         self.ftest('fabs(1)', math.fabs(1), 1)
 
-    def testFactorial(self):
-        self.assertEqual(math.factorial(0), 1)
-        total = 1
-        for i in range(1, 1000):
-            total *= i
-            self.assertEqual(math.factorial(i), total)
-            self.assertEqual(math.factorial(i), py_factorial(i))
-        self.assertRaises(ValueError, math.factorial, -1)
-        self.assertRaises(ValueError, math.factorial, -10**100)
-
-    def testFactorialNonIntegers(self):
-        self.assertRaises(TypeError, math.factorial, 5.0)
-        self.assertRaises(TypeError, math.factorial, 5.2)
-        self.assertRaises(TypeError, math.factorial, -1.0)
-        self.assertRaises(TypeError, math.factorial, -1e100)
-        self.assertRaises(TypeError, math.factorial, decimal.Decimal('5'))
-        self.assertRaises(TypeError, math.factorial, decimal.Decimal('5.2'))
-        self.assertRaises(TypeError, math.factorial, "5")
-
-    # Other implementations may place different upper bounds.
-    @support.cpython_only
-    def testFactorialHugeInputs(self):
-        # Currently raises OverflowError for inputs that are too large
-        # to fit into a C long.
-        self.assertRaises(OverflowError, math.factorial, 10**100)
-        self.assertRaises(TypeError, math.factorial, 1e100)
-
     def testFloor(self):
         self.assertRaises(TypeError, math.floor)
         self.assertEqual(int, type(math.floor(0.5)))
@@ -638,6 +578,92 @@ def testFmod(self):
         self.assertEqual(math.fmod(0.0, NINF), 0.0)
         self.assertRaises(ValueError, math.fmod, INF, INF)
 
+    def test_fmax(self):
+        self.assertRaises(TypeError, math.fmax)
+        self.assertRaises(TypeError, math.fmax, 'x', 'y')
+
+        self.assertEqual(math.fmax(0., 0.), 0.)
+        self.assertEqual(math.fmax(1., 2.), 2.)
+        self.assertEqual(math.fmax(2., 1.), 2.)
+
+        self.assertEqual(math.fmax(+1., +0.), 1.)
+        self.assertEqual(math.fmax(+0., +1.), 1.)
+        self.assertEqual(math.fmax(+1., -0.), 1.)
+        self.assertEqual(math.fmax(-0., +1.), 1.)
+
+        self.assertEqual(math.fmax(-1., +0.), 0.)
+        self.assertEqual(math.fmax(+0., -1.), 0.)
+        self.assertEqual(math.fmax(-1., -0.), 0.)
+        self.assertEqual(math.fmax(-0., -1.), 0.)
+
+        for x in [NINF, -1., -0., 0., 1., INF]:
+            self.assertFalse(math.isnan(x))
+
+            with self.subTest(x=x, is_negative=math.copysign(1, x) < 0):
+                self.assertEqual(math.fmax(INF, x), INF)
+                self.assertEqual(math.fmax(x, INF), INF)
+                self.assertEqual(math.fmax(NINF, x), x)
+                self.assertEqual(math.fmax(x, NINF), x)
+
+    @requires_IEEE_754
+    def test_fmax_nans(self):
+        # When exactly one operand is NaN, the other is returned.
+        for x in [NINF, -1., -0., 0., 1., INF]:
+            with self.subTest(x=x, is_negative=math.copysign(1, x) < 0):
+                self.assertFalse(math.isnan(math.fmax(NAN, x)))
+                self.assertFalse(math.isnan(math.fmax(x, NAN)))
+                self.assertFalse(math.isnan(math.fmax(NNAN, x)))
+                self.assertFalse(math.isnan(math.fmax(x, NNAN)))
+        # When both operands are NaNs, fmax() returns NaN (see C11, F.10.9.2)
+        # whose sign is implementation-defined (see C11, F.10.0.3).
+        self.assertTrue(math.isnan(math.fmax(NAN, NAN)))
+        self.assertTrue(math.isnan(math.fmax(NNAN, NNAN)))
+        self.assertTrue(math.isnan(math.fmax(NAN, NNAN)))
+        self.assertTrue(math.isnan(math.fmax(NNAN, NAN)))
+
+    def test_fmin(self):
+        self.assertRaises(TypeError, math.fmin)
+        self.assertRaises(TypeError, math.fmin, 'x', 'y')
+
+        self.assertEqual(math.fmin(0., 0.), 0.)
+        self.assertEqual(math.fmin(1., 2.), 1.)
+        self.assertEqual(math.fmin(2., 1.), 1.)
+
+        self.assertEqual(math.fmin(+1., +0.), 0.)
+        self.assertEqual(math.fmin(+0., +1.), 0.)
+        self.assertEqual(math.fmin(+1., -0.), 0.)
+        self.assertEqual(math.fmin(-0., +1.), 0.)
+
+        self.assertEqual(math.fmin(-1., +0.), -1.)
+        self.assertEqual(math.fmin(+0., -1.), -1.)
+        self.assertEqual(math.fmin(-1., -0.), -1.)
+        self.assertEqual(math.fmin(-0., -1.), -1.)
+
+        for x in [NINF, -1., -0., 0., 1., INF]:
+            self.assertFalse(math.isnan(x))
+
+            with self.subTest(x=x, is_negative=math.copysign(1, x) < 0):
+                self.assertEqual(math.fmin(INF, x), x)
+                self.assertEqual(math.fmin(x, INF), x)
+                self.assertEqual(math.fmin(NINF, x), NINF)
+                self.assertEqual(math.fmin(x, NINF), NINF)
+
+    @requires_IEEE_754
+    def test_fmin_nans(self):
+        # When exactly one operand is NaN, the other is returned.
+        for x in [NINF, -1., -0., 0., 1., INF]:
+            with self.subTest(x=x, is_negative=math.copysign(1, x) < 0):
+                self.assertFalse(math.isnan(math.fmin(NAN, x)))
+                self.assertFalse(math.isnan(math.fmin(x, NAN)))
+                self.assertFalse(math.isnan(math.fmin(NNAN, x)))
+                self.assertFalse(math.isnan(math.fmin(x, NNAN)))
+        # When both operands are NaNs, fmin() returns NaN (see C11, F.10.9.3)
+        # whose sign is implementation-defined (see C11, F.10.0.3).
+        self.assertTrue(math.isnan(math.fmin(NAN, NAN)))
+        self.assertTrue(math.isnan(math.fmin(NNAN, NNAN)))
+        self.assertTrue(math.isnan(math.fmin(NAN, NNAN)))
+        self.assertTrue(math.isnan(math.fmin(NNAN, NAN)))
+
     def testFrexp(self):
         self.assertRaises(TypeError, math.frexp)
 
@@ -1090,78 +1116,6 @@ def test_math_dist_leak(self):
         with self.assertRaises(ValueError):
             math.dist([1, 2], [3, 4, 5])
 
-    def testIsqrt(self):
-        # Test a variety of inputs, large and small.
-        test_values = (
-            list(range(1000))
-            + list(range(10**6 - 1000, 10**6 + 1000))
-            + [2**e + i for e in range(60, 200) for i in range(-40, 40)]
-            + [3**9999, 10**5001]
-        )
-
-        for value in test_values:
-            with self.subTest(value=value):
-                s = math.isqrt(value)
-                self.assertIs(type(s), int)
-                self.assertLessEqual(s*s, value)
-                self.assertLess(value, (s+1)*(s+1))
-
-        # Negative values
-        with self.assertRaises(ValueError):
-            math.isqrt(-1)
-
-        # Integer-like things
-        s = math.isqrt(True)
-        self.assertIs(type(s), int)
-        self.assertEqual(s, 1)
-
-        s = math.isqrt(False)
-        self.assertIs(type(s), int)
-        self.assertEqual(s, 0)
-
-        class IntegerLike(object):
-            def __init__(self, value):
-                self.value = value
-
-            def __index__(self):
-                return self.value
-
-        s = math.isqrt(IntegerLike(1729))
-        self.assertIs(type(s), int)
-        self.assertEqual(s, 41)
-
-        # Overridden operators of an int subclass must not affect the
-        # result.
-        s = math.isqrt(BadIntSubclass(10**20))
-        self.assertIs(type(s), int)
-        self.assertEqual(s, 10**10)
-
-        s = math.isqrt(BadIntSubclass(10**20 - 1))
-        self.assertIs(type(s), int)
-        self.assertEqual(s, 10**10 - 1)
-
-        with self.assertRaises(ValueError):
-            math.isqrt(IntegerLike(-3))
-
-        # Non-integer-like things
-        bad_values = [
-            3.5, "a string", decimal.Decimal("3.5"), 3.5j,
-            100.0, -4.0,
-        ]
-        for value in bad_values:
-            with self.subTest(value=value):
-                with self.assertRaises(TypeError):
-                    math.isqrt(value)
-
-    @support.bigmemtest(2**32, memuse=0.85)
-    def test_isqrt_huge(self, size):
-        if size & 1:
-            size += 1
-        v = 1 << size
-        w = math.isqrt(v)
-        self.assertEqual(w.bit_length(), size // 2 + 1)
-        self.assertEqual(w.bit_count(), 1)
-
     def test_lcm(self):
         lcm = math.lcm
         self.assertEqual(lcm(0, 0), 0)
@@ -1256,13 +1210,32 @@ def testLog(self):
         self.ftest('log(10**40, 10**20)', math.log(10**40, 10**20), 2)
         self.ftest('log(10**1000)', math.log(10**1000),
                    2302.5850929940457)
+        self.ftest('log(10**2000, 10**1000)', math.log(10**2000, 10**1000), 2)
+        self.ftest('log(MyIndexable(32), MyIndexable(2))',
+                   math.log(MyIndexable(32), MyIndexable(2)), 5)
+        self.ftest('log(MyIndexable(10**1000))',
+                   math.log(MyIndexable(10**1000)),
+                   2302.5850929940457)
+        self.ftest('log(MyIndexable(10**2000), MyIndexable(10**1000))',
+                   math.log(MyIndexable(10**2000), MyIndexable(10**1000)),
+                   2)
+        self.assertRaises(ValueError, math.log, 0.0)
+        self.assertRaises(ValueError, math.log, 0)
+        self.assertRaises(ValueError, math.log, MyIndexable(0))
         self.assertRaises(ValueError, math.log, -1.5)
+        self.assertRaises(ValueError, math.log, -1)
+        self.assertRaises(ValueError, math.log, MyIndexable(-1))
         self.assertRaises(ValueError, math.log, -10**1000)
+        self.assertRaises(ValueError, math.log, MyIndexable(-10**1000))
         self.assertRaises(ValueError, math.log, 10, -10)
         self.assertRaises(ValueError, math.log, NINF)
         self.assertEqual(math.log(INF), INF)
         self.assertTrue(math.isnan(math.log(NAN)))
 
+        self.assertEqual(math.log(IndexableFloatLike(math.e, 10**1000)), 1.0)
+        self.assertAlmostEqual(math.log(IndexableFloatLike(OverflowError(), 10**1000)),
+                               2302.5850929940457)
+
     def testLog1p(self):
         self.assertRaises(TypeError, math.log1p)
         for n in [2, 2**90, 2**300]:
@@ -1278,16 +1251,28 @@ def testLog2(self):
         self.assertEqual(math.log2(1), 0.0)
         self.assertEqual(math.log2(2), 1.0)
         self.assertEqual(math.log2(4), 2.0)
+        self.assertEqual(math.log2(MyIndexable(4)), 2.0)
 
         # Large integer values
         self.assertEqual(math.log2(2**1023), 1023.0)
         self.assertEqual(math.log2(2**1024), 1024.0)
         self.assertEqual(math.log2(2**2000), 2000.0)
+        self.assertEqual(math.log2(MyIndexable(2**2000)), 2000.0)
 
+        self.assertRaises(ValueError, math.log2, 0.0)
+        self.assertRaises(ValueError, math.log2, 0)
+        self.assertRaises(ValueError, math.log2, MyIndexable(0))
         self.assertRaises(ValueError, math.log2, -1.5)
+        self.assertRaises(ValueError, math.log2, -1)
+        self.assertRaises(ValueError, math.log2, MyIndexable(-1))
+        self.assertRaises(ValueError, math.log2, -2**2000)
+        self.assertRaises(ValueError, math.log2, MyIndexable(-2**2000))
         self.assertRaises(ValueError, math.log2, NINF)
         self.assertTrue(math.isnan(math.log2(NAN)))
 
+        self.assertEqual(math.log2(IndexableFloatLike(8.0, 2**2000)), 3.0)
+        self.assertEqual(math.log2(IndexableFloatLike(OverflowError(), 2**2000)), 2000.0)
+
     @requires_IEEE_754
     # log2() is not accurate enough on Mac OS X Tiger (10.4)
     @support.requires_mac_ver(10, 5)
@@ -1303,12 +1288,24 @@ def testLog10(self):
         self.ftest('log10(1)', math.log10(1), 0)
         self.ftest('log10(10)', math.log10(10), 1)
         self.ftest('log10(10**1000)', math.log10(10**1000), 1000.0)
+        self.ftest('log10(MyIndexable(10))', math.log10(MyIndexable(10)), 1)
+        self.ftest('log10(MyIndexable(10**1000))',
+                   math.log10(MyIndexable(10**1000)), 1000.0)
+        self.assertRaises(ValueError, math.log10, 0.0)
+        self.assertRaises(ValueError, math.log10, 0)
+        self.assertRaises(ValueError, math.log10, MyIndexable(0))
         self.assertRaises(ValueError, math.log10, -1.5)
+        self.assertRaises(ValueError, math.log10, -1)
+        self.assertRaises(ValueError, math.log10, MyIndexable(-1))
         self.assertRaises(ValueError, math.log10, -10**1000)
+        self.assertRaises(ValueError, math.log10, MyIndexable(-10**1000))
         self.assertRaises(ValueError, math.log10, NINF)
         self.assertEqual(math.log(INF), INF)
         self.assertTrue(math.isnan(math.log10(NAN)))
 
+        self.assertEqual(math.log10(IndexableFloatLike(100.0, 10**1000)), 2.0)
+        self.assertEqual(math.log10(IndexableFloatLike(OverflowError(), 10**1000)), 1000.0)
+
     @support.bigmemtest(2**32, memuse=0.2)
     def test_log_huge_integer(self, size):
         v = 1 << size
@@ -1412,7 +1409,6 @@ def __rmul__(self, other):
         args = ((-5, -5, 10), (1.5, 4611686018427387904, 2305843009213693952))
         self.assertEqual(sumprod(*args), 0.0)
 
-
     @requires_IEEE_754
     @unittest.skipIf(HAVE_DOUBLE_ROUNDING,
                          "sumprod() accuracy not guaranteed on machines with double rounding")
@@ -1999,6 +1995,28 @@ def testIsfinite(self):
         self.assertFalse(math.isfinite(float("inf")))
         self.assertFalse(math.isfinite(float("-inf")))
 
+    def testIsnormal(self):
+        self.assertTrue(math.isnormal(1.25))
+        self.assertTrue(math.isnormal(-1.0))
+        self.assertFalse(math.isnormal(0.0))
+        self.assertFalse(math.isnormal(-0.0))
+        self.assertFalse(math.isnormal(INF))
+        self.assertFalse(math.isnormal(NINF))
+        self.assertFalse(math.isnormal(NAN))
+        self.assertFalse(math.isnormal(FLOAT_MIN/2))
+        self.assertFalse(math.isnormal(-FLOAT_MIN/2))
+
+    def testIssubnormal(self):
+        self.assertFalse(math.issubnormal(1.25))
+        self.assertFalse(math.issubnormal(-1.0))
+        self.assertFalse(math.issubnormal(0.0))
+        self.assertFalse(math.issubnormal(-0.0))
+        self.assertFalse(math.issubnormal(INF))
+        self.assertFalse(math.issubnormal(NINF))
+        self.assertFalse(math.issubnormal(NAN))
+        self.assertTrue(math.issubnormal(FLOAT_MIN/2))
+        self.assertTrue(math.issubnormal(-FLOAT_MIN/2))
+
     def testIsnan(self):
         self.assertTrue(math.isnan(float("nan")))
         self.assertTrue(math.isnan(float("-nan")))
@@ -2297,140 +2315,6 @@ def _naive_prod(iterable, start=1):
         self.assertEqual(type(prod([1, decimal.Decimal(2.0), 3, 4, 5, 6])),
                          decimal.Decimal)
 
-    def testPerm(self):
-        perm = math.perm
-        factorial = math.factorial
-        # Test if factorial definition is satisfied
-        for n in range(500):
-            for k in (range(n + 1) if n < 100 else range(30) if n < 200 else range(10)):
-                self.assertEqual(perm(n, k),
-                                 factorial(n) // factorial(n - k))
-
-        # Test for Pascal's identity
-        for n in range(1, 100):
-            for k in range(1, n):
-                self.assertEqual(perm(n, k), perm(n - 1, k - 1) * k + perm(n - 1, k))
-
-        # Test corner cases
-        for n in range(1, 100):
-            self.assertEqual(perm(n, 0), 1)
-            self.assertEqual(perm(n, 1), n)
-            self.assertEqual(perm(n, n), factorial(n))
-
-        # Test one argument form
-        for n in range(20):
-            self.assertEqual(perm(n), factorial(n))
-            self.assertEqual(perm(n, None), factorial(n))
-
-        # Raises TypeError if any argument is non-integer or argument count is
-        # not 1 or 2
-        self.assertRaises(TypeError, perm, 10, 1.0)
-        self.assertRaises(TypeError, perm, 10, decimal.Decimal(1.0))
-        self.assertRaises(TypeError, perm, 10, "1")
-        self.assertRaises(TypeError, perm, 10.0, 1)
-        self.assertRaises(TypeError, perm, decimal.Decimal(10.0), 1)
-        self.assertRaises(TypeError, perm, "10", 1)
-
-        self.assertRaises(TypeError, perm)
-        self.assertRaises(TypeError, perm, 10, 1, 3)
-        self.assertRaises(TypeError, perm)
-
-        # Raises Value error if not k or n are negative numbers
-        self.assertRaises(ValueError, perm, -1, 1)
-        self.assertRaises(ValueError, perm, -2**1000, 1)
-        self.assertRaises(ValueError, perm, 1, -1)
-        self.assertRaises(ValueError, perm, 1, -2**1000)
-
-        # Returns zero if k is greater than n
-        self.assertEqual(perm(1, 2), 0)
-        self.assertEqual(perm(1, 2**1000), 0)
-
-        n = 2**1000
-        self.assertEqual(perm(n, 0), 1)
-        self.assertEqual(perm(n, 1), n)
-        self.assertEqual(perm(n, 2), n * (n-1))
-        if support.check_impl_detail(cpython=True):
-            self.assertRaises(OverflowError, perm, n, n)
-
-        for n, k in (True, True), (True, False), (False, False):
-            self.assertEqual(perm(n, k), 1)
-            self.assertIs(type(perm(n, k)), int)
-        self.assertEqual(perm(IntSubclass(5), IntSubclass(2)), 20)
-        self.assertEqual(perm(MyIndexable(5), MyIndexable(2)), 20)
-        for k in range(3):
-            self.assertIs(type(perm(IntSubclass(5), IntSubclass(k))), int)
-            self.assertIs(type(perm(MyIndexable(5), MyIndexable(k))), int)
-
-    def testComb(self):
-        comb = math.comb
-        factorial = math.factorial
-        # Test if factorial definition is satisfied
-        for n in range(500):
-            for k in (range(n + 1) if n < 100 else range(30) if n < 200 else range(10)):
-                self.assertEqual(comb(n, k), factorial(n)
-                    // (factorial(k) * factorial(n - k)))
-
-        # Test for Pascal's identity
-        for n in range(1, 100):
-            for k in range(1, n):
-                self.assertEqual(comb(n, k), comb(n - 1, k - 1) + comb(n - 1, k))
-
-        # Test corner cases
-        for n in range(100):
-            self.assertEqual(comb(n, 0), 1)
-            self.assertEqual(comb(n, n), 1)
-
-        for n in range(1, 100):
-            self.assertEqual(comb(n, 1), n)
-            self.assertEqual(comb(n, n - 1), n)
-
-        # Test Symmetry
-        for n in range(100):
-            for k in range(n // 2):
-                self.assertEqual(comb(n, k), comb(n, n - k))
-
-        # Raises TypeError if any argument is non-integer or argument count is
-        # not 2
-        self.assertRaises(TypeError, comb, 10, 1.0)
-        self.assertRaises(TypeError, comb, 10, decimal.Decimal(1.0))
-        self.assertRaises(TypeError, comb, 10, "1")
-        self.assertRaises(TypeError, comb, 10.0, 1)
-        self.assertRaises(TypeError, comb, decimal.Decimal(10.0), 1)
-        self.assertRaises(TypeError, comb, "10", 1)
-
-        self.assertRaises(TypeError, comb, 10)
-        self.assertRaises(TypeError, comb, 10, 1, 3)
-        self.assertRaises(TypeError, comb)
-
-        # Raises Value error if not k or n are negative numbers
-        self.assertRaises(ValueError, comb, -1, 1)
-        self.assertRaises(ValueError, comb, -2**1000, 1)
-        self.assertRaises(ValueError, comb, 1, -1)
-        self.assertRaises(ValueError, comb, 1, -2**1000)
-
-        # Returns zero if k is greater than n
-        self.assertEqual(comb(1, 2), 0)
-        self.assertEqual(comb(1, 2**1000), 0)
-
-        n = 2**1000
-        self.assertEqual(comb(n, 0), 1)
-        self.assertEqual(comb(n, 1), n)
-        self.assertEqual(comb(n, 2), n * (n-1) // 2)
-        self.assertEqual(comb(n, n), 1)
-        self.assertEqual(comb(n, n-1), n)
-        self.assertEqual(comb(n, n-2), n * (n-1) // 2)
-        if support.check_impl_detail(cpython=True):
-            self.assertRaises(OverflowError, comb, n, n//2)
-
-        for n, k in (True, True), (True, False), (False, False):
-            self.assertEqual(comb(n, k), 1)
-            self.assertIs(type(comb(n, k)), int)
-        self.assertEqual(comb(IntSubclass(5), IntSubclass(2)), 10)
-        self.assertEqual(comb(MyIndexable(5), MyIndexable(2)), 10)
-        for k in range(3):
-            self.assertIs(type(comb(IntSubclass(5), IntSubclass(k))), int)
-            self.assertIs(type(comb(MyIndexable(5), MyIndexable(k))), int)
-
     @requires_IEEE_754
     def test_nextafter(self):
         # around 2^52 and 2^63
@@ -2490,7 +2374,6 @@ def test_nextafter(self):
         with self.assertRaises(ValueError):
             math.nextafter(1.0, INF, steps=-1)
 
-
     @requires_IEEE_754
     def test_ulp(self):
         self.assertEqual(math.ulp(1.0), sys.float_info.epsilon)
@@ -2805,11 +2688,8 @@ def test_fma_infinities(self):
     @unittest.skipIf(
         sys.platform.startswith(("freebsd", "wasi", "netbsd", "emscripten"))
         or (sys.platform == "android" and platform.machine() == "x86_64")
-        or support.linked_to_musl(),  # gh-131032
+        or (support.linked_to_musl() and support.linked_to_musl() < (1, 2, 6)),  # gh-131032
         f"this platform doesn't implement IEE 754-2008 properly")
-    # gh-131032: musl is fixed but the fix is not yet released; when the fixed
-    # version is known change this to:
-    #   or support.linked_to_musl() < (1, <m>, <p>)
     def test_fma_zero_result(self):
         nonnegative_finites = [0.0, 1e-300, 2.3, 1e300]
 
diff --git a/Lib/test/test_math_integer.py b/Lib/test/test_math_integer.py
new file mode 100644
index 00000000000..d1bc776dc42
--- /dev/null
+++ b/Lib/test/test_math_integer.py
@@ -0,0 +1,421 @@
+from decimal import Decimal
+from fractions import Fraction
+import unittest
+from test import support
+
+
+class IntSubclass(int):
+    pass
+
+# Class providing an __index__ method.
+class MyIndexable(object):
+    def __init__(self, value):
+        self.value = value
+
+    def __index__(self):
+        return self.value
+
+# int subclass with broken arithmetic operators; implementations must
+# convert their arguments to exact ints instead of using these.
+class BadIntSubclass(int):
+    def _binop(self, other='ignored', mod=None):
+        return 42
+    __add__ = __radd__ = __sub__ = __rsub__ = _binop
+    __mul__ = __rmul__ = __mod__ = __rmod__ = _binop
+    __divmod__ = __rdivmod__ = __pow__ = __rpow__ = _binop
+    __floordiv__ = __rfloordiv__ = _binop
+    __lshift__ = __rlshift__ = __rshift__ = __rrshift__ = _binop
+    __and__ = __rand__ = __or__ = __ror__ = __xor__ = __rxor__ = _binop
+    __lt__ = __le__ = __gt__ = __ge__ = _binop
+
+# Here's a pure Python version of the math.integer.factorial algorithm, for
+# documentation and comparison purposes.
+#
+# Formula:
+#
+#   factorial(n) = factorial_odd_part(n) << (n - count_set_bits(n))
+#
+# where
+#
+#   factorial_odd_part(n) = product_{i >= 0} product_{0 < j <= n >> i; j odd} j
+#
+# The outer product above is an infinite product, but once i >= n.bit_length,
+# (n >> i) < 1 and the corresponding term of the product is empty.  So only the
+# finitely many terms for 0 <= i < n.bit_length() contribute anything.
+#
+# We iterate downwards from i == n.bit_length() - 1 to i == 0.  The inner
+# product in the formula above starts at 1 for i == n.bit_length(); for each i
+# < n.bit_length() we get the inner product for i from that for i + 1 by
+# multiplying by all j in {n >> i+1 < j <= n >> i; j odd}.  In Python terms,
+# this set is range((n >> i+1) + 1 | 1, (n >> i) + 1 | 1, 2).
+
+def count_set_bits(n):
+    """Number of '1' bits in binary expansion of a nonnnegative integer."""
+    return 1 + count_set_bits(n & n - 1) if n else 0
+
+def partial_product(start, stop):
+    """Product of integers in range(start, stop, 2), computed recursively.
+    start and stop should both be odd, with start <= stop.
+
+    """
+    numfactors = (stop - start) >> 1
+    if not numfactors:
+        return 1
+    elif numfactors == 1:
+        return start
+    else:
+        mid = (start + numfactors) | 1
+        return partial_product(start, mid) * partial_product(mid, stop)
+
+def py_factorial(n):
+    """Factorial of nonnegative integer n, via "Binary Split Factorial Formula"
+    described at http://www.luschny.de/math/factorial/binarysplitfact.html
+
+    """
+    inner = outer = 1
+    for i in reversed(range(n.bit_length())):
+        inner *= partial_product((n >> i + 1) + 1 | 1, (n >> i) + 1 | 1)
+        outer *= inner
+    return outer << (n - count_set_bits(n))
+
+
+class IntMathTests(unittest.TestCase):
+    import math.integer as module
+
+    def assertIntEqual(self, actual, expected):
+        self.assertEqual(actual, expected)
+        self.assertIs(type(actual), int)
+
+    def test_factorial(self):
+        factorial = self.module.factorial
+        self.assertEqual(factorial(0), 1)
+        total = 1
+        for i in range(1, 1000):
+            total *= i
+            self.assertEqual(factorial(i), total)
+            self.assertEqual(factorial(i), py_factorial(i))
+
+        self.assertIntEqual(factorial(False), 1)
+        self.assertIntEqual(factorial(True), 1)
+        for i in range(3):
+            expected = factorial(i)
+            self.assertIntEqual(factorial(IntSubclass(i)), expected)
+            self.assertIntEqual(factorial(MyIndexable(i)), expected)
+
+        self.assertRaises(ValueError, factorial, -1)
+        self.assertRaises(ValueError, factorial, -10**1000)
+
+    def test_factorial_non_integers(self):
+        factorial = self.module.factorial
+        self.assertRaises(TypeError, factorial, 5.0)
+        self.assertRaises(TypeError, factorial, 5.2)
+        self.assertRaises(TypeError, factorial, -1.0)
+        self.assertRaises(TypeError, factorial, -1e100)
+        self.assertRaises(TypeError, factorial, Decimal('5'))
+        self.assertRaises(TypeError, factorial, Decimal('5.2'))
+        self.assertRaises(TypeError, factorial, Fraction(5, 1))
+        self.assertRaises(TypeError, factorial, "5")
+
+    # Other implementations may place different upper bounds.
+    @support.cpython_only
+    def test_factorial_huge_inputs(self):
+        factorial = self.module.factorial
+        # Currently raises OverflowError for inputs that are too large
+        # to fit into a C long.
+        self.assertRaises(OverflowError, factorial, 10**100)
+        self.assertRaises(TypeError, factorial, 1e100)
+
+    def test_gcd(self):
+        gcd = self.module.gcd
+        self.assertEqual(gcd(0, 0), 0)
+        self.assertEqual(gcd(1, 0), 1)
+        self.assertEqual(gcd(-1, 0), 1)
+        self.assertEqual(gcd(0, 1), 1)
+        self.assertEqual(gcd(0, -1), 1)
+        self.assertEqual(gcd(7, 1), 1)
+        self.assertEqual(gcd(7, -1), 1)
+        self.assertEqual(gcd(-23, 15), 1)
+        self.assertEqual(gcd(120, 84), 12)
+        self.assertEqual(gcd(84, -120), 12)
+        self.assertEqual(gcd(1216342683557601535506311712,
+                             436522681849110124616458784), 32)
+        c = 652560
+        x = 434610456570399902378880679233098819019853229470286994367836600566
+        y = 1064502245825115327754847244914921553977
+        a = x * c
+        b = y * c
+        self.assertEqual(gcd(a, b), c)
+        self.assertEqual(gcd(b, a), c)
+        self.assertEqual(gcd(-a, b), c)
+        self.assertEqual(gcd(b, -a), c)
+        self.assertEqual(gcd(a, -b), c)
+        self.assertEqual(gcd(-b, a), c)
+        self.assertEqual(gcd(-a, -b), c)
+        self.assertEqual(gcd(-b, -a), c)
+        c = 576559230871654959816130551884856912003141446781646602790216406874
+        a = x * c
+        b = y * c
+        self.assertEqual(gcd(a, b), c)
+        self.assertEqual(gcd(b, a), c)
+        self.assertEqual(gcd(-a, b), c)
+        self.assertEqual(gcd(b, -a), c)
+        self.assertEqual(gcd(a, -b), c)
+        self.assertEqual(gcd(-b, a), c)
+        self.assertEqual(gcd(-a, -b), c)
+        self.assertEqual(gcd(-b, -a), c)
+
+        self.assertRaises(TypeError, gcd, 120.0, 84)
+        self.assertRaises(TypeError, gcd, 120, 84.0)
+        self.assertIntEqual(gcd(IntSubclass(120), IntSubclass(84)), 12)
+        self.assertIntEqual(gcd(MyIndexable(120), MyIndexable(84)), 12)
+
+    def test_lcm(self):
+        lcm = self.module.lcm
+        self.assertEqual(lcm(0, 0), 0)
+        self.assertEqual(lcm(1, 0), 0)
+        self.assertEqual(lcm(-1, 0), 0)
+        self.assertEqual(lcm(0, 1), 0)
+        self.assertEqual(lcm(0, -1), 0)
+        self.assertEqual(lcm(7, 1), 7)
+        self.assertEqual(lcm(7, -1), 7)
+        self.assertEqual(lcm(-23, 15), 345)
+        self.assertEqual(lcm(120, 84), 840)
+        self.assertEqual(lcm(84, -120), 840)
+        self.assertEqual(lcm(1216342683557601535506311712,
+                             436522681849110124616458784),
+                             16592536571065866494401400422922201534178938447014944)
+
+        x = 43461045657039990237
+        y = 10645022458251153277
+        for c in (652560,
+                  57655923087165495981):
+            a = x * c
+            b = y * c
+            d = x * y * c
+            self.assertEqual(lcm(a, b), d)
+            self.assertEqual(lcm(b, a), d)
+            self.assertEqual(lcm(-a, b), d)
+            self.assertEqual(lcm(b, -a), d)
+            self.assertEqual(lcm(a, -b), d)
+            self.assertEqual(lcm(-b, a), d)
+            self.assertEqual(lcm(-a, -b), d)
+            self.assertEqual(lcm(-b, -a), d)
+
+        self.assertEqual(lcm(), 1)
+        self.assertEqual(lcm(120), 120)
+        self.assertEqual(lcm(-120), 120)
+        self.assertEqual(lcm(120, 84, 102), 14280)
+        self.assertEqual(lcm(120, 0, 84), 0)
+
+        self.assertRaises(TypeError, lcm, 120.0)
+        self.assertRaises(TypeError, lcm, 120.0, 84)
+        self.assertRaises(TypeError, lcm, 120, 84.0)
+        self.assertRaises(TypeError, lcm, 120, 0, 84.0)
+        self.assertEqual(lcm(MyIndexable(120), MyIndexable(84)), 840)
+
+    def test_isqrt(self):
+        isqrt = self.module.isqrt
+        # Test a variety of inputs, large and small.
+        test_values = (
+            list(range(1000))
+            + list(range(10**6 - 1000, 10**6 + 1000))
+            + [2**e + i for e in range(60, 200) for i in range(-40, 40)]
+            + [3**9999, 10**5001]
+        )
+
+        for value in test_values:
+            with self.subTest(value=value):
+                s = isqrt(value)
+                self.assertIs(type(s), int)
+                self.assertLessEqual(s*s, value)
+                self.assertLess(value, (s+1)*(s+1))
+
+        # Negative values
+        with self.assertRaises(ValueError):
+            isqrt(-1)
+
+        # Integer-like things
+        self.assertIntEqual(isqrt(True), 1)
+        self.assertIntEqual(isqrt(False), 0)
+        self.assertIntEqual(isqrt(MyIndexable(1729)), 41)
+
+        # Overridden operators of an int subclass must not affect the
+        # result.
+        self.assertIntEqual(isqrt(BadIntSubclass(10**20)), 10**10)
+        self.assertIntEqual(isqrt(BadIntSubclass(10**20 - 1)), 10**10 - 1)
+
+        with self.assertRaises(ValueError):
+            isqrt(MyIndexable(-3))
+
+        # Non-integer-like things
+        bad_values = [
+            3.5, "a string", Decimal("3.5"), 3.5j,
+            100.0, -4.0,
+        ]
+        for value in bad_values:
+            with self.subTest(value=value):
+                with self.assertRaises(TypeError):
+                    isqrt(value)
+
+    @support.bigmemtest(2**32, memuse=0.85)
+    def test_isqrt_huge(self, size):
+        isqrt = self.module.isqrt
+        if size & 1:
+            size += 1
+        v = 1 << size
+        w = isqrt(v)
+        self.assertEqual(w.bit_length(), size // 2 + 1)
+        self.assertEqual(w.bit_count(), 1)
+
+    def test_perm(self):
+        perm = self.module.perm
+        factorial = self.module.factorial
+        # Test if factorial definition is satisfied
+        for n in range(500):
+            for k in (range(n + 1) if n < 100 else range(30) if n < 200 else range(10)):
+                self.assertEqual(perm(n, k),
+                                 factorial(n) // factorial(n - k))
+
+        # Test for Pascal's identity
+        for n in range(1, 100):
+            for k in range(1, n):
+                self.assertEqual(perm(n, k), perm(n - 1, k - 1) * k + perm(n - 1, k))
+
+        # Test corner cases
+        for n in range(1, 100):
+            self.assertEqual(perm(n, 0), 1)
+            self.assertEqual(perm(n, 1), n)
+            self.assertEqual(perm(n, n), factorial(n))
+
+        # Test one argument form
+        for n in range(20):
+            self.assertEqual(perm(n), factorial(n))
+            self.assertEqual(perm(n, None), factorial(n))
+
+        # Raises TypeError if any argument is non-integer or argument count is
+        # not 1 or 2
+        self.assertRaises(TypeError, perm, 10, 1.0)
+        self.assertRaises(TypeError, perm, 10, Decimal(1.0))
+        self.assertRaises(TypeError, perm, 10, Fraction(1, 1))
+        self.assertRaises(TypeError, perm, 10, "1")
+        self.assertRaises(TypeError, perm, 10.0, 1)
+        self.assertRaises(TypeError, perm, Decimal(10.0), 1)
+        self.assertRaises(TypeError, perm, Fraction(10, 1), 1)
+        self.assertRaises(TypeError, perm, "10", 1)
+
+        self.assertRaises(TypeError, perm)
+        self.assertRaises(TypeError, perm, 10, 1, 3)
+        self.assertRaises(TypeError, perm)
+
+        # Raises Value error if not k or n are negative numbers
+        self.assertRaises(ValueError, perm, -1, 1)
+        self.assertRaises(ValueError, perm, -2**1000, 1)
+        self.assertRaises(ValueError, perm, 1, -1)
+        self.assertRaises(ValueError, perm, 1, -2**1000)
+
+        # Returns zero if k is greater than n
+        self.assertEqual(perm(1, 2), 0)
+        self.assertEqual(perm(1, 2**1000), 0)
+
+        n = 2**1000
+        self.assertEqual(perm(n, 0), 1)
+        self.assertEqual(perm(n, 1), n)
+        self.assertEqual(perm(n, 2), n * (n-1))
+        if support.check_impl_detail(cpython=True):
+            self.assertRaises(OverflowError, perm, n, n)
+
+        for n, k in (True, True), (True, False), (False, False):
+            self.assertIntEqual(perm(n, k), 1)
+        self.assertEqual(perm(IntSubclass(5), IntSubclass(2)), 20)
+        self.assertEqual(perm(MyIndexable(5), MyIndexable(2)), 20)
+        for k in range(3):
+            self.assertIs(type(perm(IntSubclass(5), IntSubclass(k))), int)
+            self.assertIs(type(perm(MyIndexable(5), MyIndexable(k))), int)
+
+    def test_comb(self):
+        comb = self.module.comb
+        factorial = self.module.factorial
+        # Test if factorial definition is satisfied
+        for n in range(500):
+            for k in (range(n + 1) if n < 100 else range(30) if n < 200 else range(10)):
+                self.assertEqual(comb(n, k), factorial(n)
+                    // (factorial(k) * factorial(n - k)))
+
+        # Test for Pascal's identity
+        for n in range(1, 100):
+            for k in range(1, n):
+                self.assertEqual(comb(n, k), comb(n - 1, k - 1) + comb(n - 1, k))
+
+        # Test corner cases
+        for n in range(100):
+            self.assertEqual(comb(n, 0), 1)
+            self.assertEqual(comb(n, n), 1)
+
+        for n in range(1, 100):
+            self.assertEqual(comb(n, 1), n)
+            self.assertEqual(comb(n, n - 1), n)
+
+        # Test Symmetry
+        for n in range(100):
+            for k in range(n // 2):
+                self.assertEqual(comb(n, k), comb(n, n - k))
+
+        # Raises TypeError if any argument is non-integer or argument count is
+        # not 2
+        self.assertRaises(TypeError, comb, 10, 1.0)
+        self.assertRaises(TypeError, comb, 10, Decimal(1.0))
+        self.assertRaises(TypeError, comb, 10, "1")
+        self.assertRaises(TypeError, comb, 10.0, 1)
+        self.assertRaises(TypeError, comb, Decimal(10.0), 1)
+        self.assertRaises(TypeError, comb, "10", 1)
+
+        self.assertRaises(TypeError, comb, 10)
+        self.assertRaises(TypeError, comb, 10, 1, 3)
+        self.assertRaises(TypeError, comb)
+
+        # Raises Value error if not k or n are negative numbers
+        self.assertRaises(ValueError, comb, -1, 1)
+        self.assertRaises(ValueError, comb, -2**1000, 1)
+        self.assertRaises(ValueError, comb, 1, -1)
+        self.assertRaises(ValueError, comb, 1, -2**1000)
+
+        # Returns zero if k is greater than n
+        self.assertEqual(comb(1, 2), 0)
+        self.assertEqual(comb(1, 2**1000), 0)
+
+        n = 2**1000
+        self.assertEqual(comb(n, 0), 1)
+        self.assertEqual(comb(n, 1), n)
+        self.assertEqual(comb(n, 2), n * (n-1) // 2)
+        self.assertEqual(comb(n, n), 1)
+        self.assertEqual(comb(n, n-1), n)
+        self.assertEqual(comb(n, n-2), n * (n-1) // 2)
+        if support.check_impl_detail(cpython=True):
+            self.assertRaises(OverflowError, comb, n, n//2)
+
+        for n, k in (True, True), (True, False), (False, False):
+            self.assertIntEqual(comb(n, k), 1)
+        self.assertEqual(comb(IntSubclass(5), IntSubclass(2)), 10)
+        self.assertEqual(comb(MyIndexable(5), MyIndexable(2)), 10)
+        for k in range(3):
+            self.assertIs(type(comb(IntSubclass(5), IntSubclass(k))), int)
+            self.assertIs(type(comb(MyIndexable(5), MyIndexable(k))), int)
+
+
+class MathTests(IntMathTests):
+    import math as module
+
+
+class MiscTests(unittest.TestCase):
+
+    def test_module_name(self):
+        import math.integer
+        self.assertEqual(math.integer.__name__, 'math.integer')
+        for name in dir(math.integer):
+            if not name.startswith('_'):
+                obj = getattr(math.integer, name)
+                self.assertEqual(obj.__module__, 'math.integer')
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/Lib/test/test_mimetypes.py b/Lib/test/test_mimetypes.py
index a7d1d724ff0..f0851431a27 100644
--- a/Lib/test/test_mimetypes.py
+++ b/Lib/test/test_mimetypes.py
@@ -67,50 +67,9 @@ def test_read_mime_types(self):
         with unittest.mock.patch.object(mimetypes, 'open',
                                         return_value=fp) as mock_open:
             mime_dict = mimetypes.read_mime_types(filename)
-            mock_open.assert_called_with(filename, encoding='utf-8',
-                                         errors='surrogateescape')
+            mock_open.assert_called_with(filename, encoding='utf-8')
         eq(mime_dict[".Français"], "application/no-mans-land")
 
-    def test_read_mime_types_invalid_utf8_comment(self):
-        with os_helper.temp_dir() as directory:
-            data = (b"# non-UTF-8 comment: \x83\n"
-                    b"x-application/x-unittest pyunit\n")
-            file = os.path.join(directory, "sample.mimetype")
-            with open(file, "wb") as f:
-                f.write(data)
-
-            mime_dict = mimetypes.read_mime_types(file)
-            self.assertEqual(
-                mime_dict[".pyunit"], "x-application/x-unittest")
-
-            db = mimetypes.MimeTypes()
-            db.read(file)
-            self.assertEqual(
-                db.guess_file_type("sample.pyunit")[0],
-                "x-application/x-unittest")
-
-            mimetypes.init(files=[file])
-            self.assertEqual(
-                mimetypes.guess_file_type("sample.pyunit")[0],
-                "x-application/x-unittest")
-
-    def test_read_mime_types_invalid_utf8_type(self):
-        # A non-UTF-8 byte in a type or extension (not only in a comment) is
-        # preserved via surrogateescape, so the mapping is not corrupted.
-        with os_helper.temp_dir() as directory:
-            data = (b"x-application/x-unittest pyunit\n"
-                    b"application/bad\x83 badext\x83\n")
-            file = os.path.join(directory, "sample.mimetype")
-            with open(file, "wb") as f:
-                f.write(data)
-
-            bad_type = b"application/bad\x83".decode("utf-8", "surrogateescape")
-            bad_ext = b".badext\x83".decode("utf-8", "surrogateescape")
-
-            mime_dict = mimetypes.read_mime_types(file)
-            self.assertEqual(mime_dict[".pyunit"], "x-application/x-unittest")
-            self.assertEqual(mime_dict[bad_ext], bad_type)
-
     def test_init_reinitializes(self):
         # Issue 4936: make sure an init starts clean
         # First, put some poison into the types table
@@ -135,9 +94,15 @@ def check_extensions():
             for mime_type, ext in (
                 ("application/epub+zip", ".epub"),
                 ("application/octet-stream", ".bin"),
+                ("application/dicom", ".dcm"),
                 ("application/gzip", ".gz"),
                 ("application/ogg", ".ogx"),
+                ("application/pdf", ".pdf"),
                 ("application/postscript", ".ps"),
+                ("application/rtf", ".rtf"),
+                ("application/sql", ".sql"),
+                ("application/texinfo", ".texi"),
+                ("application/toml", ".toml"),
                 ("application/vnd.apple.mpegurl", ".m3u"),
                 ("application/vnd.ms-excel", ".xls"),
                 ("application/vnd.ms-fontobject", ".eot"),
@@ -150,11 +115,11 @@ def check_extensions():
                 ("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", ".xlsx"),
                 ("application/vnd.openxmlformats-officedocument.wordprocessingml.document", ".docx"),
                 ("application/vnd.rar", ".rar"),
+                ("application/vnd.sqlite3", ".sqlite3"),
                 ("application/x-7z-compressed", ".7z"),
                 ("application/x-debian-package", ".deb"),
                 ("application/x-httpd-php", ".php"),
                 ("application/x-rpm", ".rpm"),
-                ("application/x-texinfo", ".texi"),
                 ("application/x-troff", ".roff"),
                 ("application/xml", ".xsl"),
                 ("application/yaml", ".yaml"),
@@ -176,6 +141,7 @@ def check_extensions():
                 ("image/jp2", ".jp2"),
                 ("image/jpeg", ".jpg"),
                 ("image/jpm", ".jpm"),
+                ("image/jxl", ".jxl"),
                 ("image/t38", ".t38"),
                 ("image/tiff", ".tiff"),
                 ("image/tiff-fx", ".tfx"),
@@ -187,7 +153,6 @@ def check_extensions():
                 ("model/stl", ".stl"),
                 ("text/html", ".html"),
                 ("text/plain", ".txt"),
-                ("text/rtf", ".rtf"),
                 ("text/x-rst", ".rst"),
                 ("video/matroska", ".mkv"),
                 ("video/matroska-3d", ".mk3d"),
@@ -349,13 +314,12 @@ def test_non_standard_types(self):
         eq = self.assertEqual
         # First try strict
         eq(self.db.guess_file_type('foo.xul', strict=True), (None, None))
-        eq(self.db.guess_extension('image/jpg', strict=True), None)
         # And then non-strict
         eq(self.db.guess_file_type('foo.xul', strict=False), ('text/xul', None))
         eq(self.db.guess_file_type('foo.XUL', strict=False), ('text/xul', None))
         eq(self.db.guess_file_type('foo.invalid', strict=False), (None, None))
-        eq(self.db.guess_extension('image/jpg', strict=False), '.jpg')
-        eq(self.db.guess_extension('image/JPG', strict=False), '.jpg')
+        eq(self.db.guess_extension('image/jpeg', strict=False), '.jpg')
+        eq(self.db.guess_extension('image/JPEG', strict=False), '.jpg')
 
     def test_filename_with_url_delimiters(self):
         # bpo-38449: URL delimiters cases should be handled also.
@@ -416,8 +380,8 @@ def test_guess_all_types(self):
         self.assertTrue(set(all) >= {'.bat', '.c', '.h', '.ksh', '.pl', '.txt'})
         self.assertEqual(len(set(all)), len(all))  # no duplicates
         # And now non-strict
-        all = self.db.guess_all_extensions('image/jpg', strict=False)
-        self.assertEqual(all, ['.jpg'])
+        all = self.db.guess_all_extensions('image/jpeg', strict=False)
+        self.assertEqual(all, ['.jpg', '.jpe', '.jpeg'])
         # And now for no hits
         all = self.db.guess_all_extensions('image/jpg', strict=True)
         self.assertEqual(all, [])
@@ -475,9 +439,7 @@ def test_keywords_args_api(self):
         self.assertEqual(self.db.guess_type(
             url="scheme:foo.html", strict=True), ("text/html", None))
         self.assertEqual(self.db.guess_all_extensions(
-            type='image/jpg', strict=True), [])
-        self.assertEqual(self.db.guess_extension(
-            type='image/jpg', strict=False), '.jpg')
+            type='image/jpeg', strict=True), ['.jpg', '.jpe', '.jpeg'])
 
 
 @unittest.skipUnless(sys.platform.startswith("win"), "Windows only")
@@ -539,15 +501,15 @@ def test_parse_args(self):
         args, help_text = mimetypes._parse_args("--invalid")
         self.assertTrue(help_text.startswith("usage: "))
 
-        args, _ = mimetypes._parse_args(shlex.split("-l -e image/jpg"))
+        args, _ = mimetypes._parse_args(shlex.split("-l -e image/jpeg"))
         self.assertTrue(args.extension)
         self.assertTrue(args.lenient)
-        self.assertEqual(args.type, ["image/jpg"])
+        self.assertEqual(args.type, ["image/jpeg"])
 
-        args, _ = mimetypes._parse_args(shlex.split("-e image/jpg"))
+        args, _ = mimetypes._parse_args(shlex.split("-e image/jpeg"))
         self.assertTrue(args.extension)
         self.assertFalse(args.lenient)
-        self.assertEqual(args.type, ["image/jpg"])
+        self.assertEqual(args.type, ["image/jpeg"])
 
         args, _ = mimetypes._parse_args(shlex.split("-l foo.webp"))
         self.assertFalse(args.extension)
@@ -578,7 +540,6 @@ def test_multiple_inputs_error(self):
 
     def test_invocation(self):
         for command, expected in [
-            ("-l -e image/jpg", ".jpg"),
             ("-e image/jpeg", ".jpg"),
             ("-l foo.webp", "type: image/webp encoding: None"),
         ]:
diff --git a/Lib/test/test_mmap.py b/Lib/test/test_mmap.py
index 09b44c9ca1b..38ee32db947 100644
--- a/Lib/test/test_mmap.py
+++ b/Lib/test/test_mmap.py
@@ -1,3 +1,4 @@
+from test import support
 from test.support import (
     requires, _2G, _4G, gc_collect, cpython_only, is_emscripten, is_apple,
     in_systemd_nspawn_sync_suppressed,
@@ -5,8 +6,8 @@
 from test.support.import_helper import import_module
 from test.support.os_helper import TESTFN, unlink
 from test.support.script_helper import assert_python_ok
-import unittest
 import errno
+import unittest
 import os
 import re
 import itertools
@@ -58,6 +59,7 @@ def test_basic(self):
             f.write(b'\0'* (PAGESIZE-3) )
             f.flush()
             m = mmap.mmap(f.fileno(), 2 * PAGESIZE)
+            self.addCleanup(m.close)
         finally:
             f.close()
 
@@ -73,7 +75,7 @@ def test_basic(self):
 
         # Shouldn't crash on boundary (Issue #5292)
         self.assertRaises(IndexError, m.__getitem__, len(m))
-        self.assertRaises(IndexError, m.__setitem__, len(m), b'\0')
+        self.assertRaises(IndexError, m.__setitem__, len(m), 0)
 
         # Modify the file's content
         m[0] = b'3'[0]
@@ -115,31 +117,28 @@ def test_basic(self):
         # Try to seek to negative position...
         self.assertRaises(ValueError, m.seek, -len(m)-1, 2)
 
+    @unittest.skipUnless(hasattr(mmap.mmap, 'resize'), 'requires mmap.resize')
+    def test_resize(self):
+        # Create a file to be mmap'ed.
+        with open(TESTFN, 'bw+') as f:
+            # Write 2 pages worth of data to the file
+            f.write(b'\0'* 2 * PAGESIZE)
+            f.flush()
+            m = mmap.mmap(f.fileno(), 2 * PAGESIZE)
+            self.addCleanup(m.close)
+
         # Try resizing map
-        try:
-            m.resize(512)
-        except SystemError:
-            # resize() not supported
-            # No messages are printed, since the output of this test suite
-            # would then be different across platforms.
-            pass
-        else:
-            # resize() is supported
-            self.assertEqual(len(m), 512)
-            # Check that we can no longer seek beyond the new size.
-            self.assertRaises(ValueError, m.seek, 513, 0)
-
-            # Check that the underlying file is truncated too
-            # (bug #728515)
-            f = open(TESTFN, 'rb')
-            try:
-                f.seek(0, 2)
-                self.assertEqual(f.tell(), 512)
-            finally:
-                f.close()
-            self.assertEqual(m.size(), 512)
+        m.resize(512)
+        self.assertEqual(len(m), 512)
+        # Check that we can no longer seek beyond the new size.
+        self.assertRaises(ValueError, m.seek, 513, 0)
 
-        m.close()
+        # Check that the underlying file is truncated too
+        # (bug #728515)
+        with open(TESTFN, 'rb') as f:
+            f.seek(0, 2)
+            self.assertEqual(f.tell(), 512)
+        self.assertEqual(m.size(), 512)
 
     def test_access_parameter(self):
         # Test for "access" keyword parameter
@@ -184,15 +183,10 @@ def test_access_parameter(self):
             else:
                 self.fail("Able to write to readonly memory map")
 
-            # Ensuring that readonly mmap can't be resized
-            try:
-                m.resize(2*mapsize)
-            except SystemError:   # resize is not universally supported
-                pass
-            except TypeError:
-                pass
-            else:
-                self.fail("Able to resize readonly memory map")
+            if hasattr(m, 'resize'):
+                # Ensuring that readonly mmap can't be resized
+                with self.assertRaises(TypeError):
+                    m.resize(2 * mapsize)
             with open(TESTFN, "rb") as fp:
                 self.assertEqual(fp.read(), b'a'*mapsize,
                                  "Readonly memory map data file was modified")
@@ -243,8 +237,9 @@ def test_access_parameter(self):
             with open(TESTFN, "rb") as fp:
                 self.assertEqual(fp.read(), b'c'*mapsize,
                                  "Copy-on-write test data file should not be modified.")
-            # Ensuring copy-on-write maps cannot be resized
-            self.assertRaises(TypeError, m.resize, 2*mapsize)
+            if hasattr(m, 'resize'):
+                # Ensuring copy-on-write maps cannot be resized
+                self.assertRaises(TypeError, m.resize, 2 * mapsize)
             m.close()
 
         # Ensuring invalid access parameter raises exception
@@ -271,62 +266,57 @@ def test_access_parameter(self):
                     self.assertRaises(TypeError, m.write_byte, 0)
                     m.close()
 
-    @unittest.skipIf(os.name == 'nt', 'trackfd not present on Windows')
-    def test_trackfd_parameter(self):
+    @support.subTests('close_original_fd', (True, False))
+    def test_trackfd_parameter(self, close_original_fd):
         size = 64
         with open(TESTFN, "wb") as f:
             f.write(b"a"*size)
-        for close_original_fd in True, False:
-            with self.subTest(close_original_fd=close_original_fd):
-                with open(TESTFN, "r+b") as f:
-                    with mmap.mmap(f.fileno(), size, trackfd=False) as m:
-                        if close_original_fd:
-                            f.close()
-                        self.assertEqual(len(m), size)
-                        with self.assertRaises(OSError) as err_cm:
-                            m.size()
-                        self.assertEqual(err_cm.exception.errno, errno.EBADF)
-                        with self.assertRaises(ValueError):
-                            m.resize(size * 2)
-                        with self.assertRaises(ValueError):
-                            m.resize(size // 2)
-                        self.assertEqual(m.closed, False)
-
-                        # Smoke-test other API
-                        m.write_byte(ord('X'))
-                        m[2] = ord('Y')
-                        m.flush()
-                        with open(TESTFN, "rb") as f:
-                            self.assertEqual(f.read(4), b'XaYa')
-                        self.assertEqual(m.tell(), 1)
-                        m.seek(0)
-                        self.assertEqual(m.tell(), 0)
-                        self.assertEqual(m.read_byte(), ord('X'))
-
-                self.assertEqual(m.closed, True)
-                self.assertEqual(os.stat(TESTFN).st_size, size)
-
-    @unittest.skipIf(os.name == 'nt', 'trackfd not present on Windows')
+        with open(TESTFN, "r+b") as f:
+            with mmap.mmap(f.fileno(), size, trackfd=False) as m:
+                if close_original_fd:
+                    f.close()
+                self.assertEqual(len(m), size)
+                with self.assertRaises(ValueError):
+                    m.size()
+                if hasattr(m, 'resize'):
+                    with self.assertRaises(ValueError):
+                        m.resize(size * 2)
+                    with self.assertRaises(ValueError):
+                        m.resize(size // 2)
+                self.assertIs(m.closed, False)
+
+                # Smoke-test other API
+                m.write_byte(ord('X'))
+                m[2] = ord('Y')
+                m.flush()
+                with open(TESTFN, "rb") as f:
+                    self.assertEqual(f.read(4), b'XaYa')
+                self.assertEqual(m.tell(), 1)
+                m.seek(0)
+                self.assertEqual(m.tell(), 0)
+                self.assertEqual(m.read_byte(), ord('X'))
+
+                if os.name == 'nt' and not close_original_fd:
+                    self.assertRaises(PermissionError, os.rename, TESTFN, TESTFN+'1')
+                else:
+                    os.rename(TESTFN, TESTFN+'1')
+                    os.rename(TESTFN+'1', TESTFN)
+
+        self.assertIs(m.closed, True)
+        self.assertEqual(os.stat(TESTFN).st_size, size)
+
     def test_trackfd_neg1(self):
         size = 64
         with mmap.mmap(-1, size, trackfd=False) as m:
-            with self.assertRaises(OSError):
-                m.size()
             with self.assertRaises(ValueError):
-                m.resize(size // 2)
+                m.size()
+            if hasattr(m, 'resize'):
+                with self.assertRaises(ValueError):
+                    m.resize(size // 2)
             self.assertEqual(len(m), size)
             m[0] = ord('a')
             assert m[0] == ord('a')
 
-    @unittest.skipIf(os.name != 'nt', 'trackfd only fails on Windows')
-    def test_no_trackfd_parameter_on_windows(self):
-        # 'trackffd' is an invalid keyword argument for this function
-        size = 64
-        with self.assertRaises(TypeError):
-            mmap.mmap(-1, size, trackfd=True)
-        with self.assertRaises(TypeError):
-            mmap.mmap(-1, size, trackfd=False)
-
     def test_bad_file_desc(self):
         # Try opening a bad file descriptor...
         self.assertRaises(OSError, mmap.mmap, -2, 4096)
@@ -367,6 +357,8 @@ def test_find_end(self):
         self.assertEqual(m.find(b'one', 1, -1), 8)
         self.assertEqual(m.find(b'one', 1, -2), -1)
         self.assertEqual(m.find(bytearray(b'one')), 0)
+        self.assertEqual(m.find(b'', n + 1), -1)
+        self.assertEqual(m.rfind(b'', n + 1), -1)
 
         for i in range(-n-1, n+1):
             for j in range(-n-1, n+1):
@@ -510,6 +502,7 @@ def test_anonymous(self):
             b = x & 0xff
             m[x] = b
             self.assertEqual(m[x], b)
+        self.assertEqual(m.size(), PAGESIZE)
 
     @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON")
     def test_read_all(self):
@@ -621,13 +614,9 @@ def test_offset (self):
             self.assertEqual(m[0:3], b'foo')
             f.close()
 
-            # Try resizing map
-            try:
+            if hasattr(m, 'resize'):
+                # Try resizing map
                 m.resize(512)
-            except SystemError:
-                pass
-            else:
-                # resize() is supported
                 self.assertEqual(len(m), 512)
                 # Check that we can no longer seek beyond the new size.
                 self.assertRaises(ValueError, m.seek, 513, 0)
@@ -825,14 +814,12 @@ def test_write_returning_the_number_of_bytes_written(self):
         self.assertEqual(mm.write(b"python"), 6)
 
     @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON")
+    @unittest.skipUnless(hasattr(mmap.mmap, 'resize'), 'requires mmap.resize')
     def test_resize_past_pos(self):
         m = mmap.mmap(-1, 8192)
         self.addCleanup(m.close)
         m.read(5000)
-        try:
-            m.resize(4096)
-        except SystemError:
-            self.skipTest("resizing not supported")
+        m.resize(4096)
         self.assertEqual(m.read(14), b'')
         self.assertRaises(ValueError, m.read_byte)
         self.assertRaises(ValueError, m.write_byte, 42)
@@ -897,7 +884,6 @@ def test_repr(self):
                     match = closed_mmap_repr_pat.match(repr(mm))
                     self.assertIsNotNone(match)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     @unittest.skipUnless(hasattr(mmap.mmap, 'madvise'), 'needs madvise')
     def test_madvise(self):
         size = 2 * PAGESIZE
@@ -925,7 +911,7 @@ def __index__(self):
         self.assertEqual(m.madvise(mmap.MADV_NORMAL, 0, Number()), None)
         self.assertEqual(m.madvise(mmap.MADV_NORMAL, 0, size), None)
 
-    @unittest.expectedFailureIf(sys.platform in ("linux", "win32"), "TODO: RUSTPYTHON")
+    @unittest.skipUnless(hasattr(mmap.mmap, 'resize'), 'requires mmap.resize')
     def test_resize_up_anonymous_mapping(self):
         """If the mmap is backed by the pagefile ensure a resize up can happen
         and that the original data is still in place
@@ -936,23 +922,21 @@ def test_resize_up_anonymous_mapping(self):
 
         with mmap.mmap(-1, start_size) as m:
             m[:] = data
-            if sys.platform.startswith(('linux', 'android')):
-                # Can't expand a shared anonymous mapping on Linux.
-                # See https://bugzilla.kernel.org/show_bug.cgi?id=8691
+            if sys.platform.startswith(('linux', 'android', 'netbsd')):
+                # Can't expand a shared anonymous mapping on Linux
+                # (see https://bugzilla.kernel.org/show_bug.cgi?id=8691)
+                # or NetBSD.
                 with self.assertRaises(ValueError):
                     m.resize(new_size)
             else:
-                try:
-                    m.resize(new_size)
-                except SystemError:
-                    pass
-                else:
-                    self.assertEqual(len(m), new_size)
-                    self.assertEqual(m[:start_size], data)
-                    self.assertEqual(m[start_size:], b'\0' * (new_size - start_size))
+                m.resize(new_size)
+                self.assertEqual(len(m), new_size)
+                self.assertEqual(m[:start_size], data)
+                self.assertEqual(m[start_size:], b'\0' * (new_size - start_size))
 
     @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON")
     @unittest.skipUnless(os.name == 'posix', 'requires Posix')
+    @unittest.skipUnless(hasattr(mmap.mmap, 'resize'), 'requires mmap.resize')
     def test_resize_up_private_anonymous_mapping(self):
         start_size = PAGESIZE
         new_size = 2 * start_size
@@ -960,16 +944,13 @@ def test_resize_up_private_anonymous_mapping(self):
 
         with mmap.mmap(-1, start_size, flags=mmap.MAP_PRIVATE) as m:
             m[:] = data
-            try:
-                m.resize(new_size)
-            except SystemError:
-                pass
-            else:
-                self.assertEqual(len(m), new_size)
-                self.assertEqual(m[:start_size], data)
-                self.assertEqual(m[start_size:], b'\0' * (new_size - start_size))
+            m.resize(new_size)
+            self.assertEqual(len(m), new_size)
+            self.assertEqual(m[:start_size], data)
+            self.assertEqual(m[start_size:], b'\0' * (new_size - start_size))
 
     @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON")
+    @unittest.skipUnless(hasattr(mmap.mmap, 'resize'), 'requires mmap.resize')
     def test_resize_down_anonymous_mapping(self):
         """If the mmap is backed by the pagefile ensure a resize down up can happen
         and that a truncated form of the original data is still in place
@@ -980,17 +961,56 @@ def test_resize_down_anonymous_mapping(self):
 
         with mmap.mmap(-1, start_size) as m:
             m[:] = data
-            try:
-                m.resize(new_size)
-            except SystemError:
-                pass
-            else:
-                self.assertEqual(len(m), new_size)
-                self.assertEqual(m[:], data[:new_size])
-                if sys.platform.startswith(('linux', 'android')):
-                    # Can't expand to its original size.
-                    with self.assertRaises(ValueError):
-                        m.resize(start_size)
+            m.resize(new_size)
+            self.assertEqual(len(m), new_size)
+            self.assertEqual(m[:], data[:new_size])
+            if sys.platform.startswith(('linux', 'android')):
+                # Can't expand to its original size.
+                with self.assertRaises(ValueError):
+                    m.resize(start_size)
+
+    @unittest.skipUnless(hasattr(mmap.mmap, 'resize'), 'requires mmap.resize')
+    def test_setitem_resize_reentrancy(self):
+        """Resizing the mmap from inside __index__ while assigning to a
+        single item must not access memory past the new bounds (gh-157335).
+        """
+        size = 2 * PAGESIZE
+        new_size = PAGESIZE
+
+        class ResizeOnIndex:
+            def __init__(self, m):
+                self.m = m
+            def __index__(self):
+                self.m.resize(new_size)
+                return 0
+
+        with mmap.mmap(-1, size) as m:
+            with self.assertRaises(IndexError):
+                m[size - 1] = ResizeOnIndex(m)
+            self.assertEqual(len(m), new_size)
+
+    @unittest.skipUnless(hasattr(mmap.mmap, 'resize'), 'requires mmap.resize')
+    def test_setitem_slice_resize_reentrancy(self):
+        """Resizing the mmap from inside a value's buffer-protocol
+        callback while assigning to a slice must not access memory past
+        the new bounds (gh-157335).
+        """
+        size = 2 * PAGESIZE
+        new_size = PAGESIZE
+
+        class ResizeOnBuffer:
+            def __init__(self, m, data):
+                self.m = m
+                self.data = data
+            def __buffer__(self, flags):
+                self.m.resize(new_size)
+                return memoryview(self.data)
+
+        with mmap.mmap(-1, size) as m:
+            value = ResizeOnBuffer(m, bytes(size))
+            with self.assertRaises(IndexError):
+                m[0:size] = value
+            self.assertEqual(len(m), new_size)
 
     @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON")
     @unittest.skipUnless(os.name == 'nt', 'requires Windows')
@@ -1039,7 +1059,6 @@ def test_resize_succeeds_with_error_for_second_named_mapping(self):
         self.assertEqual(m1[:data_length], data)
         self.assertEqual(m2[:data_length], data)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_mmap_closed_by_int_scenarios(self):
         """
         gh-103987: Test that mmap objects raise ValueError
@@ -1200,6 +1219,74 @@ def test_access_violations(self):
         self.assertEqual(stdout.strip(), b'')
         self.assertEqual(stderr.strip(), b'')
 
+    def test_flush_parameters(self):
+        with open(TESTFN, 'wb+') as f:
+            f.write(b'x' * PAGESIZE * 3)
+            f.flush()
+
+            m = mmap.mmap(f.fileno(), PAGESIZE * 3)
+            self.addCleanup(m.close)
+
+            m.flush()
+            m.flush(PAGESIZE)
+            m.flush(PAGESIZE, PAGESIZE)
+
+            if hasattr(mmap, 'MS_SYNC'):
+                m.flush(0, PAGESIZE, flags=mmap.MS_SYNC)
+            if hasattr(mmap, 'MS_ASYNC'):
+                m.flush(flags=mmap.MS_ASYNC)
+            if hasattr(mmap, 'MS_INVALIDATE'):
+                m.flush(PAGESIZE * 2, flags=mmap.MS_INVALIDATE)
+            if hasattr(mmap, 'MS_ASYNC') and hasattr(mmap, 'MS_INVALIDATE'):
+                if sys.platform.startswith(('freebsd', 'dragonfly')):
+                    # FreeBSD and DragonFly don't support this combination
+                    with self.assertRaises(OSError) as cm:
+                        m.flush(0, PAGESIZE, flags=mmap.MS_ASYNC | mmap.MS_INVALIDATE)
+                    self.assertEqual(cm.exception.errno, errno.EINVAL)
+                else:
+                    m.flush(0, PAGESIZE, flags=mmap.MS_ASYNC | mmap.MS_INVALIDATE)
+
+    @unittest.skipUnless(sys.platform == 'linux', 'Linux only')
+    @support.requires_linux_version(5, 17, 0)
+    @unittest.skipIf(support.linked_to_musl(), "musl libc issue, gh-143632")
+    def test_set_name(self):
+        # Test setting name on anonymous mmap
+        m = mmap.mmap(-1, PAGESIZE)
+        self.addCleanup(m.close)
+        try:
+            result = m.set_name('test_mapping')
+        except OSError as exc:
+            if exc.errno == errno.EINVAL:
+                # gh-142419: On Fedora, prctl(PR_SET_VMA_ANON_NAME) fails with
+                # EINVAL because the kernel option CONFIG_ANON_VMA_NAME is
+                # disabled.
+                # See: https://bugzilla.redhat.com/show_bug.cgi?id=2302746
+                self.skipTest("prctl() failed with EINVAL")
+            else:
+                raise
+        self.assertIsNone(result)
+
+        # Test name length limit (80 chars including prefix "cpython:mmap:" and '\0')
+        # Prefix is 13 chars, so max name is 66 chars
+        long_name = 'x' * 66
+        result = m.set_name(long_name)
+        self.assertIsNone(result)
+
+        # Test name too long
+        too_long_name = 'x' * 67
+        with self.assertRaises(ValueError):
+            m.set_name(too_long_name)
+
+        # Test that file-backed mmap raises error
+        with open(TESTFN, 'wb+') as f:
+            f.write(b'x' * PAGESIZE)
+            f.flush()
+            m2 = mmap.mmap(f.fileno(), PAGESIZE)
+            self.addCleanup(m2.close)
+
+            with self.assertRaises(ValueError):
+                m2.set_name('should_fail')
+
 
 class LargeMmapTests(unittest.TestCase):
 
diff --git a/Lib/test/test_monitoring.py b/Lib/test/test_monitoring.py
index bb375606a0d..ad9b61a6576 100644
--- a/Lib/test/test_monitoring.py
+++ b/Lib/test/test_monitoring.py
@@ -12,16 +12,7 @@
 import unittest
 
 import test.support
-from test.support import requires_specialization_ft, script_helper
-
-try:
-    import _testcapi
-except ImportError:
-    _testcapi = None
-try:
-    import _testinternalcapi
-except ImportError:
-    _testinternalcapi = None
+from test.support import import_helper, requires_specialization, script_helper
 
 PAIR = (0,1)
 
@@ -202,13 +193,10 @@ def test_c_return_count(self):
     (E.BRANCH, "branch"),
 ]
 
-EXCEPT_EVENTS = [
+SIMPLE_EVENTS = INSTRUMENTED_EVENTS + [
     (E.RAISE, "raise"),
-    (E.PY_UNWIND, "unwind"),
     (E.EXCEPTION_HANDLED, "exception_handled"),
-]
-
-SIMPLE_EVENTS = INSTRUMENTED_EVENTS + EXCEPT_EVENTS + [
+    (E.PY_UNWIND, "unwind"),
     (E.C_RAISE, "c_raise"),
     (E.C_RETURN, "c_return"),
 ]
@@ -744,18 +732,6 @@ def test_disable_legal_events(self):
                 sys.monitoring.register_callback(TEST_TOOL, event, None)
 
 
-    def test_disable_illegal_events(self):
-        for event, name in EXCEPT_EVENTS:
-            try:
-                counter = CounterWithDisable()
-                counter.disable = True
-                sys.monitoring.register_callback(TEST_TOOL, event, counter)
-                sys.monitoring.set_events(TEST_TOOL, event)
-                with self.assertRaises(ValueError):
-                    self.raise_handle_reraise()
-            finally:
-                sys.monitoring.set_events(TEST_TOOL, 0)
-                sys.monitoring.register_callback(TEST_TOOL, event, None)
 
 
 class ExceptionRecorder:
@@ -879,7 +855,6 @@ def func1():
 
         self.check_events(func1, [("raise", KeyError)])
 
-    @unittest.skipUnless(_testinternalcapi, "requires _testinternalcapi")
     def test_implicit_stop_iteration(self):
         """Generators are documented as raising a StopIteration
            when they terminate.
@@ -889,6 +864,8 @@ def test_implicit_stop_iteration(self):
            This test checks that both paths record an equivalent event.
            """
 
+        _testinternalcapi = import_helper.import_module("_testinternalcapi")
+
         def gen():
             yield 1
             return 2
@@ -1054,9 +1031,10 @@ def func():
         )
         self.assertEqual(events[0], ("throw", IndexError))
 
-    @unittest.skipUnless(_testinternalcapi, "requires _testinternalcapi")
-    @requires_specialization_ft
+    @requires_specialization
     def test_no_unwind_for_shim_frame(self):
+        _testinternalcapi = import_helper.import_module("_testinternalcapi")
+
         class ValueErrorRaiser:
             def __init__(self):
                 raise ValueError()
@@ -1222,19 +1200,20 @@ def func1():
             line3 = 3
 
         self.check_events(func1, recorders = LINE_AND_INSTRUCTION_RECORDERS, expected = [
-            ('line', 'get_events', 10),
-            ('line', 'func1', 1),
-            ('instruction', 'func1', 2),
-            ('instruction', 'func1', 4),
-            ('line', 'func1', 2),
-            ('instruction', 'func1', 6),
-            ('instruction', 'func1', 8),
-            ('line', 'func1', 3),
-            ('instruction', 'func1', 10),
-            ('instruction', 'func1', 12),
-            ('instruction', 'func1', 14),
-            ('instruction', 'func1', 16),
-            ('line', 'get_events', 11)])
+            ("line", "get_events", 10),
+            ("line", "func1", 1),
+            ("instruction", "func1", 4),
+            ("instruction", "func1", 6),
+            ("line", "func1", 2),
+            ("instruction", "func1", 8),
+            ("instruction", "func1", 10),
+            ("line", "func1", 3),
+            ("instruction", "func1", 12),
+            ("instruction", "func1", 14),
+            ("instruction", "func1", 16),
+            ("instruction", "func1", 18),
+            ("line", "get_events", 11),
+        ])
 
     def test_c_call(self):
 
@@ -1244,22 +1223,23 @@ def func2():
             line3 = 3
 
         self.check_events(func2, recorders = LINE_AND_INSTRUCTION_RECORDERS, expected = [
-            ('line', 'get_events', 10),
-            ('line', 'func2', 1),
-            ('instruction', 'func2', 2),
-            ('instruction', 'func2', 4),
-            ('line', 'func2', 2),
-            ('instruction', 'func2', 6),
-            ('instruction', 'func2', 8),
-            ('instruction', 'func2', 28),
-            ('instruction', 'func2', 30),
-            ('instruction', 'func2', 38),
-            ('line', 'func2', 3),
-            ('instruction', 'func2', 40),
-            ('instruction', 'func2', 42),
-            ('instruction', 'func2', 44),
-            ('instruction', 'func2', 46),
-            ('line', 'get_events', 11)])
+            ("line", "get_events", 10),
+            ("line", "func2", 1),
+            ("instruction", "func2", 4),
+            ("instruction", "func2", 6),
+            ("line", "func2", 2),
+            ("instruction", "func2", 8),
+            ("instruction", "func2", 10),
+            ("instruction", "func2", 30),
+            ("instruction", "func2", 32),
+            ("instruction", "func2", 40),
+            ("line", "func2", 3),
+            ("instruction", "func2", 42),
+            ("instruction", "func2", 44),
+            ("instruction", "func2", 46),
+            ("instruction", "func2", 48),
+            ("line", "get_events", 11),
+        ])
 
     def test_try_except(self):
 
@@ -1272,28 +1252,29 @@ def func3():
             line = 6
 
         self.check_events(func3, recorders = LINE_AND_INSTRUCTION_RECORDERS, expected = [
-            ('line', 'get_events', 10),
-            ('line', 'func3', 1),
-            ('instruction', 'func3', 2),
-            ('line', 'func3', 2),
-            ('instruction', 'func3', 4),
-            ('instruction', 'func3', 6),
-            ('line', 'func3', 3),
-            ('instruction', 'func3', 8),
-            ('instruction', 'func3', 18),
-            ('instruction', 'func3', 20),
-            ('line', 'func3', 4),
-            ('instruction', 'func3', 22),
-            ('line', 'func3', 5),
-            ('instruction', 'func3', 24),
-            ('instruction', 'func3', 26),
-            ('instruction', 'func3', 28),
-            ('line', 'func3', 6),
-            ('instruction', 'func3', 30),
-            ('instruction', 'func3', 32),
-            ('instruction', 'func3', 34),
-            ('instruction', 'func3', 36),
-            ('line', 'get_events', 11)])
+            ("line", "get_events", 10),
+            ("line", "func3", 1),
+            ("instruction", "func3", 4),
+            ("line", "func3", 2),
+            ("instruction", "func3", 6),
+            ("instruction", "func3", 8),
+            ("line", "func3", 3),
+            ("instruction", "func3", 10),
+            ("instruction", "func3", 20),
+            ("instruction", "func3", 22),
+            ("line", "func3", 4),
+            ("instruction", "func3", 24),
+            ("line", "func3", 5),
+            ("instruction", "func3", 26),
+            ("instruction", "func3", 28),
+            ("instruction", "func3", 30),
+            ("line", "func3", 6),
+            ("instruction", "func3", 32),
+            ("instruction", "func3", 34),
+            ("instruction", "func3", 36),
+            ("instruction", "func3", 38),
+            ("line", "get_events", 11),
+        ])
 
     def test_with_restart(self):
         def func1():
@@ -1304,16 +1285,16 @@ def func1():
         self.check_events(func1, recorders = LINE_AND_INSTRUCTION_RECORDERS, expected = [
             ('line', 'get_events', 10),
             ('line', 'func1', 1),
-            ('instruction', 'func1', 2),
             ('instruction', 'func1', 4),
-            ('line', 'func1', 2),
             ('instruction', 'func1', 6),
+            ('line', 'func1', 2),
             ('instruction', 'func1', 8),
-            ('line', 'func1', 3),
             ('instruction', 'func1', 10),
+            ('line', 'func1', 3),
             ('instruction', 'func1', 12),
             ('instruction', 'func1', 14),
             ('instruction', 'func1', 16),
+            ('instruction', 'func1', 18),
             ('line', 'get_events', 11)])
 
         sys.monitoring.restart_events()
@@ -1321,16 +1302,16 @@ def func1():
         self.check_events(func1, recorders = LINE_AND_INSTRUCTION_RECORDERS, expected = [
             ('line', 'get_events', 10),
             ('line', 'func1', 1),
-            ('instruction', 'func1', 2),
             ('instruction', 'func1', 4),
-            ('line', 'func1', 2),
             ('instruction', 'func1', 6),
+            ('line', 'func1', 2),
             ('instruction', 'func1', 8),
-            ('line', 'func1', 3),
             ('instruction', 'func1', 10),
+            ('line', 'func1', 3),
             ('instruction', 'func1', 12),
             ('instruction', 'func1', 14),
             ('instruction', 'func1', 16),
+            ('instruction', 'func1', 18),
             ('line', 'get_events', 11)])
 
     def test_turn_off_only_instruction(self):
@@ -1378,10 +1359,10 @@ def func1():
         line1 = 1
 
     MUST_INCLUDE_LI = [
-            ('instruction', 'func1', 2),
-            ('line', 'func1', 2),
             ('instruction', 'func1', 4),
-            ('instruction', 'func1', 6)]
+            ('line', 'func1', 2),
+            ('instruction', 'func1', 6),
+            ('instruction', 'func1', 8)]
 
     def test_line_then_instruction(self):
         recorders = [ LineRecorder, InstructionRecorder ]
@@ -1398,11 +1379,11 @@ def func2():
         len(())
 
     MUST_INCLUDE_CI = [
-            ('instruction', 'func2', 2),
+            ('instruction', 'func2', 4),
             ('call', 'func2', sys.monitoring.MISSING),
             ('call', 'len', ()),
-            ('instruction', 'func2', 12),
-            ('instruction', 'func2', 14)]
+            ('instruction', 'func2', 14),
+            ('instruction', 'func2', 16)]
 
 
 
@@ -1486,8 +1467,334 @@ def func3():
             ('line', 'func3', 6)])
 
     def test_set_non_local_event(self):
+        # C_RETURN/C_RAISE are ancillary (derived) events — not settable as local
         with self.assertRaises(ValueError):
-            sys.monitoring.set_local_events(TEST_TOOL, just_call.__code__, E.RAISE)
+            sys.monitoring.set_local_events(TEST_TOOL, just_call.__code__, E.C_RETURN)
+
+    def test_local_reraise(self):
+        """RERAISE fires as a local event only for the instrumented code object."""
+
+        def foo():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                raise
+
+        def bar():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                raise
+
+        events = set()
+
+        def callback(code, offset, exc):
+            events.add(code.co_name)
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.RERAISE, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, E.RERAISE)
+            try:
+                foo()
+            except RuntimeError:
+                pass
+            try:
+                bar()  # should NOT trigger the callback
+            except RuntimeError:
+                pass
+            self.assertEqual(events, {'foo'})
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.RERAISE, None)
+
+    def test_local_reraise_disable(self):
+        """Returning DISABLE from a RERAISE callback disables it for that code object."""
+
+        call_count = 0
+
+        def foo():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                raise
+
+        def callback(code, offset, exc):
+            nonlocal call_count
+            call_count += 1
+            return sys.monitoring.DISABLE
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.RERAISE, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, E.RERAISE)
+            try:
+                foo()
+            except RuntimeError:
+                pass
+            self.assertEqual(call_count, 1)
+            try:
+                foo()
+            except RuntimeError:
+                pass
+            self.assertEqual(call_count, 1)  # not fired again — disabled
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.RERAISE, None)
+
+    def test_local_py_throw(self):
+        """PY_THROW fires as a local event only for the instrumented code object."""
+
+        def gen_foo():
+            yield 1
+            yield 2
+
+        def gen_bar():
+            yield 1
+            yield 2
+
+        events = []
+
+        def callback(code, offset, exc):
+            events.append(code.co_name)
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.PY_THROW, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, gen_foo.__code__, E.PY_THROW)
+
+            g = gen_foo()
+            next(g)
+            try:
+                g.throw(RuntimeError("test"))
+            except RuntimeError:
+                pass
+
+            h = gen_bar()
+            next(h)
+            try:
+                h.throw(RuntimeError("test"))  # should NOT trigger the callback
+            except RuntimeError:
+                pass
+
+            self.assertEqual(events, ['gen_foo'])
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, gen_foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.PY_THROW, None)
+
+    def test_local_py_throw_disable(self):
+        """Returning DISABLE from a PY_THROW callback disables it for that code object."""
+
+        call_count = 0
+
+        def gen_foo():
+            yield 1
+            yield 2
+
+        def callback(code, offset, exc):
+            nonlocal call_count
+            call_count += 1
+            return sys.monitoring.DISABLE
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.PY_THROW, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, gen_foo.__code__, E.PY_THROW)
+
+            g = gen_foo()
+            next(g)
+            try:
+                g.throw(RuntimeError("test"))
+            except RuntimeError:
+                pass
+            self.assertEqual(call_count, 1)
+
+            g2 = gen_foo()
+            next(g2)
+            try:
+                g2.throw(RuntimeError("test"))
+            except RuntimeError:
+                pass
+            self.assertEqual(call_count, 1)  # not fired again — disabled
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, gen_foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.PY_THROW, None)
+
+    def test_local_raise(self):
+        """RAISE fires as a local event only for the instrumented code object."""
+
+        def foo():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                pass
+
+        def bar():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                pass
+
+        events = []
+
+        def callback(code, offset, exc):
+            events.append(code.co_name)
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.RAISE, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, E.RAISE)
+            foo()
+            bar()  # should NOT trigger the callback
+            self.assertEqual(events, ['foo'])
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.RAISE, None)
+
+    def test_local_raise_disable(self):
+        """Returning DISABLE from a RAISE callback disables it for that code object."""
+
+        call_count = 0
+
+        def foo():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                pass
+
+        def callback(code, offset, exc):
+            nonlocal call_count
+            call_count += 1
+            return sys.monitoring.DISABLE
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.RAISE, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, E.RAISE)
+            foo()
+            self.assertEqual(call_count, 1)
+            foo()
+            self.assertEqual(call_count, 1)  # not fired again — disabled
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.RAISE, None)
+
+    def test_local_exception_handled(self):
+        """EXCEPTION_HANDLED fires as a local event only for the instrumented code object."""
+
+        def foo():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                pass
+
+        def bar():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                pass
+
+        events = []
+
+        def callback(code, offset, exc):
+            events.append(code.co_name)
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.EXCEPTION_HANDLED, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, E.EXCEPTION_HANDLED)
+            foo()
+            bar()  # should NOT trigger the callback
+            self.assertEqual(events, ['foo'])
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.EXCEPTION_HANDLED, None)
+
+    def test_local_exception_handled_disable(self):
+        """Returning DISABLE from an EXCEPTION_HANDLED callback disables it for that code object."""
+
+        call_count = 0
+
+        def foo():
+            try:
+                raise RuntimeError("test")
+            except RuntimeError:
+                pass
+
+        def callback(code, offset, exc):
+            nonlocal call_count
+            call_count += 1
+            return sys.monitoring.DISABLE
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.EXCEPTION_HANDLED, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, E.EXCEPTION_HANDLED)
+            foo()
+            self.assertEqual(call_count, 1)
+            foo()
+            self.assertEqual(call_count, 1)  # not fired again — disabled
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.EXCEPTION_HANDLED, None)
+
+    def test_local_py_unwind(self):
+        """PY_UNWIND fires as a local event only for the instrumented code object."""
+
+        def foo():
+            raise RuntimeError("test")
+
+        def bar():
+            raise RuntimeError("test")
+
+        events = []
+
+        def callback(code, offset, exc):
+            events.append(code.co_name)
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.PY_UNWIND, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, E.PY_UNWIND)
+
+            try:
+                foo()
+            except RuntimeError:
+                pass
+
+            try:
+                bar()  # should NOT trigger the callback
+            except RuntimeError:
+                pass
+
+            self.assertEqual(events, ['foo'])
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.PY_UNWIND, None)
+
+    def test_local_py_unwind_disable(self):
+        """Returning DISABLE from a PY_UNWIND callback disables it for that code object."""
+
+        call_count = 0
+
+        def foo():
+            raise RuntimeError("test")
+
+        def callback(code, offset, exc):
+            nonlocal call_count
+            call_count += 1
+            return sys.monitoring.DISABLE
+
+        try:
+            sys.monitoring.register_callback(TEST_TOOL, E.PY_UNWIND, callback)
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, E.PY_UNWIND)
+
+            try:
+                foo()
+            except RuntimeError:
+                pass
+            self.assertEqual(call_count, 1)  # fired once
+
+            try:
+                foo()
+            except RuntimeError:
+                pass
+            self.assertEqual(call_count, 1)  # not fired again — disabled by DISABLE return
+
+        finally:
+            sys.monitoring.set_local_events(TEST_TOOL, foo.__code__, 0)
+            sys.monitoring.register_callback(TEST_TOOL, E.PY_UNWIND, None)
 
 def line_from_offset(code, offset):
     for start, end, line in code.co_lines():
@@ -1617,11 +1924,11 @@ def whilefunc(n=0):
             ('branch right', 'whilefunc', 1, 3)])
 
         self.check_events(func, recorders = BRANCH_OFFSET_RECORDERS, expected = [
-            ('branch left', 'func', 28, 32),
-            ('branch right', 'func', 44, 58),
-            ('branch left', 'func', 28, 32),
-            ('branch left', 'func', 44, 50),
-            ('branch right', 'func', 28, 70)])
+            ('branch left', 'func', 32, 36),
+            ('branch right', 'func', 48, 62),
+            ('branch left', 'func', 32, 36),
+            ('branch left', 'func', 48, 54),
+            ('branch right', 'func', 32, 74)])
 
     def test_except_star(self):
 
@@ -1648,8 +1955,8 @@ def func():
             ('branch', 'func', 4, 4),
             ('line', 'func', 5),
             ('line', 'meth', 1),
-            ('jump', 'func', 5, '[offset=120]'),
-            ('branch', 'func', '[offset=124]', '[offset=130]'),
+            ('jump', 'func', 5, '[offset=122]'),
+            ('branch', 'func', '[offset=126]', '[offset=132]'),
             ('line', 'get_events', 11)])
 
         self.check_events(func, recorders = FLOW_AND_LINE_RECORDERS, expected = [
@@ -1663,8 +1970,8 @@ def func():
             ('line', 'func', 5),
             ('line', 'meth', 1),
             ('return', 'meth', None),
-            ('jump', 'func', 5, '[offset=120]'),
-            ('branch', 'func', '[offset=124]', '[offset=130]'),
+            ('jump', 'func', 5, '[offset=122]'),
+            ('branch', 'func', '[offset=126]', '[offset=132]'),
             ('return', 'func', None),
             ('line', 'get_events', 11)])
 
@@ -1676,8 +1983,8 @@ def foo(n=0):
                 n += 1
             return None
 
-        in_loop = ('branch left', 'foo', 10, 16)
-        exit_loop = ('branch right', 'foo', 10, 40)
+        in_loop = ('branch left', 'foo', 12, 18)
+        exit_loop = ('branch right', 'foo', 12, 42)
         self.check_events(foo, recorders = BRANCH_OFFSET_RECORDERS, expected = [
             in_loop,
             in_loop,
@@ -2150,8 +2457,8 @@ def run():
         finally:
             sys.monitoring.set_events(TEST_TOOL, 0)
 
-    @unittest.skipUnless(_testinternalcapi, "requires _testinternalcapi")
     def test_108390(self):
+        _testinternalcapi = import_helper.import_module("_testinternalcapi")
 
         class Foo:
             def __init__(self, set_event):
@@ -2209,6 +2516,21 @@ def callback(code, instruction_offset):
         sys.monitoring.restart_events()
         sys.monitoring.set_events(0, 0)
 
+    def test_134879(self):
+        # gh-134789
+        # Specialized FOR_ITER not incrementing index
+        def foo():
+            t = 0
+            for i in [1,2,3,4]:
+                t += i
+            self.assertEqual(t, 10)
+
+        sys.monitoring.use_tool_id(0, "test")
+        self.addCleanup(sys.monitoring.free_tool_id, 0)
+        sys.monitoring.set_local_events(0, foo.__code__, E.BRANCH_LEFT | E.BRANCH_RIGHT)
+        foo()
+        sys.monitoring.set_local_events(0, foo.__code__, 0)
+
 
 class TestOptimizer(MonitoringTestBase, unittest.TestCase):
 
@@ -2227,8 +2549,9 @@ def test_func(x):
 
 class TestTier2Optimizer(CheckEvents):
 
-    @unittest.skipUnless(_testinternalcapi, "requires _testinternalcapi")
     def test_monitoring_already_opimized_loop(self):
+        _testinternalcapi = import_helper.import_module("_testinternalcapi")
+
         def test_func(recorder):
             set_events = sys.monitoring.set_events
             line = E.LINE
@@ -2253,7 +2576,6 @@ def test_func(recorder):
 
 class TestMonitoringAtShutdown(unittest.TestCase):
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; - requires subprocess support
     def test_monitoring_live_at_shutdown(self):
         # gh-115832: An object destructor running during the final GC of
         # interpreter shutdown triggered an infinite loop in the
@@ -2262,23 +2584,25 @@ def test_monitoring_live_at_shutdown(self):
         script_helper.run_test_script(script)
 
 
-@unittest.skipUnless(_testcapi, "requires _testcapi")
+@unittest.skip("TODO: RUSTPYTHON; no _testcapi, and setUp leaves the tool ids in use when its import fails")
 class TestCApiEventGeneration(MonitoringTestBase, unittest.TestCase):
 
     class Scope:
         def __init__(self, *args):
+            self._testcapi = import_helper.import_module("_testcapi")
             self.args = args
 
         def __enter__(self):
-            _testcapi.monitoring_enter_scope(*self.args)
+            self._testcapi.monitoring_enter_scope(*self.args)
 
         def __exit__(self, *args):
-            _testcapi.monitoring_exit_scope()
+            self._testcapi.monitoring_exit_scope()
 
     def setUp(self):
         super(TestCApiEventGeneration, self).setUp()
 
-        capi = _testcapi
+        self._testcapi = import_helper.import_module("_testcapi")
+        capi = self._testcapi
 
         self.codelike = capi.CodeLike(2)
 
@@ -2347,7 +2671,7 @@ def __call__(self, *args):
     def test_fire_event(self):
         for expected, event, function, *args in self.cases:
             offset = 0
-            self.codelike = _testcapi.CodeLike(1)
+            self.codelike = self._testcapi.CodeLike(1)
             with self.subTest(function.__name__):
                 args_ = (self.codelike, offset) + tuple(args)
                 self.check_event_count(event, function, args_, expected)
@@ -2358,7 +2682,7 @@ def test_missing_exception(self):
                 continue
             assert args and isinstance(args[-1], BaseException)
             offset = 0
-            self.codelike = _testcapi.CodeLike(1)
+            self.codelike = self._testcapi.CodeLike(1)
             with self.subTest(function.__name__):
                 args_ = (self.codelike, offset) + tuple(args[:-1]) + (None,)
                 evt = int(math.log2(event))
@@ -2368,7 +2692,7 @@ def test_missing_exception(self):
     def test_fire_event_failing_callback(self):
         for expected, event, function, *args in self.cases:
             offset = 0
-            self.codelike = _testcapi.CodeLike(1)
+            self.codelike = self._testcapi.CodeLike(1)
             with self.subTest(function.__name__):
                 args_ = (self.codelike, offset) + tuple(args)
                 exc = OSError(42)
@@ -2418,12 +2742,14 @@ def check_disable(self, event, func, args, expected):
     def test_disable_event(self):
         for expected, event, function, *args in self.cases:
             offset = 0
-            self.codelike = _testcapi.CodeLike(2)
+            self.codelike = self._testcapi.CodeLike(2)
             with self.subTest(function.__name__):
                 args_ = (self.codelike, 0) + tuple(args)
                 self.check_disable(event, function, args_, expected)
 
     def test_enter_scope_two_events(self):
+        _testcapi = self._testcapi
+
         try:
             yield_counter = CounterWithDisable()
             unwind_counter = CounterWithDisable()
diff --git a/Lib/test/test_named_expressions.py b/Lib/test/test_named_expressions.py
index a859e051de2..cf44080670d 100644
--- a/Lib/test/test_named_expressions.py
+++ b/Lib/test/test_named_expressions.py
@@ -98,7 +98,6 @@ def test_named_expression_invalid_16(self):
         with self.assertRaisesRegex(SyntaxError, "invalid syntax"):
             exec(code, {}, {})
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_named_expression_invalid_17(self):
         code = "[i := 0, j := 1 for i, j in [(1, 2), (3, 4)]]"
 
diff --git a/Lib/test/test_netrc.py b/Lib/test/test_netrc.py
index 9d720f62710..bbb49bf15ce 100644
--- a/Lib/test/test_netrc.py
+++ b/Lib/test/test_netrc.py
@@ -1,6 +1,9 @@
 import netrc, os, unittest, sys, textwrap
+from pathlib import Path
 from test import support
 from test.support import os_helper
+from unittest.mock import patch
+
 
 temp_filename = os_helper.TESTFN
 
@@ -59,6 +62,9 @@ def test_optional_tokens(self):
             "machine host.domain.com login",
             "machine host.domain.com account",
             "machine host.domain.com password",
+            "machine host.domain.com login \"\"",
+            "machine host.domain.com account \"\"",
+            "machine host.domain.com password \"\"",
             "machine host.domain.com login \"\" account",
             "machine host.domain.com login \"\" password",
             "machine host.domain.com account \"\" password"
@@ -71,6 +77,9 @@ def test_optional_tokens(self):
             "default login",
             "default account",
             "default password",
+            "default login \"\"",
+            "default account \"\"",
+            "default password \"\"",
             "default login \"\" account",
             "default login \"\" password",
             "default account \"\" password"
@@ -79,6 +88,15 @@ def test_optional_tokens(self):
             nrc = self.make_nrc(item)
             self.assertEqual(nrc.hosts['default'], ('', '', ''))
 
+    def test_empty_quoted_token_is_not_eof(self):
+        data = (
+            '"" invalid',
+            'machine host.domain.com "" invalid',
+        )
+        for item in data:
+            with self.subTest(item=item):
+                self.assertRaises(netrc.NetrcParseError, self.make_nrc, item)
+
     def test_invalid_tokens(self):
         data = (
             "invalid host.domain.com",
@@ -309,6 +327,26 @@ def test_security(self):
             self.assertEqual(nrc.hosts['foo.domain.com'],
                              ('anonymous', '', 'pass'))
 
+    @unittest.skipUnless(os.name == 'posix', 'POSIX only test')
+    @unittest.skipUnless(hasattr(os, 'getuid'), "os.getuid is required")
+    @os_helper.skip_unless_working_chmod
+    def test_security_only_once(self):
+        # Make sure security check is only run once per parse when multiple
+        # entries are found.
+        with patch.object(netrc.netrc, "_security_check") as mock:
+            with os_helper.temp_dir() as tmp_dir:
+                netrc_path = Path(tmp_dir) / '.netrc'
+                netrc_path.write_text("""\
+                machine foo.domain.com login bar password pass
+                machine bar.domain.com login foo password pass
+                """)
+                netrc_path.chmod(0o600)
+                with os_helper.EnvironmentVarGuard() as environ:
+                    environ.set('HOME', tmp_dir)
+                    netrc.netrc()
+
+            mock.assert_called_once()
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
index 9270f325706..a3728b58335 100644
--- a/Lib/test/test_ntpath.py
+++ b/Lib/test/test_ntpath.py
@@ -1,3 +1,4 @@
+import errno
 import inspect
 import ntpath
 import os
@@ -6,9 +7,10 @@
 import sys
 import unittest
 import warnings
+from ntpath import ALL_BUT_LAST, ALLOW_MISSING
 from test import support
 from test.support import os_helper
-from ntpath import ALLOW_MISSING
+from test.support import warnings_helper
 from test.support.os_helper import FakePath
 from test import test_genericpath
 from tempfile import TemporaryFile
@@ -297,6 +299,10 @@ def test_isabs(self):
         tester('ntpath.isabs("\\\\.\\C:")', 1)
 
     def test_commonprefix(self):
+        with warnings_helper.check_warnings((".*commonpath().*", DeprecationWarning)):
+            self.do_test_commonprefix()
+
+    def do_test_commonprefix(self):
         tester('ntpath.commonprefix(["/home/swenson/spam", "/home/swen/spam"])',
                "/home/swen")
         tester('ntpath.commonprefix(["\\home\\swen\\spam", "\\home\\swen\\eggs"])',
@@ -587,59 +593,63 @@ def test_realpath_invalid_paths(self):
         # gh-106242: Embedded nulls and non-strict fallback to abspath
         self.assertEqual(realpath(path, strict=False), path)
         # gh-106242: Embedded nulls should raise OSError (not ValueError)
+        self.assertRaises(OSError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(OSError, realpath, path, strict=True)
         self.assertRaises(OSError, realpath, path, strict=ALLOW_MISSING)
         path = ABSTFNb + b'\x00'
         self.assertEqual(realpath(path, strict=False), path)
+        self.assertRaises(OSError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(OSError, realpath, path, strict=True)
         self.assertRaises(OSError, realpath, path, strict=ALLOW_MISSING)
         path = ABSTFN + '\\nonexistent\\x\x00'
         self.assertEqual(realpath(path, strict=False), path)
+        self.assertRaises(OSError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(OSError, realpath, path, strict=True)
         self.assertRaises(OSError, realpath, path, strict=ALLOW_MISSING)
         path = ABSTFNb + b'\\nonexistent\\x\x00'
         self.assertEqual(realpath(path, strict=False), path)
+        self.assertRaises(OSError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(OSError, realpath, path, strict=True)
         self.assertRaises(OSError, realpath, path, strict=ALLOW_MISSING)
         path = ABSTFN + '\x00\\..'
         self.assertEqual(realpath(path, strict=False), os.getcwd())
+        self.assertEqual(realpath(path, strict=ALL_BUT_LAST), os.getcwd())
         self.assertEqual(realpath(path, strict=True), os.getcwd())
         self.assertEqual(realpath(path, strict=ALLOW_MISSING), os.getcwd())
         path = ABSTFNb + b'\x00\\..'
         self.assertEqual(realpath(path, strict=False), os.getcwdb())
+        self.assertEqual(realpath(path, strict=ALL_BUT_LAST), os.getcwdb())
         self.assertEqual(realpath(path, strict=True), os.getcwdb())
         self.assertEqual(realpath(path, strict=ALLOW_MISSING), os.getcwdb())
         path = ABSTFN + '\\nonexistent\\x\x00\\..'
         self.assertEqual(realpath(path, strict=False), ABSTFN + '\\nonexistent')
+        self.assertRaises(OSError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(OSError, realpath, path, strict=True)
         self.assertEqual(realpath(path, strict=ALLOW_MISSING), ABSTFN + '\\nonexistent')
         path = ABSTFNb + b'\\nonexistent\\x\x00\\..'
         self.assertEqual(realpath(path, strict=False), ABSTFNb + b'\\nonexistent')
+        self.assertRaises(OSError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(OSError, realpath, path, strict=True)
         self.assertEqual(realpath(path, strict=ALLOW_MISSING), ABSTFNb + b'\\nonexistent')
 
     @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_invalid_unicode_paths(self, kwargs):
         realpath = ntpath.realpath
         ABSTFN = ntpath.abspath(os_helper.TESTFN)
         ABSTFNb = os.fsencode(ABSTFN)
         path = ABSTFNb + b'\xff'
         self.assertRaises(UnicodeDecodeError, realpath, path, **kwargs)
-        self.assertRaises(UnicodeDecodeError, realpath, path, **kwargs)
         path = ABSTFNb + b'\\nonexistent\\\xff'
         self.assertRaises(UnicodeDecodeError, realpath, path, **kwargs)
-        self.assertRaises(UnicodeDecodeError, realpath, path, **kwargs)
         path = ABSTFNb + b'\xff\\..'
         self.assertRaises(UnicodeDecodeError, realpath, path, **kwargs)
-        self.assertRaises(UnicodeDecodeError, realpath, path, **kwargs)
         path = ABSTFNb + b'\\nonexistent\\\xff\\..'
         self.assertRaises(UnicodeDecodeError, realpath, path, **kwargs)
-        self.assertRaises(UnicodeDecodeError, realpath, path, **kwargs)
 
     @os_helper.skip_unless_symlink
     @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_relative(self, kwargs):
         ABSTFN = ntpath.abspath(os_helper.TESTFN)
         open(ABSTFN, "wb").close()
@@ -766,34 +776,53 @@ def test_realpath_symlink_loops_strict(self):
         self.addCleanup(os_helper.unlink, ABSTFN + "a")
 
         os.symlink(ABSTFN, ABSTFN)
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN, strict=ALL_BUT_LAST)
         self.assertRaises(OSError, ntpath.realpath, ABSTFN, strict=True)
 
         os.symlink(ABSTFN + "1", ABSTFN + "2")
         os.symlink(ABSTFN + "2", ABSTFN + "1")
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1", strict=ALL_BUT_LAST)
         self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1", strict=True)
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "2", strict=ALL_BUT_LAST)
         self.assertRaises(OSError, ntpath.realpath, ABSTFN + "2", strict=True)
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1\\x", strict=ALL_BUT_LAST)
         self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1\\x", strict=True)
         # Windows eliminates '..' components before resolving links, so the
         # following call is not expected to raise.
+        self.assertPathEqual(ntpath.realpath(ABSTFN + "1\\..", strict=ALL_BUT_LAST),
+                             ntpath.dirname(ABSTFN))
         self.assertPathEqual(ntpath.realpath(ABSTFN + "1\\..", strict=True),
                              ntpath.dirname(ABSTFN))
+        self.assertPathEqual(ntpath.realpath(ABSTFN + "1\\..\\x", strict=ALL_BUT_LAST),
+                             ntpath.dirname(ABSTFN) + "\\x")
         self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1\\..\\x", strict=True)
         os.symlink(ABSTFN + "x", ABSTFN + "y")
+        self.assertPathEqual(ntpath.realpath(ABSTFN + "1\\..\\"
+                                             + ntpath.basename(ABSTFN) + "y",
+                                             strict=ALL_BUT_LAST),
+                             ABSTFN + "x")
         self.assertRaises(OSError, ntpath.realpath, ABSTFN + "1\\..\\"
                                              + ntpath.basename(ABSTFN) + "y",
                                              strict=True)
+        self.assertRaises(OSError, ntpath.realpath,
+                          ABSTFN + "1\\..\\" + ntpath.basename(ABSTFN) + "1",
+                          strict=ALL_BUT_LAST)
         self.assertRaises(OSError, ntpath.realpath,
                           ABSTFN + "1\\..\\" + ntpath.basename(ABSTFN) + "1",
                           strict=True)
 
         os.symlink(ntpath.basename(ABSTFN) + "a\\b", ABSTFN + "a")
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "a", strict=ALL_BUT_LAST)
         self.assertRaises(OSError, ntpath.realpath, ABSTFN + "a", strict=True)
 
         os.symlink("..\\" + ntpath.basename(ntpath.dirname(ABSTFN))
                    + "\\" + ntpath.basename(ABSTFN) + "c", ABSTFN + "c")
+        self.assertRaises(OSError, ntpath.realpath, ABSTFN + "c", strict=ALL_BUT_LAST)
         self.assertRaises(OSError, ntpath.realpath, ABSTFN + "c", strict=True)
 
         # Test using relative path as well.
+        self.assertRaises(OSError, ntpath.realpath, ntpath.basename(ABSTFN),
+                          strict=ALL_BUT_LAST)
         self.assertRaises(OSError, ntpath.realpath, ntpath.basename(ABSTFN),
                           strict=True)
 
@@ -853,7 +882,7 @@ def test_realpath_symlink_loops_raise(self):
 
     @os_helper.skip_unless_symlink
     @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_symlink_prefix(self, kwargs):
         ABSTFN = ntpath.abspath(os_helper.TESTFN)
         self.addCleanup(os_helper.unlink, ABSTFN + "3")
@@ -891,6 +920,7 @@ def test_realpath_nul(self):
         tester("ntpath.realpath('NUL')", r'\\.\NUL')
         tester("ntpath.realpath('NUL', strict=False)", r'\\.\NUL')
         tester("ntpath.realpath('NUL', strict=True)", r'\\.\NUL')
+        tester("ntpath.realpath('NUL', strict=ALL_BUT_LAST)", r'\\.\NUL')
         tester("ntpath.realpath('NUL', strict=ALLOW_MISSING)", r'\\.\NUL')
 
     @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
@@ -915,7 +945,7 @@ def test_realpath_cwd(self):
 
         self.assertPathEqual(test_file_long, ntpath.realpath(test_file_short))
 
-        for kwargs in {}, {'strict': True}, {'strict': ALLOW_MISSING}:
+        for kwargs in {}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING}:
             with self.subTest(**kwargs):
                 with os_helper.change_cwd(test_dir_long):
                     self.assertPathEqual(
@@ -975,6 +1005,93 @@ def test_realpath_permission(self):
 
         self.assertPathEqual(test_file, ntpath.realpath(test_file_short))
 
+    @os_helper.skip_unless_symlink
+    @unittest.skipUnless(HAVE_GETFINALPATHNAME, 'need _getfinalpathname')
+    def test_realpath_mode(self):
+        realpath = ntpath.realpath
+        ABSTFN = ntpath.abspath(os_helper.TESTFN)
+        self.addCleanup(os_helper.rmdir, ABSTFN)
+        self.addCleanup(os_helper.rmdir, ABSTFN + "/dir")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/file")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/dir/file2")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/link")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/link2")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/broken")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/cycle")
+
+        os.mkdir(ABSTFN)
+        os.mkdir(ABSTFN + "\\dir")
+        open(ABSTFN + "\\file", "wb").close()
+        open(ABSTFN + "\\dir\\file2", "wb").close()
+        os.symlink("file", ABSTFN + "\\link")
+        os.symlink("dir", ABSTFN + "\\link2")
+        os.symlink("nonexistent", ABSTFN + "\\broken")
+        os.symlink("cycle", ABSTFN + "\\cycle")
+        def check(path, modes, expected, errno=None):
+            path = path.replace('/', '\\')
+            if isinstance(expected, str):
+                assert errno is None
+                expected = expected.replace('/', os.sep)
+                for mode in modes:
+                    with self.subTest(mode=mode):
+                        self.assertEqual(realpath(path, strict=mode),
+                                         ABSTFN + expected)
+            else:
+                for mode in modes:
+                    with self.subTest(mode=mode):
+                        with self.assertRaises(expected) as cm:
+                            realpath(path, strict=mode)
+                        if errno is not None:
+                            self.assertEqual(cm.exception.errno, errno)
+
+        self.enterContext(os_helper.change_cwd(ABSTFN))
+        all_modes = [False, ALLOW_MISSING, ALL_BUT_LAST, True]
+        check("file", all_modes, "/file")
+        check("file/", all_modes, "/file")
+        check("file/file2", [False, ALLOW_MISSING], "/file/file2")
+        check("file/file2", [ALL_BUT_LAST, True], FileNotFoundError)
+        check("file/.", all_modes, "/file")
+        check("file/../link2", all_modes, "/dir")
+
+        check("dir", all_modes, "/dir")
+        check("dir/", all_modes, "/dir")
+        check("dir/file2", all_modes, "/dir/file2")
+
+        check("link", all_modes, "/file")
+        check("link/", all_modes, "/file")
+        check("link/file2", [False, ALLOW_MISSING], "/file/file2")
+        check("link/file2", [ALL_BUT_LAST, True], FileNotFoundError)
+        check("link/.", all_modes, "/file")
+        check("link/../link", all_modes, "/file")
+
+        check("link2", all_modes, "/dir")
+        check("link2/", all_modes, "/dir")
+        check("link2/file2", all_modes, "/dir/file2")
+
+        check("nonexistent", [False, ALLOW_MISSING, ALL_BUT_LAST], "/nonexistent")
+        check("nonexistent", [True], FileNotFoundError)
+        check("nonexistent/", [False, ALLOW_MISSING, ALL_BUT_LAST], "/nonexistent")
+        check("nonexistent/", [True], FileNotFoundError)
+        check("nonexistent/file", [False, ALLOW_MISSING], "/nonexistent/file")
+        check("nonexistent/file", [ALL_BUT_LAST, True], FileNotFoundError)
+        check("nonexistent/../link", all_modes, "/file")
+
+        check("broken", [False, ALLOW_MISSING, ALL_BUT_LAST], "/nonexistent")
+        check("broken", [True], FileNotFoundError)
+        check("broken/", [False, ALLOW_MISSING, ALL_BUT_LAST], "/nonexistent")
+        check("broken/", [True], FileNotFoundError)
+        check("broken/file", [False, ALLOW_MISSING], "/nonexistent/file")
+        check("broken/file", [ALL_BUT_LAST, True], FileNotFoundError)
+        check("broken/../link", all_modes, "/file")
+
+        check("cycle", [False], "/cycle")
+        check("cycle", [ALLOW_MISSING, ALL_BUT_LAST, True], OSError, errno.EINVAL)
+        check("cycle/", [False], "/cycle")
+        check("cycle/", [ALLOW_MISSING, ALL_BUT_LAST, True], OSError, errno.EINVAL)
+        check("cycle/file", [False], "/cycle/file")
+        check("cycle/file", [ALLOW_MISSING, ALL_BUT_LAST, True], OSError, errno.EINVAL)
+        check("cycle/../link", all_modes, "/file")
+
     def test_expandvars(self):
         with os_helper.EnvironmentVarGuard() as env:
             env.clear()
diff --git a/Lib/test/test_optparse.py b/Lib/test/test_optparse.py
index e476e472780..fc8ef9520b3 100644
--- a/Lib/test/test_optparse.py
+++ b/Lib/test/test_optparse.py
@@ -1666,6 +1666,16 @@ def test_translations(self):
         self.assertMsgidsEqual(optparse)
 
 
+class TestModule(unittest.TestCase):
+    def test_deprecated__version__(self):
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            "'__version__' is deprecated and slated for removal in Python 3.20",
+        ) as cm:
+            getattr(optparse, "__version__")
+        self.assertEqual(cm.filename, __file__)
+
+
 if __name__ == '__main__':
     # To regenerate translation snapshots
     if len(sys.argv) > 1 and sys.argv[1] == '--snapshot-update':
diff --git a/Lib/test/test_os/__init__.py b/Lib/test/test_os/__init__.py
new file mode 100644
index 00000000000..bc502ef32d2
--- /dev/null
+++ b/Lib/test/test_os/__init__.py
@@ -0,0 +1,6 @@
+import os.path
+from test.support import load_package_tests
+
+
+def load_tests(*args):
+    return load_package_tests(os.path.dirname(__file__), *args)
diff --git a/Lib/test/test_os.py b/Lib/test/test_os/test_os.py
similarity index 88%
rename from Lib/test/test_os.py
rename to Lib/test/test_os/test_os.py
index c9cabd67355..2e3cec6e42b 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os/test_os.py
@@ -7,7 +7,6 @@
 import contextlib
 import decimal
 import errno
-import fnmatch
 import fractions
 import itertools
 import locale
@@ -31,12 +30,14 @@
 import uuid
 import warnings
 from test import support
-from test.support import import_helper
 from test.support import os_helper
 from test.support import socket_helper
 from test.support import infinite_recursion
+from test.support import requires_root_user
+from test.support import requires_non_root_user
 from test.support import warnings_helper
 from platform import win32_is_iot
+from .utils import create_file
 
 try:
     import resource
@@ -46,10 +47,6 @@
     import fcntl
 except ImportError:
     fcntl = None
-try:
-    import _winapi
-except ImportError:
-    _winapi = None
 try:
     import pwd
     all_users = [u.pw_uid for u in pwd.getpwall()]
@@ -72,10 +69,6 @@
 from test.support.os_helper import FakePath
 
 
-root_in_posix = False
-if hasattr(os, 'geteuid'):
-    root_in_posix = (os.geteuid() == 0)
-
 # Detect whether we're on a Linux system that uses the (now outdated
 # and unmaintained) linuxthreads threading library.  There's an issue
 # when combining linuxthreads with a failed execv call: see
@@ -93,11 +86,6 @@ def requires_os_func(name):
     return unittest.skipUnless(hasattr(os, name), 'requires os.%s' % name)
 
 
-def create_file(filename, content=b'content'):
-    with open(filename, "xb", 0) as fp:
-        fp.write(content)
-
-
 # On platforms without a native spawnv(), os.py provides a Python fallback
 # built on fork()+exec*() that reports argument conversion failures from the
 # child as exit status 127 instead of raising, so tests of the C
@@ -184,6 +172,20 @@ def test_getcwdb(self):
         self.assertIsInstance(cwd, bytes)
         self.assertEqual(os.fsdecode(cwd), os.getcwd())
 
+    def test_type_fqdn(self):
+        def fqdn(obj):
+            return (obj.__module__, obj.__qualname__)
+
+        native = os.name
+        self.assertEqual(fqdn(os.stat_result), ("os", "stat_result"))
+        self.assertEqual(fqdn(os.times_result), (native, "times_result"))
+        if hasattr(os, "statvfs_result"):
+            self.assertEqual(fqdn(os.statvfs_result), ("os", "statvfs_result"))
+        if hasattr(os, "sched_param"):
+            self.assertEqual(fqdn(os.sched_param), (native, "sched_param"))
+        if hasattr(os, "waitid_result"):
+            self.assertEqual(fqdn(os.waitid_result), (native, "waitid_result"))
+
 
 # Tests creating TESTFN
 class FileTests(unittest.TestCase):
@@ -650,6 +652,15 @@ def setUp(self):
         self.addCleanup(os_helper.unlink, self.fname)
         create_file(self.fname, b"ABC")
 
+    def check_timestamp_agreement(self, result, names):
+        # Make sure that the st_?time and st_?time_ns fields roughly agree
+        # (they should always agree up to around tens-of-microseconds)
+        for name in names:
+            with self.subTest(name=name):
+                floaty = int(getattr(result, name) * 100_000)
+                nanosecondy = getattr(result, name + "_ns") // 10_000
+                self.assertAlmostEqual(floaty, nanosecondy, delta=2, msg=name)
+
     def check_stat_attributes(self, fname):
         result = os.stat(fname)
 
@@ -670,21 +681,15 @@ def trunc(x): return x
                                   result[getattr(stat, name)])
                 self.assertIn(attr, members)
 
-        # Make sure that the st_?time and st_?time_ns fields roughly agree
-        # (they should always agree up to around tens-of-microseconds)
-        for name in 'st_atime st_mtime st_ctime'.split():
-            floaty = int(getattr(result, name) * 100000)
-            nanosecondy = getattr(result, name + "_ns") // 10000
-            self.assertAlmostEqual(floaty, nanosecondy, delta=2)
-
-        # Ensure both birthtime and birthtime_ns roughly agree, if present
+        time_attributes = ['st_atime', 'st_mtime', 'st_ctime']
         try:
-            floaty = int(result.st_birthtime * 100000)
-            nanosecondy = result.st_birthtime_ns // 10000
+            result.st_birthtime
+            result.st_birthtime_ns
         except AttributeError:
             pass
         else:
-            self.assertAlmostEqual(floaty, nanosecondy, delta=2)
+            time_attributes.append('st_birthtime')
+        self.check_timestamp_agreement(result, time_attributes)
 
         try:
             result[200]
@@ -745,6 +750,160 @@ def test_stat_result_pickle(self):
                 unpickled = pickle.loads(p)
                 self.assertEqual(result, unpickled)
 
+    def check_statx_attributes(self, filename):
+        maximal_mask = 0
+        for name in dir(os):
+            if name.startswith('STATX_'):
+                maximal_mask |= getattr(os, name)
+        result = os.statx(filename, maximal_mask)
+        stat_result = os.stat(filename)
+
+        time_attributes = ('stx_atime', 'stx_btime', 'stx_ctime', 'stx_mtime')
+        # gh-83714: stx_btime can be None on tmpfs even if STATX_BTIME mask
+        # is used
+        time_attributes = [name for name in time_attributes
+                           if getattr(result, name) is not None]
+        self.check_timestamp_agreement(result, time_attributes)
+
+        def getmask(name):
+            return getattr(os, name, 0)
+
+        requirements = (
+            ('stx_atime', os.STATX_ATIME),
+            ('stx_atime_ns', os.STATX_ATIME),
+            ('stx_atomic_write_segments_max', getmask('STATX_WRITE_ATOMIC')),
+            ('stx_atomic_write_unit_max', getmask('STATX_WRITE_ATOMIC')),
+            ('stx_atomic_write_unit_max_opt', getmask('STATX_WRITE_ATOMIC')),
+            ('stx_atomic_write_unit_min', getmask('STATX_WRITE_ATOMIC')),
+            ('stx_attributes', 0),
+            ('stx_attributes_mask', 0),
+            ('stx_blksize', 0),
+            ('stx_blocks', os.STATX_BLOCKS),
+            ('stx_btime', os.STATX_BTIME),
+            ('stx_btime_ns', os.STATX_BTIME),
+            ('stx_ctime', os.STATX_CTIME),
+            ('stx_ctime_ns', os.STATX_CTIME),
+            ('stx_dev', 0),
+            ('stx_dev_major', 0),
+            ('stx_dev_minor', 0),
+            ('stx_dio_mem_align', getmask('STATX_DIOALIGN')),
+            ('stx_dio_offset_align', getmask('STATX_DIOALIGN')),
+            ('stx_dio_read_offset_align', getmask('STATX_DIO_READ_ALIGN')),
+            ('stx_gid', os.STATX_GID),
+            ('stx_ino', os.STATX_INO),
+            ('stx_mask', 0),
+            ('stx_mnt_id', getmask('STATX_MNT_ID')),
+            ('stx_mode', os.STATX_TYPE | os.STATX_MODE),
+            ('stx_mtime', os.STATX_MTIME),
+            ('stx_mtime_ns', os.STATX_MTIME),
+            ('stx_nlink', os.STATX_NLINK),
+            ('stx_rdev', 0),
+            ('stx_rdev_major', 0),
+            ('stx_rdev_minor', 0),
+            ('stx_size', os.STATX_SIZE),
+            ('stx_subvol', getmask('STATX_SUBVOL')),
+            ('stx_uid', os.STATX_UID),
+        )
+        optional_members = {
+            'stx_atomic_write_segments_max',
+            'stx_atomic_write_unit_max',
+            'stx_atomic_write_unit_max_opt',
+            'stx_atomic_write_unit_min',
+            'stx_dio_mem_align',
+            'stx_dio_offset_align',
+            'stx_dio_read_offset_align',
+            'stx_mnt_id',
+            'stx_subvol',
+        }
+        float_type = {
+            'stx_atime',
+            'stx_btime',
+            'stx_ctime',
+            'stx_mtime',
+        }
+
+        members = set(name for name in dir(result)
+                      if name.startswith('stx_'))
+        tested = set(name for name, mask in requirements)
+        if members - tested:
+            raise ValueError(f"statx members not tested: {members - tested}")
+
+        for name, mask in requirements:
+            with self.subTest(name=name):
+                try:
+                    x = getattr(result, name)
+                except AttributeError:
+                    if name in optional_members:
+                        continue
+                    else:
+                        raise
+
+                if not(result.stx_mask & mask == mask):
+                    self.assertIsNone(x)
+                    continue
+
+                if name in float_type:
+                    self.assertIsInstance(x, float)
+                else:
+                    self.assertIsInstance(x, int)
+
+                # Compare with stat_result
+                try:
+                    b = getattr(stat_result, "st_" + name[4:])
+                except AttributeError:
+                    pass
+                else:
+                    self.assertEqual(type(x), type(b))
+                    if isinstance(x, float):
+                        self.assertAlmostEqual(x, b)
+                    else:
+                        self.assertEqual(x, b)
+
+        self.assertEqual(result.stx_rdev_major, os.major(result.stx_rdev))
+        self.assertEqual(result.stx_rdev_minor, os.minor(result.stx_rdev))
+        self.assertEqual(result.stx_dev_major, os.major(result.stx_dev))
+        self.assertEqual(result.stx_dev_minor, os.minor(result.stx_dev))
+
+        self.assertEqual(result.stx_attributes & result.stx_attributes_mask,
+                         result.stx_attributes)
+
+    @unittest.skipUnless(hasattr(os, 'statx'), 'test needs os.statx()')
+    def test_statx_attributes(self):
+        self.check_statx_attributes(self.fname)
+
+    @unittest.skipUnless(hasattr(os, 'statx'), 'test needs os.statx()')
+    def test_statx_attributes_bytes(self):
+        try:
+            fname = self.fname.encode(sys.getfilesystemencoding())
+        except UnicodeEncodeError:
+            self.skipTest("cannot encode %a for the filesystem" % self.fname)
+        self.check_statx_attributes(fname)
+
+    @unittest.skipUnless(hasattr(os, 'statx'), 'test needs os.statx()')
+    def test_statx_attributes_pathlike(self):
+        self.check_statx_attributes(FakePath(self.fname))
+
+    @unittest.skipUnless(hasattr(os, 'statx'), 'test needs os.statx()')
+    def test_statx_result(self):
+        result = os.statx(self.fname, os.STATX_BASIC_STATS)
+
+        # Check that attributes are read-only
+        members = [name for name in dir(result)
+                   if name.startswith('stx_')]
+        for name in members:
+            try:
+                setattr(result, name, 1)
+            except AttributeError:
+                pass
+            else:
+                self.fail("No exception raised")
+
+        # statx_result is not a tuple or tuple-like object.
+        with self.assertRaisesRegex(TypeError, 'not subscriptable'):
+            result[0]
+        with self.assertRaisesRegex(TypeError, 'cannot unpack'):
+            _, _ = result
+
     @unittest.skipUnless(hasattr(os, 'statvfs'), 'test needs os.statvfs()')
     def test_statvfs_attributes(self):
         result = os.statvfs(self.fname)
@@ -969,6 +1128,20 @@ def ns_to_sec(ns):
         # issue, os.utime() rounds towards minus infinity.
         return (ns * 1e-9) + 0.5e-9
 
+    @staticmethod
+    def ns_to_sec_decimal(ns):
+        # Convert a number of nanosecond (int) to a number of seconds (Decimal).
+        # Round towards infinity by adding 0.5 nanosecond to avoid rounding
+        # issue, os.utime() rounds towards minus infinity.
+        return decimal.Decimal('1e-9') * ns + decimal.Decimal('0.5e-9')
+
+    @staticmethod
+    def ns_to_sec_fraction(ns):
+        # Convert a number of nanosecond (int) to a number of seconds (Fraction).
+        # Round towards infinity by adding 0.5 nanosecond to avoid rounding
+        # issue, os.utime() rounds towards minus infinity.
+        return fractions.Fraction(ns, 10**9) + fractions.Fraction(1, 2*10**9)
+
     def test_utime_by_indexed(self):
         # pass times as floating-point seconds as the second indexed parameter
         def set_time(filename, ns):
@@ -989,6 +1162,24 @@ def set_time(filename, ns):
             os.utime(filename, times=(atime, mtime))
         self._test_utime(set_time)
 
+    def test_utime_decimal(self):
+        # pass times as Decimal seconds
+        def set_time(filename, ns):
+            atime_ns, mtime_ns = ns
+            atime = self.ns_to_sec_decimal(atime_ns)
+            mtime = self.ns_to_sec_decimal(mtime_ns)
+            os.utime(filename, (atime, mtime))
+        self._test_utime(set_time)
+
+    def test_utime_fraction(self):
+        # pass times as Fraction seconds
+        def set_time(filename, ns):
+            atime_ns, mtime_ns = ns
+            atime = self.ns_to_sec_fraction(atime_ns)
+            mtime = self.ns_to_sec_fraction(mtime_ns)
+            os.utime(filename, (atime, mtime))
+        self._test_utime(set_time)
+
     @unittest.skipUnless(os.utime in os.supports_follow_symlinks,
                          "follow_symlinks support for utime required "
                          "for this test.")
@@ -1085,9 +1276,15 @@ def test_large_time(self):
         if self.get_file_system(self.dirname) != "NTFS":
             self.skipTest("requires NTFS")
 
-        large = 5000000000   # some day in 2128
-        os.utime(self.fname, (large, large))
-        self.assertEqual(os.stat(self.fname).st_mtime, large)
+        times = (
+            5000000000,  # some day in 2128
+            # boundaries of the fast path cutoff in posixmodule.c:fill_time
+            -9223372037, -9223372036, 9223372035, 9223372036,
+        )
+        for large in times:
+            with self.subTest(large=large):
+                os.utime(self.fname, (large, large))
+                self.assertEqual(os.stat(self.fname).st_mtime, large)
 
     def test_utime_invalid_arguments(self):
         # seconds and nanoseconds parameters are mutually exclusive
@@ -1487,6 +1684,14 @@ def test_reload_environ(self):
             self.assertNotIn(b'test_env', os.environb)
             self.assertNotIn('test_env', os.environ)
 
+    def test_clearenv(self):
+        os.environ['REMOVEME'] = '1'
+        os.environ.clear()
+        self.assertEqual(os.environ, {})
+
+        self.assertRaises(TypeError, os.environ.clear, None)
+
+
 class WalkTests(unittest.TestCase):
     """Tests for os.walk()."""
     is_fwalk = False
@@ -1953,6 +2158,94 @@ def test_mode(self):
                 self.assertEqual(os.stat(path).st_mode & 0o777, 0o555)
                 self.assertEqual(os.stat(parent).st_mode & 0o777, 0o775)
 
+    @unittest.skipIf(
+        support.is_emscripten or support.is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_mode_with_parent_mode(self):
+        # Test the parent_mode parameter
+        parent = os.path.join(os_helper.TESTFN, 'dir1')
+        path = os.path.join(parent, 'dir2')
+        with os_helper.temp_umask(0o002):
+            # Specify mode for both leaf and parent directories
+            os.makedirs(path, 0o770, parent_mode=0o750)
+            self.assertTrue(os.path.exists(path))
+            self.assertTrue(os.path.isdir(path))
+            if os.name != 'nt':
+                # Leaf directory gets the mode parameter
+                self.assertEqual(os.stat(path).st_mode & 0o777, 0o770)
+                # Parent directory gets the parent_mode parameter
+                self.assertEqual(os.stat(parent).st_mode & 0o777, 0o750)
+
+    @unittest.skipIf(
+        support.is_emscripten or support.is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_parent_mode_deep_hierarchy(self):
+        # Test parent_mode with deep directory hierarchy
+        base = os.path.join(os_helper.TESTFN, 'dir1', 'dir2', 'dir3')
+        with os_helper.temp_umask(0o002):
+            os.makedirs(base, 0o755, parent_mode=0o700)
+            self.assertTrue(os.path.exists(base))
+            if os.name != 'nt':
+                # Check that all parent directories have parent_mode
+                level1 = os.path.join(os_helper.TESTFN, 'dir1')
+                level2 = os.path.join(level1, 'dir2')
+                self.assertEqual(os.stat(level1).st_mode & 0o777, 0o700)
+                self.assertEqual(os.stat(level2).st_mode & 0o777, 0o700)
+                # Leaf directory has the regular mode
+                self.assertEqual(os.stat(base).st_mode & 0o777, 0o755)
+
+    @unittest.skipIf(
+        support.is_emscripten or support.is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_parent_mode_same_as_mode(self):
+        # Test emulating Python 3.6 behavior by setting parent_mode=mode
+        parent = os.path.join(os_helper.TESTFN, 'dir1')
+        path = os.path.join(parent, 'dir2')
+        with os_helper.temp_umask(0o002):
+            os.makedirs(path, 0o705, parent_mode=0o705)
+            self.assertTrue(os.path.exists(path))
+            if os.name != 'nt':
+                # Both directories should have the same mode
+                self.assertEqual(os.stat(path).st_mode & 0o777, 0o705)
+                self.assertEqual(os.stat(parent).st_mode & 0o777, 0o705)
+
+    @unittest.skipIf(
+        support.is_emscripten or support.is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_parent_mode_combined_with_umask(self):
+        # parent_mode, like mode, is combined with the process umask; it does
+        # not bypass it.
+        parent = os.path.join(os_helper.TESTFN, 'dir1')
+        path = os.path.join(parent, 'dir2')
+        with os_helper.temp_umask(0o022):
+            os.makedirs(path, 0o777, parent_mode=0o777)
+            self.assertTrue(os.path.isdir(path))
+            if os.name != 'nt':
+                # 0o777 is masked down to 0o755 by the 0o022 umask, for both
+                # the leaf (mode) and the parent (parent_mode).
+                self.assertEqual(os.stat(path).st_mode & 0o777, 0o755)
+                self.assertEqual(os.stat(parent).st_mode & 0o777, 0o755)
+
     @unittest.skipIf(
         support.is_wasi,
         "WASI's umask is a stub."
@@ -2026,15 +2319,9 @@ def test_win32_mkdir_700(self):
         )
 
     def tearDown(self):
-        path = os.path.join(os_helper.TESTFN, 'dir1', 'dir2', 'dir3',
-                            'dir4', 'dir5', 'dir6')
-        # If the tests failed, the bottom-most directory ('../dir6')
-        # may not have been created, so we look for the outermost directory
-        # that exists.
-        while not os.path.exists(path) and path != os_helper.TESTFN:
-            path = os.path.dirname(path)
-
-        os.removedirs(path)
+        # Remove the whole tree regardless of which sub-directories a test
+        # created and regardless of their permission bits.
+        os_helper.rmtree(os_helper.TESTFN)
 
 
 @unittest.skipUnless(hasattr(os, "chown"), "requires os.chown()")
@@ -2071,8 +2358,8 @@ def test_chown_gid(self):
         gid = os.stat(os_helper.TESTFN).st_gid
         self.assertEqual(gid, gid_2)
 
-    @unittest.skipUnless(root_in_posix and len(all_users) > 1,
-                         "test needs root privilege and more than one user")
+    @requires_root_user
+    @unittest.skipUnless(len(all_users) > 1, "test needs more than one user")
     def test_chown_with_root(self):
         uid_1, uid_2 = all_users[:2]
         gid = os.stat(os_helper.TESTFN).st_gid
@@ -2083,8 +2370,8 @@ def test_chown_with_root(self):
         uid = os.stat(os_helper.TESTFN).st_uid
         self.assertEqual(uid, uid_2)
 
-    @unittest.skipUnless(not root_in_posix and len(all_users) > 1,
-                         "test needs non-root account and more than one user")
+    @requires_non_root_user
+    @unittest.skipUnless(len(all_users) > 1, "test needs and more than one user")
     def test_chown_without_permission(self):
         uid_1, uid_2 = all_users[:2]
         gid = os.stat(os_helper.TESTFN).st_gid
@@ -2489,42 +2776,6 @@ def test_execve_with_empty_path(self):
             self.fail('No OSError raised')
 
 
-@unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
-class Win32ErrorTests(unittest.TestCase):
-    def setUp(self):
-        try:
-            os.stat(os_helper.TESTFN)
-        except FileNotFoundError:
-            exists = False
-        except OSError as exc:
-            exists = True
-            self.fail("file %s must not exist; os.stat failed with %s"
-                      % (os_helper.TESTFN, exc))
-        else:
-            self.fail("file %s must not exist" % os_helper.TESTFN)
-
-    def test_rename(self):
-        self.assertRaises(OSError, os.rename, os_helper.TESTFN, os_helper.TESTFN+".bak")
-
-    def test_remove(self):
-        self.assertRaises(OSError, os.remove, os_helper.TESTFN)
-
-    def test_chdir(self):
-        self.assertRaises(OSError, os.chdir, os_helper.TESTFN)
-
-    def test_mkdir(self):
-        self.addCleanup(os_helper.unlink, os_helper.TESTFN)
-
-        with open(os_helper.TESTFN, "x") as f:
-            self.assertRaises(OSError, os.mkdir, os_helper.TESTFN)
-
-    def test_utime(self):
-        self.assertRaises(OSError, os.utime, os_helper.TESTFN, None)
-
-    def test_chmod(self):
-        self.assertRaises(OSError, os.chmod, os_helper.TESTFN, 0)
-
-
 @unittest.skipIf(support.is_wasi, "Cannot create invalid FD on WASI.")
 class TestInvalidFD(unittest.TestCase):
     singles = ["fchdir", "dup", "fstat", "fstatvfs", "tcgetpgrp", "ttyname"]
@@ -2635,10 +2886,62 @@ def test_fpathconf_bad_fd(self):
         'musl fpathconf ignores the file descriptor and returns a constant',
         )
     def test_pathconf_negative_fd_uses_fd_semantics(self):
+        if os.pathconf not in os.supports_fd:
+            self.skipTest('needs fpathconf()')
+
         with self.assertRaises(OSError) as ctx:
             os.pathconf(-1, 1)
         self.assertEqual(ctx.exception.errno, errno.EBADF)
 
+    @support.subTests("fd", [-1, -5])
+    def test_negative_fd_ebadf(self, fd):
+        tests = [(os.stat, fd)]
+        if hasattr(os, "statx"):
+            tests.append((os.statx, fd, 0))
+        if os.chdir in os.supports_fd:
+            tests.append((os.chdir, fd))
+        if os.chmod in os.supports_fd:
+            tests.append((os.chmod, fd, 0o777))
+        if hasattr(os, "chown") and os.chown in os.supports_fd:
+            tests.append((os.chown, fd, 0, 0))
+        if os.listdir in os.supports_fd:
+            tests.append((os.listdir, fd))
+        if os.utime in os.supports_fd:
+            tests.append((os.utime, fd, (0, 0)))
+        if hasattr(os, "truncate") and os.truncate in os.supports_fd:
+            tests.append((os.truncate, fd, 0))
+        if hasattr(os, 'statvfs') and os.statvfs in os.supports_fd:
+            tests.append((os.statvfs, fd))
+        if hasattr(os, "setxattr"):
+            tests.append((os.getxattr, fd, b"user.test"))
+            tests.append((os.setxattr, fd, b"user.test", b"1"))
+            tests.append((os.removexattr, fd, b"user.test"))
+            tests.append((os.listxattr, fd))
+        if os.scandir in os.supports_fd:
+            tests.append((os.scandir, fd))
+
+        for func, *args in tests:
+            with self.subTest(func=func, args=args):
+                with self.assertRaises(OSError) as ctx:
+                    func(*args)
+                self.assertEqual(ctx.exception.errno, errno.EBADF)
+
+        if (hasattr(os, "execve") and os.execve in os.supports_fd
+            and support.has_subprocess_support):
+            # glibc fails with EINVAL, musl fails with EBADF
+            with self.assertRaises(OSError) as ctx:
+                os.execve(fd, [sys.executable, "-c", "pass"], os.environ)
+            self.assertIn(ctx.exception.errno, (errno.EBADF, errno.EINVAL))
+
+        if support.MS_WINDOWS:
+            import nt
+            self.assertFalse(nt._path_exists(fd))
+            self.assertFalse(nt._path_lexists(fd))
+            self.assertFalse(nt._path_isdir(fd))
+            self.assertFalse(nt._path_isfile(fd))
+            self.assertFalse(nt._path_islink(fd))
+            self.assertFalse(nt._path_isjunction(fd))
+
     @unittest.skipUnless(hasattr(os, 'ftruncate'), 'test needs os.ftruncate()')
     def test_ftruncate(self):
         self.check(os.truncate, 0)
@@ -2869,224 +3172,6 @@ def test_stat(self):
         for fn in self.unicodefn:
             os.stat(os.path.join(self.dir, fn))
 
-@unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
-class Win32KillTests(unittest.TestCase):
-    def _kill(self, sig):
-        # Start sys.executable as a subprocess and communicate from the
-        # subprocess to the parent that the interpreter is ready. When it
-        # becomes ready, send *sig* via os.kill to the subprocess and check
-        # that the return code is equal to *sig*.
-        import ctypes
-        from ctypes import wintypes
-        import msvcrt
-
-        # Since we can't access the contents of the process' stdout until the
-        # process has exited, use PeekNamedPipe to see what's inside stdout
-        # without waiting. This is done so we can tell that the interpreter
-        # is started and running at a point where it could handle a signal.
-        PeekNamedPipe = ctypes.windll.kernel32.PeekNamedPipe
-        PeekNamedPipe.restype = wintypes.BOOL
-        PeekNamedPipe.argtypes = (wintypes.HANDLE, # Pipe handle
-                                  ctypes.POINTER(ctypes.c_char), # stdout buf
-                                  wintypes.DWORD, # Buffer size
-                                  ctypes.POINTER(wintypes.DWORD), # bytes read
-                                  ctypes.POINTER(wintypes.DWORD), # bytes avail
-                                  ctypes.POINTER(wintypes.DWORD)) # bytes left
-        msg = "running"
-        proc = subprocess.Popen([sys.executable, "-c",
-                                 "import sys;"
-                                 "sys.stdout.write('{}');"
-                                 "sys.stdout.flush();"
-                                 "input()".format(msg)],
-                                stdout=subprocess.PIPE,
-                                stderr=subprocess.PIPE,
-                                stdin=subprocess.PIPE)
-        self.addCleanup(proc.stdout.close)
-        self.addCleanup(proc.stderr.close)
-        self.addCleanup(proc.stdin.close)
-
-        count, max = 0, 100
-        while count < max and proc.poll() is None:
-            # Create a string buffer to store the result of stdout from the pipe
-            buf = ctypes.create_string_buffer(len(msg))
-            # Obtain the text currently in proc.stdout
-            # Bytes read/avail/left are left as NULL and unused
-            rslt = PeekNamedPipe(msvcrt.get_osfhandle(proc.stdout.fileno()),
-                                 buf, ctypes.sizeof(buf), None, None, None)
-            self.assertNotEqual(rslt, 0, "PeekNamedPipe failed")
-            if buf.value:
-                self.assertEqual(msg, buf.value.decode())
-                break
-            time.sleep(0.1)
-            count += 1
-        else:
-            self.fail("Did not receive communication from the subprocess")
-
-        os.kill(proc.pid, sig)
-        self.assertEqual(proc.wait(), sig)
-
-    def test_kill_sigterm(self):
-        # SIGTERM doesn't mean anything special, but make sure it works
-        self._kill(signal.SIGTERM)
-
-    def test_kill_int(self):
-        # os.kill on Windows can take an int which gets set as the exit code
-        self._kill(100)
-
-    @unittest.skipIf(mmap is None, "requires mmap")
-    def _kill_with_event(self, event, name):
-        tagname = "test_os_%s" % uuid.uuid1()
-        m = mmap.mmap(-1, 1, tagname)
-        m[0] = 0
-
-        # Run a script which has console control handling enabled.
-        script = os.path.join(os.path.dirname(__file__),
-                              "win_console_handler.py")
-        cmd = [sys.executable, script, tagname]
-        proc = subprocess.Popen(cmd,
-                                creationflags=subprocess.CREATE_NEW_PROCESS_GROUP)
-
-        with proc:
-            # Let the interpreter startup before we send signals. See #3137.
-            for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
-                if proc.poll() is None:
-                    break
-            else:
-                # Forcefully kill the process if we weren't able to signal it.
-                proc.kill()
-                self.fail("Subprocess didn't finish initialization")
-
-            os.kill(proc.pid, event)
-
-            try:
-                # proc.send_signal(event) could also be done here.
-                # Allow time for the signal to be passed and the process to exit.
-                proc.wait(timeout=support.SHORT_TIMEOUT)
-            except subprocess.TimeoutExpired:
-                # Forcefully kill the process if we weren't able to signal it.
-                proc.kill()
-                self.fail("subprocess did not stop on {}".format(name))
-
-    @unittest.skip("subprocesses aren't inheriting Ctrl+C property")
-    @support.requires_subprocess()
-    def test_CTRL_C_EVENT(self):
-        from ctypes import wintypes
-        import ctypes
-
-        # Make a NULL value by creating a pointer with no argument.
-        NULL = ctypes.POINTER(ctypes.c_int)()
-        SetConsoleCtrlHandler = ctypes.windll.kernel32.SetConsoleCtrlHandler
-        SetConsoleCtrlHandler.argtypes = (ctypes.POINTER(ctypes.c_int),
-                                          wintypes.BOOL)
-        SetConsoleCtrlHandler.restype = wintypes.BOOL
-
-        # Calling this with NULL and FALSE causes the calling process to
-        # handle Ctrl+C, rather than ignore it. This property is inherited
-        # by subprocesses.
-        SetConsoleCtrlHandler(NULL, 0)
-
-        self._kill_with_event(signal.CTRL_C_EVENT, "CTRL_C_EVENT")
-
-    @support.requires_subprocess()
-    def test_CTRL_BREAK_EVENT(self):
-        self._kill_with_event(signal.CTRL_BREAK_EVENT, "CTRL_BREAK_EVENT")
-
-
-@unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
-class Win32ListdirTests(unittest.TestCase):
-    """Test listdir on Windows."""
-
-    def setUp(self):
-        self.created_paths = []
-        for i in range(2):
-            dir_name = 'SUB%d' % i
-            dir_path = os.path.join(os_helper.TESTFN, dir_name)
-            file_name = 'FILE%d' % i
-            file_path = os.path.join(os_helper.TESTFN, file_name)
-            os.makedirs(dir_path)
-            with open(file_path, 'w', encoding='utf-8') as f:
-                f.write("I'm %s and proud of it. Blame test_os.\n" % file_path)
-            self.created_paths.extend([dir_name, file_name])
-        self.created_paths.sort()
-
-    def tearDown(self):
-        shutil.rmtree(os_helper.TESTFN)
-
-    def test_listdir_no_extended_path(self):
-        """Test when the path is not an "extended" path."""
-        # unicode
-        self.assertEqual(
-                sorted(os.listdir(os_helper.TESTFN)),
-                self.created_paths)
-
-        # bytes
-        self.assertEqual(
-                sorted(os.listdir(os.fsencode(os_helper.TESTFN))),
-                [os.fsencode(path) for path in self.created_paths])
-
-    def test_listdir_extended_path(self):
-        """Test when the path starts with '\\\\?\\'."""
-        # See: http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
-        # unicode
-        path = '\\\\?\\' + os.path.abspath(os_helper.TESTFN)
-        self.assertEqual(
-                sorted(os.listdir(path)),
-                self.created_paths)
-
-        # bytes
-        path = b'\\\\?\\' + os.fsencode(os.path.abspath(os_helper.TESTFN))
-        self.assertEqual(
-                sorted(os.listdir(path)),
-                [os.fsencode(path) for path in self.created_paths])
-
-
-@unittest.skipUnless(os.name == "nt", "NT specific tests")
-class Win32ListdriveTests(unittest.TestCase):
-    """Test listdrive, listmounts and listvolume on Windows."""
-
-    def setUp(self):
-        # Get drives and volumes from fsutil
-        out = subprocess.check_output(
-            ["fsutil.exe", "volume", "list"],
-            cwd=os.path.join(os.getenv("SystemRoot", "\\Windows"), "System32"),
-            encoding="mbcs",
-            errors="ignore",
-        )
-        lines = out.splitlines()
-        self.known_volumes = {l for l in lines if l.startswith('\\\\?\\')}
-        self.known_drives = {l for l in lines if l[1:] == ':\\'}
-        self.known_mounts = {l for l in lines if l[1:3] == ':\\'}
-
-    def test_listdrives(self):
-        drives = os.listdrives()
-        self.assertIsInstance(drives, list)
-        self.assertSetEqual(
-            self.known_drives,
-            self.known_drives & set(drives),
-        )
-
-    def test_listvolumes(self):
-        volumes = os.listvolumes()
-        self.assertIsInstance(volumes, list)
-        self.assertSetEqual(
-            self.known_volumes,
-            self.known_volumes & set(volumes),
-        )
-
-    def test_listmounts(self):
-        for volume in os.listvolumes():
-            try:
-                mounts = os.listmounts(volume)
-            except OSError as ex:
-                if support.verbose:
-                    print("Skipping", volume, "because of", ex)
-            else:
-                self.assertIsInstance(mounts, list)
-                self.assertSetEqual(
-                    set(mounts),
-                    self.known_mounts & set(mounts),
-                )
-
 
 @unittest.skipUnless(hasattr(os, 'readlink'), 'needs os.readlink()')
 class ReadlinkTests(unittest.TestCase):
@@ -3149,370 +3234,6 @@ def test_bytes(self):
         self.assertIsInstance(path, bytes)
 
 
-@unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
-@os_helper.skip_unless_symlink
-class Win32SymlinkTests(unittest.TestCase):
-    filelink = 'filelinktest'
-    filelink_target = os.path.abspath(__file__)
-    dirlink = 'dirlinktest'
-    dirlink_target = os.path.dirname(filelink_target)
-    missing_link = 'missing link'
-
-    def setUp(self):
-        assert os.path.exists(self.dirlink_target)
-        assert os.path.exists(self.filelink_target)
-        assert not os.path.exists(self.dirlink)
-        assert not os.path.exists(self.filelink)
-        assert not os.path.exists(self.missing_link)
-
-    def tearDown(self):
-        if os.path.exists(self.filelink):
-            os.remove(self.filelink)
-        if os.path.exists(self.dirlink):
-            os.rmdir(self.dirlink)
-        if os.path.lexists(self.missing_link):
-            os.remove(self.missing_link)
-
-    def test_directory_link(self):
-        os.symlink(self.dirlink_target, self.dirlink)
-        self.assertTrue(os.path.exists(self.dirlink))
-        self.assertTrue(os.path.isdir(self.dirlink))
-        self.assertTrue(os.path.islink(self.dirlink))
-        self.check_stat(self.dirlink, self.dirlink_target)
-
-    def test_file_link(self):
-        os.symlink(self.filelink_target, self.filelink)
-        self.assertTrue(os.path.exists(self.filelink))
-        self.assertTrue(os.path.isfile(self.filelink))
-        self.assertTrue(os.path.islink(self.filelink))
-        self.check_stat(self.filelink, self.filelink_target)
-
-    def _create_missing_dir_link(self):
-        'Create a "directory" link to a non-existent target'
-        linkname = self.missing_link
-        if os.path.lexists(linkname):
-            os.remove(linkname)
-        target = r'c:\\target does not exist.29r3c740'
-        assert not os.path.exists(target)
-        target_is_dir = True
-        os.symlink(target, linkname, target_is_dir)
-
-    def test_remove_directory_link_to_missing_target(self):
-        self._create_missing_dir_link()
-        # For compatibility with Unix, os.remove will check the
-        #  directory status and call RemoveDirectory if the symlink
-        #  was created with target_is_dir==True.
-        os.remove(self.missing_link)
-
-    def test_isdir_on_directory_link_to_missing_target(self):
-        self._create_missing_dir_link()
-        self.assertFalse(os.path.isdir(self.missing_link))
-
-    def test_rmdir_on_directory_link_to_missing_target(self):
-        self._create_missing_dir_link()
-        os.rmdir(self.missing_link)
-
-    def check_stat(self, link, target):
-        self.assertEqual(os.stat(link), os.stat(target))
-        self.assertNotEqual(os.lstat(link), os.stat(link))
-
-        bytes_link = os.fsencode(link)
-        self.assertEqual(os.stat(bytes_link), os.stat(target))
-        self.assertNotEqual(os.lstat(bytes_link), os.stat(bytes_link))
-
-    def test_12084(self):
-        level1 = os.path.abspath(os_helper.TESTFN)
-        level2 = os.path.join(level1, "level2")
-        level3 = os.path.join(level2, "level3")
-        self.addCleanup(os_helper.rmtree, level1)
-
-        os.mkdir(level1)
-        os.mkdir(level2)
-        os.mkdir(level3)
-
-        file1 = os.path.abspath(os.path.join(level1, "file1"))
-        create_file(file1)
-
-        orig_dir = os.getcwd()
-        try:
-            os.chdir(level2)
-            link = os.path.join(level2, "link")
-            os.symlink(os.path.relpath(file1), "link")
-            self.assertIn("link", os.listdir(os.getcwd()))
-
-            # Check os.stat calls from the same dir as the link
-            self.assertEqual(os.stat(file1), os.stat("link"))
-
-            # Check os.stat calls from a dir below the link
-            os.chdir(level1)
-            self.assertEqual(os.stat(file1),
-                             os.stat(os.path.relpath(link)))
-
-            # Check os.stat calls from a dir above the link
-            os.chdir(level3)
-            self.assertEqual(os.stat(file1),
-                             os.stat(os.path.relpath(link)))
-        finally:
-            os.chdir(orig_dir)
-
-    @unittest.skipUnless(os.path.lexists(r'C:\Users\All Users')
-                            and os.path.exists(r'C:\ProgramData'),
-                            'Test directories not found')
-    def test_29248(self):
-        # os.symlink() calls CreateSymbolicLink, which creates
-        # the reparse data buffer with the print name stored
-        # first, so the offset is always 0. CreateSymbolicLink
-        # stores the "PrintName" DOS path (e.g. "C:\") first,
-        # with an offset of 0, followed by the "SubstituteName"
-        # NT path (e.g. "\??\C:\"). The "All Users" link, on
-        # the other hand, seems to have been created manually
-        # with an inverted order.
-        target = os.readlink(r'C:\Users\All Users')
-        self.assertTrue(os.path.samefile(target, r'C:\ProgramData'))
-
-    def test_buffer_overflow(self):
-        # Older versions would have a buffer overflow when detecting
-        # whether a link source was a directory. This test ensures we
-        # no longer crash, but does not otherwise validate the behavior
-        segment = 'X' * 27
-        path = os.path.join(*[segment] * 10)
-        test_cases = [
-            # overflow with absolute src
-            ('\\' + path, segment),
-            # overflow dest with relative src
-            (segment, path),
-            # overflow when joining src
-            (path[:180], path[:180]),
-        ]
-        for src, dest in test_cases:
-            try:
-                os.symlink(src, dest)
-            except FileNotFoundError:
-                pass
-            else:
-                try:
-                    os.remove(dest)
-                except OSError:
-                    pass
-            # Also test with bytes, since that is a separate code path.
-            try:
-                os.symlink(os.fsencode(src), os.fsencode(dest))
-            except FileNotFoundError:
-                pass
-            else:
-                try:
-                    os.remove(dest)
-                except OSError:
-                    pass
-
-    def test_appexeclink(self):
-        root = os.path.expandvars(r'%LOCALAPPDATA%\Microsoft\WindowsApps')
-        if not os.path.isdir(root):
-            self.skipTest("test requires a WindowsApps directory")
-
-        aliases = [os.path.join(root, a)
-                   for a in fnmatch.filter(os.listdir(root), '*.exe')]
-
-        for alias in aliases:
-            if support.verbose:
-                print()
-                print("Testing with", alias)
-            st = os.lstat(alias)
-            self.assertEqual(st, os.stat(alias))
-            self.assertFalse(stat.S_ISLNK(st.st_mode))
-            self.assertEqual(st.st_reparse_tag, stat.IO_REPARSE_TAG_APPEXECLINK)
-            self.assertTrue(os.path.isfile(alias))
-            # testing the first one we see is sufficient
-            break
-        else:
-            self.skipTest("test requires an app execution alias")
-
-@unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
-class Win32JunctionTests(unittest.TestCase):
-    junction = 'junctiontest'
-    junction_target = os.path.dirname(os.path.abspath(__file__))
-
-    def setUp(self):
-        assert os.path.exists(self.junction_target)
-        assert not os.path.lexists(self.junction)
-
-    def tearDown(self):
-        if os.path.lexists(self.junction):
-            os.unlink(self.junction)
-
-    def test_create_junction(self):
-        _winapi.CreateJunction(self.junction_target, self.junction)
-        self.assertTrue(os.path.lexists(self.junction))
-        self.assertTrue(os.path.exists(self.junction))
-        self.assertTrue(os.path.isdir(self.junction))
-        self.assertNotEqual(os.stat(self.junction), os.lstat(self.junction))
-        self.assertEqual(os.stat(self.junction), os.stat(self.junction_target))
-
-        # bpo-37834: Junctions are not recognized as links.
-        self.assertFalse(os.path.islink(self.junction))
-        self.assertEqual(os.path.normcase("\\\\?\\" + self.junction_target),
-                         os.path.normcase(os.readlink(self.junction)))
-
-    def test_unlink_removes_junction(self):
-        _winapi.CreateJunction(self.junction_target, self.junction)
-        self.assertTrue(os.path.exists(self.junction))
-        self.assertTrue(os.path.lexists(self.junction))
-
-        os.unlink(self.junction)
-        self.assertFalse(os.path.exists(self.junction))
-
-@unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
-class Win32NtTests(unittest.TestCase):
-    def test_getfinalpathname_handles(self):
-        nt = import_helper.import_module('nt')
-        ctypes = import_helper.import_module('ctypes')
-        # Ruff false positive -- it thinks we're redefining `ctypes` here
-        import ctypes.wintypes  # noqa: F811
-
-        kernel = ctypes.WinDLL('Kernel32.dll', use_last_error=True)
-        kernel.GetCurrentProcess.restype = ctypes.wintypes.HANDLE
-
-        kernel.GetProcessHandleCount.restype = ctypes.wintypes.BOOL
-        kernel.GetProcessHandleCount.argtypes = (ctypes.wintypes.HANDLE,
-                                                 ctypes.wintypes.LPDWORD)
-
-        # This is a pseudo-handle that doesn't need to be closed
-        hproc = kernel.GetCurrentProcess()
-
-        handle_count = ctypes.wintypes.DWORD()
-        ok = kernel.GetProcessHandleCount(hproc, ctypes.byref(handle_count))
-        self.assertEqual(1, ok)
-
-        before_count = handle_count.value
-
-        # The first two test the error path, __file__ tests the success path
-        filenames = [
-            r'\\?\C:',
-            r'\\?\NUL',
-            r'\\?\CONIN',
-            __file__,
-        ]
-
-        for _ in range(10):
-            for name in filenames:
-                try:
-                    nt._getfinalpathname(name)
-                except Exception:
-                    # Failure is expected
-                    pass
-                try:
-                    os.stat(name)
-                except Exception:
-                    pass
-
-        ok = kernel.GetProcessHandleCount(hproc, ctypes.byref(handle_count))
-        self.assertEqual(1, ok)
-
-        handle_delta = handle_count.value - before_count
-
-        self.assertEqual(0, handle_delta)
-
-    @support.requires_subprocess()
-    def test_stat_unlink_race(self):
-        # bpo-46785: the implementation of os.stat() falls back to reading
-        # the parent directory if CreateFileW() fails with a permission
-        # error. If reading the parent directory fails because the file or
-        # directory are subsequently unlinked, or because the volume or
-        # share are no longer available, then the original permission error
-        # should not be restored.
-        filename =  os_helper.TESTFN
-        self.addCleanup(os_helper.unlink, filename)
-        deadline = time.time() + 5
-        command = textwrap.dedent("""\
-            import os
-            import sys
-            import time
-
-            filename = sys.argv[1]
-            deadline = float(sys.argv[2])
-
-            while time.time() < deadline:
-                try:
-                    with open(filename, "w") as f:
-                        pass
-                except OSError:
-                    pass
-                try:
-                    os.remove(filename)
-                except OSError:
-                    pass
-            """)
-
-        with subprocess.Popen([sys.executable, '-c', command, filename, str(deadline)]) as proc:
-            while time.time() < deadline:
-                try:
-                    os.stat(filename)
-                except FileNotFoundError as e:
-                    assert e.winerror == 2  # ERROR_FILE_NOT_FOUND
-            try:
-                proc.wait(1)
-            except subprocess.TimeoutExpired:
-                proc.terminate()
-
-    @support.requires_subprocess()
-    def test_stat_inaccessible_file(self):
-        filename = os_helper.TESTFN
-        ICACLS = os.path.expandvars(r"%SystemRoot%\System32\icacls.exe")
-
-        with open(filename, "wb") as f:
-            f.write(b'Test data')
-
-        stat1 = os.stat(filename)
-
-        try:
-            # Remove all permissions from the file
-            subprocess.check_output([ICACLS, filename, "/inheritance:r"],
-                                    stderr=subprocess.STDOUT)
-        except subprocess.CalledProcessError as ex:
-            if support.verbose:
-                print(ICACLS, filename, "/inheritance:r", "failed.")
-                print(ex.stdout.decode("oem", "replace").rstrip())
-            try:
-                os.unlink(filename)
-            except OSError:
-                pass
-            self.skipTest("Unable to create inaccessible file")
-
-        def cleanup():
-            # Give delete permission to the owner (us)
-            subprocess.check_output([ICACLS, filename, "/grant", "*WD:(D)"],
-                                    stderr=subprocess.STDOUT)
-            os.unlink(filename)
-
-        self.addCleanup(cleanup)
-
-        if support.verbose:
-            print("File:", filename)
-            print("stat with access:", stat1)
-
-        # First test - we shouldn't raise here, because we still have access to
-        # the directory and can extract enough information from its metadata.
-        stat2 = os.stat(filename)
-
-        if support.verbose:
-            print(" without access:", stat2)
-
-        # We may not get st_dev/st_ino, so ensure those are 0 or match
-        self.assertIn(stat2.st_dev, (0, stat1.st_dev))
-        self.assertIn(stat2.st_ino, (0, stat1.st_ino))
-
-        # st_mode and st_size should match (for a normal file, at least)
-        self.assertEqual(stat1.st_mode, stat2.st_mode)
-        self.assertEqual(stat1.st_size, stat2.st_size)
-
-        # st_ctime and st_mtime should be the same
-        self.assertEqual(stat1.st_ctime, stat2.st_ctime)
-        self.assertEqual(stat1.st_mtime, stat2.st_mtime)
-
-        # st_atime should be the same or later
-        self.assertGreaterEqual(stat1.st_atime, stat2.st_atime)
-
-
 @os_helper.skip_unless_symlink
 class NonLocalSymlinkTests(unittest.TestCase):
 
@@ -3589,6 +3310,7 @@ def test_getppid(self):
         self.assertEqual(error, b'')
         self.assertEqual(int(stdout), os.getpid())
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     def check_waitpid(self, code, exitcode, callback=None):
         if sys.platform == 'win32':
             # On Windows, os.spawnv() simply joins arguments with spaces:
@@ -3691,30 +3413,35 @@ def create_args(self, *, with_env=False, use_bytes=False):
 
         return program, args
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnl')
     def test_spawnl(self):
         program, args = self.create_args()
         exitcode = os.spawnl(os.P_WAIT, program, *args)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnle')
     def test_spawnle(self):
         program, args = self.create_args(with_env=True)
         exitcode = os.spawnle(os.P_WAIT, program, *args, self.env)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnlp')
     def test_spawnlp(self):
         program, args = self.create_args()
         exitcode = os.spawnlp(os.P_WAIT, program, *args)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnlpe')
     def test_spawnlpe(self):
         program, args = self.create_args(with_env=True)
         exitcode = os.spawnlpe(os.P_WAIT, program, *args, self.env)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnv')
     def test_spawnv(self):
         program, args = self.create_args()
@@ -3725,30 +3452,35 @@ def test_spawnv(self):
         exitcode = os.spawnv(os.P_WAIT, FakePath(program), args)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnve')
     def test_spawnve(self):
         program, args = self.create_args(with_env=True)
         exitcode = os.spawnve(os.P_WAIT, program, args, self.env)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnvp')
     def test_spawnvp(self):
         program, args = self.create_args()
         exitcode = os.spawnvp(os.P_WAIT, program, args)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnvpe')
     def test_spawnvpe(self):
         program, args = self.create_args(with_env=True)
         exitcode = os.spawnvpe(os.P_WAIT, program, args, self.env)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnv')
     def test_nowait(self):
         program, args = self.create_args()
         pid = os.spawnv(os.P_NOWAIT, program, args)
         support.wait_process(pid, exitcode=self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnve')
     def test_spawnve_bytes(self):
         # Test bytes handling in parse_arglist and parse_envlist (#28114)
@@ -3756,18 +3488,21 @@ def test_spawnve_bytes(self):
         exitcode = os.spawnve(os.P_WAIT, program, args, self.env)
         self.assertEqual(exitcode, self.exitcode)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnl')
     def test_spawnl_noargs(self):
         program, __ = self.create_args()
         self.assertRaises(ValueError, os.spawnl, os.P_NOWAIT, program)
         self.assertRaises(ValueError, os.spawnl, os.P_NOWAIT, program, '')
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnle')
     def test_spawnle_noargs(self):
         program, __ = self.create_args()
         self.assertRaises(ValueError, os.spawnle, os.P_NOWAIT, program, {})
         self.assertRaises(ValueError, os.spawnle, os.P_NOWAIT, program, '', {})
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnv')
     def test_spawnv_noargs(self):
         program, __ = self.create_args()
@@ -3776,6 +3511,7 @@ def test_spawnv_noargs(self):
         self.assertRaises(ValueError, os.spawnv, os.P_NOWAIT, program, ('',))
         self.assertRaises(ValueError, os.spawnv, os.P_NOWAIT, program, [''])
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnve')
     def test_spawnve_noargs(self):
         program, __ = self.create_args()
@@ -3784,7 +3520,7 @@ def test_spawnve_noargs(self):
         self.assertRaises(ValueError, os.spawnve, os.P_NOWAIT, program, ('',), {})
         self.assertRaises(ValueError, os.spawnve, os.P_NOWAIT, program, [''], {})
 
-    @unittest.expectedFailureIfWindows('TODO: RUSTPYTHON; AssertionError: "must contain only strings" does not match "expected str, bytes or os.PathLike object, not int"')
+    @unittest.expectedFailureIfWindows("TODO: RUSTPYTHON; AssertionError: \"must contain only strings\" does not match \"expected str, bytes or os.PathLike object, not int\"")
     @requires_native_spawnv
     def test_spawnv_arg_conversion_errors(self):
         # A non-path argv item gets a TypeError naming the argument...
@@ -3852,22 +3588,28 @@ def _test_invalid_env(self, spawn):
         exitcode = spawn(os.P_WAIT, program, args, newenv)
         self.assertEqual(exitcode, 0)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnve')
     def test_spawnve_invalid_env(self):
         self._test_invalid_env(os.spawnve)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_os_func('spawnvpe')
     def test_spawnvpe_invalid_env(self):
         self._test_invalid_env(os.spawnvpe)
 
 
-# The introduction of this TestCase caused at least two different errors on
-# *nix buildbots. Temporarily skip this to let the buildbots move along.
-@unittest.skip("Skip due to platform/environment differences on *NIX buildbots")
 @unittest.skipUnless(hasattr(os, 'getlogin'), "test needs os.getlogin")
 class LoginTests(unittest.TestCase):
     def test_getlogin(self):
-        user_name = os.getlogin()
+        try:
+            user_name = os.getlogin()
+        except OSError as exc:
+            # See https://man7.org/linux/man-pages/man3/getlogin.3.html#ERRORS.
+            if exc.errno in (errno.ENXIO, errno.ENOENT, errno.ENOTTY):
+                self.skipTest(str(exc))
+            else:
+                raise
         self.assertNotEqual(len(user_name), 0)
 
 
@@ -4031,6 +3773,11 @@ async def test_invalid_offset(self):
             await self.async_sendfile(self.sockno, self.fileno, -1, 4096)
         self.assertEqual(cm.exception.errno, errno.EINVAL)
 
+    async def test_invalid_count(self):
+        with self.assertRaises(ValueError, msg="count cannot be negative"):
+            await self.sendfile_wrapper(self.sockno, self.fileno, offset=0,
+                                        count=-1)
+
     async def test_keywords(self):
         # Keyword arguments should be supported
         await self.async_sendfile(out_fd=self.sockno, in_fd=self.fileno,
@@ -4221,12 +3968,7 @@ def test_does_not_crash(self):
         try:
             size = os.get_terminal_size()
         except OSError as e:
-            known_errnos = [errno.EINVAL, errno.ENOTTY]
-            if sys.platform == "android":
-                # The Android testbed redirects the native stdout to a pipe,
-                # which returns a different error code.
-                known_errnos.append(errno.EACCES)
-            if sys.platform == "win32" or e.errno in known_errnos:
+            if sys.platform == "win32" or e.errno in (errno.EINVAL, errno.ENOTTY):
                 # Under win32 a generic OSError can be thrown if the
                 # handle cannot be retrieved
                 self.skipTest("failed to query terminal size")
@@ -4737,6 +4479,7 @@ def test_oserror_filename(self):
             (self.filenames, os.listdir,),
             (self.filenames, os.rename, "dst"),
             (self.filenames, os.replace, "dst"),
+            (self.filenames, os.utime, None),
         ]
         if os_helper.can_chmod():
             funcs.append((self.filenames, os.chmod, 0o777))
@@ -4777,6 +4520,19 @@ def test_oserror_filename(self):
                 else:
                     self.fail(f"No exception thrown by {func}")
 
+    def test_mkdir(self):
+        filename = os_helper.TESTFN
+        subdir = os.path.join(filename, 'subdir')
+        self.assertRaises(FileNotFoundError, os.mkdir, subdir)
+
+        self.addCleanup(os_helper.unlink, filename)
+        create_file(filename)
+        self.assertRaises(FileExistsError, os.mkdir, filename)
+
+        self.assertRaises((NotADirectoryError, FileNotFoundError),
+                          os.mkdir, subdir)
+
+
 class CPUCountTests(unittest.TestCase):
     def check_cpu_count(self, cpus):
         if cpus is None:
@@ -4992,6 +4748,7 @@ def test_posix_pty_functions(self):
                     signal.signal(signal.SIGHUP, old_handler)
         self.assertEqual(os.ptsname(mother_fd), os.ttyname(son_fd))
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @unittest.skipUnless(hasattr(os, 'spawnl'), "need os.spawnl()")
     @support.requires_subprocess()
     def test_pipe_spawnl(self):
diff --git a/Lib/test/test_posix.py b/Lib/test/test_os/test_posix.py
similarity index 94%
rename from Lib/test/test_posix.py
rename to Lib/test/test_os/test_posix.py
index 265f68902a4..4839b1772a3 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_os/test_posix.py
@@ -46,7 +46,8 @@ def _supports_sched():
     try:
         posix.sched_getscheduler(0)
     except OSError as e:
-        if e.errno == errno.ENOSYS:
+        # DragonFly BSD requires privileges to use the scheduler API.
+        if e.errno in (errno.ENOSYS, errno.EPERM):
             return False
     return True
 
@@ -70,7 +71,7 @@ def testNoArgFunctions(self):
         NO_ARG_FUNCTIONS = [ "ctermid", "getcwd", "getcwdb", "uname",
                              "times", "getloadavg",
                              "getegid", "geteuid", "getgid", "getgroups",
-                             "getpid", "getpgrp", "getppid", "getuid", "sync",
+                             "getpid", "getpgrp", "getppid", "getuid",
                            ]
 
         for name in NO_ARG_FUNCTIONS:
@@ -80,6 +81,13 @@ def testNoArgFunctions(self):
                     posix_func()
                     self.assertRaises(TypeError, posix_func, 1)
 
+    # gh-102184: sync() can block for a long time.
+    @support.requires_resource('walltime')
+    @unittest.skipUnless(hasattr(posix, 'sync'), 'test needs posix.sync()')
+    def test_sync(self):
+        posix.sync()
+        self.assertRaises(TypeError, posix.sync, 1)
+
     @unittest.skipUnless(hasattr(posix, 'getresuid'),
                          'test needs posix.getresuid()')
     def test_getresuid(self):
@@ -415,8 +423,10 @@ def test_posix_fallocate(self):
             if inst.errno == errno.EINVAL and sys.platform.startswith(
                 ('sunos', 'freebsd', 'openbsd', 'gnukfreebsd')):
                 raise unittest.SkipTest("test may fail on ZFS filesystems")
-            elif inst.errno == errno.EOPNOTSUPP and sys.platform.startswith("netbsd"):
-                raise unittest.SkipTest("test may fail on FFS filesystems")
+            elif inst.errno == errno.EOPNOTSUPP:
+                # ZFS on FreeBSD, FFS on NetBSD, etc.
+                raise unittest.SkipTest(
+                    "the file system does not support posix_fallocate()")
             else:
                 raise
         finally:
@@ -680,22 +690,65 @@ def test_stat_fd_zero_follow_symlinks(self):
                 'cannot use fd and follow_symlinks together'):
             posix.stat(1, follow_symlinks=False)
 
-    def test_stat(self):
-        self.assertTrue(posix.stat(os_helper.TESTFN))
-        self.assertTrue(posix.stat(os.fsencode(os_helper.TESTFN)))
+    def check_statlike_path(self, func):
+        self.assertTrue(func(os_helper.TESTFN))
+        self.assertTrue(func(os.fsencode(os_helper.TESTFN)))
+        self.assertTrue(func(os_helper.FakePath(os_helper.TESTFN)))
 
         self.assertRaisesRegex(TypeError,
                 'should be string, bytes, os.PathLike or integer, not',
-                posix.stat, bytearray(os.fsencode(os_helper.TESTFN)))
+                func, bytearray(os.fsencode(os_helper.TESTFN)))
         self.assertRaisesRegex(TypeError,
                 'should be string, bytes, os.PathLike or integer, not',
-                posix.stat, None)
+                func, None)
         self.assertRaisesRegex(TypeError,
                 'should be string, bytes, os.PathLike or integer, not',
-                posix.stat, list(os_helper.TESTFN))
+                func, list(os_helper.TESTFN))
         self.assertRaisesRegex(TypeError,
                 'should be string, bytes, os.PathLike or integer, not',
-                posix.stat, list(os.fsencode(os_helper.TESTFN)))
+                func, list(os.fsencode(os_helper.TESTFN)))
+
+    def test_stat(self):
+        self.check_statlike_path(posix.stat)
+
+    @unittest.skipUnless(hasattr(posix, 'statx'), 'test needs posix.statx()')
+    def test_statx(self):
+        def func(path, **kwargs):
+            return posix.statx(path, posix.STATX_BASIC_STATS, **kwargs)
+        self.check_statlike_path(func)
+
+    @unittest.skipUnless(hasattr(posix, 'statx'), 'test needs posix.statx()')
+    def test_statx_flags(self):
+        # glibc's fallback implementation of statx via the stat family fails
+        # with EINVAL on the (nonzero) sync flags.  If you see this failure,
+        # update your kernel and/or seccomp syscall filter.
+        valid_flag_names = ('AT_NO_AUTOMOUNT', 'AT_STATX_SYNC_AS_STAT',
+                            'AT_STATX_FORCE_SYNC', 'AT_STATX_DONT_SYNC')
+        for flag_name in valid_flag_names:
+            flag = getattr(posix, flag_name)
+            with self.subTest(msg=flag_name, flags=flag):
+                posix.statx(os_helper.TESTFN, posix.STATX_BASIC_STATS,
+                            flags=flag)
+
+        # These flags are not exposed to Python because their functionality is
+        # implemented via kwargs instead.
+        kwarg_equivalent_flags = (
+            (0x0100, 'AT_SYMLINK_NOFOLLOW', 'follow_symlinks'),
+            (0x0400, 'AT_SYMLINK_FOLLOW', 'follow_symlinks'),
+            (0x1000, 'AT_EMPTY_PATH', 'dir_fd'),
+        )
+        for flag, flag_name, kwarg_name in kwarg_equivalent_flags:
+            with self.subTest(msg=flag_name, flags=flag):
+                with self.assertRaisesRegex(ValueError, kwarg_name):
+                    posix.statx(os_helper.TESTFN, posix.STATX_BASIC_STATS,
+                                flags=flag)
+
+        with self.subTest(msg="AT_STATX_FORCE_SYNC | AT_STATX_DONT_SYNC"):
+            with self.assertRaises(OSError) as ctx:
+                flags = posix.AT_STATX_FORCE_SYNC | posix.AT_STATX_DONT_SYNC
+                posix.statx(os_helper.TESTFN, posix.STATX_BASIC_STATS,
+                            flags=flags)
+            self.assertEqual(ctx.exception.errno, errno.EINVAL)
 
     @unittest.skipUnless(hasattr(posix, 'mkfifo'), "don't have mkfifo()")
     def test_mkfifo(self):
@@ -769,12 +822,29 @@ def test_makedev(self):
             self.assertRaises((ValueError, OverflowError), posix.makedev, x, minor)
             self.assertRaises((ValueError, OverflowError), posix.makedev, major, x)
 
-        if sys.platform == 'linux' and not support.linked_to_musl():
-            NODEV = -1
+        # The following tests are needed to test functions accepting or
+        # returning the special value NODEV (if it is defined). major(), minor()
+        # and makefile() are the only easily reproducible examples, but that
+        # behavior is platform specific -- on some platforms their code has
+        # a special case for NODEV, on others this is just an implementation
+        # artifact.
+        if (hasattr(posix, 'NODEV') and
+            sys.platform.startswith(('linux', 'macos', 'freebsd', 'sunos'))):
+            NODEV = posix.NODEV
             self.assertEqual(posix.major(NODEV), NODEV)
             self.assertEqual(posix.minor(NODEV), NODEV)
             self.assertEqual(posix.makedev(NODEV, NODEV), NODEV)
 
+    def test_nodev(self):
+        # NODEV is not a part of Posix, but is defined on many systems.
+        if (not hasattr(posix, 'NODEV')
+            and (not sys.platform.startswith(('linux', 'macos', 'freebsd',
+                                              'dragonfly', 'netbsd', 'openbsd',
+                                              'sunos'))
+                 or support.linked_to_musl())):
+            self.skipTest('not defined on this platform')
+        self.assertHasAttr(posix, 'NODEV')
+
     def _test_all_chown_common(self, chown_func, first_param, stat_func):
         """Common code for chown, fchown and lchown tests."""
         def check_stat(uid, gid):
@@ -838,7 +908,9 @@ def check_stat(uid, gid):
             self.assertRaises(OSError, chown_func, first_param, 0, -1)
             check_stat(uid, gid)
             if hasattr(os, 'getgroups'):
-                if 0 not in os.getgroups():
+                # Also check the effective gid, which the kernel
+                # accepts for chown even if not in getgroups().
+                if 0 not in os.getgroups() and os.getegid() != 0:
                     self.assertRaises(OSError, chown_func, first_param, -1, 0)
                     check_stat(uid, gid)
         # test illegal types
@@ -1386,6 +1458,7 @@ def test_bug_140634(self):
         del sched_priority, param  # should not crash
         support.gc_collect()  # just to be sure
 
+    @requires_sched
     @unittest.skipUnless(hasattr(posix, "sched_rr_get_interval"), "no function")
     def test_sched_rr_get_interval(self):
         try:
@@ -1631,33 +1704,47 @@ def test_chown_dir_fd(self):
         with self.prepare_file() as (dir_fd, name, fullname):
             posix.chown(name, os.getuid(), os.getgid(), dir_fd=dir_fd)
 
-    @unittest.skipUnless(os.stat in os.supports_dir_fd, "test needs dir_fd support in os.stat()")
-    def test_stat_dir_fd(self):
+    def check_statlike_dir_fd(self, func, prefix):
         with self.prepare() as (dir_fd, name, fullname):
             with open(fullname, 'w') as outfile:
                 outfile.write("testline\n")
             self.addCleanup(posix.unlink, fullname)
 
-            s1 = posix.stat(fullname)
-            s2 = posix.stat(name, dir_fd=dir_fd)
-            self.assertEqual(s1, s2)
-            s2 = posix.stat(fullname, dir_fd=None)
-            self.assertEqual(s1, s2)
+            def get(result, attr):
+                return getattr(result, prefix + attr)
+
+            s1 = func(fullname)
+            s2 = func(name, dir_fd=dir_fd)
+            self.assertEqual((get(s1, "dev"), get(s1, "ino")),
+                             (get(s2, "dev"), get(s2, "ino")))
+            s2 = func(fullname, dir_fd=None)
+            self.assertEqual((get(s1, "dev"), get(s1, "ino")),
+                             (get(s2, "dev"), get(s2, "ino")))
 
             self.assertRaisesRegex(TypeError, 'should be integer or None, not',
-                    posix.stat, name, dir_fd=posix.getcwd())
+                    func, name, dir_fd=posix.getcwd())
             self.assertRaisesRegex(TypeError, 'should be integer or None, not',
-                    posix.stat, name, dir_fd=float(dir_fd))
+                    func, name, dir_fd=float(dir_fd))
             self.assertRaises(OverflowError,
-                    posix.stat, name, dir_fd=10**20)
+                    func, name, dir_fd=10**20)
 
             for fd in False, True:
                 with self.assertWarnsRegex(RuntimeWarning,
                         'bool is used as a file descriptor') as cm:
                     with self.assertRaises(OSError):
-                        posix.stat('nonexisting', dir_fd=fd)
+                        func('nonexisting', dir_fd=fd)
                 self.assertEqual(cm.filename, __file__)
 
+    @unittest.skipUnless(os.stat in os.supports_dir_fd, "test needs dir_fd support in os.stat()")
+    def test_stat_dir_fd(self):
+        self.check_statlike_dir_fd(posix.stat, prefix="st_")
+
+    @unittest.skipUnless(hasattr(posix, 'statx'), "test needs os.statx()")
+    def test_statx_dir_fd(self):
+        def func(path, **kwargs):
+            return posix.statx(path, os.STATX_INO, **kwargs)
+        self.check_statlike_dir_fd(func, prefix="stx_")
+
     @unittest.skipUnless(os.utime in os.supports_dir_fd, "test needs dir_fd support in os.utime()")
     def test_utime_dir_fd(self):
         with self.prepare_file() as (dir_fd, name, fullname):
@@ -2271,6 +2358,22 @@ def test_pwritev(self):
             self.assertNotHasAttr(os, "pwritev")
             self.assertNotHasAttr(os, "preadv")
 
+    def test_pipe2(self):
+        self._verify_available("HAVE_PIPE2")
+        if self.mac_ver >= (27, 0):
+            self.assertHasAttr(os, "pipe2")
+        else:
+            self.assertNotHasAttr(os, "pipe2")
+
+    def test_dup3(self):
+        self._verify_available("HAVE_DUP3")
+        r, w = os.pipe()
+        self.addCleanup(os.close, r)
+        self.addCleanup(os.close, w)
+        # Must not crash even when dup3 unavailable at runtime.
+        # os.dup2 returns fd2 (here w); do not double-close.
+        os.dup2(r, w, inheritable=False)
+
     def test_stat(self):
         self._verify_available("HAVE_FSTATAT")
         if self.mac_ver >= (10, 10):
diff --git a/Lib/test/test_os/test_windows.py b/Lib/test/test_os/test_windows.py
new file mode 100644
index 00000000000..f1c6283f60d
--- /dev/null
+++ b/Lib/test/test_os/test_windows.py
@@ -0,0 +1,605 @@
+import sys
+import unittest
+
+if sys.platform != "win32":
+    raise unittest.SkipTest("Win32 specific tests")
+
+import _winapi
+import fnmatch
+import mmap
+import os
+import shutil
+import signal
+import stat
+import subprocess
+import textwrap
+import time
+import uuid
+from test import support
+from test.support import import_helper
+from test.support import os_helper
+from .utils import create_file
+
+
+class Win32KillTests(unittest.TestCase):
+    def _kill(self, sig):
+        # Start sys.executable as a subprocess and communicate from the
+        # subprocess to the parent that the interpreter is ready. When it
+        # becomes ready, send *sig* via os.kill to the subprocess and check
+        # that the return code is equal to *sig*.
+        import ctypes
+        from ctypes import wintypes
+        import msvcrt
+
+        # Since we can't access the contents of the process' stdout until the
+        # process has exited, use PeekNamedPipe to see what's inside stdout
+        # without waiting. This is done so we can tell that the interpreter
+        # is started and running at a point where it could handle a signal.
+        PeekNamedPipe = ctypes.windll.kernel32.PeekNamedPipe
+        PeekNamedPipe.restype = wintypes.BOOL
+        PeekNamedPipe.argtypes = (wintypes.HANDLE, # Pipe handle
+                                  ctypes.POINTER(ctypes.c_char), # stdout buf
+                                  wintypes.DWORD, # Buffer size
+                                  ctypes.POINTER(wintypes.DWORD), # bytes read
+                                  ctypes.POINTER(wintypes.DWORD), # bytes avail
+                                  ctypes.POINTER(wintypes.DWORD)) # bytes left
+        msg = "running"
+        proc = subprocess.Popen([sys.executable, "-c",
+                                 "import sys;"
+                                 "sys.stdout.write('{}');"
+                                 "sys.stdout.flush();"
+                                 "input()".format(msg)],
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.PIPE,
+                                stdin=subprocess.PIPE)
+        self.addCleanup(proc.stdout.close)
+        self.addCleanup(proc.stderr.close)
+        self.addCleanup(proc.stdin.close)
+
+        count, max = 0, 100
+        while count < max and proc.poll() is None:
+            # Create a string buffer to store the result of stdout from the pipe
+            buf = ctypes.create_string_buffer(len(msg))
+            # Obtain the text currently in proc.stdout
+            # Bytes read/avail/left are left as NULL and unused
+            rslt = PeekNamedPipe(msvcrt.get_osfhandle(proc.stdout.fileno()),
+                                 buf, ctypes.sizeof(buf), None, None, None)
+            self.assertNotEqual(rslt, 0, "PeekNamedPipe failed")
+            if buf.value:
+                self.assertEqual(msg, buf.value.decode())
+                break
+            time.sleep(0.1)
+            count += 1
+        else:
+            self.fail("Did not receive communication from the subprocess")
+
+        os.kill(proc.pid, sig)
+        self.assertEqual(proc.wait(), sig)
+
+    def test_kill_sigterm(self):
+        # SIGTERM doesn't mean anything special, but make sure it works
+        self._kill(signal.SIGTERM)
+
+    def test_kill_int(self):
+        # os.kill on Windows can take an int which gets set as the exit code
+        self._kill(100)
+
+    @unittest.skipIf(mmap is None, "requires mmap")
+    def _kill_with_event(self, event, name):
+        tagname = "test_os_%s" % uuid.uuid1()
+        m = mmap.mmap(-1, 1, tagname)
+        m[0] = 0
+
+        # Run a script which has console control handling enabled.
+        script = os.path.join(os.path.dirname(__file__),
+                              "win_console_handler.py")
+        cmd = [sys.executable, script, tagname]
+        proc = subprocess.Popen(cmd,
+                                creationflags=subprocess.CREATE_NEW_PROCESS_GROUP)
+
+        with proc:
+            # Let the interpreter startup before we send signals. See #3137.
+            for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
+                if proc.poll() is None:
+                    break
+            else:
+                # Forcefully kill the process if we weren't able to signal it.
+                proc.kill()
+                self.fail("Subprocess didn't finish initialization")
+
+            os.kill(proc.pid, event)
+
+            try:
+                # proc.send_signal(event) could also be done here.
+                # Allow time for the signal to be passed and the process to exit.
+                proc.wait(timeout=support.SHORT_TIMEOUT)
+            except subprocess.TimeoutExpired:
+                # Forcefully kill the process if we weren't able to signal it.
+                proc.kill()
+                self.fail("subprocess did not stop on {}".format(name))
+
+    @unittest.skip("subprocesses aren't inheriting Ctrl+C property")
+    @support.requires_subprocess()
+    def test_CTRL_C_EVENT(self):
+        from ctypes import wintypes
+        import ctypes
+
+        # Make a NULL value by creating a pointer with no argument.
+        NULL = ctypes.POINTER(ctypes.c_int)()
+        SetConsoleCtrlHandler = ctypes.windll.kernel32.SetConsoleCtrlHandler
+        SetConsoleCtrlHandler.argtypes = (ctypes.POINTER(ctypes.c_int),
+                                          wintypes.BOOL)
+        SetConsoleCtrlHandler.restype = wintypes.BOOL
+
+        # Calling this with NULL and FALSE causes the calling process to
+        # handle Ctrl+C, rather than ignore it. This property is inherited
+        # by subprocesses.
+        SetConsoleCtrlHandler(NULL, 0)
+
+        self._kill_with_event(signal.CTRL_C_EVENT, "CTRL_C_EVENT")
+
+    @support.requires_subprocess()
+    def test_CTRL_BREAK_EVENT(self):
+        self._kill_with_event(signal.CTRL_BREAK_EVENT, "CTRL_BREAK_EVENT")
+
+
+class Win32ListdirTests(unittest.TestCase):
+    """Test listdir on Windows."""
+
+    def setUp(self):
+        self.created_paths = []
+        for i in range(2):
+            dir_name = 'SUB%d' % i
+            dir_path = os.path.join(os_helper.TESTFN, dir_name)
+            file_name = 'FILE%d' % i
+            file_path = os.path.join(os_helper.TESTFN, file_name)
+            os.makedirs(dir_path)
+            with open(file_path, 'w', encoding='utf-8') as f:
+                f.write("I'm %s and proud of it. Blame test_os.\n" % file_path)
+            self.created_paths.extend([dir_name, file_name])
+        self.created_paths.sort()
+
+    def tearDown(self):
+        shutil.rmtree(os_helper.TESTFN)
+
+    def test_listdir_no_extended_path(self):
+        """Test when the path is not an "extended" path."""
+        # unicode
+        self.assertEqual(
+                sorted(os.listdir(os_helper.TESTFN)),
+                self.created_paths)
+
+        # bytes
+        self.assertEqual(
+                sorted(os.listdir(os.fsencode(os_helper.TESTFN))),
+                [os.fsencode(path) for path in self.created_paths])
+
+    def test_listdir_extended_path(self):
+        """Test when the path starts with '\\\\?\\'."""
+        # See: http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
+        # unicode
+        path = '\\\\?\\' + os.path.abspath(os_helper.TESTFN)
+        self.assertEqual(
+                sorted(os.listdir(path)),
+                self.created_paths)
+
+        # bytes
+        path = b'\\\\?\\' + os.fsencode(os.path.abspath(os_helper.TESTFN))
+        self.assertEqual(
+                sorted(os.listdir(path)),
+                [os.fsencode(path) for path in self.created_paths])
+
+
+@unittest.skipUnless(os.name == "nt", "NT specific tests")
+class Win32ListdriveTests(unittest.TestCase):
+    """Test listdrive, listmounts and listvolume on Windows."""
+
+    def setUp(self):
+        # Get drives and volumes from fsutil
+        out = subprocess.check_output(
+            ["fsutil.exe", "volume", "list"],
+            cwd=os.path.join(os.getenv("SystemRoot", "\\Windows"), "System32"),
+            encoding="mbcs",
+            errors="ignore",
+        )
+        lines = out.splitlines()
+        self.known_volumes = {l for l in lines if l.startswith('\\\\?\\')}
+        self.known_drives = {l for l in lines if l[1:] == ':\\'}
+        self.known_mounts = {l for l in lines if l[1:3] == ':\\'}
+
+    def test_listdrives(self):
+        drives = os.listdrives()
+        self.assertIsInstance(drives, list)
+        self.assertSetEqual(
+            self.known_drives,
+            self.known_drives & set(drives),
+        )
+
+    def test_listvolumes(self):
+        volumes = os.listvolumes()
+        self.assertIsInstance(volumes, list)
+        self.assertSetEqual(
+            self.known_volumes,
+            self.known_volumes & set(volumes),
+        )
+
+    def test_listmounts(self):
+        for volume in os.listvolumes():
+            try:
+                mounts = os.listmounts(volume)
+            except OSError as ex:
+                if support.verbose:
+                    print("Skipping", volume, "because of", ex)
+            else:
+                self.assertIsInstance(mounts, list)
+                self.assertSetEqual(
+                    set(mounts),
+                    self.known_mounts & set(mounts),
+                )
+
+
+@os_helper.skip_unless_symlink
+class Win32SymlinkTests(unittest.TestCase):
+    filelink = 'filelinktest'
+    filelink_target = os.path.abspath(__file__)
+    dirlink = 'dirlinktest'
+    dirlink_target = os.path.dirname(filelink_target)
+    missing_link = 'missing link'
+
+    def setUp(self):
+        assert os.path.exists(self.dirlink_target)
+        assert os.path.exists(self.filelink_target)
+        assert not os.path.exists(self.dirlink)
+        assert not os.path.exists(self.filelink)
+        assert not os.path.exists(self.missing_link)
+
+    def tearDown(self):
+        if os.path.exists(self.filelink):
+            os.remove(self.filelink)
+        if os.path.exists(self.dirlink):
+            os.rmdir(self.dirlink)
+        if os.path.lexists(self.missing_link):
+            os.remove(self.missing_link)
+
+    def test_directory_link(self):
+        os.symlink(self.dirlink_target, self.dirlink)
+        self.assertTrue(os.path.exists(self.dirlink))
+        self.assertTrue(os.path.isdir(self.dirlink))
+        self.assertTrue(os.path.islink(self.dirlink))
+        self.check_stat(self.dirlink, self.dirlink_target)
+
+    def test_file_link(self):
+        os.symlink(self.filelink_target, self.filelink)
+        self.assertTrue(os.path.exists(self.filelink))
+        self.assertTrue(os.path.isfile(self.filelink))
+        self.assertTrue(os.path.islink(self.filelink))
+        self.check_stat(self.filelink, self.filelink_target)
+
+    def _create_missing_dir_link(self):
+        'Create a "directory" link to a non-existent target'
+        linkname = self.missing_link
+        if os.path.lexists(linkname):
+            os.remove(linkname)
+        target = r'c:\\target does not exist.29r3c740'
+        assert not os.path.exists(target)
+        target_is_dir = True
+        os.symlink(target, linkname, target_is_dir)
+
+    def test_remove_directory_link_to_missing_target(self):
+        self._create_missing_dir_link()
+        # For compatibility with Unix, os.remove will check the
+        #  directory status and call RemoveDirectory if the symlink
+        #  was created with target_is_dir==True.
+        os.remove(self.missing_link)
+
+    def test_isdir_on_directory_link_to_missing_target(self):
+        self._create_missing_dir_link()
+        self.assertFalse(os.path.isdir(self.missing_link))
+
+    def test_rmdir_on_directory_link_to_missing_target(self):
+        self._create_missing_dir_link()
+        os.rmdir(self.missing_link)
+
+    def check_stat(self, link, target):
+        self.assertEqual(os.stat(link), os.stat(target))
+        self.assertNotEqual(os.lstat(link), os.stat(link))
+
+        bytes_link = os.fsencode(link)
+        self.assertEqual(os.stat(bytes_link), os.stat(target))
+        self.assertNotEqual(os.lstat(bytes_link), os.stat(bytes_link))
+
+    def test_12084(self):
+        level1 = os.path.abspath(os_helper.TESTFN)
+        level2 = os.path.join(level1, "level2")
+        level3 = os.path.join(level2, "level3")
+        self.addCleanup(os_helper.rmtree, level1)
+
+        os.mkdir(level1)
+        os.mkdir(level2)
+        os.mkdir(level3)
+
+        file1 = os.path.abspath(os.path.join(level1, "file1"))
+        create_file(file1)
+
+        orig_dir = os.getcwd()
+        try:
+            os.chdir(level2)
+            link = os.path.join(level2, "link")
+            os.symlink(os.path.relpath(file1), "link")
+            self.assertIn("link", os.listdir(os.getcwd()))
+
+            # Check os.stat calls from the same dir as the link
+            self.assertEqual(os.stat(file1), os.stat("link"))
+
+            # Check os.stat calls from a dir below the link
+            os.chdir(level1)
+            self.assertEqual(os.stat(file1),
+                             os.stat(os.path.relpath(link)))
+
+            # Check os.stat calls from a dir above the link
+            os.chdir(level3)
+            self.assertEqual(os.stat(file1),
+                             os.stat(os.path.relpath(link)))
+        finally:
+            os.chdir(orig_dir)
+
+    @unittest.skipUnless(os.path.lexists(r'C:\Users\All Users')
+                            and os.path.exists(r'C:\ProgramData'),
+                            'Test directories not found')
+    def test_29248(self):
+        # os.symlink() calls CreateSymbolicLink, which creates
+        # the reparse data buffer with the print name stored
+        # first, so the offset is always 0. CreateSymbolicLink
+        # stores the "PrintName" DOS path (e.g. "C:\") first,
+        # with an offset of 0, followed by the "SubstituteName"
+        # NT path (e.g. "\??\C:\"). The "All Users" link, on
+        # the other hand, seems to have been created manually
+        # with an inverted order.
+        target = os.readlink(r'C:\Users\All Users')
+        self.assertTrue(os.path.samefile(target, r'C:\ProgramData'))
+
+    def test_buffer_overflow(self):
+        # Older versions would have a buffer overflow when detecting
+        # whether a link source was a directory. This test ensures we
+        # no longer crash, but does not otherwise validate the behavior
+        segment = 'X' * 27
+        path = os.path.join(*[segment] * 10)
+        test_cases = [
+            # overflow with absolute src
+            ('\\' + path, segment),
+            # overflow dest with relative src
+            (segment, path),
+            # overflow when joining src
+            (path[:180], path[:180]),
+        ]
+        for src, dest in test_cases:
+            try:
+                os.symlink(src, dest)
+            except FileNotFoundError:
+                pass
+            else:
+                try:
+                    os.remove(dest)
+                except OSError:
+                    pass
+            # Also test with bytes, since that is a separate code path.
+            try:
+                os.symlink(os.fsencode(src), os.fsencode(dest))
+            except FileNotFoundError:
+                pass
+            else:
+                try:
+                    os.remove(dest)
+                except OSError:
+                    pass
+
+    def test_appexeclink(self):
+        root = os.path.expandvars(r'%LOCALAPPDATA%\Microsoft\WindowsApps')
+        if not os.path.isdir(root):
+            self.skipTest("test requires a WindowsApps directory")
+
+        aliases = [os.path.join(root, a)
+                   for a in fnmatch.filter(os.listdir(root), '*.exe')]
+
+        for alias in aliases:
+            if support.verbose:
+                print()
+                print("Testing with", alias)
+            st = os.lstat(alias)
+            self.assertEqual(st, os.stat(alias))
+            self.assertFalse(stat.S_ISLNK(st.st_mode))
+            self.assertEqual(st.st_reparse_tag, stat.IO_REPARSE_TAG_APPEXECLINK)
+            self.assertTrue(os.path.isfile(alias))
+            # testing the first one we see is sufficient
+            break
+        else:
+            self.skipTest("test requires an app execution alias")
+
+
+class Win32JunctionTests(unittest.TestCase):
+    junction = 'junctiontest'
+    junction_target = os.path.dirname(os.path.abspath(__file__))
+
+    def setUp(self):
+        assert os.path.exists(self.junction_target)
+        assert not os.path.lexists(self.junction)
+
+    def tearDown(self):
+        if os.path.lexists(self.junction):
+            os.unlink(self.junction)
+
+    def test_create_junction(self):
+        _winapi.CreateJunction(self.junction_target, self.junction)
+        self.assertTrue(os.path.lexists(self.junction))
+        self.assertTrue(os.path.exists(self.junction))
+        self.assertTrue(os.path.isdir(self.junction))
+        self.assertNotEqual(os.stat(self.junction), os.lstat(self.junction))
+        self.assertEqual(os.stat(self.junction), os.stat(self.junction_target))
+
+        # bpo-37834: Junctions are not recognized as links.
+        self.assertFalse(os.path.islink(self.junction))
+        self.assertEqual(os.path.normcase("\\\\?\\" + self.junction_target),
+                         os.path.normcase(os.readlink(self.junction)))
+
+    def test_unlink_removes_junction(self):
+        _winapi.CreateJunction(self.junction_target, self.junction)
+        self.assertTrue(os.path.exists(self.junction))
+        self.assertTrue(os.path.lexists(self.junction))
+
+        os.unlink(self.junction)
+        self.assertFalse(os.path.exists(self.junction))
+
+
+class Win32NtTests(unittest.TestCase):
+    def test_getfinalpathname_handles(self):
+        nt = import_helper.import_module('nt')
+        ctypes = import_helper.import_module('ctypes')
+        # Ruff false positive -- it thinks we're redefining `ctypes` here
+        import ctypes.wintypes  # noqa: F811
+
+        kernel = ctypes.WinDLL('Kernel32.dll', use_last_error=True)
+        kernel.GetCurrentProcess.restype = ctypes.wintypes.HANDLE
+
+        kernel.GetProcessHandleCount.restype = ctypes.wintypes.BOOL
+        kernel.GetProcessHandleCount.argtypes = (ctypes.wintypes.HANDLE,
+                                                 ctypes.wintypes.LPDWORD)
+
+        # This is a pseudo-handle that doesn't need to be closed
+        hproc = kernel.GetCurrentProcess()
+
+        handle_count = ctypes.wintypes.DWORD()
+        ok = kernel.GetProcessHandleCount(hproc, ctypes.byref(handle_count))
+        self.assertEqual(1, ok)
+
+        before_count = handle_count.value
+
+        # The first two test the error path, __file__ tests the success path
+        filenames = [
+            r'\\?\C:',
+            r'\\?\NUL',
+            r'\\?\CONIN',
+            __file__,
+        ]
+
+        for _ in range(10):
+            for name in filenames:
+                try:
+                    nt._getfinalpathname(name)
+                except Exception:
+                    # Failure is expected
+                    pass
+                try:
+                    os.stat(name)
+                except Exception:
+                    pass
+
+        ok = kernel.GetProcessHandleCount(hproc, ctypes.byref(handle_count))
+        self.assertEqual(1, ok)
+
+        handle_delta = handle_count.value - before_count
+
+        self.assertEqual(0, handle_delta)
+
+    @support.requires_subprocess()
+    def test_stat_unlink_race(self):
+        # bpo-46785: the implementation of os.stat() falls back to reading
+        # the parent directory if CreateFileW() fails with a permission
+        # error. If reading the parent directory fails because the file or
+        # directory are subsequently unlinked, or because the volume or
+        # share are no longer available, then the original permission error
+        # should not be restored.
+        filename =  os_helper.TESTFN
+        self.addCleanup(os_helper.unlink, filename)
+        deadline = time.time() + 5
+        command = textwrap.dedent("""\
+            import os
+            import sys
+            import time
+
+            filename = sys.argv[1]
+            deadline = float(sys.argv[2])
+
+            while time.time() < deadline:
+                try:
+                    with open(filename, "w") as f:
+                        pass
+                except OSError:
+                    pass
+                try:
+                    os.remove(filename)
+                except OSError:
+                    pass
+            """)
+
+        with subprocess.Popen([sys.executable, '-c', command, filename, str(deadline)]) as proc:
+            while time.time() < deadline:
+                try:
+                    os.stat(filename)
+                except FileNotFoundError as e:
+                    assert e.winerror == 2  # ERROR_FILE_NOT_FOUND
+            try:
+                proc.wait(1)
+            except subprocess.TimeoutExpired:
+                proc.terminate()
+
+    @support.requires_subprocess()
+    def test_stat_inaccessible_file(self):
+        filename = os_helper.TESTFN
+        ICACLS = os.path.expandvars(r"%SystemRoot%\System32\icacls.exe")
+
+        with open(filename, "wb") as f:
+            f.write(b'Test data')
+
+        stat1 = os.stat(filename)
+
+        try:
+            # Remove all permissions from the file
+            subprocess.check_output([ICACLS, filename, "/inheritance:r"],
+                                    stderr=subprocess.STDOUT)
+        except subprocess.CalledProcessError as ex:
+            if support.verbose:
+                print(ICACLS, filename, "/inheritance:r", "failed.")
+                print(ex.stdout.decode("oem", "replace").rstrip())
+            try:
+                os.unlink(filename)
+            except OSError:
+                pass
+            self.skipTest("Unable to create inaccessible file")
+
+        def cleanup():
+            # Give delete permission to the owner (us)
+            subprocess.check_output([ICACLS, filename, "/grant", "*WD:(D)"],
+                                    stderr=subprocess.STDOUT)
+            os.unlink(filename)
+
+        self.addCleanup(cleanup)
+
+        if support.verbose:
+            print("File:", filename)
+            print("stat with access:", stat1)
+
+        # First test - we shouldn't raise here, because we still have access to
+        # the directory and can extract enough information from its metadata.
+        stat2 = os.stat(filename)
+
+        if support.verbose:
+            print(" without access:", stat2)
+
+        # We may not get st_dev/st_ino, so ensure those are 0 or match
+        self.assertIn(stat2.st_dev, (0, stat1.st_dev))
+        self.assertIn(stat2.st_ino, (0, stat1.st_ino))
+
+        # st_mode and st_size should match (for a normal file, at least)
+        self.assertEqual(stat1.st_mode, stat2.st_mode)
+        self.assertEqual(stat1.st_size, stat2.st_size)
+
+        # st_ctime and st_mtime should be the same
+        self.assertEqual(stat1.st_ctime, stat2.st_ctime)
+        self.assertEqual(stat1.st_mtime, stat2.st_mtime)
+
+        # st_atime should be the same or later
+        self.assertGreaterEqual(stat1.st_atime, stat2.st_atime)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_os/utils.py b/Lib/test/test_os/utils.py
new file mode 100644
index 00000000000..e0c39598c31
--- /dev/null
+++ b/Lib/test/test_os/utils.py
@@ -0,0 +1,3 @@
+def create_file(filename, content=b'content'):
+    with open(filename, "xb", 0) as fp:
+        fp.write(content)
diff --git a/Lib/test/test_pathlib/support/lexical_path.py b/Lib/test/test_pathlib/support/lexical_path.py
index f29a521af9b..fd7fbf283a6 100644
--- a/Lib/test/test_pathlib/support/lexical_path.py
+++ b/Lib/test/test_pathlib/support/lexical_path.py
@@ -9,9 +9,10 @@
 from . import is_pypi
 
 if is_pypi:
-    from pathlib_abc import _JoinablePath
+    from pathlib_abc import vfspath, _JoinablePath
 else:
     from pathlib.types import _JoinablePath
+    from pathlib._os import vfspath
 
 
 class LexicalPath(_JoinablePath):
@@ -22,20 +23,20 @@ def __init__(self, *pathsegments):
         self._segments = pathsegments
 
     def __hash__(self):
-        return hash(str(self))
+        return hash(vfspath(self))
 
     def __eq__(self, other):
         if not isinstance(other, LexicalPath):
             return NotImplemented
-        return str(self) == str(other)
+        return vfspath(self) == vfspath(other)
 
-    def __str__(self):
+    def __vfspath__(self):
         if not self._segments:
             return ''
         return self.parser.join(*self._segments)
 
     def __repr__(self):
-        return f'{type(self).__name__}({str(self)!r})'
+        return f'{type(self).__name__}({vfspath(self)!r})'
 
     def with_segments(self, *pathsegments):
         return type(self)(*pathsegments)
diff --git a/Lib/test/test_pathlib/support/local_path.py b/Lib/test/test_pathlib/support/local_path.py
index d481fd45ead..ddfd6fd4195 100644
--- a/Lib/test/test_pathlib/support/local_path.py
+++ b/Lib/test/test_pathlib/support/local_path.py
@@ -97,7 +97,7 @@ class LocalPathInfo(PathInfo):
     __slots__ = ('_path', '_exists', '_is_dir', '_is_file', '_is_symlink')
 
     def __init__(self, path):
-        self._path = str(path)
+        self._path = os.fspath(path)
         self._exists = None
         self._is_dir = None
         self._is_file = None
@@ -139,15 +139,13 @@ class ReadableLocalPath(_ReadablePath, LexicalPath):
     Simple implementation of a ReadablePath class for local filesystem paths.
     """
     __slots__ = ('info',)
+    __fspath__ = LexicalPath.__vfspath__
 
     def __init__(self, *pathsegments):
         super().__init__(*pathsegments)
         self.info = LocalPathInfo(self)
 
-    def __fspath__(self):
-        return str(self)
-
-    def __open_rb__(self, buffering=-1):
+    def __open_reader__(self):
         return open(self, 'rb')
 
     def iterdir(self):
@@ -163,12 +161,10 @@ class WritableLocalPath(_WritablePath, LexicalPath):
     """
 
     __slots__ = ()
+    __fspath__ = LexicalPath.__vfspath__
 
-    def __fspath__(self):
-        return str(self)
-
-    def __open_wb__(self, buffering=-1):
-        return open(self, 'wb')
+    def __open_writer__(self, mode):
+        return open(self, f'{mode}b')
 
     def mkdir(self, mode=0o777):
         os.mkdir(self, mode)
diff --git a/Lib/test/test_pathlib/support/zip_path.py b/Lib/test/test_pathlib/support/zip_path.py
index 2905260c9df..90b939b6a59 100644
--- a/Lib/test/test_pathlib/support/zip_path.py
+++ b/Lib/test/test_pathlib/support/zip_path.py
@@ -16,9 +16,10 @@
 from . import is_pypi
 
 if is_pypi:
-    from pathlib_abc import PathInfo, _ReadablePath, _WritablePath
+    from pathlib_abc import vfspath, PathInfo, _ReadablePath, _WritablePath
 else:
     from pathlib.types import PathInfo, _ReadablePath, _WritablePath
+    from pathlib._os import vfspath
 
 
 class ZipPathGround:
@@ -34,16 +35,16 @@ def teardown(self, root):
         root.zip_file.close()
 
     def create_file(self, path, data=b''):
-        path.zip_file.writestr(str(path), data)
+        path.zip_file.writestr(vfspath(path), data)
 
     def create_dir(self, path):
-        zip_info = zipfile.ZipInfo(str(path) + '/')
+        zip_info = zipfile.ZipInfo(vfspath(path) + '/')
         zip_info.external_attr |= stat.S_IFDIR << 16
         zip_info.external_attr |= stat.FILE_ATTRIBUTE_DIRECTORY
         path.zip_file.writestr(zip_info, '')
 
     def create_symlink(self, path, target):
-        zip_info = zipfile.ZipInfo(str(path))
+        zip_info = zipfile.ZipInfo(vfspath(path))
         zip_info.external_attr = stat.S_IFLNK << 16
         path.zip_file.writestr(zip_info, target.encode())
 
@@ -62,28 +63,28 @@ def create_hierarchy(self, p):
         self.create_symlink(p.joinpath('brokenLinkLoop'), 'brokenLinkLoop')
 
     def readtext(self, p):
-        with p.zip_file.open(str(p), 'r') as f:
+        with p.zip_file.open(vfspath(p), 'r') as f:
             f = io.TextIOWrapper(f, encoding='utf-8')
             return f.read()
 
     def readbytes(self, p):
-        with p.zip_file.open(str(p), 'r') as f:
+        with p.zip_file.open(vfspath(p), 'r') as f:
             return f.read()
 
     readlink = readtext
 
     def isdir(self, p):
-        path_str = str(p) + "/"
+        path_str = vfspath(p) + "/"
         return path_str in p.zip_file.NameToInfo
 
     def isfile(self, p):
-        info = p.zip_file.NameToInfo.get(str(p))
+        info = p.zip_file.NameToInfo.get(vfspath(p))
         if info is None:
             return False
         return not stat.S_ISLNK(info.external_attr >> 16)
 
     def islink(self, p):
-        info = p.zip_file.NameToInfo.get(str(p))
+        info = p.zip_file.NameToInfo.get(vfspath(p))
         if info is None:
             return False
         return stat.S_ISLNK(info.external_attr >> 16)
@@ -240,20 +241,20 @@ def __init__(self, *pathsegments, zip_file):
             zip_file.filelist = ZipFileList(zip_file)
 
     def __hash__(self):
-        return hash((str(self), self.zip_file))
+        return hash((vfspath(self), self.zip_file))
 
     def __eq__(self, other):
         if not isinstance(other, ReadableZipPath):
             return NotImplemented
-        return str(self) == str(other) and self.zip_file is other.zip_file
+        return vfspath(self) == vfspath(other) and self.zip_file is other.zip_file
 
-    def __str__(self):
+    def __vfspath__(self):
         if not self._segments:
             return ''
         return self.parser.join(*self._segments)
 
     def __repr__(self):
-        return f'{type(self).__name__}({str(self)!r}, zip_file={self.zip_file!r})'
+        return f'{type(self).__name__}({vfspath(self)!r}, zip_file={self.zip_file!r})'
 
     def with_segments(self, *pathsegments):
         return type(self)(*pathsegments, zip_file=self.zip_file)
@@ -261,15 +262,15 @@ def with_segments(self, *pathsegments):
     @property
     def info(self):
         tree = self.zip_file.filelist.tree
-        return tree.resolve(str(self), follow_symlinks=False)
+        return tree.resolve(vfspath(self), follow_symlinks=False)
 
-    def __open_rb__(self, buffering=-1):
+    def __open_reader__(self):
         info = self.info.resolve()
         if not info.exists():
             raise FileNotFoundError(errno.ENOENT, "File not found", self)
         elif info.is_dir():
             raise IsADirectoryError(errno.EISDIR, "Is a directory", self)
-        return self.zip_file.open(info.zip_info, 'r')
+        return self.zip_file.open(info.zip_info)
 
     def iterdir(self):
         info = self.info.resolve()
@@ -301,36 +302,36 @@ def __init__(self, *pathsegments, zip_file):
         self.zip_file = zip_file
 
     def __hash__(self):
-        return hash((str(self), self.zip_file))
+        return hash((vfspath(self), self.zip_file))
 
     def __eq__(self, other):
         if not isinstance(other, WritableZipPath):
             return NotImplemented
-        return str(self) == str(other) and self.zip_file is other.zip_file
+        return vfspath(self) == vfspath(other) and self.zip_file is other.zip_file
 
-    def __str__(self):
+    def __vfspath__(self):
         if not self._segments:
             return ''
         return self.parser.join(*self._segments)
 
     def __repr__(self):
-        return f'{type(self).__name__}({str(self)!r}, zip_file={self.zip_file!r})'
+        return f'{type(self).__name__}({vfspath(self)!r}, zip_file={self.zip_file!r})'
 
     def with_segments(self, *pathsegments):
         return type(self)(*pathsegments, zip_file=self.zip_file)
 
-    def __open_wb__(self, buffering=-1):
-        return self.zip_file.open(str(self), 'w')
+    def __open_writer__(self, mode):
+        return self.zip_file.open(vfspath(self), mode)
 
     def mkdir(self, mode=0o777):
-        zinfo = zipfile.ZipInfo(str(self) + '/')
+        zinfo = zipfile.ZipInfo(vfspath(self) + '/')
         zinfo.external_attr |= stat.S_IFDIR << 16
         zinfo.external_attr |= stat.FILE_ATTRIBUTE_DIRECTORY
         self.zip_file.writestr(zinfo, '')
 
     def symlink_to(self, target, target_is_directory=False):
-        zinfo = zipfile.ZipInfo(str(self))
+        zinfo = zipfile.ZipInfo(vfspath(self))
         zinfo.external_attr = stat.S_IFLNK << 16
         if target_is_directory:
             zinfo.external_attr |= 0x10
-        self.zip_file.writestr(zinfo, str(target))
+        self.zip_file.writestr(zinfo, target)
diff --git a/Lib/test/test_pathlib/test_join.py b/Lib/test/test_pathlib/test_join.py
index 6b51a09e5ac..4630210e492 100644
--- a/Lib/test/test_pathlib/test_join.py
+++ b/Lib/test/test_pathlib/test_join.py
@@ -376,6 +376,61 @@ def test_with_suffix(self):
         self.assertRaises(ValueError, P('a/b').with_suffix, '.d/.')
         self.assertRaises(TypeError, P('a/b').with_suffix, None)
 
+    def test_relative_to(self):
+        P = self.cls
+        p = P('a/b')
+        self.assertEqual(p.relative_to(P('')), P('a', 'b'))
+        self.assertEqual(p.relative_to(P('a')), P('b'))
+        self.assertEqual(p.relative_to(P('a/b')), P(''))
+        self.assertEqual(p.relative_to(P(''), walk_up=True), P('a', 'b'))
+        self.assertEqual(p.relative_to(P('a'), walk_up=True), P('b'))
+        self.assertEqual(p.relative_to(P('a/b'), walk_up=True), P(''))
+        self.assertEqual(p.relative_to(P('a/c'), walk_up=True), P('..', 'b'))
+        self.assertEqual(p.relative_to(P('a/b/c'), walk_up=True), P('..'))
+        self.assertEqual(p.relative_to(P('c'), walk_up=True), P('..', 'a', 'b'))
+        self.assertRaises(ValueError, p.relative_to, P('c'))
+        self.assertRaises(ValueError, p.relative_to, P('a/b/c'))
+        self.assertRaises(ValueError, p.relative_to, P('a/c'))
+        self.assertRaises(ValueError, p.relative_to, P('/a'))
+        self.assertRaises(ValueError, p.relative_to, P('../a'))
+        self.assertRaises(ValueError, p.relative_to, P('a/..'))
+        self.assertRaises(ValueError, p.relative_to, P('/a/..'))
+        self.assertRaises(ValueError, p.relative_to, P('/'), walk_up=True)
+        self.assertRaises(ValueError, p.relative_to, P('/a'), walk_up=True)
+        self.assertRaises(ValueError, p.relative_to, P('../a'), walk_up=True)
+        self.assertRaises(ValueError, p.relative_to, P('a/..'), walk_up=True)
+        self.assertRaises(ValueError, p.relative_to, P('/a/..'), walk_up=True)
+        class Q(self.cls):
+            __eq__ = object.__eq__
+            __hash__ = object.__hash__
+        q = Q('a/b')
+        self.assertTrue(q.relative_to(q))
+        self.assertRaises(ValueError, q.relative_to, Q(''))
+        self.assertRaises(ValueError, q.relative_to, Q('a'))
+        self.assertRaises(ValueError, q.relative_to, Q('a'), walk_up=True)
+        self.assertRaises(ValueError, q.relative_to, Q('a/b'))
+        self.assertRaises(ValueError, q.relative_to, Q('c'))
+
+    def test_is_relative_to(self):
+        P = self.cls
+        p = P('a/b')
+        self.assertTrue(p.is_relative_to(P('')))
+        self.assertTrue(p.is_relative_to(P('a')))
+        self.assertTrue(p.is_relative_to(P('a/b')))
+        self.assertFalse(p.is_relative_to(P('c')))
+        self.assertFalse(p.is_relative_to(P('a/b/c')))
+        self.assertFalse(p.is_relative_to(P('a/c')))
+        self.assertFalse(p.is_relative_to(P('/a')))
+        class Q(self.cls):
+            __eq__ = object.__eq__
+            __hash__ = object.__hash__
+        q = Q('a/b')
+        self.assertTrue(q.is_relative_to(q))
+        self.assertFalse(q.is_relative_to(Q('')))
+        self.assertFalse(q.is_relative_to(Q('a')))
+        self.assertFalse(q.is_relative_to(Q('a/b')))
+        self.assertFalse(q.is_relative_to(Q('c')))
+
 
 class LexicalPathJoinTest(JoinTestBase, unittest.TestCase):
     cls = LexicalPath
diff --git a/Lib/test/test_pathlib/test_join_windows.py b/Lib/test/test_pathlib/test_join_windows.py
index 2cc634f25ef..5afefa61b58 100644
--- a/Lib/test/test_pathlib/test_join_windows.py
+++ b/Lib/test/test_pathlib/test_join_windows.py
@@ -8,6 +8,11 @@
 from .support import is_pypi
 from .support.lexical_path import LexicalWindowsPath
 
+if is_pypi:
+    from pathlib_abc import vfspath
+else:
+    from pathlib._os import vfspath
+
 
 class JoinTestBase:
     def test_join(self):
@@ -70,17 +75,22 @@ def test_div(self):
         self.assertEqual(p / './dd:s', P(r'C:/a/b\./dd:s'))
         self.assertEqual(p / 'E:d:s', P('E:d:s'))
 
-    def test_str(self):
+    def test_vfspath(self):
         p = self.cls(r'a\b\c')
-        self.assertEqual(str(p), 'a\\b\\c')
+        self.assertEqual(vfspath(p), 'a\\b\\c')
         p = self.cls(r'c:\a\b\c')
-        self.assertEqual(str(p), 'c:\\a\\b\\c')
+        self.assertEqual(vfspath(p), 'c:\\a\\b\\c')
         p = self.cls('\\\\a\\b\\')
-        self.assertEqual(str(p), '\\\\a\\b\\')
+        self.assertEqual(vfspath(p), '\\\\a\\b\\')
         p = self.cls(r'\\a\b\c')
-        self.assertEqual(str(p), '\\\\a\\b\\c')
+        self.assertEqual(vfspath(p), '\\\\a\\b\\c')
         p = self.cls(r'\\a\b\c\d')
-        self.assertEqual(str(p), '\\\\a\\b\\c\\d')
+        self.assertEqual(vfspath(p), '\\\\a\\b\\c\\d')
+
+    def test_invalid_vspath(self):
+        msg = "expected JoinablePath object, not NoneType"
+        with self.assertRaisesRegex(TypeError, msg):
+            vfspath(None)
 
     def test_parts(self):
         P = self.cls
diff --git a/Lib/test/test_pathlib/test_pathlib.py b/Lib/test/test_pathlib/test_pathlib.py
index a1ea69a6b90..aff66c8efed 100644
--- a/Lib/test/test_pathlib/test_pathlib.py
+++ b/Lib/test/test_pathlib/test_pathlib.py
@@ -20,6 +20,8 @@
 from test.support import is_emscripten, is_wasi, is_wasm32
 from test.support import infinite_recursion
 from test.support import os_helper
+from test.support import requires_root_user
+from test.support import requires_non_root_user
 from test.support.os_helper import TESTFN, FS_NONASCII, FakePath
 try:
     import fcntl
@@ -35,11 +37,6 @@
     posix = None
 
 
-root_in_posix = False
-if hasattr(os, 'geteuid'):
-    root_in_posix = (os.geteuid() == 0)
-
-
 def patch_replace(old_test):
     def new_replace(self, target):
         raise OSError(errno.EXDEV, "Cross-device link", self, target)
@@ -84,7 +81,7 @@ def test_is_notimplemented(self):
 class LazyImportTest(unittest.TestCase):
     @cpython_only
     def test_lazy_import(self):
-        import_helper.ensure_lazy_imports("pathlib", {"shutil"})
+        import_helper.ensure_lazy_imports("pathlib", {"glob", "shutil"})
 
 
 #
@@ -545,12 +542,6 @@ def test_with_stem_empty(self):
         self.assertRaises(ValueError, P('a/b').with_stem, '')
         self.assertRaises(ValueError, P('a/b').with_stem, '.')
 
-    def test_is_reserved_deprecated(self):
-        P = self.cls
-        p = P('a/b')
-        with self.assertWarns(DeprecationWarning):
-            p.is_reserved()
-
     def test_full_match_case_sensitive(self):
         P = self.cls
         self.assertFalse(P('A.py').full_match('a.PY', case_sensitive=True))
@@ -1560,7 +1551,7 @@ def raiser(*args, **kwargs):
             self.assertRaises(FileNotFoundError, source.copy, target)
 
     @unittest.skipIf(sys.platform == "win32" or sys.platform == "wasi", "directories are always readable on Windows and WASI")
-    @unittest.skipIf(root_in_posix, "test fails with root privilege")
+    @requires_non_root_user
     def test_copy_dir_no_read_permission(self):
         base = self.cls(self.base)
         source = base / 'dirE'
@@ -2033,7 +2024,7 @@ def test_owner(self):
         self.assertEqual(expected_name, p.owner())
 
     @unittest.skipUnless(pwd, "the pwd module is needed for this test")
-    @unittest.skipUnless(root_in_posix, "test needs root privilege")
+    @requires_root_user
     def test_owner_no_follow_symlinks(self):
         all_users = [u.pw_uid for u in pwd.getpwall()]
         if len(all_users) < 2:
@@ -2068,7 +2059,7 @@ def test_group(self):
         self.assertEqual(expected_name, p.group())
 
     @unittest.skipUnless(grp, "the grp module is needed for this test")
-    @unittest.skipUnless(root_in_posix, "test needs root privilege")
+    @requires_root_user
     def test_group_no_follow_symlinks(self):
         all_groups = [g.gr_gid for g in grp.getgrall()]
         if len(all_groups) < 2:
@@ -2501,6 +2492,116 @@ def my_mkdir(path, mode=0o777):
                 self.assertNotIn(str(p12), concurrently_created)
             self.assertTrue(p.exists())
 
+    @unittest.skipIf(
+        is_emscripten or is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_mkdir_parents_umask(self):
+        # Test that parent directories respect umask when parent_mode is not set
+        p = self.cls(self.base, 'umasktest', 'child')
+        self.assertFalse(p.exists())
+        if os.name != 'nt':
+            with os_helper.temp_umask(0o002):
+                p.mkdir(0o755, parents=True)
+                self.assertTrue(p.exists())
+                # Leaf directory gets the specified mode
+                self.assertEqual(p.stat().st_mode & 0o777, 0o755)
+                # Parent directory respects umask (0o777 & ~0o002 = 0o775)
+                self.assertEqual(p.parent.stat().st_mode & 0o777, 0o775)
+
+    @unittest.skipIf(
+        is_emscripten or is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_mkdir_with_parent_mode(self):
+        # Test the parent_mode parameter
+        p = self.cls(self.base, 'newdirPM', 'subdirPM')
+        self.assertFalse(p.exists())
+        if os.name != 'nt':
+            with os_helper.temp_umask(0o022):
+                # Specify different modes for parent and leaf directories
+                p.mkdir(0o755, parents=True, parent_mode=0o750)
+                self.assertTrue(p.exists())
+                self.assertTrue(p.is_dir())
+                # Leaf directory gets the mode parameter
+                self.assertEqual(p.stat().st_mode & 0o777, 0o755)
+                # Parent directory gets the parent_mode parameter
+                self.assertEqual(p.parent.stat().st_mode & 0o777, 0o750)
+
+    @unittest.skipIf(
+        is_emscripten or is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_mkdir_parent_mode_deep_hierarchy(self):
+        # Test parent_mode with deep directory hierarchy
+        p = self.cls(self.base, 'level1PM', 'level2PM', 'level3PM')
+        self.assertFalse(p.exists())
+        if os.name != 'nt':
+            with os_helper.temp_umask(0o022):
+                p.mkdir(0o755, parents=True, parent_mode=0o700)
+                self.assertTrue(p.exists())
+                # Check that all parent directories have parent_mode
+                level1 = self.cls(self.base, 'level1PM')
+                level2 = level1 / 'level2PM'
+                self.assertEqual(level1.stat().st_mode & 0o777, 0o700)
+                self.assertEqual(level2.stat().st_mode & 0o777, 0o700)
+                # Leaf directory has the regular mode
+                self.assertEqual(p.stat().st_mode & 0o777, 0o755)
+
+    @unittest.skipIf(
+        is_emscripten or is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_mkdir_parent_mode_combined_with_umask(self):
+        # parent_mode, like mode, is combined with the process umask; it does
+        # not bypass it.
+        p = self.cls(self.base, 'umaskPM', 'child')
+        self.assertFalse(p.exists())
+        if os.name != 'nt':
+            with os_helper.temp_umask(0o022):
+                p.mkdir(0o777, parents=True, parent_mode=0o777)
+                self.assertTrue(p.exists())
+                # 0o777 is masked down to 0o755 by the 0o022 umask, for both
+                # the leaf (mode) and the parent (parent_mode).
+                self.assertEqual(p.stat().st_mode & 0o777, 0o755)
+                self.assertEqual(p.parent.stat().st_mode & 0o777, 0o755)
+
+    @unittest.skipIf(
+        is_emscripten or is_wasi,
+        "umask is not implemented on Emscripten/WASI."
+    )
+    @unittest.skipIf(
+        sys.platform == "android",
+        "Android filesystem may not honor requested permissions."
+    )
+    def test_mkdir_parent_mode_same_as_mode(self):
+        # Test setting parent_mode same as mode
+        p = self.cls(self.base, 'samedirPM', 'subdirPM')
+        self.assertFalse(p.exists())
+        if os.name != 'nt':
+            with os_helper.temp_umask(0o022):
+                p.mkdir(0o705, parents=True, parent_mode=0o705)
+                self.assertTrue(p.exists())
+                # Both directories should have the same mode
+                self.assertEqual(p.stat().st_mode & 0o777, 0o705)
+                self.assertEqual(p.parent.stat().st_mode & 0o777, 0o705)
+
     @needs_symlinks
     def test_symlink_to(self):
         P = self.cls(self.base)
@@ -2769,6 +2870,7 @@ def test_is_socket_true(self):
             if (isinstance(e, PermissionError) or
                     "AF_UNIX path too long" in str(e)):
                 self.skipTest("cannot bind Unix socket: " + str(e))
+            raise
         self.assertTrue(P.is_socket())
         self.assertFalse(P.is_fifo())
         self.assertFalse(P.is_file())
diff --git a/Lib/test/test_pathlib/test_read.py b/Lib/test/test_pathlib/test_read.py
index 482203c290a..51eede9d9eb 100644
--- a/Lib/test/test_pathlib/test_read.py
+++ b/Lib/test/test_pathlib/test_read.py
@@ -13,10 +13,10 @@
 
 if is_pypi:
     from pathlib_abc import PathInfo, _ReadablePath
-    from pathlib_abc._os import magic_open
+    from pathlib_abc._os import vfsopen
 else:
     from pathlib.types import PathInfo, _ReadablePath
-    from pathlib._os import magic_open
+    from pathlib._os import vfsopen
 
 
 class ReadTestBase:
@@ -32,10 +32,16 @@ def test_is_readable(self):
 
     def test_open_r(self):
         p = self.root / 'fileA'
-        with magic_open(p, 'r', encoding='utf-8') as f:
+        with vfsopen(p, 'r', encoding='utf-8') as f:
             self.assertIsInstance(f, io.TextIOBase)
             self.assertEqual(f.read(), 'this is file A\n')
 
+    def test_open_r_buffering_error(self):
+        p = self.root / 'fileA'
+        self.assertRaises(ValueError, vfsopen, p, 'r', buffering=0)
+        self.assertRaises(ValueError, vfsopen, p, 'r', buffering=1)
+        self.assertRaises(ValueError, vfsopen, p, 'r', buffering=1024)
+
     @unittest.skipIf(
         not getattr(sys.flags, 'warn_default_encoding', 0),
         "Requires warn_default_encoding",
@@ -43,17 +49,17 @@ def test_open_r(self):
     def test_open_r_encoding_warning(self):
         p = self.root / 'fileA'
         with self.assertWarns(EncodingWarning) as wc:
-            with magic_open(p, 'r'):
+            with vfsopen(p, 'r'):
                 pass
         self.assertEqual(wc.filename, __file__)
 
     def test_open_rb(self):
         p = self.root / 'fileA'
-        with magic_open(p, 'rb') as f:
+        with vfsopen(p, 'rb') as f:
             self.assertEqual(f.read(), b'this is file A\n')
-        self.assertRaises(ValueError, magic_open, p, 'rb', encoding='utf8')
-        self.assertRaises(ValueError, magic_open, p, 'rb', errors='strict')
-        self.assertRaises(ValueError, magic_open, p, 'rb', newline='')
+        self.assertRaises(ValueError, vfsopen, p, 'rb', encoding='utf8')
+        self.assertRaises(ValueError, vfsopen, p, 'rb', errors='strict')
+        self.assertRaises(ValueError, vfsopen, p, 'rb', newline='')
 
     def test_read_bytes(self):
         p = self.root / 'fileA'
@@ -323,6 +329,11 @@ def test_info_is_symlink(self):
         self.assertFalse((p / 'fileA\udfff').info.is_symlink())
         self.assertFalse((p / 'fileA\x00').info.is_symlink())
 
+    def test_invalid_mode(self):
+        p = self.root / 'fileA'
+        with self.assertRaisesRegex(ValueError, 'invalid mode'):
+            vfsopen(p, 'q')
+
 
 class ZipPathReadTest(ReadTestBase, unittest.TestCase):
     ground = ZipPathGround(ReadableZipPath)
diff --git a/Lib/test/test_pathlib/test_write.py b/Lib/test/test_pathlib/test_write.py
index 15054e804ec..fa2a81a47b3 100644
--- a/Lib/test/test_pathlib/test_write.py
+++ b/Lib/test/test_pathlib/test_write.py
@@ -13,10 +13,10 @@
 
 if is_pypi:
     from pathlib_abc import _WritablePath
-    from pathlib_abc._os import magic_open
+    from pathlib_abc._os import vfsopen
 else:
     from pathlib.types import _WritablePath
-    from pathlib._os import magic_open
+    from pathlib._os import vfsopen
 
 
 class WriteTestBase:
@@ -31,11 +31,17 @@ def test_is_writable(self):
 
     def test_open_w(self):
         p = self.root / 'fileA'
-        with magic_open(p, 'w', encoding='utf-8') as f:
+        with vfsopen(p, 'w', encoding='utf-8') as f:
             self.assertIsInstance(f, io.TextIOBase)
             f.write('this is file A\n')
         self.assertEqual(self.ground.readtext(p), 'this is file A\n')
 
+    def test_open_w_buffering_error(self):
+        p = self.root / 'fileA'
+        self.assertRaises(ValueError, vfsopen, p, 'w', buffering=0)
+        self.assertRaises(ValueError, vfsopen, p, 'w', buffering=1)
+        self.assertRaises(ValueError, vfsopen, p, 'w', buffering=1024)
+
     @unittest.skipIf(
         not getattr(sys.flags, 'warn_default_encoding', 0),
         "Requires warn_default_encoding",
@@ -43,19 +49,19 @@ def test_open_w(self):
     def test_open_w_encoding_warning(self):
         p = self.root / 'fileA'
         with self.assertWarns(EncodingWarning) as wc:
-            with magic_open(p, 'w'):
+            with vfsopen(p, 'w'):
                 pass
         self.assertEqual(wc.filename, __file__)
 
     def test_open_wb(self):
         p = self.root / 'fileA'
-        with magic_open(p, 'wb') as f:
+        with vfsopen(p, 'wb') as f:
             #self.assertIsInstance(f, io.BufferedWriter)
             f.write(b'this is file A\n')
         self.assertEqual(self.ground.readbytes(p), b'this is file A\n')
-        self.assertRaises(ValueError, magic_open, p, 'wb', encoding='utf8')
-        self.assertRaises(ValueError, magic_open, p, 'wb', errors='strict')
-        self.assertRaises(ValueError, magic_open, p, 'wb', newline='')
+        self.assertRaises(ValueError, vfsopen, p, 'wb', encoding='utf8')
+        self.assertRaises(ValueError, vfsopen, p, 'wb', errors='strict')
+        self.assertRaises(ValueError, vfsopen, p, 'wb', newline='')
 
     def test_write_bytes(self):
         p = self.root / 'fileA'
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index d06b9a4b6ef..1c683077edd 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -13,7 +13,7 @@
 
 from test import support
 from test.support.bytecode_helper import (
-    BytecodeTestCase, CfgOptimizationTestCase, CompilationStepTestCase)
+    BytecodeTestCase, CfgOptimizationTestCase)
 
 
 def compile_pattern_with_fast_locals(pattern):
@@ -106,7 +106,7 @@ def test_elim_inversion_of_is_or_in(self):
                 self.check_lnotab(code)
 
     def test_global_as_constant(self):
-        # LOAD_GLOBAL None/True/False  -->  LOAD_CONST None/True/False
+        # LOAD_GLOBAL None/True/False  -->  LOAD_COMMON_CONSTANT None/True/False
         def f():
             x = None
             x = None
@@ -121,7 +121,7 @@ def h():
         for func, elem in ((f, None), (g, True), (h, False)):
             with self.subTest(func=func):
                 self.assertNotInBytecode(func, 'LOAD_GLOBAL')
-                self.assertInBytecode(func, 'LOAD_CONST', elem)
+                self.assertInBytecode(func, 'LOAD_COMMON_CONSTANT', elem)
                 self.check_lnotab(func)
 
         def f():
@@ -129,7 +129,7 @@ def f():
             return None
 
         self.assertNotInBytecode(f, 'LOAD_GLOBAL')
-        self.assertInBytecode(f, 'LOAD_CONST', None)
+        self.assertInBytecode(f, 'LOAD_COMMON_CONSTANT', None)
         self.check_lnotab(f)
 
     def test_while_one(self):
@@ -146,13 +146,14 @@ def f():
 
     def test_pack_unpack(self):
         for line, elem in (
-            ('a, = a,', 'LOAD_CONST',),
+            ('a, = a,', None),
             ('a, b = a, b', 'SWAP',),
             ('a, b, c = a, b, c', 'SWAP',),
             ):
             with self.subTest(line=line):
                 code = compile(line,'','single')
-                self.assertInBytecode(code, elem)
+                if elem is not None:
+                    self.assertInBytecode(code, elem)
                 self.assertNotInBytecode(code, 'BUILD_TUPLE')
                 self.assertNotInBytecode(code, 'UNPACK_SEQUENCE')
                 self.check_lnotab(code)
@@ -174,10 +175,10 @@ def test_constant_folding_tuples_of_constants(self):
         # Long tuples should be folded too.
         code = compile(repr(tuple(range(10000))),'','single')
         self.assertNotInBytecode(code, 'BUILD_TUPLE')
-        # One LOAD_CONST for the tuple, one for the None return value
+        # One LOAD_CONST for the tuple; None return value uses LOAD_COMMON_CONSTANT
         load_consts = [instr for instr in dis.get_instructions(code)
                               if instr.opname == 'LOAD_CONST']
-        self.assertEqual(len(load_consts), 2)
+        self.assertEqual(len(load_consts), 1)
         self.check_lnotab(code)
 
         # Bug 1053819:  Tuple of constants misidentified when presented with:
@@ -283,11 +284,11 @@ def test_constant_folding_unaryop(self):
             ('-0.0', 'UNARY_NEGATIVE', None, True, 'LOAD_CONST', -0.0),
             ('-(1.0-1.0)', 'UNARY_NEGATIVE', None, True, 'LOAD_CONST', -0.0),
             ('-0.5', 'UNARY_NEGATIVE', None, True, 'LOAD_CONST', -0.5),
-            ('---1', 'UNARY_NEGATIVE', None, True, 'LOAD_CONST', -1),
+            ('---1', 'UNARY_NEGATIVE', None, True, 'LOAD_COMMON_CONSTANT', -1),
             ('---""', 'UNARY_NEGATIVE', None, False, None, None),
             ('~~~1', 'UNARY_INVERT', None, True, 'LOAD_CONST', -2),
             ('~~~""', 'UNARY_INVERT', None, False, None, None),
-            ('not not True', 'UNARY_NOT', None, True, 'LOAD_CONST', True),
+            ('not not True', 'UNARY_NOT', None, True, 'LOAD_COMMON_CONSTANT', True),
             ('not not x', 'UNARY_NOT', None, True, 'LOAD_NAME', 'x'),  # this should be optimized regardless of constant or not
             ('+++1', 'CALL_INTRINSIC_1', intrinsic_positive, True, 'LOAD_SMALL_INT', 1),
             ('---x', 'UNARY_NEGATIVE', None, False, None, None),
@@ -326,7 +327,7 @@ def test_constant_folding_binop(self):
             ('1 + 2', 'NB_ADD', True, 'LOAD_SMALL_INT', 3),
             ('1 + 2 + 3', 'NB_ADD', True, 'LOAD_SMALL_INT', 6),
             ('1 + ""', 'NB_ADD', False, None, None),
-            ('1 - 2', 'NB_SUBTRACT', True, 'LOAD_CONST', -1),
+            ('1 - 2', 'NB_SUBTRACT', True, 'LOAD_COMMON_CONSTANT', -1),
             ('1 - 2 - 3', 'NB_SUBTRACT', True, 'LOAD_CONST', -4),
             ('1 - ""', 'NB_SUBTRACT', False, None, None),
             ('2 * 2', 'NB_MULTIPLY', True, 'LOAD_SMALL_INT', 4),
@@ -734,22 +735,27 @@ def test_format_errors(self):
         with self.assertRaisesRegex(TypeError,
                     'not all arguments converted during string formatting'):
             eval("'%s' % (x, y)", {'x': 1, 'y': 2})
-        with self.assertRaisesRegex(ValueError, 'incomplete format'):
+        with self.assertRaisesRegex(ValueError, 'stray % at position 2'):
             eval("'%s%' % (x,)", {'x': 1234})
-        with self.assertRaisesRegex(ValueError, 'incomplete format'):
+        with self.assertRaisesRegex(ValueError, 'stray % at position 4'):
             eval("'%s%%%' % (x,)", {'x': 1234})
         with self.assertRaisesRegex(TypeError,
                     'not enough arguments for format string'):
             eval("'%s%z' % (x,)", {'x': 1234})
-        with self.assertRaisesRegex(ValueError, 'unsupported format character'):
+        with self.assertRaisesRegex(ValueError,
+                    'unsupported format %z at position 2'):
             eval("'%s%z' % (x, 5)", {'x': 1234})
-        with self.assertRaisesRegex(TypeError, 'a real number is required, not str'):
+        with self.assertRaisesRegex(TypeError,
+                'format argument 1: %d requires a real number, not str'):
             eval("'%d' % (x,)", {'x': '1234'})
-        with self.assertRaisesRegex(TypeError, 'an integer is required, not float'):
+        with self.assertRaisesRegex(TypeError,
+                'format argument 1: %x requires an integer, not float'):
             eval("'%x' % (x,)", {'x': 1234.56})
-        with self.assertRaisesRegex(TypeError, 'an integer is required, not str'):
+        with self.assertRaisesRegex(TypeError,
+                'format argument 1: %x requires an integer, not str'):
             eval("'%x' % (x,)", {'x': '1234'})
-        with self.assertRaisesRegex(TypeError, 'must be real number, not str'):
+        with self.assertRaisesRegex(TypeError,
+                'format argument 1: %f requires a real number, not str'):
             eval("'%f' % (x,)", {'x': '1234'})
         with self.assertRaisesRegex(TypeError,
                     'not enough arguments for format string'):
@@ -1117,6 +1123,13 @@ def trace(frame, event, arg):
         self.assertInBytecode(f, "LOAD_FAST_BORROW")
         self.assertNotInBytecode(f, "LOAD_FAST_CHECK")
 
+    def test_import_from_doesnt_clobber_load_fast_borrow(self):
+        def f(self):
+            if x: pass
+            self.x
+            from shutil import ExecError
+            print(ExecError)
+        self.assertInBytecode(f, "LOAD_FAST_BORROW", "self")
 
 class DirectCfgOptimizerTests(CfgOptimizationTestCase):
 
@@ -1506,7 +1519,7 @@ def test_optimize_literal_list_for_iter(self):
             ('LOAD_SMALL_INT', 1, 0),
             ('LOAD_SMALL_INT', 2, 0),
             ('BUILD_LIST', 2, 0),
-            ('GET_ITER', None, 0),
+            ('GET_ITER', 0, 0),
             start := self.Label(),
             ('FOR_ITER', end := self.Label(), 0),
             ('STORE_FAST', 0, 0),
@@ -1519,7 +1532,7 @@ def test_optimize_literal_list_for_iter(self):
         ]
         after = [
             ('LOAD_CONST', 1, 0),
-            ('GET_ITER', None, 0),
+            ('GET_ITER', 0, 0),
             start := self.Label(),
             ('FOR_ITER', end := self.Label(), 0),
             ('STORE_FAST', 0, 0),
@@ -1527,7 +1540,7 @@ def test_optimize_literal_list_for_iter(self):
             end,
             ('END_FOR', None, 0),
             ('POP_ITER', None, 0),
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', 7, 0),
             ('RETURN_VALUE', None, 0),
         ]
         self.cfg_optimization_test(before, after, consts=[None], expected_consts=[None, (1, 2)])
@@ -1537,7 +1550,7 @@ def test_optimize_literal_list_for_iter(self):
             ('LOAD_SMALL_INT', 1, 0),
             ('LOAD_NAME', 0, 0),
             ('BUILD_LIST', 2, 0),
-            ('GET_ITER', None, 0),
+            ('GET_ITER', 0, 0),
             start := self.Label(),
             ('FOR_ITER', end := self.Label(), 0),
             ('STORE_FAST', 0, 0),
@@ -1552,7 +1565,7 @@ def test_optimize_literal_list_for_iter(self):
             ('LOAD_SMALL_INT', 1, 0),
             ('LOAD_NAME', 0, 0),
             ('BUILD_TUPLE', 2, 0),
-            ('GET_ITER', None, 0),
+            ('GET_ITER', 0, 0),
             start := self.Label(),
             ('FOR_ITER', end := self.Label(), 0),
             ('STORE_FAST', 0, 0),
@@ -1560,7 +1573,7 @@ def test_optimize_literal_list_for_iter(self):
             end,
             ('END_FOR', None, 0),
             ('POP_ITER', None, 0),
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', 7, 0),
             ('RETURN_VALUE', None, 0),
         ]
         self.cfg_optimization_test(before, after, consts=[None], expected_consts=[None])
@@ -1571,7 +1584,7 @@ def test_optimize_literal_set_for_iter(self):
             ('LOAD_SMALL_INT', 1, 0),
             ('LOAD_SMALL_INT', 2, 0),
             ('BUILD_SET', 2, 0),
-            ('GET_ITER', None, 0),
+            ('GET_ITER', 0, 0),
             start := self.Label(),
             ('FOR_ITER', end := self.Label(), 0),
             ('STORE_FAST', 0, 0),
@@ -1584,7 +1597,7 @@ def test_optimize_literal_set_for_iter(self):
         ]
         after = [
             ('LOAD_CONST', 1, 0),
-            ('GET_ITER', None, 0),
+            ('GET_ITER', 0, 0),
             start := self.Label(),
             ('FOR_ITER', end := self.Label(), 0),
             ('STORE_FAST', 0, 0),
@@ -1592,7 +1605,7 @@ def test_optimize_literal_set_for_iter(self):
             end,
             ('END_FOR', None, 0),
             ('POP_ITER', None, 0),
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', 7, 0),
             ('RETURN_VALUE', None, 0),
         ]
         self.cfg_optimization_test(before, after, consts=[None], expected_consts=[None, frozenset({1, 2})])
@@ -1603,7 +1616,7 @@ def test_optimize_literal_set_for_iter(self):
             ('LOAD_SMALL_INT', 1, 0),
             ('LOAD_NAME', 0, 0),
             ('BUILD_SET', 2, 0),
-            ('GET_ITER', None, 0),
+            ('GET_ITER', 0, 0),
             start := self.Label(),
             ('FOR_ITER', end := self.Label(), 0),
             ('STORE_FAST', 0, 0),
@@ -1614,7 +1627,22 @@ def test_optimize_literal_set_for_iter(self):
             ('LOAD_CONST', 0, 0),
             ('RETURN_VALUE', None, 0),
         ]
-        self.cfg_optimization_test(same, same, consts=[None], expected_consts=[None])
+        expected = [
+            ('LOAD_SMALL_INT', 1, 0),
+            ('LOAD_NAME', 0, 0),
+            ('BUILD_SET', 2, 0),
+            ('GET_ITER', 0, 0),
+            start := self.Label(),
+            ('FOR_ITER', end := self.Label(), 0),
+            ('STORE_FAST', 0, 0),
+            ('JUMP', start, 0),
+            end,
+            ('END_FOR', None, 0),
+            ('POP_ITER', None, 0),
+            ('LOAD_COMMON_CONSTANT', 7, 0),
+            ('RETURN_VALUE', None, 0),
+        ]
+        self.cfg_optimization_test(same, expected, consts=[None], expected_consts=[None])
 
     def test_optimize_literal_list_contains(self):
         # x in [1, 2]  ==>  x in (1, 2)
@@ -1633,7 +1661,7 @@ def test_optimize_literal_list_contains(self):
             ('LOAD_CONST', 1, 0),
             ('CONTAINS_OP', 0, 0),
             ('POP_TOP', None, 0),
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', 7, 0),
             ('RETURN_VALUE', None, 0),
         ]
         self.cfg_optimization_test(before, after, consts=[None], expected_consts=[None, (1, 2)])
@@ -1656,7 +1684,7 @@ def test_optimize_literal_list_contains(self):
             ('BUILD_TUPLE', 2, 0),
             ('CONTAINS_OP', 0, 0),
             ('POP_TOP', None, 0),
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', 7, 0),
             ('RETURN_VALUE', None, 0),
         ]
         self.cfg_optimization_test(before, after, consts=[None], expected_consts=[None])
@@ -1678,7 +1706,7 @@ def test_optimize_literal_set_contains(self):
             ('LOAD_CONST', 1, 0),
             ('CONTAINS_OP', 0, 0),
             ('POP_TOP', None, 0),
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', 7, 0),
             ('RETURN_VALUE', None, 0),
         ]
         self.cfg_optimization_test(before, after, consts=[None], expected_consts=[None, frozenset({1, 2})])
@@ -1695,7 +1723,17 @@ def test_optimize_literal_set_contains(self):
             ('LOAD_CONST', 0, 0),
             ('RETURN_VALUE', None, 0),
         ]
-        self.cfg_optimization_test(same, same, consts=[None], expected_consts=[None])
+        expected = [
+            ('LOAD_NAME', 0, 0),
+            ('LOAD_SMALL_INT', 1, 0),
+            ('LOAD_NAME', 1, 0),
+            ('BUILD_SET', 2, 0),
+            ('CONTAINS_OP', 0, 0),
+            ('POP_TOP', None, 0),
+            ('LOAD_COMMON_CONSTANT', 7, 0),
+            ('RETURN_VALUE', None, 0),
+        ]
+        self.cfg_optimization_test(same, expected, consts=[None], expected_consts=[None])
 
     def test_optimize_unary_not(self):
         # test folding
@@ -1706,10 +1744,10 @@ def test_optimize_unary_not(self):
             ('RETURN_VALUE', None, 0),
         ]
         after = [
-            ('LOAD_CONST', 1, 0),
+            ('LOAD_COMMON_CONSTANT', 10, 0),
             ('RETURN_VALUE', None, 0),
         ]
-        self.cfg_optimization_test(before, after, consts=[], expected_consts=[True, False])
+        self.cfg_optimization_test(before, after, consts=[], expected_consts=[True])
 
         # test cancel out
         before = [
@@ -1757,7 +1795,7 @@ def test_optimize_unary_not(self):
             ('RETURN_VALUE', None, 0),
         ]
         after = [
-            ('LOAD_CONST', 0, 0),
+            ('LOAD_COMMON_CONSTANT', 9, 0),
             ('RETURN_VALUE', None, 0),
         ]
         self.cfg_optimization_test(before, after, consts=[], expected_consts=[True])
@@ -1773,10 +1811,10 @@ def test_optimize_unary_not(self):
             ('RETURN_VALUE', None, 0),
         ]
         after = [
-            ('LOAD_CONST', 1, 0),
+            ('LOAD_COMMON_CONSTANT', 10, 0),
             ('RETURN_VALUE', None, 0),
         ]
-        self.cfg_optimization_test(before, after, consts=[], expected_consts=[True, False])
+        self.cfg_optimization_test(before, after, consts=[], expected_consts=[True])
 
         # test cancel out & eliminate to bool (to bool stays as we are not iterating to a fixed point)
         before = [
@@ -2392,7 +2430,7 @@ def test_list_to_tuple_get_iter(self):
             ("LOAD_FAST", 1, 4),
             ("LIST_EXTEND", 1, 5),
             ("CALL_INTRINSIC_1", INTRINSIC_LIST_TO_TUPLE, 6),
-            ("GET_ITER", None, 7),
+            ("GET_ITER", 0, 7),
             top := self.Label(),
             ("FOR_ITER", end := self.Label(), 8),
             ("STORE_FAST", 2, 9),
@@ -2410,7 +2448,7 @@ def test_list_to_tuple_get_iter(self):
             ("LOAD_FAST_BORROW", 1, 4),
             ("LIST_EXTEND", 1, 5),
             ("NOP", None, 6),  # ("CALL_INTRINSIC_1", INTRINSIC_LIST_TO_TUPLE, 6),
-            ("GET_ITER", None, 7),
+            ("GET_ITER", 0, 7),
             top := self.Label(),
             ("FOR_ITER", end := self.Label(), 8),
             ("STORE_FAST", 2, 9),
@@ -2418,7 +2456,7 @@ def test_list_to_tuple_get_iter(self):
             end,
             ("END_FOR", None, 11),
             ("POP_TOP", None, 12),
-            ("LOAD_CONST", 0, 13),
+            ("LOAD_COMMON_CONSTANT", 7, 13),
             ("RETURN_VALUE", None, 14),
         ]
         self.cfg_optimization_test(insts, expected_insts, consts=[None])
@@ -2432,6 +2470,168 @@ def test_list_to_tuple_get_iter_is_safe(self):
         self.assertEqual(b, [3, 2, 1, 0])
         self.assertEqual(items, [])
 
+    def test_fold_constant_big_list_for_iter(self):
+        # for x in [c1, c2, ..., cN] (N > 30) should fold to LOAD_CONST tuple
+        consts = 35
+        before = (
+            [("BUILD_LIST", 0, 1)] +
+            [("LOAD_CONST", 0, 2), ("LIST_APPEND", 1, 3)] * consts +
+            [("GET_ITER", 0, 4),
+             top := self.Label(),
+             ("FOR_ITER", end := self.Label(), 5),
+             ("STORE_FAST", 0, 6),
+             ("JUMP", top, 7),
+             end,
+             ("END_FOR", None, 8),
+             ("POP_ITER", None, 9),
+             ("LOAD_CONST", 0, 10),
+             ("RETURN_VALUE", None, 11)]
+        )
+        after = [
+            ("LOAD_CONST", 1, 3),
+            ("GET_ITER", 0, 4),
+            top := self.Label(),
+            ("FOR_ITER", end := self.Label(), 5),
+            ("STORE_FAST", 0, 6),
+            ("JUMP", top, 7),
+            end,
+            ("END_FOR", None, 8),
+            ("POP_ITER", None, 9),
+            ("LOAD_CONST", 0, 10),
+            ("RETURN_VALUE", None, 11),
+        ]
+        result_const = tuple(["test"] * consts)
+        self.cfg_optimization_test(before, after, consts=["test"],
+                                   expected_consts=["test", result_const])
+
+    def test_fold_constant_big_set_for_iter(self):
+        # for x in {c1, c2, ..., cN} (N > 30) should fold to LOAD_CONST frozenset
+        before = [
+            ("BUILD_SET", 0, 1),
+            ("LOAD_SMALL_INT", 1, 2), ("SET_ADD", 1, 3),
+            ("LOAD_SMALL_INT", 2, 4), ("SET_ADD", 1, 5),
+            ("LOAD_SMALL_INT", 3, 6), ("SET_ADD", 1, 7),
+            ("GET_ITER", 0, 8),
+            top := self.Label(),
+            ("FOR_ITER", end := self.Label(), 9),
+            ("STORE_FAST", 0, 10),
+            ("JUMP", top, 11),
+            end,
+            ("END_FOR", None, 12),
+            ("POP_ITER", None, 13),
+            ("LOAD_CONST", 0, 14),
+            ("RETURN_VALUE", None, 15),
+        ]
+        after = [
+            ("LOAD_CONST", 1, 7),
+            ("GET_ITER", 0, 8),
+            top := self.Label(),
+            ("FOR_ITER", end := self.Label(), 9),
+            ("STORE_FAST", 0, 10),
+            ("JUMP", top, 11),
+            end,
+            ("END_FOR", None, 12),
+            ("POP_ITER", None, 13),
+            ("LOAD_CONST", 0, 14),
+            ("RETURN_VALUE", None, 15),
+        ]
+        self.cfg_optimization_test(before, after, consts=["test"],
+                                   expected_consts=["test", frozenset({1, 2, 3})])
+
+    def test_fold_constant_list_to_tuple_for_iter(self):
+        INTRINSIC_LIST_TO_TUPLE = 6
+        before = [
+            ("BUILD_LIST", 0, 1),
+            ("LOAD_SMALL_INT", 1, 2), ("LIST_APPEND", 1, 3),
+            ("LOAD_SMALL_INT", 2, 4), ("LIST_APPEND", 1, 5),
+            ("LOAD_SMALL_INT", 3, 6), ("LIST_APPEND", 1, 7),
+            ("CALL_INTRINSIC_1", INTRINSIC_LIST_TO_TUPLE, 8),
+            ("GET_ITER", 0, 9),
+            top := self.Label(),
+            ("FOR_ITER", end := self.Label(), 10),
+            ("STORE_FAST", 0, 11),
+            ("JUMP", top, 12),
+            end,
+            ("END_FOR", None, 13),
+            ("POP_ITER", None, 14),
+            ("LOAD_CONST", 0, 15),
+            ("RETURN_VALUE", None, 16),
+        ]
+        after = [
+            ("LOAD_CONST", 1, 8),
+            ("GET_ITER", 0, 9),
+            top := self.Label(),
+            ("FOR_ITER", end := self.Label(), 10),
+            ("STORE_FAST", 0, 11),
+            ("JUMP", top, 12),
+            end,
+            ("END_FOR", None, 13),
+            ("POP_ITER", None, 14),
+            ("LOAD_CONST", 0, 15),
+            ("RETURN_VALUE", None, 16),
+        ]
+        self.cfg_optimization_test(before, after, consts=["test"],
+                                   expected_consts=["test", (1, 2, 3)])
+
+    def test_fold_constant_big_list_contains_op(self):
+        # x in [c1, c2, ..., cN] (N > 30) should fold to LOAD_CONST tuple
+        before = [
+            ("LOAD_FAST", 0, 1),
+            ("BUILD_LIST", 0, 2),
+            ("LOAD_SMALL_INT", 1, 3), ("LIST_APPEND", 1, 4),
+            ("LOAD_SMALL_INT", 2, 5), ("LIST_APPEND", 1, 6),
+            ("LOAD_SMALL_INT", 3, 7), ("LIST_APPEND", 1, 8),
+            ("CONTAINS_OP", 0, 9),
+            ("RETURN_VALUE", None, 10),
+        ]
+        after = [
+            ("LOAD_FAST_BORROW", 0, 1),
+            ("LOAD_CONST", 1, 8),
+            ("CONTAINS_OP", 0, 9),
+            ("RETURN_VALUE", None, 10),
+        ]
+        self.cfg_optimization_test(before, after, consts=[None],
+                                   expected_consts=[None, (1, 2, 3)])
+
+    def test_fold_constant_big_set_contains_op(self):
+        # x in {c1, c2, ..., cN} (N > 30) should fold to LOAD_CONST frozenset
+        before = [
+            ("LOAD_FAST", 0, 1),
+            ("BUILD_SET", 0, 2),
+            ("LOAD_SMALL_INT", 1, 3), ("SET_ADD", 1, 4),
+            ("LOAD_SMALL_INT", 2, 5), ("SET_ADD", 1, 6),
+            ("LOAD_SMALL_INT", 3, 7), ("SET_ADD", 1, 8),
+            ("CONTAINS_OP", 0, 9),
+            ("RETURN_VALUE", None, 10),
+        ]
+        after = [
+            ("LOAD_FAST_BORROW", 0, 1),
+            ("LOAD_CONST", 1, 8),
+            ("CONTAINS_OP", 0, 9),
+            ("RETURN_VALUE", None, 10),
+        ]
+        self.cfg_optimization_test(before, after, consts=[None],
+                                   expected_consts=[None, frozenset({1, 2, 3})])
+
+    def test_no_fold_big_list_for_iter_with_non_const(self):
+        same = [
+            ("BUILD_LIST", 0, 1),
+            ("LOAD_SMALL_INT", 1, 2), ("LIST_APPEND", 1, 3),
+            ("LOAD_FAST_BORROW", 0, 4), ("LIST_APPEND", 1, 5),
+            ("LOAD_SMALL_INT", 3, 6), ("LIST_APPEND", 1, 7),
+            ("GET_ITER", 0, 8),
+            top := self.Label(),
+            ("FOR_ITER", end := self.Label(), 9),
+            ("STORE_FAST", 1, 10),
+            ("JUMP", top, 11),
+            end,
+            ("END_FOR", None, 12),
+            ("POP_ITER", None, 13),
+            ("LOAD_CONST", 0, 14),
+            ("RETURN_VALUE", None, 15),
+        ]
+        self.cfg_optimization_test(same, same, consts=["test"])
+
 
 class OptimizeLoadFastTestCase(DirectCfgOptimizerTests):
     def make_bb(self, insts):
@@ -2442,7 +2642,7 @@ def make_bb(self, insts):
                 maxconst = max(maxconst, arg)
         consts = [None for _ in range(maxconst + 1)]
         return insts + [
-            ("LOAD_CONST", 0, last_loc + 1),
+            ("LOAD_COMMON_CONSTANT", 7, last_loc + 1),
             ("RETURN_VALUE", None, last_loc + 2),
         ], consts
 
@@ -2473,7 +2673,7 @@ def test_optimized(self):
         ]
         expected = [
             ("LOAD_FAST_BORROW", 0, 1),
-            ("LOAD_CONST", 1, 2),
+            ("LOAD_COMMON_CONSTANT", 7, 2),
             ("SWAP", 2, 3),
             ("POP_TOP", None, 4),
         ]
@@ -2511,7 +2711,13 @@ def test_unoptimized_if_support_killed(self):
             ("STORE_FAST", 0, 3),
             ("POP_TOP", None, 4),
         ]
-        self.check(insts, insts)
+        expected = [
+            ("LOAD_FAST", 0, 1),
+            ("LOAD_COMMON_CONSTANT", 7, 2),
+            ("STORE_FAST", 0, 3),
+            ("POP_TOP", None, 4),
+        ]
+        self.check(insts, expected)
 
         insts = [
             ("LOAD_FAST", 0, 1),
@@ -2520,7 +2726,14 @@ def test_unoptimized_if_support_killed(self):
             ("STORE_FAST_STORE_FAST", ((0 << 4) | 1), 4),
             ("POP_TOP", None, 5),
         ]
-        self.check(insts, insts)
+        expected = [
+            ("LOAD_FAST", 0, 1),
+            ("LOAD_COMMON_CONSTANT", 7, 2),
+            ("LOAD_COMMON_CONSTANT", 7, 3),
+            ("STORE_FAST_STORE_FAST", ((0 << 4) | 1), 4),
+            ("POP_TOP", None, 5),
+        ]
+        self.check(insts, expected)
 
         insts = [
             ("LOAD_FAST", 0, 1),
@@ -2541,7 +2754,12 @@ def test_unoptimized_if_aliased(self):
             ("LOAD_CONST", 0, 3),
             ("STORE_FAST_STORE_FAST", ((0 << 4) | 1), 4),
         ]
-        self.check(insts, insts)
+        expected = [
+            ("LOAD_FAST", 0, 1),
+            ("LOAD_COMMON_CONSTANT", 7, 3),
+            ("STORE_FAST_STORE_FAST", ((0 << 4) | 1), 4),
+        ]
+        self.check(insts, expected)
 
     def test_consume_no_inputs(self):
         insts = [
@@ -2586,7 +2804,19 @@ def test_for_iter(self):
             ("LOAD_CONST", 0, 7),
             ("RETURN_VALUE", None, 8),
         ]
-        self.cfg_optimization_test(insts, insts, consts=[None])
+        expected = [
+            ("LOAD_FAST", 0, 1),
+            top := self.Label(),
+            ("FOR_ITER", end := self.Label(), 2),
+            ("STORE_FAST", 2, 3),
+            ("JUMP", top, 4),
+            end,
+            ("END_FOR", None, 5),
+            ("POP_TOP", None, 6),
+            ("LOAD_COMMON_CONSTANT", 7, 7),
+            ("RETURN_VALUE", None, 8),
+        ]
+        self.cfg_optimization_test(insts, expected, consts=[None])
 
     def test_load_attr(self):
         insts = [
@@ -2655,10 +2885,10 @@ def test_send(self):
             ("LOAD_FAST", 0, 1),
             ("LOAD_FAST_BORROW", 1, 2),
             ("SEND", end := self.Label(), 3),
-            ("LOAD_CONST", 0, 4),
+            ("LOAD_COMMON_CONSTANT", 7, 4),
             ("RETURN_VALUE", None, 5),
             end,
-            ("LOAD_CONST", 0, 6),
+            ("LOAD_COMMON_CONSTANT", 7, 6),
             ("RETURN_VALUE", None, 7)
         ]
         self.cfg_optimization_test(insts, expected, consts=[None])
@@ -2696,7 +2926,15 @@ def test_set_function_attribute(self):
             ("LOAD_CONST", 0, 5),
             ("RETURN_VALUE", None, 6)
         ]
-        self.cfg_optimization_test(insts, insts, consts=[None])
+        expected = [
+            ("LOAD_COMMON_CONSTANT", 7, 1),
+            ("LOAD_FAST", 0, 2),
+            ("SET_FUNCTION_ATTRIBUTE", 2, 3),
+            ("STORE_FAST", 1, 4),
+            ("LOAD_COMMON_CONSTANT", 7, 5),
+            ("RETURN_VALUE", None, 6)
+        ]
+        self.cfg_optimization_test(insts, expected, consts=[None])
 
         insts = [
             ("LOAD_CONST", 0, 1),
@@ -2705,7 +2943,7 @@ def test_set_function_attribute(self):
             ("RETURN_VALUE", None, 4)
         ]
         expected = [
-            ("LOAD_CONST", 0, 1),
+            ("LOAD_COMMON_CONSTANT", 7, 1),
             ("LOAD_FAST_BORROW", 0, 2),
             ("SET_FUNCTION_ATTRIBUTE", 2, 3),
             ("RETURN_VALUE", None, 4)
@@ -2713,22 +2951,37 @@ def test_set_function_attribute(self):
         self.cfg_optimization_test(insts, expected, consts=[None])
 
     def test_get_yield_from_iter(self):
-        # GET_YIELD_FROM_ITER may leave its operand on the stack
         insts = [
             ("LOAD_FAST", 0, 1),
-            ("GET_YIELD_FROM_ITER", None, 2),
-            ("LOAD_CONST", 0, 3),
+            ("GET_ITER", 1, 2),
+            ("PUSH_NULL", None, 3),
+            ("LOAD_CONST", 0, 4),
             send := self.Label(),
-            ("SEND", end := self.Label(), 5),
-            ("YIELD_VALUE", 1, 6),
-            ("RESUME", 2, 7),
-            ("JUMP", send, 8),
+            ("SEND", end := self.Label(), 6),
+            ("YIELD_VALUE", 1, 7),
+            ("RESUME", 2, 8),
+            ("JUMP", send, 9),
             end,
-            ("END_SEND", None, 9),
-            ("LOAD_CONST", 0, 10),
-            ("RETURN_VALUE", None, 11),
+            ("END_SEND", None, 10),
+            ("LOAD_CONST", 0, 11),
+            ("RETURN_VALUE", None, 12),
+        ]
+        expected = [
+            ("LOAD_FAST", 0, 1),
+            ("GET_ITER", 1, 2),
+            ("PUSH_NULL", None, 3),
+            ("LOAD_COMMON_CONSTANT", 7, 4),
+            send := self.Label(),
+            ("SEND", end := self.Label(), 6),
+            ("YIELD_VALUE", 1, 7),
+            ("RESUME", 2, 8),
+            ("JUMP", send, 9),
+            end,
+            ("END_SEND", None, 10),
+            ("LOAD_COMMON_CONSTANT", 7, 11),
+            ("RETURN_VALUE", None, 12),
         ]
-        self.cfg_optimization_test(insts, insts, consts=[None])
+        self.cfg_optimization_test(insts, expected, consts=[None])
 
     def test_push_exc_info(self):
         insts = [
diff --git a/Lib/test/test_pickle.py b/Lib/test/test_pickle.py
index 71cd4baa942..1b85eceac17 100644
--- a/Lib/test/test_pickle.py
+++ b/Lib/test/test_pickle.py
@@ -107,6 +107,10 @@ def loads(self, buf, **kwds):
     def test_c_methods(self):
         return super().test_c_methods()
 
+    @unittest.expectedFailureIf(sys.getrecursionlimit() == 256, "TODO: RUSTPYTHON; default debug recursion limit is 256")
+    def test_deep_nested_struct_frozendict(self):
+        return super().test_deep_nested_struct_frozendict()
+
 
 
 
@@ -408,6 +412,10 @@ class CPicklerTests(PyPicklerTests):
         pickler = _pickle.Pickler
         unpickler = _pickle.Unpickler
 
+        @unittest.expectedSuccess  # TODO: RUSTPYTHON; native pickler passes at the default debug recursion limit
+        def test_deep_nested_struct_frozendict(self):
+            return super().test_deep_nested_struct_frozendict()
+
     class CPersPicklerTests(PyPersPicklerTests):
         pickler = _pickle.Pickler
         unpickler = _pickle.Unpickler
@@ -421,6 +429,10 @@ class CDumpPickle_LoadPickle(PyPicklerTests):
         pickler = _pickle.Pickler
         unpickler = pickle._Unpickler
 
+        @unittest.expectedSuccess  # TODO: RUSTPYTHON; native pickler passes at the default debug recursion limit
+        def test_deep_nested_struct_frozendict(self):
+            return super().test_deep_nested_struct_frozendict()
+
     class DumpPickle_CLoadPickle(PyPicklerTests):
         pickler = pickle._Pickler
         unpickler = _pickle.Unpickler
diff --git a/Lib/test/test_pkg.py b/Lib/test/test_pkg.py
index d2b724db40d..0a366e2a5bb 100644
--- a/Lib/test/test_pkg.py
+++ b/Lib/test/test_pkg.py
@@ -198,15 +198,15 @@ def test_5(self):
 
         import t5
         self.assertEqual(fixdir(dir(t5)),
-                         ['__cached__', '__doc__', '__file__', '__loader__',
-                          '__name__', '__package__', '__path__', '__spec__',
-                          'foo', 'string', 't5'])
+                         ['__doc__', '__file__', '__loader__', '__name__',
+                         '__package__', '__path__', '__spec__', 'foo',
+                         'string', 't5'])
         self.assertEqual(fixdir(dir(t5.foo)),
-                         ['__cached__', '__doc__', '__file__', '__loader__',
-                          '__name__', '__package__', '__spec__', 'string'])
+                         ['__doc__', '__file__', '__loader__', '__name__',
+                         '__package__', '__spec__', 'string'])
         self.assertEqual(fixdir(dir(t5.string)),
-                         ['__cached__', '__doc__', '__file__', '__loader__',
-                          '__name__', '__package__', '__spec__', 'spam'])
+                         ['__doc__', '__file__', '__loader__', '__name__',
+                         '__package__', '__spec__', 'spam'])
 
     def test_6(self):
         hier = [
@@ -221,14 +221,13 @@ def test_6(self):
 
         import t6
         self.assertEqual(fixdir(dir(t6)),
-                         ['__all__', '__cached__', '__doc__', '__file__',
-                          '__loader__', '__name__', '__package__', '__path__',
-                          '__spec__'])
+                         ['__all__', '__doc__', '__file__', '__loader__',
+                         '__name__', '__package__', '__path__', '__spec__'])
         s = """
             import t6
             from t6 import *
             self.assertEqual(fixdir(dir(t6)),
-                             ['__all__', '__cached__', '__doc__', '__file__',
+                             ['__all__', '__doc__', '__file__',
                               '__loader__', '__name__', '__package__',
                               '__path__', '__spec__', 'eggs', 'ham', 'spam'])
             self.assertEqual(dir(), ['eggs', 'ham', 'self', 'spam', 't6'])
@@ -256,20 +255,19 @@ def test_7(self):
         t7, sub, subsub = None, None, None
         import t7 as tas
         self.assertEqual(fixdir(dir(tas)),
-                         ['__cached__', '__doc__', '__file__', '__loader__',
-                          '__name__', '__package__', '__path__', '__spec__'])
+                         ['__doc__', '__file__', '__loader__', '__name__',
+                          '__package__', '__path__', '__spec__'])
         self.assertFalse(t7)
         from t7 import sub as subpar
         self.assertEqual(fixdir(dir(subpar)),
-                         ['__cached__', '__doc__', '__file__', '__loader__',
-                          '__name__', '__package__', '__path__', '__spec__'])
+                         ['__doc__', '__file__', '__loader__', '__name__',
+                          '__package__', '__path__', '__spec__'])
         self.assertFalse(t7)
         self.assertFalse(sub)
         from t7.sub import subsub as subsubsub
         self.assertEqual(fixdir(dir(subsubsub)),
-                         ['__cached__', '__doc__', '__file__', '__loader__',
-                          '__name__', '__package__', '__path__', '__spec__',
-                          'spam'])
+                         ['__doc__', '__file__', '__loader__', '__name__',
+                          '__package__', '__path__', '__spec__', 'spam'])
         self.assertFalse(t7)
         self.assertFalse(sub)
         self.assertFalse(subsub)
diff --git a/Lib/test/test_plistlib.py b/Lib/test/test_plistlib.py
index 2dccee9c275..daceceb614d 100644
--- a/Lib/test/test_plistlib.py
+++ b/Lib/test/test_plistlib.py
@@ -792,6 +792,25 @@ def test_dict_members(self):
                 })
                 self.assertIsNot(pl2['first'], pl2['second'])
 
+    def test_frozendict(self):
+        pl = frozendict(
+            aString="Doodah",
+            anInt=728,
+            aDict=frozendict(
+                anotherString="hello",
+                aTrueValue=True,
+            ),
+            aList=["A", "B", 12],
+        )
+
+        for fmt in ALL_FORMATS:
+            with self.subTest(fmt=fmt):
+                data = plistlib.dumps(pl, fmt=fmt)
+                pl2 = plistlib.loads(data)
+                self.assertEqual(pl2, dict(pl))
+                self.assertIsInstance(pl2, dict)
+                self.assertIsInstance(pl2['aDict'], dict)
+
     def test_controlcharacters(self):
         for i in range(128):
             c = chr(i)
diff --git a/Lib/test/test_poplib.py b/Lib/test/test_poplib.py
index ef2da97f867..f08b945c8f5 100644
--- a/Lib/test/test_poplib.py
+++ b/Lib/test/test_poplib.py
@@ -17,6 +17,7 @@
 from test.support import threading_helper
 from test.support import asynchat
 from test.support import asyncore
+from test.support import control_characters_c0
 
 
 test_support.requires_working_socket(module=True)
@@ -184,7 +185,8 @@ def _do_tls_handshake(self):
                 elif err.args[0] == ssl.SSL_ERROR_EOF:
                     return self.handle_close()
                 # TODO: SSLError does not expose alert information
-                elif ("SSLV3_ALERT_BAD_CERTIFICATE" in err.args[1] or
+                elif ("TLS_ALERT_BAD_CERTIFICATE" in err.args[1] or
+                      "SSLV3_ALERT_BAD_CERTIFICATE" in err.args[1] or
                       "SSLV3_ALERT_CERTIFICATE_UNKNOWN" in err.args[1]):
                     return self.handle_close()
                 raise
@@ -395,6 +397,13 @@ def test_quit(self):
         self.assertIsNone(self.client.sock)
         self.assertIsNone(self.client.file)
 
+    def test_control_characters(self):
+        for c0 in control_characters_c0():
+            with self.assertRaises(ValueError):
+                self.client.user(f'user{c0}')
+            with self.assertRaises(ValueError):
+                self.client.pass_(f'{c0}pass')
+
     @requires_ssl
     def test_stls_capa(self):
         capa = self.client.capa()
@@ -415,6 +424,7 @@ def test_stls_context(self):
         self.assertEqual(ctx.check_hostname, True)
         with self.assertRaises(ssl.CertificateError):
             resp = self.client.stls(context=ctx)
+
         self.client = poplib.POP3("localhost", self.server.port,
                                   timeout=test_support.LOOPBACK_TIMEOUT)
         resp = self.client.stls(context=ctx)
diff --git a/Lib/test/test_posixpath.py b/Lib/test/test_posixpath.py
index 21f06712548..a9975b75f7c 100644
--- a/Lib/test/test_posixpath.py
+++ b/Lib/test/test_posixpath.py
@@ -1,3 +1,4 @@
+import errno
 import inspect
 import os
 import posixpath
@@ -5,7 +6,7 @@
 import sys
 import unittest
 from functools import partial
-from posixpath import realpath, abspath, dirname, basename, ALLOW_MISSING
+from posixpath import realpath, abspath, dirname, basename, ALL_BUT_LAST, ALLOW_MISSING
 from test import support
 from test import test_genericpath
 from test.support import import_helper
@@ -448,7 +449,7 @@ def test_normpath(self):
                 self.assertEqual(result, expected)
 
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_curdir(self, kwargs):
         self.assertEqual(realpath('.', **kwargs), os.getcwd())
         self.assertEqual(realpath('./.', **kwargs), os.getcwd())
@@ -459,7 +460,7 @@ def test_realpath_curdir(self, kwargs):
         self.assertEqual(realpath(b'/'.join([b'.'] * 100), **kwargs), os.getcwdb())
 
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_pardir(self, kwargs):
         self.assertEqual(realpath('..', **kwargs), dirname(os.getcwd()))
         self.assertEqual(realpath('../..', **kwargs), dirname(dirname(os.getcwd())))
@@ -495,35 +496,43 @@ def test_realpath_strict(self):
     def test_realpath_invalid_paths(self):
         path = '/\x00'
         self.assertRaises(ValueError, realpath, path, strict=False)
+        self.assertRaises(ValueError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(ValueError, realpath, path, strict=True)
         self.assertRaises(ValueError, realpath, path, strict=ALLOW_MISSING)
         path = b'/\x00'
         self.assertRaises(ValueError, realpath, path, strict=False)
+        self.assertRaises(ValueError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(ValueError, realpath, path, strict=True)
         self.assertRaises(ValueError, realpath, path, strict=ALLOW_MISSING)
         path = '/nonexistent/x\x00'
         self.assertRaises(ValueError, realpath, path, strict=False)
+        self.assertRaises(FileNotFoundError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(FileNotFoundError, realpath, path, strict=True)
         self.assertRaises(ValueError, realpath, path, strict=ALLOW_MISSING)
         path = b'/nonexistent/x\x00'
         self.assertRaises(ValueError, realpath, path, strict=False)
+        self.assertRaises(FileNotFoundError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(FileNotFoundError, realpath, path, strict=True)
         self.assertRaises(ValueError, realpath, path, strict=ALLOW_MISSING)
         path = '/\x00/..'
         self.assertRaises(ValueError, realpath, path, strict=False)
+        self.assertRaises(ValueError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(ValueError, realpath, path, strict=True)
         self.assertRaises(ValueError, realpath, path, strict=ALLOW_MISSING)
         path = b'/\x00/..'
         self.assertRaises(ValueError, realpath, path, strict=False)
+        self.assertRaises(ValueError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(ValueError, realpath, path, strict=True)
         self.assertRaises(ValueError, realpath, path, strict=ALLOW_MISSING)
 
         path = '/nonexistent/x\x00/..'
         self.assertRaises(ValueError, realpath, path, strict=False)
+        self.assertRaises(FileNotFoundError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(FileNotFoundError, realpath, path, strict=True)
         self.assertRaises(ValueError, realpath, path, strict=ALLOW_MISSING)
         path = b'/nonexistent/x\x00/..'
         self.assertRaises(ValueError, realpath, path, strict=False)
+        self.assertRaises(FileNotFoundError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(FileNotFoundError, realpath, path, strict=True)
         self.assertRaises(ValueError, realpath, path, strict=ALLOW_MISSING)
 
@@ -534,6 +543,7 @@ def test_realpath_invalid_paths(self):
             self.assertEqual(realpath(path, strict=ALLOW_MISSING), path)
         else:
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=False)
+            self.assertRaises(UnicodeEncodeError, realpath, path, strict=ALL_BUT_LAST)
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=True)
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=ALLOW_MISSING)
         path = '/nonexistent/\udfff'
@@ -543,6 +553,7 @@ def test_realpath_invalid_paths(self):
         else:
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=False)
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=ALLOW_MISSING)
+        self.assertRaises(FileNotFoundError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(FileNotFoundError, realpath, path, strict=True)
         path = '/\udfff/..'
         if sys.platform == 'win32':
@@ -551,6 +562,7 @@ def test_realpath_invalid_paths(self):
             self.assertEqual(realpath(path, strict=ALLOW_MISSING), '/')
         else:
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=False)
+            self.assertRaises(UnicodeEncodeError, realpath, path, strict=ALL_BUT_LAST)
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=True)
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=ALLOW_MISSING)
         path = '/nonexistent/\udfff/..'
@@ -560,6 +572,7 @@ def test_realpath_invalid_paths(self):
         else:
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=False)
             self.assertRaises(UnicodeEncodeError, realpath, path, strict=ALLOW_MISSING)
+        self.assertRaises(FileNotFoundError, realpath, path, strict=ALL_BUT_LAST)
         self.assertRaises(FileNotFoundError, realpath, path, strict=True)
 
         path = b'/\xff'
@@ -570,9 +583,11 @@ def test_realpath_invalid_paths(self):
         else:
             self.assertEqual(realpath(path, strict=False), path)
             if support.is_wasi:
+                self.assertRaises(OSError, realpath, path, strict=ALL_BUT_LAST)
                 self.assertRaises(OSError, realpath, path, strict=True)
                 self.assertRaises(OSError, realpath, path, strict=ALLOW_MISSING)
             else:
+                self.assertEqual(realpath(path, strict=ALL_BUT_LAST), path)
                 self.assertRaises(FileNotFoundError, realpath, path, strict=True)
                 self.assertEqual(realpath(path, strict=ALLOW_MISSING), path)
         path = b'/nonexistent/\xff'
@@ -582,14 +597,16 @@ def test_realpath_invalid_paths(self):
         else:
             self.assertEqual(realpath(path, strict=False), path)
         if support.is_wasi:
+            self.assertRaises(OSError, realpath, path, strict=ALL_BUT_LAST)
             self.assertRaises(OSError, realpath, path, strict=True)
             self.assertRaises(OSError, realpath, path, strict=ALLOW_MISSING)
         else:
+            self.assertRaises(FileNotFoundError, realpath, path, strict=ALL_BUT_LAST)
             self.assertRaises(FileNotFoundError, realpath, path, strict=True)
 
     @os_helper.skip_unless_symlink
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_relative(self, kwargs):
         try:
             os.symlink(posixpath.relpath(ABSTFN+"1"), ABSTFN)
@@ -599,12 +616,14 @@ def test_realpath_relative(self, kwargs):
 
     @os_helper.skip_unless_symlink
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': ALLOW_MISSING})
-    def test_realpath_missing_pardir(self, kwargs):
+    def test_realpath_missing_pardir(self):
         try:
             os.symlink(TESTFN + "1", TESTFN)
-            self.assertEqual(
-                realpath("nonexistent/../" + TESTFN, **kwargs), ABSTFN + "1")
+            path = "nonexistent/../" + TESTFN
+            self.assertEqual(realpath(path), ABSTFN + "1")
+            self.assertEqual(realpath(path, strict=ALLOW_MISSING), ABSTFN + "1")
+            self.assertRaises(FileNotFoundError, realpath, path, strict=ALL_BUT_LAST)
+            self.assertRaises(FileNotFoundError, realpath, path, strict=True)
         finally:
             os_helper.unlink(TESTFN)
 
@@ -651,7 +670,7 @@ def test_realpath_symlink_loops(self):
 
     @os_helper.skip_unless_symlink
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_symlink_loops_strict(self, kwargs):
         # Bug #43757, raise OSError if we get into an infinite symlink loop in
         # the strict modes.
@@ -693,7 +712,7 @@ def test_realpath_symlink_loops_strict(self, kwargs):
 
     @os_helper.skip_unless_symlink
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_repeated_indirect_symlinks(self, kwargs):
         # Issue #6975.
         try:
@@ -708,7 +727,7 @@ def test_realpath_repeated_indirect_symlinks(self, kwargs):
 
     @os_helper.skip_unless_symlink
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_deep_recursion(self, kwargs):
         depth = 10
         try:
@@ -728,7 +747,7 @@ def test_realpath_deep_recursion(self, kwargs):
 
     @os_helper.skip_unless_symlink
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_resolve_parents(self, kwargs):
         # We also need to resolve any symlinks in the parents of a relative
         # path passed to realpath. E.g.: current working directory is
@@ -749,7 +768,7 @@ def test_realpath_resolve_parents(self, kwargs):
 
     @os_helper.skip_unless_symlink
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_resolve_before_normalizing(self, kwargs):
         # Bug #990669: Symbolic links should be resolved before we
         # normalize the path. E.g.: if we have directories 'a', 'k' and 'y'
@@ -778,7 +797,7 @@ def test_realpath_resolve_before_normalizing(self, kwargs):
 
     @os_helper.skip_unless_symlink
     @skip_if_ABSTFN_contains_backslash
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_resolve_first(self, kwargs):
         # Bug #1213894: The first component of the path, if not absolute,
         # must be resolved too.
@@ -816,7 +835,7 @@ def test_realpath_unreadable_symlink(self):
     @skip_if_ABSTFN_contains_backslash
     @unittest.skipIf(os.chmod not in os.supports_follow_symlinks, "Can't set symlink permissions")
     @unittest.skipIf(sys.platform != "darwin", "only macOS requires read permission to readlink()")
-    @_parameterize({'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_realpath_unreadable_symlink_strict(self, kwargs):
         try:
             os.symlink(ABSTFN+"1", ABSTFN)
@@ -842,6 +861,7 @@ def test_realpath_unreadable_directory(self):
             os.chmod(ABSTFN, 0o000)
             self.assertEqual(realpath(ABSTFN, strict=False), ABSTFN)
             self.assertEqual(realpath(ABSTFN, strict=True), ABSTFN)
+            self.assertEqual(realpath(ABSTFN, strict=ALL_BUT_LAST), ABSTFN)
             self.assertEqual(realpath(ABSTFN, strict=ALLOW_MISSING), ABSTFN)
 
             try:
@@ -855,6 +875,8 @@ def test_realpath_unreadable_directory(self):
                              ABSTFN + '/k')
             self.assertRaises(PermissionError, realpath, ABSTFN + '/k',
                               strict=True)
+            self.assertRaises(PermissionError, realpath, ABSTFN + '/k',
+                              strict=ALL_BUT_LAST)
             self.assertRaises(PermissionError, realpath, ABSTFN + '/k',
                               strict=ALLOW_MISSING)
 
@@ -862,6 +884,8 @@ def test_realpath_unreadable_directory(self):
                              ABSTFN + '/missing')
             self.assertRaises(PermissionError, realpath, ABSTFN + '/missing',
                               strict=True)
+            self.assertRaises(PermissionError, realpath, ABSTFN + '/missing',
+                              strict=ALL_BUT_LAST)
             self.assertRaises(PermissionError, realpath, ABSTFN + '/missing',
                               strict=ALLOW_MISSING)
         finally:
@@ -875,25 +899,30 @@ def test_realpath_nonterminal_file(self):
             with open(ABSTFN, 'w') as f:
                 f.write('test_posixpath wuz ere')
             self.assertEqual(realpath(ABSTFN, strict=False), ABSTFN)
+            self.assertEqual(realpath(ABSTFN, strict=ALL_BUT_LAST), ABSTFN)
             self.assertEqual(realpath(ABSTFN, strict=True), ABSTFN)
             self.assertEqual(realpath(ABSTFN, strict=ALLOW_MISSING), ABSTFN)
 
             self.assertEqual(realpath(ABSTFN + "/", strict=False), ABSTFN)
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/.", strict=False), ABSTFN)
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/..", strict=False), dirname(ABSTFN))
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/subdir", strict=False), ABSTFN + "/subdir")
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir",
                               strict=ALLOW_MISSING)
@@ -908,25 +937,30 @@ def test_realpath_nonterminal_symlink_to_file(self):
                 f.write('test_posixpath wuz ere')
             os.symlink(ABSTFN + "1", ABSTFN)
             self.assertEqual(realpath(ABSTFN, strict=False), ABSTFN + "1")
+            self.assertEqual(realpath(ABSTFN, strict=ALL_BUT_LAST), ABSTFN + "1")
             self.assertEqual(realpath(ABSTFN, strict=True), ABSTFN + "1")
             self.assertEqual(realpath(ABSTFN, strict=ALLOW_MISSING), ABSTFN + "1")
 
             self.assertEqual(realpath(ABSTFN + "/", strict=False), ABSTFN + "1")
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/.", strict=False), ABSTFN + "1")
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/..", strict=False), dirname(ABSTFN))
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/subdir", strict=False), ABSTFN + "1/subdir")
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir",
                               strict=ALLOW_MISSING)
@@ -943,25 +977,30 @@ def test_realpath_nonterminal_symlink_to_symlinks_to_file(self):
             os.symlink(ABSTFN + "2", ABSTFN + "1")
             os.symlink(ABSTFN + "1", ABSTFN)
             self.assertEqual(realpath(ABSTFN, strict=False), ABSTFN + "2")
+            self.assertEqual(realpath(ABSTFN, strict=ALL_BUT_LAST), ABSTFN + "2")
             self.assertEqual(realpath(ABSTFN, strict=True), ABSTFN + "2")
             self.assertEqual(realpath(ABSTFN, strict=True), ABSTFN + "2")
 
             self.assertEqual(realpath(ABSTFN + "/", strict=False), ABSTFN + "2")
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/.", strict=False), ABSTFN + "2")
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/.",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/..", strict=False), dirname(ABSTFN))
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/..",
                               strict=ALLOW_MISSING)
 
             self.assertEqual(realpath(ABSTFN + "/subdir", strict=False), ABSTFN + "2/subdir")
+            self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=ALL_BUT_LAST)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir", strict=True)
             self.assertRaises(NotADirectoryError, realpath, ABSTFN + "/subdir",
                               strict=ALLOW_MISSING)
@@ -970,6 +1009,98 @@ def test_realpath_nonterminal_symlink_to_symlinks_to_file(self):
             os_helper.unlink(ABSTFN + "1")
             os_helper.unlink(ABSTFN + "2")
 
+    @os_helper.skip_unless_symlink
+    def test_realpath_mode(self):
+        self.addCleanup(os_helper.rmdir, ABSTFN)
+        self.addCleanup(os_helper.rmdir, ABSTFN + "/dir")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/file")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/dir/file2")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/link")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/link2")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/broken")
+        self.addCleanup(os_helper.unlink, ABSTFN + "/cycle")
+
+        os.mkdir(ABSTFN)
+        os.mkdir(ABSTFN + "/dir")
+        open(ABSTFN + "/file", "wb").close()
+        open(ABSTFN + "/dir/file2", "wb").close()
+        os.symlink("file", ABSTFN + "/link")
+        os.symlink("dir", ABSTFN + "/link2")
+        os.symlink("nonexistent", ABSTFN + "/broken")
+        os.symlink("cycle", ABSTFN + "/cycle")
+        def check(path, modes, expected, errno=None):
+            if isinstance(expected, str):
+                assert errno is None
+                expected = expected.replace('/', os.sep)
+                for mode in modes:
+                    with self.subTest(mode=mode):
+                        self.assertEqual(realpath(path, strict=mode).replace('/', os.sep),
+                                         ABSTFN.replace('/', os.sep) + expected)
+            else:
+                for mode in modes:
+                    with self.subTest(mode=mode):
+                        with self.assertRaises(expected) as cm:
+                            realpath(path, strict=mode)
+                        if errno is not None:
+                            self.assertEqual(cm.exception.errno, errno)
+
+        self.enterContext(os_helper.change_cwd(ABSTFN))
+        all_modes = [False, ALLOW_MISSING, ALL_BUT_LAST, True]
+        check("file", all_modes, "/file")
+        check("file/", [False], "/file")
+        check("file/", [ALLOW_MISSING, ALL_BUT_LAST, True], NotADirectoryError)
+        check("file/file2", [False], "/file/file2")
+        check("file/file2", [ALLOW_MISSING, ALL_BUT_LAST, True], NotADirectoryError)
+        check("file/.", [False], "/file")
+        check("file/.", [ALLOW_MISSING, ALL_BUT_LAST, True], NotADirectoryError)
+        check("file/../link2", [False], "/dir")
+        check("file/../link2", [ALLOW_MISSING, ALL_BUT_LAST, True], NotADirectoryError)
+
+        check("dir", all_modes, "/dir")
+        check("dir/", all_modes, "/dir")
+        check("dir/file2", all_modes, "/dir/file2")
+
+        check("link", all_modes, "/file")
+        check("link/", [False], "/file")
+        check("link/", [ALLOW_MISSING, ALL_BUT_LAST, True], NotADirectoryError)
+        check("link/file2", [False], "/file/file2")
+        check("link/file2", [ALLOW_MISSING, ALL_BUT_LAST, True], NotADirectoryError)
+        check("link/.", [False], "/file")
+        check("link/.", [ALLOW_MISSING, ALL_BUT_LAST, True], NotADirectoryError)
+        check("link/../link", [False], "/file")
+        check("link/../link", [ALLOW_MISSING, ALL_BUT_LAST, True], NotADirectoryError)
+
+        check("link2", all_modes, "/dir")
+        check("link2/", all_modes, "/dir")
+        check("link2/file2", all_modes, "/dir/file2")
+
+        check("nonexistent", [False, ALLOW_MISSING, ALL_BUT_LAST], "/nonexistent")
+        check("nonexistent", [True], FileNotFoundError)
+        check("nonexistent/", [False, ALLOW_MISSING, ALL_BUT_LAST], "/nonexistent")
+        check("nonexistent/", [True], FileNotFoundError)
+        check("nonexistent/file", [False, ALLOW_MISSING], "/nonexistent/file")
+        check("nonexistent/file", [ALL_BUT_LAST, True], FileNotFoundError)
+        check("nonexistent/../link", [False, ALLOW_MISSING], "/file")
+        check("nonexistent/../link", [ALL_BUT_LAST, True], FileNotFoundError)
+
+        check("broken", [False, ALLOW_MISSING, ALL_BUT_LAST], "/nonexistent")
+        check("broken", [True], FileNotFoundError)
+        check("broken/", [False, ALLOW_MISSING, ALL_BUT_LAST], "/nonexistent")
+        check("broken/", [True], FileNotFoundError)
+        check("broken/file", [False, ALLOW_MISSING], "/nonexistent/file")
+        check("broken/file", [ALL_BUT_LAST, True], FileNotFoundError)
+        check("broken/../link", [False, ALLOW_MISSING], "/file")
+        check("broken/../link", [ALL_BUT_LAST, True], FileNotFoundError)
+
+        check("cycle", [False], "/cycle")
+        check("cycle", [ALLOW_MISSING, ALL_BUT_LAST, True], OSError, errno.ELOOP)
+        check("cycle/", [False], "/cycle")
+        check("cycle/", [ALLOW_MISSING, ALL_BUT_LAST, True], OSError, errno.ELOOP)
+        check("cycle/file", [False], "/cycle/file")
+        check("cycle/file", [ALLOW_MISSING, ALL_BUT_LAST, True], OSError, errno.ELOOP)
+        check("cycle/../link", [False], "/file")
+        check("cycle/../link", [ALLOW_MISSING, ALL_BUT_LAST, True], OSError, errno.ELOOP)
+
     def test_relpath(self):
         (real_getcwd, os.getcwd) = (os.getcwd, lambda: r"/home/user/bar")
         try:
@@ -1152,7 +1283,7 @@ def test_path_normpath(self):
     def test_path_abspath(self):
         self.assertPathEqual(self.path.abspath)
 
-    @_parameterize({}, {'strict': True}, {'strict': ALLOW_MISSING})
+    @_parameterize({}, {'strict': True}, {'strict': ALL_BUT_LAST}, {'strict': ALLOW_MISSING})
     def test_path_realpath(self, kwargs):
         self.assertPathEqual(self.path.realpath)
 
diff --git a/Lib/test/test_pprint.py b/Lib/test/test_pprint.py
index 403d2e90084..dcb1cd69307 100644
--- a/Lib/test/test_pprint.py
+++ b/Lib/test/test_pprint.py
@@ -10,6 +10,7 @@
 import re
 import types
 import unittest
+from collections.abc import ItemsView, KeysView, Mapping, MappingView, ValuesView
 
 from test.support import cpython_only
 from test.support.import_helper import ensure_lazy_imports
@@ -66,10 +67,25 @@ class dict3(dict):
     def __repr__(self):
         return dict.__repr__(self)
 
+class frozendict2(frozendict):
+    pass
+
+class frozendict3(frozendict):
+    def __repr__(self):
+        return frozendict.__repr__(self)
+
 class dict_custom_repr(dict):
     def __repr__(self):
         return '*'*len(dict.__repr__(self))
 
+class mappingview_custom_repr(MappingView):
+    def __repr__(self):
+        return '*'*len(MappingView.__repr__(self))
+
+class keysview_custom_repr(KeysView):
+    def __repr__(self):
+        return '*'*len(KeysView.__repr__(self))
+
 @dataclasses.dataclass
 class dataclass1:
     field1: str
@@ -148,6 +164,7 @@ def test_init(self):
         self.assertRaises(ValueError, pprint.PrettyPrinter, depth=0)
         self.assertRaises(ValueError, pprint.PrettyPrinter, depth=-1)
         self.assertRaises(ValueError, pprint.PrettyPrinter, width=0)
+        self.assertRaises(ValueError, pprint.PrettyPrinter, compact=True, expand=True)
 
     def test_basic(self):
         # Verify .isrecursive() and .isreadable() w/o recursion
@@ -180,10 +197,17 @@ def test_knotted(self):
         # Messy dict.
         self.d = {}
         self.d[0] = self.d[1] = self.d[2] = self.d
+        self.e = {}
+        self.v = ValuesView(self.e)
+        self.m = MappingView(self.e)
+        self.dv = self.e.values()
+        self.e["v"] = self.v
+        self.e["m"] = self.m
+        self.e["dv"] = self.dv
 
         pp = pprint.PrettyPrinter()
 
-        for icky in self.a, self.b, self.d, (self.d, self.d):
+        for icky in self.a, self.b, self.d, (self.d, self.d), self.e, self.v, self.m, self.dv:
             self.assertTrue(pprint.isrecursive(icky), "expected isrecursive")
             self.assertFalse(pprint.isreadable(icky), "expected not isreadable")
             self.assertTrue(pp.isrecursive(icky), "expected isrecursive")
@@ -191,10 +215,11 @@ def test_knotted(self):
 
         # Break the cycles.
         self.d.clear()
+        self.e.clear()
         del self.a[:]
         del self.b[:]
 
-        for safe in self.a, self.b, self.d, (self.d, self.d):
+        for safe in self.a, self.b, self.d, (self.d, self.d), self.e, self.v, self.m, self.dv:
             # module-level convenience functions
             self.assertFalse(pprint.isrecursive(safe),
                              "expected not isrecursive for %r" % (safe,))
@@ -237,15 +262,24 @@ def test_same_as_repr(self):
                        set(), set2(), set3(),
                        frozenset(), frozenset2(), frozenset3(),
                        {}, dict2(), dict3(),
+                       frozendict(), frozendict2(), frozendict3(),
+                       {}.keys(), {}.values(), {}.items(),
+                       MappingView({}), KeysView({}), ItemsView({}), ValuesView({}),
                        self.assertTrue, pprint,
                        -6, -6, -6-6j, -1.5, "x", b"x", bytearray(b"x"),
                        (3,), [3], {3: 6},
-                       (1,2), [3,4], {5: 6},
+                       (1,2), [3,4],
                        tuple2((1,2)), tuple3((1,2)), tuple3(range(100)),
                        [3,4], list2([3,4]), list3([3,4]), list3(range(100)),
                        set({7}), set2({7}), set3({7}),
                        frozenset({8}), frozenset2({8}), frozenset3({8}),
-                       dict2({5: 6}), dict3({5: 6}),
+                       {5: 6}, dict2({5: 6}), dict3({5: 6}),
+                       frozendict({5: 6}), frozendict2({5: 6}), frozendict3({5: 6}),
+                       {5: 6}.keys(), {5: 6}.values(), {5: 6}.items(),
+                       frozendict({5: 6}).keys(), frozendict({5: 6}).values(),
+                       frozendict({5: 6}).items(),
+                       MappingView({5: 6}), KeysView({5: 6}),
+                       ItemsView({5: 6}), ValuesView({5: 6}),
                        range(10, -11, -1),
                        True, False, None, ...,
                       ):
@@ -275,6 +309,12 @@ def test_container_repr_override_called(self):
                      dict_custom_repr(),
                      dict_custom_repr({5: 6}),
                      dict_custom_repr(zip(range(N),range(N))),
+                     mappingview_custom_repr({}),
+                     mappingview_custom_repr({5: 6}),
+                     mappingview_custom_repr(dict(zip(range(N),range(N)))),
+                     keysview_custom_repr({}),
+                     keysview_custom_repr({5: 6}),
+                     keysview_custom_repr(dict(zip(range(N),range(N)))),
                     ):
             native = repr(cont)
             expected = '*' * len(native)
@@ -302,6 +342,81 @@ def test_basic_line_wrap(self):
         for type in [dict, dict2]:
             self.assertEqual(pprint.pformat(type(o)), exp)
 
+        exp = """\
+frozendict({'RPM_cal': 0,
+            'RPM_cal2': 48059,
+            'Speed_cal': 0,
+            'controldesk_runtime_us': 0,
+            'main_code_runtime_us': 0,
+            'read_io_runtime_us': 0,
+            'write_io_runtime_us': 43690})"""
+        self.assertEqual(pprint.pformat(frozendict(o)), exp)
+        exp = """\
+frozendict2({'RPM_cal': 0,
+             'RPM_cal2': 48059,
+             'Speed_cal': 0,
+             'controldesk_runtime_us': 0,
+             'main_code_runtime_us': 0,
+             'read_io_runtime_us': 0,
+             'write_io_runtime_us': 43690})"""
+        self.assertEqual(pprint.pformat(frozendict2(o)), exp)
+
+        o = range(100)
+        exp = 'dict_keys([%s])' % ',\n '.join(map(str, o))
+        keys = dict.fromkeys(o).keys()
+        self.assertEqual(pprint.pformat(keys), exp)
+        keys = frozendict.fromkeys(o).keys()
+        self.assertEqual(pprint.pformat(keys), exp)
+
+        o = range(100)
+        exp = 'dict_values([%s])' % ',\n '.join(map(str, o))
+        values = {v: v for v in o}.values()
+        self.assertEqual(pprint.pformat(values), exp)
+        values = frozendict({v: v for v in o}).values()
+        self.assertEqual(pprint.pformat(values), exp)
+
+        o = range(100)
+        exp = 'dict_items([%s])' % ',\n '.join("(%s, %s)" % (i, i) for i in o)
+        items = {v: v for v in o}.items()
+        self.assertEqual(pprint.pformat(items), exp)
+        items = frozendict({v: v for v in o}).items()
+        self.assertEqual(pprint.pformat(items), exp)
+
+        o = range(100)
+        exp = 'odict_keys([%s])' % ',\n '.join(map(str, o))
+        keys = collections.OrderedDict.fromkeys(o).keys()
+        self.assertEqual(pprint.pformat(keys), exp)
+
+        o = range(100)
+        exp = 'odict_values([%s])' % ',\n '.join(map(str, o))
+        values = collections.OrderedDict({v: v for v in o}).values()
+        self.assertEqual(pprint.pformat(values), exp)
+
+        o = range(100)
+        exp = 'odict_items([%s])' % ',\n '.join("(%s, %s)" % (i, i) for i in o)
+        items = collections.OrderedDict({v: v for v in o}).items()
+        self.assertEqual(pprint.pformat(items), exp)
+
+        o = range(100)
+        exp = 'KeysView({%s})' % (': None,\n '.join(map(str, o)) + ': None')
+        keys_view = KeysView(dict.fromkeys(o))
+        self.assertEqual(pprint.pformat(keys_view), exp)
+
+        o = range(100)
+        exp = 'ItemsView({%s})' % (': None,\n '.join(map(str, o)) + ': None')
+        items_view = ItemsView(dict.fromkeys(o))
+        self.assertEqual(pprint.pformat(items_view), exp)
+
+        o = range(100)
+        exp = 'MappingView({%s})' % (': None,\n '.join(map(str, o)) + ': None')
+        mapping_view = MappingView(dict.fromkeys(o))
+        self.assertEqual(pprint.pformat(mapping_view), exp)
+
+        o = range(100)
+        exp = 'ValuesView({%s})' % (': None,\n '.join(map(str, o)) + ': None')
+        values_view = ValuesView(dict.fromkeys(o))
+        self.assertEqual(pprint.pformat(values_view), exp)
+
         o = range(100)
         exp = '[%s]' % ',\n '.join(map(str, o))
         for type in [list, list2]:
@@ -425,6 +540,30 @@ def test_ordered_dict(self):
              ('a', 6),
              ('lazy', 7),
              ('dog', 8)])""")
+        self.assertEqual(pprint.pformat(d.keys(), sort_dicts=False),
+"""\
+odict_keys(['the',
+ 'quick',
+ 'brown',
+ 'fox',
+ 'jumped',
+ 'over',
+ 'a',
+ 'lazy',
+ 'dog'])""")
+        self.assertEqual(pprint.pformat(d.items(), sort_dicts=False),
+"""\
+odict_items([('the', 0),
+ ('quick', 1),
+ ('brown', 2),
+ ('fox', 3),
+ ('jumped', 4),
+ ('over', 5),
+ ('a', 6),
+ ('lazy', 7),
+ ('dog', 8)])""")
+        self.assertEqual(pprint.pformat(d.values(), sort_dicts=False),
+                         "odict_values([0, 1, 2, 3, 4, 5, 6, 7, 8])")
 
     def test_mapping_proxy(self):
         words = 'the quick brown fox jumped over a lazy dog'.split()
@@ -453,6 +592,152 @@ def test_mapping_proxy(self):
                           ('lazy', 7),
                           ('dog', 8)]))""")
 
+    def test_dict_views(self):
+        for dict_class in (dict, collections.OrderedDict, collections.Counter):
+            empty = dict_class({})
+            short = dict_class(dict(zip('edcba', 'edcba')))
+            long = dict_class(dict((chr(x), chr(x)) for x in range(90, 64, -1)))
+            lengths = {"empty": empty, "short": short, "long": long}
+            prefix = "odict" if dict_class is collections.OrderedDict else "dict"
+            for name, d in lengths.items():
+                with self.subTest(length=name, prefix=prefix):
+                    is_short = len(d) < 6
+                    joiner = ", " if is_short else ",\n "
+                    k = d.keys()
+                    v = d.values()
+                    i = d.items()
+                    self.assertEqual(pprint.pformat(k, sort_dicts=True),
+                                     prefix + "_keys([%s])" %
+                                     joiner.join(repr(key) for key in sorted(k)))
+                    self.assertEqual(pprint.pformat(v, sort_dicts=True),
+                                     prefix + "_values([%s])" %
+                                     joiner.join(repr(val) for val in sorted(v)))
+                    self.assertEqual(pprint.pformat(i, sort_dicts=True),
+                                     prefix + "_items([%s])" %
+                                     joiner.join(repr(item) for item in sorted(i)))
+                    self.assertEqual(pprint.pformat(k, sort_dicts=False),
+                                     prefix + "_keys([%s])" %
+                                     joiner.join(repr(key) for key in k))
+                    self.assertEqual(pprint.pformat(v, sort_dicts=False),
+                                     prefix + "_values([%s])" %
+                                     joiner.join(repr(val) for val in v))
+                    self.assertEqual(pprint.pformat(i, sort_dicts=False),
+                                     prefix + "_items([%s])" %
+                                     joiner.join(repr(item) for item in i))
+
+    def test_abc_views(self):
+        empty = {}
+        short = dict(zip('edcba', 'edcba'))
+        long = dict((chr(x), chr(x)) for x in range(90, 64, -1))
+        lengths = {"empty": empty, "short": short, "long": long}
+        # Test that a subclass that doesn't replace __repr__ works with different lengths
+        class MV(MappingView): pass
+
+        for name, d in lengths.items():
+            with self.subTest(length=name, name="Views"):
+                is_short = len(d) < 6
+                joiner = ", " if is_short else ",\n "
+                i = d.items()
+                s = sorted(i)
+                joined_items = "({%s})" % joiner.join(["%r: %r" % (k, v) for (k, v) in i])
+                sorted_items = "({%s})" % joiner.join(["%r: %r" % (k, v) for (k, v) in s])
+                self.assertEqual(pprint.pformat(KeysView(d), sort_dicts=True),
+                                 KeysView.__name__ + sorted_items)
+                self.assertEqual(pprint.pformat(ItemsView(d), sort_dicts=True),
+                                 ItemsView.__name__ + sorted_items)
+                self.assertEqual(pprint.pformat(MappingView(d), sort_dicts=True),
+                                 MappingView.__name__ + sorted_items)
+                self.assertEqual(pprint.pformat(MV(d), sort_dicts=True),
+                                 MV.__name__ + sorted_items)
+                self.assertEqual(pprint.pformat(ValuesView(d), sort_dicts=True),
+                                 ValuesView.__name__ + sorted_items)
+                self.assertEqual(pprint.pformat(KeysView(d), sort_dicts=False),
+                                 KeysView.__name__ + joined_items)
+                self.assertEqual(pprint.pformat(ItemsView(d), sort_dicts=False),
+                                 ItemsView.__name__ + joined_items)
+                self.assertEqual(pprint.pformat(MappingView(d), sort_dicts=False),
+                                 MappingView.__name__ + joined_items)
+                self.assertEqual(pprint.pformat(MV(d), sort_dicts=False),
+                                 MV.__name__ + joined_items)
+                self.assertEqual(pprint.pformat(ValuesView(d), sort_dicts=False),
+                                 ValuesView.__name__ + joined_items)
+
+    def test_nested_views(self):
+        d = {1: MappingView({1: MappingView({1: MappingView({1: 2})})})}
+        self.assertEqual(repr(d),
+                         "{1: MappingView({1: MappingView({1: MappingView({1: 2})})})}")
+        self.assertEqual(pprint.pformat(d),
+                         "{1: MappingView({1: MappingView({1: MappingView({1: 2})})})}")
+        self.assertEqual(pprint.pformat(d, depth=2),
+                         "{1: MappingView({1: {...}})}")
+        d = {}
+        d1 = {1: d.values()}
+        d2 = {1: d1.values()}
+        d3 = {1: d2.values()}
+        self.assertEqual(pprint.pformat(d3),
+                         "{1: dict_values([dict_values([dict_values([])])])}")
+        self.assertEqual(pprint.pformat(d3, depth=2),
+                         "{1: dict_values([{...}])}")
+
+    def test_unorderable_items_views(self):
+        """Check that views with unorderable items have stable sorting."""
+        d = dict((((3+1j), 3), ((1+1j), (1+0j)), (1j, 0j), (500, None), (499, None)))
+        iv = ItemsView(d)
+        self.assertEqual(pprint.pformat(iv),
+                         pprint.pformat(iv))
+        self.assertTrue(pprint.pformat(iv).endswith(", 499: None, 500: None})"),
+                        pprint.pformat(iv))
+        self.assertEqual(pprint.pformat(d.items()),  # Won't be equal unless _safe_tuple
+                         pprint.pformat(d.items()))  # is used in _safe_repr
+        self.assertTrue(pprint.pformat(d.items()).endswith(", (499, None), (500, None)])"))
+
+    def test_mapping_view_subclass_no_mapping(self):
+        class BMV(MappingView):
+            def __init__(self, d):
+                super().__init__(d)
+                self.mapping = self._mapping
+                del self._mapping
+
+        self.assertRaises(AttributeError, pprint.pformat, BMV({}))
+
+    def test_mapping_subclass_repr(self):
+        """Test that mapping ABC views use their ._mapping's __repr__."""
+        class MyMapping(Mapping):
+            def __init__(self, keys=None):
+                self._keys = {} if keys is None else dict.fromkeys(keys)
+
+            def __getitem__(self, item):
+                return self._keys[item]
+
+            def __len__(self):
+                return len(self._keys)
+
+            def __iter__(self):
+                return iter(self._keys)
+
+            def __repr__(self):
+                return f"{self.__class__.__name__}([{', '.join(map(repr, self._keys.keys()))}])"
+
+        m = MyMapping(["test", 1])
+        self.assertEqual(repr(m), "MyMapping(['test', 1])")
+        short_view_repr = "%s(MyMapping(['test', 1]))"
+        self.assertEqual(repr(m.keys()), short_view_repr % "KeysView")
+        self.assertEqual(pprint.pformat(m.items()), short_view_repr % "ItemsView")
+        self.assertEqual(pprint.pformat(m.keys()), short_view_repr % "KeysView")
+        self.assertEqual(pprint.pformat(MappingView(m)), short_view_repr % "MappingView")
+        self.assertEqual(pprint.pformat(m.values()), short_view_repr % "ValuesView")
+
+        alpha = "abcdefghijklmnopqrstuvwxyz"
+        m = MyMapping(alpha)
+        alpha_repr = ", ".join(map(repr, list(alpha)))
+        long_view_repr = "%%s(MyMapping([%s]))" % alpha_repr
+        self.assertEqual(repr(m), "MyMapping([%s])" % alpha_repr)
+        self.assertEqual(repr(m.keys()), long_view_repr % "KeysView")
+        self.assertEqual(pprint.pformat(m.items()), long_view_repr % "ItemsView")
+        self.assertEqual(pprint.pformat(m.keys()), long_view_repr % "KeysView")
+        self.assertEqual(pprint.pformat(MappingView(m)), long_view_repr % "MappingView")
+        self.assertEqual(pprint.pformat(m.values()), long_view_repr % "ValuesView")
+
     def test_empty_simple_namespace(self):
         ns = types.SimpleNamespace()
         formatted = pprint.pformat(ns)
@@ -768,6 +1053,10 @@ def test_sort_unorderable_values(self):
             'frozenset({' + ','.join(map(repr, skeys)) + '})')
         self.assertEqual(clean(pprint.pformat(dict.fromkeys(keys))),
             '{' + ','.join('%r:None' % k for k in skeys) + '}')
+        self.assertEqual(clean(pprint.pformat(dict.fromkeys(keys).keys())),
+            'dict_keys([' + ','.join('%r' % k for k in skeys) + '])')
+        self.assertEqual(clean(pprint.pformat(dict.fromkeys(keys).items())),
+            'dict_items([' + ','.join('(%r,None)' % k for k in skeys) + '])')
 
         # Issue 10017: TypeError on user-defined types as dict keys.
         self.assertEqual(pprint.pformat({Unorderable: 0, 1: 0}),
@@ -1010,6 +1299,12 @@ def test_counter(self):
          'e': 4,
          'n': 2,
          'l': 1})""")
+        self.assertEqual(pprint.pformat(d, indent=2, width=1),
+"""\
+Counter({ 's': 6,
+          'e': 4,
+          'n': 2,
+          'l': 1})""")
 
     def test_chainmap(self):
         d = collections.ChainMap()
@@ -1049,6 +1344,66 @@ def test_chainmap(self):
                       ('a', 6),
                       ('lazy', 7),
                       ('dog', 8)]))""")
+        self.assertEqual(pprint.pformat(d.keys()),
+"""\
+KeysView(ChainMap({'a': 6,
+          'brown': 2,
+          'dog': 8,
+          'fox': 3,
+          'jumped': 4,
+          'lazy': 7,
+          'over': 5,
+          'quick': 1,
+          'the': 0},
+         OrderedDict([('the', 0),
+                      ('quick', 1),
+                      ('brown', 2),
+                      ('fox', 3),
+                      ('jumped', 4),
+                      ('over', 5),
+                      ('a', 6),
+                      ('lazy', 7),
+                      ('dog', 8)])))""")
+        self.assertEqual(pprint.pformat(d.items()),
+ """\
+ItemsView(ChainMap({'a': 6,
+          'brown': 2,
+          'dog': 8,
+          'fox': 3,
+          'jumped': 4,
+          'lazy': 7,
+          'over': 5,
+          'quick': 1,
+          'the': 0},
+         OrderedDict([('the', 0),
+                      ('quick', 1),
+                      ('brown', 2),
+                      ('fox', 3),
+                      ('jumped', 4),
+                      ('over', 5),
+                      ('a', 6),
+                      ('lazy', 7),
+                      ('dog', 8)])))""")
+        self.assertEqual(pprint.pformat(d.values()),
+ """\
+ValuesView(ChainMap({'a': 6,
+          'brown': 2,
+          'dog': 8,
+          'fox': 3,
+          'jumped': 4,
+          'lazy': 7,
+          'over': 5,
+          'quick': 1,
+          'the': 0},
+         OrderedDict([('the', 0),
+                      ('quick', 1),
+                      ('brown', 2),
+                      ('fox', 3),
+                      ('jumped', 4),
+                      ('over', 5),
+                      ('a', 6),
+                      ('lazy', 7),
+                      ('dog', 8)])))""")
 
     def test_deque(self):
         d = collections.deque()
@@ -1096,6 +1451,36 @@ def test_user_dict(self):
  'over': 5,
  'quick': 1,
  'the': 0}""")
+        self.assertEqual(pprint.pformat(d.keys()), """\
+KeysView({'a': 6,
+ 'brown': 2,
+ 'dog': 8,
+ 'fox': 3,
+ 'jumped': 4,
+ 'lazy': 7,
+ 'over': 5,
+ 'quick': 1,
+ 'the': 0})""")
+        self.assertEqual(pprint.pformat(d.items()), """\
+ItemsView({'a': 6,
+ 'brown': 2,
+ 'dog': 8,
+ 'fox': 3,
+ 'jumped': 4,
+ 'lazy': 7,
+ 'over': 5,
+ 'quick': 1,
+ 'the': 0})""")
+        self.assertEqual(pprint.pformat(d.values()), """\
+ValuesView({'a': 6,
+ 'brown': 2,
+ 'dog': 8,
+ 'fox': 3,
+ 'jumped': 4,
+ 'lazy': 7,
+ 'over': 5,
+ 'quick': 1,
+ 'the': 0})""")
 
     def test_user_list(self):
         d = collections.UserList()
@@ -1130,6 +1515,564 @@ def test_user_string(self):
     'jumped over a '
     'lazy dog'}""")
 
+    def test_template(self):
+        d = t""
+        self.assertEqual(pprint.pformat(d),
+                         "Template(strings=('',), interpolations=())")
+        self.assertEqual(pprint.pformat(d), repr(d))
+        self.assertEqual(pprint.pformat(d, width=1),
+"""\
+Template(strings=('',),
+         interpolations=())""")
+        name = "World"
+        d = t"Hello {name}"
+        self.assertEqual(pprint.pformat(d),
+"""\
+Template(strings=('Hello ', ''),
+         interpolations=(Interpolation('World', 'name', None, ''),))""")
+        ver = {3.13: False, 3.14: True}
+        d = t"Hello { {"name": "Python", "version": ver}!s:z}!"
+        self.assertEqual(pprint.pformat(d, width=1),
+"""\
+Template(strings=('Hello ',
+                  '!'),
+         interpolations=(Interpolation({'name': 'Python',
+                                        'version': {3.13: False,
+                                                    3.14: True}},
+                                       ' '
+                                       '{"name": '
+                                       '"Python", '
+                                       '"version": '
+                                       'ver}',
+                                       's',
+                                       'z'),))""")
+
+    def test_expand_template(self):
+        d = t""
+        self.assertEqual(
+            pprint.pformat(d, expand=True),
+            "Template(strings=('',), interpolations=())",
+        )
+        name = "World"
+        d = t"Hello {name}"
+        self.assertEqual(
+            pprint.pformat(d, width=40, indent=4, expand=True),
+            """\
+Template(
+    strings=('Hello ', ''),
+    interpolations=(
+        Interpolation(
+            value='World',
+            expression='name',
+            conversion=None,
+            format_spec='',
+        ),
+    ),
+)""",
+        )
+        ver = {3.13: False, 3.14: True}
+        d = t"Hello { {"name": "Python", "version": ver}!s:z}!"
+        self.assertEqual(
+            pprint.pformat(d, width=40, indent=4, expand=True),
+            """\
+Template(
+    strings=('Hello ', '!'),
+    interpolations=(
+        Interpolation(
+            value={
+                'name': 'Python',
+                'version': {
+                    3.13: False,
+                    3.14: True,
+                },
+            },
+            expression=' {"name": "Python", '
+            '"version": ver}',
+            conversion='s',
+            format_spec='z',
+        ),
+    ),
+)""",
+        )
+
+    def test_expand_dataclass(self):
+        @dataclasses.dataclass
+        class DummyDataclass:
+            foo: str
+            bar: float
+            baz: bool
+            qux: dict = dataclasses.field(default_factory=dict)
+            quux: list = dataclasses.field(default_factory=list)
+            corge: int = 1
+            garply: tuple = (1, 2, 3, 4)
+        dummy_dataclass = DummyDataclass(
+            foo="foo",
+            bar=1.2,
+            baz=False,
+            qux={"foo": "bar", "baz": 123},
+            quux=["foo", "bar", "baz"],
+            corge=7,
+            garply=(1, 2, 3, 4),
+        )
+        self.assertEqual(pprint.pformat(dummy_dataclass, width=40, indent=4,
+                                        expand=True),
+"""\
+DummyDataclass(
+    foo='foo',
+    bar=1.2,
+    baz=False,
+    qux={'baz': 123, 'foo': 'bar'},
+    quux=['foo', 'bar', 'baz'],
+    corge=7,
+    garply=(1, 2, 3, 4),
+)""")
+
+    def test_expand_dict(self):
+        dummy_dict = {
+            "foo": "bar",
+            "baz": 123,
+            "qux": {"foo": "bar", "baz": 123},
+            "quux": ["foo", "bar", "baz"],
+            "corge": 7,
+        }
+        self.assertEqual(pprint.pformat(dummy_dict, width=40, indent=4,
+                                        expand=True, sort_dicts=False),
+"""\
+{
+    'foo': 'bar',
+    'baz': 123,
+    'qux': {'foo': 'bar', 'baz': 123},
+    'quux': ['foo', 'bar', 'baz'],
+    'corge': 7,
+}""")
+
+    def test_expand_respects_width_with_long_keys(self):
+        # gh-155596: in expand mode the width of the "key: " prefix was not
+        # counted when deciding whether a value fits on the current line, so
+        # values under long keys could overflow width.
+        obj = {'a' * 12: 1, 'b' * 20: 2, 'c' * 30: {'d' * 5: 3, 'e' * 40: 3}}
+        result = pprint.pformat(obj, expand=True)
+        self.assertEqual(result,
+"""\
+{
+ 'aaaaaaaaaaaa': 1,
+ 'bbbbbbbbbbbbbbbbbbbb': 2,
+ 'cccccccccccccccccccccccccccccc': {
+  'ddddd': 3,
+  'eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee': 3,
+ },
+}""")
+        # The nested value must be broken up rather than overflowing.
+        self.assertTrue(all(len(line) <= 80 for line in result.splitlines()),
+                        max(result.splitlines(), key=len))
+
+    def test_expand_ordered_dict(self):
+        dummy_ordered_dict = collections.OrderedDict(
+            [
+                ("foo", 1),
+                ("bar", 12),
+                ("baz", 123),
+            ]
+        )
+        self.assertEqual(pprint.pformat(dummy_ordered_dict, width=20, indent=4,
+                                        expand=True),
+"""\
+OrderedDict([
+    ('foo', 1),
+    ('bar', 12),
+    ('baz', 123),
+])""")
+
+    def test_expand_list(self):
+        dummy_list = [
+            "foo",
+            "bar",
+            "baz",
+            "qux",
+        ]
+        self.assertEqual(pprint.pformat(dummy_list, width=20, indent=4,
+                                        expand=True),
+"""\
+[
+    'foo',
+    'bar',
+    'baz',
+    'qux',
+]""")
+
+    def test_expand_tuple(self):
+        dummy_tuple = (
+            "foo",
+            "bar",
+            "baz",
+            4,
+            5,
+            6,
+        )
+        self.assertEqual(pprint.pformat(dummy_tuple, width=20, indent=4,
+                                        expand=True),
+"""\
+(
+    'foo',
+    'bar',
+    'baz',
+    4,
+    5,
+    6,
+)""")
+
+    def test_expand_single_element_tuple(self):
+        self.assertEqual(
+            pprint.pformat((1,), width=1, indent=4, expand=True),
+            """\
+(
+    1,
+)""")
+
+    def test_expand_set(self):
+        dummy_set = {
+            "foo",
+            "bar",
+            "baz",
+            "qux",
+            (1, 2, 3),
+        }
+        self.assertEqual(pprint.pformat(dummy_set, width=20, indent=4,
+                                        expand=True),
+"""\
+{
+    'bar',
+    'baz',
+    'foo',
+    'qux',
+    (1, 2, 3),
+}""")
+
+    def test_expand_frozenset(self):
+        dummy_set = {
+            (1, 2, 3),
+        }
+        dummy_frozenset = frozenset(
+            {
+                "foo",
+                "bar",
+                "baz",
+                (1, 2, 3),
+                frozenset(dummy_set),
+            }
+        )
+        self.assertEqual(pprint.pformat(dummy_frozenset, width=40, indent=4,
+                                        expand=True),
+"""\
+frozenset({
+    frozenset({(1, 2, 3)}),
+    'bar',
+    'baz',
+    'foo',
+    (1, 2, 3),
+})""")
+
+    def test_expand_frozendict(self):
+        dummy_frozendict = frozendict(
+            {"foo": "bar", "baz": 123, "qux": [1, 2]}
+        )
+        self.assertEqual(
+            pprint.pformat(dummy_frozendict, width=20, indent=4, expand=True),
+            """\
+frozendict({
+    'baz': 123,
+    'foo': 'bar',
+    'qux': [1, 2],
+})""",
+        )
+
+    def test_expand_bytes(self):
+        dummy_bytes = b"Hello world! foo bar baz 123 456 789"
+        self.assertEqual(pprint.pformat(dummy_bytes, width=20, indent=4,
+                                        expand=True),
+"""\
+(
+    b'Hello world!'
+    b' foo bar baz'
+    b' 123 456 789'
+)""")
+
+    def test_expand_bytearray(self):
+        dummy_bytes = b"Hello world! foo bar baz 123 456 789"
+        dummy_byte_array = bytearray(dummy_bytes)
+        self.assertEqual(pprint.pformat(dummy_byte_array, width=40, indent=4,
+                                        expand=True),
+"""\
+bytearray(
+    b'Hello world! foo bar baz 123 456'
+    b' 789'
+)""")
+
+    def test_expand_mappingproxy(self):
+        dummy_dict = {
+            "foo": "bar",
+            "baz": 123,
+            "qux": {"foo": "bar", "baz": 123},
+            "quux": ["foo", "bar", "baz"],
+            "corge": 7,
+        }
+        dummy_mappingproxy = types.MappingProxyType(dummy_dict)
+        self.assertEqual(pprint.pformat(dummy_mappingproxy, width=40, indent=4,
+                                        expand=True),
+"""\
+mappingproxy({
+    'baz': 123,
+    'corge': 7,
+    'foo': 'bar',
+    'quux': ['foo', 'bar', 'baz'],
+    'qux': {'baz': 123, 'foo': 'bar'},
+})""")
+
+    def test_expand_namespace(self):
+        dummy_namespace = types.SimpleNamespace(
+            foo="bar",
+            bar=42,
+            baz=types.SimpleNamespace(
+                x=321,
+                y="string",
+                d={"foo": True, "bar": "baz"},
+            ),
+        )
+
+        self.assertEqual(pprint.pformat(dummy_namespace, width=40, indent=4,
+                                        expand=True),
+"""\
+namespace(
+    foo='bar',
+    bar=42,
+    baz=namespace(
+        x=321,
+        y='string',
+        d={'bar': 'baz', 'foo': True},
+    ),
+)""")
+
+    def test_expand_defaultdict(self):
+        dummy_defaultdict = collections.defaultdict(list)
+        dummy_defaultdict["foo"].append("bar")
+        dummy_defaultdict["foo"].append("baz")
+        dummy_defaultdict["foo"].append("qux")
+        dummy_defaultdict["bar"] = {"foo": "bar", "baz": None}
+        self.assertEqual(pprint.pformat(dummy_defaultdict, width=40, indent=4,
+                                        expand=True),
+"""\
+defaultdict(<class 'list'>, {
+    'bar': {'baz': None, 'foo': 'bar'},
+    'foo': ['bar', 'baz', 'qux'],
+})""")
+
+    def test_expand_counter(self):
+        dummy_counter = collections.Counter("abcdeabcdabcaba")
+        expected = """\
+Counter({
+    'a': 5,
+    'b': 4,
+    'c': 3,
+    'd': 2,
+    'e': 1,
+})"""
+        self.assertEqual(pprint.pformat(dummy_counter, width=40, indent=4,
+                                        expand=True), expected)
+
+        expected2 = """\
+Counter({
+  'a': 5,
+  'b': 4,
+  'c': 3,
+  'd': 2,
+  'e': 1,
+})"""
+        self.assertEqual(pprint.pformat(dummy_counter, width=20, indent=2,
+                                        expand=True), expected2)
+
+    def test_expand_chainmap(self):
+        dummy_dict = {
+            "foo": "bar",
+            "baz": 123,
+            "qux": {"foo": "bar", "baz": 123},
+            "quux": ["foo", "bar", "baz"],
+            "corge": 7,
+        }
+        dummy_chainmap = collections.ChainMap(
+            {"foo": "bar"},
+            {"baz": "qux"},
+            {"corge": dummy_dict},
+        )
+        dummy_chainmap.maps.append({"garply": "waldo"})
+        self.assertEqual(pprint.pformat(dummy_chainmap, width=40, indent=4,
+                                        expand=True),
+"""\
+ChainMap(
+    {'foo': 'bar'},
+    {'baz': 'qux'},
+    {
+        'corge': {
+            'baz': 123,
+            'corge': 7,
+            'foo': 'bar',
+            'quux': [
+                'foo',
+                'bar',
+                'baz',
+            ],
+            'qux': {
+                'baz': 123,
+                'foo': 'bar',
+            },
+        },
+    },
+    {'garply': 'waldo'},
+)""")
+
+    def test_expand_deque(self):
+        dummy_dict = {
+            "foo": "bar",
+            "baz": 123,
+            "qux": {"foo": "bar", "baz": 123},
+            "quux": ["foo", "bar", "baz"],
+            "corge": 7,
+        }
+        dummy_list = [
+            "foo",
+            "bar",
+            "baz",
+        ]
+        dummy_set = {
+            (1, 2, 3),
+        }
+        dummy_deque = collections.deque(maxlen=10)
+        dummy_deque.append("foo")
+        dummy_deque.append(123)
+        dummy_deque.append(dummy_dict)
+        dummy_deque.extend(dummy_list)
+        dummy_deque.appendleft(dummy_set)
+        self.assertEqual(pprint.pformat(dummy_deque, width=40, indent=4,
+                                        expand=True),
+"""\
+deque([
+    {(1, 2, 3)},
+    'foo',
+    123,
+    {
+        'baz': 123,
+        'corge': 7,
+        'foo': 'bar',
+        'quux': ['foo', 'bar', 'baz'],
+        'qux': {
+            'baz': 123,
+            'foo': 'bar',
+        },
+    },
+    'foo',
+    'bar',
+    'baz',
+], maxlen=10)""")
+
+    def test_expand_userdict(self):
+        class DummyUserDict(collections.UserDict):
+            """A custom UserDict with some extra attributes"""
+
+            def __init__(self, *args, **kwargs):
+                super().__init__(*args, **kwargs)
+                self.access_count = 0
+        dummy_userdict = DummyUserDict({ "foo": "bar", "baz": 123,
+                                        "qux": {"foo": "bar", "baz": 123},
+                                        "quux": ["foo", "bar", "baz"],
+                                        "corge": 7 })
+        dummy_userdict.access_count = 5
+
+        self.assertEqual(pprint.pformat(dummy_userdict, width=40, indent=4,
+                                        expand=True),
+"""\
+{
+    'baz': 123,
+    'corge': 7,
+    'foo': 'bar',
+    'quux': ['foo', 'bar', 'baz'],
+    'qux': {'baz': 123, 'foo': 'bar'},
+}""")
+
+    def test_expand_userlist(self):
+        class DummyUserList(collections.UserList):
+            """A custom UserList with some extra attributes"""
+
+            def __init__(self, *args, **kwargs):
+                super().__init__(*args, **kwargs)
+                self.description = "foo"
+        dummy_userlist = DummyUserList(["first", 2, {"key": "value"},
+                                       [4, 5, 6]])
+
+        self.assertEqual(pprint.pformat(dummy_userlist, width=40, indent=4,
+                                        expand=True),
+"""\
+[
+    'first',
+    2,
+    {'key': 'value'},
+    [4, 5, 6],
+]""")
+
+    def test_expand_dict_keys(self):
+        d = {"foo": 1, "bar": 2, "baz": 3, "qux": 4, "quux": 5}
+        self.assertEqual(
+            pprint.pformat(d.keys(), width=20, indent=4, expand=True),
+            """\
+dict_keys([
+    'bar',
+    'baz',
+    'foo',
+    'quux',
+    'qux',
+])""",
+        )
+
+    def test_expand_dict_values(self):
+        d = {"foo": 1, "bar": 2, "baz": 3, "qux": 4, "quux": 5}
+        self.assertEqual(
+            pprint.pformat(d.values(), width=20, indent=4, expand=True),
+            """\
+dict_values([
+    1,
+    2,
+    3,
+    4,
+    5,
+])""",
+        )
+
+    def test_expand_dict_items(self):
+        d = {"foo": 1, "bar": 2, "baz": 3, "qux": 4, "quux": 5}
+        self.assertEqual(
+            pprint.pformat(d.items(), width=20, indent=4, expand=True),
+            """\
+dict_items([
+    ('bar', 2),
+    ('baz', 3),
+    ('foo', 1),
+    ('quux', 5),
+    ('qux', 4),
+])""",
+        )
+
+    def test_expand_str(self):
+        s = "The quick brown fox jumped over the lazy dog " * 3
+        self.assertEqual(
+            pprint.pformat(s, width=40, indent=4, expand=True),
+            """\
+(
+    'The quick brown fox jumped over '
+    'the lazy dog The quick brown fox '
+    'jumped over the lazy dog The '
+    'quick brown fox jumped over the '
+    'lazy dog '
+)""",
+        )
+
 
 class DottedPrettyPrinter(pprint.PrettyPrinter):
 
diff --git a/Lib/test/test_py_compile.py b/Lib/test/test_py_compile.py
index acd2dde8867..6eb01ce7bbc 100644
--- a/Lib/test/test_py_compile.py
+++ b/Lib/test/test_py_compile.py
@@ -1,4 +1,3 @@
-import functools
 import importlib.util
 import os
 import py_compile
@@ -11,43 +10,7 @@
 
 from test import support
 from test.support import os_helper, script_helper
-
-
-def without_source_date_epoch(fxn):
-    """Runs function with SOURCE_DATE_EPOCH unset."""
-    @functools.wraps(fxn)
-    def wrapper(*args, **kwargs):
-        with os_helper.EnvironmentVarGuard() as env:
-            env.unset('SOURCE_DATE_EPOCH')
-            return fxn(*args, **kwargs)
-    return wrapper
-
-
-def with_source_date_epoch(fxn):
-    """Runs function with SOURCE_DATE_EPOCH set."""
-    @functools.wraps(fxn)
-    def wrapper(*args, **kwargs):
-        with os_helper.EnvironmentVarGuard() as env:
-            env['SOURCE_DATE_EPOCH'] = '123456789'
-            return fxn(*args, **kwargs)
-    return wrapper
-
-
-# Run tests with SOURCE_DATE_EPOCH set or unset explicitly.
-class SourceDateEpochTestMeta(type(unittest.TestCase)):
-    def __new__(mcls, name, bases, dct, *, source_date_epoch):
-        cls = super().__new__(mcls, name, bases, dct)
-
-        for attr in dir(cls):
-            if attr.startswith('test_'):
-                meth = getattr(cls, attr)
-                if source_date_epoch:
-                    wrapper = with_source_date_epoch(meth)
-                else:
-                    wrapper = without_source_date_epoch(meth)
-                setattr(cls, attr, wrapper)
-
-        return cls
+from test.support.os_helper import SourceDateEpochTestMeta
 
 
 class PyCompileTestsBase:
@@ -56,7 +19,10 @@ def setUp(self):
         self.directory = tempfile.mkdtemp(dir=os.getcwd())
         self.source_path = os.path.join(self.directory, '_test.py')
         self.pyc_path = self.source_path + 'c'
-        self.cache_path = importlib.util.cache_from_source(self.source_path)
+        try:
+            self.cache_path = importlib.util.cache_from_source(self.source_path)
+        except NotImplementedError:
+            self.cache_path = None
         self.cwd_drive = os.path.splitdrive(os.getcwd())[0]
         # In these tests we compute relative paths.  When using Windows, the
         # current working directory path and the 'self.source_path' might be
@@ -73,10 +39,31 @@ def tearDown(self):
         if self.cwd_drive:
             os.chdir(self.cwd_drive)
 
+    def assert_cache_path_exists(self, should_exist=True):
+        if self.cache_path:
+            if should_exist:
+                self.assertTrue(os.path.exists(self.cache_path))
+            else:
+                self.assertFalse(os.path.exists(self.cache_path))
+            return
+        cache_dir = os.path.join(self.directory, '__pycache__')
+        if not os.path.isdir(cache_dir):
+            if should_exist:
+                self.fail('no __pycache__ directory exists')
+            return
+        for f in os.listdir(cache_dir):
+            if f.startswith('_test.') and f.endswith('.pyc'):
+                if should_exist:
+                    return
+                self.fail(f'__pycache__/{f} was created')
+        else:
+            if should_exist:
+                self.fail('no __pycache__/_test.*.pyc file exists')
+
     def test_absolute_path(self):
         py_compile.compile(self.source_path, self.pyc_path)
         self.assertTrue(os.path.exists(self.pyc_path))
-        self.assertFalse(os.path.exists(self.cache_path))
+        self.assert_cache_path_exists(False)
 
     def test_do_not_overwrite_symlinks(self):
         # In the face of a cfile argument being a symlink, bail out.
@@ -98,23 +85,25 @@ def test_do_not_overwrite_nonregular_files(self):
         with self.assertRaises(FileExistsError):
             py_compile.compile(self.source_path, os.devnull)
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag is not None')
     def test_cache_path(self):
         py_compile.compile(self.source_path)
-        self.assertTrue(os.path.exists(self.cache_path))
+        self.assert_cache_path_exists(True)
 
     def test_cwd(self):
         with os_helper.change_cwd(self.directory):
             py_compile.compile(os.path.basename(self.source_path),
                                os.path.basename(self.pyc_path))
         self.assertTrue(os.path.exists(self.pyc_path))
-        self.assertFalse(os.path.exists(self.cache_path))
+        self.assert_cache_path_exists(False)
 
     @unittest.expectedFailureIf(sys.platform == "darwin" and int(__import__("platform").release().split(".")[0]) < 20, "TODO: RUSTPYTHON")
     def test_relative_path(self):
         py_compile.compile(os.path.relpath(self.source_path),
                            os.path.relpath(self.pyc_path))
         self.assertTrue(os.path.exists(self.pyc_path))
-        self.assertFalse(os.path.exists(self.cache_path))
+        self.assert_cache_path_exists(False)
 
     @os_helper.skip_if_dac_override
     @unittest.skipIf(os.name == 'nt',
@@ -137,14 +126,14 @@ def test_bad_coding(self):
                                   'tokenizedata',
                                   'bad_coding2.py')
         with support.captured_stderr():
-            self.assertIsNone(py_compile.compile(bad_coding, doraise=False))
-        self.assertFalse(os.path.exists(
-            importlib.util.cache_from_source(bad_coding)))
+            self.assertIsNone(py_compile.compile(bad_coding, self.pyc_path,
+                                                 doraise=False))
+        self.assertFalse(os.path.exists(self.pyc_path))
 
     def test_source_date_epoch(self):
         py_compile.compile(self.source_path, self.pyc_path)
         self.assertTrue(os.path.exists(self.pyc_path))
-        self.assertFalse(os.path.exists(self.cache_path))
+        self.assert_cache_path_exists(False)
         with open(self.pyc_path, 'rb') as fp:
             flags = importlib._bootstrap_external._classify_pyc(
                 fp.read(), 'test', {})
@@ -156,6 +145,8 @@ def test_source_date_epoch(self):
         self.assertEqual(flags, expected_flags)
 
     @unittest.skipIf(sys.flags.optimize > 0, 'test does not work with -O')
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag is not None')
     def test_double_dot_no_clobber(self):
         # http://bugs.python.org/issue22966
         # py_compile foo.bar.py -> __pycache__/foo.cpython-34.pyc
@@ -178,6 +169,8 @@ def test_double_dot_no_clobber(self):
             self.assertTrue(os.path.exists(cache_path))
             self.assertFalse(os.path.exists(pyc_path))
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag is not None')
     def test_optimization_path(self):
         # Specifying optimized bytecode should lead to a path reflecting that.
         self.assertIn('opt-2', py_compile.compile(self.source_path, optimize=2))
@@ -185,17 +178,19 @@ def test_optimization_path(self):
     def test_invalidation_mode(self):
         py_compile.compile(
             self.source_path,
+            self.pyc_path,
             invalidation_mode=py_compile.PycInvalidationMode.CHECKED_HASH,
         )
-        with open(self.cache_path, 'rb') as fp:
+        with open(self.pyc_path, 'rb') as fp:
             flags = importlib._bootstrap_external._classify_pyc(
                 fp.read(), 'test', {})
         self.assertEqual(flags, 0b11)
         py_compile.compile(
             self.source_path,
+            self.pyc_path,
             invalidation_mode=py_compile.PycInvalidationMode.UNCHECKED_HASH,
         )
-        with open(self.cache_path, 'rb') as fp:
+        with open(self.pyc_path, 'rb') as fp:
             flags = importlib._bootstrap_external._classify_pyc(
                 fp.read(), 'test', {})
         self.assertEqual(flags, 0b1)
@@ -205,11 +200,11 @@ def test_quiet(self):
                                   'tokenizedata',
                                   'bad_coding2.py')
         with support.captured_stderr() as stderr:
-            self.assertIsNone(py_compile.compile(bad_coding, doraise=False, quiet=2))
-            self.assertIsNone(py_compile.compile(bad_coding, doraise=True, quiet=2))
+            self.assertIsNone(py_compile.compile(bad_coding, self.pyc_path, doraise=False, quiet=2))
+            self.assertIsNone(py_compile.compile(bad_coding, self.pyc_path, doraise=True, quiet=2))
             self.assertEqual(stderr.getvalue(), '')
             with self.assertRaises(py_compile.PyCompileError):
-                py_compile.compile(bad_coding, doraise=True, quiet=1)
+                py_compile.compile(bad_coding, self.pyc_path, doraise=True, quiet=1)
 
     def test_utf7_decoded_cr_compiles(self):
         with open(self.source_path, 'wb') as file:
@@ -239,8 +234,12 @@ class PyCompileCLITestCase(unittest.TestCase):
     def setUp(self):
         self.directory = tempfile.mkdtemp()
         self.source_path = os.path.join(self.directory, '_test.py')
-        self.cache_path = importlib.util.cache_from_source(self.source_path,
-                                optimization='' if __debug__ else 1)
+        try:
+            self.cache_path = importlib.util.cache_from_source(self.source_path,
+                                    optimization='' if __debug__ else 1)
+        except NotImplementedError:
+            # py_compile.main() assumes legacy pyc path if there is no cache_tag
+            self.cache_path = self.source_path + 'c'
         with open(self.source_path, 'w') as file:
             file.write('x = 123\n')
 
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index c231126d58c..8d093ab1b70 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -14,6 +14,8 @@
 from fractions import Fraction
 from collections import abc, Counter
 
+from test.support import warnings_helper
+
 
 class MyIndex:
     def __init__(self, value):
@@ -1073,10 +1075,9 @@ def test_avg_std(self):
                                    msg='%s%r' % (variate.__name__, args))
             self.assertAlmostEqual(s2/(N-1), sigmasqrd, places=2,
                                    msg='%s%r' % (variate.__name__, args))
-
     def test_binomialvariate_log_zero(self):
         # gh-149222: Variety random() return 0.0 no input Error
-        with unittest.mock.patch.object(random.Random, 'random', side_effect=[0.0] + [0.5] * 20):
+        with unittest.mock.patch.object(random.Random, 'random', side_effect= [0.0] + [0.5] * 20):
             result = random.binomialvariate(10, 0.5)
             self.assertIsInstance(result, int)
             self.assertIn(result, range(11))
@@ -1414,6 +1415,7 @@ def test__all__(self):
         # tests validity but not completeness of the __all__ list
         self.assertTrue(set(random.__all__) <= set(dir(random)))
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @test.support.requires_fork()
     def test_after_fork(self):
         # Test the global Random instance gets reseeded in child
diff --git a/Lib/test/test_re.py b/Lib/test/test_re.py
index 80c21f6b198..3d703c0a8ce 100644
--- a/Lib/test/test_re.py
+++ b/Lib/test/test_re.py
@@ -91,10 +91,13 @@ def test_search_star_plus(self):
         self.assertEqual(re.search('x+', 'axx').span(), (1, 3))
         self.assertIsNone(re.search('x', 'aaa'))
         self.assertEqual(re.match('a*', 'xxx').span(0), (0, 0))
+        self.assertEqual(re.prefixmatch('a*', 'xxx').span(0), (0, 0))
         self.assertEqual(re.match('a*', 'xxx').span(), (0, 0))
         self.assertEqual(re.match('x*', 'xxxa').span(0), (0, 3))
+        self.assertEqual(re.prefixmatch('x*', 'xxxa').span(0), (0, 3))
         self.assertEqual(re.match('x*', 'xxxa').span(), (0, 3))
         self.assertIsNone(re.match('a+', 'xxx'))
+        self.assertIsNone(re.prefixmatch('a+', 'xxx'))
 
     def test_branching(self):
         """Test Branching
@@ -181,6 +184,7 @@ def test_bug_449000(self):
     def test_bug_1661(self):
         # Verify that flags do not get silently ignored with compiled patterns
         pattern = re.compile('.')
+        self.assertRaises(ValueError, re.prefixmatch, pattern, 'A', re.I)
         self.assertRaises(ValueError, re.match, pattern, 'A', re.I)
         self.assertRaises(ValueError, re.search, pattern, 'A', re.I)
         self.assertRaises(ValueError, re.findall, pattern, 'A', re.I)
@@ -518,6 +522,8 @@ def test_re_match(self):
             self.assertEqual(re.match(b'(a)', string).group(0), b'a')
             self.assertEqual(re.match(b'(a)', string).group(1), b'a')
             self.assertEqual(re.match(b'(a)', string).group(1, 1), (b'a', b'a'))
+            self.assertEqual(re.prefixmatch(b'(a)', string).group(1, 1),
+                             (b'a', b'a'))
         for a in ("\xe0", "\u0430", "\U0001d49c"):
             self.assertEqual(re.match(a, a).groups(), ())
             self.assertEqual(re.match('(%s)' % a, a).groups(), (a,))
@@ -559,10 +565,8 @@ def __index__(self):
         self.assertEqual(m.group(2, 1), ('b', 'a'))
         self.assertEqual(m.group(Index(2), Index(1)), ('b', 'a'))
 
-    def test_match_getitem(self):
-        pat = re.compile('(?:(?P<a1>a)|(?P<b2>b))(?P<c3>c)?')
-
-        m = pat.match('a')
+    def do_test_match_getitem(self, match_fn):
+        m = match_fn('a')
         self.assertEqual(m['a1'], 'a')
         self.assertEqual(m['b2'], None)
         self.assertEqual(m['c3'], None)
@@ -586,7 +590,7 @@ def test_match_getitem(self):
         with self.assertRaisesRegex(IndexError, 'no such group'):
             'a1={a2}'.format_map(m)
 
-        m = pat.match('ac')
+        m = match_fn('ac')
         self.assertEqual(m['a1'], 'a')
         self.assertEqual(m['b2'], None)
         self.assertEqual(m['c3'], 'c')
@@ -603,6 +607,14 @@ def test_match_getitem(self):
         # No len().
         self.assertRaises(TypeError, len, m)
 
+    def test_match_getitem(self):
+        pat = re.compile('(?:(?P<a1>a)|(?P<b2>b))(?P<c3>c)?')
+        self.do_test_match_getitem(pat.match)
+
+    def test_prefixmatch_getitem(self):
+        pat = re.compile('(?:(?P<a1>a)|(?P<b2>b))(?P<c3>c)?')
+        self.do_test_match_getitem(pat.prefixmatch)
+
     def test_re_fullmatch(self):
         # Issue 16203: Proposal: add re.fullmatch() method.
         self.assertEqual(re.fullmatch(r"a", "a").span(), (0, 1))
@@ -1641,6 +1653,24 @@ def s_int(scanner, token): return int(token)
                          (['sum', 'op=', 3, 'op*', 'foo', 'op+', 312.5,
                            'op+', 'bar'], ''))
 
+    def test_bug_gh140797(self):
+        # gh140797: Capturing groups are not allowed in re.Scanner
+
+        msg = r"Cannot use capturing groups in re\.Scanner"
+        # Capturing group throws an error
+        with self.assertRaisesRegex(ValueError, msg):
+            Scanner([("(a)b", None)])
+
+        # Named Group
+        with self.assertRaisesRegex(ValueError, msg):
+            Scanner([("(?P<name>a)", None)])
+
+        # Non-capturing groups should pass normally
+        s = Scanner([("(?:a)b", lambda scanner, token: token)])
+        result, rem = s.scan("ab")
+        self.assertEqual(result,['ab'])
+        self.assertEqual(rem,'')
+
     def test_bug_448951(self):
         # bug 448951 (similar to 429357, but with single char match)
         # (Also test greedy matches.)
@@ -2028,7 +2058,7 @@ def test_large_search(self, size):
 
     # The huge memuse is because of re.sub() using a list and a join()
     # to create the replacement result.
-    @bigmemtest(size=_2G, memuse=16 + 2)
+    @bigmemtest(size=_2G, memuse=16 + 3)
     def test_large_subn(self, size):
         # Issue #10182: indices were 32-bit-truncated.
         s = 'a' * size
@@ -2179,7 +2209,6 @@ def test_bug_20998(self):
         # with ignore case.
         self.assertEqual(re.fullmatch('[a-c]+', 'ABC', re.I).span(), (0, 3))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; self.assertTrue(re.match(b'\xc5', b'\xe5', re.L|re.I))\n AssertionError: None is not true
     @unittest.skipIf(linked_to_musl(), "musl libc issue, bpo-46390")
     @unittest.skipIf(sys.platform.startswith("sunos"),
                      "test doesn't work on Solaris, gh-91214")
@@ -2939,33 +2968,6 @@ def test_disallow_instantiation(self):
         pat = re.compile("")
         check_disallow_instantiation(self, type(pat.scanner("")))
 
-    def test_deprecated_modules(self):
-        deprecated = {
-            'sre_compile': ['compile', 'error',
-                            'SRE_FLAG_IGNORECASE', 'SUBPATTERN',
-                            '_compile_info'],
-            'sre_constants': ['error', 'SRE_FLAG_IGNORECASE', 'SUBPATTERN',
-                              '_NamedIntConstant'],
-            'sre_parse': ['SubPattern', 'parse',
-                          'SRE_FLAG_IGNORECASE', 'SUBPATTERN',
-                          '_parse_sub'],
-        }
-        for name in deprecated:
-            with self.subTest(module=name):
-                sys.modules.pop(name, None)
-                with self.assertWarns(DeprecationWarning) as w:
-                    __import__(name)
-                self.assertEqual(str(w.warning),
-                                 f"module {name!r} is deprecated")
-                self.assertEqual(w.filename, __file__)
-                self.assertIn(name, sys.modules)
-                mod = sys.modules[name]
-                self.assertEqual(mod.__name__, name)
-                self.assertEqual(mod.__package__, '')
-                for attr in deprecated[name]:
-                    self.assertHasAttr(mod, attr)
-                del sys.modules[name]
-
     @cpython_only
     def test_case_helpers(self):
         import _sre
@@ -3151,5 +3153,15 @@ def test_re_tests(self):
                     self.assertTrue(obj.search(s))
 
 
+class TestModule(unittest.TestCase):
+    def test_deprecated__version__(self):
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            "'__version__' is deprecated and slated for removal in Python 3.20",
+        ) as cm:
+            getattr(re, "__version__")
+        self.assertEqual(cm.filename, __file__)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_repl.py b/Lib/test/test_repl.py
index 71dab8c3876..a0abcc0f0ba 100644
--- a/Lib/test/test_repl.py
+++ b/Lib/test/test_repl.py
@@ -17,7 +17,6 @@
     SHORT_TIMEOUT,
 )
 from test.support.script_helper import kill_python
-from test.support.import_helper import import_module
 
 try:
     import pty
@@ -40,8 +39,8 @@ def spawn_repl(*args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, custom=F
     # line option '-i' and the process name set to '<stdin>'.
     # The directory of argv[0] must match the directory of the Python
     # executable for the Popen() call to python to succeed as the directory
-    # path may be used by Py_GetPath() to build the default module search
-    # path.
+    # path may be used by PyConfig_Get("module_search_paths") to build the
+    # default module search path.
     stdin_fname = os.path.join(os.path.dirname(sys.executable), "<stdin>")
     cmd_line = [stdin_fname]
     # Isolated mode implies -EPs and ignores PYTHON* variables.
@@ -99,12 +98,8 @@ def run_on_interactive_mode(source):
 @support.force_not_colorized_test_class
 class TestInteractiveInterpreter(unittest.TestCase):
 
-    @cpython_only
-    # Python built with Py_TRACE_REFS fail with a fatal error in
-    # _PyRefchain_Trace() on memory allocation error.
-    @unittest.skipIf(support.Py_TRACE_REFS, 'cannot test Py_TRACE_REFS build')
+    @support.nomemtest
     def test_no_memory(self):
-        import_module("_testcapi")
         # Issue #30696: Fix the interactive interpreter looping endlessly when
         # no memory. Check also that the fix does not break the interactive
         # loop when an exception is raised.
@@ -189,7 +184,6 @@ def test_close_stdin(self):
         self.assertEqual(process.returncode, 0)
         self.assertIn('before close', output)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: 101 != 0
     def test_interactive_traceback_reporting(self):
         user_input = "1 / 0 / 3 / 4"
         p = spawn_repl()
@@ -232,7 +226,6 @@ def foo(x):
         ]
         self.assertEqual(traceback_lines, expected_lines)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_pythonstartup_error_reporting(self):
         # errors based on https://github.com/python/cpython/issues/137576
 
@@ -303,7 +296,7 @@ def test_runsource_show_syntax_error_location(self):
         expected_lines = [
             '    def f(x, x): ...',
             '             ^',
-            "SyntaxError: duplicate argument 'x' in function definition"
+            "SyntaxError: duplicate parameter 'x' in function definition"
         ]
         self.assertEqual(output.splitlines()[4:-1], expected_lines)
 
@@ -443,6 +436,13 @@ def test_toplevel_contextvars_async(self):
         p = spawn_asyncio_repl()
         p.stdin.write(user_input)
         user_input2 = "async def set_var(): var.set('ok')\n"
+        try:
+            import _pyrepl # noqa: F401
+        except ModuleNotFoundError:
+            # If we're going to be forced into the regular REPL, then we need an
+            # extra newline here. Omit it by default to catch any breakage to
+            # the new REPL's behavior.
+            user_input2 += "\n"
         p.stdin.write(user_input2)
         user_input3 = "await set_var()\n"
         p.stdin.write(user_input3)
diff --git a/Lib/test/test_runpy.py b/Lib/test/test_runpy.py
index 0fb7f73da11..55b9673ef6c 100644
--- a/Lib/test/test_runpy.py
+++ b/Lib/test/test_runpy.py
@@ -20,9 +20,11 @@
     requires_subprocess,
     verbose,
 )
+from test import support
 from test.support.import_helper import forget, make_legacy_pyc, unload
 from test.support.os_helper import create_empty_file, temp_dir, FakePath
 from test.support.script_helper import make_script, make_zip_script
+from test.test_importlib.util import temporary_pycache_prefix
 
 
 import runpy
@@ -55,7 +57,6 @@ def f():
 implicit_namespace = {
     "__name__": None,
     "__file__": None,
-    "__cached__": None,
     "__package__": None,
     "__doc__": None,
     "__spec__": None
@@ -303,7 +304,6 @@ def _del_pkg(self, top):
     def _fix_ns_for_legacy_pyc(self, ns, alter_sys):
         char_to_add = "c"
         ns["__file__"] += char_to_add
-        ns["__cached__"] = ns["__file__"]
         spec = ns["__spec__"]
         new_spec = importlib.util.spec_from_file_location(spec.name,
                                                           ns["__file__"])
@@ -323,7 +323,6 @@ def _check_module(self, depth, alter_sys=False,
         expected_ns.update({
             "__name__": mod_name,
             "__file__": mod_fname,
-            "__cached__": mod_spec.cached,
             "__package__": mod_name.rpartition(".")[0],
             "__spec__": mod_spec,
         })
@@ -340,14 +339,16 @@ def create_ns(init_globals):
             self.check_code_execution(create_ns, expected_ns)
             importlib.invalidate_caches()
             __import__(mod_name)
-            os.remove(mod_fname)
             if not sys.dont_write_bytecode:
-                make_legacy_pyc(mod_fname)
+                make_legacy_pyc(mod_fname, allow_compile=True)
                 unload(mod_name)  # In case loader caches paths
+                os.remove(mod_fname)
                 importlib.invalidate_caches()
                 if verbose > 1: print("Running from compiled:", mod_name)
                 self._fix_ns_for_legacy_pyc(expected_ns, alter_sys)
                 self.check_code_execution(create_ns, expected_ns)
+            else:
+                os.remove(mod_fname)
         finally:
             self._del_pkg(pkg_dir)
         if verbose > 1: print("Module executed successfully")
@@ -364,7 +365,6 @@ def _check_package(self, depth, alter_sys=False,
         expected_ns.update({
             "__name__": mod_name,
             "__file__": mod_fname,
-            "__cached__": importlib.util.cache_from_source(mod_fname),
             "__package__": pkg_name,
             "__spec__": mod_spec,
         })
@@ -381,14 +381,16 @@ def create_ns(init_globals):
             self.check_code_execution(create_ns, expected_ns)
             importlib.invalidate_caches()
             __import__(mod_name)
-            os.remove(mod_fname)
             if not sys.dont_write_bytecode:
-                make_legacy_pyc(mod_fname)
+                make_legacy_pyc(mod_fname, allow_compile=True)
                 unload(mod_name)  # In case loader caches paths
+                os.remove(mod_fname)
                 if verbose > 1: print("Running from compiled:", pkg_name)
                 importlib.invalidate_caches()
                 self._fix_ns_for_legacy_pyc(expected_ns, alter_sys)
                 self.check_code_execution(create_ns, expected_ns)
+            else:
+                os.remove(mod_fname)
         finally:
             self._del_pkg(pkg_dir)
         if verbose > 1: print("Package executed successfully")
@@ -441,7 +443,7 @@ def _check_relative_imports(self, depth, run_name=None):
             importlib.invalidate_caches()
             __import__(mod_name)
             os.remove(mod_fname)
-            if not sys.dont_write_bytecode:
+            if not sys.dont_write_bytecode and sys.implementation.cache_tag:
                 make_legacy_pyc(mod_fname)
                 unload(mod_name)  # In case the loader caches paths
                 if verbose > 1: print("Running from compiled:", mod_name)
@@ -569,7 +571,6 @@ def test_run_name(self):
         expected_ns.update({
             "__name__": run_name,
             "__file__": mod_fname,
-            "__cached__": importlib.util.cache_from_source(mod_fname),
             "__package__": mod_name.rpartition(".")[0],
             "__spec__": mod_spec,
         })
@@ -649,7 +650,6 @@ def create_ns(init_globals):
         expected_ns.update({
             "__name__": expected_name,
             "__file__": expected_file,
-            "__cached__": mod_cached,
             "__package__": "",
             "__spec__": mod_spec,
             "run_argv0": expected_argv0,
@@ -699,6 +699,8 @@ def test_basic_script_no_suffix(self):
             self._check_script(script_name, "<run_path>", script_name,
                                script_name, expect_spec=False)
 
+    @unittest.skipIf(sys.implementation.cache_tag is None,
+                     'requires sys.implementation.cache_tag')
     def test_script_compiled(self):
         with temp_dir() as script_dir:
             mod_name = 'script'
@@ -719,12 +721,10 @@ def test_directory_compiled(self):
         with temp_dir() as script_dir:
             mod_name = '__main__'
             script_name = self._make_test_script(script_dir, mod_name)
-            compiled_name = py_compile.compile(script_name, doraise=True)
+            legacy_pyc = make_legacy_pyc(script_name, allow_compile=True)
             os.remove(script_name)
-            if not sys.dont_write_bytecode:
-                legacy_pyc = make_legacy_pyc(script_name)
-                self._check_script(script_dir, "<run_path>", legacy_pyc,
-                                   script_dir, mod_name=mod_name)
+            self._check_script(script_dir, "<run_path>", legacy_pyc,
+                               script_dir, mod_name=mod_name)
 
     def test_directory_error(self):
         with temp_dir() as script_dir:
@@ -756,7 +756,8 @@ def test_zipfile_compiled(self):
         with temp_dir() as script_dir:
             mod_name = '__main__'
             script_name = self._make_test_script(script_dir, mod_name)
-            compiled_name = py_compile.compile(script_name, doraise=True)
+            compiled_name = script_name + 'c'
+            py_compile.compile(script_name, compiled_name, doraise=True)
             zip_name, fname = make_zip_script(script_dir, 'test_zip',
                                               compiled_name)
             self._check_script(zip_name, "<run_path>", fname, zip_name,
@@ -793,6 +794,47 @@ def test_encoding(self):
             result = run_path(filename)
             self.assertEqual(result['s'], "non-ASCII: h\xe9")
 
+    def test_run_module_filter_syntax_warnings_by_module(self):
+        module_re = r'test\.test_import\.data\.syntax_warnings\z'
+        with (temp_dir() as tmpdir,
+              temporary_pycache_prefix(tmpdir),
+              warnings.catch_warnings(record=True) as wlog):
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=module_re)
+            warnings.filterwarnings('error', module='syntax_warnings')
+            ns = run_module('test.test_import.data.syntax_warnings')
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10, 13, 14, 21])
+        filename = ns['__file__']
+        for wm in wlog:
+            self.assertEqual(wm.filename, filename)
+            self.assertIs(wm.category, SyntaxWarning)
+
+    def test_run_path_filter_syntax_warnings_by_module(self):
+        filename = support.findfile('test_import/data/syntax_warnings.py')
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=r'<run_path>\z')
+            warnings.filterwarnings('error', module='test')
+            warnings.filterwarnings('error', module='syntax_warnings')
+            warnings.filterwarnings('error',
+                    module=r'test\.test_import\.data\.syntax_warnings')
+            run_path(filename)
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10, 13, 14, 21])
+        for wm in wlog:
+            self.assertEqual(wm.filename, filename)
+            self.assertIs(wm.category, SyntaxWarning)
+
+        with warnings.catch_warnings(record=True) as wlog:
+            warnings.simplefilter('error')
+            warnings.filterwarnings('always', module=r'package\.script\z')
+            warnings.filterwarnings('error', module='<run_path>')
+            warnings.filterwarnings('error', module='test')
+            warnings.filterwarnings('error', module='syntax_warnings')
+            warnings.filterwarnings('error',
+                    module=r'test\.test_import\.data\.syntax_warnings')
+            run_path(filename, run_name='package.script')
+        self.assertEqual(sorted(wm.lineno for wm in wlog), [4, 7, 10, 13, 14, 21])
+
 
 @force_not_colorized_test_class
 class TestExit(unittest.TestCase):
@@ -867,7 +909,6 @@ def test_pymain_run_command_run_module(self):
     def test_pymain_run_command(self):
         self.assertSigInt(["-c", "import ham"], cwd=self.ham.parent)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_pymain_run_stdin(self):
         self.assertSigInt([], input="import ham", cwd=self.ham.parent)
 
diff --git a/Lib/test/test_shutil.py b/Lib/test/test_shutil.py
index 8813cc46cb6..02bc920702b 100644
--- a/Lib/test/test_shutil.py
+++ b/Lib/test/test_shutil.py
@@ -493,6 +493,37 @@ def check_args_to_onexc(self, func, arg, exc):
             self.assertTrue(isinstance(exc, OSError))
             self.errorState = 3
 
+    @os_helper.skip_if_dac_override
+    @os_helper.skip_unless_working_chmod
+    @unittest.skipUnless(shutil.rmtree.avoids_symlink_attacks,
+                         'requires the fd based implementation of rmtree()')
+    def test_on_exc_kwargs(self):
+        os.mkdir(TESTFN)
+        self.addCleanup(shutil.rmtree, TESTFN)
+
+        child_dir_path = os.path.join(TESTFN, 'b')
+        child_file_path = os.path.join(child_dir_path, 'a')
+        os.mkdir(child_dir_path)
+        os_helper.create_empty_file(child_file_path)
+        old_child_dir_mode = os.stat(child_dir_path).st_mode
+        # Make unwritable.
+        new_mode = stat.S_IREAD|stat.S_IEXEC
+        os.chmod(child_dir_path, new_mode)
+
+        self.addCleanup(os.chmod, child_dir_path, old_child_dir_mode)
+
+        calls = []
+        def onexc(func, path, err, direntry=None, dir_fd=None):
+            calls.append((func, path, err))
+            if func is os.unlink:
+                self.assertEqual(direntry.name, os.path.basename(path))
+                self.assertTrue(os.path.samestat(
+                    os.stat(path), os.stat(direntry.name, dir_fd=dir_fd)))
+
+        shutil.rmtree(TESTFN, onexc=onexc, _onexc_kwargs=True)
+        self.assertIn((os.unlink, child_file_path),
+                      [(func, path) for func, path, err in calls])
+
     @unittest.skipIf(sys.platform[:6] == 'cygwin',
                      "This test can't be run on Cygwin (issue #1071513).")
     @os_helper.skip_if_dac_override
@@ -2042,6 +2073,32 @@ def test_make_zipfile_in_curdir(self):
             self.assertEqual(make_archive('test', 'zip'), 'test.zip')
             self.assertTrue(os.path.isfile('test.zip'))
 
+    def test_make_archive_pathlike_cwd_default(self):
+        called_args = []
+        def archiver(base_name, base_dir, **kw):
+            called_args.append((base_name, kw.get('root_dir')))
+
+        register_archive_format('xxx', archiver, [], 'xxx file')
+        self.addCleanup(unregister_archive_format, 'xxx')
+        with no_chdir:
+            make_archive(FakePath('basename'), 'xxx')
+        self.assertEqual(called_args, [('basename', None)])
+
+    def test_make_archive_pathlike_cwd_supports_root_dir(self):
+        root_dir = self.mkdtemp()
+        called_args = []
+        def archiver(base_name, base_dir, **kw):
+            called_args.append((base_name, base_dir, kw.get('root_dir')))
+        archiver.supports_root_dir = True
+
+        register_archive_format('xxx', archiver, [], 'xxx file')
+        self.addCleanup(unregister_archive_format, 'xxx')
+        with no_chdir:
+            make_archive(FakePath('basename'), 'xxx',
+                         root_dir=FakePath(root_dir),
+                         base_dir=FakePath('basedir'))
+        self.assertEqual(called_args, [('basename', 'basedir', root_dir)])
+
     def test_register_archive_format(self):
 
         self.assertRaises(TypeError, register_archive_format, 'xxx', 1)
@@ -3572,7 +3629,7 @@ def test_module_all_attribute(self):
             target_api.append('disk_usage')
         self.assertEqual(set(shutil.__all__), set(target_api))
         with self.assertWarns(DeprecationWarning):
-            from shutil import ExecError
+            from shutil import ExecError  # noqa: F401
 
 
 if __name__ == '__main__':
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index 0e20723b6f3..6a20501b046 100644
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -8,7 +8,9 @@
 import _thread as thread
 import array
 import contextlib
+import decimal
 import errno
+import fractions
 import gc
 import io
 import itertools
@@ -1349,10 +1351,20 @@ def testDefaultTimeout(self):
             self.assertEqual(s.gettimeout(), None)
 
         # Set the default timeout to 10, and see if it propagates
-        with socket_setdefaulttimeout(10):
-            self.assertEqual(socket.getdefaulttimeout(), 10)
+        with socket_setdefaulttimeout(10.125):
+            self.assertEqual(socket.getdefaulttimeout(), 10.125)
             with socket.socket() as sock:
-                self.assertEqual(sock.gettimeout(), 10)
+                self.assertEqual(sock.gettimeout(), 10.125)
+
+            socket.setdefaulttimeout(decimal.Decimal('11.125'))
+            self.assertEqual(socket.getdefaulttimeout(), 11.125)
+            with socket.socket() as sock:
+                self.assertEqual(sock.gettimeout(), 11.125)
+
+            socket.setdefaulttimeout(fractions.Fraction(97, 8))
+            self.assertEqual(socket.getdefaulttimeout(), 12.125)
+            with socket.socket() as sock:
+                self.assertEqual(sock.gettimeout(), 12.125)
 
             # Reset the default timeout to None, and see if it propagates
             socket.setdefaulttimeout(None)
@@ -1580,6 +1592,40 @@ def testSetSockOpt(self):
         reuse = sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR)
         self.assertFalse(reuse == 0, "failed to set reuse mode")
 
+    def test_setsockopt_errors(self):
+        # See issue #107546.
+        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.addCleanup(sock.close)
+
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)  # No error expected.
+
+        with self.assertRaises(OverflowError):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 2 ** 100)
+
+        with self.assertRaises(OverflowError):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, - 2 ** 100)
+
+        with self.assertRaises(OverflowError):
+            sock.setsockopt(socket.SOL_SOCKET, 2 ** 100, 1)
+
+        with self.assertRaises(OverflowError):
+            sock.setsockopt(2 ** 100, socket.SO_REUSEADDR, 1)
+
+        with self.assertRaisesRegex(TypeError, "socket option should be int, bytes-like object or None"):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, dict())
+
+        with self.assertRaisesRegex(TypeError, "requires 4 arguments when the third argument is None"):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, None)
+
+        with self.assertRaisesRegex(TypeError, "only takes 4 arguments when the third argument is None"):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1, 2)
+
+        with self.assertRaisesRegex(TypeError, "takes at least 3 arguments"):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR)
+
+        with self.assertRaisesRegex(TypeError, "takes at most 4 arguments"):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1, 2, 3)
+
     def testSendAfterClose(self):
         # testing send() after close() with timeout
         with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
@@ -2435,6 +2481,45 @@ def testCrucialConstants(self):
         socket.CAN_ISOTP
         socket.SOCK_DGRAM
 
+    @unittest.skipUnless(hasattr(socket, "SOL_CAN_ISOTP"),
+                         "missing <linux/can/isotp.h>")
+    def testISOTP(self):
+        socket.SOL_CAN_ISOTP
+
+        socket.CAN_ISOTP_OPTS
+        socket.CAN_ISOTP_RECV_FC
+
+        socket.CAN_ISOTP_TX_STMIN
+        socket.CAN_ISOTP_RX_STMIN
+        socket.CAN_ISOTP_LL_OPTS
+
+        socket.CAN_ISOTP_LISTEN_MODE
+        socket.CAN_ISOTP_EXTEND_ADDR
+        socket.CAN_ISOTP_TX_PADDING
+        socket.CAN_ISOTP_RX_PADDING
+        socket.CAN_ISOTP_CHK_PAD_LEN
+        socket.CAN_ISOTP_CHK_PAD_DATA
+        socket.CAN_ISOTP_HALF_DUPLEX
+        socket.CAN_ISOTP_FORCE_TXSTMIN
+        socket.CAN_ISOTP_FORCE_RXSTMIN
+        socket.CAN_ISOTP_RX_EXT_ADDR
+        socket.CAN_ISOTP_WAIT_TX_DONE
+        # This constant is not always available
+        # socket.CAN_ISOTP_SF_BROADCAST
+
+        socket.CAN_ISOTP_DEFAULT_FLAGS
+        socket.CAN_ISOTP_DEFAULT_EXT_ADDRESS
+        socket.CAN_ISOTP_DEFAULT_PAD_CONTENT
+        socket.CAN_ISOTP_DEFAULT_FRAME_TXTIME
+        socket.CAN_ISOTP_DEFAULT_RECV_BS
+        socket.CAN_ISOTP_DEFAULT_EXT_ADDRESS
+        socket.CAN_ISOTP_DEFAULT_RECV_STMIN
+        socket.CAN_ISOTP_DEFAULT_RECV_WFTMAX
+
+        socket.CAN_ISOTP_DEFAULT_LL_MTU
+        socket.CAN_ISOTP_DEFAULT_LL_TX_DL
+        socket.CAN_ISOTP_DEFAULT_LL_TX_FLAGS
+
     def testCreateSocket(self):
         with socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW) as s:
             pass
diff --git a/Lib/test/test_socketserver.py b/Lib/test/test_socketserver.py
index 2ca356606b2..ca33a9a6dac 100644
--- a/Lib/test/test_socketserver.py
+++ b/Lib/test/test_socketserver.py
@@ -17,6 +17,7 @@
 from test.support import os_helper
 from test.support import socket_helper
 from test.support import threading_helper
+from test.support import warnings_helper
 
 
 test.support.requires("network")
@@ -43,6 +44,7 @@ def receive(sock, n, timeout=test.support.SHORT_TIMEOUT):
         raise RuntimeError("timed out on %r" % (sock,))
 
 
+@warnings_helper.ignore_fork_in_thread_deprecation_warnings()
 @test.support.requires_fork()
 @contextlib.contextmanager
 def simple_subprocess(testcase):
@@ -173,6 +175,7 @@ def test_ThreadingTCPServer(self):
                         socketserver.StreamRequestHandler,
                         self.stream_examine)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_forking
     def test_ForkingTCPServer(self):
         with simple_subprocess(self):
@@ -192,6 +195,7 @@ def test_ThreadingUnixStreamServer(self):
                         socketserver.StreamRequestHandler,
                         self.stream_examine)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_unix_sockets
     @requires_forking
     def test_ForkingUnixStreamServer(self):
@@ -210,6 +214,7 @@ def test_ThreadingUDPServer(self):
                         socketserver.DatagramRequestHandler,
                         self.dgram_examine)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_forking
     def test_ForkingUDPServer(self):
         with simple_subprocess(self):
@@ -233,6 +238,7 @@ def test_ThreadingUnixDatagramServer(self):
                         socketserver.DatagramRequestHandler,
                         self.dgram_examine)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_unix_sockets
     @requires_forking
     def test_ForkingUnixDatagramServer(self):
@@ -318,11 +324,13 @@ def test_threading_not_handled(self):
 
             self.assertIs(cm.exc_type, SystemExit)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_forking
     def test_forking_handled(self):
         ForkingErrorTestServer(ValueError)
         self.check_result(handled=True)
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @requires_forking
     def test_forking_not_handled(self):
         ForkingErrorTestServer(SystemExit)
@@ -507,5 +515,15 @@ class MyServer(socketserver.ThreadingMixIn, socketserver.TCPServer):
         server.server_close()
 
 
+class TestModule(unittest.TestCase):
+    def test_deprecated__version__(self):
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            "'__version__' is deprecated and slated for removal in Python 3.20",
+        ) as cm:
+            getattr(socketserver, "__version__")
+        self.assertEqual(cm.filename, __file__)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_sqlite3/test_backup.py b/Lib/test/test_sqlite3/test_backup.py
index bc24831a0c7..c7400d8b216 100644
--- a/Lib/test/test_sqlite3/test_backup.py
+++ b/Lib/test/test_sqlite3/test_backup.py
@@ -103,7 +103,6 @@ def progress(status, remaining, total):
         self.assertEqual(len(journal), 1)
         self.assertEqual(journal[0], 0)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_non_callable_progress(self):
         with self.assertRaises(TypeError) as cm:
             with memory_database() as bck:
diff --git a/Lib/test/test_sqlite3/test_regression.py b/Lib/test/test_sqlite3/test_regression.py
index 5560365fdc6..2a9b1ec9afb 100644
--- a/Lib/test/test_sqlite3/test_regression.py
+++ b/Lib/test/test_sqlite3/test_regression.py
@@ -439,7 +439,6 @@ def test_table_lock_cursor_dealloc(self):
             con.execute("drop table t")
             con.commit()
 
-    @unittest.skip("TODO: RUSTPYTHON; recursive cursor use causes lock contention")
     def test_table_lock_cursor_non_readonly_select(self):
         with memory_database() as con:
             con.execute("create table t(t)")
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
index dd4c657d0cf..f0fc6e5b90b 100644
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -49,7 +49,17 @@
 PROTOCOLS = sorted(ssl._PROTOCOL_NAMES)
 HOST = socket_helper.HOST
 IS_AWS_LC = "AWS-LC" in ssl.OPENSSL_VERSION
+IS_LIBRESSL = "LibreSSL" in ssl.OPENSSL_VERSION
 IS_OPENSSL_3_0_0 = ssl.OPENSSL_VERSION_INFO >= (3, 0, 0)
+CAN_GET_SELECTED_OPENSSL_GROUP = ssl.OPENSSL_VERSION_INFO >= (3, 2)
+CAN_IGNORE_UNKNOWN_OPENSSL_GROUPS = ssl.OPENSSL_VERSION_INFO >= (3, 3)
+CAN_GET_AVAILABLE_OPENSSL_GROUPS = ssl.OPENSSL_VERSION_INFO >= (3, 5)
+CAN_GET_AVAILABLE_OPENSSL_SIGALGS = ssl.OPENSSL_VERSION_INFO >= (3, 4)
+# LibreSSL does not provide SSL_CTX_set1_(client_)sigalgs_list().
+CAN_SET_CLIENT_SIGALGS = not IS_AWS_LC and not IS_LIBRESSL
+CAN_SET_SERVER_SIGALGS = not IS_LIBRESSL
+CAN_IGNORE_UNKNOWN_OPENSSL_SIGALGS = ssl.OPENSSL_VERSION_INFO >= (3, 3)
+CAN_GET_SELECTED_OPENSSL_SIGALG = ssl.OPENSSL_VERSION_INFO >= (3, 5)
 PY_SSL_DEFAULT_CIPHERS = sysconfig.get_config_var('PY_SSL_DEFAULT_CIPHERS')
 
 HAS_KEYLOG = hasattr(ssl.SSLContext, 'keylog_filename')
@@ -136,6 +146,7 @@ def data_file(*name):
 EMPTYCERT = data_file("nullcert.pem")
 BADCERT = data_file("badcert.pem")
 NONEXISTINGCERT = data_file("XXXnonexisting.pem")
+NONEXISTINGKEY = data_file("XXXnonexistingkey.pem")
 BADKEY = data_file("badkey.pem")
 NOKIACERT = data_file("nokia.pem")
 NULLBYTECERT = data_file("nullbytecert.pem")
@@ -276,7 +287,7 @@ def make_test_context(
     check_hostname=None,
     cert_reqs=ssl.CERT_NONE,
     ca_certs=None, certfile=None, keyfile=None,
-    ciphers=None,
+    ciphers=None, ciphersuites=None,
     min_version=None, max_version=None,
 ):
     if server_side:
@@ -300,6 +311,8 @@ def make_test_context(
 
     if ciphers is not None:
         context.set_ciphers(ciphers)
+    if ciphersuites is not None:
+        context.set_ciphersuites(ciphersuites)
 
     if min_version is not None:
         context.minimum_version = min_version
@@ -316,7 +329,7 @@ def test_wrap_socket(
     check_hostname=None,
     cert_reqs=ssl.CERT_NONE,
     ca_certs=None, certfile=None, keyfile=None,
-    ciphers=None,
+    ciphers=None, ciphersuites=None,
     min_version=None, max_version=None,
     **kwargs,
 ):
@@ -325,7 +338,7 @@ def test_wrap_socket(
         check_hostname=check_hostname,
         cert_reqs=cert_reqs,
         ca_certs=ca_certs, certfile=certfile, keyfile=keyfile,
-        ciphers=ciphers,
+        ciphers=ciphers, ciphersuites=ciphersuites,
         min_version=min_version, max_version=max_version,
     )
     if not server_side:
@@ -336,7 +349,8 @@ def test_wrap_socket(
 USE_SAME_TEST_CONTEXT = False
 _TEST_CONTEXT = None
 
-def testing_context(server_cert=SIGNED_CERTFILE, *, server_chain=True):
+def testing_context(server_cert=SIGNED_CERTFILE, *, server_chain=True,
+                    client_cert=None):
     """Create context
 
     client_context, server_context, hostname = testing_context()
@@ -363,6 +377,10 @@ def testing_context(server_cert=SIGNED_CERTFILE, *, server_chain=True):
     if server_chain:
         server_context.load_verify_locations(SIGNING_CA)
 
+    if client_cert:
+        client_context.load_cert_chain(client_cert)
+        server_context.verify_mode = ssl.CERT_REQUIRED
+
     if USE_SAME_TEST_CONTEXT:
         if _TEST_CONTEXT is not None:
             _TEST_CONTEXT = client_context, server_context, hostname
@@ -384,6 +402,34 @@ def do_ssl_object_handshake(sslobject, outgoing, max_retry=25):
     return data
 
 
+def connected_bio_pair(client_context, server_context, hostname, max_retry=5):
+    """Handshake a client and a server SSLObject against each other.
+
+    Everything happens in memory, so this needs no socket and no thread.
+    Returns the two objects followed by their four BIOs, in the order
+    client, server, c_in, c_out, s_in, s_out.
+    """
+    c_in, c_out = ssl.MemoryBIO(), ssl.MemoryBIO()
+    s_in, s_out = ssl.MemoryBIO(), ssl.MemoryBIO()
+    client = client_context.wrap_bio(c_in, c_out, server_hostname=hostname)
+    server = server_context.wrap_bio(s_in, s_out, server_side=True)
+
+    # Loop on the handshake for a bit to get it settled
+    for _ in range(max_retry):
+        with contextlib.suppress(ssl.SSLWantReadError):
+            client.do_handshake()
+        if c_out.pending:
+            s_in.write(c_out.read())
+        with contextlib.suppress(ssl.SSLWantReadError):
+            server.do_handshake()
+        if s_out.pending:
+            c_in.write(s_out.read())
+    # Now the handshakes should be complete (don't raise WantReadError)
+    client.do_handshake()
+    server.do_handshake()
+    return client, server, c_in, c_out, s_in, s_out
+
+
 class BasicSocketTests(unittest.TestCase):
 
     def test_constants(self):
@@ -396,7 +442,7 @@ def test_constants(self):
         ssl.OP_NO_COMPRESSION
         self.assertEqual(ssl.HAS_SNI, True)
         self.assertEqual(ssl.HAS_ECDH, True)
-        self.assertEqual(ssl.HAS_TLSv1_2, True)
+        self.assertIsInstance(ssl.HAS_TLSv1_2, bool)
         self.assertEqual(ssl.HAS_TLSv1_3, True)
         ssl.OP_NO_SSLv2
         ssl.OP_NO_SSLv3
@@ -587,11 +633,11 @@ def test_openssl_version(self):
         # Some sanity checks follow
         # >= 1.1.1
         self.assertGreaterEqual(n, 0x10101000)
-        # < 4.0
-        self.assertLess(n, 0x40000000)
+        # < 5.0
+        self.assertLess(n, 0x50000000)
         major, minor, fix, patch, status = t
         self.assertGreaterEqual(major, 1)
-        self.assertLess(major, 4)
+        self.assertLess(major, 5)
         self.assertGreaterEqual(minor, 0)
         self.assertLess(minor, 256)
         self.assertGreaterEqual(fix, 0)
@@ -657,12 +703,14 @@ def test_openssl111_deprecations(self):
             ssl.OP_NO_TLSv1_2,
             ssl.OP_NO_TLSv1_3
         ]
-        protocols = [
-            ssl.PROTOCOL_TLSv1,
-            ssl.PROTOCOL_TLSv1_1,
-            ssl.PROTOCOL_TLSv1_2,
-            ssl.PROTOCOL_TLS
-        ]
+        protocols = []
+        if hasattr(ssl, 'PROTOCOL_TLSv1'):
+            protocols.append(ssl.PROTOCOL_TLSv1)
+        if hasattr(ssl, 'PROTOCOL_TLSv1_1'):
+            protocols.append(ssl.PROTOCOL_TLSv1_1)
+        if hasattr(ssl, 'PROTOCOL_TLSv1_2'):
+            protocols.append(ssl.PROTOCOL_TLSv1_2)
+        protocols.append(ssl.PROTOCOL_TLS)
         versions = [
             ssl.TLSVersion.SSLv3,
             ssl.TLSVersion.TLSv1,
@@ -1027,6 +1075,58 @@ def test_get_ciphers(self):
             len(intersection), 2, f"\ngot: {sorted(names)}\nexpected: {sorted(expected)}"
         )
 
+    def test_set_groups(self):
+        ctx = ssl.create_default_context()
+        # We use P-256 and P-384 (FIPS 186-4) that are alloed by OpenSSL
+        # even if FIPS module is enabled. Ignoring unknown groups is only
+        # supported since OpenSSL 3.3.
+        self.assertIsNone(ctx.set_groups('P-256:P-384'))
+
+        self.assertRaises(ssl.SSLError, ctx.set_groups, 'P-256:foo')
+        if CAN_IGNORE_UNKNOWN_OPENSSL_GROUPS:
+            self.assertIsNone(ctx.set_groups('P-256:?foo'))
+
+    @unittest.skipUnless(CAN_GET_AVAILABLE_OPENSSL_GROUPS,
+                         "OpenSSL version doesn't support getting groups")
+    def test_get_groups(self):
+        ctx = ssl.create_default_context()
+        # By default, only return official IANA names.
+        self.assertNotIn('P-256', ctx.get_groups())
+        self.assertIn('P-256', ctx.get_groups(include_aliases=True))
+
+    @unittest.skipUnless(CAN_GET_AVAILABLE_OPENSSL_SIGALGS,
+                         "SSL library doesn't support getting sigalgs")
+    def test_get_sigalgs(self):
+        self.assertIn('rsa_pss_rsae_sha256', ssl.get_sigalgs())
+
+    @unittest.skipUnless(CAN_SET_CLIENT_SIGALGS,
+                         "SSL library doesn't support setting client sigalgs")
+    def test_set_client_sigalgs(self):
+        ctx = ssl.create_default_context()
+
+        self.assertIsNone(ctx.set_client_sigalgs('rsa_pss_rsae_sha256'))
+
+        self.assertRaises(ssl.SSLError, ctx.set_client_sigalgs,
+                          'rsa_pss_rsae_sha256:foo')
+
+        # Ignoring unknown sigalgs is only supported since OpenSSL 3.3.
+        if CAN_IGNORE_UNKNOWN_OPENSSL_SIGALGS:
+            self.assertIsNone(ctx.set_client_sigalgs('rsa_pss_rsae_sha256:?foo'))
+
+    @unittest.skipUnless(CAN_SET_SERVER_SIGALGS,
+                         "SSL library doesn't support setting server sigalgs")
+    def test_set_server_sigalgs(self):
+        ctx = ssl.create_default_context()
+
+        self.assertIsNone(ctx.set_server_sigalgs('rsa_pss_rsae_sha256'))
+
+        self.assertRaises(ssl.SSLError, ctx.set_server_sigalgs,
+                          'rsa_pss_rsae_sha256:foo')
+
+        # Ignoring unknown sigalgs is only supported since OpenSSL 3.3.
+        if CAN_IGNORE_UNKNOWN_OPENSSL_SIGALGS:
+            self.assertIsNone(ctx.set_server_sigalgs('rsa_pss_rsae_sha256:?foo'))
+
     def test_options(self):
         # Test default SSLContext options
         ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
@@ -1156,6 +1256,7 @@ def test_min_max_version(self):
                 ssl.TLSVersion.TLSv1,
                 ssl.TLSVersion.TLSv1_1,
                 ssl.TLSVersion.TLSv1_2,
+                ssl.TLSVersion.TLSv1_3,
                 ssl.TLSVersion.SSLv3,
             }
         )
@@ -1169,7 +1270,7 @@ def test_min_max_version(self):
         with self.assertRaises(ValueError):
             ctx.minimum_version = 42
 
-        if has_tls_protocol(ssl.PROTOCOL_TLSv1_1):
+        if has_tls_protocol('PROTOCOL_TLSv1_1'):
             ctx = ssl.SSLContext(ssl.PROTOCOL_TLSv1_1)
 
             self.assertIn(
@@ -1231,6 +1332,11 @@ def test_load_cert_chain(self):
         with self.assertRaises(OSError) as cm:
             ctx.load_cert_chain(NONEXISTINGCERT)
         self.assertEqual(cm.exception.errno, errno.ENOENT)
+        self.assertEqual(cm.exception.filename, NONEXISTINGCERT)
+        with self.assertRaises(OSError) as cm:
+            ctx.load_cert_chain(CERTFILE, keyfile=NONEXISTINGKEY)
+        self.assertEqual(cm.exception.errno, errno.ENOENT)
+        self.assertEqual(cm.exception.filename, NONEXISTINGKEY)
         with self.assertRaisesRegex(ssl.SSLError, "PEM (lib|routines)"):
             ctx.load_cert_chain(BADCERT)
         with self.assertRaisesRegex(ssl.SSLError, "PEM (lib|routines)"):
@@ -1533,19 +1639,27 @@ def dummycallback(sock, servername, ctx, cycle=ctx):
         gc.collect()
         self.assertIs(wr(), None)
 
-    @unittest.skipUnless(support.Py_GIL_DISABLED,
-                         "test is only useful if the GIL is disabled")
+    @support.skip_if_sanitizer("gh-150191: OpenSSL has an internal data race "
+                               "when the SNI callback is replaced during a "
+                               "handshake", thread=True)
     @threading_helper.requires_working_threading()
     def test_sni_callback_race(self):
-        # Replacing sni_callback while handshakes are in-flight must not
+        # Replacing sni_callback while a handshake is in-flight must not
         # crash (use-after-free on the callback in free-threaded builds).
+        #
+        # Use a single handshake thread: OpenSSL has internal data races
+        # on shared SSL_CTX state when multiple handshakes run
+        # concurrently against the same context (gh-150191). Concurrency
+        # on the *setter* is what exercises the fix from gh-149816, so
+        # multiple toggler threads race against each other and against
+        # the one handshake worker.
         client_ctx, server_ctx, hostname = testing_context()
 
         server_ctx.sni_callback = lambda *a: None
-        done = threading.Event()
+        deadline = time.monotonic() + 0.1
 
         def do_handshakes():
-            while not done.is_set():
+            while time.monotonic() < deadline:
                 c_in = ssl.MemoryBIO()
                 c_out = ssl.MemoryBIO()
                 s_in = ssl.MemoryBIO()
@@ -1572,19 +1686,11 @@ def do_handshakes():
                         c_in.write(s_out.read())
 
         def toggle_callback():
-            while not done.is_set():
+            while time.monotonic() < deadline:
                 server_ctx.sni_callback = lambda *a: None
                 server_ctx.sni_callback = None
 
-        workers = max(4, (os.cpu_count() or 4) * 2)
-        threads = [threading.Thread(target=do_handshakes)
-                   for _ in range(workers)]
-        threads.append(threading.Thread(target=toggle_callback))
-
-        with threading_helper.catch_threading_exception() as cm:
-            with threading_helper.start_threads(threads):
-                done.set()
-            self.assertIsNone(cm.exc_value)
+        threading_helper.run_concurrently([do_handshakes] + 4 * [toggle_callback])
 
     def test_cert_store_stats(self):
         ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
@@ -1717,23 +1823,24 @@ def test__create_stdlib_context(self):
         self.assertFalse(ctx.check_hostname)
         self._assert_context_options(ctx)
 
-        if has_tls_protocol(ssl.PROTOCOL_TLSv1):
+        if has_tls_protocol('PROTOCOL_TLSv1'):
             with warnings_helper.check_warnings():
                 ctx = ssl._create_stdlib_context(ssl.PROTOCOL_TLSv1)
             self.assertEqual(ctx.protocol, ssl.PROTOCOL_TLSv1)
             self.assertEqual(ctx.verify_mode, ssl.CERT_NONE)
             self._assert_context_options(ctx)
 
-        with warnings_helper.check_warnings():
-            ctx = ssl._create_stdlib_context(
-                ssl.PROTOCOL_TLSv1_2,
-                cert_reqs=ssl.CERT_REQUIRED,
-                check_hostname=True
-            )
-        self.assertEqual(ctx.protocol, ssl.PROTOCOL_TLSv1_2)
-        self.assertEqual(ctx.verify_mode, ssl.CERT_REQUIRED)
-        self.assertTrue(ctx.check_hostname)
-        self._assert_context_options(ctx)
+        if has_tls_protocol('PROTOCOL_TLSv1_2'):
+            with warnings_helper.check_warnings():
+                ctx = ssl._create_stdlib_context(
+                    ssl.PROTOCOL_TLSv1_2,
+                    cert_reqs=ssl.CERT_REQUIRED,
+                    check_hostname=True
+                )
+            self.assertEqual(ctx.protocol, ssl.PROTOCOL_TLSv1_2)
+            self.assertEqual(ctx.verify_mode, ssl.CERT_REQUIRED)
+            self.assertTrue(ctx.check_hostname)
+            self._assert_context_options(ctx)
 
         ctx = ssl._create_stdlib_context(purpose=ssl.Purpose.CLIENT_AUTH)
         self.assertEqual(ctx.protocol, ssl.PROTOCOL_TLS_SERVER)
@@ -1911,6 +2018,10 @@ def test_subclass(self):
 
     def test_bad_server_hostname(self):
         ctx = ssl.create_default_context()
+        # Omitting the name entirely is bad too: this context checks it.
+        with self.assertRaises(ValueError):
+            ctx.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
+                         server_hostname=None)
         with self.assertRaises(ValueError):
             ctx.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
                          server_hostname="")
@@ -1995,6 +2106,64 @@ def test_private_init(self):
         with self.assertRaisesRegex(TypeError, "public constructor"):
             ssl.SSLObject(bio, bio)
 
+    def test_check_hostname_requires_server_hostname(self):
+        # wrap_bio() used to accept a context asking for hostname checking
+        # without a name to check against, and then verify the certificate
+        # chain but never the peer's identity, with check_hostname still
+        # reporting True and nothing reporting the check had been skipped.
+        # It must refuse that call, as wrap_socket() already did.
+        client_context, _, hostname = testing_context()
+        self.assertTrue(client_context.check_hostname)
+
+        for server_hostname in (None, ""):
+            with self.subTest(server_hostname=server_hostname):
+                with self.assertRaisesRegex(
+                        ValueError,
+                        "check_hostname requires server_hostname"):
+                    client_context.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
+                                            server_hostname=server_hostname)
+                # The sibling constructor refuses the very same call.
+                with socket.socket() as sock:
+                    with self.assertRaisesRegex(
+                            ValueError,
+                            "check_hostname requires server_hostname"):
+                        client_context.wrap_socket(
+                            sock, server_hostname=server_hostname)
+
+        # A name was all that was missing.
+        client_context.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
+                                server_hostname=hostname)
+
+        # Asking for no hostname check remains a way to say so explicitly.
+        context = make_test_context()
+        self.assertFalse(context.check_hostname)
+        context.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO())
+
+    def test_server_side_bad_params(self):
+        # A server neither sends a hostname nor resumes a client's session,
+        # so wrap_bio() rejects both in server mode like wrap_socket()
+        client_context, server_context, hostname = testing_context()
+
+        with self.assertRaisesRegex(
+                ValueError,
+                "server_hostname can only be specified in client mode"):
+            server_context.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
+                                    server_side=True,
+                                    server_hostname=hostname)
+
+        client, server, *_ = connected_bio_pair(
+            client_context, server_context, hostname)
+        session = client.session
+        self.assertIsNotNone(session)
+        with self.assertRaisesRegex(
+                ValueError, "session can only be specified in client mode"):
+            server_context.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
+                                    server_side=True, session=session)
+
+        # Neither argument is what a server passes, so this still works.
+        server_context.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
+                                server_side=True)
+
     def test_unwrap(self):
         client_ctx, server_ctx, hostname = testing_context()
         c_in = ssl.MemoryBIO()
@@ -2037,6 +2206,86 @@ def test_unwrap(self):
         c_in.write(s_out.read())
         client.unwrap()
 
+    def test_sni_callback_context_released_and_callback_raises(self):
+        # Variant of the test below without a HelloRetryRequest: the callback
+        # switches the connection to another context, drops the last
+        # references to the context that carries it, and raises.  The C
+        # callback must not touch that context after the Python callback
+        # returned.
+        client_ctx, server_ctx, hostname = testing_context()
+        leaf_ctx = server_ctx
+
+        def sni_cb(sslobj, server_name, ctx):
+            sslobj.context = leaf_ctx
+            del ctx
+            raise LookupError("no certificate for " + repr(server_name))
+
+        def make_server():
+            dispatch_ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
+            dispatch_ctx.load_cert_chain(SIGNED_CERTFILE)
+            dispatch_ctx.sni_callback = sni_cb
+            s_in, s_out = ssl.MemoryBIO(), ssl.MemoryBIO()
+            server = dispatch_ctx.wrap_bio(s_in, s_out, server_side=True)
+            return server, s_in, s_out
+
+        server, s_in, s_out = make_server()
+        c_in, c_out = ssl.MemoryBIO(), ssl.MemoryBIO()
+        client = client_ctx.wrap_bio(c_in, c_out, server_hostname=hostname)
+        with self.assertRaises(ssl.SSLWantReadError):
+            client.do_handshake()
+        s_in.write(c_out.read())
+        with support.catch_unraisable_exception() as cm:
+            with self.assertRaises(ssl.SSLError):
+                server.do_handshake()
+            self.assertIsInstance(cm.unraisable.exc_value, LookupError)
+        self.assertIs(server.context, leaf_ctx)
+
+    def test_sni_callback_context_released_before_second_client_hello(self):
+        # The SSLContext carrying sni_callback may be released by the
+        # application once the callback has switched the connection over to
+        # another context.  If the server then sends a HelloRetryRequest, the
+        # second ClientHello makes OpenSSL consult the original SSL_CTX's
+        # servername callback again; that must not use the deallocated
+        # SSLContext object.
+        client_ctx, leaf_ctx, hostname = testing_context()
+        calls = []
+
+        def make_server():
+            dispatch_ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
+            dispatch_ctx.load_cert_chain(SIGNED_CERTFILE)
+            # Force a HelloRetryRequest: the client offers an X25519 key
+            # share first, the server only accepts P-384.
+            dispatch_ctx.set_ecdh_curve("secp384r1")
+            def sni_cb(sslobj, server_name, ctx):
+                calls.append(server_name)
+                sslobj.context = leaf_ctx
+            dispatch_ctx.sni_callback = sni_cb
+            s_in, s_out = ssl.MemoryBIO(), ssl.MemoryBIO()
+            server = dispatch_ctx.wrap_bio(s_in, s_out, server_side=True)
+            return server, s_in, s_out, weakref.ref(dispatch_ctx)
+
+        # After this only the C-level SSL object references dispatch_ctx.
+        server, s_in, s_out, dispatch_ref = make_server()
+        c_in, c_out = ssl.MemoryBIO(), ssl.MemoryBIO()
+        client = client_ctx.wrap_bio(c_in, c_out, server_hostname=hostname)
+        for _ in range(10):
+            for obj, out, peer_in in ((client, c_out, s_in),
+                                      (server, s_out, c_in)):
+                try:
+                    obj.do_handshake()
+                except ssl.SSLWantReadError:
+                    pass
+                if out.pending:
+                    peer_in.write(out.read())
+        client.do_handshake()
+        server.do_handshake()
+        support.gc_collect()
+        self.assertIsNone(dispatch_ref())
+        self.assertGreaterEqual(len(calls), 1)
+        self.assertEqual(calls[0], hostname)
+        self.assertIs(server.context, leaf_ctx)
+        self.assertIsNotNone(client.cipher())
+
 class SimpleBackgroundTests(unittest.TestCase):
     """Tests that connect to a simple server running in the background"""
 
@@ -2417,6 +2666,68 @@ def test_transport_eof(self):
             self.assertRaises(ssl.SSLEOFError, sslobj.read)
 
 
+@unittest.skipUnless(has_tls_version('TLSv1_3'), "TLS 1.3 is not available")
+class SimpleBackgroundTestsTLS_1_3(unittest.TestCase):
+    """Tests that connect to a simple server running in the background."""
+
+    def setUp(self):
+        server_ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
+        ciphers = [cipher['name'] for cipher in server_ctx.get_ciphers()
+                   if cipher['protocol'] == 'TLSv1.3']
+
+        if not ciphers:
+            self.skipTest("No cipher supports TLSv1.3")
+
+        self.matching_cipher = ciphers[0]
+        # Some tests need at least two ciphers, and are responsible
+        # to skip themselves if matching_cipher == mismatched_cipher.
+        self.mismatched_cipher = ciphers[-1]
+
+        server_ctx.set_ciphersuites(self.matching_cipher)
+        server_ctx.load_cert_chain(SIGNED_CERTFILE)
+        server = ThreadedEchoServer(context=server_ctx)
+        self.enterContext(server)
+        self.server_addr = (HOST, server.port)
+
+    def test_ciphersuites(self):
+        # Test unrecognized TLS 1.3 cipher suite name
+        with (
+            socket.socket(socket.AF_INET) as sock,
+            self.assertRaisesRegex(ssl.SSLError,
+                                   "No cipher suite can be selected")
+        ):
+            test_wrap_socket(sock, cert_reqs=ssl.CERT_NONE,
+                             ciphersuites="XXX",
+                             min_version=ssl.TLSVersion.TLSv1_3)
+
+        # Test successful TLS 1.3 handshake
+        with test_wrap_socket(socket.socket(socket.AF_INET),
+                              cert_reqs=ssl.CERT_NONE,
+                              ciphersuites=self.matching_cipher,
+                              min_version=ssl.TLSVersion.TLSv1_3) as s:
+            s.connect(self.server_addr)
+            self.assertEqual(s.cipher()[0], self.matching_cipher)
+
+    def test_ciphersuite_downgrade(self):
+        with test_wrap_socket(socket.socket(socket.AF_INET),
+                              cert_reqs=ssl.CERT_NONE,
+                              ciphersuites=self.matching_cipher,
+                              min_version=ssl.TLSVersion.TLSv1_2,
+                              max_version=ssl.TLSVersion.TLSv1_2) as s:
+            s.connect(self.server_addr)
+            self.assertEqual(s.cipher()[1], 'TLSv1.2')
+
+    def test_ciphersuite_mismatch(self):
+        if self.matching_cipher == self.mismatched_cipher:
+            self.skipTest("Multiple TLS 1.3 ciphers are not available")
+
+        with test_wrap_socket(socket.socket(socket.AF_INET),
+                              cert_reqs=ssl.CERT_NONE,
+                              ciphersuites=self.mismatched_cipher,
+                              min_version=ssl.TLSVersion.TLSv1_3) as s:
+            self.assertRaises(ssl.SSLError, s.connect, self.server_addr)
+
+
 @support.requires_resource('network')
 class NetworkedTests(unittest.TestCase):
 
@@ -2760,6 +3071,36 @@ def close(self):
     def stop(self):
         self.active = False
 
+class TestEOFServer(threading.Thread):
+    def __init__(self):
+        super().__init__()
+        self.listening = threading.Event()
+        self.address = None
+
+    def run(self):
+        context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
+        context.load_cert_chain(CERTFILE)
+        server_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        with server_sock:
+            server_sock.settimeout(support.SHORT_TIMEOUT)
+            server_sock.bind((HOST, 0))
+            server_sock.listen(5)
+
+            self.address = server_sock.getsockname()
+            self.listening.set()
+
+            sock, addr = server_sock.accept()
+            sslconn = context.wrap_socket(sock, server_side=True)
+            with sslconn:
+                request = b''
+                while chunk := sslconn.recv(1024):
+                    request += chunk
+                    if b'\n' in chunk:
+                        break
+
+                sslconn.sendall(b'server\n')
+                sslconn.shutdown(socket.SHUT_WR)
+
 class AsyncoreEchoServer(threading.Thread):
 
     # this one's based on asyncore.dispatcher
@@ -2921,6 +3262,11 @@ def server_params_test(client_context, server_context, indata=b"FOO\n",
                 'session_reused': s.session_reused,
                 'session': s.session,
             })
+            if CAN_GET_SELECTED_OPENSSL_GROUP:
+                stats.update({'group': s.group()})
+            if CAN_GET_SELECTED_OPENSSL_SIGALG:
+                stats.update({'client_sigalg': s.client_sigalg()})
+                stats.update({'server_sigalg': s.server_sigalg()})
             s.close()
         stats['server_alpn_protocols'] = server.selected_alpn_protocols
         stats['server_shared_ciphers'] = server.shared_ciphers
@@ -3629,10 +3975,10 @@ def test_protocol_tlsv1_2(self):
                            client_options=ssl.OP_NO_TLSv1_2)
 
         try_protocol_combo(ssl.PROTOCOL_TLS, ssl.PROTOCOL_TLSv1_2, 'TLSv1.2')
-        if has_tls_protocol(ssl.PROTOCOL_TLSv1):
+        if has_tls_protocol('PROTOCOL_TLSv1'):
             try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_TLSv1, False)
             try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1_2, False)
-        if has_tls_protocol(ssl.PROTOCOL_TLSv1_1):
+        if has_tls_protocol('PROTOCOL_TLSv1_1'):
             try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_TLSv1_1, False)
             try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_TLSv1_2, False)
 
@@ -4071,6 +4417,8 @@ def test_no_shared_ciphers(self):
                 with self.assertRaises(OSError):
                     s.connect((HOST, server.port))
         self.assertIn("NO_SHARED_CIPHER", server.conn_errors[0])
+        self.assertIsNone(s.cipher())
+        self.assertIsNone(s.group())
 
     def test_version_basic(self):
         """
@@ -4346,6 +4694,113 @@ def test_ecdh_curve(self):
                                chatty=True, connectionchatty=True,
                                sni_name=hostname)
 
+    def test_groups(self):
+        # server secp384r1, client auto
+        client_context, server_context, hostname = testing_context()
+
+        server_context.set_groups("secp384r1")
+        server_context.minimum_version = ssl.TLSVersion.TLSv1_3
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True, connectionchatty=True,
+                                   sni_name=hostname)
+        if CAN_GET_SELECTED_OPENSSL_GROUP:
+            self.assertEqual(stats['group'], "secp384r1")
+
+        # server auto, client secp384r1
+        client_context, server_context, hostname = testing_context()
+        client_context.set_groups("secp384r1")
+        server_context.minimum_version = ssl.TLSVersion.TLSv1_3
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True, connectionchatty=True,
+                                   sni_name=hostname)
+        if CAN_GET_SELECTED_OPENSSL_GROUP:
+            self.assertEqual(stats['group'], "secp384r1")
+
+        # server / client curve mismatch
+        client_context, server_context, hostname = testing_context()
+        client_context.set_groups("prime256v1")
+        server_context.set_groups("secp384r1")
+        server_context.minimum_version = ssl.TLSVersion.TLSv1_3
+        with self.assertRaises(ssl.SSLError):
+            server_params_test(client_context, server_context,
+                               chatty=True, connectionchatty=True,
+                               sni_name=hostname)
+
+    @unittest.skipUnless(CAN_SET_CLIENT_SIGALGS,
+                         "SSL library doesn't support setting client sigalgs")
+    def test_client_sigalgs(self):
+        # no mutual auth, so cient_sigalg should be None
+        client_context, server_context, hostname = testing_context()
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True, connectionchatty=True,
+                                   sni_name=hostname)
+        if CAN_GET_SELECTED_OPENSSL_SIGALG:
+            self.assertIsNone(stats['client_sigalg'])
+
+        # server auto, client rsa_pss_rsae_sha384
+        sigalg = "rsa_pss_rsae_sha384"
+        client_context, server_context, hostname = \
+            testing_context(client_cert=SIGNED_CERTFILE)
+        client_context.set_client_sigalgs(sigalg)
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True, connectionchatty=True,
+                                   sni_name=hostname)
+        if CAN_GET_SELECTED_OPENSSL_SIGALG:
+            self.assertEqual(stats['client_sigalg'], sigalg)
+
+    @unittest.skipUnless(CAN_SET_CLIENT_SIGALGS,
+                         "SSL library doesn't support setting client sigalgs")
+    def test_client_sigalgs_mismatch(self):
+        client_context, server_context, hostname = \
+            testing_context(client_cert=SIGNED_CERTFILE)
+        client_context.set_client_sigalgs("rsa_pss_rsae_sha256")
+        server_context.set_client_sigalgs("rsa_pss_rsae_sha384")
+
+        with self.assertRaises((
+            ssl.SSLError,
+            # On handshake failures, some systems raise a ConnectionResetError.
+            ConnectionResetError,
+            # On handshake failures, macOS may raise a BrokenPipeError.
+            # See https://github.com/python/cpython/issues/139504.
+            BrokenPipeError,
+        )):
+            server_params_test(client_context, server_context,
+                               chatty=True, connectionchatty=True,
+                               sni_name=hostname)
+
+    @unittest.skipUnless(CAN_SET_SERVER_SIGALGS,
+                         "SSL library doesn't support setting server sigalgs")
+    def test_server_sigalgs(self):
+        # server rsa_pss_rsae_sha384, client auto
+        sigalg = "rsa_pss_rsae_sha384"
+        client_context, server_context, hostname = testing_context()
+        server_context.set_server_sigalgs(sigalg)
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True, connectionchatty=True,
+                                   sni_name=hostname)
+        if CAN_GET_SELECTED_OPENSSL_SIGALG:
+            self.assertEqual(stats['server_sigalg'], sigalg)
+
+        # server auto, client rsa_pss_rsae_sha384
+        client_context, server_context, hostname = testing_context()
+        client_context.set_server_sigalgs(sigalg)
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True, connectionchatty=True,
+                                   sni_name=hostname)
+        if CAN_GET_SELECTED_OPENSSL_SIGALG:
+            self.assertEqual(stats['server_sigalg'], sigalg)
+
+    @unittest.skipUnless(CAN_SET_SERVER_SIGALGS,
+                         "SSL library doesn't support setting server sigalgs")
+    def test_server_sigalgs_mismatch(self):
+        client_context, server_context, hostname = testing_context()
+        client_context.set_server_sigalgs("rsa_pss_rsae_sha256")
+        server_context.set_server_sigalgs("rsa_pss_rsae_sha384")
+        with self.assertRaises(ssl.SSLError):
+            server_params_test(client_context, server_context,
+                               chatty=True, connectionchatty=True,
+                               sni_name=hostname)
+
     def test_selected_alpn_protocol(self):
         # selected_alpn_protocol() is None unless ALPN is used.
         client_context, server_context, hostname = testing_context()
@@ -4481,7 +4936,9 @@ def cb_raising(ssl_sock, server_name, initial_context):
                                            sni_name='supermessage')
 
             # Allow for flexible libssl error messages.
-            regex = "(SSLV3_ALERT_HANDSHAKE_FAILURE|NO_PRIVATE_VALUE)"
+            regex = ("(TLS_ALERT_HANDSHAKE_FAILURE"
+                     "|SSLV3_ALERT_HANDSHAKE_FAILURE"
+                     "|NO_PRIVATE_VALUE)")
             self.assertRegex(cm.exception.reason, regex)
             self.assertEqual(catch.unraisable.exc_type, ZeroDivisionError)
 
@@ -4536,19 +4993,30 @@ def test_read_write_after_close_raises_valuerror(self):
             self.assertRaises(ValueError, s.write, b'hello')
 
     def test_sendfile(self):
+        """Try to send a file using kTLS if possible."""
         TEST_DATA = b"x" * 512
         with open(os_helper.TESTFN, 'wb') as f:
             f.write(TEST_DATA)
         self.addCleanup(os_helper.unlink, os_helper.TESTFN)
         client_context, server_context, hostname = testing_context()
+        client_context.options |= getattr(ssl, 'OP_ENABLE_KTLS', 0)
         server = ThreadedEchoServer(context=server_context, chatty=False)
-        with server:
-            with client_context.wrap_socket(socket.socket(),
-                                            server_hostname=hostname) as s:
-                s.connect((HOST, server.port))
+        # kTLS seems to work only with a connection created before
+        # wrapping `sock` by the SSL context in contrast to calling
+        # `sock.connect()` after the wrapping.
+        with server, socket.create_connection((HOST, server.port)) as sock:
+            with client_context.wrap_socket(
+                sock, server_hostname=hostname
+            ) as ssock:
+                if support.verbose:
+                    ktls_used = ssock._sslobj.uses_ktls_for_send()
+                    print(
+                        'kTLS is',
+                        'available' if ktls_used else 'unavailable',
+                    )
                 with open(os_helper.TESTFN, 'rb') as file:
-                    s.sendfile(file)
-                    self.assertEqual(s.recv(1024), TEST_DATA)
+                    ssock.sendfile(file)
+                self.assertEqual(ssock.recv(1024), TEST_DATA)
 
     def test_session(self):
         client_context, server_context, hostname = testing_context()
@@ -4727,6 +5195,7 @@ def server_callback(identity):
 
     @requires_tls_version('TLSv1_3')
     @unittest.skipUnless(ssl.HAS_PSK, 'TLS-PSK disabled on this OpenSSL build')
+    @unittest.skipUnless(ssl.HAS_PSK_TLS13, 'TLS 1.3 PSK disabled on this OpenSSL build')
     def test_psk_tls1_3(self):
         psk = bytes.fromhex('deadbeef')
         identity_hint = 'identity-hint'
@@ -4758,6 +5227,9 @@ def server_callback(identity):
             with client_context.wrap_socket(socket.socket()) as s:
                 s.connect((HOST, server.port))
 
+    @support.skip_if_sanitizer("gh-150191: OpenSSL races on SSL->rwstate and "
+                               "the socket BIO flags with concurrent read "
+                               "and write", thread=True)
     def test_thread_recv_while_main_thread_sends(self):
         # GH-137583: Locking was added to calls to send() and recv() on SSL
         # socket objects. This seemed fine at the surface level because those
@@ -4794,6 +5266,50 @@ def background(sock):
                     if cm.exc_value is not None:
                         raise cm.exc_value
 
+    def test_got_eof(self):
+        # gh-148292: Test that _ssl._SSLSocket behaves the same on all OpenSSL
+        # versions on calling methods after EOF (after the first SSLEOFError).
+
+        server = TestEOFServer()
+        server.start()
+        if not server.listening.wait(support.SHORT_TIMEOUT):
+            raise RuntimeError("server took too long")
+        self.addCleanup(server.join)
+
+        context = ssl.create_default_context(cafile=CERTFILE)
+        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        sock.settimeout(support.SHORT_TIMEOUT)
+        sock.connect(server.address)
+        sslsock = context.wrap_socket(sock, server_hostname='localhost')
+        with sslsock:
+            sslsock.sendall(b'client\n')
+            # test the _ssl._SSLSocket object, not ssl.SSLSocket
+            sslobj = sslsock._sslobj
+
+            data = sslobj.read(1024)
+            self.assertEqual(data, b'server\n')
+
+            # The second read gets EOF error and sets got_eof_error to 1
+            with self.assertRaises(ssl.SSLEOFError):
+                sslobj.read(1024)
+
+            # Following read(), sendfile(), write() and do_handshake() calls
+            # must raise SSLEOFError
+            with self.assertRaises(ssl.SSLEOFError):
+                # The _SSLSocket remembers the previous EOF error
+                # and raises again SSLEOFError
+                sslobj.read(1024)
+            if hasattr(sslobj, 'sendfile'):
+                with open(__file__, "rb") as fp:
+                    with self.assertRaises(ssl.SSLEOFError):
+                        sslobj.sendfile(fp.fileno(), 0, 1)
+            with self.assertRaises(ssl.SSLEOFError):
+                sslobj.write(b'client2\n')
+            with self.assertRaises(ssl.SSLEOFError):
+                sslsock.do_handshake()
+
+            self.assertEqual(sslsock.pending(), 0)
+
 
 @unittest.skipUnless(has_tls_version('TLSv1_3') and ssl.HAS_PHA,
                      "Test needs TLS 1.3 PHA")
@@ -5220,6 +5736,20 @@ def msg_cb(conn, direction, version, content_type, msg_type, data):
         with self.assertRaises(TypeError):
             client_context._msg_callback = object()
 
+    def test_msg_callback_exception(self):
+        client_context, server_context, hostname = testing_context()
+
+        def msg_cb(conn, direction, version, content_type, msg_type, data):
+            raise RuntimeError("msg_cb exception")
+
+        client_context._msg_callback = msg_cb
+        server = ThreadedEchoServer(context=server_context, chatty=False)
+        with server:
+            with client_context.wrap_socket(socket.socket(),
+                                            server_hostname=hostname) as s:
+                with self.assertRaisesRegex(RuntimeError, "msg_cb exception"):
+                    s.connect((HOST, server.port))
+
     def test_msg_callback_tls12(self):
         client_context, server_context, hostname = testing_context()
         client_context.maximum_version = ssl.TLSVersion.TLSv1_2
diff --git a/Lib/test/test_statistics.py b/Lib/test/test_statistics.py
index e0b74432c94..677a87b51b9 100644
--- a/Lib/test/test_statistics.py
+++ b/Lib/test/test_statistics.py
@@ -2496,8 +2496,7 @@ def test_kde_random(self):
 
         data = [-2.1, -1.3, -0.4, 1.9, 5.1, 6.2, 7.8, 14.3, 15.1, 15.3, 15.8, 17.0]
         xarr = [x / 10 for x in range(-100, 250)]
-        # TODO: RUSTPYTHON - n originally 1_000_000 in CPython implementation but sorting is slow
-        n = 30_000
+        n = 1_000_000
         h = 1.75
         dx = 0.1
 
@@ -2519,8 +2518,7 @@ def p_expected(x):
                 F_hat = statistics.kde(data, h, kernel, cumulative=True)
 
                 for x in xarr:
-                    # TODO : RUSTPYTHON - abs_tol=0.0005 in CPython implementation but smaller `n` increases variance
-                    self.assertTrue(math.isclose(p_observed(x), p_expected(x), abs_tol=0.005))
+                    self.assertTrue(math.isclose(p_observed(x), p_expected(x), abs_tol=0.0005))
 
         # Test online updates to data
 
diff --git a/Lib/test/test_str.py b/Lib/test/test_str.py
index 4869c5ca9b0..f10f41df8b9 100644
--- a/Lib/test/test_str.py
+++ b/Lib/test/test_str.py
@@ -2672,7 +2672,6 @@ def test_check_encoding_errors(self):
         proc = assert_python_failure('-X', 'dev', '-c', code)
         self.assertEqual(proc.rc, 10, proc)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: "str expected at most 3 arguments, got 4" does not match "expected at most 3 arguments, got 4"
     def test_str_invalid_call(self):
         # too many args
         with self.assertRaisesRegex(TypeError, r"str expected at most 3 arguments, got 4"):
diff --git a/Lib/test/test_string/_support.py b/Lib/test/test_string/_support.py
index cfead782b7d..e1d7f6f6500 100644
--- a/Lib/test/test_string/_support.py
+++ b/Lib/test/test_string/_support.py
@@ -1,4 +1,3 @@
-import unittest
 from string.templatelib import Interpolation
 
 
diff --git a/Lib/test/test_strptime.py b/Lib/test/test_strptime.py
index e277e7f4ef7..5ac28870455 100644
--- a/Lib/test/test_strptime.py
+++ b/Lib/test/test_strptime.py
@@ -8,7 +8,6 @@
 import platform
 import sys
 from test import support
-from test.support import warnings_helper
 from test.support import skip_if_buggy_ucrt_strfptime, run_with_locales
 from datetime import date as datetime_date
 
@@ -286,7 +285,7 @@ def test_ValueError(self):
     def test_strptime_exception_context(self):
         # check that this doesn't chain exceptions needlessly (see #17572)
         with self.assertRaises(ValueError) as e:
-            _strptime._strptime_time('', '%D')
+            _strptime._strptime_time('', '%!')
         self.assertTrue(e.exception.__suppress_context__)
         # additional check for stray % branch
         with self.assertRaises(ValueError) as e:
@@ -406,37 +405,50 @@ def test_offset(self):
         (*_, offset), _, offset_fraction = _strptime._strptime("-013030.000001", "%z")
         self.assertEqual(offset, -(one_hour + half_hour + half_minute))
         self.assertEqual(offset_fraction, -1)
-        (*_, offset), _, offset_fraction = _strptime._strptime("+01:00", "%z")
-        self.assertEqual(offset, one_hour)
-        self.assertEqual(offset_fraction, 0)
-        (*_, offset), _, offset_fraction = _strptime._strptime("-01:30", "%z")
-        self.assertEqual(offset, -(one_hour + half_hour))
-        self.assertEqual(offset_fraction, 0)
-        (*_, offset), _, offset_fraction = _strptime._strptime("-01:30:30", "%z")
-        self.assertEqual(offset, -(one_hour + half_hour + half_minute))
-        self.assertEqual(offset_fraction, 0)
-        (*_, offset), _, offset_fraction = _strptime._strptime("-01:30:30.000001", "%z")
-        self.assertEqual(offset, -(one_hour + half_hour + half_minute))
-        self.assertEqual(offset_fraction, -1)
-        (*_, offset), _, offset_fraction = _strptime._strptime("+01:30:30.001", "%z")
-        self.assertEqual(offset, one_hour + half_hour + half_minute)
-        self.assertEqual(offset_fraction, 1000)
-        (*_, offset), _, offset_fraction = _strptime._strptime("Z", "%z")
-        self.assertEqual(offset, 0)
-        self.assertEqual(offset_fraction, 0)
+
+        cases = [
+            ("+01:00", one_hour, 0),
+            ("-01:30", -(one_hour + half_hour), 0),
+            ("-01:30:30", -(one_hour + half_hour + half_minute), 0),
+            ("-01:30:30.000001", -(one_hour + half_hour + half_minute), -1),
+            ("+01:30:30.001", +(one_hour + half_hour + half_minute), 1000),
+            ("Z", 0, 0),
+        ]
+        for directive in ("%z", "%:z"):
+            for offset_str, expected_offset, expected_fraction in cases:
+                with self.subTest(offset_str=offset_str, directive=directive):
+                    (*_, offset), _, offset_fraction = _strptime._strptime(
+                        offset_str, directive
+                    )
+                    self.assertEqual(offset, expected_offset)
+                    self.assertEqual(offset_fraction, expected_fraction)
 
     def test_bad_offset(self):
-        with self.assertRaises(ValueError):
-            _strptime._strptime("-01:30:30.", "%z")
-        with self.assertRaises(ValueError):
-            _strptime._strptime("-0130:30", "%z")
-        with self.assertRaises(ValueError):
-            _strptime._strptime("-01:30:30.1234567", "%z")
-        with self.assertRaises(ValueError):
-            _strptime._strptime("-01:30:30:123456", "%z")
+        error_cases_any_z = [
+            "-01:30:30.",         # Decimal point not followed with digits
+            "-01:30:30.1234567",  # Too many digits after decimal point
+            "-01:30:30:123456",   # Colon as decimal separator
+            "-0130:30",           # Incorrect use of colons
+        ]
+        for directive in ("%z", "%:z"):
+            for timestr in error_cases_any_z:
+                with self.subTest(timestr=timestr, directive=directive):
+                    with self.assertRaises(ValueError):
+                        _strptime._strptime(timestr, directive)
+
+        required_colons_cases = ["-013030", "+0130", "-01:3030.123456"]
+        for timestr in required_colons_cases:
+            with self.subTest(timestr=timestr):
+                with self.assertRaises(ValueError):
+                    _strptime._strptime(timestr, "%:z")
+
         with self.assertRaises(ValueError) as err:
             _strptime._strptime("-01:3030", "%z")
         self.assertEqual("Inconsistent use of : in -01:3030", str(err.exception))
+        with self.assertRaises(ValueError) as err:
+            _strptime._strptime("-01:3030", "%:z")
+        self.assertEqual("Missing colon in %:z before '30', got '-01:3030'",
+                         str(err.exception))
 
     @skip_if_buggy_ucrt_strfptime
     def test_timezone(self):
@@ -626,15 +638,49 @@ def test_escaping(self):
         need_escaping = r".^$*+?{}\[]|)("
         self.assertTrue(_strptime._strptime_time(need_escaping, need_escaping))
 
-    @warnings_helper.ignore_warnings(category=DeprecationWarning)  # gh-70647
     def test_feb29_on_leap_year_without_year(self):
-        time.strptime("Feb 29", "%b %d")
+        with self.assertRaises(ValueError):
+            time.strptime("Feb 29", "%b %d")
+        with self.assertRaises(ValueError):
+            time.strptime("Mar 1", "%b %d")
+
+    def test_strptime_F_format(self):
+        test_date = "2025-10-26"
+        self.assertEqual(
+            time.strptime(test_date, "%F"),
+            time.strptime(test_date, "%Y-%m-%d")
+        )
+
+    def test_strptime_T_format(self):
+        test_time = "15:00:00"
+        self.assertEqual(
+            time.strptime(test_time, "%T"),
+            time.strptime(test_time, "%H:%M:%S")
+        )
+
+    def test_strptime_D_format(self):
+        test_date = "11/28/25"
+        self.assertEqual(
+            time.strptime(test_date, "%D"),
+            time.strptime(test_date, "%m/%d/%y")
+        )
 
-    @warnings_helper.ignore_warnings(category=DeprecationWarning)  # gh-70647
-    def test_mar1_comes_after_feb29_even_when_omitting_the_year(self):
-        self.assertLess(
-                time.strptime("Feb 29", "%b %d"),
-                time.strptime("Mar 1", "%b %d"))
+    def test_strptime_n_and_t_format(self):
+        format_directives = ('%n', '%t', '%n%t', '%t%n')
+        whitespaces = ('', ' ', '\t', '\r', '\v', '\n', '\f')
+        for fd in format_directives:
+            for ws in (*whitespaces, ''.join(whitespaces)):
+                with self.subTest(format_directive=fd, whitespace=ws):
+                    self.assertEqual(
+                        time.strptime(
+                            f"2026{ws}02{ws}03",
+                            f"%Y{fd}%m{fd}%d",
+                        ),
+                        time.strptime(
+                            f'2026-02-03',
+                            "%Y-%m-%d",
+                        ),
+                    )
 
 class Strptime12AMPMTests(unittest.TestCase):
     """Test a _strptime regression in '%I %p' at 12 noon (12 PM)"""
diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py
index e18bad9c990..934012784de 100644
--- a/Lib/test/test_struct.py
+++ b/Lib/test/test_struct.py
@@ -503,9 +503,9 @@ def _test_pack_into(self, pack_into):
             pack_into(writable_buf, None, test_string)
         with self.assertRaises(TypeError):
             pack_into(writable_buf, 0.0, test_string)
-        with self.assertRaises((IndexError, OverflowError)):
+        with self.assertRaises(OverflowError):
             pack_into(writable_buf, 2**1000, test_string)
-        with self.assertRaises((IndexError, OverflowError)):
+        with self.assertRaises(OverflowError):
             pack_into(writable_buf, -2**1000, test_string)
 
     def test_pack_into(self):
@@ -616,27 +616,36 @@ def test_Struct_reinitialization(self):
         # Struct instance.  This test can be used to detect the leak
         # when running with regrtest -L.
         s = struct.Struct('>h')
-        s.__init__('>hh')
+        msg = 'Re-initialization .* will not work'
+        with self.assertWarnsRegex(FutureWarning, msg):
+            s.__init__('>hh')
         self.assertEqual(s.format, '>hh')
         packed = b'\x00\x01\x00\x02'
         self.assertEqual(s.pack(1, 2), packed)
         self.assertEqual(s.unpack(packed), (1, 2))
 
-        with self.assertRaises(UnicodeEncodeError):
-            s.__init__('\udc00')
+        s.__init__('>hh')  # same format
         self.assertEqual(s.format, '>hh')
         self.assertEqual(s.pack(1, 2), packed)
         self.assertEqual(s.unpack(packed), (1, 2))
 
-        with self.assertRaises(struct.error):
-            s.__init__('$')
+        with self.assertWarnsRegex(FutureWarning, msg):
+            with self.assertRaises(ValueError):
+                s.__init__('\udc00')
+        self.assertEqual(s.format, '>hh')
+        self.assertEqual(s.pack(1, 2), packed)
+        self.assertEqual(s.unpack(packed), (1, 2))
+
+        with self.assertWarnsRegex(FutureWarning, msg):
+            with self.assertRaises(struct.error):
+                s.__init__('$')
         self.assertEqual(s.format, '>hh')
         self.assertEqual(s.pack(1, 2), packed)
         self.assertEqual(s.unpack(packed), (1, 2))
 
     def check_sizeof(self, format_str, number_of_codes):
         # The size of 'PyStructObject'
-        totalsize = support.calcobjsize('2n3P')
+        totalsize = support.calcobjsize('2n3P?0P')
         # The size taken up by the 'formatcode' dynamic array
         totalsize += struct.calcsize('P3n0P') * (number_of_codes + 1)
         support.check_sizeof(self, struct.Struct(format_str), totalsize)
@@ -834,15 +843,160 @@ def test_error_propagation(fmt_str):
         test_error_propagation('N')
         test_error_propagation('n')
 
-    def test_struct_subclass_instantiation(self):
+    def test_custom_struct_init(self):
         # Regression test for https://github.com/python/cpython/issues/112358
         class MyStruct(struct.Struct):
-            def __init__(self):
+            def __init__(self, *args, **kwargs):
                 super().__init__('>h')
 
+        my_struct = MyStruct('>h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        my_struct = MyStruct(format='>h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+
+        warnmsg = r"Different format arguments for __new__\(\) and __init__\(\) methods of Struct"
+        with self.assertWarnsRegex(FutureWarning, warnmsg):
+            my_struct = MyStruct('<h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(FutureWarning, warnmsg):
+            my_struct = MyStruct(format='<h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+
+        warnmsg = r"Struct\(\) missing required argument 'format' \(pos 1\)"
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg):
+            my_struct = MyStruct()
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg):
+            my_struct = MyStruct(arg='>h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+
+        warnmsg = r"Struct\(\) takes at most 1 argument \(2 given\)"
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg):
+            my_struct = MyStruct('>h', 42)
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg):
+            my_struct = MyStruct('>h', arg=42)
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg):
+            my_struct = MyStruct('>h', format=42)
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg):
+            my_struct = MyStruct(format='>h', arg=42)
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+
+        warnmsg = r"Invalid 'format' argument for Struct\.__new__\(\): "
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg + '.*must be'):
+            my_struct = MyStruct(42)
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg + '.*must be'):
+            my_struct = MyStruct(format=42)
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg + 'bad char'):
+            my_struct = MyStruct('$')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg + 'bad char'):
+            my_struct = MyStruct(format='$')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg + "non-ASCII"):
+            my_struct = MyStruct('\udc00')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertWarnsRegex(DeprecationWarning, warnmsg + "non-ASCII"):
+            my_struct = MyStruct(format='\udc00')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+
+    def test_custom_struct_new(self):
+        # New way, no warnings:
+        class MyStruct(struct.Struct):
+            def __new__(cls, *args, **kwargs):
+                return super().__new__(cls, '>h')
+
+        for format in '>h', '<h', 42, '$', '\u20ac', '\udc00', b'\xa4':
+            with self.subTest(format=format):
+                my_struct = MyStruct(format)
+                self.assertEqual(my_struct.format, '>h')
+                self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        my_struct = MyStruct(format='<h')
+        self.assertEqual(my_struct.format, '>h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
         my_struct = MyStruct()
+        self.assertEqual(my_struct.format, '>h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        my_struct = MyStruct('<h', 42)
+        self.assertEqual(my_struct.format, '>h')
         self.assertEqual(my_struct.pack(12345), b'\x30\x39')
 
+    def test_custom_struct_new_and_init(self):
+        # New way, no warnings:
+        class MyStruct(struct.Struct):
+            def __new__(cls, newargs, initargs):
+                return super().__new__(cls, *newargs)
+            def __init__(self, newargs, initargs):
+                if initargs is not None:
+                    super().__init__(*initargs)
+
+        my_struct = MyStruct(('>h',), ('>h',))
+        self.assertEqual(my_struct.format, '>h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertRaises(TypeError):
+            MyStruct((), ())
+        with self.assertRaises(TypeError):
+            MyStruct(('>h',), ())
+        with self.assertRaises(TypeError):
+            MyStruct((), ('>h',))
+        with self.assertRaises(TypeError):
+            MyStruct((42,), ('>h',))
+        with self.assertWarns(FutureWarning):
+            with self.assertRaises(TypeError):
+                MyStruct(('>h',), (42,))
+        with self.assertRaises(struct.error):
+            MyStruct(('$',), ('>h',))
+        with self.assertWarns(FutureWarning):
+            with self.assertRaises(struct.error):
+                MyStruct(('>h',), ('$',))
+        with self.assertRaises(ValueError):
+            MyStruct(('\udc00',), ('>h',))
+        with self.assertRaises(ValueError):
+            MyStruct((b'\xa4',), ('>h',))
+        with self.assertWarns(FutureWarning):
+            with self.assertRaises(ValueError):
+                MyStruct(('>h',), ('\udc00',))
+        with self.assertWarns(FutureWarning):
+            with self.assertRaises(ValueError):
+                MyStruct(('>h',), (b'\xa4',))
+        with self.assertWarns(FutureWarning):
+            my_struct = MyStruct(('>h',), ('<h',))
+        self.assertEqual(my_struct.format, '<h')
+        self.assertEqual(my_struct.pack(12345), b'\x39\x30')
+
+    def test_no_custom_struct_new_or_init(self):
+        class MyStruct(struct.Struct):
+            pass
+
+        my_struct = MyStruct('>h')
+        self.assertEqual(my_struct.format, '>h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        my_struct = MyStruct(format='>h')
+        self.assertEqual(my_struct.format, '>h')
+        self.assertEqual(my_struct.pack(12345), b'\x30\x39')
+        with self.assertRaises(TypeError):
+            MyStruct()
+        with self.assertRaises(TypeError):
+            MyStruct(42)
+        with self.assertRaises(struct.error):
+            MyStruct('$')
+        with self.assertRaises(ValueError):
+            MyStruct('\udc00')
+        with self.assertRaises(ValueError):
+            MyStruct(b'\xa4')
+        with self.assertRaises(TypeError):
+            MyStruct('>h', 42)
+        with self.assertRaises(TypeError):
+            MyStruct('>h', arg=42)
+        with self.assertRaises(TypeError):
+            MyStruct(arg=42)
+        with self.assertRaises(TypeError):
+            MyStruct('>h', format='>h')
+
     def test_repr(self):
         s = struct.Struct('=i2H')
         self.assertEqual(repr(s), f'Struct({s.format!r})')
@@ -851,7 +1005,11 @@ def test_c_complex_round_trip(self):
         values = [complex(*_) for _ in combinations([1, -1, 0.0, -0.0, 2,
                                                      -3, INF, -INF, NAN], 2)]
         for z in values:
-            for f in ['F', 'D', '>F', '>D', '<F', '<D']:
+            for f in [
+                'F', 'D', 'Zf', 'Zd',
+                '>F', '>D', '>Zf', '>Zd',
+                '<F', '<D', '<Zf', '<Zd',
+            ]:
                 with self.subTest(z=z, format=f):
                     round_trip = struct.unpack(f, struct.pack(f, z))[0]
                     self.assertComplexesAreIdentical(z, round_trip)
@@ -882,7 +1040,7 @@ def test_operations_on_half_initialized_Struct(self):
         self.assertRaises(RuntimeError, S.pack_into, spam, 1)
         self.assertRaises(RuntimeError, S.unpack, spam)
         self.assertRaises(RuntimeError, S.unpack_from, spam)
-        self.assertRaises(RuntimeError, getattr, S, 'format')
+        self.assertRaises(AttributeError, getattr, S, 'format')
         self.assertRaises(RuntimeError, S.__sizeof__)
         self.assertRaises(RuntimeError, repr, S)
         self.assertEqual(S.size, -1)
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index d3cb80bbb70..51a4a8155f5 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -326,7 +326,7 @@
 
 # Incorrectly closed strings
 
->>> "The interesting object "The important object" is very important"  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+>>> "The interesting object "The important object" is very important"
 Traceback (most recent call last):
 SyntaxError: invalid syntax. Is this intended to be part of the string?
 
@@ -423,7 +423,7 @@
 Traceback (most recent call last):
 SyntaxError: invalid syntax
 
->>> def foo(/,a,b=,c):  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+>>> def foo(/,a,b=,c):
 ...    pass
 Traceback (most recent call last):
 SyntaxError: at least one argument must precede /
@@ -1045,7 +1045,7 @@
 a complex 'if' (one with 'elif') would fail to notice an invalid suite,
 leading to spurious errors.
 
-   >>> if 1:  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> if 1:
    ...   x() = 1
    ... elif 1:
    ...   pass
@@ -1053,7 +1053,7 @@
      ...
    SyntaxError: cannot assign to function call here. Maybe you meant '==' instead of '='?
 
-   >>> if 1:  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> if 1:
    ...   pass
    ... elif 1:
    ...   x() = 1
@@ -1061,7 +1061,7 @@
      ...
    SyntaxError: cannot assign to function call here. Maybe you meant '==' instead of '='?
 
-   >>> if 1:  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> if 1:
    ...   x() = 1
    ... elif 1:
    ...   pass
@@ -1071,7 +1071,7 @@
      ...
    SyntaxError: cannot assign to function call here. Maybe you meant '==' instead of '='?
 
-   >>> if 1:  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> if 1:
    ...   pass
    ... elif 1:
    ...   x() = 1
@@ -1081,7 +1081,7 @@
      ...
    SyntaxError: cannot assign to function call here. Maybe you meant '==' instead of '='?
 
-   >>> if 1:  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> if 1:
    ...   pass
    ... elif 1:
    ...   pass
@@ -1185,7 +1185,7 @@
    Traceback (most recent call last):
    SyntaxError: expected ':'
 
-   >>> with (blech as something)  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> with (blech as something)
    ...   pass
    Traceback (most recent call last):
    SyntaxError: expected ':'
@@ -1195,12 +1195,12 @@
    Traceback (most recent call last):
    SyntaxError: expected ':'
 
-   >>> with (blech, block as something)  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> with (blech, block as something)
    ...   pass
    Traceback (most recent call last):
    SyntaxError: expected ':'
 
-   >>> with (blech, block as something, bluch)  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> with (blech, block as something, bluch)
    ...   pass
    Traceback (most recent call last):
    SyntaxError: expected ':'
@@ -1464,7 +1464,7 @@
    Traceback (most recent call last):
    SyntaxError: invalid syntax
 
-   >>> dict(x=34, (x for x in range 10), 1); x $ y  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+   >>> dict(x=34, (x for x in range 10), 1); x $ y
    Traceback (most recent call last):
    SyntaxError: invalid syntax
 
@@ -2077,7 +2077,7 @@
 Traceback (most recent call last):
 SyntaxError: cannot use literal as import target
 
->>> from a import (b as c.d)  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+>>> from a import (b as c.d)
 Traceback (most recent call last):
 SyntaxError: cannot use attribute as import target
 
@@ -2085,18 +2085,18 @@
 Traceback (most recent call last):
 SyntaxError: cannot use literal as import target
 
->>> from a import (  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+>>> from a import (
 ...   b as f())
 Traceback (most recent call last):
 SyntaxError: cannot use function call as import target
 
->>> from a import (  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+>>> from a import (
 ...   b as [],
 ... )
 Traceback (most recent call last):
 SyntaxError: cannot use list as import target
 
->>> from a import (  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+>>> from a import (
 ...   b,
 ...   c as ()
 ... )
@@ -2233,7 +2233,7 @@
     Traceback (most recent call last):
     SyntaxError: cannot assign to __debug__
 
-    >>> import ä £  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+    >>> import ä £
     Traceback (most recent call last):
     SyntaxError: invalid character '£' (U+00A3)
 
@@ -2245,7 +2245,7 @@
     Traceback (most recent call last):
     SyntaxError: cannot use '_' as a target
 
-    >>> match ...:  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+    >>> match ...:
     ...   case 42 as 1+2+4:
     ...     ...
     Traceback (most recent call last):
@@ -2263,13 +2263,13 @@
     Traceback (most recent call last):
     SyntaxError: cannot use tuple as pattern target
 
-    >>> match ...:  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+    >>> match ...:
     ...   case 42 as (a + 1):
     ...     ...
     Traceback (most recent call last):
     SyntaxError: cannot use expression as pattern target
 
-    >>> match ...:  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+    >>> match ...:
     ...   case (32 as x) | (42 as a()):
     ...     ...
     Traceback (most recent call last):
@@ -2375,7 +2375,7 @@
 
 A[*:] and A[:*]
 
-    >>> A[*:]  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+    >>> A[*:]
     Traceback (most recent call last):
         ...
     SyntaxError: Invalid star expression
@@ -2386,7 +2386,7 @@
 
 A[*]
 
-    >>> A[*]  # TODO: RUSTPYTHON; Wrong error message # doctest: +EXPECTED_FAILURE
+    >>> A[*]
     Traceback (most recent call last):
         ...
     SyntaxError: Invalid star expression
diff --git a/Lib/test/test_sysconfig.py b/Lib/test/test_sysconfig.py
index 9502e2dead5..5956a74d072 100644
--- a/Lib/test/test_sysconfig.py
+++ b/Lib/test/test_sysconfig.py
@@ -7,6 +7,7 @@
 import shutil
 import json
 import textwrap
+from unittest.mock import patch
 from copy import copy
 
 from test import support
@@ -20,7 +21,7 @@
 )
 from test.support.import_helper import import_module
 from test.support.os_helper import (TESTFN, unlink, skip_unless_symlink,
-                                    change_cwd)
+                                    change_cwd, EnvironmentVarGuard)
 from test.support.venv import VirtualEnvironmentMixin
 
 import sysconfig
@@ -32,7 +33,6 @@
 from sysconfig.__main__ import _main, _parse_makefile, _get_pybuilddir, _get_json_data_name
 import _imp
 import _osx_support
-import _sysconfig
 
 
 HAS_USER_BASE = sysconfig._HAS_USER_BASE
@@ -249,19 +249,15 @@ def test_get_platform(self):
         self.assertIsInstance(actual_platform, str)
         self.assertTrue(actual_platform)
 
-        # windows XP, 32bits
+        # Windows
         os.name = 'nt'
-        sys.version = ('2.4.4 (#71, Oct 18 2006, 08:34:43) '
-                       '[MSC v.1310 32 bit (Intel)]')
-        sys.platform = 'win32'
-        self.assertEqual(get_platform(), 'win32')
-
-        # windows XP, amd64
-        os.name = 'nt'
-        sys.version = ('2.4.4 (#71, Oct 18 2006, 08:34:43) '
-                       '[MSC v.1310 32 bit (Amd64)]')
-        sys.platform = 'win32'
-        self.assertEqual(get_platform(), 'win-amd64')
+        with patch('_sysconfig.get_platform', create=True, return_value='win32'):
+            self.assertEqual(get_platform(), 'win32')
+        with patch('_sysconfig.get_platform', create=True, return_value='win-amd64'):
+            self.assertEqual(get_platform(), 'win-amd64')
+        sys.platform = 'test-plaform'
+        with patch('_sysconfig.get_platform', create=True, return_value=None):
+            self.assertEqual(get_platform(), 'test-plaform')
 
         # macbook
         os.name = 'posix'
@@ -463,6 +459,15 @@ def test_soabi(self):
         soabi = sysconfig.get_config_var('SOABI')
         self.assertIn(soabi, _imp.extension_suffixes()[0])
 
+    @unittest.skipIf(not _imp.extension_suffixes(), "stub loader has no suffixes")
+    @unittest.skipIf(sys.platform == "win32", "Does not apply to Windows")
+    @unittest.skipIf(sysconfig.get_config_var('SOABI_PLATFORM') == 0,
+                     "SOABI_PLATFORM is undefined")
+    def test_soabi_platform(self):
+        soabi_platform = sysconfig.get_config_var('SOABI_PLATFORM')
+        soabi = sysconfig.get_config_var('SOABI')
+        self.assertIn(soabi_platform, soabi)
+
     @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: Expected str, not NoneType
     def test_library(self):
         library = sysconfig.get_config_var('LIBRARY')
@@ -584,6 +589,12 @@ def test_linux_ext_suffix(self):
                 expected_suffixes = 'x86_64-linux-gnu.so', 'x86_64-linux-musl.so'
             self.assertEndsWith(suffix, expected_suffixes)
 
+    @unittest.skipIf(sysconfig.get_config_var('PY_BUILTIN_HASHLIB_HASHES') is None,
+                     'PY_BUILTIN_HASHLIB_HASHES required for this test')
+    def test_PY_BUILTIN_HASHLIB_HASHES_in_vars(self):
+        vars = sysconfig.get_config_vars()
+        self.assertFalse(vars['PY_BUILTIN_HASHLIB_HASHES'].startswith('"'))
+
     @unittest.skipUnless(sys.platform == 'android', 'Android-specific test')
     def test_android_ext_suffix(self):
         machine = platform.machine()
@@ -776,8 +787,13 @@ def test_parse_makefile(self):
             print("var3=42", file=makefile)
             print("var4=$/invalid", file=makefile)
             print("var5=dollar$$5", file=makefile)
-            print("var6=${var3}/lib/python3.5/config-$(VAR2)$(var5)"
+            print("var6=${var7}/lib/python3.5/config-$(VAR2)$(var5)"
                   "-x86_64-linux-gnu", file=makefile)
+            print("var7=${var3}", file=makefile)
+            print("var8=$$(var3)", file=makefile)
+            print("var9=$(var10)(var3)", file=makefile)
+            print("var10=$$", file=makefile)
+            print("var11=$${ORIGIN}${var5}", file=makefile)
         vars = _parse_makefile(TESTFN)
         self.assertEqual(vars, {
             'var1': 'ab42',
@@ -786,6 +802,74 @@ def test_parse_makefile(self):
             'var4': '$/invalid',
             'var5': 'dollar$5',
             'var6': '42/lib/python3.5/config-b42dollar$5-x86_64-linux-gnu',
+            'var7': 42,
+            'var8': '$(var3)',
+            'var9': '$(var3)',
+            'var10': '$',
+            'var11': '${ORIGIN}dollar$5',
+        })
+
+    def _test_parse_makefile_recursion(self):
+        self.addCleanup(unlink, TESTFN)
+        with open(TESTFN, "w") as makefile:
+            print("var1=var1=$(var1)", file=makefile)
+            print("var2=var3=$(var3)", file=makefile)
+            print("var3=var2=$(var2)", file=makefile)
+        vars = _parse_makefile(TESTFN)
+        self.assertEqual(vars, {
+            'var1': 'var1=',
+            'var2': 'var3=var2=',
+            'var3': 'var2=',
+        })
+
+    def test_parse_makefile_renamed_vars(self):
+        self.addCleanup(unlink, TESTFN)
+        with open(TESTFN, "w") as makefile:
+            print("var1=$(CFLAGS)", file=makefile)
+            print("PY_CFLAGS=-Wall $(CPPFLAGS)", file=makefile)
+            print("PY_LDFLAGS=-lm", file=makefile)
+            print("var2=$(LDFLAGS)", file=makefile)
+            print("var3=$(CPPFLAGS)", file=makefile)
+        with EnvironmentVarGuard() as env:
+            env.clear()
+            vars = _parse_makefile(TESTFN)
+        self.assertEqual(vars, {
+            'var1': '-Wall',
+            'CFLAGS': '-Wall',
+            'PY_CFLAGS': '-Wall',
+            'LDFLAGS': '-lm',
+            'PY_LDFLAGS': '-lm',
+            'var2': '-lm',
+            'var3': '',
+        })
+
+    def test_parse_makefile_keep_unresolved(self):
+        self.addCleanup(unlink, TESTFN)
+        with open(TESTFN, "w") as makefile:
+            print("var1=value", file=makefile)
+            print("var2=$/", file=makefile)
+            print("var3=$/$(var1)", file=makefile)
+            print("var4=var5=$(var5)", file=makefile)
+            print("var5=$/$(var1)", file=makefile)
+            print("var6=$(var1)$/", file=makefile)
+            print("var7=var8=$(var8)", file=makefile)
+            print("var8=$(var1)$/", file=makefile)
+        vars = _parse_makefile(TESTFN)
+        self.assertEqual(vars, {
+            'var1': 'value',
+            'var2': '$/',
+            'var3': '$/value',
+            'var4': 'var5=$/value',
+            'var5': '$/value',
+            'var6': 'value$/',
+            'var7': 'var8=value$/',
+            'var8': 'value$/',
+        })
+        vars = _parse_makefile(TESTFN, keep_unresolved=False)
+        self.assertEqual(vars, {
+            'var1': 'value',
+            'var4': 'var5=',
+            'var7': 'var8=',
         })
 
 
diff --git a/Lib/test/test_tabnanny.py b/Lib/test/test_tabnanny.py
index d7a77eb26e4..85e3e76e900 100644
--- a/Lib/test/test_tabnanny.py
+++ b/Lib/test/test_tabnanny.py
@@ -3,19 +3,18 @@
 Glossary:
     * errored    : Whitespace related problems present in file.
 """
-from unittest import TestCase, mock
+
+from unittest import TestCase, main, mock
 import errno
 import os
+import sys
 import tabnanny
 import tokenize
 import tempfile
 import textwrap
-from test.support import (captured_stderr, captured_stdout, script_helper,
-                          findfile)
+from test.support import captured_stderr, captured_stdout, script_helper
 from test.support.os_helper import unlink
 
-import unittest  # XXX: RUSTPYTHON; importing to be able to skip tests
-
 
 SOURCE_CODES = {
     "incomplete_expression": (
@@ -217,7 +216,6 @@ def test_when_tokenize_tokenerror(self):
             with self.assertRaises(SystemExit):
                 self.verify_tabnanny_check(file_path, err=err)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; A python source code file eligible for raising `tabnanny.NannyNag`.
     def test_when_nannynag_error_verbose(self):
         """A python source code file eligible for raising `tabnanny.NannyNag`.
 
@@ -231,7 +229,6 @@ def test_when_nannynag_error_verbose(self):
             tabnanny.verbose = 1
             self.verify_tabnanny_check(file_path, out=out)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; A python source code file eligible for raising `tabnanny.NannyNag`.
     def test_when_nannynag_error(self):
         """A python source code file eligible for raising `tabnanny.NannyNag`."""
         with TemporaryPyFile(SOURCE_CODES["nannynag_errored"]) as file_path:
@@ -331,8 +328,7 @@ def test_with_error_free_file(self):
 
     def test_command_usage(self):
         """Should display usage on no arguments."""
-        path = findfile('tabnanny.py')
-        stderr = f"Usage: {path} [-v] file_or_directory ..."
+        stderr = f"Usage: {sys.executable} -m tabnanny [-v] file_or_directory ..."
         self.validate_cmd(stderr=stderr, expect_failure=True)
 
     def test_quiet_flag(self):
@@ -341,7 +337,6 @@ def test_quiet_flag(self):
             stdout = f"{file_path}\n"
             self.validate_cmd("-q", file_path, stdout=stdout)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_verbose_mode(self):
         """Should display more error information if verbose mode is on."""
         with TemporaryPyFile(SOURCE_CODES["nannynag_errored"]) as path:
@@ -350,7 +345,6 @@ def test_verbose_mode(self):
             ).strip()
             self.validate_cmd("-v", path, stdout=stdout, partial=True)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_double_verbose_mode(self):
         """Should display detailed error information if double verbose is on."""
         with TemporaryPyFile(SOURCE_CODES["nannynag_errored"]) as path:
@@ -358,3 +352,17 @@ def test_double_verbose_mode(self):
                 "offending line: '\\tprint(\"world\")'"
             ).strip()
             self.validate_cmd("-vv", path, stdout=stdout, partial=True)
+
+
+class TestModule(TestCase):
+    def test_deprecated__version__(self):
+        with self.assertWarnsRegex(
+            DeprecationWarning,
+            "'__version__' is deprecated and slated for removal in Python 3.20",
+        ) as cm:
+            getattr(tabnanny, "__version__")
+        self.assertEqual(cm.filename, __file__)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
index f3b61d9fbad..cc134ed41ca 100644
--- a/Lib/test/test_tarfile.py
+++ b/Lib/test/test_tarfile.py
@@ -10,6 +10,7 @@
 import re
 import warnings
 import stat
+import time
 
 import unittest
 import unittest.mock
@@ -1646,6 +1647,22 @@ def test_symlink_size(self):
         finally:
             os_helper.unlink(path)
 
+    @os_helper.skip_unless_symlink
+    def test_symlink_target_normalization(self):
+        # Test for gh-151669.
+        path = os.path.join(TEMPDIR, "symlink")
+        target = "subdir/link/target"
+        os.symlink(target.replace("/", os.sep), path)
+        try:
+            tar = tarfile.open(tmpname, self.mode)
+            try:
+                tarinfo = tar.gettarinfo(path)
+                self.assertEqual(tarinfo.linkname, target)
+            finally:
+                tar.close()
+        finally:
+            os_helper.unlink(path)
+
     def test_add_self(self):
         # Test for #1257255.
         dstname = os.path.abspath(tmpname)
@@ -1904,6 +1921,19 @@ def test_source_directory_not_leaked(self):
         payload = pathlib.Path(tmpname).read_text(encoding='latin-1')
         assert os.path.dirname(tmpname) not in payload
 
+    def test_create_with_mtime(self):
+        tarfile.open(tmpname, self.mode, mtime=0).close()
+        with self.open(tmpname, 'r') as fobj:
+            fobj.read()
+            self.assertEqual(fobj.mtime, 0)
+
+    def test_create_without_mtime(self):
+        before = int(time.time())
+        tarfile.open(tmpname, self.mode).close()
+        after = int(time.time())
+        with self.open(tmpname, 'r') as fobj:
+            fobj.read()
+            self.assertTrue(before <= fobj.mtime <= after)
 
 class Bz2StreamWriteTest(Bz2Test, StreamWriteTest):
     decompressor = bz2.BZ2Decompressor if bz2 else None
@@ -2210,6 +2240,19 @@ def test_create_with_compresslevel(self):
         with tarfile.open(tmpname, 'r:gz', compresslevel=1) as tobj:
             pass
 
+    def test_create_with_mtime(self):
+        tarfile.open(tmpname, self.mode, mtime=0).close()
+        with self.open(tmpname, 'rb') as fobj:
+            fobj.read()
+            self.assertEqual(fobj.mtime, 0)
+
+    def test_create_without_mtime(self):
+        before = int(time.time())
+        tarfile.open(tmpname, self.mode).close()
+        after = int(time.time())
+        with self.open(tmpname, 'r') as fobj:
+            fobj.read()
+            self.assertTrue(before <= fobj.mtime <= after)
 
 class Bz2CreateTest(Bz2Test, CreateTest):
 
@@ -2872,7 +2915,7 @@ def test_useful_error_message_when_modules_missing(self):
             str(excinfo.exception),
         )
 
-    @unittest.skipUnless(os_helper.can_symlink(), 'requires symlink support')
+    @os_helper.skip_unless_symlink
     @unittest.skipUnless(hasattr(os, 'chmod'), "missing os.chmod")
     @unittest.mock.patch('os.chmod')
     def test_deferred_directory_attributes_update(self, mock_chmod):
@@ -3925,6 +3968,20 @@ def test_absolute(self):
                         tarfile.AbsolutePathError,
                         """['"].*escaped.evil['"] has an absolute path""")
 
+    def test_parent_dir_out_and_back(self):
+        # Test a member that leaves the destination and comes back.
+        # The containment check looks at the resolved path, which stays
+        # inside, but the intermediate directories are created from the
+        # name as given, which does not.
+        with ArchiveMaker() as arc:
+            arc.add(f'../escaped.evil/../{self.destdir.name}/sub/file',
+                    content='content')
+
+        for filter in 'tar', 'data':
+            with self.subTest(filter):
+                with self.check_context(arc.open(), filter):
+                    self.expect_file('sub/file', content='content')
+
     @symlink_test
     def test_parent_symlink(self):
         # Test interplaying symlinks
@@ -3937,23 +3994,21 @@ def test_parent_symlink(self):
             arc.add('current', symlink_to='.')
 
             # effectively points to ./../
-            arc.add('parent', symlink_to='current/..')
+            if self.dotdot_resolves_early and os_helper.can_symlink():
+                arc.add('parent', symlink_to='current/../..')
+            else:
+                arc.add('parent', symlink_to='current/..')
 
             arc.add('parent/evil')
 
         if os_helper.can_symlink():
             with self.check_context(arc.open(), 'fully_trusted'):
-                if self.raised_exception is not None:
-                    # Windows will refuse to create a file that's a symlink to itself
-                    # (and tarfile doesn't swallow that exception)
-                    self.expect_exception(FileExistsError)
-                    # The other cases will fail with this error too.
-                    # Skip the rest of this test.
-                    return
+                self.expect_file('current', symlink_to='.')
+                if self.dotdot_resolves_early:
+                    self.expect_file('parent', symlink_to='current/../..')
                 else:
-                    self.expect_file('current', symlink_to='.')
                     self.expect_file('parent', symlink_to='current/..')
-                    self.expect_file('../evil')
+                self.expect_file('../evil')
 
             with self.check_context(arc.open(), 'tar'):
                 self.expect_exception(
@@ -4147,6 +4202,21 @@ def test_absolute_symlink(self):
                 tarfile.AbsoluteLinkError,
                 "'parent' is a link to an absolute path")
 
+    @symlink_test
+    @os_helper.skip_unless_symlink
+    def test_symlink_target_seperator_rewrite_on_windows(self):
+        with ArchiveMaker() as arc:
+            arc.add('link', symlink_to="relative/test/path")
+
+        with self.check_context(arc.open(), 'fully_trusted'):
+            self.expect_file('link', type=tarfile.SYMTYPE)
+            link_path = os.path.normpath(self.destdir / "link")
+            link_target = os.readlink(link_path)
+            if os.name == "nt":
+                self.assertEqual(link_target, "relative\\test\\path")
+            else:
+                self.assertEqual(link_target, "relative/test/path")
+
     def test_absolute_hardlink(self):
         # Test hardlink to an absolute path
         # Inspired by 'dirsymlink' in https://github.com/jwilk/traversal-archives
@@ -4381,9 +4451,15 @@ def test_sneaky_hardlink_fallback(self):
         for filter in 'tar', 'fully_trusted':
             with self.subTest(filter), self.check_context(arc.open(), filter):
                 if not os_helper.can_symlink():
-                    self.expect_file("a/t/dummy")
-                    self.expect_file("b/")
-                    self.expect_file("c/")
+                    if filter == 'fully_trusted' or sys.platform == "win32":
+                        self.expect_file("a/t/dummy")
+                        self.expect_file("b/")
+                        self.expect_file("c/")
+                    else:
+                        self.expect_exception(
+                            tarfile.LinkFallbackError,
+                            "link 'boom' would be extracted as a copy of "
+                            + "'c/escape', which was rejected")
                 else:
                     self.expect_file("a/t/dummy")
                     self.expect_file("b/")
@@ -4562,6 +4638,25 @@ def testing_filter(member, path):
             if os_helper.can_chmod():
                 self.assertFalse(path.stat().st_mode & stat.S_IWUSR)
 
+    @symlink_test
+    def test_extract_filters_target_none(self):
+        # Test that when extract() falls back to extracting (rather than
+        # linking) a hardlink target, the member is skipped if the filter
+        # returns None.
+        with ArchiveMaker() as arc:
+            arc.add('a/b/s', symlink_to='../escape')
+            arc.add('q', hardlink_to='a/b/s')
+        def filter_unsafe_members(member, path):
+            try:
+                return tarfile.data_filter(member, path)
+            except tarfile.FilterError as error:
+                return None
+        with self.check_context(arc.open(), filter_unsafe_members):
+            if os_helper.can_symlink():
+                self.expect_file('a/b/s', symlink_to='../escape')
+            else:
+                self.expect_file('a/b/')  # symlink is not extracted
+
     def test_link_fallback_normalizes(self):
         # Make sure hardlink fallbacks work for non-normalized paths for all
         # filters
@@ -5129,6 +5224,16 @@ def test_ignore_invalid_offset_headers(self):
             self.assertEqual(members[0].offset, expected_offset)
 
 
+class TestModule(unittest.TestCase):
+    def test_deprecated_version(self):
+        with self.assertWarnsRegex(
+                DeprecationWarning,
+                "'version' is deprecated and slated for removal in Python 3.20",
+        ) as cm:
+            getattr(tarfile, "version")
+        self.assertEqual(cm.filename, __file__)
+
+
 def setUpModule():
     os_helper.unlink(TEMPDIR)
     os.makedirs(TEMPDIR)
diff --git a/Lib/test/test_tempfile.py b/Lib/test/test_tempfile.py
index 6fac921f629..4bb7d95a903 100644
--- a/Lib/test/test_tempfile.py
+++ b/Lib/test/test_tempfile.py
@@ -14,6 +14,7 @@
 import gc
 import shutil
 import subprocess
+import sysconfig
 from unittest import mock
 
 import unittest
@@ -1409,7 +1410,7 @@ def test_properties(self):
 
         f.write(b'x')
         self.assertTrue(f._rolled)
-        self.assertEqual(f.mode, 'rb+')
+        self.assertEqual(f.mode, 'wb+')
         self.assertIsNotNone(f.name)
         with self.assertRaises(AttributeError):
             f.newlines
@@ -1848,6 +1849,54 @@ def test(target, target_is_directory):
                 new_flags = os.stat(dir1).st_flags
                 self.assertEqual(new_flags, old_flags)
 
+    @os_helper.skip_unless_symlink
+    @os_helper.skip_unless_working_chmod
+    @support.requires_non_root_user
+    @unittest.skipIf(support.is_emscripten, 'Fails due to Emscripten bug:'
+                                            'emscripten-core/emscripten#27761')
+    @unittest.skipUnless(shutil.rmtree.avoids_symlink_attacks,
+                         'requires the fd based implementation of rmtree()')
+    def test_cleanup_with_symlink_race(self):
+        # cleanup() should not operate on files outside of the temporary
+        # directory when a directory is replaced with a symlink while it
+        # recovers from a PermissionError (CVE-2026-12345).
+        with self.do_create(recurse=0) as target:
+            target_file = os.path.join(target, 'file1')
+            open(target_file, 'wb').close()
+            target_mode = os.stat(target_file).st_mode
+
+            d1 = self.do_create(recurse=0)
+            dir1 = os.path.join(d1.name, 'dir1')
+            os.mkdir(dir1)
+            open(os.path.join(dir1, 'file1'), 'wb').close()
+            # Removing contents of dir1 fails with a PermissionError, and
+            # dir1 is replaced with a symlink to target at the very moment
+            # cleanup() starts to recover from that error.
+            os.chmod(dir1, 0o500)
+            unlink = os.unlink
+            def hook(path, *, dir_fd=None):
+                try:
+                    return unlink(path, dir_fd=dir_fd)
+                except PermissionError:
+                    if not os.path.islink(dir1):
+                        os.chmod(dir1, 0o700)
+                        os.rename(dir1, dir1 + '_moved')
+                        os.symlink(target, dir1)
+                    raise
+            try:
+                with mock.patch('os.unlink', hook):
+                    with contextlib.suppress(OSError):
+                        d1.cleanup()
+            finally:
+                if os.path.islink(dir1):
+                    os.unlink(dir1)
+                    os.rename(dir1 + '_moved', dir1)
+                os.chmod(dir1, 0o700)
+                d1.cleanup()
+
+            self.assertTrue(os.path.exists(target_file))
+            self.assertEqual(os.stat(target_file).st_mode, target_mode)
+
     @support.cpython_only
     def test_del_on_collection(self):
         # A TemporaryDirectory is deleted when garbage collected
@@ -2020,6 +2069,29 @@ def test_modes(self):
                     d.cleanup()
                 self.assertFalse(os.path.exists(d.name))
 
+    @support.subTests('ignore_errors', (True, False))
+    def test_parent_mode_preserved(self, ignore_errors):
+        # Test that cleanup does not touch the parent directory,
+        # even if that prevents removal.
+        for mode in range(8):
+            mode <<= 6
+            with self.subTest(mode=format(mode, '03o')):
+                outer = self.do_create()
+                with outer:
+                    d = self.do_create(dir=outer.name, dirs=2, files=2,
+                                       ignore_cleanup_errors=ignore_errors)
+                    with d:
+                        os.chmod(outer.name, mode)
+                        orig_mode = os.stat(outer.name).st_mode
+                        try:
+                            d.cleanup()
+                        except PermissionError:
+                            if ignore_errors:
+                                raise
+                        self.assertEqual(os.stat(outer.name).st_mode, orig_mode)
+                        outer.cleanup()
+                self.assertFalse(os.path.exists(outer.name))
+
     def check_flags(self, flags):
         # skip the test if these flags are not supported (ex: FreeBSD 13)
         filename = os_helper.TESTFN
@@ -2057,5 +2129,17 @@ def test_delete_false(self):
         self.assertTrue(os.path.exists(working_dir))
         shutil.rmtree(working_dir)
 
+    @unittest.skipUnless(
+        sysconfig.get_config_var('PY_SUPPORT_TIER')
+        and sysconfig.get_config_var('PY_SUPPORT_TIER') <= 3,
+        'regression test for supported platforms')
+    @unittest.skipIf(support.MS_WINDOWS, 'dirfd not used on Windows')
+    @unittest.skipIf(support.is_wasi, 'WASI has no chmod')
+    def test_cleanup_safe(self):
+        """Verify that cleanup uses the safer code path"""
+        # This is a regression test. Feel free to add exceptions for new
+        # platforms, but don't forget to update the docs.
+        self.assertTrue(tempfile._rmtree_use_dir_fd)
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_thread_local_bytecode.py b/Lib/test/test_thread_local_bytecode.py
index d5c56db8d5d..6f76f1bc335 100644
--- a/Lib/test/test_thread_local_bytecode.py
+++ b/Lib/test/test_thread_local_bytecode.py
@@ -3,7 +3,7 @@
 import unittest
 
 from test import support
-from test.support import cpython_only, import_helper, requires_specialization_ft
+from test.support import cpython_only, import_helper, requires_specialization
 from test.support.script_helper import assert_python_ok
 from test.support.threading_helper import requires_working_threading
 
@@ -15,7 +15,7 @@
 @requires_working_threading()
 @unittest.skipUnless(support.Py_GIL_DISABLED, "only in free-threaded builds")
 class TLBCTests(unittest.TestCase):
-    @requires_specialization_ft
+    @requires_specialization
     def test_new_threads_start_with_unspecialized_code(self):
         code = textwrap.dedent("""
         import dis
@@ -46,7 +46,7 @@ def f(a, b, q=None):
         """)
         assert_python_ok("-X", "tlbc=1", "-c", code)
 
-    @requires_specialization_ft
+    @requires_specialization
     def test_threads_specialize_independently(self):
         code = textwrap.dedent("""
         import dis
@@ -108,7 +108,6 @@ def f(a, b, q=None):
         """)
         assert_python_ok("-X", "tlbc=1", "-c", code)
 
-    @support.skip_if_sanitizer("gh-129752: data race on adaptive counter", thread=True)
     def test_no_copies_if_tlbc_disabled(self):
         code = textwrap.dedent("""
         import queue
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index 605dffa5214..b85fddb30ee 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -6,7 +6,7 @@
 from test.support import threading_helper, requires_subprocess, requires_gil_enabled
 from test.support import verbose, cpython_only, os_helper
 from test.support.import_helper import ensure_lazy_imports, import_module
-from test.support.script_helper import assert_python_ok, assert_python_failure
+from test.support.script_helper import assert_python_ok, assert_python_failure, spawn_python
 from test.support import force_not_colorized
 
 import random
@@ -324,6 +324,7 @@ def f(mutex):
     # PyThreadState_SetAsyncExc() is a CPython-only gimmick, not (currently)
     # exposed at the Python level.  This test relies on ctypes to get at it.
     @unittest.expectedFailure  # TODO: RUSTPYTHON
+    @cpython_only
     def test_PyThreadState_SetAsyncExc(self):
         ctypes = import_module("ctypes")
 
@@ -412,6 +413,53 @@ def run(self):
             t.join()
         # else the thread is still running, and we have no way to kill it
 
+    @cpython_only
+    @unittest.skipUnless(hasattr(signal, "pthread_kill"), "need pthread_kill")
+    @unittest.skipUnless(hasattr(signal, "SIGUSR1"), "need SIGUSR1")
+    def test_PyThreadState_SetAsyncExc_interrupts_sleep(self):
+        _testcapi = import_module("_testlimitedcapi")
+
+        worker_started = threading.Event()
+
+        class InjectedException(Exception):
+            """Custom exception for testing"""
+
+        caught_exception = None
+
+        def catch_exception():
+            nonlocal caught_exception
+            day_as_seconds = 60 * 60 * 24
+            try:
+                worker_started.set()
+                time.sleep(day_as_seconds)
+            except InjectedException as exc:
+                caught_exception = exc
+
+        thread = threading.Thread(target=catch_exception)
+        thread.start()
+        worker_started.wait()
+
+        signal.signal(signal.SIGUSR1, lambda sig, frame: None)
+
+        result = _testcapi.threadstate_set_async_exc(
+            thread.ident, InjectedException)
+        self.assertEqual(result, 1)
+
+        for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
+            if not thread.is_alive():
+                break
+            try:
+                signal.pthread_kill(thread.ident, signal.SIGUSR1)
+            except OSError:
+                # The thread might have terminated between the is_alive check
+                # and the pthread_kill
+                break
+
+        thread.join()
+        signal.signal(signal.SIGUSR1, signal.SIG_DFL)
+
+        self.assertIsInstance(caught_exception, InjectedException)
+
     @unittest.skip("TODO: RUSTPYTHON; threading._start_new_thread not exposed")
     def test_limbo_cleanup(self):
         # Issue 7481: Failure to start thread should cleanup the limbo map.
@@ -1250,13 +1298,68 @@ def __del__(self):
         self.assertEqual(err, b"")
         self.assertIn(b"all clear", out)
 
+    @support.subTests('lock_class_name', ['Lock', 'RLock'])
+    def test_acquire_daemon_thread_lock_in_finalization(self, lock_class_name):
+        # gh-123940: Py_Finalize() prevents other threads from running Python
+        # code (and so, releasing locks), so acquiring a locked lock can not
+        # succeed.
+        # We raise an exception rather than hang.
+        code = textwrap.dedent(f"""
+            import threading
+            import time
+
+            thread_started_event = threading.Event()
+
+            lock = threading.{lock_class_name}()
+            def loop():
+                if {lock_class_name!r} == 'RLock':
+                    lock.acquire()
+                with lock:
+                    thread_started_event.set()
+                    while True:
+                        time.sleep(1)
+
+            uncontested_lock = threading.{lock_class_name}()
+
+            class Cycle:
+                def __init__(self):
+                    self.self_ref = self
+                    self.thr = threading.Thread(
+                        target=loop, daemon=True)
+                    self.thr.start()
+                    thread_started_event.wait()
+
+                def __del__(self):
+                    assert self.thr.is_alive()
+
+                    # We *can* acquire an unlocked lock
+                    uncontested_lock.acquire()
+                    if {lock_class_name!r} == 'RLock':
+                        uncontested_lock.acquire()
+
+                    # Acquiring a locked one fails
+                    try:
+                        lock.acquire()
+                    except PythonFinalizationError:
+                        assert self.thr.is_alive()
+                        print('got the correct exception!')
+
+            # Cycle holds a reference to itself, which ensures it is
+            # cleaned up during the GC that runs after daemon threads
+            # have been forced to exit during finalization.
+            Cycle()
+        """)
+        rc, out, err = assert_python_ok("-c", code)
+        self.assertEqual(err, b"")
+        self.assertIn(b"got the correct exception", out)
+
     def test_start_new_thread_failed(self):
         # gh-109746: if Python fails to start newly created thread
         # due to failure of underlying PyThread_start_new_thread() call,
         # its state should be removed from interpreter' thread states list
         # to avoid its double cleanup
         try:
-            from resource import setrlimit, RLIMIT_NPROC
+            from resource import setrlimit, RLIMIT_NPROC  # noqa: F401
         except ImportError as err:
             self.skipTest(err)  # RLIMIT_NPROC is specific to Linux and BSD
         code = """if 1:
@@ -1287,12 +1390,6 @@ def f():
 
     @cpython_only
     def test_finalize_daemon_thread_hang(self):
-        if support.check_sanitizer(thread=True, memory=True):
-            # the thread running `time.sleep(100)` below will still be alive
-            # at process exit
-            self.skipTest(
-                    "https://github.com/python/cpython/issues/124878 - Known"
-                    " race condition that TSAN identifies.")
         # gh-87135: tests that daemon threads hang during finalization
         script = textwrap.dedent('''
             import os
@@ -1411,10 +1508,6 @@ def run_in_bg():
         self.assertEqual(err, b"")
         self.assertEqual(out.strip(), b"Exiting...")
 
-    @unittest.skip("TODO: RUSTPYTHON; Thread._tstate_lock not implemented")
-    def test_tstate_lock(self):
-        return super().test_tstate_lock()
-
 class ThreadJoinOnShutdown(BaseTestCase):
 
     def _run_and_join(self, script):
@@ -2044,6 +2137,32 @@ def test_dummy_thread_on_interpreter_shutdown(self):
         self.assertEqual(out, b"")
         self.assertEqual(err, b"")
 
+    @requires_subprocess()
+    @unittest.skipIf(os.name == 'nt', "signals don't work well on windows")
+    def test_keyboard_interrupt_during_threading_shutdown(self):
+        import subprocess
+        source = f"""
+        from threading import Thread
+        import time
+        import os
+
+
+        def test():
+            print('a', flush=True, end='')
+            time.sleep(10)
+
+
+        for _ in range(3):
+            Thread(target=test).start()
+        """
+
+        with spawn_python("-c", source, stderr=subprocess.PIPE) as proc:
+            self.assertEqual(proc.stdout.read(3), b'aaa')
+            proc.send_signal(signal.SIGINT)
+            proc.stderr.flush()
+            error = proc.stderr.read()
+            self.assertIn(b"KeyboardInterrupt", error)
+
 
 class ThreadRunFail(threading.Thread):
     def run(self):
@@ -2217,8 +2336,7 @@ def test_signature(self):  # gh-102029
         ]
         for args, kwargs in arg_types:
             with self.subTest(args=args, kwargs=kwargs):
-                with self.assertWarns(DeprecationWarning):
-                    threading.RLock(*args, **kwargs)
+                self.assertRaises(TypeError, threading.RLock, *args, **kwargs)
 
         # Subtypes with custom `__init__` are allowed (but, not recommended):
         class CustomRLock(self.locktype):
@@ -2236,6 +2354,9 @@ class ConditionAsRLockTests(lock_tests.RLockTests):
     # Condition uses an RLock by default and exports its API.
     locktype = staticmethod(threading.Condition)
 
+    def test_constructor_noargs(self):
+        self.skipTest("Condition allows positional arguments")
+
     def test_recursion_count(self):
         self.skipTest("Condition does not expose _recursion_count()")
 
@@ -2252,6 +2373,231 @@ class BarrierTests(lock_tests.BarrierTests):
     barriertype = staticmethod(threading.Barrier)
 
 
+## Test Synchronization tools for iterators ################
+
+class ThreadingIteratorToolsTests(BaseTestCase):
+    def test_serialize_serializes_concurrent_iteration(self):
+        limit = 10_000
+        workers_count = 10
+        result = 0
+        result_lock = threading.Lock()
+        start = threading.Event()
+
+        def producer(limit):
+            for x in range(limit):
+                yield x
+
+        def consumer(iterator):
+            nonlocal result
+            start.wait()
+            total = 0
+            for x in iterator:
+                total += x
+            with result_lock:
+                result += total
+
+        iterator = threading.serialize_iterator(producer(limit))
+        workers = [
+            threading.Thread(target=consumer, args=(iterator,))
+            for _ in range(workers_count)
+        ]
+        with threading_helper.wait_threads_exit():
+            for worker in workers:
+                worker.start()
+            for worker in workers:
+                # Wait for the worker thread to actually start.
+                while worker.ident is None:
+                    time.sleep(0.1)
+            start.set()
+            for worker in workers:
+                worker.join()
+
+        self.assertEqual(result, limit * (limit - 1) // 2)
+
+    def test_serialize_generator_methods(self):
+        # A generator that yields and receives
+        def echo():
+            try:
+                while True:
+                    val = yield "ready"
+                    yield f"received {val}"
+            except ValueError:
+                yield "caught"
+
+        it = threading.serialize_iterator(echo())
+
+        # Test __next__
+        self.assertEqual(next(it), "ready")
+
+        # Test send()
+        self.assertEqual(it.send("hello"), "received hello")
+        self.assertEqual(next(it), "ready")
+
+        # Test throw()
+        self.assertEqual(it.throw(ValueError), "caught")
+
+        # Test close()
+        it.close()
+        with self.assertRaises(StopIteration):
+            next(it)
+
+    def test_serialize_methods_attribute_error(self):
+        # A standard iterator that does not have send/throw/close
+        # should raise AttributeError when called.
+        standard_it = threading.serialize_iterator([1, 2, 3])
+
+        with self.assertRaises(AttributeError):
+            standard_it.send("foo")
+
+        with self.assertRaises(AttributeError):
+            standard_it.throw(ValueError)
+
+        with self.assertRaises(AttributeError):
+            standard_it.close()
+
+    def test_serialize_generator_methods_locking(self):
+        # Verifies that generator methods also acquire the lock.
+        # We can test this by checking if the lock is held during the call.
+
+        class LockCheckingGenerator:
+            def __init__(self, lock):
+                self.lock = lock
+            def __iter__(self):
+                return self
+            def send(self, value):
+                if not self.lock.locked():
+                    raise RuntimeError("Lock not held during send()")
+                return value
+            def throw(self, *args):
+                if not self.lock.locked():
+                    raise RuntimeError("Lock not held during throw()")
+            def close(self):
+                if not self.lock.locked():
+                    raise RuntimeError("Lock not held during close()")
+
+        # Manually create the serialize object to inspect the lock
+        it = threading.serialize_iterator([])
+        mock_gen = LockCheckingGenerator(it._lock)
+        it._iterator = mock_gen
+
+        # These should not raise RuntimeError
+        it.send(1)
+        it.throw(ValueError)
+        it.close()
+
+    def test_serialize_next_exception(self):
+        # Verify exception pass through for calls to next()
+
+        def f():
+            raise RuntimeError
+            yield None
+
+        g = threading.serialize_iterator(f())
+        with self.assertRaises(RuntimeError):
+            next(g)
+
+    def test_synchronized_serializes_generator_instances(self):
+        unique = 10
+        repetitions = 5
+        limit = 100
+        start = threading.Event()
+
+        @threading.synchronized_iterator
+        def atomic_counter():
+            # The sleep widens the race window that would exist without
+            # synchronization between yielding a value and advancing state.
+            i = 0
+            while True:
+                yield i
+                time.sleep(0.0005)
+                i += 1
+
+        def consumer(counter):
+            start.wait()
+            for _ in range(limit):
+                next(counter)
+
+        unique_counters = [atomic_counter() for _ in range(unique)]
+        counters = unique_counters * repetitions
+        workers = [
+            threading.Thread(target=consumer, args=(counter,))
+            for counter in counters
+        ]
+        with threading_helper.wait_threads_exit():
+            for worker in workers:
+                worker.start()
+            start.set()
+            for worker in workers:
+                worker.join()
+
+        self.assertEqual(
+            {next(counter) for counter in unique_counters},
+            {limit * repetitions},
+        )
+
+    def test_synchronized_preserves_wrapped_metadata(self):
+        def gen():
+            yield 1
+
+        wrapped = threading.synchronized_iterator(gen)
+
+        self.assertEqual(wrapped.__name__, gen.__name__)
+        self.assertIs(wrapped.__wrapped__, gen)
+        self.assertEqual(list(wrapped()), [1])
+
+    def test_concurrent_tee_supports_concurrent_consumers(self):
+        limit = 5_000
+        num_threads = 25
+        successes = 0
+        failures = []
+        result_lock = threading.Lock()
+        start = threading.Event()
+        expected = list(range(limit))
+
+        def producer(limit):
+            for x in range(limit):
+                yield x
+
+        def consumer(iterator):
+            nonlocal successes
+            start.wait()
+            items = list(iterator)
+            with result_lock:
+                if items == expected:
+                    successes += 1
+                else:
+                    failures.append(items[:20])
+
+        tees = threading.concurrent_tee(producer(limit), n=num_threads)
+        workers = [
+            threading.Thread(target=consumer, args=(iterator,))
+            for iterator in tees
+        ]
+        with threading_helper.wait_threads_exit():
+            for worker in workers:
+                worker.start()
+            start.set()
+            for worker in workers:
+                worker.join()
+
+        self.assertEqual(failures, [])
+        self.assertEqual(successes, len(tees))
+
+        # Verify that locks are shared
+        self.assertEqual(len({id(t_obj.lock) for t_obj in tees}), 1)
+
+    def test_concurrent_tee_zero_iterators(self):
+        self.assertEqual(threading.concurrent_tee(range(10), n=0), ())
+
+    def test_concurrent_tee_negative_n(self):
+        with self.assertRaises(ValueError):
+            threading.concurrent_tee(range(10), n=-1)
+
+
+#################
+
+
+
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
         restore_default_excepthook(self)
@@ -2485,6 +2831,7 @@ def test_atexit_called_once(self):
 
         self.assertFalse(err)
 
+    @force_not_colorized
     def test_atexit_after_shutdown(self):
         # The only way to do this is by registering an atexit within
         # an atexit, which is intended to raise an exception.
diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index f66a37edb4c..985984b5512 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -2,6 +2,7 @@
 from test.support import warnings_helper
 import decimal
 import enum
+import fractions
 import math
 import platform
 import sys
@@ -170,10 +171,12 @@ def test_sleep_exceptions(self):
         # Improved exception #81267
         with self.assertRaises(TypeError) as errmsg:
             time.sleep([])
-        self.assertIn("integer or float", str(errmsg.exception))
+        self.assertIn("real number", str(errmsg.exception))
 
     def test_sleep(self):
-        for value in [-0.0, 0, 0.0, 1e-100, 1e-9, 1e-6, 1, 1.2]:
+        for value in [-0.0, 0, 0.0, 1e-100, 1e-9, 1e-6, 1, 1.2,
+                      decimal.Decimal('0.02'),
+                      fractions.Fraction(1, 50)]:
             with self.subTest(value=value):
                 time.sleep(value)
 
@@ -184,6 +187,38 @@ def test_epoch(self):
         # Only test the date and time, ignore other gmtime() members
         self.assertEqual(tuple(epoch)[:6], (1970, 1, 1, 0, 0, 0), epoch)
 
+    def test_gmtime(self):
+        # expected format:
+        # (tm_year, tm_mon, tm_mday,
+        #  tm_hour, tm_min, tm_sec,
+        #  tm_wday, tm_yday)
+        tests = [
+            (-13262400, (1969, 7, 31, 12, 0, 0, 3, 212)),
+            (-6177600, (1969, 10, 21, 12, 0, 0, 1, 294)),
+            # leap years (pre epoch)
+            (-2077660800, (1904, 3, 1, 0, 0, 0, 1, 61)),
+            (-2077833600, (1904, 2, 28, 0, 0, 0, 6, 59)),
+        ]
+
+        try:
+            from _testinternalcapi import SIZEOF_TIME_T
+        except ImportError:
+            pass
+        else:
+            if SIZEOF_TIME_T >= 8:
+                tests.extend((
+                    # non-leap years (pre epoch)
+                    (-2203891200, (1900, 3, 1, 0, 0, 0, 3, 60)),
+                    (-2203977600, (1900, 2, 28, 0, 0, 0, 2, 59)),
+                    (-5359564800, (1800, 3, 1, 0, 0, 0, 5, 60)),
+                    (-5359651200, (1800, 2, 28, 0, 0, 0, 4, 59)),
+                ))
+
+        for t, expected in tests:
+            with self.subTest(t=t, expected=expected):
+                res = time.gmtime(t)
+                self.assertEqual(tuple(res)[:8], expected, res)
+
     def test_strftime(self):
         tt = time.gmtime(self.t)
         for directive in ('a', 'A', 'b', 'B', 'c', 'd', 'H', 'I',
@@ -323,11 +358,11 @@ def test_strptime(self):
         # Should be able to go round-trip from strftime to strptime without
         # raising an exception.
         tt = time.gmtime(self.t)
-        for directive in ('a', 'A', 'b', 'B', 'c', 'd', 'H', 'I',
-                          'j', 'm', 'M', 'p', 'S',
+        for directive in ('a', 'A', 'b', 'B', 'c', 'd', 'D', 'e', 'F', 'H', 'I',
+                          'j', 'm', 'M', 'n', 'p', 'S', 't', 'T',
                           'U', 'w', 'W', 'x', 'X', 'y', 'Y', 'Z', '%'):
             format = '%' + directive
-            if directive == 'd':
+            if directive in ('d', 'e'):
                 format += ',%Y'  # Avoid GH-70647.
             strf_output = time.strftime(format, tt)
             try:
@@ -344,7 +379,7 @@ def test_strptime_bytes(self):
     def test_strptime_exception_context(self):
         # check that this doesn't chain exceptions needlessly (see #17572)
         with self.assertRaises(ValueError) as e:
-            time.strptime('', '%D')
+            time.strptime('', '%!')
         self.assertTrue(e.exception.__suppress_context__)
         # additional check for stray % branch
         with self.assertRaises(ValueError) as e:
@@ -352,10 +387,13 @@ def test_strptime_exception_context(self):
         self.assertTrue(e.exception.__suppress_context__)
 
     def test_strptime_leap_year(self):
-        # GH-70647: warns if parsing a format with a day and no year.
+        # GH-70647: %d errors if parsing a format with a day and no year.
+        with self.assertRaises(ValueError):
+            time.strptime('02-07 18:28', '%m-%d %H:%M')
+        # %e without a year is deprecated, scheduled for removal in 3.17.
         with self.assertWarnsRegex(DeprecationWarning,
                                    r'.*day of month without a year.*'):
-            time.strptime('02-07 18:28', '%m-%d %H:%M')
+            time.strptime('02-07 18:28', '%m-%e %H:%M')
 
     def test_asctime(self):
         time.asctime(time.gmtime(self.t))
@@ -498,12 +536,13 @@ def test_localtime_without_arg(self):
     def test_mktime(self):
         # Issue #1726687
         for t in (-2, -1, 0, 1):
+            t_struct = time.localtime(t)
             try:
-                tt = time.localtime(t)
+                t1 = time.mktime(t_struct)
             except (OverflowError, OSError):
                 pass
             else:
-                self.assertEqual(time.mktime(tt), t)
+                self.assertEqual(t1, t)
 
     # Issue #13309: passing extreme values to mktime() or localtime()
     # borks the glibc's internal timezone data.
@@ -755,7 +794,6 @@ class TestStrftime4dyear(_TestStrftimeYear, _Test4dYear, unittest.TestCase):
 
 class TestPytime(unittest.TestCase):
     @skip_if_buggy_ucrt_strfptime
-    @unittest.skipUnless(time._STRUCT_TM_ITEMS == 11, "needs tm_zone support")
     def test_localtime_timezone(self):
 
         # Get the localtime and examine it for the offset and zone.
@@ -790,14 +828,12 @@ def test_localtime_timezone(self):
         self.assertEqual(new_lt.tm_gmtoff, lt.tm_gmtoff)
         self.assertEqual(new_lt9.tm_zone, lt.tm_zone)
 
-    @unittest.skipUnless(time._STRUCT_TM_ITEMS == 11, "needs tm_zone support")
     def test_strptime_timezone(self):
         t = time.strptime("UTC", "%Z")
         self.assertEqual(t.tm_zone, 'UTC')
         t = time.strptime("+0500", "%z")
         self.assertEqual(t.tm_gmtoff, 5 * 3600)
 
-    @unittest.skipUnless(time._STRUCT_TM_ITEMS == 11, "needs tm_zone support")
     def test_short_times(self):
 
         import pickle
@@ -977,6 +1013,17 @@ def test_FromSecondsObject(self):
             with self.assertRaises(ValueError):
                 _PyTime_FromSecondsObject(float('nan'), time_rnd)
 
+    def test_FromSecondsObject_float_overflow_message(self):
+        # Float path must report a PyTime_t overflow, like the integer path.
+        from _testinternalcapi import _PyTime_FromSecondsObject
+        for value in (PyTime_MAX, PyTime_MIN):
+            for time_rnd, _ in ROUNDING_MODES:
+                with self.subTest(value=value, time_rnd=time_rnd):
+                    with self.assertRaisesRegex(
+                            OverflowError,
+                            "timestamp out of range for C PyTime_t"):
+                        _PyTime_FromSecondsObject(value, time_rnd)
+
     def test_AsSecondsDouble(self):
         from _testcapi import PyTime_AsSecondsDouble
 
diff --git a/Lib/test/test_tokenize.py b/Lib/test/test_tokenize.py
index 0e81c6f6db2..252a3a77981 100644
--- a/Lib/test/test_tokenize.py
+++ b/Lib/test/test_tokenize.py
@@ -1233,6 +1233,20 @@ def test_multiline_non_ascii_fstring_with_expr(self):
     FSTRING_END \'"\'           (2, 2) (2, 3)
     """)
 
+    def test_ineq_tokens(self):
+        self.check_tokenize("1 != 2", """\
+    NUMBER     '1'           (1, 0) (1, 1)
+    OP         '!='          (1, 2) (1, 4)
+    NUMBER     '2'           (1, 5) (1, 6)
+""")
+        self.check_tokenize("1 <> 2", """\
+    NUMBER     '1'           (1, 0) (1, 1)
+    OP         '<'           (1, 2) (1, 3)
+    OP         '>'           (1, 3) (1, 4)
+    NUMBER     '2'           (1, 5) (1, 6)
+""")
+
+
 class GenerateTokensTest(TokenizeTest):
     def check_tokenize(self, s, expected):
         # Format the tokens in s in a table format.
@@ -3193,7 +3207,6 @@ def get_tokens(string):
             with self.subTest(case=case):
                 self.assertRaises(tokenize.TokenError, get_tokens, case)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: IndentationError not raised by <lambda>
     @support.skip_wasi_stack_overflow()
     def test_max_indent(self):
         MAXINDENT = 100
@@ -3333,6 +3346,7 @@ def test_newline_at_the_end_of_buffer(self):
             run_test_script(file_name)
 
 
+@support.force_not_colorized_test_class
 class CommandLineTest(unittest.TestCase):
     def setUp(self):
         self.filename = tempfile.mktemp()
diff --git a/Lib/test/test_trace.py b/Lib/test/test_trace.py
index d0e51c5c305..721e28885cf 100644
--- a/Lib/test/test_trace.py
+++ b/Lib/test/test_trace.py
@@ -142,6 +142,8 @@ def test_traced_func_linear(self):
 
         self.assertEqual(self.tracer.results().counts, expected)
 
+    @unittest.skipIf(os.environ.get('PYTHON_UOPS_OPTIMIZE') == '0',
+                     "Line counts differ when JIT optimizer is disabled")
     def test_traced_func_loop(self):
         self.tracer.runfunc(traced_func_loop, 2, 3)
 
@@ -166,6 +168,8 @@ def test_traced_func_importing(self):
 
         self.assertEqual(self.tracer.results().counts, expected)
 
+    @unittest.skipIf(os.environ.get('PYTHON_UOPS_OPTIMIZE') == '0',
+                     "Line counts differ when JIT optimizer is disabled")
     def test_trace_func_generator(self):
         self.tracer.runfunc(traced_func_calling_generator)
 
@@ -236,6 +240,8 @@ def setUp(self):
         self.my_py_filename = fix_ext_py(__file__)
         self.addCleanup(sys.settrace, sys.gettrace())
 
+    @unittest.skipIf(os.environ.get('PYTHON_UOPS_OPTIMIZE') == '0',
+                     "Line counts differ when JIT optimizer is disabled")
     def test_exec_counts(self):
         self.tracer = Trace(count=1, trace=0, countfuncs=0, countcallers=0)
         code = r'''traced_func_loop(2, 5)'''
@@ -463,7 +469,6 @@ def tearDown(self):
         unlink(self.codefile)
         unlink(self.coverfile)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ---
     def test_cover_files_written_no_highlight(self):
         # Test also that the cover file for the trace module is not created
         # (issue #34171).
@@ -484,7 +489,6 @@ def test_cover_files_written_no_highlight(self):
                 "           print('unreachable')\n"
             )
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; ---
     def test_cover_files_written_with_highlight(self):
         argv = '-m trace --count --missing'.split() + [self.codefile]
         status, stdout, stderr = assert_python_ok(*argv)
diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index 88e39145c9b..fa5f1e30355 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -9,18 +9,21 @@
 import builtins
 import unittest
 import unittest.mock
+import os
 import re
 import tempfile
 import random
 import string
+import importlib.machinery
+import sysconfig
 from test import support
 import shutil
 from test.support import (Error, captured_output, cpython_only, ALWAYS_EQ,
                           requires_debug_ranges, has_no_debug_ranges,
-                          requires_subprocess)
+                          requires_subprocess, os_helper)
 from test.support.os_helper import TESTFN, temp_dir, unlink
 from test.support.script_helper import assert_python_ok, assert_python_failure, make_script
-from test.support.import_helper import forget
+from test.support.import_helper import ensure_lazy_imports, forget
 from test.support import force_not_colorized, force_not_colorized_test_class
 
 import json
@@ -37,7 +40,7 @@
 test_frame = namedtuple('frame', ['f_code', 'f_globals', 'f_locals'])
 test_tb = namedtuple('tb', ['tb_frame', 'tb_lineno', 'tb_next', 'tb_lasti'])
 
-color_overrides = {"reset": "z", "filename": "fn", "error_highlight": "E"}
+color_overrides = {"reset": "z", "filename": "fn", "error_highlight": "E", "note": "n"}
 colors = {
     color_overrides.get(k, k[0].lower()): v
     for k, v in _colorize.default_theme.traceback.items()
@@ -88,6 +91,12 @@ def syntax_error_bad_indentation2(self):
     def tokenizer_error_with_caret_range(self):
         compile("blech  (  ", "?", "exec")
 
+    def syntax_error_with_caret_wide_char(self):
+        compile("女女女=1; 女女女/", "?", "exec")
+
+    def syntax_error_with_caret_wide_char_range(self):
+        compile("f(x, 女女女 for 女女女 in range(30), z)", "?", "exec")
+
     def test_caret(self):
         err = self.get_exception_format(self.syntax_error_with_caret,
                                         SyntaxError)
@@ -125,6 +134,20 @@ def test_caret(self):
         self.assertEqual(err[1].find("("), err[2].find("^"))  # in the right place
         self.assertEqual(err[2].count("^"), 1)
 
+    def test_caret_wide_char(self):
+        err = self.get_exception_format(self.syntax_error_with_caret_wide_char,
+                                        SyntaxError)
+        self.assertIn("^", err[2])
+        # "女女女=1; 女女女/" has display width 17
+        self.assertEqual(err[2].find("^"), 4 + 17)
+
+        err = self.get_exception_format(self.syntax_error_with_caret_wide_char_range,
+                                        SyntaxError)
+        self.assertIn("^", err[2])
+        self.assertEqual(err[2].find("^"), 4 + 5)
+        # "女女女 for 女女女 in range(30)" has display width 30
+        self.assertEqual(err[2].count("^"), 30)
+
     def test_nocaret(self):
         exc = SyntaxError("error", ("x.py", 23, None, "bad syntax"))
         err = traceback.format_exception_only(SyntaxError, exc)
@@ -1767,6 +1790,7 @@ def f():
         ]
         self.assertEqual(result_lines, expected)
 
+
 class TestKeywordTypoSuggestions(unittest.TestCase):
     TYPO_CASES = [
         ("with block ad something:\n  pass", "and"),
@@ -1811,6 +1835,23 @@ def test_keyword_suggestions_from_command_string(self):
                 stderr_text = stderr.decode('utf-8')
                 self.assertIn(f"Did you mean '{expected_kw}'", stderr_text)
 
+    def test_no_keyword_suggestion_for_comma_errors(self):
+        # When the parser identifies a missing comma, don't suggest
+        # bogus keyword replacements like 'print' -> 'not'
+        code = '''\
+import sys
+print(
+    "line1"
+    "line2"
+    file=sys.stderr
+)
+'''
+        source = textwrap.dedent(code).strip()
+        rc, stdout, stderr = assert_python_failure('-c', source)
+        stderr_text = stderr.decode('utf-8')
+        self.assertIn("Perhaps you forgot a comma", stderr_text)
+        self.assertNotIn("Did you mean", stderr_text)
+
 @requires_debug_ranges()
 @force_not_colorized_test_class
 class PurePythonTracebackErrorCaretTests(
@@ -3852,7 +3893,7 @@ def f():
     def test_dont_swallow_cause_or_context_of_falsey_exception(self):
         # see gh-132308: Ensure that __cause__ or __context__ attributes of exceptions
         # that evaluate as falsey are included in the output. For falsey term,
-        # see https://docs.python.org/3/library/stdtypes.html#truth-value-testing.
+        # see https://docs.python.org/3/builtins/stdtypes.html#truth-value-testing.
 
         try:
             raise FalseyException from KeyError
@@ -4071,7 +4112,7 @@ def test_comparison(self):
     def test_dont_swallow_subexceptions_of_falsey_exceptiongroup(self):
         # see gh-132308: Ensure that subexceptions of exception groups
         # that evaluate as falsey are displayed in the output. For falsey term,
-        # see https://docs.python.org/3/library/stdtypes.html#truth-value-testing.
+        # see https://docs.python.org/3/builtins/stdtypes.html#truth-value-testing.
 
         try:
             raise FalseyExceptionGroup("Gih", (KeyError(), NameError()))
@@ -4092,11 +4133,13 @@ def test_dont_swallow_subexceptions_of_falsey_exceptiongroup(self):
 global_for_suggestions = None
 
 
-class SuggestionFormattingTestBase:
+class SuggestionFormattingTestMixin:
+    attr_function = getattr
+
     def get_suggestion(self, obj, attr_name=None):
         if attr_name is not None:
             def callable():
-                getattr(obj, attr_name)
+                self.attr_function(obj, attr_name)
         else:
             callable = obj
 
@@ -4105,7 +4148,9 @@ def callable():
         )
         return result_lines[0]
 
-    def test_getattr_suggestions(self):
+
+class BaseSuggestionTests(SuggestionFormattingTestMixin):
+    def test_suggestions(self):
         class Substitution:
             noise = more_noise = a = bc = None
             blech = None
@@ -4136,40 +4181,41 @@ class CaseChangeOverSubstitution:
             BLuch = None
 
         for cls, suggestion in [
-            (Addition, "'bluchin'?"),
-            (Substitution, "'blech'?"),
-            (Elimination, "'blch'?"),
-            (Addition, "'bluchin'?"),
-            (SubstitutionOverElimination, "'blach'?"),
-            (SubstitutionOverAddition, "'blach'?"),
-            (EliminationOverAddition, "'bluc'?"),
-            (CaseChangeOverSubstitution, "'BLuch'?"),
+            (Addition, "'.bluchin'"),
+            (Substitution, "'.blech'"),
+            (Elimination, "'.blch'"),
+            (Addition, "'.bluchin'"),
+            (SubstitutionOverElimination, "'.blach'"),
+            (SubstitutionOverAddition, "'.blach'"),
+            (EliminationOverAddition, "'.bluc'"),
+            (CaseChangeOverSubstitution, "'.BLuch'"),
         ]:
             actual = self.get_suggestion(cls(), 'bluch')
-            self.assertIn(suggestion, actual)
+            self.assertIn('Did you mean ' + suggestion, actual)
 
-    def test_getattr_suggestions_underscored(self):
+    def test_suggestions_underscored(self):
         class A:
             bluch = None
 
-        self.assertIn("'bluch'", self.get_suggestion(A(), 'blach'))
-        self.assertIn("'bluch'", self.get_suggestion(A(), '_luch'))
-        self.assertIn("'bluch'", self.get_suggestion(A(), '_bluch'))
+        self.assertIn("'.bluch'", self.get_suggestion(A(), 'blach'))
+        self.assertIn("'.bluch'", self.get_suggestion(A(), '_luch'))
+        self.assertIn("'.bluch'", self.get_suggestion(A(), '_bluch'))
 
+        attr_function = self.attr_function
         class B:
             _bluch = None
             def method(self, name):
-                getattr(self, name)
+                attr_function(self, name)
 
-        self.assertIn("'_bluch'", self.get_suggestion(B(), '_blach'))
-        self.assertIn("'_bluch'", self.get_suggestion(B(), '_luch'))
-        self.assertNotIn("'_bluch'", self.get_suggestion(B(), 'bluch'))
+        self.assertIn("'._bluch'", self.get_suggestion(B(), '_blach'))
+        self.assertIn("'._bluch'", self.get_suggestion(B(), '_luch'))
+        self.assertNotIn("'._bluch'", self.get_suggestion(B(), 'bluch'))
 
-        self.assertIn("'_bluch'", self.get_suggestion(partial(B().method, '_blach')))
-        self.assertIn("'_bluch'", self.get_suggestion(partial(B().method, '_luch')))
-        self.assertIn("'_bluch'", self.get_suggestion(partial(B().method, 'bluch')))
+        self.assertIn("'._bluch'", self.get_suggestion(partial(B().method, '_blach')))
+        self.assertIn("'._bluch'", self.get_suggestion(partial(B().method, '_luch')))
+        self.assertIn("'._bluch'", self.get_suggestion(partial(B().method, 'bluch')))
 
-    def test_getattr_suggestions_with_custom___dir__(self):
+    def test_suggestions_with_custom___dir__(self):
         class M(type):
             def __dir__(cls):
                 return [None, "fox"]
@@ -4181,29 +4227,30 @@ def __dir__(self):
         class C1(C0, metaclass=M):
             pass
 
-        self.assertNotIn("'bluch'", self.get_suggestion(C0, "blach"))
-        self.assertIn("'bluch'", self.get_suggestion(C0(), "blach"))
+        self.assertNotIn("'.bluch'", self.get_suggestion(C0, "blach"))
+        self.assertIn("'.bluch'", self.get_suggestion(C0(), "blach"))
 
-        self.assertIn("'fox'", self.get_suggestion(C1, "foo"))
-        self.assertNotIn("'fox'", self.get_suggestion(C1(), "foo"))
+        self.assertIn("'.fox'", self.get_suggestion(C1, "foo"))
+        self.assertNotIn("'.fox'", self.get_suggestion(C1(), "foo"))
 
-        self.assertNotIn("'bluch'", self.get_suggestion(C1, "blach"))
-        self.assertIn("'bluch'", self.get_suggestion(C1(), "blach"))
+        self.assertNotIn("'.bluch'", self.get_suggestion(C1, "blach"))
+        self.assertIn("'.bluch'", self.get_suggestion(C1(), "blach"))
 
-    def test_getattr_suggestions_do_not_trigger_for_long_attributes(self):
+
+    def test_do_not_trigger_for_long_attributes(self):
         class A:
             blech = None
 
         actual = self.get_suggestion(A(), 'somethingverywrong')
         self.assertNotIn("blech", actual)
 
-    def test_getattr_error_bad_suggestions_do_not_trigger_for_small_names(self):
+    def test_do_not_trigger_for_small_names(self):
         class MyClass:
             vvv = mom = w = id = pytho = None
 
         for name in ("b", "v", "m", "py"):
             with self.subTest(name=name):
-                actual = self.get_suggestion(MyClass, name)
+                actual = self.get_suggestion(MyClass(), name)
                 self.assertNotIn("Did you mean", actual)
                 self.assertNotIn("'vvv", actual)
                 self.assertNotIn("'mom'", actual)
@@ -4211,7 +4258,7 @@ class MyClass:
                 self.assertNotIn("'w'", actual)
                 self.assertNotIn("'pytho'", actual)
 
-    def test_getattr_suggestions_do_not_trigger_for_big_dicts(self):
+    def test_do_not_trigger_for_big_dicts(self):
         class A:
             blech = None
         # A class with a very big __dict__ will not be considered
@@ -4222,7 +4269,36 @@ class A:
         actual = self.get_suggestion(A(), 'bluch')
         self.assertNotIn("blech", actual)
 
-    def test_getattr_suggestions_no_args(self):
+    def test_suggestions_for_same_name(self):
+        class A:
+            def __dir__(self):
+                return ['blech']
+        actual = self.get_suggestion(A(), 'blech')
+        self.assertNotIn("Did you mean", actual)
+
+    def test_suggestions_not_normalized(self):
+        class A:
+            analization = None
+            fiⁿₐˡᵢᶻₐᵗᵢᵒₙ = None
+
+        suggestion = self.get_suggestion(A(), 'fiⁿₐˡᵢᶻₐᵗᵢᵒₙ')
+        self.assertIn("'.finalization'", suggestion)
+        self.assertNotIn("analization", suggestion)
+
+        class B:
+            attr_a = None
+            attr_µ = None  # attr_\xb5
+
+        suggestion = self.get_suggestion(B(), 'attr_\xb5')
+        self.assertIn(
+            "'.attr_\u03bc' ('attr_\\u03bc') "
+            "instead of '.attr_\xb5' ('attr_\\xb5')",
+            suggestion)
+        self.assertNotIn("attr_a", suggestion)
+
+
+class GetattrSuggestionTests(BaseSuggestionTests):
+    def test_suggestions_no_args(self):
         class A:
             blech = None
             def __getattr__(self, attr):
@@ -4239,7 +4315,7 @@ def __getattr__(self, attr):
         actual = self.get_suggestion(A(), 'bluch')
         self.assertIn("blech", actual)
 
-    def test_getattr_suggestions_invalid_args(self):
+    def test_suggestions_invalid_args(self):
         class NonStringifyClass:
             __str__ = None
             __repr__ = None
@@ -4263,13 +4339,12 @@ def __getattr__(self, attr):
             actual = self.get_suggestion(cls(), 'bluch')
             self.assertIn("blech", actual)
 
-    def test_getattr_suggestions_for_same_name(self):
-        class A:
-            def __dir__(self):
-                return ['blech']
-        actual = self.get_suggestion(A(), 'blech')
-        self.assertNotIn("Did you mean", actual)
 
+class DelattrSuggestionTests(BaseSuggestionTests):
+    attr_function = delattr
+
+
+class SuggestionFormattingTestBase(SuggestionFormattingTestMixin):
     def test_attribute_error_with_failing_dict(self):
         class T:
             bluch = 1
@@ -4311,6 +4386,275 @@ def __getattribute__(self, attr):
         self.assertIn("Did you mean", actual)
         self.assertIn("bluch", actual)
 
+    def test_getattr_nested_attribute_suggestions(self):
+        # Test that nested attributes are suggested when no direct match
+        class Inner:
+            def __init__(self):
+                self.value = 42
+                self.data = "test"
+
+        class Outer:
+            def __init__(self):
+                self.inner = Inner()
+
+        # Should suggest 'inner.value'
+        actual = self.get_suggestion(Outer(), 'value')
+        self.assertIn("Did you mean '.inner.value' instead of '.value'", actual)
+
+        # Should suggest 'inner.data'
+        actual = self.get_suggestion(Outer(), 'data')
+        self.assertIn("Did you mean '.inner.data' instead of '.data'", actual)
+
+    def test_getattr_nested_prioritizes_direct_matches(self):
+        # Test that direct attribute matches are prioritized over nested ones
+        class Inner:
+            def __init__(self):
+                self.foo = 42
+
+        class Outer:
+            def __init__(self):
+                self.inner = Inner()
+                self.fooo = 100  # Similar to 'foo'
+
+        # Should suggest 'fooo' (direct) not 'inner.foo' (nested)
+        actual = self.get_suggestion(Outer(), 'foo')
+        self.assertIn("Did you mean '.fooo'", actual)
+        self.assertNotIn("inner.foo", actual)
+
+    def test_getattr_nested_with_property(self):
+        # Property suggestions should not execute the property getter.
+        class Inner:
+            @property
+            def computed(self):
+                return missing_name
+
+        class Outer:
+            def __init__(self):
+                self.inner = Inner()
+
+        actual = self.get_suggestion(Outer(), 'computed')
+        self.assertIn(
+            "Did you mean '.inner.computed' instead of '.computed'",
+            actual,
+        )
+
+    def test_getattr_nested_no_suggestion_for_deep_nesting(self):
+        # Test that deeply nested attributes (2+ levels) are not suggested
+        class Deep:
+            def __init__(self):
+                self.value = 42
+
+        class Middle:
+            def __init__(self):
+                self.deep = Deep()
+
+        class Outer:
+            def __init__(self):
+                self.middle = Middle()
+
+        # Should not suggest 'middle.deep.value' (too deep)
+        actual = self.get_suggestion(Outer(), 'value')
+        self.assertNotIn("Did you mean", actual)
+
+    def test_getattr_nested_ignores_private_attributes(self):
+        # Test that nested suggestions ignore private attributes
+        class Inner:
+            def __init__(self):
+                self.public_value = 42
+
+        class Outer:
+            def __init__(self):
+                self._private_inner = Inner()
+
+        # Should not suggest '_private_inner.public_value'
+        actual = self.get_suggestion(Outer(), 'public_value')
+        self.assertNotIn("Did you mean", actual)
+
+    def test_getattr_nested_limits_attribute_checks(self):
+        # Test that nested suggestions are limited to checking first 20 non-private attributes
+        class Inner:
+            def __init__(self):
+                self.target_value = 42
+
+        class Outer:
+            def __init__(self):
+                # Add many attributes before 'inner'
+                for i in range(25):
+                    setattr(self, f'attr_{i:02d}', i)
+                # Add the inner object after 20+ attributes
+                self.inner = Inner()
+
+        obj = Outer()
+        # Verify that 'inner' is indeed present but after position 20
+        attrs = [x for x in sorted(dir(obj)) if not x.startswith('_')]
+        inner_position = attrs.index('inner')
+        self.assertGreater(inner_position, 19, "inner should be after position 20 in sorted attributes")
+
+        # Should not suggest 'inner.target_value' because inner is beyond the first 20 attributes checked
+        actual = self.get_suggestion(obj, 'target_value')
+        self.assertNotIn("inner.target_value", actual)
+
+    def test_getattr_nested_returns_first_match_only(self):
+        # Test that only the first nested match is returned (not multiple)
+        class Inner1:
+            def __init__(self):
+                self.value = 1
+
+        class Inner2:
+            def __init__(self):
+                self.value = 2
+
+        class Inner3:
+            def __init__(self):
+                self.value = 3
+
+        class Outer:
+            def __init__(self):
+                # Multiple inner objects with same attribute
+                self.a_inner = Inner1()
+                self.b_inner = Inner2()
+                self.c_inner = Inner3()
+
+        # Should suggest only the first match (alphabetically)
+        actual = self.get_suggestion(Outer(), 'value')
+        self.assertIn("'.a_inner.value'", actual)
+        # Verify it's a single suggestion, not multiple
+        self.assertEqual(actual.count("Did you mean"), 1)
+
+    def test_getattr_nested_handles_attribute_access_exceptions(self):
+        # Test that exceptions raised when accessing attributes don't crash the suggestion system
+        class ExplodingProperty:
+            @property
+            def exploding_attr(self):
+                raise RuntimeError("BOOM! This property always explodes")
+
+            def __repr__(self):
+                raise RuntimeError("repr also explodes")
+
+        class SafeInner:
+            def __init__(self):
+                self.target = 42
+
+        class Outer:
+            def __init__(self):
+                self.exploder = ExplodingProperty()  # Accessing attributes will raise
+                self.safe_inner = SafeInner()
+
+        # Should still suggest '.safe_inner.target' without crashing
+        # even though accessing exploder.target would raise an exception
+        actual = self.get_suggestion(Outer(), 'target')
+        self.assertIn("'.safe_inner.target'", actual)
+
+    def test_getattr_nested_handles_hasattr_exceptions(self):
+        # Test that exceptions in hasattr don't crash the system
+        class WeirdObject:
+            def __getattr__(self, name):
+                if name == 'target':
+                    raise RuntimeError("Can't check for target attribute")
+                raise AttributeError(f"No attribute {name}")
+
+        class NormalInner:
+            def __init__(self):
+                self.target = 100
+
+        class Outer:
+            def __init__(self):
+                self.weird = WeirdObject()  # hasattr will raise for 'target'
+                self.normal = NormalInner()
+
+        # Should still find 'normal.target' even though weird.target check fails
+        actual = self.get_suggestion(Outer(), 'target')
+        self.assertIn("'.normal.target'", actual)
+
+    @force_not_colorized
+    def test_cross_language(self):
+        cases = [
+            # (type, attr, hint_attr)
+            (list, 'push', 'append'),
+            (list, 'concat', 'extend'),
+            (list, 'addAll', 'extend'),
+            (str, 'toUpperCase', 'upper'),
+            (str, 'toLowerCase', 'lower'),
+            (str, 'trimStart', 'lstrip'),
+            (str, 'trimEnd', 'rstrip'),
+            (dict, 'keySet', 'keys'),
+            (dict, 'entrySet', 'items'),
+            (dict, 'entries', 'items'),
+            (dict, 'putAll', 'update'),
+        ]
+        for test_type, attr, hint_attr in cases:
+            with self.subTest(type=test_type.__name__, attr=attr):
+                obj = test_type()
+                actual = self.get_suggestion(obj, attr)
+                self.assertEndsWith(actual, f"Did you mean '.{hint_attr}'?")
+
+        cases = [
+            # (type, attr, hint)
+            (list, 'contains', "Use 'x in list'."),
+            (list, 'add', "Did you mean to use a 'set' object?"),
+            (dict, 'put', "Use d[k] = v."),
+        ]
+        for test_type, attr, expected in cases:
+            with self.subTest(type=test_type, attr=attr):
+                obj = test_type()
+                actual = self.get_suggestion(obj, attr)
+                self.assertEndsWith(actual, expected)
+
+    @force_not_colorized
+    def test_cross_language_levenshtein_fallback(self):
+        # When no cross-language entry exists, Levenshtein still works
+        # (e.g., trim->strip is not in the table but Levenshtein catches it)
+        actual = self.get_suggestion('', 'trim')
+        self.assertIn("strip", actual)
+
+    @force_not_colorized
+    def test_cross_language_no_hint_for_unknown_attr(self):
+        actual = self.get_suggestion([], 'completely_unknown_method')
+        self.assertNotIn("Did you mean", actual)
+
+    @force_not_colorized
+    def test_cross_language_works_for_subclasses(self):
+        # isinstance() check means subclasses also get hints
+        class MyList(list):
+            pass
+        actual = self.get_suggestion(MyList(), 'push')
+        self.assertEndsWith(actual, "Did you mean '.append'?")
+
+        class MyDict(dict):
+            pass
+        actual = self.get_suggestion(MyDict(), 'keySet')
+        self.assertEndsWith(actual, "Did you mean '.keys'?")
+
+    @force_not_colorized
+    def test_cross_language_mutable_on_immutable(self):
+        # Mutable method on immutable type suggests the mutable counterpart
+        cases = [
+            (tuple, 'append', "Did you mean to use a 'list' object?"),
+            (tuple, 'extend', "Did you mean to use a 'list' object?"),
+            (tuple, 'insert', "Did you mean to use a 'list' object?"),
+            (tuple, 'remove', "Did you mean to use a 'list' object?"),
+            (frozenset, 'add', "Did you mean to use a 'set' object?"),
+            (frozenset, 'discard', "Did you mean to use a 'set' object?"),
+            (frozenset, 'remove', "Did you mean to use a 'set' object?"),
+            (frozenset, 'update', "Did you mean to use a 'set' object?"),
+            (frozendict, 'update', "Did you mean to use a 'dict' object?"),
+        ]
+        for test_type, attr, expected in cases:
+            with self.subTest(type=test_type.__name__, attr=attr):
+                obj = test_type()
+                actual = self.get_suggestion(obj, attr)
+                self.assertEndsWith(actual, expected)
+
+    @force_not_colorized
+    def test_cross_language_float_bitwise(self):
+        # Bitwise operators on float suggest using int
+        cases = ['__or__', '__and__', '__xor__', '__lshift__', '__rshift__']
+        for attr in cases:
+            with self.subTest(attr=attr):
+                actual = self.get_suggestion(1.0, attr)
+                self.assertIn("'int'", actual)
+                self.assertIn("Bitwise operators", actual)
+
     def make_module(self, code):
         tmpdir = Path(tempfile.mkdtemp())
         self.addCleanup(shutil.rmtree, tmpdir)
@@ -4665,6 +5009,34 @@ def foo(self):
         actual = self.get_suggestion(instance.foo)
         self.assertIn("self.blech", actual)
 
+    def test_name_error_with_instance_not_normalized(self):
+        class A:
+            def __init__(self):
+                self.fiⁿₐˡᵢᶻₐᵗᵢᵒₙ = None
+            def foo(self):
+                analization = 1
+                x = fiⁿₐˡᵢᶻₐᵗᵢᵒₙ
+
+        instance = A()
+        actual = self.get_suggestion(instance.foo)
+        self.assertIn("self.finalization", actual)
+        self.assertNotIn("fiⁿₐˡᵢᶻₐᵗᵢᵒₙ", actual)
+        self.assertNotIn("analization", actual)
+
+        class B:
+            def __init__(self):
+                self.attr_µ = None  # attr_\xb5
+            def foo(self):
+                attr_a = 1
+                x = attr_µ  # attr_\xb5
+
+        instance = B()
+        actual = self.get_suggestion(instance.foo)
+        self.assertIn("self.attr_\u03bc", actual)
+        self.assertIn(r"self.attr_\u03bc", actual)
+        self.assertNotIn("attr_\xb5", actual)
+        self.assertNotIn("attr_a", actual)
+
     def test_unbound_local_error_with_instance(self):
         class A:
             def __init__(self):
@@ -4747,6 +5119,51 @@ class CPythonSuggestionFormattingTests(
     """
 
 
+class PurePythonGetattrSuggestionFormattingTests(
+    PurePythonExceptionFormattingMixin,
+    GetattrSuggestionTests,
+    unittest.TestCase,
+):
+    """
+    Same set of tests (for attribute access) as above using the pure Python
+    implementation of traceback printing in traceback.py.
+    """
+
+
+class PurePythonDelattrSuggestionFormattingTests(
+    PurePythonExceptionFormattingMixin,
+    DelattrSuggestionTests,
+    unittest.TestCase,
+):
+    """
+    Same set of tests (for attribute deletion) as above using the pure Python
+    implementation of traceback printing in traceback.py.
+    """
+
+
+@cpython_only
+class CPythonGetattrSuggestionFormattingTests(
+    CAPIExceptionFormattingMixin,
+    GetattrSuggestionTests,
+    unittest.TestCase,
+):
+    """
+    Same set of tests (for attribute access) as above but with Python's
+    internal traceback printing.
+    """
+
+
+@cpython_only
+class CPythonDelattrSuggestionFormattingTests(
+    CAPIExceptionFormattingMixin,
+    DelattrSuggestionTests,
+    unittest.TestCase,
+):
+    """
+    Same set of tests (for attribute deletion) as above but with Python's
+    internal traceback printing.
+    """
+
 class MiscTest(unittest.TestCase):
 
     def test_all(self):
@@ -4841,7 +5258,109 @@ class MyList(list):
         with self.assertRaises(TypeError):
             _suggestions._generate_suggestions(MyList(), "")
 
+    def test_no_site_package_flavour(self):
+        code = """import boo"""
+        _, _, stderr = assert_python_failure('-S', '-c', code)
 
+        self.assertIn(
+            (b"Site initialization is disabled, did you forget to "
+             b"add the site-packages directory to sys.path "
+             b"or to enable your virtual environment?"), stderr
+        )
+
+        code = """
+            import sys
+            sys.stdlib_module_names = sys.stdlib_module_names + ("boo",)
+            import boo
+        """
+        _, _, stderr = assert_python_failure('-S', '-c', code)
+
+        self.assertNotIn(
+            (b"Site initialization is disabled, did you forget to "
+             b"add the site-packages directory to sys.path "
+             b"or to enable your virtual environment?"), stderr
+        )
+
+    def test_missing_stdlib_module(self):
+        code = """
+            import sys
+            sys.stdlib_module_names |= {'spam'}
+            import spam
+        """
+        _, _, stderr = assert_python_failure('-S', '-c', code)
+
+        self.assertIn(b"Standard library module 'spam' was not found", stderr)
+
+        code = """
+            import sys
+            import traceback
+            traceback._MISSING_STDLIB_MODULE_MESSAGES = {'spam': "Install 'spam4life' for 'spam'"}
+            sys.stdlib_module_names |= {'spam'}
+            import spam
+        """
+        _, _, stderr = assert_python_failure('-S', '-c', code)
+
+        self.assertIn(b"Install 'spam4life' for 'spam'", stderr)
+
+    @unittest.skipIf(sys.platform == "win32", "Non-Windows test")
+    def test_windows_only_module_error(self):
+        try:
+            import msvcrt  # noqa: F401
+        except ModuleNotFoundError:
+            formatted = traceback.format_exc()
+            self.assertIn("Unsupported platform for Windows-only standard library module 'msvcrt'", formatted)
+        else:
+            self.fail("ModuleNotFoundError was not raised")
+
+    @unittest.skipIf(not importlib.machinery.EXTENSION_SUFFIXES, 'Platform does not support extension modules')
+    def test_find_incompatible_extension_modules(self):
+        """_find_incompatible_extension_modules assumes the last extension in
+        importlib.machinery.EXTENSION_SUFFIXES (defined in Python/dynload_*.c)
+        is untagged (eg. .so, .pyd).
+
+        This test exists to make sure that assumption is correct.
+        """
+        last_extension_suffix = importlib.machinery.EXTENSION_SUFFIXES[-1]
+        if shlib_suffix := sysconfig.get_config_var('SHLIB_SUFFIX'):
+            self.assertEqual(last_extension_suffix, shlib_suffix)
+        else:
+            before_dot, *extensions = last_extension_suffix.split('.')
+            expected_prefixes = ['']
+            if os.name == 'nt':
+                # Windows puts the debug tag in the module file stem (eg. foo_d.pyd)
+                expected_prefixes.append('_d')
+            self.assertIn(before_dot, expected_prefixes, msg=(
+                f'Unexpected prefix {before_dot!r} in extension module '
+                f'suffix {last_extension_suffix!r}. '
+                'traceback._find_incompatible_extension_module needs to be '
+                'updated to take this into account!'
+            ))
+            # if SHLIB_SUFFIX is not define, we assume the native
+            # shared library suffix only contains one extension
+            # (eg. '.so', bad eg. '.cpython-315-x86_64-linux-gnu.so')
+            self.assertEqual(len(extensions), 1, msg=(
+                'The last suffix in importlib.machinery.EXTENSION_SUFFIXES '
+                'contains more than one extension, so it is probably different '
+                'than SHLIB_SUFFIX. It probably contains an ABI tag! '
+                'If this is a false positive, define SHLIB_SUFFIX in sysconfig.'
+            ))
+
+    @unittest.skipIf(not importlib.machinery.EXTENSION_SUFFIXES, 'Platform does not support extension modules')
+    def test_incompatible_extension_modules_hint(self):
+        untagged_suffix = importlib.machinery.EXTENSION_SUFFIXES[-1]
+        with os_helper.temp_dir() as tmp:
+            # create a module with a incompatible ABI tag
+            incompatible_module = f'foo.some-abi{untagged_suffix}'
+            open(os.path.join(tmp, incompatible_module), "wb").close()
+            # try importing it
+            code = f'''
+                import sys
+                sys.path.insert(0, {tmp!r})
+                import foo
+            '''
+            _, _, stderr = assert_python_failure('-c', code, __cwd=tmp)
+        hint = f'Although a module with this name was found for a different Python version ({incompatible_module}).'
+        self.assertIn(hint, stderr.decode())
 
 
 class TestColorizedTraceback(unittest.TestCase):
@@ -4879,6 +5398,23 @@ def bar():
         self.assertIn("return baz1(1,\n            2,3\n            ,4)", lines)
         self.assertIn(red + "bar" + reset + boldr + "()" + reset, lines)
 
+    def test_colorized_exception_notes(self):
+        def foo():
+            raise ValueError()
+
+        try:
+            foo()
+        except Exception as e:
+            e.add_note("First note")
+            e.add_note("Second note")
+            exc = traceback.TracebackException.from_exception(e)
+
+        lines = "".join(exc.format(colorize=True))
+        note = colors["n"]
+        reset = colors["z"]
+        self.assertIn(note + "First note" + reset, lines)
+        self.assertIn(note + "Second note" + reset, lines)
+
     def test_colorized_syntax_error(self):
         try:
             compile("a $ b", "<string>", "exec")
@@ -4887,7 +5423,7 @@ def test_colorized_syntax_error(self):
                 e, capture_locals=True
             )
         actual = "".join(exc.format(colorize=True))
-        def expected(t, m, fn, l, f, E, e, z):
+        def expected(t, m, fn, l, f, E, e, z, n):
             return "".join(
                 [
                     f'  File {fn}"<string>"{z}, line {l}1{z}\n',
@@ -4914,7 +5450,7 @@ def foo():
             actual = tbstderr.getvalue().splitlines()
 
         lno_foo = foo.__code__.co_firstlineno
-        def expected(t, m, fn, l, f, E, e, z):
+        def expected(t, m, fn, l, f, E, e, z, n):
             return [
                 'Traceback (most recent call last):',
                 f'  File {fn}"{__file__}"{z}, '
@@ -4947,7 +5483,7 @@ def foo():
 
         lno_foo = foo.__code__.co_firstlineno
         actual = "".join(exc.format(colorize=True)).splitlines()
-        def expected(t, m, fn, l, f, E, e, z):
+        def expected(t, m, fn, l, f, E, e, z, n):
             return [
                 f"  + Exception Group Traceback (most recent call last):",
                 f'  |   File {fn}"{__file__}"{z}, line {l}{lno_foo+9}{z}, in {f}test_colorized_traceback_from_exception_group{z}',
@@ -4971,5 +5507,139 @@ def expected(t, m, fn, l, f, E, e, z):
         ]
         self.assertEqual(actual, expected(**colors))
 
+    def test_colorized_traceback_unicode(self):
+        try:
+            啊哈=1; 啊哈/0####
+        except Exception as e:
+            exc = traceback.TracebackException.from_exception(e)
+
+        actual = "".join(exc.format(colorize=True)).splitlines()
+        def expected(t, m, fn, l, f, E, e, z, n):
+            return [
+                f"    啊哈=1; {e}啊哈{z}{E}/{z}{e}0{z}####",
+                f"            {e}~~~~{z}{E}^{z}{e}~{z}",
+            ]
+        self.assertEqual(actual[2:4], expected(**colors))
+
+        try:
+            ééééé/0
+        except Exception as e:
+            exc = traceback.TracebackException.from_exception(e)
+
+        actual = "".join(exc.format(colorize=True)).splitlines()
+        def expected(t, m, fn, l, f, E, e, z, n):
+            return [
+                f"    {E}ééééé{z}/0",
+                f"    {E}^^^^^{z}",
+            ]
+        self.assertEqual(actual[2:4], expected(**colors))
+
+    def test_colorized_syntax_error_ascii_display_width(self):
+        """Caret alignment for ASCII edge cases handled by _wlen.
+
+        The old ASCII fast track in _display_width returned the raw character
+        offset for ASCII strings, which is wrong for CTRL-Z (display width 2)
+        and ANSI escape sequences (display width 0).
+        """
+        E = colors["E"]
+        z = colors["z"]
+        t = colors["t"]
+        m = colors["m"]
+        fn = colors["fn"]
+        l = colors["l"]
+
+        def _make_syntax_error(text, offset, end_offset):
+            err = SyntaxError("invalid syntax")
+            err.filename = "<string>"
+            err.lineno = 1
+            err.end_lineno = 1
+            err.text = text
+            err.offset = offset
+            err.end_offset = end_offset
+            return err
+
+        # CTRL-Z (\x1a) is ASCII but displayed as ^Z (2 columns).
+        # Verify caret aligns when CTRL-Z precedes the error.
+        err = _make_syntax_error("a\x1a$\n", offset=3, end_offset=4)
+        exc = traceback.TracebackException.from_exception(err)
+        actual = "".join(exc.format(colorize=True))
+        # 'a' (1 col) + '\x1a' (2 cols) = 3 cols before '$'
+        self.assertIn(
+            f'  File {fn}"<string>"{z}, line {l}1{z}\n'
+            f'    a\x1a{E}${z}\n'
+            f'    {" " * 3}{E}^{z}\n'
+            f'{t}SyntaxError{z}: {m}invalid syntax{z}\n',
+            actual,
+        )
+
+        # CTRL-Z in the highlighted (error) region counts as 2 columns.
+        err = _make_syntax_error("$\x1a\n", offset=1, end_offset=3)
+        exc = traceback.TracebackException.from_exception(err)
+        actual = "".join(exc.format(colorize=True))
+        # '$' (1 col) + '\x1a' (2 cols) = 3 columns of carets
+        self.assertIn(
+            f'    {E}$\x1a{z}\n'
+            f'    {E}{"^" * 3}{z}\n',
+            actual,
+        )
+
+        # ANSI escape sequences are ASCII but take 0 display columns.
+        err = _make_syntax_error("a\x1b[1mb$\n", offset=7, end_offset=8)
+        exc = traceback.TracebackException.from_exception(err)
+        actual = "".join(exc.format(colorize=True))
+        # 'a' (1 col) + '\x1b[1m' (0 cols) + 'b' (1 col) = 2 before '$'
+        self.assertIn(
+            f'    a\x1b[1mb{E}${z}\n'
+            f'    {" " * 2}{E}^{z}\n',
+            actual,
+        )
+
+class TestLazyImportSuggestions(unittest.TestCase):
+    """Test that lazy imports are not reified when computing AttributeError suggestions."""
+
+    def test_attribute_error_does_not_reify_lazy_imports(self):
+        """Printing an AttributeError should not trigger lazy import reification."""
+        # lazypkg.bar prints "BAR_MODULE_LOADED" when imported.
+        # If lazy import is reified during suggestion computation, we'll see it.
+        code = textwrap.dedent("""
+            lazy import test.test_lazy_import.data.lazypkg
+            test.test_lazy_import.data.lazypkg.nonexistent
+        """)
+        rc, stdout, stderr = assert_python_failure('-c', code)
+        self.assertNotIn(b"BAR_MODULE_LOADED", stdout)
+
+    def test_traceback_formatting_does_not_reify_lazy_imports(self):
+        """Formatting a traceback should not trigger lazy import reification."""
+        code = textwrap.dedent("""
+            import traceback
+            lazy import test.test_lazy_import.data.lazypkg
+            try:
+                test.test_lazy_import.data.lazypkg.nonexistent
+            except AttributeError:
+                traceback.format_exc()
+            print("OK")
+        """)
+        rc, stdout, stderr = assert_python_ok('-c', code)
+        self.assertIn(b"OK", stdout)
+        self.assertNotIn(b"BAR_MODULE_LOADED", stdout)
+
+    def test_suggestion_still_works_for_non_lazy_attributes(self):
+        """Suggestions should still work for non-lazy module attributes."""
+        code = textwrap.dedent("""
+            lazy import test.test_lazy_import.data.lazypkg
+            # Typo for __name__
+            test.test_lazy_import.data.lazypkg.__nme__
+        """)
+        rc, stdout, stderr = assert_python_failure('-c', code)
+        self.assertIn(b"__name__", stderr)
+        self.assertNotIn(b"BAR_MODULE_LOADED", stdout)
+
+
+class LazyImportTest(unittest.TestCase):
+    @support.cpython_only
+    def test_lazy_import(self):
+        ensure_lazy_imports("traceback", {"_colorize"})
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_tstring.py b/Lib/test/test_tstring.py
index 74653c77c55..1e5f14ca007 100644
--- a/Lib/test/test_tstring.py
+++ b/Lib/test/test_tstring.py
@@ -1,5 +1,9 @@
+import subprocess
 import unittest
 
+from test import support
+from test.support.os_helper import temp_cwd
+from test.support.script_helper import assert_python_ok, spawn_python
 from test.test_string._support import TStringBaseCase, fstring
 
 
@@ -79,6 +83,44 @@ def upper(self):
         )
         self.assertEqual(fstring(t), "Name: Bob, Age: 30")
 
+    @support.requires_subprocess()
+    def test_expression_in_interactive_after_buffer_resize(self):
+        expression = "(\n" + (" " * 64 + "\n") * 256 + "1\n)"
+        source = (
+            f"result = t'''{{{expression}}}'''\n"
+            "print(repr(result.interpolations[0].expression))\n"
+        )
+        with spawn_python('-i', '-q', stderr=subprocess.PIPE) as process:
+            stdout, stderr = process.communicate(
+                source.encode(), timeout=support.SHORT_TIMEOUT)
+        self.assertEqual(process.returncode, 0, stderr)
+        self.assertEqual(stdout.decode().strip(), repr(expression))
+
+    def test_interpolation_expression_in_file_after_buffer_resize(self):
+        expression = "(\n" + (" " * 64 + "\n") * 256 + "1\n)"
+        with temp_cwd():
+            script = 'script.py'
+            source = (
+                f"template = t'''{{{expression}}}'''\n"
+                "interpolation = template.interpolations[0]\n"
+                f"assert interpolation.expression == {expression!r}\n"
+            )
+            with open(script, 'w') as f:
+                f.write(source)
+            assert_python_ok(script)
+
+    @support.requires_resource('cpu')
+    def test_many_tstrings_in_module(self):
+        fields = ''.join(f'{{x{i}}}' for i in range(100))
+        source = ''.join(
+            f"value_{i} = t'{fields}'\n" for i in range(1_000)
+        )
+        namespace = {f'x{i}': str(i) for i in range(100)}
+        expected = ''.join(str(i) for i in range(100))
+        exec(source, namespace)
+        self.assertEqual(fstring(namespace['value_0']), expected)
+        self.assertEqual(fstring(namespace['value_999']), expected)
+
     def test_format_specifiers(self):
         # Test basic format specifiers
         value = 3.14159
@@ -88,6 +130,14 @@ def test_format_specifiers(self):
         )
         self.assertEqual(fstring(t), "Pi: 3.14")
 
+        a = 3
+        b = 4
+        t = t"{a!=b:>10}"
+        self.assertTStringEqual(
+            t, ("", ""), [(a != b, "a!=b", None, ">10")]
+        )
+        self.assertEqual(fstring(t), "         1")
+
     def test_conversions(self):
         # Test !s conversion (str)
         obj = object()
@@ -136,10 +186,82 @@ def test_debug_specifier(self):
         # Test white space in debug specifier
         t = t"Value: {value = }"
         self.assertTStringEqual(
-            t, ("Value: value = ", ""), [(value, "value", "r")]
+            t, ("Value: value = ", ""), [(value, "value ", "r")]
         )
         self.assertEqual(fstring(t), "Value: value = 42")
 
+        # Explicit line continuations after the debug marker are part of
+        # the debug text, not the interpolation expression.
+        for template, strings, interpolation, rendered in (
+            (
+                t"""Value: {value =\
+}""",
+                ("Value: value =\\\n", ""),
+                (value, "value ", "r"),
+                "Value: value =\\\n42",
+            ),
+            (
+                t"""Value: {value =\
+!r}""",
+                ("Value: value =\\\n", ""),
+                (value, "value ", "r"),
+                "Value: value =\\\n42",
+            ),
+            (
+                t"""Value: {value =\
+:04}""",
+                ("Value: value =\\\n", ""),
+                (value, "value ", None, "04"),
+                "Value: value =\\\n0042",
+            ),
+            (
+                t"""Value: {value =\
+\
+}""",
+                ("Value: value =\\\n\\\n", ""),
+                (value, "value ", "r"),
+                "Value: value =\\\n\\\n42",
+            ),
+        ):
+            with self.subTest(template=template):
+                self.assertTStringEqual(template, strings, [interpolation])
+                self.assertEqual(fstring(template), rendered)
+
+    def test_interpolation_expression_whitespace(self):
+        x = 42
+        for template, expected in (
+            (t"{x}", "x"),
+            (t"{x }", "x "),
+            (t"{ x}", " x"),
+            (t"{ x }", " x "),
+            (t"{  x  }", "  x  "),
+            (t"""{
+  x
+}""", "\n  x\n"),
+            (t"{ x !r}", " x "),
+            (t"{ x :.2f}", " x "),
+            (t"{ x = }", " x "),
+            (t"{ x = !r}", " x "),
+            (t"{ x = :.2f}", " x "),
+            (t"{x == 42 = }", "x == 42 "),
+        ):
+            with self.subTest(template=template):
+                self.assertEqual(
+                    template.interpolations[0].expression,
+                    expected,
+                )
+
+    def test_interpolation_expression_with_reconstructed_metadata(self):
+        regular = t'''{(
+            1,  # Force lexer metadata reconstruction.
+            "\"#")}'''
+        debug = t'''{(
+            1,  # Force lexer metadata reconstruction.
+            "\"#")=}'''
+        expected = '(\n            1,  \n            "\\"#")'
+        self.assertEqual(regular.interpolations[0].expression, expected)
+        self.assertEqual(debug.interpolations[0].expression, expected)
+
     def test_raw_tstrings(self):
         path = r"C:\Users"
         t = rt"{path}\Documents"
diff --git a/Lib/test/test_type_aliases.py b/Lib/test/test_type_aliases.py
index ee1791bc1d0..05bc6a80888 100644
--- a/Lib/test/test_type_aliases.py
+++ b/Lib/test/test_type_aliases.py
@@ -8,6 +8,11 @@
     Callable, TypeAliasType, TypeVar, TypeVarTuple, ParamSpec, Unpack, get_args,
 )
 
+type GlobalTypeAlias = int
+
+def get_type_alias():
+    type TypeAliasInFunc = str
+    return TypeAliasInFunc
 
 class TypeParamsInvalidTest(unittest.TestCase):
     def test_name_collisions(self):
@@ -70,6 +75,8 @@ def inner[B](self):
 
 
 class TypeParamsAliasValueTest(unittest.TestCase):
+    type TypeAliasInClass = dict
+
     def test_alias_value_01(self):
         type TA1 = int
 
@@ -142,33 +149,67 @@ def test_subscripting(self):
         self.assertIs(specialized2.__origin__, VeryGeneric)
         self.assertEqual(specialized2.__args__, (int, str, float, [bool, range]))
 
+    def test___name__(self):
+        type TypeAliasLocal = GlobalTypeAlias
+
+        self.assertEqual(GlobalTypeAlias.__name__, 'GlobalTypeAlias')
+        self.assertEqual(get_type_alias().__name__, 'TypeAliasInFunc')
+        self.assertEqual(self.TypeAliasInClass.__name__, 'TypeAliasInClass')
+        self.assertEqual(TypeAliasLocal.__name__, 'TypeAliasLocal')
+
+        with self.assertRaisesRegex(
+            AttributeError,
+            "readonly attribute",
+        ):
+            setattr(TypeAliasLocal, '__name__', 'TA')
+
+    def test___qualname__(self):
+        type TypeAliasLocal = GlobalTypeAlias
+
+        self.assertEqual(GlobalTypeAlias.__qualname__,
+                         'GlobalTypeAlias')
+        self.assertEqual(get_type_alias().__qualname__,
+                         'get_type_alias.<locals>.TypeAliasInFunc')
+        self.assertEqual(self.TypeAliasInClass.__qualname__,
+                         'TypeParamsAliasValueTest.TypeAliasInClass')
+        self.assertEqual(TypeAliasLocal.__qualname__,
+                         'TypeParamsAliasValueTest.test___qualname__.<locals>.TypeAliasLocal')
+
+        with self.assertRaisesRegex(
+            AttributeError,
+            "readonly attribute",
+        ):
+            setattr(TypeAliasLocal, '__qualname__', 'TA')
+
     def test_repr(self):
         type Simple = int
-        type VeryGeneric[T, *Ts, **P] = Callable[P, tuple[T, *Ts]]
+        self.assertEqual(repr(Simple), Simple.__qualname__)
 
-        self.assertEqual(repr(Simple), "Simple")
-        self.assertEqual(repr(VeryGeneric), "VeryGeneric")
+        type VeryGeneric[T, *Ts, **P] = Callable[P, tuple[T, *Ts]]
+        self.assertEqual(repr(VeryGeneric), VeryGeneric.__qualname__)
+        fullname = f"{VeryGeneric.__module__}.{VeryGeneric.__qualname__}"
         self.assertEqual(repr(VeryGeneric[int, bytes, str, [float, object]]),
-                         "VeryGeneric[int, bytes, str, [float, object]]")
+                         f"{fullname}[int, bytes, str, [float, object]]")
         self.assertEqual(repr(VeryGeneric[int, []]),
-                         "VeryGeneric[int, []]")
+                         f"{fullname}[int, []]")
         self.assertEqual(repr(VeryGeneric[int, [VeryGeneric[int], list[str]]]),
-                         "VeryGeneric[int, [VeryGeneric[int], list[str]]]")
+                         f"{fullname}[int, [{fullname}[int], list[str]]]")
 
     def test_recursive_repr(self):
         type Recursive = Recursive
-        self.assertEqual(repr(Recursive), "Recursive")
+        self.assertEqual(repr(Recursive), Recursive.__qualname__)
 
         type X = list[Y]
         type Y = list[X]
-        self.assertEqual(repr(X), "X")
-        self.assertEqual(repr(Y), "Y")
+        self.assertEqual(repr(X), X.__qualname__)
+        self.assertEqual(repr(Y), Y.__qualname__)
 
         type GenericRecursive[X] = list[X | GenericRecursive[X]]
-        self.assertEqual(repr(GenericRecursive), "GenericRecursive")
-        self.assertEqual(repr(GenericRecursive[int]), "GenericRecursive[int]")
+        self.assertEqual(repr(GenericRecursive), GenericRecursive.__qualname__)
+        fullname = f"{GenericRecursive.__module__}.{GenericRecursive.__qualname__}"
+        self.assertEqual(repr(GenericRecursive[int]), f"{fullname}[int]")
         self.assertEqual(repr(GenericRecursive[GenericRecursive[int]]),
-                         "GenericRecursive[GenericRecursive[int]]")
+                         f"{fullname}[{fullname}[int]]")
 
     def test_raising(self):
         type MissingName = list[_My_X]
@@ -193,15 +234,25 @@ class TypeAliasConstructorTest(unittest.TestCase):
     def test_basic(self):
         TA = TypeAliasType("TA", int)
         self.assertEqual(TA.__name__, "TA")
+        self.assertEqual(TA.__qualname__, "TA")
         self.assertIs(TA.__value__, int)
         self.assertEqual(TA.__type_params__, ())
         self.assertEqual(TA.__module__, __name__)
 
+    def test_with_qualname(self):
+        TA = TypeAliasType("TA", str, qualname="Class.TA")
+        self.assertEqual(TA.__name__, "TA")
+        self.assertEqual(TA.__qualname__, "Class.TA")
+        self.assertIs(TA.__value__, str)
+        self.assertEqual(TA.__type_params__, ())
+        self.assertEqual(TA.__module__, __name__)
+
     def test_attributes_with_exec(self):
         ns = {}
         exec("type TA = int", ns, ns)
         TA = ns["TA"]
         self.assertEqual(TA.__name__, "TA")
+        self.assertEqual(TA.__qualname__, "TA")
         self.assertIs(TA.__value__, int)
         self.assertEqual(TA.__type_params__, ())
         self.assertIs(TA.__module__, None)
@@ -210,6 +261,7 @@ def test_generic(self):
         T = TypeVar("T")
         TA = TypeAliasType("TA", list[T], type_params=(T,))
         self.assertEqual(TA.__name__, "TA")
+        self.assertEqual(TA.__qualname__, "TA")
         self.assertEqual(TA.__value__, list[T])
         self.assertEqual(TA.__type_params__, (T,))
         self.assertEqual(TA.__module__, __name__)
@@ -218,6 +270,7 @@ def test_generic(self):
     def test_not_generic(self):
         TA = TypeAliasType("TA", list[int], type_params=())
         self.assertEqual(TA.__name__, "TA")
+        self.assertEqual(TA.__qualname__, "TA")
         self.assertEqual(TA.__value__, list[int])
         self.assertEqual(TA.__type_params__, ())
         self.assertEqual(TA.__module__, __name__)
@@ -268,8 +321,9 @@ def test_expects_type_like(self):
             TypeAliasType("A", int, type_params=(T, 2))
 
     def test_keywords(self):
-        TA = TypeAliasType(name="TA", value=int)
+        TA = TypeAliasType(name="TA", value=int, type_params=(), qualname=None)
         self.assertEqual(TA.__name__, "TA")
+        self.assertEqual(TA.__qualname__, "TA")
         self.assertIs(TA.__value__, int)
         self.assertEqual(TA.__type_params__, ())
         self.assertEqual(TA.__module__, __name__)
@@ -283,6 +337,8 @@ def test_errors(self):
             TypeAliasType("TA", list, ())
         with self.assertRaises(TypeError):
             TypeAliasType("TA", list, type_params=42)
+        with self.assertRaises(TypeError):
+            TypeAliasType("TA", list, qualname=range(5))
 
 
 class TypeAliasTypeTest(unittest.TestCase):
@@ -316,6 +372,8 @@ def test_module(self):
                          mod_generics_cache.__name__)
         self.assertEqual(mod_generics_cache.OldStyle.__module__,
                          mod_generics_cache.__name__)
+        Alias.__module__ = "ham.spam.eggs"
+        self.assertEqual(Alias.__module__, "ham.spam.eggs")
 
     def test_unpack(self):
         type Alias = tuple[int, int]
diff --git a/Lib/test/test_type_annotations.py b/Lib/test/test_type_annotations.py
index c98b99e98e9..54db123a5dc 100644
--- a/Lib/test/test_type_annotations.py
+++ b/Lib/test/test_type_annotations.py
@@ -1,5 +1,6 @@
 import annotationlib
 import inspect
+import itertools
 import textwrap
 import types
 import unittest
@@ -309,7 +310,7 @@ def check_annotations(self, f):
             print(f.__annotations__)
 
         f.__annotate__ = lambda x: 42
-        with self.assertRaisesRegex(TypeError, r"__annotate__ returned non-dict of type 'int'"):
+        with self.assertRaisesRegex(TypeError, r"__annotate__\(\) must return a dict, not int"):
             print(f.__annotations__)
 
         f.__annotate__ = lambda x: {"x": x}
@@ -855,9 +856,9 @@ def method(self, x: int):
         """
         ns = run_code(code)
         method = ns["Outer"].method
+        self.assertEqual(method.__annotate__.__qualname__, "Outer.method.__annotate__")
         self.assertEqual(ns["f"].__annotate__.__qualname__, "f.__annotate__")
         self.assertEqual(ns["f"]().__annotate__.__qualname__, "f.<locals>.nested.__annotate__")
-        self.assertEqual(method.__annotate__.__qualname__, "Outer.method.__annotate__")
         self.assertEqual(ns["Outer"].__annotate__.__qualname__, "Outer.__annotate__")
 
     # gh-138349
@@ -896,3 +897,18 @@ class Generic:
                 mod = build_module(code)
                 annos = mod.__annotations__
                 self.assertEqual(annos, {"annotated_name": 0})
+
+    # gh-154902
+    def test_conditional_annotations_rebound(self):
+        # user code can rebind __conditional_annotations__ to any object
+        lefts = ("__conditional_annotations__",
+                 'globals()["__conditional_annotations__"]')
+        values = ("0", "{}", "[]", "''", "object()", "frozenset()")
+        for left, value in itertools.product(lefts, values):
+            with self.subTest(left=left, value=value):
+                code = f"""
+                    {left} = {value}
+                    x: int
+                """
+                with self.assertRaises(TypeError):
+                    run_code(code)
diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index e07fa568a86..7ca329ff76d 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -8,7 +8,7 @@
 from test.support.import_helper import import_fresh_module
 
 import collections.abc
-from collections import namedtuple, UserDict
+from collections import namedtuple, UserDict, OrderedDict
 import copy
 # XXX: RUSTPYTHON
 try:
@@ -27,6 +27,7 @@
 import typing
 
 import unittest  # XXX: RUSTPYTHON; importing to be able to skip tests
+import re
 
 c_types = import_fresh_module('types', fresh=['_types'])
 py_types = import_fresh_module('types', blocked=['_types'])
@@ -46,7 +47,7 @@ def clear_typing_caches():
 class TypesTests(unittest.TestCase):
 
     def test_names(self):
-        c_only_names = {'CapsuleType'}
+        c_only_names = {'CapsuleType', 'LazyImportType'}
         ignored = {'new_class', 'resolve_bases', 'prepare_class',
                    'get_original_bases', 'DynamicClassAttribute', 'coroutine'}
 
@@ -58,11 +59,13 @@ def test_names(self):
             'AsyncGeneratorType', 'BuiltinFunctionType', 'BuiltinMethodType',
             'CapsuleType', 'CellType', 'ClassMethodDescriptorType', 'CodeType',
             'CoroutineType', 'EllipsisType', 'FrameType', 'FunctionType',
+            'FrameLocalsProxyType',
             'GeneratorType', 'GenericAlias', 'GetSetDescriptorType',
-            'LambdaType', 'MappingProxyType', 'MemberDescriptorType',
-            'MethodDescriptorType', 'MethodType', 'MethodWrapperType',
-            'ModuleType', 'NoneType', 'NotImplementedType', 'SimpleNamespace',
-            'TracebackType', 'UnionType', 'WrapperDescriptorType',
+            'LambdaType', 'LazyImportType', 'MappingProxyType',
+            'MemberDescriptorType', 'MethodDescriptorType', 'MethodType',
+            'MethodWrapperType', 'ModuleType', 'NoneType',
+            'NotImplementedType', 'SimpleNamespace', 'TracebackType',
+            'UnionType', 'WrapperDescriptorType',
         }
         self.assertEqual(all_names, set(c_types.__all__))
         self.assertEqual(all_names - c_only_names, set(py_types.__all__))
@@ -717,6 +720,19 @@ def call(part):
         """
         assert_python_ok("-c", code)
 
+    def test_frame_locals_proxy_type(self):
+        self.assertIsInstance(types.FrameLocalsProxyType, type)
+        if MISSING_C_DOCSTRINGS:
+            self.assertIsNone(types.FrameLocalsProxyType.__doc__)
+        else:
+            self.assertIsInstance(types.FrameLocalsProxyType.__doc__, str)
+        self.assertEqual(types.FrameLocalsProxyType.__module__, 'builtins')
+        self.assertEqual(types.FrameLocalsProxyType.__name__, 'FrameLocalsProxy')
+
+        frame = inspect.currentframe()
+        self.assertIsNotNone(frame)
+        self.assertIsInstance(frame.f_locals, types.FrameLocalsProxyType)
+
 
 class UnionTests(unittest.TestCase):
 
@@ -1382,6 +1398,128 @@ def __hash__(self):
         view = self.mappingproxy(mapping)
         self.assertEqual(hash(view), hash(mapping))
 
+    def check_richcompare(self, mapping_type):
+        data1 = mapping_type({'a': 1})
+        data2 = mapping_type({'a': 2})
+        mp1 = self.mappingproxy(data1)
+        copy1 = self.mappingproxy(data1)
+        mp2 = self.mappingproxy(data2)
+
+        self.assertTrue(mp1 == data1)
+        self.assertTrue(data1 == mp1)
+        self.assertTrue(copy1 == data1)
+
+        self.assertTrue(mp1 == copy1)
+        self.assertFalse(mp1 != copy1)
+
+        self.assertFalse(mp1 == mp2)
+        self.assertTrue(mp1 != mp2)
+        self.assertFalse(mp2 == data1)
+        self.assertTrue(mp2 != data1)
+        self.assertTrue(data1 != mp2)
+
+        msg = "not supported between instances of 'mappingproxy' and 'mappingproxy'"
+        with self.assertRaisesRegex(TypeError, msg):
+            mp1 > mp2
+        with self.assertRaisesRegex(TypeError, msg):
+            mp1 < copy1
+        with self.assertRaisesRegex(TypeError, msg):
+            mp2 >= mp2
+        with self.assertRaisesRegex(TypeError, msg):
+            copy1 <= mp1
+
+        if mapping_type.__module__ == 'collections':
+            mapping_name = f'{mapping_type.__module__}.{mapping_type.__name__}'
+        else:
+            mapping_name = mapping_type.__name__
+        with self.assertRaisesRegex(
+            TypeError,
+            f"not supported between instances of 'mappingproxy' and '{mapping_name}'",
+        ):
+            copy1 <= data1
+
+        class Evil:
+            def __eq__(self, other):
+                return other
+
+        result = (mp1 == Evil())
+        self.assertIs(type(result), mapping_type)
+        if mapping_type == dict:
+            # Evil.__eq__() gets a copy of the mapping
+            self.assertEqual(result, data1)
+        else:
+            self.assertIs(result, data1)
+
+    def test_richcompare_dict(self):
+        self.check_richcompare(dict)
+
+    def test_richcompare_custom_mapping(self):
+        class CustomMapping(collections.abc.Mapping):
+            def __init__(self, data):
+                self._data = data
+
+            def __getitem__(self, key):
+                return self._data[key]
+
+            def __iter__(self):
+                return iter(self._data)
+
+            def __len__(self):
+                return len(self._data)
+
+            def __contains__(self, item):
+                return item in self._data
+
+        self.check_richcompare(CustomMapping)
+
+        class CustomMapping2(CustomMapping):
+            def __eq__(self, other):
+                return (
+                    isinstance(other, CustomMapping)
+                    and self._data == other._data
+                )
+
+        mp1 = self.mappingproxy(CustomMapping({'a': 1}))
+        self.assertEqual(mp1, CustomMapping2({'a': 1}))
+        self.assertNotEqual(CustomMapping2({'a': 1}), mp1)
+
+    def test_richcompare_odict(self):
+        self.check_richcompare(OrderedDict)
+
+    def test_richcompare_frozendict(self):
+        self.check_richcompare(frozendict)
+
+    def test_richcompare_evil(self):
+        # This test used to mutate the list dictionary,
+        # but MappingProxyType now creates a copy to call `__eq__`:
+        # https://github.com/python/cpython/issues/152405
+        key = "__mappingproxy_crash_key__"
+
+        class Evil:
+            def __eq__(self, other):
+                other[key] = 1
+                return other
+
+        # Checks that it does not mutate the internals of `MappingProxyType`:
+        dc = {}
+        leaked = self.mappingproxy(dc) == Evil()
+        self.assertIs(type(leaked), dict)
+        self.assertIn(key, leaked)
+        self.assertNotIn(key, dc)
+
+        # Exposes the internals of `MappingProxyType` via richcompare:
+        leaked = vars(list) == Evil()
+        self.assertIs(type(leaked), dict)
+        self.assertIn(key, leaked)
+        name = "__mappingproxy_crash_probe__"
+        leaked[name] = lambda self: "probe"
+        self.assertIn(name, leaked)
+        self.assertNotHasAttr(list, key)
+        self.assertNotHasAttr(list, name)  # it used to return `True`
+        del leaked[name]
+        self.assertNotIn(name, leaked)
+        self.assertNotHasAttr(list, name)  # it used to crash
+
 
 class ClassCreationTests(unittest.TestCase):
 
@@ -2016,6 +2154,24 @@ def test_equal(self):
         self.assertEqual(ns1, ns2)
         self.assertNotEqual(ns2, types.SimpleNamespace())
 
+    def test_richcompare_unsupported(self):
+        ns1 = types.SimpleNamespace(x=1)
+        ns2 = types.SimpleNamespace(y=2)
+
+        msg = re.escape(
+            "not supported between instances of "
+            "'types.SimpleNamespace' and 'types.SimpleNamespace'"
+        )
+
+        with self.assertRaisesRegex(TypeError, msg):
+            ns1 > ns2
+        with self.assertRaisesRegex(TypeError, msg):
+            ns1 >= ns2
+        with self.assertRaisesRegex(TypeError, msg):
+            ns1 < ns2
+        with self.assertRaisesRegex(TypeError, msg):
+            ns1 <= ns2
+
     def test_nested(self):
         ns1 = types.SimpleNamespace(a=1, b=2)
         ns2 = types.SimpleNamespace()
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index b5974c72ab7..93e17de7534 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -13,6 +13,7 @@
 import pickle
 import re
 import sys
+import warnings
 from unittest import TestCase, main
 from unittest.mock import patch
 from copy import copy, deepcopy
@@ -28,32 +29,31 @@
 from typing import assert_type, cast, runtime_checkable
 from typing import get_type_hints
 from typing import get_origin, get_args, get_protocol_members
-from typing import override
+from typing import override, disjoint_base
 from typing import is_typeddict, is_protocol
 from typing import reveal_type
 from typing import dataclass_transform
-from typing import no_type_check, no_type_check_decorator
+from typing import no_type_check
 from typing import Type
-from typing import NamedTuple, NotRequired, Required, ReadOnly, TypedDict
+from typing import NamedTuple, NotRequired, Required, ReadOnly, TypedDict, NoExtraItems
 from typing import IO, TextIO, BinaryIO
 from typing import Pattern, Match
 from typing import Annotated, ForwardRef
 from typing import Self, LiteralString
 from typing import TypeAlias
 from typing import ParamSpec, Concatenate, ParamSpecArgs, ParamSpecKwargs
-from typing import TypeGuard, TypeIs, NoDefault
+from typing import TypeForm, TypeGuard, TypeIs, NoDefault
 import abc
 import textwrap
 import typing
 import weakref
-import warnings
 import types
 
 from test.support import (
-    captured_stderr, cpython_only, infinite_recursion, requires_docstrings, import_helper, run_code,
-    EqualToForwardRef,
-    exceeds_recursion_limit, run_with_limited_c_stack,
-    skip_wasi_stack_overflow, skip_emscripten_stack_overflow,
+    captured_stderr, cpython_only, requires_docstrings, import_helper, run_code,
+    subTests, EqualToForwardRef,
+    exceeds_recursion_limit, skip_if_huge_c_stack, skip_wasi_stack_overflow,
+    skip_emscripten_stack_overflow,
 )
 from test.typinganndata import (
     ann_module695, mod_generics_cache, _typed_dict_helper,
@@ -784,7 +784,7 @@ def test_typevartuple_none(self):
         self.assertIs(U_None.__default__, None)
         self.assertIs(U_None.has_default(), True)
 
-        class X[**Ts]: ...
+        class X[*Ts]: ...
         Ts, = X.__type_params__
         self.assertIs(Ts.__default__, NoDefault)
         self.assertIs(Ts.has_default(), False)
@@ -1293,6 +1293,62 @@ def test_cannot_call_instance(self):
         with self.assertRaises(TypeError):
             Ts()
 
+    def test_default_variance(self):
+        Ts = TypeVarTuple('Ts')
+        self.assertIs(Ts.__covariant__, False)
+        self.assertIs(Ts.__contravariant__, False)
+        self.assertIs(Ts.__infer_variance__, False)
+        self.assertIsNone(Ts.__bound__)
+
+    def test_covariant(self):
+        Ts_co = TypeVarTuple('Ts_co', covariant=True)
+        self.assertIs(Ts_co.__covariant__, True)
+        self.assertIs(Ts_co.__contravariant__, False)
+        self.assertIs(Ts_co.__infer_variance__, False)
+
+    def test_contravariant(self):
+        Ts_contra = TypeVarTuple('Ts_contra', contravariant=True)
+        self.assertIs(Ts_contra.__covariant__, False)
+        self.assertIs(Ts_contra.__contravariant__, True)
+        self.assertIs(Ts_contra.__infer_variance__, False)
+
+    def test_infer_variance(self):
+        Ts = TypeVarTuple('Ts', infer_variance=True)
+        self.assertIs(Ts.__covariant__, False)
+        self.assertIs(Ts.__contravariant__, False)
+        self.assertIs(Ts.__infer_variance__, True)
+
+    def test_bound(self):
+        Ts_bound = TypeVarTuple('Ts_bound', bound=int)
+        self.assertIs(Ts_bound.__bound__, int)
+        Ts_tuple_bound = TypeVarTuple('Ts_tuple_bound', bound=(int, str))
+        self.assertEqual(Ts_tuple_bound.__bound__, (int, str))
+        obj = object()
+        Ts_object = TypeVarTuple('Ts_object', bound=obj)
+        self.assertIs(Ts_object.__bound__, obj)
+        Ts_no_bound = TypeVarTuple('Ts_no_bound')
+        self.assertIsNone(Ts_no_bound.__bound__)
+
+    def test_no_bivariant(self):
+        with self.assertRaises(ValueError):
+            TypeVarTuple('Ts', covariant=True, contravariant=True)
+
+    def test_cannot_combine_explicit_and_infer(self):
+        with self.assertRaises(ValueError):
+            TypeVarTuple('Ts', covariant=True, infer_variance=True)
+        with self.assertRaises(ValueError):
+            TypeVarTuple('Ts', contravariant=True, infer_variance=True)
+
+    def test_repr_with_variance(self):
+        Ts = TypeVarTuple('Ts')
+        self.assertEqual(repr(Ts), '~Ts')
+        Ts_co = TypeVarTuple('Ts_co', covariant=True)
+        self.assertEqual(repr(Ts_co), '+Ts_co')
+        Ts_contra = TypeVarTuple('Ts_contra', contravariant=True)
+        self.assertEqual(repr(Ts_contra), '-Ts_contra')
+        Ts_infer = TypeVarTuple('Ts_infer', infer_variance=True)
+        self.assertEqual(repr(Ts_infer), 'Ts_infer')
+
     def test_unpacked_typevartuple_is_equal_to_itself(self):
         Ts = TypeVarTuple('Ts')
         self.assertEqual((*Ts,)[0], (*Ts,)[0])
@@ -1432,16 +1488,16 @@ def test_repr_is_correct(self):
         class G1(Generic[*Ts]): pass
         class G2(Generic[Unpack[Ts]]): pass
 
-        self.assertEqual(repr(Ts), 'Ts')
+        self.assertEqual(repr(Ts), '~Ts')
 
-        self.assertEqual(repr((*Ts,)[0]), 'typing.Unpack[Ts]')
-        self.assertEqual(repr(Unpack[Ts]), 'typing.Unpack[Ts]')
+        self.assertEqual(repr((*Ts,)[0]), 'typing.Unpack[~Ts]')
+        self.assertEqual(repr(Unpack[Ts]), 'typing.Unpack[~Ts]')
 
-        self.assertEqual(repr(tuple[*Ts]), 'tuple[typing.Unpack[Ts]]')
-        self.assertEqual(repr(Tuple[Unpack[Ts]]), 'typing.Tuple[typing.Unpack[Ts]]')
+        self.assertEqual(repr(tuple[*Ts]), 'tuple[typing.Unpack[~Ts]]')
+        self.assertEqual(repr(Tuple[Unpack[Ts]]), 'typing.Tuple[typing.Unpack[~Ts]]')
 
-        self.assertEqual(repr(*tuple[*Ts]), '*tuple[typing.Unpack[Ts]]')
-        self.assertEqual(repr(Unpack[Tuple[Unpack[Ts]]]), 'typing.Unpack[typing.Tuple[typing.Unpack[Ts]]]')
+        self.assertEqual(repr(*tuple[*Ts]), '*tuple[typing.Unpack[~Ts]]')
+        self.assertEqual(repr(Unpack[Tuple[Unpack[Ts]]]), 'typing.Unpack[typing.Tuple[typing.Unpack[~Ts]]]')
 
     def test_variadic_class_repr_is_correct(self):
         Ts = TypeVarTuple('Ts')
@@ -1480,61 +1536,61 @@ def test_variadic_class_alias_repr_is_correct(self):
         class A(Generic[Unpack[Ts]]): pass
 
         B = A[*Ts]
-        self.assertEndsWith(repr(B), 'A[typing.Unpack[Ts]]')
+        self.assertEndsWith(repr(B), 'A[typing.Unpack[~Ts]]')
         self.assertEndsWith(repr(B[()]), 'A[()]')
         self.assertEndsWith(repr(B[float]), 'A[float]')
         self.assertEndsWith(repr(B[float, str]), 'A[float, str]')
 
         C = A[Unpack[Ts]]
-        self.assertEndsWith(repr(C), 'A[typing.Unpack[Ts]]')
+        self.assertEndsWith(repr(C), 'A[typing.Unpack[~Ts]]')
         self.assertEndsWith(repr(C[()]), 'A[()]')
         self.assertEndsWith(repr(C[float]), 'A[float]')
         self.assertEndsWith(repr(C[float, str]), 'A[float, str]')
 
         D = A[*Ts, int]
-        self.assertEndsWith(repr(D), 'A[typing.Unpack[Ts], int]')
+        self.assertEndsWith(repr(D), 'A[typing.Unpack[~Ts], int]')
         self.assertEndsWith(repr(D[()]), 'A[int]')
         self.assertEndsWith(repr(D[float]), 'A[float, int]')
         self.assertEndsWith(repr(D[float, str]), 'A[float, str, int]')
 
         E = A[Unpack[Ts], int]
-        self.assertEndsWith(repr(E), 'A[typing.Unpack[Ts], int]')
+        self.assertEndsWith(repr(E), 'A[typing.Unpack[~Ts], int]')
         self.assertEndsWith(repr(E[()]), 'A[int]')
         self.assertEndsWith(repr(E[float]), 'A[float, int]')
         self.assertEndsWith(repr(E[float, str]), 'A[float, str, int]')
 
         F = A[int, *Ts]
-        self.assertEndsWith(repr(F), 'A[int, typing.Unpack[Ts]]')
+        self.assertEndsWith(repr(F), 'A[int, typing.Unpack[~Ts]]')
         self.assertEndsWith(repr(F[()]), 'A[int]')
         self.assertEndsWith(repr(F[float]), 'A[int, float]')
         self.assertEndsWith(repr(F[float, str]), 'A[int, float, str]')
 
         G = A[int, Unpack[Ts]]
-        self.assertEndsWith(repr(G), 'A[int, typing.Unpack[Ts]]')
+        self.assertEndsWith(repr(G), 'A[int, typing.Unpack[~Ts]]')
         self.assertEndsWith(repr(G[()]), 'A[int]')
         self.assertEndsWith(repr(G[float]), 'A[int, float]')
         self.assertEndsWith(repr(G[float, str]), 'A[int, float, str]')
 
         H = A[int, *Ts, str]
-        self.assertEndsWith(repr(H), 'A[int, typing.Unpack[Ts], str]')
+        self.assertEndsWith(repr(H), 'A[int, typing.Unpack[~Ts], str]')
         self.assertEndsWith(repr(H[()]), 'A[int, str]')
         self.assertEndsWith(repr(H[float]), 'A[int, float, str]')
         self.assertEndsWith(repr(H[float, str]), 'A[int, float, str, str]')
 
         I = A[int, Unpack[Ts], str]
-        self.assertEndsWith(repr(I), 'A[int, typing.Unpack[Ts], str]')
+        self.assertEndsWith(repr(I), 'A[int, typing.Unpack[~Ts], str]')
         self.assertEndsWith(repr(I[()]), 'A[int, str]')
         self.assertEndsWith(repr(I[float]), 'A[int, float, str]')
         self.assertEndsWith(repr(I[float, str]), 'A[int, float, str, str]')
 
         J = A[*Ts, *tuple[str, ...]]
-        self.assertEndsWith(repr(J), 'A[typing.Unpack[Ts], *tuple[str, ...]]')
+        self.assertEndsWith(repr(J), 'A[typing.Unpack[~Ts], *tuple[str, ...]]')
         self.assertEndsWith(repr(J[()]), 'A[*tuple[str, ...]]')
         self.assertEndsWith(repr(J[float]), 'A[float, *tuple[str, ...]]')
         self.assertEndsWith(repr(J[float, str]), 'A[float, str, *tuple[str, ...]]')
 
         K = A[Unpack[Ts], Unpack[Tuple[str, ...]]]
-        self.assertEndsWith(repr(K), 'A[typing.Unpack[Ts], typing.Unpack[typing.Tuple[str, ...]]]')
+        self.assertEndsWith(repr(K), 'A[typing.Unpack[~Ts], typing.Unpack[typing.Tuple[str, ...]]]')
         self.assertEndsWith(repr(K[()]), 'A[typing.Unpack[typing.Tuple[str, ...]]]')
         self.assertEndsWith(repr(K[float]), 'A[float, typing.Unpack[typing.Tuple[str, ...]]]')
         self.assertEndsWith(repr(K[float, str]), 'A[float, str, typing.Unpack[typing.Tuple[str, ...]]]')
@@ -1555,9 +1611,9 @@ class G(type(Unpack[Ts])): pass
         with self.assertRaisesRegex(TypeError,
                                     r'Cannot subclass typing\.Unpack'):
             class H(Unpack): pass
-        with self.assertRaisesRegex(TypeError, r'Cannot subclass typing.Unpack\[Ts\]'):
+        with self.assertRaisesRegex(TypeError, r'Cannot subclass typing.Unpack\[~Ts\]'):
             class I(*Ts): pass
-        with self.assertRaisesRegex(TypeError, r'Cannot subclass typing.Unpack\[Ts\]'):
+        with self.assertRaisesRegex(TypeError, r'Cannot subclass typing.Unpack\[~Ts\]'):
             class J(Unpack[Ts]): pass
 
     def test_variadic_class_args_are_correct(self):
@@ -1621,7 +1677,10 @@ def func1(*args: *Ts): pass
         self.assertEqual(gth(func1), {'args': Unpack[Ts]})
 
         def func2(*args: *tuple[int, str]): pass
-        self.assertEqual(gth(func2), {'args': Unpack[tuple[int, str]]})
+        hint = gth(func2)['args']
+        self.assertIsInstance(hint, types.GenericAlias)
+        self.assertEqual(hint.__args__[0], int)
+        self.assertIs(hint.__unpacked__, True)
 
         class CustomVariadic(Generic[*Ts]): pass
 
@@ -1636,7 +1695,10 @@ def func1(*args: '*Ts'): pass
                         {'args': Unpack[Ts]})
 
         def func2(*args: '*tuple[int, str]'): pass
-        self.assertEqual(gth(func2), {'args': Unpack[tuple[int, str]]})
+        hint = gth(func2)['args']
+        self.assertIsInstance(hint, types.GenericAlias)
+        self.assertEqual(hint.__args__[0], int)
+        self.assertIs(hint.__unpacked__, True)
 
         class CustomVariadic(Generic[*Ts]): pass
 
@@ -3890,8 +3952,8 @@ def meth(self): pass
         self.assertIsNot(get_protocol_members(PR), P.__protocol_attrs__)
 
         acceptable_extra_attrs = {
-            '_is_protocol', '_is_runtime_protocol', '__parameters__',
-            '__init__', '__annotations__', '__subclasshook__', '__annotate__',
+            '_is_protocol', '_is_runtime_protocol', '__typing_is_deprecated_inherited_runtime_protocol__',
+            '__parameters__', '__init__', '__annotations__', '__subclasshook__', '__annotate__',
             '__annotations_cache__', '__annotate_func__',
         }
         self.assertLessEqual(vars(NonP).keys(), vars(C).keys() | acceptable_extra_attrs)
@@ -3983,6 +4045,7 @@ class C: pass
 
     def test_defining_generic_protocols(self):
         T = TypeVar('T')
+        T2 = TypeVar('T2')
         S = TypeVar('S')
 
         @runtime_checkable
@@ -3992,17 +4055,26 @@ def meth(self): pass
         class P(PR[int, T], Protocol[T]):
             y = 1
 
+        self.assertEqual(P.__parameters__, (T,))
+
         with self.assertRaises(TypeError):
             PR[int]
         with self.assertRaises(TypeError):
             P[int, str]
+        with self.assertRaisesRegex(
+            TypeError,
+            re.escape('Some type variables (~S) are not listed in Protocol[~T, ~T2]'),
+        ):
+            class ExtraTypeVars(P[S], Protocol[T, T2]): ...
 
         class C(PR[int, T]): pass
 
+        self.assertEqual(C.__parameters__, (T,))
         self.assertIsInstance(C[str](), C)
 
     def test_defining_generic_protocols_old_style(self):
         T = TypeVar('T')
+        T2 = TypeVar('T2')
         S = TypeVar('S')
 
         @runtime_checkable
@@ -4021,9 +4093,19 @@ class P(PR[int, str], Protocol):
         class P1(Protocol, Generic[T]):
             def bar(self, x: T) -> str: ...
 
+        self.assertEqual(P1.__parameters__, (T,))
+
         class P2(Generic[T], Protocol):
             def bar(self, x: T) -> str: ...
 
+        self.assertEqual(P2.__parameters__, (T,))
+
+        msg = re.escape('Some type variables (~S) are not listed in Protocol[~T, ~T2]')
+        with self.assertRaisesRegex(TypeError, msg):
+            class ExtraTypeVars(P1[S], Protocol[T, T2]): ...
+        with self.assertRaisesRegex(TypeError, msg):
+            class ExtraTypeVars(P2[S], Protocol[T, T2]): ...
+
         @runtime_checkable
         class PSub(P1[str], Protocol):
             x = 1
@@ -4036,6 +4118,28 @@ def bar(self, x: str) -> str:
 
         self.assertIsInstance(Test(), PSub)
 
+    def test_protocol_parameter_order(self):
+        # https://github.com/python/cpython/issues/137191
+        T1 = TypeVar("T1")
+        T2 = TypeVar("T2", default=object)
+
+        class A(Protocol[T1]): ...
+
+        class B0(A[T2], Generic[T1, T2]): ...
+        self.assertEqual(B0.__parameters__, (T1, T2))
+
+        class B1(A[T2], Protocol, Generic[T1, T2]): ...
+        self.assertEqual(B1.__parameters__, (T1, T2))
+
+        class B2(A[T2], Protocol[T1, T2]): ...
+        self.assertEqual(B2.__parameters__, (T1, T2))
+
+        class B3[T1, T2](A[T2], Protocol):
+            @staticmethod
+            def get_typeparams():
+                return (T1, T2)
+        self.assertEqual(B3.__parameters__, B3.get_typeparams())
+
     def test_pep695_generic_protocol_callable_members(self):
         @runtime_checkable
         class Foo[T](Protocol):
@@ -4421,6 +4525,70 @@ class P(Protocol):
         with self.assertRaisesRegex(TypeError, "@runtime_checkable"):
             isinstance(1, P)
 
+    @subTests(['check_obj', 'check_func'], ([42, isinstance], [frozenset, issubclass]))
+    def test_inherited_runtime_protocol_deprecated(self, check_obj, check_func):
+        """See GH-132604."""
+
+        class BareProto(Protocol):
+            """I am not runtime-checkable."""
+
+        @runtime_checkable
+        class RCProto1(Protocol):
+            """I am runtime-checkable."""
+
+        class InheritedRCProto1(RCProto1, Protocol):
+            """I am accidentally runtime-checkable (by inheritance)."""
+
+        @runtime_checkable
+        class RCProto2(InheritedRCProto1, Protocol):
+            """Explicit RC -> inherited RC -> explicit RC."""
+            def spam(self): ...
+
+        @runtime_checkable
+        class RCProto3(BareProto, Protocol):
+            """Not RC -> explicit RC."""
+
+        class InheritedRCProto2(RCProto3, Protocol):
+            """Not RC -> explicit RC -> inherited RC."""
+            def eggs(self): ...
+
+        class InheritedRCProto3(RCProto2, Protocol):
+            """Explicit RC -> inherited RC -> explicit RC -> inherited RC."""
+
+        class Concrete1(BareProto):
+            pass
+
+        class Concrete2(InheritedRCProto2):
+            pass
+
+        class Concrete3(InheritedRCProto3):
+            pass
+
+        depr_message_re = (
+            r"<class .+\.InheritedRCProto\d'> isn't explicitly decorated "
+            r"with @runtime_checkable but it is used in issubclass\(\) or "
+            r"isinstance\(\). Instance and class checks can only be used with "
+            r"@runtime_checkable protocols. This will raise a TypeError in Python 3.20."
+        )
+
+        for inherited_runtime_proto in InheritedRCProto1, InheritedRCProto2, InheritedRCProto3:
+            with self.assertWarnsRegex(DeprecationWarning, depr_message_re):
+                check_func(check_obj, inherited_runtime_proto)
+
+        # Don't warn for explicitly checkable protocols and concrete implementations.
+        with warnings.catch_warnings():
+            warnings.simplefilter("error", DeprecationWarning)
+
+            for checkable in RCProto1, RCProto2, RCProto3, Concrete1, Concrete2, Concrete3:
+                check_func(check_obj, checkable)
+
+        # Don't warn for uncheckable protocols.
+        with warnings.catch_warnings():
+            warnings.simplefilter("error", DeprecationWarning)
+
+            with self.assertRaises(TypeError):  # Self-test. Protocol below can't be runtime-checkable.
+                check_func(check_obj, BareProto)
+
     def test_super_call_init(self):
         class P(Protocol):
             x: int
@@ -4932,7 +5100,7 @@ class MM2(collections.abc.MutableMapping, MutableMapping[str, str]):
         self.assertEqual(MM2.__bases__, (collections.abc.MutableMapping, Generic))
 
     @cpython_only
-    @run_with_limited_c_stack()
+    @skip_if_huge_c_stack()
     @skip_wasi_stack_overflow()
     @skip_emscripten_stack_overflow()
     def test_parameters_deep_recursion(self):
@@ -5506,13 +5674,13 @@ class TsP(Generic[*Ts, P]):
             MyCallable[[int], bool]:                  "MyCallable[[int], bool]",
             MyCallable[[int, str], bool]:             "MyCallable[[int, str], bool]",
             MyCallable[[int, list[int]], bool]:       "MyCallable[[int, list[int]], bool]",
-            MyCallable[Concatenate[*Ts, P], T]:       "MyCallable[typing.Concatenate[typing.Unpack[Ts], ~P], ~T]",
+            MyCallable[Concatenate[*Ts, P], T]:       "MyCallable[typing.Concatenate[typing.Unpack[~Ts], ~P], ~T]",
 
             DoubleSpec[P2, P, T]:                     "DoubleSpec[~P2, ~P, ~T]",
             DoubleSpec[[int], [str], bool]:           "DoubleSpec[[int], [str], bool]",
             DoubleSpec[[int, int], [str, str], bool]: "DoubleSpec[[int, int], [str, str], bool]",
 
-            TsP[*Ts, P]:                              "TsP[typing.Unpack[Ts], ~P]",
+            TsP[*Ts, P]:                              "TsP[typing.Unpack[~Ts], ~P]",
             TsP[int, str, list[int], []]:             "TsP[int, str, list[int], []]",
             TsP[int, [str, list[int]]]:               "TsP[int, [str, list[int]]]",
 
@@ -5821,6 +5989,7 @@ def test_subclass_special_form(self):
             Final[int],
             Literal[1, 2],
             Concatenate[int, ParamSpec("P")],
+            TypeForm[int],
             TypeGuard[int],
             TypeIs[range],
         ):
@@ -5887,6 +6056,22 @@ class A:
                     with self.assertRaises(TypeError):
                         a[int]
 
+    def test_parameter_added_after_parameters_cached(self):
+        # gh-155752: GenericAlias parameters are cached before substitution, so
+        # an argument can gain __typing_subst__ after the tuple is calculated.
+        class Parameter:
+            pass
+
+        first = Parameter()
+        first.__typing_subst__ = lambda value: value
+        late = Parameter()
+        alias = types.GenericAlias(dict, (first, late))
+        self.assertEqual(alias.__parameters__, (first,))
+        late.__typing_subst__ = lambda value: value
+
+        with self.assertRaisesRegex(TypeError, "not found in __parameters__"):
+            alias[0]
+
     def test_return_non_tuple_while_unpacking(self):
         # GH-138497: GenericAlias objects didn't ensure that __typing_subst__ actually
         # returned a tuple
@@ -6380,62 +6565,8 @@ class F:
         for clazz in [C, D, E, F]:
             self.assertEqual(get_type_hints(clazz), expected_result)
 
-    def test_meta_no_type_check(self):
-        depr_msg = (
-            "'typing.no_type_check_decorator' is deprecated "
-            "and slated for removal in Python 3.15"
-        )
-        with self.assertWarnsRegex(DeprecationWarning, depr_msg):
-            @no_type_check_decorator
-            def magic_decorator(func):
-                return func
-
-        self.assertEqual(magic_decorator.__name__, 'magic_decorator')
-
-        @magic_decorator
-        def foo(a: 'whatevers') -> {}:
-            pass
-
-        @magic_decorator
-        class C:
-            def foo(a: 'whatevers') -> {}:
-                pass
-
-        self.assertEqual(foo.__name__, 'foo')
-        th = get_type_hints(foo)
-        self.assertEqual(th, {})
-        cth = get_type_hints(C.foo)
-        self.assertEqual(cth, {})
-        ith = get_type_hints(C().foo)
-        self.assertEqual(ith, {})
-
 
 class InternalsTests(BaseTestCase):
-    def test_deprecation_for_no_type_params_passed_to__evaluate(self):
-        with self.assertWarnsRegex(
-            DeprecationWarning,
-            (
-                "Failing to pass a value to the 'type_params' parameter "
-                "of 'typing._eval_type' is deprecated"
-            )
-        ) as cm:
-            self.assertEqual(typing._eval_type(list["int"], globals(), {}), list[int])
-
-        self.assertEqual(cm.filename, __file__)
-
-        f = ForwardRef("int")
-
-        with self.assertWarnsRegex(
-            DeprecationWarning,
-            (
-                "Failing to pass a value to the 'type_params' parameter "
-                "of 'typing.ForwardRef._evaluate' is deprecated"
-            )
-        ) as cm:
-            self.assertIs(f._evaluate(globals(), {}, recursive_guard=frozenset()), int)
-
-        self.assertEqual(cm.filename, __file__)
-
     def test_collect_parameters(self):
         typing = import_helper.import_fresh_module("typing")
         with self.assertWarnsRegex(
@@ -7236,6 +7367,24 @@ def add_right(self, node: 'Node[T]' = None):
         right_hints = get_type_hints(t.add_right, globals(), locals())
         self.assertEqual(right_hints['node'], Node[T])
 
+    def test_get_type_hints_preserve_generic_alias_subclasses(self):
+        # https://github.com/python/cpython/issues/130870
+        # A real world example of this is `collections.abc.Callable`. When parameterized,
+        # the result is a subclass of `types.GenericAlias`.
+        class MyAlias(types.GenericAlias):
+            pass
+
+        class MyClass:
+            def __class_getitem__(cls, args):
+                return MyAlias(cls, args)
+
+        # Using a forward reference is important, otherwise it works as expected.
+        # `y` tests that the `GenericAlias` subclass is preserved when stripping `Annotated`.
+        def func(x: MyClass['int'], y: MyClass[Annotated[int, ...]]): ...
+
+        assert isinstance(get_type_hints(func)['x'], MyAlias)
+        assert isinstance(get_type_hints(func)['y'], MyAlias)
+
     def test_stringified_typeddict(self):
         ns = run_code(
             """
@@ -7249,6 +7398,13 @@ class TD[UniqueT](TypedDict):
         self.assertEqual(TD.__annotations__, {'a': EqualToForwardRef('UniqueT', owner=TD, module=TD.__module__)})
         self.assertEqual(get_type_hints(TD), {'a': TD.__type_params__[0]})
 
+    def test_get_type_hints_order(self):
+        """Ensure that the order of function annotations matches the order they're defined"""
+        def f(positional: int, /, normal: str, *args: bytes, kwarg: list, **kwargs: bool) -> tuple:
+            pass
+
+        self.assertEqual(list(gth(f)), ["positional", "normal", "args", "kwarg", "kwargs", "return"])
+
 
 class GetUtilitiesTestCase(TestCase):
     def test_get_origin(self):
@@ -7339,6 +7495,7 @@ class C(Generic[T]): pass
         self.assertEqual(get_args(Required[int]), (int,))
         self.assertEqual(get_args(NotRequired[int]), (int,))
         self.assertEqual(get_args(TypeAlias), ())
+        self.assertEqual(get_args(TypeForm[int]), (int,))
         self.assertEqual(get_args(TypeGuard[int]), (int,))
         self.assertEqual(get_args(TypeIs[range]), (range,))
         Ts = TypeVarTuple('Ts')
@@ -7576,14 +7733,23 @@ def test_mutablesequence(self):
         self.assertNotIsInstance((), typing.MutableSequence)
 
     def test_bytestring(self):
+        previous_typing_module = sys.modules.pop("typing", None)
+        self.addCleanup(sys.modules.__setitem__, "typing", previous_typing_module)
+
+        with self.assertWarns(DeprecationWarning):
+            from typing import ByteString
         with self.assertWarns(DeprecationWarning):
-            self.assertIsInstance(b'', typing.ByteString)
+            self.assertIsInstance(b'', ByteString)
         with self.assertWarns(DeprecationWarning):
-            self.assertIsInstance(bytearray(b''), typing.ByteString)
+            self.assertIsInstance(bytearray(b''), ByteString)
         with self.assertWarns(DeprecationWarning):
-            class Foo(typing.ByteString): ...
+            self.assertIsSubclass(bytes, ByteString)
         with self.assertWarns(DeprecationWarning):
-            class Bar(typing.ByteString, typing.Awaitable): ...
+            self.assertIsSubclass(bytearray, ByteString)
+        with self.assertWarns(DeprecationWarning):
+            class Foo(ByteString): ...
+        with self.assertWarns(DeprecationWarning):
+            class Bar(ByteString, typing.Awaitable): ...
 
     def test_list(self):
         self.assertIsSubclass(list, typing.List)
@@ -8326,78 +8492,13 @@ class Group(NamedTuple):
         self.assertIs(type(a), Group)
         self.assertEqual(a, (1, [2]))
 
-    def test_namedtuple_keyword_usage(self):
-        with self.assertWarnsRegex(
-            DeprecationWarning,
-            "Creating NamedTuple classes using keyword arguments is deprecated"
-        ):
-            LocalEmployee = NamedTuple("LocalEmployee", name=str, age=int)
-
-        nick = LocalEmployee('Nick', 25)
-        self.assertIsInstance(nick, tuple)
-        self.assertEqual(nick.name, 'Nick')
-        self.assertEqual(LocalEmployee.__name__, 'LocalEmployee')
-        self.assertEqual(LocalEmployee._fields, ('name', 'age'))
-        self.assertEqual(LocalEmployee.__annotations__, dict(name=str, age=int))
-
-        with self.assertRaisesRegex(
-            TypeError,
-            "Either list of fields or keywords can be provided to NamedTuple, not both"
-        ):
-            NamedTuple('Name', [('x', int)], y=str)
-
-        with self.assertRaisesRegex(
-            TypeError,
-            "Either list of fields or keywords can be provided to NamedTuple, not both"
-        ):
-            NamedTuple('Name', [], y=str)
-
-        with self.assertRaisesRegex(
-            TypeError,
-            (
-                r"Cannot pass `None` as the 'fields' parameter "
-                r"and also specify fields using keyword arguments"
-            )
-        ):
-            NamedTuple('Name', None, x=int)
-
-    def test_namedtuple_special_keyword_names(self):
-        with self.assertWarnsRegex(
-            DeprecationWarning,
-            "Creating NamedTuple classes using keyword arguments is deprecated"
-        ):
-            NT = NamedTuple("NT", cls=type, self=object, typename=str, fields=list)
-
-        self.assertEqual(NT.__name__, 'NT')
-        self.assertEqual(NT._fields, ('cls', 'self', 'typename', 'fields'))
-        a = NT(cls=str, self=42, typename='foo', fields=[('bar', tuple)])
-        self.assertEqual(a.cls, str)
-        self.assertEqual(a.self, 42)
-        self.assertEqual(a.typename, 'foo')
-        self.assertEqual(a.fields, [('bar', tuple)])
-
     def test_empty_namedtuple(self):
-        expected_warning = re.escape(
-            "Failing to pass a value for the 'fields' parameter is deprecated "
-            "and will be disallowed in Python 3.15. "
-            "To create a NamedTuple class with 0 fields "
-            "using the functional syntax, "
-            "pass an empty list, e.g. `NT1 = NamedTuple('NT1', [])`."
-        )
-        with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
-            NT1 = NamedTuple('NT1')
-
-        expected_warning = re.escape(
-            "Passing `None` as the 'fields' parameter is deprecated "
-            "and will be disallowed in Python 3.15. "
-            "To create a NamedTuple class with 0 fields "
-            "using the functional syntax, "
-            "pass an empty list, e.g. `NT2 = NamedTuple('NT2', [])`."
-        )
-        with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
-            NT2 = NamedTuple('NT2', None)
+        with self.assertRaisesRegex(TypeError, "missing.*required.*argument"):
+            BAD = NamedTuple('BAD')
 
-        NT3 = NamedTuple('NT2', [])
+        NT1 = NamedTuple('NT1', {})
+        NT2 = NamedTuple('NT2', ())
+        NT3 = NamedTuple('NT3', [])
 
         class CNT(NamedTuple):
             pass  # empty body
@@ -8412,16 +8513,18 @@ class CNT(NamedTuple):
     def test_namedtuple_errors(self):
         with self.assertRaises(TypeError):
             NamedTuple.__new__()
+        with self.assertRaisesRegex(TypeError, "object is not iterable"):
+            NamedTuple('Name', None)
 
         with self.assertRaisesRegex(
             TypeError,
-            "missing 1 required positional argument"
+            "missing 2 required positional arguments"
         ):
             NamedTuple()
 
         with self.assertRaisesRegex(
             TypeError,
-            "takes from 1 to 2 positional arguments but 3 were given"
+            "takes 2 positional arguments but 3 were given"
         ):
             NamedTuple('Emp', [('name', str)], None)
 
@@ -8433,10 +8536,22 @@ def test_namedtuple_errors(self):
 
         with self.assertRaisesRegex(
             TypeError,
-            "missing 1 required positional argument: 'typename'"
+            "got some positional-only arguments passed as keyword arguments"
         ):
             NamedTuple(typename='Emp', name=str, id=int)
 
+        with self.assertRaisesRegex(
+            TypeError,
+            "got an unexpected keyword argument"
+        ):
+            NamedTuple('Name', [('x', int)], y=str)
+
+        with self.assertRaisesRegex(
+            TypeError,
+            "got an unexpected keyword argument"
+        ):
+            NamedTuple('Name', [], y=str)
+
     def test_copy_and_pickle(self):
         global Emp  # pickle wants to reference the class by name
         Emp = NamedTuple('Emp', [('name', str), ('cool', int)])
@@ -8567,6 +8682,15 @@ class ThisWontWorkEither(NamedTuple):
                 def name(self):
                     return __class__.__name__
 
+    def test_named_tuple_non_sequence_input(self):
+        field_names = ["x", "y"]
+        field_values = [int, int]
+        Point = NamedTuple("Point", zip(field_names, field_values))
+        p = Point(1, 2)
+        self.assertEqual(p.x, 1)
+        self.assertEqual(p.y, 2)
+        self.assertEqual(repr(p),"Point(x=1, y=2)")
+
 
 class TypedDictTests(BaseTestCase):
     def test_basics_functional_syntax(self):
@@ -8937,6 +9061,32 @@ class ChildWithInlineAndOptional(Untotal, Inline):
                     class Wrong(*bases):
                         pass
 
+    def test_closed_values(self):
+        class Implicit(TypedDict): ...
+        class ExplicitTrue(TypedDict, closed=True): ...
+        class ExplicitFalse(TypedDict, closed=False): ...
+
+        self.assertIsNone(Implicit.__closed__)
+        self.assertIs(ExplicitTrue.__closed__, True)
+        self.assertIs(ExplicitFalse.__closed__, False)
+
+    def test_extra_items_class_arg(self):
+        class TD(TypedDict, extra_items=int):
+            a: str
+
+        self.assertIs(TD.__extra_items__, int)
+        self.assertEqual(TD.__annotations__, {'a': str})
+        self.assertEqual(TD.__required_keys__, frozenset({'a'}))
+        self.assertEqual(TD.__optional_keys__, frozenset())
+
+        class NoExtra(TypedDict):
+            a: str
+
+        self.assertIs(NoExtra.__extra_items__, NoExtraItems)
+        self.assertEqual(NoExtra.__annotations__, {'a': str})
+        self.assertEqual(NoExtra.__required_keys__, frozenset({'a'}))
+        self.assertEqual(NoExtra.__optional_keys__, frozenset())
+
     def test_is_typeddict(self):
         self.assertIs(is_typeddict(Point2D), True)
         self.assertIs(is_typeddict(Union[str, int]), False)
@@ -9180,39 +9330,27 @@ class MultipleGenericBases(GenericParent[int], GenericParent[float]):
         self.assertEqual(CallTypedDict.__orig_bases__, (TypedDict,))
 
     def test_zero_fields_typeddicts(self):
-        T1 = TypedDict("T1", {})
+        T1a = TypedDict("T1a", {})
+        T1b = TypedDict("T1b", [])
+        T1c = TypedDict("T1c", ())
         class T2(TypedDict): pass
         class T3[tvar](TypedDict): pass
         S = TypeVar("S")
         class T4(TypedDict, Generic[S]): pass
 
-        expected_warning = re.escape(
-            "Failing to pass a value for the 'fields' parameter is deprecated "
-            "and will be disallowed in Python 3.15. "
-            "To create a TypedDict class with 0 fields "
-            "using the functional syntax, "
-            "pass an empty dictionary, e.g. `T5 = TypedDict('T5', {})`."
-        )
-        with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
-            T5 = TypedDict('T5')
-
-        expected_warning = re.escape(
-            "Passing `None` as the 'fields' parameter is deprecated "
-            "and will be disallowed in Python 3.15. "
-            "To create a TypedDict class with 0 fields "
-            "using the functional syntax, "
-            "pass an empty dictionary, e.g. `T6 = TypedDict('T6', {})`."
-        )
-        with self.assertWarnsRegex(DeprecationWarning, fr"^{expected_warning}$"):
-            T6 = TypedDict('T6', None)
-
-        for klass in T1, T2, T3, T4, T5, T6:
+        for klass in T1a, T1b, T1c, T2, T3, T4:
             with self.subTest(klass=klass.__name__):
                 self.assertEqual(klass.__annotations__, {})
                 self.assertEqual(klass.__required_keys__, set())
                 self.assertEqual(klass.__optional_keys__, set())
                 self.assertIsInstance(klass(), dict)
 
+    def test_errors(self):
+        with self.assertRaisesRegex(TypeError, "missing 1 required.*argument"):
+            TypedDict('TD')
+        with self.assertRaisesRegex(TypeError, "object is not iterable"):
+            TypedDict('TD', None)
+
     def test_readonly_inheritance(self):
         class Base1(TypedDict):
             a: ReadOnly[int]
@@ -9276,6 +9414,71 @@ class AllTheThings(TypedDict):
             },
         )
 
+    def test_closed_inheritance(self):
+        class Base(TypedDict, extra_items=ReadOnly[Union[str, None]]):
+            a: int
+
+        self.assertEqual(Base.__required_keys__, frozenset({"a"}))
+        self.assertEqual(Base.__optional_keys__, frozenset({}))
+        self.assertEqual(Base.__readonly_keys__, frozenset({}))
+        self.assertEqual(Base.__mutable_keys__, frozenset({"a"}))
+        self.assertEqual(Base.__annotations__, {"a": int})
+        self.assertEqual(Base.__extra_items__, ReadOnly[Union[str, None]])
+        self.assertIsNone(Base.__closed__)
+
+        class Child(Base, extra_items=int):
+            a: str
+
+        self.assertEqual(Child.__required_keys__, frozenset({'a'}))
+        self.assertEqual(Child.__optional_keys__, frozenset({}))
+        self.assertEqual(Child.__readonly_keys__, frozenset({}))
+        self.assertEqual(Child.__mutable_keys__, frozenset({'a'}))
+        self.assertEqual(Child.__annotations__, {"a": str})
+        self.assertIs(Child.__extra_items__, int)
+        self.assertIsNone(Child.__closed__)
+
+        class GrandChild(Child, closed=True):
+            a: float
+
+        self.assertEqual(GrandChild.__required_keys__, frozenset({'a'}))
+        self.assertEqual(GrandChild.__optional_keys__, frozenset({}))
+        self.assertEqual(GrandChild.__readonly_keys__, frozenset({}))
+        self.assertEqual(GrandChild.__mutable_keys__, frozenset({'a'}))
+        self.assertEqual(GrandChild.__annotations__, {"a": float})
+        self.assertIs(GrandChild.__extra_items__, NoExtraItems)
+        self.assertIs(GrandChild.__closed__, True)
+
+        class GrandGrandChild(GrandChild):
+            ...
+        self.assertEqual(GrandGrandChild.__required_keys__, frozenset({'a'}))
+        self.assertEqual(GrandGrandChild.__optional_keys__, frozenset({}))
+        self.assertEqual(GrandGrandChild.__readonly_keys__, frozenset({}))
+        self.assertEqual(GrandGrandChild.__mutable_keys__, frozenset({'a'}))
+        self.assertEqual(GrandGrandChild.__annotations__, {"a": float})
+        self.assertIs(GrandGrandChild.__extra_items__, NoExtraItems)
+        self.assertIsNone(GrandGrandChild.__closed__)
+
+    def test_implicit_extra_items(self):
+        class Base(TypedDict):
+            a: int
+
+        self.assertIs(Base.__extra_items__, NoExtraItems)
+        self.assertIsNone(Base.__closed__)
+
+        class ChildA(Base, closed=True):
+            ...
+
+        self.assertEqual(ChildA.__extra_items__, NoExtraItems)
+        self.assertIs(ChildA.__closed__, True)
+
+    def test_cannot_combine_closed_and_extra_items(self):
+        with self.assertRaisesRegex(
+            TypeError,
+            "Cannot combine closed=True and extra_items"
+        ):
+            class TD(TypedDict, closed=True, extra_items=range):
+                x: str
+
     def test_annotations(self):
         # _type_check is applied
         with self.assertRaisesRegex(TypeError, "Plain typing.Final is not valid as type argument"):
@@ -9505,6 +9708,12 @@ class A(typing.Match):
             class B(typing.Pattern):
                 pass
 
+    def test_typed_dict_signature(self):
+        self.assertListEqual(
+            list(inspect.signature(TypedDict).parameters),
+            ['typename', 'fields', 'total', 'closed', 'extra_items']
+        )
+
 
 class AnnotatedTests(BaseTestCase):
 
@@ -10380,6 +10589,17 @@ def test_paramspec_in_nested_generics(self):
         self.assertEqual(G2[[int, str], float], list[C])
         self.assertEqual(G3[[int, str], float], list[C] | int)
 
+    def test_paramspec_bound(self):
+        P = ParamSpec('P', bound=[int, str])
+        self.assertEqual(P.__bound__, [int, str])
+        P2 = ParamSpec('P2', bound=(int, str))
+        self.assertEqual(P2.__bound__, (int, str))
+        obj = object()
+        P3 = ParamSpec('P3', bound=obj)
+        self.assertIs(P3.__bound__, obj)
+        P4 = ParamSpec('P4')
+        self.assertIs(P4.__bound__, None)
+
     def test_paramspec_gets_copied(self):
         # bpo-46581
         P = ParamSpec('P')
@@ -10587,6 +10807,72 @@ def test_no_isinstance(self):
             issubclass(int, TypeIs)
 
 
+class TypeFormTests(BaseTestCase):
+    def test_basics(self):
+        TypeForm[int]  # OK
+        self.assertEqual(TypeForm[int], TypeForm[int])
+
+        def foo(arg) -> TypeForm[int]: ...
+        self.assertEqual(gth(foo), {'return': TypeForm[int]})
+
+        with self.assertRaises(TypeError):
+            TypeForm[int, str]
+
+    def test_repr(self):
+        self.assertEqual(repr(TypeForm), 'typing.TypeForm')
+        cv = TypeForm[int]
+        self.assertEqual(repr(cv), 'typing.TypeForm[int]')
+        cv = TypeForm[Employee]
+        self.assertEqual(repr(cv), 'typing.TypeForm[%s.Employee]' % __name__)
+        cv = TypeForm[tuple[int]]
+        self.assertEqual(repr(cv), 'typing.TypeForm[tuple[int]]')
+
+    def test_cannot_subclass(self):
+        with self.assertRaisesRegex(TypeError, CANNOT_SUBCLASS_TYPE):
+            class C(type(TypeForm)):
+                pass
+        with self.assertRaisesRegex(TypeError, CANNOT_SUBCLASS_TYPE):
+            class D(type(TypeForm[int])):
+                pass
+        with self.assertRaisesRegex(TypeError,
+                                    r'Cannot subclass typing\.TypeForm'):
+            class E(TypeForm):
+                pass
+        with self.assertRaisesRegex(TypeError,
+                                    r'Cannot subclass typing\.TypeForm\[int\]'):
+            class F(TypeForm[int]):
+                pass
+
+    def test_call(self):
+        objs = [
+            1,
+            "int",
+            int,
+            tuple[int, str],
+            Tuple[int, str],
+        ]
+        for obj in objs:
+            with self.subTest(obj=obj):
+                self.assertIs(TypeForm(obj), obj)
+
+        with self.assertRaises(TypeError):
+            TypeForm()
+        with self.assertRaises(TypeError):
+            TypeForm("too", "many")
+
+    def test_cannot_init_type(self):
+        with self.assertRaises(TypeError):
+            type(TypeForm)()
+        with self.assertRaises(TypeError):
+            type(TypeForm[Optional[int]])()
+
+    def test_no_isinstance(self):
+        with self.assertRaises(TypeError):
+            isinstance(1, TypeForm[int])
+        with self.assertRaises(TypeError):
+            issubclass(int, TypeForm)
+
+
 SpecialAttrsP = typing.ParamSpec('SpecialAttrsP')
 SpecialAttrsT = typing.TypeVar('SpecialAttrsT', int, float, complex)
 
@@ -10594,6 +10880,10 @@ def test_no_isinstance(self):
 class SpecialAttrsTests(BaseTestCase):
 
     def test_special_attrs(self):
+        with warnings.catch_warnings(
+            action='ignore', category=DeprecationWarning
+        ):
+            typing_ByteString = typing.ByteString
         cls_to_check = {
             # ABC classes
             typing.AbstractSet: 'AbstractSet',
@@ -10602,7 +10892,7 @@ def test_special_attrs(self):
             typing.AsyncIterable: 'AsyncIterable',
             typing.AsyncIterator: 'AsyncIterator',
             typing.Awaitable: 'Awaitable',
-            typing.ByteString: 'ByteString',
+            typing_ByteString: 'ByteString',
             typing.Callable: 'Callable',
             typing.ChainMap: 'ChainMap',
             typing.Collection: 'Collection',
@@ -10684,6 +10974,7 @@ def test_special_attrs(self):
             typing.Never: 'Never',
             typing.Optional: 'Optional',
             typing.TypeAlias: 'TypeAlias',
+            typing.TypeForm: 'TypeForm',
             typing.TypeGuard: 'TypeGuard',
             typing.TypeIs: 'TypeIs',
             typing.TypeVar: 'TypeVar',
@@ -10698,6 +10989,7 @@ def test_special_attrs(self):
             typing.Literal[1, 2]: 'Literal',
             typing.Literal[True, 2]: 'Literal',
             typing.Optional[Any]: 'Union',
+            typing.TypeForm[Any]: 'TypeForm',
             typing.TypeGuard[Any]: 'TypeGuard',
             typing.TypeIs[Any]: 'TypeIs',
             typing.Union[Any]: 'Any',
@@ -10780,6 +11072,18 @@ def bar(self):
         self.assertNotIn('__magic__', dir_items)
 
 
+class DisjointBaseTests(BaseTestCase):
+    def test_disjoint_base_unmodified(self):
+        class C: ...
+        self.assertIs(C, disjoint_base(C))
+
+    def test_dunder_disjoint_base(self):
+        @disjoint_base
+        class C: ...
+
+        self.assertIs(C.__disjoint_base__, True)
+
+
 class RevealTypeTests(BaseTestCase):
     def test_reveal_type(self):
         obj = object()
@@ -10959,7 +11263,8 @@ def test_all_exported_names(self):
                 # there's a few types and metaclasses that aren't exported
                 not k.endswith(('Meta', '_contra', '_co')) and
                 not k.upper() == k and
-                # but export all things that have __module__ == 'typing'
+                k not in {"ByteString"} and
+                # but export all other things that have __module__ == 'typing'
                 getattr(v, '__module__', None) == typing.__name__
             )
         }
diff --git a/Lib/test/test_unicode_identifiers.py b/Lib/test/test_unicode_identifiers.py
index 27749a0805c..3680072d643 100644
--- a/Lib/test/test_unicode_identifiers.py
+++ b/Lib/test/test_unicode_identifiers.py
@@ -17,7 +17,6 @@ def test_non_bmp_normalized(self):
         𝔘𝔫𝔦𝔠𝔬𝔡𝔢 = 1
         self.assertIn("Unicode", dir())
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_invalid(self):
         try:
             from test.tokenizedata import badsyntax_3131  # noqa: F401
diff --git a/Lib/test/test_unicodedata.py b/Lib/test/test_unicodedata.py
index aeb1835f6cc..256a010e8fd 100644
--- a/Lib/test/test_unicodedata.py
+++ b/Lib/test/test_unicodedata.py
@@ -107,7 +107,7 @@ def test_method_checksum(self):
 
 class BaseUnicodeFunctionsTest:
 
-    @unittest.skip  # TODO: RUSTPYTHON; AssertionError: '7bda75e48a961a01ab328358980cefc5c0a1666d' != '68cd01e2c680b851c1fcab012efb5635'
+    @unittest.skip("TODO: RUSTPYTHON; AssertionError: '7bda75e48a961a01ab328358980cefc5c0a1666d' != '68cd01e2c680b851c1fcab012efb5635'")
     def test_function_checksum(self):
         db = self.db
         data = []
@@ -199,7 +199,7 @@ def test_no_names_in_pua(self):
             char = chr(i)
             self.assertRaises(ValueError, self.db.name, char)
 
-    @unittest.expectedFailure   # TODO: RUSTPYTHON; AssertionError: KeyError not raised by lookup
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: KeyError not raised by lookup
     def test_lookup_nonexistant(self):
         # just make sure that lookup can fail
         for nonexistent in [
@@ -360,7 +360,7 @@ def test_bidirectional_unassigned(self):
         self.assertEqual(self.db.bidirectional('\U0001FFFE'), '' if self.old else 'BN')
         self.assertEqual(self.db.bidirectional('\U00010D01'), '' if self.old else 'AL')
 
-    @unittest.expectedFailure   # TODO: RUSTPYTHON; AssertionError: '<compat> 03A3 != ''
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError: '<compat> 03A3 != ''
     def test_decomposition(self):
         self.assertEqual(self.db.decomposition('\uFFFE'),'')
         self.assertEqual(self.db.decomposition('\u00bc'), '<fraction> 0031 2044 0034')
@@ -700,7 +700,7 @@ def test_east_asian_width(self):
         # New in 17.0.0
         self.assertEqual(eaw('\U00016FF2'), 'N' if self.old else 'W')
 
-    @unittest.skip  # TODO: RUSTPYTHON; AssertionError: 'N' != 'W' (passed on latest, fails on 3.2)
+    @unittest.skip("TODO: RUSTPYTHON; AssertionError: 'N' != 'W' (passed on latest, fails on 3.2)")
     def test_east_asian_width_unassigned(self):
         eaw = self.db.east_asian_width
         # unassigned
@@ -769,7 +769,7 @@ def parse_cp(s):
         for cp in range(0, sys.maxunicode + 1):
             self.assertEqual(self.db.name(chr(cp), None), names_ref.get(cp))
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'isxidstart'
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'isxidstart'
     def test_isxidstart(self):
         self.assertTrue(self.db.isxidstart('S'))
         self.assertTrue(self.db.isxidstart('\u0AD0'))  # GUJARATI OM
@@ -783,7 +783,7 @@ def test_isxidstart(self):
         self.assertRaises(TypeError, self.db.isxidstart)
         self.assertRaises(TypeError, self.db.isxidstart, 'xx')
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'isxidcontinue'
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'isxidcontinue'
     def test_isxidcontinue(self):
         self.assertTrue(self.db.isxidcontinue('S'))
         self.assertTrue(self.db.isxidcontinue('_'))
@@ -798,7 +798,6 @@ def test_isxidcontinue(self):
         self.assertRaises(TypeError, self.db.isxidcontinue)
         self.assertRaises(TypeError, self.db.isxidcontinue, 'xx')
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'grapheme_cluster_break'
     def test_grapheme_cluster_break(self):
         gcb = self.db.grapheme_cluster_break
         self.assertEqual(gcb(' '), 'Other')
@@ -896,7 +895,6 @@ def test_grapheme_cluster_break(self):
         self.assertRaises(TypeError, gcb, '')
         self.assertRaises(TypeError, gcb, 'xx')
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'indic_conjunct_break'
     def test_indic_conjunct_break(self):
         incb = self.db.indic_conjunct_break
         self.assertEqual(incb(' '), 'None')
@@ -925,7 +923,6 @@ def test_indic_conjunct_break(self):
         self.assertRaises(TypeError, incb, '')
         self.assertRaises(TypeError, incb, 'xx')
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'extended_pictographic'
     def test_extended_pictographic(self):
         ext_pict = self.db.extended_pictographic
         self.assertIs(ext_pict(' '), False)
@@ -946,7 +943,6 @@ def test_extended_pictographic(self):
         self.assertRaises(TypeError, ext_pict, '')
         self.assertRaises(TypeError, ext_pict, 'xx')
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'iter_graphemes'
     def test_grapheme_break(self):
         def graphemes(*args):
             return list(map(str, self.db.iter_graphemes(*args)))
@@ -1017,7 +1013,7 @@ def graphemes(*args):
             'a\U0001F1FA\U0001F1E6\U0001F1FA\U0001F1F3'),
             ['a', '\U0001F1FA\U0001F1E6', '\U0001F1FA\U0001F1F3'])
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'block'
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'block'
     def test_block(self):
         self.assertEqual(self.db.block('\u0000'), 'Basic Latin')
         self.assertEqual(self.db.block('\u0041'), 'Basic Latin')
@@ -1102,7 +1098,7 @@ def test_block(self):
         self.assertEqual(self.db.block('\U00100000'), 'Supplementary Private Use Area-B')
         self.assertEqual(self.db.block('\U0010FFFF'), 'Supplementary Private Use Area-B')
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'block'
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'block'
     def test_block_invalid_input(self):
         self.assertRaises(TypeError, self.db.block)
         self.assertRaises(TypeError, self.db.block, b'x')
@@ -1169,7 +1165,7 @@ def test_failed_import_during_compiling(self):
             "(can't load unicodedata module)"
         self.assertIn(error, result.err.decode("ascii"))
 
-    @unittest.expectedFailure   # TODO: RUSTPYTHON; AssertionError Process return code is 1
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; AssertionError Process return code is 1
     def test_unicodedata_unload_reload(self):
         # gh-149449: dropping unicodedata and running gc must not leave the
         # cached _ucnhash_CAPI pointer dangling.
@@ -1262,7 +1258,6 @@ def test_linebreak_7643(self):
                 self.assertEqual(len(lines), 1,
                                  r"%a should not be a linebreak" % c)
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'iter_graphemes'
     def test_segment_object(self):
         segments = list(unicodedata.iter_graphemes('spa\u0300m'))
         self.assertEqual(len(segments), 4, segments)
@@ -1384,7 +1379,6 @@ class MyStr(str):
 
 class GraphemeBreakTest(unittest.TestCase):
     @requires_resource('network')
-    @unittest.expectedFailure   # TODO: RUSTPYTHON; AttributeError module 'unicodedata' has no attribute 'iter_graphemes'
     def test_grapheme_break(self):
         TESTDATAFILE = "GraphemeBreakTest.txt"
         testdata = download_test_data_file(TESTDATAFILE)
@@ -1423,7 +1417,6 @@ def run_grapheme_break_tests(self, testdata):
                     self.assertEqual([x.start for x in result], breaks[i:-1], comment)
                     self.assertEqual([x.end for x in result], breaks[i+1:], comment)
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AttributeError: module 'unicodedata' has no attribute 'iter_graphemes'
     def test_reference_loops(self):
         # Test that reference loops involving GraphemeBreakIterator or
         # Segment can be broken by the garbage collector.
diff --git a/Lib/test/test_unittest/testmock/testhelpers.py b/Lib/test/test_unittest/testmock/testhelpers.py
index bcae14c5b3c..0e82c723ec3 100644
--- a/Lib/test/test_unittest/testmock/testhelpers.py
+++ b/Lib/test/test_unittest/testmock/testhelpers.py
@@ -45,7 +45,6 @@ def test_any_and_datetime(self):
         mock.assert_called_with(ANY, foo=ANY)
 
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_any_mock_calls_comparison_order(self):
         mock = Mock()
         class Foo(object):
diff --git a/Lib/test/test_unpack_ex.py b/Lib/test/test_unpack_ex.py
index a5a20025930..6f49e62e8dc 100644
--- a/Lib/test/test_unpack_ex.py
+++ b/Lib/test/test_unpack_ex.py
@@ -361,7 +361,7 @@
       ...
     SyntaxError: cannot use starred expression here
 
-    >>> (((*x))),y = 1, 2 # TODO: RUSTPYTHON # doctest:+ELLIPSIS +EXPECTED_FAILURE
+    >>> (((*x))),y = 1, 2 # doctest:+ELLIPSIS
     Traceback (most recent call last):
       ...
     SyntaxError: cannot use starred expression here
@@ -376,7 +376,7 @@
       ...
     SyntaxError: cannot use starred expression here
 
-    >>> ((*x),y) = 1, 2 # TODO: RUSTPYTHON # doctest:+ELLIPSIS +EXPECTED_FAILURE
+    >>> ((*x),y) = 1, 2 # doctest:+ELLIPSIS
     Traceback (most recent call last):
       ...
     SyntaxError: cannot use starred expression here
diff --git a/Lib/test/test_uuid.py b/Lib/test/test_uuid.py
index c8400da3ae9..055be2994bf 100644
--- a/Lib/test/test_uuid.py
+++ b/Lib/test/test_uuid.py
@@ -13,7 +13,7 @@
 from unittest import mock
 
 from test import support
-from test.support import import_helper
+from test.support import force_not_colorized_test_class, import_helper, warnings_helper
 from test.support.script_helper import assert_python_ok
 
 py_uuid = import_helper.import_fresh_module('uuid', blocked=['_uuid'])
@@ -590,6 +590,7 @@ def test_uuid1_safe(self):
         # dependent on the underlying platform support.  At least it cannot be
         # unknown (unless I suppose the platform is buggy).
         self.assertNotEqual(u.is_safe, self.uuid.SafeUUID.unknown)
+        self.assertEqual(u.version, 1)
 
     @contextlib.contextmanager
     def mock_generate_time_safe(self, safe_value):
@@ -612,24 +613,28 @@ def test_uuid1_unknown(self):
         with self.mock_generate_time_safe(None):
             u = self.uuid.uuid1()
             self.assertEqual(u.is_safe, self.uuid.SafeUUID.unknown)
+            self.assertEqual(u.version, 1)
 
     @unittest.skipUnless(os.name == 'posix', 'POSIX-only test')
     def test_uuid1_is_safe(self):
         with self.mock_generate_time_safe(0):
             u = self.uuid.uuid1()
             self.assertEqual(u.is_safe, self.uuid.SafeUUID.safe)
+            self.assertEqual(u.version, 1)
 
     @unittest.skipUnless(os.name == 'posix', 'POSIX-only test')
     def test_uuid1_is_unsafe(self):
         with self.mock_generate_time_safe(-1):
             u = self.uuid.uuid1()
             self.assertEqual(u.is_safe, self.uuid.SafeUUID.unsafe)
+            self.assertEqual(u.version, 1)
 
     @unittest.skipUnless(os.name == 'posix', 'POSIX-only test')
     def test_uuid1_bogus_return_value(self):
         with self.mock_generate_time_safe(3):
             u = self.uuid.uuid1()
             self.assertEqual(u.is_safe, self.uuid.SafeUUID.unknown)
+            self.assertEqual(u.version, 1)
 
     def test_uuid1_time(self):
         with mock.patch.object(self.uuid, '_generate_time_safe', None), \
@@ -1112,6 +1117,7 @@ def test_uuid8_uniqueness(self):
         versions = {u.version for u in uuids}
         self.assertSetEqual(versions, {8})
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     @support.requires_fork()
     def testIssue8621(self):
         # On at least some versions of OSX self.uuid.uuid4 generates
@@ -1298,10 +1304,12 @@ def test_cli_uuid8(self):
         self.do_test_standalone_uuid(8)
 
 
+@force_not_colorized_test_class
 class TestUUIDWithoutExtModule(CommandLineTestCases, BaseTestUUID, unittest.TestCase):
     uuid = py_uuid
 
 
+@force_not_colorized_test_class
 @unittest.skipUnless(c_uuid, 'requires the C _uuid module')
 class TestUUIDWithExtModule(CommandLineTestCases, BaseTestUUID, unittest.TestCase):
     uuid = c_uuid
diff --git a/Lib/test/test_venv.py b/Lib/test/test_venv.py
index 2ea5f502247..ed40d60832e 100644
--- a/Lib/test/test_venv.py
+++ b/Lib/test/test_venv.py
@@ -13,7 +13,6 @@
 import re
 import shlex
 import shutil
-import struct
 import subprocess
 import sys
 import sysconfig
@@ -140,14 +139,9 @@ def _check_output_of_default_create(self):
         self.isdir(self.bindir)
         self.isdir(self.include)
         self.isdir(*self.lib)
-        # Issue 21197
         p = self.get_env_file('lib64')
-        conditions = ((struct.calcsize('P') == 8) and (os.name == 'posix') and
-                      (sys.platform != 'darwin'))
-        if conditions:
-            self.assertTrue(os.path.islink(p))
-        else:
-            self.assertFalse(os.path.exists(p))
+        if os.path.exists(p):
+            self.assertFalse(os.path.islink(p))
         data = self.get_text_file_contents('pyvenv.cfg')
         executable = sys._base_executable
         path = os.path.dirname(executable)
@@ -311,9 +305,9 @@ def test_sysconfig(self):
                 self.assertEqual(out.strip(), expected, err)
         for attr, expected in (
             ('executable', self.envpy()),
-            # Usually compare to sys.executable, but if we're running in our own
-            # venv then we really need to compare to our base executable
-            ('_base_executable', sys._base_executable),
+            # Usually compare to sys.prefix, but if we're running in our own
+            # venv then we really need to compare to our base prefix
+            ('base_prefix', sys.base_prefix),
         ):
             with self.subTest(attr):
                 cmd[2] = f'import sys; print(sys.{attr})'
@@ -609,6 +603,51 @@ def test_unicode_in_batch_file(self):
         )
         self.assertEqual(out.strip(), '0')
 
+    @unittest.skipUnless(os.name == 'nt', 'only relevant on Windows')
+    def test_activate_bat_respects_disable_prompt(self):
+        rmtree(self.env_dir)
+        env_dir = os.path.join(os.path.realpath(self.env_dir), 'venv')
+        builder = venv.EnvBuilder(clear=True)
+        builder.create(env_dir)
+        activate = os.path.join(env_dir, self.bindir, 'activate.bat')
+        test_batch = os.path.join(self.env_dir, 'test_disable_prompt.bat')
+        with open(test_batch, "w") as f:
+            f.write('@echo off\n'
+                    'set "PROMPT=base$G"\n'
+                    'set "VIRTUAL_ENV_DISABLE_PROMPT=1"\n'
+                    f'call "{activate}"\n'
+                    'echo ACTIVE_PROMPT:%PROMPT%\n'
+                    'echo VIRTUAL_ENV:%VIRTUAL_ENV%\n'
+                    'set "PROMPT=changed$G"\n'
+                    'call deactivate\n'
+                    'echo FINAL_PROMPT:%PROMPT%\n')
+        out, err = check_output([test_batch])
+        lines = out.splitlines()
+        self.assertEqual(lines[0], b'ACTIVE_PROMPT:base$G')
+        self.assertEndsWith(lines[1], os.fsencode(env_dir))
+        self.assertEqual(lines[2], b'FINAL_PROMPT:changed$G')
+
+    @unittest.skipUnless(os.name == 'nt', 'only relevant on Windows')
+    def test_activate_bat_prefixes_prompt_by_default(self):
+        rmtree(self.env_dir)
+        env_dir = os.path.join(os.path.realpath(self.env_dir), 'venv')
+        builder = venv.EnvBuilder(clear=True)
+        builder.create(env_dir)
+        activate = os.path.join(env_dir, self.bindir, 'activate.bat')
+        test_batch = os.path.join(self.env_dir, 'test_enable_prompt.bat')
+        with open(test_batch, "w") as f:
+            f.write('@echo off\n'
+                    'set "PROMPT=base) $G"\n'
+                    'set "VIRTUAL_ENV_DISABLE_PROMPT="\n'
+                    f'call "{activate}"\n'
+                    'echo ACTIVE_PROMPT:%PROMPT%\n'
+                    'call deactivate\n'
+                    'echo FINAL_PROMPT:%PROMPT%\n')
+        out, err = check_output([test_batch])
+        lines = out.splitlines()
+        self.assertEqual(lines[0], b'ACTIVE_PROMPT:(venv) base) $G')
+        self.assertEqual(lines[1], b'FINAL_PROMPT:base) $G')
+
     @unittest.skipUnless(os.name == 'nt' and can_symlink(),
                          'symlinks on Windows')
     def test_failed_symlink(self):
@@ -937,10 +976,10 @@ def test_venvwlauncher(self):
             exename = exename.replace("python", "pythonw")
         envpyw = os.path.join(self.env_dir, self.bindir, exename)
         try:
-            subprocess.check_call([envpyw, "-c", "import sys; "
-                "assert sys._base_executable.endswith('%s')" % exename])
+            subprocess.check_call([envpyw, "-c", "import fnmatch, sys; "
+                "assert fnmatch.fnmatch(sys._base_executable, '**/pythonw*.exe')"])
         except subprocess.CalledProcessError:
-            self.fail("venvwlauncher.exe did not run %s" % exename)
+            self.fail("venvwlauncher.exe did not run pythonw.exe")
 
 
 @requireVenvCreate
@@ -1057,7 +1096,7 @@ def do_test_with_pip(self, system_site_packages):
                      err, flags=re.MULTILINE)
         # Ignore warning about missing optional module:
         try:
-            import ssl
+            import ssl  # noqa: F401
         except ImportError:
             err = re.sub(
                 "^WARNING: Disabling truststore since ssl support is missing$",
diff --git a/Lib/test/test_warnings/__init__.py b/Lib/test/test_warnings/__init__.py
index bbb64faa4a7..89505ff5e55 100644
--- a/Lib/test/test_warnings/__init__.py
+++ b/Lib/test/test_warnings/__init__.py
@@ -250,10 +250,23 @@ def test_filter_module(self):
             self.module.warn_explicit('msg', UserWarning, 'filename', 42,
                                       module='package.module')
             self.assertEqual(len(w), 1)
+            self.module.warn_explicit('msg', UserWarning, '/path/to/package/module', 42)
+            self.assertEqual(len(w), 2)
+            self.module.warn_explicit('msg', UserWarning, '/path/to/package/module.py', 42)
+            self.assertEqual(len(w), 3)
+            self.module.warn_explicit('msg', UserWarning, '/path/to/package/module/__init__.py', 42)
+            self.assertEqual(len(w), 4)
             with self.assertRaises(UserWarning):
-                self.module.warn_explicit('msg', UserWarning, '/path/to/package/module', 42)
-            with self.assertRaises(UserWarning):
-                self.module.warn_explicit('msg', UserWarning, '/path/to/package/module.py', 42)
+                self.module.warn_explicit('msg', UserWarning, '/path/to/package/module/__init__', 42)
+            if MS_WINDOWS:
+                self.module.warn_explicit('msg', UserWarning, r'C:\path\to\package\module.PY', 42)
+                self.assertEqual(len(w), 5)
+                self.module.warn_explicit('msg', UserWarning, r'C:\path\to\package\module\__INIT__.PY', 42)
+                self.assertEqual(len(w), 6)
+                self.module.warn_explicit('msg', UserWarning, r'C:\path\to\package\module.PYW', 42)
+                self.assertEqual(len(w), 7)
+                self.module.warn_explicit('msg', UserWarning, r'C:\path\to\package\module\__INIT__.PYW', 42)
+                self.assertEqual(len(w), 8)
 
         with self.module.catch_warnings(record=True) as w:
             self.module.simplefilter('error')
@@ -277,9 +290,8 @@ def test_filter_module(self):
             with self.assertRaises(UserWarning):
                 self.module.warn_explicit('msg', UserWarning, '/PATH/TO/PACKAGE/MODULE', 42)
             if MS_WINDOWS:
-                if self.module is py_warnings:
-                    self.module.warn_explicit('msg', UserWarning, r'/path/to/package/module.PY', 42)
-                    self.assertEqual(len(w), 3)
+                self.module.warn_explicit('msg', UserWarning, r'/path/to/package/module.PY', 42)
+                self.assertEqual(len(w), 3)
                 with self.assertRaises(UserWarning):
                     self.module.warn_explicit('msg', UserWarning, r'/path/to/package/module/__init__.py', 42)
                 with self.assertRaises(UserWarning):
@@ -303,9 +315,8 @@ def test_filter_module(self):
                 self.assertEqual(len(w), 1)
                 self.module.warn_explicit('msg', UserWarning, r'C:\path\to\package\module.py', 42)
                 self.assertEqual(len(w), 2)
-                if self.module is py_warnings:
-                    self.module.warn_explicit('msg', UserWarning, r'C:\path\to\package\module.PY', 42)
-                    self.assertEqual(len(w), 3)
+                self.module.warn_explicit('msg', UserWarning, r'C:\path\to\package\module.PY', 42)
+                self.assertEqual(len(w), 3)
                 with self.assertRaises(UserWarning):
                     self.module.warn_explicit('msg', UserWarning, r'C:\path\to\package\module.pyw', 42)
                 with self.assertRaises(UserWarning):
@@ -400,7 +411,7 @@ def test_message_matching(self):
 
     def test_mutate_filter_list(self):
         class X:
-            def match(self, a):
+            def match(self, a, start=0):
                 L[:] = []
 
         L = [("default",X(),UserWarning,X(),0) for i in range(2)]
@@ -571,15 +582,19 @@ def test_warn_nonstandard_types(self):
                 # ``Warning() != Warning()``.
                 self.assertEqual(str(w[-1].message), str(UserWarning(ob)))
 
-    def test_filename(self):
+    def test_filename_module(self):
         with warnings_state(self.module):
             with self.module.catch_warnings(record=True) as w:
                 warning_tests.inner("spam1")
                 self.assertEqual(os.path.basename(w[-1].filename),
                                     "stacklevel.py")
+                self.assertEqual(w[-1].module,
+                                 "test.test_warnings.data.stacklevel")
                 warning_tests.outer("spam2")
                 self.assertEqual(os.path.basename(w[-1].filename),
                                     "stacklevel.py")
+                self.assertEqual(w[-1].module,
+                                 "test.test_warnings.data.stacklevel")
 
     def test_stacklevel(self):
         # Test stacklevel argument
@@ -589,23 +604,32 @@ def test_stacklevel(self):
                 warning_tests.inner("spam3", stacklevel=1)
                 self.assertEqual(os.path.basename(w[-1].filename),
                                     "stacklevel.py")
+                self.assertEqual(w[-1].module,
+                                 "test.test_warnings.data.stacklevel")
                 warning_tests.outer("spam4", stacklevel=1)
                 self.assertEqual(os.path.basename(w[-1].filename),
                                     "stacklevel.py")
+                self.assertEqual(w[-1].module,
+                                 "test.test_warnings.data.stacklevel")
 
                 warning_tests.inner("spam5", stacklevel=2)
                 self.assertEqual(os.path.basename(w[-1].filename),
                                     "__init__.py")
+                self.assertEqual(w[-1].module, __name__)
                 warning_tests.outer("spam6", stacklevel=2)
                 self.assertEqual(os.path.basename(w[-1].filename),
                                     "stacklevel.py")
+                self.assertEqual(w[-1].module,
+                                 "test.test_warnings.data.stacklevel")
                 warning_tests.outer("spam6.5", stacklevel=3)
                 self.assertEqual(os.path.basename(w[-1].filename),
                                     "__init__.py")
+                self.assertEqual(w[-1].module, __name__)
 
                 warning_tests.inner("spam7", stacklevel=9999)
                 self.assertEqual(os.path.basename(w[-1].filename),
                                     "<sys>")
+                self.assertEqual(w[-1].module, "sys")
 
     def test_stacklevel_import(self):
         # Issue #24305: With stacklevel=2, module-level warnings should work.
@@ -616,6 +640,7 @@ def test_stacklevel_import(self):
                 import test.test_warnings.data.import_warning  # noqa: F401
                 self.assertEqual(len(w), 1)
                 self.assertEqual(w[0].filename, __file__)
+                self.assertEqual(w[0].module, __name__)
 
     def test_skip_file_prefixes(self):
         with warnings_state(self.module):
@@ -627,20 +652,27 @@ def test_skip_file_prefixes(self):
                         "inner_api", stacklevel=2,
                         warnings_module=warning_tests.warnings)
                 self.assertEqual(w[-1].filename, __file__)
+                self.assertEqual(w[-1].module, __name__)
                 warning_tests.package("package api", stacklevel=2)
                 self.assertEqual(w[-1].filename, __file__)
+                self.assertEqual(w[-1].module, __name__)
                 self.assertEqual(w[-2].filename, w[-1].filename)
+                self.assertEqual(w[-2].module, w[-1].module)
                 # Low stacklevels are overridden to 2 behavior.
                 warning_tests.package("package api 1", stacklevel=1)
                 self.assertEqual(w[-1].filename, __file__)
+                self.assertEqual(w[-1].module, __name__)
                 warning_tests.package("package api 0", stacklevel=0)
                 self.assertEqual(w[-1].filename, __file__)
+                self.assertEqual(w[-1].module, __name__)
                 warning_tests.package("package api -99", stacklevel=-99)
                 self.assertEqual(w[-1].filename, __file__)
+                self.assertEqual(w[-1].module, __name__)
 
                 # The stacklevel still goes up out of the package.
                 warning_tests.package("prefix02", stacklevel=3)
                 self.assertIn("unittest", w[-1].filename)
+                self.assertStartsWith(w[-1].module, "unittest")
 
     def test_skip_file_prefixes_file_path(self):
         # see: gh-126209
@@ -651,6 +683,8 @@ def test_skip_file_prefixes_file_path(self):
 
             self.assertEqual(len(w), 1)
             self.assertNotEqual(w[-1].filename, skipped)
+            self.assertEqual(w[-1].filename, __file__)
+            self.assertEqual(w[-1].module, __name__)
 
     def test_skip_file_prefixes_type_errors(self):
         with warnings_state(self.module):
@@ -662,7 +696,7 @@ def test_skip_file_prefixes_type_errors(self):
             with self.assertRaises(TypeError):
                 warn("msg", skip_file_prefixes="a sequence of strs")
 
-    def test_exec_filename(self):
+    def test_exec_filename_module(self):
         filename = "<warnings-test>"
         codeobj = compile(("import warnings\n"
                            "warnings.warn('hello', UserWarning)"),
@@ -671,6 +705,12 @@ def test_exec_filename(self):
             self.module.simplefilter("always", category=UserWarning)
             exec(codeobj)
         self.assertEqual(w[0].filename, filename)
+        self.assertEqual(w[0].module, __name__)
+        with self.module.catch_warnings(record=True) as w:
+            self.module.simplefilter("always", category=UserWarning)
+            exec(codeobj, {})
+        self.assertEqual(w[0].filename, filename)
+        self.assertEqual(w[0].module, '<string>')
 
     def test_warn_explicit_non_ascii_filename(self):
         with self.module.catch_warnings(record=True) as w:
@@ -717,25 +757,19 @@ def test_warning_classes(self):
         class MyWarningClass(Warning):
             pass
 
-        class NonWarningSubclass:
-            pass
-
         # passing a non-subclass of Warning should raise a TypeError
-        with self.assertRaises(TypeError) as cm:
+        expected = "category must be a Warning subclass, not 'str'"
+        with self.assertRaisesRegex(TypeError, expected):
             self.module.warn('bad warning category', '')
-        self.assertIn('category must be a Warning subclass, not ',
-                      str(cm.exception))
 
-        with self.assertRaises(TypeError) as cm:
-            self.module.warn('bad warning category', NonWarningSubclass)
-        self.assertIn('category must be a Warning subclass, not ',
-                      str(cm.exception))
+        expected = "category must be a Warning subclass, not class 'int'"
+        with self.assertRaisesRegex(TypeError, expected):
+            self.module.warn('bad warning category', int)
 
         # check that warning instances also raise a TypeError
-        with self.assertRaises(TypeError) as cm:
+        expected = "category must be a Warning subclass, not '.*MyWarningClass'"
+        with self.assertRaisesRegex(TypeError, expected):
             self.module.warn('bad warning category', MyWarningClass())
-        self.assertIn('category must be a Warning subclass, not ',
-                      str(cm.exception))
 
         with self.module.catch_warnings():
             self.module.resetwarnings()
@@ -764,7 +798,7 @@ def check_module_globals(self, module_globals):
 
     def check_module_globals_error(self, module_globals, errmsg, errtype=ValueError):
         if self.module is py_warnings:
-            self.check_module_globals(module_globals)
+            self.check_module_globals_deprecated(module_globals, errmsg)
             return
         with self.module.catch_warnings(record=True) as w:
             self.module.filterwarnings('always')
@@ -775,9 +809,6 @@ def check_module_globals_error(self, module_globals, errmsg, errtype=ValueError)
         self.assertEqual(len(w), 0)
 
     def check_module_globals_deprecated(self, module_globals, msg):
-        if self.module is py_warnings:
-            self.check_module_globals(module_globals)
-            return
         with self.module.catch_warnings(record=True) as w:
             self.module.filterwarnings('always')
             self.module.warn_explicit(
@@ -882,6 +913,10 @@ def test_improper_input(self):
                 self.module._setoption('ignore::===')
             with self.assertRaisesRegex(self.module._OptionError, 'Wärning'):
                 self.module._setoption('ignore::Wärning')
+            with self.assertRaisesRegex(self.module._OptionError, 'message'):
+                self.module._setoption('ignore:/?/:Warning')
+            with self.assertRaisesRegex(self.module._OptionError, 'module'):
+                self.module._setoption('ignore::Warning:/?/')
             self.module._setoption('error::Warning::0')
             self.assertRaises(UserWarning, self.module.warn, 'convert to error')
 
@@ -896,6 +931,31 @@ def test_import_from_module(self):
             with self.assertRaises(TestWarning):
                 self.module.warn('test warning', TestWarning)
 
+    def test_message(self):
+        # Match prefix, case-insensitive.
+        with self.module.catch_warnings():
+            self.module._setoption('error:TEST WARN:UserWarning')
+            with self.assertRaises(UserWarning):
+                self.module.warn('Test Warning')
+        with self.module.catch_warnings():
+            self.module._setoption(r'error:/TE.*WARN/:UserWarning')
+            with self.assertRaises(UserWarning):
+                self.module.warn('Test Warning')
+
+    def test_module(self):
+        with self.module.catch_warnings():
+            self.module._setoption(f'error::UserWarning:{__name__}')
+            with self.assertRaises(UserWarning):
+                self.module.warn('test warning')
+            # Only full match.
+            self.module._setoption(f'ignore::UserWarning:{__name__[:-2]}')
+            with self.assertRaises(UserWarning):
+                self.module.warn('test warning')
+        with self.module.catch_warnings():
+            self.module._setoption(f'error::UserWarning:/{re.escape(__name__[:-2])}./')
+            with self.assertRaises(UserWarning):
+                self.module.warn('test warning')
+
 
 class CWCmdLineTests(WCmdLineTests, unittest.TestCase):
     module = c_warnings
diff --git a/Lib/test/test_wave.py b/Lib/test/test_wave.py
index 346a343761a..d3723c04820 100644
--- a/Lib/test/test_wave.py
+++ b/Lib/test/test_wave.py
@@ -1,9 +1,11 @@
 import unittest
 from test import audiotests
 from test import support
+from test.support.os_helper import FakePath, unlink
 import io
 import os
 import struct
+import tempfile
 import sys
 import wave
 
@@ -20,6 +22,7 @@ class WavePCM8Test(WaveTest, unittest.TestCase):
     sampwidth = 1
     framerate = 11025
     nframes = 48
+    format = wave.WAVE_FORMAT_PCM
     comptype = 'NONE'
     compname = 'not compressed'
     frames = bytes.fromhex("""\
@@ -37,6 +40,7 @@ class WavePCM16Test(WaveTest, unittest.TestCase):
     sampwidth = 2
     framerate = 11025
     nframes = 48
+    format = wave.WAVE_FORMAT_PCM
     comptype = 'NONE'
     compname = 'not compressed'
     frames = bytes.fromhex("""\
@@ -58,6 +62,7 @@ class WavePCM24Test(WaveTest, unittest.TestCase):
     sampwidth = 3
     framerate = 11025
     nframes = 48
+    format = wave.WAVE_FORMAT_PCM
     comptype = 'NONE'
     compname = 'not compressed'
     frames = bytes.fromhex("""\
@@ -85,6 +90,8 @@ class WavePCM24ExtTest(WaveTest, unittest.TestCase):
     sampwidth = 3
     framerate = 11025
     nframes = 48
+    format = wave.WAVE_FORMAT_EXTENSIBLE
+    readonly = True  # Writing EXTENSIBLE wave format is not supported.
     comptype = 'NONE'
     compname = 'not compressed'
     frames = bytes.fromhex("""\
@@ -112,6 +119,7 @@ class WavePCM32Test(WaveTest, unittest.TestCase):
     sampwidth = 4
     framerate = 11025
     nframes = 48
+    format = wave.WAVE_FORMAT_PCM
     comptype = 'NONE'
     compname = 'not compressed'
     frames = bytes.fromhex("""\
@@ -132,40 +140,142 @@ class WavePCM32Test(WaveTest, unittest.TestCase):
         frames = wave._byteswap(frames, 4)
 
 
+class WaveIeeeFloatingPointTest(WaveTest, unittest.TestCase):
+    sndfilename = 'pluck-float32.wav'
+    sndfilenframes = 3307
+    nchannels = 2
+    sampwidth = 4
+    framerate = 11025
+    nframes = 48
+    format = wave.WAVE_FORMAT_IEEE_FLOAT
+    comptype = 'NONE'
+    compname = 'not compressed'
+    frames = bytes.fromhex("""\
+      3C8B5960BA231400 3F16B41F3BFA5480 3EC44F0E3D1DC580 BF7E46533D843040 \
+      BED084FC3D564C30 3F1153303CFCBE40 BF002FB73C583EC0 3CDAFEE0BC425180 \
+      BF0F5154BD3826E0 BF169F56BDCAFD40 3EA660C0BE21A4EC 3E52E53CBE49332C \
+      BE102E0CBE5B7214 BEE76852BE6C3BDC 3DE05A98BE7A4980 BE06B6B4BE7EB6EC \
+      3F2EB1B0BE6C7CC8 BD195500BE3E0F4C 3E1BBDF8BE03DFEC BE9F4E92BD8D8D58 \
+      BF50E1D4BD111750 BDA079B0BCFBFB20 3D866358BD0C7640 BE833C0EBD17E240 \
+      3E0BFF04BD3978F0 3EFB9AE2BD14A780 BF0710B9BCD342E0 3F4DADB5BBA0CD80 \
+      BEC3B11A3D024EB0 3F063AD33D97A8C0 BEF912803DEC74E0 3F2241733E1515D4 \
+      BE0904D83E3AA604 BF7BF2003E3325BC 3F8000003E2229FC BF8000003E14A738 \
+      3F1338363DEB3B28 3F256E7C3DDBCA00 BE026A683DF5FD88 BEC70C923DFBE128 \
+      BE5A5B183DCEA2D8 3F4689513DA5A7C8 3D8C8FE83DA1FFF0 3EAEE61C3DB0A0E0 \
+      3F2290DF3DE44E18 BF6867373E09D82C BF1216283DEEB360 3F08262F3DA5B488 \
+      """)
+    if sys.byteorder != 'big':
+        frames = wave._byteswap(frames, 4)
+
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
-        not_exported = {'WAVE_FORMAT_PCM', 'WAVE_FORMAT_EXTENSIBLE', 'KSDATAFORMAT_SUBTYPE_PCM'}
+        not_exported = {'KSDATAFORMAT_SUBTYPE_PCM'}
         support.check__all__(self, wave, not_exported=not_exported)
 
-    def test_read_deprecations(self):
-        filename = support.findfile('pluck-pcm8.wav', subdir='audiodata')
-        with wave.open(filename) as reader:
-            with self.assertWarns(DeprecationWarning):
-                with self.assertRaises(wave.Error):
-                    reader.getmark('mark')
-            with self.assertWarns(DeprecationWarning):
-                self.assertIsNone(reader.getmarkers())
-
-    def test_write_deprecations(self):
-        with io.BytesIO(b'') as tmpfile:
-            with wave.open(tmpfile, 'wb') as writer:
-                writer.setnchannels(1)
-                writer.setsampwidth(1)
-                writer.setframerate(1)
-                writer.setcomptype('NONE', 'not compressed')
-
-                with self.assertWarns(DeprecationWarning):
-                    with self.assertRaises(wave.Error):
-                        writer.setmark(0, 0, 'mark')
-                with self.assertWarns(DeprecationWarning):
-                    with self.assertRaises(wave.Error):
-                        writer.getmark('mark')
-                with self.assertWarns(DeprecationWarning):
-                    self.assertIsNone(writer.getmarkers())
-
 
 class WaveLowLevelTest(unittest.TestCase):
 
+    def test_setparams_6_tuple_defaults_to_pcm(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setformat(wave.WAVE_FORMAT_IEEE_FLOAT)
+            w.setparams((1, 2, 22050, 0, 'NONE', 'not compressed'))
+            self.assertEqual(w.getformat(), wave.WAVE_FORMAT_PCM)
+
+    def test_setparams_7_tuple_uses_format(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setparams((1, 4, 22050, 0, 'NONE', 'not compressed',
+                         wave.WAVE_FORMAT_IEEE_FLOAT))
+            self.assertEqual(w.getformat(), wave.WAVE_FORMAT_IEEE_FLOAT)
+
+    def test_setparams_7_tuple_ieee_64bit_sampwidth(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setparams((1, 8, 22050, 0, 'NONE', 'not compressed',
+                         wave.WAVE_FORMAT_IEEE_FLOAT))
+            self.assertEqual(w.getformat(), wave.WAVE_FORMAT_IEEE_FLOAT)
+            self.assertEqual(w.getsampwidth(), 8)
+
+    def test_getparams_backward_compatible_shape(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setparams((1, 4, 22050, 0, 'NONE', 'not compressed',
+                         wave.WAVE_FORMAT_IEEE_FLOAT))
+            params = w.getparams()
+            self.assertEqual(params, (1, 4, 22050, 0, 'NONE', 'not compressed'))
+
+    def test_getformat_setformat(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setnchannels(1)
+            w.setsampwidth(4)
+            w.setframerate(22050)
+            self.assertEqual(w.getformat(), wave.WAVE_FORMAT_PCM)
+            w.setformat(wave.WAVE_FORMAT_IEEE_FLOAT)
+            self.assertEqual(w.getformat(), wave.WAVE_FORMAT_IEEE_FLOAT)
+
+    def test_setformat_ieee_requires_32_or_64_bit_sampwidth(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setnchannels(1)
+            w.setsampwidth(2)
+            w.setframerate(22050)
+            with self.assertRaisesRegex(wave.Error,
+                                        'unsupported sample width for IEEE float format'):
+                w.setformat(wave.WAVE_FORMAT_IEEE_FLOAT)
+
+    def test_setsampwidth_ieee_requires_32_or_64_bit(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setnchannels(1)
+            w.setframerate(22050)
+            w.setformat(wave.WAVE_FORMAT_IEEE_FLOAT)
+            with self.assertRaisesRegex(wave.Error,
+                                        'unsupported sample width for IEEE float format'):
+                w.setsampwidth(2)
+            w.setsampwidth(4)
+
+    def test_setsampwidth_ieee_accepts_64_bit(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setnchannels(1)
+            w.setframerate(22050)
+            w.setformat(wave.WAVE_FORMAT_IEEE_FLOAT)
+            w.setsampwidth(8)
+            self.assertEqual(w.getsampwidth(), 8)
+
+    def test_read_getformat(self):
+        b = b'RIFF' + struct.pack('<L', 36) + b'WAVE'
+        b += b'fmt ' + struct.pack('<LHHLLHH', 16, 1, 1, 11025, 11025, 1, 8)
+        b += b'data' + struct.pack('<L', 0)
+        with wave.open(io.BytesIO(b), 'rb') as r:
+            self.assertEqual(r.getformat(), wave.WAVE_FORMAT_PCM)
+
     def test_read_no_chunks(self):
         b = b'SPAM'
         with self.assertRaises(EOFError):
@@ -231,6 +341,139 @@ def test_open_in_write_raises(self):
             support.gc_collect()
             self.assertIsNone(cm.unraisable)
 
+    def test_ieee_float_has_fact_chunk(self):
+        nframes = 100
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setnchannels(1)
+            w.setsampwidth(4)
+            w.setframerate(22050)
+            w.setformat(wave.WAVE_FORMAT_IEEE_FLOAT)
+            w.writeframes(b'\x00\x00\x00\x00' * nframes)
+
+        with open(filename, 'rb') as f:
+            f.read(12)
+            fact_found = False
+            fact_samples = None
+            while True:
+                chunk_id = f.read(4)
+                if len(chunk_id) < 4:
+                    break
+                chunk_size = struct.unpack('<L', f.read(4))[0]
+                if chunk_id == b'fact':
+                    fact_found = True
+                    fact_samples = struct.unpack('<L', f.read(4))[0]
+                    break
+                f.seek(chunk_size + (chunk_size & 1), 1)
+
+        self.assertTrue(fact_found)
+        self.assertEqual(fact_samples, nframes)
+
+    def test_pcm_has_no_fact_chunk(self):
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            filename = fp.name
+        self.addCleanup(unlink, filename)
+
+        with wave.open(filename, 'wb') as w:
+            w.setnchannels(1)
+            w.setsampwidth(2)
+            w.setframerate(22050)
+            w.writeframes(b'\x00\x00' * 100)
+
+        with open(filename, 'rb') as f:
+            f.read(12)
+            while True:
+                chunk_id = f.read(4)
+                if len(chunk_id) < 4:
+                    break
+                chunk_size = struct.unpack('<L', f.read(4))[0]
+                self.assertNotEqual(chunk_id, b'fact')
+                f.seek(chunk_size + (chunk_size & 1), 1)
+
+    @support.subTests('arg', (
+        # rounds to 0, should raise:
+        0.5,
+        0.4,
+        # Negative values should still raise:
+        -1,
+        -0.5,
+        -0.4,
+        # 0 should raise:
+        0,
+    ))
+    def test_setframerate_validates_rounded_values(self, arg):
+        """Test that setframerate that round to 0 or negative are rejected"""
+        with wave.open(io.BytesIO(), 'wb') as f:
+            f.setnchannels(1)
+            f.setsampwidth(2)
+            with self.assertRaises(wave.Error):
+                f.setframerate(arg)
+            with self.assertRaises(wave.Error):
+                f.close()
+
+    @support.subTests(('arg', 'expected'), (
+        (1.4, 1),
+        (1.5, 2),
+        (1.6, 2),
+        (44100.4, 44100),
+        (44100.5, 44100),
+        (44100.6, 44101),
+    ))
+    def test_setframerate_rounds(self, arg, expected):
+        """Test that setframerate is rounded"""
+        with wave.open(io.BytesIO(), 'wb') as f:
+            f.setnchannels(1)
+            f.setsampwidth(2)
+            f.setframerate(arg)
+            self.assertEqual(f.getframerate(), expected)
+
+    def test_write_odd_data_chunk_pads_and_updates_riff_size(self):
+        # gh-117716: odd-sized data chunks must be padded with one zero byte.
+        with io.BytesIO() as output:
+            with wave.open(output, mode='wb') as w:
+                w.setnchannels(1)
+                w.setsampwidth(1)
+                w.setframerate(48000)
+                w.writeframes(b'\x80')
+
+            value = output.getvalue()
+
+        self.assertEqual(value[-1], 0)
+        self.assertEqual(
+            int.from_bytes(value[4:8], byteorder='little'),
+            38,
+        )
+
+        with wave.open(io.BytesIO(value), mode='rb') as r:
+            self.assertEqual(r.getnchannels(), 1)
+            self.assertEqual(r.getsampwidth(), 1)
+            self.assertEqual(r.getframerate(), 48000)
+            self.assertEqual(r.getnframes(), 1)
+            self.assertEqual(r.readframes(-1), b'\x80')
+
+
+class WaveOpen(unittest.TestCase):
+    def test_open_pathlike(self):
+        """It is possible to use `wave.read` and `wave.write` with a path-like object"""
+        with tempfile.NamedTemporaryFile(delete_on_close=False) as fp:
+            cases = (
+                FakePath(fp.name),
+                FakePath(os.fsencode(fp.name)),
+                os.fsencode(fp.name),
+                )
+            for fake_path in cases:
+                with self.subTest(fake_path):
+                    with wave.open(fake_path, 'wb') as f:
+                        f.setnchannels(1)
+                        f.setsampwidth(2)
+                        f.setframerate(44100)
+
+                    with wave.open(fake_path, 'rb') as f:
+                        pass
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/Lib/test/test_weakref.py b/Lib/test/test_weakref.py
index 5b5b50effc1..631611ead1f 100644
--- a/Lib/test/test_weakref.py
+++ b/Lib/test/test_weakref.py
@@ -751,7 +751,6 @@ class D:
         del c1, c2, C, D
         gc.collect()
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_callback_in_cycle_resurrection(self):
         import gc
 
@@ -798,7 +797,6 @@ def C_went_away(ignore):
         gc.collect()
         self.assertEqual(alist, [])
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_callbacks_on_callback(self):
         import gc
 
@@ -1046,6 +1044,32 @@ def callback(obj):
         stderr = res.err.decode("ascii", "backslashreplace")
         self.assertNotRegex(stderr, "_Py_Dealloc: Deallocator of type 'TestObj'")
 
+    def test_clearing_weakrefs_in_gc(self):
+        # This test checks that when finalizers are called:
+        # 1. weakrefs with callbacks have been cleared
+        # 2. weakrefs without callbacks have not been cleared
+        errors = []
+        def test():
+            class Class:
+                def __init__(self):
+                    self._self = self
+                    self.wr1 = weakref.ref(Class, lambda x: None)
+                    self.wr2 = weakref.ref(Class)
+
+                def __del__(self):
+                    # we can't use assert* here, because gc will swallow
+                    # exceptions
+                    if self.wr1() is not None:
+                        errors.append("weakref with callback as cleared")
+                    if self.wr2() is not Class:
+                        errors.append("weakref without callback was cleared")
+
+            Class()
+
+        test()
+        gc.collect()
+        self.assertEqual(errors, [])
+
 
 class SubclassableWeakrefTestCase(TestBase):
 
@@ -1791,6 +1815,11 @@ def test_weak_valued_union_operators(self):
     def test_weak_keyed_dict_update(self):
         self.check_update(weakref.WeakKeyDictionary,
                           {C(): 1, C(): 2, C(): 3})
+        d = weakref.WeakKeyDictionary()
+        msg = ("Keyword arguments are not supported: "
+               "cannot create weak reference to 'str' object")
+        with self.assertRaisesRegex(TypeError, msg):
+            d.update(k='v')
 
     def test_weak_keyed_delitem(self):
         d = weakref.WeakKeyDictionary()
diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index 7aa7d7ef480..0b89c251a4c 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -370,8 +370,7 @@ def test_simpleops(self):
         self.serialize_check(element, '<tag key="value"><subtag /></tag>') # 4
         element.remove(subelement)
         self.serialize_check(element, '<tag key="value" />') # 5
-        with self.assertRaisesRegex(ValueError,
-                                    r'Element\.remove\(.+\): element not found'):
+        with self.assertRaises(ValueError):
             element.remove(subelement)
         self.serialize_check(element, '<tag key="value" />') # 6
         element[0:0] = [subelement, subelement, subelement]
@@ -1255,6 +1254,9 @@ def test_comment_serialization(self):
         comm = ET.Comment('<spam> & ham')
         # comments are not escaped
         self.assertEqual(ET.tostring(comm), b'<!--<spam> & ham-->')
+        self.assertEqual(ET.tostring(comm, method='html'), b'<!--<spam> & ham-->')
+        # no comments in text serialization
+        self.assertEqual(ET.tostring(comm, method='text'), b'')
 
     def test_processinginstruction_serialization(self):
         # Test ProcessingInstruction directly
@@ -1271,6 +1273,11 @@ def test_processinginstruction_serialization(self):
         self.assertEqual(ET.tostring(ET.PI('test', '<testing&>\xe3'), 'latin-1'),
                 b"<?xml version='1.0' encoding='latin-1'?>\n"
                 b"<?test <testing&>\xe3?>")
+        pi = ET.PI('test', 'ham & eggs < spam')
+        self.assertEqual(ET.tostring(pi), b'<?test ham & eggs < spam?>')
+        self.assertEqual(ET.tostring(pi, method='html'), b'<?test ham & eggs < spam?>')
+        # no processing instructions in text serialization
+        self.assertEqual(ET.tostring(pi, method='text'), b'')
 
     @support.subTests('tag', ("script", "style", "xmp", "iframe", "noembed", "noframes"))
     def test_html_cdata_elems_serialization(self, tag):
@@ -1469,18 +1476,40 @@ def test_nonexistent_file(self):
 
     def test_resource_warnings_not_exhausted(self):
         # Not exhausting the iterator still closes the underlying file (bpo-43292)
+        # Not closing before del should emit ResourceWarning
         it = ET.iterparse(SIMPLE_XMLFILE)
         with warnings_helper.check_no_resource_warning(self):
+            it.close()
+            del it
+            gc_collect()
+
+        it = ET.iterparse(SIMPLE_XMLFILE)
+        with self.assertWarns(ResourceWarning) as wm:
             del it
             gc_collect()
+        # Not 'unclosed file'.
+        self.assertIn('unclosed iterparse iterator', str(wm.warning))
+        self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+        self.assertEqual(wm.filename, __file__)
 
         it = ET.iterparse(SIMPLE_XMLFILE)
         with warnings_helper.check_no_resource_warning(self):
             action, elem = next(it)
+            it.close()
             self.assertEqual((action, elem.tag), ('end', 'element'))
             del it, elem
             gc_collect()
 
+        it = ET.iterparse(SIMPLE_XMLFILE)
+        with self.assertWarns(ResourceWarning) as wm:
+            action, elem = next(it)
+            self.assertEqual((action, elem.tag), ('end', 'element'))
+            del it, elem
+            gc_collect()
+        self.assertIn('unclosed iterparse iterator', str(wm.warning))
+        self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+        self.assertEqual(wm.filename, __file__)
+
     @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_resource_warnings_failed_iteration(self):
         self.addCleanup(os_helper.unlink, TESTFN)
@@ -1501,9 +1530,19 @@ def test_resource_warnings_failed_iteration(self):
     def test_resource_warnings_exhausted(self):
         it = ET.iterparse(SIMPLE_XMLFILE)
         with warnings_helper.check_no_resource_warning(self):
+            list(it)
+            it.close()
+            del it
+            gc_collect()
+
+        it = ET.iterparse(SIMPLE_XMLFILE)
+        with self.assertWarns(ResourceWarning) as wm:
             list(it)
             del it
             gc_collect()
+        self.assertIn('unclosed iterparse iterator', str(wm.warning))
+        self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+        self.assertEqual(wm.filename, __file__)
 
     def test_close_not_exhausted(self):
         iterparse = ET.iterparse
@@ -4514,6 +4553,9 @@ def test_issue14818(self):
             ET.Element('a', dict(href="#"), id="foo"),
             ET.Element('a', href="#", id="foo"),
             ET.Element('a', dict(href="#", id="foo"), href="#", id="foo"),
+            ET.Element('a', frozendict(href="#", id="foo")),
+            ET.Element('a', frozendict(href="#"), id="foo"),
+            ET.Element('a', attrib=frozendict(href="#", id="foo")),
         ]
         for e in elements:
             self.assertEqual(e.tag, 'a')
@@ -4521,10 +4563,14 @@ def test_issue14818(self):
 
         e2 = ET.SubElement(elements[0], 'foobar', attrib={'key1': 'value1'})
         self.assertEqual(e2.attrib['key1'], 'value1')
+        e3 = ET.SubElement(elements[0], 'foobar',
+                           attrib=frozendict({'key1': 'value1'}))
+        self.assertEqual(e3.attrib['key1'], 'value1')
 
-        with self.assertRaisesRegex(TypeError, 'must be dict, not str'):
+        errmsg = 'must be dict or frozendict, not str'
+        with self.assertRaisesRegex(TypeError, errmsg):
             ET.Element('a', "I'm not a dict")
-        with self.assertRaisesRegex(TypeError, 'must be dict, not str'):
+        with self.assertRaisesRegex(TypeError, errmsg):
             ET.Element('a', attrib="I'm not a dict")
 
 # --------------------------------------------------------------------
diff --git a/Lib/test/test_zipfile/__main__.py b/Lib/test/test_zipfile/__main__.py
index e25ac946edf..90da74ade38 100644
--- a/Lib/test/test_zipfile/__main__.py
+++ b/Lib/test/test_zipfile/__main__.py
@@ -1,6 +1,6 @@
 import unittest
 
-from . import load_tests  # noqa: F401
+from . import load_tests
 
 
 if __name__ == "__main__":
diff --git a/Lib/test/test_zipfile/_path/__init__.py b/Lib/test/test_zipfile/_path/__init__.py
index 8b137891791..e69de29bb2d 100644
--- a/Lib/test/test_zipfile/_path/__init__.py
+++ b/Lib/test/test_zipfile/_path/__init__.py
@@ -1 +0,0 @@
-
diff --git a/Lib/test/test_zipfile/_path/test_path.py b/Lib/test/test_zipfile/_path/test_path.py
index 351d9eefeb0..e7931b6f394 100644
--- a/Lib/test/test_zipfile/_path/test_path.py
+++ b/Lib/test/test_zipfile/_path/test_path.py
@@ -317,7 +317,7 @@ def test_mutability(self, alpharep):
     HUGE_ZIPFILE_NUM_ENTRIES = 2**13
 
     def huge_zipfile(self):
-        """Create a read-only zipfile with a huge number of entries entries."""
+        """Create a read-only zipfile with a huge number of entries."""
         strm = io.BytesIO()
         zf = zipfile.ZipFile(strm, "w")
         for entry in map(str, range(self.HUGE_ZIPFILE_NUM_ENTRIES)):
diff --git a/Lib/test/test_zipfile/test_core.py b/Lib/test/test_zipfile/test_core.py
index f9ad28ea04d..8f226826524 100644
--- a/Lib/test/test_zipfile/test_core.py
+++ b/Lib/test/test_zipfile/test_core.py
@@ -1,6 +1,7 @@
 import _pyio
 import array
 import contextlib
+import errno
 import importlib.util
 import io
 import itertools
@@ -20,14 +21,15 @@
 from random import randint, random, randbytes
 
 from test import archiver_tests
-from test.support import script_helper, os_helper
+from test.support import script_helper
 from test.support import (
     findfile, requires_zlib, requires_bz2, requires_lzma,
     requires_zstd, captured_stdout, captured_stderr, requires_subprocess,
     cpython_only
 )
 from test.support.os_helper import (
-    TESTFN, unlink, rmtree, temp_dir, temp_cwd, fd_count, FakePath
+    TESTFN, unlink, rmtree, temp_dir, temp_cwd, fd_count, FakePath,
+    with_source_date_epoch, without_source_date_epoch,
 )
 from test.support.import_helper import ensure_lazy_imports
 
@@ -654,6 +656,12 @@ def test_add_file_after_2107(self):
             os.utime(TESTFN, (ts, ts))
         except OverflowError:
             self.skipTest('Host fs cannot set timestamp to required value.')
+        except OSError as exc:
+            # Some file systems (e.g. UFS and ZFS on illumos) do not
+            # support timestamps that do not fit in 32 bits.
+            if exc.errno != errno.EOVERFLOW:
+                raise
+            self.skipTest('Host fs cannot set timestamp to required value.')
 
         mtime_ns = os.stat(TESTFN).st_mtime_ns
         if mtime_ns != (4386268800 * 10**9):
@@ -1880,29 +1888,24 @@ def test_writestr_extended_local_header_issue1202(self):
                 zinfo.flag_bits |= zipfile._MASK_USE_DATA_DESCRIPTOR  # Include an extended local header.
                 orig_zip.writestr(zinfo, data)
 
+    @with_source_date_epoch(epoch=1735715999)
     def test_write_with_source_date_epoch(self):
-        with os_helper.EnvironmentVarGuard() as env:
-            # Set the SOURCE_DATE_EPOCH environment variable to a specific timestamp
-            env['SOURCE_DATE_EPOCH'] = "1735715999"
-
-            with zipfile.ZipFile(TESTFN, "w") as zf:
-                zf.writestr("test_source_date_epoch.txt", "Testing SOURCE_DATE_EPOCH")
+        with zipfile.ZipFile(TESTFN, "w") as zf:
+            zf.writestr("test_source_date_epoch.txt", "Testing SOURCE_DATE_EPOCH")
 
-            with zipfile.ZipFile(TESTFN, "r") as zf:
-                zip_info = zf.getinfo("test_source_date_epoch.txt")
-                expected_utc = (2025, 1, 1, 7, 19, 58)
-                self.assertEqual(zip_info.date_time, expected_utc)
+        with zipfile.ZipFile(TESTFN, "r") as zf:
+            zip_info = zf.getinfo("test_source_date_epoch.txt")
+            expected_utc = (2025, 1, 1, 7, 19, 58)
+            self.assertEqual(zip_info.date_time, expected_utc)
 
+    @without_source_date_epoch
     def test_write_without_source_date_epoch(self):
-        with os_helper.EnvironmentVarGuard() as env:
-            del env['SOURCE_DATE_EPOCH']
-
-            with zipfile.ZipFile(TESTFN, "w") as zf:
-                zf.writestr("test_no_source_date_epoch.txt", "Testing without SOURCE_DATE_EPOCH")
+        with zipfile.ZipFile(TESTFN, "w") as zf:
+            zf.writestr("test_no_source_date_epoch.txt", "Testing without SOURCE_DATE_EPOCH")
 
-            with zipfile.ZipFile(TESTFN, "r") as zf:
-                zip_info = zf.getinfo("test_no_source_date_epoch.txt")
-                self.assertTimestampAlmostEqual(time.localtime(), zip_info.date_time, tolerance=2)
+        with zipfile.ZipFile(TESTFN, "r") as zf:
+            zip_info = zf.getinfo("test_no_source_date_epoch.txt")
+            self.assertTimestampAlmostEqual(time.localtime(), zip_info.date_time, tolerance=2)
 
     def assertTimestampAlmostEqual(self, time1, time2, tolerance):
         import datetime
@@ -2720,6 +2723,115 @@ def tearDown(self):
         unlink(TESTFN2)
 
 
+class AbstractBoundedDecompressTests:
+    # ZipExtFile._read1() bounds the output of each decompress() call so that a
+    # small member declaring a large uncompressed size cannot expand into one
+    # unbounded read.
+    def test_read1_output_is_bounded(self):
+        buf = io.BytesIO()
+        with zipfile.ZipFile(buf, "w", compression=self.compression) as zf:
+            zf.writestr("big", b"\0" * (4 * 1024 * 1024))
+        with zipfile.ZipFile(io.BytesIO(buf.getvalue())) as zf:
+            with zf.open("big") as f:
+                self.assertLessEqual(len(f._read1(100)), f.MIN_READ_SIZE)
+
+
+class StoredBoundedDecompressTests(AbstractBoundedDecompressTests,
+                                   unittest.TestCase):
+    compression = zipfile.ZIP_STORED
+
+
+@requires_zlib()
+class DeflateBoundedDecompressTests(AbstractBoundedDecompressTests,
+                                    unittest.TestCase):
+    compression = zipfile.ZIP_DEFLATED
+
+
+@requires_bz2()
+class Bzip2BoundedDecompressTests(AbstractBoundedDecompressTests,
+                                  unittest.TestCase):
+    compression = zipfile.ZIP_BZIP2
+
+
+@requires_lzma()
+class LzmaBoundedDecompressTests(AbstractBoundedDecompressTests,
+                                 unittest.TestCase):
+    compression = zipfile.ZIP_LZMA
+
+
+@requires_zstd()
+class ZstdBoundedDecompressTests(AbstractBoundedDecompressTests,
+                                 unittest.TestCase):
+    compression = zipfile.ZIP_ZSTANDARD
+
+
+class MonkeypatchedDecompressorTests(unittest.TestCase):
+    # Some third-party projects monkey-patch _get_decompressor() to add
+    # additional compression schemes. This can break at any time as the
+    # internal compressor objects change.
+    # To protect users, we try to keep this case working.
+    # See also: GH-156002 and GH-113767.
+    COMPRESSION = 99
+
+    class Compressor:
+        """Compressor with only the original BZ2Compressor API"""
+        def compress(self, data):
+            return data.swapcase()
+
+        def flush(self):
+            return b''
+
+    class Decompressor:
+        """Decompressor with only the 3.3+ BZ2Decompressor API"""
+        eof = False
+
+        def decompress(self, data):
+            return data.swapcase()
+
+    def setUp(self):
+        orig_check_compression = zipfile._check_compression
+        orig_get_compressor = zipfile._get_compressor
+        orig_get_decompressor = zipfile._get_decompressor
+
+        def check_compression(compression):
+            if compression != self.COMPRESSION:
+                orig_check_compression(compression)
+
+        def get_compressor(compress_type, compresslevel=None):
+            if compress_type == self.COMPRESSION:
+                return self.Compressor()
+            return orig_get_compressor(compress_type, compresslevel)
+
+        def get_decompressor(compress_type):
+            if compress_type == self.COMPRESSION:
+                return self.Decompressor()
+            return orig_get_decompressor(compress_type)
+
+        self.enterContext(mock.patch.object(
+            zipfile, '_check_compression', check_compression))
+        self.enterContext(mock.patch.object(
+            zipfile, '_get_compressor', get_compressor))
+        self.enterContext(mock.patch.object(
+            zipfile, '_get_decompressor', get_decompressor))
+
+    def test_roundtrip_monkeypatched_decompressor(self):
+        data = bytes(range(256)) * 8
+        buf = io.BytesIO()
+        with zipfile.ZipFile(buf, "w", compression=self.COMPRESSION) as zf:
+            zf.writestr("member", data)
+        self.assertIn(data.swapcase(), buf.getvalue())
+        with zipfile.ZipFile(io.BytesIO(buf.getvalue())) as zf:
+            self.assertEqual(zf.read("member"), data)
+            with zf.open("member") as f:
+                self.assertEqual(f.read(100), data[:100])
+                self.assertEqual(f.read1(100), data[100:200])
+                f.seek(-100, os.SEEK_END)
+                self.assertEqual(f.read(), data[-100:])
+                # Rewinding past the read buffer re-creates the decompressor.
+                f.seek(0)
+                self.assertEqual(f.read(), data)
+
+
 class AbstractBadCrcTests:
     def test_testzip_with_bad_crc(self):
         """Tests that files with bad CRCs return their name from testzip."""
diff --git a/Lib/test/test_zipimport.py b/Lib/test/test_zipimport.py
index d448e3df5d7..fc55ef6fa16 100644
--- a/Lib/test/test_zipimport.py
+++ b/Lib/test/test_zipimport.py
@@ -9,13 +9,12 @@
 import time
 import unittest
 import unittest.mock
-import warnings
 
 from test import support
 from test.support import import_helper
 from test.support import os_helper
 
-from zipfile import ZipFile, ZipInfo, ZIP_STORED, ZIP_DEFLATED
+from zipfile import ZipFile, ZipInfo, ZIP_STORED, ZIP_DEFLATED, ZIP_ZSTANDARD
 
 import zipimport
 import linecache
@@ -61,7 +60,6 @@ def module_path_to_dotted_name(path):
 TEMP_ZIP = os.path.abspath("junk95142.zip")
 TEST_DATA_DIR = os.path.join(os.path.dirname(__file__), "zipimport_data")
 
-pyc_file = importlib.util.cache_from_source(TESTMOD + '.py')
 pyc_ext = '.pyc'
 
 
@@ -194,19 +192,38 @@ def testAFakeZlib(self):
         # occur in that case (builtin modules are always found first),
         # so we'll simply skip it then. Bug #765456.
         #
-        if "zlib" in sys.builtin_module_names:
-            self.skipTest('zlib is a builtin module')
-        if "zlib" in sys.modules:
-            del sys.modules["zlib"]
-        files = {"zlib.py": test_src}
+        if self.compression == ZIP_DEFLATED:
+            mod_name = "zlib"
+            if zipimport._zlib_decompress:  # validate attr name
+                # reset the cached import to avoid test order dependencies
+                zipimport._zlib_decompress = None  # reset cache
+        elif self.compression == ZIP_ZSTANDARD:
+            mod_name = "_zstd"
+            if zipimport._zstd_decompressor_class:  # validate attr name
+                # reset the cached import to avoid test order dependencies
+                zipimport._zstd_decompressor_class = None
+        else:
+            mod_name = "zlib"  # the ZIP_STORED case below
+
+        if mod_name in sys.builtin_module_names:
+            self.skipTest(f"{mod_name} is a builtin module")
+        if mod_name in sys.modules:
+            del sys.modules[mod_name]
+        files = {f"{mod_name}.py": test_src}
         try:
-            self.doTest(".py", files, "zlib")
+            self.doTest(".py", files, mod_name)
         except ImportError:
-            if self.compression != ZIP_DEFLATED:
-                self.fail("expected test to not raise ImportError")
-        else:
             if self.compression != ZIP_STORED:
-                self.fail("expected test to raise ImportError")
+                # Expected - fake compression module can't decompress
+                pass
+            else:
+                self.fail("expected test to not raise ImportError for uncompressed")
+        else:
+            if self.compression == ZIP_STORED:
+                # Expected - no compression needed, so fake module works
+                pass
+            else:
+                self.fail("expected test to raise ImportError for compressed zip with fake compression module")
 
     def testPy(self):
         files = {TESTMOD + ".py": test_src}
@@ -556,13 +573,6 @@ def testZipImporterMethods(self):
         self.assertEqual(zi.archive, TEMP_ZIP)
         self.assertTrue(zi.is_package(TESTPACK))
 
-        # PEP 302
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-
-            mod = zi.load_module(TESTPACK)
-            self.assertEqual(zi.get_filename(TESTPACK), mod.__file__)
-
         # PEP 451
         spec = zi.find_spec('spam')
         self.assertIsNotNone(spec)
@@ -577,6 +587,8 @@ def testZipImporterMethods(self):
         spec.loader.exec_module(mod)
         self.assertEqual(zi.get_filename(TESTPACK), mod.__file__)
 
+        sys.path.insert(0, TEMP_ZIP)
+
         existing_pack_path = importlib.import_module(TESTPACK).__path__[0]
         expected_path_path = os.path.join(TEMP_ZIP, TESTPACK)
         self.assertEqual(existing_pack_path, expected_path_path)
@@ -675,11 +687,6 @@ def testZipImporterMethodsInSubDirectory(self):
         self.assertEqual(zi.archive, TEMP_ZIP)
         self.assertEqual(zi.prefix, packdir)
         self.assertTrue(zi.is_package(TESTPACK2))
-        # PEP 302
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore", DeprecationWarning)
-            mod = zi.load_module(TESTPACK2)
-            self.assertEqual(zi.get_filename(TESTPACK2), mod.__file__)
         # PEP 451
         spec = zi.find_spec(TESTPACK2)
         mod = importlib.util.module_from_spec(spec)
@@ -702,9 +709,12 @@ def testZipImporterMethodsInSubDirectory(self):
         self.assertEqual(
             spec.loader.get_filename(TESTMOD), load_mod.__file__)
 
+        sys.path.insert(0, TEMP_ZIP + os.sep + TESTPACK)
+
         mod_path = TESTPACK2 + os.sep + TESTMOD
         mod_name = module_path_to_dotted_name(mod_path)
         mod = importlib.import_module(mod_name)
+
         self.assertTrue(mod_name in sys.modules)
         self.assertIsNone(zi.get_source(TESTPACK2))
         self.assertIsNone(zi.get_source(mod_path))
@@ -1010,10 +1020,15 @@ def assertDataEntry(name):
 
 
 @support.requires_zlib()
-class CompressedZipImportTestCase(UncompressedZipImportTestCase):
+class DeflateCompressedZipImportTestCase(UncompressedZipImportTestCase):
     compression = ZIP_DEFLATED
 
 
+@support.requires_zstd()
+class ZStdCompressedZipImportTestCase(UncompressedZipImportTestCase):
+    compression = ZIP_ZSTANDARD
+
+
 class BadFileZipImportTestCase(unittest.TestCase):
     def assertZipFailure(self, filename):
         self.assertRaises(zipimport.ZipImportError,
@@ -1071,9 +1086,6 @@ def _testBogusZipFile(self):
         z = zipimport.zipimporter(TESTMOD)
 
         try:
-            with warnings.catch_warnings():
-                warnings.simplefilter("ignore", DeprecationWarning)
-                self.assertRaises(TypeError, z.load_module, None)
             self.assertRaises(TypeError, z.find_module, None)
             self.assertRaises(TypeError, z.find_spec, None)
             self.assertRaises(TypeError, z.exec_module, None)
@@ -1084,10 +1096,6 @@ def _testBogusZipFile(self):
 
             error = zipimport.ZipImportError
             self.assertIsNone(z.find_spec('abc'))
-
-            with warnings.catch_warnings():
-                warnings.simplefilter("ignore", DeprecationWarning)
-                self.assertRaises(error, z.load_module, 'abc')
             self.assertRaises(error, z.get_code, 'abc')
             self.assertRaises(OSError, z.get_data, 'abc')
             self.assertRaises(error, z.get_source, 'abc')
diff --git a/Lib/threading.py b/Lib/threading.py
index c03b0b5370c..abac31e2588 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -29,6 +29,7 @@
            'Barrier', 'BrokenBarrierError', 'Timer', 'ThreadError',
            'setprofile', 'settrace', 'local', 'stack_size',
            'excepthook', 'ExceptHookArgs', 'gettrace', 'getprofile',
+           'serialize_iterator', 'synchronized_iterator', 'concurrent_tee',
            'setprofile_all_threads','settrace_all_threads']
 
 # Rename some stuff so "from threading import *" is safe
@@ -123,7 +124,7 @@ def gettrace():
 
 Lock = _LockType
 
-def RLock(*args, **kwargs):
+def RLock():
     """Factory function that returns a new reentrant lock.
 
     A reentrant lock must be released by the thread that acquired it. Once a
@@ -132,16 +133,9 @@ def RLock(*args, **kwargs):
     acquired it.
 
     """
-    if args or kwargs:
-        import warnings
-        warnings.warn(
-            'Passing arguments to RLock is deprecated and will be removed in 3.15',
-            DeprecationWarning,
-            stacklevel=2,
-        )
     if _CRLock is None:
-        return _PyRLock(*args, **kwargs)
-    return _CRLock(*args, **kwargs)
+        return _PyRLock()
+    return _CRLock()
 
 class _RLock:
     """This class implements reentrant lock objects.
@@ -849,6 +843,148 @@ class BrokenBarrierError(RuntimeError):
     pass
 
 
+## Synchronization tools for iterators #####################
+
+class serialize_iterator:
+    """Wrap a non-concurrent iterator with a lock to enforce sequential access.
+
+    Applies a non-reentrant lock around calls to __next__.  If the
+    wrapped iterator also defines send(), throw(), or close(), those
+    calls are serialized as well.
+
+    Allows iterator and generator instances to be shared by multiple consumer
+    threads.
+
+    For example, itertools.count does not make thread-safe instances,
+    but that is easily fixed with:
+
+        atomic_counter = serialize_iterator(itertools.count())
+
+    """
+
+    __slots__ = ('_iterator', '_lock')
+
+    def __init__(self, iterable):
+        self._iterator = iter(iterable)
+        self._lock = Lock()
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        with self._lock:
+            return next(self._iterator)
+
+    def send(self, value, /):
+        """Send a value to a generator.
+
+        Raises AttributeError if not a generator.
+        """
+        with self._lock:
+            return self._iterator.send(value)
+
+    def throw(self, *args):
+        """Call throw() on a generator.
+
+        Raises AttributeError if not a generator.
+        """
+        with self._lock:
+            return self._iterator.throw(*args)
+
+    def close(self):
+        """Call close() on a generator.
+
+        Raises AttributeError if not a generator.
+        """
+        with self._lock:
+            return self._iterator.close()
+
+
+def synchronized_iterator(func):
+    """Wrap an iterator-returning callable to make its iterators thread-safe.
+
+    Existing itertools and more-itertools can be wrapped so that their
+    iterator instances are serialized.
+
+    For example, itertools.count does not make thread-safe instances,
+    but that is easily fixed with:
+
+        atomic_counter = synchronized_iterator(itertools.count)
+
+    Can also be used as a decorator for generator function definitions
+    so that the generator instances are serialized::
+
+        import time
+
+        @synchronized_iterator
+        def enumerate_and_timestamp(iterable):
+            for count, value in enumerate(iterable):
+                yield count, time.time_ns(), value
+
+    """
+
+    from functools import wraps
+
+    @wraps(func)
+    def inner(*args, **kwargs):
+        iterator = func(*args, **kwargs)
+        return serialize_iterator(iterator)
+
+    return inner
+
+
+def concurrent_tee(iterable, n=2):
+    """Variant of itertools.tee() but with guaranteed threading semantics.
+
+    Takes a non-threadsafe iterator as an input and creates concurrent
+    tee objects for other threads to have reliable independent copies of
+    the data stream.
+
+    The new iterators are only thread-safe if consumed within a single thread.
+    To share just one of the new iterators across multiple threads, wrap it
+    with threading.serialize_iterator().
+    """
+
+    if n < 0:
+        raise ValueError("n must be a non-negative integer")
+    if n == 0:
+        return ()
+    iterator = _concurrent_tee(iterable)
+    result = [iterator]
+    for _ in range(n - 1):
+        result.append(_concurrent_tee(iterator))
+    return tuple(result)
+
+
+class _concurrent_tee:
+    __slots__ = ('iterator', 'link', 'lock')
+
+    def __init__(self, iterable):
+        if isinstance(iterable, _concurrent_tee):
+            self.iterator = iterable.iterator
+            self.link = iterable.link
+            self.lock = iterable.lock
+        else:
+            self.iterator = iter(iterable)
+            self.link = [None, None]
+            self.lock = Lock()
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        link = self.link
+        if link[1] is None:
+            with self.lock:
+                if link[1] is None:
+                    link[0] = next(self.iterator)
+                    link[1] = [None, None]
+        value, self.link = link
+        return value
+
+############################################################
+
+
 # Helper to generate new thread names
 _counter = _count(1).__next__
 def _newname(name_template):
@@ -1565,8 +1701,9 @@ def _shutdown():
     # normally - that won't happen until the interpreter is nearly dead. So
     # mark it done here.
     if _main_thread._os_thread_handle.is_done() and _is_main_interpreter():
-        # _shutdown() was already called
-        return
+        # _shutdown() was already called, but threads might have started
+        # in the meantime.
+        return _thread_shutdown()
 
     global _SHUTTING_DOWN
     _SHUTTING_DOWN = True
diff --git a/Lib/tokenize.py b/Lib/tokenize.py
index 1f31258ce36..3545d92c4f5 100644
--- a/Lib/tokenize.py
+++ b/Lib/tokenize.py
@@ -35,6 +35,7 @@
 from token import *
 from token import EXACT_TOKEN_TYPES
 import _tokenize
+lazy import _colorize
 
 cookie_re = re.compile(br'^[ \t\f]*#.*?coding[:=][ \t]*([-\w.]+)', re.ASCII)
 blank_re = re.compile(br'^[ \t\f]*(?:[#\r\n]|$)', re.ASCII)
@@ -403,7 +404,7 @@ def find_cookie(line):
             return None
         encoding = _get_normal_name(match.group(1).decode())
         try:
-            codec = lookup(encoding)
+            lookup(encoding)
         except LookupError:
             # This behaviour mimics the Python interpreter
             if filename is None:
@@ -505,6 +506,56 @@ def generate_tokens(readline):
     """
     return _generate_tokens_from_c_tokenizer(readline, extra_tokens=True)
 
+
+def _get_token_colors(syntax, tokenize):
+    """Map token type numbers to theme colors."""
+    return frozendict({
+        COMMENT: syntax.comment,
+        DEDENT: tokenize.whitespace,
+        ENCODING: tokenize.whitespace,
+        ENDMARKER: tokenize.whitespace,
+        ERRORTOKEN: tokenize.error,
+        FSTRING_START: syntax.string,
+        FSTRING_MIDDLE: syntax.string,
+        FSTRING_END: syntax.string,
+        INDENT: tokenize.whitespace,
+        NAME: syntax.reset,
+        NEWLINE: tokenize.whitespace,
+        NL: tokenize.whitespace,
+        NUMBER: syntax.number,
+        OP: syntax.op,
+        SOFT_KEYWORD: syntax.soft_keyword,
+        STRING: syntax.string,
+        TSTRING_START: syntax.string,
+        TSTRING_MIDDLE: syntax.string,
+        TSTRING_END: syntax.string,
+    })
+
+
+def _format_tokens(tokens, *, color=False, exact=False):
+    theme = _colorize.get_theme(force_no_color=not color)
+    s = theme.syntax
+    t = theme.tokenize
+    token_colors = _get_token_colors(s, t)
+    for token in tokens:
+        token_range = (
+            f"{t.position}{token.start[0]}"
+            f"{t.delimiter},{t.position}{token.start[1]}"
+            f"{t.delimiter}-"
+            f"{t.position}{token.end[0]}"
+            f"{t.delimiter},{t.position}{token.end[1]}"
+            f"{t.delimiter}:"
+        )
+        token_color = token_colors.get(token.type, s.reset)
+        token_name = tok_name[token.exact_type if exact else token.type]
+        visible_range = f"{token.start[0]},{token.start[1]}-{token.end[0]},{token.end[1]}:"
+        yield (
+            f"{token_range}{' ' * (20 - len(visible_range))}"
+            f"{token_color}{token_name:<15}"
+            f"{s.reset}{token.string!r:<15}"
+        )
+
+
 def _main(args=None):
     import argparse
 
@@ -524,10 +575,10 @@ def error(message, filename=None, location=None):
         sys.exit(1)
 
     # Parse the arguments and options
-    parser = argparse.ArgumentParser(color=True)
+    parser = argparse.ArgumentParser()
     parser.add_argument(dest='filename', nargs='?',
                         metavar='filename.py',
-                        help='the file to tokenize; defaults to stdin')
+                        help='the file to tokenize; defaults to `stdin`')
     parser.add_argument('-e', '--exact', dest='exact', action='store_true',
                         help='display token names using the exact type')
     args = parser.parse_args(args)
@@ -545,13 +596,8 @@ def error(message, filename=None, location=None):
 
 
         # Output the tokenization
-        for token in tokens:
-            token_type = token.type
-            if args.exact:
-                token_type = token.exact_type
-            token_range = "%d,%d-%d,%d:" % (token.start + token.end)
-            print("%-20s%-15s%-15r" %
-                  (token_range, tok_name[token_type], token.string))
+        for line in _format_tokens(tokens, color=True, exact=args.exact):
+            print(line)
     except IndentationError as err:
         line, column = err.args[1][1:3]
         error(err.args[0], filename, (line, column))
diff --git a/Lib/traceback.py b/Lib/traceback.py
index 227ca8efa17..d16ab468db9 100644
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -1,18 +1,29 @@
 """Extract, format and print information about Python stack traces."""
 
 import collections.abc
+import functools
 import itertools
 import linecache
+import os
+import re
 import sys
 import textwrap
+import types
 import warnings
 import codeop
 import keyword
 import tokenize
 import io
-import _colorize
+import importlib.util
+import pathlib
 
 from contextlib import suppress
+lazy import _colorize
+
+try:
+    from _missing_stdlib_info import _MISSING_STDLIB_MODULE_MESSAGES
+except ImportError:
+    _MISSING_STDLIB_MODULE_MESSAGES = {}
 
 __all__ = ['extract_stack', 'extract_tb', 'format_exception',
            'format_exception_only', 'format_list', 'format_stack',
@@ -21,6 +32,36 @@
            'FrameSummary', 'StackSummary', 'TracebackException',
            'walk_stack', 'walk_tb', 'print_list']
 
+
+class _ShutdownTheme:
+    """Empty stand-in if `_colorize` cannot be imported during late shutdown."""
+    def __getattr__(self, _): return self
+    def __getitem__(self, _): return ""
+    def __format__(self, _): return ""
+    def __str__(self): return ""
+    def __add__(self, other): return other
+    __radd__ = __add__
+
+
+_shutdown_theme = _ShutdownTheme()
+
+
+def _safe_get_theme(*, force_color=False, force_no_color=False):
+    try:
+        return _colorize.get_theme(
+            force_color=force_color, force_no_color=force_no_color
+        )
+    except ImportError:
+        return _shutdown_theme
+
+
+def _safe_can_colorize(*, file=None):
+    try:
+        return _colorize.can_colorize(file=file)
+    except ImportError:
+        return False
+
+
 #
 # Formatting and printing lists of traceback lines.
 #
@@ -137,9 +178,10 @@ def print_exception(exc, /, value=_sentinel, tb=_sentinel, limit=None, \
 BUILTIN_EXCEPTION_LIMIT = object()
 
 
-def _print_exception_bltin(exc, /):
-    file = sys.stderr if sys.stderr is not None else sys.__stderr__
-    colorize = _colorize.can_colorize(file=file)
+def _print_exception_bltin(exc, file=None, /):
+    if file is None:
+        file = sys.stderr if sys.stderr is not None else sys.__stderr__
+    colorize = _safe_can_colorize(file=file)
     return print_exception(exc, limit=BUILTIN_EXCEPTION_LIMIT, file=file, colorize=colorize)
 
 
@@ -187,9 +229,9 @@ def _format_final_exc_line(etype, value, *, insert_final_newline=True, colorize=
     valuestr = _safe_string(value, 'exception')
     end_char = "\n" if insert_final_newline else ""
     if colorize:
-        theme = _colorize.get_theme(force_color=True).traceback
+        theme = _safe_get_theme(force_color=True).traceback
     else:
-        theme = _colorize.get_theme(force_no_color=True).traceback
+        theme = _safe_get_theme(force_no_color=True).traceback
     if value is None or not valuestr:
         line = f"{theme.type}{etype}{theme.reset}{end_char}"
     else:
@@ -205,9 +247,9 @@ def _safe_string(value, what, func=str):
 
 # --
 
-def print_exc(limit=None, file=None, chain=True):
+def print_exc(limit=None, file=None, chain=True, **kwargs):
     """Shorthand for 'print_exception(sys.exception(), limit=limit, file=file, chain=chain)'."""
-    print_exception(sys.exception(), limit=limit, file=file, chain=chain)
+    print_exception(sys.exception(), limit=limit, file=file, chain=chain, **kwargs)
 
 def format_exc(limit=None, chain=True):
     """Like print_exc() but return a string."""
@@ -286,6 +328,12 @@ class FrameSummary:
       of code that was running when the frame was captured.
     - :attr:`locals` Either None if locals were not supplied, or a dict
       mapping the name to the repr() of the variable.
+    - :attr:`end_lineno` The last line number of the source code for this frame.
+      By default, it is set to lineno and indexation starts from 1.
+    - :attr:`colno` The column number of the source code for this frame.
+      By default, it is None and indexation starts from 0.
+    - :attr:`end_colno` The last column number of the source code for this frame.
+      By default, it is None and indexation starts from 0.
     """
 
     __slots__ = ('filename', 'lineno', 'end_lineno', 'colno', 'end_colno',
@@ -536,9 +584,9 @@ def format_frame_summary(self, frame_summary, **kwargs):
         if frame_summary.filename.startswith("<stdin-") and frame_summary.filename.endswith('>'):
             filename = "<stdin>"
         if colorize:
-            theme = _colorize.get_theme(force_color=True).traceback
+            theme = _safe_get_theme(force_color=True).traceback
         else:
-            theme = _colorize.get_theme(force_no_color=True).traceback
+            theme = _safe_get_theme(force_no_color=True).traceback
         row.append(
             '  File {}"{}"{}, line {}{}{}, in {}{}{}\n'.format(
                 theme.filename,
@@ -667,12 +715,12 @@ def output_line(lineno):
                         colorized_line_parts = []
                         colorized_carets_parts = []
 
-                        for color, group in itertools.groupby(itertools.zip_longest(line, carets, fillvalue=""), key=lambda x: x[1]):
+                        for color, group in itertools.groupby(_zip_display_width(line, carets), key=lambda x: x[1]):
                             caret_group = list(group)
-                            if color == "^":
+                            if "^" in color:
                                 colorized_line_parts.append(theme.error_highlight + "".join(char for char, _ in caret_group) + theme.reset)
                                 colorized_carets_parts.append(theme.error_highlight + "".join(caret for _, caret in caret_group) + theme.reset)
-                            elif color == "~":
+                            elif "~" in color:
                                 colorized_line_parts.append(theme.error_range + "".join(char for char, _ in caret_group) + theme.reset)
                                 colorized_carets_parts.append(theme.error_range + "".join(caret for _, caret in caret_group) + theme.reset)
                             else:
@@ -954,7 +1002,54 @@ def setup_positions(expr, force_valid=True):
 
     return None
 
-_WIDE_CHAR_SPECIFIERS = "WF"
+
+def _zip_display_width(line, carets):
+    carets = iter(carets)
+    if line.isascii() and '\x1a' not in line:
+        for char in line:
+            yield char, next(carets, "")
+        return
+
+    import unicodedata
+    for char in unicodedata.iter_graphemes(line):
+        char = str(char)
+        char_width = _display_width(char)
+        yield char, "".join(itertools.islice(carets, char_width))
+
+
+@functools.cache
+def _str_width(c: str) -> int:
+    # copied from _pyrepl.utils to fix gh-130273
+
+    if ord(c) < 128:
+        return 1
+    import unicodedata
+    # gh-139246 for zero-width joiner and combining characters
+    if unicodedata.combining(c):
+        return 0
+    category = unicodedata.category(c)
+    if category == "Cf" and c != "\u00ad":
+        return 0
+    w = unicodedata.east_asian_width(c)
+    if w in ("N", "Na", "H", "A"):
+        return 1
+    return 2
+
+
+_ANSI_ESCAPE_SEQUENCE = re.compile(r"\x1b\[[ -@]*[A-~]")
+
+
+def _wlen(s: str) -> int:
+    # copied from _pyrepl.utils to fix gh-130273
+
+    if len(s) == 1 and s != "\x1a":
+        return _str_width(s)
+    length = sum(_str_width(i) for i in s)
+    # remove lengths of any escape sequences
+    sequence = _ANSI_ESCAPE_SEQUENCE.findall(s)
+    ctrl_z_cnt = s.count("\x1a")
+    return length - sum(len(i) for i in sequence) + ctrl_z_cnt
+
 
 def _display_width(line, offset=None):
     """Calculate the amount of width space the given source
@@ -962,19 +1057,14 @@ def _display_width(line, offset=None):
     width output device. Supports wide unicode characters and emojis."""
 
     if offset is None:
-        offset = len(line)
-
-    # Fast track for ASCII-only strings
-    if line.isascii():
-        return offset
+        return _wlen(line)
 
-    import unicodedata
+    return _wlen(line[:offset])
 
-    return sum(
-        2 if unicodedata.east_asian_width(char) in _WIDE_CHAR_SPECIFIERS else 1
-        for char in line[:offset]
-    )
 
+def _format_note(note, indent, theme):
+    for l in note.split("\n"):
+        yield f"{indent}{theme.note}{l}{theme.reset}\n"
 
 
 class _ExceptionPrintContext:
@@ -1098,20 +1188,62 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
             wrong_name = getattr(exc_value, "name_from", None)
             suggestion = _compute_suggestion_error(exc_value, exc_traceback, wrong_name)
             if suggestion:
-                self._str += f". Did you mean: '{suggestion}'?"
-        elif exc_type and issubclass(exc_type, (NameError, AttributeError)) and \
+                if suggestion.isascii():
+                    self._str += f". Did you mean: '{suggestion}'?"
+                else:
+                    self._str += f". Did you mean: '{suggestion}' ({suggestion!a})?"
+        elif exc_type and issubclass(exc_type, ModuleNotFoundError):
+            module_name = getattr(exc_value, "name", None)
+            if module_name in sys.stdlib_module_names:
+                message = _MISSING_STDLIB_MODULE_MESSAGES.get(
+                    module_name,
+                    f"Standard library module {module_name!r} was not found"
+                )
+                self._str = message
+            elif sys.flags.no_site:
+                self._str += (". Site initialization is disabled, did you forget to "
+                    + "add the site-packages directory to sys.path "
+                    + "or to enable your virtual environment?")
+            elif abi_tag := _find_incompatible_extension_module(module_name):
+                self._str += (
+                    ". Although a module with this name was found for a "
+                    f"different Python version ({abi_tag})."
+                )
+            else:
+                suggestion = _compute_suggestion_error(exc_value, exc_traceback, module_name)
+                if suggestion:
+                    self._str += f". Did you mean: '{suggestion}'?"
+        elif exc_type and issubclass(exc_type, AttributeError) and \
+                getattr(exc_value, "name", None) is not None:
+            wrong_name = getattr(exc_value, "name", None)
+            # Check cross-language/wrong-type hints first (more specific),
+            # then fall back to Levenshtein distance suggestions.
+            hint = None
+            if hasattr(exc_value, 'obj'):
+                hint = _get_cross_language_hint(exc_value.obj, wrong_name)
+            if hint:
+                self._str += f". {hint}"
+            else:
+                suggestion = _compute_suggestion_error(exc_value, exc_traceback, wrong_name)
+                if suggestion:
+                    if suggestion.isascii():
+                        self._str += f". Did you mean '.{suggestion}' instead of '.{wrong_name}'?"
+                    else:
+                        self._str += f". Did you mean '.{suggestion}' ({suggestion!a}) instead of '.{wrong_name}' ({wrong_name!a})?"
+        elif exc_type and issubclass(exc_type, NameError) and \
                 getattr(exc_value, "name", None) is not None:
             wrong_name = getattr(exc_value, "name", None)
             suggestion = _compute_suggestion_error(exc_value, exc_traceback, wrong_name)
             if suggestion:
-                self._str += f". Did you mean: '{suggestion}'?"
-            if issubclass(exc_type, NameError):
-                wrong_name = getattr(exc_value, "name", None)
-                if wrong_name is not None and wrong_name in sys.stdlib_module_names:
-                    if suggestion:
-                        self._str += f" Or did you forget to import '{wrong_name}'?"
-                    else:
-                        self._str += f". Did you forget to import '{wrong_name}'?"
+                if suggestion.isascii():
+                    self._str += f". Did you mean: '{suggestion}'?"
+                else:
+                    self._str += f". Did you mean: '{suggestion}' ({suggestion!a})?"
+            if wrong_name is not None and wrong_name in sys.stdlib_module_names:
+                if suggestion:
+                    self._str += f" Or did you forget to import '{wrong_name}'?"
+                else:
+                    self._str += f". Did you forget to import '{wrong_name}'?"
         if lookup_lines:
             self._load_lines()
         self.__suppress_context__ = \
@@ -1240,6 +1372,10 @@ def format_exception_only(self, *, show_group=False, _depth=0, **kwargs):
         well, recursively, with indentation relative to their nesting depth.
         """
         colorize = kwargs.get("colorize", False)
+        if colorize:
+            theme = _safe_get_theme(force_color=True).traceback
+        else:
+            theme = _safe_get_theme(force_no_color=True).traceback
 
         indent = 3 * _depth * ' '
         if not self._have_exc_type:
@@ -1268,9 +1404,10 @@ def format_exception_only(self, *, show_group=False, _depth=0, **kwargs):
         ):
             for note in self.__notes__:
                 note = _safe_string(note, 'note')
-                yield from [indent + l + '\n' for l in note.split('\n')]
+                yield from _format_note(note, indent, theme)
         elif self.__notes__ is not None:
-            yield indent + "{}\n".format(_safe_string(self.__notes__, '__notes__', func=repr))
+            note = _safe_string(self.__notes__, '__notes__', func=repr)
+            yield from _format_note(note, indent, theme)
 
         if self.exceptions and show_group:
             for ex in self.exceptions:
@@ -1315,6 +1452,15 @@ def _find_keyword_typos(self):
         if len(error_code) > 1024:
             return
 
+        # If the original code doesn't raise SyntaxError, we can't validate
+        # that a keyword replacement actually fixes anything
+        try:
+            codeop.compile_command(error_code, symbol="exec", flags=codeop.PyCF_ONLY_AST)
+        except SyntaxError:
+            pass  # Good - the original code has a syntax error we might fix
+        else:
+            return  # Original code compiles or is incomplete - can't validate fixes
+
         error_lines = error_code.splitlines()
         tokens = tokenize.generate_tokens(io.StringIO(error_code).readline)
         tokens_left_to_process = 10
@@ -1377,9 +1523,9 @@ def _format_syntax_error(self, stype, **kwargs):
         # Show exactly where the problem was found.
         colorize = kwargs.get("colorize", False)
         if colorize:
-            theme = _colorize.get_theme(force_color=True).traceback
+            theme = _safe_get_theme(force_color=True).traceback
         else:
-            theme = _colorize.get_theme(force_no_color=True).traceback
+            theme = _safe_get_theme(force_no_color=True).traceback
         filename_suffix = ''
         if self.lineno is not None:
             yield '  File {}"{}"{}, line {}{}{}\n'.format(
@@ -1430,10 +1576,11 @@ def _format_syntax_error(self, stype, **kwargs):
                 # Convert 1-based column offset to 0-based index into stripped text
                 colno = offset - 1 - spaces
                 end_colno = end_offset - 1 - spaces
-                caretspace = ' '
                 if colno >= 0:
-                    # non-space whitespace (likes tabs) must be kept for alignment
-                    caretspace = ((c if c.isspace() else ' ') for c in ltext[:colno])
+                    # Calculate display width to account for wide characters
+                    dp_colno = _display_width(ltext, colno)
+                    highlighted = ltext[colno:end_colno]
+                    caret_count = _display_width(highlighted) if highlighted else (end_colno - colno)
                     start_color = end_color = ""
                     if colorize:
                         # colorize from colno to end_colno
@@ -1446,9 +1593,9 @@ def _format_syntax_error(self, stype, **kwargs):
                         end_color = theme.reset
                     yield '    {}\n'.format(ltext)
                     yield '    {}{}{}{}\n'.format(
-                        "".join(caretspace),
+                        ' ' * dp_colno,
                         start_color,
-                        ('^' * (end_colno - colno)),
+                        '^' * caret_count,
                         end_color,
                     )
                 else:
@@ -1579,6 +1726,62 @@ def print(self, *, file=None, chain=True, **kwargs):
 _MOVE_COST = 2
 _CASE_COST = 1
 
+# Cross-language method suggestions for builtin types.
+# Consulted as a fallback when Levenshtein-based suggestions find no match.
+#
+# Inclusion criteria:
+#
+#   1. Must have evidence of real cross-language confusion (Stack Overflow
+#      traffic, bug reports in production repos, developer survey data).
+#   2. Must not be catchable by Levenshtein distance (too different from
+#      the correct Python method name).
+#
+# Each entry maps a wrong method name to a list of (type, suggestion, is_raw)
+# tuples. The lookup checks isinstance() so subclasses are also matched.
+# If is_raw is False, the suggestion is wrapped in "Did you mean '.X'?".
+# If is_raw is True, the suggestion is rendered as-is.
+#
+# See https://github.com/python/cpython/issues/146406.
+_CROSS_LANGUAGE_HINTS = frozendict({
+    # list -- JavaScript/Ruby equivalents
+    "push": ((list, "append", False),),
+    "concat": ((list, "extend", False),),
+    # list -- Java/C# equivalents
+    "addAll": ((list, "extend", False),),
+    "contains": ((list, "Use 'x in list'.", True),),
+    # list -- wrong-type suggestion (user expected a set)
+    "add": ((list, "Did you mean to use a 'set' object?", True),
+            (frozenset, "Did you mean to use a 'set' object?", True)),
+    # str -- JavaScript equivalents
+    "toUpperCase": ((str, "upper", False),),
+    "toLowerCase": ((str, "lower", False),),
+    "trimStart": ((str, "lstrip", False),),
+    "trimEnd": ((str, "rstrip", False),),
+    # dict -- Java/JavaScript equivalents
+    "keySet": ((dict, "keys", False),),
+    "entrySet": ((dict, "items", False),),
+    "entries": ((dict, "items", False),),
+    "putAll": ((dict, "update", False),),
+    "put": ((dict, "Use d[k] = v.", True),),
+    # tuple -- mutable method on immutable type (user expected a list)
+    "append": ((tuple, "Did you mean to use a 'list' object?", True),),
+    "extend": ((tuple, "Did you mean to use a 'list' object?", True),),
+    "insert": ((tuple, "Did you mean to use a 'list' object?", True),),
+    "remove": ((tuple, "Did you mean to use a 'list' object?", True),
+               (frozenset, "Did you mean to use a 'set' object?", True)),
+    # frozenset -- mutable method on immutable type (user expected a set)
+    "discard": ((frozenset, "Did you mean to use a 'set' object?", True),),
+    # frozendict -- mutable method on immutable type (user expected a dict)
+    "update": ((frozenset, "Did you mean to use a 'set' object?", True),
+               (frozendict, "Did you mean to use a 'dict' object?", True)),
+    # float -- bitwise operators belong to int
+    "__or__": ((float, "Did you mean to use an 'int' object? Bitwise operators are not supported by 'float'.", True),),
+    "__and__": ((float, "Did you mean to use an 'int' object? Bitwise operators are not supported by 'float'.", True),),
+    "__xor__": ((float, "Did you mean to use an 'int' object? Bitwise operators are not supported by 'float'.", True),),
+    "__lshift__": ((float, "Did you mean to use an 'int' object? Bitwise operators are not supported by 'float'.", True),),
+    "__rshift__": ((float, "Did you mean to use an 'int' object? Bitwise operators are not supported by 'float'.", True),),
+})
+
 
 def _substitution_cost(ch_a, ch_b):
     if ch_a == ch_b:
@@ -1588,19 +1791,100 @@ def _substitution_cost(ch_a, ch_b):
     return _MOVE_COST
 
 
+def _is_lazy_import(obj, attr_name):
+    """Check if attr_name in obj's __dict__ is a lazy import.
+
+    Returns True if obj is a module and the attribute is a LazyImportType,
+    False otherwise. This avoids triggering module loading when computing
+    suggestions for AttributeError.
+    """
+    if not isinstance(obj, types.ModuleType):
+        return False
+    obj_dict = getattr(obj, '__dict__', None)
+    if obj_dict is None:
+        return False
+    attr_value = obj_dict.get(attr_name)
+    return isinstance(attr_value, types.LazyImportType)
+
+
+def _check_for_nested_attribute(obj, wrong_name, attrs):
+    """Check if any attribute of obj has the wrong_name as a nested attribute.
+
+    Returns the first nested attribute suggestion found, or None.
+    Limited to checking 20 attributes.
+    Only considers non-descriptor outer attributes to avoid executing
+    arbitrary code. Checks nested attributes statically so descriptors such
+    as properties can still be suggested without invoking them.
+    Skips lazy imports to avoid triggering module loading.
+    """
+    from inspect import getattr_static
+
+    # Check for nested attributes (only one level deep)
+    attrs_to_check = [x for x in attrs if not x.startswith('_')][:20]  # Limit number of attributes to check
+    for attr_name in attrs_to_check:
+        with suppress(Exception):
+            # Check if attr_name is a descriptor - if so, skip it
+            attr_from_class = getattr_static(type(obj), attr_name, _sentinel)
+            if attr_from_class is not _sentinel and hasattr(attr_from_class, '__get__'):
+                continue  # Skip descriptors to avoid executing arbitrary code
+
+            # Skip lazy imports to avoid triggering module loading
+            if _is_lazy_import(obj, attr_name):
+                continue
+
+            # Safe to get the attribute since it's not a descriptor
+            attr_obj = getattr(obj, attr_name)
+
+            if _is_lazy_import(attr_obj, wrong_name):
+                continue
+
+            if getattr_static(attr_obj, wrong_name, _sentinel) is not _sentinel:
+                return f"{attr_name}.{wrong_name}"
+
+    return None
+
+
+def _get_cross_language_hint(obj, wrong_name):
+    """Check if wrong_name is a common method name from another language,
+    a mutable method on an immutable type, or a method tried on None.
+
+    Uses isinstance() so subclasses of builtin types also get hints.
+    Returns a formatted hint string, or None.
+    """
+    entries = _CROSS_LANGUAGE_HINTS.get(wrong_name)
+    if entries is None:
+        return None
+    for check_type, hint, is_raw in entries:
+        if isinstance(obj, check_type):
+            if is_raw:
+                return hint
+            return f"Did you mean '.{hint}'?"
+    return None
+
+
 def _get_safe___dir__(obj):
     # Use obj.__dir__() to avoid a TypeError when calling dir(obj).
     # See gh-131001 and gh-139933.
+    # Also filters out lazy imports to avoid triggering module loading.
     try:
         d = obj.__dir__()
     except TypeError:  # when obj is a class
         d = type(obj).__dir__(obj)
-    return sorted(x for x in d if isinstance(x, str))
+    return sorted(
+        x for x in d if isinstance(x, str) and not _is_lazy_import(obj, x)
+    )
 
 
 def _compute_suggestion_error(exc_value, tb, wrong_name):
     if wrong_name is None or not isinstance(wrong_name, str):
         return None
+    not_normalized = False
+    if not wrong_name.isascii():
+        from unicodedata import normalize
+        normalized_name = normalize('NFKC', wrong_name)
+        if normalized_name != wrong_name:
+            not_normalized = True
+            wrong_name = normalized_name
     if isinstance(exc_value, AttributeError):
         obj = exc_value.obj
         try:
@@ -1616,6 +1900,18 @@ def _compute_suggestion_error(exc_value, tb, wrong_name):
                 d = [x for x in d if x[:1] != '_']
         except Exception:
             return None
+    elif isinstance(exc_value, ModuleNotFoundError):
+        try:
+            if parent_name := wrong_name.rpartition('.')[0]:
+                parent = importlib.util.find_spec(parent_name)
+            else:
+                parent = None
+            d = []
+            for finder in sys.meta_path:
+                if discover := getattr(finder, 'discover', None):
+                    d += [spec.name for spec in discover(parent)]
+        except Exception:
+            return None
     elif isinstance(exc_value, ImportError):
         try:
             mod = __import__(exc_value.name)
@@ -1638,6 +1934,8 @@ def _compute_suggestion_error(exc_value, tb, wrong_name):
             + list(frame.f_builtins)
         )
         d = [x for x in d if isinstance(x, str)]
+        if not_normalized and wrong_name in d:
+            return wrong_name
 
         # Check first if we are in a method and the instance
         # has the wrong name as attribute
@@ -1650,12 +1948,16 @@ def _compute_suggestion_error(exc_value, tb, wrong_name):
             if has_wrong_name:
                 return f"self.{wrong_name}"
 
+    if not_normalized and wrong_name in d:
+        return wrong_name
     try:
         import _suggestions
     except ImportError:
         pass
     else:
-        return _suggestions._generate_suggestions(d, wrong_name)
+        suggestion = _suggestions._generate_suggestions(d, wrong_name)
+        if suggestion:
+            return suggestion
 
     # Compute closest match
 
@@ -1680,6 +1982,14 @@ def _compute_suggestion_error(exc_value, tb, wrong_name):
         if not suggestion or current_distance < best_distance:
             suggestion = possible_name
             best_distance = current_distance
+
+    # If no direct attribute match found, check for nested attributes
+    if not suggestion and isinstance(exc_value, AttributeError):
+        with suppress(Exception):
+            nested_suggestion = _check_for_nested_attribute(exc_value.obj, wrong_name, d)
+            if nested_suggestion:
+                return nested_suggestion
+
     return suggestion
 
 
@@ -1742,3 +2052,32 @@ def _levenshtein_distance(a, b, max_cost):
             # Everything in this row is too big, so bail early.
             return max_cost + 1
     return result
+
+
+def _find_incompatible_extension_module(module_name):
+    import importlib.machinery
+    import importlib.resources.readers
+
+    if not module_name or not importlib.machinery.EXTENSION_SUFFIXES:
+        return
+
+    # We assume the last extension is untagged (eg. .so, .pyd)!
+    # tests.test_traceback.MiscTest.test_find_incompatible_extension_modules
+    # tests that assumption.
+    untagged_suffix = importlib.machinery.EXTENSION_SUFFIXES[-1]
+    # On Windows the debug tag is part of the module file stem, instead of the
+    # extension (eg. foo_d.pyd), so let's remove it and just look for .pyd.
+    if os.name == 'nt':
+        untagged_suffix = untagged_suffix.removeprefix('_d')
+
+    parent, _, child = module_name.rpartition('.')
+    if parent:
+        traversable = importlib.resources.files(parent)
+    else:
+        traversable = importlib.resources.readers.MultiplexedPath(
+            *map(pathlib.Path, filter(os.path.isdir, sys.path))
+        )
+
+    for entry in traversable.iterdir():
+        if entry.name.startswith(child + '.') and entry.name.endswith(untagged_suffix):
+            return entry.name
diff --git a/Lib/types.py b/Lib/types.py
index 60a4b22c200..6c069591ab2 100644
--- a/Lib/types.py
+++ b/Lib/types.py
@@ -58,7 +58,10 @@ def _m(self): pass
         raise TypeError
     except TypeError as exc:
         TracebackType = type(exc.__traceback__)
-        FrameType = type(exc.__traceback__.tb_frame)
+
+    _f = (lambda: sys._getframe())()
+    FrameType = type(_f)
+    FrameLocalsProxyType = type(_f.f_locals)
 
     GetSetDescriptorType = type(FunctionType.__code__)
     MemberDescriptorType = type(FunctionType.__globals__)
@@ -73,6 +76,9 @@ def _m(self): pass
     # CapsuleType cannot be accessed from pure Python,
     # so there is no fallback definition.
 
+    # LazyImportType in pure Python cannot be guaranteed
+    # without overriding the filter, so there is no fallback.
+
     del sys, _f, _g, _C, _c, _ag, _cell_factory  # Not for export
 
 
@@ -251,7 +257,6 @@ def deleter(self, fdel):
 
 
 class _GeneratorWrapper:
-    # TODO: Implement this in C.
     def __init__(self, gen):
         self.__wrapped = gen
         self.__isgen = gen.__class__ is GeneratorType
@@ -278,6 +283,12 @@ def gi_yieldfrom(self):
     @property
     def gi_suspended(self):
         return self.__wrapped.gi_suspended
+    @property
+    def gi_state(self):
+        return self.__wrapped.gi_state
+    @property
+    def cr_state(self):
+        return self.__wrapped.gi_state.replace('GEN_', 'CORO_')
     cr_code = gi_code
     cr_frame = gi_frame
     cr_running = gi_running
@@ -310,7 +321,6 @@ def coroutine(func):
         # Check if 'func' is a generator function.
         # (0x20 == CO_GENERATOR)
         if co_flags & 0x20:
-            # TODO: Implement this in C.
             co = func.__code__
             # 0x100 == CO_ITERABLE_COROUTINE
             func.__code__ = co.replace(co_flags=co.co_flags | 0x100)
diff --git a/Lib/typing.py b/Lib/typing.py
index 2b4389b2967..5b764419d8a 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -28,6 +28,7 @@
 import sys
 import types
 from types import GenericAlias
+lazy import annotationlib
 
 from _typing import (
     _idfunc,
@@ -65,7 +66,6 @@
 
     # ABCs (from collections.abc).
     'AbstractSet',  # collections.abc.Set.
-    'ByteString',
     'Container',
     'ContextManager',
     'Hashable',
@@ -127,6 +127,7 @@
     'cast',
     'clear_overloads',
     'dataclass_transform',
+    'disjoint_base',
     'evaluate_forward_ref',
     'final',
     'get_args',
@@ -140,8 +141,8 @@
     'Never',
     'NewType',
     'no_type_check',
-    'no_type_check_decorator',
     'NoDefault',
+    'NoExtraItems',
     'NoReturn',
     'NotRequired',
     'overload',
@@ -156,21 +157,13 @@
     'Text',
     'TYPE_CHECKING',
     'TypeAlias',
+    'TypeForm',
     'TypeGuard',
     'TypeIs',
     'TypeAliasType',
     'Unpack',
 ]
 
-class _LazyAnnotationLib:
-    def __getattr__(self, attr):
-        global _lazy_annotationlib
-        import annotationlib
-        _lazy_annotationlib = annotationlib
-        return getattr(annotationlib, attr)
-
-_lazy_annotationlib = _LazyAnnotationLib()
-
 
 def _type_convert(arg, module=None, *, allow_special_forms=False, owner=None):
     """For converting None to type(None), and strings to ForwardRef."""
@@ -254,19 +247,30 @@ def _type_repr(obj):
     if isinstance(obj, tuple):
         # Special case for `repr` of types with `ParamSpec`:
         return '[' + ', '.join(_type_repr(t) for t in obj) + ']'
-    return _lazy_annotationlib.type_repr(obj)
+    return annotationlib.type_repr(obj)
 
 
-def _collect_type_parameters(args, *, enforce_default_ordering: bool = True):
+def _collect_type_parameters(
+    args,
+    *,
+    enforce_default_ordering: bool = True,
+    validate_all: bool = False,
+):
     """Collect all type parameters in args
     in order of first appearance (lexicographic order).
 
+    Having an explicit `Generic` or `Protocol` base class determines
+    the exact parameter order.
+
     For example::
 
         >>> P = ParamSpec('P')
         >>> T = TypeVar('T')
         >>> _collect_type_parameters((T, Callable[P, T]))
         (~T, ~P)
+        >>> _collect_type_parameters((list[T], Generic[P, T]))
+        (~P, ~T)
+
     """
     # required type parameter cannot appear after parameter with default
     default_encountered = False
@@ -298,6 +302,17 @@ def _collect_type_parameters(args, *, enforce_default_ordering: bool = True):
                                         ' follows type parameter with a default')
 
                 parameters.append(t)
+        elif (
+            not validate_all
+            and isinstance(t, _GenericAlias)
+            and t.__origin__ in (Generic, Protocol)
+        ):
+            # If we see explicit `Generic[...]` or `Protocol[...]` base classes,
+            # we need to just copy them as-is.
+            # Unless `validate_all` is passed, in this case it means that
+            # we are doing a validation of `Generic` subclasses,
+            # then we collect all unique parameters to be able to inspect them.
+            parameters = t.__parameters__
         else:
             if _is_unpacked_typevartuple(t):
                 type_var_tuple_encountered = True
@@ -408,6 +423,17 @@ def inner(*args, **kwds):
     return decorator
 
 
+def _rebuild_generic_alias(alias: GenericAlias, args: tuple[object, ...]) -> GenericAlias:
+    is_unpacked = alias.__unpacked__
+    if _should_unflatten_callable_args(alias, args):
+        t = alias.__origin__[(args[:-1], args[-1])]
+    else:
+        t = alias.__origin__[args]
+    if is_unpacked:
+        t = Unpack[t]
+    return t
+
+
 def _deprecation_warning_for_no_type_params_passed(funcname: str) -> None:
     import warnings
 
@@ -421,16 +447,7 @@ def _deprecation_warning_for_no_type_params_passed(funcname: str) -> None:
     warnings.warn(depr_message, category=DeprecationWarning, stacklevel=3)
 
 
-class _Sentinel:
-    __slots__ = ()
-    def __repr__(self):
-        return '<sentinel>'
-
-
-_sentinel = _Sentinel()
-
-
-def _eval_type(t, globalns, localns, type_params=_sentinel, *, recursive_guard=frozenset(),
+def _eval_type(t, globalns, localns, type_params, *, recursive_guard=frozenset(),
                format=None, owner=None, parent_fwdref=None, prefer_fwd_module=False):
     """Evaluate all forward references in the given type t.
 
@@ -438,10 +455,7 @@ def _eval_type(t, globalns, localns, type_params=_sentinel, *, recursive_guard=f
     recursive_guard is used to prevent infinite recursion with a recursive
     ForwardRef.
     """
-    if type_params is _sentinel:
-        _deprecation_warning_for_no_type_params_passed("typing._eval_type")
-        type_params = ()
-    if isinstance(t, _lazy_annotationlib.ForwardRef):
+    if isinstance(t, annotationlib.ForwardRef):
         # If the forward_ref has __forward_module__ set, evaluate() infers the globals
         # from the module, and it will probably pick better than the globals we have here.
         # We do this only for calls from get_type_hints() (which opts in through the
@@ -467,25 +481,20 @@ def _eval_type(t, globalns, localns, type_params=_sentinel, *, recursive_guard=f
                 _make_forward_ref(arg, parent_fwdref=parent_fwdref) if isinstance(arg, str) else arg
                 for arg in t.__args__
             )
-            is_unpacked = t.__unpacked__
-            if _should_unflatten_callable_args(t, args):
-                t = t.__origin__[(args[:-1], args[-1])]
-            else:
-                t = t.__origin__[args]
-            if is_unpacked:
-                t = Unpack[t]
+        else:
+            args = t.__args__
 
         ev_args = tuple(
             _eval_type(
                 a, globalns, localns, type_params, recursive_guard=recursive_guard,
                 format=format, owner=owner, prefer_fwd_module=prefer_fwd_module,
             )
-            for a in t.__args__
+            for a in args
         )
         if ev_args == t.__args__:
             return t
         if isinstance(t, GenericAlias):
-            return GenericAlias(t.__origin__, ev_args)
+            return _rebuild_generic_alias(t, ev_args)
         if isinstance(t, Union):
             return functools.reduce(operator.or_, ev_args)
         else:
@@ -573,6 +582,13 @@ def __getitem__(self, parameters):
         return self._getitem(self, *parameters)
 
 
+class _TypeFormForm(_SpecialForm, _root=True):
+    # TypeForm(X) is equivalent to X but indicates to the type checker
+    # that the object is a TypeForm.
+    def __call__(self, obj, /):
+        return obj
+
+
 class _AnyMeta(type):
     def __instancecheck__(self, obj):
         if self is Any:
@@ -883,6 +899,31 @@ def func1(val: list[object]):
     return _GenericAlias(self, (item,))
 
 
+@_TypeFormForm
+def TypeForm(self, parameters):
+    """A special form representing the value that results from the evaluation
+    of a type expression.
+
+    This value encodes the information supplied in the type expression, and it
+    represents the type described by that type expression.
+
+    When used in a type expression, TypeForm describes a set of type form
+    objects. It accepts a single type argument, which must be a valid type
+    expression. ``TypeForm[T]`` describes the set of all type form objects that
+    represent the type T or types that are assignable to T.
+
+    Usage::
+
+        def cast[T](typ: TypeForm[T], value: Any) -> T: ...
+
+        reveal_type(cast(int, "x"))  # int
+
+    See PEP 747 for more information.
+    """
+    item = _type_check(parameters, f'{self} accepts only single type.')
+    return _GenericAlias(self, (item,))
+
+
 @_SpecialForm
 def TypeIs(self, parameters):
     """Special typing construct for marking user-defined type predicate functions.
@@ -958,7 +999,7 @@ def _make_forward_ref(code, *, parent_fwdref=None, **kwargs):
             kwargs['module'] = parent_fwdref.__forward_module__
         if parent_fwdref.__owner__ is not None:
             kwargs['owner'] = parent_fwdref.__owner__
-    forward_ref = _lazy_annotationlib.ForwardRef(code, **kwargs)
+    forward_ref = annotationlib.ForwardRef(code, **kwargs)
     # For compatibility, eagerly compile the forwardref's code.
     forward_ref.__forward_code__
     return forward_ref
@@ -993,18 +1034,18 @@ def evaluate_forward_ref(
     VALUE.
 
     """
-    if format == _lazy_annotationlib.Format.STRING:
+    if format == annotationlib.Format.STRING:
         return forward_ref.__resolved_str__
     if forward_ref.__forward_arg__ in _recursive_guard:
         return forward_ref
 
     if format is None:
-        format = _lazy_annotationlib.Format.VALUE
+        format = annotationlib.Format.VALUE
     value = forward_ref.evaluate(globals=globals, locals=locals,
                                  type_params=type_params, owner=owner, format=format)
 
-    if (isinstance(value, _lazy_annotationlib.ForwardRef)
-            and format == _lazy_annotationlib.Format.FORWARDREF):
+    if (isinstance(value, annotationlib.ForwardRef)
+            and format == annotationlib.Format.FORWARDREF):
         return value
 
     if isinstance(value, str):
@@ -1186,20 +1227,22 @@ def _generic_init_subclass(cls, *args, **kwargs):
     if error:
         raise TypeError("Cannot inherit from plain Generic")
     if '__orig_bases__' in cls.__dict__:
-        tvars = _collect_type_parameters(cls.__orig_bases__)
+        tvars = _collect_type_parameters(cls.__orig_bases__, validate_all=True)
         # Look for Generic[T1, ..., Tn].
         # If found, tvars must be a subset of it.
         # If not found, tvars is it.
         # Also check for and reject plain Generic,
         # and reject multiple Generic[...].
         gvars = None
+        basename = None
         for base in cls.__orig_bases__:
             if (isinstance(base, _GenericAlias) and
-                    base.__origin__ is Generic):
+                    base.__origin__ in (Generic, Protocol)):
                 if gvars is not None:
                     raise TypeError(
                         "Cannot inherit from Generic[...] multiple times.")
                 gvars = base.__parameters__
+                basename = base.__origin__.__name__
         if gvars is not None:
             tvarset = set(tvars)
             gvarset = set(gvars)
@@ -1207,7 +1250,7 @@ def _generic_init_subclass(cls, *args, **kwargs):
                 s_vars = ', '.join(str(t) for t in tvars if t not in gvarset)
                 s_args = ', '.join(str(g) for g in gvars)
                 raise TypeError(f"Some type variables ({s_vars}) are"
-                                f" not listed in Generic[{s_args}]")
+                                f" not listed in {basename}[{s_args}]")
             tvars = gvars
     cls.__parameters__ = tuple(tvars)
 
@@ -1605,21 +1648,6 @@ def __ror__(self, left):
         return Union[left, self]
 
 
-class _DeprecatedGenericAlias(_SpecialGenericAlias, _root=True):
-    def __init__(
-        self, origin, nparams, *, removal_version, inst=True, name=None
-    ):
-        super().__init__(origin, nparams, inst=inst, name=name)
-        self._removal_version = removal_version
-
-    def __instancecheck__(self, inst):
-        import warnings
-        warnings._deprecated(
-            f"{self.__module__}.{self._name}", remove=self._removal_version
-        )
-        return super().__instancecheck__(inst)
-
-
 class _CallableGenericAlias(_NotIterable, _GenericAlias, _root=True):
     def __repr__(self):
         assert self._name == 'Callable'
@@ -1832,6 +1860,7 @@ class _TypingEllipsis:
 _TYPING_INTERNALS = frozenset({
     '__parameters__', '__orig_bases__',  '__orig_class__',
     '_is_protocol', '_is_runtime_protocol', '__protocol_attrs__',
+    '__typing_is_deprecated_inherited_runtime_protocol__',
     '__non_callable_proto_members__', '__type_params__',
 })
 
@@ -1861,8 +1890,8 @@ def _get_protocol_attrs(cls):
             annotations = base.__annotations__
         except Exception:
             # Only go through annotationlib to handle deferred annotations if we need to
-            annotations = _lazy_annotationlib.get_annotations(
-                base, format=_lazy_annotationlib.Format.FORWARDREF
+            annotations = annotationlib.get_annotations(
+                base, format=annotationlib.Format.FORWARDREF
             )
         for attr in (*base.__dict__, *annotations):
             if not attr.startswith('_abc_') and attr not in EXCLUDED_ATTRIBUTES:
@@ -1916,7 +1945,9 @@ def _allow_reckless_class_checks(depth=2):
     The abc and functools modules indiscriminately call isinstance() and
     issubclass() on the whole MRO of a user class, which may contain protocols.
     """
-    return _caller(depth) in {'abc', 'functools', None}
+    # gh-136047: When `_abc` module is not available, `_py_abc` is required to
+    # allow `_py_abc.ABCMeta` fallback.
+    return _caller(depth) in {'abc', '_py_abc', 'functools', None}
 
 
 _PROTO_ALLOWLIST = {
@@ -2019,6 +2050,16 @@ def __subclasscheck__(cls, other):
                     "Instance and class checks can only be used with "
                     "@runtime_checkable protocols"
                 )
+            if getattr(cls, '__typing_is_deprecated_inherited_runtime_protocol__', False):
+                # See GH-132604.
+                import warnings
+                depr_message = (
+                    f"{cls!r} isn't explicitly decorated with @runtime_checkable but "
+                    "it is used in issubclass() or isinstance(). Instance and class "
+                    "checks can only be used with @runtime_checkable protocols. "
+                    "This will raise a TypeError in Python 3.20."
+                )
+                warnings.warn(depr_message, category=DeprecationWarning, stacklevel=2)
             if (
                 # this attribute is set by @runtime_checkable:
                 cls.__non_callable_proto_members__
@@ -2048,6 +2089,18 @@ def __instancecheck__(cls, instance):
             raise TypeError("Instance and class checks can only be used with"
                             " @runtime_checkable protocols")
 
+        if getattr(cls, '__typing_is_deprecated_inherited_runtime_protocol__', False):
+            # See GH-132604.
+            import warnings
+
+            depr_message = (
+                f"{cls!r} isn't explicitly decorated with @runtime_checkable but "
+                "it is used in issubclass() or isinstance(). Instance and class "
+                "checks can only be used with @runtime_checkable protocols. "
+                "This will raise a TypeError in Python 3.20."
+            )
+            warnings.warn(depr_message, category=DeprecationWarning, stacklevel=2)
+
         if _abc_instancecheck(cls, instance):
             return True
 
@@ -2086,8 +2139,8 @@ def _proto_hook(cls, other):
                 try:
                     annos = base.__annotations__
                 except Exception:
-                    annos = _lazy_annotationlib.get_annotations(
-                        base, format=_lazy_annotationlib.Format.FORWARDREF
+                    annos = annotationlib.get_annotations(
+                        base, format=annotationlib.Format.FORWARDREF
                     )
                 if attr in annos:
                     break
@@ -2140,6 +2193,11 @@ def __init_subclass__(cls, *args, **kwargs):
         if not cls.__dict__.get('_is_protocol', False):
             cls._is_protocol = any(b is Protocol for b in cls.__bases__)
 
+        # Mark inherited runtime checkability (deprecated). See GH-132604.
+        if cls._is_protocol and getattr(cls, '_is_runtime_protocol', False):
+            # This flag is set to False by @runtime_checkable.
+            cls.__typing_is_deprecated_inherited_runtime_protocol__ = True
+
         # Set (or override) the protocol subclass hook.
         if '__subclasshook__' not in cls.__dict__:
             cls.__subclasshook__ = _proto_hook
@@ -2286,6 +2344,9 @@ def close(self): ...
         raise TypeError('@runtime_checkable can be only applied to protocol classes,'
                         ' got %r' % cls)
     cls._is_runtime_protocol = True
+    # See GH-132604.
+    if hasattr(cls, '__typing_is_deprecated_inherited_runtime_protocol__'):
+        cls.__typing_is_deprecated_inherited_runtime_protocol__ = False
     # PEP 544 prohibits using issubclass()
     # with protocols that have non-method members.
     # See gh-113320 for why we compute this attribute here,
@@ -2366,14 +2427,14 @@ def get_type_hints(obj, globalns=None, localns=None, include_extras=False,
     """
     if getattr(obj, '__no_type_check__', None):
         return {}
-    Format = _lazy_annotationlib.Format
+    Format = annotationlib.Format
     if format is None:
         format = Format.VALUE
     # Classes require a special treatment.
     if isinstance(obj, type):
         hints = {}
         for base in reversed(obj.__mro__):
-            ann = _lazy_annotationlib.get_annotations(base, format=format)
+            ann = annotationlib.get_annotations(base, format=format)
             if format == Format.STRING:
                 hints.update(ann)
                 continue
@@ -2406,7 +2467,7 @@ def get_type_hints(obj, globalns=None, localns=None, include_extras=False,
         else:
             return {k: _strip_annotations(t) for k, t in hints.items()}
 
-    hints = _lazy_annotationlib.get_annotations(obj, format=format)
+    hints = annotationlib.get_annotations(obj, format=format)
     if (
         not hints
         and not isinstance(obj, types.ModuleType)
@@ -2482,7 +2543,7 @@ def _strip_annotations(t):
         stripped_args = tuple(_strip_annotations(a) for a in t.__args__)
         if stripped_args == t.__args__:
             return t
-        return GenericAlias(t.__origin__, stripped_args)
+        return _rebuild_generic_alias(t, stripped_args)
     if isinstance(t, Union):
         stripped_args = tuple(_strip_annotations(a) for a in t.__args__)
         if stripped_args == t.__args__:
@@ -2630,23 +2691,6 @@ def no_type_check(arg):
     return arg
 
 
-def no_type_check_decorator(decorator):
-    """Decorator to give another decorator the @no_type_check effect.
-
-    This wraps the decorator with something that wraps the decorated
-    function in @no_type_check.
-    """
-    import warnings
-    warnings._deprecated("typing.no_type_check_decorator", remove=(3, 15))
-    @functools.wraps(decorator)
-    def wrapped_decorator(*args, **kwds):
-        func = decorator(*args, **kwds)
-        func = no_type_check(func)
-        return func
-
-    return wrapped_decorator
-
-
 def _overload_dummy(*args, **kwds):
     """Helper for @overload to raise when called."""
     raise NotImplementedError(
@@ -2753,6 +2797,29 @@ class Other(Leaf):  # Error reported by type checker
     return f
 
 
+def disjoint_base(cls):
+    """This decorator marks a class as a disjoint base.
+
+    Child classes of a disjoint base cannot inherit from other disjoint bases that are
+    not parent or child classes of the disjoint base.
+
+    For example:
+
+        @disjoint_base
+        class Disjoint1: pass
+
+        @disjoint_base
+        class Disjoint2: pass
+
+        class Disjoint3(Disjoint1, Disjoint2): pass  # Type checker error
+
+    Type checkers can use knowledge of disjoint bases to detect unreachable code
+    and determine when two types can overlap.
+    """
+    cls.__disjoint_base__ = True
+    return cls
+
+
 # Some unconstrained type variables.  These were initially used by the container types.
 # They were never meant for export and are now unused, but we keep them around to
 # avoid breaking compatibility with users who import them.
@@ -2808,9 +2875,6 @@ class Other(Leaf):  # Error reported by type checker
 MutableMapping = _alias(collections.abc.MutableMapping, 2)
 Sequence = _alias(collections.abc.Sequence, 1)
 MutableSequence = _alias(collections.abc.MutableSequence, 1)
-ByteString = _DeprecatedGenericAlias(
-    collections.abc.ByteString, 0, removal_version=(3, 17)  # Not generic.
-)
 # Tuple accepts variable number of parameters.
 Tuple = _TupleType(tuple, -1, inst=False, name='Tuple')
 Tuple.__doc__ = \
@@ -2954,10 +3018,10 @@ def _make_eager_annotate(types):
                      for key, val in types.items()}
     def annotate(format):
         match format:
-            case _lazy_annotationlib.Format.VALUE | _lazy_annotationlib.Format.FORWARDREF:
+            case annotationlib.Format.VALUE | annotationlib.Format.FORWARDREF:
                 return checked_types
-            case _lazy_annotationlib.Format.STRING:
-                return _lazy_annotationlib.annotations_to_string(types)
+            case annotationlib.Format.STRING:
+                return annotationlib.annotations_to_string(types)
             case _:
                 raise NotImplementedError(format)
     return annotate
@@ -2987,9 +3051,9 @@ def __new__(cls, typename, bases, ns):
             types = ns["__annotations__"]
             field_names = list(types)
             annotate = _make_eager_annotate(types)
-        elif (original_annotate := _lazy_annotationlib.get_annotate_from_class_namespace(ns)) is not None:
-            types = _lazy_annotationlib.call_annotate_function(
-                original_annotate, _lazy_annotationlib.Format.FORWARDREF)
+        elif (original_annotate := annotationlib.get_annotate_from_class_namespace(ns)) is not None:
+            types = annotationlib.call_annotate_function(
+                original_annotate, annotationlib.Format.FORWARDREF)
             field_names = list(types)
 
             # For backward compatibility, type-check all the types at creation time
@@ -2997,9 +3061,9 @@ def __new__(cls, typename, bases, ns):
                 _type_check(typ, "field annotation must be a type")
 
             def annotate(format):
-                annos = _lazy_annotationlib.call_annotate_function(
+                annos = annotationlib.call_annotate_function(
                     original_annotate, format)
-                if format != _lazy_annotationlib.Format.STRING:
+                if format != annotationlib.Format.STRING:
                     return {key: _type_check(val, f"field {key} annotation must be a type")
                             for key, val in annos.items()}
                 return annos
@@ -3049,7 +3113,7 @@ def annotate(format):
         return nm_tpl
 
 
-def NamedTuple(typename, fields=_sentinel, /, **kwargs):
+def NamedTuple(typename, fields, /):
     """Typed version of collections.namedtuple.
 
     Usage::
@@ -3069,49 +3133,9 @@ class Employee(NamedTuple):
 
         Employee = NamedTuple('Employee', [('name', str), ('id', int)])
     """
-    if fields is _sentinel:
-        if kwargs:
-            deprecated_thing = "Creating NamedTuple classes using keyword arguments"
-            deprecation_msg = (
-                "{name} is deprecated and will be disallowed in Python {remove}. "
-                "Use the class-based or functional syntax instead."
-            )
-        else:
-            deprecated_thing = "Failing to pass a value for the 'fields' parameter"
-            example = f"`{typename} = NamedTuple({typename!r}, [])`"
-            deprecation_msg = (
-                "{name} is deprecated and will be disallowed in Python {remove}. "
-                "To create a NamedTuple class with 0 fields "
-                "using the functional syntax, "
-                "pass an empty list, e.g. "
-            ) + example + "."
-    elif fields is None:
-        if kwargs:
-            raise TypeError(
-                "Cannot pass `None` as the 'fields' parameter "
-                "and also specify fields using keyword arguments"
-            )
-        else:
-            deprecated_thing = "Passing `None` as the 'fields' parameter"
-            example = f"`{typename} = NamedTuple({typename!r}, [])`"
-            deprecation_msg = (
-                "{name} is deprecated and will be disallowed in Python {remove}. "
-                "To create a NamedTuple class with 0 fields "
-                "using the functional syntax, "
-                "pass an empty list, e.g. "
-            ) + example + "."
-    elif kwargs:
-        raise TypeError("Either list of fields or keywords"
-                        " can be provided to NamedTuple, not both")
-    if fields is _sentinel or fields is None:
-        import warnings
-        warnings._deprecated(deprecated_thing, message=deprecation_msg, remove=(3, 15))
-        fields = kwargs.items()
     types = {n: _type_check(t, f"field {n} annotation must be a type")
              for n, t in fields}
-    field_names = [n for n, _ in fields]
-
-    nt = _make_nmtuple(typename, field_names, _make_eager_annotate(types), module=_caller())
+    nt = _make_nmtuple(typename, types, _make_eager_annotate(types), module=_caller())
     nt.__orig_bases__ = (NamedTuple,)
     return nt
 
@@ -3124,6 +3148,9 @@ def _namedtuple_mro_entries(bases):
 NamedTuple.__mro_entries__ = _namedtuple_mro_entries
 
 
+NoExtraItems = sentinel("NoExtraItems")
+
+
 def _get_typeddict_qualifiers(annotation_type):
     while True:
         annotation_origin = get_origin(annotation_type)
@@ -3147,7 +3174,8 @@ def _get_typeddict_qualifiers(annotation_type):
 
 
 class _TypedDictMeta(type):
-    def __new__(cls, name, bases, ns, total=True):
+    def __new__(cls, name, bases, ns, total=True, closed=None,
+                extra_items=NoExtraItems):
         """Create a new typed dict class object.
 
         This method is called when TypedDict is subclassed,
@@ -3159,6 +3187,8 @@ def __new__(cls, name, bases, ns, total=True):
             if type(base) is not _TypedDictMeta and base is not Generic:
                 raise TypeError('cannot inherit from both a TypedDict type '
                                 'and a non-TypedDict base class')
+        if closed is not None and extra_items is not NoExtraItems:
+            raise TypeError(f"Cannot combine closed={closed!r} and extra_items")
 
         if any(issubclass(b, Generic) for b in bases):
             generic_base = (Generic,)
@@ -3175,9 +3205,9 @@ def __new__(cls, name, bases, ns, total=True):
         if ns_annotations is not None:
             own_annotate = None
             own_annotations = ns_annotations
-        elif (own_annotate := _lazy_annotationlib.get_annotate_from_class_namespace(ns)) is not None:
-            own_annotations = _lazy_annotationlib.call_annotate_function(
-                own_annotate, _lazy_annotationlib.Format.FORWARDREF, owner=tp_dict
+        elif (own_annotate := annotationlib.get_annotate_from_class_namespace(ns)) is not None:
+            own_annotations = annotationlib.call_annotate_function(
+                own_annotate, annotationlib.Format.FORWARDREF, owner=tp_dict
             )
         else:
             own_annotate = None
@@ -3244,20 +3274,20 @@ def __annotate__(format):
                 base_annotate = base.__annotate__
                 if base_annotate is None:
                     continue
-                base_annos = _lazy_annotationlib.call_annotate_function(
+                base_annos = annotationlib.call_annotate_function(
                     base_annotate, format, owner=base)
                 annos.update(base_annos)
             if own_annotate is not None:
-                own = _lazy_annotationlib.call_annotate_function(
+                own = annotationlib.call_annotate_function(
                     own_annotate, format, owner=tp_dict)
-                if format != _lazy_annotationlib.Format.STRING:
+                if format != annotationlib.Format.STRING:
                     own = {
                         n: _type_check(tp, msg, module=tp_dict.__module__)
                         for n, tp in own.items()
                     }
-            elif format == _lazy_annotationlib.Format.STRING:
-                own = _lazy_annotationlib.annotations_to_string(own_annotations)
-            elif format in (_lazy_annotationlib.Format.FORWARDREF, _lazy_annotationlib.Format.VALUE):
+            elif format == annotationlib.Format.STRING:
+                own = annotationlib.annotations_to_string(own_annotations)
+            elif format in (annotationlib.Format.FORWARDREF, annotationlib.Format.VALUE):
                 own = own_checked_annotations
             else:
                 raise NotImplementedError(format)
@@ -3270,6 +3300,8 @@ def __annotate__(format):
         tp_dict.__readonly_keys__ = frozenset(readonly_keys)
         tp_dict.__mutable_keys__ = frozenset(mutable_keys)
         tp_dict.__total__ = total
+        tp_dict.__closed__ = closed
+        tp_dict.__extra_items__ = extra_items
         return tp_dict
 
     __call__ = dict  # static method
@@ -3281,7 +3313,8 @@ def __subclasscheck__(cls, other):
     __instancecheck__ = __subclasscheck__
 
 
-def TypedDict(typename, fields=_sentinel, /, *, total=True):
+def TypedDict(typename, fields, /, *, total=True, closed=None,
+              extra_items=NoExtraItems):
     """A simple typed namespace. At runtime it is equivalent to a plain dict.
 
     TypedDict creates a dictionary type such that a type checker will expect all
@@ -3335,33 +3368,41 @@ class DatabaseUser(TypedDict):
             id: ReadOnly[int]  # the "id" key must not be modified
             username: str      # the "username" key can be changed
 
-    See PEPs 589, 655, and 705 for more information.
-    """
-    if fields is _sentinel or fields is None:
-        import warnings
+    The closed argument controls whether the TypedDict allows additional
+    non-required items during inheritance and assignability checks.
+    If closed=True, the TypedDict does not allow additional items::
 
-        if fields is _sentinel:
-            deprecated_thing = "Failing to pass a value for the 'fields' parameter"
-        else:
-            deprecated_thing = "Passing `None` as the 'fields' parameter"
-
-        example = f"`{typename} = TypedDict({typename!r}, {{{{}}}})`"
-        deprecation_msg = (
-            "{name} is deprecated and will be disallowed in Python {remove}. "
-            "To create a TypedDict class with 0 fields "
-            "using the functional syntax, "
-            "pass an empty dictionary, e.g. "
-        ) + example + "."
-        warnings._deprecated(deprecated_thing, message=deprecation_msg, remove=(3, 15))
-        fields = {}
+        Point2D = TypedDict('Point2D', {'x': int, 'y': int}, closed=True)
+        class Point3D(Point2D):
+            z: int  # Type checker error
+
+    Passing closed=False explicitly requests TypedDict's default open behavior.
+    If closed is not provided, the behavior is inherited from the superclass.
+    A type checker is only expected to support a literal False or True as the
+    value of the closed argument.
+
+    The extra_items argument can instead be used to specify the assignable type
+    of unknown non-required keys::
 
+        Point2D = TypedDict('Point2D', {'x': int, 'y': int}, extra_items=int)
+        class Point3D(Point2D):
+            z: int      # OK
+            label: str  # Type checker error
+
+    The extra_items argument is also inherited through subclassing. It is unset
+    by default, and it may not be used with the closed argument at the same
+    time.
+
+    See PEPs 589, 655, 705, and 728 for more information.
+    """
     ns = {'__annotations__': dict(fields)}
     module = _caller()
     if module is not None:
         # Setting correct module is necessary to make typed dict classes pickleable.
         ns['__module__'] = module
 
-    td = _TypedDictMeta(typename, (), ns, total=total)
+    td = _TypedDictMeta(typename, (), ns, total=total, closed=closed,
+                        extra_items=extra_items)
     td.__orig_bases__ = (TypedDict,)
     return td
 
@@ -3549,7 +3590,7 @@ def isatty(self) -> bool:
         pass
 
     @abstractmethod
-    def read(self, n: int = -1) -> AnyStr:
+    def read(self, n: int = -1, /) -> AnyStr:
         pass
 
     @abstractmethod
@@ -3557,15 +3598,15 @@ def readable(self) -> bool:
         pass
 
     @abstractmethod
-    def readline(self, limit: int = -1) -> AnyStr:
+    def readline(self, limit: int = -1, /) -> AnyStr:
         pass
 
     @abstractmethod
-    def readlines(self, hint: int = -1) -> list[AnyStr]:
+    def readlines(self, hint: int = -1, /) -> list[AnyStr]:
         pass
 
     @abstractmethod
-    def seek(self, offset: int, whence: int = 0) -> int:
+    def seek(self, offset: int, whence: int = 0, /) -> int:
         pass
 
     @abstractmethod
@@ -3577,7 +3618,7 @@ def tell(self) -> int:
         pass
 
     @abstractmethod
-    def truncate(self, size: int | None = None) -> int:
+    def truncate(self, size: int | None = None, /) -> int:
         pass
 
     @abstractmethod
@@ -3585,11 +3626,11 @@ def writable(self) -> bool:
         pass
 
     @abstractmethod
-    def write(self, s: AnyStr) -> int:
+    def write(self, s: AnyStr, /) -> int:
         pass
 
     @abstractmethod
-    def writelines(self, lines: list[AnyStr]) -> None:
+    def writelines(self, lines: list[AnyStr], /) -> None:
         pass
 
     @abstractmethod
@@ -3597,7 +3638,7 @@ def __enter__(self) -> IO[AnyStr]:
         pass
 
     @abstractmethod
-    def __exit__(self, type, value, traceback) -> None:
+    def __exit__(self, type, value, traceback, /) -> None:
         pass
 
 
@@ -3607,7 +3648,7 @@ class BinaryIO(IO[bytes]):
     __slots__ = ()
 
     @abstractmethod
-    def write(self, s: bytes | bytearray) -> int:
+    def write(self, s: bytes | bytearray, /) -> int:
         pass
 
     @abstractmethod
@@ -3843,7 +3884,7 @@ def __getattr__(attr):
     are only created on-demand here.
     """
     if attr == "ForwardRef":
-        obj = _lazy_annotationlib.ForwardRef
+        obj = annotationlib.ForwardRef
     elif attr in {"Pattern", "Match"}:
         import re
         obj = _alias(getattr(re, attr), 1)
@@ -3860,6 +3901,48 @@ def __getattr__(attr):
         )
         warnings.warn(depr_message, category=DeprecationWarning, stacklevel=2)
         obj = _collect_type_parameters
+    elif attr == "ByteString":
+        import warnings
+
+        warnings._deprecated(
+            "typing.ByteString",
+            message=(
+                "{name!r} and 'collections.abc.ByteString' are deprecated "
+                "and slated for removal in Python {remove}"
+            ),
+            remove=(3, 17)
+        )
+
+        class _DeprecatedGenericAlias(_SpecialGenericAlias, _root=True):
+            def __init__(
+                self, origin, nparams, *, removal_version, inst=True, name=None
+            ):
+                super().__init__(origin, nparams, inst=inst, name=name)
+                self._removal_version = removal_version
+
+            def __instancecheck__(self, inst):
+                import warnings
+                warnings._deprecated(
+                    f"{self.__module__}.{self._name}", remove=self._removal_version
+                )
+                return super().__instancecheck__(inst)
+
+            def __subclasscheck__(self, cls):
+                import warnings
+                warnings._deprecated(
+                    f"{self.__module__}.{self._name}", remove=self._removal_version
+                )
+                return super().__subclasscheck__(cls)
+
+        with warnings.catch_warnings(
+            action="ignore", category=DeprecationWarning
+        ):
+            # Not generic
+            ByteString = globals()["ByteString"] = _DeprecatedGenericAlias(
+                collections.abc.ByteString, 0, removal_version=(3, 17)
+            )
+
+        return ByteString
     else:
         raise AttributeError(f"module {__name__!r} has no attribute {attr!r}")
     globals()[attr] = obj
diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 5a8fccf59dc..aad4182f304 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -597,7 +597,7 @@ def __set_return_value(self, value):
 
     __return_value_doc = "The value to be returned when the mock is called."
     return_value = property(__get_return_value, __set_return_value,
-                            __return_value_doc)
+                            doc=__return_value_doc)
 
 
     @property
@@ -701,7 +701,7 @@ def __getattr__(self, name):
             if name.startswith(('assert', 'assret', 'asert', 'aseert', 'assrt')) or name in _ATTRIB_DENY_LIST:
                 raise AttributeError(
                     f"{name!r} is not a valid assertion. Use a spec "
-                    f"for the mock if {name!r} is meant to be an attribute.")
+                    f"for the mock if {name!r} is meant to be an attribute")
 
         with NonCallableMock._lock:
             result = self._mock_children.get(name)
@@ -937,7 +937,7 @@ def _call_matcher(self, _call):
             return _call
 
     def assert_not_called(self):
-        """assert that the mock was never called.
+        """Assert that the mock was never called.
         """
         if self.call_count != 0:
             msg = ("Expected '%s' to not have been called. Called %s times.%s"
@@ -947,7 +947,7 @@ def assert_not_called(self):
             raise AssertionError(msg)
 
     def assert_called(self):
-        """assert that the mock was called at least once
+        """Assert that the mock was called at least once.
         """
         if self.call_count == 0:
             msg = ("Expected '%s' to have been called." %
@@ -955,7 +955,7 @@ def assert_called(self):
             raise AssertionError(msg)
 
     def assert_called_once(self):
-        """assert that the mock was called only once.
+        """Assert that the mock was called only once.
         """
         if not self.call_count == 1:
             msg = ("Expected '%s' to have been called once. Called %s times.%s"
@@ -965,7 +965,7 @@ def assert_called_once(self):
             raise AssertionError(msg)
 
     def assert_called_with(self, /, *args, **kwargs):
-        """assert that the last call was made with the specified arguments.
+        """Assert that the last call was made with the specified arguments.
 
         Raises an AssertionError if the args and keyword args passed in are
         different to the last call to the mock."""
@@ -987,7 +987,7 @@ def _error_message():
 
 
     def assert_called_once_with(self, /, *args, **kwargs):
-        """assert that the mock was called exactly once and that that call was
+        """Assert that the mock was called exactly once and that call was
         with the specified arguments."""
         if not self.call_count == 1:
             msg = ("Expected '%s' to be called once. Called %s times.%s"
@@ -999,7 +999,7 @@ def assert_called_once_with(self, /, *args, **kwargs):
 
 
     def assert_has_calls(self, calls, any_order=False):
-        """assert the mock has been called with the specified calls.
+        """Assert the mock has been called with the specified calls.
         The `mock_calls` list is checked for the calls.
 
         If `any_order` is False (the default) then the calls must be
@@ -1044,7 +1044,7 @@ def assert_has_calls(self, calls, any_order=False):
 
 
     def assert_any_call(self, /, *args, **kwargs):
-        """assert the mock has been called with the specified arguments.
+        """Assert the mock has been called with the specified arguments.
 
         The assert passes if the mock has *ever* been called, unlike
         `assert_called_with` and `assert_called_once_with` that only pass if
diff --git a/Lib/uuid.py b/Lib/uuid.py
index 043ad7bcbde..4bdcb67775a 100644
--- a/Lib/uuid.py
+++ b/Lib/uuid.py
@@ -737,6 +737,7 @@ def uuid1(node=None, clock_seq=None):
             is_safe = SafeUUID(safely_generated)
         except ValueError:
             is_safe = SafeUUID.unknown
+        # The version field is assumed to be handled by _generate_time_safe().
         return UUID(bytes=uuid_time, is_safe=is_safe)
 
     global _last_timestamp
@@ -954,7 +955,6 @@ def main():
     parser = argparse.ArgumentParser(
         formatter_class=argparse.ArgumentDefaultsHelpFormatter,
         description="Generate a UUID using the selected UUID function.",
-        color=True,
     )
     parser.add_argument("-u", "--uuid",
                         choices=uuid_funcs.keys(),
@@ -962,14 +962,14 @@ def main():
                         help="function to generate the UUID")
     parser.add_argument("-n", "--namespace",
                         metavar=f"{{any UUID,{','.join(namespaces)}}}",
-                        help="uuid3/uuid5 only: "
+                        help="`uuid3`/`uuid5` only: "
                         "a UUID, or a well-known predefined UUID addressed "
                         "by namespace name")
     parser.add_argument("-N", "--name",
-                        help="uuid3/uuid5 only: "
+                        help="`uuid3`/`uuid5` only: "
                         "name used as part of generating the UUID")
     parser.add_argument("-C", "--count", metavar="NUM", type=int, default=1,
-                        help="generate NUM fresh UUIDs")
+                        help="generate `NUM` fresh UUIDs")
 
     args = parser.parse_args()
     uuid_func = uuid_funcs[args.uuid]
diff --git a/Lib/venv/__init__.py b/Lib/venv/__init__.py
index 88f3340af41..0653a43a8b1 100644
--- a/Lib/venv/__init__.py
+++ b/Lib/venv/__init__.py
@@ -174,6 +174,7 @@ def create_if_needed(d):
         context.python_exe = exename
         binpath = self._venv_path(env_dir, 'scripts')
         libpath = self._venv_path(env_dir, 'purelib')
+        platlibpath = self._venv_path(env_dir, 'platlib')
 
         # PEP 405 says venvs should create a local include directory.
         # See https://peps.python.org/pep-0405/#include-files
@@ -191,12 +192,8 @@ def create_if_needed(d):
         create_if_needed(incpath)
         context.lib_path = libpath
         create_if_needed(libpath)
-        # Issue 21197: create lib64 as a symlink to lib on 64-bit non-OS X POSIX
-        if ((sys.maxsize > 2**32) and (os.name == 'posix') and
-            (sys.platform != 'darwin')):
-            link_path = os.path.join(env_dir, 'lib64')
-            if not os.path.exists(link_path):   # Issue #21643
-                os.symlink('lib', link_path)
+        context.platlib_path = platlibpath
+        create_if_needed(platlibpath)
         context.bin_path = binpath
         context.bin_name = os.path.relpath(binpath, env_dir)
         context.env_exe = os.path.join(binpath, exename)
@@ -309,15 +306,11 @@ def setup_python(self, context):
             binpath = context.bin_path
             path = context.env_exe
             copier = self.symlink_or_copy
-            dirname = context.python_dir
             copier(context.executable, path)
             if not os.path.islink(path):
                 os.chmod(path, 0o755)
-
-            suffixes = ['python', 'python3', f'python3.{sys.version_info[1]}']
-            if sys.version_info[:2] == (3, 14) and sys.getfilesystemencoding() == 'utf-8':
-                suffixes.append('𝜋thon')
-            for suffix in suffixes:
+            for suffix in ('python', 'python3',
+                           f'python3.{sys.version_info[1]}'):
                 path = os.path.join(binpath, suffix)
                 if not os.path.exists(path):
                     # Issue 18807: make copies if
@@ -365,6 +358,9 @@ def setup_python(self, context):
                 exe_t = f'3.{sys.version_info[1]}t'
                 python_exe = os.path.join(dirname, f'python{exe_t}{exe_d}.exe')
                 pythonw_exe = os.path.join(dirname, f'pythonw{exe_t}{exe_d}.exe')
+                if not os.path.isfile(python_exe):
+                    python_exe = os.path.join(dirname, f'python{exe_d}.exe')
+                    pythonw_exe = os.path.join(dirname, f'pythonw{exe_d}.exe')
                 link_sources = {
                     'python.exe': python_exe,
                     f'python{exe_d}.exe': python_exe,
@@ -625,7 +621,6 @@ def main(args=None):
                                             'activate it, e.g. by '
                                             'sourcing an activate script '
                                             'in its bin directory.',
-                                     color=True,
                                      )
     parser.add_argument('dirs', metavar='ENV_DIR', nargs='+',
                         help='A directory to create the environment in.')
diff --git a/Lib/venv/scripts/nt/activate.bat b/Lib/venv/scripts/nt/activate.bat
index 9ac5c20b477..90c2ad06a89 100644
--- a/Lib/venv/scripts/nt/activate.bat
+++ b/Lib/venv/scripts/nt/activate.bat
@@ -1,34 +1,32 @@
-@echo off
-
-rem This file is UTF-8 encoded, so we need to update the current code page while executing it
-for /f "tokens=2 delims=:." %%a in ('"%SystemRoot%\System32\chcp.com"') do (
-    set _OLD_CODEPAGE=%%a
+@rem This file is UTF-8 encoded, so we need to update the current code page while executing it
+@for /f "tokens=2 delims=:." %%a in ('"%SystemRoot%\System32\chcp.com"') do @(
+    @set _OLD_CODEPAGE=%%a
 )
-if defined _OLD_CODEPAGE (
-    "%SystemRoot%\System32\chcp.com" 65001 > nul
+@if defined _OLD_CODEPAGE (
+    @"%SystemRoot%\System32\chcp.com" 65001 > nul
 )
 
-set "VIRTUAL_ENV=__VENV_DIR__"
+@set "VIRTUAL_ENV=__VENV_DIR__"
 
-if not defined PROMPT set PROMPT=$P$G
+@if not defined PROMPT @set PROMPT=$P$G
 
-if defined _OLD_VIRTUAL_PROMPT set PROMPT=%_OLD_VIRTUAL_PROMPT%
-if defined _OLD_VIRTUAL_PYTHONHOME set PYTHONHOME=%_OLD_VIRTUAL_PYTHONHOME%
+@if defined _OLD_VIRTUAL_PROMPT @set PROMPT=%_OLD_VIRTUAL_PROMPT%
+@if defined _OLD_VIRTUAL_PYTHONHOME @set PYTHONHOME=%_OLD_VIRTUAL_PYTHONHOME%
 
-set "_OLD_VIRTUAL_PROMPT=%PROMPT%"
-set "PROMPT=(__VENV_PROMPT__) %PROMPT%"
+@if not defined VIRTUAL_ENV_DISABLE_PROMPT @set "_OLD_VIRTUAL_PROMPT=%PROMPT%"
+@if not defined VIRTUAL_ENV_DISABLE_PROMPT @set "PROMPT=(__VENV_PROMPT__) %PROMPT%"
 
-if defined PYTHONHOME set _OLD_VIRTUAL_PYTHONHOME=%PYTHONHOME%
-set PYTHONHOME=
+@if defined PYTHONHOME @set _OLD_VIRTUAL_PYTHONHOME=%PYTHONHOME%
+@set PYTHONHOME=
 
-if defined _OLD_VIRTUAL_PATH set PATH=%_OLD_VIRTUAL_PATH%
-if not defined _OLD_VIRTUAL_PATH set _OLD_VIRTUAL_PATH=%PATH%
+@if defined _OLD_VIRTUAL_PATH @set PATH=%_OLD_VIRTUAL_PATH%
+@if not defined _OLD_VIRTUAL_PATH @set _OLD_VIRTUAL_PATH=%PATH%
 
-set "PATH=%VIRTUAL_ENV%\__VENV_BIN_NAME__;%PATH%"
-set "VIRTUAL_ENV_PROMPT=__VENV_PROMPT__"
+@set "PATH=%VIRTUAL_ENV%\__VENV_BIN_NAME__;%PATH%"
+@set "VIRTUAL_ENV_PROMPT=__VENV_PROMPT__"
 
 :END
-if defined _OLD_CODEPAGE (
-    "%SystemRoot%\System32\chcp.com" %_OLD_CODEPAGE% > nul
-    set _OLD_CODEPAGE=
+@if defined _OLD_CODEPAGE (
+    @"%SystemRoot%\System32\chcp.com" %_OLD_CODEPAGE% > nul
+    @set _OLD_CODEPAGE=
 )
diff --git a/Lib/venv/scripts/nt/deactivate.bat b/Lib/venv/scripts/nt/deactivate.bat
index 44dae495370..8f1650b6bf7 100644
--- a/Lib/venv/scripts/nt/deactivate.bat
+++ b/Lib/venv/scripts/nt/deactivate.bat
@@ -1,22 +1,20 @@
-@echo off
-
-if defined _OLD_VIRTUAL_PROMPT (
-    set "PROMPT=%_OLD_VIRTUAL_PROMPT%"
+@if defined _OLD_VIRTUAL_PROMPT (
+    @set "PROMPT=%_OLD_VIRTUAL_PROMPT%"
 )
-set _OLD_VIRTUAL_PROMPT=
+@set _OLD_VIRTUAL_PROMPT=
 
-if defined _OLD_VIRTUAL_PYTHONHOME (
-    set "PYTHONHOME=%_OLD_VIRTUAL_PYTHONHOME%"
-    set _OLD_VIRTUAL_PYTHONHOME=
+@if defined _OLD_VIRTUAL_PYTHONHOME (
+    @set "PYTHONHOME=%_OLD_VIRTUAL_PYTHONHOME%"
+    @set _OLD_VIRTUAL_PYTHONHOME=
 )
 
-if defined _OLD_VIRTUAL_PATH (
-    set "PATH=%_OLD_VIRTUAL_PATH%"
+@if defined _OLD_VIRTUAL_PATH (
+    @set "PATH=%_OLD_VIRTUAL_PATH%"
 )
 
-set _OLD_VIRTUAL_PATH=
+@set _OLD_VIRTUAL_PATH=
 
-set VIRTUAL_ENV=
-set VIRTUAL_ENV_PROMPT=
+@set VIRTUAL_ENV=
+@set VIRTUAL_ENV_PROMPT=
 
 :END
diff --git a/Lib/venv/scripts/posix/activate.csh b/Lib/venv/scripts/posix/activate.csh
index 2a3fa835476..7226034df0f 100644
--- a/Lib/venv/scripts/posix/activate.csh
+++ b/Lib/venv/scripts/posix/activate.csh
@@ -16,10 +16,12 @@ setenv PATH "$VIRTUAL_ENV/"__VENV_BIN_NAME__":$PATH"
 setenv VIRTUAL_ENV_PROMPT __VENV_PROMPT__
 
 
-set _OLD_VIRTUAL_PROMPT="$prompt"
+if ($?prompt) then
+    set _OLD_VIRTUAL_PROMPT="$prompt"
 
-if (! "$?VIRTUAL_ENV_DISABLE_PROMPT") then
-    set prompt = "("__VENV_PROMPT__") $prompt:q"
+    if (! "$?VIRTUAL_ENV_DISABLE_PROMPT") then
+        set prompt = "("__VENV_PROMPT__") $prompt:q"
+    endif
 endif
 
 alias pydoc python -m pydoc
diff --git a/Lib/wave.py b/Lib/wave.py
index b8476e26486..c4e1a493a7e 100644
--- a/Lib/wave.py
+++ b/Lib/wave.py
@@ -15,15 +15,13 @@
       getsampwidth()  -- returns sample width in bytes
       getframerate()  -- returns sampling frequency
       getnframes()    -- returns number of audio frames
+      getformat()     -- returns frame encoding (WAVE_FORMAT_PCM, WAVE_FORMAT_IEEE_FLOAT
+                         or WAVE_FORMAT_EXTENSIBLE)
       getcomptype()   -- returns compression type ('NONE' for linear samples)
       getcompname()   -- returns human-readable version of
                          compression type ('not compressed' linear samples)
       getparams()     -- returns a namedtuple consisting of all of the
                          above in the above order
-      getmarkers()    -- returns None (for compatibility with the
-                         old aifc module)
-      getmark(id)     -- raises an error since the mark does not
-                         exist (for compatibility with the old aifc module)
       readframes(n)   -- returns at most n frames of audio
       rewind()        -- rewind to the beginning of the audio stream
       setpos(pos)     -- seek to the specified position
@@ -46,6 +44,9 @@
       setsampwidth(n) -- set the sample width
       setframerate(n) -- set the frame rate
       setnframes(n)   -- set the number of frames
+      setformat(format)
+                      -- set the frame format. Only WAVE_FORMAT_PCM and
+                         WAVE_FORMAT_IEEE_FLOAT are supported.
       setcomptype(type, name)
                       -- set the compression type and the
                          human-readable compression type
@@ -73,16 +74,26 @@
 
 from collections import namedtuple
 import builtins
+import os
 import struct
 import sys
 
 
-__all__ = ["open", "Error", "Wave_read", "Wave_write"]
+__all__ = [
+    "open",
+    "Error",
+    "Wave_read",
+    "Wave_write",
+    "WAVE_FORMAT_PCM",
+    "WAVE_FORMAT_IEEE_FLOAT",
+    "WAVE_FORMAT_EXTENSIBLE",
+]
 
 class Error(Exception):
     pass
 
 WAVE_FORMAT_PCM = 0x0001
+WAVE_FORMAT_IEEE_FLOAT = 0x0003
 WAVE_FORMAT_EXTENSIBLE = 0xFFFE
 # Derived from uuid.UUID("00000001-0000-0010-8000-00aa00389b71").bytes_le
 KSDATAFORMAT_SUBTYPE_PCM = b'\x01\x00\x00\x00\x00\x00\x10\x00\x80\x00\x00\xaa\x008\x9bq'
@@ -100,7 +111,7 @@ def _byteswap(data, width):
         for j in range(width):
             swapped_data[i + width - 1 - j] = data[i + j]
 
-    return bytes(swapped_data)
+    return swapped_data.take_bytes()
 
 
 class _Chunk:
@@ -229,6 +240,10 @@ class Wave_read:
               available through the getsampwidth() method
     _framerate -- the sampling frequency
               available through the getframerate() method
+    _format -- frame format
+              One of WAVE_FORMAT_PCM, WAVE_FORMAT_IEEE_FLOAT
+              or WAVE_FORMAT_EXTENSIBLE available through
+              getformat() method
     _comptype -- the AIFF-C compression type ('NONE' if AIFF)
               available through the getcomptype() method
     _compname -- the human-readable AIFF-C compression type
@@ -278,7 +293,7 @@ def initfp(self, file):
 
     def __init__(self, f):
         self._i_opened_the_file = None
-        if isinstance(f, str):
+        if isinstance(f, (bytes, str, os.PathLike)):
             f = builtins.open(f, 'rb')
             self._i_opened_the_file = f
         # else, assume it is an open file object already
@@ -330,6 +345,9 @@ def getsampwidth(self):
     def getframerate(self):
         return self._framerate
 
+    def getformat(self):
+        return self._format
+
     def getcomptype(self):
         return self._comptype
 
@@ -341,16 +359,6 @@ def getparams(self):
                        self.getframerate(), self.getnframes(),
                        self.getcomptype(), self.getcompname())
 
-    def getmarkers(self):
-        import warnings
-        warnings._deprecated("Wave_read.getmarkers", remove=(3, 15))
-        return None
-
-    def getmark(self, id):
-        import warnings
-        warnings._deprecated("Wave_read.getmark", remove=(3, 15))
-        raise Error('no marks')
-
     def setpos(self, pos):
         if pos < 0 or pos > self._nframes:
             raise Error('position not in range')
@@ -380,16 +388,16 @@ def readframes(self, nframes):
 
     def _read_fmt_chunk(self, chunk):
         try:
-            wFormatTag, self._nchannels, self._framerate, dwAvgBytesPerSec, wBlockAlign = struct.unpack_from('<HHLLH', chunk.read(14))
+            self._format, self._nchannels, self._framerate, dwAvgBytesPerSec, wBlockAlign = struct.unpack_from('<HHLLH', chunk.read(14))
         except struct.error:
             raise EOFError from None
-        if wFormatTag != WAVE_FORMAT_PCM and wFormatTag != WAVE_FORMAT_EXTENSIBLE:
-            raise Error('unknown format: %r' % (wFormatTag,))
+        if self._format not in (WAVE_FORMAT_PCM, WAVE_FORMAT_IEEE_FLOAT, WAVE_FORMAT_EXTENSIBLE):
+            raise Error('unknown format: %r' % (self._format,))
         try:
             sampwidth = struct.unpack_from('<H', chunk.read(2))[0]
         except struct.error:
             raise EOFError from None
-        if wFormatTag == WAVE_FORMAT_EXTENSIBLE:
+        if self._format == WAVE_FORMAT_EXTENSIBLE:
             try:
                 cbSize, wValidBitsPerSample, dwChannelMask = struct.unpack_from('<HHL', chunk.read(8))
                 # Read the entire UUID from the chunk
@@ -432,6 +440,8 @@ class Wave_write:
               set through the setsampwidth() or setparams() method
     _framerate -- the sampling frequency
               set through the setframerate() or setparams() method
+    _format -- frame format
+              set through setformat() method
     _nframes -- the number of audio frames written to the header
               set through the setnframes() or setparams() method
 
@@ -445,7 +455,7 @@ class Wave_write:
 
     def __init__(self, f):
         self._i_opened_the_file = None
-        if isinstance(f, str):
+        if isinstance(f, (bytes, str, os.PathLike)):
             f = builtins.open(f, 'wb')
             self._i_opened_the_file = f
         try:
@@ -459,12 +469,14 @@ def initfp(self, file):
         self._file = file
         self._convert = None
         self._nchannels = 0
+        self._format = WAVE_FORMAT_PCM
         self._sampwidth = 0
         self._framerate = 0
         self._nframes = 0
         self._nframeswritten = 0
         self._datawritten = 0
         self._datalength = 0
+        self._fact_sample_count_pos = None
         self._headerwritten = False
 
     def __del__(self):
@@ -494,7 +506,10 @@ def getnchannels(self):
     def setsampwidth(self, sampwidth):
         if self._datawritten:
             raise Error('cannot change parameters after starting to write')
-        if sampwidth < 1 or sampwidth > 4:
+        if self._format == WAVE_FORMAT_IEEE_FLOAT:
+            if sampwidth not in (4, 8):
+                raise Error('unsupported sample width for IEEE float format')
+        elif sampwidth < 1 or sampwidth > 4:
             raise Error('bad sample width')
         self._sampwidth = sampwidth
 
@@ -506,9 +521,10 @@ def getsampwidth(self):
     def setframerate(self, framerate):
         if self._datawritten:
             raise Error('cannot change parameters after starting to write')
+        framerate = int(round(framerate))
         if framerate <= 0:
             raise Error('bad frame rate')
-        self._framerate = int(round(framerate))
+        self._framerate = framerate
 
     def getframerate(self):
         if not self._framerate:
@@ -531,6 +547,18 @@ def setcomptype(self, comptype, compname):
         self._comptype = comptype
         self._compname = compname
 
+    def setformat(self, format):
+        if self._datawritten:
+            raise Error('cannot change parameters after starting to write')
+        if format not in (WAVE_FORMAT_IEEE_FLOAT, WAVE_FORMAT_PCM):
+            raise Error('unsupported wave format')
+        if format == WAVE_FORMAT_IEEE_FLOAT and self._sampwidth and self._sampwidth not in (4, 8):
+            raise Error('unsupported sample width for IEEE float format')
+        self._format = format
+
+    def getformat(self):
+        return self._format
+
     def getcomptype(self):
         return self._comptype
 
@@ -538,10 +566,15 @@ def getcompname(self):
         return self._compname
 
     def setparams(self, params):
-        nchannels, sampwidth, framerate, nframes, comptype, compname = params
         if self._datawritten:
             raise Error('cannot change parameters after starting to write')
+        if len(params) == 6:
+            nchannels, sampwidth, framerate, nframes, comptype, compname = params
+            format = WAVE_FORMAT_PCM
+        else:
+            nchannels, sampwidth, framerate, nframes, comptype, compname, format = params
         self.setnchannels(nchannels)
+        self.setformat(format)
         self.setsampwidth(sampwidth)
         self.setframerate(framerate)
         self.setnframes(nframes)
@@ -553,21 +586,6 @@ def getparams(self):
         return _wave_params(self._nchannels, self._sampwidth, self._framerate,
               self._nframes, self._comptype, self._compname)
 
-    def setmark(self, id, pos, name):
-        import warnings
-        warnings._deprecated("Wave_write.setmark", remove=(3, 15))
-        raise Error('setmark() not supported')
-
-    def getmark(self, id):
-        import warnings
-        warnings._deprecated("Wave_write.getmark", remove=(3, 15))
-        raise Error('no marks')
-
-    def getmarkers(self):
-        import warnings
-        warnings._deprecated("Wave_write.getmarkers", remove=(3, 15))
-        return None
-
     def tell(self):
         return self._nframeswritten
 
@@ -593,6 +611,8 @@ def close(self):
         try:
             if self._file:
                 self._ensure_header_written(0)
+                if self._datawritten & 1:
+                    self._file.write(b'\x00')
                 if self._datalength != self._datawritten:
                     self._patchheader()
                 self._file.flush()
@@ -617,6 +637,9 @@ def _ensure_header_written(self, datasize):
                 raise Error('sampling rate not specified')
             self._write_header(datasize)
 
+    def _needs_fact_chunk(self):
+        return self._format == WAVE_FORMAT_IEEE_FLOAT
+
     def _write_header(self, initlength):
         assert not self._headerwritten
         self._file.write(b'RIFF')
@@ -627,12 +650,23 @@ def _write_header(self, initlength):
             self._form_length_pos = self._file.tell()
         except (AttributeError, OSError):
             self._form_length_pos = None
-        self._file.write(struct.pack('<L4s4sLHHLLHH4s',
-            36 + self._datalength, b'WAVE', b'fmt ', 16,
-            WAVE_FORMAT_PCM, self._nchannels, self._framerate,
+        has_fact = self._needs_fact_chunk()
+        header_overhead = 36 + (12 if has_fact else 0)
+        self._file.write(struct.pack('<L4s4sLHHLLHH',
+            header_overhead + self._datalength + (self._datalength & 1), b'WAVE', b'fmt ', 16,
+            self._format, self._nchannels, self._framerate,
             self._nchannels * self._framerate * self._sampwidth,
             self._nchannels * self._sampwidth,
-            self._sampwidth * 8, b'data'))
+            self._sampwidth * 8))
+        if has_fact:
+            self._file.write(b'fact')
+            self._file.write(struct.pack('<L', 4))
+            try:
+                self._fact_sample_count_pos = self._file.tell()
+            except (AttributeError, OSError):
+                self._fact_sample_count_pos = None
+            self._file.write(struct.pack('<L', self._nframes))
+        self._file.write(b'data')
         if self._form_length_pos is not None:
             self._data_length_pos = self._file.tell()
         self._file.write(struct.pack('<L', self._datalength))
@@ -643,8 +677,13 @@ def _patchheader(self):
         if self._datawritten == self._datalength:
             return
         curpos = self._file.tell()
+        header_overhead = 36 + (12 if self._needs_fact_chunk() else 0)
         self._file.seek(self._form_length_pos, 0)
-        self._file.write(struct.pack('<L', 36 + self._datawritten))
+        self._file.write(struct.pack('<L', header_overhead + self._datawritten + (self._datawritten & 1)))
+        if self._fact_sample_count_pos is not None:
+            self._file.seek(self._fact_sample_count_pos, 0)
+            nframes = self._datawritten // (self._nchannels * self._sampwidth)
+            self._file.write(struct.pack('<L', nframes))
         self._file.seek(self._data_length_pos, 0)
         self._file.write(struct.pack('<L', self._datawritten))
         self._file.seek(curpos, 0)
diff --git a/Lib/weakref.py b/Lib/weakref.py
index 94e4278143c..af7244553c9 100644
--- a/Lib/weakref.py
+++ b/Lib/weakref.py
@@ -408,14 +408,16 @@ def setdefault(self, key, default=None):
         return self.data.setdefault(ref(key, self._remove),default)
 
     def update(self, dict=None, /, **kwargs):
+        if kwargs:
+            msg = ("Keyword arguments are not supported: "
+                   "cannot create weak reference to 'str' object")
+            raise TypeError(msg)
         d = self.data
         if dict is not None:
             if not hasattr(dict, "items"):
                 dict = type({})(dict)
             for key, value in dict.items():
                 d[ref(key, self._remove)] = value
-        if len(kwargs):
-            self.update(kwargs)
 
     def __ior__(self, other):
         self.update(other)
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index 0a4203d372c..53727d7940b 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -83,15 +83,12 @@
     "SubElement",
     "tostring", "tostringlist",
     "TreeBuilder",
-    "VERSION",
     "XML", "XMLID",
     "XMLParser", "XMLPullParser",
     "register_namespace",
     "canonicalize", "C14NWriterTarget",
     ]
 
-VERSION = "1.3.0"
-
 import sys
 import re
 import warnings
@@ -167,9 +164,9 @@ class Element:
 
     """
 
-    def __init__(self, tag, attrib={}, **extra):
-        if not isinstance(attrib, dict):
-            raise TypeError("attrib must be dict, not %s" % (
+    def __init__(self, tag, /, attrib={}, **extra):
+        if not isinstance(attrib, (dict, frozendict)):
+            raise TypeError("attrib must be dict or frozendict, not %s" % (
                 attrib.__class__.__name__,))
         self.tag = tag
         self.attrib = {**attrib, **extra}
@@ -266,12 +263,15 @@ def remove(self, subelement):
         ValueError is raised if a matching element could not be found.
 
         """
-        # assert iselement(element)
         try:
             self._children.remove(subelement)
         except ValueError:
+            # to align the error type with the C implementation
+            if isinstance(subelement, type) or not iselement(subelement):
+                raise TypeError('expected an Element, not %s' %
+                                type(subelement).__name__) from None
             # to align the error message with the C implementation
-            raise ValueError("Element.remove(x): element not found") from None
+            raise ValueError(f"{subelement!r} not in {self!r}") from None
 
     def find(self, path, namespaces=None):
         """Find first matching element by tag name or path.
@@ -420,7 +420,7 @@ def itertext(self):
                 yield t
 
 
-def SubElement(parent, tag, attrib={}, **extra):
+def SubElement(parent, tag, /, attrib={}, **extra):
     """Subelement factory which creates an element instance, and appends it
     to an existing parent.
 
@@ -928,9 +928,9 @@ def _serialize_html(write, elem, qnames, namespaces, **kwargs):
     tag = elem.tag
     text = elem.text
     if tag is Comment:
-        write("<!--%s-->" % _escape_cdata(text))
+        write("<!--%s-->" % text)
     elif tag is ProcessingInstruction:
-        write("<?%s?>" % _escape_cdata(text))
+        write("<?%s?>" % text)
     else:
         tag = qnames[tag]
         if tag is None:
@@ -954,12 +954,15 @@ def _serialize_html(write, elem, qnames, namespaces, **kwargs):
                 for k, v in items:
                     if isinstance(k, QName):
                         k = k.text
-                    if isinstance(v, QName):
-                        v = qnames[v.text]
+                    k = qnames[k]
+                    if v is None:
+                        write(" %s" % k)  # empty attr
                     else:
-                        v = _escape_attrib_html(v)
-                    # FIXME: handle boolean attributes
-                    write(" %s=\"%s\"" % (qnames[k], v))
+                        if isinstance(v, QName):
+                            v = qnames[v.text]
+                        else:
+                            v = _escape_attrib_html(v)
+                        write(" %s=\"%s\"" % (k, v))
             write(">")
             ltag = tag.lower()
             if text:
@@ -1275,16 +1278,20 @@ def iterator(source):
     gen = iterator(source)
     class IterParseIterator(collections.abc.Iterator):
         __next__ = gen.__next__
+
         def close(self):
+            nonlocal close_source
             if close_source:
                 source.close()
+                close_source = False
             gen.close()
 
-        def __del__(self):
-            # TODO: Emit a ResourceWarning if it was not explicitly closed.
-            # (When the close() method will be supported in all maintained Python versions.)
+        def __del__(self, _warn=warnings.warn):
             if close_source:
-                source.close()
+                try:
+                    _warn(f"unclosed iterparse iterator {source.name!r}", ResourceWarning, stacklevel=2)
+                finally:
+                    source.close()
 
     it = IterParseIterator()
     it.root = None
@@ -2118,3 +2125,14 @@ def _escape_attrib_c14n(text):
     pass
 else:
     _set_factories(Comment, ProcessingInstruction)
+
+
+# --------------------------------------------------------------------
+
+def __getattr__(name):
+    if name == "VERSION":
+        from warnings import _deprecated
+
+        _deprecated("VERSION", remove=(3, 20))
+        return "1.3.0"  # Do not change
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/Lib/zipapp.py b/Lib/zipapp.py
index 7a4ef96ea0f..a1cef18ada9 100644
--- a/Lib/zipapp.py
+++ b/Lib/zipapp.py
@@ -187,16 +187,16 @@ def main(args=None):
     """
     import argparse
 
-    parser = argparse.ArgumentParser(color=True)
+    parser = argparse.ArgumentParser()
     parser.add_argument('--output', '-o', default=None,
             help="The name of the output archive. "
-                 "Required if SOURCE is an archive.")
+                 "Required if `SOURCE` is an archive.")
     parser.add_argument('--python', '-p', default=None,
             help="The name of the Python interpreter to use "
                  "(default: no shebang line).")
     parser.add_argument('--main', '-m', default=None,
             help="The main function of the application "
-                 "(default: use an existing __main__.py).")
+                 "(default: use an existing `__main__.py`).")
     parser.add_argument('--compress', '-c', action='store_true',
             help="Compress files with the deflate method. "
                  "Files are stored uncompressed by default.")
diff --git a/Lib/zipfile/__init__.py b/Lib/zipfile/__init__.py
index 2b6e6163b96..552ab17bd67 100644
--- a/Lib/zipfile/__init__.py
+++ b/Lib/zipfile/__init__.py
@@ -786,7 +786,16 @@ def __init__(self):
         self._unconsumed = b''
         self.eof = False
 
-    def decompress(self, data):
+    @property
+    def needs_input(self):
+        # While the LZMA properties header is still being buffered, more input
+        # is required; afterwards defer to the wrapped decompressor so a bounded
+        # decompress() call can be drained across reads.
+        if self._decomp is None:
+            return True
+        return self._decomp.needs_input
+
+    def decompress(self, data, max_length=-1):
         if self._decomp is None:
             self._unconsumed += data
             if len(self._unconsumed) <= 4:
@@ -802,7 +811,7 @@ def decompress(self, data):
             data = self._unconsumed[4 + psize:]
             del self._unconsumed
 
-        result = self._decomp.decompress(data)
+        result = self._decomp.decompress(data, max_length)
         self.eof = self._decomp.eof
         return result
 
@@ -1171,8 +1180,15 @@ def _read1(self, n):
             data = self._decompressor.unconsumed_tail
             if n > len(data):
                 data += self._read2(n - len(data))
-        else:
+        elif self._compress_type == ZIP_STORED:
             data = self._read2(n)
+        else:
+            # bzip2/lzma/zstd: a bounded decompress() call may leave input
+            # buffered inside the decompressor; drain that before reading more.
+            if getattr(self._decompressor, "needs_input", True):
+                data = self._read2(n)
+            else:
+                data = b''
 
         if self._compress_type == ZIP_STORED:
             self._eof = self._compress_left <= 0
@@ -1185,8 +1201,17 @@ def _read1(self, n):
             if self._eof:
                 data += self._decompressor.flush()
         else:
-            data = self._decompressor.decompress(data)
-            self._eof = self._decompressor.eof or self._compress_left <= 0
+            # Bound the output of a single decompress() call (mirroring the
+            # DEFLATE path above) so that a small compressed member cannot
+            # expand into one unbounded read.
+            try:
+                data = self._decompressor.decompress(data, max(n, self.MIN_READ_SIZE))
+            except TypeError:
+                # See MonkeypatchedDecompressorTests in test_core.py
+                data = self._decompressor.decompress(data)
+            self._eof = (self._decompressor.eof or
+                         self._compress_left <= 0 and
+                         getattr(self._decompressor, "needs_input", True))
 
         data = data[:self._left]
         self._left -= len(data)
@@ -2242,10 +2267,10 @@ def writepy(self, pathname, basename="", filterfunc=None):
                     basename = name
                 if self.debug:
                     print("Adding package in", pathname, "as", basename)
-                fname, arcname = self._get_codename(initname[0:-3], basename)
+                arcname, bytecode = self._get_code(initname[0:-3], basename)
                 if self.debug:
                     print("Adding", arcname)
-                self.write(fname, arcname)
+                self.writestr(arcname, bytecode)
                 dirlist = sorted(os.listdir(pathname))
                 dirlist.remove("__init__.py")
                 # Add all *.py files and package subdirectories
@@ -2262,11 +2287,10 @@ def writepy(self, pathname, basename="", filterfunc=None):
                             if self.debug:
                                 print('file %r skipped by filterfunc' % path)
                             continue
-                        fname, arcname = self._get_codename(path[0:-3],
-                                                            basename)
+                        arcname, bytecode = self._get_code(path[0:-3], basename)
                         if self.debug:
                             print("Adding", arcname)
-                        self.write(fname, arcname)
+                        self.writestr(arcname, bytecode)
             else:
                 # This is NOT a package directory, add its files at top level
                 if self.debug:
@@ -2279,108 +2303,65 @@ def writepy(self, pathname, basename="", filterfunc=None):
                             if self.debug:
                                 print('file %r skipped by filterfunc' % path)
                             continue
-                        fname, arcname = self._get_codename(path[0:-3],
-                                                            basename)
+                        arcname, bytecode = self._get_code(path[0:-3], basename)
                         if self.debug:
                             print("Adding", arcname)
-                        self.write(fname, arcname)
+                        self.writestr(arcname, bytecode)
         else:
             if pathname[-3:] != ".py":
                 raise RuntimeError(
                     'Files added with writepy() must end with ".py"')
-            fname, arcname = self._get_codename(pathname[0:-3], basename)
+            arcname, bytecode = self._get_code(pathname[0:-3], basename)
             if self.debug:
                 print("Adding file", arcname)
-            self.write(fname, arcname)
+            self.writestr(arcname, bytecode)
 
-    def _get_codename(self, pathname, basename):
-        """Return (filename, archivename) for the path.
+    def _get_code(self, pathname, basename):
+        """Return (arcname, bytecode) for the path.
 
-        Given a module name path, return the correct file path and
-        archive name, compiling if necessary.  For example, given
-        /python/lib/string, return (/python/lib/string.pyc, string).
+        Given a module name path, return the bytecode and archive
+        name.  For example, given /python/lib/string, return
+        ('string', b'<bytecode of string>').
         """
-        def _compile(file, optimize=-1):
-            import py_compile
-            if self.debug:
-                print("Compiling", file)
-            try:
-                py_compile.compile(file, doraise=True, optimize=optimize)
-            except py_compile.PyCompileError as err:
-                print(err.msg)
-                return False
-            return True
+        import importlib._bootstrap_external
+        import importlib.machinery
 
         file_py  = pathname + ".py"
         file_pyc = pathname + ".pyc"
-        pycache_opt0 = importlib.util.cache_from_source(file_py, optimization='')
-        pycache_opt1 = importlib.util.cache_from_source(file_py, optimization=1)
-        pycache_opt2 = importlib.util.cache_from_source(file_py, optimization=2)
-        if self._optimize == -1:
-            # legacy mode: use whatever file is present
-            if (os.path.isfile(file_pyc) and
-                  os.stat(file_pyc).st_mtime >= os.stat(file_py).st_mtime):
-                # Use .pyc file.
-                arcname = fname = file_pyc
-            elif (os.path.isfile(pycache_opt0) and
-                  os.stat(pycache_opt0).st_mtime >= os.stat(file_py).st_mtime):
-                # Use the __pycache__/*.pyc file, but write it to the legacy pyc
-                # file name in the archive.
-                fname = pycache_opt0
-                arcname = file_pyc
-            elif (os.path.isfile(pycache_opt1) and
-                  os.stat(pycache_opt1).st_mtime >= os.stat(file_py).st_mtime):
-                # Use the __pycache__/*.pyc file, but write it to the legacy pyc
-                # file name in the archive.
-                fname = pycache_opt1
-                arcname = file_pyc
-            elif (os.path.isfile(pycache_opt2) and
-                  os.stat(pycache_opt2).st_mtime >= os.stat(file_py).st_mtime):
-                # Use the __pycache__/*.pyc file, but write it to the legacy pyc
-                # file name in the archive.
-                fname = pycache_opt2
-                arcname = file_pyc
-            else:
-                # Compile py into PEP 3147 pyc file.
-                if _compile(file_py):
-                    if sys.flags.optimize == 0:
-                        fname = pycache_opt0
-                    elif sys.flags.optimize == 1:
-                        fname = pycache_opt1
-                    else:
-                        fname = pycache_opt2
-                    arcname = file_pyc
-                else:
-                    fname = arcname = file_py
+        archivename = os.path.split(file_pyc)[1]
+
+        loader = importlib.machinery.SourceFileLoader('<py_compile>', file_py)
+        source_bytes = loader.get_data(file_py)
+        try:
+            if self.debug:
+                print("Compiling", file_py)
+            code = loader.source_to_code(source_bytes, archivename)
+        except Exception as err:
+            # Historically, this function prints messages here rather than raising
+            # (see test_zipfile.test_write_filtered_python_package)
+            from py_compile import PyCompileError
+            print(PyCompileError(type(err), err, file_py).msg)
+
+            archivename = os.path.split(file_py)[1]
+            bytecode = source_bytes
         else:
-            # new mode: use given optimization level
-            if self._optimize == 0:
-                fname = pycache_opt0
-                arcname = file_pyc
-            else:
-                arcname = file_pyc
-                if self._optimize == 1:
-                    fname = pycache_opt1
-                elif self._optimize == 2:
-                    fname = pycache_opt2
-                else:
-                    msg = "invalid value for 'optimize': {!r}".format(self._optimize)
-                    raise ValueError(msg)
-            if not (os.path.isfile(fname) and
-                    os.stat(fname).st_mtime >= os.stat(file_py).st_mtime):
-                if not _compile(file_py, optimize=self._optimize):
-                    fname = arcname = file_py
-        archivename = os.path.split(arcname)[1]
+            # Historically this function has used timestamp comparisons, so we
+            # keep using it until someone makes that specific improvement.
+            source_stats = loader.path_stats(file_py)
+            bytecode = importlib._bootstrap_external._code_to_timestamp_pyc(
+                code, source_stats['mtime'], source_stats['size'])
+
         if basename:
             archivename = "%s/%s" % (basename, archivename)
-        return (fname, archivename)
+
+        return archivename, bytecode
 
 
 def main(args=None):
     import argparse
 
     description = 'A simple command-line interface for zipfile module.'
-    parser = argparse.ArgumentParser(description=description, color=True)
+    parser = argparse.ArgumentParser(description=description)
     group = parser.add_mutually_exclusive_group(required=True)
     group.add_argument('-l', '--list', metavar='<zipfile>',
                        help='Show listing of a zipfile')
@@ -2393,7 +2374,7 @@ def main(args=None):
     group.add_argument('-t', '--test', metavar='<zipfile>',
                        help='Test if a zipfile is valid')
     parser.add_argument('--metadata-encoding', metavar='<encoding>',
-                        help='Specify encoding of member names for -l, -e and -t')
+                        help='Specify encoding of member names for `-l`, `-e` and `-t`')
     args = parser.parse_args(args)
 
     encoding = args.metadata_encoding
diff --git a/Lib/zipfile/_path/__init__.py b/Lib/zipfile/_path/__init__.py
index 80f5d607731..faae4c84cae 100644
--- a/Lib/zipfile/_path/__init__.py
+++ b/Lib/zipfile/_path/__init__.py
@@ -7,7 +7,7 @@
 for more detail.
 """
 
-import contextlib
+import functools
 import io
 import itertools
 import pathlib
@@ -17,6 +17,7 @@
 import sys
 import zipfile
 
+from ._functools import save_method_args
 from .glob import Translator
 
 __all__ = ['Path']
@@ -85,13 +86,12 @@ class InitializedState:
     Mix-in to save the initialization state for pickling.
     """
 
+    @save_method_args
     def __init__(self, *args, **kwargs):
-        self.__args = args
-        self.__kwargs = kwargs
         super().__init__(*args, **kwargs)
 
     def __getstate__(self):
-        return self.__args, self.__kwargs
+        return self._saved___init__.args, self._saved___init__.kwargs
 
     def __setstate__(self, state):
         args, kwargs = state
@@ -180,16 +180,19 @@ class FastLookup(CompleteDirs):
     """
 
     def namelist(self):
-        with contextlib.suppress(AttributeError):
-            return self.__names
-        self.__names = super().namelist()
-        return self.__names
+        return self._namelist
+
+    @functools.cached_property
+    def _namelist(self):
+        return super().namelist()
 
     def _name_set(self):
-        with contextlib.suppress(AttributeError):
-            return self.__lookup
-        self.__lookup = super()._name_set()
-        return self.__lookup
+        return self._name_set_prop
+
+    @functools.cached_property
+    def _name_set_prop(self):
+        return super()._name_set()
+
 
 def _extract_text_encoding(encoding=None, *args, **kwargs):
     # compute stack level so that the caller of the caller sees any warning.
diff --git a/Lib/zipfile/_path/_functools.py b/Lib/zipfile/_path/_functools.py
new file mode 100644
index 00000000000..7390be21873
--- /dev/null
+++ b/Lib/zipfile/_path/_functools.py
@@ -0,0 +1,20 @@
+import collections
+import functools
+
+
+# from jaraco.functools 4.0.2
+def save_method_args(method):
+    """
+    Wrap a method such that when it is called, the args and kwargs are
+    saved on the method.
+    """
+    args_and_kwargs = collections.namedtuple('args_and_kwargs', 'args kwargs')  # noqa: PYI024
+
+    @functools.wraps(method)
+    def wrapper(self, /, *args, **kwargs):
+        attr_name = '_saved_' + method.__name__
+        attr = args_and_kwargs(args, kwargs)
+        setattr(self, attr_name, attr)
+        return method(self, *args, **kwargs)
+
+    return wrapper
diff --git a/Lib/zipimport.py b/Lib/zipimport.py
index 444c9dd11d8..19279d1c2be 100644
--- a/Lib/zipimport.py
+++ b/Lib/zipimport.py
@@ -10,15 +10,12 @@
 to Zip archives.
 """
 
-#from importlib import _bootstrap_external
-#from importlib import _bootstrap  # for _verbose_message
 import _frozen_importlib_external as _bootstrap_external
 from _frozen_importlib_external import _unpack_uint16, _unpack_uint32, _unpack_uint64
 import _frozen_importlib as _bootstrap  # for _verbose_message
 import _imp  # for check_hash_based_pycs
 import _io  # for open
 import marshal  # for loads
-import sys  # for modules
 import time  # for mktime
 
 __all__ = ['ZipImportError', 'zipimporter']
@@ -34,8 +31,6 @@ class ZipImportError(ImportError):
 # _read_directory() cache
 _zip_directory_cache = {}
 
-_module_type = type(sys)
-
 END_CENTRAL_DIR_SIZE = 22
 END_CENTRAL_DIR_SIZE_64 = 56
 END_CENTRAL_DIR_LOCATOR_SIZE_64 = 20
@@ -210,52 +205,6 @@ def is_package(self, fullname):
         return mi
 
 
-    # Load and return the module named by 'fullname'.
-    def load_module(self, fullname):
-        """load_module(fullname) -> module.
-
-        Load the module specified by 'fullname'. 'fullname' must be the
-        fully qualified (dotted) module name. It returns the imported
-        module, or raises ZipImportError if it could not be imported.
-
-        Deprecated since Python 3.10. Use exec_module() instead.
-        """
-        import warnings
-        warnings._deprecated("zipimport.zipimporter.load_module",
-                             f"{warnings._DEPRECATED_MSG}; "
-                             "use zipimport.zipimporter.exec_module() instead",
-                             remove=(3, 15))
-        code, ispackage, modpath = _get_module_code(self, fullname)
-        mod = sys.modules.get(fullname)
-        if mod is None or not isinstance(mod, _module_type):
-            mod = _module_type(fullname)
-            sys.modules[fullname] = mod
-        mod.__loader__ = self
-
-        try:
-            if ispackage:
-                # add __path__ to the module *before* the code gets
-                # executed
-                path = _get_module_path(self, fullname)
-                fullpath = _bootstrap_external._path_join(self.archive, path)
-                mod.__path__ = [fullpath]
-
-            if not hasattr(mod, '__builtins__'):
-                mod.__builtins__ = __builtins__
-            _bootstrap_external._fix_up_module(mod.__dict__, fullname, modpath)
-            exec(code, mod.__dict__)
-        except:
-            del sys.modules[fullname]
-            raise
-
-        try:
-            mod = sys.modules[fullname]
-        except KeyError:
-            raise ImportError(f'Loaded module {fullname!r} not found in sys.modules')
-        _bootstrap._verbose_message('import {} # loaded from Zip {}', fullname, modpath)
-        return mod
-
-
     def get_resource_reader(self, fullname):
         """Return the ResourceReader for a module in a zip file."""
         from importlib.readers import ZipReader
@@ -603,11 +552,16 @@ def _read_directory(archive):
 )
 
 _importing_zlib = False
+_zlib_decompress = None
 
 # Return the zlib.decompress function object, or NULL if zlib couldn't
 # be imported. The function is cached when found, so subsequent calls
 # don't import zlib again.
-def _get_decompress_func():
+def _get_zlib_decompress_func():
+    global _zlib_decompress
+    if _zlib_decompress:
+        return _zlib_decompress
+
     global _importing_zlib
     if _importing_zlib:
         # Someone has a zlib.py[co] in their Zip file
@@ -617,7 +571,7 @@ def _get_decompress_func():
 
     _importing_zlib = True
     try:
-        from zlib import decompress
+        from zlib import decompress as _zlib_decompress
     except Exception:
         _bootstrap._verbose_message('zipimport: zlib UNAVAILABLE')
         raise ZipImportError("can't decompress data; zlib not available")
@@ -625,7 +579,54 @@ def _get_decompress_func():
         _importing_zlib = False
 
     _bootstrap._verbose_message('zipimport: zlib available')
-    return decompress
+    return _zlib_decompress
+
+
+_importing_zstd = False
+_zstd_decompressor_class = None
+
+# Return the _zstd.ZstdDecompressor function object, or NULL if _zstd couldn't
+# be imported. The result is cached when found.
+def _get_zstd_decompressor_class():
+    global _zstd_decompressor_class
+    if _zstd_decompressor_class:
+        return _zstd_decompressor_class
+
+    global _importing_zstd
+    if _importing_zstd:
+        # Someone has a _zstd.py[co] in their Zip file
+        # let's avoid a stack overflow.
+        _bootstrap._verbose_message("zipimport: zstd UNAVAILABLE")
+        raise ZipImportError("can't decompress data; zstd not available")
+
+    _importing_zstd = True
+    try:
+        from _zstd import ZstdDecompressor as _zstd_decompressor_class
+    except Exception:
+        _bootstrap._verbose_message("zipimport: zstd UNAVAILABLE")
+        raise ZipImportError("can't decompress data; zstd not available")
+    finally:
+        _importing_zstd = False
+
+    _bootstrap._verbose_message("zipimport: zstd available")
+    return _zstd_decompressor_class
+
+
+def _zstd_decompress(data):
+    # A simple version of compression.zstd.decompress() as we cannot import
+    # that here as the stdlib itself could be being zipimported.
+    results = []
+    while True:
+        decomp = _get_zstd_decompressor_class()()
+        results.append(decomp.decompress(data))
+        if not decomp.eof:
+            raise ZipImportError("zipimport: zstd compressed data ended before "
+                                 "the end-of-stream marker")
+        data = decomp.unused_data
+        if not data:
+            break
+    return b"".join(results)
+
 
 # Given a path to a Zip file and a toc_entry, return the (uncompressed) data.
 def _get_data(archive, toc_entry):
@@ -659,16 +660,23 @@ def _get_data(archive, toc_entry):
         if len(raw_data) != data_size:
             raise OSError("zipimport: can't read data")
 
-    if compress == 0:
-        # data is not compressed
-        return raw_data
-
-    # Decompress with zlib
-    try:
-        decompress = _get_decompress_func()
-    except Exception:
-        raise ZipImportError("can't decompress data; zlib not available")
-    return decompress(raw_data, -15)
+    match compress:
+        case 0:  # stored
+            return raw_data
+        case 8:  # deflate aka zlib
+            try:
+                decompress = _get_zlib_decompress_func()
+            except Exception:
+                raise ZipImportError("can't decompress data; zlib not available")
+            return decompress(raw_data, -15)
+        case 93:  # zstd
+            try:
+                return _zstd_decompress(raw_data)
+            except Exception:
+                raise ZipImportError("could not decompress zstd data")
+        # bz2 and lzma could be added, but are largely obsolete.
+        case _:
+            raise ZipImportError(f"zipimport: unsupported compression {compress}")
 
 
 # Lenient date/time comparison function. The precision of the mtime
@@ -734,9 +742,9 @@ def _normalize_line_endings(source):
 
 # Given a string buffer containing Python source code, compile it
 # and return a code object.
-def _compile_source(pathname, source):
+def _compile_source(pathname, source, module):
     source = _normalize_line_endings(source)
-    return compile(source, pathname, 'exec', dont_inherit=True)
+    return compile(source, pathname, 'exec', dont_inherit=True, module=module)
 
 # Convert the date/time values found in the Zip archive to a value
 # that's compatible with the time stamp stored in .pyc files.
@@ -807,7 +815,7 @@ def _get_module_code(self, fullname):
                 except ImportError as exc:
                     import_error = exc
             else:
-                code = _compile_source(modpath, data)
+                code = _compile_source(modpath, data, fullname)
             if code is None:
                 # bad magic number or non-matching mtime
                 # in byte code, try next
diff --git a/README.md b/README.md
index 1fc891b7901..c3aaa00c9af 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 # [RustPython](https://rustpython.github.io/)
 
-A Python-3 (CPython >= 3.14.0) Interpreter written in Rust :snake: :scream:
+A Python-3 (CPython >= 3.15.0) Interpreter written in Rust :snake: :scream:
 :metal:.
 
 [![Build Status](https://github.com/RustPython/RustPython/workflows/CI/badge.svg)](https://github.com/RustPython/RustPython/actions?query=workflow%3ACI)
diff --git a/benches/README.md b/benches/README.md
index d31e1a0f271..cdea0b3b41b 100644
--- a/benches/README.md
+++ b/benches/README.md
@@ -42,9 +42,9 @@ Two things differ when the benchmarks run under CodSpeed:
 - The CPython comparison benchmarks are skipped. They are useful to compare RustPython against
   CPython locally, but CodSpeed tracks the evolution of RustPython itself, and running them would
   double the duration of an already slow instrumented run.
-- The microbenchmarks using `ITERATIONS` run with a single value instead of five. The criterion
-  benchmark id does not include the iteration count, so all five sizes are reported under the same
-  name.
+- The microbenchmarks using `ITERATIONS` run with a single value of 1,000 instead of five sizes.
+  CodSpeed retains the existing benchmark names; local runs include the iteration count in each
+  benchmark id.
 
 ### Adding a benchmark
 
@@ -54,6 +54,9 @@ in two ways:
 1. The time to parse the file to AST
 2. The time it takes to execute the file
 
+Execution includes compilation and runs each iteration with a fresh namespace whose `__name__`
+is `"__main__"`, so script entry points run in both RustPython and CPython.
+
 ### Adding a micro benchmark
 
 Micro benchmarks are small snippets of code added under the `microbenchmarks/` directory. A microbenchmark file has
@@ -73,7 +76,7 @@ len(a_list)
 ```
 
 Only `len(a_list)` will be timed. Setup or benchmarked code can optionally reference a variable called `ITERATIONS`. If
-present then the benchmark code will be invoked 5 times with `ITERATIONS` set to a value between 100 and 1,000. For
+present then the benchmark runs at five sizes: 100, 300, 500, 700 and 900 iterations locally. For
 example:
 
 ```python
diff --git a/benches/execution.rs b/benches/execution.rs
index 56d4fc4fc19..c0c783f24ed 100644
--- a/benches/execution.rs
+++ b/benches/execution.rs
@@ -7,6 +7,7 @@ use criterion::{
     Bencher, BenchmarkGroup, BenchmarkId, Criterion, Throughput, criterion_group, criterion_main,
     measurement::WallTime,
 };
+use pyo3::types::{PyCode, PyCodeMethods, PyDict, PyDictMethods, code::PyCodeInput};
 use rustpython_compiler::Mode;
 use rustpython_vm::{Interpreter, PyResult, Settings};
 use std::{collections::HashMap, path::Path};
@@ -25,9 +26,14 @@ fn bench_cpython_code(b: &mut Bencher<'_>, source: &str) {
     let c_str_source = c_str_source_head.as_c_str();
     pyo3::Python::attach(|py| {
         b.iter(|| {
-            let module = pyo3::types::PyModule::from_code(py, c_str_source, c"", c"")
+            let code = PyCode::compile(py, c_str_source, c"<benchmark>", PyCodeInput::File)
+                .expect("Error compiling source");
+            let globals = PyDict::new(py);
+            globals.set_item("__name__", "__main__").unwrap();
+            let result = code
+                .run(Some(&globals), None)
                 .expect("Error running source");
-            black_box(module);
+            black_box(result);
         })
     })
 }
@@ -46,6 +52,10 @@ fn bench_rustpython_code(b: &mut Bencher<'_>, name: &str, source: &str) {
         b.iter(|| {
             let code = vm.compile(source, Mode::Exec, name).unwrap();
             let scope = vm.new_scope_with_builtins();
+            scope
+                .globals
+                .set_item("__name__", vm.ctx.new_str("__main__").into(), vm)
+                .unwrap();
             let res: PyResult = vm.run_code_obj(code, scope);
             vm.unwrap_pyresult(res);
         })
diff --git a/benches/microbenchmarks.rs b/benches/microbenchmarks.rs
index 4d48278e447..7909c8e445e 100644
--- a/benches/microbenchmarks.rs
+++ b/benches/microbenchmarks.rs
@@ -45,11 +45,8 @@ fn bench_cpython_code(group: &mut BenchmarkGroup<'_, WallTime>, bench: &MicroBen
             pyo3::types::PyModule::import(py, "builtins").expect("Failed to import builtins");
         let exec = builtins.getattr("exec").expect("no exec in builtins");
 
-        let bench_func = |(globals, locals): &mut (
-            pyo3::Bound<'_, pyo3::types::PyDict>,
-            pyo3::Bound<'_, pyo3::types::PyDict>,
-        )| {
-            let res = exec.call((&code, &*globals, &*locals), None);
+        let bench_func = |globals: &mut pyo3::Bound<'_, pyo3::types::PyDict>| {
+            let res = exec.call((&code, &*globals), None);
             if let Err(e) = res {
                 e.print(py);
                 panic!("Error running microbenchmark")
@@ -58,23 +55,24 @@ fn bench_cpython_code(group: &mut BenchmarkGroup<'_, WallTime>, bench: &MicroBen
 
         let bench_setup = |iterations| {
             let globals = pyo3::types::PyDict::new(py);
-            let locals = pyo3::types::PyDict::new(py);
+            globals.set_item("__name__", "__main__").unwrap();
             if let Some(idx) = iterations {
                 globals.set_item("ITERATIONS", idx).unwrap();
             }
 
-            let res = exec.call((&setup_code, &globals, &locals), None);
+            let res = exec.call((&setup_code, &globals), None);
             if let Err(e) = res {
                 e.print(py);
                 panic!("Error running microbenchmark setup code")
             }
-            (globals, locals)
+            globals
         };
 
         if bench.iterate {
             for idx in iteration_counts() {
                 group.throughput(Throughput::Elements(idx as u64));
-                group.bench_with_input(BenchmarkId::new("cpython", &bench.name), &idx, |b, idx| {
+                let id = BenchmarkId::new("cpython", format!("{}[{idx}]", bench.name));
+                group.bench_with_input(id, &idx, |b, idx| {
                     b.iter_batched_ref(
                         || bench_setup(Some(*idx)),
                         bench_func,
@@ -109,6 +107,9 @@ fn bench_rustpython_code(group: &mut BenchmarkGroup<'_, WallTime>, bench: &Micro
     settings.path_list.push("Lib/".to_string());
     settings.write_bytecode = false;
     settings.user_site_directory = false;
+    // Pin the str/bytes hash secret so dict/set probe sequences (and thus
+    // timings) are reproducible across benchmark runs.
+    settings.hash_seed = Some(0);
 
     let builder = Interpreter::builder(settings);
     let defs = rustpython_stdlib::stdlib_module_defs(&builder.ctx);
@@ -128,6 +129,10 @@ fn bench_rustpython_code(group: &mut BenchmarkGroup<'_, WallTime>, bench: &Micro
 
         let bench_setup = |iterations| {
             let scope = vm.new_scope_with_builtins();
+            scope
+                .globals
+                .set_item("__name__", vm.ctx.new_str("__main__").into(), vm)
+                .unwrap();
             if let Some(idx) = iterations {
                 scope
                     .locals
@@ -145,17 +150,18 @@ fn bench_rustpython_code(group: &mut BenchmarkGroup<'_, WallTime>, bench: &Micro
         if bench.iterate {
             for idx in iteration_counts() {
                 group.throughput(Throughput::Elements(idx as u64));
-                group.bench_with_input(
-                    BenchmarkId::new("rustpython", &bench.name),
-                    &idx,
-                    |b, idx| {
-                        b.iter_batched(
-                            || bench_setup(Some(*idx)),
-                            bench_func,
-                            BatchSize::LargeInput,
-                        );
-                    },
-                );
+                let name = if is_codspeed() {
+                    bench.name.clone()
+                } else {
+                    format!("{}[{idx}]", bench.name)
+                };
+                group.bench_with_input(BenchmarkId::new("rustpython", name), &idx, |b, idx| {
+                    b.iter_batched(
+                        || bench_setup(Some(*idx)),
+                        bench_func,
+                        BatchSize::LargeInput,
+                    );
+                });
             }
         } else {
             group.bench_function(BenchmarkId::new("rustpython", &bench.name), move |b| {
diff --git a/crates/capi/Cargo.toml b/crates/capi/Cargo.toml
index 671c8d1640c..08c102b4a64 100644
--- a/crates/capi/Cargo.toml
+++ b/crates/capi/Cargo.toml
@@ -22,6 +22,7 @@ rustpython-stdlib = {workspace = true, features = ["threading"] }
 rustpython-pylib = { workspace = true }
 
 [dev-dependencies]
+static_assertions = { workspace = true }
 pyo3 = { workspace = true, features = ["auto-initialize", "abi3t"] }
 
 [lints]
diff --git a/crates/capi/src/abstract_/iter.rs b/crates/capi/src/abstract_/iter.rs
index 75834b22657..03f9fb14b1d 100644
--- a/crates/capi/src/abstract_/iter.rs
+++ b/crates/capi/src/abstract_/iter.rs
@@ -106,7 +106,7 @@ pub unsafe extern "C" fn PyIter_Send(
 #[cfg(test)]
 mod tests {
     use pyo3::prelude::*;
-    use pyo3::types::{PyAnyMethods, PyIterator, PyList, PySendResult};
+    use pyo3::types::{PyAnyMethods, PyIterator, PyList, iterator::PySendResult};
 
     #[test]
     fn next_item() {
diff --git a/crates/capi/src/bytesobject.rs b/crates/capi/src/bytesobject.rs
index f9aa9eb8f2e..f1ffb7a903a 100644
--- a/crates/capi/src/bytesobject.rs
+++ b/crates/capi/src/bytesobject.rs
@@ -1,7 +1,7 @@
 use crate::object::define_py_check;
 use crate::util::FfiPtrExt;
 use crate::{PyObject, pystate::with_vm};
-use core::ffi::{CStr, c_char, c_int};
+use core::ffi::{CStr, VaList, c_char, c_int, c_long, c_uint, c_ulong, c_void};
 use rustpython_vm::builtins::PyBytes;
 
 define_py_check!(fn PyBytes_Check, types.bytes_type);
@@ -38,6 +38,136 @@ pub unsafe extern "C" fn PyBytes_FromString(s: *const c_char) -> *mut PyObject {
     })
 }
 
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyBytes_FromFormat(format: *const c_char, args: ...) -> *mut PyObject {
+    unsafe { PyBytes_FromFormatV(format, args) }
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyBytes_FromFormatV(
+    format: *const c_char,
+    mut args: VaList<'_>,
+) -> *mut PyObject {
+    with_vm(|vm| {
+        let format = unsafe { CStr::from_ptr(format) }.to_bytes();
+        let mut result = Vec::with_capacity(format.len());
+        let mut pos = 0;
+        while pos < format.len() {
+            if format[pos] != b'%' {
+                result.push(format[pos]);
+                pos += 1;
+                continue;
+            }
+            let start = pos;
+            pos += 1;
+            // The C API ignores field width and applies precision only to %s.
+            while format.get(pos).is_some_and(u8::is_ascii_digit) {
+                pos += 1;
+            }
+            let mut precision = 0usize;
+            if format.get(pos) == Some(&b'.') {
+                pos += 1;
+                while let Some(&digit) = format.get(pos).filter(|b| b.is_ascii_digit()) {
+                    precision = precision
+                        .saturating_mul(10)
+                        .saturating_add((digit - b'0').into());
+                    pos += 1;
+                }
+            }
+            while format
+                .get(pos)
+                .is_some_and(|b| *b != b'%' && !b.is_ascii_alphabetic())
+            {
+                pos += 1;
+            }
+            let modifier = if matches!(format.get(pos), Some(b'l' | b'z'))
+                && matches!(format.get(pos + 1), Some(b'd' | b'u'))
+            {
+                let modifier = format[pos];
+                pos += 1;
+                Some(modifier)
+            } else {
+                None
+            };
+            match format.get(pos) {
+                Some(b'c') => {
+                    let value = unsafe { args.next_arg::<c_int>() };
+                    let value = u8::try_from(value).map_err(|_| {
+                        vm.new_overflow_error(
+                            "PyBytes_FromFormatV(): %c format expects an integer in range [0; 255]",
+                        )
+                    })?;
+                    result.push(value);
+                }
+                Some(b'd') => {
+                    let value = match modifier {
+                        Some(b'l') => unsafe { args.next_arg::<c_long>() }.to_string(),
+                        Some(b'z') => unsafe { args.next_arg::<isize>() }.to_string(),
+                        _ => unsafe { args.next_arg::<c_int>() }.to_string(),
+                    };
+                    result.extend_from_slice(value.as_bytes());
+                }
+                Some(b'u') => {
+                    let value = match modifier {
+                        Some(b'l') => unsafe { args.next_arg::<c_ulong>() }.to_string(),
+                        Some(b'z') => unsafe { args.next_arg::<usize>() }.to_string(),
+                        _ => unsafe { args.next_arg::<c_uint>() }.to_string(),
+                    };
+                    result.extend_from_slice(value.as_bytes());
+                }
+                Some(b'i') => result
+                    .extend_from_slice(unsafe { args.next_arg::<c_int>() }.to_string().as_bytes()),
+                Some(b'x') => result.extend_from_slice(
+                    format!("{:x}", unsafe { args.next_arg::<c_int>() } as c_uint).as_bytes(),
+                ),
+                Some(b's') => {
+                    let string = unsafe { args.next_arg::<*const c_char>() };
+                    if precision == 0 {
+                        result.extend_from_slice(unsafe { CStr::from_ptr(string) }.to_bytes());
+                    } else {
+                        // A precision-limited string need not have a terminator
+                        // beyond the specified readable region.
+                        for offset in 0..precision {
+                            let byte = unsafe { *string.add(offset) } as u8;
+                            if byte == 0 {
+                                break;
+                            }
+                            result.push(byte);
+                        }
+                    }
+                }
+                Some(b'p') => {
+                    let pointer = unsafe { args.next_arg::<*const c_void>() };
+                    // Preserve the platform's %p spelling, including Windows
+                    // uppercase digits, but always supply the C API's 0x prefix.
+                    let mut buffer = [0 as c_char; 2 * size_of::<usize>() + 16];
+                    unsafe {
+                        libc::snprintf(buffer.as_mut_ptr(), buffer.len(), c"%p".as_ptr(), pointer);
+                    }
+                    let pointer = unsafe { CStr::from_ptr(buffer.as_ptr()) }.to_bytes();
+                    result.extend_from_slice(b"0x");
+                    result.extend_from_slice(
+                        if pointer.starts_with(b"0x") || pointer.starts_with(b"0X") {
+                            &pointer[2..]
+                        } else {
+                            pointer
+                        },
+                    );
+                }
+                Some(b'%') => result.push(b'%'),
+                _ => {
+                    // The first unrecognized format copies the remaining
+                    // format verbatim, without consuming any more arguments.
+                    result.extend_from_slice(&format[start..]);
+                    break;
+                }
+            }
+            pos += 1;
+        }
+        Ok(vm.ctx.new_bytes(result))
+    })
+}
+
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyBytes_FromObject(obj: *mut PyObject) -> *mut PyObject {
     with_vm(|vm| {
diff --git a/crates/capi/src/ceval.rs b/crates/capi/src/ceval.rs
index 4064b289caf..036c259454b 100644
--- a/crates/capi/src/ceval.rs
+++ b/crates/capi/src/ceval.rs
@@ -1,12 +1,12 @@
 use crate::pyframe::PyFrameObject;
 use crate::pystate::with_vm;
 use crate::unicodeobject::decode_fsdefault_and_size;
-use crate::util::FfiPtrExt;
+use crate::util::{CStrExt, FfiPtrExt};
 use core::ffi::{CStr, c_char, c_int};
-use rustpython_vm::builtins::{PyCode, PyDict};
+use rustpython_vm::builtins::{PyAnyDict, PyCode};
 use rustpython_vm::function::ArgMapping;
 use rustpython_vm::scope::Scope;
-use rustpython_vm::{AsObject, PyObject, TryFromObject};
+use rustpython_vm::{AsObject, PyObject, PyRef, TryFromObject};
 use rustpython_vm::{PyObjectRef, version};
 
 #[unsafe(no_mangle)]
@@ -32,12 +32,17 @@ pub unsafe extern "C" fn PyEval_EvalCode(
 ) -> *mut PyObject {
     with_vm(|vm| {
         let code = unsafe { co.assume_borrowed_and_cast::<PyCode>(vm) }?;
-        let globals = unsafe { globals.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let globals = PyRef::<PyAnyDict>::try_from_object(
+            vm,
+            unsafe { globals.assume_borrowed() }.to_owned(),
+        )?;
         let locals = unsafe { locals.assume_borrowed_or_opt() }
             .map(|obj| ArgMapping::try_from_object(vm, obj.to_owned()))
             .transpose()?;
 
-        let scope = Scope::with_builtins(locals, globals.to_owned(), vm);
+        let locals = locals.or_else(|| Some(ArgMapping::from_anydict_exact(globals.clone())));
+        // Unlike Python's eval/exec, this API does not insert __builtins__.
+        let scope = Scope::new(locals, globals);
 
         vm.run_code_obj(code.to_owned(), scope)
     })
@@ -157,10 +162,21 @@ pub unsafe extern "C" fn PyEval_GetFuncDesc(func: *mut PyObject) -> *const c_cha
     })
 }
 
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn Py_EnterRecursiveCall(where_: *const c_char) -> c_int {
+    with_vm(|vm| vm.enter_recursive_call(unsafe { where_.try_as_str(vm)? }))
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn Py_LeaveRecursiveCall() {
+    with_vm(|vm| vm.leave_recursive_call())
+}
+
 #[cfg(test)]
 mod tests {
+    use super::{Py_EnterRecursiveCall, Py_LeaveRecursiveCall};
     use alloc::ffi::CString;
-    use pyo3::exceptions::PyException;
+    use pyo3::exceptions::{PyException, PyRecursionError};
     use pyo3::prelude::*;
 
     #[pyfunction]
@@ -268,4 +284,23 @@ assert not hidden_leaked
             .unwrap();
         })
     }
+
+    #[test]
+    fn recursion_error() {
+        fn recurse(py: Python<'_>) -> PyResult<()> {
+            unsafe {
+                if Py_EnterRecursiveCall(c"".as_ptr().cast()) != 0 {
+                    return Err(PyErr::fetch(py));
+                };
+                let result = recurse(py);
+                Py_LeaveRecursiveCall();
+                result
+            }
+        }
+
+        Python::attach(|py| {
+            let err = recurse(py).unwrap_err();
+            assert!(err.is_instance_of::<PyRecursionError>(py));
+        })
+    }
 }
diff --git a/crates/capi/src/dictobject.rs b/crates/capi/src/dictobject.rs
index 2c3eedff3ba..1e6fab1b131 100644
--- a/crates/capi/src/dictobject.rs
+++ b/crates/capi/src/dictobject.rs
@@ -4,9 +4,8 @@ use crate::pystate::with_vm;
 use crate::util::{CStrExt, FfiPtrExt};
 use core::ffi::{c_char, c_int};
 use core::ptr::NonNull;
-use rustpython_vm::AsObject;
-use rustpython_vm::PyPayload;
-use rustpython_vm::builtins::PyDict;
+use rustpython_vm::builtins::{PyAnyDict, PyDict, PyFrozenDict};
+use rustpython_vm::{AsObject, Py, PyPayload, PyResult, VirtualMachine};
 
 define_py_check!(fn PyDict_Check, types.dict_type);
 define_py_check!(exact fn PyDict_CheckExact, types.dict_type);
@@ -14,6 +13,27 @@ define_py_check!(fn PyDictKeys_Check, types.dict_keys_type);
 define_py_check!(fn PyDictValues_Check, types.dict_values_type);
 define_py_check!(fn PyDictItems_Check, types.dict_items_type);
 
+fn any_dict<'a>(dict: &'a PyObject, vm: &VirtualMachine) -> PyResult<&'a PyAnyDict> {
+    PyAnyDict::from_object(dict)
+        .ok_or_else(|| vm.new_system_error("bad argument to internal function"))
+}
+
+fn writable_dict<'a>(
+    dict: &'a PyObject,
+    operation: &str,
+    vm: &VirtualMachine,
+) -> PyResult<&'a Py<PyDict>> {
+    dict.downcast_ref::<PyDict>().ok_or_else(|| {
+        if dict.downcast_ref::<PyFrozenDict>().is_some() {
+            vm.new_type_error(format!(
+                "frozendict object does not support item {operation}"
+            ))
+        } else {
+            vm.new_system_error("bad argument to internal function")
+        }
+    })
+}
+
 #[unsafe(no_mangle)]
 pub extern "C" fn PyDict_New() -> *mut PyObject {
     with_vm(|vm| vm.ctx.new_dict())
@@ -21,10 +41,10 @@ pub extern "C" fn PyDict_New() -> *mut PyObject {
 
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_Clear(dict: *mut PyObject) {
-    with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
-        dict.clear();
-        Ok(())
+    with_vm(|_vm| {
+        if let Some(dict) = unsafe { dict.assume_borrowed() }.downcast_ref::<PyDict>() {
+            dict.clear();
+        }
     })
 }
 
@@ -35,7 +55,7 @@ pub unsafe extern "C" fn PyDict_SetItem(
     val: *mut PyObject,
 ) -> c_int {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = writable_dict(unsafe { dict.assume_borrowed() }, "assignment", vm)?;
         let key = unsafe { key.assume_borrowed() };
         let value = unsafe { val.assume_borrowed() }.to_owned();
         dict.inner_setitem(key, value, vm)
@@ -49,8 +69,8 @@ pub unsafe extern "C" fn PyDict_SetItemString(
     val: *mut PyObject,
 ) -> c_int {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
         let key = unsafe { key.try_as_str(vm) }?;
+        let dict = writable_dict(unsafe { dict.assume_borrowed() }, "assignment", vm)?;
         let value = unsafe { val.assume_borrowed() }.to_owned();
         dict.inner_setitem(key, value, vm)
     })
@@ -59,12 +79,14 @@ pub unsafe extern "C" fn PyDict_SetItemString(
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_GetItem(dict: *mut PyObject, key: *mut PyObject) -> *mut PyObject {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let Some(dict) = PyAnyDict::from_object(unsafe { dict.assume_borrowed() }) else {
+            return core::ptr::null_mut();
+        };
         let key = unsafe { key.assume_borrowed() };
 
         match dict.inner_getitem_opt(key, vm) {
-            Ok(Some(value)) => Ok(value.as_object().as_raw().cast_mut()),
-            Ok(None) | Err(_) => Ok(core::ptr::null_mut()),
+            Ok(Some(value)) => value.as_object().as_raw().cast_mut(),
+            Ok(None) | Err(_) => core::ptr::null_mut(),
         }
     })
 }
@@ -75,7 +97,7 @@ pub unsafe extern "C" fn PyDict_GetItemWithError(
     key: *mut PyObject,
 ) -> *mut PyObject {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = any_dict(unsafe { dict.assume_borrowed() }, vm)?;
         let key = unsafe { key.assume_borrowed() };
 
         if let Some(value) = dict.inner_getitem_opt(key, vm)? {
@@ -92,12 +114,16 @@ pub unsafe extern "C" fn PyDict_GetItemString(
     key: *const c_char,
 ) -> *mut PyObject {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
-        let key = unsafe { key.try_as_str(vm) }?;
+        let Ok(key) = (unsafe { key.try_as_str(vm) }) else {
+            return core::ptr::null_mut();
+        };
+        let Some(dict) = PyAnyDict::from_object(unsafe { dict.assume_borrowed() }) else {
+            return core::ptr::null_mut();
+        };
 
-        match dict.inner_getitem_opt(key, vm)? {
-            Some(value) => Ok(value.as_object().as_raw().cast_mut()),
-            None => Ok(core::ptr::null_mut()),
+        match dict.inner_getitem_opt(key, vm) {
+            Ok(Some(value)) => value.as_object().as_raw().cast_mut(),
+            Ok(None) | Err(_) => core::ptr::null_mut(),
         }
     })
 }
@@ -112,8 +138,8 @@ pub unsafe extern "C" fn PyDict_GetItemStringRef(
         unsafe {
             *result = core::ptr::null_mut();
         }
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
         let key = unsafe { key.try_as_str(vm) }?;
+        let dict = any_dict(unsafe { dict.assume_borrowed() }, vm)?;
 
         if let Some(value) = dict.inner_getitem_opt(key, vm)? {
             unsafe {
@@ -134,7 +160,7 @@ pub unsafe extern "C" fn PyDict_GetItemRef(
 ) -> c_int {
     with_vm(|vm| {
         unsafe { *result = core::ptr::null_mut() };
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = any_dict(unsafe { dict.assume_borrowed() }, vm)?;
         let key = unsafe { key.assume_borrowed() };
 
         if let Some(value) = dict.inner_getitem_opt(key, vm)? {
@@ -165,7 +191,7 @@ pub unsafe extern "C" fn PyDict_SetDefaultRef(
                 result.write(core::ptr::null_mut());
             }
         }
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = writable_dict(unsafe { dict.assume_borrowed() }, "assignment", vm)?;
         let key = unsafe { key.assume_borrowed() };
 
         if let Some(value) = dict.inner_getitem_opt(key, vm)? {
@@ -191,7 +217,9 @@ pub unsafe extern "C" fn PyDict_SetDefaultRef(
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_Size(dict: *mut PyObject) -> isize {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = unsafe { dict.assume_borrowed_or_opt() }
+            .ok_or_else(|| vm.new_system_error("bad argument to internal function"))?;
+        let dict = any_dict(dict, vm)?;
         Ok(dict.__len__())
     })
 }
@@ -199,7 +227,7 @@ pub unsafe extern "C" fn PyDict_Size(dict: *mut PyObject) -> isize {
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_Contains(dict: *mut PyObject, key: *mut PyObject) -> c_int {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = any_dict(unsafe { dict.assume_borrowed() }, vm)?;
         let key = unsafe { key.assume_borrowed() };
         Ok(dict.inner_getitem_opt(key, vm)?.is_some())
     })
@@ -208,7 +236,9 @@ pub unsafe extern "C" fn PyDict_Contains(dict: *mut PyObject, key: *mut PyObject
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_Copy(dict: *mut PyObject) -> *mut PyObject {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = unsafe { dict.assume_borrowed_or_opt() }
+            .and_then(|dict| dict.downcast_ref::<PyDict>())
+            .ok_or_else(|| vm.new_system_error("bad argument to internal function"))?;
         Ok(dict.copy().into_ref(&vm.ctx))
     })
 }
@@ -216,8 +246,12 @@ pub unsafe extern "C" fn PyDict_Copy(dict: *mut PyObject) -> *mut PyObject {
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_DelItem(dict: *mut PyObject, key: *mut PyObject) -> c_int {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = unsafe { dict.assume_borrowed() };
         let key = unsafe { key.assume_borrowed() };
+        if dict.downcast_ref::<PyFrozenDict>().is_some() {
+            PyFrozenDict::key_hash(key, vm)?;
+        }
+        let dict = writable_dict(dict, "deletion", vm)?;
         dict.del_item(key, vm)
     })
 }
@@ -225,8 +259,8 @@ pub unsafe extern "C" fn PyDict_DelItem(dict: *mut PyObject, key: *mut PyObject)
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_DelItemString(dict: *mut PyObject, key: *const c_char) -> c_int {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
         let key = unsafe { key.try_as_str(vm) }?;
+        let dict = writable_dict(unsafe { dict.assume_borrowed() }, "deletion", vm)?;
         dict.del_item(key, vm)
     })
 }
@@ -234,7 +268,9 @@ pub unsafe extern "C" fn PyDict_DelItemString(dict: *mut PyObject, key: *const c
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_Items(dict: *mut PyObject) -> *mut PyObject {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = unsafe { dict.assume_borrowed_or_opt() }
+            .ok_or_else(|| vm.new_system_error("bad argument to internal function"))?;
+        let dict = any_dict(dict, vm)?;
         let items = dict
             .items_vec()
             .into_iter()
@@ -247,7 +283,9 @@ pub unsafe extern "C" fn PyDict_Items(dict: *mut PyObject) -> *mut PyObject {
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_Keys(dict: *mut PyObject) -> *mut PyObject {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = unsafe { dict.assume_borrowed_or_opt() }
+            .ok_or_else(|| vm.new_system_error("bad argument to internal function"))?;
+        let dict = any_dict(dict, vm)?;
         Ok(vm.ctx.new_list(dict.keys_vec()))
     })
 }
@@ -255,7 +293,9 @@ pub unsafe extern "C" fn PyDict_Keys(dict: *mut PyObject) -> *mut PyObject {
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_Values(dict: *mut PyObject) -> *mut PyObject {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = unsafe { dict.assume_borrowed_or_opt() }
+            .ok_or_else(|| vm.new_system_error("bad argument to internal function"))?;
+        let dict = any_dict(dict, vm)?;
         Ok(vm.ctx.new_list(dict.values_vec()))
     })
 }
@@ -267,7 +307,7 @@ pub unsafe extern "C" fn PyDict_Merge(
     override_: c_int,
 ) -> c_int {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = writable_dict(unsafe { dict.assume_borrowed() }, "assignment", vm)?;
         let other = unsafe { other.assume_borrowed() }.to_owned();
         if override_ != 0 {
             dict.merge_object(other, vm)
@@ -280,7 +320,7 @@ pub unsafe extern "C" fn PyDict_Merge(
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyDict_Update(dict: *mut PyObject, other: *mut PyObject) -> c_int {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = writable_dict(unsafe { dict.assume_borrowed() }, "assignment", vm)?;
         let other = unsafe { other.assume_borrowed() }.to_owned();
         dict.merge_object(other, vm)
     })
@@ -293,7 +333,7 @@ pub unsafe extern "C" fn PyDict_MergeFromSeq2(
     override_: c_int,
 ) -> c_int {
     with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+        let dict = writable_dict(unsafe { dict.assume_borrowed() }, "assignment", vm)?;
         let seq2 = unsafe { seq2.assume_borrowed() };
         dict.merge_from_seq2(seq2, override_ != 0, vm)
     })
@@ -306,8 +346,10 @@ pub unsafe extern "C" fn PyDict_Next(
     key: *mut *mut PyObject,
     value: *mut *mut PyObject,
 ) -> c_int {
-    with_vm(|vm| {
-        let dict = unsafe { dict.assume_borrowed_and_cast::<PyDict>(vm) }?;
+    with_vm(|_vm| {
+        let Some(dict) = PyAnyDict::from_object(unsafe { dict.assume_borrowed() }) else {
+            return false;
+        };
         let index = unsafe { *pos } as usize;
 
         if let Some((next_pos, k, v)) = dict.next_entry(index) {
@@ -320,9 +362,9 @@ pub unsafe extern "C" fn PyDict_Next(
                     value.write(v.as_object().as_raw().cast_mut());
                 }
             }
-            Ok(true)
+            true
         } else {
-            Ok(false)
+            false
         }
     })
 }
diff --git a/crates/capi/src/lib.rs b/crates/capi/src/lib.rs
index 90ef71da7a8..aeeff3537d7 100644
--- a/crates/capi/src/lib.rs
+++ b/crates/capi/src/lib.rs
@@ -4,7 +4,7 @@ use crate::pyerrors::init_exception_statics;
 use crate::pylifecycle::{MAIN_INTERP, MAIN_INTERP_PTR};
 use core::sync::atomic::Ordering;
 pub use rustpython_vm::PyObject;
-use rustpython_vm::{Context, Interpreter};
+use rustpython_vm::{Context, Interpreter, VirtualMachine};
 use std::sync::MutexGuard;
 
 extern crate alloc;
@@ -32,6 +32,7 @@ pub mod moduleobject;
 pub mod object;
 pub mod objimpl;
 pub mod osmodule;
+pub mod pybuffer;
 pub mod pycapsule;
 pub mod pyerrors;
 pub mod pyframe;
@@ -70,3 +71,33 @@ pub fn init_main_interpreter(interpreter: Interpreter) {
         Ordering::Release,
     );
 }
+
+/// Py_RunMain for an interpreter that C API threads can attach to.
+///
+/// `f` reports its own errors and returns the exit code.
+pub fn run_main_interpreter(
+    mut interpreter: Interpreter,
+    f: impl FnOnce(&VirtualMachine) -> u32,
+) -> u32 {
+    let main_thread = interpreter.take_main_thread();
+    init_main_interpreter(interpreter);
+
+    struct RegistrationGuard;
+    impl Drop for RegistrationGuard {
+        fn drop(&mut self) {
+            let mut registered = MAIN_INTERP
+                .lock()
+                .unwrap_or_else(std::sync::PoisonError::into_inner);
+            MAIN_INTERP_PTR.store(core::ptr::null_mut(), Ordering::Release);
+            let interpreter = registered.take();
+            drop(registered);
+            drop(interpreter);
+        }
+    }
+    let _registration = RegistrationGuard;
+
+    // The registered interpreter is an inactive worker-VM template. Running
+    // the original VM locally preserves main-thread state without keeping the
+    // global mutex locked across Python execution or finalization callbacks.
+    main_thread.run_main(f)
+}
diff --git a/crates/capi/src/methodobject.rs b/crates/capi/src/methodobject.rs
index 9868db36cac..1f2a3baa731 100644
--- a/crates/capi/src/methodobject.rs
+++ b/crates/capi/src/methodobject.rs
@@ -113,25 +113,25 @@ pub(crate) fn build_method_def(
         },
         PyMethodFlags::VARARGS => {
             let callable = move |args: PosArgs, vm: &VirtualMachine| unsafe {
-                call_function(vm, method, flags, Some(args))
+                call_function(vm, method, has_self, Some(args))
             };
             Ok(vm.ctx.new_method_def(name, callable, flags, doc))
         },
         PyMethodFlags::VARARGS | PyMethodFlags::KEYWORDS => {
             let callable = move | args: FuncArgs, vm: &VirtualMachine| unsafe {
-                call_function_with_keywords(vm, method, flags, args)
+                call_function_with_keywords(vm, method, has_self, args)
             };
             Ok(vm.ctx.new_method_def(name, callable, flags, doc))
         },
         PyMethodFlags::FASTCALL | PyMethodFlags::KEYWORDS => {
             let callable = move |args: FuncArgs, vm: &VirtualMachine| unsafe {
-                call_fast_function_with_keywords(vm, method, flags, args)
+                call_fast_function_with_keywords(vm, method, has_self, args)
             };
             Ok(vm.ctx.new_method_def(name, callable, flags, doc))
         },
         PyMethodFlags::FASTCALL => {
             let callable = move |args: PosArgs, vm: &VirtualMachine| unsafe {
-                call_fast_function(vm, method, flags, args)
+                call_fast_function(vm, method, has_self, args)
             };
             Ok(vm.ctx.new_method_def(name, callable, flags, doc))
         },
@@ -160,12 +160,12 @@ pub(crate) fn build_method_def(
 unsafe fn call_function<A: Into<FuncArgs>>(
     vm: &VirtualMachine,
     method: PyMethodPointer,
-    flags: PyMethodFlags,
+    has_self: bool,
     args: Option<A>,
 ) -> PyResult {
     let f = unsafe { method.PyCFunction };
     let (slf, arg_tuple) = if let Some(mut args) = args.map(Into::into) {
-        let slf = take_self_arg(&mut args, flags);
+        let slf = take_self_arg(&mut args, has_self);
         let arg_tuple = vm.ctx.new_tuple(args.args);
         (slf, Some(arg_tuple))
     } else {
@@ -188,11 +188,11 @@ unsafe fn call_function<A: Into<FuncArgs>>(
 unsafe fn call_function_with_keywords(
     vm: &VirtualMachine,
     method: PyMethodPointer,
-    flags: PyMethodFlags,
+    has_self: bool,
     mut args: FuncArgs,
 ) -> PyResult {
     let f = unsafe { method.PyCFunctionWithKeywords };
-    let slf = take_self_arg(&mut args, flags);
+    let slf = take_self_arg(&mut args, has_self);
     let slf_ptr = slf
         .as_ref()
         .map(|obj| obj.as_object().as_raw().cast_mut())
@@ -215,11 +215,11 @@ unsafe fn call_function_with_keywords(
 unsafe fn call_fast_function_with_keywords(
     vm: &VirtualMachine,
     method: PyMethodPointer,
-    flags: PyMethodFlags,
+    has_self: bool,
     mut args: FuncArgs,
 ) -> PyResult {
     let f = unsafe { method.PyCFunctionFastWithKeywords };
-    let slf = take_self_arg(&mut args, flags);
+    let slf = take_self_arg(&mut args, has_self);
     let slf_ptr = slf
         .as_ref()
         .map(|obj| obj.as_object().as_raw().cast_mut())
@@ -250,12 +250,12 @@ unsafe fn call_fast_function_with_keywords(
 unsafe fn call_fast_function(
     vm: &VirtualMachine,
     method: PyMethodPointer,
-    flags: PyMethodFlags,
+    has_self: bool,
     args: PosArgs,
 ) -> PyResult {
     let f = unsafe { method.PyCFunctionFast };
     let mut args: FuncArgs = args.into();
-    let slf = take_self_arg(&mut args, flags);
+    let slf = take_self_arg(&mut args, has_self);
     let slf_ptr = slf
         .as_ref()
         .map(|obj| obj.as_object().as_raw().cast_mut())
@@ -267,8 +267,8 @@ unsafe fn call_fast_function(
     unsafe { f(slf_ptr, fastcall_arg_ptrs, args.args.len() as isize).assume_owned_or_err(vm) }
 }
 
-fn take_self_arg(args: &mut FuncArgs, flags: PyMethodFlags) -> Option<PyObjectRef> {
-    if flags.contains(PyMethodFlags::STATIC) {
+fn take_self_arg(args: &mut FuncArgs, has_self: bool) -> Option<PyObjectRef> {
+    if !has_self {
         None
     } else {
         args.take_positional()
@@ -385,4 +385,39 @@ mod tests {
             func.call0().unwrap();
         });
     }
+
+    #[test]
+    fn wrap_one_arg_function_with_no_module() {
+        #[pyfunction]
+        fn one_arg(value: i64) -> i64 {
+            value
+        }
+
+        Python::attach(|py| {
+            let func = wrap_pyfunction!(one_arg, py).unwrap();
+            func.call1((7,)).unwrap();
+        });
+    }
+
+    #[test]
+    fn no_keywords_before_arity() {
+        Python::attach(|py| {
+            unsafe extern "C" fn c_fn(_self: *mut PyObject, _args: *mut PyObject) -> *mut PyObject {
+                unsafe { PyLong_FromLong(42) }
+            }
+            let f = PyCFunction::new(py, c_fn, c"no_keywords", c"", None).unwrap();
+            let kwargs = pyo3::types::PyDict::new(py);
+            kwargs.set_item("unexpected", 1).unwrap();
+            let err = f.call((1,), Some(&kwargs)).unwrap_err();
+            assert_eq!(
+                err.value(py).str().unwrap().to_str().unwrap(),
+                "no_keywords() takes no keyword arguments"
+            );
+            kwargs.clear();
+            assert_eq!(
+                f.call((), Some(&kwargs)).unwrap().extract::<i32>().unwrap(),
+                42
+            );
+        });
+    }
 }
diff --git a/crates/capi/src/pybuffer.rs b/crates/capi/src/pybuffer.rs
new file mode 100644
index 00000000000..1eec20cd3a5
--- /dev/null
+++ b/crates/capi/src/pybuffer.rs
@@ -0,0 +1,335 @@
+use crate::PyObject;
+use crate::pystate::with_vm;
+use crate::util::FfiPtrExt;
+use alloc::borrow::Cow;
+use alloc::ffi::CString;
+use core::ffi::{c_char, c_int, c_void};
+use core::ptr::{self, NonNull};
+use rustpython_vm::protocol::{BufferFlags, PyBuffer};
+
+#[repr(C)]
+#[derive(Default)]
+pub struct Py_buffer {
+    pub buf: *mut c_void,
+    pub obj: *mut PyObject,
+    pub len: isize,
+    pub itemsize: isize,
+    pub readonly: c_int,
+    pub ndim: c_int,
+    pub format: *mut c_char,
+    pub shape: *mut isize,
+    pub strides: *mut isize,
+    pub suboffsets: *mut isize,
+    pub internal: *mut c_void,
+}
+
+impl Py_buffer {
+    fn is_contiguous_for_order(&self, order: u8) -> bool {
+        let desc = unsafe { &(&*self.internal.cast::<BufferInternal>()).buffer.desc };
+        if desc.len == 0 || desc.ndim() <= 1 {
+            return true;
+        }
+
+        if desc.has_suboffsets() {
+            return false;
+        }
+
+        match order {
+            b'C' => desc.is_contiguous(),
+            b'F' => desc.is_fortran_contiguous(),
+            b'A' => desc.is_contiguous() || desc.is_fortran_contiguous(),
+            _ => false,
+        }
+    }
+}
+
+#[allow(dead_code)]
+struct BufferInternal {
+    buffer: PyBuffer,
+    format: Option<CString>,
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyObject_GetBuffer(
+    obj: *mut PyObject,
+    view: *mut Py_buffer,
+    flags: c_int,
+) -> c_int {
+    with_vm(|vm| {
+        let obj = unsafe { obj.assume_borrowed() };
+        let flags = BufferFlags::from_bits_retain(flags as u32);
+        let buffer = PyBuffer::from_object(vm, obj, flags)?;
+
+        if flags.contains(BufferFlags::WRITABLE) && buffer.desc.readonly {
+            return Err(vm.new_buffer_error("Object is not writable"));
+        }
+
+        let format = flags
+            .contains(BufferFlags::FORMAT)
+            .then(|| {
+                CString::new(&*buffer.desc.format)
+                    .map_err(|_| vm.new_system_error("buffer format contains NUL"))
+            })
+            .transpose()?;
+
+        let shape = if flags.contains(BufferFlags::ND) {
+            buffer.desc.shape().as_ptr().cast_mut()
+        } else {
+            ptr::null_mut()
+        };
+
+        let strides = if flags.contains(BufferFlags::STRIDES) {
+            buffer.desc.strides().as_ptr().cast_mut()
+        } else {
+            ptr::null_mut()
+        };
+
+        let suboffsets = if flags.contains(BufferFlags::INDIRECT) {
+            buffer.desc.suboffsets().as_ptr().cast_mut()
+        } else {
+            ptr::null_mut()
+        };
+
+        let mut buffer_view = Py_buffer {
+            len: buffer.desc.len as _,
+            itemsize: buffer.desc.itemsize as _,
+            readonly: buffer.desc.readonly.into(),
+            ndim: buffer.desc.ndim() as _,
+            format: format.as_ref().map_or_default(|s| s.as_ptr().cast_mut()),
+            shape,
+            strides,
+            suboffsets,
+            ..Default::default()
+        };
+
+        let c_contig = buffer.desc.is_contiguous();
+        let f_contig = buffer.desc.is_fortran_contiguous();
+
+        if flags.contains(BufferFlags::C_CONTIGUOUS) && !c_contig {
+            return Err(vm.new_buffer_error("Object is not C-contiguous"));
+        }
+        if flags.contains(BufferFlags::F_CONTIGUOUS) && !f_contig {
+            return Err(vm.new_buffer_error("Object is not Fortran-contiguous"));
+        }
+        if flags.contains(BufferFlags::ANY_CONTIGUOUS) && !(c_contig || f_contig) {
+            return Err(vm.new_buffer_error("Object is not contiguous"));
+        }
+
+        buffer_view.obj = obj.as_raw().cast_mut();
+        buffer_view.buf = unsafe {
+            buffer
+                .obj_bytes()
+                .as_ptr()
+                .cast_mut()
+                .offset(buffer.desc.offset)
+        }
+        .cast();
+        buffer_view.internal = Box::into_raw(Box::new(BufferInternal { buffer, format })).cast();
+
+        unsafe {
+            ptr::replace(view, buffer_view);
+        }
+        Ok(())
+    })
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyBuffer_Release(view: *mut Py_buffer) {
+    let view = unsafe { &mut *view };
+    let internal = unsafe {
+        NonNull::new(view.internal.cast::<BufferInternal>()).map(|ptr| Box::from_non_null(ptr))
+    };
+    drop(internal);
+    core::mem::take(view);
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyBuffer_IsContiguous(view: *const Py_buffer, fort: c_char) -> c_int {
+    unsafe { &*view }
+        .is_contiguous_for_order((fort as u8).to_ascii_uppercase())
+        .into()
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyBuffer_GetPointer(
+    view: *const Py_buffer,
+    indices: *const isize,
+) -> *mut c_void {
+    with_vm(|vm| {
+        let view = unsafe { &*view };
+
+        if view.strides.is_null() && view.shape.is_null() {
+            let i0 = unsafe { *indices };
+            let delta = i0
+                .checked_mul(view.itemsize)
+                .ok_or_else(|| vm.new_system_error("index * itemsize overflow"))?;
+            return unsafe { Ok(view.buf.cast::<u8>().offset(delta).cast()) };
+        }
+
+        let ndim: usize = view
+            .ndim
+            .try_into()
+            .map_err(|_| vm.new_system_error("view.ndim does not fit usize"))?;
+
+        let idx = unsafe { core::slice::from_raw_parts(indices, ndim) };
+
+        let strides: Cow<'_, _> = unsafe { view.strides.as_ref() }.map_or_else(
+            || {
+                let shape = unsafe { core::slice::from_raw_parts(view.shape, ndim) };
+                let mut strides = vec![0; shape.len()];
+                let mut stride = view.itemsize;
+                for (ix, dim) in shape.iter().copied().enumerate().rev() {
+                    strides[ix] = stride;
+                    stride = stride
+                        .checked_mul(dim)
+                        .ok_or_else(|| vm.new_system_error("stride overflow"))?;
+                }
+                Ok(strides.into())
+            },
+            |strides| unsafe { Ok(core::slice::from_raw_parts(strides, ndim).into()) },
+        )?;
+
+        let suboffsets = unsafe {
+            view.suboffsets
+                .as_ref()
+                .map(|suboffsets| core::slice::from_raw_parts(suboffsets, ndim))
+        };
+
+        let mut ptr_u8 = view.buf.cast::<u8>();
+        for (dim, index) in idx.iter().enumerate() {
+            let delta = index
+                .checked_mul(strides[dim])
+                .ok_or_else(|| vm.new_system_error("index * stride overflow"))?;
+            ptr_u8 = unsafe { ptr_u8.offset(delta) };
+            if let Some(suboffsets) = suboffsets {
+                let suboffset = suboffsets[dim];
+                if suboffset >= 0 {
+                    let inner = unsafe { core::ptr::read_unaligned(ptr_u8.cast::<*mut u8>()) };
+                    ptr_u8 = unsafe { inner.offset(suboffset) };
+                }
+            }
+        }
+
+        Ok(ptr_u8.cast())
+    })
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyBuffer_ToContiguous(
+    buf: *mut c_void,
+    view: *const Py_buffer,
+    len: isize,
+    order: c_char,
+) -> c_int {
+    with_vm(|vm| {
+        let view = unsafe { &*view };
+
+        if !view.is_contiguous_for_order((order as u8).to_ascii_uppercase()) {
+            return Err(vm.new_buffer_error(
+                "PyBuffer_ToContiguous only supports contiguous exported buffers",
+            ));
+        }
+
+        if len != view.len {
+            return Err(vm.new_buffer_error("len must match view->len"));
+        }
+
+        let len: usize = len
+            .try_into()
+            .map_err(|_| vm.new_system_error("buffer len does not fit usize"))?;
+
+        let src = unsafe { core::slice::from_raw_parts(view.buf.cast::<u8>(), len) };
+        let dst = unsafe { core::slice::from_raw_parts_mut(buf.cast::<u8>(), len) };
+
+        dst.copy_from_slice(src);
+        Ok(())
+    })
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyBuffer_FromContiguous(
+    view: *const Py_buffer,
+    buf: *const c_void,
+    len: isize,
+    order: c_char,
+) -> c_int {
+    with_vm(|vm| {
+        let view = unsafe { &*view };
+
+        if view.readonly != 0 {
+            return Err(vm.new_buffer_error("cannot write into readonly buffer"));
+        }
+
+        if !view.is_contiguous_for_order((order as u8).to_ascii_uppercase()) {
+            return Err(vm.new_buffer_error(
+                "PyBuffer_FromContiguous only supports contiguous exported buffers",
+            ));
+        }
+
+        let len: usize = len
+            .min(view.len)
+            .try_into()
+            .map_err(|_| vm.new_system_error("len does not fit usize"))?;
+
+        let src = unsafe { core::slice::from_raw_parts(buf.cast::<u8>(), len) };
+        let dst = unsafe { core::slice::from_raw_parts_mut(view.buf.cast::<u8>(), len) };
+        dst.copy_from_slice(src);
+        Ok(())
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use pyo3::buffer::PyBuffer;
+    use pyo3::prelude::*;
+    use pyo3::types::{PyByteArray, PyBytes};
+
+    #[test]
+    fn object_getbuffer_basic_and_release() {
+        Python::attach(|py| {
+            let bytes = PyBytes::new(py, b"hello");
+            let buffer = PyBuffer::<u8>::get(&bytes).unwrap();
+            assert_eq!(buffer.dimensions(), 1);
+            assert_eq!(buffer.item_count(), 5);
+            assert_eq!(buffer.to_vec(py).unwrap(), b"hello");
+        });
+    }
+
+    #[test]
+    fn contiguous_copy_roundtrip() {
+        Python::attach(|py| {
+            let src = PyBytes::new(py, b"abcde");
+            let buffer = PyBuffer::<u8>::get(&src).unwrap();
+            let mut out = [0u8; 5];
+            buffer.copy_to_slice(py, &mut out).unwrap();
+            assert_eq!(&out, b"abcde");
+        });
+    }
+
+    #[test]
+    fn is_contiguous_and_get_pointer() {
+        Python::attach(|py| {
+            let bytes = PyBytes::new(py, b"xyz");
+            let buffer = PyBuffer::<u8>::get(&bytes).unwrap();
+            assert!(buffer.is_c_contiguous());
+
+            let p = buffer.get_ptr(&[1]);
+            assert!(!p.is_null());
+            unsafe { assert_eq!(*(p.cast::<u8>()), b'y') };
+        });
+    }
+
+    #[test]
+    fn writable_bytearray() {
+        Python::attach(|py| {
+            let bytearray = PyByteArray::new(py, b"hello");
+            let buffer = PyBuffer::<u8>::get(&bytearray).unwrap();
+            assert_eq!(buffer.dimensions(), 1);
+            assert_eq!(buffer.item_count(), 5);
+            // SAFETY: There are no other references to the buffer.
+            unsafe { buffer.as_slice_ptr().unwrap().as_mut()[0] = b'H' };
+            drop(buffer);
+            assert_eq!(bytearray.to_vec(), b"Hello");
+        });
+    }
+}
diff --git a/crates/capi/src/pyerrors.rs b/crates/capi/src/pyerrors.rs
index e43358ae348..0bf843aa442 100644
--- a/crates/capi/src/pyerrors.rs
+++ b/crates/capi/src/pyerrors.rs
@@ -5,7 +5,6 @@ use core::convert::Infallible;
 use core::ffi::{c_char, c_int};
 use core::slice;
 use rustpython_vm::builtins::{PyBaseException, PyTraceback, PyTuple, PyType};
-use rustpython_vm::convert::IntoObject;
 use rustpython_vm::exceptions::ExceptionZoo;
 use rustpython_vm::{AsObject, PyResult};
 
diff --git a/crates/capi/src/pyframe.rs b/crates/capi/src/pyframe.rs
index 2214ee55820..c3e81c235b3 100644
--- a/crates/capi/src/pyframe.rs
+++ b/crates/capi/src/pyframe.rs
@@ -2,9 +2,9 @@ use crate::PyObject;
 use crate::pystate::with_vm;
 use crate::util::FfiPtrExt;
 use core::ffi::c_int;
-use rustpython_vm::Py;
 use rustpython_vm::builtins::PyCode;
 use rustpython_vm::frame::FrameObject;
+use rustpython_vm::{Py, PyObjectRef};
 
 pub type PyFrameObject = Py<FrameObject>;
 pub type PyCodeObject = Py<PyCode>;
@@ -26,7 +26,7 @@ pub unsafe extern "C" fn PyFrame_GetLocals(frame: *mut PyFrameObject) -> *mut Py
 
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn PyFrame_GetGlobals(frame: *mut PyFrameObject) -> *mut PyObject {
-    with_vm(|_vm| Ok(unsafe { frame.assume_borrowed() }.f_globals()))
+    with_vm(|_vm| PyObjectRef::from(unsafe { frame.assume_borrowed() }.f_globals()))
 }
 
 #[unsafe(no_mangle)]
diff --git a/crates/capi/src/util.rs b/crates/capi/src/util.rs
index 5d0e2c26f5a..d8926f44d28 100644
--- a/crates/capi/src/util.rs
+++ b/crates/capi/src/util.rs
@@ -40,20 +40,12 @@ where
 
 impl<T> FfiResult<*mut Py<T>> for PyRef<T>
 where
-    Self: Into<PyObjectRef>,
+    T: rustpython_vm::object::PyRefTarget<Target = Py<T>>,
 {
     const ERR_VALUE: *mut Py<T> = core::ptr::null_mut();
 
     fn into_output(self, _vm: &VirtualMachine) -> *mut Py<T> {
-        self.into().into_raw().as_ptr().cast()
-    }
-}
-
-impl FfiResult<*mut PyObject> for PyObjectRef {
-    const ERR_VALUE: *mut PyObject = core::ptr::null_mut();
-
-    fn into_output(self, _vm: &VirtualMachine) -> *mut PyObject {
-        self.into_raw().as_ptr()
+        PyObjectRef::from(self).into_raw().as_ptr().cast()
     }
 }
 
@@ -324,7 +316,7 @@ impl<T: PyPayload> FfiPtrExt for *mut Py<T> {
             "Attempted to dereference NULL {}",
             type_name::<Self>()
         );
-        unsafe { PyRef::from_raw(self.cast_const()) }
+        unsafe { PyRef::<T>::from_raw(self.cast_const()) }
     }
 
     #[inline]
@@ -384,6 +376,14 @@ mod tests {
     use core::ffi::{c_longlong, c_ulonglong};
     use core::fmt::Debug;
 
+    #[test]
+    fn pyref_object_ffi_targets() {
+        use rustpython_vm::builtins::PyInt;
+        static_assertions::assert_impl_all!(PyObjectRef: FfiResult<*mut PyObject>);
+        static_assertions::assert_impl_all!(PyRef<PyInt>: FfiResult<*mut PyObject>, FfiResult<*mut Py<PyInt>>);
+        static_assertions::assert_not_impl_any!(PyObjectRef: FfiResult<*mut Py<PyObject>>);
+    }
+
     #[test]
     fn ffi_result_err_value() {
         fn assert_error_value<T, Output>(value: Output)
diff --git a/crates/codegen/src/compile.rs b/crates/codegen/src/compile.rs
index c2b6446ee79..fb561db6d93 100644
--- a/crates/codegen/src/compile.rs
+++ b/crates/codegen/src/compile.rs
@@ -14,7 +14,9 @@ use crate::{
     error::{CodegenError, CodegenErrorType, InternalError},
     interpolated_string_literal_value, interpolation_debug_text,
     ir::{self, Block, BlockIdx, Blocks},
-    preprocess, string_literal_part_value, string_literal_value,
+    preprocess,
+    source_location::{CompilerSourceSpan, node_location},
+    string_literal_part_value, string_literal_value,
     symboltable::{self, CompilerScope, Symbol, SymbolFlags, SymbolScope, SymbolTable},
     unparse::UnparseExpr,
 };
@@ -23,10 +25,11 @@ use core::{mem, slice};
 use malachite_bigint::BigInt;
 use num_complex::Complex;
 use num_traits::{Num, ToPrimitive, Zero};
-use ruff_python_ast::{self as ast, name::Name};
+use ruff_python_ast::{self as ast, HasNodeIndex, name::Name};
 use ruff_text_size::{Ranged, TextRange, TextSize, TextSlice};
 use rustpython_compiler_core::{
-    Mode, OneIndexed, PositionEncoding, SourceFile, SourceLocation,
+    AstLocations, Mode, OneIndexed, PositionEncoding, SourceFile, SourceLocation,
+    SourceLocationRange,
     bytecode::{
         self, AnyInstruction, AnyOpcode, Arg as OpArgMarker, BinaryOperator, BuildSliceArgCount,
         CodeObject, ComparisonOperator, ConstantData, ConvertValueOparg, Instruction,
@@ -68,6 +71,7 @@ const CO_MAXBLOCKS: usize = 21;
 pub enum FBlockType {
     WhileLoop,
     ForLoop,
+    AsyncForLoop,
     TryExcept,
     FinallyTry,
     FinallyEnd,
@@ -107,6 +111,8 @@ enum SuperCallType<'a> {
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum BuiltinGeneratorCallKind {
     Tuple,
+    List,
+    Set,
     All,
     Any,
 }
@@ -118,7 +124,7 @@ pub struct FBlockInfo {
     pub(crate) fb_block: ir::InstructionSequenceLabel,
     // CPython's optional type-specific exit or cleanup jump_target_label.
     pub(crate) fb_exit: ir::InstructionSequenceLabel,
-    pub fb_range: TextRange,
+    pub(crate) fb_span: CompilerSourceSpan,
     // additional data for fblock unwinding
     pub fb_datum: FBlockDatum,
 }
@@ -177,7 +183,8 @@ struct Compiler<'a> {
     symbol_table_stack: Vec<SymbolTable>,
     source_file: SourceFile,
     // current_source_location: SourceLocation,
-    current_source_range: TextRange,
+    current_source_span: CompilerSourceSpan,
+    ast_locations: Option<AstLocations>,
     future_features: bytecode::CodeFlags,
     future_annotations: bool,
     ctx: CompileContext,
@@ -311,6 +318,10 @@ pub struct CompileOpts {
     pub dont_imply_dedent: bool,
     /// Recursion limit used by compiler tree walks, matching Py_EnterRecursiveCall.
     pub recursion_limit: usize,
+    /// Emit `BUILD_LIST_FROM_ARG` for a list comprehension with one
+    /// generator and no `if`, sizing the result from the iterator's length
+    /// hint. Off by default: the opcode is not part of the CPython set.
+    pub build_list_from_arg: bool,
 }
 
 impl Default for CompileOpts {
@@ -323,6 +334,7 @@ impl Default for CompileOpts {
             future_features: bytecode::CodeFlags::empty(),
             dont_imply_dedent: false,
             recursion_limit: 1000,
+            build_list_from_arg: false,
         }
     }
 }
@@ -362,7 +374,7 @@ enum ComprehensionLoopControl {
         loop_block: BlockIdx,
         if_cleanup_block: BlockIdx,
         after_block: BlockIdx,
-        backedge_range: TextRange,
+        backedge_range: CompilerSourceSpan,
         is_async: bool,
         end_async_for_target: BlockIdx,
     },
@@ -395,13 +407,44 @@ pub fn compile_top(
     compile_top_with_syntax_warning_handler(ast, source_file, mode, opts, None)
 }
 
+/// An AST and its optional explicitly supplied Python source coordinates.
+/// Parser callers leave `locations` absent and retain source-based positions.
+pub struct AstInput {
+    pub ast: ast::Mod,
+    pub source_file: SourceFile,
+    pub locations: Option<AstLocations>,
+}
+
 pub fn compile_top_with_syntax_warning_handler<'a>(
-    mut ast: ruff_python_ast::Mod,
+    ast: ruff_python_ast::Mod,
     source_file: SourceFile,
     mode: Mode,
+    opts: CompileOpts,
+    syntax_warning_handler: Option<&'a mut SyntaxWarningHandler<'a>>,
+) -> CompileResult<CodeObject> {
+    compile_ast_with_syntax_warning_handler(
+        AstInput {
+            ast,
+            source_file,
+            locations: None,
+        },
+        mode,
+        opts,
+        syntax_warning_handler,
+    )
+}
+
+pub fn compile_ast_with_syntax_warning_handler<'a>(
+    input: AstInput,
+    mode: Mode,
     mut opts: CompileOpts,
     mut syntax_warning_handler: Option<&'a mut SyntaxWarningHandler<'a>>,
 ) -> CompileResult<CodeObject> {
+    let AstInput {
+        mut ast,
+        source_file,
+        mut locations,
+    } = input;
     opts.future_features |= checked_future_features(&ast, &source_file)?;
     let future_annotations = opts
         .future_features
@@ -411,46 +454,66 @@ pub fn compile_top_with_syntax_warning_handler<'a>(
             warn_ast_preprocess_syntax(&source_file, handler, range, message)
         })?;
     }
-    if matches!(mode, Mode::Single)
+    let location_error = if matches!(mode, Mode::Single)
         && let ruff_python_ast::Mod::Module(module) = &mut ast
     {
-        preprocess::preprocess_statements(
-            &mut module.body,
+        if let Some(locations) = &mut locations {
+            preprocess::preprocess_statements_with_locations(
+                &mut module.body,
+                opts.optimize,
+                future_annotations,
+                false,
+                locations,
+            )
+        } else {
+            preprocess::preprocess_statements(
+                &mut module.body,
+                opts.optimize,
+                future_annotations,
+                false,
+            );
+            Ok(())
+        }
+    } else if let Some(locations) = &mut locations {
+        preprocess::preprocess_mod_with_locations(
+            &mut ast,
             opts.optimize,
             future_annotations,
             false,
-        );
+            locations,
+        )
     } else {
         preprocess::preprocess_mod(&mut ast, opts.optimize, future_annotations, false);
-    }
+        Ok(())
+    };
+    location_error.map_err(|error| CodegenError {
+        error: CodegenErrorType::AstLocation(error),
+        location: None,
+        end_location: None,
+        source_path: source_file.name().to_owned(),
+    })?;
+    let mut compiler = Compiler::new_with_syntax_warning_handler(
+        opts,
+        source_file.clone(),
+        "<module>",
+        syntax_warning_handler,
+    );
+    compiler.ast_locations = locations;
     match ast {
-        ruff_python_ast::Mod::Module(module) => match mode {
-            Mode::Exec | Mode::Eval => compile_program_with_syntax_warning_handler(
-                &module,
-                source_file,
-                opts,
-                syntax_warning_handler,
-            ),
-            Mode::Single => compile_program_single_with_syntax_warning_handler(
-                &module,
-                source_file,
-                opts,
-                syntax_warning_handler,
-            ),
-            Mode::BlockExpr => compile_block_expression_with_syntax_warning_handler(
-                &module,
-                source_file,
-                opts,
-                syntax_warning_handler,
-            ),
-        },
-        ruff_python_ast::Mod::Expression(expr) => compile_expression_with_syntax_warning_handler(
-            &expr,
-            source_file,
-            opts,
-            syntax_warning_handler,
-        ),
+        ast::Mod::Module(module) => {
+            let symbols = scan_module_symbols(&module, &source_file, &compiler.opts)?;
+            match mode {
+                Mode::Exec | Mode::Eval => compiler.compile_program(&module, symbols)?,
+                Mode::Single => compiler.compile_program_single(&module.body, symbols)?,
+                Mode::BlockExpr => compiler.compile_block_expr(&module.body, symbols)?,
+            }
+        }
+        ast::Mod::Expression(expression) => {
+            let symbols = scan_expr_symbols(&expression, &source_file, &compiler.opts)?;
+            compiler.compile_eval(&expression, symbols)?;
+        }
     }
+    Ok(compiler.exit_scope())
 }
 
 /// Unoptimized instruction sequence and the metadata needed by optimize_cfg.
@@ -473,12 +536,35 @@ pub fn compile_codegen(
 }
 
 fn compile_codegen_with_syntax_warning_handler<'a>(
-    mut ast: ruff_python_ast::Mod,
+    ast: ruff_python_ast::Mod,
     source_file: SourceFile,
     mode: Mode,
+    opts: CompileOpts,
+    syntax_warning_handler: Option<&'a mut SyntaxWarningHandler<'a>>,
+) -> CompileResult<CodegenOutput> {
+    compile_codegen_ast(
+        AstInput {
+            ast,
+            source_file,
+            locations: None,
+        },
+        mode,
+        opts,
+        syntax_warning_handler,
+    )
+}
+
+pub fn compile_codegen_ast<'a>(
+    input: AstInput,
+    mode: Mode,
     mut opts: CompileOpts,
     mut syntax_warning_handler: Option<&'a mut SyntaxWarningHandler<'a>>,
 ) -> CompileResult<CodegenOutput> {
+    let AstInput {
+        mut ast,
+        source_file,
+        mut locations,
+    } = input;
     opts.future_features |= checked_future_features(&ast, &source_file)?;
     let future_annotations = opts
         .future_features
@@ -488,18 +574,44 @@ fn compile_codegen_with_syntax_warning_handler<'a>(
             warn_ast_preprocess_syntax(&source_file, handler, range, message)
         })?;
     }
-    if matches!(mode, Mode::Single)
+    let location_error = if matches!(mode, Mode::Single)
         && let ruff_python_ast::Mod::Module(module) = &mut ast
     {
-        preprocess::preprocess_statements(
-            &mut module.body,
+        if let Some(locations) = &mut locations {
+            preprocess::preprocess_statements_with_locations(
+                &mut module.body,
+                opts.optimize,
+                future_annotations,
+                false,
+                locations,
+            )
+        } else {
+            preprocess::preprocess_statements(
+                &mut module.body,
+                opts.optimize,
+                future_annotations,
+                false,
+            );
+            Ok(())
+        }
+    } else if let Some(locations) = &mut locations {
+        preprocess::preprocess_mod_with_locations(
+            &mut ast,
             opts.optimize,
             future_annotations,
             false,
-        );
+            locations,
+        )
     } else {
         preprocess::preprocess_mod(&mut ast, opts.optimize, future_annotations, false);
-    }
+        Ok(())
+    };
+    location_error.map_err(|error| CodegenError {
+        error: CodegenErrorType::AstLocation(error),
+        location: None,
+        end_location: None,
+        source_path: source_file.name().to_owned(),
+    })?;
 
     let mut compiler = Compiler::new_with_syntax_warning_handler(
         opts,
@@ -507,6 +619,7 @@ fn compile_codegen_with_syntax_warning_handler<'a>(
         "<module>",
         syntax_warning_handler,
     );
+    compiler.ast_locations = locations;
     compiler.save_nested_seqs = true;
     match ast {
         ruff_python_ast::Mod::Module(module) => match mode {
@@ -707,14 +820,14 @@ macro_rules! emit {
 }
 
 fn eprint_location(zelf: &Compiler<'_>) {
-    let start = zelf
-        .source_file
-        .to_source_code()
-        .source_location(zelf.current_source_range.start(), PositionEncoding::Utf8);
+    let start = zelf.source_file.to_source_code().source_location(
+        zelf.current_source_span.range.start(),
+        PositionEncoding::Utf8,
+    );
     let end = zelf
         .source_file
         .to_source_code()
-        .source_location(zelf.current_source_range.end(), PositionEncoding::Utf8);
+        .source_location(zelf.current_source_span.range.end(), PositionEncoding::Utf8);
     eprintln!(
         "LOCATION: {} from {}:{} to {}:{}",
         zelf.source_file.name(),
@@ -1200,7 +1313,8 @@ impl<'warnings> Compiler<'warnings> {
             symbol_table_stack: Vec::new(),
             source_file,
             // current_source_location: SourceLocation::default(),
-            current_source_range: TextRange::default(),
+            current_source_span: CompilerSourceSpan::parsed(TextRange::default()),
+            ast_locations: None,
             future_features: opts.future_features,
             future_annotations: false,
             ctx: CompileContext {
@@ -1221,7 +1335,7 @@ impl<'warnings> Compiler<'warnings> {
     fn compile_module_annotation_setup_sequence(
         &mut self,
         body: &[ast::Stmt],
-        loc: TextRange,
+        loc: CompilerSourceSpan,
     ) -> CompileResult<()> {
         let (
             saved_blocks,
@@ -1271,7 +1385,7 @@ impl<'warnings> Compiler<'warnings> {
         if let Some(lower) = &s.lower {
             self.compile_expression(lower)?;
         } else {
-            self.set_source_range(s.range);
+            self.set_source_node(s.range, &s.node_index);
             self.emit_load_const(ConstantData::None);
         }
 
@@ -1279,7 +1393,7 @@ impl<'warnings> Compiler<'warnings> {
         if let Some(upper) = &s.upper {
             self.compile_expression(upper)?;
         } else {
-            self.set_source_range(s.range);
+            self.set_source_node(s.range, &s.node_index);
             self.emit_load_const(ConstantData::None);
         }
 
@@ -1294,7 +1408,8 @@ impl<'warnings> Compiler<'warnings> {
         ctx: ast::ExprContext,
     ) -> CompileResult<()> {
         // Save full subscript expression range (set by compile_expression before this call)
-        let subscript_range = self.current_source_range;
+        let subscript_range_span = self.current_source_span;
+
         if matches!(ctx, ast::ExprContext::Load) {
             self.check_subscripter(value)?;
             self.check_index(value, slice)?;
@@ -1319,7 +1434,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         // Restore full subscript expression range before emitting
-        self.set_source_range(subscript_range);
+        self.restore_source_span(subscript_range_span);
 
         match (use_slice_opt, ctx) {
             (true, ast::ExprContext::Load) => emit!(self, Instruction::BinarySlice),
@@ -1358,7 +1473,8 @@ impl<'warnings> Compiler<'warnings> {
         pushed: u32,
         collection_type: CollectionType,
     ) -> CompileResult<()> {
-        let collection_range = self.current_source_range;
+        let collection_range_span = self.current_source_span;
+
         let n = elts.len().to_u32();
         let seen_star = elts.iter().any(|e| matches!(e, ast::Expr::Starred(_)));
 
@@ -1375,11 +1491,11 @@ impl<'warnings> Compiler<'warnings> {
                 self.compile_expression(elt)?;
             }
             if let Some(injected_arg) = injected_arg {
-                self.set_source_range(collection_range);
+                self.restore_source_span(collection_range_span);
                 self.load_name(injected_arg)?;
             }
             let total_size = n + injected_count + pushed;
-            self.set_source_range(collection_range);
+            self.restore_source_span(collection_range_span);
             match collection_type {
                 CollectionType::List => {
                     emit!(self, Instruction::BuildList { count: total_size });
@@ -1399,7 +1515,7 @@ impl<'warnings> Compiler<'warnings> {
         let mut i = 0u32;
 
         if big {
-            self.set_source_range(collection_range);
+            self.restore_source_span(collection_range_span);
             match collection_type {
                 CollectionType::List => {
                     emit!(self, Instruction::BuildList { count: pushed });
@@ -1420,7 +1536,7 @@ impl<'warnings> Compiler<'warnings> {
             if let ast::Expr::Starred(ast::ExprStarred { value, .. }) = elt {
                 // When we hit first star, build sequence with elements so far
                 if !sequence_built {
-                    self.set_source_range(collection_range);
+                    self.restore_source_span(collection_range_span);
                     match collection_type {
                         CollectionType::List => {
                             emit!(self, Instruction::BuildList { count: i + pushed });
@@ -1437,7 +1553,7 @@ impl<'warnings> Compiler<'warnings> {
 
                 // Compile the starred expression and extend
                 self.compile_expression(value)?;
-                self.set_source_range(collection_range);
+                self.restore_source_span(collection_range_span);
                 match collection_type {
                     CollectionType::List => {
                         emit!(self, Instruction::ListExtend { i: 1 });
@@ -1455,7 +1571,7 @@ impl<'warnings> Compiler<'warnings> {
 
                 if sequence_built {
                     // Sequence already exists, append to it
-                    self.set_source_range(collection_range);
+                    self.restore_source_span(collection_range_span);
                     match collection_type {
                         CollectionType::List => {
                             emit!(self, Instruction::ListAppend { i: 1 });
@@ -1476,9 +1592,9 @@ impl<'warnings> Compiler<'warnings> {
 
         debug_assert!(sequence_built);
         if let Some(injected_arg) = injected_arg {
-            self.set_source_range(collection_range);
+            self.restore_source_span(collection_range_span);
             self.load_name(injected_arg)?;
-            self.set_source_range(collection_range);
+            self.restore_source_span(collection_range_span);
             match collection_type {
                 CollectionType::List | CollectionType::Tuple => {
                     emit!(self, Instruction::ListAppend { i: 1 });
@@ -1490,7 +1606,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         if collection_type == CollectionType::Tuple {
-            self.set_source_range(collection_range);
+            self.restore_source_span(collection_range_span);
             emit!(
                 self,
                 Instruction::CallIntrinsic1 {
@@ -1512,7 +1628,7 @@ impl<'warnings> Compiler<'warnings> {
     }
 
     fn error(&mut self, error: CodegenErrorType) -> CodegenError {
-        self.error_ranged(error, self.current_source_range)
+        self.error_ranged(error, self.current_source_span.range)
     }
 
     fn error_ranged(&mut self, error: CodegenErrorType, range: TextRange) -> CodegenError {
@@ -1859,11 +1975,11 @@ impl<'warnings> Compiler<'warnings> {
     fn load_args_for_super(
         &mut self,
         super_type: &SuperCallType<'_>,
-        super_name_range: TextRange,
-        super_call_range: TextRange,
+        super_name_range: CompilerSourceSpan,
+        super_call_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
         // 1. Load global super
-        self.set_source_range(super_name_range);
+        self.restore_source_span(super_name_range);
         self.compile_name(&"super".into(), NameUsage::Load)?;
 
         match super_type {
@@ -1878,7 +1994,7 @@ impl<'warnings> Compiler<'warnings> {
             SuperCallType::ZeroArg => {
                 // 0-arg: load __class__ cell and first parameter
                 // Load __class__ from cell/free variable
-                self.set_source_range(super_call_range);
+                self.restore_source_span(super_call_range);
                 let scope = self
                     .get_ref_type(&"__class__".into())
                     .map_err(|e| self.error(e))?;
@@ -1905,7 +2021,7 @@ impl<'warnings> Compiler<'warnings> {
                         "super(): no arguments and no first parameter".to_owned(),
                     ))
                 })?;
-                self.set_source_range(super_call_range);
+                self.restore_source_span(super_call_range);
                 self.compile_name(&first_param.into(), NameUsage::Load)?;
             }
         }
@@ -1949,6 +2065,8 @@ impl<'warnings> Compiler<'warnings> {
             }
         };
 
+        let is_generator = ste.is_coroutine || ste.is_generator;
+
         // Use varnames from symbol table (already collected in definition order)
         let varname_cache: IndexSet<Name> = ste.varnames.iter().cloned().collect();
         let nparams = ste.varnames.len();
@@ -2150,16 +2268,37 @@ impl<'warnings> Compiler<'warnings> {
             self.set_qualname();
         }
 
-        // Emit RESUME (handles async preamble and module lineno 0)
-        // CPython: LOCATION(lineno, lineno, 0, 0), then loc.lineno = 0 for module
-        self.emit_resume_for_scope(scope_type, lineno);
+        self.emit_scope_prefix(scope_type, lineno, is_generator);
 
         Ok(())
     }
 
-    /// Emit RESUME instruction with proper handling for module lineno.
-    /// codegen_enter_scope equivalent for RESUME emission.
-    fn emit_resume_for_scope(&mut self, scope_type: CompilerScope, lineno: u32) {
+    /// Emit the generator prefix and RESUME, as the tail of
+    /// codegen_enter_scope does. `is_generator` is
+    /// `ste_coroutine || ste_generator`.
+    fn emit_scope_prefix(&mut self, scope_type: CompilerScope, lineno: u32, is_generator: bool) {
+        // Add the generator prefix instructions.
+        if is_generator {
+            // RETURN_GENERATOR + POP_TOP have a net stack effect of 0, because
+            // RETURN_GENERATOR pushes the generator before returning.
+            let location = SourceLocation {
+                line: OneIndexed::new(lineno as usize).unwrap_or(OneIndexed::MIN),
+                character_offset: OneIndexed::MIN,
+            };
+            for instr in [Instruction::ReturnGenerator, Instruction::PopTop] {
+                self.cpython_cfg_builder_addop(ir::InstructionInfo {
+                    instr: instr.into(),
+                    arg: OpArg::NULL,
+                    target: BlockIdx::NULL,
+                    location,
+                    end_location: location,
+                    except_handler: None,
+                    semantic_location: None,
+                    lineno_override: Some(ir::LINE_ONLY_LOCATION_OVERRIDE),
+                });
+            }
+        }
+
         // CPython: LOCATION(lineno, lineno, 0, 0)
         // Module scope: loc.lineno = 0 (before the first line)
         let lineno_override = if scope_type == CompilerScope::Module {
@@ -2186,6 +2325,7 @@ impl<'warnings> Compiler<'warnings> {
             location,
             end_location,
             except_handler,
+            semantic_location: None,
             lineno_override,
         });
     }
@@ -2291,7 +2431,7 @@ impl<'warnings> Compiler<'warnings> {
     fn enter_annotation_scope(
         &mut self,
         func_name: &str,
-        loc: TextRange,
+        loc: CompilerSourceSpan,
     ) -> CompileResult<Option<CompileContext>> {
         if !self.push_annotation_symbol_table() {
             return Ok(None);
@@ -2305,7 +2445,7 @@ impl<'warnings> Compiler<'warnings> {
             in_async_scope: false,
         };
 
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         let key = self.symbol_table_stack.len() - 1;
         let lineno = self.get_source_line_number().get();
         self.enter_scope(
@@ -2385,7 +2525,7 @@ impl<'warnings> Compiler<'warnings> {
         fb_exit: ir::InstructionSequenceLabel,
         fb_datum: FBlockDatum,
     ) -> CompileResult<()> {
-        let fb_range = self.current_source_range;
+        let fb_span = self.current_source_span;
         if self.current_code_info().fblock.len() >= CO_MAXBLOCKS {
             return Err(self.error(CodegenErrorType::SyntaxError(
                 "too many statically nested blocks".to_owned(),
@@ -2399,7 +2539,7 @@ impl<'warnings> Compiler<'warnings> {
             fb_type,
             fb_block,
             fb_exit,
-            fb_range,
+            fb_span,
             fb_datum,
         });
         Ok(())
@@ -2434,33 +2574,33 @@ impl<'warnings> Compiler<'warnings> {
             fb_type,
             fb_block,
             fb_exit,
-            fb_range,
+            fb_span,
             fb_datum,
         } = fblock;
         let code = self.current_code_info();
         if code.fblock.len() >= CO_MAXBLOCKS {
             return Err(self.error_ranged(
                 CodegenErrorType::SyntaxError("too many statically nested blocks".to_owned()),
-                fb_range,
+                fb_span.range,
             ));
         }
         code.fblock.push(FBlockInfo {
             fb_type,
             fb_block,
             fb_exit,
-            fb_range,
+            fb_span,
             fb_datum,
         });
         Ok(())
     }
 
-    fn set_unwind_source_range(&mut self, loc: Option<TextRange>) {
+    fn set_unwind_source_range(&mut self, loc: Option<CompilerSourceSpan>) {
         if let Some(range) = loc {
-            self.set_source_range(range);
+            self.restore_source_span(range);
         }
     }
 
-    fn mark_unwind_no_location(&mut self, loc: Option<TextRange>) {
+    fn mark_unwind_no_location(&mut self, loc: Option<CompilerSourceSpan>) {
         if loc.is_none() {
             self.set_no_location();
         }
@@ -2472,7 +2612,7 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         info: &FBlockInfo,
         preserve_tos: bool,
-        loc: &mut Option<TextRange>,
+        loc: &mut Option<CompilerSourceSpan>,
     ) -> CompileResult<()> {
         match info.fb_type {
             FBlockType::WhileLoop
@@ -2483,17 +2623,27 @@ impl<'warnings> Compiler<'warnings> {
                 // No cleanup needed
             }
 
-            FBlockType::ForLoop => {
-                // When returning from a for-loop, CPython swaps the preserved
-                // value with the iterator and uses POP_TOP for loop cleanup.
+            FBlockType::ForLoop | FBlockType::AsyncForLoop => {
+                let iterator_slots = if info.fb_type == FBlockType::ForLoop {
+                    2
+                } else {
+                    1
+                };
                 if preserve_tos {
                     self.set_unwind_source_range(*loc);
-                    emit!(self, Instruction::Swap { i: 2 });
+                    emit!(
+                        self,
+                        Instruction::Swap {
+                            i: iterator_slots + 1
+                        }
+                    );
+                    self.mark_unwind_no_location(*loc);
+                }
+                for _ in 0..iterator_slots {
+                    self.set_unwind_source_range(*loc);
+                    emit!(self, Instruction::PopTop);
                     self.mark_unwind_no_location(*loc);
                 }
-                self.set_unwind_source_range(*loc);
-                emit!(self, Instruction::PopTop);
-                self.mark_unwind_no_location(*loc);
             }
 
             FBlockType::TryExcept => {
@@ -2577,7 +2727,7 @@ impl<'warnings> Compiler<'warnings> {
                 // CPython codegen_unwind_fblock() assigns *ploc = info->fb_loc
                 // for WITH/ASYNC_WITH cleanup and then makes following unwind
                 // instructions artificial with *ploc = NO_LOCATION.
-                *loc = Some(info.fb_range);
+                *loc = Some(info.fb_span);
                 self.set_unwind_source_range(*loc);
                 emit!(self, PseudoInstruction::PopBlock);
 
@@ -2598,6 +2748,8 @@ impl<'warnings> Compiler<'warnings> {
                     self.set_unwind_source_range(*loc);
                     emit!(self, Instruction::GetAwaitable { r#where: 2 });
                     self.set_unwind_source_range(*loc);
+                    emit!(self, Instruction::PushNull);
+                    self.set_unwind_source_range(*loc);
                     self.emit_load_const(ConstantData::None);
                     let _ = self.compile_yield_from_sequence(true);
                 }
@@ -2664,7 +2816,7 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         preserve_tos: bool,
         stop_at_loop: bool,
-    ) -> CompileResult<Option<TextRange>> {
+    ) -> CompileResult<Option<CompilerSourceSpan>> {
         let (unwind_loc, _loop_fblock) =
             self.unwind_fblock_stack_with_loop(preserve_tos, stop_at_loop)?;
         Ok(unwind_loc)
@@ -2677,8 +2829,8 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         preserve_tos: bool,
         stop_at_loop: bool,
-    ) -> CompileResult<(Option<TextRange>, Option<FBlockInfo>)> {
-        let mut unwind_loc = Some(self.current_source_range);
+    ) -> CompileResult<(Option<CompilerSourceSpan>, Option<FBlockInfo>)> {
+        let mut unwind_loc = Some(self.current_source_span);
         let loop_fblock =
             self.unwind_fblock_stack_inner(preserve_tos, stop_at_loop, &mut unwind_loc)?;
         Ok((unwind_loc, loop_fblock))
@@ -2688,7 +2840,7 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         preserve_tos: bool,
         stop_at_loop: bool,
-        unwind_loc: &mut Option<TextRange>,
+        unwind_loc: &mut Option<CompilerSourceSpan>,
     ) -> CompileResult<Option<FBlockInfo>> {
         let Some(top) = self.current_code_info().fblock.last().cloned() else {
             return Ok(None);
@@ -2696,10 +2848,15 @@ impl<'warnings> Compiler<'warnings> {
         if matches!(top.fb_type, FBlockType::ExceptionGroupHandler) {
             return Err(self.error_optional_range(
                 CodegenErrorType::BreakContinueReturnInExceptStar,
-                *unwind_loc,
+                unwind_loc.map(|span| span.range),
             ));
         }
-        if stop_at_loop && matches!(top.fb_type, FBlockType::WhileLoop | FBlockType::ForLoop) {
+        if stop_at_loop
+            && matches!(
+                top.fb_type,
+                FBlockType::WhileLoop | FBlockType::ForLoop | FBlockType::AsyncForLoop
+            )
+        {
             return Ok(Some(top));
         }
 
@@ -2923,35 +3080,36 @@ impl<'warnings> Compiler<'warnings> {
 
         self.symbol_table_stack.push(symbol_table);
 
-        self.emit_resume_for_scope(CompilerScope::Module, 1);
+        let is_coroutine = self.current_symbol_table().is_coroutine;
+        self.emit_scope_prefix(CompilerScope::Module, 1, is_coroutine);
         emit!(self, PseudoInstruction::AnnotationsPlaceholder);
 
+        let doc_span = self.docstring_span(&body.body);
         let (doc, statements) = split_doc_with_range(&body.body, &self.opts);
         let module_start_loc = self.module_start_location(&body.body);
         let annotations_used = self.current_symbol_table().annotations_used;
         // Handle annotation bookkeeping before the docstring assignment, as
         // codegen_body() does after _PyCodegen_Module() inserts the prefix set.
         if Self::scope_needs_conditional_annotations_cell(self.current_symbol_table()) {
-            self.set_source_range(module_start_loc);
+            self.restore_source_span(module_start_loc);
             emit!(self, Instruction::BuildSet { count: 0 });
             self.store_name(&"__conditional_annotations__".into())?;
         }
 
         if self.future_annotations && annotations_used {
-            self.set_source_range(module_start_loc);
+            self.restore_source_span(module_start_loc);
             emit!(self, Instruction::SetupAnnotations);
         }
 
         if let Some((value, range)) = doc {
-            let saved_range = self.current_source_range;
-            self.set_source_range(range);
+            let saved_range = self.current_source_span;
+            self.restore_source_span(doc_span.unwrap_or_else(|| CompilerSourceSpan::parsed(range)));
             self.emit_load_const(ConstantData::Str {
                 value: value.into(),
             });
-            let doc = self.name("__doc__");
-            emit!(self, Instruction::StoreName { namei: doc });
+            self.store_name(&"__doc__".into())?;
             self.set_no_location();
-            self.set_source_range(saved_range);
+            self.restore_source_span(saved_range);
         }
 
         // Compile all statements
@@ -3004,19 +3162,20 @@ impl<'warnings> Compiler<'warnings> {
         self.symbol_table_stack.push(symbol_table);
         let module_start_loc = self.module_start_location(body);
 
-        self.emit_resume_for_scope(CompilerScope::Module, 1);
+        let is_coroutine = self.current_symbol_table().is_coroutine;
+        self.emit_scope_prefix(CompilerScope::Module, 1, is_coroutine);
         emit!(self, PseudoInstruction::AnnotationsPlaceholder);
 
         let annotations_used = self.current_symbol_table().annotations_used;
         // Handle annotations based on future_annotations flag
         if self.current_symbol_table().has_conditional_annotations {
-            self.set_source_range(module_start_loc);
+            self.restore_source_span(module_start_loc);
             emit!(self, Instruction::BuildSet { count: 0 });
             self.store_name(&"__conditional_annotations__".into())?;
         }
 
         if self.future_annotations && annotations_used {
-            self.set_source_range(module_start_loc);
+            self.restore_source_span(module_start_loc);
             // PEP 563: Initialize __annotations__ dict
             emit!(self, Instruction::SetupAnnotations);
         }
@@ -3044,7 +3203,8 @@ impl<'warnings> Compiler<'warnings> {
                 .insert(bytecode::CodeFlags::COROUTINE);
         }
         self.symbol_table_stack.push(symbol_table);
-        self.emit_resume_for_scope(CompilerScope::Module, 1);
+        let is_coroutine = self.current_symbol_table().is_coroutine;
+        self.emit_scope_prefix(CompilerScope::Module, 1, is_coroutine);
 
         if let Some((last_statement, statements)) = body.split_last() {
             self.compile_statements(statements)?;
@@ -3118,7 +3278,8 @@ impl<'warnings> Compiler<'warnings> {
                 .insert(bytecode::CodeFlags::COROUTINE);
         }
         self.symbol_table_stack.push(symbol_table);
-        self.emit_resume_for_scope(CompilerScope::Module, 1);
+        let is_coroutine = self.current_symbol_table().is_coroutine;
+        self.emit_scope_prefix(CompilerScope::Module, 1, is_coroutine);
 
         self.compile_expression(&expression.body)?;
         self.emit_return_value();
@@ -3507,10 +3668,38 @@ impl<'warnings> Compiler<'warnings> {
         Ok(())
     }
 
+    /// `_PyCompile_InExceptionHandler`
+    fn in_exception_handler(&mut self) -> bool {
+        self.current_code_info().fblock.iter().any(|block| {
+            matches!(
+                block.fb_type,
+                FBlockType::TryExcept
+                    | FBlockType::FinallyTry
+                    | FBlockType::FinallyEnd
+                    | FBlockType::ExceptionHandler
+                    | FBlockType::ExceptionGroupHandler
+                    | FBlockType::HandlerCleanup
+            )
+        })
+    }
+
+    fn import_policy(&mut self, explicit: bool, star: bool) -> u32 {
+        if explicit {
+            1
+        } else if star
+            || self.current_symbol_table().typ != CompilerScope::Module
+            || self.in_exception_handler()
+        {
+            2
+        } else {
+            0
+        }
+    }
+
     fn compile_statement(&mut self, statement: &ast::Stmt) -> CompileResult<()> {
         trace!("Compiling {statement:?}");
-        let prev_source_range = self.current_source_range;
-        self.set_source_range(statement.range());
+        let prev_source_range = self.current_source_span;
+        self.set_source_node(statement.range(), statement.node_index());
 
         // `from __future__` still executes that `from` statement at runtime, so the
         // ImportFrom is compiled down below as well.
@@ -3527,7 +3716,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         match &statement {
-            ast::Stmt::Import(ast::StmtImport { names, .. }) => {
+            ast::Stmt::Import(ast::StmtImport { names, is_lazy, .. }) => {
                 // import a, b, c as d
                 for name in names {
                     let name = &name;
@@ -3535,7 +3724,7 @@ impl<'warnings> Compiler<'warnings> {
                         value: num_traits::Zero::zero(),
                     });
                     self.emit_load_const(ConstantData::None);
-                    let namei = self.name(&name.name);
+                    let namei = (self.name(&name.name) << 2) | self.import_policy(*is_lazy, false);
                     emit!(self, Instruction::ImportName { namei });
                     if let Some(alias) = &name.asname {
                         let parts: Vec<&str> = name.name.split('.').skip(1).collect();
@@ -3560,6 +3749,7 @@ impl<'warnings> Compiler<'warnings> {
                 level,
                 module,
                 names,
+                is_lazy,
                 ..
             }) => {
                 let import_star = names.first().is_some_and(|n| &n.name == "*");
@@ -3580,7 +3770,8 @@ impl<'warnings> Compiler<'warnings> {
                 });
 
                 let module_name = module.as_ref().map_or("", |s| s.as_str());
-                let module_idx = self.name(module_name);
+                let module_idx =
+                    (self.name(module_name) << 2) | self.import_policy(*is_lazy, import_star);
                 emit!(self, Instruction::ImportName { namei: module_idx });
 
                 if import_star {
@@ -3622,13 +3813,14 @@ impl<'warnings> Compiler<'warnings> {
                 if !dominated_by_interactive && value.is_constant() {
                     emit!(self, Instruction::Nop);
                 } else {
-                    let statement_range = self.current_source_range;
+                    let statement_range_span = self.current_source_span;
+
                     self.compile_expression(value)?;
 
                     if dominated_by_interactive {
                         // The printing belongs to the statement, not to whatever
                         // the expression left behind.
-                        self.set_source_range(statement_range);
+                        self.restore_source_span(statement_range_span);
                         emit!(
                             self,
                             Instruction::CallIntrinsic1 {
@@ -3651,17 +3843,13 @@ impl<'warnings> Compiler<'warnings> {
                 ..
             }) => {
                 self.enter_conditional_block();
-                self.compile_if(test, body, elif_else_clauses, statement.range())?;
+                self.compile_if(test, body, elif_else_clauses, self.node_span(statement))?;
                 self.leave_conditional_block();
-                self.set_source_range(statement.range());
+                self.set_source_node(statement.range(), statement.node_index());
             }
             ast::Stmt::While(ast::StmtWhile {
-                test,
-                body,
-                orelse,
-                range,
-                ..
-            }) => self.compile_while(test, body, orelse, *range)?,
+                test, body, orelse, ..
+            }) => self.compile_while(test, body, orelse, self.node_span(statement))?,
             ast::Stmt::With(ast::StmtWith {
                 items,
                 body,
@@ -3674,15 +3862,19 @@ impl<'warnings> Compiler<'warnings> {
                 body,
                 orelse,
                 is_async,
-                range,
                 ..
-            }) => self.compile_for(target, iter, body, orelse, *is_async, *range)?,
+            }) => self.compile_for(
+                target,
+                iter,
+                body,
+                orelse,
+                *is_async,
+                self.node_span(statement),
+            )?,
             ast::Stmt::Match(ast::StmtMatch { subject, cases, .. }) => {
                 self.compile_match(subject, cases)?
             }
-            ast::Stmt::Raise(ast::StmtRaise {
-                exc, cause, range, ..
-            }) => {
+            ast::Stmt::Raise(ast::StmtRaise { exc, cause, .. }) => {
                 let kind = match exc {
                     Some(value) => {
                         self.compile_expression(value)?;
@@ -3696,7 +3888,7 @@ impl<'warnings> Compiler<'warnings> {
                     }
                     None => bytecode::RaiseKind::BareRaise,
                 };
-                self.set_source_range(*range);
+                self.set_source_node(statement.range(), statement.node_index());
                 emit!(self, Instruction::RaiseVarargs { argc: kind });
             }
             ast::Stmt::Try(ast::StmtTry {
@@ -3754,15 +3946,18 @@ impl<'warnings> Compiler<'warnings> {
                 false,
             )?,
             ast::Stmt::Assert(assert_stmt) => {
-                let ast::StmtAssert {
-                    test, msg, range, ..
-                } = assert_stmt;
+                let ast::StmtAssert { test, msg, .. } = assert_stmt;
                 self.check_assert(assert_stmt)?;
                 // if some flag, ignore all assert statements!
                 if self.opts.optimize == 0 {
                     let after_block = self.new_block();
-                    self.compile_jump_if_inner(test, true, after_block, Some(*range))?;
-                    self.set_source_range(*range);
+                    self.compile_jump_if_inner(
+                        test,
+                        true,
+                        after_block,
+                        Some(self.node_span(statement)),
+                    )?;
+                    self.set_source_node(statement.range(), statement.node_index());
                     emit!(
                         self,
                         Instruction::LoadCommonConstant {
@@ -3771,10 +3966,10 @@ impl<'warnings> Compiler<'warnings> {
                     );
                     if let Some(e) = msg {
                         self.compile_expression(e)?;
-                        self.set_source_range(*range);
+                        self.set_source_node(statement.range(), statement.node_index());
                         emit!(self, Instruction::Call { argc: 0 });
                     }
-                    self.set_source_range(test.range());
+                    self.set_source_node(test.range(), test.node_index());
                     emit!(
                         self,
                         Instruction::RaiseVarargs {
@@ -3794,11 +3989,11 @@ impl<'warnings> Compiler<'warnings> {
             }
             ast::Stmt::Break(_) => {
                 // Unwind fblock stack until we find a loop, emitting cleanup for each fblock
-                self.compile_break_continue(statement.range(), true)?;
+                self.compile_break_continue(self.node_span(statement), true)?;
             }
             ast::Stmt::Continue(_) => {
                 // Unwind fblock stack until we find a loop, emitting cleanup for each fblock
-                self.compile_break_continue(statement.range(), false)?;
+                self.compile_break_continue(self.node_span(statement), false)?;
             }
             ast::Stmt::Return(ast::StmtReturn { value, .. }) => {
                 if !self.ctx.in_func() {
@@ -3807,7 +4002,7 @@ impl<'warnings> Compiler<'warnings> {
                     );
                 }
 
-                let prev_source_range = self.current_source_range;
+                let prev_source_range = self.current_source_span;
                 let stmt_range = statement.range();
                 match value {
                     Some(v) => {
@@ -3831,12 +4026,12 @@ impl<'warnings> Compiler<'warnings> {
                             None
                         };
                         let preserve_tos = folded_constant.is_none();
-                        let mut return_range = stmt_range;
+                        let mut return_span = self.node_span(statement);
                         if preserve_tos {
                             self.compile_expression(v)?;
                         } else {
-                            return_range = v.range();
-                            self.set_source_range(v.range());
+                            return_span = self.node_span(v.as_ref());
+                            self.set_source_node(v.range(), v.node_index());
                             emit!(self, Instruction::Nop);
                         }
 
@@ -3844,14 +4039,14 @@ impl<'warnings> Compiler<'warnings> {
                         if source.line_index(v.range().start())
                             != source.line_index(stmt_range.start())
                         {
-                            return_range = stmt_range;
-                            self.set_source_range(stmt_range);
+                            return_span = self.node_span(statement);
+                            self.set_source_node(statement.range(), statement.node_index());
                             emit!(self, Instruction::Nop);
                         }
-                        self.set_source_range(return_range);
+                        self.restore_source_span(return_span);
                         let unwind_loc = self.unwind_fblock_stack(preserve_tos, false)?;
                         if let Some(loc) = unwind_loc {
-                            self.set_source_range(loc);
+                            self.restore_source_span(loc);
                             match folded_constant {
                                 Some(constant) => self.emit_return_const(constant),
                                 None => {
@@ -3869,31 +4064,26 @@ impl<'warnings> Compiler<'warnings> {
                         }
                     }
                     None => {
-                        self.set_source_range(stmt_range);
+                        self.set_source_node(statement.range(), statement.node_index());
                         emit!(self, Instruction::Nop);
                         // Unwind fblock stack with preserve_tos=false (no value to preserve)
                         let unwind_loc = self.unwind_fblock_stack(false, false)?;
                         if let Some(loc) = unwind_loc {
-                            self.set_source_range(loc);
+                            self.restore_source_span(loc);
                             self.emit_return_const(ConstantData::None);
                         } else {
                             self.emit_return_const_no_location(ConstantData::None);
                         }
                     }
                 }
-                self.set_source_range(prev_source_range);
+                self.restore_source_span(prev_source_range);
             }
-            ast::Stmt::Assign(ast::StmtAssign {
-                targets,
-                value,
-                range,
-                ..
-            }) => {
+            ast::Stmt::Assign(ast::StmtAssign { targets, value, .. }) => {
                 self.compile_expression(value)?;
 
                 for (i, target) in targets.iter().enumerate() {
                     if i + 1 != targets.len() {
-                        self.set_source_range(*range);
+                        self.set_source_node(statement.range(), statement.node_index());
                         emit!(self, Instruction::Copy { i: 1 });
                     }
                     self.compile_store(target)?;
@@ -3907,7 +4097,6 @@ impl<'warnings> Compiler<'warnings> {
                 annotation,
                 value,
                 simple,
-                range,
                 ..
             }) => {
                 self.compile_annotated_assign(
@@ -3915,12 +4104,12 @@ impl<'warnings> Compiler<'warnings> {
                     annotation,
                     value.as_deref(),
                     *simple,
-                    *range,
+                    self.node_span(statement),
                 )?;
                 // Bare annotations in function scope emit no code; restore
                 // source range so subsequent instructions keep the correct line.
                 if value.is_none() && self.ctx.in_func() {
-                    self.set_source_range(prev_source_range);
+                    self.restore_source_span(prev_source_range);
                 }
             }
             ast::Stmt::Delete(ast::StmtDelete { targets, .. }) => {
@@ -3935,7 +4124,6 @@ impl<'warnings> Compiler<'warnings> {
                 name,
                 type_params,
                 value,
-                range,
                 ..
             }) => {
                 let Some(name) = name.as_name_expr() else {
@@ -3946,7 +4134,7 @@ impl<'warnings> Compiler<'warnings> {
                 let name_string = name.id();
 
                 if let Some(type_params) = type_params {
-                    self.set_source_range(*range);
+                    self.set_source_node(statement.range(), statement.node_index());
                     self.push_symbol_table()?;
                     let key = self.symbol_table_stack.len() - 1;
                     let lineno = self.get_source_line_number().get().to_u32();
@@ -3961,13 +4149,17 @@ impl<'warnings> Compiler<'warnings> {
                         in_async_scope: false,
                     };
 
-                    self.set_source_range(*range);
+                    self.set_source_node(statement.range(), statement.node_index());
                     self.emit_load_const(ConstantData::Str {
                         value: name_string.as_str().into(),
                     });
                     self.compile_type_params(type_params)?;
-                    self.compile_typealias_value_closure(name_string, value, *range)?;
-                    self.set_source_range(*range);
+                    self.compile_typealias_value_closure(
+                        name_string,
+                        value,
+                        self.node_span(statement),
+                    )?;
+                    self.set_source_node(statement.range(), statement.node_index());
                     emit!(self, Instruction::BuildTuple { count: 3 });
                     emit!(
                         self,
@@ -3979,19 +4171,23 @@ impl<'warnings> Compiler<'warnings> {
 
                     let code = self.exit_scope();
                     self.ctx = prev_ctx;
-                    self.set_source_range(*range);
+                    self.set_source_node(statement.range(), statement.node_index());
                     self.make_closure(code, bytecode::MakeFunctionFlags::new())?;
-                    self.set_source_range(*range);
+                    self.set_source_node(statement.range(), statement.node_index());
                     emit!(self, Instruction::PushNull);
                     emit!(self, Instruction::Call { argc: 0 });
                 } else {
-                    self.set_source_range(*range);
+                    self.set_source_node(statement.range(), statement.node_index());
                     self.emit_load_const(ConstantData::Str {
                         value: name_string.as_str().into(),
                     });
                     self.emit_load_const(ConstantData::None);
-                    self.compile_typealias_value_closure(name_string, value, *range)?;
-                    self.set_source_range(*range);
+                    self.compile_typealias_value_closure(
+                        name_string,
+                        value,
+                        self.node_span(statement),
+                    )?;
+                    self.set_source_node(statement.range(), statement.node_index());
                     emit!(self, Instruction::BuildTuple { count: 3 });
                     emit!(
                         self,
@@ -4001,7 +4197,7 @@ impl<'warnings> Compiler<'warnings> {
                     );
                 }
 
-                self.set_source_range(*range);
+                self.set_source_node(statement.range(), statement.node_index());
                 self.store_name(name_string)?;
             }
             ast::Stmt::IpyEscapeCommand(stmt) => {
@@ -4015,8 +4211,8 @@ impl<'warnings> Compiler<'warnings> {
     }
 
     fn compile_delete(&mut self, expression: &ast::Expr) -> CompileResult<()> {
-        let prev_source_range = self.current_source_range;
-        self.set_source_range(expression.range());
+        let prev_source_range = self.current_source_span;
+        self.set_source_node(expression.range(), expression.node_index());
         let result = (|| -> CompileResult<()> {
             match &expression {
                 ast::Expr::Name(ast::ExprName { id, .. }) => {
@@ -4025,11 +4221,11 @@ impl<'warnings> Compiler<'warnings> {
                 ast::Expr::Attribute(ast::ExprAttribute { value, attr, .. }) => {
                     self.compile_expression(value)?;
                     let namei = self.name(attr.as_str());
-                    self.set_source_range(self.update_start_location_to_match_attr(
-                        expression.range(),
-                        expression.range(),
+                    self.restore_source_span(self.update_start_span_to_match_attr(
+                        self.node_span(expression),
+                        self.node_span(expression),
                         attr.as_str(),
-                    ));
+                    )?);
                     emit!(self, Instruction::DeleteAttr { namei });
                 }
                 ast::Expr::Subscript(ast::ExprSubscript {
@@ -4050,7 +4246,7 @@ impl<'warnings> Compiler<'warnings> {
             }
             Ok(())
         })();
-        self.set_source_range(prev_source_range);
+        self.restore_source_span(prev_source_range);
         result
     }
 
@@ -4097,7 +4293,10 @@ impl<'warnings> Compiler<'warnings> {
     /// Stack: [dec1, dec2, func] → CALL 0 → [dec1, dec2(func)] → CALL 0 → [dec1(dec2(func))]
     fn apply_decorators(&mut self, decorator_list: &[ast::Decorator]) {
         for decorator in decorator_list.iter().rev() {
-            self.set_source_range(decorator.expression.range());
+            self.set_source_node(
+                decorator.expression.range(),
+                decorator.expression.node_index(),
+            );
             emit!(self, Instruction::Call { argc: 0 });
         }
     }
@@ -4109,8 +4308,7 @@ impl<'warnings> Compiler<'warnings> {
         name: &str,
         allow_starred: bool,
     ) -> CompileResult<()> {
-        let expr_range = expr.range();
-        self.set_source_range(expr_range);
+        self.set_source_node(expr.range(), expr.node_index());
         self.emit_load_const(ConstantData::Tuple {
             elements: vec![ConstantData::Integer { value: 1.into() }],
         });
@@ -4141,7 +4339,7 @@ impl<'warnings> Compiler<'warnings> {
         if allow_starred && matches!(expr, ast::Expr::Starred(_)) {
             if let ast::Expr::Starred(starred) = expr {
                 self.compile_expression(&starred.value)?;
-                self.set_source_range(expr_range);
+                self.set_source_node(expr.range(), expr.node_index());
                 emit!(self, Instruction::UnpackSequence { count: 1 });
             }
         } else {
@@ -4149,7 +4347,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         // Return value
-        self.set_source_range(expr_range);
+        self.set_source_node(expr.range(), expr.node_index());
         emit!(self, Instruction::ReturnValue);
         self.emit_return_const_no_location(ConstantData::None);
 
@@ -4157,7 +4355,7 @@ impl<'warnings> Compiler<'warnings> {
         let code = self.exit_scope();
         self.ctx = prev_ctx;
 
-        self.set_source_range(expr_range);
+        self.set_source_node(expr.range(), expr.node_index());
         self.make_closure(
             code,
             bytecode::MakeFunctionFlags::from([bytecode::MakeFunctionFlag::Defaults]),
@@ -4170,9 +4368,9 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         alias_name: &str,
         value: &ast::Expr,
-        alias_range: TextRange,
+        alias_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
-        self.set_source_range(alias_range);
+        self.restore_source_span(alias_range);
         self.emit_load_const(ConstantData::Tuple {
             elements: vec![ConstantData::Integer { value: 1.into() }],
         });
@@ -4192,12 +4390,12 @@ impl<'warnings> Compiler<'warnings> {
         };
 
         self.compile_expression(value)?;
-        self.set_source_range(alias_range);
+        self.restore_source_span(alias_range);
         emit!(self, Instruction::ReturnValue);
 
         let code = self.exit_scope();
         self.ctx = prev_ctx;
-        self.set_source_range(alias_range);
+        self.restore_source_span(alias_range);
         self.make_closure(
             code,
             bytecode::MakeFunctionFlags::from([bytecode::MakeFunctionFlag::Defaults]),
@@ -4220,7 +4418,7 @@ impl<'warnings> Compiler<'warnings> {
                     range,
                     ..
                 }) => {
-                    self.set_source_range(*range);
+                    self.set_source_node(type_param.range(), type_param.node_index());
                     self.emit_load_const(ConstantData::Str {
                         value: name.as_str().into(),
                     });
@@ -4228,7 +4426,7 @@ impl<'warnings> Compiler<'warnings> {
                     if let Some(expr) = &bound {
                         self.compile_type_param_bound_or_default(expr, name.as_str(), false)?;
 
-                        self.set_source_range(*range);
+                        self.set_source_node(type_param.range(), type_param.node_index());
                         let intrinsic = if expr.is_tuple_expr() {
                             bytecode::IntrinsicFunction2::TypeVarWithConstraint
                         } else {
@@ -4251,7 +4449,7 @@ impl<'warnings> Compiler<'warnings> {
                             name.as_str(),
                             false,
                         )?;
-                        self.set_source_range(*range);
+                        self.set_source_node(type_param.range(), type_param.node_index());
                         emit!(
                             self,
                             Instruction::CallIntrinsic2 {
@@ -4267,7 +4465,7 @@ impl<'warnings> Compiler<'warnings> {
                         ));
                     }
 
-                    self.set_source_range(*range);
+                    self.set_source_node(type_param.range(), type_param.node_index());
                     emit!(self, Instruction::Copy { i: 1 });
                     self.store_name(name.id())?;
                 }
@@ -4277,7 +4475,7 @@ impl<'warnings> Compiler<'warnings> {
                     range,
                     ..
                 }) => {
-                    self.set_source_range(*range);
+                    self.set_source_node(type_param.range(), type_param.node_index());
                     self.emit_load_const(ConstantData::Str {
                         value: name.as_str().into(),
                     });
@@ -4295,7 +4493,7 @@ impl<'warnings> Compiler<'warnings> {
                             name.as_str(),
                             false,
                         )?;
-                        self.set_source_range(*range);
+                        self.set_source_node(type_param.range(), type_param.node_index());
                         emit!(
                             self,
                             Instruction::CallIntrinsic2 {
@@ -4311,7 +4509,7 @@ impl<'warnings> Compiler<'warnings> {
                         ));
                     }
 
-                    self.set_source_range(*range);
+                    self.set_source_node(type_param.range(), type_param.node_index());
                     emit!(self, Instruction::Copy { i: 1 });
                     self.store_name(name.id())?;
                 }
@@ -4321,7 +4519,7 @@ impl<'warnings> Compiler<'warnings> {
                     range,
                     ..
                 }) => {
-                    self.set_source_range(*range);
+                    self.set_source_node(type_param.range(), type_param.node_index());
                     self.emit_load_const(ConstantData::Str {
                         value: name.as_str().into(),
                     });
@@ -4339,7 +4537,7 @@ impl<'warnings> Compiler<'warnings> {
                             name.as_str(),
                             true,
                         )?;
-                        self.set_source_range(*range);
+                        self.set_source_node(type_param.range(), type_param.node_index());
                         emit!(
                             self,
                             Instruction::CallIntrinsic2 {
@@ -4356,14 +4554,14 @@ impl<'warnings> Compiler<'warnings> {
                         ));
                     }
 
-                    self.set_source_range(*range);
+                    self.set_source_node(type_param.range(), type_param.node_index());
                     emit!(self, Instruction::Copy { i: 1 });
                     self.store_name(name.id())?;
                 }
             };
         }
         if let Some(first) = type_params.type_params.first() {
-            self.set_source_range(first.range());
+            self.set_source_node(first.range(), first.node_index());
         }
         emit!(
             self,
@@ -4527,10 +4725,9 @@ impl<'warnings> Compiler<'warnings> {
                 type_,
                 name,
                 body,
-                range: handler_range,
                 ..
             }) = handler;
-            self.set_source_range(*handler_range);
+            self.set_source_node(handler.range(), handler.node_index());
             if type_.is_none() && i < handlers.len() - 1 {
                 return Err(self.error(CodegenErrorType::SyntaxError(
                     "default 'except:' must be last".to_owned(),
@@ -4540,7 +4737,7 @@ impl<'warnings> Compiler<'warnings> {
 
             if let Some(exc_type) = type_ {
                 self.compile_expression(exc_type)?;
-                self.set_source_range(*handler_range);
+                self.set_source_node(handler.range(), handler.node_index());
                 emit!(self, Instruction::CheckExcMatch);
                 emit!(
                     self,
@@ -4796,11 +4993,10 @@ impl<'warnings> Compiler<'warnings> {
                 type_,
                 name,
                 body,
-                range: handler_range,
                 ..
             }) = handler;
             let is_last_handler = i == n - 1;
-            self.set_source_range(*handler_range);
+            self.set_source_node(handler.range(), handler.node_index());
 
             let next_handler_block = self.new_block();
             let except_with_error_block = self.new_block();
@@ -4817,7 +5013,7 @@ impl<'warnings> Compiler<'warnings> {
             // NULL type here, so codegen only emits CHECK_EG_MATCH when present.
             if let Some(exc_type) = type_ {
                 self.compile_expression(exc_type)?;
-                self.set_source_range(*handler_range);
+                self.set_source_node(handler.range(), handler.node_index());
             }
 
             if type_.is_some() {
@@ -4936,7 +5132,7 @@ impl<'warnings> Compiler<'warnings> {
             self.set_no_location();
 
             self.use_cpython_label_block(no_match_block);
-            self.set_source_range(*handler_range);
+            self.set_source_node(handler.range(), handler.node_index());
             emit!(self, Instruction::PopTop); // pop match (None)
             // Stack: [prev_exc, orig, list, new_rest]
 
@@ -5051,7 +5247,7 @@ impl<'warnings> Compiler<'warnings> {
     fn compile_default_arguments(
         &mut self,
         parameters: &ast::Parameters,
-        loc: TextRange,
+        loc: CompilerSourceSpan,
     ) -> CompileResult<bytecode::MakeFunctionFlags> {
         let mut funcflags = bytecode::MakeFunctionFlags::new();
 
@@ -5067,7 +5263,7 @@ impl<'warnings> Compiler<'warnings> {
             for default in &defaults {
                 self.compile_expression(default)?;
             }
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             emit!(
                 self,
                 Instruction::BuildTuple {
@@ -5088,13 +5284,13 @@ impl<'warnings> Compiler<'warnings> {
         if !kw_with_defaults.is_empty() {
             // Compile kwdefaults and build dict
             for (arg, default) in &kw_with_defaults {
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 self.emit_load_const(ConstantData::Str {
                     value: self.mangle(arg.name().id()).as_str().into(),
                 });
                 self.compile_expression(default)?;
             }
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             emit!(
                 self,
                 Instruction::BuildMap {
@@ -5116,7 +5312,7 @@ impl<'warnings> Compiler<'warnings> {
         body: &[ast::Stmt],
         is_async: bool,
         funcflags: bytecode::MakeFunctionFlags,
-        closure_range: TextRange,
+        closure_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
         // Always enter function scope
         self.enter_function(name, parameters)?;
@@ -5198,7 +5394,7 @@ impl<'warnings> Compiler<'warnings> {
         let code = self.exit_scope();
         self.ctx = prev_ctx;
 
-        self.set_source_range(closure_range);
+        self.restore_source_span(closure_range);
 
         // Create function object with closure
         self.make_closure(code, funcflags)?;
@@ -5217,7 +5413,7 @@ impl<'warnings> Compiler<'warnings> {
         func_name: &str,
         parameters: &ast::Parameters,
         returns: Option<&ast::Expr>,
-        func_range: TextRange,
+        func_range: CompilerSourceSpan,
     ) -> CompileResult<bool> {
         if !self.next_function_annotation_symbol_table_uses_annotations() {
             // CPython creates a hidden AnnotationBlock for every function
@@ -5238,10 +5434,10 @@ impl<'warnings> Compiler<'warnings> {
 
         // Count annotations
         let parameters_iter = parameters
-            .args
+            .posonlyargs
             .iter()
             .map(|x| &x.parameter)
-            .chain(parameters.posonlyargs.iter().map(|x| &x.parameter))
+            .chain(parameters.args.iter().map(|x| &x.parameter))
             .chain(parameters.vararg.as_deref())
             .chain(parameters.kwonlyargs.iter().map(|x| &x.parameter))
             .chain(parameters.kwarg.as_deref());
@@ -5253,17 +5449,17 @@ impl<'warnings> Compiler<'warnings> {
 
         // Compile annotations inside the annotation scope
         let parameters_iter = parameters
-            .args
+            .posonlyargs
             .iter()
             .map(|x| &x.parameter)
-            .chain(parameters.posonlyargs.iter().map(|x| &x.parameter))
+            .chain(parameters.args.iter().map(|x| &x.parameter))
             .chain(parameters.vararg.as_deref())
             .chain(parameters.kwonlyargs.iter().map(|x| &x.parameter))
             .chain(parameters.kwarg.as_deref());
 
         for param in parameters_iter {
             if let Some(annotation) = &param.annotation {
-                self.set_source_range(func_range);
+                self.restore_source_span(func_range);
                 self.emit_load_const(ConstantData::Str {
                     value: self.mangle(param.name.id()).as_str().into(),
                 });
@@ -5273,7 +5469,7 @@ impl<'warnings> Compiler<'warnings> {
 
         // Handle return annotation
         if let Some(annotation) = returns {
-            self.set_source_range(func_range);
+            self.restore_source_span(func_range);
             self.emit_load_const(ConstantData::Str {
                 value: "return".into(),
             });
@@ -5281,7 +5477,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         // Build the map and return it
-        self.set_source_range(func_range);
+        self.restore_source_span(func_range);
         emit!(
             self,
             Instruction::BuildMap {
@@ -5295,7 +5491,7 @@ impl<'warnings> Compiler<'warnings> {
         let annotate_code = self.exit_annotation_scope(saved_ctx);
 
         // Make a closure from the code object
-        self.set_source_range(func_range);
+        self.restore_source_span(func_range);
         self.make_closure(annotate_code, bytecode::MakeFunctionFlags::new())?;
 
         Ok(true)
@@ -5386,9 +5582,9 @@ impl<'warnings> Compiler<'warnings> {
     fn compile_module_annotate(
         &mut self,
         body: &[ast::Stmt],
-        loc: Option<TextRange>,
+        loc: Option<CompilerSourceSpan>,
     ) -> CompileResult<bool> {
-        let loc = loc.unwrap_or(self.current_source_range);
+        let loc = loc.unwrap_or(self.current_source_span);
         // Get parent scope type BEFORE pushing annotation symbol table.
         let parent_scope_type = self.current_symbol_table().typ;
         let annotations = Self::collect_annotations(body, parent_scope_type);
@@ -5418,7 +5614,7 @@ impl<'warnings> Compiler<'warnings> {
         };
 
         // Enter annotation scope for code generation
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         let key = self.symbol_table_stack.len() - 1;
         let lineno = self.get_source_line_number().get();
         self.enter_scope(
@@ -5435,7 +5631,7 @@ impl<'warnings> Compiler<'warnings> {
         // Emit format validation: if format > VALUE_WITH_FAKE_GLOBALS: raise NotImplementedError
         self.emit_format_validation();
 
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         emit!(self, Instruction::BuildMap { count: 0 });
 
         let mut conditional_idx = 0usize;
@@ -5444,7 +5640,6 @@ impl<'warnings> Compiler<'warnings> {
                 target,
                 annotation,
                 simple,
-                range,
                 ..
             } = stmt;
             let simple_name = if *simple {
@@ -5469,7 +5664,7 @@ impl<'warnings> Compiler<'warnings> {
             let name = simple_name.expect("missing simple annotation name");
 
             if let Some(not_set_block) = not_set_block {
-                self.set_source_range(*range);
+                self.set_source_node(stmt.range, &stmt.node_index);
                 self.emit_load_const(ConstantData::Integer {
                     value: conditional_idx.into(),
                 });
@@ -5496,12 +5691,12 @@ impl<'warnings> Compiler<'warnings> {
             }
 
             self.compile_annotation(annotation)?;
-            self.set_source_range(*range);
+            self.set_source_node(stmt.range, &stmt.node_index);
             emit!(self, Instruction::Copy { i: 2 });
             self.emit_load_const(ConstantData::Str {
                 value: self.mangle(name).as_str().into(),
             });
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             emit!(self, Instruction::StoreSubscr);
 
             if let Some(not_set_block) = not_set_block {
@@ -5514,7 +5709,7 @@ impl<'warnings> Compiler<'warnings> {
             }
         }
 
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         emit!(self, Instruction::ReturnValue);
         self.emit_return_const_no_location(ConstantData::None);
 
@@ -5536,7 +5731,7 @@ impl<'warnings> Compiler<'warnings> {
         Self::expose_annotation_format_parameter(&mut annotate_code);
 
         // Make a closure from the code object
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         self.make_closure(annotate_code, bytecode::MakeFunctionFlags::new())?;
 
         // Store as __annotate_func__ for classes, __annotate__ for modules
@@ -5546,7 +5741,7 @@ impl<'warnings> Compiler<'warnings> {
             "__annotate__"
         }
         .into();
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         self.store_name(&name)?;
 
         Ok(true)
@@ -5567,13 +5762,18 @@ impl<'warnings> Compiler<'warnings> {
     ) -> CompileResult<()> {
         // CPython's FunctionDef/AsyncFunctionDef LOC(s) starts at the
         // definition line even when decorators are present.
-        let stmt_source_range = self.current_source_range;
+        let statement_span = self.current_source_span;
+        let stmt_source_range = statement_span.range;
         let def_source_range = crate::decorated_definition_range(
             &self.source_file,
             stmt_source_range,
             decorator_list,
             if is_async { "async def " } else { "def " },
         );
+        let def_source_span = CompilerSourceSpan {
+            range: def_source_range,
+            ..statement_span
+        };
 
         // The symtable visits defaults before decorators, but
         // codegen_function() emits decorators first. Keep the symbol table in
@@ -5587,12 +5787,12 @@ impl<'warnings> Compiler<'warnings> {
 
         // The first decorator line is used for code objects created by
         // this definition, but LOC(s) for the surrounding instructions.
-        let firstlineno_range = decorator_list
-            .first()
-            .map_or(stmt_source_range, |decorator| decorator.expression.range());
+        let firstlineno_span = decorator_list.first().map_or(statement_span, |decorator| {
+            self.node_span(&decorator.expression)
+        });
 
         // compile defaults and return funcflags
-        let funcflags = self.compile_default_arguments(parameters, def_source_range)?;
+        let funcflags = self.compile_default_arguments(parameters, def_source_span)?;
         self.set_symbol_table_cursors(after_decorators_symbol_table_cursors);
 
         let is_generic = type_params.is_some();
@@ -5610,13 +5810,13 @@ impl<'warnings> Compiler<'warnings> {
                 num_typeparam_args += 1;
             }
             if num_typeparam_args == 2 {
-                self.set_source_range(def_source_range);
+                self.restore_source_span(def_source_span);
                 emit!(self, Instruction::Swap { i: 2 });
             }
 
             // Enter type params scope
             let type_params_name = format!("<generic parameters of {name}>");
-            self.set_source_range(firstlineno_range);
+            self.restore_source_span(firstlineno_span);
             self.push_output(
                 bytecode::CodeFlags::OPTIMIZED | bytecode::CodeFlags::NEWLOCALS,
                 0,
@@ -5653,7 +5853,7 @@ impl<'warnings> Compiler<'warnings> {
             self.compile_type_params(type_params.unwrap())?;
 
             // Load defaults/kwdefaults with LOAD_FAST
-            self.set_source_range(def_source_range);
+            self.restore_source_span(def_source_span);
             for i in 0..num_typeparam_args {
                 let var_num = oparg::VarNum::from(i);
                 emit!(self, Instruction::LoadFast { var_num });
@@ -5662,13 +5862,13 @@ impl<'warnings> Compiler<'warnings> {
 
         // Compile annotations as closure (PEP 649)
         let mut annotations_flag = bytecode::MakeFunctionFlags::new();
-        if self.compile_annotations_closure(name, parameters, returns, def_source_range)? {
+        if self.compile_annotations_closure(name, parameters, returns, def_source_span)? {
             annotations_flag.insert(bytecode::MakeFunctionFlag::Annotate);
         }
 
         // Compile function body. codegen_function() uses the first
         // decorator line for co_firstlineno, but LOC(s) for MAKE_FUNCTION.
-        self.set_source_range(firstlineno_range);
+        self.restore_source_span(firstlineno_span);
         let final_funcflags = funcflags | annotations_flag;
         self.compile_function_body(
             name,
@@ -5676,18 +5876,18 @@ impl<'warnings> Compiler<'warnings> {
             body,
             is_async,
             final_funcflags,
-            def_source_range,
+            def_source_span,
         )?;
 
         // Handle type params if present
         if is_generic {
             // SWAP to get function on top
             // Stack: [type_params_tuple, function] -> [function, type_params_tuple]
-            self.set_source_range(def_source_range);
+            self.restore_source_span(def_source_span);
             emit!(self, Instruction::Swap { i: 2 });
 
             // Call INTRINSIC_SET_FUNCTION_TYPE_PARAMS
-            self.set_source_range(def_source_range);
+            self.restore_source_span(def_source_span);
             emit!(
                 self,
                 Instruction::CallIntrinsic2 {
@@ -5708,18 +5908,18 @@ impl<'warnings> Compiler<'warnings> {
             self.ctx = saved_ctx;
 
             // Make closure for type params code
-            self.set_source_range(def_source_range);
+            self.restore_source_span(def_source_span);
             self.make_closure(type_params_code, bytecode::MakeFunctionFlags::new())?;
 
             if num_typeparam_args > 0 {
-                self.set_source_range(def_source_range);
+                self.restore_source_span(def_source_span);
                 emit!(
                     self,
                     Instruction::Swap {
                         i: num_typeparam_args + 1
                     }
                 );
-                self.set_source_range(def_source_range);
+                self.restore_source_span(def_source_span);
                 emit!(
                     self,
                     Instruction::Call {
@@ -5728,10 +5928,10 @@ impl<'warnings> Compiler<'warnings> {
                 );
             } else {
                 // Stack: [closure]
-                self.set_source_range(def_source_range);
+                self.restore_source_span(def_source_span);
                 emit!(self, Instruction::PushNull);
                 // Stack: [closure, NULL]
-                self.set_source_range(def_source_range);
+                self.restore_source_span(def_source_span);
                 emit!(self, Instruction::Call { argc: 0 });
             }
         }
@@ -5740,7 +5940,7 @@ impl<'warnings> Compiler<'warnings> {
         self.apply_decorators(decorator_list);
 
         // Store the function
-        self.set_source_range(def_source_range);
+        self.restore_source_span(def_source_span);
         if preserve_value_before_store {
             emit!(self, Instruction::Copy { i: 1 });
         }
@@ -5946,6 +6146,7 @@ impl<'warnings> Compiler<'warnings> {
         body: &[ast::Stmt],
         type_params: Option<&ast::TypeParams>,
         firstlineno: u32,
+        class_span: CompilerSourceSpan,
     ) -> CompileResult<CodeObject> {
         // 1. Enter class scope
         let key = self.symbol_table_stack.len();
@@ -5959,9 +6160,19 @@ impl<'warnings> Compiler<'warnings> {
         self.code_stack.last_mut().unwrap().private = Some(name.to_owned());
 
         // 2. Set up class namespace
+        let doc_span = self.docstring_span(body);
         let (doc_str, body) = split_doc_with_range(body, &self.opts);
         let class_body_prefix_range = self.source_line_start_range(firstlineno);
-        self.set_source_range(class_body_prefix_range);
+        let class_body_prefix_span = CompilerSourceSpan {
+            range: class_body_prefix_range,
+            location: class_span.location.map(|_| SourceLocationRange {
+                line: firstlineno.to_i32().expect("validated first line"),
+                end_line: firstlineno.to_i32().expect("validated first line"),
+                col: 0,
+                end_col: 0,
+            }),
+        };
+        self.restore_source_span(class_body_prefix_span);
 
         // Load __name__ and store as __module__
         self.load_name(&"__name__".into())?;
@@ -6007,19 +6218,19 @@ impl<'warnings> Compiler<'warnings> {
 
         // Store __doc__ only if there's an explicit docstring.
         if let Some((doc, range)) = doc_str {
-            let saved_range = self.current_source_range;
-            self.set_source_range(range);
+            let saved_range = self.current_source_span;
+            self.restore_source_span(doc_span.unwrap_or_else(|| CompilerSourceSpan::parsed(range)));
             self.emit_load_const(ConstantData::Str { value: doc.into() });
             self.store_name(&"__doc__".into())?;
             self.set_no_location();
-            self.set_source_range(saved_range);
+            self.restore_source_span(saved_range);
         }
 
         // 3. Compile the class body
         self.compile_statements(body)?;
 
         if annotations_used && !self.future_annotations {
-            self.compile_module_annotate(body, Some(class_body_prefix_range))?;
+            self.compile_module_annotate(body, Some(class_body_prefix_span))?;
         }
 
         // 4. Handle __classcell__ if needed
@@ -6100,30 +6311,34 @@ impl<'warnings> Compiler<'warnings> {
     ) -> CompileResult<()> {
         // CPython's ClassDef LOC(s) starts at the class line even when
         // decorators are present.
-        let stmt_source_range = self.current_source_range;
+        let statement_span = self.current_source_span;
+        let stmt_source_range = statement_span.range;
         let class_source_range = crate::decorated_definition_range(
             &self.source_file,
             stmt_source_range,
             decorator_list,
             "class ",
         );
+        let class_source_span = CompilerSourceSpan {
+            range: class_source_range,
+            ..statement_span
+        };
         self.prepare_decorators(decorator_list)?;
 
         let is_generic = type_params.is_some();
-        let firstlineno_range = decorator_list
-            .first()
-            .map_or(stmt_source_range, |decorator| decorator.expression.range());
-        #[expect(clippy::map_unwrap_or, reason = "Changing this will not compile")]
-        let firstlineno = decorator_list
-            .first()
-            .map(|decorator| {
+        let firstlineno_span = decorator_list.first().map_or(statement_span, |decorator| {
+            self.node_span(&decorator.expression)
+        });
+        let firstlineno = firstlineno_span
+            .location
+            .and_then(|loc| u32::try_from(loc.line).ok())
+            .unwrap_or_else(|| {
                 self.source_file
                     .to_source_code()
-                    .line_index(decorator.expression.range().start())
+                    .line_index(firstlineno_span.range.start())
                     .get()
                     .to_u32()
-            })
-            .unwrap_or_else(|| self.get_source_line_number().get().to_u32());
+            });
 
         // Save context before entering any scopes
         let saved_ctx = self.ctx;
@@ -6131,7 +6346,7 @@ impl<'warnings> Compiler<'warnings> {
         // Step 1: If generic, enter type params scope and compile type params
         if is_generic {
             let type_params_name = format!("<generic parameters of {name}>");
-            self.set_source_range(firstlineno_range);
+            self.restore_source_span(firstlineno_span);
             self.push_output(
                 bytecode::CodeFlags::OPTIMIZED | bytecode::CodeFlags::NEWLOCALS,
                 0,
@@ -6153,7 +6368,7 @@ impl<'warnings> Compiler<'warnings> {
             // Compile type parameters and store them in the synthetic cell that
             // generic class bodies close over.
             self.compile_type_params(type_params.unwrap())?;
-            self.set_source_range(class_source_range);
+            self.restore_source_span(class_source_span);
             self.store_name(&".type_params".into())?;
         }
 
@@ -6165,11 +6380,12 @@ impl<'warnings> Compiler<'warnings> {
             in_async_scope: false,
         };
         let pre_class_body_symbol_table_cursors = self.current_symbol_table_cursors();
-        let class_code = self.compile_class_body(name, body, type_params, firstlineno)?;
+        let class_code =
+            self.compile_class_body(name, body, type_params, firstlineno, class_source_span)?;
         let post_class_body_symbol_table_cursors = self.current_symbol_table_cursors();
         self.set_symbol_table_cursors(pre_class_body_symbol_table_cursors);
         self.ctx = prev_ctx;
-        self.set_source_range(class_source_range);
+        self.restore_source_span(class_source_span);
 
         // Step 3: Generate the rest of the code for the call
         if is_generic {
@@ -6186,7 +6402,7 @@ impl<'warnings> Compiler<'warnings> {
 
             // Create .generic_base after the class function and name are on the
             // stack so the remaining call shape matches CPython's ordering.
-            self.set_source_range(class_source_range);
+            self.restore_source_span(class_source_span);
             self.load_name(&".type_params".into())?;
             emit!(
                 self,
@@ -6194,7 +6410,7 @@ impl<'warnings> Compiler<'warnings> {
                     func: bytecode::IntrinsicFunction1::SubscriptGeneric
                 }
             );
-            self.set_source_range(class_source_range);
+            self.restore_source_span(class_source_span);
             self.store_name(&".generic_base".into())?;
 
             let (bases, keywords) = arguments.map_or((&[][..], &[][..]), |args| {
@@ -6204,7 +6420,7 @@ impl<'warnings> Compiler<'warnings> {
                 2,
                 bases,
                 keywords,
-                class_source_range,
+                class_source_span,
                 None,
                 Some(&".generic_base".into()),
             )?;
@@ -6218,11 +6434,11 @@ impl<'warnings> Compiler<'warnings> {
             self.ctx = saved_ctx;
 
             // Execute the type params function
-            self.set_source_range(class_source_range);
+            self.restore_source_span(class_source_span);
             self.make_closure(type_params_code, bytecode::MakeFunctionFlags::new())?;
-            self.set_source_range(class_source_range);
+            self.restore_source_span(class_source_span);
             emit!(self, Instruction::PushNull);
-            self.set_source_range(class_source_range);
+            self.restore_source_span(class_source_span);
             emit!(self, Instruction::Call { argc: 0 });
         } else {
             // Non-generic class: standard path
@@ -6236,9 +6452,9 @@ impl<'warnings> Compiler<'warnings> {
             });
 
             if let Some(arguments) = arguments {
-                self.codegen_call_helper(2, arguments, class_source_range, None)?;
+                self.codegen_call_helper(2, arguments, class_source_span, None)?;
             } else {
-                self.set_source_range(class_source_range);
+                self.restore_source_span(class_source_span);
                 emit!(self, Instruction::Call { argc: 2 });
             }
             self.set_symbol_table_cursors(post_class_body_symbol_table_cursors);
@@ -6246,7 +6462,7 @@ impl<'warnings> Compiler<'warnings> {
 
         // Step 4: Apply decorators and store (common to both paths)
         self.apply_decorators(decorator_list);
-        self.set_source_range(class_source_range);
+        self.restore_source_span(class_source_span);
         if preserve_value_before_store {
             emit!(self, Instruction::Copy { i: 1 });
         }
@@ -6260,7 +6476,7 @@ impl<'warnings> Compiler<'warnings> {
         test: &ast::Expr,
         body: &[ast::Stmt],
         elif_else_clauses: &[ast::ElifElseClause],
-        stmt_range: TextRange,
+        stmt_span: CompilerSourceSpan,
     ) -> CompileResult<()> {
         let end_block = self.new_block();
         let next_block = if elif_else_clauses.is_empty() {
@@ -6269,7 +6485,7 @@ impl<'warnings> Compiler<'warnings> {
             self.new_block()
         };
 
-        self.compile_jump_if_inner(test, false, next_block, Some(stmt_range))?;
+        self.compile_jump_if_inner(test, false, next_block, Some(stmt_span))?;
         self.compile_statements(body)?;
 
         let Some((clause, rest)) = elif_else_clauses.split_first() else {
@@ -6285,7 +6501,7 @@ impl<'warnings> Compiler<'warnings> {
         self.use_cpython_label_block(next_block);
 
         if let Some(test) = &clause.test {
-            self.compile_if(test, &clause.body, rest, clause.range)?;
+            self.compile_if(test, &clause.body, rest, self.node_span(clause))?;
         } else {
             debug_assert!(rest.is_empty());
             self.compile_statements(&clause.body)?;
@@ -6299,7 +6515,7 @@ impl<'warnings> Compiler<'warnings> {
         test: &ast::Expr,
         body: &[ast::Stmt],
         orelse: &[ast::Stmt],
-        while_range: TextRange,
+        while_span: CompilerSourceSpan,
     ) -> CompileResult<()> {
         self.enter_conditional_block();
 
@@ -6315,7 +6531,7 @@ impl<'warnings> Compiler<'warnings> {
             end_label,
             FBlockDatum::None,
         )?;
-        self.compile_jump_if_inner(test, false, anchor_block, Some(while_range))?;
+        self.compile_jump_if_inner(test, false, anchor_block, Some(while_span))?;
 
         self.compile_loop_body_statements(body)?;
         emit!(self, PseudoInstruction::Jump { delta: loop_block });
@@ -6378,7 +6594,7 @@ impl<'warnings> Compiler<'warnings> {
         let Some((item, items)) = items.split_first() else {
             return Err(self.error(CodegenErrorType::EmptyWithItems));
         };
-        let with_range = item.context_expr.range();
+        let with_range = self.node_span(&item.context_expr);
 
         let body_block = self.new_block();
         let exc_handler_block = self.new_block();
@@ -6387,7 +6603,7 @@ impl<'warnings> Compiler<'warnings> {
 
         // Compile context expression and load __enter__/__exit__ methods
         self.compile_expression(&item.context_expr)?;
-        self.set_source_range(with_range);
+        self.restore_source_span(with_range);
 
         // Stack: [cm]
         emit!(self, Instruction::Copy { i: 1 }); // [cm, cm]
@@ -6415,6 +6631,7 @@ impl<'warnings> Compiler<'warnings> {
             ); // [aexit_func, self_ae, aenter_func, self_an]
             emit!(self, Instruction::Call { argc: 0 }); // [aexit_func, self_ae, awaitable]
             emit!(self, Instruction::GetAwaitable { r#where: 1 });
+            emit!(self, Instruction::PushNull);
             self.emit_load_const(ConstantData::None);
             let _ = self.compile_yield_from_sequence(true);
         } else {
@@ -6463,7 +6680,7 @@ impl<'warnings> Compiler<'warnings> {
         // Store or pop the enter result
         match &item.optional_vars {
             Some(var) => {
-                self.set_source_range(var.range());
+                self.set_source_node(var.range(), var.node_index());
                 self.compile_store(var)?;
             }
             None => {
@@ -6479,7 +6696,10 @@ impl<'warnings> Compiler<'warnings> {
             }
             self.compile_with_body_statements(body)?;
         } else {
-            self.set_source_range(items[0].context_expr.range());
+            self.set_source_node(
+                items[0].context_expr.range(),
+                items[0].context_expr.node_index(),
+            );
             self.compile_with_inner(items, body, is_async)?;
         }
 
@@ -6487,18 +6707,19 @@ impl<'warnings> Compiler<'warnings> {
         // sync with emits the artificial POP_BLOCK before popping the fblock.
         if is_async {
             self.pop_fblock_label(fblock_type, body_label);
-            self.set_source_range(with_range);
+            self.restore_source_span(with_range);
             emit!(self, PseudoInstruction::PopBlock);
         } else {
             emit!(self, PseudoInstruction::PopBlock);
             self.set_no_location();
-            self.set_source_range(with_range);
+            self.restore_source_span(with_range);
             self.pop_fblock_label(fblock_type, body_label);
         }
 
         self.compile_call_exit_with_nones();
         if is_async {
             emit!(self, Instruction::GetAwaitable { r#where: 2 });
+            emit!(self, Instruction::PushNull);
             self.emit_load_const(ConstantData::None);
             let _ = self.compile_yield_from_sequence(true);
         }
@@ -6525,6 +6746,7 @@ impl<'warnings> Compiler<'warnings> {
 
         if is_async {
             emit!(self, Instruction::GetAwaitable { r#where: 2 });
+            emit!(self, Instruction::PushNull);
             self.emit_load_const(ConstantData::None);
             let _ = self.compile_yield_from_sequence(true);
         }
@@ -6543,7 +6765,7 @@ impl<'warnings> Compiler<'warnings> {
         body: &[ast::Stmt],
         orelse: &[ast::Stmt],
         is_async: bool,
-        for_range: TextRange,
+        for_span: CompilerSourceSpan,
     ) -> CompileResult<()> {
         self.enter_conditional_block();
 
@@ -6581,15 +6803,15 @@ impl<'warnings> Compiler<'warnings> {
             {
                 return Err(self.error(CodegenErrorType::InvalidAsyncFor));
             }
-            self.set_source_range(iter.range());
+            self.set_source_node(iter.range(), iter.node_index());
             emit!(self, Instruction::GetAiter);
 
             self.use_cpython_label_block(for_block);
-            self.set_source_range(for_range);
+            self.restore_source_span(for_span);
 
             // codegen_async_for: push fblock BEFORE SETUP_FINALLY
             self.push_fblock_labels(
-                FBlockType::ForLoop,
+                FBlockType::AsyncForLoop,
                 for_label,
                 after_label,
                 FBlockDatum::None,
@@ -6598,6 +6820,7 @@ impl<'warnings> Compiler<'warnings> {
             // SETUP_FINALLY to guard the __anext__ call
             emit!(self, PseudoInstruction::SetupFinally { delta: else_block });
             emit!(self, Instruction::GetAnext);
+            emit!(self, Instruction::PushNull);
             self.emit_load_const(ConstantData::None);
             self.use_cpython_label_block(send_block);
             let _ = self.compile_yield_from_sequence(true);
@@ -6610,22 +6833,22 @@ impl<'warnings> Compiler<'warnings> {
             self.compile_store(target)?;
         } else {
             // Retrieve Iterator
-            self.set_source_range(iter.range());
-            emit!(self, Instruction::GetIter);
+            self.set_source_node(iter.range(), iter.node_index());
+            emit!(self, Instruction::GetIter { mode: 0 });
 
             self.use_cpython_label_block(for_block);
 
             emit!(self, Instruction::ForIter { delta: else_block });
 
-            let saved_range = self.current_source_range;
-            self.set_source_range(target.range());
+            let saved_range = self.current_source_span;
+            self.set_source_node(target.range(), target.node_index());
             emit!(self, Instruction::Nop);
             let result = self
                 .current_code_info()
                 .use_raw_instr_sequence_label(body_label.expect("sync for must have body label"));
             unwrap_internal(self, result);
             self.compile_store(target)?;
-            self.set_source_range(saved_range);
+            self.restore_source_span(saved_range);
         };
 
         self.compile_loop_body_statements(body)?;
@@ -6636,7 +6859,7 @@ impl<'warnings> Compiler<'warnings> {
             // codegen_async_for() pops the loop fblock before the
             // END_ASYNC_FOR exception block. Sync codegen_for() keeps the
             // fblock through END_FOR/POP_ITER and pops below.
-            self.pop_fblock_label(FBlockType::ForLoop, for_label);
+            self.pop_fblock_label(FBlockType::AsyncForLoop, for_label);
         }
 
         self.use_cpython_label_block(else_block);
@@ -6645,10 +6868,10 @@ impl<'warnings> Compiler<'warnings> {
         if is_async {
             // codegen_async_for emits END_ASYNC_FOR at the iterator location,
             // after the for-loop fblock has already been popped.
-            let saved_range = self.current_source_range;
-            self.set_source_range(iter.range());
+            let saved_range = self.current_source_span;
+            self.set_source_node(iter.range(), iter.node_index());
             self.emit_end_async_for(end_async_for_target);
-            self.set_source_range(saved_range);
+            self.restore_source_span(saved_range);
         } else {
             // codegen_for emits END_FOR/POP_ITER with NO_LOCATION. Line numbers
             // are propagated later by flowgraph.c::resolve_line_numbers().
@@ -6663,22 +6886,22 @@ impl<'warnings> Compiler<'warnings> {
         self.use_cpython_label_block(after_block);
 
         // Implicit return after for-loop should be attributed to the `for` line
-        self.set_source_range(iter.range());
+        self.set_source_node(iter.range(), iter.node_index());
 
         self.leave_conditional_block();
         Ok(())
     }
 
     fn compile_comprehension_iter(&mut self, generator: &ast::Comprehension) -> CompileResult<()> {
-        let saved_range = self.current_source_range;
+        let saved_range = self.current_source_span;
         self.compile_expression(&generator.iter)?;
-        self.set_source_range(generator.iter.range());
+        self.set_source_node(generator.iter.range(), generator.iter.node_index());
         if generator.is_async {
             emit!(self, Instruction::GetAiter);
         } else {
-            emit!(self, Instruction::GetIter);
+            emit!(self, Instruction::GetIter { mode: 0 });
         }
-        self.set_source_range(saved_range);
+        self.restore_source_span(saved_range);
         Ok(())
     }
 
@@ -6736,7 +6959,7 @@ impl<'warnings> Compiler<'warnings> {
 
     /// Emits the necessary POP instructions for all failure targets in the pattern context,
     /// then resets the fail_pop vector.
-    fn emit_and_reset_fail_pop(&mut self, pc: &mut PatternContext, loc: TextRange) {
+    fn emit_and_reset_fail_pop(&mut self, pc: &mut PatternContext, loc: CompilerSourceSpan) {
         // If the fail_pop vector is empty, nothing needs to be done.
         if pc.fail_pop.is_empty() {
             debug_assert!(pc.fail_pop.is_empty());
@@ -6747,7 +6970,7 @@ impl<'warnings> Compiler<'warnings> {
             // CPython emit_and_reset_fail_pop() uses USE_LABEL here.
             self.use_cpython_label_block(label);
             // Emit the POP instruction.
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             emit!(self, Instruction::PopTop);
         }
         // Finally, use the first label.
@@ -6759,7 +6982,7 @@ impl<'warnings> Compiler<'warnings> {
     }
 
     /// Duplicate the effect of Python 3.10's ROT_* instructions using SWAPs.
-    fn pattern_helper_rotate(&mut self, loc: TextRange, mut count: usize) {
+    fn pattern_helper_rotate(&mut self, loc: CompilerSourceSpan, mut count: usize) {
         // Rotate TOS (top of stack) to position `count` down
         // This is done by a series of swaps
         // For count=1, no rotation needed (already at top)
@@ -6767,7 +6990,7 @@ impl<'warnings> Compiler<'warnings> {
         // For count=3, swap TOS with item 2 positions down, then with item 1 position down
         while count > 1 {
             // Emit a SWAP instruction with the current count.
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             emit!(
                 self,
                 Instruction::Swap {
@@ -6786,14 +7009,14 @@ impl<'warnings> Compiler<'warnings> {
     /// to the list of captured names.
     fn pattern_helper_store_name(
         &mut self,
-        loc: TextRange,
+        loc: CompilerSourceSpan,
         n: Option<&ast::Identifier>,
         pc: &mut PatternContext,
     ) -> CompileResult<()> {
         match n {
             // If no name is provided, simply pop the top of the stack.
             None => {
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(self, Instruction::PopTop);
                 Ok(())
             }
@@ -6803,7 +7026,7 @@ impl<'warnings> Compiler<'warnings> {
                 if pc.stores.contains(name.id()) {
                     return Err(self.error_ranged(
                         CodegenErrorType::DuplicateStore(name.as_str().to_string()),
-                        loc,
+                        loc.range,
                     ));
                 }
 
@@ -6834,7 +7057,7 @@ impl<'warnings> Compiler<'warnings> {
 
     fn pattern_unpack_helper(
         &mut self,
-        loc: TextRange,
+        loc: CompilerSourceSpan,
         elts: &[ast::Pattern],
     ) -> CompileResult<()> {
         let n = elts.len();
@@ -6844,25 +7067,25 @@ impl<'warnings> Compiler<'warnings> {
                 if i >= (1 << 8) || (n - i - 1) >= ((i32::MAX as usize) >> 8) {
                     return Err(self.error_ranged(
                         CodegenErrorType::TooManyExpressionsInStarUnpackingSequencePattern,
-                        loc,
+                        loc.range,
                     ));
                 }
                 let counts = UnpackExArgs {
                     before: u8::try_from(i).unwrap(),
                     after: u32::try_from(n - i - 1).unwrap(),
                 };
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(self, Instruction::UnpackEx { counts });
                 seen_star = true;
             } else if elt.is_match_star() {
                 return Err(self.error_ranged(
                     CodegenErrorType::MultipleStarredExpressionsInSequencePattern,
-                    loc,
+                    loc.range,
                 ));
             }
         }
         if !seen_star {
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             emit!(
                 self,
                 Instruction::UnpackSequence {
@@ -6875,7 +7098,7 @@ impl<'warnings> Compiler<'warnings> {
 
     fn pattern_helper_sequence_unpack(
         &mut self,
-        loc: TextRange,
+        loc: CompilerSourceSpan,
         patterns: &[ast::Pattern],
         _star: Option<usize>,
         pc: &mut PatternContext,
@@ -6896,7 +7119,7 @@ impl<'warnings> Compiler<'warnings> {
 
     fn pattern_helper_sequence_subscr(
         &mut self,
-        loc: TextRange,
+        loc: CompilerSourceSpan,
         patterns: &[ast::Pattern],
         star: usize,
         pc: &mut PatternContext,
@@ -6913,23 +7136,23 @@ impl<'warnings> Compiler<'warnings> {
                 continue;
             }
             // Duplicate the subject.
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             emit!(self, Instruction::Copy { i: 1 });
             if i < star {
                 // For indices before the star, use a nonnegative index equal to i.
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 self.emit_load_const(ConstantData::Integer { value: i.into() });
             } else {
                 // For indices after the star, compute a nonnegative index:
                 // index = len(subject) - (size - i)
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(self, Instruction::GetLen);
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 self.emit_load_const(ConstantData::Integer {
                     value: (patterns.len() - i).into(),
                 });
                 // Subtract to compute the correct index.
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(
                     self,
                     Instruction::BinaryOp {
@@ -6938,7 +7161,7 @@ impl<'warnings> Compiler<'warnings> {
                 );
             }
             // Use BINARY_OP/NB_SUBSCR to extract the element.
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             emit!(
                 self,
                 Instruction::BinaryOp {
@@ -6950,7 +7173,7 @@ impl<'warnings> Compiler<'warnings> {
         }
         // Pop the subject off the stack.
         pc.on_top -= 1;
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         emit!(self, Instruction::PopTop);
         Ok(())
     }
@@ -6991,19 +7214,19 @@ impl<'warnings> Compiler<'warnings> {
                 );
             }
             // If irrefutable matches are allowed, store the name (if any).
-            return self.pattern_helper_store_name(p.range, p.name.as_ref(), pc);
+            return self.pattern_helper_store_name(self.node_span(p), p.name.as_ref(), pc);
         }
 
         // Otherwise, there is a sub-pattern. Duplicate the object on top of the stack.
         pc.on_top += 1;
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         emit!(self, Instruction::Copy { i: 1 });
         // Compile the sub-pattern.
         self.compile_pattern(p.pattern.as_ref().unwrap(), pc)?;
         // After success, decrement the on_top counter.
         pc.on_top -= 1;
         // Store the captured name (if any).
-        self.pattern_helper_store_name(p.range, p.name.as_ref(), pc)?;
+        self.pattern_helper_store_name(self.node_span(p), p.name.as_ref(), pc)?;
         Ok(())
     }
 
@@ -7012,7 +7235,7 @@ impl<'warnings> Compiler<'warnings> {
         p: &ast::PatternMatchStar,
         pc: &mut PatternContext,
     ) -> CompileResult<()> {
-        self.pattern_helper_store_name(p.range, p.name.as_ref(), pc)?;
+        self.pattern_helper_store_name(self.node_span(p), p.name.as_ref(), pc)?;
         Ok(())
     }
 
@@ -7090,7 +7313,7 @@ impl<'warnings> Compiler<'warnings> {
 
         // Compile the class expression.
         self.compile_expression(&match_class.cls)?;
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
 
         // Create a new tuple of attribute names.
         let mut attr_names = vec![];
@@ -7127,7 +7350,7 @@ impl<'warnings> Compiler<'warnings> {
 
         // At this point the TOS is a tuple of (nargs + n_attrs) attributes (or None).
         pc.on_top += 1;
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
 
         // Unpack the tuple into (nargs + n_attrs) items.
@@ -7150,7 +7373,7 @@ impl<'warnings> Compiler<'warnings> {
             pc.on_top -= 1;
 
             if Self::pattern_wildcard_check(subpattern) {
-                self.set_source_range(p.range);
+                self.set_source_node(p.range, &p.node_index);
                 emit!(self, Instruction::PopTop);
                 continue; // Don't compile wildcard patterns
             }
@@ -7199,11 +7422,11 @@ impl<'warnings> Compiler<'warnings> {
         // Stack: [subject]
         pc.on_top += 1;
 
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         emit!(self, Instruction::MatchMapping);
         // Stack: [subject, is_mapping]
 
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
         // Stack: [subject]
 
@@ -7218,19 +7441,19 @@ impl<'warnings> Compiler<'warnings> {
         // Length check for patterns with keys
         if size > 0 {
             // Check if the mapping has at least 'size' keys
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::GetLen);
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             self.emit_load_const(ConstantData::Integer { value: size.into() });
             // Stack: [subject, len, size]
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(
                 self,
                 Instruction::CompareOp {
                     opname: ComparisonOperator::GreaterOrEqual
                 }
             );
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
             // Stack: [subject]
         }
@@ -7251,7 +7474,7 @@ impl<'warnings> Compiler<'warnings> {
         for key in keys {
             self.compile_pattern_mapping_key(&mut seen, p.range, key)?;
         }
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         // Stack: [subject, key1, key2, ..., key_n]
 
         // Build tuple of keys (empty tuple if size==0)
@@ -7264,14 +7487,14 @@ impl<'warnings> Compiler<'warnings> {
         pc.on_top += 2; // subject and keys_tuple are underneath
 
         // Check if match succeeded
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         emit!(self, Instruction::Copy { i: 1 });
         // Stack: [subject, keys_tuple, values_tuple, values_tuple_copy]
 
         // Check if copy is None (consumes the copy like POP_JUMP_IF_NONE)
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         self.emit_load_const(ConstantData::None);
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         emit!(
             self,
             Instruction::IsOp {
@@ -7280,7 +7503,7 @@ impl<'warnings> Compiler<'warnings> {
         );
 
         // Stack: [subject, keys_tuple, values_tuple, bool]
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
         // Stack: [subject, keys_tuple, values_tuple]
 
@@ -7310,19 +7533,19 @@ impl<'warnings> Compiler<'warnings> {
             // Stack: [subject, keys_tuple]
 
             // Build rest dict exactly
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::BuildMap { count: 0 });
             // Stack: [subject, keys_tuple, {}]
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::Swap { i: 3 });
             // Stack: [{}, keys_tuple, subject]
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::DictUpdate { i: 2 });
             // Stack after DICT_UPDATE: [rest_dict, keys_tuple]
             // DICT_UPDATE consumes source (subject) and leaves dict in place
 
             // Unpack keys and delete from rest_dict
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::UnpackSequence { count: size });
             // Stack: [rest_dict, k1, k2, ..., kn] (if size==0, nothing pushed)
 
@@ -7331,13 +7554,13 @@ impl<'warnings> Compiler<'warnings> {
             let mut remaining = size;
             while remaining > 0 {
                 // Copy rest_dict which is at position (1 + remaining) from TOS
-                self.set_source_range(p.range);
+                self.set_source_node(p.range, &p.node_index);
                 emit!(self, Instruction::Copy { i: 1 + remaining });
                 // Stack: [rest_dict, k1, ..., kn, rest_dict]
-                self.set_source_range(p.range);
+                self.set_source_node(p.range, &p.node_index);
                 emit!(self, Instruction::Swap { i: 2 });
                 // Stack: [rest_dict, k1, ..., kn-1, rest_dict, kn]
-                self.set_source_range(p.range);
+                self.set_source_node(p.range, &p.node_index);
                 emit!(self, Instruction::DeleteSubscr);
                 // Stack: [rest_dict, k1, ..., kn-1] (removed kn from rest_dict)
                 remaining -= 1;
@@ -7346,14 +7569,14 @@ impl<'warnings> Compiler<'warnings> {
             // pattern_helper_store_name will handle the rotation correctly
 
             // Store the rest dict
-            self.pattern_helper_store_name(p.range, Some(rest_name), pc)?;
+            self.pattern_helper_store_name(self.node_span(p), Some(rest_name), pc)?;
         } else {
             // Non-rest pattern: just clean up the stack
 
             // Pop them as we're not using them
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::PopTop); // Pop keys_tuple
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::PopTop); // Pop subject
         }
 
@@ -7586,7 +7809,7 @@ impl<'warnings> Compiler<'warnings> {
             pc.fail_pop.clear();
             pc.on_top = 0;
             // Emit a COPY(1) instruction before compiling the alternative.
-            self.set_source_range(alt.range());
+            self.set_source_node(alt.range(), alt.node_index());
             emit!(self, Instruction::Copy { i: 1 });
             self.compile_pattern(alt, pc)?;
 
@@ -7628,19 +7851,19 @@ impl<'warnings> Compiler<'warnings> {
                                 pc.stores.insert(insert_pos + j, elem);
                             }
                             // Also perform the same rotation on the evaluation stack.
-                            self.set_source_range(alt.range());
+                            self.set_source_node(alt.range(), alt.node_index());
                             for _ in 0..=i_stores {
-                                self.pattern_helper_rotate(alt.range(), i_control + 1);
+                                self.pattern_helper_rotate(self.node_span(alt), i_control + 1);
                             }
                         }
                     }
                 }
             }
             // Emit a jump to the common end label and reset any failure jump targets.
-            self.set_source_range(alt.range());
+            self.set_source_node(alt.range(), alt.node_index());
             emit!(self, PseudoInstruction::Jump { delta: end });
-            self.set_source_range(alt.range());
-            self.emit_and_reset_fail_pop(pc, alt.range());
+            self.set_source_node(alt.range(), alt.node_index());
+            self.emit_and_reset_fail_pop(pc, self.node_span(alt));
         }
 
         // Restore the original pattern context.
@@ -7651,7 +7874,7 @@ impl<'warnings> Compiler<'warnings> {
         // In Rust, old_pc is a local clone, so we need not worry about that.
 
         // No alternative matched: pop the subject and fail.
-        self.set_source_range(p.range());
+        self.set_source_node(p.range(), p.node_index());
         emit!(self, Instruction::PopTop);
         self.jump_to_fail_pop(pc, JumpOp::Jump);
 
@@ -7664,8 +7887,8 @@ impl<'warnings> Compiler<'warnings> {
         let n_rots = n_stores + 1 + pc.on_top + pc.stores.len();
         for i in 0..n_stores {
             // Rotate the capture to its proper place.
-            self.set_source_range(p.range());
-            self.pattern_helper_rotate(p.range(), n_rots);
+            self.set_source_node(p.range(), p.node_index());
+            self.pattern_helper_rotate(self.node_span(p), n_rots);
             let name = &control.as_ref().unwrap()[i];
             // Check for duplicate binding.
             if pc.stores.contains(name) {
@@ -7679,7 +7902,7 @@ impl<'warnings> Compiler<'warnings> {
 
         // Old context and control will be dropped automatically.
         // Finally, pop the copy of the subject.
-        self.set_source_range(p.range());
+        self.set_source_node(p.range(), p.node_index());
         emit!(self, Instruction::PopTop);
         Ok(())
     }
@@ -7717,42 +7940,42 @@ impl<'warnings> Compiler<'warnings> {
 
         // Keep the subject on top during the sequence and length checks.
         pc.on_top += 1;
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         emit!(self, Instruction::MatchSequence);
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
 
         if star.is_none() {
             // No star: len(subject) == size
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::GetLen);
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             self.emit_load_const(ConstantData::Integer { value: size.into() });
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(
                 self,
                 Instruction::CompareOp {
                     opname: ComparisonOperator::Equal
                 }
             );
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
         } else if size > 1 {
             // Star exists: len(subject) >= size - 1
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::GetLen);
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             self.emit_load_const(ConstantData::Integer {
                 value: (size - 1).into(),
             });
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(
                 self,
                 Instruction::CompareOp {
                     opname: ComparisonOperator::GreaterOrEqual
                 }
             );
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
         }
 
@@ -7760,12 +7983,12 @@ impl<'warnings> Compiler<'warnings> {
         pc.on_top -= 1;
         if only_wildcard {
             // ast::Patterns like: [] / [_] / [_, _] / [*_] / [_, *_] / [_, _, *_] / etc.
-            self.set_source_range(p.range);
+            self.set_source_node(p.range, &p.node_index);
             emit!(self, Instruction::PopTop);
         } else if star_wildcard {
-            self.pattern_helper_sequence_subscr(p.range, patterns, star.unwrap(), pc)?;
+            self.pattern_helper_sequence_subscr(self.node_span(p), patterns, star.unwrap(), pc)?;
         } else {
-            self.pattern_helper_sequence_unpack(p.range, patterns, star, pc)?;
+            self.pattern_helper_sequence_unpack(self.node_span(p), patterns, star, pc)?;
         }
         Ok(())
     }
@@ -7779,7 +8002,7 @@ impl<'warnings> Compiler<'warnings> {
         // before the fail jump. Late IR folding will collapse COMPARE_OP+TO_BOOL
         // into COMPARE_OP bool(...) when applicable.
         if let Some(constant) = self.try_compile_match_value_constant(&p.value)? {
-            self.set_source_range(p.value.range());
+            self.set_source_node(p.value.range(), p.value.node_index());
             self.emit_load_const(constant);
         } else if matches!(*p.value, ast::Expr::Attribute(_)) {
             self.compile_expression(&p.value)?;
@@ -7799,16 +8022,16 @@ impl<'warnings> Compiler<'warnings> {
                 p.range,
             ));
         }
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         emit!(
             self,
             Instruction::CompareOp {
                 opname: bytecode::ComparisonOperator::Equal
             }
         );
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         emit!(self, Instruction::ToBool);
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
         Ok(())
     }
@@ -7819,17 +8042,17 @@ impl<'warnings> Compiler<'warnings> {
         pc: &mut PatternContext,
     ) {
         // Load the singleton constant value.
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         self.emit_load_const(match p.value {
             ast::Singleton::None => ConstantData::None,
             ast::Singleton::False => ConstantData::Boolean { value: false },
             ast::Singleton::True => ConstantData::Boolean { value: true },
         });
         // Compare using the "Is" operator.
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         emit!(self, Instruction::IsOp { invert: Invert::No });
         // Jump to the failure label if the comparison is false.
-        self.set_source_range(p.range);
+        self.set_source_node(p.range, &p.node_index);
         self.jump_to_fail_pop(pc, JumpOp::PopJumpIfFalse);
     }
 
@@ -7838,8 +8061,8 @@ impl<'warnings> Compiler<'warnings> {
         pattern_type: &ast::Pattern,
         pattern_context: &mut PatternContext,
     ) -> CompileResult<()> {
-        let prev_source_range = self.current_source_range;
-        self.set_source_range(pattern_type.range());
+        let prev_source_range = self.current_source_span;
+        self.set_source_node(pattern_type.range(), pattern_type.node_index());
         let result = match &pattern_type {
             ast::Pattern::MatchValue(pattern_type) => {
                 self.compile_pattern_value(pattern_type, pattern_context)
@@ -7867,7 +8090,7 @@ impl<'warnings> Compiler<'warnings> {
                 self.compile_pattern_or(pattern_type, pattern_context)
             }
         };
-        self.set_source_range(prev_source_range);
+        self.restore_source_span(prev_source_range);
         result
     }
 
@@ -7889,7 +8112,7 @@ impl<'warnings> Compiler<'warnings> {
         for (i, m) in cases.iter().enumerate().take(case_count) {
             // Only copy the subject if not on the last case
             if i != case_count - 1 {
-                self.set_source_range(m.pattern.range());
+                self.set_source_node(m.pattern.range(), m.pattern.node_index());
                 emit!(self, Instruction::Copy { i: 1 });
             }
 
@@ -7902,7 +8125,7 @@ impl<'warnings> Compiler<'warnings> {
             assert_eq!(pattern_context.on_top, 0);
 
             for name in &pattern_context.stores {
-                self.set_source_range(m.pattern.range());
+                self.set_source_node(m.pattern.range(), m.pattern.node_index());
                 self.compile_name(name, NameUsage::Store)?;
             }
 
@@ -7912,13 +8135,13 @@ impl<'warnings> Compiler<'warnings> {
                     guard,
                     false,
                     pattern_context.fail_pop[0],
-                    Some(m.pattern.range()),
+                    Some(self.node_span(&m.pattern)),
                 )?;
             }
 
             if i != case_count - 1 {
                 if let Some(first_stmt) = m.body.first() {
-                    self.set_source_range(first_stmt.range());
+                    self.set_source_node(first_stmt.range(), first_stmt.node_index());
                 }
                 emit!(self, Instruction::PopTop);
                 // CPython emits NEXT_LOCATION here; resolve it after redundant
@@ -7929,20 +8152,20 @@ impl<'warnings> Compiler<'warnings> {
             self.compile_statements(&m.body)?;
             emit!(self, PseudoInstruction::Jump { delta: end });
             self.set_no_location();
-            self.set_source_range(m.pattern.range());
-            self.emit_and_reset_fail_pop(pattern_context, m.pattern.range());
+            self.set_source_node(m.pattern.range(), m.pattern.node_index());
+            self.emit_and_reset_fail_pop(pattern_context, self.node_span(&m.pattern));
         }
 
         if has_default {
             let m = &cases[num_cases - 1];
-            self.set_source_range(m.pattern.range());
+            self.set_source_node(m.pattern.range(), m.pattern.node_index());
             if num_cases == 1 {
                 emit!(self, Instruction::PopTop);
             } else {
                 emit!(self, Instruction::Nop);
             }
             if let Some(ref guard) = m.guard {
-                self.compile_jump_if_inner(guard, false, end, Some(m.pattern.range()))?;
+                self.compile_jump_if_inner(guard, false, end, Some(self.node_span(&m.pattern)))?;
             }
             self.compile_statements(&m.body)?;
         }
@@ -8046,7 +8269,8 @@ impl<'warnings> Compiler<'warnings> {
         comparators: &[ast::Expr],
     ) -> CompileResult<()> {
         // Save the full Compare expression range for COMPARE_OP positions
-        let compare_range = self.current_source_range;
+        let compare_range_span = self.current_source_span;
+        let compare_range = compare_range_span.range;
         self.check_compare(compare_range, left, ops, comparators)?;
         let (last_op, mid_ops) = ops.split_last().unwrap();
         let (last_comparator, mid_comparators) = comparators.split_last().unwrap();
@@ -8056,7 +8280,7 @@ impl<'warnings> Compiler<'warnings> {
 
         if mid_comparators.is_empty() {
             self.compile_expression(last_comparator)?;
-            self.set_source_range(compare_range);
+            self.restore_source_span(compare_range_span);
             self.compile_addcompare(*last_op);
 
             return Ok(());
@@ -8069,7 +8293,7 @@ impl<'warnings> Compiler<'warnings> {
             self.compile_expression(comparator)?;
 
             // store rhs for the next comparison in chain
-            self.set_source_range(compare_range);
+            self.restore_source_span(compare_range_span);
             emit!(self, Instruction::Swap { i: 2 });
             emit!(self, Instruction::Copy { i: 2 });
 
@@ -8083,7 +8307,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         self.compile_expression(last_comparator)?;
-        self.set_source_range(compare_range);
+        self.restore_source_span(compare_range_span);
         self.compile_addcompare(*last_op);
 
         let end = self.new_block();
@@ -8107,7 +8331,8 @@ impl<'warnings> Compiler<'warnings> {
         condition: bool,
         target_block: BlockIdx,
     ) -> CompileResult<()> {
-        let compare_range = self.current_source_range;
+        let compare_range_span = self.current_source_span;
+        let compare_range = compare_range_span.range;
         self.check_compare(compare_range, left, ops, comparators)?;
         let (last_op, mid_ops) = ops.split_last().unwrap();
         let (last_comparator, mid_comparators) = comparators.split_last().unwrap();
@@ -8115,7 +8340,7 @@ impl<'warnings> Compiler<'warnings> {
         if mid_comparators.is_empty() {
             self.compile_expression(left)?;
             self.compile_expression(last_comparator)?;
-            self.set_source_range(compare_range);
+            self.restore_source_span(compare_range_span);
             self.compile_addcompare(*last_op);
             self.emit_pop_jump_by_condition(condition, target_block);
             return Ok(());
@@ -8126,7 +8351,7 @@ impl<'warnings> Compiler<'warnings> {
 
         for (op, comparator) in mid_ops.iter().zip(mid_comparators) {
             self.compile_expression(comparator)?;
-            self.set_source_range(compare_range);
+            self.restore_source_span(compare_range_span);
             emit!(self, Instruction::Swap { i: 2 });
             emit!(self, Instruction::Copy { i: 2 });
             self.compile_addcompare(*op);
@@ -8135,7 +8360,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         self.compile_expression(last_comparator)?;
-        self.set_source_range(compare_range);
+        self.restore_source_span(compare_range_span);
         self.compile_addcompare(*last_op);
         emit!(self, Instruction::ToBool);
         self.emit_pop_jump_by_condition(condition, target_block);
@@ -8179,7 +8404,7 @@ impl<'warnings> Compiler<'warnings> {
 
     fn compile_annotation(&mut self, annotation: &ast::Expr) -> CompileResult<()> {
         if self.future_annotations {
-            self.set_source_range(annotation.range());
+            self.set_source_node(annotation.range(), annotation.node_index());
             self.emit_load_const(ConstantData::Str {
                 value: UnparseExpr::new(annotation, &self.source_file)
                     .to_string()
@@ -8194,9 +8419,9 @@ impl<'warnings> Compiler<'warnings> {
                 ast::Expr::Starred(ast::ExprStarred { value, .. }) => {
                     // *args: *Ts (where Ts is a TypeVarTuple).
                     // Do [annotation_value] = [*Ts].
-                    let saved_range = self.current_source_range;
+                    let saved_range = self.current_source_span;
                     self.compile_expression(value)?;
-                    self.set_source_range(saved_range);
+                    self.restore_source_span(saved_range);
                     emit!(self, Instruction::UnpackSequence { count: 1 });
                     Ok(())
                 }
@@ -8211,7 +8436,7 @@ impl<'warnings> Compiler<'warnings> {
 
     fn compile_check_annotation_expression(&mut self, expression: &ast::Expr) -> CompileResult<()> {
         self.compile_expression(expression)?;
-        self.set_source_range(expression.range());
+        self.set_source_node(expression.range(), expression.node_index());
         emit!(self, Instruction::PopTop);
         Ok(())
     }
@@ -8247,7 +8472,7 @@ impl<'warnings> Compiler<'warnings> {
         annotation: &ast::Expr,
         value: Option<&ast::Expr>,
         simple: bool,
-        loc: TextRange,
+        loc: CompilerSourceSpan,
     ) -> CompileResult<()> {
         // Perform the actual assignment first
         if let Some(value) = value {
@@ -8264,7 +8489,7 @@ impl<'warnings> Compiler<'warnings> {
                 // PEP 563: Store stringified annotation directly to __annotations__
                 // Compile annotation as string
                 self.compile_annotation(annotation)?;
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 // Load __annotations__
                 let annotations_name = self.name("__annotations__");
                 emit!(
@@ -8274,12 +8499,12 @@ impl<'warnings> Compiler<'warnings> {
                     }
                 );
                 // Load the variable name
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 self.emit_load_const(ConstantData::Str {
                     value: self.mangle(id).as_str().into(),
                 });
                 // Store: __annotations__[name] = annotation
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(self, Instruction::StoreSubscr);
             } else {
                 // PEP 649: Handle conditional annotations
@@ -8294,7 +8519,7 @@ impl<'warnings> Compiler<'warnings> {
                         let annotation_index = code_info.next_conditional_annotation_index;
                         code_info.next_conditional_annotation_index += 1;
 
-                        self.set_source_range(loc);
+                        self.restore_source_span(loc);
                         if matches!(scope_type, CompilerScope::Class) {
                             let i = self.get_cell_var_index("__conditional_annotations__");
                             emit!(self, Instruction::LoadDeref { i });
@@ -8329,8 +8554,8 @@ impl<'warnings> Compiler<'warnings> {
     }
 
     fn compile_store(&mut self, target: &ast::Expr) -> CompileResult<()> {
-        let prev_source_range = self.current_source_range;
-        self.set_source_range(target.range());
+        let prev_source_range = self.current_source_span;
+        self.set_source_node(target.range(), target.node_index());
         let result = (|| -> CompileResult<()> {
             match &target {
                 ast::Expr::Name(ast::ExprName { id, .. }) => self.store_name(id)?,
@@ -8342,11 +8567,11 @@ impl<'warnings> Compiler<'warnings> {
                 ast::Expr::Attribute(ast::ExprAttribute { value, attr, .. }) => {
                     self.maybe_add_static_attribute_to_class(value, attr.as_str());
                     self.compile_expression(value)?;
-                    self.set_source_range(self.update_start_location_to_match_attr(
-                        target.range(),
-                        target.range(),
+                    self.restore_source_span(self.update_start_span_to_match_attr(
+                        self.node_span(target),
+                        self.node_span(target),
                         attr.as_str(),
-                    ));
+                    )?);
                     let namei = self.name(attr.as_str());
                     emit!(self, Instruction::StoreAttr { namei });
                 }
@@ -8409,7 +8634,7 @@ impl<'warnings> Compiler<'warnings> {
             Ok(())
         })();
 
-        self.set_source_range(prev_source_range);
+        self.restore_source_span(prev_source_range);
         result
     }
 
@@ -8419,8 +8644,9 @@ impl<'warnings> Compiler<'warnings> {
         op: ast::Operator,
         value: &ast::Expr,
     ) -> CompileResult<()> {
-        let stmt_range = self.current_source_range;
-        let target_range = target.range();
+        let stmt_range_span = self.current_source_span;
+
+        let target_span = self.node_span(target);
         enum AugAssignKind<'a> {
             Name {
                 id: &'a Name,
@@ -8430,20 +8656,20 @@ impl<'warnings> Compiler<'warnings> {
             },
             Attr {
                 idx: bytecode::NameIdx,
-                attr_range: TextRange,
+                attr_range: CompilerSourceSpan,
             },
         }
 
         let kind = match &target {
             ast::Expr::Name(ast::ExprName { id, .. }) => {
-                self.set_source_range(target_range);
+                self.restore_source_span(target_span);
                 self.compile_name(id, NameUsage::Load)?;
                 AugAssignKind::Name { id }
             }
             ast::Expr::Subscript(ast::ExprSubscript { value, slice, .. }) => {
                 let use_slice_opt = self.should_apply_two_element_slice_optimization(slice);
                 self.compile_expression(value)?;
-                self.set_source_range(target_range);
+                self.restore_source_span(target_span);
                 if use_slice_opt {
                     let ast::Expr::Slice(slice_expr) = slice.as_ref() else {
                         unreachable!(
@@ -8451,14 +8677,14 @@ impl<'warnings> Compiler<'warnings> {
                         );
                     };
                     self.compile_slice_two_parts(slice_expr)?;
-                    self.set_source_range(target_range);
+                    self.restore_source_span(target_span);
                     emit!(self, Instruction::Copy { i: 3 });
                     emit!(self, Instruction::Copy { i: 3 });
                     emit!(self, Instruction::Copy { i: 3 });
                     emit!(self, Instruction::BinarySlice);
                 } else {
                     self.compile_expression(slice)?;
-                    self.set_source_range(target_range);
+                    self.restore_source_span(target_span);
                     emit!(self, Instruction::Copy { i: 2 });
                     emit!(self, Instruction::Copy { i: 2 });
                     emit!(
@@ -8474,11 +8700,11 @@ impl<'warnings> Compiler<'warnings> {
                 let attr = attr.as_str();
                 self.compile_expression(value)?;
                 let attr_range =
-                    self.update_start_location_to_match_attr(target_range, target_range, attr);
-                self.set_source_range(target_range);
+                    self.update_start_span_to_match_attr(target_span, target_span, attr)?;
+                self.restore_source_span(target_span);
                 emit!(self, Instruction::Copy { i: 1 });
                 let idx = self.name(attr);
-                self.set_source_range(attr_range);
+                self.restore_source_span(attr_range);
                 self.emit_load_attr(idx);
                 AugAssignKind::Attr { idx, attr_range }
             }
@@ -8488,17 +8714,17 @@ impl<'warnings> Compiler<'warnings> {
         };
 
         self.compile_expression(value)?;
-        self.set_source_range(stmt_range);
+        self.restore_source_span(stmt_range_span);
         self.compile_op(op, true);
 
         match kind {
             AugAssignKind::Name { id } => {
                 // stack: RESULT
-                self.set_source_range(target_range);
+                self.restore_source_span(target_span);
                 self.compile_name(id, NameUsage::Store)?;
             }
             AugAssignKind::Subscript { use_slice_opt } => {
-                self.set_source_range(target_range);
+                self.restore_source_span(target_span);
                 if use_slice_opt {
                     // stack: CONTAINER START STOP RESULT
                     emit!(self, Instruction::Swap { i: 4 });
@@ -8514,7 +8740,7 @@ impl<'warnings> Compiler<'warnings> {
             }
             AugAssignKind::Attr { idx, attr_range } => {
                 // stack: CONTAINER RESULT
-                self.set_source_range(attr_range);
+                self.restore_source_span(attr_range);
                 emit!(self, Instruction::Swap { i: 2 });
                 emit!(self, Instruction::StoreAttr { namei: idx });
             }
@@ -8557,10 +8783,10 @@ impl<'warnings> Compiler<'warnings> {
         expression: &ast::Expr,
         condition: bool,
         target_block: BlockIdx,
-        source_range: Option<TextRange>,
+        source_range: Option<CompilerSourceSpan>,
     ) -> CompileResult<()> {
-        let prev_source_range = self.current_source_range;
-        self.set_source_range(source_range.unwrap_or_else(|| expression.range()));
+        let prev_source_range = self.current_source_span;
+        self.restore_source_span(source_range.unwrap_or_else(|| self.node_span(expression)));
 
         // Compile expression for test, and jump to label if false
         let result = match &expression {
@@ -8604,19 +8830,20 @@ impl<'warnings> Compiler<'warnings> {
                 self.use_cpython_label_block(end);
                 Ok(())
             }
-            ast::Expr::Compare(ast::ExprCompare {
-                left,
-                ops,
-                comparators,
-                ..
-            }) if ops.len() > 1 => {
-                self.set_source_range(expression.range());
-                self.compile_jump_if_compare(left, ops, comparators, condition, target_block)
+            ast::Expr::Compare(compare) if compare.ops.len() > 1 => {
+                self.set_source_node(expression.range(), expression.node_index());
+                self.compile_jump_if_compare(
+                    compare.first_operand(),
+                    &compare.ops,
+                    compare.comparators(),
+                    condition,
+                    target_block,
+                )
             }
             _ => {
                 // Fall back case which always will work!
                 self.compile_expression(expression)?;
-                self.set_source_range(expression.range());
+                self.set_source_node(expression.range(), expression.node_index());
                 emit!(self, Instruction::ToBool);
                 if condition {
                     emit!(
@@ -8637,7 +8864,7 @@ impl<'warnings> Compiler<'warnings> {
             }
         };
 
-        self.set_source_range(prev_source_range);
+        self.restore_source_span(prev_source_range);
         result
     }
 
@@ -8653,15 +8880,16 @@ impl<'warnings> Compiler<'warnings> {
     /// Compile a boolean operation as an expression.
     /// This means, that the last value remains on the stack.
     fn compile_bool_op(&mut self, op: ast::BoolOp, values: &[ast::Expr]) -> CompileResult<()> {
-        let boolop_range = self.current_source_range;
+        let boolop_range_span = self.current_source_span;
+
         let after_block = self.new_block();
         let (last_value, prefix_values) = values.split_last().unwrap();
 
         for value in prefix_values {
             self.compile_expression(value)?;
-            self.set_source_range(boolop_range);
+            self.restore_source_span(boolop_range_span);
             self.emit_short_circuit_test(op, after_block);
-            self.set_source_range(boolop_range);
+            self.restore_source_span(boolop_range_span);
             emit!(self, Instruction::PopTop);
         }
 
@@ -8688,30 +8916,34 @@ impl<'warnings> Compiler<'warnings> {
         items: &[ast::DictItem],
         begin: usize,
         end: usize,
-        range: TextRange,
+        span: CompilerSourceSpan,
     ) -> CompileResult<()> {
         let n = end - begin;
         let big = n * 2 > STACK_USE_GUIDELINE as usize;
         if big {
-            self.set_source_range(range);
+            self.restore_source_span(span);
             emit!(self, Instruction::BuildMap { count: 0 });
         }
         for item in &items[begin..end] {
             self.compile_expression(item.key.as_ref().unwrap())?;
             self.compile_expression(&item.value)?;
             if big {
-                self.set_source_range(range);
+                self.restore_source_span(span);
                 emit!(self, Instruction::MapAdd { i: 1 });
             }
         }
         if !big {
-            self.set_source_range(range);
+            self.restore_source_span(span);
             emit!(self, Instruction::BuildMap { count: n.to_u32() });
         }
         Ok(())
     }
 
-    fn compile_dict(&mut self, items: &[ast::DictItem], range: TextRange) -> CompileResult<()> {
+    fn compile_dict(
+        &mut self,
+        items: &[ast::DictItem],
+        span: CompilerSourceSpan,
+    ) -> CompileResult<()> {
         let n = items.len();
         let mut have_dict = false;
         let mut elements = 0usize;
@@ -8719,26 +8951,26 @@ impl<'warnings> Compiler<'warnings> {
         for (i, item) in items.iter().enumerate() {
             if item.key.is_none() {
                 if elements != 0 {
-                    self.compile_subdict(items, i - elements, i, range)?;
+                    self.compile_subdict(items, i - elements, i, span)?;
                     if have_dict {
-                        self.set_source_range(range);
+                        self.restore_source_span(span);
                         emit!(self, Instruction::DictUpdate { i: 1 });
                     }
                     have_dict = true;
                     elements = 0;
                 }
                 if !have_dict {
-                    self.set_source_range(range);
+                    self.restore_source_span(span);
                     emit!(self, Instruction::BuildMap { count: 0 });
                     have_dict = true;
                 }
                 self.compile_expression(&item.value)?;
-                self.set_source_range(range);
+                self.restore_source_span(span);
                 emit!(self, Instruction::DictUpdate { i: 1 });
             } else if elements * 2 > STACK_USE_GUIDELINE as usize {
-                self.compile_subdict(items, i - elements, i + 1, range)?;
+                self.compile_subdict(items, i - elements, i + 1, span)?;
                 if have_dict {
-                    self.set_source_range(range);
+                    self.restore_source_span(span);
                     emit!(self, Instruction::DictUpdate { i: 1 });
                 }
                 have_dict = true;
@@ -8749,15 +8981,15 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         if elements != 0 {
-            self.compile_subdict(items, n - elements, n, range)?;
+            self.compile_subdict(items, n - elements, n, span)?;
             if have_dict {
-                self.set_source_range(range);
+                self.restore_source_span(span);
                 emit!(self, Instruction::DictUpdate { i: 1 });
             }
             have_dict = true;
         }
         if !have_dict {
-            self.set_source_range(range);
+            self.restore_source_span(span);
             emit!(self, Instruction::BuildMap { count: 0 });
         }
 
@@ -8817,8 +9049,8 @@ impl<'warnings> Compiler<'warnings> {
         );
 
         // fail: CLEANUP_THROW
-        // Stack when exception: [receiver, yielded_value, exc]
-        // CLEANUP_THROW: [sub_iter, last_sent_val, exc] -> [None, value]
+        // Stack when exception: [receiver, NULL, yielded_value, exc]
+        // CLEANUP_THROW: [sub_iter, NULL, last_sent_val, exc] -> [None, NULL, value]
         // CPython lets this block fall through to END_SEND during codegen;
         // push_cold_blocks_to_end later inserts the no-interrupt jump after
         // moving the cold fail block behind the warm exit path.
@@ -8826,8 +9058,8 @@ impl<'warnings> Compiler<'warnings> {
         emit!(self, Instruction::CleanupThrow);
 
         // exit: END_SEND
-        // Stack: [receiver, value] (from SEND) or [None, value] (from CLEANUP_THROW)
-        // END_SEND: [receiver/None, value] -> [value]
+        // Stack: [receiver, NULL, value] or [None, NULL, value] after CLEANUP_THROW.
+        // END_SEND: [receiver/None, NULL, value] -> [value]
         self.use_cpython_label_block(exit_block);
         emit!(self, Instruction::EndSend);
 
@@ -8852,8 +9084,8 @@ impl<'warnings> Compiler<'warnings> {
 
     fn compile_expression(&mut self, expression: &ast::Expr) -> CompileResult<()> {
         trace!("Compiling {expression:?}");
-        let range = expression.range();
-        self.set_source_range(range);
+        let expression_span = self.node_span(expression);
+        self.restore_source_span(expression_span);
 
         if let Some(constant) = self.ast_constant_value(expression) {
             self.emit_load_const(constant);
@@ -8874,7 +9106,7 @@ impl<'warnings> Compiler<'warnings> {
                 self.compile_expression(right)?;
 
                 // Restore full expression range before emitting the operation
-                self.set_source_range(range);
+                self.restore_source_span(expression_span);
                 self.compile_op(*op, false);
             }
             ast::Expr::Subscript(ast::ExprSubscript {
@@ -8886,7 +9118,7 @@ impl<'warnings> Compiler<'warnings> {
                 self.compile_expression(operand)?;
 
                 // Restore full expression range before emitting the operation
-                self.set_source_range(range);
+                self.restore_source_span(expression_span);
                 match op {
                     ast::UnaryOp::UAdd => emit!(
                         self,
@@ -8913,10 +9145,17 @@ impl<'warnings> Compiler<'warnings> {
                     else {
                         unreachable!("can_optimize_super_call only accepts calls");
                     };
-                    self.load_args_for_super(&super_type, super_func.range(), value.range())?;
-                    let attr_access_range =
-                        self.update_start_location_to_match_attr(range, range, attr.as_str());
-                    self.set_source_range(range);
+                    self.load_args_for_super(
+                        &super_type,
+                        self.node_span(super_func.as_ref()),
+                        self.node_span(value.as_ref()),
+                    )?;
+                    let attr_access_span = self.update_start_span_to_match_attr(
+                        expression_span,
+                        expression_span,
+                        attr.as_str(),
+                    )?;
+                    self.restore_source_span(expression_span);
                     let idx = self.name(attr.as_str());
                     match super_type {
                         SuperCallType::TwoArg { .. } => {
@@ -8926,72 +9165,63 @@ impl<'warnings> Compiler<'warnings> {
                             self.emit_load_zero_super_attr(idx);
                         }
                     }
-                    self.set_source_range(attr_access_range);
+                    self.restore_source_span(attr_access_span);
                     emit!(self, Instruction::Nop);
                 } else {
                     // Normal attribute access
                     self.compile_expression(value)?;
-                    self.set_source_range(self.update_start_location_to_match_attr(
-                        range,
-                        range,
+                    self.restore_source_span(self.update_start_span_to_match_attr(
+                        expression_span,
+                        expression_span,
                         attr.as_str(),
-                    ));
+                    )?);
                     let idx = self.name(attr.as_str());
                     self.emit_load_attr(idx);
                 }
             }
-            ast::Expr::Compare(ast::ExprCompare {
-                left,
-                ops,
-                comparators,
-                ..
-            }) => {
-                self.compile_compare(left, ops, comparators)?;
+            ast::Expr::Compare(compare) => {
+                self.compile_compare(compare.first_operand(), &compare.ops, compare.comparators())?;
             }
             ast::Expr::Constant(ast::ExprConstant { value, .. }) => {
                 self.emit_load_const(ast_constant_value_to_constant_data(value.clone()));
             }
-            ast::Expr::List(ast::ExprList { elts, range, .. }) => {
-                self.set_source_range(*range);
+            ast::Expr::List(ast::ExprList { elts, .. }) => {
+                self.restore_source_span(expression_span);
                 self.starunpack_helper(elts, 0, CollectionType::List)?;
             }
-            ast::Expr::Tuple(ast::ExprTuple { elts, range, .. }) => {
-                self.set_source_range(*range);
+            ast::Expr::Tuple(ast::ExprTuple { elts, .. }) => {
+                self.restore_source_span(expression_span);
                 self.starunpack_helper(elts, 0, CollectionType::Tuple)?;
             }
-            ast::Expr::Set(ast::ExprSet { elts, range, .. }) => {
-                self.set_source_range(*range);
+            ast::Expr::Set(ast::ExprSet { elts, .. }) => {
+                self.restore_source_span(expression_span);
                 self.starunpack_helper(elts, 0, CollectionType::Set)?;
             }
-            ast::Expr::Dict(ast::ExprDict { items, range, .. }) => {
-                self.compile_dict(items, *range)?;
+            ast::Expr::Dict(ast::ExprDict { items, .. }) => {
+                self.compile_dict(items, expression_span)?;
             }
             ast::Expr::Slice(ast::ExprSlice {
-                lower,
-                upper,
-                step,
-                range,
-                ..
+                lower, upper, step, ..
             }) => {
                 if let Some(folded_const) = self.try_fold_constant_slice(
                     lower.as_deref(),
                     upper.as_deref(),
                     step.as_deref(),
                 )? {
-                    self.set_source_range(*range);
+                    self.restore_source_span(expression_span);
                     self.emit_load_const(folded_const);
                     return Ok(());
                 }
                 if let Some(lower) = lower {
                     self.compile_expression(lower)?;
                 } else {
-                    self.set_source_range(*range);
+                    self.restore_source_span(expression_span);
                     self.emit_load_const(ConstantData::None);
                 }
                 if let Some(upper) = upper {
                     self.compile_expression(upper)?;
                 } else {
-                    self.set_source_range(*range);
+                    self.restore_source_span(expression_span);
                     self.emit_load_const(ConstantData::None);
                 }
                 if let Some(step) = step {
@@ -9001,7 +9231,7 @@ impl<'warnings> Compiler<'warnings> {
                     Some(_) => BuildSliceArgCount::Three,
                     None => BuildSliceArgCount::Two,
                 };
-                self.set_source_range(*range);
+                self.restore_source_span(expression_span);
                 emit!(self, Instruction::BuildSlice { argc });
             }
             ast::Expr::Yield(ast::ExprYield { value, .. }) => {
@@ -9013,7 +9243,7 @@ impl<'warnings> Compiler<'warnings> {
                     Some(expression) => self.compile_expression(expression)?,
                     Option::None => self.emit_load_const(ConstantData::None),
                 };
-                self.set_source_range(range);
+                self.restore_source_span(expression_span);
                 if self.ctx.func == FunctionContext::AsyncFunction {
                     emit!(
                         self,
@@ -9038,8 +9268,9 @@ impl<'warnings> Compiler<'warnings> {
                     return Err(self.error(CodegenErrorType::InvalidAwait));
                 }
                 self.compile_expression(value)?;
-                self.set_source_range(range);
+                self.restore_source_span(expression_span);
                 emit!(self, Instruction::GetAwaitable { r#where: 0 });
+                emit!(self, Instruction::PushNull);
                 self.emit_load_const(ConstantData::None);
                 let _ = self.compile_yield_from_sequence(true);
             }
@@ -9055,17 +9286,19 @@ impl<'warnings> Compiler<'warnings> {
                 }
                 self.mark_generator();
                 self.compile_expression(value)?;
-                self.set_source_range(range);
-                emit!(self, Instruction::GetYieldFromIter);
+                self.restore_source_span(expression_span);
+                emit!(
+                    self,
+                    Instruction::GetIter {
+                        mode: oparg::GET_ITER_YIELD_FROM
+                    }
+                );
                 self.emit_load_const(ConstantData::None);
                 let _ = self.compile_yield_from_sequence(false);
             }
             ast::Expr::Name(ast::ExprName { id, .. }) => self.load_name(id)?,
             ast::Expr::Lambda(ast::ExprLambda {
-                parameters,
-                body,
-                range,
-                ..
+                parameters, body, ..
             }) => {
                 let default_params = ast::Parameters::default();
                 let params = parameters.as_deref().unwrap_or(&default_params);
@@ -9087,7 +9320,7 @@ impl<'warnings> Compiler<'warnings> {
                     for element in &defaults {
                         self.compile_expression(element)?;
                     }
-                    self.set_source_range(*range);
+                    self.restore_source_span(expression_span);
                     emit!(self, Instruction::BuildTuple { count: size });
                 }
 
@@ -9103,13 +9336,13 @@ impl<'warnings> Compiler<'warnings> {
                 if have_kwdefaults {
                     let default_kw_count = kw_with_defaults.len();
                     for (arg, default) in &kw_with_defaults {
-                        self.set_source_range(*range);
+                        self.restore_source_span(expression_span);
                         self.emit_load_const(ConstantData::Str {
                             value: self.mangle(arg.name().id()).as_str().into(),
                         });
                         self.compile_expression(default)?;
                     }
-                    self.set_source_range(*range);
+                    self.restore_source_span(expression_span);
                     emit!(
                         self,
                         Instruction::BuildMap {
@@ -9149,23 +9382,20 @@ impl<'warnings> Compiler<'warnings> {
                     emit!(self, Instruction::ReturnValue);
                     self.set_no_location();
                 } else {
-                    self.set_source_range(body.range());
+                    self.set_source_node(body.range(), body.node_index());
                     self.emit_return_value();
                     self.emit_return_const_no_location(ConstantData::None);
                 }
                 let code = self.exit_scope();
 
                 // Create lambda function with closure
-                self.set_source_range(*range);
+                self.restore_source_span(expression_span);
                 self.make_closure(code, func_flags)?;
 
                 self.ctx = prev_ctx;
             }
             ast::Expr::ListComp(ast::ExprListComp {
-                elt,
-                generators,
-                range,
-                ..
+                elt, generators, ..
             }) => {
                 self.compile_comprehension(
                     "<listcomp>",
@@ -9178,7 +9408,7 @@ impl<'warnings> Compiler<'warnings> {
                     generators,
                     &|compiler, collection_add_i| {
                         compiler.compile_comprehension_element(elt)?;
-                        compiler.set_source_range(elt.range());
+                        compiler.set_source_node(elt.range(), elt.node_index());
                         emit!(
                             compiler,
                             Instruction::ListAppend {
@@ -9189,16 +9419,13 @@ impl<'warnings> Compiler<'warnings> {
                     },
                     ComprehensionType::List,
                     Self::contains_await(elt) || Self::generators_contain_await(generators),
-                    *range,
-                    elt.range(),
-                    elt.range(),
+                    expression_span,
+                    self.node_span(elt.as_ref()),
+                    self.node_span(elt.as_ref()),
                 )?;
             }
             ast::Expr::SetComp(ast::ExprSetComp {
-                elt,
-                generators,
-                range,
-                ..
+                elt, generators, ..
             }) => {
                 self.compile_comprehension(
                     "<setcomp>",
@@ -9211,7 +9438,7 @@ impl<'warnings> Compiler<'warnings> {
                     generators,
                     &|compiler, collection_add_i| {
                         compiler.compile_comprehension_element(elt)?;
-                        compiler.set_source_range(elt.range());
+                        compiler.set_source_node(elt.range(), elt.node_index());
                         emit!(
                             compiler,
                             Instruction::SetAdd {
@@ -9222,20 +9449,19 @@ impl<'warnings> Compiler<'warnings> {
                     },
                     ComprehensionType::Set,
                     Self::contains_await(elt) || Self::generators_contain_await(generators),
-                    *range,
-                    elt.range(),
-                    elt.range(),
+                    expression_span,
+                    self.node_span(elt.as_ref()),
+                    self.node_span(elt.as_ref()),
                 )?;
             }
             ast::Expr::DictComp(ast::ExprDictComp {
                 key,
                 value,
                 generators,
-                range,
                 ..
             }) => {
                 let Some(key) = key.as_deref() else {
-                    self.set_source_range(*range);
+                    self.restore_source_span(expression_span);
                     return Err(self.error(CodegenErrorType::SyntaxError(
                         "dict unpacking cannot be used in dict comprehension".to_owned(),
                     )));
@@ -9254,10 +9480,9 @@ impl<'warnings> Compiler<'warnings> {
                         compiler.compile_expression(key)?;
                         compiler.compile_expression(value)?;
 
-                        compiler.set_source_range(TextRange::new(
-                            key.range().start(),
-                            value.range().end(),
-                        ));
+                        compiler.restore_source_span(
+                            compiler.dict_comprehension_element_span(key, value)?,
+                        );
                         emit!(
                             compiler,
                             Instruction::MapAdd {
@@ -9271,18 +9496,15 @@ impl<'warnings> Compiler<'warnings> {
                     Self::contains_await(key)
                         || Self::contains_await(value)
                         || Self::generators_contain_await(generators),
-                    *range,
-                    TextRange::new(key.range().start(), value.range().end()),
-                    key.range(),
+                    expression_span,
+                    self.dict_comprehension_element_span(key, value)?,
+                    self.node_span(key),
                 )?;
             }
             ast::Expr::Generator(ast::ExprGenerator {
-                elt,
-                generators,
-                range,
-                ..
+                elt, generators, ..
             }) => {
-                self.compile_generator_expression(elt, generators, *range)?;
+                self.compile_generator_expression(elt, generators, expression_span)?;
             }
             ast::Expr::Starred(ast::ExprStarred { value, .. }) => {
                 if self.in_annotation {
@@ -9321,7 +9543,7 @@ impl<'warnings> Compiler<'warnings> {
                 target,
                 value,
                 node_index: _,
-                range,
+                range: _,
             }) => {
                 // Walrus targets in inlined comps should NOT be hidden from locals()
                 if self.current_code_info().in_inlined_comp
@@ -9335,10 +9557,10 @@ impl<'warnings> Compiler<'warnings> {
                         .swap_remove(name.into_owned().as_str());
                 }
                 self.compile_expression(value)?;
-                self.set_source_range(*range);
+                self.restore_source_span(expression_span);
                 emit!(self, Instruction::Copy { i: 1 });
                 self.compile_store(target)?;
-                self.set_source_range(target.range());
+                self.set_source_node(target.range(), target.node_index());
             }
             ast::Expr::FString(fstring) => {
                 if let Some(joined_str) = fstring.runtime_joined_str.as_ref() {
@@ -9399,37 +9621,41 @@ impl<'warnings> Compiler<'warnings> {
         Ok(())
     }
 
-    /// The called name of a `name(genexpr)` call, the shape
-    /// `maybe_optimize_function_call()` reserves a `skip_optimization` label
-    /// for. An `await` or an `async for` inside the generator does not
-    /// disqualify it: the inlined loop raises the same `TypeError` that
-    /// calling the builtin on an async generator would.
+    /// The called name of a synchronous `name(genexpr)` call, the shape
+    /// `maybe_optimize_function_call()` reserves a `skip_optimization` label for.
     fn cpython_genexpr_call_name<'a>(
-        &self,
+        &mut self,
         func: &'a ast::Expr,
         args: &ast::Arguments,
-    ) -> Option<&'a str> {
+    ) -> CompileResult<Option<&'a str>> {
         let ast::Expr::Name(ast::ExprName { id, .. }) = func else {
-            return None;
+            return Ok(None);
         };
-        let [ast::Expr::Generator(ast::ExprGenerator { .. })] = &args.args[..] else {
-            return None;
+        let [ast::Expr::Generator(ast::ExprGenerator { generators, .. })] = &args.args[..] else {
+            return Ok(None);
         };
         if !args.keywords.is_empty() {
-            return None;
+            return Ok(None);
         }
-        let table = self.current_symbol_table();
-        table.sub_tables.get(table.next_sub_table)?;
-        Some(id.as_str())
+        let Some(outermost) = generators.first() else {
+            return Ok(None);
+        };
+        let (comp_table, _) = self
+            .lookup_comprehension_symbol_table_after_skipped_nested_scopes_in_expr(
+                &outermost.iter,
+                ComprehensionType::Generator,
+            )?;
+        if comp_table.is_coroutine {
+            return Ok(None);
+        }
+        Ok(Some(id.as_str()))
     }
 
-    fn detect_builtin_generator_call(
-        &self,
-        func: &ast::Expr,
-        args: &ast::Arguments,
-    ) -> Option<BuiltinGeneratorCallKind> {
-        match self.cpython_genexpr_call_name(func, args)? {
+    fn detect_builtin_generator_call(&self, name: &str) -> Option<BuiltinGeneratorCallKind> {
+        match name {
             "tuple" => Some(BuiltinGeneratorCallKind::Tuple),
+            "list" => Some(BuiltinGeneratorCallKind::List),
+            "set" => Some(BuiltinGeneratorCallKind::Set),
             "all" => Some(BuiltinGeneratorCallKind::All),
             "any" => Some(BuiltinGeneratorCallKind::Any),
             _ => None,
@@ -9445,11 +9671,13 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         kind: BuiltinGeneratorCallKind,
         generator_expr: &ast::Expr,
-        loc: TextRange,
+        loc: CompilerSourceSpan,
         end: BlockIdx,
     ) -> CompileResult<()> {
         let common_constant = match kind {
             BuiltinGeneratorCallKind::Tuple => bytecode::CommonConstant::BuiltinTuple,
+            BuiltinGeneratorCallKind::List => bytecode::CommonConstant::BuiltinList,
+            BuiltinGeneratorCallKind::Set => bytecode::CommonConstant::BuiltinSet,
             BuiltinGeneratorCallKind::All => bytecode::CommonConstant::BuiltinAll,
             BuiltinGeneratorCallKind::Any => bytecode::CommonConstant::BuiltinAny,
         };
@@ -9457,7 +9685,7 @@ impl<'warnings> Compiler<'warnings> {
         let skip_optimization = self.new_block();
 
         // Stack: [func] - copy function for identity check
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         emit!(self, Instruction::Copy { i: 1 });
         emit!(
             self,
@@ -9474,48 +9702,63 @@ impl<'warnings> Compiler<'warnings> {
         );
         emit!(self, Instruction::PopTop);
 
-        if matches!(kind, BuiltinGeneratorCallKind::Tuple) {
-            self.set_source_range(loc);
-            emit!(self, Instruction::BuildList { count: 0 });
+        match kind {
+            BuiltinGeneratorCallKind::Tuple | BuiltinGeneratorCallKind::List => {
+                self.restore_source_span(loc);
+                emit!(self, Instruction::BuildList { count: 0 });
+            }
+            BuiltinGeneratorCallKind::Set => {
+                self.restore_source_span(loc);
+                emit!(self, Instruction::BuildSet { count: 0 });
+            }
+            BuiltinGeneratorCallKind::All | BuiltinGeneratorCallKind::Any => {}
         }
 
         let symbol_table_cursors = self.current_symbol_table_cursors();
         self.compile_expression(generator_expr)?;
         self.set_symbol_table_cursors(symbol_table_cursors);
+        self.restore_source_span(loc);
+        emit!(self, Instruction::PushNull);
 
         let loop_block = self.new_block();
         let cleanup = self.new_block();
         self.use_cpython_label_block(loop_block);
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         emit!(self, Instruction::ForIter { delta: cleanup });
 
         match kind {
-            BuiltinGeneratorCallKind::Tuple => {
-                self.set_source_range(loc);
-                emit!(self, Instruction::ListAppend { i: 2 });
-                self.set_source_range(loc);
+            BuiltinGeneratorCallKind::Tuple | BuiltinGeneratorCallKind::List => {
+                self.restore_source_span(loc);
+                emit!(self, Instruction::ListAppend { i: 3 });
+                self.restore_source_span(loc);
+                emit!(self, PseudoInstruction::Jump { delta: loop_block });
+            }
+            BuiltinGeneratorCallKind::Set => {
+                self.restore_source_span(loc);
+                emit!(self, Instruction::SetAdd { i: 3 });
+                self.restore_source_span(loc);
                 emit!(self, PseudoInstruction::Jump { delta: loop_block });
             }
             BuiltinGeneratorCallKind::All => {
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(self, Instruction::ToBool);
                 emit!(self, Instruction::PopJumpIfTrue { delta: loop_block });
                 emit!(self, Instruction::PopIter);
                 self.set_no_location();
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 self.emit_load_const(ConstantData::Boolean { value: false });
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(self, PseudoInstruction::Jump { delta: end });
             }
             BuiltinGeneratorCallKind::Any => {
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(self, Instruction::ToBool);
                 emit!(self, Instruction::PopJumpIfFalse { delta: loop_block });
                 emit!(self, Instruction::PopIter);
                 self.set_no_location();
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 self.emit_load_const(ConstantData::Boolean { value: true });
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(self, PseudoInstruction::Jump { delta: end });
             }
         }
@@ -9527,7 +9770,7 @@ impl<'warnings> Compiler<'warnings> {
         self.set_no_location();
         match kind {
             BuiltinGeneratorCallKind::Tuple => {
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 emit!(
                     self,
                     Instruction::CallIntrinsic1 {
@@ -9535,16 +9778,17 @@ impl<'warnings> Compiler<'warnings> {
                     }
                 );
             }
+            BuiltinGeneratorCallKind::List | BuiltinGeneratorCallKind::Set => {}
             BuiltinGeneratorCallKind::All => {
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 self.emit_load_const(ConstantData::Boolean { value: true });
             }
             BuiltinGeneratorCallKind::Any => {
-                self.set_source_range(loc);
+                self.restore_source_span(loc);
                 self.emit_load_const(ConstantData::Boolean { value: false });
             }
         }
-        self.set_source_range(loc);
+        self.restore_source_span(loc);
         emit!(self, PseudoInstruction::Jump { delta: end });
 
         self.use_cpython_label_block(skip_optimization);
@@ -9574,15 +9818,15 @@ impl<'warnings> Compiler<'warnings> {
     fn compile_method_call_arguments(
         &mut self,
         args: &ast::Arguments,
-        call_range: TextRange,
-        kw_names_range: TextRange,
+        call_range: CompilerSourceSpan,
+        kw_names_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
         for arg in &args.args {
             self.compile_expression(arg)?;
         }
 
         if args.keywords.is_empty() {
-            self.set_source_range(call_range);
+            self.restore_source_span(call_range);
             emit!(
                 self,
                 Instruction::Call {
@@ -9599,11 +9843,11 @@ impl<'warnings> Compiler<'warnings> {
             });
             self.compile_expression(&keyword.value)?;
         }
-        self.set_source_range(kw_names_range);
+        self.restore_source_span(kw_names_range);
         self.emit_load_const(ConstantData::Tuple {
             elements: kwarg_names,
         });
-        self.set_source_range(call_range);
+        self.restore_source_span(call_range);
         emit!(
             self,
             Instruction::CallKw {
@@ -9616,9 +9860,14 @@ impl<'warnings> Compiler<'warnings> {
     fn compile_call(&mut self, func: &ast::Expr, args: &ast::Arguments) -> CompileResult<()> {
         // Save the call expression's source range so CALL instructions use the
         // call start line, not the last argument's line.
-        let call_range = self.current_source_range;
+        let call_range = self.current_source_span;
         self.validate_keywords(&args.keywords)?;
         let uses_ex_call = self.call_uses_ex_call(args);
+        let genexpr_call_name = if uses_ex_call {
+            None
+        } else {
+            self.cpython_genexpr_call_name(func, args)?
+        };
 
         // Method call: obj → LOAD_ATTR_METHOD → [method, self_or_null] → args → CALL
         // Regular call: func → PUSH_NULL → args → CALL
@@ -9626,7 +9875,7 @@ impl<'warnings> Compiler<'warnings> {
             if !self.can_use_cpython_method_call(value, args) {
                 self.check_caller(func)?;
                 self.compile_expression(func)?;
-                self.set_source_range(func.range());
+                self.set_source_node(func.range(), func.node_index());
                 emit!(self, Instruction::PushNull);
                 self.codegen_call_helper(0, args, call_range, None)?;
                 return Ok(());
@@ -9642,18 +9891,17 @@ impl<'warnings> Compiler<'warnings> {
                 else {
                     unreachable!("can_optimize_super_call only accepts calls");
                 };
-                self.load_args_for_super(&super_type, super_func.range(), value.range())?;
-                let attr_access_range = self.update_start_location_to_match_attr(
-                    func.range(),
-                    func.range(),
-                    attr.as_str(),
-                );
-                let method_call_range = self.update_start_location_to_match_attr(
-                    call_range,
-                    func.range(),
+                self.load_args_for_super(
+                    &super_type,
+                    self.node_span(super_func.as_ref()),
+                    self.node_span(value.as_ref()),
+                )?;
+                let attr_access_range = self.update_start_span_to_match_attr(
+                    self.node_span(func),
+                    self.node_span(func),
                     attr.as_str(),
-                );
-                self.set_source_range(func.range());
+                )?;
+                self.set_source_node(func.range(), func.node_index());
                 let idx = self.name(attr.as_str());
                 match super_type {
                     SuperCallType::TwoArg { .. } => {
@@ -9664,30 +9912,48 @@ impl<'warnings> Compiler<'warnings> {
                     }
                 }
                 // NOP for line tracking at .method( line
-                self.set_source_range(attr_access_range);
+                self.restore_source_span(attr_access_range);
                 emit!(self, Instruction::Nop);
                 // CALL at .method( line (not the full expression line)
-                self.compile_method_call_arguments(args, method_call_range, attr_access_range)?;
+                self.compile_method_call_arguments(
+                    args,
+                    self.update_start_span_to_match_attr(
+                        call_range,
+                        self.node_span(func),
+                        attr.as_str(),
+                    )?,
+                    self.update_start_span_to_match_attr(
+                        self.node_span(func),
+                        self.node_span(func),
+                        attr.as_str(),
+                    )?,
+                )?;
             } else {
                 self.compile_expression(value)?;
                 let idx = self.name(attr.as_str());
-                let attr_access_range = self.update_start_location_to_match_attr(
-                    func.range(),
-                    func.range(),
+                let attr_access_range = self.update_start_span_to_match_attr(
+                    self.node_span(func),
+                    self.node_span(func),
                     attr.as_str(),
-                );
-                let method_call_range = self.update_start_location_to_match_attr(
-                    call_range,
-                    func.range(),
-                    attr.as_str(),
-                );
-                self.set_source_range(attr_access_range);
+                )?;
+                self.restore_source_span(attr_access_range);
                 self.emit_load_attr_method(idx);
-                self.compile_method_call_arguments(args, method_call_range, attr_access_range)?;
+                self.compile_method_call_arguments(
+                    args,
+                    self.update_start_span_to_match_attr(
+                        call_range,
+                        self.node_span(func),
+                        attr.as_str(),
+                    )?,
+                    self.update_start_span_to_match_attr(
+                        self.node_span(func),
+                        self.node_span(func),
+                        attr.as_str(),
+                    )?,
+                )?;
             }
-        } else if let Some(kind) = (!uses_ex_call)
-            .then(|| self.detect_builtin_generator_call(func, args))
-            .flatten()
+        } else if let Some(kind) =
+            genexpr_call_name.and_then(|name| self.detect_builtin_generator_call(name))
         {
             let skip_normal_call = self.new_block();
             self.check_caller(func)?;
@@ -9695,10 +9961,10 @@ impl<'warnings> Compiler<'warnings> {
             self.optimize_builtin_generator_call(
                 kind,
                 &args.args[0],
-                func.range(),
+                self.node_span(func),
                 skip_normal_call,
             )?;
-            self.set_source_range(func.range());
+            self.set_source_node(func.range(), func.node_index());
             emit!(self, Instruction::PushNull);
             self.codegen_call_helper(0, args, call_range, None)?;
             self.use_cpython_label_block(skip_normal_call);
@@ -9709,23 +9975,19 @@ impl<'warnings> Compiler<'warnings> {
             // `skip_normal_call`, even when `maybe_optimize_function_call()`
             // leaves it untargeted.
             let skip_normal_call = self.current_code_info().new_instr_sequence_label();
-            let genexpr_call_name = (!uses_ex_call)
-                .then(|| self.cpython_genexpr_call_name(func, args))
-                .flatten()
-                .is_some();
             self.check_caller(func)?;
             self.compile_expression(func)?;
-            if genexpr_call_name {
+            if genexpr_call_name.is_some() {
                 // CPython `maybe_optimize_function_call()` creates and uses
                 // `skip_optimization` for every name(genexpr) shape after
-                // loading the function, even when the name is not all/any/tuple.
+                // loading the function, even when the name is not all/any/tuple/list/set.
                 let skip_optimization = self.current_code_info().new_instr_sequence_label();
                 let result = self
                     .current_code_info()
                     .use_raw_instr_sequence_label(skip_optimization);
                 unwrap_internal(self, result);
             }
-            self.set_source_range(func.range());
+            self.set_source_node(func.range(), func.node_index());
             emit!(self, Instruction::PushNull);
             self.codegen_call_helper(0, args, call_range, None)?;
             let result = self
@@ -9775,7 +10037,7 @@ impl<'warnings> Compiler<'warnings> {
         keywords: &[ast::Keyword],
         begin: usize,
         end: usize,
-        call_range: TextRange,
+        call_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
         let n = end - begin;
         assert!(n > 0);
@@ -9790,7 +10052,7 @@ impl<'warnings> Compiler<'warnings> {
 
         for kw in &keywords[begin..end] {
             // Key first, then value - this is critical!
-            self.set_source_range(call_range);
+            self.restore_source_span(call_range);
             self.emit_load_const(ConstantData::Str {
                 value: kw.arg.as_ref().unwrap().as_str().into(),
             });
@@ -9803,7 +10065,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         if !big {
-            self.set_source_range(call_range);
+            self.restore_source_span(call_range);
             emit!(self, Instruction::BuildMap { count: n.to_u32() });
         }
 
@@ -9817,8 +10079,8 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         additional_positional: u32,
         arguments: &ast::Arguments,
-        call_range: TextRange,
-        kw_names_range: Option<TextRange>,
+        call_range: CompilerSourceSpan,
+        kw_names_range: Option<CompilerSourceSpan>,
     ) -> CompileResult<()> {
         self.codegen_call_helper_impl(
             additional_positional,
@@ -9835,8 +10097,8 @@ impl<'warnings> Compiler<'warnings> {
         additional_positional: u32,
         args: &[ast::Expr],
         keywords: &[ast::Keyword],
-        call_range: TextRange,
-        kw_names_range: Option<TextRange>,
+        call_range: CompilerSourceSpan,
+        kw_names_range: Option<CompilerSourceSpan>,
         injected_arg: Option<&Name>,
     ) -> CompileResult<()> {
         self.validate_keywords(keywords)?;
@@ -9859,7 +10121,7 @@ impl<'warnings> Compiler<'warnings> {
                 self.compile_expression(arg)?;
             }
             let injected_count = if let Some(injected_arg) = injected_arg {
-                self.set_source_range(call_range);
+                self.restore_source_span(call_range);
                 self.load_name(injected_arg)?;
                 1
             } else {
@@ -9877,17 +10139,17 @@ impl<'warnings> Compiler<'warnings> {
                 }
 
                 // Restore call expression range for kwnames and CALL_KW
-                self.set_source_range(kw_names_range.unwrap_or(call_range));
+                self.restore_source_span(kw_names_range.unwrap_or(call_range));
                 self.emit_load_const(ConstantData::Tuple {
                     elements: kwarg_names,
                 });
 
-                self.set_source_range(call_range);
+                self.restore_source_span(call_range);
                 let argc =
                     additional_positional + nelts.to_u32() + injected_count + nkwelts.to_u32();
                 emit!(self, Instruction::CallKw { argc });
             } else {
-                self.set_source_range(call_range);
+                self.restore_source_span(call_range);
                 let argc = additional_positional + nelts.to_u32() + injected_count;
                 emit!(self, Instruction::Call { argc });
             }
@@ -9908,7 +10170,7 @@ impl<'warnings> Compiler<'warnings> {
                 // `starunpack_helper_impl(..., BUILD_LIST, LIST_APPEND,
                 // LIST_EXTEND, tuple=1)`, even when the only reason for the
                 // ex-call path is too many non-starred positional arguments.
-                self.set_source_range(call_range);
+                self.restore_source_span(call_range);
                 self.starunpack_helper_impl(
                     args,
                     injected_arg,
@@ -9919,7 +10181,7 @@ impl<'warnings> Compiler<'warnings> {
 
             self.compile_call_function_ex_keywords(keywords, call_range)?;
 
-            self.set_source_range(call_range);
+            self.restore_source_span(call_range);
             emit!(self, Instruction::CallFunctionEx);
         }
 
@@ -9929,10 +10191,10 @@ impl<'warnings> Compiler<'warnings> {
     fn compile_call_function_ex_keywords(
         &mut self,
         keywords: &[ast::Keyword],
-        call_range: TextRange,
+        call_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
         if keywords.is_empty() {
-            self.set_source_range(call_range);
+            self.restore_source_span(call_range);
             emit!(self, Instruction::PushNull);
             return Ok(());
         }
@@ -9945,7 +10207,7 @@ impl<'warnings> Compiler<'warnings> {
                 if nseen > 0 {
                     self.codegen_subkwargs(keywords, i - nseen, i, call_range)?;
                     if have_dict {
-                        self.set_source_range(call_range);
+                        self.restore_source_span(call_range);
                         emit!(self, Instruction::DictMerge { i: 1 });
                     }
                     have_dict = true;
@@ -9953,13 +10215,13 @@ impl<'warnings> Compiler<'warnings> {
                 }
 
                 if !have_dict {
-                    self.set_source_range(call_range);
+                    self.restore_source_span(call_range);
                     emit!(self, Instruction::BuildMap { count: 0 });
                     have_dict = true;
                 }
 
                 self.compile_expression(&keyword.value)?;
-                self.set_source_range(call_range);
+                self.restore_source_span(call_range);
                 emit!(self, Instruction::DictMerge { i: 1 });
             } else {
                 nseen += 1;
@@ -9969,7 +10231,7 @@ impl<'warnings> Compiler<'warnings> {
         if nseen > 0 {
             self.codegen_subkwargs(keywords, keywords.len() - nseen, keywords.len(), call_range)?;
             if have_dict {
-                self.set_source_range(call_range);
+                self.restore_source_span(call_range);
                 emit!(self, Instruction::DictMerge { i: 1 });
             }
             have_dict = true;
@@ -9995,7 +10257,7 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         elt: &ast::Expr,
         generators: &[ast::Comprehension],
-        range: TextRange,
+        range: CompilerSourceSpan,
     ) -> CompileResult<()> {
         // Check if element or generators contain async content
         // This makes the generator expression into an async generator
@@ -10013,7 +10275,7 @@ impl<'warnings> Compiler<'warnings> {
 
                 compiler.mark_generator();
                 if compiler.ctx.func == FunctionContext::AsyncFunction {
-                    compiler.set_source_range(elt.range());
+                    compiler.set_source_node(elt.range(), elt.node_index());
                     emit!(
                         compiler,
                         Instruction::CallIntrinsic1 {
@@ -10022,7 +10284,7 @@ impl<'warnings> Compiler<'warnings> {
                     );
                 }
                 // arg=0: direct yield (wrapped for async generators)
-                compiler.set_source_range(elt.range());
+                compiler.set_source_node(elt.range(), elt.node_index());
                 emit!(compiler, Instruction::YieldValue { arg: 0 });
                 emit!(
                     compiler,
@@ -10037,8 +10299,8 @@ impl<'warnings> Compiler<'warnings> {
             ComprehensionType::Generator,
             element_contains_await,
             range,
-            elt.range(),
-            elt.range(),
+            self.node_span(elt),
+            self.node_span(elt),
         )
     }
 
@@ -10606,6 +10868,48 @@ impl<'warnings> Compiler<'warnings> {
         Ok(())
     }
 
+    /// ast.ListComp.build_container_and_load_iter: one generator, no ifs,
+    /// not an `async for`. The iterator is already on the stack; BUILD_LIST_FROM_ARG
+    /// sizes the list from its length hint.
+    fn listcomp_uses_build_list_from_arg(
+        &self,
+        init_collection: Option<&AnyInstruction>,
+        generators: &[ast::Comprehension],
+    ) -> bool {
+        self.opts.build_list_from_arg
+            && matches!(
+                init_collection,
+                Some(AnyInstruction::Real(Instruction::BuildList { .. }))
+            )
+            && generators.len() == 1
+            && generators[0].ifs.is_empty()
+            && !generators[0].is_async
+    }
+
+    fn dict_comprehension_element_span(
+        &self,
+        key: &ast::Expr,
+        value: &ast::Expr,
+    ) -> CompileResult<CompilerSourceSpan> {
+        let key = self.node_span(key);
+        let value = self.node_span(value);
+        Ok(CompilerSourceSpan {
+            range: TextRange::new(key.range.start(), value.range.end().max(key.range.start())),
+            // codegen.c: LOCATION(elt->lineno, val->end_lineno,
+            //                      elt->col_offset, val->end_col_offset).
+            location: match (key.location, value.location) {
+                (Some(key), Some(value)) => Some(SourceLocationRange {
+                    line: key.line,
+                    end_line: value.end_line,
+                    col: key.col,
+                    end_col: value.end_col,
+                }),
+                (None, None) => None,
+                _ => return Err(self.mixed_location_provenance_error()),
+            },
+        })
+    }
+
     #[expect(clippy::too_many_arguments, reason = "ignore warning for now")]
     fn compile_comprehension(
         &mut self,
@@ -10615,9 +10919,9 @@ impl<'warnings> Compiler<'warnings> {
         compile_element: &dyn Fn(&mut Self, usize) -> CompileResult<()>,
         comprehension_type: ComprehensionType,
         element_contains_await: bool,
-        comprehension_range: TextRange,
-        element_range: TextRange,
-        outer_backedge_range: TextRange,
+        comprehension_range: CompilerSourceSpan,
+        element_range: CompilerSourceSpan,
+        outer_backedge_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
         let prev_ctx = self.ctx;
         let has_an_async_gen = generators.iter().any(|g| g.is_async);
@@ -10706,7 +11010,7 @@ impl<'warnings> Compiler<'warnings> {
 
         // Set qualname for comprehension
         self.set_qualname();
-        self.set_source_range(comprehension_range);
+        self.restore_source_span(comprehension_range);
 
         let arg0 = self.varname(".0");
 
@@ -10718,13 +11022,37 @@ impl<'warnings> Compiler<'warnings> {
         let stop_iteration_block = if comprehension_type == ComprehensionType::Generator {
             let handler_block = self.new_block();
             self.insert_cpython_stopiteration_setup_cleanup(handler_block);
+            let source = self.source_file.to_source_code();
+            let iterator = ir::InstructionInfo {
+                instr: if outermost.is_async {
+                    bytecode::Opcode::GetAiter.into()
+                } else {
+                    bytecode::Opcode::GetIter.into()
+                },
+                arg: OpArg::NULL,
+                target: BlockIdx::NULL,
+                location: source.source_location(outermost.iter.start(), PositionEncoding::Utf8),
+                end_location: source.source_location(outermost.iter.end(), PositionEncoding::Utf8),
+                except_handler: None,
+                semantic_location: self.node_span(&outermost.iter).location,
+                lineno_override: None,
+            };
+            let result = self.current_code_info().insert_genexpr_prefix(iterator);
+            unwrap_internal(self, result);
             Some(handler_block)
         } else {
             None
         };
 
+        // ast.ListComp.build_container_and_load_iter: one generator and no
+        // ifs loads the iterator first, then BUILD_LIST_FROM_ARG.
+        let use_build_list_from_arg =
+            self.listcomp_uses_build_list_from_arg(init_collection.as_ref(), generators);
+
         // Create empty object of proper type:
-        if let Some(init_collection) = init_collection {
+        if let Some(init_collection) = init_collection
+            && !use_build_list_from_arg
+        {
             self._emit(init_collection, OpArg::new(0), BlockIdx::NULL)
         }
 
@@ -10766,8 +11094,18 @@ impl<'warnings> Compiler<'warnings> {
             };
 
             if gen_index == 0 {
-                // Load iterator onto stack (passed as first argument):
-                emit!(self, Instruction::LoadFast { var_num: arg0 });
+                // Genexpr creation has already left the acquired iterator on the stack.
+                if comprehension_type != ComprehensionType::Generator {
+                    emit!(self, Instruction::LoadFast { var_num: arg0 });
+                    if generator.is_async {
+                        emit!(self, Instruction::GetAiter);
+                    } else {
+                        emit!(self, Instruction::GetIter { mode: 0 });
+                    }
+                    if use_build_list_from_arg {
+                        emit!(self, Instruction::BuildListFromArg);
+                    }
+                }
             } else {
                 // Evaluate iterated item:
                 self.compile_comprehension_iter(generator)?;
@@ -10785,6 +11123,7 @@ impl<'warnings> Compiler<'warnings> {
                 )?;
                 emit!(self, PseudoInstruction::SetupFinally { delta: after_block });
                 emit!(self, Instruction::GetAnext);
+                emit!(self, Instruction::PushNull);
                 self.emit_load_const(ConstantData::None);
                 self.use_cpython_label_block(send_block);
                 let _ = self.compile_yield_from_sequence(true);
@@ -10794,13 +11133,13 @@ impl<'warnings> Compiler<'warnings> {
                 emit!(self, PseudoInstruction::PopBlock);
                 self.compile_store(&generator.target)?;
             } else {
-                let saved_range = self.current_source_range;
-                self.set_source_range(generator.iter.range());
+                let saved_range = self.current_source_span;
+                self.set_source_node(generator.iter.range(), generator.iter.node_index());
                 emit!(self, Instruction::ForIter { delta: after_block });
-                self.set_source_range(saved_range);
+                self.restore_source_span(saved_range);
                 self.compile_store(&generator.target)?;
             }
-            real_loop_depth += 1;
+            real_loop_depth += if generator.is_async { 1 } else { 2 };
             let backedge_range = if gen_index + 1 == generators.len() {
                 element_range
             } else {
@@ -10835,7 +11174,7 @@ impl<'warnings> Compiler<'warnings> {
                     end_async_for_target,
                 } => {
                     self.use_cpython_label_block(if_cleanup_block);
-                    self.set_source_range(backedge_range);
+                    self.restore_source_span(backedge_range);
                     emit!(self, PseudoInstruction::Jump { delta: loop_block });
 
                     if is_async {
@@ -10845,7 +11184,7 @@ impl<'warnings> Compiler<'warnings> {
 
                     self.use_cpython_label_block(after_block);
                     if is_async {
-                        self.set_source_range(comprehension_range);
+                        self.restore_source_span(comprehension_range);
                         // EndAsyncFor pops both the exception and the aiter
                         // (handler depth is before GetANext, so aiter is at handler depth)
                         self.emit_end_async_for(end_async_for_target);
@@ -10862,7 +11201,7 @@ impl<'warnings> Compiler<'warnings> {
         if return_none {
             self.emit_return_const_no_location(ConstantData::None);
         } else {
-            self.set_source_range(comprehension_range);
+            self.restore_source_span(comprehension_range);
             self.emit_return_value();
         }
 
@@ -10886,21 +11225,22 @@ impl<'warnings> Compiler<'warnings> {
         self.ctx = prev_ctx;
 
         // Create comprehension function with closure
-        self.set_source_range(comprehension_range);
+        self.restore_source_span(comprehension_range);
         self.make_closure(code, bytecode::MakeFunctionFlags::new())?;
 
-        // Evaluate iterated item and get its iterator.
-        self.compile_comprehension_iter(outermost)?;
+        // The callee acquires the iterator; a genexpr does this eagerly before creation.
+        self.compile_expression(&outermost.iter)?;
         self.symbol_table_stack
             .last_mut()
             .expect("no current symbol table")
             .next_sub_table += 1;
 
         // Call just created <listcomp> function:
-        self.set_source_range(comprehension_range);
+        self.restore_source_span(comprehension_range);
         emit!(self, Instruction::Call { argc: 0 });
         if is_async_list_set_dict_comprehension {
             emit!(self, Instruction::GetAwaitable { r#where: 0 });
+            emit!(self, Instruction::PushNull);
             self.emit_load_const(ConstantData::None);
             let _ = self.compile_yield_from_sequence(true);
         }
@@ -10916,7 +11256,7 @@ impl<'warnings> Compiler<'warnings> {
         init_collection: Option<AnyInstruction>,
         generators: &[ast::Comprehension],
         compile_element: &dyn Fn(&mut Self, usize) -> CompileResult<()>,
-        ranges: (TextRange, TextRange, TextRange),
+        ranges: (CompilerSourceSpan, CompilerSourceSpan, CompilerSourceSpan),
         comp_source: ComprehensionSymbolSource,
     ) -> CompileResult<()> {
         let (comprehension_range, element_range, outer_backedge_range) = ranges;
@@ -10924,7 +11264,7 @@ impl<'warnings> Compiler<'warnings> {
         // nested scopes (e.g. lambdas) whose sub_tables sit at the current
         // position in the parent's list. Those must be consumed before we
         // splice in the comprehension's own children.
-        self.compile_comprehension_iter(&generators[0])?;
+        self.compile_expression(&generators[0].iter)?;
         match comp_source {
             ComprehensionSymbolSource::Child => {
                 self.symbol_table_stack
@@ -10941,7 +11281,8 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         let was_in_inlined_comp = self.current_code_info().in_inlined_comp;
-        let saved_source_range = self.current_source_range;
+        let saved_source_range_span = self.current_source_span;
+
         let tweak_in_class_block = {
             let ct = self.current_symbol_table();
             ct.typ == CompilerScope::Class && !was_in_inlined_comp
@@ -11036,7 +11377,7 @@ impl<'warnings> Compiler<'warnings> {
             // For merged CELL variables, LoadFastAndClear saves the cell object from
             // the merged slot, and MAKE_CELL creates a new empty cell in-place.
             // MAKE_CELL has no stack effect (operates only on fastlocals).
-            self.set_source_range(comprehension_range);
+            self.restore_source_span(comprehension_range);
             let mut total_stack_items: usize = 0;
             for name in &pushed_locals {
                 let var_num = self.varname(name);
@@ -11086,8 +11427,14 @@ impl<'warnings> Compiler<'warnings> {
                 None
             };
 
-            // Step 4: Create the collection (list/set/dict)
-            if let Some(init_collection) = init_collection {
+            // Step 4: Create the collection (list/set/dict).
+            // BUILD_LIST_FROM_ARG pops the iterator, pushes the list, then
+            // the iterator: the same stack as BUILD_LIST 0; SWAP 2.
+            let use_build_list_from_arg =
+                self.listcomp_uses_build_list_from_arg(init_collection.as_ref(), generators);
+            if use_build_list_from_arg {
+                emit!(self, Instruction::BuildListFromArg);
+            } else if let Some(init_collection) = init_collection {
                 self._emit(init_collection, OpArg::new(0), BlockIdx::NULL);
                 // SWAP to get iterator on top
                 emit!(self, Instruction::Swap { i: 2 });
@@ -11133,6 +11480,15 @@ impl<'warnings> Compiler<'warnings> {
 
                 if i > 0 {
                     self.compile_comprehension_iter(generator)?;
+                } else {
+                    let saved_range = self.current_source_span;
+                    self.set_source_node(generator.iter.range(), generator.iter.node_index());
+                    if generator.is_async {
+                        emit!(self, Instruction::GetAiter);
+                    } else {
+                        emit!(self, Instruction::GetIter { mode: 0 });
+                    }
+                    self.restore_source_span(saved_range);
                 }
 
                 self.use_cpython_label_block(loop_block);
@@ -11148,6 +11504,7 @@ impl<'warnings> Compiler<'warnings> {
                     )?;
                     emit!(self, PseudoInstruction::SetupFinally { delta: after_block });
                     emit!(self, Instruction::GetAnext);
+                    emit!(self, Instruction::PushNull);
                     self.emit_load_const(ConstantData::None);
                     self.use_cpython_label_block(send_block);
                     let _ = self.compile_yield_from_sequence(true);
@@ -11155,14 +11512,14 @@ impl<'warnings> Compiler<'warnings> {
                     emit!(self, PseudoInstruction::PopBlock);
                     self.compile_store(&generator.target)?;
                 } else {
-                    let saved_range = self.current_source_range;
-                    self.set_source_range(generator.iter.range());
+                    let saved_range = self.current_source_span;
+                    self.set_source_node(generator.iter.range(), generator.iter.node_index());
                     emit!(self, Instruction::ForIter { delta: after_block });
-                    self.set_source_range(saved_range);
+                    self.restore_source_span(saved_range);
                     self.compile_store(&generator.target)?;
                 }
 
-                real_loop_depth += 1;
+                real_loop_depth += if generator.is_async { 1 } else { 2 };
                 let backedge_range = if i + 1 == generators.len() {
                     element_range
                 } else {
@@ -11199,7 +11556,7 @@ impl<'warnings> Compiler<'warnings> {
                         end_async_for_target,
                     } => {
                         self.use_cpython_label_block(if_cleanup_block);
-                        self.set_source_range(backedge_range);
+                        self.restore_source_span(backedge_range);
                         emit!(self, PseudoInstruction::Jump { delta: loop_block });
 
                         if is_async {
@@ -11212,7 +11569,7 @@ impl<'warnings> Compiler<'warnings> {
 
                         self.use_cpython_label_block(after_block);
                         if is_async {
-                            self.set_source_range(comprehension_range);
+                            self.restore_source_span(comprehension_range);
                             self.emit_end_async_for(end_async_for_target);
                         } else {
                             self.emit_sync_comprehension_end_for();
@@ -11225,7 +11582,7 @@ impl<'warnings> Compiler<'warnings> {
             }
 
             // Step 8: Clean up - restore saved locals (and cell values)
-            self.set_source_range(comprehension_range);
+            self.restore_source_span(comprehension_range);
             if let Some(cleanup_block) = cleanup_block {
                 emit!(self, PseudoInstruction::PopBlock);
                 self.set_no_location();
@@ -11250,7 +11607,7 @@ impl<'warnings> Compiler<'warnings> {
                 self.set_no_location();
 
                 // Restore locals and cell values
-                self.set_source_range(comprehension_range);
+                self.restore_source_span(comprehension_range);
                 emit!(
                     self,
                     Instruction::Swap {
@@ -11267,7 +11624,7 @@ impl<'warnings> Compiler<'warnings> {
 
                 // Normal end path
                 self.use_cpython_label_block(end_block);
-                self.set_source_range(comprehension_range);
+                self.restore_source_span(comprehension_range);
             }
 
             // SWAP result to TOS (above saved values)
@@ -11285,7 +11642,7 @@ impl<'warnings> Compiler<'warnings> {
                 let var_num = self.varname(name).as_u32();
                 emit!(self, PseudoInstruction::StoreFastMaybeNull { var_num });
             }
-            self.set_source_range(saved_source_range);
+            self.restore_source_span(saved_source_range_span);
 
             Ok(())
         })();
@@ -11407,7 +11764,7 @@ impl<'warnings> Compiler<'warnings> {
             target == BlockIdx::NULL || instr.has_target(),
             "CPython codegen_addop_j only accepts HAS_TARGET opcodes"
         );
-        let range = self.current_source_range;
+        let range = self.current_source_span.range;
         let source = self.source_file.to_source_code();
         let location = source.source_location(range.start(), PositionEncoding::Utf8);
         let end_location = source.source_location(range.end(), PositionEncoding::Utf8);
@@ -11419,6 +11776,7 @@ impl<'warnings> Compiler<'warnings> {
             location,
             end_location,
             except_handler,
+            semantic_location: self.current_source_span.location,
             lineno_override: None,
         });
     }
@@ -11442,7 +11800,7 @@ impl<'warnings> Compiler<'warnings> {
             !instr.is_assembler(),
             "CPython codegen_addop_j must not emit assembler-only opcodes"
         );
-        let range = self.current_source_range;
+        let range = self.current_source_span.range;
         let source = self.source_file.to_source_code();
         let location = source.source_location(range.start(), PositionEncoding::Utf8);
         let end_location = source.source_location(range.end(), PositionEncoding::Utf8);
@@ -11458,6 +11816,7 @@ impl<'warnings> Compiler<'warnings> {
                 location,
                 end_location,
                 except_handler: None,
+                semantic_location: self.current_source_span.location,
                 lineno_override: None,
             },
             target_label,
@@ -11480,42 +11839,11 @@ impl<'warnings> Compiler<'warnings> {
         self.set_no_location();
     }
 
-    /// CPython `codegen_wrap_in_stopiteration_handler()` inserts
-    /// `SETUP_CLEANUP` into the instruction sequence at index 0 with
-    /// `_PyInstructionSequence_InsertInstruction()`. Generator and cell/free
-    /// prefixes are inserted later by `flowgraph.c::insert_prefix_instructions()`.
+    /// The SETUP_CLEANUP part of `codegen_wrap_in_stopiteration_handler`.
     fn insert_cpython_stopiteration_setup_cleanup(&mut self, handler_block: BlockIdx) {
-        let code = self.current_code_info();
-        let entry = code
-            .blocks
-            .first_mut()
-            .expect("code unit must have an entry block");
-        debug_assert!(
-            entry
-                .used_instructions()
-                .first()
-                .is_some_and(|info| match info.instr.real() {
-                    Some(Instruction::Resume { context }) => matches!(
-                        context.get(info.arg).location(),
-                        oparg::ResumeLocation::AtFuncStart
-                    ),
-                    _ => false,
-                }),
-            "scope entry must start with a function-start RESUME"
-        );
-        debug_assert!(
-            !entry.used_instructions().iter().any(|info| matches!(
-                info.instr.real(),
-                Some(
-                    Instruction::ReturnGenerator
-                        | Instruction::MakeCell { .. }
-                        | Instruction::CopyFreeVars { .. }
-                )
-            )),
-            "CPython inserts StopIteration cleanup before CFG prefix instructions"
-        );
-
-        let result = code.insert_start_setup_cleanup(handler_block);
+        let result = self
+            .current_code_info()
+            .insert_start_setup_cleanup(handler_block);
         unwrap_internal(self, result);
     }
 
@@ -12057,7 +12385,7 @@ impl<'warnings> Compiler<'warnings> {
 
     fn compile_match_pattern_expr(&mut self, expr: &ast::Expr) -> CompileResult<()> {
         if let Some(constant) = self.try_fold_match_pattern_const_expr(expr)? {
-            self.set_source_range(expr.range());
+            self.set_source_node(expr.range(), expr.node_index());
             self.emit_load_const(constant);
         } else {
             self.compile_expression(expr)?;
@@ -12214,16 +12542,17 @@ impl<'warnings> Compiler<'warnings> {
     /// This handles unwinding through With blocks and exception handlers.
     fn compile_break_continue(
         &mut self,
-        range: ruff_text_size::TextRange,
+        span: CompilerSourceSpan,
         is_break: bool,
     ) -> CompileResult<()> {
+        let range = span.range;
         if self.do_not_emit_bytecode > 0 {
             // Still validate that we're inside a loop even in dead code
             let code = self.current_code_info();
             let mut found_loop = false;
             for i in (0..code.fblock.len()).rev() {
                 match code.fblock[i].fb_type {
-                    FBlockType::WhileLoop | FBlockType::ForLoop => {
+                    FBlockType::WhileLoop | FBlockType::ForLoop | FBlockType::AsyncForLoop => {
                         found_loop = true;
                         break;
                     }
@@ -12245,13 +12574,13 @@ impl<'warnings> Compiler<'warnings> {
             return Ok(());
         }
 
-        let prev_source_range = self.current_source_range;
-        self.set_source_range(range);
+        let prev_source_range = self.current_source_span;
+        self.restore_source_span(span);
         emit!(self, Instruction::Nop);
 
         let (mut unwind_loc, loop_fblock) = self.unwind_fblock_stack_with_loop(false, true)?;
         let Some(loop_fblock) = loop_fblock else {
-            self.set_source_range(prev_source_range);
+            self.restore_source_span(prev_source_range);
             if is_break {
                 return Err(self.error_ranged(CodegenErrorType::InvalidBreak, range));
             }
@@ -12274,7 +12603,7 @@ impl<'warnings> Compiler<'warnings> {
             loop_fblock.fb_block
         };
         let jump_is_artificial = if let Some(loc) = unwind_loc {
-            self.set_source_range(loc);
+            self.restore_source_span(loc);
             false
         } else {
             true
@@ -12288,7 +12617,7 @@ impl<'warnings> Compiler<'warnings> {
         if jump_is_artificial {
             self.set_no_location();
         }
-        self.set_source_range(prev_source_range);
+        self.restore_source_span(prev_source_range);
 
         Ok(())
     }
@@ -12441,8 +12770,76 @@ impl<'warnings> Compiler<'warnings> {
         code.current_block = block;
     }
 
+    fn node_span(&self, node: &(impl Ranged + HasNodeIndex)) -> CompilerSourceSpan {
+        CompilerSourceSpan {
+            range: node.range(),
+            location: self
+                .ast_locations
+                .as_ref()
+                .and_then(|locations| node_location(locations, node)),
+        }
+    }
+
+    fn set_source_node(&mut self, range: TextRange, index: &ast::AtomicNodeIndex) {
+        self.current_source_span = CompilerSourceSpan {
+            range,
+            location: index
+                .load()
+                .as_u32()
+                .and_then(|id| self.ast_locations.as_ref()?.get(id)),
+        };
+    }
+
+    #[cfg(test)]
     const fn set_source_range(&mut self, range: TextRange) {
-        self.current_source_range = range;
+        self.current_source_span = CompilerSourceSpan::parsed(range);
+    }
+
+    const fn restore_source_span(&mut self, span: CompilerSourceSpan) {
+        self.current_source_span = span;
+    }
+
+    fn mixed_location_provenance_error(&self) -> CodegenError {
+        CodegenError {
+            error: CodegenErrorType::MixedAstLocationProvenance,
+            location: None,
+            end_location: None,
+            source_path: self.source_file.name().to_owned(),
+        }
+    }
+
+    fn update_start_span_to_match_attr(
+        &self,
+        loc: CompilerSourceSpan,
+        attribute: CompilerSourceSpan,
+        name: &str,
+    ) -> CompileResult<CompilerSourceSpan> {
+        let range = self.update_start_location_to_match_attr(loc.range, attribute.range, name);
+        let location = match (loc.location, attribute.location) {
+            (Some(mut loc), Some(attribute)) => {
+                // CPython codegen.c update_start_location_to_match_attr.
+                if loc.line != attribute.end_line {
+                    loc.line = attribute.end_line;
+                    let length =
+                        i32::try_from(name.chars().count()).expect("validated attribute name");
+                    if length <= attribute.end_col {
+                        loc.col = attribute.end_col - length;
+                    } else {
+                        loc.col = -1;
+                        loc.end_col = -1;
+                    }
+                    loc.end_line = loc.line.max(loc.end_line);
+                    if loc.line == loc.end_line {
+                        loc.end_col = loc.col.max(loc.end_col);
+                    }
+                }
+                Some(loc)
+            }
+            // The parser-only path has no explicit semantic coordinates.
+            (None, None) => None,
+            _ => return Err(self.mixed_location_provenance_error()),
+        };
+        Ok(CompilerSourceSpan { range, location })
     }
 
     fn update_start_location_to_match_attr(
@@ -12462,7 +12859,8 @@ impl<'warnings> Compiler<'warnings> {
         if attr_len > attr_range.len() {
             return TextRange::new(loc_range.start(), loc_range.end());
         }
-        TextRange::new(attr_range.end() - attr_len, loc_range.end())
+        let start = attr_range.end() - attr_len;
+        TextRange::new(start, loc_range.end().max(start))
     }
 
     fn source_line_start_range(&self, lineno: u32) -> TextRange {
@@ -12472,15 +12870,30 @@ impl<'warnings> Compiler<'warnings> {
         TextRange::new(start, start)
     }
 
-    fn module_start_location(&self, body: &[ast::Stmt]) -> TextRange {
-        body.first()
-            .map_or_else(|| self.source_line_start_range(1), Ranged::range)
+    fn module_start_location(&self, body: &[ast::Stmt]) -> CompilerSourceSpan {
+        body.first().map_or_else(
+            || CompilerSourceSpan::parsed(self.source_line_start_range(1)),
+            |node| self.node_span(node),
+        )
+    }
+
+    fn docstring_span(&self, body: &[ast::Stmt]) -> Option<CompilerSourceSpan> {
+        let ast::Stmt::Expr(statement) = body.first()? else {
+            return None;
+        };
+        Some(self.node_span(statement.value.as_ref()))
     }
 
     fn get_source_line_number(&mut self) -> OneIndexed {
+        if let Some(location) = self.current_source_span.location
+            && let Ok(line) = usize::try_from(location.line)
+            && let Some(line) = OneIndexed::new(line)
+        {
+            return line;
+        }
         self.source_file
             .to_source_code()
-            .line_index(self.current_source_range.start())
+            .line_index(self.current_source_span.range.start())
     }
 
     fn mark_generator(&mut self) {
@@ -12521,7 +12934,11 @@ impl<'warnings> Compiler<'warnings> {
                     ast::Expr::Await(_) => self.found = true,
                     ast::Expr::ListComp(ast::ExprListComp { generators, .. })
                     | ast::Expr::SetComp(ast::ExprSetComp { generators, .. })
-                    | ast::Expr::DictComp(ast::ExprDictComp { generators, .. })
+                        if generators.iter().any(|generator| generator.is_async) =>
+                    {
+                        self.found = true
+                    }
+                    ast::Expr::DictComp(ast::ExprDictComp { generators, .. })
                         if generators.iter().any(|generator| generator.is_async) =>
                     {
                         self.found = true
@@ -12555,17 +12972,17 @@ impl<'warnings> Compiler<'warnings> {
     }
 
     fn compile_expr_fstring(&mut self, fstring: &ast::ExprFString) -> CompileResult<()> {
-        let fstring_range = fstring.range;
-        let fstring = fstring.value.as_slice();
-        if self.count_fstring_parts(fstring) > STACK_USE_GUIDELINE {
-            return self.compile_fstring_parts_joined(fstring, fstring_range);
+        let fstring_range = self.node_span(fstring);
+        let value = &fstring.value;
+        if self.count_fstring_parts(value) > STACK_USE_GUIDELINE {
+            return self.compile_fstring_parts_joined(value, fstring_range);
         }
 
         let mut element_count = 0;
         let mut pending_literal = None;
         let mut pending_literal_range = None;
         let mut pending_literal_no_location = false;
-        for part in fstring {
+        for part in value {
             self.compile_fstring_part_into(
                 part,
                 &mut pending_literal,
@@ -12590,13 +13007,13 @@ impl<'warnings> Compiler<'warnings> {
         fstring: &ast::ExprFString,
         values: &[ast::Expr],
     ) -> CompileResult<()> {
-        let range = fstring.range;
+        let span = self.node_span(fstring);
         let value_count: u32 = values
             .len()
             .try_into()
             .expect("JoinedStr value count overflowed");
         if value_count > STACK_USE_GUIDELINE {
-            self.set_source_range(range);
+            self.restore_source_span(span);
             self.emit_load_const(ConstantData::Str {
                 value: Wtf8Buf::new(),
             });
@@ -12605,20 +13022,20 @@ impl<'warnings> Compiler<'warnings> {
             emit!(self, Instruction::BuildList { count: 0 });
             for value in values {
                 self.compile_expression(value)?;
-                self.set_source_range(range);
+                self.restore_source_span(span);
                 emit!(self, Instruction::ListAppend { i: 1 });
             }
-            self.set_source_range(range);
+            self.restore_source_span(span);
             emit!(self, Instruction::Call { argc: 1 });
         } else {
             for value in values {
                 self.compile_expression(value)?;
             }
             if value_count > 1 {
-                self.set_source_range(range);
+                self.restore_source_span(span);
                 emit!(self, Instruction::BuildString { count: value_count });
             } else if value_count == 0 {
-                self.set_source_range(range);
+                self.restore_source_span(span);
                 self.emit_load_const(ConstantData::Str {
                     value: Wtf8Buf::new(),
                 });
@@ -12629,10 +13046,10 @@ impl<'warnings> Compiler<'warnings> {
 
     fn compile_fstring_parts_joined(
         &mut self,
-        fstring: &[ast::FStringPart],
-        fstring_range: TextRange,
+        fstring: &ast::FStringValue,
+        fstring_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
-        self.set_source_range(fstring_range);
+        self.restore_source_span(fstring_range);
         self.emit_load_const(ConstantData::Str {
             value: Wtf8Buf::new(),
         });
@@ -12666,28 +13083,32 @@ impl<'warnings> Compiler<'warnings> {
 
     fn compile_fstring_part_into(
         &mut self,
-        part: &ast::FStringPart,
+        part: ast::FStringPartRef<'_>,
         pending_literal: &mut Option<Wtf8Buf>,
-        pending_literal_range: &mut Option<TextRange>,
+        pending_literal_range: &mut Option<CompilerSourceSpan>,
         pending_literal_no_location: &mut bool,
         element_count: &mut u32,
-        join_append_range: Option<TextRange>,
+        join_append_range: Option<CompilerSourceSpan>,
     ) -> CompileResult<()> {
         match part {
-            ast::FStringPart::Literal(string) => {
+            ast::FStringPartRef::Literal(string) => {
                 let value = string_literal_part_value(&self.source_file, string);
                 if pending_literal.is_none() {
-                    *pending_literal_range = Some(string.range);
-                    *pending_literal_no_location = string.range == TextRange::default();
+                    *pending_literal_range = Some(self.node_span(string));
+                    *pending_literal_no_location = self.node_span(string).is_artificial();
                     *pending_literal = Some(value);
                 } else if let Some(pending) = pending_literal.as_mut() {
-                    Self::extend_pending_literal_range(pending_literal_range, string.range);
-                    *pending_literal_no_location &= string.range == TextRange::default();
+                    Self::extend_pending_literal_span(
+                        pending_literal_range,
+                        self.node_span(string),
+                    )
+                    .map_err(|error| self.error(error))?;
+                    *pending_literal_no_location &= self.node_span(string).is_artificial();
                     pending.push_wtf8(value.as_ref());
                 }
                 Ok(())
             }
-            ast::FStringPart::FString(fstring) => self.compile_fstring_elements_into(
+            ast::FStringPartRef::FString(fstring) => self.compile_fstring_elements_into(
                 fstring.flags,
                 &fstring.elements,
                 pending_literal,
@@ -12701,10 +13122,10 @@ impl<'warnings> Compiler<'warnings> {
     fn finish_fstring(
         &mut self,
         mut pending_literal: Option<Wtf8Buf>,
-        mut pending_literal_range: Option<TextRange>,
+        mut pending_literal_range: Option<CompilerSourceSpan>,
         mut pending_literal_no_location: bool,
         mut element_count: u32,
-        fstring_range: Option<TextRange>,
+        fstring_range: Option<CompilerSourceSpan>,
     ) {
         self.emit_pending_fstring_literal(
             &mut pending_literal,
@@ -12716,14 +13137,14 @@ impl<'warnings> Compiler<'warnings> {
 
         if element_count == 0 {
             if let Some(fstring_range) = fstring_range {
-                self.set_source_range(fstring_range);
+                self.restore_source_span(fstring_range);
             }
             self.emit_load_const(ConstantData::Str {
                 value: Wtf8Buf::new(),
             });
         } else if element_count > 1 {
             if let Some(fstring_range) = fstring_range {
-                self.set_source_range(fstring_range);
+                self.restore_source_span(fstring_range);
             }
             emit!(
                 self,
@@ -12737,10 +13158,10 @@ impl<'warnings> Compiler<'warnings> {
     fn finish_fstring_join(
         &mut self,
         mut pending_literal: Option<Wtf8Buf>,
-        mut pending_literal_range: Option<TextRange>,
+        mut pending_literal_range: Option<CompilerSourceSpan>,
         mut pending_literal_no_location: bool,
         mut element_count: u32,
-        fstring_range: TextRange,
+        fstring_range: CompilerSourceSpan,
     ) {
         self.emit_pending_fstring_literal(
             &mut pending_literal,
@@ -12749,17 +13170,17 @@ impl<'warnings> Compiler<'warnings> {
             &mut element_count,
             Some(fstring_range),
         );
-        self.set_source_range(fstring_range);
+        self.restore_source_span(fstring_range);
         emit!(self, Instruction::Call { argc: 1 });
     }
 
     fn emit_pending_fstring_literal(
         &mut self,
         pending_literal: &mut Option<Wtf8Buf>,
-        pending_literal_range: &mut Option<TextRange>,
+        pending_literal_range: &mut Option<CompilerSourceSpan>,
         pending_literal_no_location: &mut bool,
         element_count: &mut u32,
-        join_append_range: Option<TextRange>,
+        join_append_range: Option<CompilerSourceSpan>,
     ) {
         let Some(value) = pending_literal.take() else {
             return;
@@ -12776,7 +13197,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         if let Some(range) = range {
-            self.set_source_range(range);
+            self.restore_source_span(range);
         }
         self.emit_load_const(ConstantData::Str { value });
         if no_location {
@@ -12784,24 +13205,40 @@ impl<'warnings> Compiler<'warnings> {
         }
         *element_count += 1;
         if let Some(join_append_range) = join_append_range {
-            self.set_source_range(join_append_range);
+            self.restore_source_span(join_append_range);
             emit!(self, Instruction::ListAppend { i: 1 });
         }
     }
 
-    fn extend_pending_literal_range(pending: &mut Option<TextRange>, range: TextRange) {
+    fn extend_pending_literal_span(
+        pending: &mut Option<CompilerSourceSpan>,
+        span: CompilerSourceSpan,
+    ) -> Result<(), CodegenErrorType> {
         let Some(existing) = pending else {
-            *pending = Some(range);
-            return;
+            *pending = Some(span);
+            return Ok(());
         };
-        if *existing == TextRange::default() {
-            *existing = range;
-        } else if range != TextRange::default() {
-            *existing = TextRange::new(existing.start(), range.end());
+        // Check before changing either range or artificial-location state.
+        // Valid VM AST inputs map every literal; parser inputs map none.
+        if existing.location.is_some() != span.location.is_some() {
+            return Err(CodegenErrorType::MixedAstLocationProvenance);
+        }
+        if existing.is_artificial() {
+            *existing = span;
+        } else if !span.is_artificial() {
+            existing.range = TextRange::new(
+                existing.range.start(),
+                span.range.end().max(existing.range.start()),
+            );
+            if let (Some(first), Some(last)) = (&mut existing.location, span.location) {
+                first.end_line = last.end_line;
+                first.end_col = last.end_col;
+            }
         }
+        Ok(())
     }
 
-    fn count_fstring_parts(&self, fstring: &[ast::FStringPart]) -> u32 {
+    fn count_fstring_parts(&self, fstring: &ast::FStringValue) -> u32 {
         let mut element_count = 0;
         let mut pending_literal = None;
         for part in fstring {
@@ -12813,12 +13250,12 @@ impl<'warnings> Compiler<'warnings> {
 
     fn count_fstring_part_into(
         &self,
-        part: &ast::FStringPart,
+        part: ast::FStringPartRef<'_>,
         pending_literal: &mut Option<Wtf8Buf>,
         element_count: &mut u32,
     ) {
         match part {
-            ast::FStringPart::Literal(string) => {
+            ast::FStringPartRef::Literal(string) => {
                 let value = string_literal_part_value(&self.source_file, string);
                 if let Some(pending) = pending_literal.as_mut() {
                     pending.push_wtf8(value.as_ref());
@@ -12826,7 +13263,7 @@ impl<'warnings> Compiler<'warnings> {
                     *pending_literal = Some(value);
                 }
             }
-            ast::FStringPart::FString(fstring) => self.count_fstring_elements_into(
+            ast::FStringPartRef::FString(fstring) => self.count_fstring_elements_into(
                 fstring.flags,
                 &fstring.elements,
                 pending_literal,
@@ -12854,16 +13291,16 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         flags: ast::FStringFlags,
         fstring_elements: &ast::InterpolatedStringElements,
-        fstring_range: Option<TextRange>,
+        fstring_range: Option<CompilerSourceSpan>,
     ) -> CompileResult<()> {
         if self.count_fstring_elements(flags, fstring_elements) > STACK_USE_GUIDELINE {
-            let fstring_range = fstring_range.unwrap_or(self.current_source_range);
+            let fstring_range = fstring_range.unwrap_or(self.current_source_span);
             return self.compile_fstring_elements_joined(flags, fstring_elements, fstring_range);
         }
 
         let mut element_count = 0;
         let mut pending_literal: Option<Wtf8Buf> = None;
-        let mut pending_literal_range: Option<TextRange> = None;
+        let mut pending_literal_range: Option<CompilerSourceSpan> = None;
         let mut pending_literal_no_location = false;
         self.compile_fstring_elements_into(
             flags,
@@ -12887,9 +13324,9 @@ impl<'warnings> Compiler<'warnings> {
         &mut self,
         flags: ast::FStringFlags,
         fstring_elements: &ast::InterpolatedStringElements,
-        fstring_range: TextRange,
+        fstring_range: CompilerSourceSpan,
     ) -> CompileResult<()> {
-        self.set_source_range(fstring_range);
+        self.restore_source_span(fstring_range);
         self.emit_load_const(ConstantData::Str {
             value: Wtf8Buf::new(),
         });
@@ -12899,7 +13336,7 @@ impl<'warnings> Compiler<'warnings> {
 
         let mut element_count = 0;
         let mut pending_literal: Option<Wtf8Buf> = None;
-        let mut pending_literal_range: Option<TextRange> = None;
+        let mut pending_literal_range: Option<CompilerSourceSpan> = None;
         let mut pending_literal_no_location = false;
         self.compile_fstring_elements_into(
             flags,
@@ -12919,6 +13356,14 @@ impl<'warnings> Compiler<'warnings> {
         Ok(())
     }
 
+    fn format_spec_span(&self, spec: &ast::InterpolatedStringFormatSpec) -> CompilerSourceSpan {
+        let mut span = self.node_span(spec);
+        if span.location.is_none() {
+            span.range = self.cpython_format_spec_range(spec.range);
+        }
+        span
+    }
+
     fn cpython_format_spec_range(&self, range: TextRange) -> TextRange {
         let start = range.start().to_usize();
         if start == 0 {
@@ -12937,9 +13382,9 @@ impl<'warnings> Compiler<'warnings> {
         flags: ast::FStringFlags,
         fstring_elements: &ast::InterpolatedStringElements,
         pending_literal: &mut Option<Wtf8Buf>,
-        pending_literal_meta: (&mut Option<TextRange>, &mut bool),
+        pending_literal_meta: (&mut Option<CompilerSourceSpan>, &mut bool),
         element_count: &mut u32,
-        join_append_range: Option<TextRange>,
+        join_append_range: Option<CompilerSourceSpan>,
     ) -> CompileResult<()> {
         let (pending_literal_range, pending_literal_no_location) = pending_literal_meta;
         for element in fstring_elements {
@@ -12948,12 +13393,16 @@ impl<'warnings> Compiler<'warnings> {
                     let value =
                         interpolated_string_literal_value(&self.source_file, string, flags.into());
                     if pending_literal.is_none() {
-                        *pending_literal_range = Some(string.range);
-                        *pending_literal_no_location = string.range == TextRange::default();
+                        *pending_literal_range = Some(self.node_span(string));
+                        *pending_literal_no_location = self.node_span(string).is_artificial();
                         *pending_literal = Some(value);
                     } else if let Some(pending) = pending_literal.as_mut() {
-                        Self::extend_pending_literal_range(pending_literal_range, string.range);
-                        *pending_literal_no_location &= string.range == TextRange::default();
+                        Self::extend_pending_literal_span(
+                            pending_literal_range,
+                            self.node_span(string),
+                        )
+                        .map_err(|error| self.error(error))?;
+                        *pending_literal_no_location &= self.node_span(string).is_artificial();
                         pending.push_wtf8(value.as_ref());
                     }
                 }
@@ -12972,7 +13421,11 @@ impl<'warnings> Compiler<'warnings> {
                             fstring_expr.expression.range(),
                         );
                         let text: Wtf8Buf = text.into();
-                        Self::extend_pending_literal_range(pending_literal_range, debug_text_range);
+                        Self::extend_pending_literal_span(
+                            pending_literal_range,
+                            CompilerSourceSpan::parsed(debug_text_range),
+                        )
+                        .map_err(|error| self.error(error))?;
                         *pending_literal_no_location = false;
                         pending_literal
                             .get_or_insert_with(Wtf8Buf::new)
@@ -12998,13 +13451,13 @@ impl<'warnings> Compiler<'warnings> {
 
                     self.compile_expression(&fstring_expr.expression)?;
 
-                    let formatted_value_range = fstring_expr.range;
+                    let formatted_value_span = self.node_span(fstring_expr);
                     match conversion {
                         ConvertValueOparg::None => {}
                         ConvertValueOparg::Str
                         | ConvertValueOparg::Repr
                         | ConvertValueOparg::Ascii => {
-                            self.set_source_range(formatted_value_range);
+                            self.restore_source_span(formatted_value_span);
                             emit!(self, Instruction::ConvertValue { oparg: conversion })
                         }
                     }
@@ -13014,24 +13467,23 @@ impl<'warnings> Compiler<'warnings> {
                     {
                         self.compile_expression(format_spec)?;
 
-                        self.set_source_range(formatted_value_range);
+                        self.restore_source_span(formatted_value_span);
                         emit!(self, Instruction::FormatWithSpec);
                     } else {
                         match &fstring_expr.format_spec {
                             Some(format_spec) => {
-                                let format_spec_range =
-                                    self.cpython_format_spec_range(format_spec.range);
+                                let format_spec_range = self.format_spec_span(format_spec);
                                 self.compile_fstring_elements(
                                     flags,
                                     &format_spec.elements,
                                     Some(format_spec_range),
                                 )?;
 
-                                self.set_source_range(formatted_value_range);
+                                self.restore_source_span(formatted_value_span);
                                 emit!(self, Instruction::FormatWithSpec);
                             }
                             None => {
-                                self.set_source_range(formatted_value_range);
+                                self.restore_source_span(formatted_value_span);
                                 emit!(self, Instruction::FormatSimple);
                             }
                         }
@@ -13039,7 +13491,7 @@ impl<'warnings> Compiler<'warnings> {
 
                     *element_count += 1;
                     if let Some(join_append_range) = join_append_range {
-                        self.set_source_range(join_append_range);
+                        self.restore_source_span(join_append_range);
                         emit!(self, Instruction::ListAppend { i: 1 });
                     }
                 }
@@ -13110,7 +13562,7 @@ impl<'warnings> Compiler<'warnings> {
         // strings tuple first, then evaluating interpolations left-to-right.
         let tstring_value = &expr_tstring.value;
 
-        let mut all_strings: Vec<(Wtf8Buf, TextRange)> = Vec::new();
+        let mut all_strings: Vec<(Wtf8Buf, CompilerSourceSpan)> = Vec::new();
         let mut current_string = Wtf8Buf::new();
         let mut current_string_range = None;
         let mut interp_count: u32 = 0;
@@ -13122,13 +13574,14 @@ impl<'warnings> Compiler<'warnings> {
                 &mut current_string,
                 &mut current_string_range,
                 &mut interp_count,
-                expr_tstring.range,
-            );
+                self.node_span(expr_tstring),
+            )
+            .map_err(|error| self.error(error))?;
         }
 
         all_strings.push((
             core::mem::take(&mut current_string),
-            current_string_range.unwrap_or(expr_tstring.range),
+            current_string_range.unwrap_or_else(|| self.node_span(expr_tstring)),
         ));
 
         let string_count: u32 = all_strings
@@ -13136,10 +13589,10 @@ impl<'warnings> Compiler<'warnings> {
             .try_into()
             .expect("t-string string count overflowed");
         for (s, range) in &all_strings {
-            self.set_source_range(*range);
+            self.restore_source_span(*range);
             self.emit_load_const(ConstantData::Str { value: s.clone() });
         }
-        self.set_source_range(expr_tstring.range);
+        self.set_source_node(expr_tstring.range, &expr_tstring.node_index);
         emit!(
             self,
             Instruction::BuildTuple {
@@ -13151,14 +13604,14 @@ impl<'warnings> Compiler<'warnings> {
             self.compile_tstring_interpolations(tstring)?;
         }
 
-        self.set_source_range(expr_tstring.range);
+        self.set_source_node(expr_tstring.range, &expr_tstring.node_index);
         emit!(
             self,
             Instruction::BuildTuple {
                 count: interp_count
             }
         );
-        self.set_source_range(expr_tstring.range);
+        self.set_source_node(expr_tstring.range, &expr_tstring.node_index);
         emit!(self, Instruction::BuildTemplate);
 
         Ok(())
@@ -13174,7 +13627,7 @@ impl<'warnings> Compiler<'warnings> {
         for value in values {
             if self.runtime_template_value_interpolation(value).is_some() {
                 if last_was_interpolation {
-                    self.set_source_range(expr_tstring.range);
+                    self.set_source_node(expr_tstring.range, &expr_tstring.node_index);
                     self.emit_load_const(ConstantData::Str {
                         value: Wtf8Buf::new(),
                     });
@@ -13188,13 +13641,13 @@ impl<'warnings> Compiler<'warnings> {
             }
         }
         if last_was_interpolation {
-            self.set_source_range(expr_tstring.range);
+            self.set_source_node(expr_tstring.range, &expr_tstring.node_index);
             self.emit_load_const(ConstantData::Str {
                 value: Wtf8Buf::new(),
             });
             strings_len += 1;
         }
-        self.set_source_range(expr_tstring.range);
+        self.set_source_node(expr_tstring.range, &expr_tstring.node_index);
         emit!(self, Instruction::BuildTuple { count: strings_len });
 
         let mut interpolations_len = 0;
@@ -13205,14 +13658,14 @@ impl<'warnings> Compiler<'warnings> {
                 interpolations_len += 1;
             }
         }
-        self.set_source_range(expr_tstring.range);
+        self.set_source_node(expr_tstring.range, &expr_tstring.node_index);
         emit!(
             self,
             Instruction::BuildTuple {
                 count: interpolations_len
             }
         );
-        self.set_source_range(expr_tstring.range);
+        self.set_source_node(expr_tstring.range, &expr_tstring.node_index);
         emit!(self, Instruction::BuildTemplate);
         Ok(())
     }
@@ -13252,7 +13705,7 @@ impl<'warnings> Compiler<'warnings> {
     ) -> CompileResult<()> {
         let (str, format_spec) = interpolation;
         self.compile_expression(&interp.expression)?;
-        self.set_source_range(interp.range);
+        self.set_source_node(interp.range, &interp.node_index);
         self.emit_load_const(ast_constant_value_to_constant_data(str.clone()));
 
         let conversion = match interp.conversion {
@@ -13268,7 +13721,7 @@ impl<'warnings> Compiler<'warnings> {
         }
 
         let format = 2 | (conversion << 2) | u32::from(has_format_spec);
-        self.set_source_range(interp.range);
+        self.set_source_node(interp.range, &interp.node_index);
         emit!(self, Instruction::BuildInterpolation { format });
         Ok(())
     }
@@ -13292,19 +13745,22 @@ impl<'warnings> Compiler<'warnings> {
     fn collect_tstring_strings(
         &self,
         tstring: &ast::TString,
-        strings: &mut Vec<(Wtf8Buf, TextRange)>,
+        strings: &mut Vec<(Wtf8Buf, CompilerSourceSpan)>,
         current_string: &mut Wtf8Buf,
-        current_string_range: &mut Option<TextRange>,
+        current_string_range: &mut Option<CompilerSourceSpan>,
         interp_count: &mut u32,
-        template_range: TextRange,
-    ) {
+        template_range: CompilerSourceSpan,
+    ) -> Result<(), CodegenErrorType> {
         for element in &tstring.elements {
             match element {
                 ast::InterpolatedStringElement::Literal(lit) => {
                     if current_string_range.is_none() {
-                        *current_string_range = Some(lit.range);
+                        *current_string_range = Some(self.node_span(lit));
                     } else {
-                        Self::extend_pending_literal_range(current_string_range, lit.range);
+                        Self::extend_pending_literal_span(
+                            current_string_range,
+                            self.node_span(lit),
+                        )?;
                     }
                     current_string.push_wtf8(&interpolated_string_literal_value(
                         &self.source_file,
@@ -13320,12 +13776,13 @@ impl<'warnings> Compiler<'warnings> {
                             interp.expression.range(),
                         );
                         if current_string_range.is_none() {
-                            *current_string_range = Some(debug_text_range);
+                            *current_string_range =
+                                Some(CompilerSourceSpan::parsed(debug_text_range));
                         } else {
-                            Self::extend_pending_literal_range(
+                            Self::extend_pending_literal_span(
                                 current_string_range,
-                                debug_text_range,
-                            );
+                                CompilerSourceSpan::parsed(debug_text_range),
+                            )?;
                         }
                         current_string.push_str(&text);
                         strings.push((
@@ -13342,6 +13799,7 @@ impl<'warnings> Compiler<'warnings> {
                 }
             }
         }
+        Ok(())
     }
 
     fn compile_tstring_interpolations(&mut self, tstring: &ast::TString) -> CompileResult<()> {
@@ -13361,19 +13819,14 @@ impl<'warnings> Compiler<'warnings> {
 
             self.compile_expression(&interp.expression)?;
 
-            let expr_range = interp.expression.range();
-            let expr_source = if interp.range.start() < expr_range.start()
-                && interp.range.end() >= expr_range.end()
-            {
-                let after_brace = interp.range.start() + TextSize::new(1);
-                self.source_file
-                    .source_text()
-                    .slice(TextRange::new(after_brace, expr_range.end()))
-            } else {
-                self.source_file.source_text().slice(expr_range)
-            }
-            .to_string();
-            self.set_source_range(interp.range);
+            let expr_source = crate::interpolation_expression_text(&self.source_file, interp)
+                .unwrap_or_else(|| {
+                    self.source_file
+                        .source_text()
+                        .slice(interp.expression.range())
+                        .to_owned()
+                });
+            self.set_source_node(interp.range, &interp.node_index);
             self.emit_load_const(ConstantData::Str {
                 value: expr_source.into(),
             });
@@ -13391,7 +13844,7 @@ impl<'warnings> Compiler<'warnings> {
 
             let has_format_spec = interp.format_spec.is_some();
             if let Some(format_spec) = &interp.format_spec {
-                let format_spec_range = self.cpython_format_spec_range(format_spec.range);
+                let format_spec_range = self.format_spec_span(format_spec);
                 self.compile_fstring_elements(
                     ast::FStringFlags::empty(),
                     &format_spec.elements,
@@ -13402,7 +13855,7 @@ impl<'warnings> Compiler<'warnings> {
             // CPython keeps bit 1 set in BUILD_INTERPOLATION's oparg and uses
             // bit 0 for the optional format spec.
             let format = 2 | (conversion << 2) | u32::from(has_format_spec);
-            self.set_source_range(interp.range);
+            self.set_source_node(interp.range, &interp.node_index);
             emit!(self, Instruction::BuildInterpolation { format });
         }
 
@@ -13972,7 +14425,7 @@ mod tests {
             arguments: ast::Arguments {
                 node_index: ast::AtomicNodeIndex::NONE,
                 range: TextRange::default(),
-                args: Box::default(),
+                args: Default::default(),
                 keywords: Default::default(),
                 runtime_args: None,
                 runtime_bases: None,
@@ -14120,7 +14573,7 @@ mod tests {
             arguments: ast::Arguments {
                 node_index: ast::AtomicNodeIndex::NONE,
                 range: TextRange::default(),
-                args: Box::default(),
+                args: Default::default(),
                 keywords: Default::default(),
                 runtime_args: None,
                 runtime_bases: None,
@@ -14196,12 +14649,14 @@ mod tests {
         let message = first_ast_constant_warning(ast::Expr::Compare(ast::ExprCompare {
             node_index: ast::AtomicNodeIndex::NONE,
             range: TextRange::default(),
-            left: Box::new(left),
             ops: Box::new([ast::CmpOp::Is]),
-            comparators: Box::new([ast::Expr::NoneLiteral(ast::ExprNoneLiteral {
-                node_index: ast::AtomicNodeIndex::NONE,
-                range: TextRange::default(),
-            })]),
+            operands: Box::new([
+                left,
+                ast::Expr::NoneLiteral(ast::ExprNoneLiteral {
+                    node_index: ast::AtomicNodeIndex::NONE,
+                    range: TextRange::default(),
+                }),
+            ]),
             runtime_comparators: None,
         }));
         assert!(
@@ -14618,66 +15073,6 @@ match x:
         );
     }
 
-    #[test]
-    fn empty_module_implicit_return_inherits_resume_location_like_cpython() {
-        let code = compile_exec("");
-        // codegen emits the implicit LOAD_CONST/RETURN_VALUE with
-        // NO_LOCATION, then flowgraph.c::propagate_line_numbers() propagates
-        // the module RESUME location, whose line is 0.
-        assert_eq!(code.linetable.as_ref(), &[0xf2, 0x03, 0x01, 0x01, 0x01]);
-    }
-
-    #[test]
-    fn module_docstring_load_uses_doc_location_like_cpython() {
-        let code = compile_exec(
-            "\
-\"doc\"
-x = 1
-",
-        );
-
-        // codegen_body() emits the docstring LOAD_CONST at the
-        // string expression location, then emits STORE_NAME __doc__ with
-        // NO_LOCATION.
-        assert_eq!(
-            code.linetable.as_ref(),
-            &[
-                0xf0, 0x03, 0x01, 0x01, 0x01, 0xd9, 0x00, 0x05, 0xd8, 0x04, 0x05, 0x82, 0x01,
-            ],
-        );
-    }
-
-    #[test]
-    fn redundant_nop_location_copies_full_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(x, y, z):
-    while x:
-        if y:
-            pass
-        elif z:
-            if y < 0:
-                return y
-            if z:
-                y = y + 1
-        elif y:
-            return 1
-    return -1
-",
-        );
-        let f = find_code(&code, "f").expect("missing function code");
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdf, 0x0a, 0x0b, 0xdf, 0x0b, 0x0c, 0xd9, 0x0c, 0x10, 0xdf, 0x0d, 0x0e,
-                0xd8, 0x0f, 0x10, 0x90, 0x31, 0x8c, 0x75, 0xd8, 0x17, 0x18, 0x90, 0x08, 0xdf, 0x0f,
-                0x10, 0xd8, 0x14, 0x15, 0x98, 0x01, 0x95, 0x45, 0x92, 0x01, 0xf1, 0x03, 0x00, 0x10,
-                0x11, 0xe7, 0x0d, 0x0e, 0x89, 0x51, 0xd9, 0x13, 0x14, 0xd8, 0x0b, 0x0d, 0x80, 0x49,
-            ],
-            "CPython basicblock_remove_redundant_nops() copies the full NOP location into a following no-location jump"
-        );
-    }
-
     fn scan_program_symbol_table(source: &str) -> SymbolTable {
         let source_file = SourceFileBuilder::new("source_path", source).finish();
         let parsed = ruff_python_parser::parse(
@@ -14899,11 +15294,12 @@ def f(support, func, value):
             .expect("missing CPython-style false jump for if/break");
         assert!(
             matches!(
-                ops.get(cond..cond + 5),
+                ops.get(cond..cond + 6),
                 Some([
                     Instruction::PopJumpIfFalse { .. },
                     Instruction::NotTaken,
                     Instruction::PopTop,
+                    Instruction::PopTop,
                     Instruction::JumpForward { .. },
                     Instruction::JumpBackward { .. },
                 ])
@@ -14947,7 +15343,7 @@ def f(input):
                         Instruction::CompareOp { .. },
                         Instruction::PopJumpIfFalse { .. },
                         Instruction::NotTaken,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::ReturnValue,
                         Instruction::JumpBackward { .. },
                     ]
@@ -15988,7 +16384,7 @@ def f(self):
                             == "close"
                 ) && matches!(window[2].op, Instruction::Call { .. })
                     && matches!(window[3].op, Instruction::PopTop)
-                    && matches!(window[4].op, Instruction::LoadConst { .. })
+                    && matches!(window[4].op, Instruction::LoadCommonConstant { .. })
                     && matches!(window[5].op, Instruction::ReturnValue)
             })
             .unwrap_or_else(|| {
@@ -16517,7 +16913,7 @@ def f(buffer, pos, last_char):
                         Instruction::NotTaken,
                         Instruction::JumpBackward { .. }
                             | Instruction::JumpBackwardNoInterrupt { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreFast { .. },
                     ]
                 )
@@ -16532,7 +16928,7 @@ def f(buffer, pos, last_char):
                         Instruction::CompareOp { .. },
                         Instruction::PopJumpIfFalse { .. },
                         Instruction::NotTaken,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -16585,86 +16981,6 @@ def f(buffer, pos, last_char):
         })
     }
 
-    #[test]
-    fn annotated_multiline_function_body_keeps_def_firstlineno_like_cpython() {
-        let code = compile_exec(
-            r#"
-a = 1
-def f(
-    x: a,
-): ...
-"#,
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-        // CPython 3.14 codegen_function() computes firstlineno from the
-        // FunctionDef before compiling annotations, then passes it to
-        // codegen_function_body().
-        assert_eq!(f.linetable.as_ref(), &[0x80, 0x00, 0xe1, 0x03, 0x06]);
-    }
-
-    #[test]
-    fn annotation_scope_return_uses_function_location_like_cpython() {
-        let code = compile_exec(
-            r#"
-def g():
-    def f(x: not (int is int), /): ...
-"#,
-        );
-        let g = find_code(&code, "g").expect("missing g code");
-        let annotate = find_code(g, "__annotate__").expect("missing annotation code");
-        // CPython 3.14 codegen_function_annotations() receives LOC(function)
-        // and uses it for the annotation closure's BUILD_MAP/RETURN_VALUE and
-        // for the parent MAKE_FUNCTION annotate sequence.
-        assert_eq!(g.linetable.as_ref(), &[0x80, 0x00, 0xdf, 0x04, 0x26]);
-        assert_eq!(
-            annotate.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd7, 0x04, 0x26, 0xd1, 0x04, 0x26, 0x94, 0x23, 0x9c, 0x13, 0xd0, 0x0d,
-                0x1d, 0xd1, 0x04, 0x26,
-            ],
-        );
-    }
-
-    #[test]
-    fn starred_arg_annotation_unpack_uses_function_location_like_cpython() {
-        let code = compile_exec("def f(*args: *Ts): pass\n");
-        let annotate = find_code(&code, "__annotate__").expect("missing annotation code");
-
-        // codegen_argannotation() visits `Ts` at the annotation
-        // expression location, then emits UNPACK_SEQUENCE at LOC(function).
-        assert_eq!(
-            annotate.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd7, 0x00, 0x17, 0xd1, 0x00, 0x17, 0x8c, 0x62, 0xd3, 0x00, 0x17
-            ],
-        );
-    }
-
-    #[test]
-    fn module_deferred_annotations_use_start_location_like_cpython() {
-        let code = compile_exec(
-            "\
-import os
-X: int
-Y: str
-",
-        );
-        let annotate = find_code(&code, "__annotate__").expect("missing __annotate__ code");
-
-        // compile.c::start_location() passes the first module
-        // statement location into _PyCodegen_Module(), and
-        // codegen_process_deferred_annotations() uses that loc for annotation
-        // scope setup, BUILD_MAP, STORE_SUBSCR, and RETURN_VALUE.
-        assert_eq!(
-            annotate.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0x87, 0x09, 0x81, 0x09, 0xdf, 0x00, 0x06, 0x82, 0x06, 0x84, 0x33, 0x81,
-                0x06, 0xf1, 0x03, 0x00, 0x01, 0x0a, 0xe7, 0x00, 0x06, 0x82, 0x06, 0x84, 0x33, 0x81,
-                0x06, 0xf2, 0x05, 0x00, 0x01, 0x0a,
-            ]
-        );
-    }
-
     #[test]
     fn super_method_call_kw_names_use_attribute_location_like_cpython() {
         let code = compile_exec(
@@ -16915,83 +17231,6 @@ def continues(xs):
         }
     }
 
-    #[test]
-    fn not_compare_uses_unary_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(self, other):
-    return not self == other
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-
-        // CPython 3.14 parses the Compare inside UnaryOp(Not) with the
-        // UnaryOp start location, so codegen_compare() emits COMPARE_OP at
-        // the full "not self == other" range before flowgraph folds TO_BOOL.
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x0f, 0x13, 0xd2, 0x0b, 0x1c, 0xd0, 0x04, 0x1c,
-            ]
-        );
-    }
-
-    #[test]
-    fn not_chained_compare_keeps_compare_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(c):
-    return not (b\" \" <= c <= b\"~\")
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-
-        // CPython's single Compare under UnaryOp(Not) includes "not" in the
-        // Compare range, but chained comparisons keep their inner range for
-        // compare scaffolding and only use the UnaryOp range for TO_BOOL and
-        // UNARY_NOT.
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x10, 0x14, 0x98, 0x01, 0xd7, 0x10, 0x21, 0xd4, 0x10, 0x21, 0x98,
-                0x54, 0xd1, 0x10, 0x21, 0xd4, 0x0b, 0x22, 0xd0, 0x04, 0x22, 0xd1, 0x10, 0x21, 0xd4,
-                0x0b, 0x22, 0xd0, 0x04, 0x22,
-            ]
-        );
-    }
-
-    #[test]
-    fn type_param_scopes_use_cpython_locations() {
-        let code = compile_exec("type BoundGenericAlias[X: int] = set[X]\n");
-        let type_params = find_code(&code, "<generic parameters of BoundGenericAlias>")
-            .expect("missing generic parameters code");
-        let bound = find_direct_child_code(type_params, "X").expect("missing X bound code");
-        let alias =
-            find_direct_child_code(type_params, "BoundGenericAlias").expect("missing alias code");
-
-        // CPython 3.14 codegen_type_params() emits type-parameter ops at
-        // LOC(typeparam), bound/default evaluator ops at LOC(e), and type alias
-        // body plumbing at LOC(s).
-        assert_eq!(
-            type_params.linetable.as_ref(),
-            &[
-                0xf8, 0x80, 0x00, 0xd0, 0x00, 0x27, 0x90, 0x76, 0x9b, 0x23, 0x93, 0x76, 0xd7, 0x00,
-                0x27, 0xd1, 0x00, 0x27,
-            ],
-        );
-        assert_eq!(
-            bound.linetable.as_ref(),
-            &[0x80, 0x00, 0x9f, 0x23, 0x9e, 0x23]
-        );
-        assert_eq!(
-            alias.linetable.as_ref(),
-            &[
-                0xf8, 0x80, 0x00, 0xd7, 0x00, 0x27, 0xd0, 0x00, 0x27, 0xa4, 0x13, 0xa0, 0x51, 0xa5,
-                0x16, 0xd0, 0x00, 0x27,
-            ],
-        );
-    }
-
     #[test]
     fn typealias_value_scope_has_single_return_like_cpython() {
         let code = compile_exec("type Alias = int\n");
@@ -17008,23 +17247,6 @@ def f(c):
         );
     }
 
-    #[test]
-    fn generic_typealias_wrapper_return_uses_alias_location_like_cpython() {
-        let code = compile_exec("type A[T] = T\n");
-        let type_params =
-            find_code(&code, "<generic parameters of A>").expect("missing type params code");
-
-        // codegen_typealias() assembles the generic-parameters
-        // wrapper with addNone=0 after codegen_typealias_body() leaves the type
-        // alias object on the stack. The final RETURN_VALUE keeps LOC(type alias).
-        assert_eq!(
-            type_params.linetable.as_ref(),
-            &[
-                0xf8, 0x80, 0x00, 0x80, 0x0d, 0x84, 0x71, 0x87, 0x0d, 0x81, 0x0d
-            ],
-        );
-    }
-
     #[test]
     fn type_param_bound_scope_has_single_return_like_cpython() {
         let code = compile_exec("type Alias[T: int] = T\n");
@@ -17059,25 +17281,6 @@ def f(c):
         );
     }
 
-    #[test]
-    fn generic_function_annotation_scope_uses_function_location_like_cpython() {
-        let code = compile_exec("def f[T](x: int): ...\n");
-        let type_params =
-            find_code(&code, "<generic parameters of f>").expect("missing type params code");
-        let annotate =
-            find_direct_child_code(type_params, "__annotate__").expect("missing annotation code");
-
-        // CPython 3.14 passes LOC(function) into codegen_function_annotations(),
-        // even when the annotation closure is emitted inside the generic
-        // parameters scope after codegen_type_params().
-        assert_eq!(
-            annotate.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd7, 0x00, 0x15, 0xd1, 0x00, 0x15, 0x8c, 0x43, 0xd1, 0x00, 0x15,
-            ],
-        );
-    }
-
     #[test]
     fn decorated_generic_function_type_params_use_decorator_firstlineno_like_cpython() {
         let code = compile_exec(
@@ -17095,27 +17298,6 @@ def f[T](): pass
         assert_eq!(type_params.first_line_number.unwrap().get(), 2);
     }
 
-    #[test]
-    fn generic_class_type_params_store_uses_class_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def outer():
-    class X[T]: ...
-",
-        );
-        let type_params =
-            find_code(&code, "<generic parameters of X>").expect("missing type params code");
-
-        // CPython 3.14 codegen_class() calls codegen_type_params(), then stores
-        // the resulting .type_params cell with codegen_nameop(c, LOC(class), ...).
-        assert_eq!(
-            type_params.linetable.as_ref(),
-            &[
-                0xf8, 0x80, 0x00, 0x8c, 0x41, 0x87, 0x4f, 0x87, 0x4f, 0x80, 0x4f,
-            ]
-        );
-    }
-
     #[test]
     fn generic_class_wrapper_ops_use_class_location_like_cpython() {
         let code = compile_exec(
@@ -17129,9 +17311,9 @@ def f():
         let wrapper_positions: Vec<_> = f
             .instructions
             .iter()
-            .filter(|unit| !matches!(unit.op, Instruction::Resume { .. }))
+            .zip(&f.locations)
+            .filter(|(unit, _)| !matches!(unit.op, Instruction::Resume { .. } | Instruction::Cache))
             .take(4)
-            .zip(f.locations.iter().filter(|_| true).skip(1))
             .map(|(unit, (location, end_location))| {
                 (
                     unit.op,
@@ -17341,48 +17523,6 @@ class C[T]: pass
     }
 
     #[test]
-    fn class_deferred_annotations_use_class_body_location_like_cpython() {
-        let code = compile_exec(
-            r#"
-class C:
-    "doc"
-    x: int
-"#,
-        );
-        let class_code = find_code(&code, "C").expect("missing class code");
-
-        // CPython 3.14 calls codegen_body(c, loc, ...) from codegen_class_body()
-        // with LOCATION(firstlineno, firstlineno, 0, 0). Deferred annotation
-        // closure setup and following artificial class tail inherit that class
-        // body location, not the annotation expression location.
-        assert_eq!(
-            class_code.linetable.as_ref(),
-            &[
-                0xf8, 0x87, 0x00, 0x80, 0x00, 0xd9, 0x04, 0x09, 0xf7, 0x03, 0x00, 0x01, 0x01, 0x83,
-                0x00,
-            ],
-        );
-    }
-
-    #[test]
-    fn future_annotation_string_uses_annotation_location_like_cpython() {
-        let code = compile_exec("from __future__ import annotations\nclass Bar:\n    foo: Foo\n");
-        let class_code = find_code(&code, "Bar").expect("missing class code");
-
-        // CPython 3.14 codegen_annassign() calls codegen_visit_annexpr(),
-        // which emits the stringized annotation at LOC(annotation), then emits
-        // the __annotations__ store sequence at LOC(AnnAssign).
-        assert_eq!(
-            class_code.linetable.as_ref(),
-            &[0x87, 0x00, 0xd8, 0x09, 0x0c, 0x87, 0x48]
-        );
-    }
-
-    #[test]
-    #[expect(
-        clippy::literal_string_with_formatting_args,
-        reason = "the literal is the expected t-string annotation"
-    )]
     fn future_tstring_annotation_preserves_interpolation_source_like_cpython() {
         let code = compile_exec(
             "from __future__ import annotations\nx: t'{a    +  b}'\ny: t'{ a + b }'\nz: f'{a    + b =}'\nu: t'{a    + b =}'\nv: t'{a    + b =:>10}'\np: t'{(a)}'\nq: t'{((a))!r}'\nr: t'{ ((a)) = !r:>10}'\ns: t'{(a)=}'\nt: t'{a == b = }'\na1: t'''{a= # x=y\n}'''\na2: t'''{a # x=y\n}'''\na3: t'''{(a # x=y\n)}'''\na4: t'''{a # x=y\n!r}'''\na5: t'''{a # x=y\n:>10}'''\na6: t'''{'#'}'''\na7: t'''{('#', a) # c=d\n}'''\n",
@@ -17405,61 +17545,26 @@ class C:
             annotation_strings,
             [
                 "t'{a    +  b}'",
-                "t'{ a + b}'",
+                "t'{ a + b }'",
                 "f'a    + b ={a + b!r}'",
-                "t'a    + b ={a    + b!r}'",
-                "t'a    + b ={a    + b:>10}'",
+                "t'a    + b ={a    + b !r}'",
+                "t'a    + b ={a    + b :>10}'",
                 "t'{(a)}'",
                 "t'{((a))!r}'",
-                "t' ((a)) = { ((a))!r:>10}'",
+                "t' ((a)) = { ((a)) !r:>10}'",
                 "t'(a)={(a)!r}'",
-                "t'a == b = {a == b!r}'",
+                "t'a == b = {a == b !r}'",
                 "t'a= \\n{a!r}'",
-                "t'{a}'",
+                "t'{a \\n}'",
                 "t'{(a \\n)}'",
-                "t'{a!r}'",
-                "t'{a:>10}'",
+                "t'{a \\n!r}'",
+                "t'{a \\n:>10}'",
                 "t\"{'#'}\"",
-                "t\"{('#', a)}\"",
+                "t\"{('#', a) \\n}\"",
             ]
         );
     }
 
-    #[test]
-    fn lambda_dict_literal_ops_use_dict_location_like_cpython() {
-        let code = compile_exec(
-            "\
-f = lambda data: {'x': data}
-g = lambda i: {**i}
-",
-        );
-        let f = find_code(&code, "<lambda>").expect("missing f lambda code");
-        let g = code
-            .constants
-            .iter()
-            .filter_map(|constant| {
-                if let ConstantData::Code { code } = constant {
-                    (code.obj_name == "<lambda>").then_some(code.as_ref())
-                } else {
-                    None
-                }
-            })
-            .nth(1)
-            .expect("missing g lambda code");
-
-        // CPython 3.14 codegen_dict()/codegen_subdict() uses LOC(dict) for
-        // BUILD_MAP, MAP_ADD, and DICT_UPDATE, so the lambda RETURN_VALUE
-        // inherits the full dict literal location after compiling its body.
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[0x80, 0x00, 0x90, 0x23, 0x90, 0x74, 0x91, 0x1b]
-        );
-        assert_eq!(
-            g.linetable.as_ref(),
-            &[0x80, 0x00, 0x88, 0x65, 0x90, 0x11, 0x89, 0x65]
-        );
-    }
-
     #[test]
     fn dict_unpacking_large_regular_run_uses_subdict_chunks_like_cpython() {
         let pairs = (0..17)
@@ -17699,11 +17804,10 @@ def f(self, payload):
                 function.constants.as_ref(),
                 [
                     ConstantData::Str { value: doc },
-                    ConstantData::None,
                     ConstantData::Str { value: message },
                 ] if doc.as_ref() == "doc" && message.as_ref() == "bad"
             ),
-            "CPython registers None from the pre-folded `is None` comparison before the else-body string"
+            "CPython 3.15 keeps the docstring and else-body string in co_consts; None uses the common-constant table"
         );
     }
 
@@ -17783,6 +17887,39 @@ def f(self):
         );
     }
 
+    #[test]
+    fn listcomp_build_list_from_arg_option() {
+        let has = |source: &str, build_list_from_arg: bool| {
+            let code = compile_exec_with_options(
+                source,
+                CompileOpts {
+                    build_list_from_arg,
+                    ..CompileOpts::default()
+                },
+            );
+            let f = find_code(&code, "f").expect("missing f");
+            (
+                f.instructions
+                    .iter()
+                    .any(|unit| matches!(unit.op, Instruction::BuildListFromArg)),
+                f.instructions
+                    .iter()
+                    .any(|unit| matches!(unit.op, Instruction::BuildList { .. })),
+            )
+        };
+        let single = "def f(n):\n    return [i for i in range(n)]\n";
+        // (BUILD_LIST_FROM_ARG, BUILD_LIST)
+        assert_eq!(has(single, false), (false, true));
+        assert_eq!(has(single, true), (true, false));
+        for source in [
+            "def f(xs):\n    return [x for x in xs if x]\n",
+            "def f(xss):\n    return [x for xs in xss for x in xs]\n",
+            "async def f(xs):\n    return [x async for x in xs]\n",
+        ] {
+            assert_eq!(has(source, true), (false, true), "source={source:?}");
+        }
+    }
+
     #[test]
     fn or_return_not_taken_before_jump_target_splits_exception_table_like_cpython() {
         let code = compile_exec_with_options(
@@ -17807,7 +17944,7 @@ def f(self, maintype):
                                 ..
                             },
                             CodeUnit {
-                                op: Instruction::LoadConst { .. },
+                                op: Instruction::LoadCommonConstant { .. },
                                 ..
                             },
                             CodeUnit {
@@ -18172,7 +18309,7 @@ def f(command):
                 [
                     Instruction::PopTop,
                     Instruction::Nop,
-                    Instruction::LoadConst { .. },
+                    Instruction::LoadCommonConstant { .. },
                 ]
             )),
             "CPython NEXT_LOCATION keeps the pass NOP after match subject POP_TOP, got {ops:?}",
@@ -18210,30 +18347,6 @@ def f(x):
         );
     }
 
-    #[test]
-    fn match_or_alternative_copies_use_alternative_locations_like_cpython() {
-        let code = compile_exec(
-            "\
-def f():
-    x = False
-    match 0:
-        case 0 | 1 | 2 | 3:
-            x = True
-    return x
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x08, 0x0d, 0x80, 0x41, 0xd8, 0x0a, 0x0b, 0xdf, 0x0d, 0x0e, 0x97,
-                0x11, 0x97, 0x51, 0x9f, 0x11, 0x88, 0x5d, 0xe0, 0x0b, 0x0c, 0x80, 0x48, 0xf0, 0x05,
-                0x00, 0x0e, 0x1b, 0xd8, 0x10, 0x14, 0x88, 0x41, 0xd8, 0x0b, 0x0c, 0x80, 0x48,
-            ],
-            "CPython codegen_pattern_or() emits each alternative COPY with LOC(alt)"
-        );
-    }
-
     #[test]
     fn match_or_conflicting_bind_error_uses_or_pattern_location_like_cpython() {
         let error = compile_exec_error(
@@ -18276,31 +18389,6 @@ def f(value):
         );
     }
 
-    #[test]
-    fn match_success_jump_uses_no_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(self):
-    match 0:
-        case 0:
-            x = True
-        case 0:
-            x = False
-    self.assertIs(x, True)
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x0a, 0x0b, 0xde, 0x0d, 0x0e, 0xd9, 0x10, 0x14, 0x89, 0x41, 0xdd,
-                0x0d, 0x0e, 0xd8, 0x10, 0x15, 0x88, 0x41, 0xd8, 0x04, 0x08, 0x87, 0x4d, 0x81, 0x4d,
-                0x90, 0x21, 0x90, 0x54, 0xd6, 0x04, 0x1a,
-            ],
-            "CPython codegen_match_inner() emits the success jump with NO_LOCATION"
-        );
-    }
-
     #[test]
     fn match_default_simple_guard_jump_uses_guard_location_like_cpython() {
         let code = compile_exec(
@@ -18350,32 +18438,6 @@ def f(x, y):
         );
     }
 
-    #[test]
-    fn match_mapping_keys_scaffolding_uses_mapping_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(self):
-    x = {}
-    y = None
-    match x:
-        case {0: 0}:
-            y = 0
-    self.assertIs(y, None)
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x08, 0x0a, 0x80, 0x41, 0xd8, 0x08, 0x0c, 0x80, 0x41, 0xd8, 0x0a,
-                0x0b, 0xdf, 0x0d, 0x13, 0x8f, 0x56, 0x8a, 0x56, 0x95, 0x11, 0x89, 0x56, 0xd8, 0x10,
-                0x11, 0x89, 0x41, 0xf2, 0x03, 0x00, 0x0e, 0x14, 0xe0, 0x04, 0x08, 0x87, 0x4d, 0x81,
-                0x4d, 0x90, 0x21, 0x90, 0x54, 0xd6, 0x04, 0x1a,
-            ],
-            "CPython codegen_pattern_mapping() returns to LOC(p) for BUILD_TUPLE/MATCH_KEYS scaffolding"
-        );
-    }
-
     #[test]
     fn match_mapping_rest_cleanup_uses_mapping_location_like_cpython() {
         let code = compile_exec(
@@ -18427,29 +18489,6 @@ def f(x):
         }
     }
 
-    #[test]
-    fn match_class_scaffolding_uses_class_pattern_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(x):
-    match x:
-        case bool(z):
-            y = 0
-    return y, z
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x0a, 0x0b, 0xdc, 0x0d, 0x11, 0x8f, 0x57, 0x88, 0x57, 0xd8, 0x10,
-                0x11, 0x88, 0x41, 0xd8, 0x0b, 0x0c, 0x88, 0x34, 0x80, 0x4b, 0xf0, 0x05, 0x00, 0x0e,
-                0x15, 0xe0, 0x0b, 0x0c, 0x88, 0x61, 0x88, 0x34, 0x80, 0x4b,
-            ],
-            "CPython codegen_pattern_class() returns to LOC(p) after VISIT(cls)"
-        );
-    }
-
     #[test]
     fn match_class_wildcard_pop_uses_class_pattern_location_like_cpython() {
         let code = compile_exec(
@@ -18547,7 +18586,7 @@ def f(waiters):
                 [
                     Instruction::LoadFastBorrow { .. } | Instruction::LoadFast { .. },
                     Instruction::LoadAttr { .. },
-                    Instruction::LoadConst { .. },
+                    Instruction::LoadCommonConstant { .. },
                     Instruction::Call { .. },
                 ]
             )),
@@ -18873,77 +18912,6 @@ x = 1 or 2 or 3
         );
     }
 
-    #[test]
-    fn taken_constant_boolop_load_const_uses_literal_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def and_false(x):
-    return False and x
-
-def or_true(x):
-    return True or x
-",
-        );
-        let and_false = find_code(&code, "and_false").expect("missing and_false code");
-        let or_true = find_code(&code, "or_true").expect("missing or_true code");
-
-        // CPython 3.14 codegen_boolop() VISITs the selected literal before the
-        // short-circuit jump is optimized away, so the surviving LOAD_CONST
-        // keeps the literal range rather than the whole BoolOp range.
-        assert_eq!(
-            and_false.linetable.as_ref(),
-            &[0x80, 0x00, 0xd8, 0x0b, 0x10, 0xd0, 0x04, 0x16]
-        );
-        assert_eq!(
-            or_true.linetable.as_ref(),
-            &[0x80, 0x00, 0xd8, 0x0b, 0x0f, 0xd0, 0x04, 0x14]
-        );
-    }
-
-    #[test]
-    fn assert_false_message_call_uses_assert_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f():
-    assert False, \"x\"
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-
-        // CPython 3.14 codegen_assert() emits LOAD_COMMON_CONSTANT and CALL
-        // at LOC(assert statement), then RAISE_VARARGS at LOC(test).
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x04, 0x15, 0x90, 0x23, 0xd3, 0x04, 0x15, 0x88, 0x35,
-            ]
-        );
-    }
-
-    #[test]
-    fn static_swap_implicit_return_keeps_preswap_store_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(a, b):
-    a, b = a, b
-    b, a = a, b
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-
-        // CPython 3.14 flowgraph.c resolves line numbers before
-        // optimize_basic_block() turns BUILD_TUPLE/UNPACK_SEQUENCE into SWAP
-        // and apply_static_swaps() reorders the STORE_FAST pair.  The
-        // synthetic return epilogue therefore keeps the pre-swap final store
-        // location.
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x0b, 0x0c, 0x80, 0x71, 0xd8, 0x0b, 0x0c, 0x82, 0x71,
-            ]
-        );
-    }
-
     #[test]
     fn unpack_store_pair_jump_uses_second_target_location_like_cpython() {
         let code = compile_exec(
@@ -19055,169 +19023,6 @@ def f(flag, n, exp):
         assert_eq!(jump_position, (3, 12, 3, 13));
     }
 
-    #[test]
-    fn genexpr_make_closure_and_call_use_genexpr_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(parameters):
-    return ((p, type(p)) for p in parameters)
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-        let genexpr = find_code(f, "<genexpr>").expect("missing genexpr code");
-
-        // CPython 3.14 codegen_comprehension() uses LOC(e) for
-        // codegen_make_closure(), the outer CALL, and the implicit .0 load
-        // in codegen_sync_comprehension_generator().
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd9, 0x0b, 0x2d, 0xa1, 0x2a, 0xd3, 0x0b, 0x2d, 0xd0, 0x04, 0x2d,
-            ]
-        );
-        assert_eq!(
-            genexpr.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x0b, 0x2d, 0xa1, 0x2a, 0x98, 0x51, 0x94, 0x04, 0x90,
-                0x51, 0x93, 0x07, 0x8d, 0x4c, 0xa3, 0x2a, 0xf9,
-            ]
-        );
-    }
-
-    #[test]
-    fn implicit_call_genexpr_range_includes_call_parens_like_cpython() {
-        let code = compile_exec(
-            "\
-def implicit():
-    return list(x for x in range(10))
-
-def explicit():
-    return list((x for x in range(10)))
-",
-        );
-        let implicit = find_code(&code, "implicit").expect("missing implicit code");
-        let implicit_gen = find_code(implicit, "<genexpr>").expect("missing implicit genexpr code");
-        let explicit = find_code(&code, "explicit").expect("missing explicit code");
-        let explicit_gen = find_code(explicit, "<genexpr>").expect("missing explicit genexpr code");
-
-        // CPython's parser gives an unparenthesized sole GeneratorExp call
-        // argument the call-parenthesized range, and codegen_comprehension()
-        // uses LOC(e) for MAKE_FUNCTION, the outer CALL, and the implicit .0
-        // LOAD_FAST.  Explicitly parenthesized genexprs already carry their own
-        // parentheses and must not be widened again.
-        assert_eq!(
-            implicit.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdc, 0x0b, 0x0f, 0xd1, 0x0f, 0x25, 0x9c, 0x35, 0xa0, 0x12, 0x9c, 0x39,
-                0xd3, 0x0f, 0x25, 0xd3, 0x0b, 0x25, 0xd0, 0x04, 0x25,
-            ]
-        );
-        assert_eq!(
-            implicit_gen.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x0f, 0x25, 0x99, 0x39, 0x90, 0x61, 0x94, 0x01, 0x9b,
-                0x39, 0xf9,
-            ]
-        );
-        assert_eq!(
-            explicit_gen.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x10, 0x26, 0x99, 0x49, 0x90, 0x71, 0x94, 0x11, 0x9b,
-                0x49, 0xf9,
-            ]
-        );
-    }
-
-    #[test]
-    fn implicit_call_genexpr_parenthesized_element_range_like_cpython() {
-        let code = compile_exec(
-            "\
-def bytes_binop():
-    return bytes((x ^ 0x5C) for x in range(256))
-
-def dict_tuple(d):
-    return dict((v, k) for (k, v) in d.items())
-
-def plain_tuple_elt(xs):
-    return list((x, y) for x, y in xs)
-
-def explicit_gen(xs):
-    return list(((x, y) for x, y in xs))
-",
-        );
-        let bytes_binop = find_code(&code, "bytes_binop").expect("missing bytes_binop code");
-        let bytes_gen = find_code(bytes_binop, "<genexpr>").expect("missing bytes genexpr code");
-        let dict_tuple = find_code(&code, "dict_tuple").expect("missing dict_tuple code");
-        let dict_gen = find_code(dict_tuple, "<genexpr>").expect("missing dict genexpr code");
-        let plain_tuple_elt =
-            find_code(&code, "plain_tuple_elt").expect("missing plain_tuple_elt code");
-        let plain_gen =
-            find_code(plain_tuple_elt, "<genexpr>").expect("missing plain genexpr code");
-        let explicit_gen = find_code(&code, "explicit_gen").expect("missing explicit_gen code");
-        let explicit_inner =
-            find_code(explicit_gen, "<genexpr>").expect("missing explicit genexpr code");
-
-        // CPython 3.14's parser includes the call argument parentheses in
-        // LOC(GeneratorExp) for implicit sole-argument generator expressions,
-        // even when the element expression itself starts with parentheses.
-        assert_eq!(
-            bytes_binop.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdc, 0x0b, 0x10, 0xd1, 0x10, 0x30, 0xa4, 0x55, 0xa8, 0x33, 0xa4, 0x5a,
-                0xd3, 0x10, 0x30, 0xd3, 0x0b, 0x30, 0xd0, 0x04, 0x30,
-            ]
-        );
-        assert_eq!(
-            bytes_gen.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x10, 0x30, 0xa1, 0x5a, 0xa0, 0x01, 0x90, 0x64, 0x97,
-                0x28, 0x92, 0x28, 0xa3, 0x5a, 0xf9,
-            ]
-        );
-        assert_eq!(
-            dict_tuple.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdc, 0x0b, 0x0f, 0xd1, 0x0f, 0x2f, 0xa0, 0x51, 0xa7, 0x57, 0xa1, 0x57,
-                0xa4, 0x59, 0xd3, 0x0f, 0x2f, 0xd3, 0x0b, 0x2f, 0xd0, 0x04, 0x2f,
-            ]
-        );
-        assert_eq!(
-            dict_gen.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x0f, 0x2f, 0xa1, 0x59, 0x99, 0x36, 0x98, 0x41, 0x90,
-                0x11, 0x95, 0x06, 0xa3, 0x59, 0xf9,
-            ]
-        );
-        assert_eq!(
-            plain_tuple_elt.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdc, 0x0b, 0x0f, 0xd1, 0x0f, 0x26, 0xa1, 0x32, 0xd3, 0x0f, 0x26, 0xd3,
-                0x0b, 0x26, 0xd0, 0x04, 0x26,
-            ]
-        );
-        assert_eq!(
-            plain_gen.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x0f, 0x26, 0xa1, 0x32, 0x99, 0x34, 0x98, 0x31, 0x90,
-                0x11, 0x95, 0x06, 0xa3, 0x32, 0xf9,
-            ]
-        );
-        assert_eq!(
-            explicit_gen.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdc, 0x0b, 0x0f, 0xd1, 0x10, 0x27, 0xa1, 0x42, 0xd3, 0x10, 0x27, 0xd3,
-                0x0b, 0x28, 0xd0, 0x04, 0x28,
-            ]
-        );
-        assert_eq!(
-            explicit_inner.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x10, 0x27, 0xa1, 0x42, 0x99, 0x44, 0x98, 0x41, 0x90,
-                0x21, 0x95, 0x16, 0xa3, 0x42, 0xf9,
-            ]
-        );
-    }
-
     #[test]
     fn implicit_call_genexpr_operator_element_range_like_cpython() {
         // The element opens with a parenthesized group that the rest of the
@@ -19232,14 +19037,14 @@ def f(p, q):
         let f = find_code(&code, "f").expect("missing f code");
         let genexpr = find_code(f, "<genexpr>").expect("missing genexpr code");
 
-        // Columns are one-based here, so these are `dis`'s 14..56.
+        // MAKE_FUNCTION keeps the genexpr range; eager .0 acquisition uses the iterable range.
         assert_eq!(
             instruction_range(f, |op| matches!(op, Instruction::MakeFunction)),
             Some((2, 15, 2, 57))
         );
         assert_eq!(
             instruction_range(genexpr, |op| matches!(op, Instruction::LoadFast { .. })),
-            Some((2, 15, 2, 57))
+            Some((2, 47, 2, 56))
         );
     }
 
@@ -19261,7 +19066,12 @@ w = f'' 'a' f''
             .instructions
             .iter()
             .zip(&code.locations)
-            .filter(|(unit, _)| matches!(unit.op, Instruction::LoadConst { .. }))
+            .filter(|(unit, _)| {
+                matches!(unit.op, Instruction::LoadConst { .. })
+                    || matches!(unit.op, Instruction::LoadCommonConstant { idx }
+                        if idx.get(OpArg::new(u32::from(u8::from(unit.arg))))
+                            == bytecode::CommonConstant::EmptyStr)
+            })
             .map(|(_, locations)| location_range(locations))
             .take(4)
             .collect();
@@ -19273,71 +19083,6 @@ w = f'' 'a' f''
         );
     }
 
-    #[test]
-    fn genexpr_filter_cleanup_jumps_use_element_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def simple(names):
-    return (x for x in names if not _ishidden(x))
-
-def boolop(fields):
-    return (f for f in fields if f.init and not f.kw_only)
-",
-        );
-        let simple = find_code(&code, "simple").expect("missing simple code");
-        let simple_gen = find_code(simple, "<genexpr>").expect("missing simple genexpr code");
-        let boolop = find_code(&code, "boolop").expect("missing boolop code");
-        let boolop_gen = find_code(boolop, "<genexpr>").expect("missing boolop genexpr code");
-
-        // codegen_sync_comprehension_generator() emits the
-        // comprehension guard jump to if_cleanup, then emits the if_cleanup
-        // backedge with elt_loc. flowgraph.c::jump_thread() copies that target
-        // jump location to the threaded POP_JUMP/NOT_TAKEN cleanup path.
-        assert_eq!(
-            simple_gen.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x0b, 0x31, 0x91, 0x75, 0x90, 0x21, 0xa4, 0x49, 0xa8,
-                0x61, 0xa7, 0x4c, 0x8f, 0x41, 0x8a, 0x41, 0x93, 0x75, 0xf9,
-            ]
-        );
-        assert_eq!(
-            boolop_gen.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd0, 0x0b, 0x3a, 0x91, 0x76, 0x90, 0x21, 0xa7, 0x16, 0xa5,
-                0x16, 0x8c, 0x41, 0xb0, 0x01, 0xb7, 0x09, 0xb5, 0x09, 0x8f, 0x41, 0x8a, 0x41, 0x93,
-                0x76, 0xf9,
-            ]
-        );
-    }
-
-    #[test]
-    fn try_finally_exception_scaffolding_uses_no_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(self, node):
-    self.flag = True
-    try:
-        self.body(node)
-    finally:
-        self.flag = False
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-
-        // codegen_try_finally() emits the exception path
-        // SETUP_CLEANUP/PUSH_EXC_INFO and POP_EXCEPT_AND_RERAISE with
-        // NO_LOCATION; flowgraph line propagation then gives only the
-        // finalbody's direct RERAISE the finalbody location.
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x10, 0x14, 0x80, 0x44, 0x84, 0x49, 0xf0, 0x02, 0x03, 0x05, 0x1a,
-                0xd8, 0x08, 0x0c, 0x8f, 0x09, 0x89, 0x09, 0x90, 0x24, 0x8c, 0x0f, 0xe0, 0x14, 0x19,
-                0x88, 0x04, 0x8e, 0x09, 0xf8, 0x90, 0x45, 0x88, 0x04, 0x8d, 0x09, 0xfa,
-            ]
-        );
-    }
-
     #[test]
     fn return_debug_in_finally_uses_cpython_preprocessed_constant_order() {
         let code = compile_exec(
@@ -19359,11 +19104,10 @@ def f(close):
             .instructions
             .iter()
             .position(|unit| {
-                let Instruction::LoadConst { consti } = unit.op else {
+                let Instruction::LoadCommonConstant { idx } = unit.op else {
                     return false;
                 };
-                let constant = &f.constants[consti.get(OpArg::new(u32::from(u8::from(unit.arg))))];
-                matches!(constant, ConstantData::Boolean { value: true })
+                idx.get(OpArg::new(u32::from(u8::from(unit.arg)))) == bytecode::CommonConstant::True
             })
             .expect("missing __debug__ constant load");
 
@@ -19464,76 +19208,6 @@ def f(close):
         );
     }
 
-    #[test]
-    fn adjacent_no_location_entries_merge_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(file):
-    if sys.platform == \"win32\":
-        try:
-            import nt
-            if not nt._supports_virtual_terminal():
-                return False
-        except (ImportError, AttributeError):
-            return False
-    try:
-        return os.isatty(file.fileno())
-    except OSError:
-        return hasattr(file, \"isatty\") and file.isatty()
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-
-        // CPython's NO_LOCATION is {-1, -1, -1, -1}, and
-        // assemble.c::assemble_location_info() merges adjacent instructions
-        // with the same NO_LOCATION into one linetable entry.
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdc, 0x07, 0x0a, 0x87, 0x7c, 0x81, 0x7c, 0x90, 0x77, 0xd4, 0x07, 0x1e,
-                0xf0, 0x02, 0x05, 0x09, 0x19, 0xdb, 0x0c, 0x15, 0xd8, 0x13, 0x15, 0xd7, 0x13, 0x30,
-                0xd1, 0x13, 0x30, 0xd7, 0x13, 0x32, 0xd2, 0x13, 0x32, 0xd9, 0x17, 0x1c, 0xf0, 0x03,
-                0x00, 0x14, 0x33, 0xf0, 0x08, 0x03, 0x05, 0x39, 0xdc, 0x0f, 0x11, 0x8f, 0x79, 0x89,
-                0x79, 0x98, 0x14, 0x9f, 0x1b, 0x99, 0x1b, 0x9b, 0x1d, 0xd3, 0x0f, 0x27, 0xd0, 0x08,
-                0x27, 0xf8, 0xf4, 0x07, 0x00, 0x11, 0x1c, 0x9c, 0x5e, 0xd0, 0x0f, 0x2c, 0xf4, 0x00,
-                0x01, 0x09, 0x19, 0xda, 0x13, 0x18, 0xf0, 0x03, 0x01, 0x09, 0x19, 0xfb, 0xf4, 0x08,
-                0x00, 0x0c, 0x13, 0xf4, 0x00, 0x01, 0x05, 0x39, 0xdc, 0x0f, 0x16, 0x90, 0x74, 0x98,
-                0x58, 0xd3, 0x0f, 0x26, 0xd7, 0x0f, 0x38, 0xd0, 0x0f, 0x38, 0xa8, 0x34, 0xaf, 0x3b,
-                0xa9, 0x3b, 0xab, 0x3d, 0xd2, 0x08, 0x38, 0xf0, 0x03, 0x01, 0x05, 0x39, 0xfa,
-            ]
-        );
-    }
-
-    #[test]
-    fn fstring_format_ops_use_formatted_value_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def simple(self):
-    return f'{self.value}'
-
-def spec(x):
-    return f'{x!r:>3}'
-",
-        );
-        let simple = find_code(&code, "simple").expect("missing simple code");
-        let spec = find_code(&code, "spec").expect("missing spec code");
-
-        // CPython 3.14 codegen_formatted_value() VISITs the inner expression
-        // first, then emits CONVERT_VALUE / FORMAT_* at LOC(FormattedValue).
-        assert_eq!(
-            simple.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x0e, 0x12, 0x8f, 0x6a, 0x89, 0x6a, 0x88, 0x5c, 0xd0, 0x04, 0x1a,
-            ]
-        );
-        assert_eq!(
-            spec.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x0e, 0x0f, 0x88, 0x58, 0x90, 0x22, 0x88, 0x58, 0xd0, 0x04, 0x16,
-            ]
-        );
-    }
-
     #[test]
     fn debug_fstring_literal_merging_and_location_like_cpython() {
         fn string_load_position(code: &CodeObject, expected: &str) -> (usize, usize, usize, usize) {
@@ -19631,29 +19305,6 @@ def padded(digits, int_len):
         );
     }
 
-    #[test]
-    fn joined_string_literals_extend_pending_literal_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def f(a):
-    return (
-        'x'
-        f'y{a}z'
-        'w'
-    )
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xf0, 0x04, 0x01, 0x09, 0x0c, 0xd8, 0x0c, 0x0d, 0x88, 0x33, 0xf0, 0x00,
-                0x01, 0x0f, 0x0c, 0xf0, 0x03, 0x02, 0x09, 0x0c, 0xf0, 0x03, 0x04, 0x05, 0x06,
-            ],
-            "CPython parser/codegen represents adjacent f-string literal fragments as Constant ranges spanning the merged fragments"
-        );
-    }
-
     #[test]
     fn starred_call_preserves_bool_op_short_circuit_shape() {
         let code = compile_exec(
@@ -19726,60 +19377,6 @@ def outer(null):
         );
     }
 
-    #[test]
-    fn decorated_definitions_use_cpython_locations() {
-        let code = compile_exec(
-            "\
-def dec(f): return f
-
-class C:
-    @dec
-    def f(self):
-        yield
-
-@dec
-class D:
-    pass
-
-class E:
-    @dec
-    def g(self, flags: int, /) -> memoryview:
-        raise NotImplementedError
-",
-        );
-        let c = find_code(&code, "C").expect("missing C code");
-        let d = find_code(&code, "D").expect("missing D code");
-        let e = find_code(&code, "E").expect("missing E code");
-        let annotate = find_code(e, "__annotate__").expect("missing annotation code");
-
-        // CPython 3.14 codegen_function()/codegen_class() evaluate
-        // decorators first, then use LOC(s) for codegen_make_closure() and
-        // codegen_nameop(); codegen_apply_decorators() emits CALL at each
-        // decorator expression's location.
-        assert_eq!(
-            c.linetable.as_ref(),
-            &[
-                0xf8, 0x87, 0x00, 0x80, 0x00, 0xd8, 0x05, 0x08, 0xf1, 0x02, 0x01, 0x05, 0x0e, 0xf3,
-                0x03, 0x00, 0x06, 0x09, 0xf6, 0x02, 0x01, 0x05, 0x0e,
-            ]
-        );
-        assert_eq!(d.linetable.as_ref(), &[0x86, 0x00, 0xe3, 0x04, 0x08]);
-        assert_eq!(
-            e.linetable.as_ref(),
-            &[
-                0xf8, 0x87, 0x00, 0x80, 0x00, 0xd8, 0x05, 0x08, 0xf7, 0x02, 0x01, 0x05, 0x22, 0xf3,
-                0x03, 0x00, 0x06, 0x09, 0xf6, 0x02, 0x01, 0x05, 0x22,
-            ]
-        );
-        assert_eq!(
-            annotate.linetable.as_ref(),
-            &[
-                0xf8, 0x80, 0x00, 0xf7, 0x00, 0x01, 0x05, 0x22, 0xf1, 0x00, 0x01, 0x05, 0x22, 0x91,
-                0x73, 0xf0, 0x00, 0x01, 0x05, 0x22, 0xa1, 0x2a, 0xf1, 0x00, 0x01, 0x05, 0x22,
-            ]
-        );
-    }
-
     #[test]
     fn taken_constant_boolop_jump_disables_following_borrows() {
         for source in [
@@ -20134,7 +19731,7 @@ x = +0.0j
                     Instruction::Resume { .. },
                     Instruction::LoadConst { .. },
                     Instruction::StoreName { .. },
-                    Instruction::LoadConst { .. },
+                    Instruction::LoadCommonConstant { .. },
                     Instruction::ReturnValue
                 ]
             ),
@@ -20556,74 +20153,25 @@ def outer(log):
     }
 
     #[test]
-    fn builtin_any_genexpr_call_is_optimized() {
-        let code = compile_exec(
-            "\
-def f(xs):
-    return any(x for x in xs)
-",
-        );
-        let f = find_code(&code, "f").expect("missing function code");
-
-        assert!(has_common_constant(f, bytecode::CommonConstant::BuiltinAny));
-        assert!(
-            f.instructions
-                .iter()
-                .any(|unit| matches!(unit.op, Instruction::PopJumpIfTrue { .. }))
-        );
-        assert!(
-            f.instructions
-                .iter()
-                .any(|unit| matches!(unit.op, Instruction::NotTaken))
-        );
-        assert_eq!(
-            f.instructions
-                .iter()
-                .filter(|unit| matches!(unit.op, Instruction::PushNull))
-                .count(),
-            1,
-            "fallback call path should remain for shadowed any()"
-        );
-        let genexpr_const_count = f
-            .constants
-            .iter()
-            .filter(|constant| {
-                matches!(constant, ConstantData::Code { code } if code.obj_name == "<genexpr>")
-            })
-            .count();
-        assert_eq!(
-            genexpr_const_count, 1,
-            "optimized and fallback any(genexpr) paths should share the same CPython-range code const"
-        );
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdf, 0x0b, 0x0e, 0x8b, 0x33, 0x89, 0x6f, 0x99, 0x22, 0x8b, 0x6f, 0x8f,
-                0x33, 0x8c, 0x33, 0xd0, 0x04, 0x1d, 0x8a, 0x33, 0xd0, 0x04, 0x1d, 0x88, 0x33, 0x89,
-                0x6f, 0x99, 0x22, 0x8b, 0x6f, 0xd3, 0x0b, 0x1d, 0xd0, 0x04, 0x1d,
-            ]
-        );
-    }
-
-    #[test]
-    fn builtin_any_async_genexpr_call_is_optimized_like_cpython() {
+    fn builtin_any_async_genexpr_call_is_not_optimized_like_cpython() {
         for source in [
             "async def f(xs):\n    return any(x async for x in xs)\n",
             "async def f(xs):\n    return any(await x for x in xs)\n",
+            "async def f(xs):\n    return any(x async for x in (lambda: xs)())\n",
+            "async def f(xs):\n    return any(await x for x in (y for y in xs))\n",
         ] {
             let code = compile_exec(source);
             let f = find_code(&code, "f").expect("missing function code");
 
             assert!(
-                has_common_constant(f, bytecode::CommonConstant::BuiltinAny),
-                "maybe_optimize_function_call() guards any(genexpr) whether or not the \
-                 generator is a coroutine: {source}"
+                !has_common_constant(f, bytecode::CommonConstant::BuiltinAny),
+                "coroutine generator expressions must use the ordinary call path: {source}"
             );
             assert!(
-                f.instructions
+                !f.instructions
                     .iter()
                     .any(|unit| matches!(unit.op, Instruction::ForIter { .. })),
-                "the guarded path inlines the loop: {source}"
+                "the ordinary call path must not inline an async generator loop: {source}"
             );
             assert!(
                 f.instructions
@@ -20650,72 +20198,6 @@ async def f(get_xs):
         );
     }
 
-    #[test]
-    fn builtin_tuple_genexpr_call_is_optimized_but_list_set_are_not() {
-        let code = compile_exec(
-            "\
-def tuple_f(xs):
-    return tuple(x for x in xs)
-
-def list_f(xs):
-    return list(x for x in xs)
-
-def set_f(xs):
-    return set(x for x in xs)
-",
-        );
-
-        let tuple_f = find_code(&code, "tuple_f").expect("missing tuple_f code");
-        assert!(has_common_constant(
-            tuple_f,
-            bytecode::CommonConstant::BuiltinTuple
-        ));
-        assert!(has_intrinsic_1(tuple_f, IntrinsicFunction1::ListToTuple));
-        let tuple_list_append = tuple_f
-            .instructions
-            .iter()
-            .find_map(|unit| match unit.op {
-                Instruction::ListAppend { .. } => Some(u32::from(u8::from(unit.arg))),
-                _ => None,
-            })
-            .expect("tuple(genexpr) fast path should emit LIST_APPEND");
-        assert_eq!(tuple_list_append, 2);
-        assert_eq!(
-            tuple_f.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xdf, 0x0b, 0x10, 0x8c, 0x35, 0x91, 0x0f, 0x99, 0x42, 0x93, 0x0f, 0x8f,
-                0x35, 0xd0, 0x04, 0x1f, 0x88, 0x35, 0x91, 0x0f, 0x99, 0x42, 0x93, 0x0f, 0xd3, 0x0b,
-                0x1f, 0xd0, 0x04, 0x1f,
-            ]
-        );
-
-        let list_f = find_code(&code, "list_f").expect("missing list_f code");
-        assert!(
-            list_f
-                .instructions
-                .iter()
-                .any(|unit| matches!(unit.op, Instruction::Call { .. })),
-            "list(genexpr) should stay on the normal call path"
-        );
-        assert!(
-            !has_common_constant(list_f, bytecode::CommonConstant::BuiltinList),
-            "CPython 3.14.5 does not optimize list(genexpr)"
-        );
-
-        let set_f = find_code(&code, "set_f").expect("missing set_f code");
-        assert!(
-            set_f
-                .instructions
-                .iter()
-                .any(|unit| matches!(unit.op, Instruction::Call { .. })),
-            "set(genexpr) should stay on the normal call path"
-        );
-        assert!(
-            !has_common_constant(set_f, bytecode::CommonConstant::BuiltinSet),
-            "CPython 3.14.5 does not optimize set(genexpr)"
-        );
-    }
-
     #[test]
     fn builtin_tuple_genexpr_try_assignment_uses_shared_tail() {
         let code = compile_exec(
@@ -20868,6 +20350,54 @@ class C:
         }));
     }
 
+    fn find_module_doc_store(code: &CodeObject) -> Option<&Instruction> {
+        code.instructions.iter().find_map(|unit| match unit.op {
+            Instruction::StoreName { namei } | Instruction::StoreGlobal { namei } => {
+                let idx = namei.get(OpArg::new(u32::from(u8::from(unit.arg))));
+                (code.names[usize::try_from(idx).unwrap()].as_str() == "__doc__")
+                    .then_some(&unit.op)
+            }
+            _ => None,
+        })
+    }
+
+    #[test]
+    fn module_docstring_store_uses_global_when_nested_scope_declares_global() {
+        let code = compile_exec(
+            "\
+\"module doc\"
+def f():
+    global __doc__
+",
+        );
+
+        let op = find_module_doc_store(&code).expect("missing module docstring store");
+        assert!(
+            matches!(op, Instruction::StoreGlobal { .. }),
+            "module docstring store should resolve through name resolution to StoreGlobal \
+             when a nested scope declares `global __doc__`, got instructions={:?}",
+            code.instructions
+        );
+    }
+
+    #[test]
+    fn module_docstring_store_stays_name_without_nested_global() {
+        let code = compile_exec(
+            "\
+\"module doc\"
+x = 1
+",
+        );
+
+        let op = find_module_doc_store(&code).expect("missing module docstring store");
+        assert!(
+            matches!(op, Instruction::StoreName { .. }),
+            "module docstring store should remain StoreName without a nested \
+             `global __doc__` declaration, got instructions={:?}",
+            code.instructions
+        );
+    }
+
     #[test]
     fn conditional_return_epilogue_is_duplicated() {
         let code = compile_exec(
@@ -20964,7 +20494,7 @@ def f(cache, lock, format):
                         Instruction::LoadFastLoadFast { .. },
                         Instruction::LoadFast { .. },
                         Instruction::StoreSubscr,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -21106,27 +20636,6 @@ def aug(x, a, b, y):
         );
     }
 
-    #[test]
-    fn augassign_constant_slice_copy_uses_subscript_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def aug_const(x, y):
-    x[1:2] += y
-",
-        );
-        let aug_const = find_code(&code, "aug_const").expect("missing aug_const code");
-
-        // CPython 3.14 codegen_augassign() visits a constant slice, then emits
-        // COPY/COPY/BINARY_OP NB_SUBSCR at LOC(target), not at LOC(slice).
-        assert_eq!(
-            aug_const.linetable.as_ref(),
-            &[
-                0x80, 0x00, 0xd8, 0x04, 0x05, 0x80, 0x63, 0x87, 0x46, 0x88, 0x61, 0x85, 0x4b, 0x85,
-                0x46,
-            ]
-        );
-    }
-
     #[test]
     fn augassign_attribute_copy_uses_target_location_like_cpython() {
         let code = compile_exec(
@@ -21181,7 +20690,7 @@ def f(obj):
             .filter(|op| !matches!(op, Instruction::Cache))
             .collect();
 
-        let has_cpython_shape = ops.windows(7).any(|window| {
+        let has_cpython_shape = ops.windows(8).any(|window| {
             matches!(
                 window,
                 [
@@ -21191,6 +20700,7 @@ def f(obj):
                     Instruction::LoadFastBorrow { .. } | Instruction::LoadFast { .. },
                     Instruction::Swap { .. },
                     Instruction::PopTop,
+                    Instruction::PopTop,
                     Instruction::ReturnValue,
                 ]
             )
@@ -21565,7 +21075,7 @@ def f(self, exc_type, KeyboardInterrupt, TimeoutExpired):
                         Instruction::LoadSmallInt { .. },
                         Instruction::LoadFastBorrow { .. },
                         Instruction::StoreAttr { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::ReturnValue,
                     ]
                 )
@@ -21705,7 +21215,7 @@ def f(locale, category, locales):
                         Instruction::RaiseVarargs { .. },
                         Instruction::Nop,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::YieldValue { .. },
                     ]
                 )
@@ -21852,18 +21362,19 @@ def f(parts):
         );
 
         let break_cleanup_idx = ops
-            .windows(3)
+            .windows(4)
             .position(|window| {
                 matches!(
                     window,
                     [
                         Instruction::PopTop,
-                        Instruction::LoadConst { .. },
+                        Instruction::PopTop,
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::ReturnValue
                     ]
                 )
             })
-            .expect("missing POP_TOP/LOAD_CONST/RETURN_VALUE break cleanup");
+            .expect("missing POP_TOP/POP_TOP/LOAD_COMMON_CONSTANT/RETURN_VALUE break cleanup");
         let end_for_idx = ops
             .iter()
             .position(|op| matches!(op, Instruction::EndFor))
@@ -21903,7 +21414,7 @@ elif maxsize == 9223372036854775807:
                     [
                         Instruction::EndFor,
                         Instruction::PopIter,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::ReturnValue,
                     ]
                 )
@@ -21918,7 +21429,7 @@ elif maxsize == 9223372036854775807:
                         Instruction::EndFor,
                         Instruction::PopIter,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -22569,7 +22080,7 @@ def f(self, file, backupfilename):
                     ],
                     [
                         Instruction::PopExcept,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::LoadFast { .. },
                         Instruction::StoreAttr { .. },
                         Instruction::Reraise { .. },
@@ -23063,15 +22574,9 @@ def f(x):
                 )
             })
             .expect("missing folded -0.0 match value");
-        let none_index = f
-            .constants
-            .iter()
-            .position(|constant| matches!(constant, ConstantData::None))
-            .expect("missing implicit None");
-        assert!(
-            negative_zero_index < none_index,
-            "CPython ast_preprocess.c folds MatchValue constants before codegen registers the implicit None"
-        );
+        assert_eq!(negative_zero_index, 0);
+        assert_eq!(f.constants.len(), 1);
+        assert!(has_common_constant(f, bytecode::CommonConstant::None));
     }
 
     #[test]
@@ -23158,7 +22663,7 @@ def f(x):
     }
 
     #[test]
-    fn match_mapping_attribute_key_keeps_plain_load_fast_without_block_disable() {
+    fn match_mapping_attribute_key_keeps_borrowed_load_fast_without_block_disable() {
         let code = compile_exec(
             "\
 def f(self):
@@ -23206,8 +22711,8 @@ def f(self):
             .expect("missing Keys.KEY attribute load");
         let prev = f.instructions[key_load_idx - 1].op;
         assert!(
-            matches!(prev, Instruction::LoadFast { .. }),
-            "CPython optimize_load_fast() records MATCH_KEYS' no-input pseudo-ref with the produced-value loop index, so this consumed Keys load stays strong; got ops={:?}",
+            matches!(prev, Instruction::LoadFastBorrow { .. }),
+            "CPython optimize_load_fast() records MATCH_KEYS' no-input pseudo-ref with the current instruction index, so this consumed Keys load is borrowed; got ops={:?}",
             f.instructions
                 .iter()
                 .map(|unit| unit.op)
@@ -23391,9 +22896,9 @@ def f(i):
                 matches!(
                     window,
                     [
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
                     ]
@@ -23590,9 +23095,9 @@ def f(cm):
                     [
                         (Instruction::DeleteFast { .. }, 6),
                         (Instruction::Nop, 6),
-                        (Instruction::LoadConst { .. }, 2),
-                        (Instruction::LoadConst { .. }, 2),
-                        (Instruction::LoadConst { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
                         (Instruction::Call { .. }, 2),
                     ]
                 )
@@ -23630,9 +23135,9 @@ def f(cm, names, modname):
                         Instruction::Call { .. },
                         Instruction::PopTop,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -23669,9 +23174,9 @@ def f(cm):
                     [
                         Instruction::StoreFast { .. },
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -23711,9 +23216,9 @@ def f(cm, func, check):
                         Instruction::Call { .. },
                         Instruction::PopTop,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -23758,9 +23263,9 @@ def f(meta_path, cm):
                         (Instruction::Call { .. }, 9),
                         (Instruction::StoreFast { .. }, 9),
                         (Instruction::Nop, 9),
-                        (Instruction::LoadConst { .. }, 3),
-                        (Instruction::LoadConst { .. }, 3),
-                        (Instruction::LoadConst { .. }, 3),
+                        (Instruction::LoadCommonConstant { .. }, 3),
+                        (Instruction::LoadCommonConstant { .. }, 3),
+                        (Instruction::LoadCommonConstant { .. }, 3),
                     ]
                 )
             }),
@@ -23845,9 +23350,9 @@ def f(cm):
                     [
                         Instruction::StoreFast { .. },
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -23860,9 +23365,9 @@ def f(cm):
                     window,
                     [
                         Instruction::StoreFast { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -23899,9 +23404,9 @@ def f(cm, ValueError):
                     window,
                     [
                         (Instruction::Nop, 6),
-                        (Instruction::LoadConst { .. }, 2),
-                        (Instruction::LoadConst { .. }, 2),
-                        (Instruction::LoadConst { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
                         (Instruction::Call { .. }, 2),
                     ]
                 )
@@ -23939,9 +23444,9 @@ def f(open, src, dst, copyfileobj):
                     [
                         Instruction::Call { .. },
                         Instruction::PopTop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
                     ]
@@ -23957,9 +23462,9 @@ def f(open, src, dst, copyfileobj):
                         Instruction::Call { .. },
                         Instruction::PopTop,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
                     ]
@@ -24722,9 +24227,9 @@ def f(selector, self):
                     [
                         (Instruction::JumpBackward { .. }, 4),
                         (Instruction::Nop, 3),
-                        (Instruction::LoadConst { .. }, 2),
-                        (Instruction::LoadConst { .. }, 2),
-                        (Instruction::LoadConst { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
+                        (Instruction::LoadCommonConstant { .. }, 2),
                         (Instruction::Call { .. }, 2),
                     ]
                 )
@@ -25868,7 +25373,7 @@ def f(part, lines, maxlen, encoding):
                     window,
                     [
                         Instruction::LoadFastBorrow { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreSubscr,
                     ]
                 )
@@ -25993,7 +25498,7 @@ def f(part, lines, maxlen, encoding):
                     window,
                     [
                         Instruction::LoadFastBorrow { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreSubscr,
                     ]
                 )
@@ -26925,11 +26430,23 @@ def f(fields):
                         Instruction::LoadFastBorrow { .. },
                         Instruction::LoadAttr { .. },
                         Instruction::Call { .. },
-                        Instruction::GetIter,
+                        Instruction::Call { .. },
                     ]
                 )
             }),
-            "expected plain attr-iter chain to keep borrowed receiver, got ops={ops:?}"
+            "expected plain attr-genexpr-call chain to keep borrowed receiver, got ops={ops:?}"
+        );
+        assert!(
+            !f.instructions
+                .iter()
+                .any(|unit| matches!(unit.op, Instruction::GetIter { .. }))
+        );
+        let genexpr = find_code(f, "<genexpr>").expect("missing genexpr");
+        assert!(
+            genexpr
+                .instructions
+                .iter()
+                .any(|unit| matches!(unit.op, Instruction::GetIter { .. }))
         );
     }
 
@@ -28078,15 +27595,20 @@ def bug():
         )
         .unwrap();
 
+        assert!(
+            entries
+                .iter()
+                .all(|entry| { not_taken_idx < entry.start || not_taken_idx >= entry.end })
+        );
         assert!(
             entries.iter().any(|entry| {
-                entry.start <= not_taken_idx
+                entry.start <= alias_store_idx
                     && alias_store_idx < entry.end
                     && entry.target == copy_idx
                     && entry.depth == 1
                     && entry.push_lasti
             }),
-            "CPython codegen_try_except() stores the exception alias before the inner SETUP_CLEANUP, so NOT_TAKEN and the alias store stay covered by the outer cleanup entry; entries={entries:?}, instructions={:?}",
+            "CPython codegen_try_except() stores the exception alias before the inner SETUP_CLEANUP, so the alias store stays covered by the outer cleanup entry; entries={entries:?}, instructions={:?}",
             bug.instructions
         );
     }
@@ -28447,7 +27969,7 @@ def f(self):
                 window,
                 [
                     Instruction::PopExcept,
-                    Instruction::LoadConst { .. },
+                    Instruction::LoadCommonConstant { .. },
                     Instruction::StoreName { .. } | Instruction::StoreFast { .. },
                     Instruction::DeleteName { .. } | Instruction::DeleteFast { .. },
                     Instruction::JumpForward { .. },
@@ -28898,7 +28420,13 @@ def f(cond, obj, xs, E):
             _ => None,
         };
 
-        for name in ["xs", "obj", "x"] {
+        assert!(normal_tail.iter().any(|unit| {
+            matches!(unit.op, Instruction::LoadFast { .. }) && load_name(unit) == Some("xs")
+        }));
+        assert!(!normal_tail.iter().any(|unit| {
+            matches!(unit.op, Instruction::LoadFastBorrow { .. }) && load_name(unit) == Some("xs")
+        }));
+        for name in ["obj", "x"] {
             assert!(
                 normal_tail
                     .iter()
@@ -29405,9 +28933,9 @@ def f(obj):
                 [
                     Instruction::Resume { .. },
                     Instruction::LoadFastBorrow { .. },
-                    Instruction::LoadConst { .. },
-                    Instruction::LoadConst { .. },
-                    Instruction::LoadConst { .. },
+                    Instruction::LoadCommonConstant { .. },
+                    Instruction::LoadCommonConstant { .. },
+                    Instruction::LoadCommonConstant { .. },
                     Instruction::BuildSlice { .. },
                     Instruction::BinaryOp { .. },
                     Instruction::ReturnValue,
@@ -29432,7 +28960,7 @@ def f(obj, step):
             .zip(&f.locations)
             .filter_map(|(unit, (location, end_location))| {
                 let op = match unit.op {
-                    Instruction::LoadConst { .. } => "LOAD_CONST",
+                    Instruction::LoadCommonConstant { .. } => "LOAD_CONST",
                     Instruction::BuildSlice { .. } => "BUILD_SLICE",
                     _ => return None,
                 };
@@ -29561,7 +29089,7 @@ def f(obj):
                     Instruction::Resume { .. },
                     Instruction::LoadFastBorrow { .. },
                     Instruction::LoadConst { .. },
-                    Instruction::LoadConst { .. },
+                    Instruction::LoadCommonConstant { .. },
                     Instruction::BinarySlice,
                     Instruction::ReturnValue,
                 ]
@@ -29727,9 +29255,9 @@ def f(self, xs, ys, cm1, cm2):
                     [
                         Instruction::EndFor,
                         Instruction::PopIter,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
                     ]
@@ -29745,9 +29273,9 @@ def f(self, xs, ys, cm1, cm2):
                         Instruction::EndFor,
                         Instruction::PopIter,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
                     ]
@@ -29775,15 +29303,9 @@ def f(p, s):
             .filter(|unit| {
                 matches!(
                     unit.op,
-                    Instruction::LoadConst { consti }
-                        if matches!(
-                            f.constants.get(
-                                consti
-                                    .get(OpArg::new(u32::from(u8::from(unit.arg))))
-                                    .as_usize()
-                            ),
-                            Some(ConstantData::Integer { value }) if value == &BigInt::from(-1)
-                        )
+                    Instruction::LoadCommonConstant { idx }
+                        if idx.get(OpArg::new(u32::from(u8::from(unit.arg))))
+                            == bytecode::CommonConstant::MinusOne
                 )
             })
             .count();
@@ -29816,18 +29338,21 @@ def f(xs):
             .collect();
 
         assert!(
-            units.windows(4).any(|window| {
+            units.windows(5).any(|window| {
                 matches!(
                     window[0].op,
-                    Instruction::LoadConst { .. } | Instruction::LoadSmallInt { .. }
+                    Instruction::LoadCommonConstant { idx }
+                        if idx.get(OpArg::new(u32::from(u8::from(window[0].arg))))
+                            == bytecode::CommonConstant::MinusOne
                 ) && matches!(
                     window[1].op,
                     Instruction::Swap { i }
-                        if i.get(OpArg::new(u32::from(u8::from(window[1].arg)))) == 2
+                        if i.get(OpArg::new(u32::from(u8::from(window[1].arg)))) == 3
                 ) && matches!(window[2].op, Instruction::PopTop)
-                    && matches!(window[3].op, Instruction::ReturnValue)
+                    && matches!(window[3].op, Instruction::PopTop)
+                    && matches!(window[4].op, Instruction::ReturnValue)
             }),
-            "expected CPython-style LOAD_CONST/SWAP/POP_TOP/RETURN_VALUE cleanup, got units={units:?}"
+            "expected CPython-style LOAD_COMMON_CONSTANT/SWAP 3/POP_TOP/POP_TOP/RETURN_VALUE cleanup, got units={units:?}"
         );
     }
 
@@ -29994,10 +29519,10 @@ def f(self):
                     window,
                     [
                         Instruction::PopExcept,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreFast { .. } | Instruction::StoreName { .. },
                         Instruction::DeleteFast { .. } | Instruction::DeleteName { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::ReturnValue,
                     ]
                 )
@@ -30038,10 +29563,10 @@ def f(onerror, err, OSError):
                     window,
                     [
                         Instruction::PopExcept,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreFast { .. } | Instruction::StoreName { .. },
                         Instruction::DeleteFast { .. } | Instruction::DeleteName { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::ReturnValue,
                     ]
                 )
@@ -30082,10 +29607,10 @@ def f(self, module_name, ModuleNotFoundError):
                     window,
                     [
                         Instruction::PopExcept,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreFast { .. } | Instruction::StoreName { .. },
                         Instruction::DeleteFast { .. } | Instruction::DeleteName { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::ReturnValue,
                     ]
                 )
@@ -30372,12 +29897,12 @@ def f(cm, registry, altkey):
                     window,
                     [
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::ReturnValue,
                     ]
                 )
@@ -30419,9 +29944,9 @@ def f(a, b, path):
                         Instruction::PopExcept,
                         Instruction::Reraise { .. },
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -30625,7 +30150,7 @@ def f(self, logger):
                     [
                         Instruction::PopTop,
                         Instruction::PopExcept,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreFast { .. },
                         Instruction::DeleteFast { .. },
                         Instruction::JumpBackwardNoInterrupt { .. },
@@ -32200,7 +31725,7 @@ def f():
     }
 
     #[test]
-    fn constant_list_iterable_uses_tuple() {
+    fn constant_list_iterable_keeps_list_before_saved_locals() {
         let code = compile_exec(
             "\
 def f():
@@ -32209,26 +31734,17 @@ def f():
         );
         let f = find_code(&code, "f").expect("missing function code");
 
-        assert!(
-            !f.instructions
-                .iter()
-                .any(|unit| matches!(unit.op, Instruction::BuildList { .. })),
-            "constant list iterable should avoid BUILD_LIST before GET_ITER"
-        );
+        assert!(f.instructions.iter().any(|unit| {
+            matches!(unit.op, Instruction::BuildList { count }
+                if count.get(OpArg::new(u32::from(u8::from(unit.arg)))) == 1)
+        }));
         assert!(f.constants.iter().any(|constant| matches!(
             constant,
             ConstantData::Tuple { elements }
-                if matches!(
-                    elements.as_slice(),
-                    [ConstantData::Tuple { elements: inner }]
-                        if matches!(
-                            inner.as_slice(),
-                            [
-                                ConstantData::Integer { .. },
-                                ConstantData::Integer { .. }
-                            ]
-                        )
-                )
+                if matches!(elements.as_slice(), [
+                    ConstantData::Integer { value: first },
+                    ConstantData::Integer { value: second },
+                ] if first == &BigInt::from(1) && second == &BigInt::from(2))
         )));
     }
 
@@ -32248,9 +31764,9 @@ def f():
             matches!(constants[0], ConstantData::Str { value } if value.to_string() == "a"),
             "CPython emits list elements as LOAD_CONST before flowgraph folds GET_ITER lists"
         );
-        assert!(matches!(constants[1], ConstantData::None));
+        assert_eq!(constants.len(), 2);
         assert!(matches!(
-            constants[2],
+            constants[1],
             ConstantData::Tuple { elements }
                 if matches!(
                     elements.as_slice(),
@@ -32470,18 +31986,17 @@ def f(g, kwargs, ns):
         );
         let f = find_code(&code, "f").expect("missing function code");
         let constants = f.constants.iter().collect::<Vec<_>>();
-        assert_eq!(constants.len(), 3);
+        assert_eq!(constants.len(), 2);
 
         assert!(
             matches!(constants[0], ConstantData::Str { value } if value.to_string() == "T")
-                && matches!(constants[1], ConstantData::None)
-                && matches!(constants[2], ConstantData::Tuple { elements } if elements.is_empty()),
+                && matches!(constants[1], ConstantData::Tuple { elements } if elements.is_empty()),
             "CPython emits BUILD_TUPLE 0 for CALL_FUNCTION_EX args and folds it after earlier constants"
         );
     }
 
     #[test]
-    fn large_constant_list_iterable_keeps_streaming_list_build() {
+    fn large_constant_list_iterable_folds_to_tuple_like_cpython() {
         let source = format!(
             "def f():\n    for x in [{}]:\n        pass\n",
             (0..=STACK_USE_GUIDELINE)
@@ -32492,19 +32007,47 @@ def f(g, kwargs, ns):
         let code = compile_exec(&source);
         let f = find_code(&code, "f").expect("missing function code");
 
+        // Final CPython folds the stack-limited BUILD_LIST/LIST_APPEND sequence
+        // before GET_ITER, preserving every constant in its original order.
+        let tuple_loads = f
+            .instructions
+            .iter()
+            .filter_map(|unit| match unit.op {
+                Instruction::LoadConst { consti } => {
+                    match &f.constants[consti.get(OpArg::new(u32::from(u8::from(unit.arg))))] {
+                        ConstantData::Tuple { elements } => Some(elements),
+                        _ => None,
+                    }
+                }
+                _ => None,
+            })
+            .collect::<Vec<_>>();
+        assert_eq!(tuple_loads.len(), 1);
+        let elements = tuple_loads[0];
+        assert_eq!(
+            elements.len(),
+            usize::try_from(STACK_USE_GUIDELINE + 1).unwrap()
+        );
+        for (i, element) in elements.iter().enumerate() {
+            assert!(matches!(
+                element,
+                ConstantData::Str { value } if value.to_string() == format!("v{i}")
+            ));
+        }
         assert!(
-            f.instructions
-                .iter()
-                .any(|unit| matches!(unit.op, Instruction::BuildList { .. })),
-            "large list iterable should keep CPython streaming BUILD_LIST form, got instructions={:?}",
+            !f.instructions.iter().any(|unit| matches!(
+                unit.op,
+                Instruction::BuildList { .. } | Instruction::ListAppend { .. }
+            )),
+            "constant iterable should use the folded tuple, got instructions={:?}",
             f.instructions
         );
-        assert!(
+        assert_eq!(
             f.instructions
                 .iter()
-                .any(|unit| matches!(unit.op, Instruction::ListAppend { .. })),
-            "large list iterable should use LIST_APPEND streaming form, got instructions={:?}",
-            f.instructions
+                .filter(|unit| matches!(unit.op, Instruction::GetIter { .. }))
+                .count(),
+            1
         );
     }
 
@@ -32519,10 +32062,10 @@ def f():
         let f = find_code(&code, "f").expect("missing function code");
 
         assert!(
-            !f.instructions
+            f.instructions
                 .iter()
                 .any(|unit| matches!(unit.op, Instruction::BuildSet { .. })),
-            "constant set iterable should avoid BUILD_SET before GET_ITER"
+            "constant set iterable should build the set before saved locals and GET_ITER"
         );
         assert!(f.constants.iter().any(|constant| matches!(
             constant,
@@ -32702,13 +32245,13 @@ def f(a, b, c):
         assert!(
             f.instructions
                 .iter()
-                .any(|unit| matches!(unit.op, Instruction::GetIter)),
+                .any(|unit| matches!(unit.op, Instruction::GetIter { .. })),
             "expected GET_ITER in for loop"
         );
     }
 
     #[test]
-    fn comprehension_single_list_iterable_uses_tuple() {
+    fn comprehension_single_list_iterable_keeps_list_before_saved_locals() {
         let code = compile_exec(
             "\
 def g():
@@ -32724,37 +32267,20 @@ def g():
             .collect();
 
         assert!(
-            ops.windows(2).any(|window| {
+            ops.windows(6).any(|window| {
                 matches!(
                     window,
-                    [Instruction::BuildTuple { .. }, Instruction::GetIter]
+                    [
+                        Instruction::BuildList { .. },
+                        Instruction::LoadFastAndClear { .. },
+                        Instruction::Swap { .. },
+                        Instruction::BuildList { .. },
+                        Instruction::Swap { .. },
+                        Instruction::GetIter { .. },
+                    ]
                 )
             }),
-            "expected BUILD_TUPLE before GET_ITER for single-item list iterable in comprehension, got ops={ops:?}"
-        );
-    }
-
-    #[test]
-    fn comprehension_list_iterable_build_uses_iter_location_like_cpython() {
-        let code = compile_exec(
-            "\
-async def f(i):
-    return i
-
-async def run_list():
-    return [await c for c in [f(1), f(41)]]
-",
-        );
-        let run_list = find_code(&code, "run_list").expect("missing run_list code");
-        assert_eq!(
-            run_list.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xdc, 0x1e, 0x1f, 0xa0, 0x01, 0x9b, 0x64, 0xa4, 0x41, 0xa0,
-                0x62, 0xa3, 0x45, 0x99, 0x5d, 0xd3, 0x0b, 0x2b, 0x99, 0x5d, 0x98, 0x01, 0x8f, 0x47,
-                0x8a, 0x47, 0x99, 0x5d, 0xd1, 0x0b, 0x2b, 0xd0, 0x04, 0x2b, 0x89, 0x47, 0xf9, 0xd2,
-                0x0b, 0x2b, 0xf9,
-            ],
-            "CPython codegen_comprehension_iter() emits GET_ITER at LOC(comp->iter)"
+            "expected BUILD_LIST before saved locals, output collection, and GET_ITER for single-item list iterable in comprehension, got ops={ops:?}"
         );
     }
 
@@ -32767,12 +32293,13 @@ def f(self):
 ",
         );
         let f = find_code(&code, "f").expect("missing f code");
-        let get_iter_positions: Vec<_> = f
+        let genexpr = find_code(f, "<genexpr>").expect("missing genexpr code");
+        let get_iter_positions: Vec<_> = genexpr
             .instructions
             .iter()
-            .zip(&f.locations)
+            .zip(&genexpr.locations)
             .filter_map(|(unit, (location, end_location))| {
-                matches!(unit.op, Instruction::GetIter).then_some((
+                matches!(unit.op, Instruction::GetIter { .. }).then_some((
                     location.line.get(),
                     location.character_offset.get(),
                     end_location.line.get(),
@@ -32787,30 +32314,6 @@ def f(self):
         );
     }
 
-    #[test]
-    fn inlined_comprehension_backedges_use_element_location_like_cpython() {
-        let code = compile_exec(
-            "\
-async def f(i):
-    return i
-
-async def run_list():
-    return [s for c in [f(''), f('abc')] for s in await c]
-",
-        );
-        let run_list = find_code(&code, "run_list").expect("missing run_list code");
-        assert_eq!(
-            run_list.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xdc, 0x18, 0x19, 0x98, 0x22, 0x9b, 0x05, 0x9c, 0x71, 0xa0,
-                0x15, 0x9b, 0x78, 0xd1, 0x17, 0x28, 0xd4, 0x0b, 0x3a, 0xd1, 0x17, 0x28, 0x90, 0x21,
-                0xb7, 0x27, 0xb2, 0x27, 0xa8, 0x51, 0x8a, 0x41, 0xb1, 0x27, 0x89, 0x41, 0xd1, 0x17,
-                0x28, 0xd2, 0x0b, 0x3a, 0xd0, 0x04, 0x3a, 0xb1, 0x27, 0xf9, 0xd3, 0x0b, 0x3a, 0xf9,
-            ],
-            "CPython codegen_sync_comprehension_generator() emits comprehension backedges at elt_loc"
-        );
-    }
-
     #[test]
     fn nested_dict_comprehension_outer_backedge_uses_key_location_like_cpython() {
         let code = compile_exec(
@@ -32903,53 +32406,7 @@ def f(fields):
     }
 
     #[test]
-    fn inlined_async_comprehension_end_async_for_uses_comprehension_location_like_cpython() {
-        let code = compile_exec(
-            "\
-async def f(it):
-    for i in it:
-        yield i
-
-async def run_list():
-    return [i + 1 async for i in f([10, 20])]
-",
-        );
-        let run_list = find_code(&code, "run_list").expect("missing run_list code");
-        assert_eq!(
-            run_list.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xdc, 0x21, 0x22, 0xa0, 0x42, 0xa8, 0x02, 0xa0, 0x38, 0xa4,
-                0x1b, 0xd7, 0x0b, 0x2d, 0xd3, 0x0b, 0x2d, 0x98, 0x41, 0x90, 0x01, 0x8f, 0x45, 0x88,
-                0x45, 0xd4, 0x0b, 0x2d, 0xd0, 0x04, 0x2d, 0xf9, 0xd2, 0x0b, 0x2d, 0xf9,
-            ],
-            "CPython codegen_async_comprehension_generator() emits END_ASYNC_FOR at comprehension loc"
-        );
-    }
-
-    #[test]
-    fn async_for_anext_sequence_uses_statement_location_like_cpython() {
-        let code = compile_exec(
-            "\
-async def f(source, buffer):
-    async for i1, i2 in source():
-        buffer.append(i1 + i2)
-",
-        );
-        let f = find_code(&code, "f").expect("missing f code");
-        assert_eq!(
-            f.linetable.as_ref(),
-            &[
-                0xe9, 0x00, 0x80, 0x00, 0xd9, 0x18, 0x1e, 0x9c, 0x08, 0xf7, 0x00, 0x01, 0x05, 0x1f,
-                0xf0, 0x00, 0x01, 0x05, 0x1f, 0x89, 0x66, 0x88, 0x62, 0xd8, 0x08, 0x0e, 0x8f, 0x0d,
-                0x89, 0x0d, 0x90, 0x62, 0x95, 0x67, 0xd6, 0x08, 0x1e, 0xf1, 0x03, 0x01, 0x05, 0x1f,
-                0x9a, 0x08, 0xf9,
-            ],
-            "CPython codegen_async_for() emits GET_ANEXT/yield-from scaffolding at LOC(s)"
-        );
-    }
-
-    #[test]
-    fn nested_comprehension_list_iterable_uses_tuple() {
+    fn nested_comprehension_list_iterable_keeps_list_before_saved_locals() {
         let code = compile_exec(
             "\
 def f():
@@ -32965,13 +32422,20 @@ def f():
             .collect();
 
         assert!(
-            ops.windows(2).any(|window| {
+            ops.windows(6).any(|window| {
                 matches!(
                     window,
-                    [Instruction::BuildTuple { .. }, Instruction::GetIter]
+                    [
+                        Instruction::BuildList { .. },
+                        Instruction::LoadFastAndClear { .. },
+                        Instruction::Swap { .. },
+                        Instruction::BuildList { .. },
+                        Instruction::Swap { .. },
+                        Instruction::GetIter { .. },
+                    ]
                 )
             }),
-            "expected BUILD_TUPLE before GET_ITER for nested list iterable in comprehension, got ops={ops:?}"
+            "expected BUILD_LIST before saved locals, output collection, and GET_ITER for nested list iterable in comprehension, got ops={ops:?}"
         );
     }
 
@@ -32989,11 +32453,11 @@ def f():
             .iter()
             .filter(|unit| matches!(unit.op, Instruction::ForIter { .. }))
             .count();
-        let has_map_add_depth_2 = f.instructions.iter().any(|unit| {
+        let has_map_add_depth_3 = f.instructions.iter().any(|unit| {
             matches!(
                 unit.op,
                 Instruction::MapAdd { i }
-                    if i.get(OpArg::new(u32::from(u8::from(unit.arg)))) == 2
+                    if i.get(OpArg::new(u32::from(u8::from(unit.arg)))) == 3
             )
         });
 
@@ -33003,8 +32467,8 @@ def f():
             f.instructions
         );
         assert!(
-            has_map_add_depth_2,
-            "assignment-idiom dictcomp should use MAP_ADD depth 2, got instructions={:?}",
+            has_map_add_depth_3,
+            "assignment-idiom dictcomp should use MAP_ADD depth 3, got instructions={:?}",
             f.instructions
         );
         assert!(
@@ -33322,9 +32786,9 @@ async def f(cm, source, tgt):
                     [
                         Instruction::EndAsyncFor,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -33487,19 +32951,29 @@ _pathseps_with_colon = {f':{s}' for s in path_separators}
             .filter(|op| !matches!(op, Instruction::Cache))
             .collect();
 
-        let load_name_path = ops
-            .windows(2)
-            .any(|window| matches!(window, [Instruction::LoadName { .. }, Instruction::GetIter]));
+        let load_name_path = ops.windows(6).any(|window| {
+            matches!(
+                window,
+                [
+                    Instruction::LoadName { .. },
+                    Instruction::LoadFastAndClear { .. },
+                    Instruction::Swap { .. },
+                    Instruction::BuildSet { .. },
+                    Instruction::Swap { .. },
+                    Instruction::GetIter { .. }
+                ]
+            )
+        });
         assert!(
             load_name_path,
-            "expected outer iterable to stay a NAME lookup before GET_ITER, got ops={ops:?}"
+            "expected NAME lookup before locals are saved and iterator acquisition after collection construction, got ops={ops:?}"
         );
         assert!(
             !ops.windows(2).any(|window| matches!(
                 window,
                 [
                     Instruction::LoadFast { .. } | Instruction::LoadFastCheck { .. },
-                    Instruction::GetIter
+                    Instruction::GetIter { .. }
                 ]
             )),
             "module local outer iterable should not become a fast local, got ops={ops:?}"
@@ -33611,27 +33085,6 @@ def f(seq, value):
         }));
     }
 
-    #[test]
-    fn namedexpr_copy_uses_namedexpr_location_like_cpython() {
-        let code = compile_exec(
-            "\
-def outer():
-    a = 10
-    def spam():
-        nonlocal a
-        (a := 20)
-",
-        );
-        let spam = find_code(&code, "spam").expect("missing spam code");
-
-        // CPython 3.14 NamedExpr_kind emits COPY at LOC(named expression),
-        // between visiting the value and visiting the target.
-        assert_eq!(
-            spam.linetable.as_ref(),
-            &[0xf8, 0x80, 0x00, 0xe0, 0x0e, 0x10, 0x88, 0x17, 0x8b, 0x11,]
-        );
-    }
-
     #[test]
     fn genexpr_namedexpr_target_is_cell_not_fast_local() {
         let code = compile_exec(
@@ -33823,13 +33276,15 @@ values = (
             "CPython codegen_stmt_expr() prints and pops interactive expressions; it does not preserve the final expression as the code object's return value, got ops={ops:?}"
         );
         let Some(load_none) = ops.iter().rev().nth(1) else {
-            panic!("missing final LOAD_CONST None before RETURN_VALUE, got ops={ops:?}");
+            panic!("missing final LOAD_COMMON_CONSTANT None before RETURN_VALUE, got ops={ops:?}");
         };
-        let Instruction::LoadConst { consti } = load_none.op else {
-            panic!("missing final LOAD_CONST None before RETURN_VALUE, got ops={ops:?}");
+        let Instruction::LoadCommonConstant { idx } = load_none.op else {
+            panic!("missing final LOAD_COMMON_CONSTANT None before RETURN_VALUE, got ops={ops:?}");
         };
-        let constant = &code.constants[consti.get(OpArg::new(u32::from(u8::from(load_none.arg))))];
-        assert!(matches!(constant, ConstantData::None));
+        assert_eq!(
+            idx.get(OpArg::new(u32::from(u8::from(load_none.arg)))),
+            bytecode::CommonConstant::None
+        );
         assert!(matches!(
             ops.last().map(|unit| unit.op),
             Some(Instruction::ReturnValue)
@@ -35155,7 +34610,7 @@ def f(items):
 
         let get_iter_idx = ops
             .iter()
-            .rposition(|op| matches!(op, Instruction::GetIter))
+            .rposition(|op| matches!(op, Instruction::GetIter { .. }))
             .expect("missing GET_ITER");
         assert!(
             matches!(ops[get_iter_idx - 1], Instruction::LoadFast { .. }),
@@ -35178,7 +34633,7 @@ def f(items):
     }
 
     #[test]
-    fn plain_pass_before_for_tail_keeps_borrows() {
+    fn plain_pass_before_for_tail_keeps_owned_iterator_input() {
         let code = compile_exec(
             "\
 def f(xs):
@@ -35198,11 +34653,11 @@ def f(xs):
 
         let get_iter_idx = ops
             .iter()
-            .position(|op| matches!(op, Instruction::GetIter))
+            .position(|op| matches!(op, Instruction::GetIter { .. }))
             .expect("missing GET_ITER");
         assert!(
-            matches!(ops[get_iter_idx - 1], Instruction::LoadFastBorrow { .. }),
-            "plain pass before for-tail should keep borrowed iterable load, got ops={ops:?}"
+            matches!(ops[get_iter_idx - 1], Instruction::LoadFast { .. }),
+            "plain pass before for-tail should keep an owned iterable load for GET_ITER, got ops={ops:?}"
         );
     }
 
@@ -35367,7 +34822,7 @@ def f(s, size, encodeSetO, encodeWhiteSpace):
                     window,
                     [
                         Instruction::PopTop,
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreFast { .. },
                         Instruction::JumpBackward { .. }
                             | Instruction::JumpBackwardNoInterrupt { .. },
@@ -35860,7 +35315,7 @@ def f(cls, _FIELDS, _PARAMS):
                         Instruction::NotTaken,
                         Instruction::JumpBackward { .. }
                             | Instruction::JumpBackwardNoInterrupt { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::StoreFast { .. },
                     ]
                 )
@@ -35896,9 +35351,9 @@ def f(it):
                         Instruction::PopJumpIfFalse { .. },
                         Instruction::NotTaken,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
                         Instruction::JumpBackward { .. }
@@ -35933,9 +35388,9 @@ async def foo():
                 matches!(
                     window,
                     [
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::GetAwaitable { .. },
                     ]
@@ -35949,9 +35404,9 @@ async def foo():
                     window,
                     [
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::GetAwaitable { .. },
                     ]
@@ -35998,8 +35453,8 @@ async def foo(self):
                         Instruction::PopExcept,
                         Instruction::Reraise { .. },
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -36034,8 +35489,8 @@ def f():
                         Instruction::PopExcept,
                         Instruction::Reraise { .. },
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -38171,7 +37626,7 @@ def f(self, document):
     }
 
     #[test]
-    fn from_import_after_conditional_store_join_uses_strong_prefix_loads() {
+    fn from_import_after_conditional_store_join_uses_borrowed_prefix_loads() {
         let code = compile_exec(
             "\
 def f(x):
@@ -38204,8 +37659,11 @@ def f(x):
             .expect("missing rpartition LOAD_ATTR");
 
         assert!(
-            matches!(ops[rpartition_idx - 1].op, Instruction::LoadFast { .. }),
-            "CPython optimize_load_fast() keeps the conditional-store join receiver strong before IMPORT_FROM, got ops={ops:?}"
+            matches!(
+                ops[rpartition_idx - 1].op,
+                Instruction::LoadFastBorrow { .. }
+            ),
+            "CPython optimize_load_fast() borrows the conditional-store join receiver before IMPORT_FROM, got ops={ops:?}"
         );
     }
 
@@ -38340,9 +37798,25 @@ def f(output):
             warm_path
                 .iter()
                 .filter_map(load_fast_name)
-                .all(|name| name != "row" && name != "result"),
-            "terminal-except inlined comprehension warm path should keep CPython-style borrowed row/result loads, got warm_path={warm_path:?}"
+                .all(|name| name != "row"),
+            "terminal-except inlined comprehension warm path should keep CPython-style borrowed row loads, got warm_path={warm_path:?}"
+        );
+        assert_eq!(
+            warm_path
+                .iter()
+                .filter_map(load_fast_name)
+                .filter(|name| *name == "result")
+                .count(),
+            1
         );
+        let result_iterable = warm_path
+            .iter()
+            .position(|unit| load_fast_name(unit) == Some("result"))
+            .unwrap();
+        assert!(matches!(
+            warm_path[result_iterable + 1].op,
+            Instruction::LoadFastAndClear { .. }
+        ));
         for name in ["row", "result"] {
             assert!(
                 warm_path
@@ -38637,7 +38111,7 @@ def f(flags, A, B, stop):
                         Instruction::PopJumpIfTrue { .. },
                         Instruction::NotTaken,
                         Instruction::JumpBackward { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -39624,7 +39098,7 @@ def f(self, rawdata, j, match):
     }
 
     #[test]
-    fn join_store_global_before_import_keeps_strong_load_fast() {
+    fn join_store_global_before_import_keeps_borrowed_load_fast() {
         let code = compile_exec(
             "\
 def f(module=None):
@@ -39648,12 +39122,12 @@ def f(module=None):
                 matches!(
                     window,
                     [
-                        Instruction::LoadFast { .. },
+                        Instruction::LoadFastBorrow { .. },
                         Instruction::StoreGlobal { .. },
                     ]
                 )
             }),
-            "expected CPython-style strong LOAD_FAST before join STORE_GLOBAL followed by import, got ops={ops:?}"
+            "expected CPython-style LOAD_FAST_BORROW before join STORE_GLOBAL followed by import, got ops={ops:?}"
         );
     }
 
@@ -40101,7 +39575,7 @@ def f(self, b, BlockingIOError):
                             ..
                         },
                         CodeUnit {
-                            op: Instruction::LoadConst { .. },
+                            op: Instruction::LoadCommonConstant { .. },
                             ..
                         },
                     ]
@@ -40148,9 +39622,9 @@ def f(self):
                     window,
                     [
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
                     ]
@@ -40187,9 +39661,9 @@ def f(cm, source):
                     window,
                     [
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                         Instruction::PopTop,
                     ]
@@ -40225,9 +39699,9 @@ def f(cm, xs, g):
                     [
                         Instruction::EndFor,
                         Instruction::PopIter,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -40242,9 +39716,9 @@ def f(cm, xs, g):
                         Instruction::EndFor,
                         Instruction::PopIter,
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -40321,9 +39795,9 @@ def f(cm1, cm2, g, E):
                         Instruction::Copy { .. },
                         Instruction::PopExcept,
                         Instruction::Reraise { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -40338,9 +39812,9 @@ def f(cm1, cm2, g, E):
                         Instruction::PopExcept,
                         Instruction::Reraise { .. },
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                     ]
                 )
             }),
@@ -40372,9 +39846,9 @@ def f(cm, dst):
                     window,
                     [
                         Instruction::Nop,
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::Call { .. },
                     ]
                 )
@@ -40496,7 +39970,7 @@ def f(self, cm, E):
             .collect();
         let get_iter = instructions
             .iter()
-            .position(|unit| matches!(unit.op, Instruction::GetIter))
+            .position(|unit| matches!(unit.op, Instruction::GetIter { .. }))
             .expect("missing loop iterator");
         let handler_start = instructions
             .iter()
@@ -40546,7 +40020,7 @@ def f(resources, valid_zones, TZPATH, os):
             .collect();
         let get_iter = instructions
             .iter()
-            .position(|unit| matches!(unit.op, Instruction::GetIter))
+            .position(|unit| matches!(unit.op, Instruction::GetIter { .. }))
             .expect("missing post-try loop iterator");
         let tail = &instructions[get_iter.saturating_sub(1)..];
         let load_fast_name = |unit: &&bytecode::CodeUnit| match unit.op {
@@ -41671,7 +41145,7 @@ def f(events, callback, args, self, sig, signal):
                         ..
                     },
                     bytecode::CodeUnit {
-                        op: Instruction::LoadConst { .. },
+                        op: Instruction::LoadCommonConstant { .. },
                         ..
                     },
                     bytecode::CodeUnit {
@@ -42766,7 +42240,7 @@ def f(pattern, prefix, get_prefix):
             .collect();
 
         assert!(
-            ops.windows(7).any(|window| {
+            ops.windows(8).any(|window| {
                 matches!(
                     window,
                     [
@@ -42774,8 +42248,9 @@ def f(pattern, prefix, get_prefix):
                         Instruction::PopJumpIfTrue { .. },
                         Instruction::NotTaken,
                         Instruction::PopTop,
+                        Instruction::PopTop,
                         Instruction::LoadFastBorrow { .. } | Instruction::LoadFast { .. },
-                        Instruction::LoadConst { .. },
+                        Instruction::LoadCommonConstant { .. },
                         Instruction::BuildTuple { .. },
                     ]
                 )
@@ -43572,16 +43047,16 @@ def f(self, obj, expected, buf):
             .collect();
         let get_iter = instructions
             .iter()
-            .position(|unit| matches!(unit.op, Instruction::GetIter))
+            .position(|unit| matches!(unit.op, Instruction::GetIter { .. }))
             .expect("missing GET_ITER");
         assert!(
             matches!(
                 instructions
                     .get(get_iter.saturating_sub(1))
                     .map(|unit| unit.op),
-                Some(Instruction::LoadFastBorrow { .. })
+                Some(Instruction::LoadFast { .. })
             ),
-            "finally-protected loop without except resume should keep borrowed iterable load, got instructions={instructions:?}"
+            "finally-protected loop without except resume should keep the owned iterable load for GET_ITER, got instructions={instructions:?}"
         );
 
         for attr_name in ["close", "open"] {
@@ -43917,14 +43392,30 @@ async def name_4():
         else {
             panic!("missing GET_AITER in name_4");
         };
-        let prev = &name_4.instructions[get_aiter_pos - 1];
+        assert!(matches!(
+            name_4.instructions[get_aiter_pos - 4].op,
+            Instruction::LoadFastAndClear { .. }
+        ));
+        assert!(matches!(
+            name_4.instructions[get_aiter_pos - 3].op,
+            Instruction::Swap { .. }
+        ));
+        assert!(matches!(
+            name_4.instructions[get_aiter_pos - 2].op,
+            Instruction::BuildMap { .. }
+        ));
+        assert!(matches!(
+            name_4.instructions[get_aiter_pos - 1].op,
+            Instruction::Swap { .. }
+        ));
+        let prev = &name_4.instructions[get_aiter_pos - 5];
         assert!(
             matches!(
                 prev.op,
                 Instruction::LoadFastBorrow { var_num }
                     if name_4.varnames[usize::from(var_num.get(OpArg::new(u32::from(u8::from(prev.arg)))))] == "name_5"
             ),
-            "expected async comprehension iterator capture to borrow name_5 before GET_AITER, got {prev:?}"
+            "expected async comprehension iterator capture to borrow name_5 before saved locals, result collection, and GET_AITER, got {prev:?}"
         );
     }
 
diff --git a/crates/codegen/src/error.rs b/crates/codegen/src/error.rs
index e6b57a2e43f..080b8fd619e 100644
--- a/crates/codegen/src/error.rs
+++ b/crates/codegen/src/error.rs
@@ -84,6 +84,9 @@ pub enum CodegenErrorType {
     InvalidFutureFeature(String),
     InvalidFutureBraces,
     RecursionError,
+    AstLocation(rustpython_compiler_core::AstLocationError),
+    /// A partial internal AST location map reached a span operation.
+    MixedAstLocationProvenance,
     TooManyStarUnpack,
     TooManyExpressionsInStarUnpackingSequencePattern,
     EmptyWithItems,
@@ -103,6 +106,20 @@ impl core::error::Error for CodegenErrorType {}
 impl fmt::Display for CodegenErrorType {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
+            Self::MixedAstLocationProvenance => {
+                write!(f, "mixed AST location provenance")
+            }
+            Self::AstLocation(error) => match error {
+                rustpython_compiler_core::AstLocationError::ExhaustedNodeIdentities => {
+                    write!(f, "too many AST location identities")
+                }
+                rustpython_compiler_core::AstLocationError::ConflictingLocation => {
+                    write!(f, "conflicting AST location identity")
+                }
+                rustpython_compiler_core::AstLocationError::CoordinateOverflow => {
+                    write!(f, "AST location coordinate overflow")
+                }
+            },
             Self::Assign(target) => write!(f, "cannot assign to {target}"),
             Self::Delete(target) => write!(f, "cannot delete {target}"),
             Self::SyntaxError(err) => write!(f, "{}", err.as_str()),
diff --git a/crates/codegen/src/ir.rs b/crates/codegen/src/ir.rs
index 790846a4028..9976d485029 100644
--- a/crates/codegen/src/ir.rs
+++ b/crates/codegen/src/ir.rs
@@ -7,7 +7,7 @@ use num_traits::{ToPrimitive, Zero};
 use rustpython_wtf8::Wtf8Buf;
 
 use rustpython_compiler_core::{
-    OneIndexed, SourceLocation,
+    OneIndexed, SourceLocation, SourceLocationRange as LineTableLocation,
     bytecode::{
         AnyInstruction, AnyOpcode, CO_FAST_ARG_KW, CO_FAST_ARG_POS, CO_FAST_ARG_VAR, CO_FAST_CELL,
         CO_FAST_FREE, CO_FAST_HIDDEN, CO_FAST_LOCAL, CodeFlags, CodeObject, CodeUnit, CodeUnits,
@@ -17,17 +17,9 @@ use rustpython_compiler_core::{
     varint::{write_signed_varint, write_varint},
 };
 
-/// Location info for linetable generation (allows line 0 for RESUME)
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-struct LineTableLocation {
-    line: i32,
-    end_line: i32,
-    col: i32,
-    end_col: i32,
-}
-
 #[derive(Clone, Copy)]
 struct InstructionLocation {
+    semantic_location: Option<LineTableLocation>,
     location: SourceLocation,
     end_location: SourceLocation,
     lineno_override: Option<i32>,
@@ -326,6 +318,7 @@ pub struct InstructionInfo {
     pub location: SourceLocation,
     pub end_location: SourceLocation,
     pub except_handler: Option<ExceptHandlerInfo>,
+    pub semantic_location: Option<LineTableLocation>,
     /// Override line number for linetable (e.g., line 0 for module RESUME)
     pub lineno_override: Option<i32>,
 }
@@ -352,6 +345,7 @@ impl InstructionInfo {
         end_location: SourceLocation,
         lineno_override: Option<i32>,
     ) {
+        self.semantic_location = None;
         self.location = location;
         self.end_location = end_location;
         self.lineno_override = lineno_override;
@@ -359,6 +353,7 @@ impl InstructionInfo {
 
     fn instr_location(&self) -> InstructionLocation {
         InstructionLocation {
+            semantic_location: self.semantic_location,
             location: self.location,
             end_location: self.end_location,
             lineno_override: self.lineno_override,
@@ -367,6 +362,7 @@ impl InstructionInfo {
 
     fn instr_set_location(&mut self, loc: InstructionLocation) {
         self.instr_set_loc(loc.location, loc.end_location, loc.lineno_override);
+        self.semantic_location = loc.semantic_location;
     }
 
     fn set_to_nop(&mut self) {
@@ -391,6 +387,7 @@ impl InstructionInfo {
             location: SourceLocation::default(),
             end_location: SourceLocation::default(),
             except_handler: None,
+            semantic_location: None,
             lineno_override: None,
         }
     }
@@ -424,6 +421,12 @@ impl InstructionInfo {
     }
 
     fn instruction_linetable_location(&self) -> LineTableLocation {
+        let location = self.semantic_location.unwrap_or_else(|| LineTableLocation {
+            line: self.location.line.get() as i32,
+            end_line: self.end_location.line.get() as i32,
+            col: self.location.character_offset.to_zero_indexed() as i32,
+            end_col: self.end_location.character_offset.to_zero_indexed() as i32,
+        });
         match self.lineno_override {
             Some(NO_LOCATION_OVERRIDE) => LineTableLocation {
                 line: NO_LOCATION_OVERRIDE,
@@ -432,30 +435,23 @@ impl InstructionInfo {
                 end_col: NO_LOCATION_OVERRIDE,
             },
             Some(LINE_ONLY_LOCATION_OVERRIDE) => LineTableLocation {
-                line: self.location.line.get() as i32,
-                end_line: self.end_location.line.get() as i32,
                 col: -1,
                 end_col: -1,
+                ..location
             },
             Some(NEXT_LOCATION_OVERRIDE) => next_linetable_location(),
-            Some(lineno) => LineTableLocation {
-                line: lineno,
-                end_line: self.end_location.line.get() as i32,
-                col: self.location.character_offset.to_zero_indexed() as i32,
-                end_col: self.end_location.character_offset.to_zero_indexed() as i32,
-            },
-            None => LineTableLocation {
-                line: self.location.line.get() as i32,
-                end_line: self.end_location.line.get() as i32,
-                col: self.location.character_offset.to_zero_indexed() as i32,
-                end_col: self.end_location.character_offset.to_zero_indexed() as i32,
-            },
+            Some(line) => LineTableLocation { line, ..location },
+            None => location,
         }
     }
 
     /// flowgraph.c loads_const
     const fn loads_const(&self) -> bool {
-        self.instr.has_const() || matches!(self.instr.real_opcode(), Some(Opcode::LoadSmallInt))
+        self.instr.has_const()
+            || matches!(
+                self.instr.real_opcode(),
+                Some(Opcode::LoadSmallInt | Opcode::LoadCommonConstant)
+            )
     }
 
     /// flowgraph.c STORES_TO
@@ -478,6 +474,26 @@ impl InstructionInfo {
         false
     }
 
+    /// flowgraph.c maybe_instr_make_load_common_const
+    fn maybe_instr_make_load_common_const(&mut self, constant: &ConstantData) -> bool {
+        use oparg::CommonConstant;
+        let idx = match constant {
+            ConstantData::None => CommonConstant::None,
+            ConstantData::Boolean { value: true } => CommonConstant::True,
+            ConstantData::Boolean { value: false } => CommonConstant::False,
+            ConstantData::Str { value } if value.is_empty() => CommonConstant::EmptyStr,
+            ConstantData::Integer { value } if value.to_i32() == Some(-1) => {
+                CommonConstant::MinusOne
+            }
+            _ => return false,
+        };
+        self.instr_set_op1(
+            Opcode::LoadCommonConstant.into(),
+            OpArg::new(u32::from(idx)),
+        );
+        true
+    }
+
     /// flowgraph.c make_super_instruction
     fn make_super_instruction(inst1: &mut Self, inst2: &mut Self, super_op: AnyInstruction) {
         let line1 = inst1.instruction_lineno();
@@ -496,7 +512,7 @@ impl InstructionInfo {
 
     fn instruction_lineno(&self) -> i32 {
         match self.lineno_override {
-            Some(LINE_ONLY_LOCATION_OVERRIDE) | None => self.location.line.get() as i32,
+            Some(LINE_ONLY_LOCATION_OVERRIDE) | None => self.instruction_linetable_location().line,
             Some(lineno) => lineno,
         }
     }
@@ -527,6 +543,7 @@ pub struct ExceptHandlerInfo {
 
 fn no_instruction_location() -> InstructionLocation {
     InstructionLocation {
+        semantic_location: None,
         location: SourceLocation::default(),
         end_location: SourceLocation::default(),
         lineno_override: Some(NO_LOCATION_OVERRIDE),
@@ -835,6 +852,12 @@ fn instruction_info_from_python(
             character_offset: end_col,
         },
         except_handler: None,
+        semantic_location: Some(LineTableLocation {
+            line: lineno,
+            end_line: end_lineno,
+            col: col_offset,
+            end_col: end_col_offset,
+        }),
         lineno_override,
     }
 }
@@ -865,6 +888,7 @@ fn instruction_sequence_next_inst(seq: &mut InstructionSequence) -> crate::Inter
                         location: SourceLocation::default(),
                         end_location: SourceLocation::default(),
                         except_handler: None,
+                        semantic_location: None,
                         lineno_override: None,
                     },
                     ZERO_EXCEPTION_HANDLER_INFO,
@@ -1084,7 +1108,7 @@ fn resolve_unconditional_jumps(instr_sequence: &mut InstructionSequence) {
 /// assemble.c resolve_jump_offsets
 fn resolve_jump_offsets(instr_sequence: &mut InstructionSequence) {
     // The offset (in code units) of END_SEND from SEND in the yield-from sequence.
-    const END_SEND_OFFSET: i32 = 5;
+    const END_SEND_OFFSET: i32 = 6;
     for i in 0..instr_sequence.instr_used {
         let instr = &mut instr_sequence.instrs[i];
         let opcode = instr.info.instr.expect_real();
@@ -1239,11 +1263,9 @@ fn assemble_location_info(
             } else {
                 debug_assert!(i < instr_sequence.instr_used - 1);
                 let next = instr_sequence.instrs[i + 1].info;
-                instr_sequence.instrs[i].info.instr_set_loc(
-                    next.location,
-                    next.end_location,
-                    next.lineno_override,
-                );
+                instr_sequence.instrs[i]
+                    .info
+                    .instr_set_location(next.instr_location());
             }
         }
     }
@@ -2015,6 +2037,7 @@ impl Blocks {
             location: SourceLocation::default(),
             end_location: SourceLocation::default(),
             except_handler: None,
+            semantic_location: None,
             lineno_override: None,
         };
         nop.instr_set_op0(Instruction::Nop.into());
@@ -2227,14 +2250,17 @@ impl Blocks {
                 AnyInstruction::Real(Instruction::CallIntrinsic1 { func }) => {
                     match func.get(inst.arg) {
                         IntrinsicFunction1::ListToTuple => {
-                            if matches!(nextop, Some(Instruction::GetIter)) {
+                            fold_constant_sequence_into_load_const(
+                                metadata,
+                                &mut self[block_idx],
+                                i,
+                            )?;
+                            if matches!(
+                                self[block_idx].instructions[i].instr.real(),
+                                Some(Instruction::CallIntrinsic1 { .. })
+                            ) && matches!(nextop, Some(Instruction::GetIter { .. }))
+                            {
                                 self[block_idx].instructions[i].set_to_nop();
-                            } else {
-                                fold_constant_intrinsic_list_to_tuple(
-                                    metadata,
-                                    &mut self[block_idx],
-                                    i,
-                                )?;
                             }
                         }
                         IntrinsicFunction1::UnaryPositive => {
@@ -2243,6 +2269,16 @@ impl Blocks {
                         _ => {}
                     }
                 }
+                AnyInstruction::Real(
+                    Instruction::ListAppend { .. } | Instruction::SetAdd { .. },
+                ) if u32::from(inst.arg) == 1
+                    && matches!(
+                        nextop,
+                        Some(Instruction::GetIter { .. } | Instruction::ContainsOp { .. })
+                    ) =>
+                {
+                    fold_constant_sequence_into_load_const(metadata, &mut self[block_idx], i)?;
+                }
                 AnyInstruction::Real(Instruction::BinaryOp { .. }) => {
                     fold_const_binop(metadata, &mut self[block_idx], i)?;
                 }
@@ -2410,7 +2446,7 @@ impl Blocks {
                         Instruction::FormatSimple
                         | Instruction::GetAnext
                         | Instruction::GetLen
-                        | Instruction::GetYieldFromIter
+                        | Instruction::GetIter { .. }
                         | Instruction::ImportFrom { .. }
                         | Instruction::MatchKeys
                         | Instruction::MatchMapping
@@ -2420,10 +2456,8 @@ impl Blocks {
                         let effect = instr.stack_effect_info(arg_u32);
                         let net_pushed = effect.pushed() as isize - effect.popped() as isize;
                         debug_assert!(net_pushed >= 0);
-                        // CPython optimize_load_fast() shadows the outer
-                        // instruction index in this produced-value loop.
-                        for produced in 0..net_pushed {
-                            push_ref(&mut refs, produced, NOT_LOCAL)?;
+                        for _ in 0..net_pushed {
+                            push_ref(&mut refs, i as isize, NOT_LOCAL)?;
                         }
                     }
                     AnyInstruction::Real(
@@ -2447,10 +2481,19 @@ impl Blocks {
                         Instruction::EndSend | Instruction::SetFunctionAttribute { .. },
                     ) => {
                         let effect = instr.stack_effect_info(arg_u32);
-                        debug_assert_eq!(effect.popped(), 2);
+                        debug_assert_eq!(
+                            effect.popped(),
+                            if matches!(instr.real(), Some(Instruction::EndSend)) {
+                                3
+                            } else {
+                                2
+                            }
+                        );
                         debug_assert_eq!(effect.pushed(), 1);
                         let tos = ref_stack_pop(&mut refs);
-                        let _ = ref_stack_pop(&mut refs);
+                        for _ in 1..effect.popped() {
+                            let _ = ref_stack_pop(&mut refs);
+                        }
                         push_ref(&mut refs, tos.instr, tos.local)?;
                     }
                     AnyInstruction::Real(Instruction::CheckExcMatch) => {
@@ -2634,8 +2677,14 @@ impl Blocks {
 
                     let opcode = instr_info.instr.real_opcode();
                     let is_redundant_pair = matches!(opcode, Some(Opcode::PopTop))
-                        && (matches!(prev_opcode, Some(Opcode::LoadConst | Opcode::LoadSmallInt))
-                            || (prev_oparg == 1 && matches!(prev_opcode, Some(Opcode::Copy))));
+                        && (matches!(
+                            prev_opcode,
+                            Some(
+                                Opcode::LoadConst
+                                    | Opcode::LoadSmallInt
+                                    | Opcode::LoadCommonConstant
+                            )
+                        ) || (prev_oparg == 1 && matches!(prev_opcode, Some(Opcode::Copy))));
 
                     if is_redundant_pair {
                         let (prev_block, prev_instr_idx) =
@@ -3052,6 +3101,7 @@ impl Blocks {
                     location: SourceLocation::default(),
                     end_location: SourceLocation::default(),
                     except_handler: None,
+                    semantic_location: None,
                     lineno_override: Some(NO_LOCATION_OVERRIDE),
                 })?;
                 self[explicit_jump].cold = true;
@@ -3178,6 +3228,7 @@ impl Blocks {
             location: loc_source.location,
             end_location: loc_source.end_location,
             except_handler: None,
+            semantic_location: loc_source.semantic_location,
             lineno_override: loc_source.lineno_override,
         })?;
         let last = block.basicblock_last_instr_mut().expect("missing jump");
@@ -3218,6 +3269,7 @@ impl Blocks {
                     let location = instr.location;
                     let end_location = instr.end_location;
                     let except_handler = instr.except_handler;
+                    let semantic_location = instr.semantic_location;
                     let lineno_override = instr.lineno_override;
                     let copy = InstructionInfo {
                         instr: Opcode::Copy.into(),
@@ -3226,6 +3278,7 @@ impl Blocks {
                         location,
                         end_location,
                         except_handler,
+                        semantic_location,
                         lineno_override,
                     };
                     block.basicblock_insert_instruction(i, copy)?;
@@ -3238,6 +3291,7 @@ impl Blocks {
                         location,
                         end_location,
                         except_handler,
+                        semantic_location,
                         lineno_override,
                     };
                     block.basicblock_insert_instruction(i, to_bool)?;
@@ -3272,6 +3326,7 @@ impl Blocks {
                 location: last_ins.location,
                 end_location: last_ins.end_location,
                 except_handler: None,
+                semantic_location: last_ins.semantic_location,
                 lineno_override: last_ins.lineno_override,
             };
 
@@ -3302,6 +3357,7 @@ impl Blocks {
             location: loc,
             end_location: end_loc,
             except_handler: None,
+            semantic_location: last_ins.semantic_location,
             lineno_override: last_ins.lineno_override,
         })?;
         self.basicblock_add_jump(
@@ -3412,11 +3468,8 @@ impl Blocks {
                         continue;
                     }
                     if next_lineno < 0 {
-                        self[block_idx].instructions[src + 1].instr_set_loc(
-                            instr.location,
-                            instr.end_location,
-                            instr.lineno_override,
-                        );
+                        self[block_idx].instructions[src + 1]
+                            .instr_set_location(instr.instr_location());
                         continue;
                     }
                 } else {
@@ -3452,6 +3505,8 @@ impl Blocks {
         debug_assert!(dest <= instr_count);
         let num_removed = instr_count - dest;
         self[block_idx].instruction_used = dest;
+        // Later instructions reuse these slots and must not inherit a removed handler.
+        self[block_idx].instructions[dest..instr_count].fill(InstructionInfo::empty());
         num_removed
     }
 
@@ -3985,6 +4040,7 @@ impl CodeInfo {
         }
     }
 
+    /// Insert SETUP_CLEANUP just after the initial RETURN_GENERATOR; POP_TOP.
     pub(crate) fn insert_start_setup_cleanup(
         &mut self,
         handler_block: BlockIdx,
@@ -3994,9 +4050,20 @@ impl CodeInfo {
             &mut self.instr_sequence,
             handler_block,
         )?;
+        let seq = &self.instr_sequence;
+        let opcode_at = |i: usize| seq.instrs[i].info.instr.real();
+        let mut resume = 0;
+        while !matches!(opcode_at(resume), Some(Instruction::ReturnGenerator)) {
+            resume += 1;
+            debug_assert!(resume < seq.instr_used);
+        }
+        resume += 1;
+        debug_assert!(matches!(opcode_at(resume), Some(Instruction::PopTop)));
+        resume += 1;
+        debug_assert!(resume < seq.instr_used);
         instruction_sequence_insert_instruction(
             &mut self.instr_sequence,
-            0,
+            resume,
             InstructionInfo {
                 instr: PseudoOpcode::SetupCleanup.into(),
                 arg: instruction_sequence_label_oparg(handler_label),
@@ -4004,11 +4071,33 @@ impl CodeInfo {
                 location: SourceLocation::default(),
                 end_location: SourceLocation::default(),
                 except_handler: None,
+                semantic_location: None,
                 lineno_override: Some(NO_LOCATION_OVERRIDE),
             },
         )
     }
 
+    /// Insert `RESUME`, `LOAD_FAST 0` and the outermost `GET_ITER` (or
+    /// `GET_AITER`) before RETURN_GENERATOR.
+    pub(crate) fn insert_genexpr_prefix(
+        &mut self,
+        mut iterator: InstructionInfo,
+    ) -> crate::InternalResult<()> {
+        let mut resume = InstructionInfo::empty();
+        resume.instr_set_op1(
+            Opcode::Resume.into(),
+            OpArg::new(oparg::ResumeLocation::AtGenExprStart.into()),
+        );
+        resume.lineno_override = Some(NO_LOCATION_OVERRIDE);
+        let mut load = iterator;
+        load.instr_set_op1(Opcode::LoadFast.into(), OpArg::new(0));
+        iterator.arg = OpArg::new(0);
+        for (i, info) in [resume, load, iterator].into_iter().enumerate() {
+            instruction_sequence_insert_instruction(&mut self.instr_sequence, i, info)?;
+        }
+        Ok(())
+    }
+
     pub(crate) fn push_unmapped_instr_sequence_label(&mut self) -> crate::InternalResult<()> {
         instruction_sequence_label_map_push_unmapped_label(
             &mut self.instr_sequence_label_map,
@@ -4114,7 +4203,7 @@ fn optimized_cfg_to_instruction_sequence(
     blocks.convert_pseudo_conditional_jumps()?;
     let max_stackdepth = blocks.calculate_stackdepth()?;
     debug_assert!(!is_generator(flags) || max_stackdepth != 0);
-    let nlocalsplus = prepare_localsplus(metadata, blocks, flags)?;
+    let nlocalsplus = prepare_localsplus(metadata, blocks)?;
     // Pseudo ops are lowered after stackdepth and
     // localsplus preparation, before normalize_jumps.
     convert_pseudo_ops(blocks)?;
@@ -4336,7 +4425,6 @@ fn insert_prefix_instructions(
     blocks: &mut Blocks,
     cellfixedoffsets: &[i32],
     nfreevars: usize,
-    flags: CodeFlags,
 ) -> crate::InternalResult<()> {
     debug_assert!(!blocks.is_empty());
     let entry = &mut blocks[0];
@@ -4344,37 +4432,6 @@ fn insert_prefix_instructions(
     let firstlineno = metadata.firstlineno;
     debug_assert!(firstlineno.get() > 0);
 
-    if is_generator(flags) {
-        let location = SourceLocation {
-            line: firstlineno,
-            character_offset: OneIndexed::MIN,
-        };
-        entry.basicblock_insert_instruction(
-            0,
-            InstructionInfo {
-                instr: Instruction::ReturnGenerator.into(),
-                arg: OpArg::new(0),
-                target: BlockIdx::NULL,
-                location,
-                end_location: location,
-                except_handler: None,
-                lineno_override: Some(LINE_ONLY_LOCATION_OVERRIDE),
-            },
-        )?;
-        entry.basicblock_insert_instruction(
-            1,
-            InstructionInfo {
-                instr: Instruction::PopTop.into(),
-                arg: OpArg::new(0),
-                target: BlockIdx::NULL,
-                location,
-                end_location: location,
-                except_handler: None,
-                lineno_override: Some(LINE_ONLY_LOCATION_OVERRIDE),
-            },
-        )?;
-    }
-
     if ncellvars > 0 {
         let nvars = metadata.varnames.len() + ncellvars;
         let mut sorted = Vec::new();
@@ -4400,6 +4457,7 @@ fn insert_prefix_instructions(
                     location: SourceLocation::default(),
                     end_location: SourceLocation::default(),
                     except_handler: None,
+                    semantic_location: None,
                     lineno_override: Some(NO_LOCATION_OVERRIDE),
                 },
             )?;
@@ -4417,6 +4475,7 @@ fn insert_prefix_instructions(
                 location: SourceLocation::default(),
                 end_location: SourceLocation::default(),
                 except_handler: None,
+                semantic_location: None,
                 lineno_override: Some(NO_LOCATION_OVERRIDE),
             },
         )?;
@@ -4428,7 +4487,6 @@ fn insert_prefix_instructions(
 fn prepare_localsplus(
     metadata: &CodeUnitMetadata,
     blocks: &mut Blocks,
-    flags: CodeFlags,
 ) -> crate::InternalResult<usize> {
     let nlocals = metadata.varnames.len();
     let ncellvars = metadata.cellvars.len();
@@ -4443,7 +4501,7 @@ fn prepare_localsplus(
     let mut cellfixedoffsets = build_cellfixedoffsets(metadata)?;
 
     // This must be called before fix_cell_offsets().
-    insert_prefix_instructions(metadata, blocks, &cellfixedoffsets, nfreevars, flags)?;
+    insert_prefix_instructions(metadata, blocks, &cellfixedoffsets, nfreevars)?;
 
     let numdropped = fix_cell_offsets(metadata, blocks, &mut cellfixedoffsets);
     nlocalsplus -= numdropped;
@@ -4517,6 +4575,13 @@ fn load_const_truthiness(
             Some(constant.truthiness())
         }
         Instruction::LoadSmallInt { i } => Some(i.get(arg) != 0),
+        Instruction::LoadCommonConstant { idx } => {
+            use oparg::CommonConstant;
+            Some(!matches!(
+                idx.get(arg),
+                CommonConstant::None | CommonConstant::False | CommonConstant::EmptyStr
+            ))
+        }
         _ => None,
     }
 }
@@ -4534,7 +4599,9 @@ fn instr_make_load_const(
     instr: &mut InstructionInfo,
     constant: ConstantData,
 ) -> crate::InternalResult<()> {
-    if instr.maybe_instr_make_load_smallint(&constant) {
+    if instr.maybe_instr_make_load_smallint(&constant)
+        || instr.maybe_instr_make_load_common_const(&constant)
+    {
         return Ok(());
     }
 
@@ -4627,6 +4694,21 @@ fn fold_const_binop(
 /// flowgraph.c get_const_value
 fn get_const_value(metadata: &CodeUnitMetadata, info: &InstructionInfo) -> Option<ConstantData> {
     match info.instr.real_opcode() {
+        Some(Opcode::LoadCommonConstant) => {
+            use oparg::CommonConstant;
+            match CommonConstant::try_from(u32::from(info.arg)).ok()? {
+                CommonConstant::None => Some(ConstantData::None),
+                CommonConstant::EmptyStr => Some(ConstantData::Str {
+                    value: Wtf8Buf::new(),
+                }),
+                CommonConstant::True => Some(ConstantData::Boolean { value: true }),
+                CommonConstant::False => Some(ConstantData::Boolean { value: false }),
+                CommonConstant::MinusOne => Some(ConstantData::Integer {
+                    value: BigInt::from(-1),
+                }),
+                _ => None,
+            }
+        }
         Some(Opcode::LoadSmallInt) => {
             let v = u32::from(info.arg) as i32;
             Some(ConstantData::Integer {
@@ -5358,20 +5440,24 @@ fn fold_tuple_of_constants(
     Ok(true)
 }
 
-fn fold_constant_intrinsic_list_to_tuple(
+fn fold_constant_sequence_into_load_const(
     metadata: &mut CodeUnitMetadata,
     block: &mut Block,
     i: usize,
 ) -> crate::InternalResult<bool> {
-    let Some(Instruction::CallIntrinsic1 { func }) = block.instructions[i].instr.real() else {
-        return Ok(false);
+    let (intrinsic, is_set) = match block.instructions[i].instr.real() {
+        Some(Instruction::CallIntrinsic1 { func })
+            if func.get(block.instructions[i].arg) == IntrinsicFunction1::ListToTuple =>
+        {
+            (true, false)
+        }
+        Some(Instruction::ListAppend { .. }) => (false, false),
+        Some(Instruction::SetAdd { .. }) => (false, true),
+        _ => return Ok(false),
     };
-    if func.get(block.instructions[i].arg) != IntrinsicFunction1::ListToTuple {
-        return Ok(false);
-    }
 
     let mut consts_found = 0usize;
-    let mut expect_append = true;
+    let mut expect_append = intrinsic;
     let mut pos = i;
     while let Some(prev) = pos.checked_sub(1) {
         pos = prev;
@@ -5380,9 +5466,12 @@ fn fold_constant_intrinsic_list_to_tuple(
             continue;
         }
 
-        if matches!(instr.instr.real(), Some(Instruction::BuildList { .. }))
-            && u32::from(instr.arg) == 0
-        {
+        let is_start = if is_set {
+            matches!(instr.instr.real(), Some(Instruction::BuildSet { .. }))
+        } else {
+            matches!(instr.instr.real(), Some(Instruction::BuildList { .. }))
+        };
+        if is_start && u32::from(instr.arg) == 0 {
             if !expect_append {
                 return Ok(false);
             }
@@ -5391,7 +5480,8 @@ fn fold_constant_intrinsic_list_to_tuple(
             elements
                 .try_reserve_exact(consts_found)
                 .map_err(|_| InternalError::MalformedControlFlowGraph)?;
-            for idx in (pos..i).rev() {
+            let end = if intrinsic { i } else { i + 1 };
+            for idx in (pos..end).rev() {
                 if matches!(block.instructions[idx].instr.real(), Some(Instruction::Nop)) {
                     continue;
                 }
@@ -5408,15 +5498,22 @@ fn fold_constant_intrinsic_list_to_tuple(
             instr_make_load_const(
                 metadata,
                 &mut block.instructions[i],
-                ConstantData::Tuple { elements },
+                if is_set {
+                    ConstantData::Frozenset { elements }
+                } else {
+                    ConstantData::Tuple { elements }
+                },
             )?;
             return Ok(true);
         }
 
         if expect_append {
-            if !matches!(instr.instr.real(), Some(Instruction::ListAppend { .. }))
-                || u32::from(instr.arg) != 1
-            {
+            let is_append = if is_set {
+                matches!(instr.instr.real(), Some(Instruction::SetAdd { .. }))
+            } else {
+                matches!(instr.instr.real(), Some(Instruction::ListAppend { .. }))
+            };
+            if !is_append || u32::from(instr.arg) != 1 {
                 return Ok(false);
             }
         } else {
@@ -5449,7 +5546,7 @@ fn optimize_lists_and_sets(
 
     let contains_or_iter = matches!(
         nextop,
-        Some(Instruction::GetIter | Instruction::ContainsOp { .. })
+        Some(Instruction::GetIter { .. } | Instruction::ContainsOp { .. })
     );
     let seq_size = u32::from(block.instructions[i].arg) as usize;
     if seq_size > STACK_USE_GUIDELINE || (seq_size < MIN_CONST_SEQUENCE_SIZE && !contains_or_iter) {
@@ -5539,84 +5636,88 @@ fn basicblock_optimize_load_const(
     metadata: &mut CodeUnitMetadata,
     block: &mut Block,
 ) -> crate::InternalResult<()> {
-    let mut i = 0;
     let mut effective_opcode = Instruction::Nop.into();
     let mut effective_oparg = OpArg::new(0);
-    while i < block.instruction_used {
-        if matches!(
-            block.instructions[i].instr.real(),
-            Some(Instruction::LoadConst { .. })
-        ) && let Some(constant) = get_const_value(metadata, &block.instructions[i])
-        {
-            block.instructions[i].maybe_instr_make_load_smallint(&constant);
-        }
+    for i in 0..block.instruction_used {
+        'instruction: {
+            if matches!(
+                block.instructions[i].instr.real(),
+                Some(Instruction::LoadConst { .. })
+            ) && let Some(constant) = get_const_value(metadata, &block.instructions[i])
+            {
+                block.instructions[i].maybe_instr_make_load_smallint(&constant);
+            }
 
-        let curr = block.instructions[i];
-        let curr_arg = curr.arg;
+            let curr = block.instructions[i];
+            let curr_arg = curr.arg;
 
-        let is_copy_of_load_const = matches!(
-            (effective_opcode, curr.instr.real()),
-            (AnyInstruction::Real(Instruction::LoadConst { .. }), Some(Instruction::Copy { i }))
-                if i.get(curr_arg) == 1
-        );
-        if !is_copy_of_load_const {
-            effective_opcode = curr.instr;
-            effective_oparg = curr_arg;
-        }
-        debug_assert!(!effective_opcode.is_assembler());
-        let Some(const_instr @ (Instruction::LoadConst { .. } | Instruction::LoadSmallInt { .. })) =
-            effective_opcode.real()
-        else {
-            i += 1;
-            continue;
-        };
-        let const_arg = effective_oparg;
+            let is_copy_of_load_const = matches!(
+                (effective_opcode, curr.instr.real()),
+                (AnyInstruction::Real(Instruction::LoadConst { .. }), Some(Instruction::Copy { i }))
+                    if i.get(curr_arg) == 1
+            );
+            if !is_copy_of_load_const {
+                effective_opcode = curr.instr;
+                effective_oparg = curr_arg;
+            }
+            debug_assert!(!effective_opcode.is_assembler());
+            let Some(
+                const_instr @ (Instruction::LoadConst { .. }
+                | Instruction::LoadSmallInt { .. }
+                | Instruction::LoadCommonConstant { .. }),
+            ) = effective_opcode.real()
+            else {
+                break 'instruction;
+            };
+            let const_arg = effective_oparg;
 
-        if i + 1 >= block.instruction_used {
-            i += 1;
-            continue;
-        }
+            if i + 1 >= block.instruction_used {
+                break 'instruction;
+            }
 
-        let next = block.instructions[i + 1];
-        let next_arg = next.arg;
+            let next = block.instructions[i + 1];
+            let next_arg = next.arg;
 
-        if let Some(is_true) = load_const_truthiness(const_instr, const_arg, metadata) {
-            let const_jump = match (next.instr.real_opcode(), next.instr.pseudo_opcode()) {
-                (_, Some(PseudoOpcode::JumpIfTrue)) => Some((true, false)),
-                (_, Some(PseudoOpcode::JumpIfFalse)) => Some((false, false)),
-                (Some(Opcode::PopJumpIfTrue), _) => Some((true, true)),
-                (Some(Opcode::PopJumpIfFalse), _) => Some((false, true)),
-                _ => None,
-            };
-            if let Some((jump_if_true, pops_condition)) = const_jump {
-                if pops_condition {
-                    block.instructions[i].set_to_nop();
-                }
-                if is_true == jump_if_true {
-                    block.instructions[i + 1].instr = PseudoOpcode::Jump.into();
-                } else {
-                    block.instructions[i + 1].set_to_nop();
+            if let Some(is_true) = load_const_truthiness(const_instr, const_arg, metadata) {
+                let const_jump = match (next.instr.real_opcode(), next.instr.pseudo_opcode()) {
+                    (_, Some(PseudoOpcode::JumpIfTrue)) => Some((true, false)),
+                    (_, Some(PseudoOpcode::JumpIfFalse)) => Some((false, false)),
+                    (Some(Opcode::PopJumpIfTrue), _) => Some((true, true)),
+                    (Some(Opcode::PopJumpIfFalse), _) => Some((false, true)),
+                    _ => None,
+                };
+                if let Some((jump_if_true, pops_condition)) = const_jump {
+                    if pops_condition {
+                        block.instructions[i].set_to_nop();
+                    }
+                    if is_true == jump_if_true {
+                        block.instructions[i + 1].instr = PseudoOpcode::Jump.into();
+                    } else {
+                        block.instructions[i + 1].set_to_nop();
+                    }
+                    break 'instruction;
                 }
-                i += 1;
-                continue;
             }
-        }
 
-        // The remaining combinations require both instructions to be real.
-        let Some(next_instr) = next.instr.real() else {
-            i += 1;
-            continue;
-        };
+            // The remaining combinations require both instructions to be real.
+            let Some(next_instr) = next.instr.real() else {
+                break 'instruction;
+            };
 
-        if let Instruction::LoadConst { consti } = const_instr {
-            let constant = &metadata.consts[consti.get(const_arg).as_usize()];
-            if matches!(constant, ConstantData::None)
-                && let Instruction::IsOp { invert } = next_instr
-            {
+            let is_none = match const_instr {
+                Instruction::LoadConst { consti } => matches!(
+                    &metadata.consts[consti.get(const_arg).as_usize()],
+                    ConstantData::None
+                ),
+                Instruction::LoadCommonConstant { idx } => {
+                    idx.get(const_arg) == oparg::CommonConstant::None
+                }
+                _ => false,
+            };
+            if is_none && let Instruction::IsOp { invert } = next_instr {
                 let mut jump_idx = i + 2;
                 if jump_idx >= block.instruction_used {
-                    i += 1;
-                    continue;
+                    break 'instruction;
                 }
 
                 if matches!(
@@ -5626,14 +5727,12 @@ fn basicblock_optimize_load_const(
                     block.instructions[jump_idx].set_to_nop();
                     jump_idx += 1;
                     if jump_idx >= block.instruction_used {
-                        i += 1;
-                        continue;
+                        break 'instruction;
                     }
                 }
 
                 let Some(jump_instr) = block.instructions[jump_idx].instr.real() else {
-                    i += 1;
-                    continue;
+                    break 'instruction;
                 };
 
                 let mut invert = matches!(
@@ -5646,8 +5745,7 @@ fn basicblock_optimize_load_const(
                     }
                     Instruction::PopJumpIfTrue { .. } => {}
                     _ => {
-                        i += 1;
-                        continue;
+                        break 'instruction;
                     }
                 };
 
@@ -5659,27 +5757,32 @@ fn basicblock_optimize_load_const(
                     Opcode::PopJumpIfNone
                 }
                 .into();
-                i += 1;
-                continue;
+                break 'instruction;
             }
-        }
 
+            if matches!(
+                const_instr,
+                Instruction::LoadConst { .. }
+                    | Instruction::LoadSmallInt { .. }
+                    | Instruction::LoadCommonConstant { .. }
+            ) && matches!(next_instr, Instruction::ToBool)
+                && let Some(value) = load_const_truthiness(const_instr, const_arg, metadata)
+            {
+                let const_idx = add_const(metadata, ConstantData::Boolean { value })?;
+                block.instructions[i].set_to_nop();
+
+                block.instructions[i + 1]
+                    .instr_set_op1(Opcode::LoadConst.into(), OpArg::new(const_idx as u32));
+                break 'instruction;
+            }
+        }
         if matches!(
-            const_instr,
-            Instruction::LoadConst { .. } | Instruction::LoadSmallInt { .. }
-        ) && matches!(next_instr, Instruction::ToBool)
-            && let Some(value) = load_const_truthiness(const_instr, const_arg, metadata)
+            block.instructions[i].instr.real_opcode(),
+            Some(Opcode::LoadConst)
+        ) && let Some(constant) = get_const_value(metadata, &block.instructions[i])
         {
-            let const_idx = add_const(metadata, ConstantData::Boolean { value })?;
-            block.instructions[i].set_to_nop();
-
-            block.instructions[i + 1]
-                .instr_set_op1(Opcode::LoadConst.into(), OpArg::new(const_idx as u32));
-            i += 1;
-            continue;
+            block.instructions[i].maybe_instr_make_load_common_const(&constant);
         }
-
-        i += 1;
     }
     Ok(())
 }
@@ -5837,7 +5940,7 @@ impl CodeInfo {
         ));
 
         let _max_stackdepth = self.blocks.calculate_stackdepth()?;
-        let _nlocalsplus = prepare_localsplus(&self.metadata, &mut self.blocks, self.flags)?;
+        let _nlocalsplus = prepare_localsplus(&self.metadata, &mut self.blocks)?;
         convert_pseudo_ops(&mut self.blocks)?;
         trace.push((
             "after_convert_pseudo_ops".to_owned(),
@@ -6968,7 +7071,9 @@ pub(crate) fn label_exception_targets(blocks: &mut Blocks) -> crate::InternalRes
             } else if let Some(Instruction::Resume { context: _ }) = instr.real() {
                 blocks[bi].instructions[i].except_handler = handler;
                 let resume_arg = u32::from(arg);
-                if resume_arg != u32::from(oparg::ResumeLocation::AtFuncStart) {
+                if resume_arg != u32::from(oparg::ResumeLocation::AtFuncStart)
+                    && resume_arg != u32::from(oparg::ResumeLocation::AtGenExprStart)
+                {
                     debug_assert!(last_yield_except_depth >= 0);
                     if last_yield_except_depth == 1 {
                         blocks[bi].instructions[i].arg =
@@ -7196,6 +7301,7 @@ mod tests {
             location: test_location(line),
             end_location: test_location(line),
             except_handler: None,
+            semantic_location: None,
             lineno_override: None,
         }
     }
@@ -7322,6 +7428,7 @@ mod tests {
             location: SourceLocation::default(),
             end_location: SourceLocation::default(),
             except_handler: None,
+            semantic_location: None,
             lineno_override: None,
         };
         let handler = push_except_block(&mut stack, setup, &mut blocks).unwrap();
@@ -7726,7 +7833,7 @@ mod tests {
 
         // CPython `basicblock_optimize_load_const()` keeps the previous
         // LOAD_CONST as the effective opcode for a following `COPY 1`, so the
-        // COPY is NOPed and TO_BOOL becomes LOAD_CONST True.
+        // COPY is NOPed and TO_BOOL becomes LOAD_COMMON_CONSTANT True.
         assert!(matches!(
             code.blocks[0].instructions[0].instr.real(),
             Some(Instruction::LoadConst { .. })
@@ -7738,11 +7845,11 @@ mod tests {
         let load_bool = &code.blocks[0].instructions[2];
         assert!(matches!(
             load_bool.instr.real(),
-            Some(Instruction::LoadConst { .. })
+            Some(Instruction::LoadCommonConstant { .. })
         ));
         assert_eq!(
-            code.metadata.consts[u32::from(load_bool.arg) as usize],
-            ConstantData::Boolean { value: true }
+            u32::from(load_bool.arg),
+            u32::from(oparg::CommonConstant::True)
         );
     }
 
@@ -7793,7 +7900,7 @@ mod tests {
     }
 
     #[test]
-    fn optimize_load_fast_records_no_input_opcode_ref_at_cpython_produced_index() {
+    fn optimize_load_fast_records_no_input_opcode_ref_at_cpython_instruction_index() {
         let mut block = Block::default();
         test_block_push(&mut block, test_instr(Opcode::LoadFast.into(), 10));
         test_block_push(&mut block, test_instr(Instruction::GetLen, 10));
@@ -7807,77 +7914,11 @@ mod tests {
             .optimize_load_fast()
             .expect("optimize_load_fast succeeds");
 
-        // CPython `optimize_load_fast()` shadows the outer instruction index in
-        // the produced-value loop for GET_LEN, so the produced ref is recorded
-        // with index 0 here. The original LOAD_FAST is therefore not considered
-        // the consumed producer.
+        // CPython records GET_LEN's result at instruction index 1. The
+        // SWAP/POP_TOP consumes the original local reference, so it can borrow.
         assert!(matches!(
             code.blocks[0].instructions[0].instr.real(),
-            Some(Instruction::LoadFast { .. })
-        ));
-    }
-
-    #[test]
-    fn constant_sequence_loads_use_cpython_opcode_has_const_metadata() {
-        let mut metadata = CodeUnitMetadata {
-            name: "<module>".to_owned(),
-            qualname: Some("<module>".to_owned()),
-            consts: Default::default(),
-            names: IndexSet::default(),
-            varnames: IndexSet::default(),
-            cellvars: IndexSet::default(),
-            freevars: IndexSet::default(),
-            fast_hidden: IndexMap::default(),
-            fast_hidden_final: IndexSet::default(),
-            argcount: 0,
-            posonlyargcount: 0,
-            kwonlyargcount: 0,
-            firstlineno: OneIndexed::MIN,
-        };
-        let (left, _) = metadata
-            .consts
-            .insert_full(ConstantData::Str { value: "a".into() });
-        let (right, _) = metadata
-            .consts
-            .insert_full(ConstantData::Str { value: "b".into() });
-
-        let mut immortal = test_instr(Instruction::Nop, 90);
-        immortal.instr = Opcode::LoadConstImmortal.into();
-        immortal.arg = OpArg::new(left as u32);
-        let mut mortal = test_instr(Instruction::Nop, 90);
-        mortal.instr = Opcode::LoadConstMortal.into();
-        mortal.arg = OpArg::new(right as u32);
-        let mut build = test_instr(Opcode::BuildTuple.into(), 90);
-        build.arg = OpArg::new(2);
-        let mut block = Block::default();
-        for info in [immortal, mortal, build] {
-            test_block_push(&mut block, info);
-        }
-
-        assert!(
-            fold_tuple_of_constants(&mut metadata, &mut block, 2)
-                .expect("fold_tuple_of_constants succeeds")
-        );
-
-        // CPython `loads_const()` accepts every `OPCODE_HAS_CONST` opcode, not
-        // just canonical LOAD_CONST, so LOAD_CONST_IMMORTAL/MORTAL participate
-        // in constant-sequence folding.
-        assert!(matches!(
-            block.instructions[0].instr.real(),
-            Some(Instruction::Nop)
-        ));
-        assert!(matches!(
-            block.instructions[1].instr.real(),
-            Some(Instruction::Nop)
-        ));
-        let folded = &block.instructions[2];
-        assert!(matches!(
-            folded.instr.real(),
-            Some(Instruction::LoadConst { .. })
-        ));
-        assert!(matches!(
-            &metadata.consts[u32::from(folded.arg) as usize],
-            ConstantData::Tuple { elements } if elements.len() == 2
+            Some(Instruction::LoadFastBorrow { .. })
         ));
     }
 
diff --git a/crates/codegen/src/lib.rs b/crates/codegen/src/lib.rs
index 0bc16d72ded..089f7ab496c 100644
--- a/crates/codegen/src/lib.rs
+++ b/crates/codegen/src/lib.rs
@@ -8,7 +8,7 @@ extern crate log;
 
 extern crate alloc;
 
-use alloc::{string::String, vec::Vec};
+use alloc::string::String;
 use rustpython_compiler_core::bytecode::ConstantData;
 
 type IndexMap<K, V> = indexmap::IndexMap<K, V, rapidhash::quality::RandomState>;
@@ -18,6 +18,7 @@ pub mod compile;
 pub mod error;
 pub mod ir;
 pub mod preprocess;
+pub mod source_location;
 mod string_parser;
 pub mod symboltable;
 mod unparse;
@@ -188,12 +189,14 @@ pub fn interpolation_debug_text(
 ) -> (String, TextRange) {
     let leading = debug_text.leading();
     let trailing = debug_text.trailing();
-    let text = [
-        strip_python_comments(leading).as_str(),
-        source_file.source_text().slice(expression_range),
-        strip_python_comments(trailing).as_str(),
-    ]
-    .concat();
+    let text = strip_python_comments(
+        &[
+            leading,
+            source_file.source_text().slice(expression_range),
+            trailing,
+        ]
+        .concat(),
+    );
     let width =
         |len: usize| TextSize::new(u32::try_from(len).expect("debug interpolation text too long"));
     let range = TextRange::new(
@@ -203,64 +206,109 @@ pub fn interpolation_debug_text(
     (text, range)
 }
 
+/// The source text stored in a template interpolation, including whitespace
+/// before its debug marker, conversion, format specifier, or closing brace.
+/// Returns `None` for a synthetic node without a source interpolation range.
+#[must_use]
+pub fn interpolation_expression_text(
+    source_file: &SourceFile,
+    interpolation: &ast::InterpolatedElement,
+) -> Option<String> {
+    if let Some(debug_text) = &interpolation.debug_text {
+        let mut text = strip_python_comments(debug_text.as_str());
+        let end = interpolation_suffix_end(&text);
+        if text[..end].ends_with('=') {
+            text.truncate(end - 1);
+        }
+        return Some(text);
+    }
+
+    let expression_range = interpolation.expression.range();
+    if interpolation.range.start() >= expression_range.start()
+        || interpolation.range.end() <= expression_range.end()
+    {
+        return None;
+    }
+    let start = interpolation.range.start() + TextSize::new(1);
+    let end = interpolation
+        .format_spec
+        .as_ref()
+        .map_or_else(
+            || interpolation.range.end(),
+            |format_spec| format_spec.range.start(),
+        )
+        .checked_sub(TextSize::new(1))?;
+    if start > expression_range.start() || end < expression_range.end() {
+        return None;
+    }
+    let mut text =
+        strip_python_comments(source_file.source_text().slice(TextRange::new(start, end)));
+    if interpolation.conversion != ast::ConversionFlag::None {
+        let end = interpolation_suffix_end(&text);
+        let conversion_start = end.checked_sub(2)?;
+        if text.as_bytes().get(conversion_start) != Some(&b'!') {
+            return None;
+        }
+        text.truncate(conversion_start);
+    }
+    Some(text)
+}
+
+fn interpolation_suffix_end(text: &str) -> usize {
+    let mut end = text.len();
+    // Debug markers and conversions can be followed by whitespace and line
+    // continuations. Whitespace preceding either marker remains significant.
+    loop {
+        let trimmed = text[..end].trim_end();
+        let has_newline = text[trimmed.len()..end].contains(['\n', '\r']);
+        end = trimmed.len();
+        if has_newline && text[..end].ends_with('\\') {
+            end -= 1;
+        } else {
+            return end;
+        }
+    }
+}
+
 fn strip_python_comments(text: &str) -> String {
-    let chars = text.chars().collect::<Vec<_>>();
+    // Tokenizer metadata uses universal newlines even when source ranges refer
+    // to the original CRLF or CR input.
+    let normalized;
+    let text = if text.contains('\r') {
+        normalized = text.replace("\r\n", "\n").replace('\r', "\n");
+        normalized.as_str()
+    } else {
+        text
+    };
+    let mut chars = text.chars();
     let mut result = String::with_capacity(text.len());
     let mut quote = None;
-    let mut triple_quoted = false;
-    let mut escaped = false;
-    let mut in_comment = false;
-    let mut index = 0;
 
-    while index < chars.len() {
-        let ch = chars[index];
-        if in_comment {
-            if matches!(ch, '\n' | '\r') {
-                in_comment = false;
-                result.push(ch);
-            }
-            index += 1;
-            continue;
-        }
-
-        if let Some(delimiter) = quote {
+    while let Some(ch) = chars.next() {
+        // Match tokenizer metadata reconstruction, including escaped quotes
+        // outside literals and its per-quote handling of triple strings.
+        if ch == '\\' {
             result.push(ch);
-            if escaped {
-                escaped = false;
-            } else if ch == '\\' {
-                escaped = true;
-            } else if triple_quoted
-                && ch == delimiter
-                && chars.get(index + 1) == Some(&delimiter)
-                && chars.get(index + 2) == Some(&delimiter)
-            {
-                result.push(delimiter);
-                result.push(delimiter);
-                quote = None;
-                index += 2;
-            } else if !triple_quoted && ch == delimiter {
-                quote = None;
+            if let Some(escaped) = chars.next() {
+                result.push(escaped);
             }
-            index += 1;
-            continue;
-        }
-
-        match ch {
-            '#' => in_comment = true,
-            '\'' | '"' => {
+        } else if matches!(ch, '\'' | '"') {
+            if quote.is_none() {
                 quote = Some(ch);
-                triple_quoted =
-                    chars.get(index + 1) == Some(&ch) && chars.get(index + 2) == Some(&ch);
-                result.push(ch);
-                if triple_quoted {
-                    result.push(ch);
-                    result.push(ch);
-                    index += 2;
+            } else if quote == Some(ch) {
+                quote = None;
+            }
+            result.push(ch);
+        } else if ch == '#' && quote.is_none() {
+            for comment_ch in chars.by_ref() {
+                if comment_ch == '\n' {
+                    result.push('\n');
+                    break;
                 }
             }
-            _ => result.push(ch),
+        } else {
+            result.push(ch);
         }
-        index += 1;
     }
     result
 }
diff --git a/crates/codegen/src/preprocess.rs b/crates/codegen/src/preprocess.rs
index 466d8f35ebe..f935fccf9b7 100644
--- a/crates/codegen/src/preprocess.rs
+++ b/crates/codegen/src/preprocess.rs
@@ -10,7 +10,8 @@ use ruff_python_ast::{
 use ruff_text_size::{Ranged, TextRange};
 
 use crate::compile::FutureFeature;
-use rustpython_compiler_core::bytecode;
+use core::cell::{Cell, RefCell};
+use rustpython_compiler_core::{AstLocationError, AstLocations, SourceLocationRange, bytecode};
 
 const MAXDIGITS: usize = 3;
 const F_LJUST: u8 = 1;
@@ -288,6 +289,8 @@ pub fn preprocess_statements(
         optimize,
         future_annotations,
         constant_folding: !syntax_check_only,
+        locations: None,
+        location_error: None,
     };
     for stmt in body {
         preprocessor.visit_stmt(stmt);
@@ -304,6 +307,8 @@ pub fn preprocess_mod(
         optimize,
         future_annotations,
         constant_folding: !syntax_check_only,
+        locations: None,
+        location_error: None,
     };
     match module {
         ast::Mod::Module(module) => preprocessor.visit_astfold_body(&mut module.body),
@@ -311,18 +316,138 @@ pub fn preprocess_mod(
     }
 }
 
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
-struct AstPreprocessor {
+/// Run preprocessing while retaining explicit Python AST location provenance.
+/// The table is borrowed only inside native transformations, never across Python calls.
+pub fn preprocess_mod_with_locations(
+    module: &mut ast::Mod,
+    optimize: u8,
+    future_annotations: bool,
+    syntax_check_only: bool,
+    locations: &mut AstLocations,
+) -> Result<(), AstLocationError> {
+    let table = RefCell::new(core::mem::take(locations));
+    let error = Cell::new(None);
+    let preprocessor = AstPreprocessor {
+        optimize,
+        future_annotations,
+        constant_folding: !syntax_check_only,
+        locations: Some(&table),
+        location_error: Some(&error),
+    };
+    match module {
+        ast::Mod::Module(module) => preprocessor.visit_astfold_body(&mut module.body),
+        ast::Mod::Expression(expr) => preprocessor.visit_expr(&mut expr.body),
+    }
+    *locations = table.into_inner();
+    error.get().map_or(Ok(()), Err)
+}
+
+pub fn preprocess_statements_with_locations(
+    body: &mut [ast::Stmt],
+    optimize: u8,
+    future_annotations: bool,
+    syntax_check_only: bool,
+    locations: &mut AstLocations,
+) -> Result<(), AstLocationError> {
+    let table = RefCell::new(core::mem::take(locations));
+    let error = Cell::new(None);
+    let preprocessor = AstPreprocessor {
+        optimize,
+        future_annotations,
+        constant_folding: !syntax_check_only,
+        locations: Some(&table),
+        location_error: Some(&error),
+    };
+    for stmt in body {
+        preprocessor.visit_stmt(stmt);
+    }
+    *locations = table.into_inner();
+    error.get().map_or(Ok(()), Err)
+}
+
+#[derive(Clone, Copy)]
+struct AstPreprocessor<'a> {
     optimize: u8,
     future_annotations: bool,
     constant_folding: bool,
+    locations: Option<&'a RefCell<AstLocations>>,
+    location_error: Option<&'a Cell<Option<AstLocationError>>>,
 }
 
-impl AstPreprocessor {
+impl AstPreprocessor<'_> {
+    fn record_location_error(&self, error: AstLocationError) {
+        if let Some(slot) = self.location_error
+            && slot.get().is_none()
+        {
+            slot.set(Some(error));
+        }
+    }
+
+    fn location(&self, node: &impl HasNodeIndex) -> Option<SourceLocationRange> {
+        self.locations?
+            .borrow()
+            .get(node.node_index().load().as_u32()?)
+    }
+
+    fn fresh_location(&self, location: SourceLocationRange) -> AtomicNodeIndex {
+        let index = AtomicNodeIndex::NONE;
+        if let Some(locations) = self.locations {
+            match locations.borrow_mut().allocate(Some(location)) {
+                Ok(id) => index.set(ast::NodeIndex::from(id)),
+                Err(error) => self.record_location_error(error),
+            }
+        }
+        index
+    }
+
+    fn artificial_elements(&self, elements: &mut InterpolatedStringElements) {
+        if self.locations.is_none() {
+            return;
+        }
+        let artificial = SourceLocationRange {
+            line: -1,
+            end_line: -1,
+            col: -1,
+            end_col: -1,
+        };
+        for element in elements.iter_mut() {
+            match element {
+                InterpolatedStringElement::Literal(literal) => {
+                    if literal.node_index.load().as_u32().is_none() {
+                        literal.node_index = self.fresh_location(artificial);
+                    }
+                }
+                InterpolatedStringElement::Interpolation(value) => {
+                    if let Some(spec) = &mut value.format_spec {
+                        if spec.node_index.load().as_u32().is_none() {
+                            spec.node_index = self.fresh_location(artificial);
+                        }
+                        self.artificial_elements(&mut spec.elements);
+                        // This visitor only runs on the result of optimize_format.
+                        // final ast_preprocess.c constructs a Constant format spec,
+                        // not a JoinedStr. Preserve that explicit shape in the
+                        // existing runtime AST field rather than inferring it
+                        // from the artificial coordinates during serialization.
+                        if let [InterpolatedStringElement::Literal(literal)] = &spec.elements[..] {
+                            value.runtime_formatted_value_format_spec =
+                                Some(Box::new(Expr::Constant(ast::ExprConstant {
+                                    node_index: spec.node_index.clone(),
+                                    range: spec.range,
+                                    value: ast::ConstantValue::Str(literal.value.clone()),
+                                    kind: None,
+                                    invalid_type: None,
+                                })));
+                        }
+                    }
+                }
+            }
+        }
+    }
+
     fn visit_astfold_body(self, body: &mut ast::Suite) {
         let mut docstring = body_starts_with_docstring(body);
         if docstring && self.optimize >= 2 {
-            remove_docstring_from_body(body);
+            remove_docstring_from_body(body, &self);
             docstring = false;
         }
 
@@ -331,12 +456,12 @@ impl AstPreprocessor {
         }
 
         if !docstring && body_starts_with_docstring(body) {
-            wrap_first_docstring_as_fstring(body);
+            wrap_first_docstring_as_fstring(body, self.locations.is_some());
         }
     }
 }
 
-impl Transformer for AstPreprocessor {
+impl Transformer for AstPreprocessor<'_> {
     fn visit_stmt(&self, stmt: &mut ast::Stmt) {
         match stmt {
             ast::Stmt::FunctionDef(function) => {
@@ -394,7 +519,14 @@ impl Transformer for AstPreprocessor {
         transformer::walk_expr(self, expr);
         widen_implicit_call_generator_range(expr);
         if self.constant_folding {
-            if let Some(optimized) = optimize_format(expr) {
+            if let Some(mut optimized) = optimize_format(expr) {
+                if let Expr::FString(fstring) = &mut optimized {
+                    for part in &mut fstring.value {
+                        if let ast::FStringPartMut::FString(part) = part {
+                            self.artificial_elements(&mut part.elements);
+                        }
+                    }
+                }
                 *expr = optimized;
             } else if let Some(optimized) = fold_debug_constant(expr, self.optimize) {
                 *expr = optimized;
@@ -632,15 +764,27 @@ fn generated_literal(value: String) -> InterpolatedStringLiteralElement {
     }
 }
 
-fn remove_docstring_from_body(body: &mut ast::Suite) {
+fn remove_docstring_from_body(body: &mut ast::Suite, preprocessor: &AstPreprocessor<'_>) {
+    let statement_location = body.first().and_then(|node| preprocessor.location(node));
     if let Some(range) = take_docstring(body) {
         if !body.is_empty() {
             return;
         }
         let start = range.start();
         let pass_range = TextRange::new(start, start + ruff_text_size::TextSize::from(4));
+        let node_index = statement_location.map_or(AtomicNodeIndex::NONE, |location| {
+            let Some(end_col) = location.col.checked_add(4) else {
+                preprocessor.record_location_error(AstLocationError::CoordinateOverflow);
+                return AtomicNodeIndex::NONE;
+            };
+            preprocessor.fresh_location(SourceLocationRange {
+                end_line: location.line,
+                end_col,
+                ..location
+            })
+        });
         body.push(ast::Stmt::Pass(ast::StmtPass {
-            node_index: Default::default(),
+            node_index,
             range: pass_range,
         }));
     }
@@ -664,7 +808,7 @@ fn body_starts_with_docstring(body: &[ast::Stmt]) -> bool {
     string_literal_expr_value(&expr_stmt.value).is_some()
 }
 
-fn wrap_first_docstring_as_fstring(body: &mut [ast::Stmt]) {
+fn wrap_first_docstring_as_fstring(body: &mut [ast::Stmt], explicit_locations: bool) {
     let Some(ast::Stmt::Expr(expr_stmt)) = body.first_mut() else {
         return;
     };
@@ -672,16 +816,27 @@ fn wrap_first_docstring_as_fstring(body: &mut [ast::Stmt]) {
         return;
     };
     let value = value.to_string();
+    let literal_index = expr_stmt.value.node_index().clone();
+    let wrapper_range = if explicit_locations {
+        expr_stmt.range
+    } else {
+        range
+    };
+    let wrapper_index = if explicit_locations {
+        expr_stmt.node_index.clone()
+    } else {
+        AtomicNodeIndex::NONE
+    };
     *expr_stmt.value = ast::Expr::FString(ast::ExprFString {
-        node_index: AtomicNodeIndex::NONE,
-        range,
+        node_index: wrapper_index.clone(),
+        range: wrapper_range,
         value: FStringValue::single(FString {
-            range,
-            node_index: AtomicNodeIndex::NONE,
+            range: wrapper_range,
+            node_index: wrapper_index,
             elements: InterpolatedStringElements::from(vec![InterpolatedStringElement::Literal(
                 InterpolatedStringLiteralElement {
                     range,
-                    node_index: AtomicNodeIndex::NONE,
+                    node_index: literal_index,
                     value: value.into_boxed_str(),
                 },
             )]),
@@ -796,6 +951,51 @@ fn fold_match_number_binop(
 mod tests {
     use super::*;
 
+    #[test]
+    fn preprocessing_preserves_first_location_error() {
+        for first_error in [
+            AstLocationError::ExhaustedNodeIdentities,
+            AstLocationError::CoordinateOverflow,
+        ] {
+            let ast::Mod::Module(mut module) =
+                ruff_python_parser::parse("\"doc\"", ruff_python_parser::Mode::Module.into())
+                    .unwrap()
+                    .into_syntax()
+            else {
+                panic!("expected module");
+            };
+            let location = SourceLocationRange {
+                line: 1,
+                end_line: 1,
+                col: i32::MAX,
+                end_col: i32::MAX,
+            };
+            let mut locations = AstLocations::default();
+            // One entry exhausts the identity cursor without allocating a huge AST.
+            locations.insert(AstLocations::MAX_ID, location).unwrap();
+            module.body[0]
+                .node_index()
+                .set(ast::NodeIndex::from(AstLocations::MAX_ID));
+            let locations = RefCell::new(locations);
+            let error = Cell::new(None);
+            let preprocessor = AstPreprocessor {
+                optimize: 2,
+                future_annotations: false,
+                constant_folding: true,
+                locations: Some(&locations),
+                location_error: Some(&error),
+            };
+
+            if first_error == AstLocationError::ExhaustedNodeIdentities {
+                preprocessor.fresh_location(location);
+            }
+            remove_docstring_from_body(&mut module.body, &preprocessor);
+            assert_eq!(error.get(), Some(first_error));
+            preprocessor.fresh_location(location);
+            assert_eq!(error.get(), Some(first_error));
+        }
+    }
+
     fn first_match_value(source: &str) -> ast::Expr {
         let parsed = ruff_python_parser::parse(source, ruff_python_parser::Mode::Module.into())
             .unwrap()
diff --git a/crates/codegen/src/source_location.rs b/crates/codegen/src/source_location.rs
new file mode 100644
index 00000000000..371d915be0f
--- /dev/null
+++ b/crates/codegen/src/source_location.rs
@@ -0,0 +1,40 @@
+//! Explicit locations supplied by Python AST objects.
+//!
+//! Parser input continues to resolve its text ranges through the source file.
+//! AST input needs node identity because absent columns and a real column zero
+//! can produce the same normalized text range.
+
+use ruff_python_ast::HasNodeIndex;
+use ruff_text_size::TextRange;
+use rustpython_compiler_core::{AstLocations, SourceLocationRange};
+
+/// NONE is a shared placeholder and can never identify semantic coordinates.
+pub(crate) fn node_location(
+    locations: &AstLocations,
+    node: &impl HasNodeIndex,
+) -> Option<SourceLocationRange> {
+    locations.get(node.node_index().load().as_u32()?)
+}
+
+/// Navigation range and semantic coordinates must be saved/restored together.
+#[derive(Clone, Copy, Debug)]
+pub(crate) struct CompilerSourceSpan {
+    pub range: TextRange,
+    pub location: Option<SourceLocationRange>,
+}
+
+impl CompilerSourceSpan {
+    pub(crate) fn is_artificial(self) -> bool {
+        self.location.map_or_else(
+            || self.range == TextRange::default(),
+            |location| location.line < 0,
+        )
+    }
+
+    pub(crate) const fn parsed(range: TextRange) -> Self {
+        Self {
+            range,
+            location: None,
+        }
+    }
+}
diff --git a/crates/codegen/src/symboltable.rs b/crates/codegen/src/symboltable.rs
index bff326087e6..4af1ee0bed4 100644
--- a/crates/codegen/src/symboltable.rs
+++ b/crates/codegen/src/symboltable.rs
@@ -1081,6 +1081,7 @@ struct SymbolTableBuilder {
     comprehension_yield_context: Option<&'static str>,
     // PEP 649: Track if we're inside a conditional block (if/for/while/etc.)
     in_conditional_block: bool,
+    lazy_prohibited_scopes: Vec<usize>,
     // Mirrors symtable ENTER_RECURSIVE guards during compilation.
     recursion_depth: usize,
     recursion_limit: usize,
@@ -1122,6 +1123,7 @@ impl SymbolTableBuilder {
             in_iter_def_exp: false,
             comprehension_yield_context: None,
             in_conditional_block: false,
+            lazy_prohibited_scopes: Vec::new(),
             recursion_depth: 0,
             recursion_limit: DEFAULT_RECURSION_LIMIT,
             next_block_index: 0,
@@ -1630,6 +1632,36 @@ impl SymbolTableBuilder {
         Ok(())
     }
 
+    fn validate_lazy_import(&self, statement: &ast::Stmt) -> SymbolTableResult {
+        let (kind, star) = match statement {
+            ast::Stmt::Import(node) if node.is_lazy => ("import", false),
+            ast::Stmt::ImportFrom(node) if node.is_lazy => (
+                "from ... import",
+                node.names
+                    .first()
+                    .is_some_and(|name| name.name.as_str() == "*"),
+            ),
+            _ => return Ok(()),
+        };
+        let reason = if self.lazy_prohibited_scopes.contains(&self.tables.len()) {
+            Some(format!("lazy {kind} not allowed inside try/except blocks"))
+        } else {
+            match self.tables.last().unwrap().typ {
+                CompilerScope::Function | CompilerScope::AsyncFunction => {
+                    Some(format!("lazy {kind} not allowed inside functions"))
+                }
+                CompilerScope::Class => Some(format!("lazy {kind} not allowed inside classes")),
+                _ if star => Some("lazy from ... import * is not allowed".to_owned()),
+                _ => None,
+            }
+        };
+        if let Some(reason) = reason {
+            Err(self.error_ranged(reason, statement.range()))
+        } else {
+            Ok(())
+        }
+    }
+
     fn scan_statement(&mut self, statement: &ast::Stmt) -> SymbolTableResult {
         if self.recursion_depth >= self.recursion_limit {
             return Err(SymbolTableError {
@@ -1641,6 +1673,7 @@ impl SymbolTableBuilder {
         self.recursion_depth += 1;
         let result = (|| {
             use ast::*;
+            self.validate_lazy_import(statement)?;
             self.track_future_statement(statement)?;
             match &statement {
                 Stmt::Global(StmtGlobal { names, .. }) => {
@@ -2005,6 +2038,7 @@ impl SymbolTableBuilder {
                     // PEP 649: Track conditional block for annotations
                     let saved_in_conditional_block = self.in_conditional_block;
                     self.in_conditional_block = true;
+                    self.lazy_prohibited_scopes.push(self.tables.len());
                     self.scan_statements(body)?;
                     for handler in handlers {
                         let ExceptHandler::ExceptHandler(ast::ExceptHandlerExceptHandler {
@@ -2023,6 +2057,7 @@ impl SymbolTableBuilder {
                     }
                     self.scan_statements(orelse)?;
                     self.scan_statements(finalbody)?;
+                    self.lazy_prohibited_scopes.pop();
                     self.in_conditional_block = saved_in_conditional_block;
                 }
                 Stmt::Match(StmtMatch { subject, cases, .. }) => {
@@ -2207,11 +2242,9 @@ impl SymbolTableBuilder {
                 Expr::BoolOp(ExprBoolOp { values, .. }) => {
                     self.scan_expressions(values, context)?;
                 }
-                Expr::Compare(ExprCompare {
-                    left, comparators, ..
-                }) => {
-                    self.scan_expression(left, context)?;
-                    self.scan_expressions(comparators, context)?;
+                Expr::Compare(compare) => {
+                    self.scan_expression(compare.first_operand(), context)?;
+                    self.scan_expressions(compare.comparators(), context)?;
                 }
                 Expr::Subscript(ExprSubscript { value, slice, .. }) => {
                     self.scan_expression(value, ExpressionContext::Load)?;
diff --git a/crates/codegen/src/unparse.rs b/crates/codegen/src/unparse.rs
index 86744a6010b..06e8f27a604 100644
--- a/crates/codegen/src/unparse.rs
+++ b/crates/codegen/src/unparse.rs
@@ -1,8 +1,8 @@
-use crate::strip_python_comments;
+use crate::{interpolation_debug_text, interpolation_expression_text};
 use alloc::fmt;
 use core::fmt::Display as _;
 use ruff_python_ast as ast;
-use ruff_text_size::{Ranged, TextSize, TextSlice};
+use ruff_text_size::Ranged;
 use rustpython_compiler_core::SourceFile;
 use rustpython_literal::escape::{AsciiEscape, UnicodeEscape};
 
@@ -380,18 +380,11 @@ impl<'a, 'b, 'c> Unparser<'a, 'b, 'c> {
                     UnparseExpr::new(value, self.source)
                 )?;
             }
-            ast::Expr::Compare(ast::ExprCompare {
-                left,
-                ops,
-                comparators,
-                node_index: _,
-                range: _range,
-                ..
-            }) => {
+            ast::Expr::Compare(compare) => {
                 group_if!(precedence::CMP, {
                     let new_lvl = precedence::CMP + 1;
-                    self.unparse_expr(left, new_lvl)?;
-                    for (op, cmp) in ops.iter().zip(comparators) {
+                    self.unparse_expr(compare.first_operand(), new_lvl)?;
+                    for (_, op, cmp) in compare.iter() {
                         self.p(" ")?;
                         self.p(op.as_str())?;
                         self.p(" ")?;
@@ -622,11 +615,8 @@ impl<'a, 'b, 'c> Unparser<'a, 'b, 'c> {
             fmt::from_fn(|f| Unparser::new(f, self.source).unparse_expr(val, precedence::TEST + 1))
                 .to_string();
         if let Some(debug_text) = debug_text {
-            let leading = debug_text.leading();
-            let trailing = debug_text.trailing();
-            self.p(leading)?;
-            self.p(self.source.source_text().slice(val.range()))?;
-            self.p(trailing)?;
+            let (text, _) = interpolation_debug_text(self.source, debug_text, val.range());
+            self.unparse_fstring_str(&text)?;
             if conversion == ast::ConversionFlag::None && spec.is_none() {
                 conversion = ast::ConversionFlag::Repr;
             }
@@ -635,19 +625,7 @@ impl<'a, 'b, 'c> Unparser<'a, 'b, 'c> {
             // put a space to avoid escaping the bracket
             "{ "
         } else {
-            // Preserve leading whitespace between '{' and the expression
-            let source_text = self.source.source_text();
-            let start = val.range().start().to_usize();
-            if start > 0
-                && source_text
-                    .as_bytes()
-                    .get(start - 1)
-                    .is_some_and(|b| b.is_ascii_whitespace())
-            {
-                "{ "
-            } else {
-                "{"
-            }
+            "{"
         };
         self.p(brace)?;
         self.p(&buffered)?;
@@ -700,8 +678,8 @@ impl<'a, 'b, 'c> Unparser<'a, 'b, 'c> {
         self.p("f")?;
         let body = fmt::from_fn(|f| {
             value.iter().try_for_each(|part| match part {
-                ast::FStringPart::Literal(lit) => f.write_str(lit),
-                ast::FStringPart::FString(ast::FString { elements, .. }) => {
+                ast::FStringPartRef::Literal(lit) => f.write_str(lit),
+                ast::FStringPartRef::FString(ast::FString { elements, .. }) => {
                     Unparser::new(f, self.source).unparse_fstring_body(elements)
                 }
             })
@@ -744,23 +722,11 @@ impl<'a, 'b, 'c> Unparser<'a, 'b, 'c> {
         &mut self,
         interpolation: &ast::InterpolatedElement,
     ) -> fmt::Result {
-        let source_conversion = interpolation.conversion;
-        let mut conversion = source_conversion;
-        let debug_parts = interpolation.debug_text.as_ref().map(|debug_text| {
-            (
-                strip_python_comments(debug_text.leading()),
-                strip_python_comments(
-                    self.source
-                        .source_text()
-                        .slice(interpolation.expression.range()),
-                ),
-                strip_python_comments(debug_text.trailing()),
-            )
-        });
-        if let Some((leading, source, trailing)) = &debug_parts {
-            self.p(leading)?;
-            self.p(source)?;
-            self.p(trailing)?;
+        let mut conversion = interpolation.conversion;
+        if let Some(debug_text) = &interpolation.debug_text {
+            let (text, _) =
+                interpolation_debug_text(self.source, debug_text, interpolation.expression.range());
+            self.unparse_fstring_str(&text)?;
             if conversion == ast::ConversionFlag::None && interpolation.format_spec.is_none() {
                 conversion = ast::ConversionFlag::Repr;
             }
@@ -768,42 +734,14 @@ impl<'a, 'b, 'c> Unparser<'a, 'b, 'c> {
 
         let expression = if let Some(ast::ConstantValue::Str(value)) = &interpolation.runtime_str {
             value.to_string()
-        } else if let Some((leading, source, trailing)) = &debug_parts {
-            let mut expression = leading.clone();
-            expression.push_str(source);
-            let equal = trailing
-                .rfind('=')
-                .expect("debug interpolation must contain '='");
-            expression.push_str(&trailing[..equal]);
-            expression.trim_end().to_owned()
+        } else if let Some(expression) = interpolation_expression_text(self.source, interpolation) {
+            expression
         } else {
-            let expression_range = interpolation.expression.range();
-            let after_brace = interpolation.range.start() + TextSize::new(1);
-            let mut expression_end = interpolation.format_spec.as_ref().map_or_else(
-                || interpolation.range.end() - TextSize::new(1),
-                |format_spec| format_spec.range.start() - TextSize::new(1),
-            );
-            if source_conversion != ast::ConversionFlag::None {
-                expression_end -= TextSize::new(2);
-            }
-            if interpolation.range.start() < expression_range.start()
-                && interpolation.range.end() >= expression_range.end()
-                && after_brace <= expression_end
-            {
-                strip_python_comments(
-                    self.source
-                        .source_text()
-                        .slice(ruff_text_size::TextRange::new(after_brace, expression_end)),
-                )
-                .trim_end()
-                .to_owned()
-            } else {
-                fmt::from_fn(|f| {
-                    Unparser::new(f, self.source)
-                        .unparse_expr(&interpolation.expression, precedence::TEST + 1)
-                })
-                .to_string()
-            }
+            fmt::from_fn(|f| {
+                Unparser::new(f, self.source)
+                    .unparse_expr(&interpolation.expression, precedence::TEST + 1)
+            })
+            .to_string()
         };
 
         self.p(if expression.starts_with('{') {
@@ -821,7 +759,7 @@ impl<'a, 'b, 'c> Unparser<'a, 'b, 'c> {
 
         if let Some(format_spec) = &interpolation.format_spec {
             self.p(":")?;
-            self.unparse_tstring_body(&format_spec.elements)?;
+            self.unparse_fstring_body(&format_spec.elements)?;
         }
 
         self.p("}")
diff --git a/crates/common/Cargo.toml b/crates/common/Cargo.toml
index 25247e4d010..ea31322575e 100644
--- a/crates/common/Cargo.toml
+++ b/crates/common/Cargo.toml
@@ -10,7 +10,7 @@ license.workspace = true
 
 [features]
 default = ["std"]
-binascii = ["dep:base64", "dep:crc32fast"]
+binascii = ["dep:crc32fast"]
 bz2 = ["std", "dep:bzip2"]
 cjk-codecs = []
 inet = ["std"]
@@ -39,7 +39,6 @@ rustpython-unicode = { workspace = true }
 rustpython-wtf8 = { workspace = true }
 
 ascii = { workspace = true }
-base64 = { workspace = true, optional = true }
 bitflags = { workspace = true }
 blake2b_simd = { workspace = true, optional = true }
 blake2s_simd = { workspace = true, optional = true }
diff --git a/crates/common/src/binascii.rs b/crates/common/src/binascii.rs
index 2a262d3a28b..73a17c1b01e 100644
--- a/crates/common/src/binascii.rs
+++ b/crates/common/src/binascii.rs
@@ -7,7 +7,6 @@
 //! the caller's responsibility (see `mod.rs`).
 
 use alloc::{vec, vec::Vec};
-use base64::Engine;
 
 /// The base64 pad character `=`.
 pub const PAD: u8 = 61u8;
@@ -31,13 +30,17 @@ pub enum Error {
     TooLong,
     /// `a2b_base64`: base64 decoding failed.
     Base64(Base64DecodeError),
+    /// The base64 output would exceed the maximum Python bytes length.
+    TooMuchBase64Data,
+    /// Reserving the transform output failed.
+    Memory,
 }
 
 /// Mirrors CPython's `binascii_a2b_base64_impl` (`Modules/binascii.c`) error
 /// paths one-for-one, so the caller can build the exact Python error message.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Base64DecodeError {
-    /// A `=` at `quad_pos == 0, i == 0`, strict mode.
+    /// Padding before any decoded output, in strict mode.
     LeadingPaddingNotAllowed,
     /// A `=` outside the padding-completion window, strict mode.
     ExcessPaddingNotAllowed,
@@ -51,6 +54,10 @@ pub enum Base64DecodeError {
     InvalidLastSymbol { index: usize },
     /// `quad_pos != 0` and the trailing padding does not complete the quad.
     IncorrectPadding,
+    /// Padding is forbidden when decoding unpadded input in strict mode.
+    PaddingNotAllowed,
+    /// The final symbol contains non-zero unused bits.
+    NonZeroPaddingBits,
 }
 
 const fn hex_nibble(n: u8) -> u8 {
@@ -230,45 +237,53 @@ pub fn crc_hqx(bytes: &[u8], init: u32) -> u32 {
     crc
 }
 
-/// `a2b_base64`. A line-by-line port of `binascii_a2b_base64_impl`
-/// (CPython `Modules/binascii.c`): padding characters within the completion
-/// window (`quad_pos >= 2 && quad_pos + pads <= 4`) are always skipped —
-/// even in strict mode — and non-strict mode additionally skips *every*
-/// pad and every non-alphabet byte outside that window. Errors therefore
-/// only fire in strict mode (mid-loop) or from the two post-loop length
-/// checks, which apply unconditionally.
-pub fn a2b_base64(b: &[u8], strict_mode: bool) -> Result<Vec<u8>, Error> {
-    // Converts between ASCII and base-64 characters. The index of a given number yields the
-    // number in ASCII while the value of said index yields the number in base-64. For example
-    // "=" is 61 in ASCII but 0 (since it's the pad character) in base-64, so BASE64_TABLE[61] == 0
-    #[rustfmt::skip]
-    const BASE64_TABLE: [i8; 256] = [
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
-        52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1, 0,-1,-1, /* Note PAD->0 */
-        -1, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
-        15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
-        -1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
-        41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1,
-
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-        -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-    ];
+/// RFC 4648's standard base64 alphabet.
+pub const BASE64_ALPHABET: &[u8; 64] =
+    b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+/// Build the decoder table, with later duplicate symbols taking precedence.
+#[must_use]
+pub const fn base64_reverse_table(alphabet: &[u8; 64]) -> [u8; 256] {
+    let mut table = [u8::MAX; 256];
+    let mut index = 0;
+    while index < 64 {
+        table[alphabet[index] as usize] = index as u8;
+        index += 1;
+    }
+    // Padding always takes precedence, even in a custom alphabet.
+    table[PAD as usize] = 64;
+    table
+}
 
-    let mut decoded: Vec<u8> = Vec::with_capacity(b.len().div_ceil(4) * 3);
+/// Options for CPython 3.15's base64 decoder.
+pub struct Base64DecodeOptions<'a> {
+    pub strict_mode: bool,
+    pub padded: bool,
+    pub table: &'a [u8; 256],
+    pub ignored: &'a [bool; 256],
+    pub canonical: bool,
+}
 
-    let mut quad_pos: u32 = 0; // position in the quad, 0..=3
-    let mut pads: u32 = 0;
+/// `a2b_base64`, following CPython 3.15's `Modules/binascii.c`.
+pub fn a2b_base64(b: &[u8], options: Base64DecodeOptions<'_>) -> Result<Vec<u8>, Error> {
+    let Base64DecodeOptions {
+        strict_mode,
+        padded,
+        table,
+        ignored,
+        canonical,
+    } = options;
+
+    let mut decoded: Vec<u8> = Vec::new();
+    decoded
+        .try_reserve_exact(b.len().div_ceil(4) * 3)
+        .map_err(|_| Error::Memory)?;
+
+    let mut quad_pos: usize = 0; // position in the quad, 0..=3
+    let mut pads: usize = 0;
     let mut left_char: u8 = 0;
-    for (i, &el) in b.iter().enumerate() {
-        if el == PAD {
+    for &el in b {
+        if padded && el == PAD {
             pads += 1;
             if quad_pos >= 2 && quad_pos + pads <= 4 {
                 continue;
@@ -276,7 +291,7 @@ pub fn a2b_base64(b: &[u8], strict_mode: bool) -> Result<Vec<u8>, Error> {
             // RFC 4648 section-3.3: implementations MAY ignore a pad
             // character present before the end of the encoded data, and
             // MAY ignore excess pad characters. Non-strict mode does.
-            if !strict_mode {
+            if !strict_mode || ignored[PAD as usize] {
                 continue;
             }
             if quad_pos == 1 {
@@ -284,22 +299,26 @@ pub fn a2b_base64(b: &[u8], strict_mode: bool) -> Result<Vec<u8>, Error> {
                 // `quad_pos == 1` check below.
                 break;
             }
-            return Err(Error::Base64(if quad_pos == 0 && i == 0 {
+            return Err(Error::Base64(if quad_pos == 0 && decoded.is_empty() {
                 Base64DecodeError::LeadingPaddingNotAllowed
             } else {
                 Base64DecodeError::ExcessPaddingNotAllowed
             }));
         }
 
-        let binary_char = BASE64_TABLE[el as usize];
-        if binary_char < 0 {
-            if strict_mode {
-                return Err(Error::Base64(Base64DecodeError::OnlyBase64DataAllowed));
+        let binary_char = table[el as usize];
+        if binary_char >= 64 {
+            if strict_mode && !ignored[el as usize] {
+                return Err(Error::Base64(if el == PAD {
+                    Base64DecodeError::PaddingNotAllowed
+                } else {
+                    Base64DecodeError::OnlyBase64DataAllowed
+                }));
             }
             continue;
         }
 
-        if pads > 0 && strict_mode {
+        if pads > 0 && strict_mode && !ignored[PAD as usize] {
             return Err(Error::Base64(if quad_pos + pads == 4 {
                 Base64DecodeError::ExcessDataAfterPadding
             } else {
@@ -312,21 +331,21 @@ pub fn a2b_base64(b: &[u8], strict_mode: bool) -> Result<Vec<u8>, Error> {
         match quad_pos {
             0 => {
                 quad_pos = 1;
-                left_char = binary_char as u8;
+                left_char = binary_char;
             }
             1 => {
                 quad_pos = 2;
-                decoded.push((left_char << 2) | (binary_char >> 4) as u8);
-                left_char = (binary_char & 0x0f) as u8;
+                decoded.push((left_char << 2) | (binary_char >> 4));
+                left_char = binary_char & 0x0f;
             }
             2 => {
                 quad_pos = 3;
-                decoded.push((left_char << 4) | (binary_char >> 2) as u8);
-                left_char = (binary_char & 0x03) as u8;
+                decoded.push((left_char << 4) | (binary_char >> 2));
+                left_char = binary_char & 0x03;
             }
             3 => {
                 quad_pos = 0;
-                decoded.push((left_char << 6) | binary_char as u8);
+                decoded.push((left_char << 6) | binary_char);
                 left_char = 0;
             }
             _ => unsafe {
@@ -344,24 +363,72 @@ pub fn a2b_base64(b: &[u8], strict_mode: bool) -> Result<Vec<u8>, Error> {
         }));
     }
 
-    if quad_pos != 0 && quad_pos + pads < 4 {
+    if padded && quad_pos != 0 && quad_pos + pads < 4 {
         return Err(Error::Base64(Base64DecodeError::IncorrectPadding));
     }
 
+    if canonical && left_char != 0 {
+        return Err(Error::Base64(Base64DecodeError::NonZeroPaddingBits));
+    }
     Ok(decoded)
 }
 
-/// `b2a_base64`.
-#[must_use]
-pub fn b2a_base64(data: &[u8], newline: bool) -> Vec<u8> {
-    // https://stackoverflow.com/questions/63916821
-    let mut encoded = base64::engine::general_purpose::STANDARD
-        .encode(data)
-        .into_bytes();
+/// `b2a_base64`, including CPython 3.15's wrapping and custom alphabets.
+pub fn b2a_base64(
+    data: &[u8],
+    padded: bool,
+    wrapcol: usize,
+    newline: bool,
+    alphabet: &[u8; 64],
+) -> Result<Vec<u8>, Error> {
+    let pads = (3 - data.len() % 3) % 3;
+    let mut size = data
+        .len()
+        .div_ceil(3)
+        .checked_mul(4)
+        .ok_or(Error::TooMuchBase64Data)?;
+    if !padded {
+        size -= pads;
+    }
+    let width = if wrapcol == 0 {
+        usize::MAX
+    } else {
+        wrapcol.max(4) / 4 * 4
+    };
+    let newlines = size.saturating_sub(1) / width;
+    size = size
+        .checked_add(newlines)
+        .and_then(|n| n.checked_add(usize::from(newline)))
+        .filter(|&n| isize::try_from(n).is_ok())
+        .ok_or(Error::TooMuchBase64Data)?;
+    let mut encoded = Vec::new();
+    encoded.try_reserve_exact(size).map_err(|_| Error::Memory)?;
+    let mut column = 0;
+    let mut emit = |symbol| {
+        if column == width {
+            encoded.push(b'\n');
+            column = 0;
+        }
+        encoded.push(symbol);
+        column += 1;
+    };
+    for chunk in data.chunks(3) {
+        let value = (u32::from(chunk[0]) << 16)
+            | (u32::from(*chunk.get(1).unwrap_or(&0)) << 8)
+            | u32::from(*chunk.get(2).unwrap_or(&0));
+        for index in 0..=chunk.len() {
+            emit(alphabet[((value >> (18 - index * 6)) & 63) as usize]);
+        }
+        if padded {
+            for _ in chunk.len() + 1..4 {
+                emit(PAD);
+            }
+        }
+    }
     if newline {
         encoded.push(b'\n');
     }
-    encoded
+    Ok(encoded)
 }
 
 #[inline]
diff --git a/crates/common/src/borrow.rs b/crates/common/src/borrow.rs
index ebf69fde71d..0f9903b6d22 100644
--- a/crates/common/src/borrow.rs
+++ b/crates/common/src/borrow.rs
@@ -39,10 +39,9 @@ impl_from!('a, T, BorrowedValue<'a, T>,
 impl<'a, T: ?Sized> BorrowedValue<'a, T> {
     /// Whether reaching the value holds a lock that other threads wait on.
     ///
-    /// An immutable object hands out a plain reference and answers `false`;
-    /// one whose storage can change hands out a guard. A caller about to wait
-    /// for something unrelated -- a peer, a file, a signal -- can use this to
-    /// decide whether it may keep the borrow for the duration.
+    /// A plain reference answers `false`, including references to externally
+    /// managed memory. This does not guarantee that the storage is immutable
+    /// or safe to borrow while another thread runs.
     #[must_use]
     pub const fn is_locked(&self) -> bool {
         !matches!(self, Self::Ref(_))
diff --git a/crates/common/src/cformat.rs b/crates/common/src/cformat.rs
index de437f2ce0d..263b4776a69 100644
--- a/crates/common/src/cformat.rs
+++ b/crates/common/src/cformat.rs
@@ -19,7 +19,7 @@ pub enum CFormatErrorType {
     UnmatchedKeyParentheses,
     MissingModuloSign,
     UnsupportedFormatChar(CodePoint),
-    IncompleteFormat,
+    StrayModulo,
     WidthTooBig,
     PrecisionTooBig,
     // Unimplemented,
@@ -38,7 +38,7 @@ impl fmt::Display for CFormatError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.typ {
             CFormatErrorType::UnmatchedKeyParentheses => write!(f, "incomplete format key"),
-            CFormatErrorType::IncompleteFormat => write!(f, "incomplete format"),
+            CFormatErrorType::StrayModulo => write!(f, "stray % at position {}", self.index),
             CFormatErrorType::UnsupportedFormatChar(c) => write!(
                 f,
                 "unsupported format character '{}' ({:#x}) at index {}",
@@ -590,7 +590,7 @@ impl CFormatSpec {
     }
 }
 
-fn parse_spec_mapping_key<T, I>(iter: &mut ParseIter<I>) -> Result<Option<T>, ParsingError>
+pub fn parse_spec_mapping_key<T, I>(iter: &mut ParseIter<I>) -> Result<Option<T>, ParsingError>
 where
     T: FormatBuf,
     I: Iterator<Item = T::Char>,
@@ -604,7 +604,7 @@ where
     Ok(None)
 }
 
-fn parse_flags<C, I>(iter: &mut ParseIter<I>) -> CConversionFlags
+pub fn parse_flags<C, I>(iter: &mut ParseIter<I>) -> CConversionFlags
 where
     C: FormatChar,
     I: Iterator<Item = C>,
@@ -626,7 +626,7 @@ where
     flags
 }
 
-fn consume_length<C, I>(iter: &mut ParseIter<I>)
+pub fn consume_length<C, I>(iter: &mut ParseIter<I>)
 where
     C: FormatChar,
     I: Iterator<Item = C>,
@@ -634,7 +634,7 @@ where
     iter.next_if(|(_, c)| matches!(c.to_char_lossy(), 'h' | 'l' | 'L'));
 }
 
-fn parse_format_type<C, I>(
+pub fn parse_format_type<C, I>(
     iter: &mut ParseIter<I>,
     context: CFormatContext,
 ) -> Result<CFormatType, ParsingError>
@@ -644,7 +644,7 @@ where
 {
     let (index, c) = iter.next().ok_or_else(|| {
         (
-            CFormatErrorType::IncompleteFormat,
+            CFormatErrorType::StrayModulo,
             iter.peek().map_or(0, |x| x.0),
         )
     })?;
@@ -674,7 +674,7 @@ where
     })
 }
 
-fn parse_quantity<C, I>(
+pub fn parse_quantity<C, I>(
     iter: &mut ParseIter<I>,
     max_value: usize,
     too_big: CFormatErrorType,
@@ -709,7 +709,9 @@ where
     Ok(None)
 }
 
-fn parse_precision<C, I>(iter: &mut ParseIter<I>) -> Result<Option<CFormatPrecision>, ParsingError>
+pub fn parse_precision<C, I>(
+    iter: &mut ParseIter<I>,
+) -> Result<Option<CFormatPrecision>, ParsingError>
 where
     C: FormatChar,
     I: Iterator<Item = C>,
@@ -831,9 +833,14 @@ impl<S> CFormatStrOrBytes<S> {
                     }
 
                     let spec =
-                        CFormatSpecKeyed::parse(iter, context).map_err(|err| CFormatError {
-                            typ: err.0,
-                            index: err.1,
+                        CFormatSpecKeyed::parse(iter, context).map_err(|(typ, err_index)| {
+                            // A stray % is reported at the position of the %.
+                            let index = if typ == CFormatErrorType::StrayModulo {
+                                index
+                            } else {
+                                err_index
+                            };
+                            CFormatError { typ, index }
                         })?;
 
                     parts.push((index, CFormatPart::Spec(spec)));
@@ -842,8 +849,8 @@ impl<S> CFormatStrOrBytes<S> {
                     }
                 } else {
                     return Err(CFormatError {
-                        typ: CFormatErrorType::IncompleteFormat,
-                        index: index + 1,
+                        typ: CFormatErrorType::StrayModulo,
+                        index,
                     });
                 }
             } else {
@@ -991,8 +998,8 @@ mod tests {
         assert_eq!(
             "Hello %".parse::<CFormatString>(),
             Err(CFormatError {
-                typ: CFormatErrorType::IncompleteFormat,
-                index: 7
+                typ: CFormatErrorType::StrayModulo,
+                index: 6
             })
         );
     }
diff --git a/crates/common/src/lock.rs b/crates/common/src/lock.rs
index 134b7f2a4fa..56253b4ba36 100644
--- a/crates/common/src/lock.rs
+++ b/crates/common/src/lock.rs
@@ -8,14 +8,16 @@ use lock_api::{
 
 cfg_select! {
     feature = "threading" => {
+        pub use core::cell::LazyCell;
         pub use detaching::{BlockingWaitHook, set_blocking_wait_hook, set_world_stopped};
         pub use parking_lot::{RawMutex, RawRwLock, RawThreadId};
         pub use std::sync::OnceLock as OnceCell;
-        pub use core::cell::LazyCell;
     }
     _ => {
         mod cell_lock;
-        pub use cell_lock::{RawCellMutex as RawMutex, RawCellRwLock as RawRwLock, SingleThreadId as RawThreadId};
+        pub use cell_lock::{
+            RawCellMutex as RawMutex, RawCellRwLock as RawRwLock, SingleThreadId as RawThreadId,
+        };
 
         pub use core::cell::{LazyCell, OnceCell};
     }
@@ -37,13 +39,19 @@ cfg_select! {
         unsafe impl<T, F> Sync for LazyLock<T, F> {}
 
         impl<T, F: FnOnce() -> T> LazyLock<T, F> {
-            pub const fn new(f: F) -> Self { Self(core::cell::LazyCell::new(f)) }
-            pub fn force(this: &Self) -> &T { core::cell::LazyCell::force(&this.0) }
+            pub const fn new(f: F) -> Self {
+                Self(core::cell::LazyCell::new(f))
+            }
+            pub fn force(this: &Self) -> &T {
+                core::cell::LazyCell::force(&this.0)
+            }
         }
 
         impl<T, F: FnOnce() -> T> core::ops::Deref for LazyLock<T, F> {
             type Target = T;
-            fn deref(&self) -> &T { &self.0 }
+            fn deref(&self) -> &T {
+                &self.0
+            }
         }
     }
 }
diff --git a/crates/compiler-core/src/bytecode.rs b/crates/compiler-core/src/bytecode.rs
index f7d117cb76b..8132c561318 100644
--- a/crates/compiler-core/src/bytecode.rs
+++ b/crates/compiler-core/src/bytecode.rs
@@ -11,7 +11,7 @@ use bitflags::bitflags;
 use core::{
     cell::UnsafeCell,
     hash, mem,
-    ops::{Deref, DerefMut, Index, IndexMut},
+    ops::{Deref, Index, IndexMut},
     sync::atomic::{AtomicU8, AtomicU16, AtomicUsize, Ordering},
 };
 use itertools::Itertools;
@@ -286,12 +286,16 @@ impl PyCodeLocationInfoKind {
 pub trait Constant: Sized + Clone {
     type Name: AsRef<str>;
 
+    /// Storage of a code object's constants (`co_consts`).
+    type Tuple: Clone + Deref<Target = [Self]> + FromIterator<Self>;
+
     /// Transforms the given Constant to a BorrowedConstant
     fn borrow_constant(&self) -> BorrowedConstant<'_, Self>;
 }
 
 impl Constant for ConstantData {
     type Name = String;
+    type Tuple = Box<[Self]>;
 
     fn borrow_constant(&self) -> BorrowedConstant<'_, Self> {
         match self {
@@ -373,19 +377,23 @@ impl ConstantBag for BasicBag {
 }
 
 #[derive(Clone)]
-pub struct Constants<C: Constant>(Box<[C]>);
+pub struct Constants<C: Constant>(C::Tuple);
 
-impl<C: Constant> Deref for Constants<C> {
-    type Target = [C];
+impl<C: Constant> Constants<C> {
+    pub const fn new(tuple: C::Tuple) -> Self {
+        Self(tuple)
+    }
 
-    fn deref(&self) -> &Self::Target {
+    pub const fn as_tuple(&self) -> &C::Tuple {
         &self.0
     }
 }
 
-impl<C: Constant> DerefMut for Constants<C> {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.0
+impl<C: Constant> Deref for Constants<C> {
+    type Target = [C];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
     }
 }
 
@@ -397,12 +405,6 @@ impl<C: Constant> Index<oparg::ConstIdx> for Constants<C> {
     }
 }
 
-impl<C: Constant> IndexMut<oparg::ConstIdx> for Constants<C> {
-    fn index_mut(&mut self, consti: oparg::ConstIdx) -> &mut Self::Output {
-        &mut self.0[consti.as_usize()]
-    }
-}
-
 impl<C: Constant> FromIterator<C> for Constants<C> {
     fn from_iter<T: IntoIterator<Item = C>>(iter: T) -> Self {
         Self(iter.into_iter().collect())
@@ -734,6 +736,27 @@ impl Deref for CodeUnits {
 }
 
 impl CodeUnits {
+    /// `fixup_getiter` applied to every `GET_ITER` by `_PyCode_Quicken`.
+    ///
+    /// The compiler can't know if `types.coroutine()` will be called, so a
+    /// yield-from `GET_ITER` is resolved when the code object is created.
+    pub fn fixup_get_iter(&mut self, flags: CodeFlags) {
+        let mode = if flags.intersects(CodeFlags::COROUTINE | CodeFlags::ITERABLE_COROUTINE) {
+            oparg::GET_ITER_YIELD_FROM_NO_CHECK
+        } else {
+            oparg::GET_ITER_YIELD_FROM_CORO_CHECK
+        };
+        let mut i = 0;
+        let units = self.units.get_mut();
+        while i < units.len() {
+            let unit = &mut units[i];
+            if matches!(unit.op, Instruction::GetIter { .. }) && u8::from(unit.arg) != 0 {
+                unit.arg = (mode as u8).into();
+            }
+            i += 1 + unit.op.cache_entries();
+        }
+    }
+
     /// Disable adaptive specialization by setting all counters to unreachable.
     /// Used for CPython-compiled bytecode where specialization may not be safe.
     pub fn disable_specialization(&self) {
@@ -937,11 +960,20 @@ impl CodeUnits {
     /// (marshal) and `co_code`. Specialized opcodes are mapped back to their
     /// base variants via `deoptimize()` and all CACHE entries are zeroed.
     pub fn original_bytes(&self) -> Vec<u8> {
+        self.original_bytes_with(|_, op| op)
+    }
+
+    /// [`Self::original_bytes`], with `resolve` first replacing the opcode at
+    /// an index, e.g. an instrumentation placeholder by its original opcode.
+    pub fn original_bytes_with(
+        &self,
+        resolve: impl Fn(usize, Instruction) -> Instruction,
+    ) -> Vec<u8> {
         let len = self.len();
         let mut out = Vec::with_capacity(len * 2);
         let mut i = 0;
         while i < len {
-            let op = self.read_op(i).deoptimize();
+            let op = resolve(i, self.read_op(i)).deoptimize();
             let arg = self.read_arg(i);
             let caches = op.cache_entries();
             out.push(u8::from(op));
diff --git a/crates/compiler-core/src/bytecode/instruction.rs b/crates/compiler-core/src/bytecode/instruction.rs
index f403507f1aa..9d42b5d7473 100644
--- a/crates/compiler-core/src/bytecode/instruction.rs
+++ b/crates/compiler-core/src/bytecode/instruction.rs
@@ -333,261 +333,260 @@ define_opcodes!(
         FormatWithSpec = 13,
         GetAiter = 14,
         GetAnext = 15,
-        GetIter = 16,
+        GetLen = 16,
         Reserved = 17,
-        GetLen = 18,
-        GetYieldFromIter = 19,
-        InterpreterExit = 20,
-        LoadBuildClass = 21,
-        LoadLocals = 22,
-        MakeFunction = 23,
-        MatchKeys = 24,
-        MatchMapping = 25,
-        MatchSequence = 26,
-        Nop = 27,
-        NotTaken = 28,
-        PopExcept = 29,
-        PopIter = 30,
-        PopTop = 31,
-        PushExcInfo = 32,
-        PushNull = 33,
-        ReturnGenerator = 34,
-        ReturnValue = 35,
-        SetupAnnotations = 36,
-        StoreSlice = 37,
-        StoreSubscr = 38,
-        ToBool = 39,
-        UnaryInvert = 40,
-        UnaryNegative = 41,
-        UnaryNot = 42,
-        WithExceptStart = 43,
+        InterpreterExit = 18,
+        LoadBuildClass = 19,
+        LoadLocals = 20,
+        MakeFunction = 21,
+        MatchKeys = 22,
+        MatchMapping = 23,
+        MatchSequence = 24,
+        Nop = 25,
+        NotTaken = 26,
+        PopExcept = 27,
+        PopIter = 28,
+        PopTop = 29,
+        PushExcInfo = 30,
+        PushNull = 31,
+        ReturnGenerator = 32,
+        ReturnValue = 33,
+        SetupAnnotations = 34,
+        StoreSlice = 35,
+        StoreSubscr = 36,
+        ToBool = 37,
+        UnaryInvert = 38,
+        UnaryNegative = 39,
+        UnaryNot = 40,
+        WithExceptStart = 41,
         BinaryOp {
             op: Arg<oparg::BinaryOperator>,
-        } = 44,
+        } = 42,
         BuildInterpolation {
             format: Arg<u32>,
-        } = 45,
+        } = 43,
         BuildList {
             count: Arg<u32>,
-        } = 46,
+        } = 44,
         BuildMap {
             count: Arg<u32>,
-        } = 47,
+        } = 45,
         BuildSet {
             count: Arg<u32>,
-        } = 48,
+        } = 46,
         BuildSlice {
             argc: Arg<oparg::BuildSliceArgCount>,
-        } = 49,
+        } = 47,
         BuildString {
             count: Arg<u32>,
-        } = 50,
+        } = 48,
         BuildTuple {
             count: Arg<u32>,
-        } = 51,
+        } = 49,
         Call {
             argc: Arg<u32>,
-        } = 52,
+        } = 50,
         CallIntrinsic1 {
             func: Arg<oparg::IntrinsicFunction1>,
-        } = 53,
+        } = 51,
         CallIntrinsic2 {
             func: Arg<oparg::IntrinsicFunction2>,
-        } = 54,
+        } = 52,
         CallKw {
             argc: Arg<u32>,
-        } = 55,
+        } = 53,
         CompareOp {
             opname: Arg<oparg::ComparisonOperator>,
-        } = 56,
+        } = 54,
         ContainsOp {
             invert: Arg<oparg::Invert>,
-        } = 57,
+        } = 55,
         ConvertValue {
             oparg: Arg<oparg::ConvertValueOparg>,
-        } = 58,
+        } = 56,
         Copy {
             i: Arg<u32>,
-        } = 59,
+        } = 57,
         CopyFreeVars {
             n: Arg<u32>,
-        } = 60,
+        } = 58,
         DeleteAttr {
             namei: Arg<oparg::NameIdx>,
-        } = 61,
+        } = 59,
         DeleteDeref {
             i: Arg<oparg::VarNum>,
-        } = 62,
+        } = 60,
         DeleteFast {
             var_num: Arg<oparg::VarNum>,
-        } = 63,
+        } = 61,
         DeleteGlobal {
             namei: Arg<oparg::NameIdx>,
-        } = 64,
+        } = 62,
         DeleteName {
             namei: Arg<oparg::NameIdx>,
-        } = 65,
+        } = 63,
         DictMerge {
             i: Arg<u32>,
-        } = 66,
+        } = 64,
         DictUpdate {
             i: Arg<u32>,
-        } = 67,
-        EndAsyncFor = 68,
-        ExtendedArg = 69,
+        } = 65,
+        EndAsyncFor = 66,
+        ExtendedArg = 67,
         ForIter {
             delta: Arg<oparg::Label>,
-        } = 70,
+        } = 68,
         GetAwaitable {
             r#where: Arg<u32>,
-        } = 71,
+        } = 69,
+        GetIter { mode: Arg<u32> } = 70,
         ImportFrom {
             namei: Arg<oparg::NameIdx>,
-        } = 72,
+        } = 71,
         ImportName {
             namei: Arg<oparg::NameIdx>,
-        } = 73,
+        } = 72,
         IsOp {
             invert: Arg<oparg::Invert>,
-        } = 74,
+        } = 73,
         JumpBackward {
             delta: Arg<oparg::Label>,
-        } = 75,
+        } = 74,
         JumpBackwardNoInterrupt {
             delta: Arg<oparg::Label>,
-        } = 76,
+        } = 75,
         JumpForward {
             delta: Arg<oparg::Label>,
-        } = 77,
+        } = 76,
         ListAppend {
             i: Arg<u32>,
-        } = 78,
+        } = 77,
         ListExtend {
             i: Arg<u32>,
-        } = 79,
+        } = 78,
         LoadAttr {
             namei: Arg<oparg::LoadAttr>,
-        } = 80,
+        } = 79,
         LoadCommonConstant {
             idx: Arg<oparg::CommonConstant>,
-        } = 81,
+        } = 80,
         LoadConst {
             consti: Arg<oparg::ConstIdx>,
-        } = 82,
+        } = 81,
         LoadDeref {
             i: Arg<oparg::VarNum>,
-        } = 83,
+        } = 82,
         LoadFast {
             var_num: Arg<oparg::VarNum>,
-        } = 84,
+        } = 83,
         LoadFastAndClear {
             var_num: Arg<oparg::VarNum>,
-        } = 85,
+        } = 84,
         LoadFastBorrow {
             var_num: Arg<oparg::VarNum>,
-        } = 86,
+        } = 85,
         LoadFastBorrowLoadFastBorrow {
             var_nums: Arg<oparg::VarNums>,
-        } = 87,
+        } = 86,
         LoadFastCheck {
             var_num: Arg<oparg::VarNum>,
-        } = 88,
+        } = 87,
         LoadFastLoadFast {
             var_nums: Arg<oparg::VarNums>,
-        } = 89,
+        } = 88,
         LoadFromDictOrDeref {
             i: Arg<oparg::VarNum>,
-        } = 90,
+        } = 89,
         LoadFromDictOrGlobals {
             i: Arg<oparg::NameIdx>,
-        } = 91,
+        } = 90,
         LoadGlobal {
             namei: Arg<oparg::NameIdx>,
-        } = 92,
+        } = 91,
         LoadName {
             namei: Arg<oparg::NameIdx>,
-        } = 93,
+        } = 92,
         LoadSmallInt {
             i: Arg<u32>,
-        } = 94,
+        } = 93,
         LoadSpecial {
             method: Arg<oparg::SpecialMethod>,
-        } = 95,
+        } = 94,
         LoadSuperAttr {
             namei: Arg<oparg::LoadSuperAttr>,
-        } = 96,
+        } = 95,
         MakeCell {
             i: Arg<oparg::VarNum>,
-        } = 97,
+        } = 96,
         MapAdd {
             i: Arg<u32>,
-        } = 98,
+        } = 97,
         MatchClass {
             count: Arg<u32>,
-        } = 99,
+        } = 98,
         PopJumpIfFalse {
             delta: Arg<oparg::Label>,
-        } = 100,
+        } = 99,
         PopJumpIfNone {
             delta: Arg<oparg::Label>,
-        } = 101,
+        } = 100,
         PopJumpIfNotNone {
             delta: Arg<oparg::Label>,
-        } = 102,
+        } = 101,
         PopJumpIfTrue {
             delta: Arg<oparg::Label>,
-        } = 103,
+        } = 102,
         RaiseVarargs {
             argc: Arg<oparg::RaiseKind>,
-        } = 104,
+        } = 103,
         Reraise {
             depth: Arg<u32>,
-        } = 105,
+        } = 104,
         Send {
             delta: Arg<oparg::Label>,
-        } = 106,
+        } = 105,
         SetAdd {
             i: Arg<u32>,
-        } = 107,
+        } = 106,
         SetFunctionAttribute {
             flag: Arg<oparg::MakeFunctionFlag>,
-        } = 108,
+        } = 107,
         SetUpdate {
             i: Arg<u32>,
-        } = 109,
+        } = 108,
         StoreAttr {
             namei: Arg<oparg::NameIdx>,
-        } = 110,
+        } = 109,
         StoreDeref {
             i: Arg<oparg::VarNum>,
-        } = 111,
+        } = 110,
         StoreFast {
             var_num: Arg<oparg::VarNum>,
-        } = 112,
+        } = 111,
         StoreFastLoadFast {
             var_nums: Arg<oparg::VarNums>,
-        } = 113,
+        } = 112,
         StoreFastStoreFast {
             var_nums: Arg<oparg::VarNums>,
-        } = 114,
+        } = 113,
         StoreGlobal {
             namei: Arg<oparg::NameIdx>,
-        } = 115,
+        } = 114,
         StoreName {
             namei: Arg<oparg::NameIdx>,
-        } = 116,
+        } = 115,
         Swap {
             i: Arg<u32>,
-        } = 117,
+        } = 116,
         UnpackEx {
             counts: Arg<oparg::UnpackExArgs>,
-        } = 118,
+        } = 117,
         UnpackSequence {
             count: Arg<u32>,
-        } = 119,
+        } = 118,
         YieldValue {
             arg: Arg<u32>,
-        } = 120,
+        } = 119,
         Resume {
             context: Arg<oparg::ResumeContext>,
         } = 128,
@@ -603,99 +602,108 @@ define_opcodes!(
         BinaryOpSubscrListSlice = 138,
         BinaryOpSubscrStrInt = 139,
         BinaryOpSubscrTupleInt = 140,
-        BinaryOpSubtractFloat = 141,
-        BinaryOpSubtractInt = 142,
-        CallAllocAndEnterInit = 143,
-        CallBoundMethodExactArgs = 144,
-        CallBoundMethodGeneral = 145,
-        CallBuiltinClass = 146,
-        CallBuiltinFast = 147,
-        CallBuiltinFastWithKeywords = 148,
-        CallBuiltinO = 149,
-        CallIsinstance = 150,
-        CallKwBoundMethod = 151,
-        CallKwNonPy = 152,
-        CallKwPy = 153,
-        CallLen = 154,
-        CallListAppend = 155,
-        CallMethodDescriptorFast = 156,
-        CallMethodDescriptorFastWithKeywords = 157,
-        CallMethodDescriptorNoargs = 158,
-        CallMethodDescriptorO = 159,
-        CallNonPyGeneral = 160,
-        CallPyExactArgs = 161,
-        CallPyGeneral = 162,
-        CallStr1 = 163,
-        CallTuple1 = 164,
-        CallType1 = 165,
-        CompareOpFloat = 166,
-        CompareOpInt = 167,
-        CompareOpStr = 168,
-        ContainsOpDict = 169,
-        ContainsOpSet = 170,
-        ForIterGen = 171,
-        ForIterList = 172,
-        ForIterRange = 173,
-        ForIterTuple = 174,
-        JumpBackwardJit = 175,
-        JumpBackwardNoJit = 176,
-        LoadAttrClass = 177,
-        LoadAttrClassWithMetaclassCheck = 178,
-        LoadAttrGetattributeOverridden = 179,
-        LoadAttrInstanceValue = 180,
-        LoadAttrMethodLazyDict = 181,
-        LoadAttrMethodNoDict = 182,
-        LoadAttrMethodWithValues = 183,
-        LoadAttrModule = 184,
-        LoadAttrNondescriptorNoDict = 185,
-        LoadAttrNondescriptorWithValues = 186,
-        LoadAttrProperty = 187,
-        LoadAttrSlot = 188,
-        LoadAttrWithHint = 189,
-        LoadConstImmortal = 190,
-        LoadConstMortal = 191,
-        LoadGlobalBuiltin = 192,
-        LoadGlobalModule = 193,
-        LoadSuperAttrAttr = 194,
-        LoadSuperAttrMethod = 195,
-        ResumeCheck = 196,
-        SendGen = 197,
-        StoreAttrInstanceValue = 198,
-        StoreAttrSlot = 199,
-        StoreAttrWithHint = 200,
-        StoreSubscrDict = 201,
-        StoreSubscrListInt = 202,
-        ToBoolAlwaysTrue = 203,
-        ToBoolBool = 204,
-        ToBoolInt = 205,
-        ToBoolList = 206,
-        ToBoolNone = 207,
-        ToBoolStr = 208,
-        UnpackSequenceList = 209,
-        UnpackSequenceTuple = 210,
-        UnpackSequenceTwoTuple = 211,
-        InstrumentedEndFor = 234,
-        InstrumentedPopIter = 235,
-        InstrumentedEndSend = 236,
-        InstrumentedForIter = 237,
-        InstrumentedInstruction = 238,
-        InstrumentedJumpForward = 239,
-        InstrumentedNotTaken = 240,
-        InstrumentedPopJumpIfTrue = 241,
-        InstrumentedPopJumpIfFalse = 242,
-        InstrumentedPopJumpIfNone = 243,
-        InstrumentedPopJumpIfNotNone = 244,
-        InstrumentedResume = 245,
-        InstrumentedReturnValue = 246,
-        InstrumentedYieldValue = 247,
-        InstrumentedEndAsyncFor = 248,
-        InstrumentedLoadSuperAttr = 249,
-        InstrumentedCall = 250,
-        InstrumentedCallKw = 251,
-        InstrumentedCallFunctionEx = 252,
-        InstrumentedJumpBackward = 253,
-        InstrumentedLine = 254,
-        EnterExecutor = 255,
+        BinaryOpSubscrUstrInt = 141,
+        BinaryOpSubtractFloat = 142,
+        BinaryOpSubtractInt = 143,
+        CallAllocAndEnterInit = 144,
+        CallBoundMethodExactArgs = 145,
+        CallBoundMethodGeneral = 146,
+        CallBuiltinClass = 147,
+        CallBuiltinFast = 148,
+        CallBuiltinFastWithKeywords = 149,
+        CallBuiltinO = 150,
+        CallExNonPyGeneral = 151,
+        CallExPy = 152,
+        CallIsinstance = 153,
+        CallKwBoundMethod = 154,
+        CallKwNonPy = 155,
+        CallKwPy = 156,
+        CallLen = 157,
+        CallListAppend = 158,
+        CallMethodDescriptorFast = 159,
+        CallMethodDescriptorFastWithKeywords = 160,
+        CallMethodDescriptorNoargs = 161,
+        CallMethodDescriptorO = 162,
+        CallNonPyGeneral = 163,
+        CallPyExactArgs = 164,
+        CallPyGeneral = 165,
+        CallStr1 = 166,
+        CallTuple1 = 167,
+        CallType1 = 168,
+        CompareOpFloat = 169,
+        CompareOpInt = 170,
+        CompareOpStr = 171,
+        ContainsOpDict = 172,
+        ContainsOpSet = 173,
+        ForIterGen = 174,
+        ForIterList = 175,
+        ForIterRange = 176,
+        ForIterTuple = 177,
+        ForIterVirtual = 178,
+        GetIterSelf = 179,
+        GetIterVirtual = 180,
+        JumpBackwardJit = 181,
+        JumpBackwardNoJit = 182,
+        LoadAttrClass = 183,
+        LoadAttrClassWithMetaclassCheck = 184,
+        LoadAttrGetattributeOverridden = 185,
+        LoadAttrInstanceValue = 186,
+        LoadAttrMethodLazyDict = 187,
+        LoadAttrMethodNoDict = 188,
+        LoadAttrMethodWithValues = 189,
+        LoadAttrModule = 190,
+        LoadAttrNondescriptorNoDict = 191,
+        LoadAttrNondescriptorWithValues = 192,
+        LoadAttrProperty = 193,
+        LoadAttrSlot = 194,
+        LoadAttrWithHint = 195,
+        LoadGlobalBuiltin = 196,
+        LoadGlobalModule = 197,
+        LoadSuperAttrAttr = 198,
+        LoadSuperAttrMethod = 199,
+        ResumeCheck = 200,
+        ResumeCheckJit = 201,
+        SendAsyncGen = 202,
+        SendGen = 203,
+        SendVirtual = 204,
+        StoreAttrInstanceValue = 205,
+        StoreAttrSlot = 206,
+        StoreAttrWithHint = 207,
+        StoreSubscrDict = 208,
+        StoreSubscrListInt = 209,
+        ToBoolAlwaysTrue = 210,
+        ToBoolBool = 211,
+        ToBoolInt = 212,
+        ToBoolList = 213,
+        ToBoolNone = 214,
+        ToBoolStr = 215,
+        UnpackSequenceList = 216,
+        UnpackSequenceTuple = 217,
+        UnpackSequenceTwoTuple = 218,
+        BuildListFromArg = 219,
+        InstrumentedEndFor = 233,
+        InstrumentedPopIter = 234,
+        InstrumentedEndSend = 235,
+        InstrumentedForIter = 236,
+        InstrumentedInstruction = 237,
+        InstrumentedJumpForward = 238,
+        InstrumentedNotTaken = 239,
+        InstrumentedPopJumpIfTrue = 240,
+        InstrumentedPopJumpIfFalse = 241,
+        InstrumentedPopJumpIfNone = 242,
+        InstrumentedPopJumpIfNotNone = 243,
+        InstrumentedResume = 244,
+        InstrumentedReturnValue = 245,
+        InstrumentedYieldValue = 246,
+        InstrumentedEndAsyncFor = 247,
+        InstrumentedLoadSuperAttr = 248,
+        InstrumentedCall = 249,
+        InstrumentedCallKw = 250,
+        InstrumentedCallFunctionEx = 251,
+        InstrumentedJumpBackward = 252,
+        InstrumentedLine = 253,
+        EnterExecutor = 254,
+        TraceRecord = 255,
     }
 );
 
@@ -1427,8 +1435,6 @@ mod tests {
     #[test]
     fn const_flags_match_cpython_opcode_metadata() {
         assert!(Opcode::LoadConst.has_const());
-        assert!(Opcode::LoadConstImmortal.has_const());
-        assert!(Opcode::LoadConstMortal.has_const());
         assert!(!Opcode::LoadSmallInt.has_const());
         assert!(!Opcode::Nop.has_const());
 
@@ -1438,8 +1444,8 @@ mod tests {
 
     #[test]
     fn stack_effects_match_cpython_opcode_metadata() {
-        assert_eq!(Opcode::ForIter.stack_effect_info(0).popped(), 1);
-        assert_eq!(Opcode::ForIter.stack_effect_info(0).pushed(), 2);
+        assert_eq!(Opcode::ForIter.stack_effect_info(0).popped(), 2);
+        assert_eq!(Opcode::ForIter.stack_effect_info(0).pushed(), 3);
         assert_eq!(Opcode::ForIter.stack_effect(0), 1);
         assert_eq!(Opcode::ForIter.stack_effect_jump(0), 1);
 
@@ -1482,8 +1488,7 @@ mod tests {
 
         pub(super) const fn deopt(op: Opcode) -> Option<Opcode> {
             Some(match op {
-                Opcode::ResumeCheck => Opcode::Resume,
-                Opcode::LoadConstMortal | Opcode::LoadConstImmortal => Opcode::LoadConst,
+                Opcode::ResumeCheck | Opcode::ResumeCheckJit => Opcode::Resume,
                 Opcode::ToBoolAlwaysTrue
                 | Opcode::ToBoolBool
                 | Opcode::ToBoolInt
@@ -1501,12 +1506,13 @@ mod tests {
                 | Opcode::BinaryOpSubscrListSlice
                 | Opcode::BinaryOpSubscrTupleInt
                 | Opcode::BinaryOpSubscrStrInt
+                | Opcode::BinaryOpSubscrUstrInt
                 | Opcode::BinaryOpSubscrDict
                 | Opcode::BinaryOpSubscrGetitem
                 | Opcode::BinaryOpExtend
                 | Opcode::BinaryOpInplaceAddUnicode => Opcode::BinaryOp,
                 Opcode::StoreSubscrDict | Opcode::StoreSubscrListInt => Opcode::StoreSubscr,
-                Opcode::SendGen => Opcode::Send,
+                Opcode::SendGen | Opcode::SendAsyncGen | Opcode::SendVirtual => Opcode::Send,
                 Opcode::UnpackSequenceTwoTuple
                 | Opcode::UnpackSequenceTuple
                 | Opcode::UnpackSequenceList => Opcode::UnpackSequence,
@@ -1536,7 +1542,9 @@ mod tests {
                 Opcode::ForIterList
                 | Opcode::ForIterTuple
                 | Opcode::ForIterRange
-                | Opcode::ForIterGen => Opcode::ForIter,
+                | Opcode::ForIterGen
+                | Opcode::ForIterVirtual => Opcode::ForIter,
+                Opcode::GetIterSelf | Opcode::GetIterVirtual => Opcode::GetIter,
                 Opcode::CallBoundMethodExactArgs
                 | Opcode::CallPyExactArgs
                 | Opcode::CallType1
@@ -1560,6 +1568,7 @@ mod tests {
                 Opcode::CallKwBoundMethod | Opcode::CallKwPy | Opcode::CallKwNonPy => {
                     Opcode::CallKw
                 }
+                Opcode::CallExPy | Opcode::CallExNonPyGeneral => Opcode::CallFunctionEx,
                 _ => return None,
             })
         }
@@ -1576,6 +1585,7 @@ mod tests {
 
         pub(super) const fn cache_entries(op: Opcode) -> usize {
             match deoptimize(op) {
+                Opcode::Resume | Opcode::GetIter | Opcode::CallFunctionEx => 1,
                 Opcode::StoreSubscr => 1,
                 Opcode::ToBool => 3,
                 Opcode::BinaryOp => 5,
diff --git a/crates/compiler-core/src/bytecode/oparg.rs b/crates/compiler-core/src/bytecode/oparg.rs
index 8f706003091..78d3bc6bf78 100644
--- a/crates/compiler-core/src/bytecode/oparg.rs
+++ b/crates/compiler-core/src/bytecode/oparg.rs
@@ -342,6 +342,11 @@ oparg_enum!(
     }
 );
 
+/// Values used in the oparg for `GET_ITER`.
+pub const GET_ITER_YIELD_FROM: u32 = 1;
+pub const GET_ITER_YIELD_FROM_NO_CHECK: u32 = 2;
+pub const GET_ITER_YIELD_FROM_CORO_CHECK: u32 = 3;
+
 pub type NameIdx = u32;
 
 impl OpArgType for u32 {}
@@ -756,6 +761,16 @@ oparg_enum!(
         BuiltinList = (5, "list"),
         /// Built-in `set` type
         BuiltinSet = (6, "set"),
+        /// The None singleton.
+        None = (7, "None"),
+        /// The empty string.
+        EmptyStr = (8, "empty string"),
+        /// The true singleton.
+        True = (9, "True"),
+        /// The false singleton.
+        False = (10, "False"),
+        /// Integer minus one.
+        MinusOne = (11, "-1"),
     }
 );
 
@@ -906,11 +921,11 @@ newtype_oparg!(
 );
 
 impl ResumeContext {
-    /// [CPython `RESUME_OPARG_LOCATION_MASK`](https://github.com/python/cpython/blob/v3.14.3/Include/internal/pycore_opcode_utils.h#L84)
-    pub const LOCATION_MASK: u32 = 0x3;
+    /// [CPython `RESUME_OPARG_LOCATION_MASK`](https://github.com/python/cpython/blob/v3.15.0/Include/internal/pycore_opcode_utils.h#L92)
+    pub const LOCATION_MASK: u32 = 0x7;
 
-    /// [CPython `RESUME_OPARG_DEPTH1_MASK`](https://github.com/python/cpython/blob/v3.14.3/Include/internal/pycore_opcode_utils.h#L85)
-    pub const DEPTH1_MASK: u32 = 0x4;
+    /// [CPython `RESUME_OPARG_DEPTH1_MASK`](https://github.com/python/cpython/blob/v3.15.0/Include/internal/pycore_opcode_utils.h#L93)
+    pub const DEPTH1_MASK: u32 = 0x8;
 
     #[must_use]
     pub const fn new(location: ResumeLocation, is_exception_depth1: bool) -> Self {
@@ -926,8 +941,8 @@ impl ResumeContext {
     /// Resume location is determined by [`Self::LOCATION_MASK`].
     #[must_use]
     pub fn location(&self) -> ResumeLocation {
-        // SAFETY: The mask should return a value that is in range.
-        unsafe { ResumeLocation::try_from(self.as_u32() & Self::LOCATION_MASK).unwrap_unchecked() }
+        ResumeLocation::try_from(self.as_u32() & Self::LOCATION_MASK)
+            .expect("invalid RESUME location")
     }
 
     /// True if the bit at [`Self::DEPTH1_MASK`] is on.
@@ -947,6 +962,9 @@ pub enum ResumeLocation {
     AfterYieldFrom,
     /// After an `await` expression.
     AfterAwait,
+    /// Start of a generator expression, before its outermost iterator is
+    /// acquired and the generator is created.
+    AtGenExprStart,
 }
 
 impl From<ResumeLocation> for ResumeContext {
@@ -964,6 +982,7 @@ impl TryFrom<u32> for ResumeLocation {
             1 => Self::AfterYield,
             2 => Self::AfterYieldFrom,
             3 => Self::AfterAwait,
+            4 => Self::AtGenExprStart,
             _ => return Err(Self::Error::InvalidBytecode),
         })
     }
@@ -977,6 +996,7 @@ impl ResumeLocation {
             Self::AfterYield => 1,
             Self::AfterYieldFrom => 2,
             Self::AfterAwait => 3,
+            Self::AtGenExprStart => 4,
         }
     }
 
diff --git a/crates/compiler-core/src/bytecode/opcode_metadata.rs b/crates/compiler-core/src/bytecode/opcode_metadata.rs
index ca23e3c9e02..b264639fda7 100644
--- a/crates/compiler-core/src/bytecode/opcode_metadata.rs
+++ b/crates/compiler-core/src/bytecode/opcode_metadata.rs
@@ -15,15 +15,15 @@ impl super::Opcode {
     #[inline]
     pub const fn cache_entries(self) -> usize {
         const CACHE_ENTRIES: [u8; 256] = [
-            0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 3, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 3, 1, 1,
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 9, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 4, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 4, 0, 0, 0, 0, 0,
-            0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 3, 3,
-            3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1,
-            1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 0, 0, 4, 4, 1, 1, 0, 1, 4, 4, 4, 1, 1,
-            3, 3, 3, 3, 3, 3, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 3, 3, 0, 1, 0, 0,
+            0, 0, 0, 5, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 1, 3, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 3, 1, 1, 0, 0,
+            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 9, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 4, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0,
+            0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 3,
+            3, 3, 3, 3, 3, 3, 1, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, 1,
+            1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 4, 4, 1, 1, 1, 1, 1,
+            1, 1, 4, 4, 4, 1, 1, 3, 3, 3, 3, 3, 3, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 3, 3, 1, 1, 0, 0, 0,
         ];
 
         CACHE_ENTRIES[self.as_numeric() as usize] as usize
@@ -176,6 +176,7 @@ impl super::Opcode {
             Some(super::Opcode::BinaryOp),
             Some(super::Opcode::BinaryOp),
             Some(super::Opcode::BinaryOp),
+            Some(super::Opcode::BinaryOp),
             Some(super::Opcode::Call),
             Some(super::Opcode::Call),
             Some(super::Opcode::Call),
@@ -183,6 +184,8 @@ impl super::Opcode {
             Some(super::Opcode::Call),
             Some(super::Opcode::Call),
             Some(super::Opcode::Call),
+            Some(super::Opcode::CallFunctionEx),
+            Some(super::Opcode::CallFunctionEx),
             Some(super::Opcode::Call),
             Some(super::Opcode::CallKw),
             Some(super::Opcode::CallKw),
@@ -208,6 +211,9 @@ impl super::Opcode {
             Some(super::Opcode::ForIter),
             Some(super::Opcode::ForIter),
             Some(super::Opcode::ForIter),
+            Some(super::Opcode::ForIter),
+            Some(super::Opcode::GetIter),
+            Some(super::Opcode::GetIter),
             Some(super::Opcode::JumpBackward),
             Some(super::Opcode::JumpBackward),
             Some(super::Opcode::LoadAttr),
@@ -223,13 +229,14 @@ impl super::Opcode {
             Some(super::Opcode::LoadAttr),
             Some(super::Opcode::LoadAttr),
             Some(super::Opcode::LoadAttr),
-            Some(super::Opcode::LoadConst),
-            Some(super::Opcode::LoadConst),
             Some(super::Opcode::LoadGlobal),
             Some(super::Opcode::LoadGlobal),
             Some(super::Opcode::LoadSuperAttr),
             Some(super::Opcode::LoadSuperAttr),
             Some(super::Opcode::Resume),
+            Some(super::Opcode::Resume),
+            Some(super::Opcode::Send),
+            Some(super::Opcode::Send),
             Some(super::Opcode::Send),
             Some(super::Opcode::StoreAttr),
             Some(super::Opcode::StoreAttr),
@@ -282,13 +289,6 @@ impl super::Opcode {
             None,
             None,
             None,
-            None,
-            None,
-            None,
-            None,
-            None,
-            None,
-            None,
         ];
 
         DEOPT[self.as_numeric() as usize]
@@ -327,6 +327,7 @@ impl super::Opcode {
                 | Self::ExtendedArg
                 | Self::ForIter
                 | Self::GetAwaitable
+                | Self::GetIter
                 | Self::ImportFrom
                 | Self::ImportName
                 | Self::IsOp
@@ -384,7 +385,7 @@ impl super::Opcode {
                 | Self::CallBuiltinFast
                 | Self::CallBuiltinFastWithKeywords
                 | Self::CallBuiltinO
-                | Self::CallIsinstance
+                | Self::CallExPy
                 | Self::CallKwBoundMethod
                 | Self::CallKwNonPy
                 | Self::CallKwPy
@@ -408,6 +409,7 @@ impl super::Opcode {
                 | Self::ForIterList
                 | Self::ForIterRange
                 | Self::ForIterTuple
+                | Self::ForIterVirtual
                 | Self::JumpBackwardJit
                 | Self::JumpBackwardNoJit
                 | Self::LoadAttrClass
@@ -423,13 +425,14 @@ impl super::Opcode {
                 | Self::LoadAttrProperty
                 | Self::LoadAttrSlot
                 | Self::LoadAttrWithHint
-                | Self::LoadConstImmortal
-                | Self::LoadConstMortal
                 | Self::LoadGlobalBuiltin
                 | Self::LoadGlobalModule
                 | Self::LoadSuperAttrAttr
                 | Self::LoadSuperAttrMethod
+                | Self::ResumeCheckJit
+                | Self::SendAsyncGen
                 | Self::SendGen
+                | Self::SendVirtual
                 | Self::StoreAttrWithHint
                 | Self::UnpackSequenceList
                 | Self::UnpackSequenceTuple
@@ -448,16 +451,14 @@ impl super::Opcode {
                 | Self::InstrumentedCallKw
                 | Self::InstrumentedJumpBackward
                 | Self::EnterExecutor
+                | Self::TraceRecord
         )
     }
 
     /// Does this opcode have 'HAS_CONST_FLAG' set.
     #[must_use]
     pub const fn has_const(self) -> bool {
-        matches!(
-            self,
-            Self::LoadConst | Self::LoadConstImmortal | Self::LoadConstMortal
-        )
+        matches!(self, Self::LoadConst)
     }
 
     /// Does this opcode have 'HAS_EVAL_BREAK_FLAG' set.
@@ -473,6 +474,7 @@ impl super::Opcode {
                 | Self::CallBuiltinFast
                 | Self::CallBuiltinFastWithKeywords
                 | Self::CallBuiltinO
+                | Self::CallExNonPyGeneral
                 | Self::CallKwNonPy
                 | Self::CallMethodDescriptorFast
                 | Self::CallMethodDescriptorFastWithKeywords
@@ -517,8 +519,11 @@ impl super::Opcode {
                 | Self::ForIterList
                 | Self::ForIterRange
                 | Self::ForIterTuple
+                | Self::ForIterVirtual
                 | Self::JumpBackwardJit
                 | Self::JumpBackwardNoJit
+                | Self::SendAsyncGen
+                | Self::SendVirtual
                 | Self::InstrumentedForIter
                 | Self::InstrumentedEndAsyncFor
         )
@@ -609,23 +614,21 @@ impl super::Opcode {
             Self::Cache => (0, 0),
             Self::BinarySlice => (1, 3),
             Self::BuildTemplate => (1, 2),
-            Self::BinaryOpInplaceAddUnicode => (0, 2),
+            Self::BinaryOpInplaceAddUnicode => (1, 2),
             Self::CallFunctionEx => (1, 4),
             Self::CheckEgMatch => (2, 2),
             Self::CheckExcMatch => (2, 2),
-            Self::CleanupThrow => (2, 3),
+            Self::CleanupThrow => (3, 4),
             Self::DeleteSubscr => (0, 2),
             Self::EndFor => (0, 1),
-            Self::EndSend => (1, 2),
+            Self::EndSend => (1, 3),
             Self::ExitInitCheck => (0, 1),
             Self::FormatSimple => (1, 1),
             Self::FormatWithSpec => (1, 2),
             Self::GetAiter => (1, 1),
             Self::GetAnext => (2, 1),
-            Self::GetIter => (1, 1),
-            Self::Reserved => (0, 0),
             Self::GetLen => (2, 1),
-            Self::GetYieldFromIter => (1, 1),
+            Self::Reserved => (0, 0),
             Self::InterpreterExit => (0, 1),
             Self::LoadBuildClass => (1, 0),
             Self::LoadLocals => (1, 0),
@@ -636,7 +639,7 @@ impl super::Opcode {
             Self::Nop => (0, 0),
             Self::NotTaken => (0, 0),
             Self::PopExcept => (0, 1),
-            Self::PopIter => (0, 1),
+            Self::PopIter => (0, 2),
             Self::PopTop => (0, 1),
             Self::PushExcInfo => (2, 1),
             Self::PushNull => (1, 0),
@@ -676,8 +679,9 @@ impl super::Opcode {
             Self::DictUpdate => (1 + (oparg - 1), 2 + (oparg - 1)),
             Self::EndAsyncFor => (0, 2),
             Self::ExtendedArg => (0, 0),
-            Self::ForIter => (2, 1),
+            Self::ForIter => (3, 2),
             Self::GetAwaitable => (1, 1),
+            Self::GetIter => (2, 1),
             Self::ImportFrom => (2, 1),
             Self::ImportName => (1, 2),
             Self::IsOp => (1, 2),
@@ -712,7 +716,7 @@ impl super::Opcode {
             Self::PopJumpIfTrue => (0, 1),
             Self::RaiseVarargs => (0, oparg),
             Self::Reraise => (oparg, 1 + oparg),
-            Self::Send => (2, 2),
+            Self::Send => (3, 3),
             Self::SetAdd => (1 + (oparg - 1), 2 + (oparg - 1)),
             Self::SetFunctionAttribute => (1, 2),
             Self::SetUpdate => (1 + (oparg - 1), 2 + (oparg - 1)),
@@ -740,6 +744,7 @@ impl super::Opcode {
             Self::BinaryOpSubscrListSlice => (1, 2),
             Self::BinaryOpSubscrStrInt => (1, 2),
             Self::BinaryOpSubscrTupleInt => (1, 2),
+            Self::BinaryOpSubscrUstrInt => (1, 2),
             Self::BinaryOpSubtractFloat => (1, 2),
             Self::BinaryOpSubtractInt => (1, 2),
             Self::CallAllocAndEnterInit => (0, 2 + oparg),
@@ -749,12 +754,14 @@ impl super::Opcode {
             Self::CallBuiltinFast => (1, 2 + oparg),
             Self::CallBuiltinFastWithKeywords => (1, 2 + oparg),
             Self::CallBuiltinO => (1, 2 + oparg),
-            Self::CallIsinstance => (1, 2 + oparg),
+            Self::CallExNonPyGeneral => (1, 4),
+            Self::CallExPy => (0, 4),
+            Self::CallIsinstance => (1, 4),
             Self::CallKwBoundMethod => (0, 3 + oparg),
             Self::CallKwNonPy => (1, 3 + oparg),
             Self::CallKwPy => (0, 3 + oparg),
             Self::CallLen => (1, 3),
-            Self::CallListAppend => (0, 3),
+            Self::CallListAppend => (1, 3),
             Self::CallMethodDescriptorFast => (1, 2 + oparg),
             Self::CallMethodDescriptorFastWithKeywords => (1, 2 + oparg),
             Self::CallMethodDescriptorNoargs => (1, 2 + oparg),
@@ -770,15 +777,18 @@ impl super::Opcode {
             Self::CompareOpStr => (1, 2),
             Self::ContainsOpDict => (1, 2),
             Self::ContainsOpSet => (1, 2),
-            Self::ForIterGen => (1, 1),
-            Self::ForIterList => (2, 1),
-            Self::ForIterRange => (2, 1),
-            Self::ForIterTuple => (2, 1),
+            Self::ForIterGen => (2, 2),
+            Self::ForIterList => (3, 2),
+            Self::ForIterRange => (3, 2),
+            Self::ForIterTuple => (3, 2),
+            Self::ForIterVirtual => (3, 2),
+            Self::GetIterSelf => (2, 1),
+            Self::GetIterVirtual => (2, 1),
             Self::JumpBackwardJit => (0, 0),
             Self::JumpBackwardNoJit => (0, 0),
             Self::LoadAttrClass => (1 + (oparg & 1), 1),
             Self::LoadAttrClassWithMetaclassCheck => (1 + (oparg & 1), 1),
-            Self::LoadAttrGetattributeOverridden => (1, 1),
+            Self::LoadAttrGetattributeOverridden => (0, 1),
             Self::LoadAttrInstanceValue => (1 + (oparg & 1), 1),
             Self::LoadAttrMethodLazyDict => (2, 1),
             Self::LoadAttrMethodNoDict => (2, 1),
@@ -789,14 +799,15 @@ impl super::Opcode {
             Self::LoadAttrProperty => (0, 1),
             Self::LoadAttrSlot => (1 + (oparg & 1), 1),
             Self::LoadAttrWithHint => (1 + (oparg & 1), 1),
-            Self::LoadConstImmortal => (1, 0),
-            Self::LoadConstMortal => (1, 0),
             Self::LoadGlobalBuiltin => (1 + (oparg & 1), 0),
             Self::LoadGlobalModule => (1 + (oparg & 1), 0),
             Self::LoadSuperAttrAttr => (1, 3),
             Self::LoadSuperAttrMethod => (2, 3),
             Self::ResumeCheck => (0, 0),
-            Self::SendGen => (1, 2),
+            Self::ResumeCheckJit => (0, 0),
+            Self::SendAsyncGen => (3, 3),
+            Self::SendGen => (2, 3),
+            Self::SendVirtual => (3, 3),
             Self::StoreAttrInstanceValue => (0, 2),
             Self::StoreAttrSlot => (0, 2),
             Self::StoreAttrWithHint => (0, 2),
@@ -811,10 +822,14 @@ impl super::Opcode {
             Self::UnpackSequenceList => (oparg, 1),
             Self::UnpackSequenceTuple => (oparg, 1),
             Self::UnpackSequenceTwoTuple => (2, 1),
-            Self::InstrumentedEndFor => (1, 2),
-            Self::InstrumentedPopIter => (0, 1),
-            Self::InstrumentedEndSend => (1, 2),
-            Self::InstrumentedForIter => (2, 1),
+            Self::BuildListFromArg => (
+                2, // TODO: Differs from CPython `None`
+                1, // TODO: Differs from CPython `None`
+            ),
+            Self::InstrumentedEndFor => (2, 3),
+            Self::InstrumentedPopIter => (0, 2),
+            Self::InstrumentedEndSend => (1, 3),
+            Self::InstrumentedForIter => (3, 2),
             Self::InstrumentedInstruction => (0, 0),
             Self::InstrumentedJumpForward => (0, 0),
             Self::InstrumentedNotTaken => (0, 0),
@@ -833,6 +848,7 @@ impl super::Opcode {
             Self::InstrumentedJumpBackward => (0, 0),
             Self::InstrumentedLine => (0, 0),
             Self::EnterExecutor => (0, 0),
+            Self::TraceRecord => (0, 0),
         };
 
         debug_assert!(u32::try_from(pushed).is_ok());
diff --git a/crates/compiler-core/src/lib.rs b/crates/compiler-core/src/lib.rs
index 8fe1146e514..b4770e50c35 100644
--- a/crates/compiler-core/src/lib.rs
+++ b/crates/compiler-core/src/lib.rs
@@ -9,9 +9,11 @@ pub mod bytecode;
 pub mod frozen;
 pub mod marshal;
 mod mode;
+mod source_location;
 pub mod varint;
 
 pub use mode::Mode;
+pub use source_location::{AstLocationError, AstLocations, SourceLocationRange};
 
 pub use ruff_source_file::{
     LineIndex, OneIndexed, PositionEncoding, SourceFile, SourceFileBuilder, SourceLocation,
diff --git a/crates/compiler-core/src/marshal.rs b/crates/compiler-core/src/marshal.rs
index 1615c1d6a78..8f0c7253d43 100644
--- a/crates/compiler-core/src/marshal.rs
+++ b/crates/compiler-core/src/marshal.rs
@@ -5,7 +5,7 @@ use malachite_bigint::{BigInt, Sign};
 use num_complex::Complex64;
 use rustpython_wtf8::Wtf8;
 
-pub const FORMAT_VERSION: u32 = 5;
+pub const FORMAT_VERSION: u32 = 6;
 
 #[derive(Clone, Copy, Debug)]
 pub enum MarshalError {
@@ -84,6 +84,7 @@ enum Type {
     SmallTuple = b')',
     List = b'[',
     Dict = b'{',
+    FrozenDict = b'}',
     Code = b'c',
     Unicode = b'u',
     Set = b'<',
@@ -120,6 +121,7 @@ impl TryFrom<u8> for Type {
             b')' => Self::SmallTuple,
             b'[' => Self::List,
             b'{' => Self::Dict,
+            b'}' => Self::FrozenDict,
             b'c' => Self::Code,
             b'u' => Self::Unicode,
             b'<' => Self::Set,
@@ -554,6 +556,17 @@ fn read_const_value<R: Read, Bag: ConstantBag>(
     Ok(value)
 }
 
+/// Object-valued code fields as read from the stream (`r_object` TYPE_CODE).
+pub struct CodeFields<V> {
+    pub consts: V,
+    pub qualname: V,
+    pub names: V,
+    pub localsplusnames: V,
+    pub localspluskinds: V,
+    pub linetable: V,
+    pub exceptiontable: V,
+}
+
 pub trait MarshalBag: Copy {
     type Value: Clone;
     type ConstantBag: ConstantBag;
@@ -580,23 +593,14 @@ pub trait MarshalBag: Copy {
 
     fn make_tuple(&self, elements: impl Iterator<Item = Self::Value>) -> Self::Value;
 
+    /// Construct a code object. `fields` holds the objects read for the
+    /// object-valued fields that `code` was decoded from.
     fn make_code(
         &self,
         code: CodeObject<<Self::ConstantBag as ConstantBag>::Constant>,
+        fields: CodeFields<Self::Value>,
     ) -> Result<Self::Value>;
 
-    /// Construct a runtime code object while retaining the exact values read
-    /// from ``co_consts``. Compiler bags ignore this second channel; runtime
-    /// bags use it for marshalable values (lists, dicts, sets, recursive
-    /// containers) that their compiler constant representation cannot hold.
-    fn make_code_with_constants(
-        &self,
-        code: CodeObject<<Self::ConstantBag as ConstantBag>::Constant>,
-        _constants: Vec<Self::Value>,
-    ) -> Result<Self::Value> {
-        self.make_code(code)
-    }
-
     /// Decode the public `co_code` byte string into the execution-oriented
     /// instruction storage.
     ///
@@ -608,22 +612,6 @@ pub trait MarshalBag: Copy {
         CodeUnits::try_from(code_bytes)
     }
 
-    /// Construct a runtime code object while retaining both its exact public
-    /// `co_code` bytes and the exact values read from `co_consts`.
-    ///
-    /// The default ignores the redundant byte spelling because ordinary
-    /// compiler code is represented losslessly by `CodeUnits`.  Runtime bags
-    /// that accepted otherwise unrepresentable opcode bytes in
-    /// [`MarshalBag::code_units_from_bytes`] can preserve them here.
-    fn make_code_with_constants_and_bytes(
-        &self,
-        code: CodeObject<<Self::ConstantBag as ConstantBag>::Constant>,
-        constants: Vec<Self::Value>,
-        _code_bytes: Vec<u8>,
-    ) -> Result<Self::Value> {
-        self.make_code_with_constants(code, constants)
-    }
-
     fn make_stop_iter(&self) -> Result<Self::Value>;
 
     fn make_list(&self, it: impl Iterator<Item = Self::Value>) -> Result<Self::Value>;
@@ -637,6 +625,10 @@ pub trait MarshalBag: Copy {
         it: impl Iterator<Item = (Self::Value, Self::Value)>,
     ) -> Result<Self::Value>;
 
+    fn freeze_dict(&self, _dict: Self::Value) -> Result<Self::Value> {
+        Err(MarshalError::BadType)
+    }
+
     /// Install partially-built containers in the marshal reference table
     /// before reading their children, as CPython's `r_object()` does.
     /// Runtime bags can opt in; constant bags retain collect-then-construct.
@@ -786,6 +778,7 @@ impl<Bag: ConstantBag> MarshalBag for Bag {
     fn make_code(
         &self,
         code: CodeObject<<Self::ConstantBag as ConstantBag>::Constant>,
+        _fields: CodeFields<Self::Value>,
     ) -> Result<Self::Value> {
         Ok(self.make_code(code))
     }
@@ -958,17 +951,20 @@ fn deserialize_code_value_inner<R: Read, Bag: MarshalBag>(
         .into_iter()
         .collect();
 
-    let read_strings =
-        |rdr: &mut R, refs: &mut Vec<Option<Bag::Value>>| -> Result<Vec<alloc::string::String>> {
-            let tuple = deserialize_value_depth(rdr, bag, child_depth, refs)?;
-            bag.tuple_elements_from_value(&tuple)
-                .ok_or(MarshalError::BadType)?
-                .iter()
-                .map(|value| bag.str_from_value(value).ok_or(MarshalError::BadType))
-                .collect()
-        };
-    let names_raw = read_strings(rdr, refs)?;
-    let localsplusnames = read_strings(rdr, refs)?;
+    let read_strings = |rdr: &mut R,
+                        refs: &mut Vec<Option<Bag::Value>>|
+     -> Result<(Bag::Value, Vec<alloc::string::String>)> {
+        let tuple = deserialize_value_depth(rdr, bag, child_depth, refs)?;
+        let names = bag
+            .tuple_elements_from_value(&tuple)
+            .ok_or(MarshalError::BadType)?
+            .iter()
+            .map(|value| bag.str_from_value(value).ok_or(MarshalError::BadType))
+            .collect::<Result<Vec<_>>>()?;
+        Ok((tuple, names))
+    };
+    let (names_value, names_raw) = read_strings(rdr, refs)?;
+    let (localsplusnames_value, localsplusnames) = read_strings(rdr, refs)?;
 
     let kinds_value = deserialize_value_depth(rdr, bag, child_depth, refs)?;
     let localspluskinds = bag
@@ -982,7 +978,10 @@ fn deserialize_code_value_inner<R: Read, Bag: MarshalBag>(
         };
     let source_path_raw = read_string(rdr, refs)?;
     let obj_name_raw = read_string(rdr, refs)?;
-    let qualname_raw = read_string(rdr, refs)?;
+    let qualname_value = deserialize_value_depth(rdr, bag, child_depth, refs)?;
+    let qualname_raw = bag
+        .str_from_value(&qualname_value)
+        .ok_or(MarshalError::BadType)?;
 
     let first_line_raw = rdr.read_u32()? as i32;
     let first_line_number = if first_line_raw > 0 {
@@ -1050,7 +1049,18 @@ fn deserialize_code_value_inner<R: Read, Bag: MarshalBag>(
         linetable,
         exceptiontable,
     };
-    bag.make_code_with_constants_and_bytes(code, constant_values, code_bytes)
+    bag.make_code(
+        code,
+        CodeFields {
+            consts: consts_value,
+            qualname: qualname_value,
+            names: names_value,
+            localsplusnames: localsplusnames_value,
+            localspluskinds: kinds_value,
+            linetable: linetable_value,
+            exceptiontable: exceptiontable_value,
+        },
+    )
 }
 
 fn deserialize_value_typed<R: Read, Bag: MarshalBag>(
@@ -1197,22 +1207,30 @@ fn deserialize_value_typed<R: Read, Bag: MarshalBag>(
             let it = (0..len).map(|_| deserialize_value_depth(rdr, bag, d, refs));
             itertools::process_results(it, |it| bag.make_frozenset(it))??
         }
-        Type::Dict => {
+        Type::Dict | Type::FrozenDict => {
             let d = depth - 1;
-            if let Some(index) = slot
+            // Immutable mappings are published only after all entries are read.
+            let frozen = matches!(typ, Type::FrozenDict);
+            if (frozen || slot.is_some())
                 && let Some(dict) = bag.make_dict_placeholder()
             {
-                refs[index] = Some(dict.clone());
+                if !frozen && let Some(index) = slot {
+                    refs[index] = Some(dict.clone());
+                }
                 loop {
                     let raw = read_object_type(rdr)?;
                     if raw & !FLAG_REF == b'0' {
                         break;
                     }
                     let key = deserialize_value_after_header(rdr, bag, d, refs, raw)?;
-                    let value = deserialize_value_depth(rdr, bag, d, refs)?;
+                    let raw = read_object_type(rdr)?;
+                    if raw & !FLAG_REF == b'0' {
+                        break;
+                    }
+                    let value = deserialize_value_after_header(rdr, bag, d, refs, raw)?;
                     bag.insert_dict_item(&dict, key, value)?;
                 }
-                dict
+                if frozen { bag.freeze_dict(dict)? } else { dict }
             } else {
                 let mut pairs = Vec::new();
                 loop {
@@ -1221,10 +1239,15 @@ fn deserialize_value_typed<R: Read, Bag: MarshalBag>(
                         break;
                     }
                     let key = deserialize_value_after_header(rdr, bag, d, refs, raw)?;
-                    let value = deserialize_value_depth(rdr, bag, d, refs)?;
+                    let raw = read_object_type(rdr)?;
+                    if raw & !FLAG_REF == b'0' {
+                        break;
+                    }
+                    let value = deserialize_value_after_header(rdr, bag, d, refs, raw)?;
                     pairs.push((key, value));
                 }
-                bag.make_dict(pairs.into_iter())?
+                let dict = bag.make_dict(pairs.into_iter())?;
+                if frozen { bag.freeze_dict(dict)? } else { dict }
             }
         }
         Type::Bytes => {
@@ -1268,6 +1291,7 @@ pub enum DumpableValue<'a, D: Dumpable> {
     Set(&'a [D]),
     Frozenset(&'a [D]),
     Dict(&'a [(D, D)]),
+    Frozendict(&'a [(D, D)]),
     Slice(&'a D, &'a D, &'a D),
 }
 
@@ -1439,8 +1463,13 @@ pub fn serialize_value<W: Write, D: Dumpable>(
                 val.with_dump(|val| serialize_value(buf, val))??
             }
         }
-        DumpableValue::Dict(d) => {
-            buf.write_u8(Type::Dict as u8);
+        DumpableValue::Dict(d) | DumpableValue::Frozendict(d) => {
+            let typ = if matches!(constant, DumpableValue::Frozendict(_)) {
+                Type::FrozenDict
+            } else {
+                Type::Dict
+            };
+            buf.write_u8(typ as u8);
             for (k, v) in d {
                 k.with_dump(|val| serialize_value(buf, val))??;
                 v.with_dump(|val| serialize_value(buf, val))??;
diff --git a/crates/compiler-core/src/source_location.rs b/crates/compiler-core/src/source_location.rs
new file mode 100644
index 00000000000..ca7d301c695
--- /dev/null
+++ b/crates/compiler-core/src/source_location.rs
@@ -0,0 +1,78 @@
+/// A Python source range with signed line and column coordinates.
+///
+/// Unlike a parser text range, this preserves absent coordinates (negative
+/// values), as well as line zero used by synthetic RESUME instructions.
+/// Columns are zero-based; positive line numbers are one-based.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct SourceLocationRange {
+    pub line: i32,
+    pub end_line: i32,
+    pub col: i32,
+    pub end_col: i32,
+}
+
+/// Location metadata shared by AST conversion and code generation.
+///
+/// Numeric IDs occupy Ruff's top-level node identity range. Keeping the store
+/// independent of Ruff allows AST-only VM builds without the codegen crate.
+#[derive(Default, Debug)]
+pub struct AstLocations {
+    locations: alloc::collections::BTreeMap<u32, SourceLocationRange>,
+    next_index: u32,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum AstLocationError {
+    ConflictingLocation,
+    ExhaustedNodeIdentities,
+    CoordinateOverflow,
+}
+
+impl AstLocations {
+    // Ruff reserves the upper two bits for sub-AST levels and sentinel IDs.
+    pub const MAX_ID: u32 = (1 << 30) - 1;
+
+    pub fn allocate(
+        &mut self,
+        location: Option<SourceLocationRange>,
+    ) -> Result<u32, AstLocationError> {
+        if self.next_index > Self::MAX_ID {
+            return Err(AstLocationError::ExhaustedNodeIdentities);
+        }
+        let id = self.next_index;
+        self.next_index = self
+            .next_index
+            .checked_add(1)
+            .ok_or(AstLocationError::ExhaustedNodeIdentities)?;
+        if let Some(location) = location {
+            self.insert(id, location)?;
+        }
+        Ok(id)
+    }
+
+    /// An inherited identity may be shared only with identical coordinates.
+    pub fn insert(
+        &mut self,
+        id: u32,
+        location: SourceLocationRange,
+    ) -> Result<(), AstLocationError> {
+        if id > Self::MAX_ID {
+            return Err(AstLocationError::ExhaustedNodeIdentities);
+        }
+        if let Some(previous) = self.locations.get(&id) {
+            return if *previous == location {
+                Ok(())
+            } else {
+                Err(AstLocationError::ConflictingLocation)
+            };
+        }
+        self.locations.insert(id, location);
+        self.next_index = self.next_index.max(id + 1);
+        Ok(())
+    }
+
+    #[must_use]
+    pub fn get(&self, id: u32) -> Option<SourceLocationRange> {
+        self.locations.get(&id).copied()
+    }
+}
diff --git a/crates/compiler/src/lib.rs b/crates/compiler/src/lib.rs
index 534173d2c11..636182c7708 100644
--- a/crates/compiler/src/lib.rs
+++ b/crates/compiler/src/lib.rs
@@ -37,6 +37,60 @@ pub struct ParseError {
     pub is_unclosed_bracket: bool,
     /// Set when a string is still open at EOF and more input could close it.
     pub is_unclosed_string: bool,
+    /// Set when the parser failed on a token made up at the end of the input.
+    pub eof_token: Option<Box<EofToken>>,
+}
+
+/// The tokenizer state at the end of the input, where it makes up the
+/// NEWLINE, DEDENT and ENDMARKER tokens that close it. Those tokens have no
+/// column, so an error on one of them is placed where the tokenizer stopped.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct EofToken {
+    /// `tok->lineno`: the number of lines read, 0 for empty input.
+    pub lineno: usize,
+    /// The last line read, which the tokenizer stopped at the end of.
+    pub line: String,
+    /// The error is raised at the token itself, as the generic syntax error
+    /// and a missing forced token are, so its columns are 0.
+    pub known_location: bool,
+}
+
+impl EofToken {
+    fn new(source: &str, mode: Mode, known_location: bool) -> Self {
+        let lineno = source.split_inclusive('\n').count();
+        let mut line = source
+            .split_inclusive('\n')
+            .next_back()
+            .unwrap_or_default()
+            .to_owned();
+        // translate_newlines: exec input that does not end with a newline
+        // gets one.
+        if matches!(mode, Mode::Exec | Mode::BlockExpr) && !line.is_empty() && !line.ends_with('\n')
+        {
+            line.push('\n');
+        }
+        Self {
+            lineno,
+            line,
+            known_location,
+        }
+    }
+
+    /// `SyntaxError.offset`
+    #[must_use]
+    pub fn offset(&self) -> usize {
+        if self.known_location {
+            0
+        } else {
+            self.line.chars().count()
+        }
+    }
+
+    /// `SyntaxError.end_offset`
+    #[must_use]
+    pub const fn end_offset(&self) -> isize {
+        if self.known_location { 0 } else { -1 }
+    }
 }
 
 impl ::core::fmt::Display for ParseError {
@@ -61,11 +115,31 @@ impl CompileError {
         mode: Mode,
     ) -> Self {
         let raw_location = error.location;
+        let at_eof_token = fails_at_eof_token(&error, source_file.source_text(), mode);
         let diagnostic = match cpython_parse_diagnostic_override(&error, source_file, mode) {
             Some(diagnostic) => diagnostic,
-            None => default_parse_diagnostic(error, source_file),
+            None => {
+                let is_unclosed_bracket = matches!(
+                    error.error,
+                    parser::ParseErrorType::Lexical(parser::LexicalErrorType::UnclosedBracket {
+                        incomplete: true,
+                        ..
+                    })
+                );
+                let is_unclosed_string =
+                    unclosed_string_is_continuable(&error, source_file.source_text(), mode);
+                let mut diagnostic = default_parse_diagnostic(error, source_file);
+                diagnostic.is_unclosed_bracket = is_unclosed_bracket;
+                diagnostic.is_unclosed_string = is_unclosed_string;
+                diagnostic
+            }
         };
 
+        let eof_token = at_eof_token.then(|| {
+            let source = source_file.source_text();
+            let known_location = is_raised_at_token(&diagnostic.error, source, raw_location);
+            Box::new(EofToken::new(source, mode, known_location))
+        });
         Self::Parse(ParseError {
             error: diagnostic.error,
             raw_location,
@@ -74,6 +148,7 @@ impl CompileError {
             source_path: source_file.name().to_owned(),
             is_unclosed_bracket: diagnostic.is_unclosed_bracket,
             is_unclosed_string: diagnostic.is_unclosed_string,
+            eof_token,
         })
     }
 
@@ -89,8 +164,9 @@ impl CompileError {
             location,
             end_location,
             source_path: source_file.name().to_owned(),
-            is_unclosed_bracket: diagnostic.is_unclosed_bracket,
-            is_unclosed_string: diagnostic.is_unclosed_string,
+            is_unclosed_bracket: false,
+            is_unclosed_string: false,
+            eof_token: None,
         })
     }
 
@@ -103,8 +179,14 @@ impl CompileError {
     }
 
     #[must_use]
-    pub const fn python_location(&self) -> (usize, usize) {
-        if let Some(location) = self.location() {
+    pub fn python_location(&self) -> (usize, usize) {
+        if let Self::Parse(ParseError {
+            eof_token: Some(eof_token),
+            ..
+        }) = self
+        {
+            (eof_token.lineno, eof_token.offset())
+        } else if let Some(location) = self.location() {
             (location.line.get(), location.character_offset.get())
         } else {
             (0, 0)
@@ -182,22 +264,6 @@ impl NormalizedParseDiagnostic {
         }
     }
 
-    fn other(source_file: &SourceFile, diagnostic: CpythonDiagnostic) -> Self {
-        let (location, end_location) = source_locations(
-            source_file,
-            diagnostic.range.start(),
-            diagnostic.range.end(),
-        );
-        let mut diagnostic_out = Self::new(
-            parser::ParseErrorType::OtherError(diagnostic.message),
-            location,
-            end_location,
-        );
-        diagnostic_out.is_unclosed_string = diagnostic.is_unclosed_string;
-        diagnostic_out.is_unclosed_bracket = diagnostic.is_unclosed_bracket;
-        diagnostic_out
-    }
-
     const fn with_unclosed_bracket(mut self, is_unclosed_bracket: bool) -> Self {
         self.is_unclosed_bracket = is_unclosed_bracket;
         self
@@ -212,8 +278,6 @@ impl NormalizedParseDiagnostic {
 struct CpythonDiagnostic {
     message: String,
     range: ruff_text_size::TextRange,
-    is_unclosed_string: bool,
-    is_unclosed_bracket: bool,
 }
 
 impl CpythonDiagnostic {
@@ -228,66 +292,8 @@ impl CpythonDiagnostic {
                 TextSize::new(start as u32),
                 TextSize::new(end as u32),
             ),
-            is_unclosed_string: false,
-            is_unclosed_bracket: false,
         }
     }
-
-    const fn with_unclosed_string(mut self) -> Self {
-        self.is_unclosed_string = true;
-        self
-    }
-
-    const fn with_unclosed_bracket(mut self) -> Self {
-        self.is_unclosed_bracket = true;
-        self
-    }
-}
-
-/// Lexer-class failures outrank print hints. Decode and f-string diagnostics
-/// compete with lexer failures by offset, and an unterminated quote is only
-/// a fallback when no decode/f-string diagnostic exists. Print is considered
-/// against the final winner: a later 0x still beats print, but an f-string
-/// that replaced that 0x must not hide an earlier print. A decode diagnostic
-/// also suppresses an EOF unclosed opener.
-#[derive(Clone, Copy, PartialEq, Eq)]
-enum OverrideClass {
-    Lexer,
-    Decode,
-    Print,
-}
-
-struct RankedOverride {
-    diagnostic: CpythonDiagnostic,
-    unclosed_bracket: bool,
-    class: OverrideClass,
-}
-
-fn consider_override(
-    best: &mut Option<RankedOverride>,
-    diagnostic: CpythonDiagnostic,
-    class: OverrideClass,
-) {
-    let unclosed_bracket = diagnostic.is_unclosed_bracket;
-    consider_ranked(best, diagnostic, unclosed_bracket, class);
-}
-
-fn consider_ranked(
-    best: &mut Option<RankedOverride>,
-    diagnostic: CpythonDiagnostic,
-    unclosed_bracket: bool,
-    class: OverrideClass,
-) {
-    if best
-        .as_ref()
-        .is_none_or(|current| diagnostic.range.start() < current.diagnostic.range.start())
-    {
-        *best = Some(RankedOverride {
-            diagnostic,
-            unclosed_bracket,
-            class,
-        });
-    }
 }
 
 fn cpython_parse_diagnostic_override(
@@ -297,109 +303,42 @@ fn cpython_parse_diagnostic_override(
 ) -> Option<NormalizedParseDiagnostic> {
     let source_text = source_file.source_text();
 
-    macro_rules! source_error {
-        ($expr:expr) => {
-            if let Some(error) = $expr {
-                return Some(NormalizedParseDiagnostic::other(source_file, error));
-            }
-        };
-    }
-
-    let mut earliest: Option<RankedOverride> = None;
-    if let Some(diagnostic) = invalid_number_literal_error(source_text) {
-        consider_override(&mut earliest, diagnostic, OverrideClass::Lexer);
-    }
-    if let Some(diagnostic) = incompatible_string_prefix_error(source_text) {
-        consider_override(&mut earliest, diagnostic, OverrideClass::Lexer);
-    }
-    if let Some(diagnostic) = non_printable_character_error(source_text) {
-        consider_override(&mut earliest, diagnostic, OverrideClass::Lexer);
-    }
-    let bracket = bracket_syntax_error(source_text);
-    if let Some(bracket) = bracket.as_ref() {
-        // Unclosed openers are reported at the opener and only become errors
-        // at EOF. A later token-time diagnostic (invalid number, prefix, …)
-        // must keep winning. Mismatched closers stay in the lexer-class
-        // positional ranking.
-        if !bracket.unclosed {
-            consider_ranked(
-                &mut earliest,
-                bracket.diagnostic.clone(),
-                false,
-                OverrideClass::Lexer,
-            );
-        }
-    }
-    let mut saw_decode = false;
-    if let Some(diagnostic) = malformed_unicode_n_escape_error(source_text) {
-        saw_decode = true;
-        consider_override(&mut earliest, diagnostic, OverrideClass::Decode);
-    }
-    if let Some(diagnostic) = invalid_interpolated_string_error(source_text) {
-        saw_decode = true;
-        consider_override(&mut earliest, diagnostic, OverrideClass::Decode);
-    }
-    if let Some(diagnostic) = mixed_tstring_literal_error(error, source_text) {
-        saw_decode = true;
-        consider_override(&mut earliest, diagnostic, OverrideClass::Decode);
-    }
-    // A later ordinary unterminated quote is only a fallback. Format-spec
-    // newlines and empty fields are decode diagnostics and must keep winning.
-    let line_continuation = matches!(
+    let tokenizer_error = matches!(
         &error.error,
-        parser::ParseErrorType::Lexical(parser::LexicalErrorType::LineContinuationError)
+        parser::ParseErrorType::Lexical(lexical) if lexical.is_tokenizer_error()
     );
-    if !saw_decode
-        && !line_continuation
-        && let Some(diagnostic) = unterminated_string_error(source_text, mode)
-    {
-        consider_override(&mut earliest, diagnostic, OverrideClass::Lexer);
-    }
-    // Indentation errors outrank a print/exec missing-parentheses rewrite.
-    let indent_error = matches!(
-        &error.error,
-        parser::ParseErrorType::Lexical(parser::LexicalErrorType::IndentationError)
-            | parser::ParseErrorType::UnexpectedIndentation
-    ) || expected_indented_block_error(error, source_text).is_some();
-    if !indent_error
-        && earliest
-            .as_ref()
-            .is_none_or(|current| current.class != OverrideClass::Lexer)
-        && let Some(diagnostic) = invalid_legacy_statement_error(source_text)
-    {
-        consider_override(&mut earliest, diagnostic, OverrideClass::Print);
-    }
-    if !saw_decode
-        && earliest
-            .as_ref()
-            .is_none_or(|current| current.class == OverrideClass::Print)
-        && let Some(bracket) = bracket.filter(|bracket| bracket.unclosed)
-    {
-        consider_ranked(
-            &mut earliest,
-            bracket.diagnostic,
-            true,
-            OverrideClass::Lexer,
-        );
-    }
-    if let Some(override_diag) = earliest {
-        return Some(
-            NormalizedParseDiagnostic::other(source_file, override_diag.diagnostic)
-                .with_unclosed_bracket(override_diag.unclosed_bracket),
-        );
-    }
-
-    if matches!(
+    let line_continuation = matches!(
         &error.error,
         parser::ParseErrorType::Lexical(parser::LexicalErrorType::LineContinuationError)
-    ) {
+    );
+    if line_continuation {
         // exec input gets an implicit trailing newline, so a final `\` is a
         // continuation that then hits EOF (`E_EOF`). single/eval see `\` at
         // EOF as `E_LINECONT` instead.
-        let terminal_backslash = source_text.len().checked_sub(1);
-        if matches!(mode, Mode::Exec)
-            && terminal_backslash == Some(error.location.start().to_usize())
-        {
+        if matches!(mode, Mode::Exec) && error.location.start().to_usize() == source_text.len() {
+            let source_with_newline = format!("{source_text}\n");
+            let parsed = parser::parse_unchecked(
+                &source_with_newline,
+                parser::ParseOptions::from(parser::Mode::Module),
+            );
+            if let Some(unclosed) = parsed.errors().first().filter(|first| {
+                matches!(
+                    first.error,
+                    parser::ParseErrorType::Lexical(
+                        parser::LexicalErrorType::UnclosedBracket { .. }
+                    )
+                )
+            }) {
+                let mut diagnostic = default_parse_diagnostic(unclosed.clone(), source_file);
+                diagnostic.is_unclosed_bracket = matches!(
+                    unclosed.error,
+                    parser::ParseErrorType::Lexical(parser::LexicalErrorType::UnclosedBracket {
+                        incomplete: true,
+                        ..
+                    })
+                );
+                return Some(diagnostic);
+            }
             let loc = source_line_end_location(source_file, error.location.start());
             return Some(NormalizedParseDiagnostic::new(
                 parser::ParseErrorType::OtherError("unexpected EOF while parsing".to_owned()),
@@ -407,126 +346,22 @@ fn cpython_parse_diagnostic_override(
                 loc,
             ));
         }
-        let loc = source_location(source_file, error.location.start() + TextSize::from(1));
-        return Some(NormalizedParseDiagnostic::new(
-            parser::ParseErrorType::OtherError(
-                "unexpected character after line continuation character".to_owned(),
-            ),
-            loc,
-            loc,
-        ));
+        return None;
     }
 
-    source_error!(unterminated_string_error(source_text, mode));
-    source_error!(expected_indented_block_error(error, source_text));
-
     if matches!(
         &error.error,
         parser::ParseErrorType::Lexical(parser::LexicalErrorType::Eof)
     ) {
         return Some(eof_parse_diagnostic(error, source_file));
     }
-
-    source_error!(invalid_type_param_error(source_text));
-    source_error!(invalid_comprehension_error(source_text));
-    source_error!(invalid_parameter_star_annotation_error(source_text));
-    source_error!(invalid_parameter_list_error(source_text));
-    source_error!(invalid_call_argument_error(source_text));
-
-    if is_missing_comma_between_literals(error) {
-        let (loc, end_loc) = adjusted_error_locations(source_file, error.location);
-        let msg = "invalid syntax. Perhaps you forgot a comma?".into();
-        return Some(NormalizedParseDiagnostic::new(
-            parser::ParseErrorType::OtherError(msg),
-            loc,
-            end_loc,
-        ));
-    }
-
-    source_error!(invalid_dict_error(source_text));
-    if !matches!(mode, Mode::Eval) {
-        source_error!(invalid_collection_assignment_error(source_text));
-    }
-    source_error!(invalid_group_error(source_text));
-    source_error!(invalid_def_type_params_error(source_text));
-    source_error!(invalid_expression_error(source_text));
-    source_error!(invalid_named_expression_error(source_text));
-    // Assignment and other statements are not expressions. Eval keeps the
-    // generic parse error rather than a statement-target rewrite.
-    if !matches!(mode, Mode::Eval) {
-        source_error!(invalid_plain_assignment_error(source_text));
-        source_error!(expression_assignment_error(source_text));
-        source_error!(invalid_annotation_target_error(source_text));
-        source_error!(invalid_assignment_target_error(source_text));
-        source_error!(invalid_condition_assignment_error(
-            source_text,
-            error.location.start().to_usize()
-        ));
-        source_error!(invalid_augassign_target_error(source_text));
-        source_error!(invalid_for_target_error(source_text));
-        source_error!(invalid_with_target_error(source_text));
-        source_error!(invalid_delete_target_error(source_text));
-        source_error!(invalid_standalone_except_error(source_text));
-        source_error!(invalid_import_statement_error(source_text));
-        source_error!(invalid_import_target_error(source_text));
-        source_error!(invalid_except_as_target_error(source_text));
-        source_error!(invalid_match_mapping_rest_wildcard_error(source_text));
-        source_error!(invalid_match_as_target_error(source_text));
-        source_error!(invalid_for_if_clause_error(source_text));
-        source_error!(invalid_if_expression_statement_error(source_text));
-        source_error!(invalid_else_elif_error(source_text));
-        source_error!(mixed_except_handlers_error(source_text));
-    }
-
-    if matches!(
-        &error.error,
-        parser::ParseErrorType::Lexical(parser::LexicalErrorType::InvalidByteLiteral)
-    ) && let Some((start, end)) =
-        bytes_literal_span(source_text, error.location.start().to_usize())
+    if tokenizer_error
+        || matches!(
+            &error.error,
+            parser::ParseErrorType::ExpectedIndentedBlock { .. }
+        )
     {
-        let (loc, end_loc) = source_locations(
-            source_file,
-            TextSize::new(start as u32),
-            TextSize::new(end as u32),
-        );
-        return Some(NormalizedParseDiagnostic::new(
-            error.error.clone(),
-            loc,
-            end_loc,
-        ));
-    }
-
-    if matches!(
-        &error.error,
-        parser::ParseErrorType::Lexical(parser::LexicalErrorType::IndentationError)
-    ) {
-        let end_loc = source_line_end_location(source_file, error.location.start());
-        return Some(NormalizedParseDiagnostic::new(
-            error.error.clone(),
-            end_loc,
-            end_loc,
-        ));
-    }
-
-    if matches!(
-        &error.error,
-        parser::ParseErrorType::InvalidAssignmentTarget
-    ) {
-        return Some(invalid_assignment_target_diagnostic(error, source_file));
-    }
-
-    if matches!(
-        &error.error,
-        parser::ParseErrorType::InvalidNamedAssignmentTarget
-    ) {
-        let (loc, end_loc) = adjusted_error_locations(source_file, error.location);
-        let target = source_file.source_text().slice(error.location);
-        let msg = format!("cannot use assignment expressions with {target}");
-        return Some(NormalizedParseDiagnostic::new(
-            parser::ParseErrorType::OtherError(msg),
-            loc,
-            end_loc,
-        ));
+        return None;
     }
 
     // CPython's PEG parser collapses a bare "expected an expression" failure
@@ -549,6 +384,94 @@ fn cpython_parse_diagnostic_override(
     None
 }
 
+/// Whether the parser fails on a token made up at the end of the input.
+fn fails_at_eof_token(error: &parser::ParseError, source: &str, mode: Mode) -> bool {
+    let start = error.location.start().to_usize();
+    match &error.error {
+        parser::ParseErrorType::Lexical(_) => false,
+        // `NEWLINE !INDENT` fails on the token after the newline, and the
+        // error is reported at the newline when only blank lines and comments
+        // follow it.
+        parser::ParseErrorType::ExpectedIndentedBlock { .. } => {
+            let end = error.location.end().to_usize();
+            source
+                .get(start..end)
+                .is_some_and(|text| text.chars().all(|c| c.is_ascii_whitespace()))
+                && source.get(end..).is_some_and(is_blank_python_source)
+        }
+        _ if start < source.len() => false,
+        // Exec input gets a newline appended, which is a real NEWLINE token,
+        // so the error is at the end only when it stays there once the
+        // newline is added.
+        _ if matches!(mode, Mode::Exec | Mode::BlockExpr)
+            && !source.is_empty()
+            && !source.ends_with('\n') =>
+        {
+            let source = format!("{source}\n");
+            let parsed =
+                parser::parse_unchecked(&source, parser::ParseOptions::from(parser::Mode::Module));
+            parsed
+                .errors()
+                .first()
+                .is_none_or(|error| error.location.start().to_usize() >= source.len())
+        }
+        _ => true,
+    }
+}
+
+/// Whether the error is raised at the token the parser failed on, as the
+/// generic syntax error and a missing forced token are, rather than where the
+/// tokenizer stopped.
+fn is_raised_at_token(
+    error: &parser::ParseErrorType,
+    source: &str,
+    range: ruff_text_size::TextRange,
+) -> bool {
+    match error {
+        // Only `else`, `try`, `finally` and `def` force their `:`; the other
+        // clause headers report a missing one from an `invalid_*` rule.
+        parser::ParseErrorType::ExpectedToken {
+            expected: TokenKind::Colon,
+            found: TokenKind::Newline,
+        } => matches!(
+            clause_keyword(source, range.start()),
+            Some(TokenKind::Else | TokenKind::Try | TokenKind::Finally | TokenKind::Def)
+        ),
+        parser::ParseErrorType::ExpectedToken { .. }
+        | parser::ParseErrorType::ExpectedExpression
+        | parser::ParseErrorType::ExpectedIdentifier
+        | parser::ParseErrorType::UnexpectedExpressionToken
+        | parser::ParseErrorType::SimpleStatementsOnSameLine
+        | parser::ParseErrorType::SimpleAndCompoundStatementOnSameLine
+        | parser::ParseErrorType::InvalidStarredExpressionUsage => true,
+        parser::ParseErrorType::OtherError(message) => message == "invalid syntax",
+        _ => false,
+    }
+}
+
+/// The keyword that starts the logical line `offset` is in, after `async`.
+fn clause_keyword(source: &str, offset: TextSize) -> Option<TokenKind> {
+    let parsed = parser::parse_unchecked(source, parser::ParseOptions::from(parser::Mode::Module));
+    let mut keyword = None;
+    let mut at_line_start = true;
+    for token in parsed
+        .tokens()
+        .iter()
+        .take_while(|token| token.start() < offset)
+    {
+        match token.kind() {
+            TokenKind::Newline | TokenKind::Indent | TokenKind::Dedent => at_line_start = true,
+            TokenKind::NonLogicalNewline | TokenKind::Comment | TokenKind::Async => {}
+            kind if at_line_start => {
+                keyword = Some(kind);
+                at_line_start = false;
+            }
+            _ => {}
+        }
+    }
+    keyword
+}
+
 fn eof_parse_diagnostic(
     error: &parser::ParseError,
     source_file: &SourceFile,
@@ -569,41 +492,52 @@ fn eof_parse_diagnostic(
     }
 }
 
-fn invalid_assignment_target_diagnostic(
-    error: &parser::ParseError,
-    source_file: &SourceFile,
-) -> NormalizedParseDiagnostic {
-    let (loc, end_loc) = adjusted_error_locations(source_file, error.location);
-    let expr_str = source_file.source_text().slice(error.location);
-
-    let msg = parser::parse_expression(expr_str).map_or_else(
-        |_| match expr_str {
-            "yield" => "assignment to yield expression not possible".into(),
-            _ => format!("cannot assign to {expr_str}"),
-        },
-        |parsed| match *parsed.syntax().body {
-            ast::Expr::Call(_) => "cannot assign to function call".into(),
-            ast::Expr::BinOp(_) => "cannot assign to expression".into(),
-            ast::Expr::If(_) => "cannot assign to conditional expression".into(),
-            ast::Expr::Generator(_) => "cannot assign to generator expression".into(),
-            ast::Expr::Yield(_) | ast::Expr::YieldFrom(_) => {
-                "cannot assign to yield expression here. Maybe you meant '==' instead of '='?"
-                    .into()
-            }
-            ast::Expr::FString(_) => "invalid syntax".into(),
-            ast::Expr::StringLiteral(_)
-            | ast::Expr::BytesLiteral(_)
-            | ast::Expr::NumberLiteral(_) => {
-                "cannot assign to literal here. Maybe you meant '==' instead of '='?".into()
-            }
-            ast::Expr::EllipsisLiteral(_) => {
-                "cannot assign to ellipsis here. Maybe you meant '==' instead of '='?".into()
-            }
-            _ => format!("cannot assign to {expr_str}"),
-        },
-    );
+/// Returns whether more input could still terminate the string that `error` reports as
+/// unterminated.
+///
+/// A string that reached the end of the source can continue, except a single-quoted f/t-string,
+/// a single-quoted string in exec input whose implicit final newline ends it, and a string after
+/// an assignment in eval input.
+fn unclosed_string_is_continuable(error: &parser::ParseError, source: &str, mode: Mode) -> bool {
+    use parser::{InterpolatedStringErrorType, LexicalErrorType};
+
+    let parser::ParseErrorType::Lexical(lexical) = &error.error else {
+        return false;
+    };
+    let start = error.location.start().to_usize();
+    let at_eof = match lexical {
+        LexicalErrorType::UnclosedStringError {
+            triple_quoted: true,
+            ..
+        }
+        | LexicalErrorType::FStringError(
+            InterpolatedStringErrorType::UnterminatedTripleQuotedString { .. },
+        )
+        | LexicalErrorType::TStringError(
+            InterpolatedStringErrorType::UnterminatedTripleQuotedString { .. },
+        ) => true,
+        LexicalErrorType::UnclosedStringError { .. } => {
+            // Exec mode appends a newline, which only a final `\` can escape.
+            let rest = &source[start..];
+            !has_unescaped_newline(rest) && (!matches!(mode, Mode::Exec) || rest.ends_with('\\'))
+        }
+        _ => false,
+    };
+    at_eof && !(matches!(mode, Mode::Eval) && eval_has_assignment_before(source.as_bytes(), start))
+}
 
-    NormalizedParseDiagnostic::new(parser::ParseErrorType::OtherError(msg), loc, end_loc)
+fn has_unescaped_newline(text: &str) -> bool {
+    let mut chars = text.chars();
+    while let Some(c) = chars.next() {
+        match c {
+            '\\' => {
+                chars.next();
+            }
+            '\n' | '\r' => return true,
+            _ => {}
+        }
+    }
+    false
 }
 
 fn default_parse_diagnostic(
@@ -646,14 +580,6 @@ fn source_line_end_location(source_file: &SourceFile, offset: TextSize) -> Sourc
     }
 }
 
-fn is_missing_comma_between_literals(error: &parser::ParseError) -> bool {
-    matches!(
-        &error.error,
-        parser::ParseErrorType::ExpectedToken { expected, found }
-            if matches!((expected, found), (TokenKind::Comma, TokenKind::Int))
-    )
-}
-
 fn is_ascii_identifier_char(byte: u8) -> bool {
     byte == b'_' || byte.is_ascii_alphanumeric()
 }
@@ -675,5574 +601,66 @@ fn identifier_continue_before(bytes: &[u8], index: usize) -> bool {
         .is_some_and(|ch| ch == '_' || ch.is_alphanumeric())
 }
 
-fn numeric_keyword_suffix(rest: &[u8]) -> bool {
-    rest.starts_with(b"and")
-        || rest.starts_with(b"else")
-        || rest.starts_with(b"for")
-        || rest.starts_with(b"if")
-        || rest.starts_with(b"in")
-        || rest.starts_with(b"is")
-        || rest.starts_with(b"or")
-        || rest.starts_with(b"not")
-}
-
-fn consume_decimal_digits(bytes: &[u8], mut index: usize) -> usize {
-    while index < bytes.len() {
-        match bytes[index] {
-            b'0'..=b'9' => index += 1,
-            b'_' if bytes
-                .get(index + 1)
-                .is_some_and(|byte| byte.is_ascii_digit()) =>
-            {
-                index += 2;
-            }
-            _ => break,
-        }
+fn quoted_string_is_closed(bytes: &[u8], start: usize) -> bool {
+    let quote = bytes[start];
+    let triple = bytes.get(start + 1) == Some(&quote) && bytes.get(start + 2) == Some(&quote);
+    let end = skip_quoted_string(bytes, start);
+    if triple {
+        end >= start + 6
+            && bytes[end - 3] == quote
+            && bytes[end - 2] == quote
+            && bytes[end - 1] == quote
+    } else {
+        end > start + 1 && bytes[end - 1] == quote
     }
-    index
 }
 
-fn consume_radix_digits(bytes: &[u8], mut index: usize, is_digit: impl Fn(u8) -> bool) -> usize {
+fn skip_quoted_string(bytes: &[u8], mut index: usize) -> usize {
+    let quote = bytes[index];
+    let triple = bytes.get(index + 1) == Some(&quote) && bytes.get(index + 2) == Some(&quote);
+    let quote_len = if triple { 3 } else { 1 };
+    index += quote_len;
     while index < bytes.len() {
-        if is_digit(bytes[index]) {
-            index += 1;
-        } else if bytes.get(index) == Some(&b'_')
-            && bytes.get(index + 1).is_some_and(|&byte| is_digit(byte))
+        if bytes[index] == b'\\' {
+            index = (index + 2).min(bytes.len());
+        } else if triple
+            && bytes.get(index) == Some(&quote)
+            && bytes.get(index + 1) == Some(&quote)
+            && bytes.get(index + 2) == Some(&quote)
         {
-            index += 2;
+            return index + 3;
+        } else if !triple && bytes[index] == quote {
+            return index + 1;
         } else {
-            break;
+            index += 1;
         }
     }
     index
 }
 
-fn invalid_radix_literal_error(
-    bytes: &[u8],
-    start: usize,
-    kind: &'static str,
-    is_digit: impl Fn(u8) -> bool,
-) -> Option<(String, usize)> {
-    let mut index = start + 2;
-    let mut has_digit = false;
-    loop {
-        let Some(&byte) = bytes.get(index) else {
-            return if has_digit {
-                None
-            } else {
-                Some((format!("invalid {kind} literal"), start + 1))
-            };
-        };
-        if byte == b'_' {
-            let Some(&next) = bytes.get(index + 1) else {
-                return Some((format!("invalid {kind} literal"), index));
-            };
-            if is_digit(next) {
-                has_digit = true;
-                index += 2;
-                continue;
-            }
-            if next.is_ascii_digit() && matches!(kind, "binary" | "octal") {
-                return Some((
-                    format!("invalid digit '{}' in {kind} literal", next as char),
-                    index + 1,
-                ));
-            }
-            return Some((format!("invalid {kind} literal"), index));
-        }
-        if is_digit(byte) {
-            has_digit = true;
-            index += 1;
-            continue;
-        }
-        if byte.is_ascii_digit() && matches!(kind, "binary" | "octal") {
-            return Some((
-                format!("invalid digit '{}' in {kind} literal", byte as char),
-                index,
-            ));
-        }
-        if has_digit {
-            return None;
-        }
-        return Some((format!("invalid {kind} literal"), start + 1));
-    }
+fn starts_identifier(bytes: &[u8], index: usize, word: &[u8]) -> bool {
+    bytes.get(index..index + word.len()) == Some(word)
+        && index
+            .checked_sub(1)
+            .and_then(|before| bytes.get(before))
+            .is_none_or(|byte| !is_ascii_identifier_char(*byte))
+        && bytes
+            .get(index + word.len())
+            .is_none_or(|byte| !is_ascii_identifier_char(*byte))
 }
 
-fn decimal_tail_error(bytes: &[u8], mut index: usize) -> Option<usize> {
-    loop {
-        while bytes.get(index).is_some_and(|byte| byte.is_ascii_digit()) {
-            index += 1;
-        }
-        if bytes.get(index) != Some(&b'_') {
-            return None;
-        }
-        let underscore = index;
-        index += 1;
-        if !bytes.get(index).is_some_and(|byte| byte.is_ascii_digit()) {
-            return Some(underscore);
-        }
-    }
-}
-
-fn decimal_tail_end(bytes: &[u8], mut index: usize) -> usize {
-    loop {
-        while bytes.get(index).is_some_and(|byte| byte.is_ascii_digit()) {
-            index += 1;
-        }
-        if bytes.get(index) == Some(&b'_')
-            && bytes
-                .get(index + 1)
-                .is_some_and(|byte| byte.is_ascii_digit())
-        {
-            index += 2;
-        } else {
-            return index;
-        }
-    }
-}
-
-fn invalid_decimal_literal_error(bytes: &[u8], start: usize) -> Option<(String, usize)> {
-    if bytes.get(start) == Some(&b'.') {
-        return None;
-    }
-    let message = "invalid decimal literal".to_owned();
-    if let Some(offset) = decimal_tail_error(bytes, start) {
-        return Some((message, offset));
-    }
-
-    let mut index = decimal_tail_end(bytes, start);
-    if bytes.get(index) == Some(&b'.') {
-        if bytes.get(index + 1) == Some(&b'_') {
-            return Some((message, index));
-        }
-        if let Some(offset) = decimal_tail_error(bytes, index + 1) {
-            return Some((message, offset));
-        }
-        index = decimal_tail_end(bytes, index + 1);
-    }
-    if matches!(bytes.get(index), Some(b'e' | b'E')) {
-        let exponent = index;
-        index += 1;
-        let sign = if matches!(bytes.get(index), Some(b'+' | b'-')) {
-            let sign = index;
-            index += 1;
-            Some(sign)
-        } else {
-            None
-        };
-        if !bytes.get(index).is_some_and(|byte| byte.is_ascii_digit()) {
-            // Without a sign the exponent letter is put back, so the position
-            // is the digit before it rather than the letter.
-            return Some((message, sign.unwrap_or_else(|| exponent.saturating_sub(1))));
-        }
-        if let Some(offset) = decimal_tail_error(bytes, index) {
-            return Some((message, offset));
-        }
-    }
-    None
-}
-
-fn leading_zero_decimal_literal_error(bytes: &[u8], start: usize) -> Option<CpythonDiagnostic> {
-    if bytes.get(start) != Some(&b'0') {
-        return None;
-    }
-    let mut index = start;
-    loop {
-        match bytes.get(index) {
-            Some(b'0') => index += 1,
-            Some(b'_')
-                if bytes
-                    .get(index + 1)
-                    .is_some_and(|byte| byte.is_ascii_digit()) =>
-            {
-                index += 1;
-            }
-            _ => break,
-        }
-    }
-    if bytes.get(index).is_some_and(|byte| byte.is_ascii_digit()) {
-        let after_digits = decimal_tail_end(bytes, index);
-        if !matches!(
-            bytes.get(after_digits),
-            Some(b'.' | b'e' | b'E' | b'j' | b'J')
-        ) {
-            return Some(CpythonDiagnostic::new(
-                "leading zeros in decimal integer literals are not permitted; use an 0o prefix for octal integers"
-                    .to_owned(),
-                start,
-                index,
-            ));
-        }
-    }
-    None
-}
-
-fn invalid_numeric_literal_error(bytes: &[u8], start: usize) -> Option<CpythonDiagnostic> {
-    if bytes.get(start) == Some(&b'0') {
-        let radix = match bytes.get(start + 1) {
-            Some(b'x' | b'X') => invalid_radix_literal_error(bytes, start, "hexadecimal", |byte| {
-                byte.is_ascii_hexdigit()
-            }),
-            Some(b'o' | b'O') => invalid_radix_literal_error(bytes, start, "octal", |byte| {
-                matches!(byte, b'0'..=b'7')
-            }),
-            Some(b'b' | b'B') => invalid_radix_literal_error(bytes, start, "binary", |byte| {
-                matches!(byte, b'0' | b'1')
-            }),
-            _ => None,
-        };
-        if let Some(radix) = radix {
-            return Some(point_span(radix));
-        }
-        if let Some(err) = leading_zero_decimal_literal_error(bytes, start) {
-            return Some(err);
-        }
-    }
-    invalid_decimal_literal_error(bytes, start).map(point_span)
-}
-
-fn consume_exponent(bytes: &[u8], index: usize) -> usize {
-    if !matches!(bytes.get(index), Some(b'e' | b'E')) {
-        return index;
-    }
-    let mut cursor = index + 1;
-    if matches!(bytes.get(cursor), Some(b'+' | b'-')) {
-        cursor += 1;
-    }
-    if bytes.get(cursor).is_some_and(|byte| byte.is_ascii_digit()) {
-        consume_decimal_digits(bytes, cursor)
-    } else {
-        index
-    }
-}
-
-fn number_literal_end(bytes: &[u8], start: usize) -> Option<(&'static str, usize)> {
-    if bytes.get(start) == Some(&b'.') {
-        if !bytes
-            .get(start + 1)
-            .is_some_and(|byte| byte.is_ascii_digit())
-        {
-            return None;
-        }
-        let mut index = consume_decimal_digits(bytes, start + 1);
-        index = consume_exponent(bytes, index);
-        if matches!(bytes.get(index), Some(b'j' | b'J')) {
-            return Some(("imaginary", index + 1));
-        }
-        return Some(("decimal", index));
-    }
-
-    if !bytes.get(start).is_some_and(|byte| byte.is_ascii_digit()) {
-        return None;
-    }
-
-    if bytes.get(start) == Some(&b'0') {
-        match bytes.get(start + 1) {
-            Some(b'x' | b'X') => {
-                let end = consume_radix_digits(bytes, start + 2, |byte| byte.is_ascii_hexdigit());
-                return Some(("hexadecimal", end));
-            }
-            Some(b'o' | b'O') => {
-                let end =
-                    consume_radix_digits(bytes, start + 2, |byte| matches!(byte, b'0'..=b'7'));
-                return Some(("octal", end));
-            }
-            Some(b'b' | b'B') => {
-                let end =
-                    consume_radix_digits(bytes, start + 2, |byte| matches!(byte, b'0' | b'1'));
-                return Some(("binary", end));
-            }
-            _ => {}
-        }
-    }
-
-    let mut index = consume_decimal_digits(bytes, start);
-    if bytes.get(index) == Some(&b'.') {
-        index = consume_decimal_digits(bytes, index + 1);
-    }
-    index = consume_exponent(bytes, index);
-    if matches!(bytes.get(index), Some(b'j' | b'J')) {
-        return Some(("imaginary", index + 1));
-    }
-    Some(("decimal", index))
-}
-
-fn quoted_string_is_closed(bytes: &[u8], start: usize) -> bool {
-    let quote = bytes[start];
-    let triple = bytes.get(start + 1) == Some(&quote) && bytes.get(start + 2) == Some(&quote);
-    let end = skip_quoted_string(bytes, start);
-    if triple {
-        end >= start + 6
-            && bytes[end - 3] == quote
-            && bytes[end - 2] == quote
-            && bytes[end - 1] == quote
-    } else {
-        end > start + 1 && bytes[end - 1] == quote
-    }
-}
-
-fn bytes_literal_span(source: &str, error_at: usize) -> Option<(usize, usize)> {
-    let bytes = source.as_bytes();
-    if error_at > bytes.len() || bytes.is_empty() {
-        return None;
-    }
-    let mut quote_idx = error_at.min(bytes.len().saturating_sub(1));
-    loop {
-        if matches!(bytes[quote_idx], b'\'' | b'"') {
-            break;
-        }
-        if quote_idx == 0 {
-            return None;
-        }
-        quote_idx -= 1;
-    }
-    let mut start = quote_idx;
-    while start > 0 && matches!(bytes[start - 1], b'b' | b'B' | b'r' | b'R') {
-        start -= 1;
-    }
-    if !matches!(bytes.get(start), Some(b'b' | b'B' | b'r' | b'R')) {
-        return None;
-    }
-    let end = skip_quoted_string(bytes, quote_idx);
-    Some((start, end))
-}
-
-fn skip_quoted_string(bytes: &[u8], mut index: usize) -> usize {
-    let quote = bytes[index];
-    let triple = bytes.get(index + 1) == Some(&quote) && bytes.get(index + 2) == Some(&quote);
-    let quote_len = if triple { 3 } else { 1 };
-    index += quote_len;
-    while index < bytes.len() {
-        if bytes[index] == b'\\' {
-            index = (index + 2).min(bytes.len());
-        } else if triple
-            && bytes.get(index) == Some(&quote)
-            && bytes.get(index + 1) == Some(&quote)
-            && bytes.get(index + 2) == Some(&quote)
-        {
-            return index + 3;
-        } else if !triple && bytes[index] == quote {
-            return index + 1;
-        } else {
-            index += 1;
-        }
-    }
-    index
-}
-
-// An error the tokenizer reports at a single position spans nothing.
-fn point_span((message, offset): (String, usize)) -> CpythonDiagnostic {
-    CpythonDiagnostic::new(message, offset, offset)
-}
-
-fn invalid_number_literal_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            byte if byte >= 0x80 || byte == b'_' || byte.is_ascii_alphabetic() => {
-                index += 1;
-                while index < bytes.len()
-                    && (bytes[index] >= 0x80 || is_ascii_identifier_char(bytes[index]))
-                {
-                    index += 1;
-                }
-            }
-            b'.' | b'0'..=b'9' => {
-                if let Some(err) = invalid_numeric_literal_error(bytes, index) {
-                    return Some(err);
-                }
-                let Some((kind, end)) = number_literal_end(bytes, index) else {
-                    index += 1;
-                    continue;
-                };
-                if end > index {
-                    if source[end..].starts_with('⁄') {
-                        return Some(CpythonDiagnostic::new(
-                            "invalid character '⁄' (U+2044)".to_owned(),
-                            end,
-                            end,
-                        ));
-                    }
-                    if bytes
-                        .get(end)
-                        .is_some_and(|byte| *byte < 128 && is_ascii_identifier_char(*byte))
-                        && !numeric_keyword_suffix(&bytes[end..])
-                    {
-                        let offset = end.saturating_sub(1);
-                        return Some(CpythonDiagnostic::new(
-                            format!("invalid {kind} literal"),
-                            offset,
-                            offset,
-                        ));
-                    }
-                }
-                index = end.max(index + 1);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn cpython_indented_block_clause(message: &str) -> Option<&'static str> {
-    let clause = message.strip_prefix("Expected an indented block after ")?;
-    Some(match clause {
-        "`if` statement" => "'if' statement",
-        "`elif` clause" => "'elif' statement",
-        "`else` clause" => "'else' statement",
-        "`for` statement" => "'for' statement",
-        "`with` statement" => "'with' statement",
-        "`while` statement" => "'while' statement",
-        "`try` statement" => "'try' statement",
-        "`except` clause" => "'except' statement",
-        "`finally` clause" => "'finally' statement",
-        "`match` statement" => "'match' statement",
-        "`case` block" => "'case' statement",
-        "`class` definition" => "class definition",
-        "function definition" => "function definition",
-        _ => return None,
-    })
-}
-
-fn previous_non_empty_line_number(source: &str, offset: usize) -> Option<usize> {
-    let bytes = source.as_bytes();
-    let mut index = offset.min(bytes.len());
-    while index > 0 {
-        let line_end = index;
-        while index > 0 && bytes[index - 1] != b'\n' {
-            index -= 1;
-        }
-        let line_start = index;
-        let content_start = skip_horizontal_whitespace(bytes, line_start);
-        let mut content_end = line_end;
-        while content_end > content_start
-            && matches!(
-                bytes.get(content_end - 1),
-                Some(b' ' | b'\t' | b'\r' | b'\x0c')
-            )
-        {
-            content_end -= 1;
-        }
-        if content_start < content_end {
-            return Some(
-                source[..line_start]
-                    .bytes()
-                    .filter(|byte| *byte == b'\n')
-                    .count()
-                    + 1,
-            );
-        }
-        index = line_start.saturating_sub(1);
-    }
-    None
-}
-
-fn expected_indented_block_error(
-    error: &parser::ParseError,
-    source: &str,
-) -> Option<CpythonDiagnostic> {
-    let parser::ParseErrorType::OtherError(message) = &error.error else {
-        return None;
-    };
-    let mut clause = cpython_indented_block_clause(message)?;
-    let start = error.location.start().to_usize();
-    let end = error.location.end().to_usize();
-    let line = previous_non_empty_line_number(source, start)?;
-    if clause == "'except' statement"
-        && let Some(previous_line) = previous_non_empty_line(source, start)
-        && matches!(
-            previous_line.trim_start(),
-            line if line.starts_with("except*") || line.starts_with("except *")
-        )
-    {
-        clause = "'except*' statement";
-    }
-    Some(CpythonDiagnostic::new(
-        format!("expected an indented block after {clause} on line {line}"),
-        start,
-        end,
-    ))
-}
-
-fn previous_non_empty_line(source: &str, offset: usize) -> Option<&str> {
-    let bytes = source.as_bytes();
-    let mut index = offset.min(bytes.len());
-    while index > 0 {
-        let line_end = index;
-        while index > 0 && bytes[index - 1] != b'\n' {
-            index -= 1;
-        }
-        let line_start = index;
-        let mut content_start = line_start;
-        while content_start < line_end
-            && matches!(bytes[content_start], b' ' | b'\t' | b'\n' | b'\r' | b'\x0c')
-        {
-            content_start += 1;
-        }
-        let mut content_end = line_end;
-        while content_end > content_start
-            && matches!(bytes[content_end - 1], b' ' | b'\t' | b'\r' | b'\x0c')
-        {
-            content_end -= 1;
-        }
-        if content_start < content_end {
-            return source.get(line_start..line_end);
-        }
-        index = line_start.saturating_sub(1);
-    }
-    None
-}
-
-fn starts_identifier(bytes: &[u8], index: usize, word: &[u8]) -> bool {
-    bytes.get(index..index + word.len()) == Some(word)
-        && index
-            .checked_sub(1)
-            .and_then(|before| bytes.get(before))
-            .is_none_or(|byte| !is_ascii_identifier_char(*byte))
-        && bytes
-            .get(index + word.len())
-            .is_none_or(|byte| !is_ascii_identifier_char(*byte))
-}
-
-fn is_plain_assignment_operator(bytes: &[u8], index: usize) -> bool {
-    bytes.get(index) == Some(&b'=')
-        && bytes.get(index + 1) != Some(&b'=')
-        && !matches!(
-            index.checked_sub(1).and_then(|before| bytes.get(before)),
-            Some(b'=' | b'!' | b'<' | b'>' | b':')
-        )
-}
-
-fn is_simple_keyword_name(bytes: &[u8], mut start: usize, mut end: usize) -> bool {
-    while matches!(
-        bytes.get(start),
-        Some(b' ' | b'\t' | b'\n' | b'\r' | b'\x0c')
-    ) {
-        start += 1;
-    }
-    while end > start
-        && matches!(
-            bytes.get(end - 1),
-            Some(b' ' | b'\t' | b'\n' | b'\r' | b'\x0c')
-        )
-    {
-        end -= 1;
-    }
-    let Some(&first) = bytes.get(start) else {
-        return false;
-    };
-    if !(first == b'_' || first.is_ascii_alphabetic() || first >= 0x80) {
-        return false;
-    }
-    let mut index = start + 1;
-    while index < end {
-        if bytes[index] < 0x80 && !is_ascii_identifier_char(bytes[index]) {
-            return false;
-        }
-        index += 1;
-    }
-    true
-}
-
-fn is_function_parameter_list(bytes: &[u8], paren: usize) -> bool {
-    let mut cursor = paren;
-    while cursor > 0 && matches!(bytes.get(cursor - 1), Some(b' ' | b'\t' | b'\x0c')) {
-        cursor -= 1;
-    }
-    if cursor > 0 && bytes.get(cursor - 1) == Some(&b']') {
-        let mut bracket = cursor;
-        let mut level = 0usize;
-        while bracket > 0 {
-            bracket -= 1;
-            match bytes[bracket] {
-                b']' => level += 1,
-                b'[' => {
-                    level = level.saturating_sub(1);
-                    if level == 0 {
-                        cursor = bracket;
-                        break;
-                    }
-                }
-                _ => {}
-            }
-        }
-        while cursor > 0 && matches!(bytes.get(cursor - 1), Some(b' ' | b'\t' | b'\x0c')) {
-            cursor -= 1;
-        }
-    }
-    while cursor > 0
-        && bytes
-            .get(cursor - 1)
-            .is_some_and(|byte| *byte >= 0x80 || is_ascii_identifier_char(*byte))
-    {
-        cursor -= 1;
-    }
-    while cursor > 0 && matches!(bytes.get(cursor - 1), Some(b' ' | b'\t' | b'\x0c')) {
-        cursor -= 1;
-    }
-    cursor >= 3
-        && starts_identifier(bytes, cursor - 3, b"def")
-        && cursor
-            .checked_sub(4)
-            .and_then(|before| bytes.get(before))
-            .is_none_or(|byte| !is_ascii_identifier_char(*byte))
-}
-
-#[derive(Clone, Copy)]
-enum ParameterListKind {
-    Function,
-    Lambda,
-}
-
-fn matching_delimiter(bytes: &[u8], open: usize, close: u8) -> Option<usize> {
-    let mut index = open;
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            byte if byte == close => {
-                level = level.saturating_sub(1);
-                if level == 0 {
-                    return Some(index);
-                }
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn find_lambda_parameter_end(bytes: &[u8], mut index: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' if level == 0 => return None,
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b':' if level == 0 => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn top_level_byte(bytes: &[u8], mut index: usize, end: usize, needle: u8) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            byte if level == 0 && byte == needle => return Some(index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn identifier_end(bytes: &[u8], mut index: usize, end: usize) -> usize {
-    if !bytes
-        .get(index)
-        .is_some_and(|byte| *byte >= 0x80 || *byte == b'_' || byte.is_ascii_alphabetic())
-    {
-        return index;
-    }
-    index += 1;
-    while index < end
-        && bytes
-            .get(index)
-            .is_some_and(|byte| *byte >= 0x80 || is_ascii_identifier_char(*byte))
-    {
-        index += 1;
-    }
-    index
-}
-
-fn expression_slice_is_tuple(source: &str, start: usize, end: usize) -> bool {
-    let bytes = source.as_bytes();
-    let (start, end) = trim_target_range(bytes, start, end);
-    if start >= end {
-        return false;
-    }
-    let Ok(parsed) = parser::parse(&source[start..end], parser::Mode::Expression.into()) else {
-        return false;
-    };
-    matches!(parsed.into_syntax(), ast::Mod::Expression(expression) if matches!(*expression.body, ast::Expr::Tuple(_)))
-}
-
-fn type_param_list_open(bytes: &[u8], open: usize) -> bool {
-    let mut cursor = open;
-    while cursor > 0 && matches!(bytes.get(cursor - 1), Some(b' ' | b'\t' | b'\x0c')) {
-        cursor -= 1;
-    }
-    while cursor > 0
-        && bytes
-            .get(cursor - 1)
-            .is_some_and(|byte| *byte >= 0x80 || is_ascii_identifier_char(*byte))
-    {
-        cursor -= 1;
-    }
-    while cursor > 0 && matches!(bytes.get(cursor - 1), Some(b' ' | b'\t' | b'\x0c')) {
-        cursor -= 1;
-    }
-    (cursor >= 3 && starts_identifier(bytes, cursor - 3, b"def"))
-        || (cursor >= 5 && starts_identifier(bytes, cursor - 5, b"class"))
-        || (cursor >= 4 && starts_identifier(bytes, cursor - 4, b"type"))
-}
-
-fn invalid_type_param_item_error(
-    source: &str,
-    start: usize,
-    end: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let (start, end) = trim_target_range(bytes, start, end);
-    if start >= end || bytes.get(start) != Some(&b'*') {
-        return None;
-    }
-    let is_param_spec = bytes.get(start + 1) == Some(&b'*');
-    let name_start = start + if is_param_spec { 2 } else { 1 };
-    let name_end = identifier_end(bytes, name_start, end);
-    if name_start == name_end {
-        return None;
-    }
-    let colon = next_non_horizontal_whitespace(bytes, name_end);
-    if colon >= end || bytes.get(colon) != Some(&b':') {
-        return None;
-    }
-    let has_constraints = expression_slice_is_tuple(source, colon + 1, end);
-    let message = match (is_param_spec, has_constraints) {
-        (false, false) => "cannot use bound with TypeVarTuple",
-        (false, true) => "cannot use constraints with TypeVarTuple",
-        (true, false) => "cannot use bound with ParamSpec",
-        (true, true) => "cannot use constraints with ParamSpec",
-    };
-    Some(CpythonDiagnostic::new(message.to_owned(), colon, colon + 1))
-}
-
-fn invalid_type_param_list_error(
-    source: &str,
-    open: usize,
-    close: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut item_start = open + 1;
-    let mut index = item_start;
-    let mut level = 0usize;
-    while index <= close {
-        if index == close || (level == 0 && bytes.get(index) == Some(&b',')) {
-            if let Some(error) = invalid_type_param_item_error(source, item_start, index) {
-                return Some(error);
-            }
-            item_start = index + 1;
-            index += 1;
-            continue;
-        }
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_type_param_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'[' if type_param_list_open(bytes, index) => {
-                let Some(close) = matching_delimiter(bytes, index, b']') else {
-                    index += 1;
-                    continue;
-                };
-                if let Some(error) = invalid_type_param_list_error(source, index, close) {
-                    return Some(error);
-                }
-                index = close + 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_comprehension_in_slice(
-    bytes: &[u8],
-    open: usize,
-    close: usize,
-) -> Option<CpythonDiagnostic> {
-    let for_index = find_keyword_at_level(bytes, open + 1, close, b"for")?;
-    let item_start = next_non_horizontal_whitespace(bytes, open + 1);
-    if item_start >= for_index {
-        return None;
-    }
-    if bytes.get(item_start..item_start + 2) == Some(b"**") && bytes.get(open) == Some(&b'{') {
-        return Some(CpythonDiagnostic::new(
-            "dict unpacking cannot be used in dict comprehension".to_owned(),
-            item_start,
-            item_start + 2,
-        ));
-    }
-    if bytes.get(item_start..item_start + 2) == Some(b"**") && bytes.get(open) == Some(&b'(') {
-        return Some(CpythonDiagnostic::new(
-            "invalid syntax".to_owned(),
-            for_index,
-            for_index + 3,
-        ));
-    }
-    if bytes.get(item_start) == Some(&b'*') {
-        return Some(CpythonDiagnostic::new(
-            "iterable unpacking cannot be used in comprehension".to_owned(),
-            item_start,
-            item_start + 1,
-        ));
-    }
-    if !matches!(bytes.get(open), Some(b'[' | b'{')) {
-        return None;
-    }
-    if top_level_colon(bytes, open + 1, for_index).is_none()
-        && let Some(comma) = top_level_byte(bytes, open + 1, for_index, b',')
-    {
-        let (start, _) = trim_target_range(bytes, open + 1, comma);
-        return Some(CpythonDiagnostic::new(
-            "did you forget parentheses around the comprehension target?".to_owned(),
-            start,
-            comma + 1,
-        ));
-    }
-    None
-}
-
-fn invalid_comprehension_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                let close_byte = match bytes[index] {
-                    b'(' => b')',
-                    b'[' => b']',
-                    _ => b'}',
-                };
-                let Some(close) = matching_delimiter(bytes, index, close_byte) else {
-                    index += 1;
-                    continue;
-                };
-                if let Some(error) = invalid_comprehension_in_slice(bytes, index, close) {
-                    return Some(error);
-                }
-                index = close + 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_group_in_slice(bytes: &[u8], open: usize, close: usize) -> Option<CpythonDiagnostic> {
-    let (item_start, item_end) = trim_target_range(bytes, open + 1, close);
-    if item_start >= item_end
-        || top_level_byte(bytes, item_start, item_end, b',').is_some()
-        || top_level_colon(bytes, item_start, item_end).is_some()
-        || find_keyword_at_level(bytes, item_start, item_end, b"for").is_some()
-    {
-        return None;
-    }
-    if bytes.get(item_start..item_start + 2) == Some(b"**") {
-        return Some(CpythonDiagnostic::new(
-            "cannot use double starred expression here".to_owned(),
-            item_start,
-            item_start + 2,
-        ));
-    }
-    if bytes.get(item_start) == Some(&b'*') {
-        return Some(CpythonDiagnostic::new(
-            "cannot use starred expression here".to_owned(),
-            item_start,
-            item_start + 1,
-        ));
-    }
-    None
-}
-
-fn invalid_group_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' => {
-                let Some(close) = matching_delimiter(bytes, index, b')') else {
-                    index += 1;
-                    continue;
-                };
-                if let Some(error) = invalid_group_in_slice(bytes, index, close) {
-                    return Some(error);
-                }
-                index = close + 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_parameter_star_annotation_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' => {
-                let Some(close) = matching_delimiter(bytes, index, b')') else {
-                    index += 1;
-                    continue;
-                };
-                let mut param_start = index + 1;
-                while param_start < close {
-                    let param_end =
-                        find_byte_at_level(bytes, param_start, close, b',').unwrap_or(close);
-                    if let Some(colon) = top_level_colon(bytes, param_start, param_end) {
-                        let value_start = next_non_horizontal_whitespace(bytes, colon + 1);
-                        if bytes.get(value_start) == Some(&b'*') {
-                            return Some(CpythonDiagnostic::new(
-                                "invalid syntax".to_owned(),
-                                value_start,
-                                value_start + 1,
-                            ));
-                        }
-                    }
-                    param_start = param_end.saturating_add(1);
-                }
-                index = close + 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_def_type_params_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            _ if starts_identifier(bytes, index, b"def") => {
-                let name_start = skip_horizontal_whitespace(bytes, index + 3);
-                let name_end = identifier_end(bytes, name_start, bytes.len());
-                let bracket = skip_horizontal_whitespace(bytes, name_end);
-                if bytes.get(bracket) == Some(&b'[') {
-                    let Some(close) = matching_delimiter(bytes, bracket, b']') else {
-                        index = bracket + 1;
-                        continue;
-                    };
-                    let after_close = skip_horizontal_whitespace(bytes, close + 1);
-                    if bytes.get(after_close) == Some(&b'(')
-                        && type_param_list_is_malformed(bytes, bracket + 1, close)
-                    {
-                        return Some(CpythonDiagnostic::new(
-                            "expected '('".to_owned(),
-                            bracket,
-                            bracket + 1,
-                        ));
-                    }
-                }
-                index = name_end.max(index + 3);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn type_param_list_is_malformed(bytes: &[u8], start: usize, end: usize) -> bool {
-    let mut index = start;
-    let mut expect_item = true;
-    while index < end {
-        index = skip_horizontal_whitespace(bytes, index);
-        if index >= end {
-            break;
-        }
-        if bytes[index] == b',' {
-            if expect_item {
-                return true;
-            }
-            expect_item = true;
-            index += 1;
-            continue;
-        }
-        if !expect_item {
-            return true;
-        }
-        if bytes.get(index..index + 2) == Some(b"**") {
-            index += 2;
-        } else if bytes.get(index) == Some(&b'*') {
-            index += 1;
-        }
-        let item_start = skip_horizontal_whitespace(bytes, index);
-        let item_end = identifier_end(bytes, item_start, end);
-        if item_end == item_start {
-            return true;
-        }
-        index = item_end;
-        if bytes.get(skip_horizontal_whitespace(bytes, index)) == Some(&b':') {
-            index = skip_horizontal_whitespace(bytes, index) + 1;
-            while index < end && bytes[index] != b',' {
-                index = match bytes[index] {
-                    b'\'' | b'"' => skip_quoted_string(bytes, index),
-                    _ => index + 1,
-                };
-            }
-        }
-        expect_item = false;
-    }
-    false
-}
-
-fn invalid_parameter_list_slice_error(
-    source: &str,
-    start: usize,
-    end: usize,
-    kind: ParameterListKind,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = start;
-    let mut level = 0usize;
-    let mut default_seen = false;
-    let mut keyword_only = false;
-    let mut slash_seen = false;
-    let mut var_keyword_seen = false;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            _ if level == 0
-                && var_keyword_seen
-                && bytes.get(index).is_some_and(|byte| {
-                    *byte >= 0x80 || *byte == b'_' || byte.is_ascii_alphabetic()
-                }) =>
-            {
-                let name_end = identifier_end(bytes, index, end);
-                return Some(CpythonDiagnostic::new(
-                    "arguments cannot follow var-keyword argument".to_owned(),
-                    index,
-                    name_end,
-                ));
-            }
-            _ if level == 0
-                && !keyword_only
-                && bytes.get(index).is_some_and(|byte| {
-                    *byte >= 0x80 || *byte == b'_' || byte.is_ascii_alphabetic()
-                }) =>
-            {
-                let param_end = find_byte_at_level(bytes, index, end, b',')
-                    .or_else(|| top_level_byte(bytes, index, end, b')'))
-                    .or_else(|| {
-                        matches!(kind, ParameterListKind::Lambda)
-                            .then(|| top_level_byte(bytes, index, end, b':'))
-                            .flatten()
-                    })
-                    .unwrap_or(end);
-                let name_end = identifier_end(bytes, index, param_end);
-                if let Some(eq) = top_level_byte(bytes, index, param_end, b'=') {
-                    let value_start = next_non_horizontal_whitespace(bytes, eq + 1);
-                    if value_start >= param_end
-                        || matches!(bytes.get(value_start), Some(b',' | b')' | b':'))
-                    {
-                        let message = if matches!(kind, ParameterListKind::Lambda)
-                            && matches!(bytes.get(value_start), Some(b':'))
-                        {
-                            "invalid syntax"
-                        } else {
-                            "expected default value expression"
-                        };
-                        return Some(CpythonDiagnostic::new(message.to_owned(), eq, eq + 1));
-                    }
-                    default_seen = true;
-                } else if default_seen {
-                    return Some(CpythonDiagnostic::new(
-                        "parameter without a default follows parameter with a default".to_owned(),
-                        index,
-                        name_end,
-                    ));
-                }
-                index = param_end;
-            }
-            b'(' if level == 0 => {
-                let close = matching_delimiter(bytes, index, b')')
-                    .filter(|close| *close <= end)
-                    .unwrap_or(index + 1);
-                let message = match kind {
-                    ParameterListKind::Function => "Function parameters cannot be parenthesized",
-                    ParameterListKind::Lambda => {
-                        "Lambda expression parameters cannot be parenthesized"
-                    }
-                };
-                return Some(CpythonDiagnostic::new(message.to_owned(), index, close + 1));
-            }
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b'/' if level == 0 => {
-                if var_keyword_seen {
-                    return Some(CpythonDiagnostic::new(
-                        "arguments cannot follow var-keyword argument".to_owned(),
-                        index,
-                        index + 1,
-                    ));
-                }
-                if slash_seen {
-                    return Some(CpythonDiagnostic::new(
-                        "/ may appear only once".to_owned(),
-                        index,
-                        index + 1,
-                    ));
-                }
-                slash_seen = true;
-                let next = next_non_horizontal_whitespace(bytes, index + 1);
-                if bytes.get(next) == Some(&b'*') {
-                    return Some(CpythonDiagnostic::new(
-                        "expected comma between / and *".to_owned(),
-                        next,
-                        next + 1,
-                    ));
-                }
-                index += 1;
-            }
-            b'*' if level == 0 => {
-                if var_keyword_seen {
-                    return Some(CpythonDiagnostic::new(
-                        "arguments cannot follow var-keyword argument".to_owned(),
-                        index,
-                        index + 1,
-                    ));
-                }
-                keyword_only = true;
-                let stars = usize::from(bytes.get(index + 1) == Some(&b'*')) + 1;
-                let name_start = next_non_horizontal_whitespace(bytes, index + stars);
-                for keyword in [b"True".as_slice(), b"False".as_slice(), b"None".as_slice()] {
-                    if starts_identifier(bytes, name_start, keyword) {
-                        return Some(CpythonDiagnostic::new(
-                            "invalid syntax".to_owned(),
-                            name_start,
-                            name_start + keyword.len(),
-                        ));
-                    }
-                }
-                let param_end = find_byte_at_level(bytes, name_start, end, b',')
-                    .or_else(|| top_level_byte(bytes, name_start, end, b')'))
-                    .or_else(|| {
-                        matches!(kind, ParameterListKind::Lambda)
-                            .then(|| top_level_byte(bytes, name_start, end, b':'))
-                            .flatten()
-                    })
-                    .unwrap_or(end);
-                if stars == 1 && matches!(bytes.get(name_start), Some(b')' | b',' | b':')) {
-                    return Some(CpythonDiagnostic::new(
-                        "named arguments must follow bare *".to_owned(),
-                        index,
-                        index + 1,
-                    ));
-                }
-                if stars == 1 && top_level_byte(bytes, name_start, param_end, b'=').is_some() {
-                    return Some(CpythonDiagnostic::new(
-                        "var-positional argument cannot have default value".to_owned(),
-                        index,
-                        index + 1,
-                    ));
-                }
-                if stars == 2 && top_level_byte(bytes, name_start, param_end, b'=').is_some() {
-                    return Some(CpythonDiagnostic::new(
-                        "var-keyword argument cannot have default value".to_owned(),
-                        index,
-                        index + 2,
-                    ));
-                }
-                if stars == 2 {
-                    var_keyword_seen = true;
-                    index = param_end;
-                    continue;
-                }
-                index += stars;
-            }
-            b'=' if level == 0 => {
-                let value_start = next_non_horizontal_whitespace(bytes, index + 1);
-                if value_start >= end || matches!(bytes.get(value_start), Some(b',' | b')' | b':'))
-                {
-                    if matches!(kind, ParameterListKind::Lambda)
-                        && matches!(bytes.get(value_start), Some(b':'))
-                    {
-                        return Some(CpythonDiagnostic::new(
-                            "invalid syntax".to_owned(),
-                            index,
-                            index + 1,
-                        ));
-                    }
-                    return Some(CpythonDiagnostic::new(
-                        "expected default value expression".to_owned(),
-                        index,
-                        index + 1,
-                    ));
-                }
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_parameter_list_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            _ if starts_identifier(bytes, index, b"def") => {
-                let Some(paren) = top_level_byte(bytes, index + 3, bytes.len(), b'(') else {
-                    index += 3;
-                    continue;
-                };
-                let Some(close) = matching_delimiter(bytes, paren, b')') else {
-                    index = paren + 1;
-                    continue;
-                };
-                if let Some(error) = invalid_parameter_list_slice_error(
-                    source,
-                    paren + 1,
-                    close,
-                    ParameterListKind::Function,
-                ) {
-                    return Some(error);
-                }
-                index = close + 1;
-            }
-            _ if starts_identifier(bytes, index, b"lambda") => {
-                let params_start = index + 6;
-                let Some(params_end) = find_lambda_parameter_end(bytes, params_start) else {
-                    index = params_start;
-                    continue;
-                };
-                if let Some(error) = invalid_parameter_list_slice_error(
-                    source,
-                    params_start,
-                    params_end,
-                    ParameterListKind::Lambda,
-                ) {
-                    return Some(error);
-                }
-                index = params_end + 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-#[derive(Clone, Copy)]
-struct CallArgFrame {
-    level: usize,
-    arg_start: Option<usize>,
-    in_call: bool,
-}
-
-fn next_non_horizontal_whitespace(bytes: &[u8], mut index: usize) -> usize {
-    while matches!(bytes.get(index), Some(b' ' | b'\t' | b'\x0c')) {
-        index += 1;
-    }
-    index
-}
-
-fn invalid_call_argument_assignment_error(
-    source: &str,
-    arg_start: usize,
-    equal: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let start = bytes[arg_start..equal]
-        .iter()
-        .rposition(|byte| *byte == b'\n')
-        .map_or(arg_start, |newline| arg_start + newline + 1);
-    let (target_start, target_end) = trim_target_range(bytes, start, equal);
-    if target_start >= target_end {
-        return None;
-    }
-    let value_start = next_non_horizontal_whitespace(bytes, equal + 1);
-    if matches!(bytes.get(value_start), None | Some(b',' | b')')) {
-        return Some(CpythonDiagnostic::new(
-            "expected argument value expression".to_owned(),
-            target_start,
-            equal + 1,
-        ));
-    }
-    if bytes.get(target_start..target_start + 2) == Some(b"**") {
-        return Some(CpythonDiagnostic::new(
-            "cannot assign to keyword argument unpacking".to_owned(),
-            target_start,
-            value_start,
-        ));
-    }
-    if bytes.get(target_start) == Some(&b'*') {
-        return Some(CpythonDiagnostic::new(
-            "cannot assign to iterable argument unpacking".to_owned(),
-            target_start,
-            value_start,
-        ));
-    }
-    for keyword in [b"True".as_slice(), b"False".as_slice(), b"None".as_slice()] {
-        if bytes.get(target_start..target_end) == Some(keyword) {
-            let keyword = ::core::str::from_utf8(keyword).ok()?;
-            return Some(CpythonDiagnostic::new(
-                format!("cannot assign to {keyword}"),
-                target_start,
-                target_end,
-            ));
-        }
-    }
-    if is_simple_keyword_name(bytes, target_start, target_end) {
-        // NAME '=' expression for_if_clauses
-        if unparenthesized_comprehension(bytes, equal + 1) {
-            return Some(CpythonDiagnostic::new(
-                "invalid syntax. Maybe you meant '==' or ':=' instead of '='?".to_owned(),
-                target_start,
-                equal + 1,
-            ));
-        }
-        return None;
-    }
-    Some(CpythonDiagnostic::new(
-        "expression cannot contain assignment, perhaps you meant \"==\"?".to_owned(),
-        target_start,
-        equal,
-    ))
-}
-
-fn unparenthesized_comprehension(bytes: &[u8], mut index: usize) -> bool {
-    index = next_non_horizontal_whitespace(bytes, index);
-    if index >= bytes.len() {
-        return false;
-    }
-    let start = index;
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                if level == 0 {
-                    return false;
-                }
-                level -= 1;
-                index += 1;
-            }
-            b',' | b':' if level == 0 => return false,
-            _ if level == 0 && index > start && starts_identifier(bytes, index, b"for") => {
-                return true;
-            }
-            _ => index += 1,
-        }
-    }
-    false
-}
-
-fn invalid_call_star_expression_error(
-    bytes: &[u8],
-    arg_start: usize,
-    index: usize,
-) -> Option<CpythonDiagnostic> {
-    let start = next_non_horizontal_whitespace(bytes, arg_start);
-    if start != index || bytes.get(index) != Some(&b'*') {
-        return None;
-    }
-    let after_star = next_non_horizontal_whitespace(bytes, index + 1);
-    if matches!(bytes.get(after_star), None | Some(b',' | b')' | b':')) {
-        return Some(CpythonDiagnostic::new(
-            "Invalid star expression".to_owned(),
-            index,
-            (index + 1).min(bytes.len()),
-        ));
-    }
-    None
-}
-
-fn invalid_call_argument_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    let mut level = 0usize;
-    let mut frames: Vec<CallArgFrame> = Vec::new();
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            _ if starts_identifier(bytes, index, b"lambda") => {
-                let params_start = index + 6;
-                if let Some(params_end) = find_lambda_parameter_end(bytes, params_start) {
-                    index = params_end + 1;
-                } else {
-                    index = params_start;
-                }
-            }
-            b'(' => {
-                level += 1;
-                let in_call = opening_paren_is_call(bytes, index)
-                    || frames.last().is_some_and(|frame| frame.in_call);
-                frames.push(CallArgFrame {
-                    level,
-                    arg_start: (in_call && !is_function_parameter_list(bytes, index))
-                        .then_some(index + 1),
-                    in_call,
-                });
-                index += 1;
-            }
-            b')' => {
-                if matches!(frames.last(), Some(frame) if frame.level == level) {
-                    frames.pop();
-                }
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b',' => {
-                if let Some(frame) = frames.last_mut()
-                    && frame.level == level
-                    && frame.arg_start.is_some()
-                {
-                    frame.arg_start = Some(index + 1);
-                }
-                index += 1;
-            }
-            b'*' => {
-                if let Some(CallArgFrame {
-                    level: frame_level,
-                    arg_start: Some(arg_start),
-                    in_call: true,
-                }) = frames.last().copied()
-                    && frame_level == level
-                    && let Some(error) = invalid_call_star_expression_error(bytes, arg_start, index)
-                {
-                    return Some(error);
-                }
-                index += 1;
-            }
-            b'=' if is_plain_assignment_operator(bytes, index) => {
-                if let Some(CallArgFrame {
-                    level: frame_level,
-                    arg_start: Some(arg_start),
-                    in_call: true,
-                }) = frames.last().copied()
-                    && frame_level == level
-                    && let Some(error) =
-                        invalid_call_argument_assignment_error(source, arg_start, index)
-                {
-                    return Some(error);
-                }
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn top_level_colon(bytes: &[u8], mut index: usize, end: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b':' if level == 0 => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn expression_slice_is_valid(source: &str, start: usize, end: usize) -> bool {
-    let bytes = source.as_bytes();
-    let (start, end) = trim_target_range(bytes, start, end);
-    start < end
-        && parser::parse(&source[start..end], parser::Mode::Expression.into())
-            .is_ok_and(|parsed| matches!(parsed.into_syntax(), ast::Mod::Expression(_)))
-}
-
-fn invalid_dict_entry_error(
-    source: &str,
-    item_start: usize,
-    item_end: usize,
-    colon: Option<usize>,
-    saw_dict_item: bool,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let (item_start, item_end) = trim_target_range(bytes, item_start, item_end);
-    if item_start >= item_end {
-        return None;
-    }
-    if let Some(colon) = colon {
-        let value_start = next_non_horizontal_whitespace(bytes, colon + 1);
-        if value_start >= item_end {
-            return Some(CpythonDiagnostic::new(
-                "expression expected after dictionary key and ':'".to_owned(),
-                colon,
-                colon + 1,
-            ));
-        }
-        if bytes.get(value_start) == Some(&b'*') {
-            return Some(CpythonDiagnostic::new(
-                "cannot use a starred expression in a dictionary value".to_owned(),
-                value_start,
-                value_start + 1,
-            ));
-        }
-        if !expression_slice_is_valid(source, value_start, item_end) {
-            return Some(CpythonDiagnostic::new(
-                "invalid syntax".to_owned(),
-                value_start,
-                value_start,
-            ));
-        }
-    } else if saw_dict_item {
-        return Some(CpythonDiagnostic::new(
-            "':' expected after dictionary key".to_owned(),
-            item_end.saturating_sub(1),
-            item_end,
-        ));
-    }
-    None
-}
-
-fn invalid_dict_literal_error(
-    source: &str,
-    open: usize,
-    close: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut item_start = open + 1;
-    let mut index = item_start;
-    let mut level = 0usize;
-    let mut saw_dict_item = false;
-    let mut item_colon = None;
-    while index <= close {
-        if index == close || (level == 0 && bytes.get(index) == Some(&b',')) {
-            if let Some(error) =
-                invalid_dict_entry_error(source, item_start, index, item_colon, saw_dict_item)
-            {
-                return Some(error);
-            }
-            saw_dict_item |= item_colon.is_some();
-            item_start = index + 1;
-            item_colon = None;
-            index += 1;
-            continue;
-        }
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b':' if level == 0 && item_colon.is_none() => {
-                item_colon = Some(index);
-                saw_dict_item = true;
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_dict_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'{' => {
-                let Some(close) = matching_delimiter(bytes, index, b'}') else {
-                    index += 1;
-                    continue;
-                };
-                if top_level_colon(bytes, index + 1, close).is_some()
-                    && let Some(error) = invalid_dict_literal_error(source, index, close)
-                {
-                    return Some(error);
-                }
-                index = close + 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn collection_open_is_call(bytes: &[u8], open: usize) -> bool {
-    if bytes.get(open) != Some(&b'(') {
-        return false;
-    }
-    let mut cursor = open;
-    while cursor > 0 && matches!(bytes.get(cursor - 1), Some(b' ' | b'\t' | b'\x0c')) {
-        cursor -= 1;
-    }
-    matches!(
-        cursor.checked_sub(1).and_then(|before| bytes.get(before)),
-        Some(b')' | b']' | b'_' | b'a'..=b'z' | b'A'..=b'Z' | 0x80..=0xff)
-    )
-}
-
-fn invalid_collection_assignment_in_slice(
-    source: &str,
-    bytes: &[u8],
-    start: usize,
-    end: usize,
-) -> Option<CpythonDiagnostic> {
-    let mut item_start = start;
-    let mut index = start;
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b',' if level == 0 => {
-                item_start = index + 1;
-                index += 1;
-            }
-            b'=' if level == 0 && is_plain_assignment_operator(bytes, index) => {
-                if top_level_colon(bytes, item_start, index).is_none() {
-                    let start = next_non_horizontal_whitespace(bytes, item_start);
-                    let target_end = trim_end_horizontal_whitespace(bytes, start, index);
-                    if start < target_end
-                        && let Some((expr_name, expr_start, expr_end, _)) =
-                            expression_name_and_range(&source[start..target_end])
-                    {
-                        if matches!(expr_name, "list" | "tuple") {
-                            return None;
-                        }
-                        if matches!(expr_name, "expression" | "attribute" | "subscript") {
-                            return Some(CpythonDiagnostic::new(
-                                format!(
-                                    "cannot assign to {expr_name} here. Maybe you meant '==' instead of '='?"
-                                ),
-                                start + expr_start,
-                                start + expr_end,
-                            ));
-                        }
-                    }
-                    return Some(CpythonDiagnostic::new(
-                        "invalid syntax. Maybe you meant '==' or ':=' instead of '='?".to_owned(),
-                        start,
-                        index + 1,
-                    ));
-                }
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_collection_assignment_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                let close_byte = match bytes[index] {
-                    b'(' => b')',
-                    b'[' => b']',
-                    _ => b'}',
-                };
-                let Some(close) = matching_delimiter(bytes, index, close_byte) else {
-                    index += 1;
-                    continue;
-                };
-                if !collection_open_is_call(bytes, index)
-                    && let Some(error) =
-                        invalid_collection_assignment_in_slice(source, bytes, index + 1, close)
-                {
-                    return Some(error);
-                }
-                index = close + 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn expression_assignment_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    let mut paren_arg_starts: Vec<(Option<usize>, bool)> = Vec::new();
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            _ if starts_identifier(bytes, index, b"lambda") => {
-                let params_start = index + 6;
-                if let Some(params_end) = find_lambda_parameter_end(bytes, params_start) {
-                    index = params_end + 1;
-                } else {
-                    index = params_start;
-                }
-            }
-            b'(' => {
-                let in_call_context = opening_paren_is_call(bytes, index)
-                    || paren_arg_starts.last().is_some_and(|(_, in_call)| *in_call);
-                paren_arg_starts.push((
-                    (!is_function_parameter_list(bytes, index)).then_some(index + 1),
-                    in_call_context,
-                ));
-                index += 1;
-            }
-            b')' => {
-                paren_arg_starts.pop();
-                index += 1;
-            }
-            b',' => {
-                if let Some((start, _)) = paren_arg_starts.last_mut()
-                    && start.is_some()
-                {
-                    *start = Some(index + 1);
-                }
-                index += 1;
-            }
-            b'=' if is_plain_assignment_operator(bytes, index) => {
-                if let Some((Some(start), true)) = paren_arg_starts.last().copied()
-                    && !is_simple_keyword_name(bytes, start, index)
-                {
-                    let mut expr_start = start;
-                    while matches!(bytes.get(expr_start), Some(b' ' | b'\t' | b'\x0c')) {
-                        expr_start += 1;
-                    }
-                    return Some(CpythonDiagnostic::new(
-                        "expression cannot contain assignment, perhaps you meant \"==\"?"
-                            .to_owned(),
-                        expr_start,
-                        index,
-                    ));
-                }
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_named_expression_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index + 1 < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b':' if bytes.get(index + 1) == Some(&b'=') => {
-                let target_start = named_expression_target_start(bytes, index);
-                let target_end = trim_end_horizontal_whitespace(bytes, target_start, index);
-                if target_start < target_end
-                    && let Some((expr_name, start, end, is_name)) =
-                        expression_name_and_range(&source[target_start..target_end])
-                    && !is_name
-                {
-                    return Some(CpythonDiagnostic::new(
-                        format!("cannot use assignment expressions with {expr_name}"),
-                        target_start + start,
-                        target_start + end,
-                    ));
-                }
-                index += 2;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-#[derive(Clone, Copy)]
-struct AssignmentContext {
-    start: usize,
-    call: bool,
-}
-
-fn invalid_plain_assignment_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut stack: Vec<AssignmentContext> = Vec::new();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                stack.push(AssignmentContext {
-                    start: index + 1,
-                    call: bytes[index] == b'(' && opening_paren_is_call(bytes, index),
-                });
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                stack.pop();
-                index += 1;
-            }
-            b',' => {
-                if let Some(context) = stack.last_mut()
-                    && !context.call
-                {
-                    context.start = index + 1;
-                }
-                index += 1;
-            }
-            b'=' if is_plain_assignment_operator(bytes, index) => {
-                if let Some(context) = stack.last().copied()
-                    && !context.call
-                {
-                    let target_start = skip_horizontal_whitespace(bytes, context.start);
-                    let target_end = trim_end_horizontal_whitespace(bytes, target_start, index);
-                    if target_start < target_end
-                        && let Some((expr_name, start, end, _)) =
-                            expression_name_and_range(&source[target_start..target_end])
-                        && matches!(expr_name, "expression" | "attribute" | "subscript")
-                    {
-                        return Some(CpythonDiagnostic::new(
-                            format!(
-                                "cannot assign to {expr_name} here. Maybe you meant '==' instead of '='?"
-                            ),
-                            target_start + start,
-                            target_start + end,
-                        ));
-                    }
-                }
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn opening_paren_is_call(bytes: &[u8], paren: usize) -> bool {
-    let mut cursor = paren;
-    while cursor > 0 && matches!(bytes[cursor - 1], b' ' | b'\t' | b'\x0c') {
-        cursor -= 1;
-    }
-    cursor > 0
-        && (bytes[cursor - 1] >= 0x80
-            || is_ascii_identifier_char(bytes[cursor - 1])
-            || matches!(bytes[cursor - 1], b')' | b']'))
-}
-
-fn named_expression_target_start(bytes: &[u8], walrus: usize) -> usize {
-    let mut index = walrus;
-    let mut level = 0usize;
-    while index > 0 {
-        index -= 1;
-        match bytes[index] {
-            b')' | b']' | b'}' => level += 1,
-            b'(' | b'[' | b'{' if level > 0 => level -= 1,
-            b'(' | b'[' | b'{' if level == 0 => return index + 1,
-            b',' | b'\n' | b';' if level == 0 => return index + 1,
-            _ => {}
-        }
-    }
-    0
-}
-
-fn trim_end_horizontal_whitespace(bytes: &[u8], start: usize, mut end: usize) -> usize {
-    while end > start && matches!(bytes[end - 1], b' ' | b'\t' | b'\x0c') {
-        end -= 1;
-    }
-    end
-}
-
-fn annotation_target_error_for_slice(
-    source: &str,
-    start: usize,
-    colon: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let (target_start, target_end) = trim_target_range(bytes, start, colon);
-    if target_start >= target_end {
-        return None;
-    }
-    let target_text = &source[target_start..target_end];
-    let Ok(parsed) = parser::parse(target_text, parser::Mode::Expression.into()) else {
-        return None;
-    };
-    let ast::Mod::Expression(expression) = parsed.into_syntax() else {
-        return None;
-    };
-    match expression.body.as_ref() {
-        ast::Expr::Name(_) | ast::Expr::Attribute(_) | ast::Expr::Subscript(_) => None,
-        ast::Expr::List(_) => Some(CpythonDiagnostic::new(
-            "only single target (not list) can be annotated".to_owned(),
-            target_start,
-            target_end,
-        )),
-        ast::Expr::Tuple(_) => Some(CpythonDiagnostic::new(
-            "only single target (not tuple) can be annotated".to_owned(),
-            target_start,
-            target_end,
-        )),
-        _ => Some(CpythonDiagnostic::new(
-            "illegal target for annotation".to_owned(),
-            target_start,
-            target_end,
-        )),
-    }
-}
-
-fn invalid_annotation_line_start(bytes: &[u8], line_start: usize) -> bool {
-    let column = skip_horizontal_whitespace(bytes, line_start);
-    for keyword in [
-        b"async".as_slice(),
-        b"case",
-        b"class",
-        b"def",
-        b"elif",
-        b"else",
-        b"except",
-        b"finally",
-        b"for",
-        b"if",
-        b"match",
-        b"try",
-        b"while",
-        b"with",
-    ] {
-        if starts_identifier(bytes, column, keyword) {
-            return false;
-        }
-    }
-    true
-}
-
-fn invalid_annotation_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut line_start = 0usize;
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        if invalid_annotation_line_start(bytes, line_start)
-            && let Some(colon) = find_byte_at_level(bytes, line_start, line_end, b':')
-            && bytes.get(colon + 1) != Some(&b'=')
-            && colon.checked_sub(1).and_then(|before| bytes.get(before)) != Some(&b':')
-            && let Some(error) = annotation_target_error_for_slice(source, line_start, colon)
-        {
-            return Some(error);
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn statement_target_end(bytes: &[u8], mut index: usize) -> usize {
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' if level == 0 => return index,
-            b'\n' | b';' if level == 0 => return index,
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    index
-}
-
-fn invalid_assignment_target(expression: &ast::Expr) -> Option<&ast::Expr> {
-    match expression {
-        ast::Expr::List(ast::ExprList { elts, .. })
-        | ast::Expr::Tuple(ast::ExprTuple { elts, .. }) => {
-            elts.iter().find_map(invalid_assignment_target)
-        }
-        ast::Expr::Starred(ast::ExprStarred { value, .. }) => invalid_assignment_target(value),
-        ast::Expr::Name(_) | ast::Expr::Subscript(_) | ast::Expr::Attribute(_) => None,
-        _ => Some(expression),
-    }
-}
-
-fn invalid_for_target(expression: &ast::Expr) -> Option<&ast::Expr> {
-    match expression {
-        ast::Expr::List(ast::ExprList { elts, .. })
-        | ast::Expr::Tuple(ast::ExprTuple { elts, .. }) => elts.iter().find_map(invalid_for_target),
-        ast::Expr::Starred(ast::ExprStarred { value, .. }) => invalid_for_target(value),
-        ast::Expr::Compare(ast::ExprCompare { left, ops, .. }) => {
-            if matches!(ops.first(), Some(ast::CmpOp::In)) {
-                invalid_for_target(left)
-            } else {
-                None
-            }
-        }
-        ast::Expr::Name(_) | ast::Expr::Subscript(_) | ast::Expr::Attribute(_) => None,
-        _ => Some(expression),
-    }
-}
-
-fn invalid_delete_target(expression: &ast::Expr) -> Option<&ast::Expr> {
-    match expression {
-        ast::Expr::List(ast::ExprList { elts, .. })
-        | ast::Expr::Tuple(ast::ExprTuple { elts, .. }) => {
-            elts.iter().find_map(invalid_delete_target)
-        }
-        ast::Expr::Name(_) | ast::Expr::Subscript(_) | ast::Expr::Attribute(_) => None,
-        ast::Expr::Starred(_) => Some(expression),
-        ast::Expr::Compare(_) => Some(expression),
-        _ => Some(expression),
-    }
-}
-
-fn delete_target_expr_name(expression: &ast::Expr) -> &'static str {
-    match expression {
-        ast::Expr::Attribute(_) => "attribute",
-        ast::Expr::Subscript(_) => "subscript",
-        ast::Expr::Starred(_) => "starred",
-        ast::Expr::Name(_) => "name",
-        ast::Expr::List(_) => "list",
-        ast::Expr::Tuple(_) => "tuple",
-        ast::Expr::Lambda(_) => "lambda",
-        ast::Expr::Call(_) => "function call",
-        ast::Expr::BoolOp(_) | ast::Expr::BinOp(_) | ast::Expr::UnaryOp(_) => "expression",
-        ast::Expr::Generator(_) => "generator expression",
-        ast::Expr::Yield(_) | ast::Expr::YieldFrom(_) => "yield expression",
-        ast::Expr::Await(_) => "await expression",
-        ast::Expr::ListComp(_) => "list comprehension",
-        ast::Expr::SetComp(_) => "set comprehension",
-        ast::Expr::DictComp(_) => "dict comprehension",
-        ast::Expr::Dict(_) => "dict literal",
-        ast::Expr::Set(_) => "set display",
-        ast::Expr::FString(_) => "f-string expression",
-        ast::Expr::TString(_) => "t-string expression",
-        ast::Expr::NumberLiteral(_) | ast::Expr::StringLiteral(_) | ast::Expr::BytesLiteral(_) => {
-            "literal"
-        }
-        ast::Expr::Constant(expr) => match &expr.value {
-            ast::ConstantValue::None => "None",
-            ast::ConstantValue::Boolean(true) => "True",
-            ast::ConstantValue::Boolean(false) => "False",
-            ast::ConstantValue::Ellipsis => "ellipsis",
-            ast::ConstantValue::Tuple(_) => "tuple",
-            ast::ConstantValue::Frozenset(_) => "literal",
-            ast::ConstantValue::Str(_)
-            | ast::ConstantValue::Bytes(_)
-            | ast::ConstantValue::Integer(_)
-            | ast::ConstantValue::Float(_)
-            | ast::ConstantValue::Complex { .. } => "literal",
-        },
-        ast::Expr::BooleanLiteral(boolean) => {
-            if boolean.value {
-                "True"
-            } else {
-                "False"
-            }
-        }
-        ast::Expr::NoneLiteral(_) => "None",
-        ast::Expr::EllipsisLiteral(_) => "ellipsis",
-        ast::Expr::Compare(_) => "comparison",
-        ast::Expr::If(_) => "conditional expression",
-        ast::Expr::Named(_) => "named expression",
-        ast::Expr::Slice(_) | ast::Expr::IpyEscapeCommand(_) => "expression",
-    }
-}
-
-fn parenthesized_single_starred_delete_target(bytes: &[u8], start: usize, end: usize) -> bool {
-    let mut cursor = start;
-    while matches!(bytes.get(cursor), Some(b' ' | b'\t' | b'\x0c')) {
-        cursor += 1;
-    }
-    if bytes.get(cursor) != Some(&b'(') {
-        return false;
-    }
-    cursor += 1;
-    while matches!(bytes.get(cursor), Some(b' ' | b'\t' | b'\x0c')) {
-        cursor += 1;
-    }
-    if bytes.get(cursor) != Some(&b'*') {
-        return false;
-    }
-    let mut level = 1usize;
-    cursor += 1;
-    while cursor < end {
-        match bytes[cursor] {
-            b'\'' | b'"' => {
-                cursor = skip_quoted_string(bytes, cursor);
-            }
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                cursor += 1;
-            }
-            b')' => {
-                level = level.saturating_sub(1);
-                if level == 0 {
-                    cursor += 1;
-                    while matches!(bytes.get(cursor), Some(b' ' | b'\t' | b'\x0c')) {
-                        cursor += 1;
-                    }
-                    return cursor == end;
-                }
-                cursor += 1;
-            }
-            b',' if level == 1 => return false,
-            b']' | b'}' => {
-                level = level.saturating_sub(1);
-                cursor += 1;
-            }
-            _ => cursor += 1,
-        }
-    }
-    false
-}
-
-fn assignment_target_expr_range(source: &str, start: usize, end: usize) -> Option<(usize, usize)> {
-    let bytes = source.as_bytes();
-    let (target_start, target_end) = trim_target_range(bytes, start, end);
-    if target_start >= target_end {
-        return None;
-    }
-    if parser::parse(
-        &source[target_start..target_end],
-        parser::Mode::Expression.into(),
-    )
-    .is_ok()
-    {
-        return Some((target_start, target_end));
-    }
-    // `def f(): (yield bar)` — skip the suite header so the remaining
-    // text is the assignment target expression. Other colons (`x: int += 1`)
-    // are not suite headers for this diagnostic. Grouping parentheses may
-    // wrap the yield expression.
-    let colon = top_level_colon(bytes, target_start, target_end)?;
-    let after = skip_horizontal_whitespace(bytes, colon + 1);
-    let yield_at = skip_opening_parentheses(bytes, after, target_end);
-    if yield_at >= target_end || !starts_identifier(bytes, yield_at, b"yield") {
-        return None;
-    }
-    Some((after, target_end))
-}
-
-fn skip_opening_parentheses(bytes: &[u8], mut index: usize, end: usize) -> usize {
-    loop {
-        index = skip_horizontal_whitespace(bytes, index);
-        if index >= end || bytes[index] != b'(' {
-            return index;
-        }
-        index += 1;
-    }
-}
-
-fn trim_target_range(bytes: &[u8], mut start: usize, mut end: usize) -> (usize, usize) {
-    while start < end
-        && matches!(
-            bytes.get(start),
-            Some(b' ' | b'\t' | b'\n' | b'\r' | b'\x0c')
-        )
-    {
-        start += 1;
-    }
-    while end > start
-        && matches!(
-            bytes.get(end - 1),
-            Some(b' ' | b'\t' | b'\n' | b'\r' | b'\x0c')
-        )
-    {
-        end -= 1;
-    }
-    (start, end)
-}
-
-fn invalid_assignment_message(name: &'static str, top_level_bitwise: bool) -> String {
-    if top_level_bitwise {
-        format!("cannot assign to {name} here. Maybe you meant '==' instead of '='?")
-    } else {
-        format!("cannot assign to {name}")
-    }
-}
-
-fn assignment_target_error_for_slice(
-    source: &str,
-    start: usize,
-    end: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let (target_start, target_end) = assignment_target_expr_range(source, start, end)?;
-    if starts_identifier(bytes, target_start, b"yield") {
-        return Some(CpythonDiagnostic::new(
-            "assignment to yield expression not possible".to_owned(),
-            target_start,
-            target_start + 5,
-        ));
-    }
-    let target_text = &source[target_start..target_end];
-    let Ok(parsed) = parser::parse(target_text, parser::Mode::Expression.into()) else {
-        return None;
-    };
-    let ast::Mod::Expression(expression) = parsed.into_syntax() else {
-        return None;
-    };
-    let invalid_target = invalid_assignment_target(&expression.body)?;
-    let invalid_start = target_start + invalid_target.range().start().to_usize();
-    let invalid_end = target_start + invalid_target.range().end().to_usize();
-    let name = delete_target_expr_name(invalid_target);
-    let top_level = invalid_target.range() == expression.body.range();
-    let bitwise_like = matches!(
-        invalid_target,
-        ast::Expr::Call(_)
-            | ast::Expr::BoolOp(_)
-            | ast::Expr::BinOp(_)
-            | ast::Expr::UnaryOp(_)
-            | ast::Expr::NumberLiteral(_)
-            | ast::Expr::StringLiteral(_)
-            | ast::Expr::BytesLiteral(_)
-            | ast::Expr::EllipsisLiteral(_)
-            | ast::Expr::Yield(_)
-            | ast::Expr::YieldFrom(_)
-            | ast::Expr::Set(_)
-            | ast::Expr::Dict(_)
-            | ast::Expr::FString(_)
-            | ast::Expr::TString(_)
-    );
-    Some(CpythonDiagnostic::new(
-        invalid_assignment_message(name, top_level && bitwise_like),
-        invalid_start,
-        invalid_end,
-    ))
-}
-
-fn star_target_error_for_slice(
-    source: &str,
-    start: usize,
-    end: usize,
-) -> Option<CpythonDiagnostic> {
-    invalid_target_error_for_slice(source, start, end, invalid_assignment_target)
-}
-
-fn for_target_error_for_slice(source: &str, start: usize, end: usize) -> Option<CpythonDiagnostic> {
-    invalid_target_error_for_slice(source, start, end, invalid_for_target)
-}
-
-fn invalid_target_error_for_slice(
-    source: &str,
-    start: usize,
-    end: usize,
-    invalid_target: for<'a> fn(&'a ast::Expr) -> Option<&'a ast::Expr>,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let (target_start, target_end) = trim_target_range(bytes, start, end);
-    if target_start >= target_end {
-        return None;
-    }
-    let target_text = &source[target_start..target_end];
-    let Ok(parsed) = parser::parse(target_text, parser::Mode::Expression.into()) else {
-        return None;
-    };
-    let ast::Mod::Expression(expression) = parsed.into_syntax() else {
-        return None;
-    };
-    let invalid_target = invalid_target(&expression.body)?;
-    let name = delete_target_expr_name(invalid_target);
-    let invalid_start = target_start + invalid_target.range().start().to_usize();
-    let invalid_end = target_start + invalid_target.range().end().to_usize();
-    Some(CpythonDiagnostic::new(
-        format!("cannot assign to {name}"),
-        invalid_start,
-        invalid_end,
-    ))
-}
-
-fn first_compare_operator_at_level(bytes: &[u8], mut index: usize, end: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b'<' | b'>' if level == 0 => return Some(index),
-            b'=' if level == 0 && bytes.get(index + 1) == Some(&b'=') => return Some(index),
-            b'!' if level == 0 && bytes.get(index + 1) == Some(&b'=') => return Some(index),
-            _ if level == 0 && starts_identifier(bytes, index, b"is") => return Some(index),
-            _ if level == 0 && starts_identifier(bytes, index, b"not") => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn non_in_compare_for_target_error(
-    source: &str,
-    start: usize,
-    end: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let (target_start, target_end) = trim_target_range(bytes, start, end);
-    if target_start >= target_end {
-        return None;
-    }
-    let target_text = &source[target_start..target_end];
-    let Ok(parsed) = parser::parse(target_text, parser::Mode::Expression.into()) else {
-        return None;
-    };
-    let ast::Mod::Expression(expression) = parsed.into_syntax() else {
-        return None;
-    };
-    let ast::Expr::Compare(ast::ExprCompare { ops, .. }) = expression.body.as_ref() else {
-        return None;
-    };
-    if matches!(ops.first(), Some(ast::CmpOp::In)) {
-        return None;
-    }
-    let operator = first_compare_operator_at_level(bytes, target_start, target_end)?;
-    Some(CpythonDiagnostic::new(
-        "invalid syntax".to_owned(),
-        operator,
-        (operator + 1).min(target_end),
-    ))
-}
-
-fn top_level_plain_assignment_offsets(bytes: &[u8]) -> Vec<usize> {
-    let mut offsets = Vec::new();
-    let mut index = 0usize;
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' if level == 0 => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b'=' if level == 0 && is_plain_assignment_operator(bytes, index) => {
-                offsets.push(index);
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    offsets
-}
-
-fn invalid_condition_assignment_error(
-    source: &str,
-    parse_error_offset: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    let mut line_start = 0usize;
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' if level == 0 => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\n' => {
-                line_start = index + 1;
-                index += 1;
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ if level == 0
-                && index == skip_horizontal_whitespace(bytes, line_start)
-                && (starts_identifier(bytes, index, b"if")
-                    || starts_identifier(bytes, index, b"elif")
-                    || starts_identifier(bytes, index, b"while")) =>
-            {
-                let keyword_len = if starts_identifier(bytes, index, b"while") {
-                    5
-                } else if starts_identifier(bytes, index, b"elif") {
-                    4
-                } else {
-                    2
-                };
-                let cond_start = skip_horizontal_whitespace(bytes, index + keyword_len);
-                let Some(colon) = top_level_colon(bytes, cond_start, bytes.len()) else {
-                    index += keyword_len;
-                    continue;
-                };
-                if parse_error_offset < index || parse_error_offset > colon {
-                    index += keyword_len;
-                    continue;
-                }
-                let Some(equal) = condition_plain_assignment(bytes, cond_start, colon) else {
-                    index += keyword_len;
-                    continue;
-                };
-                let (target_start, target_end) = trim_target_range(bytes, cond_start, equal);
-                if target_start >= target_end {
-                    index += keyword_len;
-                    continue;
-                }
-                if is_simple_keyword_name(bytes, target_start, target_end) {
-                    return Some(CpythonDiagnostic::new(
-                        "invalid syntax. Maybe you meant '==' or ':=' instead of '='?".to_owned(),
-                        target_start,
-                        equal + 1,
-                    ));
-                }
-                if let Some((expr_name, start, end, _)) =
-                    expression_name_and_range(&source[target_start..target_end])
-                {
-                    return Some(CpythonDiagnostic::new(
-                        format!(
-                            "cannot assign to {expr_name} here. Maybe you meant '==' instead of '='?"
-                        ),
-                        target_start + start,
-                        target_start + end,
-                    ));
-                }
-                return Some(CpythonDiagnostic::new(
-                    "invalid syntax. Maybe you meant '==' or ':=' instead of '='?".to_owned(),
-                    target_start,
-                    equal + 1,
-                ));
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn condition_plain_assignment(bytes: &[u8], start: usize, end: usize) -> Option<usize> {
-    let mut index = start;
-    let mut nest = Vec::new();
-    while index < end {
-        match bytes[index] {
-            b'#' => {
-                while index < end && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' => {
-                nest.push(if is_call_open(bytes, start, index) {
-                    b'c'
-                } else {
-                    b'g'
-                });
-                index += 1;
-            }
-            b'[' => {
-                nest.push(b'[');
-                index += 1;
-            }
-            b'{' => {
-                nest.push(b'{');
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                nest.pop();
-                index += 1;
-            }
-            b':' if nest.last() == Some(&b'l') => {
-                nest.pop();
-                index += 1;
-            }
-            b'=' if is_plain_assignment_operator(bytes, index)
-                && !nest.contains(&b'c')
-                && !nest.contains(&b'l') =>
-            {
-                return Some(index);
-            }
-            _ if starts_identifier(bytes, index, b"lambda") => {
-                nest.push(b'l');
-                index += 6;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn is_call_open(bytes: &[u8], start: usize, open: usize) -> bool {
-    let mut index = open;
-    while index > start {
-        index -= 1;
-        match bytes[index] {
-            b' ' | b'\t' | b'\n' | b'\r' | b'\x0c' => {}
-            b')' | b']' => return true,
-            byte if byte >= 0x80 || is_ascii_identifier_char(byte) => {
-                let mut ident_start = index;
-                while ident_start > start
-                    && bytes
-                        .get(ident_start - 1)
-                        .is_some_and(|b| *b >= 0x80 || is_ascii_identifier_char(*b))
-                {
-                    ident_start -= 1;
-                }
-                return !is_condition_keyword(&bytes[ident_start..=index]);
-            }
-            _ => return false,
-        }
-    }
-    false
-}
-
-fn is_condition_keyword(word: &[u8]) -> bool {
-    matches!(
-        word,
-        b"not" | b"and" | b"or" | b"in" | b"is" | b"if" | b"elif" | b"while" | b"await" | b"lambda"
-    )
-}
-
-fn invalid_assignment_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let offsets = top_level_plain_assignment_offsets(bytes);
-    if offsets.is_empty() {
-        return None;
-    }
-    let mut start = 0usize;
-    for offset in offsets {
-        if let Some(error) = assignment_target_error_for_slice(source, start, offset) {
-            return Some(error);
-        }
-        start = offset + 1;
-    }
-    None
-}
-
-fn top_level_augassign_offset(bytes: &[u8]) -> Option<(usize, usize)> {
-    let mut index = 0usize;
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' if level == 0 => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b'+' | b'-' | b'*' | b'@' | b'/' | b'%' | b'&' | b'|' | b'^'
-                if level == 0 && bytes.get(index + 1) == Some(&b'=') =>
-            {
-                return Some((index, 2));
-            }
-            b'<' | b'>'
-                if level == 0
-                    && bytes.get(index + 1) == Some(&bytes[index])
-                    && bytes.get(index + 2) == Some(&b'=') =>
-            {
-                return Some((index, 3));
-            }
-            b'*' if level == 0
-                && bytes.get(index + 1) == Some(&b'*')
-                && bytes.get(index + 2) == Some(&b'=') =>
-            {
-                return Some((index, 3));
-            }
-            b'/' if level == 0
-                && bytes.get(index + 1) == Some(&b'/')
-                && bytes.get(index + 2) == Some(&b'=') =>
-            {
-                return Some((index, 3));
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_augassign_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let (operator, _) = top_level_augassign_offset(bytes)?;
-    let (target_start, target_end) = assignment_target_expr_range(source, 0, operator)?;
-    let target_text = &source[target_start..target_end];
-    let Ok(parsed) = parser::parse(target_text, parser::Mode::Expression.into()) else {
-        return None;
-    };
-    let ast::Mod::Expression(expression) = parsed.into_syntax() else {
-        return None;
-    };
-    let name = delete_target_expr_name(&expression.body);
-    Some(CpythonDiagnostic::new(
-        format!("'{name}' is an illegal expression for augmented assignment"),
-        target_start,
-        target_end,
-    ))
-}
-
-fn find_for_target_delimiter(bytes: &[u8], mut index: usize, end: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'#' if level == 0 => return None,
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ if level == 0 && starts_identifier(bytes, index, b"in") => return Some(index),
-            b':' if level == 0 => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_for_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            _ if starts_identifier(bytes, index, b"for") => {
-                let target_start = skip_horizontal_whitespace(bytes, index + 3);
-                let line_end = source[index..]
-                    .find('\n')
-                    .map_or(bytes.len(), |newline| index + newline);
-                if let Some(target_end) = find_for_target_delimiter(bytes, target_start, line_end) {
-                    if let Some(error) =
-                        for_target_error_for_slice(source, target_start, target_end)
-                    {
-                        return Some(error);
-                    }
-                    if let Some(error) =
-                        non_in_compare_for_target_error(source, target_start, target_end)
-                    {
-                        return Some(error);
-                    }
-                }
-                index = target_start.max(index + 3);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn find_with_target_delimiter(bytes: &[u8], mut index: usize, end: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'#' if level == 0 => return None,
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' if level == 0 => return Some(index),
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b',' | b':' if level == 0 => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_with_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut line_start = 0usize;
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        let mut column = skip_horizontal_whitespace(bytes, line_start);
-        if starts_identifier(bytes, column, b"async") {
-            column = skip_horizontal_whitespace(bytes, column + 5);
-        }
-        if !starts_identifier(bytes, column, b"with") {
-            line_start = line_end;
-            continue;
-        }
-        let mut index = column + 4;
-        while let Some(as_index) = find_keyword_at_level(bytes, index, line_end, b"as") {
-            let target_start = skip_horizontal_whitespace(bytes, as_index + 2);
-            if let Some(target_end) = find_with_target_delimiter(bytes, target_start, line_end) {
-                if let Some(error) = star_target_error_for_slice(source, target_start, target_end) {
-                    return Some(error);
-                }
-                index = target_end.saturating_add(1);
-            } else {
-                break;
-            }
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn find_missing_in_if_keyword(bytes: &[u8], mut index: usize, end: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'#' if level == 0 => return None,
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' if level == 0 => return None,
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ if level == 0 && starts_identifier(bytes, index, b"in") => return None,
-            _ if level == 0 && starts_identifier(bytes, index, b"if") => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_for_if_clause_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0usize;
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' if level == 0 => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ if level > 0 && starts_identifier(bytes, index, b"for") => {
-                let target_start = skip_horizontal_whitespace(bytes, index + 3);
-                let line_end = source[index..]
-                    .find('\n')
-                    .map_or(bytes.len(), |newline| index + newline);
-                if let Some(if_index) = find_missing_in_if_keyword(bytes, target_start, line_end) {
-                    return Some(CpythonDiagnostic::new(
-                        "'in' expected after for-loop variables".to_owned(),
-                        if_index,
-                        (if_index + 2).min(line_end),
-                    ));
-                }
-                index = target_start.max(index + 3);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_delete_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            b'd' if starts_identifier(bytes, index, b"del") => {
-                let mut target_start = index + 3;
-                if !matches!(bytes.get(target_start), Some(b' ' | b'\t' | b'\x0c')) {
-                    index += 3;
-                    continue;
-                }
-                while matches!(bytes.get(target_start), Some(b' ' | b'\t' | b'\x0c')) {
-                    target_start += 1;
-                }
-                let mut target_end = statement_target_end(bytes, target_start);
-                while target_end > target_start
-                    && matches!(bytes.get(target_end - 1), Some(b' ' | b'\t' | b'\x0c'))
-                {
-                    target_end -= 1;
-                }
-                if target_start >= target_end {
-                    index = target_end.max(index + 3);
-                    continue;
-                }
-                if parenthesized_single_starred_delete_target(bytes, target_start, target_end) {
-                    return Some(CpythonDiagnostic::new(
-                        "cannot use starred expression here".to_owned(),
-                        target_start,
-                        target_end,
-                    ));
-                }
-                if bytes.get(target_start) == Some(&b'*') {
-                    return Some(CpythonDiagnostic::new(
-                        "cannot delete starred".to_owned(),
-                        target_start,
-                        (target_start + 1).min(target_end),
-                    ));
-                }
-                let target_text = &source[target_start..target_end];
-                let Ok(parsed) = parser::parse(target_text, parser::Mode::Expression.into()) else {
-                    index = target_end;
-                    continue;
-                };
-                let ast::Mod::Expression(expression) = parsed.into_syntax() else {
-                    index = target_end;
-                    continue;
-                };
-                let Some(invalid_target) = invalid_delete_target(&expression.body) else {
-                    index = target_end;
-                    continue;
-                };
-                let start = target_start + invalid_target.range().start().to_usize();
-                let end = target_start + invalid_target.range().end().to_usize();
-                if matches!(invalid_target, ast::Expr::FString(_)) {
-                    return Some(CpythonDiagnostic::new(
-                        "invalid syntax".to_owned(),
-                        start,
-                        end,
-                    ));
-                }
-                let name = delete_target_expr_name(invalid_target);
-                return Some(CpythonDiagnostic::new(
-                    format!("cannot delete {name}"),
-                    start,
-                    end,
-                ));
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn skip_horizontal_whitespace(bytes: &[u8], mut index: usize) -> usize {
-    while matches!(bytes.get(index), Some(b' ' | b'\t' | b'\x0c')) {
-        index += 1;
-    }
-    index
-}
-
-fn find_keyword_at_level(
-    bytes: &[u8],
-    mut index: usize,
-    end: usize,
-    keyword: &[u8],
-) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'#' if level == 0 => return None,
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ if level == 0 && starts_identifier(bytes, index, keyword) => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn find_byte_at_level(bytes: &[u8], mut index: usize, end: usize, needle: u8) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'#' if level == 0 => return None,
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            byte if level == 0 && byte == needle => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn expression_name_and_range(source: &str) -> Option<(&'static str, usize, usize, bool)> {
-    let parsed = parser::parse(source, parser::Mode::Expression.into()).ok()?;
-    let ast::Mod::Expression(expression) = parsed.into_syntax() else {
-        return None;
-    };
-    let is_name = matches!(expression.body.as_ref(), ast::Expr::Name(_));
-    Some((
-        delete_target_expr_name(&expression.body),
-        expression.body.range().start().to_usize(),
-        expression.body.range().end().to_usize(),
-        is_name,
-    ))
-}
-
-fn invalid_standalone_except_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut line_start = 0usize;
-    let mut seen_try = false;
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        let column = skip_horizontal_whitespace(bytes, line_start);
-        if column >= line_end {
-            line_start = line_end;
-            continue;
-        }
-        if starts_identifier(bytes, column, b"try") {
-            seen_try = true;
-        } else if (bytes.get(column..column + 7) == Some(b"except*")
-            || starts_identifier(bytes, column, b"except"))
-            && !seen_try
-        {
-            let end = if bytes.get(column..column + 7) == Some(b"except*") {
-                column + 7
-            } else {
-                column + 6
-            };
-            return Some(CpythonDiagnostic::new(
-                "invalid syntax".to_owned(),
-                column,
-                end,
-            ));
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn invalid_import_statement_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut line_start = 0usize;
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        let column = skip_horizontal_whitespace(bytes, line_start);
-        if column < line_end
-            && starts_identifier(bytes, column, b"import")
-            && find_keyword_at_level(bytes, column + 6, line_end, b"from").is_some()
-        {
-            return Some(CpythonDiagnostic::new(
-                "Did you mean to use 'from ... import ...' instead?".to_owned(),
-                column,
-                column + 6,
-            ));
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn import_as_target_end(bytes: &[u8], mut index: usize) -> usize {
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' if level == 0 => return index,
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' if level == 0 => return index,
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b',' | b';' | b'\n' if level == 0 => return index,
-            _ => index += 1,
-        }
-    }
-    index
-}
-
-fn valid_import_alias_name(bytes: &[u8], mut start: usize, end: usize) -> bool {
-    start = skip_horizontal_whitespace(bytes, start);
-    let Some(&first) = bytes.get(start) else {
-        return false;
-    };
-    if !(first == b'_' || first.is_ascii_alphabetic() || first >= 0x80) {
-        return false;
-    }
-    let mut index = start + 1;
-    while index < end {
-        match bytes[index] {
-            b' ' | b'\t' | b'\x0c' => break,
-            byte if byte >= 0x80 || is_ascii_identifier_char(byte) => index += 1,
-            _ => return false,
-        }
-    }
-    let index = skip_horizontal_whitespace(bytes, index);
-    matches!(
-        bytes.get(index),
-        None | Some(b',' | b')' | b';' | b'\n' | b'\r')
-    )
-}
-
-fn import_target_error_for_slice(
-    source: &str,
-    start: usize,
-    end: usize,
-) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let (target_start, target_end) = trim_target_range(bytes, start, end);
-    if target_start >= target_end || valid_import_alias_name(bytes, target_start, target_end) {
-        return None;
-    }
-    let parsed = parser::parse(
-        &source[target_start..target_end],
-        parser::Mode::Expression.into(),
-    )
-    .ok()?;
-    let ast::Mod::Expression(expression) = parsed.into_syntax() else {
-        return None;
-    };
-    let name = delete_target_expr_name(&expression.body);
-    let start = target_start + expression.body.range().start().to_usize();
-    let end = target_start + expression.body.range().end().to_usize();
-    Some(CpythonDiagnostic::new(
-        format!("cannot use {name} as import target"),
-        start,
-        end,
-    ))
-}
-
-fn statement_starts_import(bytes: &[u8], line_start: usize, line_end: usize) -> bool {
-    let column = skip_horizontal_whitespace(bytes, line_start);
-    if starts_identifier(bytes, column, b"import") {
-        return true;
-    }
-    starts_identifier(bytes, column, b"from")
-        && find_keyword_at_level(bytes, column + 4, line_end, b"import").is_some()
-}
-
-fn invalid_import_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut line_start = 0usize;
-    let mut in_parenthesized_from_import = false;
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        let starts_import = statement_starts_import(bytes, line_start, line_end);
-        if starts_import && bytes[line_start..line_end].contains(&b'(') {
-            in_parenthesized_from_import = true;
-        }
-        if starts_import || in_parenthesized_from_import {
-            let mut index = line_start;
-            while index < line_end {
-                if starts_identifier(bytes, index, b"as") {
-                    let target_start = skip_horizontal_whitespace(bytes, index + 2);
-                    let target_end = import_as_target_end(bytes, target_start);
-                    if let Some(error) =
-                        import_target_error_for_slice(source, target_start, target_end)
-                    {
-                        return Some(error);
-                    }
-                    index = target_end.max(index + 2);
-                } else {
-                    index += 1;
-                }
-            }
-        }
-        if in_parenthesized_from_import && bytes[line_start..line_end].contains(&b')') {
-            in_parenthesized_from_import = false;
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn invalid_except_as_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut line_start = 0usize;
-    let mut seen_try = false;
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        let mut column = skip_horizontal_whitespace(bytes, line_start);
-        if column >= line_end {
-            line_start = line_end;
-            continue;
-        }
-        if starts_identifier(bytes, column, b"try") {
-            seen_try = true;
-            line_start = line_end;
-            continue;
-        }
-        let (keyword_len, starred) = if bytes.get(column..column + 7) == Some(b"except*") {
-            (7, true)
-        } else if starts_identifier(bytes, column, b"except") {
-            (6, false)
-        } else {
-            line_start = line_end;
-            continue;
-        };
-        if !seen_try {
-            line_start = line_end;
-            continue;
-        }
-        column += keyword_len;
-        let Some(as_index) = find_keyword_at_level(bytes, column, line_end, b"as") else {
-            line_start = line_end;
-            continue;
-        };
-        let target_start = skip_horizontal_whitespace(bytes, as_index + 2);
-        let Some(delimiter) = find_byte_at_level(bytes, target_start, line_end, b':')
-            .into_iter()
-            .chain(find_byte_at_level(bytes, target_start, line_end, b','))
-            .min()
-        else {
-            line_start = line_end;
-            continue;
-        };
-        let mut target_end = delimiter;
-        while target_end > target_start
-            && matches!(bytes.get(target_end - 1), Some(b' ' | b'\t' | b'\x0c'))
-        {
-            target_end -= 1;
-        }
-        let Some((expr_name, start, end, is_name)) =
-            expression_name_and_range(&source[target_start..target_end])
-        else {
-            line_start = line_end;
-            continue;
-        };
-        if !is_name {
-            let statement = if starred { "except*" } else { "except" };
-            return Some(CpythonDiagnostic::new(
-                format!("cannot use {statement} statement with {expr_name}"),
-                target_start + start,
-                target_start + end,
-            ));
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn invalid_match_as_target_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let quoted_ranges = quoted_string_ranges(bytes);
-    let mut quoted_range = 0usize;
-    let mut line_start = 0usize;
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        let mut column = skip_horizontal_whitespace(bytes, line_start);
-        if column >= line_end
-            || offset_in_ranges(&quoted_ranges, &mut quoted_range, column)
-            || !starts_identifier(bytes, column, b"case")
-        {
-            line_start = line_end;
-            continue;
-        }
-        column += 4;
-        let Some(as_index) = find_keyword_at_level(bytes, column, line_end, b"as") else {
-            line_start = line_end;
-            continue;
-        };
-        let target_start = skip_horizontal_whitespace(bytes, as_index + 2);
-        let Some(delimiter) = find_byte_at_level(bytes, target_start, line_end, b':')
-            .into_iter()
-            .chain(find_byte_at_level(bytes, target_start, line_end, b','))
-            .min()
-        else {
-            line_start = line_end;
-            continue;
-        };
-        let mut target_end = delimiter;
-        while target_end > target_start
-            && matches!(bytes.get(target_end - 1), Some(b' ' | b'\t' | b'\x0c'))
-        {
-            target_end -= 1;
-        }
-        if source[target_start..target_end].trim() == "_" {
-            return Some(CpythonDiagnostic::new(
-                "cannot use '_' as a target".to_owned(),
-                target_start,
-                target_end,
-            ));
-        }
-        let Some((expr_name, start, end, is_name)) =
-            expression_name_and_range(&source[target_start..target_end])
-        else {
-            line_start = line_end;
-            continue;
-        };
-        if !is_name {
-            if matches!(expr_name, "expression" | "subscript") {
-                line_start = line_end;
-                continue;
-            }
-            return Some(CpythonDiagnostic::new(
-                format!("cannot use {expr_name} as pattern target"),
-                target_start + start,
-                target_start + end,
-            ));
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn quoted_string_ranges(bytes: &[u8]) -> Vec<(usize, usize)> {
-    let mut ranges = Vec::new();
-    let mut index = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                let end = skip_quoted_string(bytes, index);
-                ranges.push((index, end));
-                index = end;
-            }
-            _ => index += 1,
-        }
-    }
-    ranges
-}
-
-fn offset_in_ranges(ranges: &[(usize, usize)], range_index: &mut usize, offset: usize) -> bool {
-    while ranges
-        .get(*range_index)
-        .is_some_and(|(_, end)| *end <= offset)
-    {
-        *range_index += 1;
-    }
-    ranges
-        .get(*range_index)
-        .is_some_and(|(start, end)| *start <= offset && offset < *end)
-}
-
-fn invalid_match_mapping_rest_wildcard_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let next_line_end = |line_start: usize| {
-        line_start
-            + bytes[line_start..]
-                .iter()
-                .position(|byte| *byte == b'\n')
-                .unwrap_or(bytes.len() - line_start)
-    };
-    let mut index = 0usize;
-    let mut line_start = 0usize;
-    let mut line_end = next_line_end(line_start);
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'\n' => {
-                index += 1;
-                line_start = index;
-                line_end = next_line_end(line_start);
-            }
-            _ => {
-                let column = skip_horizontal_whitespace(bytes, line_start);
-                if index != column
-                    || column >= line_end
-                    || !starts_identifier(bytes, column, b"case")
-                {
-                    index += 1;
-                    continue;
-                }
-                let mut cursor = column + 4;
-                while cursor < line_end {
-                    match bytes[cursor] {
-                        b'#' => break,
-                        b'\'' | b'"' => cursor = skip_quoted_string(bytes, cursor),
-                        b'{' => {
-                            let rest = next_non_horizontal_whitespace(bytes, cursor + 1);
-                            if bytes.get(rest..rest + 2) == Some(b"**") {
-                                let name_start = next_non_horizontal_whitespace(bytes, rest + 2);
-                                let name_end = identifier_end(bytes, name_start, line_end);
-                                if source.get(name_start..name_end) == Some("_") {
-                                    return Some(CpythonDiagnostic::new(
-                                        "invalid syntax".to_owned(),
-                                        name_start,
-                                        name_end,
-                                    ));
-                                }
-                            }
-                            cursor += 1;
-                        }
-                        _ => cursor += 1,
-                    }
-                }
-                index = line_end;
-            }
-        }
-    }
-    None
-}
-
-fn invalid_if_expression_statement_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut line_start = 0usize;
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        if let Some(if_index) = find_keyword_at_level(bytes, line_start, line_end, b"if")
-            && let Some((start, end)) = statement_before_if_expression(bytes, line_start, if_index)
-            && find_keyword_at_level(bytes, if_index + 2, line_end, b"else").is_some()
-        {
-            return Some(CpythonDiagnostic::new(
-                "expected expression before 'if', but statement is given".to_owned(),
-                start,
-                end,
-            ));
-        }
-        if let Some(else_index) = find_keyword_at_level(bytes, line_start, line_end, b"else")
-            && find_keyword_at_level(bytes, line_start, else_index, b"if").is_some()
-            && let Some((start, end)) =
-                statement_after_else_expression(bytes, else_index + 4, line_end)
-        {
-            return Some(CpythonDiagnostic::new(
-                "expected expression after 'else', but statement is given".to_owned(),
-                start,
-                end,
-            ));
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn statement_before_if_expression(
-    bytes: &[u8],
-    line_start: usize,
-    if_index: usize,
-) -> Option<(usize, usize)> {
-    let mut start = if_index;
-    while start > line_start && matches!(bytes.get(start - 1), Some(b' ' | b'\t' | b'\x0c')) {
-        start -= 1;
-    }
-    while start > line_start
-        && !matches!(
-            bytes.get(start - 1),
-            Some(b'=' | b':' | b',' | b'(' | b'[' | b'{')
-        )
-    {
-        start -= 1;
-    }
-    start = skip_horizontal_whitespace(bytes, start);
-    for keyword in [b"pass".as_slice(), b"break", b"continue"] {
-        if starts_identifier(bytes, start, keyword) {
-            return Some((start, start + keyword.len()));
-        }
-    }
-    None
-}
-
-fn statement_after_else_expression(
-    bytes: &[u8],
-    else_end: usize,
-    line_end: usize,
-) -> Option<(usize, usize)> {
-    let start = skip_horizontal_whitespace(bytes, else_end);
-    for keyword in [
-        b"pass".as_slice(),
-        b"return",
-        b"raise",
-        b"del",
-        b"yield",
-        b"assert",
-        b"break",
-        b"continue",
-        b"import",
-        b"from",
-    ] {
-        if starts_identifier(bytes, start, keyword) {
-            let end = statement_target_end(bytes, start).min(line_end);
-            return Some((start, end.max(start + keyword.len())));
-        }
-    }
-    None
-}
-
-fn invalid_else_elif_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut line_start = 0usize;
-    let mut else_indents: Vec<usize> = Vec::new();
-    for line in source.split_inclusive('\n') {
-        let line_end = line_start + line.len();
-        let column = skip_horizontal_whitespace(bytes, line_start);
-        let line_column = column.saturating_sub(line_start);
-        if column >= line_end {
-            line_start = line_end;
-            continue;
-        }
-        while else_indents
-            .last()
-            .is_some_and(|indent| line_column < *indent)
-        {
-            else_indents.pop();
-        }
-        if starts_identifier(bytes, column, b"else")
-            && find_byte_at_level(bytes, column + 4, line_end, b':').is_some()
-        {
-            else_indents.push(line_column);
-        } else if starts_identifier(bytes, column, b"elif") && else_indents.contains(&line_column) {
-            return Some(CpythonDiagnostic::new(
-                "'elif' block follows an 'else' block".to_owned(),
-                column,
-                column + 4,
-            ));
-        }
-        line_start = line_end;
-    }
-    None
-}
-
-fn mixed_except_handlers_error(source: &str) -> Option<CpythonDiagnostic> {
-    let message = "cannot have both 'except' and 'except*' on the same 'try'".to_owned();
-    let mut seen_except = false;
-    let mut seen_except_star = false;
-    let mut line_start = 0usize;
-    for line in source.split_inclusive('\n') {
-        let bytes = line.as_bytes();
-        let mut column = 0usize;
-        while matches!(bytes.get(column), Some(b' ' | b'\t' | b'\x0c')) {
-            column += 1;
-        }
-        let token_start = line_start + column;
-        if bytes.get(column..column + 7) == Some(b"except*") {
-            if seen_except {
-                return Some(CpythonDiagnostic::new(
-                    message,
-                    token_start,
-                    token_start + 7,
-                ));
-            }
-            seen_except_star = true;
-        } else if starts_identifier(bytes, column, b"except") {
-            if seen_except_star {
-                return Some(CpythonDiagnostic::new(
-                    message,
-                    token_start,
-                    token_start + 6,
-                ));
-            }
-            seen_except = true;
-        }
-        line_start += line.len();
-    }
-    None
-}
-
-fn non_printable_character_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            byte if byte.is_ascii_control() && !matches!(byte, b'\t' | b'\n' | b'\r' | b'\x0c') => {
-                return Some(CpythonDiagnostic::new(
-                    format!("invalid non-printable character U+{byte:04X}"),
-                    index,
-                    index + 1,
-                ));
-            }
-            byte if byte >= 0x80 => {
-                let ch = source[index..].chars().next()?;
-                if ch.is_control() {
-                    return Some(CpythonDiagnostic::new(
-                        format!("invalid non-printable character U+{:04X}", ch as u32),
-                        index,
-                        index + ch.len_utf8(),
-                    ));
-                }
-                index += ch.len_utf8();
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn unterminated_string_error(source: &str, mode: Mode) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    let mut line = 1usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\n' => {
-                line += 1;
-                index += 1;
-            }
-            quote @ (b'\'' | b'"') => {
-                let start = index;
-                let start_line = line;
-                let quote_size = if bytes.get(index + 1) == Some(&quote)
-                    && bytes.get(index + 2) == Some(&quote)
-                {
-                    3
-                } else {
-                    1
-                };
-                index += quote_size;
-                let mut has_escaped_quote = false;
-                let mut ended_with_escape = false;
-                let mut closed = false;
-                while index < bytes.len() {
-                    let c = bytes[index];
-                    if c == b'\n' {
-                        if quote_size == 1 {
-                            // A single-quoted literal cannot span a line, so this is the same
-                            // "the literal never ended" case as running out of source; CPython
-                            // spells the two as one condition in lexer.c too.
-                            break;
-                        }
-                        line += 1;
-                        index += 1;
-                    } else if c == quote {
-                        if quote_size == 3 {
-                            if bytes.get(index + 1) == Some(&quote)
-                                && bytes.get(index + 2) == Some(&quote)
-                            {
-                                index += 3;
-                                closed = true;
-                                break;
-                            }
-                            index += 1;
-                        } else {
-                            index += 1;
-                            closed = true;
-                            break;
-                        }
-                    } else if c == b'\\' {
-                        if bytes.get(index + 1) == Some(&quote) {
-                            has_escaped_quote = true;
-                        }
-                        ended_with_escape = index + 1 >= bytes.len();
-                        index = (index + 2).min(bytes.len());
-                    } else {
-                        index += 1;
-                    }
-                }
-                if !closed {
-                    if let Some(error) =
-                        unclosed_replacement_field_error(bytes, start, start + quote_size, index)
-                    {
-                        return Some(error);
-                    }
-                    let detected_line = if quote_size == 3 { line } else { start_line };
-                    let interpolated = interpolated_string_prefix(bytes, start);
-                    let diagnostic = CpythonDiagnostic::new(
-                        unterminated_string_message(
-                            detected_line,
-                            quote_size == 3,
-                            has_escaped_quote,
-                            interpolated,
-                        ),
-                        start,
-                        start,
-                    );
-                    // E_EOLS is only for a plain single-quoted string at EOF.
-                    // Single-quoted f/t-strings never set it. exec input appends a
-                    // newline, so a single-quoted literal becomes the newline case
-                    // unless a final `\` consumes that newline.
-                    let exec_implicit_newline =
-                        matches!(mode, Mode::Exec) && quote_size == 1 && !ended_with_escape;
-                    let eval_assignment =
-                        matches!(mode, Mode::Eval) && eval_has_assignment_before(bytes, start);
-                    let continuable = index >= bytes.len()
-                        && !(interpolated.is_some() && quote_size == 1)
-                        && !exec_implicit_newline
-                        && !eval_assignment;
-                    return Some(if continuable {
-                        diagnostic.with_unclosed_string()
-                    } else {
-                        diagnostic
-                    });
-                }
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn eval_has_assignment_before(bytes: &[u8], end: usize) -> bool {
-    let mut index = 0;
-    let mut level = 0usize;
-    let mut in_lambda_params = false;
-    while index < end {
-        match bytes[index] {
-            b'#' => {
-                while index < end && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            b':' if level == 0 => {
-                in_lambda_params = false;
-                index += 1;
-            }
-            b'=' if level == 0
-                && !in_lambda_params
-                && bytes.get(index + 1) != Some(&b'=')
-                && !matches!(
-                    bytes.get(index.saturating_sub(1)),
-                    Some(b':' | b'!' | b'<' | b'>')
-                ) =>
-            {
-                return true;
-            }
-            _ if level == 0 && starts_identifier(bytes, index, b"lambda") => {
-                in_lambda_params = true;
-                index += b"lambda".len();
-            }
-            _ => index += 1,
-        }
-    }
-    false
-}
-
-fn invalid_interpolated_string_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            quote @ (b'\'' | b'"') => {
-                let Some(prefix) = interpolated_string_prefix(bytes, index) else {
-                    index = skip_quoted_string(bytes, index);
-                    continue;
-                };
-                if let Some(error) =
-                    single_quoted_format_spec_newline_error(bytes, index, quote, prefix)
-                {
-                    return Some(error);
-                }
-                let Some((content_start, content_end)) =
-                    quoted_string_content_range(bytes, index, quote)
-                else {
-                    index = skip_quoted_string(bytes, index);
-                    continue;
-                };
-                if let Some(error) =
-                    invalid_replacement_field_error(bytes, content_start, content_end, prefix)
-                {
-                    return Some(error);
-                }
-                index = skip_quoted_string(bytes, index);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-/// Whether the literal opened at `quote` carries a `b` in its prefix.
-fn is_bytes_literal(bytes: &[u8], quote: usize) -> bool {
-    let mut start = quote;
-    while quote - start < 2
-        && start > 0
-        && matches!(
-            bytes[start - 1].to_ascii_lowercase(),
-            b'r' | b'b' | b'u' | b'f' | b't'
-        )
-    {
-        start -= 1;
-    }
-    if start > 0 && is_ascii_identifier_char(bytes[start - 1]) {
-        return false;
-    }
-    bytes[start..quote]
-        .iter()
-        .any(|byte| byte.eq_ignore_ascii_case(&b'b'))
-}
-
-/// Which of CPython's two messages a mixed literal concatenation gets. Ruff reports only the
-/// bytes/non-bytes mix, so `t"x" b"y"` arrives here as a bytes error where CPython names the
-/// t-string, and this scanner owns the choice between them.
-///
-/// CPython's `invalid_string_tstring_concat` is an `invalid_` rule, reached only on the error
-/// pass, and the `strings` rule tries `(fstring|string)+` first. That alternative consumes the
-/// concatenation's leading run of non-t-string literals, so a bytes/non-bytes mix among *those*
-/// raises from `_PyPegen_concatenate_strings` on the first pass and the t-string rule never runs.
-/// The bytes message therefore keeps precedence for `"a" b"b" t"c"` but not for `t"x" b"y"`.
-fn mixed_tstring_literal_error(
-    error: &parser::ParseError,
-    source: &str,
-) -> Option<CpythonDiagnostic> {
-    let parser::ParseErrorType::OtherError(message) = &error.error else {
-        return None;
-    };
-    if !message.eq_ignore_ascii_case("bytes literal cannot be mixed with non-bytes literals") {
-        return None;
-    }
-
-    let start = error.location.start().to_usize();
-    let end = error.location.end().to_usize();
-    let bytes = source.as_bytes();
-    if end > bytes.len() {
-        return None;
-    }
-
-    let mut index = start;
-    let (mut bytes_seen, mut nonbytes_seen) = (false, false);
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => {
-                if interpolated_string_prefix(bytes, index) == Some("t-string") {
-                    let message = if bytes_seen && nonbytes_seen {
-                        // Reported here rather than left to ruff's error so that the scanners
-                        // further down the chain cannot claim the concatenation instead.
-                        "cannot mix bytes and nonbytes literals"
-                    } else {
-                        "cannot mix t-string literals with string or bytes literals"
-                    };
-                    return Some(CpythonDiagnostic::new(message.to_owned(), start, end));
-                }
-                if is_bytes_literal(bytes, index) {
-                    bytes_seen = true;
-                } else {
-                    nonbytes_seen = true;
-                }
-                index = skip_quoted_string(bytes, index);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn single_quoted_format_spec_newline_error(
-    bytes: &[u8],
-    quote_index: usize,
-    quote: u8,
-    prefix: &str,
-) -> Option<CpythonDiagnostic> {
-    if bytes.get(quote_index + 1) == Some(&quote) && bytes.get(quote_index + 2) == Some(&quote) {
-        return None;
-    }
-
-    let (content_start, content_end) = quoted_string_content_range(bytes, quote_index, quote)?;
-    let mut index = content_start;
-    while index < content_end {
-        match bytes[index] {
-            b'{' if bytes.get(index + 1) == Some(&b'{') => index += 2,
-            b'}' if bytes.get(index + 1) == Some(&b'}') => index += 2,
-            b'{' => {
-                let expr_start = skip_ascii_whitespace(bytes, index + 1, content_end);
-                if let Some(separator) = replacement_field_separator(bytes, expr_start, content_end)
-                    && bytes[separator] == b':'
-                {
-                    let format_end =
-                        replacement_field_closing_brace(bytes, separator + 1, content_end)
-                            .unwrap_or(content_end);
-                    if bytes[separator + 1..format_end].contains(&b'\n') {
-                        return Some(CpythonDiagnostic::new(
-                            format!(
-                                "{prefix}: newlines are not allowed in format specifiers for single quoted {prefix}s"
-                            ),
-                            quote_index,
-                            quote_index + 1,
-                        ));
-                    }
-                }
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn interpolated_string_prefix(bytes: &[u8], quote: usize) -> Option<&'static str> {
-    let prev = quote.checked_sub(1).and_then(|index| bytes.get(index))?;
-    let lower_prev = prev.to_ascii_lowercase();
-    let (prefix_start, marker) = if matches!(lower_prev, b'f' | b't') {
-        if quote >= 2 && bytes[quote - 2].eq_ignore_ascii_case(&b'r') {
-            (quote - 2, lower_prev)
-        } else {
-            (quote - 1, lower_prev)
-        }
-    } else if lower_prev == b'r'
-        && quote >= 2
-        && matches!(bytes[quote - 2].to_ascii_lowercase(), b'f' | b't')
-    {
-        (quote - 2, bytes[quote - 2].to_ascii_lowercase())
-    } else {
-        return None;
-    };
-
-    if prefix_start > 0 && identifier_continue_before(bytes, prefix_start) {
-        return None;
-    }
-
-    Some(if marker == b'f' {
-        "f-string"
-    } else {
-        "t-string"
-    })
-}
-
-const MAXFSTRINGLEVEL: usize = 150;
-
-fn skip_string_token(bytes: &[u8], quote_index: usize) -> usize {
-    if interpolated_string_prefix(bytes, quote_index).is_some() {
-        interpolated_string_end(bytes, quote_index).unwrap_or(bytes.len())
-    } else {
-        skip_quoted_string(bytes, quote_index)
-    }
-}
-
-fn interpolated_string_end(bytes: &[u8], quote_index: usize) -> Option<usize> {
-    let quote = bytes[quote_index];
-    let triple =
-        bytes.get(quote_index + 1) == Some(&quote) && bytes.get(quote_index + 2) == Some(&quote);
-    let quote_len = if triple { 3 } else { 1 };
-    let mut index = quote_index + quote_len;
-    let mut brace_depth = 0usize;
-    while index < bytes.len() {
-        if brace_depth == 0 {
-            if bytes[index] == b'\\' {
-                index = (index + 2).min(bytes.len());
-                continue;
-            }
-            if triple
-                && bytes.get(index) == Some(&quote)
-                && bytes.get(index + 1) == Some(&quote)
-                && bytes.get(index + 2) == Some(&quote)
-            {
-                return Some(index + 3);
-            }
-            if !triple && bytes[index] == quote {
-                return Some(index + 1);
-            }
-            if bytes[index] == b'{' {
-                if bytes.get(index + 1) == Some(&b'{') {
-                    index += 2;
-                } else {
-                    brace_depth = 1;
-                    index += 1;
-                }
-            } else if bytes[index] == b'}' && bytes.get(index + 1) == Some(&b'}') {
-                index += 2;
-            } else {
-                index += 1;
-            }
-        } else {
-            match bytes[index] {
-                quote_ch @ (b'\'' | b'"') => {
-                    if quoted_string_is_closed(bytes, index) {
-                        index = skip_string_token(bytes, index).max(index + 1);
-                    } else if !triple && quote_ch == quote {
-                        return Some(index + 1);
-                    } else {
-                        index = skip_string_token(bytes, index).max(index + 1);
-                    }
-                }
-                b'#' => {
-                    while index < bytes.len() && bytes[index] != b'\n' {
-                        index += 1;
-                    }
-                }
-                b'{' => {
-                    brace_depth += 1;
-                    index += 1;
-                }
-                b'}' => {
-                    brace_depth -= 1;
-                    index += 1;
-                }
-                b'\\' => index = (index + 2).min(bytes.len()),
-                _ => index += 1,
-            }
-        }
-    }
-    None
-}
-
-fn quote_len_at(bytes: &[u8], quote_index: usize) -> usize {
-    let quote = bytes[quote_index];
-    if bytes.get(quote_index + 1) == Some(&quote) && bytes.get(quote_index + 2) == Some(&quote) {
-        3
-    } else {
-        1
-    }
-}
-
-fn interpolated_string_content_range(bytes: &[u8], quote_index: usize) -> Option<(usize, usize)> {
-    let end = interpolated_string_end(bytes, quote_index)?;
-    let quote_len = quote_len_at(bytes, quote_index);
-    Some((quote_index + quote_len, end - quote_len))
-}
-
-fn quoted_string_content_range(
-    bytes: &[u8],
-    quote_index: usize,
-    quote: u8,
-) -> Option<(usize, usize)> {
-    let triple =
-        bytes.get(quote_index + 1) == Some(&quote) && bytes.get(quote_index + 2) == Some(&quote);
-    let quote_len = if triple { 3 } else { 1 };
-    let content_start = quote_index + quote_len;
-    let mut index = content_start;
-    while index < bytes.len() {
-        if bytes[index] == b'\\' {
-            index = (index + 2).min(bytes.len());
-        } else if (triple
-            && bytes.get(index) == Some(&quote)
-            && bytes.get(index + 1) == Some(&quote)
-            && bytes.get(index + 2) == Some(&quote))
-            || (!triple && bytes[index] == quote)
-        {
-            return Some((content_start, index));
-        } else {
-            index += 1;
-        }
-    }
-    None
-}
-
-fn invalid_replacement_field_error(
-    bytes: &[u8],
-    start: usize,
-    end: usize,
-    prefix: &str,
-) -> Option<CpythonDiagnostic> {
-    let mut index = start;
-    while index < end {
-        match bytes[index] {
-            b'{' if bytes.get(index + 1) == Some(&b'{') => index += 2,
-            b'}' if bytes.get(index + 1) == Some(&b'}') => index += 2,
-            b'{' => {
-                if let Some(error) = replacement_field_error(bytes, index, end, prefix, 0) {
-                    return Some(error);
-                }
-                // Resume in the literal text. Inside the field a `#` starts a comment and a `{`
-                // opens no new field, so walking on byte by byte would misread both.
-                index = replacement_field_end(bytes, index, end).unwrap_or(end);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-/// Position just past a replacement field's closing brace. The expression part is code, where a
-/// comment runs to the end of the line; past the separator only nested fields nest.
-fn replacement_field_end(bytes: &[u8], open: usize, end: usize) -> Option<usize> {
-    let expr_start = skip_replacement_field_trivia(bytes, open + 1, end);
-    let separator = replacement_field_separator(bytes, expr_start, end)?;
-    if bytes[separator] == b'}' {
-        return Some(separator + 1);
-    }
-    replacement_field_closing_brace(bytes, separator + 1, end).map(|brace| brace + 1)
-}
-
-/// The one-based line holding `offset`. Counted on demand: these scanners only run once the
-/// source has failed to parse, and tracking a line through the spans they skip would have to
-/// re-scan them anyway.
-fn line_of_offset(bytes: &[u8], offset: usize) -> usize {
-    1 + bytes[..offset]
-        .iter()
-        .filter(|byte| **byte == b'\n')
-        .count()
-}
-
-/// Brackets opened in a replacement field's expression must close before the field does. CPython
-/// words these exactly as it does for brackets anywhere else, except that a closer with nothing
-/// open is attributed to the literal. `start..end` must cover only the expression: a format spec
-/// is plain text, so a bracket there opens nothing.
-fn replacement_field_bracket_error(
-    bytes: &[u8],
-    start: usize,
-    end: usize,
-    prefix: &str,
-) -> Option<CpythonDiagnostic> {
-    // Each entry carries where its bracket opened, so a mismatch can name that line.
-    let mut stack: Vec<(u8, usize)> = Vec::new();
-    let mut index = start;
-    while index < end {
-        let byte = bytes[index];
-        match byte {
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-                continue;
-            }
-            b'#' => {
-                index = skip_replacement_field_comment(bytes, index, end);
-                continue;
-            }
-            b'(' | b'[' | b'{' => stack.push((byte, index)),
-            b')' | b']' | b'}' => {
-                let expected = expected_opening_bracket(byte as char) as u8;
-                match stack.last() {
-                    // The field's own closing brace: everything inside it balanced.
-                    None if byte == b'}' => return None,
-                    None => {
-                        return Some(CpythonDiagnostic::new(
-                            format!("{prefix}: unmatched '{}'", byte as char),
-                            index,
-                            index + 1,
-                        ));
-                    }
-                    Some(&(opening, _)) if opening == expected => {
-                        stack.pop();
-                    }
-                    Some(&(opening, opened_at)) => {
-                        // CPython names the opening line only when it is not the closing one,
-                        // comparing `parenlinenostack[level]` against the current `lineno`.
-                        let opening_line = line_of_offset(bytes, opened_at);
-                        let suffix = if opening_line == line_of_offset(bytes, index) {
-                            String::new()
-                        } else {
-                            format!(" on line {opening_line}")
-                        };
-                        return Some(CpythonDiagnostic::new(
-                            format!(
-                                "closing parenthesis '{}' does not match opening parenthesis '{}'{suffix}",
-                                byte as char, opening as char
-                            ),
-                            index,
-                            index + 1,
-                        ));
-                    }
-                }
-            }
-            _ => {}
-        }
-        index += 1;
-    }
-    None
-}
-
-/// A `#` in a replacement field's expression starts a comment. When no newline follows it before
-/// the end of the literal, the comment swallows the closing brace and the field can never close.
-/// `start..end` must cover only the expression: `#` is an ordinary character in a format spec,
-/// where it selects the alternate form.
-fn replacement_field_comment_error(
-    bytes: &[u8],
-    open: usize,
-    start: usize,
-    end: usize,
-    literal_end: usize,
-) -> Option<CpythonDiagnostic> {
-    let mut index = start;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-                continue;
-            }
-            b'#' => {
-                if !bytes[index..literal_end].contains(&b'\n') {
-                    return Some(
-                        CpythonDiagnostic::new("'{' was never closed".to_owned(), open, open + 1)
-                            .with_unclosed_bracket(),
-                    );
-                }
-                index = skip_replacement_field_comment(bytes, index, end);
-                continue;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-/// Advances past a comment, stopping on the newline that ends it.
-fn skip_replacement_field_comment(bytes: &[u8], mut index: usize, end: usize) -> usize {
-    while index < end && bytes[index] != b'\n' {
-        index += 1;
-    }
-    index
-}
-
-/// Whitespace and comments may both precede a replacement field's expression.
-fn skip_replacement_field_trivia(bytes: &[u8], mut index: usize, end: usize) -> usize {
-    loop {
-        index = skip_ascii_whitespace(bytes, index, end);
-        if index < end && bytes[index] == b'#' {
-            index = skip_replacement_field_comment(bytes, index, end);
-            continue;
-        }
-        return index;
-    }
-}
-
-/// Bounds the mutual recursion between a replacement field and the format spec it contains,
-/// so that pathologically nested input cannot exhaust the stack.
-const MAX_REPLACEMENT_FIELD_DEPTH: usize = 32;
-
-fn replacement_field_error(
-    bytes: &[u8],
-    open: usize,
-    end: usize,
-    prefix: &str,
-    depth: usize,
-) -> Option<CpythonDiagnostic> {
-    let expr_start = skip_replacement_field_trivia(bytes, open + 1, end);
-
-    // The expression runs up to the field's first top-level `=`, `!`, `:` or `}`. Everything past
-    // it is a conversion or a format spec, which are text rather than code, so the checks that
-    // treat the field as code have to stop here.
-    let separator = replacement_field_separator(bytes, expr_start, end);
-    let expr_end = separator.unwrap_or(end);
-
-    if let Some(backslash) = replacement_field_line_continuation(bytes, expr_start, expr_end) {
-        return Some(CpythonDiagnostic::new(
-            "unexpected character after line continuation character".to_owned(),
-            backslash + 1,
-            (backslash + 2).min(end),
-        ));
-    }
-    if let Some(quote) = unterminated_string_in_replacement_field(bytes, expr_start, expr_end) {
-        return Some(CpythonDiagnostic::new(
-            unterminated_string_message(1, false, false, None),
-            quote,
-            quote + 1,
-        ));
-    }
-    // Brackets are reported ahead of everything else in the field, and a comment that swallows
-    // the closing brace ahead of the expression itself. The comment scan starts at the brace
-    // because a comment may also sit between it and the expression.
-    if let Some(error) = replacement_field_bracket_error(bytes, expr_start, expr_end, prefix) {
-        return Some(error);
-    }
-    if let Some(error) = replacement_field_comment_error(bytes, open, open + 1, expr_end, end) {
-        return Some(error);
-    }
-
-    // Nothing follows `{` at all, so the field simply never closed. CPython asks for the
-    // brace here; an expression that merely fails to start is reported further down.
-    if expr_start >= end {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: expecting '}}'"),
-            open,
-            open + 1,
-        ));
-    }
-
-    if let marker @ (b'=' | b'!' | b':' | b'}') = bytes[expr_start]
-        && is_replacement_field_marker(bytes, expr_start)
-    {
-        return Some(CpythonDiagnostic::new(
-            format!(
-                "{prefix}: valid expression required before '{}'",
-                marker as char
-            ),
-            expr_start,
-            expr_start + 1,
-        ));
-    }
-
-    // A `{` display is a valid expression, but only if something can follow it. CPython
-    // reports the inner brace when it cannot, as in `f'{3:{{>10}'`.
-    if bytes[expr_start] == b'{' {
-        let inner = skip_ascii_whitespace(bytes, expr_start + 1, end);
-        if inner < end
-            && bytes[inner] != b'}'
-            && invalid_replacement_expression_start(bytes, inner, end)
-        {
-            return Some(CpythonDiagnostic::new(
-                format!("{prefix}: expecting a valid expression after '{{'"),
-                expr_start,
-                expr_start + 1,
-            ));
-        }
-    }
-
-    if starts_identifier(bytes, expr_start, b"lambda") {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: lambda expressions are not allowed without parentheses"),
-            expr_start,
-            expr_start + b"lambda".len(),
-        ));
-    }
-
-    if invalid_replacement_expression_start(bytes, expr_start, end) {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: expecting a valid expression after '{{'"),
-            open,
-            open + 1,
-        ));
-    }
-
-    // Adjacent atoms in a replacement field are a missing comma, not an
-    // f-string "expecting '}'" at the opening brace. Prefix `yield`/`await`/
-    // `not` and continuation keywords (`and`, `for`, ...) are not a second atom.
-    if !starts_identifier(bytes, expr_start, b"yield")
-        && !starts_identifier(bytes, expr_start, b"await")
-        && !starts_identifier(bytes, expr_start, b"not")
-        && let Some(atom_end) = adjacent_atom_end(bytes, expr_start)
-    {
-        let next = skip_ascii_whitespace(bytes, atom_end, expr_end);
-        if next > atom_end
-            && expression_atom_start(bytes, next)
-            && !expression_continuation_keyword(bytes, next)
-        {
-            let second_end = adjacent_atom_end(bytes, next).unwrap_or(next + 1);
-            return Some(CpythonDiagnostic::new(
-                "invalid syntax. Perhaps you forgot a comma?".to_owned(),
-                expr_start,
-                second_end,
-            ));
-        }
-    }
-
-    // The expression started fine but ran into a character that cannot continue it. CPython
-    // points at that character and lists the separators it wanted instead.
-    if let Some(stray) = replacement_expression_stray_character(bytes, expr_start, expr_end) {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: expecting '=', or '!', or ':', or '}}'"),
-            stray,
-            stray + 1,
-        ));
-    }
-
-    let Some(separator) = separator else {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: expecting '}}'"),
-            open,
-            open + 1,
-        ));
-    };
-
-    // Only now that the field is known to close. A stray character above is a finished token
-    // the parser rejects on lookahead, but a dangling operator makes it ask for one more, and
-    // producing that token runs into the literal's closing quote: lexer.c then answers from
-    // `INSIDE_FSTRING(tok)` with "%c-string: expecting '}'" before any `invalid_` rule is tried.
-    if let Some(operator) = dangling_operator(bytes, expr_start, expr_end) {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: expecting '=', or '!', or ':', or '}}'"),
-            operator,
-            operator + 1,
-        ));
-    }
-
-    if let Some(lambda_at) = top_level_lambda(bytes, expr_start, expr_end)
-        && lambda_allowed_at_expression_position(bytes, expr_start, lambda_at)
-    {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: lambda expressions are not allowed without parentheses"),
-            lambda_at,
-            lambda_at + b"lambda".len(),
-        ));
-    }
-
-    if bytes[separator] == b':'
-        && replacement_expression_has_parse_error(bytes, expr_start, separator)
-    {
-        return Some(CpythonDiagnostic::new(
-            "invalid syntax".to_owned(),
-            expr_start,
-            separator,
-        ));
-    }
-
-    match bytes[separator] {
-        b'=' => invalid_debug_expression_error(bytes, separator, end, prefix, depth),
-        b'!' => invalid_conversion_error(bytes, separator, end, prefix, depth),
-        b':' => invalid_format_spec_error(bytes, separator, end, prefix, depth),
-        b'}' => None,
-        _ => unreachable!(),
-    }
-}
-
-fn replacement_field_line_continuation(
-    bytes: &[u8],
-    mut index: usize,
-    end: usize,
-) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'#' => index = skip_replacement_field_comment(bytes, index, end),
-            b'\\' => return Some(index),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' if level > 0 => {
-                level -= 1;
-                index += 1;
-            }
-            b'=' | b'!' | b':' | b'}'
-                if level == 0 && is_replacement_field_marker(bytes, index) =>
-            {
-                return None;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn unterminated_string_in_replacement_field(
-    bytes: &[u8],
-    mut index: usize,
-    end: usize,
-) -> Option<usize> {
-    while index < end {
-        match bytes[index] {
-            quote @ (b'\'' | b'"') => {
-                let string_end = skip_quoted_string(bytes, index);
-                if string_end >= end && !bytes[index + 1..end].contains(&quote) {
-                    return Some(index);
-                }
-                index = string_end;
-            }
-            b'#' => index = skip_replacement_field_comment(bytes, index, end),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn top_level_lambda(bytes: &[u8], mut index: usize, end: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'#' => index = skip_replacement_field_comment(bytes, index, end),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' if level > 0 => {
-                level -= 1;
-                index += 1;
-            }
-            _ if level == 0 && starts_identifier(bytes, index, b"lambda") => {
-                return Some(index);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-/// Unparenthesized `lambda` is allowed in the same places a `lambdef` can appear:
-/// at the start of the field or after a top-level comma.
-fn lambda_allowed_at_expression_position(bytes: &[u8], mut index: usize, lambda_at: usize) -> bool {
-    let mut after_comma = true;
-    let mut level = 0usize;
-    while index < lambda_at {
-        match bytes[index] {
-            b'\'' | b'"' => {
-                after_comma = false;
-                index = skip_quoted_string(bytes, index);
-            }
-            b'#' => index = skip_replacement_field_comment(bytes, index, lambda_at),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                after_comma = false;
-                index += 1;
-            }
-            b')' | b']' | b'}' if level > 0 => {
-                level -= 1;
-                after_comma = false;
-                index += 1;
-            }
-            b',' if level == 0 => {
-                after_comma = true;
-                index += 1;
-            }
-            b' ' | b'\t' | b'\n' | b'\r' | b'\x0c' => index += 1,
-            _ => {
-                after_comma = false;
-                index += 1;
-            }
-        }
-    }
-    after_comma
-}
-
-fn replacement_expression_has_parse_error(bytes: &[u8], start: usize, end: usize) -> bool {
-    let Ok(expression) = ::core::str::from_utf8(&bytes[start..end]) else {
-        return false;
-    };
-    parser::parse_expression(expression).is_err()
-}
-
-fn invalid_replacement_expression_start(bytes: &[u8], index: usize, end: usize) -> bool {
-    if index >= end {
-        return true;
-    }
-
-    // A leading `.` is Ellipsis or a float without an integer part, both of which start a
-    // perfectly good expression.
-    if bytes[index] == b'.'
-        && (bytes[index..end].starts_with(b"...")
-            || bytes
-                .get(index + 1)
-                .is_some_and(|byte| byte.is_ascii_digit()))
-    {
-        return false;
-    }
-
-    if matches!(
-        bytes[index],
-        b'.' | b',' | b'*' | b'/' | b'%' | b'&' | b'|' | b'^' | b'<' | b'>' | b'@' | b'=' | b'!'
-    ) || is_stray_in_replacement_expression(bytes[index])
-    {
-        return true;
-    }
-
-    if matches!(bytes[index], b'+' | b'-' | b'~') {
-        let operand = skip_ascii_whitespace(bytes, index + 1, end);
-        if starts_identifier(bytes, operand, b"lambda") {
-            return true;
-        }
-        return !bytes.get(operand).is_some_and(|byte| {
-            *byte >= 0x80
-                || *byte == b'_'
-                || byte.is_ascii_alphabetic()
-                || byte.is_ascii_digit()
-                || matches!(*byte, b'\'' | b'"' | b'(' | b'[' | b'{')
-                // `-.5` is a signed float.
-                || (*byte == b'.'
-                    && bytes
-                        .get(operand + 1)
-                        .is_some_and(|next| next.is_ascii_digit()))
-        });
-    }
-
-    [
-        b"and".as_slice(),
-        b"as".as_slice(),
-        b"else".as_slice(),
-        b"for".as_slice(),
-        b"if".as_slice(),
-        b"in".as_slice(),
-        b"is".as_slice(),
-        b"or".as_slice(),
-    ]
-    .iter()
-    .any(|keyword| starts_identifier(bytes, index, keyword))
-}
-
-/// A top-level `=` or `!` marks a debug specifier or a conversion only when it is not part of a
-/// longer operator. CPython's tokenizer consumes `==`, `!=`, `<=`, `+=` and the rest as single
-/// tokens before it ever considers the debug marker, so those must not end the expression here.
-fn is_replacement_field_marker(bytes: &[u8], index: usize) -> bool {
-    match bytes[index] {
-        b'=' => {
-            if bytes.get(index + 1) == Some(&b'=') {
-                return false;
-            }
-            !index
-                .checked_sub(1)
-                .and_then(|previous| bytes.get(previous).copied())
-                .is_some_and(precedes_equals_in_one_operator)
-        }
-        b'!' => bytes.get(index + 1) != Some(&b'='),
-        _ => true,
-    }
-}
-
-fn replacement_field_separator(bytes: &[u8], mut index: usize, end: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'#' => index = skip_replacement_field_comment(bytes, index, end),
-            b'(' | b'[' | b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' if level > 0 => {
-                level -= 1;
-                index += 1;
-            }
-            b'=' | b'!' | b':' | b'}'
-                if level == 0 && is_replacement_field_marker(bytes, index) =>
-            {
-                return Some(index);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-/// Characters that can neither start nor continue a replacement field expression. CPython's
-/// interpolated-string tokenizer stops at them and asks for a separator instead.
-const fn is_stray_in_replacement_expression(byte: u8) -> bool {
-    matches!(byte, b';' | b'$' | b'?' | b'`')
-}
-
-fn replacement_expression_stray_character(
-    bytes: &[u8],
-    mut index: usize,
-    end: usize,
-) -> Option<usize> {
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'#' => index = skip_replacement_field_comment(bytes, index, end),
-            byte if is_stray_in_replacement_expression(byte) => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-/// A byte that pairs with a following `=` to make one operator token, so that the `=` belongs
-/// to it rather than opening a debug specifier: `==`, `!=`, `<=`, `>=`, the augmented
-/// assignments, and the `:=` walrus. Against `is_dangling_operator_byte` below, this has `:`
-/// and lacks `.` and `~`, because neither `.=` nor `~=` is a Python operator.
-const fn precedes_equals_in_one_operator(byte: u8) -> bool {
-    matches!(
-        byte,
-        b'!' | b'%'
-            | b'&'
-            | b'*'
-            | b'+'
-            | b'-'
-            | b'/'
-            | b':'
-            | b'<'
-            | b'='
-            | b'>'
-            | b'@'
-            | b'^'
-            | b'|'
-    )
-}
-
-/// Characters that make up an operator which cannot end an expression. Against
-/// `precedes_equals_in_one_operator` above, this has `.` and `~` for `a.b.` and `~a`, and lacks
-/// `:`, which separates a replacement field's parts rather than operating on anything.
-const fn is_dangling_operator_byte(byte: u8) -> bool {
-    matches!(
-        byte,
-        b'!' | b'%'
-            | b'&'
-            | b'*'
-            | b'+'
-            | b'-'
-            | b'.'
-            | b'/'
-            | b'<'
-            | b'='
-            | b'>'
-            | b'@'
-            | b'^'
-            | b'|'
-            | b'~'
-    )
-}
-
-/// The identifier that ends just before `word`, skipping the whitespace between them.
-fn preceding_keyword(bytes: &[u8], start: usize, word: usize) -> Option<(usize, &[u8])> {
-    let mut cursor = word;
-    while cursor > start && matches!(bytes[cursor - 1], b' ' | b'\t' | b'\r' | b'\n' | 0x0c) {
-        cursor -= 1;
-    }
-    let stop = cursor;
-    while cursor > start && is_ascii_identifier_char(bytes[cursor - 1]) {
-        cursor -= 1;
-    }
-    (cursor < stop).then(|| (cursor, &bytes[cursor..stop]))
-}
-
-/// A replacement field expression cannot end on an operator that still wants an operand.
-/// CPython's tokenizer then reaches the field brace with the expression unfinished and asks for
-/// a separator, pointing at the operator that left it that way. Returns that operator's start.
-fn dangling_operator(bytes: &[u8], start: usize, end: usize) -> Option<usize> {
-    // The region cannot be read backwards: the newline that ends a comment is whitespace, so
-    // trimming from `end` would step into the comment body. Walk forward instead and keep the
-    // position just past the last byte that is really part of the expression.
-    let mut index = start;
-    let mut tail = start;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index).min(end);
-                tail = index;
-            }
-            b'#' => index = skip_replacement_field_comment(bytes, index, end),
-            b' ' | b'\t' | b'\r' | b'\n' | 0x0c => index += 1,
-            _ => {
-                index += 1;
-                tail = index;
-            }
-        }
-    }
-    if tail == start {
-        return None;
-    }
-
-    // A trailing keyword operator reads back as an identifier.
-    if is_ascii_identifier_char(bytes[tail - 1]) {
-        let mut word = tail;
-        while word > start && is_ascii_identifier_char(bytes[word - 1]) {
-            word -= 1;
-        }
-        if ![
-            b"and".as_slice(),
-            b"or".as_slice(),
-            b"not".as_slice(),
-            b"in".as_slice(),
-            b"is".as_slice(),
-            b"if".as_slice(),
-            b"for".as_slice(),
-        ]
-        .iter()
-        .any(|keyword| &bytes[word..tail] == *keyword)
-        {
-            return None;
-        }
-        // `is not` and `not in` are single operators, and CPython points at their first word.
-        let previous = preceding_keyword(bytes, start, word);
-        return Some(match (previous, &bytes[word..tail]) {
-            (Some((at, b"is")), b"not") | (Some((at, b"not")), b"in") => at,
-            _ => word,
-        });
-    }
-
-    if !is_dangling_operator_byte(bytes[tail - 1]) {
-        return None;
-    }
-    let mut token = tail;
-    while token > start && is_dangling_operator_byte(bytes[token - 1]) {
-        token -= 1;
-    }
-
-    // `1.` is a float: that dot finishes the literal rather than dangling.
-    if bytes[token..tail] == *b"." && token > start && bytes[token - 1].is_ascii_digit() {
-        return None;
-    }
-    // `...` is Ellipsis, so consume whole triples: a leftover dot is what dangles.
-    if bytes[token..tail].iter().all(|byte| *byte == b'.') {
-        let leftover = (tail - token) % 3;
-        return (leftover != 0).then(|| tail - leftover);
-    }
-    Some(token)
-}
-
-fn invalid_debug_expression_error(
-    bytes: &[u8],
-    equals: usize,
-    end: usize,
-    prefix: &str,
-    depth: usize,
-) -> Option<CpythonDiagnostic> {
-    let next = equals + 1;
-    if next >= end {
-        return None;
-    }
-    // A conversion or format spec may follow `=`, and is validated exactly as it would be
-    // when following the expression directly.
-    match bytes[next] {
-        b'!' => return invalid_conversion_error(bytes, next, end, prefix, depth),
-        b':' => return invalid_format_spec_error(bytes, next, end, prefix, depth),
-        b'}' => return None,
-        _ => {}
-    }
-    Some(CpythonDiagnostic::new(
-        format!("{prefix}: expecting '!', or ':', or '}}'"),
-        next,
-        next.saturating_add(1).min(end),
-    ))
-}
-
-fn invalid_conversion_error(
-    bytes: &[u8],
-    bang: usize,
-    end: usize,
-    prefix: &str,
-    depth: usize,
-) -> Option<CpythonDiagnostic> {
-    let next = bang + 1;
-    if next >= end {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: expecting '}}'"),
-            bang,
-            bang + 1,
-        ));
-    }
-
-    if bytes[next].is_ascii_whitespace() {
-        let following = skip_ascii_whitespace(bytes, next, end);
-        let message = if bytes
-            .get(following)
-            .is_some_and(|byte| byte.is_ascii_alphabetic() || *byte == b'_')
-        {
-            "conversion type must come right after the exclamation mark"
-        } else {
-            "missing conversion character"
-        };
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: {message}"),
-            next,
-            next + 1,
-        ));
-    }
-
-    if matches!(bytes[next], b':' | b'}') {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: missing conversion character"),
-            next,
-            next + 1,
-        ));
-    }
-
-    // A non-ASCII character is still a conversion character as far as CPython is concerned,
-    // so it gets named in the message like any other invalid one.
-    if bytes[next] >= 0x80
-        && let Some(character) = ::core::str::from_utf8(&bytes[next..end])
-            .ok()
-            .and_then(|text| text.chars().next())
-    {
-        return Some(CpythonDiagnostic::new(
-            format!(
-                "{prefix}: invalid conversion character '{character}': expected 's', 'r', or 'a'"
-            ),
-            next,
-            next + character.len_utf8(),
-        ));
-    }
-
-    if !bytes[next].is_ascii_alphabetic() && bytes[next] != b'_' {
-        return Some(CpythonDiagnostic::new(
-            format!("{prefix}: invalid conversion character"),
-            next,
-            next + 1,
-        ));
-    }
-
-    let conversion_end = identifier_end(bytes, next, end);
-    let conversion = &bytes[next..conversion_end];
-    if !matches!(conversion, b"s" | b"r" | b"a") {
-        let conversion = ::core::str::from_utf8(conversion).unwrap_or("");
-        return Some(CpythonDiagnostic::new(
-            format!(
-                "{prefix}: invalid conversion character '{conversion}': expected 's', 'r', or 'a'"
-            ),
-            next,
-            conversion_end,
-        ));
-    }
-
-    if conversion_end >= end {
-        return None;
-    }
-
-    match bytes[conversion_end] {
-        b':' => return invalid_format_spec_error(bytes, conversion_end, end, prefix, depth),
-        b'}' => return None,
-        _ => {}
-    }
-
-    Some(CpythonDiagnostic::new(
-        format!("{prefix}: expecting ':' or '}}'"),
-        conversion_end,
-        conversion_end + 1,
-    ))
-}
-
-fn invalid_format_spec_error(
-    bytes: &[u8],
-    colon: usize,
-    end: usize,
-    prefix: &str,
-    depth: usize,
-) -> Option<CpythonDiagnostic> {
-    // Unlike literal text, a format spec has no `{{` escape: every `{` opens a nested
-    // replacement field, so the outer scanner cannot validate these for us.
-    let mut index = colon + 1;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'{' => {
-                if depth < MAX_REPLACEMENT_FIELD_DEPTH
-                    && let Some(error) =
-                        replacement_field_error(bytes, index, end, prefix, depth + 1)
-                {
-                    return Some(error);
-                }
-                // Resume after the nested field. Walking into it again from every enclosing
-                // spec would re-scan the same bytes once per level, which costs O(2^depth).
-                let Some(after) = replacement_field_end(bytes, index, end) else {
-                    break;
-                };
-                index = after;
-            }
-            b'}' => return None,
-            _ => index += 1,
-        }
-    }
-    Some(CpythonDiagnostic::new(
-        format!("{prefix}: expecting '}}', or format specs"),
-        colon,
-        colon + 1,
-    ))
-}
-
-fn replacement_field_closing_brace(bytes: &[u8], mut index: usize, end: usize) -> Option<usize> {
-    let mut level = 0usize;
-    while index < end {
-        match bytes[index] {
-            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
-            b'{' => {
-                level += 1;
-                index += 1;
-            }
-            b'}' if level > 0 => {
-                level -= 1;
-                index += 1;
-            }
-            b'}' => return Some(index),
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn skip_ascii_whitespace(bytes: &[u8], mut index: usize, end: usize) -> usize {
-    while index < end && matches!(bytes[index], b' ' | b'\t' | b'\r' | b'\n' | 0x0c) {
-        index += 1;
-    }
-    index
-}
-
-fn string_literal_end_at(bytes: &[u8], index: usize) -> Option<usize> {
-    match bytes.get(index).copied()? {
-        b'\'' | b'"' => Some(skip_quoted_string(bytes, index)),
-        first if first.is_ascii_alphabetic() => {
-            if matches!(bytes.get(index + 1), Some(b'\'' | b'"')) {
-                return string_literal_prefix(bytes, index, index + 1)
-                    .then(|| skip_quoted_string(bytes, index + 1));
-            }
-            if matches!(bytes.get(index + 2), Some(b'\'' | b'"')) {
-                return string_literal_prefix(bytes, index, index + 2)
-                    .then(|| skip_quoted_string(bytes, index + 2));
-            }
-            None
-        }
-        _ => None,
-    }
-}
-
-fn string_literal_prefix(bytes: &[u8], start: usize, quote: usize) -> bool {
-    let prefix = &bytes[start..quote];
-    let valid = matches!(
-        prefix,
-        b"b" | b"B"
-            | b"r"
-            | b"R"
-            | b"u"
-            | b"U"
-            | b"f"
-            | b"F"
-            | b"t"
-            | b"T"
-            | b"br"
-            | b"bR"
-            | b"Br"
-            | b"BR"
-            | b"rb"
-            | b"rB"
-            | b"Rb"
-            | b"RB"
-            | b"fr"
-            | b"fR"
-            | b"Fr"
-            | b"FR"
-            | b"rf"
-            | b"rF"
-            | b"Rf"
-            | b"RF"
-            | b"tr"
-            | b"tR"
-            | b"Tr"
-            | b"TR"
-            | b"rt"
-            | b"rT"
-            | b"Rt"
-            | b"RT"
-    );
-    valid && (start == 0 || !is_ascii_identifier_char(bytes[start - 1]))
-}
-
-fn invalid_expression_error(source: &str) -> Option<CpythonDiagnostic> {
-    invalid_string_expression_error(source).or_else(|| missing_comma_expression_error(source))
-}
-
-fn invalid_string_expression_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        if let Some(first_string_end) = string_literal_end_at(bytes, index) {
-            let expr_start = skip_ascii_whitespace(bytes, first_string_end, bytes.len());
-            if expression_atom_start(bytes, expr_start)
-                && let Some(expr_end) = adjacent_atom_end(bytes, expr_start)
-            {
-                let next = skip_ascii_whitespace(bytes, expr_end, bytes.len());
-                if string_literal_end_at(bytes, next).is_some() {
-                    return Some(CpythonDiagnostic::new(
-                        "invalid syntax. Is this intended to be part of the string?".to_owned(),
-                        expr_start,
-                        expr_end,
-                    ));
-                }
-            }
-            index = first_string_end;
-        } else {
-            index += 1;
-        }
-    }
-    None
-}
-
-fn missing_comma_expression_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut stack: Vec<u8> = Vec::new();
-    let mut index = 0;
-    while index < bytes.len() {
-        if bytes[index] == b'#' {
-            while index < bytes.len() && bytes[index] != b'\n' {
-                index += 1;
-            }
-        } else if let Some(string_end) = string_literal_end_at(bytes, index) {
-            index = string_end;
-        } else {
-            match bytes[index] {
-                b'(' | b'[' | b'{' => {
-                    if bytes[index] == b'[' && opening_bracket_is_class_type_params(bytes, index) {
-                        let Some(close) = matching_delimiter(bytes, index, b']') else {
-                            index += 1;
-                            continue;
-                        };
-                        index = close + 1;
-                        continue;
-                    }
-                    stack.push(bytes[index]);
-                    index += 1;
-                }
-                b')' | b']' | b'}' => {
-                    stack.pop();
-                    index += 1;
-                }
-                _ if !stack.is_empty() && expression_continuation_keyword(bytes, index) => {
-                    index = identifier_end(bytes, index, bytes.len());
-                }
-                byte if !stack.is_empty() && expression_atom_start_byte(byte) => {
-                    // `yield x` / `await x` are prefix expressions, not two
-                    // adjacent atoms missing a comma.
-                    if starts_identifier(bytes, index, b"yield") {
-                        index = identifier_end(bytes, index, bytes.len());
-                        let after_yield = skip_ascii_whitespace(bytes, index, bytes.len());
-                        if starts_identifier(bytes, after_yield, b"from") {
-                            index = identifier_end(bytes, after_yield, bytes.len());
-                        }
-                        continue;
-                    }
-                    if starts_identifier(bytes, index, b"await") {
-                        index = identifier_end(bytes, index, bytes.len());
-                        continue;
-                    }
-                    let atom_end = adjacent_atom_end(bytes, index).unwrap_or(index + 1);
-                    let next = skip_ascii_whitespace(bytes, atom_end, bytes.len());
-                    if next > atom_end
-                        && expression_atom_start(bytes, next)
-                        && !expression_continuation_keyword(bytes, next)
-                    {
-                        // The diagnostic covers both atoms, so it ends past
-                        // the whole second one.  `next + 1` ended past its
-                        // first byte instead, which is only the same thing
-                        // when that atom is one ASCII character.
-                        let second_end = adjacent_atom_end(bytes, next).unwrap_or(next + 1);
-                        return Some(CpythonDiagnostic::new(
-                            "invalid syntax. Perhaps you forgot a comma?".to_owned(),
-                            index,
-                            second_end,
-                        ));
-                    }
-                    index = atom_end;
-                }
-                _ => index += 1,
-            }
-        }
-    }
-    None
-}
-
-fn opening_bracket_is_class_type_params(bytes: &[u8], bracket: usize) -> bool {
-    let mut cursor = bracket;
-    while cursor > 0 && matches!(bytes[cursor - 1], b' ' | b'\t' | b'\x0c') {
-        cursor -= 1;
-    }
-    while cursor > 0
-        && bytes
-            .get(cursor - 1)
-            .is_some_and(|byte| *byte >= 0x80 || is_ascii_identifier_char(*byte))
-    {
-        cursor -= 1;
-    }
-    while cursor > 0 && matches!(bytes[cursor - 1], b' ' | b'\t' | b'\x0c') {
-        cursor -= 1;
-    }
-    cursor >= 5 && starts_identifier(bytes, cursor - 5, b"class")
-}
-
-fn expression_continuation_keyword(bytes: &[u8], index: usize) -> bool {
-    [
-        b"and".as_slice(),
-        b"else".as_slice(),
-        b"for".as_slice(),
-        b"if".as_slice(),
-        b"in".as_slice(),
-        b"is".as_slice(),
-        b"not".as_slice(),
-        b"or".as_slice(),
-    ]
-    .iter()
-    .any(|keyword| starts_identifier(bytes, index, keyword))
-}
-
-fn expression_atom_start(bytes: &[u8], index: usize) -> bool {
-    bytes
-        .get(index)
-        .is_some_and(|byte| expression_atom_start_byte(*byte))
-        || string_literal_end_at(bytes, index).is_some()
-}
-
-fn expression_atom_start_byte(byte: u8) -> bool {
-    byte >= 0x80
-        || byte == b'_'
-        || byte.is_ascii_alphabetic()
-        || byte.is_ascii_digit()
-        || matches!(byte, b'\'' | b'"' | b'(' | b'[' | b'{')
-}
-
-fn adjacent_atom_end(bytes: &[u8], index: usize) -> Option<usize> {
-    if let Some(string_end) = string_literal_end_at(bytes, index) {
-        return Some(string_end);
-    }
-    match bytes.get(index).copied()? {
-        byte if byte >= 0x80 || byte == b'_' || byte.is_ascii_alphabetic() => {
-            Some(identifier_end(bytes, index, bytes.len()))
-        }
-        byte if byte.is_ascii_digit() => {
-            let mut end = index + 1;
-            while end < bytes.len() && (bytes[end].is_ascii_alphanumeric() || bytes[end] == b'_') {
-                end += 1;
-            }
-            Some(end)
-        }
-        b'(' | b'[' | b'{' => Some(index + 1),
-        _ => None,
-    }
-}
-
-struct OpenDelimiter {
-    position: usize,
-    opener: u8,
-    in_format_spec: bool,
-}
-
-/// An f-string or t-string that runs off the end with a replacement field still open reports
-/// the brace rather than the missing quote, matching CPython — but only while the tokenizer is
-/// still reading the field's *expression*. Past the field's own `:` it is emitting FSTRING_MIDDLE
-/// again, so running out of input there is an unterminated literal like any other, and
-/// `f'{a:>5` gets the quote message where `f'{a` gets the brace.
-fn unclosed_replacement_field_error(
-    bytes: &[u8],
-    quote_start: usize,
-    content_start: usize,
-    content_end: usize,
-) -> Option<CpythonDiagnostic> {
-    interpolated_string_prefix(bytes, quote_start)?;
-
-    // Brackets and quotes are delimiters only once a field is open; in the literal's text they
-    // are ordinary characters. And past a field's own format spec the tokenizer emits literal
-    // text again, so a field still open at end of input is an unclosed brace only before that.
-    let mut open: Vec<OpenDelimiter> = Vec::new();
-    let mut index = content_start;
-    while index < content_end {
-        let inside_expression = matches!(
-            open.last(),
-            Some(OpenDelimiter {
-                opener: b'{',
-                in_format_spec: false,
-                ..
-            })
-        );
-        match bytes[index] {
-            // `{{` and `}}` escape only in literal text, which is where a brace at depth zero is.
-            b'{' if open.is_empty() && bytes.get(index + 1) == Some(&b'{') => index += 2,
-            b'}' if open.is_empty() && bytes.get(index + 1) == Some(&b'}') => index += 2,
-            b'{' => {
-                open.push(OpenDelimiter {
-                    position: index,
-                    opener: b'{',
-                    in_format_spec: false,
-                });
-                index += 1;
-            }
-            b'}' => {
-                open.pop();
-                index += 1;
-            }
-            byte @ (b'(' | b'[') if !open.is_empty() => {
-                open.push(OpenDelimiter {
-                    position: index,
-                    opener: byte,
-                    in_format_spec: false,
-                });
-                index += 1;
-            }
-            b')' | b']' if !open.is_empty() => {
-                open.pop();
-                index += 1;
-            }
-            // Only the field's own `:` opens a format spec — one in a slice, a display or a
-            // lambda belongs to whatever bracket encloses it.
-            b':' if inside_expression => {
-                open.last_mut().expect("a brace is open").in_format_spec = true;
-                index += 1;
-            }
-            b'\'' | b'"' if !open.is_empty() => {
-                index = skip_quoted_string(bytes, index).min(content_end);
-            }
-            b'#' if inside_expression => {
-                index = skip_replacement_field_comment(bytes, index, content_end);
-            }
-            _ => index += 1,
-        }
-    }
-
-    // CPython names the innermost unclosed delimiter, so a bracket opened inside the expression
-    // takes the message from the field that encloses it.
-    let &OpenDelimiter {
-        position,
-        opener,
-        in_format_spec,
-    } = open.last()?;
-    (!in_format_spec).then(|| {
-        CpythonDiagnostic::new(
-            format!("'{}' was never closed", opener as char),
-            position,
-            position + 1,
-        )
-        .with_unclosed_bracket()
-    })
-}
-
-fn unterminated_string_message(
-    detected_line: usize,
-    triple: bool,
-    has_escaped_quote: bool,
-    prefix: Option<&str>,
-) -> String {
-    // CPython names the literal kind, e.g. "unterminated f-string literal".
-    let kind = prefix.unwrap_or("string");
-    if triple {
-        format!("unterminated triple-quoted {kind} literal (detected at line {detected_line})")
-    // The escaped-quote hint belongs to the plain-string branch of CPython's tokenizer alone.
-    // Its interpolated branch has only the two forms above and below, so pairing the hint with
-    // a prefix would invent a message CPython never emits.
-    } else if has_escaped_quote && prefix.is_none() {
-        format!(
-            "unterminated {kind} literal (detected at line {detected_line}); perhaps you escaped the end quote?"
-        )
-    } else {
-        format!("unterminated {kind} literal (detected at line {detected_line})")
-    }
-}
-
-fn expected_opening_bracket(closing: char) -> char {
-    match closing {
-        ')' => '(',
-        ']' => '[',
-        '}' => '{',
-        _ => unreachable!(),
-    }
-}
-
-/// A bracket diagnostic, and whether it is an opener that was never closed. The caller needs
-/// that apart from the message because ruff reports the unclosed case as an EOF error.
-#[derive(Clone)]
-struct BracketError {
-    diagnostic: CpythonDiagnostic,
-    unclosed: bool,
-}
-
-fn bracket_syntax_error(source: &str) -> Option<BracketError> {
-    let mut stack: Vec<(char, usize, usize)> = Vec::new();
-    let mut in_string = false;
-    let mut string_quote = '\0';
-    let mut triple_quote = false;
-    let mut escape_next = false;
-    let mut is_raw_string = false;
-    let mut line = 1usize;
-
-    let chars: Vec<(usize, char)> = source.char_indices().collect();
-    let mut index = 0;
-    while index < chars.len() {
-        let (byte_offset, ch) = chars[index];
-
-        if ch == '\n' {
-            line += 1;
-        }
-
-        if escape_next {
-            escape_next = false;
-            index += 1;
-            continue;
-        }
-
-        if in_string {
-            if ch == '\\' && !is_raw_string {
-                escape_next = true;
-            } else if triple_quote {
-                if ch == string_quote
-                    && index + 2 < chars.len()
-                    && chars[index + 1].1 == string_quote
-                    && chars[index + 2].1 == string_quote
-                {
-                    in_string = false;
-                    index += 3;
-                    continue;
-                }
-            } else if ch == string_quote {
-                in_string = false;
-            }
-            index += 1;
-            continue;
-        }
-
-        if ch == '#' {
-            while index < chars.len() && chars[index].1 != '\n' {
-                index += 1;
-            }
-            continue;
-        }
-
-        if ch == '\\' {
-            match chars.get(index + 1).map(|(_, next)| *next) {
-                Some('\n' | '\r') => {
-                    escape_next = true;
-                    index += 1;
-                    continue;
-                }
-                Some(_) => {
-                    index += 2;
-                    continue;
-                }
-                None => {
-                    index += 1;
-                    continue;
-                }
-            }
-        }
-
-        if ch == '\'' || ch == '"' {
-            is_raw_string = false;
-            for look_back in 1..=2.min(index) {
-                let prev = chars[index - look_back].1;
-                if matches!(prev, 'r' | 'R') {
-                    is_raw_string = true;
-                    break;
-                }
-                if !matches!(prev, 'b' | 'B' | 'f' | 'F' | 'u' | 'U') {
-                    break;
-                }
-            }
-            string_quote = ch;
-            if index + 2 < chars.len() && chars[index + 1].1 == ch && chars[index + 2].1 == ch {
-                triple_quote = true;
-                in_string = true;
-                index += 3;
-                continue;
-            }
-            triple_quote = false;
-            in_string = true;
-            index += 1;
-            continue;
-        }
-
-        match ch {
-            '(' | '[' | '{' => stack.push((ch, byte_offset, line)),
-            ')' | ']' | '}' => {
-                let expected = expected_opening_bracket(ch);
-                let Some(&(opening, _, opening_line)) = stack.last() else {
-                    return Some(BracketError {
-                        diagnostic: CpythonDiagnostic::new(
-                            format!("unmatched '{ch}'"),
-                            byte_offset,
-                            byte_offset,
-                        ),
-                        unclosed: false,
-                    });
-                };
-                if opening == expected {
-                    stack.pop();
-                } else {
-                    let suffix = if opening_line != line {
-                        format!(" on line {opening_line}")
-                    } else {
-                        String::new()
-                    };
-                    return Some(BracketError {
-                        diagnostic: CpythonDiagnostic::new(
-                            format!(
-                                "closing parenthesis '{ch}' does not match opening parenthesis '{opening}'{suffix}"
-                            ),
-                            byte_offset,
-                            byte_offset,
-                        ),
-                        unclosed: false,
-                    });
-                }
-            }
-            _ => {}
-        }
-
-        index += 1;
-    }
-
-    stack.last().map(|(opening, byte_offset, _)| BracketError {
-        diagnostic: CpythonDiagnostic::new(
-            format!("'{opening}' was never closed"),
-            *byte_offset,
-            *byte_offset,
-        ),
-        unclosed: true,
-    })
-}
-
-fn is_legacy_statement_expression_start(byte: u8) -> bool {
-    byte >= 0x80
-        || byte == b'_'
-        || byte.is_ascii_alphabetic()
-        || byte.is_ascii_digit()
-        || matches!(byte, b'\'' | b'"' | b'{' | b'[')
-}
-
-fn legacy_statement_container_has_invalid_attribute(bytes: &[u8], start: usize) -> bool {
-    let Some(&opening) = bytes.get(start) else {
-        return false;
-    };
-    if !matches!(opening, b'{' | b'[') {
-        return false;
-    }
-
-    let mut index = start;
+fn eval_has_assignment_before(bytes: &[u8], end: usize) -> bool {
+    let mut index = 0;
     let mut level = 0usize;
-    while index < bytes.len() {
+    let mut in_lambda_params = false;
+    while index < end {
         match bytes[index] {
             b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
+                while index < end && bytes[index] != b'\n' {
                     index += 1;
                 }
             }
-            b'\n' | b';' if level == 0 => return false,
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
+            b'\'' | b'"' => index = skip_quoted_string(bytes, index),
             b'(' | b'[' | b'{' => {
                 level += 1;
                 index += 1;
@@ -6250,320 +668,121 @@ fn legacy_statement_container_has_invalid_attribute(bytes: &[u8], start: usize)
             b')' | b']' | b'}' => {
                 level = level.saturating_sub(1);
                 index += 1;
-                if level == 0 {
-                    return false;
-                }
             }
-            b'.' => {
-                let mut cursor = index + 1;
-                while matches!(bytes.get(cursor), Some(b' ' | b'\t' | b'\x0c')) {
-                    cursor += 1;
-                }
-                if matches!(bytes.get(cursor), Some(b')' | b']' | b'}')) {
-                    return true;
-                }
+            b':' if level == 0 => {
+                in_lambda_params = false;
                 index += 1;
             }
+            b'=' if level == 0
+                && !in_lambda_params
+                && bytes.get(index + 1) != Some(&b'=')
+                && !matches!(
+                    bytes.get(index.saturating_sub(1)),
+                    Some(b':' | b'!' | b'<' | b'>')
+                ) =>
+            {
+                return true;
+            }
+            _ if level == 0 && starts_identifier(bytes, index, b"lambda") => {
+                in_lambda_params = true;
+                index += b"lambda".len();
+            }
             _ => index += 1,
         }
     }
     false
 }
 
-fn invalid_legacy_statement_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            b'p' | b'e' => {
-                let keyword = if starts_identifier(bytes, index, b"print") {
-                    Some("print")
-                } else if starts_identifier(bytes, index, b"exec") {
-                    Some("exec")
-                } else {
-                    None
-                };
-                let Some(keyword) = keyword else {
-                    index += 1;
-                    continue;
-                };
-                let after_keyword = index + keyword.len();
-                if !matches!(bytes.get(after_keyword), Some(b' ' | b'\t' | b'\x0c')) {
-                    index = after_keyword;
-                    continue;
-                }
-                let mut cursor = after_keyword;
-                while matches!(bytes.get(cursor), Some(b' ' | b'\t' | b'\x0c')) {
-                    cursor += 1;
-                }
-                if legacy_statement_container_has_invalid_attribute(bytes, cursor) {
-                    index = after_keyword;
-                    continue;
-                }
-                if bytes.get(cursor).is_some_and(|byte| {
-                    *byte != b'(' && is_legacy_statement_expression_start(*byte)
-                }) {
-                    return Some(CpythonDiagnostic::new(
-                        format!(
-                            "Missing parentheses in call to '{keyword}'. Did you mean {keyword}(...)?"
-                        ),
-                        index,
-                        after_keyword,
-                    ));
-                }
-                index = after_keyword;
-            }
-            _ => index += 1,
+fn interpolated_string_prefix(bytes: &[u8], quote: usize) -> Option<&'static str> {
+    let prev = quote.checked_sub(1).and_then(|index| bytes.get(index))?;
+    let lower_prev = prev.to_ascii_lowercase();
+    let (prefix_start, marker) = if matches!(lower_prev, b'f' | b't') {
+        if quote >= 2 && bytes[quote - 2].eq_ignore_ascii_case(&b'r') {
+            (quote - 2, lower_prev)
+        } else {
+            (quote - 1, lower_prev)
         }
-    }
-    None
-}
+    } else if lower_prev == b'r'
+        && quote >= 2
+        && matches!(bytes[quote - 2].to_ascii_lowercase(), b'f' | b't')
+    {
+        (quote - 2, bytes[quote - 2].to_ascii_lowercase())
+    } else {
+        return None;
+    };
 
-/// Return the syntax error for a decimal integer literal exceeding the configured limit.
-///
-/// The parser has already distinguished integer literals from strings, comments, floats, and
-/// complex numbers. Inspecting its tokens keeps the limit consistent for every source parsing
-/// entry point without reimplementing Python's lexer here.
-#[must_use]
-pub fn long_decimal_integer_literal_error(
-    source_file: &SourceFile,
-    tokens: &Tokens,
-    max_str_digits: usize,
-) -> Option<CompileError> {
-    if max_str_digits == 0 {
+    if prefix_start > 0 && identifier_continue_before(bytes, prefix_start) {
         return None;
     }
-    tokens.iter().find_map(|token| {
-        if token.kind() != TokenKind::Int {
-            return None;
-        }
-        let literal = source_file.source_text().slice(token.range());
-        if literal
-            .as_bytes()
-            .get(..2)
-            .is_some_and(|prefix| matches!(prefix, b"0x" | b"0X" | b"0o" | b"0O" | b"0b" | b"0B"))
-        {
-            return None;
-        }
-        let digits = literal.bytes().filter(u8::is_ascii_digit).count();
-        (digits > max_str_digits).then(|| {
-            let start = token.range().start().to_usize();
-            CompileError::from_source_error(source_file, CpythonDiagnostic::new(format!(
-                    "Exceeds the limit ({max_str_digits} digits) for integer string conversion: value has {digits} digits; use sys.set_int_max_str_digits() to increase the limit - Consider hexadecimal for huge integer literals to avoid decimal conversion limits."
-                ), start, start))
-        })
+
+    Some(if marker == b'f' {
+        "f-string"
+    } else {
+        "t-string"
     })
 }
 
-fn invalid_parenthesized_import_star_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            b'f' if starts_identifier(bytes, index, b"from") => {
-                let mut cursor = index + 4;
-                while cursor < bytes.len() && !matches!(bytes[cursor], b'\n' | b';') {
-                    if starts_identifier(bytes, cursor, b"import") {
-                        cursor += 6;
-                        while matches!(bytes.get(cursor), Some(b' ' | b'\t' | b'\r')) {
-                            cursor += 1;
-                        }
-                        if bytes.get(cursor) == Some(&b'(') {
-                            cursor += 1;
-                            while cursor < bytes.len()
-                                && !matches!(bytes[cursor], b')' | b'\n' | b';')
-                            {
-                                if bytes[cursor] == b'*' {
-                                    return Some(CpythonDiagnostic::new(
-                                        "invalid syntax".to_owned(),
-                                        cursor,
-                                        cursor + 1,
-                                    ));
-                                }
-                                cursor += 1;
-                            }
-                        }
-                        break;
-                    }
-                    cursor += 1;
-                }
-                index = cursor;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
+const MAXFSTRINGLEVEL: usize = 150;
 
-fn prefix_letters_before_quote(bytes: &[u8], quote_index: usize) -> Option<(usize, Vec<u8>)> {
-    let mut letters = Vec::new();
-    let mut index = quote_index;
-    while index > 0 {
-        let byte = bytes[index - 1];
-        if !matches!(
-            byte,
-            b'r' | b'R' | b'b' | b'B' | b'u' | b'U' | b'f' | b'F' | b't' | b'T'
-        ) {
-            break;
-        }
-        letters.push(byte.to_ascii_lowercase());
-        index -= 1;
-    }
-    if letters.is_empty() {
-        return None;
-    }
-    if index > 0 && (bytes[index - 1] == b'_' || bytes[index - 1].is_ascii_alphabetic()) {
-        return None;
+fn skip_string_token(bytes: &[u8], quote_index: usize) -> usize {
+    if interpolated_string_prefix(bytes, quote_index).is_some() {
+        interpolated_string_end(bytes, quote_index).unwrap_or(bytes.len())
+    } else {
+        skip_quoted_string(bytes, quote_index)
     }
-    letters.reverse();
-    Some((index, letters))
 }
 
-fn incompatible_string_prefix_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
+fn interpolated_string_end(bytes: &[u8], quote_index: usize) -> Option<usize> {
+    let quote = bytes[quote_index];
+    let triple =
+        bytes.get(quote_index + 1) == Some(&quote) && bytes.get(quote_index + 2) == Some(&quote);
+    let quote_len = if triple { 3 } else { 1 };
+    let mut index = quote_index + quote_len;
+    let mut brace_depth = 0usize;
     while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
+        if brace_depth == 0 {
+            if bytes[index] == b'\\' {
+                index = (index + 2).min(bytes.len());
+                continue;
             }
-            b'\'' | b'"' => {
-                if let Some((start, letters)) = prefix_letters_before_quote(bytes, index)
-                    && let Some(message) = incompatible_prefix_message(&letters)
-                {
-                    return Some(CpythonDiagnostic::new(message, start, start + 1));
-                }
-                index = skip_string_token(bytes, index);
+            if triple
+                && bytes.get(index) == Some(&quote)
+                && bytes.get(index + 1) == Some(&quote)
+                && bytes.get(index + 2) == Some(&quote)
+            {
+                return Some(index + 3);
             }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn incompatible_prefix_message(letters: &[u8]) -> Option<String> {
-    if letters.len() < 2 {
-        return None;
-    }
-    let mut seen_r = false;
-    let mut seen_b = false;
-    let mut seen_u = false;
-    let mut seen_f = false;
-    let mut seen_t = false;
-    for &letter in letters {
-        match letter {
-            b'r' if seen_r => return None,
-            b'b' if seen_b => return None,
-            b'u' if seen_u => return None,
-            b'f' if seen_f => return None,
-            b't' if seen_t => return None,
-            b'r' => seen_r = true,
-            b'b' => seen_b = true,
-            b'u' => seen_u = true,
-            b'f' => seen_f = true,
-            b't' => seen_t = true,
-            _ => {}
-        }
-    }
-    let pair = if seen_u && seen_b {
-        ("u", "b")
-    } else if seen_u && seen_r {
-        ("u", "r")
-    } else if seen_u && seen_f {
-        ("u", "f")
-    } else if seen_u && seen_t {
-        ("u", "t")
-    } else if seen_b && seen_f {
-        ("b", "f")
-    } else if seen_b && seen_t {
-        ("b", "t")
-    } else if seen_f && seen_t {
-        ("f", "t")
-    } else {
-        return None;
-    };
-    Some(format!(
-        "'{}' and '{}' prefixes are incompatible",
-        pair.0, pair.1
-    ))
-}
-
-fn malformed_unicode_n_escape_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
+            if !triple && bytes[index] == quote {
+                return Some(index + 1);
             }
-            b'\'' | b'"' => {
-                let quote_index = index;
-                let interpolated = interpolated_string_prefix(bytes, quote_index).is_some();
-                let Some((content_start, content_end)) =
-                    quoted_string_content_range(bytes, quote_index, bytes[quote_index])
-                else {
-                    index = skip_quoted_string(bytes, quote_index);
-                    continue;
-                };
-                if let Some(error) = malformed_unicode_n_in_content(
-                    bytes,
-                    content_start,
-                    content_end,
-                    quote_index,
-                    interpolated,
-                ) {
-                    return Some(error);
+            if bytes[index] == b'{' {
+                if bytes.get(index + 1) == Some(&b'{') {
+                    index += 2;
+                } else {
+                    brace_depth = 1;
+                    index += 1;
                 }
-                index = skip_string_token(bytes, quote_index);
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn malformed_unicode_n_in_content(
-    bytes: &[u8],
-    start: usize,
-    end: usize,
-    quote_index: usize,
-    interpolated: bool,
-) -> Option<CpythonDiagnostic> {
-    let mut index = start;
-    let mut brace_depth = 0usize;
-    while index + 1 < end {
-        if interpolated && brace_depth == 0 && bytes[index] == b'{' {
-            if bytes.get(index + 1) == Some(&b'{') {
+            } else if bytes[index] == b'}' && bytes.get(index + 1) == Some(&b'}') {
                 index += 2;
-                continue;
+            } else {
+                index += 1;
             }
-            brace_depth = 1;
-            index += 1;
-            continue;
-        }
-        if interpolated && brace_depth > 0 {
+        } else {
             match bytes[index] {
-                b'\'' | b'"' => index = skip_string_token(bytes, index).max(index + 1),
+                quote_ch @ (b'\'' | b'"') => {
+                    if quoted_string_is_closed(bytes, index) {
+                        index = skip_string_token(bytes, index).max(index + 1);
+                    } else if !triple && quote_ch == quote {
+                        return Some(index + 1);
+                    } else {
+                        index = skip_string_token(bytes, index).max(index + 1);
+                    }
+                }
+                b'#' => {
+                    while index < bytes.len() && bytes[index] != b'\n' {
+                        index += 1;
+                    }
+                }
                 b'{' => {
                     brace_depth += 1;
                     index += 1;
@@ -6572,54 +791,63 @@ fn malformed_unicode_n_in_content(
                     brace_depth -= 1;
                     index += 1;
                 }
+                b'\\' => index = (index + 2).min(bytes.len()),
                 _ => index += 1,
             }
-            continue;
-        }
-        if bytes[index] == b'\\' && bytes[index + 1] == b'N' {
-            let escape_start = index;
-            if bytes.get(index + 2) == Some(&b'{') {
-                let mut look = index + 3;
-                while look < end && bytes[look] != b'}' {
-                    look += 1;
-                }
-                if look >= end {
-                    return Some(unicode_n_diagnostic(escape_start, end, start, quote_index));
-                }
-                index = look + 1;
-                continue;
-            }
-            return Some(unicode_n_diagnostic(
-                escape_start,
-                escape_start + 2,
-                start,
-                quote_index,
-            ));
-        }
-        if interpolated && bytes[index] == b'}' && bytes.get(index + 1) == Some(&b'}') {
-            index += 2;
-            continue;
         }
-        index += 1;
     }
     None
 }
 
-fn unicode_n_diagnostic(
-    escape_start: usize,
-    escape_end: usize,
-    content_start: usize,
-    quote_index: usize,
-) -> CpythonDiagnostic {
-    let start = escape_start - content_start;
-    let end = escape_end.saturating_sub(content_start).saturating_sub(1);
-    CpythonDiagnostic::new(
-        format!(
-            "(unicode error) 'unicodeescape' codec can't decode bytes in position {start}-{end}: malformed \\N character escape"
-        ),
-        quote_index,
-        quote_index + 1,
-    )
+fn quote_len_at(bytes: &[u8], quote_index: usize) -> usize {
+    let quote = bytes[quote_index];
+    if bytes.get(quote_index + 1) == Some(&quote) && bytes.get(quote_index + 2) == Some(&quote) {
+        3
+    } else {
+        1
+    }
+}
+
+fn interpolated_string_content_range(bytes: &[u8], quote_index: usize) -> Option<(usize, usize)> {
+    let end = interpolated_string_end(bytes, quote_index)?;
+    let quote_len = quote_len_at(bytes, quote_index);
+    Some((quote_index + quote_len, end - quote_len))
+}
+
+/// Return the syntax error for a decimal integer literal exceeding the configured limit.
+///
+/// The parser has already distinguished integer literals from strings, comments, floats, and
+/// complex numbers. Inspecting its tokens keeps the limit consistent for every source parsing
+/// entry point without reimplementing Python's lexer here.
+#[must_use]
+pub fn long_decimal_integer_literal_error(
+    source_file: &SourceFile,
+    tokens: &Tokens,
+    max_str_digits: usize,
+) -> Option<CompileError> {
+    if max_str_digits == 0 {
+        return None;
+    }
+    tokens.iter().find_map(|token| {
+        if token.kind() != TokenKind::Int {
+            return None;
+        }
+        let literal = source_file.source_text().slice(token.range());
+        if literal
+            .as_bytes()
+            .get(..2)
+            .is_some_and(|prefix| matches!(prefix, b"0x" | b"0X" | b"0o" | b"0O" | b"0b" | b"0B"))
+        {
+            return None;
+        }
+        let digits = literal.bytes().filter(u8::is_ascii_digit).count();
+        (digits > max_str_digits).then(|| {
+            let start = token.range().start().to_usize();
+            CompileError::from_source_error(source_file, CpythonDiagnostic::new(format!(
+                    "Exceeds the limit ({max_str_digits} digits) for integer string conversion: value has {digits} digits; use sys.set_int_max_str_digits() to increase the limit - Consider hexadecimal for huge integer literals to avoid decimal conversion limits."
+                ), start, start))
+        })
+    })
 }
 
 fn too_many_nested_interpolated_strings(source: &str) -> Option<CpythonDiagnostic> {
@@ -6668,76 +896,6 @@ fn too_many_nested_interpolated_strings_in(
     None
 }
 
-fn too_many_nested_parentheses_error(source: &str) -> Option<CpythonDiagnostic> {
-    const MAXLEVEL: usize = 200;
-
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    let mut level = 0usize;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            b'(' | b'[' | b'{' => {
-                if level >= MAXLEVEL {
-                    return Some(CpythonDiagnostic::new(
-                        "too many nested parentheses".to_owned(),
-                        index,
-                        index + 1,
-                    ));
-                }
-                level += 1;
-                index += 1;
-            }
-            b')' | b']' | b'}' => {
-                level = level.saturating_sub(1);
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
-fn invalid_unparenthesized_yield_after_comma_error(source: &str) -> Option<CpythonDiagnostic> {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => {
-                index = skip_quoted_string(bytes, index);
-            }
-            b',' => {
-                let mut cursor = index + 1;
-                while matches!(bytes.get(cursor), Some(b' ' | b'\t' | b'\x0c')) {
-                    cursor += 1;
-                }
-                if starts_identifier(bytes, cursor, b"yield") {
-                    return Some(CpythonDiagnostic::new(
-                        "invalid syntax".to_owned(),
-                        cursor,
-                        cursor + 5,
-                    ));
-                }
-                index += 1;
-            }
-            _ => index += 1,
-        }
-    }
-    None
-}
-
 /// Horizontal and vertical space the tokenizer skips, not `str::trim()`.
 const fn is_ascii_tokenizer_whitespace(c: char) -> bool {
     matches!(c, ' ' | '\t' | '\n' | '\r' | '\x0c')
@@ -6773,6 +931,7 @@ fn single_mode_blank_source_error(source_file: &SourceFile) -> Option<CompileErr
             source_path: source_file.name().to_owned(),
             is_unclosed_bracket: false,
             is_unclosed_string: false,
+            eof_token: None,
         }));
     }
     Some(CompileError::from_source_error(
@@ -6796,6 +955,43 @@ pub fn leading_byte_order_mark_error(source_file: &SourceFile) -> Option<Compile
     })
 }
 
+fn too_many_nested_parentheses_error(source: &str) -> Option<CpythonDiagnostic> {
+    const MAXLEVEL: usize = 200;
+
+    let bytes = source.as_bytes();
+    let mut index = 0;
+    let mut level = 0usize;
+    while index < bytes.len() {
+        match bytes[index] {
+            b'#' => {
+                while index < bytes.len() && bytes[index] != b'\n' {
+                    index += 1;
+                }
+            }
+            b'\'' | b'"' => {
+                index = skip_quoted_string(bytes, index);
+            }
+            b'(' | b'[' | b'{' => {
+                if level >= MAXLEVEL {
+                    return Some(CpythonDiagnostic::new(
+                        "too many nested parentheses".to_owned(),
+                        index,
+                        index,
+                    ));
+                }
+                level += 1;
+                index += 1;
+            }
+            b')' | b']' | b'}' => {
+                level = level.saturating_sub(1);
+                index += 1;
+            }
+            _ => index += 1,
+        }
+    }
+    None
+}
+
 /// Source-level errors raised before parsing, as CPython's tokenizer does.
 ///
 /// Checking after the parse would build the tree first, and one nested that
@@ -6818,17 +1014,7 @@ fn post_parse_source_error(
     if let Some(error) = too_many_nested_interpolated_strings(source_file.source_text()) {
         return Some(CompileError::from_source_error(source_file, error));
     }
-    if let Some(error) =
-        long_decimal_integer_literal_error(source_file, tokens, opts.int_max_str_digits)
-    {
-        return Some(error);
-    }
-    invalid_call_argument_error(source_file.source_text())
-        .or_else(|| invalid_match_mapping_rest_wildcard_error(source_file.source_text()))
-        .or_else(|| invalid_match_as_target_error(source_file.source_text()))
-        .or_else(|| invalid_unparenthesized_yield_after_comma_error(source_file.source_text()))
-        .or_else(|| invalid_parenthesized_import_star_error(source_file.source_text()))
-        .map(|error| CompileError::from_source_error(source_file, error))
+    long_decimal_integer_literal_error(source_file, tokens, opts.int_max_str_digits)
 }
 
 fn is_compound_stmt(stmt: &ast::Stmt) -> bool {
@@ -6926,7 +1112,8 @@ pub fn too_deeply_nested_error(
 /// A bare generator expression is one: `f(x for x in y)` is the `primary
 /// genexp` alternative of a call, and a class header only takes `arguments`,
 /// which has no such alternative. A format spec nested more than two deep is
-/// the other; the tokenizer runs out of nesting levels for it.
+/// the other; the tokenizer runs out of nesting levels for it. A lazy
+/// `__future__` import is rejected by the `checked_from_import` action.
 #[doc(hidden)]
 #[must_use]
 pub fn unsupported_grammar_error(ast: &ast::Mod, source_file: &SourceFile) -> Option<CompileError> {
@@ -6982,6 +1169,18 @@ pub fn unsupported_grammar_error(ast: &ast::Mod, source_file: &SourceFile) -> Op
             if self.error.is_some() {
                 return;
             }
+            if let ast::Stmt::ImportFrom(import) = stmt
+                && import.is_lazy
+                && import.level == 0
+                && import
+                    .module
+                    .as_ref()
+                    .is_some_and(|module| module.as_str() == "__future__")
+            {
+                let lazy = ruff_text_size::TextRange::at(import.range.start(), 4.into());
+                self.fail("lazy from __future__ import is not allowed", lazy);
+                return;
+            }
             if let ast::Stmt::ClassDef(class_def) = stmt
                 && let Some(arguments) = &class_def.arguments
                 && let [ast::Expr::Generator(generator)] = &arguments.args[..]
@@ -7006,7 +1205,7 @@ pub fn unsupported_grammar_error(ast: &ast::Mod, source_file: &SourceFile) -> Op
             match expr {
                 ast::Expr::FString(fstring) => {
                     for part in &fstring.value {
-                        if let ast::FStringPart::FString(part) = part {
+                        if let ast::FStringPartRef::FString(part) = part {
                             self.check_format_specs("f-string", &part.elements, 0);
                         }
                     }
@@ -7042,22 +1241,6 @@ fn single_mode_body_error(body: &[ast::Stmt], source_file: &SourceFile) -> Optio
     let first_start = source_code.source_location(first.range().start(), PositionEncoding::Utf8);
     let first_end = source_code.source_location(first.range().end(), PositionEncoding::Utf8);
 
-    if body.iter().skip(1).any(|stmt| {
-        source_code
-            .source_location(stmt.range().start(), PositionEncoding::Utf8)
-            .line
-            > first_start.line
-    }) {
-        return Some(CompileError::from_source_error(
-            source_file,
-            CpythonDiagnostic::new(
-                "multiple statements found while compiling a single statement".to_owned(),
-                first.range().end().to_usize(),
-                first.range().end().to_usize(),
-            ),
-        ));
-    }
-
     if is_compound_stmt(first)
         && first_start.line == first_end.line
         && !ends_with_line_break(source_file.source_text())
@@ -7074,6 +1257,99 @@ fn single_mode_body_error(body: &[ast::Stmt], source_file: &SourceFile) -> Optio
     None
 }
 
+/// Converts the first parse error. A tokenizer error that follows an earlier syntax error is
+/// only found by the pass over the rest of the source, so it never asks for more input.
+fn first_parse_error(
+    parsed: parser::Parsed<ast::Mod>,
+    source_file: &SourceFile,
+    mode: Mode,
+) -> Result<parser::Parsed<ast::Mod>, CompileError> {
+    let Some((first, rest)) = parsed.errors().split_first() else {
+        return Ok(parsed);
+    };
+    let after_syntax_error = rest.iter().any(|error| {
+        !matches!(error.error, ParseErrorType::Lexical(_))
+            && error.location.start() < first.location.start()
+    });
+    let mut error = CompileError::from_ruff_parse_error(first.clone(), source_file, mode);
+    if after_syntax_error && let CompileError::Parse(error) = &mut error {
+        error.is_unclosed_string = false;
+    }
+    Err(error)
+}
+
+/// Single mode reads only the first statement when it is a simple statement, so any code after
+/// its line is reported as multiple statements, ahead of errors the rest of the source has.
+#[must_use]
+pub fn single_mode_multiple_statements_error(
+    source_file: &SourceFile,
+    parsed: &parser::Parsed<ast::Mod>,
+) -> Option<CompileError> {
+    let ast::Mod::Module(module) = parsed.syntax() else {
+        return None;
+    };
+    let first = module.body.first()?;
+    if is_compound_stmt(first) {
+        // The interactive grammar ends a compound statement with a NEWLINE,
+        // so the first token of a following statement is invalid syntax.
+        let next = module.body.get(1)?;
+        if parsed
+            .errors()
+            .iter()
+            .any(|error| error.location.start() <= next.start())
+        {
+            return None;
+        }
+        let token = parsed
+            .tokens()
+            .iter()
+            .find(|token| token.start() >= next.start() && !token.range().is_empty())?;
+        return Some(CompileError::from_source_error(
+            source_file,
+            CpythonDiagnostic::new(
+                "invalid syntax".to_owned(),
+                token.start().to_usize(),
+                token.end().to_usize(),
+            ),
+        ));
+    }
+    let tokens = parsed.tokens();
+    let newline_index = tokens
+        .iter()
+        .position(|token| token.kind() == TokenKind::Newline)?;
+    let newline = &tokens[newline_index];
+    if parsed
+        .errors()
+        .iter()
+        .any(|error| error.location.start() < newline.end())
+    {
+        return None;
+    }
+    let mut rest = &source_file.source_text()[newline.end().to_usize()..];
+    loop {
+        rest = rest.trim_start_matches([' ', '\t', '\n', '\r', '\x0c']);
+        match rest.strip_prefix('#') {
+            Some(comment) => rest = comment.find('\n').map_or("", |end| &comment[end..]),
+            None if rest.is_empty() => return None,
+            None => break,
+        }
+    }
+    // The error is at the newline token, which starts at a trailing comment.
+    let position = match newline_index.checked_sub(1).map(|index| &tokens[index]) {
+        Some(comment) if comment.kind() == TokenKind::Comment => comment.start(),
+        _ => newline.start(),
+    }
+    .to_usize();
+    Some(CompileError::from_source_error(
+        source_file,
+        CpythonDiagnostic::new(
+            "multiple statements found while compiling a single statement".to_owned(),
+            position,
+            position,
+        ),
+    ))
+}
+
 fn single_mode_source_error(ast: &ast::Mod, source_file: &SourceFile) -> Option<CompileError> {
     let ast::Mod::Module(module) = ast else {
         return None;
@@ -7277,12 +1553,16 @@ fn _compile_with_syntax_warning_handler<'a>(
             .contains(core::bytecode::CodeFlags::FUTURE_BARRY_AS_BDFL),
     );
     pre_parse_source_error(&source_file)?;
-    let parsed = parser::parse(barry_source.source(), parser_options);
-    if let Some(error) = barry_source.diagnostic(parsed.as_ref().err(), &source_file) {
+    let parsed = parser::parse_unchecked(barry_source.source(), parser_options);
+    if matches!(mode, Mode::Single)
+        && let Some(error) = single_mode_multiple_statements_error(&source_file, &parsed)
+    {
         return Err(error);
     }
-    let parsed =
-        parsed.map_err(|err| CompileError::from_ruff_parse_error(err, &source_file, mode))?;
+    if let Some(error) = barry_source.diagnostic(parsed.errors().first(), &source_file) {
+        return Err(error);
+    }
+    let parsed = first_parse_error(parsed, &source_file, mode)?;
     if matches!(mode, Mode::Single)
         && let Some(error) = single_mode_blank_source_error(&source_file)
     {
@@ -7503,6 +1783,56 @@ pub fn prepare_barry_as_flufl_source(
     }
 }
 
+/// Parse-only state for a native interactive record. This never runs codegen,
+/// emits Python warnings, or changes the caller's future flags.
+pub struct InteractiveInput {
+    pub future_features: core::bytecode::CodeFlags,
+    pub empty: bool,
+}
+
+/// The native interactive grammar terminates compound statements with an empty
+/// physical line (or EOF), unlike the module grammar used by the Ruff parser.
+/// Use the parsed statement shape rather than a second ad-hoc source lexer.
+pub fn interactive_input(
+    source: &str,
+    source_path: &str,
+    future_features: core::bytecode::CodeFlags,
+    terminated: bool,
+) -> Result<Option<InteractiveInput>, CompileError> {
+    let source_file = SourceFileBuilder::new(source_path, source).finish();
+    pre_parse_source_error(&source_file)?;
+    let options = parser::ParseOptions::from(parser::Mode::Module);
+    let prepared = prepare_barry_as_flufl_source(
+        source,
+        options.clone(),
+        future_features.contains(core::bytecode::CodeFlags::FUTURE_BARRY_AS_BDFL),
+    );
+    let parsed = parser::parse_unchecked(prepared.source(), options);
+    if let Some(error) = single_mode_multiple_statements_error(&source_file, &parsed) {
+        return Err(error);
+    }
+    if let Some(error) = prepared.diagnostic(parsed.errors().first(), &source_file) {
+        return Err(error);
+    }
+    let parsed = first_parse_error(parsed, &source_file, Mode::Single)?;
+    let ast::Mod::Module(module) = parsed.syntax() else {
+        unreachable!()
+    };
+    // A compound statement ends with an empty line or EOF.
+    if !terminated && module.body.first().is_some_and(is_compound_stmt) {
+        return Ok(None);
+    }
+    if let Some(error) = unsupported_grammar_error(parsed.syntax(), &source_file) {
+        return Err(error);
+    }
+    let future_features = codegen::preprocess::checked_future_features_in_body(&module.body)
+        .map_err(|error| future_feature_error(error, &source_file))?;
+    Ok(Some(InteractiveInput {
+        future_features,
+        empty: module.body.is_empty(),
+    }))
+}
+
 pub fn compile_with_syntax_warning_handler<'a>(
     source: &str,
     mode: Mode,
@@ -7580,12 +1910,16 @@ pub fn _compile_symtable(
     let res = match mode {
         Mode::Exec | Mode::Single | Mode::BlockExpr => {
             pre_parse_source_error(&source_file)?;
-            let parsed = ruff_python_parser::parse(barry_source.source(), parser_options);
-            if let Some(error) = barry_source.diagnostic(parsed.as_ref().err(), &source_file) {
+            let parsed = ruff_python_parser::parse_unchecked(barry_source.source(), parser_options);
+            if matches!(mode, Mode::Single)
+                && let Some(error) = single_mode_multiple_statements_error(&source_file, &parsed)
+            {
                 return Err(error);
             }
-            let ast =
-                parsed.map_err(|e| CompileError::from_ruff_parse_error(e, &source_file, mode))?;
+            if let Some(error) = barry_source.diagnostic(parsed.errors().first(), &source_file) {
+                return Err(error);
+            }
+            let ast = first_parse_error(parsed, &source_file, mode)?;
             if let Some(error) =
                 post_parse_source_error(&source_file, ast.tokens(), &CompileOpts::default())
             {
@@ -7608,12 +1942,11 @@ pub fn _compile_symtable(
         }
         Mode::Eval => {
             pre_parse_source_error(&source_file)?;
-            let parsed = ruff_python_parser::parse(barry_source.source(), parser_options);
-            if let Some(error) = barry_source.diagnostic(parsed.as_ref().err(), &source_file) {
+            let parsed = ruff_python_parser::parse_unchecked(barry_source.source(), parser_options);
+            if let Some(error) = barry_source.diagnostic(parsed.errors().first(), &source_file) {
                 return Err(error);
             }
-            let ast =
-                parsed.map_err(|e| CompileError::from_ruff_parse_error(e, &source_file, mode))?;
+            let ast = first_parse_error(parsed, &source_file, mode)?;
             if let Some(error) =
                 post_parse_source_error(&source_file, ast.tokens(), &CompileOpts::default())
             {
@@ -7732,11 +2065,11 @@ mod tests {
             ),
             (
                 "t\"x\" b\"y\"",
-                "Cannot mix t-string literals with string or bytes literals",
+                "cannot mix t-string literals with string or bytes literals",
             ),
             (
                 "b\"x\" t\"y\"",
-                "Cannot mix t-string literals with string or bytes literals",
+                "cannot mix t-string literals with string or bytes literals",
             ),
             // The literals ahead of the first t-string already mix, so CPython's first pass
             // raises from `_PyPegen_concatenate_strings` before the t-string rule is reached.
@@ -7819,7 +2152,6 @@ mod tests {
                 "(print x; '\\N'",
                 "Missing parentheses in call to 'print'. Did you mean print(...)?",
             ),
-            ("f'{x'; '", "f-string: expecting '}'"),
             ("f'{x'; 0x", "f-string: expecting '}'"),
             (
                 "print x; f'{x'; 0x",
@@ -7835,7 +2167,10 @@ mod tests {
                 "f-string: valid expression required before '}'",
             ),
             ("{\\'a\\'}", "unexpected character after line continuation"),
-            ("\"\\\n\"(1 for c in I,\\\n\\", "'(' was never closed"),
+            (
+                "\"\\\n\"(1 for c in I,\\\n\\",
+                "unexpected character after line continuation character",
+            ),
             (
                 r"'\N'",
                 "(unicode error) 'unicodeescape' codec can't decode bytes in position 0-1: malformed \\N character escape",
diff --git a/crates/derive-impl/src/compile_bytecode.rs b/crates/derive-impl/src/compile_bytecode.rs
index d28a7db3b17..e08c230e27d 100644
--- a/crates/derive-impl/src/compile_bytecode.rs
+++ b/crates/derive-impl/src/compile_bytecode.rs
@@ -145,10 +145,16 @@ impl CompilationSource {
         let mut code_map = HashMap::new();
         let paths = fs::read_dir(path)
             .or_else(|e| {
+                // Without symlink support git checks a symlink out as a text file
+                // holding its target, which is relative to the file's own directory.
                 if cfg!(windows)
-                    && let Ok(real_path) = fs::read_to_string(path.canonicalize().unwrap())
+                    && let Ok(target) = fs::read_to_string(path)
                 {
-                    return fs::read_dir(real_path.trim());
+                    let target_dir = path
+                        .parent()
+                        .unwrap_or_else(|| Path::new(""))
+                        .join(target.trim());
+                    return fs::read_dir(target_dir);
                 }
                 Err(e)
             })
@@ -171,6 +177,10 @@ impl CompilationSource {
                 };
                 code_map.extend(self.compile_dir(base, &path, &nparent, mode, compiler)?);
             } else if file_name.ends_with(".py") {
+                // These fixtures must be parsed at import time to exercise syntax errors.
+                if parent == "test.test_lazy_import.data.badsyntax" {
+                    continue;
+                }
                 let stem = path.file_stem().unwrap().to_str().unwrap();
                 let is_init = stem == "__init__";
                 let module_name = if is_init {
diff --git a/crates/derive-impl/src/pyclass.rs b/crates/derive-impl/src/pyclass.rs
index be59d7a339d..b82082bad5d 100644
--- a/crates/derive-impl/src/pyclass.rs
+++ b/crates/derive-impl/src/pyclass.rs
@@ -1,8 +1,8 @@
 use super::Diagnostic;
 use crate::util::{
     ALL_ALLOWED_NAMES, ClassItemMeta, ContentItem, ContentItemInner, ErrorVec, ExceptionItemMeta,
-    ItemMeta, ItemMetaInner, ItemNursery, SimpleItemMeta, infer_native_call_flags,
-    internal_doc_tokens, pyclass_ident_and_attrs, pyexception_ident_and_attrs,
+    ItemMeta, ItemMetaInner, ItemNursery, SimpleItemMeta, internal_doc_tokens,
+    pyclass_ident_and_attrs, pyexception_ident_and_attrs,
 };
 use core::str::FromStr;
 use proc_macro2::{Delimiter, Group, Span, TokenStream, TokenTree};
@@ -649,7 +649,9 @@ fn generate_class_def(
     let subclass_impl = if !is_pystruct && is_repr_transparent {
         base.as_ref().map(|typ| {
             quote! {
-                impl ::rustpython_vm::class::PySubclass for #ident {
+                // SAFETY: the transparent base field has the same layout as Self;
+                // pyclass also checks the object payload offsets and alignment.
+                unsafe impl ::rustpython_vm::class::PySubclass for #ident {
                     type Base = #typ;
 
                     #[inline]
@@ -1307,9 +1309,6 @@ where
                 _ => None,
             }
         };
-        let drop_first_typed = usize::from(implicit_self.is_some());
-        let call_flags = infer_native_call_flags(func.sig(), drop_first_typed);
-
         // Add #[allow(non_snake_case)] for setter methods like set___name__
         let method_name = ident.to_string();
         if method_name.starts_with("set_") && method_name.contains("__") {
@@ -1341,7 +1340,6 @@ where
             raw,
             coexist,
             attr_name: self.inner.attr_name,
-            call_flags,
         });
         Ok(())
     }
@@ -1538,7 +1536,6 @@ struct MethodNurseryItem {
     doc: TokenStream,
     doc_body_pending: TokenStream,
     attr_name: AttrName,
-    call_flags: TokenStream,
 }
 
 impl MethodNursery {
@@ -1578,7 +1575,6 @@ impl ToTokens for MethodNursery {
                 }
                 _ => unreachable!(),
             };
-            let call_flags = &item.call_flags;
             let coexist_flags = if item.coexist {
                 quote! { | rustpython_vm::function::PyMethodFlags::COEXIST.bits() }
             } else {
@@ -1586,7 +1582,7 @@ impl ToTokens for MethodNursery {
             };
             let flags = quote! {
                 rustpython_vm::function::PyMethodFlags::from_bits_retain(
-                    (#binding_flags).bits() | (#call_flags).bits() #coexist_flags
+                    (#binding_flags).bits() #coexist_flags
                 )
             };
             // TODO: intern
diff --git a/crates/derive-impl/src/pymodule.rs b/crates/derive-impl/src/pymodule.rs
index 14ad5ea3cfb..9a2ab6878e7 100644
--- a/crates/derive-impl/src/pymodule.rs
+++ b/crates/derive-impl/src/pymodule.rs
@@ -2,8 +2,8 @@ use crate::error::Diagnostic;
 use crate::pystructseq::PyStructSequenceMeta;
 use crate::util::{
     ALL_ALLOWED_NAMES, AttrItemMeta, AttributeExt, ClassItemMeta, ContentItem, ContentItemInner,
-    ErrorVec, ItemMeta, ItemNursery, ModuleItemMeta, SimpleItemMeta, infer_native_call_flags,
-    internal_doc_tokens, iter_use_idents, pyclass_ident_and_attrs,
+    ErrorVec, ItemMeta, ItemNursery, ModuleItemMeta, SimpleItemMeta, internal_doc_tokens,
+    iter_use_idents, pyclass_ident_and_attrs,
 };
 use core::str::FromStr;
 use proc_macro2::{Delimiter, Group, TokenStream, TokenTree};
@@ -536,7 +536,6 @@ struct FunctionNurseryItem {
     ident: Ident,
     /// One internal doc per [`py_names`](Self::py_names) entry.
     docs: Vec<TokenStream>,
-    call_flags: TokenStream,
 }
 
 impl FunctionNursery {
@@ -566,14 +565,13 @@ impl ToTokens for ValidatedFunctionNursery {
             let ident = &item.ident;
             let cfgs = &item.cfgs;
             let cfgs = quote!(#(#cfgs)*);
-            let flags = &item.call_flags;
             for (py_name, doc) in item.py_names.iter().zip(&item.docs) {
                 inner_tokens.extend(quote![
                     #cfgs
                     rustpython_vm::function::PyMethodDef::new_const(
                         #py_name,
                         #ident,
-                        #flags,
+                        rustpython_vm::function::PyMethodFlags::empty(),
                         #doc,
                     ),
                 ]);
@@ -711,14 +709,12 @@ impl ModuleItem for FunctionItem {
                 internal_doc_tokens(func.sig(), py_name, None, doc, None, Some("$module"))
             })
             .collect();
-        let call_flags = infer_native_call_flags(func.sig(), 0);
 
         args.context.function_items.add_item(FunctionNurseryItem {
             ident: ident.to_owned(),
             py_names,
             cfgs: args.cfgs.to_vec(),
             docs,
-            call_flags,
         });
         Ok(())
     }
diff --git a/crates/derive-impl/src/pystructseq.rs b/crates/derive-impl/src/pystructseq.rs
index aa89b3717bb..d4352735790 100644
--- a/crates/derive-impl/src/pystructseq.rs
+++ b/crates/derive-impl/src/pystructseq.rs
@@ -602,7 +602,8 @@ pub(crate) fn impl_pystruct_sequence(
         }
 
         // PySubclass for proper inheritance
-        impl ::rustpython_vm::class::PySubclass for #pytype_ident {
+        // SAFETY: the generated payload is a transparent wrapper around PyTuple.
+        unsafe impl ::rustpython_vm::class::PySubclass for #pytype_ident {
             type Base = ::rustpython_vm::builtins::PyTuple;
 
             #[inline]
diff --git a/crates/derive-impl/src/util.rs b/crates/derive-impl/src/util.rs
index 985a8312301..6a14dd11688 100644
--- a/crates/derive-impl/src/util.rs
+++ b/crates/derive-impl/src/util.rs
@@ -936,75 +936,3 @@ pub(crate) fn internal_doc_tokens(
         }
     }
 }
-
-pub(crate) fn infer_native_call_flags(sig: &Signature, drop_first_typed: usize) -> TokenStream {
-    // Best-effort mapping of Rust function signatures to CPython-style
-    // METH_* calling convention flags used by CALL specialization.
-    let mut typed_args = Vec::new();
-    for arg in &sig.inputs {
-        let FnArg::Typed(typed) = arg else {
-            continue;
-        };
-        let ty_tokens = &typed.ty;
-        let ty = quote!(#ty_tokens).to_string().replace(' ', "");
-        // The interpreter supplies `vm` and `callee`; a Python call never
-        // passes them.
-        if (ty.starts_with('&') && ty.ends_with("VirtualMachine")) || ty.ends_with("Callee") {
-            continue;
-        }
-        typed_args.push(ty);
-    }
-
-    let mut user_args = typed_args.into_iter();
-    for _ in 0..drop_first_typed {
-        if user_args.next().is_none() {
-            break;
-        }
-    }
-
-    let mut has_keywords = false;
-    let mut variable_arity = false;
-    let mut fixed_positional = 0usize;
-
-    for ty in user_args {
-        let is_named = |name: &str| {
-            ty == name
-                || ty.starts_with(&format!("{name}<"))
-                || ty.contains(&format!("::{name}<"))
-                || ty.ends_with(&format!("::{name}"))
-        };
-
-        if is_named("FuncArgs") {
-            has_keywords = true;
-            variable_arity = true;
-            continue;
-        }
-        if is_named("KwArgs") {
-            has_keywords = true;
-            variable_arity = true;
-            continue;
-        }
-        if is_named("PosArgs") || is_named("OptionalArg") || is_named("OptionalOption") {
-            variable_arity = true;
-            continue;
-        }
-        fixed_positional += 1;
-    }
-
-    if has_keywords {
-        quote! {
-            rustpython_vm::function::PyMethodFlags::from_bits_retain(
-                rustpython_vm::function::PyMethodFlags::FASTCALL.bits()
-                    | rustpython_vm::function::PyMethodFlags::KEYWORDS.bits()
-            )
-        }
-    } else if variable_arity {
-        quote! { rustpython_vm::function::PyMethodFlags::FASTCALL }
-    } else {
-        match fixed_positional {
-            0 => quote! { rustpython_vm::function::PyMethodFlags::NOARGS },
-            1 => quote! { rustpython_vm::function::PyMethodFlags::O },
-            _ => quote! { rustpython_vm::function::PyMethodFlags::FASTCALL },
-        }
-    }
-}
diff --git a/crates/host_env/Cargo.toml b/crates/host_env/Cargo.toml
index 029c2860f33..7f9634213fc 100644
--- a/crates/host_env/Cargo.toml
+++ b/crates/host_env/Cargo.toml
@@ -98,6 +98,7 @@ windows-sys = { workspace = true, features = [
     "Win32_System_Console",
     "Win32_System_Diagnostics_Debug",
     "Win32_System_Environment",
+    "Win32_System_EventLog",
     "Win32_System_Ole",
     "Win32_System_IO",
     "Win32_System_Ioctl",
diff --git a/crates/host_env/src/crt_fd.rs b/crates/host_env/src/crt_fd.rs
index f06c5aad984..5b2cf685be1 100644
--- a/crates/host_env/src/crt_fd.rs
+++ b/crates/host_env/src/crt_fd.rs
@@ -21,6 +21,8 @@ mod c {
     unsafe extern "C" {
         #[link_name = "_chsize_s"]
         pub(super) fn ftruncate(fd: i32, len: i64) -> i32;
+        pub(super) fn _get_doserrno(value: *mut c_ulong) -> c_int;
+        pub(super) fn _set_doserrno(value: c_ulong) -> c_int;
     }
 }
 
@@ -317,7 +319,10 @@ impl AsRawFd for Borrowed<'_> {
 
 #[inline]
 fn ebadf() -> io::Error {
-    io::Error::from_raw_os_error(c::EBADF)
+    cfg_select! {
+        windows => crate::os::io_error_from_errno(c::EBADF),
+        _ => io::Error::from_raw_os_error(c::EBADF),
+    }
 }
 
 pub fn open(path: &ffi::CStr, flags: i32, mode: i32) -> io::Result<Owned> {
@@ -331,7 +336,13 @@ pub fn wopen(path: &widestring::WideCStr, flags: i32, mode: i32) -> io::Result<O
 
 #[cfg(all(any(unix, target_os = "wasi"), not(target_os = "redox")))]
 pub fn openat(dir: Borrowed<'_>, path: &ffi::CStr, flags: i32, mode: i32) -> io::Result<Owned> {
-    cvt_fd(unsafe { c::openat(dir.as_raw(), path.as_ptr(), flags, mode) })
+    openat_raw(dir.as_raw(), path, flags, mode)
+}
+
+#[cfg(all(any(unix, target_os = "wasi"), not(target_os = "redox")))]
+// Accept a descriptor number without asserting it stays open across calls.
+pub fn openat_raw(dir: Raw, path: &ffi::CStr, flags: i32, mode: i32) -> io::Result<Owned> {
+    cvt_fd(unsafe { c::openat(dir, path.as_ptr(), flags, mode) })
 }
 
 pub fn fsync(fd: Borrowed<'_>) -> io::Result<()> {
@@ -348,8 +359,53 @@ pub fn close(fd: Owned) -> io::Result<()> {
     _close(fd.into_raw())
 }
 
+#[cfg(not(any(target_os = "freebsd", target_os = "linux")))]
+pub fn closerange(fd_low: Raw, fd_high: Raw) {
+    close_range_slow(fd_low, fd_high);
+}
+
+// _Py_closerange
+#[cfg(any(target_os = "freebsd", target_os = "linux"))]
+pub fn closerange(fd_low: Raw, fd_high: Raw) {
+    // CPython clamps low to 0.
+    let fd_low = fd_low.max(0);
+    // close_range(2) is [low, high] whereas CPython's is [low, high).
+    if fd_high < fd_low {
+        return;
+    }
+    let high = fd_high - 1;
+
+    if close_range(fd_low as _, high as _) == -1
+        && io::Error::last_os_error().raw_os_error() == Some(libc::ENOSYS)
+    {
+        close_range_slow(fd_low, fd_high);
+    }
+}
+
+#[cfg(target_os = "freebsd")]
+fn close_range(low: ffi::c_uint, high: ffi::c_uint) -> ffi::c_int {
+    unsafe { libc::close_range(low, high, 0) as ffi::c_int }
+}
+
+#[cfg(target_os = "linux")]
+fn close_range(low: ffi::c_uint, high: ffi::c_uint) -> ffi::c_int {
+    unsafe { libc::syscall(libc::SYS_close_range, low, high, 0) as ffi::c_int }
+}
+
+fn close_range_slow(low: Raw, high: Raw) {
+    for fd in low..high {
+        // The range can contain closed descriptors, so it cannot use Owned.
+        let _ = _close(fd);
+    }
+}
+
 pub fn ftruncate(fd: Borrowed<'_>, len: Offset) -> io::Result<()> {
-    let ret = unsafe { suppress_iph!(c::ftruncate(fd.as_raw(), len)) };
+    ftruncate_raw(fd.as_raw(), len)
+}
+
+/// Truncate a caller-supplied descriptor, letting the CRT validate its value.
+pub fn ftruncate_raw(fd: Raw, len: Offset) -> io::Result<()> {
+    let ret = unsafe { suppress_iph!(c::ftruncate(fd, len)) };
     // On Windows, _chsize_s returns 0 on success, or a positive error code (errno value) on failure.
     // On other platforms, ftruncate returns 0 on success, or -1 on failure with errno set.
     cfg_select! {
@@ -381,14 +437,57 @@ pub fn as_handle(fd: Borrowed<'_>) -> io::Result<BorrowedHandle<'_>> {
 
 fn _write(fd: Raw, buf: &[u8]) -> io::Result<usize> {
     let count = cmp::min(buf.len(), MAX_RW);
-    let n = cvt(unsafe { suppress_iph!(c::write(fd, buf.as_ptr() as _, count as _)) })?;
-    Ok(n as usize)
+    #[cfg(windows)]
+    {
+        let mut count = count;
+        loop {
+            unsafe { c::_set_doserrno(0) };
+            let n = unsafe { suppress_iph!(c::write(fd, buf.as_ptr() as _, count as _)) };
+            if n >= 0 {
+                return Ok(n as usize);
+            }
+            let errno = crate::os::get_errno();
+            // The CRT reports a successful zero-byte WriteFile as ENOSPC.
+            // A nonblocking pipe may still accept a smaller prefix.
+            if errno != libc::ENOSPC || dos_error() != 0 {
+                return Err(crate::os::io_error_from_errno(errno));
+            }
+            count /= 2;
+            if count == 0 {
+                return Err(crate::os::io_error_from_errno(libc::EAGAIN));
+            }
+        }
+    }
+    #[cfg(not(windows))]
+    {
+        let n = cvt(unsafe { suppress_iph!(c::write(fd, buf.as_ptr() as _, count as _)) })?;
+        Ok(n as usize)
+    }
 }
 
 fn _read(fd: Raw, buf: &mut [u8]) -> io::Result<usize> {
     let count = cmp::min(buf.len(), MAX_RW);
-    let n = cvt(unsafe { suppress_iph!(libc::read(fd, buf.as_mut_ptr() as _, count as _)) })?;
-    Ok(n as usize)
+    #[cfg(windows)]
+    unsafe {
+        c::_set_doserrno(0);
+    }
+    let n = unsafe { suppress_iph!(libc::read(fd, buf.as_mut_ptr() as _, count as _)) };
+    #[cfg(windows)]
+    if n < 0
+        && crate::os::get_errno() == libc::EINVAL
+        && dos_error() == windows_sys::Win32::Foundation::ERROR_NO_DATA
+    {
+        return Err(crate::os::io_error_from_errno(libc::EAGAIN));
+    }
+    cvt(n).map(|n| n as usize)
+}
+
+#[cfg(windows)]
+fn dos_error() -> u32 {
+    let mut error = 0;
+    // SAFETY: the CRT writes to a valid unsigned long on the current thread.
+    unsafe { c::_get_doserrno(&mut error) };
+    error
 }
 
 pub fn write(fd: Borrowed<'_>, buf: &[u8]) -> io::Result<usize> {
diff --git a/crates/host_env/src/crt_fd_unsupported.rs b/crates/host_env/src/crt_fd_unsupported.rs
index 7fb8a406e32..7b5336a9b98 100644
--- a/crates/host_env/src/crt_fd_unsupported.rs
+++ b/crates/host_env/src/crt_fd_unsupported.rs
@@ -153,6 +153,8 @@ pub fn close(_fd: Owned) -> io::Result<()> {
     Err(ebadf())
 }
 
+pub fn closerange(_fd_low: Raw, _fd_high: Raw) {}
+
 pub fn ftruncate(_fd: Borrowed<'_>, _len: Offset) -> io::Result<()> {
     Err(ebadf())
 }
diff --git a/crates/host_env/src/ctypes.rs b/crates/host_env/src/ctypes.rs
index b0d15679b1f..440d2078eac 100644
--- a/crates/host_env/src/ctypes.rs
+++ b/crates/host_env/src/ctypes.rs
@@ -2809,29 +2809,7 @@ pub fn free_library(module: windows_sys::Win32::Foundation::HMODULE) -> std::io:
 }
 
 #[cfg(windows)]
-#[allow(clippy::not_unsafe_ptr_arg_deref)]
-pub fn sys_string_len(bstr: *const u16) -> usize {
-    unsafe { windows_sys::Win32::Foundation::SysStringLen(bstr) as usize }
-}
-
-#[cfg(windows)]
-#[allow(clippy::not_unsafe_ptr_arg_deref)]
-pub fn sys_free_string(bstr: *const u16) {
-    unsafe { windows_sys::Win32::Foundation::SysFreeString(bstr) };
-}
-
-#[cfg(windows)]
-pub fn sys_alloc_string_len(units: &[u16]) -> Option<*mut u16> {
-    let len = u32::try_from(units.len()).ok()?;
-    let bstr = unsafe { windows_sys::Win32::Foundation::SysAllocStringLen(units.as_ptr(), len) };
-    (!bstr.is_null()).then_some(bstr as *mut u16)
-}
-
-#[cfg(windows)]
-#[allow(clippy::not_unsafe_ptr_arg_deref)]
-pub fn co_task_mem_free(ptr: *mut core::ffi::c_void) {
-    unsafe { windows_sys::Win32::System::Com::CoTaskMemFree(ptr) };
-}
+pub use crate::windows::{co_task_mem_free, sys_alloc_string_len, sys_free_string, sys_string_len};
 
 /// `GetErrorInfo(0)`. `None` when the thread has no error object (`S_FALSE`).
 #[cfg(windows)]
diff --git a/crates/host_env/src/errno.rs b/crates/host_env/src/errno.rs
index e816a04a55f..c0a122ddbcc 100644
--- a/crates/host_env/src/errno.rs
+++ b/crates/host_env/src/errno.rs
@@ -2,7 +2,7 @@
 
 /// Return the platform `strerror(errno)` message as an owned `String`.
 /// Returns `None` when the runtime gives no description for `errno`.
-#[cfg(any(unix, windows))]
+#[cfg(any(unix, windows, target_os = "wasi"))]
 #[must_use]
 pub fn strerror_string(errno: i32) -> Option<String> {
     let ptr = unsafe { libc::strerror(errno) };
diff --git a/crates/host_env/src/fileutils.rs b/crates/host_env/src/fileutils.rs
index 8db9af89501..974484c6ec9 100644
--- a/crates/host_env/src/fileutils.rs
+++ b/crates/host_env/src/fileutils.rs
@@ -11,6 +11,10 @@ pub use windows::{StatStruct, fstat};
 
 #[cfg(not(windows))]
 pub fn fstat(fd: crate::crt_fd::Borrowed<'_>) -> std::io::Result<StatStruct> {
+    // Unlike a directory fd, fstat accepts no negative descriptor sentinels.
+    if fd.as_raw() < 0 {
+        return Err(std::io::Error::from_raw_os_error(libc::EBADF));
+    }
     rustix::fs::fstat(fd).map_err(Into::into)
 }
 
@@ -51,13 +55,13 @@ pub mod windows {
         pub st_gid: i32,
         pub st_rdev: libc::c_ulong,
         pub st_size: u64,
-        pub st_atime: libc::time_t,
+        pub st_atime: crate::time::TimeT,
         pub st_atime_nsec: i32,
-        pub st_mtime: libc::time_t,
+        pub st_mtime: crate::time::TimeT,
         pub st_mtime_nsec: i32,
-        pub st_ctime: libc::time_t,
+        pub st_ctime: crate::time::TimeT,
         pub st_ctime_nsec: i32,
-        pub st_birthtime: libc::time_t,
+        pub st_birthtime: crate::time::TimeT,
         pub st_birthtime_nsec: i32,
         pub st_file_attributes: libc::c_ulong,
         pub st_reparse_tag: u32,
@@ -151,13 +155,13 @@ pub mod windows {
         ))
     }
 
-    fn large_integer_to_time_t_nsec(input: i64) -> (libc::time_t, libc::c_int) {
+    fn large_integer_to_time_t_nsec(input: i64) -> (crate::time::TimeT, libc::c_int) {
         let nsec_out = (input % 10_000_000) * 100; // FILETIME is in units of 100 nsec.
-        let time_out = ((input / 10_000_000) - SECS_BETWEEN_EPOCHS) as libc::time_t;
+        let time_out = (input / 10_000_000) - SECS_BETWEEN_EPOCHS;
         (time_out, nsec_out as _)
     }
 
-    fn file_time_to_time_t_nsec(in_ptr: FILETIME) -> (libc::time_t, libc::c_int) {
+    fn file_time_to_time_t_nsec(in_ptr: FILETIME) -> (crate::time::TimeT, libc::c_int) {
         let in_val: i64 = unsafe { core::mem::transmute_copy(&in_ptr) };
         let nsec_out = (in_val % 10_000_000) * 100; // FILETIME is in units of 100 nsec.
         let time_out = (in_val / 10_000_000) - SECS_BETWEEN_EPOCHS;
diff --git a/crates/host_env/src/io.rs b/crates/host_env/src/io.rs
index 134e99df14d..3d8e67779ea 100644
--- a/crates/host_env/src/io.rs
+++ b/crates/host_env/src/io.rs
@@ -17,6 +17,7 @@ bitflagset::bitflag! {
         Readable = 1,
         Writable = 2,
         Appending = 3,
+        Truncating = 4,
     }
 }
 
@@ -30,6 +31,7 @@ impl FileMode {
     pub const READABLE: Self = Self::from_element(FileModeFlag::Readable);
     pub const WRITABLE: Self = Self::from_element(FileModeFlag::Writable);
     pub const APPENDING: Self = Self::from_element(FileModeFlag::Appending);
+    pub const TRUNCATING: Self = Self::from_element(FileModeFlag::Truncating);
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
@@ -72,7 +74,11 @@ impl FileMode {
             }
         } else if self.contains(&FileModeFlag::Readable) {
             if self.contains(&FileModeFlag::Writable) {
-                "rb+"
+                if self.contains(&FileModeFlag::Truncating) {
+                    "wb+"
+                } else {
+                    "rb+"
+                }
             } else {
                 "rb"
             }
@@ -109,7 +115,7 @@ pub fn parse_fileio_mode(mode_str: &str) -> Result<ParsedFileMode, FileModeError
                     return Err(FileModeError::BadRwa);
                 }
                 rwa = true;
-                mode |= FileMode::WRITABLE;
+                mode |= FileMode::WRITABLE | FileMode::TRUNCATING;
                 flags |= os::O_CREAT | os::O_TRUNC;
             }
             b'a' => {
diff --git a/crates/host_env/src/io_unsupported.rs b/crates/host_env/src/io_unsupported.rs
index a779d6f19d1..17eba9ff795 100644
--- a/crates/host_env/src/io_unsupported.rs
+++ b/crates/host_env/src/io_unsupported.rs
@@ -13,6 +13,7 @@ bitflagset::bitflag! {
         Readable = 1,
         Writable = 2,
         Appending = 3,
+        Truncating = 4,
     }
 }
 
@@ -26,6 +27,7 @@ impl FileMode {
     pub const READABLE: Self = Self::from_element(FileModeFlag::Readable);
     pub const WRITABLE: Self = Self::from_element(FileModeFlag::Writable);
     pub const APPENDING: Self = Self::from_element(FileModeFlag::Appending);
+    pub const TRUNCATING: Self = Self::from_element(FileModeFlag::Truncating);
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
@@ -68,7 +70,11 @@ impl FileMode {
             }
         } else if self.contains(&FileModeFlag::Readable) {
             if self.contains(&FileModeFlag::Writable) {
-                "rb+"
+                if self.contains(&FileModeFlag::Truncating) {
+                    "wb+"
+                } else {
+                    "rb+"
+                }
             } else {
                 "rb"
             }
@@ -106,7 +112,7 @@ pub fn parse_fileio_mode(mode_str: &str) -> Result<ParsedFileMode, FileModeError
                     return Err(FileModeError::BadRwa);
                 }
                 rwa = true;
-                mode |= FileMode::WRITABLE;
+                mode |= FileMode::WRITABLE | FileMode::TRUNCATING;
                 flags |= O_CREAT | O_TRUNC;
             }
             b'a' => {
diff --git a/crates/host_env/src/lib.rs b/crates/host_env/src/lib.rs
index ee9c5238e5d..33b5ad60b99 100644
--- a/crates/host_env/src/lib.rs
+++ b/crates/host_env/src/lib.rs
@@ -74,7 +74,7 @@ pub mod pwd;
 pub mod resource;
 #[cfg(all(unix, not(target_os = "redox"), not(target_os = "android")))]
 pub mod shm;
-#[cfg(any(unix, windows))]
+#[cfg(any(unix, windows, target_os = "wasi"))]
 pub mod signal;
 pub mod time;
 
diff --git a/crates/host_env/src/locale.rs b/crates/host_env/src/locale.rs
index e9df052c208..07dfa512d65 100644
--- a/crates/host_env/src/locale.rs
+++ b/crates/host_env/src/locale.rs
@@ -3,6 +3,53 @@ use core::{ffi::CStr, ptr};
 
 pub use libc::{LC_ALL, LC_COLLATE, LC_CTYPE, LC_MONETARY, LC_NUMERIC, LC_TIME};
 
+// CPython uses the wide-character APIs after btowc() on Apple platforms.
+// Darwin's wint_t is int; libc does not expose these declarations.
+#[cfg(target_vendor = "apple")]
+unsafe extern "C" {
+    fn btowc(ch: libc::c_int) -> libc::c_int;
+    fn iswalnum(ch: libc::c_int) -> libc::c_int;
+    fn towlower(ch: libc::c_int) -> libc::c_int;
+    fn towupper(ch: libc::c_int) -> libc::c_int;
+}
+
+/// Classify a byte using the current LC_CTYPE locale.
+pub fn byte_isalnum(ch: u8) -> bool {
+    // ctype functions require EOF or an unsigned-char value, never a signed byte.
+    #[cfg(not(target_vendor = "apple"))]
+    unsafe {
+        libc::isalnum(ch.into()) != 0
+    }
+    #[cfg(target_vendor = "apple")]
+    unsafe {
+        iswalnum(btowc(ch.into())) != 0
+    }
+}
+
+/// Lowercase a byte using the current LC_CTYPE locale.
+pub fn byte_tolower(ch: u8) -> u32 {
+    #[cfg(not(target_vendor = "apple"))]
+    unsafe {
+        libc::tolower(ch.into()) as u32
+    }
+    #[cfg(target_vendor = "apple")]
+    unsafe {
+        towlower(btowc(ch.into())) as u32
+    }
+}
+
+/// Uppercase a byte using the current LC_CTYPE locale.
+pub fn byte_toupper(ch: u8) -> u32 {
+    #[cfg(not(target_vendor = "apple"))]
+    unsafe {
+        libc::toupper(ch.into()) as u32
+    }
+    #[cfg(target_vendor = "apple")]
+    unsafe {
+        towupper(btowc(ch.into())) as u32
+    }
+}
+
 #[cfg(all(unix, not(any(target_os = "ios", target_os = "redox"))))]
 pub use libc::LC_MESSAGES;
 
diff --git a/crates/host_env/src/mmap.rs b/crates/host_env/src/mmap.rs
index 976d78e2c38..4ce4c52a40d 100644
--- a/crates/host_env/src/mmap.rs
+++ b/crates/host_env/src/mmap.rs
@@ -7,8 +7,8 @@ use std::io;
 
 #[cfg(unix)]
 pub use libc::{
-    MADV_DONTNEED, MADV_NORMAL, MADV_RANDOM, MADV_SEQUENTIAL, MADV_WILLNEED, PROT_EXEC, PROT_READ,
-    PROT_WRITE,
+    MADV_DONTNEED, MADV_NORMAL, MADV_RANDOM, MADV_SEQUENTIAL, MADV_WILLNEED, MS_ASYNC,
+    MS_INVALIDATE, MS_SYNC, PROT_EXEC, PROT_READ, PROT_WRITE,
 };
 
 #[cfg(unix)]
@@ -202,10 +202,43 @@ impl MappedFile {
         }
     }
 
-    pub fn flush_range(&self, offset: usize, size: usize) -> io::Result<()> {
+    pub fn flush_range(&self, offset: usize, size: usize, flags: i32) -> io::Result<()> {
+        #[cfg(unix)]
+        {
+            if offset > self.as_slice().len() || size > self.as_slice().len() - offset {
+                return Err(io::Error::from_raw_os_error(libc::EINVAL));
+            }
+            let ptr = unsafe { self.as_ptr().add(offset) };
+            let flags = if flags == 0 { MS_SYNC } else { flags };
+            if unsafe { libc::msync(ptr.cast_mut().cast(), size, flags) } == -1 {
+                return Err(io::Error::last_os_error());
+            }
+            Ok(())
+        }
+        #[cfg(not(unix))]
+        {
+            let _ = flags;
+            match self {
+                Self::Read(_) => Ok(()),
+                Self::Write(mmap) => mmap.flush_range(offset, size),
+            }
+        }
+    }
+
+    /// # Safety
+    /// The backing file must cover the mapping offset plus `new_size`, and no
+    /// exported pointers may remain live while the mapping is moved or shrunk.
+    #[cfg(target_os = "linux")]
+    pub unsafe fn remap(&mut self, new_size: usize) -> io::Result<()> {
+        // memmap2 permits a zero-length mapping, whereas mmap.resize(0) must
+        // preserve mremap's EINVAL result.
+        if new_size == 0 {
+            return Err(io::Error::from_raw_os_error(libc::EINVAL));
+        }
+        let options = memmap2::RemapOptions::new().may_move(true);
         match self {
-            Self::Read(_) => Ok(()),
-            Self::Write(mmap) => mmap.flush_range(offset, size),
+            Self::Read(mmap) => unsafe { mmap.remap(new_size, options) },
+            Self::Write(mmap) => unsafe { mmap.remap(new_size, options) },
         }
     }
 
@@ -216,6 +249,23 @@ impl MappedFile {
     }
 }
 
+#[cfg(target_os = "linux")]
+pub fn set_mapping_name(address: usize, size: usize, name: &core::ffi::CStr) -> io::Result<()> {
+    if unsafe {
+        libc::prctl(
+            libc::PR_SET_VMA,
+            libc::PR_SET_VMA_ANON_NAME,
+            address,
+            size,
+            name.as_ptr(),
+        )
+    } == -1
+    {
+        return Err(io::Error::last_os_error());
+    }
+    Ok(())
+}
+
 #[cfg(windows)]
 unsafe impl Send for NamedMmap {}
 #[cfg(windows)]
@@ -293,16 +343,40 @@ pub fn file_len(fd: crt_fd::Borrowed<'_>) -> io::Result<i64> {
     Ok(fileutils::fstat(fd)?.st_size.into())
 }
 
+/// Inspect Python's raw descriptor without assuming that it is a valid Rust fd.
+/// CPython ignores failed fstat calls and only bounds regular-file mappings.
 #[cfg(unix)]
-pub fn prepare_file_mapping(fd: crt_fd::Borrowed<'_>) {
-    #[cfg(target_os = "macos")]
-    {
-        let _ = posix::full_fsync(fd.into());
+pub fn regular_file_len(fd: i32) -> Option<i64> {
+    // Use the same target selection as memmap2's mmap64/off64_t aliases.
+    #[cfg(not(any(
+        target_os = "android",
+        all(target_os = "linux", not(target_env = "musl"))
+    )))]
+    use libc::{fstat, stat as Stat};
+    #[cfg(any(
+        target_os = "android",
+        all(target_os = "linux", not(target_env = "musl"))
+    ))]
+    use libc::{fstat64 as fstat, stat64 as Stat};
+
+    let mut status = core::mem::MaybeUninit::<Stat>::uninit();
+    // SAFETY: fstat accepts an arbitrary integer and initializes status only
+    // on success. No borrowed/owned descriptor is constructed from that input.
+    if unsafe { fstat(fd, status.as_mut_ptr()) } != 0 {
+        return None;
     }
-    #[cfg(not(target_os = "macos"))]
-    {
-        let _ = fd;
+    let status = unsafe { status.assume_init() };
+    if status.st_mode & libc::S_IFMT != libc::S_IFREG {
+        return None;
     }
+    #[allow(clippy::useless_conversion, reason = "needed for 32-bit platforms")]
+    i64::try_from(status.st_size).ok()
+}
+
+#[cfg(target_os = "macos")]
+pub fn prepare_file_mapping(fd: i32) {
+    // CPython intentionally ignores F_FULLFSYNC errors, including invalid fds.
+    let _ = unsafe { libc::fcntl(fd, libc::F_FULLFSYNC) };
 }
 
 #[cfg(windows)]
@@ -409,25 +483,44 @@ pub fn map_anon(size: usize) -> io::Result<MappedFile> {
 }
 
 #[cfg(unix)]
-pub fn map_file(
-    fd: crt_fd::Borrowed<'_>,
-    offset: i64,
-    size: usize,
-    access: AccessMode,
-) -> io::Result<(crt_fd::Owned, MappedFile)> {
-    let new_fd: crt_fd::Owned = posix::dup_noninheritable(fd.into())?.into();
+pub fn duplicate_descriptor(fd: i32) -> io::Result<crt_fd::Owned> {
+    // Python supplies an arbitrary integer, so validate it through fcntl before
+    // constructing a Rust descriptor. Only the successful duplicate is owned.
+    let new_fd = unsafe { libc::fcntl(fd, libc::F_DUPFD_CLOEXEC, 0) };
+    if new_fd != -1 {
+        return Ok(unsafe { crt_fd::Owned::from_raw(new_fd) });
+    }
+    let err = io::Error::last_os_error();
+    if err.raw_os_error() != Some(libc::EINVAL) {
+        return Err(err);
+    }
+    // Older kernels may not support F_DUPFD_CLOEXEC.
+    let new_fd = unsafe { libc::dup(fd) };
+    if new_fd == -1 {
+        return Err(io::Error::last_os_error());
+    }
+    let new_fd = unsafe { crt_fd::Owned::from_raw(new_fd) };
+    posix::set_inheritable(new_fd.borrow().into(), false)?;
+    Ok(new_fd)
+}
+
+#[cfg(unix)]
+pub fn map_file(fd: i32, offset: i64, size: usize, access: AccessMode) -> io::Result<MappedFile> {
     let mut mmap_opt = MmapOptions::new();
     let mmap_opt = mmap_opt.offset(offset as u64).len(size);
 
+    // len is always explicit, so memmap2 never wraps this raw fd in File to
+    // query metadata. Its mmap syscall rejects invalid descriptors directly.
+    // The caller retains any owned tracking descriptor through this call.
     let mapped = match access {
         AccessMode::Default | AccessMode::Write => {
-            unsafe { mmap_opt.map_mut(&new_fd) }.map(MappedFile::Write)?
+            unsafe { mmap_opt.map_mut(fd) }.map(MappedFile::Write)?
         }
-        AccessMode::Read => unsafe { mmap_opt.map(&new_fd) }.map(MappedFile::Read)?,
-        AccessMode::Copy => unsafe { mmap_opt.map_copy(&new_fd) }.map(MappedFile::Write)?,
+        AccessMode::Read => unsafe { mmap_opt.map(fd) }.map(MappedFile::Read)?,
+        AccessMode::Copy => unsafe { mmap_opt.map_copy(fd) }.map(MappedFile::Write)?,
     };
 
-    Ok((new_fd, mapped))
+    Ok(mapped)
 }
 
 #[cfg(all(unix, not(target_os = "redox")))]
diff --git a/crates/host_env/src/nt.rs b/crates/host_env/src/nt.rs
index 9f1c1c23de4..24c52c3edf8 100644
--- a/crates/host_env/src/nt.rs
+++ b/crates/host_env/src/nt.rs
@@ -22,6 +22,7 @@ use crate::{
     windows::{CheckWin32Bool, CheckWin32Handle, CheckWin32Sentinel, HandleToOwned},
 };
 use libc::intptr_t;
+
 use widestring::WideCString;
 use windows_sys::{
     Win32::{
@@ -75,6 +76,25 @@ pub use windows_sys::Win32::Storage::FileSystem::{
     FILE_ATTRIBUTE_TEMPORARY, FILE_ATTRIBUTE_VIRTUAL,
 };
 
+pub fn get_blocking(fd: crt_fd::Borrowed<'_>) -> io::Result<bool> {
+    let handle = crt_fd::as_handle(fd)?;
+    let mode = crate::winapi::get_named_pipe_handle_state(handle.as_raw_handle())?;
+    Ok(mode & windows_sys::Win32::System::Pipes::PIPE_NOWAIT == 0)
+}
+
+pub fn set_blocking(fd: crt_fd::Borrowed<'_>, blocking: bool) -> io::Result<()> {
+    use windows_sys::Win32::System::Pipes::PIPE_NOWAIT;
+
+    let handle = crt_fd::as_handle(fd)?;
+    let mode = crate::winapi::get_named_pipe_handle_state(handle.as_raw_handle())?;
+    let mode = if blocking {
+        mode & !PIPE_NOWAIT
+    } else {
+        mode | PIPE_NOWAIT
+    };
+    crate::winapi::set_named_pipe_handle_state(handle.as_raw_handle(), Some(mode), None, None)
+}
+
 pub type Handle = HANDLE;
 pub const MAX_PATH_USIZE: usize = MAX_PATH as usize;
 pub const ERROR_INVALID_HANDLE_I32: i32 = ERROR_INVALID_HANDLE as i32;
@@ -129,16 +149,16 @@ struct FileAttributeTagInfo {
     reparse_tag: u32,
 }
 
-const fn win32_large_integer_to_time(li: i64) -> (libc::time_t, i32) {
+const fn win32_large_integer_to_time(li: i64) -> (crate::time::TimeT, i32) {
     let nsec = ((li % 10_000_000) * 100) as i32;
-    let sec = (li / 10_000_000 - crate::fileutils::windows::SECS_BETWEEN_EPOCHS) as libc::time_t;
+    let sec = li / 10_000_000 - crate::fileutils::windows::SECS_BETWEEN_EPOCHS;
     (sec, nsec)
 }
 
-const fn win32_filetime_to_time(ft_low: u32, ft_high: u32) -> (libc::time_t, i32) {
+const fn win32_filetime_to_time(ft_low: u32, ft_high: u32) -> (crate::time::TimeT, i32) {
     let ticks = ((ft_high as i64) << 32) | (ft_low as i64);
     let nsec = ((ticks % 10_000_000) * 100) as i32;
-    let sec = (ticks / 10_000_000 - crate::fileutils::windows::SECS_BETWEEN_EPOCHS) as libc::time_t;
+    let sec = ticks / 10_000_000 - crate::fileutils::windows::SECS_BETWEEN_EPOCHS;
     (sec, nsec)
 }
 
@@ -591,10 +611,10 @@ impl ScandirEntry {
         if reparse_tag == IO_REPARSE_TAG_SYMLINK {
             mode = (mode & !libc::S_IFMT) | S_IFLNK;
         }
-        let to_time = |ticks: u64| -> (libc::time_t, i32) {
+        let to_time = |ticks: u64| -> (crate::time::TimeT, i32) {
             let ticks = ticks as i64;
             (
-                (ticks / 10_000_000 - SECS_BETWEEN_EPOCHS) as libc::time_t,
+                ticks / 10_000_000 - SECS_BETWEEN_EPOCHS,
                 ((ticks % 10_000_000) * 100) as i32,
             )
         };
diff --git a/crates/host_env/src/os.rs b/crates/host_env/src/os.rs
index 6eda6030c83..71469890587 100644
--- a/crates/host_env/src/os.rs
+++ b/crates/host_env/src/os.rs
@@ -519,8 +519,28 @@ pub fn device_encoding(_fd: i32) -> Option<String> {
     }
 }
 
+/// Terminate the process through the C `exit()`, which runs the C atexit
+/// handlers and flushes C stdio.
 pub fn exit(code: i32) -> ! {
-    std::process::exit(code)
+    cfg_select! {
+        // std::process::exit ends in ExitProcess here, which skips the CRT
+        // atexit handlers and the stdio flush.
+        windows => {
+            use std::io::Write;
+            let _ = std::io::stdout().flush();
+            unsafe { libc::exit(code) }
+        }
+        _ => std::process::exit(code),
+    }
+}
+
+/// Terminate the process through `_exit()`, without running the C atexit
+/// handlers or flushing C stdio.
+pub fn exit_immediately(code: i32) -> ! {
+    cfg_select! {
+        any(unix, windows, target_os = "wasi") => unsafe { libc::_exit(code) },
+        _ => std::process::exit(code),
+    }
 }
 
 /// Wrapper around the C `abort()` call: terminates the process abnormally.
@@ -601,6 +621,20 @@ pub fn seek_fd(
     unsafe { suppress_iph!(libc::lseek(fd.as_raw(), position, how)) }.check_libc_neg()
 }
 
+#[cfg(windows)]
+pub type FileTimeSeconds = libc::time64_t;
+#[cfg(any(unix, target_os = "wasi"))]
+#[cfg_attr(target_env = "musl", allow(deprecated))]
+pub type FileTimeSeconds = libc::time_t;
+
+/// Seconds and nanoseconds passed to filesystem timestamp operations.
+#[cfg(any(unix, windows, target_os = "wasi"))]
+#[derive(Clone, Copy)]
+pub struct FileTime {
+    pub seconds: FileTimeSeconds,
+    pub nanoseconds: libc::c_long,
+}
+
 #[cfg(windows)]
 fn filetime_from_duration(duration: Duration) -> FILETIME {
     let intervals = ((duration.as_secs() as i64 + 11644473600) * 10_000_000)
@@ -680,13 +714,17 @@ impl core::error::Error for CrtErrno {}
 
 /// Build an [`io::Error`] that preserves a raw C runtime `errno`.
 ///
-/// The [`io::ErrorKind`] is derived from the closest Win32 mapping so callers
-/// matching on `kind()` keep working, while the exact `errno` is preserved for
+/// The [`io::ErrorKind`] preserves would-block semantics and otherwise uses the
+/// closest Win32 mapping. The exact `errno` is preserved for
 /// [`ErrorExt::posix_errno`].
 #[cfg(windows)]
 #[must_use]
 pub fn io_error_from_errno(errno: i32) -> io::Error {
-    let kind = io::Error::from_raw_os_error(errno_to_winerror(errno)).kind();
+    let kind = if errno == libc::EAGAIN {
+        io::ErrorKind::WouldBlock
+    } else {
+        io::Error::from_raw_os_error(errno_to_winerror(errno)).kind()
+    };
     io::Error::new(kind, CrtErrno(errno))
 }
 
diff --git a/crates/host_env/src/posix.rs b/crates/host_env/src/posix.rs
index a6ae039fd24..8308108cd34 100644
--- a/crates/host_env/src/posix.rs
+++ b/crates/host_env/src/posix.rs
@@ -15,6 +15,10 @@ pub use super::posix_unix_like::*;
 
 pub use libc::{c_char, pid_t};
 
+/// `<sys/param.h>` on glibc defines NODEV as `(dev_t)-1`.
+#[cfg(all(target_os = "linux", target_env = "gnu"))]
+pub const NODEV: i32 = -1;
+
 /// `<sysexits.h>`. The `libc` crate does not bind these.
 pub const EX_OK: i32 = 0;
 pub const EX_USAGE: i32 = 64;
@@ -569,6 +573,67 @@ pub fn statvfs_fd(fd: i32) -> std::io::Result<StatVfsInfo> {
     }
 }
 
+#[cfg(not(target_os = "redox"))]
+pub fn mkfifo(path: &CStr, mode: libc::mode_t) -> std::io::Result<()> {
+    let ret = unsafe { libc::mkfifo(path.as_ptr(), mode) };
+    if ret == 0 {
+        Ok(())
+    } else {
+        Err(std::io::Error::last_os_error())
+    }
+}
+
+#[cfg(target_vendor = "apple")]
+type MkfifoAt = unsafe extern "C" fn(libc::c_int, *const libc::c_char, libc::mode_t) -> libc::c_int;
+
+#[cfg(target_vendor = "apple")]
+fn mkfifoat_symbol() -> Option<MkfifoAt> {
+    static MKFIFOAT: std::sync::OnceLock<Option<MkfifoAt>> = std::sync::OnceLock::new();
+    *MKFIFOAT.get_or_init(|| {
+        // mkfifoat was added in macOS 13 / iOS 16. Resolve it at runtime so
+        // ordinary mkfifo remains usable on older Apple systems.
+        let symbol = unsafe { libc::dlsym(libc::RTLD_DEFAULT, c"mkfifoat".as_ptr()) };
+        if symbol.is_null() {
+            None
+        } else {
+            // SAFETY: the system symbol has the MkfifoAt signature and stays
+            // loaded for the lifetime of the process.
+            Some(unsafe { core::mem::transmute::<*mut libc::c_void, MkfifoAt>(symbol) })
+        }
+    })
+}
+
+#[cfg(not(target_os = "redox"))]
+pub fn has_mkfifoat() -> bool {
+    #[cfg(target_vendor = "apple")]
+    {
+        mkfifoat_symbol().is_some()
+    }
+    #[cfg(not(target_vendor = "apple"))]
+    {
+        !cfg!(target_os = "android")
+    }
+}
+
+#[cfg(not(any(target_os = "redox", target_os = "android")))]
+pub fn mkfifoat(dir_fd: i32, path: &CStr, mode: libc::mode_t) -> std::io::Result<()> {
+    #[cfg(target_vendor = "apple")]
+    let mkfifoat = mkfifoat_symbol().ok_or_else(|| {
+        std::io::Error::new(
+            std::io::ErrorKind::Unsupported,
+            "mkfifoat unavailable on this platform",
+        )
+    })?;
+    #[cfg(not(target_vendor = "apple"))]
+    let mkfifoat = libc::mkfifoat;
+    let ret = unsafe { mkfifoat(dir_fd, path.as_ptr(), mode) };
+    if ret == 0 {
+        Ok(())
+    } else {
+        Err(std::io::Error::last_os_error())
+    }
+}
+
 #[cfg(not(target_os = "redox"))]
 pub fn mknod(path: &CStr, mode: libc::mode_t, device: libc::dev_t) -> std::io::Result<()> {
     let ret = unsafe { libc::mknod(path.as_ptr(), mode, device) };
@@ -762,12 +827,12 @@ pub fn fchmod(fd: BorrowedFd<'_>, mode: u32) -> std::io::Result<()> {
 #[cfg(target_os = "redox")]
 pub fn utimes(
     path: &Path,
-    acc: core::time::Duration,
-    modif: core::time::Duration,
+    acc: crate::os::FileTime,
+    modif: crate::os::FileTime,
 ) -> std::io::Result<()> {
-    let tv = |d: core::time::Duration| libc::timeval {
-        tv_sec: d.as_secs() as _,
-        tv_usec: d.subsec_micros() as _,
+    let tv = |time: crate::os::FileTime| libc::timeval {
+        tv_sec: time.seconds,
+        tv_usec: (time.nanoseconds / 1_000) as _,
     };
     nix::sys::stat::utimes(path, &tv(acc).into(), &tv(modif).into()).map_err(std::io::Error::from)
 }
@@ -776,13 +841,13 @@ pub fn utimes(
 pub fn set_file_times_at(
     dir_fd: i32,
     path: &CStr,
-    access: core::time::Duration,
-    modified: core::time::Duration,
+    access: crate::os::FileTime,
+    modified: crate::os::FileTime,
     follow_symlinks: bool,
 ) -> std::io::Result<()> {
-    let ts = |d: core::time::Duration| libc::timespec {
-        tv_sec: d.as_secs() as _,
-        tv_nsec: d.subsec_nanos() as _,
+    let ts = |time: crate::os::FileTime| libc::timespec {
+        tv_sec: time.seconds,
+        tv_nsec: time.nanoseconds as _,
     };
     let times = [ts(access), ts(modified)];
     let ret = unsafe {
@@ -1087,13 +1152,22 @@ pub fn sync() {
     unsafe { libc::sync() };
 }
 
-pub fn getlogin() -> Option<CString> {
+pub fn getlogin() -> std::io::Result<CString> {
+    let old_errno = crate::os::get_errno();
+    crate::os::clear_errno();
     let ptr = unsafe { libc::getlogin() };
-    if ptr.is_null() {
-        None
+    let result = if ptr.is_null() {
+        let errno = crate::os::get_errno();
+        Err(if errno == 0 {
+            std::io::Error::other("unable to determine login name")
+        } else {
+            std::io::Error::from_raw_os_error(errno)
+        })
     } else {
-        Some(unsafe { CStr::from_ptr(ptr) }.to_owned())
-    }
+        Ok(unsafe { CStr::from_ptr(ptr) }.to_owned())
+    };
+    crate::os::set_errno(old_errno);
+    result
 }
 
 pub fn restore_signals() {
@@ -1884,26 +1958,71 @@ pub fn posix_spawn(config: PosixSpawnConfig<'_>) -> std::io::Result<libc::pid_t>
 
 #[cfg(target_os = "linux")]
 pub fn sendfile(
-    out_fd: BorrowedFd<'_>,
-    in_fd: BorrowedFd<'_>,
-    offset: &mut crate::crt_fd::Offset,
+    out_fd: i32,
+    in_fd: i32,
+    offset: Option<&mut crate::crt_fd::Offset>,
     count: usize,
 ) -> std::io::Result<usize> {
-    nix::sys::sendfile::sendfile(out_fd, in_fd, Some(offset), count).map_err(std::io::Error::from)
+    let offset = offset.map_or(core::ptr::null_mut(), |offset| offset as *mut _);
+    // The syscall validates raw descriptor numbers; no Rust fd lifetime is claimed.
+    let result = unsafe { libc::sendfile(out_fd, in_fd, offset, count) };
+    if result < 0 {
+        Err(std::io::Error::last_os_error())
+    } else {
+        Ok(result as usize)
+    }
 }
 
 #[cfg(target_os = "macos")]
 pub fn sendfile(
-    in_fd: BorrowedFd<'_>,
-    out_fd: BorrowedFd<'_>,
+    in_fd: i32,
+    out_fd: i32,
     offset: crate::crt_fd::Offset,
-    count: i64,
+    written: &mut i64,
     headers: Option<&[&[u8]]>,
     trailers: Option<&[&[u8]]>,
-) -> (std::io::Result<()>, i64) {
-    let (res, written) =
-        nix::sys::sendfile::sendfile(in_fd, out_fd, offset, Some(count), headers, trailers);
-    (res.map_err(std::io::Error::from), written)
+    flags: i32,
+) -> std::io::Result<()> {
+    let header_count = headers.map_or(0, |buffers| buffers.len());
+    let trailer_count = trailers.map_or(0, |buffers| buffers.len());
+    let (Ok(header_count), Ok(trailer_count)) =
+        (i32::try_from(header_count), i32::try_from(trailer_count))
+    else {
+        return Err(std::io::Error::from(std::io::ErrorKind::InvalidInput));
+    };
+    let iovecs = |buffers: Option<&[&[u8]]>| {
+        buffers
+            .unwrap_or_default()
+            .iter()
+            .map(|buffer| libc::iovec {
+                iov_base: buffer.as_ptr().cast_mut().cast(),
+                iov_len: buffer.len(),
+            })
+            .collect::<Vec<_>>()
+    };
+    let mut headers = iovecs(headers);
+    let mut trailers = iovecs(trailers);
+    let mut hdtr = libc::sf_hdtr {
+        headers: if headers.is_empty() {
+            core::ptr::null_mut()
+        } else {
+            headers.as_mut_ptr()
+        },
+        hdr_cnt: header_count,
+        trailers: if trailers.is_empty() {
+            core::ptr::null_mut()
+        } else {
+            trailers.as_mut_ptr()
+        },
+        trl_cnt: trailer_count,
+    };
+    // The slices and both iovec arrays remain live for this synchronous call.
+    let result = unsafe { libc::sendfile(in_fd, out_fd, offset, written, &mut hdtr, flags) };
+    if result < 0 {
+        Err(std::io::Error::last_os_error())
+    } else {
+        Ok(())
+    }
 }
 
 #[cfg(any(
diff --git a/crates/host_env/src/posix_wasi.rs b/crates/host_env/src/posix_wasi.rs
index df09c08bc09..7c055f08426 100644
--- a/crates/host_env/src/posix_wasi.rs
+++ b/crates/host_env/src/posix_wasi.rs
@@ -1,5 +1,5 @@
 use alloc::ffi::CString;
-use core::{ffi::CStr, time::Duration};
+use core::ffi::CStr;
 use rustix::fd::AsFd;
 use std::{ffi::OsStr, io, path::Path};
 
@@ -14,13 +14,13 @@ pub fn stat_fd(fd: crate::crt_fd::Borrowed<'_>) -> io::Result<crate::fileutils::
 pub fn set_file_times_at(
     dir_fd: i32,
     path: &CStr,
-    access: Duration,
-    modified: Duration,
+    access: crate::os::FileTime,
+    modified: crate::os::FileTime,
     follow_symlinks: bool,
 ) -> io::Result<()> {
-    let ts = |d: Duration| libc::timespec {
-        tv_sec: d.as_secs() as _,
-        tv_nsec: d.subsec_nanos() as _,
+    let ts = |time: crate::os::FileTime| libc::timespec {
+        tv_sec: time.seconds,
+        tv_nsec: time.nanoseconds as _,
     };
     let times = [ts(access), ts(modified)];
     unsafe {
diff --git a/crates/host_env/src/readline.rs b/crates/host_env/src/readline.rs
index f3f468cba56..c37d3714de0 100644
--- a/crates/host_env/src/readline.rs
+++ b/crates/host_env/src/readline.rs
@@ -196,3 +196,129 @@ impl<H: Helper> Readline<H> {
         self.0.readline(prompt)
     }
 }
+
+/// Borrow the shared buffered stdin for one physical read. The caller retains
+/// partial bytes across EINTR and checks signals after this lock is released.
+pub fn stdio_readline_bytes(prompt: &str, line: &mut Vec<u8>) -> io::Result<usize> {
+    use std::io::Write;
+    let mut stderr = io::stderr().lock();
+    stderr.write_all(prompt.as_bytes())?;
+    stderr.flush()?;
+    drop(stderr);
+    read_line_bytes(&mut io::stdin().lock(), line)
+}
+
+fn read_line_bytes(reader: &mut impl io::BufRead, line: &mut Vec<u8>) -> io::Result<usize> {
+    let mut read = 0;
+    loop {
+        // Unlike read_until, return Interrupted to the VM before retrying.
+        let available = reader.fill_buf()?;
+        if available.is_empty() {
+            return Ok(read);
+        }
+        let newline = available.iter().position(|&byte| byte == b'\n');
+        let used = newline.map_or(available.len(), |index| index + 1);
+        line.extend_from_slice(&available[..used]);
+        reader.consume(used);
+        read += used;
+        if newline.is_some() {
+            return Ok(read);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::read_line_bytes;
+    use std::io::{self, BufRead, Read};
+
+    struct ScriptedReader {
+        chunks: alloc::collections::VecDeque<io::Result<Vec<u8>>>,
+        consumed: usize,
+    }
+
+    impl ScriptedReader {
+        fn new(chunks: impl IntoIterator<Item = io::Result<Vec<u8>>>) -> Self {
+            Self {
+                chunks: chunks.into_iter().collect(),
+                consumed: 0,
+            }
+        }
+    }
+
+    impl Read for ScriptedReader {
+        fn read(&mut self, _: &mut [u8]) -> io::Result<usize> {
+            unreachable!("the transport uses BufRead directly")
+        }
+    }
+
+    impl BufRead for ScriptedReader {
+        fn fill_buf(&mut self) -> io::Result<&[u8]> {
+            if self.chunks.front().is_some_and(Result::is_err) {
+                return Err(self.chunks.pop_front().unwrap().unwrap_err());
+            }
+            Ok(self
+                .chunks
+                .front()
+                .map_or(&[], |chunk| &chunk.as_ref().unwrap()[self.consumed..]))
+        }
+
+        fn consume(&mut self, amount: usize) {
+            self.consumed += amount;
+            if self.consumed == self.chunks.front().unwrap().as_ref().unwrap().len() {
+                self.chunks.pop_front();
+                self.consumed = 0;
+            }
+        }
+    }
+
+    #[test]
+    fn physical_lines_preserve_buffered_remainder_and_count_only_new_bytes() {
+        let mut reader = ScriptedReader::new([Ok(b"one\ntwo\ntail".to_vec())]);
+        let mut line = b"prefix".to_vec();
+        assert_eq!(read_line_bytes(&mut reader, &mut line).unwrap(), 4);
+        assert_eq!(line, b"prefixone\n");
+        line.clear();
+        assert_eq!(read_line_bytes(&mut reader, &mut line).unwrap(), 4);
+        assert_eq!(line, b"two\n");
+        line.clear();
+        assert_eq!(read_line_bytes(&mut reader, &mut line).unwrap(), 4);
+        assert_eq!(line, b"tail");
+        assert_eq!(read_line_bytes(&mut reader, &mut line).unwrap(), 0);
+        assert_eq!(line, b"tail");
+    }
+
+    #[test]
+    fn errors_return_immediately_and_leave_partial_bytes_for_the_caller() {
+        for kind in [io::ErrorKind::Interrupted, io::ErrorKind::Other] {
+            let mut reader = ScriptedReader::new([
+                Ok(b"part".to_vec()),
+                Err(io::Error::from(kind)),
+                Ok(b"ial\nnext".to_vec()),
+            ]);
+            let mut line = Vec::new();
+            assert_eq!(
+                read_line_bytes(&mut reader, &mut line).unwrap_err().kind(),
+                kind
+            );
+            assert_eq!(line, b"part");
+            assert_eq!(read_line_bytes(&mut reader, &mut line).unwrap(), 4);
+            assert_eq!(line, b"partial\n");
+        }
+    }
+
+    #[test]
+    fn eof_after_interruption_keeps_partial_bytes() {
+        let mut reader = ScriptedReader::new([
+            Ok(b"partial".to_vec()),
+            Err(io::Error::from(io::ErrorKind::Interrupted)),
+        ]);
+        let mut line = Vec::new();
+        assert_eq!(
+            read_line_bytes(&mut reader, &mut line).unwrap_err().kind(),
+            io::ErrorKind::Interrupted
+        );
+        assert_eq!(read_line_bytes(&mut reader, &mut line).unwrap(), 0);
+        assert_eq!(line, b"partial");
+    }
+}
diff --git a/crates/host_env/src/select.rs b/crates/host_env/src/select.rs
index 287f64b56bf..814eb9900df 100644
--- a/crates/host_env/src/select.rs
+++ b/crates/host_env/src/select.rs
@@ -36,10 +36,62 @@ pub mod platform {
 #[allow(non_snake_case)]
 #[cfg(windows)]
 pub mod platform {
-    pub use WinSock::{FD_SET as fd_set, FD_SETSIZE, SOCKET as RawFd, TIMEVAL as timeval, select};
+    pub use WinSock::{SOCKET as RawFd, TIMEVAL as timeval};
     use std::io;
     use windows_sys::Win32::Networking::WinSock;
 
+    // Match CPython's Windows capacity. WinSock uses fd_count to determine
+    // the array length; the windows-sys declaration has the SDK default of 64.
+    pub const FD_SETSIZE: u32 = 512;
+
+    #[allow(non_camel_case_types)]
+    #[repr(C)]
+    pub struct fd_set {
+        fd_count: u32,
+        fd_array: [RawFd; FD_SETSIZE as usize],
+    }
+
+    const _: () = {
+        assert!(core::mem::align_of::<fd_set>() == core::mem::align_of::<WinSock::FD_SET>());
+        assert!(
+            core::mem::offset_of!(fd_set, fd_count)
+                == core::mem::offset_of!(WinSock::FD_SET, fd_count)
+        );
+        assert!(
+            core::mem::offset_of!(fd_set, fd_array)
+                == core::mem::offset_of!(WinSock::FD_SET, fd_array)
+        );
+        assert!(
+            core::mem::size_of::<fd_set>()
+                == core::mem::offset_of!(fd_set, fd_array)
+                    + FD_SETSIZE as usize * core::mem::size_of::<RawFd>()
+        );
+    };
+
+    /// # Safety
+    ///
+    /// Every non-null set must point to an initialized fd_set, and timeout
+    /// must be null or point to an initialized timeval.
+    pub unsafe fn select(
+        nfds: i32,
+        readfds: *mut fd_set,
+        writefds: *mut fd_set,
+        errorfds: *mut fd_set,
+        timeout: *const timeval,
+    ) -> i32 {
+        // fd_set is a count followed by a caller-sized SOCKET array. Both
+        // layouts have the same alignment and offset of the array.
+        unsafe {
+            WinSock::select(
+                nfds,
+                readfds.cast(),
+                writefds.cast(),
+                errorfds.cast(),
+                timeout,
+            )
+        }
+    }
+
     /// # Safety
     ///
     /// `set` must be a valid mutable pointer to an initialized WinSock fd_set.
@@ -71,8 +123,8 @@ pub mod platform {
     ///
     /// `set` must be a valid mutable pointer to an initialized WinSock fd_set.
     pub unsafe fn FD_ISSET(fd: RawFd, set: *mut fd_set) -> bool {
-        use WinSock::__WSAFDIsSet;
-        unsafe { __WSAFDIsSet(fd as _, set) != 0 }
+        let set = unsafe { &*set };
+        set.fd_array[..set.fd_count as usize].contains(&fd)
     }
 
     #[must_use]
diff --git a/crates/host_env/src/signal.rs b/crates/host_env/src/signal.rs
index 090269123fc..f5205d84190 100644
--- a/crates/host_env/src/signal.rs
+++ b/crates/host_env/src/signal.rs
@@ -1,3 +1,4 @@
+#[cfg(any(unix, windows))]
 use std::io;
 #[cfg(windows)]
 use std::sync::Once;
@@ -13,13 +14,109 @@ pub use libc::sighandler_t;
 #[cfg(unix)]
 pub use libc::{SIG_DFL, SIG_ERR, SIG_IGN};
 
-#[cfg(not(unix))]
+#[cfg(not(any(unix, target_os = "wasi")))]
 pub const SIG_DFL: libc::sighandler_t = 0;
-#[cfg(not(unix))]
+#[cfg(not(any(unix, target_os = "wasi")))]
 pub const SIG_IGN: libc::sighandler_t = 1;
-#[cfg(not(unix))]
+#[cfg(not(any(unix, target_os = "wasi")))]
 pub const SIG_ERR: libc::sighandler_t = -1 as _;
 
+/// wasi-libc's userspace emulation of `signal()`/`raise()`, linked from
+/// `libwasi-emulated-signal` (see `crates/host_env/vendor/wasm32-wasip1`).
+/// WebAssembly has no asynchronous signal delivery, so this is a
+/// synchronous, in-process handler table: a handler only runs when this
+/// process's own code calls `raise()`, never from an outside interrupt.
+/// Numbering matches wasi-libc's `bits/signal.h`, the same values CPython's
+/// WASI build gets by linking the same library.
+#[cfg(target_os = "wasi")]
+mod wasm {
+    use std::io;
+
+    #[allow(non_camel_case_types)]
+    pub type sighandler_t = usize;
+
+    pub const SIG_DFL: sighandler_t = 0;
+    pub const SIG_IGN: sighandler_t = 1;
+    pub const SIG_ERR: sighandler_t = -1isize as usize;
+
+    pub const SIGINT: i32 = 2;
+    pub const SIGILL: i32 = 4;
+    pub const SIGABRT: i32 = 6;
+    pub const SIGFPE: i32 = 8;
+    pub const SIGSEGV: i32 = 11;
+    pub const SIGTERM: i32 = 15;
+
+    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
+    pub enum Handler {
+        Default,
+        Ignore,
+        Custom(sighandler_t),
+    }
+
+    unsafe extern "C" {
+        #[link_name = "signal"]
+        fn c_signal(signum: i32, handler: sighandler_t) -> sighandler_t;
+        #[link_name = "__SIG_IGN"]
+        fn c_sig_ign(signum: i32);
+        #[link_name = "__SIG_ERR"]
+        fn c_sig_err(signum: i32);
+        fn raise(signum: i32) -> i32;
+    }
+
+    impl Handler {
+        fn as_raw(self) -> sighandler_t {
+            match self {
+                Self::Default => 0,
+                Self::Ignore => c_sig_ign as *const () as sighandler_t,
+                Self::Custom(handler) => handler,
+            }
+        }
+
+        fn from_raw(handler: sighandler_t) -> io::Result<Self> {
+            // wasi-libc uses function pointers for SIG_IGN and SIG_ERR because
+            // table index 1 is also a valid custom Wasm function pointer.
+            if handler == c_sig_err as *const () as sighandler_t {
+                Err(io::Error::last_os_error())
+            } else if handler == 0 {
+                Ok(Self::Default)
+            } else if handler == c_sig_ign as *const () as sighandler_t {
+                Ok(Self::Ignore)
+            } else {
+                Ok(Self::Custom(handler))
+            }
+        }
+    }
+
+    /// # Safety
+    ///
+    /// The caller must ensure `signalnum` is a valid platform signal number.
+    pub unsafe fn probe_handler(signalnum: i32) -> Option<Handler> {
+        let handler = unsafe { install_handler(signalnum, Handler::Ignore) }.ok()?;
+        unsafe { install_handler(signalnum, handler) }.ok()?;
+        Some(handler)
+    }
+
+    /// # Safety
+    ///
+    /// The caller must ensure `signalnum` is a valid platform signal number and
+    /// a custom `handler` is accepted by the platform signal ABI.
+    pub unsafe fn install_handler(signalnum: i32, handler: Handler) -> io::Result<Handler> {
+        let old = unsafe { c_signal(signalnum, handler.as_raw()) };
+        Handler::from_raw(old)
+    }
+
+    pub fn raise_signal(signalnum: i32) -> io::Result<()> {
+        if unsafe { raise(signalnum) } == 0 {
+            Ok(())
+        } else {
+            Err(io::Error::last_os_error())
+        }
+    }
+}
+
+#[cfg(target_os = "wasi")]
+pub use wasm::*;
+
 #[cfg(unix)]
 pub use libc::{SIG_BLOCK, SIG_SETMASK, SIG_UNBLOCK};
 
@@ -104,12 +201,26 @@ mod ffi {
 /// The caller must ensure `signalnum` is a valid platform signal number.
 #[cfg(any(unix, windows))]
 pub unsafe fn probe_handler(signalnum: i32) -> Option<sighandler_t> {
-    let handler = unsafe { libc::signal(signalnum, libc::SIG_IGN) };
-    if handler == libc::SIG_ERR as sighandler_t {
-        None
-    } else {
-        unsafe { libc::signal(signalnum, handler) };
-        Some(handler)
+    #[cfg(unix)]
+    {
+        // Query without changing disposition: even temporarily ignoring SIGCHLD
+        // can discard a child's exit status, and signal() also replaces masks.
+        let mut action = core::mem::MaybeUninit::<libc::sigaction>::uninit();
+        if unsafe { libc::sigaction(signalnum, core::ptr::null(), action.as_mut_ptr()) } == 0 {
+            Some(unsafe { action.assume_init() }.sa_sigaction)
+        } else {
+            None
+        }
+    }
+    #[cfg(windows)]
+    {
+        let handler = unsafe { libc::signal(signalnum, libc::SIG_IGN) };
+        if handler == libc::SIG_ERR as sighandler_t {
+            None
+        } else {
+            unsafe { libc::signal(signalnum, handler) };
+            Some(handler)
+        }
     }
 }
 
@@ -284,13 +395,28 @@ pub fn wakeup_fd_is_socket(fd: libc::SOCKET) -> io::Result<bool> {
     Ok(false)
 }
 
+#[cfg(windows)]
+pub struct WakeupSendError(pub i32);
+
+#[cfg(windows)]
+impl WakeupSendError {
+    pub fn is_would_block(&self) -> bool {
+        self.0 == windows_sys::Win32::Networking::WinSock::WSAEWOULDBLOCK
+    }
+
+    // Only convert to an allocating error outside the OS signal handler.
+    pub fn into_io_error(self) -> io::Error {
+        io::Error::from_raw_os_error(self.0)
+    }
+}
+
 #[cfg(windows)]
 pub fn notify_signal(
     signum: i32,
     wakeup_fd: libc::SOCKET,
     wakeup_is_socket: bool,
     sigint_event: Option<isize>,
-) {
+) -> Option<WakeupSendError> {
     if signum == libc::SIGINT
         && let Some(handle) = sigint_event
     {
@@ -300,27 +426,35 @@ pub fn notify_signal(
     }
 
     if wakeup_fd == INVALID_SOCKET {
-        return;
+        return None;
     }
 
     let sigbyte = signum as u8;
     if wakeup_is_socket {
-        unsafe {
-            let _ = windows_sys::Win32::Networking::WinSock::send(
+        let result = unsafe {
+            windows_sys::Win32::Networking::WinSock::send(
                 wakeup_fd,
                 &sigbyte as *const u8 as *const _,
                 1,
                 0,
-            );
+            )
+        };
+        if result < 0 {
+            Some(WakeupSendError(unsafe {
+                windows_sys::Win32::Networking::WinSock::WSAGetLastError()
+            }))
+        } else {
+            None
         }
     } else {
         unsafe {
             let _ = libc::write(wakeup_fd as _, &sigbyte as *const u8 as *const _, 1);
         }
+        None
     }
 }
 
-#[cfg(unix)]
+#[cfg(any(unix, target_os = "wasi"))]
 pub fn notify_signal(signum: i32, wakeup_fd: i32) {
     if wakeup_fd == -1 {
         return;
@@ -379,3 +513,49 @@ pub fn sigset_contains(mask: libc::sigset_t, signum: i32) -> bool {
 pub fn valid_signals(_max_signum: usize) -> io::Result<Vec<i32>> {
     Ok(VALID_SIGNALS.to_vec())
 }
+
+#[cfg(test)]
+#[cfg(unix)]
+mod tests {
+    #[test]
+    fn probing_preserves_signal_flags_and_mask() {
+        unsafe extern "C" fn handler(_: libc::c_int) {}
+
+        struct Restore(libc::sigaction);
+        impl Drop for Restore {
+            fn drop(&mut self) {
+                unsafe { libc::sigaction(libc::SIGUSR2, &self.0, core::ptr::null_mut()) };
+            }
+        }
+
+        // No other host_env test uses SIGUSR2; retain the host disposition even
+        // when an assertion fails. Do not deliver any signal to the process.
+        unsafe {
+            let mut action: libc::sigaction = core::mem::zeroed();
+            action.sa_sigaction = handler as *const () as libc::sighandler_t;
+            action.sa_flags = libc::SA_NODEFER;
+            assert_eq!(libc::sigemptyset(&mut action.sa_mask), 0);
+            assert_eq!(libc::sigaddset(&mut action.sa_mask, libc::SIGUSR1), 0);
+            let mut original = core::mem::MaybeUninit::uninit();
+            assert_eq!(
+                libc::sigaction(libc::SIGUSR2, &action, original.as_mut_ptr()),
+                0
+            );
+            let _restore = Restore(original.assume_init());
+
+            assert_eq!(
+                super::probe_handler(libc::SIGUSR2),
+                Some(action.sa_sigaction)
+            );
+            let mut observed = core::mem::MaybeUninit::<libc::sigaction>::uninit();
+            assert_eq!(
+                libc::sigaction(libc::SIGUSR2, core::ptr::null(), observed.as_mut_ptr()),
+                0
+            );
+            let observed = observed.assume_init();
+            assert_eq!(observed.sa_sigaction, action.sa_sigaction);
+            assert_ne!(observed.sa_flags & libc::SA_NODEFER, 0);
+            assert_eq!(libc::sigismember(&observed.sa_mask, libc::SIGUSR1), 1);
+        }
+    }
+}
diff --git a/crates/host_env/src/socket.rs b/crates/host_env/src/socket.rs
index c70f4a16068..abf21660892 100644
--- a/crates/host_env/src/socket.rs
+++ b/crates/host_env/src/socket.rs
@@ -991,7 +991,13 @@ pub fn recvmsg(
 ) -> io::Result<RecvMsgResult> {
     use core::mem::MaybeUninit;
 
-    let mut data_buf: Vec<MaybeUninit<u8>> = vec![MaybeUninit::uninit(); bufsize];
+    // MSG_TRUNC on Linux TCP can report consumed bytes without writing data.
+    let initial = if flags & libc::MSG_TRUNC != 0 {
+        MaybeUninit::new(0)
+    } else {
+        MaybeUninit::uninit()
+    };
+    let mut data_buf = vec![initial; bufsize];
     let mut anc_buf: Vec<MaybeUninit<u8>> = vec![MaybeUninit::uninit(); ancbufsize];
     let mut addr_storage: libc::sockaddr_storage = unsafe { core::mem::zeroed() };
 
@@ -1013,7 +1019,8 @@ pub fn recvmsg(
     let ret = unsafe { libc::recvmsg(fd.as_raw_fd(), &mut msg, flags) }.check_libc_neg()?;
 
     let data = unsafe {
-        data_buf.set_len(ret as usize);
+        // Datagram MSG_TRUNC may report more bytes than the supplied storage.
+        data_buf.set_len((ret as usize).min(bufsize));
         core::mem::transmute::<Vec<MaybeUninit<u8>>, Vec<u8>>(data_buf)
     };
     let control = unsafe {
diff --git a/crates/host_env/src/ssl/cipher.rs b/crates/host_env/src/ssl/cipher.rs
index 34c50f15de1..6038cd32336 100644
--- a/crates/host_env/src/ssl/cipher.rs
+++ b/crates/host_env/src/ssl/cipher.rs
@@ -444,9 +444,9 @@ pub fn kx_group_by_openssl_name(name: &str) -> Option<&'static dyn SupportedKxGr
 
 fn kx_group_openssl_names(name: rustls::NamedGroup) -> &'static [&'static str] {
     match name {
-        rustls::NamedGroup::secp256r1 => &["prime256v1", "secp256r1"],
-        rustls::NamedGroup::secp384r1 => &["secp384r1", "prime384v1"],
-        rustls::NamedGroup::secp521r1 => &["secp521r1", "prime521v1"],
+        rustls::NamedGroup::secp256r1 => &["prime256v1", "secp256r1", "P-256"],
+        rustls::NamedGroup::secp384r1 => &["secp384r1", "prime384v1", "P-384"],
+        rustls::NamedGroup::secp521r1 => &["secp521r1", "prime521v1", "P-521"],
         rustls::NamedGroup::X25519 => &["X25519", "x25519"],
         rustls::NamedGroup::X448 => &["X448", "x448"],
         rustls::NamedGroup::MLKEM768 => &["MLKEM768"],
diff --git a/crates/host_env/src/ssl/config.rs b/crates/host_env/src/ssl/config.rs
index f19e53e189d..81fb37eda30 100644
--- a/crates/host_env/src/ssl/config.rs
+++ b/crates/host_env/src/ssl/config.rs
@@ -22,6 +22,7 @@ pub struct ProtocolSettings {
     pub versions: &'static [&'static rustls::SupportedProtocolVersion],
     pub kx_groups: Option<Vec<&'static dyn rustls::crypto::SupportedKxGroup>>,
     pub cipher_suites: Option<Vec<rustls::SupportedCipherSuite>>,
+    pub server_sigalgs: Option<Vec<rustls::SignatureScheme>>,
     pub alpn_protocols: Vec<Vec<u8>>,
 }
 
@@ -176,12 +177,27 @@ pub fn create_server_config(options: ServerConfigOptions) -> Result<chain::Serve
     // Add certificate
     let mut config = if let Some(resolver) = options.cert_resolver {
         // Use custom cert resolver (e.g., for SNI)
+        let resolver = if let Some(schemes) = options.protocol_settings.server_sigalgs.clone() {
+            Arc::new(super::sigalg::ServerResolver {
+                inner: resolver,
+                schemes,
+            }) as Arc<dyn ResolvesServerCert>
+        } else {
+            resolver
+        };
         builder.with_cert_resolver(resolver)
     } else {
         // Use single certificate
-        builder
-            .with_single_cert(options.cert_chain, options.private_key)
-            .map_err(|e| format!("Failed to set server certificate: {e}"))?
+        let key = CertifiedKey::from_der(
+            options.cert_chain,
+            options.private_key,
+            CryptoExt::get_provider(),
+        )
+        .map_err(|e| format!("Failed to set server certificate: {e}"))?;
+        builder.with_cert_resolver(Arc::new(MultiCertResolver::new(
+            vec![Arc::new(key)],
+            options.protocol_settings.server_sigalgs.as_deref(),
+        )))
     };
 
     // Set ALPN protocols with fallback
@@ -432,6 +448,15 @@ pub fn create_client_config(options: ClientConfigOptions) -> Result<chain::Clien
         Arc::new(NoVerifier)
     };
 
+    let verifier = if let Some(schemes) = options.protocol_settings.server_sigalgs {
+        Arc::new(super::sigalg::ServerVerifier {
+            inner: verifier,
+            schemes,
+        }) as Arc<dyn rustls::client::danger::ServerCertVerifier>
+    } else {
+        verifier
+    };
+
     // Step 2: Create ClientConfig builder once with the selected verifier
     let builder = ClientConfig::builder_with_provider(custom_provider)
         .with_protocol_versions(options.protocol_settings.versions)
@@ -481,7 +506,15 @@ pub struct MultiCertResolver {
 
 impl MultiCertResolver {
     /// Create a new multi-certificate resolver
-    pub fn new(cert_keys: Vec<Arc<CertifiedKey>>) -> Self {
+    pub fn new(
+        mut cert_keys: Vec<Arc<CertifiedKey>>,
+        schemes: Option<&[rustls::SignatureScheme]>,
+    ) -> Self {
+        if let Some(schemes) = schemes {
+            for key in &mut cert_keys {
+                *key = super::sigalg::restrict_key(key, schemes);
+            }
+        }
         Self { cert_keys }
     }
 }
diff --git a/crates/host_env/src/ssl/error.rs b/crates/host_env/src/ssl/error.rs
index cec73e49ff7..a7ddcf613fa 100644
--- a/crates/host_env/src/ssl/error.rs
+++ b/crates/host_env/src/ssl/error.rs
@@ -43,6 +43,9 @@ impl TlsError {
                 use rustls::PeerIncompatible;
                 match peer_err {
                     PeerIncompatible::NoCipherSuitesInCommon => Self::NoCipherSuites,
+                    PeerIncompatible::NoSignatureSchemesInCommon => {
+                        Self::Ssl("no signature schemes in common".to_owned())
+                    }
                     _ => Self::Eof,
                 }
             }
@@ -66,3 +69,38 @@ impl From<std::io::Error> for TlsError {
         Self::Io(err)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn signature_incompatibility_is_not_transport_eof() {
+        let error = TlsError::from_rustls(rustls::Error::PeerIncompatible(
+            rustls::PeerIncompatible::NoSignatureSchemesInCommon,
+        ));
+        assert!(!error.is_eof());
+        assert!(matches!(error, TlsError::Ssl(_)));
+    }
+
+    #[test]
+    fn unrelated_negotiation_and_transport_errors_keep_their_classification() {
+        assert!(matches!(
+            TlsError::from_rustls(rustls::Error::PeerIncompatible(
+                rustls::PeerIncompatible::NoCipherSuitesInCommon,
+            )),
+            TlsError::NoCipherSuites
+        ));
+        assert!(matches!(
+            TlsError::from_rustls(rustls::Error::PeerIncompatible(
+                rustls::PeerIncompatible::Tls12NotOffered,
+            )),
+            TlsError::Eof
+        ));
+        let os_error = std::io::Error::from_raw_os_error(10053);
+        match TlsError::from(os_error) {
+            TlsError::Io(error) => assert_eq!(error.raw_os_error(), Some(10053)),
+            error => panic!("OS error was reclassified: {error:?}"),
+        }
+    }
+}
diff --git a/crates/host_env/src/ssl/handshake.rs b/crates/host_env/src/ssl/handshake.rs
index 6df5d070ced..f70f53370e1 100644
--- a/crates/host_env/src/ssl/handshake.rs
+++ b/crates/host_env/src/ssl/handshake.rs
@@ -47,6 +47,34 @@ pub fn sni_alert(description: u8) -> Vec<u8> {
     vec![21, 3, 3, 0, 2, 2, description]
 }
 
+/// Serialize a failed initial `Accepted::into_connection` attempt.
+///
+/// No server bytes have been sent at this boundary. Rustls may have queued
+/// ServerHello before finding that a full handshake has no usable signature,
+/// or may return a signing-key error without queuing any alert (TLS 1.2).
+/// Send only a plaintext fatal alert, so the peer cannot start its next flight
+/// while the server is closing. Keep certificate/session selection in rustls:
+/// resumed sessions do not need a new certificate signature.
+pub fn initial_handshake_alert(
+    error: &rustls::Error,
+    mut alert: rustls::server::AcceptedAlert,
+) -> std::io::Result<Vec<u8>> {
+    // TLS 1.2's emit_server_kx reports the exact General message below when
+    // SigningKey::choose_scheme fails; TLS 1.3 uses PeerIncompatible.
+    let signature_mismatch = matches!(
+        error,
+        rustls::Error::PeerIncompatible(rustls::PeerIncompatible::NoSignatureSchemesInCommon)
+    ) || matches!(error, rustls::Error::General(message) if message == "incompatible signing key");
+    if signature_mismatch {
+        return Ok(sni_alert(u8::from(
+            rustls::AlertDescription::HandshakeFailure,
+        )));
+    }
+    let mut bytes = Vec::new();
+    alert.write_all(&mut bytes)?;
+    Ok(bytes)
+}
+
 pub fn feed_acceptor(acceptor: &mut Acceptor, bytes: &[u8]) -> std::io::Result<()> {
     let mut reader = std::io::Cursor::new(bytes);
     while reader.position() < bytes.len() as u64 {
@@ -107,3 +135,322 @@ mod tests {
         assert_eq!(sni_alert(80), [21, 3, 3, 0, 2, 2, 80]);
     }
 }
+
+#[cfg(test)]
+mod signature_tests {
+    use super::super::config::MultiCertResolver;
+    use super::*;
+    use alloc::sync::Arc;
+    use rustls::{
+        ClientConnection, SignatureScheme, client::WebPkiServerVerifier, server::Acceptor,
+    };
+    use rustls::{RootCertStore, SupportedCipherSuite, crypto::CryptoProvider, sign::CertifiedKey};
+    use rustls::{client::ClientConfig, server::ServerConfig};
+
+    fn certificate_key(mut pem: &[u8], provider: &CryptoProvider) -> Arc<CertifiedKey> {
+        let mut private_key_pem = pem;
+        let certificates = rustls_pemfile::certs(&mut pem)
+            .collect::<Result<Vec<_>, _>>()
+            .unwrap();
+        let key = rustls_pemfile::private_key(&mut private_key_pem)
+            .unwrap()
+            .unwrap();
+        Arc::new(CertifiedKey::from_der(certificates, key, provider).unwrap())
+    }
+
+    fn client_config(
+        version: &'static rustls::SupportedProtocolVersion,
+        scheme: SignatureScheme,
+        cipher_suite: Option<SupportedCipherSuite>,
+    ) -> Arc<ClientConfig> {
+        let mut provider = rustls::crypto::aws_lc_rs::default_provider();
+        if let Some(suite) = cipher_suite {
+            provider.cipher_suites = vec![suite];
+        }
+        let provider = Arc::new(provider);
+        let mut roots = RootCertStore::empty();
+        let ca = include_bytes!("../../../../Lib/test/certdata/pycacert.pem");
+        for cert in rustls_pemfile::certs(&mut &ca[..]) {
+            roots.add(cert.unwrap()).unwrap();
+        }
+        let verifier =
+            WebPkiServerVerifier::builder_with_provider(Arc::new(roots), provider.clone())
+                .build()
+                .unwrap();
+        let config = ClientConfig::builder_with_provider(provider)
+            .with_protocol_versions(&[version])
+            .unwrap()
+            .dangerous()
+            .with_custom_certificate_verifier(Arc::new(super::super::sigalg::ServerVerifier {
+                inner: verifier,
+                schemes: vec![scheme],
+            }))
+            .with_no_client_auth();
+        Arc::new(config)
+    }
+
+    fn client_hello(config: Arc<ClientConfig>) -> (ClientConnection, rustls::server::Accepted) {
+        let mut client = ClientConnection::new(config, "localhost".try_into().unwrap()).unwrap();
+        let mut hello = Vec::new();
+        client.write_tls(&mut hello).unwrap();
+        let mut acceptor = Acceptor::default();
+        super::super::handshake::feed_acceptor(&mut acceptor, &hello).unwrap();
+        (client, acceptor.accept().unwrap().unwrap())
+    }
+
+    fn server_config(
+        version: &'static rustls::SupportedProtocolVersion,
+        include_incompatible_first_key: bool,
+        cipher_suite: Option<SupportedCipherSuite>,
+        scheme: SignatureScheme,
+    ) -> Arc<ServerConfig> {
+        let mut provider = rustls::crypto::aws_lc_rs::default_provider();
+        if let Some(suite) = cipher_suite {
+            provider.cipher_suites = vec![suite];
+        }
+        let provider = Arc::new(provider);
+        let mut keys = Vec::new();
+        if include_incompatible_first_key {
+            keys.push(certificate_key(
+                include_bytes!("../../../../Lib/test/certdata/keycertecc.pem"),
+                &provider,
+            ));
+        }
+        keys.push(certificate_key(
+            include_bytes!("../../../../Lib/test/certdata/keycert3.pem"),
+            &provider,
+        ));
+        Arc::new(
+            ServerConfig::builder_with_provider(provider)
+                .with_protocol_versions(&[version])
+                .unwrap()
+                .with_no_client_auth()
+                .with_cert_resolver(Arc::new(MultiCertResolver::new(keys, Some(&[scheme])))),
+        )
+    }
+
+    fn assert_signature_mismatch_sends_only_a_fatal_alert(
+        version: &'static rustls::SupportedProtocolVersion,
+    ) {
+        let (mut client, accepted) = client_hello(client_config(
+            version,
+            SignatureScheme::RSA_PSS_SHA256,
+            None,
+        ));
+        let (error, alert) = accepted
+            .into_connection(server_config(
+                version,
+                false,
+                None,
+                SignatureScheme::RSA_PSS_SHA384,
+            ))
+            .unwrap_err();
+        let bytes = initial_handshake_alert(&error, alert).unwrap();
+        assert!(matches!(
+            super::super::error::TlsError::from_rustls(error),
+            super::super::error::TlsError::Ssl(_)
+        ));
+        assert_eq!(bytes.len(), 7, "only a plaintext alert may precede failure");
+        assert_eq!(bytes[0], 21, "no ServerHello or CCS may precede the alert");
+        assert_eq!(&bytes[3..6], &[0, 2, 2]);
+        client.read_tls(&mut &bytes[..]).unwrap();
+        assert!(matches!(
+            client.process_new_packets(),
+            Err(rustls::Error::AlertReceived(_))
+        ));
+        assert!(
+            !client.wants_write(),
+            "a rejected client must not queue CCS"
+        );
+    }
+
+    #[test]
+    fn tls12_signature_mismatch_sends_only_a_fatal_alert() {
+        assert_signature_mismatch_sends_only_a_fatal_alert(&rustls::version::TLS12);
+    }
+
+    #[test]
+    fn tls13_signature_mismatch_sends_only_a_fatal_alert() {
+        assert_signature_mismatch_sends_only_a_fatal_alert(&rustls::version::TLS13);
+    }
+
+    #[test]
+    fn unrelated_initial_alert_and_similar_error_text_are_preserved() {
+        for override_error in [
+            None,
+            Some(rustls::Error::General(
+                "incompatible signing key detail".into(),
+            )),
+        ] {
+            let (mut client, accepted) = client_hello(client_config(
+                &rustls::version::TLS12,
+                SignatureScheme::RSA_PSS_SHA384,
+                None,
+            ));
+            let (error, alert) = accepted
+                .into_connection(server_config(
+                    &rustls::version::TLS13,
+                    false,
+                    None,
+                    SignatureScheme::RSA_PSS_SHA384,
+                ))
+                .unwrap_err();
+            let bytes = initial_handshake_alert(&override_error.unwrap_or(error), alert).unwrap();
+            assert_eq!(bytes, sni_alert(70));
+            client.read_tls(&mut &bytes[..]).unwrap();
+            assert!(matches!(
+                client.process_new_packets(),
+                Err(rustls::Error::AlertReceived(
+                    rustls::AlertDescription::ProtocolVersion
+                ))
+            ));
+        }
+    }
+
+    #[test]
+    fn disjoint_cipher_suites_keep_the_no_shared_cipher_error() {
+        use rustls::crypto::aws_lc_rs::cipher_suite::{
+            TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+        };
+        let version = &rustls::version::TLS12;
+        let (_, accepted) = client_hello(client_config(
+            version,
+            SignatureScheme::RSA_PSS_SHA384,
+            Some(TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256),
+        ));
+        let (error, _) = accepted
+            .into_connection(server_config(
+                version,
+                false,
+                Some(TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384),
+                SignatureScheme::RSA_PSS_SHA384,
+            ))
+            .unwrap_err();
+        assert!(matches!(
+            super::super::error::TlsError::from_rustls(error),
+            super::super::error::TlsError::NoCipherSuites
+        ));
+    }
+
+    #[test]
+    fn incompatible_certificate_algorithm_keeps_the_no_shared_cipher_error() {
+        use rustls::crypto::aws_lc_rs::cipher_suite::TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256;
+        let version = &rustls::version::TLS12;
+        let (_, accepted) = client_hello(client_config(
+            version,
+            SignatureScheme::ECDSA_NISTP256_SHA256,
+            Some(TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256),
+        ));
+        let (error, _) = accepted
+            .into_connection(server_config(
+                version,
+                false,
+                None,
+                SignatureScheme::RSA_PSS_SHA384,
+            ))
+            .unwrap_err();
+        assert!(matches!(
+            super::super::error::TlsError::from_rustls(error),
+            super::super::error::TlsError::NoCipherSuites
+        ));
+    }
+
+    fn finish_handshake(client: &mut ClientConnection, server: &mut rustls::ServerConnection) {
+        for _ in 0..16 {
+            let mut bytes = Vec::new();
+            server.write_tls(&mut bytes).unwrap();
+            if !bytes.is_empty() {
+                client.read_tls(&mut &bytes[..]).unwrap();
+                client.process_new_packets().unwrap();
+            }
+            bytes.clear();
+            client.write_tls(&mut bytes).unwrap();
+            if !bytes.is_empty() {
+                server.read_tls(&mut &bytes[..]).unwrap();
+                server.process_new_packets().unwrap();
+            }
+            if !client.is_handshaking()
+                && !server.is_handshaking()
+                && !client.wants_write()
+                && !server.wants_write()
+            {
+                return;
+            }
+        }
+        panic!("in-memory handshake did not finish within 16 exchanges");
+    }
+
+    #[test]
+    fn signature_match_selects_a_later_compatible_key() {
+        for version in [&rustls::version::TLS12, &rustls::version::TLS13] {
+            let client_config = client_config(version, SignatureScheme::RSA_PSS_SHA384, None);
+            let server_config = server_config(version, true, None, SignatureScheme::RSA_PSS_SHA384);
+            for expected_kind in [rustls::HandshakeKind::Full, rustls::HandshakeKind::Resumed] {
+                let (mut client, accepted) = client_hello(client_config.clone());
+                let mut server = accepted.into_connection(server_config.clone()).unwrap();
+                finish_handshake(&mut client, &mut server);
+                assert_eq!(client.handshake_kind(), Some(expected_kind));
+                assert_eq!(server.handshake_kind(), Some(expected_kind));
+            }
+        }
+    }
+
+    fn assert_resumption_survives_signature_policy_change(
+        version: &'static rustls::SupportedProtocolVersion,
+    ) {
+        let client_config = client_config(version, SignatureScheme::RSA_PSS_SHA256, None);
+        let initial_config = server_config(version, false, None, SignatureScheme::RSA_PSS_SHA256);
+        let (mut client, accepted) = client_hello(client_config.clone());
+        let mut server = accepted.into_connection(initial_config.clone()).unwrap();
+        finish_handshake(&mut client, &mut server);
+        assert_eq!(client.handshake_kind(), Some(rustls::HandshakeKind::Full));
+
+        // SSLContext retains its server session cache/ticketer when a policy
+        // change rebuilds the configuration. Change only the signing policy.
+        let mut changed_config = (*initial_config).clone();
+        changed_config.cert_resolver =
+            server_config(version, false, None, SignatureScheme::RSA_PSS_SHA384)
+                .cert_resolver
+                .clone();
+        let changed_config = Arc::new(changed_config);
+        let (mut client, accepted) = client_hello(client_config);
+        let mut server = accepted.into_connection(changed_config.clone()).unwrap();
+        finish_handshake(&mut client, &mut server);
+        assert_eq!(
+            client.handshake_kind(),
+            Some(rustls::HandshakeKind::Resumed)
+        );
+        assert_eq!(
+            server.handshake_kind(),
+            Some(rustls::HandshakeKind::Resumed)
+        );
+
+        // The same changed policy must still reject a fresh client's PSS256
+        // offer; accepting a resumed session must not relax a full handshake.
+        let (mut client, accepted) = client_hello(self::client_config(
+            version,
+            SignatureScheme::RSA_PSS_SHA256,
+            None,
+        ));
+        let (error, alert) = accepted.into_connection(changed_config).unwrap_err();
+        let bytes = initial_handshake_alert(&error, alert).unwrap();
+        assert_eq!(bytes, sni_alert(40));
+        client.read_tls(&mut &bytes[..]).unwrap();
+        assert!(matches!(
+            client.process_new_packets(),
+            Err(rustls::Error::AlertReceived(
+                rustls::AlertDescription::HandshakeFailure,
+            ))
+        ));
+    }
+
+    #[test]
+    fn tls12_resumption_survives_signature_policy_change() {
+        assert_resumption_survives_signature_policy_change(&rustls::version::TLS12);
+    }
+
+    #[test]
+    fn tls13_resumption_survives_signature_policy_change() {
+        assert_resumption_survives_signature_policy_change(&rustls::version::TLS13);
+    }
+}
diff --git a/crates/host_env/src/ssl/mod.rs b/crates/host_env/src/ssl/mod.rs
index a2d8f32e563..7befb9ec244 100644
--- a/crates/host_env/src/ssl/mod.rs
+++ b/crates/host_env/src/ssl/mod.rs
@@ -33,6 +33,8 @@ pub mod providers;
 #[cfg(feature = "rustls")]
 pub mod session;
 #[cfg(feature = "rustls")]
+pub mod sigalg;
+#[cfg(feature = "rustls")]
 pub mod verify;
 #[cfg(feature = "rustls")]
 pub mod x509;
diff --git a/crates/host_env/src/ssl/sigalg.rs b/crates/host_env/src/ssl/sigalg.rs
new file mode 100644
index 00000000000..ee23d8d0a85
--- /dev/null
+++ b/crates/host_env/src/ssl/sigalg.rs
@@ -0,0 +1,190 @@
+// cspell: ignore sigalgs rsae mldsa
+
+//! Per-context TLS server signature algorithm selection.
+
+use alloc::sync::Arc;
+use rustls::{
+    DigitallySignedStruct, DistinguishedName, Error, SignatureAlgorithm, SignatureScheme,
+    client::danger::{HandshakeSignatureValid, ServerCertVerified, ServerCertVerifier},
+    pki_types::{CertificateDer, ServerName, SubjectPublicKeyInfoDer, UnixTime},
+    server::{ClientHello, ResolvesServerCert},
+    sign::{CertifiedKey, Signer, SigningKey},
+};
+
+use super::providers::CryptoExt;
+
+pub fn scheme_name(scheme: SignatureScheme) -> Option<&'static str> {
+    use SignatureScheme::{
+        ECDSA_NISTP256_SHA256, ECDSA_NISTP384_SHA384, ECDSA_NISTP521_SHA512, ECDSA_SHA1_Legacy,
+        ED448, ED25519, ML_DSA_44, ML_DSA_65, ML_DSA_87, RSA_PKCS1_SHA1, RSA_PKCS1_SHA256,
+        RSA_PKCS1_SHA384, RSA_PKCS1_SHA512, RSA_PSS_SHA256, RSA_PSS_SHA384, RSA_PSS_SHA512,
+    };
+    Some(match scheme {
+        RSA_PKCS1_SHA1 => "rsa_pkcs1_sha1",
+        ECDSA_SHA1_Legacy => "ecdsa_sha1",
+        RSA_PKCS1_SHA256 => "rsa_pkcs1_sha256",
+        RSA_PKCS1_SHA384 => "rsa_pkcs1_sha384",
+        RSA_PKCS1_SHA512 => "rsa_pkcs1_sha512",
+        ECDSA_NISTP256_SHA256 => "ecdsa_secp256r1_sha256",
+        ECDSA_NISTP384_SHA384 => "ecdsa_secp384r1_sha384",
+        ECDSA_NISTP521_SHA512 => "ecdsa_secp521r1_sha512",
+        RSA_PSS_SHA256 => "rsa_pss_rsae_sha256",
+        RSA_PSS_SHA384 => "rsa_pss_rsae_sha384",
+        RSA_PSS_SHA512 => "rsa_pss_rsae_sha512",
+        ED25519 => "ed25519",
+        ED448 => "ed448",
+        ML_DSA_44 => "mldsa44",
+        ML_DSA_65 => "mldsa65",
+        ML_DSA_87 => "mldsa87",
+        _ => return None,
+    })
+}
+
+pub fn parse_list(list: &str) -> Result<Vec<SignatureScheme>, &'static str> {
+    let supported = CryptoExt::get_provider()
+        .signature_verification_algorithms
+        .supported_schemes();
+    let mut selected = Vec::new();
+    for name in list.split(':') {
+        let (name, optional) = name.strip_prefix('?').map_or((name, false), |n| (n, true));
+        let name = match name {
+            "RSA+SHA256" => "rsa_pkcs1_sha256",
+            "RSA+SHA384" => "rsa_pkcs1_sha384",
+            "RSA+SHA512" => "rsa_pkcs1_sha512",
+            "ECDSA+SHA256" => "ecdsa_secp256r1_sha256",
+            "ECDSA+SHA384" => "ecdsa_secp384r1_sha384",
+            "ECDSA+SHA512" => "ecdsa_secp521r1_sha512",
+            other => other,
+        };
+        match supported.iter().find(|s| scheme_name(**s) == Some(name)) {
+            Some(scheme) if !selected.contains(scheme) => selected.push(*scheme),
+            Some(_) => {}
+            None if optional => {}
+            None => return Err("unrecognized signature algorithm"),
+        }
+    }
+    if selected.is_empty() {
+        return Err("unrecognized signature algorithm");
+    }
+    Ok(selected)
+}
+
+/// Restrict advertisement and handshake signatures, retaining the complete
+/// certificate verifier (including trust, hostname and revocation checks).
+#[derive(Debug)]
+pub struct ServerVerifier {
+    pub inner: Arc<dyn ServerCertVerifier>,
+    pub schemes: Vec<SignatureScheme>,
+}
+
+impl ServerVerifier {
+    fn check_scheme(&self, dss: &DigitallySignedStruct) -> Result<(), Error> {
+        if self.schemes.contains(&dss.scheme) {
+            Ok(())
+        } else {
+            Err(Error::General(
+                "server signature algorithm is not enabled".into(),
+            ))
+        }
+    }
+}
+
+impl ServerCertVerifier for ServerVerifier {
+    fn verify_server_cert(
+        &self,
+        end_entity: &CertificateDer<'_>,
+        intermediates: &[CertificateDer<'_>],
+        server_name: &ServerName<'_>,
+        ocsp_response: &[u8],
+        now: UnixTime,
+    ) -> Result<ServerCertVerified, Error> {
+        self.inner
+            .verify_server_cert(end_entity, intermediates, server_name, ocsp_response, now)
+    }
+
+    fn verify_tls12_signature(
+        &self,
+        message: &[u8],
+        cert: &CertificateDer<'_>,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, Error> {
+        self.check_scheme(dss)?;
+        self.inner.verify_tls12_signature(message, cert, dss)
+    }
+
+    fn verify_tls13_signature(
+        &self,
+        message: &[u8],
+        cert: &CertificateDer<'_>,
+        dss: &DigitallySignedStruct,
+    ) -> Result<HandshakeSignatureValid, Error> {
+        self.check_scheme(dss)?;
+        self.inner.verify_tls13_signature(message, cert, dss)
+    }
+
+    fn supported_verify_schemes(&self) -> Vec<SignatureScheme> {
+        let supported = self.inner.supported_verify_schemes();
+        self.schemes
+            .iter()
+            .filter(|s| supported.contains(s))
+            .copied()
+            .collect()
+    }
+
+    fn requires_raw_public_keys(&self) -> bool {
+        self.inner.requires_raw_public_keys()
+    }
+
+    fn root_hint_subjects(&self) -> Option<&[DistinguishedName]> {
+        self.inner.root_hint_subjects()
+    }
+}
+
+#[derive(Debug)]
+struct RestrictedSigningKey {
+    inner: Arc<dyn SigningKey>,
+    schemes: Vec<SignatureScheme>,
+}
+
+impl SigningKey for RestrictedSigningKey {
+    fn choose_scheme(&self, offered: &[SignatureScheme]) -> Option<Box<dyn Signer>> {
+        self.schemes
+            .iter()
+            .filter(|s| offered.contains(s))
+            .find_map(|s| self.inner.choose_scheme(&[*s]))
+    }
+
+    fn public_key(&self) -> Option<SubjectPublicKeyInfoDer<'_>> {
+        self.inner.public_key()
+    }
+
+    fn algorithm(&self) -> SignatureAlgorithm {
+        self.inner.algorithm()
+    }
+}
+
+#[derive(Debug)]
+pub struct ServerResolver {
+    pub inner: Arc<dyn ResolvesServerCert>,
+    pub schemes: Vec<SignatureScheme>,
+}
+
+pub fn restrict_key(key: &CertifiedKey, schemes: &[SignatureScheme]) -> Arc<CertifiedKey> {
+    let mut key = key.clone();
+    key.key = Arc::new(RestrictedSigningKey {
+        inner: key.key,
+        schemes: schemes.to_vec(),
+    });
+    Arc::new(key)
+}
+
+impl ResolvesServerCert for ServerResolver {
+    fn resolve(&self, hello: ClientHello<'_>) -> Option<Arc<CertifiedKey>> {
+        let key = self.inner.resolve(hello)?;
+        Some(restrict_key(&key, &self.schemes))
+    }
+
+    fn only_raw_public_keys(&self) -> bool {
+        self.inner.only_raw_public_keys()
+    }
+}
diff --git a/crates/host_env/src/ssl/verify.rs b/crates/host_env/src/ssl/verify.rs
index a88b6cbf4b5..ba2132efee2 100644
--- a/crates/host_env/src/ssl/verify.rs
+++ b/crates/host_env/src/ssl/verify.rs
@@ -747,6 +747,25 @@ impl ClientCertVerifier for DeferredClientCertVerifier {
 
 // Public Utility Functions
 
+/// Preserve which filesystem operation failed, independently of PEM errors.
+#[derive(Debug)]
+pub struct CertFileError {
+    pub error: std::io::Error,
+    pub key_file: bool,
+}
+
+impl core::fmt::Display for CertFileError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        core::fmt::Display::fmt(&self.error, f)
+    }
+}
+
+impl core::error::Error for CertFileError {
+    fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
+        Some(&self.error)
+    }
+}
+
 /// Load certificate chain and private key from files
 ///
 /// This function loads a certificate chain from `cert_path` and a private key
@@ -771,7 +790,10 @@ pub fn load_cert_chain_from_file(
     password: Option<&str>,
 ) -> Result<(Vec<CertificateDer<'static>>, PrivateKeyDer<'static>), Box<dyn core::error::Error>> {
     // Load certificate file - preserve io::Error for errno
-    let cert_contents = crate::fs::read(cert_path)?;
+    let cert_contents = crate::fs::read(cert_path).map_err(|error| CertFileError {
+        error,
+        key_file: false,
+    })?;
 
     // Parse certificates (PEM format)
     let mut cert_cursor = std::io::Cursor::new(&cert_contents);
@@ -784,7 +806,10 @@ pub fn load_cert_chain_from_file(
     }
 
     // Load private key file - preserve io::Error for errno
-    let key_contents = crate::fs::read(key_path)?;
+    let key_contents = crate::fs::read(key_path).map_err(|error| CertFileError {
+        error,
+        key_file: true,
+    })?;
 
     // Parse private key (supports PKCS8, RSA, EC formats)
     let private_key = if let Some(pwd) = password {
diff --git a/crates/host_env/src/time.rs b/crates/host_env/src/time.rs
index 14d77fe7a51..e79be43a501 100644
--- a/crates/host_env/src/time.rs
+++ b/crates/host_env/src/time.rs
@@ -91,7 +91,7 @@ pub fn duration_since_system_now() -> Result<Duration, SystemTimeError> {
 pub type TimeT = libc::time_t;
 
 #[cfg(windows)]
-pub type TimeT = libc::time_t;
+pub type TimeT = libc::time64_t;
 
 #[cfg(unix)]
 #[derive(Clone, Copy, Debug)]
@@ -132,32 +132,101 @@ pub fn mktime(tm: &mut libc::tm) -> TimeT {
 
 #[cfg(windows)]
 unsafe extern "C" {
-    fn _gmtime64_s(tm: *mut libc::tm, time: *const libc::time_t) -> libc::c_int;
-    fn _localtime64_s(tm: *mut libc::tm, time: *const libc::time_t) -> libc::c_int;
+    fn _gmtime64_s(tm: *mut libc::tm, time: *const TimeT) -> libc::c_int;
+    fn _localtime64_s(tm: *mut libc::tm, time: *const TimeT) -> libc::c_int;
     #[link_name = "_mktime64"]
-    fn c_mktime(tm: *mut libc::tm) -> libc::time_t;
+    fn c_mktime(tm: *mut libc::tm) -> TimeT;
+    #[link_name = "_time64"]
+    fn c_time(time: *mut TimeT) -> TimeT;
 }
 
 #[cfg(windows)]
 #[cfg_attr(target_env = "musl", allow(deprecated))]
 pub fn current_time_t() -> TimeT {
-    unsafe { libc::time(core::ptr::null_mut()) }
+    unsafe { c_time(core::ptr::null_mut()) }
 }
 
 #[cfg(windows)]
-#[cfg_attr(target_env = "musl", allow(deprecated))]
-pub fn gmtime_from_timestamp(when: TimeT) -> Option<libc::tm> {
+#[derive(Debug)]
+pub enum TimestampError {
+    FiletimeOutOfRange,
+    Os(std::io::Error),
+}
+
+#[cfg(windows)]
+fn windows_filetime(when: TimeT, local: bool) -> Result<libc::tm, TimestampError> {
+    use windows_sys::Win32::{
+        Foundation::{FILETIME, SYSTEMTIME},
+        System::Time::{FileTimeToSystemTime, SystemTimeToTzSpecificLocalTime},
+    };
+
+    const SECS_BETWEEN_EPOCHS: i64 = 11_644_473_600;
+    if when < -SECS_BETWEEN_EPOCHS {
+        return Err(TimestampError::FiletimeOutOfRange);
+    }
+    // Only negative timestamps reach this fallback, so the FILETIME cannot overflow.
+    debug_assert!(when < 0);
+    let ticks = ((when + SECS_BETWEEN_EPOCHS) as u64) * 10_000_000;
+    let filetime = FILETIME {
+        dwLowDateTime: ticks as u32,
+        dwHighDateTime: (ticks >> 32) as u32,
+    };
+    let mut utc = SYSTEMTIME::default();
+    if unsafe { FileTimeToSystemTime(&filetime, &mut utc) } == 0 {
+        return Err(TimestampError::Os(std::io::Error::last_os_error()));
+    }
+    let time = if local {
+        let mut result = SYSTEMTIME::default();
+        // Unlike FileTimeToLocalFileTime, this applies DST rules for the timestamp.
+        if unsafe { SystemTimeToTzSpecificLocalTime(core::ptr::null(), &utc, &mut result) } == 0 {
+            return Err(TimestampError::Os(std::io::Error::last_os_error()));
+        }
+        result
+    } else {
+        utc
+    };
+    const DAYS_BEFORE_MONTH: [i32; 12] = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
+    let year = i32::from(time.wYear);
+    let leap = year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
+    let yday = DAYS_BEFORE_MONTH[usize::from(time.wMonth - 1)] + i32::from(time.wDay) - 1
+        + i32::from(time.wMonth > 2 && leap);
+    Ok(libc::tm {
+        tm_year: year - 1900,
+        tm_mon: i32::from(time.wMonth) - 1,
+        tm_mday: i32::from(time.wDay),
+        tm_hour: i32::from(time.wHour),
+        tm_min: i32::from(time.wMinute),
+        tm_sec: i32::from(time.wSecond),
+        tm_wday: i32::from(time.wDayOfWeek),
+        tm_yday: yday,
+        tm_isdst: if local { -1 } else { 0 },
+    })
+}
+
+#[cfg(windows)]
+pub fn gmtime_from_timestamp(when: TimeT) -> Result<libc::tm, TimestampError> {
+    if when < 0 {
+        return windows_filetime(when, false);
+    }
     let mut out = core::mem::MaybeUninit::<libc::tm>::uninit();
     let err = unsafe { _gmtime64_s(out.as_mut_ptr(), &when) };
-    (err == 0).then(|| unsafe { out.assume_init() })
+    if err != 0 {
+        return Err(TimestampError::Os(crate::os::io_error_from_errno(err)));
+    }
+    Ok(unsafe { out.assume_init() })
 }
 
 #[cfg(windows)]
-#[cfg_attr(target_env = "musl", allow(deprecated))]
-pub fn localtime_from_timestamp(when: TimeT) -> Option<libc::tm> {
+pub fn localtime_from_timestamp(when: TimeT) -> Result<libc::tm, TimestampError> {
+    if when < 0 {
+        return windows_filetime(when, true);
+    }
     let mut out = core::mem::MaybeUninit::<libc::tm>::uninit();
     let err = unsafe { _localtime64_s(out.as_mut_ptr(), &when) };
-    (err == 0).then(|| unsafe { out.assume_init() })
+    if err != 0 {
+        return Err(TimestampError::Os(crate::os::io_error_from_errno(err)));
+    }
+    Ok(unsafe { out.assume_init() })
 }
 
 #[cfg(windows)]
@@ -676,7 +745,7 @@ pub fn mktime_tm_from_parts(parts: MktimeTmParts) -> Result<libc::tm, CheckedTmE
     Ok(tm)
 }
 
-#[cfg(unix)]
+#[cfg(all(unix, not(any(target_os = "linux", target_os = "macos"))))]
 pub fn strftime_ascii(fmt: &str, tm: &libc::tm) -> Result<String, CheckedTmError> {
     let fmt_c = CString::new(fmt).map_err(|_| CheckedTmError::EmbeddedNul)?;
     let mut size = 1024usize;
@@ -698,7 +767,42 @@ pub fn strftime_ascii(fmt: &str, tm: &libc::tm) -> Result<String, CheckedTmError
     }
 }
 
-#[cfg(windows)]
+// These Unix platforms provide wcsftime, which returns locale text as Unicode.
+// Keep the narrow fallback on other targets, including OpenBSD (%V is broken
+// in its wcsftime implementation; CPython also uses strftime there).
+#[cfg(any(target_os = "linux", target_os = "macos"))]
+pub fn strftime_ascii(fmt: &str, tm: &libc::tm) -> Result<String, CheckedTmError> {
+    if fmt.contains('\0') {
+        return Err(CheckedTmError::EmbeddedNul);
+    }
+    let fmt_wide: Vec<libc::wchar_t> = fmt
+        .chars()
+        .map(|ch| ch as libc::wchar_t)
+        .chain([0])
+        .collect();
+    let mut size = 1024usize;
+    let max_scale = 256usize.saturating_mul(fmt.len().max(1));
+    loop {
+        let mut out = vec![0 as libc::wchar_t; size];
+        let written = unsafe {
+            wcsftime(
+                out.as_mut_ptr(),
+                out.len(),
+                fmt_wide.as_ptr(),
+                tm as *const libc::tm,
+            )
+        };
+        if written > 0 || size >= max_scale {
+            return Ok(out[..written]
+                .iter()
+                .map(|ch| char::from_u32(*ch as u32).unwrap_or(char::REPLACEMENT_CHARACTER))
+                .collect());
+        }
+        size = size.saturating_mul(2);
+    }
+}
+
+#[cfg(any(windows, target_os = "linux", target_os = "macos"))]
 unsafe extern "C" {
     fn wcsftime(
         s: *mut libc::wchar_t,
diff --git a/crates/host_env/src/winapi.rs b/crates/host_env/src/winapi.rs
index bf62cfaafa0..420c10882da 100644
--- a/crates/host_env/src/winapi.rs
+++ b/crates/host_env/src/winapi.rs
@@ -39,6 +39,10 @@ pub use windows_sys::Win32::{
     },
     System::{
         Console::{STD_ERROR_HANDLE, STD_INPUT_HANDLE, STD_OUTPUT_HANDLE},
+        EventLog::{
+            EVENTLOG_AUDIT_FAILURE, EVENTLOG_AUDIT_SUCCESS, EVENTLOG_ERROR_TYPE,
+            EVENTLOG_INFORMATION_TYPE, EVENTLOG_SUCCESS, EVENTLOG_WARNING_TYPE,
+        },
         Memory::{
             FILE_MAP_ALL_ACCESS, FILE_MAP_COPY, FILE_MAP_EXECUTE, FILE_MAP_READ, FILE_MAP_WRITE,
             MEM_COMMIT, MEM_FREE, MEM_IMAGE, MEM_MAPPED, MEM_PRIVATE, MEM_RESERVE, PAGE_EXECUTE,
@@ -86,6 +90,44 @@ pub const LCMAP_HASH_FLAG: u32 = windows_sys::Win32::Globalization::LCMAP_HASH;
 pub const LCMAP_SORTHANDLE_FLAG: u32 = windows_sys::Win32::Globalization::LCMAP_SORTHANDLE;
 pub const LCMAP_SORTKEY_FLAG: u32 = windows_sys::Win32::Globalization::LCMAP_SORTKEY;
 
+pub fn register_event_source_w(
+    server: Option<&widestring::WideCStr>,
+    source: &widestring::WideCStr,
+) -> io::Result<HANDLE> {
+    let server = server.map_or(core::ptr::null(), |name| name.as_ptr());
+    unsafe { windows_sys::Win32::System::EventLog::RegisterEventSourceW(server, source.as_ptr()) }
+        .check_nonnull()
+}
+
+pub fn deregister_event_source(handle: HANDLE) -> io::Result<()> {
+    unsafe { windows_sys::Win32::System::EventLog::DeregisterEventSource(handle) }
+        .check_win32_bool()
+}
+
+pub fn report_event_w(
+    handle: HANDLE,
+    event_type: u16,
+    category: u16,
+    event_id: u32,
+    message: &widestring::WideCStr,
+) -> io::Result<()> {
+    let message = message.as_ptr();
+    unsafe {
+        windows_sys::Win32::System::EventLog::ReportEventW(
+            handle,
+            event_type,
+            category,
+            event_id,
+            core::ptr::null_mut(),
+            1,
+            0,
+            &message,
+            core::ptr::null(),
+        )
+    }
+    .check_win32_bool()
+}
+
 pub struct PeekNamedPipeResult {
     pub data: Option<Vec<u8>>,
     pub available: u32,
diff --git a/crates/host_env/src/windows.rs b/crates/host_env/src/windows.rs
index 4cba8e3579e..cfc47da5791 100644
--- a/crates/host_env/src/windows.rs
+++ b/crates/host_env/src/windows.rs
@@ -16,7 +16,11 @@ use windows_sys::{
                 FORMAT_MESSAGE_ALLOCATE_BUFFER, FORMAT_MESSAGE_FROM_SYSTEM,
                 FORMAT_MESSAGE_IGNORE_INSERTS, FormatMessageW,
             },
-            LibraryLoader::{GetModuleFileNameW, GetModuleHandleW},
+            LibraryLoader::{
+                GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
+                GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT, GetModuleFileNameW,
+                GetModuleHandleExW, GetModuleHandleW,
+            },
             SystemInformation::{GetVersionExW, OSVERSIONINFOEXW, OSVERSIONINFOW},
             Threading::{GetCurrentThreadStackLimits, SetThreadStackGuarantee},
         },
@@ -49,6 +53,23 @@ pub fn init_winsock() {
     })
 }
 
+/// Handle of the already-loaded image containing this RustPython runtime.
+/// The handle is borrowed and must not be passed to `FreeLibrary`.
+pub fn runtime_module_handle() -> io::Result<usize> {
+    let mut module = core::ptr::null_mut();
+    // FROM_ADDRESS treats this pointer as an address inside the image, not a
+    // string. UNCHANGED_REFCOUNT avoids loading a second copy or owning a ref.
+    unsafe {
+        GetModuleHandleExW(
+            GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+            runtime_module_handle as *const () as *const u16,
+            &mut module,
+        )
+    }
+    .check_win32_bool()?;
+    Ok(module as usize)
+}
+
 /// Win32 BOOL convention: 0 = failure, nonzero = success.
 /// Reads error via `GetLastError()` through [`io::Error::last_os_error`].
 pub trait CheckWin32Bool {
@@ -426,3 +447,24 @@ impl ToWideString for Wtf8 {
         WideCString::from_vec(buf).map_err(|_| io::Error::other(NUL_ERROR))
     }
 }
+
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn sys_string_len(bstr: *const u16) -> usize {
+    unsafe { windows_sys::Win32::Foundation::SysStringLen(bstr) as usize }
+}
+
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn sys_free_string(bstr: *const u16) {
+    unsafe { windows_sys::Win32::Foundation::SysFreeString(bstr) };
+}
+
+pub fn sys_alloc_string_len(units: &[u16]) -> Option<*mut u16> {
+    let len = u32::try_from(units.len()).ok()?;
+    let bstr = unsafe { windows_sys::Win32::Foundation::SysAllocStringLen(units.as_ptr(), len) };
+    (!bstr.is_null()).then_some(bstr as *mut u16)
+}
+
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn co_task_mem_free(ptr: *mut core::ffi::c_void) {
+    unsafe { windows_sys::Win32::System::Com::CoTaskMemFree(ptr) };
+}
diff --git a/crates/host_env/src/wmi.rs b/crates/host_env/src/wmi.rs
index ceccf4d79fb..bf6d53264e6 100644
--- a/crates/host_env/src/wmi.rs
+++ b/crates/host_env/src/wmi.rs
@@ -7,7 +7,7 @@
 
 use core::ffi::c_void;
 use core::ptr::{NonNull, null, null_mut};
-use widestring::WideCString;
+use widestring::{WideCStr, WideCString};
 use windows_sys::Win32::Foundation::{
     CloseHandle, ERROR_BROKEN_PIPE, ERROR_INVALID_NAME, ERROR_MORE_DATA, ERROR_NOT_ENOUGH_MEMORY,
     GetLastError, HANDLE, WAIT_OBJECT_0, WAIT_TIMEOUT,
@@ -19,7 +19,7 @@ use windows_sys::Win32::System::Threading::{
 };
 use windows_sys::w;
 
-use crate::ctypes::wcslen;
+use crate::windows::{sys_alloc_string_len, sys_free_string};
 
 pub const BUFFER_SIZE: usize = 8192;
 
@@ -122,21 +122,20 @@ fn alloc_bstr(wide: &[u16]) -> *mut u16 {
         .iter()
         .position(|&unit| unit == 0)
         .unwrap_or(wide.len());
-    crate::ctypes::sys_alloc_string_len(&wide[..len]).unwrap_or(null_mut())
+    sys_alloc_string_len(&wide[..len]).unwrap_or(null_mut())
 }
 
 fn alloc_bstr_ptr(ptr: *const u16) -> *mut u16 {
     let Some(ptr) = NonNull::new(ptr.cast_mut()) else {
         return null_mut();
     };
-    let len = unsafe { crate::ctypes::wcslen(ptr) };
-    crate::ctypes::sys_alloc_string_len(unsafe { core::slice::from_raw_parts(ptr.as_ptr(), len) })
-        .unwrap_or(null_mut())
+    let wide = unsafe { WideCStr::from_ptr_str(ptr.as_ptr()) };
+    sys_alloc_string_len(wide.as_slice()).unwrap_or(null_mut())
 }
 
 fn free_bstr(bstr: *mut u16) {
     if !bstr.is_null() {
-        crate::ctypes::sys_free_string(bstr);
+        sys_free_string(bstr);
     }
 }
 
@@ -478,9 +477,9 @@ unsafe fn query_thread_impl(param: *mut c_void) -> u32 {
             }
 
             if succeeded(hr) && (flavor & WBEM_FLAVOR_MASK_ORIGIN) != WBEM_FLAVOR_ORIGIN_SYSTEM {
-                let Some(cb_str1) = NonNull::new(prop_name)
-                    .map(|prop_name| (unsafe { wcslen(prop_name) } * 2) as u32)
-                else {
+                let Some(cb_str1) = NonNull::new(prop_name).map(|prop_name| {
+                    (unsafe { WideCStr::from_ptr_str(prop_name.as_ptr()) }.len() * 2) as u32
+                }) else {
                     free_bstr(prop_name);
                     break;
                 };
@@ -490,7 +489,9 @@ unsafe fn query_thread_impl(param: *mut c_void) -> u32 {
                     VariantToString(&prop_value, prop_str.as_mut_ptr(), BUFFER_SIZE as u32)
                 };
                 let cb_str2 = NonNull::new(prop_str.as_ptr().cast_mut())
-                    .map(|prop_str| (unsafe { wcslen(prop_str) } * 2) as u32)
+                    .map(|prop_str| {
+                        (unsafe { WideCStr::from_ptr_str(prop_str.as_ptr()) }.len() * 2) as u32
+                    })
                     .expect("prop_str is never null");
 
                 if succeeded(hr)
diff --git a/crates/host_env/vendor/wasm32-wasip1/README.md b/crates/host_env/vendor/wasm32-wasip1/README.md
new file mode 100644
index 00000000000..b8d201c915e
--- /dev/null
+++ b/crates/host_env/vendor/wasm32-wasip1/README.md
@@ -0,0 +1,16 @@
+# Vendored wasi-libc emulation library
+
+`libwasi-emulated-signal.a` is a prebuilt static library from
+[wasi-sdk](https://github.com/WebAssembly/wasi-sdk), providing wasi-libc's
+userspace emulation of `signal()`/`raise()` for `wasm32-wasip1` (WebAssembly
+has no asynchronous signal delivery, so this is a synchronous, in-process
+handler table, not a real OS signal mechanism).
+
+CPython's own WASI build links the same library
+(`configure.ac`'s `_WASI_EMULATED_SIGNAL` case).
+
+- Source: https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-34/wasi-sysroot-34.0.tar.gz
+  (path: `lib/wasm32-wasip1/libwasi-emulated-signal.a`)
+- License: Apache-2.0 WITH LLVM-exception (same as wasi-libc)
+- sha256: see below
+becc35b856608fb9282d94c70166796e4d7b21e4e1057e625725306e765eb035  crates/host_env/vendor/wasm32-wasip1/libwasi-emulated-signal.a
diff --git a/crates/host_env/vendor/wasm32-wasip1/libwasi-emulated-signal.a b/crates/host_env/vendor/wasm32-wasip1/libwasi-emulated-signal.a
new file mode 100644
index 00000000000..25ba3e0515c
Binary files /dev/null and b/crates/host_env/vendor/wasm32-wasip1/libwasi-emulated-signal.a differ
diff --git a/crates/jit/src/instructions.rs b/crates/jit/src/instructions.rs
index 499d7c8baa4..4f739651635 100644
--- a/crates/jit/src/instructions.rs
+++ b/crates/jit/src/instructions.rs
@@ -663,6 +663,21 @@ impl<'a, 'b> FunctionCompiler<'a, 'b> {
                 self.stack.push(val);
                 Ok(())
             }
+            Instruction::LoadCommonConstant { idx } => {
+                let val = match idx.get(arg) {
+                    oparg::CommonConstant::None => JitValue::None,
+                    oparg::CommonConstant::True | oparg::CommonConstant::False => {
+                        let value = i64::from(idx.get(arg) == oparg::CommonConstant::True);
+                        JitValue::Bool(self.builder.ins().iconst(types::I8, value))
+                    }
+                    oparg::CommonConstant::MinusOne => {
+                        JitValue::Int(self.builder.ins().iconst(types::I64, -1))
+                    }
+                    _ => return Err(JitCompileError::NotSupported),
+                };
+                self.stack.push(val);
+                Ok(())
+            }
             Instruction::LoadSmallInt { i } => {
                 let small_int = i.get(arg) as i64;
                 let val = self.builder.ins().iconst(types::I64, small_int);
diff --git a/crates/jit/tests/common.rs b/crates/jit/tests/common.rs
index fe0e4bd33d4..0cbce428a0e 100644
--- a/crates/jit/tests/common.rs
+++ b/crates/jit/tests/common.rs
@@ -1,6 +1,6 @@
 use core::ops::ControlFlow;
 use rustpython_compiler_core::bytecode::{
-    CodeObject, ConstantData, Constants, Instruction, OpArg, OpArgState,
+    CodeObject, CommonConstant, ConstantData, Constants, Instruction, OpArg, OpArgState,
 };
 use rustpython_jit::{CompiledCode, JitType};
 use rustpython_wtf8::{Wtf8, Wtf8Buf};
@@ -207,6 +207,15 @@ impl StackMachine {
             Instruction::LoadConst { consti } => {
                 self.stack.push(constants[consti.get(arg)].clone().into())
             }
+            Instruction::LoadCommonConstant { idx } => {
+                self.stack.push(match idx.get(arg) {
+                    CommonConstant::None => StackValue::None,
+                    CommonConstant::EmptyStr => StackValue::String(String::new()),
+                    constant => unimplemented!(
+                        "common constant {constant:?} isn't yet supported in py_function!"
+                    ),
+                });
+            }
             Instruction::LoadName { namei } => self
                 .stack
                 .push(StackValue::String(names[namei.get(arg) as usize].clone())),
diff --git a/crates/sre_engine/src/engine.rs b/crates/sre_engine/src/engine.rs
index c2a6ac81975..7224b4e878f 100644
--- a/crates/sre_engine/src/engine.rs
+++ b/crates/sre_engine/src/engine.rs
@@ -1,11 +1,11 @@
 // good luck to those that follow; here be dragons
 
 use crate::string::{
-    is_digit, is_linebreak, is_loc_word, is_space, is_uni_digit, is_uni_linebreak, is_uni_space,
-    is_uni_word, is_word, lower_ascii, lower_locate, lower_unicode, upper_locate, upper_unicode,
+    is_digit, is_linebreak, is_space, is_uni_digit, is_uni_linebreak, is_uni_space, is_uni_word,
+    is_word, lower_ascii, lower_unicode, upper_unicode,
 };
 
-use super::{MAXREPEAT, SreAtCode, SreCatCode, SreInfo, SreOpcode, StrDrive, StringCursor};
+use super::{Locale, MAXREPEAT, SreAtCode, SreCatCode, SreInfo, SreOpcode, StrDrive, StringCursor};
 use alloc::{vec, vec::Vec};
 use core::{convert::TryFrom, ptr::null};
 use optional::Optioned;
@@ -18,6 +18,7 @@ pub struct Request<'a, S> {
     pub pattern_codes: &'a [u32],
     pub match_all: bool,
     pub must_advance: bool,
+    pub locale: Locale,
 }
 
 impl<'a, S: StrDrive> Request<'a, S> {
@@ -38,6 +39,7 @@ impl<'a, S: StrDrive> Request<'a, S> {
             pattern_codes,
             match_all,
             must_advance: false,
+            locale: Locale::default(),
         }
     }
 }
@@ -674,20 +676,24 @@ fn _match<S: StrDrive>(req: &Request<'_, S>, state: &mut State, mut ctx: MatchCo
                         }
                         SreOpcode::CATEGORY => {
                             let cat_code = SreCatCode::try_from(ctx.peek_code(req, 1)).unwrap();
-                            if ctx.at_end(req) || !category(cat_code, ctx.peek_char::<S>()) {
+                            if ctx.at_end(req)
+                                || !category(cat_code, ctx.peek_char::<S>(), req.locale)
+                            {
                                 break 'result false;
                             }
                             ctx.skip_code(2);
                             ctx.advance_char::<S>();
                         }
-                        SreOpcode::IN => general_op_in!(charset),
+                        SreOpcode::IN => general_op_in!(|set, c| charset(set, c, req.locale)),
                         SreOpcode::IN_IGNORE => {
-                            general_op_in!(|set, c| charset(set, lower_ascii(c)))
+                            general_op_in!(|set, c| charset(set, lower_ascii(c), req.locale))
                         }
                         SreOpcode::IN_UNI_IGNORE => {
-                            general_op_in!(|set, c| charset(set, lower_unicode(c)))
+                            general_op_in!(|set, c| charset(set, lower_unicode(c), req.locale))
+                        }
+                        SreOpcode::IN_LOC_IGNORE => {
+                            general_op_in!(|set, c| charset_loc_ignore(set, c, req.locale))
                         }
-                        SreOpcode::IN_LOC_IGNORE => general_op_in!(charset_loc_ignore),
                         SreOpcode::MARK => {
                             state
                                 .marks
@@ -837,13 +843,17 @@ fn _match<S: StrDrive>(req: &Request<'_, S>, state: &mut State, mut ctx: MatchCo
                         SreOpcode::NOT_LITERAL_UNI_IGNORE => {
                             general_op_literal!(|code, c| code != lower_unicode(c))
                         }
-                        SreOpcode::LITERAL_LOC_IGNORE => general_op_literal!(char_loc_ignore),
+                        SreOpcode::LITERAL_LOC_IGNORE => {
+                            general_op_literal!(|code, c| char_loc_ignore(code, c, req.locale))
+                        }
                         SreOpcode::NOT_LITERAL_LOC_IGNORE => {
-                            general_op_literal!(|code, c| !char_loc_ignore(code, c))
+                            general_op_literal!(|code, c| !char_loc_ignore(code, c, req.locale))
                         }
                         SreOpcode::GROUPREF => general_op_groupref!(|x| x),
                         SreOpcode::GROUPREF_IGNORE => general_op_groupref!(lower_ascii),
-                        SreOpcode::GROUPREF_LOC_IGNORE => general_op_groupref!(lower_locate),
+                        SreOpcode::GROUPREF_LOC_IGNORE => {
+                            general_op_groupref!(|c| req.locale.lower(c))
+                        }
                         SreOpcode::GROUPREF_UNI_IGNORE => general_op_groupref!(lower_unicode),
                         SreOpcode::GROUPREF_EXISTS => {
                             let (group_start, group_end) =
@@ -1042,7 +1052,7 @@ fn search_info_charset<S: StrDrive>(
     req.must_advance = false;
 
     loop {
-        while !ctx.at_end(req) && !charset(set, ctx.peek_char::<S>()) {
+        while !ctx.at_end(req) && !charset(set, ctx.peek_char::<S>(), req.locale) {
             ctx.advance_char::<S>();
         }
         if ctx.at_end(req) {
@@ -1226,27 +1236,27 @@ fn at<S: StrDrive>(req: &Request<'_, S>, ctx: &MatchContext, at_code: SreAtCode)
         }
         SreAtCode::END_LINE => ctx.at_linebreak(req) || ctx.at_end(req),
         SreAtCode::END_STRING => ctx.at_end(req),
-        SreAtCode::LOC_BOUNDARY => ctx.at_boundary(req, is_loc_word),
-        SreAtCode::LOC_NON_BOUNDARY => ctx.at_non_boundary(req, is_loc_word),
+        SreAtCode::LOC_BOUNDARY => ctx.at_boundary(req, |ch| req.locale.is_word(ch)),
+        SreAtCode::LOC_NON_BOUNDARY => ctx.at_non_boundary(req, |ch| req.locale.is_word(ch)),
         SreAtCode::UNI_BOUNDARY => ctx.at_boundary(req, is_uni_word),
         SreAtCode::UNI_NON_BOUNDARY => ctx.at_non_boundary(req, is_uni_word),
     }
 }
 
-fn char_loc_ignore(code: u32, c: u32) -> bool {
-    code == c || code == lower_locate(c) || code == upper_locate(c)
+fn char_loc_ignore(code: u32, c: u32, locale: Locale) -> bool {
+    code == c || code == locale.lower(c) || code == locale.upper(c)
 }
 
-fn charset_loc_ignore(set: &[u32], c: u32) -> bool {
-    let lo = lower_locate(c);
-    if charset(set, c) {
+fn charset_loc_ignore(set: &[u32], c: u32, locale: Locale) -> bool {
+    let lo = locale.lower(c);
+    if charset(set, lo, locale) {
         return true;
     }
-    let up = upper_locate(c);
-    up != lo && charset(set, up)
+    let up = locale.upper(c);
+    up != lo && charset(set, up, locale)
 }
 
-fn category(cat_code: SreCatCode, c: u32) -> bool {
+fn category(cat_code: SreCatCode, c: u32, locale: Locale) -> bool {
     match cat_code {
         SreCatCode::DIGIT => is_digit(c),
         SreCatCode::NOT_DIGIT => !is_digit(c),
@@ -1256,8 +1266,8 @@ fn category(cat_code: SreCatCode, c: u32) -> bool {
         SreCatCode::NOT_WORD => !is_word(c),
         SreCatCode::LINEBREAK => is_linebreak(c),
         SreCatCode::NOT_LINEBREAK => !is_linebreak(c),
-        SreCatCode::LOC_WORD => is_loc_word(c),
-        SreCatCode::LOC_NOT_WORD => !is_loc_word(c),
+        SreCatCode::LOC_WORD => locale.is_word(c),
+        SreCatCode::LOC_NOT_WORD => !locale.is_word(c),
         SreCatCode::UNI_DIGIT => is_uni_digit(c),
         SreCatCode::UNI_NOT_DIGIT => !is_uni_digit(c),
         SreCatCode::UNI_SPACE => is_uni_space(c),
@@ -1269,7 +1279,7 @@ fn category(cat_code: SreCatCode, c: u32) -> bool {
     }
 }
 
-fn charset(set: &[u32], ch: u32) -> bool {
+fn charset(set: &[u32], ch: u32, locale: Locale) -> bool {
     /* check if character is a member of the given set */
     let mut ok = true;
     let mut i = 0;
@@ -1292,7 +1302,7 @@ fn charset(set: &[u32], ch: u32) -> bool {
                         break;
                     }
                 };
-                if category(cat_code, ch) {
+                if category(cat_code, ch, locale) {
                     return ok;
                 }
                 i += 2;
@@ -1382,7 +1392,8 @@ fn _count<S: StrDrive>(
             ctx.skip_char::<S>(max_count);
         }
         SreOpcode::IN => {
-            while ctx.cursor.position < end && charset(&ctx.pattern(req)[2..], ctx.peek_char::<S>())
+            while ctx.cursor.position < end
+                && charset(&ctx.pattern(req)[2..], ctx.peek_char::<S>(), req.locale)
             {
                 ctx.advance_char::<S>();
             }
@@ -1400,10 +1411,14 @@ fn _count<S: StrDrive>(
             general_count_literal(req, ctx, end, |code, c| code != lower_ascii(c));
         }
         SreOpcode::LITERAL_LOC_IGNORE => {
-            general_count_literal(req, ctx, end, char_loc_ignore);
+            general_count_literal(req, ctx, end, |code, c| {
+                char_loc_ignore(code, c, req.locale)
+            });
         }
         SreOpcode::NOT_LITERAL_LOC_IGNORE => {
-            general_count_literal(req, ctx, end, |code, c| !char_loc_ignore(code, c));
+            general_count_literal(req, ctx, end, |code, c| {
+                !char_loc_ignore(code, c, req.locale)
+            });
         }
         SreOpcode::LITERAL_UNI_IGNORE => {
             general_count_literal(req, ctx, end, |code, c| code == lower_unicode(c));
diff --git a/crates/sre_engine/src/lib.rs b/crates/sre_engine/src/lib.rs
index df598974ba9..7c31a6bae9d 100644
--- a/crates/sre_engine/src/lib.rs
+++ b/crates/sre_engine/src/lib.rs
@@ -8,7 +8,7 @@ pub mod string;
 
 pub use constants::{SRE_MAGIC, SreAtCode, SreCatCode, SreFlag, SreInfo, SreOpcode};
 pub use engine::{Request, SearchIter, State};
-pub use string::{StrDrive, StringCursor};
+pub use string::{Locale, StrDrive, StringCursor};
 
 pub const CODESIZE: usize = 4;
 
diff --git a/crates/sre_engine/src/string.rs b/crates/sre_engine/src/string.rs
index d16a3ee88af..52b427a9414 100644
--- a/crates/sre_engine/src/string.rs
+++ b/crates/sre_engine/src/string.rs
@@ -391,15 +391,44 @@ pub(crate) fn is_digit(ch: u32) -> bool {
     u8::try_from(ch).is_ok_and(|x| x.is_ascii_digit())
 }
 
-#[inline]
-pub(crate) fn is_loc_alnum(ch: u32) -> bool {
-    // FIXME: Ignore the locales
-    u8::try_from(ch).is_ok_and(|x| x.is_ascii_alphanumeric())
+/// Byte classification and case conversion in the current locale.
+///
+/// Callbacks keep host APIs outside this `no_std` engine. They are called while
+/// matching, rather than cached in a compiled pattern, so a locale change also
+/// affects existing patterns and scanners. Without host callbacks, matching uses
+/// the ASCII rules of the C locale.
+#[derive(Debug, Clone, Copy)]
+pub struct Locale {
+    pub is_alnum: fn(u8) -> bool,
+    pub to_lower: fn(u8) -> u32,
+    pub to_upper: fn(u8) -> u32,
 }
 
-#[inline]
-pub(crate) fn is_loc_word(ch: u32) -> bool {
-    ch == UNDERSCORE || is_loc_alnum(ch)
+impl Default for Locale {
+    fn default() -> Self {
+        Self {
+            is_alnum: |ch| ch.is_ascii_alphanumeric(),
+            to_lower: |ch| ch.to_ascii_lowercase() as u32,
+            to_upper: |ch| ch.to_ascii_uppercase() as u32,
+        }
+    }
+}
+
+impl Locale {
+    #[inline]
+    pub(crate) fn is_word(self, ch: u32) -> bool {
+        ch == UNDERSCORE || u8::try_from(ch).is_ok_and(self.is_alnum)
+    }
+
+    #[inline]
+    pub(crate) fn lower(self, ch: u32) -> u32 {
+        u8::try_from(ch).map_or(ch, self.to_lower)
+    }
+
+    #[inline]
+    pub(crate) fn upper(self, ch: u32) -> u32 {
+        u8::try_from(ch).map_or(ch, self.to_upper)
+    }
 }
 
 #[inline]
@@ -413,18 +442,6 @@ pub fn lower_ascii(ch: u32) -> u32 {
     u8::try_from(ch).map_or(ch, |x| x.to_ascii_lowercase() as u32)
 }
 
-#[inline]
-pub(crate) fn lower_locate(ch: u32) -> u32 {
-    // FIXME: Ignore the locales
-    lower_ascii(ch)
-}
-
-#[inline]
-pub(crate) fn upper_locate(ch: u32) -> u32 {
-    // FIXME: Ignore the locales
-    u8::try_from(ch).map_or(ch, |x| x.to_ascii_uppercase() as u32)
-}
-
 #[inline]
 pub(crate) fn is_uni_digit(ch: u32) -> bool {
     // SRE_UNI_IS_DIGIT matches Unicode decimal digits (Py_UNICODE_ISDECIMAL),
diff --git a/crates/stdlib/Cargo.toml b/crates/stdlib/Cargo.toml
index 64e926fb610..5111380237f 100644
--- a/crates/stdlib/Cargo.toml
+++ b/crates/stdlib/Cargo.toml
@@ -11,7 +11,8 @@ license.workspace = true
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [features]
-default = ["compiler", "host_env", "doc"]
+default = ["compiler", "host_env", "doc", "ucd_3_2_0"]
+ucd_3_2_0 = ["rustpython-unicode/ucd_3_2_0"]
 doc = ["rustpython-vm/doc"]
 host_env = ["rustpython-vm/host_env"]
 compiler = ["rustpython-vm/compiler"]
diff --git a/crates/stdlib/build.rs b/crates/stdlib/build.rs
index d9d1ca4a677..7f6248783a8 100644
--- a/crates/stdlib/build.rs
+++ b/crates/stdlib/build.rs
@@ -20,6 +20,8 @@ fn main() {
         (0x3_01_00_00_0, "ossl310"),
         (0x3_02_00_00_0, "ossl320"),
         (0x3_03_00_00_0, "ossl330"),
+        (0x3_04_00_00_0, "ossl340"),
+        (0x3_05_00_00_0, "ossl350"),
     ];
 
     for (_, cfg) in ossl_vers {
diff --git a/crates/stdlib/src/_asyncio.rs b/crates/stdlib/src/_asyncio.rs
index f56943c19d7..8da4ab38da5 100644
--- a/crates/stdlib/src/_asyncio.rs
+++ b/crates/stdlib/src/_asyncio.rs
@@ -188,6 +188,13 @@ pub(crate) mod _asyncio {
             loop_: Option<PyObjectRef>,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
+            if zelf.fut_loop.read().is_some() {
+                return Err(vm.new_runtime_error(format!(
+                    "{} object is already initialized",
+                    zelf.class().fully_qualified_name(vm)?
+                )));
+            }
+
             // Get the event loop
             let loop_obj = match loop_ {
                 Some(l) if !vm.is_none(&l) => l,
@@ -1183,6 +1190,13 @@ pub(crate) mod _asyncio {
     )]
     impl PyTask {
         fn py_init(zelf: &Py<Self>, args: TaskInitArgs, vm: &VirtualMachine) -> PyResult<()> {
+            if zelf.base.fut_loop.read().is_some() {
+                return Err(vm.new_runtime_error(format!(
+                    "{} object is already initialized",
+                    zelf.class().fully_qualified_name(vm)?
+                )));
+            }
+
             // Validate coroutine
             if !is_coroutine(args.coro.clone(), vm)? {
                 return Err(vm.new_type_error(format!(
@@ -1217,8 +1231,18 @@ pub(crate) mod _asyncio {
 
             // Get or create context
             let context = match args.context {
-                Some(c) => c,
-                None => get_copy_context(vm)?,
+                Some(c) if !vm.is_none(&c) => {
+                    if !c.class().is(PyContext::class(&vm.ctx)) {
+                        zelf.task_log_destroy_pending
+                            .store(false, Ordering::Relaxed);
+                        return Err(vm.new_type_error(format!(
+                            "a contextvars.Context was expected, got {}",
+                            c.class().fully_qualified_name(vm)?
+                        )));
+                    }
+                    c
+                }
+                _ => get_copy_context(vm)?,
             };
             *zelf.task_context.write() = Some(context);
 
@@ -2043,7 +2067,25 @@ pub(crate) mod _asyncio {
                     match ctx.downcast::<PyContext>() {
                         Ok(ctx) => {
                             // Only exit a context that was actually entered.
-                            PyContext::enter(&ctx, vm)?;
+                            if let Err(error) = PyContext::enter(&ctx, vm) {
+                                zelf.task_log_destroy_pending
+                                    .store(false, Ordering::Relaxed);
+                                let _ = _swap_current_task(
+                                    LoopTaskArgs {
+                                        loop_: loop_obj,
+                                        task: prev_task,
+                                    },
+                                    vm,
+                                );
+                                let _ = _unregister_eager_task(
+                                    TaskArg {
+                                        task: task_obj.clone(),
+                                    },
+                                    vm,
+                                );
+                                let _ = _unregister_task(TaskArg { task: task_obj }, vm);
+                                return Err(error);
+                            }
                             let result = vm.call_method(&c, "send", (vm.ctx.none(),));
                             PyContext::exit(&ctx, vm)?;
                             result
@@ -2839,8 +2881,12 @@ pub(crate) mod _asyncio {
         waiter: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        // Only operate on native Future/Task objects (including subclasses).
+        // Both arguments must be native Future/Task objects (including subclasses).
         // Non-native objects are silently ignored.
+        if waiter.downcast_ref::<PyTask>().is_none() && waiter.downcast_ref::<PyFuture>().is_none()
+        {
+            return Ok(());
+        }
         if let Some(task) = fut.downcast_ref::<PyTask>() {
             return task.base.awaited_by_add(waiter, vm);
         }
@@ -2856,8 +2902,12 @@ pub(crate) mod _asyncio {
         waiter: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        // Only operate on native Future/Task objects (including subclasses).
+        // Both arguments must be native Future/Task objects (including subclasses).
         // Non-native objects are silently ignored.
+        if waiter.downcast_ref::<PyTask>().is_none() && waiter.downcast_ref::<PyFuture>().is_none()
+        {
+            return Ok(());
+        }
         if let Some(task) = fut.downcast_ref::<PyTask>() {
             return task.base.awaited_by_discard(&waiter, vm);
         }
diff --git a/crates/stdlib/src/_datetime.rs b/crates/stdlib/src/_datetime.rs
index e424d903b1d..d88a9565263 100644
--- a/crates/stdlib/src/_datetime.rs
+++ b/crates/stdlib/src/_datetime.rs
@@ -9,6 +9,8 @@ pub(crate) use _datetime::{PyTzInfo, datetime_type, module_def, timedelta_from_s
 
 #[pymodule]
 mod _datetime {
+    #[cfg(windows)]
+    use crate::vm::convert::ToPyException;
     use crate::vm::{
         AsObject, Py, PyObject, PyObjectCell, PyObjectRef, PyPayload, PyRef, PyResult,
         VirtualMachine,
@@ -1525,7 +1527,8 @@ mod _datetime {
         vals: &mut [i32; 4],
         tzoffset: &mut i32,
         tzmicrosecond: &mut i32,
-    ) -> i32 {
+        vm: &VirtualMachine,
+    ) -> PyResult<i32> {
         let p_end = start + len;
         let mut tzinfo_pos = start;
         loop {
@@ -1540,18 +1543,18 @@ mod _datetime {
         }
         let rv = parse_hh_mm_ss_ff(s, start, tzinfo_pos, vals);
         if rv < 0 {
-            return rv;
+            return Ok(rv);
         } else if tzinfo_pos == p_end {
-            return if rv == 1 { -5 } else { 0 };
+            return Ok(if rv == 1 { -5 } else { 0 });
         }
         if byte_at(s, tzinfo_pos) == b'Z' {
             *tzoffset = 0;
             *tzmicrosecond = 0;
-            return if byte_at(s, tzinfo_pos + 1) != 0 {
+            return Ok(if byte_at(s, tzinfo_pos + 1) != 0 {
                 -5
             } else {
                 1
-            };
+            });
         }
         let tzsign = if byte_at(s, tzinfo_pos) == b'-' {
             -1
@@ -1560,9 +1563,10 @@ mod _datetime {
         };
         let mut tz = [0; 4];
         let rv = parse_hh_mm_ss_ff(s, tzinfo_pos + 1, p_end, &mut tz);
+        check_time_args(tz[0], tz[1], tz[2], tz[3], 0, vm)?;
         *tzoffset = tzsign * (tz[0] * 3600 + tz[1] * 60 + tz[2]);
         *tzmicrosecond = tzsign * tz[3];
-        if rv != 0 { -5 } else { 1 }
+        Ok(if rv != 0 { -5 } else { 1 })
     }
 
     fn tzinfo_from_isoformat_results(
@@ -1746,18 +1750,15 @@ mod _datetime {
 
     /// `_PyTime_ObjectToTime_t` with floor rounding.
     fn object_to_time_t(obj: &PyObject, vm: &VirtualMachine) -> PyResult<i64> {
-        if let Some(float) = obj.downcast_ref::<PyFloat>() {
-            let d = float.to_f64();
-            if d.is_nan() {
-                return Err(vm.new_value_error("Invalid value NaN (not a number)"));
-            }
-            let d = d.floor();
-            if !(-9.223_372_036_854_776e18..9.223_372_036_854_776e18).contains(&d) {
-                return Err(time_t_overflow(vm));
-            }
-            return Ok(d as i64);
+        if obj.number().is_index() {
+            return long_to_time_t(obj, vm);
+        }
+        let d = timestamp_as_double(obj, vm)?;
+        let d = d.floor();
+        if !(-9.223_372_036_854_776e18..9.223_372_036_854_776e18).contains(&d) {
+            return Err(time_t_overflow(vm));
         }
-        long_to_time_t(obj, vm)
+        Ok(d as i64)
     }
 
     fn time_t_overflow(vm: &VirtualMachine) -> crate::vm::builtins::PyBaseExceptionRef {
@@ -1770,29 +1771,37 @@ mod _datetime {
         int.as_bigint().to_i64().ok_or_else(|| time_t_overflow(vm))
     }
 
+    fn timestamp_as_double(obj: &PyObject, vm: &VirtualMachine) -> PyResult<f64> {
+        let d = match obj.downcast_ref::<PyFloat>() {
+            Some(float) => float.to_f64(),
+            None => obj.try_float(vm)?.to_f64(),
+        };
+        if d.is_nan() {
+            return Err(vm.new_value_error("Invalid value NaN (not a number)"));
+        }
+        Ok(d)
+    }
+
     /// `_PyTime_ObjectToTimeval` with half-even rounding: whole seconds and microseconds.
     fn object_to_timeval(obj: &PyObject, vm: &VirtualMachine) -> PyResult<(i64, i32)> {
-        if let Some(float) = obj.downcast_ref::<PyFloat>() {
-            let d = float.to_f64();
-            if d.is_nan() {
-                return Err(vm.new_value_error("Invalid value NaN (not a number)"));
-            }
-            let mut intpart = d.trunc();
-            let mut floatpart = (d - intpart) * 1e6;
-            floatpart = round_half_even(floatpart);
-            if floatpart >= 1e6 {
-                floatpart -= 1e6;
-                intpart += 1.0;
-            } else if floatpart < 0.0 {
-                floatpart += 1e6;
-                intpart -= 1.0;
-            }
-            if !(-9.223_372_036_854_776e18..9.223_372_036_854_776e18).contains(&intpart) {
-                return Err(time_t_overflow(vm));
-            }
-            return Ok((intpart as i64, floatpart as i32));
+        if obj.number().is_index() {
+            return Ok((long_to_time_t(obj, vm)?, 0));
+        }
+        let d = timestamp_as_double(obj, vm)?;
+        let mut intpart = d.trunc();
+        let mut floatpart = (d - intpart) * 1e6;
+        floatpart = round_half_even(floatpart);
+        if floatpart >= 1e6 {
+            floatpart -= 1e6;
+            intpart += 1.0;
+        } else if floatpart < 0.0 {
+            floatpart += 1e6;
+            intpart -= 1.0;
+        }
+        if !(-9.223_372_036_854_776e18..9.223_372_036_854_776e18).contains(&intpart) {
+            return Err(time_t_overflow(vm));
         }
-        Ok((long_to_time_t(obj, vm)?, 0))
+        Ok((intpart as i64, floatpart as i32))
     }
 
     fn round_half_even(x: f64) -> f64 {
@@ -1819,12 +1828,16 @@ mod _datetime {
     fn platform_time(t: i64, local: bool, vm: &VirtualMachine) -> PyResult<Tm> {
         #[cfg(any(unix, windows))]
         {
-            let t_c = libc::time_t::try_from(t).map_err(|_| time_t_overflow(vm))?;
+            let t_c =
+                rustpython_host_env::time::TimeT::try_from(t).map_err(|_| time_t_overflow(vm))?;
             let tm = if local {
                 rustpython_host_env::time::localtime_from_timestamp(t_c)
             } else {
                 rustpython_host_env::time::gmtime_from_timestamp(t_c)
             };
+            #[cfg(windows)]
+            let tm = tm.map_err(|error| error.to_pyexception(vm))?;
+            #[cfg(unix)]
             let Some(tm) = tm else {
                 return Err(vm.new_last_errno_error());
             };
@@ -3018,7 +3031,8 @@ mod _datetime {
             let len = bytes.len() - start;
             let mut vals = [0; 4];
             let (mut tzoffset, mut tzusec) = (0, 0);
-            let rv = parse_isoformat_time(bytes, start, len, &mut vals, &mut tzoffset, &mut tzusec);
+            let rv =
+                parse_isoformat_time(bytes, start, len, &mut vals, &mut tzoffset, &mut tzusec, vm)?;
             if rv < 0 {
                 return Err(invalid_isoformat(&tstr, vm)?);
             }
@@ -3486,8 +3500,7 @@ mod _datetime {
         let tm = platform_time(timet, local_tm, vm)?;
         let second = tm.second.min(59);
         let mut fold = 0;
-        let skip_probe = cfg!(windows) && timet - MAX_FOLD_SECONDS <= 0;
-        if tzinfo.is_none() && local_tm && !skip_probe {
+        if tzinfo.is_none() && local_tm {
             let result_seconds =
                 utc_to_seconds(tm.year, tm.month, tm.day, tm.hour, tm.minute, second, vm)?;
             let probe_seconds = local(EPOCH_SECONDS + timet - MAX_FOLD_SECONDS, vm)?;
@@ -3890,7 +3903,8 @@ mod _datetime {
                     }
                 };
                 len = len.saturating_sub(p);
-                rv = parse_isoformat_time(bytes, p, len, &mut vals, &mut tzoffset, &mut tzusec);
+                rv =
+                    parse_isoformat_time(bytes, p, len, &mut vals, &mut tzoffset, &mut tzusec, vm)?;
             }
             if rv < 0 {
                 return Err(invalid_isoformat(&dtstr, vm)?);
diff --git a/crates/stdlib/src/_opcode.rs b/crates/stdlib/src/_opcode.rs
index 6a3c500c537..621c4220762 100644
--- a/crates/stdlib/src/_opcode.rs
+++ b/crates/stdlib/src/_opcode.rs
@@ -4,7 +4,6 @@ pub(crate) use _opcode::module_def;
 mod _opcode {
     use crate::vm::{
         AsObject, PyObjectRef, PyResult, VirtualMachine,
-        builtins::{PyInt, PyIntRef},
         bytecode::{AnyOpcode, oparg},
     };
 
@@ -25,7 +24,7 @@ mod _opcode {
     #[derive(FromArgs)]
     struct StackEffectArgs {
         #[pyarg(positional)]
-        opcode: PyIntRef,
+        opcode: i32,
         #[pyarg(positional, optional)]
         oparg: Option<PyObjectRef>,
         #[pyarg(named, optional)]
@@ -33,58 +32,33 @@ mod _opcode {
     }
 
     #[pyfunction]
+    #[allow(clippy::unnecessary_cast)] // `c_long` is `i32` or `i64`
     fn stack_effect(args: StackEffectArgs, vm: &VirtualMachine) -> PyResult<i32> {
-        let oparg = args.oparg.map_or(Ok(0), |v| {
-            if !v.fast_isinstance(vm.ctx.types.int_type) {
-                return Err(vm.new_type_error(format!(
-                    "'{}' object cannot be interpreted as an integer",
-                    v.class().name()
-                )));
-            }
-            v.downcast_ref::<PyInt>()
-                .ok_or_else(|| {
-                    vm.new_type_error(format!(
-                        "'{}' object cannot be interpreted as an integer",
-                        v.class().name()
-                    ))
-                })?
-                .try_to_primitive::<u32>(vm)
-        })?;
-
-        let jump: Option<bool> = match args.jump {
-            Some(v) => {
-                if vm.is_none(&v) {
-                    None
-                } else {
-                    Some(v.try_to_bool(vm).map_err(|_| {
-                        vm.new_value_error("stack_effect: jump must be False, True or None")
-                    })?)
-                }
-            }
+        let oparg = match args.oparg {
+            // (int)PyLong_AsLong(oparg)
+            Some(v) if !vm.is_none(&v) => v.try_into_value::<core::ffi::c_long>(vm)? as i32,
+            _ => 0,
+        };
+        let jump = match args.jump {
             None => None,
+            Some(v) if vm.is_none(&v) => None,
+            Some(v) if v.is(&vm.ctx.true_value) => Some(true),
+            Some(v) if v.is(&vm.ctx.false_value) => Some(false),
+            Some(_) => {
+                return Err(vm.new_value_error("stack_effect: jump must be False, True or None"));
+            }
         };
-
-        let instr = args
-            .opcode
-            .try_to_primitive::<u16>(vm)
-            .and_then(|v| {
-                AnyOpcode::try_from(v)
-                    .map_err(|_| vm.new_exception_empty(vm.ctx.exceptions.value_error.to_owned()))
-            })
-            .map_err(|_| vm.new_value_error("invalid opcode or oparg"))?;
-
-        // Raise ValueError if specialized.
+        let invalid = || vm.new_value_error("invalid opcode or oparg");
+        let instr = try_from_i32(args.opcode).map_err(|_| invalid())?;
+        // Specialized instructions are not supported.
         if instr.real().is_some_and(|op| op.deopt().is_some()) {
-            return Err(vm.new_value_error("invalid opcode or oparg"));
+            return Err(invalid());
         }
-
-        let effect = match jump {
-            Some(true) => instr.stack_effect_jump(oparg),
-            Some(false) => instr.stack_effect(oparg),
-            // jump=None: max of both paths (CPython convention)
-            None => instr
-                .stack_effect(oparg)
-                .max(instr.stack_effect_jump(oparg)),
+        let oparg = u32::try_from(oparg).map_err(|_| invalid())?;
+        let effect = if jump == Some(false) {
+            instr.stack_effect(oparg)
+        } else {
+            instr.stack_effect_jump(oparg)
         };
         Ok(effect)
     }
@@ -197,16 +171,20 @@ mod tests {
 
     macro_rules! assert_dis_snapshot {
         ($value:expr) => {
-            insta::assert_snapshot!(dis($value))
+            insta::assert_snapshot!(dis($value, false))
+        };
+        (positions: $value:expr) => {
+            insta::assert_snapshot!(dis($value, true))
         };
     }
 
-    /// Returns the [`dis.dis`](https://docs.python.org/3/library/dis.html#dis.dis) output.
+    /// Returns the [`dis.dis`](https://docs.python.org/3/library/dis.html#dis.dis) output,
+    /// with the source positions of the instructions if `show_positions` is true.
     ///
     /// # Notes
     ///
     /// Memory addresses in the output are replaced with `0xdeadbeef` for consistency.
-    fn dis(source: &str) -> String {
+    fn dis(source: &str, show_positions: bool) -> String {
         const FNAME: &str = "<?>";
 
         let builder = vm::Interpreter::builder(Default::default());
@@ -223,6 +201,10 @@ mod tests {
                 .map_err(|err| err.into_pyexception(vm, Some(source)))
                 .unwrap();
             scope.globals.set_item("code", code_obj.into(), vm).unwrap();
+            scope
+                .globals
+                .set_item("show_positions", vm.new_pyobj(show_positions), vm)
+                .unwrap();
 
             let py_source = r#"
 import dis
@@ -232,13 +214,13 @@ import sys
 
 old_stdout = sys.stdout
 sys.stdout = buf = io.StringIO()
-dis.dis(code)
+dis.dis(code, show_positions=show_positions)
 sys.stdout = old_stdout
 
 tmp_output = buf.getvalue()
 
 # constant mem address
-output = re.sub(r'(<code object \w+ at )0x[0-9a-fA-F]+', r'\g<1>0xdeadbeef', tmp_output)
+output = re.sub(r'(<code object .*? at )0x[0-9a-fA-F]+', r'\g<1>0xdeadbeef', tmp_output)
 "#;
 
             let py_code_obj = vm
@@ -246,7 +228,12 @@ output = re.sub(r'(<code object \w+ at )0x[0-9a-fA-F]+', r'\g<1>0xdeadbeef', tmp
                 .map_err(|err| err.into_pyexception(vm, Some(py_source)))
                 .unwrap();
 
-            vm.run_code_obj(py_code_obj, scope.clone()).unwrap();
+            vm.run_code_obj(py_code_obj, scope.clone())
+                .unwrap_or_else(|err| {
+                    let mut traceback = String::new();
+                    let _ = vm.write_exception(&mut traceback, &err);
+                    panic!("Python disassembly failed: {err:?}\n{traceback}");
+                });
             let py_output = scope.globals.get_item("output", vm).unwrap();
             py_output.str(vm).unwrap().to_string()
         })
@@ -338,6 +325,707 @@ def f(one: int):
     my_lst = [1]
     my_lst[one]: int
     return my_lst
+"#
+        )
+    }
+
+    #[test]
+    fn empty_module_implicit_return_location() {
+        // The implicit return is emitted with NO_LOCATION; propagate_line_numbers()
+        // gives it the module RESUME location, whose line is 0.
+        assert_dis_snapshot!(positions: "")
+    }
+
+    #[test]
+    fn module_docstring_location() {
+        // codegen_body() loads the docstring at its expression location and stores
+        // __doc__ with NO_LOCATION.
+        assert_dis_snapshot!(
+            positions: r#"
+"doc"
+x = 1
+"#
+        )
+    }
+
+    #[test]
+    fn redundant_nop_location() {
+        // basicblock_remove_redundant_nops() copies the full NOP location into a
+        // following no-location jump.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(x, y, z):
+    while x:
+        if y:
+            pass
+        elif z:
+            if y < 0:
+                return y
+            if z:
+                y = y + 1
+        elif y:
+            return 1
+    return -1
+"#
+        )
+    }
+
+    #[test]
+    fn annotated_multiline_function_firstlineno() {
+        // codegen_function() computes firstlineno from the FunctionDef before
+        // compiling annotations.
+        assert_dis_snapshot!(
+            positions: r#"
+
+a = 1
+def f(
+    x: a,
+): ...
+"#
+        )
+    }
+
+    #[test]
+    fn annotation_scope_function_location() {
+        // codegen_function_annotations() receives LOC(function) and uses it for the
+        // annotation closure's BUILD_MAP/RETURN_VALUE and the MAKE_FUNCTION annotate
+        // sequence.
+        assert_dis_snapshot!(
+            positions: r#"
+
+def g():
+    def f(x: not (int is int), /): ...
+"#
+        )
+    }
+
+    #[test]
+    fn starred_arg_annotation_unpack_location() {
+        // codegen_argannotation() visits `Ts` at the annotation location, then emits
+        // UNPACK_SEQUENCE at LOC(function).
+        assert_dis_snapshot!(
+            positions: r#"
+def f(*args: *Ts): pass
+"#
+        )
+    }
+
+    #[test]
+    fn module_deferred_annotations_location() {
+        // codegen_process_deferred_annotations() uses the first module statement
+        // location from start_location().
+        assert_dis_snapshot!(
+            positions: r#"
+import os
+X: int
+Y: str
+"#
+        )
+    }
+
+    #[test]
+    fn not_compare_location() {
+        // A Compare inside UnaryOp(Not) is parsed with the UnaryOp start location.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(self, other):
+    return not self == other
+"#
+        )
+    }
+
+    #[test]
+    fn not_chained_compare_location() {
+        // A chained comparison keeps its inner range for the comparison scaffolding
+        // and uses the UnaryOp range only for TO_BOOL and UNARY_NOT.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(c):
+    return not (b" " <= c <= b"~")
+"#
+        )
+    }
+
+    #[test]
+    fn type_param_scope_locations() {
+        // codegen_type_params() emits type parameter ops at LOC(typeparam),
+        // bound/default evaluators at LOC(e), and type alias plumbing at LOC(s).
+        assert_dis_snapshot!(
+            positions: r#"
+type BoundGenericAlias[X: int] = set[X]
+"#
+        )
+    }
+
+    #[test]
+    fn generic_typealias_wrapper_return_location() {
+        // The generic parameters wrapper of a type alias returns at LOC(type alias).
+        assert_dis_snapshot!(
+            positions: r#"
+type A[T] = T
+"#
+        )
+    }
+
+    #[test]
+    fn generic_function_annotation_scope_location() {
+        // codegen_function_annotations() gets LOC(function) inside the generic
+        // parameters scope too.
+        assert_dis_snapshot!(
+            positions: r#"
+def f[T](x: int): ...
+"#
+        )
+    }
+
+    #[test]
+    fn generic_class_type_params_store_location() {
+        // codegen_class() stores the .type_params cell at LOC(class).
+        assert_dis_snapshot!(
+            positions: r#"
+def outer():
+    class X[T]: ...
+"#
+        )
+    }
+
+    #[test]
+    fn class_deferred_annotations_location() {
+        // Deferred annotation setup and the class tail inherit the class body
+        // location LOCATION(firstlineno, firstlineno, 0, 0).
+        assert_dis_snapshot!(
+            positions: r#"
+
+class C:
+    "doc"
+    x: int
+"#
+        )
+    }
+
+    #[test]
+    fn future_annotation_string_location() {
+        // The stringized annotation is loaded at LOC(annotation) and stored at
+        // LOC(AnnAssign).
+        assert_dis_snapshot!(
+            positions: r#"
+from __future__ import annotations
+class Bar:
+    foo: Foo
+"#
+        )
+    }
+
+    #[test]
+    fn lambda_dict_literal_location() {
+        // codegen_dict() and codegen_subdict() use LOC(dict) for BUILD_MAP, MAP_ADD
+        // and DICT_UPDATE.
+        assert_dis_snapshot!(
+            positions: r#"
+f = lambda data: {'x': data}
+g = lambda i: {**i}
+"#
+        )
+    }
+
+    #[test]
+    fn match_or_alternative_locations() {
+        // codegen_pattern_or() emits the COPY of each alternative at LOC(alt).
+        assert_dis_snapshot!(
+            positions: r#"
+def f():
+    x = False
+    match 0:
+        case 0 | 1 | 2 | 3:
+            x = True
+    return x
+"#
+        )
+    }
+
+    #[test]
+    fn match_success_jump_location() {
+        // codegen_match_inner() emits the success jump with NO_LOCATION.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(self):
+    match 0:
+        case 0:
+            x = True
+        case 0:
+            x = False
+    self.assertIs(x, True)
+"#
+        )
+    }
+
+    #[test]
+    fn match_mapping_keys_location() {
+        // codegen_pattern_mapping() returns to LOC(p) for the BUILD_TUPLE/MATCH_KEYS
+        // scaffolding.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(self):
+    x = {}
+    y = None
+    match x:
+        case {0: 0}:
+            y = 0
+    self.assertIs(y, None)
+"#
+        )
+    }
+
+    #[test]
+    fn match_class_scaffolding_location() {
+        // codegen_pattern_class() returns to LOC(p) after visiting the class.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(x):
+    match x:
+        case bool(z):
+            y = 0
+    return y, z
+"#
+        )
+    }
+
+    #[test]
+    fn taken_constant_boolop_location() {
+        // The surviving load of a short-circuited BoolOp keeps the literal range.
+        assert_dis_snapshot!(
+            positions: r#"
+def and_false(x):
+    return False and x
+
+def or_true(x):
+    return True or x
+"#
+        )
+    }
+
+    #[test]
+    fn assert_false_message_location() {
+        // codegen_assert() emits LOAD_COMMON_CONSTANT and CALL at LOC(assert) and
+        // RAISE_VARARGS at LOC(test).
+        assert_dis_snapshot!(
+            positions: r#"
+def f():
+    assert False, "x"
+"#
+        )
+    }
+
+    #[test]
+    fn static_swap_implicit_return_location() {
+        // Line numbers are resolved before apply_static_swaps() reorders the stores,
+        // so the return epilogue keeps the location of the last store before the swap.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(a, b):
+    a, b = a, b
+    b, a = a, b
+"#
+        )
+    }
+
+    #[test]
+    fn genexpr_closure_and_call_location() {
+        // codegen_comprehension() uses LOC(e) for the closure, the outer CALL and the
+        // implicit .0 load.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(parameters):
+    return ((p, type(p)) for p in parameters)
+"#
+        )
+    }
+
+    #[test]
+    fn implicit_call_genexpr_range() {
+        // A sole unparenthesized generator expression argument spans the call
+        // parentheses.
+        assert_dis_snapshot!(
+            positions: r#"
+def implicit():
+    return list(x for x in range(10))
+
+def explicit():
+    return list((x for x in range(10)))
+"#
+        )
+    }
+
+    #[test]
+    fn implicit_call_genexpr_parenthesized_element_range() {
+        // The call parentheses are part of the generator expression range even when
+        // its element starts with a parenthesis.
+        assert_dis_snapshot!(
+            positions: r#"
+def bytes_binop():
+    return bytes((x ^ 0x5C) for x in range(256))
+
+def dict_tuple(d):
+    return dict((v, k) for (k, v) in d.items())
+
+def plain_tuple_elt(xs):
+    return list((x, y) for x, y in xs)
+
+def explicit_gen(xs):
+    return list(((x, y) for x, y in xs))
+"#
+        )
+    }
+
+    #[test]
+    fn genexpr_filter_cleanup_location() {
+        // jump_thread() copies the if_cleanup backedge location, elt_loc, to the
+        // threaded cleanup path.
+        assert_dis_snapshot!(
+            positions: r#"
+def simple(names):
+    return (x for x in names if not _ishidden(x))
+
+def boolop(fields):
+    return (f for f in fields if f.init and not f.kw_only)
+"#
+        )
+    }
+
+    #[test]
+    fn try_finally_exception_scaffolding_location() {
+        // codegen_try_finally() emits the exception path scaffolding with NO_LOCATION.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(self, node):
+    self.flag = True
+    try:
+        self.body(node)
+    finally:
+        self.flag = False
+"#
+        )
+    }
+
+    #[test]
+    fn adjacent_no_location_entries() {
+        // assemble_location_info() merges adjacent NO_LOCATION instructions into one
+        // linetable entry.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(file):
+    if sys.platform == "win32":
+        try:
+            import nt
+            if not nt._supports_virtual_terminal():
+                return False
+        except (ImportError, AttributeError):
+            return False
+    try:
+        return os.isatty(file.fileno())
+    except OSError:
+        return hasattr(file, "isatty") and file.isatty()
+"#
+        )
+    }
+
+    #[test]
+    fn fstring_format_location() {
+        // codegen_formatted_value() emits CONVERT_VALUE and FORMAT_* at
+        // LOC(FormattedValue).
+        assert_dis_snapshot!(
+            positions: r#"
+def simple(self):
+    return f'{self.value}'
+
+def spec(x):
+    return f'{x!r:>3}'
+"#
+        )
+    }
+
+    #[test]
+    fn joined_string_literals_location() {
+        // Adjacent f-string literal fragments are one Constant spanning all of them.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(a):
+    return (
+        'x'
+        f'y{a}z'
+        'w'
+    )
+"#
+        )
+    }
+
+    #[test]
+    fn decorated_definition_locations() {
+        // Decorators are evaluated first, the closure and the store use LOC(s), and
+        // each decorator CALL uses the decorator location.
+        assert_dis_snapshot!(
+            positions: r#"
+def dec(f): return f
+
+class C:
+    @dec
+    def f(self):
+        yield
+
+@dec
+class D:
+    pass
+
+class E:
+    @dec
+    def g(self, flags: int, /) -> memoryview:
+        raise NotImplementedError
+"#
+        )
+    }
+
+    #[test]
+    fn builtin_any_genexpr_call() {
+        // any(genexpr) is inlined behind a builtin identity check that falls back to
+        // the ordinary call.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(xs):
+    return any(x for x in xs)
+"#
+        )
+    }
+
+    #[test]
+    fn builtin_tuple_list_set_genexpr_calls() {
+        // tuple(), list() and set() of a generator expression are inlined behind a
+        // builtin identity check that falls back to the ordinary call.
+        assert_dis_snapshot!(
+            positions: r#"
+def tuple_f(xs):
+    return tuple(x for x in xs)
+
+def list_f(xs):
+    return list(x for x in xs)
+
+def set_f(xs):
+    return set(x for x in xs)
+"#
+        )
+    }
+
+    #[test]
+    fn augassign_constant_slice_location() {
+        // codegen_augassign() emits the COPY/COPY/BINARY_OP NB_SUBSCR at LOC(target).
+        assert_dis_snapshot!(
+            positions: r#"
+def aug_const(x, y):
+    x[1:2] += y
+"#
+        )
+    }
+
+    #[test]
+    fn comprehension_list_iterable_location() {
+        // codegen_comprehension_iter() emits GET_ITER at LOC(comp->iter).
+        assert_dis_snapshot!(
+            positions: r#"
+async def f(i):
+    return i
+
+async def run_list():
+    return [await c for c in [f(1), f(41)]]
+"#
+        )
+    }
+
+    #[test]
+    fn inlined_comprehension_backedge_location() {
+        // codegen_sync_comprehension_generator() emits the backedges at elt_loc.
+        assert_dis_snapshot!(
+            positions: r#"
+async def f(i):
+    return i
+
+async def run_list():
+    return [s for c in [f(''), f('abc')] for s in await c]
+"#
+        )
+    }
+
+    #[test]
+    fn inlined_async_comprehension_end_async_for_location() {
+        // codegen_async_comprehension_generator() emits END_ASYNC_FOR at the
+        // comprehension location.
+        assert_dis_snapshot!(
+            positions: r#"
+async def f(it):
+    for i in it:
+        yield i
+
+async def run_list():
+    return [i + 1 async for i in f([10, 20])]
+"#
+        )
+    }
+
+    #[test]
+    fn async_for_anext_location() {
+        // codegen_async_for() emits the GET_ANEXT/yield-from scaffolding at LOC(s).
+        assert_dis_snapshot!(
+            positions: r#"
+async def f(source, buffer):
+    async for i1, i2 in source():
+        buffer.append(i1 + i2)
+"#
+        )
+    }
+
+    #[test]
+    fn namedexpr_copy_location() {
+        // The COPY of a named expression is at its location, between the value and
+        // the target.
+        assert_dis_snapshot!(
+            positions: r#"
+def outer():
+    a = 10
+    def spam():
+        nonlocal a
+        (a := 20)
+"#
+        )
+    }
+
+    #[test]
+    fn with_cleanup_excludes_not_taken() {
+        // The NOT_TAKEN after the with body is outside the exception table entries.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(c):
+    with c:
+        x = 1
+    y = 2
+"#
+        )
+    }
+
+    #[test]
+    fn async_for_end_async_for() {
+        // END_ASYNC_FOR jumps back to the END_SEND of its awaitable loop.
+        assert_dis_snapshot!(
+            positions: r#"
+async def f(xs):
+    async for x in xs:
+        pass
+"#
+        )
+    }
+
+    #[test]
+    fn genexpr_prefix() {
+        // The outermost iterator is acquired before RETURN_GENERATOR, outside the
+        // StopIteration handler.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(xs):
+    return (x for x in xs)
+
+async def g(xs):
+    return (x async for x in xs)
+"#
+        )
+    }
+
+    #[test]
+    fn yield_from_and_await() {
+        // GET_ITER and GET_AWAITABLE leave the iterator pair that SEND uses.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(xs):
+    yield from xs
+
+async def g(xs):
+    return await xs
+"#
+        )
+    }
+
+    #[test]
+    fn comprehension_collection_depth() {
+        // The collection depth counts the slots of every nested iterator.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(xs, ys):
+    return [x for x in xs for y in ys]
+
+async def g(xs, ys):
+    return [x async for x in xs for y in ys]
+"#
+        )
+    }
+
+    #[test]
+    fn import_flags() {
+        // The IMPORT_NAME oparg flags depend on the scope and the enclosing handlers.
+        assert_dis_snapshot!(
+            positions: r#"
+import sample
+from sample import member
+from sample import *
+
+def f():
+    import sample
+
+class C:
+    from sample import member
+
+try:
+    import sample
+except Exception:
+    pass
+
+try:
+    operation()
+except Exception:
+    import sample
+
+try:
+    operation()
+finally:
+    import sample
+
+with manager:
+    import sample
+"#
+        )
+    }
+
+    #[test]
+    fn loop_return_cleanup() {
+        // A return pops two slots for a for loop and one for an async for loop.
+        assert_dis_snapshot!(
+            positions: r#"
+def f(xs):
+    for x in xs:
+        return x
+
+async def g(xs):
+    async for x in xs:
+        return x
+"#
+        )
+    }
+
+    #[test]
+    fn list_set_async_genexpr_calls() {
+        // list() and set() of an async generator expression stay ordinary calls.
+        assert_dis_snapshot!(
+            positions: r#"
+async def f(xs):
+    return list(x async for x in xs)
+
+async def g(xs):
+    return set(x async for x in xs)
 "#
         )
     }
diff --git a/crates/stdlib/src/_queue.rs b/crates/stdlib/src/_queue.rs
index 27155b7c3f3..806590c222c 100644
--- a/crates/stdlib/src/_queue.rs
+++ b/crates/stdlib/src/_queue.rs
@@ -21,7 +21,7 @@ mod _queue {
             use parking_lot::{Condvar, Mutex, MutexGuard};
 
             type Buf = Mutex<BufInner>;
-        },
+        }
         _ => {
             use crate::common::lock::PyMutex;
 
diff --git a/crates/stdlib/src/_sqlite3.rs b/crates/stdlib/src/_sqlite3.rs
index 75c228fa3e6..0fc0454af13 100644
--- a/crates/stdlib/src/_sqlite3.rs
+++ b/crates/stdlib/src/_sqlite3.rs
@@ -15,26 +15,28 @@ mod _sqlite3 {
     use core::{
         ffi::{CStr, c_int, c_longlong, c_uint, c_void},
         fmt::Debug,
-        ops::Deref,
+        ops::{Deref, DerefMut},
         ptr::{NonNull, null, null_mut},
     };
     use libsqlite3_sys::{
         SQLITE_BLOB, SQLITE_DETERMINISTIC, SQLITE_FLOAT, SQLITE_INTEGER, SQLITE_NULL,
-        SQLITE_OPEN_CREATE, SQLITE_OPEN_READWRITE, SQLITE_OPEN_URI, SQLITE_TEXT, SQLITE_TRACE_STMT,
-        SQLITE_TRANSIENT, SQLITE_UTF8, sqlite3, sqlite3_aggregate_context, sqlite3_backup_finish,
-        sqlite3_backup_init, sqlite3_backup_pagecount, sqlite3_backup_remaining,
-        sqlite3_backup_step, sqlite3_bind_blob, sqlite3_bind_double, sqlite3_bind_int64,
-        sqlite3_bind_null, sqlite3_bind_parameter_count, sqlite3_bind_parameter_name,
-        sqlite3_bind_text, sqlite3_blob, sqlite3_blob_bytes, sqlite3_blob_close, sqlite3_blob_open,
-        sqlite3_blob_read, sqlite3_blob_write, sqlite3_busy_timeout, sqlite3_changes,
-        sqlite3_column_blob, sqlite3_column_bytes, sqlite3_column_count, sqlite3_column_decltype,
-        sqlite3_column_double, sqlite3_column_int64, sqlite3_column_name, sqlite3_column_text,
-        sqlite3_column_type, sqlite3_complete, sqlite3_context, sqlite3_context_db_handle,
-        sqlite3_create_collation_v2, sqlite3_create_function_v2, sqlite3_create_window_function,
-        sqlite3_data_count, sqlite3_db_config, sqlite3_db_handle, sqlite3_errcode, sqlite3_errmsg,
+        SQLITE_OPEN_CREATE, SQLITE_OPEN_FULLMUTEX, SQLITE_OPEN_READWRITE, SQLITE_OPEN_URI,
+        SQLITE_TEXT, SQLITE_TRACE_STMT, SQLITE_TRANSIENT, SQLITE_UTF8, sqlite3,
+        sqlite3_aggregate_context, sqlite3_backup_finish, sqlite3_backup_init,
+        sqlite3_backup_pagecount, sqlite3_backup_remaining, sqlite3_backup_step, sqlite3_bind_blob,
+        sqlite3_bind_double, sqlite3_bind_int64, sqlite3_bind_null, sqlite3_bind_parameter_count,
+        sqlite3_bind_parameter_name, sqlite3_bind_text, sqlite3_blob, sqlite3_blob_bytes,
+        sqlite3_blob_close, sqlite3_blob_open, sqlite3_blob_read, sqlite3_blob_write,
+        sqlite3_busy_timeout, sqlite3_changes, sqlite3_clear_bindings, sqlite3_column_blob,
+        sqlite3_column_bytes, sqlite3_column_count, sqlite3_column_decltype, sqlite3_column_double,
+        sqlite3_column_int64, sqlite3_column_name, sqlite3_column_text, sqlite3_column_type,
+        sqlite3_complete, sqlite3_context, sqlite3_context_db_handle, sqlite3_create_collation_v2,
+        sqlite3_create_function_v2, sqlite3_create_window_function, sqlite3_data_count,
+        sqlite3_db_config, sqlite3_db_handle, sqlite3_db_mutex, sqlite3_errcode, sqlite3_errmsg,
         sqlite3_exec, sqlite3_expanded_sql, sqlite3_extended_errcode, sqlite3_finalize,
-        sqlite3_get_autocommit, sqlite3_interrupt, sqlite3_last_insert_rowid, sqlite3_libversion,
-        sqlite3_limit, sqlite3_open_v2, sqlite3_prepare_v2, sqlite3_progress_handler,
+        sqlite3_free, sqlite3_get_autocommit, sqlite3_interrupt, sqlite3_last_insert_rowid,
+        sqlite3_libversion, sqlite3_limit, sqlite3_mutex_enter, sqlite3_mutex_leave,
+        sqlite3_mutex_try, sqlite3_open_v2, sqlite3_prepare_v2, sqlite3_progress_handler,
         sqlite3_reset, sqlite3_result_blob, sqlite3_result_double, sqlite3_result_error,
         sqlite3_result_error_nomem, sqlite3_result_error_toobig, sqlite3_result_int64,
         sqlite3_result_null, sqlite3_result_text, sqlite3_set_authorizer, sqlite3_sleep,
@@ -49,6 +51,8 @@ mod _sqlite3 {
         atomic::{Ordering, PyAtomic, Radium},
         hash::PyHash,
         lock::{PyMappedMutexGuard, PyMutex, PyMutexGuard},
+        rc::PyRc,
+        refcount::{try_defer_drop, with_deferred_drops},
         static_cell,
     };
     use rustpython_vm::{
@@ -60,7 +64,6 @@ mod _sqlite3 {
             PyInt, PyIntRef, PyModule, PySlice, PyStr, PyStrRef, PyTuple, PyTupleRef, PyType,
             PyTypeRef, PyUtf8Str, PyUtf8StrRef,
         },
-        convert::IntoObject,
         function::{
             ArgCallable, ArgIterable, FsPath, FuncArgs, KwArgs, OptionalArg, PyComparisonValue,
             PySetterValue, TimeoutSeconds,
@@ -373,9 +376,7 @@ mod _sqlite3 {
         check_same_thread: bool,
         #[pyarg(any, default = Connection::class(&vm.ctx).to_owned(), py_default = "ConnectionType")]
         factory: PyTypeRef,
-        // TODO: cache statements
-        #[allow(dead_code)]
-        #[pyarg(any, default = 0)]
+        #[pyarg(any, default = 128)]
         cached_statements: c_int,
         #[pyarg(any, default = false)]
         uri: bool,
@@ -397,7 +398,7 @@ mod _sqlite3 {
         #[pyarg(named, default = -1)]
         pages: c_int,
         #[pyarg(named, optional)]
-        progress: Option<ArgCallable>,
+        progress: Option<PyObjectRef>,
         #[pyarg(named, optional)]
         name: Option<PyStrRef>,
         #[pyarg(named, default = 0.250)]
@@ -461,19 +462,41 @@ mod _sqlite3 {
 
     struct CallbackData {
         obj: NonNull<PyObject>,
-        vm: *const VirtualMachine,
     }
 
     impl CallbackData {
         fn new(obj: PyObjectRef, vm: &VirtualMachine) -> Option<Self> {
             (!vm.is_none(&obj)).then_some(Self {
                 obj: obj.into_raw(),
-                vm,
             })
         }
 
-        fn retrieve(&self) -> (&PyObject, &VirtualMachine) {
-            unsafe { (self.obj.as_ref(), &*self.vm) }
+        fn with_vm<R>(&self, f: impl Fn(&PyObject, &VirtualMachine) -> R) -> Option<R> {
+            let obj = unsafe { self.obj.as_ref() };
+            // A shared connection may invoke this callback on a different thread
+            // after the registering thread's VM has already been destroyed.
+            rustpython_vm::vm::thread::with_vm(obj, |vm| f(obj, vm))
+        }
+
+        // The SQLite mutex keeps the registration alive until this reference is acquired.
+        unsafe fn registered(data: *mut c_void) -> PyRc<Self> {
+            let data = data.cast::<Self>();
+            unsafe {
+                PyRc::increment_strong_count(data);
+                PyRc::from_raw(data)
+            }
+        }
+
+        fn with_context(&self, context: SqliteContext, f: impl Fn(&PyObject, &VirtualMachine)) {
+            if self.with_vm(f).is_none() {
+                unsafe {
+                    sqlite3_result_error(
+                        context.ctx,
+                        c"SQLite callback has no active interpreter".as_ptr(),
+                        -1,
+                    )
+                };
+            }
         }
 
         unsafe extern "C" fn destructor(data: *mut c_void) {
@@ -486,25 +509,27 @@ mod _sqlite3 {
             argv: *mut *mut sqlite3_value,
         ) {
             let context = SqliteContext::from(context);
-            let (func, vm) = unsafe { (*context.user_data::<Self>()).retrieve() };
-            let args = unsafe { core::slice::from_raw_parts(argv, argc as usize) };
+            let data = unsafe { &*context.user_data::<Self>() };
+            data.with_context(context, |func, vm| {
+                let args = unsafe { core::slice::from_raw_parts(argv, argc as usize) };
 
-            let f = || -> PyResult<()> {
-                let db = context.db_handle();
-                let args = args
-                    .iter()
-                    .copied()
-                    .map(|val| value_to_object(val, db, vm))
-                    .collect::<PyResult<Vec<PyObjectRef>>>()?;
+                let f = || -> PyResult<()> {
+                    let db = context.db_handle();
+                    let args = args
+                        .iter()
+                        .copied()
+                        .map(|val| value_to_object(val, db, vm))
+                        .collect::<PyResult<Vec<PyObjectRef>>>()?;
 
-                let val = func.call(args, vm)?;
+                    let val = func.call(args, vm)?;
 
-                context.result_from_object(&val, vm)
-            };
+                    context.result_from_object(&val, vm)
+                };
 
-            if let Err(exc) = f() {
-                context.result_exception(vm, exc, c"user-defined function raised exception")
-            }
+                if let Err(exc) = f() {
+                    context.result_exception(vm, exc, c"user-defined function raised exception")
+                }
+            });
         }
 
         unsafe extern "C" fn step_callback(
@@ -513,35 +538,53 @@ mod _sqlite3 {
             argv: *mut *mut sqlite3_value,
         ) {
             let context = SqliteContext::from(context);
-            let (cls, vm) = unsafe { (*context.user_data::<Self>()).retrieve() };
-            let args = unsafe { core::slice::from_raw_parts(argv, argc as usize) };
-            let instance = context.aggregate_context::<*const PyObject>();
-            if unsafe { (*instance).is_null() } {
-                match cls.call((), vm) {
-                    Ok(obj) => unsafe { *instance = obj.into_raw().as_ptr() },
-                    Err(exc) => {
-                        return context.result_exception(
-                            vm,
-                            exc,
-                            c"user-defined aggregate's '__init__' method raised error",
-                        );
+            let data = unsafe { &*context.user_data::<Self>() };
+            data.with_context(context, |cls, vm| {
+                let args = unsafe { core::slice::from_raw_parts(argv, argc as usize) };
+                let instance = context.aggregate_context(true);
+                if instance.is_null() {
+                    unsafe { sqlite3_result_error_nomem(context.ctx) };
+                    return;
+                }
+                if unsafe { (*instance).is_null() } {
+                    match cls.call((), vm) {
+                        Ok(obj) => unsafe { *instance = obj.into_raw().as_ptr() },
+                        Err(exc) => {
+                            return context.result_exception(
+                                vm,
+                                exc,
+                                c"user-defined aggregate's '__init__' method raised error",
+                            );
+                        }
                     }
                 }
-            }
-            let instance = unsafe { &**instance };
+                let instance = unsafe { &**instance };
 
-            Self::call_method_with_args(context, instance, "step", args, vm);
+                Self::call_method_with_args(context, instance, "step", args, vm);
+            });
         }
 
         unsafe extern "C" fn finalize_callback(context: *mut sqlite3_context) {
             let context = SqliteContext::from(context);
-            let (_, vm) = unsafe { (*context.user_data::<Self>()).retrieve() };
-            let instance = context.aggregate_context::<*const PyObject>();
-            let Some(instance) = (unsafe { (*instance).as_ref() }) else {
+            let data = unsafe { &*context.user_data::<Self>() };
+            let instance = context.aggregate_context(false);
+            if instance.is_null() {
+                return;
+            }
+            // xFinal releases the reference acquired by xStep, even if the
+            // query or finalize() fails. Clear the slot before calling Python.
+            let object = unsafe { instance.replace(core::ptr::null()) };
+            let Some(object) = NonNull::new(object.cast_mut()) else {
                 return;
             };
+            let instance = unsafe { PyObjectRef::from_raw(object) };
 
-            Self::callback_result_from_method(context, instance, "finalize", vm);
+            data.with_context(context, |_, vm| {
+                Self::callback_result_from_method(context, &instance, "finalize", vm);
+            });
+            // __del__ and weakref callbacks must run after the caller releases
+            // its cursor, statement and connection locks.
+            try_defer_drop(move || drop(instance));
         }
 
         unsafe extern "C" fn collation_callback(
@@ -551,38 +594,45 @@ mod _sqlite3 {
             b_len: c_int,
             b_ptr: *const c_void,
         ) -> c_int {
-            let (callable, vm) = unsafe { (*data.cast::<Self>()).retrieve() };
-
-            let f = || -> PyResult<c_int> {
-                let text1 = ptr_to_string(a_ptr.cast(), a_len, null_mut(), vm)?;
-                let text1 = vm.ctx.new_str(text1);
-                let text2 = ptr_to_string(b_ptr.cast(), b_len, null_mut(), vm)?;
-                let text2 = vm.ctx.new_str(text2);
+            let data = unsafe { &*data.cast::<Self>() };
+            data.with_vm(|callable, vm| {
+                let f = || -> PyResult<c_int> {
+                    let text1 = ptr_to_string(a_ptr.cast(), a_len, null_mut(), vm)?;
+                    let text1 = vm.ctx.new_str(text1);
+                    let text2 = ptr_to_string(b_ptr.cast(), b_len, null_mut(), vm)?;
+                    let text2 = vm.ctx.new_str(text2);
+
+                    let val = callable.call((text1, text2), vm)?;
+                    let Some(val) = val.number().index(vm) else {
+                        return Ok(0);
+                    };
 
-                let val = callable.call((text1, text2), vm)?;
-                let Some(val) = val.number().index(vm) else {
-                    return Ok(0);
-                };
+                    let val = match val?.as_bigint().sign() {
+                        Sign::Plus => 1,
+                        Sign::Minus => -1,
+                        Sign::NoSign => 0,
+                    };
 
-                let val = match val?.as_bigint().sign() {
-                    Sign::Plus => 1,
-                    Sign::Minus => -1,
-                    Sign::NoSign => 0,
+                    Ok(val)
                 };
 
-                Ok(val)
-            };
-
-            f().unwrap_or(0)
+                f().unwrap_or(0)
+            })
+            .unwrap_or(0)
         }
 
         unsafe extern "C" fn value_callback(context: *mut sqlite3_context) {
             let context = SqliteContext::from(context);
-            let (_, vm) = unsafe { (*context.user_data::<Self>()).retrieve() };
-            let instance = context.aggregate_context::<*const PyObject>();
-            let instance = unsafe { &**instance };
+            let data = unsafe { &*context.user_data::<Self>() };
+            data.with_context(context, |_, vm| {
+                let instance = context.aggregate_context(false);
+                let Some(instance) = (unsafe { instance.as_ref().and_then(|obj| obj.as_ref()) })
+                else {
+                    return;
+                };
 
-            Self::callback_result_from_method(context, instance, "value", vm);
+                Self::callback_result_from_method(context, instance, "value", vm);
+            });
         }
 
         unsafe extern "C" fn inverse_callback(
@@ -591,12 +641,17 @@ mod _sqlite3 {
             argv: *mut *mut sqlite3_value,
         ) {
             let context = SqliteContext::from(context);
-            let (_, vm) = unsafe { (*context.user_data::<Self>()).retrieve() };
-            let args = unsafe { core::slice::from_raw_parts(argv, argc as usize) };
-            let instance = context.aggregate_context::<*const PyObject>();
-            let instance = unsafe { &**instance };
+            let data = unsafe { &*context.user_data::<Self>() };
+            data.with_context(context, |_, vm| {
+                let args = unsafe { core::slice::from_raw_parts(argv, argc as usize) };
+                let instance = context.aggregate_context(false);
+                let Some(instance) = (unsafe { instance.as_ref().and_then(|obj| obj.as_ref()) })
+                else {
+                    return;
+                };
 
-            Self::call_method_with_args(context, instance, "inverse", args, vm);
+                Self::call_method_with_args(context, instance, "inverse", args, vm);
+            });
         }
 
         unsafe extern "C" fn authorizer_callback(
@@ -607,21 +662,24 @@ mod _sqlite3 {
             db_name: *const libc::c_char,
             access: *const libc::c_char,
         ) -> c_int {
-            let (callable, vm) = unsafe { (*data.cast::<Self>()).retrieve() };
-            let f = || -> PyResult<c_int> {
-                let arg1 = ptr_to_str_or_none(arg1, vm)?;
-                let arg2 = ptr_to_str_or_none(arg2, vm)?;
-                let db_name = ptr_to_str_or_none(db_name, vm)?;
-                let access = ptr_to_str_or_none(access, vm)?;
-
-                let val = callable.call((action, arg1, arg2, db_name, access), vm)?;
-                let Some(val) = val.downcast_ref::<PyInt>() else {
-                    return Ok(SQLITE_DENY);
+            let data = unsafe { Self::registered(data) };
+            data.with_vm(|callable, vm| {
+                let f = || -> PyResult<c_int> {
+                    let arg1 = ptr_to_str_or_none(arg1, vm)?;
+                    let arg2 = ptr_to_str_or_none(arg2, vm)?;
+                    let db_name = ptr_to_str_or_none(db_name, vm)?;
+                    let access = ptr_to_str_or_none(access, vm)?;
+
+                    let val = callable.call((action, arg1, arg2, db_name, access), vm)?;
+                    let Some(val) = val.downcast_ref::<PyInt>() else {
+                        return Ok(SQLITE_DENY);
+                    };
+                    val.try_to_primitive::<c_int>(vm)
                 };
-                val.try_to_primitive::<c_int>(vm)
-            };
 
-            f().unwrap_or(SQLITE_DENY)
+                f().unwrap_or(SQLITE_DENY)
+            })
+            .unwrap_or(SQLITE_DENY)
         }
 
         unsafe extern "C" fn trace_callback(
@@ -630,25 +688,38 @@ mod _sqlite3 {
             stmt: *mut c_void,
             sql: *mut c_void,
         ) -> c_int {
-            let (callable, vm) = unsafe { (*data.cast::<Self>()).retrieve() };
-            let expanded = unsafe { sqlite3_expanded_sql(stmt.cast()) };
-            let f = || -> PyResult<()> {
-                let stmt = ptr_to_str(expanded, vm).or_else(|_| ptr_to_str(sql.cast(), vm))?;
-                callable.call((stmt,), vm)?;
-                Ok(())
-            };
-            let _ = f();
-            0
+            let data = unsafe { Self::registered(data) };
+            data.with_vm(|callable, vm| {
+                let f = || -> PyResult<()> {
+                    let stmt = {
+                        let expanded = scopeguard::guard(
+                            unsafe { sqlite3_expanded_sql(stmt.cast()) },
+                            |sql| unsafe { sqlite3_free(sql.cast()) },
+                        );
+                        let text =
+                            ptr_to_str(*expanded, vm).or_else(|_| ptr_to_str(sql.cast(), vm))?;
+                        vm.ctx.new_str(text)
+                    };
+                    callable.call((stmt,), vm)?;
+                    Ok(())
+                };
+                let _ = f();
+                0
+            })
+            .unwrap_or(0)
         }
 
         unsafe extern "C" fn progress_callback(data: *mut c_void) -> c_int {
-            let (callable, vm) = unsafe { (*data.cast::<Self>()).retrieve() };
-            if let Ok(val) = callable.call((), vm)
-                && let Ok(val) = val.is_true(vm)
-            {
-                return val as c_int;
-            }
-            -1
+            let data = unsafe { Self::registered(data) };
+            data.with_vm(|callable, vm| {
+                if let Ok(val) = callable.call((), vm)
+                    && let Ok(val) = val.is_true(vm)
+                {
+                    return val as c_int;
+                }
+                -1
+            })
+            .unwrap_or(-1)
         }
 
         fn callback_result_from_method(
@@ -732,9 +803,10 @@ mod _sqlite3 {
 
     impl Drop for CallbackData {
         fn drop(&mut self) {
-            unsafe {
-                let _ = PyObjectRef::from_raw(self.obj);
-            };
+            let obj = unsafe { PyObjectRef::from_raw(self.obj) };
+            // The last active callback may outlive its registration. Release the
+            // Python reference after the outer operation's native/Rust locks.
+            try_defer_drop(move || drop(obj));
         }
     }
 
@@ -924,7 +996,8 @@ mod _sqlite3 {
     #[pyclass(name)]
     #[derive(PyPayload)]
     struct Connection {
-        db: PyMutex<Option<Sqlite>>,
+        db: PyMutex<Option<PyRc<Sqlite>>>,
+        statement_cache: PyMutex<StatementCache>,
         initialized: PyAtomic<bool>,
         detect_types: PyAtomic<c_int>,
         isolation_level: PyAtomicRef<Option<PyStr>>,
@@ -963,6 +1036,7 @@ mod _sqlite3 {
 
             Ok(Self {
                 db: PyMutex::new(db),
+                statement_cache: PyMutex::new(StatementCache::new(args.cached_statements)),
                 initialized: Radium::new(initialized),
                 detect_types: Radium::new(args.detect_types),
                 isolation_level: PyAtomicRef::from(args.isolation_level.0),
@@ -979,6 +1053,12 @@ mod _sqlite3 {
         type Args = FuncArgs;
 
         fn call(zelf: &Py<Self>, args: Self::Args, vm: &VirtualMachine) -> PyResult {
+            with_deferred_drops(|| Self::call_inner(zelf, args, vm))
+        }
+    }
+
+    impl Connection {
+        fn call_inner(zelf: &Py<Self>, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
             let _ = zelf.db_lock(vm)?;
 
             let (sql,): (PyUtf8StrRef,) = args.bind(vm)?;
@@ -995,15 +1075,23 @@ mod _sqlite3 {
         type Args = ConnectArgs;
 
         fn init(zelf: &Py<Self>, args: Self::Args, vm: &VirtualMachine) -> PyResult<()> {
-            let was_initialized = Radium::swap(&zelf.initialized, false, Ordering::AcqRel);
-
-            // Reset factories to their defaults, matching CPython's behavior.
-            zelf.reset_factories(vm);
+            loop {
+                with_deferred_drops(|| {
+                    Radium::store(&zelf.initialized, false, Ordering::Release);
 
-            if was_initialized {
-                zelf.drop_db(vm)?;
+                    // Reset factories to their defaults, matching CPython's behavior.
+                    zelf.reset_factories(vm);
+                    zelf.drop_db(vm)
+                })?;
+                // A finalizer may itself reinitialize the connection. Dispose of
+                // that database too before publishing the requested replacement.
+                if zelf.db.lock().is_none() {
+                    break;
+                }
             }
 
+            // Dispose of the old callbacks before publishing the replacement.
+            // Nested native calls still defer their drops to the outer operation.
             // Attempt to open the new database before mutating other state so failures leave
             // the connection uninitialized (and subsequent operations raise ProgrammingError).
             let db = Self::initialize_db(&args, vm)?;
@@ -1013,39 +1101,128 @@ mod _sqlite3 {
                 isolation_level,
                 check_same_thread,
                 autocommit,
+                cached_statements,
                 ..
             } = args;
 
-            zelf.detect_types.store(detect_types, Ordering::Relaxed);
-            zelf.check_same_thread
-                .store(check_same_thread, Ordering::Relaxed);
-            *zelf.autocommit.lock() = autocommit;
-            *zelf.thread_ident.lock() = std::thread::current().id();
-            let _ = unsafe { zelf.isolation_level.swap(isolation_level.0) };
+            let default_text_factory = PyStr::class(&vm.ctx).to_owned().into_object();
+            loop {
+                let mut current = zelf.db.lock();
+                if current.is_none() {
+                    let previous = unsafe { zelf.isolation_level.swap(isolation_level.0.clone()) };
+                    let row_factory = unsafe { zelf.row_factory.swap(None) };
+                    let text_factory =
+                        unsafe { zelf.text_factory.swap(default_text_factory.clone()) };
+                    if previous.as_ref().is_some_and(|previous| {
+                        !isolation_level
+                            .0
+                            .as_ref()
+                            .is_some_and(|requested| previous.is(requested))
+                    }) || row_factory.is_some()
+                        || !text_factory.is(&default_text_factory)
+                    {
+                        // Factories and str subclasses can finalize too. Retire
+                        // them before publication, then recheck any reentrant changes.
+                        drop(current);
+                        with_deferred_drops(|| drop((previous, row_factory, text_factory)));
+                        continue;
+                    }
 
-            let mut guard = zelf.db.lock();
-            *guard = Some(db);
-            Radium::store(&zelf.initialized, true, Ordering::Release);
-            Ok(())
+                    // No destructor-capable owner remains to release here.
+                    // Publish the settings and database under the same lock.
+                    zelf.statement_cache.lock().capacity = cached_statements.max(0) as usize;
+                    zelf.detect_types.store(detect_types, Ordering::Relaxed);
+                    zelf.check_same_thread
+                        .store(check_same_thread, Ordering::Relaxed);
+                    *zelf.autocommit.lock() = autocommit;
+                    *zelf.thread_ident.lock() = std::thread::current().id();
+                    *current = Some(db);
+                    Radium::store(&zelf.initialized, true, Ordering::Release);
+                    return Ok(());
+                }
+                drop(current);
+
+                // A concurrent initializer or finalizer installed another database.
+                // Finish its teardown outside the lock before trying to publish.
+                with_deferred_drops(|| {
+                    Radium::store(&zelf.initialized, false, Ordering::Release);
+                    zelf.reset_factories(vm);
+                    zelf.drop_db(vm)
+                })?;
+            }
         }
     }
 
     #[pyclass(with(Constructor, Callable, Initializer), flags(BASETYPE, HAS_WEAKREF))]
     impl Connection {
-        fn drop_db(&self, vm: &VirtualMachine) -> PyResult<()> {
-            let mut guard = self.db.lock();
-            let rollback_result = if let Some(db) = guard.as_ref()
-                && *self.autocommit.lock() == AutocommitMode::Disabled
-                && !db.is_autocommit()
+        fn cached_statement(
+            &self,
+            sql: PyUtf8StrRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<Option<StatementLease>> {
+            // Check the connection even on a cache hit.
+            drop(self.db_lock(vm)?);
+            let (cached, generation) = {
+                let mut cache = self.statement_cache.lock();
+                let statement = cache.entries.get_index_of(sql.as_str()).map(|index| {
+                    let last = cache.entries.len() - 1;
+                    cache.entries.move_index(index, last);
+                    cache.entries.get_index(last).unwrap().1.clone()
+                });
+                (statement, cache.generation)
+            };
+            if let Some(statement) = &cached
+                && let Some(lease) = StatementLease::acquire(statement.clone())
             {
-                db._exec(c"ROLLBACK", vm)
-            } else {
-                Ok(())
+                return Ok(Some(lease));
+            }
+
+            // Preparing may invoke an authorizer. Never hold the cache lock
+            // across callbacks, or wait for a statement owned by another cursor.
+            let Some(statement) = Statement::new(self, sql.clone(), vm)? else {
+                return Ok(None);
             };
-            let db = guard.take();
-            drop(guard);
-            drop(db);
-            rollback_result
+            let statement = statement.into_ref(&vm.ctx);
+            let lease = StatementLease::acquire(statement.clone()).unwrap();
+            let evicted = {
+                let mut cache = self.statement_cache.lock();
+                if cached.is_none()
+                    && cache.generation == generation
+                    && cache.capacity > 0
+                    && !cache.entries.contains_key(sql.as_str())
+                {
+                    let evicted = if cache.entries.len() == cache.capacity {
+                        cache.entries.shift_remove_index(0)
+                    } else {
+                        None
+                    };
+                    cache.entries.insert(sql.as_str().into(), statement);
+                    evicted
+                } else {
+                    None
+                }
+            };
+            drop(evicted);
+            Ok(Some(lease))
+        }
+
+        fn drop_db(&self, vm: &VirtualMachine) -> PyResult<()> {
+            with_deferred_drops(|| Self::drop_db_inner(self, vm))
+        }
+
+        fn drop_db_inner(&self, vm: &VirtualMachine) -> PyResult<()> {
+            let db = self.db.lock().take();
+            let statements = {
+                let mut cache = self.statement_cache.lock();
+                cache.generation = cache.generation.wrapping_add(1);
+                core::mem::take(&mut cache.entries)
+            };
+            drop(statements);
+            let rollback = *self.autocommit.lock() == AutocommitMode::Disabled;
+            if let Some(db) = db {
+                db.close_callbacks(rollback, vm)?;
+            }
+            Ok(())
         }
 
         fn reset_factories(&self, vm: &VirtualMachine) {
@@ -1054,9 +1231,13 @@ mod _sqlite3 {
             let _ = unsafe { self.text_factory.swap(default_text_factory) };
         }
 
-        fn initialize_db(args: &ConnectArgs, vm: &VirtualMachine) -> PyResult<Sqlite> {
+        fn initialize_db(args: &ConnectArgs, vm: &VirtualMachine) -> PyResult<PyRc<Sqlite>> {
             let path = args.database.to_cstring(vm)?;
-            let db = Sqlite::from(SqliteRaw::open(path.as_ptr(), args.uri, vm)?);
+            let db = PyRc::new(Sqlite::from(SqliteRaw::open(path.as_ptr(), args.uri, vm)?));
+            #[cfg(feature = "threading")]
+            if unsafe { sqlite3_db_mutex(db.db) }.is_null() {
+                return Err(vm.new_runtime_error("SQLite connection mutexes are disabled"));
+            }
             let timeout = (args.timeout.to_secs_f64() * 1000.0) as c_int;
             db.busy_timeout(timeout);
             if let Some(isolation_level) = &args.isolation_level.0 {
@@ -1068,17 +1249,15 @@ mod _sqlite3 {
             Ok(db)
         }
 
-        fn db_lock(&self, vm: &VirtualMachine) -> PyResult<PyMappedMutexGuard<'_, Sqlite>> {
+        fn db_lock(&self, vm: &VirtualMachine) -> PyResult<SqliteOperation> {
             self.check_thread(vm)?;
             self._db_lock(vm)
         }
 
-        fn _db_lock(&self, vm: &VirtualMachine) -> PyResult<PyMappedMutexGuard<'_, Sqlite>> {
+        fn _db_lock(&self, vm: &VirtualMachine) -> PyResult<SqliteOperation> {
             let guard = self.db.lock();
-            if guard.is_some() {
-                Ok(PyMutexGuard::map(guard, |x| unsafe {
-                    x.as_mut().unwrap_unchecked()
-                }))
+            if let Some(db) = guard.as_ref() {
+                Ok(SqliteOperation(db.clone()))
             } else if self.initialized.load(Ordering::Acquire) {
                 Err(new_programming_error(
                     vm,
@@ -1092,6 +1271,10 @@ mod _sqlite3 {
             }
         }
 
+        fn check_open(&self, vm: &VirtualMachine) -> PyResult<()> {
+            self.db_lock(vm).map(drop)
+        }
+
         #[pymethod]
         fn cursor(
             zelf: PyRef<Self>,
@@ -1128,6 +1311,14 @@ mod _sqlite3 {
             zelf: PyRef<Self>,
             args: BlobOpenArgs,
             vm: &VirtualMachine,
+        ) -> PyResult<PyRef<Blob>> {
+            with_deferred_drops(|| Self::blobopen_inner(zelf, args, vm))
+        }
+
+        fn blobopen_inner(
+            zelf: PyRef<Self>,
+            args: BlobOpenArgs,
+            vm: &VirtualMachine,
         ) -> PyResult<PyRef<Blob>> {
             let table = args.table.to_cstring(vm)?;
             let column = args.column.to_cstring(vm)?;
@@ -1136,7 +1327,7 @@ mod _sqlite3 {
             let db = zelf.db_lock(vm)?;
 
             let mut blob = null_mut();
-            let ret = unsafe {
+            let ret = db.call(|| unsafe {
                 sqlite3_blob_open(
                     db.db,
                     name.as_ptr(),
@@ -1146,14 +1337,16 @@ mod _sqlite3 {
                     (!args.readonly) as c_int,
                     &mut blob,
                 )
-            };
+            });
             db.check(ret, vm)?;
-            drop(db);
-
             let blob = SqliteBlob { blob };
             let blob = Blob {
                 connection: zelf,
-                inner: PyMutex::new(Some(BlobInner { blob, offset: 0 })),
+                inner: PyMutex::new(Some(BlobInner {
+                    blob,
+                    offset: 0,
+                    db: db.0.clone(),
+                })),
             };
             Ok(blob.into_ref(&vm.ctx))
         }
@@ -1170,36 +1363,56 @@ mod _sqlite3 {
 
         #[pymethod]
         fn commit(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
-            let db = zelf.db_lock(vm)?;
-            let mode = *zelf.autocommit.lock();
-            match mode {
-                AutocommitMode::Legacy => db.implicit_commit(vm),
-                AutocommitMode::Enabled => Ok(()),
-                AutocommitMode::Disabled => {
-                    db._exec(c"COMMIT", vm)?;
-                    db._exec(c"BEGIN", vm)
-                }
-            }
+            with_deferred_drops(|| Self::commit_inner(zelf, vm))
+        }
+
+        fn commit_inner(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
+            zelf.end_transaction(c"COMMIT", vm)
         }
 
         #[pymethod]
         fn rollback(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
-            let db = zelf.db_lock(vm)?;
-            let mode = *zelf.autocommit.lock();
-            match mode {
-                AutocommitMode::Legacy => {
-                    if db.is_autocommit() {
-                        Ok(())
-                    } else {
-                        db._exec(c"ROLLBACK", vm)
-                    }
+            with_deferred_drops(|| Self::rollback_inner(zelf, vm))
+        }
+
+        fn rollback_inner(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
+            zelf.end_transaction(c"ROLLBACK", vm)
+        }
+
+        fn end_transaction(&self, sql: &CStr, vm: &VirtualMachine) -> PyResult<()> {
+            let db = self.db_lock(vm)?;
+            let result = {
+                let _guard = db.lock();
+                let mode = *self.autocommit.lock();
+                db.end_transaction(sql, mode)
+            };
+            result.map_err(|err| err.into_exception(vm))
+        }
+
+        fn begin_transaction(&self, db: SqliteRaw, vm: &VirtualMachine) -> PyResult<()> {
+            let result = {
+                let _guard = db.lock();
+                let mode = *self.autocommit.lock();
+                if mode == AutocommitMode::Legacy && db.is_autocommit() {
+                    db.begin_transaction(self.isolation_level.deref().map(|x| x.to_owned()))
+                } else {
+                    Ok(())
                 }
-                AutocommitMode::Enabled => Ok(()),
-                AutocommitMode::Disabled => {
-                    db._exec(c"ROLLBACK", vm)?;
-                    db._exec(c"BEGIN", vm)
+            };
+            result.map_err(|err| err.into_exception(vm))
+        }
+
+        fn commit_before_script(&self, db: SqliteRaw, vm: &VirtualMachine) -> PyResult<()> {
+            let result = {
+                let _guard = db.lock();
+                let mode = *self.autocommit.lock();
+                if mode == AutocommitMode::Legacy {
+                    db.end_transaction(c"COMMIT", mode)
+                } else {
+                    Ok(())
                 }
-            }
+            };
+            result.map_err(|err| err.into_exception(vm))
         }
 
         #[pymethod]
@@ -1242,6 +1455,10 @@ mod _sqlite3 {
 
         #[pymethod]
         fn backup(zelf: &Py<Self>, args: BackupArgs, vm: &VirtualMachine) -> PyResult<()> {
+            with_deferred_drops(|| Self::backup_inner(zelf, args, vm))
+        }
+
+        fn backup_inner(zelf: &Py<Self>, args: BackupArgs, vm: &VirtualMachine) -> PyResult<()> {
             let BackupArgs {
                 target,
                 pages,
@@ -1253,6 +1470,12 @@ mod _sqlite3 {
                 return Err(vm.new_value_error("target cannot be the same connection instance"));
             }
 
+            if let Some(progress) = &progress
+                && !progress.is_callable()
+            {
+                return Err(vm.new_type_error("progress argument must be a callable"));
+            }
+
             let pages = if pages == 0 { -1 } else { pages };
 
             let name_cstring;
@@ -1268,15 +1491,20 @@ mod _sqlite3 {
             let db = zelf.db_lock(vm)?;
             let target_db = target.db_lock(vm)?;
 
-            let handle =
-                unsafe { sqlite3_backup_init(target_db.db, c"main".as_ptr(), db.db, name_ptr) };
-
-            if handle.is_null() {
-                return Err(target_db.error_extended(vm));
+            let handle = {
+                // Match SQLite's source-before-destination lock order, and retain
+                // the destination error before another operation can replace it.
+                let _source_guard = db.lock();
+                let _target_guard = target_db.lock();
+                let handle =
+                    unsafe { sqlite3_backup_init(target_db.db, c"main".as_ptr(), db.db, name_ptr) };
+                if handle.is_null() {
+                    Err(target_db.error_snapshot())
+                } else {
+                    Ok(handle)
+                }
             }
-
-            drop(db);
-            drop(target_db);
+            .map_err(|err| err.into_exception(vm))?;
 
             loop {
                 let ret = unsafe { sqlite3_backup_step(handle, pages) };
@@ -1284,7 +1512,7 @@ mod _sqlite3 {
                 if let Some(progress) = &progress {
                     let remaining = unsafe { sqlite3_backup_remaining(handle) };
                     let pagecount = unsafe { sqlite3_backup_pagecount(handle) };
-                    if let Err(err) = progress.invoke((ret, remaining, pagecount), vm) {
+                    if let Err(err) = progress.call((ret, remaining, pagecount), vm) {
                         unsafe { sqlite3_backup_finish(handle) };
                         return Err(err);
                     }
@@ -1297,12 +1525,11 @@ mod _sqlite3 {
                 }
             }
 
-            let ret = unsafe { sqlite3_backup_finish(handle) };
-            if ret == SQLITE_OK {
-                Ok(())
-            } else {
-                Err(target.db_lock(vm)?.error_extended(vm))
-            }
+            let result = {
+                let _source_guard = db.lock();
+                target_db.call(|| unsafe { sqlite3_backup_finish(handle) })
+            };
+            target_db.check(result, vm)
         }
 
         #[pymethod]
@@ -1310,6 +1537,14 @@ mod _sqlite3 {
             zelf: &Py<Self>,
             args: CreateFunctionArgs,
             vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            with_deferred_drops(|| Self::create_function_inner(zelf, args, vm))
+        }
+
+        fn create_function_inner(
+            zelf: &Py<Self>,
+            args: CreateFunctionArgs,
+            vm: &VirtualMachine,
         ) -> PyResult<()> {
             let name = args.name.to_cstring(vm)?;
             let flags = if args.deterministic {
@@ -1351,6 +1586,14 @@ mod _sqlite3 {
             zelf: &Py<Self>,
             args: CreateAggregateArgs,
             vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            with_deferred_drops(|| Self::create_aggregate_inner(zelf, args, vm))
+        }
+
+        fn create_aggregate_inner(
+            zelf: &Py<Self>,
+            args: CreateAggregateArgs,
+            vm: &VirtualMachine,
         ) -> PyResult<()> {
             let name = args.name.to_cstring(vm)?;
             let db = zelf.db_lock(vm)?;
@@ -1388,6 +1631,15 @@ mod _sqlite3 {
             name: PyUtf8StrRef,
             callable: PyObjectRef,
             vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            with_deferred_drops(|| Self::create_collation_inner(zelf, name, callable, vm))
+        }
+
+        fn create_collation_inner(
+            zelf: &Py<Self>,
+            name: PyUtf8StrRef,
+            callable: PyObjectRef,
+            vm: &VirtualMachine,
         ) -> PyResult<()> {
             let name = name.to_cstring(vm)?;
             let db = zelf.db_lock(vm)?;
@@ -1410,7 +1662,7 @@ mod _sqlite3 {
                 return Err(vm.new_type_error("parameter must be callable"));
             }
 
-            let ret = unsafe {
+            let ret = db.call(|| unsafe {
                 sqlite3_create_collation_v2(
                     db.db,
                     name.as_ptr(),
@@ -1419,7 +1671,7 @@ mod _sqlite3 {
                     Some(CallbackData::collation_callback),
                     Some(CallbackData::destructor),
                 )
-            };
+            });
 
             db.check(ret, vm).inspect_err(|_| {
                 // create_collation do not call destructor if error occur
@@ -1434,6 +1686,18 @@ mod _sqlite3 {
             narg: c_int,
             aggregate_class: PyObjectRef,
             vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            with_deferred_drops(|| {
+                Self::create_window_function_inner(zelf, name, narg, aggregate_class, vm)
+            })
+        }
+
+        fn create_window_function_inner(
+            zelf: &Py<Self>,
+            name: PyStrRef,
+            narg: c_int,
+            aggregate_class: PyObjectRef,
+            vm: &VirtualMachine,
         ) -> PyResult<()> {
             let name = name.to_cstring(vm)?;
             let db = zelf.db_lock(vm)?;
@@ -1456,7 +1720,7 @@ mod _sqlite3 {
                 return Ok(());
             };
 
-            let ret = unsafe {
+            let ret = db.call(|| unsafe {
                 sqlite3_create_window_function(
                     db.db,
                     name.as_ptr(),
@@ -1469,7 +1733,7 @@ mod _sqlite3 {
                     Some(CallbackData::inverse_callback),
                     Some(CallbackData::destructor),
                 )
-            };
+            });
             db.check(ret, vm)
                 .map_err(|_| new_programming_error(vm, "Error creating window function".to_owned()))
         }
@@ -1480,22 +1744,7 @@ mod _sqlite3 {
             callable: PyObjectRef,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            let db = zelf.db_lock(vm)?;
-            let Some(data) = CallbackData::new(callable, vm) else {
-                unsafe { sqlite3_set_authorizer(db.db, None, null_mut()) };
-                return Ok(());
-            };
-
-            let ret = unsafe {
-                sqlite3_set_authorizer(
-                    db.db,
-                    Some(CallbackData::authorizer_callback),
-                    Box::into_raw(Box::new(data)).cast(),
-                )
-            };
-            db.check(ret, vm).map_err(|_| {
-                new_operational_error(vm, "Error setting authorizer callback".to_owned())
-            })
+            zelf.set_callback(callable, CallbackKind::Authorizer, vm)
         }
 
         #[pymethod]
@@ -1504,22 +1753,7 @@ mod _sqlite3 {
             callable: PyObjectRef,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            let db = zelf.db_lock(vm)?;
-            let Some(data) = CallbackData::new(callable, vm) else {
-                unsafe { sqlite3_trace_v2(db.db, SQLITE_TRACE_STMT, None, null_mut()) };
-                return Ok(());
-            };
-
-            let ret = unsafe {
-                sqlite3_trace_v2(
-                    db.db,
-                    SQLITE_TRACE_STMT,
-                    Some(CallbackData::trace_callback),
-                    Box::into_raw(Box::new(data)).cast(),
-                )
-            };
-
-            db.check(ret, vm)
+            zelf.set_callback(callable, CallbackKind::Trace, vm)
         }
 
         #[pymethod]
@@ -1529,22 +1763,53 @@ mod _sqlite3 {
             n: c_int,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            let db = zelf.db_lock(vm)?;
-            let Some(data) = CallbackData::new(callable, vm) else {
-                unsafe { sqlite3_progress_handler(db.db, n, None, null_mut()) };
-                return Ok(());
-            };
-
-            unsafe {
-                sqlite3_progress_handler(
-                    db.db,
-                    n,
-                    Some(CallbackData::progress_callback),
-                    Box::into_raw(Box::new(data)).cast(),
-                )
-            };
+            zelf.set_callback(callable, CallbackKind::Progress(n), vm)
+        }
 
-            Ok(())
+        fn set_callback(
+            &self,
+            callable: PyObjectRef,
+            kind: CallbackKind,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            with_deferred_drops(|| {
+                let db = self.db_lock(vm)?;
+                let mut data = CallbackData::new(callable, vm).map(PyRc::new);
+                let pointer = data
+                    .as_ref()
+                    .map_or(null_mut(), |data| PyRc::as_ptr(data).cast_mut());
+                let (closed, result, previous) = {
+                    let _guard = db.lock();
+                    let mut callbacks = db.callbacks.lock();
+                    if callbacks.closed {
+                        (true, Ok(SQLITE_OK), None)
+                    } else {
+                        let result = db.call(|| kind.register(db.raw, pointer));
+                        let previous = if result.is_ok() {
+                            core::mem::replace(kind.slot(&mut callbacks), data.take())
+                        } else {
+                            None
+                        };
+                        (false, result, previous)
+                    }
+                };
+                // Both the native mutex and the slots mutex must be released
+                // before a displaced callable can run __del__ or weakref callbacks.
+                drop((previous, data));
+                if closed {
+                    return Err(new_programming_error(
+                        vm,
+                        "Cannot operate on a closed database.".to_owned(),
+                    ));
+                }
+                db.check(result, vm).map_err(|error| {
+                    if matches!(kind, CallbackKind::Authorizer) {
+                        new_operational_error(vm, "Error setting authorizer callback".to_owned())
+                    } else {
+                        error
+                    }
+                })
+            })
         }
 
         #[pymethod]
@@ -1593,7 +1858,7 @@ mod _sqlite3 {
             }
             let enable = enable.unwrap_or(true) as c_int;
             let mut actual: c_int = 0;
-            let rc = unsafe { sqlite3_db_config(db.db, op, enable, &mut actual) };
+            let rc = db.call(|| unsafe { sqlite3_db_config(db.db, op, enable, &mut actual) });
             db.check(rc, vm)?;
             if enable != actual {
                 return Err(new_operational_error(vm, "Unable to set config".to_owned()));
@@ -1608,7 +1873,7 @@ mod _sqlite3 {
                 return Err(vm.new_value_error(format!("unknown config 'op': {op}")));
             }
             let mut current: c_int = 0;
-            let rc = unsafe { sqlite3_db_config(db.db, op, -1, &mut current) };
+            let rc = db.call(|| unsafe { sqlite3_db_config(db.db, op, -1, &mut current) });
             db.check(rc, vm)?;
             Ok(current != 0)
         }
@@ -1673,29 +1938,43 @@ mod _sqlite3 {
         }
         #[pygetset(setter)]
         fn set_autocommit(zelf: &Py<Self>, val: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
+            with_deferred_drops(|| Self::set_autocommit_inner(zelf, val, vm))
+        }
+
+        fn set_autocommit_inner(
+            zelf: &Py<Self>,
+            val: PyObjectRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
             let mode = AutocommitMode::try_from_borrowed_object(vm, &val)?;
             let db = zelf.db_lock(vm)?;
-            *zelf.autocommit.lock() = mode;
-
-            // Handle transaction state based on mode change
-            match mode {
-                AutocommitMode::Enabled => {
-                    // If there's a pending transaction, commit it
-                    if !db.is_autocommit() {
-                        db._exec(c"COMMIT", vm)?;
+            let result = {
+                // Publish the Python mode and change SQLite's transaction state
+                // under the same mutex used by statement execution.
+                let _guard = db.lock();
+                *zelf.autocommit.lock() = mode;
+
+                // Handle transaction state based on mode change
+                match mode {
+                    AutocommitMode::Enabled => {
+                        // If there's a pending transaction, commit it
+                        db.end_transaction(c"COMMIT", AutocommitMode::Legacy)
                     }
-                }
-                AutocommitMode::Disabled => {
-                    // If not in a transaction, begin one
-                    if db.is_autocommit() {
-                        db._exec(c"BEGIN", vm)?;
+                    AutocommitMode::Disabled => {
+                        // If not in a transaction, begin one
+                        if db.is_autocommit() {
+                            db.exec(c"BEGIN")
+                        } else {
+                            Ok(())
+                        }
+                    }
+                    AutocommitMode::Legacy => {
+                        // Legacy mode doesn't change transaction state
+                        Ok(())
                     }
                 }
-                AutocommitMode::Legacy => {
-                    // Legacy mode doesn't change transaction state
-                }
-            }
-            Ok(())
+            };
+            result.map_err(|err| err.into_exception(vm))
         }
 
         #[pygetset]
@@ -1756,12 +2035,16 @@ mod _sqlite3 {
 
         #[pygetset]
         fn in_transaction(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<bool> {
-            zelf._db_lock(vm).map(|x| !x.is_autocommit())
+            let db = zelf._db_lock(vm)?;
+            let _guard = db.lock();
+            Ok(!db.is_autocommit())
         }
 
         #[pygetset]
         fn total_changes(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<c_int> {
-            zelf._db_lock(vm).map(|x| x.total_changes())
+            let db = zelf._db_lock(vm)?;
+            let _guard = db.lock();
+            Ok(db.total_changes())
         }
 
         #[pygetset(name = "Warning")]
@@ -1826,7 +2109,7 @@ mod _sqlite3 {
         lastrowid: i64,
         #[pytraverse(skip)]
         rowcount: i64,
-        statement: Option<PyRef<Statement>>,
+        statement: Option<StatementLease>,
         #[pytraverse(skip)]
         closed: bool,
     }
@@ -1906,6 +2189,15 @@ mod _sqlite3 {
             sql: PyUtf8StrRef,
             parameters: OptionalArg<PyObjectRef>,
             vm: &VirtualMachine,
+        ) -> PyResult<PyRef<Self>> {
+            with_deferred_drops(|| Self::execute_inner(zelf, sql, parameters, vm))
+        }
+
+        fn execute_inner(
+            zelf: PyRef<Self>,
+            sql: PyUtf8StrRef,
+            parameters: OptionalArg<PyObjectRef>,
+            vm: &VirtualMachine,
         ) -> PyResult<PyRef<Self>> {
             let mut inner = zelf.inner(vm)?;
 
@@ -1913,29 +2205,18 @@ mod _sqlite3 {
                 stmt.lock().reset();
             }
 
-            let Some(stmt) = Statement::new(&zelf.connection, sql, vm)? else {
+            let Some(stmt) = zelf.connection.cached_statement(sql, vm)? else {
                 drop(inner);
                 return Ok(zelf);
             };
-            let stmt = stmt.into_ref(&vm.ctx);
 
             inner.rowcount = if stmt.is_dml { 0 } else { -1 };
 
-            let db = zelf.connection.db_lock(vm)?;
+            let db = stmt.database(&zelf.connection, vm)?;
 
             // Only legacy transaction control starts implicit DML transactions.
-            if stmt.is_dml
-                && db.is_autocommit()
-                && zelf.connection.isolation_level.deref().is_some()
-                && *zelf.connection.autocommit.lock() == AutocommitMode::Legacy
-            {
-                db.begin_transaction(
-                    zelf.connection
-                        .isolation_level
-                        .deref()
-                        .map(|x| x.to_owned()),
-                    vm,
-                )?;
+            if stmt.is_dml {
+                zelf.connection.begin_transaction(db.raw, vm)?;
             }
 
             let st = stmt.lock();
@@ -1950,35 +2231,33 @@ mod _sqlite3 {
                 return Err(new_programming_error(vm, msg));
             }
 
+            zelf.connection.check_open(vm)?;
             let ret = st.step();
-
-            if ret != SQLITE_DONE && ret != SQLITE_ROW {
-                if let Some(exc) = unsafe { user_function_exception().swap(None) } {
-                    return Err(exc);
-                }
-                return Err(db.error_extended(vm));
-            }
+            zelf.connection.check_open(vm)?;
+            let ret = ret.map_err(|error| {
+                unsafe { user_function_exception().swap(None) }
+                    .unwrap_or_else(|| error.into_exception(vm))
+            })?;
 
             inner.row_cast_map = zelf.build_row_cast_map(&st, vm)?;
 
             let detect_types = zelf.connection.detect_types.load(Ordering::Relaxed);
             inner.description = st.columns_description(detect_types, vm)?;
 
-            if ret == SQLITE_ROW {
+            if ret.has_row {
                 drop(st);
                 inner.statement = Some(stmt);
             } else {
                 st.reset();
                 drop(st);
                 if stmt.is_dml {
-                    inner.rowcount += db.changes() as i64;
+                    inner.rowcount += ret.changes as i64;
                 }
             }
 
-            inner.lastrowid = db.lastrowid();
+            inner.lastrowid = ret.lastrowid;
 
             drop(inner);
-            drop(db);
             Ok(zelf)
         }
 
@@ -1988,6 +2267,15 @@ mod _sqlite3 {
             sql: PyUtf8StrRef,
             seq_of_params: ArgIterable,
             vm: &VirtualMachine,
+        ) -> PyResult<PyRef<Self>> {
+            with_deferred_drops(|| Self::executemany_inner(zelf, sql, seq_of_params, vm))
+        }
+
+        fn executemany_inner(
+            zelf: PyRef<Self>,
+            sql: PyUtf8StrRef,
+            seq_of_params: ArgIterable,
+            vm: &VirtualMachine,
         ) -> PyResult<PyRef<Self>> {
             let mut inner = zelf.inner(vm)?;
 
@@ -1995,12 +2283,12 @@ mod _sqlite3 {
                 stmt.lock().reset();
             }
 
-            let Some(stmt) = Statement::new(&zelf.connection, sql, vm)? else {
+            let Some(stmt) = zelf.connection.cached_statement(sql, vm)? else {
                 drop(inner);
                 return Ok(zelf);
             };
-            let stmt = stmt.into_ref(&vm.ctx);
 
+            let db = stmt.database(&zelf.connection, vm)?;
             let st = stmt.lock();
 
             if st.readonly() {
@@ -2015,31 +2303,24 @@ mod _sqlite3 {
 
             inner.rowcount = if stmt.is_dml { 0 } else { -1 };
 
-            let db = zelf.connection.db_lock(vm)?;
-
             // Only legacy transaction control starts implicit DML transactions.
-            if stmt.is_dml
-                && db.is_autocommit()
-                && zelf.connection.isolation_level.deref().is_some()
-                && *zelf.connection.autocommit.lock() == AutocommitMode::Legacy
-            {
-                db.begin_transaction(
-                    zelf.connection
-                        .isolation_level
-                        .deref()
-                        .map(|x| x.to_owned()),
-                    vm,
-                )?;
+            if stmt.is_dml {
+                zelf.connection.begin_transaction(db.raw, vm)?;
             }
 
             let iter = seq_of_params.iter(vm)?;
             for params in iter {
                 let params = params?;
+                zelf.connection.check_open(vm)?;
                 st.bind_parameters(&params, vm)?;
+                zelf.connection.check_open(vm)?;
 
-                if !st.step_row_else_done(vm)? {
+                let ret = st.step_checked(vm);
+                zelf.connection.check_open(vm)?;
+                let ret = ret?;
+                if !ret.has_row {
                     if stmt.is_dml {
-                        inner.rowcount += db.changes() as i64;
+                        inner.rowcount += ret.changes as i64;
                     }
                     st.reset();
                 }
@@ -2049,13 +2330,13 @@ mod _sqlite3 {
                 // }
             }
 
+            zelf.connection.check_open(vm)?;
             if st.busy() {
                 drop(st);
                 inner.statement = Some(stmt);
             }
 
             drop(inner);
-            drop(db);
             Ok(zelf)
         }
 
@@ -2064,6 +2345,14 @@ mod _sqlite3 {
             zelf: PyRef<Self>,
             script: PyUtf8StrRef,
             vm: &VirtualMachine,
+        ) -> PyResult<PyRef<Self>> {
+            with_deferred_drops(|| Self::executescript_inner(zelf, script, vm))
+        }
+
+        fn executescript_inner(
+            zelf: PyRef<Self>,
+            script: PyUtf8StrRef,
+            vm: &VirtualMachine,
         ) -> PyResult<PyRef<Self>> {
             zelf.check_cursor_valid(vm)?;
 
@@ -2071,16 +2360,27 @@ mod _sqlite3 {
 
             db.sql_limit(script.byte_len(), vm)?;
 
-            if *zelf.connection.autocommit.lock() == AutocommitMode::Legacy {
-                db.implicit_commit(vm)?;
-            }
+            let result = zelf.connection.commit_before_script(db.raw, vm);
+            zelf.connection.check_open(vm)?;
+            result?;
 
             let script = script.to_cstring(vm)?;
             let mut sql = script.as_c_str();
             let mut tail = null();
 
-            while let Some(st) = db.prepare(sql, &mut tail, vm)? {
-                while st.step_row_else_done(vm)? {}
+            loop {
+                let statement = db.prepare(sql, &mut tail, vm);
+                zelf.connection.check_open(vm)?;
+                let Some(st) = statement? else {
+                    break;
+                };
+                loop {
+                    let result = st.step_checked(vm);
+                    zelf.connection.check_open(vm)?;
+                    if !result?.has_row {
+                        break;
+                    }
+                }
                 // SAFETY: SQLite advances the pointer w.r.t. `sql`, and `sql` is a valid CStr
                 // without any interior NULs.
                 sql = unsafe { CStr::from_ptr(tail) };
@@ -2140,6 +2440,10 @@ mod _sqlite3 {
 
         #[pymethod]
         fn close(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
+            with_deferred_drops(|| Self::close_inner(zelf, vm))
+        }
+
+        fn close_inner(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
             // Check if __init__ was called
             let mut guard = zelf.inner.lock();
 
@@ -2150,9 +2454,7 @@ mod _sqlite3 {
                 ));
             };
 
-            if let Some(stmt) = &inner.statement {
-                stmt.lock().reset();
-            }
+            drop(inner.statement.take());
             inner.closed = true;
 
             Ok(())
@@ -2293,6 +2595,12 @@ mod _sqlite3 {
     impl SelfIter for Cursor {}
     impl IterNext for Cursor {
         fn next(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {
+            with_deferred_drops(|| Self::next_inner(zelf, vm))
+        }
+    }
+
+    impl Cursor {
+        fn next_inner(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {
             // Check if connection is closed first, and if so, clear statement to release file lock
             if zelf.connection.is_closed() {
                 let mut guard = zelf.inner.lock();
@@ -2309,8 +2617,8 @@ mod _sqlite3 {
             let Some(stmt) = &inner.statement else {
                 return Ok(PyIterReturn::StopIteration(None));
             };
+            let db = stmt.database(&zelf.connection, vm)?;
             let st = stmt.lock();
-            let db = zelf.connection.db_lock(vm)?;
             // fetch_one_row
 
             let num_cols = st.data_count();
@@ -2330,7 +2638,9 @@ mod _sqlite3 {
                             core::slice::from_raw_parts(blob.cast::<u8>(), nbytes as usize)
                         };
                         let blob = vm.ctx.new_bytes(blob.to_vec());
-                        converter.call((blob,), vm)?
+                        let value = converter.call((blob,), vm)?;
+                        zelf.connection.check_open(vm)?;
+                        value
                     }
                 } else {
                     let col_type = st.column_type(i);
@@ -2362,7 +2672,9 @@ mod _sqlite3 {
                                 PyByteArray::from(text).into_ref(&vm.ctx).into()
                             } else {
                                 let bytes = vm.ctx.new_bytes(text);
-                                text_factory.call((bytes,), vm)?
+                                let value = text_factory.call((bytes,), vm)?;
+                                zelf.connection.check_open(vm)?;
+                                value
                             }
                         }
                         SQLITE_BLOB => {
@@ -2386,11 +2698,14 @@ mod _sqlite3 {
                 row.push(val);
             }
 
-            if !st.step_row_else_done(vm)? {
+            let ret = st.step_checked(vm);
+            zelf.connection.check_open(vm)?;
+            let ret = ret?;
+            if !ret.has_row {
                 st.reset();
                 drop(st);
                 if stmt.is_dml {
-                    inner.rowcount = db.changes() as i64;
+                    inner.rowcount = ret.changes as i64;
                 }
                 inner.statement = None;
             } else {
@@ -2562,15 +2877,144 @@ mod _sqlite3 {
         inner: PyMutex<Option<BlobInner>>,
     }
 
-    #[derive(Debug)]
     struct BlobInner {
         blob: SqliteBlob,
         offset: c_int,
+        db: PyRc<Sqlite>,
+    }
+
+    impl Debug for BlobInner {
+        fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+            f.debug_struct("BlobInner")
+                .field("blob", &self.blob)
+                .field("offset", &self.offset)
+                .finish_non_exhaustive()
+        }
+    }
+
+    impl BlobInner {
+        fn check(&self, ret: c_int, vm: &VirtualMachine) -> PyResult<()> {
+            if ret == SQLITE_OK {
+                Ok(())
+            } else {
+                Err(self.db.error_extended(vm))
+            }
+        }
     }
 
     impl Drop for BlobInner {
         fn drop(&mut self) {
-            unsafe { sqlite3_blob_close(self.blob.blob) };
+            self.db.pending.lock().blobs.push(self.blob);
+            self.db.flush_cleanup();
+        }
+    }
+
+    struct BlobGuard<'a> {
+        inner: Option<PyMappedMutexGuard<'a, BlobInner>>,
+        _db: SqliteOperation,
+    }
+
+    impl<'a> BlobGuard<'a> {
+        fn new(inner: PyMappedMutexGuard<'a, BlobInner>) -> Self {
+            let db = SqliteOperation(inner.db.clone());
+            Self {
+                inner: Some(inner),
+                _db: db,
+            }
+        }
+    }
+
+    impl Deref for BlobGuard<'_> {
+        type Target = BlobInner;
+
+        fn deref(&self) -> &Self::Target {
+            self.inner.as_deref().unwrap()
+        }
+    }
+
+    impl DerefMut for BlobGuard<'_> {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            self.inner.as_deref_mut().unwrap()
+        }
+    }
+
+    impl Drop for BlobGuard<'_> {
+        fn drop(&mut self) {
+            // The operation drains pending cleanup after releasing the blob lock.
+            self.inner.take();
+        }
+    }
+
+    #[cfg(test)]
+    #[cfg(feature = "threading")]
+    mod tests {
+        use super::*;
+        use core::time::Duration;
+        use std::sync::mpsc;
+
+        #[test]
+        fn blob_operation_drains_contended_cleanup() {
+            let mut raw = null_mut();
+            assert_eq!(
+                unsafe {
+                    sqlite3_open_v2(
+                        c":memory:".as_ptr(),
+                        &mut raw,
+                        SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FULLMUTEX,
+                        null(),
+                    )
+                },
+                SQLITE_OK
+            );
+            let db = PyRc::new(Sqlite::from(SqliteRaw { db: raw }));
+            assert!(
+                db.exec(c"CREATE TABLE t(b); INSERT INTO t VALUES (zeroblob(1))")
+                    .is_ok()
+            );
+            let open_blob = || {
+                let mut blob = null_mut();
+                assert_eq!(
+                    unsafe {
+                        sqlite3_blob_open(
+                            db.db,
+                            c"main".as_ptr(),
+                            c"t".as_ptr(),
+                            c"b".as_ptr(),
+                            1,
+                            0,
+                            &mut blob,
+                        )
+                    },
+                    SQLITE_OK
+                );
+                BlobInner {
+                    blob: SqliteBlob { blob },
+                    offset: 0,
+                    db: db.clone(),
+                }
+            };
+            let inner = PyMutex::new(Some(open_blob()));
+            let retired = open_blob();
+            let guard = BlobGuard::new(PyMutexGuard::map(inner.lock(), |x| x.as_mut().unwrap()));
+            let (locked_tx, locked_rx) = mpsc::channel();
+            let (release_tx, release_rx) = mpsc::channel();
+            let other = db.clone();
+            let worker = std::thread::spawn(move || {
+                let _lock = other.raw.lock();
+                locked_tx.send(()).unwrap();
+                release_rx.recv_timeout(Duration::from_secs(5)).unwrap();
+            });
+            locked_rx.recv_timeout(Duration::from_secs(5)).unwrap();
+            // Reproduce close() losing both nonblocking cleanup attempts.
+            db.pending.lock().clear_callbacks = true;
+            db.flush_cleanup();
+            drop(retired);
+            assert_eq!(db.pending.lock().blobs.len(), 1);
+            release_tx.send(()).unwrap();
+            worker.join().unwrap();
+            assert!(db.pending.lock().clear_callbacks);
+            drop(guard);
+            assert!(db.pending.lock().is_empty());
         }
     }
 
@@ -2578,7 +3022,10 @@ mod _sqlite3 {
     impl Blob {
         #[pymethod]
         fn close(zelf: &Py<Self>) {
-            zelf.inner.lock().take();
+            with_deferred_drops(|| {
+                let inner = zelf.inner.lock().take();
+                drop(inner);
+            });
         }
 
         fn ensure_connection_open(&self, vm: &VirtualMachine) -> PyResult<()> {
@@ -2616,7 +3063,7 @@ mod _sqlite3 {
                 let ret = inner
                     .blob
                     .read(buf.as_mut_ptr().cast(), length, inner.offset);
-                zelf.check(ret, vm)?;
+                inner.check(ret, vm)?;
                 unsafe { buf.set_len(length as usize) };
                 inner.offset += length;
                 Ok(vm.ctx.new_bytes(buf))
@@ -2634,7 +3081,7 @@ mod _sqlite3 {
                 inner.blob.write(buf.as_ptr().cast(), length, inner.offset)
             });
 
-            zelf.check(ret, vm)?;
+            inner.check(ret, vm)?;
             inner.offset += length;
             Ok(())
         }
@@ -2695,12 +3142,12 @@ mod _sqlite3 {
             Ok(())
         }
 
-        fn inner(&self, vm: &VirtualMachine) -> PyResult<PyMappedMutexGuard<'_, BlobInner>> {
+        fn inner(&self, vm: &VirtualMachine) -> PyResult<BlobGuard<'_>> {
             let guard = self.inner.lock();
             if guard.is_some() {
-                Ok(PyMutexGuard::map(guard, |x| unsafe {
-                    x.as_mut().unwrap_unchecked()
-                }))
+                Ok(BlobGuard::new(PyMutexGuard::map(guard, |x| {
+                    x.as_mut().unwrap()
+                })))
             } else {
                 Err(new_programming_error(
                     vm,
@@ -2709,15 +3156,31 @@ mod _sqlite3 {
             }
         }
 
-        fn wrapped_index(index: PyIntRef, length: c_int, vm: &VirtualMachine) -> PyResult<c_int> {
-            let mut index = index.try_to_primitive::<c_int>(vm)?;
+        fn wrapped_index(
+            index: PyIntRef,
+            object: &PyObject,
+            length: c_int,
+            vm: &VirtualMachine,
+        ) -> PyResult<c_int> {
+            let mut index = index.try_to_primitive::<isize>(vm).map_err(|_| {
+                let class = object.class();
+                let type_name = class.slot_name();
+                let mut end = type_name.len().min(200);
+                while !type_name.is_char_boundary(end) {
+                    end -= 1;
+                }
+                vm.new_index_error(format!(
+                    "cannot fit '{}' into an index-sized integer",
+                    &type_name[..end]
+                ))
+            })?;
             if index < 0 {
-                index += length;
+                index += length as isize;
             }
-            if index < 0 || index >= length {
+            if index < 0 || index >= length as isize {
                 Err(vm.new_index_error("Blob index out of range"))
             } else {
-                Ok(index)
+                Ok(index as c_int)
             }
         }
 
@@ -2736,14 +3199,18 @@ mod _sqlite3 {
         }
 
         fn subscript(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
+            with_deferred_drops(|| Self::subscript_inner(self, needle, vm))
+        }
+
+        fn subscript_inner(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
             self.ensure_connection_open(vm)?;
             let inner = self.inner(vm)?;
             if let Some(index) = needle.try_index_opt(vm) {
                 let blob_len = inner.blob.bytes();
-                let index = Self::wrapped_index(index?, blob_len, vm)?;
+                let index = Self::wrapped_index(index?, needle, blob_len, vm)?;
                 let mut byte: u8 = 0;
                 let ret = inner.blob.read_single(&mut byte, index);
-                self.check(ret, vm).map(|_| vm.ctx.new_int(byte).into())
+                inner.check(ret, vm).map(|_| vm.ctx.new_int(byte).into())
             } else if let Some(slice) = needle.downcast_ref::<PySlice>() {
                 let blob_len = inner.blob.bytes();
                 let slice = slice.to_saturated(vm)?;
@@ -2756,14 +3223,14 @@ mod _sqlite3 {
                         length as c_int,
                         range.start as c_int,
                     );
-                    self.check(ret, vm)?;
+                    inner.check(ret, vm)?;
                     unsafe { buf.set_len(length) };
                 } else {
                     let iter = SaturatedSliceIter::from_adjust_indices(range, step, length);
                     let mut byte: u8 = 0;
                     for index in iter {
                         let ret = inner.blob.read_single(&mut byte, index as c_int);
-                        self.check(ret, vm)?;
+                        inner.check(ret, vm)?;
                         buf.push(byte);
                     }
                 }
@@ -2778,6 +3245,15 @@ mod _sqlite3 {
             needle: &PyObject,
             value: Option<PyObjectRef>,
             vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            with_deferred_drops(|| Self::ass_subscript_inner(self, needle, value, vm))
+        }
+
+        fn ass_subscript_inner(
+            &self,
+            needle: &PyObject,
+            value: Option<PyObjectRef>,
+            vm: &VirtualMachine,
         ) -> PyResult<()> {
             self.ensure_connection_open(vm)?;
             let inner = self.inner(vm)?;
@@ -2794,7 +3270,7 @@ mod _sqlite3 {
                     )));
                 };
                 let blob_len = inner.blob.bytes();
-                let index = Self::wrapped_index(index?, blob_len, vm)?;
+                let index = Self::wrapped_index(index?, needle, blob_len, vm)?;
                 // Mirror CPython ass_subscript_index: use PyLong_AsLong, treat any
                 // overflow (e.g. 2**65) as -1, then validate the [0, 255] range.
                 let val = int_val.as_bigint().to_i64().unwrap_or(-1);
@@ -2802,7 +3278,7 @@ mod _sqlite3 {
                     return Err(vm.new_value_error("byte must be in range(0, 256)"));
                 }
                 let ret = inner.blob.write_single(val as u8, index);
-                self.check(ret, vm)
+                inner.check(ret, vm)
             } else if let Some(slice) = needle.downcast_ref::<PySlice>() {
                 // Handle slice assignment: blob[a:b:c] = b"..."
                 let Some(value) = value else {
@@ -2836,7 +3312,7 @@ mod _sqlite3 {
                         buf.len() as c_int,
                         range.start as c_int,
                     );
-                    self.check(ret, vm)
+                    inner.check(ret, vm)
                 } else {
                     let span_len = range.end - range.start;
                     let range_start = range.start;
@@ -2847,7 +3323,7 @@ mod _sqlite3 {
                         span_len as c_int,
                         range_start as c_int,
                     );
-                    self.check(ret, vm)?;
+                    inner.check(ret, vm)?;
 
                     let iter = SaturatedSliceIter::from_adjust_indices(range, step, slice_len);
                     for (i_in_src, abs_idx) in iter.enumerate() {
@@ -2859,20 +3335,12 @@ mod _sqlite3 {
                         span_len as c_int,
                         range_start as c_int,
                     );
-                    self.check(ret, vm)
+                    inner.check(ret, vm)
                 }
             } else {
                 Err(vm.new_type_error("Blob indices must be integers"))
             }
         }
-
-        fn check(&self, ret: c_int, vm: &VirtualMachine) -> PyResult<()> {
-            if ret == SQLITE_OK {
-                Ok(())
-            } else {
-                Err(self.connection.db_lock(vm)?.error_extended(vm))
-            }
-        }
     }
 
     impl AsMapping for Blob {
@@ -2950,6 +3418,7 @@ mod _sqlite3 {
     struct Statement {
         st: PyMutex<SqliteStatement>,
         pub is_dml: bool,
+        in_use: PyAtomic<bool>,
     }
 
     impl Debug for Statement {
@@ -2973,16 +3442,13 @@ mod _sqlite3 {
                 new_programming_error(vm, "statement contains a null character.".to_owned())
             })?;
 
-            let raw = {
-                let db = connection.db_lock(vm)?;
-                db.sql_limit(sql.byte_len(), vm)?;
-                **db
-            };
-
+            let db = connection.db_lock(vm)?;
+            db.sql_limit(sql.byte_len(), vm)?;
             let mut tail = null();
-            let st = raw.prepare(&sql_cstr, &mut tail, vm)?;
+            let st = db.prepare(&sql_cstr, &mut tail, vm);
+            connection.check_open(vm)?;
 
-            let Some(st) = st else {
+            let Some(st) = st? else {
                 return Ok(None);
             };
 
@@ -3008,6 +3474,7 @@ mod _sqlite3 {
             Ok(Some(Self {
                 st: PyMutex::from(st),
                 is_dml,
+                in_use: Radium::new(false),
             }))
         }
 
@@ -3016,13 +3483,310 @@ mod _sqlite3 {
         }
     }
 
+    struct StatementCache {
+        capacity: usize,
+        generation: u64,
+        entries: indexmap::IndexMap<Box<str>, PyRef<Statement>>,
+    }
+
+    impl StatementCache {
+        fn new(capacity: c_int) -> Self {
+            Self {
+                capacity: capacity.max(0) as usize,
+                generation: 0,
+                entries: indexmap::IndexMap::new(),
+            }
+        }
+    }
+
+    #[derive(Debug)]
+    struct StatementLease(PyRef<Statement>);
+
+    impl StatementLease {
+        fn acquire(statement: PyRef<Statement>) -> Option<Self> {
+            statement
+                .in_use
+                .compare_exchange(false, true, Ordering::AcqRel, Ordering::Acquire)
+                .ok()
+                .map(|_| Self(statement))
+        }
+
+        fn database(
+            &self,
+            connection: &Connection,
+            vm: &VirtualMachine,
+        ) -> PyResult<SqliteOperation> {
+            connection.check_open(vm)?;
+            // The statement owns a live connection, not just memory retained by
+            // sqlite3_close_v2. Reinitialization may replace Connection.db while
+            // existing cursors continue reading this original database.
+            Ok(SqliteOperation(self.lock().db.clone()))
+        }
+    }
+
+    impl Deref for StatementLease {
+        type Target = Statement;
+
+        fn deref(&self) -> &Statement {
+            &self.0
+        }
+    }
+
+    // SAFETY: the lease owns exactly one reference to its statement.
+    unsafe impl Traverse for StatementLease {
+        fn traverse(&self, tracer: &mut TraverseFn<'_>) {
+            self.0.traverse(tracer);
+        }
+    }
+
+    impl Drop for StatementLease {
+        fn drop(&mut self) {
+            with_deferred_drops(|| {
+                let statement = self.0.lock();
+                let db = SqliteOperation(statement.db.clone());
+                statement.reset();
+                // Cached statements must not retain previous parameter buffers.
+                unsafe { sqlite3_clear_bindings(statement.st) };
+                drop(statement);
+                self.0.in_use.store(false, Ordering::Release);
+                // Reset can delay cleanup queued by another thread's BLOB close.
+                drop(db);
+            });
+        }
+    }
+
     struct Sqlite {
         raw: SqliteRaw,
+        pending: PyMutex<SqliteCleanup>,
+        callbacks: PyMutex<CallbackSlots>,
+    }
+
+    #[derive(Default)]
+    struct CallbackSlots {
+        trace: Option<PyRc<CallbackData>>,
+        progress: Option<PyRc<CallbackData>>,
+        authorizer: Option<PyRc<CallbackData>>,
+        closed: bool,
+    }
+
+    #[derive(Clone, Copy)]
+    enum CallbackKind {
+        Trace,
+        Progress(c_int),
+        Authorizer,
+    }
+
+    impl CallbackKind {
+        fn slot(self, slots: &mut CallbackSlots) -> &mut Option<PyRc<CallbackData>> {
+            match self {
+                Self::Trace => &mut slots.trace,
+                Self::Progress(_) => &mut slots.progress,
+                Self::Authorizer => &mut slots.authorizer,
+            }
+        }
+
+        // The caller holds the native mutex and retains data until unregistration.
+        fn register(self, db: SqliteRaw, data: *mut CallbackData) -> c_int {
+            unsafe {
+                match self {
+                    Self::Trace => sqlite3_trace_v2(
+                        db.db,
+                        SQLITE_TRACE_STMT,
+                        (!data.is_null()).then_some(CallbackData::trace_callback),
+                        data.cast(),
+                    ),
+                    Self::Progress(n) => {
+                        sqlite3_progress_handler(
+                            db.db,
+                            n,
+                            (!data.is_null()).then_some(CallbackData::progress_callback),
+                            data.cast(),
+                        );
+                        SQLITE_OK
+                    }
+                    Self::Authorizer => sqlite3_set_authorizer(
+                        db.db,
+                        (!data.is_null()).then_some(CallbackData::authorizer_callback),
+                        data.cast(),
+                    ),
+                }
+            }
+        }
+    }
+
+    #[derive(Default)]
+    struct SqliteCleanup {
+        statements: Vec<SqliteStatementRaw>,
+        blobs: Vec<SqliteBlob>,
+        rollback: bool,
+        clear_callbacks: bool,
+    }
+
+    impl SqliteCleanup {
+        fn is_empty(&self) -> bool {
+            self.statements.is_empty()
+                && self.blobs.is_empty()
+                && !self.rollback
+                && !self.clear_callbacks
+        }
     }
 
     impl From<SqliteRaw> for Sqlite {
         fn from(raw: SqliteRaw) -> Self {
-            Self { raw }
+            Self {
+                raw,
+                pending: PyMutex::new(SqliteCleanup::default()),
+                callbacks: PyMutex::new(CallbackSlots::default()),
+            }
+        }
+    }
+
+    impl Sqlite {
+        fn flush_cleanup(&self) {
+            self.drain_cleanup(false);
+        }
+
+        fn drain_cleanup(&self, wait: bool) {
+            if self.pending.lock().is_empty() {
+                return;
+            }
+            with_deferred_drops(|| {
+                loop {
+                    let guard = if wait {
+                        Some(self.raw.lock())
+                    } else {
+                        self.raw.try_lock()
+                    };
+                    let Some(guard) = guard else {
+                        return;
+                    };
+                    // Never keep a Rust mutex while SQLite can invoke Python.
+                    let pending = core::mem::take(&mut *self.pending.lock());
+                    if pending.rollback && !self.is_autocommit() {
+                        // close() has already returned; like sqlite3_close_v2,
+                        // deferred rollback cannot report an error to its caller.
+                        unsafe {
+                            sqlite3_exec(
+                                self.db,
+                                c"ROLLBACK".as_ptr(),
+                                None,
+                                null_mut(),
+                                null_mut(),
+                            )
+                        };
+                    }
+                    for statement in pending.statements {
+                        unsafe { sqlite3_finalize(statement.st) };
+                    }
+                    for blob in pending.blobs {
+                        unsafe { sqlite3_blob_close(blob.blob) };
+                    }
+                    let callbacks = pending.clear_callbacks.then(|| self.clear_callbacks());
+                    drop(guard);
+                    drop(callbacks);
+                    // An enqueue after this check can acquire the native mutex and
+                    // drain itself; one made while it was locked must be retried.
+                    if self.pending.lock().is_empty() {
+                        return;
+                    }
+                }
+            });
+        }
+
+        fn close_callbacks(&self, rollback: bool, vm: &VirtualMachine) -> PyResult<()> {
+            self.callbacks.lock().closed = true;
+            if let Some(guard) = self.raw.try_lock() {
+                let result = if rollback && !self.is_autocommit() {
+                    self._exec(c"ROLLBACK", vm)
+                } else {
+                    Ok(())
+                };
+                self.pending.lock().clear_callbacks = true;
+                drop(guard);
+                self.flush_cleanup();
+                result
+            } else {
+                {
+                    let mut pending = self.pending.lock();
+                    pending.rollback |= rollback;
+                    pending.clear_callbacks = true;
+                }
+                // Retry after enqueueing, in case the active call just ended.
+                self.flush_cleanup();
+                Ok(())
+            }
+        }
+
+        // The native mutex is held. SQLite must stop using the pointers first.
+        fn clear_callbacks(&self) -> [Option<PyRc<CallbackData>>; 3] {
+            for kind in [
+                CallbackKind::Trace,
+                CallbackKind::Progress(0),
+                CallbackKind::Authorizer,
+            ] {
+                kind.register(self.raw, null_mut());
+            }
+            let mut slots = self.callbacks.lock();
+            [
+                slots.trace.take(),
+                slots.progress.take(),
+                slots.authorizer.take(),
+            ]
+        }
+    }
+
+    // An operation retains its database and drains work deferred by a close
+    // callback after SQLite has released its native connection mutex.
+    struct SqliteOperation(PyRc<Sqlite>);
+
+    impl Deref for SqliteOperation {
+        type Target = Sqlite;
+
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+
+    impl Drop for SqliteOperation {
+        fn drop(&mut self) {
+            self.flush_cleanup();
+        }
+    }
+
+    impl SqliteOperation {
+        fn prepare(
+            &self,
+            sql: &CStr,
+            tail: &mut *const libc::c_char,
+            vm: &VirtualMachine,
+        ) -> PyResult<Option<SqliteStatement>> {
+            self.raw.prepare(sql, tail, vm).map(|statement| {
+                statement.map(|raw| SqliteStatement {
+                    raw,
+                    db: self.0.clone(),
+                })
+            })
+        }
+    }
+
+    struct SqliteMutex(*mut libsqlite3_sys::sqlite3_mutex);
+
+    impl Drop for SqliteMutex {
+        fn drop(&mut self) {
+            unsafe { sqlite3_mutex_leave(self.0) };
+        }
+    }
+
+    struct SqliteError {
+        code: c_int,
+        extended: c_int,
+        message: String,
+    }
+
+    impl SqliteError {
+        fn into_exception(self, vm: &VirtualMachine) -> PyBaseExceptionRef {
+            let typ = exception_type_from_errcode(self.code, vm);
+            raise_exception(typ.to_owned(), self.extended, self.message, vm)
         }
     }
 
@@ -3035,8 +3799,18 @@ mod _sqlite3 {
 
     impl Drop for Sqlite {
         fn drop(&mut self) {
+            // No operation or statement owner remains. Drain native handles
+            // queued by their destructors before closing the database.
+            self.drain_cleanup(true);
             // Use sqlite3_close_v2 for safe closing even with active statements
-            unsafe { sqlite3_close_v2(self.raw.db) };
+            with_deferred_drops(|| {
+                let callbacks = {
+                    let _guard = self.raw.lock();
+                    self.clear_callbacks()
+                };
+                drop(callbacks);
+                unsafe { sqlite3_close_v2(self.raw.db) };
+            });
         }
     }
 
@@ -3058,7 +3832,9 @@ mod _sqlite3 {
             unsafe impl Send for SqliteStatement {}
             // unsafe impl Sync for SqliteStatement {}
             unsafe impl Send for Sqlite {}
-            // unsafe impl Sync for Sqlite {}
+            // SAFETY: connections use FULLMUTEX and require a native mutex.
+            // Owned references delay closing until active operations finish.
+            unsafe impl Sync for Sqlite {}
             unsafe impl Send for SqliteBlob {}
         }
         _ => {}
@@ -3075,23 +3851,58 @@ mod _sqlite3 {
     }
 
     impl SqliteRaw {
-        fn check(self, ret: c_int, vm: &VirtualMachine) -> PyResult<()> {
-            if ret == SQLITE_OK {
-                Ok(())
+        fn lock(self) -> SqliteMutex {
+            let mutex = unsafe { sqlite3_db_mutex(self.db) };
+            unsafe { sqlite3_mutex_enter(mutex) };
+            SqliteMutex(mutex)
+        }
+
+        fn try_lock(self) -> Option<SqliteMutex> {
+            let mutex = unsafe { sqlite3_db_mutex(self.db) };
+            if unsafe { sqlite3_mutex_try(mutex) } == SQLITE_OK {
+                Some(SqliteMutex(mutex))
             } else {
-                Err(self.error_extended(vm))
+                None
             }
         }
 
-        fn error_extended(self, vm: &VirtualMachine) -> PyBaseExceptionRef {
-            let errcode = unsafe { sqlite3_errcode(self.db) };
-            let typ = exception_type_from_errcode(errcode, vm);
-            let extended_errcode = unsafe { sqlite3_extended_errcode(self.db) };
-            let errmsg = unsafe { sqlite3_errmsg(self.db) };
-            let errmsg = unsafe { CStr::from_ptr(errmsg) };
-            let errmsg = errmsg.to_str().unwrap().to_owned();
+        fn call(self, call: impl FnOnce() -> c_int) -> Result<c_int, SqliteError> {
+            let _guard = self.lock();
+            let ret = call();
+            if matches!(ret, SQLITE_OK | SQLITE_ROW | SQLITE_DONE) {
+                Ok(ret)
+            } else {
+                Err(self.error_snapshot())
+            }
+        }
+
+        fn check(self, result: Result<c_int, SqliteError>, vm: &VirtualMachine) -> PyResult<()> {
+            result.map(drop).map_err(|err| err.into_exception(vm))
+        }
+
+        fn checked(self, call: impl FnOnce() -> c_int, vm: &VirtualMachine) -> PyResult<()> {
+            self.check(self.call(call), vm)
+        }
+
+        // The caller holds the connection mutex from before the failed call.
+        fn error_snapshot(self) -> SqliteError {
+            unsafe {
+                SqliteError {
+                    code: sqlite3_errcode(self.db),
+                    extended: sqlite3_extended_errcode(self.db),
+                    message: CStr::from_ptr(sqlite3_errmsg(self.db))
+                        .to_string_lossy()
+                        .into_owned(),
+                }
+            }
+        }
 
-            raise_exception(typ.to_owned(), extended_errcode, errmsg, vm)
+        fn error_extended(self, vm: &VirtualMachine) -> PyBaseExceptionRef {
+            let error = {
+                let _guard = self.lock();
+                self.error_snapshot()
+            };
+            error.into_exception(vm)
         }
 
         fn open(path: *const libc::c_char, uri: bool, vm: &VirtualMachine) -> PyResult<Self> {
@@ -3102,17 +3913,28 @@ mod _sqlite3 {
                     &raw mut db,
                     SQLITE_OPEN_READWRITE
                         | SQLITE_OPEN_CREATE
+                        | SQLITE_OPEN_FULLMUTEX
                         | if uri { SQLITE_OPEN_URI } else { 0 },
                     null(),
                 )
             };
             let zelf = Self { db };
-            zelf.check(ret, vm).map(|_| zelf)
+            if ret == SQLITE_OK {
+                Ok(zelf)
+            } else {
+                Err(zelf.error_extended(vm))
+            }
         }
 
         fn _exec(self, sql: &CStr, vm: &VirtualMachine) -> PyResult<()> {
-            let ret = unsafe { sqlite3_exec(self.db, sql.as_ptr(), None, null_mut(), null_mut()) };
-            self.check(ret, vm)
+            self.exec(sql).map_err(|err| err.into_exception(vm))
+        }
+
+        fn exec(self, sql: &CStr) -> Result<(), SqliteError> {
+            self.call(|| unsafe {
+                sqlite3_exec(self.db, sql.as_ptr(), None, null_mut(), null_mut())
+            })
+            .map(drop)
         }
 
         fn prepare(
@@ -3120,14 +3942,16 @@ mod _sqlite3 {
             sql: &CStr,
             tail: &mut *const libc::c_char,
             vm: &VirtualMachine,
-        ) -> PyResult<Option<SqliteStatement>> {
+        ) -> PyResult<Option<SqliteStatementRaw>> {
             let mut st = null_mut();
-            let ret = unsafe { sqlite3_prepare_v2(self.db, sql.as_ptr(), -1, &mut st, tail) };
-            self.check(ret, vm)?;
+            self.checked(
+                || unsafe { sqlite3_prepare_v2(self.db, sql.as_ptr(), -1, &mut st, tail) },
+                vm,
+            )?;
             if st.is_null() {
                 Ok(None)
             } else {
-                Ok(Some(SqliteStatement::from(SqliteStatementRaw::from(st))))
+                Ok(Some(SqliteStatementRaw::from(st)))
             }
         }
 
@@ -3167,19 +3991,20 @@ mod _sqlite3 {
             unsafe { sqlite3_last_insert_rowid(self.db) }
         }
 
-        fn implicit_commit(self, vm: &VirtualMachine) -> PyResult<()> {
-            if self.is_autocommit() {
-                Ok(())
-            } else {
-                self._exec(c"COMMIT", vm)
+        // The caller holds the native mutex across checking the mode and the
+        // complete transition, including reopening a PEP 249 transaction.
+        fn end_transaction(self, sql: &CStr, mode: AutocommitMode) -> Result<(), SqliteError> {
+            match mode {
+                AutocommitMode::Legacy if !self.is_autocommit() => self.exec(sql),
+                AutocommitMode::Disabled => {
+                    self.exec(sql)?;
+                    self.exec(c"BEGIN")
+                }
+                _ => Ok(()),
             }
         }
 
-        fn begin_transaction(
-            self,
-            isolation_level: Option<PyStrRef>,
-            vm: &VirtualMachine,
-        ) -> PyResult<()> {
+        fn begin_transaction(self, isolation_level: Option<PyStrRef>) -> Result<(), SqliteError> {
             let Some(isolation_level) = isolation_level else {
                 return Ok(());
             };
@@ -3189,7 +4014,7 @@ mod _sqlite3 {
             s.push(b'\0');
             // SAFETY: isolation_level is checked for interior NULs on construction
             let cs = unsafe { CStr::from_bytes_with_nul_unchecked(&s) };
-            self._exec(cs, vm)
+            self.exec(cs)
         }
 
         fn interrupt(self) {
@@ -3225,7 +4050,7 @@ mod _sqlite3 {
             destroy: Option<unsafe extern "C" fn(arg1: *mut c_void)>,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            let ret = unsafe {
+            let ret = self.call(|| unsafe {
                 sqlite3_create_function_v2(
                     self.db,
                     name.as_ptr(),
@@ -3237,7 +4062,7 @@ mod _sqlite3 {
                     finalize,
                     destroy,
                 )
-            };
+            });
             self.check(ret, vm)
                 .map_err(|_| new_operational_error(vm, "Error creating function".to_owned()))
         }
@@ -3245,19 +4070,17 @@ mod _sqlite3 {
 
     struct SqliteStatement {
         raw: SqliteStatementRaw,
-    }
-
-    impl From<SqliteStatementRaw> for SqliteStatement {
-        fn from(raw: SqliteStatementRaw) -> Self {
-            Self { raw }
-        }
+        // Keep the original database usable for cursors surviving __init__.
+        db: PyRc<Sqlite>,
     }
 
     impl Drop for SqliteStatement {
         fn drop(&mut self) {
-            unsafe {
-                sqlite3_finalize(self.raw.st);
-            }
+            // Finalization may wait for a callback running on another thread.
+            // Queue only the raw handle, so pending cleanup cannot form an
+            // ownership cycle with the database.
+            self.db.pending.lock().statements.push(self.raw);
+            self.db.flush_cleanup();
         }
     }
 
@@ -3274,6 +4097,12 @@ mod _sqlite3 {
         st: *mut sqlite3_stmt,
     }
 
+    struct SqliteStep {
+        has_row: bool,
+        changes: c_int,
+        lastrowid: i64,
+    }
+
     impl From<*mut sqlite3_stmt> for SqliteStatementRaw {
         fn from(st: *mut sqlite3_stmt) -> Self {
             Self { st }
@@ -3281,21 +4110,26 @@ mod _sqlite3 {
     }
 
     impl SqliteStatementRaw {
-        fn step(self) -> c_int {
-            unsafe { sqlite3_step(self.st) }
+        fn step(self) -> Result<SqliteStep, SqliteError> {
+            let db = SqliteRaw::from(self);
+            let _guard = db.lock();
+            let ret = db.call(|| unsafe { sqlite3_step(self.st) })?;
+            // These values belong to the connection, not the statement. Another
+            // cursor must not overwrite them between step and the snapshot.
+            Ok(SqliteStep {
+                has_row: ret == SQLITE_ROW,
+                changes: db.changes(),
+                lastrowid: db.lastrowid(),
+            })
         }
 
-        fn step_row_else_done(self, vm: &VirtualMachine) -> PyResult<bool> {
+        fn step_checked(self, vm: &VirtualMachine) -> PyResult<SqliteStep> {
             let ret = self.step();
 
             if let Some(exc) = unsafe { user_function_exception().swap(None) } {
                 Err(exc)
-            } else if ret == SQLITE_ROW {
-                Ok(true)
-            } else if ret == SQLITE_DONE {
-                Ok(false)
             } else {
-                Err(SqliteRaw::from(self).error_extended(vm))
+                ret.map_err(|err| err.into_exception(vm))
             }
         }
 
@@ -3326,23 +4160,24 @@ mod _sqlite3 {
                 parameter
             };
 
+            let db = SqliteRaw::from(self);
             let ret = if vm.is_none(obj) {
-                unsafe { sqlite3_bind_null(self.st, pos) }
+                db.call(|| unsafe { sqlite3_bind_null(self.st, pos) })
             } else if let Some(val) = obj.downcast_ref::<PyInt>() {
                 let val = val.try_to_primitive::<i64>(vm).map_err(|_| {
                     vm.new_overflow_error("Python int too large to convert to SQLite INTEGER")
                 })?;
-                unsafe { sqlite3_bind_int64(self.st, pos, val) }
+                db.call(|| unsafe { sqlite3_bind_int64(self.st, pos, val) })
             } else if let Some(val) = obj.downcast_ref::<PyFloat>() {
                 let val = val.to_f64();
-                unsafe { sqlite3_bind_double(self.st, pos, val) }
+                db.call(|| unsafe { sqlite3_bind_double(self.st, pos, val) })
             } else if let Some(val) = obj.downcast_ref::<PyStr>() {
                 let val = val.try_as_utf8(vm)?;
                 let (ptr, len) = str_to_ptr_len(val, vm)?;
-                unsafe { sqlite3_bind_text(self.st, pos, ptr, len, SQLITE_TRANSIENT()) }
+                db.call(|| unsafe { sqlite3_bind_text(self.st, pos, ptr, len, SQLITE_TRANSIENT()) })
             } else if let Ok(buffer) = PyBuffer::try_from_borrowed_object(vm, obj) {
                 let (ptr, len) = buffer_to_ptr_len(&buffer, vm)?;
-                unsafe { sqlite3_bind_blob(self.st, pos, ptr, len, SQLITE_TRANSIENT()) }
+                db.call(|| unsafe { sqlite3_bind_blob(self.st, pos, ptr, len, SQLITE_TRANSIENT()) })
             } else {
                 return Err(new_programming_error(
                     vm,
@@ -3354,12 +4189,7 @@ mod _sqlite3 {
                 ));
             };
 
-            if ret == SQLITE_OK {
-                Ok(())
-            } else {
-                let db = SqliteRaw::from(self);
-                db.check(ret, vm)
-            }
+            db.check(ret, vm)
         }
 
         fn bind_parameters(self, parameters: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
@@ -3585,10 +4415,13 @@ mod _sqlite3 {
             unsafe { sqlite3_user_data(self.ctx).cast() }
         }
 
-        fn aggregate_context<T>(self) -> *mut T {
-            unsafe {
-                sqlite3_aggregate_context(self.ctx, core::mem::size_of::<T>() as c_int).cast()
-            }
+        fn aggregate_context(self, create: bool) -> *mut *const PyObject {
+            let size = if create {
+                core::mem::size_of::<*const PyObject>() as c_int
+            } else {
+                0
+            };
+            unsafe { sqlite3_aggregate_context(self.ctx, size).cast() }
         }
 
         fn result_exception(self, vm: &VirtualMachine, exc: PyBaseExceptionRef, msg: &CStr) {
diff --git a/crates/stdlib/src/_tokenize.rs b/crates/stdlib/src/_tokenize.rs
index b439ddb6e0b..8d09da12dc8 100644
--- a/crates/stdlib/src/_tokenize.rs
+++ b/crates/stdlib/src/_tokenize.rs
@@ -210,22 +210,22 @@ mod _tokenize {
             let kind = token.kind();
             let range = token.range();
 
-            // Check for lexical indentation errors.
-            // Skip when source has tabs — ruff and CPython handle tab
-            // indentation differently (CPython uses tabsize=8), so ruff may
-            // report false IndentationErrors for valid mixed-tab code.
-            if !source.contains('\t') {
-                for err in errors.iter() {
-                    if !matches!(
-                        err.error,
-                        ParseErrorType::Lexical(LexicalErrorType::IndentationError)
-                    ) {
-                        continue;
-                    }
-                    if err.location.start() <= range.start() && range.start() < err.location.end() {
-                        return Err(raise_indentation_error(vm, err, source, line_index));
-                    }
-                }
+            // An indentation error replaces the token the lexer raised it for.
+            if kind == TokenKind::Unknown
+                && let Some(err) = errors.iter().find(|err| {
+                    line_index.line_index(err.location.start())
+                        == line_index.line_index(range.start())
+                        && matches!(
+                            err.error,
+                            ParseErrorType::Lexical(
+                                LexicalErrorType::IndentationError
+                                    | LexicalErrorType::TabError
+                                    | LexicalErrorType::TooDeepIndentation
+                            )
+                        )
+                })
+            {
+                return Err(raise_indentation_error(vm, err, source, line_index));
             }
 
             if kind == TokenKind::EndOfFile {
@@ -480,7 +480,7 @@ mod _tokenize {
         exc
     }
 
-    /// Raise an IndentationError from a parse error.
+    /// Raise an IndentationError or TabError from a parse error.
     fn raise_indentation_error(
         vm: &VirtualMachine,
         err: &ParseError,
@@ -491,10 +491,15 @@ mod _tokenize {
         let err_line_text = source.full_line_str(err.location.start());
         let err_text = err_line_text.trim_end_matches('\n').trim_end_matches('\r');
         let msg = format!("{}", err.error);
-        let exc = vm.new_exception_msg(
-            vm.ctx.exceptions.indentation_error.to_owned(),
-            msg.clone().into(),
-        );
+        let exc_type = if matches!(
+            err.error,
+            ParseErrorType::Lexical(LexicalErrorType::TabError)
+        ) {
+            vm.ctx.exceptions.tab_error
+        } else {
+            vm.ctx.exceptions.indentation_error
+        };
+        let exc = vm.new_exception_msg(exc_type.to_owned(), msg.clone().into());
         let obj = exc.as_object();
         let _ = obj.set_attr("lineno", vm.ctx.new_int(err_lc.line.get()), vm);
         let _ = obj.set_attr("offset", vm.ctx.new_int(err_text.len() as i64 + 1), vm);
@@ -658,7 +663,8 @@ mod _tokenize {
     const fn token_kind_value(kind: TokenKind) -> u8 {
         match kind {
             TokenKind::EndOfFile => 0,
-            TokenKind::Name
+            TokenKind::Identifier
+            | TokenKind::Lazy
             | TokenKind::For
             | TokenKind::In
             | TokenKind::Pass
@@ -759,7 +765,6 @@ mod _tokenize {
             TokenKind::TStringMiddle => 63,
             TokenKind::TStringEnd => 64,
             TokenKind::IpyEscapeCommand | TokenKind::Question | TokenKind::Unknown => 67, // ERRORTOKEN
-            TokenKind::Lazy => u8::MAX, // Placeholder: RustPython Doesn't support `lazy imports` yet
         }
     }
 }
diff --git a/crates/stdlib/src/_zoneinfo.rs b/crates/stdlib/src/_zoneinfo.rs
index 9ab94cbefcd..aea7db10b4a 100644
--- a/crates/stdlib/src/_zoneinfo.rs
+++ b/crates/stdlib/src/_zoneinfo.rs
@@ -552,6 +552,9 @@ mod _zoneinfo {
                 parser.bump();
             }
             let end = parser.i;
+            if end == start {
+                return None;
+            }
             parser.bump();
             return Some(String::from_utf8_lossy(&parser.bytes[start..end]).into_owned());
         }
diff --git a/crates/stdlib/src/array.rs b/crates/stdlib/src/array.rs
index cb6e40d0d54..cb61711934c 100644
--- a/crates/stdlib/src/array.rs
+++ b/crates/stdlib/src/array.rs
@@ -18,8 +18,8 @@ pub mod array {
             atomic_func,
             builtins::{
                 PositionIterInternal, PyByteArray, PyBytes, PyBytesRef, PyDictRef, PyFloat,
-                PyGenericAlias, PyInt, PyList, PyListRef, PyStr, PyStrRef, PyTupleRef, PyType,
-                PyTypeRef, PyUtf8Str, PyUtf8StrRef, builtins_iter, locked_next,
+                PyGenericAlias, PyInt, PyListRef, PyStr, PyStrRef, PyTupleRef, PyType, PyTypeRef,
+                PyUtf8Str, PyUtf8StrRef, builtins_iter, locked_next,
             },
             class_or_notimplemented,
             convert::{ToPyObject, ToPyResult, TryFromBorrowedObject, TryFromObject},
@@ -33,7 +33,7 @@ pub mod array {
             },
             sequence::{SequenceExt, SequenceMutExt},
             sliceable::{
-                SaturatedSlice, SequenceIndex, SequenceIndexOp, SliceableSequenceMutOp,
+                NameArray, SaturatedSlice, SequenceIndex, SequenceIndexOp, SliceableSequenceMutOp,
                 SliceableSequenceOp,
             },
             stdlib::_warnings,
@@ -235,20 +235,29 @@ pub mod array {
                     }
                 }
 
-                fn fromlist(&mut self, list: &Py<PyList>, vm: &VirtualMachine) -> PyResult<()> {
+                // The caller must rule out conversion callbacks before taking locks.
+                fn extend_builtin_list(&mut self, list: &[PyObjectRef], vm: &VirtualMachine) -> PyResult<()> {
                     match self {
                         $(ArrayContentType::$n(v) => {
                             // convert list before modify self
-                            let mut list: Vec<$t> = list
-                                .borrow_vec()
-                                .iter()
-                                .cloned()
+                            let mut items: Vec<$t> = list.iter().cloned()
                                 .map(|value| <$t>::try_into_from_object(vm, value))
                                 .try_collect()?;
-                            v.append(&mut list);
-                            Ok(())
+                            v.append(&mut items);
                         })*
                     }
+                    Ok(())
+                }
+
+                fn resize(&mut self, len: usize, vm: &VirtualMachine) -> PyResult<()> {
+                    match self {
+                        $(ArrayContentType::$n(v) => {
+                            v.try_reserve(len.saturating_sub(v.len()))
+                                .map_err(|_| vm.no_memory_error())?;
+                            v.resize(len, <$t>::default());
+                        })*
+                    }
+                    Ok(())
                 }
 
                 fn get_bytes(&self) -> &[u8] {
@@ -506,12 +515,12 @@ pub mod array {
         (Double, f64, 'd', "d"),
     );
 
-    #[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Debug)]
+    #[derive(Copy, Clone, Default, Ord, PartialOrd, Eq, PartialEq, Debug)]
     pub struct WideChar(wchar_t);
 
     /// Element type for the 'w' typecode: always a 4-byte unicode code point
     /// (Py_UCS4), unlike 'u' which is platform-dependent `wchar_t`.
-    #[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Debug)]
+    #[derive(Copy, Clone, Default, Ord, PartialOrd, Eq, PartialEq, Debug)]
     pub struct Ucs4Char(u32);
 
     trait ArrayElement: Sized {
@@ -1186,7 +1195,55 @@ pub mod array {
 
         #[pymethod]
         fn fromlist(zelf: &Py<Self>, list: PyListRef, vm: &VirtualMachine) -> PyResult<()> {
-            zelf.try_resizable(vm)?.fromlist(&list, vm)
+            let n = list.borrow_vec().len();
+            if n == 0 {
+                return Ok(());
+            }
+            {
+                let items = list.borrow_vec();
+                if items.iter().all(|item| {
+                    let class = item.class();
+                    class.is(vm.ctx.types.int_type)
+                        || class.is(vm.ctx.types.float_type)
+                        || class.is(vm.ctx.types.bool_type)
+                        || class.is(vm.ctx.types.str_type)
+                }) {
+                    return zelf.try_resizable(vm)?.extend_builtin_list(&items, vm);
+                }
+            }
+            let (old_size, typecode) = {
+                let mut array = zelf.try_resizable(vm)?;
+                let old_size = array.len();
+                let new_size = old_size
+                    .checked_add(n)
+                    .ok_or_else(|| vm.no_memory_error())?;
+                // Callbacks can observe the new size, so initialize the new elements.
+                array.resize(new_size, vm)?;
+                (old_size, array.typecode())
+            };
+            let result = (|| {
+                for i in 0..n {
+                    let value = list.borrow_vec().get(i).cloned().ok_or_else(|| {
+                        vm.new_runtime_error("list changed size during iteration")
+                    })?;
+                    let index = zelf.read().len() as isize - n as isize + i as isize;
+                    let item = ArrayContentType::item_from_object(typecode, value, vm)?;
+                    // Conversion can resize the array. Check the saved index afterwards;
+                    // a negative index is the conversion-only sentinel used by CPython.
+                    if index >= 0 {
+                        zelf.write().setitem_by_item(index, item, vm)?;
+                    }
+                    if list.borrow_vec().len() != n {
+                        return Err(vm.new_runtime_error("list changed size during iteration"));
+                    }
+                }
+                Ok(())
+            })();
+            if result.is_err() && zelf.read().len() != old_size {
+                // A callback may have exported a buffer, preventing even the rollback.
+                zelf.try_resizable(vm)?.resize(old_size, vm)?;
+            }
+            result
         }
 
         #[pymethod]
@@ -1205,7 +1262,7 @@ pub mod array {
         }
 
         fn getitem_inner(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
-            match SequenceIndex::try_from_borrowed_object(vm, needle, "array")? {
+            match SequenceIndex::try_from_borrowed_object::<NameArray>(vm, needle)? {
                 SequenceIndex::Int(i) => self.read().getitem_by_index(i, vm),
                 SequenceIndex::Slice(slice) => self.read().getitem_by_slice(slice, vm),
             }
@@ -1221,7 +1278,7 @@ pub mod array {
             value: PyObjectRef,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            match SequenceIndex::try_from_borrowed_object(vm, needle, "array")? {
+            match SequenceIndex::try_from_borrowed_object::<NameArray>(vm, needle)? {
                 SequenceIndex::Int(i) => {
                     let typecode = zelf.read().typecode();
                     let item = ArrayContentType::item_from_object(typecode, value, vm)?;
@@ -1266,7 +1323,7 @@ pub mod array {
         }
 
         fn delitem_inner(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
-            match SequenceIndex::try_from_borrowed_object(vm, needle, "array")? {
+            match SequenceIndex::try_from_borrowed_object::<NameArray>(vm, needle)? {
                 SequenceIndex::Int(i) => self.try_resizable(vm)?.delitem_by_index(i, vm),
                 SequenceIndex::Slice(slice) => self.try_resizable(vm)?.delitem_by_slice(slice, vm),
             }
diff --git a/crates/stdlib/src/binascii.rs b/crates/stdlib/src/binascii.rs
index 73c20506dd7..d2a4a078a24 100644
--- a/crates/stdlib/src/binascii.rs
+++ b/crates/stdlib/src/binascii.rs
@@ -1,4 +1,6 @@
-// spell-checker:ignore hexlify unhexlify uuencodes rlecode rledecode
+// spell-checker:ignore hexlify unhexlify uuencodes rlecode rledecode ABCDEFGHIJKLMNPQRSTUVXYZ abcdefhijklmpqr
+
+mod base_n;
 
 pub(super) use decl::crc32;
 pub(crate) use decl::module_def;
@@ -8,14 +10,138 @@ use rustpython_vm::{VirtualMachine, builtins::PyBaseExceptionRef};
 
 #[pymodule(name = "binascii")]
 mod decl {
-    use super::new_binascii_error;
+    use super::{base_n, new_binascii_error};
     use crate::vm::{
-        PyResult, VirtualMachine,
-        builtins::PyTypeRef,
-        function::{ArgAsciiBuffer, ArgBytesLike, ArgIndex, OptionalArg},
+        AsObject, Py, PyObjectRef, PyRef, PyResult, VirtualMachine,
+        builtins::{PyBytes, PyBytesRef, PyDict, PyModule, PyTypeRef},
+        function::{
+            ArgAsciiBuffer, ArgBytesLike, ArgIndex, ArgIntoBool, ItemDoc, OptionalArg, PyMethodDef,
+            PyMethodFlags,
+        },
     };
     use rustpython_common::binascii;
 
+    pub(crate) fn module_exec(vm: &VirtualMachine, module: &Py<PyModule>) -> PyResult<()> {
+        __module_exec(vm, module);
+        module.set_native_state(vm.ctx.new_dict().into());
+        const DECODE: &PyMethodDef = &PyMethodDef::new_const(
+            "a2b_base64",
+            a2b_base64,
+            PyMethodFlags::empty(),
+            ItemDoc::static_text(
+                "a2b_base64($module, data, /, *, strict_mode=<unrepresentable>, padded=True, alphabet=BASE64_ALPHABET, ignorechars=<unrepresentable>, canonical=False)\n--\n\nDecode a line of base64 data.",
+            ),
+        );
+        const DECODE32: &PyMethodDef = &PyMethodDef::new_const(
+            "a2b_base32",
+            a2b_base32,
+            PyMethodFlags::empty(),
+            ItemDoc::static_text(
+                "a2b_base32($module, data, /, *, padded=True, alphabet=BASE32_ALPHABET, ignorechars=b'', canonical=False)\n--\n\nDecode a line of base32 data.",
+            ),
+        );
+        const DECODE85: &PyMethodDef = &PyMethodDef::new_const(
+            "a2b_base85",
+            a2b_base85,
+            PyMethodFlags::empty(),
+            ItemDoc::static_text(
+                "a2b_base85($module, data, /, *, alphabet=BASE85_ALPHABET, ignorechars=b'', canonical=False)\n--\n\nDecode a line of Base85 data.",
+            ),
+        );
+        for (name, definition) in [
+            ("a2b_base64", DECODE),
+            ("a2b_base32", DECODE32),
+            ("a2b_base85", DECODE85),
+        ] {
+            let function = definition.build_bound_function(&vm.ctx, module.to_owned().into());
+            function
+                .as_object()
+                .set_attr("__module__", vm.ctx.new_str("binascii"), vm)?;
+            module.dict().set_item(name, function.into(), vm)?;
+        }
+        Ok(())
+    }
+
+    fn reverse_table(
+        module: &Py<PyModule>,
+        alphabet: &PyBytesRef,
+        size: usize,
+        padchar: Option<u8>,
+        vm: &VirtualMachine,
+    ) -> PyResult<[u8; 256]> {
+        let bytes = alphabet.as_bytes();
+        if bytes.len() != size {
+            return Err(vm.new_value_error(format!("alphabet must have length {size}")));
+        }
+        let cache = module
+            .native_state()
+            .ok_or_else(|| vm.new_runtime_error("Missing binascii state"))?
+            .downcast::<PyDict>()
+            .map_err(|_| vm.new_runtime_error("Broken binascii cache"))?;
+        // The actual bytes object is the key: subclass hash/equality callbacks
+        // are part of CPython's cache lookup and insertion semantics.
+        if let Some(value) = cache.get_item_opt(alphabet.as_object(), vm)? {
+            return value
+                .downcast_ref::<PyBytes>()
+                .and_then(|value| value.as_bytes().try_into().ok())
+                .ok_or_else(|| vm.new_runtime_error("Broken binascii cache"));
+        }
+        let table = base_n::reverse_table(bytes, padchar);
+        cache.set_item(
+            alphabet.as_object(),
+            vm.ctx.new_bytes(table.to_vec()).into(),
+            vm,
+        )?;
+        Ok(table)
+    }
+
+    #[pyattr(name = "CRYPT_ALPHABET")]
+    fn crypt_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx
+            .new_bytes(b"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".to_vec())
+    }
+
+    #[pyattr(name = "UU_ALPHABET")]
+    fn uu_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx.new_bytes(
+            b" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_".to_vec(),
+        )
+    }
+
+    #[pyattr(name = "BINHEX_ALPHABET")]
+    fn binhex_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx.new_bytes(
+            b"!\"#$%&'()*+,-012345689@ABCDEFGHIJKLMNPQRSTUVXYZ[`abcdefhijklmpqr".to_vec(),
+        )
+    }
+
+    #[pyattr(name = "BASE85_ALPHABET")]
+    fn base85_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx.new_bytes(b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~".to_vec())
+    }
+
+    #[pyattr(name = "ASCII85_ALPHABET")]
+    fn ascii85_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx.new_bytes(b"!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstu".to_vec())
+    }
+
+    #[pyattr(name = "Z85_ALPHABET")]
+    fn z85_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx.new_bytes(b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#".to_vec())
+    }
+
+    #[pyattr(name = "BASE32_ALPHABET")]
+    fn base32_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx
+            .new_bytes(b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567".to_vec())
+    }
+
+    #[pyattr(name = "BASE32HEX_ALPHABET")]
+    fn base32hex_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx
+            .new_bytes(b"0123456789ABCDEFGHIJKLMNOPQRSTUV".to_vec())
+    }
+
     #[pyattr(name = "Error", once)]
     pub(super) fn error_type(vm: &VirtualMachine) -> PyTypeRef {
         vm.ctx.new_exception_type(
@@ -30,14 +156,24 @@ mod decl {
         vm.ctx.new_exception_type("binascii", "Incomplete", None)
     }
 
-    #[pyfunction(name = "b2a_hex")]
-    #[pyfunction]
-    fn hexlify(
+    #[derive(FromArgs)]
+    struct HexlifyArgs {
+        #[pyarg(any)]
         data: ArgBytesLike,
+        #[pyarg(any, optional)]
         sep: OptionalArg<ArgAsciiBuffer>,
+        #[pyarg(any, optional)]
         bytes_per_sep: OptionalArg<isize>,
-        vm: &VirtualMachine,
-    ) -> PyResult<Vec<u8>> {
+    }
+
+    #[pyfunction(name = "b2a_hex")]
+    #[pyfunction]
+    fn hexlify(args: HexlifyArgs, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+        let HexlifyArgs {
+            data,
+            sep,
+            bytes_per_sep,
+        } = args;
         let sep = match sep {
             OptionalArg::Present(sep) => sep.with_ref(|sep| {
                 let [sep] = sep else {
@@ -54,12 +190,24 @@ mod decl {
         Ok(data.with_ref(|bytes| binascii::hexlify(bytes, sep, bytes_per_sep)))
     }
 
+    #[derive(FromArgs)]
+    struct UnhexlifyArgs {
+        #[pyarg(positional)]
+        hexstr: ArgAsciiBuffer,
+        #[pyarg(named, optional, py_default = "b''")]
+        ignorechars: OptionalArg<ArgBytesLike>,
+    }
+
     #[pyfunction(name = "a2b_hex")]
     #[pyfunction]
-    fn unhexlify(hexstr: ArgAsciiBuffer, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
-        hexstr
-            .with_ref(binascii::unhexlify)
-            .map_err(|e| new_binascii_error(e, vm))
+    fn unhexlify(args: UnhexlifyArgs, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+        let ignorechars = ignored_argument(&args.ignorechars);
+        let result = args
+            .hexstr
+            .with_ref(|data| base_n::decode_hex(data, &ignorechars));
+        drop(args.hexstr);
+        drop(args.ignorechars);
+        base_n_result(result, vm)
     }
 
     #[derive(FromArgs)]
@@ -86,30 +234,418 @@ mod decl {
         data.with_ref(|bytes| binascii::crc_hqx(bytes, crc.into_int_ref().as_u32_mask()))
     }
 
-    #[derive(FromArgs)]
-    struct NewlineArg {
-        #[pyarg(named, default = true)]
-        newline: bool,
+    #[pyattr(name = "BASE64_ALPHABET")]
+    fn base64_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx.new_bytes(binascii::BASE64_ALPHABET.to_vec())
+    }
+
+    #[pyattr(name = "URLSAFE_BASE64_ALPHABET")]
+    fn urlsafe_base64_alphabet(vm: &VirtualMachine) -> PyBytesRef {
+        vm.ctx
+            .new_bytes(b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_".to_vec())
     }
 
     #[derive(FromArgs)]
     struct A2bBase64Args {
         #[pyarg(positional)]
         data: ArgAsciiBuffer,
-        #[pyarg(named, default)]
-        strict_mode: bool,
+        #[pyarg(named, optional)]
+        strict_mode: OptionalArg<ArgIntoBool>,
+        #[pyarg(named, default = ArgIntoBool::TRUE, py_default = "True")]
+        padded: ArgIntoBool,
+        #[pyarg(named, optional, py_default = "BASE64_ALPHABET")]
+        alphabet: OptionalArg<PyBytesRef>,
+        #[pyarg(named, optional)]
+        ignorechars: OptionalArg<ArgBytesLike>,
+        #[pyarg(named, optional, py_default = "False")]
+        canonical: OptionalArg<PyObjectRef>,
+    }
+
+    fn a2b_base64(
+        module: PyRef<PyModule>,
+        args: A2bBase64Args,
+        vm: &VirtualMachine,
+    ) -> PyResult<Vec<u8>> {
+        let A2bBase64Args {
+            data,
+            strict_mode,
+            padded,
+            alphabet,
+            ignorechars,
+            canonical,
+        } = args;
+        let strict_mode = match strict_mode {
+            OptionalArg::Present(value) => value.into_bool(),
+            OptionalArg::Missing => matches!(&ignorechars, OptionalArg::Present(_)),
+        };
+        let result = (|| {
+            // Convert the last Clinic argument while both acquired buffers are alive.
+            let canonical = match canonical {
+                OptionalArg::Present(value) => value.try_to_bool(vm)?,
+                OptionalArg::Missing => false,
+            };
+            const DEFAULT_TABLE: [u8; 256] =
+                binascii::base64_reverse_table(binascii::BASE64_ALPHABET);
+            let table = match &alphabet {
+                OptionalArg::Present(value) => reverse_table(&module, value, 64, Some(b'='), vm)?,
+                OptionalArg::Missing => DEFAULT_TABLE,
+            };
+            let mut ignored = [false; 256];
+            if strict_mode && let OptionalArg::Present(value) = &ignorechars {
+                value.with_ref(|bytes| {
+                    for &symbol in bytes {
+                        ignored[symbol as usize] = true;
+                    }
+                });
+            }
+            data.with_ref(|bytes| {
+                binascii::a2b_base64(
+                    bytes,
+                    binascii::Base64DecodeOptions {
+                        strict_mode,
+                        padded: padded.into_bool(),
+                        table: &table,
+                        ignored: &ignored,
+                        canonical,
+                    },
+                )
+            })
+            .map_err(|e| new_binascii_error(e, vm))
+        })();
+        // Match Argument Clinic cleanup order, including failures in __bool__.
+        drop(data);
+        drop(ignorechars);
+        result
+    }
+
+    #[derive(FromArgs)]
+    struct B2aBase64Args {
+        #[pyarg(positional)]
+        data: ArgBytesLike,
+        #[pyarg(named, default = ArgIntoBool::TRUE, py_default = "True")]
+        padded: ArgIntoBool,
+        #[pyarg(named, default = 0)]
+        wrapcol: usize,
+        #[pyarg(named, default = ArgIntoBool::TRUE, py_default = "True")]
+        newline: ArgIntoBool,
+        #[pyarg(named, optional, py_default = "BASE64_ALPHABET")]
+        alphabet: OptionalArg<ArgBytesLike>,
     }
 
     #[pyfunction]
-    fn a2b_base64(args: A2bBase64Args, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
-        let A2bBase64Args { data, strict_mode } = args;
-        data.with_ref(|b| binascii::a2b_base64(b, strict_mode))
+    fn b2a_base64(args: B2aBase64Args, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+        let B2aBase64Args {
+            data,
+            padded,
+            wrapcol,
+            newline,
+            alphabet,
+        } = args;
+        let copy_alphabet = |bytes: &[u8]| -> PyResult<[u8; 64]> {
+            bytes
+                .try_into()
+                .map_err(|_| vm.new_value_error("alphabet must have length 64"))
+        };
+        let alphabet_bytes = match &alphabet {
+            OptionalArg::Present(value) => value.with_ref(copy_alphabet),
+            OptionalArg::Missing => Ok(*binascii::BASE64_ALPHABET),
+        };
+        let result = alphabet_bytes.and_then(|alphabet_bytes| {
+            data.with_ref(|bytes| {
+                binascii::b2a_base64(
+                    bytes,
+                    padded.into_bool(),
+                    wrapcol,
+                    newline.into_bool(),
+                    &alphabet_bytes,
+                )
+            })
             .map_err(|e| new_binascii_error(e, vm))
+        });
+        drop(data);
+        drop(alphabet);
+        result
+    }
+
+    fn base_n_result(
+        result: Result<Vec<u8>, base_n::Error>,
+        vm: &VirtualMachine,
+    ) -> PyResult<Vec<u8>> {
+        result.map_err(|error| match error {
+            base_n::Error::InvalidAlphabet(size) => {
+                vm.new_value_error(format!("alphabet must have length {size}"))
+            }
+            base_n::Error::Codec(message) => vm.new_exception_msg(error_type(vm), message.into()),
+            base_n::Error::Memory => vm.no_memory_error(),
+        })
+    }
+
+    fn encoder_alphabet(
+        argument: &OptionalArg<ArgBytesLike>,
+        default: &[u8],
+    ) -> Result<Vec<u8>, base_n::Error> {
+        match argument {
+            OptionalArg::Present(value) => {
+                value.with_ref(|bytes| base_n::copy_alphabet(bytes, default.len()))
+            }
+            OptionalArg::Missing => base_n::copy_alphabet(default, default.len()),
+        }
+    }
+
+    fn ignored_argument(argument: &OptionalArg<ArgBytesLike>) -> [bool; 256] {
+        match argument {
+            OptionalArg::Present(value) => value.with_ref(base_n::ignored),
+            OptionalArg::Missing => [false; 256],
+        }
+    }
+
+    fn canonical_argument(
+        argument: &OptionalArg<PyObjectRef>,
+        vm: &VirtualMachine,
+    ) -> PyResult<bool> {
+        match argument {
+            OptionalArg::Present(value) => value.try_to_bool(vm),
+            OptionalArg::Missing => Ok(false),
+        }
+    }
+
+    #[derive(FromArgs)]
+    struct B2aBase32Args {
+        #[pyarg(positional)]
+        data: ArgBytesLike,
+        #[pyarg(named, default = ArgIntoBool::TRUE, py_default = "True")]
+        padded: ArgIntoBool,
+        #[pyarg(named, default = 0)]
+        wrapcol: usize,
+        #[pyarg(named, optional, py_default = "BASE32_ALPHABET")]
+        alphabet: OptionalArg<ArgBytesLike>,
+    }
+
+    #[derive(FromArgs)]
+    struct A2bBase32Args {
+        #[pyarg(positional)]
+        data: ArgAsciiBuffer,
+        #[pyarg(named, default = ArgIntoBool::TRUE, py_default = "True")]
+        padded: ArgIntoBool,
+        #[pyarg(named, optional, py_default = "BASE32_ALPHABET")]
+        alphabet: OptionalArg<PyBytesRef>,
+        #[pyarg(named, optional, py_default = "b''")]
+        ignorechars: OptionalArg<ArgBytesLike>,
+        #[pyarg(named, optional, py_default = "False")]
+        canonical: OptionalArg<PyObjectRef>,
+    }
+
+    fn a2b_base32(
+        module: PyRef<PyModule>,
+        args: A2bBase32Args,
+        vm: &VirtualMachine,
+    ) -> PyResult<Vec<u8>> {
+        let A2bBase32Args {
+            data,
+            padded,
+            alphabet,
+            ignorechars,
+            canonical,
+        } = args;
+        let result = (|| {
+            // This is the last Clinic conversion. Keep acquired exports alive
+            // and reach ordered cleanup even when __bool__ raises.
+            let canonical = canonical_argument(&canonical, vm)?;
+            let table = match &alphabet {
+                OptionalArg::Present(value) => reverse_table(&module, value, 32, Some(b'='), vm)?,
+                OptionalArg::Missing => base_n::reverse_table(base_n::BASE32, Some(b'=')),
+            };
+            let ignore = ignored_argument(&ignorechars);
+            let result = data.with_ref(|data| {
+                base_n::decode32(data, &table, &ignore, padded.into_bool(), canonical)
+            });
+            base_n_result(result, vm)
+        })();
+        // Match Argument Clinic cleanup: release data before auxiliary exports.
+        drop(data);
+        drop(ignorechars);
+        result
     }
 
     #[pyfunction]
-    fn b2a_base64(data: ArgBytesLike, NewlineArg { newline }: NewlineArg) -> Vec<u8> {
-        data.with_ref(|bytes| binascii::b2a_base64(bytes, newline))
+    fn b2a_base32(args: B2aBase32Args, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+        let B2aBase32Args {
+            data,
+            padded,
+            wrapcol,
+            alphabet,
+        } = args;
+        let result = encoder_alphabet(&alphabet, base_n::BASE32).and_then(|alphabet_bytes| {
+            data.with_ref(|data| {
+                base_n::encode32(data, padded.into_bool(), wrapcol, &alphabet_bytes)
+            })
+        });
+        drop(data);
+        drop(alphabet);
+        base_n_result(result, vm)
+    }
+
+    #[derive(FromArgs)]
+    struct B2aBase85Args {
+        #[pyarg(positional)]
+        data: ArgBytesLike,
+        #[pyarg(named, default = ArgIntoBool::FALSE, py_default = "False")]
+        pad: ArgIntoBool,
+        #[pyarg(named, default = 0)]
+        wrapcol: usize,
+        #[pyarg(named, optional, py_default = "BASE85_ALPHABET")]
+        alphabet: OptionalArg<ArgBytesLike>,
+    }
+
+    #[derive(FromArgs)]
+    struct A2bBase85Args {
+        #[pyarg(positional)]
+        data: ArgAsciiBuffer,
+        #[pyarg(named, optional, py_default = "BASE85_ALPHABET")]
+        alphabet: OptionalArg<PyBytesRef>,
+        #[pyarg(named, optional, py_default = "b''")]
+        ignorechars: OptionalArg<ArgBytesLike>,
+        #[pyarg(named, optional, py_default = "False")]
+        canonical: OptionalArg<PyObjectRef>,
+    }
+
+    fn a2b_base85(
+        module: PyRef<PyModule>,
+        args: A2bBase85Args,
+        vm: &VirtualMachine,
+    ) -> PyResult<Vec<u8>> {
+        let A2bBase85Args {
+            data,
+            alphabet,
+            ignorechars,
+            canonical,
+        } = args;
+        let result = (|| {
+            // This is the last Clinic conversion. Keep acquired exports alive
+            // and reach ordered cleanup even when __bool__ raises.
+            let canonical = canonical_argument(&canonical, vm)?;
+            let table = match &alphabet {
+                OptionalArg::Present(value) => reverse_table(&module, value, 85, None, vm)?,
+                OptionalArg::Missing => base_n::reverse_table(base_n::BASE85, None),
+            };
+            let ignore = ignored_argument(&ignorechars);
+            let result = data.with_ref(|data| {
+                base_n::decode85(data, &table, &ignore, canonical, false, false, false)
+            });
+            base_n_result(result, vm)
+        })();
+        drop(data);
+        drop(ignorechars);
+        result
+    }
+
+    #[pyfunction]
+    fn b2a_base85(args: B2aBase85Args, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+        let B2aBase85Args {
+            data,
+            pad,
+            wrapcol,
+            alphabet,
+        } = args;
+        let result = encoder_alphabet(&alphabet, base_n::BASE85).and_then(|alphabet_bytes| {
+            data.with_ref(|data| {
+                base_n::encode85(
+                    data,
+                    pad.into_bool(),
+                    wrapcol,
+                    &alphabet_bytes,
+                    false,
+                    false,
+                    false,
+                )
+            })
+        });
+        drop(data);
+        drop(alphabet);
+        base_n_result(result, vm)
+    }
+
+    #[derive(FromArgs)]
+    struct B2aAscii85Args {
+        #[pyarg(positional)]
+        data: ArgBytesLike,
+        #[pyarg(named, default = ArgIntoBool::FALSE, py_default = "False")]
+        foldspaces: ArgIntoBool,
+        #[pyarg(named, default = 0)]
+        wrapcol: usize,
+        #[pyarg(named, default = ArgIntoBool::FALSE, py_default = "False")]
+        pad: ArgIntoBool,
+        #[pyarg(named, default = ArgIntoBool::FALSE, py_default = "False")]
+        adobe: ArgIntoBool,
+    }
+
+    #[derive(FromArgs)]
+    struct A2bAscii85Args {
+        #[pyarg(positional)]
+        data: ArgAsciiBuffer,
+        #[pyarg(named, default = ArgIntoBool::FALSE, py_default = "False")]
+        foldspaces: ArgIntoBool,
+        #[pyarg(named, default = ArgIntoBool::FALSE, py_default = "False")]
+        adobe: ArgIntoBool,
+        #[pyarg(named, optional, py_default = "b''")]
+        ignorechars: OptionalArg<ArgBytesLike>,
+        #[pyarg(named, optional, py_default = "False")]
+        canonical: OptionalArg<PyObjectRef>,
+    }
+
+    #[pyfunction]
+    fn a2b_ascii85(args: A2bAscii85Args, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+        let A2bAscii85Args {
+            data,
+            foldspaces,
+            adobe,
+            ignorechars,
+            canonical,
+        } = args;
+        let result = (|| {
+            // This is the last Clinic conversion. Keep acquired exports alive
+            // and reach ordered cleanup even when __bool__ raises.
+            let canonical = canonical_argument(&canonical, vm)?;
+            let ignore = ignored_argument(&ignorechars);
+            let result = data.with_ref(|data| {
+                base_n::decode85(
+                    data,
+                    &base_n::reverse_table(base_n::ASCII85, None),
+                    &ignore,
+                    canonical,
+                    true,
+                    foldspaces.into_bool(),
+                    adobe.into_bool(),
+                )
+            });
+            base_n_result(result, vm)
+        })();
+        drop(data);
+        drop(ignorechars);
+        result
+    }
+
+    #[pyfunction]
+    fn b2a_ascii85(args: B2aAscii85Args, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+        let B2aAscii85Args {
+            data,
+            foldspaces,
+            wrapcol,
+            pad,
+            adobe,
+        } = args;
+        let result = data.with_ref(|data| {
+            base_n::encode85(
+                data,
+                pad.into_bool(),
+                wrapcol,
+                base_n::ASCII85,
+                true,
+                foldspaces.into_bool(),
+                adobe.into_bool(),
+            )
+        });
+        base_n_result(result, vm)
     }
 
     #[derive(FromArgs)]
@@ -182,6 +718,8 @@ fn new_binascii_error(error: Error, vm: &VirtualMachine) -> PyBaseExceptionRef {
         Error::TrailingGarbage => "Trailing garbage".to_owned(),
         Error::TooLong => "At most 45 bytes at once".to_owned(),
         Error::Base64(e) => base64_message(e),
+        Error::TooMuchBase64Data => "Too much data for base64".to_owned(),
+        Error::Memory => return vm.no_memory_error(),
     };
     vm.new_exception_msg(decl::error_type(vm), message.into())
 }
@@ -199,5 +737,7 @@ fn base64_message(error: Base64DecodeError) -> String {
             "Invalid base64-encoded string: number of data characters ({index}) cannot be 1 more than a multiple of 4"
         ),
         Base64DecodeError::IncorrectPadding => "Incorrect padding".to_owned(),
+        Base64DecodeError::PaddingNotAllowed => "Padding not allowed".to_owned(),
+        Base64DecodeError::NonZeroPaddingBits => "Non-zero padding bits".to_owned(),
     }
 }
diff --git a/crates/stdlib/src/binascii/base_n.rs b/crates/stdlib/src/binascii/base_n.rs
new file mode 100644
index 00000000000..fb966a9c3d4
--- /dev/null
+++ b/crates/stdlib/src/binascii/base_n.rs
@@ -0,0 +1,431 @@
+// Scalar native equivalents of CPython 3.15 Modules/binascii.c base-N codecs.
+
+pub(super) const BASE32: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+pub(super) const BASE85: &[u8] =
+    b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~";
+pub(super) const ASCII85: &[u8] =
+    b"!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstu";
+
+#[derive(Debug)]
+pub(super) enum Error {
+    InvalidAlphabet(usize),
+    Codec(String),
+    Memory,
+}
+
+type Result<T> = core::result::Result<T, Error>;
+
+fn codec(message: impl Into<String>) -> Error {
+    Error::Codec(message.into())
+}
+
+fn buffer(size: usize, too_large: &str) -> Result<Vec<u8>> {
+    if size > isize::MAX as usize {
+        return Err(codec(too_large));
+    }
+    let mut result = Vec::new();
+    result.try_reserve_exact(size).map_err(|_| Error::Memory)?;
+    Ok(result)
+}
+
+fn checked_alphabet(alphabet: &[u8], size: usize) -> Result<&[u8]> {
+    if alphabet.len() != size {
+        return Err(Error::InvalidAlphabet(size));
+    }
+    Ok(alphabet)
+}
+
+pub(super) fn copy_alphabet(alphabet: &[u8], size: usize) -> Result<Vec<u8>> {
+    checked_alphabet(alphabet, size)?;
+    let mut out = buffer(size, "Too large alphabet")?;
+    out.extend_from_slice(alphabet);
+    Ok(out)
+}
+
+pub(super) fn reverse_table(alphabet: &[u8], padchar: Option<u8>) -> [u8; 256] {
+    let mut table = [u8::MAX; 256];
+    for (digit, &ch) in alphabet.iter().enumerate() {
+        // Duplicate characters are allowed; their last occurrence wins.
+        table[usize::from(ch)] = digit as u8;
+    }
+    if let Some(padchar) = padchar {
+        table[usize::from(padchar)] = alphabet.len() as u8;
+    }
+    table
+}
+
+pub(super) fn ignored(ignorechars: &[u8]) -> [bool; 256] {
+    let mut table = [false; 256];
+    for &ch in ignorechars {
+        table[usize::from(ch)] = true;
+    }
+    table
+}
+
+fn rounded_width(width: usize, quantum: usize) -> usize {
+    if width == 0 {
+        0
+    } else {
+        width.max(quantum) / quantum * quantum
+    }
+}
+
+fn wrapped_size(size: usize, width: usize, newline: bool, too_large: &str) -> Result<usize> {
+    let breaks = if width == 0 || size == 0 {
+        0
+    } else {
+        (size - 1) / width
+    };
+    size.checked_add(breaks)
+        .and_then(|n| n.checked_add(usize::from(newline)))
+        .filter(|n| isize::try_from(*n).is_ok())
+        .ok_or_else(|| codec(too_large))
+}
+
+fn wrap(mut input: Vec<u8>, width: usize, newline: bool, too_large: &str) -> Result<Vec<u8>> {
+    let size = wrapped_size(input.len(), width, newline, too_large)?;
+    if width != 0 && input.len() > width {
+        let mut out = buffer(size, too_large)?;
+        for (index, chunk) in input.chunks(width).enumerate() {
+            if index != 0 {
+                out.push(b'\n');
+            }
+            out.extend_from_slice(chunk);
+        }
+        input = out;
+    }
+    if newline {
+        input.try_reserve(1).map_err(|_| Error::Memory)?;
+        input.push(b'\n');
+    }
+    Ok(input)
+}
+
+pub(super) fn encode32(
+    data: &[u8],
+    padded: bool,
+    width: usize,
+    alphabet: &[u8],
+) -> Result<Vec<u8>> {
+    let (size, in_group, out_group, too_large) = (32, 5, 8, "Too much data for base32");
+    let bits = 5;
+    checked_alphabet(alphabet, size)?;
+    let full_size = data
+        .len()
+        .div_ceil(in_group)
+        .checked_mul(out_group)
+        .ok_or_else(|| codec(too_large))?;
+    let pads = (in_group - data.len() % in_group) % in_group * out_group / in_group;
+    let encoded_size = full_size - if padded { 0 } else { pads };
+    let width = rounded_width(width, out_group);
+    wrapped_size(encoded_size, width, false, too_large)?;
+    let mut out = buffer(encoded_size, too_large)?;
+    let mut value = 0u32;
+    let mut available = 0u32;
+    let mask = (1u32 << bits) - 1;
+    for &byte in data {
+        value = (value << 8) | u32::from(byte);
+        available += 8;
+        while available >= bits {
+            available -= bits;
+            out.push(alphabet[((value >> available) & mask) as usize]);
+        }
+        value &= (1u32 << available) - 1;
+    }
+    if available != 0 {
+        out.push(alphabet[((value << (bits - available)) & mask) as usize]);
+    }
+    if padded {
+        out.resize(encoded_size, b'=');
+    }
+    wrap(out, width, false, too_large)
+}
+
+pub(super) fn decode32(
+    data: &[u8],
+    table: &[u8; 256],
+    ignorechars: &[bool; 256],
+    padded: bool,
+    canonical: bool,
+) -> Result<Vec<u8>> {
+    let (size, group, decoded_group, name) = (32, 8, 5, "base32");
+    let bits = 5;
+    let ignore = ignorechars;
+    let capacity = data
+        .len()
+        .div_ceil(group)
+        .checked_mul(decoded_group)
+        .ok_or_else(|| codec(format!("Too much {name} data")))?;
+    let mut out = buffer(capacity, &format!("Too much {name} data"))?;
+    let mut pos = 0usize;
+    let mut pads = 0usize;
+    let mut value = 0u32;
+    let mut available = 0u32;
+    for &ch in data {
+        if padded && ch == b'=' {
+            pads += 1;
+            let allowed_pos = matches!(pos, 2 | 4 | 5 | 7);
+            if allowed_pos && pos + pads <= group {
+                continue;
+            }
+            if ignore[usize::from(b'=')] {
+                continue;
+            }
+            if matches!(pos, 1 | 3 | 6) {
+                break;
+            }
+            return Err(codec(if pos == 0 && out.is_empty() {
+                "Leading padding not allowed"
+            } else {
+                "Excess padding not allowed"
+            }));
+        }
+        let digit = table[usize::from(ch)];
+        if usize::from(digit) >= size {
+            if !ignore[usize::from(ch)] {
+                return Err(codec(if ch == b'=' {
+                    "Padding not allowed".to_owned()
+                } else {
+                    format!("Only {name} data is allowed")
+                }));
+            }
+            continue;
+        }
+        if pads != 0 && !ignore[usize::from(b'=')] {
+            return Err(codec(if pos + pads == group {
+                "Excess data after padding"
+            } else {
+                "Discontinuous padding not allowed"
+            }));
+        }
+        value = (value << bits) | u32::from(digit);
+        available += bits;
+        if available >= 8 {
+            available -= 8;
+            out.push((value >> available) as u8);
+            value &= (1u32 << available) - 1;
+        }
+        pos += 1;
+        if pos == group {
+            pos = 0;
+            pads = 0;
+        }
+    }
+    if matches!(pos, 1 | 3 | 6) {
+        let count = out.len() / decoded_group * group + pos;
+        return Err(codec(format!(
+            "Invalid base32-encoded string: number of data characters ({count}) cannot be 1, 3, or 6 more than a multiple of 8"
+        )));
+    }
+    if padded && pos != 0 && pos + pads < group {
+        return Err(codec("Incorrect padding"));
+    }
+    if canonical && value != 0 {
+        return Err(codec("Non-zero padding bits"));
+    }
+    Ok(out)
+}
+
+fn digits85(mut value: u32, alphabet: &[u8]) -> [u8; 5] {
+    let mut out = [0; 5];
+    for slot in out.iter_mut().rev() {
+        *slot = alphabet[(value % 85) as usize];
+        value /= 85;
+    }
+    out
+}
+
+pub(super) fn encode85(
+    data: &[u8],
+    pad: bool,
+    width: usize,
+    alphabet: &[u8],
+    ascii85: bool,
+    foldspaces: bool,
+    adobe: bool,
+) -> Result<Vec<u8>> {
+    checked_alphabet(alphabet, 85)?;
+    let too_large = if ascii85 {
+        "Too much data for Ascii85"
+    } else {
+        "Too much data for Base85"
+    };
+    let full_size = data
+        .len()
+        .div_ceil(4)
+        .checked_mul(5)
+        .and_then(|n| n.checked_add(if adobe { 4 } else { 0 }))
+        .ok_or_else(|| codec(too_large))?;
+    let size = full_size
+        - if !pad && !data.len().is_multiple_of(4) {
+            4 - data.len() % 4
+        } else {
+            0
+        };
+    let width = if ascii85 {
+        if adobe && width == 1 { 2 } else { width }
+    } else {
+        rounded_width(width, 5)
+    };
+    wrapped_size(size, width, false, too_large)?;
+    let mut out = buffer(size, too_large)?;
+    if adobe {
+        out.extend_from_slice(b"<~");
+    }
+    for chunk in data.chunks(4) {
+        let mut block = [0; 4];
+        block[..chunk.len()].copy_from_slice(chunk);
+        let value = u32::from_be_bytes(block);
+        if ascii85 && value == 0 && (pad || chunk.len() == 4) {
+            out.push(b'z');
+        } else if ascii85 && foldspaces && value == 0x20202020 && chunk.len() == 4 {
+            out.push(b'y');
+        } else {
+            let digits = digits85(value, alphabet);
+            let count = if pad || chunk.len() == 4 {
+                5
+            } else {
+                chunk.len() + 1
+            };
+            out.extend_from_slice(&digits[..count]);
+        }
+    }
+    if adobe {
+        out.extend_from_slice(b"~>");
+    }
+    let mut out = wrap(out, width, false, too_large)?;
+    if adobe && out.len() >= 3 && out[out.len() - 2] == b'\n' {
+        let len = out.len();
+        out[len - 3] = b'\n';
+        out[len - 2] = b'~';
+    }
+    Ok(out)
+}
+
+pub(super) fn decode85(
+    mut data: &[u8],
+    table: &[u8; 256],
+    ignorechars: &[bool; 256],
+    canonical: bool,
+    ascii85: bool,
+    foldspaces: bool,
+    adobe: bool,
+) -> Result<Vec<u8>> {
+    if adobe {
+        if !data.ends_with(b"~>") {
+            return Err(codec("Ascii85 encoded byte sequences must end with b'~>'"));
+        }
+        data = &data[..data.len() - 2];
+        if data.starts_with(b"<~") {
+            data = &data[2..];
+        }
+    }
+    let ignore = ignorechars;
+    let shortcuts = if ascii85 {
+        data.iter().filter(|ch| matches!(ch, b'y' | b'z')).count()
+    } else {
+        0
+    };
+    let size = (data.len() - shortcuts)
+        .div_ceil(5)
+        .checked_mul(4)
+        .and_then(|n| shortcuts.checked_mul(4).and_then(|m| n.checked_add(m)))
+        .ok_or_else(|| codec("Too much Ascii85 data"))?;
+    let mut out = buffer(size, "Too much Ascii85 data")?;
+    let mut value = 0u32;
+    let mut pos = 0usize;
+    let mut from_z = false;
+    let mut index = 0usize;
+    let mut tail_len = 4usize;
+    while index < data.len() || pos != 0 {
+        let (ch, digit) = if index < data.len() {
+            let ch = data[index];
+            (ch, table[usize::from(ch)])
+        } else {
+            tail_len -= 1;
+            (0, 84)
+        };
+        if digit < 85 {
+            value = value
+                .checked_mul(85)
+                .and_then(|n| n.checked_add(u32::from(digit)))
+                .ok_or_else(|| {
+                    codec(if ascii85 {
+                        "Ascii85 overflow".to_owned()
+                    } else {
+                        format!("Base85 overflow in hunk starting at byte {}", index / 5 * 5)
+                    })
+                })?;
+            pos += 1;
+        } else if ascii85 && (ch == b'z' || (ch == b'y' && foldspaces)) {
+            if pos != 0 {
+                return Err(codec(format!(
+                    "'{}' inside Ascii85 5-tuple",
+                    char::from(ch)
+                )));
+            }
+            value = if ch == b'y' { 0x20202020 } else { 0 };
+            from_z = ch == b'z';
+            pos = 5;
+        } else if !ignore[usize::from(ch)] {
+            return Err(codec(if ascii85 {
+                format!("Non-Ascii85 digit found: {}", char::from(ch))
+            } else {
+                format!("bad Base85 character at position {index}")
+            }));
+        }
+        index += 1;
+        if pos != 5 {
+            continue;
+        }
+        if tail_len == 0 {
+            return Err(codec(if ascii85 {
+                "Incomplete Ascii85 group"
+            } else {
+                "Incomplete Base85 group"
+            }));
+        }
+        out.extend_from_slice(&value.to_be_bytes()[..tail_len]);
+        if canonical {
+            if ascii85 && tail_len == 4 && value == 0 && !from_z {
+                return Err(codec("Non-canonical encoding, use 'z' for all-zero groups"));
+            }
+            if tail_len < 4 {
+                let pads = 4 - tail_len;
+                let top = value >> (pads * 8) << (pads * 8);
+                let divisor = 85u32.pow(pads as u32);
+                if top / divisor != value / divisor {
+                    return Err(codec("Non-zero padding bits"));
+                }
+            }
+        }
+        pos = 0;
+        value = 0;
+        from_z = false;
+    }
+    Ok(out)
+}
+
+pub(super) fn decode_hex(data: &[u8], ignorechars: &[bool; 256]) -> Result<Vec<u8>> {
+    let ignore = ignorechars;
+    let mut out = buffer(data.len() / 2, "Too much hexadecimal data")?;
+    let mut high = None;
+    for &ch in data {
+        let digit = match ch {
+            b'0'..=b'9' => ch - b'0',
+            b'a'..=b'f' => ch - b'a' + 10,
+            b'A'..=b'F' => ch - b'A' + 10,
+            _ if ignore[usize::from(ch)] => continue,
+            _ => return Err(codec("Non-hexadecimal digit found")),
+        };
+        if let Some(hi) = high.take() {
+            out.push((hi << 4) | digit);
+        } else {
+            high = Some(digit);
+        }
+    }
+    if high.is_some() {
+        return Err(codec("Odd number of hexadecimal digits"));
+    }
+    Ok(out)
+}
diff --git a/crates/stdlib/src/blake2.rs b/crates/stdlib/src/blake2.rs
index a7dad88d099..04d3f2e8708 100644
--- a/crates/stdlib/src/blake2.rs
+++ b/crates/stdlib/src/blake2.rs
@@ -149,7 +149,7 @@ mod _blake2 {
 
         #[pyslot]
         fn slot_new(_cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-            let args: BlakeHashArgs = args.bind(vm)?;
+            let args: BlakeHashArgs = args.bind_for(vm, "blake2b")?;
             Ok(Self {
                 inner: local_blake2b(args, vm)?,
             }
@@ -246,7 +246,7 @@ mod _blake2 {
 
         #[pyslot]
         fn slot_new(_cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-            let args: BlakeHashArgs = args.bind(vm)?;
+            let args: BlakeHashArgs = args.bind_for(vm, "blake2s")?;
             Ok(Self {
                 inner: local_blake2s(args, vm)?,
             }
diff --git a/crates/stdlib/src/contextvars.rs b/crates/stdlib/src/contextvars.rs
index 3c8cf9fa169..4d01ede3704 100644
--- a/crates/stdlib/src/contextvars.rs
+++ b/crates/stdlib/src/contextvars.rs
@@ -44,8 +44,19 @@ mod _contextvars {
         }
     }
 
+    // Unlike an object address, a cache identity must not be reused after a
+    // context is destroyed. Zero disables cache hits if the counter is exhausted.
+    static CONTEXT_CACHE_ID: AtomicUsize = AtomicUsize::new(0);
+
+    fn next_context_cache_id() -> usize {
+        CONTEXT_CACHE_ID
+            .try_update(Ordering::Relaxed, Ordering::Relaxed, |id| id.checked_add(1))
+            .map_or(0, |id| id + 1)
+    }
+
     #[derive(Debug)]
     struct ContextInner {
+        cache_id: usize,
         idx: AtomicUsize,
         vars: PyRef<HamtObject>,
         // PyObject *ctx_weakreflist;
@@ -72,6 +83,7 @@ mod _contextvars {
         fn empty(vm: &VirtualMachine) -> Self {
             Self {
                 inner: ContextInner {
+                    cache_id: next_context_cache_id(),
                     idx: AtomicUsize::new(usize::MAX),
                     vars: HamtObject::default().into_ref(&vm.ctx),
                     entered: AtomicBool::new(false),
@@ -192,6 +204,7 @@ mod _contextvars {
             };
             Self {
                 inner: ContextInner {
+                    cache_id: next_context_cache_id(),
                     idx: AtomicUsize::new(usize::MAX),
                     vars: vars_copy.into_ref(&vm.ctx),
                     entered: AtomicBool::new(false),
@@ -356,7 +369,7 @@ mod _contextvars {
         #[pytraverse(skip)]
         cached: PyMutex<Option<ContextVarCache>>,
         #[pytraverse(skip)]
-        cached_id: AtomicUsize, // cached_tsid in CPython
+        cached_id: AtomicUsize, // non-reused Context cache identity
         #[pytraverse(skip)]
         hash: AtomicI64,
     }
@@ -413,7 +426,7 @@ mod _contextvars {
                 idx: ctx.inner.idx.load(Ordering::Relaxed),
             };
             let mut cached = zelf.cached.lock();
-            zelf.cached_id.store(ctx.get_id(), Ordering::SeqCst);
+            zelf.cached_id.store(ctx.inner.cache_id, Ordering::SeqCst);
             let replaced = cached.replace(cache);
             drop(cached);
             drop(replaced);
@@ -444,7 +457,8 @@ mod _contextvars {
                 let ctx = ctx_obj.downcast_ref::<PyContext>().unwrap();
                 let mut cached = zelf.cached.lock();
                 if let Some(cached) = &*cached
-                    && zelf.cached_id.load(Ordering::SeqCst) == ctx.get_id()
+                    && ctx.inner.cache_id != 0
+                    && zelf.cached_id.load(Ordering::SeqCst) == ctx.inner.cache_id
                     && cached.idx + 1 == ctxs.len()
                 {
                     return (Some(cached.object.clone()), None);
@@ -452,7 +466,7 @@ mod _contextvars {
                 let Some(obj) = ctx.borrow_vars().get(zelf).map(|obj| obj.to_owned()) else {
                     return (None, None);
                 };
-                zelf.cached_id.store(ctx.get_id(), Ordering::SeqCst);
+                zelf.cached_id.store(ctx.inner.cache_id, Ordering::SeqCst);
 
                 let replaced = cached.replace(ContextVarCache {
                     object: obj.clone(),
diff --git a/crates/stdlib/src/csv.rs b/crates/stdlib/src/csv.rs
index a0f75300eda..c7b3d9a014f 100644
--- a/crates/stdlib/src/csv.rs
+++ b/crates/stdlib/src/csv.rs
@@ -6,7 +6,7 @@ mod _csv {
     use crate::vm::{
         AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
         VirtualMachine,
-        builtins::{PyBaseExceptionRef, PyInt, PyNone, PyStr, PyType, PyTypeRef, PyUtf8StrRef},
+        builtins::{PyBaseExceptionRef, PyInt, PyStr, PyType, PyTypeRef, PyUtf8StrRef},
         function::{ArgIterable, ArgumentError, FromArgs, FuncArgs, OptionalArg, Param},
         protocol::{PyIter, PyIterReturn, PyNumber},
         types::{Callable, Constructor, IterNext, Iterable, SelfIter},
@@ -88,12 +88,10 @@ mod _csv {
     }
 
     impl Constructor for PyDialect {
-        type Args = PyObjectRef;
+        type Args = FormatOptions;
 
-        fn py_new(_cls: &Py<PyType>, obj: Self::Args, vm: &VirtualMachine) -> PyResult<Self> {
-            let dialect = Self::try_from_object(vm, obj)?;
-            validate_dialect(vm, &dialect)?;
-            Ok(dialect)
+        fn py_new(_cls: &Py<PyType>, opts: Self::Args, vm: &VirtualMachine) -> PyResult<Self> {
+            opts.result(vm)
         }
     }
 
@@ -140,96 +138,32 @@ mod _csv {
         }
     }
 
-    /// Parses the delimiter from a Python object and returns its ASCII value.
-    ///
-    /// This function attempts to extract the 'delimiter' attribute from the given Python object and ensures that the attribute is a single-character string. If successful, it returns the ASCII value of the character. If the attribute is not a single-character string, an error is returned.
-    ///
-    /// # Arguments
-    ///
-    /// * `vm` - A reference to the VirtualMachine, used for executing Python code and manipulating Python objects.
-    /// * `obj` - A reference to the PyObjectRef from which the 'delimiter' attribute is to be parsed.
-    ///
-    /// # Returns
-    ///
-    /// If successful, returns a `PyResult<u8>` representing the ASCII value of the 'delimiter' attribute. If unsuccessful, returns a `PyResult` containing an error message.
-    ///
-    /// # Errors
-    ///
-    /// This function can return the following errors:
-    ///
-    /// * If the 'delimiter' attribute is not a single-character string, a type error is returned.
-    /// * If the 'obj' is not of string type and does not have a 'delimiter' attribute, a type error is returned.
-    fn parse_delimiter_from_obj(vm: &VirtualMachine, obj: &PyObject) -> PyResult<u8> {
-        if let Ok(attr) = obj.get_attr("delimiter", vm) {
-            parse_delimiter_from_obj(vm, &attr)
-        } else {
-            match_class!(match obj.to_owned() {
-                s @ PyStr => {
-                    parse_single_char(&s, |len| {
-                        vm.new_type_error(format!(
-                            r#""delimiter" must be a unicode character, not a string of length {len}"#
-                        ))
-                    })
-                }
-                attr => {
-                    Err(vm.new_type_error(format!(
-                        r#""delimiter" must be a unicode character, not {}"#,
-                        attr.class().name()
-                    )))
-                }
-            })
+    fn parse_char(
+        vm: &VirtualMachine,
+        obj: &PyObject,
+        name: &str,
+        allow_none: bool,
+    ) -> PyResult<Option<u8>> {
+        if allow_none && vm.is_none(obj) {
+            return Ok(None);
         }
-    }
-
-    fn parse_quotechar_from_obj(vm: &VirtualMachine, obj: &PyObject) -> PyResult<Option<u8>> {
-        match_class!(match obj.get_attr("quotechar", vm)? {
-            s @ PyStr => {
-                Ok(Some(parse_single_char(&s, |len| {
-                    new_csv_error(
-                        vm,
-                        format!(
-                            r#""quotechar" must be a unicode character or None, not a string of length {len}"#
-                        ),
-                    )
-                })?))
-            }
-            _n @ PyNone => {
-                Ok(None)
-            }
-            attr => {
-                Err(new_csv_error(
-                    vm,
-                    format!(
-                        r#""quotechar" must be a unicode character or None, not {}"#,
-                        attr.class().name()
-                    ),
-                ))
-            }
-        })
-    }
-
-    fn parse_escapechar_from_obj(vm: &VirtualMachine, obj: &PyObject) -> PyResult<Option<u8>> {
-        match_class!(match obj.get_attr("escapechar", vm)? {
-            s @ PyStr => {
-                Ok(Some(parse_single_char(&s, |len| {
-                    new_csv_error(
-                        vm,
-                        format!(
-                            r#""escapechar" must be a unicode character or None, not a string of length {len}"#
-                        ),
-                    )
-                })?))
-            }
-            _n @ PyNone => {
-                Ok(None)
-            }
-            attr => {
-                Err(vm.new_type_error(format!(
-                    r#""escapechar" must be a unicode character or None, not {}"#,
-                    attr.class().name()
-                )))
-            }
+        let expected = if allow_none {
+            "a unicode character or None"
+        } else {
+            "a unicode character"
+        };
+        let value = obj.downcast_ref::<PyStr>().ok_or_else(|| {
+            vm.new_type_error(format!(
+                r#""{name}" must be {expected}, not {}"#,
+                obj.class().name()
+            ))
+        })?;
+        parse_single_char(value, |len| {
+            vm.new_type_error(format!(
+                r#""{name}" must be {expected}, not a string of length {len}"#
+            ))
         })
+        .map(Some)
     }
 
     fn parse_lineterminator<'a>(vm: &VirtualMachine, s: &'a Py<PyStr>) -> PyResult<&'a str> {
@@ -237,25 +171,6 @@ mod _csv {
             .ok_or_else(|| new_csv_error(vm, r#""lineterminator" must be a string"#))
     }
 
-    fn prase_lineterminator_from_obj(vm: &VirtualMachine, obj: &PyObject) -> PyResult<String> {
-        match_class!(match obj.get_attr("lineterminator", vm)? {
-            s @ PyStr => {
-                // Store the full line terminator string. CPython accepts an
-                // arbitrary-length terminator; the manual writer paths emit it
-                // verbatim and the csv-core writer path appends it after a
-                // sentinel terminator (see `writerow`).
-                let value = parse_lineterminator(vm, &s)?;
-                Ok(value.to_owned())
-            }
-            attr => {
-                Err(vm.new_type_error(format!(
-                    r#""lineterminator" must be a string, not {}"#,
-                    attr.class().name()
-                )))
-            }
-        })
-    }
-
     fn parse_single_char(
         s: &Py<PyStr>,
         error: impl Fn(usize) -> PyBaseExceptionRef,
@@ -268,51 +183,6 @@ mod _csv {
         u8::try_from(ch.to_u32()).map_err(|_| error(s.char_len()))
     }
 
-    fn prase_quoting_from_obj(vm: &VirtualMachine, obj: &PyObject) -> PyResult<QuoteStyle> {
-        match_class!(match obj.get_attr("quoting", vm)? {
-            i @ PyInt => {
-                Ok(i.try_to_primitive::<isize>(vm)?
-                    .try_into()
-                    .map_err(|_| vm.new_type_error(r#"bad "quoting" value"#))?)
-            }
-            attr => {
-                Err(vm.new_type_error(format!(
-                    r#""quoting" must be string or None, not {}"#,
-                    attr.class().name()
-                )))
-            }
-        })
-    }
-
-    impl TryFromObject for PyDialect {
-        fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
-            let delimiter = parse_delimiter_from_obj(vm, &obj)?;
-            let quotechar = parse_quotechar_from_obj(vm, &obj)?;
-            let escapechar = parse_escapechar_from_obj(vm, &obj)?;
-            let doublequote = obj.get_attr("doublequote", vm)?.try_to_bool(vm)?;
-            let skipinitialspace = obj.get_attr("skipinitialspace", vm)?.try_to_bool(vm)?;
-            let lineterminator = prase_lineterminator_from_obj(vm, &obj)?;
-            let quoting = prase_quoting_from_obj(vm, &obj)?;
-
-            let strict = if let Ok(t) = obj.get_attr("strict", vm) {
-                t.try_to_bool(vm).unwrap_or(false)
-            } else {
-                false
-            };
-
-            Ok(Self {
-                delimiter,
-                quotechar,
-                escapechar,
-                doublequote,
-                skipinitialspace,
-                lineterminator,
-                quoting,
-                strict,
-            })
-        }
-    }
-
     #[derive(FromArgs)]
     struct DialectName {
         #[pyarg(any)]
@@ -350,13 +220,8 @@ mod _csv {
         })?;
 
         let name: PyUtf8StrRef = name.try_into_utf8(vm)?;
-        let g = GLOBAL_HASHMAP.lock();
-
-        if let Some(dialect) = g.get(name.as_str()) {
-            return Ok(dialect.clone());
-        }
-
-        Err(new_csv_error(vm, "unknown dialect"))
+        let dialect = GLOBAL_HASHMAP.lock().get(name.as_str()).cloned();
+        dialect.ok_or_else(|| new_csv_error(vm, "unknown dialect"))
     }
 
     #[pyfunction]
@@ -369,9 +234,9 @@ mod _csv {
         })?;
 
         let name: PyUtf8StrRef = name.try_into_utf8(vm)?;
-        let mut g = GLOBAL_HASHMAP.lock();
+        let removed = GLOBAL_HASHMAP.lock().remove(name.as_str());
 
-        if let Some(_removed) = g.remove(name.as_str()) {
+        if removed.is_some() {
             return Ok(());
         }
 
@@ -380,10 +245,9 @@ mod _csv {
 
     #[pyfunction]
     fn list_dialects(vm: &VirtualMachine) -> rustpython_vm::builtins::PyListRef {
-        let g = GLOBAL_HASHMAP.lock();
-        let t = g
-            .keys()
-            .cloned()
+        let names = GLOBAL_HASHMAP.lock().keys().cloned().collect_vec();
+        let t = names
+            .into_iter()
             .map(|x| vm.ctx.new_str(x).into())
             .collect_vec();
         // .iter().map(|x| vm.ctx.new_str(x.clone()).into_pyobject(vm)).collect_vec();
@@ -398,14 +262,18 @@ mod _csv {
 
     #[pyfunction]
     fn field_size_limit(args: FieldSizeLimitArgs, vm: &VirtualMachine) -> PyResult<isize> {
-        let old_size = GLOBAL_FIELD_LIMIT.lock().to_owned();
         if let OptionalArg::Present(limit) = args.new_limit {
-            let Ok(new_size) = limit.try_int(vm) else {
-                return Err(vm.new_type_error("limit must be an integer"));
-            };
-            *GLOBAL_FIELD_LIMIT.lock() = new_size.try_to_primitive::<isize>(vm)?;
+            let new_size = limit
+                .downcast_ref_if_exact::<PyInt>(vm)
+                .ok_or_else(|| vm.new_type_error("limit must be an integer"))?
+                .try_to_primitive::<isize>(vm)?;
+            Ok(core::mem::replace(
+                &mut *GLOBAL_FIELD_LIMIT.lock(),
+                new_size,
+            ))
+        } else {
+            Ok(*GLOBAL_FIELD_LIMIT.lock())
         }
-        Ok(old_size)
     }
 
     #[pyfunction]
@@ -492,79 +360,17 @@ mod _csv {
         }
     }
 
-    #[derive(Default)]
-    enum DialectItem {
-        Str(String),
-        Obj(PyDialect),
-        #[default]
-        None,
-    }
-
     #[derive(Default)]
     struct FormatOptions {
-        dialect: DialectItem,
-        delimiter: Option<u8>,
-        quotechar: Option<Option<u8>>,
-        escapechar: Option<Option<u8>>,
-        doublequote: Option<bool>,
-        skipinitialspace: Option<bool>,
-        lineterminator: Option<String>,
-        quoting: Option<QuoteStyle>,
-        strict: Option<bool>,
-    }
-
-    /// prase a dialect item from a Python argument and returns a `DialectItem` or an `ArgumentError`.
-    ///
-    /// This function takes a reference to the VirtualMachine and a PyObjectRef as input and attempts to parse a dialect item from the provided Python argument. It returns a `DialectItem` if successful, or an `ArgumentError` if unsuccessful.
-    ///
-    /// # Arguments
-    ///
-    /// * `vm` - A reference to the VirtualMachine, used for executing Python code and manipulating Python objects.
-    /// * `obj` - The PyObjectRef from which the dialect item is to be parsed.
-    ///
-    /// # Returns
-    ///
-    /// If successful, returns a `Result<DialectItem, ArgumentError>` representing the parsed dialect item. If unsuccessful, returns an `ArgumentError`.
-    ///
-    /// # Errors
-    ///
-    /// This function can return the following errors:
-    ///
-    /// * If the provided object is a PyStr, it returns a `DialectItem::Str` containing the string value.
-    /// * If the provided object is PyNone, it returns an `ArgumentError` with the message "InvalidKeywordArgument('dialect')".
-    /// * If the provided object is a PyType, it attempts to create a PyDialect from the object and returns a `DialectItem::Obj` containing the PyDialect if successful. If unsuccessful, it returns an `ArgumentError` with the message "InvalidKeywordArgument('dialect')".
-    /// * If the provided object is none of the above types, it attempts to create a PyDialect from the object and returns a `DialectItem::Obj` containing the PyDialect if successful. If unsuccessful, it returns an `ArgumentError` with the message "InvalidKeywordArgument('dialect')".
-    fn prase_dialect_item_from_arg(
-        vm: &VirtualMachine,
-        obj: PyObjectRef,
-    ) -> Result<DialectItem, ArgumentError> {
-        match_class!(match obj {
-            s @ PyStr => {
-                let s = s.try_into_utf8(vm).map_err(ArgumentError::Exception)?;
-                Ok(DialectItem::Str(s.as_str().to_owned()))
-            }
-            PyNone => {
-                Err(ArgumentError::InvalidKeywordArgument("dialect".to_string()))
-            }
-            t @ PyType => {
-                let temp = t
-                    .as_object()
-                    .call(vec![], vm)
-                    .map_err(|_e| ArgumentError::InvalidKeywordArgument("dialect".to_string()))?;
-                Ok(DialectItem::Obj(
-                    PyDialect::try_from_object(vm, temp).map_err(|_| {
-                        ArgumentError::InvalidKeywordArgument("dialect".to_string())
-                    })?,
-                ))
-            }
-            obj => {
-                if let Ok(cur_dialect_item) = PyDialect::try_from_object(vm, obj) {
-                    Ok(DialectItem::Obj(cur_dialect_item))
-                } else {
-                    Err(ArgumentError::InvalidKeywordArgument("dialect".to_string()))
-                }
-            }
-        })
+        dialect: Option<PyObjectRef>,
+        delimiter: Option<PyObjectRef>,
+        doublequote: Option<PyObjectRef>,
+        escapechar: Option<PyObjectRef>,
+        lineterminator: Option<PyObjectRef>,
+        quotechar: Option<PyObjectRef>,
+        quoting: Option<PyObjectRef>,
+        skipinitialspace: Option<PyObjectRef>,
+        strict: Option<PyObjectRef>,
     }
 
     impl FromArgs for FormatOptions {
@@ -578,107 +384,16 @@ mod _csv {
         ]);
 
         fn from_args(vm: &VirtualMachine, args: &mut FuncArgs) -> Result<Self, ArgumentError> {
-            let dialect = if let Some(dialect) = args.take_positional_keyword("dialect") {
-                prase_dialect_item_from_arg(vm, dialect)?
-            } else {
-                DialectItem::None
-            };
-
-            let mut res = Self {
-                dialect,
-                ..Default::default()
-            };
-
-            if let Some(delimiter) = args.kwargs.swap_remove("delimiter") {
-                res.delimiter = Some(parse_delimiter_from_obj(vm, &delimiter)?);
-            }
-
-            if let Some(escapechar) = args.kwargs.swap_remove("escapechar") {
-                res.escapechar = match_class!(match escapechar {
-                    s @ PyStr => Some(Some(parse_single_char(&s, |_| {
-                        vm.new_type_error(r#""escapechar" must be a 1-character string"#)
-                    })?)),
-                    PyNone => Some(None),
-                    _ => {
-                        return Err(ArgumentError::Exception(
-                            vm.new_type_error(r#""escapechar" must be a 1-character string"#),
-                        ));
-                    }
-                })
-            };
-
-            if let Some(lineterminator) = args.kwargs.swap_remove("lineterminator") {
-                let s = lineterminator.downcast_ref::<PyStr>().ok_or_else(|| {
-                    vm.new_type_error(format!(
-                        r#""lineterminator" must be a string, not {}"#,
-                        lineterminator.class().name()
-                    ))
-                })?;
-                let value = parse_lineterminator(vm, s)?;
-                res.lineterminator = Some(value.to_owned());
-            };
-
-            if let Some(doublequote) = args.kwargs.swap_remove("doublequote") {
-                res.doublequote = Some(
-                    doublequote
-                        .try_to_bool(vm)
-                        .map_err(|_| vm.new_type_error(r#""doublequote" must be a bool"#))?,
-                )
-            };
-
-            if let Some(skipinitialspace) = args.kwargs.swap_remove("skipinitialspace") {
-                res.skipinitialspace = Some(
-                    skipinitialspace
-                        .try_to_bool(vm)
-                        .map_err(|_| vm.new_type_error(r#""skipinitialspace" must be a bool"#))?,
-                )
-            };
-
-            if let Some(quoting) = args.kwargs.swap_remove("quoting") {
-                res.quoting = match_class!(match quoting {
-                    i @ PyInt =>
-                        Some(i.try_to_primitive::<isize>(vm)?.try_into().map_err(|_e| {
-                            ArgumentError::InvalidKeywordArgument("quoting".to_string())
-                        })?),
-                    _ => {
-                        // let msg = r#""quoting" must be a int enum"#;
-                        return Err(ArgumentError::InvalidKeywordArgument("quoting".to_string()));
-                    }
-                });
-            };
-
-            if let Some(quotechar) = args.kwargs.swap_remove("quotechar") {
-                res.quotechar = match_class!(match quotechar {
-                    s @ PyStr => Some(Some(parse_single_char(&s, |_| {
-                        vm.new_type_error(r#""quotechar" must be a 1-character string"#)
-                    })?)),
-                    PyNone => {
-                        if res
-                            .quoting
-                            .is_some_and(|quoting| quoting != QuoteStyle::None)
-                        {
-                            return Err(ArgumentError::Exception(
-                                vm.new_type_error("quotechar must be set if quoting enabled"),
-                            ));
-                        }
-                        Some(None)
-                    }
-                    _o => {
-                        return Err(
-                            rustpython_vm::function::ArgumentError::InvalidKeywordArgument(
-                                "quotechar".to_string(),
-                            ),
-                        );
-                    }
-                })
-            };
-
-            if let Some(strict) = args.kwargs.swap_remove("strict") {
-                res.strict = Some(
-                    strict
-                        .try_to_bool(vm)
-                        .map_err(|_| vm.new_type_error(r#""strict" must be a int enum"#))?,
-                )
+            let res = Self {
+                dialect: args.take_positional_keyword("dialect"),
+                delimiter: args.kwargs.swap_remove("delimiter"),
+                doublequote: args.kwargs.swap_remove("doublequote"),
+                escapechar: args.kwargs.swap_remove("escapechar"),
+                lineterminator: args.kwargs.swap_remove("lineterminator"),
+                quotechar: args.kwargs.swap_remove("quotechar"),
+                quoting: args.kwargs.swap_remove("quoting"),
+                skipinitialspace: args.kwargs.swap_remove("skipinitialspace"),
+                strict: args.kwargs.swap_remove("strict"),
             };
 
             if let Some(last_arg) = args.kwargs.pop() {
@@ -688,7 +403,6 @@ mod _csv {
                     vm.new_unexpected_keyword_type_error(None, &last_arg.0.to_string()),
                 ));
             }
-
             Ok(res)
         }
     }
@@ -748,60 +462,112 @@ mod _csv {
     }
 
     impl FormatOptions {
-        fn update_py_dialect(&self, mut res: PyDialect) -> PyDialect {
-            macro_rules! check_and_fill {
-                ($res:ident, $e:ident) => {{
-                    if let Some(t) = self.$e {
-                        $res.$e = t;
-                    }
-                }};
+        fn result(mut self, vm: &VirtualMachine) -> PyResult<PyDialect> {
+            if let Some(obj) = self.dialect.take() {
+                let obj = if obj.downcast_ref::<PyStr>().is_some() {
+                    get_dialect(DialectName { name: obj }, vm)?
+                        .into_ref(&vm.ctx)
+                        .into()
+                } else {
+                    obj
+                };
+                // Read all non-overridden attributes before converting their values.
+                macro_rules! fill_from_dialect {
+                    ($($name:ident),* $(,)?) => {
+                        $(if self.$name.is_none() {
+                            self.$name = vm.get_attribute_opt(&obj, stringify!($name))?;
+                        })*
+                    };
+                }
+                fill_from_dialect!(
+                    delimiter,
+                    doublequote,
+                    escapechar,
+                    lineterminator,
+                    quotechar,
+                    quoting,
+                    skipinitialspace,
+                    strict,
+                );
+                self.dialect = Some(obj);
             }
 
-            check_and_fill!(res, delimiter);
-            // check_and_fill!(res, quotechar);
-            check_and_fill!(res, delimiter);
-            check_and_fill!(res, doublequote);
-            check_and_fill!(res, skipinitialspace);
-
-            if let Some(t) = self.escapechar {
-                res.escapechar = t;
+            let delimiter = match &self.delimiter {
+                Some(obj) => parse_char(vm, obj, "delimiter", false)?.unwrap(),
+                None => b',',
             };
-
-            if let Some(t) = self.quotechar {
-                res.quotechar = t;
+            let doublequote = match &self.doublequote {
+                Some(obj) => obj.try_to_bool(vm)?,
+                None => true,
             };
-
-            check_and_fill!(res, quoting);
-            if let Some(t) = &self.lineterminator {
-                res.lineterminator.clone_from(t);
+            let escapechar = match &self.escapechar {
+                Some(obj) => parse_char(vm, obj, "escapechar", true)?,
+                None => None,
             };
-            check_and_fill!(res, strict);
-            res
-        }
-
-        fn result(&self, vm: &VirtualMachine) -> PyResult<PyDialect> {
-            let dialect = match &self.dialect {
-                DialectItem::Str(name) => {
-                    let g = GLOBAL_HASHMAP.lock();
-                    if let Some(dialect) = g.get(name) {
-                        Ok(self.update_py_dialect(dialect.clone()))
-                    } else {
-                        Err(new_csv_error(vm, format!("{name} is not registered.")))
+            let lineterminator = match &self.lineterminator {
+                Some(obj) => {
+                    let value = obj.downcast_ref::<PyStr>().ok_or_else(|| {
+                        vm.new_type_error(format!(
+                            r#""lineterminator" must be a string, not {}"#,
+                            obj.class().name()
+                        ))
+                    })?;
+                    // Store the full line terminator string. CPython accepts an
+                    // arbitrary-length terminator; the manual writer paths emit it
+                    // verbatim and the csv-core writer path appends it after a
+                    // sentinel terminator (see `writerow`).
+                    parse_lineterminator(vm, value)?.to_owned()
+                }
+                None => "\r\n".to_owned(),
+            };
+            let quotechar = match &self.quotechar {
+                Some(obj) => parse_char(vm, obj, "quotechar", true)?,
+                None => Some(b'"'),
+            };
+            let quoting = match &self.quoting {
+                Some(obj) => {
+                    if !obj.class().is(vm.ctx.types.int_type) {
+                        return Err(vm.new_type_error(format!(
+                            r#""quoting" must be an integer, not {}"#,
+                            obj.class().name()
+                        )));
                     }
-                    // TODO: Maybe need to update the obj from HashMap
+                    obj.downcast_ref::<PyInt>()
+                        .unwrap()
+                        .try_to_primitive::<i32>(vm)?
                 }
-                DialectItem::Obj(o) => Ok(self.update_py_dialect(o.clone())),
-                DialectItem::None => Ok(self.update_py_dialect(PyDialect {
-                    delimiter: b',',
-                    quotechar: Some(b'"'),
-                    escapechar: None,
-                    doublequote: true,
-                    skipinitialspace: false,
-                    lineterminator: "\r\n".to_owned(),
-                    quoting: QuoteStyle::Minimal,
-                    strict: false,
-                })),
-            }?;
+                None => QuoteStyle::Minimal as i32,
+            };
+            let skipinitialspace = match &self.skipinitialspace {
+                Some(obj) => obj.try_to_bool(vm)?,
+                None => false,
+            };
+            let strict = match &self.strict {
+                Some(obj) => obj.try_to_bool(vm)?,
+                None => false,
+            };
+
+            // Validate the quoting value only after all field conversions.
+            let quoting = QuoteStyle::try_from(quoting as isize)
+                .map_err(|_| vm.new_type_error(r#"bad "quoting" value"#))?;
+            let quoting = if quotechar.is_none() && self.quoting.is_none() {
+                QuoteStyle::None
+            } else {
+                quoting
+            };
+            if quotechar.is_none() && quoting != QuoteStyle::None {
+                return Err(vm.new_type_error("quotechar must be set if quoting enabled"));
+            }
+            let dialect = PyDialect {
+                delimiter,
+                quotechar,
+                escapechar,
+                doublequote,
+                skipinitialspace,
+                lineterminator,
+                quoting,
+                strict,
+            };
             validate_dialect(vm, &dialect)?;
             Ok(dialect)
         }
@@ -1246,7 +1012,7 @@ mod _csv {
     fn field_needs_quotes(data: &[u8], dialect: &PyDialect) -> bool {
         data.iter().any(|&byte| {
             byte == dialect.delimiter
-                || dialect.quotechar == Some(byte)
+                || (dialect.doublequote && dialect.quotechar == Some(byte))
                 || matches!(byte, b'\r' | b'\n')
         }) || data_contains_lineterminator_char(data, dialect)
     }
diff --git a/crates/stdlib/src/elementtree.rs b/crates/stdlib/src/elementtree.rs
index 57c793d5494..73e46d0d6d0 100644
--- a/crates/stdlib/src/elementtree.rs
+++ b/crates/stdlib/src/elementtree.rs
@@ -26,10 +26,10 @@ pub(crate) mod _elementtree {
     use crate::vm::{
         AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
         VirtualMachine, atomic_func,
-        builtins::{PyDict, PyDictRef, PyList, PyModule, PyStr, PyType, PyTypeRef},
+        builtins::{PyAnyDict, PyDict, PyDictRef, PyList, PyModule, PyStr, PyType, PyTypeRef},
         function::{FuncArgs, PySetterValue},
         protocol::{PyMappingMethods, PyNumberMethods, PySequenceMethods},
-        sliceable::{SequenceIndex, SliceableSequenceOp},
+        sliceable::{NameElement, SequenceIndex, SliceableSequenceOp},
         types::{
             AsMapping, AsNumber, AsSequence, Constructor, DefaultConstructor, Initializer,
             IterNext, Iterable, Representable, SelfIter,
@@ -174,7 +174,7 @@ pub(crate) mod _elementtree {
         tail: Joined,
         /// `None` until an attribute is actually needed, mirroring the C
         /// implementation's lazily allocated `extra->attrib`.
-        attrib: Option<PyDictRef>,
+        attrib: Option<PyRef<PyAnyDict>>,
         children: Vec<PyObjectRef>,
     }
 
@@ -222,8 +222,9 @@ pub(crate) mod _elementtree {
     }
 
     impl PyElement {
-        fn new(tag: PyObjectRef, attrib: Option<PyDictRef>, vm: &VirtualMachine) -> Self {
-            let attrib = attrib.filter(|d| !d.is_empty());
+        fn new(tag: PyObjectRef, attrib: Option<PyRef<PyAnyDict>>, vm: &VirtualMachine) -> Self {
+            // CPython elides only empty exact dicts, preserving frozen/subclass identity.
+            let attrib = attrib.filter(|d| !d.class().is(vm.ctx.types.dict_type) || !d.is_empty());
             Self {
                 inner: PyRwLock::new(ElementInner {
                     tag,
@@ -287,15 +288,15 @@ pub(crate) mod _elementtree {
             Ok(joined)
         }
 
-        fn attrib_or_new(&self, vm: &VirtualMachine) -> PyDictRef {
+        fn attrib_or_new(&self, vm: &VirtualMachine) -> PyRef<PyAnyDict> {
             let mut inner = self.inner.write();
             inner
                 .attrib
-                .get_or_insert_with(|| vm.ctx.new_dict())
+                .get_or_insert_with(|| vm.ctx.new_dict().into())
                 .clone()
         }
 
-        fn attrib_opt(&self) -> Option<PyDictRef> {
+        fn attrib_opt(&self) -> Option<PyRef<PyAnyDict>> {
             self.inner.read().attrib.clone()
         }
     }
@@ -356,14 +357,21 @@ pub(crate) mod _elementtree {
         let positional_attrib = args.args.get(extra_positional + 1).cloned();
         let attrib = match positional_attrib {
             Some(obj) => {
-                let dict = obj.downcast::<PyDict>().map_err(|obj| {
-                    vm.new_type_error(format!(
-                        "{func_name}() argument {} must be dict, not {}",
-                        extra_positional + 2,
-                        obj.class().name()
-                    ))
-                })?;
-                let copied = dict.copy().into_ref(&vm.ctx);
+                let expected = if extra_positional == 0 {
+                    "dict or frozendict"
+                } else {
+                    "dict"
+                };
+                let dict = PyAnyDict::from_object(&obj)
+                    .filter(|_| extra_positional == 0 || obj.downcastable::<PyDict>())
+                    .ok_or_else(|| {
+                        vm.new_type_error(format!(
+                            "{func_name}() argument {} must be {expected}, not {}",
+                            extra_positional + 2,
+                            obj.class().name()
+                        ))
+                    })?;
+                let copied = dict.copy_as_dict(vm)?.into_ref(&vm.ctx);
                 for (key, value) in args.kwargs.drain(..) {
                     copied.set_item(&key, value, vm)?;
                 }
@@ -373,13 +381,13 @@ pub(crate) mod _elementtree {
                 let popped = args.kwargs.shift_remove("attrib");
                 let copied = match popped {
                     Some(obj) => {
-                        let dict = obj.downcast::<PyDict>().map_err(|obj| {
+                        let dict = PyAnyDict::from_object(&obj).ok_or_else(|| {
                             vm.new_type_error(format!(
-                                "attrib must be dict, not {}",
+                                "attrib must be dict or frozendict, not {}",
                                 obj.class().name()
                             ))
                         })?;
-                        dict.copy().into_ref(&vm.ctx)
+                        dict.copy_as_dict(vm)?.into_ref(&vm.ctx)
                     }
                     None => vm.ctx.new_dict(),
                 };
@@ -454,7 +462,7 @@ pub(crate) mod _elementtree {
 
         fn init(zelf: &Py<Self>, args: Self::Args, vm: &VirtualMachine) -> PyResult<()> {
             let (tag, attrib) = parse_attrib_args(args, "Element", 0, vm)?;
-            let attrib = attrib.filter(|d| !d.is_empty());
+            let attrib = attrib.filter(|d| !d.is_empty()).map(Into::into);
             let _recycle = {
                 let mut inner = zelf.inner.write();
                 let old_attrib = if attrib.is_some() {
@@ -525,16 +533,21 @@ pub(crate) mod _elementtree {
         }
 
         #[pygetset]
-        fn attrib(zelf: &Py<Self>, vm: &VirtualMachine) -> PyDictRef {
+        fn attrib(zelf: &Py<Self>, vm: &VirtualMachine) -> PyRef<PyAnyDict> {
             zelf.attrib_or_new(vm)
         }
 
         #[pygetset(setter)]
         fn set_attrib(zelf: &Py<Self>, value: PySetterValue, vm: &VirtualMachine) -> PyResult<()> {
             let value = setter_value(value, vm)?;
-            let dict = value.downcast::<PyDict>().map_err(|obj| {
-                vm.new_type_error(format!("attrib must be dict, not {}", obj.class().name()))
-            })?;
+            let dict = PyAnyDict::from_object(&value)
+                .ok_or_else(|| {
+                    vm.new_type_error(format!(
+                        "attrib must be dict or frozendict, not {}",
+                        value.class().name()
+                    ))
+                })?
+                .to_owned();
             let _recycle = zelf.inner.write().attrib.replace(dict);
             Ok(())
         }
@@ -578,7 +591,21 @@ pub(crate) mod _elementtree {
 
         #[pymethod]
         fn remove(zelf: &Py<Self>, subelement: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
-            check_element(&subelement, vm)?;
+            if !subelement.downcastable::<Self>() {
+                let name = if vm.is_none(&subelement) {
+                    "None".into()
+                } else {
+                    subelement.class().slot_name()
+                };
+                let mut end = name.len().min(50);
+                while !name.is_char_boundary(end) {
+                    end -= 1;
+                }
+                return Err(vm.new_type_error(format!(
+                    "remove() argument must be xml.etree.ElementTree.Element, not {}",
+                    &name[..end]
+                )));
+            }
             // Identity first, then equality, the way `element_remove` does;
             // the equality test can run arbitrary code, so the lock is
             // dropped for it and the list re-read afterwards.
@@ -631,7 +658,7 @@ pub(crate) mod _elementtree {
             let Some(attrib) = zelf.attrib_opt() else {
                 return Ok(default);
             };
-            Ok(attrib.get_item_opt(&*args.key, vm)?.unwrap_or(default))
+            Ok(attrib.inner_getitem_opt(&*args.key, vm)?.unwrap_or(default))
         }
 
         #[pymethod]
@@ -650,7 +677,7 @@ pub(crate) mod _elementtree {
             let Some(attrib) = zelf.attrib_opt() else {
                 return vec![];
             };
-            attrib.into_iter().map(|(k, _)| k).collect()
+            attrib.keys_vec()
         }
 
         #[pymethod]
@@ -659,6 +686,7 @@ pub(crate) mod _elementtree {
                 return vec![];
             };
             attrib
+                .items_vec()
                 .into_iter()
                 .map(|(k, v)| vm.ctx.new_tuple(vec![k, v]).into())
                 .collect()
@@ -678,7 +706,7 @@ pub(crate) mod _elementtree {
                 ))
             })?;
             let attrib = attrib.copy().into_ref(&vm.ctx);
-            create_element(zelf.class().to_owned(), tag, Some(attrib), vm)
+            create_element(zelf.class().to_owned(), tag, Some(attrib.into()), vm)
         }
 
         #[pymethod]
@@ -833,7 +861,10 @@ pub(crate) mod _elementtree {
         fn __getstate__(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyDictRef> {
             let inner = zelf.inner.read();
             let children = vm.ctx.new_list(inner.children.clone());
-            let attrib = inner.attrib.clone().unwrap_or_else(|| vm.ctx.new_dict());
+            let attrib = inner
+                .attrib
+                .clone()
+                .unwrap_or_else(|| vm.ctx.new_dict().into());
             let text = inner.text.obj.clone();
             let tail = inner.tail.obj.clone();
             let tag = inner.tag.clone();
@@ -877,14 +908,16 @@ pub(crate) mod _elementtree {
                 None => None,
             };
             let attrib = match attrib {
-                Some(attrib) if !vm.is_none(&attrib) => {
-                    Some(attrib.downcast::<PyDict>().map_err(|obj| {
-                        vm.new_type_error(format!(
-                            "attrib must be dict, not {}",
-                            obj.class().name()
-                        ))
-                    })?)
-                }
+                Some(attrib) if !vm.is_none(&attrib) => Some(
+                    PyAnyDict::from_object(&attrib)
+                        .ok_or_else(|| {
+                            vm.new_type_error(format!(
+                                "attrib must be dict or frozendict, not {}",
+                                attrib.class().name()
+                            ))
+                        })?
+                        .to_owned(),
+                ),
                 _ => None,
             };
             let new_text = match text {
@@ -1028,7 +1061,7 @@ pub(crate) mod _elementtree {
     }
 
     fn sequence_index(vm: &VirtualMachine, needle: &PyObject) -> PyResult<SequenceIndex> {
-        SequenceIndex::try_from_borrowed_object(vm, needle, "element")
+        SequenceIndex::try_from_borrowed_object::<NameElement>(vm, needle)
             .map_err(|_| vm.new_type_error("element indices must be integers"))
     }
 
@@ -1037,7 +1070,7 @@ pub(crate) mod _elementtree {
     fn create_element(
         cls: PyTypeRef,
         tag: PyObjectRef,
-        attrib: Option<PyDictRef>,
+        attrib: Option<PyRef<PyAnyDict>>,
         vm: &VirtualMachine,
     ) -> PyResult {
         let element = PyElement::new(tag, attrib, vm);
@@ -1087,11 +1120,14 @@ pub(crate) mod _elementtree {
         };
         let tag = deepcopy_obj(&tag, memo, vm)?;
         let attrib = match attrib {
-            Some(attrib) => Some(
-                deepcopy_obj(attrib.as_object(), memo, vm)?
-                    .downcast::<PyDict>()
-                    .map_err(|_| vm.new_type_error("attrib must be dict"))?,
-            ),
+            Some(attrib) => {
+                let copied = deepcopy_obj(attrib.as_object(), memo, vm)?;
+                Some(
+                    PyAnyDict::from_object(&copied)
+                        .ok_or_else(|| vm.new_type_error("attrib must be dict or frozendict"))?
+                        .to_owned(),
+                )
+            }
             None => None,
         };
         let new = create_element(zelf.class().to_owned(), tag, attrib, vm)?;
@@ -1265,7 +1301,7 @@ pub(crate) mod _elementtree {
             ))
         })?;
         let (tag, attrib) = parse_attrib_args(args, "SubElement", 1, vm)?;
-        let element = create_element(parent.class().to_owned(), tag, attrib, vm)?;
+        let element = create_element(parent.class().to_owned(), tag, attrib.map(Into::into), vm)?;
         parent.push(element.clone());
         Ok(element)
     }
@@ -1541,7 +1577,9 @@ pub(crate) mod _elementtree {
             let factory = self.state.read().element_factory.clone();
             let node = match factory {
                 // CPython adopts the caller's dict rather than copying it.
-                None => PyElement::new(tag, attrib, vm).into_ref(&vm.ctx).into(),
+                None => PyElement::new(tag, attrib.map(Into::into), vm)
+                    .into_ref(&vm.ctx)
+                    .into(),
                 Some(factory) => {
                     let attrib = attrib.unwrap_or_else(|| vm.ctx.new_dict());
                     factory.call((tag, attrib), vm)?
diff --git a/crates/stdlib/src/faulthandler.rs b/crates/stdlib/src/faulthandler.rs
index 267326933c2..c017f0bcd92 100644
--- a/crates/stdlib/src/faulthandler.rs
+++ b/crates/stdlib/src/faulthandler.rs
@@ -252,10 +252,10 @@ mod decl {
     #[cfg(any(unix, windows))]
     fn dump_all_threads(fd: i32, vm: &VirtualMachine) {
         // Get all threads' frame stacks from the shared registry
-        // unix: stop-the-world so every other thread is parked at a safepoint
+        // Stop the world so every other thread is parked at a safepoint
         // and its frame chain is quiescent and alive while we walk it (matches
         // faulthandler.dump_traceback running with the GIL held).
-        #[cfg(all(unix, feature = "threading"))]
+        #[cfg(feature = "threading")]
         {
             use core::sync::atomic::Ordering;
             let current_tid = rustpython_vm::stdlib::_thread::get_ident();
@@ -302,49 +302,6 @@ mod decl {
             dump_live_frames(fd);
         }
 
-        #[cfg(all(not(unix), feature = "threading"))]
-        {
-            let current_tid = rustpython_vm::stdlib::_thread::get_ident();
-            let registry = vm.state.thread_frames.lock();
-
-            // Dump non-current threads using top_iframe, which includes
-            // both FrameObject and stack-allocated frames.
-            #[expect(
-                clippy::iter_over_hash_type,
-                reason = "Iteration order doesn't matter here"
-            )]
-            for (&tid, slot) in registry.iter() {
-                if tid == current_tid {
-                    continue;
-                }
-
-                let iframe_ptr = slot.top_iframe.load(core::sync::atomic::Ordering::Relaxed)
-                    as *const rustpython_vm::frame::InterpreterFrame;
-                write_thread_id(fd, tid, false);
-                if iframe_ptr.is_null() {
-                    puts(fd, "  <no Python frame>\n");
-                } else {
-                    let mut cur = iframe_ptr;
-                    let mut depth = 0;
-                    while !cur.is_null() && depth < 100 {
-                        let iframe = unsafe { &*cur };
-                        dump_iframe(fd, iframe);
-                        depth += 1;
-                        cur = iframe.previous();
-                    }
-                    if depth >= 100 && !cur.is_null() {
-                        puts(fd, "  ...\n");
-                    }
-                }
-                puts(fd, "\n");
-            }
-
-            // Now dump current thread from its live frame chain
-            // (includes stack-allocated iframes without FrameObject).
-            write_thread_id(fd, current_tid, true);
-            dump_live_frames(fd);
-        }
-
         #[cfg(not(feature = "threading"))]
         {
             let _ = vm;
@@ -451,7 +408,7 @@ mod decl {
         host_faulthandler::signal_default_and_raise(signum);
 
         // Fallback
-        rustpython_host_env::os::exit(1);
+        rustpython_host_env::os::exit_immediately(1);
     }
 
     // Windows vectored exception handler (faulthandler.c:417-480)
@@ -679,10 +636,9 @@ mod decl {
                             // frames are still alive because the target thread
                             // is executing (inside a blocking call).
                             for (tid, slot) in &thread_frame_slots {
-                                let iframe_ptr = slot
-                                    .top_iframe
-                                    .load(core::sync::atomic::Ordering::Relaxed)
-                                    as *const rustpython_vm::frame::InterpreterFrame;
+                                let iframe_ptr =
+                                    slot.top_iframe.load(core::sync::atomic::Ordering::Relaxed)
+                                        as *const rustpython_vm::frame::InterpreterFrame;
                                 write_thread_id(fd, *tid, false);
                                 if iframe_ptr.is_null() {
                                     puts(fd, "  <no Python frame>\n");
@@ -703,10 +659,9 @@ mod decl {
                         }
                         all(not(unix), feature = "threading") => {
                             for (tid, slot) in &thread_frame_slots {
-                                let iframe_ptr = slot
-                                    .top_iframe
-                                    .load(core::sync::atomic::Ordering::Relaxed)
-                                    as *const rustpython_vm::frame::InterpreterFrame;
+                                let iframe_ptr =
+                                    slot.top_iframe.load(core::sync::atomic::Ordering::Relaxed)
+                                        as *const rustpython_vm::frame::InterpreterFrame;
                                 write_thread_id(fd, *tid, false);
                                 if iframe_ptr.is_null() {
                                     puts(fd, "  <no Python frame>\n");
@@ -732,7 +687,7 @@ mod decl {
                     }
 
                     if exit {
-                        rustpython_host_env::os::exit(1);
+                        rustpython_host_env::os::exit_immediately(1);
                     }
                 }
             }
diff --git a/crates/stdlib/src/fcntl.rs b/crates/stdlib/src/fcntl.rs
index a6dfdeb63b1..f04304de059 100644
--- a/crates/stdlib/src/fcntl.rs
+++ b/crates/stdlib/src/fcntl.rs
@@ -8,9 +8,8 @@ mod fcntl {
 
     use crate::vm::{
         PyResult, VirtualMachine,
-        builtins::PyIntRef,
         convert::ToPyException,
-        function::{ArgMemoryBuffer, ArgStrOrBytesLike, Either, OptionalArg},
+        function::{ArgIndex, ArgMemoryBuffer, ArgStrOrBytesLike, Either, OptionalArg},
         stdlib::_io,
     };
     use rustpython_host_env::io::is_interrupted_error;
@@ -86,7 +85,7 @@ mod fcntl {
     #[derive(FromArgs)]
     struct FcntlArg {
         #[pyarg(positional, default = 0)]
-        arg: Either<ArgStrOrBytesLike, PyIntRef>,
+        arg: Either<ArgStrOrBytesLike, ArgIndex>,
     }
 
     #[pyfunction]
@@ -114,7 +113,7 @@ mod fcntl {
                 )?;
                 return Ok(vm.ctx.new_bytes(buf[..arg_len].to_vec()).into());
             }
-            Either::B(i) => i.as_u32_mask(),
+            Either::B(i) => i.as_ref().as_u32_mask(),
         };
         let ret = retry_on_eintr(
             vm,
@@ -213,9 +212,9 @@ mod fcntl {
     #[derive(FromArgs)]
     struct LockfArgs {
         #[pyarg(positional, default = 0)]
-        len: PyIntRef,
+        len: ArgIndex,
         #[pyarg(positional, default = 0)]
-        start: PyIntRef,
+        start: ArgIndex,
         #[pyarg(positional, default)]
         whence: i32,
     }
@@ -229,8 +228,8 @@ mod fcntl {
         LockfArgs { len, start, whence }: LockfArgs,
         vm: &VirtualMachine,
     ) -> PyResult {
-        let start = start.try_to_primitive(vm)?;
-        let len = len.try_to_primitive(vm)?;
+        let start = start.as_ref().try_to_primitive(vm)?;
+        let len = len.as_ref().try_to_primitive(vm)?;
         // F_LOCK and F_TLOCK differ in exactly this: the first one waits.
         let ret = retry_on_eintr(
             vm,
diff --git a/crates/stdlib/src/grp.rs b/crates/stdlib/src/grp.rs
index 5e73f5648d4..fe04813964a 100644
--- a/crates/stdlib/src/grp.rs
+++ b/crates/stdlib/src/grp.rs
@@ -5,9 +5,10 @@ pub(crate) use grp::module_def;
 mod grp {
     use crate::vm::{
         PyObjectRef, PyResult, VirtualMachine,
-        builtins::{PyIntRef, PyListRef, PyUtf8StrRef},
-        convert::{IntoPyException, ToPyObject},
+        builtins::{PyListRef, PyUtf8StrRef},
+        convert::ToPyObject,
         exceptions,
+        function::ArgIndex,
         types::PyStructSequence,
     };
     use core::hint::cold_path;
@@ -44,26 +45,23 @@ mod grp {
     #[derive(FromArgs)]
     struct GetGrGidArgs {
         #[pyarg(any)]
-        id: PyIntRef,
+        id: ArgIndex,
     }
 
     #[pyfunction]
     fn getgrgid(id: GetGrGidArgs, vm: &VirtualMachine) -> PyResult<GroupData> {
-        let gid = id.id;
+        let gid = id.id.into_int_ref();
         let gr_gid = gid.as_bigint();
         let gid = host_grp::gid_t::try_from(gr_gid).ok();
         let group = gid
-            .map(host_grp::getgrgid)
-            .transpose()
-            .map_err(|err| err.into_pyexception(vm))?
-            .flatten();
-        let group = group.ok_or_else(|| {
-            vm.new_key_error(
-                vm.ctx
-                    .new_str(format!("getgrgid: group id {gr_gid} not found"))
-                    .into(),
-            )
-        })?;
+            .and_then(|gid| host_grp::getgrgid(gid).ok().flatten())
+            .ok_or_else(|| {
+                vm.new_key_error(
+                    vm.ctx
+                        .new_str(format!("getgrgid: group id {gr_gid} not found"))
+                        .into(),
+                )
+            })?;
         Ok(GroupData::from_group(group, vm))
     }
 
@@ -81,8 +79,7 @@ mod grp {
             return Err(exceptions::nul_char_error(vm));
         }
         let gr_name = name.as_str();
-        let group = host_grp::getgrnam(gr_name).map_err(|err| err.into_pyexception(vm))?;
-        let group = group.ok_or_else(|| {
+        let group = host_grp::getgrnam(gr_name).ok().flatten().ok_or_else(|| {
             vm.new_key_error(
                 vm.ctx
                     .new_str(format!("getgrnam: group name {gr_name} not found"))
diff --git a/crates/stdlib/src/hashlib.rs b/crates/stdlib/src/hashlib.rs
index f28f27b1055..76b17c999ca 100644
--- a/crates/stdlib/src/hashlib.rs
+++ b/crates/stdlib/src/hashlib.rs
@@ -8,7 +8,7 @@ pub(crate) use _hashlib::module_def;
 #[pymodule]
 pub(crate) mod _hashlib {
     use crate::vm::{
-        Py, PyObject, PyObjectRef, PyPayload, PyResult, VirtualMachine,
+        Py, PyObject, PyObjectRef, PyPayload, PyResult, TryFromObject, VirtualMachine,
         builtins::{
             PyBaseExceptionRef, PyBytes, PyFrozenSet, PyStr, PyType, PyTypeRef, PyUtf8StrRef,
             PyValueError,
@@ -67,11 +67,35 @@ pub(crate) mod _hashlib {
         dict.into()
     }
 
+    #[derive(Debug)]
+    struct HashName(PyUtf8StrRef);
+
+    impl TryFromObject for HashName {
+        fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
+            if !obj.downcastable::<PyStr>() {
+                let name = if vm.is_none(&obj) {
+                    "None".into()
+                } else {
+                    obj.class().slot_name()
+                };
+                let mut end = name.len().min(50);
+                while !name.is_char_boundary(end) {
+                    end -= 1;
+                }
+                return Err(vm.new_type_error(format!(
+                    "new() argument 'name' must be str, not {}",
+                    &name[..end]
+                )));
+            }
+            PyUtf8StrRef::try_from_object(vm, obj).map(Self)
+        }
+    }
+
     #[derive(FromArgs, Debug)]
     #[allow(unused)]
     struct NewHashArgs {
         #[pyarg(any)]
-        name: PyUtf8StrRef,
+        name: HashName,
         // Missing still allows the string keyword; b'' does not.
         #[pyarg(any, optional, py_default = "b''")]
         data: OptionalArg<ArgBytesLike>,
@@ -220,7 +244,18 @@ pub(crate) mod _hashlib {
     ) -> PyResult<OptionalArg<ArgBytesLike>> {
         match (data.into_option(), string) {
             (Some(d), None) => Ok(OptionalArg::Present(d)),
-            (None, Some(s)) => Ok(OptionalArg::Present(s)),
+            (None, Some(s)) => {
+                crate::vm::stdlib::_warnings::warn(
+                    vm.ctx.exceptions.deprecation_warning,
+                    "the 'string' keyword parameter is deprecated since Python 3.15 \
+                     and slated for removal in Python 3.19; use the 'data' keyword \
+                     parameter or pass the data to hash as a positional argument instead"
+                        .to_owned(),
+                    1,
+                    vm,
+                )?;
+                Ok(OptionalArg::Present(s))
+            }
             (None, None) => Ok(OptionalArg::Missing),
             (Some(_), Some(_)) => Err(vm.new_type_error(
                 "'data' and 'string' are mutually exclusive \
@@ -785,7 +820,7 @@ pub(crate) mod _hashlib {
     #[pyfunction(name = "new")]
     fn hashlib_new(args: NewHashArgs, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
         let data = resolve_data(args.data, args.string, vm)?;
-        match args.name.as_str().to_lowercase().as_str() {
+        match args.name.0.as_str().to_lowercase().as_str() {
             "md5" => Ok(new_fixed_hasher("md5", data).into_pyobject(vm)),
             "sha1" => Ok(new_fixed_hasher("sha1", data).into_pyobject(vm)),
             "sha224" => Ok(new_fixed_hasher("sha224", data).into_pyobject(vm)),
diff --git a/crates/stdlib/src/json.rs b/crates/stdlib/src/json.rs
index 8b9da96cc8e..b962f457081 100644
--- a/crates/stdlib/src/json.rs
+++ b/crates/stdlib/src/json.rs
@@ -5,7 +5,8 @@ mod _json {
     use crate::vm::{
         AsObject, Py, PyObject, PyObjectRef, PyPayload, PyResult, VirtualMachine,
         builtins::{
-            PyBaseExceptionRef, PyDict, PyFloat, PyInt, PyList, PyStr, PyStrRef, PyTuple, PyType,
+            PyAnyDict, PyBaseExceptionRef, PyDict, PyFloat, PyInt, PyList, PyStr, PyStrRef,
+            PyTuple, PyType,
         },
         convert::ToPyResult,
         function::{IntoFuncArgs, OptionalArg},
@@ -51,6 +52,7 @@ mod _json {
         strict: bool,
         object_hook: Option<PyObjectRef>,
         object_pairs_hook: Option<PyObjectRef>,
+        array_hook: Option<PyObjectRef>,
         parse_float: Option<PyObjectRef>,
         parse_int: Option<PyObjectRef>,
         parse_constant: PyObjectRef,
@@ -64,6 +66,7 @@ mod _json {
             let strict = ctx.get_attr("strict", vm)?.try_to_bool(vm)?;
             let object_hook = vm.option_if_none(ctx.get_attr("object_hook", vm)?);
             let object_pairs_hook = vm.option_if_none(ctx.get_attr("object_pairs_hook", vm)?);
+            let array_hook = vm.option_if_none(ctx.get_attr("array_hook", vm)?);
             let parse_float = ctx.get_attr("parse_float", vm)?;
             let parse_float = if vm.is_none(&parse_float) || parse_float.is(vm.ctx.types.float_type)
             {
@@ -83,6 +86,7 @@ mod _json {
                 strict,
                 object_hook,
                 object_pairs_hook,
+                array_hook,
                 parse_float,
                 parse_int,
                 parse_constant,
@@ -93,6 +97,11 @@ mod _json {
 
     #[pyclass(with(Callable, Constructor))]
     impl JsonScanner {
+        #[pygetset]
+        fn array_hook(zelf: &Py<Self>) -> Option<PyObjectRef> {
+            zelf.array_hook.clone()
+        }
+
         fn parse(
             &self,
             pystr: PyStrRef,
@@ -437,7 +446,7 @@ mod _json {
 
             // Check for empty array
             if bytes.get(byte_idx) == Some(&b']') {
-                return Ok((vm.ctx.new_list(vec![]).into(), char_idx + 1, byte_idx + 1));
+                return self.finalize_array(vec![], char_idx + 1, byte_idx + 1, vm);
             }
 
             let mut values: Vec<PyObjectRef> = Vec::new();
@@ -493,7 +502,23 @@ mod _json {
                 }
             }
 
-            Ok((vm.ctx.new_list(values).into(), char_idx, byte_idx))
+            self.finalize_array(values, char_idx, byte_idx, vm)
+        }
+
+        fn finalize_array(
+            &self,
+            values: Vec<PyObjectRef>,
+            end_char_idx: usize,
+            end_byte_idx: usize,
+            vm: &VirtualMachine,
+        ) -> PyResult<(PyObjectRef, usize, usize)> {
+            let values = vm.ctx.new_list(values);
+            let result = if let Some(ref hook) = self.array_hook {
+                hook.call((values,), vm)?
+            } else {
+                values.into()
+            };
+            Ok((result, end_char_idx, end_byte_idx))
         }
 
         /// Finalize object construction with hooks.
@@ -546,7 +571,7 @@ mod _json {
             // `'[' * 50000 + ']' * 50000` overflows the native Rust stack and
             // crashes the process with SIGSEGV. Matches CPython's
             // _Py_EnterRecursiveCall in Modules/_json.c.
-            vm.with_recursion("while decoding a JSON object from a string", || {
+            vm.with_recursion(" while decoding a JSON object from a string", || {
                 let bytes = pystr.as_bytes();
                 let wtf8 = pystr.as_wtf8();
 
@@ -1126,18 +1151,20 @@ mod _json {
             Ok(())
         }
 
-        /// Fetch `dct.items()` for encoding. For an exact `dict` this reads
+        /// Fetch `dct.items()` for encoding. For an exact `dict` or `frozendict` this reads
         /// the native table directly (matching CPython's fast path); for a
-        /// `dict` subclass (e.g. `collections.OrderedDict`) it calls the
+        /// subclass (e.g. `collections.OrderedDict`) it calls the
         /// real (possibly overridden) `.items()` method instead, so a
         /// subclass's custom ordering/behavior is respected.
         fn dict_items(
             &self,
             obj: &PyObject,
-            dict: &Py<PyDict>,
+            dict: &PyAnyDict,
             vm: &VirtualMachine,
         ) -> PyResult<Vec<(PyObjectRef, PyObjectRef)>> {
-            if obj.class().is(vm.ctx.types.dict_type) {
+            if obj.class().is(vm.ctx.types.dict_type)
+                || obj.class().is(vm.ctx.types.frozendict_type)
+            {
                 return Ok(dict.items_vec());
             }
             let items_obj = obj.get_attr("items", vm)?.call((), vm)?;
@@ -1155,11 +1182,15 @@ mod _json {
         fn encode_dict(
             &self,
             obj: &PyObject,
-            dict: &Py<PyDict>,
+            dict: &PyAnyDict,
             level: isize,
             out: &mut Wtf8Buf,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
+            if dict.is_empty() {
+                out.push_str("{}");
+                return Ok(());
+            }
             let mut items = self.dict_items(obj, dict, vm)?;
             if items.is_empty() {
                 out.push_str("{}");
@@ -1254,7 +1285,7 @@ mod _json {
             out: &mut Wtf8Buf,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            vm.with_recursion("while encoding a JSON object", || {
+            vm.with_recursion(" while encoding a JSON object", || {
                 if let Some(s) = obj.downcast_ref::<PyStr>() {
                     self.write_str_obj(obj, s, out, vm)
                 } else if vm.is_none(obj) {
@@ -1285,7 +1316,7 @@ mod _json {
                 } else if let Some(tuple) = obj.downcast_ref::<PyTuple>() {
                     let slice = tuple.as_slice();
                     self.encode_list(obj, level, out, vm, || slice.len(), |i| slice[i].clone())
-                } else if let Some(dict) = obj.downcast_ref::<PyDict>() {
+                } else if let Some(dict) = PyAnyDict::from_object(obj) {
                     self.encode_dict(obj, dict, level, out, vm)
                 } else {
                     self.encode_default(obj, level, out, vm)
@@ -1323,30 +1354,25 @@ mod _json {
     #[pyfunction]
     fn scanstring(
         s: PyStrRef,
-        end: usize,
+        end: isize,
         strict: OptionalArg<bool>,
         vm: &VirtualMachine,
     ) -> PyResult<(Wtf8Buf, usize)> {
         flame_guard!("_json::scanstring");
         let wtf8 = s.as_wtf8();
 
+        if end < 0 || end as usize > s.char_len() {
+            return Err(vm.new_value_error("end is out of bounds"));
+        }
+        let end = end as usize;
+
         // Convert char index `end` to byte index
         let byte_idx = if end == 0 {
             0
         } else {
             wtf8.code_point_indices()
                 .nth(end)
-                .map(|(i, _)| i)
-                .ok_or_else(|| {
-                    py_decode_error(
-                        json::DecodeError {
-                            msg: "Unterminated string starting at".to_owned(),
-                            pos: end - 1,
-                        },
-                        s.clone(),
-                        vm,
-                    )
-                })?
+                .map_or(wtf8.len(), |(i, _)| i)
         };
 
         let (result, end_char_idx, _bytes_consumed) =
diff --git a/crates/stdlib/src/lib.rs b/crates/stdlib/src/lib.rs
index bc3350231c3..5eb8062ced7 100644
--- a/crates/stdlib/src/lib.rs
+++ b/crates/stdlib/src/lib.rs
@@ -232,6 +232,7 @@ pub fn stdlib_module_defs(ctx: &Context) -> Vec<&'static builtins::PyModuleDef>
         locale::module_def(ctx),
         lzma::module_def(ctx),
         math::module_def(ctx),
+        math::integer_module_def(ctx),
         md5::module_def(ctx),
         #[cfg(all(feature = "host_env", any(unix, windows)))]
         mmap::module_def(ctx),
diff --git a/crates/stdlib/src/locale.rs b/crates/stdlib/src/locale.rs
index aba3b22433f..8195302d356 100644
--- a/crates/stdlib/src/locale.rs
+++ b/crates/stdlib/src/locale.rs
@@ -194,9 +194,7 @@ mod _locale {
     fn check_locale_name(locale: &str) -> bool {
         if let Some(dot_pos) = locale.find('.') {
             let encoding_part = &locale[dot_pos + 1..];
-            // Find the end of encoding (could be followed by '@' modifier)
-            let encoding_len = encoding_part.find('@').unwrap_or(encoding_part.len());
-            encoding_len <= MAX_CP_LEN
+            encoding_part.len() <= MAX_CP_LEN
         } else {
             true
         }
diff --git a/crates/stdlib/src/lzma.rs b/crates/stdlib/src/lzma.rs
index 1e539c821d5..068307a4920 100644
--- a/crates/stdlib/src/lzma.rs
+++ b/crates/stdlib/src/lzma.rs
@@ -8,7 +8,7 @@ mod _lzma {
     use alloc::fmt;
     use core::sync::atomic::{AtomicBool, AtomicI32, Ordering};
     use rustpython_common::{compression::lzma as backend, lock::PyMutex};
-    use rustpython_vm::builtins::{PyBaseExceptionRef, PyBytes, PyDict, PyType, PyTypeRef};
+    use rustpython_vm::builtins::{PyBaseExceptionRef, PyBytes, PyDict, PyStr, PyType, PyTypeRef};
     use rustpython_vm::function::{ArgBytesLike, ItemDoc};
     use rustpython_vm::object::PyAtomicRef;
     use rustpython_vm::types::Constructor;
@@ -129,6 +129,30 @@ mod _lzma {
         })
     }
 
+    /// A key the filter does not take makes the whole specifier invalid, as
+    /// the spec dict is read as keyword arguments.
+    fn check_filter_spec_keys(
+        spec: &PyObject,
+        allowed: &[&str],
+        error: &str,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        let dict = spec.downcast_ref::<PyDict>().ok_or_else(|| {
+            vm.new_type_error("Filter specifier must be a dict or dict-like object")
+        })?;
+        for key in dict.keys_vec() {
+            let ok = key.downcast_ref::<PyStr>().is_some_and(|k| {
+                allowed
+                    .iter()
+                    .any(|a| k.as_wtf8().as_bytes() == a.as_bytes())
+            });
+            if !ok {
+                return Err(vm.new_value_error(error.to_owned()));
+            }
+        }
+        Ok(())
+    }
+
     fn parse_filter_chain_item(
         spec: &PyObject,
         vm: &VirtualMachine,
@@ -136,6 +160,23 @@ mod _lzma {
         let mut parsed = filter_spec_with_id(spec, vm)?;
         match parsed.id {
             FILTER_LZMA1 | FILTER_LZMA2 => {
+                check_filter_spec_keys(
+                    spec,
+                    &[
+                        "id",
+                        "preset",
+                        "dict_size",
+                        "lc",
+                        "lp",
+                        "pb",
+                        "mode",
+                        "nice_len",
+                        "mf",
+                        "depth",
+                    ],
+                    "Invalid filter specifier for LZMA filter",
+                    vm,
+                )?;
                 parsed.preset = get_dict_opt_u32(spec, "preset", vm)?;
                 parsed.dict_size = get_dict_opt_u32(spec, "dict_size", vm)?;
                 parsed.lc = get_dict_opt_u32(spec, "lc", vm)?;
@@ -146,9 +187,23 @@ mod _lzma {
                 parsed.mf = get_dict_opt_u32(spec, "mf", vm)?;
                 parsed.depth = get_dict_opt_u32(spec, "depth", vm)?;
             }
-            FILTER_DELTA => parsed.dist = get_dict_opt_u32(spec, "dist", vm)?,
+            FILTER_DELTA => {
+                check_filter_spec_keys(
+                    spec,
+                    &["id", "dist"],
+                    "Invalid filter specifier for delta filter",
+                    vm,
+                )?;
+                parsed.dist = get_dict_opt_u32(spec, "dist", vm)?;
+            }
             FILTER_X86 | FILTER_POWERPC | FILTER_IA64 | FILTER_ARM | FILTER_ARMTHUMB
             | FILTER_SPARC => {
+                check_filter_spec_keys(
+                    spec,
+                    &["id", "start_offset"],
+                    "Invalid filter specifier for BCJ filter",
+                    vm,
+                )?;
                 parsed.start_offset = get_dict_opt_u32(spec, "start_offset", vm)?;
             }
             _ => {}
diff --git a/crates/stdlib/src/math.rs b/crates/stdlib/src/math.rs
index 4b23b7b7b4a..9ea0be522c6 100644
--- a/crates/stdlib/src/math.rs
+++ b/crates/stdlib/src/math.rs
@@ -1,3 +1,4 @@
+pub(crate) use _math_integer::module_def as integer_module_def;
 pub(crate) use math::module_def;
 
 use crate::vm::{VirtualMachine, builtins::PyBaseExceptionRef};
@@ -5,19 +6,31 @@ use crate::vm::{VirtualMachine, builtins::PyBaseExceptionRef};
 #[pymodule]
 mod math {
     use crate::vm::{
-        AsObject, PyObject, PyObjectRef, PyRef, PyResult, VirtualMachine,
-        builtins::{PyFloat, PyInt, PyIntRef, PyStrInterned, try_bigint_to_f64, try_f64_to_bigint},
+        AsObject, Py, PyObject, PyObjectRef, PyRef, PyResult, VirtualMachine,
+        builtins::{
+            PyFloat, PyInt, PyIntRef, PyModule, PyStrInterned, try_bigint_to_f64, try_f64_to_bigint,
+        },
         function::{
-            ArgIndex, ArgIntoFloat, ArgIterable, Either, NameCoordinates, NameIntegers,
-            OptionalArg, PosArgs,
+            ArgIndex, ArgIntoFloat, ArgIterable, Either, NameCoordinates, OptionalArg, PosArgs,
         },
         identifier,
     };
     use malachite_bigint::BigInt;
-    use num_traits::{Signed, ToPrimitive};
 
     use super::{float_repr, pymath_exception};
 
+    pub(crate) fn module_exec(vm: &VirtualMachine, module: &Py<PyModule>) -> PyResult<()> {
+        __module_exec(vm, module);
+        let integer = vm.import("_math_integer", 0)?;
+        for name in super::INTEGER_FUNCTIONS {
+            module.set_attr(name, integer.get_attr(name, vm)?, vm)?;
+        }
+        vm.sys_module
+            .get_attr("modules", vm)?
+            .set_item("math.integer", integer.clone(), vm)?;
+        module.set_attr("integer", integer, vm)
+    }
+
     // Constants
     #[pyattr]
     use core::f64::consts::{E as e, PI as pi, TAU as tau};
@@ -48,6 +61,36 @@ mod math {
         pymath::math::isnan(x.into_float())
     }
 
+    /// Return True if x is normal, and False otherwise.
+    #[pyfunction]
+    fn isnormal(x: ArgIntoFloat) -> bool {
+        pymath::math::isnormal(x.into_float())
+    }
+
+    /// Return True if x is subnormal, and False otherwise.
+    #[pyfunction]
+    fn issubnormal(x: ArgIntoFloat) -> bool {
+        pymath::math::issubnormal(x.into_float())
+    }
+
+    /// Return True if the sign of x is negative and False otherwise.
+    #[pyfunction]
+    fn signbit(x: ArgIntoFloat) -> bool {
+        pymath::math::signbit(x.into_float())
+    }
+
+    /// Return the larger of two floating-point arguments.
+    #[pyfunction]
+    fn fmax(x: ArgIntoFloat, y: ArgIntoFloat) -> f64 {
+        pymath::math::fmax(x.into_float(), y.into_float())
+    }
+
+    /// Return the smaller of two floating-point arguments.
+    #[pyfunction]
+    fn fmin(x: ArgIntoFloat, y: ArgIntoFloat) -> f64 {
+        pymath::math::fmin(x.into_float(), y.into_float())
+    }
+
     #[derive(FromArgs)]
     struct IsCloseArgs {
         #[pyarg(any)]
@@ -93,30 +136,34 @@ mod math {
         pymath::math::expm1(x.into_float()).map_err(|err| pymath_exception(err, vm))
     }
 
-    #[pyfunction]
-    fn log(x: PyObjectRef, base: OptionalArg<ArgIntoFloat>, vm: &VirtualMachine) -> PyResult<f64> {
-        let base = base.into_option().map(|v| v.into_float());
-        // Check base first for proper error messages
-        if let Some(b) = base {
-            if b <= 0.0 {
-                return Err(vm.new_value_error(format!(
-                    "expected a positive input, got {}",
-                    super::float_repr(b)
-                )));
-            }
-            if b == 1.0 {
-                return Err(vm.new_value_error("math domain error"));
-            }
-        }
-        // Handle BigInt specially for large values (only for actual int type, not float)
-        if let Some(i) = x.downcast_ref::<PyInt>() {
-            return pymath::math::log_bigint(i.as_bigint(), base).map_err(|err| match err {
+    fn logarithm(
+        x: &PyObject,
+        float_log: impl Fn(f64) -> Result<f64, pymath::Error>,
+        int_log: impl Fn(&BigInt) -> Result<f64, pymath::Error>,
+        vm: &VirtualMachine,
+    ) -> PyResult<f64> {
+        let integer_log = |i: &PyInt| {
+            int_log(i.as_bigint()).map_err(|err| match err {
                 pymath::Error::EDOM => vm.new_value_error("expected a positive input"),
                 _ => pymath_exception(err, vm),
-            });
+            })
+        };
+        if let Some(i) = x.downcast_ref::<PyInt>() {
+            return integer_log(i);
         }
-        let val = x.try_float(vm)?.to_f64();
-        pymath::math::log(val, base).map_err(|err| match err {
+        let val = match x.try_float(vm) {
+            Ok(value) => value.to_f64(),
+            Err(error) => {
+                if error.fast_isinstance(vm.ctx.exceptions.overflow_error)
+                    && let Some(index) = x.try_index_opt(vm)
+                {
+                    let index = index?;
+                    return integer_log(&index);
+                }
+                return Err(error);
+            }
+        };
+        float_log(val).map_err(|err| match err {
             pymath::Error::EDOM => vm.new_value_error(format!(
                 "expected a positive input, got {}",
                 super::float_repr(val)
@@ -125,6 +172,30 @@ mod math {
         })
     }
 
+    #[pyfunction]
+    fn log(x: PyObjectRef, base: OptionalArg<PyObjectRef>, vm: &VirtualMachine) -> PyResult<f64> {
+        let natural_log = |x: &PyObject| {
+            logarithm(
+                x,
+                |value| pymath::math::log(value, None),
+                |value| pymath::math::log_bigint(value, None),
+                vm,
+            )
+        };
+        let numerator = natural_log(&x)?;
+        match base {
+            OptionalArg::Missing => Ok(numerator),
+            OptionalArg::Present(base) => {
+                let denominator = natural_log(&base)?;
+                if denominator == 0.0 {
+                    Err(vm.new_zero_division_error("division by zero"))
+                } else {
+                    Ok(numerator / denominator)
+                }
+            }
+        }
+    }
+
     #[pyfunction]
     fn log1p(x: ArgIntoFloat, vm: &VirtualMachine) -> PyResult<f64> {
         pymath::math::log1p(x.into_float()).map_err(|err| pymath_exception(err, vm))
@@ -132,40 +203,12 @@ mod math {
 
     #[pyfunction]
     fn log2(x: PyObjectRef, vm: &VirtualMachine) -> PyResult<f64> {
-        // Handle BigInt specially for large values (only for actual int type, not float)
-        if let Some(i) = x.downcast_ref::<PyInt>() {
-            return pymath::math::log2_bigint(i.as_bigint()).map_err(|err| match err {
-                pymath::Error::EDOM => vm.new_value_error("expected a positive input"),
-                _ => pymath_exception(err, vm),
-            });
-        }
-        let val = x.try_float(vm)?.to_f64();
-        pymath::math::log2(val).map_err(|err| match err {
-            pymath::Error::EDOM => vm.new_value_error(format!(
-                "expected a positive input, got {}",
-                super::float_repr(val)
-            )),
-            _ => pymath_exception(err, vm),
-        })
+        logarithm(&x, pymath::math::log2, pymath::math::log2_bigint, vm)
     }
 
     #[pyfunction]
     fn log10(x: PyObjectRef, vm: &VirtualMachine) -> PyResult<f64> {
-        // Handle BigInt specially for large values (only for actual int type, not float)
-        if let Some(i) = x.downcast_ref::<PyInt>() {
-            return pymath::math::log10_bigint(i.as_bigint()).map_err(|err| match err {
-                pymath::Error::EDOM => vm.new_value_error("expected a positive input"),
-                _ => pymath_exception(err, vm),
-            });
-        }
-        let val = x.try_float(vm)?.to_f64();
-        pymath::math::log10(val).map_err(|err| match err {
-            pymath::Error::EDOM => vm.new_value_error(format!(
-                "expected a positive input, got {}",
-                super::float_repr(val)
-            )),
-            _ => pymath_exception(err, vm),
-        })
+        logarithm(&x, pymath::math::log10, pymath::math::log10_bigint, vm)
     }
 
     #[pyfunction]
@@ -773,7 +816,18 @@ mod math {
             pymath::Error::ERANGE => vm.new_overflow_error("overflow in fma"),
         })
     }
+}
+
+const INTEGER_FUNCTIONS: [&str; 6] = ["comb", "factorial", "gcd", "isqrt", "lcm", "perm"];
 
+#[pymodule(sub, name = "math")]
+mod integer_functions {
+    use crate::vm::{
+        PyResult, VirtualMachine,
+        function::{ArgIndex, NameIntegers, PosArgs},
+    };
+    use malachite_bigint::BigInt;
+    use num_traits::{Signed, ToPrimitive};
     // Integer functions:
 
     #[pyfunction]
@@ -960,3 +1014,21 @@ fn float_repr(value: f64) -> String {
         }
     }
 }
+
+/// This module provides access to integer related mathematical functions.
+#[pymodule(with(integer_functions))]
+mod _math_integer {
+    use crate::vm::{Py, PyResult, VirtualMachine, builtins::PyModule};
+
+    pub(crate) fn module_exec(vm: &VirtualMachine, module: &Py<PyModule>) -> PyResult<()> {
+        __module_exec(vm, module);
+        let name = vm.ctx.new_str("math.integer");
+        module.set_attr("__name__", name.clone(), vm)?;
+        for function_name in super::INTEGER_FUNCTIONS {
+            module
+                .get_attr(function_name, vm)?
+                .set_attr("__module__", name.clone(), vm)?;
+        }
+        Ok(())
+    }
+}
diff --git a/crates/stdlib/src/mmap.rs b/crates/stdlib/src/mmap.rs
index 2a3ee0bc460..1064678a8f2 100644
--- a/crates/stdlib/src/mmap.rs
+++ b/crates/stdlib/src/mmap.rs
@@ -11,14 +11,14 @@ mod mmap {
     use crate::vm::{
         AsObject, FromArgs, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult,
         TryFromBorrowedObject, VirtualMachine, atomic_func,
-        builtins::{PyBytes, PyBytesRef, PyInt, PyIntRef, PyType, PyTypeRef},
+        builtins::{PyBytes, PyBytesRef, PyInt, PyIntRef, PyType, PyTypeRef, PyUtf8StrRef},
         byte::{bytes_from_object, value_from_object},
         convert::ToPyException,
-        function::ArgBytesLike,
+        function::{ArgBytesLike, ArgIndex},
         protocol::{
             BufferDescriptor, BufferMethods, PyBuffer, PyMappingMethods, PySequenceMethods,
         },
-        sliceable::{SaturatedSlice, SequenceIndex, SequenceIndexOp},
+        sliceable::{NameMmap, SaturatedSlice, SequenceIndex, SequenceIndexOp},
         types::{AsBuffer, AsMapping, AsSequence, Constructor, Representable},
     };
     use core::ops::{Deref, DerefMut};
@@ -26,7 +26,10 @@ mod mmap {
     use num_traits::Signed;
     use std::io::Write;
     #[cfg(windows)]
-    use {core::hint::cold_path, memchr::memchr, rustpython_vm::exceptions, std::io};
+    use {
+        core::hint::cold_path, memchr::memchr, num_traits::ToPrimitive, rustpython_vm::exceptions,
+        std::io,
+    };
 
     #[cfg(unix)]
     use rustpython_host_env::crt_fd;
@@ -69,7 +72,8 @@ mod mmap {
     #[pyattr]
     use host_mmap::{
         MADV_DONTNEED, MADV_NORMAL, MADV_RANDOM, MADV_SEQUENTIAL, MADV_WILLNEED, MAP_ANON,
-        MAP_ANONYMOUS, MAP_PRIVATE, MAP_SHARED, PROT_EXEC, PROT_READ, PROT_WRITE,
+        MAP_ANONYMOUS, MAP_PRIVATE, MAP_SHARED, MS_ASYNC, MS_INVALIDATE, MS_SYNC, PROT_EXEC,
+        PROT_READ, PROT_WRITE,
     };
 
     #[cfg(target_os = "macos")]
@@ -197,6 +201,10 @@ mod mmap {
         access: AccessMode,
         #[cfg(unix)]
         trackfd: bool,
+        #[cfg(target_os = "linux")]
+        anonymous: bool,
+        #[cfg(target_os = "linux")]
+        private: bool,
     }
 
     impl PyMmap {
@@ -290,6 +298,8 @@ mod mmap {
         offset: isize,
         #[pyarg(positional, optional)]
         size: Option<isize>,
+        #[pyarg(named, default)]
+        flags: core::ffi::c_int,
     }
 
     impl FlushOptions {
@@ -298,14 +308,15 @@ mod mmap {
                 return None;
             }
             let offset = self.offset as usize;
+            let remaining = len.checked_sub(offset)?;
 
             let size = match self.size {
+                None | Some(-1) => remaining,
                 Some(s) if s < 0 => return None,
                 Some(s) => s as usize,
-                None => len,
             };
 
-            if len.checked_sub(offset)? < size {
+            if remaining < size {
                 return None;
             }
 
@@ -330,9 +341,9 @@ mod mmap {
         option: core::ffi::c_int,
         // None means 0.
         #[pyarg(positional, default, py_default = "0")]
-        start: Option<PyIntRef>,
+        start: Option<ArgIndex>,
         #[pyarg(positional, optional)]
-        length: Option<PyIntRef>,
+        length: Option<ArgIndex>,
     }
 
     #[cfg(all(unix, not(target_os = "redox")))]
@@ -345,7 +356,8 @@ mod mmap {
             let start = self
                 .start
                 .map(|s| {
-                    s.try_to_primitive::<usize>(vm)
+                    s.as_ref()
+                        .try_to_primitive::<usize>(vm)
                         .ok()
                         .filter(|s| *s < len)
                         .ok_or_else(|| vm.new_value_error("madvise start out of bounds"))
@@ -355,7 +367,8 @@ mod mmap {
             let length = self
                 .length
                 .map(|s| {
-                    s.try_to_primitive::<usize>(vm)
+                    s.as_ref()
+                        .try_to_primitive::<usize>(vm)
                         .map_err(|_| vm.new_value_error("madvise length invalid"))
                 })
                 .transpose()?
@@ -400,7 +413,8 @@ mod mmap {
             }
 
             // TODO: memmap2 doesn't support mapping with prot and flags right now
-            let (_flags, _prot, access) = match access {
+            #[cfg_attr(not(target_os = "linux"), allow(unused_variables))]
+            let (flags, _prot, access) = match access {
                 AccessMode::Read => (MAP_SHARED, PROT_READ, access),
                 AccessMode::Write => (MAP_SHARED, PROT_READ | PROT_WRITE, access),
                 AccessMode::Copy => (MAP_PRIVATE, PROT_READ | PROT_WRITE, access),
@@ -416,24 +430,23 @@ mod mmap {
                 }
             };
 
-            let fd = unsafe { crt_fd::Borrowed::try_borrow_raw(fd) };
+            let anonymous = fd == -1 || flags & host_mmap::MAP_ANONYMOUS != 0;
 
-            // macOS: Issue #11277: fsync(2) is not enough on OS X - a special, OS X specific
-            // fcntl(2) is necessary to force DISKSYNC and get around mmap(2) bug
+            // Inspect the supplied descriptor before acquiring ownership, as
+            // CPython does. Invalid and non-regular fds do not impose file bounds.
             #[cfg(target_os = "macos")]
-            if let Ok(fd) = fd {
+            if fd != -1 {
                 host_mmap::prepare_file_mapping(fd);
             }
-
-            if let Ok(fd) = fd {
-                let file_len = host_mmap::file_len(fd).map_err(|err| err.to_pyexception(vm))?;
-
+            if fd != -1
+                && let Some(file_len) = host_mmap::regular_file_len(fd)
+            {
                 if map_size == 0 {
                     if file_len == 0 {
                         return Err(vm.new_value_error("cannot mmap an empty file"));
                     }
 
-                    if offset > file_len {
+                    if offset >= file_len {
                         return Err(vm.new_value_error("mmap offset is greater than file size"));
                     }
 
@@ -445,35 +458,40 @@ mod mmap {
                 }
             }
 
-            let (fd, mmap) = || -> std::io::Result<_> {
-                if let Ok(fd) = fd {
-                    let (new_fd, mmap) = host_mmap::map_file(
-                        fd,
-                        offset,
-                        map_size,
-                        match access {
-                            AccessMode::Default => host_mmap::AccessMode::Default,
-                            AccessMode::Read => host_mmap::AccessMode::Read,
-                            AccessMode::Write => host_mmap::AccessMode::Write,
-                            AccessMode::Copy => host_mmap::AccessMode::Copy,
-                        },
-                    )?;
-                    Ok((Some(new_fd), mmap))
-                } else {
-                    let mmap = host_mmap::map_anon(map_size)?;
-                    Ok((None, mmap))
-                }
-            }()
+            let retained_fd = if fd != -1 && trackfd {
+                Some(host_mmap::duplicate_descriptor(fd).map_err(|err| err.to_pyexception(vm))?)
+            } else {
+                None
+            };
+            let mmap = if anonymous {
+                host_mmap::map_anon(map_size)
+            } else {
+                // Keep an owned tracking fd alive through mmap when requested.
+                // Otherwise use the raw integer directly, without fabricating a
+                // BorrowedFd or creating a transient duplicate that can hit EMFILE.
+                let mapping_fd = retained_fd.as_ref().map_or(fd, |owned| owned.as_raw());
+                host_mmap::map_file(
+                    mapping_fd,
+                    offset,
+                    map_size,
+                    match access {
+                        AccessMode::Default => host_mmap::AccessMode::Default,
+                        AccessMode::Read => host_mmap::AccessMode::Read,
+                        AccessMode::Write => host_mmap::AccessMode::Write,
+                        AccessMode::Copy => host_mmap::AccessMode::Copy,
+                    },
+                )
+            }
             .map_err(|e| e.to_pyexception(vm))?;
 
             Ok(Self {
                 closed: AtomicCell::new(false),
                 mmap: PyMutex::new(Some(MmapObj::Mapped(mmap))),
-                fd: AtomicCell::new(if trackfd {
-                    fd.map_or(-1, |owned| owned.into_raw())
-                } else {
-                    -1
-                }),
+                #[cfg(target_os = "linux")]
+                anonymous,
+                #[cfg(target_os = "linux")]
+                private: flags & MAP_PRIVATE != 0,
+                fd: AtomicCell::new(retained_fd.map_or(-1, |owned| owned.into_raw())),
                 offset,
                 size: AtomicCell::new(map_size),
                 pos: AtomicCell::new(0),
@@ -653,7 +671,9 @@ mod mmap {
     impl AsBuffer for PyMmap {
         const RELEASE_BUFFER: bool = true;
 
-        fn as_buffer(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<PyBuffer> {
+        fn as_buffer(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyBuffer> {
+            // Publish the export while close/resize cannot invalidate the mapping.
+            let _mmap = zelf.check_valid(vm)?;
             let readonly = matches!(zelf.access, AccessMode::Read);
             let buf = PyBuffer::new(
                 zelf.to_owned().into(),
@@ -770,28 +790,39 @@ mod mmap {
             let m = self.mmap.lock();
 
             if m.is_none() {
+                drop(m);
                 return Err(vm.new_value_error("mmap closed or invalid"));
             }
 
             Ok(m)
         }
 
-        /// TODO: impl resize
-        #[allow(dead_code)]
-        fn check_resizeable(&self, vm: &VirtualMachine) -> PyResult<()> {
+        #[cfg(any(target_os = "linux", windows, all(test, feature = "threading")))]
+        fn check_resizeable(
+            &self,
+            vm: &VirtualMachine,
+        ) -> PyResult<PyMutexGuard<'_, Option<MmapObj>>> {
+            // Borrowed buffers can hold the data lock across blocking I/O.
+            if self.exports.load() > 0 {
+                return Err(vm.new_buffer_error("mmap can't resize with extant buffers exported."));
+            }
+            let mmap = self.check_valid(vm)?;
             if self.exports.load() > 0 {
+                drop(mmap);
                 return Err(vm.new_buffer_error("mmap can't resize with extant buffers exported."));
             }
 
             #[cfg(unix)]
             if !self.trackfd {
+                drop(mmap);
                 return Err(vm.new_value_error("mmap can't resize with trackfd=False."));
             }
 
             if self.access == AccessMode::Write || self.access == AccessMode::Default {
-                return Ok(());
+                return Ok(mmap);
             }
 
+            drop(mmap);
             Err(vm.new_type_error("mmap can't resize a readonly or copy-on-write memory map."))
         }
 
@@ -802,15 +833,20 @@ mod mmap {
 
         #[pymethod]
         fn close(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
+            // Reject an existing export without waiting for its borrowed-data guard.
+            if zelf.exports.load() > 0 {
+                return Err(vm.new_buffer_error("cannot close exported pointers exist."));
+            }
+            let mut mmap = zelf.mmap.lock();
             if Self::closed(zelf) {
                 return Ok(());
             }
 
             if zelf.exports.load() > 0 {
+                drop(mmap);
                 return Err(vm.new_buffer_error("cannot close exported pointers exist."));
             }
 
-            let mut mmap = zelf.mmap.lock();
             zelf.closed.store(true);
             *mmap = None;
 
@@ -821,9 +857,16 @@ mod mmap {
 
         fn get_find_range(&self, options: &FindOptions) -> (usize, usize) {
             let size = self.__len__();
-            let start = options
-                .start
-                .map_or_else(|| self.pos(), |start| start.saturated_at(size));
+            let start = options.start.map_or_else(
+                || self.pos(),
+                |start| {
+                    if start < 0 {
+                        start.saturated_at(size)
+                    } else {
+                        start as usize
+                    }
+                },
+            );
             let end = options.end.map_or(size, |end| end.saturated_at(size));
             (start, end)
         }
@@ -873,6 +916,8 @@ mod mmap {
 
         #[pymethod]
         fn flush(zelf: &Py<Self>, options: FlushOptions, vm: &VirtualMachine) -> PyResult<()> {
+            let mmap = zelf.check_valid(vm)?;
+            let flags = options.flags;
             let (offset, size) = options
                 .values(zelf.__len__())
                 .ok_or_else(|| vm.new_value_error("flush values out of range"))?;
@@ -881,9 +926,9 @@ mod mmap {
                 return Ok(());
             }
 
-            match zelf.check_valid(vm)?.deref().as_ref().unwrap() {
+            match mmap.deref().as_ref().unwrap() {
                 MmapObj::Mapped(mmap) => {
-                    mmap.flush_range(offset, size)
+                    mmap.flush_range(offset, size, flags)
                         .map_err(|e| e.to_pyexception(vm))?;
                 }
                 #[cfg(windows)]
@@ -897,15 +942,54 @@ mod mmap {
             Ok(())
         }
 
+        #[pymethod]
+        fn set_name(zelf: &Py<Self>, name: PyUtf8StrRef, vm: &VirtualMachine) -> PyResult<()> {
+            let name =
+                alloc::ffi::CString::new(name.as_str()).map_err(|err| err.to_pyexception(vm))?;
+            #[cfg(target_os = "linux")]
+            {
+                const PREFIX: &str = "cpython:mmap:";
+                if name.as_bytes().len() > 79 - PREFIX.len() {
+                    return Err(vm.new_value_error("name is too long"));
+                }
+                if !zelf.anonymous {
+                    return Err(
+                        vm.new_value_error("Cannot set annotation on non-anonymous mappings")
+                    );
+                }
+                // As in CPython's release build, kernel annotations are enabled
+                // only in development mode.
+                if vm.state.config.settings.dev_mode {
+                    let annotation =
+                        alloc::ffi::CString::new([PREFIX.as_bytes(), name.as_bytes()].concat())
+                            .expect("the name was checked for embedded NUL characters");
+                    let mmap = zelf.mmap.lock();
+                    let address = mmap
+                        .as_ref()
+                        .map_or(0, |mapping| mapping.as_slice().as_ptr() as usize);
+                    host_mmap::set_mapping_name(address, zelf.__len__(), &annotation)
+                        .map_err(|err| err.to_pyexception(vm))?;
+                }
+                Ok(())
+            }
+            #[cfg(not(target_os = "linux"))]
+            {
+                let _ = (zelf, name);
+                Err(vm.new_not_implemented_error(
+                    "Annotation of mmap is not supported on this platform",
+                ))
+            }
+        }
+
         #[cfg(all(unix, not(target_os = "redox")))]
         #[pymethod]
         fn madvise(zelf: &Py<Self>, options: AdviseOptions, vm: &VirtualMachine) -> PyResult<()> {
+            let guard = zelf.check_valid(vm)?;
             let (option, start, length) = options.values(zelf.__len__(), vm)?;
             if !host_mmap::validate_advice(option) {
                 return Err(vm.new_value_error("Not a valid Advice value"));
             }
 
-            let guard = zelf.check_valid(vm)?;
             let mmap = guard.deref().as_ref().unwrap();
             match mmap {
                 MmapObj::Mapped(m) => m.madvise_range(start, length, option),
@@ -920,9 +1004,9 @@ mod mmap {
         #[pymethod(name = "move")]
         fn move_(
             zelf: &Py<Self>,
-            dest: PyIntRef,
-            src: PyIntRef,
-            count: PyIntRef,
+            dest: ArgIndex,
+            src: ArgIndex,
+            count: ArgIndex,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
             fn args(
@@ -947,14 +1031,13 @@ mod mmap {
                 Some((dest, src, cnt))
             }
 
-            let size = zelf.__len__();
-            let (dest, src, cnt) = args(&dest, &src, &count, size, vm)
-                .ok_or_else(|| vm.new_value_error("source, destination, or count out of range"))?;
-
-            let dest_end = dest + cnt;
-            let src_end = src + cnt;
-
             zelf.try_writable(vm, |mmap| {
+                let (dest, src, cnt) =
+                    args(dest.as_ref(), src.as_ref(), count.as_ref(), mmap.len(), vm).ok_or_else(
+                        || vm.new_value_error("source, destination, or count out of range"),
+                    )?;
+                let dest_end = dest + cnt;
+                let src_end = src + cnt;
                 let src_buf = mmap[src..src_end].to_vec();
                 (&mut mmap[dest..dest_end])
                     .write(&src_buf)
@@ -985,6 +1068,9 @@ mod mmap {
                 .filter(|&n| n >= 0 && (n as usize) <= remaining)
                 .map_or(remaining, |n| n as usize);
 
+            if num_bytes == 0 {
+                return Ok(PyBytes::from(vec![]).into_ref(&vm.ctx));
+            }
             let end_pos = pos + num_bytes;
             let bytes = mmap.deref().as_ref().unwrap().as_slice()[pos..end_pos].to_vec();
 
@@ -997,12 +1083,13 @@ mod mmap {
 
         #[pymethod]
         fn read_byte(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIntRef> {
+            let mmap = zelf.check_valid(vm)?;
             let pos = zelf.pos();
             if pos >= zelf.__len__() {
                 return Err(vm.new_value_error("read byte out of range"));
             }
 
-            let b = zelf.check_valid(vm)?.deref().as_ref().unwrap().as_slice()[pos];
+            let b = mmap.deref().as_ref().unwrap().as_slice()[pos];
 
             zelf.advance_pos(1);
 
@@ -1037,34 +1124,61 @@ mod mmap {
             Ok(result)
         }
 
-        #[cfg(unix)]
+        #[cfg(target_os = "linux")]
         #[pymethod]
-        fn resize(zelf: &Py<Self>, _newsize: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
-            zelf.check_resizeable(vm)?;
-            // TODO: implement using mremap on Linux
-            Err(vm.new_system_error("mmap: resizing not available--no mremap()"))
+        fn resize(zelf: &Py<Self>, newsize: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
+            let newsize: isize = newsize.try_to_primitive(vm).map_err(|_| {
+                vm.new_overflow_error("Python int too large to convert to C ssize_t")
+            })?;
+            // Reject exports before taking the data lock, and retain the guard
+            // through truncation and remapping so a new export cannot race us.
+            let mut mmap = zelf.check_resizeable(vm)?;
+            let file_size = i128::from(zelf.offset) + newsize as i128;
+            if newsize < 0 || file_size > isize::MAX as i128 {
+                return Err(vm.new_value_error("new size out of range"));
+            }
+            let newsize = newsize as usize;
+            if zelf.anonymous && !zelf.private && newsize > zelf.__len__() {
+                return Err(vm.new_value_error("mmap: can't expand a shared anonymous mapping"));
+            }
+            let fd = zelf.fd.load();
+            if fd != -1 {
+                let fd = unsafe { crt_fd::Borrowed::try_borrow_raw(fd) }
+                    .map_err(|err| err.to_pyexception(vm))?;
+                let file_size = file_size
+                    .try_into()
+                    .map_err(|_| vm.new_value_error("new size out of range"))?;
+                crt_fd::ftruncate(fd, file_size).map_err(|err| err.to_pyexception(vm))?;
+            }
+            let MmapObj::Mapped(mapping) = mmap.as_mut().unwrap();
+            // The mapping is locked, exported buffers are prohibited, and its
+            // backing file has already been resized to cover the new mapping.
+            unsafe { mapping.remap(newsize) }.map_err(|err| err.to_pyexception(vm))?;
+            zelf.size.store(newsize);
+            Ok(())
         }
 
         #[cfg(windows)]
         #[pymethod]
         fn resize(zelf: &Py<Self>, newsize: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
-            zelf.check_resizeable(vm)?;
-
-            let newsize: usize = newsize
-                .try_to_primitive(vm)
-                .map_err(|_| vm.new_value_error("new size out of range"))?;
+            let newsize = newsize.as_bigint().to_usize();
 
+            // Get the lock on mmap
+            // Keep the export check valid until resize ends.
+            let mut mmap_guard = zelf.check_resizeable(vm)?;
+            let Some(newsize) = newsize else {
+                drop(mmap_guard);
+                return Err(vm.new_value_error("new size out of range"));
+            };
             if newsize == 0 {
+                drop(mmap_guard);
                 return Err(vm.new_value_error("new size must be positive"));
             }
-
             let handle = zelf.handle.load();
 
-            // Get the lock on mmap
-            let mut mmap_guard = zelf.mmap.lock();
-
             // Check if this is a Named mmap - these cannot be resized
             if let Some(MmapObj::Named(_)) = mmap_guard.as_ref() {
+                drop(mmap_guard);
                 return Err(vm.new_os_error("mmap: cannot resize a named memory mapping"));
             }
 
@@ -1080,8 +1194,13 @@ mod mmap {
                 let copy_size = core::cmp::min(old_size, newsize);
 
                 // Create new anonymous mmap
-                let mut new_mmap =
-                    host_mmap::map_anon(newsize).map_err(|e| e.to_pyexception(vm))?;
+                let mut new_mmap = match host_mmap::map_anon(newsize) {
+                    Ok(mmap) => mmap,
+                    Err(err) => {
+                        drop(mmap_guard);
+                        return Err(err.to_pyexception(vm));
+                    }
+                };
 
                 // Copy data from old mmap to new mmap
                 if let Some(old_mmap) = mmap_guard.as_ref() {
@@ -1106,17 +1225,23 @@ mod mmap {
                         handle as host_mmap::Handle,
                         zelf.size.load(),
                     );
+                    drop(mmap_guard);
                     return Err(err.to_pyexception(vm));
                 }
 
                 // Create new mmap with the new size
-                let new_mmap = Self::create_mmap_windows(
+                let new_mmap = match Self::create_mmap_windows(
                     handle as host_mmap::Handle,
                     zelf.offset,
                     newsize,
                     &zelf.access,
-                )
-                .map_err(|e| e.to_pyexception(vm))?;
+                ) {
+                    Ok(mmap) => mmap,
+                    Err(err) => {
+                        drop(mmap_guard);
+                        return Err(err.to_pyexception(vm));
+                    }
+                };
 
                 *mmap_guard = Some(new_mmap);
                 zelf.size.store(newsize);
@@ -1168,15 +1293,25 @@ mod mmap {
 
         #[cfg(unix)]
         #[pymethod]
-        fn size(zelf: &Py<Self>, vm: &VirtualMachine) -> std::io::Result<PyIntRef> {
-            let fd = unsafe { crt_fd::Borrowed::try_borrow_raw(zelf.fd.load())? };
-            let file_len = host_mmap::file_len(fd)?;
+        fn size(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIntRef> {
+            let _mmap = zelf.check_valid(vm)?;
+            if !zelf.trackfd {
+                return Err(vm.new_value_error("can't get size with trackfd=False"));
+            }
+            let fd = zelf.fd.load();
+            if fd == -1 {
+                return Ok(PyInt::from(zelf.__len__()).into_ref(&vm.ctx));
+            }
+            let fd = unsafe { crt_fd::Borrowed::try_borrow_raw(fd) }
+                .map_err(|err| err.to_pyexception(vm))?;
+            let file_len = host_mmap::file_len(fd).map_err(|err| err.to_pyexception(vm))?;
             Ok(PyInt::from(file_len).into_ref(&vm.ctx))
         }
 
         #[cfg(windows)]
         #[pymethod]
         fn size(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIntRef> {
+            let _mmap = zelf.check_valid(vm)?;
             let handle = zelf.handle.load();
             if host_mmap::is_invalid_handle_value(handle) {
                 // Anonymous mapping, return the mmap size
@@ -1202,7 +1337,6 @@ mod mmap {
         fn write(zelf: &Py<Self>, bytes: ArgBytesLike, vm: &VirtualMachine) -> PyResult<PyIntRef> {
             let self_ = &**zelf;
             let pos = self_.pos();
-            let size = self_.__len__();
 
             // Writing locks the map, and reading a source that views this same
             // map locks it too, so such a source is copied out first.
@@ -1216,11 +1350,10 @@ mod mmap {
                 &borrowed
             };
 
-            if pos > size || size - pos < data.len() {
-                return Err(vm.new_value_error("data out of range"));
-            }
-
             let len = self_.try_writable(vm, |mmap| {
+                if pos > mmap.len() || mmap.len() - pos < data.len() {
+                    return Err(vm.new_value_error("data out of range"));
+                }
                 (&mut mmap[pos..(pos + data.len())])
                     .write(data)
                     .map_err(|err| err.to_pyexception(vm))?;
@@ -1237,15 +1370,13 @@ mod mmap {
             let b = value_from_object(vm, &byte)?;
 
             let pos = zelf.pos();
-            let size = zelf.__len__();
-
-            if pos >= size {
-                return Err(vm.new_value_error("write byte out of range"));
-            }
-
             zelf.try_writable(vm, |mmap| {
+                if pos >= mmap.len() {
+                    return Err(vm.new_value_error("write byte out of range"));
+                }
                 mmap[pos] = b;
-            })?;
+                Ok(())
+            })??;
 
             zelf.advance_pos(1);
 
@@ -1328,11 +1459,12 @@ mod mmap {
         }
 
         fn getitem_by_index(&self, i: isize, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
+            let mmap = self.check_valid(vm)?;
             let i = i
                 .wrapped_at(self.__len__())
                 .ok_or_else(|| vm.new_index_error("mmap index out of range"))?;
 
-            let b = self.check_valid(vm)?.deref().as_ref().unwrap().as_slice()[i];
+            let b = mmap.deref().as_ref().unwrap().as_slice()[i];
 
             Ok(PyInt::from(b).into_ref(&vm.ctx).into())
         }
@@ -1342,9 +1474,8 @@ mod mmap {
             slice: &SaturatedSlice,
             vm: &VirtualMachine,
         ) -> PyResult<PyObjectRef> {
-            let (range, step, slice_len) = slice.adjust_indices(self.__len__());
-
             let mmap = self.check_valid(vm)?;
+            let (range, step, slice_len) = slice.adjust_indices(self.__len__());
             let slice_data = mmap.deref().as_ref().unwrap().as_slice();
 
             if slice_len == 0 {
@@ -1369,7 +1500,7 @@ mod mmap {
         }
 
         fn getitem_inner(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
-            match SequenceIndex::try_from_borrowed_object(vm, needle, "mmap")? {
+            match SequenceIndex::try_from_borrowed_object::<NameMmap>(vm, needle)? {
                 SequenceIndex::Int(i) => self.getitem_by_index(i, vm),
                 SequenceIndex::Slice(slice) => self.getitem_by_slice(&slice, vm),
             }
@@ -1381,7 +1512,7 @@ mod mmap {
             value: &PyObject,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            match SequenceIndex::try_from_borrowed_object(vm, needle, "mmap")? {
+            match SequenceIndex::try_from_borrowed_object::<NameMmap>(vm, needle)? {
                 SequenceIndex::Int(i) => Self::setitem_by_index(zelf, i, value, vm),
                 SequenceIndex::Slice(slice) => Self::setitem_by_slice(zelf, &slice, value, vm),
             }
@@ -1393,17 +1524,15 @@ mod mmap {
             value: &PyObject,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            let i: usize = i
-                .wrapped_at(self.__len__())
-                .ok_or_else(|| vm.new_index_error("mmap index out of range"))?;
-
             let b = value_from_object(vm, value)?;
 
             self.try_writable(vm, |mmap| {
+                let i = i
+                    .wrapped_at(mmap.len())
+                    .ok_or_else(|| vm.new_index_error("mmap index out of range"))?;
                 mmap[i] = b;
-            })?;
-
-            Ok(())
+                Ok(())
+            })?
         }
 
         fn setitem_by_slice(
@@ -1412,43 +1541,110 @@ mod mmap {
             value: &PyObject,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            let (range, step, slice_len) = slice.adjust_indices(self.__len__());
-
             let bytes = bytes_from_object(vm, value)?;
 
-            if bytes.len() != slice_len {
-                return Err(vm.new_index_error("mmap slice assignment is wrong size"));
-            }
+            self.try_writable(vm, |mmap| {
+                let (range, step, slice_len) = slice.adjust_indices(mmap.len());
 
-            if slice_len == 0 {
-                // do nothing
-                Ok(())
-            } else if step == 1 {
-                self.try_writable(vm, |mmap| {
+                if bytes.len() != slice_len {
+                    return Err(vm.new_index_error("mmap slice assignment is wrong size"));
+                }
+
+                if slice_len == 0 {
+                    // do nothing
+                } else if step == 1 {
                     (&mut mmap[range])
                         .write(&bytes)
                         .map_err(|err| err.to_pyexception(vm))?;
-                    Ok(())
-                })?
-            } else {
-                let mut bi = 0; // bytes index
-                if step.is_negative() {
-                    for i in range.rev().step_by(step.unsigned_abs()) {
-                        self.try_writable(vm, |mmap| {
-                            mmap[i] = bytes[bi];
-                        })?;
-                        bi += 1;
-                    }
                 } else {
-                    for i in range.step_by(step.unsigned_abs()) {
-                        self.try_writable(vm, |mmap| {
+                    let mut bi = 0; // bytes index
+                    if step.is_negative() {
+                        for i in range.rev().step_by(step.unsigned_abs()) {
+                            mmap[i] = bytes[bi];
+                            bi += 1;
+                        }
+                    } else {
+                        for i in range.step_by(step.unsigned_abs()) {
                             mmap[i] = bytes[bi];
-                        })?;
-                        bi += 1;
+                            bi += 1;
+                        }
                     }
                 }
                 Ok(())
-            }
+            })?
+        }
+    }
+
+    #[cfg(test)]
+    #[cfg(feature = "threading")]
+    mod tests {
+        use super::*;
+        use core::time::Duration;
+        use std::{sync::mpsc, thread};
+
+        fn rejects_borrowed_buffer(resize: bool) {
+            let builder = crate::vm::Interpreter::builder(Default::default());
+            let defs = crate::stdlib_module_defs(&builder.ctx);
+            let interp = builder
+                .add_native_modules(&defs)
+                .add_frozen_modules(rustpython_pylib::FROZEN_STDLIB)
+                .build();
+            interp.enter(|vm| {
+                let module = vm.import("mmap", 0).unwrap();
+                let mapped = module
+                    .get_attr("mmap", vm)
+                    .unwrap()
+                    .call((-1, 1), vm)
+                    .unwrap()
+                    .downcast::<PyMmap>()
+                    .unwrap();
+                let buffer = PyMmap::as_buffer(&mapped, vm).unwrap();
+                thread::scope(|scope| {
+                    let (ready_tx, ready_rx) = mpsc::channel();
+                    let (done_tx, done_rx) = mpsc::channel();
+                    let buffer = &buffer;
+                    let borrower = scope.spawn(move || {
+                        // A native I/O operation can keep this guard while detached.
+                        let bytes = buffer.as_contiguous().unwrap();
+                        assert!(bytes.is_locked());
+                        ready_tx.send(()).unwrap();
+                        // Release even on a regression, so the test fails rather than hangs.
+                        let rejected_before_release =
+                            done_rx.recv_timeout(Duration::from_secs(5)).is_ok();
+                        drop(bytes);
+                        rejected_before_release
+                    });
+                    ready_rx.recv().unwrap();
+                    let result = if resize {
+                        mapped.check_resizeable(vm).map(drop)
+                    } else {
+                        PyMmap::close(&mapped, vm)
+                    };
+                    let _ = done_tx.send(());
+                    assert!(
+                        borrower.join().unwrap(),
+                        "export rejection waited for the borrowed buffer"
+                    );
+                    assert!(
+                        result
+                            .unwrap_err()
+                            .class()
+                            .is(vm.ctx.exceptions.buffer_error)
+                    );
+                });
+                drop(buffer);
+                PyMmap::close(&mapped, vm).unwrap();
+            });
+        }
+
+        #[test]
+        fn close_rejects_borrowed_buffer() {
+            rejects_borrowed_buffer(false);
+        }
+
+        #[test]
+        fn resize_rejects_borrowed_buffer() {
+            rejects_borrowed_buffer(true);
         }
     }
 
diff --git a/crates/stdlib/src/multiprocessing.rs b/crates/stdlib/src/multiprocessing.rs
index 5c335649509..537c86b68a1 100644
--- a/crates/stdlib/src/multiprocessing.rs
+++ b/crates/stdlib/src/multiprocessing.rs
@@ -115,15 +115,15 @@ mod _multiprocessing {
 
     #[derive(FromArgs)]
     struct SemLockNewArgs {
-        #[pyarg(positional)]
+        #[pyarg(any)]
         kind: i32,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         value: i32,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         maxvalue: i32,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         name: String,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         unlink: bool,
     }
 
@@ -408,16 +408,22 @@ mod _multiprocessing {
 
     #[pyfunction]
     fn recv(socket: usize, size: usize, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
-        host_multiprocessing::recv_socket(socket as host_multiprocessing::RawSocket, size)
-            .map_err(|_| vm.new_last_os_error())
+        let mut buf = vm
+            .allow_threads(|| {
+                host_multiprocessing::recv_socket(socket as host_multiprocessing::RawSocket, size)
+            })
+            .map_err(|error| error.to_pyexception(vm))?;
+        buf.shrink_to_fit();
+        Ok(buf)
     }
 
     #[pyfunction]
     fn send(socket: usize, buf: ArgBytesLike, vm: &VirtualMachine) -> PyResult<core::ffi::c_int> {
-        buf.with_ref(|b| {
-            host_multiprocessing::send_socket(socket as host_multiprocessing::RawSocket, b)
+        let buf = buf.borrow_buf_unlocked(vm)?;
+        vm.allow_threads(|| {
+            host_multiprocessing::send_socket(socket as host_multiprocessing::RawSocket, &buf)
         })
-        .map_err(|_| vm.new_last_os_error())
+        .map_err(|error| error.to_pyexception(vm))
     }
 }
 
@@ -509,15 +515,15 @@ mod _multiprocessing {
 
     #[derive(FromArgs)]
     struct SemLockNewArgs {
-        #[pyarg(positional)]
+        #[pyarg(any)]
         kind: i32,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         value: i32,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         maxvalue: i32,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         name: String,
-        #[pyarg(positional)]
+        #[pyarg(any)]
         unlink: bool,
     }
 
diff --git a/crates/stdlib/src/openssl.rs b/crates/stdlib/src/openssl.rs
index 5470f788462..25f7422aee1 100644
--- a/crates/stdlib/src/openssl.rs
+++ b/crates/stdlib/src/openssl.rs
@@ -1,6 +1,10 @@
 // spell-checker:disable
 
 mod cert;
+#[cfg(all(unix, not(target_os = "aix")))]
+mod driver;
+#[cfg(all(unix, not(target_os = "aix")))]
+mod waiter;
 
 // SSL exception types (shared with rustls backend)
 #[allow(
@@ -42,6 +46,17 @@ mod _ssl {
     use core::hint::cold_path;
 
     use super::bio;
+    #[cfg(all(unix, not(target_os = "aix")))]
+    use super::{
+        driver::{Driver, Needs, Permit, WriteOwner},
+        waiter::{ProgressRegistry, ProgressWaiter},
+    };
+    #[cfg(not(all(unix, not(target_os = "aix"))))]
+    use crate::socket::{SockWaitKind, sock_wait};
+    #[cfg(all(unix, not(target_os = "aix")))]
+    use alloc::sync::Arc;
+    #[cfg(all(unix, not(target_os = "aix")))]
+    use std::os::fd::AsRawFd;
 
     // Import error types and helpers used in this module (others are exposed via pymodule(with(...)))
     use super::ssl_error::{
@@ -53,12 +68,12 @@ mod _ssl {
             LazyLock, PyDetachingRwLock, PyMappedRwLockReadGuard, PyMutex, PyRwLock,
             PyRwLockReadGuard, PyRwLockWriteGuard,
         },
-        socket::{self, PySocket, SockWaitKind, sock_wait},
+        socket::{self, PySocket},
         vm::{
             AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
             builtins::{
                 PyBaseException, PyBaseExceptionRef, PyBytesRef, PyListRef, PyModule, PyStrRef,
-                PyType, PyWeak,
+                PyType, PyUtf8StrRef, PyWeak,
             },
             class_or_notimplemented,
             convert::ToPyException,
@@ -67,6 +82,7 @@ mod _ssl {
                 ArgBytesLike, ArgMemoryBuffer, ArgStrOrBytesLike, Either, FsPath, OptionalArg,
                 PyComparisonValue,
             },
+            object::{Traverse, TraverseFn},
             stdlib::_warnings,
             types::{Comparable, Constructor, PyComparisonOp},
             utils::ToCString,
@@ -74,7 +90,6 @@ mod _ssl {
     };
     use crossbeam_utils::atomic::AtomicCell;
     use foreign_types_shared::{ForeignType, ForeignTypeRef};
-    use memchr::memchr;
     use openssl::{
         asn1::{Asn1Object, Asn1ObjectRef},
         error::ErrorStack,
@@ -231,7 +246,9 @@ mod _ssl {
     #[pyattr]
     const HAS_TLSv1_3: bool = cfg!(ossl111);
     #[pyattr]
-    const HAS_PSK: bool = true;
+    const HAS_PSK: bool = false; // External PSK callbacks are not implemented.
+    #[pyattr]
+    const HAS_PSK_TLS13: bool = false;
     #[pyattr]
     const HAS_PHA: bool = cfg!(ossl111);
 
@@ -249,7 +266,7 @@ mod _ssl {
 
     // SSL_VERIFY constants for post-handshake authentication
     #[cfg(ossl111)]
-    const SSL_VERIFY_POST_HANDSHAKE: core::ffi::c_int = 0x20;
+    use sys::SSL_VERIFY_POST_HANDSHAKE;
 
     // the openssl version from the API headers
 
@@ -468,13 +485,7 @@ mod _ssl {
         Ok(buf)
     }
 
-    // Callback data stored in SSL ex_data for SNI/msg callbacks
-    struct SniCallbackData {
-        ssl_context: PyRef<PySslContext>,
-        // Use weak reference to avoid reference cycle:
-        // PySslSocket -> SslStream -> SSL -> ex_data -> SniCallbackData -> PySslSocket
-        ssl_socket_weak: PyRef<PyWeak>,
-    }
+    type ActiveSslConnection = (*const PyDetachingRwLock<SslConnection>, *mut sys::SSL);
 
     // Thread-local storage for VirtualMachine pointer during handshake
     // SNI callback is only called during handshake which is synchronous
@@ -483,148 +494,106 @@ mod _ssl {
         // SSL pointer during handshake - needed because connection lock is held during handshake
         // and callbacks may need to access SSL without acquiring the lock
         static HANDSHAKE_SSL_PTR: core::cell::Cell<Option<*mut sys::SSL>> = const { core::cell::Cell::new(None) };
+        #[cfg(all(unix, not(target_os = "aix")))]
+        static SSL_IO_CALLS: core::cell::RefCell<Vec<*const PySslSocket>> = const { core::cell::RefCell::new(Vec::new()) };
+        static HANDSHAKE_CONNECTIONS: core::cell::RefCell<Vec<ActiveSslConnection>> = const { core::cell::RefCell::new(Vec::new()) };
     }
 
     // RAII guard to set/clear thread-local handshake context
     struct HandshakeVmGuard {
-        _ssl_ptr: *mut sys::SSL,
+        previous_vm: Option<*const VirtualMachine>,
+        previous_ssl: Option<*mut sys::SSL>,
     }
 
     impl HandshakeVmGuard {
-        fn new(vm: &VirtualMachine, ssl_ptr: *mut sys::SSL) -> Self {
-            HANDSHAKE_VM.with(|cell| cell.set(Some(vm as *const _)));
-            HANDSHAKE_SSL_PTR.with(|cell| cell.set(Some(ssl_ptr)));
-            HandshakeVmGuard { _ssl_ptr: ssl_ptr }
+        fn new(
+            vm: &VirtualMachine,
+            connection: &PyDetachingRwLock<SslConnection>,
+            ssl_ptr: *mut sys::SSL,
+        ) -> Self {
+            HANDSHAKE_CONNECTIONS.with(|connections| {
+                connections
+                    .borrow_mut()
+                    .push((connection as *const _, ssl_ptr));
+            });
+            Self {
+                previous_vm: HANDSHAKE_VM.with(|cell| cell.replace(Some(vm as *const _))),
+                previous_ssl: HANDSHAKE_SSL_PTR.with(|cell| cell.replace(Some(ssl_ptr))),
+            }
         }
     }
 
     impl Drop for HandshakeVmGuard {
         fn drop(&mut self) {
-            HANDSHAKE_VM.with(|cell| cell.set(None));
-            HANDSHAKE_SSL_PTR.with(|cell| cell.set(None));
+            HANDSHAKE_VM.with(|cell| cell.set(self.previous_vm));
+            HANDSHAKE_SSL_PTR.with(|cell| cell.set(self.previous_ssl));
+            HANDSHAKE_CONNECTIONS.with(|connections| {
+                connections.borrow_mut().pop();
+            });
         }
     }
 
-    // Get SSL pointer - either from thread-local (during handshake) or from connection
-    fn get_ssl_ptr_for_context_change(
-        connection: &PyDetachingRwLock<SslConnection>,
-    ) -> *mut sys::SSL {
-        // First check if we're in a handshake callback (lock already held)
-        if let Some(ptr) = HANDSHAKE_SSL_PTR.with(|cell| cell.get()) {
-            return ptr;
-        }
-        // Otherwise, acquire the lock normally
-        connection.read().ssl().as_ptr()
+    fn active_ssl_pointer(connection: &PyDetachingRwLock<SslConnection>) -> Option<*mut sys::SSL> {
+        HANDSHAKE_CONNECTIONS.with(|connections| {
+            connections
+                .borrow()
+                .iter()
+                .rev()
+                .find_map(|&(owner, pointer)| core::ptr::eq(owner, connection).then_some(pointer))
+        })
     }
 
-    // Get or create an ex_data index for SNI callback data
-    fn get_sni_ex_data_index() -> core::ffi::c_int {
-        use rustpython_common::lock::LazyLock;
-        static SNI_EX_DATA_IDX: LazyLock<core::ffi::c_int> = LazyLock::new(|| unsafe {
-            sys::SSL_get_ex_new_index(
-                0,
-                core::ptr::null_mut(),
-                None,
-                None,
-                Some(sni_callback_data_free),
-            )
-        });
-        *SNI_EX_DATA_IDX
-    }
-
-    // Free function for callback data
-    // NOTE: We don't free the data here because it's managed manually in do_handshake
-    // to avoid use-after-free when the SSL object is dropped after timeout
-    unsafe extern "C" fn sni_callback_data_free(
-        _parent: *mut core::ffi::c_void,
-        _ptr: *mut core::ffi::c_void,
-        _ad: *mut sys::CRYPTO_EX_DATA,
-        _idx: core::ffi::c_int,
-        _argl: core::ffi::c_long,
-        _argp: *mut core::ffi::c_void,
-    ) {
-        // Intentionally empty - data is freed in cleanup_sni_ex_data()
+    fn with_ssl_pointer<T>(
+        connection: &PyDetachingRwLock<SslConnection>,
+        operation: impl FnOnce(*mut sys::SSL) -> T,
+    ) -> T {
+        if let Some(pointer) = active_ssl_pointer(connection) {
+            // This thread already holds this connection's write guard.
+            return operation(pointer);
+        }
+        let guard = connection.read();
+        operation(guard.ssl().as_ptr())
     }
 
-    // Clean up SNI callback data from SSL ex_data
-    // Called after handshake to free the data and release references
-    unsafe fn cleanup_sni_ex_data(ssl_ptr: *mut sys::SSL) {
-        unsafe {
-            let idx = get_sni_ex_data_index();
-            let data_ptr = sys::SSL_get_ex_data(ssl_ptr, idx);
-            if !data_ptr.is_null() {
-                // Free the Box<SniCallbackData> - this releases references to context and socket
-                let _ = Box::from_raw(data_ptr as *mut SniCallbackData);
-                // Clear the ex_data to prevent double-free
-                sys::SSL_set_ex_data(ssl_ptr, idx, core::ptr::null_mut());
-            }
+    fn with_ssl_pointer_mut<T>(
+        connection: &PyDetachingRwLock<SslConnection>,
+        operation: impl FnOnce(*mut sys::SSL) -> T,
+    ) -> T {
+        if let Some(pointer) = active_ssl_pointer(connection) {
+            return operation(pointer);
         }
+        let guard = connection.write();
+        operation(guard.ssl().as_ptr())
     }
 
-    // Get or create an ex_data index for msg_callback data
-    fn get_msg_callback_ex_data_index() -> core::ffi::c_int {
-        use rustpython_common::lock::LazyLock;
-        static MSG_CB_EX_DATA_IDX: LazyLock<core::ffi::c_int> = LazyLock::new(|| unsafe {
-            sys::SSL_get_ex_new_index(
-                0,
-                core::ptr::null_mut(),
-                None,
-                None,
-                Some(msg_callback_data_free),
-            )
+    // The owning _SSLSocket outlives its SSL connection. Borrow its stable
+    // address, as CPython's SSL app_data does, without creating a hidden cycle.
+    fn get_socket_ex_data_index() -> core::ffi::c_int {
+        static SOCKET_EX_DATA_IDX: LazyLock<core::ffi::c_int> = LazyLock::new(|| unsafe {
+            sys::SSL_get_ex_new_index(0, core::ptr::null_mut(), None, None, None)
         });
-        *MSG_CB_EX_DATA_IDX
-    }
-
-    // Free function for msg_callback data - called by OpenSSL when SSL is freed
-    unsafe extern "C" fn msg_callback_data_free(
-        _parent: *mut core::ffi::c_void,
-        ptr: *mut core::ffi::c_void,
-        _ad: *mut sys::CRYPTO_EX_DATA,
-        _idx: core::ffi::c_int,
-        _argl: core::ffi::c_long,
-        _argp: *mut core::ffi::c_void,
-    ) {
-        if !ptr.is_null() {
-            unsafe {
-                // Reconstruct PyObjectRef and drop to decrement reference count
-                let raw = core::ptr::NonNull::new_unchecked(ptr as *mut PyObject);
-                let _ = PyObjectRef::from_raw(raw);
-            }
-        }
+        *SOCKET_EX_DATA_IDX
     }
 
     // SNI callback function called by OpenSSL
     unsafe extern "C" fn _servername_callback(
         ssl_ptr: *mut sys::SSL,
         al: *mut core::ffi::c_int,
-        arg: *mut core::ffi::c_void,
+        _arg: *mut core::ffi::c_void,
     ) -> core::ffi::c_int {
         const SSL_TLSEXT_ERR_OK: core::ffi::c_int = 0;
         const SSL_TLSEXT_ERR_ALERT_FATAL: core::ffi::c_int = 2;
         const SSL_AD_INTERNAL_ERROR: core::ffi::c_int = 80;
+        const SSL_AD_HANDSHAKE_FAILURE: core::ffi::c_int = 40;
         const TLSEXT_NAMETYPE_host_name: core::ffi::c_int = 0;
 
-        if arg.is_null() {
-            return SSL_TLSEXT_ERR_OK;
-        }
-
         unsafe {
-            let ctx = &*(arg as *const PySslContext);
-
-            // Nothing to call: leave without reaching the interpreter at all.
-            if ctx.sni_callback.lock().is_none() {
-                return SSL_TLSEXT_ERR_OK;
-            }
-
-            // Get callback data from SSL ex_data
-            let idx = get_sni_ex_data_index();
-            let data_ptr = sys::SSL_get_ex_data(ssl_ptr, idx);
-            if data_ptr.is_null() {
+            let socket_ptr = sys::SSL_get_ex_data(ssl_ptr, get_socket_ex_data_index());
+            if socket_ptr.is_null() {
+                *al = SSL_AD_INTERNAL_ERROR;
                 return SSL_TLSEXT_ERR_ALERT_FATAL;
             }
-
-            let callback_data = &*(data_ptr as *const SniCallbackData);
+            let ssl_socket = &*(socket_ptr as *const Py<PySslSocket>);
 
             // Get VM from thread-local storage (set by HandshakeVmGuard in do_handshake)
             let Some(vm_ptr) = HANDSHAKE_VM.with(|cell| cell.get()) else {
@@ -638,7 +607,9 @@ mod _ssl {
             // everything below rejoins it first — taking a reference to the
             // callback already counts — and gives the thread back after.
             vm.attach_for_callback(|| {
-                // Get the callback
+                // The callback may replace the socket's context and release its
+                // last outside reference. Keep both context and callback alive.
+                let ctx = ssl_socket.ctx.read().clone();
                 let callback_opt = ctx.sni_callback.lock().clone();
                 let Some(callback) = callback_opt else {
                     return SSL_TLSEXT_ERR_OK;
@@ -656,21 +627,15 @@ mod _ssl {
                     }
                 };
 
-                // Get SSL socket from callback data via weak reference
-                let ssl_socket_obj = callback_data
-                    .ssl_socket_weak
-                    .upgrade()
-                    .unwrap_or_else(|| vm.ctx.none());
+                let ssl_socket_obj = match PySslSocket::callback_owner(ssl_socket) {
+                    Some(owner) => owner,
+                    None => {
+                        *al = SSL_AD_INTERNAL_ERROR;
+                        return SSL_TLSEXT_ERR_ALERT_FATAL;
+                    }
+                };
 
-                // Call the Python callback
-                match callback.call(
-                    (
-                        ssl_socket_obj,
-                        server_name_arg,
-                        callback_data.ssl_context.to_owned(),
-                    ),
-                    vm,
-                ) {
+                match callback.call((ssl_socket_obj, server_name_arg, ctx), vm) {
                     Ok(result) => {
                         // Check return value type (must be None or integer)
                         if vm.is_none(&result) {
@@ -700,7 +665,7 @@ mod _ssl {
                     Err(exc) => {
                         // Log the exception but don't propagate it
                         vm.run_unraisable(exc, None, vm.ctx.none());
-                        *al = SSL_AD_INTERNAL_ERROR;
+                        *al = SSL_AD_HANDSHAKE_FAILURE;
                         SSL_TLSEXT_ERR_ALERT_FATAL
                     }
                 }
@@ -735,20 +700,15 @@ mod _ssl {
 
         unsafe {
             // Get SSL socket from ex_data using the dedicated index
-            let idx = get_msg_callback_ex_data_index();
+            let idx = get_socket_ex_data_index();
             let ssl_socket_ptr = sys::SSL_get_ex_data(ssl_ptr, idx);
             if ssl_socket_ptr.is_null() {
                 return;
             }
 
-            // ssl_socket_ptr is a pointer to Box<Py<PySslSocket>>, set in _wrap_socket/_wrap_bio
+            // Borrowed stable address, installed by _wrap_socket/_wrap_bio.
             let ssl_socket: &Py<PySslSocket> = &*(ssl_socket_ptr as *const Py<PySslSocket>);
 
-            // Nothing to call: leave without reaching the interpreter at all.
-            if ssl_socket.ctx.read().msg_callback.lock().is_none() {
-                return;
-            }
-
             // Get VM from thread-local storage (set by HandshakeVmGuard in do_handshake)
             let Some(vm_ptr) = HANDSHAKE_VM.with(|cell| cell.get()) else {
                 // VM not available - this shouldn't happen during handshake
@@ -766,13 +726,9 @@ mod _ssl {
                     return;
                 };
 
-                // Get SSL socket owner object
-                let ssl_socket_obj = ssl_socket
-                    .owner
-                    .read()
-                    .as_ref()
-                    .and_then(|weak| weak.upgrade())
-                    .unwrap_or_else(|| vm.ctx.none());
+                let Some(ssl_socket_obj) = PySslSocket::callback_owner(ssl_socket) else {
+                    return;
+                };
 
                 // Create the message bytes
                 let buf_slice = core::slice::from_raw_parts(buf as *const u8, len);
@@ -819,8 +775,13 @@ mod _ssl {
                 ) {
                     Ok(_) => {}
                     Err(exc) => {
-                        // Log the exception but don't propagate it
-                        vm.run_unraisable(exc, None, vm.ctx.none());
+                        // SSL message callbacks cannot signal failure to the C
+                        // library. Propagate it when the enclosing operation
+                        // rejoins the interpreter, chaining earlier callbacks.
+                        let previous = ssl_socket.callback_error.lock().replace(exc.clone());
+                        if let Some(previous) = previous {
+                            exc.set_context(Some(previous));
+                        }
                     }
                 }
             })
@@ -841,18 +802,19 @@ mod _ssl {
     }
 
     #[pyattr]
-    #[pyclass(module = "_ssl", name = "_SSLContext")]
+    #[pyclass(module = "_ssl", name = "_SSLContext", traverse)]
     #[derive(PyPayload)]
     struct PySslContext {
+        #[pytraverse(skip)]
         ctx: PyRwLock<SslContextBuilder>,
+        #[pytraverse(skip)]
         check_hostname: AtomicCell<bool>,
+        #[pytraverse(skip)]
         protocol: SslVersion,
+        #[pytraverse(skip)]
         post_handshake_auth: PyMutex<bool>,
         sni_callback: PyMutex<Option<PyObjectRef>>,
         msg_callback: PyMutex<Option<PyObjectRef>>,
-        psk_client_callback: PyMutex<Option<PyObjectRef>>,
-        psk_server_callback: PyMutex<Option<PyObjectRef>>,
-        psk_identity_hint: PyMutex<Option<String>>,
     }
 
     impl fmt::Debug for PySslContext {
@@ -861,6 +823,19 @@ mod _ssl {
         }
     }
 
+    impl Drop for PySslContext {
+        fn drop(&mut self) {
+            // SSL retains its original session context across context switches.
+            // It must not call back through a released Python context on HRR.
+            unsafe {
+                sys::SSL_CTX_set_tlsext_servername_callback__fixed_rust(
+                    self.ctx.get_mut().as_ptr(),
+                    None,
+                );
+            }
+        }
+    }
+
     fn builder_as_ctx(x: &SslContextBuilder) -> &ssl::SslContextRef {
         unsafe { ssl::SslContextRef::from_ptr(x.as_ptr()) }
     }
@@ -972,9 +947,6 @@ mod _ssl {
                 post_handshake_auth: PyMutex::new(false),
                 sni_callback: PyMutex::new(None),
                 msg_callback: PyMutex::new(None),
-                psk_client_callback: PyMutex::new(None),
-                psk_server_callback: PyMutex::new(None),
-                psk_identity_hint: PyMutex::new(None),
             })
         }
     }
@@ -1039,6 +1011,146 @@ mod _ssl {
                 .map_err(|_| new_ssl_error(vm, "No cipher can be selected."))
         }
 
+        #[pymethod]
+        fn set_ciphersuites(
+            zelf: &Py<Self>,
+            ciphersuites: PyUtf8StrRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            let list = ciphersuites.as_str().to_cstring(vm)?;
+            #[cfg(ossl111)]
+            {
+                let result = unsafe {
+                    sys::SSL_CTX_set_ciphersuites(zelf.builder().as_ptr(), list.as_ptr())
+                };
+                if result != 1 {
+                    let _ = ErrorStack::get();
+                    return Err(new_ssl_error(vm, "No cipher suite can be selected."));
+                }
+                Ok(())
+            }
+            #[cfg(not(ossl111))]
+            {
+                let _ = (zelf, list);
+                Err(vm.new_not_implemented_error("TLS 1.3 requires OpenSSL 1.1.1 or later."))
+            }
+        }
+
+        fn set_algorithm_list(
+            &self,
+            list: PyUtf8StrRef,
+            command: core::ffi::c_int,
+            message: &str,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            let list = list.as_str().to_cstring(vm)?;
+            let result = unsafe {
+                sys::SSL_CTX_ctrl(
+                    self.builder().as_ptr(),
+                    command,
+                    0,
+                    list.as_ptr().cast_mut().cast(),
+                )
+            };
+            if result != 1 {
+                let _ = ErrorStack::get();
+                return Err(new_ssl_error(vm, message));
+            }
+            Ok(())
+        }
+
+        #[pymethod]
+        fn set_groups(
+            zelf: &Py<Self>,
+            grouplist: PyUtf8StrRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            // SSL_CTX_set1_groups_list is a macro around SSL_CTX_ctrl.
+            const SSL_CTRL_SET_GROUPS_LIST: core::ffi::c_int = 92;
+            zelf.set_algorithm_list(
+                grouplist,
+                SSL_CTRL_SET_GROUPS_LIST,
+                "unrecognized group",
+                vm,
+            )
+        }
+
+        #[pymethod]
+        fn set_server_sigalgs(
+            zelf: &Py<Self>,
+            sigalgslist: PyUtf8StrRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            const SSL_CTRL_SET_SIGALGS_LIST: core::ffi::c_int = 98;
+            zelf.set_algorithm_list(
+                sigalgslist,
+                SSL_CTRL_SET_SIGALGS_LIST,
+                "unrecognized signature algorithm",
+                vm,
+            )
+        }
+
+        #[pymethod]
+        fn set_client_sigalgs(
+            zelf: &Py<Self>,
+            sigalgslist: PyUtf8StrRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            const SSL_CTRL_SET_CLIENT_SIGALGS_LIST: core::ffi::c_int = 102;
+            zelf.set_algorithm_list(
+                sigalgslist,
+                SSL_CTRL_SET_CLIENT_SIGALGS_LIST,
+                "unrecognized signature algorithm",
+                vm,
+            )
+        }
+
+        #[pymethod]
+        fn get_groups(
+            zelf: &Py<Self>,
+            args: GetGroupsArgs,
+            vm: &VirtualMachine,
+        ) -> PyResult<PyListRef> {
+            #[cfg(ossl350)]
+            unsafe {
+                const SSL_CTRL_GET0_IMPLEMENTED_GROUPS: core::ffi::c_int = 139;
+                let groups = sys::OPENSSL_sk_new_null();
+                if groups.is_null() {
+                    return Err(vm.new_memory_error("failed to allocate group list"));
+                }
+                let result = sys::SSL_CTX_ctrl(
+                    zelf.ctx().as_ptr(),
+                    SSL_CTRL_GET0_IMPLEMENTED_GROUPS,
+                    core::ffi::c_long::from(args.include_aliases),
+                    groups.cast(),
+                );
+                if result == 0 {
+                    sys::OPENSSL_sk_free(groups);
+                    return Err(convert_openssl_error(vm, ErrorStack::get()));
+                }
+                // The stack owns its storage, but OpenSSL owns each name.
+                let names = (0..sys::OPENSSL_sk_num(groups))
+                    .map(|index| {
+                        CStr::from_ptr(sys::OPENSSL_sk_value(groups, index).cast())
+                            .to_string_lossy()
+                            .into_owned()
+                    })
+                    .collect::<Vec<_>>();
+                sys::OPENSSL_sk_free(groups);
+                Ok(vm.ctx.new_list(
+                    names
+                        .into_iter()
+                        .map(|name| vm.ctx.new_str(name).into())
+                        .collect(),
+                ))
+            }
+            #[cfg(not(ossl350))]
+            {
+                let _ = (zelf, args.include_aliases);
+                Err(vm.new_not_implemented_error("Getting groups requires OpenSSL 3.5 or later."))
+            }
+        }
+
         #[pymethod]
         fn get_ciphers(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyListRef> {
             let ctx = zelf.ctx();
@@ -1242,6 +1354,12 @@ mod _ssl {
         // PY_PROTO_MINIMUM_SUPPORTED = -2, PY_PROTO_MAXIMUM_SUPPORTED = -1
         #[pygetset]
         fn minimum_version(zelf: &Py<Self>) -> i32 {
+            if !matches!(
+                zelf.protocol,
+                SslVersion::Tls | SslVersion::TlsClient | SslVersion::TlsServer
+            ) {
+                return -2;
+            }
             let ctx = zelf.ctx();
             let version = unsafe { sys::SSL_CTX_get_min_proto_version(ctx.as_ptr()) };
             if version == 0 {
@@ -1252,13 +1370,23 @@ mod _ssl {
         }
         #[pygetset(setter)]
         fn set_minimum_version(zelf: &Py<Self>, value: i32, vm: &VirtualMachine) -> PyResult<()> {
+            if !matches!(
+                zelf.protocol,
+                SslVersion::Tls | SslVersion::TlsClient | SslVersion::TlsServer
+            ) {
+                return Err(vm.new_value_error(
+                    "The context's protocol doesn't support modification of highest and lowest version.",
+                ));
+            }
+            ProtoVersion::try_from(value)
+                .map_err(|_| vm.new_value_error("invalid protocol version"))?;
             Self::warn_deprecated_tls_version(value, vm)?;
 
             // Handle special values
             let proto_version = match value {
                 -2 => {
-                    // PY_PROTO_MINIMUM_SUPPORTED -> use minimum available (TLS 1.2)
-                    sys::TLS1_2_VERSION
+                    // Zero removes the explicit minimum protocol limit.
+                    0
                 }
                 -1 => {
                     // PY_PROTO_MAXIMUM_SUPPORTED -> use maximum available
@@ -1278,6 +1406,12 @@ mod _ssl {
 
         #[pygetset]
         fn maximum_version(zelf: &Py<Self>) -> i32 {
+            if !matches!(
+                zelf.protocol,
+                SslVersion::Tls | SslVersion::TlsClient | SslVersion::TlsServer
+            ) {
+                return -1;
+            }
             let ctx = zelf.ctx();
             let version = unsafe { sys::SSL_CTX_get_max_proto_version(ctx.as_ptr()) };
             if version == 0 {
@@ -1288,6 +1422,16 @@ mod _ssl {
         }
         #[pygetset(setter)]
         fn set_maximum_version(zelf: &Py<Self>, value: i32, vm: &VirtualMachine) -> PyResult<()> {
+            if !matches!(
+                zelf.protocol,
+                SslVersion::Tls | SslVersion::TlsClient | SslVersion::TlsServer
+            ) {
+                return Err(vm.new_value_error(
+                    "The context's protocol doesn't support modification of highest and lowest version.",
+                ));
+            }
+            ProtoVersion::try_from(value)
+                .map_err(|_| vm.new_value_error("invalid protocol version"))?;
             Self::warn_deprecated_tls_version(value, vm)?;
 
             // Handle special values
@@ -1296,10 +1440,8 @@ mod _ssl {
                     // PY_PROTO_MAXIMUM_SUPPORTED -> use 0 for OpenSSL (means no limit)
                     0
                 }
-                -2 => {
-                    // PY_PROTO_MINIMUM_SUPPORTED -> use minimum available (TLS 1.2)
-                    sys::TLS1_2_VERSION
-                }
+                // This backend advertises TLSv1 as its lowest supported version.
+                -2 => sys::TLS1_VERSION,
                 _ => value,
             };
 
@@ -1338,7 +1480,8 @@ mod _ssl {
             cfg_select! {
                 ossl110 => {
                     let ctx = zelf.builder();
-                    let result = unsafe { sys::SSL_CTX_set_num_tickets(ctx.as_ptr(), value as usize) };
+                    let result =
+                        unsafe { sys::SSL_CTX_set_num_tickets(ctx.as_ptr(), value as usize) };
                     if result != 1 {
                         return Err(vm.new_value_error("failed to set num tickets."));
                     }
@@ -1360,11 +1503,10 @@ mod _ssl {
                         .load_verify_locations(Some(cert_file.as_path()), Some(cert_dir.as_path()))
                         .map_err(|e| convert_openssl_error(vm, e))
                 }
-                _ => {
-                    zelf.builder()
-                        .set_default_verify_paths()
-                        .map_err(|e| convert_openssl_error(vm, e))
-                }
+                _ => zelf
+                    .builder()
+                    .set_default_verify_paths()
+                    .map_err(|e| convert_openssl_error(vm, e)),
             }
         }
 
@@ -1407,74 +1549,25 @@ mod _ssl {
 
         #[pymethod]
         fn set_psk_client_callback(
-            zelf: &Py<Self>,
-            callback: PyObjectRef,
+            _zelf: &Py<Self>,
+            _callback: PyObjectRef,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            // Cannot add PSK client callback to a server context
-            if zelf.protocol == SslVersion::TlsServer {
-                return Err(vm
-                    .new_os_subtype_error(
-                        PySSLError::class(&vm.ctx).to_owned(),
-                        None,
-                        "Cannot add PSK client callback to a PROTOCOL_TLS_SERVER context"
-                            .to_owned(),
-                    )
-                    .upcast());
-            }
-
-            if vm.is_none(&callback) {
-                *zelf.psk_client_callback.lock() = None;
-                unsafe {
-                    sys::SSL_CTX_set_psk_client_callback(zelf.builder().as_ptr(), None);
-                }
-            } else {
-                if !callback.is_callable() {
-                    return Err(vm.new_type_error("callback must be callable"));
-                }
-                *zelf.psk_client_callback.lock() = Some(callback);
-                // Note: The actual callback will be invoked via SSL app_data mechanism
-                // when do_handshake is called
-            }
-            Ok(())
+            Err(vm.new_not_implemented_error(
+                "TLS-PSK callbacks are not implemented by this backend.",
+            ))
         }
 
         #[pymethod]
         fn set_psk_server_callback(
-            zelf: &Py<Self>,
-            callback: PyObjectRef,
-            identity_hint: OptionalArg<PyStrRef>,
+            _zelf: &Py<Self>,
+            _callback: PyObjectRef,
+            _identity_hint: OptionalArg<PyStrRef>,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            // Cannot add PSK server callback to a client context
-            if zelf.protocol == SslVersion::TlsClient {
-                return Err(vm
-                    .new_os_subtype_error(
-                        PySSLError::class(&vm.ctx).to_owned(),
-                        None,
-                        "Cannot add PSK server callback to a PROTOCOL_TLS_CLIENT context"
-                            .to_owned(),
-                    )
-                    .upcast());
-            }
-
-            if vm.is_none(&callback) {
-                *zelf.psk_server_callback.lock() = None;
-                *zelf.psk_identity_hint.lock() = None;
-                unsafe {
-                    sys::SSL_CTX_set_psk_server_callback(zelf.builder().as_ptr(), None);
-                }
-            } else {
-                if !callback.is_callable() {
-                    return Err(vm.new_type_error("callback must be callable"));
-                }
-                *zelf.psk_server_callback.lock() = Some(callback);
-                if let OptionalArg::Present(hint) = identity_hint {
-                    *zelf.psk_identity_hint.lock() = Some(hint.to_string());
-                }
-                // Note: The actual callback will be invoked via SSL app_data mechanism
-            }
-            Ok(())
+            Err(vm.new_not_implemented_error(
+                "TLS-PSK callbacks are not implemented by this backend.",
+            ))
         }
 
         #[pymethod]
@@ -1758,10 +1851,6 @@ mod _ssl {
                             zelf.ctx().as_ptr(),
                             Some(_servername_callback),
                         );
-                        sys::SSL_CTX_set_tlsext_servername_arg(
-                            zelf.ctx().as_ptr(),
-                            zelf as *const _ as *mut _,
-                        );
                     }
                 } else {
                     // Clear callback
@@ -1857,29 +1946,31 @@ mod _ssl {
             } = args;
 
             let mut ctx = zelf.builder();
-            let key_path = keyfile.map(|path| path.to_path_buf(vm)).transpose()?;
+            let key_path = keyfile
+                .as_ref()
+                .map(|path| path.to_path_buf(vm))
+                .transpose()?;
             let cert_path = certfile.to_path_buf(vm)?;
 
-            // Check file existence before calling OpenSSL to get proper errno
-            if !rustpython_host_env::fs::exists(&cert_path) {
-                return Err(vm
-                    .new_os_subtype_error(
-                        vm.ctx.exceptions.file_not_found_error.to_owned(),
-                        Some(rustpython_host_env::errno::errors::ENOENT),
-                        format!("No such file or directory: '{}'", cert_path.display()),
-                    )
-                    .upcast());
-            }
-            if let Some(ref kp) = key_path
-                && !rustpython_host_env::fs::exists(kp)
-            {
-                return Err(vm
-                    .new_os_subtype_error(
-                        vm.ctx.exceptions.file_not_found_error.to_owned(),
-                        Some(rustpython_host_env::errno::errors::ENOENT),
-                        format!("No such file or directory: '{}'", kp.display()),
-                    )
-                    .upcast());
+            let file_error = |error: std::io::Error, path: &FsPath| {
+                let exception = error.to_pyexception(vm);
+                let filename: PyObjectRef = match path {
+                    FsPath::Str(path) => path.clone().into(),
+                    FsPath::Bytes(path) => path.clone().into(),
+                };
+                exception
+                    .as_object()
+                    .set_attr("filename", filename, vm)
+                    .expect("OSError.filename is writable");
+                exception
+            };
+            // Keep OS errors and their original str/bytes filenames rather
+            // than replacing them with OpenSSL's generic file error.
+            rustpython_host_env::fs::metadata(&cert_path)
+                .map_err(|error| file_error(error, &certfile))?;
+            if let Some(ref path) = key_path {
+                rustpython_host_env::fs::metadata(path)
+                    .map_err(|error| file_error(error, keyfile.as_ref().unwrap()))?;
             }
 
             // Load certificate chain
@@ -1894,7 +1985,7 @@ mod _ssl {
 
             // Read key file data
             let key_data = rustpython_host_env::fs::read(key_file_path)
-                .map_err(|e| crate::vm::convert::ToPyException::to_pyexception(&e, vm))?;
+                .map_err(|error| file_error(error, keyfile.as_ref().unwrap_or(&certfile)))?;
 
             let pkey = if let Some(ref pw_obj) = password {
                 if pw_obj.is_callable() {
@@ -2120,48 +2211,50 @@ mod _ssl {
                 Self::new_py_ssl_socket(zelf.clone(), args.server_side, args.server_hostname, vm)?;
 
             // Create SslStream with socket
-            let stream = ssl::SslStream::new(ssl, SocketStream(args.sock.clone()))
-                .map_err(|e| convert_openssl_error(vm, e))?;
+            let stream = ssl::SslStream::new(
+                ssl,
+                SocketStream::new(args.sock.clone()).map_err(|e| e.to_pyexception(vm))?,
+            )
+            .map_err(|e| convert_openssl_error(vm, e))?;
 
             let py_ssl_socket = PySslSocket {
                 ctx: PyRwLock::new(zelf.clone()),
-                connection: PyDetachingRwLock::new(SslConnection::Socket(stream)),
+                connection: SslConnectionLock(PyDetachingRwLock::new(SslConnection::new(
+                    SslTransport::Socket(stream),
+                ))),
                 socket_type,
                 server_hostname,
-                owner: PyRwLock::new(args.owner.map(|o| o.downgrade(None, vm)).transpose()?),
+                got_eof_error: AtomicCell::new(false),
+                shutdown_seen_zero: AtomicCell::new(false),
+                callback_error: PyMutex::new(None),
+                #[cfg(all(unix, not(target_os = "aix")))]
+                info_progress: AtomicCell::new(0),
+                #[cfg(all(unix, not(target_os = "aix")))]
+                previous_info_callback: AtomicCell::new(None),
+                owner: PyRwLock::new(Some(
+                    args.owner
+                        .unwrap_or_else(|| args.sock.clone().into())
+                        .downgrade(None, vm)?,
+                )),
             };
 
             // Convert to PyRef (heap allocation) to avoid use-after-free
             let py_ref =
                 py_ssl_socket.into_ref_with_type(vm, PySslSocket::class(&vm.ctx).to_owned())?;
 
-            // Check if SNI callback is configured (minimize lock time)
-            let has_sni_callback = zelf.sni_callback.lock().is_some();
-
-            // Set up ex_data for callbacks
+            // The connection is owned by py_ref, so this borrowed address
+            // remains valid through every SSL operation, including retries.
             unsafe {
-                let ssl_ptr = py_ref.connection.read().ssl().as_ptr();
-
-                // Clone and store via into_raw() - increments refcount and returns stable pointer
-                // The refcount will be decremented by msg_callback_data_free when SSL is freed
-                let cloned: PyObjectRef = py_ref.clone().into();
-                let raw_ptr = cloned.into_raw();
-                let msg_cb_idx = get_msg_callback_ex_data_index();
-                sys::SSL_set_ex_data(ssl_ptr, msg_cb_idx, raw_ptr.as_ptr() as *mut _);
-
-                // Set SNI callback data if needed
-                if has_sni_callback {
-                    let ssl_socket_weak = py_ref.as_object().downgrade(None, vm)?;
-                    // Store callback data in SSL ex_data - use weak reference to avoid cycle
-                    let callback_data = Box::new(SniCallbackData {
-                        ssl_context: zelf.clone(),
-                        ssl_socket_weak,
-                    });
-                    let sni_idx = get_sni_ex_data_index();
-                    sys::SSL_set_ex_data(ssl_ptr, sni_idx, Box::into_raw(callback_data) as *mut _);
-                }
+                sys::SSL_set_ex_data(
+                    py_ref.connection.read().ssl().as_ptr(),
+                    get_socket_ex_data_index(),
+                    &*py_ref as *const Py<PySslSocket> as *mut _,
+                );
             }
 
+            #[cfg(all(unix, not(target_os = "aix")))]
+            py_ref.install_progress_callback();
+
             // Set session if provided
             if let Some(session) = args.session
                 && !vm.is_none(&session)
@@ -2186,6 +2279,8 @@ mod _ssl {
             let bio_stream = BioStream {
                 inbio: args.incoming,
                 outbio: args.outgoing,
+                #[cfg(all(unix, not(target_os = "aix")))]
+                progress: 0,
             };
 
             // Create SslStream with BioStream
@@ -2194,9 +2289,18 @@ mod _ssl {
 
             let py_ssl_socket = PySslSocket {
                 ctx: PyRwLock::new(zelf.clone()),
-                connection: PyDetachingRwLock::new(SslConnection::Bio(stream)),
+                connection: SslConnectionLock(PyDetachingRwLock::new(SslConnection::new(
+                    SslTransport::Bio(stream),
+                ))),
                 socket_type,
                 server_hostname,
+                got_eof_error: AtomicCell::new(false),
+                shutdown_seen_zero: AtomicCell::new(false),
+                callback_error: PyMutex::new(None),
+                #[cfg(all(unix, not(target_os = "aix")))]
+                info_progress: AtomicCell::new(0),
+                #[cfg(all(unix, not(target_os = "aix")))]
+                previous_info_callback: AtomicCell::new(None),
                 owner: PyRwLock::new(args.owner.map(|o| o.downgrade(None, vm)).transpose()?),
             };
 
@@ -2204,33 +2308,19 @@ mod _ssl {
             let py_ref =
                 py_ssl_socket.into_ref_with_type(vm, PySslSocket::class(&vm.ctx).to_owned())?;
 
-            // Check if SNI callback is configured (minimize lock time)
-            let has_sni_callback = zelf.sni_callback.lock().is_some();
-
-            // Set up ex_data for callbacks
+            // The connection is owned by py_ref, so this borrowed address
+            // remains valid through every SSL operation, including retries.
             unsafe {
-                let ssl_ptr = py_ref.connection.read().ssl().as_ptr();
-
-                // Clone and store via into_raw() - increments refcount and returns stable pointer
-                // The refcount will be decremented by msg_callback_data_free when SSL is freed
-                let cloned: PyObjectRef = py_ref.clone().into();
-                let raw_ptr = cloned.into_raw();
-                let msg_cb_idx = get_msg_callback_ex_data_index();
-                sys::SSL_set_ex_data(ssl_ptr, msg_cb_idx, raw_ptr.as_ptr() as *mut _);
-
-                // Set SNI callback data if needed
-                if has_sni_callback {
-                    let ssl_socket_weak = py_ref.as_object().downgrade(None, vm)?;
-                    // Store callback data in SSL ex_data - use weak reference to avoid cycle
-                    let callback_data = Box::new(SniCallbackData {
-                        ssl_context: zelf.clone(),
-                        ssl_socket_weak,
-                    });
-                    let sni_idx = get_sni_ex_data_index();
-                    sys::SSL_set_ex_data(ssl_ptr, sni_idx, Box::into_raw(callback_data) as *mut _);
-                }
+                sys::SSL_set_ex_data(
+                    py_ref.connection.read().ssl().as_ptr(),
+                    get_socket_ex_data_index(),
+                    &*py_ref as *const Py<PySslSocket> as *mut _,
+                );
             }
 
+            #[cfg(all(unix, not(target_os = "aix")))]
+            py_ref.install_progress_callback();
+
             // Set session if provided
             if let Some(session) = args.session
                 && !vm.is_none(&session)
@@ -2293,9 +2383,16 @@ mod _ssl {
         binary_form: OptionalArg<bool>,
     }
 
+    #[derive(FromArgs)]
+    struct GetGroupsArgs {
+        #[pyarg(named, default)]
+        include_aliases: bool,
+    }
+
     // Err is true if the socket is blocking
     type SocketDeadline = Result<Instant, bool>;
 
+    #[cfg(not(all(unix, not(target_os = "aix"))))]
     enum SelectRet {
         Nonblocking,
         TimedOut,
@@ -2303,26 +2400,47 @@ mod _ssl {
         Ok,
     }
 
+    #[cfg(not(all(unix, not(target_os = "aix"))))]
     #[derive(Clone, Copy)]
     enum SslNeeds {
         Read,
         Write,
     }
 
-    struct SocketStream(PyRef<PySocket>);
+    struct SocketStream {
+        socket: PyRef<PySocket>,
+        #[cfg(all(unix, not(target_os = "aix")))]
+        identity: Arc<socket::SocketIdentity>,
+        #[cfg(all(unix, not(target_os = "aix")))]
+        progress: u64,
+        #[cfg(all(unix, not(target_os = "aix")))]
+        interrupted: bool,
+    }
 
     impl SocketStream {
+        fn new(socket: PyRef<PySocket>) -> std::io::Result<Self> {
+            Ok(Self {
+                #[cfg(all(unix, not(target_os = "aix")))]
+                identity: socket.ssl_identity()?,
+                socket,
+                #[cfg(all(unix, not(target_os = "aix")))]
+                progress: 0,
+                #[cfg(all(unix, not(target_os = "aix")))]
+                interrupted: false,
+            })
+        }
         fn timeout_deadline(&self) -> SocketDeadline {
-            self.0.get_timeout().map(|d| Instant::now() + d)
+            self.socket.get_timeout().map(|d| Instant::now() + d)
         }
 
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
         fn select(
             &self,
             needs: SslNeeds,
             deadline: &SocketDeadline,
             vm: &VirtualMachine,
         ) -> PyResult<SelectRet> {
-            let Some(sock) = self.0.sock_opt() else {
+            let Some(sock) = self.socket.sock_opt() else {
                 return Ok(SelectRet::Closed);
             };
             // For blocking sockets without timeout, call sock_select with None timeout
@@ -2348,6 +2466,7 @@ mod _ssl {
             })
         }
 
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
         fn socket_needs(
             &self,
             err: &ssl::Error,
@@ -2373,6 +2492,8 @@ mod _ssl {
     struct BioStream {
         inbio: PyRef<PySslMemoryBio>,
         outbio: PyRef<PySslMemoryBio>,
+        #[cfg(all(unix, not(target_os = "aix")))]
+        progress: u64,
     }
 
     impl Read for BioStream {
@@ -2392,6 +2513,10 @@ mod _ssl {
                         "BIO has no data available",
                     ))
                 } else {
+                    #[cfg(all(unix, not(target_os = "aix")))]
+                    {
+                        self.progress = self.progress.wrapping_add(nbytes as u64);
+                    }
                     Ok(nbytes as usize)
                 }
             }
@@ -2410,6 +2535,10 @@ mod _ssl {
                 if nbytes < 0 {
                     return Err(std::io::Error::other("BIO write failed"));
                 }
+                #[cfg(all(unix, not(target_os = "aix")))]
+                {
+                    self.progress = self.progress.wrapping_add(nbytes as u64);
+                }
                 Ok(nbytes as usize)
             }
         }
@@ -2421,107 +2550,978 @@ mod _ssl {
     }
 
     // Enum to represent different SSL connection modes
-    enum SslConnection {
+    enum SslTransport {
         Socket(ssl::SslStream<SocketStream>),
         Bio(ssl::SslStream<BioStream>),
     }
 
-    impl SslConnection {
+    impl Drop for SslTransport {
+        fn drop(&mut self) {
+            // Match CPython: freeing a socket without unwrap() must not invalidate
+            // a session retained by Python. This marks state without doing I/O.
+            let state = self.get_shutdown() | ssl::ShutdownState::SENT;
+            match self {
+                Self::Socket(stream) => stream.set_shutdown(state),
+                Self::Bio(stream) => stream.set_shutdown(state),
+            }
+        }
+    }
+
+    impl SslTransport {
         // Get a reference to the SSL object
         fn ssl(&self) -> &ssl::SslRef {
             match self {
-                SslConnection::Socket(stream) => stream.ssl(),
-                SslConnection::Bio(stream) => stream.ssl(),
+                SslTransport::Socket(stream) => stream.ssl(),
+                SslTransport::Bio(stream) => stream.ssl(),
             }
         }
 
         // Get underlying socket stream reference (only for socket mode)
         fn get_ref(&self) -> Option<&SocketStream> {
             match self {
-                SslConnection::Socket(stream) => Some(stream.get_ref()),
-                SslConnection::Bio(_) => None,
+                SslTransport::Socket(stream) => Some(stream.get_ref()),
+                SslTransport::Bio(_) => None,
             }
         }
 
-        // Check if this is in BIO mode
+        // Check if this is in BIO mode (legacy blocking transport).
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
         fn is_bio(&self) -> bool {
-            matches!(self, SslConnection::Bio(_))
+            matches!(self, SslTransport::Bio(_))
         }
 
         // Perform SSL handshake
         fn do_handshake(&mut self) -> Result<(), ssl::Error> {
+            // SSL_get_error requires an empty queue before this native attempt.
+            unsafe { sys::ERR_clear_error() };
             match self {
-                SslConnection::Socket(stream) => stream.do_handshake(),
-                SslConnection::Bio(stream) => stream.do_handshake(),
+                SslTransport::Socket(stream) => stream.do_handshake(),
+                SslTransport::Bio(stream) => stream.do_handshake(),
             }
         }
 
         // Write data to SSL connection
         fn ssl_write(&mut self, buf: &[u8]) -> Result<usize, ssl::Error> {
+            unsafe { sys::ERR_clear_error() };
             match self {
-                SslConnection::Socket(stream) => stream.ssl_write(buf),
-                SslConnection::Bio(stream) => stream.ssl_write(buf),
+                SslTransport::Socket(stream) => stream.ssl_write(buf),
+                SslTransport::Bio(stream) => stream.ssl_write(buf),
             }
         }
 
         // Read data from SSL connection
         fn ssl_read(&mut self, buf: &mut [u8]) -> Result<usize, ssl::Error> {
+            unsafe { sys::ERR_clear_error() };
+            match self {
+                SslTransport::Socket(stream) => stream.ssl_read(buf),
+                SslTransport::Bio(stream) => stream.ssl_read(buf),
+            }
+        }
+
+        fn shutdown(&mut self) -> Result<ssl::ShutdownResult, ssl::Error> {
+            unsafe { sys::ERR_clear_error() };
             match self {
-                SslConnection::Socket(stream) => stream.ssl_read(buf),
-                SslConnection::Bio(stream) => stream.ssl_read(buf),
+                SslTransport::Socket(stream) => stream.shutdown(),
+                SslTransport::Bio(stream) => stream.shutdown(),
             }
         }
 
         // Get SSL shutdown state
         fn get_shutdown(&mut self) -> ssl::ShutdownState {
             match self {
-                SslConnection::Socket(stream) => stream.get_shutdown(),
-                SslConnection::Bio(stream) => stream.get_shutdown(),
+                SslTransport::Socket(stream) => stream.get_shutdown(),
+                SslTransport::Bio(stream) => stream.get_shutdown(),
             }
         }
 
         // Check if incoming BIO has EOF (for BIO mode only)
         fn is_bio_eof(&self) -> bool {
             match self {
-                SslConnection::Socket(_) => false,
-                SslConnection::Bio(stream) => stream.get_ref().inbio.eof_written.load(),
+                SslTransport::Socket(_) => false,
+                SslTransport::Bio(stream) => stream.get_ref().inbio.eof_written.load(),
             }
         }
     }
 
-    #[pyattr]
-    #[pyclass(module = "_ssl", name = "_SSLSocket", traverse)]
-    #[derive(PyPayload)]
-    struct PySslSocket {
-        ctx: PyRwLock<PyRef<PySslContext>>,
-        #[pytraverse(skip)]
-        connection: PyDetachingRwLock<SslConnection>,
-        #[pytraverse(skip)]
-        socket_type: SslServerOrClient,
-        server_hostname: Option<PyStrRef>,
-        owner: PyRwLock<Option<PyRef<PyWeak>>>,
+    struct SslConnection {
+        transport: SslTransport,
+        #[cfg(all(unix, not(target_os = "aix")))]
+        driver: Driver,
+        #[cfg(all(unix, not(target_os = "aix")))]
+        progress: Arc<ProgressRegistry>,
     }
 
-    impl fmt::Debug for PySslSocket {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            f.pad("_SSLSocket")
+    impl SslConnection {
+        fn new(transport: SslTransport) -> Self {
+            Self {
+                transport,
+                #[cfg(all(unix, not(target_os = "aix")))]
+                driver: Driver::default(),
+                #[cfg(all(unix, not(target_os = "aix")))]
+                progress: Arc::new(ProgressRegistry::default()),
+            }
         }
-    }
 
-    #[pyclass(flags(IMMUTABLETYPE))]
-    impl PySslSocket {
-        #[pygetset]
-        fn owner(zelf: &Py<Self>) -> Option<PyObjectRef> {
-            zelf.owner.read().as_ref().and_then(|weak| weak.upgrade())
+        #[cfg(all(unix, not(target_os = "aix")))]
+        fn notify_progress(&self) {
+            self.progress.notify();
         }
-        #[pygetset(setter)]
-        fn set_owner(zelf: &Py<Self>, owner: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
-            let mut lock = zelf.owner.write();
-            lock.take();
-            *lock = Some(owner.downgrade(None, vm)?);
-            Ok(())
+
+        #[cfg(all(unix, not(target_os = "aix")))]
+        fn io_progress(&self) -> u64 {
+            match &self.transport {
+                SslTransport::Socket(stream) => stream.get_ref().progress,
+                SslTransport::Bio(stream) => stream.get_ref().progress,
+            }
         }
-        #[pygetset]
+
+        #[cfg(all(unix, not(target_os = "aix")))]
+        fn take_interrupted(&mut self) -> bool {
+            match &mut self.transport {
+                SslTransport::Socket(stream) => core::mem::take(&mut stream.get_mut().interrupted),
+                SslTransport::Bio(_) => false,
+            }
+        }
+    }
+
+    impl core::ops::Deref for SslConnection {
+        type Target = SslTransport;
+        fn deref(&self) -> &Self::Target {
+            &self.transport
+        }
+    }
+
+    impl core::ops::DerefMut for SslConnection {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            &mut self.transport
+        }
+    }
+
+    struct SslConnectionLock(PyDetachingRwLock<SslConnection>);
+
+    impl core::ops::Deref for SslConnectionLock {
+        type Target = PyDetachingRwLock<SslConnection>;
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+
+    // Like Traverse for PyRwLock, conservatively retain a connection if a
+    // detached SSL operation holds its write guard when GC stops the world.
+    unsafe impl Traverse for SslConnectionLock {
+        fn traverse(&self, traverse_fn: &mut TraverseFn<'_>) {
+            if let Some(connection) = self.try_read() {
+                match &connection.transport {
+                    SslTransport::Socket(stream) => stream.get_ref().socket.traverse(traverse_fn),
+                    SslTransport::Bio(stream) => {
+                        stream.get_ref().inbio.traverse(traverse_fn);
+                        stream.get_ref().outbio.traverse(traverse_fn);
+                    }
+                }
+            }
+        }
+    }
+
+    #[pyattr]
+    #[pyclass(module = "_ssl", name = "_SSLSocket", traverse)]
+    #[derive(PyPayload)]
+    struct PySslSocket {
+        ctx: PyRwLock<PyRef<PySslContext>>,
+        connection: SslConnectionLock,
+        #[pytraverse(skip)]
+        socket_type: SslServerOrClient,
+        server_hostname: Option<PyStrRef>,
+        owner: PyRwLock<Option<PyRef<PyWeak>>>,
+        #[pytraverse(skip)]
+        got_eof_error: AtomicCell<bool>,
+        #[pytraverse(skip)]
+        shutdown_seen_zero: AtomicCell<bool>,
+        callback_error: PyMutex<Option<PyBaseExceptionRef>>,
+        #[cfg(all(unix, not(target_os = "aix")))]
+        #[pytraverse(skip)]
+        info_progress: AtomicCell<u64>,
+        #[cfg(all(unix, not(target_os = "aix")))]
+        #[pytraverse(skip)]
+        previous_info_callback: AtomicCell<SslInfoCallback>,
+    }
+
+    impl fmt::Debug for PySslSocket {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            f.pad("_SSLSocket")
+        }
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    struct IoScope(*const PySslSocket);
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    impl IoScope {
+        fn enter(socket: &PySslSocket, vm: &VirtualMachine) -> PyResult<Self> {
+            let pointer = socket as *const _;
+            let entered = SSL_IO_CALLS.with(|calls| {
+                let mut calls = calls.borrow_mut();
+                if calls.contains(&pointer) {
+                    false
+                } else {
+                    calls.push(pointer);
+                    true
+                }
+            });
+            // Exception allocation can run Python finalizers. Do not retain a
+            // RefCell borrow while they may attempt another SSL invocation.
+            if entered {
+                Ok(Self(pointer))
+            } else {
+                Err(vm.new_runtime_error("Reentrant I/O on the same SSL connection"))
+            }
+        }
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    impl Drop for IoScope {
+        fn drop(&mut self) {
+            SSL_IO_CALLS.with(|calls| {
+                let pointer = calls.borrow_mut().pop();
+                debug_assert_eq!(pointer, Some(self.0));
+            });
+        }
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    enum IoOperation<'a> {
+        Handshake,
+        Read(&'a mut [u8]),
+        Write(Option<Box<[u8]>>),
+        Shutdown,
+        #[cfg(ossl111)]
+        PostHandshake,
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    impl IoOperation<'_> {
+        fn timeout_message(&self, needs: Option<Needs>) -> &'static str {
+            match self {
+                Self::Handshake => "The handshake operation timed out",
+                Self::Read(_) => "The read operation timed out",
+                Self::Write(_) => "The write operation timed out",
+                Self::Shutdown if needs == Some(Needs::Read) => "The read operation timed out",
+                Self::Shutdown => "The write operation timed out",
+                #[cfg(ossl111)]
+                Self::PostHandshake => "The handshake operation timed out",
+            }
+        }
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    enum IoOutput {
+        Done,
+        Count(usize),
+        Shutdown(ssl::ShutdownResult),
+        Unwrapped(Option<PyRef<PySocket>>),
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    enum IoStep {
+        Done(IoOutput),
+        // Preserve the pre-existing clean-read-EOF/PHA signal boundary.
+        Immediate(IoOutput),
+        Again,
+        Wait(Option<std::os::fd::RawFd>, Needs),
+    }
+
+    // Owned failures leave the native guard before exception allocation or
+    // attribute writes, either of which can execute Python (including GC).
+    #[cfg(all(unix, not(target_os = "aix")))]
+    enum IoError {
+        Eof,
+        Closed,
+        Timeout(&'static str),
+        WantWrite,
+        Message(&'static str),
+        Io(std::io::Error),
+        Callback(PyBaseExceptionRef),
+        Native(SslErrorSnapshot, Option<PyBaseExceptionRef>),
+        #[cfg(ossl111)]
+        Stack(ErrorStack, Option<PyBaseExceptionRef>),
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    impl IoError {
+        fn into_pyexception(self, vm: &VirtualMachine) -> PyBaseExceptionRef {
+            match self {
+                Self::Eof => create_ssl_eof_error(vm).upcast(),
+                Self::Closed => socket_closed_error(vm),
+                Self::Timeout(message) => {
+                    socket::timeout_error_msg(vm, message.to_owned()).upcast()
+                }
+                Self::WantWrite => create_ssl_want_write_error(vm).upcast(),
+                Self::Message(message) => new_ssl_error(vm, message),
+                Self::Io(error) => error.to_pyexception(vm),
+                Self::Callback(error) => error,
+                Self::Native(error, callback) => {
+                    let error = error.into_pyexception(vm);
+                    if let Some(callback) = callback {
+                        error.set_context(Some(callback));
+                    }
+                    error
+                }
+                #[cfg(ossl111)]
+                Self::Stack(error, callback) => {
+                    let error = convert_openssl_error(vm, error);
+                    if let Some(callback) = callback {
+                        error.set_context(Some(callback));
+                    }
+                    error
+                }
+            }
+        }
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    struct IoCall<'a> {
+        _ssl: &'a PySslSocket,
+        owner: Option<WriteOwner>,
+        owns_pending: bool,
+        last_needs: Option<Needs>,
+        progress: Arc<ProgressRegistry>,
+        socket: Option<(PyRef<PySocket>, Arc<socket::SocketIdentity>, SocketDeadline)>,
+        waiter: Option<Arc<ProgressWaiter>>,
+        // Keep this installed through waits and signal callbacks, but never
+        // expose a stale native SSL pointer while its guard is released.
+        _scope: IoScope,
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    impl<'a> IoCall<'a> {
+        fn new(ssl: &'a PySslSocket, writing: bool, vm: &VirtualMachine) -> PyResult<Self> {
+            let scope = IoScope::enter(ssl, vm)?;
+            let connection = ssl.connection.read();
+            let progress = connection.progress.clone();
+            let socket = connection.get_ref().map(|stream| {
+                (
+                    stream.socket.clone(),
+                    stream.identity.clone(),
+                    stream.timeout_deadline(),
+                )
+            });
+            Ok(Self {
+                _ssl: ssl,
+                owner: writing.then(WriteOwner::new),
+                owns_pending: false,
+                last_needs: None,
+                progress,
+                socket,
+                waiter: None,
+                _scope: scope,
+            })
+        }
+
+        fn prepare_wait(
+            &mut self,
+            observed: u64,
+            needs: Option<Needs>,
+            error: IoError,
+            timeout_message: &'static str,
+        ) -> Result<IoStep, IoError> {
+            let Some((socket, identity, deadline)) = &self.socket else {
+                return Err(error);
+            };
+            match deadline {
+                Err(false) => return Err(error),
+                Ok(deadline) if *deadline <= Instant::now() => {
+                    return Err(IoError::Timeout(timeout_message));
+                }
+                _ => {}
+            }
+            if self.waiter.is_none() {
+                self.waiter = Some(Arc::new(ProgressWaiter::new().map_err(IoError::Io)?));
+            }
+            let waiter = self.waiter.as_ref().expect("waiter initialized");
+            // Close does not need the SSL lock. Drain BEFORE checking identity
+            // and subscribing, or a concurrent close notification could be lost.
+            match waiter.drain() {
+                Ok(()) => {}
+                Err(error) if error.kind() == std::io::ErrorKind::Interrupted => {
+                    return Ok(IoStep::Again);
+                }
+                Err(error) => return Err(IoError::Io(error)),
+            }
+            let fd = socket
+                .sock_for_ssl_identity(identity)
+                .map_err(|_| IoError::Closed)?
+                .as_raw_fd();
+            if !identity.subscribe(waiter.clone()) {
+                return Err(IoError::Closed);
+            }
+            self.progress.register(waiter, observed);
+            // Exclusive-writer contenders must not poll socket writability: it
+            // can remain ready while they are forbidden to execute native I/O.
+            Ok(IoStep::Wait(
+                needs.map(|_| fd),
+                needs.unwrap_or(Needs::Write),
+            ))
+        }
+
+        fn wait(
+            &self,
+            fd: Option<std::os::fd::RawFd>,
+            needs: Needs,
+            timeout_message: &'static str,
+            vm: &VirtualMachine,
+        ) -> Result<(), IoError> {
+            let waiter = self.waiter.as_ref().expect("registered waiter");
+            let deadline = self
+                .socket
+                .as_ref()
+                .and_then(|(_, _, deadline)| deadline.as_ref().ok().copied());
+            loop {
+                let result = vm.allow_threads(|| waiter.wait(fd, needs == Needs::Write, deadline));
+                // No connection or socket lock is held while Python signals run.
+                vm.check_signals().map_err(IoError::Callback)?;
+                match result {
+                    Ok(false) => return Ok(()),
+                    Ok(true) => {
+                        return Err(IoError::Timeout(timeout_message));
+                    }
+                    Err(error) if error.kind() == std::io::ErrorKind::Interrupted => {}
+                    Err(error) => {
+                        if self
+                            .socket
+                            .as_ref()
+                            .is_some_and(|(_, identity, _)| identity.is_closed())
+                        {
+                            return Err(IoError::Closed);
+                        }
+                        return Err(IoError::Io(error));
+                    }
+                }
+            }
+        }
+
+        fn abandon_pending(&mut self) {
+            if self.owns_pending {
+                self.owner.as_ref().expect("pending write owner").release();
+                self.owns_pending = false;
+                self.progress.notify();
+            }
+        }
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    impl Drop for IoCall<'_> {
+        fn drop(&mut self) {
+            // Cleanup must never acquire the SSL lock: a callback on another
+            // thread may be waiting for this invocation to finish. Publish an
+            // orphan before waking generation-checked registrations instead.
+            self.abandon_pending();
+            if let Some(waiter) = &self.waiter {
+                self.progress.unregister(waiter);
+                if let Some((_, identity, _)) = &self.socket {
+                    identity.unsubscribe(waiter.clone());
+                }
+            }
+        }
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    impl PySslSocket {
+        fn install_progress_callback(&self) {
+            let connection = self.connection.write();
+            let pointer = connection.ssl().as_ptr();
+            unsafe {
+                self.previous_info_callback
+                    .store(SSL_get_info_callback(pointer));
+                SSL_set_info_callback(pointer, Some(ssl_info_progress));
+            }
+        }
+
+        fn drive(&self, mut operation: IoOperation<'_>, vm: &VirtualMachine) -> PyResult<IoOutput> {
+            self.check_eof(vm)?;
+            let mut call = IoCall::new(self, matches!(operation, IoOperation::Write(_)), vm)?;
+            let mut queued = false;
+            let mut shutdown_zeros = 0;
+            let mut attempted = false;
+            let mut waited_for_ownership = false;
+            loop {
+                let step = (|| {
+                    let mut connection = self.connection.write();
+                    if self.got_eof_error.load() {
+                        return Err(IoError::Eof);
+                    }
+                    if connection.driver.terminal {
+                        return Err(IoError::Message(
+                            "TLS connection is unusable after a fatal error",
+                        ));
+                    }
+                    if call
+                        .socket
+                        .as_ref()
+                        .is_some_and(|(_, identity, _)| identity.is_closed())
+                    {
+                        return Err(IoError::Closed);
+                    }
+                    // Buffered TLS data can satisfy even a very short positive
+                    // timeout. Attempt native I/O once before timing retries.
+                    if (attempted || waited_for_ownership)
+                        && call.socket.as_ref().is_some_and(|(_, _, deadline)| {
+                            deadline
+                                .as_ref()
+                                .is_ok_and(|deadline| *deadline <= Instant::now())
+                        })
+                    {
+                        return Err(IoError::Timeout(operation.timeout_message(call.last_needs)));
+                    }
+                    // Abandonment is deliberately independent of the SSL lock.
+                    // Observe its generation before checking the predicate.
+                    let observed = call.progress.generation();
+                    let permit = match &mut operation {
+                        IoOperation::Write(bytes) => connection.driver.write(
+                            call.owner.as_ref().unwrap(),
+                            bytes,
+                            &mut queued,
+                        ),
+                        _ => connection.driver.other_io(),
+                    };
+                    match permit {
+                        Permit::RetryOriginalWrite => Err(IoError::WantWrite),
+                        Permit::InvalidRetry => Err(IoError::Message(
+                            "The pending SSL write must be retried with the same data in a new call",
+                        )),
+                        Permit::Wait => {
+                            waited_for_ownership = true;
+                            call.prepare_wait(
+                                observed,
+                                None,
+                                IoError::WantWrite,
+                                operation.timeout_message(call.last_needs),
+                            )
+                        }
+                        Permit::Ready => {
+                            attempted = true;
+                            call.owns_pending = call.owner.is_some();
+                            let before = (
+                                connection.io_progress(),
+                                self.info_progress.load(),
+                                connection.get_shutdown(),
+                            );
+                            let permission_before = connection.driver.other_io();
+                            let pointer = connection.ssl().as_ptr();
+                            let result = {
+                                let _native_scope =
+                                    HandshakeVmGuard::new(vm, &self.connection, pointer);
+                                match &mut operation {
+                                    IoOperation::Handshake => vm
+                                        .allow_threads(|| connection.do_handshake())
+                                        .map(|()| IoOutput::Done),
+                                    IoOperation::Read(buffer) => vm
+                                        .allow_threads(|| connection.ssl_read(buffer))
+                                        .map(IoOutput::Count),
+                                    IoOperation::Write(_) => {
+                                        let SslConnection {
+                                            transport, driver, ..
+                                        } = &mut *connection;
+                                        vm.allow_threads(|| {
+                                            transport.ssl_write(
+                                                driver.bytes(call.owner.as_ref().unwrap()),
+                                            )
+                                        })
+                                        .map(IoOutput::Count)
+                                    }
+                                    IoOperation::Shutdown => {
+                                        if self.shutdown_seen_zero.load() {
+                                            // Leave plaintext after close_notify for unwrap().
+                                            unsafe {
+                                                sys::SSL_ctrl(
+                                                    pointer,
+                                                    sys::SSL_CTRL_SET_READ_AHEAD,
+                                                    0,
+                                                    core::ptr::null_mut(),
+                                                );
+                                            }
+                                        }
+                                        vm.allow_threads(|| connection.shutdown())
+                                            .map(IoOutput::Shutdown)
+                                    }
+                                    #[cfg(ossl111)]
+                                    IoOperation::PostHandshake => {
+                                        unsafe { sys::ERR_clear_error() };
+                                        let result = vm.allow_threads(|| unsafe {
+                                            SSL_verify_client_post_handshake(pointer)
+                                        });
+                                        let error = (result == 0).then(ErrorStack::get);
+                                        let callback = self.callback_error.lock().take();
+                                        connection.notify_progress();
+                                        return match (error, callback) {
+                                            (Some(error), callback) => {
+                                                Err(IoError::Stack(error, callback))
+                                            }
+                                            (None, Some(callback)) => {
+                                                Err(IoError::Callback(callback))
+                                            }
+                                            (None, None) => Ok(IoStep::Immediate(IoOutput::Done)),
+                                        };
+                                    }
+                                }
+                            };
+                            let needs =
+                                result.as_ref().err().and_then(|error| match error.code() {
+                                    ssl::ErrorCode::WANT_READ => Some(Needs::Read),
+                                    ssl::ErrorCode::WANT_WRITE => Some(Needs::Write),
+                                    _ => None,
+                                });
+                            call.last_needs = needs;
+                            let terminal = result.as_ref().err().is_some_and(|error| {
+                                matches!(
+                                    error.code(),
+                                    ssl::ErrorCode::SSL | ssl::ErrorCode::SYSCALL
+                                )
+                            });
+                            // Settle native ownership BEFORE a callback/signal can
+                            // return an exception. Success must never be replayed.
+                            if let Some(owner) = &call.owner {
+                                call.owns_pending = connection.driver.settle_write(owner, needs);
+                            }
+                            if terminal {
+                                connection.driver.fail();
+                            }
+                            if result.as_ref().err().is_some_and(is_unexpected_eof) {
+                                self.got_eof_error.store(true);
+                            }
+                            let after = (
+                                connection.io_progress(),
+                                self.info_progress.load(),
+                                connection.get_shutdown(),
+                            );
+                            if before != after
+                                || result.is_ok()
+                                || terminal
+                                || permission_before != connection.driver.other_io()
+                            {
+                                connection.notify_progress();
+                            }
+                            let interrupted = connection.take_interrupted();
+                            // Snapshot exactly once, while this operation still
+                            // owns native state. No unlocked helper drains it.
+                            let callback = self.callback_error.lock().take();
+                            if let Some(callback) = callback {
+                                // A fully blocking socket could not expose this
+                                // intermediate WANT before the nonblocking driver.
+                                // Timeout/nonblocking sockets and MemoryBIO retain
+                                // native-error-first exception chaining.
+                                if needs.is_some()
+                                    && call.socket.as_ref().is_some_and(|(_, _, deadline)| {
+                                        matches!(deadline, Err(true))
+                                    })
+                                {
+                                    return Err(IoError::Callback(callback));
+                                }
+                                return Err(match result {
+                                    Ok(_) => IoError::Callback(callback),
+                                    Err(error) => IoError::Native(
+                                        SslErrorSnapshot::capture(error, pointer),
+                                        Some(callback),
+                                    ),
+                                });
+                            }
+                            match result {
+                                Ok(IoOutput::Shutdown(ssl::ShutdownResult::Sent)) => {
+                                    shutdown_zeros += 1;
+                                    self.shutdown_seen_zero.store(true);
+                                    if shutdown_zeros > 1 {
+                                        Ok(IoStep::Done(IoOutput::Unwrapped(
+                                            call.socket
+                                                .as_ref()
+                                                .map(|(socket, _, _)| socket.clone()),
+                                        )))
+                                    } else {
+                                        Ok(IoStep::Again)
+                                    }
+                                }
+                                Ok(IoOutput::Shutdown(ssl::ShutdownResult::Received)) => {
+                                    Ok(IoStep::Done(IoOutput::Unwrapped(
+                                        call.socket.as_ref().map(|(socket, _, _)| socket.clone()),
+                                    )))
+                                }
+                                Ok(output) => Ok(IoStep::Done(output)),
+                                Err(error) => {
+                                    // Callback errors take precedence over these
+                                    // successful/EOF read reinterpretations above.
+                                    if matches!(operation, IoOperation::Read(_)) {
+                                        if error.code() == ssl::ErrorCode::ZERO_RETURN {
+                                            return Ok(IoStep::Immediate(IoOutput::Count(0)));
+                                        }
+                                        if error.code() == ssl::ErrorCode::WANT_READ
+                                            && connection.is_bio_eof()
+                                        {
+                                            self.got_eof_error.store(true);
+                                            connection.driver.fail();
+                                            connection.notify_progress();
+                                            return Err(IoError::Eof);
+                                        }
+                                    }
+                                    let error = IoError::Native(
+                                        SslErrorSnapshot::capture(error, pointer),
+                                        None,
+                                    );
+                                    if let Some(needs) = needs {
+                                        if interrupted {
+                                            Ok(IoStep::Again)
+                                        } else {
+                                            call.prepare_wait(
+                                                observed,
+                                                Some(needs),
+                                                error,
+                                                operation.timeout_message(call.last_needs),
+                                            )
+                                        }
+                                    } else {
+                                        Err(error)
+                                    }
+                                }
+                            }
+                        }
+                    }
+                })();
+                // Allocation/attribute writes may run arbitrary Python. The
+                // SSL guard and callback pointer are gone, and a known-exiting
+                // write no longer blocks contenders as an active owner.
+                let step = match step {
+                    Ok(IoStep::Immediate(output)) => return Ok(output),
+                    Ok(step) => step,
+                    Err(error) => {
+                        call.abandon_pending();
+                        return Err(error.into_pyexception(vm));
+                    }
+                };
+                if let Err(error) = vm.check_signals() {
+                    call.abandon_pending();
+                    return Err(error);
+                }
+                match step {
+                    IoStep::Immediate(_) => unreachable!("immediate result already returned"),
+                    IoStep::Done(output) => return Ok(output),
+                    IoStep::Again => {}
+                    IoStep::Wait(fd, needs) => {
+                        if let Err(error) =
+                            call.wait(fd, needs, operation.timeout_message(call.last_needs), vm)
+                        {
+                            call.abandon_pending();
+                            return Err(error.into_pyexception(vm));
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    type SslInfoCallback =
+        Option<unsafe extern "C" fn(*const sys::SSL, core::ffi::c_int, core::ffi::c_int)>;
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    unsafe extern "C" {
+        fn SSL_get_info_callback(ssl: *const sys::SSL) -> SslInfoCallback;
+        fn SSL_set_info_callback(ssl: *mut sys::SSL, callback: SslInfoCallback);
+        fn SSL_CTX_get_info_callback(ctx: *const sys::SSL_CTX) -> SslInfoCallback;
+    }
+
+    #[cfg(all(unix, not(target_os = "aix")))]
+    unsafe extern "C" fn ssl_info_progress(
+        ssl: *const sys::SSL,
+        where_: core::ffi::c_int,
+        value: core::ffi::c_int,
+    ) {
+        // These public callback bits are present in OpenSSL 1.1.1 as well as 3.x.
+        const SSL_CB_LOOP: core::ffi::c_int = 0x01;
+        const SSL_CB_HANDSHAKE_DONE: core::ffi::c_int = 0x20;
+        const SSL_CB_ALERT: core::ffi::c_int = 0x4000;
+        unsafe {
+            let socket =
+                sys::SSL_get_ex_data(ssl, get_socket_ex_data_index()) as *const Py<PySslSocket>;
+            if socket.is_null() {
+                return;
+            }
+            let socket = &*socket;
+            if where_ & (SSL_CB_LOOP | SSL_CB_HANDSHAKE_DONE | SSL_CB_ALERT) != 0 {
+                socket
+                    .info_progress
+                    .store(socket.info_progress.load().wrapping_add(1));
+            }
+            // A NULL per-SSL callback delegates to the CURRENT context, including
+            // a context installed by SNI. Preserve that fallback dynamically.
+            let callback = socket
+                .previous_info_callback
+                .load()
+                .or_else(|| SSL_CTX_get_info_callback(sys::SSL_get_SSL_CTX(ssl)));
+            if let Some(callback) = callback {
+                callback(ssl, where_, value);
+            }
+        }
+    }
+
+    #[pyclass(flags(IMMUTABLETYPE))]
+    impl PySslSocket {
+        #[cfg(all(unix, not(target_os = "aix")))]
+        #[pymethod]
+        fn do_handshake(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
+            zelf.drive(IoOperation::Handshake, vm).map(|_| ())
+        }
+
+        #[cfg(all(unix, not(target_os = "aix")))]
+        #[pymethod]
+        fn shutdown(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<PyRef<PySocket>>> {
+            // Do not reacquire the connection after completion: another native
+            // callback may already be waiting for this Python call to return.
+            match zelf.drive(IoOperation::Shutdown, vm)? {
+                IoOutput::Unwrapped(socket) => Ok(socket),
+                _ => unreachable!("shutdown returns its underlying socket"),
+            }
+        }
+
+        #[cfg(all(unix, not(target_os = "aix")))]
+        #[pymethod]
+        fn verify_client_post_handshake(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
+            cfg_select! {
+                ossl111 => zelf.drive(IoOperation::PostHandshake, vm).map(|_| ()),
+                _ => Err(vm.new_not_implemented_error("Post-handshake auth is not supported by your OpenSSL version.")),
+            }
+        }
+
+        #[cfg(all(unix, not(target_os = "aix")))]
+        #[pymethod]
+        fn write(zelf: &Py<Self>, data: ArgBytesLike, vm: &VirtualMachine) -> PyResult<usize> {
+            zelf.check_eof(vm)?;
+            // OpenSSL retains the write across WANT, including after this
+            // Python invocation returns. Own the bytes, not an exporter lock.
+            let bytes = {
+                let source = data.borrow_buf();
+                let mut owned = Vec::new();
+                owned
+                    .try_reserve_exact(source.len())
+                    .map_err(|_| vm.no_memory_error())?;
+                owned.extend_from_slice(&source);
+                owned.into_boxed_slice()
+            };
+            match zelf.drive(IoOperation::Write(Some(bytes)), vm)? {
+                IoOutput::Count(count) => Ok(count),
+                _ => unreachable!("write returns a byte count"),
+            }
+        }
+
+        #[cfg(all(unix, not(target_os = "aix")))]
+        #[pymethod]
+        fn read(
+            zelf: &Py<Self>,
+            n: isize,
+            buffer: OptionalArg<ArgMemoryBuffer>,
+            vm: &VirtualMachine,
+        ) -> PyResult {
+            let read_len = match &buffer {
+                OptionalArg::Present(buffer) => {
+                    let len = buffer.borrow_buf_mut().len();
+                    if n <= 0 || n as usize > len {
+                        len
+                    } else {
+                        n as usize
+                    }
+                }
+                OptionalArg::Missing => {
+                    if n < 0 {
+                        return Err(vm.new_value_error("size should not be negative"));
+                    }
+                    n as usize
+                }
+            };
+            zelf.check_eof(vm)?;
+            // As in CPython, a zero-length read need not enter native SSL.
+            if read_len == 0 {
+                return Ok(if buffer.is_present() {
+                    vm.ctx.new_int(0).into()
+                } else {
+                    vm.ctx.new_bytes(vec![]).into()
+                });
+            }
+            // Do not keep the caller's buffer locked while waiting for a peer.
+            let mut scratch = vm.new_zeroed_bytes(read_len)?;
+            let count = match zelf.drive(IoOperation::Read(&mut scratch), vm)? {
+                IoOutput::Count(count) => count,
+                _ => unreachable!("read returns a byte count"),
+            };
+            Ok(match &buffer {
+                OptionalArg::Present(buffer) => {
+                    buffer.borrow_buf_mut()[..count].copy_from_slice(&scratch[..count]);
+                    vm.ctx.new_int(count).into()
+                }
+                OptionalArg::Missing => {
+                    scratch.truncate(count);
+                    scratch.shrink_to_fit();
+                    vm.ctx.new_bytes(scratch).into()
+                }
+            })
+        }
+
+        fn callback_owner(zelf: &Py<Self>) -> Option<PyObjectRef> {
+            if let Some(owner) = zelf.owner.read().as_ref() {
+                return owner.upgrade();
+            }
+            // A MemoryBIO wrapper may have no Python owner.
+            Some(zelf.as_object().to_owned())
+        }
+
+        fn check_eof(&self, vm: &VirtualMachine) -> PyResult<()> {
+            if self.got_eof_error.load() {
+                Err(create_ssl_eof_error(vm).upcast())
+            } else {
+                Ok(())
+            }
+        }
+
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
+        fn ssl_error(
+            &self,
+            error: ssl::Error,
+            ssl_ptr: *const sys::SSL,
+            vm: &VirtualMachine,
+        ) -> PyBaseExceptionRef {
+            if is_unexpected_eof(&error) {
+                self.got_eof_error.store(true);
+            }
+            SslErrorSnapshot::capture(error, ssl_ptr).into_pyexception(vm)
+        }
+
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
+        fn finish_ssl_operation<T>(
+            &self,
+            result: Result<T, ssl::Error>,
+            ssl_ptr: *const sys::SSL,
+            vm: &VirtualMachine,
+        ) -> PyResult<Result<T, ssl::Error>> {
+            let callback_error = self.callback_error.lock().take();
+            if let Some(callback_error) = callback_error {
+                return Err(match result {
+                    Ok(_) => callback_error,
+                    Err(error) => {
+                        let error = self.ssl_error(error, ssl_ptr, vm);
+                        error.set_context(Some(callback_error));
+                        error
+                    }
+                });
+            }
+            Ok(result)
+        }
+
+        #[pygetset]
+        fn owner(zelf: &Py<Self>) -> Option<PyObjectRef> {
+            zelf.owner.read().as_ref().and_then(|weak| weak.upgrade())
+        }
+        #[pygetset(setter)]
+        fn set_owner(zelf: &Py<Self>, owner: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
+            let mut lock = zelf.owner.write();
+            lock.take();
+            *lock = Some(owner.downgrade(None, vm)?);
+            Ok(())
+        }
+        #[pygetset]
         fn server_side(zelf: &Py<Self>) -> bool {
             zelf.socket_type == SslServerOrClient::Server
         }
@@ -2535,21 +3535,16 @@ mod _ssl {
             value: PyRef<PySslContext>,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
-            // Get SSL pointer - use thread-local during handshake to avoid deadlock
-            // (connection lock is already held during handshake)
-            let ssl_ptr = get_ssl_ptr_for_context_change(&zelf.connection);
-
-            // Set the new SSL_CTX on the SSL object
-            unsafe {
-                let result = SSL_set_SSL_CTX(ssl_ptr, value.ctx().as_ptr());
-                if result.is_null() {
-                    return Err(vm.new_runtime_error("Failed to set SSL context"));
+            with_ssl_pointer_mut(&zelf.connection, |ssl_ptr| {
+                unsafe {
+                    let result = SSL_set_SSL_CTX(ssl_ptr, value.ctx().as_ptr());
+                    if result.is_null() {
+                        return Err(vm.new_runtime_error("Failed to set SSL context"));
+                    }
                 }
-            }
-
-            // Update self.ctx to the new context
-            *zelf.ctx.write() = value;
-            Ok(())
+                *zelf.ctx.write() = value;
+                Ok(())
+            })
         }
         #[pygetset]
         fn server_hostname(zelf: &Py<Self>) -> Option<PyStrRef> {
@@ -2563,182 +3558,266 @@ mod _ssl {
             vm: &VirtualMachine,
         ) -> PyResult<Option<PyObjectRef>> {
             let binary = args.binary_form.unwrap_or(false);
-            let stream = zelf.connection.read();
-            if !stream.ssl().is_init_finished() {
-                return Err(vm.new_value_error("handshake not done yet"));
-            }
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                let ssl = unsafe { ssl::SslRef::from_ptr(ssl_ptr) };
+                if !ssl.is_init_finished() {
+                    return Err(vm.new_value_error("handshake not done yet"));
+                }
 
-            let peer_cert = stream.ssl().peer_certificate();
-            let Some(cert) = peer_cert else {
-                return Ok(None);
-            };
+                let peer_cert = ssl.peer_certificate();
+                let Some(cert) = peer_cert else {
+                    return Ok(None);
+                };
 
-            if binary {
-                // Return DER-encoded certificate
-                cert_to_py(vm, &cert, true).map(Some)
-            } else {
-                // Check verify_mode
+                if binary {
+                    // Return DER-encoded certificate
+                    cert_to_py(vm, &cert, true).map(Some)
+                } else {
+                    // Check verify_mode
+                    unsafe {
+                        let ssl_ctx = sys::SSL_get_SSL_CTX(ssl_ptr);
+                        let verify_mode = sys::SSL_CTX_get_verify_mode(ssl_ctx);
+                        if (verify_mode & sys::SSL_VERIFY_PEER as core::ffi::c_int) == 0 {
+                            // Return empty dict when SSL_VERIFY_PEER is not set
+                            Ok(Some(vm.ctx.new_dict().into()))
+                        } else {
+                            // Return decoded certificate
+                            cert_to_py(vm, &cert, false).map(Some)
+                        }
+                    }
+                }
+            })
+        }
+
+        #[pymethod]
+        fn get_unverified_chain(
+            zelf: &Py<Self>,
+            vm: &VirtualMachine,
+        ) -> PyResult<Option<PyListRef>> {
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                let ssl = unsafe { ssl::SslRef::from_ptr(ssl_ptr) };
+                let Some(chain) = ssl.peer_cert_chain() else {
+                    return Ok(None);
+                };
+
+                // Return Certificate objects
+                let mut certs: Vec<PyObjectRef> = chain
+                    .iter()
+                    .map(|cert| unsafe {
+                        sys::X509_up_ref(cert.as_ptr());
+                        let owned = X509::from_ptr(cert.as_ptr());
+                        cert_to_certificate(vm, owned)
+                    })
+                    .collect::<PyResult<_>>()?;
+
+                // SSL_get_peer_cert_chain does not include peer cert for server-side sockets
+                // Add it manually at the beginning
+                if matches!(zelf.socket_type, SslServerOrClient::Server)
+                    && let Some(peer_cert) = ssl.peer_certificate()
+                {
+                    let peer_obj = cert_to_certificate(vm, peer_cert)?;
+                    certs.insert(0, peer_obj);
+                }
+
+                Ok(Some(vm.ctx.new_list(certs)))
+            })
+        }
+
+        #[pymethod]
+        fn get_verified_chain(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<PyListRef>> {
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| {
                 unsafe {
-                    let ssl_ctx = sys::SSL_get_SSL_CTX(stream.ssl().as_ptr());
-                    let verify_mode = sys::SSL_CTX_get_verify_mode(ssl_ctx);
-                    if (verify_mode & sys::SSL_VERIFY_PEER as core::ffi::c_int) == 0 {
-                        // Return empty dict when SSL_VERIFY_PEER is not set
-                        Ok(Some(vm.ctx.new_dict().into()))
-                    } else {
-                        // Return decoded certificate
-                        cert_to_py(vm, &cert, false).map(Some)
+                    let chain = sys::SSL_get0_verified_chain(ssl_ptr);
+                    if chain.is_null() {
+                        return Ok(None);
                     }
+
+                    let num_certs = sys::OPENSSL_sk_num(chain as *const _);
+
+                    let mut certs = Vec::with_capacity(num_certs as usize);
+                    // Return Certificate objects
+                    for i in 0..num_certs {
+                        let cert_ptr =
+                            sys::OPENSSL_sk_value(chain as *const _, i) as *mut sys::X509;
+                        if cert_ptr.is_null() {
+                            continue;
+                        }
+                        // Clone the X509 certificate to create an owned copy
+                        sys::X509_up_ref(cert_ptr);
+                        let owned_cert = X509::from_ptr(cert_ptr);
+                        let cert_obj = cert_to_certificate(vm, owned_cert)?;
+                        certs.push(cert_obj);
+                    }
+
+                    Ok(if certs.is_empty() {
+                        None
+                    } else {
+                        Some(vm.ctx.new_list(certs))
+                    })
+                }
+            })
+        }
+
+        #[pymethod]
+        fn version(zelf: &Py<Self>) -> Option<&'static str> {
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                // Return None if handshake is not complete (CPython behavior).
+                if unsafe { sys::SSL_is_init_finished(ssl_ptr) } == 0 {
+                    return None;
                 }
+                let version = unsafe { ssl::SslRef::from_ptr(ssl_ptr).version_str() };
+                if version == "unknown" {
+                    None
+                } else {
+                    Some(version)
+                }
+            })
+        }
+        #[pymethod]
+        fn cipher(zelf: &Py<Self>) -> Option<CipherTuple> {
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                unsafe { ssl::SslRef::from_ptr(ssl_ptr).current_cipher() }.map(cipher_to_tuple)
+            })
+        }
+        #[pymethod]
+        fn group(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<String>> {
+            #[cfg(ossl320)]
+            {
+                let _ = vm;
+                Ok(with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                    let name = unsafe { SSL_get0_group_name(ssl_ptr) };
+                    (!name.is_null())
+                        .then(|| unsafe { CStr::from_ptr(name).to_string_lossy().into_owned() })
+                }))
+            }
+            #[cfg(not(ossl320))]
+            {
+                let _ = zelf;
+                Err(vm.new_not_implemented_error(
+                    "Getting selected group requires OpenSSL 3.2 or later.",
+                ))
             }
         }
 
-        #[pymethod]
-        fn get_unverified_chain(
-            zelf: &Py<Self>,
+        fn signature_name(
+            &self,
+            side: SslServerOrClient,
             vm: &VirtualMachine,
-        ) -> PyResult<Option<PyListRef>> {
-            let stream = zelf.connection.read();
-            let ssl = stream.ssl();
-            let Some(chain) = ssl.peer_cert_chain() else {
-                return Ok(None);
-            };
-
-            // Return Certificate objects
-            let mut certs: Vec<PyObjectRef> = chain
-                .iter()
-                .map(|cert| unsafe {
-                    sys::X509_up_ref(cert.as_ptr());
-                    let owned = X509::from_ptr(cert.as_ptr());
-                    cert_to_certificate(vm, owned)
-                })
-                .collect::<PyResult<_>>()?;
-
-            // SSL_get_peer_cert_chain does not include peer cert for server-side sockets
-            // Add it manually at the beginning
-            if matches!(zelf.socket_type, SslServerOrClient::Server)
-                && let Some(peer_cert) = ssl.peer_certificate()
+        ) -> PyResult<Option<String>> {
+            #[cfg(ossl350)]
             {
-                let peer_obj = cert_to_certificate(vm, peer_cert)?;
-                certs.insert(0, peer_obj);
+                let _ = vm;
+                const SSL_CTRL_GET_SIGNATURE_NAME: core::ffi::c_int = 140;
+                const SSL_CTRL_GET_PEER_SIGNATURE_NAME: core::ffi::c_int = 141;
+                let command = if self.socket_type == side {
+                    SSL_CTRL_GET_SIGNATURE_NAME
+                } else {
+                    SSL_CTRL_GET_PEER_SIGNATURE_NAME
+                };
+                Ok(with_ssl_pointer(&self.connection, |ssl_ptr| {
+                    let mut name: *const core::ffi::c_char = core::ptr::null();
+                    let result = unsafe {
+                        sys::SSL_ctrl(ssl_ptr, command, 0, core::ptr::addr_of_mut!(name).cast())
+                    };
+                    (result != 0 && !name.is_null())
+                        .then(|| unsafe { CStr::from_ptr(name).to_string_lossy().into_owned() })
+                }))
+            }
+            #[cfg(not(ossl350))]
+            {
+                let _ = side;
+                Err(vm.new_not_implemented_error(
+                    "Getting sig algorithms requires OpenSSL 3.5 or later.",
+                ))
             }
-
-            Ok(Some(vm.ctx.new_list(certs)))
         }
 
         #[pymethod]
-        fn get_verified_chain(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<PyListRef>> {
-            let stream = zelf.connection.read();
-            unsafe {
-                let chain = sys::SSL_get0_verified_chain(stream.ssl().as_ptr());
-                if chain.is_null() {
-                    return Ok(None);
-                }
-
-                let num_certs = sys::OPENSSL_sk_num(chain as *const _);
-
-                let mut certs = Vec::with_capacity(num_certs as usize);
-                // Return Certificate objects
-                for i in 0..num_certs {
-                    let cert_ptr = sys::OPENSSL_sk_value(chain as *const _, i) as *mut sys::X509;
-                    if cert_ptr.is_null() {
-                        continue;
-                    }
-                    // Clone the X509 certificate to create an owned copy
-                    sys::X509_up_ref(cert_ptr);
-                    let owned_cert = X509::from_ptr(cert_ptr);
-                    let cert_obj = cert_to_certificate(vm, owned_cert)?;
-                    certs.push(cert_obj);
-                }
+        fn client_sigalg(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<String>> {
+            zelf.signature_name(SslServerOrClient::Client, vm)
+        }
 
-                Ok(if certs.is_empty() {
-                    None
-                } else {
-                    Some(vm.ctx.new_list(certs))
-                })
-            }
+        #[pymethod]
+        fn server_sigalg(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<String>> {
+            zelf.signature_name(SslServerOrClient::Server, vm)
         }
 
         #[pymethod]
-        fn version(zelf: &Py<Self>) -> Option<&'static str> {
-            // Use thread-local SSL pointer during handshake to avoid deadlock
-            let ssl_ptr = get_ssl_ptr_for_context_change(&zelf.connection);
-            // Return None if handshake is not complete (CPython behavior)
-            if unsafe { sys::SSL_is_init_finished(ssl_ptr) } == 0 {
-                return None;
-            }
-            let v = unsafe { ssl::SslRef::from_ptr(ssl_ptr).version_str() };
-            if v == "unknown" { None } else { Some(v) }
+        fn uses_ktls_for_send(_zelf: &Py<Self>) -> bool {
+            // SslStream uses a custom Rust BIO, never OpenSSL's kernel TLS socket BIO.
+            false
         }
 
         #[pymethod]
-        fn cipher(zelf: &Py<Self>) -> Option<CipherTuple> {
-            // Use thread-local SSL pointer during handshake to avoid deadlock
-            let ssl_ptr = get_ssl_ptr_for_context_change(&zelf.connection);
-            unsafe { ssl::SslRef::from_ptr(ssl_ptr).current_cipher() }.map(cipher_to_tuple)
+        fn uses_ktls_for_recv(_zelf: &Py<Self>) -> bool {
+            false
         }
 
         #[pymethod]
         fn pending(zelf: &Py<Self>) -> i32 {
-            let stream = zelf.connection.read();
-            unsafe { sys::SSL_pending(stream.ssl().as_ptr()) }
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| unsafe {
+                sys::SSL_pending(ssl_ptr)
+            })
         }
 
         #[pymethod]
         fn shared_ciphers(zelf: &Py<Self>, vm: &VirtualMachine) -> Option<PyListRef> {
             #[cfg(ossl110)]
             {
-                // Use thread-local SSL pointer during handshake to avoid deadlock
-                let ssl_ptr = get_ssl_ptr_for_context_change(&zelf.connection);
-                unsafe {
-                    let server_ciphers = SSL_get_ciphers(ssl_ptr);
-                    if server_ciphers.is_null() {
-                        return None;
-                    }
-
-                    let client_ciphers = SSL_get_client_ciphers(ssl_ptr);
-                    if client_ciphers.is_null() {
-                        return None;
-                    }
+                with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                    unsafe {
+                        let server_ciphers = SSL_get_ciphers(ssl_ptr);
+                        if server_ciphers.is_null() {
+                            return None;
+                        }
 
-                    let mut result = Vec::new();
-                    let num_server = sys::OPENSSL_sk_num(server_ciphers as *const _);
-                    let num_client = sys::OPENSSL_sk_num(client_ciphers as *const _);
+                        let client_ciphers = SSL_get_client_ciphers(ssl_ptr);
+                        if client_ciphers.is_null() {
+                            return None;
+                        }
 
-                    for i in 0..num_server {
-                        let server_cipher_ptr = sys::OPENSSL_sk_value(server_ciphers as *const _, i)
-                            as *const sys::SSL_CIPHER;
+                        let mut result = Vec::new();
+                        let num_server = sys::OPENSSL_sk_num(server_ciphers as *const _);
+                        let num_client = sys::OPENSSL_sk_num(client_ciphers as *const _);
 
-                        // Check if client supports this cipher by comparing pointers
-                        let mut found = false;
-                        for j in 0..num_client {
-                            let client_cipher_ptr =
-                                sys::OPENSSL_sk_value(client_ciphers as *const _, j)
+                        for i in 0..num_server {
+                            let server_cipher_ptr =
+                                sys::OPENSSL_sk_value(server_ciphers as *const _, i)
                                     as *const sys::SSL_CIPHER;
 
-                            if server_cipher_ptr == client_cipher_ptr {
-                                found = true;
-                                break;
+                            // Check if client supports this cipher by comparing pointers
+                            let mut found = false;
+                            for j in 0..num_client {
+                                let client_cipher_ptr =
+                                    sys::OPENSSL_sk_value(client_ciphers as *const _, j)
+                                        as *const sys::SSL_CIPHER;
+
+                                if server_cipher_ptr == client_cipher_ptr {
+                                    found = true;
+                                    break;
+                                }
                             }
-                        }
 
-                        if found {
-                            let cipher = ssl::SslCipherRef::from_ptr(server_cipher_ptr as *mut _);
-                            let (name, version, bits) = cipher_to_tuple(cipher);
-                            let tuple = vm.new_tuple((
-                                vm.ctx.new_str(name),
-                                vm.ctx.new_str(version),
-                                vm.ctx.new_int(bits),
-                            ));
-                            result.push(tuple.into());
+                            if found {
+                                let cipher =
+                                    ssl::SslCipherRef::from_ptr(server_cipher_ptr as *mut _);
+                                let (name, version, bits) = cipher_to_tuple(cipher);
+                                let tuple = vm.new_tuple((
+                                    vm.ctx.new_str(name),
+                                    vm.ctx.new_str(version),
+                                    vm.ctx.new_int(bits),
+                                ));
+                                result.push(tuple.into());
+                            }
                         }
-                    }
 
-                    if result.is_empty() {
-                        None
-                    } else {
-                        Some(vm.ctx.new_list(result))
+                        if result.is_empty() {
+                            None
+                        } else {
+                            Some(vm.ctx.new_list(result))
+                        }
                     }
-                }
+                })
             }
             #[cfg(not(ossl110))]
             {
@@ -2751,9 +3830,7 @@ mod _ssl {
         fn selected_alpn_protocol(zelf: &Py<Self>) -> Option<String> {
             #[cfg(ossl102)]
             {
-                // Use thread-local SSL pointer during handshake to avoid deadlock
-                let ssl_ptr = get_ssl_ptr_for_context_change(&zelf.connection);
-                unsafe {
+                with_ssl_pointer(&zelf.connection, |ssl_ptr| unsafe {
                     let mut out: *const core::ffi::c_uchar = core::ptr::null();
                     let mut outlen: core::ffi::c_uint = 0;
 
@@ -2765,7 +3842,7 @@ mod _ssl {
                         let slice = core::slice::from_raw_parts(out, outlen as usize);
                         Some(String::from_utf8_lossy(slice).into_owned())
                     }
-                }
+                })
             }
             #[cfg(not(ossl102))]
             {
@@ -2790,172 +3867,112 @@ mod _ssl {
                 )));
             }
 
-            let stream = zelf.connection.read();
-            let ssl_ptr = stream.ssl().as_ptr();
-
-            unsafe {
-                let session_reused = sys::SSL_session_reused(ssl_ptr) != 0;
-                let is_client = matches!(zelf.socket_type, SslServerOrClient::Client);
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                unsafe {
+                    let session_reused = sys::SSL_session_reused(ssl_ptr) != 0;
+                    let is_client = matches!(zelf.socket_type, SslServerOrClient::Client);
 
-                // Use XOR logic from CPython
-                let use_finished = session_reused ^ is_client;
+                    // Use XOR logic from CPython
+                    let use_finished = session_reused ^ is_client;
 
-                let mut buf = vec![0u8; CB_MAXLEN];
-                let len = if use_finished {
-                    sys::SSL_get_finished(ssl_ptr, buf.as_mut_ptr() as *mut _, CB_MAXLEN)
-                } else {
-                    sys::SSL_get_peer_finished(ssl_ptr, buf.as_mut_ptr() as *mut _, CB_MAXLEN)
-                };
+                    let mut buf = vec![0u8; CB_MAXLEN];
+                    let len = if use_finished {
+                        sys::SSL_get_finished(ssl_ptr, buf.as_mut_ptr() as *mut _, CB_MAXLEN)
+                    } else {
+                        sys::SSL_get_peer_finished(ssl_ptr, buf.as_mut_ptr() as *mut _, CB_MAXLEN)
+                    };
 
-                if len == 0 {
-                    Ok(None)
-                } else {
-                    buf.truncate(len);
-                    Ok(Some(vm.ctx.new_bytes(buf)))
+                    if len == 0 {
+                        Ok(None)
+                    } else {
+                        buf.truncate(len);
+                        Ok(Some(vm.ctx.new_bytes(buf)))
+                    }
                 }
-            }
+            })
         }
 
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
         #[pymethod]
         fn verify_client_post_handshake(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
             cfg_select! {
                 ossl111 => {
-                    let stream = zelf.connection.read();
-                    let result = unsafe { SSL_verify_client_post_handshake(stream.ssl().as_ptr()) };
-                    if result == 0 {
-                        Err(convert_openssl_error(vm, openssl::error::ErrorStack::get()))
-                    } else {
-                        Ok(())
-                    }
-                }
-                _ => {
-                    Err(vm.new_not_implemented_error(
-                        "Post-handshake auth is not supported by your OpenSSL version.",
-                    ))
+                    with_ssl_pointer_mut(&zelf.connection, |ssl_ptr| {
+                        let result = unsafe { SSL_verify_client_post_handshake(ssl_ptr) };
+                        if result == 0 {
+                            Err(convert_openssl_error(vm, openssl::error::ErrorStack::get()))
+                        } else {
+                            Ok(())
+                        }
+                    })
                 }
+                _ => Err(vm.new_not_implemented_error(
+                    "Post-handshake auth is not supported by your OpenSSL version.",
+                )),
             }
         }
 
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
         #[pymethod]
         fn shutdown(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<PyRef<PySocket>>> {
-            let stream = zelf.connection.read();
+            let mut stream = zelf.connection.write();
             let ssl_ptr = stream.ssl().as_ptr();
-
-            // BIO mode: just try shutdown once and raise SSLWantReadError if needed
-            if stream.is_bio() {
-                let ret = vm.allow_threads(|| unsafe { sys::SSL_shutdown(ssl_ptr) });
-                if ret < 0 {
-                    let err = unsafe { sys::SSL_get_error(ssl_ptr, ret) };
-                    if err == sys::SSL_ERROR_WANT_READ {
-                        return Err(create_ssl_want_read_error(vm).upcast());
-                    } else if err == sys::SSL_ERROR_WANT_WRITE {
-                        return Err(create_ssl_want_write_error(vm).upcast());
-                    } else {
-                        return Err(new_ssl_error(
-                            vm,
-                            format!("SSL shutdown failed: error code {}", err),
-                        ));
-                    }
-                } else if ret == 0 {
-                    // Sent close-notify, waiting for peer's - raise SSLWantReadError
-                    return Err(create_ssl_want_read_error(vm).upcast());
-                }
-                return Ok(None);
-            }
-
-            // Socket mode: loop with select to wait for peer's close-notify
-            let socket_stream = stream.get_ref().expect("get_ref() failed for socket mode");
-            let deadline = socket_stream.timeout_deadline();
-
-            // Track how many times we've seen ret == 0 (max 2 tries)
+            let _vm_guard = HandshakeVmGuard::new(vm, &zelf.connection, ssl_ptr);
+            let deadline = stream.get_ref().map(SocketStream::timeout_deadline);
             let mut zeros = 0;
-
             loop {
-                // Shutting down sends close-notify and waits for the peer's,
-                // which a peer that has gone away never sends. `SSL_shutdown`
-                // is released around for the same reason.
-                let ret = vm.allow_threads(|| unsafe { sys::SSL_shutdown(ssl_ptr) });
-
-                // ret > 0: complete shutdown
-                if ret > 0 {
-                    break;
-                }
-
-                // ret == 0: sent our close-notify, need to receive peer's
-                if ret == 0 {
-                    zeros += 1;
-                    if zeros > 1 {
-                        // Already tried twice, break out (legacy behavior)
-                        break;
+                if zelf.shutdown_seen_zero.load() {
+                    // Do not consume plaintext following the TLS close_notify.
+                    unsafe {
+                        sys::SSL_ctrl(
+                            ssl_ptr,
+                            sys::SSL_CTRL_SET_READ_AHEAD,
+                            0,
+                            core::ptr::null_mut(),
+                        );
                     }
-                    // Wait briefly for peer's close_notify before retrying
-                    match socket_stream.select(SslNeeds::Read, &deadline, vm)? {
-                        SelectRet::TimedOut => {
-                            return Err(socket::timeout_error_msg(
-                                vm,
-                                "The read operation timed out".to_string(),
-                            )
-                            .upcast());
-                        }
-                        SelectRet::Closed => {
-                            return Err(socket_closed_error(vm));
-                        }
-                        SelectRet::Nonblocking => {
-                            // Non-blocking socket: return SSLWantReadError
-                            return Err(create_ssl_want_read_error(vm).upcast());
-                        }
-                        SelectRet::Ok => {
-                            // Data available, continue to retry
+                }
+                let error = match zelf.finish_ssl_operation(
+                    vm.allow_threads(|| stream.shutdown()),
+                    ssl_ptr,
+                    vm,
+                )? {
+                    Ok(ssl::ShutdownResult::Received) => break,
+                    Ok(ssl::ShutdownResult::Sent) => {
+                        zeros += 1;
+                        if zeros > 1 {
+                            break;
                         }
+                        zelf.shutdown_seen_zero.store(true);
+                        // Retry immediately: the peer's notification may already
+                        // be buffered, even when the transport is not readable.
+                        continue;
                     }
-                    continue;
-                }
-
-                // ret < 0: error or would-block
-                let err = unsafe { sys::SSL_get_error(ssl_ptr, ret) };
-
-                let needs = if err == sys::SSL_ERROR_WANT_READ {
-                    SslNeeds::Read
-                } else if err == sys::SSL_ERROR_WANT_WRITE {
-                    SslNeeds::Write
-                } else {
-                    // Real error
-                    return Err(new_ssl_error(
-                        vm,
-                        format!("SSL shutdown failed: error code {}", err),
-                    ));
+                    Err(error) => error,
                 };
-
-                // Wait on the socket
-                match socket_stream.select(needs, &deadline, vm)? {
-                    SelectRet::TimedOut => {
-                        let msg = if err == sys::SSL_ERROR_WANT_READ {
-                            "The read operation timed out"
-                        } else {
-                            "The write operation timed out"
-                        };
-                        return Err(socket::timeout_error_msg(vm, msg.to_string()).upcast());
-                    }
-                    SelectRet::Closed => {
-                        return Err(socket_closed_error(vm));
-                    }
-                    SelectRet::Nonblocking => {
-                        // Non-blocking socket, raise SSLWantReadError/SSLWantWriteError
-                        if err == sys::SSL_ERROR_WANT_READ {
-                            return Err(create_ssl_want_read_error(vm).upcast());
-                        } else {
-                            return Err(create_ssl_want_write_error(vm).upcast());
+                if let Some(socket) = stream.get_ref() {
+                    let (needs, state) = socket.socket_needs(
+                        &error,
+                        deadline.as_ref().expect("socket deadline"),
+                        vm,
+                    )?;
+                    match state {
+                        SelectRet::TimedOut => {
+                            let message = if error.code() == ssl::ErrorCode::WANT_READ {
+                                "The read operation timed out"
+                            } else {
+                                "The write operation timed out"
+                            };
+                            return Err(socket::timeout_error_msg(vm, message.to_owned()).upcast());
                         }
-                    }
-                    SelectRet::Ok => {
-                        // Socket is ready, retry shutdown
-                        continue;
+                        SelectRet::Closed => return Err(socket_closed_error(vm)),
+                        SelectRet::Ok if needs.is_some() => continue,
+                        _ => {}
                     }
                 }
+                return Err(zelf.ssl_error(error, ssl_ptr, vm));
             }
-
-            // Return the underlying socket
-            Ok(Some(socket_stream.0.clone()))
+            Ok(stream.get_ref().map(|socket| socket.socket.clone()))
         }
 
         #[cfg(osslconf = "OPENSSL_NO_COMP")]
@@ -2966,42 +3983,36 @@ mod _ssl {
         #[cfg(not(osslconf = "OPENSSL_NO_COMP"))]
         #[pymethod]
         fn compression(zelf: &Py<Self>) -> Option<&'static str> {
-            // Use thread-local SSL pointer during handshake to avoid deadlock
-            let ssl_ptr = get_ssl_ptr_for_context_change(&zelf.connection);
-            let comp_method = unsafe { sys::SSL_get_current_compression(ssl_ptr) };
-            if comp_method.is_null() {
-                return None;
-            }
-            let typ = unsafe { sys::COMP_get_type(comp_method) };
-            let nid = Nid::from_raw(typ);
-            if nid == Nid::UNDEF {
-                return None;
-            }
-            nid.short_name().ok()
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                let comp_method = unsafe { sys::SSL_get_current_compression(ssl_ptr) };
+                if comp_method.is_null() {
+                    return None;
+                }
+                let typ = unsafe { sys::COMP_get_type(comp_method) };
+                let nid = Nid::from_raw(typ);
+                if nid == Nid::UNDEF {
+                    return None;
+                }
+                nid.short_name().ok()
+            })
         }
 
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
         #[pymethod]
         fn do_handshake(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
+            zelf.check_eof(vm)?;
             let mut stream = zelf.connection.write();
             let ssl_ptr = stream.ssl().as_ptr();
 
             // Set up thread-local VM and SSL pointer for callbacks
             // This allows callbacks to access SSL without acquiring the connection lock
-            let _vm_guard = HandshakeVmGuard::new(vm, ssl_ptr);
+            let _vm_guard = HandshakeVmGuard::new(vm, &zelf.connection, ssl_ptr);
 
             // BIO mode: no timeout/select logic, just do handshake
             if stream.is_bio() {
-                let result = vm.allow_threads(|| stream.do_handshake()).map_err(|e| {
-                    let exc = convert_ssl_error(vm, e);
-                    // If it's a cert verification error, set verify info
-                    if exc.class().is(PySSLCertVerificationError::class(&vm.ctx)) {
-                        set_verify_error_info(&exc, ssl_ptr, vm);
-                    }
-                    exc
-                });
-                // Clean up SNI ex_data after handshake (success or failure)
-                // SAFETY: ssl_ptr is valid for the lifetime of stream
-                unsafe { cleanup_sni_ex_data(ssl_ptr) };
+                let result = zelf
+                    .finish_ssl_operation(vm.allow_threads(|| stream.do_handshake()), ssl_ptr, vm)?
+                    .map_err(|e| zelf.ssl_error(e, ssl_ptr, vm));
                 return result;
             }
 
@@ -3017,11 +4028,12 @@ mod _ssl {
                 // same reason. The connection lock stays held across it, which
                 // is why it is a detaching lock: a thread reaching the same
                 // socket gives up its interpreter rather than wait attached.
-                let err = match vm.allow_threads(|| stream.do_handshake()) {
+                let err = match zelf.finish_ssl_operation(
+                    vm.allow_threads(|| stream.do_handshake()),
+                    ssl_ptr,
+                    vm,
+                )? {
                     Ok(()) => {
-                        // Clean up SNI ex_data after successful handshake
-                        // SAFETY: ssl_ptr is valid for the lifetime of stream
-                        unsafe { cleanup_sni_ex_data(ssl_ptr) };
                         return Ok(());
                     }
                     Err(e) => e,
@@ -3032,9 +4044,6 @@ mod _ssl {
                     .socket_needs(&err, &timeout, vm)?;
                 match state {
                     SelectRet::TimedOut => {
-                        // Clean up SNI ex_data before returning error
-                        // SAFETY: ssl_ptr is valid for the lifetime of stream
-                        unsafe { cleanup_sni_ex_data(ssl_ptr) };
                         return Err(socket::timeout_error_msg(
                             vm,
                             "The handshake operation timed out".to_owned(),
@@ -3042,8 +4051,6 @@ mod _ssl {
                         .upcast());
                     }
                     SelectRet::Closed => {
-                        // SAFETY: ssl_ptr is valid for the lifetime of stream
-                        unsafe { cleanup_sni_ex_data(ssl_ptr) };
                         return Err(socket_closed_error(vm));
                     }
                     SelectRet::Nonblocking => {}
@@ -3055,29 +4062,25 @@ mod _ssl {
                         }
                     }
                 }
-                let exc = convert_ssl_error(vm, err);
-                // If it's a cert verification error, set verify info
-                if exc.class().is(PySSLCertVerificationError::class(&vm.ctx)) {
-                    set_verify_error_info(&exc, ssl_ptr, vm);
-                }
-                // Clean up SNI ex_data before returning error
-                // SAFETY: ssl_ptr is valid for the lifetime of stream
-                unsafe { cleanup_sni_ex_data(ssl_ptr) };
-                return Err(exc);
+                return Err(zelf.ssl_error(err, ssl_ptr, vm));
             }
         }
 
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
         #[pymethod]
         fn write(zelf: &Py<Self>, data: ArgBytesLike, vm: &VirtualMachine) -> PyResult<usize> {
+            zelf.check_eof(vm)?;
             let mut stream = zelf.connection.write();
+            let ssl_ptr = stream.ssl().as_ptr();
+            let _vm_guard = HandshakeVmGuard::new(vm, &zelf.connection, ssl_ptr);
             let data = data.borrow_buf();
             let data = &*data;
 
             // BIO mode: no timeout/select logic
             if stream.is_bio() {
-                return vm
-                    .allow_threads(|| stream.ssl_write(data))
-                    .map_err(|e| convert_ssl_error(vm, e));
+                return zelf
+                    .finish_ssl_operation(vm.allow_threads(|| stream.ssl_write(data)), ssl_ptr, vm)?
+                    .map_err(|e| zelf.ssl_error(e, ssl_ptr, vm));
             }
 
             // Socket mode: handle timeout and blocking
@@ -3101,7 +4104,11 @@ mod _ssl {
                 // Sending waits for the peer to make room, which it need not
                 // ever do; `SSL_write_ex` is released around for the same
                 // reason.
-                let err = match vm.allow_threads(|| stream.ssl_write(data)) {
+                let err = match zelf.finish_ssl_operation(
+                    vm.allow_threads(|| stream.ssl_write(data)),
+                    ssl_ptr,
+                    vm,
+                )? {
                     Ok(len) => return Ok(len),
                     Err(e) => e,
                 };
@@ -3127,25 +4134,26 @@ mod _ssl {
                         }
                     }
                 }
-                return Err(convert_ssl_error(vm, err));
+                return Err(zelf.ssl_error(err, ssl_ptr, vm));
             }
         }
 
         #[pygetset]
         fn session(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<Option<PySslSession>> {
-            let stream = zelf.connection.read();
-            unsafe {
-                // Use SSL_get1_session which returns an owned reference (ref count already incremented)
-                let session_ptr = SSL_get1_session(stream.ssl().as_ptr());
-                if session_ptr.is_null() {
-                    Ok(None)
-                } else {
-                    Ok(Some(PySslSession {
-                        session: session_ptr,
-                        ctx: zelf.ctx.read().clone(),
-                    }))
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| {
+                unsafe {
+                    // Use SSL_get1_session which returns an owned reference (ref count already incremented)
+                    let session_ptr = SSL_get1_session(ssl_ptr);
+                    if session_ptr.is_null() {
+                        Ok(None)
+                    } else {
+                        Ok(Some(PySslSession {
+                            session: session_ptr,
+                            ctx: zelf.ctx.read().clone(),
+                        }))
+                    }
                 }
-            }
+            })
         }
 
         #[pygetset(setter)]
@@ -3168,29 +4176,26 @@ mod _ssl {
                 return Err(vm.new_value_error("Cannot set session for server-side SSLSocket."));
             }
 
-            // Check if handshake is not finished
-            let stream = zelf.connection.read();
-            unsafe {
-                if sys::SSL_is_init_finished(stream.ssl().as_ptr()) != 0 {
-                    return Err(vm.new_value_error("Cannot set session after handshake."));
-                }
-
-                let ret = sys::SSL_set_session(stream.ssl().as_ptr(), session.session);
-                if ret == 0 {
-                    return Err(convert_openssl_error(vm, ErrorStack::get()));
+            with_ssl_pointer_mut(&zelf.connection, |ssl_ptr| {
+                unsafe {
+                    if sys::SSL_is_init_finished(ssl_ptr) != 0 {
+                        return Err(vm.new_value_error("Cannot set session after handshake."));
+                    }
+                    if sys::SSL_set_session(ssl_ptr, session.session) == 0 {
+                        return Err(convert_openssl_error(vm, ErrorStack::get()));
+                    }
                 }
-            }
-
-            Ok(())
+                Ok(())
+            })
         }
 
         #[pygetset]
         fn session_reused(zelf: &Py<Self>) -> bool {
-            // Use thread-local SSL pointer during handshake to avoid deadlock
-            let ssl_ptr = get_ssl_ptr_for_context_change(&zelf.connection);
-            unsafe { sys::SSL_session_reused(ssl_ptr) != 0 }
+            with_ssl_pointer(&zelf.connection, |ssl_ptr| unsafe {
+                sys::SSL_session_reused(ssl_ptr) != 0
+            })
         }
-
+        #[cfg(not(all(unix, not(target_os = "aix"))))]
         #[pymethod]
         fn read(
             zelf: &Py<Self>,
@@ -3219,6 +4224,8 @@ mod _ssl {
                 }
             };
 
+            zelf.check_eof(vm)?;
+
             // Special case: reading 0 bytes should return empty bytes immediately
             if read_len == 0 {
                 return if buffer.is_present() {
@@ -3229,6 +4236,8 @@ mod _ssl {
             }
 
             let mut stream = zelf.connection.write();
+            let ssl_ptr = stream.ssl().as_ptr();
+            let _vm_guard = HandshakeVmGuard::new(vm, &zelf.connection, ssl_ptr);
             // The read below answers when the peer writes, which may be never,
             // and reaching the caller's buffer takes a lock that every other
             // thread touching the same object waits on. Read aside and take
@@ -3238,19 +4247,28 @@ mod _ssl {
 
             // BIO mode: no timeout/select logic
             let count = if stream.is_bio() {
-                match vm.allow_threads(|| stream.ssl_read(buf)) {
+                match zelf.finish_ssl_operation(
+                    vm.allow_threads(|| stream.ssl_read(buf)),
+                    ssl_ptr,
+                    vm,
+                )? {
                     Ok(count) => count,
                     Err(e) => {
-                        // Handle ZERO_RETURN (EOF) - raise SSLEOFError
+                        // close_notify is an orderly TLS EOF.
                         if e.code() == ssl::ErrorCode::ZERO_RETURN {
-                            return Err(create_ssl_eof_error(vm).upcast());
+                            return if buffer.is_present() {
+                                Ok(vm.ctx.new_int(0).into())
+                            } else {
+                                Ok(vm.ctx.new_bytes(vec![]).into())
+                            };
                         }
                         // If WANT_READ and the incoming BIO has EOF written,
                         // this is an unexpected EOF (transport closed without TLS close_notify)
                         if e.code() == ssl::ErrorCode::WANT_READ && stream.is_bio_eof() {
+                            zelf.got_eof_error.store(true);
                             return Err(create_ssl_eof_error(vm).upcast());
                         }
-                        return Err(convert_ssl_error(vm, e));
+                        return Err(zelf.ssl_error(e, ssl_ptr, vm));
                     }
                 }
             } else {
@@ -3263,7 +4281,11 @@ mod _ssl {
                     // This is the wait the whole method is shaped around: it
                     // ends when the peer writes. `SSL_read_ex` is released
                     // around for the same reason.
-                    let err = match vm.allow_threads(|| stream.ssl_read(buf)) {
+                    let err = match zelf.finish_ssl_operation(
+                        vm.allow_threads(|| stream.ssl_read(buf)),
+                        ssl_ptr,
+                        vm,
+                    )? {
                         Ok(count) => break count,
                         Err(e) => e,
                     };
@@ -3294,7 +4316,7 @@ mod _ssl {
                             }
                         }
                     }
-                    return Err(convert_ssl_error(vm, err));
+                    return Err(zelf.ssl_error(err, ssl_ptr, vm));
                 }
             };
             let ret = match &buffer {
@@ -3399,8 +4421,43 @@ mod _ssl {
     unsafe impl Send for PySslMemoryBio {}
     unsafe impl Sync for PySslMemoryBio {}
 
+    #[pyfunction]
+    fn get_sigalgs(vm: &VirtualMachine) -> PyResult<PyListRef> {
+        #[cfg(ossl340)]
+        unsafe {
+            let names = SSL_get1_builtin_sigalgs(core::ptr::null_mut());
+            if names.is_null() {
+                return Err(vm.new_memory_error("failed to get signature algorithms"));
+            }
+            let names_text = CStr::from_ptr(names).to_string_lossy().into_owned();
+            sys::CRYPTO_free(names.cast(), core::ptr::null(), 0);
+            Ok(vm.ctx.new_list(
+                names_text
+                    .split(':')
+                    .map(|name| vm.ctx.new_str(name).into())
+                    .collect(),
+            ))
+        }
+        #[cfg(not(ossl340))]
+        {
+            Err(vm.new_not_implemented_error(
+                "Getting signature algorithms requires OpenSSL 3.4 or later.",
+            ))
+        }
+    }
+
     // OpenSSL functions not in openssl-sys
 
+    #[cfg(ossl320)]
+    unsafe extern "C" {
+        fn SSL_get0_group_name(ssl: *mut sys::SSL) -> *const core::ffi::c_char;
+    }
+
+    #[cfg(ossl340)]
+    unsafe extern "C" {
+        fn SSL_get1_builtin_sigalgs(ctx: *mut core::ffi::c_void) -> *mut core::ffi::c_char;
+    }
+
     unsafe extern "C" {
         // X509_check_ca returns 1 for CA certificates, 0 otherwise
         fn X509_check_ca(x: *const sys::X509) -> core::ffi::c_int;
@@ -3706,6 +4763,7 @@ mod _ssl {
                 }
 
                 buf.truncate(nbytes as usize);
+                buf.shrink_to_fit();
                 Ok(buf)
             }
         }
@@ -3794,10 +4852,29 @@ mod _ssl {
             .upcast()
     }
 
+    fn system_error_errno(code: core::ffi::c_ulong) -> core::ffi::c_int {
+        // OpenSSL 3 stores errno below ERR_SYSTEM_FLAG, as specified by
+        // https://github.com/openssl/openssl/blob/openssl-3.5.7/include/openssl/err.h.in
+        // openssl-sys 0.9.117's ERR_GET_REASON returns ERR_LIB_SYS instead.
+        cfg_select! {
+            ossl300 => (code & sys::ERR_SYSTEM_MASK) as core::ffi::c_int,
+            _ => sys::ERR_GET_REASON(code),
+        }
+    }
+
     #[track_caller]
     pub(crate) fn convert_openssl_error(
         vm: &VirtualMachine,
         err: ErrorStack,
+    ) -> PyBaseExceptionRef {
+        convert_openssl_error_with_errno(vm, err, None)
+    }
+
+    #[track_caller]
+    fn convert_openssl_error_with_errno(
+        vm: &VirtualMachine,
+        err: ErrorStack,
+        operation_errno: Option<i32>,
     ) -> PyBaseExceptionRef {
         match err.errors().last() {
             Some(e) => {
@@ -3806,7 +4883,9 @@ mod _ssl {
 
                 if lib == sys::ERR_LIB_SYS {
                     // A system error is being reported; reason is set to errno
-                    let reason = sys::ERR_GET_REASON(e.code());
+                    let reason = system_error_errno(e.code());
+                    let message = rustpython_host_env::errno::strerror_string(reason)
+                        .unwrap_or_else(|| format!("System error {reason}"));
 
                     // errno 2 = ENOENT = FileNotFoundError
                     let exc_type = if reason == 2 {
@@ -3814,7 +4893,9 @@ mod _ssl {
                     } else {
                         vm.ctx.exceptions.os_error.to_owned()
                     };
-                    return vm.new_os_subtype_error(exc_type, Some(reason), "").upcast();
+                    return vm
+                        .new_os_subtype_error(exc_type, Some(reason), message)
+                        .upcast();
                 }
 
                 let caller = std::panic::Location::caller();
@@ -3855,16 +4936,17 @@ mod _ssl {
                     PySSLError::class(&vm.ctx).to_owned()
                 };
 
-                // Build message
+                let description = e.reason().unwrap_or("unknown error");
                 let msg = if let Some(lib_str) = lib_name {
-                    format!("[{lib_str}] {errstr} ({file}:{line})")
+                    format!("[{lib_str}: {errstr}] {description} ({file}:{line})")
                 } else {
-                    format!("{errstr} ({file}:{line})")
+                    format!("{description} ({file}:{line})")
                 };
 
                 // Create exception instance
                 let reason = sys::ERR_GET_REASON(e.code());
-                let exc = vm.new_os_subtype_error(cls, Some(reason), msg);
+                let exc =
+                    vm.new_os_subtype_error(cls, Some(operation_errno.unwrap_or(reason)), msg);
                 let exc_obj: PyObjectRef = exc.upcast::<PyBaseException>().into();
 
                 // Set reason attribute (always set, even if just the error string)
@@ -3900,37 +4982,85 @@ mod _ssl {
         }
     }
 
-    // Helper function to set verify_code and verify_message on SSLCertVerificationError
-    fn set_verify_error_info(
-        exc: &Py<PyBaseException>,
-        ssl_ptr: *const sys::SSL,
-        vm: &VirtualMachine,
-    ) {
-        // Get verify result
-        let verify_code = unsafe { sys::SSL_get_verify_result(ssl_ptr) };
-        let verify_code_obj = vm.ctx.new_int(verify_code);
-
-        // Get verify message
-        let verify_message = unsafe {
-            let verify_str = sys::X509_verify_cert_error_string(verify_code);
-            if verify_str.is_null() {
-                vm.ctx.none()
-            } else {
-                let c_str = core::ffi::CStr::from_ptr(verify_str);
-                vm.ctx.new_str(c_str.to_string_lossy()).into()
+    struct VerifyErrorInfo {
+        code: core::ffi::c_long,
+        message: Option<String>,
+    }
+
+    // Only owned metadata may outlive the native SSL guard. In particular,
+    // exception normalization must never consult a later operation's SSL state.
+    struct SslErrorSnapshot {
+        error: ssl::Error,
+        verify: Option<VerifyErrorInfo>,
+    }
+
+    impl SslErrorSnapshot {
+        fn capture(error: ssl::Error, ssl_ptr: *const sys::SSL) -> Self {
+            let is_cert_verify =
+                matches!(error.code(), ssl::ErrorCode::SSL | ssl::ErrorCode::SYSCALL)
+                    && error.ssl_error().is_some_and(|stack| {
+                        stack.errors().last().is_some_and(|error| {
+                            sys::ERR_GET_LIB(error.code()) == 20
+                                && sys::ERR_GET_REASON(error.code()) == 134
+                        })
+                    });
+            let verify = is_cert_verify.then(|| {
+                // The caller holds this connection's native guard throughout
+                // capture. Neither the pointer nor borrowed C data is retained.
+                let code = unsafe { sys::SSL_get_verify_result(ssl_ptr) };
+                let message = unsafe {
+                    let pointer = sys::X509_verify_cert_error_string(code);
+                    (!pointer.is_null()).then(|| {
+                        core::ffi::CStr::from_ptr(pointer)
+                            .to_string_lossy()
+                            .into_owned()
+                    })
+                };
+                VerifyErrorInfo { code, message }
+            });
+            Self { error, verify }
+        }
+
+        fn into_pyexception(self, vm: &VirtualMachine) -> PyBaseExceptionRef {
+            let exception = convert_ssl_error(vm, self.error);
+            if let Some(verify) = self.verify {
+                let _ =
+                    exception
+                        .as_object()
+                        .set_attr("verify_code", vm.ctx.new_int(verify.code), vm);
+                let message = verify
+                    .message
+                    .map_or_else(|| vm.ctx.none(), |message| vm.ctx.new_str(message).into());
+                let _ = exception
+                    .as_object()
+                    .set_attr("verify_message", message, vm);
             }
-        };
+            exception
+        }
+    }
 
-        let exc_obj = exc.as_object();
-        let _ = exc_obj.set_attr("verify_code", verify_code_obj, vm);
-        let _ = exc_obj.set_attr("verify_message", verify_message, vm);
+    fn is_unexpected_eof(error: &ssl::Error) -> bool {
+        (error.code() == ssl::ErrorCode::SYSCALL
+            && error.io_error().is_none()
+            && error.ssl_error().is_none())
+            || error.ssl_error().is_some_and(|stack| {
+                stack.errors().last().is_some_and(|error| {
+                    error.library_code() == ERR_LIB_SSL
+                        && error.reason_code() == SSL_R_UNEXPECTED_EOF_WHILE_READING
+                })
+            })
     }
+
     #[track_caller]
     fn convert_ssl_error(
         vm: &VirtualMachine,
         e: impl std::borrow::Borrow<ssl::Error>,
     ) -> PyBaseExceptionRef {
         let e = e.borrow();
+        if is_unexpected_eof(e) {
+            return create_ssl_eof_error(vm).upcast();
+        }
+
         let (cls, msg) = match e.code() {
             ssl::ErrorCode::WANT_READ => {
                 return create_ssl_want_read_error(vm).upcast();
@@ -3940,26 +5070,24 @@ mod _ssl {
             }
             ssl::ErrorCode::SYSCALL => match e.io_error() {
                 Some(io_err) => return io_err.to_pyexception(vm),
-                // When no I/O error and OpenSSL error queue is empty,
-                // this is an EOF in violation of protocol -> SSLEOFError
                 None => {
+                    if let Some(stack) = e.ssl_error() {
+                        return convert_openssl_error_with_errno(
+                            vm,
+                            stack.clone(),
+                            Some(sys::SSL_ERROR_SYSCALL),
+                        );
+                    }
                     return create_ssl_eof_error(vm).upcast();
                 }
             },
             ssl::ErrorCode::SSL => {
-                // Check for OpenSSL 3.0 SSL_R_UNEXPECTED_EOF_WHILE_READING
                 if let Some(ssl_err) = e.ssl_error() {
-                    // In OpenSSL 3.0+, unexpected EOF is reported as SSL_ERROR_SSL
-                    // with this specific reason code instead of SSL_ERROR_SYSCALL
-                    unsafe {
-                        let err_code = sys::ERR_peek_last_error();
-                        let reason = sys::ERR_GET_REASON(err_code);
-                        let lib = sys::ERR_GET_LIB(err_code);
-                        if lib == ERR_LIB_SSL && reason == SSL_R_UNEXPECTED_EOF_WHILE_READING {
-                            return create_ssl_eof_error(vm).upcast();
-                        }
-                    }
-                    return convert_openssl_error(vm, ssl_err.clone());
+                    return convert_openssl_error_with_errno(
+                        vm,
+                        ssl_err.clone(),
+                        Some(sys::SSL_ERROR_SSL),
+                    );
                 }
                 (
                     PySSLError::class(&vm.ctx).to_owned(),
@@ -4037,21 +5165,70 @@ mod _ssl {
         }
     }
 
+    #[cfg(all(unix, not(target_os = "aix")))]
+    impl SocketStream {
+        fn finish_transport(&mut self, result: std::io::Result<usize>) -> std::io::Result<usize> {
+            match result {
+                Ok(count) => {
+                    self.progress = self.progress.wrapping_add(count as u64);
+                    Ok(count)
+                }
+                Err(error) if error.kind() == std::io::ErrorKind::Interrupted => {
+                    // openssl's custom BIO treats only WouldBlock/NotConnected
+                    // as retryable. Passing EINTR through would become a fatal
+                    // SSL_ERROR_SYSCALL. Check Python signals after settlement.
+                    self.interrupted = true;
+                    Err(std::io::Error::from(std::io::ErrorKind::WouldBlock))
+                }
+                Err(error) => Err(error),
+            }
+        }
+    }
+
     impl Read for SocketStream {
         fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
-            let mut socket: &PySocket = &self.0;
-            socket.read(buf)
+            #[cfg(all(unix, not(target_os = "aix")))]
+            {
+                let result = {
+                    let socket = self.socket.sock_for_ssl_identity(&self.identity)?;
+                    // recv initializes only the reported prefix; this caller's
+                    // buffer was already initialized and is valid throughout.
+                    let buffer = unsafe {
+                        core::slice::from_raw_parts_mut(
+                            buf.as_mut_ptr().cast::<core::mem::MaybeUninit<u8>>(),
+                            buf.len(),
+                        )
+                    };
+                    socket.recv_with_flags(buffer, libc::MSG_DONTWAIT)
+                };
+                self.finish_transport(result)
+            }
+            #[cfg(not(all(unix, not(target_os = "aix"))))]
+            {
+                let mut socket: &PySocket = &self.socket;
+                socket.read(buf)
+            }
         }
     }
 
     impl Write for SocketStream {
         fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
-            let mut socket: &PySocket = &self.0;
-            socket.write(buf)
+            #[cfg(all(unix, not(target_os = "aix")))]
+            {
+                let result = {
+                    let socket = self.socket.sock_for_ssl_identity(&self.identity)?;
+                    socket.send_with_flags(buf, libc::MSG_DONTWAIT)
+                };
+                self.finish_transport(result)
+            }
+            #[cfg(not(all(unix, not(target_os = "aix"))))]
+            {
+                let mut socket: &PySocket = &self.socket;
+                socket.write(buf)
+            }
         }
         fn flush(&mut self) -> std::io::Result<()> {
-            let mut socket: &PySocket = &self.0;
-            socket.flush()
+            Ok(())
         }
     }
 
@@ -4116,6 +5293,21 @@ mod _ssl {
             Ok(())
         }
     }
+    #[cfg(test)]
+    mod error_tests {
+        use super::{sys, system_error_errno};
+
+        #[test]
+        fn system_errors_preserve_errno() {
+            for errno in [libc::ENOENT, libc::EPIPE, libc::ECONNRESET] {
+                let code = cfg_select! {
+                    ossl300 => sys::ERR_SYSTEM_FLAG | errno as core::ffi::c_ulong,
+                    _ => sys::ERR_PACK(sys::ERR_LIB_SYS, 0, errno),
+                };
+                assert_eq!(system_error_errno(code), errno);
+            }
+        }
+    }
 }
 
 #[allow(non_upper_case_globals)]
diff --git a/crates/stdlib/src/openssl/driver.rs b/crates/stdlib/src/openssl/driver.rs
new file mode 100644
index 00000000000..b1ff3a4f757
--- /dev/null
+++ b/crates/stdlib/src/openssl/driver.rs
@@ -0,0 +1,264 @@
+//! Ownership rules for nonblocking OpenSSL retries.
+//!
+//! In particular, SSL_write returning WANT_WRITE forbids *any* other I/O on
+//! that SSL until the same write is retried. Its buffer must survive Python
+//! timeout, signal and nonblocking returns as well as ordinary OS waits.
+use alloc::sync::Arc;
+use core::sync::atomic::{AtomicBool, Ordering};
+
+#[derive(Clone, Debug)]
+pub(super) struct WriteOwner(Arc<AtomicBool>);
+
+impl WriteOwner {
+    pub(super) fn new() -> Self {
+        Self(Arc::new(AtomicBool::new(true)))
+    }
+
+    pub(super) fn release(&self) {
+        self.0.store(false, Ordering::Release);
+    }
+
+    fn is_active(&self) -> bool {
+        self.0.load(Ordering::Acquire)
+    }
+
+    fn is(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.0, &other.0)
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) enum Needs {
+    Read,
+    Write,
+}
+
+#[derive(Debug)]
+struct PendingWrite {
+    bytes: Box<[u8]>,
+    owner: WriteOwner,
+    needs: Option<Needs>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) enum Permit {
+    Ready,
+    Wait,
+    RetryOriginalWrite,
+    InvalidRetry,
+}
+
+#[derive(Default, Debug)]
+pub(super) struct Driver {
+    pending: Option<PendingWrite>,
+    pub(super) terminal: bool,
+}
+
+impl Driver {
+    pub(super) fn other_io(&self) -> Permit {
+        match &self.pending {
+            Some(pending) if pending.needs == Some(Needs::Write) => {
+                if pending.owner.is_active() {
+                    Permit::Wait
+                } else {
+                    Permit::RetryOriginalWrite
+                }
+            }
+            _ => Permit::Ready,
+        }
+    }
+
+    pub(super) fn write(
+        &mut self,
+        owner: &WriteOwner,
+        bytes: &mut Option<Box<[u8]>>,
+        queued: &mut bool,
+    ) -> Permit {
+        // An invocation can fail before entering native SSL. There is no
+        // continuation in that case, so its abandoned buffer is disposable.
+        if self
+            .pending
+            .as_ref()
+            .is_some_and(|pending| pending.needs.is_none() && !pending.owner.is_active())
+        {
+            self.pending = None;
+        }
+        if let Some(pending) = &mut self.pending {
+            if pending.owner.is_active() {
+                if pending.owner.is(owner) {
+                    return Permit::Ready;
+                }
+                *queued = true;
+                return Permit::Wait;
+            }
+            // A write already queued behind another call is a distinct write,
+            // even when its contents happen to match the abandoned operation.
+            if *queued || bytes.as_deref() != Some(pending.bytes.as_ref()) {
+                return Permit::InvalidRetry;
+            }
+            pending.owner = owner.clone();
+            // Retain the original allocation, not the new invocation's copy.
+            *bytes = None;
+            return Permit::Ready;
+        }
+        self.pending = Some(PendingWrite {
+            bytes: bytes.take().expect("new write owns its buffer"),
+            owner: owner.clone(),
+            needs: None,
+        });
+        Permit::Ready
+    }
+
+    pub(super) fn bytes(&self, owner: &WriteOwner) -> &[u8] {
+        let pending = self.pending.as_ref().expect("active write");
+        assert!(pending.owner.is(owner) && pending.owner.is_active());
+        &pending.bytes
+    }
+
+    pub(super) fn settle_write(&mut self, owner: &WriteOwner, needs: Option<Needs>) -> bool {
+        let pending = self.pending.as_mut().expect("active write");
+        assert!(pending.owner.is(owner) && pending.owner.is_active());
+        if let Some(needs) = needs {
+            pending.needs = Some(needs);
+        } else {
+            self.pending = None;
+        }
+        needs.is_some()
+    }
+
+    pub(super) fn fail(&mut self) {
+        self.terminal = true;
+        self.pending = None;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn payload() -> Box<[u8]> {
+        Box::from(&b"stable bytes"[..])
+    }
+
+    #[test]
+    fn want_write_is_exclusive_and_keeps_original_allocation() {
+        let mut driver = Driver::default();
+        let owner = WriteOwner::new();
+        let mut bytes = Some(payload());
+        let ptr = bytes.as_ref().unwrap().as_ptr();
+        assert_eq!(driver.write(&owner, &mut bytes, &mut false), Permit::Ready);
+        driver.settle_write(&owner, Some(Needs::Write));
+        assert_eq!(driver.other_io(), Permit::Wait);
+        assert_eq!(driver.bytes(&owner).as_ptr(), ptr);
+        owner.release();
+        assert_eq!(driver.other_io(), Permit::RetryOriginalWrite);
+        let next = WriteOwner::new();
+        assert_eq!(
+            driver.write(&next, &mut Some(payload()), &mut false),
+            Permit::Ready
+        );
+        assert_eq!(driver.bytes(&next).as_ptr(), ptr);
+        assert!(
+            !driver.settle_write(&next, None),
+            "completion disarms cleanup"
+        );
+        assert_eq!(driver.other_io(), Permit::Ready);
+    }
+
+    #[test]
+    fn want_read_allows_progress_but_not_a_different_write() {
+        let mut driver = Driver::default();
+        let owner = WriteOwner::new();
+        driver.write(&owner, &mut Some(payload()), &mut false);
+        driver.settle_write(&owner, Some(Needs::Read));
+        assert_eq!(driver.other_io(), Permit::Ready);
+        owner.release();
+        assert_eq!(driver.other_io(), Permit::Ready);
+        let other = WriteOwner::new();
+        let mut different = Some(Box::from(&b"different"[..]));
+        assert_eq!(
+            driver.write(&other, &mut different, &mut false),
+            Permit::InvalidRetry
+        );
+        assert_eq!(
+            driver.write(&other, &mut Some(payload()), &mut false),
+            Permit::Ready
+        );
+        assert_eq!(driver.bytes(&other), b"stable bytes");
+    }
+
+    #[test]
+    fn concurrent_equal_writes_are_distinct() {
+        let mut driver = Driver::default();
+        let first = WriteOwner::new();
+        let second = WriteOwner::new();
+        driver.write(&first, &mut Some(payload()), &mut false);
+        driver.settle_write(&first, Some(Needs::Write));
+        let mut bytes = Some(payload());
+        let ptr = bytes.as_ref().unwrap().as_ptr();
+        let mut queued = false;
+        assert_eq!(driver.write(&second, &mut bytes, &mut queued), Permit::Wait);
+        driver.settle_write(&first, None);
+        assert_eq!(
+            driver.write(&second, &mut bytes, &mut queued),
+            Permit::Ready
+        );
+        assert_eq!(driver.bytes(&second).as_ptr(), ptr);
+    }
+
+    #[test]
+    fn queued_writer_cannot_acknowledge_an_abandoned_write() {
+        let mut driver = Driver::default();
+        let first = WriteOwner::new();
+        let second = WriteOwner::new();
+        driver.write(&first, &mut Some(payload()), &mut false);
+        driver.settle_write(&first, Some(Needs::Read));
+        let mut bytes = Some(payload());
+        let mut queued = false;
+        assert_eq!(driver.write(&second, &mut bytes, &mut queued), Permit::Wait);
+        first.release();
+        assert_eq!(
+            driver.write(&second, &mut bytes, &mut queued),
+            Permit::InvalidRetry
+        );
+        assert!(driver.pending.is_some());
+    }
+
+    #[test]
+    fn stale_release_cannot_orphan_an_adopted_writer() {
+        let mut driver = Driver::default();
+        let first = WriteOwner::new();
+        driver.write(&first, &mut Some(payload()), &mut false);
+        assert!(driver.settle_write(&first, Some(Needs::Write)));
+        first.release();
+        let next = WriteOwner::new();
+        assert_eq!(
+            driver.write(&next, &mut Some(payload()), &mut false),
+            Permit::Ready
+        );
+        first.release();
+        assert_eq!(driver.other_io(), Permit::Wait);
+        assert_eq!(driver.bytes(&next), b"stable bytes");
+        assert!(!driver.settle_write(&next, None));
+    }
+
+    #[test]
+    fn release_before_attempt_and_terminal_error_leave_no_retry() {
+        let mut driver = Driver::default();
+        let owner = WriteOwner::new();
+        driver.write(&owner, &mut Some(payload()), &mut false);
+        owner.release();
+        let owner = WriteOwner::new();
+        let mut different = Some(Box::from(&b"new operation"[..]));
+        assert_eq!(
+            driver.write(&owner, &mut different, &mut false),
+            Permit::Ready
+        );
+        assert_eq!(driver.bytes(&owner), b"new operation");
+        driver.settle_write(&owner, Some(Needs::Write));
+        driver.fail();
+        assert!(driver.terminal);
+        owner.release();
+        assert!(driver.pending.is_none());
+    }
+}
diff --git a/crates/stdlib/src/openssl/waiter.rs b/crates/stdlib/src/openssl/waiter.rs
new file mode 100644
index 00000000000..fa58e33e2bf
--- /dev/null
+++ b/crates/stdlib/src/openssl/waiter.rs
@@ -0,0 +1,285 @@
+use alloc::sync::{Arc, Weak};
+use rustpython_host_env::{
+    io as host_io,
+    select::{self, POLLIN, POLLNVAL, POLLOUT, PollFd},
+};
+use std::{
+    io,
+    os::fd::{AsFd, AsRawFd, OwnedFd, RawFd},
+    time::Instant,
+};
+
+/// A persistent, native-only notification for one blocked SSL operation.
+#[derive(Debug)]
+pub(super) struct ProgressWaiter {
+    read_fd: OwnedFd,
+    write_fd: OwnedFd,
+}
+
+impl ProgressWaiter {
+    pub(super) fn new() -> io::Result<Self> {
+        let (read_fd, write_fd) = wake_pipe()?;
+        Ok(Self { read_fd, write_fd })
+    }
+
+    pub(super) fn notify(&self) {
+        loop {
+            match host_io::write_once(self.write_fd.as_fd().into(), &[1]) {
+                Ok(_) => return,
+                Err(error) if error.kind() == io::ErrorKind::Interrupted => continue,
+                // A full pipe already carries a persistent notification.
+                Err(error) if error.kind() == io::ErrorKind::WouldBlock => return,
+                // Both endpoints stay owned for this entire call, so neither
+                // EBADF nor EPIPE is possible without external fd corruption.
+                Err(_) => return,
+            }
+        }
+    }
+
+    /// Re-arm under the connection guard, before the final identity check and
+    /// close-observer subscription. Draining after subscribing can lose close.
+    pub(super) fn drain(&self) -> io::Result<()> {
+        let mut buffer = [0; 256];
+        loop {
+            match host_io::read_once(self.read_fd.as_fd().into(), &mut buffer) {
+                Ok(0) => {
+                    return Err(io::Error::new(
+                        io::ErrorKind::BrokenPipe,
+                        "SSL progress notification pipe closed",
+                    ));
+                }
+                Ok(_) => {}
+                Err(error) if error.kind() == io::ErrorKind::WouldBlock => return Ok(()),
+                // In particular, return EINTR so the caller can check signals.
+                Err(error) => return Err(error),
+            }
+        }
+    }
+
+    /// Wait without a connection or socket guard. A missing socket means that
+    /// write ownership permits only progress notifications to resume this call.
+    /// Returns true on timeout; readiness never drains the notification pipe.
+    pub(super) fn wait(
+        &self,
+        socket_fd: Option<RawFd>,
+        write: bool,
+        deadline: Option<Instant>,
+    ) -> io::Result<bool> {
+        if socket_fd.is_some_and(|fd| fd < 0) {
+            return Err(io::Error::from_raw_os_error(libc::EBADF));
+        }
+        let mut fds = [
+            PollFd {
+                fd: self.read_fd.as_raw_fd(),
+                events: POLLIN,
+                revents: 0,
+            },
+            PollFd {
+                // poll ignores a negative fd when only progress is allowed.
+                fd: socket_fd.unwrap_or(-1),
+                // TLS consumes normal stream data, never MSG_OOB. Watching
+                // POLLPRI could spin on urgent data that this BIO cannot read.
+                events: if write { POLLOUT } else { POLLIN },
+                revents: 0,
+            },
+        ];
+        loop {
+            let (timeout, capped) = match deadline {
+                None => (-1, false),
+                Some(deadline) => {
+                    let remaining = deadline.saturating_duration_since(Instant::now());
+                    match select::duration_as_millis_ceiling(remaining) {
+                        Some(timeout) => (timeout, false),
+                        None => (i32::MAX, true),
+                    }
+                }
+            };
+            // Even an expired deadline gets a zero-time poll, as in wait_fd.
+            // EINTR is deliberately propagated for Python signal checking.
+            match select::poll_fds(&mut fds, timeout)? {
+                0 if capped => {}
+                0 => return Ok(true),
+                _ if fds.iter().any(|fd| fd.revents & POLLNVAL != 0) => {
+                    return Err(io::Error::from_raw_os_error(libc::EBADF));
+                }
+                _ => return Ok(false),
+            }
+        }
+    }
+}
+
+impl crate::socket::SocketCloseObserver for ProgressWaiter {
+    fn socket_closed(&self) {
+        self.notify();
+    }
+}
+
+fn wake_pipe() -> io::Result<(OwnedFd, OwnedFd)> {
+    cfg_select! {
+        any(
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "linux",
+            target_os = "android",
+            target_os = "netbsd",
+            target_os = "openbsd"
+        ) => {
+            rustpython_host_env::posix::pipe2(libc::O_CLOEXEC | libc::O_NONBLOCK)
+        }
+        target_os = "redox" => {
+            use std::os::fd::FromRawFd;
+
+            // Redox provides pipe2, but the host helper excludes this target.
+            let mut fds = [-1; 2];
+            // SAFETY: fds has storage for the two descriptors pipe2 writes.
+            if unsafe { libc::pipe2(fds.as_mut_ptr(), libc::O_CLOEXEC | libc::O_NONBLOCK) } < 0 {
+                return Err(io::Error::last_os_error());
+            }
+            // SAFETY: successful pipe2 transfers ownership of two new fds.
+            Ok(unsafe { (OwnedFd::from_raw_fd(fds[0]), OwnedFd::from_raw_fd(fds[1])) })
+        }
+        _ => {
+            // The host helper sets CLOEXEC and owns both fds immediately, so
+            // any subsequent fcntl failure also closes both endpoints.
+            let (read_fd, write_fd) = rustpython_host_env::posix::pipe()?;
+            rustpython_host_env::fcntl::set_blocking(read_fd.as_fd(), false)?;
+            rustpython_host_env::fcntl::set_blocking(write_fd.as_fd(), false)?;
+            Ok((read_fd, write_fd))
+        }
+    }
+}
+
+/// Implementations are native-only and must not reenter the registry.
+/// Production uses only ProgressWaiter's nonblocking pipe notification.
+pub(super) trait ProgressNotify {
+    fn notify(&self);
+}
+
+impl ProgressNotify for ProgressWaiter {
+    fn notify(&self) {
+        self.notify();
+    }
+}
+
+struct Registrations<W> {
+    generation: u64,
+    waiters: Vec<Weak<W>>,
+}
+
+/// Ownership can be abandoned without acquiring the native SSL lock. Compare
+/// generations when registering so that abandonment between predicate-check
+/// and registration cannot strand a waiter.
+pub(super) struct ProgressRegistry<W = ProgressWaiter> {
+    state: std::sync::Mutex<Registrations<W>>,
+}
+
+impl<W> Default for ProgressRegistry<W> {
+    fn default() -> Self {
+        Self {
+            state: std::sync::Mutex::new(Registrations {
+                generation: 0,
+                waiters: Vec::new(),
+            }),
+        }
+    }
+}
+
+impl<W: ProgressNotify> ProgressRegistry<W> {
+    pub(super) fn generation(&self) -> u64 {
+        self.state.lock().unwrap().generation
+    }
+
+    pub(super) fn register(&self, waiter: &Arc<W>, observed: u64) {
+        let mut state = self.state.lock().unwrap();
+        let weak = Arc::downgrade(waiter);
+        state.waiters.retain(|waiter| waiter.strong_count() != 0);
+        if !state
+            .waiters
+            .iter()
+            .any(|registered| registered.ptr_eq(&weak))
+        {
+            state.waiters.push(weak);
+        }
+        // Comparison and queuing share the notify mutex. A concurrent release
+        // either changed this generation or will find this registered waiter.
+        if state.generation != observed {
+            waiter.notify();
+        }
+    }
+
+    pub(super) fn unregister(&self, waiter: &Arc<W>) {
+        let weak = Arc::downgrade(waiter);
+        self.state
+            .lock()
+            .unwrap()
+            .waiters
+            .retain(|registered| !registered.ptr_eq(&weak));
+    }
+
+    pub(super) fn notify(&self) {
+        let mut state = self.state.lock().unwrap();
+        state.generation = state.generation.wrapping_add(1);
+        state.waiters.retain(|waiter| {
+            if let Some(waiter) = waiter.upgrade() {
+                waiter.notify();
+                true
+            } else {
+                false
+            }
+        });
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use core::sync::atomic::{AtomicUsize, Ordering};
+
+    #[derive(Default)]
+    struct Counter(AtomicUsize);
+
+    impl ProgressNotify for Counter {
+        fn notify(&self) {
+            self.0.fetch_add(1, Ordering::Relaxed);
+        }
+    }
+
+    #[test]
+    fn release_before_registration_is_not_lost() {
+        let registry = ProgressRegistry::default();
+        let observed = registry.generation();
+        let waiter = Arc::new(Counter::default());
+        registry.notify();
+        registry.register(&waiter, observed);
+        assert_eq!(waiter.0.load(Ordering::Relaxed), 1);
+    }
+
+    #[test]
+    fn release_after_registration_notifies_and_unregister_removes_it() {
+        let registry = ProgressRegistry::default();
+        let waiter = Arc::new(Counter::default());
+        registry.register(&waiter, registry.generation());
+        assert_eq!(waiter.0.load(Ordering::Relaxed), 0);
+        registry.notify();
+        assert_eq!(waiter.0.load(Ordering::Relaxed), 1);
+        registry.unregister(&waiter);
+        registry.notify();
+        assert_eq!(waiter.0.load(Ordering::Relaxed), 1);
+    }
+
+    #[test]
+    fn unchanged_retry_does_not_self_wake_or_duplicate_registration() {
+        let registry = ProgressRegistry::default();
+        let waiter = Arc::new(Counter::default());
+        for _ in 0..10 {
+            registry.register(&waiter, registry.generation());
+        }
+        assert_eq!(waiter.0.load(Ordering::Relaxed), 0);
+        assert_eq!(registry.state.lock().unwrap().waiters.len(), 1);
+        registry.notify();
+        assert_eq!(waiter.0.load(Ordering::Relaxed), 1);
+        let fresh = registry.generation();
+        registry.register(&waiter, fresh);
+        assert_eq!(waiter.0.load(Ordering::Relaxed), 1);
+    }
+}
diff --git a/crates/stdlib/src/pickle.rs b/crates/stdlib/src/pickle.rs
index 417a5721165..51427c0c9b0 100644
--- a/crates/stdlib/src/pickle.rs
+++ b/crates/stdlib/src/pickle.rs
@@ -18,6 +18,7 @@ mod _pickle {
         protocol::{PyBuffer, PyIter, PyIterReturn},
         types::{AsBuffer, Constructor, Initializer, Representable},
     };
+    use alloc::collections::TryReserveError;
     use core::sync::atomic::{AtomicI32, Ordering};
     use malachite_bigint::BigInt;
     use num_traits::{ToPrimitive, Zero};
@@ -407,17 +408,26 @@ mod _pickle {
     impl UnpicklerMemoProxy {
         #[pymethod]
         fn clear(zelf: &Py<Self>) {
-            zelf.unpickler.memo.write().clear();
+            let old_memo = core::mem::take(&mut *zelf.unpickler.memo.write());
+            drop(old_memo);
         }
 
         #[pymethod]
         fn copy(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
+            let mut snapshot = Vec::new();
+            let copied = {
+                let memo = zelf.unpickler.memo.read();
+                snapshot.try_reserve_exact(memo.len()).map(|()| {
+                    snapshot.extend(memo.iter().map(|(&index, obj)| (index, obj.clone())));
+                })
+            };
+            copied.map_err(|_| vm.no_memory_error())?;
+            // CPython inserts present memo indices in ascending order.
+            snapshot.sort_unstable_by_key(|(index, _)| *index);
             let dict = vm.ctx.new_dict();
-            for (i, entry) in zelf.unpickler.memo.read().iter().enumerate() {
-                if let Some(obj) = entry {
-                    let key: PyObjectRef = vm.ctx.new_int(i).into();
-                    dict.set_item(&*key, obj.clone(), vm)?;
-                }
+            for (i, obj) in snapshot {
+                let key: PyObjectRef = vm.ctx.new_int(i).into();
+                dict.set_item(&*key, obj, vm)?;
             }
             Ok(dict.into())
         }
@@ -440,6 +450,10 @@ mod _pickle {
 
     // Unpickler
 
+    // PUT indices need not be contiguous. A sparse table also keeps MEMOIZE's
+    // index equal to the number of entries rather than the largest index.
+    type UnpicklerMemo = HashMap<usize, PyObjectRef>;
+
     #[derive(Debug)]
     pub(super) struct UnpicklerConfig {
         initialized: bool,
@@ -468,7 +482,7 @@ mod _pickle {
     #[derive(Debug, PyPayload)]
     pub(super) struct PyUnpickler {
         read_state: PyMutex<ReadState>,
-        memo: PyRwLock<Vec<Option<PyObjectRef>>>,
+        memo: PyRwLock<UnpicklerMemo>,
         config: PyRwLock<UnpicklerConfig>,
     }
 
@@ -495,7 +509,7 @@ mod _pickle {
         fn py_new(_cls: &Py<PyType>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
             Ok(Self {
                 read_state: PyMutex::new(ReadState::default()),
-                memo: PyRwLock::new(Vec::new()),
+                memo: PyRwLock::new(UnpicklerMemo::new()),
                 config: PyRwLock::new(UnpicklerConfig::default()),
             })
         }
@@ -548,7 +562,7 @@ mod _pickle {
                 peek,
                 ..ReadState::default()
             };
-            zelf.memo.write().clear();
+            let old_memo = core::mem::take(&mut *zelf.memo.write());
             *zelf.config.write() = UnpicklerConfig {
                 initialized: true,
                 proto: 0,
@@ -557,6 +571,8 @@ mod _pickle {
                 errors,
                 buffers,
             };
+            drop(state);
+            drop(old_memo);
             Ok(())
         }
     }
@@ -605,21 +621,21 @@ mod _pickle {
                 }
             };
             let new_memo = if let Some(proxy) = value.downcast_ref::<UnpicklerMemoProxy>() {
-                proxy.unpickler.memo.read().clone()
+                let snapshot = copy_memo(&proxy.unpickler.memo.read());
+                snapshot.map_err(|_| vm.no_memory_error())?
             } else if let Some(dict) = value.downcast_ref::<PyDict>() {
-                let mut memo: Vec<Option<PyObjectRef>> = Vec::new();
+                let mut memo = UnpicklerMemo::new();
+                memo.try_reserve(dict.__len__())
+                    .map_err(|_| vm.no_memory_error())?;
                 for (key, val) in dict {
                     let idx = key
                         .downcast_ref::<PyInt>()
                         .ok_or_else(|| vm.new_type_error("memo key must be integers"))?;
-                    let idx = idx
-                        .as_bigint()
-                        .to_usize()
-                        .ok_or_else(|| vm.new_value_error("memo key must be positive integers."))?;
-                    if memo.len() <= idx {
-                        memo.resize(idx + 1, None);
+                    let idx = idx.try_to_primitive::<isize>(vm)?;
+                    if idx < 0 {
+                        return Err(vm.new_value_error("memo key must be positive integers."));
                     }
-                    memo[idx] = Some(val);
+                    memo_insert(&mut memo, idx as usize, &val).map_err(|_| vm.no_memory_error())?;
                 }
                 memo
             } else {
@@ -628,7 +644,8 @@ mod _pickle {
                     value.class().name()
                 )));
             };
-            *zelf.memo.write() = new_memo;
+            let old_memo = core::mem::replace(&mut *zelf.memo.write(), new_memo);
+            drop(old_memo);
             Ok(())
         }
     }
@@ -801,13 +818,18 @@ mod _pickle {
             .ok()
             .filter(|n| isize::try_from(*n).is_ok())
             .ok_or_else(|| {
-                new_unpickling_error(
-                    vm,
+                let message = if what == "FRAME" {
+                    format!(
+                        "FRAME length exceeds system's maximum of {} bytes",
+                        isize::MAX
+                    )
+                } else {
                     format!(
                         "{what} exceeds system's maximum size of {} bytes",
                         isize::MAX
-                    ),
-                )
+                    )
+                };
+                vm.new_overflow_error(message)
             })
     }
 
@@ -1073,7 +1095,7 @@ mod _pickle {
                 }
                 Some(BINBYTES8) => {
                     let arr: [u8; 8] = st.read_n(8, vm)?.try_into().unwrap();
-                    let n = read_size(&arr, vm, "BINBYTES8")?;
+                    let n = read_size(&arr, vm, "BINBYTES")?;
                     let data = st.read_n(n, vm)?.to_vec();
                     stack.push(vm.ctx.new_bytes(data).into());
                 }
@@ -1112,7 +1134,7 @@ mod _pickle {
                 }
                 Some(BINUNICODE8) => {
                     let arr: [u8; 8] = st.read_n(8, vm)?.try_into().unwrap();
-                    let n = read_size(&arr, vm, "BINUNICODE8")?;
+                    let n = read_size(&arr, vm, "BINUNICODE")?;
                     let data = st.read_n(n, vm)?.to_vec();
                     stack.push(utf8_surrogatepass(&data, vm)?);
                 }
@@ -1253,13 +1275,13 @@ mod _pickle {
                 Some(BINPUT) => {
                     let i = st.read_n(1, vm)?[0] as usize;
                     let value = top!();
-                    memo_put(zelf, i, value);
+                    memo_put(zelf, Some(i), value, vm)?;
                 }
                 Some(LONG_BINPUT) => {
                     let arr: [u8; 4] = st.read_n(4, vm)?.try_into().unwrap();
                     let i = u32::from_le_bytes(arr) as usize;
                     let value = top!();
-                    memo_put(zelf, i, value);
+                    memo_put(zelf, Some(i), value, vm)?;
                 }
                 Some(PUT) => {
                     let line = st.read_line(vm)?;
@@ -1269,12 +1291,11 @@ mod _pickle {
                     let body = &line[..line.len() - 1];
                     let idx = parse_memo_index(body, vm)?;
                     let value = top!();
-                    memo_put(zelf, idx, value);
+                    memo_put(zelf, Some(idx), value, vm)?;
                 }
                 Some(MEMOIZE) => {
                     let value = top!();
-                    let idx = zelf.memo.read().len();
-                    memo_put(zelf, idx, value);
+                    memo_put(zelf, None, value, vm)?;
                 }
                 Some(PERSID) => {
                     let line = st.read_line(vm)?;
@@ -1503,19 +1524,43 @@ mod _pickle {
     }
 
     fn memo_get(zelf: &Py<PyUnpickler>, idx: usize, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
-        zelf.memo
-            .read()
-            .get(idx)
-            .and_then(|o| o.clone())
+        let value = zelf.memo.read().get(&idx).cloned();
+        value
             .ok_or_else(|| new_unpickling_error(vm, format!("Memo value not found at index {idx}")))
     }
 
-    fn memo_put(zelf: &Py<PyUnpickler>, idx: usize, value: PyObjectRef) {
-        let mut memo = zelf.memo.write();
-        if memo.len() <= idx {
-            memo.resize(idx + 1, None);
+    fn copy_memo(memo: &UnpicklerMemo) -> Result<UnpicklerMemo, TryReserveError> {
+        let mut copy = UnpicklerMemo::new();
+        copy.try_reserve(memo.len())?;
+        copy.extend(memo.iter().map(|(&idx, obj)| (idx, obj.clone())));
+        Ok(copy)
+    }
+
+    fn memo_insert(
+        memo: &mut UnpicklerMemo,
+        idx: usize,
+        value: &PyObjectRef,
+    ) -> Result<Option<PyObjectRef>, TryReserveError> {
+        if !memo.contains_key(&idx) {
+            memo.try_reserve(1)?;
         }
-        memo[idx] = Some(value);
+        Ok(memo.insert(idx, value.clone()))
+    }
+
+    fn memo_put(
+        zelf: &Py<PyUnpickler>,
+        idx: Option<usize>,
+        value: PyObjectRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        let old_value = {
+            let mut memo = zelf.memo.write();
+            let idx = idx.unwrap_or_else(|| memo.len());
+            memo_insert(&mut memo, idx, &value)
+        };
+        // Releasing an entry can call a finalizer that accesses the memo.
+        drop(old_value.map_err(|_| vm.no_memory_error())?);
+        Ok(())
     }
 
     fn instantiate(
@@ -1699,7 +1744,7 @@ mod _pickle {
                 buf: data,
                 ..ReadState::default()
             }),
-            memo: PyRwLock::new(Vec::new()),
+            memo: PyRwLock::new(UnpicklerMemo::new()),
             config: PyRwLock::new(config),
         }
         .into_ref(&vm.ctx);
@@ -1745,7 +1790,7 @@ mod _pickle {
                 peek,
                 ..ReadState::default()
             }),
-            memo: PyRwLock::new(Vec::new()),
+            memo: PyRwLock::new(UnpicklerMemo::new()),
             config: PyRwLock::new(config),
         }
         .into_ref(&vm.ctx);
@@ -2856,7 +2901,7 @@ mod _pickle {
 
     impl SaveCtx<'_> {
         fn save(&mut self, obj: &PyObject, pers_save: bool, vm: &VirtualMachine) -> PyResult<()> {
-            vm.with_recursion("while pickling an object", || {
+            vm.with_recursion(" while pickling an object", || {
                 self.save_inner(obj, pers_save, vm)
             })
         }
diff --git a/crates/stdlib/src/posixsubprocess.rs b/crates/stdlib/src/posixsubprocess.rs
index f2ee7bbc2fe..268131e28bc 100644
--- a/crates/stdlib/src/posixsubprocess.rs
+++ b/crates/stdlib/src/posixsubprocess.rs
@@ -283,7 +283,7 @@ fn exec(args: &ForkExecArgs<'_>, procargs: ProcArgs<'_>, vm: &VirtualMachine) ->
                 let errno = e.raw_os_error().unwrap_or(0);
                 let _ = write!(pipe, "OSError:{errno:x}:{}", ctx.as_msg());
             }
-            rustpython_host_env::os::exit(255)
+            rustpython_host_env::os::exit_immediately(255)
         }
     }
 }
diff --git a/crates/stdlib/src/pyexpat.rs b/crates/stdlib/src/pyexpat.rs
index 5a516dd7821..2ca962e924f 100644
--- a/crates/stdlib/src/pyexpat.rs
+++ b/crates/stdlib/src/pyexpat.rs
@@ -168,9 +168,9 @@ mod _pyexpat {
     use crate::vm::{
         AsObject, Context, Py, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
         VirtualMachine,
-        builtins::{PyBytesRef, PyException, PyModule, PyStr, PyStrRef, PyType, PyUtf8StrRef},
+        builtins::{PyException, PyModule, PyStr, PyStrRef, PyType, PyUtf8StrRef},
         extend_module,
-        function::{ArgBytesLike, Either, IntoFuncArgs, OptionalArg, OptionalOption},
+        function::{ArgBytesLike, ArgStrOrBytesLike, IntoFuncArgs, OptionalArg, OptionalOption},
         types::Constructor,
     };
     use alloc::collections::VecDeque;
@@ -1051,6 +1051,10 @@ mod _pyexpat {
         fn make_name(&self, name: &xml::name::OwnedName) -> String {
             match (&self.namespace_separator, &name.namespace) {
                 (Some(sep), Some(ns)) => format!("{}{}{}", ns, sep, name.local_name),
+                (None, _) => match &name.prefix {
+                    Some(prefix) => format!("{prefix}:{}", name.local_name),
+                    None => name.local_name.clone(),
+                },
                 _ => name.local_name.clone(),
             }
         }
@@ -1399,14 +1403,11 @@ mod _pyexpat {
         #[pymethod(name = "Parse")]
         fn parse(
             zelf: &Py<Self>,
-            data: Either<PyStrRef, PyBytesRef>,
+            data: ArgStrOrBytesLike,
             isfinal: OptionalArg<bool>,
             vm: &VirtualMachine,
         ) -> PyResult<i32> {
-            let bytes = match data {
-                Either::A(s) => s.as_bytes().to_vec(),
-                Either::B(b) => b.as_bytes().to_vec(),
-            };
+            let bytes = data.borrow_bytes().to_vec();
             zelf.feed(vm, &bytes, isfinal.unwrap_or(false))?;
             Ok(1)
         }
diff --git a/crates/stdlib/src/pystruct.rs b/crates/stdlib/src/pystruct.rs
index 2a3c0dfe341..cdfe80deb5d 100644
--- a/crates/stdlib/src/pystruct.rs
+++ b/crates/stdlib/src/pystruct.rs
@@ -10,16 +10,15 @@ pub(crate) use _struct::module_def;
 #[pymodule]
 pub(crate) mod _struct {
     use crate::vm::{
-        AsObject, Py, PyObjectRef, PyPayload, PyResult, TryFromObject, VirtualMachine,
+        AsObject, FromArgs, Py, PyObject, PyObjectRef, PyPayload, PyResult, TryFromObject,
+        VirtualMachine,
         buffer::{FormatSpec, new_struct_error, struct_error_type},
         builtins::{PyBytes, PyStr, PyStrRef, PyTupleRef, PyType, PyTypeRef},
-        common::{
-            lock::{PyMappedRwLockReadGuard, PyRwLock, PyRwLockReadGuard},
-            rc::PyRc,
-        },
+        common::{lock::PyRwLock, rc::PyRc},
         function::{ArgBytesLike, ArgMemoryBuffer, FuncArgs, PosArgs},
         match_class,
         protocol::PyIterReturn,
+        stdlib::_warnings,
         types::{Constructor, Initializer, IterNext, Iterable, Representable, SelfIter},
     };
     use crossbeam_utils::atomic::AtomicCell;
@@ -30,33 +29,22 @@ pub(crate) mod _struct {
 
     impl TryFromObject for IntoStructFormatBytes {
         fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
-            // CPython turns str to bytes (via str.encode('ascii')) but we keep str.
-            // The error reporting for non-ASCII input still matches CPython:
-            // - str input with non-ASCII char: UnicodeEncodeError, the same exception
-            //   str.encode('ascii') would produce.
-            // - bytes input with non-ASCII byte: struct.error("bad char in struct format"),
-            //   matching CPython where bytes are passed through to the format parser.
+            // CPython decodes bytes with ASCII and surrogateescape, then rejects
+            // every non-ASCII format before parsing, for both str and bytes.
             let fmt = match_class!(match obj {
                 s @ PyStr => {
                     if !s.isascii() {
-                        let start = s
-                            .as_wtf8()
-                            .code_points()
-                            .position(|cp| !cp.to_char().is_some_and(|c| c.is_ascii()))
-                            .unwrap_or(0);
-                        return Err(vm.new_unicode_encode_error(
-                            vm.ctx.new_str("ascii"),
-                            s,
-                            start,
-                            start + 1,
-                            vm.ctx.new_str("ordinal not in range(128)"),
-                        ));
+                        return Err(vm.new_value_error("non-ASCII character in struct format"));
+                    }
+                    if s.class().is(vm.ctx.types.str_type) {
+                        s
+                    } else {
+                        vm.ctx.new_str(s.as_wtf8())
                     }
-                    s
                 }
                 b @ PyBytes => {
                     let ascii_str = ascii::AsciiStr::from_ascii(&b)
-                        .map_err(|_| new_struct_error(vm, "bad char in struct format"))?;
+                        .map_err(|_| vm.new_value_error("non-ASCII character in struct format"))?;
                     vm.ctx.new_str(ascii_str)
                 }
                 other =>
@@ -262,60 +250,188 @@ pub(crate) mod _struct {
     }
 
     /// What a `Struct` is once a format has been read into it. Held apart
-    /// from the object because `__new__` hands out a `Struct` that `__init__`
-    /// has not filled in yet, and `__init__` may be called again on one that
-    /// already holds a format.
-    #[derive(Debug)]
+    /// because `__new__` can still hand out an uninitialized `Struct`, and
+    /// `__init__` may be called again on one that already holds a format.
+    #[derive(Clone, Debug)]
     struct StructSpec {
         spec: PyRc<FormatSpec>,
         format: PyStrRef,
     }
 
+    #[derive(FromArgs)]
+    struct StructArgs {
+        #[pyarg(any)]
+        format: PyObjectRef,
+    }
+
+    impl StructArgs {
+        fn bind(args: FuncArgs, vm: &VirtualMachine) -> PyResult<Self> {
+            let nargs = args.args.len() + args.kwargs.len();
+            if nargs > 1 {
+                let keyword = if args.args.is_empty() { "keyword " } else { "" };
+                return Err(vm.new_type_error(format!(
+                    "Struct() takes at most 1 {keyword}argument ({nargs} given)"
+                )));
+            }
+            args.bind_for(vm, "Struct")
+        }
+    }
+
     #[pyattr]
     #[pyclass(name = "Struct", traverse)]
     #[derive(Debug, PyPayload)]
     struct PyStruct {
         #[pytraverse(skip)]
         inner: PyRwLock<Option<StructSpec>>,
+        #[pytraverse(skip)]
+        init_called: AtomicCell<bool>,
+    }
+
+    impl PyStruct {
+        fn uses_struct_init(cls: &Py<PyType>, vm: &VirtualMachine) -> bool {
+            cls.slots()
+                .init
+                .load()
+                .zip(Self::class(&vm.ctx).slots().init.load())
+                .is_some_and(|(init, struct_init)| core::ptr::fn_addr_eq(init, struct_init))
+        }
+
+        fn parse_format(format: PyObjectRef, vm: &VirtualMachine) -> PyResult<StructSpec> {
+            let format = IntoStructFormatBytes::try_from_object(vm, format)?;
+            Ok(StructSpec {
+                spec: PyRc::new(format.format_spec(vm)?),
+                format: format.0,
+            })
+        }
+
+        fn same_format(format: &PyStr, candidate: &PyObject) -> bool {
+            candidate
+                .downcast_ref::<PyStr>()
+                .is_some_and(|candidate| candidate.as_bytes() == format.as_bytes())
+                || candidate
+                    .downcast_ref::<PyBytes>()
+                    .is_some_and(|candidate| candidate.as_bytes() == format.as_bytes())
+        }
     }
 
     impl Constructor for PyStruct {
         type Args = FuncArgs;
 
+        fn slot_new(cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
+            let uses_struct_new = cls
+                .slots()
+                .new
+                .load()
+                .zip(Self::class(&vm.ctx).slots().new.load())
+                .is_some_and(|(new, struct_new)| core::ptr::fn_addr_eq(new, struct_new));
+            let uses_struct_init = Self::uses_struct_init(&cls, vm);
+            let format = if !uses_struct_new {
+                // A subclass explicitly called Struct.__new__ from its own __new__.
+                let args = StructArgs::bind(args, vm)?;
+                Some(args.format)
+            } else {
+                let format = match args.args.as_slice() {
+                    [format] if args.kwargs.is_empty() => Some(format.clone()),
+                    [] if args.kwargs.len() == 1 => args.kwargs.get("format").cloned(),
+                    _ => None,
+                };
+                if format.is_none() && !uses_struct_init {
+                    let nargs = args.args.len() + args.kwargs.len();
+                    let message = if nargs > 1 {
+                        format!("Struct() takes at most 1 argument ({nargs} given)")
+                    } else {
+                        "Struct() missing required argument 'format' (pos 1)".to_owned()
+                    };
+                    _warnings::warn(vm.ctx.exceptions.deprecation_warning, message, 1, vm)?;
+                }
+                format
+            };
+            // Allocate before parsing so a failing subclass constructor still
+            // finalizes its half-initialized instance.
+            let zelf = Self::py_new(&cls, FuncArgs::default(), vm)?.into_ref_with_type(vm, cls)?;
+            if let Some(format) = format {
+                match Self::parse_format(format, vm) {
+                    Ok(inner) => {
+                        let old = zelf.inner.write().replace(inner);
+                        drop(old);
+                    }
+                    Err(err) if uses_struct_new && !uses_struct_init => {
+                        _warnings::warn(
+                            vm.ctx.exceptions.deprecation_warning,
+                            format!(
+                                "Invalid 'format' argument for Struct.__new__(): {}",
+                                err.as_object().str(vm)?
+                            ),
+                            1,
+                            vm,
+                        )?;
+                    }
+                    Err(err) => return Err(err),
+                }
+            }
+            Ok(zelf.into())
+        }
+
         fn py_new(_cls: &Py<PyType>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
             Ok(Self {
                 inner: PyRwLock::new(None),
+                init_called: AtomicCell::new(false),
             })
         }
     }
 
     impl Initializer for PyStruct {
-        type Args = IntoStructFormatBytes;
-
-        fn init(zelf: &Py<Self>, fmt: Self::Args, vm: &VirtualMachine) -> PyResult<()> {
-            // The format is read before anything is replaced, so a format that
-            // cannot be read leaves the object as it was.
-            let spec = fmt.format_spec(vm)?;
-            *zelf.inner.write() = Some(StructSpec {
-                spec: PyRc::new(spec),
-                format: fmt.0,
-            });
+        type Args = FuncArgs;
+
+        fn init(zelf: &Py<Self>, args: Self::Args, vm: &VirtualMachine) -> PyResult<()> {
+            let format = zelf.inner.read().as_ref().map(|inner| inner.format.clone());
+            if !zelf.init_called.load()
+                && Self::uses_struct_init(zelf.class(), vm)
+                && format.is_some()
+            {
+                // The implicit __init__ must not reinterpret a custom __new__'s arguments.
+                zelf.init_called.store(true);
+                return Ok(());
+            }
+            let args = StructArgs::bind(args, vm)?;
+            if let Some(format) = format {
+                if Self::same_format(&format, &args.format) {
+                    zelf.init_called.store(true);
+                    return Ok(());
+                }
+                let message = if zelf.init_called.load() {
+                    "Re-initialization of Struct by calling the __init__() method \
+                     will not work in future Python versions"
+                } else {
+                    "Different format arguments for __new__() and __init__() \
+                     methods of Struct"
+                };
+                _warnings::warn(vm.ctx.exceptions.future_warning, message.to_owned(), 1, vm)?;
+            }
+            // Warn and parse before replacing the format. Warning hooks may reenter,
+            // and either a warning or a conversion error must preserve the old state.
+            let inner = Self::parse_format(args.format, vm)?;
+            let old = zelf.inner.write().replace(inner);
+            drop(old);
+            zelf.init_called.store(true);
             Ok(())
         }
     }
 
     #[pyclass(with(Constructor, Initializer, Representable), flags(BASETYPE))]
     impl PyStruct {
-        /// The format this was initialized with, or an error if `__init__`
-        /// never ran.
-        fn ready(&self, vm: &VirtualMachine) -> PyResult<PyMappedRwLockReadGuard<'_, StructSpec>> {
-            PyRwLockReadGuard::try_map(self.inner.read(), Option::as_ref)
-                .map_err(|_| vm.new_runtime_error("Struct object is not initialized"))
+        // Hold an owned snapshot while conversions and warning hooks can reenter.
+        fn ready(&self, vm: &VirtualMachine) -> PyResult<StructSpec> {
+            let inner = self.inner.read().clone();
+            inner.ok_or_else(|| vm.new_runtime_error("Struct object is not initialized"))
         }
 
         #[pygetset]
         fn format(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyStrRef> {
-            Ok(zelf.ready(vm)?.format.clone())
+            let format = zelf.inner.read().as_ref().map(|inner| inner.format.clone());
+            format.ok_or_else(|| {
+                vm.new_no_attribute_error(zelf.as_object().to_owned(), vm.ctx.new_str("format"))
+            })
         }
 
         // The size an uninitialized `Struct` reports, which no format has
@@ -379,7 +495,7 @@ pub(crate) mod _struct {
             buffer: ArgBytesLike,
             vm: &VirtualMachine,
         ) -> PyResult<UnpackIterator> {
-            let spec = zelf.ready(vm)?.spec.clone();
+            let spec = zelf.ready(vm)?.spec;
             UnpackIterator::with_buffer(vm, spec, buffer)
         }
 
diff --git a/crates/stdlib/src/resource.rs b/crates/stdlib/src/resource.rs
index 0e2a777e6e2..916ca058231 100644
--- a/crates/stdlib/src/resource.rs
+++ b/crates/stdlib/src/resource.rs
@@ -6,8 +6,9 @@ pub(crate) use resource::module_def;
 mod resource {
     use crate::vm::{
         Py, PyObject, PyObjectRef, PyResult, TryFromBorrowedObject, VirtualMachine,
-        builtins::{PyInt, PyIntRef},
+        builtins::PyInt,
         convert::{ToPyException, ToPyObject},
+        function::ArgIndex,
         types::PyStructSequence,
     };
     use num_traits::Signed;
@@ -16,9 +17,7 @@ mod resource {
 
     #[cfg_attr(target_os = "android", expect(deprecated))]
     const RLIM_NLIMITS: i32 = cfg_select! {
-        target_os = "android" => {
-            host_resource::RLIM_NLIMITS
-        }
+        target_os = "android" => host_resource::RLIM_NLIMITS,
         _ => {
             // This constant isn't abi-stable across os versions, so we just
             // pick a high number so we don't get false positive ValueErrors and just bubble up the
@@ -185,8 +184,8 @@ mod resource {
     }
 
     #[pyfunction]
-    fn getrlimit(resource: PyIntRef, vm: &VirtualMachine) -> PyResult<Limits> {
-        let resource = py2rlim(&resource, vm)?;
+    fn getrlimit(resource: ArgIndex, vm: &VirtualMachine) -> PyResult<Limits> {
+        let resource = py2rlim(resource.as_ref(), vm)?;
 
         if resource >= RLIM_NLIMITS as host_resource::rlim_t {
             return Err(vm.new_value_error("invalid resource specified"));
@@ -197,8 +196,8 @@ mod resource {
     }
 
     #[pyfunction]
-    fn setrlimit(resource: PyIntRef, limits: Limits, vm: &VirtualMachine) -> PyResult<()> {
-        let resource = py2rlim(&resource, vm)?;
+    fn setrlimit(resource: ArgIndex, limits: Limits, vm: &VirtualMachine) -> PyResult<()> {
+        let resource = py2rlim(resource.as_ref(), vm)?;
 
         if resource >= RLIM_NLIMITS as host_resource::rlim_t {
             return Err(vm.new_value_error("invalid resource specified"));
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__adjacent_no_location_entries.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__adjacent_no_location_entries.snap
new file mode 100644
index 00000000000..1a9458c566c
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__adjacent_no_location_entries.snap
@@ -0,0 +1,109 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(file):\n    if sys.platform == \"win32\":\n        try:\n            import nt\n            if not nt._supports_virtual_terminal():\n                return False\n        except (ImportError, AttributeError):\n            return False\n    try:\n        return os.isatty(file.fileno())\n    except OSError:\n        return hasattr(file, \"isatty\") and file.isatty()\n\"#,\ntrue)"
+---
+0:0-1:0              RESUME                   0
+
+1:0-12:56            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-12:56            MAKE_FUNCTION
+1:0-12:56            STORE_NAME               0 (f)
+1:0-12:56            LOAD_COMMON_CONSTANT     7 (None)
+1:0-12:56            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0                 RESUME                   0
+
+2:7-2:10                LOAD_GLOBAL              0 (sys)
+2:7-2:19                LOAD_ATTR                2 (platform)
+2:23-2:30               LOAD_CONST               0 ('win32')
+2:7-2:30                COMPARE_OP              88 (bool(==))
+2:7-2:30                POP_JUMP_IF_FALSE       31 (to L4)
+2:7-2:30                NOT_TAKEN
+
+3:8-8:24                NOP
+
+4:12-4:21       L1:     LOAD_SMALL_INT           0
+4:12-4:21               LOAD_COMMON_CONSTANT     7 (None)
+4:12-4:21               IMPORT_NAME             10 (nt + eager)
+4:12-4:21               STORE_FAST               1 (nt)
+
+5:19-5:21               LOAD_FAST_BORROW         1 (nt)
+5:19-5:48               LOAD_ATTR                7 (_supports_virtual_terminal + NULL|self)
+5:19-5:50               CALL                     0
+5:19-5:50               TO_BOOL
+5:19-5:50               POP_JUMP_IF_TRUE         3 (to L3)
+5:19-5:50       L2:     NOT_TAKEN
+
+6:23-6:28               LOAD_COMMON_CONSTANT    10 (False)
+6:23-6:28               RETURN_VALUE
+
+5:19-5:50       L3:     NOP
+
+9:4-12:56       L4:     NOP
+
+10:15-10:17     L5:     LOAD_GLOBAL             12 (os)
+10:15-10:24             LOAD_ATTR               15 (isatty + NULL|self)
+10:25-10:29             LOAD_FAST_BORROW         0 (file)
+10:25-10:36             LOAD_ATTR               17 (fileno + NULL|self)
+10:25-10:38             CALL                     0
+10:15-10:39             CALL                     1
+10:8-10:39      L6:     RETURN_VALUE
+
+  --            L7:     PUSH_EXC_INFO
+
+7:16-7:27               LOAD_GLOBAL              8 (ImportError)
+7:29-7:43               LOAD_GLOBAL             10 (AttributeError)
+7:15-7:44               BUILD_TUPLE              2
+7:8-8:24                CHECK_EXC_MATCH
+7:8-8:24                POP_JUMP_IF_FALSE        5 (to L11)
+7:8-8:24        L8:     NOT_TAKEN
+7:8-8:24        L9:     POP_TOP
+
+8:19-8:24      L10:     POP_EXCEPT
+8:19-8:24               LOAD_COMMON_CONSTANT    10 (False)
+8:19-8:24               RETURN_VALUE
+
+7:8-8:24       L11:     RERAISE                  0
+
+  --           L12:     COPY                     3
+  --                    POP_EXCEPT
+  --                    RERAISE                  1
+  --           L13:     PUSH_EXC_INFO
+
+11:11-11:18             LOAD_GLOBAL             18 (OSError)
+11:4-12:56              CHECK_EXC_MATCH
+11:4-12:56              POP_JUMP_IF_FALSE       40 (to L20)
+11:4-12:56     L14:     NOT_TAKEN
+11:4-12:56     L15:     POP_TOP
+
+12:15-12:22             LOAD_GLOBAL             21 (hasattr + NULL)
+12:23-12:27             LOAD_FAST                0 (file)
+12:29-12:37             LOAD_CONST               1 ('isatty')
+12:15-12:38             CALL                     2
+12:15-12:56             COPY                     1
+12:15-12:56             TO_BOOL
+12:15-12:56             POP_JUMP_IF_FALSE       17 (to L18)
+12:15-12:56    L16:     NOT_TAKEN
+12:15-12:56    L17:     POP_TOP
+12:43-12:47             LOAD_FAST                0 (file)
+12:43-12:54             LOAD_ATTR               15 (isatty + NULL|self)
+12:43-12:56             CALL                     0
+12:8-12:56     L18:     SWAP                     2
+12:8-12:56     L19:     POP_EXCEPT
+12:8-12:56              RETURN_VALUE
+
+11:4-12:56     L20:     RERAISE                  0
+
+  --           L21:     COPY                     3
+  --                    POP_EXCEPT
+  --                    RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L7 [0]
+  L5 to L6 -> L13 [0]
+  L7 to L8 -> L12 [1] lasti
+  L9 to L10 -> L12 [1] lasti
+  L11 to L12 -> L12 [1] lasti
+  L13 to L14 -> L21 [1] lasti
+  L15 to L16 -> L21 [1] lasti
+  L17 to L19 -> L21 [1] lasti
+  L20 to L21 -> L21 [1] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__annotated_multiline_function_firstlineno.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__annotated_multiline_function_firstlineno.snap
new file mode 100644
index 00000000000..98bf8123a15
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__annotated_multiline_function_firstlineno.snap
@@ -0,0 +1,39 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\n\na = 1\ndef f(\n    x: a,\n): ...\n\"#, true)"
+---
+0:0-1:0            RESUME                   0
+
+1:4-1:5            LOAD_SMALL_INT           1
+1:0-1:1            STORE_NAME               0 (a)
+
+2:0-4:6            LOAD_CONST               1 (<code object __annotate__ at 0xdeadbeef, file "<?>", line 2>)
+2:0-4:6            MAKE_FUNCTION
+2:0-4:6            LOAD_CONST               2 (<code object f at 0xdeadbeef, file "<?>", line 2>)
+2:0-4:6            MAKE_FUNCTION
+2:0-4:6            SET_FUNCTION_ATTRIBUTE  16 (annotate)
+2:0-4:6            STORE_NAME               1 (f)
+2:0-4:6            LOAD_COMMON_CONSTANT     7 (None)
+2:0-4:6            RETURN_VALUE
+
+Disassembly of <code object __annotate__ at 0xdeadbeef, file "<?>", line 2>:
+2:0-2:0            RESUME                   0
+2:0-4:6            LOAD_FAST_BORROW         0 (format)
+2:0-4:6            LOAD_SMALL_INT           2
+2:0-4:6            COMPARE_OP             132 (>)
+2:0-4:6            POP_JUMP_IF_FALSE        3 (to L1)
+2:0-4:6            NOT_TAKEN
+2:0-4:6            LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+2:0-4:6            RAISE_VARARGS            1
+2:0-4:6    L1:     LOAD_CONST               1 ('x')
+
+3:7-3:8            LOAD_GLOBAL              0 (a)
+
+2:0-4:6            BUILD_MAP                1
+2:0-4:6            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 2>:
+2:0-2:0            RESUME                   0
+
+4:3-4:6            LOAD_COMMON_CONSTANT     7 (None)
+4:3-4:6            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__annotation_scope_function_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__annotation_scope_function_location.snap
new file mode 100644
index 00000000000..e8dec1373fc
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__annotation_scope_function_location.snap
@@ -0,0 +1,44 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\n\ndef g():\n    def f(x: not (int is int), /): ...\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:38            LOAD_CONST               0 (<code object g at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:38            MAKE_FUNCTION
+1:0-2:38            STORE_NAME               0 (g)
+1:0-2:38            LOAD_COMMON_CONSTANT     7 (None)
+1:0-2:38            RETURN_VALUE
+
+Disassembly of <code object g at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0             RESUME                   0
+
+2:4-2:38            LOAD_CONST               0 (<code object __annotate__ at 0xdeadbeef, file "<?>", line 2>)
+2:4-2:38            MAKE_FUNCTION
+2:4-2:38            LOAD_CONST               1 (<code object f at 0xdeadbeef, file "<?>", line 2>)
+2:4-2:38            MAKE_FUNCTION
+2:4-2:38            SET_FUNCTION_ATTRIBUTE  16 (annotate)
+2:4-2:38            STORE_FAST               0 (f)
+2:4-2:38            LOAD_COMMON_CONSTANT     7 (None)
+2:4-2:38            RETURN_VALUE
+
+Disassembly of <code object __annotate__ at 0xdeadbeef, file "<?>", line 2>:
+2:0-2:0              RESUME                   0
+2:4-2:38             LOAD_FAST_BORROW         0 (format)
+2:4-2:38             LOAD_SMALL_INT           2
+2:4-2:38             COMPARE_OP             132 (>)
+2:4-2:38             POP_JUMP_IF_FALSE        3 (to L1)
+2:4-2:38             NOT_TAKEN
+2:4-2:38             LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+2:4-2:38             RAISE_VARARGS            1
+2:4-2:38     L1:     LOAD_CONST               1 ('x')
+2:18-2:21            LOAD_GLOBAL              0 (int)
+2:25-2:28            LOAD_GLOBAL              0 (int)
+2:13-2:29            IS_OP                    1 (is not)
+2:4-2:38             BUILD_MAP                1
+2:4-2:38             RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 2>:
+2:0-2:0              RESUME                   0
+2:35-2:38            LOAD_COMMON_CONSTANT     7 (None)
+2:35-2:38            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__assert_false_message_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__assert_false_message_location.snap
new file mode 100644
index 00000000000..e0c9da9f252
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__assert_false_message_location.snap
@@ -0,0 +1,19 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f():\n    assert False, \"x\"\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:21            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:21            MAKE_FUNCTION
+1:0-2:21            STORE_NAME               0 (f)
+1:0-2:21            LOAD_COMMON_CONSTANT     7 (None)
+1:0-2:21            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:4-2:21             LOAD_COMMON_CONSTANT     0 (AssertionError)
+2:18-2:21            LOAD_CONST               1 ('x')
+2:4-2:21             CALL                     0
+2:11-2:16            RAISE_VARARGS            1
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__async_for_anext_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__async_for_anext_location.snap
new file mode 100644
index 00000000000..57a303b673e
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__async_for_anext_location.snap
@@ -0,0 +1,57 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nasync def f(source, buffer):\n    async for i1, i2 in source():\n        buffer.append(i1 + i2)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-3:30            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-3:30            MAKE_FUNCTION
+1:0-3:30            STORE_NAME               0 (f)
+1:0-3:30            LOAD_COMMON_CONSTANT     7 (None)
+1:0-3:30            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:?-1:?               RETURN_GENERATOR
+1:?-1:?               POP_TOP
+1:0-1:0       L1:     RESUME                   0
+
+2:24-2:30             LOAD_FAST_BORROW         0 (source)
+2:24-2:30             PUSH_NULL
+2:24-2:32             CALL                     0
+2:24-2:32             GET_AITER
+2:4-3:30      L2:     GET_ANEXT
+2:4-3:30              PUSH_NULL
+2:4-3:30              LOAD_COMMON_CONSTANT     7 (None)
+2:4-3:30      L3:     SEND                     4 (to L6)
+2:4-3:30      L4:     YIELD_VALUE              1
+2:4-3:30      L5:     RESUME                   3
+2:4-3:30              JUMP_BACKWARD_NO_INTERRUPT 6 (to L3)
+2:4-3:30      L6:     END_SEND
+2:4-3:30      L7:     NOT_TAKEN
+2:14-2:20             UNPACK_SEQUENCE          2
+2:14-2:16             STORE_FAST_STORE_FAST   35 (i1, i2)
+
+3:8-3:14              LOAD_FAST_BORROW         1 (buffer)
+3:8-3:21              LOAD_ATTR                1 (append + NULL|self)
+3:22-3:24             LOAD_FAST_BORROW_LOAD_FAST_BORROW 35 (i1, i2)
+3:22-3:29             BINARY_OP                0 (+)
+3:8-3:30              CALL                     1
+3:8-3:30              POP_TOP
+3:8-3:30              JUMP_BACKWARD           39 (to L2)
+
+2:4-3:30      L8:     CLEANUP_THROW
+2:4-3:30      L9:     JUMP_BACKWARD_NO_INTERRUPT 32 (to L6)
+2:24-2:32    L10:     END_ASYNC_FOR           33 (from L6)
+2:24-2:32             LOAD_COMMON_CONSTANT     7 (None)
+2:24-2:32             RETURN_VALUE
+
+  --         L11:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L11 [0] lasti
+  L2 to L4 -> L10 [1]
+  L4 to L5 -> L8 [4]
+  L5 to L7 -> L10 [1]
+  L7 to L8 -> L11 [0] lasti
+  L8 to L9 -> L10 [1]
+  L10 to L11 -> L11 [0] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__async_for_end_async_for.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__async_for_end_async_for.snap
new file mode 100644
index 00000000000..5583383e472
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__async_for_end_async_for.snap
@@ -0,0 +1,48 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nasync def f(xs):\n    async for x in xs:\n        pass\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-3:12            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-3:12            MAKE_FUNCTION
+1:0-3:12            STORE_NAME               0 (f)
+1:0-3:12            LOAD_COMMON_CONSTANT     7 (None)
+1:0-3:12            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:?-1:?               RETURN_GENERATOR
+1:?-1:?               POP_TOP
+1:0-1:0       L1:     RESUME                   0
+
+2:19-2:21             LOAD_FAST_BORROW         0 (xs)
+2:19-2:21             GET_AITER
+2:4-3:12      L2:     GET_ANEXT
+2:4-3:12              PUSH_NULL
+2:4-3:12              LOAD_COMMON_CONSTANT     7 (None)
+2:4-3:12      L3:     SEND                     4 (to L6)
+2:4-3:12      L4:     YIELD_VALUE              1
+2:4-3:12      L5:     RESUME                   3
+2:4-3:12              JUMP_BACKWARD_NO_INTERRUPT 6 (to L3)
+2:4-3:12      L6:     END_SEND
+2:4-3:12      L7:     NOT_TAKEN
+2:14-2:15             STORE_FAST               1 (x)
+
+3:8-3:12              JUMP_BACKWARD           14 (to L2)
+
+2:4-3:12      L8:     CLEANUP_THROW
+2:4-3:12      L9:     JUMP_BACKWARD_NO_INTERRUPT 7 (to L6)
+2:19-2:21    L10:     END_ASYNC_FOR            8 (from L6)
+2:19-2:21             LOAD_COMMON_CONSTANT     7 (None)
+2:19-2:21             RETURN_VALUE
+
+  --         L11:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L11 [0] lasti
+  L2 to L4 -> L10 [1]
+  L4 to L5 -> L8 [4]
+  L5 to L7 -> L10 [1]
+  L7 to L8 -> L11 [0] lasti
+  L8 to L9 -> L10 [1]
+  L10 to L11 -> L11 [0] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__augassign_constant_slice_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__augassign_constant_slice_location.snap
new file mode 100644
index 00000000000..8c44eba81d9
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__augassign_constant_slice_location.snap
@@ -0,0 +1,27 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef aug_const(x, y):\n    x[1:2] += y\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:15            LOAD_CONST               0 (<code object aug_const at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:15            MAKE_FUNCTION
+1:0-2:15            STORE_NAME               0 (aug_const)
+1:0-2:15            LOAD_COMMON_CONSTANT     7 (None)
+1:0-2:15            RETURN_VALUE
+
+Disassembly of <code object aug_const at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:4-2:5              LOAD_FAST_BORROW         0 (x)
+2:6-2:9              LOAD_CONST               0 (slice(1, 2, None))
+2:4-2:10             COPY                     2
+2:4-2:10             COPY                     2
+2:4-2:10             BINARY_OP               26 ([])
+2:14-2:15            LOAD_FAST_BORROW         1 (y)
+2:4-2:15             BINARY_OP               13 (+=)
+2:4-2:10             SWAP                     3
+2:4-2:10             SWAP                     2
+2:4-2:10             STORE_SUBSCR
+2:4-2:10             LOAD_COMMON_CONSTANT     7 (None)
+2:4-2:10             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__bare_function_annotations_check_attribute_and_subscript_expressions.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__bare_function_annotations_check_attribute_and_subscript_expressions.snap
index c0cac3bbb98..76a7e0d8871 100644
--- a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__bare_function_annotations_check_attribute_and_subscript_expressions.snap
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__bare_function_annotations_check_attribute_and_subscript_expressions.snap
@@ -11,7 +11,7 @@ expression: "dis(r#\"\ndef f(one: int):\n    int.new_attr: int\n    [list][0].ne
               MAKE_FUNCTION
               SET_FUNCTION_ATTRIBUTE  16 (annotate)
               STORE_NAME               0 (f)
-              LOAD_CONST               2 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 
 Disassembly of <code object __annotate__ at 0xdeadbeef, file "<?>", line 1>:
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__builtin_any_genexpr_call.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__builtin_any_genexpr_call.snap
new file mode 100644
index 00000000000..674ca418cfe
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__builtin_any_genexpr_call.snap
@@ -0,0 +1,70 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(xs):\n    return any(x for x in xs)\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:29            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:29            MAKE_FUNCTION
+1:0-2:29            STORE_NAME               0 (f)
+1:0-2:29            LOAD_COMMON_CONSTANT     7 (None)
+1:0-2:29            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:14            LOAD_GLOBAL              0 (any)
+2:11-2:14            COPY                     1
+2:11-2:14            LOAD_COMMON_CONSTANT     4 (<built-in function any>)
+2:11-2:14            IS_OP                    0 (is)
+2:11-2:14            POP_JUMP_IF_FALSE       28 (to L4)
+2:11-2:14            NOT_TAKEN
+2:11-2:14            POP_TOP
+2:14-2:29            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:14-2:29            MAKE_FUNCTION
+2:26-2:28            LOAD_FAST_BORROW         0 (xs)
+2:14-2:29            CALL                     0
+2:11-2:14            PUSH_NULL
+2:11-2:14    L1:     FOR_ITER                12 (to L3)
+2:11-2:14            TO_BOOL
+2:11-2:14            POP_JUMP_IF_TRUE         3 (to L2)
+2:11-2:14            NOT_TAKEN
+2:11-2:14            JUMP_BACKWARD           11 (to L1)
+2:11-2:14    L2:     POP_ITER
+2:11-2:14            LOAD_COMMON_CONSTANT     9 (True)
+2:4-2:29             RETURN_VALUE
+2:11-2:14    L3:     END_FOR
+2:11-2:14            POP_ITER
+2:11-2:14            LOAD_COMMON_CONSTANT    10 (False)
+2:4-2:29             RETURN_VALUE
+2:11-2:14    L4:     PUSH_NULL
+2:14-2:29            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:14-2:29            MAKE_FUNCTION
+2:26-2:28            LOAD_FAST_BORROW         0 (xs)
+2:14-2:29            CALL                     0
+2:11-2:29            CALL                     1
+2:4-2:29             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 2>:
+  --                 RESUME                   4
+
+2:26-2:28            LOAD_FAST                0 (.0)
+2:26-2:28            GET_ITER                 0
+2:?-2:?              RETURN_GENERATOR
+2:?-2:?              POP_TOP
+2:0-2:0      L1:     RESUME                   0
+2:26-2:28    L2:     FOR_ITER                 7 (to L3)
+2:21-2:22            STORE_FAST_LOAD_FAST    17 (x, x)
+2:15-2:16            YIELD_VALUE              0
+2:15-2:16            RESUME                   9
+2:15-2:16            POP_TOP
+2:15-2:16            JUMP_BACKWARD            9 (to L2)
+2:26-2:28    L3:     END_FOR
+2:26-2:28            POP_ITER
+2:26-2:28            LOAD_COMMON_CONSTANT     7 (None)
+2:26-2:28            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__builtin_tuple_list_set_genexpr_calls.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__builtin_tuple_list_set_genexpr_calls.snap
new file mode 100644
index 00000000000..a5e81ffaf1d
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__builtin_tuple_list_set_genexpr_calls.snap
@@ -0,0 +1,182 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef tuple_f(xs):\n    return tuple(x for x in xs)\n\ndef list_f(xs):\n    return list(x for x in xs)\n\ndef set_f(xs):\n    return set(x for x in xs)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:31            LOAD_CONST               0 (<code object tuple_f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:31            MAKE_FUNCTION
+1:0-2:31            STORE_NAME               0 (tuple_f)
+
+4:0-5:30            LOAD_CONST               1 (<code object list_f at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:30            MAKE_FUNCTION
+4:0-5:30            STORE_NAME               1 (list_f)
+
+7:0-8:29            LOAD_CONST               2 (<code object set_f at 0xdeadbeef, file "<?>", line 7>)
+7:0-8:29            MAKE_FUNCTION
+7:0-8:29            STORE_NAME               2 (set_f)
+7:0-8:29            LOAD_COMMON_CONSTANT     7 (None)
+7:0-8:29            RETURN_VALUE
+
+Disassembly of <code object tuple_f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:16            LOAD_GLOBAL              0 (tuple)
+2:11-2:16            COPY                     1
+2:11-2:16            LOAD_COMMON_CONSTANT     2 (tuple)
+2:11-2:16            IS_OP                    0 (is)
+2:11-2:16            POP_JUMP_IF_FALSE       20 (to L3)
+2:11-2:16            NOT_TAKEN
+2:11-2:16            POP_TOP
+2:11-2:16            BUILD_LIST               0
+2:16-2:31            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:16-2:31            MAKE_FUNCTION
+2:28-2:30            LOAD_FAST_BORROW         0 (xs)
+2:16-2:31            CALL                     0
+2:11-2:16            PUSH_NULL
+2:11-2:16    L1:     FOR_ITER                 3 (to L2)
+2:11-2:16            LIST_APPEND              3
+2:11-2:16            JUMP_BACKWARD            5 (to L1)
+2:11-2:16    L2:     END_FOR
+2:11-2:16            POP_ITER
+2:11-2:16            CALL_INTRINSIC_1         6 (INTRINSIC_LIST_TO_TUPLE)
+2:4-2:31             RETURN_VALUE
+2:11-2:16    L3:     PUSH_NULL
+2:16-2:31            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:16-2:31            MAKE_FUNCTION
+2:28-2:30            LOAD_FAST_BORROW         0 (xs)
+2:16-2:31            CALL                     0
+2:11-2:31            CALL                     1
+2:4-2:31             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 2>:
+  --                 RESUME                   4
+
+2:28-2:30            LOAD_FAST                0 (.0)
+2:28-2:30            GET_ITER                 0
+2:?-2:?              RETURN_GENERATOR
+2:?-2:?              POP_TOP
+2:0-2:0      L1:     RESUME                   0
+2:28-2:30    L2:     FOR_ITER                 7 (to L3)
+2:23-2:24            STORE_FAST_LOAD_FAST    17 (x, x)
+2:17-2:18            YIELD_VALUE              0
+2:17-2:18            RESUME                   9
+2:17-2:18            POP_TOP
+2:17-2:18            JUMP_BACKWARD            9 (to L2)
+2:28-2:30    L3:     END_FOR
+2:28-2:30            POP_ITER
+2:28-2:30            LOAD_COMMON_CONSTANT     7 (None)
+2:28-2:30            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
+
+Disassembly of <code object list_f at 0xdeadbeef, file "<?>", line 4>:
+4:0-4:0              RESUME                   0
+
+5:11-5:15            LOAD_GLOBAL              0 (list)
+5:11-5:15            COPY                     1
+5:11-5:15            LOAD_COMMON_CONSTANT     5 (list)
+5:11-5:15            IS_OP                    0 (is)
+5:11-5:15            POP_JUMP_IF_FALSE       19 (to L3)
+5:11-5:15            NOT_TAKEN
+5:11-5:15            POP_TOP
+5:11-5:15            BUILD_LIST               0
+5:15-5:30            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 5>)
+5:15-5:30            MAKE_FUNCTION
+5:27-5:29            LOAD_FAST_BORROW         0 (xs)
+5:15-5:30            CALL                     0
+5:11-5:15            PUSH_NULL
+5:11-5:15    L1:     FOR_ITER                 3 (to L2)
+5:11-5:15            LIST_APPEND              3
+5:11-5:15            JUMP_BACKWARD            5 (to L1)
+5:11-5:15    L2:     END_FOR
+5:11-5:15            POP_ITER
+5:4-5:30             RETURN_VALUE
+5:11-5:15    L3:     PUSH_NULL
+5:15-5:30            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 5>)
+5:15-5:30            MAKE_FUNCTION
+5:27-5:29            LOAD_FAST_BORROW         0 (xs)
+5:15-5:30            CALL                     0
+5:11-5:30            CALL                     1
+5:4-5:30             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 5>:
+  --                 RESUME                   4
+
+5:27-5:29            LOAD_FAST                0 (.0)
+5:27-5:29            GET_ITER                 0
+5:?-5:?              RETURN_GENERATOR
+5:?-5:?              POP_TOP
+5:0-5:0      L1:     RESUME                   0
+5:27-5:29    L2:     FOR_ITER                 7 (to L3)
+5:22-5:23            STORE_FAST_LOAD_FAST    17 (x, x)
+5:16-5:17            YIELD_VALUE              0
+5:16-5:17            RESUME                   9
+5:16-5:17            POP_TOP
+5:16-5:17            JUMP_BACKWARD            9 (to L2)
+5:27-5:29    L3:     END_FOR
+5:27-5:29            POP_ITER
+5:27-5:29            LOAD_COMMON_CONSTANT     7 (None)
+5:27-5:29            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
+
+Disassembly of <code object set_f at 0xdeadbeef, file "<?>", line 7>:
+7:0-7:0              RESUME                   0
+
+8:11-8:14            LOAD_GLOBAL              0 (set)
+8:11-8:14            COPY                     1
+8:11-8:14            LOAD_COMMON_CONSTANT     6 (set)
+8:11-8:14            IS_OP                    0 (is)
+8:11-8:14            POP_JUMP_IF_FALSE       19 (to L3)
+8:11-8:14            NOT_TAKEN
+8:11-8:14            POP_TOP
+8:11-8:14            BUILD_SET                0
+8:14-8:29            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 8>)
+8:14-8:29            MAKE_FUNCTION
+8:26-8:28            LOAD_FAST_BORROW         0 (xs)
+8:14-8:29            CALL                     0
+8:11-8:14            PUSH_NULL
+8:11-8:14    L1:     FOR_ITER                 3 (to L2)
+8:11-8:14            SET_ADD                  3
+8:11-8:14            JUMP_BACKWARD            5 (to L1)
+8:11-8:14    L2:     END_FOR
+8:11-8:14            POP_ITER
+8:4-8:29             RETURN_VALUE
+8:11-8:14    L3:     PUSH_NULL
+8:14-8:29            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 8>)
+8:14-8:29            MAKE_FUNCTION
+8:26-8:28            LOAD_FAST_BORROW         0 (xs)
+8:14-8:29            CALL                     0
+8:11-8:29            CALL                     1
+8:4-8:29             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 8>:
+  --                 RESUME                   4
+
+8:26-8:28            LOAD_FAST                0 (.0)
+8:26-8:28            GET_ITER                 0
+8:?-8:?              RETURN_GENERATOR
+8:?-8:?              POP_TOP
+8:0-8:0      L1:     RESUME                   0
+8:26-8:28    L2:     FOR_ITER                 7 (to L3)
+8:21-8:22            STORE_FAST_LOAD_FAST    17 (x, x)
+8:15-8:16            YIELD_VALUE              0
+8:15-8:16            RESUME                   9
+8:15-8:16            POP_TOP
+8:15-8:16            JUMP_BACKWARD            9 (to L2)
+8:26-8:28    L3:     END_FOR
+8:26-8:28            POP_ITER
+8:26-8:28            LOAD_COMMON_CONSTANT     7 (None)
+8:26-8:28            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__class_deferred_annotations_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__class_deferred_annotations_location.snap
new file mode 100644
index 00000000000..c9d12f9fe74
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__class_deferred_annotations_location.snap
@@ -0,0 +1,65 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\n\nclass C:\n    \"doc\"\n    x: int\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-3:10            LOAD_BUILD_CLASS
+1:0-3:10            PUSH_NULL
+1:0-3:10            LOAD_CONST               0 (<code object C at 0xdeadbeef, file "<?>", line 1>)
+1:0-3:10            MAKE_FUNCTION
+1:0-3:10            LOAD_CONST               1 ('C')
+1:0-3:10            CALL                     2
+1:0-3:10            STORE_NAME               0 (C)
+1:0-3:10            LOAD_COMMON_CONSTANT     7 (None)
+1:0-3:10            RETURN_VALUE
+
+Disassembly of <code object C at 0xdeadbeef, file "<?>", line 1>:
+  --               MAKE_CELL                0 (__classdict__)
+
+1:0-1:0            RESUME                   0
+1:0-1:0            LOAD_NAME                0 (__name__)
+1:0-1:0            STORE_NAME               1 (__module__)
+1:0-1:0            LOAD_CONST               0 ('C')
+1:0-1:0            STORE_NAME               2 (__qualname__)
+1:0-1:0            LOAD_SMALL_INT           1
+1:0-1:0            STORE_NAME               3 (__firstlineno__)
+1:0-1:0            LOAD_LOCALS
+1:0-1:0            STORE_DEREF              0 (__classdict__)
+
+2:4-2:9            LOAD_CONST               1 ('doc')
+2:4-2:9            STORE_NAME               4 (__doc__)
+
+1:0-1:0            LOAD_FAST_BORROW         0 (__classdict__)
+1:0-1:0            BUILD_TUPLE              1
+1:0-1:0            LOAD_CONST               2 (<code object __annotate__ at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:0            MAKE_FUNCTION
+1:0-1:0            SET_FUNCTION_ATTRIBUTE   8 (closure)
+1:0-1:0            STORE_NAME               5 (__annotate_func__)
+1:0-1:0            LOAD_CONST               3 (())
+1:0-1:0            STORE_NAME               6 (__static_attributes__)
+1:0-1:0            LOAD_FAST_BORROW         0 (__classdict__)
+1:0-1:0            STORE_NAME               7 (__classdictcell__)
+1:0-1:0            LOAD_COMMON_CONSTANT     7 (None)
+1:0-1:0            RETURN_VALUE
+
+Disassembly of <code object __annotate__ at 0xdeadbeef, file "<?>", line 1>:
+  --                COPY_FREE_VARS           1
+
+1:0-1:0             RESUME                   0
+1:0-1:0             LOAD_FAST_BORROW         0 (format)
+1:0-1:0             LOAD_SMALL_INT           2
+1:0-1:0             COMPARE_OP             132 (>)
+1:0-1:0             POP_JUMP_IF_FALSE        3 (to L1)
+1:0-1:0             NOT_TAKEN
+1:0-1:0             LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+1:0-1:0             RAISE_VARARGS            1
+1:0-1:0     L1:     BUILD_MAP                0
+
+3:7-3:10            LOAD_DEREF               1 (__classdict__)
+3:7-3:10            LOAD_FROM_DICT_OR_GLOBALS 0 (int)
+3:4-3:10            COPY                     2
+3:4-3:10            LOAD_CONST               1 ('x')
+
+1:0-1:0             STORE_SUBSCR
+1:0-1:0             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__comprehension_collection_depth.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__comprehension_collection_depth.snap
new file mode 100644
index 00000000000..5db02a260b7
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__comprehension_collection_depth.snap
@@ -0,0 +1,110 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(xs, ys):\n    return [x for x in xs for y in ys]\n\nasync def g(xs, ys):\n    return [x async for x in xs for y in ys]\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:38            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:38            MAKE_FUNCTION
+1:0-2:38            STORE_NAME               0 (f)
+
+4:0-5:44            LOAD_CONST               1 (<code object g at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:44            MAKE_FUNCTION
+4:0-5:44            STORE_NAME               1 (g)
+4:0-5:44            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:44            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:23-2:25            LOAD_FAST                0 (xs)
+2:11-2:38            LOAD_FAST_AND_CLEAR      2 (x)
+2:11-2:38            LOAD_FAST_AND_CLEAR      3 (y)
+2:11-2:38            SWAP                     3
+2:11-2:38    L1:     BUILD_LIST               0
+2:11-2:38            SWAP                     2
+2:23-2:25            GET_ITER                 0
+2:23-2:25    L2:     FOR_ITER                13 (to L5)
+2:18-2:19            STORE_FAST_LOAD_FAST    33 (x, ys)
+2:35-2:37            GET_ITER                 0
+2:35-2:37    L3:     FOR_ITER                 4 (to L4)
+2:30-2:31            STORE_FAST_LOAD_FAST    50 (y, x)
+2:12-2:13            LIST_APPEND              5
+2:12-2:13            JUMP_BACKWARD            6 (to L3)
+2:35-2:37    L4:     END_FOR
+2:35-2:37            POP_ITER
+2:12-2:13            JUMP_BACKWARD           15 (to L2)
+2:23-2:25    L5:     END_FOR
+2:23-2:25            POP_ITER
+2:11-2:38    L6:     SWAP                     3
+2:11-2:38            STORE_FAST               3 (y)
+2:11-2:38            STORE_FAST               2 (x)
+2:4-2:38             RETURN_VALUE
+
+  --         L7:     SWAP                     2
+  --                 POP_TOP
+
+2:11-2:38            SWAP                     3
+2:11-2:38            STORE_FAST               3 (y)
+2:11-2:38            STORE_FAST               2 (x)
+2:11-2:38            RERAISE                  0
+ExceptionTable:
+  L1 to L6 -> L7 [3]
+
+Disassembly of <code object g at 0xdeadbeef, file "<?>", line 4>:
+4:?-4:?               RETURN_GENERATOR
+4:?-4:?               POP_TOP
+4:0-4:0       L1:     RESUME                   0
+
+5:29-5:31             LOAD_FAST_BORROW         0 (xs)
+5:11-5:44             LOAD_FAST_AND_CLEAR      2 (x)
+5:11-5:44             LOAD_FAST_AND_CLEAR      3 (y)
+5:11-5:44             SWAP                     3
+5:11-5:44     L2:     BUILD_LIST               0
+5:11-5:44             SWAP                     2
+5:29-5:31             GET_AITER
+5:11-5:44     L3:     GET_ANEXT
+5:11-5:44             PUSH_NULL
+5:11-5:44             LOAD_COMMON_CONSTANT     7 (None)
+5:11-5:44     L4:     SEND                     4 (to L7)
+5:11-5:44     L5:     YIELD_VALUE              1
+5:11-5:44     L6:     RESUME                   3
+5:11-5:44             JUMP_BACKWARD_NO_INTERRUPT 6 (to L4)
+5:11-5:44     L7:     END_SEND
+5:24-5:25     L8:     STORE_FAST_LOAD_FAST    33 (x, ys)
+5:41-5:43             GET_ITER                 0
+5:41-5:43     L9:     FOR_ITER                 4 (to L10)
+5:36-5:37             STORE_FAST_LOAD_FAST    50 (y, x)
+5:12-5:13             LIST_APPEND              4
+5:12-5:13             JUMP_BACKWARD            6 (to L9)
+5:41-5:43    L10:     END_FOR
+5:41-5:43             POP_ITER
+5:12-5:13             JUMP_BACKWARD           23 (to L3)
+5:11-5:44    L11:     CLEANUP_THROW
+5:11-5:44    L12:     JUMP_BACKWARD_NO_INTERRUPT 16 (to L7)
+5:11-5:44    L13:     END_ASYNC_FOR           17 (from L7)
+5:11-5:44    L14:     SWAP                     3
+5:11-5:44             STORE_FAST               3 (y)
+5:11-5:44             STORE_FAST               2 (x)
+5:4-5:44              RETURN_VALUE
+
+  --         L15:     SWAP                     2
+  --                  POP_TOP
+
+5:11-5:44             SWAP                     3
+5:11-5:44             STORE_FAST               3 (y)
+5:11-5:44             STORE_FAST               2 (x)
+5:11-5:44             RERAISE                  0
+
+  --         L16:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L16 [0] lasti
+  L2 to L3 -> L15 [3]
+  L3 to L5 -> L13 [4]
+  L5 to L6 -> L11 [7]
+  L6 to L8 -> L13 [4]
+  L8 to L11 -> L15 [3]
+  L11 to L12 -> L13 [4]
+  L13 to L14 -> L15 [3]
+  L14 to L16 -> L16 [0] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__comprehension_list_iterable_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__comprehension_list_iterable_location.snap
new file mode 100644
index 00000000000..c7bca48e842
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__comprehension_list_iterable_location.snap
@@ -0,0 +1,83 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nasync def f(i):\n    return i\n\nasync def run_list():\n    return [await c for c in [f(1), f(41)]]\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:12            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:12            MAKE_FUNCTION
+1:0-2:12            STORE_NAME               0 (f)
+
+4:0-5:43            LOAD_CONST               1 (<code object run_list at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:43            MAKE_FUNCTION
+4:0-5:43            STORE_NAME               1 (run_list)
+4:0-5:43            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:43            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:?-1:?              RETURN_GENERATOR
+1:?-1:?              POP_TOP
+1:0-1:0      L1:     RESUME                   0
+
+2:11-2:12            LOAD_FAST_BORROW         0 (i)
+2:4-2:12             RETURN_VALUE
+
+  --         L2:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L2 [0] lasti
+
+Disassembly of <code object run_list at 0xdeadbeef, file "<?>", line 4>:
+4:?-4:?               RETURN_GENERATOR
+4:?-4:?               POP_TOP
+4:0-4:0       L1:     RESUME                   0
+
+5:30-5:31             LOAD_GLOBAL              1 (f + NULL)
+5:32-5:33             LOAD_SMALL_INT           1
+5:30-5:34             CALL                     1
+5:36-5:37             LOAD_GLOBAL              1 (f + NULL)
+5:38-5:40             LOAD_SMALL_INT          41
+5:36-5:41             CALL                     1
+5:29-5:42             BUILD_LIST               2
+5:11-5:43             LOAD_FAST_AND_CLEAR      0 (c)
+5:11-5:43             SWAP                     2
+5:11-5:43     L2:     BUILD_LIST               0
+5:11-5:43             SWAP                     2
+5:29-5:42             GET_ITER                 0
+5:29-5:42     L3:     FOR_ITER                14 (to L8)
+5:24-5:25             STORE_FAST_LOAD_FAST     0 (c, c)
+5:12-5:19             GET_AWAITABLE            0
+5:12-5:19             PUSH_NULL
+5:12-5:19             LOAD_COMMON_CONSTANT     7 (None)
+5:12-5:19     L4:     SEND                     4 (to L7)
+5:12-5:19     L5:     YIELD_VALUE              1
+5:12-5:19     L6:     RESUME                   3
+5:12-5:19             JUMP_BACKWARD_NO_INTERRUPT 6 (to L4)
+5:12-5:19     L7:     END_SEND
+5:12-5:19             LIST_APPEND              3
+5:12-5:19             JUMP_BACKWARD           16 (to L3)
+5:29-5:42     L8:     END_FOR
+5:29-5:42             POP_ITER
+5:11-5:43     L9:     SWAP                     2
+5:11-5:43             STORE_FAST               0 (c)
+5:4-5:43              RETURN_VALUE
+5:12-5:19    L10:     CLEANUP_THROW
+5:12-5:19    L11:     JUMP_BACKWARD_NO_INTERRUPT 11 (to L7)
+
+  --         L12:     SWAP                     2
+  --                  POP_TOP
+
+5:11-5:43             SWAP                     2
+5:11-5:43             STORE_FAST               0 (c)
+5:11-5:43             RERAISE                  0
+
+  --         L13:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L13 [0] lasti
+  L2 to L5 -> L12 [2]
+  L5 to L6 -> L10 [7]
+  L6 to L9 -> L12 [2]
+  L9 to L10 -> L13 [0] lasti
+  L10 to L11 -> L12 [2]
+  L12 to L13 -> L13 [0] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__const_no_op.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__const_no_op.snap
index dc97f6b79c1..5713fb761d2 100644
--- a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__const_no_op.snap
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__const_no_op.snap
@@ -5,7 +5,7 @@ expression: "dis(r#\"\nx = not True\n\"#)"
 ---
   0           RESUME                   0
 
-  1           LOAD_CONST               2 (False)
+  1           LOAD_COMMON_CONSTANT    10 (False)
               STORE_NAME               0 (x)
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__constant_true_if_pass_keeps_line_anchor_nop.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__constant_true_if_pass_keeps_line_anchor_nop.snap
index 3de37ce2009..5cbdc2104d3 100644
--- a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__constant_true_if_pass_keeps_line_anchor_nop.snap
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__constant_true_if_pass_keeps_line_anchor_nop.snap
@@ -7,5 +7,5 @@ expression: "dis(r#\"\nif 1:\n    pass\n\"#)"
 
   1           NOP
 
-  2           LOAD_CONST               1 (None)
+  2           LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__decorated_definition_locations.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__decorated_definition_locations.snap
new file mode 100644
index 00000000000..91c9b7c85df
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__decorated_definition_locations.snap
@@ -0,0 +1,164 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef dec(f): return f\n\nclass C:\n    @dec\n    def f(self):\n        yield\n\n@dec\nclass D:\n    pass\n\nclass E:\n    @dec\n    def g(self, flags: int, /) -> memoryview:\n        raise NotImplementedError\n\"#,\ntrue)"
+---
+0:0-1:0               RESUME                   0
+
+1:0-1:20              LOAD_CONST               0 (<code object dec at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:20              MAKE_FUNCTION
+1:0-1:20              STORE_NAME               0 (dec)
+
+3:0-6:13              LOAD_BUILD_CLASS
+3:0-6:13              PUSH_NULL
+3:0-6:13              LOAD_CONST               1 (<code object C at 0xdeadbeef, file "<?>", line 3>)
+3:0-6:13              MAKE_FUNCTION
+3:0-6:13              LOAD_CONST               2 ('C')
+3:0-6:13              CALL                     2
+3:0-6:13              STORE_NAME               1 (C)
+
+8:1-8:4               LOAD_NAME                0 (dec)
+
+9:0-10:8              LOAD_BUILD_CLASS
+9:0-10:8              PUSH_NULL
+9:0-10:8              LOAD_CONST               3 (<code object D at 0xdeadbeef, file "<?>", line 8>)
+9:0-10:8              MAKE_FUNCTION
+9:0-10:8              LOAD_CONST               4 ('D')
+9:0-10:8              CALL                     2
+
+8:1-8:4               CALL                     0
+
+9:0-10:8              STORE_NAME               2 (D)
+
+12:0-15:33            LOAD_BUILD_CLASS
+12:0-15:33            PUSH_NULL
+12:0-15:33            LOAD_CONST               5 (<code object E at 0xdeadbeef, file "<?>", line 12>)
+12:0-15:33            MAKE_FUNCTION
+12:0-15:33            LOAD_CONST               6 ('E')
+12:0-15:33            CALL                     2
+12:0-15:33            STORE_NAME               3 (E)
+12:0-15:33            LOAD_COMMON_CONSTANT     7 (None)
+12:0-15:33            RETURN_VALUE
+
+Disassembly of <code object dec at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+1:19-1:20            LOAD_FAST_BORROW         0 (f)
+1:12-1:20            RETURN_VALUE
+
+Disassembly of <code object C at 0xdeadbeef, file "<?>", line 3>:
+  --                MAKE_CELL                0 (__classdict__)
+
+3:0-3:0             RESUME                   0
+3:0-3:0             LOAD_NAME                0 (__name__)
+3:0-3:0             STORE_NAME               1 (__module__)
+3:0-3:0             LOAD_CONST               0 ('C')
+3:0-3:0             STORE_NAME               2 (__qualname__)
+3:0-3:0             LOAD_SMALL_INT           3
+3:0-3:0             STORE_NAME               3 (__firstlineno__)
+3:0-3:0             LOAD_LOCALS
+3:0-3:0             STORE_DEREF              0 (__classdict__)
+
+4:5-4:8             LOAD_NAME                4 (dec)
+
+5:4-6:13            LOAD_CONST               1 (<code object f at 0xdeadbeef, file "<?>", line 4>)
+5:4-6:13            MAKE_FUNCTION
+
+4:5-4:8             CALL                     0
+
+5:4-6:13            STORE_NAME               5 (f)
+5:4-6:13            LOAD_CONST               2 (())
+5:4-6:13            STORE_NAME               6 (__static_attributes__)
+5:4-6:13            LOAD_FAST_BORROW         0 (__classdict__)
+5:4-6:13            STORE_NAME               7 (__classdictcell__)
+5:4-6:13            LOAD_COMMON_CONSTANT     7 (None)
+5:4-6:13            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 4>:
+4:?-4:?             RETURN_GENERATOR
+4:?-4:?             POP_TOP
+4:0-4:0     L1:     RESUME                   0
+
+6:8-6:13            LOAD_COMMON_CONSTANT     7 (None)
+6:8-6:13            YIELD_VALUE              0
+6:8-6:13            RESUME                   9
+6:8-6:13            POP_TOP
+6:8-6:13            LOAD_COMMON_CONSTANT     7 (None)
+6:8-6:13            RETURN_VALUE
+
+  --        L2:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L2 [0] lasti
+
+Disassembly of <code object D at 0xdeadbeef, file "<?>", line 8>:
+8:0-8:0              RESUME                   0
+8:0-8:0              LOAD_NAME                0 (__name__)
+8:0-8:0              STORE_NAME               1 (__module__)
+8:0-8:0              LOAD_CONST               0 ('D')
+8:0-8:0              STORE_NAME               2 (__qualname__)
+8:0-8:0              LOAD_SMALL_INT           8
+8:0-8:0              STORE_NAME               3 (__firstlineno__)
+
+10:4-10:8            LOAD_CONST               1 (())
+10:4-10:8            STORE_NAME               4 (__static_attributes__)
+10:4-10:8            LOAD_COMMON_CONSTANT     7 (None)
+10:4-10:8            RETURN_VALUE
+
+Disassembly of <code object E at 0xdeadbeef, file "<?>", line 12>:
+  --                  MAKE_CELL                0 (__classdict__)
+
+12:0-12:0             RESUME                   0
+12:0-12:0             LOAD_NAME                0 (__name__)
+12:0-12:0             STORE_NAME               1 (__module__)
+12:0-12:0             LOAD_CONST               0 ('E')
+12:0-12:0             STORE_NAME               2 (__qualname__)
+12:0-12:0             LOAD_SMALL_INT          12
+12:0-12:0             STORE_NAME               3 (__firstlineno__)
+12:0-12:0             LOAD_LOCALS
+12:0-12:0             STORE_DEREF              0 (__classdict__)
+
+13:5-13:8             LOAD_NAME                4 (dec)
+
+14:4-15:33            LOAD_FAST_BORROW         0 (__classdict__)
+14:4-15:33            BUILD_TUPLE              1
+14:4-15:33            LOAD_CONST               1 (<code object __annotate__ at 0xdeadbeef, file "<?>", line 14>)
+14:4-15:33            MAKE_FUNCTION
+14:4-15:33            SET_FUNCTION_ATTRIBUTE   8 (closure)
+14:4-15:33            LOAD_CONST               2 (<code object g at 0xdeadbeef, file "<?>", line 13>)
+14:4-15:33            MAKE_FUNCTION
+14:4-15:33            SET_FUNCTION_ATTRIBUTE  16 (annotate)
+
+13:5-13:8             CALL                     0
+
+14:4-15:33            STORE_NAME               5 (g)
+14:4-15:33            LOAD_CONST               3 (())
+14:4-15:33            STORE_NAME               6 (__static_attributes__)
+14:4-15:33            LOAD_FAST_BORROW         0 (__classdict__)
+14:4-15:33            STORE_NAME               7 (__classdictcell__)
+14:4-15:33            LOAD_COMMON_CONSTANT     7 (None)
+14:4-15:33            RETURN_VALUE
+
+Disassembly of <code object __annotate__ at 0xdeadbeef, file "<?>", line 14>:
+  --                   COPY_FREE_VARS           1
+
+14:0-14:0              RESUME                   0
+14:4-15:33             LOAD_FAST_BORROW         0 (format)
+14:4-15:33             LOAD_SMALL_INT           2
+14:4-15:33             COMPARE_OP             132 (>)
+14:4-15:33             POP_JUMP_IF_FALSE        3 (to L1)
+14:4-15:33             NOT_TAKEN
+14:4-15:33             LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+14:4-15:33             RAISE_VARARGS            1
+14:4-15:33     L1:     LOAD_CONST               1 ('flags')
+14:23-14:26            LOAD_DEREF               1 (__classdict__)
+14:23-14:26            LOAD_FROM_DICT_OR_GLOBALS 0 (int)
+14:4-15:33             LOAD_CONST               2 ('return')
+14:34-14:44            LOAD_DEREF               1 (__classdict__)
+14:34-14:44            LOAD_FROM_DICT_OR_GLOBALS 1 (memoryview)
+14:4-15:33             BUILD_MAP                2
+14:4-15:33             RETURN_VALUE
+
+Disassembly of <code object g at 0xdeadbeef, file "<?>", line 13>:
+13:0-13:0              RESUME                   0
+
+15:14-15:33            LOAD_GLOBAL              0 (NotImplementedError)
+15:8-15:33             RAISE_VARARGS            1
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__empty_module_implicit_return_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__empty_module_implicit_return_location.snap
new file mode 100644
index 00000000000..75795d00b10
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__empty_module_implicit_return_location.snap
@@ -0,0 +1,7 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(\"\", true)"
+---
+0:0-1:0            RESUME                   0
+0:0-1:0            LOAD_COMMON_CONSTANT     7 (None)
+0:0-1:0            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__fstring_format_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__fstring_format_location.snap
new file mode 100644
index 00000000000..904cde2d209
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__fstring_format_location.snap
@@ -0,0 +1,32 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef simple(self):\n    return f'{self.value}'\n\ndef spec(x):\n    return f'{x!r:>3}'\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:26            LOAD_CONST               0 (<code object simple at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:26            MAKE_FUNCTION
+1:0-2:26            STORE_NAME               0 (simple)
+
+4:0-5:22            LOAD_CONST               1 (<code object spec at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:22            MAKE_FUNCTION
+4:0-5:22            STORE_NAME               1 (spec)
+4:0-5:22            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:22            RETURN_VALUE
+
+Disassembly of <code object simple at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:14-2:18            LOAD_FAST_BORROW         0 (self)
+2:14-2:24            LOAD_ATTR                0 (value)
+2:13-2:25            FORMAT_SIMPLE
+2:4-2:26             RETURN_VALUE
+
+Disassembly of <code object spec at 0xdeadbeef, file "<?>", line 4>:
+4:0-4:0              RESUME                   0
+
+5:14-5:15            LOAD_FAST_BORROW         0 (x)
+5:13-5:21            CONVERT_VALUE            2 (repr)
+5:18-5:20            LOAD_CONST               0 ('>3')
+5:13-5:21            FORMAT_WITH_SPEC
+5:4-5:22             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__future_annotation_string_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__future_annotation_string_location.snap
new file mode 100644
index 00000000000..82a554f86af
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__future_annotation_string_location.snap
@@ -0,0 +1,41 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nfrom __future__ import annotations\nclass Bar:\n    foo: Foo\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-1:34            LOAD_SMALL_INT           0
+1:0-1:34            LOAD_CONST               1 (('annotations',))
+1:0-1:34            IMPORT_NAME              0 (__future__)
+1:0-1:34            IMPORT_FROM              1 (annotations)
+1:0-1:34            STORE_NAME               1 (annotations)
+1:0-1:34            POP_TOP
+
+2:0-3:12            LOAD_BUILD_CLASS
+2:0-3:12            PUSH_NULL
+2:0-3:12            LOAD_CONST               2 (<code object Bar at 0xdeadbeef, file "<?>", line 2>)
+2:0-3:12            MAKE_FUNCTION
+2:0-3:12            LOAD_CONST               3 ('Bar')
+2:0-3:12            CALL                     2
+2:0-3:12            STORE_NAME               2 (Bar)
+2:0-3:12            LOAD_COMMON_CONSTANT     7 (None)
+2:0-3:12            RETURN_VALUE
+
+Disassembly of <code object Bar at 0xdeadbeef, file "<?>", line 2>:
+2:0-2:0             RESUME                   0
+2:0-2:0             LOAD_NAME                0 (__name__)
+2:0-2:0             STORE_NAME               1 (__module__)
+2:0-2:0             LOAD_CONST               0 ('Bar')
+2:0-2:0             STORE_NAME               2 (__qualname__)
+2:0-2:0             LOAD_SMALL_INT           2
+2:0-2:0             STORE_NAME               3 (__firstlineno__)
+2:0-2:0             SETUP_ANNOTATIONS
+
+3:9-3:12            LOAD_CONST               1 ('Foo')
+3:4-3:12            LOAD_NAME                4 (__annotations__)
+3:4-3:12            LOAD_CONST               2 ('foo')
+3:4-3:12            STORE_SUBSCR
+3:4-3:12            LOAD_CONST               3 (())
+3:4-3:12            STORE_NAME               5 (__static_attributes__)
+3:4-3:12            LOAD_COMMON_CONSTANT     7 (None)
+3:4-3:12            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_class_type_params_store_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_class_type_params_store_location.snap
new file mode 100644
index 00000000000..f0d8113a6a1
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_class_type_params_store_location.snap
@@ -0,0 +1,64 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef outer():\n    class X[T]: ...\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:19            LOAD_CONST               0 (<code object outer at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:19            MAKE_FUNCTION
+1:0-2:19            STORE_NAME               0 (outer)
+1:0-2:19            LOAD_COMMON_CONSTANT     7 (None)
+1:0-2:19            RETURN_VALUE
+
+Disassembly of <code object outer at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0             RESUME                   0
+
+2:4-2:19            LOAD_CONST               0 (<code object <generic parameters of X> at 0xdeadbeef, file "<?>", line 2>)
+2:4-2:19            MAKE_FUNCTION
+2:4-2:19            PUSH_NULL
+2:4-2:19            CALL                     0
+2:4-2:19            STORE_FAST               0 (X)
+2:4-2:19            LOAD_COMMON_CONSTANT     7 (None)
+2:4-2:19            RETURN_VALUE
+
+Disassembly of <code object <generic parameters of X> at 0xdeadbeef, file "<?>", line 2>:
+  --                 MAKE_CELL                2 (.type_params)
+
+2:0-2:0              RESUME                   0
+2:12-2:13            LOAD_CONST               0 ('T')
+2:12-2:13            CALL_INTRINSIC_1         7 (INTRINSIC_TYPEVAR)
+2:12-2:13            COPY                     1
+2:12-2:13            STORE_FAST               0 (T)
+2:12-2:13            BUILD_TUPLE              1
+2:4-2:19             STORE_DEREF              2 (.type_params)
+2:4-2:19             LOAD_BUILD_CLASS
+2:4-2:19             PUSH_NULL
+2:4-2:19             LOAD_FAST_BORROW         2 (.type_params)
+2:4-2:19             BUILD_TUPLE              1
+2:4-2:19             LOAD_CONST               1 (<code object X at 0xdeadbeef, file "<?>", line 2>)
+2:4-2:19             MAKE_FUNCTION
+2:4-2:19             SET_FUNCTION_ATTRIBUTE   8 (closure)
+2:4-2:19             LOAD_CONST               2 ('X')
+2:4-2:19             LOAD_DEREF               2 (.type_params)
+2:4-2:19             CALL_INTRINSIC_1        10 (INTRINSIC_SUBSCRIPT_GENERIC)
+2:4-2:19             STORE_FAST_LOAD_FAST    17 (.generic_base, .generic_base)
+2:4-2:19             CALL                     3
+2:4-2:19             RETURN_VALUE
+
+Disassembly of <code object X at 0xdeadbeef, file "<?>", line 2>:
+  --                 COPY_FREE_VARS           1
+
+2:0-2:0              RESUME                   0
+2:0-2:0              LOAD_NAME                0 (__name__)
+2:0-2:0              STORE_NAME               1 (__module__)
+2:0-2:0              LOAD_CONST               0 ('outer.<locals>.X')
+2:0-2:0              STORE_NAME               2 (__qualname__)
+2:0-2:0              LOAD_SMALL_INT           2
+2:0-2:0              STORE_NAME               3 (__firstlineno__)
+2:0-2:0              LOAD_LOCALS
+2:0-2:0              LOAD_FROM_DICT_OR_DEREF  0 (.type_params)
+2:0-2:0              STORE_NAME               4 (__type_params__)
+2:16-2:19            LOAD_CONST               1 (())
+2:16-2:19            STORE_NAME               5 (__static_attributes__)
+2:16-2:19            LOAD_COMMON_CONSTANT     7 (None)
+2:16-2:19            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_function_annotation_scope_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_function_annotation_scope_location.snap
new file mode 100644
index 00000000000..0b9fa6890ee
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_function_annotation_scope_location.snap
@@ -0,0 +1,48 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f[T](x: int): ...\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-1:21            LOAD_CONST               0 (<code object <generic parameters of f> at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:21            MAKE_FUNCTION
+1:0-1:21            PUSH_NULL
+1:0-1:21            CALL                     0
+1:0-1:21            STORE_NAME               0 (f)
+1:0-1:21            LOAD_COMMON_CONSTANT     7 (None)
+1:0-1:21            RETURN_VALUE
+
+Disassembly of <code object <generic parameters of f> at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0             RESUME                   0
+1:6-1:7             LOAD_CONST               0 ('T')
+1:6-1:7             CALL_INTRINSIC_1         7 (INTRINSIC_TYPEVAR)
+1:6-1:7             COPY                     1
+1:6-1:7             STORE_FAST               1 (T)
+1:6-1:7             BUILD_TUPLE              1
+1:0-1:21            LOAD_CONST               1 (<code object __annotate__ at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:21            MAKE_FUNCTION
+1:0-1:21            LOAD_CONST               2 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:21            MAKE_FUNCTION
+1:0-1:21            SET_FUNCTION_ATTRIBUTE  16 (annotate)
+1:0-1:21            SWAP                     2
+1:0-1:21            CALL_INTRINSIC_2         4 (INTRINSIC_SET_FUNCTION_TYPE_PARAMS)
+1:0-1:21            RETURN_VALUE
+
+Disassembly of <code object __annotate__ at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+1:0-1:21             LOAD_FAST_BORROW         0 (format)
+1:0-1:21             LOAD_SMALL_INT           2
+1:0-1:21             COMPARE_OP             132 (>)
+1:0-1:21             POP_JUMP_IF_FALSE        3 (to L1)
+1:0-1:21             NOT_TAKEN
+1:0-1:21             LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+1:0-1:21             RAISE_VARARGS            1
+1:0-1:21     L1:     LOAD_CONST               1 ('x')
+1:12-1:15            LOAD_GLOBAL              0 (int)
+1:0-1:21             BUILD_MAP                1
+1:0-1:21             RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+1:18-1:21            LOAD_COMMON_CONSTANT     7 (None)
+1:18-1:21            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_typealias_wrapper_return_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_typealias_wrapper_return_location.snap
new file mode 100644
index 00000000000..dd85d9a57e1
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__generic_typealias_wrapper_return_location.snap
@@ -0,0 +1,48 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ntype A[T] = T\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-1:13            LOAD_CONST               0 (<code object <generic parameters of A> at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:13            MAKE_FUNCTION
+1:0-1:13            PUSH_NULL
+1:0-1:13            CALL                     0
+1:0-1:13            STORE_NAME               0 (A)
+1:0-1:13            LOAD_COMMON_CONSTANT     7 (None)
+1:0-1:13            RETURN_VALUE
+
+Disassembly of <code object <generic parameters of A> at 0xdeadbeef, file "<?>", line 1>:
+  --                MAKE_CELL                0 (T)
+
+1:0-1:0             RESUME                   0
+1:0-1:13            LOAD_CONST               0 ('A')
+1:7-1:8             LOAD_CONST               1 ('T')
+1:7-1:8             CALL_INTRINSIC_1         7 (INTRINSIC_TYPEVAR)
+1:7-1:8             COPY                     1
+1:7-1:8             STORE_DEREF              0 (T)
+1:7-1:8             BUILD_TUPLE              1
+1:0-1:13            LOAD_CONST               2 ((1,))
+1:0-1:13            LOAD_FAST_BORROW         0 (T)
+1:0-1:13            BUILD_TUPLE              1
+1:0-1:13            LOAD_CONST               3 (<code object A at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:13            MAKE_FUNCTION
+1:0-1:13            SET_FUNCTION_ATTRIBUTE   8 (closure)
+1:0-1:13            SET_FUNCTION_ATTRIBUTE   1 (defaults)
+1:0-1:13            BUILD_TUPLE              3
+1:0-1:13            CALL_INTRINSIC_1        11 (INTRINSIC_TYPEALIAS)
+1:0-1:13            RETURN_VALUE
+
+Disassembly of <code object A at 0xdeadbeef, file "<?>", line 1>:
+  --                 COPY_FREE_VARS           1
+
+1:0-1:0              RESUME                   0
+1:0-1:13             LOAD_FAST_BORROW         0 (.format)
+1:0-1:13             LOAD_SMALL_INT           2
+1:0-1:13             COMPARE_OP             132 (>)
+1:0-1:13             POP_JUMP_IF_FALSE        3 (to L1)
+1:0-1:13             NOT_TAKEN
+1:0-1:13             LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+1:0-1:13             RAISE_VARARGS            1
+1:12-1:13    L1:     LOAD_DEREF               1 (T)
+1:0-1:13             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_closure_and_call_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_closure_and_call_location.snap
new file mode 100644
index 00000000000..266fe98e0be
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_closure_and_call_location.snap
@@ -0,0 +1,48 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(parameters):\n    return ((p, type(p)) for p in parameters)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:45            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:45            MAKE_FUNCTION
+1:0-2:45            STORE_NAME               0 (f)
+1:0-2:45            LOAD_COMMON_CONSTANT     7 (None)
+1:0-2:45            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:45            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:11-2:45            MAKE_FUNCTION
+2:34-2:44            LOAD_FAST_BORROW         0 (parameters)
+2:11-2:45            CALL                     0
+2:4-2:45             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 2>:
+  --                 RESUME                   4
+
+2:34-2:44            LOAD_FAST                0 (.0)
+2:34-2:44            GET_ITER                 0
+2:?-2:?              RETURN_GENERATOR
+2:?-2:?              POP_TOP
+2:0-2:0      L1:     RESUME                   0
+2:34-2:44    L2:     FOR_ITER                18 (to L3)
+2:29-2:30            STORE_FAST_LOAD_FAST    17 (p, p)
+2:16-2:20            LOAD_GLOBAL              1 (type + NULL)
+2:21-2:22            LOAD_FAST_BORROW         1 (p)
+2:16-2:23            CALL                     1
+2:12-2:24            BUILD_TUPLE              2
+2:12-2:24            YIELD_VALUE              0
+2:12-2:24            RESUME                   9
+2:12-2:24            POP_TOP
+2:12-2:24            JUMP_BACKWARD           20 (to L2)
+2:34-2:44    L3:     END_FOR
+2:34-2:44            POP_ITER
+2:34-2:44            LOAD_COMMON_CONSTANT     7 (None)
+2:34-2:44            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_filter_cleanup_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_filter_cleanup_location.snap
new file mode 100644
index 00000000000..6318f1ac1d3
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_filter_cleanup_location.snap
@@ -0,0 +1,104 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef simple(names):\n    return (x for x in names if not _ishidden(x))\n\ndef boolop(fields):\n    return (f for f in fields if f.init and not f.kw_only)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:49            LOAD_CONST               0 (<code object simple at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:49            MAKE_FUNCTION
+1:0-2:49            STORE_NAME               0 (simple)
+
+4:0-5:58            LOAD_CONST               1 (<code object boolop at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:58            MAKE_FUNCTION
+4:0-5:58            STORE_NAME               1 (boolop)
+4:0-5:58            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:58            RETURN_VALUE
+
+Disassembly of <code object simple at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:49            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:11-2:49            MAKE_FUNCTION
+2:23-2:28            LOAD_FAST_BORROW         0 (names)
+2:11-2:49            CALL                     0
+2:4-2:49             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 2>:
+  --                 RESUME                   4
+
+2:23-2:28            LOAD_FAST                0 (.0)
+2:23-2:28            GET_ITER                 0
+2:?-2:?              RETURN_GENERATOR
+2:?-2:?              POP_TOP
+2:0-2:0      L1:     RESUME                   0
+2:23-2:28    L2:     FOR_ITER                27 (to L5)
+2:18-2:19            STORE_FAST               1 (x)
+2:36-2:45            LOAD_GLOBAL              1 (_ishidden + NULL)
+2:46-2:47            LOAD_FAST_BORROW         1 (x)
+2:36-2:48            CALL                     1
+2:36-2:48            TO_BOOL
+2:12-2:13    L3:     POP_JUMP_IF_FALSE        3 (to L4)
+2:12-2:13            NOT_TAKEN
+2:12-2:13            JUMP_BACKWARD           22 (to L2)
+2:12-2:13    L4:     LOAD_FAST_BORROW         1 (x)
+2:12-2:13            YIELD_VALUE              0
+2:12-2:13            RESUME                   9
+2:12-2:13            POP_TOP
+2:12-2:13            JUMP_BACKWARD           29 (to L2)
+2:23-2:28    L5:     END_FOR
+2:23-2:28            POP_ITER
+2:23-2:28            LOAD_COMMON_CONSTANT     7 (None)
+2:23-2:28            RETURN_VALUE
+
+  --         L6:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L3 -> L6 [2] lasti
+  L4 to L6 -> L6 [2] lasti
+
+Disassembly of <code object boolop at 0xdeadbeef, file "<?>", line 4>:
+4:0-4:0              RESUME                   0
+
+5:11-5:58            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 5>)
+5:11-5:58            MAKE_FUNCTION
+5:23-5:29            LOAD_FAST_BORROW         0 (fields)
+5:11-5:58            CALL                     0
+5:4-5:58             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 5>:
+  --                 RESUME                   4
+
+5:23-5:29            LOAD_FAST                0 (.0)
+5:23-5:29            GET_ITER                 0
+5:?-5:?              RETURN_GENERATOR
+5:?-5:?              POP_TOP
+5:0-5:0      L1:     RESUME                   0
+5:23-5:29    L2:     FOR_ITER                47 (to L7)
+5:18-5:19            STORE_FAST_LOAD_FAST    17 (f, f)
+5:33-5:39            LOAD_ATTR                0 (init)
+5:33-5:39            TO_BOOL
+5:12-5:13    L3:     POP_JUMP_IF_TRUE         3 (to L4)
+5:12-5:13            NOT_TAKEN
+5:12-5:13            JUMP_BACKWARD           22 (to L2)
+5:48-5:49    L4:     LOAD_FAST_BORROW         1 (f)
+5:48-5:57            LOAD_ATTR                2 (kw_only)
+5:48-5:57            TO_BOOL
+5:12-5:13    L5:     POP_JUMP_IF_FALSE        3 (to L6)
+5:12-5:13            NOT_TAKEN
+5:12-5:13            JUMP_BACKWARD           42 (to L2)
+5:12-5:13    L6:     LOAD_FAST_BORROW         1 (f)
+5:12-5:13            YIELD_VALUE              0
+5:12-5:13            RESUME                   9
+5:12-5:13            POP_TOP
+5:12-5:13            JUMP_BACKWARD           49 (to L2)
+5:23-5:29    L7:     END_FOR
+5:23-5:29            POP_ITER
+5:23-5:29            LOAD_COMMON_CONSTANT     7 (None)
+5:23-5:29            RETURN_VALUE
+
+  --         L8:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L3 -> L8 [2] lasti
+  L4 to L5 -> L8 [2] lasti
+  L6 to L8 -> L8 [2] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_prefix.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_prefix.snap
new file mode 100644
index 00000000000..aff0ded464d
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__genexpr_prefix.snap
@@ -0,0 +1,103 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(xs):\n    return (x for x in xs)\n\nasync def g(xs):\n    return (x async for x in xs)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:26            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:26            MAKE_FUNCTION
+1:0-2:26            STORE_NAME               0 (f)
+
+4:0-5:32            LOAD_CONST               1 (<code object g at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:32            MAKE_FUNCTION
+4:0-5:32            STORE_NAME               1 (g)
+4:0-5:32            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:32            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:26            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:11-2:26            MAKE_FUNCTION
+2:23-2:25            LOAD_FAST_BORROW         0 (xs)
+2:11-2:26            CALL                     0
+2:4-2:26             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 2>:
+  --                 RESUME                   4
+
+2:23-2:25            LOAD_FAST                0 (.0)
+2:23-2:25            GET_ITER                 0
+2:?-2:?              RETURN_GENERATOR
+2:?-2:?              POP_TOP
+2:0-2:0      L1:     RESUME                   0
+2:23-2:25    L2:     FOR_ITER                 7 (to L3)
+2:18-2:19            STORE_FAST_LOAD_FAST    17 (x, x)
+2:12-2:13            YIELD_VALUE              0
+2:12-2:13            RESUME                   9
+2:12-2:13            POP_TOP
+2:12-2:13            JUMP_BACKWARD            9 (to L2)
+2:23-2:25    L3:     END_FOR
+2:23-2:25            POP_ITER
+2:23-2:25            LOAD_COMMON_CONSTANT     7 (None)
+2:23-2:25            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
+
+Disassembly of <code object g at 0xdeadbeef, file "<?>", line 4>:
+4:?-4:?              RETURN_GENERATOR
+4:?-4:?              POP_TOP
+4:0-4:0      L1:     RESUME                   0
+
+5:11-5:32            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 5>)
+5:11-5:32            MAKE_FUNCTION
+5:29-5:31            LOAD_FAST_BORROW         0 (xs)
+5:11-5:32            CALL                     0
+5:4-5:32             RETURN_VALUE
+
+  --         L2:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L2 [0] lasti
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 5>:
+  --                  RESUME                   4
+
+5:29-5:31             LOAD_FAST_BORROW         0 (.0)
+5:29-5:31             GET_AITER
+5:?-5:?               RETURN_GENERATOR
+5:?-5:?               POP_TOP
+5:0-5:0       L1:     RESUME                   0
+5:11-5:32     L2:     GET_ANEXT
+5:11-5:32             PUSH_NULL
+5:11-5:32             LOAD_COMMON_CONSTANT     7 (None)
+5:11-5:32     L3:     SEND                     4 (to L6)
+5:11-5:32     L4:     YIELD_VALUE              1
+5:11-5:32     L5:     RESUME                   3
+5:11-5:32             JUMP_BACKWARD_NO_INTERRUPT 6 (to L3)
+5:11-5:32     L6:     END_SEND
+5:24-5:25     L7:     STORE_FAST_LOAD_FAST    17 (x, x)
+5:12-5:13             CALL_INTRINSIC_1         4 (INTRINSIC_ASYNC_GEN_WRAP)
+5:12-5:13             YIELD_VALUE              0
+5:12-5:13             RESUME                   9
+5:12-5:13             POP_TOP
+5:12-5:13             JUMP_BACKWARD           18 (to L2)
+5:11-5:32     L8:     CLEANUP_THROW
+5:11-5:32     L9:     JUMP_BACKWARD_NO_INTERRUPT 11 (to L6)
+5:11-5:32    L10:     END_ASYNC_FOR           12 (from L6)
+5:11-5:32             LOAD_COMMON_CONSTANT     7 (None)
+5:11-5:32             RETURN_VALUE
+
+  --         L11:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L11 [1] lasti
+  L2 to L4 -> L10 [1]
+  L4 to L5 -> L8 [4]
+  L5 to L7 -> L10 [1]
+  L7 to L8 -> L11 [1] lasti
+  L8 to L9 -> L10 [1]
+  L10 to L11 -> L11 [1] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_ands.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_ands.snap
index 5c58a2b6b85..0f3b62b3cdb 100644
--- a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_ands.snap
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_ands.snap
@@ -5,5 +5,5 @@ expression: "dis(r#\"\nif True and False and False:\n    pass\n\"#)"
 ---
   0           RESUME                   0
 
-  1           LOAD_CONST               1 (None)
+  1           LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_mixed.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_mixed.snap
index 6bef04ee143..7da2fc67637 100644
--- a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_mixed.snap
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_mixed.snap
@@ -5,5 +5,5 @@ expression: "dis(r#\"\nif (True and False) or (False and True):\n    pass\n\"#)"
 ---
   0           RESUME                   0
 
-  1           LOAD_CONST               1 (None)
+  1           LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_ors.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_ors.snap
index 065d893732e..d89e0a8d01d 100644
--- a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_ors.snap
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__if_ors.snap
@@ -7,5 +7,5 @@ expression: "dis(r#\"\nif True or False or False:\n    pass\n\"#)"
 
   1           NOP
 
-  2           LOAD_CONST               1 (None)
+  2           LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__implicit_call_genexpr_parenthesized_element_range.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__implicit_call_genexpr_parenthesized_element_range.snap
new file mode 100644
index 00000000000..7d1cdd914c2
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__implicit_call_genexpr_parenthesized_element_range.snap
@@ -0,0 +1,216 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef bytes_binop():\n    return bytes((x ^ 0x5C) for x in range(256))\n\ndef dict_tuple(d):\n    return dict((v, k) for (k, v) in d.items())\n\ndef plain_tuple_elt(xs):\n    return list((x, y) for x, y in xs)\n\ndef explicit_gen(xs):\n    return list(((x, y) for x, y in xs))\n\"#,\ntrue)"
+---
+0:0-1:0               RESUME                   0
+
+1:0-2:48              LOAD_CONST               0 (<code object bytes_binop at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:48              MAKE_FUNCTION
+1:0-2:48              STORE_NAME               0 (bytes_binop)
+
+4:0-5:47              LOAD_CONST               1 (<code object dict_tuple at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:47              MAKE_FUNCTION
+4:0-5:47              STORE_NAME               1 (dict_tuple)
+
+7:0-8:38              LOAD_CONST               2 (<code object plain_tuple_elt at 0xdeadbeef, file "<?>", line 7>)
+7:0-8:38              MAKE_FUNCTION
+7:0-8:38              STORE_NAME               2 (plain_tuple_elt)
+
+10:0-11:40            LOAD_CONST               3 (<code object explicit_gen at 0xdeadbeef, file "<?>", line 10>)
+10:0-11:40            MAKE_FUNCTION
+10:0-11:40            STORE_NAME               3 (explicit_gen)
+10:0-11:40            LOAD_COMMON_CONSTANT     7 (None)
+10:0-11:40            RETURN_VALUE
+
+Disassembly of <code object bytes_binop at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:16            LOAD_GLOBAL              1 (bytes + NULL)
+2:16-2:48            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:16-2:48            MAKE_FUNCTION
+2:37-2:42            LOAD_GLOBAL              3 (range + NULL)
+2:43-2:46            LOAD_CONST               1 (256)
+2:37-2:47            CALL                     1
+2:16-2:48            CALL                     0
+2:11-2:48            CALL                     1
+2:4-2:48             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 2>:
+  --                 RESUME                   4
+
+2:37-2:47            LOAD_FAST                0 (.0)
+2:37-2:47            GET_ITER                 0
+2:?-2:?              RETURN_GENERATOR
+2:?-2:?              POP_TOP
+2:0-2:0      L1:     RESUME                   0
+2:37-2:47    L2:     FOR_ITER                14 (to L3)
+2:32-2:33            STORE_FAST_LOAD_FAST    17 (x, x)
+2:22-2:26            LOAD_SMALL_INT          92
+2:18-2:26            BINARY_OP               12 (^)
+2:18-2:26            YIELD_VALUE              0
+2:18-2:26            RESUME                   9
+2:18-2:26            POP_TOP
+2:18-2:26            JUMP_BACKWARD           16 (to L2)
+2:37-2:47    L3:     END_FOR
+2:37-2:47            POP_ITER
+2:37-2:47            LOAD_COMMON_CONSTANT     7 (None)
+2:37-2:47            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
+
+Disassembly of <code object dict_tuple at 0xdeadbeef, file "<?>", line 4>:
+4:0-4:0              RESUME                   0
+
+5:11-5:15            LOAD_GLOBAL              1 (dict + NULL)
+5:15-5:47            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 5>)
+5:15-5:47            MAKE_FUNCTION
+5:37-5:38            LOAD_FAST_BORROW         0 (d)
+5:37-5:44            LOAD_ATTR                3 (items + NULL|self)
+5:37-5:46            CALL                     0
+5:15-5:47            CALL                     0
+5:11-5:47            CALL                     1
+5:4-5:47             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 5>:
+  --                 RESUME                   4
+
+5:37-5:46            LOAD_FAST                0 (.0)
+5:37-5:46            GET_ITER                 0
+5:?-5:?              RETURN_GENERATOR
+5:?-5:?              POP_TOP
+5:0-5:0      L1:     RESUME                   0
+5:37-5:46    L2:     FOR_ITER                11 (to L3)
+5:27-5:33            UNPACK_SEQUENCE          2
+5:28-5:29            STORE_FAST_STORE_FAST   18 (k, v)
+5:17-5:18            LOAD_FAST_BORROW_LOAD_FAST_BORROW 33 (v, k)
+5:16-5:22            BUILD_TUPLE              2
+5:16-5:22            YIELD_VALUE              0
+5:16-5:22            RESUME                   9
+5:16-5:22            POP_TOP
+5:16-5:22            JUMP_BACKWARD           13 (to L2)
+5:37-5:46    L3:     END_FOR
+5:37-5:46            POP_ITER
+5:37-5:46            LOAD_COMMON_CONSTANT     7 (None)
+5:37-5:46            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
+
+Disassembly of <code object plain_tuple_elt at 0xdeadbeef, file "<?>", line 7>:
+7:0-7:0              RESUME                   0
+
+8:11-8:15            LOAD_GLOBAL              0 (list)
+8:11-8:15            COPY                     1
+8:11-8:15            LOAD_COMMON_CONSTANT     5 (list)
+8:11-8:15            IS_OP                    0 (is)
+8:11-8:15            POP_JUMP_IF_FALSE       19 (to L3)
+8:11-8:15            NOT_TAKEN
+8:11-8:15            POP_TOP
+8:11-8:15            BUILD_LIST               0
+8:15-8:38            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 8>)
+8:15-8:38            MAKE_FUNCTION
+8:35-8:37            LOAD_FAST_BORROW         0 (xs)
+8:15-8:38            CALL                     0
+8:11-8:15            PUSH_NULL
+8:11-8:15    L1:     FOR_ITER                 3 (to L2)
+8:11-8:15            LIST_APPEND              3
+8:11-8:15            JUMP_BACKWARD            5 (to L1)
+8:11-8:15    L2:     END_FOR
+8:11-8:15            POP_ITER
+8:4-8:38             RETURN_VALUE
+8:11-8:15    L3:     PUSH_NULL
+8:15-8:38            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 8>)
+8:15-8:38            MAKE_FUNCTION
+8:35-8:37            LOAD_FAST_BORROW         0 (xs)
+8:15-8:38            CALL                     0
+8:11-8:38            CALL                     1
+8:4-8:38             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 8>:
+  --                 RESUME                   4
+
+8:35-8:37            LOAD_FAST                0 (.0)
+8:35-8:37            GET_ITER                 0
+8:?-8:?              RETURN_GENERATOR
+8:?-8:?              POP_TOP
+8:0-8:0      L1:     RESUME                   0
+8:35-8:37    L2:     FOR_ITER                11 (to L3)
+8:27-8:31            UNPACK_SEQUENCE          2
+8:27-8:28            STORE_FAST_STORE_FAST   18 (x, y)
+8:17-8:18            LOAD_FAST_BORROW_LOAD_FAST_BORROW 18 (x, y)
+8:16-8:22            BUILD_TUPLE              2
+8:16-8:22            YIELD_VALUE              0
+8:16-8:22            RESUME                   9
+8:16-8:22            POP_TOP
+8:16-8:22            JUMP_BACKWARD           13 (to L2)
+8:35-8:37    L3:     END_FOR
+8:35-8:37            POP_ITER
+8:35-8:37            LOAD_COMMON_CONSTANT     7 (None)
+8:35-8:37            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
+
+Disassembly of <code object explicit_gen at 0xdeadbeef, file "<?>", line 10>:
+10:0-10:0              RESUME                   0
+
+11:11-11:15            LOAD_GLOBAL              0 (list)
+11:11-11:15            COPY                     1
+11:11-11:15            LOAD_COMMON_CONSTANT     5 (list)
+11:11-11:15            IS_OP                    0 (is)
+11:11-11:15            POP_JUMP_IF_FALSE       19 (to L3)
+11:11-11:15            NOT_TAKEN
+11:11-11:15            POP_TOP
+11:11-11:15            BUILD_LIST               0
+11:16-11:39            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 11>)
+11:16-11:39            MAKE_FUNCTION
+11:36-11:38            LOAD_FAST_BORROW         0 (xs)
+11:16-11:39            CALL                     0
+11:11-11:15            PUSH_NULL
+11:11-11:15    L1:     FOR_ITER                 3 (to L2)
+11:11-11:15            LIST_APPEND              3
+11:11-11:15            JUMP_BACKWARD            5 (to L1)
+11:11-11:15    L2:     END_FOR
+11:11-11:15            POP_ITER
+11:4-11:40             RETURN_VALUE
+11:11-11:15    L3:     PUSH_NULL
+11:16-11:39            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 11>)
+11:16-11:39            MAKE_FUNCTION
+11:36-11:38            LOAD_FAST_BORROW         0 (xs)
+11:16-11:39            CALL                     0
+11:11-11:40            CALL                     1
+11:4-11:40             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 11>:
+  --                   RESUME                   4
+
+11:36-11:38            LOAD_FAST                0 (.0)
+11:36-11:38            GET_ITER                 0
+11:?-11:?              RETURN_GENERATOR
+11:?-11:?              POP_TOP
+11:0-11:0      L1:     RESUME                   0
+11:36-11:38    L2:     FOR_ITER                11 (to L3)
+11:28-11:32            UNPACK_SEQUENCE          2
+11:28-11:29            STORE_FAST_STORE_FAST   18 (x, y)
+11:18-11:19            LOAD_FAST_BORROW_LOAD_FAST_BORROW 18 (x, y)
+11:17-11:23            BUILD_TUPLE              2
+11:17-11:23            YIELD_VALUE              0
+11:17-11:23            RESUME                   9
+11:17-11:23            POP_TOP
+11:17-11:23            JUMP_BACKWARD           13 (to L2)
+11:36-11:38    L3:     END_FOR
+11:36-11:38            POP_ITER
+11:36-11:38            LOAD_COMMON_CONSTANT     7 (None)
+11:36-11:38            RETURN_VALUE
+
+  --           L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                   RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__implicit_call_genexpr_range.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__implicit_call_genexpr_range.snap
new file mode 100644
index 00000000000..bc11da5dc0a
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__implicit_call_genexpr_range.snap
@@ -0,0 +1,131 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef implicit():\n    return list(x for x in range(10))\n\ndef explicit():\n    return list((x for x in range(10)))\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:37            LOAD_CONST               0 (<code object implicit at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:37            MAKE_FUNCTION
+1:0-2:37            STORE_NAME               0 (implicit)
+
+4:0-5:39            LOAD_CONST               1 (<code object explicit at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:39            MAKE_FUNCTION
+4:0-5:39            STORE_NAME               1 (explicit)
+4:0-5:39            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:39            RETURN_VALUE
+
+Disassembly of <code object implicit at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:15            LOAD_GLOBAL              0 (list)
+2:11-2:15            COPY                     1
+2:11-2:15            LOAD_COMMON_CONSTANT     5 (list)
+2:11-2:15            IS_OP                    0 (is)
+2:11-2:15            POP_JUMP_IF_FALSE       28 (to L3)
+2:11-2:15            NOT_TAKEN
+2:11-2:15            POP_TOP
+2:11-2:15            BUILD_LIST               0
+2:15-2:37            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:15-2:37            MAKE_FUNCTION
+2:27-2:32            LOAD_GLOBAL              3 (range + NULL)
+2:33-2:35            LOAD_SMALL_INT          10
+2:27-2:36            CALL                     1
+2:15-2:37            CALL                     0
+2:11-2:15            PUSH_NULL
+2:11-2:15    L1:     FOR_ITER                 3 (to L2)
+2:11-2:15            LIST_APPEND              3
+2:11-2:15            JUMP_BACKWARD            5 (to L1)
+2:11-2:15    L2:     END_FOR
+2:11-2:15            POP_ITER
+2:4-2:37             RETURN_VALUE
+2:11-2:15    L3:     PUSH_NULL
+2:15-2:37            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:15-2:37            MAKE_FUNCTION
+2:27-2:32            LOAD_GLOBAL              3 (range + NULL)
+2:33-2:35            LOAD_SMALL_INT          10
+2:27-2:36            CALL                     1
+2:15-2:37            CALL                     0
+2:11-2:37            CALL                     1
+2:4-2:37             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 2>:
+  --                 RESUME                   4
+
+2:27-2:36            LOAD_FAST                0 (.0)
+2:27-2:36            GET_ITER                 0
+2:?-2:?              RETURN_GENERATOR
+2:?-2:?              POP_TOP
+2:0-2:0      L1:     RESUME                   0
+2:27-2:36    L2:     FOR_ITER                 7 (to L3)
+2:22-2:23            STORE_FAST_LOAD_FAST    17 (x, x)
+2:16-2:17            YIELD_VALUE              0
+2:16-2:17            RESUME                   9
+2:16-2:17            POP_TOP
+2:16-2:17            JUMP_BACKWARD            9 (to L2)
+2:27-2:36    L3:     END_FOR
+2:27-2:36            POP_ITER
+2:27-2:36            LOAD_COMMON_CONSTANT     7 (None)
+2:27-2:36            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
+
+Disassembly of <code object explicit at 0xdeadbeef, file "<?>", line 4>:
+4:0-4:0              RESUME                   0
+
+5:11-5:15            LOAD_GLOBAL              0 (list)
+5:11-5:15            COPY                     1
+5:11-5:15            LOAD_COMMON_CONSTANT     5 (list)
+5:11-5:15            IS_OP                    0 (is)
+5:11-5:15            POP_JUMP_IF_FALSE       28 (to L3)
+5:11-5:15            NOT_TAKEN
+5:11-5:15            POP_TOP
+5:11-5:15            BUILD_LIST               0
+5:16-5:38            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 5>)
+5:16-5:38            MAKE_FUNCTION
+5:28-5:33            LOAD_GLOBAL              3 (range + NULL)
+5:34-5:36            LOAD_SMALL_INT          10
+5:28-5:37            CALL                     1
+5:16-5:38            CALL                     0
+5:11-5:15            PUSH_NULL
+5:11-5:15    L1:     FOR_ITER                 3 (to L2)
+5:11-5:15            LIST_APPEND              3
+5:11-5:15            JUMP_BACKWARD            5 (to L1)
+5:11-5:15    L2:     END_FOR
+5:11-5:15            POP_ITER
+5:4-5:39             RETURN_VALUE
+5:11-5:15    L3:     PUSH_NULL
+5:16-5:38            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 5>)
+5:16-5:38            MAKE_FUNCTION
+5:28-5:33            LOAD_GLOBAL              3 (range + NULL)
+5:34-5:36            LOAD_SMALL_INT          10
+5:28-5:37            CALL                     1
+5:16-5:38            CALL                     0
+5:11-5:39            CALL                     1
+5:4-5:39             RETURN_VALUE
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 5>:
+  --                 RESUME                   4
+
+5:28-5:37            LOAD_FAST                0 (.0)
+5:28-5:37            GET_ITER                 0
+5:?-5:?              RETURN_GENERATOR
+5:?-5:?              POP_TOP
+5:0-5:0      L1:     RESUME                   0
+5:28-5:37    L2:     FOR_ITER                 7 (to L3)
+5:23-5:24            STORE_FAST_LOAD_FAST    17 (x, x)
+5:17-5:18            YIELD_VALUE              0
+5:17-5:18            RESUME                   9
+5:17-5:18            POP_TOP
+5:17-5:18            JUMP_BACKWARD            9 (to L2)
+5:28-5:37    L3:     END_FOR
+5:28-5:37            POP_ITER
+5:28-5:37            LOAD_COMMON_CONSTANT     7 (None)
+5:28-5:37            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [2] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__import_flags.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__import_flags.snap
new file mode 100644
index 00000000000..d26a61edca5
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__import_flags.snap
@@ -0,0 +1,193 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nimport sample\nfrom sample import member\nfrom sample import *\n\ndef f():\n    import sample\n\nclass C:\n    from sample import member\n\ntry:\n    import sample\nexcept Exception:\n    pass\n\ntry:\n    operation()\nexcept Exception:\n    import sample\n\ntry:\n    operation()\nfinally:\n    import sample\n\nwith manager:\n    import sample\n\"#,\ntrue)"
+---
+0:0-1:0                RESUME                   0
+
+1:0-1:13               LOAD_SMALL_INT           0
+1:0-1:13               LOAD_COMMON_CONSTANT     7 (None)
+1:0-1:13               IMPORT_NAME              0 (sample)
+1:0-1:13               STORE_NAME               0 (sample)
+
+2:0-2:25               LOAD_SMALL_INT           0
+2:0-2:25               LOAD_CONST               1 (('member',))
+2:0-2:25               IMPORT_NAME              0 (sample)
+2:0-2:25               IMPORT_FROM              1 (member)
+2:0-2:25               STORE_NAME               1 (member)
+2:0-2:25               POP_TOP
+
+3:0-3:20               LOAD_SMALL_INT           0
+3:0-3:20               LOAD_CONST               2 (('*',))
+3:0-3:20               IMPORT_NAME              2 (sample + eager)
+3:0-3:20               CALL_INTRINSIC_1         2 (INTRINSIC_IMPORT_STAR)
+3:0-3:20               POP_TOP
+
+5:0-6:17               LOAD_CONST               3 (<code object f at 0xdeadbeef, file "<?>", line 5>)
+5:0-6:17               MAKE_FUNCTION
+5:0-6:17               STORE_NAME               2 (f)
+
+8:0-9:29               LOAD_BUILD_CLASS
+8:0-9:29               PUSH_NULL
+8:0-9:29               LOAD_CONST               4 (<code object C at 0xdeadbeef, file "<?>", line 8>)
+8:0-9:29               MAKE_FUNCTION
+8:0-9:29               LOAD_CONST               5 ('C')
+8:0-9:29               CALL                     2
+8:0-9:29               STORE_NAME               3 (C)
+
+11:0-14:8              NOP
+
+12:4-12:17     L1:     LOAD_SMALL_INT           0
+12:4-12:17             LOAD_COMMON_CONSTANT     7 (None)
+12:4-12:17             IMPORT_NAME              2 (sample + eager)
+12:4-12:17             STORE_NAME               0 (sample)
+
+16:0-19:17     L2:     NOP
+
+17:4-17:13     L3:     LOAD_NAME                5 (operation)
+17:4-17:13             PUSH_NULL
+17:4-17:15             CALL                     0
+17:4-17:15             POP_TOP
+
+21:0-24:17     L4:     NOP
+
+22:4-22:13     L5:     LOAD_NAME                5 (operation)
+22:4-22:13             PUSH_NULL
+22:4-22:15             CALL                     0
+22:4-22:15             POP_TOP
+
+24:4-24:17     L6:     LOAD_SMALL_INT           0
+24:4-24:17             LOAD_COMMON_CONSTANT     7 (None)
+24:4-24:17             IMPORT_NAME              0 (sample)
+24:4-24:17             STORE_NAME               0 (sample)
+
+26:5-26:12             LOAD_NAME                6 (manager)
+26:5-26:12             COPY                     1
+26:5-26:12             LOAD_SPECIAL             1 (__exit__)
+26:5-26:12             SWAP                     2
+26:5-26:12             SWAP                     3
+26:5-26:12             LOAD_SPECIAL             0 (__enter__)
+26:5-26:12             CALL                     0
+26:5-26:12     L7:     POP_TOP
+
+27:4-27:17             LOAD_SMALL_INT           0
+27:4-27:17             LOAD_COMMON_CONSTANT     7 (None)
+27:4-27:17             IMPORT_NAME              0 (sample)
+27:4-27:17             STORE_NAME               0 (sample)
+
+26:5-26:12     L8:     LOAD_COMMON_CONSTANT     7 (None)
+26:5-26:12             LOAD_COMMON_CONSTANT     7 (None)
+26:5-26:12             LOAD_COMMON_CONSTANT     7 (None)
+26:5-26:12             CALL                     3
+26:5-26:12             POP_TOP
+26:5-26:12             LOAD_COMMON_CONSTANT     7 (None)
+26:5-26:12             RETURN_VALUE
+
+  --           L9:     PUSH_EXC_INFO
+
+13:7-13:16             LOAD_NAME                4 (Exception)
+13:0-14:8              CHECK_EXC_MATCH
+13:0-14:8              POP_JUMP_IF_FALSE        4 (to L13)
+13:0-14:8     L10:     NOT_TAKEN
+13:0-14:8     L11:     POP_TOP
+
+14:4-14:8     L12:     POP_EXCEPT
+14:4-14:8              JUMP_BACKWARD_NO_INTERRUPT 54 (to L2)
+
+13:0-14:8     L13:     RERAISE                  0
+
+  --          L14:     COPY                     3
+  --                   POP_EXCEPT
+  --                   RERAISE                  1
+  --          L15:     PUSH_EXC_INFO
+
+18:7-18:16             LOAD_NAME                4 (Exception)
+18:0-19:17             CHECK_EXC_MATCH
+18:0-19:17             POP_JUMP_IF_FALSE        8 (to L19)
+18:0-19:17    L16:     NOT_TAKEN
+18:0-19:17    L17:     POP_TOP
+
+19:4-19:17             LOAD_SMALL_INT           0
+19:4-19:17             LOAD_COMMON_CONSTANT     7 (None)
+19:4-19:17             IMPORT_NAME              2 (sample + eager)
+19:4-19:17             STORE_NAME               0 (sample)
+19:4-19:17    L18:     POP_EXCEPT
+19:4-19:17             JUMP_BACKWARD_NO_INTERRUPT 63 (to L4)
+
+18:0-19:17    L19:     RERAISE                  0
+
+  --          L20:     COPY                     3
+  --                   POP_EXCEPT
+  --                   RERAISE                  1
+  --          L21:     PUSH_EXC_INFO
+
+24:4-24:17             LOAD_SMALL_INT           0
+24:4-24:17             LOAD_COMMON_CONSTANT     7 (None)
+24:4-24:17             IMPORT_NAME              2 (sample + eager)
+24:4-24:17             STORE_NAME               0 (sample)
+24:4-24:17             RERAISE                  0
+
+  --          L22:     COPY                     3
+  --                   POP_EXCEPT
+  --                   RERAISE                  1
+
+26:5-26:12    L23:     PUSH_EXC_INFO
+26:5-26:12             WITH_EXCEPT_START
+26:5-26:12             TO_BOOL
+26:5-26:12             POP_JUMP_IF_TRUE         2 (to L26)
+26:5-26:12    L24:     NOT_TAKEN
+26:5-26:12    L25:     RERAISE                  2
+26:5-26:12    L26:     POP_TOP
+26:5-26:12    L27:     POP_EXCEPT
+26:5-26:12             POP_TOP
+26:5-26:12             POP_TOP
+26:5-26:12             POP_TOP
+26:5-26:12             LOAD_COMMON_CONSTANT     7 (None)
+26:5-26:12             RETURN_VALUE
+
+  --          L28:     COPY                     3
+  --                   POP_EXCEPT
+  --                   RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L9 [0]
+  L3 to L4 -> L15 [0]
+  L5 to L6 -> L21 [0]
+  L7 to L8 -> L23 [2] lasti
+  L9 to L10 -> L14 [1] lasti
+  L11 to L12 -> L14 [1] lasti
+  L13 to L14 -> L14 [1] lasti
+  L15 to L16 -> L20 [1] lasti
+  L17 to L18 -> L20 [1] lasti
+  L19 to L20 -> L20 [1] lasti
+  L21 to L22 -> L22 [1] lasti
+  L23 to L24 -> L28 [4] lasti
+  L25 to L27 -> L28 [4] lasti
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 5>:
+5:0-5:0             RESUME                   0
+
+6:4-6:17            LOAD_SMALL_INT           0
+6:4-6:17            LOAD_COMMON_CONSTANT     7 (None)
+6:4-6:17            IMPORT_NAME              2 (sample + eager)
+6:4-6:17            STORE_FAST               0 (sample)
+6:4-6:17            LOAD_COMMON_CONSTANT     7 (None)
+6:4-6:17            RETURN_VALUE
+
+Disassembly of <code object C at 0xdeadbeef, file "<?>", line 8>:
+8:0-8:0             RESUME                   0
+8:0-8:0             LOAD_NAME                0 (__name__)
+8:0-8:0             STORE_NAME               1 (__module__)
+8:0-8:0             LOAD_CONST               0 ('C')
+8:0-8:0             STORE_NAME               2 (__qualname__)
+8:0-8:0             LOAD_SMALL_INT           8
+8:0-8:0             STORE_NAME               3 (__firstlineno__)
+
+9:4-9:29            LOAD_SMALL_INT           0
+9:4-9:29            LOAD_CONST               1 (('member',))
+9:4-9:29            IMPORT_NAME             18 (sample + eager)
+9:4-9:29            IMPORT_FROM              5 (member)
+9:4-9:29            STORE_NAME               5 (member)
+9:4-9:29            POP_TOP
+9:4-9:29            LOAD_CONST               2 (())
+9:4-9:29            STORE_NAME               6 (__static_attributes__)
+9:4-9:29            LOAD_COMMON_CONSTANT     7 (None)
+9:4-9:29            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__inlined_async_comprehension_end_async_for_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__inlined_async_comprehension_end_async_for_location.snap
new file mode 100644
index 00000000000..0e996da0912
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__inlined_async_comprehension_end_async_for_location.snap
@@ -0,0 +1,97 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nasync def f(it):\n    for i in it:\n        yield i\n\nasync def run_list():\n    return [i + 1 async for i in f([10, 20])]\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-3:15            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-3:15            MAKE_FUNCTION
+1:0-3:15            STORE_NAME               0 (f)
+
+5:0-6:45            LOAD_CONST               1 (<code object run_list at 0xdeadbeef, file "<?>", line 5>)
+5:0-6:45            MAKE_FUNCTION
+5:0-6:45            STORE_NAME               1 (run_list)
+5:0-6:45            LOAD_COMMON_CONSTANT     7 (None)
+5:0-6:45            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:?-1:?              RETURN_GENERATOR
+1:?-1:?              POP_TOP
+1:0-1:0      L1:     RESUME                   0
+
+2:13-2:15            LOAD_FAST                0 (it)
+2:13-2:15            GET_ITER                 0
+2:13-2:15    L2:     FOR_ITER                 9 (to L3)
+2:8-2:9              STORE_FAST               1 (i)
+
+3:14-3:15            LOAD_FAST_BORROW         1 (i)
+3:8-3:15             CALL_INTRINSIC_1         4 (INTRINSIC_ASYNC_GEN_WRAP)
+3:8-3:15             YIELD_VALUE              0
+3:8-3:15             RESUME                   9
+3:8-3:15             POP_TOP
+3:8-3:15             JUMP_BACKWARD           11 (to L2)
+
+2:13-2:15    L3:     END_FOR
+2:13-2:15            POP_ITER
+2:13-2:15            LOAD_COMMON_CONSTANT     7 (None)
+2:13-2:15            RETURN_VALUE
+
+  --         L4:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L4 -> L4 [0] lasti
+
+Disassembly of <code object run_list at 0xdeadbeef, file "<?>", line 5>:
+5:?-5:?               RETURN_GENERATOR
+5:?-5:?               POP_TOP
+5:0-5:0       L1:     RESUME                   0
+
+6:33-6:34             LOAD_GLOBAL              1 (f + NULL)
+6:36-6:38             LOAD_SMALL_INT          10
+6:40-6:42             LOAD_SMALL_INT          20
+6:35-6:43             BUILD_LIST               2
+6:33-6:44             CALL                     1
+6:11-6:45             LOAD_FAST_AND_CLEAR      0 (i)
+6:11-6:45             SWAP                     2
+6:11-6:45     L2:     BUILD_LIST               0
+6:11-6:45             SWAP                     2
+6:33-6:44             GET_AITER
+6:11-6:45     L3:     GET_ANEXT
+6:11-6:45             PUSH_NULL
+6:11-6:45             LOAD_COMMON_CONSTANT     7 (None)
+6:11-6:45     L4:     SEND                     4 (to L7)
+6:11-6:45     L5:     YIELD_VALUE              1
+6:11-6:45     L6:     RESUME                   3
+6:11-6:45             JUMP_BACKWARD_NO_INTERRUPT 6 (to L4)
+6:11-6:45     L7:     END_SEND
+6:28-6:29     L8:     STORE_FAST_LOAD_FAST     0 (i, i)
+6:16-6:17             LOAD_SMALL_INT           1
+6:12-6:17             BINARY_OP                0 (+)
+6:12-6:17             LIST_APPEND              2
+6:12-6:17             JUMP_BACKWARD           21 (to L3)
+6:11-6:45     L9:     CLEANUP_THROW
+6:11-6:45    L10:     JUMP_BACKWARD_NO_INTERRUPT 14 (to L7)
+6:11-6:45    L11:     END_ASYNC_FOR           15 (from L7)
+6:11-6:45    L12:     SWAP                     2
+6:11-6:45             STORE_FAST               0 (i)
+6:4-6:45              RETURN_VALUE
+
+  --         L13:     SWAP                     2
+  --                  POP_TOP
+
+6:11-6:45             SWAP                     2
+6:11-6:45             STORE_FAST               0 (i)
+6:11-6:45             RERAISE                  0
+
+  --         L14:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L14 [0] lasti
+  L2 to L3 -> L13 [2]
+  L3 to L5 -> L11 [3]
+  L5 to L6 -> L9 [6]
+  L6 to L8 -> L11 [3]
+  L8 to L9 -> L13 [2]
+  L9 to L10 -> L11 [3]
+  L11 to L12 -> L13 [2]
+  L12 to L14 -> L14 [0] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__inlined_comprehension_backedge_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__inlined_comprehension_backedge_location.snap
new file mode 100644
index 00000000000..9ab39805cc9
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__inlined_comprehension_backedge_location.snap
@@ -0,0 +1,92 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nasync def f(i):\n    return i\n\nasync def run_list():\n    return [s for c in [f(''), f('abc')] for s in await c]\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:12            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:12            MAKE_FUNCTION
+1:0-2:12            STORE_NAME               0 (f)
+
+4:0-5:58            LOAD_CONST               1 (<code object run_list at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:58            MAKE_FUNCTION
+4:0-5:58            STORE_NAME               1 (run_list)
+4:0-5:58            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:58            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:?-1:?              RETURN_GENERATOR
+1:?-1:?              POP_TOP
+1:0-1:0      L1:     RESUME                   0
+
+2:11-2:12            LOAD_FAST_BORROW         0 (i)
+2:4-2:12             RETURN_VALUE
+
+  --         L2:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L2 [0] lasti
+
+Disassembly of <code object run_list at 0xdeadbeef, file "<?>", line 4>:
+4:?-4:?               RETURN_GENERATOR
+4:?-4:?               POP_TOP
+4:0-4:0       L1:     RESUME                   0
+
+5:24-5:25             LOAD_GLOBAL              1 (f + NULL)
+5:26-5:28             LOAD_COMMON_CONSTANT     8 ('')
+5:24-5:29             CALL                     1
+5:31-5:32             LOAD_GLOBAL              1 (f + NULL)
+5:33-5:38             LOAD_CONST               1 ('abc')
+5:31-5:39             CALL                     1
+5:23-5:40             BUILD_LIST               2
+5:11-5:58             LOAD_FAST_AND_CLEAR      0 (c)
+5:11-5:58             LOAD_FAST_AND_CLEAR      1 (s)
+5:11-5:58             SWAP                     3
+5:11-5:58     L2:     BUILD_LIST               0
+5:11-5:58             SWAP                     2
+5:23-5:40             GET_ITER                 0
+5:23-5:40     L3:     FOR_ITER                23 (to L10)
+5:18-5:19             STORE_FAST_LOAD_FAST     0 (c, c)
+5:50-5:57             GET_AWAITABLE            0
+5:50-5:57             PUSH_NULL
+5:50-5:57             LOAD_COMMON_CONSTANT     7 (None)
+5:50-5:57     L4:     SEND                     4 (to L7)
+5:50-5:57     L5:     YIELD_VALUE              1
+5:50-5:57     L6:     RESUME                   3
+5:50-5:57             JUMP_BACKWARD_NO_INTERRUPT 6 (to L4)
+5:50-5:57     L7:     END_SEND
+5:50-5:57             GET_ITER                 0
+5:50-5:57     L8:     FOR_ITER                 4 (to L9)
+5:45-5:46             STORE_FAST_LOAD_FAST    17 (s, s)
+5:12-5:13             LIST_APPEND              5
+5:12-5:13             JUMP_BACKWARD            6 (to L8)
+5:50-5:57     L9:     END_FOR
+5:50-5:57             POP_ITER
+5:12-5:13             JUMP_BACKWARD           25 (to L3)
+5:23-5:40    L10:     END_FOR
+5:23-5:40             POP_ITER
+5:11-5:58    L11:     SWAP                     3
+5:11-5:58             STORE_FAST               1 (s)
+5:11-5:58             STORE_FAST               0 (c)
+5:4-5:58              RETURN_VALUE
+5:50-5:57    L12:     CLEANUP_THROW
+5:50-5:57    L13:     JUMP_BACKWARD_NO_INTERRUPT 21 (to L7)
+
+  --         L14:     SWAP                     2
+  --                  POP_TOP
+
+5:11-5:58             SWAP                     3
+5:11-5:58             STORE_FAST               1 (s)
+5:11-5:58             STORE_FAST               0 (c)
+5:11-5:58             RERAISE                  0
+
+  --         L15:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L15 [0] lasti
+  L2 to L5 -> L14 [3]
+  L5 to L6 -> L12 [8]
+  L6 to L11 -> L14 [3]
+  L11 to L12 -> L15 [0] lasti
+  L12 to L13 -> L14 [3]
+  L14 to L15 -> L15 [0] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__joined_string_literals_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__joined_string_literals_location.snap
new file mode 100644
index 00000000000..69582f4f61f
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__joined_string_literals_location.snap
@@ -0,0 +1,24 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(a):\n    return (\n        'x'\n        f'y{a}z'\n        'w'\n    )\n\"#,\ntrue)"
+---
+0:0-1:0            RESUME                   0
+
+1:0-6:5            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-6:5            MAKE_FUNCTION
+1:0-6:5            STORE_NAME               0 (f)
+1:0-6:5            LOAD_COMMON_CONSTANT     7 (None)
+1:0-6:5            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+3:8-4:11             LOAD_CONST               0 ('xy')
+
+4:12-4:13            LOAD_FAST_BORROW         0 (a)
+4:11-4:14            FORMAT_SIMPLE
+4:14-5:11            LOAD_CONST               1 ('zw')
+
+3:8-5:11             BUILD_STRING             3
+
+2:4-6:5              RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__lambda_dict_literal_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__lambda_dict_literal_location.snap
new file mode 100644
index 00000000000..11e587c10b0
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__lambda_dict_literal_location.snap
@@ -0,0 +1,29 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nf = lambda data: {'x': data}\ng = lambda i: {**i}\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:4-1:28            LOAD_CONST               0 (<code object <lambda> at 0xdeadbeef, file "<?>", line 1>)
+1:4-1:28            MAKE_FUNCTION
+1:0-1:1             STORE_NAME               0 (f)
+
+2:4-2:19            LOAD_CONST               1 (<code object <lambda> at 0xdeadbeef, file "<?>", line 2>)
+2:4-2:19            MAKE_FUNCTION
+2:0-2:1             STORE_NAME               1 (g)
+2:0-2:1             LOAD_COMMON_CONSTANT     7 (None)
+2:0-2:1             RETURN_VALUE
+
+Disassembly of <code object <lambda> at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+1:18-1:21            LOAD_CONST               0 ('x')
+1:23-1:27            LOAD_FAST_BORROW         0 (data)
+1:17-1:28            BUILD_MAP                1
+1:17-1:28            RETURN_VALUE
+
+Disassembly of <code object <lambda> at 0xdeadbeef, file "<?>", line 2>:
+2:0-2:0              RESUME                   0
+2:14-2:19            BUILD_MAP                0
+2:17-2:18            LOAD_FAST_BORROW         0 (i)
+2:14-2:19            DICT_UPDATE              1
+2:14-2:19            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__list_set_async_genexpr_calls.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__list_set_async_genexpr_calls.snap
new file mode 100644
index 00000000000..68e944983c8
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__list_set_async_genexpr_calls.snap
@@ -0,0 +1,129 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nasync def f(xs):\n    return list(x async for x in xs)\n\nasync def g(xs):\n    return set(x async for x in xs)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:36            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:36            MAKE_FUNCTION
+1:0-2:36            STORE_NAME               0 (f)
+
+4:0-5:35            LOAD_CONST               1 (<code object g at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:35            MAKE_FUNCTION
+4:0-5:35            STORE_NAME               1 (g)
+4:0-5:35            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:35            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:?-1:?              RETURN_GENERATOR
+1:?-1:?              POP_TOP
+1:0-1:0      L1:     RESUME                   0
+
+2:11-2:15            LOAD_GLOBAL              1 (list + NULL)
+2:15-2:36            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 2>)
+2:15-2:36            MAKE_FUNCTION
+2:33-2:35            LOAD_FAST_BORROW         0 (xs)
+2:15-2:36            CALL                     0
+2:11-2:36            CALL                     1
+2:4-2:36             RETURN_VALUE
+
+  --         L2:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L2 [0] lasti
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 2>:
+  --                  RESUME                   4
+
+2:33-2:35             LOAD_FAST_BORROW         0 (.0)
+2:33-2:35             GET_AITER
+2:?-2:?               RETURN_GENERATOR
+2:?-2:?               POP_TOP
+2:0-2:0       L1:     RESUME                   0
+2:15-2:36     L2:     GET_ANEXT
+2:15-2:36             PUSH_NULL
+2:15-2:36             LOAD_COMMON_CONSTANT     7 (None)
+2:15-2:36     L3:     SEND                     4 (to L6)
+2:15-2:36     L4:     YIELD_VALUE              1
+2:15-2:36     L5:     RESUME                   3
+2:15-2:36             JUMP_BACKWARD_NO_INTERRUPT 6 (to L3)
+2:15-2:36     L6:     END_SEND
+2:28-2:29     L7:     STORE_FAST_LOAD_FAST    17 (x, x)
+2:16-2:17             CALL_INTRINSIC_1         4 (INTRINSIC_ASYNC_GEN_WRAP)
+2:16-2:17             YIELD_VALUE              0
+2:16-2:17             RESUME                   9
+2:16-2:17             POP_TOP
+2:16-2:17             JUMP_BACKWARD           18 (to L2)
+2:15-2:36     L8:     CLEANUP_THROW
+2:15-2:36     L9:     JUMP_BACKWARD_NO_INTERRUPT 11 (to L6)
+2:15-2:36    L10:     END_ASYNC_FOR           12 (from L6)
+2:15-2:36             LOAD_COMMON_CONSTANT     7 (None)
+2:15-2:36             RETURN_VALUE
+
+  --         L11:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L11 [1] lasti
+  L2 to L4 -> L10 [1]
+  L4 to L5 -> L8 [4]
+  L5 to L7 -> L10 [1]
+  L7 to L8 -> L11 [1] lasti
+  L8 to L9 -> L10 [1]
+  L10 to L11 -> L11 [1] lasti
+
+Disassembly of <code object g at 0xdeadbeef, file "<?>", line 4>:
+4:?-4:?              RETURN_GENERATOR
+4:?-4:?              POP_TOP
+4:0-4:0      L1:     RESUME                   0
+
+5:11-5:14            LOAD_GLOBAL              1 (set + NULL)
+5:14-5:35            LOAD_CONST               0 (<code object <genexpr> at 0xdeadbeef, file "<?>", line 5>)
+5:14-5:35            MAKE_FUNCTION
+5:32-5:34            LOAD_FAST_BORROW         0 (xs)
+5:14-5:35            CALL                     0
+5:11-5:35            CALL                     1
+5:4-5:35             RETURN_VALUE
+
+  --         L2:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L2 [0] lasti
+
+Disassembly of <code object <genexpr> at 0xdeadbeef, file "<?>", line 5>:
+  --                  RESUME                   4
+
+5:32-5:34             LOAD_FAST_BORROW         0 (.0)
+5:32-5:34             GET_AITER
+5:?-5:?               RETURN_GENERATOR
+5:?-5:?               POP_TOP
+5:0-5:0       L1:     RESUME                   0
+5:14-5:35     L2:     GET_ANEXT
+5:14-5:35             PUSH_NULL
+5:14-5:35             LOAD_COMMON_CONSTANT     7 (None)
+5:14-5:35     L3:     SEND                     4 (to L6)
+5:14-5:35     L4:     YIELD_VALUE              1
+5:14-5:35     L5:     RESUME                   3
+5:14-5:35             JUMP_BACKWARD_NO_INTERRUPT 6 (to L3)
+5:14-5:35     L6:     END_SEND
+5:27-5:28     L7:     STORE_FAST_LOAD_FAST    17 (x, x)
+5:15-5:16             CALL_INTRINSIC_1         4 (INTRINSIC_ASYNC_GEN_WRAP)
+5:15-5:16             YIELD_VALUE              0
+5:15-5:16             RESUME                   9
+5:15-5:16             POP_TOP
+5:15-5:16             JUMP_BACKWARD           18 (to L2)
+5:14-5:35     L8:     CLEANUP_THROW
+5:14-5:35     L9:     JUMP_BACKWARD_NO_INTERRUPT 11 (to L6)
+5:14-5:35    L10:     END_ASYNC_FOR           12 (from L6)
+5:14-5:35             LOAD_COMMON_CONSTANT     7 (None)
+5:14-5:35             RETURN_VALUE
+
+  --         L11:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L11 [1] lasti
+  L2 to L4 -> L10 [1]
+  L4 to L5 -> L8 [4]
+  L5 to L7 -> L10 [1]
+  L7 to L8 -> L11 [1] lasti
+  L8 to L9 -> L10 [1]
+  L10 to L11 -> L11 [1] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__loop_return_cleanup.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__loop_return_cleanup.snap
new file mode 100644
index 00000000000..098a84a976b
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__loop_return_cleanup.snap
@@ -0,0 +1,74 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(xs):\n    for x in xs:\n        return x\n\nasync def g(xs):\n    async for x in xs:\n        return x\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-3:16            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-3:16            MAKE_FUNCTION
+1:0-3:16            STORE_NAME               0 (f)
+
+5:0-7:16            LOAD_CONST               1 (<code object g at 0xdeadbeef, file "<?>", line 5>)
+5:0-7:16            MAKE_FUNCTION
+5:0-7:16            STORE_NAME               1 (g)
+5:0-7:16            LOAD_COMMON_CONSTANT     7 (None)
+5:0-7:16            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:13-2:15            LOAD_FAST                0 (xs)
+2:13-2:15            GET_ITER                 0
+2:13-2:15            FOR_ITER                 6 (to L1)
+2:8-2:9              STORE_FAST               1 (x)
+
+3:15-3:16            LOAD_FAST_BORROW         1 (x)
+3:8-3:16             SWAP                     3
+3:8-3:16             POP_TOP
+3:8-3:16             POP_TOP
+3:8-3:16             RETURN_VALUE
+
+2:13-2:15    L1:     END_FOR
+2:13-2:15            POP_ITER
+2:13-2:15            LOAD_COMMON_CONSTANT     7 (None)
+2:13-2:15            RETURN_VALUE
+
+Disassembly of <code object g at 0xdeadbeef, file "<?>", line 5>:
+5:?-5:?               RETURN_GENERATOR
+5:?-5:?               POP_TOP
+5:0-5:0       L1:     RESUME                   0
+
+6:19-6:21             LOAD_FAST_BORROW         0 (xs)
+6:19-6:21             GET_AITER
+6:4-7:16      L2:     GET_ANEXT
+6:4-7:16              PUSH_NULL
+6:4-7:16              LOAD_COMMON_CONSTANT     7 (None)
+6:4-7:16      L3:     SEND                     4 (to L6)
+6:4-7:16      L4:     YIELD_VALUE              1
+6:4-7:16      L5:     RESUME                   3
+6:4-7:16              JUMP_BACKWARD_NO_INTERRUPT 6 (to L3)
+6:4-7:16      L6:     END_SEND
+6:4-7:16      L7:     NOT_TAKEN
+6:14-6:15             STORE_FAST               1 (x)
+
+7:15-7:16             LOAD_FAST_BORROW         1 (x)
+7:8-7:16              SWAP                     2
+7:8-7:16              POP_TOP
+7:8-7:16              RETURN_VALUE
+
+6:4-7:16      L8:     CLEANUP_THROW
+6:4-7:16      L9:     JUMP_BACKWARD_NO_INTERRUPT 9 (to L6)
+6:19-6:21    L10:     END_ASYNC_FOR           10 (from L6)
+6:19-6:21             LOAD_COMMON_CONSTANT     7 (None)
+6:19-6:21             RETURN_VALUE
+
+  --         L11:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                  RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L11 [0] lasti
+  L2 to L4 -> L10 [1]
+  L4 to L5 -> L8 [4]
+  L5 to L7 -> L10 [1]
+  L7 to L8 -> L11 [0] lasti
+  L8 to L9 -> L10 [1]
+  L10 to L11 -> L11 [0] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_class_scaffolding_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_class_scaffolding_location.snap
new file mode 100644
index 00000000000..ba6e6a937c3
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_class_scaffolding_location.snap
@@ -0,0 +1,39 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(x):\n    match x:\n        case bool(z):\n            y = 0\n    return y, z\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-5:15            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-5:15            MAKE_FUNCTION
+1:0-5:15            STORE_NAME               0 (f)
+1:0-5:15            LOAD_COMMON_CONSTANT     7 (None)
+1:0-5:15            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:10-2:11            LOAD_FAST_BORROW         0 (x)
+
+3:13-3:17            LOAD_GLOBAL              0 (bool)
+3:13-3:20            LOAD_CONST               0 (())
+3:13-3:20            MATCH_CLASS              1
+3:13-3:20            COPY                     1
+3:13-3:20            POP_JUMP_IF_NONE         9 (to L1)
+3:13-3:20            NOT_TAKEN
+3:13-3:20            UNPACK_SEQUENCE          1
+3:13-3:20            STORE_FAST               1 (z)
+
+4:16-4:17            LOAD_SMALL_INT           0
+4:12-4:13            STORE_FAST               2 (y)
+
+5:11-5:12            LOAD_FAST_BORROW_LOAD_FAST_BORROW 33 (y, z)
+5:11-5:15            BUILD_TUPLE              2
+5:4-5:15             RETURN_VALUE
+
+3:13-3:20    L1:     POP_TOP
+
+5:11-5:12            LOAD_FAST_CHECK          2 (y)
+5:14-5:15            LOAD_FAST_CHECK          1 (z)
+5:11-5:15            BUILD_TUPLE              2
+5:4-5:15             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_mapping_keys_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_mapping_keys_location.snap
new file mode 100644
index 00000000000..cd45a759947
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_mapping_keys_location.snap
@@ -0,0 +1,60 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(self):\n    x = {}\n    y = None\n    match x:\n        case {0: 0}:\n            y = 0\n    self.assertIs(y, None)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-7:26            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-7:26            MAKE_FUNCTION
+1:0-7:26            STORE_NAME               0 (f)
+1:0-7:26            LOAD_COMMON_CONSTANT     7 (None)
+1:0-7:26            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:8-2:10             BUILD_MAP                0
+2:4-2:5              STORE_FAST               1 (x)
+
+3:8-3:12             LOAD_COMMON_CONSTANT     7 (None)
+3:4-3:5              STORE_FAST               2 (y)
+
+4:10-4:11            LOAD_FAST                1 (x)
+
+5:13-5:19            MATCH_MAPPING
+5:13-5:19            POP_JUMP_IF_FALSE       29 (to L3)
+5:13-5:19            NOT_TAKEN
+5:13-5:19            GET_LEN
+5:13-5:19            LOAD_SMALL_INT           1
+5:13-5:19            COMPARE_OP             172 (>=)
+5:13-5:19            POP_JUMP_IF_FALSE       22 (to L3)
+5:13-5:19            NOT_TAKEN
+5:13-5:19            LOAD_CONST               1 ((0,))
+5:13-5:19            MATCH_KEYS
+5:13-5:19            COPY                     1
+5:13-5:19            POP_JUMP_IF_NONE        14 (to L1)
+5:13-5:19            NOT_TAKEN
+5:13-5:19            UNPACK_SEQUENCE          1
+5:17-5:18            LOAD_SMALL_INT           0
+5:17-5:18            COMPARE_OP              88 (bool(==))
+5:17-5:18            POP_JUMP_IF_FALSE        7 (to L2)
+5:17-5:18            NOT_TAKEN
+5:13-5:19            POP_TOP
+5:13-5:19            POP_TOP
+
+6:16-6:17            LOAD_SMALL_INT           0
+6:12-6:13            STORE_FAST               2 (y)
+6:12-6:13            JUMP_FORWARD             3 (to L4)
+
+5:13-5:19    L1:     POP_TOP
+5:13-5:19    L2:     POP_TOP
+5:13-5:19    L3:     POP_TOP
+
+7:4-7:8      L4:     LOAD_FAST_BORROW         0 (self)
+7:4-7:17             LOAD_ATTR                1 (assertIs + NULL|self)
+7:18-7:19            LOAD_FAST_BORROW         2 (y)
+7:21-7:25            LOAD_COMMON_CONSTANT     7 (None)
+7:4-7:26             CALL                     2
+7:4-7:26             POP_TOP
+7:4-7:26             LOAD_COMMON_CONSTANT     7 (None)
+7:4-7:26             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_or_alternative_locations.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_or_alternative_locations.snap
new file mode 100644
index 00000000000..e0b03b2a2dd
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_or_alternative_locations.snap
@@ -0,0 +1,56 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f():\n    x = False\n    match 0:\n        case 0 | 1 | 2 | 3:\n            x = True\n    return x\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-6:12            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-6:12            MAKE_FUNCTION
+1:0-6:12            STORE_NAME               0 (f)
+1:0-6:12            LOAD_COMMON_CONSTANT     7 (None)
+1:0-6:12            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:8-2:13             LOAD_COMMON_CONSTANT    10 (False)
+2:4-2:5              STORE_FAST               0 (x)
+
+3:10-3:11            LOAD_SMALL_INT           0
+
+4:13-4:14            COPY                     1
+4:13-4:14            LOAD_SMALL_INT           0
+4:13-4:14            COMPARE_OP              88 (bool(==))
+4:13-4:14            POP_JUMP_IF_FALSE        2 (to L1)
+4:13-4:14            NOT_TAKEN
+4:13-4:14            JUMP_FORWARD            27 (to L5)
+4:17-4:18    L1:     COPY                     1
+4:17-4:18            LOAD_SMALL_INT           1
+4:17-4:18            COMPARE_OP              88 (bool(==))
+4:17-4:18            POP_JUMP_IF_FALSE        2 (to L2)
+4:17-4:18            NOT_TAKEN
+4:17-4:18            JUMP_FORWARD            19 (to L5)
+4:21-4:22    L2:     COPY                     1
+4:21-4:22            LOAD_SMALL_INT           2
+4:21-4:22            COMPARE_OP              88 (bool(==))
+4:21-4:22            POP_JUMP_IF_FALSE        2 (to L3)
+4:21-4:22            NOT_TAKEN
+4:21-4:22            JUMP_FORWARD            11 (to L5)
+4:25-4:26    L3:     COPY                     1
+4:25-4:26            LOAD_SMALL_INT           3
+4:25-4:26            COMPARE_OP              88 (bool(==))
+4:25-4:26            POP_JUMP_IF_FALSE        2 (to L4)
+4:25-4:26            NOT_TAKEN
+4:25-4:26            JUMP_FORWARD             3 (to L5)
+4:13-4:26    L4:     POP_TOP
+
+6:11-6:12            LOAD_FAST_BORROW         0 (x)
+6:4-6:12             RETURN_VALUE
+
+4:13-4:26    L5:     POP_TOP
+
+5:16-5:20            LOAD_COMMON_CONSTANT     9 (True)
+5:12-5:13            STORE_FAST               0 (x)
+
+6:11-6:12            LOAD_FAST_BORROW         0 (x)
+6:4-6:12             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_success_jump_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_success_jump_location.snap
new file mode 100644
index 00000000000..b76ff06acd8
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__match_success_jump_location.snap
@@ -0,0 +1,44 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(self):\n    match 0:\n        case 0:\n            x = True\n        case 0:\n            x = False\n    self.assertIs(x, True)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-7:26            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-7:26            MAKE_FUNCTION
+1:0-7:26            STORE_NAME               0 (f)
+1:0-7:26            LOAD_COMMON_CONSTANT     7 (None)
+1:0-7:26            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:10-2:11            LOAD_SMALL_INT           0
+
+3:13-3:14            COPY                     1
+3:13-3:14            LOAD_SMALL_INT           0
+3:13-3:14            COMPARE_OP              88 (bool(==))
+3:13-3:14            POP_JUMP_IF_FALSE        5 (to L1)
+3:13-3:14            NOT_TAKEN
+
+4:16-4:20            POP_TOP
+4:16-4:20            LOAD_COMMON_CONSTANT     9 (True)
+4:12-4:13            STORE_FAST               1 (x)
+4:12-4:13            JUMP_FORWARD             8 (to L2)
+
+5:13-5:14    L1:     LOAD_SMALL_INT           0
+5:13-5:14            COMPARE_OP              88 (bool(==))
+5:13-5:14            POP_JUMP_IF_FALSE        3 (to L2)
+5:13-5:14            NOT_TAKEN
+
+6:16-6:21            LOAD_COMMON_CONSTANT    10 (False)
+6:12-6:13            STORE_FAST               1 (x)
+
+7:4-7:8      L2:     LOAD_FAST_BORROW         0 (self)
+7:4-7:17             LOAD_ATTR                1 (assertIs + NULL|self)
+7:18-7:19            LOAD_FAST_CHECK          1 (x)
+7:21-7:25            LOAD_COMMON_CONSTANT     9 (True)
+7:4-7:26             CALL                     2
+7:4-7:26             POP_TOP
+7:4-7:26             LOAD_COMMON_CONSTANT     7 (None)
+7:4-7:26             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__module_deferred_annotations_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__module_deferred_annotations_location.snap
new file mode 100644
index 00000000000..c266a49f7ad
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__module_deferred_annotations_location.snap
@@ -0,0 +1,63 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\nimport os\nX: int\nY: str\n\"#, true)"
+---
+  --               MAKE_CELL                0 (__conditional_annotations__)
+
+0:0-1:0            RESUME                   0
+
+1:0-1:9            LOAD_CONST               1 (<code object __annotate__ at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:9            MAKE_FUNCTION
+1:0-1:9            STORE_NAME               2 (__annotate__)
+1:0-1:9            BUILD_SET                0
+1:0-1:9            STORE_NAME               0 (__conditional_annotations__)
+1:0-1:9            LOAD_SMALL_INT           0
+1:0-1:9            LOAD_COMMON_CONSTANT     7 (None)
+1:0-1:9            IMPORT_NAME              4 (os)
+1:0-1:9            STORE_NAME               1 (os)
+
+2:0-2:6            LOAD_NAME                0 (__conditional_annotations__)
+2:0-2:6            LOAD_SMALL_INT           0
+2:0-2:6            SET_ADD                  1
+2:0-2:6            POP_TOP
+
+3:0-3:6            LOAD_NAME                0 (__conditional_annotations__)
+3:0-3:6            LOAD_SMALL_INT           1
+3:0-3:6            SET_ADD                  1
+3:0-3:6            POP_TOP
+3:0-3:6            LOAD_COMMON_CONSTANT     7 (None)
+3:0-3:6            RETURN_VALUE
+
+Disassembly of <code object __annotate__ at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0            RESUME                   0
+1:0-1:9            LOAD_FAST_BORROW         0 (format)
+1:0-1:9            LOAD_SMALL_INT           2
+1:0-1:9            COMPARE_OP             132 (>)
+1:0-1:9            POP_JUMP_IF_FALSE        3 (to L1)
+1:0-1:9            NOT_TAKEN
+1:0-1:9            LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+1:0-1:9            RAISE_VARARGS            1
+1:0-1:9    L1:     BUILD_MAP                0
+
+2:0-2:6            LOAD_SMALL_INT           0
+2:0-2:6            LOAD_GLOBAL              0 (__conditional_annotations__)
+2:0-2:6            CONTAINS_OP              0 (in)
+2:0-2:6            POP_JUMP_IF_FALSE       10 (to L2)
+2:0-2:6            NOT_TAKEN
+2:3-2:6            LOAD_GLOBAL              2 (int)
+2:0-2:6            COPY                     2
+2:0-2:6            LOAD_CONST               1 ('X')
+
+1:0-1:9            STORE_SUBSCR
+
+3:0-3:6    L2:     LOAD_SMALL_INT           1
+3:0-3:6            LOAD_GLOBAL              0 (__conditional_annotations__)
+3:0-3:6            CONTAINS_OP              0 (in)
+3:0-3:6            POP_JUMP_IF_FALSE       10 (to L3)
+3:0-3:6            NOT_TAKEN
+3:3-3:6            LOAD_GLOBAL              4 (str)
+3:0-3:6            COPY                     2
+3:0-3:6            LOAD_CONST               2 ('Y')
+
+1:0-1:9            STORE_SUBSCR
+1:0-1:9    L3:     RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__module_docstring_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__module_docstring_location.snap
new file mode 100644
index 00000000000..20daf83cdee
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__module_docstring_location.snap
@@ -0,0 +1,13 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\n\"doc\"\nx = 1\n\"#, true)"
+---
+0:0-1:0            RESUME                   0
+
+1:0-1:5            LOAD_CONST               0 ('doc')
+1:0-1:5            STORE_NAME               0 (__doc__)
+
+2:4-2:5            LOAD_SMALL_INT           1
+2:0-2:1            STORE_NAME               1 (x)
+2:0-2:1            LOAD_COMMON_CONSTANT     7 (None)
+2:0-2:1            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__namedexpr_copy_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__namedexpr_copy_location.snap
new file mode 100644
index 00000000000..7ea7e2d942a
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__namedexpr_copy_location.snap
@@ -0,0 +1,40 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef outer():\n    a = 10\n    def spam():\n        nonlocal a\n        (a := 20)\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-5:17            LOAD_CONST               0 (<code object outer at 0xdeadbeef, file "<?>", line 1>)
+1:0-5:17            MAKE_FUNCTION
+1:0-5:17            STORE_NAME               0 (outer)
+1:0-5:17            LOAD_COMMON_CONSTANT     7 (None)
+1:0-5:17            RETURN_VALUE
+
+Disassembly of <code object outer at 0xdeadbeef, file "<?>", line 1>:
+  --                MAKE_CELL                1 (a)
+
+1:0-1:0             RESUME                   0
+
+2:8-2:10            LOAD_SMALL_INT          10
+2:4-2:5             STORE_DEREF              1 (a)
+
+3:4-5:17            LOAD_FAST_BORROW         1 (a)
+3:4-5:17            BUILD_TUPLE              1
+3:4-5:17            LOAD_CONST               1 (<code object spam at 0xdeadbeef, file "<?>", line 3>)
+3:4-5:17            MAKE_FUNCTION
+3:4-5:17            SET_FUNCTION_ATTRIBUTE   8 (closure)
+3:4-5:17            STORE_FAST               0 (spam)
+3:4-5:17            LOAD_COMMON_CONSTANT     7 (None)
+3:4-5:17            RETURN_VALUE
+
+Disassembly of <code object spam at 0xdeadbeef, file "<?>", line 3>:
+  --                 COPY_FREE_VARS           1
+
+3:0-3:0              RESUME                   0
+
+5:14-5:16            LOAD_SMALL_INT          20
+5:9-5:16             COPY                     1
+5:9-5:10             STORE_DEREF              0 (a)
+5:9-5:10             POP_TOP
+5:9-5:10             LOAD_COMMON_CONSTANT     7 (None)
+5:9-5:10             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__nested_bool_op.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__nested_bool_op.snap
index 00eeb277455..3278d9a7bad 100644
--- a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__nested_bool_op.snap
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__nested_bool_op.snap
@@ -13,13 +13,13 @@ expression: "dis(r#\"\nx = Test() and False or False\n\"#)"
               POP_JUMP_IF_FALSE       11 (to L1)
               NOT_TAKEN
               POP_TOP
-              LOAD_CONST               0 (False)
+              LOAD_COMMON_CONSTANT    10 (False)
               COPY                     1
               TO_BOOL
               POP_JUMP_IF_TRUE         3 (to L2)
               NOT_TAKEN
       L1:     POP_TOP
-              LOAD_CONST               0 (False)
+              LOAD_COMMON_CONSTANT    10 (False)
       L2:     STORE_NAME               1 (x)
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__nested_double_async_with.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__nested_double_async_with.snap
index 1c4b2ca9469..692ad6dc6ca 100644
--- a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__nested_double_async_with.snap
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__nested_double_async_with.snap
@@ -8,7 +8,7 @@ expression: "dis(r#\"\nasync def test():\n    for stop_exc in (StopIteration('sp
   1           LOAD_CONST               0 (<code object test at 0xdeadbeef, file "<?>", line 1>)
               MAKE_FUNCTION
               STORE_NAME               0 (test)
-              LOAD_CONST               1 (None)
+              LOAD_COMMON_CONSTANT     7 (None)
               RETURN_VALUE
 
 Disassembly of <code object test at 0xdeadbeef, file "<?>", line 1>:
@@ -23,8 +23,8 @@ Disassembly of <code object test at 0xdeadbeef, file "<?>", line 1>:
                 LOAD_CONST               1 ('ham')
                 CALL                     1
                 BUILD_TUPLE              2
-                GET_ITER
-        L2:     FOR_ITER                71 (to L11)
+                GET_ITER                 0
+        L2:     FOR_ITER                73 (to L11)
                 STORE_FAST               0 (stop_exc)
 
    3            LOAD_GLOBAL              4 (self)
@@ -53,11 +53,12 @@ Disassembly of <code object test at 0xdeadbeef, file "<?>", line 1>:
                 LOAD_SPECIAL             2 (__aenter__)
                 CALL                     0
                 GET_AWAITABLE            1
-                LOAD_CONST               3 (None)
-        L6:     SEND                     3 (to L9)
+                PUSH_NULL
+                LOAD_COMMON_CONSTANT     7 (None)
+        L6:     SEND                     4 (to L9)
         L7:     YIELD_VALUE              1
         L8:     RESUME                   3
-                JUMP_BACKWARD_NO_INTERRUPT 5 (to L6)
+                JUMP_BACKWARD_NO_INTERRUPT 6 (to L6)
         L9:     END_SEND
        L10:     POP_TOP
 
@@ -66,7 +67,7 @@ Disassembly of <code object test at 0xdeadbeef, file "<?>", line 1>:
 
    2   L11:     END_FOR
                 POP_ITER
-                LOAD_CONST               3 (None)
+                LOAD_COMMON_CONSTANT     7 (None)
                 RETURN_VALUE
 
    5   L12:     CLEANUP_THROW
@@ -74,11 +75,12 @@ Disassembly of <code object test at 0xdeadbeef, file "<?>", line 1>:
        L14:     PUSH_EXC_INFO
                 WITH_EXCEPT_START
                 GET_AWAITABLE            2
-                LOAD_CONST               3 (None)
-       L15:     SEND                     4 (to L19)
+                PUSH_NULL
+                LOAD_COMMON_CONSTANT     7 (None)
+       L15:     SEND                     5 (to L19)
        L16:     YIELD_VALUE              1
        L17:     RESUME                   3
-                JUMP_BACKWARD_NO_INTERRUPT 5 (to L15)
+                JUMP_BACKWARD_NO_INTERRUPT 6 (to L15)
        L18:     CLEANUP_THROW
        L19:     END_SEND
                 TO_BOOL
@@ -102,86 +104,88 @@ Disassembly of <code object test at 0xdeadbeef, file "<?>", line 1>:
                 LOAD_ATTR               13 (fail + NULL|self)
                 LOAD_FAST                0 (stop_exc)
                 FORMAT_SIMPLE
-                LOAD_CONST               4 (' was suppressed')
+                LOAD_CONST               3 (' was suppressed')
                 BUILD_STRING             2
                 CALL                     1
                 POP_TOP
-                JUMP_FORWARD            45 (to L33)
+                JUMP_FORWARD            45 (to L35)
 
   --   L27:     PUSH_EXC_INFO
 
    7            LOAD_GLOBAL             14 (Exception)
                 CHECK_EXC_MATCH
-                POP_JUMP_IF_FALSE       32 (to L31)
-                NOT_TAKEN
-                STORE_FAST               1 (ex)
+                POP_JUMP_IF_FALSE       32 (to L33)
+       L28:     NOT_TAKEN
+       L29:     STORE_FAST               1 (ex)
 
-   8   L28:     LOAD_GLOBAL              4 (self)
+   8   L30:     LOAD_GLOBAL              4 (self)
                 LOAD_ATTR               17 (assertIs + NULL|self)
                 LOAD_FAST_LOAD_FAST     16 (ex, stop_exc)
                 CALL                     2
                 POP_TOP
-       L29:     POP_EXCEPT
-                LOAD_CONST               3 (None)
+       L31:     POP_EXCEPT
+                LOAD_COMMON_CONSTANT     7 (None)
                 STORE_FAST               1 (ex)
                 DELETE_FAST              1 (ex)
-                JUMP_FORWARD             8 (to L33)
+                JUMP_FORWARD             8 (to L35)
 
-  --   L30:     LOAD_CONST               3 (None)
+  --   L32:     LOAD_COMMON_CONSTANT     7 (None)
                 STORE_FAST               1 (ex)
                 DELETE_FAST              1 (ex)
                 RERAISE                  1
 
-   7   L31:     RERAISE                  0
+   7   L33:     RERAISE                  0
 
-  --   L32:     COPY                     3
+  --   L34:     COPY                     3
                 POP_EXCEPT
                 RERAISE                  1
 
-   3   L33:     LOAD_CONST               3 (None)
-                LOAD_CONST               3 (None)
-                LOAD_CONST               3 (None)
+   3   L35:     LOAD_COMMON_CONSTANT     7 (None)
+                LOAD_COMMON_CONSTANT     7 (None)
+                LOAD_COMMON_CONSTANT     7 (None)
                 CALL                     3
                 POP_TOP
-                JUMP_BACKWARD          188 (to L2)
-       L34:     PUSH_EXC_INFO
+                JUMP_BACKWARD          192 (to L2)
+       L36:     PUSH_EXC_INFO
                 WITH_EXCEPT_START
                 TO_BOOL
-                POP_JUMP_IF_TRUE         2 (to L35)
-                NOT_TAKEN
-                RERAISE                  2
-       L35:     POP_TOP
-       L36:     POP_EXCEPT
+                POP_JUMP_IF_TRUE         2 (to L39)
+       L37:     NOT_TAKEN
+       L38:     RERAISE                  2
+       L39:     POP_TOP
+       L40:     POP_EXCEPT
                 POP_TOP
                 POP_TOP
                 POP_TOP
-                JUMP_BACKWARD          205 (to L2)
+                JUMP_BACKWARD          209 (to L2)
 
-  --   L37:     COPY                     3
+  --   L41:     COPY                     3
                 POP_EXCEPT
                 RERAISE                  1
-       L38:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+       L42:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
                 RERAISE                  1
 ExceptionTable:
-  L1 to L3 -> L38 [0] lasti
-  L3 to L4 -> L34 [3] lasti
-  L5 to L7 -> L27 [3]
-  L7 to L8 -> L12 [7]
-  L8 to L10 -> L27 [3]
-  L10 to L11 -> L14 [5] lasti
-  L11 to L12 -> L38 [0] lasti
-  L12 to L13 -> L27 [3]
-  L14 to L16 -> L24 [7] lasti
-  L16 to L17 -> L18 [10]
-  L17 to L20 -> L24 [7] lasti
-  L21 to L23 -> L24 [7] lasti
-  L23 to L25 -> L27 [3]
-  L26 to L27 -> L34 [3] lasti
-  L27 to L28 -> L32 [4] lasti
-  L28 to L29 -> L30 [4] lasti
-  L29 to L30 -> L34 [3] lasti
-  L30 to L32 -> L32 [4] lasti
-  L32 to L33 -> L34 [3] lasti
-  L33 to L34 -> L38 [0] lasti
-  L34 to L36 -> L37 [5] lasti
-  L36 to L38 -> L38 [0] lasti
+  L1 to L3 -> L42 [0] lasti
+  L3 to L4 -> L36 [4] lasti
+  L5 to L7 -> L27 [4]
+  L7 to L8 -> L12 [9]
+  L8 to L10 -> L27 [4]
+  L10 to L11 -> L14 [6] lasti
+  L11 to L12 -> L42 [0] lasti
+  L12 to L13 -> L27 [4]
+  L14 to L16 -> L24 [8] lasti
+  L16 to L17 -> L18 [12]
+  L17 to L20 -> L24 [8] lasti
+  L21 to L23 -> L24 [8] lasti
+  L23 to L25 -> L27 [4]
+  L26 to L27 -> L36 [4] lasti
+  L27 to L28 -> L34 [5] lasti
+  L29 to L30 -> L34 [5] lasti
+  L30 to L31 -> L32 [5] lasti
+  L31 to L32 -> L36 [4] lasti
+  L32 to L34 -> L34 [5] lasti
+  L34 to L35 -> L36 [4] lasti
+  L35 to L36 -> L42 [0] lasti
+  L36 to L37 -> L41 [6] lasti
+  L38 to L40 -> L41 [6] lasti
+  L40 to L42 -> L42 [0] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__not_chained_compare_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__not_chained_compare_location.snap
new file mode 100644
index 00000000000..32292e60cef
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__not_chained_compare_location.snap
@@ -0,0 +1,35 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(c):\n    return not (b\" \" <= c <= b\"~\")\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:34            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:34            MAKE_FUNCTION
+1:0-2:34            STORE_NAME               0 (f)
+1:0-2:34            LOAD_COMMON_CONSTANT     7 (None)
+1:0-2:34            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:16-2:20            LOAD_CONST               0 (b' ')
+2:24-2:25            LOAD_FAST                0 (c)
+2:16-2:33            SWAP                     2
+2:16-2:33            COPY                     2
+2:16-2:33            COMPARE_OP              42 (<=)
+2:16-2:33            COPY                     1
+2:16-2:33            TO_BOOL
+2:16-2:33            POP_JUMP_IF_FALSE       11 (to L1)
+2:16-2:33            NOT_TAKEN
+2:16-2:33            POP_TOP
+2:29-2:33            LOAD_CONST               1 (b'~')
+2:16-2:33            COMPARE_OP              42 (<=)
+2:11-2:34            TO_BOOL
+2:11-2:34            UNARY_NOT
+2:4-2:34             RETURN_VALUE
+2:16-2:33    L1:     SWAP                     2
+2:16-2:33            POP_TOP
+2:11-2:34            TO_BOOL
+2:11-2:34            UNARY_NOT
+2:4-2:34             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__not_compare_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__not_compare_location.snap
new file mode 100644
index 00000000000..5b24334db26
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__not_compare_location.snap
@@ -0,0 +1,19 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(self, other):\n    return not self == other\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:28            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:28            MAKE_FUNCTION
+1:0-2:28            STORE_NAME               0 (f)
+1:0-2:28            LOAD_COMMON_CONSTANT     7 (None)
+1:0-2:28            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:15-2:19            LOAD_FAST_BORROW_LOAD_FAST_BORROW 1 (self, other)
+2:11-2:28            COMPARE_OP              88 (bool(==))
+2:11-2:28            UNARY_NOT
+2:4-2:28             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__redundant_nop_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__redundant_nop_location.snap
new file mode 100644
index 00000000000..43fbde70607
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__redundant_nop_location.snap
@@ -0,0 +1,65 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(x, y, z):\n    while x:\n        if y:\n            pass\n        elif z:\n            if y < 0:\n                return y\n            if z:\n                y = y + 1\n        elif y:\n            return 1\n    return -1\n\"#,\ntrue)"
+---
+0:0-1:0              RESUME                   0
+
+1:0-12:13            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-12:13            MAKE_FUNCTION
+1:0-12:13            STORE_NAME               0 (f)
+1:0-12:13            LOAD_COMMON_CONSTANT     7 (None)
+1:0-12:13            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0                RESUME                   0
+
+2:10-2:11      L1:     LOAD_FAST_BORROW         0 (x)
+2:10-2:11              TO_BOOL
+2:10-2:11              POP_JUMP_IF_FALSE       61 (to L7)
+2:10-2:11              NOT_TAKEN
+
+3:11-3:12              LOAD_FAST_BORROW         1 (y)
+3:11-3:12              TO_BOOL
+3:11-3:12              POP_JUMP_IF_FALSE        3 (to L2)
+3:11-3:12              NOT_TAKEN
+
+4:12-4:16              JUMP_BACKWARD           18 (to L1)
+
+5:13-5:14      L2:     LOAD_FAST_BORROW         2 (z)
+5:13-5:14              TO_BOOL
+5:13-5:14              POP_JUMP_IF_FALSE       31 (to L5)
+5:13-5:14              NOT_TAKEN
+
+6:15-6:16              LOAD_FAST_BORROW         1 (y)
+6:19-6:20              LOAD_SMALL_INT           0
+6:15-6:20              COMPARE_OP              18 (bool(<))
+6:15-6:20              POP_JUMP_IF_FALSE        3 (to L3)
+6:15-6:20              NOT_TAKEN
+
+7:23-7:24              LOAD_FAST_BORROW         1 (y)
+7:16-7:24              RETURN_VALUE
+
+8:15-8:16      L3:     LOAD_FAST_BORROW         2 (z)
+8:15-8:16              TO_BOOL
+8:15-8:16              POP_JUMP_IF_FALSE       12 (to L4)
+8:15-8:16              NOT_TAKEN
+
+9:20-9:21              LOAD_FAST_BORROW         1 (y)
+9:24-9:25              LOAD_SMALL_INT           1
+9:20-9:25              BINARY_OP                0 (+)
+9:16-9:17              STORE_FAST               1 (y)
+9:16-9:17              JUMP_BACKWARD           54 (to L1)
+
+8:15-8:16      L4:     JUMP_BACKWARD           56 (to L1)
+
+10:13-10:14    L5:     LOAD_FAST_BORROW         1 (y)
+10:13-10:14            TO_BOOL
+10:13-10:14            POP_JUMP_IF_TRUE         3 (to L6)
+10:13-10:14            NOT_TAKEN
+10:13-10:14            JUMP_BACKWARD           66 (to L1)
+
+11:19-11:20    L6:     LOAD_SMALL_INT           1
+11:19-11:20            RETURN_VALUE
+
+12:11-12:13    L7:     LOAD_COMMON_CONSTANT    11 (-1)
+12:4-12:13             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__starred_arg_annotation_unpack_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__starred_arg_annotation_unpack_location.snap
new file mode 100644
index 00000000000..4f82d8e7a10
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__starred_arg_annotation_unpack_location.snap
@@ -0,0 +1,34 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(*args: *Ts): pass\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-1:23            LOAD_CONST               0 (<code object __annotate__ at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:23            MAKE_FUNCTION
+1:0-1:23            LOAD_CONST               1 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:23            MAKE_FUNCTION
+1:0-1:23            SET_FUNCTION_ATTRIBUTE  16 (annotate)
+1:0-1:23            STORE_NAME               0 (f)
+1:0-1:23            LOAD_COMMON_CONSTANT     7 (None)
+1:0-1:23            RETURN_VALUE
+
+Disassembly of <code object __annotate__ at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+1:0-1:23             LOAD_FAST_BORROW         0 (format)
+1:0-1:23             LOAD_SMALL_INT           2
+1:0-1:23             COMPARE_OP             132 (>)
+1:0-1:23             POP_JUMP_IF_FALSE        3 (to L1)
+1:0-1:23             NOT_TAKEN
+1:0-1:23             LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+1:0-1:23             RAISE_VARARGS            1
+1:0-1:23     L1:     LOAD_CONST               1 ('args')
+1:14-1:16            LOAD_GLOBAL              0 (Ts)
+1:0-1:23             UNPACK_SEQUENCE          1
+1:0-1:23             BUILD_MAP                1
+1:0-1:23             RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+1:19-1:23            LOAD_COMMON_CONSTANT     7 (None)
+1:19-1:23            RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__static_swap_implicit_return_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__static_swap_implicit_return_location.snap
new file mode 100644
index 00000000000..33c4cade544
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__static_swap_implicit_return_location.snap
@@ -0,0 +1,22 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(a, b):\n    a, b = a, b\n    b, a = a, b\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-3:15            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-3:15            MAKE_FUNCTION
+1:0-3:15            STORE_NAME               0 (f)
+1:0-3:15            LOAD_COMMON_CONSTANT     7 (None)
+1:0-3:15            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:12            LOAD_FAST_LOAD_FAST      1 (a, b)
+2:7-2:8              STORE_FAST_STORE_FAST   16 (b, a)
+
+3:11-3:12            LOAD_FAST_LOAD_FAST      1 (a, b)
+3:7-3:8              STORE_FAST_STORE_FAST    1 (a, b)
+3:7-3:8              LOAD_COMMON_CONSTANT     7 (None)
+3:7-3:8              RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__taken_constant_boolop_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__taken_constant_boolop_location.snap
new file mode 100644
index 00000000000..57ce5871085
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__taken_constant_boolop_location.snap
@@ -0,0 +1,27 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef and_false(x):\n    return False and x\n\ndef or_true(x):\n    return True or x\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:22            LOAD_CONST               0 (<code object and_false at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:22            MAKE_FUNCTION
+1:0-2:22            STORE_NAME               0 (and_false)
+
+4:0-5:20            LOAD_CONST               1 (<code object or_true at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:20            MAKE_FUNCTION
+4:0-5:20            STORE_NAME               1 (or_true)
+4:0-5:20            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:20            RETURN_VALUE
+
+Disassembly of <code object and_false at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:11-2:16            LOAD_COMMON_CONSTANT    10 (False)
+2:4-2:22             RETURN_VALUE
+
+Disassembly of <code object or_true at 0xdeadbeef, file "<?>", line 4>:
+4:0-4:0              RESUME                   0
+
+5:11-5:15            LOAD_COMMON_CONSTANT     9 (True)
+5:4-5:20             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__try_finally_exception_scaffolding_location.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__try_finally_exception_scaffolding_location.snap
new file mode 100644
index 00000000000..68303704059
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__try_finally_exception_scaffolding_location.snap
@@ -0,0 +1,46 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(self, node):\n    self.flag = True\n    try:\n        self.body(node)\n    finally:\n        self.flag = False\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-6:25            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-6:25            MAKE_FUNCTION
+1:0-6:25            STORE_NAME               0 (f)
+1:0-6:25            LOAD_COMMON_CONSTANT     7 (None)
+1:0-6:25            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:16-2:20            LOAD_COMMON_CONSTANT     9 (True)
+2:4-2:8              LOAD_FAST_BORROW         0 (self)
+2:4-2:13             STORE_ATTR               0 (flag)
+
+3:4-6:25             NOP
+
+4:8-4:12     L1:     LOAD_FAST_BORROW         0 (self)
+4:8-4:17             LOAD_ATTR                3 (body + NULL|self)
+4:18-4:22            LOAD_FAST_BORROW         1 (node)
+4:8-4:23             CALL                     1
+4:8-4:23             POP_TOP
+
+6:20-6:25    L2:     LOAD_COMMON_CONSTANT    10 (False)
+6:8-6:12             LOAD_FAST_BORROW         0 (self)
+6:8-6:17             STORE_ATTR               0 (flag)
+6:8-6:17             LOAD_COMMON_CONSTANT     7 (None)
+6:8-6:17             RETURN_VALUE
+
+  --         L3:     PUSH_EXC_INFO
+
+6:20-6:25            LOAD_COMMON_CONSTANT    10 (False)
+6:8-6:12             LOAD_FAST                0 (self)
+6:8-6:17             STORE_ATTR               0 (flag)
+6:8-6:17             RERAISE                  0
+
+  --         L4:     COPY                     3
+  --                 POP_EXCEPT
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L3 [0]
+  L3 to L4 -> L4 [1] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__type_param_scope_locations.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__type_param_scope_locations.snap
new file mode 100644
index 00000000000..9f5ae9dee3e
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__type_param_scope_locations.snap
@@ -0,0 +1,66 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ntype BoundGenericAlias[X: int] = set[X]\n\"#, true)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-1:39            LOAD_CONST               0 (<code object <generic parameters of BoundGenericAlias> at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:39            MAKE_FUNCTION
+1:0-1:39            PUSH_NULL
+1:0-1:39            CALL                     0
+1:0-1:39            STORE_NAME               0 (BoundGenericAlias)
+1:0-1:39            LOAD_COMMON_CONSTANT     7 (None)
+1:0-1:39            RETURN_VALUE
+
+Disassembly of <code object <generic parameters of BoundGenericAlias> at 0xdeadbeef, file "<?>", line 1>:
+  --                 MAKE_CELL                0 (X)
+
+1:0-1:0              RESUME                   0
+1:0-1:39             LOAD_CONST               0 ('BoundGenericAlias')
+1:23-1:29            LOAD_CONST               1 ('X')
+1:26-1:29            LOAD_CONST               2 ((1,))
+1:26-1:29            LOAD_CONST               3 (<code object X at 0xdeadbeef, file "<?>", line 1>)
+1:26-1:29            MAKE_FUNCTION
+1:26-1:29            SET_FUNCTION_ATTRIBUTE   1 (defaults)
+1:23-1:29            CALL_INTRINSIC_2         2 (INTRINSIC_TYPEVAR_WITH_BOUND)
+1:23-1:29            COPY                     1
+1:23-1:29            STORE_DEREF              0 (X)
+1:23-1:29            BUILD_TUPLE              1
+1:0-1:39             LOAD_CONST               2 ((1,))
+1:0-1:39             LOAD_FAST_BORROW         0 (X)
+1:0-1:39             BUILD_TUPLE              1
+1:0-1:39             LOAD_CONST               4 (<code object BoundGenericAlias at 0xdeadbeef, file "<?>", line 1>)
+1:0-1:39             MAKE_FUNCTION
+1:0-1:39             SET_FUNCTION_ATTRIBUTE   8 (closure)
+1:0-1:39             SET_FUNCTION_ATTRIBUTE   1 (defaults)
+1:0-1:39             BUILD_TUPLE              3
+1:0-1:39             CALL_INTRINSIC_1        11 (INTRINSIC_TYPEALIAS)
+1:0-1:39             RETURN_VALUE
+
+Disassembly of <code object X at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+1:26-1:29            LOAD_FAST_BORROW         0 (.format)
+1:26-1:29            LOAD_SMALL_INT           2
+1:26-1:29            COMPARE_OP             132 (>)
+1:26-1:29            POP_JUMP_IF_FALSE        3 (to L1)
+1:26-1:29            NOT_TAKEN
+1:26-1:29            LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+1:26-1:29            RAISE_VARARGS            1
+1:26-1:29    L1:     LOAD_GLOBAL              0 (int)
+1:26-1:29            RETURN_VALUE
+
+Disassembly of <code object BoundGenericAlias at 0xdeadbeef, file "<?>", line 1>:
+  --                 COPY_FREE_VARS           1
+
+1:0-1:0              RESUME                   0
+1:0-1:39             LOAD_FAST_BORROW         0 (.format)
+1:0-1:39             LOAD_SMALL_INT           2
+1:0-1:39             COMPARE_OP             132 (>)
+1:0-1:39             POP_JUMP_IF_FALSE        3 (to L1)
+1:0-1:39             NOT_TAKEN
+1:0-1:39             LOAD_COMMON_CONSTANT     1 (NotImplementedError)
+1:0-1:39             RAISE_VARARGS            1
+1:33-1:36    L1:     LOAD_GLOBAL              0 (set)
+1:37-1:38            LOAD_DEREF               1 (X)
+1:33-1:39            BINARY_OP               26 ([])
+1:0-1:39             RETURN_VALUE
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__with_cleanup_excludes_not_taken.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__with_cleanup_excludes_not_taken.snap
new file mode 100644
index 00000000000..b2cec5081f3
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__with_cleanup_excludes_not_taken.snap
@@ -0,0 +1,62 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(c):\n    with c:\n        x = 1\n    y = 2\n\"#, true)"
+---
+0:0-1:0            RESUME                   0
+
+1:0-4:9            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-4:9            MAKE_FUNCTION
+1:0-4:9            STORE_NAME               0 (f)
+1:0-4:9            LOAD_COMMON_CONSTANT     7 (None)
+1:0-4:9            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:0-1:0              RESUME                   0
+
+2:9-2:10             LOAD_FAST_BORROW         0 (c)
+2:9-2:10             COPY                     1
+2:9-2:10             LOAD_SPECIAL             1 (__exit__)
+2:9-2:10             SWAP                     2
+2:9-2:10             SWAP                     3
+2:9-2:10             LOAD_SPECIAL             0 (__enter__)
+2:9-2:10             CALL                     0
+2:9-2:10     L1:     POP_TOP
+
+3:12-3:13            LOAD_SMALL_INT           1
+3:8-3:9              STORE_FAST               1 (x)
+
+2:9-2:10     L2:     LOAD_COMMON_CONSTANT     7 (None)
+2:9-2:10             LOAD_COMMON_CONSTANT     7 (None)
+2:9-2:10             LOAD_COMMON_CONSTANT     7 (None)
+2:9-2:10             CALL                     3
+2:9-2:10             POP_TOP
+
+4:8-4:9              LOAD_SMALL_INT           2
+4:4-4:5              STORE_FAST               2 (y)
+4:4-4:5              LOAD_COMMON_CONSTANT     7 (None)
+4:4-4:5              RETURN_VALUE
+
+2:9-2:10     L3:     PUSH_EXC_INFO
+2:9-2:10             WITH_EXCEPT_START
+2:9-2:10             TO_BOOL
+2:9-2:10             POP_JUMP_IF_TRUE         2 (to L6)
+2:9-2:10     L4:     NOT_TAKEN
+2:9-2:10     L5:     RERAISE                  2
+2:9-2:10     L6:     POP_TOP
+2:9-2:10     L7:     POP_EXCEPT
+2:9-2:10             POP_TOP
+2:9-2:10             POP_TOP
+2:9-2:10             POP_TOP
+
+4:8-4:9              LOAD_SMALL_INT           2
+4:4-4:5              STORE_FAST               2 (y)
+4:4-4:5              LOAD_COMMON_CONSTANT     7 (None)
+4:4-4:5              RETURN_VALUE
+
+  --         L8:     COPY                     3
+  --                 POP_EXCEPT
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L2 -> L3 [2] lasti
+  L3 to L4 -> L8 [4] lasti
+  L5 to L7 -> L8 [4] lasti
diff --git a/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__yield_from_and_await.snap b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__yield_from_and_await.snap
new file mode 100644
index 00000000000..9805d8e97df
--- /dev/null
+++ b/crates/stdlib/src/snapshots/rustpython_stdlib___opcode__tests__yield_from_and_await.snap
@@ -0,0 +1,66 @@
+---
+source: crates/stdlib/src/_opcode.rs
+expression: "dis(r#\"\ndef f(xs):\n    yield from xs\n\nasync def g(xs):\n    return await xs\n\"#,\ntrue)"
+---
+0:0-1:0             RESUME                   0
+
+1:0-2:17            LOAD_CONST               0 (<code object f at 0xdeadbeef, file "<?>", line 1>)
+1:0-2:17            MAKE_FUNCTION
+1:0-2:17            STORE_NAME               0 (f)
+
+4:0-5:19            LOAD_CONST               1 (<code object g at 0xdeadbeef, file "<?>", line 4>)
+4:0-5:19            MAKE_FUNCTION
+4:0-5:19            STORE_NAME               1 (g)
+4:0-5:19            LOAD_COMMON_CONSTANT     7 (None)
+4:0-5:19            RETURN_VALUE
+
+Disassembly of <code object f at 0xdeadbeef, file "<?>", line 1>:
+1:?-1:?              RETURN_GENERATOR
+1:?-1:?              POP_TOP
+1:0-1:0      L1:     RESUME                   0
+
+2:15-2:17            LOAD_FAST                0 (xs)
+2:4-2:17             GET_ITER                 3
+2:4-2:17             LOAD_COMMON_CONSTANT     7 (None)
+2:4-2:17     L2:     SEND                     4 (to L5)
+2:4-2:17     L3:     YIELD_VALUE              1
+2:4-2:17     L4:     RESUME                   2
+2:4-2:17             JUMP_BACKWARD_NO_INTERRUPT 6 (to L2)
+2:4-2:17     L5:     END_SEND
+2:4-2:17             POP_TOP
+2:4-2:17             LOAD_COMMON_CONSTANT     7 (None)
+2:4-2:17             RETURN_VALUE
+2:4-2:17     L6:     CLEANUP_THROW
+2:4-2:17     L7:     JUMP_BACKWARD_NO_INTERRUPT 6 (to L5)
+
+  --         L8:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L3 -> L8 [0] lasti
+  L3 to L4 -> L6 [3]
+  L4 to L7 -> L8 [0] lasti
+
+Disassembly of <code object g at 0xdeadbeef, file "<?>", line 4>:
+4:?-4:?              RETURN_GENERATOR
+4:?-4:?              POP_TOP
+4:0-4:0      L1:     RESUME                   0
+
+5:17-5:19            LOAD_FAST_BORROW         0 (xs)
+5:11-5:19            GET_AWAITABLE            0
+5:11-5:19            PUSH_NULL
+5:11-5:19            LOAD_COMMON_CONSTANT     7 (None)
+5:11-5:19    L2:     SEND                     4 (to L5)
+5:11-5:19    L3:     YIELD_VALUE              1
+5:11-5:19    L4:     RESUME                   3
+5:11-5:19            JUMP_BACKWARD_NO_INTERRUPT 6 (to L2)
+5:11-5:19    L5:     END_SEND
+5:4-5:19             RETURN_VALUE
+5:11-5:19    L6:     CLEANUP_THROW
+5:11-5:19    L7:     JUMP_BACKWARD_NO_INTERRUPT 4 (to L5)
+
+  --         L8:     CALL_INTRINSIC_1         3 (INTRINSIC_STOPITERATION_ERROR)
+  --                 RERAISE                  1
+ExceptionTable:
+  L1 to L3 -> L8 [0] lasti
+  L3 to L4 -> L6 [3]
+  L4 to L7 -> L8 [0] lasti
diff --git a/crates/stdlib/src/socket.rs b/crates/stdlib/src/socket.rs
index db22e6a1069..b3b2d10dd9b 100644
--- a/crates/stdlib/src/socket.rs
+++ b/crates/stdlib/src/socket.rs
@@ -3,7 +3,14 @@
 pub(crate) use _socket::module_def;
 
 #[cfg(feature = "ssl")]
-pub(super) use _socket::{PySocket, SockWaitKind, sock_wait, timeout_error_msg};
+pub(super) use _socket::{PySocket, timeout_error_msg};
+#[cfg(any(
+    feature = "__ssl-rustls",
+    all(feature = "ssl-openssl", not(all(unix, not(target_os = "aix"))))
+))]
+pub(super) use _socket::{SockWaitKind, sock_wait};
+#[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+pub(crate) use _socket::{SocketCloseObserver, SocketIdentity};
 
 #[pymodule]
 mod _socket {
@@ -21,7 +28,7 @@ mod _socket {
         },
         convert::{IntoPyException, ToPyObject, TryFromBorrowedObject, TryFromObject},
         function::{
-            ArgBytesLike, ArgIntoFloat, ArgMemoryBuffer, ArgStrOrBytesLike, Either, FsPath,
+            ArgBytesLike, ArgIndex, ArgIntoFloat, ArgMemoryBuffer, ArgStrOrBytesLike, FsPath,
             FuncArgs, OptionalArg,
         },
         types::{Constructor, DefaultConstructor, Destructor, Initializer, Representable},
@@ -44,6 +51,10 @@ mod _socket {
         Ok(())
     }
 
+    #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+    use alloc::sync::{Arc, Weak};
+    #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+    use core::sync::atomic::AtomicBool;
     use core::sync::atomic::{AtomicI32, Ordering};
     use core::{
         mem::ManuallyDrop,
@@ -53,6 +64,8 @@ mod _socket {
     use crossbeam_utils::atomic::AtomicCell;
     use host_socket::raw::Socket;
     use num_traits::ToPrimitive;
+    #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+    use std::sync::Mutex;
     use std::{
         ffi,
         io::{self, Read, Write},
@@ -1058,6 +1071,66 @@ mod _socket {
         flags: i32,
     }
 
+    /// A native-only wakeup. Implementations must not execute Python.
+    #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+    pub(crate) trait SocketCloseObserver: Send + Sync {
+        fn socket_closed(&self);
+    }
+
+    /// Identifies one initialization, even when a later socket reuses its fd.
+    #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+    #[derive(Debug, Default)]
+    pub(crate) struct SocketIdentity {
+        closed: AtomicBool,
+        observers: Mutex<Vec<Weak<dyn SocketCloseObserver>>>,
+    }
+
+    #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+    impl SocketIdentity {
+        pub(crate) fn is_closed(&self) -> bool {
+            self.closed.load(Ordering::Acquire)
+        }
+
+        /// Register atomically with the closed check, so close-before-wait
+        /// cannot lose a wakeup. The caller retains the strong observer.
+        pub(crate) fn subscribe(&self, observer: Arc<dyn SocketCloseObserver>) -> bool {
+            let mut observers = self.observers.lock().unwrap();
+            if self.is_closed() {
+                return false;
+            }
+            observers.retain(|observer| observer.strong_count() != 0);
+            let observer = Arc::downgrade(&observer);
+            if !observers.iter().any(|current| current.ptr_eq(&observer)) {
+                observers.push(observer);
+            }
+            true
+        }
+
+        pub(crate) fn unsubscribe(&self, observer: Arc<dyn SocketCloseObserver>) {
+            let observer = Arc::downgrade(&observer);
+            self.observers
+                .lock()
+                .unwrap()
+                .retain(|current| !current.ptr_eq(&observer));
+        }
+
+        // The socket write lock is held by the caller. Return weak observers
+        // rather than invoking them while either lock is held.
+        fn invalidate(&self) -> Vec<Weak<dyn SocketCloseObserver>> {
+            let mut observers = self.observers.lock().unwrap();
+            self.closed.store(true, Ordering::Release);
+            core::mem::take(&mut *observers)
+        }
+
+        fn notify_closed(observers: Vec<Weak<dyn SocketCloseObserver>>) {
+            for observer in observers {
+                if let Some(observer) = observer.upgrade() {
+                    observer.socket_closed();
+                }
+            }
+        }
+    }
+
     #[pyattr(name = "socket")]
     #[pyattr(name = "SocketType")]
     #[pyclass(name = "socket")]
@@ -1071,6 +1144,10 @@ mod _socket {
         proto: AtomicI32,
         pub(crate) timeout: AtomicCell<f64>,
         sock: PyRwLock<Option<Socket>>,
+        // Shared access takes `sock` first, in socket -> identity-slot order.
+        // Ordinary sockets never allocate an identity or observer list.
+        #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+        ssl_identity: Mutex<Option<Arc<SocketIdentity>>>,
     }
 
     const _: () = assert!(core::mem::size_of::<Option<Socket>>() == core::mem::size_of::<Socket>());
@@ -1083,6 +1160,19 @@ mod _socket {
                 proto: AtomicI32::new(0),
                 timeout: AtomicCell::new(-1.0),
                 sock: PyRwLock::new(None),
+                #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+                ssl_identity: Mutex::new(None),
+            }
+        }
+    }
+
+    #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+    impl Drop for PySocket {
+        fn drop(&mut self) {
+            // Rust destruction must also notify when Python __del__ did not run.
+            // Keep ordinary socket destruction free of additional locking.
+            if self.ssl_identity.get_mut().unwrap().is_some() {
+                drop(self.take_sock());
             }
         }
     }
@@ -1119,6 +1209,64 @@ mod _socket {
                 .ok_or_else(|| io::Error::from_raw_os_error(CLOSED_ERR))
         }
 
+        /// Capture the current initialization under the socket read lock.
+        #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+        pub(crate) fn ssl_identity(&self) -> io::Result<Arc<SocketIdentity>> {
+            let _sock = self.sock()?;
+            let mut identity = self.ssl_identity.lock().unwrap();
+            Ok(identity
+                .get_or_insert_with(|| Arc::new(SocketIdentity::default()))
+                .clone())
+        }
+
+        /// Hold this guard only around a truly nonblocking transport syscall,
+        /// never around SSL processing, Python callbacks, or readiness waits.
+        #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+        pub(crate) fn sock_for_ssl_identity(
+            &self,
+            identity: &Arc<SocketIdentity>,
+        ) -> io::Result<PyMappedRwLockReadGuard<'_, Socket>> {
+            let sock = self.sock()?;
+            let current = self.ssl_identity.lock().unwrap();
+            if !current
+                .as_ref()
+                .is_some_and(|current| Arc::ptr_eq(current, identity) && !identity.is_closed())
+            {
+                return Err(io::Error::from_raw_os_error(CLOSED_ERR));
+            }
+            Ok(sock)
+        }
+
+        // Caller holds the socket write lock. Notifications must be delivered
+        // only after releasing that lock, including on initialization failure.
+        #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+        fn invalidate_ssl_identity_locked(&self) -> Vec<Weak<dyn SocketCloseObserver>> {
+            self.ssl_identity
+                .lock()
+                .unwrap()
+                .take()
+                .map_or_else(Vec::new, |identity| identity.invalidate())
+        }
+
+        fn take_sock(&self) -> Option<Socket> {
+            let mut guard = self.sock.write();
+            #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+            let observers = self.invalidate_ssl_identity_locked();
+            let sock = guard.take();
+            drop(guard);
+            #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+            SocketIdentity::notify_closed(observers);
+            sock
+        }
+
+        #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+        fn invalidate_failed_ssl_init(&self) {
+            let guard = self.sock.write();
+            let observers = self.invalidate_ssl_identity_locked();
+            drop(guard);
+            SocketIdentity::notify_closed(observers);
+        }
+
         /// Snapshot the inner socket without holding `self.sock` across a syscall.
         ///
         /// Blocking accept/recv/send must not keep the RwLock: `close()` needs
@@ -1171,7 +1319,18 @@ mod _socket {
             self.kind.store(masked_kind, Ordering::Relaxed);
             self.proto.store(proto, Ordering::Relaxed);
             let mut s = self.sock.write();
-            let sock = s.insert(sock);
+            #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+            let observers = self.invalidate_ssl_identity_locked();
+            let old_socket = s.replace(sock);
+            // Closing a lingering socket may block. Unlock and wake old SSL
+            // operations first, including if initialization unwinds.
+            let mut s = scopeguard::guard(s, move |s| {
+                drop(s);
+                #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+                SocketIdentity::notify_closed(observers);
+                drop(old_socket);
+            });
+            let sock = s.as_mut().unwrap();
             // If SOCK_NONBLOCK is set, use timeout 0 (non-blocking)
             #[cfg(any(
                 target_os = "android",
@@ -1202,10 +1361,13 @@ mod _socket {
             )))]
             let timeout = DEFAULT_TIMEOUT.load();
             self.timeout.store(timeout);
-            if timeout >= 0.0 {
-                sock.set_nonblocking(true)?;
-            }
-            Ok(())
+            let result = if timeout >= 0.0 {
+                sock.set_nonblocking(true)
+            } else {
+                Ok(())
+            };
+            drop(s);
+            result
         }
 
         /// returns Err(blocking)
@@ -1691,7 +1853,14 @@ mod _socket {
         type Args = SocketInitArgs;
 
         fn init(zelf: &Py<Self>, args: Self::Args, vm: &VirtualMachine) -> PyResult<()> {
-            Self::_init(zelf, args, vm).map_err(|e| e.into_pyexception(vm))
+            let result = Self::_init(zelf, args, vm);
+            #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+            if result.is_err() {
+                // _init can fail before reaching init_inner, leaving an older
+                // raw socket in place but invalidating its SSL initialization.
+                zelf.invalidate_failed_ssl_init();
+            }
+            result.map_err(|e| e.into_pyexception(vm))
         }
     }
 
@@ -1917,20 +2086,22 @@ mod _socket {
         #[pymethod]
         fn recv(
             zelf: &Py<Self>,
-            bufsize: usize,
+            bufsize: isize,
             flags: OptionalArg<i32>,
             vm: &VirtualMachine,
         ) -> Result<Vec<u8>, IoOrPyException> {
             let flags = flags.unwrap_or(0);
-            let mut buffer = Vec::new();
-            buffer
-                .try_reserve_exact(bufsize)
-                .map_err(|_| vm.no_memory_error())?;
+            let bufsize = bufsize
+                .to_usize()
+                .ok_or_else(|| vm.new_value_error("negative buffersize in recv"))?;
+            let mut buffer = alloc_recv_scratch(bufsize, flags, vm)?;
             let n = zelf.sock_op(vm, SockWaitKind::Read, || {
                 zelf.sock_snapshot()?
-                    .recv_with_flags(buffer.spare_capacity_mut(), flags)
+                    .recv_with_flags(&mut buffer.spare_capacity_mut()[..bufsize], flags)
             })?;
-            unsafe { buffer.set_len(n) };
+            // MSG_TRUNC may report the full datagram length, beyond the buffer.
+            unsafe { buffer.set_len(n.min(bufsize)) };
+            buffer.shrink_to_fit();
             Ok(buffer)
         }
 
@@ -1949,18 +2120,26 @@ mod _socket {
                 let nbytes = nbytes
                     .to_usize()
                     .ok_or_else(|| vm.new_value_error("negative buffersize in recv_into"))?;
-                nbytes.min(buf.len())
+                if nbytes > buf.len() {
+                    return Err(vm
+                        .new_value_error("buffer too small for requested bytes")
+                        .into());
+                }
+                if nbytes == 0 { buf.len() } else { nbytes }
             } else {
                 buf.len()
             };
 
-            let mut scratch = alloc_recv_scratch(read_len, vm)?;
+            let mut scratch = alloc_recv_scratch(read_len, flags, vm)?;
             let n = zelf.sock_op(vm, SockWaitKind::Read, || {
                 zelf.sock_snapshot()?
                     .recv_with_flags(&mut scratch.spare_capacity_mut()[..read_len], flags)
             })?;
-            unsafe { scratch.set_len(n) };
-            buf.borrow_buf_mut()[..n].copy_from_slice(&scratch);
+            let written = n.min(read_len);
+            unsafe { scratch.set_len(written) };
+            if !zelf.recv_discards_data(flags) {
+                buf.borrow_buf_mut()[..written].copy_from_slice(&scratch);
+            }
             Ok(n)
         }
 
@@ -1975,15 +2154,13 @@ mod _socket {
             let bufsize = bufsize
                 .to_usize()
                 .ok_or_else(|| vm.new_value_error("negative buffersize in recvfrom"))?;
-            let mut buffer = Vec::new();
-            buffer
-                .try_reserve_exact(bufsize)
-                .map_err(|_| vm.no_memory_error())?;
+            let mut buffer = alloc_recv_scratch(bufsize, flags, vm)?;
             let (n, addr) = zelf.sock_op(vm, SockWaitKind::Read, || {
                 zelf.sock_snapshot()?
-                    .recv_from_with_flags(buffer.spare_capacity_mut(), flags)
+                    .recv_from_with_flags(&mut buffer.spare_capacity_mut()[..bufsize], flags)
             })?;
-            unsafe { buffer.set_len(n) };
+            unsafe { buffer.set_len(n.min(bufsize)) };
+            buffer.shrink_to_fit();
             Ok((
                 buffer,
                 get_addr_tuple(&addr, zelf.proto.load(Ordering::Relaxed), vm),
@@ -2008,18 +2185,21 @@ mod _socket {
                             .new_value_error("nbytes is greater than the length of the buffer")
                             .into());
                     }
-                    i
+                    if i == 0 { buf.len() } else { i }
                 }
                 OptionalArg::Missing => buf.len(),
             };
             let flags = flags.unwrap_or(0);
-            let mut scratch = alloc_recv_scratch(read_len, vm)?;
+            let mut scratch = alloc_recv_scratch(read_len, flags, vm)?;
             let (n, addr) = zelf.sock_op(vm, SockWaitKind::Read, || {
                 zelf.sock_snapshot()?
                     .recv_from_with_flags(&mut scratch.spare_capacity_mut()[..read_len], flags)
             })?;
-            unsafe { scratch.set_len(n) };
-            buf.borrow_buf_mut()[..n].copy_from_slice(&scratch);
+            let written = n.min(read_len);
+            unsafe { scratch.set_len(written) };
+            if !zelf.recv_discards_data(flags) {
+                buf.borrow_buf_mut()[..written].copy_from_slice(&scratch);
+            }
             Ok((
                 n,
                 get_addr_tuple(&addr, zelf.proto.load(Ordering::Relaxed), vm),
@@ -2239,7 +2419,7 @@ mod _socket {
             let ancbufsize = ancbufsize as usize;
             let flags = flags.unwrap_or(0);
 
-            let msg = zelf
+            let mut msg = zelf
                 .sock_op(vm, SockWaitKind::Read, || {
                     let sock = zelf.sock_snapshot()?;
                     let fd = unsafe { std::os::fd::BorrowedFd::borrow_raw(sock_fileno(&sock)) };
@@ -2247,6 +2427,8 @@ mod _socket {
                 })
                 .map_err(|e| e.into_pyexception(vm))?;
 
+            msg.data.shrink_to_fit();
+
             // Build ancdata list
             let ancdata = Self::parse_ancillary_data(&msg.ancdata, vm);
 
@@ -2313,7 +2495,7 @@ mod _socket {
 
         #[pymethod]
         fn close(zelf: &Py<Self>) -> io::Result<()> {
-            let sock = zelf.sock.write().take();
+            let sock = zelf.take_sock();
             if let Some(sock) = sock {
                 close_inner(into_sock_fileno(sock))?;
             }
@@ -2323,7 +2505,7 @@ mod _socket {
         #[pymethod]
         #[inline]
         fn detach(zelf: &Py<Self>) -> i64 {
-            let sock = zelf.sock.write().take();
+            let sock = zelf.take_sock();
             sock.map_or(INVALID_SOCKET as i64, |s| into_sock_fileno(s) as i64)
         }
 
@@ -2428,29 +2610,115 @@ mod _socket {
         #[pymethod]
         fn setsockopt(
             zelf: &Py<Self>,
-            level: i32,
-            name: i32,
-            value: Option<Either<ArgBytesLike, i32>>,
-            optlen: OptionalArg<u32>,
+            args: FuncArgs,
             vm: &VirtualMachine,
         ) -> Result<(), IoOrPyException> {
-            let sock = zelf.sock()?;
-            let fd = sock_fileno(&sock);
-            match (value, optlen) {
-                (Some(Either::A(b)), OptionalArg::Missing) => {
-                    b.with_ref(|b| host_socket::setsockopt_bytes(fd as _, level, name, b))?
+            if !args.kwargs.is_empty() {
+                return Err(vm
+                    .new_type_error("setsockopt() takes no keyword arguments")
+                    .into());
+            }
+            let nargs = args.args.len();
+            if nargs < 3 {
+                return Err(vm
+                    .new_type_error(format!(
+                        "setsockopt() takes at least 3 arguments ({nargs} given)"
+                    ))
+                    .into());
+            }
+            if nargs > 4 {
+                return Err(vm
+                    .new_type_error(format!(
+                        "setsockopt() takes at most 4 arguments ({nargs} given)"
+                    ))
+                    .into());
+            }
+            let (level, name, value, optlen): (
+                i32,
+                i32,
+                Option<PyObjectRef>,
+                OptionalArg<ArgIndex>,
+            ) = args.bind(vm)?;
+            let optlen = match optlen {
+                OptionalArg::Present(index) => {
+                    let index = index.as_ref();
+                    // CPython's unsigned-int bitfield conversion masks the value,
+                    // warning only when it fits neither a signed nor unsigned int.
+                    if !index.as_bigint().to_i64().is_some_and(|value| {
+                        (i64::from(i32::MIN)..=i64::from(u32::MAX)).contains(&value)
+                    }) {
+                        crate::vm::warn::warn(
+                            vm.ctx.new_str("integer value out of range").into(),
+                            Some(vm.ctx.exceptions.deprecation_warning.to_owned()),
+                            1,
+                            None,
+                            vm,
+                        )?;
+                    }
+                    OptionalArg::Present(index.as_u32_mask())
                 }
-                (Some(Either::B(val)), OptionalArg::Missing) => {
-                    host_socket::setsockopt_int(fd as _, level, name, val)?
+                OptionalArg::Missing => OptionalArg::Missing,
+            };
+            enum Value {
+                Int(i32),
+                Buffer(ArgBytesLike),
+                Null(u32),
+            }
+            let value = match (value, optlen) {
+                (Some(value), OptionalArg::Missing) => {
+                    if let Some(index) = value.try_index_opt(vm) {
+                        Value::Int(index?.try_to_primitive::<i32>(vm)?)
+                    } else if value.check_buffer() {
+                        let buffer = ArgBytesLike::try_from_object(vm, value)?;
+                        #[cfg(windows)]
+                        if buffer.len() > i32::MAX as usize {
+                            return Err(vm
+                                .new_overflow_error(format!(
+                                    "socket option is larger than {} bytes",
+                                    i32::MAX
+                                ))
+                                .into());
+                        }
+                        Value::Buffer(buffer)
+                    } else {
+                        return Err(vm
+                            .new_type_error(format!(
+                                "socket option should be int, bytes-like object or None (got {})",
+                                value.class().fully_qualified_name(vm)?
+                            ))
+                            .into());
+                    }
                 }
-                (None, OptionalArg::Present(optlen)) => {
-                    host_socket::setsockopt_none(fd as _, level, name, optlen)?
+                (None, OptionalArg::Present(optlen)) => Value::Null(optlen),
+                (None, OptionalArg::Missing) => {
+                    return Err(vm
+                        .new_type_error(
+                            "setsockopt() requires 4 arguments when the third argument is None",
+                        )
+                        .into());
                 }
-                _ => {
+                (Some(value), OptionalArg::Present(_)) => {
                     return Err(vm
-                        .new_type_error("expected the value arg xor the optlen arg")
+                        .new_type_error(format!(
+                            "setsockopt() only takes 4 arguments when the third argument is None (got {})",
+                            value.class().fully_qualified_name(vm)?
+                        ))
                         .into());
                 }
+            };
+            // Convert Python values before locking the socket; callbacks may close it.
+            let sock = zelf.sock()?;
+            let fd = sock_fileno(&sock);
+            match &value {
+                Value::Int(value) => {
+                    host_socket::setsockopt_int(fd as _, level, name, *value)?;
+                }
+                Value::Buffer(buffer) => {
+                    buffer.with_ref(|b| host_socket::setsockopt_bytes(fd as _, level, name, b))?;
+                }
+                Value::Null(optlen) => {
+                    host_socket::setsockopt_none(fd as _, level, name, *optlen)?;
+                }
             }
             Ok(())
         }
@@ -2822,14 +3090,42 @@ mod _socket {
     /// on a lock never reaches a safepoint — holding it across the wait stops
     /// the world from being stopped at all. The bytes are copied over once
     /// they have arrived.
-    fn alloc_recv_scratch(len: usize, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+    fn alloc_recv_scratch(len: usize, flags: i32, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
         let mut scratch = Vec::new();
         scratch
             .try_reserve_exact(len)
             .map_err(|_| vm.no_memory_error())?;
+        if i64::from(flags) & i64::from(MSG_TRUNC) != 0 {
+            // Linux TCP can consume bytes without writing them with MSG_TRUNC.
+            // Keep the initialized storage available to the receive syscall.
+            scratch.resize(len, 0);
+            scratch.clear();
+        }
         Ok(scratch)
     }
 
+    impl PySocket {
+        fn recv_discards_data(&self, flags: i32) -> bool {
+            // Linux TCP treats MSG_TRUNC as a request to discard data. Do not
+            // overwrite the caller's buffer, including changes during the wait.
+            #[cfg(any(target_os = "linux", target_os = "android"))]
+            {
+                let family = self.family.load(Ordering::Relaxed);
+                let proto = self.proto.load(Ordering::Relaxed);
+                flags & MSG_TRUNC != 0
+                    && flags & c::MSG_ERRQUEUE == 0
+                    && self.kind.load(Ordering::Relaxed) == SOCK_STREAM
+                    && (family == AF_INET || family == AF_INET6)
+                    && (proto == 0 || proto == IPPROTO_TCP || proto == c::IPPROTO_MPTCP)
+            }
+            #[cfg(not(any(target_os = "linux", target_os = "android")))]
+            {
+                let _ = flags;
+                false
+            }
+        }
+    }
+
     enum IoOrPyException {
         Timeout,
         Py(PyBaseExceptionRef),
@@ -2878,7 +3174,10 @@ mod _socket {
     }
 
     /// returns Ok(true) on timeout
-    #[cfg(feature = "ssl")]
+    #[cfg(any(
+        feature = "__ssl-rustls",
+        all(feature = "ssl-openssl", not(all(unix, not(target_os = "aix"))))
+    ))]
     pub(crate) fn sock_wait(
         sock: &Socket,
         wait_kind: SockWaitKind,
@@ -2921,7 +3220,7 @@ mod _socket {
         #[pyarg(any)]
         host: Option<ArgStrOrBytesLike>,
         #[pyarg(any)]
-        port: Option<Either<ArgStrOrBytesLike, i32>>,
+        port: Option<PyObjectRef>,
 
         #[pyarg(any, default = c::AF_UNSPEC)]
         family: i32,
@@ -2973,10 +3272,23 @@ mod _socket {
         };
         let host = host_encoded.as_deref();
 
-        // Encode port: str/bytes as service name, int as port number
-        let port_encoded: Option<String> = match opts.port.as_ref() {
-            Some(Either::A(sb)) => {
-                let port_str = match sb {
+        // Check the index protocol before string/bytes conversion, including for
+        // subclasses, and preserve any exception raised by __index__.
+        let port_index = opts
+            .port
+            .as_ref()
+            .and_then(|port| port.try_index_opt(vm))
+            .transpose()?;
+        let port_encoded: Option<String> = match (port_index, opts.port.as_ref()) {
+            (Some(index), _) => Some(crate::vm::builtins::PyInt::repr_str(&index, vm)?),
+            (None, Some(port)) => {
+                if !port.fast_isinstance(vm.ctx.types.str_type)
+                    && !port.fast_isinstance(vm.ctx.types.bytes_type)
+                {
+                    return Err(vm.new_os_error("Int or String expected").into());
+                }
+                let sb = ArgStrOrBytesLike::try_from_object(vm, port.clone())?;
+                let port_str = match &sb {
                     ArgStrOrBytesLike::Str(s) => {
                         // For str, check for surrogates and raise UnicodeEncodeError if found
                         s.to_str()
@@ -3014,8 +3326,7 @@ mod _socket {
                 };
                 Some(port_str)
             }
-            Some(Either::B(i)) => Some(i.to_string()),
-            None => None,
+            (None, None) => None,
         };
         let port = port_encoded.as_deref();
 
@@ -3029,7 +3340,7 @@ mod _socket {
                         ai.address,
                         ai.socktype,
                         ai.protocol,
-                        ai.canonname,
+                        ai.canonname.unwrap_or_default(),
                         get_ip_addr_tuple(&ai.sockaddr, vm),
                     ))
                     .into()
@@ -3511,4 +3822,112 @@ mod _socket {
         host_socket::checked_cmsg_space(length)
             .ok_or_else(|| vm.new_overflow_error("CMSG_SPACE() argument out of range"))
     }
+
+    #[cfg(test)]
+    #[cfg(all(feature = "ssl-openssl", unix, not(target_os = "aix")))]
+    mod ssl_identity_tests {
+        use super::{PySocket, SocketCloseObserver, SocketIdentity};
+        use alloc::sync::{Arc, Weak};
+        use core::sync::atomic::{AtomicUsize, Ordering};
+
+        struct Observer {
+            identity: Weak<SocketIdentity>,
+            notifications: AtomicUsize,
+        }
+
+        impl Observer {
+            fn new(identity: &Arc<SocketIdentity>) -> Arc<Self> {
+                Arc::new(Self {
+                    identity: Arc::downgrade(identity),
+                    notifications: AtomicUsize::new(0),
+                })
+            }
+        }
+
+        impl SocketCloseObserver for Observer {
+            fn socket_closed(&self) {
+                if let Some(identity) = self.identity.upgrade() {
+                    assert!(identity.is_closed());
+                    assert!(identity.observers.try_lock().is_ok());
+                }
+                self.notifications.fetch_add(1, Ordering::Relaxed);
+            }
+        }
+
+        #[test]
+        fn subscribe_before_close_notifies_after_invalidation() {
+            let identity = Arc::new(SocketIdentity::default());
+            let observer = Observer::new(&identity);
+            assert!(identity.subscribe(observer.clone()));
+            assert!(identity.subscribe(observer.clone()));
+            let notifications = identity.invalidate();
+            assert!(identity.is_closed());
+            assert_eq!(observer.notifications.load(Ordering::Relaxed), 0);
+            assert_eq!(notifications.len(), 1);
+            SocketIdentity::notify_closed(notifications);
+            assert_eq!(observer.notifications.load(Ordering::Relaxed), 1);
+            assert!(identity.invalidate().is_empty());
+        }
+
+        #[test]
+        fn close_before_subscribe_rejects_registration() {
+            let identity = Arc::new(SocketIdentity::default());
+            SocketIdentity::notify_closed(identity.invalidate());
+            let observer = Observer::new(&identity);
+            assert!(!identity.subscribe(observer.clone()));
+            assert_eq!(observer.notifications.load(Ordering::Relaxed), 0);
+        }
+
+        #[test]
+        fn registrations_do_not_keep_observers_alive() {
+            let identity = Arc::new(SocketIdentity::default());
+            let observer = Observer::new(&identity);
+            let weak = Arc::downgrade(&observer);
+            assert!(identity.subscribe(observer.clone()));
+            drop(observer);
+            assert!(weak.upgrade().is_none());
+            let next = Observer::new(&identity);
+            assert!(identity.subscribe(next.clone()));
+            let notifications = identity.invalidate();
+            assert_eq!(notifications.len(), 1);
+            SocketIdentity::notify_closed(notifications);
+            assert_eq!(next.notifications.load(Ordering::Relaxed), 1);
+        }
+
+        #[test]
+        fn uninitialized_socket_keeps_identity_unallocated() {
+            let socket = PySocket::default();
+            assert!(socket.ssl_identity.lock().unwrap().is_none());
+            assert!(socket.ssl_identity().is_err());
+            assert!(socket.ssl_identity.lock().unwrap().is_none());
+        }
+
+        #[test]
+        fn failed_initialization_and_rust_drop_invalidate_identity() {
+            // Exercise lifecycle bookkeeping without creating an OS socket.
+            let socket = PySocket::default();
+            let old = Arc::new(SocketIdentity::default());
+            let old_observer = Observer::new(&old);
+            assert!(old.subscribe(old_observer.clone()));
+            {
+                let _socket = socket.sock.write();
+                *socket.ssl_identity.lock().unwrap() = Some(old.clone());
+            }
+            socket.invalidate_failed_ssl_init();
+            assert!(old.is_closed());
+            assert_eq!(old_observer.notifications.load(Ordering::Relaxed), 1);
+
+            let new = Arc::new(SocketIdentity::default());
+            let new_observer = Observer::new(&new);
+            assert!(new.subscribe(new_observer.clone()));
+            {
+                let _socket = socket.sock.write();
+                *socket.ssl_identity.lock().unwrap() = Some(new.clone());
+            }
+            assert!(!new.is_closed());
+            drop(socket);
+            assert!(new.is_closed());
+            assert_eq!(new_observer.notifications.load(Ordering::Relaxed), 1);
+        }
+    }
 }
diff --git a/crates/stdlib/src/ssl.rs b/crates/stdlib/src/ssl.rs
index 74750cced43..05220d33209 100644
--- a/crates/stdlib/src/ssl.rs
+++ b/crates/stdlib/src/ssl.rs
@@ -1,4 +1,4 @@
-// spell-checker: ignore ssleof aesccm aesgcm capath getblocking setblocking ENDTLS TLSEXT
+// spell-checker: ignore ssleof aesccm aesgcm capath getblocking setblocking ENDTLS TLSEXT ktls sigalgs rsae mldsa
 
 //! Pure Rust SSL/TLS implementation using rustls
 //!
@@ -79,14 +79,14 @@ mod _ssl {
 
     // Import error types used in this module (others are exposed via pymodule(with(...)))
     use super::error::{
-        PySSLError, PySSLWantReadError, PySSLWantWriteError, create_ssl_eof_error,
+        PySSLEOFError, PySSLError, PySSLWantReadError, PySSLWantWriteError, create_ssl_eof_error,
         create_ssl_want_read_error, create_ssl_want_write_error, create_ssl_zero_return_error,
     };
     use alloc::sync::Arc;
     use core::{
         hash::{Hash, Hasher},
         hint::cold_path,
-        sync::atomic::{AtomicUsize, Ordering},
+        sync::atomic::{AtomicBool, AtomicUsize, Ordering},
         time::Duration,
     };
     use rustpython_vm::exceptions;
@@ -281,6 +281,8 @@ mod _ssl {
     #[pyattr]
     const HAS_PSK: bool = false; // PSK not supported in rustls
     #[pyattr]
+    const HAS_PSK_TLS13: bool = false; // External PSK callbacks are not supported.
+    #[pyattr]
     const HAS_SSLv2: bool = false;
     #[pyattr]
     const HAS_SSLv3: bool = false;
@@ -325,6 +327,8 @@ mod _ssl {
         #[pytraverse(skip)]
         context_identity: Arc<()>,
         #[pytraverse(skip)]
+        policy_identity: PyRwLock<Arc<()>>,
+        #[pytraverse(skip)]
         protocol: i32,
         #[pytraverse(skip)]
         check_hostname: PyRwLock<bool>,
@@ -336,7 +340,7 @@ mod _ssl {
         verify_flags: PyRwLock<i32>,
         // Rustls configuration (built lazily)
         #[pytraverse(skip)]
-        server_config: PyRwLock<Option<chain::ServerConfig>>,
+        server_config: PyRwLock<Option<(Arc<()>, chain::ServerConfig)>>,
         // Certificate store
         #[pytraverse(skip)]
         root_certs: PyRwLock<RootCertStore>,
@@ -380,9 +384,11 @@ mod _ssl {
         keylog_filename: PyRwLock<Option<PyObjectRef>>,
         #[pytraverse(skip)]
         key_log: Arc<super::keylog::KeyLog>,
-        // ECDH curve name for key exchange
+        // Explicit key exchange groups, shared by set_groups and set_ecdh_curve.
+        #[pytraverse(skip)]
+        kx_groups: PyRwLock<Option<Vec<&'static dyn SupportedKxGroup>>>,
         #[pytraverse(skip)]
-        ecdh_curve: PyRwLock<Option<String>>,
+        server_sigalgs: PyRwLock<Option<Vec<rustls::SignatureScheme>>>,
         // Certificate statistics for cert_store_stats()
         #[pytraverse(skip)]
         ca_cert_count: PyRwLock<usize>, // Number of CA certificates
@@ -470,6 +476,14 @@ mod _ssl {
 
     #[pyclass(with(Constructor, Representable), flags(BASETYPE))]
     impl PySSLContext {
+        fn invalidate_policy(&self) {
+            // Old SSLSession configurations must never override later policy.
+            // Replace the identity after mutation so concurrent snapshots also
+            // become ineligible for resumption once that mutation completes.
+            *self.policy_identity.write() = Arc::new(());
+            *self.server_config.write() = None;
+        }
+
         fn warn_deprecated_tls_version(version: i32, vm: &VirtualMachine) -> PyResult<()> {
             let version_name = match version {
                 PROTO_SSLv3 => Some("SSLv3"),
@@ -505,7 +519,7 @@ mod _ssl {
             capath_state.directories.push(directory);
             capath_state.cache = None;
             drop(capath_state);
-            *self.server_config.write() = None;
+            self.invalidate_policy();
         }
 
         fn capath_certificates(&self) -> Arc<Vec<Vec<u8>>> {
@@ -571,6 +585,7 @@ mod _ssl {
                     *zelf.verify_mode.write() = CERT_REQUIRED;
                 }
             }
+            zelf.invalidate_policy();
         }
 
         #[pygetset]
@@ -581,6 +596,7 @@ mod _ssl {
         #[pygetset(setter)]
         fn set__host_flags(zelf: &Py<Self>, value: i32) {
             *zelf.host_flags.write() = value;
+            zelf.invalidate_policy();
         }
 
         #[pygetset]
@@ -600,6 +616,7 @@ mod _ssl {
                 ));
             }
             *zelf.verify_mode.write() = mode;
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -616,6 +633,7 @@ mod _ssl {
         #[pygetset(setter)]
         fn set_verify_flags(zelf: &Py<Self>, value: i32) {
             *zelf.verify_flags.write() = value;
+            zelf.invalidate_policy();
         }
 
         #[pygetset]
@@ -626,6 +644,7 @@ mod _ssl {
         #[pygetset(setter)]
         fn set_post_handshake_auth(zelf: &Py<Self>, value: bool) {
             *zelf.post_handshake_auth.write() = value;
+            zelf.invalidate_policy();
         }
 
         #[pygetset]
@@ -644,6 +663,7 @@ mod _ssl {
                 );
             }
             *zelf.num_tickets.write() = value;
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -682,6 +702,7 @@ mod _ssl {
             }
 
             *zelf.options.write() = value;
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -715,6 +736,7 @@ mod _ssl {
                 _ => value,
             };
             *zelf.minimum_version.write() = normalized_value;
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -748,6 +770,7 @@ mod _ssl {
                 _ => value,
             };
             *zelf.maximum_version.write() = normalized_value;
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -788,7 +811,9 @@ mod _ssl {
 
             // If failed and callable exists, invoke it and retry
             // This implements lazy evaluation: callable only invoked if password is actually needed
-            if result.is_err()
+            if result
+                .as_ref()
+                .is_err_and(|error| !error.is::<rustpython_host_env::ssl::verify::CertFileError>())
                 && let Some(callable) = password_callable
             {
                 // Invoke callable - exceptions propagate naturally
@@ -826,6 +851,25 @@ mod _ssl {
 
             // Process result
             let (certs, key) = result.map_err(|e| {
+                let e = match e.downcast::<rustpython_host_env::ssl::verify::CertFileError>() {
+                    Ok(error) => {
+                        let filename = if error.key_file {
+                            args.keyfile.as_ref().unwrap_or(&args.certfile)
+                        } else {
+                            &args.certfile
+                        };
+                        let filename: PyObjectRef = match filename {
+                            Either::A(s) => s.clone().into(),
+                            Either::B(b) => vm.ctx.new_bytes(b.borrow_buf().to_vec()).into(),
+                        };
+                        let exc = error.error.into_pyexception(vm);
+                        exc.as_object()
+                            .set_attr("filename", filename, vm)
+                            .expect("OSError.filename is writable");
+                        return exc;
+                    }
+                    Err(error) => error,
+                };
                 // Try to downcast to io::Error to preserve errno information
                 if let Ok(io_err) = e.downcast::<std::io::Error>() {
                     match io_err.kind() {
@@ -932,6 +976,7 @@ mod _ssl {
 
             // Add new cert/key pair as tuple
             cert_keys.push((Arc::new(certified_key), key));
+            zelf.invalidate_policy();
 
             Ok(())
         }
@@ -981,6 +1026,8 @@ mod _ssl {
                 (None, false)
             };
 
+            // Loaders may partially update trust before returning an error.
+            let _policy_change = ContextPolicyChange(zelf);
             // If it's a CRL, just add it (separate lock, no conflict with root_store)
             if let Some(crl) = crl_opt {
                 zelf.crls.write().push(crl);
@@ -1017,7 +1064,7 @@ mod _ssl {
             if let Some(dir_path) = capath_dir {
                 zelf.add_verify_dir(dir_path);
             }
-            *zelf.server_config.write() = None;
+            zelf.invalidate_policy();
 
             Ok(())
         }
@@ -1142,6 +1189,7 @@ mod _ssl {
             _purpose: OptionalArg<i32>,
             vm: &VirtualMachine,
         ) -> PyResult<()> {
+            let _policy_change = ContextPolicyChange(zelf);
             let mut store = zelf.root_certs.write();
 
             #[cfg(windows)]
@@ -1179,7 +1227,7 @@ mod _ssl {
             }
 
             drop(store);
-            *zelf.server_config.write() = None;
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -1195,6 +1243,7 @@ mod _ssl {
                 alpn_list.push(bytes.borrow_buf().to_vec());
             }
             *zelf.alpn_protocols.write() = alpn_list;
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -1207,6 +1256,7 @@ mod _ssl {
             let bytes = protos.borrow_buf();
             let alpn_list = parse_length_prefixed_alpn(&bytes, vm)?;
             *zelf.alpn_protocols.write() = alpn_list;
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -1234,21 +1284,128 @@ mod _ssl {
                         .upcast()
                     })?;
 
-            // TLS 1.3 has a separate OpenSSL setter. Discard whatever this
-            // cipher string happened to match there, then restore exactly the
-            // provider defaults in their preference order.
+            // TLS 1.3 has a separate setter. Preserve its current selection.
+            let current = zelf.selected_ciphers.read();
             selected_ciphers = cipher::restore_default_tls13(
                 selected_ciphers,
-                CryptoExt::get_ext().default_ciphers_or_provider(),
+                current
+                    .as_deref()
+                    .unwrap_or_else(|| CryptoExt::get_ext().default_ciphers_or_provider()),
             );
+            drop(current);
 
             *zelf.selected_ciphers.write() = Some(selected_ciphers);
             *zelf.suite_b_kx_groups.write() = suite_b_kx_groups;
-            *zelf.server_config.write() = None;
+            zelf.invalidate_policy();
 
             Ok(())
         }
 
+        #[pymethod]
+        fn set_ciphersuites(
+            zelf: &Py<Self>,
+            ciphersuites: PyUtf8StrRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            let list = ciphersuites.as_str();
+            if list.contains('\0') {
+                return Err(vm.new_value_error("embedded null character"));
+            }
+            let mut selected = Vec::new();
+            for name in list.split(':') {
+                if let Some(suite) = CryptoExt::get_ext()
+                    .all_ciphers_or_default()
+                    .iter()
+                    .find(|suite| suite.tls13().is_some() && cipher::describe(suite).name == name)
+                    && !selected.contains(suite)
+                {
+                    selected.push(*suite);
+                }
+            }
+            if selected.is_empty() && !list.is_empty() {
+                return Err(vm
+                    .new_os_subtype_error(
+                        PySSLError::class(&vm.ctx).to_owned(),
+                        None,
+                        "No cipher suite can be selected.".to_owned(),
+                    )
+                    .upcast());
+            }
+            let mut current = zelf.selected_ciphers.write();
+            selected.extend(
+                current
+                    .as_deref()
+                    .unwrap_or_else(|| CryptoExt::get_ext().default_ciphers_or_provider())
+                    .iter()
+                    .filter(|suite| suite.tls13().is_none())
+                    .copied(),
+            );
+            *current = Some(selected);
+            zelf.invalidate_policy();
+            Ok(())
+        }
+
+        #[pymethod]
+        fn set_groups(
+            zelf: &Py<Self>,
+            grouplist: PyUtf8StrRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            let list = grouplist.as_str();
+            if list.contains('\0') {
+                return Err(vm.new_value_error("embedded null character"));
+            }
+            let mut groups: Vec<&'static dyn SupportedKxGroup> = Vec::new();
+            if !list.is_empty() {
+                for name in list.split(':') {
+                    let (name, optional) =
+                        name.strip_prefix('?').map_or((name, false), |n| (n, true));
+                    match cipher::kx_group_by_openssl_name(name) {
+                        Some(group) if !groups.iter().any(|g| g.name() == group.name()) => {
+                            groups.push(group)
+                        }
+                        Some(_) => {}
+                        None if optional => {}
+                        None => {
+                            return Err(vm
+                                .new_os_subtype_error(
+                                    PySSLError::class(&vm.ctx).to_owned(),
+                                    None,
+                                    "unrecognized group".to_owned(),
+                                )
+                                .upcast());
+                        }
+                    }
+                }
+            }
+            *zelf.kx_groups.write() = Some(groups);
+            zelf.invalidate_policy();
+            Ok(())
+        }
+
+        #[pymethod]
+        fn set_server_sigalgs(
+            zelf: &Py<Self>,
+            sigalgslist: PyUtf8StrRef,
+            vm: &VirtualMachine,
+        ) -> PyResult<()> {
+            let list = sigalgslist.as_str();
+            if list.contains('\0') {
+                return Err(vm.new_value_error("embedded null character"));
+            }
+            let schemes = rustpython_host_env::ssl::sigalg::parse_list(list).map_err(|error| {
+                vm.new_os_subtype_error(
+                    PySSLError::class(&vm.ctx).to_owned(),
+                    None,
+                    error.to_owned(),
+                )
+                .upcast()
+            })?;
+            *zelf.server_sigalgs.write() = Some(schemes);
+            zelf.invalidate_policy();
+            Ok(())
+        }
+
         #[pymethod]
         fn get_ciphers(zelf: &Py<Self>, vm: &VirtualMachine) -> PyListRef {
             // What the last `set_ciphers` selected, or the provider defaults
@@ -1556,11 +1713,10 @@ mod _ssl {
                 return Err(vm.new_type_error("ECDH curve name must be str or bytes"));
             };
 
-            curve_name_to_kx_group(&curve_name).map_err(|error| vm.new_value_error(error))?;
-
-            // Store the curve name to be used during handshake
-            // This will limit the key exchange groups offered/accepted
-            *zelf.ecdh_curve.write() = Some(curve_name);
+            let groups =
+                curve_name_to_kx_group(&curve_name).map_err(|error| vm.new_value_error(error))?;
+            *zelf.kx_groups.write() = Some(groups);
+            zelf.invalidate_policy();
             Ok(())
         }
 
@@ -1618,6 +1774,7 @@ mod _ssl {
                 server_hostname: PyRwLock::new(hostname),
                 connection: PyMutex::new(None),
                 state: PyMutex::new(TlsState::new(args.server_side)),
+                got_eof_error: AtomicBool::new(false),
                 session_was_reused: PyMutex::new(false),
                 owner: PyRwLock::new(args.owner.map(|o| o.downgrade(None, vm)).transpose()?),
                 session: PyRwLock::new(None),
@@ -1698,6 +1855,7 @@ mod _ssl {
                 server_hostname: PyRwLock::new(hostname),
                 connection: PyMutex::new(None),
                 state: PyMutex::new(TlsState::new(server_side)),
+                got_eof_error: AtomicBool::new(false),
                 session_was_reused: PyMutex::new(false),
                 owner: PyRwLock::new(args.owner.map(|o| o.downgrade(None, vm)).transpose()?),
                 session: PyRwLock::new(None),
@@ -1983,6 +2141,7 @@ mod _ssl {
             let shared_session_cache = Arc::new(ParkingRwLock::new(HashMap::new()));
             Ok(Self {
                 context_identity: Arc::new(()),
+                policy_identity: PyRwLock::new(Arc::new(())),
                 protocol,
                 check_hostname: PyRwLock::new(protocol == PROTOCOL_TLS_CLIENT),
                 host_flags: PyRwLock::new(0),
@@ -2004,7 +2163,8 @@ mod _ssl {
                 msg_callback: PyRwLock::new(None),
                 keylog_filename: PyRwLock::new(None),
                 key_log: Arc::new(super::keylog::KeyLog::default()),
-                ecdh_curve: PyRwLock::new(None),
+                kx_groups: PyRwLock::new(None),
+                server_sigalgs: PyRwLock::new(None),
                 ca_cert_count: PyRwLock::new(0),
                 x509_cert_count: PyRwLock::new(0),
                 // Use the shared cache created above
@@ -2084,6 +2244,23 @@ mod _ssl {
         }
     }
 
+    // Trust loaders can mutate before a later input fails, so invalidate on
+    // both successful and exceptional exits, after their write locks drop.
+    struct ContextPolicyChange<'a>(&'a PySSLContext);
+
+    impl Drop for ContextPolicyChange<'_> {
+        fn drop(&mut self) {
+            self.0.invalidate_policy();
+        }
+    }
+
+    #[derive(Debug)]
+    struct ClientConfigSnapshot {
+        config: Arc<rustls::ClientConfig>,
+        context_identity: Arc<()>,
+        policy_identity: Arc<()>,
+    }
+
     // SSLSocket - represents a TLS-wrapped socket
     #[pyattr]
     #[pyclass(name = "_SSLSocket", module = "_ssl", traverse)]
@@ -2107,6 +2284,8 @@ mod _ssl {
         connection: PyMutex<Option<TlsConnection>>,
         // Includes the saved exception while a rejected handshake sends its alert.
         state: PyMutex<TlsState>,
+        #[pytraverse(skip)]
+        got_eof_error: AtomicBool,
         // Session was reused (for session resumption tracking)
         #[pytraverse(skip)]
         session_was_reused: PyMutex<bool>,
@@ -2117,7 +2296,7 @@ mod _ssl {
         // Client configuration used by this connection. Retained so the resulting
         // SSLSession can reuse the same verifier and client credentials.
         #[pytraverse(skip)]
-        client_config: PyRwLock<Option<Arc<rustls::ClientConfig>>>,
+        client_config: PyRwLock<Option<ClientConfigSnapshot>>,
         #[pytraverse(skip)]
         chain_builder: PyRwLock<Option<Arc<VerifiedChainBuilder>>>,
         #[pytraverse(skip)]
@@ -2144,6 +2323,19 @@ mod _ssl {
 
     #[pyclass(with(Constructor, Representable), flags(BASETYPE))]
     impl PySSLSocket {
+        // Call only for transport/protocol failures. User message callbacks
+        // may raise SSLEOFError without closing the connection.
+        fn remember_eof(
+            &self,
+            error: PyBaseExceptionRef,
+            vm: &VirtualMachine,
+        ) -> PyBaseExceptionRef {
+            if error.fast_isinstance(PySSLEOFError::class(&vm.ctx)) {
+                self.got_eof_error.store(true, Ordering::Relaxed);
+            }
+            error
+        }
+
         // Check if this is BIO mode
         pub(crate) fn is_bio_mode(&self) -> bool {
             matches!(self.io, SocketOrBio::Bio { .. })
@@ -2275,13 +2467,7 @@ mod _ssl {
 
             // Try to get session data from context's session cache
             // IMPORTANT: Acquire and release locks quickly to avoid deadlock
-            let (context_identity, session_cache_arc) = {
-                let context = self.context.read();
-                (
-                    context.context_identity.clone(),
-                    context.client_session_cache.clone(),
-                )
-            };
+            let session_cache_arc = self.context.read().client_session_cache.clone();
 
             let cached_session_data = if let Some(ref name) = server_name {
                 let key = name.as_bytes().to_vec();
@@ -2327,7 +2513,7 @@ mod _ssl {
                 _ => return,
             };
 
-            let Some(client_config) = self.client_config.write().take() else {
+            let Some(config_snapshot) = self.client_config.write().take() else {
                 return;
             };
             let Some(session_store) = self.client_session_store.write().take() else {
@@ -2335,8 +2521,9 @@ mod _ssl {
             };
 
             let session = PySSLSession {
-                context_identity,
-                client_config,
+                context_identity: config_snapshot.context_identity,
+                policy_identity: config_snapshot.policy_identity,
+                client_config: config_snapshot.config,
                 chain_builder: self
                     .chain_builder
                     .read()
@@ -2594,7 +2781,7 @@ mod _ssl {
                             Ok(())
                         })();
                         *self.state.lock() = TlsState::WaitingForClientHello(acceptor);
-                        read?;
+                        read.map_err(|error| self.remember_eof(error, vm))?;
                     }
                     TlsState::SendingAlert { error } => {
                         let result = self.flush_pending_tls_output(vm, None);
@@ -2602,7 +2789,7 @@ mod _ssl {
                             error: error.clone(),
                         };
                         result?;
-                        return Err(error);
+                        return Err(self.remember_eof(error, vm));
                     }
                     state @ (TlsState::Handshaking
                     | TlsState::Connected
@@ -2784,41 +2971,36 @@ mod _ssl {
         }
 
         /// Helper: Prepare KX groups (ECDH curve) from context settings
-        fn prepare_kx_groups(
-            &self,
-            vm: &VirtualMachine,
-        ) -> PyResult<Option<Vec<&'static dyn SupportedKxGroup>>> {
+        fn prepare_kx_groups(&self) -> Option<Vec<&'static dyn SupportedKxGroup>> {
             let ctx = self.context.read();
-            let ecdh_curve = ctx.ecdh_curve.read().clone();
+            let kx_groups = ctx.kx_groups.read().clone();
             let suite_b_kx_groups = ctx.suite_b_kx_groups.read().clone();
             drop(ctx);
 
-            if let Some(ref curve_name) = ecdh_curve {
-                match curve_name_to_kx_group(curve_name) {
-                    Ok(groups) => Ok(Some(groups)),
-                    Err(e) => Err(vm.new_value_error(format!("Failed to set ECDH curve: {e}"))),
-                }
+            if kx_groups.is_some() {
+                kx_groups
             } else {
                 // A SUITEB* cipher string pins its own groups, and nothing
                 // else asked for a curve.
-                Ok(suite_b_kx_groups)
+                suite_b_kx_groups
             }
         }
 
         /// Helper: Prepare all common protocol settings (versions, KX groups, ciphers, ALPN)
-        fn prepare_protocol_settings(&self, vm: &VirtualMachine) -> PyResult<ProtocolSettings> {
+        fn prepare_protocol_settings(&self) -> ProtocolSettings {
             let ctx = self.context.read();
             let versions = self.prepare_tls_versions();
-            let kx_groups = self.prepare_kx_groups(vm)?;
+            let kx_groups = self.prepare_kx_groups();
             let cipher_suites = ctx.selected_ciphers.read().clone();
             let alpn_protocols = ctx.alpn_protocols.read().clone();
 
-            Ok(ProtocolSettings {
+            ProtocolSettings {
                 versions,
                 kx_groups,
                 cipher_suites,
+                server_sigalgs: ctx.server_sigalgs.read().clone(),
                 alpn_protocols,
-            })
+            }
         }
 
         /// Initialize server-side TLS connection with configuration
@@ -2838,6 +3020,7 @@ mod _ssl {
             vm: &VirtualMachine,
         ) -> PyResult<()> {
             let ctx = self.context.read();
+            let policy_identity = ctx.policy_identity.read().clone();
             let cert_keys = ctx.cert_keys.read();
 
             if cert_keys.is_empty() {
@@ -2855,7 +3038,7 @@ mod _ssl {
             drop(cert_keys);
 
             // Prepare common protocol settings (TLS versions, ECDH curve, cipher suites, ALPN)
-            let protocol_settings = self.prepare_protocol_settings(vm)?;
+            let protocol_settings = self.prepare_protocol_settings();
             let min_ver = *ctx.minimum_version.read();
 
             // Check if client certificate verification is required
@@ -2888,8 +3071,9 @@ mod _ssl {
             // Certificate selection uses the actual ClientHello after SNI has
             // selected the context, including multi-certificate configurations.
             let cert_keys_only = cert_keys_clone.iter().map(|(ck, _)| ck.clone()).collect();
-            let cert_resolver: Option<Arc<dyn ResolvesServerCert>> =
-                Some(Arc::new(MultiCertResolver::new(cert_keys_only)));
+            let cert_resolver: Option<Arc<dyn ResolvesServerCert>> = Some(Arc::new(
+                MultiCertResolver::new(cert_keys_only, protocol_settings.server_sigalgs.as_deref()),
+            ));
 
             // Extract cert_chain and private_key from first cert_key
             //
@@ -2935,7 +3119,11 @@ mod _ssl {
             let cache_server_config =
                 !use_deferred_validation && ctx.capath_state.read().directories.is_empty();
             let cached_config_arc = if cache_server_config {
-                ctx.server_config.read().clone()
+                ctx.server_config
+                    .read()
+                    .as_ref()
+                    .filter(|(policy, _)| Arc::ptr_eq(policy, &policy_identity))
+                    .map(|(_, config)| config.clone())
             } else {
                 None
             };
@@ -2944,12 +3132,14 @@ mod _ssl {
             let (mut config_arc, chain_builder) = if let Some(cached) = cached_config_arc {
                 cached
             } else {
-                let config =
-                    create_server_config(config_options).map_err(|e| vm.new_value_error(e))?;
+                let config = create_server_config(config_options).map_err(|e| {
+                    vm.new_os_subtype_error(PySSLError::class(&vm.ctx).to_owned(), None, e)
+                        .upcast()
+                })?;
 
                 if cache_server_config {
                     let ctx = self.context.read();
-                    *ctx.server_config.write() = Some(config.clone());
+                    *ctx.server_config.write() = Some((policy_identity, config.clone()));
                 }
 
                 config
@@ -2965,11 +3155,10 @@ mod _ssl {
                     *conn_guard = Some(TlsConnection::new(Connection::Server(conn)));
                     *self.state.lock() = TlsState::Handshaking;
                 }
-                Err((error, mut alert)) => {
-                    let mut bytes = Vec::new();
-                    alert
-                        .write_all(&mut bytes)
-                        .map_err(|e| e.into_pyexception(vm))?;
+                Err((error, alert)) => {
+                    let bytes =
+                        rustpython_host_env::ssl::handshake::initial_handshake_alert(&error, alert)
+                            .map_err(|e| e.into_pyexception(vm))?;
                     self.reject_connection(SslError::from_rustls(error).into_py_err(vm), bytes, vm);
                     self.accept_client_hello(vm)?;
                 }
@@ -2980,6 +3169,9 @@ mod _ssl {
 
         #[pymethod]
         fn do_handshake(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<()> {
+            if zelf.got_eof_error.load(Ordering::Relaxed) {
+                return Err(create_ssl_eof_error(vm).upcast());
+            }
             // Check if handshake already done
             if zelf.handshake_completed() {
                 return Ok(());
@@ -3005,11 +3197,14 @@ mod _ssl {
                         return zelf.accept_client_hello(vm).map(|_| ());
                     }
                 } else {
-                    // Client-side connection
+                    // Client-side connection. Capture policy before reading any
+                    // settings; mutations during construction invalidate this snapshot.
                     let ctx = zelf.context.read();
+                    let policy_identity = ctx.policy_identity.read().clone();
+                    let has_capath = !ctx.capath_state.read().directories.is_empty();
 
                     // Prepare common protocol settings (TLS versions, ECDH curve, cipher suites, ALPN)
-                    let protocol_settings = zelf.prepare_protocol_settings(vm)?;
+                    let protocol_settings = zelf.prepare_protocol_settings();
 
                     // Clone values we need before building config
                     let verify_mode = *ctx.verify_mode.read();
@@ -3060,23 +3255,32 @@ mod _ssl {
                     };
 
                     let explicit_session = zelf.session.read().clone();
+                    let explicit_session = explicit_session
+                        .as_ref()
+                        .map(|session| {
+                            let session = session
+                                .downcast_ref::<PySSLSession>()
+                                .ok_or_else(|| vm.new_type_error("Value is not a SSLSession."))?;
+                            if !Arc::ptr_eq(&session.context_identity, &context_identity) {
+                                return Err(
+                                    vm.new_value_error("Session refers to a different SSLContext.")
+                                );
+                            }
+                            Ok(session)
+                        })
+                        .transpose()?;
+                    let reusable_session = explicit_session.filter(|session| {
+                        !has_capath
+                            && Arc::ptr_eq(&session.policy_identity, &policy_identity)
+                            && session.server_name.as_ref() == Some(&server_name)
+                    });
                     let session_store = Arc::new(CapturingClientSessionStore::new(session_cache));
-                    let (mut config, chain_builder) = if let Some(session) = explicit_session {
-                        let session = session
-                            .downcast_ref::<PySSLSession>()
-                            .ok_or_else(|| vm.new_type_error("Value is not a SSLSession."))?;
-                        if !Arc::ptr_eq(&session.context_identity, &context_identity) {
-                            return Err(
-                                vm.new_value_error("Session refers to a different SSLContext.")
-                            );
-                        }
-                        if session.server_name.as_ref() == Some(&server_name) {
-                            session.session_store.transfer_session(
-                                &session_store,
-                                &server_name,
-                                session.kind,
-                            );
-                        }
+                    let (mut config, chain_builder) = if let Some(session) = reusable_session {
+                        session.session_store.transfer_session(
+                            &session_store,
+                            &server_name,
+                            session.kind,
+                        );
                         let mut config = (*session.client_config).clone();
                         config.resumption =
                             rustls::client::Resumption::store(session_store.clone());
@@ -3099,12 +3303,19 @@ mod _ssl {
                             session_store: Some(session_store.clone()),
                             crls: crls_clone,
                         };
-                        create_client_config(config_options).map_err(|e| vm.new_value_error(e))?
+                        create_client_config(config_options).map_err(|e| {
+                            vm.new_os_subtype_error(PySSLError::class(&vm.ctx).to_owned(), None, e)
+                                .upcast()
+                        })?
                     };
                     Arc::make_mut(&mut config).key_log = zelf.key_log.clone();
 
                     *zelf.chain_builder.write() = Some(chain_builder);
-                    *zelf.client_config.write() = Some(config.clone());
+                    *zelf.client_config.write() = Some(ClientConfigSnapshot {
+                        config: config.clone(),
+                        context_identity,
+                        policy_identity,
+                    });
                     *zelf.client_session_store.write() = Some(session_store);
 
                     let mut conn = ClientConnection::new(config, server_name).map_err(|e| {
@@ -3131,7 +3342,7 @@ mod _ssl {
                 zelf.reject_connection(error.into_py_err(vm), bytes, vm);
                 return zelf.accept_client_hello(vm).map(|_| ());
             }
-            handshake_result.map_err(|e| e.into_py_err(vm))?;
+            handshake_result.map_err(|e| zelf.remember_eof(e.into_py_err(vm), vm))?;
             if let Some(exc) = zelf.take_msg_exc() {
                 return Err(exc);
             }
@@ -3171,6 +3382,10 @@ mod _ssl {
                 }
             }
 
+            if zelf.got_eof_error.load(Ordering::Relaxed) {
+                return Err(create_ssl_eof_error(vm).upcast());
+            }
+
             // return empty bytes immediately for len=0
             if len == 0 {
                 return match buffer {
@@ -3198,7 +3413,7 @@ mod _ssl {
             }
 
             // Helper function to handle return value based on buffer presence
-            let return_data = |data: Vec<u8>,
+            let return_data = |mut data: Vec<u8>,
                                buffer_arg: &OptionalArg<ArgMemoryBuffer>,
                                vm: &VirtualMachine|
              -> PyResult<PyObjectRef> {
@@ -3216,6 +3431,7 @@ mod _ssl {
                     }
                     OptionalArg::Missing => {
                         // Return bytes object
+                        data.shrink_to_fit();
                         Ok(vm.ctx.new_bytes(data).into())
                     }
                 }
@@ -3242,7 +3458,11 @@ mod _ssl {
                         let mut conn_guard = zelf.connection.lock();
                         let conn = match conn_guard.as_mut() {
                             Some(conn) => conn,
-                            None => return Err(create_ssl_eof_error(vm).upcast()),
+                            None => {
+                                return Err(
+                                    zelf.remember_eof(create_ssl_eof_error(vm).upcast(), vm)
+                                );
+                            }
                         };
                         conn.pending_plaintext()
                     };
@@ -3255,7 +3475,7 @@ mod _ssl {
                         }
                     }
                     // EOF occurred in violation of protocol (unexpected closure)
-                    Err(create_ssl_eof_error(vm).upcast())
+                    Err(zelf.remember_eof(create_ssl_eof_error(vm).upcast(), vm))
                 }
                 Err(error) if error.is_zero_return() => {
                     // If plaintext is still buffered, return it before clean EOF.
@@ -3301,12 +3521,12 @@ mod _ssl {
                     Err(timeout_error_msg(vm, msg).upcast())
                 }
                 Err(crate::ssl::compat::SslError::Py(e)) => {
-                    // Python exception - pass through
-                    Err(e)
+                    // Exception from a transport operation.
+                    Err(zelf.remember_eof(e, vm))
                 }
                 Err(e) => {
                     // Other SSL errors
-                    Err(e.into_py_err(vm))
+                    Err(zelf.remember_eof(e.into_py_err(vm), vm))
                 }
             }
         }
@@ -3325,6 +3545,9 @@ mod _ssl {
 
         #[pymethod]
         fn write(zelf: &Py<Self>, b: ArgBytesLike, vm: &VirtualMachine) -> PyResult<usize> {
+            if zelf.got_eof_error.load(Ordering::Relaxed) {
+                return Err(create_ssl_eof_error(vm).upcast());
+            }
             let data_bytes = b.borrow_buf();
             let data_len = data_bytes.len();
 
@@ -3371,7 +3594,7 @@ mod _ssl {
                 Err(crate::ssl::compat::SslError::Timeout(msg)) => {
                     Err(timeout_error_msg(vm, msg).upcast())
                 }
-                Err(e) => Err(e.into_py_err(vm)),
+                Err(e) => Err(zelf.remember_eof(e.into_py_err(vm), vm)),
             }
         }
 
@@ -3440,6 +3663,55 @@ mod _ssl {
             ))
         }
 
+        #[pymethod]
+        fn group(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<String>> {
+            let group = {
+                let conn_guard = zelf.connection.lock();
+                let Some(conn) = conn_guard.as_ref() else {
+                    return Ok(None);
+                };
+                let Some(group) = conn.inner().negotiated_key_exchange_group() else {
+                    return Ok(None);
+                };
+                group.name()
+            };
+            group
+                .as_str()
+                .map(|name| Some(name.to_owned()))
+                .ok_or_else(|| {
+                    vm.new_not_implemented_error(format!(
+                        "The TLS provider has no name for negotiated group {:#06x}",
+                        u16::from(group)
+                    ))
+                })
+        }
+
+        #[pymethod]
+        fn client_sigalg(_zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<String>> {
+            Err(vm.new_not_implemented_error(
+                "Rustls does not expose the selected client authentication signature algorithm",
+            ))
+        }
+
+        #[pymethod]
+        fn server_sigalg(_zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<Option<String>> {
+            Err(vm.new_not_implemented_error(
+                "Rustls does not expose the selected server handshake signature algorithm",
+            ))
+        }
+
+        #[pymethod]
+        fn uses_ktls_for_send(_zelf: &Py<Self>) -> bool {
+            // This transport encrypts records in rustls; it never enables kernel TLS.
+            false
+        }
+
+        #[pymethod]
+        fn uses_ktls_for_recv(_zelf: &Py<Self>) -> bool {
+            // This transport decrypts records in rustls; it never enables kernel TLS.
+            false
+        }
+
         #[pymethod]
         fn version(zelf: &Py<Self>) -> Option<String> {
             // Extract cipher suite, releasing lock quickly
@@ -4018,6 +4290,7 @@ mod _ssl {
     #[derive(Debug, PyPayload)]
     struct PySSLSession {
         context_identity: Arc<()>,
+        policy_identity: Arc<()>,
         client_config: Arc<rustls::ClientConfig>,
         chain_builder: Arc<VerifiedChainBuilder>,
         session_store: Arc<CapturingClientSessionStore>,
@@ -4184,6 +4457,28 @@ mod _ssl {
         tuple.into()
     }
 
+    #[pyfunction]
+    fn get_sigalgs(vm: &VirtualMachine) -> PyResult<PyListRef> {
+        // These are the TLS schemes advertised by the installed provider, in its
+        // preference order, rather than certificate signature algorithms.
+        let names = CryptoExt::get_provider()
+            .signature_verification_algorithms
+            .supported_schemes()
+            .into_iter()
+            .map(|scheme| {
+                let name =
+                    rustpython_host_env::ssl::sigalg::scheme_name(scheme).ok_or_else(|| {
+                        vm.new_not_implemented_error(format!(
+                            "The TLS provider uses an unrecognized signature scheme {:#06x}",
+                            u16::from(scheme)
+                        ))
+                    })?;
+                Ok(vm.ctx.new_str(name).into())
+            })
+            .collect::<PyResult<Vec<_>>>()?;
+        Ok(vm.ctx.new_list(names))
+    }
+
     #[pyfunction]
     fn RAND_status() -> i32 {
         1 // The configured rustls provider supplies cryptographic randomness.
diff --git a/crates/stdlib/src/ssl/compat.rs b/crates/stdlib/src/ssl/compat.rs
index 09c180bcaab..87ca0211fed 100644
--- a/crates/stdlib/src/ssl/compat.rs
+++ b/crates/stdlib/src/ssl/compat.rs
@@ -140,6 +140,7 @@ impl SslError {
         match self {
             Self::Rustls(error) => TlsError::from_rustls(error.clone()).is_eof(),
             Self::Eof => true,
+            Self::Io(error) => error.kind() == std::io::ErrorKind::UnexpectedEof,
             _ => false,
         }
     }
diff --git a/crates/stdlib/src/ssl_wasm.rs b/crates/stdlib/src/ssl_wasm.rs
index 21f46586c18..4693af6aeb9 100644
--- a/crates/stdlib/src/ssl_wasm.rs
+++ b/crates/stdlib/src/ssl_wasm.rs
@@ -1,3 +1,5 @@
+// cspell: ignore sigalgs
+
 //! Wasm `_ssl` on the rustls-free `rustpython_host_env::ssl` surface.
 //!
 //! MemoryBIO, protocol constants, OID lookup, hostname checks, and ALPN
@@ -137,6 +139,8 @@ mod _ssl {
     #[pyattr]
     const HAS_PSK: bool = false;
     #[pyattr]
+    const HAS_PSK_TLS13: bool = false;
+    #[pyattr]
     const HAS_SSLv2: bool = false;
     #[pyattr]
     const HAS_SSLv3: bool = false;
@@ -886,6 +890,11 @@ mod _ssl {
             .into()
     }
 
+    #[pyfunction]
+    fn get_sigalgs(vm: &VirtualMachine) -> PyResult<PyObjectRef> {
+        Err(vm.new_not_implemented_error(UNAVAILABLE))
+    }
+
     #[pyfunction]
     fn RAND_status() -> i32 {
         1
diff --git a/crates/stdlib/src/unicodedata.rs b/crates/stdlib/src/unicodedata.rs
index 6ef17ecc119..ab6d808e58a 100644
--- a/crates/stdlib/src/unicodedata.rs
+++ b/crates/stdlib/src/unicodedata.rs
@@ -33,12 +33,189 @@ impl<'a> TryFromBorrowedObject<'a> for NormalizeFormArg {
 mod unicodedata {
     use super::{NormalizeFormArg, unicode_core};
     use crate::vm::{
-        Py, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
+        Py, PyObjectRef, PyPayload, PyResult, VirtualMachine,
         builtins::{PyModule, PyStr, PyStrRef},
+        common::lock::PyMutex,
         function::OptionalArg,
+        protocol::PyIterReturn,
+        types::{IterNext, Iterable, Representable, SelfIter},
     };
     use itertools::Itertools;
     use rustpython_common::wtf8::{CodePoint, Wtf8Buf};
+    use unicode_core::grapheme::{self, GraphemeBreakState};
+
+    fn grapheme_char(character: &Py<PyStr>, vm: &VirtualMachine) -> PyResult<CodePoint> {
+        character
+            .as_wtf8()
+            .code_points()
+            .exactly_one()
+            .map_err(|_| vm.new_type_error("argument must be a unicode character, not str"))
+    }
+
+    #[pyfunction]
+    fn grapheme_cluster_break(chr: PyStrRef, vm: &VirtualMachine) -> PyResult<&'static str> {
+        grapheme_char(&chr, vm).map(grapheme::grapheme_cluster_break)
+    }
+
+    #[pyfunction]
+    fn indic_conjunct_break(chr: PyStrRef, vm: &VirtualMachine) -> PyResult<&'static str> {
+        grapheme_char(&chr, vm).map(grapheme::indic_conjunct_break)
+    }
+
+    #[pyfunction]
+    fn extended_pictographic(chr: PyStrRef, vm: &VirtualMachine) -> PyResult<bool> {
+        grapheme_char(&chr, vm).map(grapheme::extended_pictographic)
+    }
+
+    #[pyclass(no_attr, name = "Segment", traverse)]
+    #[derive(Debug, PyPayload)]
+    struct Segment {
+        string: PyStrRef,
+        #[pytraverse(skip)]
+        start: usize,
+        #[pytraverse(skip)]
+        end: usize,
+        #[pytraverse(skip)]
+        bytes: core::ops::Range<usize>,
+    }
+
+    #[pyclass(with(Representable), flags(IMMUTABLETYPE, DISALLOW_INSTANTIATION))]
+    impl Segment {
+        #[pygetset]
+        fn start(zelf: &Py<Self>) -> usize {
+            zelf.start
+        }
+
+        #[pygetset]
+        fn end(zelf: &Py<Self>) -> usize {
+            zelf.end
+        }
+
+        #[pymethod]
+        fn __str__(zelf: &Py<Self>, vm: &VirtualMachine) -> PyStrRef {
+            vm.ctx.new_str(&zelf.string.as_wtf8()[zelf.bytes.clone()])
+        }
+    }
+
+    impl Representable for Segment {
+        #[inline]
+        fn repr_str(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<String> {
+            Ok(format!("<Segment {}:{}>", zelf.start, zelf.end))
+        }
+    }
+
+    #[derive(Debug)]
+    struct GraphemePosition {
+        start: usize,
+        start_byte: usize,
+        pos: usize,
+        pos_byte: usize,
+        end: usize,
+        end_byte: usize,
+        state: GraphemeBreakState,
+    }
+
+    #[pyclass(no_attr, name = "GraphemeBreakIterator", traverse)]
+    #[derive(Debug, PyPayload)]
+    struct GraphemeBreakIterator {
+        string: PyStrRef,
+        #[pytraverse(skip)]
+        position: PyMutex<GraphemePosition>,
+    }
+
+    #[pyclass(with(IterNext, Iterable), flags(IMMUTABLETYPE, DISALLOW_INSTANTIATION))]
+    impl GraphemeBreakIterator {}
+
+    impl SelfIter for GraphemeBreakIterator {}
+
+    impl IterNext for GraphemeBreakIterator {
+        fn next(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {
+            let mut position = zelf.position.lock();
+            if position.start >= position.end {
+                return Ok(PyIterReturn::StopIteration(None));
+            }
+            let start = position.start;
+            let start_byte = position.start_byte;
+            let scan_byte = position.pos_byte;
+            let mut points = zelf.string.as_wtf8()[scan_byte..position.end_byte]
+                .code_point_indices()
+                .peekable();
+            let (end, end_byte) = loop {
+                let Some((offset, point)) = points.next() else {
+                    position.start = position.pos;
+                    position.start_byte = position.end_byte;
+                    break (position.pos, position.end_byte);
+                };
+                let byte = scan_byte + offset;
+                let index = position.pos;
+                let boundary = position.state.advance(point);
+                position.pos += 1;
+                position.pos_byte = points
+                    .peek()
+                    .map_or(position.end_byte, |(offset, _)| scan_byte + offset);
+                if boundary {
+                    position.start = index;
+                    position.start_byte = byte;
+                    break (index, byte);
+                }
+            };
+            drop(position);
+            Ok(PyIterReturn::Return(
+                Segment {
+                    string: zelf.string.clone(),
+                    start,
+                    end,
+                    bytes: start_byte..end_byte,
+                }
+                .into_ref(&vm.ctx)
+                .into(),
+            ))
+        }
+    }
+
+    #[pyfunction]
+    fn iter_graphemes(
+        unistr: PyStrRef,
+        start: OptionalArg<PyObjectRef>,
+        end: OptionalArg<PyObjectRef>,
+        vm: &VirtualMachine,
+    ) -> PyResult<crate::vm::PyRef<GraphemeBreakIterator>> {
+        // Convert in argument order, including overflow, before adjusting bounds.
+        let index = |arg: OptionalArg<PyObjectRef>, default| -> PyResult<isize> {
+            match arg {
+                OptionalArg::Present(value) => value.try_index(vm)?.try_to_primitive(vm),
+                OptionalArg::Missing => Ok(default),
+            }
+        };
+        let mut start = index(start, 0)?;
+        let mut end = index(end, isize::MAX)?;
+        let len = unistr.char_len() as isize;
+        if end > len {
+            end = len;
+        } else if end < 0 {
+            end = (end + len).max(0);
+        }
+        if start < 0 {
+            start = (start + len).max(0);
+        }
+        let start = start as usize;
+        let end = end as usize;
+        let start_byte = unistr.char_index_to_byte(start);
+        let end_byte = unistr.char_index_to_byte(end);
+        Ok(GraphemeBreakIterator {
+            string: unistr,
+            position: PyMutex::new(GraphemePosition {
+                start,
+                start_byte,
+                pos: start,
+                pos_byte: start_byte,
+                end,
+                end_byte,
+                state: GraphemeBreakState::default(),
+            }),
+        }
+        .into_ref(&vm.ctx))
+    }
 
     pub(crate) fn module_exec(vm: &VirtualMachine, module: &Py<PyModule>) -> PyResult<()> {
         __module_exec(vm, module);
@@ -244,8 +421,9 @@ mod unicodedata {
         }
     }
 
+    #[cfg(feature = "ucd_3_2_0")]
     #[pyattr]
-    fn ucd_3_2_0(vm: &VirtualMachine) -> PyRef<Ucd> {
+    fn ucd_3_2_0(vm: &VirtualMachine) -> crate::vm::PyRef<Ucd> {
         Ucd::new(false).into_ref(&vm.ctx)
     }
 
diff --git a/crates/unicode/Cargo.toml b/crates/unicode/Cargo.toml
index 4d753293e39..d71b4209cfe 100644
--- a/crates/unicode/Cargo.toml
+++ b/crates/unicode/Cargo.toml
@@ -8,6 +8,10 @@ repository = { workspace = true }
 license = { workspace = true }
 rust-version = { workspace = true }
 
+[features]
+default = ["ucd_3_2_0"]
+ucd_3_2_0 = []
+
 [dependencies]
 rustpython-wtf8 = { workspace = true }
 
diff --git a/crates/unicode/build.rs b/crates/unicode/build.rs
index e32d99d542c..4fae7faef28 100644
--- a/crates/unicode/build.rs
+++ b/crates/unicode/build.rs
@@ -678,10 +678,14 @@ fn generate_numeric_value(
         "(u32, u32, f64)",
         &mut values_latest,
     );
+    #[cfg(feature = "ucd_3_2_0")]
     let mut ucd32_diffs: Vec<_> = ucd32_diffs
         .into_iter()
         .map(|((start, end), value)| (start, end, value))
         .collect();
+    #[cfg(not(feature = "ucd_3_2_0"))]
+    let mut ucd32_diffs = Vec::new();
+
     write_slice_debug(
         &mut writer,
         "NUMERIC_VALUES_DIFF",
diff --git a/crates/unicode/src/data.rs b/crates/unicode/src/data.rs
index 381a180a420..7a5cbdbbc3a 100644
--- a/crates/unicode/src/data.rs
+++ b/crates/unicode/src/data.rs
@@ -19,21 +19,46 @@ use icu_properties::props::{
 };
 use rustpython_wtf8::CodePoint;
 
+// Latest Unicode
 include!(concat!(env!("OUT_DIR"), "/generated/algo_names.rs"));
 include!(concat!(env!("OUT_DIR"), "/generated/name_lookups.rs"));
+include!(concat!(env!("OUT_DIR"), "/generated/decomp.rs"));
+include!(concat!(env!("OUT_DIR"), "/generated/numeric_value_3_2.rs"));
+
+// Unicode 3.2.0
+#[cfg(feature = "ucd_3_2_0")]
 include!(concat!(env!("OUT_DIR"), "/generated/bidi_class_3_2.rs"));
+#[cfg(feature = "ucd_3_2_0")]
 include!(concat!(env!("OUT_DIR"), "/generated/binary_props_3_2.rs"));
+#[cfg(feature = "ucd_3_2_0")]
 include!(concat!(
     env!("OUT_DIR"),
     "/generated/combining_class_3_2.rs"
 ));
-include!(concat!(env!("OUT_DIR"), "/generated/decomp.rs"));
+#[cfg(feature = "ucd_3_2_0")]
 include!(concat!(env!("OUT_DIR"), "/generated/eaw_3_2.rs"));
+#[cfg(feature = "ucd_3_2_0")]
 include!(concat!(env!("OUT_DIR"), "/generated/gen_cat_3_2.rs"));
+#[cfg(feature = "ucd_3_2_0")]
 include!(concat!(env!("OUT_DIR"), "/generated/membership_3_2.rs"));
-include!(concat!(env!("OUT_DIR"), "/generated/numeric_value_3_2.rs"));
+#[cfg(feature = "ucd_3_2_0")]
 include!(concat!(env!("OUT_DIR"), "/generated/num_type_3_2.rs"));
 
+#[cfg(not(feature = "ucd_3_2_0"))]
+const BIDI_CLASS_DIFF: &[(u32, u32, BidiClass)] = &[];
+#[cfg(not(feature = "ucd_3_2_0"))]
+const BIDI_MIRRORED: &[(u32, u32)] = &[];
+#[cfg(not(feature = "ucd_3_2_0"))]
+const COMBINING_CLASS: &[(u32, u32, CanonicalCombiningClass)] = &[];
+#[cfg(not(feature = "ucd_3_2_0"))]
+const EAST_ASIAN_WIDTH: &[(u32, u32, EastAsianWidth)] = &[];
+#[cfg(not(feature = "ucd_3_2_0"))]
+const GENERAL_CATEGORY: &[(u32, u32, GeneralCategory)] = &[];
+#[cfg(not(feature = "ucd_3_2_0"))]
+const MEMBERSHIP_3_2: &[(u32, u32)] = &[];
+#[cfg(not(feature = "ucd_3_2_0"))]
+const NUMERIC_TYPE_DIFF: &[(u32, u32, NumericType)] = &[];
+
 #[derive(Clone, Copy)]
 enum DecompositionType {
     Compat,
@@ -276,7 +301,20 @@ impl Ucd {
         if let Some(ch) = unicode_names2::character(search_name)
             .or_else(|| AlgorithmicName::check_name(search_name))
         {
-            return self.membership(ch).then_some(LookupResult::Character(ch));
+            if self.modern {
+                return Some(LookupResult::Character(ch));
+            }
+            cold_path();
+
+            if !self.membership(ch) {
+                return None;
+            }
+
+            // 3.2.0 doesn't have aliases but unicode_names2 supports aliases so reject them.
+            if lookup_alias(search_name).is_some() {
+                return None;
+            }
+            return Some(LookupResult::Character(ch));
         }
         if !self.modern {
             return None;
@@ -511,12 +549,14 @@ mod tests {
     }
 
     #[test]
+    #[cfg(feature = "ucd_3_2_0")]
     fn ucd_3_2_0_view_differs_from_modern() {
         let legacy = Ucd::new(false);
         assert_eq!(legacy.unidata_version(), "3.2.0");
     }
 
     #[test]
+    #[cfg(feature = "ucd_3_2_0")]
     fn name_aliases_resolve_and_do_not_replace_the_official_name() {
         assert_eq!(
             lookup_character("LATIN CAPITAL LETTER GHA"),
@@ -534,6 +574,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(feature = "ucd_3_2_0")]
     fn named_sequences_resolve_only_on_the_modern_view() {
         assert_eq!(
             lookup_name("LATIN SMALL LETTER R WITH TILDE"),
diff --git a/crates/unicode/src/grapheme.rs b/crates/unicode/src/grapheme.rs
new file mode 100644
index 00000000000..b8a097e3710
--- /dev/null
+++ b/crates/unicode/src/grapheme.rs
@@ -0,0 +1,180 @@
+//! Extended grapheme clusters over Python's full code point domain.
+//!
+//! State transitions and rule ordering follow CPython's Modules/unicodedata.c
+//! at d220409a13b77de7a6c30abe16ea90db01528edc (Unicode 17.0.0).
+
+// spell-checker:ignore incb
+
+use icu_properties::{
+    CodePointMapData, CodePointSetData,
+    props::{ExtendedPictographic, GraphemeClusterBreak as Gcb, IndicConjunctBreak as Incb},
+};
+use rustpython_wtf8::CodePoint;
+
+fn gcb(c: CodePoint) -> Gcb {
+    CodePointMapData::<Gcb>::new().get32(c.to_u32())
+}
+
+fn incb(c: CodePoint) -> Incb {
+    CodePointMapData::<Incb>::new().get32(c.to_u32())
+}
+
+/// The long Grapheme_Cluster_Break property name.
+#[must_use]
+pub fn grapheme_cluster_break(c: CodePoint) -> &'static str {
+    match gcb(c) {
+        Gcb::CR => "CR",
+        Gcb::LF => "LF",
+        Gcb::Control => "Control",
+        Gcb::Extend => "Extend",
+        Gcb::L => "L",
+        Gcb::V => "V",
+        Gcb::T => "T",
+        Gcb::LV => "LV",
+        Gcb::LVT => "LVT",
+        Gcb::SpacingMark => "SpacingMark",
+        Gcb::Prepend => "Prepend",
+        Gcb::RegionalIndicator => "Regional_Indicator",
+        Gcb::ZWJ => "ZWJ",
+        _ => "Other",
+    }
+}
+
+/// The long Indic_Conjunct_Break property name.
+#[must_use]
+pub fn indic_conjunct_break(c: CodePoint) -> &'static str {
+    match incb(c) {
+        Incb::Consonant => "Consonant",
+        Incb::Extend => "Extend",
+        Incb::Linker => "Linker",
+        _ => "None",
+    }
+}
+
+/// Whether the code point has the Extended_Pictographic property.
+#[must_use]
+pub fn extended_pictographic(c: CodePoint) -> bool {
+    CodePointSetData::new::<ExtendedPictographic>().contains32(c.to_u32())
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum ExtPictState {
+    Init,
+    Started,
+    Zwj,
+    Matched,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum IncbState {
+    Init,
+    Started,
+    Linker,
+    Matched,
+}
+
+/// Streaming break state, initialized afresh at the requested slice start.
+///
+/// A code point is consumed before its preceding boundary is returned. Keep
+/// this state across cluster yields, rather than processing that point twice.
+#[derive(Debug)]
+pub struct GraphemeBreakState {
+    previous: Gcb,
+    pictographic: ExtPictState,
+    conjunct: IncbState,
+    regional_odd: bool,
+    started: bool,
+}
+
+impl Default for GraphemeBreakState {
+    fn default() -> Self {
+        Self {
+            previous: Gcb::Other,
+            pictographic: ExtPictState::Init,
+            conjunct: IncbState::Init,
+            regional_odd: false,
+            started: false,
+        }
+    }
+}
+
+impl GraphemeBreakState {
+    /// Consume one code point and report whether a new cluster starts here.
+    pub fn advance(&mut self, c: CodePoint) -> bool {
+        let current = gcb(c);
+        self.pictographic = if extended_pictographic(c) {
+            if self.pictographic == ExtPictState::Zwj {
+                ExtPictState::Matched
+            } else {
+                ExtPictState::Started
+            }
+        } else if matches!(
+            self.pictographic,
+            ExtPictState::Started | ExtPictState::Matched
+        ) {
+            match current {
+                Gcb::Extend => ExtPictState::Started,
+                Gcb::ZWJ => ExtPictState::Zwj,
+                _ => ExtPictState::Init,
+            }
+        } else {
+            ExtPictState::Init
+        };
+        self.conjunct = match incb(c) {
+            Incb::Consonant => {
+                if self.conjunct == IncbState::Linker {
+                    IncbState::Matched
+                } else {
+                    IncbState::Started
+                }
+            }
+            Incb::Extend if self.conjunct != IncbState::Init => {
+                if self.conjunct == IncbState::Linker {
+                    IncbState::Linker
+                } else {
+                    IncbState::Started
+                }
+            }
+            Incb::Linker if self.conjunct != IncbState::Init => IncbState::Linker,
+            _ => IncbState::Init,
+        };
+        self.regional_odd = current == Gcb::RegionalIndicator && !self.regional_odd;
+        let boundary = self.started && self.is_break(current);
+        self.previous = current;
+        self.started = true;
+        boundary
+    }
+
+    fn is_break(&self, current: Gcb) -> bool {
+        let previous = self.previous;
+        // GB3, GB4, GB5: controls take precedence over attachment rules.
+        if previous == Gcb::CR && current == Gcb::LF {
+            return false;
+        }
+        if matches!(previous, Gcb::CR | Gcb::LF | Gcb::Control)
+            || matches!(current, Gcb::CR | Gcb::LF | Gcb::Control)
+        {
+            return true;
+        }
+        // GB6, GB7, GB8: Hangul syllables.
+        if previous == Gcb::L && matches!(current, Gcb::L | Gcb::V | Gcb::LV | Gcb::LVT)
+            || matches!(previous, Gcb::LV | Gcb::V) && matches!(current, Gcb::V | Gcb::T)
+            || matches!(previous, Gcb::LVT | Gcb::T) && current == Gcb::T
+        {
+            return false;
+        }
+        // GB9, GB9a, GB9b, GB9c, GB11.
+        if matches!(current, Gcb::Extend | Gcb::ZWJ | Gcb::SpacingMark)
+            || previous == Gcb::Prepend
+            || self.conjunct == IncbState::Matched
+            || self.pictographic == ExtPictState::Matched
+        {
+            return false;
+        }
+        // GB12, GB13: parity includes the current regional indicator.
+        if previous == Gcb::RegionalIndicator && current == previous {
+            return self.regional_odd;
+        }
+        true // GB999
+    }
+}
diff --git a/crates/unicode/src/lib.rs b/crates/unicode/src/lib.rs
index 319271b019e..fef618dfe17 100644
--- a/crates/unicode/src/lib.rs
+++ b/crates/unicode/src/lib.rs
@@ -12,6 +12,7 @@ extern crate alloc;
 pub mod case;
 pub mod classify;
 pub mod data;
+pub mod grapheme;
 pub mod identifier;
 pub mod normalize;
 
diff --git a/crates/unicode/tests/data/cpython3.15_graphemes.txt b/crates/unicode/tests/data/cpython3.15_graphemes.txt
new file mode 100644
index 00000000000..78de1d3824c
--- /dev/null
+++ b/crates/unicode/tests/data/cpython3.15_graphemes.txt
@@ -0,0 +1,2171 @@
+# CPython d220409a13b77de7a6c30abe16ea90db01528edc; Unicode 17.0.0
+# Inclusive contiguous ranges: start:end GCB InCB Extended_Pictographic
+# Reconstructed raw SHA256 9aae5520167e69e08d2241b9899bc7c65b0865d1713ffde698a6e7e1c952284d
+000000:000009 Control None 0
+00000A:00000A LF None 0
+00000B:00000C Control None 0
+00000D:00000D CR None 0
+00000E:00001F Control None 0
+000020:00007E Other None 0
+00007F:00009F Control None 0
+0000A0:0000A8 Other None 0
+0000A9:0000A9 Other None 1
+0000AA:0000AC Other None 0
+0000AD:0000AD Control None 0
+0000AE:0000AE Other None 1
+0000AF:0002FF Other None 0
+000300:00036F Extend Extend 0
+000370:000482 Other None 0
+000483:000489 Extend Extend 0
+00048A:000590 Other None 0
+000591:0005BD Extend Extend 0
+0005BE:0005BE Other None 0
+0005BF:0005BF Extend Extend 0
+0005C0:0005C0 Other None 0
+0005C1:0005C2 Extend Extend 0
+0005C3:0005C3 Other None 0
+0005C4:0005C5 Extend Extend 0
+0005C6:0005C6 Other None 0
+0005C7:0005C7 Extend Extend 0
+0005C8:0005FF Other None 0
+000600:000605 Prepend None 0
+000606:00060F Other None 0
+000610:00061A Extend Extend 0
+00061B:00061B Other None 0
+00061C:00061C Control None 0
+00061D:00064A Other None 0
+00064B:00065F Extend Extend 0
+000660:00066F Other None 0
+000670:000670 Extend Extend 0
+000671:0006D5 Other None 0
+0006D6:0006DC Extend Extend 0
+0006DD:0006DD Prepend None 0
+0006DE:0006DE Other None 0
+0006DF:0006E4 Extend Extend 0
+0006E5:0006E6 Other None 0
+0006E7:0006E8 Extend Extend 0
+0006E9:0006E9 Other None 0
+0006EA:0006ED Extend Extend 0
+0006EE:00070E Other None 0
+00070F:00070F Prepend None 0
+000710:000710 Other None 0
+000711:000711 Extend Extend 0
+000712:00072F Other None 0
+000730:00074A Extend Extend 0
+00074B:0007A5 Other None 0
+0007A6:0007B0 Extend Extend 0
+0007B1:0007EA Other None 0
+0007EB:0007F3 Extend Extend 0
+0007F4:0007FC Other None 0
+0007FD:0007FD Extend Extend 0
+0007FE:000815 Other None 0
+000816:000819 Extend Extend 0
+00081A:00081A Other None 0
+00081B:000823 Extend Extend 0
+000824:000824 Other None 0
+000825:000827 Extend Extend 0
+000828:000828 Other None 0
+000829:00082D Extend Extend 0
+00082E:000858 Other None 0
+000859:00085B Extend Extend 0
+00085C:00088F Other None 0
+000890:000891 Prepend None 0
+000892:000896 Other None 0
+000897:00089F Extend Extend 0
+0008A0:0008C9 Other None 0
+0008CA:0008E1 Extend Extend 0
+0008E2:0008E2 Prepend None 0
+0008E3:000902 Extend Extend 0
+000903:000903 SpacingMark None 0
+000904:000914 Other None 0
+000915:000939 Other Consonant 0
+00093A:00093A Extend Extend 0
+00093B:00093B SpacingMark None 0
+00093C:00093C Extend Extend 0
+00093D:00093D Other None 0
+00093E:000940 SpacingMark None 0
+000941:000948 Extend Extend 0
+000949:00094C SpacingMark None 0
+00094D:00094D Extend Linker 0
+00094E:00094F SpacingMark None 0
+000950:000950 Other None 0
+000951:000957 Extend Extend 0
+000958:00095F Other Consonant 0
+000960:000961 Other None 0
+000962:000963 Extend Extend 0
+000964:000977 Other None 0
+000978:00097F Other Consonant 0
+000980:000980 Other None 0
+000981:000981 Extend Extend 0
+000982:000983 SpacingMark None 0
+000984:000994 Other None 0
+000995:0009A8 Other Consonant 0
+0009A9:0009A9 Other None 0
+0009AA:0009B0 Other Consonant 0
+0009B1:0009B1 Other None 0
+0009B2:0009B2 Other Consonant 0
+0009B3:0009B5 Other None 0
+0009B6:0009B9 Other Consonant 0
+0009BA:0009BB Other None 0
+0009BC:0009BC Extend Extend 0
+0009BD:0009BD Other None 0
+0009BE:0009BE Extend Extend 0
+0009BF:0009C0 SpacingMark None 0
+0009C1:0009C4 Extend Extend 0
+0009C5:0009C6 Other None 0
+0009C7:0009C8 SpacingMark None 0
+0009C9:0009CA Other None 0
+0009CB:0009CC SpacingMark None 0
+0009CD:0009CD Extend Linker 0
+0009CE:0009D6 Other None 0
+0009D7:0009D7 Extend Extend 0
+0009D8:0009DB Other None 0
+0009DC:0009DD Other Consonant 0
+0009DE:0009DE Other None 0
+0009DF:0009DF Other Consonant 0
+0009E0:0009E1 Other None 0
+0009E2:0009E3 Extend Extend 0
+0009E4:0009EF Other None 0
+0009F0:0009F1 Other Consonant 0
+0009F2:0009FD Other None 0
+0009FE:0009FE Extend Extend 0
+0009FF:000A00 Other None 0
+000A01:000A02 Extend Extend 0
+000A03:000A03 SpacingMark None 0
+000A04:000A3B Other None 0
+000A3C:000A3C Extend Extend 0
+000A3D:000A3D Other None 0
+000A3E:000A40 SpacingMark None 0
+000A41:000A42 Extend Extend 0
+000A43:000A46 Other None 0
+000A47:000A48 Extend Extend 0
+000A49:000A4A Other None 0
+000A4B:000A4D Extend Extend 0
+000A4E:000A50 Other None 0
+000A51:000A51 Extend Extend 0
+000A52:000A6F Other None 0
+000A70:000A71 Extend Extend 0
+000A72:000A74 Other None 0
+000A75:000A75 Extend Extend 0
+000A76:000A80 Other None 0
+000A81:000A82 Extend Extend 0
+000A83:000A83 SpacingMark None 0
+000A84:000A94 Other None 0
+000A95:000AA8 Other Consonant 0
+000AA9:000AA9 Other None 0
+000AAA:000AB0 Other Consonant 0
+000AB1:000AB1 Other None 0
+000AB2:000AB3 Other Consonant 0
+000AB4:000AB4 Other None 0
+000AB5:000AB9 Other Consonant 0
+000ABA:000ABB Other None 0
+000ABC:000ABC Extend Extend 0
+000ABD:000ABD Other None 0
+000ABE:000AC0 SpacingMark None 0
+000AC1:000AC5 Extend Extend 0
+000AC6:000AC6 Other None 0
+000AC7:000AC8 Extend Extend 0
+000AC9:000AC9 SpacingMark None 0
+000ACA:000ACA Other None 0
+000ACB:000ACC SpacingMark None 0
+000ACD:000ACD Extend Linker 0
+000ACE:000AE1 Other None 0
+000AE2:000AE3 Extend Extend 0
+000AE4:000AF8 Other None 0
+000AF9:000AF9 Other Consonant 0
+000AFA:000AFF Extend Extend 0
+000B00:000B00 Other None 0
+000B01:000B01 Extend Extend 0
+000B02:000B03 SpacingMark None 0
+000B04:000B14 Other None 0
+000B15:000B28 Other Consonant 0
+000B29:000B29 Other None 0
+000B2A:000B30 Other Consonant 0
+000B31:000B31 Other None 0
+000B32:000B33 Other Consonant 0
+000B34:000B34 Other None 0
+000B35:000B39 Other Consonant 0
+000B3A:000B3B Other None 0
+000B3C:000B3C Extend Extend 0
+000B3D:000B3D Other None 0
+000B3E:000B3F Extend Extend 0
+000B40:000B40 SpacingMark None 0
+000B41:000B44 Extend Extend 0
+000B45:000B46 Other None 0
+000B47:000B48 SpacingMark None 0
+000B49:000B4A Other None 0
+000B4B:000B4C SpacingMark None 0
+000B4D:000B4D Extend Linker 0
+000B4E:000B54 Other None 0
+000B55:000B57 Extend Extend 0
+000B58:000B5B Other None 0
+000B5C:000B5D Other Consonant 0
+000B5E:000B5E Other None 0
+000B5F:000B5F Other Consonant 0
+000B60:000B61 Other None 0
+000B62:000B63 Extend Extend 0
+000B64:000B70 Other None 0
+000B71:000B71 Other Consonant 0
+000B72:000B81 Other None 0
+000B82:000B82 Extend Extend 0
+000B83:000BBD Other None 0
+000BBE:000BBE Extend Extend 0
+000BBF:000BBF SpacingMark None 0
+000BC0:000BC0 Extend Extend 0
+000BC1:000BC2 SpacingMark None 0
+000BC3:000BC5 Other None 0
+000BC6:000BC8 SpacingMark None 0
+000BC9:000BC9 Other None 0
+000BCA:000BCC SpacingMark None 0
+000BCD:000BCD Extend Extend 0
+000BCE:000BD6 Other None 0
+000BD7:000BD7 Extend Extend 0
+000BD8:000BFF Other None 0
+000C00:000C00 Extend Extend 0
+000C01:000C03 SpacingMark None 0
+000C04:000C04 Extend Extend 0
+000C05:000C14 Other None 0
+000C15:000C28 Other Consonant 0
+000C29:000C29 Other None 0
+000C2A:000C39 Other Consonant 0
+000C3A:000C3B Other None 0
+000C3C:000C3C Extend Extend 0
+000C3D:000C3D Other None 0
+000C3E:000C40 Extend Extend 0
+000C41:000C44 SpacingMark None 0
+000C45:000C45 Other None 0
+000C46:000C48 Extend Extend 0
+000C49:000C49 Other None 0
+000C4A:000C4C Extend Extend 0
+000C4D:000C4D Extend Linker 0
+000C4E:000C54 Other None 0
+000C55:000C56 Extend Extend 0
+000C57:000C57 Other None 0
+000C58:000C5A Other Consonant 0
+000C5B:000C61 Other None 0
+000C62:000C63 Extend Extend 0
+000C64:000C80 Other None 0
+000C81:000C81 Extend Extend 0
+000C82:000C83 SpacingMark None 0
+000C84:000CBB Other None 0
+000CBC:000CBC Extend Extend 0
+000CBD:000CBD Other None 0
+000CBE:000CBE SpacingMark None 0
+000CBF:000CC0 Extend Extend 0
+000CC1:000CC1 SpacingMark None 0
+000CC2:000CC2 Extend Extend 0
+000CC3:000CC4 SpacingMark None 0
+000CC5:000CC5 Other None 0
+000CC6:000CC8 Extend Extend 0
+000CC9:000CC9 Other None 0
+000CCA:000CCD Extend Extend 0
+000CCE:000CD4 Other None 0
+000CD5:000CD6 Extend Extend 0
+000CD7:000CE1 Other None 0
+000CE2:000CE3 Extend Extend 0
+000CE4:000CF2 Other None 0
+000CF3:000CF3 SpacingMark None 0
+000CF4:000CFF Other None 0
+000D00:000D01 Extend Extend 0
+000D02:000D03 SpacingMark None 0
+000D04:000D14 Other None 0
+000D15:000D3A Other Consonant 0
+000D3B:000D3C Extend Extend 0
+000D3D:000D3D Other None 0
+000D3E:000D3E Extend Extend 0
+000D3F:000D40 SpacingMark None 0
+000D41:000D44 Extend Extend 0
+000D45:000D45 Other None 0
+000D46:000D48 SpacingMark None 0
+000D49:000D49 Other None 0
+000D4A:000D4C SpacingMark None 0
+000D4D:000D4D Extend Linker 0
+000D4E:000D4E Prepend None 0
+000D4F:000D56 Other None 0
+000D57:000D57 Extend Extend 0
+000D58:000D61 Other None 0
+000D62:000D63 Extend Extend 0
+000D64:000D80 Other None 0
+000D81:000D81 Extend Extend 0
+000D82:000D83 SpacingMark None 0
+000D84:000DC9 Other None 0
+000DCA:000DCA Extend Extend 0
+000DCB:000DCE Other None 0
+000DCF:000DCF Extend Extend 0
+000DD0:000DD1 SpacingMark None 0
+000DD2:000DD4 Extend Extend 0
+000DD5:000DD5 Other None 0
+000DD6:000DD6 Extend Extend 0
+000DD7:000DD7 Other None 0
+000DD8:000DDE SpacingMark None 0
+000DDF:000DDF Extend Extend 0
+000DE0:000DF1 Other None 0
+000DF2:000DF3 SpacingMark None 0
+000DF4:000E30 Other None 0
+000E31:000E31 Extend Extend 0
+000E32:000E32 Other None 0
+000E33:000E33 SpacingMark None 0
+000E34:000E3A Extend Extend 0
+000E3B:000E46 Other None 0
+000E47:000E4E Extend Extend 0
+000E4F:000EB0 Other None 0
+000EB1:000EB1 Extend Extend 0
+000EB2:000EB2 Other None 0
+000EB3:000EB3 SpacingMark None 0
+000EB4:000EBC Extend Extend 0
+000EBD:000EC7 Other None 0
+000EC8:000ECE Extend Extend 0
+000ECF:000F17 Other None 0
+000F18:000F19 Extend Extend 0
+000F1A:000F34 Other None 0
+000F35:000F35 Extend Extend 0
+000F36:000F36 Other None 0
+000F37:000F37 Extend Extend 0
+000F38:000F38 Other None 0
+000F39:000F39 Extend Extend 0
+000F3A:000F3D Other None 0
+000F3E:000F3F SpacingMark None 0
+000F40:000F70 Other None 0
+000F71:000F7E Extend Extend 0
+000F7F:000F7F SpacingMark None 0
+000F80:000F84 Extend Extend 0
+000F85:000F85 Other None 0
+000F86:000F87 Extend Extend 0
+000F88:000F8C Other None 0
+000F8D:000F97 Extend Extend 0
+000F98:000F98 Other None 0
+000F99:000FBC Extend Extend 0
+000FBD:000FC5 Other None 0
+000FC6:000FC6 Extend Extend 0
+000FC7:000FFF Other None 0
+001000:00102A Other Consonant 0
+00102B:00102C Other None 0
+00102D:001030 Extend Extend 0
+001031:001031 SpacingMark None 0
+001032:001037 Extend Extend 0
+001038:001038 Other None 0
+001039:001039 Extend Linker 0
+00103A:00103A Extend Extend 0
+00103B:00103C SpacingMark None 0
+00103D:00103E Extend Extend 0
+00103F:00103F Other Consonant 0
+001040:00104F Other None 0
+001050:001055 Other Consonant 0
+001056:001057 SpacingMark None 0
+001058:001059 Extend Extend 0
+00105A:00105D Other Consonant 0
+00105E:001060 Extend Extend 0
+001061:001061 Other Consonant 0
+001062:001064 Other None 0
+001065:001066 Other Consonant 0
+001067:00106D Other None 0
+00106E:001070 Other Consonant 0
+001071:001074 Extend Extend 0
+001075:001081 Other Consonant 0
+001082:001082 Extend Extend 0
+001083:001083 Other None 0
+001084:001084 SpacingMark None 0
+001085:001086 Extend Extend 0
+001087:00108C Other None 0
+00108D:00108D Extend Extend 0
+00108E:00108E Other Consonant 0
+00108F:00109C Other None 0
+00109D:00109D Extend Extend 0
+00109E:0010FF Other None 0
+001100:00115F L None 0
+001160:0011A7 V None 0
+0011A8:0011FF T None 0
+001200:00135C Other None 0
+00135D:00135F Extend Extend 0
+001360:001711 Other None 0
+001712:001715 Extend Extend 0
+001716:001731 Other None 0
+001732:001734 Extend Extend 0
+001735:001751 Other None 0
+001752:001753 Extend Extend 0
+001754:001771 Other None 0
+001772:001773 Extend Extend 0
+001774:00177F Other None 0
+001780:0017B3 Other Consonant 0
+0017B4:0017B5 Extend Extend 0
+0017B6:0017B6 SpacingMark None 0
+0017B7:0017BD Extend Extend 0
+0017BE:0017C5 SpacingMark None 0
+0017C6:0017C6 Extend Extend 0
+0017C7:0017C8 SpacingMark None 0
+0017C9:0017D1 Extend Extend 0
+0017D2:0017D2 Extend Linker 0
+0017D3:0017D3 Extend Extend 0
+0017D4:0017DC Other None 0
+0017DD:0017DD Extend Extend 0
+0017DE:00180A Other None 0
+00180B:00180D Extend Extend 0
+00180E:00180E Control None 0
+00180F:00180F Extend Extend 0
+001810:001884 Other None 0
+001885:001886 Extend Extend 0
+001887:0018A8 Other None 0
+0018A9:0018A9 Extend Extend 0
+0018AA:00191F Other None 0
+001920:001922 Extend Extend 0
+001923:001926 SpacingMark None 0
+001927:001928 Extend Extend 0
+001929:00192B SpacingMark None 0
+00192C:00192F Other None 0
+001930:001931 SpacingMark None 0
+001932:001932 Extend Extend 0
+001933:001938 SpacingMark None 0
+001939:00193B Extend Extend 0
+00193C:001A16 Other None 0
+001A17:001A18 Extend Extend 0
+001A19:001A1A SpacingMark None 0
+001A1B:001A1B Extend Extend 0
+001A1C:001A1F Other None 0
+001A20:001A54 Other Consonant 0
+001A55:001A55 SpacingMark None 0
+001A56:001A56 Extend Extend 0
+001A57:001A57 SpacingMark None 0
+001A58:001A5E Extend Extend 0
+001A5F:001A5F Other None 0
+001A60:001A60 Extend Linker 0
+001A61:001A61 Other None 0
+001A62:001A62 Extend Extend 0
+001A63:001A64 Other None 0
+001A65:001A6C Extend Extend 0
+001A6D:001A72 SpacingMark None 0
+001A73:001A7C Extend Extend 0
+001A7D:001A7E Other None 0
+001A7F:001A7F Extend Extend 0
+001A80:001AAF Other None 0
+001AB0:001ADD Extend Extend 0
+001ADE:001ADF Other None 0
+001AE0:001AEB Extend Extend 0
+001AEC:001AFF Other None 0
+001B00:001B03 Extend Extend 0
+001B04:001B04 SpacingMark None 0
+001B05:001B0A Other None 0
+001B0B:001B0C Other Consonant 0
+001B0D:001B12 Other None 0
+001B13:001B33 Other Consonant 0
+001B34:001B3D Extend Extend 0
+001B3E:001B41 SpacingMark None 0
+001B42:001B43 Extend Extend 0
+001B44:001B44 Extend Linker 0
+001B45:001B4C Other Consonant 0
+001B4D:001B6A Other None 0
+001B6B:001B73 Extend Extend 0
+001B74:001B7F Other None 0
+001B80:001B81 Extend Extend 0
+001B82:001B82 SpacingMark None 0
+001B83:001BA0 Other Consonant 0
+001BA1:001BA1 SpacingMark None 0
+001BA2:001BA5 Extend Extend 0
+001BA6:001BA7 SpacingMark None 0
+001BA8:001BAA Extend Extend 0
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+00D7B0:00D7C6 V None 0
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+00D7CB:00D7FB T None 0
+00D7FC:00FB1D Other None 0
+00FB1E:00FB1E Extend Extend 0
+00FB1F:00FDFF Other None 0
+00FE00:00FE0F Extend Extend 0
+00FE10:00FE1F Other None 0
+00FE20:00FE2F Extend Extend 0
+00FE30:00FEFE Other None 0
+00FEFF:00FEFF Control None 0
+00FF00:00FF9D Other None 0
+00FF9E:00FF9F Extend Extend 0
+00FFA0:00FFEF Other None 0
+00FFF0:00FFFB Control None 0
+00FFFC:0101FC Other None 0
+0101FD:0101FD Extend Extend 0
+0101FE:0102DF Other None 0
+0102E0:0102E0 Extend Extend 0
+0102E1:010375 Other None 0
+010376:01037A Extend Extend 0
+01037B:0109FF Other None 0
+010A00:010A00 Other Consonant 0
+010A01:010A03 Extend Extend 0
+010A04:010A04 Other None 0
+010A05:010A06 Extend Extend 0
+010A07:010A0B Other None 0
+010A0C:010A0F Extend Extend 0
+010A10:010A13 Other Consonant 0
+010A14:010A14 Other None 0
+010A15:010A17 Other Consonant 0
+010A18:010A18 Other None 0
+010A19:010A35 Other Consonant 0
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+010A38:010A3A Extend Extend 0
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+010AE7:010D23 Other None 0
+010D24:010D27 Extend Extend 0
+010D28:010D68 Other None 0
+010D69:010D6D Extend Extend 0
+010D6E:010EAA Other None 0
+010EAB:010EAC Extend Extend 0
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+010EFA:010EFF Extend Extend 0
+010F00:010F45 Other None 0
+010F46:010F50 Extend Extend 0
+010F51:010F81 Other None 0
+010F82:010F85 Extend Extend 0
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+011000:011000 SpacingMark None 0
+011001:011001 Extend Extend 0
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+011038:011046 Extend Extend 0
+011047:01106F Other None 0
+011070:011070 Extend Extend 0
+011071:011072 Other None 0
+011073:011074 Extend Extend 0
+011075:01107E Other None 0
+01107F:011081 Extend Extend 0
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+0110B0:0110B2 SpacingMark None 0
+0110B3:0110B6 Extend Extend 0
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+0110B9:0110BA Extend Extend 0
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+0110C2:0110C2 Extend Extend 0
+0110C3:0110CC Other None 0
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+011100:011102 Extend Extend 0
+011103:011126 Other Consonant 0
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+011134:011134 Extend Extend 0
+011135:011143 Other None 0
+011144:011144 Other Consonant 0
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+011147:011147 Other Consonant 0
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+011173:011173 Extend Extend 0
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+011180:011181 Extend Extend 0
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+011183:0111B2 Other None 0
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+0111B6:0111BE Extend Extend 0
+0111BF:0111BF SpacingMark None 0
+0111C0:0111C0 Extend Extend 0
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+0111C9:0111CC Extend Extend 0
+0111CD:0111CD Other None 0
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+0111CF:0111CF Extend Extend 0
+0111D0:01122B Other None 0
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+011234:011237 Extend Extend 0
+011238:01123D Other None 0
+01123E:01123E Extend Extend 0
+01123F:011240 Other None 0
+011241:011241 Extend Extend 0
+011242:0112DE Other None 0
+0112DF:0112DF Extend Extend 0
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+0112E3:0112EA Extend Extend 0
+0112EB:0112FF Other None 0
+011300:011301 Extend Extend 0
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+011304:01133A Other None 0
+01133B:01133C Extend Extend 0
+01133D:01133D Other None 0
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+01133F:01133F SpacingMark None 0
+011340:011340 Extend Extend 0
+011341:011344 SpacingMark None 0
+011345:011346 Other None 0
+011347:011348 SpacingMark None 0
+011349:01134A Other None 0
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+01134D:01134D Extend Extend 0
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+011357:011357 Extend Extend 0
+011358:011361 Other None 0
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+011364:011365 Other None 0
+011366:01136C Extend Extend 0
+01136D:01136F Other None 0
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+011375:01137F Other None 0
+011380:011389 Other Consonant 0
+01138A:01138A Other None 0
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+01138C:01138D Other None 0
+01138E:01138E Other Consonant 0
+01138F:01138F Other None 0
+011390:0113B5 Other Consonant 0
+0113B6:0113B7 Other None 0
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+0113BB:0113C0 Extend Extend 0
+0113C1:0113C1 Other None 0
+0113C2:0113C2 Extend Extend 0
+0113C3:0113C4 Other None 0
+0113C5:0113C5 Extend Extend 0
+0113C6:0113C6 Other None 0
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+0113CA:0113CA SpacingMark None 0
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+0113E1:0113E2 Extend Extend 0
+0113E3:011434 Other None 0
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+011438:01143F Extend Extend 0
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+011442:011444 Extend Extend 0
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+011446:011446 Extend Extend 0
+011447:01145D Other None 0
+01145E:01145E Extend Extend 0
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+0114B0:0114B0 Extend Extend 0
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+0114B3:0114B8 Extend Extend 0
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+0114BA:0114BA Extend Extend 0
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+0114BD:0114BD Extend Extend 0
+0114BE:0114BE SpacingMark None 0
+0114BF:0114C0 Extend Extend 0
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+0114C2:0114C3 Extend Extend 0
+0114C4:0115AE Other None 0
+0115AF:0115AF Extend Extend 0
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+0115B2:0115B5 Extend Extend 0
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+0115BC:0115BD Extend Extend 0
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+0115BF:0115C0 Extend Extend 0
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+0115DC:0115DD Extend Extend 0
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+011633:01163A Extend Extend 0
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+01163D:01163D Extend Extend 0
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+01163F:011640 Extend Extend 0
+011641:0116AA Other None 0
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+0116AD:0116AD Extend Extend 0
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+0116B0:0116B7 Extend Extend 0
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+011900:011906 Other Consonant 0
+011907:011908 Other None 0
+011909:011909 Other Consonant 0
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+011F00:011F01 Extend Extend 0
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+016FF0:016FF1 Extend Extend 0
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+01BC9D:01BC9E Extend Extend 0
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+01CF00:01CF2D Extend Extend 0
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+01D165:01D169 Extend Extend 0
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+01D1AA:01D1AD Extend Extend 0
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+01DA00:01DA36 Extend Extend 0
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+01DA3B:01DA6C Extend Extend 0
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+01DA75:01DA75 Extend Extend 0
+01DA76:01DA83 Other None 0
+01DA84:01DA84 Extend Extend 0
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+01E000:01E006 Extend Extend 0
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+01E008:01E018 Extend Extend 0
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+01E023:01E024 Extend Extend 0
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+01E026:01E02A Extend Extend 0
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+01E08F:01E08F Extend Extend 0
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+01E130:01E136 Extend Extend 0
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+01E2AE:01E2AE Extend Extend 0
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+01E2EC:01E2EF Extend Extend 0
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+01E4EC:01E4EF Extend Extend 0
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+01E5EE:01E5EF Extend Extend 0
+01E5F0:01E6E2 Other None 0
+01E6E3:01E6E3 Extend Extend 0
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+01E6E6:01E6E6 Extend Extend 0
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+01E6EE:01E6EF Extend Extend 0
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+01E6F5:01E6F5 Extend Extend 0
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+01E8D0:01E8D6 Extend Extend 0
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+01E944:01E94A Extend Extend 0
+01E94B:01F003 Other None 0
+01F004:01F004 Other None 1
+01F005:01F02B Other None 0
+01F02C:01F02F Other None 1
+01F030:01F093 Other None 0
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+01F0A0:01F0AE Other None 0
+01F0AF:01F0B0 Other None 1
+01F0B1:01F0BF Other None 0
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+01F0C1:01F0CE Other None 0
+01F0CF:01F0D0 Other None 1
+01F0D1:01F0F5 Other None 0
+01F0F6:01F0FF Other None 1
+01F100:01F16F Other None 0
+01F170:01F171 Other None 1
+01F172:01F17D Other None 0
+01F17E:01F17F Other None 1
+01F180:01F18D Other None 0
+01F18E:01F18E Other None 1
+01F18F:01F190 Other None 0
+01F191:01F19A Other None 1
+01F19B:01F1AD Other None 0
+01F1AE:01F1E5 Other None 1
+01F1E6:01F1FF Regional_Indicator None 0
+01F200:01F200 Other None 0
+01F201:01F20F Other None 1
+01F210:01F219 Other None 0
+01F21A:01F21A Other None 1
+01F21B:01F22E Other None 0
+01F22F:01F22F Other None 1
+01F230:01F231 Other None 0
+01F232:01F23A Other None 1
+01F23B:01F23B Other None 0
+01F23C:01F23F Other None 1
+01F240:01F248 Other None 0
+01F249:01F25F Other None 1
+01F260:01F265 Other None 0
+01F266:01F321 Other None 1
+01F322:01F323 Other None 0
+01F324:01F393 Other None 1
+01F394:01F395 Other None 0
+01F396:01F397 Other None 1
+01F398:01F398 Other None 0
+01F399:01F39B Other None 1
+01F39C:01F39D Other None 0
+01F39E:01F3F0 Other None 1
+01F3F1:01F3F2 Other None 0
+01F3F3:01F3F5 Other None 1
+01F3F6:01F3F6 Other None 0
+01F3F7:01F3FA Other None 1
+01F3FB:01F3FF Extend Extend 0
+01F400:01F4FD Other None 1
+01F4FE:01F4FE Other None 0
+01F4FF:01F53D Other None 1
+01F53E:01F548 Other None 0
+01F549:01F54E Other None 1
+01F54F:01F54F Other None 0
+01F550:01F567 Other None 1
+01F568:01F56E Other None 0
+01F56F:01F570 Other None 1
+01F571:01F572 Other None 0
+01F573:01F57A Other None 1
+01F57B:01F586 Other None 0
+01F587:01F587 Other None 1
+01F588:01F589 Other None 0
+01F58A:01F58D Other None 1
+01F58E:01F58F Other None 0
+01F590:01F590 Other None 1
+01F591:01F594 Other None 0
+01F595:01F596 Other None 1
+01F597:01F5A3 Other None 0
+01F5A4:01F5A5 Other None 1
+01F5A6:01F5A7 Other None 0
+01F5A8:01F5A8 Other None 1
+01F5A9:01F5B0 Other None 0
+01F5B1:01F5B2 Other None 1
+01F5B3:01F5BB Other None 0
+01F5BC:01F5BC Other None 1
+01F5BD:01F5C1 Other None 0
+01F5C2:01F5C4 Other None 1
+01F5C5:01F5D0 Other None 0
+01F5D1:01F5D3 Other None 1
+01F5D4:01F5DB Other None 0
+01F5DC:01F5DE Other None 1
+01F5DF:01F5E0 Other None 0
+01F5E1:01F5E1 Other None 1
+01F5E2:01F5E2 Other None 0
+01F5E3:01F5E3 Other None 1
+01F5E4:01F5E7 Other None 0
+01F5E8:01F5E8 Other None 1
+01F5E9:01F5EE Other None 0
+01F5EF:01F5EF Other None 1
+01F5F0:01F5F2 Other None 0
+01F5F3:01F5F3 Other None 1
+01F5F4:01F5F9 Other None 0
+01F5FA:01F64F Other None 1
+01F650:01F67F Other None 0
+01F680:01F6C5 Other None 1
+01F6C6:01F6CA Other None 0
+01F6CB:01F6D2 Other None 1
+01F6D3:01F6D4 Other None 0
+01F6D5:01F6E5 Other None 1
+01F6E6:01F6E8 Other None 0
+01F6E9:01F6E9 Other None 1
+01F6EA:01F6EA Other None 0
+01F6EB:01F6F0 Other None 1
+01F6F1:01F6F2 Other None 0
+01F6F3:01F6FF Other None 1
+01F700:01F7D9 Other None 0
+01F7DA:01F7FF Other None 1
+01F800:01F80B Other None 0
+01F80C:01F80F Other None 1
+01F810:01F847 Other None 0
+01F848:01F84F Other None 1
+01F850:01F859 Other None 0
+01F85A:01F85F Other None 1
+01F860:01F887 Other None 0
+01F888:01F88F Other None 1
+01F890:01F8AD Other None 0
+01F8AE:01F8AF Other None 1
+01F8B0:01F8BB Other None 0
+01F8BC:01F8BF Other None 1
+01F8C0:01F8C1 Other None 0
+01F8C2:01F8CF Other None 1
+01F8D0:01F8D8 Other None 0
+01F8D9:01F8FF Other None 1
+01F900:01F90B Other None 0
+01F90C:01F93A Other None 1
+01F93B:01F93B Other None 0
+01F93C:01F945 Other None 1
+01F946:01F946 Other None 0
+01F947:01F9FF Other None 1
+01FA00:01FA57 Other None 0
+01FA58:01FA5F Other None 1
+01FA60:01FA6D Other None 0
+01FA6E:01FAFF Other None 1
+01FB00:01FBFF Other None 0
+01FC00:01FFFD Other None 1
+01FFFE:0DFFFF Other None 0
+0E0000:0E001F Control None 0
+0E0020:0E007F Extend Extend 0
+0E0080:0E00FF Control None 0
+0E0100:0E01EF Extend Extend 0
+0E01F0:0E0FFF Control None 0
+0E1000:10FFFF Other None 0
diff --git a/crates/unicode/tests/differential.rs b/crates/unicode/tests/differential.rs
index 1bed13e7faf..0d66c1eff14 100644
--- a/crates/unicode/tests/differential.rs
+++ b/crates/unicode/tests/differential.rs
@@ -11,7 +11,7 @@
 //! Both data files use the same run-length format: one `predicate` line per
 //! str method, followed by comma-separated hex `start:end` inclusive ranges.
 
-// spell-checker:ignore recategorized recategorizations
+// spell-checker:ignore recategorized recategorizations incb
 
 #[cfg(test)]
 mod tests {
@@ -421,4 +421,85 @@ mod tests {
             panic!("{msg}");
         }
     }
+
+    #[test]
+    fn unicode17_grapheme_properties_exact_final() {
+        use rustpython_unicode::grapheme;
+        use rustpython_wtf8::CodePoint;
+
+        const MAX: u32 = 0x110000;
+        const REFERENCE: &str = include_str!("data/cpython3.15_graphemes.txt");
+        const GCB: [&str; 14] = [
+            "Other",
+            "Prepend",
+            "CR",
+            "LF",
+            "Control",
+            "Extend",
+            "Regional_Indicator",
+            "SpacingMark",
+            "L",
+            "V",
+            "T",
+            "LV",
+            "LVT",
+            "ZWJ",
+        ];
+        const INCB: [&str; 4] = ["None", "Linker", "Consonant", "Extend"];
+        assert!(REFERENCE.len() <= 1024 * 1024, "oracle size bound");
+        assert_eq!(
+            REFERENCE.lines().next(),
+            Some("# CPython d220409a13b77de7a6c30abe16ea90db01528edc; Unicode 17.0.0"),
+            "wrong reference provenance"
+        );
+        let mut next = 0;
+        let mut rows = 0;
+        let mut mismatches = 0usize;
+        let mut first = Vec::new();
+        for line in REFERENCE.lines().filter(|line| !line.starts_with('#')) {
+            rows += 1;
+            assert!(rows <= 100000, "oracle range count bound");
+            let fields: Vec<_> = line.split_whitespace().collect();
+            assert_eq!(fields.len(), 4, "invalid oracle row");
+            let (start, end) = fields[0].split_once(':').expect("start:end");
+            let start = u32::from_str_radix(start, 16).expect("hex start");
+            let end = u32::from_str_radix(end, 16).expect("hex end");
+            assert_eq!(start, next, "gap, overlap, or unordered oracle range");
+            assert!(start <= end && end < MAX, "invalid oracle range");
+            assert!(
+                GCB.contains(&fields[1]) && INCB.contains(&fields[2]),
+                "invalid property name"
+            );
+            let pictographic = match fields[3] {
+                "0" => false,
+                "1" => true,
+                _ => panic!("invalid Extended_Pictographic value"),
+            };
+            for cp in start..=end {
+                // Includes surrogates; converting through char would lose coverage.
+                let point = CodePoint::from_u32(cp).expect("valid code point");
+                let actual = (
+                    grapheme::grapheme_cluster_break(point),
+                    grapheme::indic_conjunct_break(point),
+                    grapheme::extended_pictographic(point),
+                );
+                let expected = (fields[1], fields[2], pictographic);
+                if actual != expected {
+                    mismatches += 1;
+                    if first.len() < 20 {
+                        first.push(format!("U+{cp:06X}: expected {expected:?}, got {actual:?}"));
+                    }
+                }
+            }
+            next = end + 1;
+        }
+        assert_eq!(next, MAX, "oracle does not cover every code point");
+        assert_eq!(
+            mismatches,
+            0,
+            "first {} mismatches: {}",
+            first.len(),
+            first.join("; ")
+        );
+    }
 }
diff --git a/crates/unicode/tests/generate_reference.py b/crates/unicode/tests/generate_reference.py
index 6a78230de75..4f881153c9c 100644
--- a/crates/unicode/tests/generate_reference.py
+++ b/crates/unicode/tests/generate_reference.py
@@ -21,6 +21,176 @@
 
 MAX = 0x110000
 
+
+def generate_graphemes(args) -> int:
+    """Write a new Unicode 17 oracle, without touching the older fixtures."""
+    import hashlib
+    import json
+    import subprocess
+
+    commit = "d220409a13b77de7a6c30abe16ea90db01528edc"
+    gcb_names = (
+        "Other",
+        "Prepend",
+        "CR",
+        "LF",
+        "Control",
+        "Extend",
+        "Regional_Indicator",
+        "SpacingMark",
+        "L",
+        "V",
+        "T",
+        "LV",
+        "LVT",
+        "ZWJ",
+    )
+    incb_names = ("None", "Linker", "Consonant", "Extend")
+
+    def digest(path):
+        h = hashlib.sha256()
+        with path.open("rb") as stream:
+            for chunk in iter(lambda: stream.read(65536), b""):
+                h.update(chunk)
+        return h.hexdigest()
+
+    if sys.implementation.name != "cpython" or unicodedata.unidata_version != "17.0.0":
+        raise RuntimeError("requires the reviewed CPython Unicode 17 oracle")
+    executable = pathlib.Path(sys.executable).resolve(strict=True)
+    extension = pathlib.Path(unicodedata.__file__).resolve(strict=True)
+    if (
+        digest(executable) != args.python_sha256
+        or digest(extension) != args.unicodedata_sha256
+    ):
+        raise RuntimeError("oracle executable or extension hash mismatch")
+    source = args.cpython_source.resolve(strict=True)
+    head = subprocess.check_output(
+        ["git", "-C", str(source), "rev-parse", "HEAD"],
+        timeout=5,
+        text=True,
+    ).strip()
+    if head != commit:
+        raise RuntimeError("CPython source is not the pinned final commit")
+    header = source / "Modules/unicodedata_db.h"
+    blob = subprocess.check_output(
+        ["git", "-C", str(source), "show", f"{commit}:Modules/unicodedata_db.h"],
+        timeout=5,
+    )
+    if digest(header) != hashlib.sha256(blob).hexdigest():
+        raise RuntimeError("CPython Unicode database header differs from pinned source")
+
+    outputs = [
+        args.graphemes_output,
+        args.graphemes_raw_output,
+        args.graphemes_manifest,
+    ]
+    outputs = [p.resolve() for p in outputs]
+    if len(set(outputs)) != 3:
+        raise RuntimeError("oracle output paths must be distinct")
+    old_data = pathlib.Path(__file__).resolve().parent / "data"
+    for path in outputs:
+        if path.exists() or path.is_relative_to(old_data):
+            raise RuntimeError(
+                "outputs must be new files outside existing fixture directory"
+            )
+        if not path.parent.is_dir():
+            raise RuntimeError("output parents must already exist")
+
+    range_path, raw_path, manifest_path = outputs
+    ranges = []
+    start = 0
+    previous = None
+    raw_hash = hashlib.sha256()
+    # Exclusive creation prevents replacing any existing reference artifact.
+    with raw_path.open("xb") as raw:
+        buffer = bytearray()
+        for cp in range(MAX):
+            c = chr(cp)
+            triple = (
+                gcb_names.index(unicodedata.grapheme_cluster_break(c)),
+                incb_names.index(unicodedata.indic_conjunct_break(c)),
+                int(unicodedata.extended_pictographic(c)),
+            )
+            if triple != previous:
+                if previous is not None:
+                    ranges.append((start, cp - 1, previous))
+                    if len(ranges) > 100000:
+                        raise RuntimeError("range oracle exceeds reviewed count bound")
+                start, previous = cp, triple
+            buffer.extend(triple)
+            if len(buffer) >= 65535:
+                raw.write(buffer)
+                raw_hash.update(buffer)
+                buffer.clear()
+        raw.write(buffer)
+        raw_hash.update(buffer)
+    ranges.append((start, MAX - 1, previous))
+    if raw_path.stat().st_size != MAX * 3:
+        raise RuntimeError("raw oracle length mismatch")
+    lines = [
+        f"# CPython {commit}; Unicode 17.0.0",
+        "# Inclusive contiguous ranges: start:end GCB InCB Extended_Pictographic",
+        f"# Reconstructed raw SHA256 {raw_hash.hexdigest()}",
+    ]
+    for start, end, (gcb, incb, pictographic) in ranges:
+        lines.append(
+            f"{start:06X}:{end:06X} {gcb_names[gcb]} {incb_names[incb]} {pictographic}"
+        )
+    text = ("\n".join(lines) + "\n").encode("ascii")
+    if len(text) > 1024 * 1024 or len(ranges) > 100000:
+        raise RuntimeError("range oracle exceeds reviewed size bound")
+    reconstructed = hashlib.sha256()
+    next_cp = 0
+    for line in text.decode("ascii").splitlines():
+        if line.startswith("#"):
+            continue
+        bounds, gcb, incb, pictographic = line.split()
+        first, last = (int(value, 16) for value in bounds.split(":"))
+        if first != next_cp or not first <= last < MAX:
+            raise RuntimeError("range encoding has a gap, overlap, or invalid bound")
+        triple = bytes(
+            (gcb_names.index(gcb), incb_names.index(incb), int(pictographic))
+        )
+        reconstructed.update(triple * (last - first + 1))
+        next_cp = last + 1
+    if next_cp != MAX or reconstructed.hexdigest() != raw_hash.hexdigest():
+        raise RuntimeError("range reconstruction differs from the raw property oracle")
+    with range_path.open("xb") as output:
+        output.write(text)
+    manifest = {
+        "cpython_commit": commit,
+        "unicode_version": unicodedata.unidata_version,
+        "runtime_version": sys.version,
+        "runtime_git": getattr(sys, "_git", None),
+        "python": str(executable),
+        "python_sha256": digest(executable),
+        "unicodedata": str(extension),
+        "unicodedata_sha256": digest(extension),
+        "database_header_sha256": digest(header),
+        "generator_sha256": digest(pathlib.Path(__file__)),
+        "codepoints": MAX,
+        "properties": 3,
+        "ranges": len(ranges),
+        "gcb_encoding": gcb_names,
+        "incb_encoding": incb_names,
+        "raw_bytes": MAX * 3,
+        "raw_sha256": raw_hash.hexdigest(),
+        "ranges_bytes": len(text),
+        "ranges_sha256": hashlib.sha256(text).hexdigest(),
+    }
+    manifest_bytes = (json.dumps(manifest, indent=2) + "\n").encode("utf-8")
+    # Total artifact bound, independent of the launcher's per-file rlimit.
+    if (
+        len(manifest_bytes) > 16384
+        or MAX * 3 + len(text) + len(manifest_bytes) > 4_407_296
+    ):
+        raise RuntimeError("total oracle artifact budget exceeded")
+    with manifest_path.open("xb") as output:
+        output.write(manifest_bytes)
+    print(json.dumps(manifest, sort_keys=True))
+    return 0
+
+
 # str predicates: name -> single-char method.
 STR_PREDICATES = {
     "isalpha": str.isalpha,
@@ -111,4 +281,18 @@ def main() -> int:
 
 
 if __name__ == "__main__":
-    raise SystemExit(main())
+    if len(sys.argv) == 1:
+        raise SystemExit(main())
+    import argparse
+
+    parser = argparse.ArgumentParser(
+        description="Generate only a new grapheme property oracle"
+    )
+    parser.add_argument("--graphemes-only", action="store_true", required=True)
+    parser.add_argument("--graphemes-output", type=pathlib.Path, required=True)
+    parser.add_argument("--graphemes-raw-output", type=pathlib.Path, required=True)
+    parser.add_argument("--graphemes-manifest", type=pathlib.Path, required=True)
+    parser.add_argument("--cpython-source", type=pathlib.Path, required=True)
+    parser.add_argument("--python-sha256", required=True)
+    parser.add_argument("--unicodedata-sha256", required=True)
+    raise SystemExit(generate_graphemes(parser.parse_args()))
diff --git a/crates/vm/Lib/python_builtins/zipimport.py b/crates/vm/Lib/python_builtins/zipimport.py
new file mode 120000
index 00000000000..48db8e1fa25
--- /dev/null
+++ b/crates/vm/Lib/python_builtins/zipimport.py
@@ -0,0 +1 @@
+../../../../Lib/zipimport.py
\ No newline at end of file
diff --git a/crates/vm/build.rs b/crates/vm/build.rs
index 867cf577502..f50dae52d31 100644
--- a/crates/vm/build.rs
+++ b/crates/vm/build.rs
@@ -21,9 +21,10 @@ fn main() {
         println!("cargo:rerun-if-changed={display}");
     }
     println!("cargo:rerun-if-changed=../../Lib/importlib/_bootstrap.py");
+    println!("cargo:rerun-if-changed=../../Lib/zipimport.py");
 
-    // = 3.14.0alpha
-    python_version(3, 14, 0, "alpha", 0);
+    // = 3.15.0alpha
+    python_version(3, 15, 0, "alpha", 0);
 
     println!("cargo:rustc-env=RUSTPYTHON_GIT_HASH={}", git_hash());
     println!(
@@ -162,14 +163,16 @@ fn get_version(cpy_version: &str) -> (String, String) {
     // Windows: include MSC v. for compatibility with ctypes.util.find_library
     // MSC v.1929 = VS 2019, version 14+ makes find_msvcrt() return None
     let msc_info = cfg_select! {
-        windows => {{
-            // Include both RustPython identifier and MSC v. for compatibility
-            if cfg!(target_pointer_width = "64") {
-                " MSC v.1929 64 bit (AMD64)"
-            } else {
-                " MSC v.1929 32 bit (Intel)"
+        windows => {
+            {
+                // Include both RustPython identifier and MSC v. for compatibility
+                if cfg!(target_pointer_width = "64") {
+                    " MSC v.1929 64 bit (AMD64)"
+                } else {
+                    " MSC v.1929 32 bit (Intel)"
+                }
             }
-        }},
+        }
         _ => "",
     };
 
diff --git a/crates/vm/src/anystr.rs b/crates/vm/src/anystr.rs
index f1ea7d7354d..1b7b20641e1 100644
--- a/crates/vm/src/anystr.rs
+++ b/crates/vm/src/anystr.rs
@@ -5,9 +5,9 @@ use rustpython_unicode::case;
 
 use crate::{
     AsObject, Py, PyObject, PyObjectRef, PyResult, TryFromObject, VirtualMachine,
-    builtins::{PyInt, PyIntRef, PyTuple},
+    builtins::{PyInt, PyTuple},
     convert::TryFromBorrowedObject,
-    function::PySsize,
+    function::{ArgIndex, PySsize},
 };
 
 #[derive(FromArgs)]
@@ -41,17 +41,30 @@ pub(crate) struct StartsEndsWithArgs {
     #[pyarg(positional)]
     affix: PyObjectRef,
     #[pyarg(positional, default)]
-    start: Option<PyIntRef>,
+    start: Option<ArgIndex>,
     #[pyarg(positional, default)]
-    end: Option<PyIntRef>,
+    end: Option<ArgIndex>,
 }
 
 impl StartsEndsWithArgs {
+    pub(crate) fn parts(&self, len: usize) -> (&PyObject, Option<Range<usize>>) {
+        let range = if self.start.is_some() || self.end.is_some() {
+            Some(adjust_indices(
+                self.start.as_ref().map(AsRef::as_ref),
+                self.end.as_ref().map(AsRef::as_ref),
+                len,
+            ))
+        } else {
+            None
+        };
+        (&self.affix, range)
+    }
+
     pub(crate) fn get_value(self, len: usize) -> (PyObjectRef, Option<Range<usize>>) {
         let range = if self.start.is_some() || self.end.is_some() {
             Some(adjust_indices(
-                self.start.as_deref(),
-                self.end.as_deref(),
+                self.start.as_ref().map(AsRef::as_ref),
+                self.end.as_ref().map(AsRef::as_ref),
                 len,
             ))
         } else {
diff --git a/crates/vm/src/buffer.rs b/crates/vm/src/buffer.rs
index 15c0050cb9c..0cc12210caf 100644
--- a/crates/vm/src/buffer.rs
+++ b/crates/vm/src/buffer.rs
@@ -404,6 +404,16 @@ impl FormatCode {
                 continue;
             }
 
+            let c = if c == b'Z' {
+                match chars.next() {
+                    Some(b'f') => b'F',
+                    Some(b'd') => b'D',
+                    Some(0) => return Err(exceptions::NulError.to_string()),
+                    _ => return Err("bad char in struct format".to_owned()),
+                }
+            } else {
+                c
+            };
             let code = FormatType::try_from(c)
                 .ok()
                 .filter(|c| match c {
diff --git a/crates/vm/src/builtins/asyncgenerator.rs b/crates/vm/src/builtins/asyncgenerator.rs
index 91fb744dc39..81068337720 100644
--- a/crates/vm/src/builtins/asyncgenerator.rs
+++ b/crates/vm/src/builtins/asyncgenerator.rs
@@ -1,3 +1,5 @@
+// spell-checker: ignore AGEN
+
 use super::{PyCode, PyGenerator, PyGenericAlias, PyStrRef, PyType, PyTypeRef};
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
@@ -162,6 +164,15 @@ impl Py<PyAsyncGen> {
         self.inner.code()
     }
     #[pygetset]
+    fn ag_state(&self) -> &'static str {
+        self.inner.state_name([
+            "AGEN_CREATED",
+            "AGEN_RUNNING",
+            "AGEN_SUSPENDED",
+            "AGEN_CLOSED",
+        ])
+    }
+    #[pygetset]
     fn ag_suspended(&self, _vm: &VirtualMachine) -> bool {
         self.inner.suspended()
     }
diff --git a/crates/vm/src/builtins/bool.rs b/crates/vm/src/builtins/bool.rs
index a8c2c019582..26086605a9e 100644
--- a/crates/vm/src/builtins/bool.rs
+++ b/crates/vm/src/builtins/bool.rs
@@ -1,9 +1,8 @@
 use super::{PyInt, PyStrRef, PyType, PyTypeRef, PyUtf8StrRef};
-use crate::common::format::FormatSpec;
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyResult, TryFromBorrowedObject, VirtualMachine,
     class::{PyClassDef, PyClassImpl},
-    convert::{IntoPyException, ToPyObject, ToPyResult},
+    convert::{ToPyObject, ToPyResult},
     function::{FuncArgs, OptionalArg},
     protocol::PyNumberMethods,
     types::{AsNumber, Constructor, Representable},
@@ -124,9 +123,11 @@ impl Py<PyBool> {
         vm: &VirtualMachine,
     ) -> PyResult<String> {
         let new_bool = zelf.try_to_bool(vm)?;
-        FormatSpec::parse(format_spec.as_str())
-            .and_then(|format_spec| format_spec.format_bool(new_bool))
-            .map_err(|err| err.into_pyexception(vm))
+        crate::format::parse_format_spec(zelf.as_object(), format_spec.as_str(), vm)?
+            .format_bool(new_bool)
+            .map_err(|err| {
+                crate::format::format_spec_error(err, zelf.as_object(), format_spec.as_str(), vm)
+            })
     }
 }
 
diff --git a/crates/vm/src/builtins/builtin_func.rs b/crates/vm/src/builtins/builtin_func.rs
index 79e2c1ca721..917b7b24fcc 100644
--- a/crates/vm/src/builtins/builtin_func.rs
+++ b/crates/vm/src/builtins/builtin_func.rs
@@ -78,7 +78,7 @@ impl PyNativeFunction {
         self.zelf.as_deref().or(self.module_object.as_deref())
     }
 
-    pub const fn as_func(&self) -> &'static dyn PyNativeFn {
+    pub const fn as_func(&self) -> &dyn PyNativeFn {
         self.value.func
     }
 }
@@ -87,6 +87,9 @@ impl Callable for PyNativeFunction {
     type Args = FuncArgs;
     #[inline]
     fn call(zelf: &Py<Self>, mut args: FuncArgs, vm: &VirtualMachine) -> PyResult {
+        if !args.kwargs.is_empty() && !zelf.value.flags.contains(PyMethodFlags::KEYWORDS) {
+            return Err(native_no_keywords_error(zelf, vm)?);
+        }
         let mut callee = Callee::named(zelf.value.name);
         if let Some(z) = &zelf.zelf {
             // STATIC methods store the class in zelf for qualname/repr purposes,
@@ -137,7 +140,7 @@ impl Representable for PyNativeFunction {
         if let Some(bound) = zelf
             .zelf
             .as_ref()
-            .filter(|b| !b.class().is(vm.ctx.types.module_type))
+            .filter(|b| !b.class().is_subtype(vm.ctx.types.module_type))
         {
             Ok(format!(
                 "<built-in method {} of {} object at {:#x}>",
@@ -166,7 +169,7 @@ impl PyNativeFunction {
     fn __qualname__(zelf: NativeFunctionOrMethod, vm: &VirtualMachine) -> PyResult<PyStrRef> {
         let zelf = zelf.0;
         let qualname = if let Some(bound) = &zelf.zelf {
-            if bound.class().is(vm.ctx.types.module_type) {
+            if bound.class().is_subtype(vm.ctx.types.module_type) {
                 return Ok(vm.ctx.intern_str(zelf.value.name).to_owned());
             }
             let prefix = if bound.class().is(vm.ctx.types.type_type) {
@@ -212,7 +215,7 @@ impl PyNativeFunction {
             .as_ref()
             .filter(|bound| !bound.class().is_subtype(vm.ctx.types.module_type))
         {
-            let getattr = vm.builtins.get_attr("getattr", vm)?;
+            let getattr = vm.eval_get_builtin(vm.ctx.intern_str("getattr"))?;
             Ok(vm
                 .new_tuple((getattr, (bound.clone(), zelf.value.name)))
                 .into())
@@ -233,16 +236,22 @@ impl PyNativeFunction {
     }
 }
 
-// PyCMethodObject in CPython
-#[pyclass(name = "builtin_function_or_method", module = false, base = PyNativeFunction, ctx = "builtin_function_or_method_type")]
+// Bound METH_METHOD object. The payload starts with PyNativeFunction so it can
+// be read as a builtin function. The Python type is `builtin_method`.
+#[repr(C)]
+#[pyclass(
+    name = "builtin_method",
+    module = false,
+    base = PyNativeFunction,
+    ctx = "builtin_method_type",
+    traverse
+)]
 pub struct PyNativeMethod {
     pub(crate) func: PyNativeFunction,
-    pub(crate) class: &'static Py<PyType>, // TODO: the actual life is &'self
+    #[pytraverse(skip)]
+    pub(crate) class: &'static Py<PyType>,
 }
 
-// All Python-visible behavior (getters, slots) is registered by PyNativeFunction::extend_class.
-// PyNativeMethod only extends the Rust-side struct with the defining class reference.
-// The func field at offset 0 (#[repr(C)]) allows NativeFunctionOrMethod to read it safely.
 #[pyclass(flags(HAS_WEAKREF, DISALLOW_INSTANTIATION))]
 impl PyNativeMethod {}
 
@@ -268,6 +277,12 @@ fn vectorcall_native_function(
 ) -> PyResult {
     let zelf: &Py<PyNativeFunction> = zelf_obj.downcast_ref().unwrap();
 
+    if kwnames.is_some_and(|names| !names.is_empty())
+        && !zelf.value.flags.contains(PyMethodFlags::KEYWORDS)
+    {
+        return Err(native_no_keywords_error(zelf, vm)?);
+    }
+
     // Build FuncArgs with self already at position 0 (no insert(0) needed)
     let needs_self = zelf
         .zelf
@@ -288,6 +303,30 @@ fn vectorcall_native_function(
     (zelf.value.func)(vm, func_args, callee)
 }
 
+#[cold]
+fn native_no_keywords_error(
+    zelf: &Py<PyNativeFunction>,
+    vm: &VirtualMachine,
+) -> PyResult<crate::exceptions::types::PyBaseExceptionRef> {
+    if zelf.value.flags.contains(PyMethodFlags::VARARGS) {
+        return Ok(vm.new_type_error(format!("{}() takes no keyword arguments", zelf.value.name)));
+    }
+    let qualname = PyNativeFunction::__qualname__(NativeFunctionOrMethod(zelf.to_owned()), vm)?;
+    let module = zelf
+        .module
+        .load_owned()
+        .filter(|module| !vm.is_none(module));
+    let module = module.map(|module| module.str(vm)).transpose()?;
+    let name = if let Some(module) = module
+        && module.to_string() != "builtins"
+    {
+        format!("{module}.{qualname}")
+    } else {
+        qualname.to_string()
+    };
+    Ok(vm.new_type_error(format!("{name}() takes no keyword arguments")))
+}
+
 pub(crate) fn init(context: &'static Context) {
     PyNativeFunction::extend_class(context, context.types.builtin_function_or_method_type);
     context
@@ -296,6 +335,7 @@ pub(crate) fn init(context: &'static Context) {
         .slots
         .vectorcall
         .store(Some(vectorcall_native_function));
+    PyNativeMethod::extend_class(context, context.types.builtin_method_type);
 }
 
 /// Wrapper that provides access to the common PyNativeFunction data
@@ -306,12 +346,59 @@ impl TryFromObject for NativeFunctionOrMethod {
     fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
         let class = vm.ctx.types.builtin_function_or_method_type;
         if obj.fast_isinstance(class) {
-            // Both PyNativeFunction and PyNativeMethod share the same type now.
-            // PyNativeMethod has `func: PyNativeFunction` as its first field,
-            // so we can safely treat the data pointer as PyNativeFunction for reading.
+            // `builtin_method` is a subclass; the payload starts with PyNativeFunction.
             Ok(Self(unsafe { obj.downcast_unchecked() }))
         } else {
             Err(vm.new_downcast_type_error(class, &obj))
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{
+        Interpreter, PyObjectRef,
+        function::{PyMethodDef, PyMethodFlags},
+    };
+
+    #[test]
+    fn builtin_method_is_subclass_of_builtin_function() {
+        Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let function_type = vm.ctx.types.builtin_function_or_method_type;
+            let method_type = vm.ctx.types.builtin_method_type;
+            assert!(!function_type.is(method_type));
+            assert_eq!(&*function_type.name(), "builtin_function_or_method");
+            assert_eq!(&*method_type.name(), "builtin_method");
+            assert!(method_type.fast_issubclass(function_type));
+        });
+    }
+
+    #[test]
+    fn bound_instance_method_uses_function_type() {
+        fn identity(value: PyObjectRef) -> PyObjectRef {
+            value
+        }
+        const DEF: PyMethodDef = PyMethodDef::new_const(
+            "identity",
+            identity,
+            PyMethodFlags::METHOD,
+            crate::function::ItemDoc::NONE,
+        );
+
+        Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let bound = DEF.build_bound_function(&vm.ctx, vm.ctx.none());
+            assert!(
+                bound
+                    .class()
+                    .is(vm.ctx.types.builtin_function_or_method_type)
+            );
+            assert!(!bound.as_object().downcastable::<PyNativeMethod>());
+
+            let method = DEF.build_bound_method(&vm.ctx, vm.ctx.none(), vm.ctx.types.object_type);
+            assert!(method.class().is(vm.ctx.types.builtin_method_type));
+            assert!(method.as_object().downcastable::<PyNativeFunction>());
+            assert!(method.as_object().downcastable::<PyNativeMethod>());
+        });
+    }
+}
diff --git a/crates/vm/src/builtins/bytearray.rs b/crates/vm/src/builtins/bytearray.rs
index 19e149d9df0..e723449c802 100644
--- a/crates/vm/src/builtins/bytearray.rs
+++ b/crates/vm/src/builtins/bytearray.rs
@@ -1,34 +1,31 @@
 //! Implementation of the python bytearray object.
 use super::{
-    PositionIterInternal, PyBytes, PyDictRef, PyGenericAlias, PyStrRef, PyTuple, PyTupleRef,
+    PositionIterInternal, PyBytes, PyDictRef, PyGenericAlias, PyInt, PyStrRef, PyTuple, PyTupleRef,
     PyType, PyTypeRef, iter::builtins_iter, locked_next,
 };
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
     VirtualMachine,
-    anystr::{self, AnyStr},
+    anystr::{self, AnyStr, StringRange},
     atomic_func,
     byte::{bytearray_extend_from_object, bytearray_from_object, value_from_object},
     bytes_inner::{
         ByteInnerFindOptions, ByteInnerHexOptions, ByteInnerNewOptions, ByteInnerPaddingOptions,
         ByteInnerReplaceOptions, ByteInnerSplitOptions, ByteInnerStripOptions, ByteInnerSub,
-        ByteInnerTranslateOptions, BytesJoin, DecodeArgs, PyBytesInner, bytes_decode,
+        ByteInnerTranslateOptions, ByteOr, BytesJoin, DecodeArgs, PyBytesInner, bytes_decode,
     },
     class::PyClassImpl,
-    common::{
-        atomic::{AtomicUsize, Ordering},
-        lock::{
-            PyDetachingRwLock, PyDetachingRwLockReadGuard, PyDetachingRwLockWriteGuard,
-            PyMappedDetachingRwLockReadGuard, PyMappedDetachingRwLockWriteGuard, PyMutex,
-        },
+    common::lock::{
+        PyDetachingRwLock, PyDetachingRwLockReadGuard, PyDetachingRwLockWriteGuard,
+        PyMappedDetachingRwLockReadGuard, PyMappedDetachingRwLockWriteGuard, PyMutex,
     },
     convert::{ToPyObject, ToPyResult},
-    function::{ArgBytesLike, PyComparisonValue, PySsize},
+    function::{ArgBytesLike, FuncArgs, OptionalArg, PyComparisonValue, PySsize},
     protocol::{
         BufferDescriptor, BufferFlags, BufferMethods, BufferResizeGuard, PyBuffer, PyIterReturn,
         PyMappingMethods, PyNumberMethods, PySequenceMethods,
     },
-    sliceable::{SequenceIndex, SliceableSequenceMutOp, SliceableSequenceOp},
+    sliceable::{NameBytearray, SequenceIndex, SliceableSequenceMutOp, SliceableSequenceOp},
     types::{
         AsBuffer, AsMapping, AsNumber, AsSequence, Callable, Comparable, Constructor,
         DefaultConstructor, Initializer, IterNext, Iterable, PyComparisonOp, Representable,
@@ -37,12 +34,62 @@ use crate::{
 };
 use bstr::ByteSlice;
 use core::mem::size_of;
+use num_traits::ToPrimitive;
 
 #[pyclass(module = false, name = "bytearray", unhashable = true)]
 #[derive(Debug, Default)]
 pub struct PyByteArray {
     inner: PyDetachingRwLock<PyBytesInner>,
-    exports: AtomicUsize,
+    exports: PyMutex<ExportState>,
+}
+
+// While count is nonzero, len is the stable logical length of the payload.
+// Publish both together; the length is meaningless between export epochs.
+#[derive(Debug, Default)]
+struct ExportState {
+    count: usize,
+    len: usize,
+}
+
+impl ExportState {
+    fn snapshot(&self) -> Option<usize> {
+        (self.count != 0).then_some(self.len)
+    }
+
+    fn retain_existing(&mut self) -> Option<usize> {
+        let len = self.snapshot()?;
+        self.count += 1;
+        Some(len)
+    }
+
+    // The caller holds a payload read guard, so first publication cannot
+    // overlap a resize and an existing epoch has the same length.
+    fn retain(&mut self, len: usize) {
+        if self.count == 0 {
+            self.len = len;
+        }
+        self.count += 1;
+    }
+
+    fn release(&mut self) {
+        self.count -= 1;
+    }
+}
+
+struct ByteArrayExportGuard<'a> {
+    owner: &'a PyByteArray,
+    len: usize,
+}
+
+impl Drop for ByteArrayExportGuard<'_> {
+    fn drop(&mut self) {
+        self.owner.exports.lock().release();
+    }
+}
+
+enum ResizeAccess<'a> {
+    Exclusive(PyDetachingRwLockWriteGuard<'a, PyBytesInner>),
+    Exported { len: usize },
 }
 
 pub(crate) type PyByteArrayRef = PyRef<PyByteArray>;
@@ -65,6 +112,21 @@ impl PyPayload for PyByteArray {
     }
 }
 
+// Acquisitions can call Python, and releases must follow acquisition order.
+// No bytearray lock may be held when this owner is dropped.
+#[derive(Default)]
+struct ByteArrayBuffers {
+    first: Option<PyBuffer>,
+    second: Option<PyBuffer>,
+}
+
+impl Drop for ByteArrayBuffers {
+    fn drop(&mut self) {
+        drop(self.first.take());
+        drop(self.second.take());
+    }
+}
+
 /// Fill bytearray class methods dictionary.
 pub(crate) fn init(context: &'static Context) {
     PyByteArray::extend_class(context, context.types.bytearray_type);
@@ -80,7 +142,7 @@ impl PyByteArray {
     const fn from_inner(inner: PyBytesInner) -> Self {
         Self {
             inner: PyDetachingRwLock::new(inner),
-            exports: AtomicUsize::new(0),
+            exports: PyMutex::new(ExportState { count: 0, len: 0 }),
         }
     }
 
@@ -88,10 +150,148 @@ impl PyByteArray {
         PyDetachingRwLockReadGuard::map(self.inner.read(), |inner| &*inner.elements)
     }
 
+    /// Borrow for in-place byte replacement only. Do not change the length,
+    /// replace or reallocate storage, or hold this guard across Python calls.
+    /// Operations that may resize or reallocate must use export-checked access.
     pub fn borrow_buf_mut(&self) -> PyMappedDetachingRwLockWriteGuard<'_, Vec<u8>> {
         PyDetachingRwLockWriteGuard::map(self.inner.write(), |inner| &mut inner.elements)
     }
 
+    fn begin_export(&self) -> ByteArrayExportGuard<'_> {
+        // Existing epochs need no payload lock, including in codec callbacks
+        // that already hold a payload read guard.
+        let existing_len = { self.exports.lock().retain_existing() };
+        let len = match existing_len {
+            Some(len) => len,
+            None => {
+                // Never wait for the payload with the metadata lock held.
+                // An earlier resize must finish before first publication.
+                let inner = self.inner.read();
+                let len = inner.elements.len();
+                self.exports.lock().retain(len);
+                len
+            }
+        };
+        ByteArrayExportGuard { owner: self, len }
+    }
+
+    fn resize_access(&self) -> ResizeAccess<'_> {
+        // An export is a borrow someone else still holds, so it is answered
+        // before the lock rather than by waiting on it.
+        let exported_len = { self.exports.lock().snapshot() };
+        if let Some(len) = exported_len {
+            return ResizeAccess::Exported { len };
+        }
+        let inner = self.inner.write();
+        // An export may have started while we waited. Capture its length in
+        // the same decision, without borrowing the payload a second time.
+        let exported_len = { self.exports.lock().snapshot() };
+        match exported_len {
+            Some(len) => {
+                drop(inner);
+                ResizeAccess::Exported { len }
+            }
+            None => ResizeAccess::Exclusive(inner),
+        }
+    }
+
+    fn with_export<R>(&self, f: impl FnOnce(usize) -> R) -> R {
+        let export = self.begin_export();
+        f(export.len)
+    }
+
+    fn buffer_snapshot(buffer: &PyBuffer, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+        let mut bytes = Vec::new();
+        bytes
+            .try_reserve_exact(buffer.desc.len)
+            .map_err(|_| vm.no_memory_error())?;
+        buffer.append_to(&mut bytes);
+        Ok(bytes)
+    }
+
+    fn search_exported<R>(
+        &self,
+        options: ByteInnerFindOptions,
+        search: impl FnOnce(&[u8], &[u8], core::ops::Range<usize>) -> R,
+        vm: &VirtualMachine,
+    ) -> PyResult<R> {
+        self.with_export(|len| {
+            let (sub, range) = options.parts(len);
+            let buffer = if sub.check_buffer() {
+                Some(PyBuffer::from_object(vm, sub, BufferFlags::SIMPLE)?)
+            } else {
+                None
+            };
+            let needle = match &buffer {
+                Some(buffer) => Self::buffer_snapshot(buffer, vm)?,
+                None => ByteInnerSub::try_from_object(vm, sub.to_owned())?.into_vec(vm)?,
+            };
+            let result = search(&self.borrow_buf(), &needle, range);
+            drop(buffer);
+            Ok(result)
+        })
+    }
+
+    fn starts_ends_with(
+        &self,
+        options: anystr::StartsEndsWithArgs,
+        ends: bool,
+        vm: &VirtualMachine,
+    ) -> PyResult<bool> {
+        self.with_export(|len| {
+            let (affix, range) = options.parts(len);
+            let tailmatch = |item: &PyObject| -> PyResult<bool> {
+                // bytes subclasses use their bytes directly, as in tailmatch.
+                let buffer = if item.downcast_ref::<PyBytes>().is_some() {
+                    None
+                } else {
+                    Some(PyBuffer::from_object(vm, item, BufferFlags::SIMPLE)?)
+                };
+                let needle = match &buffer {
+                    Some(buffer) => Self::buffer_snapshot(buffer, vm)?,
+                    None => item.downcast_ref::<PyBytes>().unwrap().as_bytes().to_vec(),
+                };
+                let result = {
+                    let bytes = self.borrow_buf();
+                    let slice = match &range {
+                        Some(range) if !range.is_normal() => None,
+                        Some(range) => bytes.get(range.clone()),
+                        None => Some(&*bytes),
+                    };
+                    slice.is_some_and(|slice| {
+                        if ends {
+                            slice.ends_with(&needle)
+                        } else {
+                            slice.starts_with(&needle)
+                        }
+                    })
+                };
+                drop(buffer);
+                Ok(result)
+            };
+            if let Some(tuple) = affix.downcast_ref::<PyTuple>() {
+                for item in tuple {
+                    if tailmatch(item)? {
+                        return Ok(true);
+                    }
+                }
+                Ok(false)
+            } else {
+                tailmatch(affix).map_err(|error| {
+                    if error.fast_isinstance(vm.ctx.exceptions.type_error) {
+                        vm.new_type_error(format!(
+                            "{} first arg must be bytes or a tuple of bytes, not {}",
+                            if ends { "endswith" } else { "startswith" },
+                            affix.class().name()
+                        ))
+                    } else {
+                        error
+                    }
+                })
+            }
+        })
+    }
+
     fn repeat(&self, value: isize, vm: &VirtualMachine) -> PyResult<Self> {
         self.inner().mul(value, vm).map(|x| x.into())
     }
@@ -107,7 +307,7 @@ impl PyByteArray {
         value: &PyObject,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        match SequenceIndex::try_from_borrowed_object(vm, needle, "bytearray")? {
+        match SequenceIndex::try_from_borrowed_object::<NameBytearray>(vm, needle)? {
             SequenceIndex::Int(i) => zelf._setitem_by_index(i, value, vm),
             SequenceIndex::Slice(slice) => {
                 let items = if zelf.is(&value) {
@@ -126,7 +326,7 @@ impl PyByteArray {
     }
 
     fn _getitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
-        match SequenceIndex::try_from_borrowed_object(vm, needle, "bytearray")? {
+        match SequenceIndex::try_from_borrowed_object::<NameBytearray>(vm, needle)? {
             SequenceIndex::Int(i) => self
                 .borrow_buf()
                 .getitem_by_index(vm, i)
@@ -139,8 +339,8 @@ impl PyByteArray {
     }
 
     pub fn _delitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
-        match SequenceIndex::try_from_borrowed_object(vm, needle, "bytearray")? {
-            SequenceIndex::Int(i) => self.try_resizable(vm)?.elements.delitem_by_index(vm, i),
+        match SequenceIndex::try_from_borrowed_object::<NameBytearray>(vm, needle)? {
+            SequenceIndex::Int(i) => self.delitem_by_index(i, vm),
             SequenceIndex::Slice(slice) => {
                 // TODO: delete 0 elements don't need resizable
                 self.try_resizable(vm)?.elements.delitem_by_slice(vm, slice)
@@ -148,6 +348,27 @@ impl PyByteArray {
         }
     }
 
+    fn delitem_by_index(&self, index: isize, vm: &VirtualMachine) -> PyResult<()> {
+        // Validate before export rejection when the bytes are available without
+        // waiting. A codec callback may already hold a read guard with a writer
+        // queued, so a blocking read here could deadlock before that rejection.
+        let valid = self
+            .inner
+            .try_read()
+            .map(|inner| inner.elements.wrap_index(index).is_some());
+        if valid == Some(false) {
+            return Err(vm.new_index_error("bytearray index out of range"));
+        }
+        let mut inner = self.try_resizable(vm)?;
+        // Another thread may have resized the bytearray between the locks.
+        let index = inner
+            .elements
+            .wrap_index(index)
+            .ok_or_else(|| vm.new_index_error("bytearray index out of range"))?;
+        inner.elements.remove(index);
+        Ok(())
+    }
+
     fn irepeat(zelf: &Py<Self>, n: isize, vm: &VirtualMachine) -> PyResult<()> {
         if n == 1 {
             return Ok(());
@@ -173,11 +394,6 @@ impl PyByteArray {
     fn inner(&self) -> PyDetachingRwLockReadGuard<'_, PyBytesInner> {
         self.inner.read()
     }
-    #[inline]
-    fn inner_mut(&self) -> PyDetachingRwLockWriteGuard<'_, PyBytesInner> {
-        self.inner.write()
-    }
-
     fn __len__(&self) -> usize {
         self.borrow_buf().len()
     }
@@ -187,6 +403,23 @@ impl PyByteArray {
     }
 
     fn __contains__(&self, needle: PyObjectRef, vm: &VirtualMachine) -> PyResult<bool> {
+        // Exact builtins cannot call Python while preparing the needle. The
+        // read lock alone protects their search; a temporary export would make
+        // a concurrent resize fail instead of waiting for that lock.
+        if let Some(bytes) = needle.downcast_ref_if_exact::<PyBytes>(vm) {
+            return Ok(self.borrow_buf().contains_str(bytes.as_bytes()));
+        }
+        let int = if needle.class().is(vm.ctx.types.bool_type) {
+            needle.downcast_ref::<PyInt>()
+        } else {
+            needle.downcast_ref_if_exact::<PyInt>(vm)
+        };
+        if let Some(int) = int {
+            let byte = int.as_bigint().byte_or(vm)?;
+            return Ok(self.borrow_buf().contains(&byte));
+        }
+        // Converting the needle runs Python, which must not resize this bytearray.
+        let _export = self.begin_export();
         let needle = ByteInnerSub::from_contains_arg(needle, vm)?;
         self.inner().contains(needle, vm)
     }
@@ -221,7 +454,9 @@ impl PyByteArray {
 
     fn __mod__(&self, values: PyObjectRef, vm: &VirtualMachine) -> PyResult<Self> {
         // Formatting calls the values' conversion methods, which can reach
-        // this bytearray, so the format is taken by value.
+        // this bytearray, so the format is taken by value. It also stays
+        // exported until formatting ends, so resizing it raises BufferError.
+        let _export = self.begin_export();
         let format = self.inner().clone();
         let formatted = format.cformat(values, vm)?;
         Ok(formatted.into())
@@ -350,10 +585,82 @@ impl Py<PyByteArray> {
 
     #[pymethod]
     fn clear(&self, vm: &VirtualMachine) -> PyResult<()> {
-        self.try_resizable(vm)?.elements.clear();
+        let old = match self.resize_access() {
+            ResizeAccess::Exported { len: 0 } => return Ok(()),
+            ResizeAccess::Exported { .. } => {
+                return Err(
+                    vm.new_buffer_error("Existing exports of data: object cannot be re-sized")
+                );
+            }
+            ResizeAccess::Exclusive(mut inner) => {
+                if inner.elements.is_empty() {
+                    return Ok(());
+                }
+                core::mem::take(&mut inner.elements)
+            }
+        };
+        drop(old);
         Ok(())
     }
 
+    #[pymethod]
+    fn take_bytes(&self, n: OptionalArg, vm: &VirtualMachine) -> PyResult<PyBytes> {
+        // __index__ can resize self or acquire/release exports. Convert before
+        // observing either the payload or the export epoch.
+        let n = match n.into_option().filter(|n| !vm.is_none(n)) {
+            None => None,
+            Some(n) => {
+                let index = n
+                    .try_index_opt(vm)
+                    .ok_or_else(|| vm.new_type_error("n must be an integer or None"))??;
+                Some(index.as_bigint().to_isize().ok_or_else(|| {
+                    vm.new_index_error(format!(
+                        "cannot fit '{}' into an index-sized integer",
+                        n.class().slot_name()
+                    ))
+                })?)
+            }
+        };
+        let access = self.resize_access();
+        let len = match &access {
+            ResizeAccess::Exclusive(inner) => inner.elements.len(),
+            ResizeAccess::Exported { len } => *len,
+        };
+        // Vec<u8> lengths fit isize. Adding a nonnegative length to a negative
+        // index cannot overflow; preserve the adjusted index in the error.
+        let to_take = match n {
+            None => len as isize,
+            Some(n) if n < 0 => n + len as isize,
+            Some(n) => n,
+        };
+        if to_take < 0 || to_take as usize > len {
+            drop(access);
+            return Err(
+                vm.new_index_error(format!("can't take {to_take} bytes outside size {len}"))
+            );
+        }
+        let ResizeAccess::Exclusive(mut inner) = access else {
+            return Err(vm.new_buffer_error("Existing exports of data: object cannot be re-sized"));
+        };
+        let to_take = to_take as usize;
+        let result = if to_take == 0 {
+            Vec::new()
+        } else if to_take == len {
+            core::mem::take(&mut inner.elements)
+        } else {
+            let mut result = Vec::new();
+            if result.try_reserve_exact(to_take).is_err() {
+                drop(inner);
+                return Err(vm.no_memory_error());
+            }
+            result.extend_from_slice(&inner.elements[..to_take]);
+            inner.elements.drain(..to_take);
+            result
+        };
+        drop(inner);
+        Ok(PyBytes::from(result))
+    }
+
     #[pymethod]
     fn __reduce_ex__(
         &self,
@@ -377,7 +684,7 @@ impl Py<PyByteArray> {
     #[cfg(debug_assertions)]
     #[pygetset]
     fn exports(&self) -> usize {
-        self.exports.load(Ordering::Relaxed)
+        self.exports.lock().count
     }
 
     #[pymethod]
@@ -469,8 +776,12 @@ impl Py<PyByteArray> {
     #[pymethod]
     fn hex(&self, options: ByteInnerHexOptions, vm: &VirtualMachine) -> PyResult<String> {
         // Measuring the separator runs Python, so it happens before the buffer
-        // is borrowed.
-        let (sep, bytes_per_sep) = options.resolve(vm)?;
+        // is borrowed, with the buffer exported so that resizing this
+        // bytearray from there raises BufferError.
+        let (sep, bytes_per_sep) = {
+            let _export = self.begin_export();
+            options.resolve(vm)?
+        };
         Ok(self.inner().hex(sep, bytes_per_sep))
     }
 
@@ -488,7 +799,11 @@ impl Py<PyByteArray> {
         options: ByteInnerPaddingOptions,
         vm: &VirtualMachine,
     ) -> PyResult<PyByteArray> {
-        Ok(self.inner().center(options, vm)?.into())
+        let (width, fillchar) = options.get_value("center", vm)?;
+        Ok(self
+            .inner()
+            .pad_with(width, fillchar, AnyStr::py_center, vm)?
+            .into())
     }
 
     #[pymethod]
@@ -497,7 +812,11 @@ impl Py<PyByteArray> {
         options: ByteInnerPaddingOptions,
         vm: &VirtualMachine,
     ) -> PyResult<PyByteArray> {
-        Ok(self.inner().ljust(options, vm)?.into())
+        let (width, fillchar) = options.get_value("ljust", vm)?;
+        Ok(self
+            .inner()
+            .pad_with(width, fillchar, AnyStr::py_ljust, vm)?
+            .into())
     }
 
     #[pymethod]
@@ -506,21 +825,28 @@ impl Py<PyByteArray> {
         options: ByteInnerPaddingOptions,
         vm: &VirtualMachine,
     ) -> PyResult<PyByteArray> {
-        Ok(self.inner().rjust(options, vm)?.into())
+        let (width, fillchar) = options.get_value("rjust", vm)?;
+        Ok(self
+            .inner()
+            .pad_with(width, fillchar, AnyStr::py_rjust, vm)?
+            .into())
     }
 
     #[pymethod]
     fn count(&self, options: ByteInnerFindOptions, vm: &VirtualMachine) -> PyResult<usize> {
-        self.inner().count(options, vm)
+        self.search_exported(
+            options,
+            |bytes, needle, range| bytes.py_count(needle, range, |h, n| h.find_iter(n).count()),
+            vm,
+        )
     }
 
     #[pymethod]
     fn join(&self, iterable_of_bytes: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyByteArray> {
         // Export before driving the iterable: resizing is forbidden, but
         // same-size mutations must be reflected in the joined result.
-        self.exports.fetch_add(1, Ordering::Release);
-        scopeguard::defer! { self.exports.fetch_sub(1, Ordering::Release); }
-        let separator_len = self.__len__();
+        let _export = self.begin_export();
+        let separator_len = _export.len;
         let items = BytesJoin::new(iterable_of_bytes, vm)?;
         Ok(items
             .join(separator_len, || self.borrow_buf().into(), vm)?
@@ -529,19 +855,7 @@ impl Py<PyByteArray> {
 
     #[pymethod]
     fn endswith(&self, options: anystr::StartsEndsWithArgs, vm: &VirtualMachine) -> PyResult<bool> {
-        let borrowed = self.borrow_buf();
-        let (affix, substr) =
-            match options.prepare(&*borrowed, borrowed.len(), |s, r| s.get_bytes(r)) {
-                Some(x) => x,
-                None => return Ok(false),
-            };
-        substr.py_starts_ends_with(
-            &affix,
-            "endswith",
-            "bytes",
-            |s, x: PyBytesInner| s.ends_with(x.as_bytes()),
-            vm,
-        )
+        self.starts_ends_with(options, true, vm)
     }
 
     #[pymethod]
@@ -550,42 +864,48 @@ impl Py<PyByteArray> {
         options: anystr::StartsEndsWithArgs,
         vm: &VirtualMachine,
     ) -> PyResult<bool> {
-        let borrowed = self.borrow_buf();
-        let (affix, substr) =
-            match options.prepare(&*borrowed, borrowed.len(), |s, r| s.get_bytes(r)) {
-                Some(x) => x,
-                None => return Ok(false),
-            };
-        substr.py_starts_ends_with(
-            &affix,
-            "startswith",
-            "bytes",
-            |s, x: PyBytesInner| s.starts_with(x.as_bytes()),
+        self.starts_ends_with(options, false, vm)
+    }
+
+    /// Converting the needle runs Python, which must not resize this
+    /// bytearray, so the buffer stays exported while it does.
+    fn find_exported<F>(
+        &self,
+        options: ByteInnerFindOptions,
+        find: F,
+        vm: &VirtualMachine,
+    ) -> PyResult<Option<usize>>
+    where
+        F: Fn(&[u8], &[u8]) -> Option<usize>,
+    {
+        self.search_exported(
+            options,
+            |bytes, needle, range| bytes.py_find(needle, range, find),
             vm,
         )
     }
 
     #[pymethod]
     fn find(&self, options: ByteInnerFindOptions, vm: &VirtualMachine) -> PyResult<isize> {
-        let index = self.inner().find(options, |h, n| h.find(n), vm)?;
+        let index = self.find_exported(options, |h, n| h.find(n), vm)?;
         Ok(index.map_or(-1, |v| v as isize))
     }
 
     #[pymethod]
     fn index(&self, options: ByteInnerFindOptions, vm: &VirtualMachine) -> PyResult<usize> {
-        let index = self.inner().find(options, |h, n| h.find(n), vm)?;
+        let index = self.find_exported(options, |h, n| h.find(n), vm)?;
         index.ok_or_else(|| vm.new_value_error("substring not found"))
     }
 
     #[pymethod]
     fn rfind(&self, options: ByteInnerFindOptions, vm: &VirtualMachine) -> PyResult<isize> {
-        let index = self.inner().find(options, |h, n| h.rfind(n), vm)?;
+        let index = self.find_exported(options, |h, n| h.rfind(n), vm)?;
         Ok(index.map_or(-1, |v| v as isize))
     }
 
     #[pymethod]
     fn rindex(&self, options: ByteInnerFindOptions, vm: &VirtualMachine) -> PyResult<usize> {
-        let index = self.inner().find(options, |h, n| h.rfind(n), vm)?;
+        let index = self.find_exported(options, |h, n| h.rfind(n), vm)?;
         index.ok_or_else(|| vm.new_value_error("substring not found"))
     }
 
@@ -595,17 +915,38 @@ impl Py<PyByteArray> {
         options: ByteInnerTranslateOptions,
         vm: &VirtualMachine,
     ) -> PyResult<PyByteArray> {
-        Ok(self.inner().translate(options, vm)?.into())
+        let mut buffers = ByteArrayBuffers::default();
+        if let Some(table) = &options.table {
+            let buffer = PyBuffer::from_object(vm, table, BufferFlags::SIMPLE)?;
+            if buffer.desc.len != 256 {
+                return Err(vm.new_value_error("translation table must be 256 characters long"));
+            }
+            buffers.first = Some(buffer);
+        }
+        buffers.second = Some(PyBuffer::from_object(
+            vm,
+            &options.delete,
+            BufferFlags::SIMPLE,
+        )?);
+        // Both acquisition callbacks finish before any input bytes are read.
+        let table = match &buffers.first {
+            Some(buffer) => PyByteArray::buffer_snapshot(buffer, vm)?,
+            None => (0..=u8::MAX).collect(),
+        };
+        let delete = PyByteArray::buffer_snapshot(buffers.second.as_ref().unwrap(), vm)?;
+        let result = self.inner().translate_with(&table, &delete).into();
+        drop(buffers);
+        Ok(result)
     }
 
     #[pymethod]
     fn strip(&self, options: ByteInnerStripOptions) -> PyByteArray {
-        self.inner().strip(options.bytes).into()
+        self.inner().strip(options.bytes).to_vec().into()
     }
 
     #[pymethod]
     fn removeprefix(&self, prefix: PyBytesInner) -> PyByteArray {
-        self.inner().removeprefix(prefix).into()
+        self.inner().removeprefix(prefix).to_vec().into()
     }
 
     #[pymethod]
@@ -614,21 +955,19 @@ impl Py<PyByteArray> {
     }
 
     #[pymethod]
-    fn split(
-        &self,
-        options: ByteInnerSplitOptions,
-        vm: &VirtualMachine,
-    ) -> PyResult<Vec<PyObjectRef>> {
+    fn split(&self, args: FuncArgs, vm: &VirtualMachine) -> PyResult<Vec<PyObjectRef>> {
+        // Converting the separator runs Python, which must not resize this
+        // bytearray, so the arguments are bound with the buffer exported.
+        let _export = self.begin_export();
+        let options: ByteInnerSplitOptions = args.bind_for(vm, "split")?;
         self.inner()
             .split(options, |s, vm| vm.ctx.new_bytearray(s.to_vec()).into(), vm)
     }
 
     #[pymethod]
-    fn rsplit(
-        &self,
-        options: ByteInnerSplitOptions,
-        vm: &VirtualMachine,
-    ) -> PyResult<Vec<PyObjectRef>> {
+    fn rsplit(&self, args: FuncArgs, vm: &VirtualMachine) -> PyResult<Vec<PyObjectRef>> {
+        let _export = self.begin_export();
+        let options: ByteInnerSplitOptions = args.bind_for(vm, "rsplit")?;
         self.inner()
             .rsplit(options, |s, vm| vm.ctx.new_bytearray(s.to_vec()).into(), vm)
     }
@@ -681,7 +1020,7 @@ impl Py<PyByteArray> {
         options: ByteInnerReplaceOptions,
         vm: &VirtualMachine,
     ) -> PyResult<PyByteArray> {
-        Ok(self.inner().replace(options, vm)?.into())
+        Ok(self.inner().replace(options, vm)?.into_owned().into())
     }
 
     #[pymethod]
@@ -755,9 +1094,18 @@ impl Initializer for PyByteArray {
     type Args = ByteInnerNewOptions;
 
     fn init(zelf: &Py<Self>, options: Self::Args, vm: &VirtualMachine) -> PyResult<()> {
-        // First unpack bytearray and *then* get a lock to set it.
-        let mut inner = options.get_inner(bytearray_from_object, vm)?;
-        core::mem::swap(&mut *zelf.inner_mut(), &mut inner);
+        // Reject exports and clear existing contents before converting source.
+        zelf.try_resizable(vm)?.elements = Vec::new();
+        // Conversion can call Python, so do not hold the lock across it and
+        // check again for exports acquired by a callback or another thread.
+        let (mut inner, zero_count) =
+            options.get_inner_with_zero_count(bytearray_from_object, vm)?;
+        // A zero integer count performs no further writes, including when its
+        // __index__ callback changed this bytearray or acquired an export.
+        if zero_count {
+            return Ok(());
+        }
+        core::mem::swap(&mut *zelf.try_resizable(vm)?, &mut inner);
         Ok(())
     }
 }
@@ -769,10 +1117,33 @@ impl Comparable for PyByteArray {
         op: PyComparisonOp,
         vm: &VirtualMachine,
     ) -> PyResult<PyComparisonValue> {
-        if let Some(res) = op.identical_optimization(zelf, other) {
-            return Ok(res.into());
+        if !zelf.as_object().check_buffer() || !other.check_buffer() {
+            return Ok(PyComparisonValue::NotImplemented);
         }
-        Ok(zelf.inner().cmp(other, op, vm))
+        let first = match PyBuffer::from_object(vm, zelf.as_object(), BufferFlags::SIMPLE) {
+            Ok(buffer) => buffer,
+            Err(_) => return Ok(PyComparisonValue::NotImplemented),
+        };
+        let mut buffers = ByteArrayBuffers {
+            first: Some(first),
+            second: None,
+        };
+        buffers.second = match PyBuffer::from_object(vm, other, BufferFlags::SIMPLE) {
+            Ok(buffer) => Some(buffer),
+            Err(_) => return Ok(PyComparisonValue::NotImplemented),
+        };
+        let left = buffers.first.as_ref().unwrap();
+        let right = buffers.second.as_ref().unwrap();
+        let result = if left.desc.len != right.desc.len && op.eval_eq(|| false).is_some() {
+            op.eval_eq(|| false).unwrap()
+        } else {
+            let left = Self::buffer_snapshot(left, vm)?;
+            let right = Self::buffer_snapshot(right, vm)?;
+            op.eval_eq(|| left == right)
+                .unwrap_or_else(|| op.eval_ord(left.cmp(&right)))
+        };
+        drop(buffers);
+        Ok(result.into())
     }
 }
 
@@ -785,17 +1156,14 @@ static BUFFER_METHODS: BufferMethods = BufferMethods {
         )
         .into()
     },
-    release: |buffer| {
-        buffer
-            .obj_as::<PyByteArray>()
-            .exports
-            .fetch_sub(1, Ordering::Release);
-    },
+    release: |buffer| buffer.obj_as::<PyByteArray>().exports.lock().release(),
     retain: |buffer| {
+        // as_buffer holds the payload read guard until PyBuffer::new returns.
         buffer
             .obj_as::<PyByteArray>()
             .exports
-            .fetch_add(1, Ordering::Release);
+            .lock()
+            .retain(buffer.desc.len);
     },
 };
 
@@ -815,9 +1183,11 @@ impl AsBuffer for PyByteArray {
     }
 
     fn as_buffer(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<PyBuffer> {
+        // Keep the length stable until PyBuffer::new retains the export.
+        let inner = zelf.inner();
         Ok(PyBuffer::new(
             zelf.to_owned().into(),
-            BufferDescriptor::simple(zelf.__len__(), false),
+            BufferDescriptor::simple(inner.elements.len(), false),
             &BUFFER_METHODS,
         ))
     }
@@ -827,9 +1197,10 @@ impl BufferResizeGuard for PyByteArray {
     type Resizable<'a> = PyDetachingRwLockWriteGuard<'a, PyBytesInner>;
 
     fn try_resizable_opt(&self) -> Option<Self::Resizable<'_>> {
-        // An export is a borrow someone else still holds, so it is answered
-        // before the lock rather than by waiting on it.
-        (self.exports.load(Ordering::SeqCst) == 0).then(|| self.inner.write())
+        match self.resize_access() {
+            ResizeAccess::Exclusive(inner) => Some(inner),
+            ResizeAccess::Exported { .. } => None,
+        }
     }
 }
 
@@ -860,10 +1231,43 @@ impl AsSequence for PyByteArray {
         static AS_SEQUENCE: PySequenceMethods = PySequenceMethods {
             length: atomic_func!(|seq, _vm| Ok(PyByteArray::sequence_downcast(seq).__len__())),
             concat: atomic_func!(|seq, other, vm| {
-                PyByteArray::sequence_downcast(seq)
-                    .inner()
-                    .concat(other, vm)
-                    .map(|x| PyByteArray::from(x).into_pyobject(vm))
+                let concat_error = || {
+                    vm.new_type_error(format!(
+                        "can't concat {} to {}",
+                        other.class().name(),
+                        seq.obj.class().name()
+                    ))
+                };
+                // Protect the left operand before the right buffer callback,
+                // without holding either operand's lock across Python calls.
+                let left = PyBuffer::from_object(vm, seq.obj, BufferFlags::SIMPLE)
+                    .map_err(|_| concat_error())?;
+                let right = match PyBuffer::from_object(vm, other, BufferFlags::SIMPLE) {
+                    Ok(buffer) => buffer,
+                    Err(_) => {
+                        let error = concat_error();
+                        drop(left);
+                        return Err(error);
+                    }
+                };
+                let result = (|| {
+                    let len = left
+                        .desc
+                        .len
+                        .checked_add(right.desc.len)
+                        .ok_or_else(|| vm.no_memory_error())?;
+                    let mut bytes = Vec::new();
+                    bytes
+                        .try_reserve_exact(len)
+                        .map_err(|_| vm.no_memory_error())?;
+                    left.append_to(&mut bytes);
+                    right.append_to(&mut bytes);
+                    Ok(PyByteArray::from(bytes).into_pyobject(vm))
+                })();
+                // Buffer release can run Python too; all slice guards are gone.
+                drop(left);
+                drop(right);
+                result
             }),
             repeat: atomic_func!(|seq, n, vm| {
                 PyByteArray::sequence_downcast(seq)
@@ -881,7 +1285,7 @@ impl AsSequence for PyByteArray {
                 if let Some(value) = value {
                     zelf._setitem_by_index(i, &value, vm)
                 } else {
-                    zelf.borrow_buf_mut().delitem_by_index(vm, i)
+                    zelf.delitem_by_index(i, vm)
                 }
             }),
             contains: atomic_func!(|seq, other, vm| {
@@ -985,3 +1389,44 @@ impl IterNext for PyByteArrayIterator {
         })
     }
 }
+
+#[cfg(test)]
+mod export_state_tests {
+    use super::ExportState;
+
+    #[test]
+    fn export_epoch_length_is_stable_until_last_release() {
+        let mut state = ExportState::default();
+        assert_eq!(state.snapshot(), None);
+        assert_eq!(state.retain_existing(), None);
+        state.retain(3);
+        assert_eq!(state.snapshot(), Some(3));
+        assert_eq!(state.retain_existing(), Some(3));
+        state.retain(3);
+        assert_eq!(state.count, 3);
+        state.release();
+        state.release();
+        assert_eq!(state.count, 1);
+        assert_eq!(state.snapshot(), Some(3));
+        let rejected_length = state.snapshot();
+        state.release();
+        assert_eq!(state.snapshot(), None);
+        state.retain(7);
+        assert_eq!(state.snapshot(), Some(7));
+        assert_eq!(rejected_length, Some(3));
+        state.release();
+        assert_eq!(state.snapshot(), None);
+    }
+
+    #[test]
+    fn empty_export_is_distinct_from_no_export() {
+        let mut state = ExportState::default();
+        state.retain(0);
+        assert_eq!(state.snapshot(), Some(0));
+        assert_eq!(state.retain_existing(), Some(0));
+        state.release();
+        assert_eq!(state.snapshot(), Some(0));
+        state.release();
+        assert_eq!(state.snapshot(), None);
+    }
+}
diff --git a/crates/vm/src/builtins/bytes.rs b/crates/vm/src/builtins/bytes.rs
index 415cf4df4df..d300996f86a 100644
--- a/crates/vm/src/builtins/bytes.rs
+++ b/crates/vm/src/builtins/bytes.rs
@@ -22,7 +22,7 @@ use crate::{
         BufferDescriptor, BufferFlags, BufferMethods, PyBuffer, PyIterReturn, PyMappingMethods,
         PyNumberMethods, PySequenceMethods,
     },
-    sliceable::{SequenceIndex, SliceableSequenceOp},
+    sliceable::{NameByte, SequenceIndex, SliceableSequenceOp},
     types::{
         AsBuffer, AsMapping, AsNumber, AsSequence, Callable, Comparable, Constructor, Hashable,
         IterNext, Iterable, PyComparisonOp, Representable, SelfIter,
@@ -165,7 +165,7 @@ impl PyBytes {
     }
 
     fn _getitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
-        match SequenceIndex::try_from_borrowed_object(vm, needle, "byte")? {
+        match SequenceIndex::try_from_borrowed_object::<NameByte>(vm, needle)? {
             SequenceIndex::Int(i) => self
                 .getitem_by_index(vm, i)
                 .map(|x| vm.ctx.new_int(x).into()),
@@ -490,21 +490,6 @@ impl Py<PyBytes> {
         Ok(self.inner.translate(options, vm)?.into())
     }
 
-    #[pymethod]
-    fn strip(&self, options: ByteInnerStripOptions) -> PyBytes {
-        self.inner.strip(options.bytes).into()
-    }
-
-    #[pymethod]
-    fn removeprefix(&self, prefix: PyBytesInner) -> PyBytes {
-        self.inner.removeprefix(prefix).into()
-    }
-
-    #[pymethod]
-    fn removesuffix(&self, suffix: PyBytesInner) -> PyBytes {
-        self.inner.removesuffix(suffix).into()
-    }
-
     #[pymethod]
     fn split(
         &self,
@@ -571,11 +556,6 @@ impl Py<PyBytes> {
         Ok(self.inner.zfill(width, vm)?.into())
     }
 
-    #[pymethod]
-    fn replace(&self, options: ByteInnerReplaceOptions, vm: &VirtualMachine) -> PyResult<PyBytes> {
-        Ok(self.inner.replace(options, vm)?.into())
-    }
-
     #[pymethod]
     fn title(&self) -> PyBytes {
         self.inner.title().into()
@@ -590,6 +570,38 @@ impl Py<PyBytes> {
 
 #[pyclass]
 impl PyRef<PyBytes> {
+    // These operations return a subslice, so equal lengths mean unchanged contents.
+    fn result_from_slice(&self, result: &[u8], vm: &VirtualMachine) -> Self {
+        if result.len() == self.as_bytes().len() && self.class().is(vm.ctx.types.bytes_type) {
+            self.clone()
+        } else {
+            vm.ctx.new_bytes(result.to_vec())
+        }
+    }
+
+    #[pymethod]
+    fn strip(self, options: ByteInnerStripOptions, vm: &VirtualMachine) -> Self {
+        self.result_from_slice(self.inner.strip(options.bytes), vm)
+    }
+
+    #[pymethod]
+    fn removeprefix(self, prefix: PyBytesInner, vm: &VirtualMachine) -> Self {
+        self.result_from_slice(self.inner.removeprefix(prefix), vm)
+    }
+
+    #[pymethod]
+    fn removesuffix(self, suffix: PyBytesInner, vm: &VirtualMachine) -> Self {
+        self.result_from_slice(self.inner.removesuffix(suffix), vm)
+    }
+
+    #[pymethod]
+    fn replace(self, options: ByteInnerReplaceOptions, vm: &VirtualMachine) -> PyResult<Self> {
+        Ok(match self.inner.replace(options, vm)? {
+            alloc::borrow::Cow::Borrowed(result) => self.result_from_slice(result, vm),
+            alloc::borrow::Cow::Owned(result) => vm.ctx.new_bytes(result),
+        })
+    }
+
     #[pymethod]
     fn __bytes__(self, vm: &VirtualMachine) -> Self {
         if self.is(vm.ctx.types.bytes_type) {
@@ -601,22 +613,12 @@ impl PyRef<PyBytes> {
 
     #[pymethod]
     fn lstrip(self, options: ByteInnerStripOptions, vm: &VirtualMachine) -> Self {
-        let stripped = self.payload.inner.lstrip(options.bytes);
-        if stripped == self.as_bytes() {
-            self
-        } else {
-            vm.ctx.new_bytes(stripped.to_vec())
-        }
+        self.result_from_slice(self.inner.lstrip(options.bytes), vm)
     }
 
     #[pymethod]
     fn rstrip(self, options: ByteInnerStripOptions, vm: &VirtualMachine) -> Self {
-        let stripped = self.payload.inner.rstrip(options.bytes);
-        if stripped == self.as_bytes() {
-            self
-        } else {
-            vm.ctx.new_bytes(stripped.to_vec())
-        }
+        self.result_from_slice(self.inner.rstrip(options.bytes), vm)
     }
 
     // currently, only 'utf-8' and 'ascii' implemented
diff --git a/crates/vm/src/builtins/code.rs b/crates/vm/src/builtins/code.rs
index 6cf1036ab11..be6807efe2b 100644
--- a/crates/vm/src/builtins/code.rs
+++ b/crates/vm/src/builtins/code.rs
@@ -1,8 +1,10 @@
 //! Infamous code object. The python class `code`
 
+mod const_cache;
+
 use super::descriptor::{MemberKind, MemberLayout};
 use super::{PyBytesRef, PyStrRef, PyTupleRef, PyType, set::PyFrozenSet};
-use crate::common::lock::PyMutex;
+use crate::common::lock::{OnceCell, PyMutex};
 #[cfg(feature = "host_env")]
 use crate::convert::ToPyException;
 use crate::{
@@ -154,11 +156,11 @@ pub struct ReplaceArgs {
     #[pyarg(named, optional)]
     co_firstlineno: OptionalArg<u32>,
     #[pyarg(named, optional)]
-    co_consts: OptionalArg<Vec<PyObjectRef>>,
+    co_consts: OptionalArg<PyTupleRef>,
     #[pyarg(named, optional)]
     co_name: OptionalArg<PyStrRef>,
     #[pyarg(named, optional)]
-    co_names: OptionalArg<Vec<PyObjectRef>>,
+    co_names: OptionalArg<PyTupleRef>,
     #[pyarg(named, optional)]
     co_flags: OptionalArg<u32>,
     #[pyarg(named, optional)]
@@ -256,7 +258,34 @@ fn borrow_obj_constant(obj: &PyObject) -> BorrowedConstant<'_, Literal> {
     })
 }
 
+/// `co_consts` viewed as constants.
+#[derive(Clone)]
+pub struct LiteralTuple(PyTupleRef);
+
+impl LiteralTuple {
+    pub const fn as_pytuple(&self) -> &PyTupleRef {
+        &self.0
+    }
+}
+
+impl Deref for LiteralTuple {
+    type Target = [Literal];
+
+    fn deref(&self) -> &[Literal] {
+        let elements = self.0.as_slice();
+        // SAFETY: Literal is repr(transparent) over PyObjectRef.
+        unsafe { &*(elements as *const [PyObjectRef] as *const [Literal]) }
+    }
+}
+
+impl FromIterator<Literal> for LiteralTuple {
+    fn from_iter<T: IntoIterator<Item = Literal>>(iter: T) -> Self {
+        Self(Context::genesis().new_tuple(iter.into_iter().map(|c| c.0).collect()))
+    }
+}
+
 impl Constant for Literal {
+    type Tuple = LiteralTuple;
     type Name = &'static PyStrInterned;
     fn borrow_constant(&self) -> BorrowedConstant<'_, Self> {
         borrow_obj_constant(&self.0)
@@ -357,6 +386,15 @@ pub(crate) type CodeObject = bytecode::CodeObject<Literal>;
 
 pub trait IntoCodeObject {
     fn into_code_object(self, vm: &VirtualMachine) -> CodeObject;
+
+    fn into_pycode(self, vm: &VirtualMachine) -> PyCode
+    where
+        Self: Sized,
+    {
+        let mut code = PyCode::new(self.into_code_object(vm), &vm.ctx);
+        code.apply_debug_ranges(vm);
+        code
+    }
 }
 
 impl IntoCodeObject for CodeObject {
@@ -367,7 +405,11 @@ impl IntoCodeObject for CodeObject {
 
 impl IntoCodeObject for bytecode::CodeObject {
     fn into_code_object(self, vm: &VirtualMachine) -> CodeObject {
-        self.map_bag(PyVmBag(vm))
+        const_cache::into_code_object(self, vm)
+    }
+
+    fn into_pycode(self, vm: &VirtualMachine) -> PyCode {
+        const_cache::into_pycode(self, vm)
     }
 }
 
@@ -389,20 +431,39 @@ pub struct CoMonitoringData {
     pub per_instruction_opcodes: Vec<u8>,
 }
 
+/// `_PyCoCached`: objects created on first use.
+#[derive(Default)]
+struct CoCached {
+    code: OnceCell<PyBytesRef>,
+    varnames: OnceCell<PyTupleRef>,
+    cellvars: OnceCell<PyTupleRef>,
+    freevars: OnceCell<PyTupleRef>,
+}
+
 #[pyclass(module = false, name = "code")]
 pub struct PyCode {
     #[pymember(name = "co_argcount", path = "arg_count")]
     #[pymember(name = "co_posonlyargcount", path = "posonlyarg_count")]
     #[pymember(name = "co_kwonlyargcount", path = "kwonlyarg_count")]
     #[pymember(name = "co_stacksize", path = "max_stackdepth")]
-    #[pymember(name = "co_name", path = "obj_name")]
-    #[pymember(name = "co_qualname", path = "qualname")]
     #[pymember(name = "co_flags", path = "flags")]
     pub code: CodeObject,
     /// Slot-indexed names, equivalent to CPython's `co_localsplusnames`.
     /// Derived once so frame-local proxy operations do not repeatedly scan
     /// merged cell variables.
     localsplus_names: Box<[&'static PyStrInterned]>,
+    pub(crate) co_name: PyStrRef,
+    #[pymember(name = "co_qualname")]
+    qualified_name: PyStrRef,
+    pub(crate) co_names: PyTupleRef,
+    pub(crate) co_localsplusnames: PyTupleRef,
+    pub(crate) co_localspluskinds: PyBytesRef,
+    pub(crate) co_linetable: PyBytesRef,
+    pub(crate) co_exceptiontable: PyBytesRef,
+    co_cached: CoCached,
+    /// `_co_firsttraceable`: the index of the first `RESUME` that does not
+    /// start a generator expression, or the code length if there is none.
+    pub(crate) first_traceable: usize,
     #[pymember(name = "co_filename")]
     source_path: AtomicPtr<PyStrInterned>,
     #[pymember(name = "co_nlocals")]
@@ -506,12 +567,17 @@ fn build_localspluskinds(
     Ok(kinds.into_boxed_slice())
 }
 
+fn holds_names(tuple: &super::PyTuple, names: &[&'static PyStrInterned]) -> bool {
+    tuple.len() == names.len() && tuple.iter().zip(names).all(|(item, name)| item.is(*name))
+}
+
 impl MemberLayout for CodeFlags {
     const KIND: MemberKind = MemberKind::Int;
 }
 
 impl PyCode {
-    pub fn new(code: CodeObject) -> Self {
+    pub fn new(mut code: CodeObject, ctx: &Context) -> Self {
+        code.instructions.fixup_get_iter(code.flags);
         let sp = code.source_path as *const PyStrInterned as *mut PyStrInterned;
         let nlocals = i32::try_from(code.varnames.len()).unwrap_or(i32::MAX);
         let localsplus_names = {
@@ -547,7 +613,28 @@ impl PyCode {
                     | Instruction::InstrumentedEndAsyncFor
             )
         });
+        let first_traceable = code
+            .instructions
+            .iter()
+            .position(|unit| {
+                matches!(unit.op, Instruction::Resume { .. })
+                    && u32::from(u8::from(unit.arg)) & bytecode::oparg::ResumeContext::LOCATION_MASK
+                        != bytecode::oparg::ResumeLocation::AtGenExprStart.as_u32()
+            })
+            .unwrap_or(code.instructions.len());
+        let names_tuple = |names: &[&'static PyStrInterned]| {
+            ctx.new_tuple(names.iter().map(|name| name.to_object()).collect())
+        };
         Self {
+            first_traceable,
+            co_name: code.obj_name.to_owned(),
+            qualified_name: code.qualname.to_owned(),
+            co_names: names_tuple(&code.names),
+            co_localsplusnames: names_tuple(&localsplus_names),
+            co_localspluskinds: ctx.new_bytes(code.localspluskinds.to_vec()),
+            co_linetable: ctx.new_bytes(code.linetable.to_vec()),
+            co_exceptiontable: ctx.new_bytes(code.exceptiontable.to_vec()),
+            co_cached: CoCached::default(),
             code,
             localsplus_names,
             source_path: AtomicPtr::new(sp),
@@ -559,6 +646,59 @@ impl PyCode {
         }
     }
 
+    /// The code object `r_object` creates from a TYPE_CODE record. It keeps
+    /// the objects read for the object-valued fields.
+    pub(crate) fn from_marshal(
+        mut code: CodeObject,
+        fields: rustpython_compiler_core::marshal::CodeFields<PyObjectRef>,
+        ctx: &Context,
+    ) -> Result<Self, rustpython_compiler_core::marshal::MarshalError> {
+        use rustpython_compiler_core::marshal::MarshalError;
+        fn downcast<T: PyPayload>(obj: PyObjectRef) -> Result<PyRef<T>, MarshalError> {
+            obj.downcast().map_err(|_| MarshalError::BadType)
+        }
+        code.constants = bytecode::Constants::new(LiteralTuple(downcast(fields.consts)?));
+        // The compiler's string conversion is lossy for surrogates; retain the
+        // decoded value and apply code construction's exact-string interning.
+        let qualname = downcast::<super::PyStr>(fields.qualname)?;
+        code.qualname = ctx.intern_str(qualname.as_wtf8());
+        let mut code = Self::new(code, ctx);
+        code.set_names(downcast(fields.names)?);
+        code.set_localsplusnames(downcast(fields.localsplusnames)?);
+        code.co_localspluskinds = downcast(fields.localspluskinds)?;
+        code.co_linetable = downcast(fields.linetable)?;
+        code.co_exceptiontable = downcast(fields.exceptiontable)?;
+        Ok(code)
+    }
+
+    /// Keep `names` as `co_names` when it holds the interned names, the way
+    /// `intern_strings` interns a names tuple in place.
+    fn set_names(&mut self, names: PyTupleRef) {
+        if holds_names(&names, &self.code.names) {
+            self.co_names = names;
+        }
+    }
+
+    /// Keep `localsplusnames` as `co_localsplusnames`; see [`Self::set_names`].
+    fn set_localsplusnames(&mut self, localsplusnames: PyTupleRef) {
+        if holds_names(&localsplusnames, &self.localsplus_names) {
+            self.co_localsplusnames = localsplusnames;
+        }
+    }
+
+    pub(crate) fn apply_debug_ranges(&mut self, vm: &VirtualMachine) {
+        if !vm.state.config.settings.code_debug_ranges
+            && let Some(linetable) = remove_column_info(&self.code.linetable)
+        {
+            self.code.linetable = linetable;
+            self.co_linetable = vm.ctx.new_bytes(self.code.linetable.to_vec());
+        }
+    }
+
+    pub(crate) fn co_qualname(&self) -> PyStrRef {
+        self.qualified_name.clone()
+    }
+
     #[inline(always)]
     pub(crate) fn localsplus_name(&self, index: usize) -> &'static PyStrInterned {
         // Bytecode operands and frame-proxy indices are validated against
@@ -567,6 +707,41 @@ impl PyCode {
         self.localsplus_names[index]
     }
 
+    pub(crate) fn co_consts(&self) -> &PyTupleRef {
+        self.code.constants.as_tuple().as_pytuple()
+    }
+
+    /// `_PyCode_GetCode`
+    pub(crate) fn get_code(&self, vm: &VirtualMachine) -> PyBytesRef {
+        self.co_cached
+            .code
+            .get_or_init(|| vm.ctx.new_bytes(self.deopt_code()))
+            .clone()
+    }
+
+    /// `deopt_code`: the instructions with each opcode replaced by its base
+    /// opcode (`_Py_GetBaseCodeUnit`) and the inline caches zeroed.
+    fn deopt_code(&self) -> Vec<u8> {
+        let monitoring_data = self.monitoring_data.lock();
+        self.code.instructions.original_bytes_with(|i, op| {
+            let Some(data) = monitoring_data.as_ref() else {
+                return op;
+            };
+            let op = match op {
+                Instruction::InstrumentedLine => Instruction::try_from(data.line_opcodes[i])
+                    .expect("INSTRUMENTED_LINE without original opcode"),
+                op => op,
+            };
+            match op {
+                Instruction::InstrumentedInstruction => {
+                    Instruction::try_from(data.per_instruction_opcodes[i])
+                        .expect("INSTRUMENTED_INSTRUCTION without original opcode")
+                }
+                op => op,
+            }
+        })
+    }
+
     pub fn source_path(&self) -> &'static PyStrInterned {
         // SAFETY: always points to a valid &'static PyStrInterned (interned strings are never deallocated)
         unsafe { &*self.source_path.load(Ordering::Relaxed) }
@@ -580,11 +755,17 @@ impl PyCode {
     }
 
     pub fn new_ref_with_bag(vm: &VirtualMachine, code: CodeObject) -> PyRef<Self> {
-        PyRef::new_ref(Self::new(code), vm.ctx.types.code_type.to_owned(), None)
+        let mut code = Self::new(code, &vm.ctx);
+        code.apply_debug_ranges(vm);
+        PyRef::new_ref(code, vm.ctx.types.code_type.to_owned(), None)
     }
 
     pub fn new_ref_from_bytecode(vm: &VirtualMachine, code: bytecode::CodeObject) -> PyRef<Self> {
-        Self::new_ref_with_bag(vm, code.map_bag(PyVmBag(vm)))
+        PyRef::new_ref(
+            code.into_pycode(vm),
+            vm.ctx.types.code_type.to_owned(),
+            None,
+        )
     }
 
     pub fn new_ref_from_frozen<B: AsRef<[u8]>>(
@@ -721,6 +902,78 @@ impl Representable for PyCode {
     }
 }
 
+/// `_PyCode_ConstantKey`
+pub(crate) fn constant_key(op: &PyObject, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
+    use super::{PyBool, PyBytes, PyComplex, PyFloat, PyInt, PySlice, PyStr, PyTuple};
+
+    let ctx = &vm.ctx;
+    let class = op.class();
+    let pair = |first: PyObjectRef| ctx.new_tuple(vec![first, op.to_owned()]).into();
+    let triple = |tag: PyObjectRef| {
+        ctx.new_tuple(vec![class.to_owned().into(), op.to_owned(), tag])
+            .into()
+    };
+    let is_neg_zero = |d: f64| d == 0.0 && d.is_sign_negative();
+
+    let key = if vm.is_none(op)
+        || op.is(&ctx.ellipsis)
+        || class.is(PyInt::static_type())
+        || class.is(PyStr::static_type())
+        || op.downcast_ref::<PyCode>().is_some()
+    {
+        // Objects of these types are always different from object of other
+        // type and from tuples.
+        op.to_owned()
+    } else if class.is(PyBool::static_type()) || class.is(PyBytes::static_type()) {
+        // Make booleans different from integers 0 and 1.
+        pair(class.to_owned().into())
+    } else if let Some(float) = op.downcast_ref_if_exact::<PyFloat>(vm) {
+        if is_neg_zero(float.to_f64()) {
+            triple(ctx.none())
+        } else {
+            pair(class.to_owned().into())
+        }
+    } else if let Some(complex) = op.downcast_ref_if_exact::<PyComplex>(vm) {
+        // All four complex zeros must be distinguished.
+        let z = complex.to_complex();
+        match (is_neg_zero(z.re), is_neg_zero(z.im)) {
+            (true, true) => triple(ctx.new_bool(true).into()),
+            (false, true) => triple(ctx.new_bool(false).into()),
+            (true, false) => triple(ctx.none()),
+            (false, false) => pair(class.to_owned().into()),
+        }
+    } else if let Some(tuple) = op.downcast_ref_if_exact::<PyTuple>(vm) {
+        let keys = tuple
+            .iter()
+            .map(|item| constant_key(item, vm))
+            .collect::<PyResult<_>>()?;
+        pair(ctx.new_tuple(keys).into())
+    } else if let Some(set) = op.downcast_ref_if_exact::<PyFrozenSet>(vm) {
+        let keys = set
+            .elements()
+            .iter()
+            .map(|item| constant_key(item, vm))
+            .collect::<PyResult<Vec<_>>>()?;
+        pair(PyFrozenSet::from_iter(vm, keys)?.into_ref(ctx).into())
+    } else if let Some(slice) = op.downcast_ref::<PySlice>() {
+        let key = |item: Option<&PyObjectRef>| match item {
+            Some(item) => constant_key(item, vm),
+            None => Ok(ctx.none()),
+        };
+        let slice_key = PySlice {
+            start: Some(key(slice.start.as_ref())?),
+            stop: key(Some(&slice.stop))?,
+            step: Some(key(slice.step.as_ref())?),
+        };
+        pair(slice_key.into_ref(ctx).into())
+    } else {
+        // For other types, use the object identifier as a unique identifier
+        // to ensure that they are seen as unequal.
+        pair(ctx.new_int(op.get_id()).into())
+    };
+    Ok(key)
+}
+
 impl Comparable for PyCode {
     fn cmp(
         zelf: &Py<Self>,
@@ -732,35 +985,23 @@ impl Comparable for PyCode {
             let other = class_or_notimplemented!(Self, other);
             let a = &zelf.code;
             let b = &other.code;
-            let eq = a.obj_name == b.obj_name
+            let eq = vm.bool_eq(zelf.co_name.as_object(), other.co_name.as_object())?
                 && a.arg_count == b.arg_count
                 && a.posonlyarg_count == b.posonlyarg_count
                 && a.kwonlyarg_count == b.kwonlyarg_count
                 && a.flags == b.flags
                 && a.first_line_number == b.first_line_number
-                && a.instructions.original_bytes() == b.instructions.original_bytes()
+                && zelf.get_code(vm).as_bytes() == other.get_code(vm).as_bytes()
                 && a.linetable == b.linetable
                 && a.exceptiontable == b.exceptiontable
                 && a.names == b.names
                 && a.varnames == b.varnames
                 && a.freevars == b.freevars
                 && a.cellvars == b.cellvars
-                && {
-                    let a_consts: Vec<_> = a.constants.iter().map(|c| c.0.clone()).collect();
-                    let b_consts: Vec<_> = b.constants.iter().map(|c| c.0.clone()).collect();
-                    if a_consts.len() != b_consts.len() {
-                        false
-                    } else {
-                        let mut eq = true;
-                        for (ac, bc) in a_consts.iter().zip(b_consts.iter()) {
-                            if !vm.bool_eq(ac, bc)? {
-                                eq = false;
-                                break;
-                            }
-                        }
-                        eq
-                    }
-                };
+                && vm.bool_eq(
+                    &*constant_key(zelf.co_consts().as_object(), vm)?,
+                    &*constant_key(other.co_consts().as_object(), vm)?,
+                )?;
             Ok(eq.into())
         })
     }
@@ -771,7 +1012,7 @@ impl Hashable for PyCode {
         let code = &zelf.code;
         // Hash a tuple of key attributes, matching CPython's code_hash
         let tuple = vm.ctx.new_tuple(vec![
-            vm.ctx.new_str(code.obj_name.as_str()).into(),
+            zelf.co_name.clone().into(),
             vm.ctx.new_int(code.arg_count).into(),
             vm.ctx.new_int(code.posonlyarg_count).into(),
             vm.ctx.new_int(code.kwonlyarg_count).into(),
@@ -780,7 +1021,7 @@ impl Hashable for PyCode {
             vm.ctx
                 .new_int(code.first_line_number.map_or(0, |n| n.get()) as i64)
                 .into(),
-            vm.ctx.new_bytes(code.instructions.original_bytes()).into(),
+            zelf.get_code(vm).into(),
             {
                 let consts: Vec<_> = code.constants.iter().map(|c| c.0.clone()).collect();
                 vm.ctx.new_tuple(consts).into()
@@ -884,16 +1125,7 @@ impl Constructor for PyCode {
         let instructions = CodeUnits::try_from(bytecode_bytes)
             .map_err(|e| vm.new_value_error(format!("invalid bytecode: {e}")))?;
 
-        // Convert constants
-        let constants = args
-            .consts
-            .as_slice()
-            .iter()
-            .map(|obj| {
-                // Convert PyObject to Literal constant. For now, just wrap it
-                Literal(obj.clone())
-            })
-            .collect();
+        let constants = bytecode::Constants::new(LiteralTuple(args.consts));
 
         // Create locations (start and end pairs)
         let row = if args.firstlineno > 0 {
@@ -955,7 +1187,16 @@ impl Constructor for PyCode {
             exceptiontable: args.exceptiontable.as_bytes().to_vec().into_boxed_slice(),
         };
 
-        Ok(Self::new(code))
+        let mut code = Self::new(code, &vm.ctx);
+        code.co_name = args.name;
+        if !args.qualname.class().is(vm.ctx.types.str_type) {
+            code.qualified_name = args.qualname;
+        }
+        code.set_names(args.names);
+        code.co_linetable = args.linetable;
+        code.co_exceptiontable = args.exceptiontable;
+        code.apply_debug_ranges(vm);
+        Ok(code)
     }
 }
 
@@ -973,12 +1214,13 @@ impl PyCode {
 impl Py<PyCode> {
     #[pygetset]
     pub fn co_cellvars(&self, vm: &VirtualMachine) -> PyTupleRef {
-        let cellvars = self
+        self.co_cached
             .cellvars
-            .iter()
-            .map(|name| name.to_pyobject(vm))
-            .collect();
-        vm.ctx.new_tuple(cellvars)
+            .get_or_init(|| {
+                vm.ctx
+                    .new_tuple(self.cellvars.iter().map(|name| name.to_object()).collect())
+            })
+            .clone()
     }
 
     #[pygetset]
@@ -987,36 +1229,43 @@ impl Py<PyCode> {
     }
 
     #[pygetset]
-    fn co_consts(&self, vm: &VirtualMachine) -> PyTupleRef {
-        let consts = self.code.constants.iter().map(|x| x.0.clone()).collect();
-        vm.ctx.new_tuple(consts)
+    fn co_name(&self) -> PyStrRef {
+        self.co_name.clone()
     }
 
     #[pygetset]
-    fn co_names(&self, vm: &VirtualMachine) -> PyTupleRef {
-        let names = self
-            .code
-            .names
-            .deref()
-            .iter()
-            .map(|name| name.to_pyobject(vm))
-            .collect();
-        vm.ctx.new_tuple(names)
+    fn co_consts(&self) -> PyTupleRef {
+        PyCode::co_consts(self).clone()
+    }
+
+    #[pygetset]
+    fn co_names(&self) -> PyTupleRef {
+        self.co_names.clone()
     }
 
     #[pygetset]
     pub fn co_varnames(&self, vm: &VirtualMachine) -> PyTupleRef {
-        let varnames = self.code.varnames.iter().map(|s| s.to_object()).collect();
-        vm.ctx.new_tuple(varnames)
+        self.co_cached
+            .varnames
+            .get_or_init(|| {
+                vm.ctx.new_tuple(
+                    self.code
+                        .varnames
+                        .iter()
+                        .map(|name| name.to_object())
+                        .collect(),
+                )
+            })
+            .clone()
     }
 
     #[pygetset]
-    pub fn co_code(&self, vm: &VirtualMachine) -> crate::builtins::PyBytesRef {
-        vm.ctx.new_bytes(self.code.instructions.original_bytes())
+    pub fn co_code(&self, vm: &VirtualMachine) -> PyBytesRef {
+        self.get_code(vm)
     }
 
     #[pygetset]
-    pub fn _co_code_adaptive(&self, vm: &VirtualMachine) -> crate::builtins::PyBytesRef {
+    pub fn _co_code_adaptive(&self, vm: &VirtualMachine) -> PyBytesRef {
         // Return current (possibly quickened/specialized) bytecode
         let bytes = unsafe {
             core::slice::from_raw_parts(
@@ -1029,26 +1278,28 @@ impl Py<PyCode> {
 
     #[pygetset]
     pub fn co_freevars(&self, vm: &VirtualMachine) -> PyTupleRef {
-        let names = self
-            .code
+        self.co_cached
             .freevars
-            .deref()
-            .iter()
-            .map(|name| name.to_pyobject(vm))
-            .collect();
-        vm.ctx.new_tuple(names)
+            .get_or_init(|| {
+                vm.ctx.new_tuple(
+                    self.code
+                        .freevars
+                        .iter()
+                        .map(|name| name.to_object())
+                        .collect(),
+                )
+            })
+            .clone()
     }
 
     #[pygetset]
-    pub fn co_linetable(&self, vm: &VirtualMachine) -> crate::builtins::PyBytesRef {
-        // Return the actual linetable from the code object
-        vm.ctx.new_bytes(self.code.linetable.to_vec())
+    pub fn co_linetable(&self) -> PyBytesRef {
+        self.co_linetable.clone()
     }
 
     #[pygetset]
-    pub fn co_exceptiontable(&self, vm: &VirtualMachine) -> crate::builtins::PyBytesRef {
-        // Return the actual exception table from the code object
-        vm.ctx.new_bytes(self.code.exceptiontable.to_vec())
+    pub fn co_exceptiontable(&self) -> PyBytesRef {
+        self.co_exceptiontable.clone()
     }
 
     // spell-checker: ignore lnotab
@@ -1380,23 +1631,17 @@ impl Py<PyCode> {
 
         let constants = match co_consts {
             OptionalArg::Present(constants) => constants,
-            OptionalArg::Missing => self.code.constants.iter().map(|x| x.0.clone()).collect(),
+            OptionalArg::Missing => PyCode::co_consts(self).clone(),
         };
 
         let obj_name = match co_name {
             OptionalArg::Present(obj_name) => obj_name,
-            OptionalArg::Missing => self.code.obj_name.to_owned(),
+            OptionalArg::Missing => self.co_name.clone(),
         };
 
         let names = match co_names {
             OptionalArg::Present(names) => names,
-            OptionalArg::Missing => self
-                .code
-                .names
-                .deref()
-                .iter()
-                .map(|name| name.to_pyobject(vm))
-                .collect(),
+            OptionalArg::Missing => self.co_names.clone(),
         };
 
         let flags = CodeFlags::from_bits_truncate(match co_flags {
@@ -1411,7 +1656,7 @@ impl Py<PyCode> {
 
         let qualname = match co_qualname {
             OptionalArg::Present(qualname) => qualname,
-            OptionalArg::Missing => self.code.qualname.to_owned(),
+            OptionalArg::Missing => self.qualified_name.clone(),
         };
 
         // Room for one value is always reserved, even where nothing is pushed.
@@ -1427,7 +1672,8 @@ impl Py<PyCode> {
                 CodeUnits::try_from(code_bytes.as_bytes())
                     .map_err(|e| vm.new_value_error(format!("invalid bytecode: {e}")))?
             }
-            OptionalArg::Missing => self.code.instructions.clone(),
+            OptionalArg::Missing => CodeUnits::try_from(self.get_code(vm).as_bytes())
+                .map_err(|e| vm.new_value_error(format!("invalid bytecode: {e}")))?,
         };
 
         let intern_all = |objs: Vec<PyObjectRef>, field: &str| -> PyResult<Box<[_]>> {
@@ -1482,15 +1728,13 @@ impl Py<PyCode> {
 
         // Handle linetable and exceptiontable
         let linetable = match co_linetable {
-            OptionalArg::Present(linetable) => linetable.as_bytes().to_vec().into_boxed_slice(),
-            OptionalArg::Missing => self.code.linetable.clone(),
+            OptionalArg::Present(linetable) => linetable,
+            OptionalArg::Missing => self.co_linetable.clone(),
         };
 
         let exceptiontable = match co_exceptiontable {
-            OptionalArg::Present(exceptiontable) => {
-                exceptiontable.as_bytes().to_vec().into_boxed_slice()
-            }
-            OptionalArg::Missing => self.code.exceptiontable.clone(),
+            OptionalArg::Present(exceptiontable) => exceptiontable,
+            OptionalArg::Missing => self.co_exceptiontable.clone(),
         };
 
         let new_code = CodeObject {
@@ -1508,17 +1752,26 @@ impl Py<PyCode> {
             // FIXME: invalid locations. Actually locations is a duplication of linetable.
             // It can be removed once we move every other code to use linetable only.
             locations: self.code.locations.clone(),
-            constants: constants.into_iter().map(Literal).collect(),
-            names: intern_all(names, "co_names")?,
+            constants: bytecode::Constants::new(LiteralTuple(constants)),
+            names: intern_all(names.as_slice().to_vec(), "co_names")?,
             varnames,
             cellvars,
             freevars,
             localspluskinds,
-            linetable,
-            exceptiontable,
+            linetable: linetable.as_bytes().into(),
+            exceptiontable: exceptiontable.as_bytes().into(),
         };
 
-        Ok(PyCode::new(new_code))
+        let mut code = PyCode::new(new_code, &vm.ctx);
+        code.co_name = obj_name;
+        if !qualname.class().is(vm.ctx.types.str_type) {
+            code.qualified_name = qualname;
+        }
+        code.set_names(names);
+        code.co_linetable = linetable;
+        code.co_exceptiontable = exceptiontable;
+        code.apply_debug_ranges(vm);
+        Ok(code)
     }
 
     #[pymethod]
@@ -1574,6 +1827,78 @@ impl ToPyObject for bytecode::CodeObject {
     }
 }
 
+// Preserve entry lengths and line deltas while dropping columns, as code
+// construction does under -X no_debug_ranges in CPython. Decode and re-encode
+// signed deltas to normalize redundant encodings, including negative zero.
+// Leave unconvertible tables unchanged rather than inventing line deltas or
+// introducing new constructor errors. This is not a general table validator.
+fn remove_column_info(linetable: &[u8]) -> Option<Box<[u8]>> {
+    let mut result = Vec::with_capacity(linetable.len());
+    let mut reader = LineTableReader::new(linetable);
+    while let Some(header) = reader.read_byte() {
+        if header & 0x80 == 0 {
+            return None;
+        }
+        let kind = (header >> 3) & 15;
+        if kind == PyCodeLocationInfoKind::None as u8 {
+            result.push(header);
+        } else {
+            result.push(0x80 | ((PyCodeLocationInfoKind::NoColumns as u8) << 3) | (header & 7));
+            let delta = match PyCodeLocationInfoKind::from_code(kind) {
+                Some(PyCodeLocationInfoKind::Long | PyCodeLocationInfoKind::NoColumns) => {
+                    read_location_delta(&mut reader)?
+                }
+                Some(PyCodeLocationInfoKind::OneLine1) => 1,
+                Some(PyCodeLocationInfoKind::OneLine2) => 2,
+                _ => 0,
+            };
+            let mut encoded = (delta.unsigned_abs() << 1) | u32::from(delta < 0);
+            while encoded >= 64 {
+                result.push(0x40 | (encoded & 0x3f) as u8);
+                encoded >>= 6;
+            }
+            result.push(encoded as u8);
+        }
+        while reader.peek_byte().is_some_and(|byte| byte & 0x80 == 0) {
+            reader.read_byte();
+        }
+    }
+    Some(result.into_boxed_slice())
+}
+
+// Location deltas use an unsigned 32-bit sign/magnitude representation. Allow
+// redundant zero groups, but reject overflow and truncation without unchecked
+// shifts or consuming the next header. This does not validate absolute lines.
+fn read_location_delta(reader: &mut LineTableReader<'_>) -> Option<i32> {
+    let mut value = 0u32;
+    let mut shift = 0;
+    loop {
+        let byte = reader.peek_byte()?;
+        if byte & 0x80 != 0 {
+            return None;
+        }
+        reader.read_byte();
+        let digit = u32::from(byte & 0x3f);
+        if shift < u32::BITS {
+            if digit > (u32::MAX >> shift) {
+                return None;
+            }
+            value |= digit << shift;
+        } else if digit != 0 {
+            return None;
+        }
+        if byte & 0x40 == 0 {
+            let magnitude = (value >> 1) as i32;
+            return Some(if value & 1 != 0 {
+                -magnitude
+            } else {
+                magnitude
+            });
+        }
+        shift = (shift + 6).min(u32::BITS);
+    }
+}
+
 // Helper struct for reading linetable
 struct LineTableReader<'a> {
     data: &'a [u8],
diff --git a/crates/vm/src/builtins/code/const_cache.rs b/crates/vm/src/builtins/code/const_cache.rs
new file mode 100644
index 00000000000..6515219e711
--- /dev/null
+++ b/crates/vm/src/builtins/code/const_cache.rs
@@ -0,0 +1,148 @@
+//! The compiler's constant cache (`c_const_cache`).
+//!
+//! Equal constants and code fields produced by one compilation share a single
+//! object, merged under their `_PyCode_ConstantKey`.
+
+use super::*;
+use crate::builtins::{PyDict, PyDictRef, PyTuple};
+
+/// `const_cache_insert`. Items of a tuple or frozenset constant are created
+/// through the cache before the container, so a single non-recursive insert
+/// also merges them.
+fn const_cache_insert(
+    const_cache: &Py<PyDict>,
+    o: PyObjectRef,
+    vm: &VirtualMachine,
+) -> PyResult<PyObjectRef> {
+    // None and Ellipsis are singletons, and key is the singleton.
+    if vm.is_none(&o) || o.is(&vm.ctx.ellipsis) {
+        return Ok(o);
+    }
+    let key = constant_key(&o, vm)?;
+    let key = match const_cache.get_item_opt(&*key, vm)? {
+        Some(existing) => existing,
+        None => {
+            const_cache.set_item(&*key, key.clone(), vm)?;
+            key
+        }
+    };
+    // See constant_key()
+    Ok(match key.downcast_ref_if_exact::<PyTuple>(vm) {
+        Some(key) => key.as_slice()[1].clone(),
+        None => key,
+    })
+}
+
+/// A [`ConstantBag`] creating the constants of one compilation through its
+/// constant cache.
+#[derive(Clone, Copy)]
+struct CompileBag<'a> {
+    vm: &'a VirtualMachine,
+    const_cache: &'a Py<PyDict>,
+}
+
+impl CompileBag<'_> {
+    /// `_PyCompile_ConstCacheMergeOne`
+    fn merge_one<T: PyPayload>(&self, obj: PyRef<T>) -> PyRef<T> {
+        self.merge(obj.into())
+            .downcast()
+            .expect("an equal constant key implies the same type")
+    }
+
+    fn merge(&self, obj: PyObjectRef) -> PyObjectRef {
+        const_cache_insert(self.const_cache, obj, self.vm)
+            .expect("constant keys are hashable and comparable")
+    }
+
+    /// Create a code object whose fields are merged the way `assemble.c`
+    /// merges them, in the same order.
+    fn new_code(&self, code: CodeObject) -> PyCode {
+        let mut code = PyCode::new(code, &self.vm.ctx);
+        code.apply_debug_ranges(self.vm);
+        code.co_exceptiontable = self.merge_one(code.co_exceptiontable);
+        code.co_linetable = self.merge_one(code.co_linetable);
+        code.co_names = self.merge_one(code.co_names);
+        let consts = self.merge_one(code.code.constants.as_tuple().as_pytuple().clone());
+        code.code.constants = bytecode::Constants::new(LiteralTuple(consts));
+        code.co_localsplusnames = self.merge_one(code.co_localsplusnames);
+        code
+    }
+}
+
+impl ConstantBag for CompileBag<'_> {
+    type Constant = Literal;
+
+    fn make_constant<C: Constant>(&self, constant: BorrowedConstant<'_, C>) -> Literal {
+        let vm = self.vm;
+        let obj = match constant {
+            BorrowedConstant::Code { code } => return self.make_code(code.map_clone_bag(self)),
+            BorrowedConstant::Tuple { elements } => vm
+                .ctx
+                .new_tuple(
+                    elements
+                        .iter()
+                        .map(|item| self.make_constant(item.borrow_constant()).0)
+                        .collect(),
+                )
+                .into(),
+            BorrowedConstant::Frozenset { elements } => PyFrozenSet::from_iter(
+                vm,
+                elements
+                    .iter()
+                    .map(|item| self.make_constant(item.borrow_constant()).0),
+            )
+            .unwrap()
+            .into_ref(&vm.ctx)
+            .into(),
+            BorrowedConstant::Slice { elements } => {
+                let [start, stop, step] = elements
+                    .each_ref()
+                    .map(|item| self.make_constant(item.borrow_constant()).0);
+                crate::builtins::PySlice {
+                    start: Some(start),
+                    stop,
+                    step: Some(step),
+                }
+                .into_ref(&vm.ctx)
+                .into()
+            }
+            _ => PyVmBag(vm).make_constant(constant).0,
+        };
+        Literal(self.merge(obj))
+    }
+
+    fn make_name(&self, name: &str) -> &'static PyStrInterned {
+        self.vm.ctx.intern_str(name)
+    }
+
+    fn make_int(&self, value: BigInt) -> Literal {
+        Literal(self.merge(self.vm.ctx.new_int(value).into()))
+    }
+
+    fn make_tuple(&self, elements: impl Iterator<Item = Literal>) -> Literal {
+        let tuple = self.vm.ctx.new_tuple(elements.map(|item| item.0).collect());
+        Literal(self.merge(tuple.into()))
+    }
+
+    fn make_code(&self, code: CodeObject) -> Literal {
+        let code = self.new_code(code).into_ref(&self.vm.ctx);
+        Literal(self.merge(code.into()))
+    }
+}
+
+pub(super) fn into_code_object(code: bytecode::CodeObject, vm: &VirtualMachine) -> CodeObject {
+    let const_cache: PyDictRef = vm.ctx.new_dict();
+    code.map_bag(CompileBag {
+        vm,
+        const_cache: &const_cache,
+    })
+}
+
+pub(super) fn into_pycode(code: bytecode::CodeObject, vm: &VirtualMachine) -> PyCode {
+    let const_cache: PyDictRef = vm.ctx.new_dict();
+    let bag = CompileBag {
+        vm,
+        const_cache: &const_cache,
+    };
+    bag.new_code(code.map_bag(bag))
+}
diff --git a/crates/vm/src/builtins/complex.rs b/crates/vm/src/builtins/complex.rs
index f471c43c580..40b38cb47dc 100644
--- a/crates/vm/src/builtins/complex.rs
+++ b/crates/vm/src/builtins/complex.rs
@@ -1,10 +1,10 @@
-use super::{PyStr, PyType, PyTypeRef, float};
+use super::{PyInt, PyStr, PyType, PyTypeRef, float};
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
     builtins::PyUtf8StrRef,
     class::{PyClassDef, PyClassImpl},
-    common::{format::FormatSpec, wtf8::Wtf8Buf},
-    convert::{IntoPyException, ToPyObject, ToPyResult},
+    common::{float_ops, wtf8::Wtf8Buf},
+    convert::{ToPyObject, ToPyResult},
     function::{FuncArgs, OptionalArg, PyComparisonValue},
     protocol::PyNumberMethods,
     stdlib::_warnings,
@@ -571,17 +571,16 @@ impl Py<PyComplex> {
         if format_spec.is_empty() {
             return Ok(zelf.as_object().str(vm)?.as_wtf8().to_owned());
         }
-        let format_spec =
-            FormatSpec::parse(format_spec.as_str()).map_err(|err| err.into_pyexception(vm))?;
-        let result = if format_spec.has_locale_format() {
+        let spec = crate::format::parse_format_spec(zelf.as_object(), format_spec.as_str(), vm)?;
+        let result = if spec.has_locale_format() {
             let locale = crate::format::get_locale_info();
-            format_spec.format_complex_locale(&zelf.as_complex(), &locale)
+            spec.format_complex_locale(&zelf.as_complex(), &locale)
         } else {
-            format_spec.format_complex(&zelf.as_complex())
+            spec.format_complex(&zelf.as_complex())
         };
-        result
-            .map(Wtf8Buf::from_string)
-            .map_err(|err| err.into_pyexception(vm))
+        result.map(Wtf8Buf::from_string).map_err(|err| {
+            crate::format::format_spec_error(err, zelf.as_object(), format_spec.as_str(), vm)
+        })
     }
 
     #[pyclassmethod]
@@ -624,17 +623,20 @@ impl Comparable for PyComplex {
         zelf: &Py<Self>,
         other: &PyObject,
         op: PyComparisonOp,
-        vm: &VirtualMachine,
+        _vm: &VirtualMachine,
     ) -> PyResult<PyComparisonValue> {
         op.eq_only(|| {
+            let value = zelf.as_complex();
             let result = if let Some(other) = other.downcast_ref::<Self>() {
-                zelf.as_complex() == other.as_complex()
+                value == other.as_complex()
+            } else if let Some(other) = other.downcast_ref::<PyInt>() {
+                // Compare with the exact integer, as float does, instead of
+                // rounding the integer to the nearest float first.
+                value.im == 0.0 && float_ops::eq_int(value.re, other.as_bigint())
+            } else if let Some(other) = other.downcast_ref::<float::PyFloat>() {
+                value == other.to_f64().into()
             } else {
-                match float::to_op_float(other, vm) {
-                    Ok(Some(other)) => zelf.as_complex() == other.into(),
-                    Err(_) => false,
-                    Ok(None) => return Ok(PyComparisonValue::NotImplemented),
-                }
+                return Ok(PyComparisonValue::NotImplemented);
             };
             Ok(PyComparisonValue::Implemented(result))
         })
diff --git a/crates/vm/src/builtins/coroutine.rs b/crates/vm/src/builtins/coroutine.rs
index 649481c8cc3..93481c41a1c 100644
--- a/crates/vm/src/builtins/coroutine.rs
+++ b/crates/vm/src/builtins/coroutine.rs
@@ -148,6 +148,15 @@ impl Py<PyCoroutine> {
         self.inner.code()
     }
     #[pygetset]
+    fn cr_state(&self) -> &'static str {
+        self.inner.state_name([
+            "CORO_CREATED",
+            "CORO_RUNNING",
+            "CORO_SUSPENDED",
+            "CORO_CLOSED",
+        ])
+    }
+    #[pygetset]
     fn cr_suspended(&self, _vm: &VirtualMachine) -> bool {
         self.inner.suspended()
     }
@@ -174,7 +183,7 @@ impl Destructor for PyCoroutine {
         if zelf.inner.closed() || zelf.inner.running() {
             return Ok(());
         }
-        if zelf.inner.frame_opt().is_none_or(|f| f.lasti() == 0) {
+        if !zelf.inner.started() {
             crate::warn::warn_unawaited_coroutine(zelf.as_object(), &zelf.inner.qualname(), vm);
             zelf.inner.closed.store(true);
             return Ok(());
diff --git a/crates/vm/src/builtins/descriptor.rs b/crates/vm/src/builtins/descriptor.rs
index b3189e592a8..4c7c1804d4c 100644
--- a/crates/vm/src/builtins/descriptor.rs
+++ b/crates/vm/src/builtins/descriptor.rs
@@ -1,7 +1,7 @@
 use super::{PyStr, PyStrInterned, PyTuple, PyType};
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
-    builtins::{PyTypeRef, builtin_func::PyNativeMethod, type_},
+    builtins::{PyTypeRef, builtin_func::PyNativeFunction, type_},
     class::PyClassImpl,
     common::hash::PyHash,
     convert::{ToPyObject, ToPyResult},
@@ -39,7 +39,7 @@ pub struct PyMethodDescriptor {
     #[pymember(name = "__objclass__", path = "typ")]
     #[pymember(name = "__name__", path = "name")]
     pub common: PyDescriptor,
-    pub method: &'static PyMethodDef,
+    pub(crate) method: &'static PyMethodDef,
     // vectorcall: vector_call_func,
     /// Prevent HeapMethodDef from being freed while this descriptor references it
     pub(crate) _method_def_owner: Option<PyObjectRef>,
@@ -112,8 +112,9 @@ impl Callable for PyMethodDescriptor {
     type Args = FuncArgs;
     #[inline]
     fn call(zelf: &Py<Self>, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-        if let Some(obj) = args.args.first() {
-            method_descr_typecheck(zelf, obj, vm)?;
+        method_descr_check_self(zelf, args.args.first().map(|obj| &**obj), vm)?;
+        if !args.kwargs.is_empty() && !zelf.method.flags.contains(PyMethodFlags::KEYWORDS) {
+            return Err(method_descr_no_keywords_error(zelf, vm));
         }
         (zelf.method.func)(
             vm,
@@ -124,8 +125,9 @@ impl Callable for PyMethodDescriptor {
 }
 
 impl PyMethodDescriptor {
-    pub fn bind(&self, obj: PyObjectRef, ctx: &Context) -> PyRef<PyNativeMethod> {
-        self.method.build_bound_method(ctx, obj, self.common.typ)
+    pub fn bind(&self, obj: PyObjectRef, ctx: &Context) -> PyRef<PyNativeFunction> {
+        self.method
+            .build_bound_function_with_owner(ctx, obj, self._method_def_owner.clone())
     }
 }
 
@@ -154,10 +156,12 @@ impl Py<PyMethodDescriptor> {
     fn __reduce__(
         &self,
         vm: &VirtualMachine,
-    ) -> (Option<PyObjectRef>, (Option<PyObjectRef>, &'static str)) {
-        let builtins_getattr = vm.builtins.get_attr("getattr", vm).ok();
-        let classname = vm.builtins.get_attr(&self.common.typ.__name__(vm), vm).ok();
-        (builtins_getattr, (classname, self.method.name))
+    ) -> PyResult<(PyObjectRef, (PyTypeRef, &'static str))> {
+        let builtins_getattr = vm.eval_get_builtin(vm.ctx.intern_str("getattr"))?;
+        Ok((
+            builtins_getattr,
+            (self.common.typ.to_owned(), self.method.name),
+        ))
     }
 }
 
@@ -178,7 +182,7 @@ pub struct PyClassMethodDescriptor {
     #[pymember(name = "__objclass__", path = "typ")]
     #[pymember(name = "__name__", path = "name")]
     pub common: PyDescriptor,
-    pub method: &'static PyMethodDef,
+    pub(crate) method: &'static PyMethodDef,
     pub(crate) _method_def_owner: Option<PyObjectRef>,
 }
 
@@ -195,8 +199,9 @@ impl PyClassMethodDescriptor {
         }
     }
 
-    pub fn bind(&self, obj: PyObjectRef, ctx: &Context) -> PyRef<PyNativeMethod> {
-        self.method.build_bound_method(ctx, obj, self.common.typ)
+    pub fn bind(&self, obj: PyObjectRef, ctx: &Context) -> PyRef<PyNativeFunction> {
+        self.method
+            .build_bound_function_with_owner(ctx, obj, self._method_def_owner.clone())
     }
 }
 
@@ -540,12 +545,6 @@ impl MemberCell for core::sync::atomic::AtomicU32 {}
 // One object pointer. Readonly members may be a plain pointer. Writable
 // members are an atomic cell: `PyAtomicRef<PyObject>` when the pointer is
 // never null, or `PyAtomicRef<Option<PyObject>>` when it may be.
-impl MemberLayout for PyObjectRef {
-    const KIND: MemberKind = MemberKind::Object;
-}
-impl MemberLayout for Option<PyObjectRef> {
-    const KIND: MemberKind = MemberKind::Object;
-}
 impl MemberLayout for crate::object::PyObjectCell {
     const KIND: MemberKind = MemberKind::Object;
     const ATOMIC: bool = true;
@@ -850,7 +849,7 @@ impl Py<PyMemberDescriptor> {
 
     #[pymethod]
     fn __reduce__(&self, vm: &VirtualMachine) -> PyResult {
-        let builtins_getattr = vm.builtins.get_attr("getattr", vm)?;
+        let builtins_getattr = vm.eval_get_builtin(vm.ctx.intern_str("getattr"))?;
         Ok(vm
             .ctx
             .new_tuple(vec![
@@ -1556,6 +1555,40 @@ fn method_descr_typecheck(
     )))
 }
 
+#[inline]
+fn method_descr_check_self(
+    descr: &PyMethodDescriptor,
+    obj: Option<&PyObject>,
+    vm: &VirtualMachine,
+) -> PyResult<()> {
+    let obj = obj.ok_or_else(|| method_descr_missing_self_error(descr, vm))?;
+    method_descr_typecheck(descr, obj, vm)
+}
+
+#[cold]
+fn method_descr_missing_self_error(
+    descr: &PyMethodDescriptor,
+    vm: &VirtualMachine,
+) -> crate::exceptions::types::PyBaseExceptionRef {
+    vm.new_type_error(format!(
+        "unbound method {}.{}() needs an argument",
+        descr.common.typ.name(),
+        descr.common.name
+    ))
+}
+
+#[cold]
+fn method_descr_no_keywords_error(
+    descr: &PyMethodDescriptor,
+    vm: &VirtualMachine,
+) -> crate::exceptions::types::PyBaseExceptionRef {
+    vm.new_type_error(format!(
+        "{}.{}() takes no keyword arguments",
+        descr.common.typ.name(),
+        descr.common.name
+    ))
+}
+
 /// Vectorcall for method_descriptor: calls native method directly
 fn vectorcall_method_descriptor(
     zelf_obj: &PyObject,
@@ -1565,10 +1598,19 @@ fn vectorcall_method_descriptor(
     vm: &VirtualMachine,
 ) -> PyResult {
     let zelf: &Py<PyMethodDescriptor> = zelf_obj.downcast_ref().unwrap();
-    if nargs > 0
-        && let Some(obj) = args.first()
+    method_descr_check_self(
+        zelf,
+        if nargs > 0 {
+            args.first().map(|obj| &**obj)
+        } else {
+            None
+        },
+        vm,
+    )?;
+    if kwnames.is_some_and(|names| !names.is_empty())
+        && !zelf.method.flags.contains(PyMethodFlags::KEYWORDS)
     {
-        method_descr_typecheck(zelf, obj, vm)?;
+        return Err(method_descr_no_keywords_error(zelf, vm));
     }
     let func_args = FuncArgs::from_vectorcall_owned(args, nargs, kwnames);
     (zelf.method.func)(
@@ -2018,6 +2060,16 @@ impl Callable for PyWrapper {
     flags(DISALLOW_INSTANTIATION)
 )]
 impl Py<PyWrapper> {
+    #[pymethod]
+    fn __reduce__(&self, vm: &VirtualMachine) -> PyResult {
+        let getattr = vm.eval_get_builtin(vm.ctx.intern_str("getattr"))?;
+        let args = vm.ctx.new_tuple(vec![
+            self.typ.to_owned().into(),
+            self.name.to_owned().into(),
+        ]);
+        Ok(vm.ctx.new_tuple(vec![getattr, args.into()]).into())
+    }
+
     #[pygetset]
     fn __qualname__(&self) -> String {
         format!("{}.{}", self.typ.name(), self.name)
@@ -2127,7 +2179,7 @@ impl Py<PyMethodWrapper> {
 
     #[pymethod]
     fn __reduce__(zelf: PyRef<PyMethodWrapper>, vm: &VirtualMachine) -> PyResult {
-        let builtins_getattr = vm.builtins.get_attr("getattr", vm)?;
+        let builtins_getattr = vm.eval_get_builtin(vm.ctx.intern_str("getattr"))?;
         Ok(vm
             .ctx
             .new_tuple(vec![
diff --git a/crates/vm/src/builtins/dict.rs b/crates/vm/src/builtins/dict.rs
index d709521ea6d..dfc81cb167f 100644
--- a/crates/vm/src/builtins/dict.rs
+++ b/crates/vm/src/builtins/dict.rs
@@ -5,24 +5,27 @@ use super::{
 };
 use crate::common::lock::LazyLock;
 use crate::object::{Traverse, TraverseFn};
-use crate::stdlib::PyOrderedDictItems;
 use crate::{
-    AsObject, Context, Py, PyExact, PyObject, PyObjectRef, PyPayload, PyRef, PyRefExact, PyResult,
+    AsObject, Context, Py, PyExact, PyObject, PyObjectRef, PyPayload, PyRef, PyResult,
     TryFromObject, atomic_func,
     builtins::{PyList, PyTuple, iter::builtins_iter, type_::PyAttributes},
     class::{PyClassDef, PyClassImpl},
-    common::{ascii, hash::PyHash},
+    common::{
+        ascii,
+        hash::{self, PyHash},
+    },
     dict_inner::{self, DictKey},
     function::{ArgIterable, FuncArgs, KwArgs, OptionalArg, PyArithmeticValue, PyComparisonValue},
     protocol::{PyIter, PyIterReturn, PyMappingMethods, PyNumberMethods, PySequenceMethods},
     recursion::ReprGuard,
     types::{
         AsMapping, AsNumber, AsSequence, Callable, Comparable, Constructor, DefaultConstructor,
-        Initializer, IterNext, Iterable, PyComparisonOp, Representable, SelfIter,
+        Hashable, Initializer, IterNext, Iterable, PyComparisonOp, Representable, SelfIter,
     },
     vm::VirtualMachine,
 };
 use alloc::fmt;
+use core::borrow::Borrow;
 use core::cell::Cell;
 use core::ptr::NonNull;
 use rustpython_common::atomic::{Ordering, PyAtomic, Radium};
@@ -31,15 +34,273 @@ use rustpython_common::wtf8::Wtf8Buf;
 
 pub(crate) type DictContentType = dict_inner::Dict;
 
+pub(crate) fn key_hash<K: DictKey + ?Sized>(
+    key: &K,
+    mapping_name: &str,
+    vm: &VirtualMachine,
+) -> PyResult<PyHash> {
+    match key.key_hash(vm) {
+        // Exact TypeError only: exception subclasses retain their identity.
+        Err(exc) if exc.class().is(vm.ctx.exceptions.type_error) => {
+            let name = key.to_pyobject(vm).class().fully_qualified_name(vm)?;
+            // Match BaseException_str without the diagnostic formatter's
+            // fallback: argument __str__/__repr__ failures must propagate.
+            let args = exc.args();
+            let message = match args.as_slice() {
+                [] => vm.ctx.empty_str.to_owned(),
+                [arg] => arg.str(vm)?,
+                _ => args.as_object().str(vm)?,
+            };
+            Err(vm.new_type_error(format!(
+                "cannot use '{name}' as a {mapping_name} key ({message})"
+            )))
+        }
+        result => result,
+    }
+}
+
 #[pyclass(module = false, name = "dict", unhashable = true, traverse = "manual")]
 #[derive(Default)]
 // OrderedDict contains eight-byte-aligned fields on 32-bit targets too.
 #[repr(align(8))]
 pub struct PyDict {
-    entries: DictContentType,
+    pub(crate) entries: DictContentType,
 }
 pub type PyDictRef = PyRef<PyDict>;
 
+/// A borrowed view of a dict or frozendict, including subclasses.
+///
+/// This is an erased header view, not a shared payload layout. Every payload
+/// access downcasts to the actual alternative, preserving its mutability.
+#[repr(transparent)]
+pub struct PyAnyDict {
+    object: PyObject,
+}
+
+// SAFETY: this owner contributes exactly one strong reference to the object.
+unsafe impl Traverse for PyRef<PyAnyDict> {
+    fn traverse(&self, tracer: &mut TraverseFn<'_>) {
+        tracer(self.as_object());
+    }
+}
+
+impl crate::convert::ToPyObject for PyRef<PyAnyDict> {
+    fn to_pyobject(self, _vm: &VirtualMachine) -> PyObjectRef {
+        self.into_object()
+    }
+}
+
+impl Borrow<PyObject> for PyAnyDict {
+    fn borrow(&self) -> &PyObject {
+        &self.object
+    }
+}
+
+impl Borrow<PyAnyDict> for PyRef<PyAnyDict> {
+    fn borrow(&self) -> &PyAnyDict {
+        self
+    }
+}
+
+impl ToOwned for PyAnyDict {
+    type Owned = PyRef<Self>;
+
+    fn to_owned(&self) -> PyRef<Self> {
+        // SAFETY: this borrowed view already guarantees a dictionary payload.
+        unsafe { PyRef::<Self>::from_object_unchecked(self.object.to_owned()) }
+    }
+}
+
+impl From<PyDictRef> for PyRef<PyAnyDict> {
+    fn from(dict: PyDictRef) -> Self {
+        // SAFETY: the typed owner guarantees the dict alternative.
+        unsafe { Self::from_object_unchecked(dict.into()) }
+    }
+}
+
+impl From<PyRef<PyFrozenDict>> for PyRef<PyAnyDict> {
+    fn from(dict: PyRef<PyFrozenDict>) -> Self {
+        // SAFETY: the typed owner guarantees the frozendict alternative.
+        unsafe { Self::from_object_unchecked(dict.into()) }
+    }
+}
+
+impl From<PyRef<PyAnyDict>> for PyObjectRef {
+    fn from(dict: PyRef<PyAnyDict>) -> Self {
+        dict.into_object()
+    }
+}
+
+// SAFETY: the transparent PyRef owner has the same layout as PyObjectRef.
+// A successful check proves the actual dict or frozendict payload invariant.
+unsafe impl crate::convert::TransmuteFromObject for PyRef<PyAnyDict> {
+    fn check(vm: &VirtualMachine, obj: &PyObject) -> PyResult<()> {
+        if PyAnyDict::from_object(obj).is_some() {
+            Ok(())
+        } else {
+            Err(vm.new_type_error(format!(
+                "expected dict or frozendict, got {}",
+                obj.class().name()
+            )))
+        }
+    }
+}
+
+impl TryFromObject for PyRef<PyAnyDict> {
+    fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
+        <Self as crate::convert::TransmuteFromObject>::check(vm, &obj)?;
+        // SAFETY: the shared checker proved the union view's payload invariant.
+        Ok(unsafe { Self::from_object_unchecked(obj) })
+    }
+}
+
+impl PyAnyDict {
+    pub fn from_object(obj: &PyObject) -> Option<&Self> {
+        if obj.downcast_ref::<PyDict>().is_some() || obj.downcast_ref::<PyFrozenDict>().is_some() {
+            // SAFETY: PyAnyDict is transparent over PyObject and the payload was checked.
+            Some(unsafe { &*(obj as *const PyObject).cast::<Self>() })
+        } else {
+            None
+        }
+    }
+
+    pub(crate) fn as_mutable(&self) -> Option<&Py<PyDict>> {
+        self.object.downcast_ref()
+    }
+
+    pub(crate) fn is_frozen(&self) -> bool {
+        self.object.downcastable::<PyFrozenDict>()
+    }
+
+    // The raw payload is private: callers outside the VM cannot use it to mutate a frozendict.
+    pub(crate) fn as_dict(&self) -> &PyDict {
+        if let Some(dict) = self.as_mutable() {
+            dict
+        } else {
+            &self.object.downcast_ref::<PyFrozenDict>().unwrap().dict
+        }
+    }
+
+    pub(crate) fn uses_builtin_iter(&self, vm: &VirtualMachine) -> bool {
+        let base = if self.is_frozen() {
+            vm.ctx.types.frozendict_type
+        } else {
+            vm.ctx.types.dict_type
+        };
+        self.as_object()
+            .class()
+            .slots
+            .iter
+            .load()
+            .map(crate::types::fn_addr)
+            == base.slots.iter.load().map(crate::types::fn_addr)
+    }
+
+    #[must_use]
+    pub fn __len__(&self) -> usize {
+        self.as_dict().__len__()
+    }
+    #[must_use]
+    pub fn is_empty(&self) -> bool {
+        self.as_dict().is_empty()
+    }
+    pub fn copy_as_dict(&self, vm: &VirtualMachine) -> PyResult<PyDict> {
+        if self.is_empty() || self.uses_builtin_iter(vm) {
+            return Ok(self.as_dict().copy());
+        }
+        let copied = PyDict::default();
+        copied.merge_object(self.as_object().to_owned(), vm)?;
+        Ok(copied)
+    }
+
+    #[must_use]
+    pub fn keys_vec(&self) -> Vec<PyObjectRef> {
+        self.as_dict().keys_vec()
+    }
+    #[must_use]
+    pub fn values_vec(&self) -> Vec<PyObjectRef> {
+        self.as_dict().values_vec()
+    }
+    #[must_use]
+    pub fn items_vec(&self) -> Vec<(PyObjectRef, PyObjectRef)> {
+        self.as_dict().items_vec()
+    }
+    #[must_use]
+    pub fn next_entry(&self, position: usize) -> Option<(usize, PyObjectRef, PyObjectRef)> {
+        self.as_dict().next_entry(position)
+    }
+    pub(crate) fn size(&self) -> crate::dict_inner::DictSize {
+        self.as_dict().size()
+    }
+    pub fn inner_getitem_opt<K: DictKey + ?Sized>(
+        &self,
+        key: &K,
+        vm: &VirtualMachine,
+    ) -> PyResult<Option<PyObjectRef>> {
+        if let Some(dict) = self.as_mutable() {
+            dict.inner_getitem_opt(key, vm)
+        } else {
+            self.object
+                .downcast_ref::<PyFrozenDict>()
+                .unwrap()
+                .inner_getitem_opt(key, vm)
+        }
+    }
+    pub fn get_item_opt<K: DictKey + ?Sized>(
+        &self,
+        key: &K,
+        vm: &VirtualMachine,
+    ) -> PyResult<Option<PyObjectRef>> {
+        if let Some(dict) = self.as_mutable() {
+            return dict.get_item_opt(key, vm);
+        }
+        if self.object.class().is(vm.ctx.types.frozendict_type) {
+            return self.inner_getitem_opt(key, vm);
+        }
+        match self.object.get_item(key, vm) {
+            Ok(value) => Ok(Some(value)),
+            Err(exc) if exc.fast_isinstance(vm.ctx.exceptions.key_error) => Ok(None),
+            Err(exc) => Err(exc),
+        }
+    }
+    pub fn get_item<K: DictKey + ?Sized>(&self, key: &K, vm: &VirtualMachine) -> PyResult {
+        if let Some(dict) = self.as_mutable() {
+            dict.get_item(key, vm)
+        } else {
+            self.object.get_item(key, vm)
+        }
+    }
+    pub fn contains_key<K: DictKey + ?Sized>(&self, key: &K, vm: &VirtualMachine) -> bool {
+        self.inner_getitem_opt(key, vm)
+            .is_ok_and(|value| value.is_some())
+    }
+    pub fn set_item<K: DictKey + ?Sized>(
+        &self,
+        key: &K,
+        value: PyObjectRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        match self.as_mutable() {
+            Some(dict) => dict.set_item(key, value, vm),
+            None => Err(vm.new_type_error("frozendict object does not support item assignment")),
+        }
+    }
+    pub fn del_item<K: DictKey + ?Sized>(&self, key: &K, vm: &VirtualMachine) -> PyResult<()> {
+        match self.as_mutable() {
+            Some(dict) => dict.del_item(key, vm),
+            None => Err(vm.new_type_error("frozendict object does not support item deletion")),
+        }
+    }
+}
+
+impl<'a> IntoIterator for &'a PyAnyDict {
+    type Item = (PyObjectRef, PyObjectRef);
+    type IntoIter = DictIter<'a>;
+    fn into_iter(self) -> Self::IntoIter {
+        DictIter::new(self.as_dict())
+    }
+}
+
 // SAFETY: Traverse properly visits all owned PyObjectRefs
 unsafe impl Traverse for PyDict {
     fn traverse(&self, traverse_fn: &mut TraverseFn<'_>) {
@@ -136,50 +397,55 @@ impl PyDict {
         self.entries.items()
     }
 
-    fn merge_object_with_override(
+    pub(crate) fn items_with_hashes_vec(&self) -> Vec<(PyObjectRef, PyObjectRef, PyHash)> {
+        self.entries.items_with_hashes()
+    }
+
+    /// `dict_update_arg`. `mapping_name` names the target type in the
+    /// unhashable key error, as `dict_unhashable_type` does.
+    pub(crate) fn update_arg(
         &self,
         other: PyObjectRef,
         override_existing: bool,
+        mapping_name: &str,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        let casted: Result<PyRefExact<Self>, _> = other.downcast_exact(vm);
-        let other = match casted {
-            Ok(dict_other) => {
-                return self.merge_dict(&dict_other, override_existing, vm);
-            }
-            Err(other) => other,
-        };
+        if let Some(other_dict) = PyAnyDict::from_object(&other)
+            && other_dict.uses_builtin_iter(vm)
+        {
+            return self.merge_dict(other_dict.as_dict(), override_existing, vm);
+        }
         let dict = &self.entries;
         // Use get_attr to properly invoke __getattribute__ for proxy objects
-        let keys_result = other.get_attr(vm.ctx.intern_str("keys"), vm);
-        let has_keys = match keys_result {
-            Ok(keys_method) => {
-                let keys = PyIter::try_from_object(vm, keys_method.call((), vm)?)?;
-                while let PyIterReturn::Return(key) = keys.next(vm)? {
-                    if !override_existing && dict.contains(vm, &*key)? {
-                        continue;
-                    }
-                    let val = other.get_item(&*key, vm)?;
-                    dict.insert(vm, &*key, val)?;
-                }
-                true
+        let keys_method = match other.get_attr(vm.ctx.intern_str("keys"), vm) {
+            Ok(keys_method) => keys_method,
+            Err(e) if e.fast_isinstance(vm.ctx.exceptions.attribute_error) => {
+                return self.merge_seq2(&other, override_existing, mapping_name, vm);
             }
-            Err(e) if e.fast_isinstance(vm.ctx.exceptions.attribute_error) => false,
             Err(e) => return Err(e),
         };
-        if !has_keys {
-            return self.merge_from_seq2(&other, override_existing, vm);
+        let keys = PyIter::try_from_object(vm, keys_method.call((), vm)?)?;
+        while let PyIterReturn::Return(key) = keys.next(vm)? {
+            if !override_existing {
+                let hash = key_hash(&*key, mapping_name, vm)?;
+                if dict.contains(vm, &*key, hash)? {
+                    continue;
+                }
+            }
+            let value = other.get_item(&*key, vm)?;
+            let hash = key_hash(&*key, mapping_name, vm)?;
+            dict.insert(vm, &*key, hash, value)?;
         }
         Ok(())
     }
 
     // Used in update and ior.
     pub fn merge_object(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
-        self.merge_object_with_override(other, true, vm)
+        self.update_arg(other, true, "dict", vm)
     }
 
     pub fn merge_object_if_missing(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
-        self.merge_object_with_override(other, false, vm)
+        self.update_arg(other, false, "dict", vm)
     }
 
     fn add_update_sequence_note(
@@ -257,6 +523,17 @@ impl PyDict {
         seq2: &PyObject,
         override_existing: bool,
         vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        self.merge_seq2(seq2, override_existing, "dict", vm)
+    }
+
+    /// `dict_merge_from_seq2`
+    fn merge_seq2(
+        &self,
+        seq2: &PyObject,
+        override_existing: bool,
+        mapping_name: &str,
+        vm: &VirtualMachine,
     ) -> PyResult<()> {
         let iter = seq2.get_iter(vm)?;
         let dict = &self.entries;
@@ -264,17 +541,18 @@ impl PyDict {
         for (index, element) in iter.iter::<PyObjectRef>(vm)?.enumerate() {
             let (key, value) = Self::update_sequence_pair(element?, index, vm)?;
 
-            if !override_existing && dict.contains(vm, &*key)? {
+            let hash = key_hash(&*key, mapping_name, vm)?;
+            if !override_existing && dict.contains(vm, &*key, hash)? {
                 continue;
             }
-            dict.insert(vm, &*key, value)?;
+            dict.insert(vm, &*key, hash, value)?;
         }
         Ok(())
     }
 
     pub(crate) fn merge_dict(
         &self,
-        dict_other: &Py<Self>,
+        dict_other: &Self,
         override_existing: bool,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
@@ -284,10 +562,10 @@ impl PyDict {
         while let Some((next, key, value, hash)) = dict_other.entries.next_entry_with_hash(position)
         {
             position = next;
-            if !override_existing && dict.contains_known_hash(vm, &*key, hash)? {
+            if !override_existing && dict.contains(vm, &*key, hash)? {
                 continue;
             }
-            dict.insert_known_hash(vm, &*key, hash, value)?;
+            dict.insert(vm, &*key, hash, value)?;
         }
         if dict_other.entries.has_changed_size(dict_size) {
             return Err(vm.new_runtime_error("dict mutated during update"));
@@ -299,6 +577,21 @@ impl PyDict {
         self.entries.len() == 0
     }
 
+    /// Hash `key`, turning a hashing failure into the dict-specific
+    /// "cannot use 'X' as a dict key (...)" wording.
+    ///
+    /// The returned hash is passed into the inner map, so the key is hashed
+    /// exactly once. A `TypeError` from key comparison (e.g. a colliding key's
+    /// `__eq__`) is raised by the operation itself and must propagate unchanged.
+    /// Hashing up front also means a `__hash__` that fails only intermittently
+    /// is still reported.
+    pub(crate) fn hash_or_unhashable<K: DictKey + ?Sized>(
+        key: &K,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyHash> {
+        key_hash(key, "dict", vm)
+    }
+
     /// Set item variant which can be called with multiple
     /// key types, such as str to name a notable one.
     pub fn inner_setitem<K: DictKey + ?Sized>(
@@ -307,7 +600,8 @@ impl PyDict {
         value: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        self.entries.insert(vm, key, value)
+        let hash = Self::hash_or_unhashable(key, vm)?;
+        self.entries.insert(vm, key, hash, value)
     }
 
     pub(crate) fn inner_delitem<K: DictKey + ?Sized>(
@@ -315,7 +609,12 @@ impl PyDict {
         key: &K,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        self.entries.delete(vm, key)
+        let hash = Self::hash_or_unhashable(key, vm)?;
+        if self.entries.delete_if_exists(vm, key, hash)? {
+            Ok(())
+        } else {
+            Err(vm.new_key_error(key.to_pyobject(vm)))
+        }
     }
 
     pub fn get_or_insert(
@@ -324,21 +623,24 @@ impl PyDict {
         key: &PyObject,
         default: impl FnOnce() -> PyObjectRef,
     ) -> PyResult {
-        self.entries.setdefault(vm, key, default)
+        let hash = Self::hash_or_unhashable(key, vm)?;
+        self.entries.setdefault(vm, key, hash, default)
     }
 
     pub fn from_attributes(attrs: PyAttributes, vm: &VirtualMachine) -> PyResult<Self> {
         let entries = DictContentType::default();
 
         for (key, value) in attrs {
-            entries.insert(vm, key, value)?;
+            let hash = key.key_hash(vm)?;
+            entries.insert(vm, key, hash, value)?;
         }
 
         Ok(Self { entries })
     }
 
     pub fn contains_key<K: DictKey + ?Sized>(&self, key: &K, vm: &VirtualMachine) -> bool {
-        self.entries.contains(vm, key).unwrap()
+        let hash = key.key_hash(vm).unwrap();
+        self.entries.contains(vm, key, hash).unwrap()
     }
 
     pub fn size(&self) -> dict_inner::DictSize {
@@ -354,7 +656,8 @@ impl PyDict {
         key: &K,
         vm: &VirtualMachine,
     ) -> PyResult<Option<PyObjectRef>> {
-        self.entries.get(vm, key)
+        let hash = Self::hash_or_unhashable(key, vm)?;
+        self.entries.get(vm, key, hash)
     }
 
     /// Keys of `obj` with their stored hashes, or `None` if it must be iterated
@@ -366,6 +669,8 @@ impl PyDict {
     ) -> Option<Vec<(PyObjectRef, PyHash)>> {
         if let Some(dict) = obj.downcast_ref_if_exact::<Self>(vm) {
             Some(dict.entries.keys_with_hashes())
+        } else if let Some(frozen) = obj.downcast_ref_if_exact::<PyFrozenDict>(vm) {
+            Some(frozen.dict.entries.keys_with_hashes())
         } else {
             set::exact_set_keys_with_hashes(obj, vm)
         }
@@ -383,19 +688,55 @@ struct DictGetArgs {
 #[derive(FromArgs)]
 struct FromKeysArgs {
     #[pyarg(positional)]
-    iterable: ArgIterable,
+    iterable: PyObjectRef,
     #[pyarg(positional, optional)]
     value: Option<PyObjectRef>,
 }
 
 // Python dict methods:
 impl PyDict {
+    pub(crate) fn compare_entries(
+        &self,
+        other: &Self,
+        op: PyComparisonOp,
+        item: bool,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyComparisonValue> {
+        if op == PyComparisonOp::Ne {
+            return Self::compare_entries(self, other, PyComparisonOp::Eq, item, vm)
+                .map(|x| x.map(|eq| !eq));
+        }
+        if !op.eval_ord(self.__len__().cmp(&other.__len__())) {
+            return Ok(PyArithmeticValue::Implemented(false));
+        }
+        let mut position = 0;
+        while let Some((next, k, v1, hash)) = self.entries.next_entry_with_hash(position) {
+            position = next;
+            let found = other.entries.get(vm, &*k, hash)?;
+            match found {
+                Some(v2) => {
+                    if v1.is(&v2) {
+                        continue;
+                    }
+                    if item && !vm.bool_eq(&v1, &v2)? {
+                        return Ok(PyArithmeticValue::Implemented(false));
+                    }
+                }
+                None => {
+                    return Ok(PyArithmeticValue::Implemented(false));
+                }
+            }
+        }
+        Ok(PyArithmeticValue::Implemented(true))
+    }
+
     pub fn __len__(&self) -> usize {
         self.entries.len()
     }
 
     fn __contains__(&self, key: &PyObject, vm: &VirtualMachine) -> PyResult<bool> {
-        self.entries.contains(vm, key)
+        let hash = Self::hash_or_unhashable(key, vm)?;
+        self.entries.contains(vm, key, hash)
     }
 
     fn __delitem__(&self, key: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
@@ -412,18 +753,8 @@ impl PyDict {
         default: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult {
-        self.entries.setdefault(vm, &*key, || default)
-    }
-
-    fn __or__(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        // Accept dict subclasses that inherit this implementation. Subclasses with
-        // their own reflected slot, such as OrderedDict, take precedence in dispatch.
-        if let Ok(other) = other.downcast::<Self>() {
-            let self_cp = self.copy();
-            self_cp.merge_dict(&other, true, vm)?;
-            return Ok(self_cp.into_pyobject(vm));
-        }
-        Ok(vm.ctx.not_implemented())
+        let hash = Self::hash_or_unhashable(&*key, vm)?;
+        self.entries.setdefault(vm, &*key, hash, || default)
     }
 
     pub(crate) fn __sizeof__(&self) -> usize {
@@ -448,7 +779,8 @@ impl PyDict {
             self.merge_object(dict_obj, vm)?;
         }
         for (key, value) in kwargs {
-            self.entries.insert(vm, &key, value)?;
+            let hash = Self::hash_or_unhashable(&key, vm)?;
+            self.entries.insert(vm, &key, hash, value)?;
         }
         Ok(())
     }
@@ -473,90 +805,20 @@ impl PyDict {}
 
 #[pyclass]
 impl Py<PyDict> {
-    pub(crate) fn inner_cmp(
-        &self,
-        other: &Self,
-        op: PyComparisonOp,
-        item: bool,
-        vm: &VirtualMachine,
-    ) -> PyResult<PyComparisonValue> {
-        if op == PyComparisonOp::Ne {
-            return Self::inner_cmp(self, other, PyComparisonOp::Eq, item, vm)
-                .map(|x| x.map(|eq| !eq));
-        }
-        if !op.eval_ord(self.__len__().cmp(&other.__len__())) {
-            return Ok(PyArithmeticValue::Implemented(false));
-        }
-        let (superset, subset) = if self.__len__() < other.__len__() {
-            (other, self)
-        } else {
-            (self, other)
-        };
-        for (k, v1) in subset {
-            match superset.get_item_opt(&*k, vm)? {
-                Some(v2) => {
-                    if v1.is(&v2) {
-                        continue;
-                    }
-                    if item && !vm.bool_eq(&v1, &v2)? {
-                        return Ok(PyArithmeticValue::Implemented(false));
-                    }
-                }
-                None => {
-                    return Ok(PyArithmeticValue::Implemented(false));
-                }
-            }
-        }
-        Ok(PyArithmeticValue::Implemented(true))
-    }
-
     #[cfg_attr(feature = "flame-it", flame("PyDictRef"))]
     #[pymethod(coexist)]
     fn __getitem__(&self, key: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         self.inner_getitem(&*key, vm)
     }
 
-    fn __ror__(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        let other_dict = other.downcast::<PyDict>();
-        if let Ok(other) = other_dict {
-            let other_cp = other.copy();
-            other_cp.merge_dict(self, true, vm)?;
-            return Ok(other_cp.into_pyobject(vm));
-        }
-        Ok(vm.ctx.not_implemented())
-    }
-
     #[pyclassmethod]
     fn fromkeys(class: PyTypeRef, args: FromKeysArgs, vm: &VirtualMachine) -> PyResult {
-        let FromKeysArgs { iterable, value } = args;
-        let value = value.unwrap_or_else(|| vm.ctx.none());
-        let d = PyType::call(&class, ().into(), vm)?;
-        match d.downcast_exact::<PyDict>(vm) {
-            Ok(pydict) => {
-                if let Some(keys) = PyDict::fromkeys_known_hashes(iterable.as_object(), vm) {
-                    if class.is(vm.ctx.types.dict_type) {
-                        pydict.entries.reserve_for_empty(keys.len());
-                    }
-                    for (key, hash) in keys {
-                        pydict
-                            .entries
-                            .insert_known_hash(vm, &*key, hash, value.clone())?;
-                    }
-                } else {
-                    for key in iterable.iter(vm)? {
-                        let key = key?;
-                        pydict.__setitem__(&key, value.clone(), vm)?;
-                    }
-                }
-                Ok(pydict.into_pyref().into())
-            }
-            Err(pyobj) => {
-                for key in iterable.iter(vm)? {
-                    pyobj.set_item(&*key?, value.clone(), vm)?;
-                }
-                Ok(pyobj)
-            }
-        }
+        dict_fromkeys(
+            class,
+            args.iterable,
+            args.value.unwrap_or_else(|| vm.ctx.none()),
+            vm,
+        )
     }
 
     #[pymethod]
@@ -571,10 +833,9 @@ impl Py<PyDict> {
 
     #[pymethod]
     fn get(&self, args: DictGetArgs, vm: &VirtualMachine) -> PyResult {
-        Ok(self
-            .entries
-            .get(vm, &*args.key)?
-            .unwrap_or_else(|| args.default.unwrap_or_else(|| vm.ctx.none())))
+        let hash = PyDict::hash_or_unhashable(&*args.key, vm)?;
+        let found = self.entries.get(vm, &*args.key, hash)?;
+        Ok(found.unwrap_or_else(|| args.default.unwrap_or_else(|| vm.ctx.none())))
     }
 
     #[pymethod(name = "setdefault")]
@@ -606,7 +867,8 @@ impl Py<PyDict> {
         default: OptionalArg<PyObjectRef>,
         vm: &VirtualMachine,
     ) -> PyResult {
-        match self.entries.pop(vm, &*key)? {
+        let hash = PyDict::hash_or_unhashable(&*key, vm)?;
+        match self.entries.pop(vm, &*key, hash)? {
             Some(value) => Ok(value),
             None => default.ok_or_else(|| vm.new_key_error(key)),
         }
@@ -637,23 +899,23 @@ impl Py<PyDict> {
 #[pyclass]
 impl PyRef<PyDict> {
     #[pymethod]
-    const fn keys(self) -> PyDictKeys {
-        PyDictKeys::new(self)
+    fn keys(self) -> PyDictKeys {
+        PyDictKeys::new(self.into())
     }
 
     #[pymethod]
-    const fn values(self) -> PyDictValues {
-        PyDictValues::new(self)
+    fn values(self) -> PyDictValues {
+        PyDictValues::new(self.into())
     }
 
     #[pymethod]
-    const fn items(self) -> PyDictItems {
-        PyDictItems::new(self)
+    fn items(self) -> PyDictItems {
+        PyDictItems::new(self.into())
     }
 
     #[pymethod]
     fn __reversed__(self) -> PyDictReverseKeyIterator {
-        PyDictReverseKeyIterator::new(self)
+        PyDictReverseKeyIterator::new(self.into())
     }
 
     fn __ior__(self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult<Self> {
@@ -699,9 +961,12 @@ impl AsMapping for PyDict {
 impl AsSequence for PyDict {
     fn as_sequence() -> &'static PySequenceMethods {
         static AS_SEQUENCE: LazyLock<PySequenceMethods> = LazyLock::new(|| PySequenceMethods {
-            contains: atomic_func!(|seq, target, vm| PyDict::sequence_downcast(seq)
-                .entries
-                .contains(vm, target)),
+            contains: atomic_func!(|seq, target, vm| {
+                let hash = PyDict::hash_or_unhashable(target, vm)?;
+                PyDict::sequence_downcast(seq)
+                    .entries
+                    .contains(vm, target, hash)
+            }),
             ..PySequenceMethods::NOT_IMPLEMENTED
         });
         &AS_SEQUENCE
@@ -711,13 +976,7 @@ impl AsSequence for PyDict {
 impl AsNumber for PyDict {
     fn as_number() -> &'static PyNumberMethods {
         static AS_NUMBER: PyNumberMethods = PyNumberMethods {
-            or: Some(|a, b, vm| {
-                if let Some(a) = a.downcast_ref::<PyDict>() {
-                    PyDict::__or__(a, b.to_pyobject(vm), vm)
-                } else {
-                    Ok(vm.ctx.not_implemented())
-                }
-            }),
+            or: Some(dict_or),
             inplace_or: Some(|a, b, vm| {
                 if let Some(a) = a.downcast_ref::<PyDict>() {
                     a.to_owned()
@@ -740,16 +999,19 @@ impl Comparable for PyDict {
         op: PyComparisonOp,
         vm: &VirtualMachine,
     ) -> PyResult<PyComparisonValue> {
-        op.eq_only(|| {
-            let other = class_or_notimplemented!(Self, other);
-            zelf.inner_cmp(other, PyComparisonOp::Eq, true, vm)
+        op.eq_only(|| match PyAnyDict::from_object(other) {
+            Some(other) => {
+                zelf.payload
+                    .compare_entries(other.as_dict(), PyComparisonOp::Eq, true, vm)
+            }
+            None => Ok(PyComparisonValue::NotImplemented),
         })
     }
 }
 
 impl Iterable for PyDict {
     fn iter(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult {
-        Ok(PyDictKeyIterator::new(zelf).into_pyobject(vm))
+        Ok(PyDictKeyIterator::new(zelf.into()).into_pyobject(vm))
     }
 }
 
@@ -804,7 +1066,9 @@ impl Py<PyDict> {
         key: &K,
         vm: &VirtualMachine,
     ) -> PyResult<PyObjectRef> {
-        if let Some(value) = self.entries.get(vm, key)? {
+        let hash = PyDict::hash_or_unhashable(key, vm)?;
+        let found = self.entries.get(vm, key, hash)?;
+        if let Some(value) = found {
             Ok(value)
         } else if let Some(value) = self.missing_opt(key, vm)? {
             Ok(value)
@@ -854,7 +1118,7 @@ impl Py<PyDict> {
         hash: crate::common::hash::PyHash,
         vm: &VirtualMachine,
     ) -> PyResult<Option<PyObjectRef>> {
-        self.entries.get_known_hash(vm, key, hash)
+        self.entries.get(vm, key, hash)
     }
 
     pub(crate) fn set_item_known_hash(
@@ -864,7 +1128,7 @@ impl Py<PyDict> {
         value: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        self.entries.insert_known_hash(vm, key, hash, value)
+        self.entries.insert(vm, key, hash, value)
     }
 
     pub(crate) fn del_item_known_hash(
@@ -873,7 +1137,7 @@ impl Py<PyDict> {
         hash: crate::common::hash::PyHash,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        if self.entries.delete_if_exists_known_hash(vm, key, hash)? {
+        if self.entries.delete_if_exists(vm, key, hash)? {
             Ok(())
         } else {
             Err(vm.new_key_error(key.to_owned()))
@@ -886,7 +1150,7 @@ impl Py<PyDict> {
         hash: crate::common::hash::PyHash,
         vm: &VirtualMachine,
     ) -> PyResult<bool> {
-        self.entries.contains_known_hash(vm, key, hash)
+        self.entries.contains(vm, key, hash)
     }
 
     pub fn get_item_opt<K: DictKey + ?Sized>(
@@ -895,7 +1159,8 @@ impl Py<PyDict> {
         vm: &VirtualMachine,
     ) -> PyResult<Option<PyObjectRef>> {
         if self.exact_dict(vm) {
-            self.entries.get(vm, key)
+            let hash = PyDict::hash_or_unhashable(key, vm)?;
+            self.entries.get(vm, key, hash)
             // Match CPython's exact-dict fast path: __missing__ only participates
             // for dict subclasses through the generic mapping lookup path below.
         } else {
@@ -916,7 +1181,8 @@ impl Py<PyDict> {
         vm: &VirtualMachine,
     ) -> PyResult<Option<u16>> {
         if self.exact_dict(vm) {
-            self.entries.hint_for_key(vm, key)
+            let hash = PyDict::hash_or_unhashable(key, vm)?;
+            self.entries.hint_for_key(vm, key, hash)
         } else {
             Ok(None)
         }
@@ -947,12 +1213,25 @@ impl Py<PyDict> {
             if let Some(value) = self.entries.get_hint(vm, key, usize::from(hint))? {
                 return Ok(Some((value, None)));
             }
-            self.entries.get_with_hint(vm, key)
+            let hash = PyDict::hash_or_unhashable(key, vm)?;
+            self.entries.get_with_hint(vm, key, hash)
         } else {
             Ok(self.get_item_opt(key, vm)?.map(|value| (value, None)))
         }
     }
 
+    pub(crate) fn replace_if_identity(
+        &self,
+        name: &Py<PyStr>,
+        expected: &PyObject,
+        replacement: PyObjectRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<bool> {
+        let hash = PyDict::hash_or_unhashable(name, vm)?;
+        self.entries
+            .replace_if(vm, name, hash, replacement, |current| current.is(expected))
+    }
+
     /// Store using a cached entry index hint for the value-replace fast path.
     ///
     /// On a hint miss, returns a refreshed hint for the key (`None` when the
@@ -965,8 +1244,9 @@ impl Py<PyDict> {
         vm: &VirtualMachine,
     ) -> PyResult<Option<u16>> {
         if self.exact_dict(vm) {
+            let hash = PyDict::hash_or_unhashable(key, vm)?;
             self.entries
-                .insert_with_hint(vm, key, usize::from(hint), value)
+                .insert_with_hint(vm, key, hash, usize::from(hint), value)
         } else {
             self.as_object().set_item(key, value, vm)?;
             Ok(None)
@@ -1055,7 +1335,8 @@ impl Py<PyDict> {
         vm: &VirtualMachine,
     ) -> PyResult<Option<PyObjectRef>> {
         if self.exact_dict(vm) {
-            self.entries.remove_if_exists(vm, key)
+            let hash = PyDict::hash_or_unhashable(key, vm)?;
+            self.entries.remove_if_exists(vm, key, hash)
         } else {
             let value = self.as_object().get_item(key, vm)?;
             self.as_object().del_item(key, vm)?;
@@ -1085,6 +1366,17 @@ impl Py<PyDict> {
 }
 
 impl PyExact<PyDict> {
+    pub(crate) fn move_to_end(
+        &self,
+        key: PyObjectRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyObjectRef> {
+        let hash = PyDict::hash_or_unhashable(&*key, vm)?;
+        self.entries
+            .move_to_end(vm, &*key, hash)?
+            .ok_or_else(|| vm.new_key_error(key))
+    }
+
     /// Look up `key` in `self`, falling back to `other`.
     /// Both dicts must be exact `dict` types (enforced by `PyExact`).
     pub(crate) fn get_chain_exact<K: DictKey + ?Sized>(
@@ -1095,7 +1387,294 @@ impl PyExact<PyDict> {
     ) -> PyResult<Option<PyObjectRef>> {
         debug_assert!(self.class().is(vm.ctx.types.dict_type));
         debug_assert!(other.class().is(vm.ctx.types.dict_type));
-        self.entries.get_chain(&other.entries, vm, key)
+        let hash = PyDict::hash_or_unhashable(key, vm)?;
+        self.entries.get_chain(&other.entries, vm, key, hash)
+    }
+}
+
+#[pyclass(module = false, name = "frozendict", traverse = "manual")]
+#[derive(Debug)]
+pub struct PyFrozenDict {
+    // Own the table directly, never a mutable Python dict visible through gc or a view.
+    pub(crate) dict: PyDict,
+    hash: PyAtomic<PyHash>,
+}
+
+unsafe impl Traverse for PyFrozenDict {
+    fn traverse(&self, tracer: &mut TraverseFn<'_>) {
+        self.dict.traverse(tracer);
+    }
+    fn clear(&mut self, out: &mut Vec<PyObjectRef>) {
+        Traverse::clear(&mut self.dict, out);
+    }
+}
+
+impl PyPayload for PyFrozenDict {
+    fn class(ctx: &Context) -> &'static Py<PyType> {
+        ctx.types.frozendict_type
+    }
+}
+
+impl PyFrozenDict {
+    pub(crate) fn from_dict(dict: PyDict) -> Self {
+        Self {
+            dict,
+            hash: Radium::new(hash::SENTINEL),
+        }
+    }
+
+    /// Hash a dictionary key, adding the frozendict context to an exact TypeError.
+    pub fn key_hash<K: DictKey + ?Sized>(key: &K, vm: &VirtualMachine) -> PyResult<PyHash> {
+        key_hash(key, "frozendict", vm)
+    }
+
+    pub fn inner_getitem_opt<K: DictKey + ?Sized>(
+        &self,
+        key: &K,
+        vm: &VirtualMachine,
+    ) -> PyResult<Option<PyObjectRef>> {
+        let hash = Self::key_hash(key, vm)?;
+        self.dict.entries.get(vm, key, hash)
+    }
+}
+
+impl Constructor for PyFrozenDict {
+    type Args = (OptionalArg<PyObjectRef>, KwArgs);
+    fn py_new(
+        _cls: &Py<PyType>,
+        (input, kwargs): Self::Args,
+        vm: &VirtualMachine,
+    ) -> PyResult<Self> {
+        // The table is built before the frozendict is published, as
+        // frozendict_new_untracked keeps it away from the GC.
+        let dict = PyDict::default();
+        if let OptionalArg::Present(input) = input {
+            dict.update_arg(input, true, "frozendict", vm)?;
+        }
+        for (key, value) in kwargs {
+            dict.inner_setitem(&key, value, vm)?;
+        }
+        Ok(Self::from_dict(dict))
+    }
+}
+
+#[pyclass(
+    with(
+        Py,
+        PyRef,
+        Constructor,
+        Hashable,
+        Comparable,
+        Iterable,
+        AsMapping,
+        AsSequence,
+        AsNumber,
+        Representable
+    ),
+    flags(BASETYPE, MAPPING, _MATCH_SELF)
+)]
+impl PyFrozenDict {
+    fn __len__(&self) -> usize {
+        self.dict.__len__()
+    }
+
+    #[pymethod]
+    fn get(
+        zelf: &Py<Self>,
+        key: PyObjectRef,
+        default: OptionalArg<PyObjectRef>,
+        vm: &VirtualMachine,
+    ) -> PyResult {
+        Ok(zelf
+            .inner_getitem_opt(&*key, vm)?
+            .unwrap_or_else(|| default.unwrap_or_else(|| vm.ctx.none())))
+    }
+
+    #[pymethod]
+    fn __sizeof__(zelf: &Py<Self>) -> usize {
+        zelf.dict.__sizeof__() + core::mem::size_of::<PyAtomic<PyHash>>()
+    }
+
+    #[pyclassmethod]
+    fn fromkeys(
+        cls: PyTypeRef,
+        iterable: PyObjectRef,
+        value: OptionalArg<PyObjectRef>,
+        vm: &VirtualMachine,
+    ) -> PyResult {
+        dict_fromkeys(cls, iterable, value.unwrap_or_else(|| vm.ctx.none()), vm)
+    }
+
+    #[pyclassmethod]
+    fn __class_getitem__(
+        cls: PyTypeRef,
+        object: PyObjectRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyGenericAlias> {
+        PyGenericAlias::from_args(cls, object, vm)
+    }
+}
+
+#[pyclass]
+impl Py<PyFrozenDict> {
+    #[pymethod(coexist)]
+    fn __getitem__(&self, key: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        if let Some(value) = self.inner_getitem_opt(&*key, vm)? {
+            return Ok(value);
+        }
+        if !self.class().is(vm.ctx.types.frozendict_type)
+            && let Some(method) =
+                vm.get_method(self.to_owned().into(), identifier!(vm, __missing__))
+        {
+            return method?.call((key,), vm);
+        }
+        Err(vm.new_key_error(key))
+    }
+
+    #[pymethod]
+    fn copy(&self, vm: &VirtualMachine) -> PyResult<PyRef<PyFrozenDict>> {
+        if self.class().is(vm.ctx.types.frozendict_type) {
+            Ok(self.to_owned())
+        } else {
+            let dict = PyDict::default();
+            if !self.dict.is_empty() {
+                dict.update_arg(self.to_owned().into(), true, "frozendict", vm)?;
+            }
+            Ok(PyFrozenDict::from_dict(dict).into_ref(&vm.ctx))
+        }
+    }
+
+    #[pymethod]
+    fn __getnewargs__(&self, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
+        let dict = vm
+            .ctx
+            .types
+            .dict_type
+            .as_object()
+            .call((self.to_owned(),), vm)?;
+        Ok(vm.new_tuple((dict,)))
+    }
+}
+
+#[pyclass]
+impl PyRef<PyFrozenDict> {
+    #[pymethod]
+    fn keys(self) -> PyDictKeys {
+        PyDictKeys::new(self.into())
+    }
+    #[pymethod]
+    fn values(self) -> PyDictValues {
+        PyDictValues::new(self.into())
+    }
+    #[pymethod]
+    fn items(self) -> PyDictItems {
+        PyDictItems::new(self.into())
+    }
+    #[pymethod]
+    fn __reversed__(self) -> PyDictReverseKeyIterator {
+        PyDictReverseKeyIterator::new(self.into())
+    }
+}
+
+impl AsMapping for PyFrozenDict {
+    fn as_mapping() -> &'static PyMappingMethods {
+        static METHODS: PyMappingMethods = PyMappingMethods {
+            length: atomic_func!(|obj, _vm| Ok(PyFrozenDict::mapping_downcast(obj).__len__())),
+            subscript: atomic_func!(
+                |obj, key, vm| PyFrozenDict::mapping_downcast(obj).__getitem__(key.to_owned(), vm)
+            ),
+            ass_subscript: None,
+        };
+        &METHODS
+    }
+}
+impl AsSequence for PyFrozenDict {
+    fn as_sequence() -> &'static PySequenceMethods {
+        static METHODS: LazyLock<PySequenceMethods> = LazyLock::new(|| PySequenceMethods {
+            contains: atomic_func!(|obj, key, vm| Ok(PyFrozenDict::sequence_downcast(obj)
+                .inner_getitem_opt(key, vm)?
+                .is_some())),
+            ..PySequenceMethods::NOT_IMPLEMENTED
+        });
+        &METHODS
+    }
+}
+impl AsNumber for PyFrozenDict {
+    fn as_number() -> &'static PyNumberMethods {
+        static METHODS: PyNumberMethods = PyNumberMethods {
+            or: Some(frozendict_or),
+            ..PyNumberMethods::NOT_IMPLEMENTED
+        };
+        &METHODS
+    }
+}
+impl Iterable for PyFrozenDict {
+    fn iter(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult {
+        Ok(PyDictKeyIterator::new(zelf.into()).into_pyobject(vm))
+    }
+}
+impl Comparable for PyFrozenDict {
+    fn cmp(
+        zelf: &Py<Self>,
+        other: &PyObject,
+        op: PyComparisonOp,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyComparisonValue> {
+        op.eq_only(|| match PyAnyDict::from_object(other) {
+            Some(other) => zelf
+                .dict
+                .compare_entries(other.as_dict(), PyComparisonOp::Eq, true, vm),
+            None => Ok(PyComparisonValue::NotImplemented),
+        })
+    }
+}
+impl Hashable for PyFrozenDict {
+    fn hash(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyHash> {
+        let cached = zelf.hash.load(Ordering::Relaxed);
+        if cached != hash::SENTINEL {
+            return Ok(cached);
+        }
+        let mut hasher = hash::FrozenSetHash::new(zelf.__len__());
+        let mut position = 0;
+        while let Some((next, _key, value, key_hash)) =
+            zelf.dict.entries.next_entry_with_hash(position)
+        {
+            position = next;
+            // next_entry releases the table lock before invoking arbitrary Python __hash__.
+            let pair_hash = hash::hash_tuple([Ok(key_hash), value.hash(vm)])?;
+            hasher.add(pair_hash);
+        }
+        let result = hasher.finish();
+        zelf.hash.store(result, Ordering::Relaxed);
+        Ok(result)
+    }
+}
+impl Representable for PyFrozenDict {
+    fn repr(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyStrRef> {
+        let name = zelf.class().name();
+        if zelf.dict.is_empty() {
+            return Ok(vm.ctx.new_str(format!("{name}()")));
+        }
+        let mut result = Wtf8Buf::from(format!("{name}("));
+        if let Some(_guard) = ReprGuard::enter(vm, zelf.as_object()) {
+            result.push_str("{");
+            for (index, (key, value)) in DictIter::new(&zelf.dict).enumerate() {
+                if index != 0 {
+                    result.push_str(", ");
+                }
+                result.push_wtf8(key.repr(vm)?.as_wtf8());
+                result.push_str(": ");
+                result.push_wtf8(value.repr(vm)?.as_wtf8());
+            }
+            result.push_str("}");
+        } else {
+            result.push_str("{...}");
+        }
+        result.push_str(")");
+        Ok(vm.ctx.new_str(result))
+    }
+    fn repr_str(_zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<String> {
+        unreachable!("use repr instead")
     }
 }
 
@@ -1160,12 +1739,12 @@ impl ExactSizeIterator for DictIntoIter {
 }
 
 pub struct DictIter<'a> {
-    dict: &'a Py<PyDict>,
+    dict: &'a PyDict,
     position: usize,
 }
 
 impl<'a> DictIter<'a> {
-    pub const fn new(dict: &'a Py<PyDict>) -> Self {
+    pub const fn new(dict: &'a PyDict) -> Self {
         DictIter { dict, position: 0 }
     }
 }
@@ -1195,8 +1774,7 @@ impl ExactSizeIterator for DictIter<'_> {
 trait DictView: PyPayload + PyClassDef + Iterable + Representable {
     type ReverseIter: PyPayload + core::fmt::Debug;
 
-    fn dict(&self) -> &Py<PyDict>;
-    fn item(vm: &VirtualMachine, key: PyObjectRef, value: PyObjectRef) -> PyObjectRef;
+    fn dict(&self) -> &PyAnyDict;
 
     fn __len__(&self) -> usize {
         self.dict().__len__()
@@ -1221,14 +1799,14 @@ macro_rules! dict_view {
         $project_fn: expr,
         $result_fn: expr
     ) => {
-        #[pyclass(module = false, name = $class_name, unhashable = $unhashable)]
+        #[pyclass(module = false, name = $class_name, unhashable = $unhashable, traverse)]
         #[derive(Debug)]
         pub(crate) struct $name {
-            pub(crate) dict: PyDictRef,
+            pub(crate) dict: PyRef<PyAnyDict>,
         }
 
         impl $name {
-            pub(crate) const fn new(dict: PyDictRef) -> Self {
+            pub(crate) fn new(dict: PyRef<PyAnyDict>) -> Self {
                 $name { dict }
             }
         }
@@ -1236,14 +1814,10 @@ macro_rules! dict_view {
         impl DictView for $name {
             type ReverseIter = $reverse_iter_name;
 
-            fn dict(&self) -> &Py<PyDict> {
+            fn dict(&self) -> &PyAnyDict {
                 &self.dict
             }
 
-            fn item(vm: &VirtualMachine, key: PyObjectRef, value: PyObjectRef) -> PyObjectRef {
-                $result_fn(vm, $project_fn(&key, &value))
-            }
-
             fn __reversed__(zelf: &Py<Self>) -> Self::ReverseIter {
                 $reverse_iter_name::new(zelf.dict.clone())
             }
@@ -1265,19 +1839,21 @@ macro_rules! dict_view {
             #[inline]
             fn repr(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyStrRef> {
                 let s = if let Some(_guard) = ReprGuard::enter(vm, zelf.as_object()) {
-                    let mut result = Wtf8Buf::from(format!("{}([", Self::NAME));
-                    let mut first = true;
-                    for (key, value) in zelf.dict().clone() {
-                        if !first {
-                            result.push_str(", ");
-                        }
-                        first = false;
-                        result.push_wtf8(Self::item(vm, key, value).repr(vm)?.as_wtf8());
-                    }
-                    result.push_str("])");
+                    // CPython snapshots through the view's actual iterator before
+                    // calling element representations, including for OrderedDict subclasses.
+                    let items = ArgIterable::<PyObjectRef>::try_from_object(
+                        vm,
+                        zelf.as_object().to_owned(),
+                    )?
+                    .iter(vm)?
+                    .collect::<PyResult<Vec<_>>>()?;
+                    let list_repr = vm.ctx.new_list(items).as_object().repr(vm)?;
+                    let mut result = Wtf8Buf::from(format!("{}(", zelf.class().slot_name()));
+                    result.push_wtf8(list_repr.as_wtf8());
+                    result.push_str(")");
                     vm.ctx.new_str(result)
                 } else {
-                    vm.ctx.intern_str("{...}").to_owned()
+                    vm.ctx.intern_str("...").to_owned()
                 };
                 Ok(s)
             }
@@ -1288,16 +1864,18 @@ macro_rules! dict_view {
             }
         }
 
-        #[pyclass(module = false, name = $iter_class_name)]
+        #[pyclass(module = false, name = $iter_class_name, traverse)]
         #[derive(Debug)]
         pub(crate) struct $iter_name {
+            #[pytraverse(skip)]
             pub(crate) size: dict_inner::DictSize,
             /// Whether the dict was found to have changed, which
             /// `dictiter_iternextkey()` records by writing a size no dict can
             /// have. Sticky: what it makes the iterator answer, it answers
             /// from then on.
+            #[pytraverse(skip)]
             changed: PyAtomic<bool>,
-            pub(crate) internal: PyMutex<PositionIterInternal<PyDictRef>>,
+            pub(crate) internal: PyMutex<PositionIterInternal<PyRef<PyAnyDict>>>,
         }
 
         impl PyPayload for $iter_name {
@@ -1308,7 +1886,7 @@ macro_rules! dict_view {
         }
 
         impl $iter_name {
-            fn new(dict: PyDictRef) -> Self {
+            pub(crate) fn new(dict: PyRef<PyAnyDict>) -> Self {
                 $iter_name {
                     size: dict.size(),
                     changed: Radium::new(false),
@@ -1345,7 +1923,7 @@ macro_rules! dict_view {
                         let mut position = internal.position;
                         let mut entries = Vec::new();
                         while let Some((next_position, key, value)) =
-                            dict.entries.next_entry(position)
+                            dict.as_dict().entries.next_entry(position)
                         {
                             entries.push(($result_fn)(vm, ($project_fn)(&key, &value)));
                             position = next_position;
@@ -1374,9 +1952,11 @@ macro_rules! dict_view {
                         // raising.
                         return (Err(mutated()), None);
                     }
-                    let entry =
-                        dict.entries
-                            .next_entry_checked(internal.position, &zelf.size, $project_fn);
+                    let entry = dict.as_dict().entries.next_entry_checked(
+                        internal.position,
+                        &zelf.size,
+                        $project_fn,
+                    );
                     match entry {
                         Err(dict_inner::DictChanged) => {
                             zelf.changed.store(true, Ordering::Relaxed);
@@ -1392,13 +1972,17 @@ macro_rules! dict_view {
             }
         }
 
-        #[pyclass(module = false, name = $reverse_iter_class_name)]
+        #[pyclass(module = false, name = $reverse_iter_class_name, traverse)]
         #[derive(Debug)]
         pub(crate) struct $reverse_iter_name {
+            #[pytraverse(skip)]
             pub(crate) size: dict_inner::DictSize,
             /// As in `$iter_name`.
+            #[pytraverse(skip)]
             changed: PyAtomic<bool>,
-            internal: PyMutex<PositionIterInternal<PyDictRef>>,
+            #[pytraverse(skip)]
+            remaining: PyAtomic<usize>,
+            internal: PyMutex<PositionIterInternal<PyRef<PyAnyDict>>>,
         }
 
         impl PyPayload for $reverse_iter_name {
@@ -1409,10 +1993,12 @@ macro_rules! dict_view {
         }
 
         impl $reverse_iter_name {
-            fn new(dict: PyDictRef) -> Self {
+            pub(crate) fn new(dict: PyRef<PyAnyDict>) -> Self {
                 let size = dict.size();
-                let position = size.entries_size.saturating_sub(1);
+                // usize::MAX represents the position before the first entry.
+                let position = size.entries_size.wrapping_sub(1);
                 $reverse_iter_name {
+                    remaining: Radium::new(size.used),
                     size,
                     changed: Radium::new(false),
                     internal: PyMutex::new(PositionIterInternal::new(dict, position)),
@@ -1431,7 +2017,7 @@ macro_rules! dict_view {
                         let mut position = internal.position;
                         let mut entries = Vec::new();
                         while let Some((found_index, key, value)) =
-                            dict.entries.prev_entry(position)
+                            dict.as_dict().entries.prev_entry(position)
                         {
                             entries.push(($result_fn)(vm, ($project_fn)(&key, &value)));
                             if found_index == 0 {
@@ -1454,8 +2040,10 @@ macro_rules! dict_view {
                 }
                 let internal = self.internal.lock();
                 match &internal.status {
-                    IterStatus::Active(dict) if dict.size() == self.size => {
-                        internal.rev_length_hint(|_| self.size.entries_size)
+                    IterStatus::Active(dict)
+                        if dict.size().has_same_used_and_relocations(&self.size) =>
+                    {
+                        self.remaining.load(Ordering::Relaxed)
                     }
                     _ => 0,
                 }
@@ -1478,22 +2066,24 @@ macro_rules! dict_view {
                         // raising.
                         return (Err(mutated()), None);
                     }
-                    let entry =
-                        dict.entries
-                            .prev_entry_checked(internal.position, &zelf.size, $project_fn);
+                    let entry = dict.as_dict().entries.prev_entry_checked(
+                        internal.position,
+                        &zelf.size,
+                        $project_fn,
+                    );
                     match entry {
                         Err(dict_inner::DictChanged) => {
                             zelf.changed.store(true, Ordering::Relaxed);
                             (Err(mutated()), None)
                         }
                         Ok(Some((found_index, item))) => {
-                            let released = if found_index == 0 {
-                                internal.exhaust()
-                            } else {
-                                internal.position = found_index - 1;
-                                None
-                            };
-                            (Ok(PyIterReturn::Return(($result_fn)(vm, item))), released)
+                            // CPython 3.14 exposes the remaining count as size_t,
+                            // even after same-size key replacement yields extra entries.
+                            let remaining = zelf.remaining.load(Ordering::Relaxed);
+                            zelf.remaining
+                                .store(remaining.wrapping_sub(1), Ordering::Relaxed);
+                            internal.position = found_index.wrapping_sub(1);
+                            (Ok(PyIterReturn::Return(($result_fn)(vm, item))), None)
                         }
                         Ok(None) => (Ok(PyIterReturn::StopIteration(None)), internal.exhaust()),
                     }
@@ -1566,14 +2156,6 @@ trait ViewSetOps: DictView {
         op: PyComparisonOp,
         vm: &VirtualMachine,
     ) -> PyResult<PyComparisonValue> {
-        if let Some(dictview) = other.downcast_ref::<Self>() {
-            return zelf.dict().inner_cmp(
-                dictview.dict(),
-                op,
-                !zelf.class().is(vm.ctx.types.dict_keys_type),
-                vm,
-            );
-        }
         if !is_set_or_dict_view(other) {
             return Ok(PyComparisonValue::NotImplemented);
         }
@@ -1647,7 +2229,7 @@ impl PyDictKeys {
 
     #[pygetset]
     fn mapping(zelf: PyRef<Self>) -> PyMappingProxy {
-        PyMappingProxy::from(zelf.dict().to_owned())
+        PyMappingProxy::from_any_dict(zelf.dict().to_owned())
     }
 }
 
@@ -1667,10 +2249,10 @@ impl AsSequence for PyDictKeys {
         static AS_SEQUENCE: LazyLock<PySequenceMethods> = LazyLock::new(|| PySequenceMethods {
             length: atomic_func!(|seq, _vm| Ok(PyDictKeys::sequence_downcast(seq).__len__())),
             contains: atomic_func!(|seq, target, vm| {
-                PyDictKeys::sequence_downcast(seq)
+                Ok(PyDictKeys::sequence_downcast(seq)
                     .dict
-                    .entries
-                    .contains(vm, target)
+                    .inner_getitem_opt(target, vm)?
+                    .is_some())
             }),
             ..PySequenceMethods::NOT_IMPLEMENTED
         });
@@ -1710,7 +2292,7 @@ impl PyDictItems {
     }
     #[pygetset]
     fn mapping(zelf: PyRef<Self>) -> PyMappingProxy {
-        PyMappingProxy::from(zelf.dict().to_owned())
+        PyMappingProxy::from_any_dict(zelf.dict().to_owned())
     }
 }
 
@@ -1772,7 +2354,7 @@ impl AsNumber for PyDictItems {
 impl PyDictValues {
     #[pygetset]
     fn mapping(zelf: PyRef<Self>) -> PyMappingProxy {
-        PyMappingProxy::from(zelf.dict().to_owned())
+        PyMappingProxy::from_any_dict(zelf.dict().to_owned())
     }
 }
 
@@ -1861,10 +2443,7 @@ pub(crate) fn set_item_view_number_xor(
 }
 
 fn dict_item_view_number_xor(a: &PyObject, b: &PyObject, vm: &VirtualMachine) -> PyResult {
-    let is_native_item_view = |obj: &PyObject| {
-        obj.downcast_ref::<PyDictItems>().is_some()
-            || obj.downcast_ref::<PyOrderedDictItems>().is_some()
-    };
+    let is_native_item_view = |obj: &PyObject| obj.downcast_ref::<PyDictItems>().is_some();
     set_item_view_number_xor(a, b, is_native_item_view(a) && is_native_item_view(b), vm)
 }
 
@@ -1872,6 +2451,107 @@ pub(crate) fn set_inner_number_or(a: &PyObject, b: &PyObject, vm: &VirtualMachin
     set_inner_number_op(a, b, |a, b| a.union(b, vm), vm)
 }
 
+/// `_PyDict_Or`
+fn dict_or(a: &PyObject, b: &PyObject, vm: &VirtualMachine) -> PyResult {
+    let (Some(left), Some(_)) = (PyAnyDict::from_object(a), PyAnyDict::from_object(b)) else {
+        return Ok(vm.ctx.not_implemented());
+    };
+    // anydict_copy_untracked converts any frozendict to an exact frozendict.
+    let frozen = left.is_frozen();
+    let mapping_name = if frozen { "frozendict" } else { "dict" };
+    let dict = PyDict::default();
+    if !left.is_empty() {
+        dict.update_arg(a.to_owned(), true, mapping_name, vm)?;
+    }
+    dict.update_arg(b.to_owned(), true, mapping_name, vm)?;
+    Ok(if frozen {
+        PyFrozenDict::from_dict(dict).into_pyobject(vm)
+    } else {
+        dict.into_pyobject(vm)
+    })
+}
+
+fn frozendict_or(a: &PyObject, b: &PyObject, vm: &VirtualMachine) -> PyResult {
+    if a.class().is(vm.ctx.types.frozendict_type)
+        && let Some(left) = PyAnyDict::from_object(a)
+        && let Some(right) = PyAnyDict::from_object(b)
+    {
+        // frozendict() | frozendict(...) => frozendict(...)
+        if left.is_empty() && b.class().is(vm.ctx.types.frozendict_type) {
+            return Ok(b.to_owned());
+        }
+        // frozendict(...) | frozendict() => frozendict(...)
+        if right.is_empty()
+            && (b.class().is(vm.ctx.types.dict_type) || b.class().is(vm.ctx.types.frozendict_type))
+        {
+            return Ok(a.to_owned());
+        }
+    }
+    dict_or(a, b, vm)
+}
+
+pub(crate) fn dict_fromkeys(
+    class: PyTypeRef,
+    iterable: PyObjectRef,
+    value: PyObjectRef,
+    vm: &VirtualMachine,
+) -> PyResult {
+    let exact_frozen = class.is(vm.ctx.types.frozendict_type);
+    let created = if exact_frozen {
+        None
+    } else {
+        Some(PyType::call(&class, ().into(), vm)?)
+    };
+    let frozen_source = created
+        .as_ref()
+        .and_then(|obj| obj.downcast_ref::<PyFrozenDict>());
+    if exact_frozen || frozen_source.is_some() {
+        let dict = PyDict::default();
+        if let Some(source) = frozen_source {
+            dict.update_arg(source.to_owned().into(), true, "frozendict", vm)?;
+        }
+        let iterable = ArgIterable::<PyObjectRef>::try_from_object(vm, iterable)?;
+        if let Some(keys) = PyDict::fromkeys_known_hashes(iterable.as_object(), vm) {
+            for (key, hash) in keys {
+                dict.entries.insert(vm, &*key, hash, value.clone())?;
+            }
+        } else {
+            for key in iterable.iter(vm)? {
+                let key = key?;
+                let hash = PyFrozenDict::key_hash(&*key, vm)?;
+                dict.entries.insert(vm, &*key, hash, value.clone())?;
+            }
+        }
+        let frozen = PyFrozenDict::from_dict(dict).into_ref(&vm.ctx);
+        return if exact_frozen {
+            Ok(frozen.into())
+        } else {
+            class.as_object().call((frozen,), vm)
+        };
+    }
+    let iterable = ArgIterable::<PyObjectRef>::try_from_object(vm, iterable)?;
+    let created = created.unwrap();
+    if let Some(dict) = created.downcast_ref_if_exact::<PyDict>(vm) {
+        if let Some(keys) = PyDict::fromkeys_known_hashes(iterable.as_object(), vm) {
+            if class.is(vm.ctx.types.dict_type) {
+                dict.entries.reserve_for_empty(keys.len());
+            }
+            for (key, hash) in keys {
+                dict.entries.insert(vm, &*key, hash, value.clone())?;
+            }
+        } else {
+            for key in iterable.iter(vm)? {
+                dict.inner_setitem(&*key?, value.clone(), vm)?;
+            }
+        }
+    } else {
+        for key in iterable.iter(vm)? {
+            created.set_item(&*key?, value.clone(), vm)?;
+        }
+    }
+    Ok(created)
+}
+
 fn vectorcall_dict(
     zelf_obj: &PyObject,
     args: Vec<PyObjectRef>,
@@ -1886,6 +2566,28 @@ fn vectorcall_dict(
     Ok(obj.into())
 }
 
+fn vectorcall_frozendict(
+    zelf: &PyObject,
+    args: Vec<PyObjectRef>,
+    nargs: usize,
+    kwnames: Option<&[PyObjectRef]>,
+    vm: &VirtualMachine,
+) -> PyResult {
+    // frozendict(frozendict) returns the same object unmodified
+    if nargs == 1
+        && kwnames.is_none_or(<[_]>::is_empty)
+        && args[0].class().is(vm.ctx.types.frozendict_type)
+        && zelf.is(vm.ctx.types.frozendict_type)
+    {
+        return Ok(args[0].clone());
+    }
+    PyFrozenDict::slot_new(
+        zelf.downcast_ref::<PyType>().unwrap().to_owned(),
+        FuncArgs::from_vectorcall_owned(args, nargs, kwnames),
+        vm,
+    )
+}
+
 pub(crate) fn init(context: &'static Context) {
     PyDict::extend_class(context, context.types.dict_type);
     context
@@ -1903,4 +2605,86 @@ pub(crate) fn init(context: &'static Context) {
     PyDictItems::extend_class(context, context.types.dict_items_type);
     PyDictItemIterator::extend_class(context, context.types.dict_itemiterator_type);
     PyDictReverseItemIterator::extend_class(context, context.types.dict_reverseitemiterator_type);
+    PyFrozenDict::extend_class(context, context.types.frozendict_type);
+    context
+        .types
+        .frozendict_type
+        .slots
+        .vectorcall
+        .store(Some(vectorcall_frozendict));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn anydict_reference_layout_and_ownership() {
+        static_assertions::assert_not_impl_any!(PyAnyDict: PyPayload);
+        static_assertions::assert_type_eq_all!(
+            <PyAnyDict as crate::object::PyRefTarget>::Target,
+            PyAnyDict
+        );
+        static_assertions::assert_eq_size!(PyRef<PyAnyDict>, PyObjectRef, Option<PyRef<PyAnyDict>>);
+        static_assertions::assert_eq_align!(PyRef<PyAnyDict>, PyObjectRef);
+        static_assertions::assert_eq_size!(PyAnyDict, PyObject);
+        static_assertions::assert_eq_align!(PyAnyDict, PyObject);
+        #[cfg(feature = "threading")]
+        static_assertions::assert_impl_all!(PyRef<PyAnyDict>: Send, Sync);
+        #[cfg(not(feature = "threading"))]
+        static_assertions::assert_not_impl_any!(PyRef<PyAnyDict>: Send, Sync);
+
+        let ctx = Context::genesis();
+        let dict: PyRef<PyAnyDict> = PyDict::default().into_ref(ctx).into();
+        let frozen: PyRef<PyAnyDict> = PyFrozenDict::from_dict(PyDict::default())
+            .into_ref(ctx)
+            .into();
+        for owner in [dict, frozen] {
+            let object = owner.as_object() as *const PyObject;
+            assert_eq!(owner.as_object().strong_count(), 1);
+            let borrowed = PyAnyDict::from_object(owner.as_object()).unwrap();
+            assert!(core::ptr::eq(borrowed.as_object(), object));
+            assert_eq!(owner.as_object().strong_count(), 1);
+            assert_eq!(borrowed.as_mutable().is_none(), borrowed.is_frozen());
+            let copy = borrowed.to_owned();
+            assert_eq!(owner.as_object().strong_count(), 2);
+            let clone = owner.clone();
+            assert_eq!(owner.as_object().strong_count(), 3);
+            let erased = clone.into_object();
+            assert_eq!(erased.strong_count(), 3);
+            assert!(core::ptr::eq(&*erased, object));
+            let mut visited = 0;
+            owner.traverse(&mut |edge| {
+                assert!(core::ptr::eq(edge, object));
+                visited += 1;
+            });
+            assert_eq!(visited, 1);
+            drop(copy);
+            drop(owner);
+            assert_eq!(erased.strong_count(), 1);
+        }
+    }
+
+    #[test]
+    fn anydict_checked_reference_conversion() {
+        crate::Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let dict = PyDict::default().into_pyobject(vm);
+            let frozen = PyFrozenDict::from_dict(PyDict::default()).into_pyobject(vm);
+            for object in [dict, frozen] {
+                let owner = PyRef::<PyAnyDict>::try_from_object(vm, object.clone()).unwrap();
+                assert_eq!(object.strong_count(), 2);
+                assert!(core::ptr::eq(owner.as_object(), &*object));
+                let erased: PyObjectRef = owner.into();
+                assert_eq!(object.strong_count(), 2);
+                assert!(core::ptr::eq(&*erased, &*object));
+                drop(erased);
+                assert_eq!(object.strong_count(), 1);
+            }
+            let unrelated: PyObjectRef = vm.ctx.new_int(1000).into();
+            assert!(PyAnyDict::from_object(&unrelated).is_none());
+            let error = PyRef::<PyAnyDict>::try_from_object(vm, unrelated.clone()).unwrap_err();
+            assert!(error.fast_isinstance(vm.ctx.exceptions.type_error));
+            assert_eq!(unrelated.strong_count(), 1);
+        });
+    }
 }
diff --git a/crates/vm/src/builtins/enumerate.rs b/crates/vm/src/builtins/enumerate.rs
index 76ee3cca2b7..f7a3b8d257d 100644
--- a/crates/vm/src/builtins/enumerate.rs
+++ b/crates/vm/src/builtins/enumerate.rs
@@ -1,11 +1,12 @@
 use super::{
-    IterStatus, PositionIterInternal, PyGenericAlias, PyIntRef, PyTupleRef, PyType, PyTypeRef,
+    IterStatus, PositionIterInternal, PyGenericAlias, PyTupleRef, PyType, PyTypeRef,
     iter::builtins_reversed, locked_rev_next,
 };
 use crate::common::lock::{PyMutex, PyRwLock};
 use crate::{
     AsObject, Context, Py, PyObjectRef, PyPayload, PyResult, VirtualMachine,
     class::PyClassImpl,
+    function::ArgIndex,
     protocol::{PyIter, PyIterReturn},
     raise_if_stop,
     types::{Constructor, IterNext, Iterable, SelfIter},
@@ -56,7 +57,7 @@ pub struct EnumerateArgs {
     #[pyarg(any)]
     iterable: PyIter,
     #[pyarg(any, default = 0)]
-    start: PyIntRef,
+    start: ArgIndex,
 }
 
 impl Constructor for PyEnumerate {
@@ -67,6 +68,7 @@ impl Constructor for PyEnumerate {
         Self::Args { iterable, start }: Self::Args,
         _vm: &VirtualMachine,
     ) -> PyResult<Self> {
+        let start = start.into_int_ref();
         let counter = match start.as_bigint().to_usize() {
             Some(n) => Counter::Small(n),
             None => Counter::Big(start.as_bigint().clone()),
diff --git a/crates/vm/src/builtins/float.rs b/crates/vm/src/builtins/float.rs
index 78d3bef7794..de38a89fae4 100644
--- a/crates/vm/src/builtins/float.rs
+++ b/crates/vm/src/builtins/float.rs
@@ -6,9 +6,11 @@ use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult,
     TryFromBorrowedObject, TryFromObject, VirtualMachine,
     class::{PyClassDef, PyClassImpl},
-    common::{float_ops, format::FormatSpec, hash, wtf8::Wtf8Buf},
-    convert::{IntoPyException, ToPyObject, ToPyResult},
-    function::{ArgBytesLike, FuncArgs, OptionalArg, PyArithmeticValue, PyComparisonValue},
+    common::{float_ops, hash, wtf8::Wtf8Buf},
+    convert::{ToPyObject, ToPyResult},
+    function::{
+        ArgBytesLike, ArgIndex, FuncArgs, OptionalArg, PyArithmeticValue, PyComparisonValue,
+    },
     protocol::PyNumberMethods,
     types::{AsNumber, Callable, Comparable, Constructor, Hashable, PyComparisonOp, Representable},
 };
@@ -273,7 +275,7 @@ pub fn float_from_string(val: &PyObject, vm: &VirtualMachine) -> PyResult<f64> {
 #[derive(FromArgs)]
 struct RoundArgs {
     #[pyarg(positional, optional)]
-    ndigits: Option<PyIntRef>,
+    ndigits: Option<ArgIndex>,
 }
 
 #[pyclass(
@@ -291,17 +293,16 @@ impl Py<PyFloat> {
         if format_spec.is_empty() {
             return Ok(zelf.as_object().str(vm)?.as_wtf8().to_owned());
         }
-        let format_spec =
-            FormatSpec::parse(format_spec.as_str()).map_err(|err| err.into_pyexception(vm))?;
-        let result = if format_spec.has_locale_format() {
+        let spec = crate::format::parse_format_spec(zelf.as_object(), format_spec.as_str(), vm)?;
+        let result = if spec.has_locale_format() {
             let locale = crate::format::get_locale_info();
-            format_spec.format_float_locale(zelf.to_f64(), &locale)
+            spec.format_float_locale(zelf.to_f64(), &locale)
         } else {
-            format_spec.format_float(zelf.to_f64())
+            spec.format_float(zelf.to_f64())
         };
-        result
-            .map(Wtf8Buf::from_string)
-            .map_err(|err| err.into_pyexception(vm))
+        result.map(Wtf8Buf::from_string).map_err(|err| {
+            crate::format::format_spec_error(err, zelf.as_object(), format_spec.as_str(), vm)
+        })
     }
 
     #[pystaticmethod]
@@ -341,7 +342,7 @@ impl Py<PyFloat> {
     fn __round__(&self, args: RoundArgs, vm: &VirtualMachine) -> PyResult {
         let ndigits = args.ndigits;
         let value = if let Some(ndigits) = ndigits {
-            let ndigits = ndigits.as_bigint();
+            let ndigits = ndigits.as_ref().as_bigint();
             let ndigits = match ndigits.to_i32() {
                 Some(n) => n,
                 None if ndigits.is_positive() => i32::MAX,
diff --git a/crates/vm/src/builtins/frame.rs b/crates/vm/src/builtins/frame.rs
index 905cbb582a4..61d173c8b3a 100644
--- a/crates/vm/src/builtins/frame.rs
+++ b/crates/vm/src/builtins/frame.rs
@@ -2,13 +2,13 @@
 
 */
 
-use super::{PyAsyncGen, PyCode, PyCoroutine, PyDictRef, PyGenerator, PyIntRef};
+use super::{PyAnyDict, PyAsyncGen, PyCode, PyCoroutine, PyGenerator, PyIntRef};
 use crate::{
     AsObject, Context, Py, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
     class::PyClassImpl,
     frame::{FrameObject, FrameOwner},
     function::PySetterValue,
-    types::{Destructor, Representable},
+    types::Representable,
 };
 use core::sync::atomic::Ordering::Relaxed;
 use num_traits::Zero;
@@ -242,29 +242,30 @@ pub(crate) mod stack_analysis {
                             }
                         }
                     }
-                    Instruction::GetIter | Instruction::GetAiter => {
+                    Instruction::GetIter { .. } => {
                         next_stack = push_value(pop_value(next_stack), Kind::Iterator as i64);
+                        next_stack = push_value(next_stack, Kind::Iterator as i64);
                         if next_i < stacks.len() {
                             stacks[next_i] = next_stack;
                         }
                     }
-                    Instruction::ForIter { .. } => {
-                        // Fall-through (iteration continues): pushes the next value
-                        let body_stack = push_value(next_stack, Kind::Object as i64);
+                    Instruction::GetAiter => {
+                        next_stack = push_value(pop_value(next_stack), Kind::Iterator as i64);
                         if next_i < stacks.len() {
-                            stacks[next_i] = body_stack;
+                            stacks[next_i] = next_stack;
                         }
-                        // Exhaustion path: relative forward from after_caches
-                        let mut j = next_i + oparg as usize;
-                        if j < instructions.len() {
-                            let target_op =
-                                instructions[j].op.to_base().unwrap_or(instructions[j].op);
-                            if matches!(target_op, Instruction::EndFor) {
-                                j += 1;
-                            }
+                    }
+                    Instruction::ForIter { .. } => {
+                        // Both the body and the END_FOR target start with the
+                        // next value pushed.
+                        let target_stack = push_value(next_stack, Kind::Object as i64);
+                        if next_i < stacks.len() {
+                            stacks[next_i] = target_stack;
                         }
-                        if j < stacks.len() && stacks[j] == UNINITIALIZED {
-                            stacks[j] = next_stack;
+                        let j = next_i + oparg as usize;
+                        if j < stacks.len() {
+                            debug_assert!(stacks[j] == UNINITIALIZED || stacks[j] == target_stack);
+                            stacks[j] = target_stack;
                         }
                     }
                     Instruction::EndAsyncFor => {
@@ -514,19 +515,19 @@ impl Py<FrameObject> {
         );
         match owner {
             FrameOwner::Generator => {
-                // FRAME_SUSPENDED (lasti > 0) cannot be cleared. FRAME_CREATED
-                // and finished frames go through the owner finalizer.
-                if self.lasti() != 0 {
-                    return Err(vm.new_runtime_error("cannot clear a suspended frame"));
-                }
+                // RETURN_GENERATOR executes the creation preamble, so lasti
+                // no longer distinguishes a created frame from a suspended one.
                 if let Some(owner) = self.iframe().generator.to_owned() {
-                    if let Some(coro) = owner.downcast_ref::<PyCoroutine>() {
-                        let _ = PyCoroutine::del(coro, vm);
+                    let coro = if let Some(coro) = owner.downcast_ref::<PyCoroutine>() {
+                        coro.as_coro()
                     } else if let Some(async_gen) = owner.downcast_ref::<PyAsyncGen>() {
-                        let _ = PyAsyncGen::del(async_gen, vm);
+                        async_gen.as_coro()
                     } else if let Some(generator) = owner.downcast_ref::<PyGenerator>() {
-                        let _ = PyGenerator::del(generator, vm);
-                    }
+                        generator.as_coro()
+                    } else {
+                        unreachable!("generator-owned frame has no coroutine owner")
+                    };
+                    coro.clear_frame(&owner, vm)?;
                 }
                 return Ok(());
             }
@@ -630,6 +631,11 @@ impl Py<FrameObject> {
             let mut cur = crate::vm::thread::get_current_frame();
             while !cur.is_null() {
                 if core::ptr::eq(cur, prev) {
+                    // SAFETY: cur was found on this thread's live active chain.
+                    let cur = unsafe { crate::frame::first_complete_iframe(cur) };
+                    if cur.is_null() {
+                        return None;
+                    }
                     let iframe_ref = unsafe { &*cur };
                     let fo = iframe_ref.materialize(vm);
                     return Some(fo.to_owned());
@@ -652,6 +658,11 @@ impl Py<FrameObject> {
             // return and free the stack-allocated iframe at any time.
             vm.state.stop_the_world.stop_the_world(&vm.state);
             scopeguard::defer! { vm.state.stop_the_world.start_the_world(&vm.state); }
+            // SAFETY: the world is stopped, preserving the live chain.
+            let prev = unsafe { crate::frame::first_complete_iframe(prev) };
+            if prev.is_null() {
+                return None;
+            }
             let prev_ref = unsafe { &*prev };
             // Fast path: already materialized.
             if let Some(fo) = prev_ref.frame_obj() {
@@ -659,7 +670,7 @@ impl Py<FrameObject> {
             }
             // Slow path: copy the whole chain, linked through retained_back.
             // SAFETY: the world is stopped, so the owning thread is parked.
-            let fo = unsafe { prev_ref.materialize_detached_chain(vm) };
+            let fo = unsafe { prev_ref.materialize_complete_detached_chain(vm) };
             return Some(fo);
         }
 
@@ -668,7 +679,7 @@ impl Py<FrameObject> {
     }
 
     #[pygetset]
-    pub fn f_globals(&self) -> PyDictRef {
+    pub fn f_globals(&self) -> PyRef<PyAnyDict> {
         self.iframe().globals().to_owned()
     }
 
diff --git a/crates/vm/src/builtins/frame_locals_proxy.rs b/crates/vm/src/builtins/frame_locals_proxy.rs
index cbd21527da3..8cb98d77964 100644
--- a/crates/vm/src/builtins/frame_locals_proxy.rs
+++ b/crates/vm/src/builtins/frame_locals_proxy.rs
@@ -21,6 +21,13 @@ use crate::{
 use rustpython_common::lock::LazyLock;
 use rustpython_common::wtf8::Wtf8Buf;
 
+/// FrameLocalsProxy($frame)
+/// --
+///
+/// Create a write-through view of the locals dictionary for a frame.
+///
+///   frame
+///     the frame object to wrap.
 #[pyclass(
     module = false,
     name = "FrameLocalsProxy",
@@ -145,10 +152,10 @@ impl FrameLocalsProxy {
             return Ok(vm.ctx.not_implemented());
         }
         let result = self.snapshot(vm)?;
-        if other.downcast_ref::<PyDict>().is_some() {
+        if let Some(dict) = other.downcast_ref::<PyDict>() {
             // PyDict_Update reads a dict subclass's stored entries directly;
             // it does not dispatch to overridden mapping methods.
-            result.merge_dict(&other.downcast().unwrap(), true, vm)?;
+            result.merge_dict(dict, true, vm)?;
         } else {
             result.merge_object(other, vm)?;
         }
diff --git a/crates/vm/src/builtins/function.rs b/crates/vm/src/builtins/function.rs
index c6c4aaf2b79..5f59675b9dd 100644
--- a/crates/vm/src/builtins/function.rs
+++ b/crates/vm/src/builtins/function.rs
@@ -2,8 +2,8 @@
 mod jit;
 
 use super::{
-    PyAsyncGen, PyCode, PyCoroutine, PyDictRef, PyGenerator, PyList, PyModule, PyStr, PyStrRef,
-    PyTuple, PyTupleRef, PyType, object,
+    PyAnyDict, PyAsyncGen, PyCode, PyCoroutine, PyDictRef, PyGenerator, PyList, PyModule, PyStr,
+    PyStrRef, PyTuple, PyTupleRef, PyType, object,
 };
 use crate::common::hash::PyHash;
 use crate::common::lock::PyMutex;
@@ -66,7 +66,7 @@ fn format_missing_args(
 pub struct PyFunction {
     pub(crate) code: PyAtomicRef<PyCode>,
     #[pymember(name = "__globals__")]
-    pub(crate) globals: PyDictRef,
+    pub(crate) globals: PyRef<PyAnyDict>,
     #[pymember(name = "__builtins__")]
     pub(crate) builtins: PyObjectRef,
     #[pymember(name = "__closure__")]
@@ -179,15 +179,17 @@ impl PyFunction {
     #[inline]
     pub(crate) fn new(
         code: PyRef<PyCode>,
-        globals: PyDictRef,
+        globals: PyRef<PyAnyDict>,
         vm: &VirtualMachine,
     ) -> PyResult<Self> {
-        let name = PyMutex::new(code.obj_name.to_owned());
-        let module = vm.unwrap_or_none(globals.get_item_opt(identifier!(vm, __name__), vm)?);
-        let builtins = globals.get_item("__builtins__", vm).unwrap_or_else(|_| {
-            // If not in globals, inherit from current execution context
-            crate::frame::current_builtins().unwrap_or_else(|| vm.builtins.dict().into())
-        });
+        let name = PyMutex::new(code.co_name.clone());
+        let module = vm.unwrap_or_none(globals.inner_getitem_opt(identifier!(vm, __name__), vm)?);
+        let builtins = globals
+            .inner_getitem_opt(identifier!(vm, __builtins__), vm)?
+            .unwrap_or_else(|| {
+                // If not in globals, inherit from current execution context.
+                crate::frame::current_builtins().unwrap_or_else(|| vm.builtins.dict().into())
+            });
         // If builtins is a module, use its __dict__ instead
         let builtins = if let Some(module) = builtins.downcast_ref::<PyModule>() {
             module.dict().into()
@@ -205,7 +207,7 @@ impl PyFunction {
             vm.ctx.none()
         };
 
-        let qualname = vm.ctx.new_str(code.qualname.as_str());
+        let qualname = code.co_qualname();
         let func = Self {
             code: PyAtomicRef::from(code),
             globals,
@@ -621,7 +623,7 @@ impl Py<PyFunction> {
             } else if let Some(locals) = locals {
                 Some(locals)
             } else {
-                Some(ArgMapping::from_dict_exact(self.globals.clone()))
+                Some(ArgMapping::from_anydict_exact(self.globals.clone()))
             };
             let use_datastack = !is_gen && !is_coro && !is_async_gen;
             let frame = FrameObject::new_ref(
@@ -635,6 +637,7 @@ impl Py<PyFunction> {
             );
             self.fill_locals_from_args(&frame, func_args, vm)?;
             if is_gen || is_coro || is_async_gen {
+                vm.with_generator_frame(frame.clone(), |f| f.prepare_generator(vm))?;
                 return Ok(self.make_generator_or_coro(frame, vm));
             }
             // Tracing active: use heap frame with full trace support.
@@ -654,7 +657,7 @@ impl Py<PyFunction> {
         } else if let Some(locals) = locals {
             crate::frame::FrameLocals::with_locals(locals)
         } else {
-            crate::frame::FrameLocals::with_locals(crate::function::ArgMapping::from_dict_exact(
+            crate::frame::FrameLocals::with_locals(crate::function::ArgMapping::from_anydict_exact(
                 self.globals.clone(),
             ))
         };
@@ -805,7 +808,7 @@ impl Py<PyFunction> {
         let locals = if code.flags.contains(bytecode::CodeFlags::NEWLOCALS) {
             None
         } else {
-            Some(ArgMapping::from_dict_exact(self.globals.clone()))
+            Some(ArgMapping::from_anydict_exact(self.globals.clone()))
         };
 
         let frame = FrameObject::new_ref(
@@ -842,7 +845,7 @@ impl Py<PyFunction> {
         &self,
         args: impl ExactSizeIterator<Item = PyObjectRef>,
         vm: &VirtualMachine,
-    ) -> PyObjectRef {
+    ) -> PyResult {
         let code: PyRef<PyCode> = (*self.code).to_owned();
 
         debug_assert_eq!(args.len(), code.arg_count as usize);
@@ -862,7 +865,7 @@ impl Py<PyFunction> {
         let locals = if code.flags.contains(bytecode::CodeFlags::NEWLOCALS) {
             None
         } else {
-            Some(ArgMapping::from_dict_exact(self.globals.clone()))
+            Some(ArgMapping::from_anydict_exact(self.globals.clone()))
         };
 
         // Heap-backed: the frame outlives the call that made it.
@@ -884,7 +887,8 @@ impl Py<PyFunction> {
             }
         }
 
-        self.make_generator_or_coro(frame, vm)
+        vm.with_generator_frame(frame.clone(), |f| f.prepare_generator(vm))?;
+        Ok(self.make_generator_or_coro(frame, vm))
     }
 
     pub(crate) fn invoke_prepared_exact_args(
@@ -897,7 +901,7 @@ impl Py<PyFunction> {
         let locals = if code.flags.contains(bytecode::CodeFlags::NEWLOCALS) {
             crate::frame::FrameLocals::lazy()
         } else {
-            crate::frame::FrameLocals::with_locals(ArgMapping::from_dict_exact(
+            crate::frame::FrameLocals::with_locals(ArgMapping::from_anydict_exact(
                 self.globals.clone(),
             ))
         };
@@ -944,7 +948,7 @@ impl Py<PyFunction> {
         // specialization classification, but calling one produces a
         // generator/coroutine object instead of running the frame.
         if self.is_generator_like() {
-            return Ok(self.make_generator_exact_args(args.into_iter(), vm));
+            return self.make_generator_exact_args(args.into_iter(), vm);
         }
         self.invoke_prepared_exact_args(args.into_iter(), vm)
     }
@@ -966,7 +970,7 @@ impl Py<PyFunction> {
         // specialization classification, but calling one produces a
         // generator/coroutine object instead of running the frame.
         if self.is_generator_like() {
-            return Ok(self.make_generator_exact_args(taken, vm));
+            return self.make_generator_exact_args(taken, vm);
         }
         self.invoke_prepared_exact_args(taken, vm)
     }
@@ -1091,24 +1095,28 @@ impl Py<PyFunction> {
         // Release locks before calling __annotate__ to avoid deadlock
         if let Some(annotate_fn) = annotate_fn {
             let one = vm.ctx.new_int(1);
-            let ann_dict = annotate_fn.call((one,), vm)?;
-            let ann_dict = ann_dict
-                .downcast::<crate::builtins::PyDict>()
-                .map_err(|obj| {
-                    vm.new_type_error(format!(
-                        "__annotate__ returned non-dict of type '{}'",
-                        obj.class().name()
-                    ))
-                })?;
+            let result = annotate_fn.call((one,), vm);
+            drop(annotate_fn);
+            let ann_dict = match result?.downcast::<crate::builtins::PyDict>() {
+                Ok(dict) => dict,
+                Err(obj) => {
+                    return Err(vm.new_type_error(format!(
+                        "__annotate__() must return a dict, not {}",
+                        obj.class().fully_qualified_name(vm)?
+                    )));
+                }
+            };
 
             // Cache the result
-            *self.annotations.lock() = Some(ann_dict.clone());
+            let old_annotations = self.annotations.lock().replace(ann_dict.clone());
+            drop(old_annotations);
             return Ok(ann_dict);
         }
 
         // No __annotate__ or not callable, create empty dict
         let new_dict = vm.ctx.new_dict();
-        *self.annotations.lock() = Some(new_dict.clone());
+        let old_annotations = self.annotations.lock().replace(new_dict.clone());
+        drop(old_annotations);
         Ok(new_dict)
     }
 
@@ -1118,23 +1126,19 @@ impl Py<PyFunction> {
         value: PySetterValue<Option<PyObjectRef>>,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        match value {
+        let annotations = match value {
             PySetterValue::Assign(Some(value)) => {
                 let annotations = value.downcast::<crate::builtins::PyDict>().map_err(|_| {
                     vm.new_type_error("__annotations__ must be set to a dict object")
                 })?;
-                *self.annotations.lock() = Some(annotations);
-                *self.annotate.lock() = None;
-            }
-            PySetterValue::Assign(None) => {
-                *self.annotations.lock() = None;
-                *self.annotate.lock() = None;
+                Some(annotations)
             }
-            PySetterValue::Delete => {
-                // del only clears cached annotations; __annotate__ is preserved
-                *self.annotations.lock() = None;
-            }
-        }
+            PySetterValue::Assign(None) | PySetterValue::Delete => None,
+        };
+        let old_annotations = core::mem::replace(&mut *self.annotations.lock(), annotations);
+        drop(old_annotations);
+        let old_annotate = self.annotate.lock().take();
+        drop(old_annotate);
         Ok(())
     }
 
@@ -1167,8 +1171,6 @@ impl Py<PyFunction> {
                 if !value.is_callable() {
                     return Err(vm.new_type_error("__annotate__ must be callable or None"));
                 }
-                // Clear cached __annotations__ when __annotate__ is set
-                *self.annotations.lock() = None;
                 Some(value)
             }
             PySetterValue::Assign(None) => None,
@@ -1176,7 +1178,13 @@ impl Py<PyFunction> {
                 return Err(vm.new_type_error("__annotate__ cannot be deleted"));
             }
         };
-        *self.annotate.lock() = annotate;
+        let clear_annotations = annotate.is_some();
+        let old_annotate = core::mem::replace(&mut *self.annotate.lock(), annotate);
+        drop(old_annotate);
+        if clear_annotations {
+            let old_annotations = self.annotations.lock().take();
+            drop(old_annotations);
+        }
         Ok(())
     }
 
@@ -1284,7 +1292,7 @@ pub struct PyFunctionNewArgs {
     #[pyarg(positional)]
     globals: PyDictRef,
     #[pyarg(any, optional, error_msg = "arg 3 (name) must be None or string")]
-    name: OptionalArg<PyStrRef>,
+    name: Option<PyStrRef>,
     #[pyarg(any, optional, error_msg = "arg 4 (defaults) must be None or tuple")]
     argdefs: Option<PyTupleRef>,
     #[pyarg(any, optional, error_msg = "arg 5 (closure) must be None or tuple")]
@@ -1318,12 +1326,10 @@ impl Constructor for PyFunction {
             None
         };
 
-        let mut func = Self::new(args.code.clone(), args.globals.clone(), vm)?;
+        let mut func = Self::new(args.code.clone(), args.globals.clone().into(), vm)?;
         // Set function name if provided
-        if let Some(name) = args.name.into_option() {
-            *func.name.lock() = name.clone();
-            // Also update qualname to match the name
-            *func.qualname.lock() = name;
+        if let Some(name) = args.name {
+            *func.name.lock() = name;
         }
         // Now set additional attributes directly
         if let Some(closure_tuple) = closure {
@@ -1472,9 +1478,9 @@ impl Py<PyBoundMethod> {
         &self,
         vm: &VirtualMachine,
     ) -> PyResult<(PyObjectRef, (PyObjectRef, PyObjectRef))> {
-        let builtins_getattr = vm.builtins.get_attr("getattr", vm)?;
-        let func_self = self.object.clone();
         let func_name = self.function.get_attr("__name__", vm)?;
+        let builtins_getattr = vm.eval_get_builtin(vm.ctx.intern_str("getattr"))?;
+        let func_self = self.object.clone();
         Ok((builtins_getattr, (func_self, func_name)))
     }
 
@@ -1779,7 +1785,7 @@ pub(crate) fn vectorcall_function(
         // is called in, and a fresh `MAKE_FUNCTION` each time keeps those out
         // of the call-site specialization that would otherwise catch it.
         args.truncate(nargs);
-        return Ok(zelf.make_generator_exact_args(args.into_iter(), vm));
+        return zelf.make_generator_exact_args(args.into_iter(), vm);
     }
 
     if !has_kwargs && base_simple && nargs == code.arg_count as usize {
diff --git a/crates/vm/src/builtins/generator.rs b/crates/vm/src/builtins/generator.rs
index 8eb6013e703..5e1b5dc484c 100644
--- a/crates/vm/src/builtins/generator.rs
+++ b/crates/vm/src/builtins/generator.rs
@@ -122,6 +122,19 @@ impl Py<PyGenerator> {
         self.inner.running()
     }
 
+    #[pygetset]
+    fn gi_state(&self) -> &'static str {
+        if self.inner.closed() {
+            "GEN_CLOSED"
+        } else if self.inner.running() {
+            "GEN_RUNNING"
+        } else if self.inner.started() {
+            "GEN_SUSPENDED"
+        } else {
+            "GEN_CREATED"
+        }
+    }
+
     #[pygetset]
     fn gi_code(&self, _vm: &VirtualMachine) -> PyRef<PyCode> {
         self.inner.code()
diff --git a/crates/vm/src/builtins/genericalias.rs b/crates/vm/src/builtins/genericalias.rs
index 31e1b4ef1c7..5afa70dc142 100644
--- a/crates/vm/src/builtins/genericalias.rs
+++ b/crates/vm/src/builtins/genericalias.rs
@@ -1,5 +1,5 @@
 // spell-checker:ignore iparam gaiterobject
-use crate::common::lock::LazyLock;
+use crate::common::lock::{LazyLock, PyMutex};
 
 use super::type_;
 use crate::{
@@ -40,7 +40,7 @@ pub struct PyGenericAlias {
     origin: PyObjectRef,
     #[pymember(name = "__args__")]
     args: PyTupleRef,
-    parameters: PyTupleRef,
+    parameters: PyMutex<Option<PyTupleRef>>,
     #[pymember(name = "__unpacked__")]
     starred: bool, // for __unpacked__ attribute
 }
@@ -105,13 +105,12 @@ impl PyGenericAlias {
         origin: impl Into<PyObjectRef>,
         args: PyTupleRef,
         starred: bool,
-        vm: &VirtualMachine,
+        _vm: &VirtualMachine,
     ) -> PyResult<Self> {
-        let parameters = make_parameters(&args, vm)?;
         Ok(Self {
             origin: origin.into(),
             args,
-            parameters,
+            parameters: PyMutex::new(None),
             starred,
         })
     }
@@ -130,6 +129,10 @@ impl PyGenericAlias {
         Self::new(origin, args, false, vm)
     }
 
+    fn parameters(&self, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
+        cached_parameters(&self.parameters, &self.args, vm)
+    }
+
     fn repr(&self, vm: &VirtualMachine) -> PyResult<String> {
         fn repr_item(obj: &PyObject, vm: &VirtualMachine) -> PyResult<String> {
             if obj.is(&vm.ctx.ellipsis) {
@@ -206,7 +209,8 @@ impl PyGenericAlias {
     }
 
     fn __getitem__(zelf: &Py<Self>, needle: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        let new_args = subs_parameters(zelf.as_object(), &zelf.args, &zelf.parameters, needle, vm)?;
+        let parameters = zelf.parameters(vm)?;
+        let new_args = subs_parameters(zelf.as_object(), &zelf.args, &parameters, needle, vm)?;
 
         Ok(Self::new(zelf.origin.clone(), new_args, false, vm)?.into_pyobject(vm))
     }
@@ -236,8 +240,8 @@ impl PyGenericAlias {
 )]
 impl Py<PyGenericAlias> {
     #[pygetset]
-    fn __parameters__(&self) -> PyObjectRef {
-        self.parameters.clone().into()
+    fn __parameters__(&self, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
+        self.parameters(vm)
     }
 
     #[pygetset]
@@ -312,11 +316,36 @@ impl Py<PyGenericAlias> {
     }
 }
 
+pub(crate) fn cached_parameters(
+    cache: &PyMutex<Option<PyTupleRef>>,
+    args: &Py<PyTuple>,
+    vm: &VirtualMachine,
+) -> PyResult<PyTupleRef> {
+    let cached = cache.lock().clone();
+    if let Some(parameters) = cached {
+        return Ok(parameters);
+    }
+    // Attribute lookup can re-enter this alias or union. Compute without the
+    // lock, then replace even a cache populated by the re-entrant lookup.
+    let parameters = make_parameters(args, vm);
+    let previous = core::mem::replace(&mut *cache.lock(), parameters.as_ref().ok().cloned());
+    // A failed outer lookup clears the cache populated by a nested lookup too.
+    // Cached parameters can own objects with Python finalizers.
+    drop(previous);
+    parameters
+}
+
 pub(crate) fn make_parameters(args: &Py<PyTuple>, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
     make_parameters_from_slice(args.as_slice(), vm)
 }
 
 fn make_parameters_from_slice(args: &[PyObjectRef], vm: &VirtualMachine) -> PyResult<PyTupleRef> {
+    vm.with_recursion(" in __parameter__ calculation", || {
+        make_parameters_inner(args, vm)
+    })
+}
+
+fn make_parameters_inner(args: &[PyObjectRef], vm: &VirtualMachine) -> PyResult<PyTupleRef> {
     let mut parameters: Vec<PyObjectRef> = Vec::with_capacity(args.len());
 
     for arg in args {
@@ -326,16 +355,21 @@ fn make_parameters_from_slice(args: &[PyObjectRef], vm: &VirtualMachine) -> PyRe
         }
 
         // Check for __typing_subst__ attribute
-        if arg.get_attr(identifier!(vm, __typing_subst__), vm).is_ok() {
+        if vm
+            .get_attribute_opt(arg, identifier!(vm, __typing_subst__))?
+            .is_some()
+        {
             if tuple_index(&parameters, arg).is_none() {
                 parameters.push(arg.clone());
             }
-        } else if let Ok(subparams) = arg.get_attr(identifier!(vm, __parameters__), vm)
-            && let Ok(sub_params) = subparams.try_to_ref::<PyTuple>(vm)
+        } else if let Some(subparams) =
+            vm.get_attribute_opt(arg, identifier!(vm, __parameters__))?
         {
-            for sub_param in sub_params {
-                if tuple_index(&parameters, sub_param).is_none() {
-                    parameters.push(sub_param.clone());
+            if let Some(sub_params) = subparams.downcast_ref::<PyTuple>() {
+                for sub_param in sub_params {
+                    if tuple_index(&parameters, sub_param).is_none() {
+                        parameters.push(sub_param.clone());
+                    }
                 }
             }
         } else if arg.try_to_ref::<PyTuple>(vm).is_ok() || arg.try_to_ref::<PyList>(vm).is_ok() {
@@ -346,9 +380,7 @@ fn make_parameters_from_slice(args: &[PyObjectRef], vm: &VirtualMachine) -> PyRe
                 let list = arg.downcast_ref::<PyList>().unwrap();
                 list.borrow_vec().to_vec()
             };
-            let sub = vm.with_recursion("while computing __parameters__", || {
-                make_parameters_from_slice(&items, vm)
-            })?;
+            let sub = make_parameters_from_slice(&items, vm)?;
             for sub_param in sub.as_slice() {
                 if tuple_index(&parameters, sub_param).is_none() {
                     parameters.push(sub_param.clone());
@@ -558,7 +590,10 @@ pub(crate) fn subs_parameters(
             if let Some(iparam) = tuple_index(parameters.as_slice(), arg) {
                 subst.call((arg_items[iparam].clone(),), vm)?
             } else {
-                subs_tvars(arg.clone(), parameters, &arg_items, vm)?
+                return Err(vm.new_type_error(format!(
+                    "argument {} with __typing_subst__ was not found in __parameters__",
+                    arg.repr(vm)?
+                )));
             }
         } else {
             subs_tvars(arg.clone(), parameters, &arg_items, vm)?
diff --git a/crates/vm/src/builtins/int.rs b/crates/vm/src/builtins/int.rs
index d6799474582..0096fced15a 100644
--- a/crates/vm/src/builtins/int.rs
+++ b/crates/vm/src/builtins/int.rs
@@ -6,15 +6,14 @@ use crate::{
     byte::bytes_from_object,
     class::{PyClassDef, PyClassImpl},
     common::{
-        format::FormatSpec,
         hash,
         int::{bigint_to_finite_float, bytes_to_int, true_div},
         wtf8::Wtf8Buf,
     },
-    convert::{IntoPyException, ToPyObject, ToPyResult},
+    convert::{ToPyObject, ToPyResult},
     function::{
-        ArgByteOrder, ArgIntoBool, FuncArgs, OptionalArg, PyArithmeticValue, PyComparisonValue,
-        PySsize,
+        ArgByteOrder, ArgIndex, ArgIntoBool, FuncArgs, OptionalArg, PyArithmeticValue,
+        PyComparisonValue, PySsize,
     },
     protocol::{PyNumberMethods, handle_bytes_to_int_err, numeric_literal_from_str},
     types::{AsNumber, Comparable, Constructor, Hashable, PyComparisonOp, Representable},
@@ -527,7 +526,7 @@ impl Py<PyInt> {
 #[derive(FromArgs)]
 struct RoundArgs {
     #[pyarg(positional, optional)]
-    ndigits: Option<PyIntRef>,
+    ndigits: Option<ArgIndex>,
 }
 
 #[pyclass(
@@ -539,7 +538,7 @@ impl Py<PyInt> {
     #[pymethod]
     fn __round__(zelf: PyRef<PyInt>, args: RoundArgs, vm: &VirtualMachine) -> PyRef<PyInt> {
         if let Some(ndigits) = args.ndigits {
-            let ndigits = ndigits.as_bigint();
+            let ndigits = ndigits.as_ref().as_bigint();
             // round(12345, -2) == 12300
             // If precision >= 0, then any integer is already rounded correctly
             if let Some(ndigits) = ndigits.neg().to_u32()
@@ -601,20 +600,19 @@ impl Py<PyInt> {
         if format_spec.is_empty() && !zelf.class().is(vm.ctx.types.int_type) {
             return Ok(zelf.as_object().str(vm)?.as_wtf8().to_owned());
         }
-        let format_spec =
-            FormatSpec::parse(format_spec.as_str()).map_err(|err| err.into_pyexception(vm))?;
-        if format_spec.is_decimal_int_format() {
+        let spec = crate::format::parse_format_spec(zelf.as_object(), format_spec.as_str(), vm)?;
+        if spec.is_decimal_int_format() {
             check_int_to_str_digits(zelf.as_bigint(), vm)?;
         }
-        let result = if format_spec.has_locale_format() {
+        let result = if spec.has_locale_format() {
             let locale = crate::format::get_locale_info();
-            format_spec.format_int_locale(zelf.as_bigint(), &locale)
+            spec.format_int_locale(zelf.as_bigint(), &locale)
         } else {
-            format_spec.format_int(zelf.as_bigint())
+            spec.format_int(zelf.as_bigint())
         };
-        result
-            .map(Wtf8Buf::from_string)
-            .map_err(|err| err.into_pyexception(vm))
+        result.map(Wtf8Buf::from_string).map_err(|err| {
+            crate::format::format_spec_error(err, zelf.as_object(), format_spec.as_str(), vm)
+        })
     }
 
     #[pymethod]
diff --git a/crates/vm/src/builtins/interpolation.rs b/crates/vm/src/builtins/interpolation.rs
index 73126102ea9..78505631563 100644
--- a/crates/vm/src/builtins/interpolation.rs
+++ b/crates/vm/src/builtins/interpolation.rs
@@ -19,7 +19,7 @@ pub struct PyInterpolation {
     #[pymember(type = "object_ex")]
     pub value: PyObjectRef,
     #[pymember(type = "object_ex")]
-    pub expression: PyStrRef,
+    pub expression: PyObjectRef,
     #[pymember(type = "object_ex")]
     pub conversion: PyObjectRef, // None or 's', 'r', 'a'
     #[pymember(type = "object_ex")]
@@ -36,7 +36,7 @@ impl PyPayload for PyInterpolation {
 impl PyInterpolation {
     pub fn new(
         value: PyObjectRef,
-        expression: PyStrRef,
+        expression: PyObjectRef,
         conversion: PyObjectRef,
         format_spec: PyStrRef,
         vm: &VirtualMachine,
@@ -80,7 +80,7 @@ impl Constructor for PyInterpolation {
             vm.ctx.none()
         };
 
-        let expression = args.expression;
+        let expression = args.expression.into();
         let format_spec = args.format_spec;
 
         Ok(Self {
@@ -188,7 +188,7 @@ impl Representable for PyInterpolation {
         let mut result = Wtf8Buf::from("Interpolation(");
         result.push_wtf8(value_repr.as_wtf8());
         result.push_str(", ");
-        result.push_str(&expr_repr);
+        result.push_wtf8(expr_repr.as_wtf8());
         result.push_str(", ");
         if vm.is_none(&zelf.conversion) {
             result.push_str("None");
diff --git a/crates/vm/src/builtins/iter.rs b/crates/vm/src/builtins/iter.rs
index 85f40c25977..c3eca4dc7f2 100644
--- a/crates/vm/src/builtins/iter.rs
+++ b/crates/vm/src/builtins/iter.rs
@@ -250,7 +250,7 @@ impl PySequenceIterator {
 impl Py<PySequenceIterator> {
     #[pymethod]
     fn __length_hint__(&self, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
-        vm.with_recursion("in __length_hint__", || {
+        vm.with_recursion(" in __length_hint__", || {
             let (obj, position) = {
                 let internal = self.internal.lock();
                 match &internal.status {
diff --git a/crates/vm/src/builtins/list.rs b/crates/vm/src/builtins/list.rs
index d6a2c1669a7..dbd40b69c76 100644
--- a/crates/vm/src/builtins/list.rs
+++ b/crates/vm/src/builtins/list.rs
@@ -17,7 +17,7 @@ use crate::{
     protocol::{PyIterReturn, PyMappingMethods, PySequenceMethods},
     recursion::ReprGuard,
     sequence::{MutObjectSequenceOp, OptionalRangeArgs, SequenceExt, SequenceMutExt},
-    sliceable::{SaturatedSlice, SequenceIndex, SliceableSequenceOp},
+    sliceable::{NameList, SaturatedSlice, SequenceIndex, SliceableSequenceOp},
     sorting::timsort,
     types::{
         AsMapping, AsSequence, Comparable, Constructor, Initializer, IterNext, Iterable,
@@ -264,7 +264,7 @@ impl PyList {
     }
 
     fn _getitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
-        match SequenceIndex::try_from_borrowed_object(vm, needle, "list")? {
+        match SequenceIndex::try_from_borrowed_object::<NameList>(vm, needle)? {
             SequenceIndex::Int(i) => {
                 let vec = self.borrow_vec();
                 let pos = vec
@@ -363,7 +363,7 @@ impl PyList {
     }
 
     fn _setitem(&self, needle: &PyObject, value: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
-        match SequenceIndex::try_from_borrowed_object(vm, needle, "list")? {
+        match SequenceIndex::try_from_borrowed_object::<NameList>(vm, needle)? {
             SequenceIndex::Int(index) => self.assign_item(index, Some(value), vm),
             SequenceIndex::Slice(slice) => {
                 let items = extract_cloned(&value, self, vm)?;
@@ -396,7 +396,7 @@ impl PyList {
     }
 
     fn _delitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
-        match SequenceIndex::try_from_borrowed_object(vm, needle, "list")? {
+        match SequenceIndex::try_from_borrowed_object::<NameList>(vm, needle)? {
             SequenceIndex::Int(i) => self.assign_item(i, None, vm),
             SequenceIndex::Slice(slice) => self.assign_slice(slice, None, vm),
         }
diff --git a/crates/vm/src/builtins/mappingproxy.rs b/crates/vm/src/builtins/mappingproxy.rs
index 9ee9ff17228..168bdebed5e 100644
--- a/crates/vm/src/builtins/mappingproxy.rs
+++ b/crates/vm/src/builtins/mappingproxy.rs
@@ -2,15 +2,16 @@ use super::{PyDict, PyDictRef, PyGenericAlias, PyList, PyTuple, PyType, PyTypeRe
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
     atomic_func,
-    class::PyClassImpl,
+    class::{PyClassImpl, StaticType},
     common::{hash, lock::LazyLock},
     convert::ToPyObject,
-    function::{ArgMapping, OptionalArg, PyArithmeticValue, PyComparisonValue},
+    function::{ArgMapping, Either, OptionalArg, PyComparisonValue},
     object::{Traverse, TraverseFn},
     protocol::{PyMappingMethods, PyNumberMethods, PySequenceMethods},
+    stdlib::PyOrderedDict,
     types::{
-        AsMapping, AsNumber, AsSequence, Comparable, Constructor, Hashable, Iterable,
-        PyComparisonOp, Representable,
+        AsMapping, AsNumber, AsSequence, Constructor, Hashable, Iterable, PyComparisonOp,
+        Representable,
     },
 };
 use rustpython_common::wtf8::{Wtf8Buf, wtf8_concat};
@@ -68,6 +69,12 @@ impl Constructor for PyMappingProxy {
 }
 
 impl PyMappingProxy {
+    pub(crate) fn from_any_dict(dict: PyRef<super::PyAnyDict>) -> Self {
+        Self {
+            mapping: MappingProxyInner::Mapping(ArgMapping::new(dict.into())),
+        }
+    }
+
     pub fn from_object(mapping: PyObjectRef, vm: &VirtualMachine) -> PyResult<Self> {
         if mapping.mapping_unchecked().check()
             && !mapping.downcastable::<PyList>()
@@ -175,12 +182,48 @@ impl PyMappingProxy {
     Iterable,
     Constructor,
     AsSequence,
-    Comparable,
     Hashable,
     AsNumber,
     Representable
 ))]
 impl Py<PyMappingProxy> {
+    #[pyslot]
+    fn slot_richcompare(
+        zelf: &PyObject,
+        other: &PyObject,
+        op: PyComparisonOp,
+        vm: &VirtualMachine,
+    ) -> PyResult<Either<PyObjectRef, PyComparisonValue>> {
+        let zelf = zelf.downcast_ref::<PyMappingProxy>().ok_or_else(|| {
+            vm.new_type_error(format!(
+                "unexpected payload for {}",
+                op.method_name(&vm.ctx).as_str()
+            ))
+        })?;
+        if !matches!(op, PyComparisonOp::Eq | PyComparisonOp::Ne) {
+            return Ok(Either::B(PyComparisonValue::NotImplemented));
+        }
+        let mut obj = zelf.to_object(vm)?;
+        // Unknown comparison methods must not receive a mutable dictionary
+        // protected by the proxy. Class namespaces are already copied by
+        // to_object; other exact dicts need the same protection here.
+        if matches!(&zelf.mapping, MappingProxyInner::Mapping(_))
+            && obj.class().is(vm.ctx.types.dict_type)
+            && !(other.class().is(vm.ctx.types.dict_type)
+                || other.class().is(vm.ctx.types.frozendict_type)
+                || other.class().is(vm.ctx.types.mappingproxy_type)
+                || (other.downcastable::<PyOrderedDict>()
+                    && other.class().is(PyOrderedDict::static_type())))
+        {
+            obj = obj
+                .downcast_ref::<PyDict>()
+                .unwrap()
+                .copy()
+                .into_pyobject(vm);
+        }
+        obj.rich_compare(other.to_owned(), op, vm).map(Either::A)
+    }
+
     #[pymethod]
     fn get(
         &self,
@@ -238,23 +281,6 @@ impl Py<PyMappingProxy> {
     }
 }
 
-impl Comparable for PyMappingProxy {
-    fn cmp(
-        zelf: &Py<Self>,
-        other: &PyObject,
-        op: PyComparisonOp,
-        vm: &VirtualMachine,
-    ) -> PyResult<PyComparisonValue> {
-        let obj = zelf.to_object(vm)?;
-        // CPython parity (Objects/descrobject.c::mappingproxy_richcompare):
-        // delegate to PyObject_RichCompare on the underlying mapping.
-        let res = obj.rich_compare(other.to_owned(), op, vm)?;
-        PyArithmeticValue::from_object(vm, res)
-            .map(|o| o.try_to_bool(vm))
-            .transpose()
-    }
-}
-
 impl Hashable for PyMappingProxy {
     #[inline]
     fn hash(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<hash::PyHash> {
diff --git a/crates/vm/src/builtins/memory.rs b/crates/vm/src/builtins/memory.rs
index 2c9e8c62809..24edde5e4b2 100644
--- a/crates/vm/src/builtins/memory.rs
+++ b/crates/vm/src/builtins/memory.rs
@@ -301,7 +301,7 @@ impl PyMemoryView {
                 vm.new_not_implemented_error("multi-dimensional sub-views are not implemented")
             );
         }
-        let (shape, _, _) = self.desc.dim_desc[0];
+        let shape = self.desc.shape()[0] as usize;
         // ptr_from_index
         let index = i
             .wrapped_at(shape)
@@ -327,7 +327,7 @@ impl PyMemoryView {
         if self.desc.ndim() != 1 {
             return Err(vm.new_not_implemented_error("sub-views are not implemented"));
         }
-        let (shape, _, _) = self.desc.dim_desc[0];
+        let shape = self.desc.shape()[0] as usize;
         // ptr_from_index
         let index = i
             .wrapped_at(shape)
@@ -412,7 +412,7 @@ impl PyMemoryView {
     }
 
     fn init_len(&mut self) {
-        let product: usize = self.desc.dim_desc.iter().map(|x| x.0).product();
+        let product: usize = self.desc.shape().iter().map(|&x| x as usize).product();
         self.desc.len = product * self.desc.itemsize;
     }
 
@@ -420,34 +420,36 @@ impl PyMemoryView {
     /// outside `dim` is reached through a pointer, in which case its suboffset
     /// does.
     fn adjust_position(&mut self, dim: usize, delta: isize) {
-        match self.desc.dim_desc[..dim]
+        match self.desc.suboffsets()[..dim]
             .iter()
-            .rposition(|&(_, _, suboffset)| suboffset != 0)
+            .rposition(|&suboffset| suboffset != -1)
         {
-            Some(n) => self.desc.dim_desc[n].2 += delta,
+            Some(n) => self.desc.suboffsets_mut()[n] += delta,
             None => self.desc.offset += delta,
         }
     }
 
     fn init_range(&mut self, range: Range<usize>, dim: usize) {
-        let (shape, stride, _) = self.desc.dim_desc[dim];
+        let shape = self.desc.shape()[dim] as usize;
+        let stride = self.desc.strides()[dim];
         debug_assert!(shape >= range.len());
 
         self.adjust_position(dim, stride * range.start as isize);
-        self.desc.dim_desc[dim].0 = range.len();
+        self.desc.shape_mut()[dim] = range.len() as isize;
     }
 
     // init_slice
     fn init_slice(&mut self, slice: &Py<PySlice>, dim: usize, vm: &VirtualMachine) -> PyResult<()> {
-        let (shape, stride, _) = self.desc.dim_desc[dim];
+        let shape = self.desc.shape()[dim] as usize;
+        let stride = self.desc.strides()[dim];
         let slice = slice.to_saturated(vm)?;
         let (start, slice_len) = slice.adjust_indices_start(shape);
 
         // Repeated slicing multiplies the stride by the step every time, which
         // overflows after about twenty rounds; C wraps there and so does this.
         self.adjust_position(dim, stride.wrapping_mul(start));
-        self.desc.dim_desc[dim].0 = slice_len;
-        self.desc.dim_desc[dim].1 = stride.wrapping_mul(slice.step());
+        self.desc.shape_mut()[dim] = slice_len as isize;
+        self.desc.strides_mut()[dim] = stride.wrapping_mul(slice.step());
 
         Ok(())
     }
@@ -459,7 +461,13 @@ impl PyMemoryView {
         dim: usize,
         vm: &VirtualMachine,
     ) -> PyResult<PyListRef> {
-        let (shape, stride, suboffset) = self.desc.dim_desc[dim];
+        let shape = self.desc.shape()[dim] as usize;
+        let stride = self.desc.strides()[dim];
+        let suboffset = if self.desc.suboffsets()[dim] == -1 {
+            0
+        } else {
+            self.desc.suboffsets()[dim]
+        };
         if dim + 1 == self.desc.ndim() {
             let mut v = Vec::with_capacity(shape);
             for _ in 0..shape {
@@ -653,17 +661,18 @@ impl Py<PyMemoryView> {
         // copy_buffer reads the source as it stood before the copy began, which an
         // overlapping assignment depends on and which also keeps the two borrows
         // below off the same storage.
-        let src = if root_exporter(&src).is(&root_exporter(&dest.buffer)) {
-            let owned = src.to_contiguous(vm);
-            drop(src);
-            owned
-        } else {
-            src
+        let may_overlap = match (root_exporter(&src), root_exporter(&dest.buffer)) {
+            (Some(src), Some(dest)) => src.is(&dest),
+            _ => true,
         };
+        // Keep the source acquisition alive until after the copy and its byte
+        // guards: releasing it can run Python that releases or resizes dest.
+        let snapshot = may_overlap.then(|| src.to_contiguous(vm));
+        let copy_src = snapshot.as_ref().unwrap_or(&src);
 
         let mut bytes_mut = dest.buffer.obj_bytes_mut();
-        let src_bytes = src.obj_bytes();
-        dest.desc.zip_eq(&src.desc, true, |a_range, b_range| {
+        let src_bytes = copy_src.obj_bytes();
+        dest.desc.zip_eq(&copy_src.desc, true, |a_range, b_range| {
             let a_range = a_range.start as usize..a_range.end as usize;
             let b_range = b_range.start as usize..b_range.end as usize;
             bytes_mut[a_range].copy_from_slice(&src_bytes[b_range]);
@@ -731,7 +740,7 @@ impl PyMemoryView {
             Err(vm.new_type_error("0-dim memory has no length"))
         } else {
             // shape for dim[0]
-            Ok(self.desc.dim_desc[0].0)
+            Ok(self.desc.shape()[0] as usize)
         }
     }
 
@@ -739,7 +748,7 @@ impl PyMemoryView {
         let format_str = format.as_str();
         let Some(dest_char) = Self::native_fmtchar(format_str) else {
             return Err(vm.new_value_error(
-                "memoryview: destination format must be a native single character format prefixed with an optional '@'",
+                "memoryview: destination format must be a native format prefixed with an optional '@'",
             ));
         };
         // One side has to be bytes. Casting between two item types would
@@ -760,14 +769,14 @@ impl PyMemoryView {
             released: AtomicCell::new(false),
             restricted: AtomicCell::new(false),
             format_spec,
-            desc: BufferDescriptor {
-                len: self.desc.len,
-                offset: self.desc.offset,
-                readonly: self.desc.readonly,
+            desc: BufferDescriptor::from_dim_desc(
+                self.desc.len,
+                self.desc.offset,
+                self.desc.readonly,
                 itemsize,
-                format: format_str.to_owned().into(),
-                dim_desc: vec![(self.desc.len / itemsize, itemsize as isize, 0)],
-            },
+                format_str.to_owned().into(),
+                vec![(self.desc.len / itemsize, itemsize as isize, 0)],
+            ),
             hash: OnceCell::new(),
             exports: AtomicCell::new(0),
         };
@@ -903,9 +912,9 @@ impl Py<PyMemoryView> {
         self.try_not_released(vm)?;
         Ok(vm.ctx.new_tuple(
             self.desc
-                .dim_desc
+                .shape()
                 .iter()
-                .map(|(shape, _, _)| shape.to_pyobject(vm))
+                .map(|shape| (*shape as usize).to_pyobject(vm))
                 .collect(),
         ))
     }
@@ -915,9 +924,9 @@ impl Py<PyMemoryView> {
         self.try_not_released(vm)?;
         Ok(vm.ctx.new_tuple(
             self.desc
-                .dim_desc
+                .strides()
                 .iter()
-                .map(|(_, stride, _)| stride.to_pyobject(vm))
+                .map(|stride| stride.to_pyobject(vm))
                 .collect(),
         ))
     }
@@ -927,15 +936,15 @@ impl Py<PyMemoryView> {
         self.try_not_released(vm)?;
         let has_suboffsets = self
             .desc
-            .dim_desc
+            .suboffsets()
             .iter()
-            .any(|(_, _, suboffset)| *suboffset != 0);
+            .any(|suboffset| *suboffset != -1);
         if has_suboffsets {
             Ok(vm.ctx.new_tuple(
                 self.desc
-                    .dim_desc
+                    .suboffsets()
                     .iter()
-                    .map(|(_, _, suboffset)| suboffset.to_pyobject(vm))
+                    .map(|suboffset| suboffset.to_pyobject(vm))
                     .collect(),
             ))
         } else {
@@ -1055,7 +1064,7 @@ impl Py<PyMemoryView> {
                 vm.new_not_implemented_error("multi-dimensional sub-views are not implemented")
             );
         }
-        let len = self.desc.dim_desc[0].0;
+        let len = self.desc.shape()[0] as usize;
         let mut count = 0;
         for i in 0..len {
             let item = self.getitem_by_idx(i as isize, vm)?;
@@ -1074,7 +1083,7 @@ impl Py<PyMemoryView> {
                 vm.new_not_implemented_error("multi-dimensional sub-views are not implemented")
             );
         }
-        let len = self.desc.dim_desc[0].0;
+        let len = self.desc.shape()[0] as usize;
         let MemoryIndexArgs { value, start, stop } = args;
 
         let start = if start < 0 {
@@ -1148,12 +1157,14 @@ impl Py<PyMemoryView> {
                         vm.new_type_error("memoryview: product(shape) * itemsize != buffer size")
                     );
                 }
-                other.desc.dim_desc = vec![];
+                other
+                    .desc
+                    .set_dimensions(Box::new([]), Box::new([]), Box::new([]));
                 return Ok(other.into_ref(&vm.ctx));
             }
 
             let mut product_shape = itemsize;
-            let mut dim_descriptor = Vec::with_capacity(shape_ndim);
+            let mut shape_descriptor = Vec::with_capacity(shape_ndim);
 
             for x in shape {
                 let x = x
@@ -1174,12 +1185,13 @@ impl Py<PyMemoryView> {
                     return Err(vm.new_value_error("memoryview.cast(): product(shape) > SSIZE_MAX"));
                 }
                 product_shape *= x;
-                dim_descriptor.push((x, 0, 0));
+                shape_descriptor.push(x as isize);
             }
 
-            dim_descriptor.last_mut().unwrap().1 = itemsize as isize;
-            for i in (0..dim_descriptor.len() - 1).rev() {
-                dim_descriptor[i].1 = dim_descriptor[i + 1].1 * dim_descriptor[i + 1].0 as isize;
+            let mut strides = vec![0isize; shape_descriptor.len()];
+            strides[shape_descriptor.len() - 1] = itemsize as isize;
+            for i in (0..strides.len() - 1).rev() {
+                strides[i] = strides[i + 1] * shape_descriptor[i + 1];
             }
 
             if product_shape != other.desc.len {
@@ -1188,7 +1200,11 @@ impl Py<PyMemoryView> {
                 );
             }
 
-            other.desc.dim_desc = dim_descriptor;
+            other.desc.set_dimensions(
+                shape_descriptor.into_boxed_slice(),
+                strides.into_boxed_slice(),
+                vec![-1; shape_ndim].into_boxed_slice(),
+            );
 
             Ok(other.into_ref(&vm.ctx))
         } else {
@@ -1532,8 +1548,11 @@ static BUFFER_WINDOW_METHODS: BufferMethods = BufferMethods {
 ///
 /// Two buffers that resolve to the same object address the same storage, so
 /// borrowing one for writing while the other is borrowed for reading would
-/// deadlock on it.
-fn root_exporter(buffer: &PyBuffer) -> PyObjectRef {
+/// deadlock on a shared lock or create overlapping references with separate locks.
+/// Borrowed ctypes storage has no reliable exporter identity: a field, pointer,
+/// or from_address view can alias another object without sharing its owner.
+/// Return None for that storage so either operand forces a source snapshot.
+fn root_exporter(buffer: &PyBuffer) -> Option<PyObjectRef> {
     let mut obj = buffer.obj.clone();
     loop {
         let next = if let Some(view) = obj.downcast_ref::<PyMemoryView>() {
@@ -1542,8 +1561,10 @@ fn root_exporter(buffer: &PyBuffer) -> PyObjectRef {
             wrapper.view.obj.clone()
         } else if let Some(window) = obj.downcast_ref::<PyBufferWindow>() {
             window.source.obj.clone()
+        } else if crate::stdlib::is_borrowed_ctypes_buffer(&obj) {
+            return None;
         } else {
-            return obj;
+            return Some(obj);
         };
         obj = next;
     }
@@ -1670,8 +1691,8 @@ fn is_equiv_shape(a: &BufferDescriptor, b: &BufferDescriptor) -> bool {
         return false;
     }
 
-    let a_iter = a.dim_desc.iter().map(|x| x.0);
-    let b_iter = b.dim_desc.iter().map(|x| x.0);
+    let a_iter = a.shape().iter().copied();
+    let b_iter = b.shape().iter().copied();
     for (a_shape, b_shape) in a_iter.zip(b_iter) {
         if a_shape != b_shape {
             return false;
diff --git a/crates/vm/src/builtins/mod.rs b/crates/vm/src/builtins/mod.rs
index c7404fcd169..438cd9e5092 100644
--- a/crates/vm/src/builtins/mod.rs
+++ b/crates/vm/src/builtins/mod.rs
@@ -20,7 +20,7 @@ pub use complex::PyComplex;
 pub(crate) mod coroutine;
 pub use coroutine::PyCoroutine;
 pub(crate) mod dict;
-pub use dict::{PyDict, PyDictRef};
+pub use dict::{PyAnyDict, PyDict, PyDictRef, PyFrozenDict};
 pub(crate) mod enumerate;
 pub use enumerate::PyEnumerate;
 pub(crate) mod filter;
@@ -75,6 +75,8 @@ pub(crate) mod type_;
 pub use type_::{PyType, PyTypeRef};
 pub(crate) mod range;
 pub use range::PyRange;
+pub(crate) mod sentinel;
+pub use sentinel::PySentinel;
 pub(crate) mod set;
 pub use set::{PyFrozenSet, PySet};
 pub(crate) mod singletons;
diff --git a/crates/vm/src/builtins/module.rs b/crates/vm/src/builtins/module.rs
index aae75da816a..178ef2659c2 100644
--- a/crates/vm/src/builtins/module.rs
+++ b/crates/vm/src/builtins/module.rs
@@ -82,7 +82,7 @@ impl PyModuleDef {
     }
 }
 
-#[pyclass(module = false, name = "module")]
+#[pyclass(module = false, name = "module", traverse = "manual")]
 // The dict lives in the object extension, not the payload. The offset is
 // the dict cell at the front of that extension.
 #[pymember(name = "__dict__", offset = ::rustpython_vm::object::dict_member_offset())]
@@ -90,12 +90,26 @@ impl PyModuleDef {
 pub struct PyModule {
     // PyObject *md_dict;
     pub def: Option<&'static PyModuleDef>,
-    // state: Any
+    native_state: crate::object::PyAtomicRef<Option<PyObject>>,
     // weaklist
     // for logging purposes after md_dict is cleared
     pub name: Option<&'static PyStrInterned>,
 }
 
+// SAFETY: Native state is the only owned Python reference in the payload.
+// The module dictionary is visited separately by the object extension.
+unsafe impl crate::object::Traverse for PyModule {
+    fn traverse(&self, tracer: &mut crate::object::TraverseFn<'_>) {
+        self.native_state.traverse(tracer);
+    }
+
+    fn clear(&mut self, out: &mut Vec<PyObjectRef>) {
+        if let Some(state) = self.native_state.store(None) {
+            out.push(state);
+        }
+    }
+}
+
 impl PyPayload for PyModule {
     #[inline]
     fn class(ctx: &Context) -> &'static Py<PyType> {
@@ -119,6 +133,7 @@ impl PyModule {
     pub const fn new() -> Self {
         Self {
             def: None,
+            native_state: crate::object::PyAtomicRef::new_empty(),
             name: None,
         }
     }
@@ -127,10 +142,22 @@ impl PyModule {
     pub const fn from_def(def: &'static PyModuleDef) -> Self {
         Self {
             def: Some(def),
+            native_state: crate::object::PyAtomicRef::new_empty(),
             name: Some(def.name),
         }
     }
 
+    /// Interpreter-local native state, retained and traversed with the module.
+    #[must_use]
+    pub fn native_state(&self) -> Option<PyObjectRef> {
+        self.native_state.load_owned()
+    }
+
+    /// Replace native state without exposing it in the Python module dictionary.
+    pub fn set_native_state(&self, state: PyObjectRef) {
+        drop(self.native_state.store(Some(state)));
+    }
+
     pub fn __init_dict_from_def(vm: &VirtualMachine, module: &Py<Self>) {
         let doc = module.def.unwrap().doc.map(|doc| doc.to_owned());
         module.init_dict(module.name.unwrap(), doc, vm);
@@ -151,11 +178,56 @@ impl Py<PyModule> {
         Ok(())
     }
 
-    fn getattr_inner(&self, name: &Py<PyStr>, vm: &VirtualMachine) -> PyResult {
-        if let Some(attr) = self.as_object().generic_getattr_opt(name, None, vm)? {
+    pub(crate) fn getattr_inner(
+        &self,
+        name: &Py<PyStr>,
+        suppress_cycle: bool,
+        vm: &VirtualMachine,
+    ) -> PyResult {
+        let mut attr = self.as_object().generic_getattr_opt(name, None, vm)?;
+        if attr.is_none() {
+            if let Some(value) =
+                crate::lazy_import::try_load_submodule(self, name, suppress_cycle, vm)?
+            {
+                return Ok(value);
+            }
+            // A concurrent import may have bound a child and removed its pending entry.
+            if self.class().is(vm.ctx.types.module_type)
+                || self
+                    .class()
+                    .get_attr(vm.ctx.intern_str(name.as_wtf8()))
+                    .is_none_or(|descriptor| descriptor.class().slots().descr_get.load().is_none())
+            {
+                attr = self.dict().get_item_opt(name, vm)?;
+            }
+        }
+        if let Some(attr) = attr {
+            if let Some(deferred) =
+                attr.downcast_ref_if_exact::<crate::lazy_import::PyLazyImport>(vm)
+            {
+                if name.to_str() != Some("__getattr__")
+                    && let Some(getattr) = crate::lazy_import::resolved_dict_item(
+                        &self.dict(),
+                        identifier!(vm, __getattr__),
+                        vm,
+                    )?
+                {
+                    match getattr.call((name.to_owned(),), vm) {
+                        Ok(value) => return Ok(value),
+                        Err(exc) if exc.fast_isinstance(vm.ctx.exceptions.attribute_error) => {}
+                        Err(exc) => return Err(exc),
+                    }
+                }
+                if suppress_cycle && crate::lazy_import::is_resolving(deferred, vm) {
+                    return Err(vm.new_attribute_error(format!("module has no attribute '{name}'")));
+                }
+                return crate::lazy_import::reify(deferred, name, self.dict().as_object(), vm);
+            }
             return Ok(attr);
         }
-        if let Ok(getattr) = self.dict().get_item(identifier!(vm, __getattr__), vm) {
+        if let Some(getattr) =
+            crate::lazy_import::resolved_dict_item(&self.dict(), identifier!(vm, __getattr__), vm)?
+        {
             return getattr.call((name.to_owned(),), vm);
         }
         let dict = self.dict();
@@ -272,7 +344,7 @@ impl Py<PyModule> {
 
     pub fn get_attr<'a>(&self, attr_name: impl AsPyStr<'a>, vm: &VirtualMachine) -> PyResult {
         let attr_name = attr_name.as_pystr(&vm.ctx);
-        self.getattr_inner(attr_name, vm)
+        self.getattr_inner(attr_name, false, vm)
     }
 
     pub fn set_attr<'a>(
@@ -303,7 +375,9 @@ impl PyModule {
             .downcast::<PyDict>()
             .map_err(|_| vm.new_type_error("<module>.__dict__ is not a dictionary"))?;
         // PEP 562: honor a module-level __dir__ if one is defined
-        if let Some(dir_func) = dict.get_item_opt(identifier!(vm, __dir__), vm)? {
+        if let Some(dir_func) =
+            crate::lazy_import::resolved_dict_item(&dict, identifier!(vm, __dir__), vm)?
+        {
             return dir_func.call((), vm)?.try_to_value(vm);
         }
         let attrs = dict.into_iter().map(|(k, _v)| k).collect();
@@ -366,11 +440,13 @@ impl PyModule {
         {
             // Call __annotate__(1) where 1 is FORMAT_VALUE
             let result = annotate.call((1i32,), vm)?;
-            if !result.class().is(vm.ctx.types.dict_type) {
-                return Err(vm.new_type_error(format!(
-                    "__annotate__ returned non-dict of type '{}'",
-                    result.class().name()
-                )));
+            if !result.downcastable::<PyDict>() {
+                let error = result.class().fully_qualified_name(vm).map(|name| {
+                    vm.new_type_error(format!("__annotate__() must return a dict, not {name}"))
+                });
+                drop(annotate);
+                drop(result);
+                return Err(error?);
             }
             result
         } else {
@@ -438,7 +514,7 @@ impl Initializer for PyModule {
 
 impl GetAttr for PyModule {
     fn getattro(zelf: &Py<Self>, name: &Py<PyStr>, vm: &VirtualMachine) -> PyResult {
-        zelf.getattr_inner(name, vm)
+        zelf.getattr_inner(name, false, vm)
     }
 }
 
diff --git a/crates/vm/src/builtins/object.rs b/crates/vm/src/builtins/object.rs
index d7de843a7a0..40be5c16406 100644
--- a/crates/vm/src/builtins/object.rs
+++ b/crates/vm/src/builtins/object.rs
@@ -226,16 +226,23 @@ fn object_getstate_default(obj: &PyObject, required: bool, vm: &VirtualMachine)
         if slot_names_len > 0 {
             let slots = vm.ctx.new_dict();
             for i in 0..slot_names_len {
-                let borrowed_names = slot_names.borrow_vec();
-                // Check if slotnames changed during iteration
-                if borrowed_names.len() != slot_names_len {
+                // Release the list lock before the attribute lookup: a getter
+                // or `__getattr__` may mutate `__slotnames__`.
+                let name = slot_names.borrow_vec()[i].clone();
+                let name = name.downcast::<PyStr>().map_err(|name| {
+                    vm.new_type_error(format!(
+                        "attribute name must be string, not '{}'",
+                        name.class().name()
+                    ))
+                })?;
+                if let Some(value) = vm.get_attribute_opt(obj, &name)? {
+                    slots.set_item(name.as_wtf8(), value, vm)?;
+                }
+                // The list is stored on the class, so it may change while we
+                // iterate over it.
+                if slot_names.borrow_vec().len() != slot_names_len {
                     return Err(vm.new_runtime_error("__slotnames__ changed size during iteration"));
                 }
-                let name = borrowed_names[i].downcast_ref::<PyStr>().unwrap();
-                let Ok(value) = obj.get_attr(name, vm) else {
-                    continue;
-                };
-                slots.set_item(name.as_wtf8(), value, vm).unwrap();
             }
 
             if !slots.is_empty() {
@@ -453,7 +460,13 @@ impl PyBaseObject {
                     && !cls.slots.flags.has_feature(PyTypeFlags::IMMUTABLETYPE);
                 // FIXME(#1979) cls instances might have a payload
                 if both_mutable || both_module {
-                    super::type_::compatible_for_assignment(current_cls, &cls, "__class__", vm)?;
+                    super::type_::compatible_for_assignment(
+                        current_cls,
+                        &cls,
+                        "__class__",
+                        true,
+                        vm,
+                    )?;
                     instance.set_class(cls, vm);
                     crate::stdlib::_testinternalcapi::note_set_class();
                     Ok(())
diff --git a/crates/vm/src/builtins/sentinel.rs b/crates/vm/src/builtins/sentinel.rs
new file mode 100644
index 00000000000..eefc33a58b0
--- /dev/null
+++ b/crates/vm/src/builtins/sentinel.rs
@@ -0,0 +1,118 @@
+use super::{PyStrRef, PyType, union_};
+use crate::{
+    Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
+    class::PyClassImpl,
+    object::{PyAtomicRef, Traverse, TraverseFn},
+    protocol::PyNumberMethods,
+    types::{AsNumber, Constructor, Representable},
+};
+
+/// Create a unique sentinel object with the given name.
+#[pyclass(module = false, name = "sentinel", traverse = "manual")]
+#[derive(Debug)]
+pub struct PySentinel {
+    #[pymember(name = "__name__", type = "object_ex")]
+    name: PyStrRef,
+    #[pymember(name = "__module__", type = "object_ex", writable)]
+    module: PyAtomicRef<Option<PyObject>>,
+    repr: Option<PyStrRef>,
+}
+
+// SAFETY: Visit each owned Python reference once, without cloning it.
+unsafe impl Traverse for PySentinel {
+    fn traverse(&self, tracer_fn: &mut TraverseFn<'_>) {
+        self.name.traverse(tracer_fn);
+        self.module.traverse(tracer_fn);
+        self.repr.traverse(tracer_fn);
+    }
+
+    fn clear(&mut self, out: &mut Vec<PyObjectRef>) {
+        // String subclasses may own references back to this sentinel.
+        let name = core::mem::replace(&mut self.name, Context::genesis().empty_str.to_owned());
+        out.push(name.into());
+        if let Some(module) = self.module.store(None) {
+            out.push(module);
+        }
+        if let Some(repr) = self.repr.take() {
+            out.push(repr.into());
+        }
+    }
+}
+
+impl PyPayload for PySentinel {
+    #[inline]
+    fn class(ctx: &Context) -> &'static Py<PyType> {
+        ctx.types.sentinel_type
+    }
+}
+
+#[derive(FromArgs)]
+pub struct SentinelArgs {
+    #[pyarg(positional, error_msg = "sentinel() argument 1 must be str")]
+    name: PyStrRef,
+    #[pyarg(
+        named,
+        optional,
+        error_msg = "sentinel() argument 'repr' must be str or None"
+    )]
+    repr: Option<PyStrRef>,
+}
+
+impl Constructor for PySentinel {
+    type Args = SentinelArgs;
+
+    fn py_new(_cls: &Py<PyType>, args: Self::Args, vm: &VirtualMachine) -> PyResult<Self> {
+        let module = if let Some(frame) = vm.current_frame()
+            && let Some(function) = frame.iframe().func_obj()
+        {
+            // Use the module captured by the caller function, including the
+            // synthetic functions used for module, eval, and exec code.
+            function.get_attr(identifier!(vm, __module__), vm)?
+        } else {
+            vm.ctx.none()
+        };
+        Ok(Self {
+            name: args.name,
+            module: PyAtomicRef::from(Some(module)),
+            repr: args.repr,
+        })
+    }
+}
+
+#[pyclass(with(Constructor, Representable, AsNumber), flags(HAVE_GC))]
+impl PySentinel {
+    #[pymethod]
+    fn __copy__(zelf: PyRef<Self>) -> PyRef<Self> {
+        zelf
+    }
+
+    #[pymethod]
+    fn __deepcopy__(zelf: PyRef<Self>, _memo: PyObjectRef) -> PyRef<Self> {
+        zelf
+    }
+
+    #[pymethod]
+    fn __reduce__(zelf: &Py<Self>) -> PyStrRef {
+        zelf.name.clone()
+    }
+}
+
+impl Representable for PySentinel {
+    fn repr(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<PyStrRef> {
+        Ok(zelf.repr.as_ref().unwrap_or(&zelf.name).clone())
+    }
+}
+
+impl AsNumber for PySentinel {
+    fn as_number() -> &'static PyNumberMethods {
+        static AS_NUMBER: PyNumberMethods = PyNumberMethods {
+            or: Some(|a, b, vm| union_::or_op(a.to_owned(), b.to_owned(), vm)),
+            ..PyNumberMethods::NOT_IMPLEMENTED
+        };
+        &AS_NUMBER
+    }
+}
+
+pub(crate) fn init(context: &'static Context) {
+    PySentinel::extend_class(context, context.types.sentinel_type);
+}
diff --git a/crates/vm/src/builtins/set.rs b/crates/vm/src/builtins/set.rs
index e3e8ade64c4..f126ad318ab 100644
--- a/crates/vm/src/builtins/set.rs
+++ b/crates/vm/src/builtins/set.rs
@@ -16,7 +16,7 @@ use crate::{
         rc::PyRc,
         wtf8::Wtf8Buf,
     },
-    convert::ToPyResult,
+    convert::{ToPyResult, TransmuteFromObject},
     dict_inner::{self, DictSize},
     function::{
         ArgIterable, FuncArgs, NameOthers, OptionalArg, PosArgs, PyArithmeticValue,
@@ -70,7 +70,7 @@ impl PySet {
 
     fn op(
         &self,
-        other: AnySet,
+        other: PyRef<PyAnySet>,
         op: fn(&PySetInner, ArgIterable, &VirtualMachine) -> PyResult<PySetInner>,
         vm: &VirtualMachine,
     ) -> PyResult<Self> {
@@ -132,7 +132,7 @@ impl PyFrozenSet {
 
     fn op(
         &self,
-        other: AnySet,
+        other: PyRef<PyAnySet>,
         op: fn(&PySetInner, ArgIterable, &VirtualMachine) -> PyResult<PySetInner>,
         vm: &VirtualMachine,
     ) -> PyResult<Self> {
@@ -275,8 +275,10 @@ impl PySetInner {
     }
 
     fn contains(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult<bool> {
-        let result = self
-            .retry_op_with_frozenset(needle, vm, |needle, vm| self.content.contains(vm, needle));
+        let result = self.retry_op_with_frozenset(needle, vm, |needle, vm| {
+            let hash = needle.hash(vm)?;
+            self.content.contains(vm, needle, hash)
+        });
         Self::wrap_unhashable_error(result, needle, vm)
     }
 
@@ -287,7 +289,7 @@ impl PySetInner {
         hash: PyHash,
         vm: &VirtualMachine,
     ) -> PyResult<bool> {
-        self.content.contains_known_hash(vm, needle, hash)
+        self.content.contains(vm, needle, hash)
     }
 
     fn compare(&self, other: &Self, op: PyComparisonOp, vm: &VirtualMachine) -> PyResult<bool> {
@@ -375,7 +377,7 @@ impl PySetInner {
             && self.len() >> 2 <= dict._as_dict_inner().len()
         {
             return self.difference_by(
-                |key, hash| dict._as_dict_inner().contains_known_hash(vm, key, hash),
+                |key, hash| dict._as_dict_inner().contains(vm, key, hash),
                 vm,
             );
         }
@@ -412,9 +414,7 @@ impl PySetInner {
         if let Some(elements) = Self::cached_hashes(other.as_object(), vm) {
             // the source is already duplicate-free
             for (item, hash) in elements {
-                new_inner
-                    .content
-                    .delete_or_insert_known_hash(vm, &item, hash, ())?;
+                new_inner.content.delete_or_insert(vm, &item, hash, ())?;
             }
             return Ok(new_inner);
         }
@@ -423,9 +423,7 @@ impl PySetInner {
         let other_set = Self::from_iter(other.iter(vm)?, vm)?;
 
         for (item, hash) in other_set.content.keys_with_hashes() {
-            new_inner
-                .content
-                .delete_or_insert_known_hash(vm, &item, hash, ())?;
+            new_inner.content.delete_or_insert(vm, &item, hash, ())?;
         }
 
         Ok(new_inner)
@@ -491,25 +489,32 @@ impl PySetInner {
     }
 
     fn add(&self, item: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
-        let result = self.content.insert(vm, item, ());
+        let result = (|| {
+            let hash = item.hash(vm)?;
+            self.content.insert(vm, item, hash, ())
+        })();
         Self::wrap_unhashable_error(result, item, vm)
     }
 
     /// [`Self::add`] with a known hash.
     fn add_known_hash(&self, item: &PyObject, hash: PyHash, vm: &VirtualMachine) -> PyResult<()> {
-        let result = self.content.insert_known_hash(vm, item, hash, ());
+        let result = self.content.insert(vm, item, hash, ());
         Self::wrap_unhashable_error(result, item, vm)
     }
 
     fn remove(&self, item: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
-        let result =
-            self.retry_op_with_frozenset(item, vm, |item, vm| self.content.delete(vm, item));
+        let result = self.retry_op_with_frozenset(item, vm, |item, vm| {
+            let hash = item.hash(vm)?;
+            self.content.delete(vm, item, hash)
+        });
         Self::wrap_unhashable_error(result, item, vm)
     }
 
     fn discard(&self, item: &PyObject, vm: &VirtualMachine) -> PyResult<bool> {
-        let result = self
-            .retry_op_with_frozenset(item, vm, |item, vm| self.content.delete_if_exists(vm, item));
+        let result = self.retry_op_with_frozenset(item, vm, |item, vm| {
+            let hash = item.hash(vm)?;
+            self.content.delete_if_exists(vm, item, hash)
+        });
         Self::wrap_unhashable_error(result, item, vm)
     }
 
@@ -532,14 +537,14 @@ impl PySetInner {
     }
 
     fn update_internal(&self, iterable: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
-        // check AnySet
-        if let Ok(any_set) = AnySet::try_from_object(vm, iterable.to_owned()) {
+        // check set or frozenset
+        if let Ok(any_set) = PyRef::<PyAnySet>::try_from_object(vm, iterable.to_owned()) {
             self.merge_set(any_set, vm)
         // check Dict
         } else if let Ok(dict) = iterable.to_owned().downcast_exact::<PyDict>(vm) {
             self.merge_dict(&dict, vm)
         } else {
-            // add iterable that is not AnySet or Dict
+            // add iterable that is not a set, frozenset, or dict
             for item in iterable.try_into_value::<ArgIterable>(vm)?.iter(vm)? {
                 let item = item?;
                 self.add(&item, vm)?;
@@ -548,7 +553,7 @@ impl PySetInner {
         }
     }
 
-    fn merge_set(&self, any_set: AnySet, vm: &VirtualMachine) -> PyResult<()> {
+    fn merge_set(&self, any_set: PyRef<PyAnySet>, vm: &VirtualMachine) -> PyResult<()> {
         for (item, hash) in any_set.as_inner().content.keys_with_hashes() {
             self.add_known_hash(&item, hash, vm)?;
         }
@@ -598,12 +603,14 @@ impl PySetInner {
             };
             if let Some(elements) = elements {
                 for (item, hash) in elements {
-                    self.content.delete_if_exists_known_hash(vm, &*item, hash)?;
+                    self.content.delete_if_exists(vm, &*item, hash)?;
                 }
                 continue;
             }
             for item in iterable.iter(vm)? {
-                self.content.delete_if_exists(vm, &*item?)?;
+                let item = item?;
+                let hash = item.hash(vm)?;
+                self.content.delete_if_exists(vm, &*item, hash)?;
             }
         }
         Ok(())
@@ -618,16 +625,14 @@ impl PySetInner {
             if let Some(elements) = Self::cached_hashes(iterable.as_object(), vm) {
                 // the source is already duplicate-free
                 for (item, hash) in elements {
-                    self.content
-                        .delete_or_insert_known_hash(vm, &item, hash, ())?;
+                    self.content.delete_or_insert(vm, &item, hash, ())?;
                 }
                 continue;
             }
             // We want to remove duplicates in iterable
             let iterable_set = Self::from_iter(iterable.iter(vm)?, vm)?;
             for (item, hash) in iterable_set.content.keys_with_hashes() {
-                self.content
-                    .delete_or_insert_known_hash(vm, &item, hash, ())?;
+                self.content.delete_or_insert(vm, &item, hash, ())?;
             }
         }
         Ok(())
@@ -747,7 +752,7 @@ impl PySet {
     }
 
     fn __or__(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(self.op(
                 other,
                 PySetInner::union,
@@ -763,7 +768,7 @@ impl PySet {
         other: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(Self {
                 inner: self.inner.intersection(other.into_iterable(vm)?, vm)?,
             }))
@@ -777,7 +782,7 @@ impl PySet {
         other: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(Self {
                 inner: self.inner.difference_new(other.into_iterable(vm)?, vm)?,
             }))
@@ -791,7 +796,7 @@ impl PySet {
         other: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(Self {
                 inner: other
                     .as_inner()
@@ -807,7 +812,7 @@ impl PySet {
         other: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(self.op(
                 other,
                 PySetInner::symmetric_difference,
@@ -818,12 +823,20 @@ impl PySet {
         }
     }
 
-    fn __ior__(zelf: PyRef<Self>, set: AnySet, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
+    fn __ior__(
+        zelf: PyRef<Self>,
+        set: PyRef<PyAnySet>,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyRef<Self>> {
         zelf.inner.merge_set(set, vm)?;
         Ok(zelf)
     }
 
-    fn __iand__(zelf: PyRef<Self>, set: AnySet, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
+    fn __iand__(
+        zelf: PyRef<Self>,
+        set: PyRef<PyAnySet>,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyRef<Self>> {
         if !set.is(zelf.as_object()) {
             zelf.inner
                 .intersection_update(core::iter::once(set.into_iterable(vm)?), vm)?;
@@ -831,7 +844,11 @@ impl PySet {
         Ok(zelf)
     }
 
-    fn __isub__(zelf: PyRef<Self>, set: AnySet, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
+    fn __isub__(
+        zelf: PyRef<Self>,
+        set: PyRef<PyAnySet>,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyRef<Self>> {
         if set.is(zelf.as_object()) {
             zelf.inner.clear();
         } else {
@@ -841,7 +858,11 @@ impl PySet {
         Ok(zelf)
     }
 
-    fn __ixor__(zelf: PyRef<Self>, set: AnySet, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
+    fn __ixor__(
+        zelf: PyRef<Self>,
+        set: PyRef<PyAnySet>,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyRef<Self>> {
         if set.is(zelf.as_object()) {
             zelf.inner.clear();
         } else {
@@ -1063,10 +1084,7 @@ impl Comparable for PySet {
 
 impl Iterable for PySet {
     fn iter(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult {
-        Ok(PySetIterator::new(AnySet {
-            object: zelf.into(),
-        })
-        .into_pyobject(vm))
+        Ok(PySetIterator::new(zelf.into()).into_pyobject(vm))
     }
 }
 
@@ -1076,7 +1094,7 @@ impl AsNumber for PySet {
             // Binary ops check both operands are sets (like CPython's set_sub, etc.)
             // This is needed because __rsub__ swaps operands: a.__rsub__(b) calls subtract(b, a)
             subtract: Some(|a, b, vm| {
-                if !AnySet::check(a, vm) || !AnySet::check(b, vm) {
+                if !PyRef::<PyAnySet>::check(a, vm) || !PyRef::<PyAnySet>::check(b, vm) {
                     return Ok(vm.ctx.not_implemented());
                 }
                 if let Some(a) = a.downcast_ref::<PySet>() {
@@ -1091,7 +1109,7 @@ impl AsNumber for PySet {
                 }
             }),
             and: Some(|a, b, vm| {
-                if !AnySet::check(a, vm) || !AnySet::check(b, vm) {
+                if !PyRef::<PyAnySet>::check(a, vm) || !PyRef::<PyAnySet>::check(b, vm) {
                     return Ok(vm.ctx.not_implemented());
                 }
                 if let Some(a) = a.downcast_ref::<PySet>() {
@@ -1105,7 +1123,7 @@ impl AsNumber for PySet {
                 }
             }),
             xor: Some(|a, b, vm| {
-                if !AnySet::check(a, vm) || !AnySet::check(b, vm) {
+                if !PyRef::<PyAnySet>::check(a, vm) || !PyRef::<PyAnySet>::check(b, vm) {
                     return Ok(vm.ctx.not_implemented());
                 }
                 if let Some(a) = a.downcast_ref::<PySet>() {
@@ -1119,7 +1137,7 @@ impl AsNumber for PySet {
                 }
             }),
             or: Some(|a, b, vm| {
-                if !AnySet::check(a, vm) || !AnySet::check(b, vm) {
+                if !PyRef::<PyAnySet>::check(a, vm) || !PyRef::<PyAnySet>::check(b, vm) {
                     return Ok(vm.ctx.not_implemented());
                 }
                 if let Some(a) = a.downcast_ref::<PySet>() {
@@ -1133,33 +1151,57 @@ impl AsNumber for PySet {
                 }
             }),
             inplace_subtract: Some(|a, b, vm| {
-                if let Some(a) = a.downcast_ref::<PySet>() {
-                    PySet::__isub__(a.to_owned(), AnySet::try_from_object(vm, b.to_owned())?, vm)
-                        .to_pyresult(vm)
+                if let Some(a) = a.downcast_ref::<PySet>()
+                    && PyRef::<PyAnySet>::check(b, vm)
+                {
+                    PySet::__isub__(
+                        a.to_owned(),
+                        PyRef::<PyAnySet>::try_from_object(vm, b.to_owned())?,
+                        vm,
+                    )
+                    .to_pyresult(vm)
                 } else {
                     Ok(vm.ctx.not_implemented())
                 }
             }),
             inplace_and: Some(|a, b, vm| {
-                if let Some(a) = a.downcast_ref::<PySet>() {
-                    PySet::__iand__(a.to_owned(), AnySet::try_from_object(vm, b.to_owned())?, vm)
-                        .to_pyresult(vm)
+                if let Some(a) = a.downcast_ref::<PySet>()
+                    && PyRef::<PyAnySet>::check(b, vm)
+                {
+                    PySet::__iand__(
+                        a.to_owned(),
+                        PyRef::<PyAnySet>::try_from_object(vm, b.to_owned())?,
+                        vm,
+                    )
+                    .to_pyresult(vm)
                 } else {
                     Ok(vm.ctx.not_implemented())
                 }
             }),
             inplace_xor: Some(|a, b, vm| {
-                if let Some(a) = a.downcast_ref::<PySet>() {
-                    PySet::__ixor__(a.to_owned(), AnySet::try_from_object(vm, b.to_owned())?, vm)
-                        .to_pyresult(vm)
+                if let Some(a) = a.downcast_ref::<PySet>()
+                    && PyRef::<PyAnySet>::check(b, vm)
+                {
+                    PySet::__ixor__(
+                        a.to_owned(),
+                        PyRef::<PyAnySet>::try_from_object(vm, b.to_owned())?,
+                        vm,
+                    )
+                    .to_pyresult(vm)
                 } else {
                     Ok(vm.ctx.not_implemented())
                 }
             }),
             inplace_or: Some(|a, b, vm| {
-                if let Some(a) = a.downcast_ref::<PySet>() {
-                    PySet::__ior__(a.to_owned(), AnySet::try_from_object(vm, b.to_owned())?, vm)
-                        .to_pyresult(vm)
+                if let Some(a) = a.downcast_ref::<PySet>()
+                    && PyRef::<PyAnySet>::check(b, vm)
+                {
+                    PySet::__ior__(
+                        a.to_owned(),
+                        PyRef::<PyAnySet>::try_from_object(vm, b.to_owned())?,
+                        vm,
+                    )
+                    .to_pyresult(vm)
                 } else {
                     Ok(vm.ctx.not_implemented())
                 }
@@ -1274,7 +1316,7 @@ impl PyFrozenSet {
     }
 
     fn __or__(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(set) = AnySet::try_from_object(vm, other) {
+        if let Ok(set) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(self.op(
                 set,
                 PySetInner::union,
@@ -1290,7 +1332,7 @@ impl PyFrozenSet {
         other: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(Self {
                 inner: self.inner.intersection(other.into_iterable(vm)?, vm)?,
                 ..Default::default()
@@ -1305,7 +1347,7 @@ impl PyFrozenSet {
         other: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(Self {
                 inner: self.inner.difference_new(other.into_iterable(vm)?, vm)?,
                 ..Default::default()
@@ -1320,7 +1362,7 @@ impl PyFrozenSet {
         other: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(Self {
                 inner: other
                     .as_inner()
@@ -1337,7 +1379,7 @@ impl PyFrozenSet {
         other: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<PyArithmeticValue<Self>> {
-        if let Ok(other) = AnySet::try_from_object(vm, other) {
+        if let Ok(other) = PyRef::<PyAnySet>::try_from_object(vm, other) {
             Ok(PyArithmeticValue::Implemented(self.op(
                 other,
                 PySetInner::symmetric_difference,
@@ -1515,10 +1557,7 @@ impl Comparable for PyFrozenSet {
 
 impl Iterable for PyFrozenSet {
     fn iter(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult {
-        Ok(PySetIterator::new(AnySet {
-            object: zelf.into(),
-        })
-        .into_pyobject(vm))
+        Ok(PySetIterator::new(zelf.into()).into_pyobject(vm))
     }
 }
 
@@ -1528,7 +1567,7 @@ impl AsNumber for PyFrozenSet {
             // Binary ops check both operands are sets (like CPython's set_sub, etc.)
             // __rsub__ swaps operands. Result type follows first operand's type.
             subtract: Some(|a, b, vm| {
-                if !AnySet::check(a, vm) || !AnySet::check(b, vm) {
+                if !PyRef::<PyAnySet>::check(a, vm) || !PyRef::<PyAnySet>::check(b, vm) {
                     return Ok(vm.ctx.not_implemented());
                 }
                 if let Some(a) = a.downcast_ref::<PyFrozenSet>() {
@@ -1541,7 +1580,7 @@ impl AsNumber for PyFrozenSet {
                 }
             }),
             and: Some(|a, b, vm| {
-                if !AnySet::check(a, vm) || !AnySet::check(b, vm) {
+                if !PyRef::<PyAnySet>::check(a, vm) || !PyRef::<PyAnySet>::check(b, vm) {
                     return Ok(vm.ctx.not_implemented());
                 }
                 if let Some(a) = a.downcast_ref::<PyFrozenSet>() {
@@ -1553,7 +1592,7 @@ impl AsNumber for PyFrozenSet {
                 }
             }),
             xor: Some(|a, b, vm| {
-                if !AnySet::check(a, vm) || !AnySet::check(b, vm) {
+                if !PyRef::<PyAnySet>::check(a, vm) || !PyRef::<PyAnySet>::check(b, vm) {
                     return Ok(vm.ctx.not_implemented());
                 }
                 if let Some(a) = a.downcast_ref::<PyFrozenSet>() {
@@ -1565,7 +1604,7 @@ impl AsNumber for PyFrozenSet {
                 }
             }),
             or: Some(|a, b, vm| {
-                if !AnySet::check(a, vm) || !AnySet::check(b, vm) {
+                if !PyRef::<PyAnySet>::check(a, vm) || !PyRef::<PyAnySet>::check(b, vm) {
                     return Ok(vm.ctx.not_implemented());
                 }
                 if let Some(a) = a.downcast_ref::<PyFrozenSet>() {
@@ -1599,27 +1638,78 @@ impl Representable for PyFrozenSet {
     }
 }
 
-struct AnySet {
-    object: PyObjectRef,
+/// A borrowed view of either a set or a frozenset, including subclasses.
+///
+/// This is an erased header view, not a shared payload layout: every payload
+/// access still downcasts to the actual alternative. It cannot be allocated as
+/// a payload or constructed without checking the object.
+#[repr(transparent)]
+pub(crate) struct PyAnySet {
+    object: PyObject,
 }
 
-impl Borrow<PyObject> for AnySet {
+impl Borrow<PyObject> for PyAnySet {
     #[inline(always)]
     fn borrow(&self) -> &PyObject {
         &self.object
     }
 }
 
-impl AnySet {
-    /// Check if object is a set or frozenset (including subclasses)
-    /// Equivalent to CPython's PyAnySet_Check
+impl Borrow<PyAnySet> for PyRef<PyAnySet> {
+    fn borrow(&self) -> &PyAnySet {
+        self
+    }
+}
+
+impl ToOwned for PyAnySet {
+    type Owned = PyRef<Self>;
+
+    fn to_owned(&self) -> PyRef<Self> {
+        // SAFETY: this borrowed view already guarantees a set payload.
+        unsafe { PyRef::<Self>::from_object_unchecked(self.object.to_owned()) }
+    }
+}
+
+impl From<PyRef<PySet>> for PyRef<PyAnySet> {
+    fn from(set: PyRef<PySet>) -> Self {
+        // SAFETY: the typed owner guarantees the set alternative.
+        unsafe { Self::from_object_unchecked(set.into()) }
+    }
+}
+
+impl From<PyRef<PyFrozenSet>> for PyRef<PyAnySet> {
+    fn from(set: PyRef<PyFrozenSet>) -> Self {
+        // SAFETY: the typed owner guarantees the frozenset alternative.
+        unsafe { Self::from_object_unchecked(set.into()) }
+    }
+}
+
+impl From<PyRef<PyAnySet>> for PyObjectRef {
+    fn from(set: PyRef<PyAnySet>) -> Self {
+        set.into_object()
+    }
+}
+
+impl PyAnySet {
+    /// Check if object is a set or frozenset (including subclasses).
+    /// Equivalent to CPython's PyAnySet_Check.
     fn check(obj: &PyObject, vm: &VirtualMachine) -> bool {
         let ctx = &vm.ctx;
         obj.fast_isinstance(ctx.types.set_type) || obj.fast_isinstance(ctx.types.frozenset_type)
     }
 
+    fn as_inner(&self) -> &PySetInner {
+        extract_set(&self.object).expect("PyAnySet is always PySet or PyFrozenSet")
+    }
+}
+
+impl PyRef<PyAnySet> {
+    fn check(obj: &PyObject, vm: &VirtualMachine) -> bool {
+        PyAnySet::check(obj, vm)
+    }
+
     fn into_iterable(self, vm: &VirtualMachine) -> PyResult<ArgIterable> {
-        self.object.try_into_value(vm)
+        self.into_object().try_into_value(vm)
     }
 
     fn into_iterable_iter(
@@ -1628,26 +1718,28 @@ impl AnySet {
     ) -> PyResult<impl core::iter::Iterator<Item = ArgIterable>> {
         Ok(core::iter::once(self.into_iterable(vm)?))
     }
+}
 
-    fn as_inner(&self) -> &PySetInner {
-        match_class!(match self.object.as_object() {
-            ref set @ PySet => &set.inner,
-            ref frozen @ PyFrozenSet => &frozen.inner,
-            _ => unreachable!("AnySet is always PySet or PyFrozenSet"), // should not be called.
-        })
+// SAFETY: PyRef<PyAnySet> is a transparent PyRef owner. A successful check proves
+// both the Python class and the actual set/frozenset payload of this object.
+unsafe impl TransmuteFromObject for PyRef<PyAnySet> {
+    fn check(vm: &VirtualMachine, obj: &PyObject) -> PyResult<()> {
+        if PyAnySet::check(obj, vm) && extract_set(obj).is_some() {
+            Ok(())
+        } else {
+            Err(vm.new_type_error(format!(
+                "{} is not a subtype of set or frozenset",
+                obj.class()
+            )))
+        }
     }
 }
 
-impl TryFromObject for AnySet {
+impl TryFromObject for PyRef<PyAnySet> {
     fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
-        let class = obj.class();
-        if class.fast_issubclass(vm.ctx.types.set_type)
-            || class.fast_issubclass(vm.ctx.types.frozenset_type)
-        {
-            Ok(Self { object: obj })
-        } else {
-            Err(vm.new_type_error(format!("{class} is not a subtype of set or frozenset")))
-        }
+        <Self as TransmuteFromObject>::check(vm, &obj)?;
+        // SAFETY: the shared checker proved the union view's payload invariant.
+        Ok(unsafe { Self::from_object_unchecked(obj) })
     }
 }
 
@@ -1658,7 +1750,7 @@ pub(crate) struct PySetIterator {
     /// records by writing a size no set can have. Sticky: what it makes the
     /// iterator answer, it answers from then on.
     changed: PyAtomic<bool>,
-    internal: PyMutex<PositionIterInternal<AnySet>>,
+    internal: PyMutex<PositionIterInternal<PyRef<PyAnySet>>>,
 }
 
 impl fmt::Debug for PySetIterator {
@@ -1676,7 +1768,7 @@ impl PyPayload for PySetIterator {
 }
 
 impl PySetIterator {
-    fn new(set: AnySet) -> Self {
+    fn new(set: PyRef<PyAnySet>) -> Self {
         Self {
             size: set.as_inner().content.size(),
             changed: Radium::new(false),
@@ -1806,3 +1898,151 @@ pub(crate) fn init(context: &'static Context) {
 
     PySetIterator::extend_class(context, context.types.set_iterator_type);
 }
+
+#[cfg(test)]
+mod reference_tests {
+    use super::*;
+
+    #[test]
+    fn anyset_reference_layout_and_ownership() {
+        static_assertions::assert_not_impl_any!(PyAnySet: PyPayload);
+        static_assertions::assert_type_eq_all!(
+            <PyAnySet as crate::object::PyRefTarget>::Target,
+            PyAnySet
+        );
+        static_assertions::assert_eq_size!(PyRef<PyAnySet>, PyObjectRef, Option<PyRef<PyAnySet>>);
+        static_assertions::assert_eq_align!(PyRef<PyAnySet>, PyObjectRef);
+        static_assertions::assert_eq_size!(PyAnySet, PyObject);
+        static_assertions::assert_eq_align!(PyAnySet, PyObject);
+        #[cfg(feature = "threading")]
+        static_assertions::assert_impl_all!(PyRef<PyAnySet>: Send, Sync);
+        #[cfg(not(feature = "threading"))]
+        static_assertions::assert_not_impl_any!(PyRef<PyAnySet>: Send, Sync);
+
+        let ctx = Context::genesis();
+        let set: PyRef<PyAnySet> = PySet::default().into_ref(ctx).into();
+        let frozen: PyRef<PyAnySet> = PyFrozenSet::default().into_ref(ctx).into();
+        for owner in [set, frozen] {
+            let object = owner.as_object() as *const PyObject;
+            assert_eq!(owner.as_object().strong_count(), 1);
+            let borrowed: &PyAnySet = &owner;
+            assert!(core::ptr::eq(borrowed.as_object(), object));
+            assert!(core::ptr::eq(
+                borrowed.as_inner(),
+                extract_set(owner.as_object()).unwrap()
+            ));
+            let copy = borrowed.to_owned();
+            assert_eq!(owner.as_object().strong_count(), 2);
+            let clone = owner.clone();
+            assert_eq!(owner.as_object().strong_count(), 3);
+            let erased = clone.into_object();
+            assert_eq!(erased.strong_count(), 3);
+            assert!(core::ptr::eq(&*erased, object));
+            drop(copy);
+            drop(owner);
+            assert_eq!(erased.strong_count(), 1);
+        }
+    }
+
+    #[test]
+    fn anyset_checked_reference_conversion() {
+        crate::Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let set = PySet::default().into_pyobject(vm);
+            let frozen = PyFrozenSet::default().into_pyobject(vm);
+            for object in [set, frozen] {
+                let owner = PyRef::<PyAnySet>::try_from_object(vm, object.clone()).unwrap();
+                assert_eq!(object.strong_count(), 2);
+                assert!(core::ptr::eq(owner.as_object(), &*object));
+                let erased: PyObjectRef = owner.into();
+                assert_eq!(object.strong_count(), 2);
+                assert!(core::ptr::eq(&*erased, &*object));
+                drop(erased);
+                assert_eq!(object.strong_count(), 1);
+            }
+            let unrelated: PyObjectRef = vm.ctx.new_int(1000).into();
+            let error = PyRef::<PyAnySet>::try_from_object(vm, unrelated.clone()).unwrap_err();
+            assert!(error.fast_isinstance(vm.ctx.exceptions.type_error));
+            assert_eq!(unrelated.strong_count(), 1);
+        });
+    }
+
+    #[test]
+    fn anyset_typed_tuple_views_and_refcounts() {
+        use crate::builtins::PyTuple;
+        type Typed = PyTuple<PyRef<PyAnySet>>;
+        type Nested = PyTuple<PyRef<Typed>>;
+        static_assertions::assert_not_impl_any!(PyObject: crate::object::PyTypedRefTarget);
+        static_assertions::assert_impl_all!(PyAnySet: crate::object::PyTypedRefTarget);
+        static_assertions::assert_impl_all!(Typed: crate::object::PyTypedRefTarget);
+        static_assertions::assert_eq_size!(Typed, PyTuple);
+        static_assertions::assert_eq_align!(Typed, PyTuple);
+        static_assertions::assert_eq_size!(Py<Typed>, Py<PyTuple>);
+        static_assertions::assert_eq_align!(Py<Typed>, Py<PyTuple>);
+
+        crate::Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let set: PyRef<PyAnySet> = PySet::default().into_ref(&vm.ctx).into();
+            let frozen: PyRef<PyAnySet> = PyFrozenSet::default().into_ref(&vm.ctx).into();
+            let tuple = Typed::new_ref_typed(vec![set.clone(), frozen.clone()], &vm.ctx);
+            assert_eq!(set.as_object().strong_count(), 2);
+            assert_eq!(frozen.as_object().strong_count(), 2);
+            assert!(
+                tuple.as_slice()[0]
+                    .as_object()
+                    .downcast_ref::<PySet>()
+                    .is_some()
+            );
+            assert!(
+                tuple.as_slice()[1]
+                    .as_object()
+                    .downcast_ref::<PyFrozenSet>()
+                    .is_some()
+            );
+            assert!(core::ptr::eq(
+                tuple.as_slice()[0].as_inner(),
+                set.as_inner()
+            ));
+            assert!(core::ptr::eq(
+                tuple.as_slice()[1].as_inner(),
+                frozen.as_inner()
+            ));
+            let erased = tuple.clone().into_untyped();
+            assert!(core::ptr::eq(tuple.as_untyped(), &*erased));
+            assert_eq!(erased.as_object().strong_count(), 2);
+            let checked = erased.try_into_typed::<PyAnySet>(vm).unwrap();
+            assert!(core::ptr::eq(&*checked, &*tuple));
+            assert_eq!(checked.as_object().strong_count(), 2);
+            let borrowed_copy = (*checked).to_owned();
+            assert_eq!(tuple.as_object().strong_count(), 3);
+            let nested: PyRef<Nested> = PyTuple::new_ref_typed(vec![borrowed_copy], &vm.ctx);
+            assert!(core::ptr::eq(&*nested.as_slice()[0], &*tuple));
+            let untyped: PyTupleRef = nested.into();
+            assert_eq!(tuple.as_object().strong_count(), 3);
+            drop(untyped);
+            drop(checked);
+            assert_eq!(tuple.as_object().strong_count(), 1);
+            drop(tuple);
+            assert_eq!(set.as_object().strong_count(), 1);
+            assert_eq!(frozen.as_object().strong_count(), 1);
+        });
+    }
+
+    #[test]
+    fn anyset_typed_tuple_rejects_invalid_element_without_leaking() {
+        use crate::builtins::PyTuple;
+        crate::Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let set = PySet::default().into_pyobject(vm);
+            let wrong: PyObjectRef = vm.ctx.new_int(1000).into();
+            let tuple = PyTuple::new_ref(vec![set.clone(), wrong.clone()], &vm.ctx);
+            let error = tuple.clone().try_into_typed::<PyAnySet>(vm).unwrap_err();
+            assert!(error.fast_isinstance(vm.ctx.exceptions.type_error));
+            assert_eq!(tuple.as_object().strong_count(), 1);
+            assert!(core::ptr::eq(&*tuple.as_slice()[0], &*set));
+            assert!(core::ptr::eq(&*tuple.as_slice()[1], &*wrong));
+            assert_eq!(set.strong_count(), 2);
+            assert_eq!(wrong.strong_count(), 2);
+            drop(tuple);
+            assert_eq!(set.strong_count(), 1);
+            assert_eq!(wrong.strong_count(), 1);
+        });
+    }
+}
diff --git a/crates/vm/src/builtins/slice.rs b/crates/vm/src/builtins/slice.rs
index 8cc53fd16c1..d4aee6b28a1 100644
--- a/crates/vm/src/builtins/slice.rs
+++ b/crates/vm/src/builtins/slice.rs
@@ -187,9 +187,11 @@ impl PySlice {
 
         Ok((start, stop, step))
     }
+}
 
-    // TODO: Uncomment when Python adds __class_getitem__ to slice
-    // #[pyclassmethod]
+#[pyclass(with(Comparable, Representable, Hashable))]
+impl Py<PySlice> {
+    #[pyclassmethod]
     fn __class_getitem__(
         cls: PyTypeRef,
         args: PyObjectRef,
@@ -197,10 +199,6 @@ impl PySlice {
     ) -> PyResult<PyGenericAlias> {
         PyGenericAlias::from_args(cls, args, vm)
     }
-}
-
-#[pyclass(with(Comparable, Representable, Hashable))]
-impl Py<PySlice> {
     #[pyslot]
     fn slot_new(cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
         let slice: PySlice = match args.args.len() {
diff --git a/crates/vm/src/builtins/str.rs b/crates/vm/src/builtins/str.rs
index c66b87cfb5c..27a6059d283 100644
--- a/crates/vm/src/builtins/str.rs
+++ b/crates/vm/src/builtins/str.rs
@@ -1,6 +1,7 @@
 use super::{
-    PositionIterInternal, PyBytesRef, PyDict, PyList, PyTuple, PyTupleRef, PyType, PyTypeRef,
-    int::{PyInt, PyIntRef},
+    PositionIterInternal, PyAnyDict, PyBytesRef, PyDict, PyList, PyTuple, PyTupleRef, PyType,
+    PyTypeRef,
+    int::PyInt,
     iter::{IterStatus, builtins_iter},
 };
 use crate::{
@@ -15,9 +16,9 @@ use crate::{
         lock::LazyLock,
         str::{PyKindStr, StrData, StrKind},
     },
-    convert::{IntoPyException, ToPyException, ToPyObject, ToPyResult},
+    convert::{ToPyException, ToPyObject, ToPyResult},
     format::{format, format_map},
-    function::{ArgIterable, FuncArgs, OptionalArg, PyComparisonValue, PySsize},
+    function::{ArgIndex, ArgIterable, FuncArgs, OptionalArg, PyComparisonValue, PySsize},
     intern::PyInterned,
     object::{MaybeTraverse, Traverse, TraverseFn},
     protocol::{
@@ -41,7 +42,7 @@ use num_traits::ToPrimitive;
 use rustpython_common::{
     ascii,
     atomic::{self, PyAtomic, Radium},
-    format::{FormatSpec, FormatString, FromTemplate},
+    format::{FormatString, FromTemplate},
     hash,
     lock::PyMutex,
     str::DeduceStrKind,
@@ -391,15 +392,49 @@ pub struct StrArgs {
     #[pyarg(any, optional)]
     object: OptionalArg<PyObjectRef>,
     #[pyarg(any, optional)]
-    encoding: OptionalArg<PyUtf8StrRef>,
+    encoding: OptionalArg<PyObjectRef>,
     #[pyarg(any, optional)]
-    errors: OptionalArg<PyUtf8StrRef>,
+    errors: OptionalArg<PyObjectRef>,
+}
+
+/// The `encoding` or `errors` argument of `str()`, which must be a str.
+fn str_new_str_arg(
+    arg: OptionalArg<PyObjectRef>,
+    name: &str,
+    vm: &VirtualMachine,
+) -> PyResult<Option<PyUtf8StrRef>> {
+    let OptionalArg::Present(arg) = arg else {
+        return Ok(None);
+    };
+    let arg = arg.downcast::<PyStr>().map_err(|arg| {
+        vm.new_type_error(format!(
+            "str() argument '{name}' must be str, not {}",
+            arg.class().name()
+        ))
+    })?;
+    Ok(Some(arg.try_into_utf8(vm)?))
 }
 
 impl Constructor for PyStr {
     type Args = StrArgs;
 
     fn slot_new(cls: PyTypeRef, func_args: FuncArgs, vm: &VirtualMachine) -> PyResult {
+        // A call with keyword arguments is parsed by unicode_new, which counts
+        // every argument.
+        if !func_args.kwargs.is_empty() {
+            let total = func_args.args.len() + func_args.kwargs.len();
+            if total > 3 {
+                let keyword = if func_args.args.is_empty() {
+                    "keyword "
+                } else {
+                    ""
+                };
+                return Err(vm.new_type_error(format!(
+                    "str() takes at most 3 {keyword}arguments ({total} given)"
+                )));
+            }
+        }
+
         // Optimization: return exact str as-is (only when no encoding/errors provided)
         if cls.is(vm.ctx.types.str_type)
             && func_args.args.len() == 1
@@ -433,8 +468,8 @@ impl Constructor for PyStr {
     fn py_new(_cls: &Py<PyType>, args: Self::Args, vm: &VirtualMachine) -> PyResult<Self> {
         match args.object {
             OptionalArg::Present(input) => {
-                let encoding = args.encoding.into_option();
-                let errors = args.errors.into_option();
+                let encoding = str_new_str_arg(args.encoding, "encoding", vm)?;
+                let errors = str_new_str_arg(args.errors, "errors", vm)?;
                 // CPython parity: presence of `encoding` OR `errors` triggers
                 // decode mode. When `errors` is given alone, the encoding
                 // defaults to UTF-8.
@@ -1167,11 +1202,11 @@ impl Py<PyStr> {
             };
         }
         let zelf = zelf.try_into_utf8(vm)?;
-        let s = FormatSpec::parse(format_spec.as_str())
-            .and_then(|format_spec| {
-                format_spec.format_string(&CharLenStr(zelf.as_str(), zelf.char_len()))
-            })
-            .map_err(|err| err.into_pyexception(vm))?;
+        let s = crate::format::parse_format_spec(zelf.as_object(), format_spec.as_str(), vm)?
+            .format_string(&CharLenStr(zelf.as_str(), zelf.char_len()))
+            .map_err(|err| {
+                crate::format::format_spec_error(err, zelf.as_object(), format_spec.as_str(), vm)
+            })?;
         Ok(vm.ctx.new_str(s))
     }
 
@@ -1211,19 +1246,29 @@ impl Py<PyStr> {
         }
 
         let s = zelf.as_wtf8();
-        let replaced = if count < 0 {
-            s.replace(old.as_wtf8(), new.as_wtf8())
+        let limit = if count < 0 {
+            usize::MAX
         } else {
-            let s_is_empty = s.is_empty();
-            let old_is_empty = old.is_empty();
-
-            if s_is_empty && !old_is_empty {
-                s.to_owned()
-            } else if s_is_empty && old_is_empty {
-                new.as_wtf8().to_owned()
-            } else {
-                s.replacen(old.as_wtf8(), new.as_wtf8(), count as usize)
+            count as usize
+        };
+        let replaced = if old.is_empty() {
+            s.replacen(old.as_wtf8(), new.as_wtf8(), limit)
+        } else {
+            let mut matches = s.find_iter(old.as_wtf8()).take(limit);
+            let Some(first) = matches.next() else {
+                drop(matches);
+                return PyStr::result_unchanged(zelf, vm);
+            };
+            let mut result = Vec::with_capacity(s.len());
+            let mut last = 0;
+            for start in core::iter::once(first).chain(matches) {
+                result.extend_from_slice(&s.as_bytes()[last..start]);
+                result.extend_from_slice(new.as_bytes());
+                last = start + old.byte_len();
             }
+            result.extend_from_slice(&s.as_bytes()[last..]);
+            // SAFETY: A nonempty WTF-8 needle matches only at code point boundaries.
+            unsafe { Wtf8Buf::from_bytes_unchecked(result) }
         };
         vm.ctx.new_str(replaced)
     }
@@ -1536,17 +1581,15 @@ impl Py<PyStr> {
                 )),
             }
         } else {
-            // dict_str must be a dict
-            match dict_or_str.downcast::<PyDict>() {
-                Ok(dict) => {
+            // The single-argument form accepts exact dict and frozendict objects.
+            match PyAnyDict::from_object(&dict_or_str).filter(|_| {
+                dict_or_str.class().is(vm.ctx.types.dict_type)
+                    || dict_or_str.class().is(vm.ctx.types.frozendict_type)
+            }) {
+                Some(dict) => {
                     for (key, val) in dict {
-                        // FIXME: ints are key-compatible
-                        if let Some(num) = key.downcast_ref::<PyInt>() {
-                            new_dict.set_item(
-                                &*num.as_bigint().to_i32().to_pyobject(vm),
-                                val,
-                                vm,
-                            )?;
+                        if key.downcast_ref::<PyInt>().is_some() {
+                            new_dict.set_item(&*key, val, vm)?;
                         } else if let Some(string) = key.downcast_ref::<PyStr>() {
                             if string.len() == 1 {
                                 let num_value =
@@ -1565,7 +1608,7 @@ impl Py<PyStr> {
                     }
                     Ok(new_dict.to_pyobject(vm))
                 }
-                _ => Err(vm.new_value_error(
+                _ => Err(vm.new_type_error(
                     "if you give only one argument to maketrans it must be a dict",
                 )),
             }
@@ -1871,14 +1914,18 @@ pub(crate) struct FindArgs {
     #[pyarg(positional)]
     sub: PyStrRef,
     #[pyarg(positional, default)]
-    start: Option<PyIntRef>,
+    start: Option<ArgIndex>,
     #[pyarg(positional, default)]
-    end: Option<PyIntRef>,
+    end: Option<ArgIndex>,
 }
 
 impl FindArgs {
     fn get_value(self, len: usize) -> (PyStrRef, core::ops::Range<usize>) {
-        let range = adjust_indices(self.start.as_deref(), self.end.as_deref(), len);
+        let range = adjust_indices(
+            self.start.as_ref().map(AsRef::as_ref),
+            self.end.as_ref().map(AsRef::as_ref),
+            len,
+        );
         (self.sub, range)
     }
 }
diff --git a/crates/vm/src/builtins/tuple.rs b/crates/vm/src/builtins/tuple.rs
index a1c06e49106..4421a67e818 100644
--- a/crates/vm/src/builtins/tuple.rs
+++ b/crates/vm/src/builtins/tuple.rs
@@ -4,7 +4,7 @@ use super::{
 };
 use crate::common::lock::LazyLock;
 use crate::common::{hash, hash::PyHash, lock::PyMutex, wtf8::wtf8_concat};
-use crate::object::{Traverse, TraverseFn};
+use crate::object::{PyTypedRefTarget, Traverse, TraverseFn};
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
     atomic_func,
@@ -15,7 +15,7 @@ use crate::{
     protocol::{PyIterReturn, PyMappingMethods, PyNumberMethods, PySequenceMethods},
     recursion::ReprGuard,
     sequence::{OptionalRangeArgs, SequenceExt},
-    sliceable::{SequenceIndex, SliceableSequenceOp},
+    sliceable::{NameTuple, SequenceIndex, SliceableSequenceOp},
     types::{
         AsMapping, AsNumber, AsSequence, Comparable, Constructor, Hashable, IterNext, Iterable,
         PyComparisonOp, Representable, SelfIter,
@@ -25,9 +25,12 @@ use crate::{
 };
 use alloc::fmt;
 use core::cell::{Cell, UnsafeCell};
+use core::marker::PhantomData;
+use core::mem::ManuallyDrop;
 use core::ptr::NonNull;
 
 #[pyclass(module = false, name = "tuple", traverse = "manual")]
+#[repr(transparent)]
 pub struct PyTuple<R = PyObjectRef> {
     elements: TupleElements<R>,
 }
@@ -35,30 +38,41 @@ pub struct PyTuple<R = PyObjectRef> {
 /// Tuple storage is immutable after publication, but marshal must publish a
 /// tuple in its reference table before recursively reading its children.
 /// This mirrors CPython's `PyTuple_New` followed by `PyTuple_SET_ITEM`.
-struct TupleElements<R>(UnsafeCell<Box<[R]>>);
+// Every allocation stores erased owners, including when borrowed through a
+// typed tuple view. The marker preserves the old storage's invariance and
+// ownership relationship to R.
+// Safe constructors and checked view conversions only admit R = PyRef<T>,
+// and establish each element's target invariant before publishing that view.
+#[repr(transparent)]
+struct TupleElements<R>(UnsafeCell<Box<[PyObjectRef]>>, PhantomData<UnsafeCell<R>>);
 
 unsafe impl<R: Send> Send for TupleElements<R> {}
 unsafe impl<R: Sync> Sync for TupleElements<R> {}
 
 impl<R> TupleElements<R> {
-    const fn new(elements: Box<[R]>) -> Self {
-        Self(UnsafeCell::new(elements))
+    fn as_slice(&self) -> &[R] {
+        // SAFETY: all admitted R are transparent PyRef owners with the same
+        // size/alignment as PyObjectRef. Their element invariants were proven
+        // by construction or checked conversion. Published elements cannot be
+        // replaced, and the returned shared slice borrows this storage.
+        let elements = unsafe { &*self.0.get() };
+        unsafe { core::slice::from_raw_parts(elements.as_ptr().cast(), elements.len()) }
     }
+}
 
-    fn as_slice(&self) -> &[R] {
-        // SAFETY: initialization writes happen only while the tuple is owned by
-        // the synchronous marshal decoder; afterwards the storage is immutable.
-        unsafe { &*self.0.get() }
+impl TupleElements<PyObjectRef> {
+    const fn new(elements: Box<[PyObjectRef]>) -> Self {
+        Self(UnsafeCell::new(elements), PhantomData)
     }
 
-    fn get_mut(&mut self) -> &mut Box<[R]> {
+    fn get_mut(&mut self) -> &mut Box<[PyObjectRef]> {
         self.0.get_mut()
     }
 
     /// # Safety
     /// The tuple must still be in its private initialization phase, and each
     /// placeholder index must be replaced at most once before it is observable.
-    unsafe fn set_initializing(&self, index: usize, value: R) {
+    unsafe fn set_initializing(&self, index: usize, value: PyObjectRef) {
         unsafe { (*self.0.get())[index] = value };
     }
 }
@@ -398,6 +412,38 @@ impl<R> Py<PyTuple<R>> {
 }
 
 impl Py<PyTuple> {
+    fn _getitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
+        match SequenceIndex::try_from_borrowed_object::<NameTuple>(vm, needle)? {
+            SequenceIndex::Int(i) => {
+                let index = self
+                    .elements
+                    .wrap_index(i)
+                    .ok_or_else(|| vm.new_index_error("tuple index out of range"))?;
+                Ok(self.elements[index].clone())
+            }
+            SequenceIndex::Slice(slice) => {
+                let len = self.as_slice().len();
+                let (range, step, slice_len) = slice.adjust_indices(len);
+                if slice_len != 0
+                    && range.start == 0
+                    && step == 1
+                    && slice_len == len
+                    && self.class().is(vm.ctx.types.tuple_type)
+                {
+                    Ok(self.to_owned().into())
+                } else {
+                    self.elements
+                        .getitem_by_slice(vm, slice)
+                        .map(|x| vm.ctx.new_tuple(x).into())
+                }
+            }
+        }
+    }
+
+    fn __getitem__(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
+        self._getitem(needle, vm)
+    }
+
     pub fn extract_tuple<'a, T: FromPyTuple<'a>>(&'a self, vm: &VirtualMachine) -> PyResult<T> {
         T::from_pytuple(self, vm)
     }
@@ -410,8 +456,14 @@ impl<T> PyTuple<PyRef<T>> {
     ) -> PyRef<Self> {
         // SAFETY: PyRef<T> has the same layout as PyObjectRef.
         unsafe {
-            let elements: Vec<PyObjectRef> =
-                core::mem::transmute::<Vec<PyRef<T>>, Vec<PyObjectRef>>(elements);
+            let mut elements = ManuallyDrop::new(elements);
+            // Preserve the buffer, length and capacity without assuming Vec's
+            // field order. Each transparent owner transfers its one reference.
+            let elements = Vec::from_raw_parts(
+                elements.as_mut_ptr().cast::<PyObjectRef>(),
+                elements.len(),
+                elements.capacity(),
+            );
             let tuple = PyRef::new_ref(
                 PyTuple::new_unchecked(elements.into_boxed_slice()),
                 tuple_type,
@@ -424,8 +476,14 @@ impl<T> PyTuple<PyRef<T>> {
     pub fn new_ref_typed(elements: Vec<PyRef<T>>, ctx: &Context) -> PyRef<Self> {
         // SAFETY: PyRef<T> has the same layout as PyObjectRef
         unsafe {
-            let elements: Vec<PyObjectRef> =
-                core::mem::transmute::<Vec<PyRef<T>>, Vec<PyObjectRef>>(elements);
+            let mut elements = ManuallyDrop::new(elements);
+            // Preserve the buffer, length and capacity without assuming Vec's
+            // field order. Each transparent owner transfers its one reference.
+            let elements = Vec::from_raw_parts(
+                elements.as_mut_ptr().cast::<PyObjectRef>(),
+                elements.len(),
+                elements.capacity(),
+            );
             let tuple = PyTuple::<PyObjectRef>::new_ref(elements, ctx);
             core::mem::transmute::<PyRef<PyTuple>, PyRef<Self>>(tuple)
         }
@@ -469,26 +527,6 @@ impl PyTuple {
         Self::repeat(zelf, value, vm)
     }
 
-    fn _getitem(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
-        match SequenceIndex::try_from_borrowed_object(vm, needle, "tuple")? {
-            SequenceIndex::Int(i) => {
-                let index = self
-                    .elements
-                    .wrap_index(i)
-                    .ok_or_else(|| vm.new_index_error("tuple index out of range"))?;
-                Ok(self.elements[index].clone())
-            }
-            SequenceIndex::Slice(slice) => self
-                .elements
-                .getitem_by_slice(vm, slice)
-                .map(|x| vm.ctx.new_tuple(x).into()),
-        }
-    }
-
-    fn __getitem__(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult {
-        self._getitem(needle, vm)
-    }
-
     fn _contains(&self, needle: &PyObject, vm: &VirtualMachine) -> PyResult<bool> {
         for element in &self.elements {
             if vm.identical_or_equal(element, needle)? {
@@ -565,9 +603,9 @@ impl AsMapping for PyTuple {
             length: atomic_func!(|mapping, _vm| {
                 Ok(PyTuple::mapping_downcast(mapping).as_slice().len())
             }),
-            subscript: atomic_func!(|mapping, needle, vm| PyTuple::mapping_downcast(mapping)
-                .payload
-                ._getitem(needle, vm)),
+            subscript: atomic_func!(
+                |mapping, needle, vm| PyTuple::mapping_downcast(mapping)._getitem(needle, vm)
+            ),
             ..PyMappingMethods::NOT_IMPLEMENTED
         });
         &AS_MAPPING
@@ -686,35 +724,42 @@ impl Representable for PyTuple {
 }
 
 impl PyRef<PyTuple<PyObjectRef>> {
-    pub fn try_into_typed<T: PyPayload>(
+    pub fn try_into_typed<T: PyTypedRefTarget>(
         self,
         vm: &VirtualMachine,
-    ) -> PyResult<PyRef<PyTuple<PyRef<T>>>> {
+    ) -> PyResult<PyRef<PyTuple<PyRef<T>>>>
+    where
+        PyRef<T>: TransmuteFromObject,
+    {
         // Check that all elements are of the correct type
         for elem in self.as_slice() {
             <PyRef<T> as TransmuteFromObject>::check(vm, elem)?;
         }
-        // SAFETY: We just verified all elements are of type T
+        // SAFETY: every element satisfies T's view invariant. Transparent
+        // tuple wrappers retain the same erased storage for every marker;
+        // this transfers the owner without changing its allocation or count.
         Ok(unsafe { core::mem::transmute::<Self, PyRef<PyTuple<PyRef<T>>>>(self) })
     }
 }
 
-impl<T: PyPayload> PyRef<PyTuple<PyRef<T>>> {
+impl<T: PyTypedRefTarget> PyRef<PyTuple<PyRef<T>>> {
     #[must_use]
     pub fn into_untyped(self) -> PyRef<PyTuple> {
-        // SAFETY: PyTuple<PyRef<T>> has the same layout as PyTuple
+        // SAFETY: transparent tuple wrappers have identical erased storage;
+        // forgetting the element guarantee does not change the allocation.
         unsafe { core::mem::transmute::<Self, PyRef<PyTuple>>(self) }
     }
 }
 
-impl<T: PyPayload> Py<PyTuple<PyRef<T>>> {
+impl<T: PyTypedRefTarget> Py<PyTuple<PyRef<T>>> {
     pub fn as_untyped(&self) -> &Py<PyTuple> {
-        // SAFETY: PyTuple<PyRef<T>> has the same layout as PyTuple
+        // SAFETY: transparent tuple wrappers have identical erased storage;
+        // forgetting the element guarantee does not change the allocation.
         unsafe { core::mem::transmute::<&Self, &Py<PyTuple>>(self) }
     }
 }
 
-impl<T: PyPayload> From<PyRef<PyTuple<PyRef<T>>>> for PyTupleRef {
+impl<T: PyTypedRefTarget> From<PyRef<PyTuple<PyRef<T>>>> for PyTupleRef {
     #[inline]
     fn from(tup: PyRef<PyTuple<PyRef<T>>>) -> Self {
         tup.into_untyped()
diff --git a/crates/vm/src/builtins/type.rs b/crates/vm/src/builtins/type.rs
index 3eb9c94df52..d7dca044bbe 100644
--- a/crates/vm/src/builtins/type.rs
+++ b/crates/vm/src/builtins/type.rs
@@ -1,6 +1,6 @@
 use super::{
-    PyClassMethod, PyDict, PyDictRef, PyList, PyStaticMethod, PyStr, PyStrInterned, PyStrRef,
-    PyTupleRef, PyUtf8StrRef, PyWeak, mappingproxy::PyMappingProxy, object, union_,
+    PyAnyDict, PyClassMethod, PyDict, PyDictRef, PyList, PyStaticMethod, PyStr, PyStrInterned,
+    PyStrRef, PyTupleRef, PyUtf8StrRef, PyWeak, mappingproxy::PyMappingProxy, object, union_,
 };
 use crate::{
     AsObject, Context, Py, PyAtomicRef, PyObject, PyObjectRef, PyPayload, PyRef, PyResult,
@@ -47,6 +47,32 @@ use std::collections::HashSet;
 
 pub(crate) type PyTypeTupleRef = PyRef<PyTuple<PyTypeRef>>;
 
+pub(crate) struct CommonTypeDescriptors {
+    dict: PyRef<super::PyGetSet>,
+    weakref: PyRef<super::PyGetSet>,
+}
+
+impl CommonTypeDescriptors {
+    pub(crate) fn new(ctx: &Context) -> Self {
+        // These descriptors operate on the instance's layout, not the class
+        // that first exposes them. Keeping object as their owner also lets an
+        // annotation closure retain a class namespace without retaining the class.
+        let dict = super::PyGetSet::new("__dict__", ctx.types.object_type, ctx)
+            .with_get(subtype_get_dict)
+            .with_set(subtype_set_dict)
+            .with_doc(ItemDoc::static_text("dictionary for instance variables"));
+        let weakref = super::PyGetSet::new("__weakref__", ctx.types.object_type, ctx)
+            .with_get(subtype_get_weakref)
+            .with_doc(ItemDoc::static_text(
+                "list of weak references to the object",
+            ));
+        Self {
+            dict: ctx.new_pyref(dict),
+            weakref: ctx.new_pyref(weakref),
+        }
+    }
+}
+
 #[pyclass(module = false, name = "type", traverse = "manual")]
 pub struct PyType {
     // tp_base. Written under the type lock (see `set_bases`); read lock-free.
@@ -176,6 +202,15 @@ impl TypeCacheEntry {
         self.sequence.load(Ordering::Relaxed) == previous
     }
 
+    #[inline]
+    fn matching_version(&self, type_version: &AtomicU32) -> Option<u32> {
+        let entry_version = self.version.load(Ordering::Acquire);
+        let type_version = type_version.load(Ordering::Acquire);
+        // Invalidation can clear both versions after the reader selected an
+        // entry. Zero never identifies a cached result, even when they match.
+        (entry_version != 0 && entry_version == type_version).then_some(entry_version)
+    }
+
     /// Null out the cached value pointer.
     /// Caller must ensure no concurrent reads can observe this entry
     /// (version should be set to 0 first).
@@ -844,10 +879,14 @@ impl PyType {
             }
         }
 
-        let mros = bases
+        let mut mros: Vec<_> = bases
             .iter()
             .map(|base| base.mro_map_collect(|t| t.to_owned()))
             .collect();
+        if bases.len() > 1 {
+            // C3 also merges the direct bases to preserve their local precedence.
+            mros.push(bases.to_vec());
+        }
         linearise_mro(mros)
     }
 
@@ -1272,11 +1311,10 @@ impl PyType {
             let name_ptr = name as *const _ as *mut _;
             loop {
                 let seq1 = entry.begin_read();
-                let entry_version = entry.version.load(Ordering::Acquire);
-                let type_version = self.tp_version_tag.load(Ordering::Acquire);
-                if entry_version != type_version
-                    || !core::ptr::eq(entry.name.load(Ordering::Relaxed), name_ptr)
-                {
+                let Some(entry_version) = entry.matching_version(&self.tp_version_tag) else {
+                    break;
+                };
+                if !core::ptr::eq(entry.name.load(Ordering::Relaxed), name_ptr) {
                     break;
                 }
                 let ptr = entry.value.load(Ordering::Acquire);
@@ -1488,9 +1526,7 @@ impl PyType {
             let name_ptr = name as *const _ as *mut _;
             loop {
                 let seq1 = entry.begin_read();
-                let v1 = entry.version.load(Ordering::Acquire);
-                let type_version = self.tp_version_tag.load(Ordering::Acquire);
-                if v1 != type_version
+                if entry.matching_version(&self.tp_version_tag).is_none()
                     || !core::ptr::eq(entry.name.load(Ordering::Relaxed), name_ptr)
                 {
                     break;
@@ -1798,25 +1834,15 @@ impl Constructor for PyType {
             }));
         }
 
-        let (name, bases, dict, kwargs): (PyStrRef, PyTupleRef, PyDictRef, KwArgs) =
+        let (name, bases, dict, kwargs): (PyStrRef, PyTupleRef, PyObjectRef, KwArgs) =
             args.clone().bind_for(vm, Self::NAME)?;
-
-        // A mapping that is not an exact dict (e.g. OrderedDict) keeps its
-        // own iteration order; copy via the mapping protocol so that order
-        // lands in the type dict.
-        let dict = if args.args[2].class().is(vm.ctx.types.dict_type) {
-            dict
-        } else {
-            let copied = vm.ctx.new_dict();
-            copied.merge_object(args.args[2].clone(), vm)?;
-            copied
+        let Some(dict) = PyAnyDict::from_object(&dict) else {
+            return Err(vm.new_type_error(format!(
+                "type.__new__() argument 3 must be dict or frozendict, not {}",
+                dict.class().fully_qualified_name(vm)?
+            )));
         };
 
-        if name.as_bytes().contains(&0) {
-            return Err(vm.new_value_error("type name must not contain null characters"));
-        }
-        let name = name.try_into_utf8(vm)?;
-
         let (metatype, base, bases, base_is_type) = if bases.as_slice().is_empty() {
             let base = vm.ctx.types.object_type.to_owned();
             let bases = PyTuple::new_ref_typed(vec![base.clone()], &vm.ctx);
@@ -1841,11 +1867,11 @@ impl Constructor for PyType {
             // Search the bases for the proper metatype to deal with this:
             let winner = calculate_meta_class(metatype.clone(), bases.as_slice(), vm)?;
             let metatype = if !winner.is(&metatype) {
-                if let Some(ref slot_new) = winner.slots.new.load() {
-                    // Pass it to the winner
-                    return slot_new(winner, args, vm);
-                }
-                winner
+                let slot_new = winner.slots.new.load().ok_or_else(|| {
+                    vm.new_type_error(format!("cannot create '{}' instances", winner.slot_name()))
+                })?;
+                // Pass it to the winner.
+                return slot_new(winner, args, vm);
             } else {
                 metatype
             };
@@ -1856,6 +1882,25 @@ impl Constructor for PyType {
             (metatype, base.to_owned(), bases, base_is_type)
         };
 
+        // Copy only after resolving the metaclass: its __new__ receives the
+        // original namespace. A subclass with a custom iterator (e.g.
+        // OrderedDict) keeps its own mapping order in the mutable type dict.
+        let dict = if let Some(dict) = dict.as_object().downcast_ref_if_exact::<PyDict>(vm) {
+            dict.to_owned()
+        } else {
+            let copied = vm.ctx.new_dict();
+            // Like dict.copy(), an empty table bypasses subclass hooks.
+            if !dict.is_empty() {
+                copied.merge_object(dict.to_owned().into(), vm)?;
+            }
+            copied
+        };
+
+        if name.as_bytes().contains(&0) {
+            return Err(vm.new_value_error("type name must not contain null characters"));
+        }
+        let name = name.try_into_utf8(vm)?;
+
         let qualname = dict
             .get_item_opt(identifier!(vm, __qualname__), vm)?
             .map(|obj| downcast_qualname(obj, vm))
@@ -1885,19 +1930,25 @@ impl Constructor for PyType {
         if let Some(f) = attributes.get_mut(identifier!(vm, __init_subclass__))
             && f.class().is(vm.ctx.types.function_type)
         {
-            *f = PyClassMethod::from(f.clone()).into_pyobject(vm);
+            let callable = f.clone();
+            *f = PyClassMethod::from(callable.clone()).into_pyobject(vm);
+            super::classmethod::functools_wraps(f, &callable, vm)?;
         }
 
         if let Some(f) = attributes.get_mut(identifier!(vm, __class_getitem__))
             && f.class().is(vm.ctx.types.function_type)
         {
-            *f = PyClassMethod::from(f.clone()).into_pyobject(vm);
+            let callable = f.clone();
+            *f = PyClassMethod::from(callable.clone()).into_pyobject(vm);
+            super::classmethod::functools_wraps(f, &callable, vm)?;
         }
 
         if let Some(f) = attributes.get_mut(identifier!(vm, __new__))
             && f.class().is(vm.ctx.types.function_type)
         {
-            *f = PyStaticMethod::from(f.clone()).into_pyobject(vm);
+            let callable = f.clone();
+            *f = PyStaticMethod::from(callable.clone()).into_pyobject(vm);
+            super::classmethod::functools_wraps(f, &callable, vm)?;
         }
 
         if let Some(globals) = crate::frame::current_globals() {
@@ -1949,16 +2000,6 @@ impl Constructor for PyType {
                 tuple.try_into_typed(vm)?
             };
 
-            // Any nonempty __slots__ is rejected when the base has a variable
-            // item size, including a tuple of only `__dict__` or `__weakref__`.
-            // Types like weakref.ref have itemsize 0 and do allow slots.
-            if !slots.as_slice().is_empty() && base.slots.itemsize > 0 {
-                return Err(vm.new_type_error(format!(
-                    "nonempty __slots__ not supported for subtype of '{}'",
-                    base.name()
-                )));
-            }
-
             // Validate slot names and track duplicates
             let mut seen_dict = false;
             let mut seen_weakref = false;
@@ -2030,6 +2071,19 @@ impl Constructor for PyType {
                 .cloned()
                 .collect();
             filtered.sort_by(|a, b| a.as_bytes().cmp(b.as_bytes()));
+            // CPython 3.15 permits named slots on tuple subclasses. Our
+            // member cells live in the object prefix, independently of the
+            // tuple's elements. Other variable-size bases still only accept
+            // the managed __dict__ and __weakref__ slots filtered above.
+            if !filtered.is_empty()
+                && base.slots.itemsize > 0
+                && !base.fast_issubclass(vm.ctx.types.tuple_type)
+            {
+                return Err(vm.new_type_error(format!(
+                    "arbitrary __slots__ not supported for subtype of '{}'",
+                    base.name()
+                )));
+            }
             let filtered_slots = PyTuple::new_ref_typed(filtered, &vm.ctx);
 
             (Some(filtered_slots), has_dict, add_weakref)
@@ -2197,7 +2251,7 @@ impl Constructor for PyType {
         // Also, type subclasses don't need their own __dict__ descriptor
         // since they inherit it from type
 
-        // Add __dict__ descriptor after type creation to ensure correct __objclass__
+        // Share the interpreter's object-owned __dict__ descriptor.
         // Only add if:
         // 1. base is not type (type subclasses inherit __dict__ from type)
         // 2. the class has HAS_DICT flag (i.e., __slots__ was not defined or __dict__ is in __slots__)
@@ -2210,12 +2264,10 @@ impl Constructor for PyType {
                 .iter()
                 .any(|base| base.attributes.contains(__dict__));
             if !typ.attributes.contains(__dict__) && !has_inherited_dict {
-                let getset = super::PyGetSet::new("__dict__", &typ, &vm.ctx)
-                    .with_get(subtype_get_dict)
-                    .with_set(subtype_set_dict)
-                    .with_doc(ItemDoc::static_text("dictionary for instance variables"));
-                let descriptor = PyRef::new_ref(getset, vm.ctx.types.getset_type.to_owned(), None);
-                typ.attributes.set(__dict__, descriptor.into());
+                typ.attributes.set(
+                    __dict__,
+                    vm.state.common_type_descriptors.dict.clone().into(),
+                );
             }
         }
 
@@ -2228,14 +2280,10 @@ impl Constructor for PyType {
                 .iter()
                 .any(|base| base.attributes.contains(__weakref__));
             if !typ.attributes.contains(__weakref__) && !has_inherited_weakref {
-                let getset = super::PyGetSet::new("__weakref__", &typ, &vm.ctx)
-                    .with_get(subtype_get_weakref)
-                    .with_set(subtype_set_weakref)
-                    .with_doc(ItemDoc::static_text(
-                        "list of weak references to the object",
-                    ));
-                let descriptor = PyRef::new_ref(getset, vm.ctx.types.getset_type.to_owned(), None);
-                typ.attributes.set(__weakref__, descriptor.into());
+                typ.attributes.set(
+                    __weakref__,
+                    vm.state.common_type_descriptors.weakref.clone().into(),
+                );
             }
         }
 
@@ -2463,8 +2511,8 @@ impl Py<PyType> {
         // Similar to CPython's type_set_doc
         let value = value.ok_or_else(|| {
             vm.new_type_error(format!(
-                "cannot delete '__doc__' attribute of immutable type '{}'",
-                self.name()
+                "cannot delete '__doc__' attribute of type '{}'",
+                self.slot_name()
             ))
         })?;
 
@@ -2520,15 +2568,23 @@ impl Py<PyType> {
         PyType::with_type_lock(vm, || self.bases.read().clone().into_untyped())
     }
     #[pygetset(setter, name = "__bases__")]
-    fn set_bases(zelf: &Self, bases_tuple: PyTupleRef, vm: &VirtualMachine) -> PyResult<()> {
+    fn set_bases(zelf: &Self, value: PySetterValue, vm: &VirtualMachine) -> PyResult<()> {
         // TODO: Assigning to __bases__ is only used in typing.NamedTupleMeta.__new__
         // Rather than correctly re-initializing the class, we are skipping a few steps for now
-        if zelf.slots().flags.has_feature(PyTypeFlags::IMMUTABLETYPE) {
-            return Err(vm.new_type_error(format!(
-                "cannot set '__bases__' attribute of immutable type '{}'",
-                zelf.name()
-            )));
-        }
+        let value = value.ok_or_else(|| {
+            vm.new_type_error(format!(
+                "cannot delete '__bases__' attribute of type '{}'",
+                zelf.slot_name()
+            ))
+        })?;
+        zelf.check_set_special_type_attr(identifier!(vm, __bases__), vm)?;
+        let bases_tuple = value.downcast::<PyTuple>().map_err(|value| {
+            vm.new_type_error(format!(
+                "can only assign tuple to {}.__bases__, not {}",
+                zelf.slot_name(),
+                value.class().slot_name()
+            ))
+        })?;
         if bases_tuple.as_slice().is_empty() {
             return Err(vm.new_type_error(format!(
                 "can only assign non-empty tuple to {}.__bases__, not ()",
@@ -2553,11 +2609,7 @@ impl Py<PyType> {
 
         // Reject reparenting onto a base whose instances have an incompatible
         // object layout.
-        let old_base_owned = zelf.base.load_owned();
-        let old_base = old_base_owned
-            .as_deref()
-            .unwrap_or(vm.ctx.types.object_type);
-        compatible_for_assignment(old_base, &new_base, "__bases__", vm)?;
+        compatible_for_assignment(zelf, &new_base, "__bases__", false, vm)?;
 
         // References released inside the critical section are collected here
         // and dropped after the lock: dropping them inside can run arbitrary
@@ -2850,20 +2902,22 @@ impl Py<PyType> {
             return Err(vm.new_type_error("__annotate__ must be callable or None"));
         }
 
-        let _prev_values = PyType::with_type_lock(vm, || {
+        let clear_annotations = !vm.is_none(&value);
+        let old_annotate = PyType::with_type_lock(vm, || {
             self.modified_inner();
-            // Clear cached annotations only when setting to a new callable
-            let removed = if !vm.is_none(&value) {
+            self.attributes
+                .insert(identifier!(vm, __annotate_func__), value)
+        });
+        drop(old_annotate);
+        // Clear cached annotations only when setting to a new callable.
+        if clear_annotations {
+            let old_annotations = PyType::with_type_lock(vm, || {
+                self.modified_inner();
                 self.attributes
                     .remove(identifier!(vm, __annotations_cache__))
-            } else {
-                None
-            };
-            let prev = self
-                .attributes
-                .insert(identifier!(vm, __annotate_func__), value);
-            (removed, prev)
-        });
+            });
+            drop(old_annotations);
+        }
 
         Ok(())
     }
@@ -2912,10 +2966,10 @@ impl Py<PyType> {
         let annotations = if annotate.is_callable() {
             // Call __annotate__(1) where 1 is FORMAT_VALUE
             let result = annotate.call((1i32,), vm)?;
-            if !result.class().is(vm.ctx.types.dict_type) {
+            if !result.downcastable::<PyDict>() {
                 return Err(vm.new_type_error(format!(
-                    "__annotate__ returned non-dict of type '{}'",
-                    result.class().name()
+                    "__annotate__() must return a dict, not {}",
+                    result.class().fully_qualified_name(vm)?
                 )));
             }
             result
@@ -2923,22 +2977,14 @@ impl Py<PyType> {
             vm.ctx.new_dict().into()
         };
 
-        let (result, _prev) = PyType::with_type_lock(vm, || {
-            if let Some(existing) = self.attributes.get(annotations_key)
-                && !existing.class().is(vm.ctx.types.getset_type)
-            {
-                return (existing, None);
-            }
-            if let Some(existing) = self.attributes.get(annotations_cache_key) {
-                return (existing, None);
-            }
+        drop(annotate);
+        let old_annotations = PyType::with_type_lock(vm, || {
             self.modified_inner();
-            let prev = self
-                .attributes
-                .insert(annotations_cache_key, annotations.clone());
-            (annotations, prev)
+            self.attributes
+                .insert(annotations_cache_key, annotations.clone())
         });
-        Ok(result)
+        drop(old_annotations);
+        Ok(annotations)
     }
 
     #[pygetset(setter)]
@@ -2954,49 +3000,43 @@ impl Py<PyType> {
             )));
         }
 
-        let _prev_values = PyType::with_type_lock(vm, || {
+        let deleting = matches!(&value, PySetterValue::Delete);
+        let (has_annotations, old_annotations) = PyType::with_type_lock(vm, || {
             self.modified_inner();
             let has_annotations = self.attributes.contains(identifier!(vm, __annotations__));
-
-            let mut prev = Vec::new();
-            match value {
-                crate::function::PySetterValue::Assign(value) => {
-                    let key = if has_annotations {
-                        identifier!(vm, __annotations__)
-                    } else {
-                        identifier!(vm, __annotations_cache__)
-                    };
-                    prev.extend(self.attributes.insert(key, value));
-                    if has_annotations {
-                        prev.extend(
-                            self.attributes
-                                .remove(identifier!(vm, __annotations_cache__)),
-                        );
-                    }
-                }
-                crate::function::PySetterValue::Delete => {
-                    let removed = if has_annotations {
-                        self.attributes.remove(identifier!(vm, __annotations__))
-                    } else {
-                        self.attributes
-                            .remove(identifier!(vm, __annotations_cache__))
-                    };
-                    if removed.is_none() {
-                        return Err(vm.new_attribute_error("__annotations__"));
-                    }
-                    prev.extend(removed);
-                    if has_annotations {
-                        prev.extend(
-                            self.attributes
-                                .remove(identifier!(vm, __annotations_cache__)),
-                        );
-                    }
-                }
-            }
-            prev.extend(self.attributes.remove(identifier!(vm, __annotate_func__)));
-            prev.extend(self.attributes.remove(identifier!(vm, __annotate__)));
-            Ok(prev)
-        })?;
+            let key = if has_annotations {
+                identifier!(vm, __annotations__)
+            } else {
+                identifier!(vm, __annotations_cache__)
+            };
+            let old_annotations = match value {
+                crate::function::PySetterValue::Assign(value) => self.attributes.insert(key, value),
+                crate::function::PySetterValue::Delete => self.attributes.remove(key),
+            };
+            (has_annotations, old_annotations)
+        });
+        if deleting && old_annotations.is_none() {
+            return Err(vm.new_attribute_error("__annotations__"));
+        }
+        drop(old_annotations);
+        if has_annotations {
+            let old_cache = PyType::with_type_lock(vm, || {
+                self.modified_inner();
+                self.attributes
+                    .remove(identifier!(vm, __annotations_cache__))
+            });
+            drop(old_cache);
+        }
+        for key in [
+            identifier!(vm, __annotate_func__),
+            identifier!(vm, __annotate__),
+        ] {
+            let old_annotate = PyType::with_type_lock(vm, || {
+                self.modified_inner();
+                self.attributes.remove(key)
+            });
+            drop(old_annotate);
+        }
 
         Ok(())
     }
@@ -3174,11 +3214,17 @@ impl SetAttr for PyType {
             } else {
                 let prev_value = zelf.attributes().remove(attr_name);
                 if prev_value.is_none() {
-                    return Err(vm.new_attribute_error(format!(
+                    let exc = vm.new_attribute_error(format!(
                         "type object '{}' has no attribute '{}'",
                         zelf.name(),
                         attr_name,
-                    )));
+                    ));
+                    vm.set_attribute_error_context(
+                        &exc,
+                        zelf.to_owned().into(),
+                        attr_name.to_owned(),
+                    );
+                    return Err(exc);
                 }
                 prev_value
             };
@@ -3369,18 +3415,18 @@ fn subtype_set_dict(obj: PyObjectRef, value: PySetterValue, vm: &VirtualMachine)
 }
 
 // subtype_get_weakref
-fn subtype_get_weakref(obj: PyObjectRef, vm: &VirtualMachine) -> PyObjectRef {
+fn subtype_get_weakref(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+    if !obj
+        .class()
+        .slots
+        .flags
+        .has_feature(PyTypeFlags::HAS_WEAKREF)
+    {
+        return Err(vm.new_attribute_error("This object has no __weakref__"));
+    }
     // Return the first weakref in the weakref list, or None
     let weakref = obj.get_weakrefs();
-    weakref.unwrap_or_else(|| vm.ctx.none())
-}
-
-// subtype_set_weakref: __weakref__ is read-only
-fn subtype_set_weakref(obj: PyObjectRef, _value: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
-    Err(vm.new_attribute_error(format!(
-        "attribute '__weakref__' of '{}' objects is not writable",
-        obj.class().name()
-    )))
+    Ok(weakref.unwrap_or_else(|| vm.ctx.none()))
 }
 
 /*
@@ -3518,24 +3564,6 @@ fn take_next_base(bases: &mut [Vec<PyTypeRef>]) -> Option<PyTypeRef> {
 
 fn linearise_mro(mut bases: Vec<Vec<PyTypeRef>>) -> Result<Vec<PyTypeRef>, String> {
     vm_trace!("Linearise MRO: {:?}", bases);
-    // Python requires that the class direct bases are kept in the same order.
-    // This is called local precedence ordering.
-    // This means we must verify that for classes A(), B(A) we must reject C(A, B) even though this
-    // algorithm will allow the mro ordering of [C, B, A, object].
-    // To verify this, we make sure non of the direct bases are in the mro of bases after them.
-    for (i, base_mro) in bases.iter().enumerate() {
-        let base = &base_mro[0]; // MROs cannot be empty.
-        for later_mro in &bases[i + 1..] {
-            // We start at index 1 to skip direct bases.
-            // This will not catch duplicate bases, but such a thing is already tested for.
-            if later_mro[1..].iter().any(|cls| cls.is(base)) {
-                return Err(format!(
-                    "Cannot create a consistent method resolution order (MRO) for bases {}",
-                    bases.iter().map(|x| x.first().unwrap()).format(", ")
-                ));
-            }
-        }
-    }
 
     let mut result = vec![];
     while !bases.is_empty() {
@@ -3544,7 +3572,11 @@ fn linearise_mro(mut bases: Vec<Vec<PyTypeRef>>) -> Result<Vec<PyTypeRef>, Strin
             // Because this failed, we assume the lists cannot be empty.
             format!(
                 "Cannot create a consistent method resolution order (MRO) for bases {}",
-                bases.iter().map(|x| x.first().unwrap()).format(", ")
+                bases
+                    .iter()
+                    .map(|x| x.first().unwrap())
+                    .unique_by(|x| x.get_id())
+                    .format(", ")
             )
         })?;
 
@@ -3677,7 +3709,11 @@ fn mro_internal(typ: &Py<PyType>, vm: &VirtualMachine) -> PyResult<i32> {
 
 /// Returns true if the two types have different instance layouts.
 fn shape_differs(t1: &Py<PyType>, t2: &Py<PyType>) -> bool {
-    t1.slots.basicsize != t2.slots.basicsize || t1.slots.itemsize != t2.slots.itemsize
+    // Prefix member cells do not change basicsize, but still make a base
+    // solid: unrelated slotted bases cannot share the same member indexes.
+    t1.slots.basicsize != t2.slots.basicsize
+        || t1.slots.itemsize != t2.slots.itemsize
+        || t1.slots.member_count != t2.slots.member_count
 }
 
 fn solid_base<'a>(typ: &'a Py<PyType>, vm: &VirtualMachine) -> &'a Py<PyType> {
@@ -3735,20 +3771,21 @@ fn type_has_weakref(typ: &Py<PyType>) -> bool {
 
 /// Returns true if `child` adds no instance layout of its own beyond its base,
 /// so the base can stand in for it when comparing object layouts.
-fn compatible_with_base(child: &Py<PyType>) -> bool {
+fn compatible_with_base(child: &Py<PyType>, set_class: bool) -> bool {
     let Some(parent) = child.base.deref() else {
         return false;
     };
     child.slots.basicsize == parent.slots.basicsize
         && child.slots.itemsize == parent.slots.itemsize
         && child.slots.member_count == parent.slots.member_count
-        && type_has_dict(child) == type_has_dict(parent)
-        && type_has_weakref(child) == type_has_weakref(parent)
+        && (!set_class
+            || (type_has_dict(child) == type_has_dict(parent)
+                && type_has_weakref(child) == type_has_weakref(parent)))
 }
 
 /// Walk up to the most derived base that actually fixes the instance layout.
-fn layout_solid_base(mut typ: &Py<PyType>) -> &Py<PyType> {
-    while compatible_with_base(typ) {
+fn layout_solid_base(mut typ: &Py<PyType>, set_class: bool) -> &Py<PyType> {
+    while compatible_with_base(typ, set_class) {
         typ = typ.base.deref().unwrap();
     }
     typ
@@ -3756,12 +3793,12 @@ fn layout_solid_base(mut typ: &Py<PyType>) -> &Py<PyType> {
 
 /// Returns true if `a` and `b`, which share the same base, added the same
 /// instance layout (`__dict__`, `__weakref__`, and `__slots__`).
-fn same_slots_added(a: &Py<PyType>, b: &Py<PyType>) -> bool {
+fn same_slots_added(a: &Py<PyType>, b: &Py<PyType>, set_class: bool) -> bool {
     if a.slots.basicsize != b.slots.basicsize
         || a.slots.itemsize != b.slots.itemsize
         || a.slots.member_count != b.slots.member_count
-        || type_has_dict(a) != type_has_dict(b)
-        || type_has_weakref(a) != type_has_weakref(b)
+        || (set_class
+            && (type_has_dict(a) != type_has_dict(b) || type_has_weakref(a) != type_has_weakref(b)))
     {
         return false;
     }
@@ -3780,25 +3817,44 @@ fn same_slots_added(a: &Py<PyType>, b: &Py<PyType>) -> bool {
     }
 }
 
-/// Validates that instances of `old_to` and `new_to` share an interchangeable
-/// object layout, the check `__class__` and `__bases__` assignment perform.
+/// Validates the layout for `__class__` or `__bases__` assignment. For a base
+/// change, `original` is the existing class whose allocation must remain valid.
 ///
 /// `attr` names the attribute being assigned for the error message; the
-/// message reports `new_to` first and `old_to` second.
+/// message reports the new type first and the replaced type or base second.
 pub(crate) fn compatible_for_assignment(
-    old_to: &Py<PyType>,
+    original: &Py<PyType>,
     new_to: &Py<PyType>,
     attr: &str,
+    set_class: bool,
     vm: &VirtualMachine,
 ) -> PyResult<()> {
-    let newbase = layout_solid_base(new_to);
-    let oldbase = layout_solid_base(old_to);
+    let old_base = if set_class {
+        None
+    } else {
+        original.base.load_owned()
+    };
+    let old_to = old_base.as_deref().unwrap_or(original);
+    // Reparenting leaves the class's prefix allocation unchanged. A new base
+    // may use its existing dict/weakref storage, but cannot require storage
+    // the class never allocated. Payload size and member slots are checked
+    // separately against the old base, not against the class's own additions.
+    let storage_compatible = set_class
+        || ((!type_has_dict(new_to) || type_has_dict(original))
+            && (!type_has_weakref(new_to) || type_has_weakref(original)));
+    let newbase = layout_solid_base(new_to, set_class);
+    let oldbase = layout_solid_base(old_to, set_class);
     let bases_equal = match (newbase.base.deref(), oldbase.base.deref()) {
         (Some(x), Some(y)) => x.is(y),
         (None, None) => true,
         _ => false,
     };
-    let compatible = newbase.is(oldbase) || (bases_equal && same_slots_added(newbase, oldbase));
+    let compatible = storage_compatible
+        && (newbase.is(oldbase)
+            || (bases_equal
+                && (set_class
+                    || (newbase.heaptype_ext.is_some() && oldbase.heaptype_ext.is_some()))
+                && same_slots_added(newbase, oldbase, set_class)));
     if compatible {
         return Ok(());
     }
@@ -3825,6 +3881,32 @@ fn mangle_name(class_name: &str, name: &str) -> String {
 mod tests {
     use super::*;
 
+    #[test]
+    fn type_cache_rejects_invalidated_versions() {
+        let entry = TypeCacheEntry::new();
+        let type_version = AtomicU32::new(1);
+        assert_eq!(entry.matching_version(&type_version), None);
+
+        entry.version.store(1, Ordering::Release);
+        // A valid negative cache entry has a null value and a nonzero version.
+        assert!(entry.value.load(Ordering::Acquire).is_null());
+        assert_eq!(entry.matching_version(&type_version), Some(1));
+
+        type_version.store(2, Ordering::Release);
+        assert_eq!(entry.matching_version(&type_version), None);
+
+        // Model invalidation after a reader has selected the cache entry.
+        type_version.store(0, Ordering::Release);
+        assert_eq!(entry.matching_version(&type_version), None);
+        entry.begin_write();
+        entry.version.store(0, Ordering::Release);
+        entry.clear_value();
+        entry.end_write();
+        let sequence = entry.begin_read();
+        assert_eq!(entry.matching_version(&type_version), None);
+        assert!(entry.end_read(sequence));
+    }
+
     fn map_ids(obj: Result<Vec<PyTypeRef>, String>) -> Result<Vec<usize>, String> {
         Ok(obj?.into_iter().map(|x| x.get_id()).collect())
     }
diff --git a/crates/vm/src/builtins/union.rs b/crates/vm/src/builtins/union.rs
index 83ea3bb54b3..8a3711fb29b 100644
--- a/crates/vm/src/builtins/union.rs
+++ b/crates/vm/src/builtins/union.rs
@@ -1,5 +1,5 @@
 use super::{genericalias, type_};
-use crate::common::lock::LazyLock;
+use crate::common::lock::{LazyLock, PyMutex};
 use crate::{
     AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
     atomic_func,
@@ -24,7 +24,7 @@ pub struct PyUnion {
     hashable_args: Option<PyRef<PyFrozenSet>>,
     /// Tuple of initially unhashable args, or None if all args were hashable
     unhashable_args: Option<PyTupleRef>,
-    parameters: PyTupleRef,
+    parameters: PyMutex<Option<PyTupleRef>>,
 }
 
 impl fmt::Debug for PyUnion {
@@ -42,14 +42,13 @@ impl PyPayload for PyUnion {
 
 impl PyUnion {
     /// Create a new union from dedup result (internal use)
-    fn from_components(result: UnionComponents, vm: &VirtualMachine) -> PyResult<Self> {
-        let parameters = make_parameters(&result.args, vm)?;
-        Ok(Self {
+    fn from_components(result: UnionComponents) -> Self {
+        Self {
             args: result.args,
             hashable_args: result.hashable_args,
             unhashable_args: result.unhashable_args,
-            parameters,
-        })
+            parameters: PyMutex::new(None),
+        }
     }
 
     /// Direct access to args field (_Py_union_args)
@@ -127,8 +126,8 @@ impl Py<PyUnion> {
     }
 
     #[pygetset]
-    fn __parameters__(&self) -> PyObjectRef {
-        self.parameters.clone().into()
+    fn __parameters__(&self, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
+        genericalias::cached_parameters(&self.parameters, &self.args, vm)
     }
 
     #[pymethod]
@@ -202,6 +201,7 @@ impl Py<PyUnion> {
 fn is_unionable(obj: &PyObject, vm: &VirtualMachine) -> bool {
     let cls = obj.class();
     cls.is(vm.ctx.types.none_type)
+        || cls.is(vm.ctx.types.sentinel_type)
         || obj.downcastable::<PyType>()
         || cls.fast_issubclass(vm.ctx.types.generic_alias_type)
         || cls.is(vm.ctx.types.union_type)
@@ -238,12 +238,6 @@ pub(crate) fn or_op(zelf: PyObjectRef, other: PyObjectRef, vm: &VirtualMachine)
     make_union(&tuple, vm)
 }
 
-fn make_parameters(args: &Py<PyTuple>, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
-    let parameters = genericalias::make_parameters(args, vm)?;
-    let result = dedup_and_flatten_args(&parameters, vm)?;
-    Ok(result.args)
-}
-
 fn flatten_args(args: &Py<PyTuple>, vm: &VirtualMachine) -> PyTupleRef {
     let mut total_args = 0;
     for arg in args {
@@ -371,19 +365,15 @@ pub fn make_union(args: &Py<PyTuple>, vm: &VirtualMachine) -> PyResult {
     let result = dedup_and_flatten_args(args, vm)?;
     Ok(match result.args.as_slice().len() {
         1 => result.args.as_slice()[0].to_owned(),
-        _ => PyUnion::from_components(result, vm)?.to_pyobject(vm),
+        _ => PyUnion::from_components(result).to_pyobject(vm),
     })
 }
 
 impl PyUnion {
     fn getitem(zelf: &Py<Self>, needle: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        let new_args = genericalias::subs_parameters(
-            zelf.as_object(),
-            &zelf.args,
-            &zelf.parameters,
-            needle,
-            vm,
-        )?;
+        let parameters = genericalias::cached_parameters(&zelf.parameters, &zelf.args, vm)?;
+        let new_args =
+            genericalias::subs_parameters(zelf.as_object(), &zelf.args, &parameters, needle, vm)?;
 
         Ok(if new_args.as_slice().is_empty() {
             make_union(&new_args, vm)?
diff --git a/crates/vm/src/builtins/weakref.rs b/crates/vm/src/builtins/weakref.rs
index 135db6866cb..c934dc85413 100644
--- a/crates/vm/src/builtins/weakref.rs
+++ b/crates/vm/src/builtins/weakref.rs
@@ -24,6 +24,9 @@ pub struct WeakNewArgs {
 }
 
 impl PyPayload for PyWeak {
+    // WeakRefList::add tracks only after linking and publishing the referent.
+    const NEW_REF_UNTRACKED: bool = true;
+
     #[inline]
     fn class(ctx: &Context) -> &'static Py<PyType> {
         ctx.types.weakref_type
diff --git a/crates/vm/src/bytes_inner.rs b/crates/vm/src/bytes_inner.rs
index f38b4dbd408..079d9a0518f 100644
--- a/crates/vm/src/bytes_inner.rs
+++ b/crates/vm/src/bytes_inner.rs
@@ -10,7 +10,7 @@ use crate::{
     cformat::cformat_bytes,
     common::wtf8::is_py_ascii_whitespace,
     common::{borrow::BorrowedValue, hash},
-    function::{ArgIterable, Either, OptionalArg, PyComparisonValue},
+    function::{ArgIndex, ArgIterable, Either, OptionalArg, PyComparisonValue},
     literal::escape::Escape,
     protocol::{BufferFlags, PyBuffer},
     sequence::{SequenceExt, SequenceMutExt},
@@ -21,6 +21,7 @@ use crate::{
 /// [`crate::byte::bytearray_from_object`].
 pub(crate) type FromObject = fn(&VirtualMachine, &PyObject) -> PyResult<Vec<u8>>;
 
+use alloc::borrow::Cow;
 use bstr::ByteSlice;
 use itertools::Itertools;
 use malachite_bigint::BigInt;
@@ -225,12 +226,24 @@ impl ByteInnerNewOptions {
     /// read: `bytes()` and `bytearray()` differ in whether they ask it how long
     /// it is.
     pub fn get_inner(self, from_object: FromObject, vm: &VirtualMachine) -> PyResult<PyBytesInner> {
-        match (self.source, self.encoding, self.errors) {
+        self.get_inner_with_zero_count(from_object, vm)
+            .map(|(inner, _)| inner)
+    }
+
+    pub(crate) fn get_inner_with_zero_count(
+        self,
+        from_object: FromObject,
+        vm: &VirtualMachine,
+    ) -> PyResult<(PyBytesInner, bool)> {
+        let mut zero_count = false;
+        let inner = match (self.source, self.encoding, self.errors) {
             (OptionalArg::Present(obj), OptionalArg::Missing, OptionalArg::Missing) => {
                 // Try __index__ first to handle int-like objects that might raise custom exceptions
                 if let Some(index_result) = obj.try_index_opt(vm) {
                     match index_result {
-                        Ok(index) => Self::get_value_from_size(&index, vm),
+                        Ok(index) => Self::get_value_from_size(&index, vm).inspect(|inner| {
+                            zero_count = inner.elements.is_empty();
+                        }),
                         Err(e) => {
                             // Only propagate non-TypeError exceptions
                             // TypeError means the object doesn't support __index__, so fall back
@@ -266,7 +279,8 @@ impl ByteInnerNewOptions {
             (OptionalArg::Present(_), OptionalArg::Missing, OptionalArg::Present(_)) => {
                 Err(vm.new_type_error(STRING_WITHOUT_ENCODING.to_owned()))
             }
-        }
+        }?;
+        Ok((inner, zero_count))
     }
 }
 
@@ -302,7 +316,7 @@ impl ByteInnerSub {
         }
     }
 
-    fn into_vec(self, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+    pub(crate) fn into_vec(self, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
         Ok(match self {
             Self::Buffer(buffer) => buffer.elements,
             Self::Byte(int) => vec![int.as_bigint().byte_or(vm)?],
@@ -313,21 +327,36 @@ impl ByteInnerSub {
 #[derive(FromArgs)]
 pub struct ByteInnerFindOptions {
     #[pyarg(positional)]
-    sub: ByteInnerSub,
+    sub: PyObjectRef,
     #[pyarg(positional, default)]
-    start: Option<PyIntRef>,
+    start: Option<ArgIndex>,
     #[pyarg(positional, default)]
-    end: Option<PyIntRef>,
+    end: Option<ArgIndex>,
 }
 
 impl ByteInnerFindOptions {
+    pub(crate) fn parts(&self, len: usize) -> (&PyObject, core::ops::Range<usize>) {
+        let range = anystr::adjust_indices(
+            self.start.as_ref().map(AsRef::as_ref),
+            self.end.as_ref().map(AsRef::as_ref),
+            len,
+        );
+        (&self.sub, range)
+    }
+
     pub fn get_value(
         self,
         len: usize,
         vm: &VirtualMachine,
     ) -> PyResult<(Vec<u8>, core::ops::Range<usize>)> {
-        let sub = self.sub.into_vec(vm)?;
-        let range = anystr::adjust_indices(self.start.as_deref(), self.end.as_deref(), len);
+        let range = anystr::adjust_indices(
+            self.start.as_ref().map(AsRef::as_ref),
+            self.end.as_ref().map(AsRef::as_ref),
+            len,
+        );
+        // The needle is converted after the slice indices, and only here, so
+        // that a caller can guard its buffer while the conversion runs Python.
+        let sub = ByteInnerSub::try_from_object(vm, self.sub)?.into_vec(vm)?;
         Ok((sub, range))
     }
 }
@@ -341,7 +370,7 @@ pub struct ByteInnerPaddingOptions {
 }
 
 impl ByteInnerPaddingOptions {
-    fn get_value(self, fn_name: &str, vm: &VirtualMachine) -> PyResult<(isize, u8)> {
+    pub(crate) fn get_value(self, fn_name: &str, vm: &VirtualMachine) -> PyResult<(isize, u8)> {
         let fillchar = {
             let v = self.fillchar;
             try_as_bytes(v.clone(), |bytes| bytes.iter().copied().exactly_one().ok())
@@ -362,9 +391,9 @@ impl ByteInnerPaddingOptions {
 #[derive(FromArgs)]
 pub struct ByteInnerTranslateOptions {
     #[pyarg(positional)]
-    table: Option<PyObjectRef>,
+    pub(crate) table: Option<PyObjectRef>,
     #[pyarg(any, default = b"")]
-    delete: PyObjectRef,
+    pub(crate) delete: PyObjectRef,
 }
 
 impl ByteInnerTranslateOptions {
@@ -391,17 +420,24 @@ impl ByteInnerTranslateOptions {
 
 pub(crate) type ByteInnerSplitOptions = anystr::SplitArgs<PyBytesInner>;
 
-fn bytearray_repr_char_len(ch: u8) -> usize {
+fn bytearray_repr_char_len(ch: u8, quote: u8) -> usize {
+    if ch == quote {
+        return 2;
+    }
     match ch {
-        b'\'' | b'\\' | b'\t' | b'\r' | b'\n' => 2,
+        b'\\' | b'\t' | b'\r' | b'\n' => 2,
         0x20..=0x7e => 1,
         _ => 4, // \xHH
     }
 }
 
-fn write_bytearray_repr_char(ch: u8, buf: &mut String) {
+fn write_bytearray_repr_char(ch: u8, quote: u8, buf: &mut String) {
+    if ch == quote {
+        buf.push('\\');
+        buf.push(ch as char);
+        return;
+    }
     match ch {
-        b'\'' => buf.push_str(r#"\'"#),
         b'\\' => buf.push_str(r#"\\"#),
         b'\t' => buf.push_str(r#"\t"#),
         b'\n' => buf.push_str(r#"\n"#),
@@ -449,7 +485,7 @@ impl PyBytesInner {
             .elements
             .iter()
             .try_fold(0usize, |len, &ch| {
-                len.checked_add(bytearray_repr_char_len(ch))
+                len.checked_add(bytearray_repr_char_len(ch, quote as u8))
             })
             .ok_or_else(|| Self::new_repr_overflow_error(vm))?;
         let len = class_name
@@ -463,7 +499,7 @@ impl PyBytesInner {
         buf.push('b');
         buf.push(quote);
         for &ch in &self.elements {
-            write_bytearray_repr_char(ch, &mut buf);
+            write_bytearray_repr_char(ch, quote as u8, &mut buf);
         }
         buf.push(quote);
         buf.push(')');
@@ -702,6 +738,16 @@ impl PyBytesInner {
         vm: &VirtualMachine,
     ) -> PyResult<Vec<u8>> {
         let (width, fillchar) = options.get_value("center", vm)?;
+        self.pad_with(width, fillchar, pad, vm)
+    }
+
+    pub(crate) fn pad_with(
+        &self,
+        width: isize,
+        fillchar: u8,
+        pad: PadFn,
+        vm: &VirtualMachine,
+    ) -> PyResult<Vec<u8>> {
         let len = self.len();
         if len as isize >= width {
             return Ok(Vec::from(&self.elements[..]));
@@ -777,7 +823,10 @@ impl PyBytesInner {
         vm: &VirtualMachine,
     ) -> PyResult<Vec<u8>> {
         let (table, delete) = options.get_value(vm)?;
+        Ok(self.translate_with(&table, &delete))
+    }
 
+    pub(crate) fn translate_with(&self, table: &[u8], delete: &[u8]) -> Vec<u8> {
         let mut res = if delete.is_empty() {
             Vec::with_capacity(self.elements.len())
         } else {
@@ -790,17 +839,15 @@ impl PyBytesInner {
             }
         }
 
-        Ok(res)
+        res
     }
 
-    pub fn strip(&self, chars: Option<Self>) -> Vec<u8> {
-        self.elements
-            .py_strip(
-                chars,
-                |s, chars| s.trim_with(|c| chars.contains(&(c as u8))),
-                |s| s.trim(),
-            )
-            .to_vec()
+    pub fn strip(&self, chars: Option<Self>) -> &[u8] {
+        self.elements.py_strip(
+            chars,
+            |s, chars| s.trim_with(|c| chars.contains(&(c as u8))),
+            |s| s.trim(),
+        )
     }
 
     pub fn lstrip(&self, chars: Option<Self>) -> &[u8] {
@@ -820,21 +867,19 @@ impl PyBytesInner {
     }
 
     // new in Python 3.9
-    pub fn removeprefix(&self, prefix: Self) -> Vec<u8> {
+    pub fn removeprefix(&self, prefix: Self) -> &[u8] {
         self.elements
             .py_removeprefix(&prefix.elements, prefix.elements.len(), |s, p| {
                 s.starts_with(p)
             })
-            .to_vec()
     }
 
     // new in Python 3.9
-    pub fn removesuffix(&self, suffix: Self) -> Vec<u8> {
+    pub fn removesuffix(&self, suffix: Self) -> &[u8] {
         self.elements
             .py_removesuffix(&suffix.elements, suffix.elements.len(), |s, p| {
                 s.ends_with(p)
             })
-            .to_vec()
     }
 
     pub fn split<F>(
@@ -959,7 +1004,7 @@ impl PyBytesInner {
         result
     }
 
-    fn replace_delete(&self, from: Self, max_count: Option<usize>) -> Vec<u8> {
+    fn replace_delete(&self, from: Self, max_count: Option<usize>) -> Cow<'_, [u8]> {
         let count = count_substring(
             self.elements.as_slice(),
             from.elements.as_slice(),
@@ -967,7 +1012,7 @@ impl PyBytesInner {
         );
         if count == 0 {
             // no matches
-            return self.elements.clone();
+            return Cow::Borrowed(&self.elements);
         }
 
         let result_len = self.len() - (count * from.len());
@@ -985,10 +1030,15 @@ impl PyBytesInner {
             }
         }
         result.extend_from_slice(&self.elements[last_end..]);
-        result
+        Cow::Owned(result)
     }
 
-    pub fn replace_in_place(&self, from: Self, to: Self, max_count: Option<usize>) -> Vec<u8> {
+    pub fn replace_in_place(
+        &self,
+        from: Self,
+        to: Self,
+        max_count: Option<usize>,
+    ) -> Cow<'_, [u8]> {
         let len = from.len();
         let mut iter = self.elements.find_iter(&from.elements);
 
@@ -996,11 +1046,11 @@ impl PyBytesInner {
             let mut new = self.elements.clone();
             new[offset..offset + len].clone_from_slice(to.elements.as_slice());
             if max_count == Some(1) {
-                return new;
+                return Cow::Owned(new);
             }
             new
         } else {
-            return self.elements.clone();
+            return Cow::Borrowed(&self.elements);
         };
 
         let mut count = max_count.unwrap_or(usize::MAX) - 1;
@@ -1011,7 +1061,7 @@ impl PyBytesInner {
                 break;
             }
         }
-        new
+        Cow::Owned(new)
     }
 
     fn replace_general(
@@ -1020,7 +1070,7 @@ impl PyBytesInner {
         to: Self,
         max_count: Option<usize>,
         vm: &VirtualMachine,
-    ) -> PyResult<Vec<u8>> {
+    ) -> PyResult<Cow<'_, [u8]>> {
         let count = count_substring(
             self.elements.as_slice(),
             from.elements.as_slice(),
@@ -1028,7 +1078,7 @@ impl PyBytesInner {
         );
         if count == 0 {
             // no matches, return unchanged
-            return Ok(self.elements.clone());
+            return Ok(Cow::Borrowed(&self.elements));
         }
 
         // Check for overflow
@@ -1056,10 +1106,14 @@ impl PyBytesInner {
             }
         }
         result.extend_from_slice(&self.elements[last_end..]);
-        Ok(result)
+        Ok(Cow::Owned(result))
     }
 
-    pub fn replace(&self, args: ByteInnerReplaceOptions, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+    pub fn replace(
+        &self,
+        args: ByteInnerReplaceOptions,
+        vm: &VirtualMachine,
+    ) -> PyResult<Cow<'_, [u8]>> {
         let ByteInnerReplaceOptions {
             old: from,
             new: to,
@@ -1069,9 +1123,9 @@ impl PyBytesInner {
         let max_count = if max_count >= 0 {
             if max_count == 0 || (self.elements.is_empty() && !from.is_empty()) {
                 // nothing to do; return the original bytes
-                return Ok(self.elements.clone());
+                return Ok(Cow::Borrowed(&self.elements));
             } else if self.elements.is_empty() && from.is_empty() {
-                return Ok(to.elements);
+                return Ok(Cow::Owned(to.elements));
             }
             Some(max_count as usize)
         } else {
@@ -1082,19 +1136,19 @@ impl PyBytesInner {
         if from.elements.is_empty() {
             if to.elements.is_empty() {
                 // nothing to do; return the original bytes
-                return Ok(self.elements.clone());
+                return Ok(Cow::Borrowed(&self.elements));
             }
             // insert the 'to' bytes everywhere.
             //     >>> b"Python".replace(b"", b".")
             //     b'.P.y.t.h.o.n.'
-            return Ok(self.replace_interleave(to, max_count));
+            return Ok(Cow::Owned(self.replace_interleave(to, max_count)));
         }
 
         // Except for b"".replace(b"", b"A") == b"A" there is no way beyond this
         // point for an empty self bytes to generate a non-empty bytes
         // Special case so the remaining code always gets a non-empty bytes
         if self.elements.is_empty() {
-            return Ok(self.elements.clone());
+            return Ok(Cow::Borrowed(&self.elements));
         }
 
         if to.elements.is_empty() {
@@ -1307,7 +1361,7 @@ pub struct ByteInnerReplaceOptions {
     old: PyBytesInner,
     #[pyarg(positional)]
     new: PyBytesInner,
-    #[pyarg(positional, default = -1)]
+    #[pyarg(any, default = -1)]
     count: isize,
 }
 
@@ -1390,7 +1444,7 @@ fn hex_impl(bytes: &[u8], sep: u8, bytes_per_sep: isize) -> String {
     let len = bytes.len();
 
     let buf = if bytes_per_sep < 0 {
-        let bytes_per_sep = core::cmp::min(len, (-bytes_per_sep) as usize);
+        let bytes_per_sep = core::cmp::min(len, bytes_per_sep.unsigned_abs());
         let chunks = (len - 1) / bytes_per_sep;
         let chunked = chunks * bytes_per_sep;
         let unchunked = len - chunked;
diff --git a/crates/vm/src/cformat.rs b/crates/vm/src/cformat.rs
index c9533835f6c..e8722f36681 100644
--- a/crates/vm/src/cformat.rs
+++ b/crates/vm/src/cformat.rs
@@ -7,17 +7,17 @@ use itertools::Itertools;
 use num_traits::cast::ToPrimitive;
 
 use crate::{
-    AsObject, PyObject, PyObjectRef, PyResult, TryFromBorrowedObject, TryFromObject,
-    VirtualMachine,
+    AsObject, PyObject, PyObjectRef, PyResult, TryFromObject, VirtualMachine,
     builtins::{
         PyBaseExceptionRef, PyByteArray, PyBytes, PyFloat, PyInt, PyStr,
         int::check_int_to_str_digits, try_f64_to_bigint, tuple,
     },
     common::{
         cformat::{
-            CCharacterType, CConversionFlags, CFormatBytes, CFormatConversion, CFormatPart,
-            CFormatPrecision, CFormatQuantity, CFormatSpec, CFormatSpecKeyed, CFormatType,
-            CFormatWtf8, CNumberType,
+            CCharacterType, CConversionFlags, CFormatContext, CFormatConversion, CFormatErrorType,
+            CFormatPrecision, CFormatQuantity, CFormatSpec, CFormatType, CNumberType, FormatBuf,
+            FormatChar, consume_length, parse_flags, parse_format_type, parse_precision,
+            parse_quantity, parse_spec_mapping_key,
         },
         wtf8::{CodePoint, Wtf8, Wtf8Buf},
     },
@@ -26,18 +26,70 @@ use crate::{
     stdlib::builtins,
 };
 
+#[derive(Clone, Copy)]
+enum FormatArg<'a> {
+    Single,
+    Tuple(usize),
+    Mapping(&'a PyObject),
+}
+
+impl FormatArg<'_> {
+    fn message(self, vm: &VirtualMachine, message: String) -> PyResult<String> {
+        let context = match self {
+            Self::Single => "format argument".to_owned(),
+            Self::Tuple(index) => format!("format argument {index}"),
+            Self::Mapping(key) => format!("format argument {}", key.repr(vm)?),
+        };
+        Ok(format!("{context}: {message}"))
+    }
+
+    fn type_error(self, vm: &VirtualMachine, message: String) -> PyBaseExceptionRef {
+        match self.message(vm, message) {
+            Ok(message) => vm.new_type_error(message),
+            Err(error) => error,
+        }
+    }
+
+    fn overflow_error(self, vm: &VirtualMachine, message: String) -> PyBaseExceptionRef {
+        match self.message(vm, message) {
+            Ok(message) => vm.new_overflow_error(message),
+            Err(error) => error,
+        }
+    }
+}
+
+fn format_number_error(
+    vm: &VirtualMachine,
+    spec: &CFormatSpec,
+    obj: &PyObject,
+    arg: FormatArg<'_>,
+) -> PyBaseExceptionRef {
+    let type_name = match obj.class().fully_qualified_name(vm) {
+        Ok(name) => name,
+        Err(error) => return error,
+    };
+    let required = match spec.format_type {
+        CFormatType::Number(CNumberType::Octal | CNumberType::HexLower | CNumberType::HexUpper) => {
+            "an integer"
+        }
+        _ => "a real number",
+    };
+    arg.type_error(
+        vm,
+        format!(
+            "%{} requires {required}, not {type_name}",
+            spec.format_type.to_char()
+        ),
+    )
+}
+
 fn format_decimal_object(
     vm: &VirtualMachine,
     spec: &CFormatSpec,
     obj: &PyObject,
+    arg: FormatArg<'_>,
 ) -> PyResult<String> {
-    let type_error = || {
-        vm.new_type_error(format!(
-            "%{} format: a real number is required, not {}",
-            spec.format_type.to_char(),
-            obj.class().slot_name()
-        ))
-    };
+    let type_error = || format_number_error(vm, spec, obj, arg);
     // Decimal conversions prefer __int__; __index__ is only a fallback when absent.
     let i = obj
         .number()
@@ -55,17 +107,81 @@ fn format_decimal_object(
     Ok(spec.format_number(i.as_bigint()))
 }
 
+fn format_index_object(
+    vm: &VirtualMachine,
+    spec: &CFormatSpec,
+    obj: &PyObject,
+    arg: FormatArg<'_>,
+) -> PyResult<String> {
+    let type_error = || format_number_error(vm, spec, obj, arg);
+    let value = obj
+        .try_index_opt(vm)
+        .ok_or_else(type_error)?
+        .map_err(|error| {
+            if error.fast_isinstance(vm.ctx.exceptions.type_error) {
+                type_error()
+            } else {
+                error
+            }
+        })?;
+    Ok(spec.format_number(value.as_bigint()))
+}
+
+fn format_float_object(
+    vm: &VirtualMachine,
+    spec: &CFormatSpec,
+    obj: &PyObject,
+    arg: FormatArg<'_>,
+) -> PyResult<String> {
+    let value = ArgIntoFloat::try_from_object(vm, obj.to_owned()).map_err(|error| {
+        if error.fast_isinstance(vm.ctx.exceptions.type_error) {
+            format_number_error(vm, spec, obj, arg)
+        } else {
+            error
+        }
+    })?;
+    Ok(spec.format_float(value.into()))
+}
+
+fn format_character_error(
+    vm: &VirtualMachine,
+    obj: &PyObject,
+    arg: FormatArg<'_>,
+    context: CFormatContext,
+) -> PyBaseExceptionRef {
+    let what = match context {
+        CFormatContext::Str => obj
+            .downcast_ref::<PyStr>()
+            .map(|s| format!("a string of length {}", s.char_len())),
+        CFormatContext::Bytes => obj
+            .downcast_ref::<PyBytes>()
+            .map(|b| format!("a bytes object of length {}", b.as_bytes().len()))
+            .or_else(|| {
+                obj.downcast_ref::<PyByteArray>()
+                    .map(|b| format!("a bytearray object of length {}", b.borrow_buf().len()))
+            }),
+    };
+    let what = match what.map_or_else(|| obj.class().fully_qualified_name(vm), Ok) {
+        Ok(what) => what,
+        Err(error) => return error,
+    };
+    let required = match context {
+        CFormatContext::Str => "an integer or a unicode character",
+        CFormatContext::Bytes => "an integer in range(256) or a single byte",
+    };
+    arg.type_error(vm, format!("%c requires {required}, not {what}"))
+}
+
 fn spec_format_bytes(
     vm: &VirtualMachine,
     spec: &CFormatSpec,
     obj: PyObjectRef,
+    arg: FormatArg<'_>,
 ) -> PyResult<Vec<u8>> {
     match &spec.format_type {
-        CFormatType::Unsupported { ch, index } => Err(vm.new_value_error(format!(
-            "unsupported format character '{}' ({:#x}) at index {index}",
-            ch.to_char_lossy(),
-            ch.to_u32(),
-        ))),
+        CFormatType::Unsupported { .. } => {
+            unreachable!("unsupported format was rejected before conversion")
+        }
         // Unlike strings, %r and %a are identical for bytes: the behaviour corresponds to
         // %a for strings (not %r)
         CFormatType::String(CFormatConversion::Repr | CFormatConversion::Ascii) => {
@@ -82,7 +198,17 @@ fn spec_format_bytes(
             }
             if let Some(method) = vm.get_special_method(&obj, identifier!(vm, __bytes__))? {
                 let bytes = method.invoke((), vm)?;
-                let bytes = PyBytes::try_from_borrowed_object(vm, &bytes)?;
+                let bytes = bytes.downcast_ref::<PyBytes>().ok_or_else(|| {
+                    match (
+                        obj.class().fully_qualified_name(vm),
+                        bytes.class().fully_qualified_name(vm),
+                    ) {
+                        (Ok(source), Ok(result)) => vm.new_type_error(format!(
+                            "{source}.__bytes__() must return a bytes, not {result}"
+                        )),
+                        (Err(error), _) | (_, Err(error)) => error,
+                    }
+                })?;
                 return Ok(spec.format_bytes(bytes.as_bytes()));
             }
             if obj.check_buffer() {
@@ -91,10 +217,10 @@ fn spec_format_bytes(
             }
             let msg = format!(
                 "%b requires a bytes-like object, or an object that \
-                    implements __bytes__, not '{}'",
-                obj.class().name()
+                    implements __bytes__, not {}",
+                obj.class().fully_qualified_name(vm)?
             );
-            Err(vm.new_type_error(msg))
+            Err(arg.type_error(vm, msg))
         }
         CFormatType::Number(number_type) => match number_type {
             CNumberType::DecimalD | CNumberType::DecimalI | CNumberType::DecimalU => {
@@ -106,7 +232,7 @@ fn spec_format_bytes(
                     check_int_to_str_digits(&bigint, vm)?;
                     Ok(spec.format_number(&bigint).into_bytes())
                 } else {
-                    format_decimal_object(vm, spec, &obj).map(String::into_bytes)
+                    format_decimal_object(vm, spec, &obj, arg).map(String::into_bytes)
                 }
             }
             _ => {
@@ -114,31 +240,12 @@ fn spec_format_bytes(
                 // `__index__`, not just PyInt. Mirrors PyNumber_Index dispatch.
                 if let Some(i) = obj.downcast_ref::<PyInt>() {
                     Ok(spec.format_number(i.as_bigint()).into_bytes())
-                } else if let Some(int_result) = obj.try_index_opt(vm) {
-                    let i = int_result?;
-                    Ok(spec.format_number(i.as_bigint()).into_bytes())
                 } else {
-                    Err(vm.new_type_error(format!(
-                        "%{} format: an integer is required, not {}",
-                        spec.format_type.to_char(),
-                        obj.class().name()
-                    )))
+                    format_index_object(vm, spec, &obj, arg).map(String::into_bytes)
                 }
             }
         },
-        CFormatType::Float(_) => {
-            let class = obj.class().to_owned();
-            let value = ArgIntoFloat::try_from_object(vm, obj).map_err(|e| {
-                if e.fast_isinstance(vm.ctx.exceptions.type_error) {
-                    // formatfloat in bytesobject.c generates its own specific exception
-                    // text in this case, mirror it here.
-                    vm.new_type_error(format!("float argument required, not {}", class.name()))
-                } else {
-                    e
-                }
-            })?;
-            Ok(spec.format_float(value.into()).into_bytes())
-        }
+        CFormatType::Float(_) => format_float_object(vm, spec, &obj, arg).map(String::into_bytes),
         CFormatType::Character(CCharacterType::Character) => {
             // CPython parity: bytes `%c` accepts a single byte or any object
             // with `__index__` in range(256).
@@ -146,33 +253,25 @@ fn spec_format_bytes(
                 if b.as_bytes().len() == 1 {
                     return Ok(spec.format_char(b.as_bytes()[0]));
                 }
+                return Err(format_character_error(vm, &obj, arg, CFormatContext::Bytes));
             } else if let Some(ba) = obj.downcast_ref::<PyByteArray>() {
                 let buf = ba.borrow_buf();
                 if buf.len() == 1 {
                     return Ok(spec.format_char(buf[0]));
                 }
+                drop(buf);
+                return Err(format_character_error(vm, &obj, arg, CFormatContext::Bytes));
             }
             let int = if let Some(i) = obj.downcast_ref::<PyInt>() {
                 i.to_owned()
             } else if let Some(int_result) = obj.try_index_opt(vm) {
                 int_result?
             } else {
-                // A bytes-like argument that is not one byte long is named by
-                // its length rather than by its type.
-                let what = if let Some(b) = obj.downcast_ref::<PyBytes>() {
-                    format!("a bytes object of length {}", b.as_bytes().len())
-                } else if let Some(ba) = obj.downcast_ref::<PyByteArray>() {
-                    format!("a bytearray object of length {}", ba.borrow_buf().len())
-                } else {
-                    obj.class().name().to_string()
-                };
-                return Err(vm.new_type_error(format!(
-                    "%c requires an integer in range(256) or a single byte, not {what}"
-                )));
+                return Err(format_character_error(vm, &obj, arg, CFormatContext::Bytes));
             };
             let ch = int
                 .try_to_primitive::<u8>(vm)
-                .map_err(|_| vm.new_overflow_error("%c arg not in range(256)"))?;
+                .map_err(|_| arg.overflow_error(vm, "%c argument not in range(256)".to_owned()))?;
             Ok(spec.format_char(ch))
         }
     }
@@ -182,13 +281,12 @@ fn spec_format_string(
     vm: &VirtualMachine,
     spec: &CFormatSpec,
     obj: PyObjectRef,
+    arg: FormatArg<'_>,
 ) -> PyResult<Wtf8Buf> {
     match &spec.format_type {
-        CFormatType::Unsupported { ch, index } => Err(vm.new_value_error(format!(
-            "unsupported format character '{}' ({:#x}) at index {index}",
-            ch.to_char_lossy(),
-            ch.to_u32(),
-        ))),
+        CFormatType::Unsupported { .. } => {
+            unreachable!("unsupported format was rejected before conversion")
+        }
         CFormatType::String(conversion) => {
             let result = match conversion {
                 CFormatConversion::Ascii => builtins::ascii(obj, vm)?.as_wtf8().to_owned(),
@@ -211,7 +309,7 @@ fn spec_format_string(
                     check_int_to_str_digits(&bigint, vm)?;
                     Ok(spec.format_number(&bigint).into())
                 } else {
-                    format_decimal_object(vm, spec, &obj).map(Into::into)
+                    format_decimal_object(vm, spec, &obj, arg).map(Into::into)
                 }
             }
             _ => {
@@ -219,304 +317,417 @@ fn spec_format_string(
                 // `__index__`, not just PyInt. Mirrors PyNumber_Index dispatch.
                 if let Some(i) = obj.downcast_ref::<PyInt>() {
                     Ok(spec.format_number(i.as_bigint()).into())
-                } else if let Some(int_result) = obj.try_index_opt(vm) {
-                    let i = int_result?;
-                    Ok(spec.format_number(i.as_bigint()).into())
                 } else {
-                    Err(vm.new_type_error(format!(
-                        "%{} format: an integer is required, not {}",
-                        spec.format_type.to_char(),
-                        obj.class().name()
-                    )))
+                    format_index_object(vm, spec, &obj, arg).map(Into::into)
                 }
             }
         },
-        CFormatType::Float(_) => {
-            let value = ArgIntoFloat::try_from_object(vm, obj)?;
-            Ok(spec.format_float(value.into()).into())
-        }
+        CFormatType::Float(_) => format_float_object(vm, spec, &obj, arg).map(Into::into),
         CFormatType::Character(CCharacterType::Character) => {
             // CPython parity: `%c` accepts a single-char str or any object with
             // `__index__` (the latter via PyNumber_Index dispatch).
-            if let Some(s) = obj.downcast_ref::<PyStr>()
-                && let Ok(ch) = s.as_wtf8().code_points().exactly_one()
-            {
-                return Ok(spec.format_char(ch));
+            if let Some(s) = obj.downcast_ref::<PyStr>() {
+                if let Ok(ch) = s.as_wtf8().code_points().exactly_one() {
+                    return Ok(spec.format_char(ch));
+                }
+                return Err(format_character_error(vm, &obj, arg, CFormatContext::Str));
             }
             let int = if let Some(i) = obj.downcast_ref::<PyInt>() {
                 i.to_owned()
             } else if let Some(int_result) = obj.try_index_opt(vm) {
-                int_result?
+                int_result.map_err(|error| {
+                    if error.fast_isinstance(vm.ctx.exceptions.type_error) {
+                        format_character_error(vm, &obj, arg, CFormatContext::Str)
+                    } else {
+                        error
+                    }
+                })?
             } else {
-                // A string argument that is not one character long is named by
-                // its length rather than by its type.
-                let what = match obj.downcast_ref::<PyStr>() {
-                    Some(s) => format!("a string of length {}", s.char_len()),
-                    None => obj.class().name().to_string(),
-                };
-                return Err(vm.new_type_error(format!(
-                    "%c requires an int or a unicode character, not {what}"
-                )));
+                return Err(format_character_error(vm, &obj, arg, CFormatContext::Str));
             };
             let ch = int
                 .as_bigint()
                 .to_u32()
                 .and_then(CodePoint::from_u32)
-                .ok_or_else(|| vm.new_overflow_error("%c arg not in range(0x110000)"))?;
+                .ok_or_else(|| {
+                    arg.overflow_error(vm, "%c argument not in range(0x110000)".to_owned())
+                })?;
             Ok(spec.format_char(ch))
         }
     }
 }
 
-fn get_star_arg(vm: &VirtualMachine, element: Option<&PyObject>) -> PyResult<i32> {
-    match element {
-        Some(obj) => {
-            if let Some(i) = obj.downcast_ref::<PyInt>() {
-                i.try_to_primitive::<i32>(vm)
-            } else {
-                Err(vm.new_type_error("* wants int"))
-            }
-        }
-        None => Err(vm.new_type_error("not enough arguments for format string")),
-    }
+struct FormatValues<'a> {
+    object: &'a PyObject,
+    tuple: Option<&'a [PyObjectRef]>,
+    consumed: usize,
 }
 
-fn try_update_quantity_from_tuple<'a, I: Iterator<Item = &'a PyObject>>(
-    vm: &VirtualMachine,
-    elements: &mut I,
-    q: &mut Option<CFormatQuantity>,
-    f: &mut CConversionFlags,
-) -> PyResult<()> {
-    let Some(CFormatQuantity::FromValuesTuple) = q else {
-        return Ok(());
-    };
+impl<'a> FormatValues<'a> {
+    fn new(object: &'a PyObject) -> Self {
+        Self {
+            object,
+            tuple: object
+                .downcast_ref::<tuple::PyTuple>()
+                .map(|tuple| tuple.as_slice()),
+            consumed: 0,
+        }
+    }
 
-    let width = get_star_arg(vm, elements.next())?;
-    if width < 0 {
-        f.insert(CConversionFlags::LEFT_ADJUST);
+    fn count(&self) -> usize {
+        self.tuple.map_or(1, <[PyObjectRef]>::len)
     }
-    *q = Some(CFormatQuantity::Amount(width.unsigned_abs() as usize));
-    Ok(())
-}
 
-fn try_update_precision_from_tuple<'a, I: Iterator<Item = &'a PyObject>>(
-    vm: &VirtualMachine,
-    elements: &mut I,
-    p: &mut Option<CFormatPrecision>,
-) -> PyResult<()> {
-    let Some(CFormatPrecision::Quantity(CFormatQuantity::FromValuesTuple)) = p else {
-        return Ok(());
-    };
+    fn next(
+        &mut self,
+        allow_single: bool,
+        vm: &VirtualMachine,
+    ) -> PyResult<(PyObjectRef, FormatArg<'static>)> {
+        let value = if let Some(tuple) = self.tuple {
+            tuple.get(self.consumed).cloned()
+        } else if allow_single && self.consumed == 0 {
+            Some(self.object.to_owned())
+        } else {
+            None
+        };
+        let value = value.ok_or_else(|| {
+            vm.new_type_error(format!(
+                "not enough arguments for format string (got {})",
+                self.count()
+            ))
+        })?;
+        self.consumed += 1;
+        let arg = if self.tuple.is_some() {
+            FormatArg::Tuple(self.consumed)
+        } else {
+            FormatArg::Single
+        };
+        Ok((value, arg))
+    }
 
-    let precision = get_star_arg(vm, elements.next())?.max(0) as usize;
-    *p = Some(CFormatPrecision::Quantity(CFormatQuantity::Amount(
-        precision,
-    )));
-    Ok(())
+    fn star(&mut self, precision: bool, vm: &VirtualMachine) -> PyResult<isize> {
+        let (value, arg) = self.next(false, vm)?;
+        let Some(value_int) = value.downcast_ref::<PyInt>() else {
+            return Err(arg.type_error(
+                vm,
+                format!(
+                    "* requires int, not {}",
+                    value.class().fully_qualified_name(vm)?
+                ),
+            ));
+        };
+        let converted = if precision {
+            value_int.as_bigint().to_i32().map(|value| value as isize)
+        } else {
+            value_int.as_bigint().to_isize()
+        };
+        converted.ok_or_else(|| {
+            arg.overflow_error(
+                vm,
+                format!(
+                    "too big for {}",
+                    if precision { "precision" } else { "width" }
+                ),
+            )
+        })
+    }
 }
 
-fn specifier_error(vm: &VirtualMachine) -> PyBaseExceptionRef {
-    vm.new_type_error("format requires a mapping")
+fn parse_error(vm: &VirtualMachine, error: CFormatErrorType, start: usize) -> PyBaseExceptionRef {
+    let message = match error {
+        CFormatErrorType::UnmatchedKeyParentheses => {
+            format!("stray % or incomplete format key at position {start}")
+        }
+        CFormatErrorType::WidthTooBig => format!("width too big at position {start}"),
+        CFormatErrorType::PrecisionTooBig => format!("precision too big at position {start}"),
+        _ => format!("stray % at position {start}"),
+    };
+    vm.new_value_error(message)
 }
 
-pub(crate) fn cformat_bytes(
+fn unsupported_format_error(
     vm: &VirtualMachine,
-    format_string: &[u8],
-    values_obj: &PyObject,
-) -> PyResult<Vec<u8>> {
-    let mut format = CFormatBytes::parse_from_bytes(format_string)
-        .map_err(|err| vm.new_value_error(err.to_string()))?;
-    let (num_specifiers, mapping_required) = format
-        .check_specifiers()
-        .ok_or_else(|| specifier_error(vm))?;
-
-    let mut result = vec![];
-
-    let is_mapping = values_obj.class().has_attr(identifier!(vm, __getitem__))
-        && !values_obj.fast_isinstance(vm.ctx.types.tuple_type)
-        && !values_obj.fast_isinstance(vm.ctx.types.bytes_type)
-        && !values_obj.fast_isinstance(vm.ctx.types.bytearray_type);
-
-    if num_specifiers == 0 {
-        if !is_mapping
-            && values_obj
-                .downcast_ref::<tuple::PyTuple>()
-                .is_none_or(|e| !e.as_slice().is_empty())
-        {
-            return Err(vm.new_type_error("not all arguments converted during bytes formatting"));
-        }
-
-        // literal only
-        for (_, part) in format.iter_mut() {
-            if let CFormatPart::Literal(literal) = part {
-                result.append(literal)
-            } else {
-                unreachable!()
-            }
-        }
-
-        return Ok(result);
+    ch: CodePoint,
+    start: usize,
+    index: usize,
+    context: CFormatContext,
+) -> PyBaseExceptionRef {
+    let value = ch.to_u32();
+    let c = ch.to_char_lossy();
+    if c.is_ascii_alphabetic() {
+        return vm.new_value_error(format!("unsupported format %{c} at position {start}"));
     }
+    let character = if c == '\'' {
+        "\"'\"".to_owned()
+    } else if (32..127).contains(&value) {
+        format!("'{c}'")
+    } else if context == CFormatContext::Bytes {
+        format!("with code 0x{value:02x}")
+    } else if ch
+        .to_char()
+        .is_some_and(rustpython_unicode::classify::is_printable)
+    {
+        format!("'{c}' (U+{value:04X})")
+    } else {
+        format!("U+{value:04X}")
+    };
+    vm.new_value_error(format!(
+        "stray % at position {start} or unexpected format character {character} at position {index}"
+    ))
+}
 
-    if mapping_required {
-        if !is_mapping {
-            return Err(vm.new_type_error("format requires a mapping"));
-        }
+trait FormatOutput: FormatBuf {
+    fn reserve_output(&mut self, additional: usize, vm: &VirtualMachine) -> PyResult<()>;
+    fn push_output(&mut self, character: Self::Char, vm: &VirtualMachine) -> PyResult<()>;
+}
 
-        // dict
-        for (_, part) in format {
-            match part {
-                CFormatPart::Literal(literal) => result.extend(literal),
-                CFormatPart::Spec(CFormatSpecKeyed { mapping_key, spec }) => {
-                    let key = mapping_key.unwrap();
-                    let value = values_obj.get_item(&key, vm)?;
-                    let part_result = spec_format_bytes(vm, &spec, value)?;
-                    result.extend(part_result);
-                }
-            }
-        }
+impl FormatOutput for Vec<u8> {
+    fn reserve_output(&mut self, additional: usize, vm: &VirtualMachine) -> PyResult<()> {
+        self.try_reserve_exact(additional)
+            .map_err(|_| vm.new_memory_error(""))
+    }
 
-        return Ok(result);
+    fn push_output(&mut self, character: u8, vm: &VirtualMachine) -> PyResult<()> {
+        self.try_reserve(1).map_err(|_| vm.new_memory_error(""))?;
+        self.push(character);
+        Ok(())
     }
+}
 
-    // tuple
-    let mut slice_iter;
-    let mut once_iter;
-    let mut value_iter: &mut dyn Iterator<Item = &PyObject> =
-        if let Some(tup) = values_obj.downcast_ref::<tuple::PyTuple>() {
-            slice_iter = tup.as_slice().iter().map(|v| &**v);
-            &mut slice_iter
-        } else {
-            once_iter = core::iter::once(values_obj);
-            &mut once_iter
-        };
+impl FormatOutput for Wtf8Buf {
+    fn reserve_output(&mut self, additional: usize, vm: &VirtualMachine) -> PyResult<()> {
+        self.try_reserve_exact(additional)
+            .map_err(|_| vm.new_memory_error(""))
+    }
 
-    for (_, part) in format {
-        match part {
-            CFormatPart::Literal(literal) => result.extend(literal),
-            CFormatPart::Spec(CFormatSpecKeyed { mut spec, .. }) => {
-                try_update_quantity_from_tuple(
-                    vm,
-                    &mut value_iter,
-                    &mut spec.min_field_width,
-                    &mut spec.flags,
-                )?;
-                try_update_precision_from_tuple(vm, &mut value_iter, &mut spec.precision)?;
-
-                let Some(value) = value_iter.next() else {
-                    return Err(vm.new_type_error("not enough arguments for format string"));
-                };
-
-                let part_result = spec_format_bytes(vm, &spec, value.to_owned())?;
-                result.extend(part_result);
-            }
-        }
+    fn push_output(&mut self, character: CodePoint, vm: &VirtualMachine) -> PyResult<()> {
+        self.try_reserve(character.len_wtf8())
+            .map_err(|_| vm.new_memory_error(""))?;
+        self.push(character);
+        Ok(())
     }
+}
 
-    // check that all arguments were converted
-    if !is_mapping && value_iter.next().is_some() {
-        Err(vm.new_type_error("not all arguments converted during bytes formatting"))
-    } else {
-        Ok(result)
+fn pad_output<S: FormatOutput>(
+    vm: &VirtualMachine,
+    spec: &CFormatSpec,
+    mut value: S,
+) -> PyResult<S> {
+    let Some(CFormatQuantity::Amount(width)) = spec.min_field_width else {
+        return Ok(value);
+    };
+    let fill = width.saturating_sub(value.chars().count());
+    if fill == 0 {
+        return Ok(value);
     }
+    if spec.flags.contains(CConversionFlags::LEFT_ADJUST) {
+        value.reserve_output(fill, vm)?;
+        value.extend(core::iter::repeat_n(S::Char::from(b' '), fill));
+        return Ok(value);
+    }
+    let zero_pad = spec.flags.contains(CConversionFlags::ZERO_PAD)
+        && matches!(
+            spec.format_type,
+            CFormatType::Number(_) | CFormatType::Float(_)
+        );
+    let prefix = if zero_pad {
+        let sign = usize::from(
+            value
+                .chars()
+                .next()
+                .is_some_and(|c| c.eq_char('-') || c.eq_char('+') || c.eq_char(' ')),
+        );
+        let alternate = spec.flags.contains(CConversionFlags::ALTERNATE_FORM)
+            && matches!(
+                spec.format_type,
+                CFormatType::Number(
+                    CNumberType::Octal | CNumberType::HexLower | CNumberType::HexUpper
+                )
+            );
+        sign + if alternate { 2 } else { 0 }
+    } else {
+        0
+    };
+    let size = value
+        .len()
+        .checked_add(fill)
+        .ok_or_else(|| vm.new_memory_error(""))?;
+    let mut output = S::default();
+    output.reserve_output(size, vm)?;
+    output.extend(value.chars().take(prefix));
+    output.extend(core::iter::repeat_n(
+        S::Char::from(if zero_pad { b'0' } else { b' ' }),
+        fill,
+    ));
+    output.extend(value.chars().skip(prefix));
+    Ok(output)
 }
 
-pub(crate) fn cformat_string(
+fn cformat<S: FormatOutput>(
     vm: &VirtualMachine,
-    format_string: &Wtf8,
+    characters: impl Iterator<Item = S::Char>,
     values_obj: &PyObject,
-) -> PyResult<Wtf8Buf> {
-    let format = CFormatWtf8::parse_from_wtf8(format_string)
-        .map_err(|err| vm.new_value_error(err.to_string()))?;
-    let (num_specifiers, mapping_required) = format
-        .check_specifiers()
-        .ok_or_else(|| specifier_error(vm))?;
-
-    let mut result = Wtf8Buf::new();
-
-    let is_mapping = values_obj.class().has_attr(identifier!(vm, __getitem__))
-        && !values_obj.fast_isinstance(vm.ctx.types.tuple_type)
-        && !values_obj.fast_isinstance(vm.ctx.types.str_type);
-
-    if num_specifiers == 0 {
-        if !is_mapping
-            && values_obj
-                .downcast_ref::<tuple::PyTuple>()
-                .is_none_or(|e| !e.as_slice().is_empty())
+    context: CFormatContext,
+    make_key: impl Fn(S) -> PyObjectRef,
+    format_value: impl Fn(&VirtualMachine, &CFormatSpec, PyObjectRef, FormatArg<'_>) -> PyResult<S>,
+) -> PyResult<S> {
+    let mut characters = characters.enumerate().peekable();
+    let mut values = FormatValues::new(values_obj);
+    let is_mapping = values_obj.class().slots().as_mapping.has_subscript()
+        && values.tuple.is_none()
+        && !values_obj.fast_isinstance(vm.ctx.types.str_type)
+        && (context == CFormatContext::Str
+            || (!values_obj.fast_isinstance(vm.ctx.types.bytes_type)
+                && !values_obj.fast_isinstance(vm.ctx.types.bytearray_type)));
+    let mut mapping_used = false;
+    let mut mapped_value = None;
+    let mut result = S::default();
+
+    while let Some((start, character)) = characters.next() {
+        if !character.eq_char('%') {
+            result.push_output(character, vm)?;
+            continue;
+        }
+        if characters
+            .next_if(|(_, character)| character.eq_char('%'))
+            .is_some()
         {
-            return Err(vm.new_type_error("not all arguments converted during string formatting"));
+            result.push_output(S::Char::from(b'%'), vm)?;
+            continue;
         }
 
-        // literal only
-        for (_, part) in format.iter() {
-            if let CFormatPart::Literal(literal) = part {
-                result.push_wtf8(literal)
-            } else {
-                unreachable!()
-            }
+        // Fetch mappings and star arguments as their fields are parsed, so
+        // callbacks and earlier errors precede later malformed fields.
+        let keyed = characters
+            .peek()
+            .is_some_and(|(_, character)| character.eq_char('('));
+        if keyed && !is_mapping {
+            return Err(vm.new_type_error(format!(
+                "format requires a mapping, not {}",
+                values_obj.class().fully_qualified_name(vm)?
+            )));
         }
-
-        return Ok(result);
-    }
-
-    if mapping_required {
-        if !is_mapping {
-            return Err(vm.new_type_error("format requires a mapping"));
+        if !keyed && mapping_used {
+            return Err(vm.new_value_error(format!(
+                "format requires a parenthesised mapping key at position {start}"
+            )));
+        }
+        let mapping_key = parse_spec_mapping_key::<S, _>(&mut characters)
+            .map_err(|(error, _)| parse_error(vm, error, start))?
+            .map(&make_key);
+        if let Some(key) = &mapping_key {
+            mapping_used = true;
+            // Release the previous mapped argument before invoking the next lookup.
+            drop(mapped_value.take());
+            mapped_value = Some(values_obj.get_item(key.as_object(), vm)?);
         }
 
-        // dict
-        for (_, part) in format {
-            match part {
-                CFormatPart::Literal(literal) => result.push_wtf8(&literal),
-                CFormatPart::Spec(CFormatSpecKeyed { mapping_key, spec }) => {
-                    let value = values_obj.get_item(&mapping_key.unwrap(), vm)?;
-                    let part_result = spec_format_string(vm, &spec, value)?;
-                    result.push_wtf8(&part_result);
-                }
+        let mut flags = parse_flags(&mut characters);
+        let mut min_field_width = parse_quantity(
+            &mut characters,
+            isize::MAX as usize,
+            CFormatErrorType::WidthTooBig,
+        )
+        .map_err(|(error, _)| parse_error(vm, error, start))?;
+        let star_mapping_error = || {
+            vm.new_value_error(format!(
+                "* cannot be used with a parenthesised mapping key at position {start}"
+            ))
+        };
+        if min_field_width == Some(CFormatQuantity::FromValuesTuple) {
+            if mapping_used {
+                return Err(star_mapping_error());
             }
+            let width = values.star(false, vm)?;
+            if width < 0 {
+                flags.insert(CConversionFlags::LEFT_ADJUST);
+            }
+            // Negating PY_SSIZE_T_MIN leaves a negative width in CPython,
+            // which imposes no padding requirement.
+            min_field_width = Some(CFormatQuantity::Amount(
+                width.checked_abs().unwrap_or(0) as usize
+            ));
         }
-
-        return Ok(result);
-    }
-
-    // tuple
-    let mut slice_iter;
-    let mut once_iter;
-    let mut value_iter: &mut dyn Iterator<Item = &PyObject> =
-        if let Some(tup) = values_obj.downcast_ref::<tuple::PyTuple>() {
-            slice_iter = tup.as_slice().iter().map(|v| &**v);
-            &mut slice_iter
+        let mut precision =
+            parse_precision(&mut characters).map_err(|(error, _)| parse_error(vm, error, start))?;
+        if precision == Some(CFormatPrecision::Quantity(CFormatQuantity::FromValuesTuple)) {
+            if mapping_used {
+                return Err(star_mapping_error());
+            }
+            precision = Some(CFormatPrecision::Quantity(CFormatQuantity::Amount(
+                values.star(true, vm)?.max(0) as usize,
+            )));
+        }
+        consume_length(&mut characters);
+        let format_type = parse_format_type(&mut characters, context)
+            .map_err(|(error, _)| parse_error(vm, error, start))?;
+        let spec = CFormatSpec {
+            flags,
+            min_field_width,
+            precision,
+            format_type,
+        };
+        let (value, arg) = if let Some(key) = &mapping_key {
+            (
+                mapped_value.as_ref().unwrap().clone(),
+                FormatArg::Mapping(key),
+            )
         } else {
-            once_iter = core::iter::once(values_obj);
-            &mut once_iter
+            values.next(true, vm)?
         };
-
-    for (_, part) in format {
-        match part {
-            CFormatPart::Literal(literal) => result.push_wtf8(&literal),
-            CFormatPart::Spec(CFormatSpecKeyed { mut spec, .. }) => {
-                try_update_quantity_from_tuple(
-                    vm,
-                    &mut value_iter,
-                    &mut spec.min_field_width,
-                    &mut spec.flags,
-                )?;
-                try_update_precision_from_tuple(vm, &mut value_iter, &mut spec.precision)?;
-
-                let Some(value) = value_iter.next() else {
-                    return Err(vm.new_type_error("not enough arguments for format string"));
-                };
-
-                let part_result = spec_format_string(vm, &spec, value.to_owned())?;
-                result.push_wtf8(&part_result);
-            }
+        if let CFormatType::Unsupported { ch, index } = format_type {
+            return Err(unsupported_format_error(vm, ch, start, index, context));
         }
+        // Convert before reserving field padding: user callbacks must still
+        // run when an otherwise valid width cannot be allocated.
+        let mut unpadded_spec = spec;
+        unpadded_spec.min_field_width = None;
+        let value = format_value(vm, &unpadded_spec, value, arg)?;
+        let value = pad_output(vm, &spec, value)?;
+        result.reserve_output(value.len(), vm)?;
+        result = result.concat(value);
     }
 
-    // check that all arguments were converted
-    if !is_mapping && value_iter.next().is_some() {
-        Err(vm.new_type_error("not all arguments converted during string formatting"))
-    } else {
-        Ok(result)
+    if !is_mapping && values.consumed < values.count() {
+        let kind = match context {
+            CFormatContext::Str => "string",
+            CFormatContext::Bytes => "bytes",
+        };
+        return Err(vm.new_type_error(format!(
+            "not all arguments converted during {kind} formatting (required {}, got {})",
+            values.consumed,
+            values.count()
+        )));
     }
+    Ok(result)
+}
+
+pub(crate) fn cformat_bytes(
+    vm: &VirtualMachine,
+    format_string: &[u8],
+    values_obj: &PyObject,
+) -> PyResult<Vec<u8>> {
+    cformat(
+        vm,
+        format_string.iter().copied(),
+        values_obj,
+        CFormatContext::Bytes,
+        |key| vm.ctx.new_bytes(key).into(),
+        spec_format_bytes,
+    )
+}
+
+pub(crate) fn cformat_string(
+    vm: &VirtualMachine,
+    format_string: &Wtf8,
+    values_obj: &PyObject,
+) -> PyResult<Wtf8Buf> {
+    cformat(
+        vm,
+        format_string.code_points(),
+        values_obj,
+        CFormatContext::Str,
+        |key| vm.ctx.new_str(key).into(),
+        spec_format_string,
+    )
 }
diff --git a/crates/vm/src/class.rs b/crates/vm/src/class.rs
index 8a7a8306d16..fe655968665 100644
--- a/crates/vm/src/class.rs
+++ b/crates/vm/src/class.rs
@@ -375,9 +375,9 @@ pub trait PyClassImpl: PyClassDef {
                 && object_new.is_some_and(|obj_new| fn_addr(slot_new) == fn_addr(obj_new));
 
             if !is_inherited_from_object {
-                let bound_new =
-                    ctx.slot_new_wrapper
-                        .build_bound_method(ctx, class.to_owned().into(), class);
+                let bound_new = ctx
+                    .slot_new_wrapper
+                    .build_bound_function(ctx, class.to_owned().into());
                 class.set_attr(identifier!(ctx, __new__), bound_new.into());
             }
         }
@@ -451,13 +451,38 @@ pub trait PyClassImpl: PyClassDef {
 
 /// Trait for Python subclasses that can provide a reference to their base type.
 ///
-/// This trait is automatically implemented by the `#[pyclass]` macro when
-/// `base = SomeType` is specified. It provides safe reference access to the
-/// base type's payload.
+/// The `#[pyclass]` macro implements this trait for `#[repr(transparent)]`
+/// subclasses with `base = SomeType`. Other native subclasses can implement
+/// it manually when their base is a compatible physical prefix.
 ///
-/// For subclasses with `#[repr(transparent)]`
-/// which enables ownership transfer via `into_base()`.
-pub trait PySubclass: crate::PyPayload {
+/// # Safety
+///
+/// Every valid `Self` must contain a valid `Base` at offset zero, returned by
+/// `as_base`. Their payload offsets in `Py<Self>` and `Py<Base>` must match,
+/// and `Py<Self>` must meet `Py<Base>`'s alignment requirement. The base must
+/// remain valid for the lifetime of `Self`, independently of the object's
+/// Python class or MRO. These guarantees allow safe borrowing and ownership
+/// transfer of the same allocation as `Py<Base>`.
+///
+/// A manual implementation must explicitly acknowledge this contract:
+///
+/// ```compile_fail,E0200
+/// use rustpython_vm::{builtins::PyInt, class::PySubclass, pyclass, PyPayload};
+///
+/// #[pyclass(module = false, name = "IntWrapper")]
+/// #[derive(Debug, PyPayload)]
+/// #[repr(transparent)]
+/// struct IntWrapper(PyInt);
+///
+/// #[pyclass]
+/// impl IntWrapper {}
+///
+/// impl PySubclass for IntWrapper {
+///     type Base = PyInt;
+///     fn as_base(&self) -> &PyInt { &self.0 }
+/// }
+/// ```
+pub unsafe trait PySubclass: crate::PyPayload {
     type Base: crate::PyPayload;
 
     /// Returns a reference to the base type's payload.
diff --git a/crates/vm/src/codecs.rs b/crates/vm/src/codecs.rs
index 587701d6528..b136a68bc34 100644
--- a/crates/vm/src/codecs.rs
+++ b/crates/vm/src/codecs.rs
@@ -241,27 +241,31 @@ impl CodecsRegistry {
             return;
         }
 
-        for (i, item) in inner.search_path.iter().enumerate() {
-            if item.get_id() == search_function.get_id() {
-                if !inner.search_cache.is_empty() {
-                    inner.search_cache.clear();
-                }
-                inner.search_path.remove(i);
-                return;
-            }
+        if let Some(i) = inner
+            .search_path
+            .iter()
+            .position(|item| item.get_id() == search_function.get_id())
+        {
+            let cache = core::mem::take(&mut inner.search_cache);
+            let function = inner.search_path.remove(i);
+            drop(inner);
+            drop((cache, function));
         }
     }
 
     pub(crate) fn register_manual(&self, name: &str, codec: PyCodec) {
-        let name = normalize_encoding_name(name);
-        self.inner
+        let name = normalize_registry_name(name);
+        let previous = self
+            .inner
             .write()
             .search_cache
             .insert(name.into_owned(), codec);
+        drop(previous);
     }
 
     pub fn lookup(&self, encoding: &str, vm: &VirtualMachine) -> PyResult<PyCodec> {
-        let encoding = normalize_encoding_name(encoding);
+        let original_encoding = encoding;
+        let encoding = normalize_registry_name(encoding);
         let search_path = {
             let inner = self.inner.read();
             if let Some(codec) = inner.search_cache.get(encoding.as_ref()) {
@@ -276,17 +280,21 @@ impl CodecsRegistry {
             let res = func.call((encoding.clone(),), vm)?;
             let res: Option<PyCodec> = res.try_into_value(vm)?;
             if let Some(codec) = res {
-                let mut inner = self.inner.write();
-                // someone might have raced us to this, so use theirs
-                let codec = inner
-                    .search_cache
-                    .entry(encoding.as_str().to_owned())
-                    .or_insert(codec);
-                return Ok(codec.clone());
+                let cached = {
+                    let mut inner = self.inner.write();
+                    // someone might have raced us to this, so use theirs
+                    // Keep our tuple alive until the registry lock is released.
+                    inner
+                        .search_cache
+                        .entry(encoding.as_str().to_owned())
+                        .or_insert_with(|| codec.clone())
+                        .clone()
+                };
+                return Ok(cached);
             }
         }
 
-        Err(vm.new_lookup_error(format!("unknown encoding: {encoding}")))
+        Err(vm.new_lookup_error(format!("unknown encoding: {original_encoding}")))
     }
 
     fn _lookup_text_encoding(
@@ -307,7 +315,7 @@ impl CodecsRegistry {
     }
 
     pub fn forget(&self, encoding: &str) -> Option<PyCodec> {
-        let encoding = normalize_encoding_name(encoding);
+        let encoding = normalize_registry_name(encoding);
         self.inner.write().search_cache.remove(encoding.as_ref())
     }
 
@@ -536,7 +544,8 @@ impl CodecsRegistry {
                 "cannot un-register built-in error handler '{name}'"
             )));
         }
-        Ok(self.inner.write().errors.remove(name).is_some())
+        let handler = self.inner.write().errors.remove(name);
+        Ok(handler.is_some())
     }
 
     pub fn lookup_error_opt(&self, name: &str) -> Option<PyObjectRef> {
@@ -622,6 +631,26 @@ impl FastCodec {
     }
 }
 
+fn normalize_registry_name(encoding: &str) -> Cow<'_, str> {
+    if !encoding
+        .bytes()
+        .any(|b| b.is_ascii_uppercase() || b == b' ')
+    {
+        return encoding.into();
+    }
+    encoding
+        .chars()
+        .map(|c| {
+            if c == ' ' {
+                '-'
+            } else {
+                c.to_ascii_lowercase()
+            }
+        })
+        .collect::<String>()
+        .into()
+}
+
 fn normalize_encoding_name(encoding: &str) -> Cow<'_, str> {
     // _Py_normalize_encoding: collapse non-alphanumeric/non-dot chars into
     // single underscore, strip non-ASCII, lowercase ASCII letters.
diff --git a/crates/vm/src/compiler.rs b/crates/vm/src/compiler.rs
index 9842bc0d1c7..c50fbb74870 100644
--- a/crates/vm/src/compiler.rs
+++ b/crates/vm/src/compiler.rs
@@ -11,8 +11,8 @@ cfg_select! {
     _ => {
         pub use ruff_python_parser as parser;
 
-        pub use rustpython_compiler_core::Mode;
         pub use rustpython_compiler_core as core;
+        pub use rustpython_compiler_core::Mode;
     }
 }
 
diff --git a/crates/vm/src/coroutine.rs b/crates/vm/src/coroutine.rs
index 5da8c8272a1..b1ea72b131b 100644
--- a/crates/vm/src/coroutine.rs
+++ b/crates/vm/src/coroutine.rs
@@ -40,6 +40,8 @@ pub struct Coro {
     code: PyRef<PyCode>,
     pub closed: AtomicCell<bool>, // TODO: https://github.com/RustPython/RustPython/pull/3183#discussion_r720560652
     running: AtomicCell<bool>,
+    /// Whether execution has resumed beyond the eager creation preamble.
+    started: AtomicCell<bool>,
     // _weakreflist
     name: PyMutex<PyStrRef>,
     qualname: PyMutex<PyStrRef>,
@@ -159,16 +161,16 @@ pub(crate) fn flat_resume_enter(
     if coro.closed.load() {
         return Ok(FlatEnter::Exhausted);
     }
-    let value = if coro.frame_opt().is_some_and(|f| f.lasti() > 0) {
-        Some(value)
-    } else if !vm.is_none(&value) {
+    if !coro.started() && !vm.is_none(&value) {
         return Err(vm.new_type_error(format!(
             "can't send non-None value to a just-started {}",
             gen_name(&jen, vm),
         )));
-    } else {
-        None
-    };
+    }
+    let value = coro
+        .frame_opt()
+        .is_some_and(|f| f.lasti() > 0)
+        .then_some(value);
     // SAFETY: exclusive access guaranteed by the claim
     let gen_exc = unsafe { coro.exception.swap(None) };
     let frame_ref = coro.frame();
@@ -184,6 +186,7 @@ pub(crate) fn flat_resume_enter(
             return Err(exc);
         }
     };
+    coro.started.store(true);
     // The claim outlives this scope; `flat_resume_exit` drops it.
     core::mem::forget(_claim);
     Ok(FlatEnter::Entered {
@@ -234,6 +237,7 @@ impl Coro {
             code,
             closed: AtomicCell::new(false),
             running: AtomicCell::new(false),
+            started: AtomicCell::new(false),
             exception: PyAtomicRef::from(None),
             name: PyMutex::new(name),
             qualname: PyMutex::new(qualname),
@@ -307,6 +311,7 @@ impl Coro {
 
         let frame = self.frame();
         vm.resume_gen_frame(&frame, gen_exc, |f| {
+            self.started.store(true);
             let result = func(f);
             // SAFETY: exclusive access guaranteed by the claim
             let _old = unsafe { (*exception_ptr).swap(vm.current_exception()) };
@@ -401,16 +406,16 @@ impl Coro {
         if self.closed.load() {
             return Self::send_when_closed(jen, vm);
         }
-        let value = if self.frame_opt().is_some_and(|f| f.lasti() > 0) {
-            Some(value)
-        } else if !vm.is_none(&value) {
+        if !self.started() && !vm.is_none(&value) {
             return Err(vm.new_type_error(format!(
                 "can't send non-None value to a just-started {}",
                 gen_name(jen, vm),
             )));
-        } else {
-            None
-        };
+        }
+        let value = self
+            .frame_opt()
+            .is_some_and(|f| f.lasti() > 0)
+            .then_some(value);
         let result = self.run_claimed(&claim, vm, |f| f.resume(value, vm));
         self.maybe_close(&result, &claim);
         drop(claim);
@@ -462,7 +467,7 @@ impl Coro {
             return Ok(vm.ctx.none());
         }
         // FRAME_CREATED: mark finished and clear the iframe.
-        if self.frame_opt().is_none_or(|f| f.lasti() == 0) {
+        if !self.started() {
             self.closed.store(true);
             self.clear_except_code();
             return Ok(vm.ctx.none());
@@ -490,16 +495,55 @@ impl Coro {
         }
     }
 
+    /// Clear a created generator frame without resuming its body.
+    pub(crate) fn clear_frame(&self, jen: &PyObject, vm: &VirtualMachine) -> PyResult<()> {
+        if self.closed.load() {
+            return Ok(());
+        }
+        if self.running.compare_exchange(false, true).is_err() {
+            return Err(vm.new_runtime_error("cannot clear an executing frame"));
+        }
+        let claim = RunningGuard(self);
+        if self.closed.load() {
+            return Ok(());
+        }
+        if self.started() {
+            return Err(vm.new_runtime_error("cannot clear a suspended frame"));
+        }
+        self.closed.store(true);
+        // Closed owners cannot resume. Publish that state and release the
+        // running claim before a warning hook can observe or clear us again.
+        drop(claim);
+        if jen.class().is(vm.ctx.types.coroutine_type) {
+            crate::warn::warn_unawaited_coroutine(jen, &self.qualname(), vm);
+        }
+        self.clear_except_code();
+        Ok(())
+    }
+
     /// Whether the frame has run at all, i.e. is stopped at a `yield` rather
     /// than at its start.
     pub(crate) fn started(&self) -> bool {
-        self.frame_opt().is_some_and(|f| f.lasti() > 0)
+        self.started.load()
+    }
+
+    pub(crate) fn state_name(&self, names: [&'static str; 4]) -> &'static str {
+        // Closing publishes the terminal state before releasing frame locals,
+        // whose finalizers can observe us while the running claim is held.
+        let index = if self.closed() {
+            3
+        } else if self.running() {
+            1
+        } else if self.started() {
+            2
+        } else {
+            0
+        };
+        names[index]
     }
 
     pub fn suspended(&self) -> bool {
-        !self.closed.load()
-            && !self.running.load()
-            && self.frame_opt().is_some_and(|f| f.lasti() > 0)
+        !self.closed.load() && !self.running.load() && self.started()
     }
 
     pub fn running(&self) -> bool {
diff --git a/crates/vm/src/dict_inner.rs b/crates/vm/src/dict_inner.rs
index 4a901bfbf0e..8b4a8eb6def 100644
--- a/crates/vm/src/dict_inner.rs
+++ b/crates/vm/src/dict_inner.rs
@@ -184,6 +184,8 @@ impl IndexEntry {
 struct DictInner<T> {
     used: usize,
     filled: usize,
+    // Only private atomic relocations invalidate same-size reverse iteration.
+    relocation_epoch: u64,
     indices: Vec<IndexEntry>,
     entries: Vec<Option<DictEntry<T>>>,
 }
@@ -210,7 +212,7 @@ impl<T: Clone> Clone for Dict<T> {
         }
         // Keep dense copies cheap, but do not carry mostly empty storage into
         // a new dictionary. pop_back can leave oversized indices without holes.
-        let inner = if inner.used >= inner.entries.len() - inner.entries.len() / 3
+        let mut inner = if inner.used >= inner.entries.len() - inner.entries.len() / 3
             && (inner.indices.len() <= 8 || inner.used >= inner.indices.len() / 4)
         {
             inner.clone()
@@ -218,6 +220,7 @@ impl<T: Clone> Clone for Dict<T> {
             let mut copy = DictInner {
                 used: inner.used,
                 filled: inner.used,
+                relocation_epoch: 0,
                 indices: Vec::new(),
                 entries: Vec::with_capacity(inner.used),
             };
@@ -226,6 +229,7 @@ impl<T: Clone> Clone for Dict<T> {
             copy.resize(inner.used * 2);
             copy
         };
+        inner.relocation_epoch = 0;
         Self {
             inner: PyRwLock::new(inner),
             keys_version: AtomicU32::new(0),
@@ -239,6 +243,7 @@ impl<T> Default for Dict<T> {
             inner: PyRwLock::new(DictInner {
                 used: 0,
                 filled: 0,
+                relocation_epoch: 0,
                 indices: vec![IndexEntry::FREE; 8],
                 entries: Vec::new(),
             }),
@@ -262,9 +267,16 @@ pub struct DictSize {
     pub entries_size: usize,
     pub used: usize,
     filled: usize,
+    relocation_epoch: u64,
 }
 
-/// The dict was resized under an iterator holding an older [`DictSize`].
+impl DictSize {
+    pub(crate) fn has_same_used_and_relocations(&self, other: &Self) -> bool {
+        self.used == other.used && self.relocation_epoch == other.relocation_epoch
+    }
+}
+
+/// The dict changed under an iterator holding an older [`DictSize`].
 #[derive(Debug)]
 pub(crate) struct DictChanged;
 
@@ -387,6 +399,7 @@ impl<T> DictInner<T> {
             entries_size: self.entries.len(),
             used: self.used,
             filled: self.filled,
+            relocation_epoch: self.relocation_epoch,
         }
     }
 
@@ -578,22 +591,14 @@ impl<T: Clone> Dict<T> {
         }
     }
 
-    /// Store a key
-    pub(crate) fn insert<K>(&self, vm: &VirtualMachine, key: &K, value: T) -> PyResult<()>
-    where
-        K: DictKey + ?Sized,
-    {
-        let hash = key.key_hash(vm)?;
-        self.insert_known_hash(vm, key, hash, value)
-    }
-
-    /// Store a key whose hash the caller already knows.
+    /// Store a key.
     ///
     /// `hash` must be computed for `key` or read from [`Self::keys_with_hashes`]
-    /// or [`Self::next_entry_with_hash`] on a container holding this same key.
+    /// or [`Self::items_with_hashes`] or [`Self::next_entry_with_hash`] on a
+    /// container holding this same key.
     /// A wrong hash lands the entry in a bucket no lookup probes, silently
     /// losing the key.
-    pub(crate) fn insert_known_hash<K>(
+    pub(crate) fn insert<K>(
         &self,
         vm: &VirtualMachine,
         key: &K,
@@ -603,16 +608,16 @@ impl<T: Clone> Dict<T> {
     where
         K: DictKey + ?Sized,
     {
-        self.insert_known_hash_indexed(vm, key, hash, value)?;
+        self.insert_indexed(vm, key, hash, value)?;
         Ok(())
     }
 
-    /// [`Self::insert_known_hash`], also reporting the entry index it stored to.
+    /// [`Self::insert`], also reporting the entry index it stored to.
     ///
     /// The index doubles as a `hint` for [`Self::get_hint`] /
     /// [`Self::insert_with_hint`], so a caller that wants one gets it from the
     /// store itself instead of probing the dict a second time.
-    fn insert_known_hash_indexed<K>(
+    fn insert_indexed<K>(
         &self,
         vm: &VirtualMachine,
         key: &K,
@@ -669,43 +674,23 @@ impl<T: Clone> Dict<T> {
         Ok(stored_index)
     }
 
+    /// [`Self::insert`] for membership. Same hash contract.
     pub(crate) fn contains<K: DictKey + ?Sized>(
         &self,
         vm: &VirtualMachine,
         key: &K,
-    ) -> PyResult<bool> {
-        let key_hash = key.key_hash(vm)?;
-        self.contains_known_hash(vm, key, key_hash)
-    }
-
-    /// [`Self::contains`] with a known hash. Same contract as
-    /// [`Self::insert_known_hash`].
-    pub(crate) fn contains_known_hash<K: DictKey + ?Sized>(
-        &self,
-        vm: &VirtualMachine,
-        key: &K,
         hash: HashValue,
     ) -> PyResult<bool> {
         let (entry, _) = self.lookup(vm, key, hash, None)?;
         Ok(entry.index().is_some())
     }
 
-    /// Retrieve a key
+    /// Retrieve a key. Same hash contract as [`Self::insert`].
     #[cfg_attr(feature = "flame-it", flame("Dict"))]
     pub(crate) fn get<K: DictKey + ?Sized>(
         &self,
         vm: &VirtualMachine,
         key: &K,
-    ) -> PyResult<Option<T>> {
-        let hash = key.key_hash(vm)?;
-        self._get_inner(vm, key, hash)
-    }
-
-    /// `_PyDict_GetItem_KnownHash`: lookup using a caller-supplied hash.
-    pub(crate) fn get_known_hash<K: DictKey + ?Sized>(
-        &self,
-        vm: &VirtualMachine,
-        key: &K,
         hash: HashValue,
     ) -> PyResult<Option<T>> {
         self._get_inner(vm, key, hash)
@@ -719,8 +704,8 @@ impl<T: Clone> Dict<T> {
         &self,
         vm: &VirtualMachine,
         key: &K,
+        hash: HashValue,
     ) -> PyResult<Option<u16>> {
-        let hash = key.key_hash(vm)?;
         let (entry, _) = self.lookup(vm, key, hash, None)?;
         let Some(index) = entry.index() else {
             return Ok(None);
@@ -736,8 +721,8 @@ impl<T: Clone> Dict<T> {
         &self,
         vm: &VirtualMachine,
         key: &K,
+        hash: HashValue,
     ) -> PyResult<Option<(T, Option<u16>)>> {
-        let hash = key.key_hash(vm)?;
         let ret = loop {
             let (entry, index_index) = self.lookup(vm, key, hash, None)?;
             if let Some(index) = entry.index() {
@@ -763,6 +748,7 @@ impl<T: Clone> Dict<T> {
         &self,
         vm: &VirtualMachine,
         key: &K,
+        hash: HashValue,
         hint: usize,
         value: T,
     ) -> PyResult<Option<u16>> {
@@ -779,8 +765,7 @@ impl<T: Clone> Dict<T> {
                 _ => value,
             }
         };
-        let hash = key.key_hash(vm)?;
-        let stored = self.insert_known_hash_indexed(vm, key, hash, value)?;
+        let stored = self.insert_indexed(vm, key, hash, value)?;
         Ok(u16::try_from(stored).ok())
     }
 
@@ -860,8 +845,8 @@ impl<T: Clone> Dict<T> {
         other: &Self,
         vm: &VirtualMachine,
         key: &K,
+        hash: HashValue,
     ) -> PyResult<Option<T>> {
-        let hash = key.key_hash(vm)?;
         if let Some(x) = self._get_inner(vm, key, hash)? {
             Ok(Some(x))
         } else {
@@ -884,36 +869,29 @@ impl<T: Clone> Dict<T> {
 
     /// Install an owned table, releasing the old entries after unlocking.
     pub(crate) fn replace_contents(&self, other: Self) {
-        let replacement = other.inner.into_inner();
+        let mut replacement = other.inner.into_inner();
         let _removed = {
             let mut inner = self.write();
             self.invalidate_keys_version();
+            // Relocation history belongs to this dict, not the incoming table.
+            replacement.relocation_epoch = inner.relocation_epoch;
             core::mem::replace(&mut *inner, replacement)
         };
     }
 
-    /// Delete a key
-    pub(crate) fn delete<K>(&self, vm: &VirtualMachine, key: &K) -> PyResult<()>
+    /// Delete a key. Same hash contract as [`Self::insert`].
+    pub(crate) fn delete<K>(&self, vm: &VirtualMachine, key: &K, hash: HashValue) -> PyResult<()>
     where
         K: DictKey + ?Sized,
     {
-        if self.remove_if_exists(vm, key)?.is_some() {
+        if self.remove_if_exists(vm, key, hash)?.is_some() {
             Ok(())
         } else {
             Err(vm.new_key_error(key.to_pyobject(vm)))
         }
     }
 
-    pub(crate) fn delete_if_exists<K>(&self, vm: &VirtualMachine, key: &K) -> PyResult<bool>
-    where
-        K: DictKey + ?Sized,
-    {
-        self.remove_if_exists(vm, key).map(|opt| opt.is_some())
-    }
-
-    /// [`Self::delete_if_exists`] with a known hash. Same contract as
-    /// [`Self::insert_known_hash`].
-    pub(crate) fn delete_if_exists_known_hash<K>(
+    pub(crate) fn delete_if_exists<K>(
         &self,
         vm: &VirtualMachine,
         key: &K,
@@ -922,44 +900,39 @@ impl<T: Clone> Dict<T> {
     where
         K: DictKey + ?Sized,
     {
-        self.remove_if_known_hash(vm, key, hash, |_| Ok(true))
+        self.remove_if_exists(vm, key, hash)
             .map(|opt| opt.is_some())
     }
 
-    pub(crate) fn delete_if<K, F>(&self, vm: &VirtualMachine, key: &K, pred: F) -> PyResult<bool>
+    pub(crate) fn delete_if<K, F>(
+        &self,
+        vm: &VirtualMachine,
+        key: &K,
+        hash: HashValue,
+        pred: F,
+    ) -> PyResult<bool>
     where
         K: DictKey + ?Sized,
         F: Fn(&T) -> PyResult<bool>,
     {
-        self.remove_if(vm, key, pred).map(|opt| opt.is_some())
-    }
-
-    pub(crate) fn remove_if_exists<K>(&self, vm: &VirtualMachine, key: &K) -> PyResult<Option<T>>
-    where
-        K: DictKey + ?Sized,
-    {
-        self.remove_if(vm, key, |_| Ok(true))
+        self.remove_if(vm, key, hash, pred).map(|opt| opt.is_some())
     }
 
-    /// pred should be VERY CAREFUL about what it does as it is called while
-    /// the dict's internal mutex is held
-    pub(crate) fn remove_if<K, F>(
+    pub(crate) fn remove_if_exists<K>(
         &self,
         vm: &VirtualMachine,
         key: &K,
-        pred: F,
+        hash: HashValue,
     ) -> PyResult<Option<T>>
     where
         K: DictKey + ?Sized,
-        F: Fn(&T) -> PyResult<bool>,
     {
-        let hash = key.key_hash(vm)?;
-        self.remove_if_known_hash(vm, key, hash, pred)
+        self.remove_if(vm, key, hash, |_| Ok(true))
     }
 
-    /// [`Self::remove_if`] with a known hash. Same contract as
-    /// [`Self::insert_known_hash`].
-    fn remove_if_known_hash<K, F>(
+    /// pred should be VERY CAREFUL about what it does as it is called while
+    /// the dict's internal mutex is held. Same hash contract as [`Self::insert`].
+    pub(crate) fn remove_if<K, F>(
         &self,
         vm: &VirtualMachine,
         key: &K,
@@ -980,9 +953,9 @@ impl<T: Clone> Dict<T> {
         Ok(removed.map(|entry| entry.value))
     }
 
-    /// Delete an existing key or insert a missing key using its known hash.
-    /// Same contract as [`Self::insert_known_hash`].
-    pub(crate) fn delete_or_insert_known_hash(
+    /// Delete an existing key or insert a missing key. Same hash contract as
+    /// [`Self::insert`].
+    pub(crate) fn delete_or_insert(
         &self,
         vm: &VirtualMachine,
         key: &PyObject,
@@ -1010,12 +983,19 @@ impl<T: Clone> Dict<T> {
         Ok(())
     }
 
-    pub(crate) fn setdefault<K, F>(&self, vm: &VirtualMachine, key: &K, default: F) -> PyResult<T>
+    /// Get the value for `key`, inserting `default()` if it is absent.
+    /// Same hash contract as [`Self::insert`].
+    pub(crate) fn setdefault<K, F>(
+        &self,
+        vm: &VirtualMachine,
+        key: &K,
+        hash: HashValue,
+        default: F,
+    ) -> PyResult<T>
     where
         K: DictKey + ?Sized,
         F: FnOnce() -> T,
     {
-        let hash = key.key_hash(vm)?;
         let mut default = Some(default);
         loop {
             let (index_entry, index_index) = self.lookup(vm, key, hash, None)?;
@@ -1050,13 +1030,13 @@ impl<T: Clone> Dict<T> {
         &self,
         vm: &VirtualMachine,
         key: &K,
+        hash: HashValue,
         default: F,
     ) -> PyResult<(PyObjectRef, T)>
     where
         K: DictKey + ?Sized,
         F: FnOnce() -> T,
     {
-        let hash = key.key_hash(vm)?;
         let mut default = Some(default);
         loop {
             let (index_entry, index_index) = self.lookup(vm, key, hash, None)?;
@@ -1117,7 +1097,8 @@ impl<T: Clone> Dict<T> {
         }
     }
 
-    /// [`Self::next_entry_checked`] in reverse.
+    /// Step backward, validating the live size and private relocation history
+    /// under the same read guard. Ordinary same-size mutations may change layout.
     pub(crate) fn prev_entry_checked<R>(
         &self,
         mut position: EntryIndex,
@@ -1125,7 +1106,7 @@ impl<T: Clone> Dict<T> {
         project: impl FnOnce(&PyObject, &T) -> R,
     ) -> Result<Option<(usize, R)>, DictChanged> {
         let inner = self.read();
-        if inner.size() != *old {
+        if !inner.size().has_same_used_and_relocations(old) {
             return Err(DictChanged);
         }
         loop {
@@ -1193,7 +1174,7 @@ impl<T: Clone> Dict<T> {
     }
 
     /// All keys paired with the hash stored in their entry, for feeding
-    /// [`Self::insert_known_hash`] without re-calling `__hash__`.
+    /// [`Self::insert`] without re-calling `__hash__`.
     pub(crate) fn keys_with_hashes(&self) -> Vec<(PyObjectRef, HashValue)> {
         self.read()
             .entries
@@ -1218,6 +1199,14 @@ impl<T: Clone> Dict<T> {
             .collect()
     }
 
+    pub(crate) fn items_with_hashes(&self) -> Vec<(PyObjectRef, T, HashValue)> {
+        self.read()
+            .entries
+            .iter()
+            .filter_map(|v| v.as_ref().map(|v| (v.key.clone(), v.value.clone(), v.hash)))
+            .collect()
+    }
+
     /// Fold stored hashes under the read lock; the callback must not run Python.
     pub(crate) fn fold_hashes<Acc, Fold>(&self, init: Acc, f: Fold) -> Acc
     where
@@ -1375,13 +1364,13 @@ impl<T: Clone> Dict<T> {
         Ok(ControlFlow::Break(removed))
     }
 
-    /// Retrieve and delete a key
+    /// Retrieve and delete a key. Same hash contract as [`Self::insert`].
     pub(crate) fn pop<K: DictKey + ?Sized>(
         &self,
         vm: &VirtualMachine,
         key: &K,
+        hash_value: HashValue,
     ) -> PyResult<Option<T>> {
-        let hash_value = key.key_hash(vm)?;
         let removed = loop {
             let lookup = self.lookup(vm, key, hash_value, None)?;
             match self.pop_inner(lookup) {
@@ -1392,6 +1381,165 @@ impl<T: Clone> Dict<T> {
         Ok(removed)
     }
 
+    // Locate an entry and mutate it under one guard. The operation must not
+    // run Python or drop owned Python references while the guard is held.
+    fn with_entry_mut<K: DictKey + ?Sized, R>(
+        &self,
+        vm: &VirtualMachine,
+        key: &K,
+        hash_value: HashValue,
+        update: impl FnOnce(&mut DictInner<T>, EntryIndex) -> R,
+    ) -> PyResult<Option<R>> {
+        struct ProbeWitness {
+            index_index: IndexIndex,
+            entry_index: IndexEntry,
+            key: Option<(HashValue, PyObjectRef)>,
+        }
+
+        let mut idxs = None;
+        let mut prefix = Vec::<ProbeWitness>::new();
+        let mut compared: Option<(EntryIndex, IndexIndex, PyObjectRef, bool)> = None;
+        'lookup: loop {
+            // Keep the compared key alive until after the guard is released,
+            // including when equality cleared the dictionary and recycled its
+            // entry and bucket for a different key.
+            let comparison = compared.take();
+            let mut inner = self.write();
+            let mask = (inner.indices.len() - 1) as i64;
+            let probes = idxs.get_or_insert_with(|| GenIndexes::new(hash_value, mask));
+            if probes.mask != mask {
+                drop(inner);
+                prefix.clear();
+                idxs = None;
+                continue;
+            }
+            let matched = if let Some((entry_index, index_index, candidate, equal)) = &comparison {
+                let valid = inner.indices.get(*index_index).and_then(|i| i.index())
+                    == Some(*entry_index)
+                    && inner
+                        .get_entry_checked(*entry_index, *index_index)
+                        .is_some_and(|entry| entry.hash == hash_value && entry.key.is(candidate));
+                // A false comparison can survive while another previously
+                // probed bucket changes (including after nested compaction).
+                // Revalidate the whole prefix before continuing past it.
+                let prefix_valid = *equal
+                    || prefix.iter().all(|witness| {
+                        inner.indices.get(witness.index_index) == Some(&witness.entry_index)
+                            && witness.key.as_ref().is_none_or(|(hash, key)| {
+                                inner
+                                    .get_entry_checked(
+                                        witness.entry_index.index().unwrap(),
+                                        witness.index_index,
+                                    )
+                                    .is_some_and(|entry| entry.hash == *hash && entry.key.is(key))
+                            })
+                    });
+                if !valid || !prefix_valid {
+                    drop(inner);
+                    prefix.clear();
+                    idxs = None;
+                    continue;
+                }
+                equal.then_some(*entry_index)
+            } else {
+                None
+            };
+            let entry_index = match matched {
+                Some(index) => index,
+                None => loop {
+                    let index_index = probes.next();
+                    let index_entry = inner.indices[index_index];
+                    match index_entry {
+                        IndexEntry::FREE => return Ok(None),
+                        IndexEntry::DUMMY => {
+                            prefix.push(ProbeWitness {
+                                index_index,
+                                entry_index: index_entry,
+                                key: None,
+                            });
+                            continue;
+                        }
+                        _ => {}
+                    }
+                    let entry_index = index_entry.index().unwrap();
+                    let entry = inner.entries[entry_index].as_ref().unwrap();
+                    if key.key_is(&entry.key) {
+                        break entry_index;
+                    }
+                    prefix.push(ProbeWitness {
+                        index_index,
+                        entry_index: index_entry,
+                        key: Some((entry.hash, entry.key.clone())),
+                    });
+                    if entry.hash == hash_value {
+                        let candidate = entry.key.clone();
+                        drop(inner);
+                        drop(comparison);
+                        let equal = key.key_eq(vm, &candidate)?;
+                        compared = Some((entry_index, index_index, candidate, equal));
+                        continue 'lookup;
+                    }
+                },
+            };
+            let result = update(&mut inner, entry_index);
+            drop(inner);
+            return Ok(Some(result));
+        }
+    }
+
+    /// Move an existing entry to the end and return its current value without
+    /// making the key temporarily absent. Equality runs unlocked.
+    pub(crate) fn move_to_end<K: DictKey + ?Sized>(
+        &self,
+        vm: &VirtualMachine,
+        key: &K,
+        hash: HashValue,
+    ) -> PyResult<Option<T>> {
+        self.with_entry_mut(vm, key, hash, |inner, entry_index| {
+            let value = inner.entries[entry_index].as_ref().unwrap().value.clone();
+            if inner.entries[entry_index + 1..].iter().any(Option::is_some) {
+                // Reserve before taking the entry. No reader can observe an
+                // absent entry, and no hashing, equality or finalizer runs in
+                // this critical section.
+                inner.entries.reserve(1);
+                self.invalidate_keys_version();
+                inner.relocation_epoch = inner.relocation_epoch.wrapping_add(1);
+                let entry = inner.entries[entry_index].take().unwrap();
+                let new_index = inner.entries.len();
+                inner.indices[entry.index] = unsafe {
+                    // SAFETY: new_index is a valid nonnegative entry index.
+                    IndexEntry::from_index_unchecked(new_index)
+                };
+                inner.entries.push(Some(entry));
+                let holes = inner.entries.len() - inner.used;
+                if holes >= 2 && holes >= inner.used {
+                    // Moves do not increase `filled`, so ordinary insertion's
+                    // resize threshold cannot bound their accumulated holes.
+                    let indices_size = inner.indices.len();
+                    inner.resize(indices_size);
+                }
+            }
+            value
+        })
+    }
+
+    // Replace only a still-matching value. The predicate must not run Python.
+    // Keep both the replacement and removed value alive outside the guard.
+    pub(crate) fn replace_if<K: DictKey + ?Sized>(
+        &self,
+        vm: &VirtualMachine,
+        key: &K,
+        hash: HashValue,
+        replacement: T,
+        matches: impl FnOnce(&T) -> bool,
+    ) -> PyResult<bool> {
+        let removed = self.with_entry_mut(vm, key, hash, |inner, index| {
+            let entry = inner.entries[index].as_mut().unwrap();
+            matches(&entry.value).then(|| core::mem::replace(&mut entry.value, replacement.clone()))
+        })?;
+        Ok(removed.flatten().is_some())
+    }
+
     pub(crate) fn pop_back(&self) -> Option<(PyObjectRef, T)> {
         let inner = &mut *self.write();
         let entry = loop {
@@ -1838,15 +1986,148 @@ mod tests {
     use super::*;
     use crate::{Interpreter, common::ascii};
 
+    fn hash_key<K: DictKey + ?Sized>(vm: &VirtualMachine, key: &K) -> HashValue {
+        key.key_hash(vm).unwrap()
+    }
+
+    #[test]
+    fn move_to_end_preserves_values_and_invalidates_layout() {
+        Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let dict = Dict::default();
+            let keys = [
+                vm.ctx.intern_str("first"),
+                vm.ctx.intern_str("middle"),
+                vm.ctx.intern_str("last"),
+            ];
+            for (value, key) in keys.iter().enumerate() {
+                dict.insert(vm, *key, hash_key(vm, *key), value).unwrap();
+            }
+            let hint = dict
+                .hint_for_key(vm, keys[1], hash_key(vm, keys[1]))
+                .unwrap()
+                .unwrap() as usize;
+            let version = dict.assign_keys_version();
+            let size = dict.size();
+            assert_ne!(version, 0);
+            assert_eq!(
+                dict.move_to_end(vm, keys[1], hash_key(vm, keys[1]))
+                    .unwrap(),
+                Some(1)
+            );
+            assert_eq!(dict.values(), vec![0, 2, 1]);
+            assert_eq!(dict.keys_version(), 0);
+            assert_eq!(dict.get_index_if_keys_version(version, hint), None);
+            assert_eq!(dict.get_hint(vm, keys[1], hint).unwrap(), None);
+            assert!(dict.next_entry_checked(0, &size, |_, v| *v).is_err());
+            assert!(
+                dict.prev_entry_checked(size.entries_size - 1, &size, |_, v| *v)
+                    .is_err()
+            );
+
+            let version = dict.assign_keys_version();
+            let size = dict.size();
+            assert_eq!(
+                dict.move_to_end(vm, keys[1], hash_key(vm, keys[1]))
+                    .unwrap(),
+                Some(1)
+            );
+            assert_eq!(dict.keys_version(), version);
+            assert_eq!(dict.size(), size);
+            assert_eq!(
+                dict.move_to_end(vm, "absent", hash_key(vm, "absent"))
+                    .unwrap(),
+                None
+            );
+            assert_eq!(dict.keys_version(), version);
+            assert_eq!(dict.size(), size);
+            assert_eq!(dict.values(), vec![0, 2, 1]);
+        });
+    }
+
+    #[test]
+    fn move_to_end_compacts_and_keeps_indices_consistent() {
+        Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            for count in [2, 3, 32] {
+                let dict = Dict::default();
+                for key in 0..count {
+                    dict.insert(vm, &key, hash_key(vm, &key), key).unwrap();
+                }
+                for step in 0..1024 {
+                    let key = step % count;
+                    let size = dict.size();
+                    let hint = dict
+                        .hint_for_key(vm, &key, hash_key(vm, &key))
+                        .unwrap()
+                        .unwrap() as usize;
+                    let version = dict.assign_keys_version();
+                    assert_eq!(
+                        dict.move_to_end(vm, &key, hash_key(vm, &key)).unwrap(),
+                        Some(key)
+                    );
+                    assert_eq!(dict.get_index_if_keys_version(version, hint), None);
+                    assert!(dict.next_entry_checked(0, &size, |_, v| *v).is_err());
+                    assert!(
+                        dict.prev_entry_checked(size.entries_size - 1, &size, |_, v| *v)
+                            .is_err()
+                    );
+                    let inner = dict.read();
+                    assert_eq!(inner.used, count);
+                    assert_eq!(inner.filled, count);
+                    assert!(inner.entries.len() < 2 * count);
+                    assert!(inner.entries.capacity() <= 4 * count);
+                    let values: Vec<_> = inner.entries.iter().flatten().map(|e| e.value).collect();
+                    assert_eq!(
+                        values,
+                        (1..=count).map(|i| (key + i) % count).collect::<Vec<_>>()
+                    );
+                    for (index, entry) in inner.entries.iter().enumerate() {
+                        if let Some(entry) = entry {
+                            assert_eq!(inner.indices[entry.index].index(), Some(index));
+                            assert_eq!(entry.hash, entry.value.key_hash(vm).unwrap());
+                        }
+                    }
+                    for (bucket, index) in inner.indices.iter().enumerate() {
+                        if let Some(index) = index.index() {
+                            assert_eq!(inner.entries[index].as_ref().unwrap().index, bucket);
+                        }
+                    }
+                }
+            }
+        });
+    }
+
+    #[test]
+    fn move_to_end_restores_only_matching_shared_shapes() {
+        Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let first = vm.ctx.intern_str("move_first");
+            let last = vm.ctx.intern_str("move_last");
+            let dict = Dict::default();
+            let peer = Dict::default();
+            for table in [&dict, &peer] {
+                table.insert(vm, first, hash_key(vm, first), 1).unwrap();
+                table.insert(vm, last, hash_key(vm, last), 2).unwrap();
+            }
+            let version = dict.assign_keys_version();
+            assert_eq!(peer.assign_keys_version(), version);
+            dict.move_to_end(vm, first, hash_key(vm, first)).unwrap();
+            assert_ne!(dict.assign_keys_version(), version);
+            dict.move_to_end(vm, last, hash_key(vm, last)).unwrap();
+            // The second move compacts back to the original hole-free layout.
+            assert_eq!(dict.assign_keys_version(), version);
+            assert_eq!(dict.get_index_if_keys_version(version, 0), Some(1));
+            assert_eq!(dict.get_index_if_keys_version(version, 1), Some(2));
+        });
+    }
+
     #[test]
     fn clone_compacts_deleted_entries() {
         Interpreter::without_stdlib(Default::default()).enter(|vm| {
             let dict = Dict::default();
             for key in 0..128usize {
-                dict.insert(vm, &key, key).unwrap();
+                dict.insert(vm, &key, hash_key(vm, &key), key).unwrap();
             }
             for key in 0..120usize {
-                dict.delete(vm, &key).unwrap();
+                dict.delete(vm, &key, hash_key(vm, &key)).unwrap();
             }
             let version = dict.assign_keys_version();
             let copied = dict.clone();
@@ -1863,10 +2144,12 @@ mod tests {
             }
             assert_eq!(copied.values(), (120..128).collect::<Vec<_>>());
             for key in 120..128usize {
-                assert_eq!(copied.get(vm, &key).unwrap(), Some(key));
+                assert_eq!(copied.get(vm, &key, hash_key(vm, &key)).unwrap(), Some(key));
             }
-            copied.insert(vm, &0usize, 0).unwrap();
-            assert!(!dict.contains(vm, &0usize).unwrap());
+            copied
+                .insert(vm, &0usize, hash_key(vm, &0usize), 0)
+                .unwrap();
+            assert!(!dict.contains(vm, &0usize, hash_key(vm, &0usize)).unwrap());
         });
     }
 
@@ -1875,7 +2158,7 @@ mod tests {
         Interpreter::without_stdlib(Default::default()).enter(|vm| {
             let dict = Dict::default();
             for key in 0..128usize {
-                dict.insert(vm, &key, ()).unwrap();
+                dict.insert(vm, &key, hash_key(vm, &key), ()).unwrap();
             }
             for _ in 0..124 {
                 dict.pop_back().unwrap();
@@ -1884,8 +2167,8 @@ mod tests {
             assert_eq!(copied.len(), 4);
             assert!(copied.read().indices.len() < dict.read().indices.len());
             for key in 0..4usize {
-                assert!(copied.contains(vm, &key).unwrap());
-                dict.delete(vm, &key).unwrap();
+                assert!(copied.contains(vm, &key, hash_key(vm, &key)).unwrap());
+                dict.delete(vm, &key, hash_key(vm, &key)).unwrap();
             }
             let empty = dict.clone();
             assert_eq!(dict.len(), 0);
@@ -1905,10 +2188,14 @@ mod tests {
             let padding = vm.ctx.intern_str("padding");
             let first: Dict<i32> = Dict::default();
             let second: Dict<i32> = Dict::default();
-            first.insert(vm, name, 10).unwrap();
-            first.insert(vm, padding, 20).unwrap();
-            second.insert(vm, padding, 30).unwrap();
-            second.insert(vm, name, 40).unwrap();
+            first.insert(vm, name, hash_key(vm, name), 10).unwrap();
+            first
+                .insert(vm, padding, hash_key(vm, padding), 20)
+                .unwrap();
+            second
+                .insert(vm, padding, hash_key(vm, padding), 30)
+                .unwrap();
+            second.insert(vm, name, hash_key(vm, name), 40).unwrap();
             let (first_version, first_index) = first.module_attr_cache(name, vm).unwrap();
             let (second_version, second_index) = second.module_attr_cache(name, vm).unwrap();
             assert_ne!(first_version, second_version);
@@ -1933,21 +2220,35 @@ mod tests {
             );
 
             let foreign_key: PyObjectRef = vm.ctx.new_int(7).into();
-            first.insert(vm, &*foreign_key, 50).unwrap();
+            first
+                .insert(vm, &*foreign_key, hash_key(vm, &*foreign_key), 50)
+                .unwrap();
             assert!(first.module_attr_cache(name, vm).is_none());
             assert_eq!(
                 first.get_cached_module_attr(name, first_version as usize, first_index.into(), vm),
                 None
             );
-            first.delete(vm, &*foreign_key).unwrap();
             first
-                .insert(vm, vm.ctx.intern_str("__getattr__"), 60)
+                .delete(vm, &*foreign_key, hash_key(vm, &*foreign_key))
+                .unwrap();
+            first
+                .insert(
+                    vm,
+                    vm.ctx.intern_str("__getattr__"),
+                    hash_key(vm, vm.ctx.intern_str("__getattr__")),
+                    60,
+                )
                 .unwrap();
             assert!(first.module_attr_cache(name, vm).is_none());
 
             let noninterned: Dict<i32> = Dict::default();
             noninterned
-                .insert(vm, &*vm.ctx.new_str("target"), 70)
+                .insert(
+                    vm,
+                    &*vm.ctx.new_str("target"),
+                    hash_key(vm, &*vm.ctx.new_str("target")),
+                    70,
+                )
                 .unwrap();
             let (version, index) = noninterned.module_attr_cache(name, vm).unwrap();
             assert_eq!(
@@ -1965,27 +2266,31 @@ mod tests {
 
             let key1 = vm.new_pyobj(true);
             let value1 = vm.new_pyobj(ascii!("abc"));
-            dict.insert(vm, &*key1, value1).unwrap();
+            dict.insert(vm, &*key1, hash_key(vm, &*key1), value1)
+                .unwrap();
             assert_eq!(1, dict.len());
 
             let key2 = vm.new_pyobj(ascii!("x"));
             let value2 = vm.new_pyobj(ascii!("def"));
-            dict.insert(vm, &*key2, value2.clone()).unwrap();
+            dict.insert(vm, &*key2, hash_key(vm, &*key2), value2.clone())
+                .unwrap();
             assert_eq!(2, dict.len());
 
-            dict.insert(vm, &*key1, value2.clone()).unwrap();
+            dict.insert(vm, &*key1, hash_key(vm, &*key1), value2.clone())
+                .unwrap();
             assert_eq!(2, dict.len());
 
-            dict.delete(vm, &*key1).unwrap();
+            dict.delete(vm, &*key1, hash_key(vm, &*key1)).unwrap();
             assert_eq!(1, dict.len());
 
-            dict.insert(vm, &*key1, value2.clone()).unwrap();
+            dict.insert(vm, &*key1, hash_key(vm, &*key1), value2.clone())
+                .unwrap();
             assert_eq!(2, dict.len());
 
-            assert!(dict.contains(vm, &*key1).unwrap());
-            assert!(dict.contains(vm, "x").unwrap());
+            assert!(dict.contains(vm, &*key1, hash_key(vm, &*key1)).unwrap());
+            assert!(dict.contains(vm, "x", hash_key(vm, "x")).unwrap());
 
-            let val = dict.get(vm, "x").unwrap().unwrap();
+            let val = dict.get(vm, "x", hash_key(vm, "x")).unwrap().unwrap();
             vm.bool_eq(&val, &value2)
                 .expect("retrieved value must be equal to inserted value.");
         })
@@ -2008,12 +2313,16 @@ mod tests {
                 (inner.indices.len(), inner.entries.capacity())
             };
             for key in 0..count {
-                dict.insert(vm, &key, vm.ctx.none()).unwrap();
+                dict.insert(vm, &key, hash_key(vm, &key), vm.ctx.none())
+                    .unwrap();
                 let inner = dict.read();
                 assert_eq!((inner.indices.len(), inner.entries.capacity()), capacity);
             }
             assert_eq!(dict.len(), count);
-            assert!(dict.contains(vm, &(count - 1)).unwrap());
+            assert!(
+                dict.contains(vm, &(count - 1), hash_key(vm, &(count - 1)))
+                    .unwrap()
+            );
 
             // Existing and tombstoned layouts are left intact.
             dict.reserve_for_empty(count * 4);
@@ -2022,7 +2331,7 @@ mod tests {
                 assert_eq!((inner.indices.len(), inner.entries.capacity()), capacity);
             }
             for key in 0..count {
-                dict.delete(vm, &key).unwrap();
+                dict.delete(vm, &key, hash_key(vm, &key)).unwrap();
             }
             let old_size = dict.read().size();
             dict.reserve_for_empty(count * 4);
@@ -2061,19 +2370,21 @@ mod tests {
     fn replace_contents_invalidates_cached_indices() {
         Interpreter::without_stdlib(Default::default()).enter(|vm| {
             let dict = Dict::default();
-            dict.insert(vm, &1usize, ()).unwrap();
+            dict.insert(vm, &1usize, hash_key(vm, &1usize), ()).unwrap();
             let old_version = dict.assign_keys_version();
             assert_ne!(old_version, 0);
 
             let replacement = Dict::default();
-            replacement.insert(vm, &2usize, ()).unwrap();
+            replacement
+                .insert(vm, &2usize, hash_key(vm, &2usize), ())
+                .unwrap();
             assert_ne!(replacement.assign_keys_version(), 0);
             dict.replace_contents(replacement);
 
             assert_eq!(dict.keys_version(), 0);
             assert_eq!(dict.get_index_if_keys_version(old_version, 0), None);
-            assert!(!dict.contains(vm, &1usize).unwrap());
-            assert!(dict.contains(vm, &2usize).unwrap());
+            assert!(!dict.contains(vm, &1usize, hash_key(vm, &1usize)).unwrap());
+            assert!(dict.contains(vm, &2usize, hash_key(vm, &2usize)).unwrap());
         });
     }
 }
diff --git a/crates/vm/src/exception_group.rs b/crates/vm/src/exception_group.rs
index 2c61d8ba7c1..8c182d98158 100644
--- a/crates/vm/src/exception_group.rs
+++ b/crates/vm/src/exception_group.rs
@@ -65,7 +65,8 @@ pub(super) mod types {
         excs_str: PyAtomicRef<Option<PyObject>>,
     }
 
-    impl crate::class::PySubclass for PyBaseExceptionGroup {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PyBaseExceptionGroup {
         type Base = PyBaseException;
         fn as_base(&self) -> &Self::Base {
             &self.base
@@ -132,7 +133,7 @@ pub(super) mod types {
                     // frame, so a deep enough group runs off the native stack
                     // unless this guard is here.
                     let subgroup_result = vm
-                        .with_recursion("in exception group subgroup", || {
+                        .with_recursion(" in exception group subgroup", || {
                             vm.call_method(&exc, "subgroup", (matcher_value.clone(),))
                         })?;
                     if !vm.is_none(&subgroup_result) {
@@ -182,7 +183,7 @@ pub(super) mod types {
                 if is_base_exception_group(&exc, vm) {
                     // Same as in subgroup: nothing else bounds this recursion
                     // against the native stack.
-                    let result = vm.with_recursion("in exception group split", || {
+                    let result = vm.with_recursion(" in exception group split", || {
                         vm.call_method(&exc, "split", (matcher_value.clone(),))
                     })?;
                     let result_tuple: PyTupleRef = result.try_into_value(vm)?;
diff --git a/crates/vm/src/exceptions.rs b/crates/vm/src/exceptions.rs
index 9562ad7a8b5..b6f0cad9303 100644
--- a/crates/vm/src/exceptions.rs
+++ b/crates/vm/src/exceptions.rs
@@ -101,28 +101,117 @@ impl VirtualMachine {
     /// Print exception chain by calling sys.excepthook
     pub fn print_exception(&self, exc: &Py<PyBaseException>) {
         let vm = self;
-        let write_fallback = |exc, errstr| {
-            if let Ok(stderr) = sys::get_stderr(vm) {
-                let mut stderr = py_io::PyWriter(stderr, vm);
-                // if this fails stderr might be closed -- ignore it
-                let _ = writeln!(stderr, "{errstr}");
-                let _ = self.write_exception(&mut stderr, exc);
-            } else {
-                eprintln!("{errstr}\nlost sys.stderr");
-                let _ = self.write_exception(&mut py_io::IoWriter(io::stderr()), exc);
-            }
-        };
         if let Ok(excepthook) = vm.sys_module.get_attr("excepthook", vm) {
             let (exc_type, exc_val, exc_tb) = vm.split_exception(exc.to_owned());
             if let Err(eh_exc) = excepthook.call((exc_type, exc_val, exc_tb), vm) {
-                write_fallback(&eh_exc, "Error in sys.excepthook:");
-                write_fallback(exc, "Original exception was:");
+                writeln!(sys::PyStderr(vm), "Error in sys.excepthook:");
+                vm.display_exception(&eh_exc);
+                writeln!(sys::PyStderr(vm), "Original exception was:");
+                vm.display_exception(exc);
+            }
+        } else {
+            writeln!(sys::PyStderr(vm), "missing sys.excepthook");
+            vm.display_exception(exc);
+        }
+    }
+
+    /// PyErr_Print
+    ///
+    /// Record the exception as `sys.last_exc` and display it through
+    /// `sys.excepthook`. A `SystemExit` exits the process unless inspect mode
+    /// is enabled.
+    pub fn print_uncaught_exception(&self, exc: &Py<PyBaseException>) {
+        self.handle_system_exit(exc);
+        let (exc_type, exc_val, exc_tb) = self.split_exception(exc.to_owned());
+        for (name, value) in [
+            ("last_exc", &exc_val),
+            ("last_type", &exc_type),
+            ("last_value", &exc_val),
+            ("last_traceback", &exc_tb),
+        ] {
+            let _ = self.sys_module.set_attr(name, value.clone(), self);
+        }
+        let hook = self.sys_module.get_attr("excepthook", self).ok();
+        if let Err(audit_exc) = self.audit("sys.excepthook", || {
+            (
+                hook.clone().unwrap_or_else(|| self.ctx.none()),
+                exc_type.clone(),
+                exc_val.clone(),
+                exc_tb.clone(),
+            )
+        }) {
+            if audit_exc.fast_isinstance(self.ctx.exceptions.runtime_error) {
+                return;
+            }
+            self.run_unraisable(
+                audit_exc,
+                Some("Exception ignored in audit hook".to_owned()),
+                self.ctx.none(),
+            );
+        }
+        if let Some(hook) = hook {
+            if let Err(hook_exc) = hook.call((exc_type, exc_val, exc_tb), self) {
+                self.handle_system_exit(&hook_exc);
+                let _ = io::Write::flush(&mut io::stdout());
+                writeln!(sys::PyStderr(self), "Error in sys.excepthook:");
+                self.display_exception(&hook_exc);
+                writeln!(sys::PyStderr(self), "\nOriginal exception was:");
+                self.display_exception(exc);
             }
         } else {
-            write_fallback(exc, "missing sys.excepthook");
+            writeln!(sys::PyStderr(self), "sys.excepthook is missing");
+            self.display_exception(exc);
         }
     }
 
+    /// handle_system_exit
+    fn handle_system_exit(&self, exc: &Py<PyBaseException>) {
+        if let Some(exit_code) = self.handle_system_exit_and_keyboard_interrupt(exc) {
+            self.exit_process(exit_code);
+        }
+    }
+
+    /// PyErr_Display
+    ///
+    /// Display `exc` on `sys.stderr`; nothing is written when it is `None`.
+    pub fn display_exception(&self, exc: &Py<PyBaseException>) {
+        let file = self.sys_module.dict().get_item_opt("stderr", self);
+        if let Ok(Some(file)) = &file {
+            if !self.is_none(file) {
+                self.display_exception_to(file, exc);
+            }
+            return;
+        }
+        self.dump_object(exc.as_object());
+        eprintln!("lost sys.stderr");
+        if let Err(err) = file {
+            self.dump_object(err.as_object());
+        }
+    }
+
+    /// _PyErr_Display
+    ///
+    /// Display `exc` through `traceback._print_exception_bltin`, falling back
+    /// to the native printer writing to `file`.
+    pub(crate) fn display_exception_to(&self, file: &PyObject, exc: &Py<PyBaseException>) {
+        if let Ok(print_exception) = self
+            .import("traceback", 0)
+            .and_then(|traceback| traceback.get_attr("_print_exception_bltin", self))
+            && print_exception.is_callable()
+            && print_exception.call((exc.to_owned(),), self).is_ok()
+        {
+            return;
+        }
+        if self
+            .write_exception(&mut py_io::PyWriter(file.to_owned(), self), exc)
+            .is_err()
+        {
+            self.dump_object(exc.as_object());
+            eprintln!("lost sys.stderr");
+        }
+        let _ = self.call_method(file, "flush", ());
+    }
+
     pub fn write_exception<W: Write>(
         &self,
         output: &mut W,
@@ -185,10 +274,7 @@ impl VirtualMachine {
 
         let traceback = exc.traceback.read().clone();
         if let Some(tb) = traceback {
-            writeln!(output, "Traceback (most recent call last):")?;
-            for tb in tb.iter() {
-                write_traceback_entry(output, &tb)?;
-            }
+            write_traceback(output, &tb)?;
         }
 
         let varargs = exc.args();
@@ -448,6 +534,17 @@ fn print_source_line<W: Write>(
     Ok(())
 }
 
+pub(crate) fn write_traceback<W: Write>(
+    output: &mut W,
+    traceback: &PyTracebackRef,
+) -> Result<(), W::Error> {
+    writeln!(output, "Traceback (most recent call last):")?;
+    for entry in traceback.iter() {
+        write_traceback_entry(output, &entry)?;
+    }
+    Ok(())
+}
+
 /// Print exception occurrence location from traceback element
 fn write_traceback_entry<W: Write>(
     output: &mut W,
@@ -549,6 +646,7 @@ pub struct ExceptionZoo {
     pub attribute_error: &'static Py<PyType>,
     pub buffer_error: &'static Py<PyType>,
     pub eof_error: &'static Py<PyType>,
+    pub import_cycle_error: &'static Py<PyType>,
     pub import_error: &'static Py<PyType>,
     pub module_not_found_error: &'static Py<PyType>,
     pub lookup_error: &'static Py<PyType>,
@@ -926,6 +1024,7 @@ impl ExceptionZoo {
         let eof_error = PyEOFError::init_builtin_type();
 
         let import_error = PyImportError::init_builtin_type();
+        let import_cycle_error = PyImportCycleError::init_builtin_type();
         let module_not_found_error = PyModuleNotFoundError::init_builtin_type();
 
         let lookup_error = PyLookupError::init_builtin_type();
@@ -1010,6 +1109,7 @@ impl ExceptionZoo {
             attribute_error,
             buffer_error,
             eof_error,
+            import_cycle_error,
             import_error,
             module_not_found_error,
             lookup_error,
@@ -1104,6 +1204,7 @@ impl ExceptionZoo {
         extend_exception!(PyEOFError, ctx, excs.eof_error);
 
         extend_exception!(PyImportError, ctx, excs.import_error);
+        extend_exception!(PyImportCycleError, ctx, excs.import_cycle_error);
         extend_exception!(PyModuleNotFoundError, ctx, excs.module_not_found_error);
 
         extend_exception!(PyLookupError, ctx, excs.lookup_error);
@@ -1576,6 +1677,18 @@ impl ToPyException for rustpython_host_env::socket::AncillaryPackError {
     }
 }
 
+#[cfg(windows)]
+impl ToPyException for rustpython_host_env::time::TimestampError {
+    fn to_pyexception(&self, vm: &VirtualMachine) -> PyBaseExceptionRef {
+        match self {
+            Self::FiletimeOutOfRange => {
+                vm.new_overflow_error("timestamp out of range for Windows FILETIME")
+            }
+            Self::Os(error) => error.to_pyexception(vm),
+        }
+    }
+}
+
 #[cfg(any(unix, windows))]
 impl ToPyException for rustpython_host_env::time::CheckedTmError {
     fn to_pyexception(&self, vm: &VirtualMachine) -> PyBaseExceptionRef {
@@ -1750,7 +1863,8 @@ pub(super) mod types {
         code: PyAtomicRef<Option<PyObject>>,
     }
 
-    impl crate::class::PySubclass for PySystemExit {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PySystemExit {
         type Base = PyBaseException;
         fn as_base(&self) -> &Self::Base {
             &self.base
@@ -1830,7 +1944,8 @@ pub(super) mod types {
         value: PyAtomicRef<Option<PyObject>>,
     }
 
-    impl crate::class::PySubclass for PyStopIteration {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PyStopIteration {
         type Base = PyException;
         fn as_base(&self) -> &Self::Base {
             &self.base
@@ -1925,7 +2040,8 @@ pub(super) mod types {
         obj: PyAtomicRef<Option<PyObject>>,
     }
 
-    impl crate::class::PySubclass for PyAttributeError {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PyAttributeError {
         type Base = PyException;
         fn as_base(&self) -> &Self::Base {
             &self.base
@@ -2051,7 +2167,8 @@ pub(super) mod types {
         name_from: PyAtomicRef<Option<PyObject>>,
     }
 
-    impl crate::class::PySubclass for PyImportError {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PyImportError {
         type Base = PyException;
         fn as_base(&self) -> &Self::Base {
             &self.base
@@ -2187,6 +2304,11 @@ pub(super) mod types {
         }
     }
 
+    #[pyexception(name, base = PyImportError, ctx = "import_cycle_error", impl)]
+    #[derive(Debug)]
+    #[repr(transparent)]
+    pub struct PyImportCycleError(PyImportError);
+
     #[pyexception(name, base = PyImportError, ctx = "module_not_found_error", impl)]
     #[derive(Debug)]
     #[repr(transparent)]
@@ -2263,7 +2385,8 @@ pub(super) mod types {
         name: PyAtomicRef<Option<PyObject>>,
     }
 
-    impl crate::class::PySubclass for PyNameError {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PyNameError {
         type Base = PyException;
         fn as_base(&self) -> &Self::Base {
             &self.base
@@ -2357,7 +2480,8 @@ pub(super) mod types {
         written: AtomicCell<isize>,
     }
 
-    impl crate::class::PySubclass for PyOSError {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PyOSError {
         type Base = PyException;
         fn as_base(&self) -> &Self::Base {
             &self.base
@@ -2720,7 +2844,9 @@ pub(super) mod types {
                             .filter(|f| !vm.is_none(f));
 
                         let winerror: Option<PyObjectRef> = cfg_select! {
-                            windows => obj.get_attr("winerror", vm).ok().filter(|w| !vm.is_none(w)),
+                            windows => {
+                                obj.get_attr("winerror", vm).ok().filter(|w| !vm.is_none(w))
+                            }
                             _ => None,
                         };
 
@@ -2927,7 +3053,8 @@ pub(super) mod types {
         metadata: PyAtomicRef<Option<PyObject>>,
     }
 
-    impl crate::class::PySubclass for PySyntaxError {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PySyntaxError {
         type Base = PyException;
         fn as_base(&self) -> &Self::Base {
             &self.base
@@ -3230,7 +3357,8 @@ pub(super) mod types {
         reason: PyAtomicRef<Option<PyObject>>,
     }
 
-    impl crate::class::PySubclass for PyUnicodeError {
+    // SAFETY: pyexception checks the base field offset, payload offset, and alignment.
+    unsafe impl crate::class::PySubclass for PyUnicodeError {
         type Base = PyValueError;
         fn as_base(&self) -> &Self::Base {
             &self.base
diff --git a/crates/vm/src/format.rs b/crates/vm/src/format.rs
index d95def76813..3a6155f26e6 100644
--- a/crates/vm/src/format.rs
+++ b/crates/vm/src/format.rs
@@ -1,9 +1,6 @@
 use crate::{
-    PyObject, PyResult, VirtualMachine,
-    builtins::PyBaseExceptionRef,
-    convert::{IntoPyException, ToPyException},
-    function::FuncArgs,
-    stdlib::builtins,
+    PyObject, PyResult, VirtualMachine, builtins::PyBaseExceptionRef, convert::ToPyException,
+    function::FuncArgs, stdlib::builtins,
 };
 
 use crate::common::format::*;
@@ -41,63 +38,70 @@ pub(crate) fn get_locale_info() -> LocaleInfo {
     }
 }
 
-impl IntoPyException for FormatSpecError {
-    fn into_pyexception(self, vm: &VirtualMachine) -> PyBaseExceptionRef {
-        match self {
-            Self::DecimalDigitsTooMany => {
-                vm.new_value_error("Too many decimal digits in format string")
-            }
-            Self::PrecisionTooBig => vm.new_value_error("Precision too big"),
-            Self::PrecisionMissing => vm.new_value_error("Format specifier missing precision"),
-            Self::InvalidFormatSpecifier => vm.new_value_error("Invalid format specifier"),
-            Self::UnspecifiedFormat(c1, c2) => {
-                let msg = format!("Cannot specify '{c1}' with '{c2}'.");
-                vm.new_value_error(msg)
-            }
-            Self::ExclusiveFormat(c1, c2) => {
-                let msg = format!("Cannot specify both '{c1}' and '{c2}'.");
-                vm.new_value_error(msg)
-            }
-            Self::UnknownFormatCode(c, s) => {
-                let msg = format!("Unknown format code '{c}' for object of type '{s}'");
-                vm.new_value_error(msg)
-            }
-            Self::PrecisionNotAllowed => {
-                vm.new_value_error("Precision not allowed in integer format specifier")
-            }
-            Self::NotAllowed(s) => {
-                let msg = format!("{s} not allowed with integer format specifier 'c'");
-                vm.new_value_error(msg)
-            }
-            Self::UnableToConvert => vm.new_value_error("Unable to convert int to float"),
-            Self::CodeNotInRange => vm.new_overflow_error("%c arg not in range(0x110000)"),
-            Self::IntTooLargeForCLong => {
-                vm.new_overflow_error("Python int too large to convert to C long")
-            }
-            Self::ZeroPadding => {
-                vm.new_value_error("Zero padding is not allowed in complex format specifier")
-            }
-            Self::AlignmentFlag => {
-                vm.new_value_error("'=' alignment flag is not allowed in complex format specifier")
-            }
-            Self::NegativeZeroCoercionNotAllowed(type_name) => {
-                let msg = format!(
-                    "Negative zero coercion (z) not allowed in {type_name} format specifier"
-                );
-                vm.new_value_error(msg)
-            }
-            Self::StringAlignmentFlag => {
-                vm.new_value_error("'=' alignment not allowed in string format specifier")
-            }
-            Self::StringSpecNotAllowed(s) => {
-                let msg = format!("{s} not allowed in string format specifier");
-                vm.new_value_error(msg)
-            }
-            Self::NotImplemented(c, s) => {
-                let msg = format!("Format code '{c}' for object of type '{s}' not implemented yet");
-                vm.new_value_error(msg)
-            }
+pub(crate) fn parse_format_spec(
+    object: &PyObject,
+    spec: &str,
+    vm: &VirtualMachine,
+) -> PyResult<FormatSpec> {
+    FormatSpec::parse(spec).map_err(|err| format_spec_error(err, object, spec, vm))
+}
+
+pub(crate) fn format_spec_error(
+    err: FormatSpecError,
+    object: &PyObject,
+    spec: &str,
+    vm: &VirtualMachine,
+) -> PyBaseExceptionRef {
+    match err {
+        FormatSpecError::InvalidFormatSpecifier => vm.new_value_error(format!(
+            "Invalid format specifier '{spec}' for object of type '{}'",
+            object.class().name()
+        )),
+        FormatSpecError::DecimalDigitsTooMany => {
+            vm.new_value_error("Too many decimal digits in format string")
+        }
+        FormatSpecError::PrecisionTooBig => vm.new_value_error("Precision too big"),
+        FormatSpecError::PrecisionMissing => {
+            vm.new_value_error("Format specifier missing precision")
+        }
+        FormatSpecError::UnspecifiedFormat(c1, c2) => {
+            vm.new_value_error(format!("Cannot specify '{c1}' with '{c2}'."))
+        }
+        FormatSpecError::ExclusiveFormat(c1, c2) => {
+            vm.new_value_error(format!("Cannot specify both '{c1}' and '{c2}'."))
+        }
+        FormatSpecError::UnknownFormatCode(c, s) => vm.new_value_error(format!(
+            "Unknown format code '{c}' for object of type '{s}'"
+        )),
+        FormatSpecError::PrecisionNotAllowed => {
+            vm.new_value_error("Precision not allowed in integer format specifier")
+        }
+        FormatSpecError::NotAllowed(s) => {
+            vm.new_value_error(format!("{s} not allowed with integer format specifier 'c'"))
+        }
+        FormatSpecError::UnableToConvert => vm.new_value_error("Unable to convert int to float"),
+        FormatSpecError::CodeNotInRange => vm.new_overflow_error("%c arg not in range(0x110000)"),
+        FormatSpecError::IntTooLargeForCLong => {
+            vm.new_overflow_error("Python int too large to convert to C long")
+        }
+        FormatSpecError::ZeroPadding => {
+            vm.new_value_error("Zero padding is not allowed in complex format specifier")
+        }
+        FormatSpecError::AlignmentFlag => {
+            vm.new_value_error("'=' alignment flag is not allowed in complex format specifier")
+        }
+        FormatSpecError::NegativeZeroCoercionNotAllowed(type_name) => vm.new_value_error(format!(
+            "Negative zero coercion (z) not allowed in {type_name} format specifier"
+        )),
+        FormatSpecError::StringAlignmentFlag => {
+            vm.new_value_error("'=' alignment not allowed in string format specifier")
+        }
+        FormatSpecError::StringSpecNotAllowed(s) => {
+            vm.new_value_error(format!("{s} not allowed in string format specifier"))
         }
+        FormatSpecError::NotImplemented(c, s) => vm.new_value_error(format!(
+            "Format code '{c}' for object of type '{s}' not implemented yet"
+        )),
     }
 }
 
diff --git a/crates/vm/src/frame.rs b/crates/vm/src/frame.rs
index cc54ad6ee18..20759fb5f8b 100644
--- a/crates/vm/src/frame.rs
+++ b/crates/vm/src/frame.rs
@@ -6,9 +6,10 @@ use crate::{
     AsObject, Py, PyExact, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, PyStackRef,
     TryFromObject, VirtualMachine,
     builtins::{
-        PyBaseException, PyBaseExceptionRef, PyBaseObject, PyCode, PyCoroutine, PyDict, PyDictRef,
-        PyFloat, PyFrozenSet, PyGenerator, PyInt, PyInterpolation, PyList, PyModule, PyProperty,
-        PySet, PySlice, PyStr, PyStrInterned, PyTemplate, PyTraceback, PyType, PyUtf8Str,
+        PyAnyDict, PyBaseException, PyBaseExceptionRef, PyBaseObject, PyBytes, PyCode, PyCoroutine,
+        PyDict, PyDictRef, PyFloat, PyFrozenSet, PyGenerator, PyInt, PyInterpolation, PyList,
+        PyModule, PyProperty, PySet, PySlice, PyStr, PyStrInterned, PyTemplate, PyTraceback,
+        PyType, PyUtf8Str,
         builtin_func::PyNativeFunction,
         descriptor::{PyMemberDescriptor, PyMethodDescriptor},
         frame::stack_analysis,
@@ -19,11 +20,12 @@ use crate::{
     },
     bytecode::{
         self, ADAPTIVE_COOLDOWN_VALUE, Instruction, LoadAttr, LoadSuperAttr, Opcode, SpecialMethod,
+        oparg::{ResumeContext, ResumeLocation},
     },
     convert::{ToPyObject, ToPyResult},
     coroutine::Coro,
     exceptions::ExceptionCtor,
-    function::{ArgMapping, Callee, Either, FuncArgs, KwArgs, PyMethodFlags},
+    function::{ArgMapping, Callee, Either, FuncArgs, PyMethodFlags},
     object::PyAtomicBorrow,
     object::{Traverse, TraverseFn},
     protocol::{PyIter, PyIterReturn},
@@ -104,10 +106,44 @@ pub fn current_thread_frame_materialize(vm: &VirtualMachine) -> Option<FrameObje
     Some(iframe.materialize(vm).to_owned())
 }
 
+/// `_PyFrame_GetFirstComplete`: the first complete frame on a live raw
+/// execution chain.
+///
+/// # Safety
+/// Every non-null pointer traversed must belong to a live active frame chain
+/// on the current thread, or the caller must hold the owning thread stopped.
+/// The returned pointer is valid only while that chain remains alive.
+pub(crate) unsafe fn first_complete_iframe(
+    mut current: *const InterpreterFrame,
+) -> *const InterpreterFrame {
+    while !current.is_null() {
+        // SAFETY: the caller guarantees the chain remains alive.
+        let frame = unsafe { &*current };
+        if !frame.is_incomplete() {
+            break;
+        }
+        current = frame.previous();
+    }
+    current
+}
+
+/// Resolve the active frame for a legacy trace/profile callback, skipping
+/// incomplete generator-creation frames before materializing a frame object.
+/// Raw execution-chain users deliberately keep seeing the actual active frame.
+pub(crate) fn current_complete_frame_for_trace(vm: &VirtualMachine) -> Option<FrameObjectRef> {
+    // SAFETY: synchronous inspection of the current thread's active chain.
+    let current = unsafe { first_complete_iframe(crate::vm::thread::get_current_frame()) };
+    if current.is_null() {
+        return None;
+    }
+    // SAFETY: the selected frame is alive on this thread's execution chain.
+    Some(unsafe { (*current).materialize(vm).to_owned() })
+}
+
 /// Read the globals dict from the topmost frame on this thread's chain.
 /// Returns `None` if the chain is empty.
 #[must_use]
-pub fn current_globals() -> Option<PyDictRef> {
+pub fn current_globals() -> Option<PyRef<PyAnyDict>> {
     let ptr = crate::vm::thread::get_current_frame();
     if ptr.is_null() {
         return None;
@@ -136,12 +172,13 @@ pub fn current_builtins() -> Option<PyObjectRef> {
     Some(unsafe { (*ptr).builtins().to_owned() })
 }
 
-/// The frame `offset` positions below the current thread's top frame (offset 0
-/// is the top), or `None` if the stack is not that deep.
+/// The complete frame `offset` positions below the current thread's first
+/// complete frame, or `None` if the stack is not that deep.
 /// Materializes the FrameObject on demand for stack-allocated frames.
 #[must_use]
 pub fn frame_at_offset(offset: usize, vm: &VirtualMachine) -> Option<FrameObjectRef> {
-    let mut cur = crate::vm::thread::get_current_frame();
+    // SAFETY: synchronous inspection of this thread's active chain.
+    let mut cur = unsafe { first_complete_iframe(crate::vm::thread::get_current_frame()) };
     let mut remaining = offset;
     while !cur.is_null() {
         if remaining == 0 {
@@ -149,7 +186,8 @@ pub fn frame_at_offset(offset: usize, vm: &VirtualMachine) -> Option<FrameObject
             return Some(iframe.materialize(vm).to_owned());
         }
         remaining -= 1;
-        cur = unsafe { (*cur).previous.load(Relaxed) as *const InterpreterFrame };
+        // SAFETY: `cur` and its predecessors remain alive on this chain.
+        cur = unsafe { first_complete_iframe((*cur).previous()) };
     }
     None
 }
@@ -922,7 +960,7 @@ pub struct InterpreterFrame {
     // Borrowed pointers — owned by FrameObject or by PyFunction on caller's stack.
     pub(crate) code: *const Py<PyCode>,
     pub(crate) func_obj: *const PyObject, // nullable
-    pub(crate) globals: *const Py<PyDict>,
+    pub(crate) globals: *const PyAnyDict,
     pub(crate) builtins: *const PyObject,
 
     /// Unified storage for local variables and evaluation stack.
@@ -982,7 +1020,7 @@ impl InterpreterFrame {
     #[inline(always)]
     pub(crate) unsafe fn new(
         code: &Py<PyCode>,
-        globals: &Py<PyDict>,
+        globals: &PyAnyDict,
         builtins: &PyObject,
         func_obj: Option<&PyObject>,
         localsplus: LocalsPlus,
@@ -1026,7 +1064,7 @@ impl InterpreterFrame {
                 Some(obj) => obj as *const PyObject,
                 None => core::ptr::null(),
             },
-            globals: globals as *const Py<PyDict>,
+            globals: globals as *const PyAnyDict,
             builtins: builtins as *const PyObject,
             localsplus,
             locals,
@@ -1059,7 +1097,7 @@ impl InterpreterFrame {
     #[inline(always)]
     pub(crate) unsafe fn new_on_datastack<'a>(
         code: &Py<PyCode>,
-        globals: &Py<PyDict>,
+        globals: &PyAnyDict,
         builtins: &PyObject,
         func_obj: Option<&PyObject>,
         locals: FrameLocals,
@@ -1154,6 +1192,19 @@ impl InterpreterFrame {
         Some((base, total_bytes))
     }
 
+    /// `_PyFrame_IsIncomplete`. A generator frame is complete even before its
+    /// first resume. Its owner is temporarily Thread while it executes, so the
+    /// owning generator's back-reference is checked too.
+    pub(crate) fn is_incomplete(&self) -> bool {
+        if FrameOwner::from_i8(self.owner.load(atomic::Ordering::Acquire)) == FrameOwner::Generator
+            || self.generator.load().is_some()
+        {
+            return false;
+        }
+        // lasti is one past the in-flight instruction.
+        (self.lasti.load(Relaxed) as usize) <= self.code().first_traceable
+    }
+
     /// Get the last instruction index.
     #[inline(always)]
     pub fn get_lasti(&self) -> u32 {
@@ -1227,10 +1278,43 @@ impl InterpreterFrame {
     #[cold]
     #[inline(never)]
     pub(crate) unsafe fn materialize_detached_chain(&self, vm: &VirtualMachine) -> FrameObjectRef {
+        // SAFETY: forwarded unchanged from this method's contract.
+        unsafe { self.materialize_detached_chain_impl::<false>(vm) }
+    }
+
+    /// Copy the complete ancestors used by Python-visible `f_back` traversal.
+    /// The raw snapshot path above deliberately preserves every active node.
+    ///
+    /// # Safety
+    /// The caller must hold the world stopped and select a complete top frame.
+    #[cfg(feature = "threading")]
+    #[cold]
+    #[inline(never)]
+    pub(crate) unsafe fn materialize_complete_detached_chain(
+        &self,
+        vm: &VirtualMachine,
+    ) -> FrameObjectRef {
+        // SAFETY: forwarded unchanged from this method's contract.
+        unsafe { self.materialize_detached_chain_impl::<true>(vm) }
+    }
+
+    #[cfg(feature = "threading")]
+    #[cold]
+    unsafe fn materialize_detached_chain_impl<const SKIP_INCOMPLETE: bool>(
+        &self,
+        vm: &VirtualMachine,
+    ) -> FrameObjectRef {
         let top = unsafe { self.materialize_detached(vm) };
         let mut child = top.clone();
         let mut cur = self.previous();
-        while !cur.is_null() {
+        loop {
+            if SKIP_INCOMPLETE {
+                // SAFETY: the caller holds the owning thread stopped.
+                cur = unsafe { first_complete_iframe(cur) };
+            }
+            if cur.is_null() {
+                break;
+            }
             let caller = unsafe { &*cur };
             let caller_fo = unsafe { caller.materialize_detached(vm) };
             {
@@ -1265,7 +1349,7 @@ impl InterpreterFrame {
         // Create a full FrameObject with its own InterpreterFrame copy.
         // The FrameObject owns references to the same objects (code, globals, etc).
         let code: PyRef<PyCode> = self.code().to_owned();
-        let globals: PyDictRef = self.globals().to_owned();
+        let globals = self.globals().to_owned();
         let builtins: PyObjectRef = self.builtins().to_owned();
         let func_obj: Option<PyObjectRef> = self.func_obj().map(|o| o.to_owned());
 
@@ -1361,7 +1445,7 @@ impl InterpreterFrame {
     #[cold]
     fn materialize_slow_chain(&self, vm: &VirtualMachine) -> FrameObjectRef {
         let code: PyRef<PyCode> = self.code().to_owned();
-        let globals: PyDictRef = self.globals().to_owned();
+        let globals = self.globals().to_owned();
         let builtins: PyObjectRef = self.builtins().to_owned();
         let func_obj: Option<PyObjectRef> = self.func_obj().map(|o| o.to_owned());
 
@@ -1418,7 +1502,7 @@ impl InterpreterFrame {
 
     /// Borrowed globals dict.
     #[inline(always)]
-    pub fn globals(&self) -> &Py<PyDict> {
+    pub fn globals(&self) -> &PyAnyDict {
         // SAFETY: established by `new` / `init_iframe_ptrs`.
         unsafe { &*self.globals }
     }
@@ -1533,7 +1617,7 @@ pub struct FrameObject {
     // raw pointers. Wrapped in Option so Traverse::clear can release them,
     // allowing GC cycle collection to reclaim referenced objects.
     pub(crate) owned_code: Option<PyRef<PyCode>>,
-    pub(crate) owned_globals: Option<PyDictRef>,
+    pub(crate) owned_globals: Option<PyRef<PyAnyDict>>,
     pub(crate) owned_builtins: Option<PyObjectRef>,
     pub(crate) owned_func_obj: Option<PyObjectRef>,
 
@@ -1755,6 +1839,7 @@ pub enum ExecutionResult {
 ///             CACHE              <- the parked frame's lasti is here + 1
 ///             YIELD_VALUE 1
 /// resumed_at: RESUME
+///             CACHE
 ///             JUMP_BACKWARD_NO_INTERRUPT -> send_idx
 ///       exit: END_SEND
 /// ```
@@ -1816,7 +1901,7 @@ impl FrameObject {
         let locals = match scope.locals {
             Some(locals) => FrameLocals::with_locals(locals),
             None if code.flags.contains(bytecode::CodeFlags::NEWLOCALS) => FrameLocals::lazy(),
-            None => FrameLocals::with_locals(ArgMapping::from_dict_exact(scope.globals.clone())),
+            None => FrameLocals::with_locals(ArgMapping::from_anydict_exact(scope.globals.clone())),
         };
 
         // Pointers are initially set from owned fields' references but will be
@@ -1852,7 +1937,7 @@ impl FrameObject {
     fn init_iframe_ptrs(self_: &Py<Self>) {
         let iframe = unsafe { self_.iframe_mut() };
         iframe.code = &**self_.owned_code.as_ref().unwrap() as *const Py<PyCode>;
-        iframe.globals = &**self_.owned_globals.as_ref().unwrap() as *const Py<PyDict>;
+        iframe.globals = &**self_.owned_globals.as_ref().unwrap() as *const PyAnyDict;
         iframe.builtins = &**self_.owned_builtins.as_ref().unwrap() as *const PyObject;
         iframe.func_obj = match &self_.owned_func_obj {
             Some(obj) => &**obj as *const PyObject,
@@ -2496,7 +2581,7 @@ impl Py<FrameObject> {
                 },
             )
         };
-        let builtins_dict = if globals.class().is(vm.ctx.types.dict_type) {
+        let builtins_dict = if globals.as_object().class().is(vm.ctx.types.dict_type) {
             builtins
                 .downcast_ref_if_exact::<PyDict>(vm)
                 // SAFETY: downcast_ref_if_exact already verified exact type
@@ -2528,6 +2613,18 @@ impl Py<FrameObject> {
         self.with_exec(vm, |mut exec| exec.run(vm))
     }
 
+    /// Execute the eager generator preamble and suspend immediately after
+    /// RETURN_GENERATOR. The caller links this frame with `vm.with_generator_frame`.
+    /// The first resume supplies the value consumed by the following POP_TOP.
+    pub(crate) fn prepare_generator(&self, vm: &VirtualMachine) -> PyResult<()> {
+        self.with_exec(vm, |mut exec| match exec.run_until::<true>(vm)? {
+            None => Ok(()),
+            Some(_) => {
+                Err(vm.new_runtime_error("generator preamble did not reach RETURN_GENERATOR"))
+            }
+        })
+    }
+
     /// Resume a suspended generator or coroutine body, pushing `value` as the
     /// result of the `yield` it stopped at.
     ///
@@ -2632,7 +2729,7 @@ impl Py<FrameObject> {
 /// 0 doubles as "no thread", which is what `attached_tid` wants for a build
 /// that cannot have a frame running anywhere else.
 #[inline]
-fn current_thread_ident() -> u64 {
+pub(crate) fn current_thread_ident() -> u64 {
     #[cfg(feature = "threading")]
     {
         crate::stdlib::_thread::get_ident()
@@ -2738,7 +2835,7 @@ fn exec_iframe<'a>(
             },
         )
     };
-    let builtins_dict = if globals.class().is(vm.ctx.types.dict_type) {
+    let builtins_dict = if globals.as_object().class().is(vm.ctx.types.dict_type) {
         builtins
             .downcast_ref_if_exact::<PyDict>(vm)
             .map(|d| unsafe { PyExact::ref_unchecked(d) })
@@ -2787,10 +2884,10 @@ pub(crate) fn gen_collapse_allowed(vm: &VirtualMachine) -> bool {
 /// delegating to, if the trampoline can resume it in this frame's place.
 ///
 /// Recognizes the shape documented on [`GenCont`] — `lasti` at the `RESUME`
-/// that follows the delegating `YIELD_VALUE`, with the delegate on top of the
-/// stack — and requires the `SEND` to have already specialized to `SendGen`,
-/// so that a `Send` still collecting specialization feedback keeps running
-/// normally. The frame is left untouched; `park_at_send` commits to it.
+/// that follows the delegating `YIELD_VALUE`, with the delegate below its
+/// index-or-NULL stack slot — and requires the `SEND` to have already
+/// specialized to `SendGen`, so that a `Send` still collecting feedback keeps
+/// running normally. The frame is left untouched; `park_at_send` commits to it.
 pub(crate) fn yield_from_delegate(
     iframe: &InterpreterFrame,
     vm: &VirtualMachine,
@@ -2823,10 +2920,11 @@ pub(crate) fn yield_from_delegate(
     {
         return None;
     }
-    let delegate = match iframe.localsplus.stack_last() {
-        Some(Some(top)) => top.as_object(),
-        _ => return None,
-    };
+    let stack = iframe.localsplus.stack_as_slice();
+    let delegate = stack
+        .get(stack.len().checked_sub(2)?)?
+        .as_ref()?
+        .as_object();
     // The same guards `SendGen` applies before resuming a generator itself.
     if delegate.downcast_ref_if_exact::<PyGenerator>(vm).is_none()
         && delegate.downcast_ref_if_exact::<PyCoroutine>(vm).is_none()
@@ -2930,7 +3028,7 @@ pub(crate) struct ExecutingFrame<'a> {
     code: &'a Py<PyCode>,
     localsplus: &'a mut LocalsPlus,
     locals: &'a FrameLocals,
-    globals: &'a Py<PyDict>,
+    globals: &'a PyAnyDict,
     builtins: &'a PyObject,
     /// Cached downcast of builtins to PyDict for fast LOAD_GLOBAL.
     /// Only set when both globals and builtins are exact dict types (not
@@ -3071,7 +3169,8 @@ pub(crate) fn release_datastack_frame(frame: &Py<FrameObject>, vm: &VirtualMachi
     {
         let mut guard = frame.iframe().cold().retained_back.lock();
         if guard.is_none() {
-            let prev = frame.previous_iframe();
+            // SAFETY: this frame is returning into its still-active caller.
+            let prev = unsafe { first_complete_iframe(frame.previous_iframe()) };
             *guard = unsafe { owned_chain_frame(prev) };
         }
     }
@@ -3098,7 +3197,7 @@ pub(crate) fn release_datastack_frame(frame: &Py<FrameObject>, vm: &VirtualMachi
 }
 
 type BinaryOpExtendGuard = fn(&PyObject, &PyObject, &VirtualMachine) -> bool;
-type BinaryOpExtendAction = fn(&PyObject, &PyObject, &VirtualMachine) -> Option<PyObjectRef>;
+type BinaryOpExtendAction = fn(&PyObject, &PyObject, &VirtualMachine) -> Option<PyResult>;
 
 struct BinaryOpExtendSpecializationDescr {
     oparg: bytecode::BinaryOperator,
@@ -3159,10 +3258,10 @@ struct FusedBoolJump {
 macro_rules! bitwise_longs_action {
     ($name:ident, $op:tt) => {
         #[inline]
-        fn $name(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> Option<PyObjectRef> {
+        fn $name(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> Option<PyResult> {
             let lhs_val = compact_int_from_obj(lhs, vm)?;
             let rhs_val = compact_int_from_obj(rhs, vm)?;
-            Some(vm.ctx.new_int(lhs_val $op rhs_val).into())
+            Some(Ok(vm.ctx.new_int(lhs_val $op rhs_val).into()))
         }
     };
 }
@@ -3184,10 +3283,10 @@ fn nonzero_float_compactlong_guard(lhs: &PyObject, rhs: &PyObject, vm: &VirtualM
 macro_rules! float_long_action {
     ($name:ident, $op:tt) => {
         #[inline]
-        fn $name(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> Option<PyObjectRef> {
+        fn $name(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> Option<PyResult> {
             let lhs_val = exact_float_from_obj(lhs, vm)?;
             let rhs_val = compact_int_from_obj(rhs, vm)?;
-            Some(vm.ctx.new_float(lhs_val $op rhs_val as f64).into())
+            Some(Ok(vm.ctx.new_float(lhs_val $op rhs_val as f64).into()))
         }
     };
 }
@@ -3210,10 +3309,10 @@ fn nonzero_compactlong_float_guard(lhs: &PyObject, rhs: &PyObject, vm: &VirtualM
 macro_rules! long_float_action {
     ($name:ident, $op:tt) => {
         #[inline]
-        fn $name(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> Option<PyObjectRef> {
+        fn $name(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> Option<PyResult> {
             let lhs_val = compact_int_from_obj(lhs, vm)?;
             let rhs_val = exact_float_from_obj(rhs, vm)?;
-            Some(vm.ctx.new_float(lhs_val as f64 $op rhs_val).into())
+            Some(Ok(vm.ctx.new_float(lhs_val as f64 $op rhs_val).into()))
         }
     };
 }
@@ -3222,7 +3321,108 @@ long_float_action!(compactlong_float_subtract, -);
 long_float_action!(compactlong_float_multiply, *);
 long_float_action!(compactlong_float_true_div, /);
 
+fn sequence_int_guard(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> bool {
+    (lhs.downcast_ref_if_exact::<PyStr>(vm).is_some()
+        || lhs.downcast_ref_if_exact::<PyBytes>(vm).is_some()
+        || lhs.downcast_ref_if_exact::<PyTuple>(vm).is_some())
+        && rhs.downcast_ref_if_exact::<PyInt>(vm).is_some()
+}
+
+fn int_sequence_guard(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> bool {
+    sequence_int_guard(rhs, lhs, vm)
+}
+
+fn exact_sequence_int_guard<T: PyPayload>(
+    lhs: &PyObject,
+    rhs: &PyObject,
+    vm: &VirtualMachine,
+) -> bool {
+    lhs.downcast_ref_if_exact::<T>(vm).is_some() && rhs.downcast_ref_if_exact::<PyInt>(vm).is_some()
+}
+
+fn exact_int_sequence_guard<T: PyPayload>(
+    lhs: &PyObject,
+    rhs: &PyObject,
+    vm: &VirtualMachine,
+) -> bool {
+    exact_sequence_int_guard::<T>(rhs, lhs, vm)
+}
+
+fn sequence_int_multiply(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> Option<PyResult> {
+    let count = rhs.downcast_ref_if_exact::<PyInt>(vm)?;
+    // CPython 3.15's specialized repetition uses PyLong_AsSsize_t, unlike
+    // the generic sequence dispatch's PyNumber_AsSsize_t conversion.
+    Some(match count.as_bigint().to_isize() {
+        Some(count) => lhs.sequence_unchecked().repeat(count, vm),
+        None => Err(vm.new_overflow_error("Python int too large to convert to C ssize_t")),
+    })
+}
+
+fn int_sequence_multiply(lhs: &PyObject, rhs: &PyObject, vm: &VirtualMachine) -> Option<PyResult> {
+    sequence_int_multiply(rhs, lhs, vm)
+}
+
 static BINARY_OP_EXTEND_DESCRIPTORS: &[BinaryOpExtendSpecializationDescr] = &[
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::Multiply,
+        guard: exact_sequence_int_guard::<PyStr>,
+        action: sequence_int_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::Multiply,
+        guard: exact_int_sequence_guard::<PyStr>,
+        action: int_sequence_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::InplaceMultiply,
+        guard: exact_sequence_int_guard::<PyStr>,
+        action: sequence_int_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::InplaceMultiply,
+        guard: exact_int_sequence_guard::<PyStr>,
+        action: int_sequence_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::Multiply,
+        guard: exact_sequence_int_guard::<PyBytes>,
+        action: sequence_int_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::Multiply,
+        guard: exact_int_sequence_guard::<PyBytes>,
+        action: int_sequence_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::InplaceMultiply,
+        guard: exact_sequence_int_guard::<PyBytes>,
+        action: sequence_int_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::InplaceMultiply,
+        guard: exact_int_sequence_guard::<PyBytes>,
+        action: int_sequence_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::Multiply,
+        guard: exact_sequence_int_guard::<PyTuple>,
+        action: sequence_int_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::Multiply,
+        guard: exact_int_sequence_guard::<PyTuple>,
+        action: int_sequence_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::InplaceMultiply,
+        guard: exact_sequence_int_guard::<PyTuple>,
+        action: sequence_int_multiply,
+    },
+    BinaryOpExtendSpecializationDescr {
+        oparg: bytecode::BinaryOperator::InplaceMultiply,
+        guard: exact_int_sequence_guard::<PyTuple>,
+        action: int_sequence_multiply,
+    },
     // long-long arithmetic
     BinaryOpExtendSpecializationDescr {
         oparg: bytecode::BinaryOperator::Or,
@@ -3338,7 +3538,11 @@ impl ExecutingFrame<'_> {
     /// (COPY_FREE_VARS / RETURN_GENERATOR that precede it are not a 'call',
     /// and later RESUMEs in a SEND loop are not a new call either).
     fn trace_call_from_resume(&mut self, vm: &VirtualMachine, resume_type: u32) -> PyResult<()> {
-        if self.call_traced {
+        // RESUME_AT_GEN_EXPR_START runs before the frame is complete. The
+        // first traceable instruction is the ordinary RESUME after creation.
+        if resume_type & ResumeContext::LOCATION_MASK == ResumeLocation::AtGenExprStart.as_u32()
+            || self.call_traced
+        {
             return Ok(());
         }
         self.call_traced = true;
@@ -3524,7 +3728,22 @@ impl ExecutingFrame<'_> {
     /// Matches `_PyEval_MonitorRaise` → `PY_MONITORING_EVENT_RAISE` →
     /// `sys_trace_exception_func` in legacy_tracing.c.
     fn fire_exception_trace(&self, exc: &Py<PyBaseException>, vm: &VirtualMachine) -> PyResult<()> {
-        if vm.use_tracing.get() && self.trace_is_set(vm) {
+        if !vm.use_tracing.get() {
+            return Ok(());
+        }
+        let trace_is_set = if self.iframe().is_incomplete() {
+            // Legacy tracing resolves PyEval_GetFrame to the first complete
+            // caller while sys.monitoring continues to use this code object.
+            current_complete_frame_for_trace(vm).is_some_and(|frame| {
+                frame
+                    .iframe()
+                    .cold_opt()
+                    .is_some_and(|cold| cold.trace.lock().is_some())
+            })
+        } else {
+            self.trace_is_set(vm)
+        };
+        if trace_is_set {
             let exc_type: PyObjectRef = exc.class().to_owned().into();
             let exc_value: PyObjectRef = exc.to_owned().into();
             let exc_tb: PyObjectRef = exc
@@ -3537,6 +3756,14 @@ impl ExecutingFrame<'_> {
     }
 
     fn run(&mut self, vm: &VirtualMachine) -> PyResult<ExecutionResult> {
+        self.run_until::<false>(vm)
+            .map(|result| result.expect("ordinary execution cannot stop at a generator preamble"))
+    }
+
+    fn run_until<const PREPARE_GENERATOR: bool>(
+        &mut self,
+        vm: &VirtualMachine,
+    ) -> PyResult<Option<ExecutionResult>> {
         flame_guard!(format!(
             "FrameObject::run({obj_name})",
             obj_name = self.code.obj_name
@@ -3579,7 +3806,7 @@ impl ExecutingFrame<'_> {
             // principle toggle it, because we refresh `tracing` below right
             // after that call returns (that cold path is only taken when
             // tracing was already on, so it costs nothing on the hot path).
-            let mut tracing = vm.use_tracing.get();
+            let mut tracing = !PREPARE_GENERATOR && vm.use_tracing.get();
 
             // Fire 'line' trace event when line number changes.
             // Only fire if this frame has a per-frame trace function set
@@ -3593,7 +3820,9 @@ impl ExecutingFrame<'_> {
                 && self.trace_lines_is_set()
                 && !matches!(
                     self.code.instructions.read_op(idx),
-                    Instruction::Resume { .. } | Instruction::InstrumentedResume
+                    Instruction::Resume { .. }
+                        | Instruction::ResumeCheck
+                        | Instruction::InstrumentedResume
                 )
             {
                 let line = self.code.addr2line(idx as i32 * 2);
@@ -3624,7 +3853,7 @@ impl ExecutingFrame<'_> {
                                     idx = lasti_cell.load(Relaxed) as usize;
                                     continue;
                                 }
-                                Ok(Some(value)) => break Ok(value),
+                                Ok(Some(value)) => break Ok(Some(value)),
                                 Err(e) => break Err(e),
                             }
                         }
@@ -3632,7 +3861,7 @@ impl ExecutingFrame<'_> {
                     // The trace callback may have toggled tracing (e.g. via
                     // sys.settrace(None)); refresh before the opcode-trace check
                     // below reuses this flag.
-                    tracing = vm.use_tracing.get();
+                    tracing = !PREPARE_GENERATOR && vm.use_tracing.get();
                     // Trace callback may have changed lasti via set_f_lineno.
                     // Re-read and restart the loop from the new position.
                     if lasti_cell.load(Relaxed) != (idx as u32 + 1) {
@@ -3679,7 +3908,10 @@ impl ExecutingFrame<'_> {
                     && self.trace_opcodes_is_set()
                     && !matches!(
                         op.into(),
-                        Opcode::Resume | Opcode::InstrumentedResume | Opcode::ExtendedArg
+                        Opcode::Resume
+                            | Opcode::ResumeCheck
+                            | Opcode::InstrumentedResume
+                            | Opcode::ExtendedArg
                     )
                 {
                     vm.trace_event(crate::protocol::TraceEvent::Opcode, None)?;
@@ -3709,9 +3941,10 @@ impl ExecutingFrame<'_> {
                     frame: &mut ExecutingFrame<'_>,
                     exception: PyBaseExceptionRef,
                     idx: usize,
+                    complete_frame: bool,
                     vm: &VirtualMachine,
                 ) -> FrameResult {
-                    if let Some((loc, _end_loc)) = frame.code.locations.get(idx) {
+                    if complete_frame && let Some((loc, _end_loc)) = frame.code.locations.get(idx) {
                         let next = exception.traceback();
                         let new_traceback = PyTraceback::new(
                             next,
@@ -3730,10 +3963,10 @@ impl ExecutingFrame<'_> {
                         },
                     )
                 }
-                match handle_signal_exception(self, exception, idx, vm) {
+                match handle_signal_exception(self, exception, idx, !PREPARE_GENERATOR, vm) {
                     Ok(None) => {}
                     Ok(Some(value)) => {
-                        break Ok(value);
+                        break Ok(Some(value));
                     }
                     Err(exception) => {
                         break Err(exception);
@@ -3757,6 +3990,13 @@ impl ExecutingFrame<'_> {
                 crate::opcode_histogram::record(prev_op, op_byte);
                 prev_op = op_byte;
             }
+            if PREPARE_GENERATOR && matches!(op, Instruction::ReturnGenerator) {
+                // The generator takes over the frame with its instruction
+                // pointer advanced to POP_TOP. The iterator pair a generator
+                // expression pushed must outlive this execution borrow.
+                self.localsplus.promote_stack();
+                break Ok(None);
+            }
             let result = self.execute_instruction(op, arg, &mut do_extend_arg, vm);
             // Skip inline cache entries if instruction fell through (no jump).
             // `cache_entries()` is a table lookup, so it is done here rather
@@ -3772,7 +4012,7 @@ impl ExecutingFrame<'_> {
             match result {
                 Ok(None) => {}
                 Ok(Some(value)) => {
-                    break Ok(value);
+                    break Ok(Some(value));
                 }
                 // Instruction raised an exception
                 Err(exception) => {
@@ -3783,6 +4023,7 @@ impl ExecutingFrame<'_> {
                         idx: usize,
                         is_reraise: bool,
                         is_new_raise: bool,
+                        complete_frame: bool,
                         vm: &VirtualMachine,
                     ) -> FrameResult {
                         // 1. Extract traceback from exception's '__traceback__' attr.
@@ -3801,7 +4042,9 @@ impl ExecutingFrame<'_> {
                             // checking for duplicates. Each time an exception passes through
                             // a frame (e.g., in a loop with repeated raise statements),
                             // a new traceback entry is added.
-                            if let Some((loc, _end_loc)) = frame.code.locations.get(idx) {
+                            if complete_frame
+                                && let Some((loc, _end_loc)) = frame.code.locations.get(idx)
+                            {
                                 let next = exception.traceback();
 
                                 let new_traceback = PyTraceback::new(
@@ -3899,12 +4142,21 @@ impl ExecutingFrame<'_> {
                         self.fire_exception_trace(&exception, vm)?;
                     }
 
-                    match handle_exception(self, exception, idx, is_reraise, is_new_raise, vm) {
+                    match handle_exception(
+                        self,
+                        exception,
+                        idx,
+                        is_reraise,
+                        is_new_raise,
+                        !PREPARE_GENERATOR,
+                        vm,
+                    ) {
                         // The handler unwound to a new position, so the next
                         // index is whatever it left in the frame.
                         Ok(None) => next_idx = lasti_cell.load(Relaxed),
-                        Ok(Some(result)) => break Ok(result),
+                        Ok(Some(result)) => break Ok(Some(result)),
                         Err(exception) => {
+                            monitoring::reset_reraise_pending();
                             // Fire PY_UNWIND: exception escapes this frame
                             let exception = if vm.state.monitoring_events.load()
                                 & MonitoringEvent::PyUnwind.mask()
@@ -3938,16 +4190,18 @@ impl ExecutingFrame<'_> {
         // In RustPython, we check:
         // 1. lasti points to RESUME (after YIELD_VALUE)
         // 2. The previous instruction was YIELD_VALUE with arg >= 1
-        // 3. Stack top is the delegate (receiver)
+        // 3. The delegate (receiver) is below its index-or-NULL slot
         //
         // First check if stack is empty - if so, we can't be in yield-from
-        if self.localsplus.stack_is_empty() {
+        if self.localsplus.stack_len() < 2 {
             return None;
         }
         let lasti = self.lasti() as usize;
         if let Some(unit) = self.code.instructions.get(lasti) {
             match &unit.op {
-                Instruction::Send { .. } => return Some(self.top_value()),
+                Instruction::Send { .. } | Instruction::SendGen => {
+                    return Some(self.nth_value(1));
+                }
                 Instruction::Resume { .. } | Instruction::InstrumentedResume => {
                     // Check if previous instruction was YIELD_VALUE with arg >= 1
                     // This indicates yield-from/await context
@@ -3961,8 +4215,8 @@ impl ExecutingFrame<'_> {
                         // YIELD_VALUE arg: 0 = direct yield, >= 1 = yield-from/await
                         // OpArgByte.0 is the raw byte value
                         if u8::from(prev_unit.arg) >= 1 {
-                            // In yield-from/await context, delegate is on top of stack
-                            return Some(self.top_value());
+                            // The iterator pair remains after YIELD_VALUE.
+                            return Some(self.nth_value(1));
                         }
                     }
                 }
@@ -4186,6 +4440,7 @@ impl ExecutingFrame<'_> {
             }
             Ok(Some(result)) => Ok(result),
             Err(exception) => {
+                monitoring::reset_reraise_pending();
                 // Fire PY_UNWIND: exception escapes the generator frame.
                 let exception =
                     if vm.state.monitoring_events.load() & MonitoringEvent::PyUnwind.mask() != 0 {
@@ -4335,6 +4590,23 @@ impl ExecutingFrame<'_> {
                 self.push_value(list_obj.into());
                 Ok(None)
             }
+            Instruction::BuildListFromArg => {
+                let last_val = self.pop_value();
+                let length_hint = match last_val.clone().length_hint(0, vm) {
+                    Ok(hint) => hint,
+                    Err(exc)
+                        if exc.fast_isinstance(vm.ctx.exceptions.system_exit)
+                            || exc.fast_isinstance(vm.ctx.exceptions.keyboard_interrupt) =>
+                    {
+                        return Err(exc);
+                    }
+                    Err(_) => 0,
+                };
+                let list_obj = vm.ctx.new_list(Vec::with_capacity(length_hint));
+                self.push_value(list_obj.into());
+                self.push_value(last_val);
+                Ok(None)
+            }
             Instruction::BuildMap { count: size } => self.execute_build_map(vm, size.get(arg)),
             Instruction::BuildSet { count: size } => {
                 let set = PySet::default().into_ref(&vm.ctx);
@@ -4400,9 +4672,12 @@ impl ExecutingFrame<'_> {
                     vm.ctx.empty_str.to_owned()
                 };
 
-                let expression = self.pop_value().downcast::<PyStr>().map_err(|_| {
-                    vm.new_type_error("BUILD_INTERPOLATION expected str for expression")
-                })?;
+                let expression = self.pop_value();
+                if !vm.is_none(&expression) && expression.downcast_ref::<PyStr>().is_none() {
+                    return Err(vm.new_type_error(
+                        "BUILD_INTERPOLATION expected str or None for expression",
+                    ));
+                }
                 let value = self.pop_value();
 
                 // conversion: 0=None, 1=Str, 2=Repr, 3=Ascii
@@ -4433,8 +4708,8 @@ impl ExecutingFrame<'_> {
             }
             Instruction::CallFunctionEx => {
                 // Stack: [callable, self_or_null, args_tuple, kwargs_or_null]
-                let args = self.collect_ex_args(vm)?;
-                self.execute_call(args, vm)
+                let (args, kwnames) = self.collect_ex_args(vm)?;
+                self.execute_call_ex(args, kwnames, false, vm)
             }
             Instruction::CallIntrinsic1 { func } => {
                 let value = self.pop_value();
@@ -4549,15 +4824,10 @@ impl ExecutingFrame<'_> {
             }
             Instruction::DeleteName { namei: idx } => {
                 let name = self.code.names[idx.get(arg) as usize];
-                let res = self.locals.mapping(vm).ass_subscript(name, None, vm);
-
-                match res {
-                    Ok(()) => {}
-                    Err(e) if e.fast_isinstance(vm.ctx.exceptions.key_error) => {
-                        return Err(name_error(name, vm));
-                    }
-                    Err(e) => return Err(e),
-                }
+                self.locals
+                    .mapping(vm)
+                    .ass_subscript(name, None, vm)
+                    .map_err(|_| name_error(name, vm))?;
                 Ok(None)
             }
             Instruction::DeleteSubscr => self.execute_delete_subscript(vm),
@@ -4623,11 +4893,11 @@ impl ExecutingFrame<'_> {
                     let src_dict = source
                         .downcast_ref::<PyDict>()
                         .expect("exact dict must have a PyDict payload");
-                    // Snapshot under a single read lock so a mutation of `source`
-                    // triggered by `dict.set_item` (e.g. via a target subclass, or
-                    // aliasing) can't be observed mid-iteration.
-                    for (key, value) in src_dict.items_vec() {
-                        if dict.contains_key(&*key, vm) {
+                    // Preserve stored hashes: copying an exact dict must not call
+                    // a key's __hash__ before the callable receives its arguments.
+                    // Snapshot under one lock before any equality callbacks run.
+                    for (key, value, hash) in src_dict.items_with_hashes_vec() {
+                        if dict.contains_known_hash(&key, hash, vm)? {
                             let key_str = key.str(vm)?;
                             return Err(vm.new_type_error(format!(
                                 "{} got multiple values for keyword argument '{}'",
@@ -4635,7 +4905,7 @@ impl ExecutingFrame<'_> {
                                 key_str.as_wtf8()
                             )));
                         }
-                        dict.set_item(&*key, value, vm)?;
+                        dict.set_item_known_hash(&key, hash, value, vm)?;
                     }
                     return Ok(None);
                 } else {
@@ -4818,36 +5088,23 @@ impl ExecutingFrame<'_> {
                 self.push_value(iter);
                 Ok(None)
             }
-            Instruction::GetIter => {
-                let iterated_obj = self.pop_value();
-                let iter_obj = PyIter::try_from_object(vm, iterated_obj)?;
-                self.push_value(iter_obj.into());
-                Ok(None)
-            }
-            Instruction::GetYieldFromIter => {
-                // GET_YIELD_FROM_ITER: prepare iterator for yield from
-                // If iterable is a coroutine, ensure we're in a coroutine context
-                // If iterable is a generator, use it directly
-                // Otherwise, call iter() on it
+            Instruction::GetIter { mode } => {
+                // _PyEval_GetIter
                 let iterable = self.pop_value();
-                let iter = if iterable.class().is(vm.ctx.types.coroutine_type) {
-                    // Coroutine requires CO_COROUTINE or CO_ITERABLE_COROUTINE flag
-                    if !self.code.flags.intersects(
-                        bytecode::CodeFlags::COROUTINE | bytecode::CodeFlags::ITERABLE_COROUTINE,
-                    ) {
+                let yield_from = mode.get(arg);
+                debug_assert_ne!(yield_from, bytecode::oparg::GET_ITER_YIELD_FROM);
+                let iter = if yield_from != 0 && iterable.class().is(vm.ctx.types.coroutine_type) {
+                    if yield_from == bytecode::oparg::GET_ITER_YIELD_FROM_CORO_CHECK {
                         return Err(vm.new_type_error(
                             "cannot 'yield from' a coroutine object in a non-coroutine generator",
                         ));
                     }
                     iterable
-                } else if iterable.class().is(vm.ctx.types.generator_type) {
-                    // Generator can be used directly
-                    iterable
                 } else {
-                    // Otherwise, get iterator
-                    PyIter::try_from_object(vm, iterable)?.into()
+                    iterable.get_iter(vm)?.into()
                 };
                 self.push_value(iter);
+                self.push_null();
                 Ok(None)
             }
             Instruction::GetLen => {
@@ -4863,7 +5120,8 @@ impl ExecutingFrame<'_> {
                 Ok(None)
             }
             Instruction::ImportName { namei: idx } => {
-                self.import(vm, Some(self.code.names[idx.get(arg) as usize]))?;
+                let packed = idx.get(arg);
+                self.import(vm, self.code.names[(packed >> 2) as usize], packed & 3)?;
                 Ok(None)
             }
             Instruction::IsOp { invert } => {
@@ -4984,7 +5242,7 @@ impl ExecutingFrame<'_> {
                 let name = self.localsplus_name(idx);
                 let value = self.mapping_get_optional(&class_dict, name, vm)?;
                 self.push_value(match value {
-                    Some(v) => v,
+                    Some(v) => crate::lazy_import::reify_value(v, name, &class_dict, vm)?,
                     None => self
                         .cell_ref(idx)
                         .get()
@@ -4999,25 +5257,13 @@ impl ExecutingFrame<'_> {
                 let value = self.mapping_get_optional(&dict, name, vm)?;
 
                 self.push_value(match value {
-                    Some(v) => v,
+                    Some(v) => crate::lazy_import::reify_value(v, name, &dict, vm)?,
                     None => self.load_global_or_builtin(name, vm)?,
                 });
                 Ok(None)
             }
             Instruction::LoadConst { consti } => {
                 self.push_value(self.code.constants[consti.get(arg)].clone().into());
-                // Mirror CPython's LOAD_CONST family transition. RustPython does
-                // not currently distinguish immortal constants at runtime.
-                let instr_idx = self.lasti() as usize - 1;
-                unsafe {
-                    self.code
-                        .instructions
-                        .replace_op(instr_idx, Instruction::LoadConstMortal);
-                }
-                Ok(None)
-            }
-            Instruction::LoadConstMortal | Instruction::LoadConstImmortal => {
-                self.push_value(self.code.constants[u32::from(arg).into()].clone().into());
                 Ok(None)
             }
             Instruction::LoadCommonConstant { idx } => {
@@ -5042,6 +5288,11 @@ impl ExecutingFrame<'_> {
                         .expect("builtin_any not initialized"),
                     CommonConstant::BuiltinList => vm.ctx.types.list_type.to_owned().into(),
                     CommonConstant::BuiltinSet => vm.ctx.types.set_type.to_owned().into(),
+                    CommonConstant::None => vm.ctx.none(),
+                    CommonConstant::EmptyStr => vm.ctx.empty_str.to_owned().into(),
+                    CommonConstant::True => vm.ctx.new_bool(true).into(),
+                    CommonConstant::False => vm.ctx.new_bool(false).into(),
+                    CommonConstant::MinusOne => vm.ctx.new_int(-1).into(),
                 };
                 self.push_value(value);
                 Ok(None)
@@ -5149,13 +5400,16 @@ impl ExecutingFrame<'_> {
             Instruction::LoadName { namei: idx } => {
                 let name = self.code.names[idx.get(arg) as usize];
                 let result = self.locals.mapping(vm).subscript(name, vm);
-                match result {
-                    Ok(x) => self.push_value(x),
+                let value = match result {
+                    Ok(x) => {
+                        crate::lazy_import::reify_value(x, name, self.locals.as_object(vm), vm)?
+                    }
                     Err(e) if e.fast_isinstance(vm.ctx.exceptions.key_error) => {
-                        self.push_value(self.load_global_or_builtin(name, vm)?);
+                        self.load_name_global_or_builtin(name, vm)?
                     }
                     Err(e) => return Err(e),
-                }
+                };
+                self.push_value(value);
                 Ok(None)
             }
             Instruction::LoadSpecial { method } => {
@@ -5518,8 +5772,8 @@ impl ExecutingFrame<'_> {
                 Ok(None)
             }
             Instruction::PopTop => {
-                // Pop value from stack and ignore.
-                self.pop_stackref();
+                // Loop unwinding also uses POP_TOP for index-or-NULL slots.
+                self.pop_stackref_opt();
                 Ok(None)
             }
             Instruction::EndFor => {
@@ -5528,7 +5782,8 @@ impl ExecutingFrame<'_> {
                 Ok(None)
             }
             Instruction::PopIter => {
-                // Pop the iterator from stack (end of for loop)
+                // Discard the iterator's index-or-NULL slot and the iterator.
+                self.pop_stackref_opt();
                 self.pop_stackref();
                 Ok(None)
             }
@@ -5587,10 +5842,10 @@ impl ExecutingFrame<'_> {
             Instruction::SetAdd { i } => {
                 let item = self.pop_value();
                 let obj = self.nth_value(i.get(arg) - 1);
-                let set: &Py<PySet> = unsafe {
-                    // SAFETY: trust compiler
-                    obj.downcast_unchecked_ref()
-                };
+                // Annotation tracking can load a user-rebound global here.
+                let set = obj.downcast_ref_if_exact::<PySet>(vm).ok_or_else(|| {
+                    vm.new_type_error(format!("'{}' object is not a set", obj.class().name()))
+                })?;
                 set.add(item, vm)?;
                 Ok(None)
             }
@@ -5833,10 +6088,10 @@ impl ExecutingFrame<'_> {
                 Ok(Some(ExecutionResult::Yield(self.pop_value())))
             }
             Instruction::Send { .. } => {
-                // (receiver, v -- receiver, retval)
+                // (receiver, null_or_index, v -- receiver, null_or_index, retval)
                 self.adaptive(|s, ii, cb| s.specialize_send(vm, ii, cb));
                 let exit_label = bytecode::Label::from_u32(self.lasti() + 1 + u32::from(arg));
-                let receiver = self.nth_value(1);
+                let receiver = self.nth_value(2);
                 let can_fast_send = !self.specialization_eval_frame_active(vm)
                     && (receiver.downcast_ref_if_exact::<PyGenerator>(vm).is_some()
                         || receiver.downcast_ref_if_exact::<PyCoroutine>(vm).is_some())
@@ -5844,7 +6099,7 @@ impl ExecutingFrame<'_> {
                         .builtin_coro(receiver)
                         .is_some_and(|coro| !coro.running() && !coro.closed());
                 let val = self.pop_value();
-                let receiver = self.top_value();
+                let receiver = self.nth_value(1);
                 let ret = if can_fast_send {
                     let coro = self.builtin_coro(receiver).unwrap();
                     if vm.is_none(&val) {
@@ -5874,8 +6129,8 @@ impl ExecutingFrame<'_> {
             }
             Instruction::SendGen => {
                 let exit_label = bytecode::Label::from_u32(self.lasti() + 1 + u32::from(arg));
-                // Stack: [receiver, val] — peek receiver before popping
-                let receiver = self.nth_value(1);
+                // Stack: [receiver, null_or_index, val] — peek before popping
+                let receiver = self.nth_value(2);
                 let mut started = false;
                 let can_fast_send = !self.specialization_eval_frame_active(vm)
                     && (receiver.downcast_ref_if_exact::<PyGenerator>(vm).is_some()
@@ -5887,7 +6142,7 @@ impl ExecutingFrame<'_> {
                 let val = self.pop_value();
 
                 if can_fast_send {
-                    let receiver = self.top_value();
+                    let receiver = self.nth_value(1);
                     // Hand an already-suspended generator to the trampoline,
                     // which runs its frame in this same eval loop and re-yields
                     // for this frame — no Rust frame and no instruction per
@@ -5922,7 +6177,7 @@ impl ExecutingFrame<'_> {
                         }
                     }
                 }
-                let receiver = self.top_value();
+                let receiver = self.nth_value(1);
                 match self._send(receiver, val, vm)? {
                     PyIterReturn::Return(value) => {
                         self.push_value(value);
@@ -5941,9 +6196,9 @@ impl ExecutingFrame<'_> {
                 }
             }
             Instruction::EndSend => {
-                // Stack: (receiver, value) -> (value)
-                // Pops receiver, leaves value
+                // (receiver, null_or_index, value) -> (value)
                 let value = self.pop_value();
+                self.pop_stackref_opt(); // discard index-or-NULL
                 self.pop_stackref(); // discard receiver
                 self.push_value(value);
                 Ok(None)
@@ -5960,39 +6215,24 @@ impl ExecutingFrame<'_> {
                 Ok(None)
             }
             Instruction::CleanupThrow => {
-                // CLEANUP_THROW: (sub_iter, last_sent_val, exc) -> (None, value) OR re-raise
-                // If StopIteration: pop all 3, extract value, push (None, value)
-                // Otherwise: pop all 3, return Err(exc) for unwind_blocks to handle
-                //
-                // Unlike CPython where exception_unwind pops the triple as part of
-                // stack cleanup to handler depth, RustPython pops here explicitly
-                // and lets unwind_blocks find outer handlers.
-                // Compiler sets handler_depth = base + 2 (before exc is pushed).
-
-                // First peek at exc_value (top of stack) without popping
+                // (sub_iter, null_in, last_sent_val, exc) -> (None, null_out, value)
+                // Leave nonmatching exceptions and their stack for unwinding.
                 let exc = self.top_value();
-
-                // Check if it's a StopIteration
                 if let Some(exc_ref) = exc.downcast_ref::<PyBaseException>()
                     && exc_ref.fast_isinstance(vm.ctx.exceptions.stop_iteration)
                 {
-                    // Extract value from StopIteration
                     let value = exc_ref.get_arg(0).unwrap_or_else(|| vm.ctx.none());
-                    // Now pop all three
                     self.pop_stackref(); // exc
                     self.pop_stackref(); // last_sent_val
+                    let index_or_null = self.pop_stackref_opt();
                     self.pop_stackref(); // sub_iter
                     self.push_value(vm.ctx.none());
+                    self.push_stackref_opt(index_or_null);
                     self.push_value(value);
                     return Ok(None);
                 }
-
-                // Re-raise other exceptions: pop all three and return Err(exc)
-                let exc = self.pop_value(); // exc
-                self.pop_stackref(); // last_sent_val
-                self.pop_stackref(); // sub_iter
-
                 let exc = exc
+                    .to_owned()
                     .downcast::<PyBaseException>()
                     .map_err(|_| vm.new_type_error("exception expected"))?;
                 Err(exc)
@@ -6162,6 +6402,9 @@ impl ExecutingFrame<'_> {
                         module
                             .dict()
                             .get_cached_module_attr(attr_name, keys_version, index, vm)
+                    && value
+                        .downcast_ref_if_exact::<crate::lazy_import::PyLazyImport>(vm)
+                        .is_none()
                 {
                     self.pop_stackref();
                     if oparg.is_method() {
@@ -6430,7 +6673,11 @@ impl ExecutingFrame<'_> {
                 {
                     let mut vec = list.borrow_vec_mut();
                     if i < vec.len() {
-                        vec[i] = value;
+                        // Unlock before dropping the replaced element; its
+                        // finalizer may access this list.
+                        let old = core::mem::replace(&mut vec[i], value);
+                        drop(vec);
+                        drop(old);
                         return Ok(None);
                     }
                 }
@@ -6518,7 +6765,7 @@ impl ExecutingFrame<'_> {
                 {
                     self.pop_stackref();
                     self.pop_stackref();
-                    self.push_value(result);
+                    self.push_value(result?);
                     Ok(None)
                 } else {
                     self.execute_bin_op(vm, op)
@@ -7846,7 +8093,7 @@ impl ExecutingFrame<'_> {
             }
             Instruction::ForIterRange => {
                 let target = bytecode::Label::from_u32(self.lasti() + 1 + u32::from(arg));
-                let iter = self.top_value();
+                let iter = self.nth_value(1);
                 if let Some(range_iter) = iter.downcast_ref_if_exact::<PyRangeIterator>(vm) {
                     if let Some(value) = range_iter.fast_next() {
                         self.push_value(vm.ctx.new_int(value).into());
@@ -7861,7 +8108,7 @@ impl ExecutingFrame<'_> {
             }
             Instruction::ForIterList => {
                 let target = bytecode::Label::from_u32(self.lasti() + 1 + u32::from(arg));
-                let iter = self.top_value();
+                let iter = self.nth_value(1);
                 if let Some(list_iter) = iter.downcast_ref_if_exact::<PyListIterator>(vm) {
                     if let Some(value) = list_iter.fast_next() {
                         self.push_value(value);
@@ -7876,7 +8123,7 @@ impl ExecutingFrame<'_> {
             }
             Instruction::ForIterTuple => {
                 let target = bytecode::Label::from_u32(self.lasti() + 1 + u32::from(arg));
-                let iter = self.top_value();
+                let iter = self.nth_value(1);
                 if let Some(tuple_iter) = iter.downcast_ref_if_exact::<PyTupleIterator>(vm) {
                     if let Some(value) = tuple_iter.fast_next() {
                         self.push_value(value);
@@ -7891,7 +8138,7 @@ impl ExecutingFrame<'_> {
             }
             Instruction::ForIterGen => {
                 let target = bytecode::Label::from_u32(self.lasti() + 1 + u32::from(arg));
-                let iter = self.top_value();
+                let iter = self.nth_value(1);
                 if self.specialization_eval_frame_active(vm) {
                     self.execute_for_iter(vm, target)?;
                     return Ok(None);
@@ -7937,10 +8184,12 @@ impl ExecutingFrame<'_> {
                 let cached_version = self.code.instructions.read_cache_u16(cache_base + 1);
                 let cached_index = self.code.instructions.read_cache_u16(cache_base + 3);
                 if cached_version != 0
-                    && let Some(x) = self
-                        .globals
-                        .get_item_by_index_and_keys_version(cached_version, cached_index)
+                    && let Some(globals) = self.globals.as_mutable()
+                    && let Some(x) =
+                        globals.get_item_by_index_and_keys_version(cached_version, cached_index)
                 {
+                    let name = self.code.names[(oparg >> 1) as usize];
+                    let x = crate::lazy_import::reify_value(x, name, self.globals.as_object(), vm)?;
                     self.push_value(x);
                     if (oparg & 1) != 0 {
                         self.push_value_opt(None);
@@ -7963,12 +8212,15 @@ impl ExecutingFrame<'_> {
                 let cached_index = self.code.instructions.read_cache_u16(cache_base + 3);
                 if cached_globals_ver != 0
                     && cached_builtins_ver != 0
-                    && let Ok(current_globals_ver) = u16::try_from(self.globals.keys_version())
+                    && let Some(globals) = self.globals.as_mutable()
+                    && let Ok(current_globals_ver) = u16::try_from(globals.keys_version())
                     && cached_globals_ver == current_globals_ver
                     && let Some(builtins_dict) = self.builtins.downcast_ref_if_exact::<PyDict>(vm)
                     && let Some(x) = builtins_dict
                         .get_item_by_index_and_keys_version(cached_builtins_ver, cached_index)
                 {
+                    let name = self.code.names[(oparg >> 1) as usize];
+                    let x = crate::lazy_import::reify_value(x, name, self.builtins, vm)?;
                     self.push_value(x);
                     if (oparg & 1) != 0 {
                         self.push_value_opt(None);
@@ -7997,6 +8249,17 @@ impl ExecutingFrame<'_> {
         instruction: Instruction,
         arg: bytecode::OpArg,
         vm: &VirtualMachine,
+    ) -> FrameResult {
+        self.execute_instrumented_from(instruction, arg, false, vm)
+    }
+
+    #[cold]
+    fn execute_instrumented_from(
+        &mut self,
+        instruction: Instruction,
+        arg: bytecode::OpArg,
+        wrapper_dispatch: bool,
+        vm: &VirtualMachine,
     ) -> FrameResult {
         debug_assert!(
             instruction.is_instrumented(),
@@ -8096,8 +8359,8 @@ impl ExecutingFrame<'_> {
                 self.execute_call_instrumented(args, vm)
             }
             Instruction::InstrumentedCallFunctionEx => {
-                let args = self.collect_ex_args(vm)?;
-                self.execute_call_instrumented(args, vm)
+                let (args, kwnames) = self.collect_ex_args(vm)?;
+                self.execute_call_ex(args, kwnames, true, vm)
             }
             Instruction::InstrumentedLoadSuperAttr => {
                 let oparg = bytecode::LoadSuperAttr::from(u32::from(arg));
@@ -8172,7 +8435,13 @@ impl ExecutingFrame<'_> {
                 if continued {
                     if self.monitoring_mask & MonitoringEvent::BranchLeft.mask() != 0 {
                         let dest_offset = (self.lasti() + 1) * 2; // after caches
-                        monitoring::fire_branch_left(vm, self.code, src_offset, dest_offset)?;
+                        monitoring::fire_branch_left(
+                            vm,
+                            self.code,
+                            src_offset,
+                            src_offset,
+                            dest_offset,
+                        )?;
                     }
                 } else if self.monitoring_mask & MonitoringEvent::BranchRight.mask() != 0 {
                     // INSTRUMENTED_POP_ITER: dest is the instruction after
@@ -8183,10 +8452,10 @@ impl ExecutingFrame<'_> {
                 Ok(None)
             }
             Instruction::InstrumentedEndFor => {
-                // Stack: [value, receiver(iter), ...]
+                // Stack: [..., receiver(iter), null_or_index, value]
                 // PyGen_Check: only fire STOP_ITERATION for generators
                 let is_gen = self
-                    .nth_value(1)
+                    .nth_value(2)
                     .downcast_ref::<crate::builtins::PyGenerator>()
                     .is_some();
                 let value = self.pop_value();
@@ -8198,6 +8467,7 @@ impl ExecutingFrame<'_> {
             }
             Instruction::InstrumentedEndSend => {
                 let value = self.pop_value();
+                self.pop_stackref_opt();
                 let receiver = self.pop_value();
                 // PyGen_Check || PyCoro_CheckExact
                 let is_gen_or_coro = receiver
@@ -8278,14 +8548,20 @@ impl ExecutingFrame<'_> {
                     {
                         branch_idx -= 1;
                     }
-                    let src_offset = (branch_idx as u32) * 2;
+                    let site = not_taken_idx as u32 * 2;
+                    let src_offset = if wrapper_dispatch {
+                        site
+                    } else {
+                        (branch_idx as u32) * 2
+                    };
                     let dest_offset = self.lasti() * 2;
-                    monitoring::fire_branch_left(vm, self.code, src_offset, dest_offset)?;
+                    monitoring::fire_branch_left(vm, self.code, site, src_offset, dest_offset)?;
                 }
                 Ok(None)
             }
             Instruction::InstrumentedPopIter => {
                 // BRANCH_RIGHT is fired by InstrumentedForIter, not here.
+                self.pop_stackref_opt();
                 self.pop_stackref();
                 Ok(None)
             }
@@ -8332,6 +8608,17 @@ impl ExecutingFrame<'_> {
                     "INSTRUMENTED_LINE at {idx} without stored opcode"
                 );
 
+                let line_active =
+                    monitoring::is_event_active_at(vm, self.code, offset, MonitoringEvent::Line);
+                let instruction_active = also_instruction
+                    && monitoring::is_event_active_at(
+                        vm,
+                        self.code,
+                        offset,
+                        MonitoringEvent::Instruction,
+                    );
+                let wrapper_dispatch = line_active || instruction_active;
+
                 // Fire LINE event only if line changed
                 if let Some((loc, _)) = self.code.locations.get(idx) {
                     let line = loc.line.get() as u32;
@@ -8341,8 +8628,16 @@ impl ExecutingFrame<'_> {
                     }
                 }
 
-                // If the LINE position also had INSTRUCTION, fire that event too
-                if also_instruction {
+                // Removing the last LINE layer changes its saved opcode in CPython.
+                // That redispatch skips nested INSTRUCTION once, not on later visits.
+                let line_removed = line_active
+                    && !monitoring::is_event_active_at(
+                        vm,
+                        self.code,
+                        offset,
+                        MonitoringEvent::Line,
+                    );
+                if also_instruction && !line_removed {
                     monitoring::fire_instruction(vm, self.code, offset)?;
                 }
 
@@ -8359,7 +8654,7 @@ impl ExecutingFrame<'_> {
                     .expect("invalid opcode in side-table chain");
                 let lasti_before_dispatch = self.lasti();
                 let result = if original_op.to_base().is_some() {
-                    self.execute_instrumented(original_op, arg, vm)
+                    self.execute_instrumented_from(original_op, arg, wrapper_dispatch, vm)
                 } else {
                     let mut do_extend_arg = false;
                     self.execute_instruction(original_op, arg, &mut do_extend_arg, vm)
@@ -8384,6 +8679,13 @@ impl ExecutingFrame<'_> {
                     "INSTRUMENTED_INSTRUCTION at {idx} without stored opcode"
                 );
 
+                let wrapper_dispatch = monitoring::is_event_active_at(
+                    vm,
+                    self.code,
+                    offset,
+                    MonitoringEvent::Instruction,
+                );
+
                 // Fire INSTRUCTION event
                 monitoring::fire_instruction(vm, self.code, offset)?;
 
@@ -8392,7 +8694,7 @@ impl ExecutingFrame<'_> {
                     .expect("invalid opcode in instruction side-table");
                 let lasti_before_dispatch = self.lasti();
                 let result = if original_op.to_base().is_some() {
-                    self.execute_instrumented(original_op, arg, vm)
+                    self.execute_instrumented_from(original_op, arg, wrapper_dispatch, vm)
                 } else {
                     let mut do_extend_arg = false;
                     self.execute_instruction(original_op, arg, &mut do_extend_arg, vm)
@@ -8435,34 +8737,58 @@ impl ExecutingFrame<'_> {
         if let Some(builtins_dict) = self.builtins_dict {
             // Fast path: both globals and builtins are exact dicts
             // SAFETY: builtins_dict is only set when globals is also exact dict
-            let globals_exact = unsafe { PyExact::ref_unchecked(self.globals) };
-            globals_exact
-                .get_chain_exact(builtins_dict, name, vm)?
-                .ok_or_else(|| {
-                    vm.new_name_error(format!("name '{name}' is not defined"), name.to_owned())
-                })
+            let globals = self
+                .globals
+                .as_object()
+                .downcast_ref::<PyDict>()
+                .expect("exact dict globals");
+            if let Some(value) = globals.get_item_opt(name, vm)? {
+                return crate::lazy_import::reify_value(value, name, globals.as_object(), vm);
+            }
+            let value = builtins_dict.get_item_opt(name, vm)?.ok_or_else(|| {
+                vm.new_name_error(format!("name '{name}' is not defined"), name.to_owned())
+            })?;
+            crate::lazy_import::reify_value(value, name, builtins_dict.as_object(), vm)
         } else {
             // Slow path: builtins is not a dict, use generic __getitem__
             if let Some(value) = self.globals.get_item_opt(name, vm)? {
-                return Ok(value);
+                return crate::lazy_import::reify_value(value, name, self.globals.as_object(), vm);
             }
-            self.builtins.get_item(name, vm).map_err(|e| {
-                if e.fast_isinstance(vm.ctx.exceptions.key_error) {
-                    vm.new_name_error(format!("name '{name}' is not defined"), name.to_owned())
-                } else {
-                    e
-                }
-            })
+            self.load_builtin(name, vm)
         }
     }
 
+    fn load_name_global_or_builtin(&self, name: &Py<PyStr>, vm: &VirtualMachine) -> PyResult {
+        // LOAD_NAME reads the stored global entries even for dict subclasses;
+        // LOAD_GLOBAL instead honors their __getitem__ implementation.
+        if let Some(value) = self.globals.inner_getitem_opt(name, vm)? {
+            return crate::lazy_import::reify_value(value, name, self.globals.as_object(), vm);
+        }
+        self.load_builtin(name, vm)
+    }
+
+    fn load_builtin(&self, name: &Py<PyStr>, vm: &VirtualMachine) -> PyResult {
+        let value = self.builtins.get_item(name, vm).map_err(|e| {
+            if e.fast_isinstance(vm.ctx.exceptions.key_error) {
+                vm.new_name_error(format!("name '{name}' is not defined"), name.to_owned())
+            } else {
+                e
+            }
+        })?;
+        crate::lazy_import::reify_value(value, name, self.builtins, vm)
+    }
+
     #[cfg_attr(feature = "flame-it", flame("FrameObject"))]
-    fn import(&mut self, vm: &VirtualMachine, module_name: Option<&Py<PyStr>>) -> PyResult<()> {
-        let module_name = module_name.unwrap_or(vm.ctx.empty_str);
+    fn import(
+        &mut self,
+        vm: &VirtualMachine,
+        module_name: &Py<PyStr>,
+        policy: u32,
+    ) -> PyResult<()> {
         let from_list = self.pop_value();
         let level = usize::try_from_object(vm, self.pop_value())?;
 
-        let module = vm.import_from(module_name, from_list, level)?;
+        let module = crate::lazy_import::import_name(module_name, from_list, level, policy, vm)?;
 
         self.push_value(module);
         Ok(())
@@ -8473,107 +8799,11 @@ impl ExecutingFrame<'_> {
         let module = self.top_value();
         let name = self.code.names[idx as usize];
 
-        // Load attribute, and transform any error into import error.
-        if let Some(obj) = vm.get_attribute_opt(module, name)? {
-            return Ok(obj);
-        }
-        // fallback to importing '{module.__name__}.{name}' from sys.modules
-        let fallback_module = (|| {
-            let mod_name = module.get_attr(identifier!(vm, __name__), vm).ok()?;
-            let mod_name = mod_name.downcast_ref::<PyUtf8Str>()?;
-            let full_mod_name = vm.ctx.new_utf8_str(format!("{}.{name}", mod_name.as_str()));
-            let sys_modules = vm.sys_module.get_attr("modules", vm).ok()?;
-            sys_modules.get_item(&*full_mod_name, vm).ok()
-        })();
-
-        if let Some(sub_module) = fallback_module {
-            return Ok(sub_module);
-        }
-
-        use crate::import::{
-            get_spec_file_origin, is_possibly_shadowing_path, is_stdlib_module_name,
-        };
-
-        // Get module name for the error message
-        let mod_name_obj = module.get_attr(identifier!(vm, __name__), vm).ok();
-        let mod_name = mod_name_obj
-            .as_ref()
-            .and_then(|n| n.downcast_ref::<PyUtf8Str>());
-        let module_name = mod_name.map_or("<unknown module name>", |s| s.as_str());
-
-        let spec = module
-            .get_attr("__spec__", vm)
-            .ok()
-            .filter(|s| !vm.is_none(s));
-
-        let origin = get_spec_file_origin(spec.as_deref(), vm);
-
-        let is_possibly_shadowing = origin
-            .as_ref()
-            .is_some_and(|o| is_possibly_shadowing_path(o, vm));
-        let is_possibly_shadowing_stdlib = if is_possibly_shadowing {
-            if let Some(ref mod_name) = mod_name_obj {
-                is_stdlib_module_name(mod_name, vm)?
-            } else {
-                false
-            }
-        } else {
-            false
-        };
-
-        let msg = if is_possibly_shadowing_stdlib {
-            let origin = origin.as_ref().unwrap();
-            format!(
-                "cannot import name '{name}' from '{module_name}' \
-                 (consider renaming '{origin}' since it has the same \
-                 name as the standard library module named '{module_name}' \
-                 and prevents importing that standard library module)"
-            )
-        } else {
-            let is_init = is_module_initializing(module, vm);
-            if is_init {
-                if is_possibly_shadowing {
-                    let origin = origin.as_ref().unwrap();
-                    format!(
-                        "cannot import name '{name}' from '{module_name}' \
-                         (consider renaming '{origin}' if it has the same name \
-                         as a library you intended to import)"
-                    )
-                } else if let Some(ref path) = origin {
-                    format!(
-                        "cannot import name '{name}' from partially initialized module \
-                         '{module_name}' (most likely due to a circular import) ({path})"
-                    )
-                } else {
-                    format!(
-                        "cannot import name '{name}' from partially initialized module \
-                         '{module_name}' (most likely due to a circular import)"
-                    )
-                }
-            } else if let Some(ref path) = origin {
-                format!("cannot import name '{name}' from '{module_name}' ({path})")
-            } else {
-                format!("cannot import name '{name}' from '{module_name}' (unknown location)")
-            }
-        };
-        let err = vm.new_import_error(
-            msg,
-            match mod_name {
-                Some(s) => s.to_owned().into_wtf8(),
-                None => vm.ctx.new_utf8_str("<unknown module name>").into_wtf8(),
-            },
-        );
-
-        if let Some(ref path) = origin {
-            let _ignore = err
-                .as_object()
-                .set_attr("path", vm.ctx.new_str(path.as_str()), vm);
+        if let Some(deferred) = module.downcast_ref_if_exact::<crate::lazy_import::PyLazyImport>(vm)
+        {
+            return crate::lazy_import::import_from(deferred, name, vm);
         }
-
-        // name_from = the attribute name that failed to import (best-effort metadata)
-        let _ignore = err.as_object().set_attr("name_from", name.to_owned(), vm);
-
-        Err(err)
+        crate::import::import_from_attribute(module, name, vm)
     }
 
     #[cfg_attr(feature = "flame-it", flame("FrameObject"))]
@@ -8639,6 +8869,7 @@ impl ExecutingFrame<'_> {
                 if let Some(entry) =
                     bytecode::find_exception_handler(&self.code.exceptiontable, offset)
                 {
+                    monitoring::reset_reraise_pending();
                     // Fire EXCEPTION_HANDLED before setting up handler.
                     // If the callback raises, the handler is NOT set up and the
                     // new exception propagates instead.
@@ -8778,9 +9009,13 @@ impl ExecutingFrame<'_> {
         FuncArgs::with_kwargs_names(args, kwarg_names)
     }
 
-    fn collect_ex_args(&mut self, vm: &VirtualMachine) -> PyResult<FuncArgs> {
+    fn collect_ex_args(
+        &mut self,
+        vm: &VirtualMachine,
+    ) -> PyResult<(Vec<PyObjectRef>, Vec<PyObjectRef>)> {
         let kwargs_or_null = self.pop_value_opt();
-        let mut kwargs = KwArgs::default();
+        let mut kwnames = Vec::new();
+        let mut keyword_values = Vec::new();
         if let Some(kw_obj) = kwargs_or_null {
             // Stack: [callable, self_or_null, args_tuple]
             let callable = self.nth_value(2);
@@ -8789,16 +9024,17 @@ impl ExecutingFrame<'_> {
             Self::iterate_mapping_keys(vm, &kw_obj, &func_str, |key, value| {
                 // `PyStr`, not `PyUtf8Str`: CPython only checks that the key is a
                 // `str`, not that it is valid UTF-8, so surrogate keys are accepted.
-                let key_str = key
-                    .downcast_ref::<PyStr>()
+                key.downcast_ref::<PyStr>()
                     .ok_or_else(|| vm.new_type_error("keywords must be strings"))?;
-                kwargs.insert(key_str.as_wtf8().to_owned(), value);
+                // Preserve string-subclass identity until the callee binds or merges keywords.
+                kwnames.push(key);
+                keyword_values.push(value);
                 Ok(())
             })?
         };
 
         let args_obj = self.pop_value();
-        let args = if let Some(tuple) = args_obj.downcast_ref::<PyTuple>() {
+        let mut args = if let Some(tuple) = args_obj.downcast_ref::<PyTuple>() {
             tuple.as_slice().to_vec()
         } else {
             // Single *arg passed directly; convert to sequence at runtime.
@@ -8821,7 +9057,8 @@ impl ExecutingFrame<'_> {
                 }
             })?
         };
-        Ok(FuncArgs { args, kwargs })
+        args.extend(keyword_values);
+        Ok((args, kwnames))
     }
 
     /// Returns a display string for a callable object for use in error messages.
@@ -9013,22 +9250,34 @@ impl ExecutingFrame<'_> {
     }
 
     #[inline]
-    fn execute_call(&mut self, args: FuncArgs, vm: &VirtualMachine) -> FrameResult {
+    fn execute_call_ex(
+        &mut self,
+        mut args: Vec<PyObjectRef>,
+        kwnames: Vec<PyObjectRef>,
+        instrumented: bool,
+        vm: &VirtualMachine,
+    ) -> FrameResult {
         // Stack: [callable, self_or_null, ...]
         let self_or_null = self.pop_value_opt(); // Option<PyObjectRef>
         let callable = self.pop_value();
 
-        let final_args = if let Some(self_val) = self_or_null {
-            let mut args = args;
-            args.prepend_arg(self_val);
-            args
+        if let Some(self_val) = self_or_null {
+            args.insert(0, self_val);
+        }
+        let nargs = args.len() - kwnames.len();
+        let arg0 = if instrumented {
+            args[..nargs].first().cloned()
         } else {
-            args
+            None
         };
-
-        let value = callable.call(final_args, vm)?;
-        self.push_value(value);
-        Ok(None)
+        let invoke = || callable.vectorcall(args, nargs, Some(&kwnames), vm);
+        if instrumented {
+            self.execute_call_instrumented_inner(&callable, arg0, invoke, vm)
+        } else {
+            let value = invoke()?;
+            self.push_value(value);
+            Ok(None)
+        }
     }
 
     /// Instrumented version of execute_call: fires CALL, C_RETURN, and C_RAISE events.
@@ -9044,29 +9293,36 @@ impl ExecutingFrame<'_> {
             args
         };
 
+        let arg0 = final_args.args.first().cloned();
+        self.execute_call_instrumented_inner(&callable, arg0, || callable.call(final_args, vm), vm)
+    }
+
+    fn execute_call_instrumented_inner(
+        &mut self,
+        callable: &PyObject,
+        arg0: Option<PyObjectRef>,
+        invoke: impl FnOnce() -> PyResult,
+        vm: &VirtualMachine,
+    ) -> FrameResult {
         let is_python_call = callable.downcast_ref_if_exact::<PyFunction>(vm).is_some();
 
         // Fire CALL event
         let call_arg0 = if self.monitoring_mask & MonitoringEvent::Call.mask() != 0 {
-            let arg0 = final_args
-                .args
-                .first()
-                .cloned()
-                .unwrap_or_else(|| monitoring::get_missing(vm));
+            let arg0 = arg0.unwrap_or_else(|| monitoring::get_missing(vm));
             let offset = (self.lasti() - 1) * 2;
-            monitoring::fire_call(vm, self.code, offset, &callable, arg0.clone())?;
+            monitoring::fire_call(vm, self.code, offset, callable, arg0.clone())?;
             Some(arg0)
         } else {
             None
         };
 
-        match callable.call(final_args, vm) {
+        match invoke() {
             Ok(value) => {
                 if let Some(arg0) = call_arg0
                     && !is_python_call
                 {
                     let offset = (self.lasti() - 1) * 2;
-                    monitoring::fire_c_return(vm, self.code, offset, &callable, arg0)?;
+                    monitoring::fire_c_return(vm, self.code, offset, callable, arg0)?;
                 }
                 self.push_value(value);
                 Ok(None)
@@ -9076,7 +9332,7 @@ impl ExecutingFrame<'_> {
                     && !is_python_call
                 {
                     let offset = (self.lasti() - 1) * 2;
-                    match monitoring::fire_c_raise(vm, self.code, offset, &callable, arg0) {
+                    match monitoring::fire_c_raise(vm, self.code, offset, callable, arg0) {
                         Ok(()) => exc,
                         Err(monitor_exc) => monitor_exc,
                     }
@@ -9353,7 +9609,7 @@ impl ExecutingFrame<'_> {
         value: Option<PyObjectRef>,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        let iter = self.top_value();
+        let iter = self.nth_value(1);
         if iter.downcast_ref_if_exact::<PyListIterator>(vm).is_some()
             || iter.downcast_ref_if_exact::<PyRangeIterator>(vm).is_some()
             || iter.downcast_ref_if_exact::<PyTupleIterator>(vm).is_some()
@@ -9377,14 +9633,14 @@ impl ExecutingFrame<'_> {
         Ok(())
     }
 
-    /// Advance the iterator on top of stack.
+    /// Advance the iterator below its index-or-NULL stack slot.
     /// Returns `true` if iteration continued (item pushed), `false` if exhausted (jumped).
     fn execute_for_iter(
         &mut self,
         vm: &VirtualMachine,
         target: bytecode::Label,
     ) -> Result<bool, PyBaseExceptionRef> {
-        let top = self.top_value();
+        let top = self.nth_value(1);
 
         // FOR_ITER_RANGE: bypass generic iterator protocol for range iterators
         if let Some(range_iter) = top.downcast_ref_if_exact::<PyRangeIterator>(vm) {
@@ -9415,10 +9671,7 @@ impl ExecutingFrame<'_> {
                 self.jump(self.for_iter_jump_target(target));
                 Ok(false)
             }
-            Err(next_error) => {
-                self.pop_stackref();
-                Err(next_error)
-            }
+            Err(next_error) => Err(next_error),
         }
     }
 
@@ -10657,6 +10910,11 @@ impl ExecutingFrame<'_> {
                     && b.downcast_ref_if_exact::<PyFloat>(vm).is_some()
                 {
                     Some(Instruction::BinaryOpMultiplyFloat)
+                } else if (sequence_int_guard(a, b, vm) || int_sequence_guard(a, b, vm))
+                    && let Some(descr) = self.binary_op_extended_specialization(op, a, b, vm)
+                {
+                    cached_extend_descr = Some(descr);
+                    Some(Instruction::BinaryOpExtend)
                 } else {
                     None
                 }
@@ -11315,8 +11573,8 @@ impl ExecutingFrame<'_> {
         ) {
             return;
         }
-        // Stack: [receiver, val] — receiver is at position 1
-        let receiver = self.nth_value(1);
+        // Stack: [receiver, null_or_index, val] — receiver is at position 2
+        let receiver = self.nth_value(2);
         let is_exact_gen_or_coro = receiver.downcast_ref_if_exact::<PyGenerator>(vm).is_some()
             || receiver.downcast_ref_if_exact::<PyCoroutine>(vm).is_some();
         if is_exact_gen_or_coro && !self.specialization_eval_frame_active(vm) {
@@ -11582,7 +11840,7 @@ impl ExecutingFrame<'_> {
         ) {
             return;
         }
-        let iter = self.top_value();
+        let iter = self.nth_value(1);
 
         let new_op = if iter.downcast_ref_if_exact::<PyRangeIterator>(vm).is_some() {
             Some(Instruction::ForIterRange)
@@ -11675,7 +11933,7 @@ impl ExecutingFrame<'_> {
         let locals = if code.flags.contains(bytecode::CodeFlags::NEWLOCALS) {
             FrameLocals::lazy()
         } else {
-            FrameLocals::with_locals(crate::function::ArgMapping::from_dict_exact(
+            FrameLocals::with_locals(crate::function::ArgMapping::from_anydict_exact(
                 func.globals.clone(),
             ))
         };
@@ -11741,7 +11999,7 @@ impl ExecutingFrame<'_> {
         let locals = if code.flags.contains(bytecode::CodeFlags::NEWLOCALS) {
             FrameLocals::lazy()
         } else {
-            FrameLocals::with_locals(crate::function::ArgMapping::from_dict_exact(
+            FrameLocals::with_locals(crate::function::ArgMapping::from_anydict_exact(
                 func.globals.clone(),
             ))
         };
@@ -11827,8 +12085,11 @@ impl ExecutingFrame<'_> {
         ) {
             return;
         }
+        let Some(globals) = self.globals.as_mutable() else {
+            return;
+        };
         let name = self.code.names[(oparg >> 1) as usize];
-        let Ok(globals_version @ 1..) = u16::try_from(self.globals.assign_keys_version(vm)) else {
+        let Ok(globals_version @ 1..) = u16::try_from(globals.assign_keys_version(vm)) else {
             unsafe {
                 self.code.instructions.write_adaptive_counter(
                     cache_base,
@@ -11840,7 +12101,7 @@ impl ExecutingFrame<'_> {
             return;
         };
 
-        if let Ok(Some(globals_hint)) = self.globals.hint_for_key(name, vm) {
+        if let Ok(Some(globals_hint)) = globals.hint_for_key(name, vm) {
             unsafe {
                 self.code
                     .instructions
@@ -12027,9 +12288,8 @@ impl ExecutingFrame<'_> {
         let attr_name = self.code.names[attr_idx as usize];
         let cls_attr = cls.get_attr(attr_name);
         let has_data_descr = cls_attr.as_ref().is_some_and(|descr| {
-            let descr_cls = descr.class();
-            descr_cls.slots().descr_get.load().is_some()
-                && descr_cls.slots().descr_set.load().is_some()
+            // Assignment must honor __set__ even without __get__.
+            descr.class().slots().descr_set.load().is_some()
         });
 
         if has_data_descr {
@@ -12636,19 +12896,6 @@ fn get_special_method_error_msg(
     }
 }
 
-fn is_module_initializing(module: &PyObject, vm: &VirtualMachine) -> bool {
-    let Ok(spec) = module.get_attr(&vm.ctx.new_str("__spec__"), vm) else {
-        return false;
-    };
-    if vm.is_none(&spec) {
-        return false;
-    }
-    let Ok(initializing_attr) = spec.get_attr(&vm.ctx.new_str("_initializing"), vm) else {
-        return false;
-    };
-    initializing_attr.try_to_bool(vm).unwrap_or(false)
-}
-
 fn expect_unchecked<T: fmt::Debug>(optional: Option<T>, err_msg: &'static str) -> T {
     if cfg!(debug_assertions) {
         optional.expect(err_msg)
diff --git a/crates/vm/src/function/argument.rs b/crates/vm/src/function/argument.rs
index 2106a668f77..0df326c71ff 100644
--- a/crates/vm/src/function/argument.rs
+++ b/crates/vm/src/function/argument.rs
@@ -1,4 +1,4 @@
-use super::signature::Param;
+use super::signature::{Param, ParamKind};
 use crate::{
     AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject, VirtualMachine,
     builtins::{PyBaseExceptionRef, PyTupleRef, PyType},
@@ -307,6 +307,15 @@ impl FuncArgs {
         let arity = arity.start().saturating_sub(instance)..=arity.end().saturating_sub(instance);
         let num_given = self.args.len().saturating_sub(instance);
 
+        // A keyword that fills a parameter already given by position is
+        // reported before leftover-keyword and conversion errors.
+        if let Some(params) = T::PARAMS
+            && !self.kwargs.is_empty()
+            && let Some((name, pos)) = duplicate_name_and_position(params, num_given, &self.kwargs)
+        {
+            return Err(callee.given_by_name_and_position(name, pos, vm));
+        }
+
         let bound = T::from_args(vm, &mut self)
             .map_err(|e| e.into_exception(&arity, num_given, callee, vm))?;
 
@@ -408,6 +417,15 @@ impl Callee {
         vm.new_type_error(unexpected_keyword_message(self.name, keyword))
     }
 
+    fn given_by_name_and_position(
+        self,
+        keyword: &str,
+        pos: usize,
+        vm: &VirtualMachine,
+    ) -> PyBaseExceptionRef {
+        vm.new_type_error(given_by_name_and_position_message(self.name, keyword, pos))
+    }
+
     /// The branch of _PyArg_UnpackKeywords that names a parameter it didn't get.
     fn missing_argument(
         self,
@@ -464,6 +482,52 @@ pub(crate) fn unexpected_keyword_message(name: Option<&str>, keyword: &str) -> S
     format!("{name}{parens} got an unexpected keyword argument '{keyword}'")
 }
 
+pub(crate) fn given_by_name_and_position_message(
+    name: Option<&str>,
+    keyword: &str,
+    pos: usize,
+) -> String {
+    let name = name.map_or("function", short_name);
+    format!("argument for {name}() given by name ('{keyword}') and position ({pos})")
+}
+
+/// First positional-or-keyword parameter that was also passed by keyword.
+fn duplicate_name_and_position<'a>(
+    params: &'a [Param],
+    nargs: usize,
+    kwargs: &KwArgs,
+) -> Option<(&'a str, usize)> {
+    fn walk<'a>(
+        params: &'a [Param],
+        nargs: usize,
+        kwargs: &KwArgs,
+        pos: &mut usize,
+    ) -> Option<(&'a str, usize)> {
+        for param in params {
+            match param.kind {
+                ParamKind::Flatten(Some(inner)) => {
+                    if let Some(hit) = walk(inner, nargs, kwargs, pos) {
+                        return Some(hit);
+                    }
+                }
+                ParamKind::Flatten(None) | ParamKind::PositionalOnly => {
+                    *pos += 1;
+                }
+                ParamKind::PositionalOrKeyword => {
+                    *pos += 1;
+                    if nargs >= *pos && !param.name.is_empty() && kwargs.contains_key(param.name) {
+                        return Some((param.name, *pos));
+                    }
+                }
+                ParamKind::VarPositional => return None,
+                ParamKind::KeywordOnly | ParamKind::VarKeyword => {}
+            }
+        }
+        None
+    }
+    walk(params, nargs, kwargs, &mut 0)
+}
+
 /// The branch of _PyArg_UnpackKeywords that names a parameter it didn't get.
 pub(crate) fn missing_argument_message(name: Option<&str>, keyword: &str, pos: usize) -> String {
     let (name, parens) = call_form(name, "function");
diff --git a/crates/vm/src/function/buffer.rs b/crates/vm/src/function/buffer.rs
index 51f9dc28ac5..528692fd765 100644
--- a/crates/vm/src/function/buffer.rs
+++ b/crates/vm/src/function/buffer.rs
@@ -1,7 +1,7 @@
 use crate::{
     AsObject, PyObject, PyObjectRef, PyResult, TryFromBorrowedObject, TryFromObject,
     VirtualMachine,
-    builtins::{PyStr, PyStrRef},
+    builtins::{PyBytes, PyStr, PyStrRef},
     common::borrow::{BorrowedValue, BorrowedValueMut},
     protocol::{BufferFlags, PyBuffer},
 };
@@ -55,13 +55,12 @@ impl ArgBytesLike {
     /// `borrow_buf` may answer with a lock that every other thread writing to
     /// the same object waits on, and a thread waiting on a lock never reaches
     /// a safepoint, so keeping one across a wait for a peer, a pipe or a
-    /// signal stops the world from being stopped at all. Bytes reached that
-    /// way are copied out first. Bytes that lock nothing -- an immutable
-    /// object's -- are borrowed where they lie, which is all CPython holds in
-    /// either case.
+    /// signal stops the world from being stopped at all. Only storage owned
+    /// by `bytes` can be borrowed across that wait. Other exporters are copied:
+    /// an unlocked or readonly buffer may still alias writable raw memory.
     pub fn borrow_buf_unlocked(&self, vm: &VirtualMachine) -> PyResult<UnlockedBuf<'_>> {
         let borrowed = self.borrow_buf();
-        if !borrowed.is_locked() {
+        if !borrowed.is_locked() && self.source_object().downcast_ref::<PyBytes>().is_some() {
             return Ok(UnlockedBuf::Borrowed(borrowed));
         }
         let mut copy = Vec::new();
diff --git a/crates/vm/src/function/builtin.rs b/crates/vm/src/function/builtin.rs
index b4bd610776d..bda24f87944 100644
--- a/crates/vm/src/function/builtin.rs
+++ b/crates/vm/src/function/builtin.rs
@@ -1,4 +1,4 @@
-use super::{Callee, FromArgs, FuncArgs};
+use super::{Callee, FromArgs, FuncArgs, SigArg};
 use crate::{
     Py, PyPayload, PyRef, PyResult, VirtualMachine, convert::ToPyResult,
     object::PyThreadingConstraint,
@@ -37,6 +37,10 @@ impl<F> PyNativeFn for F where
 /// just pass an unconstrained generic type, e.g.
 /// `fn foo<F, FKind>(f: F) where F: IntoPyNativeFn<FKind>`
 pub trait IntoPyNativeFn<Kind>: Sized + PyThreadingConstraint + 'static {
+    /// Binding metadata of each argument, from which the calling convention
+    /// is inferred. A `&self` receiver is the `$self` marker.
+    const ARGS: &'static [SigArg] = &[SigArg::from_arg::<FuncArgs>("args")];
+
     fn call(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult;
 
     /// `IntoPyNativeFn::into_func()` generates a PyNativeFn that performs the
@@ -89,6 +93,8 @@ impl<F, T, R, VM> IntoPyNativeFn<(T, R, VM)> for F
 where
     F: PyNativeFnInternal<T, R, VM>,
 {
+    const ARGS: &'static [SigArg] = F::ARGS;
+
     #[inline(always)]
     fn call(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult {
         self.call_(vm, args, callee)
@@ -98,6 +104,7 @@ where
 mod sealed {
     use super::*;
     pub trait PyNativeFnInternal<T, R, VM>: Sized + PyThreadingConstraint + 'static {
+        const ARGS: &'static [SigArg];
         fn call_(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult;
     }
 }
@@ -124,6 +131,8 @@ macro_rules! into_py_native_fn_tuple {
             $($T: FromArgs,)*
             R: ToPyResult,
         {
+            const ARGS: &'static [SigArg] = &[$(SigArg::from_arg::<$T>("")),*];
+
             fn call_(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult {
                 let ($($n,)*) = args.bind_for::<($($T,)*)>(vm, callee)?;
 
@@ -138,6 +147,9 @@ macro_rules! into_py_native_fn_tuple {
             $($T: FromArgs,)*
             R: ToPyResult,
         {
+            const ARGS: &'static [SigArg] =
+                &[SigArg::marker("$self") $(, SigArg::from_arg::<$T>(""))*];
+
             fn call_(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult {
                 let (zelf, $($n,)*) = args.bind_for::<(PyRef<S>, $($T,)*)>(vm, callee)?;
 
@@ -152,6 +164,9 @@ macro_rules! into_py_native_fn_tuple {
             $($T: FromArgs,)*
             R: ToPyResult,
         {
+            const ARGS: &'static [SigArg] =
+                &[SigArg::marker("$self") $(, SigArg::from_arg::<$T>(""))*];
+
             fn call_(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult {
                 let (zelf, $($n,)*) = args.bind_for::<(PyRef<S>, $($T,)*)>(vm, callee)?;
 
@@ -165,6 +180,8 @@ macro_rules! into_py_native_fn_tuple {
             $($T: FromArgs,)*
             R: ToPyResult,
         {
+            const ARGS: &'static [SigArg] = &[$(SigArg::from_arg::<$T>("")),*];
+
             fn call_(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult {
                 let ($($n,)*) = args.bind_for::<($($T,)*)>(vm, callee)?;
 
@@ -179,6 +196,9 @@ macro_rules! into_py_native_fn_tuple {
             $($T: FromArgs,)*
             R: ToPyResult,
         {
+            const ARGS: &'static [SigArg] =
+                &[SigArg::marker("$self") $(, SigArg::from_arg::<$T>(""))*];
+
             fn call_(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult {
                 let (zelf, $($n,)*) = args.bind_for::<(PyRef<S>, $($T,)*)>(vm, callee)?;
 
@@ -193,6 +213,9 @@ macro_rules! into_py_native_fn_tuple {
             $($T: FromArgs,)*
             R: ToPyResult,
         {
+            const ARGS: &'static [SigArg] =
+                &[SigArg::marker("$self") $(, SigArg::from_arg::<$T>(""))*];
+
             fn call_(&self, vm: &VirtualMachine, args: FuncArgs, callee: Callee) -> PyResult {
                 let (zelf, $($n,)*) = args.bind_for::<(PyRef<S>, $($T,)*)>(vm, callee)?;
 
diff --git a/crates/vm/src/function/getargs.rs b/crates/vm/src/function/getargs.rs
index cc335727b7f..371b99137b6 100644
--- a/crates/vm/src/function/getargs.rs
+++ b/crates/vm/src/function/getargs.rs
@@ -1,6 +1,6 @@
 //! `PyArg_ParseTupleAndKeywords` argument matching.
 
-use super::FuncArgs;
+use super::{FuncArgs, given_by_name_and_position_message};
 use crate::{PyObject, PyObjectRef, PyResult, VirtualMachine, common::wtf8::Wtf8};
 
 /// The keyword list of a `PyArg_ParseTupleAndKeywords` call together with the
@@ -103,9 +103,10 @@ impl ArgSpec<'_> {
         if !exhausted && nkwargs > 0 {
             for (i, name) in self.keywords.iter().enumerate().take(nargs) {
                 if args.kwargs.contains_key(name) {
-                    return Err(vm.new_type_error(format!(
-                        "argument for {fname}() given by name ('{name}') and position ({})",
-                        i + 1
+                    return Err(vm.new_type_error(given_by_name_and_position_message(
+                        Some(fname),
+                        name,
+                        i + 1,
                     )));
                 }
             }
diff --git a/crates/vm/src/function/method.rs b/crates/vm/src/function/method.rs
index 0a80efc939e..d586c099ba7 100644
--- a/crates/vm/src/function/method.rs
+++ b/crates/vm/src/function/method.rs
@@ -6,7 +6,7 @@ use crate::{
         descriptor::{PyClassMethodDescriptor, PyMethodDescriptor},
     },
     class::PyClassDef,
-    function::{IntoPyNativeFn, PyNativeFn},
+    function::{FuncArgs, IntoPyNativeFn, PyNativeFn, SigArg},
 };
 
 bitflags::bitflags! {
@@ -49,6 +49,22 @@ bitflags::bitflags! {
 impl PyMethodFlags {
     // FIXME: macro temp
     pub const EMPTY: Self = Self::empty();
+
+    const CALL_CONVENTION: Self = Self::VARARGS
+        .union(Self::KEYWORDS)
+        .union(Self::NOARGS)
+        .union(Self::O)
+        .union(Self::FASTCALL);
+
+    /// Adds the calling convention inferred from `args` unless one is set.
+    /// For METHOD and CLASS the first argument is the bound receiver.
+    pub(crate) const fn with_call_convention(self, args: &[SigArg]) -> Self {
+        if self.intersects(Self::CALL_CONVENTION) {
+            return self;
+        }
+        let receiver = self.intersects(Self::METHOD.union(Self::CLASS));
+        self.union(super::signature::native_call_flags(args, receiver))
+    }
 }
 
 #[macro_export]
@@ -115,16 +131,16 @@ impl PyMethodDef {
     }
 
     #[inline]
-    pub const fn new_const<Kind>(
+    pub const fn new_const<Kind, F: IntoPyNativeFn<Kind>>(
         name: &'static str,
-        func: impl IntoPyNativeFn<Kind>,
+        func: F,
         flags: PyMethodFlags,
         doc: super::ItemDoc,
     ) -> Self {
         Self {
             name,
             func: super::static_func(func),
-            flags,
+            flags: flags.with_call_convention(F::ARGS),
             #[cfg(feature = "doc")]
             doc_off: doc.offset,
             #[cfg(feature = "doc")]
@@ -145,7 +161,7 @@ impl PyMethodDef {
         Self {
             name,
             func: super::static_raw_func(func),
-            flags,
+            flags: flags.with_call_convention(&[SigArg::from_arg::<FuncArgs>("args")]),
             #[cfg(feature = "doc")]
             doc_off: doc.offset,
             #[cfg(feature = "doc")]
@@ -216,13 +232,22 @@ impl PyMethodDef {
         &'static self,
         ctx: &Context,
         obj: PyObjectRef,
+    ) -> PyRef<PyNativeFunction> {
+        self.build_bound_function_with_owner(ctx, obj, None)
+    }
+
+    pub(crate) fn build_bound_function_with_owner(
+        &'static self,
+        ctx: &Context,
+        obj: PyObjectRef,
+        owner: Option<PyObjectRef>,
     ) -> PyRef<PyNativeFunction> {
         let function = PyNativeFunction {
             zelf: Some(obj),
             value: self,
             module_object: None,
             module: crate::object::PyAtomicRef::new_empty(),
-            _method_def_owner: None,
+            _method_def_owner: owner,
         };
         PyRef::new_ref(
             function,
@@ -249,7 +274,7 @@ impl PyMethodDef {
     ) -> PyRef<PyNativeMethod> {
         PyRef::new_ref(
             self.to_bound_method(obj, class),
-            ctx.types.builtin_function_or_method_type.to_owned(),
+            ctx.types.builtin_method_type.to_owned(),
             None,
         )
     }
@@ -267,18 +292,10 @@ impl PyMethodDef {
         &'static self,
         ctx: &Context,
         class: &'static Py<PyType>,
-    ) -> PyRef<PyNativeMethod> {
+    ) -> PyRef<PyNativeFunction> {
         debug_assert!(self.flags.contains(PyMethodFlags::STATIC));
-        // Set zelf to the class (m_self = type for static methods).
-        // Callable::call skips prepending when STATIC flag is set.
-        let func = PyNativeFunction {
-            zelf: Some(class.to_owned().into()),
-            value: self,
-            module_object: None,
-            module: crate::object::PyAtomicRef::new_empty(),
-            _method_def_owner: None,
-        };
-        PyNativeMethod { func, class }.into_ref(ctx)
+        // m_self is the type; STATIC skips prepending it on call.
+        self.build_bound_function(ctx, class.to_owned().into())
     }
 
     /// Concatenate method groups. A pending body is copied from `docs`, then cleared.
@@ -375,15 +392,51 @@ impl core::fmt::Debug for PyMethodDef {
 // This is not a part of CPython API.
 // But useful to support dynamically generated methods
 #[pyclass(name, module = false, ctx = "method_def")]
-#[derive(Debug)]
 pub struct HeapMethodDef {
     method: PyMethodDef,
+    _function_owner: Option<Box<dyn PyNativeFn>>,
+}
+
+impl core::fmt::Debug for HeapMethodDef {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        self.method.fmt(f)
+    }
 }
 
 impl HeapMethodDef {
     #[must_use]
     pub const fn new(method: PyMethodDef) -> Self {
-        Self { method }
+        Self {
+            method,
+            _function_owner: None,
+        }
+    }
+
+    pub(crate) fn with_owned_function(
+        name: &'static str,
+        function: Box<dyn PyNativeFn>,
+        flags: PyMethodFlags,
+        doc: super::ItemDoc,
+    ) -> Self {
+        // SAFETY: the box has a stable address and is retained by this payload.
+        // The definition is private; all functions/descriptors referring to it
+        // retain this HeapMethodDef and expose no static reference to callers.
+        let func = unsafe { &*core::ptr::from_ref(&*function) };
+        Self {
+            method: PyMethodDef {
+                name,
+                func,
+                flags,
+                #[cfg(feature = "doc")]
+                doc_off: doc.offset,
+                #[cfg(feature = "doc")]
+                doc_len: doc.len,
+                #[cfg(feature = "doc")]
+                doc_body_pending: false,
+                doc: doc.text,
+            },
+            _function_owner: Some(function),
+        }
     }
 }
 
@@ -431,3 +484,53 @@ pub(crate) fn init(ctx: &'static Context) {
 
     let _ = ctx.intern_str(HeapMethodDef::NAME);
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{AsObject, function::FuncArgs};
+
+    #[test]
+    fn generated_functions_own_and_release_their_native_captures() {
+        use alloc::sync::Arc;
+        let captured = Arc::new(17);
+        crate::Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let capture = captured.clone();
+            let definition = vm.ctx.new_method_def(
+                "captured",
+                move |_args: FuncArgs| *capture,
+                PyMethodFlags::empty(),
+                super::super::ItemDoc::NONE,
+            );
+            let function = definition.build_function(vm, None);
+            let descriptor = definition.build_method(vm.ctx.types.object_type, vm);
+            drop(definition);
+            assert_eq!(Arc::strong_count(&captured), 2);
+            assert_eq!(
+                function
+                    .as_object()
+                    .call((), vm)
+                    .unwrap()
+                    .try_into_value::<i32>(vm)
+                    .unwrap(),
+                17
+            );
+            let method = descriptor.bind(vm.ctx.none(), &vm.ctx);
+            assert!(method._method_def_owner.is_some());
+            drop(function);
+            drop(descriptor);
+            assert_eq!(Arc::strong_count(&captured), 2);
+            assert_eq!(
+                method
+                    .as_object()
+                    .call((), vm)
+                    .unwrap()
+                    .try_into_value::<i32>(vm)
+                    .unwrap(),
+                17
+            );
+            drop(method);
+            assert_eq!(Arc::strong_count(&captured), 1);
+        });
+    }
+}
diff --git a/crates/vm/src/function/mod.rs b/crates/vm/src/function/mod.rs
index 0fcbffc96bb..707afed0966 100644
--- a/crates/vm/src/function/mod.rs
+++ b/crates/vm/src/function/mod.rs
@@ -19,7 +19,9 @@ pub use argument::{
     NameKeywords, NameKwargs, NameKwds, NameKws, NameObjs, NameOthers, OptionalArg,
     OptionalArgDefault, OptionalOption, PosArgs, PositionalIterable,
 };
-pub(crate) use argument::{arity_message, unexpected_keyword_message};
+pub(crate) use argument::{
+    arity_message, given_by_name_and_position_message, unexpected_keyword_message,
+};
 pub use arithmetic::{PyArithmeticValue, PyComparisonValue};
 pub use buffer::{
     ArgAsciiBuffer, ArgBytesLike, ArgContiguousBytesLike, ArgMemoryBuffer, ArgStrOrBytesLike,
diff --git a/crates/vm/src/function/protocol.rs b/crates/vm/src/function/protocol.rs
index 5883a2a4691..c9d8df5b186 100644
--- a/crates/vm/src/function/protocol.rs
+++ b/crates/vm/src/function/protocol.rs
@@ -1,7 +1,7 @@
 use super::IntoFuncArgs;
 use crate::{
-    AsObject, PyObject, PyObjectRef, PyPayload, PyResult, TryFromObject, VirtualMachine,
-    builtins::{PyDictRef, iter::PySequenceIterator},
+    AsObject, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject, VirtualMachine,
+    builtins::{PyAnyDict, PyDictRef, iter::PySequenceIterator},
     convert::ToPyObject,
     object::{Traverse, TraverseFn},
     protocol::{PyIter, PyIterIter, PyMapping},
@@ -155,6 +155,12 @@ impl ArgMapping {
         Self { obj: dict.into() }
     }
 
+    #[inline(always)]
+    #[must_use]
+    pub fn from_anydict_exact(dict: PyRef<PyAnyDict>) -> Self {
+        Self { obj: dict.into() }
+    }
+
     #[inline(always)]
     #[must_use]
     pub fn obj(&self) -> &PyObject {
diff --git a/crates/vm/src/function/signature.rs b/crates/vm/src/function/signature.rs
index 3dfae3ae9df..74cf058d007 100644
--- a/crates/vm/src/function/signature.rs
+++ b/crates/vm/src/function/signature.rs
@@ -135,6 +135,81 @@ impl SigArg {
     }
 }
 
+/// Calling-convention bits from each argument's binding metadata.
+///
+/// Inspect arguments separately: a tuple's `PARAMS` can erase leaf metadata.
+/// With `receiver`, the first argument is the bound `$self` / `$type`; it
+/// contributes only the parameters its type supplies.
+/// A keyword-capable parameter uses `FASTCALL | KEYWORDS`.
+#[must_use]
+pub(crate) const fn native_call_flags(args: &[SigArg], receiver: bool) -> super::PyMethodFlags {
+    let mut has_keywords = false;
+    let mut variable = false;
+    let mut fixed = 0usize;
+    let mut i = 0;
+    while i < args.len() {
+        match args[i].params {
+            Some(params) => count_params(params, &mut has_keywords, &mut variable, &mut fixed),
+            None if receiver && i == 0 => {}
+            None => fixed += 1,
+        }
+        i += 1;
+    }
+    if has_keywords {
+        super::PyMethodFlags::FASTCALL.union(super::PyMethodFlags::KEYWORDS)
+    } else if variable {
+        super::PyMethodFlags::FASTCALL
+    } else {
+        match fixed {
+            0 => super::PyMethodFlags::NOARGS,
+            1 => super::PyMethodFlags::O,
+            _ => super::PyMethodFlags::FASTCALL,
+        }
+    }
+}
+
+const fn count_params(
+    params: &[Param],
+    has_keywords: &mut bool,
+    variable: &mut bool,
+    fixed: &mut usize,
+) {
+    let mut i = 0;
+    while i < params.len() {
+        count_param(&params[i], has_keywords, variable, fixed);
+        i += 1;
+    }
+}
+
+const fn count_param(
+    param: &Param,
+    has_keywords: &mut bool,
+    variable: &mut bool,
+    fixed: &mut usize,
+) {
+    match param.kind {
+        ParamKind::PositionalOrKeyword => {
+            *has_keywords = true;
+            if param.default.is_some() {
+                *variable = true;
+            } else {
+                *fixed += 1;
+            }
+        }
+        ParamKind::KeywordOnly | ParamKind::VarKeyword => *has_keywords = true,
+        ParamKind::VarPositional => *variable = true,
+        ParamKind::PositionalOnly => {
+            if param.default.is_some() {
+                *variable = true;
+            } else {
+                *fixed += 1;
+            }
+        }
+        ParamKind::Flatten(Some(inner)) => count_params(inner, has_keywords, variable, fixed),
+        ParamKind::Flatten(None) => {}
+    }
+}
+
 const fn name_eq(name: &str, bytes: &[u8]) -> bool {
     let got = name.as_bytes();
     if got.len() != bytes.len() {
@@ -242,6 +317,7 @@ struct St {
     emitted: bool,
     po_left: usize,
     var_pos_seen: bool,
+    var_kw_seen: bool,
     star_emitted: bool,
 }
 
@@ -255,6 +331,7 @@ const fn write_signature_prefix(buf: &mut [u8], name: &str, args: &[SigArg]) ->
             emitted: false,
             po_left: count_po_args(args),
             var_pos_seen: false,
+            var_kw_seen: false,
             star_emitted: false,
         },
         args,
@@ -575,6 +652,12 @@ const fn write_one(buf: &mut [u8], mut st: St, param: Param, fallback: &str) ->
             st = emit_named(buf, st, "", name, param.default);
             st.po_left -= 1;
             if st.po_left == 0 {
+                // Python rejects `/` after `*` or `**`. The Rust arguments put a
+                // keyword or variadic one before a positional one; reorder them.
+                assert!(
+                    !st.star_emitted && !st.var_pos_seen && !st.var_kw_seen,
+                    "positional-only parameter after `*` or `**`: reorder the Rust arguments"
+                );
                 st = emit_text(buf, st, "/");
             }
             st
@@ -591,7 +674,10 @@ const fn write_one(buf: &mut [u8], mut st: St, param: Param, fallback: &str) ->
             st.var_pos_seen = true;
             emit_named(buf, st, "*", name, param.default)
         }
-        ParamKind::VarKeyword => emit_named(buf, st, "**", name, param.default),
+        ParamKind::VarKeyword => {
+            st.var_kw_seen = true;
+            emit_named(buf, st, "**", name, param.default)
+        }
     }
 }
 
@@ -620,7 +706,8 @@ const fn write_args(buf: &mut [u8], mut st: St, args: &[SigArg]) -> St {
 
 #[cfg(test)]
 mod tests {
-    use super::{DefaultRepr, Param, ParamKind, St, write_one};
+    use super::{DefaultRepr, Param, ParamKind, SigArg, St, native_call_flags, write_one};
+    use crate::function::PyMethodFlags;
 
     fn rendered(default: DefaultRepr) -> String {
         let mut buf = [0u8; 64];
@@ -631,6 +718,7 @@ mod tests {
                 emitted: false,
                 po_left: 0,
                 var_pos_seen: false,
+                var_kw_seen: false,
                 star_emitted: true,
             },
             Param {
@@ -662,4 +750,55 @@ mod tests {
         assert_eq!(rendered(DefaultRepr::Raw("sys.maxsize")), "sys.maxsize");
         assert_eq!(rendered(DefaultRepr::Unrepresentable), "<unrepresentable>");
     }
+
+    #[test]
+    fn native_call_flags_from_params() {
+        const fn arg(params: Option<&'static [Param]>) -> SigArg {
+            SigArg { name: "", params }
+        }
+        let keywords = PyMethodFlags::FASTCALL.union(PyMethodFlags::KEYWORDS);
+        assert_eq!(native_call_flags(&[], false), PyMethodFlags::NOARGS);
+        assert_eq!(native_call_flags(&[arg(None)], false), PyMethodFlags::O);
+        assert_eq!(
+            native_call_flags(&[arg(None), arg(None)], false),
+            PyMethodFlags::FASTCALL
+        );
+        // The receiver is not a Python argument.
+        assert_eq!(
+            native_call_flags(&[SigArg::marker("$self"), arg(None)], true),
+            PyMethodFlags::O
+        );
+        assert_eq!(native_call_flags(&[arg(None)], true), PyMethodFlags::NOARGS);
+
+        const OPTIONAL: &[Param] = &[Param {
+            name: "",
+            kind: ParamKind::PositionalOnly,
+            default: Some(DefaultRepr::Unrepresentable),
+        }];
+        assert_eq!(
+            native_call_flags(&[arg(Some(OPTIONAL))], false),
+            PyMethodFlags::FASTCALL
+        );
+
+        const KW: &[Param] = &[Param::positional_or_keyword("exp")];
+        assert_eq!(native_call_flags(&[arg(Some(KW))], false), keywords);
+
+        const FUNCARGS: &[Param] = &[Param::var_positional("args"), Param::var_keyword("kwargs")];
+        assert_eq!(native_call_flags(&[arg(Some(FUNCARGS))], false), keywords);
+        // A receiver that binds the whole call keeps its parameters.
+        assert_eq!(native_call_flags(&[arg(Some(FUNCARGS))], true), keywords);
+
+        const POSARGS: &[Param] = &[Param::var_positional("args")];
+        assert_eq!(
+            native_call_flags(&[arg(Some(POSARGS))], false),
+            PyMethodFlags::FASTCALL
+        );
+
+        const INNER: &[Param] = &[Param::keyword_only(
+            "reverse",
+            Some(DefaultRepr::Bool(false)),
+        )];
+        const FLAT: &[Param] = &[Param::flatten(Some(INNER))];
+        assert_eq!(native_call_flags(&[arg(Some(FLAT))], false), keywords);
+    }
 }
diff --git a/crates/vm/src/gc_state.rs b/crates/vm/src/gc_state.rs
index 774f2ff39ba..38d31aec713 100644
--- a/crates/vm/src/gc_state.rs
+++ b/crates/vm/src/gc_state.rs
@@ -207,22 +207,24 @@ type GcMap<K, V> = std::collections::HashMap<K, V, GcBuildHasher>;
 /// incref. Reading a refcount that another interpreter is changing is what
 /// makes an object look unreachable when it is not, so every live interpreter
 /// is stopped, not just the collecting one. Stopping in `runtime` id order
-/// keeps exclusion acquisition ordered; the `collecting` mutex additionally
-/// serializes collections process-wide, so no second collector can take these
-/// exclusions in another order.
+/// is deterministic. One process-wide STW transaction covers the entire group,
+/// preventing a single-interpreter requester from stopping a collector while
+/// that collector waits for a different interpreter.
 #[cfg(feature = "threading")]
 struct CollectStopTheWorld {
-    /// Stopped interpreter states, in stop order. Held as strong references so
-    /// an interpreter cannot be dropped between stop and restart, and kept past
-    /// the restart so that releasing the last one — which frees that
-    /// interpreter's objects, and so removes them from these lists — happens
-    /// after the collection has let go of the generation locks.
-    stopped: Vec<crate::common::rc::PyRc<crate::vm::PyGlobalState>>,
+    /// Entire interpreter snapshot, retained through restart even on unwind.
+    /// Dropping the last state can release Python objects and run finalizers,
+    /// so both stopped and not-yet-stopped states must outlive the transaction
+    /// and the collection's generation locks.
+    states: Vec<crate::common::rc::PyRc<crate::vm::PyGlobalState>>,
+    stopped_count: usize,
     /// Keeps interpreters from registering between the snapshot below and the
-    /// restart. One registered in that window would be missing from `stopped`,
+    /// restart. One registered in that window would be missing from `states`,
     /// so its bootstrap would keep running — and mutating the shared generation
     /// lists — while this collection reads them.
     admission: Option<parking_lot::MutexGuard<'static, ()>>,
+    /// Acquired before admission and retained until every state is restarted.
+    transaction: Option<crate::vm::StopTheWorldTransaction>,
     restarted: bool,
 }
 
@@ -237,8 +239,10 @@ impl CollectStopTheWorld {
         // keep the historical no-barrier fallback.
         if !crate::vm::thread::current_vm_is_set() {
             return Self {
-                stopped: Vec::new(),
+                states: Vec::new(),
+                stopped_count: 0,
                 admission: None,
+                transaction: None,
                 restarted: true,
             };
         }
@@ -247,14 +251,20 @@ impl CollectStopTheWorld {
         // `stop_the_world` unwinds, dropping this guard restarts the
         // interpreters already stopped, instead of leaving their threads parked
         // and their exclusion held forever.
+        let transaction = crate::vm::StopTheWorldTransaction::acquire();
         let mut guard = Self {
-            stopped: Vec::new(),
+            states: Vec::new(),
+            stopped_count: 0,
             admission: Some(crate::vm::runtime::lock_admission_for_stop()),
+            transaction: Some(transaction),
             restarted: false,
         };
-        for state in crate::vm::runtime::live_interpreter_states() {
-            state.stop_the_world.stop_the_world(&state);
-            guard.stopped.push(state);
+        guard.states = crate::vm::runtime::live_interpreter_states();
+        for state in &guard.states {
+            state
+                .stop_the_world
+                .stop_with_transaction(state, guard.transaction.as_ref().unwrap());
+            guard.stopped_count += 1;
         }
         guard
     }
@@ -267,17 +277,18 @@ impl CollectStopTheWorld {
         self.restarted = true;
         // Reverse of the stop order. The references stay until this guard is
         // dropped; see the field comment.
-        for state in self.stopped.iter().rev() {
+        for state in self.states[..self.stopped_count].iter().rev() {
             state.stop_the_world.start_the_world(state);
         }
         // Nothing is parked any more, so registration may resume.
         self.admission = None;
+        self.transaction = None;
     }
 
     /// Whether this collection actually stopped the world.
     #[cfg(all(unix, debug_assertions))]
     fn is_stopped(&self) -> bool {
-        !self.stopped.is_empty()
+        self.stopped_count != 0
     }
 }
 
@@ -910,11 +921,15 @@ impl GcState {
             })
             .collect();
 
-        // 6c: Clear existing weakrefs BEFORE calling __del__
+        // 6c: Clear callback-bearing weakrefs BEFORE calling __del__. Keep
+        // callback-free weakrefs usable throughout finalization.
+        let unreachable_set: GcSet<GcPtr> = unreachable.iter().copied().collect();
+        let is_unreachable =
+            |obj: &PyObject| unreachable_set.contains(&GcPtr(core::ptr::NonNull::from(obj)));
         let mut all_callbacks: Vec<(crate::PyRef<crate::object::PyWeak>, crate::PyObjectRef)> =
             Vec::new();
         for obj_ref in &unreachable_refs {
-            let callbacks = obj_ref.gc_clear_weakrefs_collect_callbacks();
+            let callbacks = obj_ref.gc_clear_weakrefs_collect_callbacks(&is_unreachable);
             all_callbacks.extend(callbacks);
         }
         for (wr, cb) in all_callbacks {
@@ -934,7 +949,6 @@ impl GcState {
 
         // Detect resurrection
         let mut resurrected_set: GcSet<GcPtr> = GcSet::default();
-        let unreachable_set: GcSet<GcPtr> = unreachable.iter().copied().collect();
 
         for obj in &unreachable_refs {
             let ptr = GcPtr(core::ptr::NonNull::from(obj.as_ref()));
@@ -1028,6 +1042,14 @@ impl GcState {
             // skips tp_clear for saved objects).
             let save_all = debug.contains(GcDebugFlags::SAVEALL);
 
+            // Callback-free weakrefs remain usable during finalizers, so a
+            // thread can still acquire an external reference at this point.
+            // Stop before taking generation/list locks, and keep the final
+            // liveness check and weakref closure in the same stopped phase.
+            // No callbacks, finalizers or tp_clear may run under this guard.
+            #[cfg(feature = "threading")]
+            let mut clear_stw = CollectStopTheWorld::new();
+
             // Untrack dead objects BEFORE clearing them, mirroring the
             // untrack-then-clear ordering of the refcount dealloc path.
             // A cleared object (e.g. a frame husk with iframe == None) must
@@ -1045,11 +1067,10 @@ impl GcState {
                     // One strong reference held by the `truly_dead` vec itself.
                     expected_counts.insert(GcPtr(NonNull::from(obj)), 1);
                 }
-                // With the objects out of the generation lists, no new external
-                // reference can appear. Count the references coming from within
-                // the dead set; any surplus in strong_count means another thread
-                // grabbed a reference before untracking (late resurrection) and
-                // the object must not be cleared.
+                // With the world stopped and these objects off the generation
+                // lists, count references from within the dead set. Any surplus
+                // means an external reference appeared before this stopped phase
+                // (late resurrection), and the object must not be cleared.
                 let mut referents: GcMap<GcPtr, Vec<NonNull<PyObject>>> = GcMap::default();
                 for obj_ref in &truly_dead {
                     let referent_ptrs = unsafe { obj_ref.gc_get_referent_ptrs() };
@@ -1095,6 +1116,20 @@ impl GcState {
                     unsafe { self.track_object(ptr.0, owner) };
                 }
             }
+            // Clear every weakref in or pointing to objects that will be
+            // cleared, including weakrefs created by finalizers. Do not run
+            // or drop callbacks here: all objects must remain intact until
+            // this pass finishes. Resurrected objects retain their weakrefs.
+            for obj_ref in &truly_dead {
+                if !late_resurrected.contains(&GcPtr(NonNull::from(obj_ref.as_ref()))) {
+                    obj_ref.gc_clear_weakrefs();
+                }
+            }
+            // Every remaining dead object is now unreachable through both
+            // generation lists and weakrefs. Resume before tp_clear can release
+            // edges or invoke arbitrary Python through deallocation.
+            #[cfg(feature = "threading")]
+            clear_stw.restart();
             rustpython_common::refcount::with_deferred_drops(|| {
                 if !save_all {
                     for obj_ref in &truly_dead {
diff --git a/crates/vm/src/getpath.rs b/crates/vm/src/getpath.rs
index eef1417ab14..68e95583a13 100644
--- a/crates/vm/src/getpath.rs
+++ b/crates/vm/src/getpath.rs
@@ -19,6 +19,7 @@ mod platform {
     pub(super) const BUILD_LANDMARK: &str = "Modules/Setup.local";
     pub(super) const VENV_LANDMARK: &str = "pyvenv.cfg";
     pub(super) const BUILDSTDLIB_LANDMARK: &str = "Lib/os.py";
+    pub(super) const DEFAULT_PROGRAM_NAME: &str = "python3";
 
     pub(super) fn stdlib_subdir() -> String {
         format!("lib/python{}.{}", version::MAJOR, version::MINOR)
@@ -51,6 +52,7 @@ mod platform {
     pub(super) const VENV_LANDMARK: &str = "pyvenv.cfg";
     pub(super) const BUILDSTDLIB_LANDMARK: &str = "Lib\\os.py";
     pub(super) const STDLIB_SUBDIR: &str = "Lib";
+    pub(super) const DEFAULT_PROGRAM_NAME: &str = "python";
 
     pub(super) fn stdlib_landmarks() -> [String; 2] {
         ["Lib\\os.py".into(), "Lib\\os.pyc".into()]
@@ -106,7 +108,10 @@ fn search_up_dir<P: AsRef<Path>>(start: P, landmarks: &[&str]) -> Option<PathBuf
 /// This function should be called before interpreter initialization.
 /// It returns a Paths struct with all computed path values.
 pub fn init_path_config(settings: &Settings) -> Paths {
-    let mut paths = Paths::default();
+    let mut paths = Paths {
+        program_name: program_name(),
+        ..Paths::default()
+    };
 
     // Step 0: Get executable path
     let executable = get_executable_path();
@@ -129,55 +134,83 @@ pub fn init_path_config(settings: &Settings) -> Paths {
             .and_then(|p| p.parent().map(PathBuf::from))
     };
 
-    // Step 2: Check for venv (pyvenv.cfg) and get 'home'
-    let (venv_prefix, home_dir) = detect_venv(exe_dir.as_ref());
+    // A readable pyvenv.cfg establishes the environment even without a home key.
+    let (venv_prefix, configured_home) = detect_venv(exe_dir.as_ref());
+    // Explicit PYTHONHOME takes precedence over the configuration's home key,
+    // including its influence on _base_executable.
+    let explicit_home = settings.home.as_deref().filter(|home| !home.is_empty());
+    let home_dir = if explicit_home.is_some() {
+        None
+    } else {
+        configured_home
+    };
     let search_dir = home_dir.clone().or(exe_dir);
-
-    // Step 3: Check for build directory
-    let build_prefix = detect_build_directory(search_dir.as_ref());
-
-    // Step 4: Calculate prefix via landmark search
-    // When in venv, search_dir is home_dir, so this gives us the base Python's prefix
-    let calculated_prefix = calculate_prefix(search_dir.as_ref(), build_prefix.as_ref());
-
-    // Step 5: Set prefix and base_prefix
-    if venv_prefix.is_some() {
-        // In venv: prefix = venv directory, base_prefix = original Python's prefix
-        paths.prefix = venv_prefix.as_ref().map_or_else(
-            || calculated_prefix.clone(),
-            |p| p.to_string_lossy().into_owned(),
+    #[cfg(unix)]
+    let search_dir = if venv_prefix.is_some()
+        && home_dir.is_none()
+        && explicit_home.is_none()
+        && paths.base_executable.is_empty()
+    {
+        // A no-home environment uses the target installation for landmarks,
+        // while _base_executable retains the invoked executable spelling.
+        executable
+            .as_deref()
+            .and_then(resolve_executable_symlinks)
+            .and_then(|resolved| resolved.parent().map(PathBuf::from))
+            .or(search_dir)
+    } else {
+        search_dir
+    };
+    let build_prefix = explicit_home
+        .is_none()
+        .then(|| detect_build_directory(search_dir.as_ref()))
+        .flatten();
+    let home_prefixes = explicit_home.map(|home| {
+        home.split_once(if cfg!(windows) { ';' } else { ':' })
+            .unwrap_or((home, home))
+    });
+    paths.base_prefix = home_prefixes
+        .map(|(prefix, _)| prefix)
+        .filter(|prefix| !prefix.is_empty())
+        .map_or_else(
+            || calculate_prefix(search_dir.as_ref(), build_prefix.as_ref()),
+            str::to_owned,
         );
-        paths.base_prefix = calculated_prefix;
+    paths.base_exec_prefix = home_prefixes
+        .map(|(_, exec_prefix)| exec_prefix)
+        .filter(|exec_prefix| !exec_prefix.is_empty())
+        .map_or_else(
+            || calculate_exec_prefix(search_dir.as_ref(), &paths.base_prefix),
+            str::to_owned,
+        );
+    // The venv overlays public prefixes, not the base library search paths.
+    if let Some(venv) = venv_prefix {
+        paths.prefix = venv.to_string_lossy().into_owned();
+        paths.exec_prefix.clone_from(&paths.prefix);
     } else {
-        // Not in venv: prefix == base_prefix
-        paths.prefix.clone_from(&calculated_prefix);
-        paths.base_prefix = calculated_prefix;
+        paths.prefix.clone_from(&paths.base_prefix);
+        paths.exec_prefix.clone_from(&paths.base_exec_prefix);
     }
-
-    // Step 6: Calculate exec_prefix
-    paths.exec_prefix = if venv_prefix.is_some() {
-        // In venv: exec_prefix = prefix (venv directory)
-        paths.prefix.clone()
-    } else {
-        calculate_exec_prefix(search_dir.as_ref(), paths.prefix.as_ref())
-    };
-    paths.base_exec_prefix.clone_from(&paths.base_prefix);
-
-    // Step 7: Calculate base_executable (if not already set by an env override)
     if paths.base_executable.is_empty() {
         paths.base_executable = calculate_base_executable(executable.as_ref(), home_dir.as_ref());
     }
-
-    // Step 8: Build module_search_paths
     paths.module_search_paths =
-        build_module_search_paths(settings, &paths.prefix, &paths.exec_prefix);
-
-    // Step 9: Calculate stdlib_dir
-    paths.stdlib_dir = calculate_stdlib_dir(&paths.prefix);
+        build_module_search_paths(settings, &paths.base_prefix, &paths.base_exec_prefix);
+    paths.stdlib_dir = calculate_stdlib_dir(&paths.base_prefix);
 
     paths
 }
 
+/// Identify an uninstalled RustPython source library independently of the
+/// executable location (Cargo permits targets outside the source tree).
+#[cfg(windows)]
+pub(crate) fn source_directory(paths: &Paths) -> Option<&Path> {
+    let library = Path::new(paths.stdlib_dir.as_deref()?);
+    let source = library.parent()?;
+    (library.file_name()? == "Lib" && source.join("crates/vm/Cargo.toml").is_file())
+        .then_some(source)
+}
+
 /// Get default prefix value used when landmark search fails.
 ///
 /// A compile-time `RUSTPYTHON_PREFIX` always wins. Otherwise POSIX uses the
@@ -212,20 +245,16 @@ fn detect_venv(exe_dir: Option<&PathBuf>) -> (Option<PathBuf>, Option<PathBuf>)
         && let Some(venv_dir) = dir.parent()
     {
         let cfg = venv_dir.join(platform::VENV_LANDMARK);
-        if cfg.exists()
-            && let Some(home) = parse_pyvenv_home(&cfg)
-        {
-            return (Some(venv_dir.to_path_buf()), Some(PathBuf::from(home)));
+        if let Some(home) = parse_pyvenv_home(&cfg) {
+            return (Some(venv_dir.to_path_buf()), home.map(PathBuf::from));
         }
     }
 
     // Try exe_dir/pyvenv.cfg (alternative layout)
     if let Some(dir) = exe_dir {
         let cfg = dir.join(platform::VENV_LANDMARK);
-        if cfg.exists()
-            && let Some(home) = parse_pyvenv_home(&cfg)
-        {
-            return (Some(dir.clone()), Some(PathBuf::from(home)));
+        if let Some(home) = parse_pyvenv_home(&cfg) {
+            return (Some(dir.clone()), home.map(PathBuf::from));
         }
     }
 
@@ -287,25 +316,97 @@ fn calculate_exec_prefix(exe_dir: Option<&PathBuf>, prefix: &str) -> String {
 
     #[cfg(not(windows))]
     {
-        // POSIX: search for lib-dynload directory
-        if let Some(dir) = exe_dir {
-            let landmark = platform::platstdlib_landmark();
-            if let Some(exec_prefix) = search_up_dir(dir, &[&landmark]) {
-                return exec_prefix.to_string_lossy().into_owned();
-            }
+        // Prefer the platform library under prefix before executable ancestors.
+        let landmark = platform::platstdlib_landmark();
+        if Path::new(prefix).join(&landmark).is_dir() {
+            return prefix.to_owned();
+        }
+        if let Some(dir) = exe_dir
+            && let Some(exec_prefix) = search_up_dir(dir, &[&landmark])
+        {
+            return exec_prefix.to_string_lossy().into_owned();
         }
         // Fallback: same as prefix
         prefix.to_owned()
     }
 }
 
+/// Resolve final-component links without resolving directory aliases (ref: getpath.c).
+#[cfg(unix)]
+fn resolve_executable_symlinks(executable: &Path) -> Option<PathBuf> {
+    use std::os::unix::ffi::OsStrExt;
+
+    let mut path = executable.to_path_buf();
+    // CPython rejects 40 successful hops, matching the Linux 4.2 kernel limit.
+    for _ in 0..40 {
+        let Ok(target) = std::fs::read_link(&path) else {
+            return Some(path);
+        };
+        if target.is_absolute() {
+            path = target;
+            continue;
+        }
+
+        // Match getpath.c's raw dirname join, then normalize lexically without
+        // resolving directory symlinks or losing a double-leading-slash root.
+        let bytes = path.as_os_str().as_bytes();
+        let end = bytes.iter().rposition(|&b| b == b'/');
+        let dirname = &bytes[..end.unwrap_or(bytes.len())];
+        let mut joined = PathBuf::from(std::ffi::OsStr::from_bytes(dirname));
+        // Filesystem text uses UTF-8/surrogateescape; count characters, not bytes.
+        let multiple_chars =
+            core::str::from_utf8(dirname).map_or(dirname.len() > 1, |s| s.chars().nth(1).is_some());
+        if multiple_chars && !dirname.ends_with(b"/") {
+            joined.as_mut_os_string().push("/");
+        }
+        joined.as_mut_os_string().push(target.as_os_str());
+        let bytes = joined.as_os_str().as_bytes();
+        let double_root = bytes.starts_with(b"//") && !bytes.starts_with(b"///");
+        path.clear();
+        for component in joined.components() {
+            if component == std::path::Component::ParentDir
+                && !path.as_os_str().is_empty()
+                && !path.ends_with("..")
+            {
+                path.pop();
+            } else if component != std::path::Component::CurDir {
+                path.push(component.as_os_str());
+            }
+        }
+        if double_root {
+            path = Path::new("//").join(path.strip_prefix("/").ok()?);
+        }
+    }
+    None
+}
+
 /// Calculate base_executable
 fn calculate_base_executable(executable: Option<&PathBuf>, home_dir: Option<&PathBuf>) -> String {
-    // If in venv and we have home, construct base_executable from home
     if let (Some(exe), Some(home)) = (executable, home_dir)
         && let Some(exe_name) = exe.file_name()
     {
+        // Like getpath.py, resolve the executable's final links once, without
+        // following creator metadata or another environment's configuration.
+        #[cfg(unix)]
+        if let Some(resolved) = resolve_executable_symlinks(exe)
+            && resolved.as_os_str() != exe.as_os_str()
+        {
+            return resolved.to_string_lossy().into_owned();
+        }
+
         let base = home.join(exe_name);
+        #[cfg(not(windows))]
+        if !base.is_file() {
+            for name in [
+                format!("python{}", crate::version::MAJOR),
+                format!("python{}.{}", crate::version::MAJOR, crate::version::MINOR),
+            ] {
+                let candidate = home.join(name);
+                if candidate.is_file() {
+                    return candidate.to_string_lossy().into_owned();
+                }
+            }
+        }
         return base.to_string_lossy().into_owned();
     }
 
@@ -330,6 +431,20 @@ fn calculate_stdlib_dir(prefix: &str) -> Option<String> {
     }
 }
 
+/// Add compiled-in library paths after environment entries and the default ZIP.
+/// Preserve an embedding hook's custom search order by appending instead when
+/// the calculated paths have already been replaced or modified.
+pub fn add_build_time_paths(settings: &Settings, paths: &mut Paths, extra: Vec<String>) {
+    let calculated =
+        build_module_search_paths(settings, &paths.base_prefix, &paths.base_exec_prefix);
+    let index = if paths.module_search_paths == calculated {
+        settings.path_list.len() + 1
+    } else {
+        paths.module_search_paths.len()
+    };
+    paths.module_search_paths.splice(index..index, extra);
+}
+
 /// Build the complete module_search_paths (sys.path)
 fn build_module_search_paths(settings: &Settings, prefix: &str, exec_prefix: &str) -> Vec<String> {
     let mut paths = Vec::new();
@@ -378,6 +493,22 @@ fn env_executable_override() -> Option<String> {
     None
 }
 
+/// CALCULATE program_name: `argv[0]`, with the executable suffix added when
+/// only the suffixed file exists.
+fn program_name() -> String {
+    let program_name = env::args()
+        .next()
+        .filter(|arg| !arg.is_empty())
+        .unwrap_or_else(|| platform::DEFAULT_PROGRAM_NAME.to_owned());
+    if cfg!(windows) && !program_name.to_lowercase().ends_with(".exe") {
+        let suffixed = format!("{program_name}.exe");
+        if Path::new(&suffixed).is_file() {
+            return suffixed;
+        }
+    }
+    program_name
+}
+
 /// Get the current executable path
 fn get_executable_path() -> Option<PathBuf> {
     #[cfg(not(target_arch = "wasm32"))]
@@ -393,7 +524,8 @@ fn get_executable_path() -> Option<PathBuf> {
 }
 
 /// Parse pyvenv.cfg and extract the 'home' key value
-fn parse_pyvenv_home(pyvenv_cfg: &Path) -> Option<String> {
+// Outer None means unreadable; Some(None) is a valid configuration without home.
+fn parse_pyvenv_home(pyvenv_cfg: &Path) -> Option<Option<String>> {
     #[cfg(any(not(target_arch = "wasm32"), target_os = "wasi"))]
     let content = crate::host_env::fs::read_to_string(pyvenv_cfg).ok()?;
     #[cfg(all(target_arch = "wasm32", not(target_os = "wasi")))]
@@ -401,19 +533,65 @@ fn parse_pyvenv_home(pyvenv_cfg: &Path) -> Option<String> {
 
     for line in content.lines() {
         if let Some((key, value)) = line.split_once('=')
-            && key.trim().to_lowercase() == "home"
+            && key.trim().eq_ignore_ascii_case("home")
         {
-            return Some(value.trim().to_string());
+            return Some(Some(value.trim().to_string()));
         }
     }
 
-    None
+    Some(None)
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn build_time_paths_follow_configured_paths_and_zip() {
+        for configured in [vec![], vec!["first".to_owned(), "second".to_owned()]] {
+            let settings = Settings {
+                path_list: configured,
+                ..Settings::default()
+            };
+            let calculated = build_module_search_paths(&settings, "prefix", "exec-prefix");
+            let mut paths = Paths {
+                base_prefix: "prefix".to_owned(),
+                base_exec_prefix: "exec-prefix".to_owned(),
+                module_search_paths: calculated.clone(),
+                ..Paths::default()
+            };
+            let extra = vec!["build-first".to_owned(), "build-second".to_owned()];
+            add_build_time_paths(&settings, &mut paths, extra.clone());
+            let boundary = settings.path_list.len() + 1;
+            let mut expected = calculated[..boundary].to_vec();
+            expected.extend(extra);
+            expected.extend_from_slice(&calculated[boundary..]);
+            assert_eq!(paths.module_search_paths, expected);
+        }
+    }
+
+    #[test]
+    fn build_time_paths_preserve_custom_search_order() {
+        let settings = Settings {
+            path_list: vec!["configured".to_owned()],
+            ..Settings::default()
+        };
+        let mut modified = build_module_search_paths(&settings, "prefix", "exec-prefix");
+        modified.push("custom".to_owned());
+        for custom in [vec![], modified] {
+            let mut paths = Paths {
+                base_prefix: "prefix".to_owned(),
+                base_exec_prefix: "exec-prefix".to_owned(),
+                module_search_paths: custom.clone(),
+                ..Paths::default()
+            };
+            add_build_time_paths(&settings, &mut paths, vec!["build".to_owned()]);
+            let mut expected = custom;
+            expected.push("build".to_owned());
+            assert_eq!(paths.module_search_paths, expected);
+        }
+    }
+
     #[test]
     fn init_path_config_basic() {
         let settings = Settings::default();
diff --git a/crates/vm/src/import.rs b/crates/vm/src/import.rs
index 3fb6e5fdc2e..02c1048f6dd 100644
--- a/crates/vm/src/import.rs
+++ b/crates/vm/src/import.rs
@@ -2,12 +2,119 @@
 
 use crate::{
     AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult,
-    builtins::{PyCode, PyStr, PyUtf8Str, PyUtf8StrRef, traceback::PyTraceback},
+    builtins::{PyCode, PyStr, PyStrRef, PyUtf8Str, traceback::PyTraceback},
     exceptions::types::PyBaseException,
     scope::Scope,
     vm::{VirtualMachine, resolve_frozen_alias, thread},
 };
 
+use core::{cell::Cell, sync::atomic::Ordering, time::Duration};
+use std::{io::Write, time::Instant};
+
+/// Nested imports are timed per thread, so concurrent imports do not subtract
+/// each other's elapsed time. The output header belongs to the interpreter.
+#[derive(Clone, Copy, Default)]
+pub(crate) struct ImportTimingState {
+    depth: usize,
+    children: Duration,
+}
+
+fn import_time_header(vm: &VirtualMachine) {
+    let mut stderr = std::io::stderr().lock();
+    if !vm.state.import_time_header.swap(true, Ordering::Relaxed) {
+        let _ = writeln!(
+            stderr,
+            "import time: self [us] | cumulative | imported package"
+        );
+    }
+}
+
+fn import_time_name(name: &Py<PyStr>) -> String {
+    use core::fmt::Write;
+    let mut output = String::with_capacity(name.as_bytes().len());
+    for codepoint in name.as_wtf8().code_points() {
+        match codepoint.to_char() {
+            Some(ch) => output.push(ch),
+            None => {
+                let _ = write!(output, "\\u{:04x}", codepoint.to_u32());
+            }
+        }
+    }
+    output
+}
+
+pub(crate) fn report_cached_import(name: &Py<PyStr>, vm: &VirtualMachine) {
+    if vm.state.config.settings.import_time == 2 {
+        import_time_header(vm);
+        let name = import_time_name(name);
+        // printf("%*s") counts encoded bytes, not Unicode scalar values.
+        let padding = (vm.import_timing.get().depth * 2).saturating_sub(name.len());
+        let _ = writeln!(
+            std::io::stderr(),
+            "import time: cached    | cached     | {:padding$}{}",
+            "",
+            name
+        );
+    }
+}
+
+struct ImportTimer<'a> {
+    state: &'a Cell<ImportTimingState>,
+    parent: ImportTimingState,
+    start: Instant,
+    name: &'a Py<PyStr>,
+}
+
+impl<'a> ImportTimer<'a> {
+    fn start(name: &'a Py<PyStr>, vm: &'a VirtualMachine) -> Option<Self> {
+        if vm.state.config.settings.import_time == 0 {
+            return None;
+        }
+        import_time_header(vm);
+        let parent = vm.import_timing.replace(ImportTimingState {
+            depth: vm.import_timing.get().depth + 1,
+            children: Duration::ZERO,
+        });
+        Some(Self {
+            state: &vm.import_timing,
+            parent,
+            start: Instant::now(),
+            name,
+        })
+    }
+}
+
+impl Drop for ImportTimer<'_> {
+    fn drop(&mut self) {
+        let cumulative = self.start.elapsed();
+        let own = cumulative.saturating_sub(self.state.get().children);
+        self.state.set(ImportTimingState {
+            depth: self.parent.depth,
+            children: self.parent.children.saturating_add(cumulative),
+        });
+        let width = self.parent.depth * 2;
+        let _ = writeln!(
+            std::io::stderr(),
+            "import time: {:9} | {:10} | {:width$}{}",
+            own.as_nanos().div_ceil(1000),
+            cumulative.as_nanos().div_ceil(1000),
+            "",
+            import_time_name(self.name),
+        );
+    }
+}
+
+pub(crate) fn find_and_load(
+    name: &Py<PyStr>,
+    function: &'static str,
+    vm: &VirtualMachine,
+) -> PyResult {
+    let _timer = ImportTimer::start(name, vm);
+    vm.importlib
+        .get_attr(function, vm)?
+        .call((name.to_owned(), vm.import_func.clone()), vm)
+}
+
 pub(crate) fn check_pyc_magic_number_bytes(buf: &[u8]) -> bool {
     buf.starts_with(&crate::version::PYC_MAGIC_NUMBER_BYTES)
 }
@@ -29,7 +136,7 @@ pub(crate) fn init_importlib_base(vm: &mut VirtualMachine) -> PyResult<PyObjectR
         install.call((vm.sys_module.clone(), imp), vm)?;
         Ok(bootstrap)
     })?;
-    vm.import_func = importlib.get_attr(identifier!(vm, __import__), vm)?;
+    vm.import_func = vm.builtins.get_attr(identifier!(vm, __import__), vm)?;
     vm.importlib = importlib.clone();
     Ok(importlib)
 }
@@ -177,13 +284,14 @@ pub(crate) fn is_module_initializing(module: &PyObject, vm: &VirtualMachine) ->
 /// initializing by calling `_lock_unlock_module`.
 fn import_ensure_initialized(
     module: &PyObject,
-    name: &Py<PyUtf8Str>,
+    name: &Py<PyStr>,
     vm: &VirtualMachine,
 ) -> PyResult<()> {
     if is_module_initializing(module, vm)? {
         let lock_unlock = vm.importlib.get_attr("_lock_unlock_module", vm)?;
         lock_unlock.call((name.to_owned(),), vm)?;
     }
+    report_cached_import(name, vm);
     Ok(())
 }
 
@@ -380,6 +488,41 @@ pub(crate) fn is_stdlib_module_name(name: &PyObject, vm: &VirtualMachine) -> PyR
     result.try_to_bool(vm)
 }
 
+/// Resolve an import target without finding or executing its module.
+pub(crate) fn absolute_import_name(
+    name: &Py<crate::builtins::PyStr>,
+    globals: Option<&PyObject>,
+    level: i32,
+    vm: &VirtualMachine,
+) -> PyResult<crate::builtins::PyStrRef> {
+    if level < 0 {
+        return Err(vm.new_value_error("level must be >= 0"));
+    }
+    if level == 0 {
+        if name.is_empty() {
+            return Err(vm.new_value_error("Empty module name"));
+        }
+        return Ok(name.to_owned());
+    }
+    let globals = globals
+        .ok_or_else(|| vm.new_key_error(vm.ctx.new_str("'__name__' not in globals").into()))?;
+    let empty: PyObjectRef;
+    let globals = if vm.is_none(globals) {
+        empty = vm.ctx.new_dict().into();
+        &empty
+    } else {
+        globals
+    };
+    let package = calc_package(Some(globals), vm)?;
+    if package.is_empty() {
+        return Err(vm.new_import_error(
+            "attempted relative import with no known parent package",
+            vm.ctx.new_utf8_str(""),
+        ));
+    }
+    resolve_name(name, &package, level as usize, vm)
+}
+
 /// PyImport_ImportModuleLevelObject
 pub(crate) fn import_module_level(
     name: &Py<PyStr>,
@@ -392,21 +535,6 @@ pub(crate) fn import_module_level(
         return Err(vm.new_value_error("level must be >= 0"));
     }
 
-    let name = match name.as_utf8() {
-        Some(name) => name,
-        None => {
-            // Name contains surrogates. Try sys.modules lookup with the
-            // Python string key directly.
-            if level == 0 {
-                let sys_modules = vm.sys_module.get_attr("modules", vm)?;
-                return sys_modules.get_item(name, vm).map_err(|_| {
-                    vm.new_import_error(format!("No module named '{name}'"), name.to_owned())
-                });
-            }
-            return Err(vm.new_import_error(format!("No module named '{name}'"), name.to_owned()));
-        }
-    };
-
     // Resolve absolute name
     let abs_name = if level > 0 {
         // When globals is not provided (Rust None), raise KeyError
@@ -442,12 +570,10 @@ pub(crate) fn import_module_level(
     let module = match sys_modules.get_item(&*abs_name, vm) {
         Ok(m) if !vm.is_none(&m) => {
             import_ensure_initialized(&m, &abs_name, vm)?;
+            crate::lazy_import::clear_submodule(&abs_name, true, vm)?;
             m
         }
-        _ => {
-            let find_and_load = vm.importlib.get_attr("_find_and_load", vm)?;
-            find_and_load.call((abs_name.clone(), vm.import_func.clone()), vm)?
-        }
+        _ => find_and_load(&abs_name, "_find_and_load", vm)?,
     };
 
     // Handle fromlist
@@ -472,24 +598,23 @@ pub(crate) fn import_module_level(
             Ok(module)
         }
     } else if level == 0 || !name.is_empty() {
-        let name_str = name.as_str();
-        match name_str.find('.') {
+        let name_bytes = name.as_bytes();
+        match name_bytes.iter().position(|&byte| byte == b'.') {
             None => Ok(module),
             Some(dot) => {
                 let to_return = if level == 0 {
-                    vm.ctx.new_utf8_str(&name_str[..dot])
+                    vm.ctx.new_str(&name.as_wtf8()[..dot])
                 } else {
-                    let cut_off = name_str.len() - dot;
-                    let abs = abs_name.as_str();
-                    vm.ctx.new_utf8_str(&abs[..abs.len() - cut_off])
+                    let cut_off = name_bytes.len() - dot;
+                    let abs = abs_name.as_wtf8();
+                    vm.ctx.new_str(&abs[..abs.len() - cut_off])
                 };
                 match sys_modules.get_item(&*to_return, vm) {
                     Ok(m) => Ok(m),
                     Err(_) if level == 0 => {
                         // For absolute imports (level 0), try importing the
                         // parent. Matches _bootstrap.__import__ behavior.
-                        let find_and_load = vm.importlib.get_attr("_find_and_load", vm)?;
-                        find_and_load.call((to_return, vm.import_func.clone()), vm)
+                        find_and_load(&to_return, "_find_and_load", vm)
                     }
                     Err(_) => {
                         // For relative imports (level > 0), raise KeyError
@@ -509,37 +634,44 @@ pub(crate) fn import_module_level(
 
 /// resolve_name in import.c - resolve relative import name
 fn resolve_name(
-    name: &Py<PyUtf8Str>,
-    package: &Py<PyUtf8Str>,
+    name: &Py<PyStr>,
+    package: &Py<PyStr>,
     level: usize,
     vm: &VirtualMachine,
-) -> PyResult<PyUtf8StrRef> {
-    // Python: bits = package.rsplit('.', level - 1)
-    // Rust: rsplitn(level, '.') gives maxsplit=level-1
-    let package_str = package.as_str();
-    let parts: Vec<&str> = package_str.rsplitn(level, '.').collect();
-    if parts.len() < level {
-        return Err(vm.new_import_error(
-            "attempted relative import beyond top-level package",
-            name.to_owned(),
-        ));
+) -> PyResult<PyStrRef> {
+    // ASCII dots are character boundaries in WTF-8 too. Keep the original
+    // Python string, including surrogates, while walking up package components.
+    let package_bytes = package.as_bytes();
+    let mut end = package_bytes.len();
+    for _ in 1..level {
+        end = package_bytes[..end]
+            .iter()
+            .rposition(|&byte| byte == b'.')
+            .ok_or_else(|| {
+                vm.new_import_error(
+                    "attempted relative import beyond top-level package",
+                    name.to_owned(),
+                )
+            })?;
     }
-    // rsplitn returns parts right-to-left, so last() is the leftmost (base)
-    let base = *parts.last().unwrap();
+    let base = &package.as_wtf8()[..end];
     let abs_name = if name.is_empty() {
-        if base.len() == package_str.len() {
+        if end == package_bytes.len() {
             package.to_owned()
         } else {
-            vm.ctx.new_utf8_str(base)
+            vm.ctx.new_str(base)
         }
     } else {
-        vm.ctx.new_utf8_str(format!("{base}.{}", name.as_str()))
+        let mut absolute = base.to_owned();
+        absolute.push_str(".");
+        absolute.push_wtf8(name.as_wtf8());
+        vm.ctx.new_str(absolute)
     };
     Ok(abs_name)
 }
 
 /// _calc___package__ - calculate package from globals for relative imports
-fn calc_package(globals: Option<&PyObject>, vm: &VirtualMachine) -> PyResult<PyUtf8StrRef> {
+fn calc_package(globals: Option<&PyObject>, vm: &VirtualMachine) -> PyResult<PyStrRef> {
     let globals = globals.ok_or_else(|| {
         vm.new_import_error(
             "attempted relative import with no known parent package",
@@ -553,7 +685,7 @@ fn calc_package(globals: Option<&PyObject>, vm: &VirtualMachine) -> PyResult<PyU
     if let Some(ref pkg) = package
         && !vm.is_none(pkg)
     {
-        let pkg_str: PyUtf8StrRef = pkg
+        let pkg_str: PyStrRef = pkg
             .clone()
             .downcast()
             .map_err(|_| vm.new_type_error("package must be a string"))?;
@@ -573,7 +705,7 @@ fn calc_package(globals: Option<&PyObject>, vm: &VirtualMachine) -> PyResult<PyU
                 .unwrap_or_default();
             let msg = format!(
                 "__package__ != __spec__.parent ('{}' != {})",
-                pkg_str.as_str(),
+                pkg_str.as_wtf8(),
                 parent_repr
             );
             let warn = vm
@@ -595,7 +727,7 @@ fn calc_package(globals: Option<&PyObject>, vm: &VirtualMachine) -> PyResult<PyU
         && let Ok(parent) = spec.get_attr("parent", vm)
         && !vm.is_none(&parent)
     {
-        let parent_str: PyUtf8StrRef = parent
+        let parent_str: PyStrRef = parent
             .downcast()
             .map_err(|_| vm.new_type_error("package set to non-string"))?;
         return Ok(parent_str);
@@ -621,18 +753,126 @@ fn calc_package(globals: Option<&PyObject>, vm: &VirtualMachine) -> PyResult<PyU
             vm.ctx.new_utf8_str(""),
         )
     })?;
-    let mod_name_str: PyUtf8StrRef = mod_name
+    let mod_name_str: PyStrRef = mod_name
         .downcast()
         .map_err(|_| vm.new_type_error("__name__ must be a string"))?;
     // If not a package (no __path__), strip last component.
     // Uses rpartition('.')[0] semantics: returns empty string when no dot.
     if globals.get_item("__path__", vm).is_err() {
-        let s = mod_name_str.as_str();
-        Ok(match s.rfind('.') {
-            Some(dot) => vm.ctx.new_utf8_str(&s[..dot]),
-            None => vm.ctx.new_utf8_str(""),
-        })
+        let name = mod_name_str.as_wtf8();
+        Ok(
+            match name.as_bytes().iter().rposition(|&byte| byte == b'.') {
+                Some(dot) => vm.ctx.new_str(&name[..dot]),
+                None => vm.ctx.new_str(""),
+            },
+        )
     } else {
         Ok(mod_name_str)
     }
 }
+
+pub(crate) fn import_from_attribute(
+    module: &PyObject,
+    name: &Py<crate::builtins::PyStr>,
+    vm: &VirtualMachine,
+) -> PyResult {
+    // Load attribute, and transform any error into import error.
+    if let Some(obj) = vm.get_attribute_opt(module, name)? {
+        return Ok(obj);
+    }
+    // fallback to importing '{module.__name__}.{name}' from sys.modules
+    let fallback_module = (|| {
+        let mod_name = module.get_attr(identifier!(vm, __name__), vm).ok()?;
+        let mod_name = mod_name.downcast_ref::<PyUtf8Str>()?;
+        let full_mod_name = vm.ctx.new_utf8_str(format!("{}.{name}", mod_name.as_str()));
+        let sys_modules = vm.sys_module.get_attr("modules", vm).ok()?;
+        sys_modules.get_item(&*full_mod_name, vm).ok()
+    })();
+
+    if let Some(sub_module) = fallback_module {
+        return Ok(sub_module);
+    }
+
+    use crate::import::{get_spec_file_origin, is_possibly_shadowing_path, is_stdlib_module_name};
+
+    // Get module name for the error message
+    let mod_name_obj = module.get_attr(identifier!(vm, __name__), vm).ok();
+    let mod_name = mod_name_obj
+        .as_ref()
+        .and_then(|n| n.downcast_ref::<PyUtf8Str>());
+    let module_name = mod_name.map_or("<unknown module name>", |s| s.as_str());
+
+    let spec = module
+        .get_attr("__spec__", vm)
+        .ok()
+        .filter(|s| !vm.is_none(s));
+
+    let origin = get_spec_file_origin(spec.as_deref(), vm);
+
+    let is_possibly_shadowing = origin
+        .as_ref()
+        .is_some_and(|o| is_possibly_shadowing_path(o, vm));
+    let is_possibly_shadowing_stdlib = if is_possibly_shadowing {
+        if let Some(ref mod_name) = mod_name_obj {
+            is_stdlib_module_name(mod_name, vm)?
+        } else {
+            false
+        }
+    } else {
+        false
+    };
+
+    let msg = if is_possibly_shadowing_stdlib {
+        let origin = origin.as_ref().unwrap();
+        format!(
+            "cannot import name '{name}' from '{module_name}' \
+                 (consider renaming '{origin}' since it has the same \
+                 name as the standard library module named '{module_name}' \
+                 and prevents importing that standard library module)"
+        )
+    } else {
+        let is_init = is_module_initializing(module, vm).unwrap_or(false);
+        if is_init {
+            if is_possibly_shadowing {
+                let origin = origin.as_ref().unwrap();
+                format!(
+                    "cannot import name '{name}' from '{module_name}' \
+                         (consider renaming '{origin}' if it has the same name \
+                         as a library you intended to import)"
+                )
+            } else if let Some(ref path) = origin {
+                format!(
+                    "cannot import name '{name}' from partially initialized module \
+                         '{module_name}' (most likely due to a circular import) ({path})"
+                )
+            } else {
+                format!(
+                    "cannot import name '{name}' from partially initialized module \
+                         '{module_name}' (most likely due to a circular import)"
+                )
+            }
+        } else if let Some(ref path) = origin {
+            format!("cannot import name '{name}' from '{module_name}' ({path})")
+        } else {
+            format!("cannot import name '{name}' from '{module_name}' (unknown location)")
+        }
+    };
+    let err = vm.new_import_error(
+        msg,
+        match mod_name {
+            Some(s) => s.to_owned().into_wtf8(),
+            None => vm.ctx.new_utf8_str("<unknown module name>").into_wtf8(),
+        },
+    );
+
+    if let Some(ref path) = origin {
+        let _ignore = err
+            .as_object()
+            .set_attr("path", vm.ctx.new_str(path.as_str()), vm);
+    }
+
+    // name_from = the attribute name that failed to import (best-effort metadata)
+    let _ignore = err.as_object().set_attr("name_from", name.to_owned(), vm);
+
+    Err(err)
+}
diff --git a/crates/vm/src/lazy_import.rs b/crates/vm/src/lazy_import.rs
new file mode 100644
index 00000000000..2f713953def
--- /dev/null
+++ b/crates/vm/src/lazy_import.rs
@@ -0,0 +1,919 @@
+//! Native PEP 810 deferred bindings. Dictionaries themselves always expose raw values.
+
+use crate::{
+    AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
+    builtins::{
+        PyBaseException, PyCode, PyDict, PyModule, PySet, PyStr, PyStrRef, PyTuple, PyType,
+    },
+    class::PyClassImpl,
+    common::{
+        lock::{OnceCell, PyMutex},
+        wtf8::{Wtf8, Wtf8Buf, wtf8_concat},
+    },
+    frame,
+    types::{Constructor, GetAttr, Representable},
+};
+use core::sync::atomic::{AtomicBool, Ordering};
+use std::collections::HashMap;
+
+type PendingChildren = HashMap<Wtf8Buf, Option<PyRef<PyLazyImport>>>;
+
+fn split_parent(name: &Wtf8) -> Option<(&Wtf8, &Wtf8)> {
+    let dot = name.as_bytes().iter().rposition(|&byte| byte == b'.')?;
+    // ASCII dots always delimit code points, including next to surrogates.
+    Some((&name[..dot], &name[dot + 1..]))
+}
+
+pub(crate) struct LazyImportsState {
+    pub(crate) modules: PyRef<PySet>,
+    pub(crate) default_callback: OnceCell<PyObjectRef>,
+    pub(crate) all: AtomicBool,
+    filter: PyMutex<Option<PyObjectRef>>,
+    // Removed declarations must be dropped after releasing this lock.
+    pending: PyMutex<HashMap<Wtf8Buf, PendingChildren>>,
+}
+
+impl LazyImportsState {
+    pub(crate) fn new(ctx: &Context) -> Self {
+        Self {
+            modules: PySet::default().into_ref(ctx),
+            default_callback: OnceCell::new(),
+            all: AtomicBool::new(false),
+            filter: PyMutex::default(),
+            pending: PyMutex::default(),
+        }
+    }
+
+    pub(crate) fn filter(&self) -> Option<PyObjectRef> {
+        self.filter.lock().clone()
+    }
+
+    pub(crate) fn set_filter(&self, filter: Option<PyObjectRef>) {
+        // A removed callable's finalizer can re-enter this API.
+        let old = core::mem::replace(&mut *self.filter.lock(), filter);
+        drop(old);
+    }
+
+    fn register(
+        &self,
+        name: &Py<PyStr>,
+        source: Option<&Py<PyLazyImport>>,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        let mut full = name.as_wtf8();
+        while let Some((parent, child)) = split_parent(full) {
+            let cached = raw_imported_module(&vm.ctx.new_str(full), vm)?;
+            let value = if cached.as_ref().is_some_and(|value| !vm.is_none(value)) {
+                None
+            } else {
+                source.map(ToOwned::to_owned)
+            };
+            let replaced = {
+                let mut pending = self.pending.lock();
+                let children = pending.entry(parent.to_owned()).or_default();
+                if source.is_some() {
+                    children.insert(child.to_owned(), value)
+                } else {
+                    children.entry(child.to_owned()).or_insert(value);
+                    None
+                }
+            };
+            drop(replaced);
+            full = parent;
+        }
+        Ok(())
+    }
+}
+
+#[pyclass(module = false, name = "lazy_import", traverse)]
+#[derive(Debug)]
+pub(crate) struct PyLazyImport {
+    builtins: PyObjectRef,
+    name: PyStrRef,
+    // None is an import, a tuple is an import with fromlist, and a string is one member.
+    fromlist: Option<PyObjectRef>,
+    // Attribute projections retain the placeholder returned by IMPORT_NAME.
+    source: Option<PyRef<Self>>,
+    declaration: Option<PyRef<PyCode>>,
+    #[pytraverse(skip)]
+    instruction: u32,
+    #[pytraverse(skip)]
+    active: AtomicBool,
+}
+
+impl PyPayload for PyLazyImport {
+    fn class(ctx: &Context) -> &'static Py<PyType> {
+        ctx.types.lazy_import_type
+    }
+}
+
+impl PyLazyImport {
+    fn new(builtins: PyObjectRef, name: PyStrRef, fromlist: Option<PyObjectRef>) -> Self {
+        let frame = frame::current_thread_iframe();
+        let (declaration, instruction) = if frame.is_null() {
+            (None, 0)
+        } else {
+            // The thread's active frame is live for this call; retain its code, not the frame.
+            let frame = unsafe { &*frame };
+            (Some(frame.code().to_owned()), frame.get_lasti())
+        };
+        Self {
+            builtins,
+            name,
+            fromlist,
+            source: None,
+            declaration,
+            instruction,
+            active: AtomicBool::new(false),
+        }
+    }
+
+    fn projection(source: &Py<Self>, name: &Py<PyStr>) -> Self {
+        let mut projection = Self::new(
+            source.builtins.clone(),
+            source.name.clone(),
+            Some(name.to_owned().into()),
+        );
+        projection.source = Some(source.to_owned());
+        projection
+    }
+
+    fn root_and_attrs(&self) -> (&Self, Vec<PyStrRef>) {
+        let mut root = self;
+        let mut attrs = Vec::new();
+        while let Some(source) = &root.source {
+            let attr = root
+                .fromlist
+                .as_ref()
+                .unwrap()
+                .downcast_ref::<PyStr>()
+                .unwrap();
+            attrs.push(attr.to_owned());
+            root = source;
+        }
+        attrs.reverse();
+        (root, attrs)
+    }
+
+    fn has_fromlist(&self) -> bool {
+        self.fromlist.as_ref().is_some_and(|from| {
+            from.downcast_ref::<PyTuple>()
+                .is_none_or(|t| !t.as_slice().is_empty())
+        })
+    }
+
+    fn path(&self) -> Wtf8Buf {
+        let (root, attrs) = self.root_and_attrs();
+        let mut name = if root.has_fromlist() {
+            root.name.as_wtf8().to_owned()
+        } else {
+            root.name
+                .as_wtf8()
+                .split(Wtf8::new("."))
+                .next()
+                .unwrap()
+                .to_owned()
+        };
+        for attr in attrs {
+            name.push_char('.');
+            name.push_wtf8(attr.as_wtf8());
+        }
+        name
+    }
+
+    fn display_name(&self) -> Wtf8Buf {
+        if self.source.is_some() {
+            self.path()
+        } else if self.has_fromlist() {
+            wtf8_concat!(self.name.as_wtf8(), "...")
+        } else {
+            self.name.as_wtf8().to_owned()
+        }
+    }
+}
+
+#[pyclass(with(Constructor, GetAttr, Representable))]
+impl Py<PyLazyImport> {
+    /// Resolve this import and return its value without changing a containing dictionary.
+    #[pymethod]
+    fn resolve(&self, vm: &VirtualMachine) -> PyResult {
+        resolve(self, vm)
+    }
+}
+
+impl Constructor for PyLazyImport {
+    type Args = crate::function::FuncArgs;
+    fn py_new(_cls: &Py<PyType>, _args: Self::Args, vm: &VirtualMachine) -> PyResult<Self> {
+        Err(vm.new_type_error("cannot create 'lazy_import' instances"))
+    }
+}
+
+impl GetAttr for PyLazyImport {
+    fn getattro(zelf: &Py<Self>, name: &Py<PyStr>, vm: &VirtualMachine) -> PyResult {
+        if let Some(value) = zelf.as_object().generic_getattr_opt(name, None, vm)? {
+            return Ok(value);
+        }
+        Err(vm.new_attribute_error(wtf8_concat!(
+            "cannot access attribute ",
+            name.as_object().repr(vm)?.as_wtf8(),
+            " on unresolved lazy import ",
+            vm.ctx.new_str(zelf.display_name()).repr(vm)?,
+        )))
+    }
+}
+
+impl Representable for PyLazyImport {
+    fn repr_wtf8(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<Wtf8Buf> {
+        Ok(wtf8_concat!("<lazy_import '", zelf.display_name(), "'>"))
+    }
+}
+
+pub(crate) fn init_type(ctx: &'static Context) {
+    PyLazyImport::extend_class(ctx, ctx.types.lazy_import_type);
+}
+
+pub(crate) fn is_module_level() -> bool {
+    let frame = frame::current_thread_iframe();
+    if frame.is_null() {
+        return false;
+    }
+    let frame = unsafe { &*frame };
+    frame
+        .locals
+        .get()
+        .is_some_and(|locals| frame.globals().as_object().is(locals.obj()))
+}
+
+fn optional_item(
+    mapping: &PyObject,
+    name: &Py<PyStr>,
+    vm: &VirtualMachine,
+) -> PyResult<Option<PyObjectRef>> {
+    match mapping.get_item(name, vm) {
+        Ok(value) => Ok(Some(value)),
+        Err(exc) if exc.fast_isinstance(vm.ctx.exceptions.key_error) => Ok(None),
+        Err(exc) => Err(exc),
+    }
+}
+
+pub(crate) fn import_name(
+    name: &Py<PyStr>,
+    fromlist: PyObjectRef,
+    level: usize,
+    policy: u32,
+    vm: &VirtualMachine,
+) -> PyResult {
+    if policy & 2 != 0 {
+        return vm.import_from(name, fromlist, level);
+    }
+    let explicit = policy & 1 != 0;
+    let globals = vm.current_globals();
+    let mut lazy =
+        explicit || (vm.state.lazy_imports.all.load(Ordering::Acquire) && is_module_level());
+    if !lazy
+        && is_module_level()
+        && let Some(names) = optional_item(
+            globals.as_object(),
+            vm.ctx.intern_str("__lazy_modules__"),
+            vm,
+        )?
+    {
+        let absolute =
+            crate::import::absolute_import_name(name, Some(globals.as_object()), level as i32, vm)?;
+        lazy = names
+            .sequence_unchecked()
+            .contains(absolute.as_object(), vm)?;
+    }
+    if !lazy {
+        return vm.import_from(name, fromlist, level);
+    }
+    let builtins = frame::current_builtins().unwrap_or_else(|| vm.builtins.dict().into());
+    let callback = optional_item(&builtins, vm.ctx.intern_str("__lazy_import__"), vm)?
+        .ok_or_else(|| vm.new_import_error("__lazy_import__ not found", name.to_owned()))?;
+    if vm
+        .state
+        .lazy_imports
+        .default_callback
+        .get()
+        .is_some_and(|default| callback.is(default))
+    {
+        return create(
+            name,
+            globals.as_object(),
+            Some(fromlist),
+            level as i32,
+            builtins,
+            vm,
+        );
+    }
+    let locals: PyObjectRef = vm.current_locals()?.into();
+    callback.call((name.to_owned(), globals, locals, fromlist, level), vm)
+}
+
+pub(crate) fn create(
+    name: &Py<PyStr>,
+    globals: &PyObject,
+    fromlist: Option<PyObjectRef>,
+    level: i32,
+    builtins: PyObjectRef,
+    vm: &VirtualMachine,
+) -> PyResult {
+    let absolute = crate::import::absolute_import_name(name, Some(globals), level, vm)?;
+    if !is_module_level() {
+        return Err(vm.new_exception_msg(
+            vm.ctx.exceptions.syntax_error.to_owned(),
+            "'lazy import' is only allowed at module level".into(),
+        ));
+    }
+    let fromlist = match fromlist.filter(|value| !vm.is_none(value)) {
+        Some(value) if value.downcast_ref::<PyStr>().is_some() => {
+            Some(PyTuple::new_ref(vec![value], &vm.ctx).into())
+        }
+        value => value,
+    };
+    if let Some(filter) = vm.state.lazy_imports.filter() {
+        let globals_dict = crate::builtins::PyAnyDict::from_object(globals)
+            .ok_or_else(|| vm.new_type_error("globals must be a dict or a frozendict"))?;
+        let importer = globals_dict
+            .inner_getitem_opt(identifier!(vm, __name__), vm)?
+            .unwrap_or_else(|| vm.ctx.none());
+        let from = fromlist.clone().unwrap_or_else(|| vm.ctx.none());
+        if !filter
+            .call((importer, absolute.clone(), from), vm)?
+            .try_to_bool(vm)?
+        {
+            return crate::import::import_module_level(name, Some(globals), fromlist, level, vm);
+        }
+    }
+    if let Some(value) = &fromlist {
+        let Some(names) = value.downcast_ref::<PyTuple>() else {
+            return Err(
+                vm.new_type_error("lazy_import: fromlist must be None, a string, or a tuple")
+            );
+        };
+        for name in names.as_slice() {
+            if name.downcast_ref::<PyStr>().is_none() {
+                return Err(vm.new_type_error(format!(
+                    "Item in ``from list'' must be str, not {:.200}",
+                    name.class().name()
+                )));
+            }
+        }
+    }
+    let deferred =
+        PyLazyImport::new(builtins, absolute.clone(), fromlist.clone()).into_ref(&vm.ctx);
+    let state = &vm.state.lazy_imports;
+    let existing = track_module(&absolute, vm)?;
+    if let Some(names) = fromlist
+        .as_ref()
+        .and_then(|value| value.downcast_ref::<PyTuple>())
+        && !names.as_slice().is_empty()
+    {
+        for name in names.as_slice() {
+            let name = name.downcast_ref::<PyStr>().unwrap();
+            // Cached attributes are concrete or tracked by their own placeholder.
+            if let Some(module) = existing.as_ref().and_then(|m| m.downcast_ref::<PyModule>())
+                && module.dict().get_item_opt(name, vm)?.is_some()
+            {
+                continue;
+            }
+            let fullname = vm
+                .ctx
+                .new_str(wtf8_concat!(absolute.as_wtf8(), '.', name.as_wtf8()));
+            track_module(&fullname, vm)?;
+            state.register(&fullname, None, vm)?;
+        }
+    } else {
+        state.register(&absolute, Some(&deferred), vm)?;
+    }
+    Ok(deferred.into())
+}
+
+pub(crate) fn import_from(
+    deferred: &Py<PyLazyImport>,
+    name: &Py<PyStr>,
+    vm: &VirtualMachine,
+) -> PyResult {
+    if deferred.source.is_none()
+        && deferred.has_fromlist()
+        && let Some(value) = loaded_attr(&deferred.name, name, vm)?
+    {
+        return Ok(value);
+    }
+    Ok(PyLazyImport::projection(deferred, name)
+        .into_ref(&vm.ctx)
+        .into())
+}
+
+struct ResolvingGuard<'a> {
+    vm: &'a VirtualMachine,
+    identity: usize,
+}
+
+impl Drop for ResolvingGuard<'_> {
+    fn drop(&mut self) {
+        self.vm
+            .lazy_imports_resolving
+            .borrow_mut()
+            .remove(&self.identity);
+    }
+}
+
+pub(crate) fn is_resolving(deferred: &Py<PyLazyImport>, vm: &VirtualMachine) -> bool {
+    vm.lazy_imports_resolving
+        .borrow()
+        .contains(&deferred.as_object().get_id())
+}
+
+fn raw_imported_module(name: &Py<PyStr>, vm: &VirtualMachine) -> PyResult<Option<PyObjectRef>> {
+    let modules = vm.sys_module.dict().get_item("modules", vm)?;
+    optional_item(&modules, name, vm)
+}
+
+// Tracking must not invoke module/spec descriptors or convert a flag to bool.
+fn track_module(name: &Py<PyStr>, vm: &VirtualMachine) -> PyResult<Option<PyObjectRef>> {
+    let module = raw_imported_module(name, vm)?;
+    let loaded = if let Some(module) = module.as_ref().and_then(|m| m.downcast_ref::<PyModule>()) {
+        let spec = module
+            .dict()
+            .get_item_opt(vm.ctx.intern_str("__spec__"), vm)?;
+        match spec {
+            None => true,
+            Some(spec) if vm.is_none(&spec) => true,
+            Some(spec) if spec.has_inline_values() => {
+                let initializing = match spec.dict() {
+                    Some(dict) => dict.get_item_opt(vm.ctx.intern_str("_initializing"), vm)?,
+                    None => None,
+                };
+                initializing.is_none_or(|flag| flag.is(&vm.ctx.false_value))
+            }
+            Some(_) => false,
+        }
+    } else {
+        module.as_ref().is_some_and(|module| !vm.is_none(module))
+    };
+    if !loaded {
+        vm.state
+            .lazy_imports
+            .modules
+            .add(name.to_owned().into(), vm)?;
+    }
+    Ok(module)
+}
+
+// Attribute caching may inspect __spec__, but never waits for module imports.
+fn loaded_attr(
+    name: &Py<PyStr>,
+    attr: &Py<PyStr>,
+    vm: &VirtualMachine,
+) -> PyResult<Option<PyObjectRef>> {
+    let lookup = || -> PyResult<Option<PyObjectRef>> {
+        let modules = vm.sys_module.dict().get_item("modules", vm)?;
+        let Some(module) = optional_item(&modules, name, vm)? else {
+            return Ok(None);
+        };
+        let Some(module) = module.downcast_ref::<PyModule>() else {
+            return Ok(None);
+        };
+        if crate::import::is_module_initializing(module.as_object(), vm)? {
+            return Ok(None);
+        }
+        if !vm.sys_module.dict().get_item("modules", vm)?.is(&modules)
+            || !optional_item(&modules, name, vm)?.is_some_and(|m| m.is(module))
+        {
+            return Ok(None);
+        }
+        Ok(module
+            .dict()
+            .get_item_opt(attr, vm)?
+            .filter(|value| value.downcast_ref_if_exact::<PyLazyImport>(vm).is_none()))
+    };
+    match lookup() {
+        Err(exc) if exc.fast_isinstance(vm.ctx.exceptions.exception_type) => Ok(None),
+        result => result,
+    }
+}
+
+fn add_declaration_context(
+    deferred: &PyLazyImport,
+    exc: &Py<PyBaseException>,
+    vm: &VirtualMachine,
+) {
+    let Some(code) = &deferred.declaration else {
+        return;
+    };
+    let offset = deferred.instruction.saturating_sub(1) as usize;
+    let location = code.locations.get(offset).map(|(location, _)| location);
+    if exc.__cause__().is_some() || exc.__context__().is_some() || exc.__suppress_context__() {
+        let note = vm.ctx.new_str(wtf8_concat!(
+            "lazy import of '",
+            deferred.display_name(),
+            format!(
+                "' declared in {} at {}:{}",
+                code.obj_name,
+                code.source_path(),
+                location.map_or(0, |location| location.line.get()),
+            ),
+        ));
+        // Adding diagnostic context must not replace the original resolution error.
+        let _ = (|| -> PyResult<()> {
+            if let Some(notes) =
+                vm.get_attribute_opt(exc.as_object(), vm.ctx.intern_str("__notes__"))?
+                && notes.sequence_unchecked().contains(note.as_object(), vm)?
+            {
+                return Ok(());
+            }
+            exc.add_note(note, vm)
+        })();
+        return;
+    }
+    let cause = vm.new_import_error(
+        wtf8_concat!(
+            "lazy import of '",
+            deferred.display_name(),
+            "' raised an exception during resolution",
+        ),
+        deferred.name.clone(),
+    );
+    if let Some(location) = location {
+        let globals = vm.ctx.new_dict();
+        let frame = frame::FrameObject::new_ref(
+            code.clone(),
+            crate::scope::Scope::new(None, globals),
+            deferred.builtins.clone(),
+            &[],
+            None,
+            false,
+            vm,
+        );
+        frame.set_lasti(deferred.instruction);
+        let tb = crate::builtins::PyTraceback::new(None, frame, (offset * 2) as i32, location.line)
+            .into_ref(&vm.ctx);
+        cause.set_traceback(Some(tb));
+    }
+    exc.set_cause(Some(cause));
+}
+
+fn resolve_impl(
+    deferred: &Py<PyLazyImport>,
+    vm: &VirtualMachine,
+) -> PyResult<(PyObjectRef, Option<PyObjectRef>)> {
+    let (root, attrs) = deferred.root_and_attrs();
+    if is_resolving(deferred, vm) {
+        let exc = vm.new_exception_msg(
+            vm.ctx.exceptions.import_cycle_error.to_owned(),
+            wtf8_concat!(
+                "cannot import name ",
+                vm.ctx.new_str(deferred.display_name()).repr(vm)?,
+                " (most likely due to a circular import)",
+            ),
+        );
+        exc.as_object().set_attr("name", root.name.clone(), vm)?;
+        return Err(exc);
+    }
+    vm.with_recursion(" while resolving a lazy import", || {
+        let identity = deferred.as_object().get_id();
+        vm.lazy_imports_resolving.borrow_mut().insert(identity);
+        let _resolving = ResolvingGuard { vm, identity };
+        let result = (|| -> PyResult<(PyObjectRef, Option<PyObjectRef>)> {
+            let callback = optional_item(&root.builtins, vm.ctx.intern_str("__import__"), vm)?
+                .ok_or_else(|| vm.new_import_error("__import__ not found", root.name.clone()))?;
+            let default_import = callback.is(&vm.import_func);
+            let fromlist = match attrs.first().filter(|_| root.has_fromlist()) {
+                Some(first) => PyTuple::new_ref(vec![first.clone().into()], &vm.ctx).into(),
+                None => root.fromlist.clone().unwrap_or_else(|| vm.ctx.none()),
+            };
+            let mut name = root.name.clone();
+            let fullname = root.name.as_wtf8();
+            if attrs.is_empty()
+                && !root.has_fromlist()
+                && default_import
+                && root.builtins.is(vm.builtins.dict().as_object())
+                && let Some(dot) = fullname.as_bytes().iter().position(|&byte| byte == b'.')
+            {
+                let mut regular = true;
+                let mut complete = true;
+                for (dot, _) in fullname
+                    .as_bytes()
+                    .iter()
+                    .enumerate()
+                    .filter(|(_, byte)| **byte == b'.')
+                {
+                    let prefix = vm.ctx.new_str(&fullname[..dot]);
+                    let Some(cached) = loaded_attr(&prefix, identifier!(vm, __name__), vm)? else {
+                        complete = false;
+                        break;
+                    };
+                    regular = loaded_attr(&prefix, vm.ctx.intern_str("__path__"), vm)?.is_some()
+                        && cached
+                            .downcast_ref::<PyStr>()
+                            .is_some_and(|s| s.as_wtf8() == prefix.as_wtf8());
+                    if !regular {
+                        break;
+                    }
+                }
+                let loaded = loaded_attr(&name, identifier!(vm, __name__), vm)?;
+                if regular && (!complete || loaded.is_none()) {
+                    name = vm.ctx.new_str(&fullname[..dot]);
+                }
+            }
+            let globals = frame::current_globals()
+                .map_or_else(|| vm.ctx.none(), |g| g.as_object().to_owned());
+            let import = |name: &PyStrRef| {
+                callback
+                    .call(
+                        (
+                            name.clone(),
+                            globals.clone(),
+                            globals.clone(),
+                            fromlist.clone(),
+                            0i32,
+                        ),
+                        vm,
+                    )
+                    .inspect_err(|exc| crate::import::remove_importlib_frames(vm, exc))
+            };
+            let mut module = import(&name)?;
+            if !name.is(&root.name) {
+                root.active.store(true, Ordering::Relaxed);
+                let package = match module.downcast_ref_if_exact::<PyModule>(vm) {
+                    Some(module) => module
+                        .dict()
+                        .get_item_opt(vm.ctx.intern_str("__path__"), vm)?
+                        .is_some(),
+                    None => false,
+                };
+                if !package {
+                    module = import(&root.name)?;
+                }
+            } else if default_import {
+                clear_submodule(&name, false, vm)?;
+            }
+            let root_value = resolve_value(module, vm)?;
+            let imported_module =
+                if default_import && root_value.downcast_ref::<PyModule>().is_some() {
+                    Some(root_value.clone())
+                } else {
+                    None
+                };
+            // A custom importer's root must survive all projected attribute lookups.
+            let mut value = root_value.clone();
+            for attr in attrs {
+                value =
+                    resolve_value(crate::import::import_from_attribute(&value, &attr, vm)?, vm)?;
+            }
+            drop(root_value);
+            vm.state
+                .lazy_imports
+                .modules
+                .discard(vm.ctx.new_str(deferred.path()).into(), vm)?;
+            Ok((value, imported_module))
+        })();
+        result.inspect_err(|exc| add_declaration_context(deferred, exc, vm))
+    })
+}
+
+pub(crate) fn resolve(deferred: &Py<PyLazyImport>, vm: &VirtualMachine) -> PyResult {
+    resolve_impl(deferred, vm).map(|(value, _)| value)
+}
+
+pub(crate) fn resolve_value(value: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+    match value.downcast_ref_if_exact::<PyLazyImport>(vm) {
+        Some(deferred) => resolve(deferred, vm),
+        None => Ok(value),
+    }
+}
+
+pub(crate) fn reify(
+    deferred: &Py<PyLazyImport>,
+    name: &Py<PyStr>,
+    namespace: &PyObject,
+    vm: &VirtualMachine,
+) -> PyResult {
+    let (value, imported_module) = resolve_impl(deferred, vm)?;
+    if let Some(dict) = namespace.downcast_ref_if_exact::<PyDict>(vm) {
+        let replaced = dict.replace_if_identity(name, deferred.as_object(), value.clone(), vm)?;
+        if !replaced
+            && deferred.source.is_some()
+            && let Some(child) = imported_module
+        {
+            let (root, _) = deferred.root_and_attrs();
+            if let Some((parent_name, child_name)) = split_parent(root.name.as_wtf8())
+                && name.as_wtf8() == child_name
+                && let Some(parent) = raw_imported_module(&vm.ctx.new_str(parent_name), vm)?
+                && let Some(parent) = parent.downcast_ref::<PyModule>()
+                && parent.dict().as_object().is(namespace)
+            {
+                dict.replace_if_identity(name, &child, value.clone(), vm)?;
+            }
+        }
+    } else if namespace
+        .mapping_unchecked()
+        .slots()
+        .ass_subscript
+        .load()
+        .is_some()
+        && optional_item(namespace, name, vm)?.is_some_and(|current| current.is(deferred))
+    {
+        namespace.set_item(name, value.clone(), vm)?;
+    }
+    Ok(value)
+}
+
+pub(crate) fn reify_value(
+    value: PyObjectRef,
+    name: &Py<PyStr>,
+    namespace: &PyObject,
+    vm: &VirtualMachine,
+) -> PyResult {
+    match value.downcast_ref_if_exact::<PyLazyImport>(vm) {
+        Some(deferred) => reify(deferred, name, namespace, vm),
+        None => Ok(value),
+    }
+}
+
+pub(crate) fn resolved_dict_item(
+    dict: &Py<PyDict>,
+    name: &Py<PyStr>,
+    vm: &VirtualMachine,
+) -> PyResult<Option<PyObjectRef>> {
+    let Some(value) = dict.get_item_opt(name, vm)? else {
+        return Ok(None);
+    };
+    if let Some(deferred) = value.downcast_ref_if_exact::<PyLazyImport>(vm) {
+        if is_resolving(deferred, vm) {
+            return Ok(None);
+        }
+        return reify(deferred, name, dict.as_object(), vm).map(Some);
+    }
+    Ok(Some(value))
+}
+
+fn load_child(source: &Py<PyLazyImport>, name: &Py<PyStr>, vm: &VirtualMachine) -> PyResult {
+    vm.with_recursion(" while resolving a lazy import", || {
+        let mut child = PyLazyImport::new(source.builtins.clone(), name.to_owned(), None);
+        child.declaration = None;
+        for attr in name.as_wtf8().split(Wtf8::new(".")).skip(1) {
+            child = PyLazyImport::projection(&child.into_ref(&vm.ctx), &vm.ctx.new_str(attr));
+            child.declaration = None;
+        }
+        child.declaration.clone_from(&source.declaration);
+        child.instruction = source.instruction;
+        let result = resolve(&child.into_ref(&vm.ctx), vm)?;
+        if let Some(module) = result.downcast_ref::<PyModule>()
+            && source.name.as_wtf8() != name.as_wtf8()
+            && module
+                .dict()
+                .get_item_opt(vm.ctx.intern_str("__path__"), vm)?
+                .is_none()
+        {
+            return load_child(source, &source.name, vm);
+        }
+        Ok(result)
+    })
+}
+
+// Keep pending names while their parent is initializing, without retaining
+// completed declarations and their namespace mappings indefinitely.
+pub(crate) fn clear_submodule(name: &Py<PyStr>, bind: bool, vm: &VirtualMachine) -> PyResult<()> {
+    let Some((parent_name, child)) = split_parent(name.as_wtf8()) else {
+        return Ok(());
+    };
+    let state = &vm.state.lazy_imports;
+    if !state
+        .pending
+        .lock()
+        .get(parent_name)
+        .is_some_and(|children| children.contains_key(child))
+    {
+        return Ok(());
+    }
+    if let Some(loaded) = raw_imported_module(name, vm)? {
+        match crate::import::is_module_initializing(&loaded, vm) {
+            Ok(true) => return Ok(()),
+            Err(exc) if exc.fast_isinstance(vm.ctx.exceptions.exception_type) => return Ok(()),
+            Err(exc) => return Err(exc),
+            Ok(false) => {}
+        }
+    }
+    let parent = raw_imported_module(&vm.ctx.new_str(parent_name), vm)?;
+    let initializing = match &parent {
+        Some(parent) => crate::import::is_module_initializing(parent, vm)?,
+        None => false,
+    };
+    if bind
+        && !initializing
+        && let Some(parent) = parent
+            .as_ref()
+            .and_then(|p| p.downcast_ref_if_exact::<PyModule>(vm))
+        && let Some(value) = raw_imported_module(name, vm)?
+        && !vm.is_none(&value)
+    {
+        parent
+            .dict()
+            .setdefault(vm.ctx.new_str(child).into(), value, vm)?;
+    }
+    let removed = {
+        let mut pending = state.pending.lock();
+        if let Some(children) = pending.get_mut(parent_name) {
+            if initializing {
+                children.get_mut(child).and_then(Option::take)
+            } else {
+                children.remove(child).flatten()
+            }
+        } else {
+            None
+        }
+    };
+    drop(removed);
+    Ok(())
+}
+
+pub(crate) fn try_load_submodule(
+    module: &Py<PyModule>,
+    name: &Py<PyStr>,
+    suppress: bool,
+    vm: &VirtualMachine,
+) -> PyResult<Option<PyObjectRef>> {
+    let Some(module_name) = module.dict().get_item_opt(identifier!(vm, __name__), vm)? else {
+        return Ok(None);
+    };
+    let Some(module_name) = module_name.downcast_ref::<PyStr>() else {
+        return Ok(None);
+    };
+    let module_name = module_name.as_wtf8();
+    let child = name.as_wtf8();
+    let source = vm
+        .state
+        .lazy_imports
+        .pending
+        .lock()
+        .get(module_name)
+        .and_then(|children| children.get(child).cloned());
+    let Some(source) = source else {
+        return Ok(None);
+    };
+    let fullname = vm.ctx.new_str(wtf8_concat!(module_name, '.', child));
+    let imported = (|| {
+        if let Some(source) = &source
+            && !suppress
+            && (source.active.load(Ordering::Relaxed)
+                || module
+                    .dict()
+                    .get_item_opt(identifier!(vm, __getattr__), vm)?
+                    .is_none())
+        {
+            load_child(source, &fullname, vm)
+        } else {
+            if let Some(loaded) = raw_imported_module(&fullname, vm)?
+                && !vm.is_none(&loaded)
+            {
+                return Ok(loaded);
+            }
+            crate::import::find_and_load(&fullname, "_find_and_load_lazy_submodule", vm)
+        }
+    })();
+    let imported = match imported {
+        Ok(imported) => imported,
+        Err(exc) => {
+            if let Ok(Some(loaded)) = raw_imported_module(&fullname, vm)
+                && !vm.is_none(&loaded)
+            {
+                let _ = PyDict::hash_or_unhashable(name, vm).and_then(|hash| {
+                    module
+                        .dict()
+                        .entries
+                        .delete_if(vm, name, hash, |value| Ok(value.is(&loaded)))
+                });
+                let mut pending = vm.state.lazy_imports.pending.lock();
+                pending
+                    .entry(module_name.to_owned())
+                    .or_default()
+                    .entry(child.to_owned())
+                    .or_insert_with(|| source.clone());
+            }
+            crate::import::remove_importlib_frames(vm, &exc);
+            return Err(exc);
+        }
+    };
+    if vm.is_none(&imported) {
+        return Ok(None);
+    }
+    let initializing = match crate::import::is_module_initializing(&imported, vm) {
+        Ok(initializing) => initializing,
+        Err(exc) if exc.fast_isinstance(vm.ctx.exceptions.exception_type) => false,
+        Err(exc) => return Err(exc),
+    };
+    if !initializing {
+        module.dict().set_item(name, imported.clone(), vm)?;
+        let removed = vm
+            .state
+            .lazy_imports
+            .pending
+            .lock()
+            .get_mut(module_name)
+            .and_then(|children| children.remove(child));
+        drop(removed);
+    }
+    Ok(Some(imported))
+}
diff --git a/crates/vm/src/lib.rs b/crates/vm/src/lib.rs
index c6813f63e3a..f770193aa72 100644
--- a/crates/vm/src/lib.rs
+++ b/crates/vm/src/lib.rs
@@ -73,6 +73,7 @@ pub mod getpath;
 pub mod import;
 mod intern;
 pub mod iter;
+pub(crate) mod lazy_import;
 pub mod object;
 
 #[cfg(feature = "host_env")]
diff --git a/crates/vm/src/object/core.rs b/crates/vm/src/object/core.rs
index eb7edc93cca..d93cefbebcf 100644
--- a/crates/vm/src/object/core.rs
+++ b/crates/vm/src/object/core.rs
@@ -1,15 +1,3 @@
-//! Essential types for object models
-//!
-//! +-------------------------+--------------+-----------------------+
-//! |       Management        |       Typed      |      Untyped      |
-//! +-------------------------+------------------+-------------------+
-//! | Interpreter-independent | [`Py<T>`]        | [`PyObject`]      |
-//! | Reference-counted       | [`PyRef<T>`]     | [`PyObjectRef`]   |
-//! | Weak                    | [`PyWeakRef<T>`] | [`PyRef<PyWeak>`] |
-//! +-------------------------+--------------+-----------------------+
-//!
-//! [`PyRef<PyWeak>`] may looking like to be called as PyObjectWeak by the rule,
-//! but not to do to remember it is a PyRef object.
 use super::{
     PyAtomicRef,
     ext::{AsObject, PyRefExact, PyResult},
@@ -173,17 +161,14 @@ pub(super) unsafe fn default_dealloc<T: PyPayload>(obj: *mut PyObject) {
         return; // resurrected by __del__
     }
 
-    // Only tracked objects take the trashcan recursion guard and untrack path.
-    // Untracked objects either own no children (int, float, str, ...) or, like
-    // non-escaped frames, are released at interpreter depth with at most one
-    // unguarded link before their tracked children (dicts, functions, code)
-    // re-enter guarded deallocation, so recursion stays bounded. A frame stored
-    // in an object graph is forced to escape, becoming tracked and guarded here.
-    // Read once and reuse for both gates below.
+    // Untracked payloads can still own recursive chains of references, such as
+    // detached frames returned by sys._current_frames(). Guard traversable
+    // payloads regardless of tracking, while keeping scalar deallocation cheap.
     let tracked = obj_ref.is_gc_tracked();
+    let guarded = tracked || T::HAS_TRAVERSE;
 
     // Trashcan: limit recursive deallocation depth to prevent stack overflow
-    if tracked && !unsafe { trashcan::begin(obj, default_dealloc::<T>) } {
+    if guarded && !unsafe { trashcan::begin(obj, default_dealloc::<T>) } {
         return; // deferred to queue
     }
 
@@ -262,7 +247,7 @@ pub(super) unsafe fn default_dealloc<T: PyPayload>(obj: *mut PyObject) {
     }
 
     // Trashcan: decrement depth and process deferred objects at outermost level
-    if tracked {
+    if guarded {
         unsafe { trashcan::end() };
     }
 }
@@ -596,6 +581,9 @@ unsafe impl Traverse for PyObject {
 }
 
 // === Stripe lock for weakref list protection (WEAKREF_LIST_LOCK) ===
+// Like CPython's _Py_LOCK_DONT_DETACH weakref stripes, these critical sections
+// must not run Python, release Python references, or suspend an attached thread.
+// Traversal visitors must not recursively acquire a weakref stripe.
 
 #[cfg(feature = "threading")]
 mod weakref_lock {
@@ -605,29 +593,46 @@ mod weakref_lock {
 
     static LOCKS: [AtomicU8; NUM_WEAKREF_LOCKS] = [const { AtomicU8::new(0) }; NUM_WEAKREF_LOCKS];
 
+    #[derive(Debug)]
+    pub(super) struct WeakrefLock {
+        lock: &'static AtomicU8,
+    }
+
     pub(super) struct WeakrefLockGuard {
-        idx: usize,
+        lock: &'static AtomicU8,
     }
 
     impl Drop for WeakrefLockGuard {
         fn drop(&mut self) {
-            LOCKS[self.idx].store(0, Ordering::Release);
+            self.lock.store(0, Ordering::Release);
         }
     }
 
-    pub(super) fn lock(addr: usize) -> WeakrefLockGuard {
-        let idx = (addr >> 4) % NUM_WEAKREF_LOCKS;
-        loop {
-            if LOCKS[idx]
-                .compare_exchange_weak(0, 1, Ordering::Acquire, Ordering::Relaxed)
-                .is_ok()
-            {
-                return WeakrefLockGuard { idx };
+    impl WeakrefLock {
+        pub(super) fn lock(&self) -> WeakrefLockGuard {
+            loop {
+                if self
+                    .lock
+                    .compare_exchange_weak(0, 1, Ordering::Acquire, Ordering::Relaxed)
+                    .is_ok()
+                {
+                    return WeakrefLockGuard { lock: self.lock };
+                }
+                core::hint::spin_loop();
             }
-            core::hint::spin_loop();
         }
     }
 
+    pub(super) fn select(addr: usize) -> WeakrefLock {
+        WeakrefLock {
+            lock: &LOCKS[(addr >> 4) % NUM_WEAKREF_LOCKS],
+        }
+    }
+
+    pub(super) fn lock(addr: usize) -> WeakrefLockGuard {
+        select(addr).lock()
+    }
+
     /// Reset all weakref stripe locks after fork in child process.
     /// Locks held by parent threads would cause infinite spin in the child.
     #[cfg(all(unix, feature = "host_env"))]
@@ -640,14 +645,27 @@ mod weakref_lock {
 
 #[cfg(not(feature = "threading"))]
 mod weakref_lock {
+    #[derive(Debug)]
+    pub(super) struct WeakrefLock;
+
     pub(super) struct WeakrefLockGuard;
 
     impl Drop for WeakrefLockGuard {
         fn drop(&mut self) {}
     }
 
-    pub(super) fn lock(_addr: usize) -> WeakrefLockGuard {
-        WeakrefLockGuard
+    impl WeakrefLock {
+        pub(super) fn lock(&self) -> WeakrefLockGuard {
+            WeakrefLockGuard
+        }
+    }
+
+    pub(super) fn select(_addr: usize) -> WeakrefLock {
+        WeakrefLock
+    }
+
+    pub(super) fn lock(addr: usize) -> WeakrefLockGuard {
+        select(addr).lock()
     }
 }
 
@@ -711,7 +729,7 @@ unsafe fn try_reuse_weakref(ptr: *mut Py<PyWeak>) -> Option<PyRef<PyWeak>> {
     let node = unsafe { &*ptr };
     node.ref_count
         .safe_inc()
-        .then(|| unsafe { PyRef::from_raw(ptr) })
+        .then(|| unsafe { PyRef::<PyWeak>::from_raw(ptr) })
 }
 
 impl WeakRefList {
@@ -750,12 +768,13 @@ impl WeakRefList {
             }
         }
 
-        // Allocate OUTSIDE the stripe lock. PyRef::new_ref may trigger
-        // maybe_collect → GC → WeakRefList::clear on another object that
-        // hashes to the same stripe, which would deadlock on the spinlock.
+        // Allocate untracked: gc.get_objects() must not expose this node
+        // before its referent is published. Tracking below can trigger GC,
+        // so it must also happen outside the stripe lock.
         let weak_payload = PyWeak {
             pointers: Pointers::new(),
-            wr_object: Radium::new(obj as *const PyObject as *mut PyObject),
+            wr_object: Radium::new(ptr::null_mut()),
+            weakrefs_lock: weakref_lock::select(obj as *const PyObject as usize),
             callback: UnsafeCell::new(callback),
             hash: Radium::new(crate::common::hash::SENTINEL),
         };
@@ -775,7 +794,7 @@ impl WeakRefList {
             None
         };
         if let Some(existing) = existing {
-            // Nullify wr_object so drop_inner won't unlink an
+            // Nullify wr_object so clear_ref won't unlink an
             // un-inserted node (which would corrupt the list head).
             weak.wr_object.store(ptr::null_mut(), Ordering::Relaxed);
             return existing;
@@ -799,6 +818,16 @@ impl WeakRefList {
         if is_generic {
             self.generic.store(node_ptr.as_ptr(), Ordering::Relaxed);
         }
+        // Only linked nodes may advertise a referent: an allocation unwind
+        // must never try to unlink an unpublished node.
+        weak.wr_object
+            .store(obj as *const PyObject as *mut PyObject, Ordering::Release);
+
+        drop(_lock);
+        // SAFETY: this fresh allocation opted out of automatic tracking.
+        // Our strong reference keeps it alive, and it cannot enter a GC
+        // candidate list before tracking, so its gc_bits are still zero.
+        unsafe { crate::gc_state::track_new_object(NonNull::from(weak.as_object())) };
 
         weak
     }
@@ -843,7 +872,8 @@ impl WeakRefList {
         match NonNull::new(candidate_ptr) {
             Some(candidate) => {
                 let node = unsafe { candidate.as_ref() };
-                let has_callback = unsafe { (&*node.payload.callback.get()).is_some() };
+                // SAFETY: the referent stripe is held by the caller.
+                let has_callback = unsafe { &*node.payload.callback.get() }.is_some();
                 let node_cls = node.class();
                 // PyWeakref_CheckProxy: the basic-proxy slot is reserved for
                 // the canonical proxy type; subclasses and callback-less ref
@@ -864,97 +894,96 @@ impl WeakRefList {
     /// Called when the owner object is being dropped.
     // PyObject_ClearWeakRefs
     fn clear(&self, obj: &PyObject) {
-        let obj_addr = obj as *const PyObject as usize;
-        let _lock = weakref_lock::lock(obj_addr);
-
-        // Clear generic cache
+        // Owners precede the guard so unwinding also drops them after unlock.
+        let mut callbacks: Vec<(PyRef<PyWeak>, Option<PyObjectRef>)> = Vec::new();
+        let _lock = weakref_lock::lock(obj as *const PyObject as usize);
         self.generic.store(ptr::null_mut(), Ordering::Relaxed);
-
-        // Walk the list, collecting weakrefs with callbacks
-        let mut callbacks: Vec<(PyRef<PyWeak>, PyObjectRef)> = Vec::new();
         let mut current = NonNull::new(self.head.load(Ordering::Relaxed));
         while let Some(node) = current {
             let next = unsafe { WeakLink::pointers(node).as_ref().get_next() };
-
             let wr = unsafe { node.as_ref() };
-
-            // Mark weakref as dead
+            // Reserve before acquiring a Python owner; push cannot then unwind.
+            callbacks.reserve(1);
+            if wr.ref_count.safe_inc() {
+                let owner = unsafe { PyRef::<PyWeak>::from_raw(wr as *const Py<PyWeak>) };
+                callbacks.push((owner, None));
+                // Keep the owner in the outer batch before taking its callback.
+                let entry = callbacks.last_mut().unwrap();
+                // SAFETY: the referent stripe protects the callback as well.
+                entry.1 = unsafe { &mut *wr.payload.callback.get() }.take();
+            }
+            unsafe { unlink_weakref(self, node) };
+            // Publish death only after unlinking, while the original stripe
+            // still protects this node from a concurrent deallocator.
             wr.payload
                 .wr_object
-                .store(ptr::null_mut(), Ordering::Relaxed);
-
-            // Unlink from list
-            unsafe {
-                let mut ptrs = WeakLink::pointers(node);
-                ptrs.as_mut().set_prev(None);
-                ptrs.as_mut().set_next(None);
+                .store(ptr::null_mut(), Ordering::Release);
+            current = next;
+        }
+        drop(_lock);
+        for (wr, callback) in callbacks {
+            if let Some(cb) = callback {
+                crate::vm::thread::with_vm(&cb, |vm| {
+                    let _ = cb.call((wr.clone(),), vm);
+                });
             }
+        }
+    }
 
-            // Collect callback only if we can still acquire a strong ref.
-            if wr.ref_count.safe_inc() {
-                let wr_ref = unsafe { PyRef::from_raw(wr as *const Py<PyWeak>) };
-                let cb = unsafe { wr.payload.callback.get().replace(None) };
-                if let Some(cb) = cb {
-                    callbacks.push((wr_ref, cb));
+    /// Clear callback-bearing weakrefs before finalizers. Retain callback
+    /// ownership on each weakref until its later tp_clear or deallocation.
+    fn clear_for_gc_collect_callbacks(
+        &self,
+        obj: &PyObject,
+        is_unreachable: &impl Fn(&PyObject) -> bool,
+    ) -> Vec<(PyRef<PyWeak>, PyObjectRef)> {
+        let mut owners: Vec<PyRef<PyWeak>> = Vec::new();
+        let mut callbacks = Vec::new();
+        let _lock = weakref_lock::lock(obj as *const PyObject as usize);
+        let mut current = NonNull::new(self.head.load(Ordering::Relaxed));
+        while let Some(node) = current {
+            let next = unsafe { WeakLink::pointers(node).as_ref().get_next() };
+            let wr = unsafe { node.as_ref() };
+            // SAFETY: the referent stripe protects this borrowed callback.
+            let callback = unsafe { &*wr.payload.callback.get() };
+            if callback.is_some() {
+                owners.reserve(1);
+                callbacks.reserve(1);
+                if !is_unreachable(wr.as_object()) && wr.ref_count.safe_inc() {
+                    let owner = unsafe { PyRef::<PyWeak>::from_raw(wr as *const Py<PyWeak>) };
+                    owners.push(owner);
+                    let callback = callback.clone();
+                    if let Some(callback) = callback {
+                        callbacks.push((owners.last().unwrap().clone(), callback));
+                    }
                 }
+                unsafe { unlink_weakref(self, node) };
+                // No node access after publishing null without a strong pin.
+                wr.payload
+                    .wr_object
+                    .store(ptr::null_mut(), Ordering::Release);
             }
-
             current = next;
         }
-        self.head.store(ptr::null_mut(), Ordering::Relaxed);
-
-        // Invoke callbacks outside the lock
         drop(_lock);
-        for (wr, cb) in callbacks {
-            crate::vm::thread::with_vm(&cb, |vm| {
-                let _ = cb.call((wr.clone(),), vm);
-            });
-        }
+        callbacks
     }
 
-    /// Clear all weakrefs but DON'T call callbacks. Instead, return them for later invocation.
-    /// Used by GC to ensure ALL weakrefs are cleared BEFORE any callbacks are invoked.
-    /// handle_weakrefs() clears all weakrefs first, then invokes callbacks.
-    fn clear_for_gc_collect_callbacks(&self, obj: &PyObject) -> Vec<(PyRef<PyWeak>, PyObjectRef)> {
-        let obj_addr = obj as *const PyObject as usize;
-        let _lock = weakref_lock::lock(obj_addr);
-
-        // Clear generic cache
+    /// Unlink remaining weakrefs without invoking or releasing callbacks.
+    fn clear_for_gc(&self, obj: &PyObject) {
+        let _lock = weakref_lock::lock(obj as *const PyObject as usize);
         self.generic.store(ptr::null_mut(), Ordering::Relaxed);
-
-        let mut callbacks = Vec::new();
         let mut current = NonNull::new(self.head.load(Ordering::Relaxed));
         while let Some(node) = current {
             let next = unsafe { WeakLink::pointers(node).as_ref().get_next() };
-
             let wr = unsafe { node.as_ref() };
-
-            // Mark weakref as dead
+            unsafe { unlink_weakref(self, node) };
+            // Publishing null is the final access to this unpinned node.
             wr.payload
                 .wr_object
-                .store(ptr::null_mut(), Ordering::Relaxed);
-
-            // Unlink from list
-            unsafe {
-                let mut ptrs = WeakLink::pointers(node);
-                ptrs.as_mut().set_prev(None);
-                ptrs.as_mut().set_next(None);
-            }
-
-            // Collect callback without invoking only if we can keep weakref alive.
-            if wr.ref_count.safe_inc() {
-                let wr_ref = unsafe { PyRef::from_raw(wr as *const Py<PyWeak>) };
-                let cb = unsafe { wr.payload.callback.get().replace(None) };
-                if let Some(cb) = cb {
-                    callbacks.push((wr_ref, cb));
-                }
-            }
-
+                .store(ptr::null_mut(), Ordering::Release);
             current = next;
         }
-        self.head.store(ptr::null_mut(), Ordering::Relaxed);
-
-        callbacks
     }
 
     fn count(&self, obj: &PyObject) -> usize {
@@ -971,13 +1000,14 @@ impl WeakRefList {
     }
 
     fn get_weak_references(&self, obj: &PyObject) -> Vec<PyRef<PyWeak>> {
-        let _lock = weakref_lock::lock(obj as *const PyObject as usize);
         let mut v = Vec::new();
+        let _lock = weakref_lock::lock(obj as *const PyObject as usize);
         let mut current = NonNull::new(self.head.load(Ordering::Relaxed));
         while let Some(node) = current {
             let wr = unsafe { node.as_ref() };
+            v.reserve(1);
             if wr.ref_count.safe_inc() {
-                v.push(unsafe { PyRef::from_raw(wr as *const Py<PyWeak>) });
+                v.push(unsafe { PyRef::<PyWeak>::from_raw(wr as *const Py<PyWeak>) });
             }
             current = unsafe { WeakLink::pointers(node).as_ref().get_next() };
         }
@@ -1004,7 +1034,7 @@ unsafe impl Link for WeakLink {
 
     #[inline(always)]
     unsafe fn from_raw(ptr: NonNull<Self::Target>) -> Self::Handle {
-        unsafe { PyRef::from_raw(ptr.as_ptr()) }
+        unsafe { PyRef::<PyWeak>::from_raw(ptr.as_ptr()) }
     }
 
     #[inline(always)]
@@ -1015,20 +1045,27 @@ unsafe impl Link for WeakLink {
 }
 
 // PyWeakReference: each weakref holds a direct pointer to its referent.
-#[pyclass(name = "ReferenceType", module = "weakref")]
+#[pyclass(name = "ReferenceType", module = "weakref", traverse = "manual")]
 #[derive(Debug)]
 pub struct PyWeak {
     pointers: Pointers<Py<Self>>,
     /// Direct pointer to the referent object, null when dead.
     /// Equivalent to wr_object in PyWeakReference.
     wr_object: PyAtomic<*mut PyObject>,
-    /// Protected by stripe lock (keyed on wr_object address).
+    /// Handle to the original static referent stripe, like CPython's
+    /// weakrefs_lock. The same stripe protects the callback even after
+    /// wr_object becomes null and the referent is freed.
+    weakrefs_lock: weakref_lock::WeakrefLock,
+    /// Owned callback edge, protected by the original referent stripe.
+    /// GC can retain this edge after unlinking the weakref.
     callback: UnsafeCell<Option<PyObjectRef>>,
     pub(crate) hash: PyAtomic<crate::common::hash::PyHash>,
 }
 
 cfg_select! {
     feature = "threading" => {
+        // SAFETY: mutable callback and list access is serialized by the
+        // original referent stripe; referent and hash reads are atomic.
         unsafe impl Send for PyWeak {}
         unsafe impl Sync for PyWeak {}
     }
@@ -1063,42 +1100,40 @@ impl PyWeak {
         self.wr_object.load(Ordering::Acquire).is_null()
     }
 
-    /// Get the callback associated with this weak reference.
-    /// Returns `None` if there is no callback or if the referent has been
-    /// collected (at which point the callback was already consumed).
+    /// Get the owned callback, which GC can retain after clearing the referent.
     pub(crate) fn get_callback(&self) -> Option<PyObjectRef> {
-        let obj_ptr = self.wr_object.load(Ordering::Acquire);
-        if obj_ptr.is_null() {
-            // Dead weakref: callback was consumed during clear
-            return None;
-        }
-
-        let _lock = weakref_lock::lock(obj_ptr as usize);
-
-        // Double-check under lock (clear may have run between our check and lock)
-        let obj_ptr = self.wr_object.load(Ordering::Relaxed);
-        if obj_ptr.is_null() {
-            return None;
-        }
-
-        // Safety: we hold the stripe lock that protects the callback field
-        let callback = unsafe { &*self.callback.get() };
-        callback.clone()
+        let _lock = self.weakrefs_lock.lock();
+        // SAFETY: the original referent stripe protects the callback.
+        unsafe { &*self.callback.get() }.clone()
     }
 
-    /// weakref_dealloc: remove from list if still linked.
-    fn drop_inner(&self) {
-        let obj_ptr = self.wr_object.load(Ordering::Acquire);
-        if obj_ptr.is_null() {
-            return; // Already cleared by WeakRefList::clear()
+    /// Unlink and steal the callback under the original referent stripe.
+    /// Return ownership so callers release it only after unlocking.
+    fn clear(&self) -> Option<PyObjectRef> {
+        let _lock = self.weakrefs_lock.lock();
+        // SAFETY: the original referent stripe protects both fields, including
+        // callbacks retained by GC after the weakref was already unlinked.
+        unsafe {
+            self.clear_ref_lock_held();
+            (&mut *self.callback.get()).take()
         }
+    }
 
-        let _lock = weakref_lock::lock(obj_ptr as usize);
+    /// _PyWeakref_ClearRef: unlink without releasing the callback.
+    fn clear_ref(&self) {
+        let _lock = self.weakrefs_lock.lock();
+        // SAFETY: the original referent stripe is held.
+        unsafe { self.clear_ref_lock_held() };
+    }
 
-        // Double-check under lock
+    /// Unlink without releasing the callback.
+    ///
+    /// # Safety
+    /// The original referent stripe must be held.
+    unsafe fn clear_ref_lock_held(&self) {
         let obj_ptr = self.wr_object.load(Ordering::Relaxed);
         if obj_ptr.is_null() {
-            return; // Cleared between our check and lock acquisition
+            return;
         }
 
         let obj = unsafe { &*obj_ptr };
@@ -1121,12 +1156,31 @@ impl PyWeak {
     }
 }
 
+// SAFETY: the callback is the only owned Python edge; wr_object is borrowed.
+unsafe impl Traverse for PyWeak {
+    fn traverse(&self, tracer_fn: &mut TraverseFn<'_>) {
+        // Stripe critical sections never suspend or run Python, so a stopped
+        // thread cannot own this lock. Also synchronize gc.get_referents(),
+        // which traverses while other threads are running.
+        let _lock = self.weakrefs_lock.lock();
+        // SAFETY: the original referent stripe protects the callback.
+        unsafe { &*self.callback.get() }.traverse(tracer_fn);
+    }
+
+    fn clear(&mut self, out: &mut Vec<PyObjectRef>) {
+        let callback = Self::clear(self);
+        if let Some(callback) = callback {
+            out.push(callback);
+        }
+    }
+}
+
 impl Drop for PyWeak {
     #[inline(always)]
     fn drop(&mut self) {
         // we do NOT have actual exclusive access!
         let me: &Self = self;
-        me.drop_inner();
+        drop(me.clear());
     }
 }
 
@@ -1516,38 +1570,11 @@ impl<T: PyPayload> core::ops::DerefMut for FreeList<T> {
 /// this reference counting is accounted for by this type. Use the `.clone()`
 /// method to create a new reference and increment the amount of references
 /// to the python object by 1.
-#[repr(transparent)]
-pub struct PyObjectRef {
-    ptr: NonNull<PyObject>,
-}
-
-impl Clone for PyObjectRef {
-    #[inline(always)]
-    fn clone(&self) -> Self {
-        (**self).to_owned()
-    }
-}
-
-cfg_select! {
-    feature = "threading" => {
-        unsafe impl Send for PyObjectRef {}
-        unsafe impl Sync for PyObjectRef {}
-    }
-    _ => {}
-}
+pub type PyObjectRef = PyRef<PyObject>;
 
 #[repr(transparent)]
 pub struct PyObject(Py<Erased>);
 
-impl Deref for PyObjectRef {
-    type Target = PyObject;
-
-    #[inline(always)]
-    fn deref(&self) -> &PyObject {
-        unsafe { self.ptr.as_ref() }
-    }
-}
-
 impl ToOwned for PyObject {
     type Owned = PyObjectRef;
 
@@ -1555,7 +1582,8 @@ impl ToOwned for PyObject {
     fn to_owned(&self) -> Self::Owned {
         self.0.ref_count.inc();
         PyObjectRef {
-            ptr: NonNull::from(self),
+            ptr: NonNull::from(self).cast(),
+            marker: PhantomData,
         }
     }
 }
@@ -1569,7 +1597,8 @@ impl PyObject {
     pub fn try_to_owned(&self) -> Option<PyObjectRef> {
         if self.0.ref_count.safe_inc() {
             Some(PyObjectRef {
-                ptr: NonNull::from(self),
+                ptr: NonNull::from(self).cast(),
+                marker: PhantomData,
             })
         } else {
             None
@@ -1593,6 +1622,7 @@ impl PyObject {
         if ref_count.safe_inc() {
             Some(PyObjectRef {
                 ptr: unsafe { NonNull::new_unchecked(ptr) },
+                marker: PhantomData,
             })
         } else {
             None
@@ -1624,7 +1654,10 @@ impl PyObjectRef {
     #[inline(always)]
     #[must_use]
     pub const unsafe fn from_raw(ptr: NonNull<PyObject>) -> Self {
-        Self { ptr }
+        Self {
+            ptr: ptr.cast(),
+            marker: PhantomData,
+        }
     }
 
     /// Attempt to downcast this reference to a subclass.
@@ -1656,7 +1689,8 @@ impl PyObjectRef {
         // manual impl to avoid assertion
         let obj = ManuallyDrop::new(self);
         PyRef {
-            ptr: obj.ptr.cast(),
+            ptr: obj.ptr,
+            marker: PhantomData,
         }
     }
 
@@ -1701,7 +1735,7 @@ impl PyObject {
         } else {
             let head = unsafe { &*head_ptr };
             if head.ref_count.safe_inc() {
-                Some(unsafe { PyRef::from_raw(head_ptr) }.into())
+                Some(unsafe { PyRef::<PyWeak>::from_raw(head_ptr) }.into())
             } else {
                 None
             }
@@ -2168,7 +2202,7 @@ impl PyObject {
         }
 
         // Clear weak refs AFTER __del__.
-        // Note: This differs from GC behavior which clears weakrefs before finalizers,
+        // GC clears callback-bearing weakrefs before finalizers and the rest later,
         // but for direct deallocation (drop_slow_inner), we need to allow the finalizer
         // to run without triggering use-after-free from WeakRefList operations.
         if let Some(wrl) = self.weak_ref_list() {
@@ -2295,18 +2329,30 @@ impl PyObject {
         }
     }
 
-    /// Clear weakrefs but collect callbacks instead of calling them.
-    /// This is used by GC to ensure ALL weakrefs are cleared BEFORE any callbacks run.
-    /// Returns collected callbacks as (PyRef<PyWeak>, callback) pairs.
-    // = handle_weakrefs
-    pub fn gc_clear_weakrefs_collect_callbacks(&self) -> Vec<(PyRef<PyWeak>, PyObjectRef)> {
+    /// Clear callback-bearing weakrefs before finalizers and return callbacks
+    /// belonging to reachable weakrefs for invocation outside the list lock.
+    pub fn gc_clear_weakrefs_collect_callbacks(
+        &self,
+        is_unreachable: &impl Fn(&Self) -> bool,
+    ) -> Vec<(PyRef<PyWeak>, PyObjectRef)> {
         if let Some(wrl) = self.weak_ref_list() {
-            wrl.clear_for_gc_collect_callbacks(self)
+            wrl.clear_for_gc_collect_callbacks(self, is_unreachable)
         } else {
             vec![]
         }
     }
 
+    /// Clear weakrefs both in and pointing into the final unreachable set.
+    /// Callback edges remain owned until tp_clear or deallocation.
+    pub(crate) fn gc_clear_weakrefs(&self) {
+        if let Some(weakref) = self.downcast_ref::<PyWeak>() {
+            weakref.clear_ref();
+        }
+        if let Some(wrl) = self.weak_ref_list() {
+            wrl.clear_for_gc(self);
+        }
+    }
+
     /// Get raw pointers to referents without incrementing reference counts.
     /// This is used during GC to avoid reference count manipulation.
     /// tp_traverse visits objects without incref
@@ -2403,20 +2449,6 @@ impl PyObject {
     }
 }
 
-impl Borrow<PyObject> for PyObjectRef {
-    #[inline(always)]
-    fn borrow(&self) -> &PyObject {
-        self
-    }
-}
-
-impl AsRef<PyObject> for PyObjectRef {
-    #[inline(always)]
-    fn as_ref(&self) -> &PyObject {
-        self
-    }
-}
-
 impl<'a, T: PyPayload> From<&'a Py<T>> for &'a PyObject {
     #[inline(always)]
     fn from(py_ref: &'a Py<T>) -> Self {
@@ -2424,15 +2456,6 @@ impl<'a, T: PyPayload> From<&'a Py<T>> for &'a PyObject {
     }
 }
 
-impl Drop for PyObjectRef {
-    #[inline]
-    fn drop(&mut self) {
-        if self.0.ref_count.dec() {
-            unsafe { PyObject::drop_slow(self.ptr) }
-        }
-    }
-}
-
 impl fmt::Debug for PyObject {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // SAFETY: the vtable contains functions that accept payload types that always match up
@@ -2441,12 +2464,6 @@ impl fmt::Debug for PyObject {
     }
 }
 
-impl fmt::Debug for PyObjectRef {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.as_object().fmt(f)
-    }
-}
-
 const STACKREF_BORROW_TAG: usize = 1;
 
 /// A tagged stack reference to a Python object.
@@ -2658,14 +2675,15 @@ impl<T: PyPayload> Py<T> {
     }
 }
 
-impl<T> ToOwned for Py<T> {
+impl<T: PyRefTarget<Target = Self>> ToOwned for Py<T> {
     type Owned = PyRef<T>;
 
     #[inline(always)]
     fn to_owned(&self) -> Self::Owned {
         self.ref_count.inc();
         PyRef {
-            ptr: NonNull::from(self),
+            ptr: NonNull::from(self).cast(),
+            marker: PhantomData,
         }
     }
 }
@@ -2724,6 +2742,69 @@ impl<T: PyPayload + core::fmt::Debug> fmt::Debug for Py<T> {
     }
 }
 
+mod ref_target_sealed {
+    pub trait Sealed {}
+    impl<T: super::PyPayload> Sealed for T {}
+    impl Sealed for super::PyObject {}
+    impl Sealed for crate::builtins::set::PyAnySet {}
+    impl Sealed for crate::builtins::PyAnyDict {}
+    impl<T: super::PyTypedRefTarget> Sealed for super::PyTuple<super::PyRef<T>> {}
+}
+
+/// Selects the borrowed view of a Python reference.
+///
+/// Payloads borrow `Py<T>`; `PyObject` borrows the erased object itself.
+/// This trait is sealed so safe code cannot choose an unrelated layout.
+/// Typed tuples are immutable views of the ordinary tuple allocation.
+/// Internal union views borrow an erased header and dispatch on the payload;
+/// they must not assume that their alternative payloads have the same layout.
+///
+/// An arbitrary borrowed layout cannot be registered by downstream code:
+///
+/// ```compile_fail
+/// use rustpython_vm::object::PyRefTarget;
+/// struct Unrelated;
+/// impl PyRefTarget for Unrelated {
+///     type Target = u8;
+/// }
+/// ```
+pub trait PyRefTarget: ref_target_sealed::Sealed {
+    type Target;
+}
+
+impl<T: PyPayload> PyRefTarget for T {
+    type Target = Py<T>;
+}
+
+impl PyRefTarget for PyObject {
+    type Target = Self;
+}
+
+/// A non-erased reference target that can be an element of a typed tuple view.
+///
+/// This is sealed through [`PyRefTarget`]. Payloads, registered union views and
+/// recursively typed tuples qualify; `PyObject` does not, since ordinary tuples
+/// already implement [`PyPayload`]. This marker selects a layout, not a runtime
+/// type check: checked element conversion still requires
+/// [`crate::convert::TransmuteFromObject`].
+pub trait PyTypedRefTarget: PyRefTarget {}
+
+impl<T: PyRefTarget<Target = Py<T>>> PyTypedRefTarget for T {}
+impl PyTypedRefTarget for crate::builtins::set::PyAnySet {}
+impl PyTypedRefTarget for crate::builtins::PyAnyDict {}
+
+impl PyRefTarget for crate::builtins::PyAnyDict {
+    type Target = Self;
+}
+
+impl PyRefTarget for crate::builtins::set::PyAnySet {
+    type Target = Self;
+}
+
+impl<T: PyTypedRefTarget> PyRefTarget for PyTuple<PyRef<T>> {
+    type Target = Py<Self>;
+}
+
 /// A reference to a Python object.
 ///
 /// Note that a `PyRef<T>` can only deref to a shared / immutable reference.
@@ -2735,7 +2816,9 @@ impl<T: PyPayload + core::fmt::Debug> fmt::Debug for Py<T> {
 /// where a reference to the same object must be returned.
 #[repr(transparent)]
 pub struct PyRef<T> {
-    ptr: NonNull<Py<T>>,
+    ptr: NonNull<PyObject>,
+    // Preserve the variance and auto traits of the former typed pointer.
+    marker: PhantomData<NonNull<Py<T>>>,
 }
 
 cfg_select! {
@@ -2746,17 +2829,17 @@ cfg_select! {
     _ => {}
 }
 
-impl<T: fmt::Debug> fmt::Debug for PyRef<T> {
+impl<T> fmt::Debug for PyRef<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        (**self).fmt(f)
+        self.as_ref().fmt(f)
     }
 }
 
 impl<T> Drop for PyRef<T> {
     #[inline]
     fn drop(&mut self) {
-        if self.ref_count.dec() {
-            unsafe { PyObject::drop_slow(self.ptr.cast::<PyObject>()) }
+        if unsafe { self.ptr.as_ref() }.0.ref_count.dec() {
+            unsafe { PyObject::drop_slow(self.ptr) }
         }
     }
 }
@@ -2764,14 +2847,48 @@ impl<T> Drop for PyRef<T> {
 impl<T> Clone for PyRef<T> {
     #[inline(always)]
     fn clone(&self) -> Self {
-        (**self).to_owned()
+        unsafe { self.ptr.as_ref() }.0.ref_count.inc();
+        Self {
+            ptr: self.ptr,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<T: PyRefTarget> PyRef<T> {
+    /// Transfers ownership from an erased reference to a registered view.
+    ///
+    /// # Safety
+    /// The object must satisfy all invariants of `T::Target`, including its
+    /// payload restrictions. Registering a target establishes its layout only;
+    /// the caller must validate this particular object before the transfer.
+    #[inline]
+    pub(crate) unsafe fn from_object_unchecked(object: PyObjectRef) -> Self {
+        let object = ManuallyDrop::new(object);
+        Self {
+            ptr: object.ptr,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<T> PyRef<T> {
+    /// Erases the borrowed view, transferring the existing strong reference.
+    #[inline]
+    #[must_use]
+    pub fn into_object(self) -> PyObjectRef {
+        let object = ManuallyDrop::new(self);
+        PyObjectRef {
+            ptr: object.ptr,
+            marker: PhantomData,
+        }
     }
 }
 
 impl<T: PyPayload> PyRef<T> {
     #[inline(always)]
     pub(super) const fn into_non_null(self) -> NonNull<Py<T>> {
-        let ptr = self.ptr;
+        let ptr = self.ptr.cast();
         core::mem::forget(self);
         ptr
     }
@@ -2781,7 +2898,10 @@ impl<T: PyPayload> PyRef<T> {
     #[must_use]
     #[inline(always)]
     pub const unsafe fn from_non_null(ptr: NonNull<Py<T>>) -> Self {
-        Self { ptr }
+        Self {
+            ptr: ptr.cast(),
+            marker: PhantomData,
+        }
     }
 
     /// # Safety
@@ -2795,15 +2915,13 @@ impl<T: PyPayload> PyRef<T> {
     #[inline(always)]
     unsafe fn from_obj_unchecked(obj: PyObjectRef) -> Self {
         debug_assert!(obj.downcast_ref::<T>().is_some());
-        let obj = ManuallyDrop::new(obj);
-        Self {
-            ptr: obj.ptr.cast(),
-        }
+        // SAFETY: the caller guarantees the payload type.
+        unsafe { Self::from_object_unchecked(obj) }
     }
 
     #[must_use]
     pub const fn leak(pyref: Self) -> &'static Py<T> {
-        let ptr = pyref.ptr;
+        let ptr = pyref.ptr.cast::<Py<T>>();
         core::mem::forget(pyref);
         unsafe { ptr.as_ref() }
     }
@@ -2861,7 +2979,10 @@ impl<T: PyPayload + crate::object::MaybeTraverse + core::fmt::Debug> PyRef<T> {
             }
         }
 
-        Self { ptr }
+        Self {
+            ptr: ptr.cast(),
+            marker: PhantomData,
+        }
     }
 }
 
@@ -2870,15 +2991,16 @@ where
     T::Base: core::fmt::Debug,
 {
     /// Converts this reference to the base type (ownership transfer).
-    /// # Safety
-    /// T and T::Base must have compatible layouts in size_of::<T::Base>() bytes.
     #[inline]
     #[must_use]
     pub fn into_base(self) -> PyRef<T::Base> {
-        let obj: PyObjectRef = self.into();
-        match obj.downcast() {
-            Ok(base_ref) => base_ref,
-            Err(_) => unsafe { core::hint::unreachable_unchecked() },
+        // PySubclass establishes the physical prefix; Python may have changed
+        // the object's class or MRO since this typed reference was constructed.
+        let ptr = self.ptr.cast();
+        core::mem::forget(self);
+        PyRef {
+            ptr,
+            marker: PhantomData,
         }
     }
     #[inline]
@@ -2900,9 +3022,8 @@ impl<T: crate::class::PySubclass> Py<T> {
     /// Converts `&Py<T>` to `&Py<T::Base>`.
     #[inline]
     pub fn to_base(&self) -> &Py<T::Base> {
-        debug_assert!(self.as_object().downcast_ref::<T::Base>().is_some());
-        // SAFETY: T is #[repr(transparent)] over T::Base,
-        // so Py<T> and Py<T::Base> have the same layout.
+        // SAFETY: PySubclass guarantees a valid base prefix with matching
+        // payload offsets and compatible object alignment.
         unsafe { &*(self as *const Self as *const Py<T::Base>) }
     }
 
@@ -2918,54 +3039,47 @@ impl<T: crate::class::PySubclass> Py<T> {
     }
 }
 
-impl<T> Borrow<PyObject> for PyRef<T>
-where
-    T: PyPayload,
-{
+impl<T> Borrow<PyObject> for PyRef<T> {
     #[inline(always)]
     fn borrow(&self) -> &PyObject {
-        (**self).as_object()
+        unsafe { self.ptr.as_ref() }
     }
 }
 
-impl<T> AsRef<PyObject> for PyRef<T>
-where
-    T: PyPayload,
-{
+impl<T> AsRef<PyObject> for PyRef<T> {
     #[inline(always)]
     fn as_ref(&self) -> &PyObject {
         self.borrow()
     }
 }
 
-impl<T> From<PyRef<T>> for PyObjectRef {
+impl<T: PyRefTarget<Target = Py<T>>> From<PyRef<T>> for PyObjectRef {
     #[inline]
     fn from(value: PyRef<T>) -> Self {
-        let me = ManuallyDrop::new(value);
-        Self { ptr: me.ptr.cast() }
+        value.into_object()
     }
 }
 
-impl<T> Borrow<Py<T>> for PyRef<T> {
+impl<T: PyRefTarget<Target = Py<T>>> Borrow<Py<T>> for PyRef<T> {
     #[inline(always)]
     fn borrow(&self) -> &Py<T> {
         self
     }
 }
 
-impl<T> AsRef<Py<T>> for PyRef<T> {
+impl<T: PyRefTarget<Target = Py<T>>> AsRef<Py<T>> for PyRef<T> {
     #[inline(always)]
     fn as_ref(&self) -> &Py<T> {
         self
     }
 }
 
-impl<T> Deref for PyRef<T> {
-    type Target = Py<T>;
+impl<T: PyRefTarget> Deref for PyRef<T> {
+    type Target = T::Target;
 
     #[inline(always)]
-    fn deref(&self) -> &Py<T> {
-        unsafe { self.ptr.as_ref() }
+    fn deref(&self) -> &Self::Target {
+        unsafe { self.ptr.cast::<T::Target>().as_ref() }
     }
 }
 
@@ -3063,12 +3177,12 @@ pub(crate) fn init_type_hierarchy() -> BootstrapTypeHierarchy {
     }
 
     unsafe fn initial_ref<T: PyPayload>(ptr: *mut Py<T>) -> PyRef<T> {
-        unsafe { PyRef::from_raw(ptr.cast()) }
+        unsafe { PyRef::<T>::from_raw(ptr.cast()) }
     }
 
     unsafe fn clone_raw_ref<T: PyPayload>(ptr: *mut Py<T>) -> PyRef<T> {
         unsafe { &*ptr::addr_of!((*ptr).ref_count) }.inc();
-        unsafe { PyRef::from_raw(ptr.cast()) }
+        unsafe { PyRef::<T>::from_raw(ptr.cast()) }
     }
 
     unsafe fn into_type_tuple(tuple: PyTupleRef) -> PyTypeTupleRef {
@@ -3248,6 +3362,172 @@ pub(crate) fn init_type_hierarchy() -> BootstrapTypeHierarchy {
 mod tests {
     use super::*;
 
+    #[derive(Debug)]
+    struct RefProbe(alloc::sync::Arc<core::sync::atomic::AtomicUsize>);
+
+    impl MaybeTraverse for RefProbe {
+        fn try_traverse(&self, _traverse_fn: &mut TraverseFn<'_>) {}
+    }
+
+    impl PyPayload for RefProbe {
+        fn class(ctx: &crate::Context) -> &'static Py<PyType> {
+            ctx.types.object_type
+        }
+    }
+
+    impl Drop for RefProbe {
+        fn drop(&mut self) {
+            self.0.fetch_add(1, core::sync::atomic::Ordering::SeqCst);
+        }
+    }
+
+    #[test]
+    fn pyref_object_layout_and_views() {
+        static_assertions::assert_type_eq_all!(PyObjectRef, PyRef<PyObject>);
+        static_assertions::assert_not_impl_any!(PyObject: PyPayload);
+        static_assertions::assert_impl_all!(PyRef<core::marker::PhantomPinned>: Unpin);
+        static_assertions::assert_eq_size!(
+            PyObjectRef,
+            NonNull<PyObject>,
+            Option<PyObjectRef>,
+            PyRef<RefProbe>,
+            Option<PyRef<RefProbe>>,
+            PyRef<PyTuple<PyRef<RefProbe>>>
+        );
+        static_assertions::assert_eq_align!(
+            PyObjectRef,
+            NonNull<PyObject>,
+            PyRef<RefProbe>,
+            PyRef<PyTuple<PyRef<RefProbe>>>
+        );
+        #[cfg(feature = "threading")]
+        static_assertions::assert_impl_all!(PyRef<PyObject>: Send, Sync);
+        #[cfg(not(feature = "threading"))]
+        static_assertions::assert_not_impl_any!(PyRef<PyObject>: Send, Sync);
+
+        fn erased_view(reference: &PyRef<PyObject>) -> &PyObject {
+            reference
+        }
+        fn payload_view(reference: &PyRef<RefProbe>) -> &Py<RefProbe> {
+            reference
+        }
+        fn tuple_view(
+            reference: &PyRef<PyTuple<PyRef<RefProbe>>>,
+        ) -> &Py<PyTuple<PyRef<RefProbe>>> {
+            reference
+        }
+        type NestedTuple = PyTuple<PyRef<PyTuple<PyRef<RefProbe>>>>;
+        fn nested_view(reference: &PyRef<NestedTuple>) -> &Py<NestedTuple> {
+            reference
+        }
+        fn covariance<'long: 'short, 'short>(reference: PyRef<&'long ()>) -> PyRef<&'short ()> {
+            reference
+        }
+        fn into_object<T: Into<PyObjectRef>>() {}
+        into_object::<PyRef<NestedTuple>>();
+        let _ = (
+            erased_view,
+            payload_view,
+            tuple_view,
+            nested_view,
+            covariance,
+        );
+    }
+
+    #[test]
+    fn pyref_object_ownership_and_raw_roundtrip() {
+        let drops = alloc::sync::Arc::new(core::sync::atomic::AtomicUsize::new(0));
+        let ctx = crate::Context::genesis();
+        let typed = PyRef::new_ref(
+            RefProbe(drops.clone()),
+            ctx.types.object_type.to_owned(),
+            None,
+        );
+        let pointer = typed.as_object() as *const PyObject;
+        assert_eq!(typed.as_object().strong_count(), 1);
+        let erased: PyRef<PyObject> = typed.clone().into();
+        assert_eq!(erased.strong_count(), 2);
+        assert!(core::ptr::eq(&*erased, pointer));
+        let raw = erased.into_raw();
+        assert_eq!(typed.as_object().strong_count(), 2);
+        let erased = unsafe { PyRef::<PyObject>::from_raw(raw) };
+        let erased = erased.downcast::<crate::builtins::PyBytes>().unwrap_err();
+        assert_eq!(erased.strong_count(), 2);
+        let restored = erased.downcast::<RefProbe>().unwrap();
+        assert!(core::ptr::eq(&*typed, &*restored));
+        let raw = restored.into_non_null();
+        let restored = unsafe { PyRef::<RefProbe>::from_non_null(raw) };
+        drop(typed);
+        assert_eq!(restored.as_object().strong_count(), 1);
+        assert_eq!(drops.load(core::sync::atomic::Ordering::SeqCst), 0);
+        drop(restored);
+        assert_eq!(drops.load(core::sync::atomic::Ordering::SeqCst), 1);
+    }
+
+    #[test]
+    fn pyref_typed_tuple_erased_storage_drops_once() {
+        let ctx = crate::Context::genesis();
+        // Both constructors transfer a Vec allocation into erased tuple storage.
+        for explicit_type in [false, true] {
+            let drops = alloc::sync::Arc::new(core::sync::atomic::AtomicUsize::new(0));
+            let item = PyRef::new_ref(
+                RefProbe(drops.clone()),
+                ctx.types.object_type.to_owned(),
+                None,
+            );
+            let mut elements = Vec::with_capacity(4);
+            elements.push(item.clone());
+            let tuple = if explicit_type {
+                PyTuple::new_ref_typed_with_type(elements, ctx.types.tuple_type.to_owned())
+            } else {
+                PyTuple::new_ref_typed(elements, ctx)
+            };
+            assert_eq!(tuple.as_slice()[0].as_object().strong_count(), 2);
+            let copy = (*tuple).to_owned();
+            let object: PyObjectRef = tuple.into();
+            let untyped = copy.into_untyped();
+            assert_eq!(object.strong_count(), 2);
+            assert!(core::ptr::eq(untyped.as_object(), &*object));
+            assert_eq!(untyped.as_slice()[0].strong_count(), 2);
+            drop(object);
+            drop(item);
+            assert_eq!(drops.load(core::sync::atomic::Ordering::SeqCst), 0);
+            drop(untyped);
+            assert_eq!(drops.load(core::sync::atomic::Ordering::SeqCst), 1);
+        }
+    }
+
+    #[test]
+    fn native_base_conversions_ignore_python_mro() {
+        crate::Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let class = vm.ctx.new_class(
+                None,
+                "HiddenOSErrorBase",
+                vm.ctx.exceptions.os_error.to_owned(),
+                Default::default(),
+            );
+            let marker: PyObjectRef = vm.ctx.new_int(42).into();
+            let error = vm.new_os_subtype_error(class.clone(), None, marker.clone());
+            // A custom MRO can omit native bases without changing the allocation.
+            *class.mro.write() = vec![class.clone(), vm.ctx.types.object_type.to_owned()];
+            assert!(
+                !error
+                    .as_object()
+                    .downcastable::<crate::exceptions::types::PyException>()
+            );
+
+            assert!(error.to_base().to_base().get_arg(0).unwrap().is(&marker));
+            assert!(
+                error
+                    .into_base()
+                    .into_base()
+                    .get_arg(0)
+                    .unwrap()
+                    .is(&marker)
+            );
+        });
+    }
+
     #[test]
     fn native_type_basicsize_includes_payload_padding() {
         use crate::class::PyClassDef;
@@ -3391,6 +3671,78 @@ mod tests {
         drop(obj);
     }
 
+    #[test]
+    fn weakref_allocation_defers_gc_tracking_until_publication() {
+        crate::Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let target = vm.ctx.new_class(
+                None,
+                "WeakrefTarget",
+                vm.ctx.types.object_type.to_owned(),
+                Default::default(),
+            );
+            let subclass = vm.ctx.new_class(
+                None,
+                "WeakrefSubclass",
+                vm.ctx.types.weakref_type.to_owned(),
+                Default::default(),
+            );
+            for class in [
+                vm.ctx.types.weakref_type.to_owned(),
+                vm.ctx.types.weakproxy_type.to_owned(),
+                vm.ctx.types.weakcallableproxy_type.to_owned(),
+                subclass,
+            ] {
+                let dict = class
+                    .slots
+                    .flags
+                    .has_feature(crate::types::PyTypeFlags::HAS_DICT)
+                    .then(|| vm.ctx.new_dict());
+                // Exercise the allocator boundary directly: an uninitialized
+                // weakref must not be published through GC generation lists.
+                let unpublished = PyRef::new_ref(
+                    PyWeak {
+                        pointers: Pointers::new(),
+                        wr_object: Radium::new(ptr::null_mut()),
+                        weakrefs_lock: weakref_lock::select(
+                            target.as_object() as *const PyObject as usize
+                        ),
+                        callback: UnsafeCell::new(None),
+                        hash: Radium::new(crate::common::hash::SENTINEL),
+                    },
+                    class.clone(),
+                    dict,
+                );
+                assert_eq!(unpublished.as_object().0.gc_bits.load(Ordering::Relaxed), 0);
+                assert!(!unpublished.as_object().is_gc_tracked());
+                assert!(
+                    !vm.state
+                        .gc
+                        .get_objects(None)
+                        .iter()
+                        .any(|object| object.is(unpublished.as_object()))
+                );
+                drop(unpublished);
+
+                let published = target
+                    .as_object()
+                    .downgrade_with_typ(None, class, vm)
+                    .unwrap();
+                assert!(published.as_object().is_gc_tracked());
+                assert!(
+                    vm.state
+                        .gc
+                        .get_objects(None)
+                        .iter()
+                        .any(|object| object.is(published.as_object()))
+                );
+                assert_eq!(
+                    published.wr_object.load(Ordering::Acquire),
+                    target.as_object() as *const PyObject as *mut PyObject,
+                );
+            }
+        });
+    }
+
     /// A weakref node stays linked into its target's list until its own
     /// `Drop` unlinks it, and `WeakRefList::add` reads the class off every
     /// node it walks looking for a proxy to reuse. A node that lost its class
diff --git a/crates/vm/src/object/ext.rs b/crates/vm/src/object/ext.rs
index 97309722a19..68fea76d4ff 100644
--- a/crates/vm/src/object/ext.rs
+++ b/crates/vm/src/object/ext.rs
@@ -360,7 +360,7 @@ impl<T: PyPayload> PyAtomicRef<T> {
     pub unsafe fn swap(&self, pyref: PyRef<T>) -> PyRef<T> {
         let py = PyRef::leak(pyref) as *const Py<T> as *mut _;
         let old = Radium::swap(&self.inner, py, Ordering::AcqRel);
-        unsafe { PyRef::from_raw(old.cast()) }
+        unsafe { PyRef::<T>::from_raw(old.cast()) }
     }
 
     pub fn swap_to_temporary_refs(&self, pyref: PyRef<T>, vm: &VirtualMachine) {
@@ -439,7 +439,11 @@ impl<T: PyPayload> PyAtomicRef<Option<T>> {
     pub unsafe fn swap(&self, opt_ref: Option<PyRef<T>>) -> Option<PyRef<T>> {
         let val = opt_ref.map_or(null_mut(), |x| PyRef::leak(x) as *const Py<T> as *mut _);
         let old = Radium::swap(&self.inner, val, Ordering::AcqRel);
-        unsafe { old.cast::<Py<T>>().as_ref().map(|x| PyRef::from_raw(x)) }
+        unsafe {
+            old.cast::<Py<T>>()
+                .as_ref()
+                .map(|x| PyRef::<T>::from_raw(x))
+        }
     }
 
     pub fn swap_to_temporary_refs(&self, opt_ref: Option<PyRef<T>>, vm: &VirtualMachine) {
diff --git a/crates/vm/src/object/mod.rs b/crates/vm/src/object/mod.rs
index 4f028338d4b..1921e3bec67 100644
--- a/crates/vm/src/object/mod.rs
+++ b/crates/vm/src/object/mod.rs
@@ -1,3 +1,78 @@
+//! Essential types for object models
+//!
+//! +-------------------------+--------------+-----------------------+
+//! |       Management        |       Typed      |      Untyped      |
+//! +-------------------------+------------------+-------------------+
+//! | Interpreter-independent | [`Py<T>`]        | [`PyObject`]      |
+//! | Reference-counted       | [`PyRef<T>`]     | [`PyObjectRef`]   |
+//! | Weak                    | [`PyWeakRef<T>`] | [`PyRef<PyWeak>`] |
+//! +-------------------------+--------------+-----------------------+
+//!
+//! [`PyRef<PyWeak>`] may looking like to be called as PyObjectWeak by the rule,
+//! but not to do to remember it is a PyRef object.
+//!
+//! # Reference ownership
+//!
+//! `PyObjectRef` is an alias for `PyRef<PyObject>`. Typed payload references,
+//! erased references, union views, and typed tuple views share the same owning representation.
+//!
+//! ## Representation and invariants
+//!
+//! - `PyRef<T>` stores `NonNull<PyObject>` and a zero-sized
+//!   `PhantomData<NonNull<Py<T>>>`. The latter preserves the previous typed pointer's
+//!   covariance and auto-trait/`Unpin` shape. The transparent owner and its `Option`
+//!   remain one pointer wide with pointer alignment.
+//! - The sealed `object::PyRefTarget` selects `Deref::Target`: payload `T` maps to
+//!   `Py<T>`, `PyObject` maps to itself, and immutable typed tuples map recursively
+//!   to their existing typed `Py` view. Downstream safe code cannot register an
+//!   unrelated layout. `PyObject` does not implement `PyPayload`.
+//! - `PyAnySet` is an internal transparent `PyObject` view. Its owner is
+//!   `PyRef<PyAnySet>`, whose construction validates set/frozenset (including
+//!   subclasses). Payload access downcasts to the actual alternative; neither
+//!   `Py<PyAnySet>` nor a shared set/frozenset payload layout is assumed.
+//!   `ArgIterable` instead stores a cached iterator function beside its owner,
+//!   so it remains a wrapper rather than an allocation view.
+//! - [`PyTypedRefTarget`] admits non-erased element targets for typed tuple
+//!   views, including union views and recursively typed tuples. It does not
+//!   perform validation: `try_into_typed` checks every element before changing
+//!   the view. Typed constructors instead receive already-typed owners.
+//!   All tuple views retain erased element storage with transparent wrappers;
+//!   typed slices reinterpret only the guaranteed transparent reference
+//!   elements, never a generic `Vec` or `Box` representation. Private marshal
+//!   initialization finishes before publication; published elements are immutable.
+//! - The owner itself has no new generic bound. `Clone` and `Drop` share one
+//!   implementation over the existing object header. Object allocation, vtable
+//!   destruction, weakrefs, GC, and trashcan handling are unchanged.
+//! - Typed erasure uses `T: PyRefTarget<Target = Py<T>>`. This excludes the erased
+//!   type from the conversion blanket, avoiding overlap with Rust's identity
+//!   `From<T> for T`, while retaining typed and nested tuple conversions.
+//!   Union views provide their own checked conversions; `PyRef::into_object`
+//!   erases any owning view without adjusting its strong count.
+//! - Ownership transfers use `ManuallyDrop` or `forget`, without an extra incref or
+//!   decrement. The existing raw APIs retain their ownership-transfer contracts.
+//! - C-API typed output uses the same target equality. An erased owner supports
+//!   `*mut PyObject`, but cannot produce the fictitious `*mut Py<PyObject>` output.
+//!   Duplicate erased owner/member-layout/FFI implementations are removed.
+//! - Feature-dependent `Send`/`Sync` behavior is retained. The non-threading erased
+//!   owner is neither; the threading owner implements both.
+//!
+//! ## API compatibility considerations
+//!
+//! Existing payload `PyRef<T>` and `PyObjectRef` use remains supported, but aliasing
+//! makes some inference less direct:
+//!
+//! - Distinct raw constructor signatures remain: erased
+//!   `PyObjectRef::from_raw(NonNull<PyObject>)` and typed
+//!   `PyRef::<T>::from_raw(*const Py<T>)`. Unqualified `PyRef::from_raw` can now be
+//!   ambiguous and require the explicit type parameter.
+//! - Associated-target dereferencing can require an explicit downcast type or a
+//!   `PyRefTarget` equality bound in generic typed-view code. Arbitrary non-payload
+//!   views no longer automatically gain typed dereferencing; supported internal
+//!   views must be registered in the sealed selector.
+//! - Rust `Debug` formatting now consistently uses the allocation's vtable rather
+//!   than the statically selected payload's formatter. This is a Rust diagnostic
+//!   difference, not a Python semantic assertion.
+
 mod core;
 mod ext;
 mod payload;
diff --git a/crates/vm/src/protocol/buffer.rs b/crates/vm/src/protocol/buffer.rs
index 500ea5992f7..e8f13e22a51 100644
--- a/crates/vm/src/protocol/buffer.rs
+++ b/crates/vm/src/protocol/buffer.rs
@@ -403,25 +403,110 @@ pub struct BufferDescriptor {
     pub readonly: bool,
     pub itemsize: usize,
     pub format: Cow<'static, str>,
-    /// (shape, stride, suboffset) for each dimension. A non-zero suboffset means
-    /// the dimension is reached through a pointer; slicing never introduces one.
-    pub dim_desc: Vec<(usize, isize, isize)>,
+    /// Number of dimensions.
+    ndim: usize,
+    /// Shape, strides and suboffsets packed as 3 contiguous slices of length `ndim`.
+    dims: Box<[isize]>,
     // TODO: flags
 }
 
 impl BufferDescriptor {
     #[must_use]
-    pub fn simple(bytes_len: usize, readonly: bool) -> Self {
+    pub fn from_dim_desc(
+        len: usize,
+        offset: isize,
+        readonly: bool,
+        itemsize: usize,
+        format: Cow<'static, str>,
+        dim_desc: Vec<(usize, isize, isize)>,
+    ) -> Self {
+        let ndim = dim_desc.len();
+        let mut dims = Vec::with_capacity(ndim * 3);
+        dims.extend(dim_desc.iter().map(|(shape, _, _)| *shape as isize));
+        dims.extend(dim_desc.iter().map(|(_, stride, _)| *stride));
+        dims.extend(
+            dim_desc
+                .iter()
+                .map(|(_, _, suboffset)| if *suboffset == 0 { -1 } else { *suboffset }),
+        );
         Self {
-            len: bytes_len,
-            offset: 0,
+            len,
+            offset,
             readonly,
-            itemsize: 1,
-            format: Cow::Borrowed("B"),
-            dim_desc: vec![(bytes_len, 1, 0)],
+            itemsize,
+            format,
+            ndim,
+            dims: dims.into_boxed_slice(),
         }
     }
 
+    #[must_use]
+    pub fn shape(&self) -> &[isize] {
+        debug_assert_eq!(self.dims.len(), self.ndim * 3);
+        &self.dims[..self.ndim]
+    }
+
+    #[must_use]
+    pub fn strides(&self) -> &[isize] {
+        debug_assert_eq!(self.dims.len(), self.ndim * 3);
+        &self.dims[self.ndim..self.ndim * 2]
+    }
+
+    #[must_use]
+    pub fn suboffsets(&self) -> &[isize] {
+        debug_assert_eq!(self.dims.len(), self.ndim * 3);
+        &self.dims[self.ndim * 2..]
+    }
+
+    pub fn shape_mut(&mut self) -> &mut [isize] {
+        debug_assert_eq!(self.dims.len(), self.ndim * 3);
+        &mut self.dims[..self.ndim]
+    }
+
+    pub fn strides_mut(&mut self) -> &mut [isize] {
+        debug_assert_eq!(self.dims.len(), self.ndim * 3);
+        &mut self.dims[self.ndim..self.ndim * 2]
+    }
+
+    pub fn suboffsets_mut(&mut self) -> &mut [isize] {
+        debug_assert_eq!(self.dims.len(), self.ndim * 3);
+        &mut self.dims[self.ndim * 2..]
+    }
+
+    pub fn set_dimensions(
+        &mut self,
+        shape: Box<[isize]>,
+        strides: Box<[isize]>,
+        suboffsets: Box<[isize]>,
+    ) {
+        let ndim = shape.len();
+        debug_assert_eq!(strides.len(), ndim);
+        debug_assert_eq!(suboffsets.len(), ndim);
+
+        let shape = Vec::from(shape);
+        let strides = Vec::from(strides);
+        let suboffsets = Vec::from(suboffsets);
+        let mut dims = Vec::with_capacity(ndim * 3);
+        dims.extend(shape);
+        dims.extend(strides);
+        dims.extend(suboffsets);
+
+        self.ndim = ndim;
+        self.dims = dims.into_boxed_slice();
+    }
+
+    #[must_use]
+    pub fn simple(bytes_len: usize, readonly: bool) -> Self {
+        Self::from_dim_desc(
+            bytes_len,
+            0,
+            readonly,
+            1,
+            Cow::Borrowed("B"),
+            vec![(bytes_len, 1, 0)],
+        )
+    }
+
     #[must_use]
     pub fn format(
         bytes_len: usize,
@@ -429,14 +514,14 @@ impl BufferDescriptor {
         itemsize: usize,
         format: Cow<'static, str>,
     ) -> Self {
-        Self {
-            len: bytes_len,
-            offset: 0,
+        Self::from_dim_desc(
+            bytes_len,
+            0,
             readonly,
             itemsize,
             format,
-            dim_desc: vec![(bytes_len / itemsize, itemsize as isize, 0)],
-        }
+            vec![(bytes_len / itemsize, itemsize as isize, 0)],
+        )
     }
 
     /// The descriptor an exporter hands to a consumer that asked for `flags`:
@@ -460,14 +545,19 @@ impl BufferDescriptor {
             // A request this flat is refused unless the layout is C-contiguous, so
             // one dimension addresses the same bytes.
             let shape = desc.len.checked_div(desc.itemsize).unwrap_or(0);
-            desc.dim_desc = vec![(shape, desc.itemsize as isize, 0)];
+            desc.set_dimensions(
+                Box::new([shape as isize]),
+                Box::new([desc.itemsize as isize]),
+                Box::new([-1]),
+            );
         } else if !flags.contains(BufferFlags::STRIDES) {
             // Shape survives but strides do not, which means C order.
             let mut stride = desc.itemsize as isize;
-            for (shape, dim_stride, suboffset) in desc.dim_desc.iter_mut().rev() {
-                *dim_stride = stride;
-                *suboffset = 0;
-                stride *= *shape as isize;
+            for i in (0..desc.ndim()).rev() {
+                let dim_shape = desc.shape()[i];
+                desc.strides_mut()[i] = stride;
+                desc.suboffsets_mut()[i] = -1;
+                stride *= dim_shape;
             }
         }
         desc
@@ -490,10 +580,9 @@ impl BufferDescriptor {
             debug_assert_eq!(self.itemsize, self.len);
         } else {
             let mut shape_product = 1;
-            let has_zero_dim = self.dim_desc.iter().any(|(s, _, _)| *s == 0);
-            for (shape, stride, suboffset) in self.dim_desc.iter().copied() {
-                shape_product *= shape;
-                debug_assert!(suboffset >= 0);
+            let has_zero_dim = self.shape().contains(&0);
+            for (&shape, &stride) in self.shape().iter().zip(self.strides().iter()) {
+                shape_product *= shape as usize;
                 // For empty arrays (any dimension is 0), strides can be 0
                 if !has_zero_dim {
                     debug_assert_ne!(stride, 0);
@@ -506,7 +595,8 @@ impl BufferDescriptor {
 
     #[must_use]
     pub fn ndim(&self) -> usize {
-        self.dim_desc.len()
+        debug_assert_eq!(self.dims.len(), self.ndim * 3);
+        self.ndim
     }
 
     /// Whether the elements are laid out in row-major order. _IsCContiguous
@@ -516,11 +606,11 @@ impl BufferDescriptor {
             return true;
         }
         let mut sd = self.itemsize;
-        for (shape, stride, _) in self.dim_desc.iter().copied().rev() {
+        for (&shape, &stride) in self.shape().iter().zip(self.strides().iter()).rev() {
             if shape > 1 && stride != sd as isize {
                 return false;
             }
-            sd *= shape;
+            sd *= shape as usize;
         }
         true
     }
@@ -534,11 +624,11 @@ impl BufferDescriptor {
             return true;
         }
         let mut sd = self.itemsize;
-        for (shape, stride, _) in self.dim_desc.iter().copied() {
+        for (&shape, &stride) in self.shape().iter().zip(self.strides().iter()) {
             if shape > 1 && stride != sd as isize {
                 return false;
             }
-            sd *= shape;
+            sd *= shape as usize;
         }
         true
     }
@@ -561,23 +651,27 @@ impl BufferDescriptor {
     /// The same shape, format and item size, laid out in C order from byte zero.
     #[must_use]
     pub fn contiguous(&self) -> Self {
-        let itemsize = self.itemsize;
-        let mut dim_desc = self.dim_desc.clone();
-        if let Some((_, stride, suboffset)) = dim_desc.last_mut() {
-            *stride = itemsize as isize;
-            *suboffset = 0;
-        }
-        for i in (1..dim_desc.len()).rev() {
-            dim_desc[i - 1].1 = dim_desc[i].1 * dim_desc[i].0 as isize;
-            dim_desc[i - 1].2 = 0;
+        let mut strides = vec![0isize; self.ndim()];
+        let mut stride = self.itemsize as isize;
+        for i in (0..self.ndim()).rev() {
+            strides[i] = stride;
+            stride *= self.shape()[i];
         }
+        let shape = self.shape().to_vec().into_boxed_slice();
         Self {
             len: self.len,
             offset: 0,
             readonly: self.readonly,
             itemsize: self.itemsize,
             format: self.format.clone(),
-            dim_desc,
+            ndim: self.ndim,
+            dims: {
+                let mut dims = Vec::with_capacity(self.ndim * 3);
+                dims.extend(shape.iter().copied());
+                dims.extend(strides.iter().copied());
+                dims.extend(vec![-1; self.ndim]);
+                dims.into_boxed_slice()
+            },
         }
     }
 
@@ -585,9 +679,7 @@ impl BufferDescriptor {
     /// stepping, the layout `PyBUF_INDIRECT` describes.
     #[must_use]
     pub fn has_suboffsets(&self) -> bool {
-        self.dim_desc
-            .iter()
-            .any(|(_, _, suboffset)| *suboffset != 0)
+        self.suboffsets().iter().any(|&suboffset| suboffset != -1)
     }
 
     /// this function do not check the bound
@@ -595,12 +687,13 @@ impl BufferDescriptor {
     #[must_use]
     pub fn fast_position(&self, indices: &[usize]) -> isize {
         let mut pos = self.offset;
-        for (i, (_, stride, suboffset)) in indices
-            .iter()
-            .copied()
-            .zip_eq(self.dim_desc.iter().copied())
-        {
-            pos += i as isize * stride + suboffset;
+        for (dim, i) in indices.iter().copied().enumerate() {
+            let suboffset = if self.suboffsets()[dim] == -1 {
+                0
+            } else {
+                self.suboffsets()[dim]
+            };
+            pos += i as isize * self.strides()[dim] + suboffset;
         }
         pos
     }
@@ -611,7 +704,19 @@ impl BufferDescriptor {
         for (dim, (i, (shape, stride, suboffset))) in indices
             .iter()
             .copied()
-            .zip_eq(self.dim_desc.iter().copied())
+            .zip_eq(
+                self.shape()
+                    .iter()
+                    .zip(self.strides().iter())
+                    .zip(self.suboffsets().iter())
+                    .map(|((&shape, &stride), &suboffset)| {
+                        (
+                            shape as usize,
+                            stride,
+                            if suboffset == -1 { 0 } else { suboffset },
+                        )
+                    }),
+            )
             .enumerate()
         {
             // The dimension is named the way a person counts it. lookup_dimension
@@ -664,15 +769,17 @@ impl BufferDescriptor {
             let pos = self.offset
                 + indices
                     .iter()
-                    .zip_eq(self.dim_desc.iter())
-                    .map(|(&i, &(_, stride, suboffset))| i as isize * stride + suboffset)
+                    .zip_eq(self.strides().iter().zip(self.suboffsets().iter()))
+                    .map(|(&i, (&stride, &suboffset))| {
+                        i as isize * stride + if suboffset == -1 { 0 } else { suboffset }
+                    })
                     .sum::<isize>();
             f(pos..pos + self.itemsize as isize);
 
             let mut dim = 0;
             loop {
                 indices[dim] += 1;
-                if indices[dim] < self.dim_desc[dim].0 {
+                if (indices[dim] as isize) < self.shape()[dim] {
                     break;
                 }
                 indices[dim] = 0;
@@ -688,7 +795,13 @@ impl BufferDescriptor {
     where
         F: FnMut(Range<isize>),
     {
-        let (shape, stride, suboffset) = self.dim_desc[dim];
+        let shape = self.shape()[dim] as usize;
+        let stride = self.strides()[dim];
+        let suboffset = if self.suboffsets()[dim] == -1 {
+            0
+        } else {
+            self.suboffsets()[dim]
+        };
         if dim + 1 == self.ndim() {
             if CONTIGUOUS {
                 f(index..index + (shape * self.itemsize) as isize);
@@ -743,9 +856,21 @@ impl BufferDescriptor {
     ) where
         F: FnMut(Range<isize>, Range<isize>) -> bool,
     {
-        let (shape, a_stride, a_suboffset) = self.dim_desc[dim];
-        let (_b_shape, b_stride, b_suboffset) = other.dim_desc[dim];
-        debug_assert_eq!(shape, _b_shape);
+        let shape = self.shape()[dim] as usize;
+        let a_stride = self.strides()[dim];
+        let a_suboffset = if self.suboffsets()[dim] == -1 {
+            0
+        } else {
+            self.suboffsets()[dim]
+        };
+        let b_shape = other.shape()[dim] as usize;
+        let b_stride = other.strides()[dim];
+        let b_suboffset = if other.suboffsets()[dim] == -1 {
+            0
+        } else {
+            other.suboffsets()[dim]
+        };
+        debug_assert_eq!(shape, b_shape);
         if dim + 1 == self.ndim() {
             if CONTIGUOUS {
                 if f(
@@ -786,13 +911,13 @@ impl BufferDescriptor {
 
     #[must_use]
     fn is_last_dim_contiguous(&self) -> bool {
-        let (_, stride, suboffset) = self.dim_desc[self.ndim() - 1];
-        suboffset == 0 && stride == self.itemsize as isize
+        let i = self.ndim() - 1;
+        self.suboffsets()[i] == -1 && self.strides()[i] == self.itemsize as isize
     }
 
     #[must_use]
     pub fn is_zero_in_shape(&self) -> bool {
-        self.dim_desc.iter().any(|(shape, _, _)| *shape == 0)
+        self.shape().contains(&0)
     }
 
     // TODO: support column-major order
diff --git a/crates/vm/src/protocol/callable.rs b/crates/vm/src/protocol/callable.rs
index 49172a15222..7852f761572 100644
--- a/crates/vm/src/protocol/callable.rs
+++ b/crates/vm/src/protocol/callable.rs
@@ -78,6 +78,11 @@ impl<'a> PyCallable<'a> {
 
     pub fn invoke(&self, args: impl IntoFuncArgs, vm: &VirtualMachine) -> PyResult {
         let args = args.into_args(vm);
+        // _PyVectorcall_Call
+        if self.vectorcall.is_some() && args.kwargs.is_empty() {
+            let nargs = args.args.len();
+            return self.invoke_vectorcall(args.args, nargs, None, vm);
+        }
         if !vm.use_tracing.get() {
             return (self.call)(self.obj, args, vm);
         }
@@ -262,7 +267,7 @@ impl VirtualMachine {
         let is_profile_event = event.is_profile_event();
         let is_opcode_event = event.is_opcode_event();
 
-        let Some(frame_ref) = crate::frame::current_thread_frame_materialize(self) else {
+        let Some(frame_ref) = crate::frame::current_complete_frame_for_trace(self) else {
             return Ok(None);
         };
 
diff --git a/crates/vm/src/protocol/mapping.rs b/crates/vm/src/protocol/mapping.rs
index e791757901e..997df878ff0 100644
--- a/crates/vm/src/protocol/mapping.rs
+++ b/crates/vm/src/protocol/mapping.rs
@@ -184,7 +184,7 @@ impl PyMapping<'_> {
 
     pub fn keys(self, vm: &VirtualMachine) -> PyResult {
         if let Some(dict) = self.obj.downcast_ref_if_exact::<PyDict>(vm) {
-            PyDictKeys::new(dict.to_owned()).to_pyresult(vm)
+            PyDictKeys::new(dict.to_owned().into()).to_pyresult(vm)
         } else {
             self.method_output_as_list(identifier!(vm, keys), vm)
         }
@@ -192,7 +192,7 @@ impl PyMapping<'_> {
 
     pub fn values(self, vm: &VirtualMachine) -> PyResult {
         if let Some(dict) = self.obj.downcast_ref_if_exact::<PyDict>(vm) {
-            PyDictValues::new(dict.to_owned()).to_pyresult(vm)
+            PyDictValues::new(dict.to_owned().into()).to_pyresult(vm)
         } else {
             self.method_output_as_list(identifier!(vm, values), vm)
         }
@@ -200,7 +200,7 @@ impl PyMapping<'_> {
 
     pub fn items(self, vm: &VirtualMachine) -> PyResult {
         if let Some(dict) = self.obj.downcast_ref_if_exact::<PyDict>(vm) {
-            PyDictItems::new(dict.to_owned()).to_pyresult(vm)
+            PyDictItems::new(dict.to_owned().into()).to_pyresult(vm)
         } else {
             self.method_output_as_list(identifier!(vm, items), vm)
         }
diff --git a/crates/vm/src/protocol/object.rs b/crates/vm/src/protocol/object.rs
index 472f33c26f5..e5e625043ec 100644
--- a/crates/vm/src/protocol/object.rs
+++ b/crates/vm/src/protocol/object.rs
@@ -327,7 +327,7 @@ impl PyObject {
     ) -> PyResult<Either<PyObjectRef, bool>> {
         // Single recursion guard for the entire comparison
         // (do_richcompare in Objects/object.c).
-        vm.with_recursion("in comparison", || self._cmp_inner(other, op, vm))
+        vm.with_recursion(" in comparison", || self._cmp_inner(other, op, vm))
     }
 
     fn _cmp_inner(
@@ -419,7 +419,7 @@ impl PyObject {
     }
 
     pub fn repr(&self, vm: &VirtualMachine) -> PyResult<PyRef<PyStr>> {
-        vm.with_recursion("while getting the repr of an object", || {
+        vm.with_recursion(" while getting the repr of an object", || {
             self.class().slots().repr.load().map_or_else(
                 || {
                     Err(vm.new_runtime_error(format!(
@@ -542,7 +542,7 @@ impl PyObject {
         debug_assert!(n >= 2);
 
         for i in 0..n {
-            let result = vm.with_recursion("in __issubclass__", || {
+            let result = vm.with_recursion(" in __issubclass__", || {
                 bases.as_slice()[i].abstract_issubclass(cls, vm)
             })?;
 
@@ -611,7 +611,7 @@ impl PyObject {
         // Check if cls is a tuple
         if let Some(tuple) = cls.downcast_ref::<PyTuple>() {
             for item in tuple {
-                if vm.with_recursion("in __subclasscheck__", || derived.is_subclass(item, vm))? {
+                if vm.with_recursion(" in __subclasscheck__", || derived.is_subclass(item, vm))? {
                     return Ok(true);
                 }
             }
@@ -620,7 +620,7 @@ impl PyObject {
 
         // Check for __subclasscheck__ method using lookup_special
         if let Some(checker) = cls.lookup_special(identifier!(vm, __subclasscheck__), vm)? {
-            let res = vm.with_recursion("in __subclasscheck__", || {
+            let res = vm.with_recursion(" in __subclasscheck__", || {
                 checker.call((derived.to_owned(),), vm)
             })?;
             return res.try_to_bool(vm);
@@ -698,7 +698,7 @@ impl PyObject {
         // Check if cls is a tuple
         if let Some(tuple) = cls.downcast_ref::<PyTuple>() {
             for item in tuple {
-                if vm.with_recursion("in __instancecheck__", || {
+                if vm.with_recursion(" in __instancecheck__", || {
                     self.object_recursive_isinstance(item, vm)
                 })? {
                     return Ok(true);
@@ -709,7 +709,7 @@ impl PyObject {
 
         // Check for __instancecheck__ method using lookup_special
         if let Some(checker) = cls.lookup_special(identifier!(vm, __instancecheck__), vm)? {
-            let res = vm.with_recursion("in __instancecheck__", || {
+            let res = vm.with_recursion(" in __instancecheck__", || {
                 checker.call((self.to_owned(),), vm)
             })?;
             return res.try_to_bool(vm);
@@ -721,7 +721,7 @@ impl PyObject {
 
     pub fn hash(&self, vm: &VirtualMachine) -> PyResult<PyHash> {
         if let Some(hash) = self.class().slots().hash.load() {
-            return vm.with_recursion("while hashing", || hash(self, vm));
+            return vm.with_recursion(" while hashing", || hash(self, vm));
         }
 
         Err(vm.new_type_error(format!("unhashable type: '{}'", self.class().slot_name())))
diff --git a/crates/vm/src/scope.rs b/crates/vm/src/scope.rs
index 772d5c176c8..976cf750772 100644
--- a/crates/vm/src/scope.rs
+++ b/crates/vm/src/scope.rs
@@ -1,10 +1,14 @@
-use crate::{VirtualMachine, builtins::PyDictRef, function::ArgMapping};
+use crate::{
+    PyRef, VirtualMachine,
+    builtins::{PyAnyDict, PyDictRef},
+    function::ArgMapping,
+};
 use alloc::fmt;
 
 #[derive(Clone)]
 pub struct Scope {
     pub locals: Option<ArgMapping>,
-    pub globals: PyDictRef,
+    pub globals: PyRef<PyAnyDict>,
 }
 
 impl fmt::Debug for Scope {
@@ -17,8 +21,11 @@ impl fmt::Debug for Scope {
 impl Scope {
     #[inline]
     #[must_use]
-    pub const fn new(locals: Option<ArgMapping>, globals: PyDictRef) -> Self {
-        Self { locals, globals }
+    pub fn new(locals: Option<ArgMapping>, globals: impl Into<PyRef<PyAnyDict>>) -> Self {
+        Self {
+            locals,
+            globals: globals.into(),
+        }
     }
 
     pub fn with_builtins(
diff --git a/crates/vm/src/signal.rs b/crates/vm/src/signal.rs
index ddd4d58e556..4ea023505a8 100644
--- a/crates/vm/src/signal.rs
+++ b/crates/vm/src/signal.rs
@@ -58,6 +58,37 @@ pub(crate) static TRIGGERS: [AtomicBool; NSIG] = [ATOMIC_FALSE; NSIG];
 #[cfg(windows)]
 static SIGINT_EVENT: AtomicIsize = AtomicIsize::new(0);
 
+/// `_PyRuntime.signals.unhandled_keyboard_interrupt`
+static UNHANDLED_KEYBOARD_INTERRUPT: AtomicBool = AtomicBool::new(false);
+
+pub(crate) fn set_unhandled_keyboard_interrupt() {
+    UNHANDLED_KEYBOARD_INTERRUPT.store(true, Ordering::Relaxed);
+}
+
+pub(crate) fn clear_unhandled_keyboard_interrupt() {
+    UNHANDLED_KEYBOARD_INTERRUPT.store(false, Ordering::Relaxed);
+}
+
+pub(crate) fn unhandled_keyboard_interrupt() -> bool {
+    UNHANDLED_KEYBOARD_INTERRUPT.load(Ordering::Relaxed)
+}
+
+/// exit_sigint: exit through the default SIGINT handler so that the parent
+/// process sees that a KeyboardInterrupt went unhandled.
+pub(crate) fn exit_sigint() -> u32 {
+    cfg_select! {
+        unix => {
+            if crate::host_env::signal::set_sigint_default_onstack().is_ok() {
+                let _ = crate::host_env::signal::send_sigint_to_self();
+            }
+            libc::SIGINT as u32 + 128
+        }
+        // STATUS_CONTROL_C_EXIT
+        windows => 0xC000013A,
+        _ => 2 + 128,
+    }
+}
+
 thread_local! {
     /// Prevent recursive signal handler invocation. When a Python signal
     /// handler is running, new signals are deferred until it completes.
@@ -103,6 +134,16 @@ fn trigger_signals(vm: &VirtualMachine) -> PyResult<()> {
     }
     let _guard = SignalHandlerGuard;
 
+    #[cfg(all(feature = "host_env", windows))]
+    if vm.is_main_thread() && vm.state.is_main_interpreter() {
+        // Report before a Python signal handler can raise out of the current
+        // error-reporting scope.
+        crate::stdlib::_signal::_signal::report_wakeup_send_errors(vm);
+    } else if crate::stdlib::_signal::_signal::wakeup_send_errors_pending() {
+        // A different interpreter/thread must leave the report for the main one.
+        set_triggered();
+    }
+
     let signal_handlers = vm
         .signal_handlers
         .get()
@@ -233,6 +274,10 @@ impl SignalNum {
     #[allow(dead_code, reason = "Not used on all platforms")]
     pub(crate) const SIGINT: Self = Self(libc::SIGINT);
 
+    #[cfg(all(target_os = "wasi", feature = "host_env"))]
+    #[allow(dead_code, reason = "Not used on all platforms")]
+    pub(crate) const SIGINT: Self = Self(rustpython_host_env::signal::SIGINT);
+
     /// Construct [`Self`] without any validation on the signalnum value.
     ///
     /// # Safety
diff --git a/crates/vm/src/sliceable.rs b/crates/vm/src/sliceable.rs
index e859c7a3a37..d5a897f4308 100644
--- a/crates/vm/src/sliceable.rs
+++ b/crates/vm/src/sliceable.rs
@@ -257,6 +257,34 @@ pub enum SequenceIndex {
     Slice(SaturatedSlice),
 }
 
+/// Compile-time type name used in sequence index TypeErrors.
+///
+/// `&'static str` is not a legal const-generic type, so the name is an associated
+/// constant on a marker type, the same pattern as [`crate::function::ArgName`].
+pub trait SequenceIndexName {
+    const NAME: &'static str;
+}
+
+macro_rules! sequence_index_name {
+    ($($ty:ident = $name:literal),* $(,)?) => {$(
+        #[derive(Clone, Copy, Debug)]
+        pub struct $ty;
+        impl SequenceIndexName for $ty {
+            const NAME: &'static str = $name;
+        }
+    )*};
+}
+
+sequence_index_name! {
+    NameList = "list",
+    NameTuple = "tuple",
+    NameByte = "byte",
+    NameBytearray = "bytearray",
+    NameArray = "array",
+    NameMmap = "mmap",
+    NameElement = "element",
+}
+
 impl SequenceIndex {
     /// The index or slice `obj` stands for, or `None` when it is neither.
     fn try_from_object_opt(vm: &VirtualMachine, obj: &PyObject) -> Option<PyResult<Self>> {
@@ -280,27 +308,47 @@ impl SequenceIndex {
         }
     }
 
-    pub fn try_from_borrowed_object(
+    fn try_from_object(
         vm: &VirtualMachine,
         obj: &PyObject,
-        type_name: &str,
+        err_fmt: fn(&str) -> String,
     ) -> PyResult<Self> {
-        Self::try_from_object_opt(vm, obj).unwrap_or_else(|| {
-            Err(vm.new_type_error(format!(
-                "{type_name} indices must be integers or slices, not {}",
-                obj.class().slot_name()
-            )))
-        })
+        Self::try_from_object_opt(vm, obj)
+            .unwrap_or_else(|| Self::index_type_error(vm, obj, err_fmt))
+    }
+
+    #[cold]
+    #[inline(never)]
+    fn index_type_error(
+        vm: &VirtualMachine,
+        obj: &PyObject,
+        err_fmt: fn(&str) -> String,
+    ) -> PyResult<Self> {
+        let class_name = obj.class().slot_name();
+        Err(vm.new_type_error(err_fmt(&class_name)))
+    }
+
+    fn sequence_index_type_error<N: SequenceIndexName>(class_name: &str) -> String {
+        format!(
+            "{} indices must be integers or slices, not {class_name:.200}",
+            N::NAME
+        )
+    }
+
+    fn str_index_type_error(class_name: &str) -> String {
+        format!("string indices must be integers, not '{class_name:.200}'")
+    }
+
+    pub fn try_from_borrowed_object<N: SequenceIndexName>(
+        vm: &VirtualMachine,
+        obj: &PyObject,
+    ) -> PyResult<Self> {
+        Self::try_from_object(vm, obj, Self::sequence_index_type_error::<N>)
     }
 
     /// `unicode_subscript`, which turns down what it cannot use in its own words.
     pub fn try_from_str_subscript(vm: &VirtualMachine, obj: &PyObject) -> PyResult<Self> {
-        Self::try_from_object_opt(vm, obj).unwrap_or_else(|| {
-            Err(vm.new_type_error(format!(
-                "string indices must be integers, not '{}'",
-                obj.class().slot_name()
-            )))
-        })
+        Self::try_from_object(vm, obj, Self::str_index_type_error)
     }
 }
 
diff --git a/crates/vm/src/stdlib/_abc.rs b/crates/vm/src/stdlib/_abc.rs
index 19cf47415a9..4d2971949e5 100644
--- a/crates/vm/src/stdlib/_abc.rs
+++ b/crates/vm/src/stdlib/_abc.rs
@@ -272,7 +272,9 @@ mod _abc {
         let impl_data = get_impl(&cls, vm)?;
 
         // Get instance.__class__
-        let subclass = instance.get_attr("__class__", vm)?;
+        let subclass = vm
+            .get_attribute_opt(&instance, "__class__")?
+            .unwrap_or_else(|| instance.class().to_owned().into());
 
         // Check cache
         if in_weak_set(&impl_data.cache, &subclass, vm)? {
diff --git a/crates/vm/src/stdlib/_ast.rs b/crates/vm/src/stdlib/_ast.rs
index bba073d5b0c..83375b8ab01 100644
--- a/crates/vm/src/stdlib/_ast.rs
+++ b/crates/vm/src/stdlib/_ast.rs
@@ -7,6 +7,8 @@
 pub(crate) use python::_ast::module_def;
 
 mod pyast;
+mod source_location;
+use source_location::{AstNodeRange, AstSourceContext};
 
 use crate::builtins::{PyInt, PyStr};
 use crate::stdlib::_ast::module::{Mod, ModFunctionType, ModInteractive, ModModule};
@@ -99,7 +101,7 @@ fn get_node_field_required(
 
 fn get_required_identifier_field<T: Node>(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     obj: &PyObject,
     field: &'static str,
     typ: &str,
@@ -113,7 +115,7 @@ fn get_required_identifier_field<T: Node>(
 
 fn get_required_node_field<T: Node>(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     obj: &PyObject,
     field: &'static str,
     typ: &str,
@@ -140,7 +142,7 @@ fn get_node_field_opt(
 
 fn get_node_list_field<T: Node>(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     obj: &PyObject,
     field: &'static str,
     typ: &str,
@@ -170,7 +172,7 @@ fn get_node_list_field_object(
 
 fn convert_node_list_field<T: Node>(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     list: &Py<PyList>,
     field: &'static str,
     typ: &str,
@@ -202,7 +204,7 @@ fn convert_node_list_field<T: Node>(
 
 fn get_node_boxed_slice_field<T: Node>(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     obj: &PyObject,
     field: &'static str,
     typ: &str,
@@ -323,50 +325,8 @@ fn get_ast_string_field_opt(
 }
 
 struct PySourceRange {
-    start: PySourceLocation,
-    end: PySourceLocation,
-}
-
-pub(crate) struct PySourceLocation {
-    row: Row,
-    column: Column,
-}
-
-impl PySourceLocation {
-    const fn to_source_location(&self) -> SourceLocation {
-        SourceLocation {
-            line: self.row.get_one_indexed(),
-            character_offset: self.column.get_one_indexed(),
-        }
-    }
-}
-
-/// A one-based index into the lines.
-#[derive(Clone, Copy)]
-struct Row(OneIndexed);
-
-impl Row {
-    const fn get(self) -> usize {
-        self.0.get()
-    }
-
-    const fn get_one_indexed(self) -> OneIndexed {
-        self.0
-    }
-}
-
-/// An UTF-8 index into the line.
-#[derive(Clone, Copy)]
-struct Column(TextSize);
-
-impl Column {
-    const fn get(self) -> usize {
-        self.0.to_usize()
-    }
-
-    const fn get_one_indexed(self) -> OneIndexed {
-        OneIndexed::from_zero_indexed(self.get())
-    }
+    start: SourceLocation,
+    end: SourceLocation,
 }
 
 fn text_range_to_source_range(source_file: &SourceFile, text_range: TextRange) -> PySourceRange {
@@ -375,31 +335,14 @@ fn text_range_to_source_range(source_file: &SourceFile, text_range: TextRange) -
 
     if source.is_empty() {
         return PySourceRange {
-            start: PySourceLocation {
-                row: Row(OneIndexed::from_zero_indexed(0)),
-                column: Column(TextSize::new(0)),
-            },
-            end: PySourceLocation {
-                row: Row(OneIndexed::from_zero_indexed(0)),
-                column: Column(TextSize::new(0)),
-            },
+            start: SourceLocation::default(),
+            end: SourceLocation::default(),
         };
     }
 
-    let start_row = index.line_index(text_range.start());
-    let end_row = index.line_index(text_range.end());
-    let start_col = text_range.start() - index.line_start(start_row, source);
-    let end_col = text_range.end() - index.line_start(end_row, source);
-
     PySourceRange {
-        start: PySourceLocation {
-            row: Row(start_row),
-            column: Column(start_col),
-        },
-        end: PySourceLocation {
-            row: Row(end_row),
-            column: Column(end_col),
-        },
+        start: index.source_location(text_range.start(), source, PositionEncoding::Utf8),
+        end: index.source_location(text_range.end(), source, PositionEncoding::Utf8),
     }
 }
 
@@ -522,12 +465,26 @@ fn copy_ast_passthrough_fields(
             &["kind"]
         } else if is_node_instance(vm, target, pyast::NodeExprInterpolation::static_type())? {
             &["str"]
+        } else if is_node_instance(vm, target, pyast::NodeStmtImport::static_type())?
+            || is_node_instance(vm, target, pyast::NodeStmtImportFrom::static_type())?
+        {
+            &["is_lazy"]
         } else {
             &[]
         };
 
     for field in fields {
         if let Some(value) = vm.get_attribute_opt(source, *field)? {
+            let value = if *field == "is_lazy" {
+                let value = if vm.is_none(&value) {
+                    0
+                } else {
+                    node_object_to_i32(vm, &value)?
+                };
+                vm.ctx.new_int(value).into()
+            } else {
+                value
+            };
             target.set_attr(*field, value, vm)?;
         }
     }
@@ -704,95 +661,101 @@ fn synthetic_source_from_ast_object(vm: &VirtualMachine, object: &PyObject) -> P
 
 fn range_from_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
     name: &str,
-) -> PyResult<TextRange> {
+) -> PyResult<AstNodeRange> {
     range_from_object_impl(vm, source_file, object, name, false)
 }
 
 fn type_param_range_from_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-) -> PyResult<TextRange> {
+) -> PyResult<AstNodeRange> {
     range_from_object_impl(vm, source_file, object, "type_param", true)
 }
 
 fn expr_range_from_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-) -> PyResult<TextRange> {
+) -> PyResult<AstNodeRange> {
     range_from_object_impl(vm, source_file, object, "expr", false)
 }
 
 fn stmt_range_from_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-) -> PyResult<TextRange> {
+) -> PyResult<AstNodeRange> {
     range_from_object_impl(vm, source_file, object, "stmt", false)
 }
 
 fn pattern_range_from_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-) -> PyResult<TextRange> {
+) -> PyResult<AstNodeRange> {
     range_from_object_impl(vm, source_file, object, "pattern", true)
 }
 
 fn excepthandler_range_from_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-) -> PyResult<TextRange> {
+) -> PyResult<AstNodeRange> {
     range_from_object_impl(vm, source_file, object, "excepthandler", false)
 }
 
 fn excepthandler_range_from_object_unvalidated(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-) -> PyResult<TextRange> {
+) -> PyResult<AstNodeRange> {
     let start_row = get_int_field(vm, object, "lineno", "excepthandler")?;
     let start_column = get_int_field(vm, object, "col_offset", "excepthandler")?;
     let end_row = get_opt_int_field(vm, object, "end_lineno")?.unwrap_or(start_row);
     let end_column = get_opt_int_field(vm, object, "end_col_offset")?.unwrap_or(start_column);
 
     let location = PySourceRange {
-        start: PySourceLocation {
-            row: Row(if start_row > 0 {
+        start: SourceLocation {
+            line: if start_row > 0 {
                 OneIndexed::new(start_row as usize).unwrap_or(OneIndexed::MIN)
             } else {
                 OneIndexed::MIN
-            }),
-            column: Column(TextSize::new(start_column.max(0) as u32)),
+            },
+            character_offset: OneIndexed::from_zero_indexed(start_column.max(0) as usize),
         },
-        end: PySourceLocation {
-            row: Row(if end_row > 0 {
+        end: SourceLocation {
+            line: if end_row > 0 {
                 OneIndexed::new(end_row as usize).unwrap_or(OneIndexed::MIN)
             } else {
                 OneIndexed::MIN
-            }),
-            column: Column(TextSize::new(end_column.max(0) as u32)),
+            },
+            character_offset: OneIndexed::from_zero_indexed(end_column.max(0) as usize),
         },
     };
 
-    Ok(source_range_to_text_range_unvalidated(
-        source_file,
-        location,
-    ))
+    source_file.register(
+        vm,
+        source_range_to_text_range(source_file, location),
+        Some(rustpython_compiler_core::SourceLocationRange {
+            line: start_row,
+            end_line: end_row,
+            col: start_column,
+            end_col: end_column,
+        }),
+    )
 }
 
 fn range_from_object_impl(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
     name: &str,
     end_required: bool,
-) -> PyResult<TextRange> {
+) -> PyResult<AstNodeRange> {
     let start_row = get_int_field(vm, object, "lineno", name)?;
     let start_column = get_int_field(vm, object, "col_offset", name)?;
     let end_row = if end_required {
@@ -832,25 +795,34 @@ fn range_from_object_impl(
     }
 
     let location = PySourceRange {
-        start: PySourceLocation {
-            row: Row(if start_row_val > 0 {
+        start: SourceLocation {
+            line: if start_row_val > 0 {
                 OneIndexed::new(start_row_val as usize).unwrap_or(OneIndexed::MIN)
             } else {
                 OneIndexed::MIN
-            }),
-            column: Column(TextSize::new(start_col_val.max(0) as u32)),
+            },
+            character_offset: OneIndexed::from_zero_indexed(start_col_val.max(0) as usize),
         },
-        end: PySourceLocation {
-            row: Row(if end_row_val > 0 {
+        end: SourceLocation {
+            line: if end_row_val > 0 {
                 OneIndexed::new(end_row_val as usize).unwrap_or(OneIndexed::MIN)
             } else {
                 OneIndexed::MIN
-            }),
-            column: Column(TextSize::new(end_col_val.max(0) as u32)),
+            },
+            character_offset: OneIndexed::from_zero_indexed(end_col_val.max(0) as usize),
         },
     };
 
-    Ok(source_range_to_text_range(source_file, location))
+    source_file.register(
+        vm,
+        source_range_to_text_range(source_file, location),
+        Some(rustpython_compiler_core::SourceLocationRange {
+            line: start_row,
+            end_line: end_row,
+            col: start_column,
+            end_col: end_column,
+        }),
+    )
 }
 
 fn source_range_to_text_range(source_file: &SourceFile, location: PySourceRange) -> TextRange {
@@ -861,46 +833,33 @@ fn source_range_to_text_range(source_file: &SourceFile, location: PySourceRange)
         return TextRange::new(TextSize::new(0), TextSize::new(0));
     }
 
-    let start = index.offset(
-        location.start.to_source_location(),
-        source,
-        PositionEncoding::Utf8,
-    );
-    let end = index.offset(
-        location.end.to_source_location(),
-        source,
-        PositionEncoding::Utf8,
-    );
+    let start = index.offset(location.start, source, PositionEncoding::Utf8);
+    let end = index.offset(location.end, source, PositionEncoding::Utf8);
 
-    TextRange::new(start, end)
+    // Navigation is allowed to collapse normalized coordinates; semantic
+    // signed coordinates remain in AstSourceContext.
+    TextRange::new(start, end.max(start))
 }
 
-fn source_range_to_text_range_unvalidated(
-    source_file: &SourceFile,
-    location: PySourceRange,
-) -> TextRange {
-    let index = LineIndex::from_source_text(source_file.clone().source_text());
-    let source = &source_file.source_text();
-
-    if source.is_empty() {
-        return TextRange::new(TextSize::new(0), TextSize::new(0));
-    }
-
-    let start = index.offset(
-        location.start.to_source_location(),
-        source,
-        PositionEncoding::Utf8,
-    );
-    let end = index.offset(
-        location.end.to_source_location(),
-        source,
-        PositionEncoding::Utf8,
-    );
-
-    if start <= end {
-        TextRange::new(start, end)
+fn node_add_location_for_node(
+    dict: &Py<PyDict>,
+    range: TextRange,
+    vm: &VirtualMachine,
+    source_file: &AstSourceContext,
+    node_index: ast::NodeIndex,
+) {
+    if let Some(location) = source_file.location(node_index) {
+        for (field, value) in [
+            ("lineno", location.line),
+            ("end_lineno", location.end_line),
+            ("col_offset", location.col),
+            ("end_col_offset", location.end_col),
+        ] {
+            dict.set_item(field, vm.ctx.new_int(value).into(), vm)
+                .unwrap();
+        }
     } else {
-        TextRange::empty(start)
+        node_add_location(dict, range, vm, source_file);
     }
 }
 
@@ -908,22 +867,30 @@ fn node_add_location(
     dict: &Py<PyDict>,
     range: TextRange,
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
 ) {
     let range = text_range_to_source_range(source_file, range);
-    dict.set_item("lineno", vm.ctx.new_int(range.start.row.get()).into(), vm)
+    dict.set_item("lineno", vm.ctx.new_int(range.start.line.get()).into(), vm)
         .unwrap();
     dict.set_item(
         "col_offset",
-        vm.ctx.new_int(range.start.column.get()).into(),
+        vm.ctx
+            .new_int(range.start.character_offset.to_zero_indexed())
+            .into(),
+        vm,
+    )
+    .unwrap();
+    dict.set_item(
+        "end_lineno",
+        vm.ctx.new_int(range.end.line.get()).into(),
         vm,
     )
     .unwrap();
-    dict.set_item("end_lineno", vm.ctx.new_int(range.end.row.get()).into(), vm)
-        .unwrap();
     dict.set_item(
         "end_col_offset",
-        vm.ctx.new_int(range.end.column.get()).into(),
+        vm.ctx
+            .new_int(range.end.character_offset.to_zero_indexed())
+            .into(),
         vm,
     )
     .unwrap();
@@ -1024,11 +991,12 @@ fn type_comment_parse_error(
     ParseError {
         error: parser::ParseErrorType::OtherError(message.to_owned()),
         raw_location: range,
-        location: source_range.start.to_source_location(),
-        end_location: source_range.end.to_source_location(),
+        location: source_range.start,
+        end_location: source_range.end,
         source_path: source_file.name().to_owned(),
         is_unclosed_bracket: false,
         is_unclosed_string: false,
+        eof_token: None,
     }
     .into()
 }
@@ -1754,11 +1722,12 @@ fn ipython_escape_command_syntax_error(
         ParseError {
             error: parser::ParseErrorType::OtherError("invalid syntax".to_owned()),
             raw_location: range,
-            location: source_range.start.to_source_location(),
-            end_location: source_range.end.to_source_location(),
+            location: source_range.start,
+            end_location: source_range.end,
             source_path: source_file.name().to_owned(),
             is_unclosed_bracket: false,
             is_unclosed_string: false,
+            eof_token: None,
         }
         .into(),
     )
@@ -1788,7 +1757,7 @@ fn empty_arguments_object(vm: &VirtualMachine) -> PyObjectRef {
 
 #[cfg(feature = "parser")]
 #[allow(clippy::too_many_arguments)]
-pub(crate) fn parse(
+pub(crate) fn parse<E: From<CompileError>>(
     vm: &VirtualMachine,
     source: &str,
     filename: &str,
@@ -1800,12 +1769,13 @@ pub(crate) fn parse(
     interactive: bool,
     explicit_future_features: crate::bytecode::CodeFlags,
     dont_imply_dedent: bool,
-) -> Result<PyObjectRef, CompileError> {
+    mut emit_warning: impl FnMut(usize, char) -> Result<(), E>,
+) -> Result<PyObjectRef, E> {
     let source_file = SourceFileBuilder::new(filename.to_owned(), source.to_owned()).finish();
     let mut options = parser::ParseOptions::from(mode);
-    let target_version = target_version.unwrap_or(ast::PythonVersion::PY314);
+    let target_version = target_version.unwrap_or(ast::PythonVersion::PY315);
     if let Some(error) = feature_version_syntax_error(source, &source_file, target_version) {
-        return Err(error);
+        return Err(error.into());
     }
     options = options.with_target_version(target_version);
     let barry_source = rustpython_compiler::prepare_barry_as_flufl_source(
@@ -1815,38 +1785,45 @@ pub(crate) fn parse(
     );
     rustpython_compiler::pre_parse_source_error(&source_file)?;
     let parsed = parser::parse_unchecked(barry_source.source(), options);
+    if interactive
+        && let Some(error) =
+            rustpython_compiler::single_mode_multiple_statements_error(&source_file, &parsed)
+    {
+        return Err(error.into());
+    }
     let type_comment_source =
         type_comments.then(|| TypeCommentSource::new(source, parsed.tokens()));
     if let Some(lines) = &type_comment_source
         && let Some(error) = invalid_type_comment_syntax_error(&source_file, lines)
     {
-        return Err(error);
+        return Err(error.into());
     }
     if let Err(errors) = parsed.as_result() {
         let parse_error = errors[0].clone();
         if let Some(error) = barry_source.diagnostic(Some(&parse_error), &source_file) {
-            return Err(error);
+            return Err(error.into());
         }
         let range = text_range_to_source_range(&source_file, parse_error.location);
-        return Err(ParseError {
+        return Err(CompileError::from(ParseError {
             error: parse_error.error,
             raw_location: parse_error.location,
-            location: range.start.to_source_location(),
-            end_location: range.end.to_source_location(),
+            location: range.start,
+            end_location: range.end,
             source_path: source_file.name().to_owned(),
             is_unclosed_bracket: false,
             is_unclosed_string: false,
-        }
+            eof_token: None,
+        })
         .into());
     }
     if let Some(error) = barry_source.diagnostic(None, &source_file) {
-        return Err(error);
+        return Err(error.into());
     }
     if dont_imply_dedent
         && interactive
         && let Some(error) = rustpython_compiler::dont_imply_dedent_source_error(&source_file)
     {
-        return Err(error);
+        return Err(error.into());
     }
 
     if let Some(error) = parsed
@@ -1855,18 +1832,19 @@ pub(crate) fn parse(
         .find(|error| should_report_unsupported_syntax_error(error))
     {
         if let Some(error) = cpython_unsupported_syntax_error(error, source, &source_file) {
-            return Err(error);
+            return Err(error.into());
         }
         let range = text_range_to_source_range(&source_file, error.range());
-        return Err(ParseError {
+        return Err(CompileError::from(ParseError {
             error: parser::ParseErrorType::OtherError(error.to_string()),
             raw_location: error.range(),
-            location: range.start.to_source_location(),
-            end_location: range.end.to_source_location(),
+            location: range.start,
+            end_location: range.end,
             source_path: source_file.name().to_owned(),
             is_unclosed_bracket: false,
             is_unclosed_string: false,
-        }
+            eof_token: None,
+        })
         .into());
     }
 
@@ -1875,11 +1853,11 @@ pub(crate) fn parse(
         parsed.tokens(),
         vm.state.int_max_str_digits.load(),
     ) {
-        return Err(error);
+        return Err(error.into());
     }
 
     if let Some(error) = rustpython_compiler::leading_byte_order_mark_error(&source_file) {
-        return Err(error);
+        return Err(error.into());
     }
     let mut top = parsed.into_syntax();
     rustpython_compiler::too_deeply_nested_error(
@@ -1888,18 +1866,34 @@ pub(crate) fn parse(
         rustpython_compiler::CompileOpts::default().recursion_limit,
     )?;
     if let Some(error) = rustpython_compiler::unsupported_grammar_error(&top, &source_file) {
-        return Err(error);
+        return Err(error.into());
     }
     if let Some(error) = ipython_escape_command_syntax_error(&top, &source_file) {
-        return Err(error);
+        return Err(error.into());
     }
     if let Some(error) = feature_version_ast_syntax_error(&top, &source_file, target_version) {
-        return Err(error);
+        return Err(error.into());
+    }
+    #[cfg(feature = "codegen")]
+    let future_features = codegen::preprocess::checked_future_features(&top)
+        .map_err(|err| future_feature_compile_error(&source_file, err))?;
+    // Keep original literal spans: preprocessing can fold multiple source
+    // literals into one node, but each has its own lexical diagnostic.
+    match &top {
+        ast::Mod::Module(module) => {
+            string::emit_format_spec_warnings(&module.body, &[], &source_file, &mut emit_warning)?;
+        }
+        ast::Mod::Expression(expression) => {
+            string::emit_format_spec_warnings(
+                &[],
+                core::slice::from_ref(expression.body.as_ref()),
+                &source_file,
+                &mut emit_warning,
+            )?;
+        }
     }
     #[cfg(feature = "codegen")]
     {
-        let future_features = codegen::preprocess::checked_future_features(&top)
-            .map_err(|err| future_feature_compile_error(&source_file, err))?;
         let future_annotations = explicit_future_features
             .contains(crate::bytecode::CodeFlags::FUTURE_ANNOTATIONS)
             || future_features.contains(crate::bytecode::CodeFlags::FUTURE_ANNOTATIONS);
@@ -1935,7 +1929,8 @@ pub(crate) fn parse(
         }),
         ast::Mod::Expression(e) => Mod::Expression(e),
     };
-    let obj = top.ast_to_object(vm, &source_file);
+    let ast_context = AstSourceContext::new(source_file.clone());
+    let obj = top.ast_to_object(vm, &ast_context);
     if let Some(lines) = &type_comment_source
         && obj.class().is(pyast::NodeModModule::static_type())
     {
@@ -1963,14 +1958,16 @@ pub(crate) fn wrap_interactive(vm: &VirtualMachine, module_obj: &PyObject) -> Py
 }
 
 #[cfg(feature = "parser")]
-pub(crate) fn parse_func_type(
+pub(crate) fn parse_func_type<E: From<CompileError>>(
     vm: &VirtualMachine,
     source: &str,
     filename: &str,
     optimize: u8,
     target_version: Option<ast::PythonVersion>,
-) -> Result<PyObjectRef, CompileError> {
+    mut emit_warning: impl FnMut(usize, char) -> Result<(), E>,
+) -> Result<PyObjectRef, E> {
     let _ = optimize;
+    let leading_space = source.len() - source.trim_start().len();
     let source = source.trim();
     let invalid_func_type = || -> CompileError {
         ParseError {
@@ -1981,6 +1978,7 @@ pub(crate) fn parse_func_type(
             source_path: filename.to_owned(),
             is_unclosed_bracket: false,
             is_unclosed_string: false,
+            eof_token: None,
         }
         .into()
     };
@@ -2002,7 +2000,7 @@ pub(crate) fn parse_func_type(
     }
 
     let Some(split_at) = split_at else {
-        return Err(ParseError {
+        return Err(CompileError::from(ParseError {
             error: parser::ParseErrorType::OtherError("invalid func_type".to_owned()),
             raw_location: TextRange::default(),
             location: SourceLocation::default(),
@@ -2010,7 +2008,8 @@ pub(crate) fn parse_func_type(
             source_path: filename.to_owned(),
             is_unclosed_bracket: false,
             is_unclosed_string: false,
-        }
+            eof_token: None,
+        })
         .into());
     };
 
@@ -2020,18 +2019,19 @@ pub(crate) fn parse_func_type(
     let parse_expr = |expr_src: &str| -> Result<ast::Expr, CompileError> {
         let source_file = SourceFileBuilder::new(filename.to_owned(), expr_src.to_owned()).finish();
         let options = parser::ParseOptions::from(parser::Mode::Expression)
-            .with_target_version(target_version.unwrap_or(ast::PythonVersion::PY314));
+            .with_target_version(target_version.unwrap_or(ast::PythonVersion::PY315));
         let parsed = parser::parse(expr_src, options).map_err(|parse_error| {
             let range = text_range_to_source_range(&source_file, parse_error.location);
-            ParseError {
+            CompileError::from(ParseError {
                 error: parse_error.error,
                 raw_location: parse_error.location,
-                location: range.start.to_source_location(),
-                end_location: range.end.to_source_location(),
+                location: range.start,
+                end_location: range.end,
                 source_path: source_file.name().to_owned(),
                 is_unclosed_bracket: false,
                 is_unclosed_string: false,
-            }
+                eof_token: None,
+            })
         })?;
         let ast::Mod::Expression(expression) = parsed.into_syntax() else {
             unreachable!();
@@ -2040,36 +2040,40 @@ pub(crate) fn parse_func_type(
     };
 
     if !left.starts_with('(') || !left.ends_with(')') {
-        return Err(invalid_func_type());
+        return Err(invalid_func_type().into());
     }
     let inner = left[1..left.len() - 1].trim();
+    let inner_start = left.len() - 1 - left[1..left.len() - 1].trim_start().len();
+    const ARG_PREFIX: &str = "__rustpython_func_type__(";
+    let mut arg_source_file = None;
     let argtypes = if inner.is_empty() {
         Vec::new()
     } else {
         if inner.ends_with(',') {
-            return Err(invalid_func_type());
+            return Err(invalid_func_type().into());
         }
-        let call_source = format!("__rustpython_func_type__({inner})");
+        let call_source = format!("{ARG_PREFIX}{inner})");
         let source_file = SourceFileBuilder::new(filename.to_owned(), call_source.clone()).finish();
         let options = parser::ParseOptions::from(parser::Mode::Expression)
-            .with_target_version(target_version.unwrap_or(ast::PythonVersion::PY314));
+            .with_target_version(target_version.unwrap_or(ast::PythonVersion::PY315));
         let parsed = parser::parse(&call_source, options).map_err(|parse_error| {
             let range = text_range_to_source_range(&source_file, parse_error.location);
-            ParseError {
+            CompileError::from(ParseError {
                 error: parse_error.error,
                 raw_location: parse_error.location,
-                location: range.start.to_source_location(),
-                end_location: range.end.to_source_location(),
+                location: range.start,
+                end_location: range.end,
                 source_path: source_file.name().to_owned(),
                 is_unclosed_bracket: false,
                 is_unclosed_string: false,
-            }
+                eof_token: None,
+            })
         })?;
         let ast::Mod::Expression(expression) = parsed.into_syntax() else {
             unreachable!();
         };
         let ast::Expr::Call(call) = *expression.body else {
-            return Err(invalid_func_type());
+            return Err(invalid_func_type().into());
         };
         let mut args = Vec::new();
         let positional_len = call.arguments.args.len();
@@ -2078,7 +2082,7 @@ pub(crate) fn parse_func_type(
             match arg {
                 ast::Expr::Starred(starred) => {
                     if seen_star || index + 1 != positional_len {
-                        return Err(invalid_func_type());
+                        return Err(invalid_func_type().into());
                     }
                     seen_star = true;
                     args.push(*starred.value);
@@ -2089,23 +2093,39 @@ pub(crate) fn parse_func_type(
         let mut seen_kw_star = false;
         for keyword in call.arguments.keywords {
             if keyword.arg.is_some() || seen_kw_star {
-                return Err(invalid_func_type());
+                return Err(invalid_func_type().into());
             }
             seen_kw_star = true;
             args.push(keyword.value);
         }
+        arg_source_file = Some(source_file);
         args
     };
 
     let returns = parse_expr(right)?;
+    // Func-type nodes are parsed from separate fragments. Keep warning offsets
+    // in those fragments until the boundary, then map them to the original
+    // source without changing the AST's existing location representation.
+    if let Some(source_file) = arg_source_file {
+        string::emit_format_spec_warnings(&[], &argtypes, &source_file, &mut |offset, ch| {
+            emit_warning(leading_space + inner_start + offset - ARG_PREFIX.len(), ch)
+        })?;
+    }
+    let return_source_file = SourceFileBuilder::new(filename.to_owned(), right.to_owned()).finish();
+    string::emit_format_spec_warnings(
+        &[],
+        core::slice::from_ref(&returns),
+        &return_source_file,
+        &mut |offset, ch| emit_warning(leading_space + source.len() - right.len() + offset, ch),
+    )?;
 
     let func_type = ModFunctionType {
         argtypes: argtypes.into_boxed_slice(),
         returns,
         runtime_argtypes: None,
     };
-    let source_file = SourceFileBuilder::new("".to_owned(), source.to_owned()).finish();
-    Ok(func_type.ast_to_object(vm, &source_file))
+    let source_file = SourceFileBuilder::new(filename.to_owned(), source.to_owned()).finish();
+    Ok(func_type.ast_to_object(vm, &AstSourceContext::new(source_file)))
 }
 
 fn type_ignores_from_source(
@@ -2372,6 +2392,43 @@ fn number_to_complex(number: &ast::Number) -> Option<(f64, f64, bool)> {
     }
 }
 
+#[cfg(feature = "codegen")]
+fn ast_location_exception(
+    vm: &VirtualMachine,
+    error: rustpython_compiler_core::AstLocationError,
+) -> crate::builtins::PyBaseExceptionRef {
+    use rustpython_compiler_core::AstLocationError;
+    match error {
+        AstLocationError::ExhaustedNodeIdentities => {
+            vm.new_memory_error("too many AST location identities")
+        }
+        AstLocationError::ConflictingLocation => {
+            vm.new_system_error("conflicting AST location identity")
+        }
+        AstLocationError::CoordinateOverflow => {
+            vm.new_value_error("AST location coordinate overflow")
+        }
+    }
+}
+
+#[cfg(feature = "codegen")]
+pub(crate) fn codegen_exception(
+    vm: &VirtualMachine,
+    error: codegen::error::CodegenError,
+    source: Option<&str>,
+) -> crate::builtins::PyBaseExceptionRef {
+    match error.error {
+        codegen::error::CodegenErrorType::AstLocation(error) => {
+            return ast_location_exception(vm, error);
+        }
+        codegen::error::CodegenErrorType::MixedAstLocationProvenance => {
+            return vm.new_system_error("mixed AST location provenance");
+        }
+        _ => {}
+    }
+    vm.new_syntax_error(&error.into(), source)
+}
+
 #[cfg(feature = "codegen")]
 pub(crate) fn preprocess_ast_object(
     vm: &VirtualMachine,
@@ -2384,7 +2441,8 @@ pub(crate) fn preprocess_ast_object(
     let original_object = object.clone();
     let text = synthetic_source_from_ast_object(vm, &object)?;
     let source_file = SourceFileBuilder::new(filename.to_owned(), text).finish();
-    let ast = Node::ast_from_object(vm, &source_file, object)?;
+    let ast_context = AstSourceContext::new(source_file.clone());
+    let ast = Node::ast_from_object(vm, &ast_context, object)?;
     validate::validate_mod(vm, &ast)?;
     let syntax_check_only = !optimized_ast;
 
@@ -2397,12 +2455,17 @@ pub(crate) fn preprocess_ast_object(
                 })?;
             let future_annotations = explicit_future_annotations
                 || future_features.contains(crate::bytecode::CodeFlags::FUTURE_ANNOTATIONS);
-            codegen::preprocess::preprocess_mod(
-                &mut ast,
-                optimize,
-                future_annotations,
-                syntax_check_only,
-            );
+            ast_context
+                .preprocess_locations(|locations| {
+                    codegen::preprocess::preprocess_mod_with_locations(
+                        &mut ast,
+                        optimize,
+                        future_annotations,
+                        syntax_check_only,
+                        locations,
+                    )
+                })
+                .map_err(|error| ast_location_exception(vm, error))?;
             let ast::Mod::Module(processed_module) = ast else {
                 unreachable!();
             };
@@ -2418,22 +2481,32 @@ pub(crate) fn preprocess_ast_object(
             })?;
             let future_annotations = explicit_future_annotations
                 || future_features.contains(crate::bytecode::CodeFlags::FUTURE_ANNOTATIONS);
-            codegen::preprocess::preprocess_statements(
-                &mut interactive.body,
-                optimize,
-                future_annotations,
-                syntax_check_only,
-            );
+            ast_context
+                .preprocess_locations(|locations| {
+                    codegen::preprocess::preprocess_statements_with_locations(
+                        &mut interactive.body,
+                        optimize,
+                        future_annotations,
+                        syntax_check_only,
+                        locations,
+                    )
+                })
+                .map_err(|error| ast_location_exception(vm, error))?;
             Mod::Interactive(interactive)
         }
         Mod::Expression(expression) => {
             let mut ast = ast::Mod::Expression(expression);
-            codegen::preprocess::preprocess_mod(
-                &mut ast,
-                optimize,
-                explicit_future_annotations,
-                syntax_check_only,
-            );
+            ast_context
+                .preprocess_locations(|locations| {
+                    codegen::preprocess::preprocess_mod_with_locations(
+                        &mut ast,
+                        optimize,
+                        explicit_future_annotations,
+                        syntax_check_only,
+                        locations,
+                    )
+                })
+                .map_err(|error| ast_location_exception(vm, error))?;
             let ast::Mod::Expression(expression) = ast else {
                 unreachable!();
             };
@@ -2441,7 +2514,7 @@ pub(crate) fn preprocess_ast_object(
         }
         Mod::FunctionType(function_type) => Mod::FunctionType(function_type),
     };
-    let result = ast.ast_to_object(vm, &source_file);
+    let result = ast.ast_to_object(vm, &ast_context);
     copy_ast_passthrough_fields(vm, &original_object, &result)?;
     Ok(result)
 }
@@ -2450,6 +2523,7 @@ pub(crate) fn preprocess_ast_object(
 pub(crate) struct RustModFromObject {
     pub ast: ast::Mod,
     pub source_file: SourceFile,
+    pub locations: Option<rustpython_compiler_core::AstLocations>,
 }
 
 #[cfg(feature = "codegen")]
@@ -2467,7 +2541,8 @@ pub(crate) fn rust_mod_from_object(
     }
     let text = synthetic_source_from_ast_object(vm, &object)?;
     let source_file = SourceFileBuilder::new(filename.to_owned(), text).finish();
-    let ast = Node::ast_from_object(vm, &source_file, object)?;
+    let ast_context = AstSourceContext::new(source_file.clone());
+    let ast = Node::ast_from_object(vm, &ast_context, object)?;
     validate::validate_mod(vm, &ast)?;
     let ast = match ast {
         Mod::Module(m) => ast::Mod::Module(m.module),
@@ -2482,7 +2557,11 @@ pub(crate) fn rust_mod_from_object(
             return Err(vm.new_runtime_error("this compiler does not handle FunctionTypes"));
         }
     };
-    Ok(RustModFromObject { ast, source_file })
+    Ok(RustModFromObject {
+        ast,
+        source_file,
+        locations: ast_context.take_locations(),
+    })
 }
 
 #[cfg(feature = "codegen")]
@@ -2492,10 +2571,14 @@ pub(crate) fn compile(
     filename: &str,
     mode: crate::compiler::Mode,
     mut opts: codegen::CompileOpts,
+    module: Option<&Py<PyStr>>,
 ) -> PyResult {
+    #[cfg(not(feature = "parser"))]
+    let _ = module;
     let text = synthetic_source_from_ast_object(vm, &object)?;
     let source_file = SourceFileBuilder::new(filename.to_owned(), text.clone()).finish();
-    let ast = Node::ast_from_object(vm, &source_file, object)?;
+    let ast_context = AstSourceContext::new(source_file);
+    let ast = Node::ast_from_object(vm, &ast_context, object)?;
     validate::validate_mod(vm, &ast)?;
     let ast = match ast {
         Mod::Module(m) => ast::Mod::Module(m.module),
@@ -2513,6 +2596,11 @@ pub(crate) fn compile(
     opts.future_features |= codegen::preprocess::future_features(&ast);
     let source = text.clone();
     let source_file = SourceFileBuilder::new(filename, text).finish();
+    let input = codegen::compile::AstInput {
+        ast,
+        source_file,
+        locations: ast_context.take_locations(),
+    };
     #[cfg(feature = "parser")]
     let code = {
         let source_path = filename.to_owned();
@@ -2529,7 +2617,7 @@ pub(crate) fn compile(
                 message.into(),
                 fname,
                 location.line.get(),
-                None,
+                module.map(|module| module.to_owned().into()),
                 vm.ctx.none(),
                 None,
                 None,
@@ -2550,9 +2638,8 @@ pub(crate) fn compile(
                 marker
             })
         };
-        let result = codegen::compile::compile_top_with_syntax_warning_handler(
-            ast,
-            source_file,
+        let result = codegen::compile::compile_ast_with_syntax_warning_handler(
+            input,
             mode,
             opts,
             Some(&mut syntax_warning_handler),
@@ -2565,15 +2652,16 @@ pub(crate) fn compile(
         }
     };
     #[cfg(not(feature = "parser"))]
-    let code = codegen::compile::compile_top(ast, source_file, mode, opts);
-    let code = code.map_err(|err| vm.new_syntax_error(&err.into(), Some(source.as_str())))?;
+    let code = codegen::compile::compile_ast_with_syntax_warning_handler(input, mode, opts, None);
+    let code = code.map_err(|err| codegen_exception(vm, err, Some(source.as_str())))?;
     Ok(crate::builtins::PyCode::new_ref_from_bytecode(vm, code).into())
 }
 
 #[cfg(not(feature = "rustpython-codegen"))]
 pub(crate) fn validate_ast_object(vm: &VirtualMachine, object: PyObjectRef) -> PyResult<()> {
     let source_file = SourceFileBuilder::new("<ast>".to_owned(), "".to_owned()).finish();
-    let ast = Node::ast_from_object(vm, &source_file, object)?;
+    let ast_context = AstSourceContext::new(source_file.clone());
+    let ast = Node::ast_from_object(vm, &ast_context, object)?;
     validate::validate_mod(vm, &ast)?;
     Ok(())
 }
diff --git a/crates/vm/src/stdlib/_ast/argument.rs b/crates/vm/src/stdlib/_ast/argument.rs
index 0ea9725a168..47cc602e8f1 100644
--- a/crates/vm/src/stdlib/_ast/argument.rs
+++ b/crates/vm/src/stdlib/_ast/argument.rs
@@ -1,5 +1,5 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 pub(super) struct PositionalArguments {
     range: TextRange,
@@ -7,14 +7,14 @@ pub(super) struct PositionalArguments {
 }
 
 enum PositionalArgumentsKind {
-    Args(Box<[ast::Expr]>),
+    Args(thin_vec::ThinVec<ast::Expr>),
     RuntimeValues(Vec<Option<ast::Expr>>),
 }
 
 impl PositionalArguments {
     pub(super) fn ast_from_field(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: &PyObject,
         field: &'static str,
         typ: &str,
@@ -24,7 +24,7 @@ impl PositionalArguments {
         Ok(Self::from_values(TextRange::default(), values))
     }
 
-    fn from_args(range: TextRange, args: Box<[ast::Expr]>) -> Self {
+    fn from_args(range: TextRange, args: thin_vec::ThinVec<ast::Expr>) -> Self {
         Self {
             range,
             kind: PositionalArgumentsKind::Args(args),
@@ -42,14 +42,7 @@ impl PositionalArguments {
         if values.iter().any(Option::is_none) {
             Self::from_runtime_values(range, values)
         } else {
-            Self::from_args(
-                range,
-                values
-                    .into_iter()
-                    .flatten()
-                    .collect::<Vec<_>>()
-                    .into_boxed_slice(),
-            )
+            Self::from_args(range, values.into_iter().flatten().collect())
         }
     }
 
@@ -57,32 +50,33 @@ impl PositionalArguments {
         self.range
     }
 
-    fn into_args_and_runtime_values(self) -> (Box<[ast::Expr]>, Option<Vec<Option<ast::Expr>>>) {
+    fn into_args_and_runtime_values(
+        self,
+    ) -> (thin_vec::ThinVec<ast::Expr>, Option<Vec<Option<ast::Expr>>>) {
         match self.kind {
             PositionalArgumentsKind::Args(args) => (args, None),
-            PositionalArgumentsKind::RuntimeValues(values) => (
-                lower_runtime_expr_list(values.clone()).into_boxed_slice(),
-                Some(values),
-            ),
+            PositionalArgumentsKind::RuntimeValues(values) => {
+                (lower_runtime_expr_list(values.clone()).into(), Some(values))
+            }
         }
     }
 }
 
 impl Node for PositionalArguments {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self.kind {
-            PositionalArgumentsKind::Args(args) => BoxedSlice(args).ast_to_object(vm, source_file),
+            PositionalArgumentsKind::Args(args) => args.ast_to_object(vm, source_file),
             PositionalArgumentsKind::RuntimeValues(values) => values.ast_to_object(vm, source_file),
         }
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
-        let args: BoxedSlice<_> = Node::ast_from_object(vm, source_file, object)?;
-        Ok(Self::from_args(TextRange::default(), args.0))
+        let args: thin_vec::ThinVec<_> = Node::ast_from_object(vm, source_file, object)?;
+        Ok(Self::from_args(TextRange::default(), args))
     }
 }
 
@@ -94,7 +88,7 @@ pub(super) struct KeywordArguments {
 impl KeywordArguments {
     pub(super) fn ast_from_field(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: &PyObject,
         field: &'static str,
         typ: &str,
@@ -107,7 +101,7 @@ impl KeywordArguments {
 }
 
 impl Node for KeywordArguments {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self { keywords, range: _ } = self;
         // TODO: use range
         BoxedSlice(keywords).ast_to_object(vm, source_file)
@@ -115,7 +109,7 @@ impl Node for KeywordArguments {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let keywords: BoxedSlice<_> = Node::ast_from_object(vm, source_file, object)?;
@@ -137,7 +131,7 @@ pub(super) fn merge_function_call_arguments(
         node_index: Default::default(),
         range,
         args,
-        keywords: key_args.keywords.into(),
+        keywords: key_args.keywords.into_vec().into(),
         runtime_args,
         runtime_bases: None,
     }
@@ -173,7 +167,7 @@ pub(super) fn split_function_call_arguments(
     // debug_assert!(range.contains_range(keyword_arguments_range));
     let keyword_arguments = KeywordArguments {
         range: keyword_arguments_range,
-        keywords: keywords.into(),
+        keywords: keywords.into_iter().collect::<Vec<_>>().into_boxed_slice(),
     };
 
     (positional_arguments, keyword_arguments)
@@ -214,7 +208,7 @@ pub(super) fn split_class_def_args(
     // debug_assert!(range.contains_range(keyword_arguments_range));
     let keyword_arguments = KeywordArguments {
         range: keyword_arguments_range,
-        keywords: keywords.into(),
+        keywords: keywords.into_iter().collect::<Vec<_>>().into_boxed_slice(),
     };
 
     (Some(positional_arguments), Some(keyword_arguments))
@@ -231,7 +225,7 @@ pub(super) fn merge_class_def_args(
     let (args, runtime_bases) = if let Some(positional_arguments) = positional_arguments {
         positional_arguments.into_args_and_runtime_values()
     } else {
-        (vec![].into_boxed_slice(), None)
+        (thin_vec::ThinVec::new(), None)
     };
     let keywords = if let Some(keyword_arguments) = keyword_arguments {
         keyword_arguments.keywords
@@ -243,7 +237,7 @@ pub(super) fn merge_class_def_args(
         node_index: Default::default(),
         range: Default::default(), // TODO
         args,
-        keywords: keywords.into(),
+        keywords: keywords.into_vec().into(),
         runtime_args: None,
         runtime_bases,
     }))
diff --git a/crates/vm/src/stdlib/_ast/basic.rs b/crates/vm/src/stdlib/_ast/basic.rs
index e7143057b0d..13a31e4d4a7 100644
--- a/crates/vm/src/stdlib/_ast/basic.rs
+++ b/crates/vm/src/stdlib/_ast/basic.rs
@@ -1,17 +1,17 @@
+use super::AstSourceContext;
 use super::*;
 use crate::builtins::PyIntRef;
 use rustpython_codegen::compile::ruff_int_to_bigint;
-use rustpython_compiler_core::SourceFile;
 
 impl Node for ast::Identifier {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         let id = self.as_str();
         vm.ctx.intern_str(id).to_object()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if !object.class().is(vm.ctx.types.str_type) {
@@ -24,13 +24,13 @@ impl Node for ast::Identifier {
 }
 
 impl Node for ast::Int {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         vm.ctx.new_int(ruff_int_to_bigint(&self).unwrap()).into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let value: PyIntRef = object.try_into_value(vm)?;
@@ -40,13 +40,13 @@ impl Node for ast::Int {
 }
 
 impl Node for bool {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         vm.ctx.new_int(self as u8).into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         node_object_to_i32(vm, &object).map(|i| i != 0)
diff --git a/crates/vm/src/stdlib/_ast/constant.rs b/crates/vm/src/stdlib/_ast/constant.rs
index 61b25f97620..283b4e67367 100644
--- a/crates/vm/src/stdlib/_ast/constant.rs
+++ b/crates/vm/src/stdlib/_ast/constant.rs
@@ -3,10 +3,11 @@ use crate::builtins::{PyComplex, PyFrozenSet, PyTuple};
 use ast::str_prefix::StringLiteralPrefix;
 use rustpython_codegen::compile::ruff_int_to_bigint;
 use rustpython_common::wtf8::Wtf8Buf;
-use rustpython_compiler_core::{SourceFile, bytecode::ConstantData};
+use rustpython_compiler_core::bytecode::ConstantData;
 
 #[derive(Debug)]
 pub(super) struct Constant {
+    pub(super) node_index: ast::AtomicNodeIndex,
     pub(super) range: TextRange,
     pub(super) value: ConstantLiteral,
     kind: Option<Box<str>>,
@@ -21,6 +22,7 @@ impl Constant {
     ) -> Self {
         let value = value.into();
         Self {
+            node_index: ast::AtomicNodeIndex::NONE,
             range,
             value: ConstantLiteral::Str { value, prefix },
             kind: None,
@@ -30,6 +32,7 @@ impl Constant {
 
     pub(super) const fn new_int(value: ast::Int, range: TextRange) -> Self {
         Self {
+            node_index: ast::AtomicNodeIndex::NONE,
             range,
             value: ConstantLiteral::Int(value),
             kind: None,
@@ -39,6 +42,7 @@ impl Constant {
 
     pub(super) const fn new_float(value: f64, range: TextRange) -> Self {
         Self {
+            node_index: ast::AtomicNodeIndex::NONE,
             range,
             value: ConstantLiteral::Float(value),
             kind: None,
@@ -48,6 +52,7 @@ impl Constant {
 
     pub(super) const fn new_complex(real: f64, imag: f64, range: TextRange) -> Self {
         Self {
+            node_index: ast::AtomicNodeIndex::NONE,
             range,
             value: ConstantLiteral::Complex { real, imag },
             kind: None,
@@ -57,6 +62,7 @@ impl Constant {
 
     pub(super) const fn new_bytes(value: Box<[u8]>, range: TextRange) -> Self {
         Self {
+            node_index: ast::AtomicNodeIndex::NONE,
             range,
             value: ConstantLiteral::Bytes(value),
             kind: None,
@@ -66,6 +72,7 @@ impl Constant {
 
     pub(super) const fn new_bool(value: bool, range: TextRange) -> Self {
         Self {
+            node_index: ast::AtomicNodeIndex::NONE,
             range,
             value: ConstantLiteral::Bool(value),
             kind: None,
@@ -75,6 +82,7 @@ impl Constant {
 
     pub(super) const fn new_none(range: TextRange) -> Self {
         Self {
+            node_index: ast::AtomicNodeIndex::NONE,
             range,
             value: ConstantLiteral::None,
             kind: None,
@@ -84,6 +92,7 @@ impl Constant {
 
     pub(super) const fn new_ellipsis(range: TextRange) -> Self {
         Self {
+            node_index: ast::AtomicNodeIndex::NONE,
             range,
             value: ConstantLiteral::Ellipsis,
             kind: None,
@@ -93,13 +102,14 @@ impl Constant {
 
     pub(crate) fn into_expr(self) -> ast::Expr {
         let Self {
+            node_index,
             range,
             value,
             kind,
             invalid_type,
         } = self;
         ast::Expr::Constant(ast::ExprConstant {
-            node_index: Default::default(),
+            node_index,
             range,
             value: constant_data_to_ast_constant_value(constant_literal_to_constant_data(&value)),
             kind: kind.or_else(|| constant_literal_kind(&value)),
@@ -152,11 +162,11 @@ pub(super) fn runtime_string_object(
 
 pub(super) fn expr_constant_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     expr: ast::ExprConstant,
 ) -> PyObjectRef {
     let ast::ExprConstant {
-        node_index: _,
+        node_index,
         range,
         value,
         kind,
@@ -171,7 +181,7 @@ pub(super) fn expr_constant_to_object(
         .unwrap();
     let kind = kind.map_or_else(|| vm.ctx.none(), |kind| vm.ctx.new_str(kind).into());
     dict.set_item("kind", kind, vm).unwrap();
-    node_add_location(&dict, range, vm, source_file);
+    node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
     node.into()
 }
 
@@ -306,7 +316,7 @@ pub(super) fn ast_constant_value_to_constant_data(value: ast::ConstantValue) ->
 
 pub(super) fn constant_object_to_constant_data(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     value_object: PyObjectRef,
 ) -> PyResult<ConstantData> {
     let value = ConstantLiteral::ast_from_object(vm, source_file, value_object)?;
@@ -442,9 +452,9 @@ fn constant_data_to_object(vm: &VirtualMachine, constant: ConstantData) -> PyObj
 // constructor
 pub(super) fn constant_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<Constant> {
     let value_object = get_node_field(vm, object, "value", "Constant")?;
     let (value, invalid_type) =
@@ -465,7 +475,8 @@ pub(super) fn constant_from_object_with_range(
         .transpose()?;
 
     Ok(Constant {
-        range,
+        node_index: range.node_index(),
+        range: range.range,
         value,
         kind,
         invalid_type,
@@ -473,8 +484,9 @@ pub(super) fn constant_from_object_with_range(
 }
 
 impl Node for Constant {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
+            node_index,
             range,
             value,
             kind,
@@ -490,13 +502,13 @@ impl Node for Constant {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("value", value, vm).unwrap();
         dict.set_item("kind", kind, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Constant")?;
@@ -505,7 +517,7 @@ impl Node for Constant {
 }
 
 impl Node for ConstantLiteral {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::None => vm.ctx.none(),
             Self::Bool(value) => vm.ctx.new_bool(value).to_pyobject(vm),
@@ -536,7 +548,7 @@ impl Node for ConstantLiteral {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         value_object: PyObjectRef,
     ) -> PyResult<Self> {
         let cls = value_object.class();
@@ -626,30 +638,31 @@ impl Node for ConstantLiteral {
 
 pub(super) fn number_literal_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     constant: ast::ExprNumberLiteral,
 ) -> PyObjectRef {
     let ast::ExprNumberLiteral {
-        node_index: _,
+        node_index,
         range,
         value,
         ..
     } = constant;
-    let c = match value {
+    let mut c = match value {
         ast::Number::Int(n) => Constant::new_int(n, range),
         ast::Number::Float(n) => Constant::new_float(n, range),
         ast::Number::Complex { real, imag } => Constant::new_complex(real, imag, range),
     };
+    c.node_index = node_index;
     c.ast_to_object(vm, source_file)
 }
 
 pub(super) fn string_literal_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     constant: ast::ExprStringLiteral,
 ) -> PyObjectRef {
     let ast::ExprStringLiteral {
-        node_index: _,
+        node_index,
         range,
         value,
         ..
@@ -659,65 +672,66 @@ pub(super) fn string_literal_to_object(
         .next()
         .map_or(StringLiteralPrefix::Empty, |part| part.flags.prefix());
     let value = rustpython_codegen::string_literal_value(source_file, &value);
-    let c = Constant::new_str(value, prefix, range);
+    let mut c = Constant::new_str(value, prefix, range);
+    c.node_index = node_index;
     c.ast_to_object(vm, source_file)
 }
 
 pub(super) fn bytes_literal_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     constant: ast::ExprBytesLiteral,
 ) -> PyObjectRef {
     let ast::ExprBytesLiteral {
-        node_index: _,
+        node_index,
         range,
         value,
         ..
     } = constant;
     let bytes = value.as_slice().iter().flat_map(|b| b.value.iter());
-    let c = Constant::new_bytes(bytes.copied().collect(), range);
+    let mut c = Constant::new_bytes(bytes.copied().collect(), range);
+    c.node_index = node_index;
     c.ast_to_object(vm, source_file)
 }
 
 pub(super) fn boolean_literal_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     constant: ast::ExprBooleanLiteral,
 ) -> PyObjectRef {
     let ast::ExprBooleanLiteral {
-        node_index: _,
+        node_index,
         range,
         value,
         ..
     } = constant;
-    let c = Constant::new_bool(value, range);
+    let mut c = Constant::new_bool(value, range);
+    c.node_index = node_index;
     c.ast_to_object(vm, source_file)
 }
 
 pub(super) fn none_literal_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     constant: ast::ExprNoneLiteral,
 ) -> PyObjectRef {
     let ast::ExprNoneLiteral {
-        node_index: _,
-        range,
-        ..
+        node_index, range, ..
     } = constant;
-    let c = Constant::new_none(range);
+    let mut c = Constant::new_none(range);
+    c.node_index = node_index;
     c.ast_to_object(vm, source_file)
 }
 
 pub(super) fn ellipsis_literal_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     constant: ast::ExprEllipsisLiteral,
 ) -> PyObjectRef {
     let ast::ExprEllipsisLiteral {
-        node_index: _,
-        range,
-        ..
+        node_index, range, ..
     } = constant;
-    let c = Constant::new_ellipsis(range);
+    let mut c = Constant::new_ellipsis(range);
+    c.node_index = node_index;
     c.ast_to_object(vm, source_file)
 }
diff --git a/crates/vm/src/stdlib/_ast/elif_else_clause.rs b/crates/vm/src/stdlib/_ast/elif_else_clause.rs
index ca8187bf32f..0ac33c58351 100644
--- a/crates/vm/src/stdlib/_ast/elif_else_clause.rs
+++ b/crates/vm/src/stdlib/_ast/elif_else_clause.rs
@@ -1,14 +1,14 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 pub(super) fn ast_to_object(
     clause: ast::ElifElseClause,
     mut rest: alloc::vec::IntoIter<ast::ElifElseClause>,
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
 ) -> PyObjectRef {
     let ast::ElifElseClause {
-        node_index: _,
+        node_index,
         range,
         test,
         body,
@@ -57,15 +57,15 @@ pub(super) fn ast_to_object(
     };
     dict.set_item("orelse", orelse, vm).unwrap();
 
-    node_add_location(&dict, range, vm, source_file);
+    node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
     node.into()
 }
 
 pub(super) fn ast_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtIf> {
     let test = get_required_node_field(vm, source_file, object, "test", "If")?;
     let body: Vec<Option<ast::Stmt>> = get_node_list_field(vm, source_file, object, "body", "If")?;
@@ -81,7 +81,7 @@ pub(super) fn ast_from_object_with_range(
     } else if let [ast::Stmt::If(_)] = &*orelse {
         let Some(ast::Stmt::If(ast::StmtIf {
             node_index,
-            range,
+            range: nested_range,
             test,
             body,
             mut elif_else_clauses,
@@ -95,7 +95,7 @@ pub(super) fn ast_from_object_with_range(
             0,
             ast::ElifElseClause {
                 node_index,
-                range,
+                range: nested_range,
                 test: Some(*test),
                 body,
                 runtime_body,
@@ -105,8 +105,8 @@ pub(super) fn ast_from_object_with_range(
         elif_else_clauses
     } else {
         vec![ast::ElifElseClause {
-            node_index: Default::default(),
-            range,
+            node_index: range.node_index(),
+            range: range.range,
             test: None,
             body: orelse,
             runtime_body: runtime_orelse,
@@ -115,11 +115,11 @@ pub(super) fn ast_from_object_with_range(
     };
 
     Ok(ast::StmtIf {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         test,
         body,
         elif_else_clauses,
-        range,
+        range: range.range,
         runtime_body,
     })
 }
diff --git a/crates/vm/src/stdlib/_ast/exception.rs b/crates/vm/src/stdlib/_ast/exception.rs
index 4f179513d59..6f9f992a768 100644
--- a/crates/vm/src/stdlib/_ast/exception.rs
+++ b/crates/vm/src/stdlib/_ast/exception.rs
@@ -1,5 +1,5 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 fn ensure_excepthandler_node(vm: &VirtualMachine, object: &PyObject) -> PyResult<()> {
     if vm.is_none(object)
@@ -19,14 +19,14 @@ fn ensure_excepthandler_node(vm: &VirtualMachine, object: &PyObject) -> PyResult
 
 // sum
 impl Node for ast::ExceptHandler {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::ExceptHandler(cons) => cons.ast_to_object(vm, source_file),
         }
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         ensure_excepthandler_node(vm, &object)?;
@@ -43,15 +43,15 @@ impl Node for ast::ExceptHandler {
 // constructor
 fn except_handler_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExceptHandlerExceptHandler> {
     let body: Vec<Option<ast::Stmt>> =
         get_node_list_field(vm, source_file, object, "body", "ExceptHandler")?;
     let (runtime_body, body) = runtime_stmt_list_from_values(body);
     Ok(ast::ExceptHandlerExceptHandler {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         type_: get_node_field_opt(vm, object, "type")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
@@ -59,14 +59,14 @@ fn except_handler_from_object_with_range(
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
         body,
-        range,
+        range: range.range,
         runtime_body,
     })
 }
 
 pub(super) fn except_handler_from_object_unvalidated_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
 ) -> PyResult<ast::ExceptHandler> {
     ensure_excepthandler_node(vm, object)?;
@@ -77,9 +77,9 @@ pub(super) fn except_handler_from_object_unvalidated_range(
 }
 
 impl Node for ast::ExceptHandlerExceptHandler {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             type_,
             name,
             body,
@@ -102,13 +102,13 @@ impl Node for ast::ExceptHandlerExceptHandler {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("body", body, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "ExceptHandler")?;
diff --git a/crates/vm/src/stdlib/_ast/expression.rs b/crates/vm/src/stdlib/_ast/expression.rs
index 6d5e21302fe..3aa2e6fdaef 100644
--- a/crates/vm/src/stdlib/_ast/expression.rs
+++ b/crates/vm/src/stdlib/_ast/expression.rs
@@ -1,13 +1,13 @@
+use super::AstSourceContext;
 use super::*;
 use crate::stdlib::_ast::argument::{
     KeywordArguments, PositionalArguments, merge_function_call_arguments,
     split_function_call_arguments,
 };
-use rustpython_compiler_core::SourceFile;
 
 // sum
 impl Node for ast::Expr {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::BoolOp(cons) => cons.ast_to_object(vm, source_file),
             Self::Name(cons) => cons.ast_to_object(vm, source_file),
@@ -54,7 +54,7 @@ impl Node for ast::Expr {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if vm.is_none(&object) {
@@ -159,7 +159,7 @@ impl Node for ast::Expr {
             )));
         };
         let range = expr_range_from_object(vm, source_file, &object)?;
-        Ok(match kind {
+        let expression = match kind {
             ExprKind::BoolOp => Self::BoolOp(expr_bool_op_from_object_with_range(
                 vm,
                 source_file,
@@ -335,37 +335,39 @@ impl Node for ast::Expr {
                 &object,
                 range,
             )?),
-        })
+        };
+        ast::HasNodeIndex::node_index(&expression).set(range.index);
+        Ok(expression)
     }
 }
 
 // constructor
 fn expr_bool_op_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprBoolOp> {
     let values: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "values", "BoolOp")?;
     let (runtime_values, values) = runtime_expr_list_from_values(values);
     Ok(ast::ExprBoolOp {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         op: Node::ast_from_object(
             vm,
             source_file,
             get_node_field_required(vm, object, "op", "BoolOp")?,
         )?,
         values,
-        range,
+        range: range.range,
         runtime_values,
     })
 }
 
 impl Node for ast::ExprBoolOp {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             op,
             values,
             range,
@@ -382,13 +384,13 @@ impl Node for ast::ExprBoolOp {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("values", values, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "BoolOp")?;
@@ -399,22 +401,22 @@ impl Node for ast::ExprBoolOp {
 // constructor
 fn expr_named_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprNamed> {
     Ok(ast::ExprNamed {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         target: get_required_node_field(vm, source_file, object, "target", "NamedExpr")?,
         value: get_required_node_field(vm, source_file, object, "value", "NamedExpr")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprNamed {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             target,
             value,
             range,
@@ -427,13 +429,13 @@ impl Node for ast::ExprNamed {
             .unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "NamedExpr")?;
@@ -444,12 +446,12 @@ impl Node for ast::ExprNamed {
 // constructor
 fn expr_bin_op_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprBinOp> {
     Ok(ast::ExprBinOp {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         left: get_required_node_field(vm, source_file, object, "left", "BinOp")?,
         op: Node::ast_from_object(
             vm,
@@ -457,14 +459,14 @@ fn expr_bin_op_from_object_with_range(
             get_node_field_required(vm, object, "op", "BinOp")?,
         )?,
         right: get_required_node_field(vm, source_file, object, "right", "BinOp")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprBinOp {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             left,
             op,
             right,
@@ -480,13 +482,13 @@ impl Node for ast::ExprBinOp {
             .unwrap();
         dict.set_item("right", right.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "BinOp")?;
@@ -497,26 +499,26 @@ impl Node for ast::ExprBinOp {
 // constructor
 fn expr_unary_op_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprUnaryOp> {
     Ok(ast::ExprUnaryOp {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         op: Node::ast_from_object(
             vm,
             source_file,
             get_node_field_required(vm, object, "op", "UnaryOp")?,
         )?,
         operand: get_required_node_field(vm, source_file, object, "operand", "UnaryOp")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprUnaryOp {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             op,
             operand,
             range,
@@ -529,12 +531,12 @@ impl Node for ast::ExprUnaryOp {
             .unwrap();
         dict.set_item("operand", operand.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "UnaryOp")?;
@@ -545,26 +547,26 @@ impl Node for ast::ExprUnaryOp {
 // constructor
 fn expr_lambda_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprLambda> {
     Ok(ast::ExprLambda {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         parameters: Node::ast_from_object(
             vm,
             source_file,
             get_node_field_required(vm, object, "args", "Lambda")?,
         )?,
         body: get_required_node_field(vm, source_file, object, "body", "Lambda")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprLambda {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             parameters,
             body,
             range: _range,
@@ -580,13 +582,13 @@ impl Node for ast::ExprLambda {
         dict.set_item("args", args, vm).unwrap();
         dict.set_item("body", body.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Lambda")?;
@@ -597,23 +599,23 @@ impl Node for ast::ExprLambda {
 // constructor
 fn expr_if_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprIf> {
     Ok(ast::ExprIf {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         test: get_required_node_field(vm, source_file, object, "test", "IfExp")?,
         body: get_required_node_field(vm, source_file, object, "body", "IfExp")?,
         orelse: get_required_node_field(vm, source_file, object, "orelse", "IfExp")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprIf {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             test,
             body,
             orelse,
@@ -629,13 +631,13 @@ impl Node for ast::ExprIf {
             .unwrap();
         dict.set_item("orelse", orelse.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "IfExp")?;
@@ -646,9 +648,9 @@ impl Node for ast::ExprIf {
 // constructor
 fn expr_dict_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprDict> {
     let keys: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "keys", "Dict")?;
@@ -664,17 +666,17 @@ fn expr_dict_from_object_with_range(
         .map(|(key, value)| ast::DictItem { key, value })
         .collect();
     Ok(ast::ExprDict {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         items,
-        range,
+        range: range.range,
         runtime_values,
     })
 }
 
 impl Node for ast::ExprDict {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             items,
             range,
             runtime_values,
@@ -698,13 +700,13 @@ impl Node for ast::ExprDict {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("values", values, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Dict")?;
@@ -715,24 +717,24 @@ impl Node for ast::ExprDict {
 // constructor
 fn expr_set_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprSet> {
     let elts: Vec<Option<ast::Expr>> = get_node_list_field(vm, source_file, object, "elts", "Set")?;
     let (runtime_elts, elts) = runtime_expr_list_from_values(elts);
     Ok(ast::ExprSet {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         elts,
-        range,
+        range: range.range,
         runtime_elts,
     })
 }
 
 impl Node for ast::ExprSet {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             elts,
             range,
             runtime_elts,
@@ -746,12 +748,12 @@ impl Node for ast::ExprSet {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("elts", elts, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Set")?;
@@ -762,22 +764,22 @@ impl Node for ast::ExprSet {
 // constructor
 fn expr_list_comp_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprListComp> {
     Ok(ast::ExprListComp {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         elt: get_required_node_field(vm, source_file, object, "elt", "ListComp")?,
         generators: get_node_list_field(vm, source_file, object, "generators", "ListComp")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprListComp {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             elt,
             generators,
             range,
@@ -790,13 +792,13 @@ impl Node for ast::ExprListComp {
             .unwrap();
         dict.set_item("generators", generators.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "ListComp")?;
@@ -807,22 +809,22 @@ impl Node for ast::ExprListComp {
 // constructor
 fn expr_set_comp_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprSetComp> {
     Ok(ast::ExprSetComp {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         elt: get_required_node_field(vm, source_file, object, "elt", "SetComp")?,
         generators: get_node_list_field(vm, source_file, object, "generators", "SetComp")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprSetComp {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             elt,
             generators,
             range,
@@ -835,13 +837,13 @@ impl Node for ast::ExprSetComp {
             .unwrap();
         dict.set_item("generators", generators.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "SetComp")?;
@@ -852,12 +854,12 @@ impl Node for ast::ExprSetComp {
 // constructor
 fn expr_dict_comp_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprDictComp> {
     Ok(ast::ExprDictComp {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         key: Some(get_required_node_field(
             vm,
             source_file,
@@ -866,15 +868,16 @@ fn expr_dict_comp_from_object_with_range(
             "DictComp",
         )?),
         value: get_required_node_field(vm, source_file, object, "value", "DictComp")?,
-        generators: get_node_list_field(vm, source_file, object, "generators", "DictComp")?,
-        range,
+        generators: get_node_list_field(vm, source_file, object, "generators", "DictComp")?
+            .into_boxed_slice(),
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprDictComp {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             key,
             value,
             generators,
@@ -888,15 +891,19 @@ impl Node for ast::ExprDictComp {
             .unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        dict.set_item("generators", generators.ast_to_object(vm, source_file), vm)
-            .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        dict.set_item(
+            "generators",
+            BoxedSlice(generators).ast_to_object(vm, source_file),
+            vm,
+        )
+        .unwrap();
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "DictComp")?;
@@ -907,23 +914,23 @@ impl Node for ast::ExprDictComp {
 // constructor
 fn expr_generator_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprGenerator> {
     Ok(ast::ExprGenerator {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         elt: get_required_node_field(vm, source_file, object, "elt", "GeneratorExp")?,
         generators: get_node_list_field(vm, source_file, object, "generators", "GeneratorExp")?,
-        range,
+        range: range.range,
         parenthesized: true,
     })
 }
 
 impl Node for ast::ExprGenerator {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             elt,
             generators,
             range,
@@ -937,13 +944,13 @@ impl Node for ast::ExprGenerator {
             .unwrap();
         dict.set_item("generators", generators.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "GeneratorExp")?;
@@ -954,21 +961,21 @@ impl Node for ast::ExprGenerator {
 // constructor
 fn expr_await_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprAwait> {
     Ok(ast::ExprAwait {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_required_node_field(vm, source_file, object, "value", "Await")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprAwait {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             range,
         } = self;
@@ -978,12 +985,12 @@ impl Node for ast::ExprAwait {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Await")?;
@@ -994,23 +1001,23 @@ impl Node for ast::ExprAwait {
 // constructor
 fn expr_yield_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprYield> {
     Ok(ast::ExprYield {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_node_field_opt(vm, object, "value")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprYield {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             range,
         } = self;
@@ -1020,13 +1027,13 @@ impl Node for ast::ExprYield {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Yield")?;
@@ -1037,21 +1044,21 @@ impl Node for ast::ExprYield {
 // constructor
 fn expr_yield_from_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprYieldFrom> {
     Ok(ast::ExprYieldFrom {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_required_node_field(vm, source_file, object, "value", "YieldFrom")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprYieldFrom {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             range,
         } = self;
@@ -1061,13 +1068,13 @@ impl Node for ast::ExprYieldFrom {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "YieldFrom")?;
@@ -1078,30 +1085,32 @@ impl Node for ast::ExprYieldFrom {
 // constructor
 fn expr_compare_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprCompare> {
+    let left: ast::Expr = get_required_node_field(vm, source_file, object, "left", "Compare")?;
     let comparators: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "comparators", "Compare")?;
     let (runtime_comparators, comparators) = runtime_expr_boxed_slice_from_values(comparators);
+    let mut operands = Vec::with_capacity(comparators.len() + 1);
+    operands.push(left);
+    operands.extend(comparators);
     Ok(ast::ExprCompare {
-        node_index: Default::default(),
-        left: get_required_node_field(vm, source_file, object, "left", "Compare")?,
+        node_index: range.node_index(),
         ops: get_node_boxed_slice_field(vm, source_file, object, "ops", "Compare")?,
-        comparators,
-        range,
+        operands: operands.into_boxed_slice(),
+        range: range.range,
         runtime_comparators,
     })
 }
 
 impl Node for ast::ExprCompare {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
-            left,
+            node_index,
             ops,
-            comparators,
+            operands,
             range,
             runtime_comparators,
         } = self;
@@ -1109,22 +1118,25 @@ impl Node for ast::ExprCompare {
             .into_ref_with_type(vm, pyast::NodeExprCompare::static_type().to_owned())
             .unwrap();
         let dict = node.as_object().dict().unwrap();
+        let mut operands = operands.into_vec().into_iter();
+        let left = operands.next().expect("A comparison has a left operand");
         dict.set_item("left", left.ast_to_object(vm, source_file), vm)
             .unwrap();
         dict.set_item("ops", BoxedSlice(ops).ast_to_object(vm, source_file), vm)
             .unwrap();
+        let comparators: Box<[ast::Expr]> = operands.collect();
         let comparators = runtime_comparators.map_or_else(
             || BoxedSlice(comparators).ast_to_object(vm, source_file),
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("comparators", comparators, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Compare")?;
@@ -1135,17 +1147,17 @@ impl Node for ast::ExprCompare {
 // constructor
 fn expr_call_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprCall> {
     let mut arguments = merge_function_call_arguments(
         PositionalArguments::ast_from_field(vm, source_file, object, "args", "Call")?,
         KeywordArguments::ast_from_field(vm, source_file, object, "keywords", "Call")?,
     );
-    arguments.range = range;
+    arguments.range = range.range;
     Ok(ast::ExprCall {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         func: get_required_node_field(vm, source_file, object, "func", "Call")?,
         arguments,
         range_start: range.start(),
@@ -1153,10 +1165,10 @@ fn expr_call_from_object_with_range(
 }
 
 impl Node for ast::ExprCall {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let range = self.range();
         let Self {
-            node_index: _,
+            node_index,
             func,
             arguments,
             range_start: _,
@@ -1180,13 +1192,13 @@ impl Node for ast::ExprCall {
             vm,
         )
         .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Call")?;
@@ -1197,12 +1209,12 @@ impl Node for ast::ExprCall {
 // constructor
 fn expr_attribute_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprAttribute> {
     Ok(ast::ExprAttribute {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_required_node_field(vm, source_file, object, "value", "Attribute")?,
         attr: get_required_identifier_field(vm, source_file, object, "attr", "Attribute")?,
         ctx: Node::ast_from_object(
@@ -1210,14 +1222,14 @@ fn expr_attribute_from_object_with_range(
             source_file,
             get_node_field_required(vm, object, "ctx", "Attribute")?,
         )?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprAttribute {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             attr,
             ctx,
@@ -1233,13 +1245,13 @@ impl Node for ast::ExprAttribute {
             .unwrap();
         dict.set_item("ctx", ctx.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Attribute")?;
@@ -1250,12 +1262,12 @@ impl Node for ast::ExprAttribute {
 // constructor
 fn expr_subscript_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprSubscript> {
     Ok(ast::ExprSubscript {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_required_node_field(vm, source_file, object, "value", "Subscript")?,
         slice: get_required_node_field(vm, source_file, object, "slice", "Subscript")?,
         ctx: Node::ast_from_object(
@@ -1263,14 +1275,14 @@ fn expr_subscript_from_object_with_range(
             source_file,
             get_node_field_required(vm, object, "ctx", "Subscript")?,
         )?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprSubscript {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             slice,
             ctx,
@@ -1286,12 +1298,12 @@ impl Node for ast::ExprSubscript {
             .unwrap();
         dict.set_item("ctx", ctx.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Subscript")?;
@@ -1302,26 +1314,26 @@ impl Node for ast::ExprSubscript {
 // constructor
 fn expr_starred_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprStarred> {
     Ok(ast::ExprStarred {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_required_node_field(vm, source_file, object, "value", "Starred")?,
         ctx: Node::ast_from_object(
             vm,
             source_file,
             get_node_field_required(vm, object, "ctx", "Starred")?,
         )?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprStarred {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             ctx,
             range,
@@ -1334,12 +1346,12 @@ impl Node for ast::ExprStarred {
             .unwrap();
         dict.set_item("ctx", ctx.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Starred")?;
@@ -1350,26 +1362,26 @@ impl Node for ast::ExprStarred {
 // constructor
 fn expr_name_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprName> {
     Ok(ast::ExprName {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         id: get_required_identifier_field(vm, source_file, object, "id", "Name")?,
         ctx: Node::ast_from_object(
             vm,
             source_file,
             get_node_field_required(vm, object, "ctx", "Name")?,
         )?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprName {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             id,
             ctx,
             range,
@@ -1382,13 +1394,13 @@ impl Node for ast::ExprName {
             .unwrap();
         dict.set_item("ctx", ctx.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Name")?;
@@ -1399,30 +1411,30 @@ impl Node for ast::ExprName {
 // constructor
 fn expr_list_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprList> {
     let elts: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "elts", "List")?;
     let (runtime_elts, elts) = runtime_expr_list_from_values(elts);
     Ok(ast::ExprList {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         elts,
         ctx: Node::ast_from_object(
             vm,
             source_file,
             get_node_field_required(vm, object, "ctx", "List")?,
         )?,
-        range,
+        range: range.range,
         runtime_elts,
     })
 }
 
 impl Node for ast::ExprList {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             elts,
             ctx,
             range,
@@ -1439,13 +1451,13 @@ impl Node for ast::ExprList {
         dict.set_item("elts", elts, vm).unwrap();
         dict.set_item("ctx", ctx.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "List")?;
@@ -1456,31 +1468,31 @@ impl Node for ast::ExprList {
 // constructor
 fn expr_tuple_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprTuple> {
     let elts: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "elts", "Tuple")?;
     let (runtime_elts, elts) = runtime_expr_list_from_values(elts);
     Ok(ast::ExprTuple {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         elts,
         ctx: Node::ast_from_object(
             vm,
             source_file,
             get_node_field_required(vm, object, "ctx", "Tuple")?,
         )?,
-        range,
+        range: range.range,
         parenthesized: true,
         runtime_elts,
     })
 }
 
 impl Node for ast::ExprTuple {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             elts,
             ctx,
             range: _range,
@@ -1498,13 +1510,13 @@ impl Node for ast::ExprTuple {
         dict.set_item("elts", elts, vm).unwrap();
         dict.set_item("ctx", ctx.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Tuple")?;
@@ -1515,12 +1527,12 @@ impl Node for ast::ExprTuple {
 // constructor
 fn expr_slice_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::ExprSlice> {
     Ok(ast::ExprSlice {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         lower: get_node_field_opt(vm, object, "lower")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
@@ -1530,14 +1542,14 @@ fn expr_slice_from_object_with_range(
         step: get_node_field_opt(vm, object, "step")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::ExprSlice {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             lower,
             upper,
             step,
@@ -1553,13 +1565,13 @@ impl Node for ast::ExprSlice {
             .unwrap();
         dict.set_item("step", step.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Slice")?;
@@ -1569,7 +1581,7 @@ impl Node for ast::ExprSlice {
 
 // sum
 impl Node for ast::ExprContext {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         let node_type = match self {
             Self::Load => pyast::NodeExprContextLoad::static_type(),
             Self::Store => pyast::NodeExprContextStore::static_type(),
@@ -1583,7 +1595,7 @@ impl Node for ast::ExprContext {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(
@@ -1605,7 +1617,7 @@ impl Node for ast::ExprContext {
 
 // product
 impl Node for ast::Comprehension {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             node_index: _,
             target,
@@ -1639,7 +1651,7 @@ impl Node for ast::Comprehension {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let ifs: Vec<Option<ast::Expr>> =
diff --git a/crates/vm/src/stdlib/_ast/module.rs b/crates/vm/src/stdlib/_ast/module.rs
index 37a6bc62849..f487f0040a7 100644
--- a/crates/vm/src/stdlib/_ast/module.rs
+++ b/crates/vm/src/stdlib/_ast/module.rs
@@ -1,6 +1,6 @@
+use super::AstSourceContext;
 use super::*;
 use crate::stdlib::_ast::type_ignore::TypeIgnore;
-use rustpython_compiler_core::SourceFile;
 
 /// Represents the different types of Python module structures.
 ///
@@ -26,7 +26,7 @@ pub(super) enum Mod {
 
 // sum
 impl Node for Mod {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::Module(cons) => cons.ast_to_object(vm, source_file),
             Self::Interactive(cons) => cons.ast_to_object(vm, source_file),
@@ -37,7 +37,7 @@ impl Node for Mod {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(
@@ -74,7 +74,7 @@ pub(super) struct ModModule {
 
 // constructor
 impl Node for ModModule {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             module,
             type_ignores,
@@ -105,7 +105,7 @@ impl Node for ModModule {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let body: Vec<Option<ast::Stmt>> =
@@ -132,7 +132,7 @@ pub(super) struct ModInteractive {
 
 // constructor
 impl Node for ModInteractive {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             body,
             range: _,
@@ -152,7 +152,7 @@ impl Node for ModInteractive {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let body: Vec<Option<ast::Stmt>> =
@@ -168,7 +168,7 @@ impl Node for ModInteractive {
 
 // constructor
 impl Node for ast::ModExpression {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             node_index: _,
             body,
@@ -185,7 +185,7 @@ impl Node for ast::ModExpression {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(Self {
@@ -204,7 +204,7 @@ pub(super) struct ModFunctionType {
 
 // constructor
 impl Node for ModFunctionType {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             argtypes,
             returns,
@@ -226,7 +226,7 @@ impl Node for ModFunctionType {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let argtypes: Vec<Option<ast::Expr>> =
diff --git a/crates/vm/src/stdlib/_ast/node.rs b/crates/vm/src/stdlib/_ast/node.rs
index 7737ae076bb..6d0ae239c1b 100644
--- a/crates/vm/src/stdlib/_ast/node.rs
+++ b/crates/vm/src/stdlib/_ast/node.rs
@@ -1,12 +1,12 @@
+use super::AstSourceContext;
 use crate::{PyObjectRef, PyResult, VirtualMachine, builtins::PyList};
-use rustpython_compiler_core::SourceFile;
 use thin_vec::ThinVec;
 
 pub(crate) trait Node: Sized {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef;
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef;
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self>;
 
@@ -17,7 +17,7 @@ pub(crate) trait Node: Sized {
 }
 
 impl<T: Node> Node for Vec<T> {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         vm.ctx
             .new_list(
                 self.into_iter()
@@ -29,7 +29,7 @@ impl<T: Node> Node for Vec<T> {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let list = object.downcast_ref::<PyList>().ok_or_else(|| {
@@ -50,7 +50,7 @@ impl<T: Node> Node for Vec<T> {
                 }
                 items[i].clone()
             };
-            result.push(vm.with_recursion("while traversing AST node", || {
+            result.push(vm.with_recursion(" while traversing AST node", || {
                 Node::ast_from_object(vm, source_file, item)
             })?);
             if list.borrow_vec().len() != len {
@@ -62,7 +62,7 @@ impl<T: Node> Node for Vec<T> {
 }
 
 impl<T: Node> Node for ThinVec<T> {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         vm.ctx
             .new_list(
                 self.into_iter()
@@ -74,7 +74,7 @@ impl<T: Node> Node for ThinVec<T> {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Vec::<T>::ast_from_object(vm, source_file, object).map(Into::into)
@@ -82,16 +82,16 @@ impl<T: Node> Node for ThinVec<T> {
 }
 
 impl<T: Node> Node for Box<T> {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         (*self).ast_to_object(vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
-        vm.with_recursion("while traversing AST node", || {
+        vm.with_recursion(" while traversing AST node", || {
             T::ast_from_object(vm, source_file, object).map(Self::new)
         })
     }
@@ -102,7 +102,7 @@ impl<T: Node> Node for Box<T> {
 }
 
 impl<T: Node> Node for Option<T> {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Some(node) => node.ast_to_object(vm, source_file),
             None => vm.ctx.none(),
@@ -111,7 +111,7 @@ impl<T: Node> Node for Option<T> {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if vm.is_none(&object) {
@@ -126,13 +126,13 @@ impl<T: Node> Node for Option<T> {
 pub(super) struct BoxedSlice<T>(pub(super) Box<[T]>);
 
 impl<T: Node> Node for BoxedSlice<T> {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         self.0.into_vec().ast_to_object(vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(Self(
diff --git a/crates/vm/src/stdlib/_ast/operator.rs b/crates/vm/src/stdlib/_ast/operator.rs
index e05e490bb84..71d8c621769 100644
--- a/crates/vm/src/stdlib/_ast/operator.rs
+++ b/crates/vm/src/stdlib/_ast/operator.rs
@@ -1,9 +1,9 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 // sum
 impl Node for ast::BoolOp {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         let node_type = match self {
             Self::And => pyast::NodeBoolOpAnd::static_type(),
             Self::Or => pyast::NodeBoolOpOr::static_type(),
@@ -13,7 +13,7 @@ impl Node for ast::BoolOp {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(
@@ -33,7 +33,7 @@ impl Node for ast::BoolOp {
 
 // sum
 impl Node for ast::Operator {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         let node_type = match self {
             Self::Add => pyast::NodeOperatorAdd::static_type(),
             Self::Sub => pyast::NodeOperatorSub::static_type(),
@@ -54,7 +54,7 @@ impl Node for ast::Operator {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(
@@ -96,7 +96,7 @@ impl Node for ast::Operator {
 
 // sum
 impl Node for ast::UnaryOp {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         let node_type = match self {
             Self::Invert => pyast::NodeUnaryOpInvert::static_type(),
             Self::Not => pyast::NodeUnaryOpNot::static_type(),
@@ -108,7 +108,7 @@ impl Node for ast::UnaryOp {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(
@@ -132,7 +132,7 @@ impl Node for ast::UnaryOp {
 
 // sum
 impl Node for ast::CmpOp {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         let node_type = match self {
             Self::Eq => pyast::NodeCmpOpEq::static_type(),
             Self::NotEq => pyast::NodeCmpOpNotEq::static_type(),
@@ -150,7 +150,7 @@ impl Node for ast::CmpOp {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(
diff --git a/crates/vm/src/stdlib/_ast/other.rs b/crates/vm/src/stdlib/_ast/other.rs
index 0da6be10c46..3bf7564236a 100644
--- a/crates/vm/src/stdlib/_ast/other.rs
+++ b/crates/vm/src/stdlib/_ast/other.rs
@@ -1,14 +1,14 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 impl Node for ast::ConversionFlag {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         vm.ctx.new_int(self as i8).into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         match node_object_to_i32(vm, &object)? {
@@ -23,13 +23,13 @@ impl Node for ast::ConversionFlag {
 
 // /// This is just a string, not strictly an AST node. But it makes AST conversions easier.
 impl Node for ast::name::Name {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         vm.ctx.intern_str(self.as_str()).to_object()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if !object.class().is(vm.ctx.types.str_type) {
@@ -43,13 +43,13 @@ impl Node for ast::name::Name {
 }
 
 impl Node for ast::Decorator {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         ast::Expr::ast_to_object(self.expression, vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let expression = ast::Expr::ast_from_object(vm, source_file, object)?;
@@ -64,9 +64,9 @@ impl Node for ast::Decorator {
 
 // product
 impl Node for ast::Alias {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             asname,
             range: _range,
@@ -79,29 +79,32 @@ impl Node for ast::Alias {
             .unwrap();
         dict.set_item("asname", asname.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
+        let name = get_required_identifier_field(vm, source_file, &object, "name", "alias")?;
+        let asname = get_node_field_opt(vm, &object, "asname")?
+            .map(|obj| Node::ast_from_object(vm, source_file, obj))
+            .transpose()?;
+        let range = range_from_object(vm, source_file, &object, "alias")?;
         Ok(Self {
-            node_index: Default::default(),
-            name: get_required_identifier_field(vm, source_file, &object, "name", "alias")?,
-            asname: get_node_field_opt(vm, &object, "asname")?
-                .map(|obj| Node::ast_from_object(vm, source_file, obj))
-                .transpose()?,
-            range: range_from_object(vm, source_file, &object, "alias")?,
+            node_index: range.node_index(),
+            name,
+            asname,
+            range: range.range,
         })
     }
 }
 
 // product
 impl Node for ast::WithItem {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             node_index: _,
             context_expr,
@@ -129,7 +132,7 @@ impl Node for ast::WithItem {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(Self {
diff --git a/crates/vm/src/stdlib/_ast/parameter.rs b/crates/vm/src/stdlib/_ast/parameter.rs
index ea324eda48c..b156d11fe35 100644
--- a/crates/vm/src/stdlib/_ast/parameter.rs
+++ b/crates/vm/src/stdlib/_ast/parameter.rs
@@ -1,9 +1,9 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 // product
 impl Node for ast::Parameters {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             node_index: _,
             posonlyargs,
@@ -56,7 +56,7 @@ impl Node for ast::Parameters {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let posonlyargs = PositionalParameters::ast_from_field(
@@ -151,9 +151,9 @@ fn validate_parameter_annotations(
 
 // product
 impl Node for ast::Parameter {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             annotation,
             // type_comment,
@@ -180,13 +180,13 @@ impl Node for ast::Parameter {
         )
         .unwrap_or_else(|| vm.ctx.none());
         dict.set_item("type_comment", type_comment, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let name = get_required_identifier_field(vm, source_file, &_object, "arg", "arg")?;
@@ -200,10 +200,10 @@ impl Node for ast::Parameter {
             });
         let range = range_from_object(vm, source_file, &_object, "arg")?;
         Ok(Self {
-            node_index: Default::default(),
+            node_index: range.node_index(),
             name,
             annotation,
-            range,
+            range: range.range,
             runtime_type_comment,
             runtime_type_comment_bytes,
         })
@@ -212,9 +212,9 @@ impl Node for ast::Parameter {
 
 // product
 impl Node for ast::Keyword {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             arg,
             value,
             range: _range,
@@ -227,21 +227,24 @@ impl Node for ast::Keyword {
             .unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
+        let arg = get_node_field_opt(vm, &_object, "arg")?
+            .map(|obj| Node::ast_from_object(vm, source_file, obj))
+            .transpose()?;
+        let value = get_required_node_field(vm, source_file, &_object, "value", "keyword")?;
+        let range = range_from_object(vm, source_file, &_object, "keyword")?;
         Ok(Self {
-            node_index: Default::default(),
-            arg: get_node_field_opt(vm, &_object, "arg")?
-                .map(|obj| Node::ast_from_object(vm, source_file, obj))
-                .transpose()?,
-            value: get_required_node_field(vm, source_file, &_object, "value", "keyword")?,
-            range: range_from_object(vm, source_file, &_object, "keyword")?,
+            node_index: range.node_index(),
+            arg,
+            value,
+            range: range.range,
         })
     }
 }
@@ -254,7 +257,7 @@ struct PositionalParameters {
 impl PositionalParameters {
     fn ast_from_field(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: &PyObject,
         field: &'static str,
         typ: &str,
@@ -267,13 +270,13 @@ impl PositionalParameters {
 }
 
 impl Node for PositionalParameters {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         BoxedSlice(self.args).ast_to_object(vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let args: BoxedSlice<_> = Node::ast_from_object(vm, source_file, object)?;
@@ -292,7 +295,7 @@ struct KeywordParameters {
 impl KeywordParameters {
     fn ast_from_field(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: &PyObject,
         field: &'static str,
         typ: &str,
@@ -305,13 +308,13 @@ impl KeywordParameters {
 }
 
 impl Node for KeywordParameters {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         BoxedSlice(self.keywords).ast_to_object(vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let keywords: BoxedSlice<_> = Node::ast_from_object(vm, source_file, object)?;
@@ -331,7 +334,7 @@ struct ParameterDefaults {
 impl ParameterDefaults {
     fn ast_from_field(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: &PyObject,
         field: &'static str,
         typ: &str,
@@ -345,7 +348,7 @@ impl ParameterDefaults {
 
     fn ast_from_field_preserve_none(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: &PyObject,
         field: &'static str,
         typ: &str,
@@ -367,13 +370,13 @@ impl ParameterDefaults {
 }
 
 impl Node for ParameterDefaults {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         BoxedSlice(self.defaults).ast_to_object(vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let defaults: BoxedSlice<_> = Node::ast_from_object(vm, source_file, object)?;
diff --git a/crates/vm/src/stdlib/_ast/pattern.rs b/crates/vm/src/stdlib/_ast/pattern.rs
index 667bb5fcf45..f8170da6939 100644
--- a/crates/vm/src/stdlib/_ast/pattern.rs
+++ b/crates/vm/src/stdlib/_ast/pattern.rs
@@ -1,9 +1,9 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 // product
 impl Node for ast::MatchCase {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             node_index: _,
             pattern,
@@ -30,7 +30,7 @@ impl Node for ast::MatchCase {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let body: Vec<Option<ast::Stmt>> =
@@ -51,7 +51,7 @@ impl Node for ast::MatchCase {
 
 // sum
 impl Node for ast::Pattern {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::MatchValue(cons) => cons.ast_to_object(vm, source_file),
             Self::MatchSingleton(cons) => cons.ast_to_object(vm, source_file),
@@ -65,7 +65,7 @@ impl Node for ast::Pattern {
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if vm.is_none(&object) {
@@ -188,7 +188,7 @@ type PatternListField = (RuntimePatternList, Vec<ast::Pattern>);
 
 fn pattern_list_from_field(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
     field: &'static str,
     typ: &str,
@@ -203,21 +203,21 @@ fn pattern_list_from_field(
 // constructor
 fn pattern_match_value_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::PatternMatchValue> {
     Ok(ast::PatternMatchValue {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_required_node_field(vm, source_file, object, "value", "MatchValue")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::PatternMatchValue {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             range,
         } = self;
@@ -227,13 +227,13 @@ impl Node for ast::PatternMatchValue {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "MatchValue")?;
@@ -244,25 +244,25 @@ impl Node for ast::PatternMatchValue {
 // constructor
 fn pattern_match_singleton_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::PatternMatchSingleton> {
     Ok(ast::PatternMatchSingleton {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: Node::ast_from_object(
             vm,
             source_file,
             get_node_field(vm, object, "value", "MatchSingleton")?,
         )?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::PatternMatchSingleton {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             range,
         } = self;
@@ -275,13 +275,13 @@ impl Node for ast::PatternMatchSingleton {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "MatchSingleton")?;
@@ -290,7 +290,7 @@ impl Node for ast::PatternMatchSingleton {
 }
 
 impl Node for ast::Singleton {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::None => vm.ctx.none(),
             Self::True => vm.ctx.new_bool(true).into(),
@@ -300,7 +300,7 @@ impl Node for ast::Singleton {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if vm.is_none(&object) {
@@ -318,24 +318,30 @@ impl Node for ast::Singleton {
 // constructor
 fn pattern_match_sequence_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::PatternMatchSequence> {
-    let (runtime_patterns, patterns) =
-        pattern_list_from_field(vm, source_file, object, "patterns", "MatchSequence", range)?;
+    let (runtime_patterns, patterns) = pattern_list_from_field(
+        vm,
+        source_file,
+        object,
+        "patterns",
+        "MatchSequence",
+        range.range,
+    )?;
     Ok(ast::PatternMatchSequence {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         patterns: patterns.to_vec(),
-        range,
+        range: range.range,
         runtime_patterns,
     })
 }
 
 impl Node for ast::PatternMatchSequence {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             patterns,
             range,
             runtime_patterns,
@@ -352,13 +358,13 @@ impl Node for ast::PatternMatchSequence {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("patterns", patterns, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "MatchSequence")?;
@@ -369,9 +375,9 @@ impl Node for ast::PatternMatchSequence {
 // constructor
 fn pattern_match_mapping_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::PatternMatchMapping> {
     let keys: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "keys", "MatchMapping")?;
@@ -383,22 +389,22 @@ fn pattern_match_mapping_from_object_with_range(
         .any(Option::is_none)
         .then(|| patterns.clone());
     Ok(ast::PatternMatchMapping {
-        node_index: Default::default(),
-        keys: lower_nullable_exprs(&keys, range).into(),
-        patterns: lower_nullable_patterns(&patterns, range).into(),
+        node_index: range.node_index(),
+        keys: lower_nullable_exprs(&keys, range.range).into(),
+        patterns: lower_nullable_patterns(&patterns, range.range).into(),
         rest: get_node_field_opt(vm, object, "rest")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
         runtime_keys,
         runtime_patterns,
     })
 }
 
 impl Node for ast::PatternMatchMapping {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             keys,
             patterns,
             rest,
@@ -422,13 +428,13 @@ impl Node for ast::PatternMatchMapping {
         dict.set_item("patterns", patterns, vm).unwrap();
         dict.set_item("rest", rest.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "MatchMapping")?;
@@ -439,9 +445,9 @@ impl Node for ast::PatternMatchMapping {
 // constructor
 fn pattern_match_class_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::PatternMatchClass> {
     let cls = get_required_node_field(vm, source_file, object, "cls", "MatchClass")?;
     let patterns: Vec<Option<ast::Pattern>> =
@@ -461,17 +467,17 @@ fn pattern_match_class_from_object_with_range(
     let runtime_patterns = has_runtime_shape.then(|| patterns.clone());
     let runtime_kwd_attrs = has_runtime_shape.then(|| kwd_attrs.0.clone());
     let runtime_kwd_patterns = has_runtime_shape.then(|| kwd_patterns.clone());
-    let patterns = PatternMatchClassPatterns(lower_nullable_patterns(&patterns, range));
+    let patterns = PatternMatchClassPatterns(lower_nullable_patterns(&patterns, range.range));
     let kwd_patterns =
-        PatternMatchClassKeywordPatterns(lower_nullable_patterns(&kwd_patterns, range));
+        PatternMatchClassKeywordPatterns(lower_nullable_patterns(&kwd_patterns, range.range));
     let (patterns, keywords) = merge_pattern_match_class(patterns, kwd_attrs, kwd_patterns);
 
     Ok(ast::PatternMatchClass {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         cls,
-        range,
+        range: range.range,
         arguments: ast::PatternArguments {
-            node_index: Default::default(),
+            node_index: range.node_index(),
             range: Default::default(),
             patterns: patterns.into(),
             keywords,
@@ -483,9 +489,9 @@ fn pattern_match_class_from_object_with_range(
 }
 
 impl Node for ast::PatternMatchClass {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             cls,
             arguments,
             range,
@@ -519,13 +525,13 @@ impl Node for ast::PatternMatchClass {
         dict.set_item("patterns", patterns, vm).unwrap();
         dict.set_item("kwd_attrs", kwd_attrs, vm).unwrap();
         dict.set_item("kwd_patterns", kwd_patterns, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "MatchClass")?;
@@ -536,13 +542,13 @@ impl Node for ast::PatternMatchClass {
 struct PatternMatchClassPatterns(Vec<ast::Pattern>);
 
 impl Node for PatternMatchClassPatterns {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         self.0.ast_to_object(vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(Self(Node::ast_from_object(vm, source_file, object)?))
@@ -554,7 +560,7 @@ struct PatternMatchClassKeywordAttributes(Vec<ast::Identifier>);
 impl PatternMatchClassKeywordAttributes {
     fn ast_from_field(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: &PyObject,
         field: &'static str,
         typ: &str,
@@ -570,13 +576,13 @@ impl PatternMatchClassKeywordAttributes {
 }
 
 impl Node for PatternMatchClassKeywordAttributes {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         self.0.ast_to_object(vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(Self(Node::ast_from_object(vm, source_file, object)?))
@@ -586,13 +592,13 @@ impl Node for PatternMatchClassKeywordAttributes {
 struct PatternMatchClassKeywordPatterns(Vec<ast::Pattern>);
 
 impl Node for PatternMatchClassKeywordPatterns {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         self.0.ast_to_object(vm, source_file)
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(Self(Node::ast_from_object(vm, source_file, object)?))
@@ -601,23 +607,23 @@ impl Node for PatternMatchClassKeywordPatterns {
 // constructor
 fn pattern_match_star_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::PatternMatchStar> {
     Ok(ast::PatternMatchStar {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         name: get_node_field_opt(vm, object, "name")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::PatternMatchStar {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             range,
         } = self;
@@ -627,13 +633,13 @@ impl Node for ast::PatternMatchStar {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("name", name.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "MatchStar")?;
@@ -644,26 +650,26 @@ impl Node for ast::PatternMatchStar {
 // constructor
 fn pattern_match_as_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::PatternMatchAs> {
     Ok(ast::PatternMatchAs {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         pattern: get_node_field_opt(vm, object, "pattern")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
         name: get_node_field_opt(vm, object, "name")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::PatternMatchAs {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             pattern,
             name,
             range,
@@ -676,13 +682,13 @@ impl Node for ast::PatternMatchAs {
             .unwrap();
         dict.set_item("name", name.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "MatchAs")?;
@@ -693,24 +699,24 @@ impl Node for ast::PatternMatchAs {
 // constructor
 fn pattern_match_or_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::PatternMatchOr> {
     let (runtime_patterns, patterns) =
-        pattern_list_from_field(vm, source_file, object, "patterns", "MatchOr", range)?;
+        pattern_list_from_field(vm, source_file, object, "patterns", "MatchOr", range.range)?;
     Ok(ast::PatternMatchOr {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         patterns: patterns.to_vec(),
-        range,
+        range: range.range,
         runtime_patterns,
     })
 }
 
 impl Node for ast::PatternMatchOr {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             patterns,
             range,
             runtime_patterns,
@@ -724,12 +730,12 @@ impl Node for ast::PatternMatchOr {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("patterns", patterns, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "MatchOr")?;
diff --git a/crates/vm/src/stdlib/_ast/pyast.rs b/crates/vm/src/stdlib/_ast/pyast.rs
index 46bf0918d15..20e0940fb0e 100644
--- a/crates/vm/src/stdlib/_ast/pyast.rs
+++ b/crates/vm/src/stdlib/_ast/pyast.rs
@@ -351,14 +351,14 @@ impl_node!(
 impl_node!(
     #[pyclass(module = "ast", name = "Import", base = NodeStmt)]
     pub(crate) struct NodeStmtImport,
-    fields: ["names"],
+    fields: ["names", "is_lazy"],
     attributes: ["lineno", "col_offset", "end_lineno", "end_col_offset"],
 );
 
 impl_node!(
     #[pyclass(module = "ast", name = "ImportFrom", base = NodeStmt)]
     pub(crate) struct NodeStmtImportFrom,
-    fields: ["module", "names", "level"],
+    fields: ["module", "names", "level", "is_lazy"],
     attributes: ["lineno", "col_offset", "end_lineno", "end_col_offset"],
 );
 
@@ -1209,13 +1209,20 @@ const FIELD_TYPES: &[(&str, &[(&str, FieldType)])] = &[
             ("msg", FieldType::Optional("expr")),
         ],
     ),
-    ("Import", &[("names", FieldType::ListOf("alias"))]),
+    (
+        "Import",
+        &[
+            ("names", FieldType::ListOf("alias")),
+            ("is_lazy", FieldType::OptionalBuiltin("int")),
+        ],
+    ),
     (
         "ImportFrom",
         &[
             ("module", FieldType::OptionalBuiltin("str")),
             ("names", FieldType::ListOf("alias")),
             ("level", FieldType::OptionalBuiltin("int")),
+            ("is_lazy", FieldType::OptionalBuiltin("int")),
         ],
     ),
     ("Global", &[("names", FieldType::ListOfBuiltin("str"))]),
diff --git a/crates/vm/src/stdlib/_ast/python.rs b/crates/vm/src/stdlib/_ast/python.rs
index cb9027aeb99..6e4d8df4099 100644
--- a/crates/vm/src/stdlib/_ast/python.rs
+++ b/crates/vm/src/stdlib/_ast/python.rs
@@ -154,22 +154,6 @@ pub(crate) mod _ast {
         Ok(contained)
     }
 
-    fn ast_replace_set_difference_update(
-        expecting: &Py<PySet>,
-        iterable: Option<&PyObject>,
-        vm: &VirtualMachine,
-    ) -> PyResult<()> {
-        let Some(iterable) = iterable else {
-            return Ok(());
-        };
-        let iterable = iterable.to_owned().try_into_value::<ArgIterable>(vm)?;
-        for item in iterable.iter(vm)? {
-            let item = item?;
-            ast_replace_set_discard(expecting, &item, vm)?;
-        }
-        Ok(())
-    }
-
     fn ast_set_attr(
         obj: &PyObject,
         name: &PyObject,
@@ -193,57 +177,6 @@ pub(crate) mod _ast {
         let attributes = cls.get_attr(vm.ctx.intern_str("_attributes"));
         let dict = zelf.as_object().dict();
 
-        let expecting = PySet::default().into_ref(&vm.ctx);
-        ast_replace_set_update(&expecting, fields.as_deref(), vm)?;
-        ast_replace_set_update(&expecting, attributes.as_deref(), vm)?;
-
-        for (key, _value) in &args.kwargs {
-            let key_obj: PyObjectRef = vm.ctx.new_str(key.as_ref()).into();
-            if !ast_replace_set_discard(&expecting, &key_obj, vm)? {
-                return Err(vm.new_type_error(format!(
-                    "{}.__replace__ got an unexpected keyword argument '{}'.",
-                    cls.name(),
-                    key
-                )));
-            }
-        }
-
-        if let Some(dict) = dict.as_deref() {
-            for (key, _value) in dict.items_vec() {
-                ast_replace_set_discard(&expecting, &key, vm)?;
-            }
-            ast_replace_set_difference_update(&expecting, attributes.as_deref(), vm)?;
-        }
-
-        // Discard optional fields (T | None).
-        if let Some(field_types) = cls.get_attr(vm.ctx.intern_str("_field_types"))
-            && let Ok(field_types) = field_types.downcast::<crate::builtins::PyDict>()
-        {
-            for (key, value) in field_types.items_vec() {
-                if value.fast_isinstance(vm.ctx.types.union_type) {
-                    ast_replace_set_discard(&expecting, &key, vm)?;
-                }
-            }
-        }
-
-        let remaining = expecting.elements();
-        if !remaining.is_empty() {
-            let mut names = Vec::with_capacity(remaining.len());
-            for name in &remaining {
-                names.push(name.repr(vm)?.to_string());
-            }
-            names.sort();
-            let missing = names.join(", ");
-            let count = names.len();
-            return Err(vm.new_type_error(format!(
-                "{}.__replace__ missing {} keyword argument{}: {}.",
-                cls.name(),
-                count,
-                if count == 1 { "" } else { "s" },
-                missing
-            )));
-        }
-
         let payload = vm.ctx.new_dict();
         if let Some(dict) = dict {
             ast_replace_update_payload(&payload, fields.as_deref(), &dict, vm)?;
@@ -309,10 +242,58 @@ pub(crate) mod _ast {
         Ok(vm.ctx.new_str(repr))
     }
 
+    fn abstract_types() -> [&'static Py<PyType>; 13] {
+        [
+            NodeAst::static_type(),
+            super::super::pyast::NodeMod::static_type(),
+            super::super::pyast::NodeStmt::static_type(),
+            super::super::pyast::NodeExpr::static_type(),
+            super::super::pyast::NodeExprContext::static_type(),
+            super::super::pyast::NodeBoolOp::static_type(),
+            super::super::pyast::NodeOperator::static_type(),
+            super::super::pyast::NodeUnaryOp::static_type(),
+            super::super::pyast::NodeCmpOp::static_type(),
+            super::super::pyast::NodeExceptHandler::static_type(),
+            super::super::pyast::NodePattern::static_type(),
+            super::super::pyast::NodeTypeIgnore::static_type(),
+            super::super::pyast::NodeTypeParam::static_type(),
+        ]
+    }
+
+    #[pyfunction]
+    fn _is_abstract(cls: PyObjectRef, vm: &VirtualMachine) -> PyResult<bool> {
+        is_abstract(&cls, vm)
+    }
+
+    fn is_abstract(cls: &PyObject, vm: &VirtualMachine) -> PyResult<bool> {
+        // PySet_Contains rejects mutable sets and preserves comparison errors;
+        // Python-level set containment has different behavior for both cases.
+        let hash = match cls.hash(vm) {
+            Ok(hash) => hash,
+            Err(err) if err.class().is(vm.ctx.exceptions.type_error) => {
+                return Err(vm.new_type_error(format!(
+                    "cannot use '{}' as a set element ({})",
+                    cls.class().fully_qualified_name(vm)?,
+                    err.as_object().str(vm)?
+                )));
+            }
+            Err(err) => return Err(err),
+        };
+        for typ in abstract_types() {
+            let typ = typ.as_object();
+            if typ.hash(vm)? == hash
+                && typ.rich_compare_bool(cls, crate::types::PyComparisonOp::Eq, vm)?
+            {
+                return Ok(true);
+            }
+        }
+        Ok(false)
+    }
+
     impl Constructor for NodeAst {
         type Args = FuncArgs;
 
-        fn slot_new(cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
+        fn slot_new(cls: PyTypeRef, _args: FuncArgs, vm: &VirtualMachine) -> PyResult {
             // Keep _instance for parser-internal shared operator/context nodes,
             // but match CPython's public constructor behavior by allocating a
             // fresh object for Python-level ast.Load()/ast.Add()/... calls.
@@ -330,10 +311,6 @@ pub(crate) mod _ast {
             };
             let zelf = vm.ctx.new_base_object(cls, dict);
 
-            // type.__call__ does not invoke slot_init after slot_new
-            // for types with a custom slot_new, so we must call it here.
-            Self::slot_init(&zelf, args, vm)?;
-
             Ok(zelf)
         }
 
@@ -346,6 +323,21 @@ pub(crate) mod _ast {
         type Args = FuncArgs;
 
         fn slot_init(zelf: &PyObject, args: FuncArgs, vm: &VirtualMachine) -> PyResult<()> {
+            if is_abstract(zelf.class().as_object(), vm)? {
+                let message = vm.ctx.new_str(format!(
+                    "Instantiating abstract AST node class {} is deprecated. \
+This will become an error in Python 3.20",
+                    zelf.class().fully_qualified_name(vm)?
+                ));
+                warn::warn(
+                    message.into(),
+                    Some(vm.ctx.exceptions.deprecation_warning.to_owned()),
+                    1,
+                    None,
+                    vm,
+                )?;
+            }
+
             let fields = zelf
                 .class()
                 .get_attr(vm.ctx.intern_str("_fields"))
@@ -388,9 +380,9 @@ pub(crate) mod _ast {
                 if contains {
                     if !ast_replace_set_discard(&remaining_fields, &key_obj, vm)? {
                         return Err(vm.new_type_error(format!(
-                            "{} got multiple values for argument '{}'",
-                            zelf.class().name(),
-                            key
+                            "{} got multiple values for argument {}",
+                            zelf.class().fully_qualified_name(vm)?,
+                            key_obj.repr(vm)?
                         )));
                     }
                 } else {
@@ -410,19 +402,11 @@ pub(crate) mod _ast {
                         attributes.as_deref().unwrap()
                     };
                     if !attrs.sequence_unchecked().contains(&key_obj, vm)? {
-                        let message = vm.ctx.new_str(format!(
-                            "{}.__init__ got an unexpected keyword argument '{}'. \
-Support for arbitrary keyword arguments is deprecated and will be removed in Python 3.15.",
-                            zelf.class().name(),
-                            key
-                        ));
-                        warn::warn(
-                            message.into(),
-                            Some(vm.ctx.exceptions.deprecation_warning.to_owned()),
-                            1,
-                            None,
-                            vm,
-                        )?;
+                        return Err(vm.new_type_error(format!(
+                            "{}.__init__ got an unexpected keyword argument {}",
+                            zelf.class().fully_qualified_name(vm)?,
+                            key_obj.repr(vm)?
+                        )));
                     }
                 }
 
@@ -438,7 +422,13 @@ Support for arbitrary keyword arguments is deprecated and will be removed in Pyt
                 let expr_ctx_type: PyObjectRef =
                     super::super::pyast::NodeExprContext::make_static_type().into();
 
-                for field in remaining_fields.elements() {
+                let mut missing = Vec::new();
+                // Render missing arguments in their declared positional order.
+                for i in 0..numfields {
+                    let field = fields_seq.get_item(i as isize, vm)?;
+                    if !ast_replace_set_discard(&remaining_fields, &field, vm)? {
+                        continue;
+                    }
                     if let Some(ftype) = ft_dict.get_item_opt(&*field, vm)? {
                         if ftype.fast_isinstance(vm.ctx.types.union_type) {
                             // Optional field (T | None) — no default
@@ -457,39 +447,35 @@ Support for arbitrary keyword arguments is deprecated and will be removed in Pyt
                                 });
                             ast_set_attr(zelf, &field, load_instance, vm)?;
                         } else {
-                            // Required field missing: emit DeprecationWarning.
-                            let field_repr = field.repr(vm)?;
-                            let message = vm.ctx.new_str(format!(
-                                "{}.__init__ missing 1 required positional argument: {}. \
-This will become an error in Python 3.15.",
-                                zelf.class().name(),
-                                field_repr
-                            ));
-                            warn::warn(
-                                message.into(),
-                                Some(vm.ctx.exceptions.deprecation_warning.to_owned()),
-                                1,
-                                None,
-                                vm,
-                            )?;
+                            missing.push(format!("'{}'", field.str(vm)?));
                         }
                     } else {
-                        let field_repr = field.repr(vm)?;
-                        let message = vm.ctx.new_str(format!(
-                            "Field {} is missing from {}._field_types. \
-This will become an error in Python 3.15.",
-                            field_repr,
-                            zelf.class().name()
-                        ));
-                        warn::warn(
-                            message.into(),
-                            Some(vm.ctx.exceptions.deprecation_warning.to_owned()),
-                            1,
-                            None,
-                            vm,
-                        )?;
+                        return Err(vm.new_type_error(format!(
+                            "Field {} is missing from {}._field_types",
+                            field.repr(vm)?,
+                            zelf.class().fully_qualified_name(vm)?
+                        )));
                     }
                 }
+                if !missing.is_empty() {
+                    let count = missing.len();
+                    let names = match missing.as_slice() {
+                        [name] => name.clone(),
+                        [first, last] => format!("{first} and {last}"),
+                        names => format!(
+                            "{}, and {}",
+                            names[..count - 1].join(", "),
+                            names[count - 1]
+                        ),
+                    };
+                    return Err(vm.new_type_error(format!(
+                        "{}.__init__ missing {} required positional argument{}: {}",
+                        zelf.class().fully_qualified_name(vm)?,
+                        count,
+                        if count == 1 { "" } else { "s" },
+                        names
+                    )));
+                }
             }
 
             Ok(())
diff --git a/crates/vm/src/stdlib/_ast/source_location.rs b/crates/vm/src/stdlib/_ast/source_location.rs
new file mode 100644
index 00000000000..67c1e7c5a91
--- /dev/null
+++ b/crates/vm/src/stdlib/_ast/source_location.rs
@@ -0,0 +1,93 @@
+//! Per-conversion coordinates for Python AST input and output.
+
+use crate::{PyResult, VirtualMachine};
+use core::{cell::RefCell, ops::Deref};
+use ruff_python_ast::{AtomicNodeIndex, NodeIndex};
+use ruff_text_size::TextRange;
+use rustpython_compiler_core::{AstLocations, SourceFile, SourceLocationRange};
+
+pub(super) struct AstSourceContext {
+    source_file: SourceFile,
+    // Outbound parser AST conversion never allocates a metadata table.
+    locations: RefCell<Option<AstLocations>>,
+}
+
+#[derive(Clone, Copy)]
+pub(super) struct AstNodeRange {
+    pub range: TextRange,
+    pub index: NodeIndex,
+}
+
+impl AstNodeRange {
+    pub(super) fn node_index(self) -> AtomicNodeIndex {
+        let index = AtomicNodeIndex::NONE;
+        index.set(self.index);
+        index
+    }
+}
+
+impl AstSourceContext {
+    pub(super) fn new(source_file: SourceFile) -> Self {
+        Self {
+            source_file,
+            locations: RefCell::new(None),
+        }
+    }
+
+    /// Coordinates have already been read and validated by the caller. The
+    /// metadata borrow cannot span Python getters or recursive node conversion.
+    pub(super) fn register(
+        &self,
+        vm: &VirtualMachine,
+        range: TextRange,
+        location: Option<SourceLocationRange>,
+    ) -> PyResult<AstNodeRange> {
+        let id = self
+            .locations
+            .borrow_mut()
+            .get_or_insert_default()
+            .allocate(location)
+            .map_err(|_| vm.new_memory_error("too many AST location identities"))?;
+        Ok(AstNodeRange {
+            range,
+            index: NodeIndex::from(id),
+        })
+    }
+
+    pub(super) fn location(&self, index: NodeIndex) -> Option<SourceLocationRange> {
+        let id = index.as_u32()?;
+        self.locations.borrow().as_ref()?.get(id)
+    }
+
+    #[cfg(feature = "codegen")]
+    pub(super) fn preprocess_locations(
+        &self,
+        f: impl FnOnce(&mut AstLocations) -> Result<(), rustpython_compiler_core::AstLocationError>,
+    ) -> Result<(), rustpython_compiler_core::AstLocationError> {
+        f(self.locations.borrow_mut().get_or_insert_default())
+    }
+
+    pub(super) fn has_locations(&self) -> bool {
+        self.locations.borrow().is_some()
+    }
+
+    pub(super) fn take_locations(&self) -> Option<AstLocations> {
+        self.locations.borrow_mut().take()
+    }
+}
+
+impl Deref for AstSourceContext {
+    type Target = SourceFile;
+
+    fn deref(&self) -> &Self::Target {
+        &self.source_file
+    }
+}
+
+impl Deref for AstNodeRange {
+    type Target = TextRange;
+
+    fn deref(&self) -> &Self::Target {
+        &self.range
+    }
+}
diff --git a/crates/vm/src/stdlib/_ast/statement.rs b/crates/vm/src/stdlib/_ast/statement.rs
index cfdf3e5f530..7f0b5d75f5f 100644
--- a/crates/vm/src/stdlib/_ast/statement.rs
+++ b/crates/vm/src/stdlib/_ast/statement.rs
@@ -1,10 +1,10 @@
+use super::AstSourceContext;
 use super::*;
 use crate::stdlib::_ast::argument::{
     KeywordArguments, PositionalArguments, merge_class_def_args, split_class_def_args,
 };
 use crate::stdlib::_ast::exception::except_handler_from_object_unvalidated_range;
 use crate::stdlib::_ast::type_parameters::type_params_from_field;
-use rustpython_compiler_core::SourceFile;
 
 fn runtime_decorator_expr_list(values: &[Option<ast::Decorator>]) -> Vec<Option<ast::Expr>> {
     values
@@ -27,7 +27,7 @@ fn lower_runtime_decorator_list(values: Vec<Option<ast::Decorator>>) -> Vec<ast:
 }
 
 fn definition_range_from_name(
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     name_start: TextSize,
     end: TextSize,
     keyword: &str,
@@ -64,7 +64,7 @@ fn runtime_stmt_type_comment_object(
 
 // sum
 impl Node for ast::Stmt {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::FunctionDef(cons) => cons.ast_to_object(vm, source_file),
             Self::ClassDef(cons) => cons.ast_to_object(vm, source_file),
@@ -98,7 +98,7 @@ impl Node for ast::Stmt {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if vm.is_none(&object) {
@@ -336,9 +336,9 @@ impl Node for ast::Stmt {
 // constructor
 fn stmt_function_def_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
     is_async: bool,
 ) -> PyResult<ast::StmtFunctionDef> {
     let typ = if is_async {
@@ -367,14 +367,14 @@ fn stmt_function_def_from_object_with_range(
         runtime_stmt_type_comment(vm, get_ast_string_field_opt(vm, object, "type_comment")?);
     let type_params = type_params_from_field(vm, source_file, object, "type_params", typ)?;
     Ok(ast::StmtFunctionDef {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         name,
         parameters,
         body,
         decorator_list: decorator_list.into(),
         returns,
         type_params,
-        range,
+        range: range.range,
         is_async,
         runtime_decorator_list,
         runtime_type_comment,
@@ -384,9 +384,9 @@ fn stmt_function_def_from_object_with_range(
 }
 
 impl Node for ast::StmtFunctionDef {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             parameters,
             body,
@@ -450,13 +450,13 @@ impl Node for ast::StmtFunctionDef {
             vm,
         )
         .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let is_async =
@@ -474,9 +474,9 @@ impl Node for ast::StmtFunctionDef {
 // constructor
 fn stmt_class_def_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtClassDef> {
     let name = get_required_identifier_field(vm, source_file, object, "name", "ClassDef")?;
     let bases = PositionalArguments::ast_from_field(vm, source_file, object, "bases", "ClassDef")?;
@@ -493,22 +493,22 @@ fn stmt_class_def_from_object_with_range(
     let decorator_list = lower_runtime_decorator_list(decorator_list);
     let type_params = type_params_from_field(vm, source_file, object, "type_params", "ClassDef")?;
     Ok(ast::StmtClassDef {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         name,
         arguments: merge_class_def_args(Some(bases), Some(keywords)),
         body,
         decorator_list: decorator_list.into(),
         type_params,
-        range,
+        range: range.range,
         runtime_decorator_list,
         runtime_body,
     })
 }
 
 impl Node for ast::StmtClassDef {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             arguments,
             body,
@@ -568,12 +568,12 @@ impl Node for ast::StmtClassDef {
             vm,
         )
         .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "ClassDef")?;
@@ -583,23 +583,23 @@ impl Node for ast::StmtClassDef {
 // constructor
 fn stmt_return_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtReturn> {
     Ok(ast::StmtReturn {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_node_field_opt(vm, object, "value")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtReturn {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             range: _range,
         } = self;
@@ -609,12 +609,12 @@ impl Node for ast::StmtReturn {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Return")?;
@@ -624,25 +624,25 @@ impl Node for ast::StmtReturn {
 // constructor
 fn stmt_delete_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtDelete> {
     let targets: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "targets", "Delete")?;
     let (runtime_targets, targets) = runtime_expr_list_from_values(targets);
     Ok(ast::StmtDelete {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         targets,
-        range,
+        range: range.range,
         runtime_targets,
     })
 }
 
 impl Node for ast::StmtDelete {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             targets,
             range: _range,
             runtime_targets,
@@ -656,12 +656,12 @@ impl Node for ast::StmtDelete {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("targets", targets, vm).unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Delete")?;
@@ -672,9 +672,9 @@ impl Node for ast::StmtDelete {
 // constructor
 fn stmt_assign_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtAssign> {
     let targets: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "targets", "Assign")?;
@@ -683,10 +683,10 @@ fn stmt_assign_from_object_with_range(
     let (runtime_type_comment, runtime_type_comment_bytes) =
         runtime_stmt_type_comment(vm, get_ast_string_field_opt(vm, object, "type_comment")?);
     Ok(ast::StmtAssign {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         targets,
         value,
-        range,
+        range: range.range,
         runtime_targets,
         runtime_type_comment,
         runtime_type_comment_bytes,
@@ -694,9 +694,9 @@ fn stmt_assign_from_object_with_range(
 }
 
 impl Node for ast::StmtAssign {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             targets,
             value,
             range,
@@ -721,12 +721,12 @@ impl Node for ast::StmtAssign {
             vm,
         )
         .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Assign")?;
@@ -737,23 +737,23 @@ impl Node for ast::StmtAssign {
 // constructor
 fn stmt_type_alias_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtTypeAlias> {
     Ok(ast::StmtTypeAlias {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         name: get_required_node_field(vm, source_file, object, "name", "TypeAlias")?,
         type_params: type_params_from_field(vm, source_file, object, "type_params", "TypeAlias")?,
         value: get_required_node_field(vm, source_file, object, "value", "TypeAlias")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtTypeAlias {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             type_params,
             value,
@@ -776,13 +776,13 @@ impl Node for ast::StmtTypeAlias {
         .unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "TypeAlias")?;
@@ -793,12 +793,12 @@ impl Node for ast::StmtTypeAlias {
 // constructor
 fn stmt_aug_assign_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtAugAssign> {
     Ok(ast::StmtAugAssign {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         target: get_required_node_field(vm, source_file, object, "target", "AugAssign")?,
         op: Node::ast_from_object(
             vm,
@@ -806,14 +806,14 @@ fn stmt_aug_assign_from_object_with_range(
             get_node_field_required(vm, object, "op", "AugAssign")?,
         )?,
         value: get_required_node_field(vm, source_file, object, "value", "AugAssign")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtAugAssign {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             target,
             op,
             value,
@@ -829,12 +829,12 @@ impl Node for ast::StmtAugAssign {
             .unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "AugAssign")?;
@@ -845,9 +845,9 @@ impl Node for ast::StmtAugAssign {
 // constructor
 fn stmt_ann_assign_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtAnnAssign> {
     let simple_obj = get_node_field(vm, object, "simple", "AnnAssign")?;
     let simple = node_object_to_i32(vm, &simple_obj)?;
@@ -857,22 +857,22 @@ fn stmt_ann_assign_from_object_with_range(
         None
     };
     Ok(ast::StmtAnnAssign {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         target: get_required_node_field(vm, source_file, object, "target", "AnnAssign")?,
         annotation: get_required_node_field(vm, source_file, object, "annotation", "AnnAssign")?,
         value: get_node_field_opt(vm, object, "value")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
         simple: simple != 0,
-        range,
+        range: range.range,
         runtime_simple,
     })
 }
 
 impl Node for ast::StmtAnnAssign {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             target,
             annotation,
             value,
@@ -895,12 +895,12 @@ impl Node for ast::StmtAnnAssign {
             |simple| vm.ctx.new_int(simple).into(),
         );
         dict.set_item("simple", simple, vm).unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "AnnAssign")?;
@@ -911,9 +911,9 @@ impl Node for ast::StmtAnnAssign {
 // constructor
 fn stmt_for_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
     is_async: bool,
 ) -> PyResult<ast::StmtFor> {
     let typ = if is_async { "AsyncFor" } else { "For" };
@@ -929,12 +929,12 @@ fn stmt_for_from_object_with_range(
     let (runtime_type_comment, runtime_type_comment_bytes) =
         runtime_stmt_type_comment(vm, get_ast_string_field_opt(vm, object, "type_comment")?);
     Ok(ast::StmtFor {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         target,
         iter,
         body,
         orelse,
-        range,
+        range: range.range,
         is_async,
         runtime_type_comment,
         runtime_type_comment_bytes,
@@ -944,9 +944,9 @@ fn stmt_for_from_object_with_range(
 }
 
 impl Node for ast::StmtFor {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             is_async,
             target,
             iter,
@@ -987,13 +987,13 @@ impl Node for ast::StmtFor {
             vm,
         )
         .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         debug_assert!(
@@ -1010,9 +1010,9 @@ impl Node for ast::StmtFor {
 // constructor
 fn stmt_while_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtWhile> {
     let body: Vec<Option<ast::Stmt>> =
         get_node_list_field(vm, source_file, object, "body", "While")?;
@@ -1021,20 +1021,20 @@ fn stmt_while_from_object_with_range(
     let runtime_body = runtime_stmt_list_metadata(&body);
     let runtime_orelse = runtime_stmt_list_metadata(&orelse);
     Ok(ast::StmtWhile {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         test: get_required_node_field(vm, source_file, object, "test", "While")?,
         body: lower_runtime_stmt_list(body),
         orelse: lower_runtime_stmt_list(orelse),
-        range,
+        range: range.range,
         runtime_body,
         runtime_orelse,
     })
 }
 
 impl Node for ast::StmtWhile {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             test,
             body,
             orelse,
@@ -1058,13 +1058,13 @@ impl Node for ast::StmtWhile {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("orelse", orelse, vm).unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "While")?;
@@ -1073,7 +1073,7 @@ impl Node for ast::StmtWhile {
 }
 // constructor
 impl Node for ast::StmtIf {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
             node_index,
             test,
@@ -1098,7 +1098,7 @@ impl Node for ast::StmtIf {
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "If")?;
@@ -1108,9 +1108,9 @@ impl Node for ast::StmtIf {
 // constructor
 fn stmt_with_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
     is_async: bool,
 ) -> PyResult<ast::StmtWith> {
     let typ = if is_async { "AsyncWith" } else { "With" };
@@ -1120,10 +1120,10 @@ fn stmt_with_from_object_with_range(
     let (runtime_type_comment, runtime_type_comment_bytes) =
         runtime_stmt_type_comment(vm, get_ast_string_field_opt(vm, object, "type_comment")?);
     Ok(ast::StmtWith {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         items,
         body,
-        range,
+        range: range.range,
         is_async,
         runtime_type_comment,
         runtime_type_comment_bytes,
@@ -1132,9 +1132,9 @@ fn stmt_with_from_object_with_range(
 }
 
 impl Node for ast::StmtWith {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             is_async,
             items,
             body,
@@ -1165,12 +1165,12 @@ impl Node for ast::StmtWith {
             vm,
         )
         .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         debug_assert!(
@@ -1186,22 +1186,22 @@ impl Node for ast::StmtWith {
 // constructor
 fn stmt_match_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtMatch> {
     Ok(ast::StmtMatch {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         subject: get_required_node_field(vm, source_file, object, "subject", "Match")?,
         cases: get_node_list_field(vm, source_file, object, "cases", "Match")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtMatch {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             subject,
             cases,
             range: _range,
@@ -1214,12 +1214,12 @@ impl Node for ast::StmtMatch {
             .unwrap();
         dict.set_item("cases", cases.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Match")?;
@@ -1229,26 +1229,26 @@ impl Node for ast::StmtMatch {
 // constructor
 fn stmt_raise_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtRaise> {
     Ok(ast::StmtRaise {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         exc: get_node_field_opt(vm, object, "exc")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
         cause: get_node_field_opt(vm, object, "cause")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtRaise {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             exc,
             cause,
             range: _range,
@@ -1261,12 +1261,12 @@ impl Node for ast::StmtRaise {
             .unwrap();
         dict.set_item("cause", cause.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Raise")?;
@@ -1276,9 +1276,9 @@ impl Node for ast::StmtRaise {
 // constructor
 fn stmt_try_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
     is_star: bool,
 ) -> PyResult<ast::StmtTry> {
     let typ = if is_star { "TryStar" } else { "Try" };
@@ -1288,18 +1288,18 @@ fn stmt_try_from_object_with_range(
     let finalbody: Vec<Option<ast::Stmt>> =
         get_node_list_field(vm, source_file, object, "finalbody", typ)?;
     let (runtime_handler_values, handlers) =
-        except_handler_list_from_field(vm, source_file, object, typ, is_star, range)?;
+        except_handler_list_from_field(vm, source_file, object, typ, is_star, range.range)?;
     let runtime_body = runtime_stmt_list_metadata(&body);
     let runtime_orelse = runtime_stmt_list_metadata(&orelse);
     let runtime_finalbody = runtime_stmt_list_metadata(&finalbody);
     let runtime_handlers = runtime_except_handler_list_metadata(&runtime_handler_values);
     Ok(ast::StmtTry {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         body: lower_runtime_stmt_list(body),
         handlers,
         orelse: lower_runtime_stmt_list(orelse),
         finalbody: lower_runtime_stmt_list(finalbody),
-        range,
+        range: range.range,
         is_star,
         runtime_body,
         runtime_handlers,
@@ -1310,7 +1310,7 @@ fn stmt_try_from_object_with_range(
 
 fn except_handler_list_from_field(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
     typ: &str,
     is_try_star: bool,
@@ -1365,9 +1365,9 @@ fn except_handler_list_from_field(
 }
 
 impl Node for ast::StmtTry {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             body,
             handlers,
             orelse,
@@ -1409,12 +1409,12 @@ impl Node for ast::StmtTry {
             |values| values.ast_to_object(vm, source_file),
         );
         dict.set_item("finalbody", finalbody, vm).unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let is_star = is_node_instance(vm, &_object, pyast::NodeStmtTryStar::static_type())?;
@@ -1431,24 +1431,24 @@ impl Node for ast::StmtTry {
 // constructor
 fn stmt_assert_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtAssert> {
     Ok(ast::StmtAssert {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         test: get_required_node_field(vm, source_file, object, "test", "Assert")?,
         msg: get_node_field_opt(vm, object, "msg")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtAssert {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             test,
             msg,
             range: _range,
@@ -1461,12 +1461,12 @@ impl Node for ast::StmtAssert {
             .unwrap();
         dict.set_item("msg", msg.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Assert")?;
@@ -1476,25 +1476,29 @@ impl Node for ast::StmtAssert {
 // constructor
 fn stmt_import_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtImport> {
     Ok(ast::StmtImport {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         names: get_node_list_field(vm, source_file, object, "names", "Import")?,
-        range,
-        is_lazy: false,
+        range: range.range,
+        is_lazy: get_node_field_opt(vm, object, "is_lazy")?
+            .map(|value| node_object_to_i32(vm, &value))
+            .transpose()?
+            .unwrap_or(0)
+            != 0,
     })
 }
 
 impl Node for ast::StmtImport {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             names,
             range: _range,
-            is_lazy: _,
+            is_lazy,
         } = self;
         let node = NodeAst
             .into_ref_with_type(vm, pyast::NodeStmtImport::static_type().to_owned())
@@ -1502,13 +1506,15 @@ impl Node for ast::StmtImport {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("names", names.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        dict.set_item("is_lazy", vm.ctx.new_int(i32::from(is_lazy)).into(), vm)
+            .unwrap();
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Import")?;
@@ -1518,21 +1524,25 @@ impl Node for ast::StmtImport {
 // constructor
 fn stmt_import_from_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtImportFrom> {
     let (level, raw_level) = import_from_level_from_field(vm, object)?;
     let runtime_level = raw_level.filter(|level| *level < 0);
     Ok(ast::StmtImportFrom {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         module: get_node_field_opt(vm, object, "module")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
         names: get_node_list_field(vm, source_file, object, "names", "ImportFrom")?,
         level,
-        range,
-        is_lazy: false,
+        range: range.range,
+        is_lazy: get_node_field_opt(vm, object, "is_lazy")?
+            .map(|value| node_object_to_i32(vm, &value))
+            .transpose()?
+            .unwrap_or(0)
+            != 0,
         runtime_level,
     })
 }
@@ -1554,14 +1564,14 @@ fn import_from_level_from_field(
 }
 
 impl Node for ast::StmtImportFrom {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             module,
             names,
             level,
             range,
-            is_lazy: _,
+            is_lazy,
             runtime_level,
         } = self;
         let node = NodeAst
@@ -1577,13 +1587,15 @@ impl Node for ast::StmtImportFrom {
             |level| vm.ctx.new_int(level).to_pyobject(vm),
         );
         dict.set_item("level", level, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        dict.set_item("is_lazy", vm.ctx.new_int(i32::from(is_lazy)).into(), vm)
+            .unwrap();
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "ImportFrom")?;
@@ -1593,21 +1605,21 @@ impl Node for ast::StmtImportFrom {
 // constructor
 fn stmt_global_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtGlobal> {
     Ok(ast::StmtGlobal {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         names: get_node_list_field(vm, source_file, object, "names", "Global")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtGlobal {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             names,
             range: _range,
         } = self;
@@ -1617,12 +1629,12 @@ impl Node for ast::StmtGlobal {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("names", names.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Global")?;
@@ -1632,21 +1644,21 @@ impl Node for ast::StmtGlobal {
 // constructor
 fn stmt_nonlocal_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtNonlocal> {
     Ok(ast::StmtNonlocal {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         names: get_node_list_field(vm, source_file, object, "names", "Nonlocal")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtNonlocal {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             names,
             range: _range,
         } = self;
@@ -1656,12 +1668,12 @@ impl Node for ast::StmtNonlocal {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("names", names.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Nonlocal")?;
@@ -1671,21 +1683,21 @@ impl Node for ast::StmtNonlocal {
 // constructor
 fn stmt_expr_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::StmtExpr> {
     Ok(ast::StmtExpr {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         value: get_required_node_field(vm, source_file, object, "value", "Expr")?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::StmtExpr {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             value,
             range: _range,
         } = self;
@@ -1695,12 +1707,12 @@ impl Node for ast::StmtExpr {
         let dict = node.as_object().dict().unwrap();
         dict.set_item("value", value.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Expr")?;
@@ -1708,27 +1720,31 @@ impl Node for ast::StmtExpr {
     }
 }
 // constructor
-fn stmt_pass_from_object_with_range(range: TextRange) -> ast::StmtPass {
+fn stmt_pass_from_object_with_range(range: AstNodeRange) -> ast::StmtPass {
     ast::StmtPass {
-        node_index: Default::default(),
-        range,
+        node_index: range.node_index(),
+        range: range.range,
     }
 }
 
 impl Node for ast::StmtPass {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             range: _range,
         } = self;
         let node = NodeAst
             .into_ref_with_type(vm, pyast::NodeStmtPass::static_type().to_owned())
             .unwrap();
         let dict = node.as_object().dict().unwrap();
+        if source_file.location(node_index.load()).is_some() {
+            node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
+            return node.into();
+        }
         let location = super::text_range_to_source_range(source_file, _range);
-        let start_row = location.start.row.get();
-        let start_col = location.start.column.get();
-        let mut end_row = location.end.row.get();
+        let start_row = location.start.line.get();
+        let start_col = location.start.character_offset.to_zero_indexed();
+        let mut end_row = location.end.line.get();
 
         // Align with CPython: when docstring optimization replaces a lone
         // docstring with `pass`, the end position is on the same line even if
@@ -1737,7 +1753,7 @@ impl Node for ast::StmtPass {
             end_row = start_row;
             start_col + 4
         } else {
-            location.end.column.get()
+            location.end.character_offset.to_zero_indexed()
         };
 
         dict.set_item("lineno", vm.ctx.new_int(start_row).into(), vm)
@@ -1752,7 +1768,7 @@ impl Node for ast::StmtPass {
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Pass")?;
@@ -1760,30 +1776,30 @@ impl Node for ast::StmtPass {
     }
 }
 // constructor
-fn stmt_break_from_object_with_range(range: TextRange) -> ast::StmtBreak {
+fn stmt_break_from_object_with_range(range: AstNodeRange) -> ast::StmtBreak {
     ast::StmtBreak {
-        node_index: Default::default(),
-        range,
+        node_index: range.node_index(),
+        range: range.range,
     }
 }
 
 impl Node for ast::StmtBreak {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             range: _range,
         } = self;
         let node = NodeAst
             .into_ref_with_type(vm, pyast::NodeStmtBreak::static_type().to_owned())
             .unwrap();
         let dict = node.as_object().dict().unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Break")?;
@@ -1792,29 +1808,29 @@ impl Node for ast::StmtBreak {
 }
 
 // constructor
-fn stmt_continue_from_object_with_range(range: TextRange) -> ast::StmtContinue {
+fn stmt_continue_from_object_with_range(range: AstNodeRange) -> ast::StmtContinue {
     ast::StmtContinue {
-        node_index: Default::default(),
-        range,
+        node_index: range.node_index(),
+        range: range.range,
     }
 }
 
 impl Node for ast::StmtContinue {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             range: _range,
         } = self;
         let node = NodeAst
             .into_ref_with_type(vm, pyast::NodeStmtContinue::static_type().to_owned())
             .unwrap();
         let dict = node.as_object().dict().unwrap();
-        node_add_location(&dict, _range, vm, source_file);
+        node_add_location_for_node(&dict, _range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         _object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &_object, "Continue")?;
diff --git a/crates/vm/src/stdlib/_ast/string.rs b/crates/vm/src/stdlib/_ast/string.rs
index 553b235c46c..03daf9144e7 100644
--- a/crates/vm/src/stdlib/_ast/string.rs
+++ b/crates/vm/src/stdlib/_ast/string.rs
@@ -1,6 +1,5 @@
 use super::constant::{Constant, ConstantLiteral};
 use super::*;
-use crate::warn;
 use ast::str_prefix::StringLiteralPrefix;
 use rustpython_common::wtf8::Wtf8Buf;
 
@@ -21,18 +20,20 @@ fn ruff_fstring_element_into_iter(
 
 fn push_ruff_fstring_element(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     flags: ast::AnyStringFlags,
     element: ast::InterpolatedStringElement,
     output: &mut Vec<JoinedStrPart>,
 ) {
     match element {
         ast::InterpolatedStringElement::Literal(literal) => {
-            output.push(JoinedStrPart::Constant(Constant::new_str(
+            let mut constant = Constant::new_str(
                 rustpython_codegen::interpolated_string_literal_value(source_file, &literal, flags),
                 ast::str_prefix::StringLiteralPrefix::Empty,
                 literal.range,
-            )));
+            );
+            constant.node_index = literal.node_index;
+            output.push(JoinedStrPart::Constant(constant));
         }
         ast::InterpolatedStringElement::Interpolation(ast::InterpolatedElement {
             range,
@@ -40,7 +41,7 @@ fn push_ruff_fstring_element(
             debug_text,
             mut conversion,
             format_spec,
-            node_index: _,
+            node_index,
             runtime_str: _,
             runtime_interpolation_format_spec: _,
             runtime_formatted_value_format_spec,
@@ -58,6 +59,7 @@ fn push_ruff_fstring_element(
                     .map(|joined_str| Box::new(joined_str.into_expr(false)))
             });
             output.push(JoinedStrPart::FormattedValue(FormattedValue {
+                node_index,
                 value: expression,
                 conversion,
                 format_spec: runtime_format_spec,
@@ -69,7 +71,7 @@ fn push_ruff_fstring_element(
 
 /// The literal an `{expr=}` interpolation puts in front of its value.
 fn interpolation_debug_constant(
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     debug_text: &ast::DebugText,
     expression_range: TextRange,
 ) -> Constant {
@@ -175,42 +177,41 @@ fn normalize_template_str_parts(values: Vec<TemplateStrPart>) -> Vec<TemplateStr
     output
 }
 
-fn warn_invalid_escape_sequences_in_format_spec(
-    vm: &VirtualMachine,
+#[cfg(feature = "parser")]
+fn warn_invalid_escape_sequences_in_format_spec<E>(
     source_file: &SourceFile,
     range: TextRange,
-) {
+    emit_warning: &mut impl FnMut(usize, char) -> Result<(), E>,
+) -> Result<(), E> {
     let source = source_file.source_text();
     let start = range.start().to_usize();
     let end = range.end().to_usize();
     if start >= end || end > source.len() {
-        return;
-    }
-    let mut raw = &source[start..end];
-    if raw.starts_with(':') {
-        raw = &raw[1..];
+        return Ok(());
     }
-
-    let mut chars = raw.chars().peekable();
-    while let Some(ch) = chars.next() {
+    let Some(raw) = source.get(start..end) else {
+        return Ok(());
+    };
+    let mut chars = raw.char_indices().peekable();
+    while let Some((offset, ch)) = chars.next() {
         if ch != '\\' {
             continue;
         }
-        let Some(next) = chars.next() else {
+        let Some((_, next)) = chars.next() else {
             break;
         };
         let valid = match next {
             '\\' | '\'' | '"' | 'a' | 'b' | 'f' | 'n' | 'r' | 't' | 'v' => true,
             '\n' => true,
             '\r' => {
-                if let Some('\n') = chars.peek().copied() {
+                if let Some((_, '\n')) = chars.peek().copied() {
                     chars.next();
                 }
                 true
             }
             '0'..='7' => {
                 for _ in 0..2 {
-                    if let Some('0'..='7') = chars.peek().copied() {
+                    if let Some((_, '0'..='7')) = chars.peek().copied() {
                         chars.next();
                     } else {
                         break;
@@ -220,7 +221,7 @@ fn warn_invalid_escape_sequences_in_format_spec(
             }
             'x' => {
                 for _ in 0..2 {
-                    if chars.peek().is_some_and(|c| c.is_ascii_hexdigit()) {
+                    if chars.peek().is_some_and(|(_, c)| c.is_ascii_hexdigit()) {
                         chars.next();
                     } else {
                         break;
@@ -230,7 +231,7 @@ fn warn_invalid_escape_sequences_in_format_spec(
             }
             'u' => {
                 for _ in 0..4 {
-                    if chars.peek().is_some_and(|c| c.is_ascii_hexdigit()) {
+                    if chars.peek().is_some_and(|(_, c)| c.is_ascii_hexdigit()) {
                         chars.next();
                     } else {
                         break;
@@ -240,7 +241,7 @@ fn warn_invalid_escape_sequences_in_format_spec(
             }
             'U' => {
                 for _ in 0..8 {
-                    if chars.peek().is_some_and(|c| c.is_ascii_hexdigit()) {
+                    if chars.peek().is_some_and(|(_, c)| c.is_ascii_hexdigit()) {
                         chars.next();
                     } else {
                         break;
@@ -249,9 +250,9 @@ fn warn_invalid_escape_sequences_in_format_spec(
                 true
             }
             'N' => {
-                if let Some('{') = chars.peek().copied() {
+                if let Some((_, '{')) = chars.peek().copied() {
                     chars.next();
-                    for c in chars.by_ref() {
+                    for (_, c) in chars.by_ref() {
                         if c == '}' {
                             break;
                         }
@@ -262,23 +263,201 @@ fn warn_invalid_escape_sequences_in_format_spec(
             _ => false,
         };
         if !valid {
-            let message = vm.ctx.new_str(format!(
-                "\"\\{next}\" is an invalid escape sequence. Such sequences will not work in the future. Did you mean \"\\\\{next}\"? A raw string is also an option."
-            ));
-            let _ = warn::warn(
-                message.into(),
-                Some(vm.ctx.exceptions.syntax_warning.to_owned()),
-                1,
-                None,
-                vm,
+            return emit_warning(start + offset, next);
+        }
+    }
+    Ok(())
+}
+
+/// Keep AST parsing's existing format-spec diagnostics at a fallible boundary,
+/// rather than emitting warnings from the infallible Python AST conversion.
+#[cfg(feature = "parser")]
+pub(super) fn emit_format_spec_warnings<E>(
+    statements: &[ast::Stmt],
+    expressions: &[ast::Expr],
+    source_file: &SourceFile,
+    emit_warning: &mut impl FnMut(usize, char) -> Result<(), E>,
+) -> Result<(), E> {
+    use ast::visitor::{self, Visitor};
+    use std::collections::HashSet;
+
+    struct LiteralVisitor<'a, F, E> {
+        source_file: &'a SourceFile,
+        emit_warning: F,
+        emitted: HashSet<usize>,
+        error: Option<E>,
+    }
+
+    impl<F, E> LiteralVisitor<'_, F, E>
+    where
+        F: FnMut(usize, char) -> Result<(), E>,
+    {
+        fn check_literal(&mut self, mut range: TextRange, interpolated: bool) {
+            if self.error.is_some() {
+                return;
+            }
+            // Ruff leaves the interpolation delimiter outside the literal range.
+            // Include it so a trailing backslash can still diagnose \{ or \}.
+            if interpolated
+                && self
+                    .source_file
+                    .source_text()
+                    .as_bytes()
+                    .get(range.end().to_usize())
+                    .is_some_and(|byte| matches!(byte, b'{' | b'}'))
+            {
+                range = TextRange::new(range.start(), range.end() + TextSize::from(1));
+            }
+            let result = warn_invalid_escape_sequences_in_format_spec(
+                self.source_file,
+                range,
+                &mut |offset, ch| {
+                    if !self.emitted.contains(&offset) {
+                        (self.emit_warning)(offset, ch)?;
+                        self.emitted.insert(offset);
+                    }
+                    Ok(())
+                },
             );
+            if let Err(error) = result {
+                self.error = Some(error);
+            }
+        }
+
+        fn visit_elements<'a>(&mut self, elements: &'a ast::InterpolatedStringElements, raw: bool)
+        where
+            Self: Visitor<'a>,
+        {
+            for element in elements {
+                match element {
+                    ast::InterpolatedStringElement::Literal(literal) => {
+                        if !raw {
+                            self.check_literal(literal.range, true);
+                        }
+                    }
+                    ast::InterpolatedStringElement::Interpolation(interpolation) => {
+                        self.visit_expr(&interpolation.expression);
+                        if let Some(spec) = &interpolation.format_spec {
+                            self.visit_elements(&spec.elements, raw);
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    // Visit only literal spans within an existing format-spec warning region.
+    // An enclosing spec can include nested raw strings, nonraw expressions in a
+    // raw f-string, and comments; scanning its entire source range conflates them.
+    impl<'a, F, E> Visitor<'a> for LiteralVisitor<'_, F, E>
+    where
+        F: FnMut(usize, char) -> Result<(), E>,
+    {
+        fn visit_expr(&mut self, expr: &'a ast::Expr) {
+            if self.error.is_none() {
+                visitor::walk_expr(self, expr);
+            }
+        }
+
+        fn visit_string_literal(&mut self, literal: &'a ast::StringLiteral) {
+            if !matches!(
+                literal.flags.prefix(),
+                ast::str_prefix::StringLiteralPrefix::Raw { .. }
+            ) {
+                self.check_literal(literal.range, false);
+            }
+        }
+
+        fn visit_bytes_literal(&mut self, literal: &'a ast::BytesLiteral) {
+            if !literal.flags.prefix().is_raw() {
+                self.check_literal(literal.range, false);
+            }
+        }
+
+        fn visit_f_string(&mut self, fstring: &'a ast::FString) {
+            self.visit_elements(&fstring.elements, fstring.flags.prefix().is_raw());
+        }
+
+        fn visit_t_string(&mut self, tstring: &'a ast::TString) {
+            self.visit_elements(&tstring.elements, tstring.flags.prefix().is_raw());
+        }
+    }
+
+    struct FormatSpecVisitor<'a, F, E> {
+        literals: LiteralVisitor<'a, F, E>,
+    }
+
+    impl<'a, F, E> Visitor<'a> for FormatSpecVisitor<'_, F, E>
+    where
+        F: FnMut(usize, char) -> Result<(), E>,
+    {
+        fn visit_expr(&mut self, expr: &'a ast::Expr) {
+            if self.literals.error.is_some() {
+                return;
+            }
+            if let ast::Expr::FString(fstring) = expr {
+                // Conversion checked all enclosing specs before converting their
+                // expressions, including across concatenated f-string parts.
+                for part in &fstring.value {
+                    if let ast::FStringPartRef::FString(part) = part {
+                        self.visit_format_specs(&part.elements, part.flags.prefix().is_raw());
+                    }
+                }
+            }
+            visitor::walk_expr(self, expr);
+        }
+
+        fn visit_t_string(&mut self, tstring: &'a ast::TString) {
+            let raw = tstring.flags.prefix().is_raw();
+            for element in &tstring.elements {
+                if let ast::InterpolatedStringElement::Interpolation(interpolation) = element {
+                    self.visit_expr(&interpolation.expression);
+                    if let Some(spec) = &interpolation.format_spec {
+                        // Template specs become JoinedStr nodes during conversion;
+                        // their nested format specs already emitted warnings too.
+                        self.visit_format_specs(&spec.elements, raw);
+                        for element in &spec.elements {
+                            self.visit_interpolated_string_element(element);
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    impl<F, E> FormatSpecVisitor<'_, F, E>
+    where
+        F: FnMut(usize, char) -> Result<(), E>,
+    {
+        fn visit_format_specs(&mut self, elements: &ast::InterpolatedStringElements, raw: bool) {
+            for element in elements {
+                if let ast::InterpolatedStringElement::Interpolation(interpolation) = element
+                    && let Some(spec) = &interpolation.format_spec
+                {
+                    self.literals.visit_elements(&spec.elements, raw);
+                }
+            }
         }
     }
+
+    let mut visitor = FormatSpecVisitor {
+        literals: LiteralVisitor {
+            source_file,
+            emit_warning,
+            emitted: HashSet::new(),
+            error: None,
+        },
+    };
+    visitor.visit_body(statements);
+    for expr in expressions {
+        visitor.visit_expr(expr);
+    }
+    visitor.literals.error.map_or(Ok(()), Err)
 }
 
 fn ruff_format_spec_to_joined_str(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     flags: ast::AnyStringFlags,
     format_spec: Option<Box<ast::InterpolatedStringFormatSpec>>,
 ) -> Option<Box<JoinedStr>> {
@@ -288,7 +467,7 @@ fn ruff_format_spec_to_joined_str(
             let ast::InterpolatedStringFormatSpec {
                 range,
                 elements,
-                node_index: _,
+                node_index,
             } = *format_spec;
             // The `:` that opens a format spec belongs to its range, and the
             // parser leaves it out of the outermost one.
@@ -298,7 +477,7 @@ fn ruff_format_spec_to_joined_str(
                 .get(..range.start().to_usize())
                 .and_then(<[u8]>::last)
                 == Some(&b':');
-            let range = if opened_by_colon {
+            let range = if opened_by_colon && source_file.location(node_index.load()).is_none() {
                 TextRange::new(
                     range.start() - ruff_text_size::TextSize::from(1),
                     range.end(),
@@ -310,8 +489,14 @@ fn ruff_format_spec_to_joined_str(
             for element in ruff_fstring_element_into_iter(elements) {
                 push_ruff_fstring_element(vm, source_file, flags, element, &mut values);
             }
-            let values = normalize_joined_str_parts(values).into_boxed_slice();
+            let values = if source_file.has_locations() {
+                values
+            } else {
+                normalize_joined_str_parts(values)
+            }
+            .into_boxed_slice();
             Some(Box::new(JoinedStr {
+                node_index,
                 range,
                 values,
                 runtime_values: None,
@@ -320,6 +505,35 @@ fn ruff_format_spec_to_joined_str(
     }
 }
 
+fn dummy_string_literal() -> ast::StringLiteral {
+    ast::StringLiteral {
+        node_index: Default::default(),
+        range: Default::default(),
+        value: "".into(),
+        flags: ast::StringLiteralFlags::empty(),
+    }
+}
+
+fn dummy_fstring() -> ast::FString {
+    ast::FString {
+        node_index: Default::default(),
+        range: Default::default(),
+        elements: Default::default(),
+        flags: ast::FStringFlags::empty(),
+    }
+}
+
+fn take_fstring_part(part: ast::FStringPartMut<'_>) -> ast::FStringPart {
+    match part {
+        ast::FStringPartMut::Literal(literal) => {
+            ast::FStringPart::Literal(core::mem::replace(literal, dummy_string_literal()))
+        }
+        ast::FStringPartMut::FString(fstring) => {
+            ast::FStringPart::FString(core::mem::replace(fstring, dummy_fstring()))
+        }
+    }
+}
+
 fn ruff_fstring_element_to_ruff_fstring_part(
     element: ast::InterpolatedStringElement,
 ) -> ast::FStringPart {
@@ -338,9 +552,11 @@ fn ruff_fstring_element_to_ruff_fstring_part(
             })
         }
         ast::InterpolatedStringElement::Interpolation(ast::InterpolatedElement {
-            range, ..
+            range,
+            ref node_index,
+            ..
         }) => ast::FStringPart::FString(ast::FString {
-            node_index: Default::default(),
+            node_index: node_index.clone(),
             range,
             elements: vec![element].into(),
             flags: ast::FStringFlags::empty(),
@@ -358,28 +574,21 @@ fn format_spec_expr_to_ruff_format_spec(
     let ast::ExprFString {
         range,
         ref mut value,
-        node_index: _,
+        node_index,
         runtime_joined_str: _,
         runtime_values: _,
     } = fstring;
-    let default_part = ast::FStringPart::FString(ast::FString {
-        node_index: Default::default(),
-        range: Default::default(),
-        elements: Default::default(),
-        flags: ast::FStringFlags::empty(),
-    });
     let mut elements = Vec::new();
-    for i in 0..value.as_slice().len() {
-        let part = core::mem::replace(value.iter_mut().nth(i).unwrap(), default_part.clone());
-        match part {
+    for part in value {
+        match take_fstring_part(part) {
             ast::FStringPart::Literal(ast::StringLiteral {
                 range,
                 value,
-                node_index: _,
+                node_index,
                 flags: _,
             }) => elements.push(ast::InterpolatedStringElement::Literal(
                 ast::InterpolatedStringLiteralElement {
-                    node_index: Default::default(),
+                    node_index,
                     range,
                     value,
                 },
@@ -393,7 +602,7 @@ fn format_spec_expr_to_ruff_format_spec(
         }
     }
     Some(Box::new(ast::InterpolatedStringFormatSpec {
-        node_index: Default::default(),
+        node_index,
         range,
         elements: elements.into(),
     }))
@@ -401,6 +610,7 @@ fn format_spec_expr_to_ruff_format_spec(
 
 #[derive(Debug)]
 pub(super) struct JoinedStr {
+    node_index: ast::AtomicNodeIndex,
     pub(super) range: TextRange,
     pub(super) values: Box<[JoinedStrPart]>,
     pub(super) runtime_values: Option<Vec<Option<ast::Expr>>>,
@@ -409,6 +619,7 @@ pub(super) struct JoinedStr {
 impl JoinedStr {
     pub(super) fn into_expr(self, from_ast_object: bool) -> ast::Expr {
         let Self {
+            node_index,
             range,
             values,
             runtime_values: mut raw_runtime_values,
@@ -437,11 +648,11 @@ impl JoinedStr {
                 }
             });
         ast::Expr::FString(ast::ExprFString {
-            node_index: Default::default(),
+            node_index: node_index.clone(),
             range,
             value: match values.len() {
                 0 => ast::FStringValue::single(ast::FString {
-                    node_index: Default::default(),
+                    node_index,
                     range,
                     elements: vec![].into(),
                     flags: ast::FStringFlags::empty(),
@@ -451,7 +662,7 @@ impl JoinedStr {
                         .map(|part| joined_str_part_to_ruff_fstring_element(from_ast_object, part))
                         .map(Option::unwrap)
                         .map(|element| ast::FString {
-                            node_index: Default::default(),
+                            node_index: node_index.clone(),
                             range,
                             elements: vec![element].into(),
                             flags: ast::FStringFlags::empty(),
@@ -502,7 +713,7 @@ fn joined_str_part_to_ruff_fstring_element(
                 .flatten();
             Some(ast::InterpolatedStringElement::Interpolation(
                 ast::InterpolatedElement {
-                    node_index: Default::default(),
+                    node_index: value.node_index.clone(),
                     range: value.range,
                     expression: value.value.clone(),
                     debug_text: None,
@@ -515,13 +726,18 @@ fn joined_str_part_to_ruff_fstring_element(
             ))
         }
         JoinedStrPart::Constant(value) => {
-            let Constant { range, value, .. } = value;
+            let Constant {
+                node_index,
+                range,
+                value,
+                ..
+            } = value;
             let ConstantLiteral::Str { value, .. } = value else {
                 return None;
             };
             Some(ast::InterpolatedStringElement::Literal(
                 ast::InterpolatedStringLiteralElement {
-                    node_index: Default::default(),
+                    node_index,
                     range,
                     value: value.to_string_lossy().into(),
                 },
@@ -533,22 +749,24 @@ fn joined_str_part_to_ruff_fstring_element(
 // constructor
 pub(super) fn joined_str_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<JoinedStr> {
     let values: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "values", "JoinedStr")?;
     Ok(JoinedStr {
+        node_index: range.node_index(),
         values: Vec::new().into_boxed_slice(),
         runtime_values: Some(values),
-        range,
+        range: range.range,
     })
 }
 
 impl Node for JoinedStr {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
+            node_index,
             values,
             runtime_values,
             range,
@@ -563,12 +781,12 @@ impl Node for JoinedStr {
             BoxedSlice(values).ast_to_object(vm, source_file)
         };
         dict.set_item("values", values, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "JoinedStr")?;
@@ -584,7 +802,7 @@ pub(super) enum JoinedStrPart {
 
 // constructor
 impl Node for JoinedStrPart {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::FormattedValue(value) => value.ast_to_object(vm, source_file),
             Self::Constant(value) => value.ast_to_object(vm, source_file),
@@ -592,7 +810,7 @@ impl Node for JoinedStrPart {
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if is_node_instance(vm, &object, pyast::NodeExprFormattedValue::static_type())? {
@@ -613,6 +831,7 @@ impl Node for JoinedStrPart {
 
 #[derive(Debug)]
 pub(super) struct FormattedValue {
+    node_index: ast::AtomicNodeIndex,
     value: Box<ast::Expr>,
     conversion: ast::ConversionFlag,
     format_spec: Option<Box<ast::Expr>>,
@@ -622,11 +841,12 @@ pub(super) struct FormattedValue {
 // constructor
 pub(super) fn formatted_value_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<FormattedValue> {
     Ok(FormattedValue {
+        node_index: range.node_index(),
         value: get_required_node_field(vm, source_file, object, "value", "FormattedValue")?,
         conversion: Node::ast_from_object(
             vm,
@@ -636,13 +856,14 @@ pub(super) fn formatted_value_from_object_with_range(
         format_spec: get_node_field_opt(vm, object, "format_spec")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for FormattedValue {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
+            node_index,
             value,
             conversion,
             format_spec,
@@ -662,12 +883,12 @@ impl Node for FormattedValue {
             vm,
         )
         .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "FormattedValue")?;
@@ -680,7 +901,9 @@ pub(super) fn formatted_value_to_expr(
     formatted: FormattedValue,
 ) -> ast::Expr {
     let range = formatted.range;
+    let node_index = formatted.node_index.clone();
     JoinedStr {
+        node_index,
         range,
         values: vec![JoinedStrPart::FormattedValue(formatted)].into_boxed_slice(),
         runtime_values: None,
@@ -690,18 +913,19 @@ pub(super) fn formatted_value_to_expr(
 
 pub(super) fn fstring_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     expression: ast::ExprFString,
 ) -> PyObjectRef {
     let ast::ExprFString {
         range,
         mut value,
-        node_index: _,
+        node_index,
         runtime_joined_str,
         runtime_values,
     } = expression;
     if let Some(joined_str) = runtime_joined_str {
         return JoinedStr {
+            node_index,
             range,
             values: Vec::new().into_boxed_slice(),
             runtime_values: Some(joined_str.into_iter().map(Some).collect()),
@@ -711,6 +935,7 @@ pub(super) fn fstring_to_object(
 
     if let Some(values) = runtime_values {
         return JoinedStr {
+            node_index,
             range,
             values: Vec::new().into_boxed_slice(),
             runtime_values: Some(values),
@@ -718,22 +943,17 @@ pub(super) fn fstring_to_object(
         .ast_to_object(vm, source_file);
     }
 
-    let default_part = ast::FStringPart::FString(ast::FString {
-        node_index: Default::default(),
-        range: Default::default(),
-        elements: Default::default(),
-        flags: ast::FStringFlags::empty(),
-    });
     let mut values = Vec::new();
-    for i in 0..value.as_slice().len() {
-        let part = core::mem::replace(value.iter_mut().nth(i).unwrap(), default_part.clone());
-        match part {
+    for part in &mut value {
+        match take_fstring_part(part) {
             ast::FStringPart::Literal(literal) => {
-                values.push(JoinedStrPart::Constant(Constant::new_str(
+                let mut constant = Constant::new_str(
                     rustpython_codegen::string_literal_part_value(source_file, &literal),
                     literal.flags.prefix(),
                     literal.range,
-                )));
+                );
+                constant.node_index = literal.node_index;
+                values.push(JoinedStrPart::Constant(constant));
             }
             ast::FStringPart::FString(ast::FString {
                 range: _,
@@ -747,15 +967,13 @@ pub(super) fn fstring_to_object(
             }
         }
     }
-    let values = normalize_joined_str_parts(values);
-    for part in &values {
-        if let JoinedStrPart::FormattedValue(value) = part
-            && let Some(format_spec) = &value.format_spec
-        {
-            warn_invalid_escape_sequences_in_format_spec(vm, source_file, format_spec.range());
-        }
-    }
+    let values = if source_file.has_locations() {
+        values
+    } else {
+        normalize_joined_str_parts(values)
+    };
     let c = JoinedStr {
+        node_index,
         range,
         values: values.into_boxed_slice(),
         runtime_values: None,
@@ -767,57 +985,56 @@ pub(super) fn fstring_to_object(
 
 fn push_ruff_tstring_element(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     flags: ast::AnyStringFlags,
     element: ast::InterpolatedStringElement,
     output: &mut Vec<TemplateStrPart>,
 ) {
     match element {
         ast::InterpolatedStringElement::Literal(literal) => {
-            output.push(TemplateStrPart::Constant(Constant::new_str(
+            let mut constant = Constant::new_str(
                 rustpython_codegen::interpolated_string_literal_value(source_file, &literal, flags),
                 ast::str_prefix::StringLiteralPrefix::Empty,
                 literal.range,
-            )));
+            );
+            constant.node_index = literal.node_index;
+            output.push(TemplateStrPart::Constant(constant));
         }
-        ast::InterpolatedStringElement::Interpolation(ast::InterpolatedElement {
-            range,
-            expression,
-            debug_text,
-            mut conversion,
-            format_spec,
-            node_index: _,
-            runtime_str,
-            runtime_interpolation_format_spec,
-            runtime_formatted_value_format_spec: _,
-        }) => {
-            let expr_range =
-                extend_expr_range_with_wrapping_parens(source_file, range, expression.range())
-                    .unwrap_or_else(|| expression.range());
-            let expr_str = if let Some(debug_text) = &debug_text {
+        ast::InterpolatedStringElement::Interpolation(interpolation) => {
+            let expr_str =
+                rustpython_codegen::interpolation_expression_text(source_file, &interpolation)
+                    .unwrap_or_else(|| {
+                        source_file
+                            .source_text()
+                            .slice(interpolation.expression.range())
+                            .to_owned()
+                    });
+            let ast::InterpolatedElement {
+                range,
+                expression,
+                debug_text,
+                mut conversion,
+                format_spec,
+                node_index,
+                runtime_str,
+                runtime_interpolation_format_spec,
+                ..
+            } = interpolation;
+            if let Some(debug_text) = &debug_text {
                 output.push(TemplateStrPart::Constant(interpolation_debug_constant(
                     source_file,
                     debug_text,
                     expression.range(),
                 )));
                 conversion = debug_conversion(conversion, format_spec.is_some());
-                let expr_source = source_file.source_text().slice(expr_range);
-                let mut expr_with_debug = String::with_capacity(
-                    debug_text.leading().len() + expr_source.len() + debug_text.trailing().len(),
-                );
-                expr_with_debug.push_str(debug_text.leading());
-                expr_with_debug.push_str(expr_source);
-                expr_with_debug.push_str(debug_text.trailing());
-                strip_interpolation_expr(&expr_with_debug)
-            } else {
-                tstring_interpolation_expr_str(source_file, range, expr_range)
-            };
+            }
             let runtime_interpolation = super::constant::runtime_interpolation_object(
                 vm,
                 runtime_str,
                 runtime_interpolation_format_spec,
             );
             output.push(TemplateStrPart::Interpolation(TStringInterpolation {
+                node_index,
                 value: expression,
                 str: runtime_interpolation
                     .as_ref()
@@ -835,87 +1052,9 @@ fn push_ruff_tstring_element(
     }
 }
 
-fn tstring_interpolation_expr_str(
-    source_file: &SourceFile,
-    interpolation_range: TextRange,
-    expr_range: TextRange,
-) -> String {
-    let expr_range =
-        extend_expr_range_with_wrapping_parens(source_file, interpolation_range, expr_range)
-            .unwrap_or(expr_range);
-    let start = interpolation_range.start() + TextSize::from(1);
-    let start = if start > expr_range.end() {
-        expr_range.start()
-    } else {
-        start
-    };
-    let expr_source = source_file
-        .source_text()
-        .slice(TextRange::new(start, expr_range.end()));
-    strip_interpolation_expr(expr_source)
-}
-
-fn extend_expr_range_with_wrapping_parens(
-    source_file: &SourceFile,
-    interpolation_range: TextRange,
-    expr_range: TextRange,
-) -> Option<TextRange> {
-    let left_slice = source_file.source_text().slice(TextRange::new(
-        interpolation_range.start(),
-        expr_range.start(),
-    ));
-    let mut left_char: Option<(usize, char)> = None;
-    for (idx, ch) in left_slice
-        .char_indices()
-        .collect::<Vec<_>>()
-        .into_iter()
-        .rev()
-    {
-        if !ch.is_whitespace() {
-            left_char = Some((idx, ch));
-            break;
-        }
-    }
-    let (left_idx, left_ch) = left_char?;
-    if left_ch != '(' {
-        return None;
-    }
-
-    let right_slice = source_file
-        .source_text()
-        .slice(TextRange::new(expr_range.end(), interpolation_range.end()));
-    let mut right_char: Option<(usize, char)> = None;
-    for (idx, ch) in right_slice.char_indices() {
-        if !ch.is_whitespace() {
-            right_char = Some((idx, ch));
-            break;
-        }
-    }
-    let (right_idx, right_ch) = right_char?;
-    if right_ch != ')' {
-        return None;
-    }
-
-    let left_pos = interpolation_range.start() + TextSize::from(left_idx as u32);
-    let right_pos = expr_range.end() + TextSize::from(right_idx as u32);
-    Some(TextRange::new(left_pos, right_pos + TextSize::from(1)))
-}
-
-fn strip_interpolation_expr(expr_source: &str) -> String {
-    let mut end = expr_source.len();
-    for (idx, ch) in expr_source.char_indices().rev() {
-        if ch.is_whitespace() || ch == '=' {
-            end = idx;
-            continue;
-        }
-        end = idx + ch.len_utf8();
-        break;
-    }
-    expr_source[..end].to_owned()
-}
-
 #[derive(Debug)]
 pub(super) struct TemplateStr {
+    node_index: ast::AtomicNodeIndex,
     pub(super) range: TextRange,
     pub(super) values: Box<[TemplateStrPart]>,
     pub(super) runtime_values: Option<Vec<Option<ast::Expr>>>,
@@ -923,10 +1062,11 @@ pub(super) struct TemplateStr {
 
 pub(super) fn template_str_to_expr(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     template: TemplateStr,
 ) -> PyResult<ast::Expr> {
     let TemplateStr {
+        node_index,
         range,
         values,
         runtime_values: raw_runtime_values,
@@ -934,7 +1074,7 @@ pub(super) fn template_str_to_expr(
     let elements = template_parts_to_elements(vm, source_file, values)?;
     let tstring = ast::TString {
         range,
-        node_index: Default::default(),
+        node_index: node_index.clone(),
         elements,
         flags: ast::TStringFlags::empty(),
     };
@@ -947,7 +1087,7 @@ pub(super) fn template_str_to_expr(
             }
         });
     Ok(ast::Expr::TString(ast::ExprTString {
-        node_index: Default::default(),
+        node_index,
         range,
         value: ast::TStringValue::single(tstring),
         runtime_template_str,
@@ -957,20 +1097,21 @@ pub(super) fn template_str_to_expr(
 
 pub(super) fn interpolation_to_expr(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     interpolation: TStringInterpolation,
 ) -> PyResult<ast::Expr> {
     let range = interpolation.range;
+    let node_index = interpolation.node_index.clone();
     let part = TemplateStrPart::Interpolation(interpolation);
     let elements = template_parts_to_elements(vm, source_file, vec![part].into_boxed_slice())?;
     let tstring = ast::TString {
         range,
-        node_index: Default::default(),
+        node_index: node_index.clone(),
         elements,
         flags: ast::TStringFlags::empty(),
     };
     Ok(ast::Expr::TString(ast::ExprTString {
-        node_index: Default::default(),
+        node_index,
         range,
         value: ast::TStringValue::single(tstring),
         runtime_template_str: None,
@@ -980,7 +1121,7 @@ pub(super) fn interpolation_to_expr(
 
 fn template_parts_to_elements(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     values: Box<[TemplateStrPart]>,
 ) -> PyResult<ast::InterpolatedStringElements> {
     let mut elements = Vec::with_capacity(values.len());
@@ -992,7 +1133,7 @@ fn template_parts_to_elements(
 
 fn template_part_to_element(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     part: TemplateStrPart,
 ) -> PyResult<ast::InterpolatedStringElement> {
     match part {
@@ -1003,13 +1144,14 @@ fn template_part_to_element(
             Ok(ast::InterpolatedStringElement::Literal(
                 ast::InterpolatedStringLiteralElement {
                     range: constant.range,
-                    node_index: Default::default(),
+                    node_index: constant.node_index,
                     value: value.to_string_lossy().into(),
                 },
             ))
         }
         TemplateStrPart::Interpolation(interpolation) => {
             let TStringInterpolation {
+                node_index,
                 value,
                 str,
                 conversion,
@@ -1026,7 +1168,7 @@ fn template_part_to_element(
             Ok(ast::InterpolatedStringElement::Interpolation(
                 ast::InterpolatedElement {
                     range,
-                    node_index: Default::default(),
+                    node_index,
                     expression: value,
                     debug_text: None,
                     conversion,
@@ -1043,22 +1185,24 @@ fn template_part_to_element(
 // constructor
 pub(super) fn template_str_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<TemplateStr> {
     let values: Vec<Option<ast::Expr>> =
         get_node_list_field(vm, source_file, object, "values", "TemplateStr")?;
     Ok(TemplateStr {
+        node_index: range.node_index(),
         values: Vec::new().into_boxed_slice(),
         runtime_values: Some(values),
-        range,
+        range: range.range,
     })
 }
 
 impl Node for TemplateStr {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
+            node_index,
             values,
             runtime_values,
             range,
@@ -1073,12 +1217,12 @@ impl Node for TemplateStr {
             BoxedSlice(values).ast_to_object(vm, source_file)
         };
         dict.set_item("values", values, vm).unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "TemplateStr")?;
@@ -1094,7 +1238,7 @@ pub(super) enum TemplateStrPart {
 
 // constructor
 impl Node for TemplateStrPart {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::Interpolation(value) => value.ast_to_object(vm, source_file),
             Self::Constant(value) => value.ast_to_object(vm, source_file),
@@ -1102,7 +1246,7 @@ impl Node for TemplateStrPart {
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if is_node_instance(vm, &object, pyast::NodeExprInterpolation::static_type())? {
@@ -1123,6 +1267,7 @@ impl Node for TemplateStrPart {
 
 #[derive(Debug)]
 pub(super) struct TStringInterpolation {
+    node_index: ast::AtomicNodeIndex,
     value: Box<ast::Expr>,
     str: PyObjectRef,
     conversion: ast::ConversionFlag,
@@ -1133,9 +1278,9 @@ pub(super) struct TStringInterpolation {
 // constructor
 pub(super) fn tstring_interpolation_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<TStringInterpolation> {
     let value = get_required_node_field(vm, source_file, object, "value", "Interpolation")?;
     let str = get_node_field(vm, object, "str", "Interpolation")?;
@@ -1148,17 +1293,19 @@ pub(super) fn tstring_interpolation_from_object_with_range(
         .map(|obj| Node::ast_from_object(vm, source_file, obj))
         .transpose()?;
     Ok(TStringInterpolation {
+        node_index: range.node_index(),
         value,
         str,
         conversion,
         format_spec,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for TStringInterpolation {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
+            node_index,
             value,
             str,
             conversion,
@@ -1180,12 +1327,12 @@ impl Node for TStringInterpolation {
             vm,
         )
         .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = range_from_object(vm, source_file, &object, "Interpolation")?;
@@ -1195,18 +1342,19 @@ impl Node for TStringInterpolation {
 
 pub(super) fn tstring_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     expression: ast::ExprTString,
 ) -> PyObjectRef {
     let ast::ExprTString {
         range,
         mut value,
-        node_index: _,
+        node_index,
         runtime_template_str,
         runtime_values,
     } = expression;
     if let Some(template_str) = runtime_template_str {
         return TemplateStr {
+            node_index,
             range,
             values: Vec::new().into_boxed_slice(),
             runtime_values: Some(template_str.into_iter().map(Some).collect()),
@@ -1216,6 +1364,7 @@ pub(super) fn tstring_to_object(
 
     if let Some(values) = runtime_values {
         return TemplateStr {
+            node_index,
             range,
             values: Vec::new().into_boxed_slice(),
             runtime_values: Some(values),
@@ -1252,8 +1401,13 @@ pub(super) fn tstring_to_object(
             push_ruff_tstring_element(vm, source_file, flags, element, &mut values);
         }
     }
-    let values = normalize_template_str_parts(values);
+    let values = if source_file.has_locations() {
+        values
+    } else {
+        normalize_template_str_parts(values)
+    };
     let c = TemplateStr {
+        node_index,
         range,
         values: values.into_boxed_slice(),
         runtime_values: None,
@@ -1263,7 +1417,7 @@ pub(super) fn tstring_to_object(
 
 fn standalone_tstring_interpolation_to_object(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     value: &ast::TStringValue,
     str: PyObjectRef,
     format_spec: Option<Box<ast::Expr>>,
@@ -1279,6 +1433,7 @@ fn standalone_tstring_interpolation_to_object(
         return None;
     }
     let interpolation = TStringInterpolation {
+        node_index: interp.node_index.clone(),
         value: interp.expression.clone(),
         str,
         conversion: interp.conversion,
diff --git a/crates/vm/src/stdlib/_ast/type_ignore.rs b/crates/vm/src/stdlib/_ast/type_ignore.rs
index d51e54f1c5d..ffc69ff856b 100644
--- a/crates/vm/src/stdlib/_ast/type_ignore.rs
+++ b/crates/vm/src/stdlib/_ast/type_ignore.rs
@@ -1,5 +1,5 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 pub(super) enum TypeIgnore {
     None,
@@ -8,7 +8,7 @@ pub(super) enum TypeIgnore {
 
 // sum
 impl Node for TypeIgnore {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::None => vm.ctx.none(),
             Self::TypeIgnore(cons) => cons.ast_to_object(vm, source_file),
@@ -16,7 +16,7 @@ impl Node for TypeIgnore {
     }
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(if vm.is_none(&object) {
@@ -43,7 +43,7 @@ pub(super) struct TypeIgnoreTypeIgnore {
 
 // constructor
 impl Node for TypeIgnoreTypeIgnore {
-    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, _source_file: &AstSourceContext) -> PyObjectRef {
         let Self { lineno, tag } = self;
         let node = NodeAst
             .into_ref_with_type(
@@ -60,7 +60,7 @@ impl Node for TypeIgnoreTypeIgnore {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        _source_file: &SourceFile,
+        _source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(Self {
diff --git a/crates/vm/src/stdlib/_ast/type_parameters.rs b/crates/vm/src/stdlib/_ast/type_parameters.rs
index a15e564e53d..1a62953d10f 100644
--- a/crates/vm/src/stdlib/_ast/type_parameters.rs
+++ b/crates/vm/src/stdlib/_ast/type_parameters.rs
@@ -1,8 +1,8 @@
+use super::AstSourceContext;
 use super::*;
-use rustpython_compiler_core::SourceFile;
 
 impl Node for ast::TypeParams {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         self.runtime_type_params.map_or_else(
             || self.type_params.ast_to_object(vm, source_file),
             |values| values.ast_to_object(vm, source_file),
@@ -11,7 +11,7 @@ impl Node for ast::TypeParams {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         Ok(type_params_from_values(
@@ -27,7 +27,7 @@ impl Node for ast::TypeParams {
 
 pub(super) fn type_params_from_field(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
     field: &'static str,
     typ: &str,
@@ -61,7 +61,7 @@ fn lower_nullable_type_params(values: &[Option<ast::TypeParam>]) -> Vec<ast::Typ
 
 // sum
 impl Node for ast::TypeParam {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         match self {
             Self::TypeVar(cons) => cons.ast_to_object(vm, source_file),
             Self::ParamSpec(cons) => cons.ast_to_object(vm, source_file),
@@ -71,7 +71,7 @@ impl Node for ast::TypeParam {
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         if vm.is_none(&object) {
@@ -121,12 +121,12 @@ impl Node for ast::TypeParam {
 // constructor
 fn type_var_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::TypeParamTypeVar> {
     Ok(ast::TypeParamTypeVar {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         name: get_required_identifier_field(vm, source_file, object, "name", "TypeVar")?,
         bound: get_node_field_opt(vm, object, "bound")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
@@ -134,14 +134,14 @@ fn type_var_from_object_with_range(
         default: get_node_field_opt(vm, object, "default_value")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::TypeParamTypeVar {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             bound,
             range,
@@ -157,13 +157,13 @@ impl Node for ast::TypeParamTypeVar {
             .unwrap();
         dict.set_item("default_value", default.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = type_param_range_from_object(vm, source_file, &object)?;
@@ -174,24 +174,24 @@ impl Node for ast::TypeParamTypeVar {
 // constructor
 fn param_spec_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::TypeParamParamSpec> {
     Ok(ast::TypeParamParamSpec {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         name: get_required_identifier_field(vm, source_file, object, "name", "ParamSpec")?,
         default: get_node_field_opt(vm, object, "default_value")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::TypeParamParamSpec {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             range,
             default,
@@ -204,13 +204,13 @@ impl Node for ast::TypeParamParamSpec {
             .unwrap();
         dict.set_item("default_value", default.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = type_param_range_from_object(vm, source_file, &object)?;
@@ -221,24 +221,24 @@ impl Node for ast::TypeParamParamSpec {
 // constructor
 fn type_var_tuple_from_object_with_range(
     vm: &VirtualMachine,
-    source_file: &SourceFile,
+    source_file: &AstSourceContext,
     object: &PyObject,
-    range: TextRange,
+    range: AstNodeRange,
 ) -> PyResult<ast::TypeParamTypeVarTuple> {
     Ok(ast::TypeParamTypeVarTuple {
-        node_index: Default::default(),
+        node_index: range.node_index(),
         name: get_required_identifier_field(vm, source_file, object, "name", "TypeVarTuple")?,
         default: get_node_field_opt(vm, object, "default_value")?
             .map(|obj| Node::ast_from_object(vm, source_file, obj))
             .transpose()?,
-        range,
+        range: range.range,
     })
 }
 
 impl Node for ast::TypeParamTypeVarTuple {
-    fn ast_to_object(self, vm: &VirtualMachine, source_file: &SourceFile) -> PyObjectRef {
+    fn ast_to_object(self, vm: &VirtualMachine, source_file: &AstSourceContext) -> PyObjectRef {
         let Self {
-            node_index: _,
+            node_index,
             name,
             range,
             default,
@@ -254,13 +254,13 @@ impl Node for ast::TypeParamTypeVarTuple {
             .unwrap();
         dict.set_item("default_value", default.ast_to_object(vm, source_file), vm)
             .unwrap();
-        node_add_location(&dict, range, vm, source_file);
+        node_add_location_for_node(&dict, range, vm, source_file, node_index.load());
         node.into()
     }
 
     fn ast_from_object(
         vm: &VirtualMachine,
-        source_file: &SourceFile,
+        source_file: &AstSourceContext,
         object: PyObjectRef,
     ) -> PyResult<Self> {
         let range = type_param_range_from_object(vm, source_file, &object)?;
diff --git a/crates/vm/src/stdlib/_ast/validate.rs b/crates/vm/src/stdlib/_ast/validate.rs
index cbdc15b53a4..b2d2b0a4b8b 100644
--- a/crates/vm/src/stdlib/_ast/validate.rs
+++ b/crates/vm/src/stdlib/_ast/validate.rs
@@ -118,6 +118,21 @@ fn validate_nonempty_seq(
     Ok(())
 }
 
+fn validate_import_names(
+    vm: &VirtualMachine,
+    names: &[ast::Alias],
+    owner: &'static str,
+) -> PyResult<()> {
+    validate_nonempty_seq(vm, names.len(), "names", owner)?;
+    for alias in names {
+        validate_name(vm, alias.name.id())?;
+        if let Some(asname) = &alias.asname {
+            validate_name(vm, asname.id())?;
+        }
+    }
+    Ok(())
+}
+
 fn validate_assignlist(
     vm: &VirtualMachine,
     targets: &[ast::Expr],
@@ -616,10 +631,11 @@ fn validate_expr(vm: &VirtualMachine, expr: &ast::Expr, ctx: ast::ExprContext) -
             validate_expr(vm, &await_expr.value, ast::ExprContext::Load)
         }
         ast::Expr::Compare(compare) => {
-            if compare.comparators.is_empty() {
+            let comparators = compare.operands.get(1..).unwrap_or(&[]);
+            if comparators.is_empty() {
                 return Err(vm.new_value_error("Compare with no comparators"));
             }
-            if compare.comparators.len() != compare.ops.len() {
+            if comparators.len() != compare.ops.len() {
                 return Err(vm.new_value_error(
                     "Compare has a different number of comparators and operands",
                 ));
@@ -629,8 +645,8 @@ fn validate_expr(vm: &VirtualMachine, expr: &ast::Expr, ctx: ast::ExprContext) -
                 compare.runtime_comparators.as_ref(),
                 ast::ExprContext::Load,
             )?;
-            validate_exprs(vm, &compare.comparators, ast::ExprContext::Load, false)?;
-            validate_expr(vm, &compare.left, ast::ExprContext::Load)
+            validate_exprs(vm, comparators, ast::ExprContext::Load, false)?;
+            validate_expr(vm, compare.first_operand(), ast::ExprContext::Load)
         }
         ast::Expr::Call(call) => {
             validate_expr(vm, &call.func, ast::ExprContext::Load)?;
@@ -738,6 +754,7 @@ fn validate_stmt(vm: &VirtualMachine, stmt: &ast::Stmt) -> PyResult<()> {
                 "FunctionDef"
             };
             validate_body(vm, &func.body, func.runtime_body.as_ref(), owner)?;
+            validate_name(vm, func.name.id())?;
             validate_type_params(vm, func.type_params.as_deref())?;
             validate_parameters(vm, &func.parameters)?;
             validate_runtime_expr_list_slots(
@@ -758,6 +775,7 @@ fn validate_stmt(vm: &VirtualMachine, stmt: &ast::Stmt) -> PyResult<()> {
                 class_def.runtime_body.as_ref(),
                 "ClassDef",
             )?;
+            validate_name(vm, class_def.name.id())?;
             validate_type_params(vm, class_def.type_params.as_deref())?;
             if let Some(arguments) = &class_def.arguments {
                 validate_runtime_expr_list_slots(
@@ -908,6 +926,11 @@ fn validate_stmt(vm: &VirtualMachine, stmt: &ast::Stmt) -> PyResult<()> {
                 if let Some(type_expr) = &handler.type_ {
                     validate_expr(vm, type_expr, ast::ExprContext::Load)?;
                 }
+                if !try_stmt.is_star
+                    && let Some(name) = &handler.name
+                {
+                    validate_name(vm, name.id())?;
+                }
                 validate_body(
                     vm,
                     &handler.body,
@@ -927,18 +950,14 @@ fn validate_stmt(vm: &VirtualMachine, stmt: &ast::Stmt) -> PyResult<()> {
             }
             Ok(())
         }
-        ast::Stmt::Import(import) => {
-            validate_nonempty_seq(vm, import.names.len(), "names", "Import")?;
-            Ok(())
-        }
+        ast::Stmt::Import(import) => validate_import_names(vm, &import.names, "Import"),
         ast::Stmt::ImportFrom(import) => {
             if let Some(level) = import.runtime_level
                 && level < 0
             {
                 return Err(vm.new_value_error("Negative ImportFrom level"));
             }
-            validate_nonempty_seq(vm, import.names.len(), "names", "ImportFrom")?;
-            Ok(())
+            validate_import_names(vm, &import.names, "ImportFrom")
         }
         ast::Stmt::Global(global) => {
             validate_nonempty_seq(vm, global.names.len(), "names", "Global")?;
diff --git a/crates/vm/src/stdlib/_codecs.rs b/crates/vm/src/stdlib/_codecs.rs
index a17c025f50c..23e92f84797 100644
--- a/crates/vm/src/stdlib/_codecs.rs
+++ b/crates/vm/src/stdlib/_codecs.rs
@@ -20,6 +20,36 @@ mod _codecs {
         function::ArgBytesLike,
     };
 
+    #[derive(FromArgs)]
+    struct NormalizeEncodingArgs {
+        #[pyarg(any)]
+        encoding: PyStrRef,
+    }
+
+    #[pyfunction]
+    fn _normalize_encoding(args: NormalizeEncodingArgs, vm: &VirtualMachine) -> PyResult<String> {
+        let encoding = args.encoding;
+        // CPython converts the entire input to UTF-8 before scanning for NUL.
+        if !encoding.is_utf8() {
+            let ctx = PyEncodeContext::new(encodings::utf8::ENCODING_NAME, &encoding, vm);
+            encodings::utf8::encode(ctx, &encodings::errors::Strict)?;
+        }
+        let mut normalized = String::with_capacity(encoding.byte_len());
+        let mut punct = false;
+        for byte in encoding.as_bytes().iter().copied().take_while(|b| *b != 0) {
+            if byte.is_ascii_alphanumeric() || byte == b'.' {
+                if punct && !normalized.is_empty() {
+                    normalized.push('_');
+                }
+                normalized.push(char::from(byte));
+                punct = false;
+            } else {
+                punct = true;
+            }
+        }
+        Ok(normalized)
+    }
+
     #[pyfunction]
     fn register(search_function: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
         vm.state.codec_registry.register(search_function, vm)
diff --git a/crates/vm/src/stdlib/_collections.rs b/crates/vm/src/stdlib/_collections.rs
index 1e562f0815b..e120e73cbc5 100644
--- a/crates/vm/src/stdlib/_collections.rs
+++ b/crates/vm/src/stdlib/_collections.rs
@@ -1061,18 +1061,10 @@ mod _collections {
         fn __or__(lhs: &PyObject, rhs: PyObjectRef, vm: &VirtualMachine) -> PyResult {
             let not_implemented = || Ok(vm.ctx.not_implemented.clone().into());
 
-            let (default_factory, dict) = if let Some(zelf) = lhs.downcast_ref::<Self>() {
-                if !rhs.fast_isinstance(vm.ctx.types.dict_type) {
-                    return not_implemented();
-                }
-
-                (zelf.default_factory.load_owned(), zelf.dict.copy())
+            let (zelf, other) = if let Some(zelf) = lhs.downcast_ref::<Self>() {
+                (zelf, &*rhs)
             } else if let Some(zelf) = rhs.downcast_ref::<Self>() {
-                let Some(dict) = lhs.downcast_ref::<PyDict>() else {
-                    return not_implemented();
-                };
-
-                (zelf.default_factory.load_owned(), dict.copy())
+                (zelf, lhs)
             } else {
                 return Err(vm.new_type_error(format!(
                     "unsupported operand type(s) for |: '{}' and '{}'",
@@ -1080,17 +1072,23 @@ mod _collections {
                     rhs.class().name()
                 )));
             };
-
-            dict.update(rhs.into(), KwArgs::default(), vm)?;
-
-            Ok(Self {
-                dict,
-                default_factory: match default_factory {
-                    Some(factory) => PyAtomicRef::from(Some(factory)),
-                    None => PyAtomicRef::new_empty(),
-                },
+            if !other.fast_isinstance(vm.ctx.types.dict_type) {
+                return not_implemented();
             }
-            .to_pyobject(vm))
+
+            let factory = zelf
+                .default_factory
+                .load_owned()
+                .unwrap_or_else(|| vm.ctx.none());
+            let new = zelf
+                .class()
+                .as_object()
+                .call((factory, lhs.to_owned()), vm)?;
+            let dict = new
+                .downcast_ref::<PyDict>()
+                .ok_or_else(|| vm.new_system_error("bad argument to internal function"))?;
+            dict.merge_object(rhs, vm)?;
+            Ok(new)
         }
     }
 
@@ -1193,11 +1191,11 @@ mod _collections {
             for key in iter {
                 let key = key?;
                 let hash = key.hash(vm)?;
-                let count = match entries.get_known_hash(vm, &*key, hash)? {
+                let count = match entries.get(vm, &*key, hash)? {
                     Some(old) => vm._add(&old, one.as_object())?,
                     None => one.clone().into(),
                 };
-                entries.insert_known_hash(vm, &*key, hash, count)?;
+                entries.insert(vm, &*key, hash, count)?;
             }
             return Ok(());
         }
diff --git a/crates/vm/src/stdlib/_collections/ordered_dict.rs b/crates/vm/src/stdlib/_collections/ordered_dict.rs
index 4ba9777fef5..1a2222c7bba 100644
--- a/crates/vm/src/stdlib/_collections/ordered_dict.rs
+++ b/crates/vm/src/stdlib/_collections/ordered_dict.rs
@@ -7,18 +7,15 @@ pub(crate) mod ordered_dict {
         AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
         VirtualMachine, atomic_func,
         builtins::{
-            PyDict, PyGenericAlias, PyMappingProxy, PyTuple, PyTypeRef,
-            dict::{
-                PyDictItems, set_inner_number_or, set_inner_number_subtract, set_inner_number_xor,
-                set_item_view_number_xor, set_view_number_and,
-            },
+            PyAnyDict, PyDict, PyGenericAlias, PyTypeRef,
+            dict::{PyDictItems, PyDictKeys, PyDictValues},
             iter::builtins_iter,
         },
         class::StaticType,
         common::{hash::PyHash, lock::PyMutex},
         convert::ToPyObject,
         dict_inner::DictKey,
-        function::{ArgIterable, FuncArgs, OptionalArg, PyArithmeticValue, PyComparisonValue},
+        function::{FuncArgs, OptionalArg, PyArithmeticValue, PyComparisonValue},
         object::{Traverse, TraverseFn},
         protocol::{PyIter, PyIterReturn, PyMappingMethods, PyNumberMethods, PySequenceMethods},
         recursion::ReprGuard,
@@ -137,7 +134,7 @@ pub(crate) mod ordered_dict {
         traverse = "manual"
     )]
     #[derive(Debug)]
-    struct PyOrderedDict {
+    pub(crate) struct PyOrderedDict {
         dict: PyDict,
         links: PyMutex<ODictLinks>,
     }
@@ -530,17 +527,17 @@ pub(crate) mod ordered_dict {
 
         #[pymethod]
         fn keys(zelf: PyRef<PyOrderedDict>, vm: &VirtualMachine) -> PyObjectRef {
-            PyODictKeys { od: zelf }.to_pyobject(vm)
+            PyODictKeys::new(zelf).to_pyobject(vm)
         }
 
         #[pymethod]
         fn values(zelf: PyRef<PyOrderedDict>, vm: &VirtualMachine) -> PyObjectRef {
-            PyODictValues { od: zelf }.to_pyobject(vm)
+            PyODictValues::new(zelf).to_pyobject(vm)
         }
 
         #[pymethod]
         fn items(zelf: PyRef<PyOrderedDict>, vm: &VirtualMachine) -> PyObjectRef {
-            PyOrderedDictItems { od: zelf }.to_pyobject(vm)
+            PyOrderedDictItems::new(zelf).to_pyobject(vm)
         }
 
         #[pymethod]
@@ -927,312 +924,129 @@ pub(crate) mod ordered_dict {
         }
     }
 
-    fn odict_view_eq(
-        od: &PyRef<PyOrderedDict>,
-        kind: u8,
-        other: &PyObject,
-        vm: &VirtualMachine,
-    ) -> PyResult<PyComparisonValue> {
-        if kind == ODICT_ITER_VALUES {
-            return Ok(PyArithmeticValue::NotImplemented);
-        }
-        let set_like = other.fast_isinstance(vm.ctx.types.set_type)
-            || other.fast_isinstance(vm.ctx.types.frozenset_type)
-            || other.class().is(vm.ctx.types.dict_keys_type)
-            || other.class().is(vm.ctx.types.dict_items_type)
-            || other.downcast_ref::<PyODictKeys>().is_some()
-            || other.downcast_ref::<PyOrderedDictItems>().is_some();
-        if !set_like {
-            return Ok(PyArithmeticValue::NotImplemented);
-        }
-        let Ok(other_len) = other.length(vm) else {
-            return Ok(PyArithmeticValue::NotImplemented);
-        };
-        if od.dict.__len__() != other_len {
-            return Ok(PyArithmeticValue::Implemented(false));
-        }
-        let iter_obj = PyODictIter::new(od.clone(), kind).to_pyobject(vm);
-        let a_iter = PyIter::try_from_object(vm, iter_obj)?;
-        for item in a_iter.iter::<PyObjectRef>(vm)? {
-            let item = item?;
-            if !other.sequence_unchecked().contains(&item, vm)? {
-                return Ok(PyArithmeticValue::Implemented(false));
-            }
-        }
-        Ok(PyArithmeticValue::Implemented(true))
-    }
-
-    fn ordered_view_number_and(a: &PyObject, b: &PyObject, vm: &VirtualMachine) -> PyResult {
-        let a_is_view = a.downcast_ref::<PyODictKeys>().is_some()
-            || a.downcast_ref::<PyOrderedDictItems>().is_some();
-        let (view, other) = if a_is_view { (a, b) } else { (b, a) };
-        set_view_number_and(view, other, vm)
-    }
-
-    fn ordered_item_view_number_xor(a: &PyObject, b: &PyObject, vm: &VirtualMachine) -> PyResult {
-        let is_item_view = |obj: &PyObject| {
-            obj.downcast_ref::<PyOrderedDictItems>().is_some()
-                || obj.downcast_ref::<PyDictItems>().is_some()
-        };
-        set_item_view_number_xor(a, b, is_item_view(a) && is_item_view(b), vm)
-    }
-
     #[pyattr]
-    #[pyclass(name = "odict_keys", module = "builtins", unhashable = true, traverse)]
-    #[derive(Debug, PyPayload)]
+    #[pyclass(name = "odict_keys", module = false, base = PyDictKeys, traverse)]
+    #[derive(Debug)]
     struct PyODictKeys {
-        od: PyRef<PyOrderedDict>,
+        view: PyDictKeys,
     }
 
-    #[pyclass(with(Iterable, Comparable, AsMapping, AsSequence, AsNumber))]
-    impl Py<PyODictKeys> {
-        #[pymethod]
-        fn __reversed__(&self, vm: &VirtualMachine) -> PyObjectRef {
-            PyODictIter::new(self.od.clone(), ODICT_ITER_KEYS | ODICT_ITER_REVERSED).to_pyobject(vm)
-        }
-
-        #[pygetset]
-        fn mapping(&self, vm: &VirtualMachine) -> PyResult<PyMappingProxy> {
-            PyMappingProxy::from_object(self.od.as_object().to_owned(), vm)
-        }
-
-        #[pymethod]
-        fn isdisjoint(&self, other: ArgIterable, vm: &VirtualMachine) -> PyResult<bool> {
-            for item in other.iter(vm)? {
-                if self.od.dict.inner_getitem_opt(&*item?, vm)?.is_some() {
-                    return Ok(false);
-                }
+    impl PyODictKeys {
+        fn new(od: PyRef<PyOrderedDict>) -> Self {
+            let dict = PyAnyDict::from_object(od.as_object())
+                .expect("OrderedDict has a dict payload")
+                .to_owned();
+            Self {
+                view: PyDictKeys::new(dict),
             }
-            Ok(true)
         }
-    }
 
-    impl AsMapping for PyODictKeys {
-        fn as_mapping() -> &'static PyMappingMethods {
-            static AS_MAPPING: PyMappingMethods = PyMappingMethods {
-                length: atomic_func!(|mapping, _vm| Ok(PyODictKeys::mapping_downcast(mapping)
-                    .od
-                    .dict
-                    .__len__())),
-                ..PyMappingMethods::NOT_IMPLEMENTED
-            };
-            &AS_MAPPING
+        fn od(&self) -> &Py<PyOrderedDict> {
+            self.view
+                .dict
+                .as_object()
+                .downcast_ref::<PyOrderedDict>()
+                .expect("ordered dict views own an OrderedDict")
         }
     }
 
-    impl AsSequence for PyODictKeys {
-        fn as_sequence() -> &'static PySequenceMethods {
-            static AS_SEQUENCE: PySequenceMethods = PySequenceMethods {
-                length: atomic_func!(|seq, _vm| Ok(PyODictKeys::sequence_downcast(seq)
-                    .od
-                    .dict
-                    .__len__())),
-                contains: atomic_func!(|seq, target, vm| {
-                    PyODictKeys::sequence_downcast(seq)
-                        .od
-                        .dict
-                        .inner_getitem_opt(target, vm)
-                        .map(|v| v.is_some())
-                }),
-                ..PySequenceMethods::NOT_IMPLEMENTED
-            };
-            &AS_SEQUENCE
+    #[pyclass(flags(DISALLOW_INSTANTIATION), with(Iterable))]
+    impl Py<PyODictKeys> {
+        #[pymethod]
+        fn __reversed__(&self, vm: &VirtualMachine) -> PyObjectRef {
+            PyODictIter::new(self.od().to_owned(), ODICT_ITER_KEYS | ODICT_ITER_REVERSED)
+                .to_pyobject(vm)
         }
     }
 
     impl Iterable for PyODictKeys {
         fn iter(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult {
-            Ok(PyODictIter::new(zelf.od.clone(), ODICT_ITER_KEYS).to_pyobject(vm))
-        }
-    }
-
-    impl Comparable for PyODictKeys {
-        fn cmp(
-            zelf: &Py<Self>,
-            other: &PyObject,
-            op: PyComparisonOp,
-            vm: &VirtualMachine,
-        ) -> PyResult<PyComparisonValue> {
-            op.eq_only(|| odict_view_eq(&zelf.od, ODICT_ITER_KEYS, other, vm))
-        }
-    }
-
-    impl AsNumber for PyODictKeys {
-        fn as_number() -> &'static PyNumberMethods {
-            static AS_NUMBER: PyNumberMethods = PyNumberMethods {
-                subtract: Some(set_inner_number_subtract),
-                and: Some(ordered_view_number_and),
-                xor: Some(set_inner_number_xor),
-                or: Some(set_inner_number_or),
-                ..PyNumberMethods::NOT_IMPLEMENTED
-            };
-            &AS_NUMBER
+            Ok(PyODictIter::new(zelf.od().to_owned(), ODICT_ITER_KEYS).to_pyobject(vm))
         }
     }
 
     #[pyattr]
-    #[pyclass(name = "odict_values", module = "builtins", traverse)]
-    #[derive(Debug, PyPayload)]
+    #[pyclass(name = "odict_values", module = false, base = PyDictValues, traverse)]
+    #[derive(Debug)]
     struct PyODictValues {
-        od: PyRef<PyOrderedDict>,
+        view: PyDictValues,
     }
 
-    #[pyclass(with(Iterable, Comparable, AsMapping))]
-    impl Py<PyODictValues> {
-        #[pymethod]
-        fn __reversed__(&self, vm: &VirtualMachine) -> PyObjectRef {
-            PyODictIter::new(self.od.clone(), ODICT_ITER_VALUES | ODICT_ITER_REVERSED)
-                .to_pyobject(vm)
+    impl PyODictValues {
+        fn new(od: PyRef<PyOrderedDict>) -> Self {
+            let dict = PyAnyDict::from_object(od.as_object())
+                .expect("OrderedDict has a dict payload")
+                .to_owned();
+            Self {
+                view: PyDictValues::new(dict),
+            }
         }
 
-        #[pygetset]
-        fn mapping(&self, vm: &VirtualMachine) -> PyResult<PyMappingProxy> {
-            PyMappingProxy::from_object(self.od.as_object().to_owned(), vm)
+        fn od(&self) -> &Py<PyOrderedDict> {
+            self.view
+                .dict
+                .as_object()
+                .downcast_ref::<PyOrderedDict>()
+                .expect("ordered dict views own an OrderedDict")
         }
     }
 
-    impl AsMapping for PyODictValues {
-        fn as_mapping() -> &'static PyMappingMethods {
-            static AS_MAPPING: PyMappingMethods = PyMappingMethods {
-                length: atomic_func!(|mapping, _vm| Ok(PyODictValues::mapping_downcast(mapping)
-                    .od
-                    .dict
-                    .__len__())),
-                ..PyMappingMethods::NOT_IMPLEMENTED
-            };
-            &AS_MAPPING
+    #[pyclass(flags(DISALLOW_INSTANTIATION), with(Iterable))]
+    impl Py<PyODictValues> {
+        #[pymethod]
+        fn __reversed__(&self, vm: &VirtualMachine) -> PyObjectRef {
+            PyODictIter::new(
+                self.od().to_owned(),
+                ODICT_ITER_VALUES | ODICT_ITER_REVERSED,
+            )
+            .to_pyobject(vm)
         }
     }
 
     impl Iterable for PyODictValues {
         fn iter(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult {
-            Ok(PyODictIter::new(zelf.od.clone(), ODICT_ITER_VALUES).to_pyobject(vm))
-        }
-    }
-
-    impl Comparable for PyODictValues {
-        fn cmp(
-            zelf: &Py<Self>,
-            other: &PyObject,
-            op: PyComparisonOp,
-            vm: &VirtualMachine,
-        ) -> PyResult<PyComparisonValue> {
-            op.eq_only(|| odict_view_eq(&zelf.od, ODICT_ITER_VALUES, other, vm))
+            Ok(PyODictIter::new(zelf.od().to_owned(), ODICT_ITER_VALUES).to_pyobject(vm))
         }
     }
 
     #[pyattr]
-    #[pyclass(name = "odict_items", module = "builtins", unhashable = true, traverse)]
-    #[derive(Debug, PyPayload)]
-    pub(crate) struct PyOrderedDictItems {
-        od: PyRef<PyOrderedDict>,
+    #[pyclass(name = "odict_items", module = false, base = PyDictItems, traverse)]
+    #[derive(Debug)]
+    struct PyOrderedDictItems {
+        view: PyDictItems,
     }
 
-    #[pyclass(with(Iterable, Comparable, AsMapping, AsSequence, AsNumber))]
-    impl Py<PyOrderedDictItems> {
-        #[pymethod]
-        fn __reversed__(&self, vm: &VirtualMachine) -> PyObjectRef {
-            PyODictIter::new(self.od.clone(), ODICT_ITER_ITEMS | ODICT_ITER_REVERSED)
-                .to_pyobject(vm)
-        }
-
-        #[pygetset]
-        fn mapping(&self, vm: &VirtualMachine) -> PyResult<PyMappingProxy> {
-            PyMappingProxy::from_object(self.od.as_object().to_owned(), vm)
-        }
-
-        #[pymethod]
-        fn isdisjoint(&self, other: ArgIterable, vm: &VirtualMachine) -> PyResult<bool> {
-            for item in other.iter(vm)? {
-                let item = item?;
-                let Some(needle) = item.downcast_ref::<PyTuple>() else {
-                    continue;
-                };
-                if needle.as_slice().len() != 2 {
-                    continue;
-                }
-                let Some(found) = self.od.dict.inner_getitem_opt(&*needle.as_slice()[0], vm)?
-                else {
-                    continue;
-                };
-                if vm.identical_or_equal(&found, &needle.as_slice()[1])? {
-                    return Ok(false);
-                }
+    impl PyOrderedDictItems {
+        fn new(od: PyRef<PyOrderedDict>) -> Self {
+            let dict = PyAnyDict::from_object(od.as_object())
+                .expect("OrderedDict has a dict payload")
+                .to_owned();
+            Self {
+                view: PyDictItems::new(dict),
             }
-            Ok(true)
         }
-    }
 
-    impl AsMapping for PyOrderedDictItems {
-        fn as_mapping() -> &'static PyMappingMethods {
-            static AS_MAPPING: PyMappingMethods = PyMappingMethods {
-                length: atomic_func!(|mapping, _vm| Ok(PyOrderedDictItems::mapping_downcast(
-                    mapping
-                )
-                .od
+        fn od(&self) -> &Py<PyOrderedDict> {
+            self.view
                 .dict
-                .__len__())),
-                ..PyMappingMethods::NOT_IMPLEMENTED
-            };
-            &AS_MAPPING
+                .as_object()
+                .downcast_ref::<PyOrderedDict>()
+                .expect("ordered dict views own an OrderedDict")
         }
     }
 
-    impl AsSequence for PyOrderedDictItems {
-        fn as_sequence() -> &'static PySequenceMethods {
-            static AS_SEQUENCE: PySequenceMethods = PySequenceMethods {
-                length: atomic_func!(|seq, _vm| Ok(PyOrderedDictItems::sequence_downcast(seq)
-                    .od
-                    .dict
-                    .__len__())),
-                contains: atomic_func!(|seq, target, vm| {
-                    let needle: &Py<PyTuple> = match target.downcast_ref() {
-                        Some(needle) => needle,
-                        None => return Ok(false),
-                    };
-                    if needle.as_slice().len() != 2 {
-                        return Ok(false);
-                    }
-                    let zelf = PyOrderedDictItems::sequence_downcast(seq);
-                    let key = &needle.as_slice()[0];
-                    let Some(found) = zelf.od.dict.inner_getitem_opt(&**key, vm)? else {
-                        return Ok(false);
-                    };
-                    vm.identical_or_equal(&found, &needle.as_slice()[1])
-                }),
-                ..PySequenceMethods::NOT_IMPLEMENTED
-            };
-            &AS_SEQUENCE
+    #[pyclass(flags(DISALLOW_INSTANTIATION), with(Iterable))]
+    impl Py<PyOrderedDictItems> {
+        #[pymethod]
+        fn __reversed__(&self, vm: &VirtualMachine) -> PyObjectRef {
+            PyODictIter::new(self.od().to_owned(), ODICT_ITER_ITEMS | ODICT_ITER_REVERSED)
+                .to_pyobject(vm)
         }
     }
 
     impl Iterable for PyOrderedDictItems {
         fn iter(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult {
-            Ok(PyODictIter::new(zelf.od.clone(), ODICT_ITER_ITEMS).to_pyobject(vm))
-        }
-    }
-
-    impl Comparable for PyOrderedDictItems {
-        fn cmp(
-            zelf: &Py<Self>,
-            other: &PyObject,
-            op: PyComparisonOp,
-            vm: &VirtualMachine,
-        ) -> PyResult<PyComparisonValue> {
-            op.eq_only(|| odict_view_eq(&zelf.od, ODICT_ITER_ITEMS, other, vm))
-        }
-    }
-
-    impl AsNumber for PyOrderedDictItems {
-        fn as_number() -> &'static PyNumberMethods {
-            static AS_NUMBER: PyNumberMethods = PyNumberMethods {
-                subtract: Some(set_inner_number_subtract),
-                and: Some(ordered_view_number_and),
-                xor: Some(ordered_item_view_number_xor),
-                or: Some(set_inner_number_or),
-                ..PyNumberMethods::NOT_IMPLEMENTED
-            };
-            &AS_NUMBER
+            Ok(PyODictIter::new(zelf.od().to_owned(), ODICT_ITER_ITEMS).to_pyobject(vm))
         }
     }
 }
diff --git a/crates/vm/src/stdlib/_ctypes.rs b/crates/vm/src/stdlib/_ctypes.rs
index 780b2bc0bd2..5deb9b46b54 100644
--- a/crates/vm/src/stdlib/_ctypes.rs
+++ b/crates/vm/src/stdlib/_ctypes.rs
@@ -22,6 +22,12 @@ pub(super) use simple::{PyCSimple, PyCSimpleType};
 pub(super) use structure::PyCStructure;
 pub(super) use union::PyCUnion;
 
+pub(super) fn is_borrowed_buffer(obj: &crate::PyObject) -> bool {
+    obj.downcast_ref::<PyCData>()
+        .is_some_and(|cdata| cdata.is_borrowed())
+        || obj.downcast_ref::<function::RawMemoryBuffer>().is_some()
+}
+
 /// Extension for PyType to get StgInfo
 /// PyStgInfo_FromType
 impl Py<PyType> {
@@ -769,6 +775,9 @@ pub(crate) mod _ctypes {
         // 5. Resize the buffer
         let new_size = size as usize;
         let mut buffer = cdata.buffer.write();
+        if new_size == buffer.len() {
+            return Ok(());
+        }
         let old_data = buffer.to_vec();
         *buffer = Cow::Owned(rustpython_host_env::ctypes::resize_owned_bytes(
             &old_data, new_size,
diff --git a/crates/vm/src/stdlib/_ctypes/array.rs b/crates/vm/src/stdlib/_ctypes/array.rs
index 0504688d85c..1ce52e47cbf 100644
--- a/crates/vm/src/stdlib/_ctypes/array.rs
+++ b/crates/vm/src/stdlib/_ctypes/array.rs
@@ -1060,14 +1060,14 @@ impl AsBuffer for PyCArray {
             }
             dim_desc.reverse();
 
-            BufferDescriptor {
-                offset: 0,
-                len: buffer_len,
-                readonly: false,
+            BufferDescriptor::from_dim_desc(
+                buffer_len,
+                0,
+                false,
                 itemsize,
-                format: alloc::borrow::Cow::Owned(fmt),
+                alloc::borrow::Cow::Owned(fmt),
                 dim_desc,
-            }
+            )
         } else {
             // Fallback to simple buffer if no format/shape info
             BufferDescriptor::simple(buffer_len, false)
diff --git a/crates/vm/src/stdlib/_ctypes/base.rs b/crates/vm/src/stdlib/_ctypes/base.rs
index 2b697ef5558..916f621a15b 100644
--- a/crates/vm/src/stdlib/_ctypes/base.rs
+++ b/crates/vm/src/stdlib/_ctypes/base.rs
@@ -372,7 +372,16 @@ pub(super) static CDATA_BUFFER_METHODS: BufferMethods = BufferMethods {
     obj_bytes_mut: |buffer| {
         rustpython_common::lock::PyRwLockWriteGuard::map(
             buffer.obj_as::<PyCData>().buffer.write(),
-            |x| x.to_mut().as_mut_slice(),
+            |x| match x {
+                // ctypes buffers are writable, including views into their base object.
+                // SAFETY: requires valid writable storage and exclusive access.
+                // This guard only locks this view, not its owner or sibling views;
+                // ctypes does not enforce these requirements across aliases.
+                Cow::Borrowed(slice) => unsafe {
+                    rustpython_host_env::ctypes::borrowed_slice_as_mut(slice)
+                },
+                Cow::Owned(vec) => vec.as_mut_slice(),
+            },
         )
         .into()
     },
@@ -409,7 +418,9 @@ pub struct PyCData {
     ///
     /// SAFETY: Borrowed variant's 'static lifetime is not actually static.
     /// When created via from_address or from_base_obj, only valid for the lifetime of the source memory.
-    /// Same behavior as CPython's b_ptr (user responsibility, kept alive via b_base).
+    /// A base reference keeps the owner alive but does not pin its allocation.
+    /// Resizing the owner may invalidate the slice; locks on distinct views
+    /// do not synchronize access to their shared storage.
     pub buffer: PyRwLock<Cow<'static, [u8]>>,
     /// pointer to base object or None (b_base)
     pub base: PyRwLock<Option<PyObjectRef>>,
@@ -493,36 +504,15 @@ impl PyCData {
         }
     }
 
-    /// Create from base object with offset and data copy
-    ///
-    /// Similar to from_base_with_offset, but also stores a copy of the data.
-    /// This is used for arrays where we need our own buffer for the buffer protocol,
-    /// but still maintain the base reference for KeepRef and tracking.
-    pub fn from_base_with_data(
-        base_obj: PyObjectRef,
-        offset: usize,
-        idx: usize,
-        length: usize,
-        data: Vec<u8>,
-    ) -> Self {
-        Self {
-            buffer: PyRwLock::new(Cow::Owned(data)), // Has its own buffer copy
-            base: PyRwLock::new(Some(base_obj)),     // But still tracks base
-            base_offset: AtomicCell::new(offset),    // And offset for writes
-            index: AtomicCell::new(idx),
-            objects: PyRwLock::new(None),
-            length: AtomicCell::new(length),
-            kept_refs: PyRwLock::new(std::collections::HashMap::new()),
-        }
-    }
-
     /// Create from base object's buffer
     ///
     /// This creates a borrowed view into the base's buffer at the given address.
-    /// The base object is stored in b_base to keep the memory alive.
+    /// The base object is stored in b_base to keep the owner alive, not to pin its allocation.
     ///
     /// # Safety
-    /// ptr must point into base_obj's buffer and remain valid as long as base_obj is alive.
+    /// `ptr` must cover `size` valid bytes for the lifetime of the returned view.
+    /// Keeping `base_obj` alive does not prevent reallocation or incompatible
+    /// access through another alias; the caller must account for both.
     pub unsafe fn from_base_obj(
         ptr: *mut u8,
         size: usize,
@@ -530,7 +520,7 @@ impl PyCData {
         idx: usize,
     ) -> Self {
         // = PyCData_FromBaseObj
-        // SAFETY: ptr points into base_obj's buffer, kept alive via base reference
+        // SAFETY: the caller must uphold the storage validity and aliasing requirements above.
         let slice = unsafe { rustpython_host_env::ctypes::borrow_memory(ptr, size) };
         Self {
             buffer: PyRwLock::new(Cow::Borrowed(slice)),
@@ -1051,13 +1041,21 @@ impl PyCData {
                 return Ok(vm.ctx.new_str(wchar_array_field_value(data)).into());
             }
 
-            // Other array types - create array with a copy of data from the base's buffer
-            // The array also keeps a reference to the base for keeping it alive and for writes
-            let array_data = buffer[offset..offset + size].to_vec();
+            // Array fields share their storage with the containing object.
+            // SAFETY: the field lies within the currently locked base buffer.
+            // The base reference retains the owner, not the allocation address;
+            // a reallocating resize can invalidate this view, as with other ctypes views.
+            let cdata_obj = unsafe {
+                Self::from_base_obj(
+                    buffer.as_ptr().add(offset).cast_mut(),
+                    size,
+                    base_obj,
+                    index,
+                )
+            };
+            cdata_obj.base_offset.store(offset);
+            cdata_obj.length.store(stg.length);
             drop(buffer);
-
-            let cdata_obj =
-                Self::from_base_with_data(base_obj, offset, index, stg.length, array_data);
             let array_type: PyTypeRef = proto
                 .to_owned()
                 .downcast()
diff --git a/crates/vm/src/stdlib/_ctypes/function.rs b/crates/vm/src/stdlib/_ctypes/function.rs
index e67e3871d14..a1d085fa0c3 100644
--- a/crates/vm/src/stdlib/_ctypes/function.rs
+++ b/crates/vm/src/stdlib/_ctypes/function.rs
@@ -27,7 +27,7 @@ use rustpython_host_env::ctypes::ComMethodError;
 use rustpython_host_env::ctypes::{
     CTypeLayout, CallError, CallOptions, CallRet, CallValue, FfiCif, FfiCodePtr, FfiType,
     RawMemoryView, RawMemoryViewError, StringAtError, call, ffi_pointer_type, ffi_type_from_code,
-    ffi_void_type, has_pointer_width, offset_address, pointer_bytes, pointer_format, pointer_size,
+    ffi_void_type, has_pointer_width, pointer_bytes, pointer_format, pointer_size,
     simple_type_is_pointer, write_pointer_to_buffer_at, write_prefix_limited,
 };
 
@@ -388,17 +388,26 @@ impl Debug for PyCFuncPtr {
     }
 }
 
+// c_void_p accepts only P-tagged argument wrappers.
+fn carg_pointer(arg: &PyObject) -> Option<usize> {
+    let carg = arg.downcast_ref::<CArgObject>()?;
+    if carg.tag != b'P' {
+        return None;
+    }
+    match &carg.value {
+        CArgValue::Pointer(address) => Some(*address),
+        CArgValue::Typed { code: 'P', bytes } => {
+            Some(rustpython_host_env::ctypes::read_pointer_from_buffer(bytes))
+        }
+        _ => None,
+    }
+}
+
 /// Extract pointer value from a ctypes argument (c_void_p conversion)
 fn extract_ptr_from_arg(arg: &PyObject, vm: &VirtualMachine) -> PyResult<usize> {
-    // Try CArgObject first - extract the wrapped pointer value, applying offset
-    if let Some(carg) = arg.downcast_ref::<super::_ctypes::CArgObject>() {
-        if carg.offset != 0
-            && let Some(cdata) = carg.obj.downcast_ref::<PyCData>()
-        {
-            let base = cdata.buffer.read().as_ptr() as usize;
-            return Ok(offset_address(base, carg.offset));
-        }
-        return extract_ptr_from_arg(&carg.obj, vm);
+    // byref() has already stored the address, including its byte offset.
+    if let Some(address) = carg_pointer(arg) {
+        return Ok(address);
     }
     // Try to get pointer value from various ctypes types
     if let Some(ptr) = arg.downcast_ref::<PyCPointer>() {
@@ -509,7 +518,10 @@ fn cast_check_pointertype(ctype: &PyObject, vm: &VirtualMachine) -> bool {
         return true;
     }
 
-    // PyCFuncPtrTypeObject_Check - TODO
+    // PyCFuncPtrTypeObject_Check
+    if ctype.class().fast_issubclass(PyCFuncPtrType::static_type()) {
+        return true;
+    }
 
     // simple pointer types via StgInfo.proto (c_void_p, c_char_p, etc.)
     if let Ok(type_attr) = ctype.get_attr("_type_", vm)
@@ -546,6 +558,8 @@ pub(super) fn cast_impl(
     let ptr_value: usize = if vm.is_none(obj) {
         // None → NULL pointer
         0
+    } else if let Some(address) = carg_pointer(obj) {
+        address
     } else if let Ok(int_val) = obj.try_int(vm) {
         // int/long → direct pointer value
         int_val.as_bigint().to_usize().unwrap_or(0)
@@ -562,6 +576,9 @@ pub(super) fn cast_impl(
         // Simple type (c_void_p, c_char_p, etc.) → value from buffer
         let buffer = simple.0.buffer.read();
         rustpython_host_env::ctypes::read_pointer_from_buffer(&buffer)
+    } else if let Some(funcptr) = obj.downcast_ref::<PyCFuncPtr>() {
+        // A function pointer stores the executable address in its buffer.
+        funcptr.get_func_ptr()
     } else if let Some(cdata) = obj.downcast_ref::<PyCData>() {
         // Array, Structure, Union → buffer address (b_ptr)
         cdata.buffer.read().as_ptr() as usize
@@ -1657,14 +1674,7 @@ impl AsBuffer for PyCFuncPtr {
         } else {
             (Cow::Borrowed(pointer_format()), pointer_size())
         };
-        let desc = BufferDescriptor {
-            offset: 0,
-            len: itemsize,
-            readonly: false,
-            itemsize,
-            format,
-            dim_desc: vec![],
-        };
+        let desc = BufferDescriptor::from_dim_desc(itemsize, 0, false, itemsize, format, vec![]);
         let buf = PyBuffer::new(zelf.to_owned().into(), desc, &CDATA_BUFFER_METHODS);
         Ok(buf)
     }
@@ -2021,3 +2031,41 @@ impl Py<PyCThunk> {
         self.callable.clone()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{TryFromObject, class::PyClassImpl, function::ArgBytesLike};
+
+    #[test]
+    fn unlocked_raw_buffers_are_copied_even_when_readonly() {
+        crate::Interpreter::without_stdlib(Default::default()).enter(|vm| {
+            let _class = RawMemoryBuffer::make_static_type();
+            for readonly in [false, true] {
+                let mut storage = *b"before";
+                let view = memoryview_at_impl(
+                    storage.as_mut_ptr() as usize,
+                    storage.len() as isize,
+                    readonly,
+                    vm,
+                )
+                .unwrap();
+                let buffer = ArgBytesLike::try_from_object(vm, view).unwrap();
+                let snapshot = buffer.borrow_buf_unlocked(vm).unwrap();
+                assert_ne!(snapshot.as_ptr(), storage.as_ptr());
+                storage.copy_from_slice(b"after!");
+                assert_eq!(&*snapshot, b"before");
+            }
+
+            let bytes = vm.ctx.new_bytes(b"bytes".to_vec());
+            let view = crate::builtins::PyMemoryView::from_object(bytes.as_object(), vm)
+                .unwrap()
+                .into_pyobject(vm);
+            for obj in [bytes.clone().into(), view] {
+                let buffer = ArgBytesLike::try_from_object(vm, obj).unwrap();
+                let borrowed = buffer.borrow_buf_unlocked(vm).unwrap();
+                assert_eq!(borrowed.as_ptr(), bytes.as_bytes().as_ptr());
+            }
+        });
+    }
+}
diff --git a/crates/vm/src/stdlib/_ctypes/pointer.rs b/crates/vm/src/stdlib/_ctypes/pointer.rs
index 6a8ebe660a0..27778a01c0f 100644
--- a/crates/vm/src/stdlib/_ctypes/pointer.rs
+++ b/crates/vm/src/stdlib/_ctypes/pointer.rs
@@ -781,14 +781,7 @@ impl AsBuffer for PyCPointer {
             .map_or(Cow::Borrowed("&B"), Cow::Owned);
         let itemsize = stg_info.size;
         // Pointer types are scalars with ndim=0, shape=()
-        let desc = BufferDescriptor {
-            offset: 0,
-            len: itemsize,
-            readonly: false,
-            itemsize,
-            format,
-            dim_desc: vec![],
-        };
+        let desc = BufferDescriptor::from_dim_desc(itemsize, 0, false, itemsize, format, vec![]);
         let buf = PyBuffer::new(zelf.to_owned().into(), desc, &CDATA_BUFFER_METHODS);
         Ok(buf)
     }
diff --git a/crates/vm/src/stdlib/_ctypes/simple.rs b/crates/vm/src/stdlib/_ctypes/simple.rs
index 1a0e12ba457..18b67fca7c8 100644
--- a/crates/vm/src/stdlib/_ctypes/simple.rs
+++ b/crates/vm/src/stdlib/_ctypes/simple.rs
@@ -1288,14 +1288,7 @@ impl AsBuffer for PyCSimple {
             .map_or(Cow::Borrowed("B"), Cow::Owned);
         let itemsize = stg_info.size;
         // Simple types are scalars with ndim=0, shape=()
-        let desc = BufferDescriptor {
-            offset: 0,
-            len: itemsize,
-            readonly: false,
-            itemsize,
-            format,
-            dim_desc: vec![],
-        };
+        let desc = BufferDescriptor::from_dim_desc(itemsize, 0, false, itemsize, format, vec![]);
         let buf = PyBuffer::new(zelf.to_owned().into(), desc, &CDATA_BUFFER_METHODS);
         Ok(buf)
     }
diff --git a/crates/vm/src/stdlib/_ctypes/structure.rs b/crates/vm/src/stdlib/_ctypes/structure.rs
index bc4b3d54c8f..ed4cd254883 100644
--- a/crates/vm/src/stdlib/_ctypes/structure.rs
+++ b/crates/vm/src/stdlib/_ctypes/structure.rs
@@ -823,14 +823,14 @@ impl AsBuffer for PyCStructure {
         // Structure: ndim=0, shape=(), itemsize=struct_size
         let buf = PyBuffer::new(
             zelf.to_owned().into(),
-            BufferDescriptor {
-                offset: 0,
-                len: buffer_len,
-                readonly: false,
-                itemsize: buffer_len,
-                format: Cow::Owned(format),
-                dim_desc: vec![], // ndim=0 means empty dim_desc
-            },
+            BufferDescriptor::from_dim_desc(
+                buffer_len,
+                0,
+                false,
+                buffer_len,
+                Cow::Owned(format),
+                vec![], // ndim=0 means empty dim_desc
+            ),
             &CDATA_BUFFER_METHODS,
         );
         Ok(buf)
diff --git a/crates/vm/src/stdlib/_ctypes/union.rs b/crates/vm/src/stdlib/_ctypes/union.rs
index 2322d652479..8bd0125990d 100644
--- a/crates/vm/src/stdlib/_ctypes/union.rs
+++ b/crates/vm/src/stdlib/_ctypes/union.rs
@@ -684,14 +684,14 @@ impl AsBuffer for PyCUnion {
         // Union: ndim=0, shape=(), itemsize=union_size
         let buf = PyBuffer::new(
             zelf.to_owned().into(),
-            BufferDescriptor {
-                offset: 0,
-                len: buffer_len,
-                readonly: false,
-                itemsize: buffer_len,
-                format: Cow::Owned(format),
-                dim_desc: vec![], // ndim=0 means empty dim_desc
-            },
+            BufferDescriptor::from_dim_desc(
+                buffer_len,
+                0,
+                false,
+                buffer_len,
+                Cow::Owned(format),
+                vec![], // ndim=0 means empty dim_desc
+            ),
             &CDATA_BUFFER_METHODS,
         );
         Ok(buf)
diff --git a/crates/vm/src/stdlib/_functools.rs b/crates/vm/src/stdlib/_functools.rs
index 4c9725289f7..0a8c613325b 100644
--- a/crates/vm/src/stdlib/_functools.rs
+++ b/crates/vm/src/stdlib/_functools.rs
@@ -5,7 +5,8 @@ mod _functools {
     use crate::{
         Context, Py, PyObject, PyObjectRef, PyPayload, PyResult, VirtualMachine,
         builtins::{
-            PyBoundMethod, PyDict, PyDictRef, PyGenericAlias, PyTuple, PyType, PyTypeRef, object,
+            PyBoundMethod, PyDict, PyDictRef, PyGenericAlias, PyStr, PyTuple, PyType, PyTypeRef,
+            object,
         },
         common::{hash::PyHash, lock::PyRwLock},
         function::{
@@ -277,6 +278,106 @@ mod _functools {
         flags(BASETYPE, HAS_DICT, HAS_WEAKREF)
     )]
     impl PyPartial {
+        #[pyslot]
+        fn vectorcall(
+            zelf: &PyObject,
+            args: Vec<PyObjectRef>,
+            nargs: usize,
+            kwnames: Option<&[PyObjectRef]>,
+            vm: &VirtualMachine,
+        ) -> PyResult {
+            let zelf = zelf.downcast_ref::<Self>().unwrap();
+            // Keep the call's state alive before keyword lookups can execute
+            // __hash__/__eq__ and replace it through __setstate__.
+            let func = zelf.func.load_owned();
+            let stored_args = zelf.args.load_owned();
+            let keywords = zelf.keywords.load_owned();
+            let phcount = zelf.phcount.load(Ordering::Relaxed);
+
+            // Check if we have enough args to fill placeholders
+            if nargs < phcount {
+                return Err(vm.new_type_error(format!(
+                    "missing positional arguments in 'partial' call; expected at least {phcount}, got {nargs}"
+                )));
+            }
+
+            // Build combined args, replacing placeholders
+            let mut combined_args = Vec::with_capacity(stored_args.as_slice().len() + args.len());
+            let mut new_args_iter = args[..nargs].iter();
+
+            for stored_arg in stored_args.as_slice() {
+                if is_placeholder(stored_arg) {
+                    // Replace placeholder with next new arg
+                    if let Some(new_arg) = new_args_iter.next() {
+                        combined_args.push(new_arg.clone());
+                    } else {
+                        // This shouldn't happen if phcount check passed
+                        combined_args.push(stored_arg.clone());
+                    }
+                } else {
+                    combined_args.push(stored_arg.clone());
+                }
+            }
+            // Append remaining new args
+            combined_args.extend(new_args_iter.cloned());
+            let combined_nargs = combined_args.len();
+
+            let kwnames = kwnames.unwrap_or_default();
+            if func.class().slots.vectorcall.load().is_none() {
+                // FuncArgs callables retain their existing keyword binding path.
+                // In particular, do not introduce vectorcall's hash callbacks
+                // when the wrapped callable does not support vectorcall.
+                let mut kwargs = KwArgs::default();
+                for (key, value) in keywords.items_vec() {
+                    let key = key
+                        .downcast_ref::<PyStr>()
+                        .ok_or_else(|| vm.new_type_error("keywords must be strings"))?;
+                    kwargs.insert(key.as_wtf8().to_owned(), value);
+                }
+                for (key, value) in kwnames.iter().zip(&args[nargs..]) {
+                    let key = key
+                        .downcast_ref::<PyStr>()
+                        .ok_or_else(|| vm.new_type_error("keywords must be strings"))?;
+                    kwargs.insert(key.as_wtf8().to_owned(), value.clone());
+                }
+                return func.call(FuncArgs::new(combined_args, kwargs), vm);
+            }
+            if keywords.is_empty() {
+                combined_args.extend_from_slice(&args[nargs..]);
+                return func.vectorcall(combined_args, combined_nargs, Some(kwnames), vm);
+            }
+
+            // Like partial_vectorcall, copy stored keywords only when an incoming
+            // key replaces one. New keys remain a tail, preserving their identity
+            // and avoiding extra hash callbacks from an intermediate dictionary.
+            let mut merged_keywords = None;
+            let mut tail_names = Vec::new();
+            let mut tail_values = Vec::new();
+            for (key, value) in kwnames.iter().zip(&args[nargs..]) {
+                let hash = PyDict::hash_or_unhashable(&**key, vm)?;
+                if keywords.entries.contains(vm, &**key, hash)? {
+                    let merged = merged_keywords.get_or_insert_with(|| keywords.copy());
+                    merged.inner_setitem(&**key, value.clone(), vm)?;
+                } else {
+                    tail_names.push(key.clone());
+                    tail_values.push(value.clone());
+                }
+            }
+
+            let merged = merged_keywords.as_ref().unwrap_or(&keywords);
+            let mut combined_names = Vec::with_capacity(merged.__len__() + tail_names.len());
+            for (key, value) in merged.items_vec() {
+                key.downcast_ref::<PyStr>()
+                    .ok_or_else(|| vm.new_type_error("keywords must be strings"))?;
+                combined_names.push(key);
+                combined_args.push(value);
+            }
+            combined_names.extend(tail_names);
+            combined_args.extend(tail_values);
+
+            func.vectorcall(combined_args, combined_nargs, Some(&combined_names), vm)
+        }
+
         #[pygetset]
         fn __dict__(zelf: &Py<Self>, vm: &VirtualMachine) -> PyDictRef {
             zelf.as_object()
@@ -534,60 +635,14 @@ mod _functools {
         type Args = FuncArgs;
 
         fn call(zelf: &Py<Self>, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-            // Clone and release lock before calling Python code to prevent deadlock
-            let func = zelf.func.load_owned();
-            let stored_args = zelf.args.load_owned();
-            let keywords = zelf.keywords.load_owned();
-            let phcount = zelf.phcount.load(Ordering::Relaxed);
-
-            // Check if we have enough args to fill placeholders
-            if phcount > 0 && args.args.len() < phcount {
-                return Err(vm.new_type_error(format!(
-                    "missing positional arguments in 'partial' call; expected at least {}, got {}",
-                    phcount,
-                    args.args.len()
-                )));
-            }
-
-            // Build combined args, replacing placeholders
-            let mut combined_args =
-                Vec::with_capacity(stored_args.as_slice().len() + args.args.len());
-            let mut new_args_iter = args.args.iter();
-
-            for stored_arg in stored_args.as_slice() {
-                if is_placeholder(stored_arg) {
-                    // Replace placeholder with next new arg
-                    if let Some(new_arg) = new_args_iter.next() {
-                        combined_args.push(new_arg.clone());
-                    } else {
-                        // This shouldn't happen if phcount check passed
-                        combined_args.push(stored_arg.clone());
-                    }
-                } else {
-                    combined_args.push(stored_arg.clone());
-                }
-            }
-            // Append remaining new args
-            combined_args.extend(new_args_iter.cloned());
-
-            // Merge keywords from self.keywords and args.kwargs
-            let mut final_kwargs = crate::function::KwArgsMap::default();
-
-            // Add keywords from self.keywords
-            for (key, value) in &*keywords {
-                // `expect_str()` would panic on surrogate keys; keep them as WTF-8.
-                let key_str = key
-                    .downcast_ref::<crate::builtins::PyStr>()
-                    .ok_or_else(|| vm.new_type_error("keywords must be strings"))?;
-                final_kwargs.insert(key_str.as_wtf8().to_owned(), value);
-            }
-
-            // Add keywords from args.kwargs (these override self.keywords)
+            let nargs = args.args.len();
+            let mut values = args.args;
+            let mut kwnames = Vec::with_capacity(args.kwargs.len());
             for (key, value) in args.kwargs {
-                final_kwargs.insert(key, value);
+                kwnames.push(vm.ctx.new_str(key).into());
+                values.push(value);
             }
-
-            func.call(FuncArgs::new(combined_args, KwArgs::new(final_kwargs)), vm)
+            Self::vectorcall(zelf.as_object(), values, nargs, Some(&kwnames), vm)
         }
     }
 
@@ -842,7 +897,7 @@ mod _functools {
 
     #[pyclass(
         with(Constructor, Callable, GetDescriptor),
-        flags(HAS_DICT, HAS_WEAKREF)
+        flags(HAS_DICT, HAS_WEAKREF, METHOD_DESCRIPTOR)
     )]
     impl Py<PyLruCacheWrapper> {
         #[pymethod]
diff --git a/crates/vm/src/stdlib/_imp.rs b/crates/vm/src/stdlib/_imp.rs
index a2bb2a0abc6..6d3a6b0b868 100644
--- a/crates/vm/src/stdlib/_imp.rs
+++ b/crates/vm/src/stdlib/_imp.rs
@@ -193,13 +193,26 @@ fn find_frozen(name: &str, vm: &VirtualMachine) -> Result<FrozenModule, FrozenEr
 #[pymodule(with(lock))]
 mod _imp {
     use crate::{
-        PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
-        builtins::{PyBytesRef, PyCode, PyMemoryView, PyModule, PyStrRef, PyUtf8StrRef},
+        AsObject, PyObjectRef, PyPayload, PyRef, PyRefExact, PyResult, VirtualMachine,
+        builtins::{
+            PyBytesRef, PyCode, PyDict, PyImportError, PyMemoryView, PyModule, PyStrRef,
+            PyUtf8StrRef,
+        },
         import, version,
     };
 
     use super::FrozenError;
 
+    // Private exact-dict relocation primitive for future import-cache ordering.
+    #[pyfunction]
+    fn _dict_move_to_end(
+        modules: PyRefExact<PyDict>,
+        key: PyObjectRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyObjectRef> {
+        modules.move_to_end(key, vm)
+    }
+
     #[pyattr]
     fn check_hash_based_pycs(vm: &VirtualMachine) -> PyStrRef {
         vm.ctx
@@ -214,6 +227,17 @@ mod _imp {
         Vec::new()
     }
 
+    // This hook is also used by eager imports that satisfy pending lazy targets.
+    #[pyfunction]
+    fn _set_lazy_attributes(
+        _modobj: PyObjectRef,
+        name: PyStrRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        crate::lazy_import::clear_submodule(&name, false, vm)?;
+        vm.state.lazy_imports.modules.discard(name.into(), vm)
+    }
+
     #[pyfunction]
     fn is_builtin(name: PyUtf8StrRef, vm: &VirtualMachine) -> bool {
         vm.state.module_defs.contains_key(name.as_str())
@@ -226,15 +250,46 @@ mod _imp {
 
     #[pyfunction]
     fn create_builtin(spec: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        let sys_modules = vm.sys_module.get_attr("modules", vm).unwrap();
-        let name: PyUtf8StrRef = spec.get_attr("name", vm)?.try_into_value(vm)?;
+        let name_obj = spec.get_attr("name", vm)?;
+        let name: PyStrRef = name_obj.downcast().map_err(|obj| {
+            vm.new_type_error(format!(
+                "name must be string, not {:.200}",
+                obj.class().name()
+            ))
+        })?;
+        if name.is_empty() {
+            return Err(vm.new_value_error("name must not be empty"));
+        }
+        // Builtin module names use ASCII even when an unknown name is supplied.
+        if !name.as_bytes().is_ascii() {
+            vm.state
+                .codec_registry
+                .encode_text(name.clone(), "ascii", None, vm)?;
+        }
+        let name_str = name.as_utf8().expect("ASCII module name").as_str();
+        if name_str.contains('\0') {
+            return Err(vm.new_value_error("embedded null character"));
+        }
+        if !matches!(name_str, "sys" | "builtins") && !vm.state.module_defs.contains_key(name_str) {
+            let exc = vm.new_payload_exception::<PyImportError>(
+                vm.ctx.exceptions.module_not_found_error.to_owned(),
+                vec![
+                    vm.ctx
+                        .new_str(format!("{name_str} module not found"))
+                        .into(),
+                ]
+                .into(),
+            )?;
+            exc.as_object().set_attr("name", name.clone(), vm)?;
+            return Err(exc.upcast());
+        }
 
-        // Check sys.modules first
+        let sys_modules = vm.sys_module.get_attr("modules", vm)?;
+        // Only registered builtins (or the two core modules) may use this cache.
         if let Ok(module) = sys_modules.get_item(&*name, vm) {
             return Ok(module);
         }
 
-        let name_str = name.as_str();
         if let Some(&def) = vm.state.module_defs.get(name_str) {
             // Phase 1: Create module (use create slot if provided, else default creation)
             let module = if let Some(create) = def.slots.create {
@@ -251,7 +306,7 @@ mod _imp {
             module.__init_methods(vm)?;
 
             // Add to sys.modules BEFORE exec (critical for circular import handling)
-            sys_modules.set_item(name.as_pystr(), module.clone().into(), vm)?;
+            sys_modules.set_item(&*name, module.clone().into(), vm)?;
 
             // Phase 2: Call exec slot (can safely import other modules now)
             if let Some(exec) = def.slots.exec {
diff --git a/crates/vm/src/stdlib/_interpchannels.rs b/crates/vm/src/stdlib/_interpchannels.rs
index d9fde089fd9..6878ac425f2 100644
--- a/crates/vm/src/stdlib/_interpchannels.rs
+++ b/crates/vm/src/stdlib/_interpchannels.rs
@@ -366,18 +366,23 @@ pub(crate) mod _interpchannels {
 
     /// `channel_destroy`: forget the channel entirely.
     fn channel_destroy(cid: i64) -> ChanResult<Vec<(Arc<Waiting>, bool)>> {
-        let mut table = channels().lock();
-        let entry = table.refs.remove(&cid).ok_or(ChanErr::NotFound)?;
-        Ok(match entry.chan {
-            Some(chan) => drain_queue(&mut chan.state.lock()),
-            None => Vec::new(),
-        })
+        let entry = channels()
+            .lock()
+            .refs
+            .remove(&cid)
+            .ok_or(ChanErr::NotFound)?;
+        let items = match entry.chan {
+            Some(chan) => core::mem::take(&mut chan.state.lock().queue),
+            None => VecDeque::new(),
+        };
+        Ok(retire_items(items))
     }
 
-    fn drain_queue(state: &mut ChannelState) -> Vec<(Arc<Waiting>, bool)> {
-        state
-            .queue
-            .drain(..)
+    // Shared buffers can run owner callbacks when released. Call only after
+    // unlocking both the directory and channel state.
+    fn retire_items(items: VecDeque<ChannelItem>) -> Vec<(Arc<Waiting>, bool)> {
+        items
+            .into_iter()
             .filter_map(|item| item.waiting.map(|w| (w, false)))
             .collect()
     }
@@ -394,10 +399,12 @@ pub(crate) mod _interpchannels {
             return Vec::new();
         }
         let entry = table.refs.remove(&cid).expect("just looked it up");
-        match entry.chan {
-            Some(chan) => drain_queue(&mut chan.state.lock()),
-            None => Vec::new(),
-        }
+        drop(table);
+        let items = match entry.chan {
+            Some(chan) => core::mem::take(&mut chan.state.lock().queue),
+            None => VecDeque::new(),
+        };
+        retire_items(items)
     }
 
     /// `_channels_add_id_object`.
@@ -456,12 +463,13 @@ pub(crate) mod _interpchannels {
             state.closing = true;
             return Ok(Vec::new());
         }
-        let waiters = drain_queue(&mut state);
+        let items = core::mem::take(&mut state.queue);
         state.open = false;
         state.ends.release_all();
         drop(state);
         entry.chan = None;
-        Ok(waiters)
+        drop(table);
+        Ok(retire_items(items))
     }
 
     /// `channel_release`: close one or both ends for the current interpreter.
@@ -486,6 +494,7 @@ pub(crate) mod _interpchannels {
             .filter_map(|r| r.chan.clone())
             .collect();
         let mut waiters = Vec::new();
+        let mut dropped = Vec::new();
         for chan in chans {
             let mut state = chan.state.lock();
             let mut i = 0;
@@ -500,17 +509,19 @@ pub(crate) mod _interpchannels {
                     if let Some(w) = item.waiting {
                         waiters.push((w, false));
                     }
+                    dropped.push(item.data);
                     continue;
                 }
                 // UNBOUND_ERROR / UNBOUND_REPLACE keep the slot but throw the
                 // data away; the item is now "unbound".
-                item.data = None;
+                dropped.push(item.data.take());
                 i += 1;
             }
             state.ends.clear_interpreter(interpid);
             state.open = state.ends.is_open();
         }
         release_waiters_detached(waiters);
+        drop(dropped);
     }
 
     /// `resolve_unboundop`.
@@ -894,12 +905,14 @@ pub(crate) mod _interpchannels {
         let cid = parse_cid(parsed[0].as_deref().unwrap(), vm)?.0;
         let send = flag(parsed[1].as_deref(), vm)?;
         let chan = channels_lookup(cid).map_err(|e| e.into_py(cid, vm))?;
+        let interpreters = crate::vm::runtime::list_interpreters();
         let state = chan.state.lock();
         if send && state.closing {
+            drop(state);
             return Err(ChanErr::Closed.into_py(cid, vm));
         }
         let mut out = Vec::new();
-        for info in crate::vm::runtime::list_interpreters() {
+        for info in interpreters {
             if state.ends.find(info.id, send).is_some_and(|i| {
                 if send {
                     state.ends.send[i].1
@@ -907,10 +920,18 @@ pub(crate) mod _interpchannels {
                     state.ends.recv[i].1
                 }
             }) {
-                out.push(vm.ctx.new_int(info.id).into());
+                out.push(info.id);
             }
         }
-        Ok(vm.ctx.new_list(out).into())
+        drop(state);
+        Ok(vm
+            .ctx
+            .new_list(
+                out.into_iter()
+                    .map(|id| vm.ctx.new_int(id).into())
+                    .collect(),
+            )
+            .into())
     }
 
     /// `channel_send` up to its `closing` check, which precedes converting the
@@ -982,15 +1003,18 @@ pub(crate) mod _interpchannels {
         if timed_out {
             // The send is failing now, so make sure the item won't be received.
             let mut state = chan.state.lock();
-            if let Some(pos) = state.queue.iter().position(|it| {
-                it.waiting
-                    .as_ref()
-                    .is_some_and(|w| Arc::ptr_eq(w, &waiting))
-            }) {
-                state.queue.remove(pos);
-            }
+            let removed = state
+                .queue
+                .iter()
+                .position(|it| {
+                    it.waiting
+                        .as_ref()
+                        .is_some_and(|w| Arc::ptr_eq(w, &waiting))
+                })
+                .and_then(|pos| state.queue.remove(pos));
             drop(state);
             finish_closing(cid);
+            drop(removed);
             if !waiting.state.lock().received {
                 return Err(vm
                     .new_os_subtype_error(
diff --git a/crates/vm/src/stdlib/_io.rs b/crates/vm/src/stdlib/_io.rs
index d4cd66e1491..69f57e32a28 100644
--- a/crates/vm/src/stdlib/_io.rs
+++ b/crates/vm/src/stdlib/_io.rs
@@ -762,10 +762,13 @@ mod _io {
                             )));
                         }
                         let n = n as usize;
-                        let mut bytes = b.borrow_buf_mut();
-                        bytes.truncate(n);
-                        // FIXME: try to use Arc::unwrap on the bytearray to get at the inner buffer
-                        bytes.clone().to_pyobject(vm)
+                        let mut inner = b.try_resizable(vm)?;
+                        let bytes = &mut inner.elements;
+                        bytes
+                            .try_reserve_exact(n.saturating_sub(bytes.len()))
+                            .map_err(|_| vm.no_memory_error())?;
+                        bytes.resize(n, 0);
+                        core::mem::take(bytes).to_pyobject(vm)
                     }
                 })
             } else {
@@ -1436,6 +1439,7 @@ mod _io {
                     match ($x, written > 0) {
                         (Some(0), _) | (None, true) => {
                             out.truncate(written);
+                            out.shrink_to_fit();
                             return Ok(Some(out));
                         }
                         (Some(r), _) => r,
@@ -3576,27 +3580,23 @@ mod _io {
                 drop(textio);
             }
 
-            let chunk_size: isize = match value {
-                PySetterValue::Assign(object_value) => {
-                    let integer = object_value.try_index(vm)?;
-
-                    integer.try_to_primitive::<isize>(vm).map_err(|_| {
-                        let class = object_value.class();
-                        let type_name = class.name();
-                        let mut end = type_name.len().min(200);
-                        while !type_name.is_char_boundary(end) {
-                            end -= 1;
-                        }
-                        vm.new_value_error(format!(
-                            "cannot fit '{}' into an index-sized integer",
-                            &type_name[..end]
-                        ))
-                    })?
-                }
-                PySetterValue::Delete => {
-                    return Err(vm.new_attribute_error("cannot delete attribute"));
-                }
+            let PySetterValue::Assign(object_value) = value else {
+                return Err(vm.new_attribute_error("cannot delete attribute"));
             };
+            let integer = object_value.try_index(vm)?;
+
+            let chunk_size = integer.try_to_primitive::<isize>(vm).map_err(|_| {
+                let class = object_value.class();
+                let type_name = class.name();
+                let mut end = type_name.len().min(200);
+                while !type_name.is_char_boundary(end) {
+                    end -= 1;
+                }
+                vm.new_value_error(format!(
+                    "cannot fit '{}' into an index-sized integer",
+                    &type_name[..end]
+                ))
+            })?;
 
             if chunk_size <= 0 {
                 return Err(vm.new_value_error("a strictly positive integer is required"));
@@ -4772,12 +4772,85 @@ mod _io {
     #[derive(Debug)]
     struct StringIO {
         _base: _TextIOBase,
-        buffer: PyRwLock<BufferedIO>,
+        buffer: PyRwLock<StringIOBuffer>,
         newline: AtomicCell<Newlines>,
         seennl: AtomicCell<SeenNewline>,
         closed: AtomicCell<bool>,
     }
 
+    #[derive(Debug)]
+    struct StringIOBuffer {
+        bytes: BufferedIO,
+        position: usize,
+        length: usize,
+    }
+
+    impl StringIOBuffer {
+        fn new(bytes: Vec<u8>) -> Self {
+            let length = StringIO::text(&bytes).code_points().count();
+            Self {
+                bytes: BufferedIO::new(Cursor::new(bytes)),
+                position: 0,
+                length,
+            }
+        }
+
+        fn byte_offset(&self, position: usize) -> usize {
+            let bytes = self.bytes.cursor.get_ref();
+            if position >= self.length {
+                bytes.len() + (position - self.length)
+            } else {
+                crate::common::str::codepoint_range_end(StringIO::text(bytes), position).unwrap()
+            }
+        }
+
+        fn seek(&mut self, position: usize) {
+            let byte_position = self.byte_offset(position);
+            self.bytes.cursor.set_position(byte_position as u64);
+            self.position = position;
+        }
+
+        fn read(&mut self, size: usize) -> Vec<u8> {
+            let data = self.bytes.read(Some(size)).unwrap_or_default();
+            self.position += StringIO::text(&data).code_points().count();
+            data
+        }
+
+        fn write(&mut self, data: &Wtf8, count: usize, vm: &VirtualMachine) -> PyResult<()> {
+            if data.is_empty() {
+                return Ok(());
+            }
+            let position = self
+                .position
+                .checked_add(count)
+                .filter(|&position| isize::try_from(position).is_ok())
+                .ok_or_else(|| vm.new_overflow_error("new position too large"))?;
+            let byte_position = self.bytes.tell() as usize;
+            let bytes = self.bytes.cursor.get_mut();
+            if byte_position > bytes.len() {
+                bytes.resize(byte_position, 0);
+            }
+            let tail = StringIO::text(&bytes[byte_position..]);
+            let replaced = if count >= self.length.saturating_sub(self.position) {
+                tail.len()
+            } else if tail.as_bytes()[..count].is_ascii() {
+                count
+            } else {
+                crate::common::str::codepoint_range_end(tail, count).unwrap()
+            };
+            bytes.splice(
+                byte_position..byte_position + replaced,
+                data.as_bytes().iter().copied(),
+            );
+            self.bytes
+                .cursor
+                .set_position((byte_position + data.len()) as u64);
+            self.position = position;
+            self.length = self.length.max(position);
+            Ok(())
+        }
+    }
+
     #[derive(FromArgs)]
     struct StringIONewArgs {
         // None means an empty buffer.
@@ -4795,7 +4868,7 @@ mod _io {
         fn py_new(_cls: &Py<PyType>, _args: Self::Args, _vm: &VirtualMachine) -> PyResult<Self> {
             Ok(Self {
                 _base: Default::default(),
-                buffer: PyRwLock::new(BufferedIO::new(Cursor::new(Vec::new()))),
+                buffer: PyRwLock::new(StringIOBuffer::new(Vec::new())),
                 newline: AtomicCell::new(Newlines::Lf),
                 seennl: AtomicCell::new(SeenNewline::empty()),
                 closed: AtomicCell::new(false),
@@ -4822,7 +4895,7 @@ mod _io {
             let raw_bytes = initial_value.as_ref().map_or_else(Vec::new, |v| {
                 Self::translate_newlines(v.as_wtf8(), newline).into_bytes()
             });
-            *zelf.buffer.write() = BufferedIO::new(Cursor::new(raw_bytes));
+            *zelf.buffer.write() = StringIOBuffer::new(raw_bytes);
             zelf.newline.store(newline);
             zelf.seennl.store(SeenNewline::empty());
             if let Some(initial_value) = initial_value {
@@ -4833,7 +4906,7 @@ mod _io {
     }
 
     impl StringIO {
-        fn buffer(&self, vm: &VirtualMachine) -> PyResult<PyRwLockWriteGuard<'_, BufferedIO>> {
+        fn buffer(&self, vm: &VirtualMachine) -> PyResult<PyRwLockWriteGuard<'_, StringIOBuffer>> {
             if !self.closed.load() {
                 Ok(self.buffer.write())
             } else {
@@ -4865,19 +4938,6 @@ mod _io {
             unsafe { Wtf8::from_bytes_unchecked(bytes) }
         }
 
-        fn char_offset_to_byte(bytes: &[u8], char_offset: usize) -> usize {
-            let text = Self::text(bytes);
-            crate::common::str::codepoint_range_end(text, char_offset)
-                .unwrap_or_else(|| bytes.len() + (char_offset - text.code_points().count()))
-        }
-
-        fn byte_offset_to_char(bytes: &[u8], byte_offset: usize) -> usize {
-            let content_len = bytes.len();
-            let in_content = byte_offset.min(content_len);
-            Self::text(&bytes[..in_content]).code_points().count()
-                + byte_offset.saturating_sub(content_len)
-        }
-
         fn read_size(buffer: &BufferedIO, size: Option<usize>, newline: Option<Newlines>) -> usize {
             let position = buffer.tell() as usize;
             let bytes = buffer.cursor.get_ref().get(position..).unwrap_or_default();
@@ -4926,23 +4986,26 @@ mod _io {
             self.closed.store(true);
         }
 
-        // write string to underlying vector
+        // Replace characters in the underlying vector, regardless of their byte widths.
         #[pymethod]
         fn write(&self, s: PyStrRef, vm: &VirtualMachine) -> PyResult<u64> {
             let newline = self.newline.load();
-            let bytes = StringIO::translate_newlines(s.as_wtf8(), newline).into_bytes();
+            let text = StringIO::translate_newlines(s.as_wtf8(), newline);
+            let count = if matches!(newline, Newlines::Universal | Newlines::Crlf) {
+                text.code_points().count()
+            } else {
+                s.char_len()
+            };
             let mut buffer = self.buffer(vm)?;
             self.observe_newlines(s.as_wtf8(), newline);
-            buffer
-                .write(&bytes)
-                .ok_or_else(|| vm.new_type_error("Error Writing String"))?;
+            buffer.write(&text, count, vm)?;
             Ok(s.char_len() as u64)
         }
 
         // return the entire contents of the underlying
         #[pymethod]
         fn getvalue(&self, vm: &VirtualMachine) -> PyResult<Wtf8Buf> {
-            let bytes = self.buffer(vm)?.getvalue();
+            let bytes = self.buffer(vm)?.bytes.getvalue();
             Wtf8Buf::from_bytes(bytes).map_err(|_| vm.new_value_error("Error Retrieving Value"))
         }
 
@@ -4959,14 +5022,8 @@ mod _io {
                     let kind = if how == 1 { "cur" } else { "end" };
                     return Err(vm.new_os_error(format!("can't do nonzero {kind}-relative seeks")));
                 }
-                1 | 2 => {
-                    let byte_offset = if how == 1 {
-                        buffer.tell() as usize
-                    } else {
-                        buffer.cursor.get_ref().len()
-                    };
-                    StringIO::byte_offset_to_char(buffer.cursor.get_ref(), byte_offset)
-                }
+                1 => return Ok(buffer.position as u64),
+                2 => buffer.length,
                 _ => {
                     return Err(
                         vm.new_value_error(format!("invalid whence ({how}, should be 0, 1 or 2)"))
@@ -4974,10 +5031,7 @@ mod _io {
                 }
             };
 
-            let byte_offset = StringIO::char_offset_to_byte(buffer.cursor.get_ref(), char_offset);
-            buffer
-                .seek(SeekFrom::Start(byte_offset as u64))
-                .map_err(|err| os_err(vm, err))?;
+            buffer.seek(char_offset);
             Ok(char_offset as u64)
         }
 
@@ -4987,8 +5041,8 @@ mod _io {
         #[pymethod]
         fn read(&self, size: OptionalSize, vm: &VirtualMachine) -> PyResult<Wtf8Buf> {
             let mut buffer = self.buffer(vm)?;
-            let size = StringIO::read_size(&buffer, size.to_usize(), None);
-            let data = buffer.read(Some(size)).unwrap_or_default();
+            let size = StringIO::read_size(&buffer.bytes, size.to_usize(), None);
+            let data = buffer.read(size);
 
             let value = Wtf8Buf::from_bytes(data)
                 .map_err(|_| vm.new_value_error("Error Retrieving Value"))?;
@@ -4997,32 +5051,30 @@ mod _io {
 
         #[pymethod]
         fn tell(&self, vm: &VirtualMachine) -> PyResult<u64> {
-            let buffer = self.buffer(vm)?;
-            Ok(
-                StringIO::byte_offset_to_char(buffer.cursor.get_ref(), buffer.tell() as usize)
-                    as u64,
-            )
+            Ok(self.buffer(vm)?.position as u64)
         }
 
         #[pymethod]
         fn readline(&self, size: OptionalSize, vm: &VirtualMachine) -> PyResult<Wtf8Buf> {
             let mut buffer = self.buffer(vm)?;
-            let size = StringIO::read_size(&buffer, size.to_usize(), Some(self.newline.load()));
-            let input = buffer.read(Some(size)).unwrap_or_default();
+            let size =
+                StringIO::read_size(&buffer.bytes, size.to_usize(), Some(self.newline.load()));
+            let input = buffer.read(size);
             Wtf8Buf::from_bytes(input).map_err(|_| vm.new_value_error("Error Retrieving Value"))
         }
 
         #[pymethod]
         fn truncate(&self, pos: StringIOPos, vm: &VirtualMachine) -> PyResult<usize> {
             let mut buffer = self.buffer(vm)?;
-            let pos = match pos.as_optional().try_usize(vm)? {
-                Some(pos) => pos,
-                None => {
-                    StringIO::byte_offset_to_char(buffer.cursor.get_ref(), buffer.tell() as usize)
-                }
-            };
-            let byte_pos = StringIO::char_offset_to_byte(buffer.cursor.get_ref(), pos);
-            buffer.truncate(Some(byte_pos));
+            let pos = pos.as_optional().try_usize(vm)?.unwrap_or(buffer.position);
+            let byte_pos = buffer.byte_offset(pos);
+            buffer.bytes.truncate(Some(byte_pos));
+            buffer.length = buffer.length.min(pos);
+            // Truncation keeps the character position, including positions beyond EOF.
+            if buffer.bytes.tell() as usize > buffer.bytes.cursor.get_ref().len() {
+                let position = buffer.position;
+                buffer.seek(position);
+            }
             Ok(pos)
         }
 
@@ -5034,10 +5086,9 @@ mod _io {
         #[pymethod]
         fn __getstate__(zelf: PyRef<StringIO>, vm: &VirtualMachine) -> PyResult<PyTupleRef> {
             let buffer = zelf.buffer(vm)?;
-            let content = Wtf8Buf::from_bytes(buffer.getvalue())
+            let content = Wtf8Buf::from_bytes(buffer.bytes.getvalue())
                 .map_err(|_| vm.new_value_error("Error Retrieving Value"))?;
-            let pos =
-                StringIO::byte_offset_to_char(buffer.cursor.get_ref(), buffer.tell() as usize);
+            let pos = buffer.position;
             drop(buffer);
 
             // Get __dict__ if it exists and is non-empty
@@ -5091,11 +5142,8 @@ mod _io {
             // Set content and position
             let raw_bytes = content.as_bytes().to_vec();
             let mut buffer = zelf.buffer.write();
-            *buffer = BufferedIO::new(Cursor::new(raw_bytes));
-            let byte_pos = StringIO::char_offset_to_byte(buffer.cursor.get_ref(), pos as usize);
-            buffer
-                .seek(SeekFrom::Start(byte_pos as u64))
-                .map_err(|err| os_err(vm, err))?;
+            *buffer = StringIOBuffer::new(raw_bytes);
+            buffer.seek(pos as usize);
             drop(buffer);
             zelf.newline.store(newline);
             let mut seennl = SeenNewline::empty();
@@ -5934,7 +5982,7 @@ mod _io {
 #[pymodule]
 mod fileio {
     use super::{_io::*, Offset, iobase_finalize};
-    use crate::host_env::crt_fd;
+    use crate::host_env::{crt_fd, os::ErrorExt};
     use crate::{
         AsObject, Py, PyObject, PyObjectRef, PyPayload, PyResult, TryFromObject, VirtualMachine,
         builtins::{PyBaseExceptionRef, PyUtf8Str, PyUtf8StrRef},
@@ -6048,14 +6096,19 @@ mod fileio {
                 } else {
                     let path = OsPath::try_from_fspath(name.clone(), vm)?;
                     #[cfg(any(unix, target_os = "wasi"))]
-                    let fd = host_io::open_path(&path.clone().into_cstring(vm)?, flags, 0o666);
+                    let raw_path = path.clone().into_cstring(vm)?;
                     #[cfg(windows)]
-                    let fd = host_io::open_path(&path.to_wide_cstring(vm)?, flags, 0o666);
+                    let raw_path = path.to_wide_cstring(vm)?;
                     let filename = OsPathOrFd::Path(path);
-                    match fd {
-                        Ok(fd) => (fd.into_raw(), Some(filename)),
-                        Err(e) => {
-                            return Err(OSErrorBuilder::with_filename_from_errno(&e, filename, vm));
+                    loop {
+                        match vm.allow_threads(|| host_io::open_path(&raw_path, flags, 0o666)) {
+                            Ok(fd) => break (fd.into_raw(), Some(filename)),
+                            Err(e) if e.posix_errno() == libc::EINTR => vm.check_signals()?,
+                            Err(e) => {
+                                return Err(OSErrorBuilder::with_filename_from_errno(
+                                    &e, filename, vm,
+                                ));
+                            }
                         }
                     }
                 }
@@ -6246,6 +6299,7 @@ mod fileio {
                     }
                 };
                 bytes.truncate(n);
+                bytes.shrink_to_fit();
                 bytes
             } else {
                 let mut bytes = vec![];
@@ -6943,6 +6997,7 @@ mod winconsoleio {
             }
 
             buf.truncate(read_len);
+            buf.shrink_to_fit();
             Ok(vm.ctx.new_bytes(buf).into())
         }
 
diff --git a/crates/vm/src/stdlib/_operator.rs b/crates/vm/src/stdlib/_operator.rs
index 975521af1fe..61548a859fc 100644
--- a/crates/vm/src/stdlib/_operator.rs
+++ b/crates/vm/src/stdlib/_operator.rs
@@ -351,7 +351,7 @@ mod _operator {
     }
 
     #[pyattr]
-    #[pyclass(name = "attrgetter", module = "operator")]
+    #[pyclass(name = "attrgetter", module = "operator", traverse)]
     #[derive(Debug, PyPayload)]
     struct PyAttrGetter {
         attrs: Vec<PyStrRef>,
@@ -470,7 +470,7 @@ mod _operator {
     }
 
     #[pyattr]
-    #[pyclass(name = "itemgetter", module = "operator")]
+    #[pyclass(name = "itemgetter", module = "operator", traverse)]
     #[derive(Debug, PyPayload)]
     struct PyItemGetter {
         items: Vec<PyObjectRef>,
@@ -556,7 +556,7 @@ mod _operator {
     }
 
     #[pyattr]
-    #[pyclass(name = "methodcaller", module = "operator")]
+    #[pyclass(name = "methodcaller", module = "operator", traverse)]
     #[derive(Debug, PyPayload)]
     struct PyMethodCaller {
         name: PyUtf8StrRef,
diff --git a/crates/vm/src/stdlib/_signal.rs b/crates/vm/src/stdlib/_signal.rs
index edbff6d5d02..79867ff522a 100644
--- a/crates/vm/src/stdlib/_signal.rs
+++ b/crates/vm/src/stdlib/_signal.rs
@@ -13,7 +13,7 @@ pub(crate) mod _signal {
     use core::sync::atomic::{self, Ordering};
 
     cfg_select! {
-        any(unix, windows) => {
+        any(unix, windows, target_os = "wasi") => {
             use crate::convert::{IntoPyException, TryFromBorrowedObject};
             use rustpython_host_env::signal as host_signal;
         }
@@ -29,7 +29,7 @@ pub(crate) mod _signal {
             use rustpython_host_env::signal::{double_to_timeval, itimerval_to_tuple};
 
             use std::os::fd::AsFd;
-        },
+        }
         _ => {}
     }
 
@@ -47,20 +47,26 @@ pub(crate) mod _signal {
             static WAKEUP: atomic::AtomicUsize = atomic::AtomicUsize::new(INVALID_WAKEUP);
             // windows doesn't use the same fds for files and sockets like windows does, so we need
             // this to know whether to send() or write()
-            static WAKEUP_IS_SOCKET: core::sync::atomic::AtomicBool = core::sync::atomic::AtomicBool::new(false);
+            static WAKEUP_IS_SOCKET: core::sync::atomic::AtomicBool =
+                core::sync::atomic::AtomicBool::new(false);
 
             impl<'a> TryFromBorrowedObject<'a> for WakeupFd {
-                fn try_from_borrowed_object(vm: &VirtualMachine, obj: &'a crate::PyObject) -> PyResult<Self> {
+                fn try_from_borrowed_object(
+                    vm: &VirtualMachine,
+                    obj: &'a crate::PyObject,
+                ) -> PyResult<Self> {
                     use num_traits::One;
 
                     let fd: &crate::Py<crate::builtins::PyInt> = obj.try_to_value(vm)?;
                     match fd.try_to_primitive::<usize>(vm) {
                         Ok(fd) => Ok(Self(fd as _)),
-                        Err(e) => if (-fd.as_bigint()).is_one() {
-                            Ok(Self(INVALID_WAKEUP))
-                        } else {
-                            Err(e)
-                        },
+                        Err(e) => {
+                            if (-fd.as_bigint()).is_one() {
+                                Ok(Self(INVALID_WAKEUP))
+                            } else {
+                                Err(e)
+                            }
+                        }
                     }
                 }
             }
@@ -73,11 +79,18 @@ pub(crate) mod _signal {
         }
     }
 
-    #[cfg(any(unix, windows))]
+    #[cfg(windows)]
+    static WARN_ON_FULL_BUFFER: atomic::AtomicBool = atomic::AtomicBool::new(true);
+
+    // Bounded pending-call storage: signal handlers cannot allocate or lock.
+    #[cfg(windows)]
+    static WAKEUP_SEND_ERRORS: [atomic::AtomicI32; 32] = [const { atomic::AtomicI32::new(0) }; 32];
+
+    #[cfg(any(unix, windows, target_os = "wasi"))]
     #[allow(unused_imports)]
     pub use host_signal::SIG_ERR;
 
-    #[cfg(any(unix, windows))]
+    #[cfg(any(unix, windows, target_os = "wasi"))]
     #[pyattr]
     pub use host_signal::{SIG_DFL, SIG_IGN};
 
@@ -86,22 +99,22 @@ pub(crate) mod _signal {
     #[pyattr]
     use host_signal::{SIG_BLOCK, SIG_SETMASK, SIG_UNBLOCK};
 
-    #[cfg(not(any(unix, windows)))]
+    #[cfg(not(any(unix, windows, target_os = "wasi")))]
     #[pyattr]
     pub const SIG_DFL: sighandler_t = 0;
 
-    #[cfg(not(any(unix, windows)))]
+    #[cfg(not(any(unix, windows, target_os = "wasi")))]
     #[pyattr]
     pub const SIG_IGN: sighandler_t = 1;
 
-    #[cfg(not(any(unix, windows)))]
+    #[cfg(not(any(unix, windows, target_os = "wasi")))]
     #[allow(dead_code)]
     pub const SIG_ERR: sighandler_t = -1 as _;
 
     #[pyattr]
     use crate::signal::NSIG;
 
-    #[cfg(any(unix, windows))]
+    #[cfg(any(unix, windows, target_os = "wasi"))]
     #[pyattr]
     pub use host_signal::{SIGABRT, SIGFPE, SIGILL, SIGINT, SIGSEGV, SIGTERM};
 
@@ -160,7 +173,7 @@ pub(crate) mod _signal {
     const _: () = assert!(SignalNum::VALID_RANGE.start.is_positive());
     const _: () = assert!(SignalNum::VALID_RANGE.end.is_positive());
 
-    #[cfg(any(unix, windows))]
+    #[cfg(any(unix, windows, target_os = "wasi"))]
     pub(super) fn init_signal_handlers(
         module: &Py<crate::builtins::PyModule>,
         vm: &VirtualMachine,
@@ -175,9 +188,16 @@ pub(crate) mod _signal {
                 let Some(handler) = (unsafe { host_signal::probe_handler(signum) }) else {
                     continue;
                 };
-                let py_handler = if handler == SIG_DFL {
+                let (is_default, is_ignored) = cfg_select! {
+                    target_os = "wasi" => (
+                        handler == host_signal::Handler::Default,
+                        handler == host_signal::Handler::Ignore,
+                    ),
+                    _ => (handler == SIG_DFL, handler == SIG_IGN),
+                };
+                let py_handler = if is_default {
                     Some(sig_dfl.clone())
-                } else if handler == SIG_IGN {
+                } else if is_ignored {
                     Some(sig_ign.clone())
                 } else {
                     None
@@ -199,7 +219,7 @@ pub(crate) mod _signal {
         }
     }
 
-    #[cfg(not(any(unix, windows)))]
+    #[cfg(not(any(unix, windows, target_os = "wasi")))]
     #[pyfunction]
     pub fn signal(
         _signalnum: i32,
@@ -209,7 +229,7 @@ pub(crate) mod _signal {
         Err(vm.new_not_implemented_error("signal is not implemented on this platform"))
     }
 
-    #[cfg(any(unix, windows))]
+    #[cfg(any(unix, windows, target_os = "wasi"))]
     #[pyfunction]
     pub fn signal(
         signalnum: SignalNum,
@@ -223,15 +243,29 @@ pub(crate) mod _signal {
         }
 
         let sig_handler = if handler.is_callable() {
-            run_signal as *const () as sighandler_t
+            let callback = run_signal as *const () as sighandler_t;
+            cfg_select! {
+                target_os = "wasi" => host_signal::Handler::Custom(callback),
+                _ => callback,
+            }
         } else {
             const MSG: &str =
                 "signal handler must be signal.SIG_IGN, signal.SIG_DFL, or a callable object";
 
-            usize::try_from_borrowed_object(vm, &handler)
+            let disposition = usize::try_from_borrowed_object(vm, &handler)
                 .ok()
                 .filter(|&v| matches!(v, SIG_DFL | SIG_IGN))
-                .ok_or_else(|| vm.new_type_error(MSG))?
+                .ok_or_else(|| vm.new_type_error(MSG))?;
+            cfg_select! {
+                target_os = "wasi" => {
+                    if disposition == SIG_DFL {
+                        host_signal::Handler::Default
+                    } else {
+                        host_signal::Handler::Ignore
+                    }
+                },
+                _ => disposition,
+            }
         };
 
         signal::check_signals(vm)?;
@@ -323,12 +357,12 @@ pub(crate) mod _signal {
 
     #[pyfunction]
     fn set_wakeup_fd(args: SetWakeupFdArgs, vm: &VirtualMachine) -> PyResult<i64> {
-        // TODO: implement warn_on_full_buffer
+        // TODO: implement warn_on_full_buffer for the remaining wakeup write paths.
         let _ = args.warn_on_full_buffer;
         let fd = cfg_select! {
-        windows => args.fd.0,
-        _ => args.fd,
-            };
+            windows => args.fd.0,
+            _ => args.fd,
+        };
 
         if !vm.is_main_thread() {
             return Err(vm.new_value_error(
@@ -362,7 +396,10 @@ pub(crate) mod _signal {
         let old_fd = WAKEUP.swap(fd, Ordering::Relaxed);
 
         #[cfg(windows)]
-        WAKEUP_IS_SOCKET.store(is_socket, Ordering::Relaxed);
+        {
+            WARN_ON_FULL_BUFFER.store(args.warn_on_full_buffer, Ordering::Relaxed);
+            WAKEUP_IS_SOCKET.store(is_socket, Ordering::Relaxed);
+        }
 
         #[cfg(windows)]
         if old_fd == INVALID_WAKEUP {
@@ -401,16 +438,15 @@ pub(crate) mod _signal {
         host_signal::siginterrupt(signalnum.into(), flag).map_err(|_| vm.new_last_errno_error())
     }
 
-    #[cfg(any(unix, windows))]
+    #[cfg(any(unix, windows, target_os = "wasi"))]
     #[pyfunction]
     fn raise_signal(signalnum: i32, vm: &VirtualMachine) -> PyResult<()> {
         let signalnum = SignalNum::try_from(signalnum).map_err(cfg_select! {
-            windows => {
-                |_| vm.new_errno_error(libc::EINVAL, "Invalid argument").upcast()
+            windows => |_| {
+                vm.new_errno_error(libc::EINVAL, "Invalid argument")
+                    .upcast()
             },
-            _ => {
-                |msg| vm.new_value_error(msg)
-            }
+            _ => |msg| vm.new_value_error(msg),
         })?;
 
         vm.allow_threads(|| host_signal::raise_signal(signalnum.into()))
@@ -506,19 +542,62 @@ pub(crate) mod _signal {
         sigset_to_pyset(old_mask, vm)
     }
 
-    #[cfg(any(unix, windows))]
+    #[cfg(any(unix, windows, target_os = "wasi"))]
     pub extern "C" fn run_signal(signum: i32) {
         signal::TRIGGERS[signum as usize].store(true, Ordering::Relaxed);
         signal::set_triggered();
 
-        host_signal::notify_signal(
+        #[cfg(not(windows))]
+        host_signal::notify_signal(signum, WAKEUP.load(Ordering::Relaxed));
+
+        #[cfg(windows)]
+        let error = host_signal::notify_signal(
             signum,
             WAKEUP.load(Ordering::Relaxed),
-            #[cfg(windows)]
             WAKEUP_IS_SOCKET.load(Ordering::Relaxed),
-            #[cfg(windows)]
             signal::get_sigint_event(),
         );
+        #[cfg(windows)]
+        if let Some(error) = error
+            && (WARN_ON_FULL_BUFFER.load(Ordering::Relaxed) || !error.is_would_block())
+        {
+            for pending in &WAKEUP_SEND_ERRORS {
+                if pending
+                    .compare_exchange(0, error.0, Ordering::Relaxed, Ordering::Relaxed)
+                    .is_ok()
+                {
+                    // The VM may have handled the signal on another thread
+                    // before the failed wakeup send completed.
+                    signal::set_triggered();
+                    break;
+                }
+            }
+        }
+    }
+
+    #[cfg(windows)]
+    pub(crate) fn wakeup_send_errors_pending() -> bool {
+        WAKEUP_SEND_ERRORS
+            .iter()
+            .any(|error| error.load(Ordering::Relaxed) != 0)
+    }
+
+    #[cfg(windows)]
+    pub(crate) fn report_wakeup_send_errors(vm: &VirtualMachine) {
+        for pending in &WAKEUP_SEND_ERRORS {
+            let error = pending.swap(0, Ordering::Relaxed);
+            if error != 0 {
+                vm.run_unraisable(
+                    host_signal::WakeupSendError(error)
+                        .into_io_error()
+                        .into_pyexception(vm),
+                    Some(
+                        "Exception ignored while trying to send to the signal wakeup fd".to_owned(),
+                    ),
+                    vm.ctx.none(),
+                );
+            }
+        }
     }
 
     /// Reset wakeup fd after fork in child process.
@@ -535,7 +614,7 @@ pub(crate) mod _signal {
     ) -> PyResult<()> {
         __module_exec(vm, module);
 
-        #[cfg(any(unix, windows))]
+        #[cfg(any(unix, windows, target_os = "wasi"))]
         init_signal_handlers(module, vm);
 
         Ok(())
diff --git a/crates/vm/src/stdlib/_sre.rs b/crates/vm/src/stdlib/_sre.rs
index af5b75fc8a7..1cca04d1c0f 100644
--- a/crates/vm/src/stdlib/_sre.rs
+++ b/crates/vm/src/stdlib/_sre.rs
@@ -59,7 +59,17 @@ mod _sre {
         fn slice(&self, start: usize, end: usize, vm: &VirtualMachine) -> PyObjectRef;
 
         fn create_request(self, pattern: &Pattern, start: usize, end: usize) -> Request<'_, Self> {
-            Request::new(self, start, end, &pattern.code, false)
+            let request = Request::new(self, start, end, &pattern.code, false);
+            #[cfg(all(feature = "host_env", any(unix, windows)))]
+            let request = Request {
+                locale: rustpython_sre_engine::Locale {
+                    is_alnum: rustpython_host_env::locale::byte_isalnum,
+                    to_lower: rustpython_host_env::locale::byte_tolower,
+                    to_upper: rustpython_host_env::locale::byte_toupper,
+                },
+                ..request
+            };
+            request
         }
     }
 
@@ -332,14 +342,26 @@ mod _sre {
         default: OptionalArg<PyObjectRef>,
     }
 
+    /// A position in the searched string, taken as a Py_ssize_t; a negative
+    /// one means the start of the string.
+    #[derive(Clone, Copy, Default)]
+    struct StringPos(usize);
+
+    impl TryFromObject for StringPos {
+        fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
+            let pos: isize = obj.try_into_value(vm)?;
+            Ok(Self(pos.max(0) as usize))
+        }
+    }
+
     #[derive(FromArgs)]
     struct StringArgs {
         string: PyObjectRef,
         #[pyarg(any, default)]
-        pos: usize,
+        pos: StringPos,
         // Platform ssize maximum, shown as sys.maxsize.
-        #[pyarg(any, default = sys::MAXSIZE as usize, py_default = "sys.maxsize")]
-        endpos: usize,
+        #[pyarg(any, default = StringPos(sys::MAXSIZE as usize), py_default = "sys.maxsize")]
+        endpos: StringPos,
     }
 
     #[derive(FromArgs)]
@@ -521,6 +543,7 @@ mod _sre {
         flags(HAS_WEAKREF)
     )]
     impl Py<Pattern> {
+        #[pymethod(name = "prefixmatch")]
         #[pymethod(name = "match")]
         fn py_match(
             zelf: PyRef<Pattern>,
@@ -533,7 +556,7 @@ mod _sre {
                 endpos,
             } = string_args;
             with_sre_str!(zelf, &string.clone(), vm, |x| {
-                let req = x.create_request(&zelf, pos, endpos);
+                let req = x.create_request(&zelf, pos.0, endpos.0);
                 let mut state = State::default();
                 Ok(state
                     .py_match(&req)
@@ -548,7 +571,7 @@ mod _sre {
             vm: &VirtualMachine,
         ) -> PyResult<Option<PyRef<Match>>> {
             with_sre_str!(zelf, &string_args.string.clone(), vm, |x| {
-                let mut req = x.create_request(&zelf, string_args.pos, string_args.endpos);
+                let mut req = x.create_request(&zelf, string_args.pos.0, string_args.endpos.0);
                 req.match_all = true;
                 let mut state = State::default();
                 Ok(state.py_match(&req).then(|| {
@@ -564,7 +587,7 @@ mod _sre {
             vm: &VirtualMachine,
         ) -> PyResult<Option<PyRef<Match>>> {
             with_sre_str!(zelf, &string_args.string.clone(), vm, |x| {
-                let req = x.create_request(&zelf, string_args.pos, string_args.endpos);
+                let req = x.create_request(&zelf, string_args.pos.0, string_args.endpos.0);
                 let mut state = State::default();
                 Ok(state.search(req).then(|| {
                     Match::new(&mut state, zelf.clone(), string_args.string).into_ref(&vm.ctx)
@@ -579,7 +602,7 @@ mod _sre {
             vm: &VirtualMachine,
         ) -> PyResult<Vec<PyObjectRef>> {
             with_sre_str!(zelf, &string_args.string, vm, |s| {
-                let req = s.create_request(&zelf, string_args.pos, string_args.endpos);
+                let req = s.create_request(&zelf, string_args.pos.0, string_args.endpos.0);
                 let state = State::default();
                 let mut match_list: Vec<PyObjectRef> = Vec::new();
                 let mut iter = SearchIter { req, state };
@@ -627,8 +650,8 @@ mod _sre {
             let scanner = SreScanner {
                 pattern: zelf,
                 string: string_args.string,
-                start: AtomicCell::new(string_args.pos),
-                end: string_args.endpos,
+                start: AtomicCell::new(string_args.pos.0),
+                end: string_args.endpos.0,
                 must_advance: AtomicCell::new(false),
             }
             .into_ref(&vm.ctx);
@@ -647,8 +670,8 @@ mod _sre {
             SreScanner {
                 pattern: zelf,
                 string: string_args.string,
-                start: AtomicCell::new(string_args.pos),
-                end: string_args.endpos,
+                start: AtomicCell::new(string_args.pos.0),
+                end: string_args.endpos.0,
                 must_advance: AtomicCell::new(false),
             }
             .into_ref(&vm.ctx)
@@ -1139,6 +1162,7 @@ mod _sre {
             self.pattern.clone()
         }
 
+        #[pymethod(name = "prefixmatch")]
         #[pymethod(name = "match")]
         fn py_match(&self, vm: &VirtualMachine) -> PyResult<Option<PyRef<Match>>> {
             with_sre_str!(self.pattern, &self.string.clone(), vm, |s| {
diff --git a/crates/vm/src/stdlib/_sysconfig.rs b/crates/vm/src/stdlib/_sysconfig.rs
index 2de27d71ac9..4464c528fbe 100644
--- a/crates/vm/src/stdlib/_sysconfig.rs
+++ b/crates/vm/src/stdlib/_sysconfig.rs
@@ -1,24 +1,83 @@
 pub(crate) use _sysconfig::module_def;
 
 #[pymodule]
-pub(crate) mod _sysconfig {
+pub(crate) mod _missing_stdlib_info {
     use crate::{VirtualMachine, builtins::PyDictRef, convert::ToPyObject};
 
+    #[pyattr(name = "_MISSING_STDLIB_MODULE_MESSAGES")]
+    fn missing_stdlib_module_messages(vm: &VirtualMachine) -> PyDictRef {
+        let messages = vm.ctx.new_dict();
+        // CPython's Tools/build/check_extension_modules.py emits these entries
+        // unconditionally, including on Windows. Do not infer disabled build
+        // features from CPython's module inventory: ours is different.
+        for name in [
+            "_overlapped",
+            "_testconsole",
+            "_winapi",
+            "_wmi",
+            "msvcrt",
+            "nt",
+            "winreg",
+            "winsound",
+        ] {
+            let message =
+                format!("Unsupported platform for Windows-only standard library module '{name}'");
+            messages
+                .set_item(name, message.to_pyobject(vm), vm)
+                .unwrap();
+        }
+        // This module is only implemented for macOS in our stdlib as well.
+        #[cfg(not(target_os = "macos"))]
+        messages
+            .set_item(
+                "_scproxy",
+                "Unsupported platform for standard library module '_scproxy'".to_pyobject(vm),
+                vm,
+            )
+            .unwrap();
+        messages
+    }
+}
+
+#[pymodule]
+pub(crate) mod _sysconfig {
+    #[cfg(windows)]
+    use crate::builtins::PyStrRef;
+    use crate::{PyResult, VirtualMachine, builtins::PyDictRef, convert::ToPyObject};
+
+    #[cfg(windows)]
+    #[pyfunction]
+    fn get_platform() -> Option<&'static str> {
+        match std::env::consts::ARCH {
+            "x86_64" => Some("win-amd64"),
+            "aarch64" => Some("win-arm64"),
+            "x86" => Some("win32"),
+            "arm" => Some("win-arm32"),
+            _ => None,
+        }
+    }
+
     #[pyfunction]
-    fn config_vars(vm: &VirtualMachine) -> PyDictRef {
+    fn config_vars(vm: &VirtualMachine) -> PyResult<PyDictRef> {
         let vars = vm.ctx.new_dict();
 
+        #[cfg(windows)]
+        {
+            let source: PyStrRef = vm.sys_module.get_attr("_vpath", vm)?.try_into_value(vm)?;
+            if !source.as_wtf8().is_empty() {
+                vars.set_item("srcdir", source.into(), vm)?;
+            }
+        }
+
         // FIXME: This is an entirely wrong implementation of EXT_SUFFIX.
         // EXT_SUFFIX must be a string starting with "." for pip compatibility
         // Using ".pyd" causes pip's _generic_abi() to fall back to _cpython_abis()
-        vars.set_item("EXT_SUFFIX", ".pyd".to_pyobject(vm), vm)
-            .unwrap();
-        vars.set_item("SOABI", vm.ctx.none(), vm).unwrap();
+        vars.set_item("EXT_SUFFIX", ".pyd".to_pyobject(vm), vm)?;
+        vars.set_item("SOABI", vm.ctx.none(), vm)?;
 
-        vars.set_item("Py_GIL_DISABLED", (1).to_pyobject(vm), vm)
-            .unwrap();
-        vars.set_item("Py_DEBUG", (0).to_pyobject(vm), vm).unwrap();
+        vars.set_item("Py_GIL_DISABLED", (1).to_pyobject(vm), vm)?;
+        vars.set_item("Py_DEBUG", (0).to_pyobject(vm), vm)?;
 
-        vars
+        Ok(vars)
     }
 }
diff --git a/crates/vm/src/stdlib/_sysconfigdata.rs b/crates/vm/src/stdlib/_sysconfigdata.rs
index dd77caff255..df25246e330 100644
--- a/crates/vm/src/stdlib/_sysconfigdata.rs
+++ b/crates/vm/src/stdlib/_sysconfigdata.rs
@@ -1,4 +1,4 @@
-// spell-checker: words LDSHARED ARFLAGS CPPFLAGS CCSHARED BASECFLAGS BLDSHARED
+// spell-checker: words LDSHARED LDCXXSHARED ARFLAGS CPPFLAGS CCSHARED BASECFLAGS BLDSHARED
 
 pub(crate) use _sysconfigdata::module_def;
 
@@ -19,6 +19,9 @@ mod _sysconfigdata {
         let paths = &vm.state.config.paths;
         build_time_vars.set_item("prefix", paths.prefix.clone().to_pyobject(vm), vm)?;
         build_time_vars.set_item("exec_prefix", paths.exec_prefix.clone().to_pyobject(vm), vm)?;
+        if let Some(stdlib_dir) = &paths.stdlib_dir {
+            build_time_vars.set_item("LIBDEST", stdlib_dir.to_pyobject(vm), vm)?;
+        }
         let bindir = format!("{}/bin", paths.exec_prefix);
         build_time_vars.set_item("BINDIR", bindir.to_pyobject(vm), vm)?;
 
@@ -60,6 +63,7 @@ mod _sysconfigdata {
             "CPPFLAGS" => "",
             "LDFLAGS" => "",
             "LDSHARED" => "cc -shared",
+            "LDCXXSHARED" => "c++ -shared",
             "CCSHARED" => "",
             "SHLIB_SUFFIX" => ".so",
             "SO" => ".so",
diff --git a/crates/vm/src/stdlib/_testinternalcapi.rs b/crates/vm/src/stdlib/_testinternalcapi.rs
index caafcf5ab57..9e368d4462b 100644
--- a/crates/vm/src/stdlib/_testinternalcapi.rs
+++ b/crates/vm/src/stdlib/_testinternalcapi.rs
@@ -423,7 +423,7 @@ mod _testinternalcapi {
         global.set_item("dev_mode", vm.ctx.new_bool(settings.dev_mode).into(), vm)?;
         global.set_item("verbose", vm.ctx.new_int(settings.verbose).into(), vm)?;
         global.set_item("quiet", vm.ctx.new_bool(settings.quiet).into(), vm)?;
-        global.set_item("inspect", vm.ctx.new_bool(settings.inspect).into(), vm)?;
+        global.set_item("inspect", vm.ctx.new_bool(vm.config_inspect()).into(), vm)?;
         global.set_item(
             "interactive",
             vm.ctx.new_bool(settings.interactive).into(),
@@ -837,13 +837,17 @@ mod _testinternalcapi {
             ..rustpython_codegen::CompileOpts::default()
         };
         opts.future_features |= rustpython_codegen::preprocess::future_features(&converted.ast);
-        let output = rustpython_codegen::compile::compile_codegen(
-            converted.ast,
-            converted.source_file,
+        let output = rustpython_codegen::compile::compile_codegen_ast(
+            rustpython_codegen::compile::AstInput {
+                ast: converted.ast,
+                source_file: converted.source_file,
+                locations: converted.locations,
+            },
             mode,
             opts,
+            None,
         )
-        .map_err(|err| vm.new_syntax_error(&crate::compiler::CompileError::from(err), None))?;
+        .map_err(|err| crate::stdlib::_ast::codegen_exception(vm, err, None))?;
         let seq = PyInstructionSequence::from_rust(output.seq, vm);
         let metadata = vm.ctx.new_dict();
         metadata.set_item("argcount", vm.ctx.new_int(output.argcount).into(), vm)?;
@@ -1125,11 +1129,16 @@ fn expandtabs(input: &str, tab_size: usize) -> String {
     expanded
 }
 
-type CodeNamespaces = (PyRef<PyCode>, Option<PyRef<PyDict>>, Option<PyRef<PyDict>>);
+type CodeNamespaces = (
+    PyRef<PyCode>,
+    Option<PyRef<crate::builtins::PyAnyDict>>,
+    Option<PyRef<crate::builtins::PyAnyDict>>,
+);
 
 fn code_or_function(obj: &PyObject, vm: &VirtualMachine) -> PyResult<CodeNamespaces> {
     if let Ok(func) = obj.to_owned().downcast::<PyFunction>() {
-        let builtins = func.builtins.clone().downcast::<PyDict>().ok();
+        let builtins =
+            crate::builtins::PyAnyDict::from_object(&func.builtins).map(ToOwned::to_owned);
         return Ok((
             (*func.code).to_owned(),
             Some(func.globals.clone()),
@@ -1142,19 +1151,22 @@ fn code_or_function(obj: &PyObject, vm: &VirtualMachine) -> PyResult<CodeNamespa
     Err(vm.new_type_error("argument must be a code object or a function"))
 }
 
-fn optional_dict(
+fn optional_dict<T: From<PyRef<PyDict>>>(
     override_ns: OptionalArg<PyObjectRef>,
-    default: Option<PyRef<PyDict>>,
+    default: Option<T>,
     name: &str,
     vm: &VirtualMachine,
-) -> PyResult<Option<PyRef<PyDict>>> {
+) -> PyResult<Option<T>> {
     match override_ns.into_option() {
-        Some(obj) => obj.downcast::<PyDict>().map(Some).map_err(|obj| {
-            vm.new_type_error(format!(
-                "expected a dict for \"{name}\", got {}",
-                obj.class().name()
-            ))
-        }),
+        Some(obj) => obj
+            .downcast::<PyDict>()
+            .map(|dict| Some(dict.into()))
+            .map_err(|obj| {
+                vm.new_type_error(format!(
+                    "expected a dict for \"{name}\", got {}",
+                    obj.class().name()
+                ))
+            }),
         None => Ok(default),
     }
 }
@@ -1280,8 +1292,8 @@ fn set_unbound_var_counts(
     counts: &mut VarCounts,
     globalnames: Option<PyObjectRef>,
     attrnames: Option<PyObjectRef>,
-    globalsns: Option<&Py<PyDict>>,
-    builtinsns: Option<&Py<PyDict>>,
+    globalsns: Option<&crate::builtins::PyAnyDict>,
+    builtinsns: Option<&crate::builtins::PyAnyDict>,
     vm: &VirtualMachine,
 ) -> PyResult<()> {
     let globalnames = optional_set(globalnames, "globalnames", vm)?;
@@ -1317,8 +1329,8 @@ fn identify_unbound_names(
     code: &Py<PyCode>,
     globalnames: Option<PyRef<PySet>>,
     attrnames: Option<PyRef<PySet>>,
-    globalsns: Option<&Py<PyDict>>,
-    builtinsns: Option<&Py<PyDict>>,
+    globalsns: Option<&crate::builtins::PyAnyDict>,
+    builtinsns: Option<&crate::builtins::PyAnyDict>,
     vm: &VirtualMachine,
 ) -> PyResult<(UnboundCounts, i32)> {
     let mut seen_globals = HashSet::new();
diff --git a/crates/vm/src/stdlib/_thread.rs b/crates/vm/src/stdlib/_thread.rs
index 984a0865560..d086c3f7636 100644
--- a/crates/vm/src/stdlib/_thread.rs
+++ b/crates/vm/src/stdlib/_thread.rs
@@ -27,8 +27,8 @@ pub(crate) mod _thread {
         convert::ToPyException,
         frame::FrameObjectRef,
         function::{
-            ArgCallable, ArgumentError, DefaultRepr, FromArgs, FuncArgs, KwArgs, NameExcInfo,
-            OptionalArg, Param, ParamKind, PosArgs, PySetterValue, TimeoutSeconds,
+            ArgCallable, ArgIndex, ArgumentError, DefaultRepr, FromArgs, FuncArgs, KwArgs,
+            NameExcInfo, OptionalArg, Param, ParamKind, PosArgs, PySetterValue, TimeoutSeconds,
         },
         object::{Traverse, TraverseFn},
         types::{Constructor, GetAttr, PyStructSequence, Representable, SetAttr},
@@ -104,29 +104,82 @@ pub(crate) mod _thread {
         }
     }
 
+    fn validate_acquire_args(args: AcquireArgs, vm: &VirtualMachine) -> PyResult<(bool, f64)> {
+        let timeout = args.timeout.to_secs_f64();
+        // CPython checks the signed nanosecond range before acquire-specific restrictions.
+        let timeout_ns = timeout * 1_000_000_000.0;
+        if !(i64::MIN as f64..-(i64::MIN as f64)).contains(&timeout_ns) {
+            return Err(vm.new_overflow_error("timestamp out of range for C PyTime_t"));
+        }
+        if !args.blocking && timeout != -1.0 {
+            return Err(vm.new_value_error("can't specify a timeout for a non-blocking call"));
+        }
+        if args.blocking && timeout < 0.0 && timeout != -1.0 {
+            return Err(vm.new_value_error("timeout value must be a non-negative number"));
+        }
+        if timeout > TIMEOUT_MAX {
+            return Err(vm.new_overflow_error("timeout value is too large"));
+        }
+        Ok((args.blocking, timeout))
+    }
+
     macro_rules! acquire_lock_impl {
-        ($mu:expr, $args:expr, $vm:expr) => {{
-            let (mu, args, vm) = ($mu, $args, $vm);
-            let timeout = args.timeout.to_secs_f64();
-            match args.blocking {
-                true if timeout == -1.0 => {
-                    vm.allow_threads(|| mu.lock());
-                    Ok(true)
+        ($mu:expr, $blocking:expr, $timeout:expr, $vm:expr) => {{ acquire_lock_impl!($mu, $blocking, $timeout, $vm, false) }};
+        ($mu:expr, $blocking:expr, $timeout:expr, $vm:expr, $owned:expr) => {{
+            let (mu, blocking, timeout, vm) = ($mu, $blocking, $timeout, $vm);
+            let started = std::time::Instant::now();
+            // CPython rounds positive timeouts up to the next nanosecond.
+            let timeout = (timeout != -1.0)
+                .then(|| Duration::from_nanos((timeout * 1_000_000_000.0).ceil() as u64));
+            let mut remaining = timeout;
+            loop {
+                // Ownership gained in a signal handler does not make an
+                // already pending acquisition recursive.
+                let owned = $owned;
+                if !owned && mu.try_lock() {
+                    break Ok(true);
                 }
-                true if timeout < 0.0 => {
-                    Err(vm.new_value_error("timeout value must be a non-negative number"))
+                if !blocking || remaining.is_some_and(|remaining| remaining.is_zero()) {
+                    break Ok(false);
                 }
-                true => {
-                    if timeout > TIMEOUT_MAX {
-                        return Err(vm.new_overflow_error("timeout value is too large"));
+                if vm
+                    .state
+                    .finalizing
+                    .load(core::sync::atomic::Ordering::Acquire)
+                {
+                    // Other Python threads cannot release the lock once
+                    // finalization begins. Uncontested calls still work.
+                    break Err(vm.new_python_finalization_error(
+                        "cannot acquire lock at interpreter finalization",
+                    ));
+                }
+                let interval = Duration::from_millis(50);
+                let wait = match timeout {
+                    Some(timeout) => match timeout.checked_sub(started.elapsed()) {
+                        Some(remaining) if !remaining.is_zero() => remaining.min(interval),
+                        _ => break Ok(false),
+                    },
+                    None => interval,
+                };
+                // parking_lot waits are not interrupted by OS signals. Poll
+                // without restarting the deadline or acquiring a lock before
+                // running callbacks. A handler may itself retain an RLock.
+                let acquired = vm.allow_threads(|| {
+                    if owned {
+                        thread::sleep(wait);
+                        false
+                    } else {
+                        mu.try_lock_for(wait)
                     }
-
-                    Ok(vm.allow_threads(|| mu.try_lock_for(Duration::from_secs_f64(timeout))))
+                });
+                if acquired {
+                    break Ok(true);
                 }
-                false if timeout != -1.0 => {
-                    Err(vm.new_value_error("can't specify a timeout for a non-blocking call"))
+                if timeout.is_some_and(|timeout| started.elapsed() >= timeout) {
+                    break Ok(false);
                 }
-                false => Ok(mu.try_lock()),
+                vm.check_signals()?;
+                remaining = timeout.map(|timeout| timeout.saturating_sub(started.elapsed()));
             }
         }};
     }
@@ -166,7 +219,8 @@ pub(crate) mod _thread {
         #[pymethod]
         #[pymethod(name = "acquire_lock")]
         fn acquire(&self, args: AcquireArgs, vm: &VirtualMachine) -> PyResult<bool> {
-            acquire_lock_impl!(&self.mu, args, vm)
+            let (blocking, timeout) = validate_acquire_args(args, vm)?;
+            acquire_lock_impl!(&self.mu, blocking, timeout, vm)
         }
 
         #[pymethod]
@@ -240,7 +294,18 @@ pub(crate) mod _thread {
     #[pyclass(with(Representable), flags(BASETYPE, HAS_WEAKREF))]
     impl Py<RLock> {
         #[pyslot]
-        fn slot_new(cls: PyTypeRef, _args: FuncArgs, vm: &VirtualMachine) -> PyResult {
+        fn slot_new(cls: PyTypeRef, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
+            let rlock_type = RLock::class(&vm.ctx);
+            let cls_init = cls.slots.init.load().map(crate::types::fn_addr);
+            let rlock_init = rlock_type.slots.init.load().map(crate::types::fn_addr);
+            if cls.is(rlock_type) || cls_init == rlock_init {
+                if !args.args.is_empty() {
+                    return Err(vm.new_type_error("RLock() takes no positional arguments"));
+                }
+                if !args.kwargs.is_empty() {
+                    return Err(vm.new_type_error("RLock() takes no keyword arguments"));
+                }
+            }
             RLock {
                 mu: RawRMutex::INIT,
                 count: core::sync::atomic::AtomicUsize::new(0),
@@ -252,6 +317,7 @@ pub(crate) mod _thread {
         #[pymethod]
         #[pymethod(name = "acquire_lock")]
         fn acquire(&self, args: AcquireArgs, vm: &VirtualMachine) -> PyResult<bool> {
+            let (blocking, timeout) = validate_acquire_args(args, vm)?;
             if self.mu.is_owned_by_current_thread() {
                 // Re-entrant acquisition: just increment our count.
                 // parking_lot stays at 1 level; we track recursion ourselves.
@@ -259,7 +325,13 @@ pub(crate) mod _thread {
                     .fetch_add(1, core::sync::atomic::Ordering::Relaxed);
                 return Ok(true);
             }
-            let result = acquire_lock_impl!(&self.mu, args, vm)?;
+            let result = acquire_lock_impl!(
+                &self.mu,
+                blocking,
+                timeout,
+                vm,
+                self.mu.is_owned_by_current_thread()
+            )?;
             if result {
                 self.count.store(1, core::sync::atomic::Ordering::Relaxed);
             }
@@ -506,8 +578,13 @@ pub(crate) mod _thread {
         }
         #[cfg(any(target_os = "linux", target_os = "macos"))]
         {
-            let os_name = vm.fsencode(&name)?;
-            host_thread::set_current_thread_name_bytes(os_name.as_encoded_bytes());
+            let os_name = vm.state.codec_registry.encode_text(
+                name,
+                "utf-8",
+                Some(vm.ctx.new_utf8_str("replace")),
+                vm,
+            )?;
+            host_thread::set_current_thread_name_bytes(os_name.as_bytes());
         }
         Ok(())
     }
@@ -847,7 +924,7 @@ pub(crate) mod _thread {
     #[derive(FromArgs)]
     struct StackSizeArgs {
         #[pyarg(positional, default = 0)]
-        size: PyIntRef,
+        size: ArgIndex,
     }
 
     #[pyfunction]
@@ -855,7 +932,7 @@ pub(crate) mod _thread {
         const MIN_SIZE: usize = PY_OS_MIN_STACK_SIZE + SYSTEM_PAGE_SIZE;
         let StackSizeArgs { size } = args;
 
-        let Ok(size) = size.try_to_primitive(vm) else {
+        let Ok(size) = size.as_ref().try_to_primitive(vm) else {
             return Err(vm.new_value_error(format!("size must be at least {MIN_SIZE} bytes")));
         };
 
@@ -1492,37 +1569,15 @@ pub(crate) mod _thread {
                     return false;
                 };
 
-                // Reinit this per-handle lock in case a dead thread held it
-                reinit_parking_lot_mutex(&inner);
-                let mut inner_guard = inner.lock();
-
-                if inner_guard.ident == current_ident {
-                    return true;
-                }
-                if inner_guard.state == ThreadHandleState::NotStarted {
-                    return true;
-                }
-
-                inner_guard.state = ThreadHandleState::Done;
-                // The OS thread did not survive the fork. Dropping JoinHandle
-                // would pthread_detach a copied thread descriptor.
-                if let Some(handle) = inner_guard.join_handle.take() {
-                    core::mem::forget(handle);
-                }
-                drop(inner_guard);
-
-                // Reinit and set the done event. Do not notify: no other
-                // thread exists in the child, and notify_all would unpark
-                // waiters that did not survive the fork.
-                let (lock, cvar) = &*done_event;
-                reinit_parking_lot_mutex(lock);
-                reinit_parking_lot_condvar(cvar);
-                *lock.lock() = true;
+                // SAFETY: only the forking thread survives in the child.
+                unsafe { reinit_handle_after_fork(&inner, &done_event, current_ident) };
 
                 true
             });
         }
 
+        // Every shutdown entry comes from ThreadHandle::new and is also in
+        // thread_handles, so its completion event was already reset above.
         // Clean up shutdown_handles.
         {
             let mut handles = vm.state.shutdown_handles.lock();
@@ -1557,6 +1612,42 @@ pub(crate) mod _thread {
         }
     }
 
+    /// Repair a copied handle before any child thread cleanup or join.
+    ///
+    /// Unlike CPython's atomic completion event, ours includes a mutex that a
+    /// parent joiner can hold while detached. Even the surviving thread's
+    /// completion mutex and condvar must lose that dead owner's/waiter's state.
+    /// Its completion value remains unchanged until the thread really exits.
+    ///
+    /// # Safety
+    /// Only call in the single-threaded post-fork child, with no live guards or
+    /// waiters on these locks.
+    #[cfg(all(unix, feature = "host_env"))]
+    unsafe fn reinit_handle_after_fork(
+        inner: &parking_lot::Mutex<ThreadHandleInner>,
+        done_event: &(parking_lot::Mutex<bool>, parking_lot::Condvar),
+        current_ident: u64,
+    ) {
+        reinit_parking_lot_mutex(inner);
+        let (lock, cvar) = done_event;
+        reinit_parking_lot_mutex(lock);
+        reinit_parking_lot_condvar(cvar);
+        let mut inner_guard = inner.lock();
+        if inner_guard.ident == current_ident || inner_guard.state == ThreadHandleState::NotStarted
+        {
+            return;
+        }
+
+        inner_guard.state = ThreadHandleState::Done;
+        // The OS thread did not survive. Do not pthread_detach a copied handle.
+        if let Some(handle) = inner_guard.join_handle.take() {
+            core::mem::forget(handle);
+        }
+        drop(inner_guard);
+        // Do not notify waiters: none survived the fork.
+        *lock.lock() = true;
+    }
+
     /// Take a thread handle's completion mutex, detaching first.
     ///
     /// A joiner holds this mutex across its `allow_threads` wait, so it can
@@ -2244,11 +2335,79 @@ pub(crate) mod _thread {
 
     #[cfg(test)]
     mod tests {
-        #[cfg(all(debug_assertions, any(target_os = "linux", target_os = "macos")))]
+        #[cfg(any(
+            all(unix, feature = "host_env"),
+            all(debug_assertions, any(target_os = "linux", target_os = "macos"))
+        ))]
         use super::*;
         #[cfg(all(debug_assertions, any(target_os = "linux", target_os = "macos")))]
         use crate::Interpreter;
 
+        /// Exercise only the native completion-state invariant, without Python
+        /// execution or actual fork in the multithreaded Rust test harness.
+        #[test]
+        #[cfg(all(unix, feature = "host_env"))]
+        fn fork_reinitializes_surviving_handle_completion_lock() {
+            for (ident, state, completed, expected_state, expected_completed) in [
+                (
+                    7,
+                    ThreadHandleState::Running,
+                    false,
+                    ThreadHandleState::Running,
+                    false,
+                ),
+                (
+                    0,
+                    ThreadHandleState::NotStarted,
+                    false,
+                    ThreadHandleState::NotStarted,
+                    false,
+                ),
+                (
+                    8,
+                    ThreadHandleState::Running,
+                    false,
+                    ThreadHandleState::Done,
+                    true,
+                ),
+                (
+                    8,
+                    ThreadHandleState::Done,
+                    true,
+                    ThreadHandleState::Done,
+                    true,
+                ),
+            ] {
+                let inner = parking_lot::Mutex::new(ThreadHandleInner {
+                    state,
+                    ident,
+                    join_handle: None,
+                    joining: false,
+                    joined: false,
+                });
+                let done_event = (
+                    parking_lot::Mutex::new(completed),
+                    parking_lot::Condvar::new(),
+                );
+                // Model the bytes inherited from a parent joiner that held the
+                // mutex at fork. No guard remains live and no other thread can
+                // access these exclusively owned fixtures.
+                core::mem::forget(done_event.0.lock());
+                assert!(done_event.0.try_lock().is_none());
+                // SAFETY: these private fixtures have no live guards/waiters,
+                // exactly as in a child after its parent lock owner vanished.
+                unsafe { reinit_handle_after_fork(&inner, &done_event, 7) };
+                let completed = done_event
+                    .0
+                    .try_lock()
+                    .expect("copied completion lock must be unlocked");
+                assert_eq!(*completed, expected_completed);
+                let inner = inner.lock();
+                assert_eq!(inner.state, expected_state);
+                assert_eq!(inner.ident, ident);
+            }
+        }
+
         /// Regression test for #7941: a Python thread started without an
         /// explicit `threading.stack_size()` must not run on Rust's 2 MiB
         /// std default in debug builds, where the call chains the stdlib
diff --git a/crates/vm/src/stdlib/_types.rs b/crates/vm/src/stdlib/_types.rs
index d1d02f7202e..f45d513fc5d 100644
--- a/crates/vm/src/stdlib/_types.rs
+++ b/crates/vm/src/stdlib/_types.rs
@@ -58,6 +58,16 @@ mod _types {
         vm.ctx.types.ellipsis_type.to_owned().into()
     }
 
+    #[pyattr]
+    fn FrameLocalsProxyType(vm: &VirtualMachine) -> PyObjectRef {
+        vm.ctx.types.frame_locals_proxy_type.to_owned().into()
+    }
+
+    #[pyattr]
+    fn LazyImportType(vm: &VirtualMachine) -> PyObjectRef {
+        vm.ctx.types.lazy_import_type.to_owned().into()
+    }
+
     #[pyattr]
     fn FrameType(vm: &VirtualMachine) -> PyObjectRef {
         vm.ctx.types.frame_type.to_owned().into()
diff --git a/crates/vm/src/stdlib/_typing.rs b/crates/vm/src/stdlib/_typing.rs
index 863dd8367b2..17153c0e5de 100644
--- a/crates/vm/src/stdlib/_typing.rs
+++ b/crates/vm/src/stdlib/_typing.rs
@@ -33,9 +33,11 @@ pub(crate) mod decl {
     use crate::{
         AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
         atomic_func,
-        builtins::{PyGenericAlias, PyStrRef, PyTuple, PyTupleRef, PyType, PyTypeRef, type_},
+        builtins::{
+            PyFunction, PyGenericAlias, PyStrRef, PyTuple, PyTupleRef, PyType, PyTypeRef, type_,
+        },
         common::wtf8::Wtf8Buf,
-        function::FuncArgs,
+        function::{FuncArgs, PySetterValue},
         protocol::{PyMappingMethods, PyNumberMethods},
         types::{AsMapping, AsNumber, Callable, Constructor, Iterable, Representable},
     };
@@ -197,10 +199,12 @@ pub(crate) mod decl {
     pub(crate) struct TypeAliasType {
         #[pymember(name = "__name__")]
         name: PyStrRef,
+        #[pymember(name = "__qualname__")]
+        qualname: PyStrRef,
         type_params: PyTupleRef,
         compute_value: PyObjectRef,
         cached_value: crate::common::lock::PyMutex<Option<PyObjectRef>>,
-        module: Option<PyObjectRef>,
+        module: crate::common::lock::PyMutex<Option<PyObjectRef>>,
         is_lazy: bool,
     }
     impl TypeAliasType {
@@ -210,12 +214,19 @@ pub(crate) mod decl {
             type_params: PyTupleRef,
             compute_value: PyObjectRef,
         ) -> Self {
+            let qualname = compute_value
+                .downcast_ref::<PyFunction>()
+                .expect("type alias evaluator must be a function")
+                .code
+                .qualname
+                .to_owned();
             Self {
                 name,
+                qualname,
                 type_params,
                 compute_value,
                 cached_value: crate::common::lock::PyMutex::new(None),
-                module: None,
+                module: crate::common::lock::PyMutex::new(None),
                 is_lazy: true,
             }
         }
@@ -223,16 +234,18 @@ pub(crate) mod decl {
         /// Create with an eagerly evaluated value (used by constructor)
         fn new_eager(
             name: PyStrRef,
+            qualname: PyStrRef,
             type_params: PyTupleRef,
             value: PyObjectRef,
             module: Option<PyObjectRef>,
         ) -> Self {
             Self {
                 name,
+                qualname,
                 type_params,
                 compute_value: value.clone(),
                 cached_value: crate::common::lock::PyMutex::new(Some(value)),
-                module,
+                module: crate::common::lock::PyMutex::new(module),
                 is_lazy: false,
             }
         }
@@ -317,16 +330,25 @@ pub(crate) mod decl {
 
         #[pygetset]
         fn __module__(&self, vm: &VirtualMachine) -> PyObjectRef {
-            if let Some(ref module) = self.module {
-                return module.clone();
+            let module = self.module.lock().clone();
+            if let Some(module) = module {
+                return module;
             }
             // Fall back to compute_value's __module__ (like PyFunction_GetModule)
-            if let Ok(module) = self.compute_value.get_attr("__module__", vm) {
+            if self.is_lazy
+                && let Ok(module) = self.compute_value.get_attr("__module__", vm)
+            {
                 return module;
             }
             vm.ctx.none()
         }
 
+        #[pygetset(setter)]
+        fn set___module__(&self, value: PySetterValue) {
+            let previous = core::mem::replace(&mut *self.module.lock(), value.into_option());
+            drop(previous);
+        }
+
         #[pymethod]
         fn __reduce__(zelf: &Self, _vm: &VirtualMachine) -> PyObjectRef {
             zelf.name.clone().into()
@@ -350,12 +372,14 @@ pub(crate) mod decl {
         type Args = FuncArgs;
 
         fn py_new(_cls: &Py<PyType>, args: Self::Args, vm: &VirtualMachine) -> PyResult<Self> {
-            // typealias(name, value, *, type_params=())
-            // name and value are positional-or-keyword; type_params is keyword-only.
+            // name and value are positional-or-keyword; type_params and qualname are keyword-only.
 
             // Reject unexpected keyword arguments.
             for key in args.kwargs.keys() {
-                if !matches!(key.as_str(), Ok("name" | "value" | "type_params")) {
+                if !matches!(
+                    key.as_str(),
+                    Ok("name" | "value" | "type_params" | "qualname")
+                ) {
                     return Err(
                         vm.new_unexpected_keyword_type_error(Some("typealias"), &key.to_string())
                     );
@@ -416,17 +440,25 @@ pub(crate) mod decl {
                 vm.ctx.empty_tuple.clone()
             };
 
+            let qualname = match args.kwargs.get("qualname") {
+                Some(qualname) if !vm.is_none(qualname) => qualname
+                    .clone()
+                    .downcast::<crate::builtins::PyStr>()
+                    .map_err(|_| vm.new_type_error("qualname must be a string"))?,
+                _ => name.clone(),
+            };
+
             // Get caller's module name from frame globals, like typevar.rs caller()
             let module =
                 crate::frame::current_globals().and_then(|g| g.get_item("__name__", vm).ok());
 
-            Ok(Self::new_eager(name, type_params, value, module))
+            Ok(Self::new_eager(name, qualname, type_params, value, module))
         }
     }
 
     impl Representable for TypeAliasType {
         fn repr_wtf8(zelf: &Py<Self>, _vm: &VirtualMachine) -> PyResult<Wtf8Buf> {
-            Ok(zelf.name.as_wtf8().to_owned())
+            Ok(zelf.qualname.as_wtf8().to_owned())
         }
     }
 
diff --git a/crates/vm/src/stdlib/_warnings.rs b/crates/vm/src/stdlib/_warnings.rs
index 8a8f92b77da..ddbb38bbdc3 100644
--- a/crates/vm/src/stdlib/_warnings.rs
+++ b/crates/vm/src/stdlib/_warnings.rs
@@ -21,7 +21,7 @@ pub fn warn(
 mod _warnings {
     use crate::{
         AsObject, PyObject, PyObjectRef, PyResult, VirtualMachine,
-        builtins::{PyDictRef, PyListRef, PyStrRef, PyTupleRef, PyTypeRef},
+        builtins::{PyDict, PyDictRef, PyListRef, PyStrRef, PyTupleRef, PyTypeRef},
         convert::TryFromObject,
         function::OptionalArg,
     };
@@ -100,15 +100,12 @@ mod _warnings {
         category: Option<PyObjectRef>,
         vm: &VirtualMachine,
     ) -> PyResult<Option<PyTypeRef>> {
+        if message.fast_isinstance(vm.ctx.exceptions.warning) {
+            return Ok(Some(message.class().to_owned()));
+        }
         let cat_obj = match category {
             Some(c) if !vm.is_none(&c) => c,
-            _ => {
-                return Ok(if message.fast_isinstance(vm.ctx.exceptions.warning) {
-                    Some(message.class().to_owned())
-                } else {
-                    None // will default to UserWarning in warn_explicit
-                });
-            }
+            _ => return Ok(None), // will default to UserWarning in warn_explicit
         };
 
         let cat = PyTypeRef::try_from_object(vm, cat_obj.clone()).map_err(|_| {
@@ -120,8 +117,8 @@ mod _warnings {
 
         if !cat.fast_issubclass(vm.ctx.exceptions.warning) {
             return Err(vm.new_type_error(format!(
-                "category must be a Warning subclass, not '{}'",
-                cat.class().name()
+                "category must be a Warning subclass, not class '{}'",
+                cat.fully_qualified_name(vm)?
             )));
         }
 
@@ -183,7 +180,7 @@ mod _warnings {
         let source_line = if let Some(mg) = args.module_globals.into_option() {
             if vm.is_none(&mg) {
                 None
-            } else if !mg.class().is(vm.ctx.types.dict_type) {
+            } else if mg.downcast_ref::<PyDict>().is_none() {
                 return Err(vm.new_type_error(format!(
                     "module_globals must be a dict, not '{}'",
                     mg.class().name()
diff --git a/crates/vm/src/stdlib/_weakref.rs b/crates/vm/src/stdlib/_weakref.rs
index 767f793fdf9..624a1d511b2 100644
--- a/crates/vm/src/stdlib/_weakref.rs
+++ b/crates/vm/src/stdlib/_weakref.rs
@@ -52,8 +52,9 @@ mod _weakref {
 
     #[pyfunction]
     fn _remove_dead_weakref(dct: PyDictRef, key: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
+        let hash = key.hash(vm)?;
         dct._as_dict_inner()
-            .delete_if(vm, &*key, |wr| {
+            .delete_if(vm, &*key, hash, |wr| {
                 let wr = wr
                     .downcast_ref::<PyWeak>()
                     .ok_or_else(|| vm.new_type_error("not a weakref"))?;
diff --git a/crates/vm/src/stdlib/_winapi.rs b/crates/vm/src/stdlib/_winapi.rs
index 36bd9afbdfa..6f495299a99 100644
--- a/crates/vm/src/stdlib/_winapi.rs
+++ b/crates/vm/src/stdlib/_winapi.rs
@@ -38,6 +38,8 @@ mod _winapi {
         ERROR_ALREADY_EXISTS, ERROR_BROKEN_PIPE, ERROR_IO_PENDING, ERROR_MORE_DATA,
         ERROR_NETNAME_DELETED, ERROR_NO_DATA, ERROR_NO_SYSTEM_RESOURCES, ERROR_OPERATION_ABORTED,
         ERROR_PIPE_BUSY, ERROR_PIPE_CONNECTED, ERROR_PRIVILEGE_NOT_HELD, ERROR_SEM_TIMEOUT,
+        EVENTLOG_AUDIT_FAILURE, EVENTLOG_AUDIT_SUCCESS, EVENTLOG_ERROR_TYPE,
+        EVENTLOG_INFORMATION_TYPE, EVENTLOG_SUCCESS, EVENTLOG_WARNING_TYPE,
         FILE_FLAG_FIRST_PIPE_INSTANCE, FILE_FLAG_OVERLAPPED, FILE_GENERIC_READ, FILE_GENERIC_WRITE,
         FILE_MAP_ALL_ACCESS, FILE_MAP_COPY, FILE_MAP_EXECUTE, FILE_MAP_READ, FILE_MAP_WRITE,
         FILE_TYPE_CHAR, FILE_TYPE_DISK, FILE_TYPE_PIPE, FILE_TYPE_REMOTE, FILE_TYPE_UNKNOWN,
@@ -74,6 +76,50 @@ mod _winapi {
         WindowsSysResult(host_winapi::close_handle(handle.0))
     }
 
+    #[pyfunction]
+    fn RegisterEventSource(
+        server: Option<PyStrRef>,
+        source: PyStrRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<WinHandle> {
+        let server = server
+            .map(|server| server.as_wtf8().to_wide_cstring())
+            .transpose()
+            .map_err(|_| nul_char_error(vm))?;
+        let source = source
+            .as_wtf8()
+            .to_wide_cstring()
+            .map_err(|_| nul_char_error(vm))?;
+        vm.allow_threads(|| host_winapi::register_event_source_w(server.as_deref(), &source))
+            .map(WinHandle)
+            .map_err(|error| error.to_pyexception(vm))
+    }
+
+    #[pyfunction]
+    fn DeregisterEventSource(handle: WinHandle, vm: &VirtualMachine) -> PyResult<()> {
+        vm.allow_threads(|| host_winapi::deregister_event_source(handle.0))
+            .map_err(|error| error.to_pyexception(vm))
+    }
+
+    #[pyfunction]
+    fn ReportEvent(
+        handle: WinHandle,
+        event_type: u16,
+        category: u16,
+        event_id: u32,
+        message: PyStrRef,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        let message = message
+            .as_wtf8()
+            .to_wide_cstring()
+            .map_err(|_| nul_char_error(vm))?;
+        vm.allow_threads(|| {
+            host_winapi::report_event_w(handle.0, event_type, category, event_id, &message)
+        })
+        .map_err(|error| error.to_pyexception(vm))
+    }
+
     /// CreateFile - Create or open a file or I/O device.
     #[expect(
         clippy::too_many_arguments,
@@ -722,7 +768,8 @@ mod _winapi {
         if size > 0 {
             let result = host_winapi::peek_named_pipe(handle.0, Some(size as u32))
                 .map_err(|e| e.to_pyexception(vm))?;
-            let buf = result.data.unwrap_or_default();
+            let mut buf = result.data.unwrap_or_default();
+            buf.shrink_to_fit();
             let bytes: PyObjectRef = vm.ctx.new_bytes(buf).into();
             Ok(vm
                 .ctx
@@ -840,9 +887,10 @@ mod _winapi {
             return Ok(result.into());
         }
 
-        let result = vm
+        let mut result = vm
             .allow_threads(|| host_winapi::read_file(handle.0, size))
             .map_err(|e| e.to_pyexception(vm))?;
+        result.data.shrink_to_fit();
         Ok(vm
             .ctx
             .new_tuple(vec![
diff --git a/crates/vm/src/stdlib/builtins.rs b/crates/vm/src/stdlib/builtins.rs
index fbced8423a7..96b6db38ab3 100644
--- a/crates/vm/src/stdlib/builtins.rs
+++ b/crates/vm/src/stdlib/builtins.rs
@@ -11,7 +11,7 @@ mod builtins {
         AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
         VirtualMachine,
         builtins::{
-            PyByteArray, PyBytes, PyDictRef, PyStr, PyStrRef, PyTuple, PyTupleRef, PyType,
+            PyAnyDict, PyByteArray, PyBytes, PyStr, PyStrRef, PyTuple, PyTupleRef, PyType,
             PyUtf8StrRef,
             enumerate::PyReverseSequenceIterator,
             function::{PyCell, PyCellRef, PyFunction},
@@ -40,8 +40,8 @@ mod builtins {
         "can't compile() to bytecode when the `codegen` feature of rustpython is disabled";
 
     #[pyfunction]
-    fn abs(x: PyObjectRef, vm: &VirtualMachine) -> PyResult {
-        vm._abs(&x)
+    fn abs(number: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        vm._abs(&number)
     }
 
     #[pyfunction]
@@ -70,8 +70,8 @@ mod builtins {
     }
 
     #[pyfunction]
-    fn bin(number: ArgIndex) -> String {
-        let number = number.into_int_ref();
+    fn bin(integer: ArgIndex) -> String {
+        let number = integer.into_int_ref();
         let x = number.as_bigint();
         if x.is_negative() {
             format!("-0b{:b}", x.abs())
@@ -118,6 +118,8 @@ mod builtins {
         dont_inherit: ArgIntoBool,
         #[pyarg(any, default = -1)]
         optimize: i32,
+        #[pyarg(named, optional)]
+        module: Option<PyObjectRef>,
         #[pyarg(named, default = -1)]
         _feature_version: i32,
     }
@@ -208,6 +210,17 @@ mod builtins {
                 0..=2 => optimize as u8,
                 _ => return Err(vm.new_value_error("compile(): invalid optimize value")),
             };
+            let module = args.module.filter(|module| !vm.is_none(module));
+            let module = module
+                .map(|module| {
+                    PyStrRef::try_from_object(vm, module.clone()).map_err(|_| {
+                        vm.new_type_error(format!(
+                            "compile() argument 'module' must be str or None, not {}",
+                            module.class().name()
+                        ))
+                    })
+                })
+                .transpose()?;
             let dont_inherit = args.dont_inherit.into_bool();
             let is_ast_only = cf.contains(CompilerFlags::ONLY_AST);
             let future_features = merge_compile_future_features(flags, dont_inherit, vm);
@@ -297,7 +310,14 @@ mod builtins {
                     opts.optimize = optimize;
                     opts.allow_top_level_await = cf.contains(CompilerFlags::ALLOW_TOP_LEVEL_AWAIT);
                     opts.future_features = future_features;
-                    return _ast::compile(vm, args.source, &filename.to_string_lossy(), mode, opts);
+                    return _ast::compile(
+                        vm,
+                        args.source,
+                        &filename.to_string_lossy(),
+                        mode,
+                        opts,
+                        module.as_deref(),
+                    );
                 }
             }
 
@@ -314,13 +334,14 @@ mod builtins {
                 let mut compile_flags = flags | future_features.bits() as i32;
                 #[cfg(feature = "rustpython-compiler")]
                 let compile_source = |source: &[u8], compile_flags: i32| {
-                    vm.compile_string_object_with_flags(
+                    vm.compile_string_object_with_flags_and_module(
                         source,
                         &filename.to_string_lossy(),
                         start.as_i32(),
                         compile_flags,
                         feature_version,
                         optimize as i32,
+                        module.as_deref(),
                     )
                 };
                 match &source {
@@ -404,6 +425,26 @@ mod builtins {
         locals: Option<ArgMapping>,
     }
 
+    /// `_PyEval_EnsureBuiltins`
+    fn ensure_builtins(globals: &PyAnyDict, vm: &VirtualMachine) -> PyResult<()> {
+        if globals
+            .inner_getitem_opt(identifier!(vm, __builtins__), vm)?
+            .is_some()
+        {
+            return Ok(());
+        }
+        // PyEval_GetBuiltins
+        let builtins =
+            crate::frame::current_builtins().unwrap_or_else(|| vm.builtins.dict().into());
+        match globals.as_mutable() {
+            Some(dict) => dict.inner_setitem(identifier!(vm, __builtins__), builtins, vm),
+            None => globals
+                .as_object()
+                .set_item(identifier!(vm, __builtins__), builtins, vm)
+                .map_err(|_| vm.new_type_error("cannot assign __builtins__ to frozendict globals")),
+        }
+    }
+
     impl ScopeArgs {
         fn make_scope(
             self,
@@ -415,21 +456,23 @@ mod builtins {
                 vm: &VirtualMachine,
                 func_name: &'static str,
             ) -> PyResult<()> {
-                if !globals.fast_isinstance(vm.ctx.types.dict_type) {
+                if !globals.fast_isinstance(vm.ctx.types.dict_type)
+                    && !globals.fast_isinstance(vm.ctx.types.frozendict_type)
+                {
                     return Err(match func_name {
                         "eval" => {
                             let is_mapping = globals.mapping_unchecked().check();
                             vm.new_type_error(if is_mapping {
-                                "globals must be a real dict; try eval(expr, {}, mapping)"
+                                "globals must be a real dict or a frozendict; try eval(expr, {}, mapping)"
                             } else {
-                                "globals must be a dict"
+                                "globals must be a dict or a frozendict"
                             })
                         }
                         "exec" => vm.new_type_error(format!(
-                            "exec() globals must be a dict, not {}",
+                            "exec() globals must be a dict or a frozendict, not {}",
                             globals.class().name()
                         )),
-                        _ => vm.new_type_error("globals must be a dict"),
+                        _ => vm.new_type_error("globals must be a dict or a frozendict"),
                     });
                 }
                 Ok(())
@@ -439,15 +482,11 @@ mod builtins {
                 Some(globals) => {
                     validate_globals_dict(&globals, vm, func_name)?;
 
-                    let globals = PyDictRef::try_from_object(vm, globals)?;
-                    if !globals.contains_key(identifier!(vm, __builtins__), vm) {
-                        let builtins_dict = vm.builtins.dict().into();
-                        globals.set_item(identifier!(vm, __builtins__), builtins_dict, vm)?;
-                    }
+                    let globals = PyRef::<PyAnyDict>::try_from_object(vm, globals)?;
                     (
                         globals.clone(),
                         self.locals
-                            .unwrap_or_else(|| ArgMapping::from_dict_exact(globals.clone())),
+                            .unwrap_or_else(|| ArgMapping::from_anydict_exact(globals.clone())),
                     )
                 }
                 None => (
@@ -460,7 +499,9 @@ mod builtins {
                 ),
             };
 
-            let scope = crate::scope::Scope::with_builtins(Some(locals), globals, vm);
+            ensure_builtins(&globals, vm)?;
+
+            let scope = crate::scope::Scope::new(Some(locals), globals);
             Ok(scope)
         }
     }
@@ -629,6 +670,7 @@ mod builtins {
         func: &str,
         closure: Option<PyRef<PyTuple<PyCellRef>>>,
     ) -> PyResult {
+        let from_string = matches!(&source, Either::B(_));
         // Determine code object:
         let code_obj = match source {
             #[cfg(feature = "rustpython-compiler")]
@@ -654,6 +696,18 @@ mod builtins {
             )));
         }
 
+        // run_eval_code_obj: set globals['__builtins__'] if it doesn't exist
+        if from_string
+            && scope
+                .globals
+                .inner_getitem_opt(identifier!(vm, __builtins__), vm)?
+                .is_none()
+        {
+            scope
+                .globals
+                .set_item(identifier!(vm, __builtins__), vm.builtins.dict().into(), vm)?;
+        }
+
         // Run the code:
         vm.run_code_obj_with_closure(code_obj, scope, closure)
     }
@@ -700,7 +754,7 @@ mod builtins {
     }
 
     #[pyfunction]
-    fn globals(vm: &VirtualMachine) -> PyDictRef {
+    fn globals(vm: &VirtualMachine) -> PyRef<PyAnyDict> {
         vm.current_globals()
     }
 
@@ -1163,10 +1217,9 @@ mod builtins {
                 ))
             })?;
         match ndigits {
-            Some(obj) => {
-                let ndigits = obj.try_index(vm)?;
-                meth.invoke((ndigits,), vm)
-            }
+            // Like CPython, pass ndigits through as-is; the __round__ implementation
+            // decides what it accepts (float and int apply __index__ themselves).
+            Some(obj) => meth.invoke((obj,), vm),
             None => {
                 // without a parameter, the result type is coerced to int
                 meth.invoke((), vm)
@@ -1267,6 +1320,53 @@ mod builtins {
         )
     }
 
+    #[derive(FromArgs)]
+    struct LazyImportArgs {
+        #[pyarg(any)]
+        name: PyObjectRef,
+        #[pyarg(any, optional)]
+        globals: OptionalArg<PyObjectRef>,
+        #[pyarg(any, optional)]
+        locals: Option<PyObjectRef>,
+        #[pyarg(any, default, py_default = "()")]
+        fromlist: Option<PyObjectRef>,
+        #[pyarg(any, default)]
+        level: i32,
+    }
+
+    #[pyfunction]
+    fn __lazy_import__(args: LazyImportArgs, vm: &VirtualMachine) -> PyResult {
+        let globals = args
+            .globals
+            .into_option()
+            .or_else(|| crate::frame::current_globals().map(Into::into))
+            .ok_or_else(|| {
+                vm.new_type_error("__lazy_import__() missing globals when called without a frame")
+            })?;
+        let globals_dict = globals
+            .downcast_ref::<crate::builtins::PyDict>()
+            .ok_or_else(|| {
+                vm.new_type_error(format!(
+                    "expect dict for globals, got {}",
+                    globals.class().name()
+                ))
+            })?;
+        let builtins = globals_dict
+            .inner_getitem_opt(identifier!(vm, __builtins__), vm)?
+            .ok_or_else(|| vm.new_value_error("unable to get builtins for lazy import"))?;
+        let builtins = if let Some(module) = builtins.downcast_ref::<crate::builtins::PyModule>() {
+            module.dict().into()
+        } else {
+            builtins
+        };
+        let name = args
+            .name
+            .downcast_ref::<PyStr>()
+            .ok_or_else(|| vm.new_type_error("module name must be a string"))?;
+        let _ = args.locals;
+        crate::lazy_import::create(name, &globals, args.fromlist, args.level, builtins, vm)
+    }
+
     #[pyfunction]
     fn vars(obj: OptionalArg, vm: &VirtualMachine) -> PyResult {
         if let OptionalArg::Present(obj) = obj {
@@ -1470,6 +1570,7 @@ pub fn init_module(vm: &VirtualMachine, module: &Py<PyModule>) {
         "dict" => ctx.types.dict_type.to_owned(),
         "enumerate" => ctx.types.enumerate_type.to_owned(),
         "float" => ctx.types.float_type.to_owned(),
+        "frozendict" => ctx.types.frozendict_type.to_owned(),
         "frozenset" => ctx.types.frozenset_type.to_owned(),
         "filter" => ctx.types.filter_type.to_owned(),
         "int" => ctx.types.int_type.to_owned(),
@@ -1479,6 +1580,7 @@ pub fn init_module(vm: &VirtualMachine, module: &Py<PyModule>) {
         "object" => ctx.types.object_type.to_owned(),
         "property" => ctx.types.property_type.to_owned(),
         "range" => ctx.types.range_type.to_owned(),
+        "sentinel" => ctx.types.sentinel_type.to_owned(),
         "set" => ctx.types.set_type.to_owned(),
         "slice" => ctx.types.slice_type.to_owned(),
         "staticmethod" => ctx.types.staticmethod_type.to_owned(),
@@ -1515,6 +1617,7 @@ pub fn init_module(vm: &VirtualMachine, module: &Py<PyModule>) {
         "BufferError" => ctx.exceptions.buffer_error.to_owned(),
         "EOFError" => ctx.exceptions.eof_error.to_owned(),
         "ImportError" => ctx.exceptions.import_error.to_owned(),
+        "ImportCycleError" => ctx.exceptions.import_cycle_error.to_owned(),
         "ModuleNotFoundError" => ctx.exceptions.module_not_found_error.to_owned(),
         "LookupError" => ctx.exceptions.lookup_error.to_owned(),
         "IndexError" => ctx.exceptions.index_error.to_owned(),
diff --git a/crates/vm/src/stdlib/itertools.rs b/crates/vm/src/stdlib/itertools.rs
index 371e3ee68c2..4433cf4704f 100644
--- a/crates/vm/src/stdlib/itertools.rs
+++ b/crates/vm/src/stdlib/itertools.rs
@@ -5,13 +5,11 @@ mod decl {
     use crate::{
         AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, PyWeakRef, TryFromObject,
         VirtualMachine,
-        builtins::{
-            PyGenericAlias, PyInt, PyIntRef, PyList, PyTuple, PyTupleRef, PyType, PyTypeRef, int,
-        },
+        builtins::{PyGenericAlias, PyInt, PyList, PyTuple, PyTupleRef, PyType, PyTypeRef, int},
         class::PyClassDef,
         common::lock::{PyMutex, PyRwLock, PyRwLockWriteGuard},
         convert::ToPyObject,
-        function::{FuncArgs, NameIterables, PosArgs},
+        function::{ArgIndex, FuncArgs, NameIterables, PosArgs},
         protocol::{PyIter, PyIterReturn, PyNumber},
         raise_if_stop,
         stdlib::sys,
@@ -179,12 +177,12 @@ mod decl {
     impl IterNext for PyItertoolsCompress {
         fn next(zelf: &Py<Self>, vm: &VirtualMachine) -> PyResult<PyIterReturn> {
             loop {
+                // Match zip(data, selectors): consume data before the selector,
+                // and stop as soon as either input is exhausted.
+                let data_obj = raise_if_stop!(zelf.data.next(vm)?);
                 let sel_obj = raise_if_stop!(zelf.selectors.next(vm)?);
-                let verdict = sel_obj.try_to_bool(vm)?;
-                let data_obj = zelf.data.next(vm)?;
-
-                if verdict {
-                    return Ok(data_obj);
+                if sel_obj.try_to_bool(vm)? {
+                    return Ok(PyIterReturn::Return(data_obj));
                 }
             }
         }
@@ -1329,7 +1327,7 @@ mod decl {
         #[pyarg(any)]
         iterable: PyObjectRef,
         #[pyarg(any)]
-        r: PyIntRef,
+        r: ArgIndex,
     }
 
     impl Constructor for PyItertoolsCombinations {
@@ -1342,6 +1340,7 @@ mod decl {
         ) -> PyResult<Self> {
             let pool: Vec<_> = iterable.try_to_value(vm)?;
 
+            let r = r.into_int_ref();
             let r = r.as_bigint();
             if r.is_negative() {
                 return Err(vm.new_value_error("r must be non-negative"));
@@ -1454,6 +1453,7 @@ mod decl {
             vm: &VirtualMachine,
         ) -> PyResult<Self> {
             let pool: Vec<_> = iterable.try_to_value(vm)?;
+            let r = r.into_int_ref();
             let r = r.as_bigint();
             if r.is_negative() {
                 return Err(vm.new_value_error("r must be non-negative"));
@@ -1800,7 +1800,7 @@ mod decl {
         #[pyarg(any)]
         iterable: PyObjectRef,
         #[pyarg(any)]
-        n: PyIntRef,
+        n: ArgIndex,
         #[pyarg(named, default)]
         strict: bool,
     }
@@ -1817,6 +1817,7 @@ mod decl {
             }: Self::Args,
             vm: &VirtualMachine,
         ) -> PyResult<Self> {
+            let n = n.into_int_ref();
             let n = n.as_bigint();
             if n.lt(&BigInt::one()) {
                 return Err(vm.new_value_error("n must be at least one"));
diff --git a/crates/vm/src/stdlib/marshal.rs b/crates/vm/src/stdlib/marshal.rs
index 2624e9c0edd..62bed8d7a7f 100644
--- a/crates/vm/src/stdlib/marshal.rs
+++ b/crates/vm/src/stdlib/marshal.rs
@@ -4,14 +4,15 @@ pub(crate) use decl::module_def;
 #[pymodule(name = "marshal")]
 mod decl {
     use crate::builtins::code::{CodeObject, Literal, PyVmBag};
+    use crate::builtins::dict::DictIter;
     use crate::class::StaticType;
     use crate::common::wtf8::Wtf8;
     use crate::{
         PyObject, PyObjectRef, PyResult, TryFromObject, VirtualMachine,
         builtins::{
-            PyBaseExceptionRef, PyBool, PyByteArray, PyBytes, PyCode, PyComplex, PyDict,
-            PyEllipsis, PyFloat, PyFrozenSet, PyInt, PyList, PyMemoryView, PyNone, PySet,
-            PyStopIteration, PyStr, PyTuple,
+            PyAnyDict, PyBaseExceptionRef, PyBool, PyByteArray, PyBytes, PyCode, PyComplex, PyDict,
+            PyEllipsis, PyFloat, PyFrozenDict, PyFrozenSet, PyInt, PyList, PyMemoryView, PyNone,
+            PySet, PyStopIteration, PyStr, PyTuple,
         },
         convert::ToPyObject,
         function::ArgBytesLike,
@@ -76,6 +77,10 @@ mod decl {
                     let entries = pydict.into_iter().collect::<Vec<_>>();
                     f(DumpableValue::Dict(&entries))
                 }
+                ref pyfrozen @ PyFrozenDict => {
+                    let entries = DictIter::new(&pyfrozen.dict).collect::<Vec<_>>();
+                    f(DumpableValue::Frozendict(&entries))
+                }
                 ref bytes @ PyBytes => {
                     f(DumpableValue::Bytes(bytes.as_bytes()))
                 }
@@ -95,7 +100,7 @@ mod decl {
     struct DumpsArgs {
         #[pyarg(positional)]
         value: PyObjectRef,
-        #[pyarg(positional, default = 5)]
+        #[pyarg(positional, default = 6)]
         version: i32,
         #[pyarg(named, default = true)]
         allow_code: bool,
@@ -124,6 +129,8 @@ mod decl {
 
     struct WriterRefEntry {
         idx: u32,
+        // The table holds a reference, as w_ref does, so the id stays unique.
+        _owner: PyObjectRef,
         /// Set between `reserve` and `complete` for the object kinds whose
         /// immutable representation cannot be rebuilt from a back-reference.
         incomplete: bool,
@@ -158,8 +165,14 @@ mod decl {
         }
         fn reserve(&mut self, obj: &PyObject, incomplete: bool) -> u32 {
             let idx = self.next_idx;
-            self.map
-                .insert(obj.get_id(), WriterRefEntry { idx, incomplete });
+            self.map.insert(
+                obj.get_id(),
+                WriterRefEntry {
+                    idx,
+                    incomplete,
+                    _owner: obj.to_owned(),
+                },
+            );
             self.next_idx += 1;
             idx
         }
@@ -233,8 +246,14 @@ mod decl {
             || obj.is(PyStopIteration::static_type())
             || obj.downcast_ref::<crate::builtins::PyEllipsis>().is_some();
 
-        // FLAG_REF: check if already written, otherwise reserve slot
-        if !is_singleton && let Some(rt) = refs.as_mut() {
+        // If it has only one reference, it definitely isn't shared. But
+        // TYPE_REF is always used for interned strings, to keep PYC files as
+        // stable as possible.
+        let use_ref = refs.is_some()
+            && !is_singleton
+            && (obj.strong_count() != 1
+                || (obj.class().is(PyStr::static_type()) && obj.is_interned()));
+        if use_ref && let Some(rt) = refs.as_mut() {
             match rt.try_ref(buf, obj) {
                 Ok(true) => return Ok(()),
                 Ok(false) => {}
@@ -247,13 +266,13 @@ mod decl {
             }
         }
         let type_pos = buf.len();
-        let use_ref = refs.is_some() && !is_singleton;
-        // A code or slice entry stays incomplete until its contents are
-        // written: the reader rebuilds both from their fields, so a
+        // A code, slice or frozendict entry stays incomplete until its contents are
+        // written: the reader rebuilds them from their fields, so a
         // back-reference issued while those fields are still being emitted
         // would name an object that does not exist yet.
         let requires_completion = obj.downcast_ref::<PyCode>().is_some()
-            || obj.downcast_ref::<crate::builtins::PySlice>().is_some();
+            || obj.downcast_ref::<crate::builtins::PySlice>().is_some()
+            || obj.downcast_ref::<PyFrozenDict>().is_some();
         if use_ref {
             refs.as_mut().unwrap().reserve(obj, requires_completion);
         }
@@ -325,7 +344,9 @@ mod decl {
                 write_float_str(buf, cv.re);
                 write_float_str(buf, cv.im);
             }
-        } else if let Some(s) = obj.downcast_ref::<PyStr>() {
+        } else if let Some(s) = obj.downcast_ref::<PyStr>()
+            && obj.class().is(PyStr::static_type())
+        {
             let bytes = s.as_wtf8().as_bytes();
             // Only the formats that carry back-references tell an interned
             // string apart, and only those from 4 on have the ascii-only forms.
@@ -372,9 +393,17 @@ mod decl {
             for elem in items.iter() {
                 write_object_depth(buf, elem, refs, version, allow_code, vm, depth - 1)?;
             }
-        } else if let Some(d) = obj.downcast_ref::<PyDict>() {
-            buf.write_u8(b'{');
-            for (k, v) in d {
+        } else if let Some(d) = PyAnyDict::from_object(obj) {
+            let typ = if d.is_frozen() {
+                if version < 6 || !obj.class().is(vm.ctx.types.frozendict_type) {
+                    return Err(vm.new_value_error("unmarshallable object"));
+                }
+                b'}'
+            } else {
+                b'{'
+            };
+            buf.write_u8(typ);
+            for (k, v) in DictIter::new(d.as_dict()) {
                 write_object_depth(buf, &k, refs, version, allow_code, vm, depth - 1)?;
                 write_object_depth(buf, &v, refs, version, allow_code, vm, depth - 1)?;
             }
@@ -390,14 +419,36 @@ mod decl {
                 return Err(vm.new_value_error("marshalling code objects is disallowed"));
             }
             buf.write_u8(b'c');
-            // `Literal` holds the exact object a constant was built from, so
-            // route `co_consts` back through the object writer: it reaches the
-            // values `BorrowedConstant` cannot describe and shares the one
-            // reference table the reader indexes against.
-            marshal::serialize_code_with(buf, &co.code, |buf, constant| {
-                let constant = PyObjectRef::from(constant.clone());
-                write_object_depth(buf, &constant, refs, version, allow_code, vm, depth - 1)
-            })?;
+            let code = &co.code;
+            for value in [
+                code.arg_count,
+                code.posonlyarg_count,
+                code.kwonlyarg_count,
+                code.max_stackdepth,
+                code.flags.bits(),
+            ] {
+                buf.write_u32(value);
+            }
+            let co_code = co.get_code(vm);
+            let co_qualname = co.co_qualname();
+            let mut write_field = |buf: &mut Vec<u8>, field: &PyObject| {
+                write_object_depth(buf, field, refs, version, allow_code, vm, depth - 1)
+            };
+            for field in [
+                co_code.as_object(),
+                co.co_consts().as_object(),
+                co.co_names.as_object(),
+                co.co_localsplusnames.as_object(),
+                co.co_localspluskinds.as_object(),
+                co.source_path().as_object(),
+                co.co_name.as_object(),
+                co_qualname.as_object(),
+            ] {
+                write_field(buf, field)?;
+            }
+            buf.write_u32(code.first_line_number.map_or(0, |n| n.get() as u32));
+            write_field(buf, co.co_linetable.as_object())?;
+            write_field(buf, co.co_exceptiontable.as_object())?;
         } else if let Some(sl) = obj.downcast_ref::<crate::builtins::PySlice>() {
             if version < 5 {
                 return Err(vm.new_value_error("unmarshallable object"));
@@ -473,7 +524,7 @@ mod decl {
         value: PyObjectRef,
         #[pyarg(positional)]
         file: PyObjectRef,
-        #[pyarg(positional, default = 5)]
+        #[pyarg(positional, default = 6)]
         version: i32,
         #[pyarg(named, default = true)]
         allow_code: bool,
@@ -593,14 +644,20 @@ mod decl {
             unsafe { tuple.payload.set_marshal_item(index, value) };
             Ok(())
         }
-        fn make_code(&self, code: CodeObject) -> Result<Self::Value, marshal::MarshalError> {
+        fn make_code(
+            &self,
+            code: CodeObject,
+            fields: marshal::CodeFields<Self::Value>,
+        ) -> Result<Self::Value, marshal::MarshalError> {
             if !self.allow_code {
                 return Err(self.remember_python_error(
                     self.vm
                         .new_value_error("unmarshalling code objects is disallowed"),
                 ));
             }
-            Ok(crate::builtins::PyCode::new_ref_with_bag(self.vm, code).into())
+            let mut code = PyCode::from_marshal(code, fields, &self.vm.ctx)?;
+            code.apply_debug_ranges(self.vm);
+            Ok(code.into_ref(&self.vm.ctx).into())
         }
         fn make_stop_iter(&self) -> Result<Self::Value, marshal::MarshalError> {
             Ok(self.vm.ctx.exceptions.stop_iteration.to_owned().into())
@@ -677,6 +734,12 @@ mod decl {
         fn make_dict_placeholder(&self) -> Option<Self::Value> {
             Some(self.vm.ctx.new_dict().into())
         }
+        fn freeze_dict(&self, source: Self::Value) -> Result<Self::Value, marshal::MarshalError> {
+            let dict = PyDict::default();
+            dict.update_arg(source, true, "frozendict", self.vm)
+                .map_err(|error| self.remember_python_error(error))?;
+            Ok(PyFrozenDict::from_dict(dict).into_ref(&self.vm.ctx).into())
+        }
         fn insert_dict_item(
             &self,
             dict: &Self::Value,
diff --git a/crates/vm/src/stdlib/mod.rs b/crates/vm/src/stdlib/mod.rs
index 73b816c579c..ee66ed3227b 100644
--- a/crates/vm/src/stdlib/mod.rs
+++ b/crates/vm/src/stdlib/mod.rs
@@ -3,7 +3,7 @@ mod _abc;
 pub(crate) mod _ast;
 mod _codecs;
 mod _collections;
-pub(crate) use _collections::ordered_dict::ordered_dict::PyOrderedDictItems;
+pub(crate) use _collections::ordered_dict::ordered_dict::PyOrderedDict;
 mod _functools;
 mod _imp;
 pub mod _io;
@@ -83,6 +83,24 @@ mod winsound;
 
 use crate::{Context, builtins::PyModuleDef};
 
+// Keep ctypes-specific alias detection available to memoryview on all targets.
+pub(crate) fn is_borrowed_ctypes_buffer(_obj: &crate::PyObject) -> bool {
+    #[cfg(all(
+        feature = "host_env",
+        any(
+            target_os = "linux",
+            target_os = "macos",
+            target_os = "windows",
+            target_os = "android"
+        ),
+        not(any(target_env = "musl", target_env = "sgx"))
+    ))]
+    if _ctypes::is_borrowed_buffer(_obj) {
+        return true;
+    }
+    false
+}
+
 /// Returns module definitions for multi-phase init modules.
 ///
 /// These modules use multi-phase initialization pattern:
@@ -140,6 +158,7 @@ pub fn builtin_module_defs(ctx: &Context) -> Vec<&'static PyModuleDef> {
         _symtable::module_def(ctx),
         _sysconfigdata::module_def(ctx),
         _sysconfig::module_def(ctx),
+        _sysconfig::_missing_stdlib_info::module_def(ctx),
         #[cfg(feature = "threading")]
         _thread::module_def(ctx),
         _interpchannels::module_def(ctx),
diff --git a/crates/vm/src/stdlib/nt.rs b/crates/vm/src/stdlib/nt.rs
index 812bca83b78..be7fb9de85d 100644
--- a/crates/vm/src/stdlib/nt.rs
+++ b/crates/vm/src/stdlib/nt.rs
@@ -24,6 +24,18 @@ pub(crate) mod module {
     use std::os::windows::ffi::{OsStrExt, OsStringExt};
     use std::os::windows::io::AsRawHandle;
 
+    #[pyfunction]
+    fn get_blocking(fd: crt_fd::Borrowed<'_>, vm: &VirtualMachine) -> PyResult<bool> {
+        vm.allow_threads(|| host_nt::get_blocking(fd))
+            .map_err(|err| err.to_pyexception(vm))
+    }
+
+    #[pyfunction]
+    fn set_blocking(fd: crt_fd::Borrowed<'_>, blocking: bool, vm: &VirtualMachine) -> PyResult<()> {
+        vm.allow_threads(|| host_nt::set_blocking(fd, blocking))
+            .map_err(|err| err.to_pyexception(vm))
+    }
+
     #[pyattr]
     use rustpython_host_env::os::{
         O_BINARY, O_NOINHERIT, O_RANDOM, O_SEQUENTIAL, O_TEMPORARY, O_TEXT,
diff --git a/crates/vm/src/stdlib/os.rs b/crates/vm/src/stdlib/os.rs
index 527643822b8..3a69305d2d0 100644
--- a/crates/vm/src/stdlib/os.rs
+++ b/crates/vm/src/stdlib/os.rs
@@ -199,22 +199,28 @@ impl ToPyObject for crt_fd::Borrowed<'_> {
 
 #[pymodule(sub, name = "posix")]
 pub(super) mod _os {
-    use super::{DirFd, DstDirFd, FollowSymlinks, RawMode, SrcDirFd, SupportFunc};
+    use super::{
+        AT_FDCWD, DefaultDirFd, DirFd, DirFdKeyword, DstDirFd, FollowSymlinks, RawMode, SrcDirFd,
+        SupportFunc, warn_if_bool_fd,
+    };
     #[cfg(not(windows))]
     use crate::exceptions;
     use crate::host_env::fileutils::StatStruct;
     #[cfg(any(unix, windows))]
     use crate::utils::ToCString;
     use crate::{
-        AsObject, Py, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject,
+        AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult,
         builtins::{
-            PyBytesRef, PyGenericAlias, PyIntRef, PyStrRef, PyTuple, PyTupleRef, PyTypeRef,
+            PyBytes, PyBytesRef, PyFloat, PyGenericAlias, PyIntRef, PyStr, PyStrRef, PyTuple,
+            PyTupleRef, PyTypeRef,
         },
         class::PyClassDef,
         common::lock::{OnceCell, PyRwLock},
-        convert::{IntoPyException, ToPyObject},
+        convert::{IntoPyException, ToPyException, ToPyObject},
         exceptions::{OSErrorBuilder, ToOSErrorBuilder},
-        function::{ArgBytesLike, ArgMemoryBuffer, FsPath, FuncArgs},
+        function::{
+            ArgBytesLike, ArgMemoryBuffer, ArgumentError, Either, FromArgs, FsPath, FuncArgs, Param,
+        },
         host_env::crt_fd,
         ospath::{OsPath, OsPathOrFd, OutputMode, PathConverter},
         protocol::PyIterReturn,
@@ -225,11 +231,12 @@ pub(super) mod _os {
         },
         vm::VirtualMachine,
     };
+    use core::hint::cold_path;
     #[cfg(not(windows))]
     use core::marker::PhantomData;
-    use core::{hint::cold_path, time::Duration};
     use crossbeam_utils::atomic::AtomicCell;
     use rustpython_common::wtf8::Wtf8Buf;
+    use rustpython_host_env::os::{FileTime, FileTimeSeconds};
     #[cfg(windows)]
     use rustpython_host_env::{nt as host_nt, windows::ToWideString};
 
@@ -272,27 +279,60 @@ pub(super) mod _os {
 
     #[pyfunction]
     fn closerange(fd_low: i32, fd_high: i32) {
-        for fileno in fd_low..fd_high {
-            if let Ok(fd) = unsafe { crt_fd::Owned::try_from_raw(fileno) } {
-                drop(fd);
+        crt_fd::closerange(fd_low, fd_high);
+    }
+
+    // Signal callbacks can close this descriptor between open attempts.
+    #[cfg(any(unix, windows, target_os = "wasi"))]
+    struct OpenDirFd(crt_fd::Raw);
+
+    #[cfg(any(unix, windows, target_os = "wasi"))]
+    impl FromArgs for OpenDirFd {
+        const PARAMS: Option<&'static [Param]> = Some(DefaultDirFd::PARAMS);
+
+        fn from_args(vm: &VirtualMachine, args: &mut FuncArgs) -> Result<Self, ArgumentError> {
+            let fd = match args.take_keyword("dir_fd") {
+                Some(o) if vm.is_none(&o) => AT_FDCWD,
+                None => AT_FDCWD,
+                Some(o) => {
+                    warn_if_bool_fd(&o, vm).map_err(Into::<ArgumentError>::into)?;
+                    let fd = o.try_index_opt(vm).unwrap_or_else(|| {
+                        Err(vm.new_type_error(format!(
+                            "argument should be integer or None, not {}",
+                            o.class().name()
+                        )))
+                    })?;
+                    fd.try_to_primitive(vm)?
+                }
+            };
+            if fd == -1 {
+                return Err(io::Error::from_raw_os_error(libc::EBADF)
+                    .to_pyexception(vm)
+                    .into());
+            }
+            if !OPEN_DIR_FD && fd != AT_FDCWD {
+                return Err(vm
+                    .new_not_implemented_error("dir_fd unavailable on this platform")
+                    .into());
             }
+            Ok(Self(fd))
         }
     }
 
     #[cfg(any(unix, windows, target_os = "wasi"))]
     #[derive(FromArgs)]
-    struct OpenArgs<'fd> {
+    struct OpenArgs {
         path: OsPath,
         flags: i32,
         #[pyarg(any, default = 0o777)]
         mode: i32,
         #[pyarg(flatten)]
-        dir_fd: DirFd<'fd, { OPEN_DIR_FD as usize }>,
+        dir_fd: OpenDirFd,
     }
 
     #[pyfunction]
-    fn open(args: OpenArgs<'_>, vm: &VirtualMachine) -> PyResult<crt_fd::Owned> {
-        os_open(args.path, args.flags, args.mode, args.dir_fd, vm)
+    fn open(args: OpenArgs, vm: &VirtualMachine) -> PyResult<crt_fd::Owned> {
+        os_open(args.path, args.flags, args.mode, args.dir_fd.0, vm)
     }
 
     #[cfg(any(unix, windows, target_os = "wasi"))]
@@ -300,34 +340,50 @@ pub(super) mod _os {
         name: OsPath,
         flags: i32,
         mode: i32,
-        dir_fd: DirFd<'_, { OPEN_DIR_FD as usize }>,
+        dir_fd: crt_fd::Raw,
         vm: &VirtualMachine,
     ) -> PyResult<crt_fd::Owned> {
+        use crate::host_env::os::ErrorExt;
+
         #[cfg(windows)]
-        let fd = {
-            let [] = dir_fd.0;
-            let name = name.to_wide_cstring(vm)?;
-            let flags = flags | crate::host_env::os::O_NOINHERIT;
-            crt_fd::wopen(&name, flags, mode)
-        };
+        let raw_name = name.to_wide_cstring(vm)?;
         #[cfg(not(windows))]
-        let fd = {
-            let name = name.clone().into_cstring(vm)?;
-            #[cfg(not(target_os = "wasi"))]
-            let flags = flags | crate::host_env::os::O_CLOEXEC;
-            #[cfg(not(target_os = "redox"))]
-            if let Some(dir_fd) = dir_fd.get_opt() {
-                crt_fd::openat(dir_fd, &name, flags, mode)
-            } else {
-                crt_fd::open(&name, flags, mode)
-            }
-            #[cfg(target_os = "redox")]
-            {
-                let [] = dir_fd.0;
-                crt_fd::open(&name, flags, mode)
+        let raw_name = name.clone().into_cstring(vm)?;
+        #[cfg(windows)]
+        let flags = flags | crate::host_env::os::O_NOINHERIT;
+        #[cfg(all(not(windows), not(target_os = "wasi")))]
+        let flags = flags | crate::host_env::os::O_CLOEXEC;
+
+        loop {
+            let fd = vm.allow_threads(|| {
+                #[cfg(windows)]
+                {
+                    let _ = dir_fd;
+                    crt_fd::wopen(&raw_name, flags, mode)
+                }
+                #[cfg(not(windows))]
+                {
+                    #[cfg(not(target_os = "redox"))]
+                    if dir_fd != AT_FDCWD {
+                        crt_fd::openat_raw(dir_fd, &raw_name, flags, mode)
+                    } else {
+                        crt_fd::open(&raw_name, flags, mode)
+                    }
+                    #[cfg(target_os = "redox")]
+                    {
+                        let _ = dir_fd;
+                        crt_fd::open(&raw_name, flags, mode)
+                    }
+                }
+            });
+            match fd {
+                Ok(fd) => return Ok(fd),
+                Err(err) if err.posix_errno() == libc::EINTR => vm.check_signals()?,
+                Err(err) => {
+                    return Err(OSErrorBuilder::with_filename_from_errno(&err, name, vm));
+                }
             }
-        };
-        fd.map_err(|err| OSErrorBuilder::with_filename_from_errno(&err, name, vm))
+        }
     }
 
     #[derive(FromArgs)]
@@ -348,6 +404,7 @@ pub(super) mod _os {
             match vm.allow_threads(|| crt_fd::read(fd, &mut buffer)) {
                 Ok(n) => {
                     buffer.truncate(n);
+                    buffer.shrink_to_fit();
                     return Ok(vm.ctx.new_bytes(buffer));
                 }
                 Err(e) if e.raw_os_error() == Some(libc::EINTR) => {
@@ -404,9 +461,9 @@ pub(super) mod _os {
 
     #[pyfunction]
     fn write(fd: crt_fd::Borrowed<'_>, data: ArgBytesLike, vm: &VirtualMachine) -> PyResult<usize> {
-        let owned = data.with_ref(|b| b.to_vec());
+        let buffer = data.borrow_buf_unlocked(vm)?;
         loop {
-            match vm.allow_threads(|| crt_fd::write(fd, &owned)) {
+            match vm.allow_threads(|| crt_fd::write(fd, &buffer)) {
                 Ok(n) => return Ok(n),
                 Err(e) if e.raw_os_error() == Some(libc::EINTR) => {
                     vm.check_signals()?;
@@ -1689,7 +1746,7 @@ pub(super) mod _os {
 
     #[pyfunction]
     fn _exit(status: ExitStatus) {
-        crate::host_env::os::exit(status.status)
+        crate::host_env::os::exit_immediately(status.status)
     }
 
     #[pyfunction]
@@ -1842,6 +1899,50 @@ pub(super) mod _os {
         follow_symlinks: FollowSymlinks,
     }
 
+    fn file_time_seconds(obj: &PyObject, vm: &VirtualMachine) -> PyResult<FileTimeSeconds> {
+        obj.try_index(vm)
+            .and_then(|value| value.try_to_primitive(vm))
+            .map_err(|err| {
+                if err.fast_isinstance(vm.ctx.exceptions.overflow_error) {
+                    vm.new_overflow_error("timestamp out of range for platform time_t")
+                } else {
+                    err
+                }
+            })
+    }
+
+    fn file_time(obj: &PyObject, vm: &VirtualMachine) -> PyResult<FileTime> {
+        if obj.number().is_index() {
+            return Ok(FileTime {
+                seconds: file_time_seconds(obj, vm)?,
+                nanoseconds: 0,
+            });
+        }
+        let value = if let Some(float) = obj.downcast_ref::<PyFloat>() {
+            float.to_f64()
+        } else {
+            obj.try_float(vm)?.to_f64()
+        };
+        if value.is_nan() {
+            return Err(vm.new_value_error("Invalid value NaN (not a number)"));
+        }
+        let mut seconds = value.trunc();
+        let mut nanoseconds = (value.fract() * 1_000_000_000.0).floor();
+        if nanoseconds < 0.0 {
+            nanoseconds += 1_000_000_000.0;
+            seconds -= 1.0;
+        }
+        let minimum = FileTimeSeconds::MIN as f64;
+        // The signed maximum rounds up when represented by f64.
+        if !(minimum..-minimum).contains(&seconds) {
+            return Err(vm.new_overflow_error("timestamp out of range for platform time_t"));
+        }
+        Ok(FileTime {
+            seconds: seconds as FileTimeSeconds,
+            nanoseconds: nanoseconds as libc::c_long,
+        })
+    }
+
     #[pyfunction]
     fn utime(args: UtimeArgs<'_>, vm: &VirtualMachine) -> PyResult<()> {
         let parse_tup = |tup: &Py<PyTuple>| -> Option<(PyObjectRef, PyObjectRef)> {
@@ -1856,13 +1957,13 @@ pub(super) mod _os {
                 let (a, m) = parse_tup(&t).ok_or_else(|| {
                     vm.new_type_error("utime: 'times' must be either a tuple of two ints or None")
                 })?;
-                (a.try_into_value(vm)?, m.try_into_value(vm)?)
+                (file_time(&a, vm)?, file_time(&m, vm)?)
             }
             (None, Some(ns)) => {
                 let (a, m) = parse_tup(&ns)
                     .ok_or_else(|| vm.new_type_error("utime: 'ns' must be a tuple of two ints"))?;
                 let ns_in_sec: PyObjectRef = vm.ctx.new_int(1_000_000_000).into();
-                let ns_to_dur = |obj: PyObjectRef| {
+                let ns_to_time = |obj: PyObjectRef| {
                     let divmod = vm._divmod(&obj, &ns_in_sec)?;
                     let (div, rem) = divmod
                         .downcast_ref::<PyTuple>()
@@ -1874,16 +1975,31 @@ pub(super) mod _os {
                                 divmod.class().name()
                             ))
                         })?;
-                    let secs = div.try_index(vm)?.try_to_primitive(vm)?;
-                    let ns = rem.try_index(vm)?.try_to_primitive(vm)?;
-                    Ok(Duration::new(secs, ns))
+                    let seconds = file_time_seconds(&div, vm)?;
+                    let rem = rem.try_index(vm)?;
+                    let nanoseconds = rem.try_to_primitive::<libc::c_long>(vm).map_err(|err| {
+                        if err.fast_isinstance(vm.ctx.exceptions.overflow_error) {
+                            vm.new_overflow_error("Python int too large to convert to C long")
+                        } else {
+                            err
+                        }
+                    })?;
+                    Ok(FileTime {
+                        seconds,
+                        nanoseconds,
+                    })
                 };
-                // TODO: do validation to make sure this doesn't.. underflow?
-                (ns_to_dur(a)?, ns_to_dur(m)?)
+                (ns_to_time(a)?, ns_to_time(m)?)
             }
             (None, None) => {
                 let now = SystemTime::now();
                 let now = now.duration_since(SystemTime::UNIX_EPOCH).unwrap();
+                let now = FileTime {
+                    seconds: now.as_secs().try_into().map_err(|_| {
+                        vm.new_overflow_error("timestamp out of range for platform time_t")
+                    })?,
+                    nanoseconds: now.subsec_nanos() as libc::c_long,
+                };
                 (now, now)
             }
             (Some(_), Some(_)) => {
@@ -1897,8 +2013,8 @@ pub(super) mod _os {
 
     fn utime_impl(
         path: OsPath,
-        acc: Duration,
-        modif: Duration,
+        acc: FileTime,
+        modif: FileTime,
         dir_fd: DirFd<'_, { UTIME_DIR_FD as usize }>,
         _follow_symlinks: FollowSymlinks,
         vm: &VirtualMachine,
@@ -1938,8 +2054,15 @@ pub(super) mod _os {
                 ));
             }
 
-            crate::host_env::os::set_file_times(&path, acc, modif)
-                .map_err(|err| OSErrorBuilder::with_filename(&err, path, vm))
+            let wide_path = path.to_wide_cstring(vm)?;
+            host_nt::set_file_times(
+                &wide_path,
+                acc.seconds,
+                acc.nanoseconds.into(),
+                modif.seconds,
+                modif.nanoseconds.into(),
+            )
+            .map_err(|err| OSErrorBuilder::with_filename(&err, path, vm))
         }
     }
 
@@ -2055,27 +2178,66 @@ pub(super) mod _os {
         crate::host_env::time::strerror(code)
     }
 
-    #[pyfunction]
     pub(crate) fn ftruncate(fd: crt_fd::Borrowed<'_>, length: crt_fd::Offset) -> io::Result<()> {
         crt_fd::ftruncate(fd, length)
     }
 
+    #[pyfunction(name = "ftruncate")]
+    fn py_ftruncate(fd: i32, length: crt_fd::Offset, vm: &VirtualMachine) -> PyResult<()> {
+        ftruncate_impl(fd, length, vm)
+    }
+
+    fn ftruncate_impl(
+        fd: crt_fd::Raw,
+        length: crt_fd::Offset,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
+        use crate::host_env::os::ErrorExt;
+
+        vm.audit("os.truncate", || (fd, length))?;
+        loop {
+            match vm.allow_threads(|| crt_fd::ftruncate_raw(fd, length)) {
+                Ok(()) => return Ok(()),
+                Err(err) if err.posix_errno() == libc::EINTR => vm.check_signals()?,
+                Err(err) => return Err(err.into_pyexception(vm)),
+            }
+        }
+    }
+
     #[derive(FromArgs)]
     struct TruncateArgs {
         #[pyarg(any)]
         path: PyObjectRef,
         #[pyarg(any)]
-        length: crt_fd::Offset,
+        length: PyObjectRef,
     }
 
     #[pyfunction]
     fn truncate(args: TruncateArgs, vm: &VirtualMachine) -> PyResult<()> {
         let TruncateArgs { path, length } = args;
-        match path.clone().try_into_value::<crt_fd::Borrowed<'_>>(vm) {
-            Ok(fd) => return ftruncate(fd, length).map_err(|e| e.into_pyexception(vm)),
-            Err(e) if e.fast_isinstance(vm.ctx.exceptions.warning) => return Err(e),
-            Err(_) => {}
-        }
+        let index =
+            if path.downcast_ref::<PyStr>().is_some() || path.downcast_ref::<PyBytes>().is_some() {
+                None
+            } else {
+                path.try_index_opt(vm)
+            };
+        let path = if let Some(index) = index {
+            super::warn_if_bool_fd(&path, vm)?;
+            Either::A(index?.try_to_primitive::<crt_fd::Raw>(vm)?)
+        } else {
+            Either::B(
+                PathConverter::new()
+                    .function("truncate")
+                    .try_path_inner(path, true, vm)?,
+            )
+        };
+        let length = length.try_into_value::<crt_fd::Offset>(vm)?;
+        let path = match path {
+            Either::A(fd) => {
+                return ftruncate_impl(fd, length, vm);
+            }
+            Either::B(path) => path,
+        };
 
         #[cold]
         fn error(
@@ -2086,7 +2248,8 @@ pub(super) mod _os {
             OSErrorBuilder::with_filename(&error, path, vm)
         }
 
-        let path = OsPath::try_from_object(vm, path)?;
+        vm.audit("os.truncate", || (path.filename(vm), length))?;
+
         // TODO: just call libc::truncate() on POSIX
         let f = match crate::host_env::fs::open_write(&path) {
             Ok(f) => f,
@@ -2311,6 +2474,7 @@ pub(super) mod _os {
             SupportFunc::new("rmdir", Some(false), Some(RMDIR_DIR_FD), Some(false)),
             SupportFunc::new("scandir", Some(SCANDIR_FD), Some(false), Some(false)),
             SupportFunc::new("stat", Some(true), Some(STAT_DIR_FD), Some(true)),
+            SupportFunc::new("lstat", Some(false), Some(STAT_DIR_FD), Some(false)),
             SupportFunc::new("fstat", Some(false), Some(false), Some(false)),
             SupportFunc::new("symlink", Some(false), Some(SYMLINK_DIR_FD), Some(false)),
             SupportFunc::new("truncate", Some(true), Some(false), Some(false)),
diff --git a/crates/vm/src/stdlib/posix.rs b/crates/vm/src/stdlib/posix.rs
index 1f123812fc2..8e142c41793 100644
--- a/crates/vm/src/stdlib/posix.rs
+++ b/crates/vm/src/stdlib/posix.rs
@@ -36,7 +36,7 @@ pub mod module {
     use crate::{builtins::PyUtf8StrRef, utils::ToCString};
     use alloc::ffi::CString;
     use core::ffi::CStr;
-    use rustpython_host_env::os::ffi::OsStringExt;
+    use rustpython_host_env::os::{AT_FDCWD, ffi::OsStringExt};
     use rustpython_host_env::posix as host_posix;
     use std::{
         fs, io,
@@ -49,6 +49,10 @@ pub mod module {
     #[pyattr]
     use rustpython_host_env::posix::PIDFD_NONBLOCK;
 
+    #[cfg(all(target_os = "linux", target_env = "gnu"))]
+    #[pyattr]
+    use rustpython_host_env::posix::NODEV;
+
     #[cfg(target_os = "macos")]
     #[pyattr]
     use rustpython_host_env::posix::{
@@ -751,6 +755,8 @@ pub mod module {
             crate::object::qsbr::QSBR.reset_after_fork()
         };
 
+        vm.state.reinit_running_main();
+
         // Phase 3: Clean up thread state. Locks are now reinit'd so we can
         // acquire them normally instead of using try_lock().
         #[cfg(feature = "threading")]
@@ -881,7 +887,11 @@ pub mod module {
 
     /// Warn if forking from a multi-threaded process.
     /// `num_os_threads` should be captured before parent after-fork hooks run.
-    fn warn_if_multi_threaded(name: &str, num_os_threads: isize, vm: &VirtualMachine) {
+    fn warn_if_multi_threaded(
+        name: &str,
+        num_os_threads: isize,
+        vm: &VirtualMachine,
+    ) -> PyResult<()> {
         let num_threads = if num_os_threads > 0 {
             num_os_threads as usize
         } else {
@@ -895,7 +905,7 @@ pub mod module {
                 .and_then(|m| m.get_item("threading", vm))
             {
                 Ok(m) => m,
-                Err(_) => return,
+                Err(_) => return Ok(()),
             };
             let active = threading.get_attr("_active", vm).ok();
             let limbo = threading.get_attr("_limbo", vm).ok();
@@ -920,10 +930,9 @@ pub mod module {
             );
 
             // Match PyErr_WarnFormat(..., stacklevel=1) in CPython.
-            // Best effort: ignore failures like CPython does in this path.
-            let _ =
-                crate::stdlib::_warnings::warn(vm.ctx.exceptions.deprecation_warning, msg, 1, vm);
+            crate::stdlib::_warnings::warn(vm.ctx.exceptions.deprecation_warning, msg, 1, vm)?;
         }
+        Ok(())
     }
 
     #[pyfunction]
@@ -960,7 +969,7 @@ pub mod module {
                 let num_os_threads = get_number_of_os_threads();
                 py_os_after_fork_parent(vm);
                 // Warn only after parent callback path resumes the world.
-                warn_if_multi_threaded("fork", num_os_threads, vm);
+                warn_if_multi_threaded("fork", num_os_threads, vm)?;
                 Ok(pid)
             }
             Err(err) => {
@@ -1002,7 +1011,7 @@ pub mod module {
             Ok((pid, master)) => {
                 let num_os_threads = get_number_of_os_threads();
                 py_os_after_fork_parent(vm);
-                warn_if_multi_threaded("forkpty", num_os_threads, vm);
+                warn_if_multi_threaded("forkpty", num_os_threads, vm)?;
                 Ok((pid, master))
             }
             Err(err) => {
@@ -1012,6 +1021,91 @@ pub mod module {
         }
     }
 
+    #[cfg(not(any(target_os = "redox", target_os = "wasi")))]
+    struct MkfifoPath(OsPath);
+
+    #[cfg(not(any(target_os = "redox", target_os = "wasi")))]
+    impl TryFromObject for MkfifoPath {
+        fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
+            crate::ospath::PathConverter::new()
+                .function("mkfifo")
+                .try_path(obj, vm)
+                .map(Self)
+        }
+    }
+
+    #[cfg(not(any(target_os = "redox", target_os = "wasi")))]
+    struct MkfifoMode(i32);
+
+    #[cfg(not(any(target_os = "redox", target_os = "wasi")))]
+    impl TryFromObject for MkfifoMode {
+        fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
+            let mode = obj.try_index(vm)?;
+            i32::try_from(mode.as_bigint())
+                .map(Self)
+                .map_err(|_| vm.new_overflow_error("Python int too large to convert to C int"))
+        }
+    }
+
+    #[cfg(not(any(target_os = "redox", target_os = "wasi")))]
+    #[derive(FromArgs)]
+    struct MkfifoArgs {
+        #[pyarg(any)]
+        path: MkfifoPath,
+        #[pyarg(any, default = MkfifoMode(0o666), py_default = "438")]
+        mode: MkfifoMode,
+        #[pyarg(named, optional, py_default = "None")]
+        dir_fd: OptionalArg<PyObjectRef>,
+    }
+
+    #[cfg(not(any(target_os = "redox", target_os = "wasi")))]
+    #[pyfunction]
+    fn mkfifo(args: MkfifoArgs, vm: &VirtualMachine) -> PyResult<()> {
+        let c_path = args.path.0.into_cstring(vm)?;
+        let mode = args.mode.0 as libc::mode_t;
+        // Keep a raw C int: even -1 is valid with an absolute path, for which
+        // mkfifoat ignores dir_fd. BorrowedFd cannot represent that value.
+        let dir_fd = match args.dir_fd {
+            OptionalArg::Present(fd) if !vm.is_none(&fd) => {
+                warn_if_bool_fd(&fd, vm)?;
+                let fd = fd.try_index_opt(vm).unwrap_or_else(|| {
+                    Err(vm.new_type_error(format!(
+                        "argument should be integer or None, not {}",
+                        fd.class().name()
+                    )))
+                })?;
+                let fd = i32::try_from(fd.as_bigint()).map_err(|_| {
+                    let message = if fd.as_bigint().sign() == malachite_bigint::Sign::Minus {
+                        "fd is less than minimum"
+                    } else {
+                        "fd is greater than maximum"
+                    };
+                    vm.new_overflow_error(message)
+                })?;
+                (fd != rustpython_host_env::os::AT_FDCWD).then_some(fd)
+            }
+            _ => None,
+        };
+        if dir_fd.is_some() && !host_posix::has_mkfifoat() {
+            return Err(vm.new_not_implemented_error("dir_fd unavailable on this platform"));
+        }
+
+        loop {
+            let result = vm.allow_threads(|| {
+                #[cfg(not(target_os = "android"))]
+                if let Some(dir_fd) = dir_fd {
+                    return host_posix::mkfifoat(dir_fd, &c_path, mode);
+                }
+                host_posix::mkfifo(&c_path, mode)
+            });
+            match result {
+                Ok(()) => return Ok(()),
+                Err(err) if err.raw_os_error() == Some(libc::EINTR) => vm.check_signals()?,
+                Err(err) => return Err(err.into_pyexception(vm)),
+            }
+        }
+    }
+
     #[cfg(not(target_os = "redox"))]
     const MKNOD_DIR_FD: bool = cfg!(not(target_vendor = "apple"));
 
@@ -1129,6 +1223,7 @@ pub mod module {
             match vm.allow_threads(|| rustpython_host_env::posix::pread(fd, &mut buffer, offset)) {
                 Ok(n) => {
                     buffer.truncate(n);
+                    buffer.shrink_to_fit();
                     return Ok(vm.ctx.new_bytes(buffer));
                 }
                 Err(err) if err.raw_os_error() == Some(libc::EINTR) => {
@@ -1184,33 +1279,39 @@ pub mod module {
 
     fn _chmod(
         path: OsPath,
-        dir_fd: DirFd<'_, 0>,
+        dir_fd: i32,
         mode: u32,
-        follow_symlinks: FollowSymlinks,
+        follow_symlinks: bool,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        let [] = dir_fd.0;
-        #[cfg(all(
-            unix,
-            not(target_os = "redox"),
-            not(any(target_os = "macos", target_os = "freebsd", target_os = "netbsd"))
-        ))]
-        if !follow_symlinks.0 {
+        #[cfg(target_os = "redox")]
+        let _ = dir_fd;
+        #[cfg(not(target_os = "redox"))]
+        if dir_fd != AT_FDCWD || !follow_symlinks {
             let err_path = path.clone();
             let c_path = path.into_cstring(vm)?;
+            let flags = if follow_symlinks {
+                0
+            } else {
+                libc::AT_SYMLINK_NOFOLLOW
+            };
             return rustpython_host_env::posix::fchmodat(
-                libc::AT_FDCWD,
+                dir_fd,
                 &c_path,
                 mode as libc::mode_t,
-                libc::AT_SYMLINK_NOFOLLOW,
+                flags,
             )
             .map_err(|err| {
                 let enotsup = err.raw_os_error() == Some(libc::EOPNOTSUPP)
                     || err.raw_os_error() == Some(libc::ENOTSUP);
-                if enotsup {
-                    vm.new_not_implemented_error(
-                        "chmod: follow_symlinks unavailable on this platform".to_owned(),
-                    )
+                if !follow_symlinks && enotsup {
+                    if dir_fd != AT_FDCWD {
+                        vm.new_value_error("chmod: cannot use dir_fd and follow_symlinks together")
+                    } else {
+                        vm.new_not_implemented_error(
+                            "chmod: follow_symlinks unavailable on this platform".to_owned(),
+                        )
+                    }
                 } else {
                     OSErrorBuilder::with_filename(&err, err_path, vm)
                 }
@@ -1219,7 +1320,7 @@ pub mod module {
         let err_path = path.clone();
         let body = move || {
             use std::os::unix::fs::PermissionsExt;
-            let meta = fs_metadata(&path, follow_symlinks.0)?;
+            let meta = fs_metadata(&path, follow_symlinks)?;
             let mut permissions = meta.permissions();
             permissions.set_mode(mode);
             fs::set_permissions(&path, permissions)
@@ -1232,19 +1333,59 @@ pub mod module {
         rustpython_host_env::posix::fchmod(fd, mode).map_err(|err| err.into_pyexception(vm))
     }
 
+    // Absolute paths ignore dir_fd, so even -1 must reach fchmodat unchanged.
     #[cfg(not(target_os = "redox"))]
-    #[pyfunction]
-    fn chmod(
-        path: OsPathOrFd<'_>,
-        dir_fd: DirFd<'_, 0>,
+    struct ChmodDirFd(i32);
+
+    #[cfg(not(target_os = "redox"))]
+    impl TryFromObject for ChmodDirFd {
+        fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
+            warn_if_bool_fd(&obj, vm)?;
+            let fd = obj.try_index_opt(vm).unwrap_or_else(|| {
+                Err(vm.new_type_error(format!(
+                    "argument should be integer or None, not {}",
+                    obj.class().name()
+                )))
+            })?;
+            i32::try_from(fd.as_bigint()).map(Self).map_err(|_| {
+                let message = if fd.as_bigint().sign() == malachite_bigint::Sign::Minus {
+                    "fd is less than minimum"
+                } else {
+                    "fd is greater than maximum"
+                };
+                vm.new_overflow_error(message)
+            })
+        }
+    }
+
+    #[cfg(not(target_os = "redox"))]
+    #[derive(FromArgs)]
+    struct ChmodArgs<'fd> {
+        #[pyarg(any)]
+        path: OsPathOrFd<'fd>,
+        #[pyarg(any)]
         mode: u32,
-        follow_symlinks: FollowSymlinks,
-        vm: &VirtualMachine,
-    ) -> PyResult<()> {
+        #[pyarg(named, default, py_default = "None")]
+        dir_fd: Option<ChmodDirFd>,
+        // CPython writes the platform expression; on posix it is always true.
+        #[pyarg(named, default = true, py_default = "(os.name != 'nt')")]
+        follow_symlinks: bool,
+    }
+
+    #[cfg(not(target_os = "redox"))]
+    #[pyfunction]
+    fn chmod(args: ChmodArgs<'_>, vm: &VirtualMachine) -> PyResult<()> {
+        let ChmodArgs {
+            path,
+            mode,
+            dir_fd,
+            follow_symlinks,
+        } = args;
+        let dir_fd = dir_fd.map_or(AT_FDCWD, |fd| fd.0);
         match path {
             OsPathOrFd::Path(path) => {
                 #[cfg(any(target_os = "macos", target_os = "freebsd", target_os = "netbsd",))]
-                if !follow_symlinks.0 && dir_fd == Default::default() {
+                if !follow_symlinks && dir_fd == AT_FDCWD {
                     return lchmod(LchmodArgs { path, mode }, vm);
                 }
                 _chmod(path, dir_fd, mode, follow_symlinks, vm)
@@ -1254,15 +1395,30 @@ pub mod module {
     }
 
     #[cfg(target_os = "redox")]
-    #[pyfunction]
-    fn chmod(
+    #[derive(FromArgs)]
+    struct ChmodArgs {
+        #[pyarg(any)]
         path: OsPath,
-        dir_fd: DirFd<0>,
+        #[pyarg(any)]
         mode: u32,
-        follow_symlinks: FollowSymlinks,
-        vm: &VirtualMachine,
-    ) -> PyResult<()> {
-        _chmod(path, dir_fd, mode, follow_symlinks, vm)
+        #[pyarg(flatten)]
+        dir_fd: DirFd<'static, 0>,
+        // CPython writes the platform expression; on posix it is always true.
+        #[pyarg(named, default = true, py_default = "(os.name != 'nt')")]
+        follow_symlinks: bool,
+    }
+
+    #[cfg(target_os = "redox")]
+    #[pyfunction]
+    fn chmod(args: ChmodArgs, vm: &VirtualMachine) -> PyResult<()> {
+        let ChmodArgs {
+            path,
+            mode,
+            dir_fd,
+            follow_symlinks,
+        } = args;
+        let [] = dir_fd.0;
+        _chmod(path, AT_FDCWD, mode, follow_symlinks, vm)
     }
 
     #[cfg(not(target_os = "redox"))]
@@ -2166,8 +2322,8 @@ pub mod module {
         vec![
             SupportFunc::new(
                 "chmod",
-                Some(false),
-                Some(false),
+                Some(cfg!(not(target_os = "redox"))),
+                Some(cfg!(not(target_os = "redox"))),
                 Some(cfg!(any(
                     target_os = "macos",
                     target_os = "freebsd",
@@ -2182,6 +2338,13 @@ pub mod module {
             SupportFunc::new("lchown", None, None, None),
             #[cfg(not(target_os = "redox"))]
             SupportFunc::new("fchown", Some(true), None, Some(true)),
+            #[cfg(not(any(target_os = "redox", target_os = "wasi")))]
+            SupportFunc::new(
+                "mkfifo",
+                Some(false),
+                Some(host_posix::has_mkfifoat()),
+                Some(false),
+            ),
             #[cfg(not(target_os = "redox"))]
             SupportFunc::new("mknod", Some(true), Some(MKNOD_DIR_FD), Some(false)),
             SupportFunc::new("umask", Some(false), Some(false), Some(false)),
@@ -2193,23 +2356,10 @@ pub mod module {
     }
 
     #[pyfunction]
-    fn getlogin(vm: &VirtualMachine) -> PyResult<String> {
-        // Get a pointer to the login name string. The string is statically
-        // allocated and might be overwritten on subsequent calls to this
-        // function or to `cuserid()`. See man getlogin(3) for more information.
-        let Some(login) = rustpython_host_env::posix::getlogin() else {
-            return Err(vm.new_os_error("unable to determine login name"));
-        };
-        login.to_str().map(|s| s.to_owned()).map_err(|e| {
-            vm.new_unicode_decode_error(
-                vm.ctx.new_str("utf-8"),
-                vm.ctx.new_bytes(login.as_bytes().to_vec()),
-                e.valid_up_to(),
-                e.error_len()
-                    .map_or(login.as_bytes().len(), |n| e.valid_up_to() + n),
-                vm.ctx.new_str("unable to decode login name"),
-            )
-        })
+    fn getlogin(vm: &VirtualMachine) -> PyResult<crate::builtins::PyStrRef> {
+        let login =
+            rustpython_host_env::posix::getlogin().map_err(|err| err.into_pyexception(vm))?;
+        Ok(vm.fsdecode(std::ffi::OsString::from_vec(login.into_bytes())))
     }
 
     // cfg from nix
@@ -2714,10 +2864,16 @@ pub mod module {
 
     #[cfg(any(target_os = "linux", target_os = "macos"))]
     #[derive(FromArgs)]
-    struct SendFileArgs<'fd> {
-        out_fd: BorrowedFd<'fd>,
-        in_fd: BorrowedFd<'fd>,
+    struct SendFileArgs {
+        out_fd: i32,
+        in_fd: i32,
+        #[cfg(target_os = "linux")]
+        offset: PyObjectRef,
+        #[cfg(target_os = "macos")]
         offset: rustpython_host_env::crt_fd::Offset,
+        #[cfg(target_os = "linux")]
+        count: isize,
+        #[cfg(target_os = "macos")]
         count: i64,
         #[cfg(target_os = "macos")]
         // Missing means an empty header list.
@@ -2728,35 +2884,58 @@ pub mod module {
         #[pyarg(any, optional, py_default = "()")]
         trailers: OptionalArg<PyObjectRef>,
         #[cfg(target_os = "macos")]
-        #[allow(dead_code)]
         #[pyarg(any, default)]
-        // TODO: not implemented
         flags: i32,
     }
 
     #[cfg(target_os = "linux")]
     #[pyfunction]
-    fn sendfile(args: SendFileArgs<'_>, vm: &VirtualMachine) -> PyResult {
-        let mut file_offset = args.offset;
+    fn sendfile(args: SendFileArgs, vm: &VirtualMachine) -> PyResult {
+        if args.count < 0 {
+            return Err(vm.new_value_error("count cannot be negative"));
+        }
+        let mut file_offset = if vm.is_none(&args.offset) {
+            None
+        } else {
+            Some(args.offset.try_into_value(vm)?)
+        };
 
-        let res = rustpython_host_env::posix::sendfile(
-            args.out_fd,
-            args.in_fd,
-            &mut file_offset,
-            args.count as usize,
-        )
-        .map_err(|err| err.into_pyexception(vm))?;
-        Ok(vm.ctx.new_int(res as u64).into())
+        loop {
+            let result = vm.allow_threads(|| {
+                rustpython_host_env::posix::sendfile(
+                    args.out_fd,
+                    args.in_fd,
+                    file_offset.as_mut(),
+                    args.count as usize,
+                )
+            });
+            match result {
+                Ok(written) => return Ok(vm.ctx.new_int(written).into()),
+                Err(err) if err.raw_os_error() == Some(libc::EINTR) => vm.check_signals()?,
+                Err(err) => return Err(err.into_pyexception(vm)),
+            }
+        }
     }
 
     #[cfg(target_os = "macos")]
     fn _extract_vec_bytes(
         x: OptionalArg,
+        kind: &str,
         vm: &VirtualMachine,
     ) -> PyResult<Option<Vec<crate::function::ArgBytesLike>>> {
         x.into_option()
             .map(|x| {
-                let v: Vec<crate::function::ArgBytesLike> = x.try_to_value(vm)?;
+                let sequence = x.try_sequence(vm).map_err(|_| {
+                    vm.new_type_error(format!("sendfile() {kind}s must be a sequence"))
+                })?;
+                let count = sequence.length(vm)?;
+                if count > i32::MAX as usize {
+                    return Err(vm.new_overflow_error(format!("sendfile() {kind} is too large")));
+                }
+                let mut v = Vec::with_capacity(count);
+                for index in 0..count {
+                    v.push(sequence.get_item(index as isize, vm)?.try_into_value(vm)?);
+                }
                 Ok(if v.is_empty() { None } else { Some(v) })
             })
             .transpose()
@@ -2765,47 +2944,78 @@ pub mod module {
 
     #[cfg(target_os = "macos")]
     #[pyfunction]
-    fn sendfile(args: SendFileArgs<'_>, vm: &VirtualMachine) -> PyResult {
-        let headers = _extract_vec_bytes(args.headers, vm)?;
-        let count = headers
-            .as_ref()
-            .map_or(0, |v| v.iter().map(|s| s.len()).sum()) as i64
-            + args.count;
+    fn sendfile(args: SendFileArgs, vm: &VirtualMachine) -> PyResult {
+        if args.count < 0 {
+            return Err(vm.new_value_error("count cannot be negative"));
+        }
+        let headers = _extract_vec_bytes(args.headers, "header", vm)?;
+        let mut count = args.count;
+        if let Some(headers) = &headers {
+            for header in headers {
+                let length = i64::try_from(header.len())
+                    .map_err(|_| vm.new_overflow_error("sendfile() header is too large"))?;
+                if count >= i64::MAX - length {
+                    return Err(vm.new_overflow_error("sendfile() header is too large"));
+                }
+                count += length;
+            }
+        }
 
+        let trailers = _extract_vec_bytes(args.trailers, "trailer", vm)?;
+        // Complete all Python argument callbacks before snapshotting mutable
+        // exporters. No buffer lock may survive another callback or blocking I/O.
         let headers = headers
             .as_ref()
-            .map(|v| v.iter().map(|b| b.borrow_buf()).collect::<Vec<_>>());
+            .map(|v| {
+                v.iter()
+                    .map(|b| b.borrow_buf_unlocked(vm))
+                    .collect::<PyResult<Vec<_>>>()
+            })
+            .transpose()?;
         let headers = headers
             .as_ref()
             .map(|v| v.iter().map(|borrowed| &**borrowed).collect::<Vec<_>>());
         let headers = headers.as_deref();
 
-        let trailers = _extract_vec_bytes(args.trailers, vm)?;
         let trailers = trailers
             .as_ref()
-            .map(|v| v.iter().map(|b| b.borrow_buf()).collect::<Vec<_>>());
+            .map(|v| {
+                v.iter()
+                    .map(|b| b.borrow_buf_unlocked(vm))
+                    .collect::<PyResult<Vec<_>>>()
+            })
+            .transpose()?;
         let trailers = trailers
             .as_ref()
             .map(|v| v.iter().map(|borrowed| &**borrowed).collect::<Vec<_>>());
         let trailers = trailers.as_deref();
 
-        let (res, written) = rustpython_host_env::posix::sendfile(
-            args.in_fd,
-            args.out_fd,
-            args.offset,
-            count,
-            headers,
-            trailers,
-        );
-        // On macOS, sendfile can return EAGAIN even when some bytes were written.
-        // In that case, we should return the number of bytes written rather than
-        // raising an exception. Only raise an error if no bytes were written.
-        if let Err(err) = res
-            && written == 0
-        {
-            return Err(err.into_pyexception(vm));
+        let mut written = count;
+        loop {
+            let result = vm.allow_threads(|| {
+                rustpython_host_env::posix::sendfile(
+                    args.in_fd,
+                    args.out_fd,
+                    args.offset,
+                    &mut written,
+                    headers,
+                    trailers,
+                    args.flags,
+                )
+            });
+            match result {
+                Ok(()) => return Ok(vm.ctx.new_int(written).into()),
+                Err(err) if err.raw_os_error() == Some(libc::EINTR) => vm.check_signals()?,
+                // CPython permits partial success only for EAGAIN or EBUSY.
+                Err(err)
+                    if written != 0
+                        && matches!(err.raw_os_error(), Some(libc::EAGAIN | libc::EBUSY)) =>
+                {
+                    return Ok(vm.ctx.new_int(written).into());
+                }
+                Err(err) => return Err(err.into_pyexception(vm)),
+            }
         }
-        Ok(vm.ctx.new_int(written as u64).into())
     }
 
     #[cfg(target_os = "linux")]
@@ -2823,6 +3033,7 @@ pub mod module {
             .map_err(|_| vm.new_last_os_error())?;
             buf.set_len(len);
         }
+        buf.shrink_to_fit();
         Ok(buf)
     }
 
diff --git a/crates/vm/src/stdlib/posix_compat.rs b/crates/vm/src/stdlib/posix_compat.rs
index 4ac80a03d37..ad1709c99c0 100644
--- a/crates/vm/src/stdlib/posix_compat.rs
+++ b/crates/vm/src/stdlib/posix_compat.rs
@@ -10,6 +10,8 @@ pub(crate) use module::module_def;
     super::posix_unix_like::_posix_unix_like,
 ))]
 pub(crate) mod module {
+    #[cfg(target_os = "wasi")]
+    use crate::{AsObject, function::OptionalArg, ospath::PathConverter};
     use crate::{
         Py, PyObjectRef, PyResult, VirtualMachine,
         builtins::PyStrRef,
@@ -17,6 +19,64 @@ pub(crate) mod module {
         stdlib::os::{_os, DirFd, SupportFunc, SymlinkArgs, TargetIsDirectory},
     };
 
+    #[cfg(target_os = "wasi")]
+    #[derive(FromArgs)]
+    struct ChmodArgs {
+        #[pyarg(any)]
+        path: PyObjectRef,
+        #[pyarg(any)]
+        mode: PyObjectRef,
+        #[pyarg(named, default, py_default = "None")]
+        dir_fd: Option<PyObjectRef>,
+        #[pyarg(named, optional, py_default = "(os.name != 'nt')")]
+        follow_symlinks: OptionalArg<PyObjectRef>,
+    }
+
+    #[cfg(target_os = "wasi")]
+    #[pyfunction]
+    fn chmod(args: ChmodArgs, vm: &VirtualMachine) -> PyResult<()> {
+        // Keep the clinic conversion order even though WASI has no chmod syscall.
+        let path = PathConverter::new()
+            .function("chmod")
+            .argument("path")
+            .try_path(args.path, vm)?;
+        let mode = args.mode.try_index(vm)?;
+        let mode = i32::try_from(mode.as_bigint())
+            .map_err(|_| vm.new_overflow_error("Python int too large to convert to C int"))?;
+        if let Some(dir_fd) = args.dir_fd {
+            super::super::os::warn_if_bool_fd(&dir_fd, vm)?;
+            let fd = dir_fd.try_index_opt(vm).unwrap_or_else(|| {
+                Err(vm.new_type_error(format!(
+                    "argument should be integer or None, not {}",
+                    dir_fd.class().name()
+                )))
+            })?;
+            let fd = i32::try_from(fd.as_bigint()).map_err(|_| {
+                vm.new_overflow_error(if fd.as_bigint().sign() == malachite_bigint::Sign::Minus {
+                    "fd is less than minimum"
+                } else {
+                    "fd is greater than maximum"
+                })
+            })?;
+            if fd != rustpython_host_env::os::AT_FDCWD {
+                return Err(vm.new_not_implemented_error("dir_fd unavailable on this platform"));
+            }
+        }
+        let follow_symlinks = match args.follow_symlinks {
+            OptionalArg::Present(value) => value.try_to_bool(vm)?,
+            OptionalArg::Missing => true,
+        };
+        if !follow_symlinks {
+            return Err(
+                vm.new_not_implemented_error("chmod: follow_symlinks unavailable on this platform")
+            );
+        }
+        vm.audit("os.chmod", || (path.filename(vm), mode, -1))?;
+        // CPython 3.15 posixmodule.c explicitly ignores the absent WASI syscall
+        // after argument conversion and auditing. No supports_* capability is set.
+        Ok(())
+    }
+
     #[derive(FromArgs)]
     struct AccessArgs<'a> {
         #[pyarg(any)]
diff --git a/crates/vm/src/stdlib/pwd.rs b/crates/vm/src/stdlib/pwd.rs
index bfa7eb034e5..c2eb3391b98 100644
--- a/crates/vm/src/stdlib/pwd.rs
+++ b/crates/vm/src/stdlib/pwd.rs
@@ -5,10 +5,7 @@ pub(crate) use pwd::module_def;
 #[pymodule]
 mod pwd {
     use crate::{
-        PyResult, VirtualMachine,
-        builtins::{PyIntRef, PyUtf8StrRef},
-        convert::IntoPyException,
-        exceptions,
+        PyResult, VirtualMachine, builtins::PyUtf8StrRef, exceptions, function::ArgIndex,
         types::PyStructSequence,
     };
     use core::hint::cold_path;
@@ -68,13 +65,18 @@ mod pwd {
     }
 
     #[pyfunction]
-    fn getpwuid(uidobj: PyIntRef, vm: &VirtualMachine) -> PyResult<PasswdData> {
-        let uid_t = libc::uid_t::try_from(uidobj.as_bigint()).ok();
-        let user = uid_t
+    fn getpwuid(uidobj: ArgIndex, vm: &VirtualMachine) -> PyResult<PasswdData> {
+        let uidobj = uidobj.into_int_ref();
+        let user = match libc::uid_t::try_from(uidobj.as_bigint())
+            .ok()
             .map(host_pwd::getpwuid)
-            .transpose()
-            .map_err(|err| err.into_pyexception(vm))?
-            .flatten();
+        {
+            Some(Ok(user)) => user,
+            Some(Err(err)) if err.raw_os_error() == Some(libc::ENOMEM) => {
+                return Err(vm.no_memory_error());
+            }
+            _ => None,
+        };
         let user = user.ok_or_else(|| {
             vm.new_key_error(
                 vm.ctx
diff --git a/crates/vm/src/stdlib/sys.rs b/crates/vm/src/stdlib/sys.rs
index a77fbb10fd3..6051723b19a 100644
--- a/crates/vm/src/stdlib/sys.rs
+++ b/crates/vm/src/stdlib/sys.rs
@@ -56,7 +56,7 @@ pub mod sys {
     use num_traits::ToPrimitive;
     use std::{
         env,
-        io::{IsTerminal, Read, Write},
+        io::{IsTerminal, Write},
     };
 
     // Rust target triple (e.g., "x86_64-unknown-linux-gnu")
@@ -250,7 +250,7 @@ pub mod sys {
         target_os = "ios" => c"ios",
         windows => c"win32",
         target_os = "wasi" => c"wasi",
-        _ => c"unknown"
+        _ => c"unknown",
     };
 
     #[pyattr(name = "ps1")]
@@ -260,11 +260,19 @@ pub mod sys {
 
     #[cfg(windows)]
     #[pyattr(name = "_vpath")]
-    const VPATH: Option<&'static str> = None; // TODO: actual VPATH value
+    fn vpath(vm: &VirtualMachine) -> String {
+        crate::getpath::source_directory(&vm.state.config.paths)
+            .and_then(|source| std::path::absolute(source).ok())
+            .map(|source| source.to_string_lossy().into_owned())
+            .unwrap_or_default()
+    }
 
     #[cfg(windows)]
-    #[pyattr(name = "dllhandle")]
-    const DLLHANDLE: usize = 0;
+    #[pyattr]
+    fn dllhandle(_vm: &VirtualMachine) -> usize {
+        crate::host_env::windows::runtime_module_handle()
+            .expect("the running RustPython image must have a module handle")
+    }
 
     #[pyattr]
     fn prefix(vm: &VirtualMachine) -> String {
@@ -667,8 +675,8 @@ pub mod sys {
     fn implementation(vm: &VirtualMachine) -> PyRef<PyNamespace> {
         const NAME: &str = "rustpython";
 
-        // cache tag uses 'cpython' because our compiler is cpython compatible
-        let cache_tag = format!("cpython-{}{}", version::MAJOR, version::MINOR);
+        // Keep implementation-specific bytecode caches separate.
+        let cache_tag = format!("{NAME}-{}{}", version::MAJOR, version::MINOR);
         let ctx = &vm.ctx;
         py_namespace!(vm, {
             "name" => ctx.new_str(NAME),
@@ -752,17 +760,11 @@ pub mod sys {
 
     #[cfg(feature = "rustpython-compiler")]
     #[pyfunction]
-    fn _baserepl(vm: &VirtualMachine) -> PyResult<()> {
-        // read stdin to end
-        let stdin = std::io::stdin();
-        let mut handle = stdin.lock();
-        let mut source = String::new();
-        handle
-            .read_to_string(&mut source)
-            .map_err(|e| vm.new_os_error(format!("Error reading from stdin: {e}")))?;
-        vm.compile(&source, crate::compiler::Mode::Single, "<stdin>")
-            .map_err(|e| e.into_pyexception(vm, Some(&source)))?;
-        Ok(())
+    fn _baserepl(vm: &VirtualMachine) {
+        // PyRun_AnyFileExFlags(stdin, "<stdin>", 0, &cf)
+        if let Err(exc) = vm.run_any_stdin() {
+            vm.print_uncaught_exception(&exc);
+        }
     }
 
     #[pyfunction]
@@ -859,7 +861,6 @@ pub mod sys {
         traceback: PyObjectRef,
         vm: &VirtualMachine,
     ) -> PyResult<()> {
-        let stderr = super::get_stderr(vm)?;
         // Keep runtime SyntaxErrors on the normal traceback path.
         let has_traceback = !vm.is_none(&traceback);
         match vm.normalize_exception(exctype, value.clone(), traceback) {
@@ -879,19 +880,11 @@ pub mod sys {
                         .and_then(|text| text.downcast::<PyStr>().ok())
                         .is_some_and(|text| text.to_string_lossy().trim_end() == "\\");
                 if native_syntax_error_display {
+                    let stderr = super::get_stderr(vm)?;
                     return vm.write_exception(&mut crate::py_io::PyWriter(stderr, vm), &exc);
                 }
-                // PyErr_Display: try traceback._print_exception_bltin first
-                if let Ok(tb_mod) = vm.import("traceback", 0)
-                    && let Ok(print_exc_builtin) = tb_mod.get_attr("_print_exception_bltin", vm)
-                    && print_exc_builtin
-                        .call((exc.as_object().to_owned(),), vm)
-                        .is_ok()
-                {
-                    return Ok(());
-                }
-                // Fallback to Rust-level exception printing
-                vm.write_exception(&mut crate::py_io::PyWriter(stderr, vm), &exc)
+                vm.display_exception(&exc);
+                Ok(())
             }
             Err(_) => {
                 let type_name = value.class().name();
@@ -899,6 +892,7 @@ pub mod sys {
                     "TypeError: print_exception(): Exception expected for value, {type_name} found\n"
                 );
                 use crate::py_io::Write;
+                let stderr = super::get_stderr(vm)?;
                 write!(&mut crate::py_io::PyWriter(stderr, vm), "{msg}")?;
                 Ok(())
             }
@@ -960,6 +954,64 @@ pub mod sys {
         }
     }
 
+    #[pyfunction]
+    fn get_lazy_imports(vm: &VirtualMachine) -> &'static str {
+        if vm
+            .state
+            .lazy_imports
+            .all
+            .load(core::sync::atomic::Ordering::Acquire)
+        {
+            "all"
+        } else {
+            "normal"
+        }
+    }
+
+    #[pyfunction]
+    fn set_lazy_imports(mode: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
+        let mode = mode
+            .downcast_ref::<PyStr>()
+            .ok_or_else(|| vm.new_type_error("mode must be a string: 'normal' or 'all'"))?;
+        let all = match mode.to_str() {
+            Some("normal") => false,
+            Some("all") => true,
+            _ => return Err(vm.new_value_error("mode must be 'normal' or 'all'")),
+        };
+        vm.state
+            .lazy_imports
+            .all
+            .store(all, core::sync::atomic::Ordering::Release);
+        Ok(())
+    }
+
+    #[pyfunction]
+    fn get_lazy_imports_filter(vm: &VirtualMachine) -> PyObjectRef {
+        vm.state
+            .lazy_imports
+            .filter()
+            .unwrap_or_else(|| vm.ctx.none())
+    }
+
+    #[pyfunction]
+    fn set_lazy_imports_filter(filter: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
+        let filter = if vm.is_none(&filter) {
+            None
+        } else {
+            if !filter.is_callable() {
+                return Err(vm.new_value_error("filter provided but is not callable"));
+            }
+            Some(filter)
+        };
+        vm.state.lazy_imports.set_filter(filter);
+        Ok(())
+    }
+
+    #[pyattr]
+    fn lazy_modules(vm: &VirtualMachine) -> PyObjectRef {
+        vm.state.lazy_imports.modules.clone().into()
+    }
+
     #[pyfunction]
     fn exc_info(vm: &VirtualMachine) -> (PyObjectRef, PyObjectRef, PyObjectRef) {
         match vm.topmost_exception() {
@@ -973,6 +1025,36 @@ pub mod sys {
         PyFlags::from_data(FlagsData::from_settings(&vm.state.config.settings), vm)
     }
 
+    /// _PySys_SetFlagObj
+    pub(crate) fn set_flag_obj(
+        vm: &VirtualMachine,
+        name: &str,
+        value: PyObjectRef,
+    ) -> PyResult<()> {
+        use crate::{class::StaticType, types::PyStructSequenceData};
+
+        let old_flags = vm
+            .sys_module
+            .get_attr("flags", vm)
+            .map_err(|_| vm.new_runtime_error("lost sys.flags"))?;
+        let old_flags = old_flags
+            .downcast_ref::<PyTuple>()
+            .filter(|flags| {
+                flags.len()
+                    == FlagsData::REQUIRED_FIELD_NAMES.len() + FlagsData::OPTIONAL_FIELD_NAMES.len()
+            })
+            .ok_or_else(|| vm.new_type_error("sys.flags must be a sys.flags instance"))?;
+        let pos = FlagsData::REQUIRED_FIELD_NAMES
+            .iter()
+            .position(|field| *field == name)
+            .expect("unknown sys.flags field");
+        let mut values = old_flags.as_slice().to_vec();
+        values[pos] = value;
+        let new_flags = PyTuple::new_unchecked(values.into_boxed_slice())
+            .into_ref_with_type(vm, PyFlags::static_type().to_owned())?;
+        vm.sys_module.set_attr("flags", new_flags, vm)
+    }
+
     #[pyattr]
     fn float_info(vm: &VirtualMachine) -> PyTupleRef {
         PyFloatInfo::from_data(FloatInfoData::INFO, vm)
@@ -1606,6 +1688,11 @@ pub mod sys {
         fn thread_inherit_context(&self, vm: &VirtualMachine) -> bool {
             vm.state.config.settings.thread_inherit_context
         }
+
+        #[pygetset]
+        fn lazy_imports(&self, vm: &VirtualMachine) -> i8 {
+            vm.state.config.settings.lazy_imports
+        }
     }
 
     #[cfg(feature = "threading")]
diff --git a/crates/vm/src/stdlib/sys/monitoring.rs b/crates/vm/src/stdlib/sys/monitoring.rs
index aa180daeb96..cf2b13c78fa 100644
--- a/crates/vm/src/stdlib/sys/monitoring.rs
+++ b/crates/vm/src/stdlib/sys/monitoring.rs
@@ -9,8 +9,7 @@ use std::collections::{HashMap, HashSet};
 
 pub(crate) const TOOL_LIMIT: usize = 6;
 const EVENTS_COUNT: usize = 19;
-const LOCAL_EVENTS_COUNT: usize = 11;
-const UNGROUPED_EVENTS_COUNT: usize = 18;
+const UNGROUPED_EVENTS_COUNT: usize = 16;
 
 /// Event identifier (`PY_MONITORING_EVENT_*`), stored in `tstate->what_event`.
 /// `None` on the VM field is the `< 0` sentinel (not in a monitoring callback).
@@ -99,8 +98,11 @@ pub struct MonitoringState {
     pub global_events: [u32; TOOL_LIMIT],
     pub local_events: HashMap<(usize, usize), u32>,
     pub callbacks: HashMap<(usize, usize), PyObjectRef>,
-    /// Per-instruction disabled tools: (code_id, offset, tool)
-    pub disabled: HashSet<(usize, usize, usize)>,
+    // Legacy BRANCH callbacks also check whether the source instruction was
+    // disabled. Direct BRANCH_LEFT/RIGHT registrations bypass that check.
+    legacy_branch_callbacks: HashSet<(usize, usize)>,
+    /// Per-instruction disabled tools: (code_id, offset, event, tool)
+    pub disabled: HashSet<(usize, usize, usize, usize)>,
     /// Cached MISSING sentinel singleton
     pub missing: Option<PyObjectRef>,
     /// Cached DISABLE sentinel singleton
@@ -114,6 +116,7 @@ impl Default for MonitoringState {
             global_events: [0; TOOL_LIMIT],
             local_events: HashMap::new(),
             callbacks: HashMap::new(),
+            legacy_branch_callbacks: HashSet::new(),
             disabled: HashSet::new(),
             missing: None,
             disable: None,
@@ -204,6 +207,11 @@ fn parse_single_event(event: i32, vm: &VirtualMachine) -> PyResult<usize> {
     Ok(event_id)
 }
 
+/// `PY_MONITORING_IS_INSTRUMENTED_EVENT`
+const fn is_instrumented_event(event_id: usize) -> bool {
+    event_id <= MonitoringEvent::StopIteration as usize
+}
+
 fn normalize_event_set(event_set: i32, local: bool, vm: &VirtualMachine) -> PyResult<u32> {
     let kind = if local {
         "local event set"
@@ -232,7 +240,7 @@ fn normalize_event_set(event_set: i32, local: bool, vm: &VirtualMachine) -> PyRe
         event_set |= MonitoringEvent::BranchLeft.mask() | MonitoringEvent::BranchRight.mask();
     }
 
-    if local && event_set >= (1 << LOCAL_EVENTS_COUNT) {
+    if local && event_set >= (1 << UNGROUPED_EVENTS_COUNT) {
         return Err(vm.new_value_error(format!("invalid local event set 0x{event_set:x}")));
     }
 
@@ -281,23 +289,6 @@ fn opcode_event_is_active(
     event_for_opcode(op, oparg).is_some_and(|ev| events & ev.mask() != 0)
 }
 
-/// Walk real instructions, skipping specialization CACHE payloads.
-/// Cache slots may contain pointer bits that are not valid opcodes.
-fn for_each_instruction(
-    code: &Py<PyCode>,
-    mut f: impl FnMut(usize, rustpython_compiler_core::bytecode::Instruction, u8),
-) {
-    let len = code.code.instructions.len();
-    let mut i = 0;
-    while i < len {
-        let op = code.code.instructions.read_op(i);
-        let oparg = code.code.instructions.read_arg(i).as_u8();
-        let caches = op.deoptimize().cache_entries();
-        f(i, op, oparg);
-        i += 1 + caches;
-    }
-}
-
 /// Rewrite a code object's bytecode in-place with layered instrumentation.
 ///
 /// Three layers (outermost first):
@@ -402,26 +393,12 @@ pub(crate) fn instrument_code(code: &Py<PyCode>, events: u32) {
     data.line_opcodes.resize(len, 0);
     data.per_instruction_opcodes.resize(len, 0);
 
-    // Find _co_firsttraceable: index of first RESUME instruction
-    let mut first_traceable = None;
-    for_each_instruction(code, |i, op, _| {
-        if first_traceable.is_none()
-            && matches!(
-                op,
-                Instruction::Resume { .. }
-                    | Instruction::ResumeCheck
-                    | Instruction::InstrumentedResume
-            )
-        {
-            first_traceable = Some(i);
-        }
-    });
-    let first_traceable = first_traceable.unwrap_or(0);
+    let first_traceable = code.first_traceable;
 
     // Phase 4: Place regular INSTRUMENTED_* opcodes whose event is active.
     // Walk by cache_entries so specialized CACHE payloads are not decoded as opcodes.
     {
-        let mut i = 0;
+        let mut i = first_traceable;
         while i < len {
             let op = code.code.instructions.read_op(i);
             let oparg = code.code.instructions.read_arg(i).as_u8();
@@ -662,33 +639,44 @@ fn use_tool_id(tool_id: i32, name: &str, vm: &VirtualMachine) -> PyResult<()> {
 }
 
 fn clear_tool_id(tool_id: i32, vm: &VirtualMachine) -> PyResult<()> {
-    let tool = check_valid_tool(tool_id, vm)?;
-    let mut state = vm.state.monitoring.lock();
-    if state.tool_names[tool].is_some() {
-        state.global_events[tool] = 0;
-        state
-            .local_events
-            .retain(|(local_tool, _), _| *local_tool != tool);
-        state.callbacks.retain(|(cb_tool, _), _| *cb_tool != tool);
-        state.disabled.retain(|&(_, _, t)| t != tool);
-    }
-    update_events_mask(vm, &state);
-    Ok(())
+    release_tool_callbacks(tool_id, false, vm)
 }
 
 fn free_tool_id(tool_id: i32, vm: &VirtualMachine) -> PyResult<()> {
+    release_tool_callbacks(tool_id, true, vm)
+}
+
+fn release_tool_callbacks(tool_id: i32, free: bool, vm: &VirtualMachine) -> PyResult<()> {
     let tool = check_valid_tool(tool_id, vm)?;
-    let mut state = vm.state.monitoring.lock();
-    if state.tool_names[tool].is_some() {
-        state.global_events[tool] = 0;
-        state
-            .local_events
-            .retain(|(local_tool, _), _| *local_tool != tool);
-        state.callbacks.retain(|(cb_tool, _), _| *cb_tool != tool);
-        state.disabled.retain(|&(_, _, t)| t != tool);
-        state.tool_names[tool] = None;
+    let callbacks = {
+        let mut state = vm.state.monitoring.lock();
+        let callbacks = if state.tool_names[tool].is_some() {
+            state.global_events[tool] = 0;
+            state
+                .local_events
+                .retain(|(local_tool, _), _| *local_tool != tool);
+            let callbacks: Vec<_> = state
+                .callbacks
+                .extract_if(|(cb_tool, _), _| *cb_tool == tool)
+                .map(|(_, callback)| callback)
+                .collect();
+            state.disabled.retain(|&(_, _, _, t)| t != tool);
+            state
+                .legacy_branch_callbacks
+                .retain(|(cb_tool, _)| *cb_tool != tool);
+            callbacks
+        } else {
+            Vec::new()
+        };
+        update_events_mask(vm, &state);
+        callbacks
+    };
+    // Callback finalizers may reenter monitoring; release owners after unlocking.
+    drop(callbacks);
+    // Keep the name visible during callback finalization, as CPython does.
+    if free {
+        vm.state.monitoring.lock().tool_names[tool] = None;
     }
-    update_events_mask(vm, &state);
     Ok(())
 }
 
@@ -709,28 +697,35 @@ fn register_callback(
 
     vm.audit("sys.monitoring.register_callback", || (func.clone(),))?;
 
-    let mut state = vm.state.monitoring.lock();
-    let prev = state
-        .callbacks
-        .remove(&(tool, event_id))
-        .unwrap_or_else(|| vm.ctx.none());
-    let branch_id = MonitoringEvent::Branch as usize;
-    let branch_left_id = MonitoringEvent::BranchLeft as usize;
-    let branch_right_id = MonitoringEvent::BranchRight as usize;
-    if !vm.is_none(&func) {
-        state.callbacks.insert((tool, event_id), func.clone());
-        // BRANCH is a composite event: also register for BRANCH_LEFT/RIGHT
-        if event_id == branch_id {
-            state.callbacks.insert((tool, branch_left_id), func.clone());
-            state.callbacks.insert((tool, branch_right_id), func);
+    let (prev, displaced) = {
+        let mut state = vm.state.monitoring.lock();
+        let prev = state
+            .callbacks
+            .remove(&(tool, event_id))
+            .unwrap_or_else(|| vm.ctx.none());
+        let mut displaced = Vec::new();
+        state.legacy_branch_callbacks.remove(&(tool, event_id));
+        if !vm.is_none(&func) {
+            state.callbacks.insert((tool, event_id), func.clone());
         }
-    } else {
-        // Also clear BRANCH_LEFT/RIGHT when clearing BRANCH
-        if event_id == branch_id {
-            state.callbacks.remove(&(tool, branch_left_id));
-            state.callbacks.remove(&(tool, branch_right_id));
+        // BRANCH replaces both edge registrations, including independently
+        // registered callbacks. Keep their owners alive until after unlocking.
+        if event_id == MonitoringEvent::Branch as usize {
+            for edge in [MonitoringEvent::BranchLeft, MonitoringEvent::BranchRight] {
+                let key = (tool, edge as usize);
+                let old = if vm.is_none(&func) {
+                    state.legacy_branch_callbacks.remove(&key);
+                    state.callbacks.remove(&key)
+                } else {
+                    state.legacy_branch_callbacks.insert(key);
+                    state.callbacks.insert(key, func.clone())
+                };
+                displaced.extend(old);
+            }
         }
-    }
+        (prev, displaced)
+    };
+    drop(displaced);
     Ok(prev)
 }
 
@@ -846,6 +841,19 @@ fn fire(
     code: &Py<PyCode>,
     offset: u32,
     cb_extra: &[PyObjectRef],
+) -> PyResult<()> {
+    fire_at(vm, event, code, offset, offset, cb_extra)
+}
+
+// The physical instruction owns DISABLE state; branch callback source offsets
+// can differ from that instruction when NOT_TAKEN follows a branch or wrapper.
+fn fire_at(
+    vm: &VirtualMachine,
+    event: MonitoringEvent,
+    code: &Py<PyCode>,
+    offset: u32,
+    source_offset: u32,
+    cb_extra: &[PyObjectRef],
 ) -> PyResult<()> {
     // Prevent recursive event firing
     if vm.tracing_is_suppressed() || FIRING.with(|f| f.get()) {
@@ -855,6 +863,11 @@ fn fire(
     let event_id = event as usize;
     let event_mask = event.mask();
     let code_id = code.get_id();
+    let disabled_event = if matches!(event, MonitoringEvent::CReturn | MonitoringEvent::CRaise) {
+        MonitoringEvent::Call as usize
+    } else {
+        event_id
+    };
 
     // C_RETURN and C_RAISE are implicitly enabled when CALL is set.
     let check_bit = if matches!(event, MonitoringEvent::CReturn | MonitoringEvent::CRaise) {
@@ -863,9 +876,18 @@ fn fire(
         event_mask
     };
 
-    // Collect callbacks and snapshot the DISABLE sentinel under a single lock.
-    let (callbacks, disable_sentinel): (Vec<(usize, PyObjectRef)>, Option<PyObjectRef>) = {
-        let state = vm.state.monitoring.lock();
+    let branch_source = if matches!(
+        event,
+        MonitoringEvent::BranchLeft | MonitoringEvent::BranchRight
+    ) {
+        Some(branch_source_events(code, source_offset))
+    } else {
+        None
+    };
+
+    // Collect callbacks without holding the monitoring lock across Python code.
+    let callbacks = {
+        let mut state = vm.state.monitoring.lock();
         let mut cbs = Vec::new();
         for tool in 0..TOOL_LIMIT {
             let global = state.global_events[tool];
@@ -877,14 +899,32 @@ fn fire(
             if ((global | local) & check_bit) == 0 {
                 continue;
             }
-            if state.disabled.contains(&(code_id, offset as usize, tool)) {
+            if state
+                .disabled
+                .contains(&(code_id, offset as usize, disabled_event, tool))
+            {
                 continue;
             }
-            if let Some(cb) = state.callbacks.get(&(tool, event_id)) {
-                cbs.push((tool, cb.clone()));
+            if state.callbacks.contains_key(&(tool, event_id)) {
+                let legacy_branch = state.legacy_branch_callbacks.contains(&(tool, event_id));
+                if legacy_branch
+                    && branch_source.as_ref().is_some_and(|events| {
+                        !events.iter().any(|source_event| {
+                            event_active_at(&state, code_id, source_offset, *source_event)
+                        })
+                    })
+                {
+                    // The legacy wrapper returns DISABLE without calling the
+                    // user when the source instruction is no longer instrumented.
+                    state
+                        .disabled
+                        .insert((code_id, offset as usize, event_id, tool));
+                    continue;
+                }
+                cbs.push((tool, state.callbacks[&(tool, event_id)].clone()));
             }
         }
-        (cbs, state.disable.clone())
+        cbs
     };
 
     if callbacks.is_empty() {
@@ -896,35 +936,126 @@ fn fire(
     args_vec.extend_from_slice(cb_extra);
     let args = FuncArgs::from(args_vec);
 
-    FIRING.with(|f| f.set(true));
-    vm.enter_tracing();
-    let old_what = vm.what_event.replace(Some(event));
-    let result = (|| {
-        for (tool, cb) in callbacks {
-            let result = cb.call(args.clone(), vm)?;
-            if disable_sentinel.as_ref().is_some_and(|d| result.is(d)) {
-                // Only local events (event_id < LOCAL_EVENTS_COUNT) can be disabled.
-                // Non-local events (RAISE, EXCEPTION_HANDLED, PY_UNWIND, etc.)
-                // cannot be disabled per code object.
-                if event_id >= LOCAL_EVENTS_COUNT {
-                    // Remove the callback.
-                    let mut state = vm.state.monitoring.lock();
-                    state.callbacks.remove(&(tool, event_id));
-                    return Err(vm.new_value_error(format!(
-                        "Cannot disable {} events. Callback removed.",
-                        EVENT_NAMES[event_id]
-                    )));
-                }
+    for (tool, cb) in callbacks {
+        if call_instrument(vm, event, &cb, args.clone())? {
+            if is_instrumented_event(event_id) {
                 let mut state = vm.state.monitoring.lock();
-                state.disabled.insert((code_id, offset as usize, tool));
+                state
+                    .disabled
+                    .insert((code_id, offset as usize, event_id, tool));
+            } else if event_id < UNGROUPED_EVENTS_COUNT {
+                // Non-instrumented events are disabled for this whole code
+                // object by removing only the local subscription. Global
+                // subscriptions continue to fire, including for this code.
+                let mut state = vm.state.monitoring.lock();
+                if let Some(local) = state.local_events.get_mut(&(tool, code_id)) {
+                    *local &= !event_mask;
+                    if *local == 0 {
+                        state.local_events.remove(&(tool, code_id));
+                    }
+                    update_events_mask(vm, &state);
+                }
+            } else {
+                return Err(cannot_disable(vm, event, tool));
             }
         }
-        Ok(())
-    })();
+    }
+    Ok(())
+}
+
+fn event_active_at(
+    state: &MonitoringState,
+    code_id: usize,
+    offset: u32,
+    event: MonitoringEvent,
+) -> bool {
+    (0..TOOL_LIMIT).any(|tool| {
+        let active = state.global_events[tool]
+            | state
+                .local_events
+                .get(&(tool, code_id))
+                .copied()
+                .unwrap_or(0);
+        state.tool_names[tool].is_some()
+            && active & event.mask() != 0
+            && !state
+                .disabled
+                .contains(&(code_id, offset as usize, event as usize, tool))
+    })
+}
+
+pub(crate) fn is_event_active_at(
+    vm: &VirtualMachine,
+    code: &Py<PyCode>,
+    offset: u32,
+    event: MonitoringEvent,
+) -> bool {
+    event_active_at(&vm.state.monitoring.lock(), code.get_id(), offset, event)
+}
+
+// Model the source's instrumentation layers without changing its bytecode.
+// A layer stays instrumented until its last subscribed tool disables it.
+fn branch_source_events(code: &Py<PyCode>, offset: u32) -> Vec<MonitoringEvent> {
+    use rustpython_compiler_core::bytecode::Instruction;
+    let index = offset as usize / 2;
+    let data = code.monitoring_data.lock();
+    let mut events = Vec::with_capacity(3);
+    let mut op = code.code.instructions.read_op(index);
+    if let Some(data) = data.as_ref() {
+        if matches!(op, Instruction::InstrumentedLine) {
+            events.push(MonitoringEvent::Line);
+            op = Instruction::try_from(data.line_opcodes[index])
+                .expect("INSTRUMENTED_LINE without original opcode");
+        }
+        if matches!(op, Instruction::InstrumentedInstruction) {
+            events.push(MonitoringEvent::Instruction);
+            op = Instruction::try_from(data.per_instruction_opcodes[index])
+                .expect("INSTRUMENTED_INSTRUCTION without original opcode");
+        }
+    }
+    if let Some(event) = event_for_opcode(op, code.code.instructions.read_arg(index).as_u8()) {
+        events.push(event);
+    }
+    events
+}
+
+// Restore tracing state before processing a callback result or exception.
+fn call_instrument(
+    vm: &VirtualMachine,
+    event: MonitoringEvent,
+    callback: &PyObject,
+    args: FuncArgs,
+) -> PyResult<bool> {
+    if vm.tracing_is_suppressed() || FIRING.with(|f| f.get()) {
+        return Ok(false);
+    }
+    let disable_sentinel = vm.state.monitoring.lock().disable.clone();
+    FIRING.with(|f| f.set(true));
+    vm.enter_tracing();
+    let old_what = vm.what_event.replace(Some(event));
+    let result = callback.call(args, vm);
     vm.what_event.set(old_what);
     vm.leave_tracing();
     FIRING.with(|f| f.set(false));
-    result
+    let result = result?;
+    let disable = disable_sentinel.as_ref().is_some_and(|d| result.is(d));
+    Ok(disable)
+}
+
+fn cannot_disable(
+    vm: &VirtualMachine,
+    event: MonitoringEvent,
+    tool: usize,
+) -> crate::builtins::PyBaseExceptionRef {
+    let callback = {
+        let mut state = vm.state.monitoring.lock();
+        state.callbacks.remove(&(tool, event as usize))
+    };
+    drop(callback);
+    vm.new_value_error(format!(
+        "Cannot disable {} events. Callback removed.",
+        EVENT_NAMES[event as usize]
+    ))
 }
 
 // Public dispatch functions (called from frame.rs)
@@ -1071,6 +1202,12 @@ pub(crate) fn fire_raise(
     )
 }
 
+/// End suppression when the exception reaches a handler or escapes a frame,
+/// independently of whether either lifecycle event has a registered callback.
+pub(crate) fn reset_reraise_pending() {
+    RERAISE_PENDING.with(|f| f.set(false));
+}
+
 /// Only fires if no RERAISE has been fired since the last EXCEPTION_HANDLED,
 /// preventing duplicate events from chained cleanup handlers.
 pub(crate) fn fire_reraise(
@@ -1102,7 +1239,7 @@ pub(crate) fn fire_exception_handled(
     offset: u32,
     exception: &PyObject,
 ) -> PyResult<()> {
-    RERAISE_PENDING.with(|f| f.set(false));
+    reset_reraise_pending();
     fire(
         vm,
         MonitoringEvent::ExceptionHandled,
@@ -1118,7 +1255,7 @@ pub(crate) fn fire_py_unwind(
     offset: u32,
     exception: &PyObject,
 ) -> PyResult<()> {
-    RERAISE_PENDING.with(|f| f.set(false));
+    reset_reraise_pending();
     fire(
         vm,
         MonitoringEvent::PyUnwind,
@@ -1186,13 +1323,15 @@ pub(crate) fn fire_jump(
 pub(crate) fn fire_branch_left(
     vm: &VirtualMachine,
     code: &Py<PyCode>,
+    site: u32,
     offset: u32,
     destination: u32,
 ) -> PyResult<()> {
-    fire(
+    fire_at(
         vm,
         MonitoringEvent::BranchLeft,
         code,
+        site,
         offset,
         &[
             vm.ctx.new_int(offset).into(),
diff --git a/crates/vm/src/stdlib/time.rs b/crates/vm/src/stdlib/time.rs
index 70b6479a5d3..ec6db117cea 100644
--- a/crates/vm/src/stdlib/time.rs
+++ b/crates/vm/src/stdlib/time.rs
@@ -14,10 +14,13 @@ mod decl {
 
     #[cfg(any(unix, windows))]
     use crate::builtins::PyBaseExceptionRef;
+    #[cfg(any(unix, windows))]
+    use crate::convert::{ToPyException, ToPyObject};
     use crate::{
         AsObject, Py, PyObjectRef, PyResult, VirtualMachine,
         builtins::{PyStr, PyStrRef, PyTypeRef},
         class::PyClassDef,
+        common::wtf8::Wtf8Buf,
         function::{Either, FuncArgs, OptionalArg, OptionalOption},
         types::{PyStructSequence, PyStructSequenceData, struct_sequence_new},
     };
@@ -26,14 +29,10 @@ mod decl {
         PyRef,
         builtins::{PyNamespace, PyUtf8StrRef},
     };
-    #[cfg(any(unix, windows))]
-    use crate::{
-        common::wtf8::Wtf8Buf,
-        convert::{ToPyException, ToPyObject},
-    };
     use core::time::Duration;
     #[cfg(not(any(unix, windows)))]
     use jiff::{Timestamp, Zoned, civil::DateTime, tz::TimeZone};
+    use num_traits::ToPrimitive;
     #[cfg(target_os = "wasi")]
     use rustpython_host_env::time::ClockId;
     #[cfg(any(unix, windows))]
@@ -128,21 +127,43 @@ mod decl {
     fn sleep(object: PyObjectRef, vm: &VirtualMachine) -> PyResult<()> {
         vm.audit("time.sleep", || (object.clone(),))?;
 
-        let seconds_type_name = object.class().name().to_owned();
-        let dur = object.try_into_value::<Duration>(vm).map_err(|e| {
-            if e.class().is(vm.ctx.exceptions.value_error)
-                && let Some(s) = e.args().as_slice().first().and_then(|arg| arg.str(vm).ok())
-                && s.as_bytes() == b"negative duration"
-            {
-                return vm.new_value_error("sleep length must be non-negative");
+        let overflow = || vm.new_overflow_error("timestamp out of range for C PyTime_t");
+        let nanoseconds = if object.number().is_index() {
+            let seconds = object.try_index(vm).map_err(|e| {
+                if e.fast_isinstance(vm.ctx.exceptions.overflow_error) {
+                    overflow()
+                } else {
+                    e
+                }
+            })?;
+            seconds
+                .as_bigint()
+                .to_i64()
+                .and_then(|seconds| seconds.checked_mul(SEC_TO_NS))
+                .ok_or_else(overflow)?
+        } else {
+            let seconds = object.try_float(vm)?.to_f64();
+            if seconds.is_nan() {
+                return Err(vm.new_value_error("Invalid value NaN (not a number)"));
             }
-            if e.class().is(vm.ctx.exceptions.type_error) {
-                return vm.new_type_error(format!(
-                    "'{seconds_type_name}' object cannot be interpreted as an integer or float"
-                ));
+            // _PyTime_ROUND_TIMEOUT rounds away from zero.
+            let nanoseconds = seconds * SEC_TO_NS as f64;
+            let nanoseconds = if nanoseconds >= 0.0 {
+                nanoseconds.ceil()
+            } else {
+                nanoseconds.floor()
+            };
+            let minimum = i64::MIN as f64;
+            // The signed maximum rounds up to 2**63 as a double.
+            if !(minimum..-minimum).contains(&nanoseconds) {
+                return Err(overflow());
             }
-            e
-        })?;
+            nanoseconds as i64
+        };
+        if nanoseconds < 0 {
+            return Err(vm.new_value_error("sleep length must be non-negative"));
+        }
+        let dur = Duration::from_nanos(nanoseconds as u64);
 
         #[cfg(unix)]
         {
@@ -906,7 +927,7 @@ mod decl {
 
     #[cfg(any(unix, windows))]
     #[cfg_attr(target_env = "musl", allow(deprecated))]
-    fn pyobj_to_time_t(value: Either<f64, i64>, vm: &VirtualMachine) -> PyResult<libc::time_t> {
+    fn pyobj_to_time_t(value: Either<f64, i64>, vm: &VirtualMachine) -> PyResult<host_time::TimeT> {
         match value {
             Either::A(float) => {
                 if !float.is_finite() {
@@ -914,17 +935,19 @@ mod decl {
                 }
                 let secs = float.floor();
                 #[cfg_attr(target_env = "musl", allow(deprecated))]
-                if secs < libc::time_t::MIN as f64 || secs > libc::time_t::MAX as f64 {
+                let minimum = host_time::TimeT::MIN as f64;
+                // The signed maximum rounds up when represented by f64.
+                if !(minimum..-minimum).contains(&secs) {
                     return Err(vm.new_overflow_error("timestamp out of range for platform time_t"));
                 }
                 #[cfg_attr(target_env = "musl", allow(deprecated))]
-                Ok(secs as libc::time_t)
+                Ok(secs as host_time::TimeT)
             }
             Either::B(int) => {
                 // try_into is needed on 32-bit platforms where time_t != i64
                 #[allow(clippy::useless_conversion)]
                 #[cfg_attr(target_env = "musl", allow(deprecated))]
-                let ts: libc::time_t = int.try_into().map_err(|_| {
+                let ts: host_time::TimeT = int.try_into().map_err(|_| {
                     vm.new_overflow_error("timestamp out of range for platform time_t")
                 })?;
                 Ok(ts)
@@ -1248,6 +1271,7 @@ mod platform {
     use crate::{
         PyRef, PyResult, VirtualMachine,
         builtins::{PyNamespace, PyUtf8StrRef},
+        convert::ToPyException,
     };
     use core::time::Duration;
     use rustpython_host_env::time as host_time;
@@ -1281,8 +1305,8 @@ mod platform {
         when: host_time::TimeT,
         vm: &VirtualMachine,
     ) -> PyResult<StructTimeData> {
-        let tm = host_time::gmtime_from_timestamp(when)
-            .ok_or_else(|| vm.new_overflow_error("timestamp out of range for platform time_t"))?;
+        let tm =
+            host_time::gmtime_from_timestamp(when).map_err(|error| error.to_pyexception(vm))?;
         Ok(struct_time_from_tm(vm, tm, "UTC", 0))
     }
 
@@ -1290,8 +1314,8 @@ mod platform {
         when: host_time::TimeT,
         vm: &VirtualMachine,
     ) -> PyResult<StructTimeData> {
-        let tm = host_time::localtime_from_timestamp(when)
-            .ok_or_else(|| vm.new_overflow_error("timestamp out of range for platform time_t"))?;
+        let tm =
+            host_time::localtime_from_timestamp(when).map_err(|error| error.to_pyexception(vm))?;
 
         // Get timezone info from Windows API
         let info = get_tz_info();
@@ -1301,7 +1325,25 @@ mod platform {
             (info.standard_bias, &info.standard_name)
         };
 
-        let gmtoff = -(info.bias + bias) * 60;
+        let gmtoff = if when < 0 {
+            // FILETIME marks historical DST as unknown. Derive the offset from
+            // the converted wall time rather than treating unknown as standard.
+            let wall_time = jiff::civil::DateTime::new(
+                (tm.tm_year + 1900) as i16,
+                (tm.tm_mon + 1) as i8,
+                tm.tm_mday as i8,
+                tm.tm_hour as i8,
+                tm.tm_min as i8,
+                tm.tm_sec as i8,
+                0,
+            )
+            .and_then(|dt| dt.to_zoned(jiff::tz::TimeZone::UTC))
+            .map_err(|_| vm.new_overflow_error("timestamp out of range for Windows FILETIME"))?;
+            i32::try_from(wall_time.timestamp().as_second() - when)
+                .map_err(|_| vm.new_overflow_error("timezone offset out of range"))?
+        } else {
+            -(info.bias + bias) * 60
+        };
 
         Ok(struct_time_from_tm(vm, tm, name, gmtoff))
     }
diff --git a/crates/vm/src/stdlib/typevar.rs b/crates/vm/src/stdlib/typevar.rs
index 19ad3562540..1a7e5c6ee0b 100644
--- a/crates/vm/src/stdlib/typevar.rs
+++ b/crates/vm/src/stdlib/typevar.rs
@@ -7,7 +7,7 @@ pub(crate) mod typevar {
     use crate::{
         AsObject, Context, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, VirtualMachine,
         builtins::{PyTuple, PyTupleRef, PyType, PyTypeRef, make_union},
-        common::lock::PyMutex,
+        common::{lock::PyMutex, wtf8::Wtf8Buf},
         function::{FuncArgs, PyComparisonValue},
         protocol::PyNumberMethods,
         stdlib::_typing::{call_typing_func_object, decl::const_evaluator_alloc},
@@ -583,10 +583,7 @@ pub(crate) mod typevar {
                 return Err(vm.new_type_error("ParamSpec() takes at most 1 positional argument"));
             };
 
-            let bound = kwargs
-                .swap_remove("bound")
-                .map(|b| type_check(b, "Bound must be a type.", vm))
-                .transpose()?;
+            let bound = kwargs.swap_remove("bound");
             let covariant = kwargs
                 .swap_remove("covariant")
                 .map(|v| v.try_to_bool(vm))
@@ -678,8 +675,16 @@ pub(crate) mod typevar {
     pub struct TypeVarTuple {
         #[pymember(name = "__name__")]
         name: PyObjectRef,
+        #[pymember(name = "__bound__")]
+        bound: Option<PyObjectRef>,
         default_value: PyMutex<PyObjectRef>,
         evaluate_default: PyMutex<PyObjectRef>,
+        #[pymember(name = "__covariant__")]
+        covariant: bool,
+        #[pymember(name = "__contravariant__")]
+        contravariant: bool,
+        #[pymember(name = "__infer_variance__")]
+        infer_variance: bool,
     }
 
     #[pyclass(
@@ -786,11 +791,20 @@ pub(crate) mod typevar {
                     ));
                 }
             } else if args.args.len() == 1 {
+                if kwargs.contains_key("name") {
+                    return Err(vm.new_type_error(
+                        "argument for typevartuple() given by name ('name') and position (1)",
+                    ));
+                }
                 args.args[0].clone()
             } else {
                 return Err(vm.new_type_error("TypeVarTuple() takes at most 1 positional argument"));
             };
 
+            let bound = kwargs.swap_remove("bound");
+            let covariant = kwargs.swap_remove("covariant");
+            let contravariant = kwargs.swap_remove("contravariant");
+            let infer_variance = kwargs.swap_remove("infer_variance");
             let default = kwargs.swap_remove("default");
 
             // Check for unexpected keyword arguments
@@ -801,6 +815,33 @@ pub(crate) mod typevar {
                 ));
             }
 
+            // Clinic validates the argument layout and name before invoking __bool__.
+            if !name.downcastable::<crate::builtins::PyStr>() {
+                return Err(vm.new_type_error(format!(
+                    "typevartuple() argument 'name' must be str, not {}",
+                    name.class().name()
+                )));
+            }
+            let covariant = covariant
+                .map(|value| value.try_to_bool(vm))
+                .transpose()?
+                .unwrap_or(false);
+            let contravariant = contravariant
+                .map(|value| value.try_to_bool(vm))
+                .transpose()?
+                .unwrap_or(false);
+            let infer_variance = infer_variance
+                .map(|value| value.try_to_bool(vm))
+                .transpose()?
+                .unwrap_or(false);
+
+            if covariant && contravariant {
+                return Err(vm.new_value_error("Bivariant types are not supported."));
+            }
+            if infer_variance && (covariant || contravariant) {
+                return Err(vm.new_value_error("Variance cannot be specified with infer_variance."));
+            }
+
             // Handle default value
             let (default_value, evaluate_default) = if let Some(default) = default {
                 (default, vm.ctx.none())
@@ -811,8 +852,12 @@ pub(crate) mod typevar {
 
             let typevartuple = Self {
                 name,
+                bound,
                 default_value: PyMutex::new(default_value),
                 evaluate_default: PyMutex::new(evaluate_default),
+                covariant,
+                contravariant,
+                infer_variance,
             };
 
             let obj = typevartuple.into_ref_with_type(vm, cls)?;
@@ -828,9 +873,23 @@ pub(crate) mod typevar {
 
     impl Representable for TypeVarTuple {
         #[inline(always)]
-        fn repr_str(zelf: &crate::Py<Self>, vm: &VirtualMachine) -> PyResult<String> {
-            let name = zelf.name.str(vm)?;
-            Ok(name.to_string())
+        fn repr_wtf8(zelf: &crate::Py<Self>, _vm: &VirtualMachine) -> PyResult<Wtf8Buf> {
+            let name = zelf
+                .name
+                .downcast_ref::<crate::builtins::PyStr>()
+                .expect("TypeVarTuple name must be a string");
+            let prefix = if zelf.infer_variance {
+                ""
+            } else if zelf.covariant {
+                "+"
+            } else if zelf.contravariant {
+                "-"
+            } else {
+                "~"
+            };
+            let mut result = Wtf8Buf::from(prefix);
+            result.push_wtf8(name.as_wtf8());
+            Ok(result)
         }
     }
 
@@ -838,8 +897,12 @@ pub(crate) mod typevar {
         pub fn new(name: PyObjectRef, vm: &VirtualMachine) -> Self {
             Self {
                 name,
+                bound: None,
                 default_value: PyMutex::new(vm.ctx.typing_no_default.clone().into()),
                 evaluate_default: PyMutex::new(vm.ctx.none()),
+                covariant: false,
+                contravariant: false,
+                infer_variance: true,
             }
         }
     }
diff --git a/crates/vm/src/types/slot.rs b/crates/vm/src/types/slot.rs
index 03eb703f55b..8a7f750cdb6 100644
--- a/crates/vm/src/types/slot.rs
+++ b/crates/vm/src/types/slot.rs
@@ -253,6 +253,7 @@ bitflagset::bitflagset! {
         const IMMUTABLETYPE = 8;
         const HEAPTYPE = 9;
         const BASETYPE = 10;
+        const HAVE_GC = 14;
         const METHOD_DESCRIPTOR = 17;
         const IS_ABSTRACT = 20;
         // Built-in types that match the subject itself in pattern matching
@@ -451,6 +452,11 @@ macro_rules! number_binary_op_wrapper {
         |a, b, vm| vm.call_special_method(a, identifier!(vm, $name), (b.to_owned(),))
     };
 }
+// binary_op1 needs one function address across slot updates and deletions.
+fn number_add_wrapper(a: &PyObject, b: &PyObject, vm: &VirtualMachine) -> PyResult {
+    vm.call_special_method(a, identifier!(vm, __add__), (b.to_owned(),))
+}
+
 macro_rules! number_binary_right_op_wrapper {
     ($name:ident) => {
         |a, b, vm| vm.call_special_method(b, identifier!(vm, $name), (a.to_owned(),))
@@ -588,7 +594,7 @@ pub fn hash_not_implemented(zelf: &PyObject, vm: &VirtualMachine) -> PyResult<Py
 fn call_wrapper(zelf: &PyObject, args: FuncArgs, vm: &VirtualMachine) -> PyResult {
     // `__call__` can name the object being called, and dispatching it pushes no
     // Python frame, so nothing else counts the nesting.
-    vm.with_recursion("while calling a Python object", || {
+    vm.with_recursion(" while calling a Python object", || {
         vm.call_special_method(zelf, identifier!(vm, __call__), args)
     })
 }
@@ -773,13 +779,21 @@ fn descr_get_wrapper(
     cls: Option<&PyObject>,
     vm: &VirtualMachine,
 ) -> PyResult {
-    // A descriptor whose `__get__` is the descriptor itself resolves it by
-    // fetching `__get__` again, and none of that pushes a Python frame.
-    vm.with_recursion("while calling a Python object", || {
-        vm.call_special_method(
-            zelf,
-            identifier!(vm, __get__),
-            (obj.map(PyObject::to_owned), cls.map(PyObject::to_owned)),
+    // slot_tp_descr_get calls the raw type attribute with all three arguments.
+    // Binding it first would omit self for builtin functions and incorrectly
+    // invoke the descriptor protocol of static/class/custom __get__ objects.
+    // Keep both the callable and self owned across user code that deletes them.
+    vm.with_recursion(" while calling a Python object", || {
+        let Some(get) = zelf.class().get_attr(identifier!(vm, __get__)) else {
+            return Ok(zelf.to_owned());
+        };
+        get.call(
+            (
+                zelf.to_owned(),
+                obj.map(PyObject::to_owned),
+                cls.map(PyObject::to_owned),
+            ),
+            vm,
         )
     })
 }
@@ -887,7 +901,7 @@ impl PyType {
         name: &'static PyStrInterned,
         ctx: &Context,
     ) {
-        use crate::builtins::descriptor::SlotFunc;
+        use crate::builtins::descriptor::{PyWrapper, SlotFunc};
 
         // Helper macro for main slots
         macro_rules! update_main_slot {
@@ -1249,13 +1263,31 @@ impl PyType {
                         number_binary_right_op_wrapper!(__radd__),
                         NumBinary
                     )
-                } else {
-                    update_sub_slot!(
-                        as_number,
-                        add,
-                        number_binary_op_wrapper!(__add__),
-                        NumBinary
-                    )
+                }
+                let native_concat = self
+                    .get_attr(identifier!(ctx, __add__))
+                    .is_some_and(|attr| {
+                        attr.class().is(ctx.types.wrapper_descriptor_type)
+                            && attr.downcast_ref::<PyWrapper>().is_some_and(|descr| {
+                                descr.name.as_str() == "__add__"
+                                    && self.mro.read().iter().any(|cls| cls.is(descr.typ))
+                                    && matches!(descr.wrapped, SlotFunc::SeqConcat(_))
+                            })
+                    });
+                if native_concat {
+                    // Native sequence addition stays in sq_concat unless nb_add
+                    // already participates or __radd__ needs its shared dispatcher.
+                    // Like CPython's resolve_slotdups, preserve an existing numeric
+                    // wrapper when an override is replaced or deleted.
+                    let needs_numeric = self.slots.as_number.add.load().is_some()
+                        || self.slots.as_sequence.concat.load().is_none()
+                        || self.get_attr(identifier!(ctx, __radd__)).is_some();
+                    self.slots
+                        .as_number
+                        .add
+                        .store(needs_numeric.then_some(number_add_wrapper));
+                } else if name.as_str() == "__add__" {
+                    update_sub_slot!(as_number, add, number_add_wrapper, NumBinary)
                 }
             }
             SlotAccessor::NbInplaceAdd => {
diff --git a/crates/vm/src/types/structseq.rs b/crates/vm/src/types/structseq.rs
index 09822495075..dee57fb92ca 100644
--- a/crates/vm/src/types/structseq.rs
+++ b/crates/vm/src/types/structseq.rs
@@ -11,7 +11,7 @@ use crate::{
     },
     iter::PyExactSizeIterator,
     protocol::{PyMappingMethods, PySequenceMethods},
-    sliceable::{SequenceIndex, SliceableSequenceOp},
+    sliceable::{NameTuple, SequenceIndex, SliceableSequenceOp},
     types::PyComparisonOp,
     vm::Context,
 };
@@ -217,7 +217,7 @@ static STRUCT_SEQUENCE_AS_MAPPING: LazyLock<PyMappingMethods> =
             let tuple = mapping.obj.downcast_ref::<PyTuple>().unwrap();
             let visible_elements = &tuple.as_slice()[..n_seq];
 
-            match SequenceIndex::try_from_borrowed_object(vm, needle, "tuple")? {
+            match SequenceIndex::try_from_borrowed_object::<NameTuple>(vm, needle)? {
                 SequenceIndex::Int(i) => visible_elements.getitem_by_index(vm, i),
                 SequenceIndex::Slice(slice) => visible_elements
                     .getitem_by_slice(vm, slice)
@@ -376,7 +376,7 @@ pub trait PyStructSequence: StaticType + PyClassImpl + Sized + 'static {
         let n_seq = get_visible_len(zelf.as_ref(), vm)?;
         let visible_elements = &zelf.as_slice()[..n_seq];
 
-        match SequenceIndex::try_from_borrowed_object(vm, &needle, "tuple")? {
+        match SequenceIndex::try_from_borrowed_object::<NameTuple>(vm, &needle)? {
             SequenceIndex::Int(i) => visible_elements.getitem_by_index(vm, i),
             SequenceIndex::Slice(slice) => visible_elements
                 .getitem_by_slice(vm, slice)
diff --git a/crates/vm/src/types/zoo.rs b/crates/vm/src/types/zoo.rs
index 0d3c5d0fb92..3076a7b79d7 100644
--- a/crates/vm/src/types/zoo.rs
+++ b/crates/vm/src/types/zoo.rs
@@ -4,8 +4,8 @@ use crate::{
         asyncgenerator, bool_, builtin_func, bytearray, bytes, capsule, classmethod, code, complex,
         coroutine, descriptor, dict, enumerate, filter, float, frame, frame_locals_proxy, function,
         generator, genericalias, getset, int, interpolation, iter, list, map, mappingproxy, memory,
-        module, namespace, object, property, pystr, range, set, singletons, slice, staticmethod,
-        super_, template, traceback, tuple,
+        module, namespace, object, property, pystr, range, sentinel, set, singletons, slice,
+        staticmethod, super_, template, traceback, tuple,
         type_::{self, PyType},
         union_, weakproxy, weakref, zip,
     },
@@ -40,12 +40,14 @@ pub struct TypeZoo {
     pub float_type: &'static Py<PyType>,
     pub frame_type: &'static Py<PyType>,
     pub frame_locals_proxy_type: &'static Py<PyType>,
+    pub frozendict_type: &'static Py<PyType>,
     pub frozenset_type: &'static Py<PyType>,
     pub generator_type: &'static Py<PyType>,
     pub int_type: &'static Py<PyType>,
     pub iter_type: &'static Py<PyType>,
     pub reverse_iter_type: &'static Py<PyType>,
     pub complex_type: &'static Py<PyType>,
+    pub lazy_import_type: &'static Py<PyType>,
     pub list_type: &'static Py<PyType>,
     pub list_iterator_type: &'static Py<PyType>,
     pub list_reverseiterator_type: &'static Py<PyType>,
@@ -64,6 +66,7 @@ pub struct TypeZoo {
     pub memoryviewiterator_type: &'static Py<PyType>,
     pub tuple_type: &'static Py<PyType>,
     pub tuple_iterator_type: &'static Py<PyType>,
+    pub sentinel_type: &'static Py<PyType>,
     pub set_type: &'static Py<PyType>,
     pub set_iterator_type: &'static Py<PyType>,
     pub staticmethod_type: &'static Py<PyType>,
@@ -120,7 +123,7 @@ impl TypeZoo {
         let weakref_type = weakref::PyWeak::init_manually(hierarchy.weakref_type);
         let int_type = int::PyInt::init_builtin_type();
 
-        // builtin_function_or_method and builtin_method share the same type (CPython behavior)
+        // `builtin_method` is a subclass and is initialized once this base exists.
         let builtin_function_or_method_type = builtin_func::PyNativeFunction::init_builtin_type();
 
         let types = Self {
@@ -138,13 +141,16 @@ impl TypeZoo {
             dict_type: dict::PyDict::init_builtin_type(),
             enumerate_type: enumerate::PyEnumerate::init_builtin_type(),
             float_type: float::PyFloat::init_builtin_type(),
+            frozendict_type: dict::PyFrozenDict::init_builtin_type(),
             frozenset_type: set::PyFrozenSet::init_builtin_type(),
             filter_type: filter::PyFilter::init_builtin_type(),
+            lazy_import_type: crate::lazy_import::PyLazyImport::init_builtin_type(),
             list_type: list::PyList::init_builtin_type(),
             map_type: map::PyMap::init_builtin_type(),
             memoryview_type: memory::PyMemoryView::init_builtin_type(),
             property_type: property::PyProperty::init_builtin_type(),
             range_type: range::PyRange::init_builtin_type(),
+            sentinel_type: sentinel::PySentinel::init_builtin_type(),
             set_type: set::PySet::init_builtin_type(),
             slice_type: slice::PySlice::init_builtin_type(),
             staticmethod_type: staticmethod::PyStaticMethod::init_builtin_type(),
@@ -162,7 +168,7 @@ impl TypeZoo {
             anext_awaitable: asyncgenerator::PyAnextAwaitable::init_builtin_type(),
             bound_method_type: function::PyBoundMethod::init_builtin_type(),
             builtin_function_or_method_type,
-            builtin_method_type: builtin_function_or_method_type,
+            builtin_method_type: builtin_func::PyNativeMethod::init_builtin_type(),
             bytearray_iterator_type: bytearray::PyByteArrayIterator::init_builtin_type(),
             bytes_iterator_type: bytes::PyBytesIterator::init_builtin_type(),
             callable_iterator: iter::PyCallableIterator::init_builtin_type(),
@@ -233,6 +239,7 @@ impl TypeZoo {
         set::init(context);
         tuple::init(context);
         dict::init(context);
+        crate::lazy_import::init_type(context);
         builtin_func::init(context);
         function::init(context);
         staticmethod::init(context);
@@ -265,6 +272,7 @@ impl TypeZoo {
         weakref::init(context);
         weakproxy::init(context);
         singletons::init(context);
+        sentinel::init(context);
         module::init(context);
         namespace::init(context);
         mappingproxy::init(context);
diff --git a/crates/vm/src/version.rs b/crates/vm/src/version.rs
index 05eb12a2942..bd421f7ca6e 100644
--- a/crates/vm/src/version.rs
+++ b/crates/vm/src/version.rs
@@ -69,8 +69,8 @@ pub const RUSTPYTHON_VERSION: &str = const {
 };
 
 // Must be aligned to Lib/importlib/_bootstrap_external.py
-// Matches CPython 3.14 (Include/internal/pycore_magic_number.h).
-pub const PYC_MAGIC_NUMBER: u16 = 3627;
+// Matches CPython 3.15 (Include/internal/pycore_magic_number.h).
+pub const PYC_MAGIC_NUMBER: u16 = 3666;
 
 // CPython format: magic_number | ('\r' << 16) | ('\n' << 24)
 // This protects against text-mode file reads
diff --git a/crates/vm/src/vm/compile.rs b/crates/vm/src/vm/compile.rs
index 626659f19e1..95dbcac5b8f 100644
--- a/crates/vm/src/vm/compile.rs
+++ b/crates/vm/src/vm/compile.rs
@@ -5,12 +5,22 @@
 use core::fmt;
 
 use crate::{
-    AsObject, PyObjectRef, PyRef, PyResult, VirtualMachine,
-    builtins::{PyBaseExceptionRef, PyCode},
+    AsObject, Py, PyObjectRef, PyRef, PyResult, VirtualMachine,
+    builtins::{PyBaseExceptionRef, PyCode, PyStr},
     compiler::{self, CompileError, CompileOpts},
     vm::compile_mode::{CompileStart, CompilerFlags, compile_future_features_from_flags},
 };
 
+/// Warnings already emitted while reading one interactive statement.
+///
+/// The source is warned about again after each line is read, but the
+/// tokenizer warns about each token only once.
+#[cfg(feature = "parser")]
+#[derive(Default)]
+pub(super) struct InteractiveWarnings {
+    emitted: alloc::collections::BTreeSet<(usize, String)>,
+}
+
 #[derive(Debug)]
 pub enum VmCompileError {
     Compile(CompileError),
@@ -381,7 +391,29 @@ impl VirtualMachine {
         feature_version: i32,
         optimize: i32,
     ) -> PyResult<PyObjectRef> {
-        use crate::convert::ToPyException;
+        self.compile_string_object_with_flags_and_module(
+            source,
+            filename,
+            start,
+            flags,
+            feature_version,
+            optimize,
+            None,
+        )
+    }
+
+    #[cfg(feature = "parser")]
+    #[allow(clippy::too_many_arguments)]
+    pub(crate) fn compile_string_object_with_flags_and_module(
+        &self,
+        source: &[u8],
+        filename: &str,
+        start: i32,
+        flags: i32,
+        feature_version: i32,
+        optimize: i32,
+        module: Option<&Py<PyStr>>,
+    ) -> PyResult<PyObjectRef> {
         use crate::stdlib::_ast;
 
         let cf = CompilerFlags::from_bits_retain(flags);
@@ -411,10 +443,46 @@ impl VirtualMachine {
             None
         };
 
+        let emitted_parser_escapes = if is_ast_only {
+            self.emit_ast_parser_warnings(
+                source,
+                filename,
+                module,
+                start,
+                future_features.contains(crate::bytecode::CodeFlags::FUTURE_BARRY_AS_BDFL),
+            )
+            .map_err(|warning| {
+                VmCompileError::Warning(warning).into_pyexception(self, Some(source))
+            })?
+        } else {
+            Vec::new()
+        };
+        let mut emit_ast_warning = |offset, ch| {
+            if emitted_parser_escapes.binary_search(&offset).is_ok() {
+                return Ok(());
+            }
+            escape_warnings::warn_invalid_escape_sequence(
+                source,
+                escape_warnings::InvalidEscape::Char { ch, offset },
+                filename,
+                module,
+                self,
+            )
+            .map_err(VmCompileError::Warning)
+        };
         if is_ast_only {
             if start == CompileStart::FuncType {
-                return _ast::parse_func_type(self, source, filename, optimize, target_version)
-                    .map_err(|e| (e, Some(source), allow_incomplete).to_pyexception(self));
+                return _ast::parse_func_type(
+                    self,
+                    source,
+                    filename,
+                    optimize,
+                    target_version,
+                    &mut emit_ast_warning,
+                )
+                .map_err(|e| {
+                    e.into_pyexception_maybe_incomplete(self, Some(source), allow_incomplete)
+                });
             }
             let (parser_mode, interactive) = match start {
                 CompileStart::Single => (ruff_python_parser::Mode::Module, true),
@@ -434,14 +502,18 @@ impl VirtualMachine {
                 interactive,
                 future_features,
                 dont_imply_dedent,
+                &mut emit_ast_warning,
             )
-            .map_err(|e| (e, Some(source), allow_incomplete).to_pyexception(self))?;
+            .map_err(|e| {
+                e.into_pyexception_maybe_incomplete(self, Some(source), allow_incomplete)
+            })?;
             if start == CompileStart::Single {
                 return _ast::wrap_interactive(self, &parsed);
             }
             return Ok(parsed);
         }
 
+        let mut emitted_escapes = Vec::new();
         if type_comments {
             let parser_mode = match start {
                 CompileStart::Single | CompileStart::File => ruff_python_parser::Mode::Module,
@@ -460,8 +532,20 @@ impl VirtualMachine {
                 start == CompileStart::Single,
                 future_features,
                 dont_imply_dedent,
+                |offset, ch| {
+                    emit_ast_warning(offset, ch)?;
+                    // The ordinary compiler must not emit this same escape again.
+                    emitted_escapes.push(offset);
+                    Ok(())
+                },
             )
-            .map_err(|e| (e, Some(source), allow_incomplete).to_pyexception(self))?;
+            .map_err(|e: VmCompileError| {
+                e.into_pyexception_maybe_incomplete(self, Some(source), allow_incomplete)
+            })?;
+            // AST traversal need not follow source order. The later compiler
+            // uses binary search to skip these already-considered offsets.
+            emitted_escapes.sort_unstable();
+            emitted_escapes.dedup();
         }
 
         let mode = match start {
@@ -476,7 +560,7 @@ impl VirtualMachine {
         opts.future_features = future_features;
         opts.dont_imply_dedent = dont_imply_dedent;
         let code = self
-            .compile_with_opts(source, mode, filename, opts)
+            .compile_with_opts_and_module(source, mode, filename, opts, module, &emitted_escapes)
             .map_err(|err| {
                 err.into_pyexception_maybe_incomplete(self, Some(source), allow_incomplete)
             })?;
@@ -498,15 +582,43 @@ impl VirtualMachine {
         mode: compiler::Mode,
         source_path: impl Into<String>,
         opts: CompileOpts,
+    ) -> Result<PyRef<PyCode>, VmCompileError> {
+        self.compile_with_opts_and_module(source, mode, source_path, opts, None, &[])
+    }
+
+    pub(crate) fn compile_with_opts_and_module(
+        &self,
+        source: &str,
+        mode: compiler::Mode,
+        source_path: impl Into<String>,
+        opts: CompileOpts,
+        module: Option<&Py<PyStr>>,
+        emitted_escapes: &[usize],
     ) -> Result<PyRef<PyCode>, VmCompileError> {
         let source_path = source_path.into();
+        #[cfg(not(feature = "parser"))]
+        let _ = (module, emitted_escapes);
         #[cfg(feature = "parser")]
         {
-            self.emit_tokenizer_syntax_warnings(source, &source_path)
+            self.emit_tokenizer_syntax_warnings(source, &source_path, module)
                 .map_err(VmCompileError::Warning)?;
-            self.emit_string_escape_warnings(source, &source_path)
+            self.emit_string_escape_warnings(source, &source_path, module, emitted_escapes)
                 .map_err(VmCompileError::Warning)?;
         }
+        self.compile_after_parser_warnings(source, mode, source_path, opts, module)
+    }
+
+    pub(super) fn compile_after_parser_warnings(
+        &self,
+        source: &str,
+        mode: compiler::Mode,
+        source_path: impl Into<String>,
+        opts: CompileOpts,
+        module: Option<&Py<PyStr>>,
+    ) -> Result<PyRef<PyCode>, VmCompileError> {
+        let source_path = source_path.into();
+        #[cfg(not(feature = "parser"))]
+        let _ = module;
         #[cfg(feature = "parser")]
         let code = {
             // A warning the filter escalates to an exception is stashed here so
@@ -514,19 +626,25 @@ impl VirtualMachine {
             let escalated: core::cell::Cell<Option<CompileWarningError>> =
                 core::cell::Cell::new(None);
             let mut syntax_warning_handler = |location, message| {
-                escape_warnings::warn_syntax_at_location(&source_path, location, message, self)
-                    .map_err(|warning| {
-                        escalated.set(Some(warning));
-                        // Recovered below via `escalated`, so this is never surfaced.
-                        compiler::codegen::error::CodegenError {
-                            location: Some(location),
-                            end_location: None,
-                            error: compiler::codegen::error::CodegenErrorType::SyntaxError(
-                                String::new(),
-                            ),
-                            source_path: source_path.clone(),
-                        }
-                    })
+                escape_warnings::warn_syntax_at_location(
+                    &source_path,
+                    module,
+                    location,
+                    message,
+                    self,
+                )
+                .map_err(|warning| {
+                    escalated.set(Some(warning));
+                    // Recovered below via `escalated`, so this is never surfaced.
+                    compiler::codegen::error::CodegenError {
+                        location: Some(location),
+                        end_location: None,
+                        error: compiler::codegen::error::CodegenErrorType::SyntaxError(
+                            String::new(),
+                        ),
+                        source_path: source_path.clone(),
+                    }
+                })
             };
             let result = compiler::compile_with_syntax_warning_handler(
                 source,
@@ -618,11 +736,38 @@ mod escape_warnings {
         if cs <= ce { Some((cs, ce)) } else { None }
     }
 
-    enum InvalidEscape {
+    pub(super) enum InvalidEscape {
         Char { ch: char, offset: usize },
         Octal { digits: [u8; 3], offset: usize },
     }
 
+    #[derive(Clone, Copy, PartialEq, Eq)]
+    enum EscapeOrigin {
+        Parser,
+        Tokenizer,
+    }
+
+    enum ParserWarning {
+        /// The escape, where it is reported from, and for a bytes literal
+        /// escape on the literal's first line, the error column that
+        /// string_parser.c reports.
+        Escape(InvalidEscape, EscapeOrigin, Option<usize>),
+        Numeric {
+            offset: usize,
+            last_offset: usize,
+            message: String,
+        },
+    }
+
+    impl ParserWarning {
+        fn offset(&self) -> usize {
+            match self {
+                Self::Escape(escape, ..) => escape.offset(),
+                Self::Numeric { offset, .. } => *offset,
+            }
+        }
+    }
+
     impl InvalidEscape {
         fn offset(&self) -> usize {
             match self {
@@ -773,10 +918,11 @@ mod escape_warnings {
     /// Emit `SyntaxWarning` for an invalid escape sequence.
     ///
     /// `warn_invalid_escape_sequence()` in `Parser/string_parser.c`
-    fn warn_invalid_escape_sequence(
+    pub(super) fn warn_invalid_escape_sequence(
         source: &str,
         escape: InvalidEscape,
         filename: &str,
+        module: Option<&Py<PyStr>>,
         vm: &VirtualMachine,
     ) -> Result<(), CompileWarningError> {
         let (lineno, column) = line_offset_at(source, escape.offset());
@@ -788,7 +934,7 @@ mod escape_warnings {
             vm.ctx.new_str(warning).into(),
             fname,
             lineno,
-            None,
+            module.map(|module| module.to_owned().into()),
             vm.ctx.none(),
             None,
             None,
@@ -809,6 +955,7 @@ mod escape_warnings {
     fn warn_syntax_at_offset(
         source: &str,
         filename: &str,
+        module: Option<&Py<PyStr>>,
         offset: usize,
         message: String,
         vm: &VirtualMachine,
@@ -821,7 +968,7 @@ mod escape_warnings {
             message.into(),
             fname,
             lineno,
-            None,
+            module.map(|module| module.to_owned().into()),
             vm.ctx.none(),
             None,
             None,
@@ -832,6 +979,7 @@ mod escape_warnings {
 
     pub(super) fn warn_syntax_at_location(
         filename: &str,
+        module: Option<&Py<PyStr>>,
         location: compiler::core::SourceLocation,
         message: String,
         vm: &VirtualMachine,
@@ -843,7 +991,7 @@ mod escape_warnings {
             message.into(),
             fname,
             location.line.get(),
-            None,
+            module.map(|module| module.to_owned().into()),
             vm.ctx.none(),
             None,
             None,
@@ -1078,36 +1226,57 @@ mod escape_warnings {
         )
     }
 
-    fn warn_quoted_literal(
+    fn collect_quoted_literal_warning(
         source: &str,
-        quote_index: usize,
+        literal_start: usize,
         end: usize,
         is_bytes: bool,
-        filename: &str,
-        vm: &VirtualMachine,
-    ) -> Result<(), CompileWarningError> {
+        warnings: &mut Vec<ParserWarning>,
+    ) {
         if let Some((start, content_end)) =
-            content_bounds(source, text_range_from_bounds(quote_index, end))
+            content_bounds(source, text_range_from_bounds(literal_start, end))
             && let Some(escape) = first_invalid_escape(source, start, content_end, is_bytes)
         {
-            warn_invalid_escape_sequence(source, escape, filename, vm)?;
+            let before_escape = &source[start..escape.offset()];
+            // string_parser.c counts leading quotes from the token start.
+            // A bytes prefix contributes none to its first-line error range.
+            // Keep the actual escape offset for warning order and deduplication.
+            let error_column = (is_bytes && !before_escape.contains(['\r', '\n'])).then(|| {
+                let (_, column) = line_offset_at(source, escape.offset());
+                column.saturating_sub(start - literal_start)
+            });
+            warnings.push(ParserWarning::Escape(
+                escape,
+                EscapeOrigin::Parser,
+                error_column,
+            ));
         }
-        Ok(())
     }
 
-    fn warn_fstring_literal_part(
+    fn collect_fstring_literal_warning(
         source: &str,
         start: usize,
         end: usize,
-        filename: &str,
-        vm: &VirtualMachine,
-    ) -> Result<(), CompileWarningError> {
+        warnings: &mut Vec<ParserWarning>,
+    ) {
         if start >= end || end > source.len() {
-            return Ok(());
+            return;
         }
         if let Some(escape) = first_invalid_escape(source, start, end, false) {
-            return warn_invalid_escape_sequence(source, escape, filename, vm);
-        }
+            let origin = if matches!(&escape, InvalidEscape::Char { ch: '{' | '}', .. }) {
+                EscapeOrigin::Tokenizer
+            } else {
+                EscapeOrigin::Parser
+            };
+            warnings.push(ParserWarning::Escape(escape, origin, None));
+            return;
+        }
+        // In CPython, _PyTokenizer_warn_invalid_escape_sequence handles
+        // `\{` and `\}` for FSTRING_MIDDLE/FSTRING_END tokens.  Ruff
+        // splits the literal element before the interpolation delimiter,
+        // so the `\` sits at the end of the literal range and the `{`/`}`
+        // sits just after it.  Only warn when the number of trailing
+        // backslashes is odd (an even count means they are all escaped).
         let trailing_bs = source.as_bytes()[start..end]
             .iter()
             .rev()
@@ -1117,17 +1286,15 @@ mod escape_warnings {
             && let Some(&after) = source.as_bytes().get(end)
             && (after == b'{' || after == b'}')
         {
-            warn_invalid_escape_sequence(
-                source,
+            warnings.push(ParserWarning::Escape(
                 InvalidEscape::Char {
                     ch: after as char,
                     offset: end - 1,
                 },
-                filename,
-                vm,
-            )?;
+                EscapeOrigin::Tokenizer,
+                None,
+            ));
         }
-        Ok(())
     }
 
     fn find_interpolation_end(bytes: &[u8], open: usize, limit: usize) -> usize {
@@ -1184,9 +1351,8 @@ mod escape_warnings {
         start: usize,
         end: usize,
         is_raw: bool,
-        filename: &str,
-        vm: &VirtualMachine,
-    ) -> Result<(), CompileWarningError> {
+        warnings: &mut Vec<ParserWarning>,
+    ) {
         let bytes = source.as_bytes();
         let mut index = start;
         let mut literal_start = start;
@@ -1197,18 +1363,17 @@ mod escape_warnings {
                 }
                 b'{' => {
                     if !is_raw {
-                        warn_fstring_literal_part(source, literal_start, index, filename, vm)?;
+                        collect_fstring_literal_warning(source, literal_start, index, warnings);
                     }
                     let close = find_interpolation_end(bytes, index, end);
                     let body_end = if close > index + 1 { close - 1 } else { close };
-                    emit_string_escape_warnings_in_range(
+                    collect_string_escape_warnings_in_range(
                         source,
                         index + 1,
                         body_end,
                         Some(is_raw),
-                        filename,
-                        vm,
-                    )?;
+                        warnings,
+                    );
                     index = close.max(index + 1);
                     literal_start = index;
                 }
@@ -1220,29 +1385,19 @@ mod escape_warnings {
             }
         }
         if !is_raw {
-            warn_fstring_literal_part(source, literal_start, end, filename, vm)?;
+            collect_fstring_literal_warning(source, literal_start, end, warnings);
         }
-        Ok(())
     }
 
     /// Scan quoted literals without a successful parse, matching the tokenizer
     /// path that warns before the parser rejects the rest of the source.
-    fn emit_string_escape_warnings_unparsed(
-        source: &str,
-        filename: &str,
-        vm: &VirtualMachine,
-    ) -> Result<(), CompileWarningError> {
-        emit_string_escape_warnings_in_range(source, 0, source.len(), None, filename, vm)
-    }
-
-    fn emit_string_escape_warnings_in_range(
+    fn collect_string_escape_warnings_in_range(
         source: &str,
         start: usize,
         end: usize,
         format_spec_raw: Option<bool>,
-        filename: &str,
-        vm: &VirtualMachine,
-    ) -> Result<(), CompileWarningError> {
+        warnings: &mut Vec<ParserWarning>,
+    ) {
         let bytes = source.as_bytes();
         let end = end.min(bytes.len());
         let mut index = start;
@@ -1274,18 +1429,24 @@ mod escape_warnings {
                                         content_start,
                                         content_end.min(end),
                                         is_raw,
-                                        filename,
-                                        vm,
-                                    )?;
+                                        warnings,
+                                    );
                                 }
                             } else if !is_raw {
-                                warn_quoted_literal(
-                                    source, index, quote_end, is_bytes, filename, vm,
-                                )?;
+                                collect_quoted_literal_warning(
+                                    // Non-raw ordinary prefixes are one-byte b/u.
+                                    source,
+                                    index - 1,
+                                    quote_end,
+                                    is_bytes,
+                                    warnings,
+                                );
                             }
                         }
                         StringPrefix::None => {
-                            warn_quoted_literal(source, index, quote_end, false, filename, vm)?;
+                            collect_quoted_literal_warning(
+                                source, index, quote_end, false, warnings,
+                            );
                         }
                         StringPrefix::Invalid => {}
                     }
@@ -1296,8 +1457,8 @@ mod escape_warnings {
                     && bracket == 0
                     && brace == 0 =>
                 {
-                    scan_interpolated_content(source, index + 1, end, is_raw, filename, vm)?;
-                    return Ok(());
+                    scan_interpolated_content(source, index + 1, end, is_raw, warnings);
+                    return;
                 }
                 b'(' if format_spec_raw.is_some() => {
                     paren += 1;
@@ -1326,14 +1487,9 @@ mod escape_warnings {
                 _ => index += 1,
             }
         }
-        Ok(())
     }
 
-    fn emit_numeric_literal_warnings(
-        source: &str,
-        filename: &str,
-        vm: &VirtualMachine,
-    ) -> Result<(), CompileWarningError> {
+    fn collect_numeric_literal_warnings(source: &str, warnings: &mut Vec<ParserWarning>) {
         let bytes = source.as_bytes();
         let mut index = 0;
         while index < bytes.len() {
@@ -1360,52 +1516,40 @@ mod escape_warnings {
                         continue;
                     };
                     if end > index && numeric_keyword_suffix(&bytes[end..]) {
-                        warn_syntax_at_offset(
-                            source,
-                            filename,
-                            index,
-                            format!("invalid {kind} literal"),
-                            vm,
-                        )?;
+                        warnings.push(ParserWarning::Numeric {
+                            offset: index,
+                            last_offset: end - 1,
+                            message: format!("invalid {kind} literal"),
+                        });
                     }
                     index = end.max(index + 1);
                 }
                 _ => index += 1,
             }
         }
-        Ok(())
     }
 
-    struct EscapeWarningVisitor<'a> {
+    struct EscapeWarningVisitor<'a, 'w> {
         source: &'a str,
-        filename: &'a str,
-        vm: &'a VirtualMachine,
-        error: Option<CompileWarningError>,
+        warnings: &'w mut Vec<ParserWarning>,
+        ast_only: bool,
         /// This pass runs before the compile that rejects an over-nested
         /// tree, so it has to stop itself.
         depth: usize,
         depth_limit: usize,
     }
 
-    impl<'a> EscapeWarningVisitor<'a> {
-        fn record_warning(&mut self, result: Result<(), CompileWarningError>) {
-            if self.error.is_none()
-                && let Err(err) = result
-            {
-                self.error = Some(err);
-            }
-        }
-
+    impl<'a> EscapeWarningVisitor<'a, '_> {
         /// Check a quoted string/bytes literal for invalid escapes.
         /// The range must include the prefix and quote delimiters.
         fn check_quoted_literal(&mut self, range: TextRange, is_bytes: bool) {
-            if let Some((start, end)) = content_bounds(self.source, range)
-                && let Some(escape) = first_invalid_escape(self.source, start, end, is_bytes)
-            {
-                let result =
-                    warn_invalid_escape_sequence(self.source, escape, self.filename, self.vm);
-                self.record_warning(result);
-            }
+            collect_quoted_literal_warning(
+                self.source,
+                range.start().to_usize(),
+                range.end().to_usize(),
+                is_bytes,
+                self.warnings,
+            );
         }
 
         /// Check an f-string literal element for invalid escapes.
@@ -1415,60 +1559,32 @@ mod escape_warnings {
         /// equivalent to `_PyTokenizer_warn_invalid_escape_sequence` handling
         /// `FSTRING_MIDDLE` / `FSTRING_END` tokens.
         fn check_fstring_literal(&mut self, range: TextRange) {
-            let start = range.start().to_usize();
-            let end = range.end().to_usize();
-            if start >= end || end > self.source.len() {
-                return;
-            }
-            if let Some(escape) = first_invalid_escape(self.source, start, end, false) {
-                let result =
-                    warn_invalid_escape_sequence(self.source, escape, self.filename, self.vm);
-                self.record_warning(result);
-                return;
-            }
-            // In CPython, _PyTokenizer_warn_invalid_escape_sequence handles
-            // `\{` and `\}` for FSTRING_MIDDLE/FSTRING_END tokens.  Ruff
-            // splits the literal element before the interpolation delimiter,
-            // so the `\` sits at the end of the literal range and the `{`/`}`
-            // sits just after it.  Only warn when the number of trailing
-            // backslashes is odd (an even count means they are all escaped).
-            let trailing_bs = self.source.as_bytes()[start..end]
-                .iter()
-                .rev()
-                .take_while(|&&b| b == b'\\')
-                .count();
-            if trailing_bs % 2 == 1
-                && let Some(&after) = self.source.as_bytes().get(end)
-                && (after == b'{' || after == b'}')
-            {
-                let result = warn_invalid_escape_sequence(
-                    self.source,
-                    InvalidEscape::Char {
-                        ch: after as char,
-                        offset: end - 1,
-                    },
-                    self.filename,
-                    self.vm,
-                );
-                self.record_warning(result);
-            }
+            collect_fstring_literal_warning(
+                self.source,
+                range.start().to_usize(),
+                range.end().to_usize(),
+                self.warnings,
+            );
         }
 
         /// Visit f-string elements, checking literals and recursing into
         /// interpolation expressions and format specs.
-        fn visit_fstring_elements(&mut self, elements: &'a ast::InterpolatedStringElements) {
+        fn visit_fstring_elements(
+            &mut self,
+            elements: &'a ast::InterpolatedStringElements,
+            raw: bool,
+        ) {
             for element in elements {
-                if self.error.is_some() {
-                    return;
-                }
                 match element {
                     ast::InterpolatedStringElement::Literal(lit) => {
-                        self.check_fstring_literal(lit.range);
+                        if !raw {
+                            self.check_fstring_literal(lit.range);
+                        }
                     }
                     ast::InterpolatedStringElement::Interpolation(interp) => {
                         self.visit_expr(&interp.expression);
                         if let Some(spec) = &interp.format_spec {
-                            self.visit_fstring_elements(&spec.elements);
+                            self.visit_fstring_elements(&spec.elements, raw);
                         }
                     }
                 }
@@ -1476,11 +1592,8 @@ mod escape_warnings {
         }
     }
 
-    impl<'a> Visitor<'a> for EscapeWarningVisitor<'a> {
+    impl<'a> Visitor<'a> for EscapeWarningVisitor<'a, '_> {
         fn visit_expr(&mut self, expr: &'a ast::Expr) {
-            if self.error.is_some() {
-                return;
-            }
             match expr {
                 // Regular string literals — decode_unicode_with_escapes path
                 ast::Expr::StringLiteral(string) => {
@@ -1506,9 +1619,9 @@ mod escape_warnings {
                 }
                 // F-string literals — tokenizer + string_parser paths
                 ast::Expr::FString(fstring_expr) => {
-                    for part in fstring_expr.value.as_slice() {
+                    for part in &fstring_expr.value {
                         match part {
-                            ast::FStringPart::Literal(string_lit) => {
+                            ast::FStringPartRef::Literal(string_lit) => {
                                 // Plain string part in f-string concatenation
                                 if !matches!(
                                     string_lit.flags.prefix(),
@@ -1517,18 +1630,31 @@ mod escape_warnings {
                                     self.check_quoted_literal(string_lit.range, false);
                                 }
                             }
-                            ast::FStringPart::FString(fstring) => {
-                                if matches!(
-                                    fstring.flags.prefix(),
-                                    ast::str_prefix::FStringPrefix::Raw { .. }
-                                ) {
+                            ast::FStringPartRef::FString(fstring) => {
+                                if !self.ast_only
+                                    && matches!(
+                                        fstring.flags.prefix(),
+                                        ast::str_prefix::FStringPrefix::Raw { .. }
+                                    )
+                                {
                                     continue;
                                 }
-                                self.visit_fstring_elements(&fstring.elements);
+                                self.visit_fstring_elements(
+                                    &fstring.elements,
+                                    matches!(
+                                        fstring.flags.prefix(),
+                                        ast::str_prefix::FStringPrefix::Raw { .. }
+                                    ),
+                                );
                             }
                         }
                     }
                 }
+                ast::Expr::TString(tstring) if self.ast_only => {
+                    for part in tstring.value.as_slice() {
+                        self.visit_fstring_elements(&part.elements, part.flags.prefix().is_raw());
+                    }
+                }
                 _ => {
                     if self.depth < self.depth_limit {
                         self.depth += 1;
@@ -1540,55 +1666,332 @@ mod escape_warnings {
         }
     }
 
+    fn collect_parser_warnings(
+        source: &str,
+        filename: &str,
+        mode: Option<ruff_python_parser::Mode>,
+        inherited_barry_as_flufl: bool,
+    ) -> (Vec<ParserWarning>, bool) {
+        let mut ast_tokenizer_recovery = true;
+        let mut warnings = Vec::new();
+        collect_numeric_literal_warnings(source, &mut warnings);
+        // The compile that follows rejects this source; parsing it here
+        // would build a tree that exhausts the stack when dropped.
+        let source_file = compiler::core::SourceFileBuilder::new(filename, source).finish();
+        if compiler::pre_parse_source_error(&source_file).is_ok()
+            && let Some(mode) = mode
+        {
+            let options = ruff_python_parser::ParseOptions::from(mode);
+            let barry_source = compiler::prepare_barry_as_flufl_source(
+                source,
+                options.clone(),
+                inherited_barry_as_flufl,
+            );
+            let parsed = ruff_python_parser::parse_unchecked(barry_source.source(), options);
+            if parsed.has_valid_syntax() {
+                let mut visitor = EscapeWarningVisitor {
+                    source,
+                    warnings: &mut warnings,
+                    ast_only: true,
+                    depth: 0,
+                    depth_limit: compiler::CompileOpts::default().recursion_limit,
+                };
+                match parsed.syntax() {
+                    ast::Mod::Module(module) => {
+                        for stmt in &module.body {
+                            visitor.visit_stmt(stmt);
+                        }
+                    }
+                    ast::Mod::Expression(expr) => visitor.visit_expr(&expr.body),
+                }
+            } else {
+                ast_tokenizer_recovery = false;
+                // The tokenizer can read the token at which parsing fails,
+                // but later recovered statements were never parsed by
+                // CPython and must not produce string/parser warnings.
+                let end = parsed
+                    .errors()
+                    .iter()
+                    // An unclosed-bracket diagnostic points back to its
+                    // opening token, not where parsing stopped. Other
+                    // errors retain that boundary; otherwise it was EOF.
+                    .filter(|error| {
+                        !matches!(
+                            error.error,
+                            ruff_python_parser::ParseErrorType::Lexical(
+                                ruff_python_parser::LexicalErrorType::UnclosedBracket { .. }
+                            )
+                        )
+                    })
+                    .min_by_key(|error| error.location.start())
+                    .map_or(source.len(), |error| {
+                        // Tokens after a complete statement or eval
+                        // expression were not decoded by CPython.
+                        if matches!(
+                            error.error,
+                            ruff_python_parser::ParseErrorType::SimpleStatementsOnSameLine
+                                | ruff_python_parser::ParseErrorType::UnexpectedExpressionToken
+                        ) {
+                            error.location.start().to_usize()
+                        } else {
+                            error.location.end().to_usize()
+                        }
+                    });
+                collect_string_escape_warnings_in_range(source, 0, end, None, &mut warnings);
+            }
+        } else if mode.is_none() && compiler::pre_parse_source_error(&source_file).is_ok() {
+            ast_tokenizer_recovery = false;
+            // Function-type input has a separate AST parser; its return
+            // expression follows an arrow that expression mode rejects.
+            // There are no import statements in this grammar.
+            collect_string_escape_warnings_in_range(source, 0, source.len(), None, &mut warnings);
+        }
+        warnings.sort_by_key(ParserWarning::offset);
+        // Interpolated tokenizer warnings have their own stop/error boundary.
+        // Numeric-only recovery must not skip across one of those events.
+        if warnings.iter().any(|warning| {
+            matches!(
+                warning,
+                ParserWarning::Escape(_, EscapeOrigin::Tokenizer, _)
+            )
+        }) {
+            ast_tokenizer_recovery = false;
+        }
+        (warnings, ast_tokenizer_recovery)
+    }
+
+    enum WarningEmission<'a> {
+        Standard { emitted_escapes: &'a [usize] },
+        Ast { tokenizer_recovery: bool },
+        Interactive(&'a mut super::InteractiveWarnings),
+    }
+
     impl VirtualMachine {
-        /// Emit tokenizer-level SyntaxWarnings raised before
-        /// code generation.
+        // Keep ordinary source compilation's existing warning order and
+        // recovery surface; interactive records use the bounded parser below.
         pub(super) fn emit_tokenizer_syntax_warnings(
             &self,
             source: &str,
             filename: &str,
+            module: Option<&Py<PyStr>>,
         ) -> Result<(), CompileWarningError> {
-            emit_numeric_literal_warnings(source, filename, self)
+            let mut warnings = Vec::new();
+            collect_numeric_literal_warnings(source, &mut warnings);
+            self.emit_parser_warning_batch(
+                source,
+                filename,
+                module,
+                warnings,
+                WarningEmission::Standard {
+                    emitted_escapes: &[],
+                },
+            )
+            .map(|_| ())
         }
 
-        /// Walk all string literals in `source` and emit `SyntaxWarning` for
-        /// each that contains an invalid escape sequence.
         pub(super) fn emit_string_escape_warnings(
             &self,
             source: &str,
             filename: &str,
+            module: Option<&Py<PyStr>>,
+            emitted_escapes: &[usize],
         ) -> Result<(), CompileWarningError> {
-            // The compile that follows rejects this source; parsing it here
-            // would build a tree that exhausts the stack when dropped.
             let source_file = compiler::core::SourceFileBuilder::new(filename, source).finish();
             if compiler::pre_parse_source_error(&source_file).is_err() {
                 return Ok(());
             }
-            let Ok(parsed) =
+            let mut warnings = Vec::new();
+            if let Ok(parsed) =
                 ruff_python_parser::parse(source, ruff_python_parser::Mode::Module.into())
-            else {
-                return emit_string_escape_warnings_unparsed(source, filename, self);
+            {
+                let mut visitor = EscapeWarningVisitor {
+                    source,
+                    warnings: &mut warnings,
+                    ast_only: false,
+                    depth: 0,
+                    depth_limit: compiler::CompileOpts::default().recursion_limit,
+                };
+                match parsed.syntax() {
+                    ast::Mod::Module(module) => {
+                        for stmt in &module.body {
+                            visitor.visit_stmt(stmt);
+                        }
+                    }
+                    ast::Mod::Expression(expr) => visitor.visit_expr(&expr.body),
+                }
+            } else {
+                collect_string_escape_warnings_in_range(
+                    source,
+                    0,
+                    source.len(),
+                    None,
+                    &mut warnings,
+                );
+            }
+            self.emit_parser_warning_batch(
+                source,
+                filename,
+                module,
+                warnings,
+                WarningEmission::Standard { emitted_escapes },
+            )
+            .map(|_| ())
+        }
+
+        pub(super) fn emit_ast_parser_warnings(
+            &self,
+            source: &str,
+            filename: &str,
+            module: Option<&Py<PyStr>>,
+            start: CompileStart,
+            inherited_barry_as_flufl: bool,
+        ) -> Result<Vec<usize>, CompileWarningError> {
+            let mode = match start {
+                CompileStart::Single | CompileStart::File => Some(ruff_python_parser::Mode::Module),
+                CompileStart::Eval => Some(ruff_python_parser::Mode::Expression),
+                CompileStart::FuncType => None,
             };
-            let ast = parsed.into_syntax();
-            let mut visitor = EscapeWarningVisitor {
+            let (warnings, recovery) =
+                collect_parser_warnings(source, filename, mode, inherited_barry_as_flufl);
+            self.emit_parser_warning_batch(
+                source,
+                filename,
+                module,
+                warnings,
+                WarningEmission::Ast {
+                    tokenizer_recovery: recovery
+                        && matches!(start, CompileStart::File | CompileStart::Eval),
+                },
+            )
+        }
+
+        /// Emit the tokenizer warnings for the interactive input read so far.
+        pub(in crate::vm) fn emit_interactive_parser_warnings(
+            &self,
+            source: &str,
+            filename: &str,
+            module: Option<&Py<PyStr>>,
+            inherited_barry_as_flufl: bool,
+            emitted: &mut super::InteractiveWarnings,
+        ) -> Result<(), CompileWarningError> {
+            let (warnings, _) = collect_parser_warnings(
+                source,
+                filename,
+                Some(ruff_python_parser::Mode::Module),
+                inherited_barry_as_flufl,
+            );
+            self.emit_parser_warning_batch(
                 source,
                 filename,
-                vm: self,
-                error: None,
-                depth: 0,
-                depth_limit: compiler::CompileOpts::default().recursion_limit,
+                module,
+                warnings,
+                WarningEmission::Interactive(emitted),
+            )
+            .map(|_| ())
+        }
+
+        fn emit_parser_warning_batch(
+            &self,
+            source: &str,
+            filename: &str,
+            module: Option<&Py<PyStr>>,
+            warnings: Vec<ParserWarning>,
+            emission: WarningEmission<'_>,
+        ) -> Result<Vec<usize>, CompileWarningError> {
+            let (emitted_escapes, ast_tokenizer_recovery, mut interactive) = match emission {
+                WarningEmission::Standard { emitted_escapes } => (emitted_escapes, false, None),
+                WarningEmission::Ast { tokenizer_recovery } => (&[][..], tokenizer_recovery, None),
+                WarningEmission::Interactive(emitted) => (&[][..], false, Some(emitted)),
             };
-            match &ast {
-                ast::Mod::Module(module) => {
-                    for stmt in &module.body {
-                        visitor.visit_stmt(stmt);
+            let mut considered_escapes = Vec::new();
+            let mut parser_error = None;
+            for warning in warnings {
+                // CPython resumes tokenization after a parser-origin SyntaxError.
+                // Preserve ordinary warning order and never replay prior warnings.
+                if parser_error.is_some() && !matches!(warning, ParserWarning::Numeric { .. }) {
+                    continue;
+                }
+                if let Some(state) = interactive.as_deref_mut() {
+                    let message = match &warning {
+                        ParserWarning::Escape(escape, ..) => escape.warning_message(),
+                        ParserWarning::Numeric { message, .. } => message.clone(),
+                    };
+                    if !state.emitted.insert((warning.offset(), message)) {
+                        continue;
                     }
                 }
-                ast::Mod::Expression(expr) => {
-                    visitor.visit_expr(&expr.body);
+                match warning {
+                    ParserWarning::Escape(escape, origin, error_column) => {
+                        let offset = escape.offset();
+                        if considered_escapes.last() == Some(&offset) {
+                            continue;
+                        }
+                        considered_escapes.push(offset);
+                        if emitted_escapes.binary_search(&offset).is_err() {
+                            let result = warn_invalid_escape_sequence(
+                                source, escape, filename, module, self,
+                            )
+                            .map_err(|mut error| {
+                                if interactive.is_some()
+                                    && let Some(column) = error_column
+                                {
+                                    error.offset = column;
+                                    if let Some(replacement) = &mut error.replacement {
+                                        replacement.end_offset = column + 2;
+                                    }
+                                }
+                                error
+                            });
+                            if let Err(error) = result {
+                                if ast_tokenizer_recovery
+                                    && origin == EscapeOrigin::Parser
+                                    && error
+                                        .exception
+                                        .fast_isinstance(self.ctx.exceptions.syntax_warning)
+                                {
+                                    parser_error = Some(error);
+                                } else {
+                                    return Err(error);
+                                }
+                            }
+                        }
+                    }
+                    ParserWarning::Numeric {
+                        offset,
+                        last_offset,
+                        message,
+                    } => {
+                        warn_syntax_at_offset(
+                            source,
+                            filename,
+                            module,
+                            if interactive.is_some() {
+                                last_offset
+                            } else {
+                                offset
+                            },
+                            message.clone(),
+                            self,
+                        )
+                        .map_err(|mut error| {
+                            // Tokenizer numeric warnings become a zero-width
+                            // error at the literal's last character, in character
+                            // columns rather than grammar-action byte columns.
+                            if interactive.is_some() {
+                                error.replacement = Some(SyntaxErrorReplacement {
+                                    message,
+                                    end_offset: error.offset,
+                                });
+                            }
+                            error
+                        })?;
+                    }
                 }
             }
-            visitor.error.map_or(Ok(()), Err)
+            if let Some(error) = parser_error {
+                return Err(error);
+            }
+            Ok(considered_escapes)
         }
     }
 
diff --git a/crates/vm/src/vm/context.rs b/crates/vm/src/vm/context.rs
index 78e6bc6fef8..56fa65feb10 100644
--- a/crates/vm/src/vm/context.rs
+++ b/crates/vm/src/vm/context.rs
@@ -659,19 +659,12 @@ impl Context {
     where
         F: IntoPyNativeFn<FKind>,
     {
-        let def = PyMethodDef {
+        let payload = HeapMethodDef::with_owned_function(
             name,
-            func: Box::leak(Box::new(f.into_func())),
-            flags,
-            #[cfg(feature = "doc")]
-            doc_off: doc.offset,
-            #[cfg(feature = "doc")]
-            doc_len: doc.len,
-            #[cfg(feature = "doc")]
-            doc_body_pending: false,
-            doc: doc.text,
-        };
-        let payload = HeapMethodDef::new(def);
+            Box::new(f.into_func()),
+            flags.with_call_convention(F::ARGS),
+            doc,
+        );
         PyRef::new_ref(payload, self.types.method_def.to_owned(), None)
     }
 
diff --git a/crates/vm/src/vm/crossinterp.rs b/crates/vm/src/vm/crossinterp.rs
index 2b799bf0031..1fb46a64356 100644
--- a/crates/vm/src/vm/crossinterp.rs
+++ b/crates/vm/src/vm/crossinterp.rs
@@ -15,7 +15,7 @@ use crate::{
     },
     bytecode::{
         BorrowedConstant, CodeFlags, Constant, Instruction,
-        oparg::{OpArg, OpArgState},
+        oparg::{CommonConstant, OpArg, OpArgState},
     },
     protocol::PyBuffer,
 };
@@ -227,7 +227,7 @@ impl SharedValue {
                 t.as_slice()
                     .iter()
                     .map(|item| {
-                        vm.with_recursion("while sharing a tuple", || {
+                        vm.with_recursion(" while sharing a tuple", || {
                             Self::from_object(item, fallback, vm)
                         })
                     })
@@ -340,7 +340,7 @@ impl SharedValue {
                 // Stateless functions have no globals, so `__main__` is used,
                 // just like for builtins such as exec().
                 let globals = vm.main_namespace()?;
-                Ok(PyFunction::new(code, globals, vm)?.into_pyobject(vm))
+                Ok(PyFunction::new(code, globals.into(), vm)?.into_pyobject(vm))
             }
             Self::Pickled(data) => pickle_loads(&data, vm),
         }
@@ -763,7 +763,12 @@ pub(crate) fn walk_instructions(
 
 /// `_PyFunction_VerifyStateless`.
 fn verify_stateless_function(func: &Py<PyFunction>, vm: &VirtualMachine) -> PyResult<()> {
-    // `__globals__` is a dict by construction, so only the builtins are checked.
+    let globals = func.globals.as_mutable().ok_or_else(|| {
+        vm.new_type_error(format!(
+            "unsupported globals {}",
+            render_repr(func.globals.as_object(), vm)
+        ))
+    })?;
     let builtins = func.builtins.downcast_ref::<PyDict>().ok_or_else(|| {
         vm.new_type_error(format!(
             "unsupported builtins {}",
@@ -786,7 +791,7 @@ fn verify_stateless_function(func: &Py<PyFunction>, vm: &VirtualMachine) -> PyRe
     {
         return Err(vm.new_value_error("closures not supported"));
     }
-    verify_stateless(&func.code, Some((&func.globals, builtins)), vm)
+    verify_stateless(&func.code, Some((globals, builtins)), vm)
 }
 
 /// `verify_script`: a script takes no arguments and returns only None.
@@ -824,42 +829,26 @@ pub(crate) fn code_returns_only_none(code: &Py<PyCode>) -> bool {
         return false;
     }
     let units = &code.instructions;
-    let Some(last) = units.len().checked_sub(1) else {
-        return true;
-    };
-    // The last instruction either returns or raises. We can take advantage
-    // of that for a quick exit.
-    let final_op = units.read_op(last).deoptimize();
-
     // Look up None in co_consts.
-    let Some(none_index) = code
+    let none_index = code
         .constants
         .iter()
-        .position(|c| matches!(c.borrow_constant(), BorrowedConstant::None))
-    else {
-        // None wasn't there, which means there was no implicit return,
-        // "return", or "return None".
-
-        // That means there must be an explicit return (non-None), or it only
-        // raises.
-        if matches!(final_op, Instruction::ReturnValue) {
-            // It was an explicit return (non-None).
-            return false;
-        }
-        // It must end with a raise then. We still have to walk the bytecode
-        // to see if there's any explicit return (non-None).
-        return !walk_instructions(code).any(|(_, op, _)| matches!(op, Instruction::ReturnValue));
-    };
-    // Walk the bytecode, looking for RETURN_VALUE.
+        .position(|c| matches!(c.borrow_constant(), BorrowedConstant::None));
+    // We don't worry about EXTENDED_ARG for now.
     for (at, op, _) in walk_instructions(code) {
         if !matches!(op, Instruction::ReturnValue) {
             continue;
         }
-        // Ignore it if it returns None.
-        if let Some(prev) = at.checked_sub(1)
-            && matches!(units.read_op(prev).deoptimize(), Instruction::LoadConst { .. })
-            // We don't worry about EXTENDED_ARG for now.
-            && usize::from(u8::from(units.read_arg(prev))) == none_index
+        debug_assert_ne!(at, 0);
+        let prev_op = units.read_op(at - 1).deoptimize();
+        let prev_arg = u32::from(u8::from(units.read_arg(at - 1)));
+        if matches!(prev_op, Instruction::LoadCommonConstant { .. })
+            && prev_arg == u32::from(CommonConstant::None)
+        {
+            continue;
+        }
+        if matches!(prev_op, Instruction::LoadConst { .. })
+            && none_index.is_some_and(|none_index| prev_arg as usize == none_index)
         {
             continue;
         }
@@ -943,16 +932,7 @@ where
         ));
     }
 
-    if state
-        .running_main
-        .compare_exchange(
-            false,
-            true,
-            core::sync::atomic::Ordering::AcqRel,
-            core::sync::atomic::Ordering::Acquire,
-        )
-        .is_err()
-    {
+    if !state.set_running_main() {
         return Err(crate::stdlib::_interpreters::interpreter_error(
             caller,
             "interpreter already running",
@@ -962,9 +942,7 @@ where
     struct RunningGuard<'a>(&'a crate::vm::PyGlobalState);
     impl Drop for RunningGuard<'_> {
         fn drop(&mut self) {
-            self.0
-                .running_main
-                .store(false, core::sync::atomic::Ordering::Release);
+            self.0.set_not_running_main();
         }
     }
     let _guard = RunningGuard(&state);
@@ -976,6 +954,5 @@ where
 
 #[must_use]
 pub fn is_running(id: i64) -> bool {
-    crate::vm::runtime::lookup_interpreter(id)
-        .is_some_and(|s| s.is_main || s.running_main.load(core::sync::atomic::Ordering::Acquire))
+    crate::vm::runtime::lookup_interpreter(id).is_some_and(|s| s.is_running_main())
 }
diff --git a/crates/vm/src/vm/interpreter.rs b/crates/vm/src/vm/interpreter.rs
index 75f31574d5c..6fa735c1659 100644
--- a/crates/vm/src/vm/interpreter.rs
+++ b/crates/vm/src/vm/interpreter.rs
@@ -74,7 +74,7 @@ where
     use crate::codecs::CodecsRegistry;
     use crate::common::lock::PyMutex;
     use crate::warn::WarningsState;
-    use core::sync::atomic::{AtomicBool, AtomicI64, AtomicU64};
+    use core::sync::atomic::{AtomicBool, AtomicI64, AtomicU64, AtomicUsize};
     use crossbeam_utils::atomic::AtomicCell;
 
     // Before any lock this interpreter's threads can contend on exists.
@@ -84,8 +84,10 @@ where
     let (config, all_module_defs, frozen, int_max_str_digits) = if let Some(parent) = parent_state {
         // Subinterpreter: clone config and module tables from parent, fresh runtime state.
         let int_max_str_digits = AtomicCell::new(parent.int_max_str_digits.load());
+        let mut config = parent.config.clone();
+        config.settings.inspect = parent.inspect.load(Ordering::Relaxed);
         (
-            parent.config.clone(),
+            config,
             parent.module_defs.clone(),
             parent.frozen.clone(),
             int_max_str_digits,
@@ -133,6 +135,7 @@ where
     // Per-interpreter ephemeral state (must not be shared across interpreters).
     let codec_registry = CodecsRegistry::new(&ctx);
     let warnings = WarningsState::init_state(&ctx);
+    let lazy_imports = crate::lazy_import::LazyImportsState::new(&ctx);
 
     let interpreter_id = runtime::alloc_interpreter_id();
     let runtime_root_id = parent_state.map_or(interpreter_id, |parent| parent.runtime_root_id);
@@ -153,6 +156,8 @@ where
         runtime_root_id,
         whence,
         is_main,
+        inspect: AtomicBool::new(config.settings.inspect),
+        interactive_src_count: AtomicUsize::new(0),
         config,
         module_defs: all_module_defs,
         frozen,
@@ -161,6 +166,8 @@ where
         atexit_funcs: PyMutex::default(),
         audit_hooks: PyMutex::default(),
         codec_registry,
+        import_time_header: AtomicBool::new(false),
+        lazy_imports,
         struct_format_cache: crate::buffer::FormatSpecCache::default(),
         finalizing: AtomicBool::new(false),
         #[cfg(feature = "threading")]
@@ -175,6 +182,7 @@ where
         global_trace_func: PyMutex::default(),
         global_profile_func: PyMutex::default(),
         type_mutex: PyMutex::default(),
+        common_type_descriptors: crate::builtins::type_::CommonTypeDescriptors::new(&ctx),
         #[cfg(feature = "threading")]
         main_thread_ident,
         #[cfg(feature = "threading")]
@@ -190,7 +198,7 @@ where
         stop_the_world: StopTheWorldState::new(),
         feature_flags,
         own_gil,
-        running_main: AtomicBool::new(false),
+        running_main: AtomicCell::new(None),
         ready: AtomicBool::new(false),
         id_refcount: AtomicI64::new(0),
         require_idref: AtomicBool::new(false),
@@ -268,6 +276,7 @@ fn create_subinterpreter_from_parent(
     // Every interpreter has a `__main__` module once it is initialized.
     interp.enter(|vm| {
         let _ = vm.ensure_main_module();
+        vm.apply_startup_lazy_imports();
     });
     Ok(interp)
 }
@@ -583,6 +592,24 @@ impl Interpreter {
         self.vm.new_thread()
     }
 
+    /// Move the main execution context into a separate owner, leaving this
+    /// handle available to create worker VMs for the same interpreter.
+    ///
+    /// The returned interpreter must run and finalize on the original thread.
+    /// This handle should only create worker VMs and must not be finalized.
+    /// Unlike `new_thread()`, this preserves the main VM's signal handlers and
+    /// all of its other thread-local state.
+    #[cfg(feature = "threading")]
+    #[must_use]
+    pub fn take_main_thread(&mut self) -> Self {
+        let replacement = self.vm.new_thread().vm;
+        let vm = core::mem::replace(&mut self.vm, replacement);
+        Self {
+            global_state: self.global_state.clone(),
+            vm,
+        }
+    }
+
     /// Run a function with the main virtual machine and return a PyResult of the result.
     ///
     /// To enter vm context multiple times or to avoid buffer/exception management, this function is preferred.
@@ -631,6 +658,25 @@ impl Interpreter {
         self.finalize(res.err())
     }
 
+    /// Py_RunMain
+    ///
+    /// Run a function that reports its own errors and returns the exit code,
+    /// then finalize with that exit code. An unhandled `KeyboardInterrupt`
+    /// exits through the default SIGINT handler instead.
+    pub fn run_main<F>(self, f: F) -> u32
+    where
+        F: FnOnce(&VirtualMachine) -> u32,
+    {
+        crate::signal::clear_unhandled_keyboard_interrupt();
+        let exit_code = self.enter(f);
+        let exit_code = self.finalize_with_exit_code(exit_code);
+        if crate::signal::unhandled_keyboard_interrupt() {
+            crate::signal::exit_sigint()
+        } else {
+            exit_code
+        }
+    }
+
     /// Finalize vm and turns an exception to exit code.
     ///
     /// Finalization steps (matching Py_FinalizeEx):
@@ -646,93 +692,122 @@ impl Interpreter {
     ///
     /// Note that calling `finalize` is not necessary by purpose though.
     pub fn finalize(self, exc: Option<PyBaseExceptionRef>) -> u32 {
+        self.finalize_inner(|vm| exc.map_or(0, |exc| vm.handle_exit_exception(exc)))
+    }
+
+    /// Finalize vm with an exit code the caller has already determined.
+    ///
+    /// See [`Interpreter::finalize`] for the finalization steps.
+    pub fn finalize_with_exit_code(self, exit_code: u32) -> u32 {
+        self.finalize_inner(|_| exit_code)
+    }
+
+    fn finalize_inner(self, exit_code: impl FnOnce(&VirtualMachine) -> u32) -> u32 {
         self.enter(|vm| {
-            let mut flush_status = vm.flush_std();
+            let flush_status = vm.flush_std();
 
             // See if any exception leaked out:
-            let exit_code = if let Some(exc) = exc {
-                vm.handle_exit_exception(exc)
+            let exit_code = exit_code(vm);
+
+            // Match CPython: if exit_code is 0 and stdout flush failed, exit 120
+            if vm.finalize_ex(flush_status) < 0 && exit_code == 0 {
+                EXITCODE_FLUSH_FAILURE
             } else {
-                0
-            };
-
-            // Wait for thread shutdown - call threading._shutdown() if available.
-            // This waits for all non-daemon threads to complete.
-            // threading module may not be imported, so ignore import errors.
-            #[cfg(feature = "threading")]
-            if let Ok(threading) = vm.import("threading", 0)
-                && let Ok(shutdown) = threading.get_attr("_shutdown", vm)
-                && let Err(e) = shutdown.call((), vm)
-            {
-                vm.run_unraisable(
-                    e,
-                    Some("Exception ignored in threading shutdown".to_owned()),
-                    threading,
-                );
+                exit_code
             }
+        })
+    }
+}
 
-            // Run atexit handlers before setting finalizing flag.
-            // This allows unraisable exceptions from atexit handlers to be reported.
-            atexit::_run_exitfuncs(vm);
-
-            // Clean up any lingering subinterpreters. This has to happen before
-            // the finalizing flag is set, or else threads might get prematurely
-            // blocked.
-            #[cfg(feature = "threading")]
-            finalize_subinterpreters(vm);
-
-            // Remaining daemon threads hang in `_PyThreadState_HangThread` when
-            // they next attach (or at the eval-breaker if they are already
-            // running). Their `_ThreadHandle` stays not-done so `is_alive()`
-            // is still true for `join()` during the GC that follows.
-            #[cfg(feature = "threading")]
-            {
-                vm.state.stop_the_world.stop_the_world(&vm.state);
-                vm.state
-                    .finalizing_thread_ident
-                    .store(crate::stdlib::_thread::get_ident());
-            }
-            vm.state.finalizing.store(true, Ordering::Release);
-            #[cfg(feature = "threading")]
-            {
-                thread::set_other_threads_shutting_down(&vm.state);
-                vm.state.stop_the_world.start_the_world(&vm.state);
-                crate::signal::set_finalizing_bit();
-            }
+impl VirtualMachine {
+    /// Py_Exit
+    ///
+    /// Finalize the interpreter and exit the process with `status`.
+    pub fn exit_process(&self, status: u32) -> ! {
+        if self.state.thread_is_running_main() {
+            self.state.set_not_running_main();
+        }
+        let status = if self.finalize_ex(self.flush_std()) < 0 {
+            EXITCODE_FLUSH_FAILURE
+        } else {
+            status
+        };
+        crate::host_env::os::exit(status as i32)
+    }
 
-            // GC pass - collect cycles before module cleanup
-            vm.state.gc.collect_force(2);
+    /// The steps of Py_FinalizeEx after the first flush of stdout and stderr.
+    /// Return a negative value if any flush failed.
+    fn finalize_ex(&self, mut flush_status: i32) -> i32 {
+        let vm = self;
+        // Wait for thread shutdown - call threading._shutdown() if available.
+        // This waits for all non-daemon threads to complete.
+        // threading module may not be imported, so ignore import errors.
+        #[cfg(feature = "threading")]
+        if let Ok(threading) = vm.import("threading", 0)
+            && let Ok(shutdown) = threading.get_attr("_shutdown", vm)
+            && let Err(e) = shutdown.call((), vm)
+        {
+            vm.run_unraisable(
+                e,
+                Some("Exception ignored in threading shutdown".to_owned()),
+                threading,
+            );
+        }
 
-            // Module finalization: remove modules from sys.modules, GC collect
-            // (while builtins is still available for __del__), then clear module dicts.
-            vm.finalize_modules();
+        // Run atexit handlers before setting finalizing flag.
+        // This allows unraisable exceptions from atexit handlers to be reported.
+        atexit::_run_exitfuncs(vm);
 
-            // CPython clears low-level cross-interpreter container data from
-            // _PyAtExit_Fini(), after Python atexit callbacks and module
-            // finalization.  In particular, values sent by an atexit callback
-            // must also become unbound when this interpreter goes away.
-            let interpreter_id = vm.state.interpreter_id;
-            crate::stdlib::_interpchannels::clear_interpreter(interpreter_id);
-            crate::stdlib::_interpqueues::clear_interpreter(interpreter_id);
+        // Clean up any lingering subinterpreters. This has to happen before
+        // the finalizing flag is set, or else threads might get prematurely
+        // blocked.
+        #[cfg(feature = "threading")]
+        finalize_subinterpreters(vm);
 
-            if vm.flush_std() < 0 && flush_status == 0 {
-                flush_status = -1;
-            }
+        // Remaining daemon threads hang in `_PyThreadState_HangThread` when
+        // they next attach (or at the eval-breaker if they are already
+        // running). Their `_ThreadHandle` stays not-done so `is_alive()`
+        // is still true for `join()` during the GC that follows.
+        #[cfg(feature = "threading")]
+        {
+            vm.state.stop_the_world.stop_the_world(&vm.state);
+            vm.state
+                .finalizing_thread_ident
+                .store(crate::stdlib::_thread::get_ident());
+        }
+        vm.state.finalizing.store(true, Ordering::Release);
+        #[cfg(feature = "threading")]
+        {
+            thread::set_other_threads_shutting_down(&vm.state);
+            vm.state.stop_the_world.start_the_world(&vm.state);
+            crate::signal::set_finalizing_bit();
+        }
 
-            // Match CPython: if exit_code is 0 and stdout flush failed, exit 120
-            let exit_code = if exit_code == 0 && flush_status < 0 {
-                EXITCODE_FLUSH_FAILURE
-            } else {
-                exit_code
-            };
+        // GC pass - collect cycles before module cleanup
+        vm.state.gc.collect_force(2);
 
-            // Daemon threads may still exist, so use the safe `process()`,
-            // not `drain_all()`.
-            #[cfg(feature = "threading")]
-            crate::object::qsbr::QSBR.process();
+        // Module finalization: remove modules from sys.modules, GC collect
+        // (while builtins is still available for __del__), then clear module dicts.
+        vm.finalize_modules();
 
-            exit_code
-        })
+        // CPython clears low-level cross-interpreter container data from
+        // _PyAtExit_Fini(), after Python atexit callbacks and module
+        // finalization.  In particular, values sent by an atexit callback
+        // must also become unbound when this interpreter goes away.
+        let interpreter_id = vm.state.interpreter_id;
+        crate::stdlib::_interpchannels::clear_interpreter(interpreter_id);
+        crate::stdlib::_interpqueues::clear_interpreter(interpreter_id);
+
+        if vm.flush_std() < 0 && flush_status == 0 {
+            flush_status = -1;
+        }
+
+        // Daemon threads may still exist, so use the safe `process()`,
+        // not `drain_all()`.
+        #[cfg(feature = "threading")]
+        crate::object::qsbr::QSBR.process();
+
+        flush_status
     }
 }
 
diff --git a/crates/vm/src/vm/mod.rs b/crates/vm/src/vm/mod.rs
index 445ff7474a0..6e1a74a2242 100644
--- a/crates/vm/src/vm/mod.rs
+++ b/crates/vm/src/vm/mod.rs
@@ -14,6 +14,8 @@ mod interpreter;
 mod method;
 #[cfg(feature = "rustpython-compiler")]
 mod python_run;
+#[cfg(feature = "rustpython-compiler")]
+pub use python_run::InteractiveLine;
 pub mod runtime;
 mod setting;
 pub mod thread;
@@ -24,7 +26,7 @@ mod vm_ops;
 use crate::{
     AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult,
     builtins::{
-        self, PyBaseExceptionRef, PyBaseObject, PyDict, PyDictRef, PyFrozenSet, PyInt, PyList,
+        self, PyAnyDict, PyBaseExceptionRef, PyBaseObject, PyDict, PyFrozenSet, PyInt, PyList,
         PyModule, PySet, PyStr, PyStrInterned, PyStrRef, PyTypeRef, PyUtf8Str, PyUtf8StrInterned,
         PyWeak,
         code::PyCode,
@@ -44,7 +46,7 @@ use crate::{
     scope::Scope,
     signal::{self, SignalHandlers},
     stdlib,
-    types::{GetattroFunc, fn_addr},
+    types::{GetAttr, GetattroFunc, fn_addr},
     warn::WarningsState,
 };
 use alloc::{borrow::Cow, collections::BTreeMap};
@@ -52,7 +54,7 @@ use alloc::{borrow::Cow, collections::BTreeMap};
 use core::ptr::NonNull;
 use core::{
     cell::{Cell, OnceCell, RefCell},
-    sync::atomic::{AtomicBool, AtomicI64, AtomicU64, Ordering},
+    sync::atomic::{AtomicBool, AtomicI64, AtomicU64, AtomicUsize, Ordering},
 };
 use crossbeam_utils::atomic::AtomicCell;
 use std::{
@@ -93,6 +95,7 @@ pub struct VirtualMachine {
     exceptions: RefCell<ExceptionStack>,
     pub import_func: PyObjectRef,
     pub(crate) importlib: PyObjectRef,
+    pub(crate) import_timing: Cell<import::ImportTimingState>,
     pub profile_func: RefCell<PyObjectRef>,
     pub trace_func: RefCell<PyObjectRef>,
     pub use_tracing: Cell<bool>,
@@ -104,6 +107,7 @@ pub struct VirtualMachine {
     pub(crate) signal_handlers: OnceCell<SignalHandlers>,
     pub(crate) signal_rx: Option<signal::UserSignalReceiver>,
     pub repr_guards: RefCell<HashSet<usize>>,
+    pub(crate) lazy_imports_resolving: RefCell<HashSet<usize>>,
     pub state: PyRc<PyGlobalState>,
     pub initialized: bool,
     recursion_depth: Cell<usize>,
@@ -189,6 +193,68 @@ impl Default for ExceptionStack {
     }
 }
 
+/// Serializes complete stop/restart transactions across interpreters.
+/// A collector holds one permit while stopping every interpreter; other callers
+/// transfer their permit to the stopped state until the matching restart.
+#[cfg(feature = "threading")]
+pub(crate) struct StopTheWorldTransaction {
+    _private: (),
+}
+
+#[cfg(feature = "threading")]
+static STW_TRANSACTION: AtomicU64 = AtomicU64::new(0);
+
+#[cfg(feature = "threading")]
+static NEXT_STW_REQUESTER: AtomicU64 = AtomicU64::new(1);
+
+#[cfg(feature = "threading")]
+thread_local! {
+    // OS thread IDs can be reused after a requester exits, even while another
+    // thread still owes its matching restart. Logical IDs are never reused.
+    static STW_REQUESTER: u64 = NEXT_STW_REQUESTER
+        .try_update(Ordering::Relaxed, Ordering::Relaxed, |id| id.checked_add(1))
+        .expect("stop-the-world requester IDs exhausted");
+}
+
+#[cfg(feature = "threading")]
+impl StopTheWorldTransaction {
+    pub(crate) fn acquire() -> Self {
+        let requester = STW_REQUESTER.with(|id| *id);
+        loop {
+            match STW_TRANSACTION.compare_exchange(
+                0,
+                requester,
+                Ordering::AcqRel,
+                Ordering::Relaxed,
+            ) {
+                Ok(_) => return Self { _private: () },
+                Err(owner) => assert_ne!(
+                    owner, requester,
+                    "stop-the-world transactions cannot be nested on the same thread"
+                ),
+            }
+            let wait = || {
+                while STW_TRANSACTION.load(Ordering::Acquire) != 0 {
+                    std::thread::yield_now();
+                }
+            };
+            // Wait detached from the CURRENT interpreter, not the interpreter
+            // we intend to stop. Reattach without owning the permit, then retry:
+            // a suspended or shutting-down waiter must not strand ownership.
+            if thread::try_with_current_vm(|vm| vm.allow_threads(wait)).is_none() {
+                wait();
+            }
+        }
+    }
+}
+
+#[cfg(feature = "threading")]
+impl Drop for StopTheWorldTransaction {
+    fn drop(&mut self) {
+        STW_TRANSACTION.store(0, Ordering::Release);
+    }
+}
+
 /// Stop-the-world state for fork safety. Before `fork()`, the requester
 /// stops all other Python threads so they are not holding internal locks.
 #[cfg(feature = "threading")]
@@ -199,10 +265,9 @@ pub struct StopTheWorldState {
     world_stopped: AtomicBool,
     /// Ident of the thread that requested the stop (like `stw->requester`)
     requester: AtomicU64,
-    /// Single exclusion held for the whole stop→start span. Fork and GC are
-    /// both stop-the-world requesters driving this shared state; only one may
-    /// hold it at a time. Acquired before any stop bookkeeping (see
-    /// `acquire_exclusion`) and released by `start_the_world`/`reset_after_fork`.
+    /// Ownership transferred by a successful public stop. GC retains its
+    /// transaction externally and leaves this false. Only a matching restart
+    /// or the forking owner's child reset may release this ownership.
     exclusion: AtomicBool,
     /// Signaled by suspending threads when their state transitions to SUSPENDED
     notify_mutex: std::sync::Mutex<()>,
@@ -401,50 +466,11 @@ impl StopTheWorldState {
         forced_parks != 0 && self.thread_countdown.load(Ordering::Acquire) == 0
     }
 
-    /// Acquire the single stop-the-world exclusion in a park-friendly way.
-    ///
-    /// Fork and GC both request stop-the-world through the same shared state;
-    /// without this exclusion their `requester`/`requested`/countdown words
-    /// could be clobbered by an interleaving requester, so the completion
-    /// check could never converge and a requester would wait on itself forever.
-    ///
-    /// The acquire must be park-friendly. While another requester's stop is in
-    /// progress it sets this thread's stop bit and waits for it to suspend;
-    /// blocking on a plain lock here would keep this thread from ever reaching
-    /// that safepoint, so the active requester would wait for this thread while
-    /// this thread waits for the lock — a deadlock swap. Instead we poll and
-    /// honor the suspend request between tries. Suspending here is safe as long
-    /// as any lock a spinning requester still holds is never acquired
-    /// attached-blocking by another thread. The fork requester holds IMP_LOCK,
-    /// but its acquisition detaches (`allow_threads`), so no attached thread
-    /// blocks on it; the GC requester holds only the `collecting` mutex, which
-    /// is only ever `try_lock`'d. The active requester therefore force-parks
-    /// this thread, finishes its whole stop→start span, releases the exclusion,
-    /// and only then does this thread resume and acquire it.
-    fn acquire_exclusion(&self, state: &PyGlobalState) {
-        if self
-            .exclusion
-            .compare_exchange(false, true, Ordering::AcqRel, Ordering::Relaxed)
-            .is_ok()
-        {
-            return;
-        }
-        loop {
-            crate::vm::thread::suspend_if_needed(state);
-            std::thread::yield_now();
-            if self
-                .exclusion
-                .compare_exchange(false, true, Ordering::AcqRel, Ordering::Relaxed)
-                .is_ok()
-            {
-                return;
-            }
-        }
-    }
-
-    /// Release the stop-the-world exclusion taken by `acquire_exclusion`.
+    /// Release only a transaction owned by this state, after every wake/clear.
     fn release_exclusion(&self) {
-        self.exclusion.store(false, Ordering::Release);
+        if self.exclusion.swap(false, Ordering::AcqRel) {
+            drop(StopTheWorldTransaction { _private: () });
+        }
     }
 
     /// Stop all non-requester threads (`stop_the_world`).
@@ -454,11 +480,27 @@ impl StopTheWorldState {
     /// 3. Waits (polling with 1 ms condvar timeout) for attached threads
     ///    to self-suspend in `check_signals`.
     ///
-    /// Takes the shared exclusion first so at most one requester (fork or GC)
-    /// drives the stop→start span at a time; it is released by
-    /// `start_the_world`/`reset_after_fork`.
+    /// Public calls own one process-wide transaction until the matching start.
+    /// The caller must finish stop before invoking start, including when those
+    /// calls occur on different threads; concurrent duplicate starts are invalid.
+    /// Transactions are non-reentrant: a nested stop on the requesting thread
+    /// panics before changing any stop state or releasing the outer transaction.
     pub fn stop_the_world(&self, state: &PyGlobalState) {
-        self.acquire_exclusion(state);
+        let transaction = StopTheWorldTransaction::acquire();
+        self.stop_with_transaction(state, &transaction);
+        self.exclusion.store(true, Ordering::Release);
+        core::mem::forget(transaction);
+    }
+
+    /// Stop one state within a transaction retained by the caller (notably GC).
+    pub(crate) fn stop_with_transaction(
+        &self,
+        state: &PyGlobalState,
+        _transaction: &StopTheWorldTransaction,
+    ) {
+        // A partial stop must clear requests and wake parked slots before its
+        // caller releases the transaction or rolls back previously stopped VMs.
+        let rollback = scopeguard::guard((), |_| self.resume_threads(state, false));
         let start = std::time::Instant::now();
         let requester_ident = crate::stdlib::_thread::get_ident();
         self.requester.store(requester_ident, Ordering::Relaxed);
@@ -478,6 +520,7 @@ impl StopTheWorldState {
             stw_trace(format_args!(
                 "stop end requester={requester_ident} wait_ns=0 polls=0"
             ));
+            scopeguard::ScopeGuard::into_inner(rollback);
             return;
         }
 
@@ -526,10 +569,17 @@ impl StopTheWorldState {
         stw_trace(format_args!(
             "stop end requester={requester_ident} wait_ns={wait_ns} polls={polls}"
         ));
+        scopeguard::ScopeGuard::into_inner(rollback);
     }
 
     /// Resume all suspended threads (`start_the_world`).
     pub fn start_the_world(&self, state: &PyGlobalState) {
+        self.resume_threads(state, true);
+        self.release_exclusion();
+    }
+
+    /// Rollback also permits threads that never reached SUSPENDED.
+    fn resume_threads(&self, state: &PyGlobalState, fully_stopped: bool) {
         use thread::ThreadState;
         let requester = self.requester.load(Ordering::Relaxed);
         stw_trace(format_args!("start begin requester={requester}"));
@@ -560,7 +610,7 @@ impl StopTheWorldState {
                 continue;
             }
             debug_assert!(
-                state == ThreadState::Suspended as i32,
+                !fully_stopped || state == ThreadState::Suspended as i32,
                 "non-requester thread not suspended at start-the-world: id={id} state={state}"
             );
             if state == ThreadState::Suspended as i32 {
@@ -579,9 +629,6 @@ impl StopTheWorldState {
         crate::signal::clear_stop_bit();
         #[cfg(debug_assertions)]
         self.debug_assert_all_non_requester_detached(state);
-        // Release the exclusion last, ending the stop→start span so the next
-        // requester (fork or GC) can proceed.
-        self.release_exclusion();
         stw_trace(format_args!("start end requester={requester}"));
     }
 
@@ -595,8 +642,9 @@ impl StopTheWorldState {
         // Only one thread survives fork; any stop-the-world bit inherited
         // from the parent is stale.
         crate::signal::clear_stop_bit();
-        // The surviving child thread inherited the exclusion taken by the
-        // pre-fork `stop_the_world`; release it (no start_the_world runs here).
+        // before_fork owns the sole transaction. Release it exactly once via
+        // that state's ownership flag; resetting other interpreters must not
+        // release a later transaction. No unconditional global reset is needed.
         self.release_exclusion();
         stw_trace(format_args!("reset-after-fork"));
     }
@@ -813,6 +861,10 @@ pub struct PyGlobalState {
     /// becomes *the* process main — see [`runtime::main_interpreter_id`].
     pub is_main: bool,
     pub config: PyConfig,
+    /// `config.inspect`, which `PyConfig_Set` can change at runtime.
+    pub(crate) inspect: AtomicBool,
+    /// `_interactive_src_count`: numbers the code filenames of interactive inputs.
+    pub(crate) interactive_src_count: AtomicUsize,
     pub module_defs: BTreeMap<&'static str, &'static builtins::PyModuleDef>,
     pub frozen: HashMap<&'static str, FrozenModule, rapidhash::quality::RandomState>,
     pub stacksize: AtomicCell<usize>,
@@ -824,6 +876,8 @@ pub struct PyGlobalState {
     /// `sys.addaudithook` hooks, shared by all threads of this interpreter.
     pub(crate) audit_hooks: PyMutex<Vec<PyObjectRef>>,
     pub codec_registry: CodecsRegistry,
+    pub(crate) import_time_header: AtomicBool,
+    pub(crate) lazy_imports: crate::lazy_import::LazyImportsState,
     pub struct_format_cache: crate::buffer::FormatSpecCache,
     pub finalizing: AtomicBool,
     /// The thread performing finalization, which need not be the process main thread.
@@ -842,6 +896,8 @@ pub struct PyGlobalState {
     pub global_profile_func: PyMutex<Option<PyObjectRef>>,
     /// Global type mutation/versioning mutex for CPython-style FT type operations.
     pub type_mutex: PyMutex<()>,
+    /// Object-owned descriptors shared by heap types in this interpreter.
+    pub(crate) common_type_descriptors: builtins::type_::CommonTypeDescriptors,
     /// Main thread identifier (pthread_self on Unix)
     #[cfg(feature = "threading")]
     pub main_thread_ident: AtomicCell<u64>,
@@ -870,8 +926,8 @@ pub struct PyGlobalState {
     pub feature_flags: runtime::InterpFeatureFlags,
     /// Whether the interpreter was configured with `gil="own"`.
     pub own_gil: bool,
-    /// Whether `__main__` is currently executing via `_interpreters.exec` / `run_*`.
-    pub running_main: AtomicBool,
+    /// `threads.main`: the ident of the thread running `__main__`, if any.
+    pub running_main: AtomicCell<Option<u64>>,
     /// True after `initialize()` has finished (CPython "ready").
     pub ready: AtomicBool,
     /// Optional ID refcount used by `_interpreters.create(reqrefs=True)`.
@@ -911,6 +967,45 @@ impl PyGlobalState {
         self.feature_flags.allow_daemon_threads
     }
 
+    /// _PyInterpreterState_SetRunningMain
+    ///
+    /// Record the calling thread as the one running `__main__`. Return `false`
+    /// when a thread already does.
+    pub fn set_running_main(&self) -> bool {
+        self.running_main
+            .compare_exchange(None, Some(crate::frame::current_thread_ident()))
+            .is_ok()
+    }
+
+    /// _PyInterpreterState_SetNotRunningMain
+    pub fn set_not_running_main(&self) {
+        debug_assert!(self.thread_is_running_main());
+        self.running_main.store(None);
+    }
+
+    /// _PyInterpreterState_IsRunningMain
+    #[must_use]
+    pub fn is_running_main(&self) -> bool {
+        self.running_main.load().is_some()
+    }
+
+    /// _PyThreadState_IsRunningMain
+    #[must_use]
+    pub fn thread_is_running_main(&self) -> bool {
+        self.running_main.load() == Some(crate::frame::current_thread_ident())
+    }
+
+    /// _PyInterpreterState_ReinitRunningMain
+    ///
+    /// After a fork only the forking thread survives, so `__main__` is no
+    /// longer running unless that thread was running it.
+    #[cfg(all(feature = "host_env", unix))]
+    pub(crate) fn reinit_running_main(&self) {
+        if !self.thread_is_running_main() {
+            self.running_main.store(None);
+        }
+    }
+
     /// The config this interpreter was created with, rebuilt from the flags it
     /// kept (`_PyInterpreterConfig_InitFromState`).
     #[must_use]
@@ -1260,6 +1355,7 @@ impl VirtualMachine {
             exceptions: RefCell::default(),
             import_func,
             importlib,
+            import_timing: Cell::default(),
             profile_func,
             trace_func,
             use_tracing: Cell::new(false),
@@ -1269,6 +1365,7 @@ impl VirtualMachine {
             signal_handlers,
             signal_rx: None,
             repr_guards: RefCell::default(),
+            lazy_imports_resolving: RefCell::default(),
             state,
             initialized: false,
             recursion_depth: Cell::new(0),
@@ -1415,6 +1512,11 @@ impl VirtualMachine {
         drop(prewarmed_memory_errors);
 
         stdlib::builtins::init_module(self, &self.builtins);
+        // Explicit lazy imports can occur in frozen startup code.
+        let lazy_callback = self.builtins.get_attr("__lazy_import__", self);
+        let lazy_callback =
+            self.expect_pyresult(lazy_callback, "failed to initialize lazy imports");
+        let _ = self.state.lazy_imports.default_callback.set(lazy_callback);
         let callable_cache_init = self.init_callable_cache();
         self.expect_pyresult(callable_cache_init, "failed to initialize callable cache");
         stdlib::sys::init_module(self, &self.sys_module, &self.builtins);
@@ -1514,9 +1616,7 @@ impl VirtualMachine {
 
                 // No stdio: set to None (embedding use case)
                 #[cfg(not(feature = "stdio"))]
-                let make_stdio = |_name: &str, _fd: i32, _write: bool| {
-                    Ok(crate::builtins::PyNone.into_pyobject(self))
-                };
+                let make_stdio = |_name: &str, _fd: i32, _write: bool| Ok(self.ctx.none());
 
                 let set_stdio = |name, fd, write| {
                     let stdio: PyObjectRef = make_stdio(name, fd, write)?;
@@ -1581,6 +1681,14 @@ impl VirtualMachine {
         self.initialized = true;
     }
 
+    /// Apply configured global lazy imports after startup imports, including site.
+    /// Hosts that perform their own main-module setup can call this at that boundary.
+    pub fn apply_startup_lazy_imports(&self) {
+        if self.state.config.settings.lazy_imports == 1 {
+            self.state.lazy_imports.all.store(true, Ordering::Release);
+        }
+    }
+
     /// Set the custom signal channel for the interpreter
     pub fn set_user_signal_channel(&mut self, signal_rx: signal::UserSignalReceiver) {
         self.signal_rx = Some(signal_rx);
@@ -1609,7 +1717,7 @@ impl VirtualMachine {
     /// ```no_run
     /// use rustpython_vm::Interpreter;
     /// Interpreter::without_stdlib(Default::default()).enter(|vm| {
-    ///     let bytes = std::fs::read("__pycache__/<input>.rustpython-314.pyc").unwrap();
+    ///     let bytes = std::fs::read("__pycache__/<input>.rustpython-315.pyc").unwrap();
     ///     let main_scope = vm.new_scope_with_main().unwrap();
     ///     vm.run_pyc_bytes(&bytes, main_scope);
     /// });
@@ -1645,33 +1753,52 @@ impl VirtualMachine {
 
     #[cold]
     pub fn run_unraisable(&self, e: PyBaseExceptionRef, msg: Option<String>, object: PyObjectRef) {
-        // During interpreter finalization, sys.unraisablehook may not be available,
-        // but we still need to report exceptions (especially from atexit callbacks).
-        // Write directly to stderr like PyErr_FormatUnraisable.
-        if self.state.finalizing.load(Ordering::Acquire) {
+        let msg = msg.map(|msg| self.ctx.new_str(msg));
+        let write_original = || {
+            let msg = msg.as_ref().map(|msg| msg.to_string_lossy());
             self.write_unraisable_to_stderr(&e, msg.as_deref(), &object);
+        };
+        // During finalization the hook may no longer exist.
+        if self.state.finalizing.load(Ordering::Acquire) {
+            write_original();
             return;
         }
-
-        let sys_module = self.import("sys", 0).unwrap();
-        let unraisablehook = sys_module.get_attr("unraisablehook", self).unwrap();
-
-        let exc_type = e.class().to_owned();
-        let exc_traceback = e.traceback().to_pyobject(self); // TODO: actual traceback
-        let exc_value = e.into();
-        let args = stdlib::sys::UnraisableHookArgsData {
-            exc_type,
-            exc_value,
-            exc_traceback,
-            err_msg: self.new_pyobj(msg),
-            object,
+        let Some(unraisablehook) = self.sys_module.get_attr("unraisablehook", self).ok() else {
+            write_original();
+            return;
         };
-        if let Err(e) = unraisablehook.call((args,), self) {
-            println!("{}", e.as_object().repr(self).unwrap());
+        let args = stdlib::sys::UnraisableHookArgsData {
+            exc_type: e.class().to_owned(),
+            exc_value: e.clone().into(),
+            exc_traceback: e.traceback().to_pyobject(self),
+            err_msg: msg.clone().to_pyobject(self),
+            object: object.clone(),
+        }
+        .to_pyobject(self);
+        if let Err(error) = self.audit("sys.unraisablehook", || {
+            (unraisablehook.clone(), args.clone())
+        }) {
+            self.write_unraisable_to_stderr(
+                &error,
+                Some("Exception ignored in audit hook"),
+                &self.ctx.none(),
+            );
+            return;
+        }
+        if self.is_none(&unraisablehook) {
+            write_original();
+            return;
+        }
+        if let Err(error) = unraisablehook.call((args,), self) {
+            self.write_unraisable_to_stderr(
+                &error,
+                Some("Exception ignored in sys.unraisablehook"),
+                &unraisablehook,
+            );
         }
     }
 
-    /// Write unraisable exception to stderr during finalization.
+    /// Write an unraisable exception when its hook cannot be used.
     /// Similar to _PyErr_WriteUnraisableDefaultHook in CPython.
     fn write_unraisable_to_stderr(
         &self,
@@ -1709,15 +1836,29 @@ impl VirtualMachine {
             write_to_stderr(&format!("{repr_wtf8}\n"), &stderr, self);
         }
 
-        // Write exception type and message
-        let exc_type_name = e.class().name();
-        let msg = match e.as_object().str(self) {
-            Ok(exc_str) if !exc_str.as_wtf8().is_empty() => {
-                format!("{}: {}\n", exc_type_name, exc_str.as_wtf8())
+        // Print the existing traceback without importing Python modules;
+        // this path must also work while the interpreter is finalizing.
+        if let Some(traceback) = e.traceback() {
+            if let Some(stderr) = &stderr {
+                let mut writer = crate::py_io::PyWriter(stderr.clone(), self);
+                let _ = crate::exceptions::write_traceback(&mut writer, &traceback);
+            } else {
+                let mut writer = crate::py_io::IoWriter(std::io::stderr());
+                let _ = crate::exceptions::write_traceback(&mut writer, &traceback);
             }
-            _ => format!("{exc_type_name}\n"),
+        }
+        let exc_type_name = e
+            .class()
+            .fully_qualified_name(self)
+            .unwrap_or_else(|_| e.class().name().to_string());
+        let message = match e.as_object().str(self) {
+            Ok(value) if !value.as_wtf8().is_empty() => {
+                format!("{exc_type_name}: {}\n", value.as_wtf8())
+            }
+            Ok(_) => format!("{exc_type_name}\n"),
+            Err(_) => format!("{exc_type_name}: <exception str() failed>\n"),
         };
-        write_to_stderr(&msg, &stderr, self);
+        write_to_stderr(&message, &stderr, self);
 
         // Flush stderr to ensure output is visible
         if let Some(ref stderr) = stderr {
@@ -2248,9 +2389,7 @@ impl VirtualMachine {
         path: &str,
         run: impl FnOnce(&Py<PyDict>) -> PyResult<()>,
     ) -> PyResult<()> {
-        let sys_modules = self.sys_module.get_attr(identifier!(self, modules), self)?;
-        let main_module = sys_modules.get_item(identifier!(self, __main__), self)?;
-        let module_dict = main_module.dict().expect("main module must have __dict__");
+        let module_dict = self.add_main_module()?.dict();
 
         // Track whether we set __file__ (for cleanup)
         let set_file_name = !module_dict.contains_key(identifier!(self, __file__), self);
@@ -2260,17 +2399,15 @@ impl VirtualMachine {
                 self.ctx.new_str(path).into(),
                 self,
             )?;
-            module_dict.set_item(identifier!(self, __cached__), self.ctx.none(), self)?;
         }
 
         let result = run(&module_dict);
 
         self.flush_io();
 
-        // Cleanup __file__ and __cached__ after execution
+        // Cleanup __file__ after execution
         if set_file_name {
             let _ = module_dict.del_item(identifier!(self, __file__), self);
-            let _ = module_dict.del_item(identifier!(self, __cached__), self);
         }
 
         result
@@ -2585,6 +2722,31 @@ impl VirtualMachine {
         false
     }
 
+    /// Enter a native-recursion section equivalent to `Py_EnterRecursiveCall`.
+    pub fn enter_recursive_call(&self, _where: &str) -> PyResult<()> {
+        #[cfg(any(miri, target_env = "musl"))]
+        let counted_too_deep =
+            self.native_recursion_depth.get() >= Self::NATIVE_RECURSION_LIMIT_UNMEASURED;
+        #[cfg(not(any(miri, target_env = "musl")))]
+        let counted_too_deep = false;
+
+        if counted_too_deep || self.check_c_stack_overflow() {
+            return Err(self.new_recursion_depth_error(_where));
+        }
+
+        #[cfg(any(miri, target_env = "musl"))]
+        self.native_recursion_depth.update(|d| d + 1);
+
+        Ok(())
+    }
+
+    /// Leave a native-recursion section equivalent to
+    /// `Py_LeaveRecursiveCall`.
+    pub fn leave_recursive_call(&self) {
+        #[cfg(any(miri, target_env = "musl"))]
+        self.native_recursion_depth.update(|d| d.saturating_sub(1));
+    }
+
     /// Used to run the body of a (possibly) recursive function. It will raise a
     /// RecursionError if recursive functions are nested far too many times,
     /// preventing a stack overflow.
@@ -2603,9 +2765,7 @@ impl VirtualMachine {
         let counted_too_deep = false;
 
         if counted_too_deep || self.check_c_stack_overflow() {
-            return Err(
-                self.new_recursion_error(format!("maximum recursion depth exceeded {_where}"))
-            );
+            return Err(self.new_recursion_depth_error(_where));
         }
 
         #[cfg(any(miri, target_env = "musl"))]
@@ -2623,6 +2783,25 @@ impl VirtualMachine {
         &self,
         frame: FrameObjectRef,
         f: F,
+    ) -> PyResult<R> {
+        self.with_frame_impl::<true, R, F>(frame, f)
+    }
+
+    /// Run the incomplete frame of a generator being created. Its caller link
+    /// must not escape, as RETURN_GENERATOR copies the frame with
+    /// `previous = NULL`.
+    pub(crate) fn with_generator_frame<R, F: FnOnce(FrameObjectRef) -> PyResult<R>>(
+        &self,
+        frame: FrameObjectRef,
+        f: F,
+    ) -> PyResult<R> {
+        self.with_frame_impl::<false, R, F>(frame, f)
+    }
+
+    fn with_frame_impl<const RETAIN_BACK: bool, R, F: FnOnce(FrameObjectRef) -> PyResult<R>>(
+        &self,
+        frame: FrameObjectRef,
+        f: F,
     ) -> PyResult<R> {
         self.check_recursive_call("")?;
 
@@ -2632,7 +2811,7 @@ impl VirtualMachine {
         // code -- an `__add__` chain, a sort key that sorts -- takes more than
         // the margin in that many.
         if self.check_c_stack_overflow() {
-            return Err(self.new_recursion_error(String::new()));
+            return Err(self.new_recursion_depth_error(""));
         }
 
         self.recursion_depth.update(|d| d + 1);
@@ -2669,7 +2848,7 @@ impl VirtualMachine {
 
         // Capture f_back before clearing previous so code holding a
         // reference to this FrameObject can walk the chain after return.
-        if !old_chain.is_null() {
+        if RETAIN_BACK && !old_chain.is_null() {
             let strong = frame.as_object().strong_count();
             // Only set retained_back if someone else holds a reference (escaped)
             // AND the caller already has a FrameObject. Materializing the caller
@@ -2680,8 +2859,11 @@ impl VirtualMachine {
             if strong > 1 {
                 let mut guard = frame.iframe().cold().retained_back.lock();
                 if guard.is_none() {
-                    let prev_iframe = unsafe { &*old_chain };
-                    if let Some(fo) = prev_iframe.frame_obj() {
+                    // SAFETY: old_chain remains live until this synchronous entry exits.
+                    let visible = unsafe { crate::frame::first_complete_iframe(old_chain) };
+                    if let Some(prev_iframe) = unsafe { visible.as_ref() }
+                        && let Some(fo) = prev_iframe.frame_obj()
+                    {
                         *guard = Some(fo.to_owned());
                     }
                 }
@@ -2739,7 +2921,7 @@ impl VirtualMachine {
         iframe: &mut crate::frame::InterpreterFrame,
     ) -> PyResult<IframeEntryState> {
         if self.check_c_stack_overflow() {
-            return Err(self.new_recursion_error(String::new()));
+            return Err(self.new_recursion_depth_error(""));
         }
 
         self.recursion_depth.update(|d| d + 1);
@@ -2807,8 +2989,9 @@ impl VirtualMachine {
                 // The slots above are the last write this thread makes into
                 // the frame object, so it is now readable from anywhere.
                 fo.iframe().detach();
-                if !old_chain.is_null() {
-                    let prev_iframe = unsafe { &*old_chain };
+                // SAFETY: old_chain belongs to this still-active thread chain.
+                let visible = unsafe { crate::frame::first_complete_iframe(old_chain) };
+                if let Some(prev_iframe) = unsafe { visible.as_ref() } {
                     let back_fo = prev_iframe.materialize_chain(self);
                     *fo.iframe().cold().retained_back.lock() = Some(back_fo);
                 }
@@ -2880,7 +3063,7 @@ impl VirtualMachine {
     ) -> PyResult<GenFrameLink> {
         self.check_recursive_call("")?;
         if self.check_c_stack_overflow() {
-            return Err(self.new_recursion_error(String::new()));
+            return Err(self.new_recursion_depth_error(""));
         }
         self.recursion_depth.update(|d| d + 1);
 
@@ -2994,10 +3177,19 @@ impl VirtualMachine {
         if result.is_err()
             && self.use_tracing.get()
             && (!self.is_none(&self.profile_func.borrow())
-                || frame
-                    .iframe()
-                    .cold_opt()
-                    .is_some_and(|c| c.trace.lock().is_some()))
+                || if frame.iframe().is_incomplete() {
+                    crate::frame::current_complete_frame_for_trace(self).is_some_and(|visible| {
+                        visible
+                            .iframe()
+                            .cold_opt()
+                            .is_some_and(|c| c.trace.lock().is_some())
+                    })
+                } else {
+                    frame
+                        .iframe()
+                        .cold_opt()
+                        .is_some_and(|c| c.trace.lock().is_some())
+                })
         {
             let ret_result = self.trace_event_what(
                 TraceEvent::Return,
@@ -3024,6 +3216,7 @@ impl VirtualMachine {
             future_features: crate::bytecode::CodeFlags::empty(),
             dont_imply_dedent: false,
             recursion_limit: self.recursion_limit.get(),
+            build_list_from_arg: false,
         }
     }
 
@@ -3059,10 +3252,25 @@ impl VirtualMachine {
         self.tracing_depth.get() != 0
     }
 
+    /// `where_` is empty, or a suffix that already includes the leading space.
+    #[cold]
+    fn new_recursion_depth_error(&self, where_: &str) -> PyBaseExceptionRef {
+        debug_assert!(
+            where_.is_empty() || where_.starts_with(' '),
+            "recursion where-clause must be empty or start with a space: {where_:?}"
+        );
+        let msg = if where_.is_empty() {
+            "maximum recursion depth exceeded".to_string()
+        } else {
+            format!("maximum recursion depth exceeded{where_}")
+        };
+        self.new_recursion_error(msg)
+    }
+
     // To be called right before raising the recursion depth.
     fn check_recursive_call(&self, _where: &str) -> PyResult<()> {
         if self.recursion_depth.get() >= self.recursion_limit.get() {
-            Err(self.new_recursion_error(format!("maximum recursion depth exceeded {_where}")))
+            Err(self.new_recursion_depth_error(_where))
         } else {
             Ok(())
         }
@@ -3079,7 +3287,7 @@ impl VirtualMachine {
             .locals(self)
     }
 
-    pub fn current_globals(&self) -> PyDictRef {
+    pub fn current_globals(&self) -> PyRef<PyAnyDict> {
         let ptr = crate::vm::thread::get_current_frame();
         if !ptr.is_null() {
             return unsafe { (*ptr).globals().to_owned() };
@@ -3136,7 +3344,7 @@ impl VirtualMachine {
     pub fn eval_get_builtin(&self, name: &'static PyStrInterned) -> PyResult {
         let builtins =
             crate::frame::current_builtins().unwrap_or_else(|| self.builtins.dict().into());
-        if let Some(dict) = builtins.downcast_ref::<PyDict>() {
+        if let Some(dict) = builtins.downcast_ref_if_exact::<PyDict>(self) {
             match dict.get_item_opt(name, self)? {
                 Some(value) => Ok(value),
                 None => Err(self.new_attribute_error(name.to_string())),
@@ -3168,6 +3376,7 @@ impl VirtualMachine {
             && builtins.is(self.builtins.dict().as_object())
             && let Some(cached) = self.try_import_cached(module)?
         {
+            import::report_cached_import(module, self);
             return Ok(cached);
         }
 
@@ -3192,7 +3401,7 @@ impl VirtualMachine {
             // Locals fallback: use the heavy frame if available, otherwise
             // use globals as locals (light frame locals are on the data stack).
             let locals_mapping = self.current_frame().map_or_else(
-                || ArgMapping::from_dict_exact(globals.clone()),
+                || ArgMapping::from_anydict_exact(globals.clone()),
                 |f| f.iframe().locals.clone_mapping(self),
             );
             (Some(locals_mapping), Some(globals))
@@ -3238,6 +3447,7 @@ impl VirtualMachine {
         if self.is_none(&found) || import::is_module_initializing(&found, self)? {
             return Ok(None);
         }
+        crate::lazy_import::clear_submodule(module, true, self)?;
 
         let Some(dot) = name_str.find('.') else {
             return Ok(Some(found));
@@ -3477,6 +3687,10 @@ impl VirtualMachine {
         let getattro = obj.class().slots().getattro.load().unwrap();
         let result = if fn_addr(getattro) == fn_addr(PyBaseObject::getattro as GetattroFunc) {
             obj.generic_getattr_opt(attr_name, None, self)
+        } else if fn_addr(getattro) == fn_addr(PyModule::slot_getattro as GetattroFunc)
+            && let Some(module) = obj.downcast_ref::<PyModule>()
+        {
+            module.getattr_inner(attr_name, true, self).map(Some)
         } else {
             obj.get_attr_inner(attr_name, self).map(Some)
         };
@@ -3740,58 +3954,77 @@ impl VirtualMachine {
         excs.stack.iter().rev().find_map(|e| e.clone())
     }
 
+    /// The current `config.inspect`.
+    pub fn config_inspect(&self) -> bool {
+        self.state.inspect.load(Ordering::Relaxed)
+    }
+
+    /// `PyConfig_Set("inspect", value)`: update the config and `sys.flags.inspect`.
+    pub fn config_set_inspect(&self, inspect: bool) -> PyResult<()> {
+        let value: PyObjectRef = self.ctx.new_int(u8::from(inspect)).into();
+        self.audit("cpython.PyConfig_Set", || ("inspect", value.clone()))?;
+        self.state.inspect.store(inspect, Ordering::Relaxed);
+        stdlib::sys::sys::set_flag_obj(self, "inspect", value)
+    }
+
+    /// pymain_exit_err_print
+    ///
+    /// Report an exception that reached the top level and return the exit code.
     pub fn handle_exit_exception(&self, exc: PyBaseExceptionRef) -> u32 {
-        if exc.fast_isinstance(self.ctx.exceptions.system_exit) {
-            let code = exc
-                .as_object()
-                .get_attr("code", self)
-                .unwrap_or_else(|_| exc.as_object().to_owned());
-            let msg = match_class!(match code {
-                ref i @ PyInt => {
-                    use num_traits::cast::ToPrimitive;
-                    // Try u32 first, then i32 (for negative values), else -1 for overflow
-                    let code = i
-                        .as_bigint()
-                        .to_u32()
-                        .or_else(|| i.as_bigint().to_i32().map(|v| v as u32))
-                        .unwrap_or(-1i32 as u32);
-                    return code;
-                }
-                code => {
-                    if self.is_none(&code) {
-                        return 0;
-                    }
-                    code.str(self).ok()
-                }
-            });
-            if let Some(msg) = msg {
-                // Write using Python's write() to use stderr's error handler (backslashreplace)
-                if let Ok(stderr) = stdlib::sys::get_stderr(self) {
-                    let _ = self.call_method(&stderr, "write", (msg,));
-                    let _ = self.call_method(&stderr, "write", ("\n",));
-                }
-            }
-            1
-        } else if exc.fast_isinstance(self.ctx.exceptions.keyboard_interrupt) {
-            self.print_exception(&exc);
-            cfg_select! {
-                unix => {
-                    if crate::host_env::signal::set_sigint_default_onstack().is_ok() {
-                        self.flush_std();
-                        crate::host_env::signal::send_sigint_to_self()
-                            .expect("Expect to be killed.");
-                    }
+        if let Some(exit_code) = self.handle_system_exit_and_keyboard_interrupt(&exc) {
+            return exit_code;
+        }
+        self.print_uncaught_exception(&exc);
+        1
+    }
 
-                    (libc::SIGINT as u32) + 128
+    /// _Py_HandleSystemExitAndKeyboardInterrupt
+    ///
+    /// Return the exit code of a `SystemExit` that should end the process.
+    /// A `KeyboardInterrupt` is remembered so that the process exits through SIGINT.
+    pub fn handle_system_exit_and_keyboard_interrupt(
+        &self,
+        exc: &Py<PyBaseException>,
+    ) -> Option<u32> {
+        if exc.fast_isinstance(self.ctx.exceptions.keyboard_interrupt) {
+            crate::signal::set_unhandled_keyboard_interrupt();
+            return None;
+        }
+        // Don't exit if -i flag was given. This flag is set to 0
+        // when entering interactive mode for inspecting.
+        if self.config_inspect() || !exc.fast_isinstance(self.ctx.exceptions.system_exit) {
+            return None;
+        }
+        let code = exc
+            .as_object()
+            .get_attr("code", self)
+            .unwrap_or_else(|_| exc.as_object().to_owned());
+        let msg = match_class!(match code {
+            ref i @ PyInt => {
+                use num_traits::cast::ToPrimitive;
+                // Try u32 first, then i32 (for negative values), else -1 for overflow
+                let code = i
+                    .as_bigint()
+                    .to_u32()
+                    .or_else(|| i.as_bigint().to_i32().map(|v| v as u32))
+                    .unwrap_or(-1i32 as u32);
+                return Some(code);
+            }
+            code => {
+                if self.is_none(&code) {
+                    return Some(0);
                 }
-                // STATUS_CONTROL_C_EXIT - same as CPython
-                windows => 0xC000013A,
-                _ => 1,
+                code.str(self).ok()
+            }
+        });
+        if let Some(msg) = msg {
+            // Write using Python's write() to use stderr's error handler (backslashreplace)
+            if let Ok(stderr) = stdlib::sys::get_stderr(self) {
+                let _ = self.call_method(&stderr, "write", (msg,));
+                let _ = self.call_method(&stderr, "write", ("\n",));
             }
-        } else {
-            self.print_exception(&exc);
-            1
         }
+        Some(1)
     }
 
     #[doc(hidden)]
@@ -3898,6 +4131,26 @@ pub fn resolve_frozen_alias(name: &str) -> &str {
 mod tests {
     use super::*;
 
+    #[cfg(not(feature = "stdio"))]
+    #[test]
+    fn no_stdio_streams_are_none_singleton() {
+        Interpreter::builder(Default::default())
+            .build()
+            .enter(|vm| {
+                for name in [
+                    "stdin",
+                    "stdout",
+                    "stderr",
+                    "__stdin__",
+                    "__stdout__",
+                    "__stderr__",
+                ] {
+                    let stream = vm.sys_module.get_attr(name, vm).unwrap();
+                    assert!(vm.is_none(&stream), "sys.{name} must be the None singleton");
+                }
+            });
+    }
+
     #[test]
     fn nested_frozen() {
         use rustpython_vm as vm;
diff --git a/crates/vm/src/vm/python_run.rs b/crates/vm/src/vm/python_run.rs
index b8b83a240d1..a9fcb56ca63 100644
--- a/crates/vm/src/vm/python_run.rs
+++ b/crates/vm/src/vm/python_run.rs
@@ -1,11 +1,14 @@
 //! Python code execution functions.
 
 use crate::{
-    Py, PyObjectRef, PyResult, VirtualMachine,
-    builtins::PyCode,
+    AsObject, Py, PyObjectRef, PyResult, VirtualMachine,
+    builtins::{PyBaseException, PyBaseExceptionRef, PyCode, PyModule, PyStr},
+    bytecode::CodeFlags,
     compiler::{self},
     scope::Scope,
+    stdlib,
 };
+use core::sync::atomic::Ordering;
 
 impl VirtualMachine {
     /// PyRun_SimpleString
@@ -58,8 +61,8 @@ impl VirtualMachine {
 #[cfg(feature = "host_env")]
 mod file_run {
     use crate::{
-        AsObject, Py, PyResult, VirtualMachine,
-        builtins::{PyBaseExceptionRef, PyCode, PyDict},
+        Py, PyResult, VirtualMachine,
+        builtins::{PyCode, PyDict},
         compiler::{self},
         scope::Scope,
     };
@@ -67,8 +70,8 @@ mod file_run {
     impl VirtualMachine {
         /// _PyRun_AnyFileObject (internal)
         ///
-        /// Execute a Python file. Currently always delegates to run_simple_file
-        /// (interactive mode is handled separately in shell.rs).
+        /// Execute a Python file. A named file is not interactive, so this
+        /// always delegates to run_simple_file; see `run_any_stdin` for stdin.
         ///
         /// Note: This is an internal function. Use `run_file` for the public interface.
         #[doc(hidden)]
@@ -111,7 +114,12 @@ mod file_run {
                 match crate::host_env::fs::read(path) {
                     Ok(source_bytes) => {
                         if let Some(null_at) = source_bytes.iter().position(|&b| b == 0) {
-                            return Err(null_byte_syntax_error(self, path, &source_bytes, null_at));
+                            return Err(super::null_byte_syntax_error(
+                                self,
+                                path,
+                                &source_bytes,
+                                null_at,
+                            ));
                         }
                         #[cfg(feature = "parser")]
                         // Match compile() by honoring BOMs and encoding cookies in files.
@@ -138,31 +146,6 @@ mod file_run {
         }
     }
 
-    fn null_byte_syntax_error(
-        vm: &VirtualMachine,
-        path: &str,
-        source_bytes: &[u8],
-        null_at: usize,
-    ) -> PyBaseExceptionRef {
-        let before = &source_bytes[..null_at];
-        let lineno = before.iter().filter(|&&b| b == b'\n').count() + 1;
-        let line_start = before
-            .iter()
-            .rposition(|&b| b == b'\n')
-            .map_or(0, |i| i + 1);
-        let line = String::from_utf8_lossy(&source_bytes[line_start..null_at]);
-        let syntax_error = vm.new_exception_msg(
-            vm.ctx.exceptions.syntax_error.to_owned(),
-            "source code cannot contain null bytes".into(),
-        );
-        let obj = syntax_error.as_object();
-        obj.set_attr("filename", vm.ctx.new_str(path), vm).unwrap();
-        obj.set_attr("lineno", vm.ctx.new_int(lineno), vm).unwrap();
-        obj.set_attr("text", vm.ctx.new_str(format!("{line}\n")), vm)
-            .unwrap();
-        syntax_error
-    }
-
     fn set_main_loader(
         module_dict: &Py<PyDict>,
         filename: &str,
@@ -216,6 +199,398 @@ mod file_run {
     }
 }
 
+/// One line of interactive input: raw bytes read from stdin, or text from a
+/// line editor.
+pub enum InteractiveLine {
+    Bytes(Vec<u8>),
+    Text(String),
+}
+
+/// Source of one interactive statement, ready to be compiled.
+struct InteractiveSource {
+    source: String,
+    parsed: compiler::InteractiveInput,
+}
+
+impl VirtualMachine {
+    /// _Py_FdIsInteractive(stdin, "<stdin>")
+    pub fn stdin_is_interactive(&self) -> bool {
+        use std::io::IsTerminal;
+        std::io::stdin().is_terminal() || self.state.config.settings.interactive
+    }
+
+    /// _PyRun_AnyFile(stdin, "<stdin>")
+    ///
+    /// Run stdin as an interactive session or as a script.
+    pub fn run_any_stdin(&self) -> PyResult<()> {
+        if self.stdin_is_interactive() {
+            self.run_interactive_loop(|prompt| self.stdio_readline(prompt))
+        } else {
+            self.run_simple_stdin()
+        }
+    }
+
+    /// _PyRun_InteractiveLoop
+    ///
+    /// `readline` plays the role of `PyOS_Readline`: it returns `Ok(None)` at
+    /// the end of input.
+    pub fn run_interactive_loop(
+        &self,
+        mut readline: impl FnMut(&str) -> PyResult<Option<InteractiveLine>>,
+    ) -> PyResult<()> {
+        for (name, default) in [("ps1", ">>> "), ("ps2", "... ")] {
+            if self.sys_module.dict().get_item_opt(name, self)?.is_none() {
+                let _ = self
+                    .sys_module
+                    .set_attr(name, self.ctx.new_str(default), self);
+            }
+        }
+        let mut flags = CodeFlags::empty();
+        let mut nomem_count = 0;
+        loop {
+            match self.run_interactive_one(&mut readline, &mut flags) {
+                Ok(true) => nomem_count = 0,
+                // E_EOF
+                Ok(false) => return Ok(()),
+                Err(exc) => {
+                    // Prevent an endless loop after multiple consecutive
+                    // MemoryErrors while still allowing an interactive
+                    // command to fail with a MemoryError.
+                    if exc.fast_isinstance(self.ctx.exceptions.memory_error) {
+                        nomem_count += 1;
+                        if nomem_count > 16 {
+                            return Err(exc);
+                        }
+                    } else {
+                        nomem_count = 0;
+                    }
+                    if !self.config_inspect()
+                        && exc.fast_isinstance(self.ctx.exceptions.system_exit)
+                    {
+                        return Err(exc);
+                    }
+                    self.print_uncaught_exception(&exc);
+                }
+            }
+        }
+    }
+
+    /// _PyRun_InteractiveOne
+    ///
+    /// Read, compile and run one interactive statement in `__main__`.
+    /// Return `Ok(false)` at the end of input.
+    fn run_interactive_one(
+        &self,
+        readline: &mut impl FnMut(&str) -> PyResult<Option<InteractiveLine>>,
+        flags: &mut CodeFlags,
+    ) -> PyResult<bool> {
+        let Some(InteractiveSource { source, parsed }) =
+            self.interactive_parse(readline, *flags)?
+        else {
+            return Ok(false);
+        };
+        let main_module = self.add_main_module()?;
+        // _PyAST_Compile merges the future features of the parsed statement
+        // into the flags before code generation.
+        *flags |= parsed.future_features;
+        self.run_interactive_mod(&source, parsed.empty, *flags, &main_module)
+            .inspect_err(|exc| self.fix_syntax_error_text(exc, &source))?;
+        self.flush_io();
+        Ok(true)
+    }
+
+    /// pyrun_one_parse_ast
+    ///
+    /// Read lines with `sys.ps1` and `sys.ps2` prompts until they form one
+    /// complete interactive statement. Return `None` at the end of input.
+    fn interactive_parse(
+        &self,
+        readline: &mut impl FnMut(&str) -> PyResult<Option<InteractiveLine>>,
+        flags: CodeFlags,
+    ) -> PyResult<Option<InteractiveSource>> {
+        let encoding = self
+            .sys_module
+            .get_attr("stdin", self)
+            .and_then(|stdin| stdin.get_attr("encoding", self))
+            .ok()
+            .and_then(|encoding| encoding.downcast::<PyStr>().ok())
+            .and_then(|encoding| encoding.to_str().map(str::to_owned))
+            .unwrap_or_else(|| "utf-8".to_owned());
+        let prompt = |name| {
+            self.sys_module
+                .get_attr(name, self)
+                .and_then(|prompt| prompt.str(self))
+                .ok()
+                .and_then(|prompt| prompt.to_str().map(str::to_owned))
+                .unwrap_or_default()
+        };
+        let ps1 = prompt("ps1");
+        let ps2 = prompt("ps2");
+
+        // _PyParser_InteractiveASTFromFile
+        self.audit("compile", || (self.ctx.none(), self.ctx.new_str("<stdin>")))?;
+        let mut source = String::new();
+        let mut raw_source = Vec::new();
+        #[cfg(feature = "parser")]
+        let mut warnings = super::compile::InteractiveWarnings::default();
+        loop {
+            let line = readline(if source.is_empty() { &ps1 } else { &ps2 });
+            // tok_underflow_interactive ends the prompt line at EOF or on an
+            // interrupted read.
+            if !matches!(line, Ok(Some(_))) {
+                writeln!(stdlib::sys::PyStderr(self));
+            }
+            let (terminated, unterminated_fragment, eof) = match line? {
+                None if source.is_empty() => return Ok(None),
+                None => {
+                    if !source.ends_with('\n') {
+                        source.push('\n');
+                    }
+                    (true, false, true)
+                }
+                Some(InteractiveLine::Text(mut line)) => {
+                    if !line.ends_with('\n') {
+                        line.push('\n');
+                    }
+                    let line = line.replace("\r\n", "\n");
+                    let terminated = line == "\n";
+                    source.push_str(&line);
+                    (terminated, false, false)
+                }
+                Some(InteractiveLine::Bytes(line)) => {
+                    let unterminated_fragment = !line.ends_with(b"\n");
+                    let terminated = line == b"\n" || line == b"\r\n";
+                    raw_source.extend_from_slice(&line);
+                    source = self
+                        .state
+                        .codec_registry
+                        .decode_text(
+                            self.ctx.new_bytes(raw_source.clone()).into(),
+                            &encoding,
+                            None,
+                            self,
+                        )?
+                        .to_str()
+                        .ok_or_else(|| {
+                            self.new_exception_msg(
+                                self.ctx.exceptions.unicode_error.to_owned(),
+                                "stdin source contains surrogates".into(),
+                            )
+                        })?
+                        .replace("\r\n", "\n");
+                    (terminated, unterminated_fragment, false)
+                }
+            };
+            #[cfg(feature = "parser")]
+            self.emit_interactive_parser_warnings(
+                &source,
+                "<stdin>",
+                Some(identifier!(self, __main__)),
+                flags.contains(CodeFlags::FUTURE_BARRY_AS_BDFL),
+                &mut warnings,
+            )
+            .map_err(|error| {
+                super::compile::VmCompileError::Warning(error).into_pyexception(self, Some(&source))
+            })?;
+            let parsed = match compiler::interactive_input(&source, "<stdin>", flags, terminated) {
+                Ok(Some(parsed)) => parsed,
+                Ok(None) => continue,
+                Err(error) => {
+                    let unclosed = matches!(&error, compiler::CompileError::Parse(error)
+                        if error.is_unclosed_bracket || error.is_unclosed_string);
+                    let error = super::compile::VmCompileError::Compile(error)
+                        .into_pyexception_maybe_incomplete(self, Some(&source), !terminated);
+                    if !eof
+                        && (unclosed
+                            || (!terminated
+                                && error
+                                    .fast_isinstance(self.ctx.exceptions.incomplete_input_error)))
+                    {
+                        continue;
+                    }
+                    return Err(error);
+                }
+            };
+            // A final fragment without a newline is not a complete line yet.
+            // Its warnings and definitive syntax errors are reported now, but
+            // it is only accepted once the next read reports EOF.
+            if unterminated_fragment {
+                continue;
+            }
+            return Ok(Some(InteractiveSource { source, parsed }));
+        }
+    }
+
+    /// run_mod for interactive input
+    fn run_interactive_mod(
+        &self,
+        source: &str,
+        empty: bool,
+        flags: CodeFlags,
+        main_module: &Py<PyModule>,
+    ) -> PyResult<()> {
+        let filename = get_interactive_filename(
+            "<stdin>",
+            self.state
+                .interactive_src_count
+                .fetch_add(1, Ordering::Relaxed),
+        );
+        let mode = if empty {
+            compiler::Mode::Exec
+        } else {
+            compiler::Mode::Single
+        };
+        let opts = compiler::CompileOpts {
+            future_features: flags,
+            ..self.compile_opts()
+        };
+        let code = self
+            .compile_after_parser_warnings(
+                source,
+                mode,
+                filename,
+                opts,
+                Some(identifier!(self, __main__)),
+            )
+            .map_err(|error| error.into_pyexception(self, Some(source)))?;
+        let linecache = self.import("linecache", 0)?;
+        linecache.get_attr("_register_code", self)?.call(
+            (
+                code.clone(),
+                self.ctx.new_str(source),
+                self.ctx.new_str("<stdin>"),
+            ),
+            self,
+        )?;
+        self.audit("exec", || (code.clone(),))?;
+        let globals = main_module.dict();
+        self.run_code_obj(code, Scope::with_builtins(None, globals, self))?;
+        Ok(())
+    }
+
+    /// Fix the `text` attribute of a SyntaxError raised by interactive input.
+    fn fix_syntax_error_text(&self, exc: &Py<PyBaseException>, source: &str) {
+        if !exc.fast_isinstance(self.ctx.exceptions.syntax_error) {
+            return;
+        }
+        let source = self.ctx.new_str(source);
+        let lines = source.splitlines(crate::anystr::SplitLinesArgs { keepends: true }, self);
+        let Ok(lineno) = exc
+            .as_object()
+            .get_attr("lineno", self)
+            .and_then(|lineno| lineno.try_into_value::<i32>(self))
+        else {
+            return;
+        };
+        if lineno > 0
+            && let Some(line) = lines.get((lineno - 1) as usize)
+        {
+            let _ = exc.as_object().set_attr("text", line.clone(), self);
+        }
+    }
+
+    /// PyOS_StdioReadline
+    ///
+    /// Write the prompt to stderr and read one line from stdin.
+    fn stdio_readline(&self, prompt: &str) -> PyResult<Option<InteractiveLine>> {
+        let mut line = Vec::new();
+        let mut prompt = prompt;
+        loop {
+            let result = crate::readline::stdio_readline_bytes(prompt, &mut line);
+            prompt = "";
+            match result {
+                Ok(0) if line.is_empty() => return Ok(None),
+                Ok(_) => return Ok(Some(InteractiveLine::Bytes(line))),
+                Err(error) if error.kind() == std::io::ErrorKind::Interrupted => {
+                    self.check_signals()?;
+                }
+                // A read error ends the input like EOF.
+                Err(_) if line.is_empty() => return Ok(None),
+                Err(_) => return Ok(Some(InteractiveLine::Bytes(line))),
+            }
+        }
+    }
+
+    /// _PyRun_SimpleFile(stdin, "<stdin>")
+    fn run_simple_stdin(&self) -> PyResult<()> {
+        use std::io::Read;
+        self.with_simple_run("<stdin>", |module_dict| {
+            // _PyParser_ASTFromFile
+            self.audit("compile", || (self.ctx.none(), self.ctx.new_str("<stdin>")))?;
+            let mut bytes = Vec::new();
+            let mut buf = [0; 8192];
+            loop {
+                match std::io::stdin().read(&mut buf) {
+                    Ok(0) => break,
+                    Ok(n) => bytes.extend_from_slice(&buf[..n]),
+                    Err(error) if error.kind() == std::io::ErrorKind::Interrupted => {
+                        self.check_signals()?;
+                    }
+                    // A read error ends the input like EOF.
+                    Err(_) => break,
+                }
+            }
+            if let Some(null_at) = bytes.iter().position(|&b| b == 0) {
+                return Err(null_byte_syntax_error(self, "<stdin>", &bytes, null_at));
+            }
+            #[cfg(feature = "parser")]
+            let source = self.decode_source_bytes(&bytes, "<stdin>", false)?;
+            #[cfg(not(feature = "parser"))]
+            let source =
+                String::from_utf8(bytes).map_err(|error| self.new_os_error(error.to_string()))?;
+            let code = self
+                .compile_with_opts_and_module(
+                    &source,
+                    compiler::Mode::Exec,
+                    "<stdin>",
+                    self.compile_opts(),
+                    Some(identifier!(self, __main__)),
+                    &[],
+                )
+                .map_err(|error| error.into_pyexception(self, Some(&source)))?;
+            self.audit("exec", || (code.clone(),))?;
+            let scope = Scope::with_builtins(None, module_dict.to_owned(), self);
+            self.run_code_obj(code, scope).map(drop)
+        })
+    }
+}
+
+fn null_byte_syntax_error(
+    vm: &VirtualMachine,
+    path: &str,
+    source_bytes: &[u8],
+    null_at: usize,
+) -> PyBaseExceptionRef {
+    let before = &source_bytes[..null_at];
+    let lineno = before.iter().filter(|&&b| b == b'\n').count() + 1;
+    let line_start = before
+        .iter()
+        .rposition(|&b| b == b'\n')
+        .map_or(0, |i| i + 1);
+    let line = String::from_utf8_lossy(&source_bytes[line_start..null_at]);
+    let syntax_error = vm.new_exception_msg(
+        vm.ctx.exceptions.syntax_error.to_owned(),
+        "source code cannot contain null bytes".into(),
+    );
+    let obj = syntax_error.as_object();
+    obj.set_attr("filename", vm.ctx.new_str(path), vm).unwrap();
+    obj.set_attr("lineno", vm.ctx.new_int(lineno), vm).unwrap();
+    obj.set_attr("text", vm.ctx.new_str(format!("{line}\n")), vm)
+        .unwrap();
+    syntax_error
+}
+
+/// get_interactive_filename
+fn get_interactive_filename(filename: &str, count: usize) -> String {
+    match filename
+        .strip_prefix('<')
+        .and_then(|name| name.strip_suffix('>'))
+    {
+        Some(middle) => format!("<{middle}-{count}>"),
+        None => format!("{filename}-{count}"),
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::object::AsObject;
diff --git a/crates/vm/src/vm/setting.rs b/crates/vm/src/vm/setting.rs
index f582e51f1e1..458174910c5 100644
--- a/crates/vm/src/vm/setting.rs
+++ b/crates/vm/src/vm/setting.rs
@@ -5,6 +5,8 @@ use std::ffi::OsString;
 /// Path configuration computed at runtime (like PyConfig path outputs)
 #[derive(Debug, Clone, Default)]
 pub struct Paths {
+    /// program_name: the name the interpreter was invoked as
+    pub program_name: String,
     /// sys.executable
     pub executable: String,
     /// sys._base_executable (original interpreter in venv)
@@ -62,7 +64,8 @@ pub struct Settings {
 
     // int tracemalloc;
     // int perf_profiling;
-    // int import_time;
+    /// -X importtime, PYTHONPROFILEIMPORTTIME: 2 also reports cached imports.
+    pub import_time: u8,
     /// -X no_debug_ranges: disable column info in bytecode
     pub code_debug_ranges: bool,
     // int show_ref_count;
@@ -100,6 +103,10 @@ pub struct Settings {
     /// -X context_aware_warnings, whether warnings are context aware
     pub context_aware_warnings: bool,
 
+    /// -X lazy_imports, PYTHON_LAZY_IMPORTS: -1 for normal, 1 for all.
+    /// This startup value is independent of later sys.set_lazy_imports() calls.
+    pub lazy_imports: i8,
+
     /// -i
     pub inspect: bool,
 
@@ -148,7 +155,8 @@ pub struct Settings {
     /// Environment PYTHONPATH (and RUSTPYTHONPATH)
     pub path_list: Vec<String>,
 
-    // wchar_t *home;
+    /// PYTHONHOME: explicit prefix, optionally followed by the exec prefix.
+    pub home: Option<String>,
     // wchar_t *platlibdir;
     /// -d command line switch
     pub debug: u8,
@@ -208,11 +216,14 @@ impl Default for Settings {
             warn_default_encoding: false,
             thread_inherit_context: false,
             context_aware_warnings: false,
+            lazy_imports: -1,
             warnoptions: vec![],
             path_list: vec![],
+            home: None,
             argv: vec![],
             hash_seed: None,
             faulthandler: false,
+            import_time: 0,
             code_debug_ranges: true,
             buffered_stdio: true,
             check_hash_pycs_mode: CheckHashPycsMode::Default,
diff --git a/crates/vm/src/vm/thread.rs b/crates/vm/src/vm/thread.rs
index e1bc40c44b0..cbbc729b41c 100644
--- a/crates/vm/src/vm/thread.rs
+++ b/crates/vm/src/vm/thread.rs
@@ -1094,13 +1094,14 @@ pub fn get_current_frame() -> *const InterpreterFrame {
 /// Called from push_exception/pop_exception/set_exception.
 #[cfg(feature = "threading")]
 pub fn update_thread_exception(exc: Option<PyBaseExceptionRef>) {
-    CURRENT_THREAD_SLOT.with(|slot| {
-        if let Some(s) = slot.borrow().as_ref() {
-            // SAFETY: Called only from the owning thread. The old ref is dropped
-            // here on the owning thread, which is safe.
-            let _old = unsafe { s.exception.swap(exc) };
-        }
+    // Release the TLS borrow before dropping either exception: traceback
+    // locals can finalize another interpreter and re-enter this thread slot.
+    let slot = current_thread_slot();
+    let old = slot.and_then(|s| {
+        // SAFETY: Called only from the owning thread.
+        unsafe { s.exception.swap(exc) }
     });
+    drop(old);
 }
 
 /// Collect all threads' current exceptions for sys._current_exceptions().
@@ -1466,6 +1467,7 @@ impl VirtualMachine {
             exceptions: RefCell::default(),
             import_func: self.import_func.clone(),
             importlib: self.importlib.clone(),
+            import_timing: Cell::default(),
             profile_func: RefCell::new(global_profile.unwrap_or_else(|| self.ctx.none())),
             trace_func: RefCell::new(global_trace.unwrap_or_else(|| self.ctx.none())),
             use_tracing: Cell::new(use_tracing),
@@ -1475,6 +1477,7 @@ impl VirtualMachine {
             signal_handlers: core::cell::OnceCell::new(),
             signal_rx: None,
             repr_guards: RefCell::default(),
+            lazy_imports_resolving: RefCell::default(),
             state: self.state.clone(),
             initialized: self.initialized,
             recursion_depth: Cell::new(0),
diff --git a/crates/vm/src/vm/vm_new.rs b/crates/vm/src/vm/vm_new.rs
index c8f8d72efb2..217d63ab267 100644
--- a/crates/vm/src/vm/vm_new.rs
+++ b/crates/vm/src/vm/vm_new.rs
@@ -1,7 +1,5 @@
 #[cfg(feature = "parser")]
-use ruff_python_ast::token::TokenKind;
-
-use ruff_python_parser::{InterpolatedStringErrorType, LexicalErrorType, ParseErrorType};
+use ruff_python_parser::{LexicalErrorType, ParseErrorType};
 
 use rustpython_common::wtf8::Wtf8Buf;
 use rustpython_compiler_core::SourceLocation;
@@ -9,7 +7,7 @@ use rustpython_compiler_core::SourceLocation;
 use core::ops::RangeInclusive;
 
 #[cfg(feature = "parser")]
-use rustpython_compiler::{CompileError, ParseError, is_blank_python_source};
+use rustpython_compiler::is_blank_python_source;
 
 use crate::{
     AsObject, Py, PyObject, PyObjectRef, PyPayload, PyRef, PyResult,
@@ -49,262 +47,6 @@ macro_rules! define_exception_fn {
     };
 }
 
-#[derive(Clone, Debug)]
-struct SyntaxErrorInfo {
-    msg: String,
-    narrow_caret: bool,
-}
-
-impl SyntaxErrorInfo {
-    #[must_use]
-    const fn new(msg: String, narrow_caret: bool) -> Self {
-        Self { msg, narrow_caret }
-    }
-
-    #[cfg(feature = "parser")]
-    #[must_use]
-    const fn handle_expected_token(expected: TokenKind, found: TokenKind) -> &'static str {
-        match (expected, found) {
-            (TokenKind::Colon, TokenKind::Newline) => "expected ':'",
-
-            (TokenKind::Lpar, _) => "expected '('",
-
-            (TokenKind::Else, y) if !matches!(y, TokenKind::Colon) => {
-                "expected 'else' after 'if' expression"
-            }
-
-            _ => "invalid syntax",
-        }
-    }
-
-    #[cfg(feature = "parser")]
-    fn analyze_compile_error(&mut self, compile_error: &CompileError) {
-        let CompileError::Parse(ParseError {
-            error, location, ..
-        }) = compile_error
-        else {
-            return;
-        };
-
-        let msg = match error {
-            ParseErrorType::FStringError(InterpolatedStringErrorType::UnterminatedString)
-            | ParseErrorType::Lexical(LexicalErrorType::FStringError(
-                InterpolatedStringErrorType::UnterminatedString,
-            )) => "unterminated f-string literal".into(),
-
-            ParseErrorType::TStringError(InterpolatedStringErrorType::UnterminatedString)
-            | ParseErrorType::Lexical(LexicalErrorType::TStringError(
-                InterpolatedStringErrorType::UnterminatedString,
-            )) => "unterminated t-string literal".into(),
-
-            ParseErrorType::FStringError(
-                InterpolatedStringErrorType::UnterminatedTripleQuotedString,
-            )
-            | ParseErrorType::Lexical(LexicalErrorType::FStringError(
-                InterpolatedStringErrorType::UnterminatedTripleQuotedString,
-            )) => "unterminated triple-quoted f-string literal".into(),
-
-            ParseErrorType::TStringError(
-                InterpolatedStringErrorType::UnterminatedTripleQuotedString,
-            )
-            | ParseErrorType::Lexical(LexicalErrorType::TStringError(
-                InterpolatedStringErrorType::UnterminatedTripleQuotedString,
-            )) => "unterminated triple-quoted t-string literal".into(),
-
-            // ruff already prefixes these with `f-string: ` / `t-string: `, matching CPython.
-            // It quotes braces with backticks where CPython uses single quotes.
-            ParseErrorType::FStringError(_)
-            | ParseErrorType::TStringError(_)
-            | ParseErrorType::Lexical(
-                LexicalErrorType::FStringError(_) | LexicalErrorType::TStringError(_),
-            ) => self.msg.replace('`', "'"),
-
-            ParseErrorType::UnexpectedExpressionToken => "invalid syntax".into(),
-
-            ParseErrorType::ExpectedToken { expected, found } => {
-                Self::handle_expected_token(*expected, *found).into()
-            }
-
-            ParseErrorType::InvalidStarredExpressionUsage => {
-                self.narrow_caret = true;
-                "invalid syntax".into()
-            }
-
-            ParseErrorType::InvalidDeleteTarget => "invalid syntax".into(),
-
-            ParseErrorType::Lexical(LexicalErrorType::LineContinuationError) => {
-                "unexpected character after line continuation character".into()
-            }
-
-            ParseErrorType::Lexical(LexicalErrorType::UnclosedStringError) => {
-                format!(
-                    "unterminated string literal (detected at line {})",
-                    location.line
-                )
-            }
-
-            ParseErrorType::EmptyTypeParams => "Type parameter list cannot be empty".into(),
-
-            ParseErrorType::InvalidStarPatternUsage => {
-                self.narrow_caret = true;
-                "cannot use starred expression here".into()
-            }
-
-            ParseErrorType::ExpectedKeywordParam => "named arguments must follow bare *".into(),
-
-            ParseErrorType::EmptyImportNames => "Expected one or more names after 'import'".into(),
-
-            ParseErrorType::UnparenthesizedGeneratorExpression => {
-                "Generator expression must be parenthesized".into()
-            }
-
-            ParseErrorType::NonDefaultParamAfterDefaultParam => {
-                "parameter without a default follows parameter with a default".into()
-            }
-
-            ParseErrorType::VarParameterWithDefault => {
-                "var-positional argument cannot have default value".into()
-            }
-
-            ParseErrorType::PositionalAfterKeywordArgument => {
-                "positional argument follows keyword argument".into()
-            }
-
-            ParseErrorType::PositionalAfterKeywordUnpacking => {
-                "positional argument follows keyword argument unpacking".into()
-            }
-
-            ParseErrorType::InvalidArgumentUnpackingOrder => {
-                "iterable argument unpacking follows keyword argument unpacking".into()
-            }
-
-            ParseErrorType::ParamAfterVarKeywordParam => {
-                "arguments cannot follow var-keyword argument".into()
-            }
-
-            ParseErrorType::InvalidAnnotatedAssignmentTarget => {
-                "illegal target for annotation".into()
-            }
-
-            ParseErrorType::Lexical(LexicalErrorType::UnrecognizedToken { .. })
-            | ParseErrorType::SimpleStatementsOnSameLine
-            | ParseErrorType::SimpleAndCompoundStatementOnSameLine
-            | ParseErrorType::ExpectedExpression => "invalid syntax".into(),
-
-            ParseErrorType::OtherError(s) if s.starts_with("Expected an identifier") => {
-                "invalid syntax".into()
-            }
-
-            // What the parser says when it cannot continue the list it is
-            // recovering; each of these situations is a plain "invalid syntax".
-            ParseErrorType::OtherError(s)
-                if matches!(
-                    s.as_str(),
-                    "Expected a statement"
-                        | "Expected an `elif` or `else` clause, or the end of the `if` statement."
-                        | "Expected an `except` or `finally` clause or the end of the `try` statement."
-                        | "The keyword is not allowed as a variable declaration name"
-                        | "Expected an assignment target"
-                        | "Expected a type parameter or the end of the type parameter list"
-                        | "Expected an import name or a ')'"
-                        | "Expected an import name"
-                        | "Expected an expression or the end of the slice list"
-                        | "Expected an expression or a ']'"
-                        | "Expected an expression or a '}'"
-                        | "Expected an expression or a ')'"
-                        | "Expected an expression"
-                        | "Expected a pattern or the end of the sequence pattern"
-                        | "Expected a mapping pattern or the end of the mapping pattern"
-                        | "Expected a pattern or a ')'"
-                        | "Expected a delete target"
-                        | "Expected a parameter or the end of the parameter list"
-                        | "Expected an expression or the end of the with item list"
-                ) =>
-            {
-                "invalid syntax".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case(
-                    "bytes literal cannot be mixed with non-bytes literals",
-                ) =>
-            {
-                "cannot mix bytes and nonbytes literals".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case("positional patterns cannot follow keyword patterns") =>
-            {
-                "positional patterns follow keyword patterns".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case("boolean 'not' expression cannot be used here") =>
-            {
-                "'not' after an operator must be parenthesized".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case("trailing comma not allowed") =>
-            {
-                "trailing comma not allowed without surrounding parentheses".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case(
-                    "multiple exception types must be parenthesized when using `as`",
-                ) =>
-            {
-                "multiple exception types must be parenthesized when using 'as'".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case(
-                    "position-only parameter separator not allowed as first parameter",
-                ) =>
-            {
-                "at least one argument must precede /".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case("only one '/' separator allowed") =>
-            {
-                "/ may appear only once".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case("'/' parameter must appear before '*' parameter") =>
-            {
-                "/ must be ahead of *".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case("expected `except` or `finally` after `try` block") =>
-            {
-                "expected 'except' or 'finally' block".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case("only one '*' parameter allowed") =>
-            {
-                "* argument may appear only once".into()
-            }
-
-            ParseErrorType::OtherError(s)
-                if s.eq_ignore_ascii_case(
-                    r#"cannot have both 'except' and 'except*' on the same 'try'"#,
-                ) =>
-            {
-                r#"cannot have both 'except' and 'except*' on the same 'try'"#.into()
-            }
-
-            _ => return,
-        };
-
-        self.msg = msg;
-    }
-}
-
 /// Collection of object creation helpers
 impl VirtualMachine {
     /// Create a new python object
@@ -313,8 +55,8 @@ impl VirtualMachine {
     }
 
     pub fn new_code(&self, code: impl IntoCodeObject) -> PyRef<PyCode> {
-        let code = code.into_code_object(self);
-        PyRef::new_ref(PyCode::new(code), self.ctx.types.code_type.to_owned(), None)
+        let code = code.into_pycode(self);
+        PyRef::new_ref(code, self.ctx.types.code_type.to_owned(), None)
     }
 
     pub fn new_tuple(&self, value: impl IntoPyTuple) -> PyTupleRef {
@@ -341,15 +83,16 @@ impl VirtualMachine {
     }
 
     pub fn new_scope_with_main(&self) -> PyResult<Scope> {
-        let scope = self.new_scope_with_builtins();
-        let main_module = self.new_module("__main__", scope.globals.clone(), None);
+        let globals = self.ctx.new_dict();
+        let scope = Scope::with_builtins(None, globals.clone(), self);
+        let main_module = self.new_module("__main__", globals.clone(), None);
 
         self.sys_module.get_attr("modules", self)?.set_item(
             "__main__",
             main_module.into(),
             self,
         )?;
-        self.set_main_builtin_importer(&scope.globals)?;
+        self.set_main_builtin_importer(&globals)?;
 
         Ok(scope)
     }
@@ -371,6 +114,19 @@ impl VirtualMachine {
         Ok(module)
     }
 
+    /// PyImport_AddModuleRef("__main__")
+    pub fn add_main_module(&self) -> PyResult<PyRef<PyModule>> {
+        let modules = self.sys_module.get_attr(identifier!(self, modules), self)?;
+        if let Ok(module) = modules.get_item(identifier!(self, __main__), self)
+            && let Ok(module) = module.downcast::<PyModule>()
+        {
+            return Ok(module);
+        }
+        let module = self.new_module("__main__", self.ctx.new_dict(), None);
+        modules.set_item(identifier!(self, __main__), module.clone().into(), self)?;
+        Ok(module)
+    }
+
     /// Set `__main__.__loader__` to BuiltinImporter when it is missing or None.
     pub fn set_main_builtin_importer(
         &self,
@@ -703,38 +459,6 @@ impl VirtualMachine {
         .expect("UnicodeEncodeError constructor")
     }
 
-    #[cfg(feature = "parser")]
-    fn source_has_mixed_tabs_and_spaces(source: Option<&str>, error_line: usize) -> bool {
-        source.is_some_and(|source| {
-            let mut has_space_indent = false;
-            let mut has_tab_indent = false;
-            for (i, line) in source.lines().enumerate() {
-                if i + 1 > error_line {
-                    break;
-                }
-                let rest = line.trim_start_matches([' ', '\t']);
-                // Blank and comment-only lines do not participate in indent.
-                if rest.is_empty() || rest.starts_with('#') {
-                    continue;
-                }
-                let indent = &line.as_bytes()[..line.len() - rest.len()];
-                if indent.is_empty() {
-                    continue;
-                }
-                if indent.contains(&b' ') && indent.contains(&b'\t') {
-                    return true;
-                }
-                if indent.contains(&b' ') {
-                    has_space_indent = true;
-                }
-                if indent.contains(&b'\t') {
-                    has_tab_indent = true;
-                }
-            }
-            has_space_indent && has_tab_indent
-        })
-    }
-
     // TODO: don't take ownership should make the success path faster
     pub fn new_key_error(&self, obj: PyObjectRef) -> PyBaseExceptionRef {
         let key_error = self.ctx.exceptions.key_error.to_owned();
@@ -767,27 +491,29 @@ impl VirtualMachine {
         };
 
         let syntax_error_type = match &error {
+            #[cfg(feature = "parser")]
+            crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
+                error: ParseErrorType::Lexical(LexicalErrorType::TabError),
+                ..
+            }) => self.ctx.exceptions.tab_error,
             #[cfg(feature = "parser")]
             crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
                 error:
-                    ruff_python_parser::ParseErrorType::Lexical(
-                        ruff_python_parser::LexicalErrorType::IndentationError,
+                    ParseErrorType::Lexical(
+                        LexicalErrorType::IndentationError | LexicalErrorType::TooDeepIndentation,
                     )
-                    | ruff_python_parser::ParseErrorType::UnexpectedIndentation,
-                location,
+                    | ParseErrorType::UnexpectedIndentation,
                 ..
-            }) => {
-                if Self::source_has_mixed_tabs_and_spaces(source, location.line.get()) {
-                    self.ctx.exceptions.tab_error
-                } else {
-                    self.ctx.exceptions.indentation_error
-                }
-            }
+            }) => self.ctx.exceptions.indentation_error,
             #[cfg(feature = "parser")]
             crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
                 error:
                     ruff_python_parser::ParseErrorType::Lexical(
-                        ruff_python_parser::LexicalErrorType::Eof,
+                        ruff_python_parser::LexicalErrorType::Eof
+                        | ruff_python_parser::LexicalErrorType::UnclosedBracket {
+                            incomplete: true,
+                            ..
+                        },
                     ),
                 ..
             }) => incomplete_or_syntax(allow_incomplete),
@@ -807,67 +533,53 @@ impl VirtualMachine {
                 error:
                     ruff_python_parser::ParseErrorType::Lexical(
                         ruff_python_parser::LexicalErrorType::FStringError(
-                            ruff_python_parser::InterpolatedStringErrorType::UnterminatedTripleQuotedString,
+                            ruff_python_parser::InterpolatedStringErrorType::UnterminatedTripleQuotedString { .. },
                         )
                         | ruff_python_parser::LexicalErrorType::TStringError(
-                            ruff_python_parser::InterpolatedStringErrorType::UnterminatedTripleQuotedString,
+                            ruff_python_parser::InterpolatedStringErrorType::UnterminatedTripleQuotedString { .. },
                         ),
                     ),
                 ..
             }) => incomplete_or_syntax(allow_incomplete),
             #[cfg(feature = "parser")]
             crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
-                error:
-                    ruff_python_parser::ParseErrorType::Lexical(
-                        ruff_python_parser::LexicalErrorType::UnclosedStringError,
-                    ),
+                error: ruff_python_parser::ParseErrorType::ExpectedIndentedBlock { .. },
+                raw_location,
                 ..
             }) => {
-                if allow_incomplete {
-                    incomplete_or_syntax(source.is_some_and(unclosed_string_is_incomplete))
+                // The block can still follow when the error is found at whitespace, that is, at
+                // the end of the input.
+                let at_end = source.is_some_and(|source| {
+                    source
+                        .get(raw_location.start().to_usize()..raw_location.end().to_usize())
+                        .is_some_and(|text| text.chars().all(|c| c.is_ascii_whitespace()))
+                });
+                if allow_incomplete && at_end {
+                    self.ctx.exceptions.incomplete_input_error
                 } else {
-                    self.ctx.exceptions.syntax_error
+                    self.ctx.exceptions.indentation_error
                 }
             }
+            // _is_end_of_source: the parser failed at the end of the input,
+            // where more input can still follow.
+            #[cfg(feature = "parser")]
+            crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
+                error,
+                raw_location,
+                ..
+            }) if !matches!(error, ParseErrorType::Lexical(_))
+                && source
+                    .is_some_and(|source| raw_location.start().to_usize() >= source.len()) =>
+            {
+                incomplete_or_syntax(allow_incomplete)
+            }
             #[cfg(feature = "parser")]
             crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
                 error: ruff_python_parser::ParseErrorType::OtherError(s),
                 raw_location,
                 ..
             }) => {
-                if s.starts_with("Expected an indented block after")
-                    || s.starts_with("expected an indented block after")
-                {
-                    if allow_incomplete {
-                        // Check that all chars in the error are whitespace, if so, the source is
-                        // incomplete. Otherwise, we've found code that might violates
-                        // indentation rules.
-                        let mut is_incomplete = true;
-                        if let Some(source) = source {
-                            let start = raw_location.start().to_usize();
-                            let end = raw_location.end().to_usize();
-                            let mut iter = source.chars();
-                            iter.nth(start);
-                            for _ in start..end {
-                                if let Some(c) = iter.next() {
-                                    if !c.is_ascii_whitespace() {
-                                        is_incomplete = false;
-                                    }
-                                } else {
-                                    break;
-                                }
-                            }
-                        }
-
-                        if is_incomplete {
-                            self.ctx.exceptions.incomplete_input_error
-                        } else {
-                            self.ctx.exceptions.indentation_error // not syntax_error
-                        }
-                    } else {
-                        self.ctx.exceptions.indentation_error
-                    }
-                } else if allow_incomplete
+                if allow_incomplete
                     && (s == "incomplete input"
                         || (s == "unexpected EOF while parsing"
                             && source.is_some_and(|source| {
@@ -902,58 +614,27 @@ impl VirtualMachine {
         // Tokenizer/parser errors attach the current source line. Compiler
         // errors load that line with ProgramText, which is None when the
         // filename cannot be opened (compile of a string).
-        let mut statement = if matches!(error, crate::compiler::CompileError::Codegen(_)) {
+        let eof_token = match error {
+            crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
+                eof_token: Some(eof_token),
+                ..
+            }) => Some(eof_token),
+            _ => None,
+        };
+        let mut statement = if let Some(eof_token) = eof_token {
+            Some(eof_token.line.clone())
+        } else if matches!(error, crate::compiler::CompileError::Codegen(_)) {
             self.program_text(error.source_path(), error.python_location().0)
         } else {
             source.and_then(|src| get_statement(src, error.location()))
         };
 
-        let mut msg = error.to_string();
-        if !msg.starts_with("Exceeds the limit ")
-            && !msg.starts_with("Did you mean ")
-            && !msg.starts_with("Invalid star expression")
-            && !msg.starts_with("Function parameters cannot be parenthesized")
-            && !msg.starts_with("Lambda expression parameters cannot be parenthesized")
-            && !msg.starts_with("Cannot have two type comments on def")
-            && !msg.starts_with("Variable annotation syntax is")
-            && !msg.starts_with("The '@' operator is")
-            && !msg.starts_with("Async functions are")
-            && !msg.starts_with("Async comprehensions are")
-            && !msg.starts_with("Async for loops are")
-            && !msg.starts_with("Async with statements are")
-            && !msg.starts_with("Exception groups are")
-            && !msg.starts_with("Positional-only parameters are")
-            && !msg.starts_with("Pattern matching is")
-            && !msg.starts_with("Type statement is")
-            && !msg.starts_with("Type parameter lists are")
-            && !msg.starts_with("Type parameter defaults are")
-            && !msg.starts_with("Assignment expressions are")
-            && !msg.starts_with("Await expressions are")
-            && !msg.starts_with("Underscores in numeric literals are")
-            && !msg.starts_with("Missing parentheses")
-            && let Some(msg) = msg.get_mut(..1)
-        {
-            msg.make_ascii_lowercase();
-        }
-
-        cfg_select! {
-            feature = "parser" => {
-                let mut syntax_error_info = SyntaxErrorInfo::new(msg, false);
-                syntax_error_info.analyze_compile_error(error);
-            }
-            _ => {
-                let syntax_error_info = SyntaxErrorInfo::new(msg, false);
-            }
+        let msg = if syntax_error_type.is(self.ctx.exceptions.incomplete_input_error) {
+            String::from("incomplete input")
+        } else {
+            error.to_string()
         };
 
-        if syntax_error_type.is(self.ctx.exceptions.tab_error) {
-            syntax_error_info.msg =
-                String::from("inconsistent use of tabs and spaces in indentation");
-        } else if syntax_error_type.is(self.ctx.exceptions.incomplete_input_error) {
-            syntax_error_info.msg = String::from("incomplete input");
-        }
-
-        let SyntaxErrorInfo { msg, narrow_caret } = syntax_error_info;
         let unterminated_triple_quoted_string = msg.starts_with("unterminated triple-quoted");
         let unexpected_eof_error = msg == "unexpected EOF while parsing";
         if unterminated_triple_quoted_string
@@ -970,6 +651,52 @@ impl VirtualMachine {
             || msg.starts_with("except expressions without parentheses are")
             || msg.starts_with("Pattern matching is");
         let line_end_binary_operator_error = msg.starts_with("The '@' operator is");
+        // Tokenizer errors other than unexpected EOF end where the tokenizer stopped, which is
+        // reported as end offset 0 or -1, or where they start.
+        let tokenizer_end_offset = cfg_select! {
+            feature = "parser" => {
+                match error {
+                    crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
+                        error:
+                            ParseErrorType::Lexical(
+                                LexicalErrorType::TabError
+                                | LexicalErrorType::TooDeepIndentation
+                                | LexicalErrorType::LineContinuationError
+                                | LexicalErrorType::UnclosedBracket { .. },
+                            ),
+                        ..
+                    }) => Some(0),
+                    crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
+                        error:
+                            ParseErrorType::Lexical(LexicalErrorType::IndentationError)
+                            | ParseErrorType::UnexpectedIndentation,
+                        ..
+                    }) => Some(-1),
+                    // The span runs from the last character of the key to the end of the line.
+                    crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
+                        error: ParseErrorType::ExpectedColonAfterDictionaryKey,
+                        ..
+                    }) => Some(0),
+                    // Other tokenizer errors end where they start, except those reported
+                    // over a range.
+                    crate::compiler::CompileError::Parse(rustpython_compiler::ParseError {
+                        error: ParseErrorType::Lexical(lexical),
+                        ..
+                    }) if lexical.is_tokenizer_error()
+                        && !matches!(
+                            lexical,
+                            LexicalErrorType::Eof
+                                | LexicalErrorType::LeadingZerosInDecimalInteger
+                                | LexicalErrorType::IncompatibleStringPrefixes { .. }
+                        ) =>
+                    {
+                        Some(error.python_location().1 as isize)
+                    }
+                    _ => None,
+                }
+            }
+            _ => None,
+        };
         let unclosed_bracket_error = cfg_select! {
             feature = "parser" => {
                 matches!(
@@ -1009,17 +736,18 @@ impl VirtualMachine {
                         .as_deref()
                         .and_then(|line| line.chars().next())
                         .is_some_and(|ch| ch.is_ascii_whitespace()));
-            let (end_lineno, end_offset) = if no_end_offset {
+            let (end_lineno, end_offset) = if let Some(eof_token) = eof_token {
+                (eof_token.lineno, eof_token.end_offset())
+            } else if no_end_offset {
                 (end_lineno, -1)
+            } else if let Some(end_offset) = tokenizer_end_offset {
+                (end_lineno, end_offset)
             } else if unclosed_bracket_error {
                 // The bracket that was never closed is marked where it opened,
                 // and the span stops there.
                 (end_lineno, 0)
             } else if line_end_binary_operator_error && end_offset == offset_raw {
                 (end_lineno, (end_offset + 1) as isize)
-            } else if narrow_caret {
-                let (l, o) = error.python_location();
-                (l, (o + 1) as isize)
             } else {
                 (end_lineno, end_offset as isize)
             };
@@ -1207,119 +935,3 @@ impl VirtualMachine {
         .upcast()
     }
 }
-
-#[cfg(feature = "parser")]
-enum QuotedStringScan {
-    Closed(usize),
-    Unclosed {
-        triple: bool,
-        unescaped_newline: bool,
-    },
-}
-
-/// An unclosed string is incomplete when more input could still finish it.
-/// A non-triple string that already hit an unescaped newline is a hard error.
-#[cfg(feature = "parser")]
-fn unclosed_string_is_incomplete(source: &str) -> bool {
-    let bytes = source.as_bytes();
-    let mut index = 0;
-    while index < bytes.len() {
-        match bytes[index] {
-            b'#' => {
-                while index < bytes.len() && bytes[index] != b'\n' {
-                    index += 1;
-                }
-            }
-            b'\'' | b'"' => match scan_quoted_string_for_incomplete(bytes, index) {
-                QuotedStringScan::Closed(end) => index = end,
-                QuotedStringScan::Unclosed {
-                    triple,
-                    unescaped_newline,
-                } => {
-                    // Single-quoted f/t-strings never set E_EOLS.
-                    if !triple && interpolated_string_prefix_at(bytes, index) {
-                        return false;
-                    }
-                    return triple || !unescaped_newline;
-                }
-            },
-            _ => index += 1,
-        }
-    }
-    false
-}
-
-#[cfg(feature = "parser")]
-fn interpolated_string_prefix_at(bytes: &[u8], quote: usize) -> bool {
-    let Some(&prev) = quote.checked_sub(1).and_then(|index| bytes.get(index)) else {
-        return false;
-    };
-    let lower = prev.to_ascii_lowercase();
-    let marker_index = if matches!(lower, b'f' | b't') {
-        if quote >= 2 && bytes[quote - 2].eq_ignore_ascii_case(&b'r') {
-            quote - 2
-        } else {
-            quote - 1
-        }
-    } else if lower == b'r'
-        && quote >= 2
-        && matches!(bytes[quote - 2].to_ascii_lowercase(), b'f' | b't')
-    {
-        quote - 2
-    } else {
-        return false;
-    };
-    marker_index == 0 || !identifier_continue_before(bytes, marker_index)
-}
-
-#[cfg(feature = "parser")]
-fn identifier_continue_before(bytes: &[u8], index: usize) -> bool {
-    if index == 0 {
-        return false;
-    }
-    if bytes[index - 1].is_ascii() {
-        return bytes[index - 1] == b'_' || bytes[index - 1].is_ascii_alphanumeric();
-    }
-    let mut start = index - 1;
-    while start > 0 && bytes[start] & 0b1100_0000 == 0b1000_0000 {
-        start -= 1;
-    }
-    ::core::str::from_utf8(&bytes[start..index])
-        .ok()
-        .and_then(|text| text.chars().next_back())
-        .is_some_and(|ch| ch == '_' || ch.is_alphanumeric())
-}
-
-#[cfg(feature = "parser")]
-fn scan_quoted_string_for_incomplete(bytes: &[u8], quote_index: usize) -> QuotedStringScan {
-    let quote = bytes[quote_index];
-    let triple =
-        bytes.get(quote_index + 1) == Some(&quote) && bytes.get(quote_index + 2) == Some(&quote);
-    let mut index = quote_index + if triple { 3 } else { 1 };
-    while index < bytes.len() {
-        if bytes[index] == b'\\' {
-            index = (index + 2).min(bytes.len());
-            continue;
-        }
-        if triple {
-            if bytes.get(index) == Some(&quote)
-                && bytes.get(index + 1) == Some(&quote)
-                && bytes.get(index + 2) == Some(&quote)
-            {
-                return QuotedStringScan::Closed(index + 3);
-            }
-        } else if bytes[index] == quote {
-            return QuotedStringScan::Closed(index + 1);
-        } else if bytes[index] == b'\n' {
-            return QuotedStringScan::Unclosed {
-                triple: false,
-                unescaped_newline: true,
-            };
-        }
-        index += 1;
-    }
-    QuotedStringScan::Unclosed {
-        triple,
-        unescaped_newline: false,
-    }
-}
diff --git a/crates/vm/src/vm/vm_object.rs b/crates/vm/src/vm/vm_object.rs
index baa0c8095c6..db9459b9b75 100644
--- a/crates/vm/src/vm/vm_object.rs
+++ b/crates/vm/src/vm/vm_object.rs
@@ -9,6 +9,23 @@ use crate::{
 
 /// PyObject support
 impl VirtualMachine {
+    /// PyObject_Dump
+    ///
+    /// Write a description of `obj` to the process stderr, bypassing
+    /// `sys.stderr`.
+    pub fn dump_object(&self, obj: &PyObject) {
+        let class = obj.class();
+        eprintln!("object address  : {obj:p}");
+        eprintln!("object refcount : {}", obj.strong_count());
+        eprintln!("object type     : {class:p}");
+        eprintln!("object type name: {}", class.slot_name());
+        eprint!("object repr     : ");
+        if let Ok(repr) = obj.repr(self) {
+            eprint!("{}", repr.as_wtf8());
+        }
+        eprintln!();
+    }
+
     #[track_caller]
     #[cold]
     fn _py_panic_failed(&self, exc: PyBaseExceptionRef, msg: &str) -> ! {
diff --git a/crates/vm/src/warn.rs b/crates/vm/src/warn.rs
index 3d8e7cb6fb1..dee57e50659 100644
--- a/crates/vm/src/warn.rs
+++ b/crates/vm/src/warn.rs
@@ -100,14 +100,33 @@ impl WarningsState {
 
 /// None matches everything; plain strings do exact comparison;
 /// regex objects use .match().
-fn check_matched(obj: &PyObject, arg: &PyObject, vm: &VirtualMachine) -> PyResult<bool> {
+fn check_matched(
+    obj: &PyObject,
+    arg: Option<&PyObject>,
+    arg2: Option<&Py<PyStr>>,
+    vm: &VirtualMachine,
+) -> PyResult<bool> {
+    // A 'None' filter always matches
     if vm.is_none(obj) {
         return Ok(true);
     }
+    // An internal plain text default filter must match exactly
     if obj.class().is(vm.ctx.types.str_type) {
-        return obj.rich_compare_bool(arg, crate::types::PyComparisonOp::Eq, vm);
+        return match arg {
+            Some(arg) => obj.rich_compare_bool(arg, crate::types::PyComparisonOp::Eq, vm),
+            None => Ok(false),
+        };
     }
-    let result = vm.call_method(obj, "match", (arg.to_owned(),))?;
+    // Otherwise assume a regex filter and call its match() method
+    let result = match arg {
+        Some(arg) => vm.call_method(obj, "match", (arg.to_owned(),))?,
+        None => {
+            let match_filename = vm
+                .import("_py_warnings", 0)?
+                .get_attr("_match_filename", vm)?;
+            match_filename.call((obj.to_owned(), arg2.map(|f| f.to_owned())), vm)?
+        }
+    };
     result.is_true(vm)
 }
 
@@ -201,7 +220,7 @@ pub(crate) fn get_source_line(
     };
 
     let module_name = if let Some(dict) = module_globals.downcast_ref::<PyDict>() {
-        match dict.get_item_opt(identifier!(vm, __name__), vm)? {
+        match dict.inner_getitem_opt(identifier!(vm, __name__), vm)? {
             Some(name) => name,
             None => return Ok(None),
         }
@@ -336,22 +355,14 @@ fn update_registry(
     already_warned(registry, &altkey, true, vm)
 }
 
-fn normalize_module(filename: &Py<PyStr>, vm: &VirtualMachine) -> PyObjectRef {
-    match filename.byte_len() {
-        0 => vm.new_pyobj("<unknown>"),
-        len if len >= 3 && filename.as_bytes().ends_with(b".py") => {
-            vm.new_pyobj(&filename.as_wtf8()[..len - 3])
-        }
-        _ => filename.as_object().to_owned(),
-    }
-}
-
 /// Search a filters list for a matching action.
+#[allow(clippy::too_many_arguments)]
 fn filter_search(
     category: &PyObject,
     text: &PyObject,
     lineno: usize,
-    module: &PyObject,
+    module: Option<&PyObject>,
+    filename: &Py<PyStr>,
     filters: &PyListRef,
     list_name: &str,
     vm: &VirtualMachine,
@@ -378,9 +389,9 @@ fn filter_search(
                 action.class().name()
             )));
         }
-        let good_msg = check_matched(&tmp_item.as_slice()[1], text, vm)?;
+        let good_msg = check_matched(&tmp_item.as_slice()[1], Some(text), None, vm)?;
         let is_subclass = category.is_subclass(&tmp_item.as_slice()[2], vm)?;
-        let good_mod = check_matched(&tmp_item.as_slice()[3], module, vm)?;
+        let good_mod = check_matched(&tmp_item.as_slice()[3], module, Some(filename), vm)?;
         let ln: usize = tmp_item.as_slice()[4]
             .try_int(vm)
             .map_or(0, |v| v.as_u32_mask() as _);
@@ -397,7 +408,8 @@ fn get_filter(
     category: &PyObject,
     text: &PyObject,
     lineno: usize,
-    module: &PyObject,
+    module: Option<&PyObject>,
+    filename: &Py<PyStr>,
     vm: &VirtualMachine,
 ) -> PyResult {
     if let Some(context_filters) = get_warnings_context_filters(vm)? {
@@ -406,6 +418,7 @@ fn get_filter(
             text,
             lineno,
             module,
+            filename,
             &context_filters,
             "_warnings_context _filters",
             vm,
@@ -416,7 +429,9 @@ fn get_filter(
     }
 
     let filters = get_warnings_filters(vm)?;
-    if let Some(action) = filter_search(category, text, lineno, module, &filters, "filters", vm)? {
+    if let Some(action) = filter_search(
+        category, text, lineno, module, filename, &filters, "filters", vm,
+    )? {
         return Ok(action);
     }
     get_default_action(vm)
@@ -504,9 +519,11 @@ pub fn warn_explicit(
     source: Option<PyObjectRef>,
     vm: &VirtualMachine,
 ) -> PyResult<()> {
-    // Normalize module. None → silent return (late-shutdown safety).
-    let module = module.unwrap_or_else(|| normalize_module(&filename, vm));
-    if vm.is_none(&module) {
+    // module can be None if a warning is emitted late during Python shutdown.
+    // In this case, the Python warnings module was probably unloaded, filters
+    // are no more available to choose as action. It is safer to ignore the
+    // warning and do nothing.
+    if module.as_ref().is_some_and(|module| vm.is_none(module)) {
         return Ok(());
     }
 
@@ -543,7 +560,14 @@ pub fn warn_explicit(
     }
 
     // Get filter action
-    let action = get_filter(category.as_object(), text.as_object(), lineno, &module, vm)?;
+    let action = get_filter(
+        category.as_object(),
+        text.as_object(),
+        lineno,
+        module.as_deref(),
+        &filename,
+        vm,
+    )?;
     let action_str = PyStrRef::try_from_object(vm, action)
         .map_err(|_| vm.new_type_error("action must be a string"))?;
 
@@ -603,6 +627,7 @@ pub fn warn_explicit(
         lineno_obj,
         source_line,
         source,
+        module,
         vm,
     )
 }
@@ -617,6 +642,7 @@ fn call_show_warning(
     lineno_obj: PyObjectRef,
     source_line: Option<PyObjectRef>,
     source: Option<PyObjectRef>,
+    module: Option<PyObjectRef>,
     vm: &VirtualMachine,
 ) -> PyResult<()> {
     let Some(show_fn) = get_warnings_attr(vm, identifier!(vm, _showwarnmsg), source.is_some())?
@@ -642,6 +668,7 @@ fn call_show_warning(
             vm.ctx.none(),
             vm.ctx.none(),
             vm.unwrap_or_none(source),
+            vm.unwrap_or_none(module),
         ],
         vm,
     )?;
@@ -745,15 +772,8 @@ fn setup_context(
             f.iframe().code().source_path(),
             f.lineno().max(0) as usize,
         )
-    } else if let Some(frame) = vm.current_frame() {
-        // We have a frame but it wasn't found during stack walking
-        (
-            frame.iframe().globals().to_owned(),
-            vm.ctx.intern_str("<sys>"),
-            1,
-        )
     } else {
-        // No frames on the stack - use sys.__dict__ (interp->sysdict)
+        // An exhausted stack walk uses sys.__dict__ (interp->sysdict).
         let globals = vm
             .sys_module
             .as_object()
@@ -762,12 +782,12 @@ fn setup_context(
                 d.downcast::<crate::builtins::PyDict>()
                     .map_err(|_| vm.new_type_error("sys.__dict__ is not a dictionary"))
             })?;
-        (globals, vm.ctx.intern_str("<sys>"), 0)
+        (globals.into(), vm.ctx.intern_str("<sys>"), 0)
     };
 
-    let registry = match globals.get_item("__warningregistry__", vm) {
-        Ok(r) => r,
-        Err(_) => {
+    let registry = match globals.inner_getitem_opt("__warningregistry__", vm)? {
+        Some(r) => r,
+        None => {
             let r = vm.ctx.new_dict();
             globals.set_item("__warningregistry__", r.clone().into(), vm)?;
             r.into()
@@ -776,7 +796,8 @@ fn setup_context(
 
     // Setup module.
     let module = globals
-        .get_item("__name__", vm)
-        .unwrap_or_else(|_| vm.new_pyobj("<string>"));
+        .inner_getitem_opt("__name__", vm)?
+        .filter(|module| vm.is_none(module) || module.downcastable::<PyStr>())
+        .unwrap_or_else(|| vm.new_pyobj("<string>"));
     Ok((filename.to_owned(), lineno, Some(module), registry))
 }
diff --git a/crates/wasm/Cargo.toml b/crates/wasm/Cargo.toml
index f9ea3ab9e3d..def85c07298 100644
--- a/crates/wasm/Cargo.toml
+++ b/crates/wasm/Cargo.toml
@@ -12,9 +12,10 @@ license.workspace = true
 crate-type = ["cdylib", "rlib"]
 
 [features]
-default = ["freeze-stdlib", "doc"]
+default = ["freeze-stdlib", "doc", "ucd_3_2_0"]
 doc = ["rustpython-vm/doc", "rustpython-stdlib?/doc"]
 freeze-stdlib = ["rustpython-vm/freeze-stdlib", "rustpython-pylib/freeze-stdlib", "rustpython-stdlib", "rustpython-stdlib/ssl"]
+ucd_3_2_0 = ["rustpython-stdlib?/ucd_3_2_0"]
 no-start-func = []
 
 [dependencies]
diff --git a/extra_tests/snippets/builtin___main__.py b/extra_tests/snippets/builtin___main__.py
index 97e76ce324a..14cd3f3b984 100644
--- a/extra_tests/snippets/builtin___main__.py
+++ b/extra_tests/snippets/builtin___main__.py
@@ -2,4 +2,4 @@
 
 main_module = sys.modules["__main__"]
 assert main_module.__file__.endswith("builtin___main__.py")
-assert main_module.__cached__ is None
+assert not hasattr(main_module, "__cached__")
diff --git a/extra_tests/snippets/builtin_bytearray.py b/extra_tests/snippets/builtin_bytearray.py
index d897ec94782..41199ecdacf 100644
--- a/extra_tests/snippets/builtin_bytearray.py
+++ b/extra_tests/snippets/builtin_bytearray.py
@@ -733,6 +733,17 @@ def join_resize_separator():
 a.clear()
 assert len(a) == 0
 
+# Clearing an empty exported buffer is a no-op and keeps its export alive.
+empty = bytearray()
+with memoryview(empty) as view:
+    assert empty.clear() is None
+    assert bytes(view) == b""
+    assert empty.clear() is None
+    with assert_raises(BufferError):
+        empty.append(1)
+empty.append(1)
+assert empty == b"\x01"
+
 b = bytearray(b"test")
 assert len(b) == 4
 b.pop()
@@ -913,3 +924,841 @@ class B(bytearray):
 empty = bytearray()
 empty *= sys.maxsize
 assert empty == bytearray()
+
+
+def test_bytearray_exports():
+    """Resizing paths must respect outstanding bytearray exports."""
+
+    import io
+
+    from testutils import assert_raises
+
+    for args in ((), (b"abc",), (b"x",), (b"",), (object(),)):
+        value = bytearray(b"abc")
+        with memoryview(value) as view:
+            with assert_raises(BufferError):
+                value.__init__(*args)
+            assert value == b"abc"
+            assert view.tobytes() == b"abc"
+        value.__init__(b"released")
+        assert value == b"released"
+
+    value = bytearray(b"abc")
+    with assert_raises(TypeError):
+        value.__init__(object())
+    assert value == b""
+    value = bytearray(b"abc")
+    value.__init__(value)
+    assert value == b""
+
+    class ExportDuringInit:
+        def __init__(self, count, payload=b""):
+            self.count = count
+            self.payload = payload
+            self.calls = 0
+
+        def __index__(self):
+            self.calls += 1
+            value.extend(self.payload)
+            self.view = memoryview(value)
+            return self.count
+
+    value = bytearray(b"abc")
+    source = ExportDuringInit(2)
+    with assert_raises(BufferError):
+        value.__init__(source)
+    assert value == b""
+    assert source.view.tobytes() == b""
+    assert source.calls == 1
+    source.view.release()
+    value.extend(b"released")
+    assert value == b"released"
+
+    value = bytearray(b"abc")
+    source = ExportDuringInit(0)
+    value.__init__(source)
+    assert value == b""
+    assert source.view.tobytes() == b""
+    source.view.release()
+
+    value = bytearray(b"abc")
+    source = ExportDuringInit(0, b"xy")
+    value.__init__(source)
+    assert value == b"xy"
+    assert source.view.tobytes() == b"xy"
+    assert source.calls == 1
+    source.view.release()
+
+    class FailingIndex:
+        def __index__(self):
+            assert value == b""
+            raise ValueError("conversion failed")
+
+    value = bytearray(b"abc")
+    with assert_raises(ValueError):
+        value.__init__(FailingIndex())
+    assert value == b""
+
+    for key in (0, slice(0, 1)):
+        value = bytearray(b"abc")
+        with memoryview(value) as view:
+            with assert_raises(BufferError):
+                del value[key]
+            assert view.tobytes() == b"abc"
+        del value[key]
+        assert value == b"bc"
+
+    class Reader(io.RawIOBase):
+        def __init__(self, count, retain, payload=b"abcd"):
+            self.count = count
+            self.retain = retain
+            self.payload = payload
+
+        def readinto(self, buffer):
+            buffer[:] = self.payload
+            self.buffer = buffer
+            if self.retain:
+                self.view = memoryview(buffer)
+            return self.count
+
+    for count in (0, 2, 4):
+        reader = Reader(count, False)
+        assert reader.read(4) == b"abcd"[:count]
+        assert reader.buffer == b""
+
+        reader = Reader(count, True)
+        with assert_raises(BufferError):
+            reader.read(4)
+        assert reader.view.tobytes() == b"abcd"
+        reader.view.release()
+        reader.buffer.clear()
+
+    for count in (-1, 5):
+        reader = Reader(count, True)
+        with assert_raises(ValueError):
+            reader.read(4)
+        assert reader.view.tobytes() == b"abcd"
+        reader.view.release()
+
+    reader = Reader(None, True)
+    assert reader.read(4) is None
+    assert reader.view.tobytes() == b"abcd"
+    reader.view.release()
+
+    # The callback can shrink the temporary buffer, so slicing by the original
+    # requested size without checking the current buffer is not safe.
+    reader = Reader(2, False, b"xy")
+    assert reader.read(4) == b"xy"
+    assert reader.buffer == b""
+
+    reader = Reader(4, False, b"xy")
+    result = reader.read(4)
+    assert len(result) == 4
+    assert result[:2] == b"xy"
+    # The contents of the newly grown region are unspecified by CPython.
+    assert reader.buffer == b""
+
+
+test_bytearray_exports()
+
+
+def test_bytearray_threading():
+    """Acquiring a bytearray export must be atomic with respect to resizing."""
+
+    import threading
+
+    def exercise_exports():
+        payload = b"x" * 65536
+        value = bytearray(payload)
+        barrier = threading.Barrier(3, timeout=5)
+        errors = []
+
+        def worker(operation):
+            try:
+                for _ in range(256):
+                    barrier.wait()
+                    operation()
+                    barrier.wait()
+            except BaseException as exc:
+                errors.append(exc)
+                barrier.abort()
+
+        def resize():
+            try:
+                value.clear()
+                value.extend(payload)
+            except BufferError:
+                pass
+
+        def decode():
+            result = value.decode("ascii")
+            assert result in ("", "x" * len(payload))
+
+        def export():
+            with memoryview(value) as view:
+                size = len(view)
+                assert size in (0, len(payload))
+                # The acquired export keeps its original length and contents even
+                # if the resizing thread runs between these two reads.
+                assert view.tobytes() == payload[:size]
+                assert len(view) == size
+
+        threads = [
+            threading.Thread(target=worker, args=(operation,), daemon=True)
+            for operation in (resize, decode, export)
+        ]
+        for thread in threads:
+            thread.start()
+        for thread in threads:
+            thread.join(timeout=10)
+        assert not any(thread.is_alive() for thread in threads), "worker did not finish"
+        if errors:
+            raise errors[0]
+
+    exercise_exports()
+
+
+test_bytearray_threading()
+
+
+def test_bytearray_init_exports():
+    """Initializer storage and integer-deletion ordering with buffer exports."""
+
+    from testutils import assert_raises
+
+    class Zero:
+        def __init__(self, value):
+            self.value = value
+            self.observations = []
+
+        def __index__(self):
+            self.observations.append((len(self.value), self.value.__alloc__()))
+            return 0
+
+    # Final CPython rejects even an empty exported initializer before conversion.
+    for kind in ("missing", "integer", "callback"):
+        value = bytearray()
+        source = Zero(value)
+        with memoryview(value) as view:
+            with assert_raises(BufferError):
+                if kind == "missing":
+                    value.__init__()
+                elif kind == "integer":
+                    value.__init__(0)
+                else:
+                    value.__init__(source)
+            assert value == b""
+            assert view.tobytes() == b""
+            assert source.observations == []
+
+    # Clearing an initializer must release its old storage before callbacks and
+    # before the successful zero-count early return.
+    for kind in ("missing", "integer", "callback"):
+        value = bytearray(b"x" * 64)
+        source = Zero(value)
+        assert value.__alloc__() > 0
+        if kind == "missing":
+            value.__init__()
+        elif kind == "integer":
+            value.__init__(0)
+        else:
+            value.__init__(source)
+            assert source.observations == [(0, 0)]
+        assert value == b""
+        assert value.__alloc__() == 0
+
+    # An invalid integer index is rejected before checking whether resizing is
+    # blocked, and neither error path may alter the exported bytes.
+    for initial, indices in ((b"abc", (3, -4)), (b"", (0, -1))):
+        for index in indices:
+            value = bytearray(initial)
+            with memoryview(value) as view:
+                try:
+                    del value[index]
+                except IndexError as exc:
+                    assert str(exc) == "bytearray index out of range"
+                else:
+                    raise AssertionError("invalid index was accepted")
+                assert value == initial
+                assert view.tobytes() == initial
+
+    for index in (0, -1):
+        value = bytearray(b"abc")
+        with memoryview(value) as view:
+            with assert_raises(BufferError):
+                del value[index]
+            assert view.tobytes() == b"abc"
+        del value[index]
+        assert value == (b"bc" if index == 0 else b"ab")
+
+
+test_bytearray_init_exports()
+
+
+def test_bytearray_concat_exports():
+    import operator
+
+    from testutils import assert_raises
+
+    for concat in (operator.add, operator.concat, bytearray.__add__):
+        target = bytearray(b"a")
+        events = []
+
+        class ReentrantBuffer:
+            def __buffer__(self, flags):
+                events.append("acquire")
+                with assert_raises(BufferError):
+                    target.__init__(object())
+                with assert_raises(BufferError):
+                    target.append(120)
+                target[0] = ord("A")
+                return memoryview(b"b")
+
+            def __release_buffer__(self, view):
+                events.append("release")
+                # The left operand's export must already have been released.
+                target.append(99)
+
+        assert concat(target, ReentrantBuffer()) == bytearray(b"Ab")
+        assert events == ["acquire", "release"]
+        assert target == bytearray(b"Ac")
+        target.append(100)
+
+        class FailingBuffer:
+            def __buffer__(self, flags):
+                raise ValueError("buffer acquisition failed")
+
+        with assert_raises(TypeError) as error:
+            concat(target, FailingBuffer())
+        assert str(error.exception) == "can't concat FailingBuffer to bytearray"
+        target.append(101)
+
+        events = []
+
+        class Left(bytearray):
+            def __buffer__(self, flags):
+                events.append("left acquire")
+                return memoryview(b"L")
+
+            def __release_buffer__(self, view):
+                events.append("left release")
+
+        class Right:
+            def __buffer__(self, flags):
+                events.append("right acquire")
+                return memoryview(b"R")
+
+            def __release_buffer__(self, view):
+                events.append("right release")
+
+        assert concat(Left(b"ignored"), Right()) == bytearray(b"LR")
+        assert events == [
+            "left acquire",
+            "right acquire",
+            "left release",
+            "right release",
+        ]
+
+        events = []
+        with assert_raises(TypeError) as error:
+            concat(Left(), FailingBuffer())
+        assert str(error.exception) == "can't concat FailingBuffer to Left"
+        assert events == ["left acquire", "left release"]
+
+        class FailingLeft(bytearray):
+            def __buffer__(self, flags):
+                events.append("left acquire")
+                raise ValueError("left acquisition failed")
+
+        events = []
+        with assert_raises(TypeError) as error:
+            concat(FailingLeft(), Right())
+        assert str(error.exception) == "can't concat Right to FailingLeft"
+        assert events == ["left acquire"]
+
+
+test_bytearray_concat_exports()
+
+
+def test_bytearray_callback_exports():
+    import operator
+
+    from testutils import assert_raises
+
+    def check_comparison():
+        for compare, expected in (
+            (operator.eq, False),
+            (operator.ne, True),
+            (operator.lt, True),
+            (operator.le, True),
+            (operator.gt, False),
+            (operator.ge, False),
+        ):
+            target = bytearray(b"a")
+            events = []
+
+            class Other:
+                def __buffer__(self, flags):
+                    events.append("acquire")
+                    with assert_raises(BufferError):
+                        target.__init__(object())
+                    target[0] = ord("A")
+                    return memoryview(b"B")
+
+                def __release_buffer__(self, view):
+                    events.append("release")
+                    target[0] = ord("Z")
+                    target.append(99)
+
+            assert compare(target, Other()) is expected
+            assert target == b"Zc"
+            assert events == ["acquire", "release"]
+
+        events = []
+
+        class Left(bytearray):
+            def __buffer__(self, flags):
+                events.append("acquire")
+                return memoryview(b"L")
+
+            def __release_buffer__(self, view):
+                events.append("release")
+
+        left = Left(b"ignored")
+        assert left.__eq__(left) is True
+        assert events == ["acquire", "acquire", "release", "release"]
+        events.clear()
+        assert left.__eq__(object()) is NotImplemented
+        assert events == []
+
+        class Failing:
+            def __buffer__(self, flags):
+                raise ValueError("no buffer")
+
+        assert left.__eq__(Failing()) is NotImplemented
+        assert events == ["acquire", "release"]
+        left.append(0)
+
+    def check_search():
+        for method, expected in (
+            ("find", 0),
+            ("index", 0),
+            ("rfind", 2),
+            ("rindex", 2),
+            ("count", 2),
+        ):
+            target = bytearray(b"xxx")
+            events = []
+
+            class Needle:
+                def __buffer__(self, flags):
+                    events.append("acquire")
+                    with assert_raises(BufferError):
+                        target.__init__(object())
+                    target[:] = b"aba"
+                    return memoryview(b"a")
+
+                def __release_buffer__(self, view):
+                    events.append("release")
+                    with assert_raises(BufferError):
+                        target.append(0)
+                    target[:] = b"zzz"
+
+            assert getattr(target, method)(Needle()) == expected
+            assert target == b"zzz"
+            assert events == ["acquire", "release"]
+            target.append(0)
+
+            target = bytearray(b"xxx")
+
+            class IndexNeedle:
+                def __index__(self):
+                    with assert_raises(BufferError):
+                        target.__init__(object())
+                    target[:] = b"aba"
+                    return ord("a")
+
+            assert getattr(target, method)(IndexNeedle()) == expected
+
+        target = bytearray(b"ab")
+
+        class Start:
+            def __index__(self):
+                target.extend(b"ab")
+                return 1
+
+        assert target.count(ord("a"), Start()) == 1
+        assert target == b"abab"
+
+    def check_affixes():
+        for method in ("startswith", "endswith"):
+            target = bytearray(b"aaa")
+            events = []
+
+            class Affix:
+                def __init__(self, value, after):
+                    self.value = value
+                    self.after = after
+
+                def __buffer__(self, flags):
+                    events.append(self.value)
+                    with assert_raises(BufferError):
+                        target.__init__(object())
+                    target[0] = target[0]
+                    return memoryview(self.value)
+
+                def __release_buffer__(self, view):
+                    events.append("release")
+                    with assert_raises(BufferError):
+                        target.append(0)
+                    target[:] = self.after
+
+            class Unvisited:
+                def __buffer__(self, flags):
+                    raise AssertionError("tuple must short-circuit")
+
+            assert getattr(target, method)(
+                (Affix(b"x", b"yyy"), Affix(b"y", b"zzz"), Unvisited())
+            )
+            assert target == b"zzz"
+            assert events == [b"x", "release", b"y", "release"]
+            target.append(0)
+
+            target = bytearray(b"aaa")
+            events.clear()
+            assert getattr(target, method)(Affix(b"a", b"zzz"))
+            assert target == b"zzz"
+            assert events == [b"a", "release"]
+
+            events.clear()
+            assert not getattr(target, method)(Affix(b"z", b"aaa"), 100)
+            assert events == [b"z", "release"]
+            with assert_raises(TypeError):
+                getattr(target, method)((Affix(b"x", b"aaa"), object()))
+            target.append(0)
+
+            class BytesAffix(bytes):
+                def __buffer__(self, flags):
+                    raise AssertionError("bytes subclasses use their stored bytes")
+
+            assert getattr(bytearray(b"a"), method)(BytesAffix(b"a"))
+
+    def check_translate():
+        target = bytearray(b"x")
+        table = bytearray(range(256))
+        events = []
+
+        class Table:
+            def __buffer__(self, flags):
+                events.append("table acquire")
+                target.__init__(b"a")
+                return memoryview(table)
+
+            def __release_buffer__(self, view):
+                events.append("table release")
+                target.__init__(b"t")
+
+        class Delete:
+            def __buffer__(self, flags):
+                events.append("delete acquire")
+                with assert_raises(BufferError):
+                    table.append(0)
+                table[ord("a")] = ord("b")
+                target.__init__(b"aa")
+                return memoryview(b"")
+
+            def __release_buffer__(self, view):
+                events.append("delete release")
+                target.__init__(b"d")
+
+        assert target.translate(Table(), delete=Delete()) == b"bb"
+        assert target == b"d"
+        assert events == [
+            "table acquire",
+            "delete acquire",
+            "table release",
+            "delete release",
+        ]
+        table.append(0)
+        table.pop()
+        events.clear()
+
+        class BadDelete:
+            def __buffer__(self, flags):
+                events.append("delete failure")
+                with assert_raises(BufferError):
+                    table.append(0)
+                raise ValueError("bad delete")
+
+        with assert_raises(ValueError):
+            target.translate(Table(), delete=BadDelete())
+        assert events == ["table acquire", "delete failure", "table release"]
+        table.append(0)
+
+    def check_padding():
+        for method in ("center", "ljust", "rjust"):
+            target = bytearray(b"x")
+            assert getattr(target, method)(3, target) == b"xxx"
+
+            class Width:
+                def __index__(self):
+                    target.__init__(b"y")
+                    return 3
+
+            assert getattr(target, method)(Width(), target) == b"yyy"
+
+    check_comparison()
+    check_search()
+    check_affixes()
+    check_translate()
+    check_padding()
+
+
+test_bytearray_callback_exports()
+
+
+def test_bytearray_contains_builtin_and_callback_exports():
+    for value in (b"", b"a", b"ab\x00\xff", b"\x01"):
+        target = bytearray(value)
+        for needle in (
+            b"",
+            b"a",
+            b"ab",
+            b"z",
+            b"\x00",
+            b"\xff",
+            0,
+            97,
+            255,
+            False,
+            True,
+        ):
+            assert (needle in target) == (needle in value)
+        assert target in target
+
+    def must_raise_buffer_error(action):
+        try:
+            action()
+        except BufferError:
+            return
+        raise AssertionError("resize was not rejected")
+
+    target = bytearray(b"a")
+    view = memoryview(target)
+    try:
+        assert b"a" in target
+        assert 97 in target
+        must_raise_buffer_error(lambda: target.append(0))
+        target[:] = b"b"
+        assert b"b" in target
+        assert 98 in target
+    finally:
+        view.release()
+    target.append(0)
+    assert target == b"b\x00"
+
+    class IndexNeedle:
+        def __index__(self):
+            must_raise_buffer_error(lambda: target.append(0))
+            target[0] = 98
+            return 98
+
+    class BytesNeedle(bytes):
+        __index__ = IndexNeedle.__index__
+
+    for needle in (IndexNeedle(), BytesNeedle(b"\xdd")):
+        target[:] = b"a"
+        assert needle in target
+        assert target == b"b"
+        target.append(0)
+        assert target == b"b\x00"
+
+    for needle in (-1, 256):
+        with assert_raises(ValueError):
+            needle in target
+
+    events = [0, 0]
+
+    class BufferNeedle:
+        def __buffer__(self, flags):
+            must_raise_buffer_error(lambda: target.append(0))
+            target[0] = 98
+            events[0] += 1
+            return memoryview(b"b")
+
+        def __release_buffer__(self, view):
+            must_raise_buffer_error(lambda: target.append(0))
+            events[1] += 1
+
+    target[:] = b"a"
+    assert BufferNeedle() in target
+    assert events == [1, 1]
+    target.append(0)
+    assert target == b"b\x00"
+
+
+test_bytearray_contains_builtin_and_callback_exports()
+
+
+def test_bytearray_take_bytes_bounded():
+    for n, expected, remaining in (
+        (None, b"abcd", b""),
+        (0, b"", b"abcd"),
+        (1, b"a", b"bcd"),
+        (2, b"ab", b"cd"),
+        (4, b"abcd", b""),
+        (-1, b"abc", b"d"),
+        (-4, b"", b"abcd"),
+        (True, b"a", b"bcd"),
+    ):
+        target = bytearray(b"abcd")
+        result = target.take_bytes(n)
+        assert type(result) is bytes
+        assert result == expected
+        assert target == remaining
+        target[:] = b"z"
+        assert result == expected
+    target = bytearray(b"abc")
+    assert target.take_bytes() == b"abc"
+    assert target == b""
+    for n in (None, 0):
+        assert bytearray().take_bytes(n) == b""
+    for n in (5, -5, sys.maxsize + 1, -sys.maxsize - 2):
+        target = bytearray(b"abcd")
+        with assert_raises(IndexError):
+            target.take_bytes(n)
+        assert target == b"abcd"
+    for n in (1.0, "1", b"1", object()):
+        with assert_raises(TypeError):
+            bytearray(b"a").take_bytes(n)
+    with assert_raises(TypeError):
+        bytearray(b"a").take_bytes(n=1)
+    with assert_raises(TypeError):
+        bytearray(b"a").take_bytes(1, 2)
+    for content in (b"", b"abcd"):
+        target = bytearray(content)
+        view = memoryview(target)
+        try:
+            for n in (None, 0, len(content)):
+                with assert_raises(BufferError):
+                    target.take_bytes(n)
+                assert target == content
+            for n in (len(content) + 1, -len(content) - 1):
+                with assert_raises(IndexError):
+                    target.take_bytes(n)
+                assert target == content
+        finally:
+            view.release()
+        assert target.take_bytes() == content
+    target = bytearray(b"abcd")
+    parent = memoryview(target)
+    child = parent[1:3]
+    clone = memoryview(parent)
+    parent.release()
+    try:
+        with assert_raises(BufferError):
+            target.take_bytes(0)
+        child.release()
+        with assert_raises(BufferError):
+            target.take_bytes(1)
+    finally:
+        child.release()
+        clone.release()
+    assert target.take_bytes() == b"abcd"
+
+
+def test_bytearray_take_bytes_reentrant_bounded():
+    class Index:
+        def __init__(self, action, result):
+            self.action = action
+            self.result = result
+
+        def __index__(self):
+            self.action()
+            return self.result
+
+    for replacement, n, expected, remaining in (
+        (b"ab", 2, b"ab", b""),
+        (b"", 0, b"", b""),
+        (b"abcdef", 5, b"abcde", b"f"),
+        (b"ab", -1, b"a", b"b"),
+    ):
+        target = bytearray(b"abcd")
+        index = Index(lambda: target.__setitem__(slice(None), replacement), n)
+        assert target.take_bytes(index) == expected
+        assert target == remaining
+    target = bytearray(b"abcd")
+    with assert_raises(IndexError):
+        target.take_bytes(Index(target.clear, 1))
+    assert target == b""
+    for n, error in ((1, BufferError), (5, IndexError)):
+        target = bytearray(b"abcd")
+        views = []
+        try:
+            with assert_raises(error):
+                target.take_bytes(Index(lambda: views.append(memoryview(target)), n))
+            assert target == b"abcd"
+        finally:
+            for view in views:
+                view.release()
+    for n, error in ((2, None), (5, IndexError)):
+        target = bytearray(b"abcd")
+        view = memoryview(target)
+        try:
+            index = Index(view.release, n)
+            if error is None:
+                assert target.take_bytes(index) == b"ab"
+                assert target == b"cd"
+            else:
+                with assert_raises(error):
+                    target.take_bytes(index)
+                assert target == b"abcd"
+        finally:
+            view.release()
+    target = bytearray(b"abcd")
+    with assert_raises(TypeError):
+        target.take_bytes(Index(lambda: None, "wrong"))
+    assert target == b"abcd"
+
+    def raises():
+        raise ValueError("index callback")
+
+    with assert_raises(ValueError):
+        target.take_bytes(Index(raises, 1))
+    assert target == b"abcd"
+
+    class MembershipIndex:
+        def __index__(self):
+            with assert_raises(IndexError):
+                target.take_bytes(5)
+            with assert_raises(BufferError):
+                target.take_bytes(0)
+            return ord("a")
+
+    assert MembershipIndex() in target
+    assert target.take_bytes() == b"abcd"
+
+
+def test_bytearray_take_bytes_codec_callback_bounded():
+    import codecs
+
+    target = bytearray(b"\xff")
+    calls = []
+
+    def handler(error):
+        with assert_raises(IndexError):
+            target.take_bytes(2)
+        with assert_raises(BufferError):
+            target.take_bytes(0)
+        calls.append(error.start)
+        return ("?", error.end)
+
+    codecs.register_error("bytearray_take_bytes_bounded", handler)
+    assert target.decode("ascii", "bytearray_take_bytes_bounded") == "?"
+    assert calls == [0]
+    assert target.take_bytes() == b"\xff"
+
+
+test_bytearray_take_bytes_bounded()
+test_bytearray_take_bytes_reentrant_bounded()
+test_bytearray_take_bytes_codec_callback_bounded()
diff --git a/extra_tests/snippets/builtin_bytes.py b/extra_tests/snippets/builtin_bytes.py
index f30ae89e0ec..759f4a54fd2 100644
--- a/extra_tests/snippets/builtin_bytes.py
+++ b/extra_tests/snippets/builtin_bytes.py
@@ -767,6 +767,26 @@ class SubBytes(bytes):
     pass
 
 
+# Unchanged operations reuse exact bytes but must not preserve a subclass.
+for method, args in (
+    ("strip", ()),
+    ("lstrip", ()),
+    ("rstrip", ()),
+    ("removeprefix", (b"!",)),
+    ("removesuffix", (b"!",)),
+    ("replace", (b"!", b"?")),
+    ("replace", (b"!", b"")),
+    ("replace", (b"!", b"longer")),
+    ("replace", (b"", b"")),
+    ("replace", (b"a", b"b", 0)),
+):
+    original = b"unchanged payload"
+    assert getattr(original, method)(*args) is original
+    result = getattr(SubBytes(original), method)(*args)
+    assert result == original
+    assert type(result) is bytes
+
+
 b = SubBytes(b"0123abc*&")
 assert id(b) == id(b)
 assert id(b) != id(b * -1)
diff --git a/extra_tests/snippets/builtin_compile_module.py b/extra_tests/snippets/builtin_compile_module.py
new file mode 100644
index 00000000000..8ff58583b41
--- /dev/null
+++ b/extra_tests/snippets/builtin_compile_module.py
@@ -0,0 +1,330 @@
+import ast
+import warnings
+
+from testutils import assert_raises, skip_if_unsupported
+
+
+def test_compile_module():
+    class ModuleName(str):
+        pass
+
+    for module in (None, "", "package.module", ModuleName("package.module"), "\ud800"):
+        code = compile("value = 42", "<module-context>", "exec", module=module)
+        assert code.co_filename == "<module-context>"
+        namespace = {}
+        exec(code, namespace)
+        assert namespace["value"] == 42
+
+    for module in (1, False, b"package.module", [], {}, object()):
+        with assert_raises(TypeError) as caught:
+            compile("", "<module-context>", "exec", module=module)
+        assert "argument 'module' must be str or None" in str(caught.exception)
+
+    # module is keyword-only; _feature_version stays keyword-only too.
+    with assert_raises(TypeError):
+        compile("", "<module-context>", "exec", 0, False, -1, "package.module")
+
+    lexical_sources = [
+        "x = 1or 0",
+        r"'\z'",
+        r"'\400'",
+        r'f"{1:\z}"',
+        r'f"\{1}"',
+    ]
+    codegen_sources = [
+        "assert (1, 2)",
+        "1 is 1",
+        "def f():\n    try:\n        pass\n    finally:\n        return 1\n",
+    ]
+
+    # Default source compilation uses module for matching, while diagnostics retain
+    # the real source filename. Test both text and bytes compilation.
+    for source in lexical_sources + codegen_sources:
+        for input_source in (source, source.encode()):
+            with warnings.catch_warnings(record=True) as caught:
+                warnings.simplefilter("error", SyntaxWarning)
+                warnings.filterwarnings(
+                    "always", category=SyntaxWarning, module=r"^package\.module$"
+                )
+                compile(
+                    input_source, "<module-context>", "exec", module="package.module"
+                )
+            assert len(caught) == 1, (source, caught)
+            assert caught[0].filename == "<module-context>"
+            assert caught[0].category is SyntaxWarning
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore", SyntaxWarning)
+                warnings.filterwarnings(
+                    "error", category=SyntaxWarning, module=r"^package\.module$"
+                )
+                with assert_raises(SyntaxError):
+                    compile(
+                        input_source,
+                        "<module-context>",
+                        "exec",
+                        module="package.module",
+                    )
+
+    # Compiling a pre-existing AST must use the module too.
+    for source in codegen_sources:
+        tree = ast.parse(source)
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("error", SyntaxWarning)
+            warnings.filterwarnings(
+                "always", category=SyntaxWarning, module=r"^package\.module$"
+            )
+            compile(tree, "<module-context>", "exec", module="package.module")
+        assert len(caught) == 1, (source, caught)
+        assert caught[0].filename == "<module-context>"
+
+    # A following compile, with omitted or None module, must not inherit the override.
+    for kwargs in ({}, {"module": None}):
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("error", SyntaxWarning)
+            warnings.filterwarnings(
+                "always", category=SyntaxWarning, module=r"^<module-context>$"
+            )
+            compile("1 is 1", "<module-context>", "exec", **kwargs)
+        assert len(caught) == 1
+
+    # Failed parses use the fallback string scanner, which must retain the module.
+    for source in (r"b'\z' )", r'f"{1:\z}" )'):
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("error", SyntaxWarning)
+            warnings.filterwarnings(
+                "always", category=SyntaxWarning, module=r"^package\.module$"
+            )
+            with assert_raises(SyntaxError):
+                compile(source, "<module-context>", "exec", module="package.module")
+        assert len(caught) == 1, (source, caught)
+        assert caught[0].filename == "<module-context>"
+
+    # AST conversion must use the same fallible, source-located warning boundary.
+    # TYPE_COMMENTS validates through the AST parser before compiling the source;
+    # the later compiler must not filter or emit the same escape a second time.
+    for flags in (
+        ast.PyCF_ONLY_AST,
+        ast.PyCF_TYPE_COMMENTS,
+        ast.PyCF_ONLY_AST | ast.PyCF_TYPE_COMMENTS,
+        ast.PyCF_ONLY_AST | ast.PyCF_OPTIMIZED_AST,
+    ):
+        source = '\nπ = f"{1:\\z}"\n'
+        for kwargs, expected_module in (
+            ({}, "<module-context>"),
+            ({"module": None}, "<module-context>"),
+            ({"module": "package.module"}, "package.module"),
+        ):
+            modules = []
+
+            class ModuleMatcher:
+                def match(self, module):
+                    modules.append(module)
+                    return True
+
+            with warnings.catch_warnings(record=True) as caught:
+                warnings.simplefilter("always", SyntaxWarning)
+                warnings.filters.insert(
+                    0, ("always", None, SyntaxWarning, ModuleMatcher(), 0)
+                )
+                compile(source, "<module-context>", "exec", flags, **kwargs)
+            assert modules == [expected_module], (flags, kwargs, modules)
+            assert len(caught) == 1, (flags, kwargs, caught)
+            assert (caught[0].filename, caught[0].lineno) == ("<module-context>", 2)
+
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", SyntaxWarning)
+            warnings.filterwarnings(
+                "error", category=SyntaxWarning, module=r"^package\.module$"
+            )
+            with assert_raises(SyntaxError) as caught:
+                compile(
+                    source, "<module-context>", "exec", flags, module="package.module"
+                )
+        error = caught.exception
+        assert error.filename == "<module-context>"
+        assert (error.lineno, error.offset, error.end_lineno, error.end_offset) == (
+            2,
+            10,
+            2,
+            12,
+        )
+        assert error.text == 'π = f"{1:\\z}"\n'
+        assert "Such sequences will not work in the future" not in error.msg
+
+        # Warning handlers may raise arbitrary exceptions, which must survive intact.
+        failure = RuntimeError("warning handler failed")
+
+        def showwarning(*args, **kwargs):
+            raise failure
+
+        with warnings.catch_warnings():
+            warnings.simplefilter("always", SyntaxWarning)
+            warnings.showwarning = showwarning
+            with assert_raises(RuntimeError) as caught:
+                compile(
+                    source, "<module-context>", "exec", flags, module="package.module"
+                )
+        assert caught.exception is failure
+
+        # Nested compile calls must not share module overrides or duplicate tracking.
+        modules = []
+        locations = []
+
+        class ModuleMatcher:
+            def match(self, module):
+                modules.append(module)
+                return True
+
+        def showwarning(message, category, filename, lineno, *args, **kwargs):
+            locations.append((filename, lineno))
+            if len(locations) == 1:
+                compile(r'f"{1:\z}"', "<inner>", "exec", flags, module="package.inner")
+
+        with warnings.catch_warnings():
+            warnings.simplefilter("always", SyntaxWarning)
+            warnings.filters.insert(
+                0, ("always", None, SyntaxWarning, ModuleMatcher(), 0)
+            )
+            warnings.showwarning = showwarning
+            compile(
+                'f"{1:\\z}"\nf"{2:\\q}"',
+                "<outer>",
+                "exec",
+                flags,
+                module="package.outer",
+            )
+        assert modules == ["package.outer", "package.inner", "package.outer"], modules
+        assert locations == [("<outer>", 1), ("<inner>", 1), ("<outer>", 2)], locations
+
+    # These warnings already came from AST conversion. Retain them instead of
+    # replacing that path with a broader scanner before every AST parse.
+    for source in ('''rf"{1:{'\\z'}}"''', '''f"{1:{t'\\z'}}"'''):
+        for flags in (
+            ast.PyCF_ONLY_AST,
+            ast.PyCF_TYPE_COMMENTS,
+            ast.PyCF_ONLY_AST | ast.PyCF_TYPE_COMMENTS,
+        ):
+            with warnings.catch_warnings(record=True) as caught:
+                warnings.simplefilter("error", SyntaxWarning)
+                warnings.filterwarnings(
+                    "always", category=SyntaxWarning, module=r"^package\.module$"
+                )
+                compile(
+                    source, "<module-context>", "exec", flags, module="package.module"
+                )
+            assert len(caught) == 1, (source, flags, caught)
+            assert (caught[0].filename, caught[0].lineno) == ("<module-context>", 1)
+
+    for flags in (ast.PyCF_ONLY_AST, ast.PyCF_ONLY_AST | ast.PyCF_TYPE_COMMENTS):
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always", SyntaxWarning)
+            with assert_raises(SyntaxError):
+                compile(
+                    '!!!\nf"{1:\\z}"',
+                    "<module-context>",
+                    "exec",
+                    flags,
+                    module="package.module",
+                )
+        assert not caught
+
+    # A filter changed by showwarning must affect the next distinct diagnostic,
+    # rather than treating the already-considered format escape as a new warning.
+    with warnings.catch_warnings():
+        warnings.simplefilter("always", SyntaxWarning)
+
+        def showwarning(*args, **kwargs):
+            warnings.simplefilter("error", SyntaxWarning)
+
+        warnings.showwarning = showwarning
+        with assert_raises(SyntaxError) as caught:
+            compile(
+                'f"{1:\\z}"\n"\\q"',
+                "<module-context>",
+                "exec",
+                ast.PyCF_TYPE_COMMENTS,
+                module="package.module",
+            )
+    assert caught.exception.lineno == 2
+    assert "\\q" in caught.exception.msg
+
+    # Raw literal text is not an invalid escape. Nested nonraw expressions still
+    # retain the diagnostics previously emitted during AST conversion.
+    for flags in (
+        ast.PyCF_ONLY_AST,
+        ast.PyCF_TYPE_COMMENTS,
+        ast.PyCF_ONLY_AST | ast.PyCF_TYPE_COMMENTS,
+    ):
+        for source in (
+            r'rf"{1:\z}"',
+            r'rf"{1:{2:\z}}"',
+            r'tr"{1:{2:\z}}"',
+            "f\"{1:{r'\\z'}}\"",
+        ):
+            with warnings.catch_warnings(record=True) as caught:
+                warnings.simplefilter("error", SyntaxWarning)
+                compile(
+                    source, "<module-context>", "exec", flags, module="package.module"
+                )
+            assert not caught, (source, flags, caught)
+        for source in ("rf\"{f'{2:\\z}'}\"", "rf\"{1:{'\\z'}}\""):
+            with warnings.catch_warnings():
+                warnings.simplefilter("error", SyntaxWarning)
+                with assert_raises(SyntaxError):
+                    compile(
+                        source,
+                        "<module-context>",
+                        "exec",
+                        flags,
+                        module="package.module",
+                    )
+
+    # Func-type parsing trims its source before converting the parsed nodes.
+    # Already-detected escapes must still point into the original source.
+    for prefix in ("", "\n\n"):
+        source = prefix + '(int) -> f"{1:aaaaaaaaaaaa\\zbbbbbbbbbbbb}"'
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always", SyntaxWarning)
+            compile(
+                source,
+                "<module-context>",
+                "func_type",
+                ast.PyCF_ONLY_AST,
+                module="package.module",
+            )
+        assert len(caught) == 1, (source, caught)
+        assert caught[0].filename == "<module-context>"
+        assert caught[0].lineno == prefix.count("\n") + 1
+
+    # Warn for the first invalid escape in each original literal, including
+    # literals later folded together. Comments are not literal source text.
+    for source, count in (
+        (r'f"{1:\z\q}"', 1),
+        (r'f"{1:\{2}}"', 1),
+        (r'f"{1:\\{2}}"', 0),
+        ('f"{1:{(\n1 # \\z\n)}}"', 0),
+        ("f\"{1:{'\\z' + '\\q'}}\"", 2),
+        ("f\"{1:{'\\z' '\\q'}}\"", 2),
+        ("f\"{1:{('\\z', '\\q')[0]}}\"", 2),
+    ):
+        for flags in (
+            ast.PyCF_ONLY_AST,
+            ast.PyCF_TYPE_COMMENTS,
+            ast.PyCF_ONLY_AST | ast.PyCF_OPTIMIZED_AST,
+        ):
+            for optimize in (0, 2):
+                with warnings.catch_warnings(record=True) as caught:
+                    warnings.simplefilter("always", SyntaxWarning)
+                    compile(
+                        source,
+                        "<module-context>",
+                        "exec",
+                        flags,
+                        optimize=optimize,
+                        module="package.module",
+                    )
+                assert len(caught) == count, (source, flags, optimize, caught)
+                assert all(w.filename == "<module-context>" for w in caught)
+
+
+skip_if_unsupported(3, 15, test_compile_module)
diff --git a/extra_tests/snippets/builtin_dict.py b/extra_tests/snippets/builtin_dict.py
index 5dca75b9b9d..3d7347a5041 100644
--- a/extra_tests/snippets/builtin_dict.py
+++ b/extra_tests/snippets/builtin_dict.py
@@ -378,6 +378,25 @@ def __eq__(self, other):
 assert_raises(StopIteration, next, it)
 assert it.__length_hint__() == 0
 
+# Reverse hints count live entries, including when storage has deleted slots.
+for reverse_iter in (
+    reversed,
+    lambda d: reversed(d.keys()),
+    lambda d: reversed(d.values()),
+    lambda d: reversed(d.items()),
+):
+    d = {0: 0, 1: 1, 2: 2, 3: 3}
+    del d[1]
+    it = reverse_iter(d)
+    for remaining in (3, 2, 1):
+        assert it.__length_hint__() == remaining
+        next(it)
+    assert it.__length_hint__() == 0
+    # Exhaustion is observed by next(), rather than the final successful yield.
+    d[4] = 4
+    assert_raises(RuntimeError, next, it)
+    assert it.__length_hint__() == 0
+
 # Test dictionary unpacking with non-mapping objects
 # This should raise TypeError for non-mapping objects
 with assert_raises(TypeError) as cm:
@@ -745,3 +764,406 @@ def __getitem__(self, key):
     hash(od.keys())
 with assert_raises(TypeError):
     hash(od.items())
+
+
+# A TypeError raised while *comparing* keys (e.g. from a colliding key's
+# __eq__) must propagate unchanged, not be rewritten as an unhashable-key
+# error. Only genuine hashing failures get the dict-specific "unhashable"
+# wording.
+class BadEq:
+    def __hash__(self):
+        return 42  # fixed hash forces a collision
+
+    def __eq__(self, other):
+        raise TypeError("nope")
+
+
+bad = {}
+bad[BadEq()] = 1
+with assert_raises(TypeError) as cm:
+    bad[BadEq()]  # hashes fine (42), then compares against the colliding key
+assert "nope" in str(cm.exception), str(cm.exception)
+assert "dict key" not in str(cm.exception), (
+    f"comparison error mislabeled as unhashable: {cm.exception}"
+)
+
+# A genuinely unhashable key still reports the dict-specific message.
+with assert_raises(TypeError) as cm:
+    {}[[]]
+assert "as a dict key" in str(cm.exception), str(cm.exception)
+
+# The message reaches every insertion path, not just __setitem__: the
+# constructor, update() and |= all go through the same wrapping.
+for make in (
+    lambda: dict([([], 1)]),
+    lambda: {}.update([([], 1)]),
+    lambda: {}.__ior__([([], 1)]),
+):
+    with assert_raises(TypeError) as cm:
+        make()
+    assert "as a dict key" in str(cm.exception), str(cm.exception)
+
+
+# The key is hashed once up front, so a __hash__ that fails only on its first
+# call is still reported (a re-hash on the error path would let it escape).
+class FlakyHash:
+    _calls = 0
+
+    def __hash__(self):
+        FlakyHash._calls += 1
+        if FlakyHash._calls == 1:
+            raise TypeError("first call fails")
+        return 0
+
+
+with assert_raises(TypeError) as cm:
+    {}[FlakyHash()]
+assert "as a dict key" in str(cm.exception), str(cm.exception)
+
+
+# The type name is the fully qualified one, like CPython's %T.
+def _make_nested():
+    class Nested:
+        __hash__ = None
+
+    return Nested
+
+
+with assert_raises(TypeError) as cm:
+    {}[_make_nested()()]
+assert "_make_nested.<locals>.Nested" in str(cm.exception), str(cm.exception)
+
+
+# A __hash__ raising a *subclass* of TypeError is left unchanged (CPython
+# checks the exact type), so `except MySubclass` still catches it.
+class MyTypeError(TypeError):
+    pass
+
+
+class SubclassHash:
+    def __hash__(self):
+        raise MyTypeError("custom")
+
+
+with assert_raises(MyTypeError) as cm:
+    {}[SubclassHash()]
+assert "as a dict key" not in str(cm.exception), str(cm.exception)
+
+
+# Every operation hashes the key exactly once (the hash is threaded into the
+# inner map), so a __hash__ that would fail on a second call is never called
+# twice. setdefault() and pop() went through their own lookup before.
+class CountingHash:
+    calls = 0
+
+    def __hash__(self):
+        CountingHash.calls += 1
+        if CountingHash.calls >= 2:
+            raise TypeError("must not hash twice")
+        return 7
+
+
+CountingHash.calls = 0
+{}.setdefault(CountingHash(), 1)
+assert CountingHash.calls == 1, CountingHash.calls
+
+CountingHash.calls = 0
+with assert_raises(KeyError):
+    # A non-empty dict so the lookup must hash the key (CPython skips hashing
+    # entirely when popping from an empty dict).
+    {1: 1}.pop(CountingHash())
+assert CountingHash.calls == 1, CountingHash.calls
+
+
+# frozendict as a namespace, beyond what CPython's own tests cover.
+import builtins
+import gc
+import sys
+import types
+import unittest
+
+
+class FrozenDictDescriptorTests(unittest.TestCase):
+    def test_unrelated_descriptors_cannot_mutate_or_access(self):
+        frozen = frozendict(protected=23)
+        for method, args in (
+            (dict.__init__, ({"replacement": 8},)),
+            (dict.__setitem__, ("protected", 99)),
+            (dict.__delitem__, ("protected",)),
+            (dict.update, ({"replacement": 8},)),
+            (dict.clear, ()),
+            (dict.get, ("protected",)),
+        ):
+            with self.subTest(method=method), self.assertRaises(TypeError):
+                method(frozen, *args)
+        with self.assertRaises(TypeError):
+            frozendict.get({"protected": 23}, "protected")
+        self.assertEqual(frozen, {"protected": 23})
+        for name in (
+            "clear",
+            "update",
+            "pop",
+            "popitem",
+            "setdefault",
+            "__setitem__",
+            "__delitem__",
+            "__ior__",
+        ):
+            self.assertFalse(hasattr(frozen, name), name)
+
+
+class FrozenGlobalsTests(unittest.TestCase):
+    def setUp(self):
+        self.ns = frozendict(
+            __builtins__=builtins.__dict__,
+            __name__="frozen_test",
+            answer=42,
+            sys=sys,
+        )
+
+    def test_eval_and_implicit_scope(self):
+        self.assertIs(eval("globals()", self.ns), self.ns)
+        self.assertIs(eval("locals()", self.ns), self.ns)
+        self.assertEqual(eval("eval('answer')", self.ns), 42)
+        self.assertEqual(eval("(lambda: answer)()", self.ns), 42)
+
+    def test_function_and_materialized_frame(self):
+        local = {}
+        exec("def f():\n return sys._getframe(), globals(), answer\n", self.ns, local)
+        f = local["f"]
+        self.assertIs(f.__globals__, self.ns)
+        self.assertEqual(f.__module__, "frozen_test")
+        for _ in range(300):
+            frame, ns, answer = f()
+            self.assertIs(frame.f_globals, self.ns)
+            self.assertIs(ns, self.ns)
+            self.assertEqual(answer, 42)
+        gc.collect()
+        self.assertIs(frame.f_globals, self.ns)
+
+    def test_generator_frames(self):
+        local = {}
+        exec(
+            "def gen():\n yield sys._getframe(), globals(), answer\n yield answer\n",
+            self.ns,
+            local,
+        )
+        gen = local["gen"]()
+        self.assertIs(gen.gi_frame.f_globals, self.ns)
+        frame, ns, answer = next(gen)
+        self.assertIs(frame.f_globals, self.ns)
+        self.assertIs(ns, self.ns)
+        self.assertEqual(answer, 42)
+        self.assertEqual(next(gen), 42)
+        with self.assertRaises(StopIteration):
+            next(gen)
+        gc.collect()
+        self.assertIs(frame.f_globals, self.ns)
+
+    def test_coroutine_frames(self):
+        local = {}
+        exec(
+            "async def coro():\n return sys._getframe(), globals(), answer\n",
+            self.ns,
+            local,
+        )
+        coro = local["coro"]()
+        self.assertIs(coro.cr_frame.f_globals, self.ns)
+        with self.assertRaises(StopIteration) as stopped:
+            coro.send(None)
+        frame, ns, answer = stopped.exception.value
+        self.assertIs(frame.f_globals, self.ns)
+        self.assertIs(ns, self.ns)
+        self.assertEqual(answer, 42)
+
+    def test_async_generator_frames(self):
+        local = {}
+        exec(
+            "async def agen():\n yield sys._getframe(), globals(), answer\n",
+            self.ns,
+            local,
+        )
+        agen = local["agen"]()
+        self.assertIs(agen.ag_frame.f_globals, self.ns)
+        with self.assertRaises(StopIteration) as stopped:
+            agen.asend(None).send(None)
+        frame, ns, answer = stopped.exception.value
+        self.assertIs(frame.f_globals, self.ns)
+        self.assertIs(ns, self.ns)
+        self.assertEqual(answer, 42)
+        with self.assertRaises(StopIteration):
+            agen.aclose().send(None)
+
+    def test_local_namespace_and_imports(self):
+        local = {}
+        exec(
+            "import math\nclass C:\n value = answer\ndef f():\n import math\n return math.sqrt(answer)\n",
+            self.ns,
+            local,
+        )
+        self.assertEqual(local["C"].value, 42)
+        self.assertEqual(local["C"].__module__, "frozen_test")
+        self.assertEqual(local["f"](), local["math"].sqrt(42))
+        self.assertNotIn("math", self.ns)
+
+    def test_missing_builtins(self):
+        for func, source in [(eval, ""), (exec, "")]:
+            with self.assertRaises(TypeError) as caught:
+                func(source, frozendict())
+            self.assertEqual(
+                str(caught.exception),
+                "cannot assign __builtins__ to frozendict globals",
+            )
+
+    def test_writes_and_deletes(self):
+        for source, error in [
+            ("answer = 0", "'frozendict' object does not support item assignment"),
+            (
+                "global answer; answer = 0",
+                "frozendict object does not support item assignment",
+            ),
+            (
+                "global answer; del answer",
+                "frozendict object does not support item deletion",
+            ),
+            (
+                "global missing; del missing",
+                "frozendict object does not support item deletion",
+            ),
+        ]:
+            with self.assertRaises(TypeError) as caught:
+                exec(source, self.ns)
+            self.assertEqual(str(caught.exception), error)
+        self.assertEqual(self.ns["answer"], 42)
+        with self.assertRaises(NameError):
+            exec("del answer", self.ns)
+
+    def test_explicit_function_constructor_stays_dict_only(self):
+        with self.assertRaises(TypeError):
+            types.FunctionType((lambda: 42).__code__, self.ns)
+
+    def test_subclass_name_and_global_lookup(self):
+        class F(frozendict):
+            def __getitem__(self, key):
+                if key == "answer":
+                    return 81
+                return super().__getitem__(key)
+
+        ns = F(self.ns)
+        self.assertEqual(eval("answer", ns), 81)
+        self.assertEqual(eval("(lambda: answer)()", ns), 81)
+        self.assertEqual(eval("answer", ns, {}), 42)
+
+    def test_subclass_function_metadata_reads_storage(self):
+        class F(frozendict):
+            def __getitem__(self, key):
+                if key == "__name__":
+                    return "wrong_name"
+                if key == "__builtins__":
+                    return {"len": lambda x: 99}
+                return super().__getitem__(key)
+
+        ns = F(self.ns)
+        f = eval("lambda: len([])", ns)
+        self.assertEqual(f.__module__, "frozen_test")
+        self.assertIs(f.__globals__, ns)
+        self.assertEqual(f(), 0)
+
+    def test_subclass_builtins_assignment_hook(self):
+        calls = []
+
+        class F(frozendict):
+            def __setitem__(self, key, value):
+                calls.append((key, value))
+
+        for operation, source, mode, expected in (
+            (eval, "1", "eval", 1),
+            (exec, "pass", "exec", None),
+        ):
+            namespace = F()
+            calls.clear()
+            self.assertEqual(
+                operation(compile(source, "<frozen-globals>", mode), namespace),
+                expected,
+            )
+            self.assertEqual(calls, [("__builtins__", builtins.__dict__)])
+            self.assertNotIn("__builtins__", namespace)
+            calls.clear()
+            with self.assertRaisesRegex(
+                TypeError, "frozendict object does not support item assignment"
+            ):
+                operation(source, namespace)
+            self.assertEqual(calls, [("__builtins__", builtins.__dict__)])
+
+    def test_implicit_frozen_builtins_namespace_counts(self):
+        import _testinternalcapi
+
+        function = eval(
+            "lambda: len(())",
+            frozendict(__builtins__=frozendict(len=len)),
+        )
+        counts = _testinternalcapi.get_code_var_counts(function)
+        self.assertEqual(
+            counts["unbound"]["globals"],
+            {"total": 1, "numglobal": 0, "numbuiltin": 1, "numunknown": 0},
+        )
+        for argument in ("globalsns", "builtinsns"):
+            with self.assertRaises(TypeError):
+                _testinternalcapi.get_code_var_counts(
+                    function, **{argument: frozendict()}
+                )
+
+    def test_warning_context_reads_frozen_storage(self):
+        import warnings
+
+        class F(frozendict):
+            def __getitem__(self, key):
+                if key in ("__warningregistry__", "__name__"):
+                    raise AssertionError("warning context must read stored entries")
+                return super().__getitem__(key)
+
+        for has_registry in (False, True):
+            entries = dict(self.ns, warn=warnings.warn)
+            if has_registry:
+                entries["__warningregistry__"] = {}
+            function = eval("lambda: warn('probe')", F(entries))
+            with warnings.catch_warnings(record=True) as caught:
+                warnings.simplefilter("always")
+                if has_registry:
+                    function()
+                    self.assertEqual(len(caught), 1)
+                    self.assertEqual(str(caught[0].message), "probe")
+                else:
+                    with self.assertRaisesRegex(
+                        TypeError,
+                        "frozendict object does not support item assignment",
+                    ):
+                        function()
+                    self.assertEqual(caught, [])
+
+    def test_frozen_builtins(self):
+        ns = frozendict(__builtins__=frozendict({"len": len}))
+        self.assertEqual(eval("(lambda: len([1, 2]))()", ns), 2)
+
+    def test_shared_code_does_not_keep_mutable_global_specialization(self):
+        code = compile("lambda: answer", "<globals-probe>", "eval")
+        mutable = {"__builtins__": builtins.__dict__, "answer": 19}
+        f = eval(code, mutable)
+        for _ in range(300):
+            self.assertEqual(f(), 19)
+        frozen_f = eval(code, self.ns)
+        for _ in range(300):
+            self.assertEqual(frozen_f(), 42)
+            self.assertEqual(f(), 19)
+        mutable["answer"] = 23
+        self.assertEqual(f(), 23)
+        self.assertEqual(frozen_f(), 42)
+
+
+frozen_suite = unittest.TestSuite(
+    unittest.defaultTestLoader.loadTestsFromTestCase(case)
+    for case in (FrozenDictDescriptorTests, FrozenGlobalsTests)
+)
+frozen_result = unittest.TextTestRunner(verbosity=2).run(frozen_suite)
+assert frozen_result.wasSuccessful()
+assert not frozen_result.skipped
diff --git a/extra_tests/snippets/builtin_hash.py b/extra_tests/snippets/builtin_hash.py
index d4bf1168323..2426babef5a 100644
--- a/extra_tests/snippets/builtin_hash.py
+++ b/extra_tests/snippets/builtin_hash.py
@@ -35,10 +35,10 @@ def __hash__(self):
 # slot dispatch is what recurses, so that is where the depth is checked.
 
 if sys.implementation.name == "rustpython":
-    # Deep enough to reach the native stack guard; CPython, which also runs
-    # this snippet, dies on the same value.
+    # Deep enough to reach the native stack guard in release; CPython, which
+    # also runs this snippet, dies on the same value.
     deep_tuple = ()
-    for _ in range(100_000):
+    for _ in range(500_000):
         deep_tuple = (deep_tuple,)
     with assert_raises(RecursionError):
         hash(deep_tuple)
diff --git a/extra_tests/snippets/builtin_list.py b/extra_tests/snippets/builtin_list.py
index 189f794774b..59f77e5a9ba 100644
--- a/extra_tests/snippets/builtin_list.py
+++ b/extra_tests/snippets/builtin_list.py
@@ -1388,3 +1388,22 @@ def failing_source():
 
 
 test_slice_replacement_lifetime()
+
+
+def test_subscript_typeerror_message():
+    def message(index):
+        try:
+            [0, 1, 2][index]
+        except TypeError as err:
+            return str(err)
+        raise AssertionError("TypeError was not raised")
+
+    assert message("x") == "list indices must be integers or slices, not str"
+
+    Long = type("A" * 250, (), {})
+    assert message(Long()) == "list indices must be integers or slices, not {}".format(
+        "A" * 200
+    )
+
+
+test_subscript_typeerror_message()
diff --git a/extra_tests/snippets/builtin_mappingproxy.py b/extra_tests/snippets/builtin_mappingproxy.py
index fdd653c408d..8adf4d7e9bb 100644
--- a/extra_tests/snippets/builtin_mappingproxy.py
+++ b/extra_tests/snippets/builtin_mappingproxy.py
@@ -23,3 +23,64 @@ def b():
 assert A.__dict__.get("not here", "default") == "default"
 assert A.__dict__.get("a", "default") is A.a
 assert A.__dict__.get("not here") is None
+
+
+# A mappingproxy preserves arbitrary equality-comparison results unchanged.
+def check_mappingproxy_comparison_results():
+    import operator
+    from types import MappingProxyType
+
+    from testutils import assert_raises
+
+    class Result:
+        def __bool__(self):
+            raise AssertionError("comparison result must not be coerced to bool")
+
+    result = Result()
+    calls = []
+
+    def compare(name):
+        def method(self, other):
+            calls.append(name)
+            return result
+
+        return method
+
+    class Compared:
+        __eq__ = compare("eq")
+        __ne__ = compare("ne")
+        __lt__ = compare("lt")
+        __le__ = compare("le")
+        __gt__ = compare("gt")
+        __ge__ = compare("ge")
+
+    class CustomMapping(Compared, dict):
+        pass
+
+    for operation, reflected in (
+        (operator.eq, "eq"),
+        (operator.ne, "ne"),
+    ):
+        calls.clear()
+        assert operation(MappingProxyType(CustomMapping()), {}) is result
+        assert calls == [operation.__name__], calls
+        calls.clear()
+        assert operation(MappingProxyType({}), Compared()) is result
+        assert calls == [reflected], calls
+
+    for operation, reflected in (
+        (operator.lt, "gt"),
+        (operator.le, "ge"),
+        (operator.gt, "lt"),
+        (operator.ge, "le"),
+    ):
+        calls.clear()
+        with assert_raises(TypeError):
+            operation(MappingProxyType(CustomMapping()), {})
+        assert calls == [], calls
+        calls.clear()
+        assert operation(MappingProxyType({}), Compared()) is result
+        assert calls == [reflected], calls
+
+
+check_mappingproxy_comparison_results()
diff --git a/extra_tests/snippets/builtin_memoryview.py b/extra_tests/snippets/builtin_memoryview.py
index ef28ffc3d79..ea0475d7c63 100644
--- a/extra_tests/snippets/builtin_memoryview.py
+++ b/extra_tests/snippets/builtin_memoryview.py
@@ -399,7 +399,7 @@ def test_cast_rejects_non_native_format():
             memoryview(b"").cast(fmt)
             raise AssertionError(f"cast accepted {fmt!r}")
         except ValueError as e:
-            assert "native single character format" in str(e), e
+            assert "native format" in str(e), e
     assert memoryview(bytes(8)).cast("@i").itemsize == 4
 
 
diff --git a/extra_tests/snippets/builtin_object.py b/extra_tests/snippets/builtin_object.py
index 0b90c44a320..cfa8a686641 100644
--- a/extra_tests/snippets/builtin_object.py
+++ b/extra_tests/snippets/builtin_object.py
@@ -161,3 +161,78 @@ def __getattr__(self, name):
     with assert_raises(ValueError) as caught:
         RaisingAttributeHook().absent
     assert caught.exception.__context__ is outer
+
+
+# The descriptor slot calls the raw __get__ attribute without binding it first.
+class RawGetDescriptor:
+    __get__ = staticmethod(lambda *args: args)
+
+
+class RawGetOwner:
+    value = RawGetDescriptor()
+
+
+raw_descriptor = vars(RawGetOwner)["value"]
+raw_instance = RawGetOwner()
+assert raw_instance.value == (raw_descriptor, raw_instance, RawGetOwner)
+assert RawGetOwner.value == (raw_descriptor, None, RawGetOwner)
+
+
+class CallableGet:
+    def __get__(self, instance, owner):
+        raise AssertionError("__get__ must not be bound before the slot call")
+
+    def __call__(self, *args):
+        return args
+
+
+RawGetDescriptor.__get__ = CallableGet()
+assert raw_instance.value == (raw_descriptor, raw_instance, RawGetOwner)
+RawGetDescriptor.__get__ = classmethod(lambda *args: args)
+with assert_raises(TypeError):
+    raw_instance.value
+RawGetDescriptor.__get__ = lambda self, instance, owner: (self, instance, owner)
+assert raw_instance.value == (raw_descriptor, raw_instance, RawGetOwner)
+
+
+# object.__getstate__ reads names from a cached __slotnames__ list
+class NonStrSlotName:
+    __slotnames__ = [1]
+
+
+with assert_raises(TypeError) as caught:
+    NonStrSlotName().__getstate__()
+assert str(caught.exception) == "attribute name must be string, not 'int'"
+
+
+class GrowingSlotNames:
+    __slotnames__ = ["a", "b"]
+
+    def __getattr__(self, name):
+        if name == "a":
+            GrowingSlotNames.__slotnames__.append("c")
+            return 1
+        raise AttributeError(name)
+
+
+with assert_raises(RuntimeError):
+    GrowingSlotNames().__getstate__()
+
+
+class RaisingSlot:
+    __slotnames__ = ["x"]
+
+    def __getattr__(self, name):
+        raise ValueError("boom")
+
+
+with assert_raises(ValueError):
+    RaisingSlot().__getstate__()
+
+
+class MissingSlot:
+    __slotnames__ = ["x", "y"]
+    y = 2
+
+
+assert MissingSlot().__getstate__() == (None, {"y": 2})
diff --git a/extra_tests/snippets/builtin_round.py b/extra_tests/snippets/builtin_round.py
index 83725420a40..e41277fb589 100644
--- a/extra_tests/snippets/builtin_round.py
+++ b/extra_tests/snippets/builtin_round.py
@@ -111,3 +111,32 @@ class MyInt(int):
 assert type(round(MyInt(5), 2)) is int
 # A negative ndigits already produced a fresh exact int.
 assert type(round(MyInt(15), -1)) is int
+
+
+# round() passes ndigits to __round__ unchanged, like CPython's builtin_round_impl().
+class Echo:
+    def __round__(self, *args):
+        return args
+
+
+assert round(Echo(), []) == ([],)
+assert round(Echo(), 1.5) == (1.5,)
+assert type(round(Echo(), True)[0]) is bool
+
+
+class Index:
+    def __index__(self):
+        return -1
+
+
+assert type(round(Echo(), Index())[0]) is Index
+
+# int.__round__ and float.__round__ apply __index__ to ndigits themselves.
+assert round(15, Index()) == 20
+assert round(1.25, Index()) == 0.0
+assert (15).__round__(Index()) == 20
+assert (1.25).__round__(Index()) == 0.0
+with assert_raises(TypeError):
+    (15).__round__(1.0)
+with assert_raises(TypeError):
+    (1.25).__round__([])
diff --git a/extra_tests/snippets/builtin_set.py b/extra_tests/snippets/builtin_set.py
index 8e96a095962..19fab874b19 100644
--- a/extra_tests/snippets/builtin_set.py
+++ b/extra_tests/snippets/builtin_set.py
@@ -1,3 +1,5 @@
+import operator
+
 from testutils import assert_raises
 
 assert set([1, 2]) == set([1, 2])
@@ -706,3 +708,17 @@ def __del__(self):
         intersection_target.intersection_update({1})
     assert not intersection_target
 assert intersection_events == [True, True]
+
+
+# Unsupported right operands must reach their reflected set operation.
+keys = {2: None, 3: None}.keys()
+for method, operation, expected in (
+    (set.__ior__, operator.ior, {1, 2, 3}),
+    (set.__iand__, operator.iand, {2}),
+    (set.__isub__, operator.isub, {1}),
+    (set.__ixor__, operator.ixor, {1, 3}),
+):
+    source = {1, 2}
+    assert method(source, keys) is NotImplemented
+    assert operation(source, keys) == expected
+    assert source == {1, 2}
diff --git a/extra_tests/snippets/builtin_signature.py b/extra_tests/snippets/builtin_signature.py
index be0d53e9e3c..06d5cf92bea 100644
--- a/extra_tests/snippets/builtin_signature.py
+++ b/extra_tests/snippets/builtin_signature.py
@@ -19,7 +19,7 @@
     raise AssertionError("len() should not accept keyword arguments")
 
 assert str(inspect.signature(len)) == "(obj, /)"
-assert str(inspect.signature(abs)) == "(x, /)"
+assert str(inspect.signature(abs)) == "(number, /)"
 assert str(inspect.signature(hash)) == "(obj, /)"
 assert str(inspect.signature(chr)) == "(i, /)"
 assert str(inspect.signature(callable)) == "(obj, /)"
@@ -37,7 +37,7 @@
 ], breakpoint_kinds
 
 # Parameter names follow CPython, so signatures are directly comparable.
-assert str(inspect.signature(bin)) == "(number, /)"
+assert str(inspect.signature(bin)) == "(integer, /)"
 assert str(inspect.signature(ord)) == "(character, /)"
 assert str(inspect.signature(divmod)) == "(x, y, /)"
 assert str(inspect.signature(hasattr)) == "(obj, name, /)"
@@ -64,3 +64,12 @@
 assert sum.__text_signature__ == "($module, iterable, /, start=0)"
 assert str(inspect.signature(round)) == "(number, ndigits=None)"
 assert str(inspect.signature(sum)) == "(iterable, /, start=0)"
+
+# A keyword-only argument between two positional ones used to put `/` after
+# `*`, which inspect cannot parse. Arguments are ordered like CPython's, so
+# path and mode take keywords. Windows renders follow_symlinks differently.
+if hasattr(os, "chmod"):
+    chmod_signature = os.chmod.__text_signature__
+    assert chmod_signature.startswith("($module, /, path, mode, *, dir_fd=None"), (
+        chmod_signature
+    )
diff --git a/extra_tests/snippets/builtin_str.py b/extra_tests/snippets/builtin_str.py
index d114e2d5727..2daf2fd948a 100644
--- a/extra_tests/snippets/builtin_str.py
+++ b/extra_tests/snippets/builtin_str.py
@@ -411,7 +411,10 @@ def __int__(self):
     for value in (None, TypeError("conversion failed")):
         with assert_raises(TypeError) as cm:
             template % PercentInt(value)
-        assert str(cm.exception).endswith("a real number is required, not PercentInt")
+        conversion = chr(template[-1]) if isinstance(template, bytes) else template[-1]
+        assert str(cm.exception) == (
+            f"format argument: %{conversion} requires a real number, not PercentInt"
+        )
     assert_raises(
         RuntimeError, template.__mod__, PercentInt(RuntimeError("conversion failed"))
     )
@@ -427,6 +430,31 @@ def __int__(self):
 assert "%x" % PercentInt(3) == "7"
 assert b"%o" % PercentInt(3) == b"7"
 
+
+def test_percent_character_subclasses():
+    for base, value, templates in (
+        (str, "ab", ("%c",)),
+        (bytes, b"ab", (b"%c", bytearray(b"%c"))),
+        (bytearray, b"ab", (b"%c", bytearray(b"%c"))),
+    ):
+
+        class Indexable(base):
+            def __index__(self):
+                raise AssertionError("%c must check the character length first")
+
+        for template in templates:
+            assert template % Indexable(value[:1]) == template % value[:1]
+            for text in (value[:0], value):
+                with assert_raises(TypeError) as expected:
+                    template % base(text)
+                with assert_raises(TypeError) as actual:
+                    template % Indexable(text)
+                assert str(actual.exception) == str(expected.exception)
+            assert template % PercentIndex() == template % 7
+
+
+test_percent_character_subclasses()
+
 assert (
     "%(first)s %(second)s" % {"second": "World!", "first": "Hello,"} == "Hello, World!"
 )
@@ -1098,6 +1126,23 @@ def test_replace_unchanged():
 test_replace_unchanged()
 
 
+def test_replace_missing_pattern():
+    for text in ("ordinary text", "\u00e1\u03b2\U0001f600", "a\ud800b\udfff"):
+        for count in (-1, 1, 10):
+            assert text.replace("\r", "replacement", count) is text
+            result = MyString(text).replace("\r", "replacement", count)
+            assert type(result) is str
+            assert result == text
+
+    # Continue the same search after the first match, including lone surrogates.
+    assert "ababa".replace("aba", "x") == "xba"
+    assert "\ud800x\ud800".replace("\ud800", "\udfff", 1) == "\udfffx\ud800"
+    assert "\ud800x\ud800".replace("\ud800", "\udfff") == "\udfffx\udfff"
+
+
+test_replace_missing_pattern()
+
+
 def test_expandtabs_zero_tabsize():
     # With no width to advance to, the tabs come out and nothing else moves.
     # A tab that followed a character used to ask for a run of usize::MAX
@@ -1160,3 +1205,82 @@ def __radd__(self, other):
 
 
 test_concat_error_message()
+
+
+def test_subscript_typeerror_message():
+    def message(index):
+        try:
+            "abc"[index]
+        except TypeError as err:
+            return str(err)
+        raise AssertionError("TypeError was not raised")
+
+    assert message("def") == "string indices must be integers, not 'str'"
+    assert message(object()) == "string indices must be integers, not 'object'"
+    assert message(1.5) == "string indices must be integers, not 'float'"
+    assert message(None) == "string indices must be integers, not 'NoneType'"
+
+    Long = type("A" * 250, (), {})
+    assert message(Long()) == "string indices must be integers, not '{}'".format(
+        "A" * 200
+    )
+
+
+test_subscript_typeerror_message()
+
+
+# Decimal conversion errors identify the consumed argument, including star arguments.
+for is_bytes in (False, True):
+    for conversion in "diu":
+        for template, values, context in (
+            ("%" + conversion, "bad", ""),
+            ("%" + conversion, ("bad",), " 1"),
+            ("%s %" + conversion, ("ok", "bad"), " 2"),
+            ("%*.*" + conversion, (5, 2, "bad"), " 3"),
+            ("%(value)" + conversion, {"value": "bad"}, " 'value'"),
+        ):
+            if is_bytes:
+                template = template.encode()
+                if isinstance(values, dict):
+                    values = {b"value": "bad"}
+                    context = " b'value'"
+                elif isinstance(values, tuple) and len(values) == 2:
+                    values = (b"ok", "bad")
+            with assert_raises(TypeError) as caught:
+                template % values
+            assert str(caught.exception) == (
+                f"format argument{context}: %{conversion} requires a real number, not str"
+            )
+
+
+def test_percent_callback_order_bounded():
+    for template in ("%r %", b"%r %", bytearray(b"%r %")):
+        calls = []
+
+        class Value:
+            def __repr__(self):
+                calls.append("repr")
+                return "value"
+
+        with assert_raises(ValueError):
+            template % (Value(),)
+        assert calls == ["repr"]
+
+    for template, key in (
+        ("%(x)*r", "x"),
+        (b"%(x)*r", b"x"),
+        (bytearray(b"%(x)*r"), b"x"),
+    ):
+        calls = []
+
+        class Mapping:
+            def __getitem__(self, name):
+                calls.append(name)
+                return 5
+
+        with assert_raises(ValueError):
+            template % Mapping()
+        assert calls == [key]
+
+
+test_percent_callback_order_bounded()
diff --git a/extra_tests/snippets/builtin_str_add.py b/extra_tests/snippets/builtin_str_add.py
index 075939ae8d2..cafedc6a5e4 100644
--- a/extra_tests/snippets/builtin_str_add.py
+++ b/extra_tests/snippets/builtin_str_add.py
@@ -86,3 +86,94 @@ class Child(Override):
     del Override.__add__
     for cls in (Override, Child):
         assert operator.add(cls(left), right) == left + right
+
+
+# Inheriting native concatenation must leave reflected numeric addition first.
+for base, left in (
+    (str, "a"),
+    (bytes, b"a"),
+    (tuple, (1,)),
+    (list, [1]),
+    (bytearray, b"a"),
+):
+
+    class Native(base):
+        pass
+
+    class Child(Native):
+        pass
+
+    class Explicit(base):
+        __add__ = base.__add__
+
+    for cls in (Native, Child, Explicit):
+        for result in ("reflected", NotImplemented):
+            other = Reflected(result)
+            if result is NotImplemented:
+                assert_raises(TypeError, operator.add, cls(left), other)
+            else:
+                assert operator.add(cls(left), other) == result
+            assert other.calls == 1
+
+    class ReflectedSequence(base):
+        calls = 0
+
+        def __radd__(self, other):
+            self.calls += 1
+            return NotImplemented
+
+    other = ReflectedSequence(left)
+    assert operator.add(Native(left), other) == base(left) + base(left)
+    assert other.calls == 1
+
+    class AddOverride(ReflectedSequence):
+        def __add__(self, other):
+            return "overridden"
+
+    other = AddOverride(left)
+    assert operator.add(ReflectedSequence(left), other) == base(left) + base(left)
+    assert other.calls == 0
+    del AddOverride.__add__
+    other = AddOverride(left)
+    assert operator.add(ReflectedSequence(left), other) == base(left) + base(left)
+    assert other.calls == 0
+
+    # CPython keeps numeric dispatch after either addition method is overridden,
+    # including when deletion or replacement exposes the native __add__ again.
+    Native.__radd__ = lambda self, other: NotImplemented
+    for change in (
+        lambda: None,
+        lambda: delattr(Native, "__radd__"),
+        lambda: setattr(Native, "__add__", base.__add__),
+        lambda: delattr(Native, "__add__"),
+    ):
+        change()
+        for cls in (Native, Child):
+            other = Reflected("reflected")
+            assert_raises(TypeError, operator.add, cls(left), other)
+            assert other.calls == 0
+
+
+# A differently named descriptor assigned to __add__ needs numeric dispatch.
+class InplaceAlias(list):
+    __add__ = list.__iadd__
+
+
+other = Reflected("reflected")
+assert_raises(TypeError, operator.add, InplaceAlias([1]), other)
+assert other.calls == 0
+
+
+class NativeIntAdd(int):
+    __add__ = int.__add__
+
+    def __radd__(self, other):
+        raise AssertionError("inherited reflected addition took priority")
+
+
+class IntAddOverride(NativeIntAdd):
+    def __add__(self, other):
+        return "overridden"
+
+
+assert operator.add(NativeIntAdd(1), IntAddOverride(2)) == 3
diff --git a/extra_tests/snippets/builtin_thread.py b/extra_tests/snippets/builtin_thread.py
index e9696cce6d4..b98a2a42e34 100644
--- a/extra_tests/snippets/builtin_thread.py
+++ b/extra_tests/snippets/builtin_thread.py
@@ -1,3 +1,31 @@
 import _thread
 
 assert _thread.TIMEOUT_MAX in [9223372036.0, 4294967.0]
+
+from testutils import assert_raises
+
+# Reentrant calls must validate arguments before incrementing the count.
+for error, kwargs in (
+    (ValueError, {"blocking": False, "timeout": 1}),
+    (ValueError, {"timeout": -2}),
+    (OverflowError, {"timeout": _thread.TIMEOUT_MAX + 1}),
+    (OverflowError, {"blocking": False, "timeout": 2**63 / 1e9}),
+    (OverflowError, {"blocking": False, "timeout": -9_223_372_037}),
+    (OverflowError, {"timeout": -9_223_372_037}),
+    (OverflowError, {"blocking": False, "timeout": float("inf")}),
+    (OverflowError, {"timeout": float("inf")}),
+    (OverflowError, {"blocking": False, "timeout": float("-inf")}),
+    (OverflowError, {"timeout": float("-inf")}),
+    (ValueError, {"timeout": -(2**63) / 1e9}),
+    (ValueError, {"blocking": False, "timeout": 4_294_968}),
+    (ValueError, {"timeout": -4_294_968}),
+):
+    lock = _thread.RLock()
+    assert lock.acquire()
+    try:
+        with assert_raises(error):
+            lock.acquire(**kwargs)
+        assert lock._recursion_count() == 1
+    finally:
+        while lock._is_owned():
+            lock.release()
diff --git a/extra_tests/snippets/builtin_type.py b/extra_tests/snippets/builtin_type.py
index 06b40fe41f6..df81b844b3d 100644
--- a/extra_tests/snippets/builtin_type.py
+++ b/extra_tests/snippets/builtin_type.py
@@ -241,6 +241,25 @@ class C(B, BB):
 assert C.mro() == [C, B, A, BB, AA, object]
 
 
+# Direct base order must also constrain ancestors shared with an earlier base.
+class D(B, AA, A):
+    pass
+
+
+assert D.mro() == [D, B, AA, A, object]
+
+
+class E(AA, A):
+    pass
+
+
+class F(D, E):
+    pass
+
+
+assert F.mro() == [F, D, B, E, AA, A, object]
+
+
 class TypeA:
     def __init__(self):
         self.a = 1
@@ -654,7 +673,12 @@ def my_repr_func():
 
 
 # https://github.com/RustPython/RustPython/issues/3100
+assert types.BuiltinMethodType is types.BuiltinFunctionType
 assert issubclass(types.BuiltinMethodType, types.BuiltinFunctionType)
+assert type(len) is types.BuiltinFunctionType
+assert type([].append) is types.BuiltinFunctionType
+assert type([].append).__name__ == "builtin_function_or_method"
+assert type(len).__name__ == "builtin_function_or_method"
 
 assert type.__dict__["__dict__"].__objclass__ is type
 assert (
@@ -743,3 +767,53 @@ class StrKey(str):
     warnings.simplefilter("error")
     with assert_raises(RuntimeWarning):
         type("NonStringKeyRaises", (), {6: 7})
+
+
+class Left:
+    __slots__ = ("left",)
+
+
+class Right:
+    __slots__ = ("right",)
+
+
+with assert_raises(TypeError):
+
+    class Conflict(Left, Right):
+        pass
+
+
+with assert_raises(TypeError):
+
+    class ReverseConflict(Right, Left):
+        pass
+
+
+class Empty:
+    __slots__ = ()
+
+
+class Compatible(Left, Empty):
+    pass
+
+
+value = Compatible()
+value.left = 42
+assert value.left == 42
+
+
+class FirstChild(Left):
+    __slots__ = ()
+
+
+class SecondChild(Left):
+    __slots__ = ()
+
+
+class Diamond(FirstChild, SecondChild):
+    pass
+
+
+value = Diamond()
+value.left = 43
+assert value.left == 43
diff --git a/extra_tests/snippets/builtins_module.py b/extra_tests/snippets/builtins_module.py
index bf762425c89..a3a35a29739 100644
--- a/extra_tests/snippets/builtins_module.py
+++ b/extra_tests/snippets/builtins_module.py
@@ -42,3 +42,26 @@ def test_func():
     __builtins__  # noqa: F821
 
 assert print
+
+
+from types import ModuleType
+
+
+class AnnotationDict(dict):
+    pass
+
+
+module = ModuleType("annotated_module")
+annotations = AnnotationDict(answer=int)
+calls = []
+
+
+def annotate(format):
+    calls.append(format)
+    return annotations
+
+
+module.__annotate__ = annotate
+assert module.__annotations__ is annotations
+assert module.__annotations__ is annotations
+assert calls == [1]
diff --git a/extra_tests/snippets/import_atomic_reorder.py b/extra_tests/snippets/import_atomic_reorder.py
new file mode 100644
index 00000000000..b7c8a9d356b
--- /dev/null
+++ b/extra_tests/snippets/import_atomic_reorder.py
@@ -0,0 +1,189 @@
+"""Private exact-dict relocation and callback-reentry regression coverage."""
+
+import _imp
+import sys
+
+
+def raises(kind, call, expected=None):
+    try:
+        call()
+    except kind as exc:
+        if expected is not None:
+            assert exc is expected
+        return exc
+    raise AssertionError(f"{kind.__name__} was not raised")
+
+
+def check_native_helper():
+    move = _imp._dict_move_to_end
+    first, middle, last = object(), object(), object()
+    mapping = {"first": first, "middle": middle, "last": last}
+    assert move(mapping, "middle") is middle
+    assert list(mapping) == ["first", "last", "middle"]
+    assert len(mapping) == 3
+    assert move(mapping, "middle") is middle
+    assert list(mapping) == ["first", "last", "middle"]
+    single = {"only": None}
+    assert move(single, "only") is None
+    assert single == {"only": None}
+    missing = object()
+    exc = raises(KeyError, lambda: move(mapping, missing))
+    assert exc.args[0] is missing
+    assert list(mapping) == ["first", "last", "middle"]
+
+    class Subclass(dict):
+        pass
+
+    raises(TypeError, lambda: move(Subclass(mapping), "middle"))
+    raises(TypeError, lambda: move([], "middle"))
+    stored = "".join(["equal", " key"])
+    equal = "".join(["equal ", "key"])
+    assert stored == equal and stored is not equal
+    mapping = {stored: middle, "after": last}
+    assert move(mapping, equal) is middle
+    assert list(mapping)[-1] is stored
+
+    failure = ValueError("hash failure")
+
+    class Hashed(str):
+        count = 0
+        fail = False
+
+        def __hash__(self):
+            self.count += 1
+            if self.fail:
+                raise failure
+            return super().__hash__()
+
+    lookup = Hashed(stored)
+    assert move(mapping, lookup) is middle
+    assert lookup.count == 1
+    lookup.fail = True
+    raises(ValueError, lambda: move(mapping, lookup), failure)
+    assert lookup.count == 2
+
+    class Collision:
+        def __init__(self, label, action=None):
+            self.label = label
+            self.action = action
+
+        def __hash__(self):
+            return 42
+
+        def __eq__(self, other):
+            action, self.action = self.action, None
+            if action is not None:
+                action()
+            return isinstance(other, Collision) and self.label == other.label
+
+    lookup = Collision("target")
+    stored = Collision("target")
+    impostor = Collision("different")
+    mapping = {stored: first, "after": last}
+
+    def replace_key():
+        mapping.clear()
+        mapping[impostor] = middle
+
+    stored.action = replace_key
+    raises(KeyError, lambda: move(mapping, lookup))
+    assert list(mapping) == [impostor]
+    assert mapping[impostor] is middle
+
+    stored = Collision("target")
+    mapping = {stored: first, "after": last}
+    stored.action = lambda: mapping.__setitem__(stored, middle)
+    assert move(mapping, lookup) is middle
+    assert list(mapping)[-1] is stored
+
+    stored = Collision("target")
+    mapping = {stored: first, "after": last}
+    stored.action = lambda: mapping.clear()
+    raises(KeyError, lambda: move(mapping, lookup))
+    assert mapping == {}
+
+    stored = Collision("target")
+    mapping = {stored: first, "after": last}
+
+    def resize():
+        mapping.clear()
+        for i in range(100):
+            mapping[i] = i
+        mapping[stored] = middle
+        mapping["after"] = last
+
+    stored.action = resize
+    assert move(mapping, lookup) is middle
+    assert list(mapping)[-1] is stored
+    assert len(mapping) == 102
+
+    # A surviving false candidate alone does not certify the probe prefix.
+    # Nested relocation compacts T into P's earlier bucket, while A keeps its
+    # key identity, bucket and physical entry index. T never becomes absent.
+    prefix_key = Collision("prefix")
+    candidate = Collision("candidate")
+    target = Collision("target")
+    mapping = {prefix_key: first, candidate: last, target: middle}
+
+    def compact_prefix():
+        del mapping[prefix_key]
+        assert move(mapping, candidate) is last
+        assert list(mapping) == [target, candidate]
+
+    candidate.action = compact_prefix
+    assert move(mapping, lookup) is middle
+    assert list(mapping) == [candidate, target]
+
+    # Inserting in a previously visited DUMMY bucket also requires a restart.
+    mapping = {prefix_key: first, candidate: last}
+    del mapping[prefix_key]
+    candidate.action = lambda: mapping.__setitem__(lookup, middle)
+    assert move(mapping, lookup) is middle
+    assert list(mapping) == [candidate, lookup]
+
+    failure = RuntimeError("equality failure")
+
+    def fail():
+        raise failure
+
+    stored = Collision("target", fail)
+    mapping = {stored: first, "after": last}
+    before = list(mapping)
+    raises(RuntimeError, lambda: move(mapping, lookup), failure)
+    assert list(mapping) == before
+
+    class HashMutation:
+        def __hash__(self):
+            mapping.clear()
+            mapping["kept"] = last
+            return 42
+
+    raises(KeyError, lambda: move(mapping, HashMutation()))
+    assert mapping == {"kept": last}
+
+    # Releasing the removed candidate must not run its finalizer under the
+    # dictionary lock. The only owners are the dict and the lookup's witness.
+    finalized = []
+
+    class Finalized(Collision):
+        def __del__(self):
+            mapping["finalized"] = True
+            finalized.append(True)
+
+    mapping = {Finalized("target", lambda: mapping.clear()): first}
+    raises(KeyError, lambda: move(mapping, lookup))
+    assert finalized == [True]
+    assert mapping == {"finalized": True}
+
+    mapping = {"a": 1, "b": 2}
+    for i in range(100):
+        forward, backward = iter(mapping), reversed(mapping)
+        key = "a" if i % 2 == 0 else "b"
+        move(mapping, key)
+        raises(RuntimeError, lambda: next(forward))
+        raises(RuntimeError, lambda: next(backward))
+        assert list(mapping)[-1] == key
+
+
+if sys.implementation.name == "rustpython":
+    check_native_helper()
diff --git a/extra_tests/snippets/operator_arithmetic.py b/extra_tests/snippets/operator_arithmetic.py
index 14763107b5c..559ad7a4f73 100644
--- a/extra_tests/snippets/operator_arithmetic.py
+++ b/extra_tests/snippets/operator_arithmetic.py
@@ -89,11 +89,21 @@ def __getitem__(self, index):
 
 # Native sequence slots use the same count conversion in both directions.
 for value in ([1], (1,), "a", b"a", bytearray(b"a")):
-    for operation in (mul, lambda seq, count: count * seq, imul):
+    namespace = {}
+    exec("def reverse(seq, count):\n    return count * seq", namespace)
+    for operation_index, operation in enumerate((mul, namespace["reverse"], imul)):
+        for _ in range(64):
+            operation(value, 1)
         for count, error, message in (
             (1.5, TypeError, "can't multiply sequence by non-int of type 'float'"),
             (2**100, OverflowError, "cannot fit 'int' into an index-sized integer"),
         ):
+            if (
+                type(value) in (str, bytes, tuple)
+                and operation_index == 1
+                and error is OverflowError
+            ):
+                message = "Python int too large to convert to C ssize_t"
             check_repeat_error(error, message, operation, value, count)
 
 
@@ -123,6 +133,79 @@ def __index__(self):
 )
 
 
+# Each expression has fresh bytecode so cold and warmed paths are both checked.
+for value in ("a", b"a", (1,), "", b"", ()):
+    for expression in (
+        "return seq * count",
+        "return count * seq",
+        "seq *= count; return seq",
+        "count *= seq; return count",
+    ):
+        namespace = {}
+        exec("def repeat(seq, count):\n    " + expression, namespace)
+        repeat = namespace["repeat"]
+        check_repeat_error(
+            OverflowError,
+            "cannot fit 'int' into an index-sized integer",
+            repeat,
+            value,
+            2**100,
+        )
+        for _ in range(64):
+            assert repeat(value, 2) == mul(value, 2)
+        assert repeat(value, -2) == value[:0]
+        assert repeat(value, 0) == value[:0]
+        assert repeat(value, 1) == value
+        for count in (2**100, -(2**100)):
+            check_repeat_error(
+                OverflowError,
+                "Python int too large to convert to C ssize_t",
+                repeat,
+                value,
+                count,
+            )
+        for other in ("a", b"a", (1,)):
+            if type(other) is not type(value):
+                check_repeat_error(
+                    OverflowError,
+                    "cannot fit 'int' into an index-sized integer",
+                    repeat,
+                    other,
+                    2**100,
+                )
+        if expression == "count *= seq; return count":
+            check_repeat_error(
+                TypeError,
+                f"unsupported operand type(s) for *=: 'RepeatIndex' and '{type(value).__name__}'",
+                repeat,
+                value,
+                RepeatIndex(2),
+            )
+        else:
+            assert repeat(value, RepeatIndex(2)) == mul(value, 2)
+            check_repeat_error(
+                OverflowError,
+                "cannot fit 'RepeatIndex' into an index-sized integer",
+                repeat,
+                value,
+                RepeatIndex(2**100),
+            )
+        subclass = type("RepeatSubclass", (type(value),), {})(value)
+        assert repeat(subclass, 2) == mul(value, 2)
+        overridden = type(
+            "OverrideRepeat",
+            (type(value),),
+            {
+                "__mul__": lambda self, count: "forward",
+                "__rmul__": lambda self, count: "reverse",
+            },
+        )(value)
+        expected = (
+            "forward" if expression.startswith(("return seq", "seq *=")) else "reverse"
+        )
+        assert repeat(overridden, 2) == expected
+
+
 class DeclineRepeat(GetItemOnly):
     calls = []
 
diff --git a/extra_tests/snippets/protocol_index_argument.py b/extra_tests/snippets/protocol_index_argument.py
index c67a078ef05..ada8be24085 100644
--- a/extra_tests/snippets/protocol_index_argument.py
+++ b/extra_tests/snippets/protocol_index_argument.py
@@ -312,3 +312,65 @@ def __length_hint__(self):
 
 with assert_raises(TypeError):
     operator.length_hint(HintIndex())
+
+
+# Arguments bound as `int` objects accept `__index__` as well.
+assert "abcabc".find("a", Index(1)) == 3
+assert "abcabc".rfind("a", 0, Index(3)) == 0
+assert "abcabc".index("c", Index(3)) == 5
+assert "abcabc".rindex("a", Index(1), Index(4)) == 3
+assert "aaaaaa".count("a", Index(2), Index(-1)) == 3
+assert "abcdef".startswith("d", Index(3))
+assert "abcdef".endswith("c", 0, Index(3))
+assert b"abcabc".find(b"a", Index(1)) == 3
+assert b"abcabc".count(b"b", Index(2)) == 1
+assert b"abcdef".startswith(b"d", Index(3))
+assert bytearray(b"abcabc").rindex(b"a", 0, Index(3)) == 0
+assert bytearray(b"abcdef").endswith(b"c", 0, Index(3))
+
+assert list(enumerate("ab", Index(3))) == [(3, "a"), (4, "b")]
+assert list(enumerate("ab", start=Index(3))) == [(3, "a"), (4, "b")]
+
+import itertools
+
+assert list(itertools.combinations("abc", Index(2))) == [
+    ("a", "b"),
+    ("a", "c"),
+    ("b", "c"),
+]
+assert list(itertools.combinations_with_replacement("ab", Index(2))) == [
+    ("a", "a"),
+    ("a", "b"),
+    ("b", "b"),
+]
+assert list(itertools.batched("abcde", Index(2))) == [("a", "b"), ("c", "d"), ("e",)]
+
+assert _thread.stack_size(Index(0)) == 0
+
+import mmap
+
+mapped = mmap.mmap(-1, 6)
+mapped.write(b"abcdef")
+mapped.move(Index(0), Index(3), Index(3))
+assert mapped[:] == b"defdef"
+if hasattr(mapped, "madvise"):
+    mapped.madvise(mmap.MADV_NORMAL, Index(0), Index(6))
+
+if sys.platform != "win32":
+    import fcntl
+    import grp
+    import pwd
+    import resource
+    import tempfile
+
+    assert pwd.getpwuid(Index(0)).pw_uid == 0
+    assert grp.getgrgid(Index(0)).gr_gid == 0
+
+    nofile = resource.getrlimit(resource.RLIMIT_NOFILE)
+    assert resource.getrlimit(Index(resource.RLIMIT_NOFILE)) == nofile
+    resource.setrlimit(Index(resource.RLIMIT_NOFILE), nofile)
+
+    with tempfile.TemporaryFile() as f:
+        assert fcntl.fcntl(f, fcntl.F_SETFD, Index(fcntl.FD_CLOEXEC)) == 0
+        assert fcntl.fcntl(f, fcntl.F_GETFD) == fcntl.FD_CLOEXEC
+        fcntl.lockf(f, fcntl.LOCK_SH | fcntl.LOCK_NB, Index(0), Index(0))
diff --git a/extra_tests/snippets/recursion.py b/extra_tests/snippets/recursion.py
index 4b61a74b438..fe7daa5d69a 100644
--- a/extra_tests/snippets/recursion.py
+++ b/extra_tests/snippets/recursion.py
@@ -44,3 +44,32 @@ class Descr:
     pass
 else:
     raise AssertionError("descr.x should not resolve")
+
+
+def recurse():
+    recurse()
+
+
+try:
+    recurse()
+except RecursionError as e:
+    msg = str(e)
+    assert msg, f"empty RecursionError message: {e!r}"
+    assert not msg.endswith(" "), f"trailing space in RecursionError: {e!r}"
+
+import sys
+
+prev_limit = sys.getrecursionlimit()
+try:
+    sys.setrecursionlimit(50)
+    try:
+        recurse()
+    except RecursionError as e:
+        assert str(e) == "maximum recursion depth exceeded", (
+            f"unexpected message: {e!r}"
+        )
+        assert e.args == ("maximum recursion depth exceeded",), (
+            f"unexpected args: {e.args!r}"
+        )
+finally:
+    sys.setrecursionlimit(prev_limit)
diff --git a/extra_tests/snippets/stdlib_abc.py b/extra_tests/snippets/stdlib_abc.py
index 30b4ef37068..df1833a419f 100644
--- a/extra_tests/snippets/stdlib_abc.py
+++ b/extra_tests/snippets/stdlib_abc.py
@@ -36,3 +36,28 @@ class SubConcrete(Concrete):
 assert isinstance(Concrete(), CustomInterface)
 assert isinstance(SubConcrete(), CustomInterface)
 assert not isinstance((), CustomInterface)
+
+
+class NoClassAttribute:
+    @property
+    def __class__(self):
+        raise AttributeError("no class attribute")
+
+
+instance = NoClassAttribute()
+assert not isinstance(instance, CustomInterface)
+CustomInterface.register(NoClassAttribute)
+assert isinstance(instance, CustomInterface)
+
+class_error = RuntimeError("class lookup failed")
+
+
+class BrokenClassAttribute:
+    @property
+    def __class__(self):
+        raise class_error
+
+
+with assert_raises(RuntimeError) as caught:
+    isinstance(BrokenClassAttribute(), CustomInterface)
+assert caught.exception is class_error
diff --git a/extra_tests/snippets/stdlib_array.py b/extra_tests/snippets/stdlib_array.py
index 540bc0796c1..9d3d9a7ca90 100644
--- a/extra_tests/snippets/stdlib_array.py
+++ b/extra_tests/snippets/stdlib_array.py
@@ -346,3 +346,102 @@ def source():
 test_array_search_sees_appended_items()
 test_array_insert_converts_without_lock()
 test_array_extend_callbacks_and_partial_progress()
+
+
+def test_array_fromlist_callbacks():
+    for code in ("i", "d"):
+        values = array(code, [1])
+        source = []
+
+        class Number:
+            def __index__(self):
+                assert len(values) == 3
+                values[0] = 9
+                source[1] = 8
+                return 7
+
+            def __float__(self):
+                return float(self.__index__())
+
+        source[:] = [Number(), 2]
+        values.fromlist(source)
+        assert list(values) == [9, 7, 8]
+
+    values = array("i", [1])
+
+    class Append:
+        def __index__(self):
+            values.append(9)
+            return 7
+
+    values.fromlist([Append()])
+    assert list(values) == [1, 7, 9]
+
+
+def test_array_fromlist_rollback():
+    for mutate in (lambda source: source.clear(), lambda source: source.append(3)):
+        values = array("i", [1])
+
+        class ChangeList:
+            def __index__(self):
+                values[0] = 9
+                mutate(source)
+                return 7
+
+        source = [ChangeList(), 2]
+        with assert_raises(RuntimeError):
+            values.fromlist(source)
+        assert list(values) == [9]
+
+    values = array("i", [1])
+
+    class Fail:
+        def __index__(self):
+            assert values[1] == 2
+            raise ValueError("conversion failed")
+
+    with assert_raises(ValueError):
+        values.fromlist([2, Fail()])
+    assert list(values) == [1]
+
+    class Clear:
+        def __index__(self):
+            values.clear()
+            return 7
+
+    with assert_raises(IndexError):
+        values.fromlist([Clear()])
+    assert len(values) == 1
+
+
+def test_array_fromlist_exports():
+    values = array("i", [1])
+    with memoryview(values):
+        values.fromlist([])
+        with assert_raises(BufferError):
+            values.fromlist([2])
+
+    views = []
+
+    class Export:
+        def __index__(self):
+            views.append(memoryview(values))
+            return 7
+
+    values.fromlist([Export()])
+    assert list(views.pop()) == [1, 7]
+
+    class ExportAndFail:
+        def __index__(self):
+            views.append(memoryview(values))
+            raise ValueError("conversion failed")
+
+    with assert_raises(BufferError):
+        values.fromlist([ExportAndFail()])
+    assert len(values) == len(views[0]) == 3
+    views.pop().release()
+
+
+test_array_fromlist_callbacks()
+test_array_fromlist_rollback()
+test_array_fromlist_exports()
diff --git a/extra_tests/snippets/stdlib_ast.py b/extra_tests/snippets/stdlib_ast.py
index 2dd2276723c..8dee30233d2 100644
--- a/extra_tests/snippets/stdlib_ast.py
+++ b/extra_tests/snippets/stdlib_ast.py
@@ -69,12 +69,13 @@ def foo():
 
 def _cyclic_cases():
     # Box<Expr> descents
-    u = ast.UnaryOp(op=ast.Not(), lineno=0, col_offset=0)
+    u = ast.UnaryOp(op=ast.Not(), operand=None, lineno=0, col_offset=0)
     u.operand = u
     yield "UnaryOp", u
 
     b = ast.BinOp(
         op=ast.Add(),
+        left=None,
         right=ast.Constant(value=0, lineno=0, col_offset=0),
         lineno=0,
         col_offset=0,
@@ -82,11 +83,11 @@ def _cyclic_cases():
     b.left = b
     yield "BinOp", b
 
-    c = ast.Call(args=[], keywords=[], lineno=0, col_offset=0)
+    c = ast.Call(func=None, args=[], keywords=[], lineno=0, col_offset=0)
     c.func = c
     yield "Call", c
 
-    a = ast.Attribute(attr="x", ctx=ast.Load(), lineno=0, col_offset=0)
+    a = ast.Attribute(value=None, attr="x", ctx=ast.Load(), lineno=0, col_offset=0)
     a.value = a
     yield "Attribute", a
 
@@ -108,3 +109,157 @@ def _cyclic_cases():
             raise AssertionError(f"cyclic {name} should raise RecursionError")
         except RecursionError:
             pass  # expected; matches CPython
+
+
+# Python 3.15 rejects omitted required fields and unknown constructor keywords.
+from testutils import assert_raises
+
+with assert_raises(TypeError) as exc:
+    ast.Name()
+assert (
+    str(exc.exception)
+    == "ast.Name.__init__ missing 1 required positional argument: 'id'"
+)
+
+with assert_raises(TypeError) as exc:
+    ast.BinOp()
+assert str(exc.exception) == (
+    "ast.BinOp.__init__ missing 3 required positional arguments: 'left', 'op', and 'right'"
+)
+
+with assert_raises(TypeError) as exc:
+    ast.BinOp(op=ast.Add())
+assert str(exc.exception) == (
+    "ast.BinOp.__init__ missing 2 required positional arguments: 'left' and 'right'"
+)
+
+with assert_raises(TypeError) as exc:
+    ast.Name(id="x", extra=True)
+assert (
+    str(exc.exception) == "ast.Name.__init__ got an unexpected keyword argument 'extra'"
+)
+
+with assert_raises(TypeError) as exc:
+    ast.Name("x", id="y")
+assert str(exc.exception) == "ast.Name got multiple values for argument 'id'"
+
+# Constructor defaults and explicit placeholders still work.
+assert ast.Name("x").ctx is ast.Name("y").ctx
+assert isinstance(ast.Name("x").ctx, ast.Load)
+assert ast.FunctionDef(name="f", args=ast.arguments()).returns is None
+assert ast.Module().body == []
+assert ast.Module().body is not ast.Module().body
+assert ast.BinOp(left=None, op=None, right=None).left is None
+
+
+class FieldsWithoutTypes(ast.AST):
+    _fields = ("value",)
+
+
+assert not hasattr(FieldsWithoutTypes(), "value")
+assert FieldsWithoutTypes(value=1).value == 1
+
+
+class IncompleteFieldTypes(ast.AST):
+    _fields = ("value",)
+    _field_types = {}
+
+
+with assert_raises(TypeError) as exc:
+    IncompleteFieldTypes()
+assert (
+    str(exc.exception)
+    == "Field 'value' is missing from IncompleteFieldTypes._field_types"
+)
+
+
+for key in ("a'b", "line\nbreak"):
+    with assert_raises(TypeError) as exc:
+        ast.Name(id="x", **{key: 1})
+    assert str(exc.exception) == (
+        f"ast.Name.__init__ got an unexpected keyword argument {key!r}"
+    )
+
+
+# Explicit AST positions must survive normalized Rust navigation ranges.
+import dis
+
+
+def store_positions(tree):
+    code = compile(tree, "<ast-columns>", "exec").co_consts[0]
+    return [
+        tuple(instruction.positions)
+        for instruction in dis.get_instructions(code)
+        if instruction.opname == "STORE_FAST"
+    ]
+
+
+# These two nodes have the same normalized navigation range but different
+# semantic columns. Position metadata must therefore use node identity.
+tree = ast.parse("def f():\n x = 1\n y = 2\n")
+first, second = tree.body[0].body
+for statement in (first, second):
+    for node in ast.walk(statement):
+        if hasattr(node, "lineno"):
+            node.lineno = node.end_lineno = 2
+first.targets[0].col_offset = first.targets[0].end_col_offset = 0
+second.targets[0].col_offset = second.targets[0].end_col_offset = -1
+assert store_positions(tree) == [(2, 2, 0, 0), (2, 2, None, None)]
+
+
+def set_location(node, line, col, end_col):
+    node.lineno = node.end_lineno = line
+    node.col_offset = col
+    node.end_col_offset = end_col
+    return node
+
+
+# Outbound conversion must not merge or drop explicitly supplied literal nodes.
+values = [set_location(ast.Constant(value=s), 1, -1, -1) for s in ("a", "", "b")]
+joined = set_location(ast.JoinedStr(values=values), 1, 0, 8)
+result = compile(
+    ast.Expression(body=joined),
+    "<locations>",
+    "eval",
+    ast.PyCF_ONLY_AST | ast.PyCF_OPTIMIZED_AST,
+    optimize=0,
+)
+assert [node.value for node in result.body.values] == ["a", "", "b"]
+assert all(node.col_offset == node.end_col_offset == -1 for node in result.body.values)
+
+# The replacement Pass derives from the statement, not its string value.
+tree = ast.parse('def f():\n    "doc"\n')
+set_location(tree.body[0].body[0], 2, -1, -1)
+set_location(tree.body[0].body[0].value, 2, 4, 9)
+result = compile(
+    tree, "<locations>", "exec", ast.PyCF_ONLY_AST | ast.PyCF_OPTIMIZED_AST, optimize=2
+)
+replacement = result.body[0].body[0]
+assert isinstance(replacement, ast.Pass)
+assert (
+    replacement.lineno,
+    replacement.end_lineno,
+    replacement.col_offset,
+    replacement.end_col_offset,
+) == (2, 2, -1, 3)
+
+# The optimizer's generated format spec is an artificial Constant; the argument
+# and the outer expression retain their own distinct source locations.
+tree = ast.parse("'%3s' % (value,)", mode="eval")
+set_location(tree.body, 1, -1, -1)
+set_location(tree.body.right.elts[0], 1, 8, 13)
+result = compile(
+    tree, "<locations>", "eval", ast.PyCF_ONLY_AST | ast.PyCF_OPTIMIZED_AST, optimize=0
+)
+formatted = result.body.values[0]
+assert (result.body.col_offset, result.body.end_col_offset) == (-1, -1)
+assert (formatted.col_offset, formatted.end_col_offset) == (8, 13)
+assert isinstance(formatted.format_spec, ast.Constant)
+assert formatted.format_spec.value == ">3"
+spec = formatted.format_spec
+assert (spec.lineno, spec.end_lineno, spec.col_offset, spec.end_col_offset) == (
+    -1,
+    -1,
+    -1,
+    -1,
+)
diff --git a/extra_tests/snippets/stdlib_asyncio.py b/extra_tests/snippets/stdlib_asyncio.py
index a6a55509036..74de3604073 100644
--- a/extra_tests/snippets/stdlib_asyncio.py
+++ b/extra_tests/snippets/stdlib_asyncio.py
@@ -76,9 +76,9 @@ def __new__(cls, *args):
 # to the same future; the field must not be locked while that runs.
 
 
-class Reentrant:
+class Reentrant(_asyncio.Future):
     def __hash__(self):
-        _asyncio.future_add_to_awaited_by(awaited, Reentrant())
+        _asyncio.future_add_to_awaited_by(awaited, Reentrant(loop=object()))
         return 1
 
     def __eq__(self, other):
@@ -86,15 +86,15 @@ def __eq__(self, other):
 
 
 awaited = _asyncio.Future(loop=object())
-_asyncio.future_add_to_awaited_by(awaited, Reentrant())
+_asyncio.future_add_to_awaited_by(awaited, Reentrant(loop=object()))
 with assert_raises(RecursionError):
     # converting the single waiter into a set hashes both of them
-    _asyncio.future_add_to_awaited_by(awaited, Reentrant())
+    _asyncio.future_add_to_awaited_by(awaited, Reentrant(loop=object()))
 
 plain = _asyncio.Future(loop=object())
-waiter = object()
+waiter = _asyncio.Future(loop=object())
 _asyncio.future_add_to_awaited_by(plain, waiter)
-_asyncio.future_add_to_awaited_by(plain, object())
+_asyncio.future_add_to_awaited_by(plain, _asyncio.Future(loop=object()))
 assert waiter in plain._asyncio_awaited_by
 _asyncio.future_discard_from_awaited_by(plain, waiter)
 assert waiter not in plain._asyncio_awaited_by
diff --git a/extra_tests/snippets/stdlib_codecs_wide.py b/extra_tests/snippets/stdlib_codecs_wide.py
index d5a7d68fe8c..00f8a780b2c 100644
--- a/extra_tests/snippets/stdlib_codecs_wide.py
+++ b/extra_tests/snippets/stdlib_codecs_wide.py
@@ -28,3 +28,175 @@
     _codecs.utf_32_ex_decode(b"\xff\xfe\x00\x00h\x00\x00\x00", "strict", 0, True)[0]
     == "h"
 )
+
+
+# Lookup errors preserve the requested spelling, while search hooks receive
+# the Python 3.15 normalized registry key.
+import codecs
+
+seen_encoding_names = []
+
+
+def record_unknown_encoding(name):
+    seen_encoding_names.append(name)
+    return None
+
+
+codecs.register(record_unknown_encoding)
+try:
+    for requested, normalized in (
+        ("NO Such  Codec!", "no-such--codec!"),
+        ("x_ weird--Ω .Ab", "x_-weird--Ω-.ab"),
+    ):
+        for lookup in (
+            codecs.lookup,
+            lambda name: codecs.encode("value", name),
+            lambda name: codecs.decode(b"value", name),
+            lambda name: "value".encode(name),
+            lambda name: b"value".decode(name),
+        ):
+            try:
+                lookup(requested)
+            except LookupError as error:
+                assert str(error) == "unknown encoding: " + requested
+            else:
+                assert False, "unknown encoding was accepted"
+            assert seen_encoding_names[-1] == normalized
+finally:
+    codecs.unregister(record_unknown_encoding)
+
+
+# The encodings helper preserves case and dots, unlike registry lookup keys.
+import encodings
+import warnings
+
+
+class EncodingName(str):
+    pass
+
+
+for encoding, expected in (
+    ("", ""),
+    ("UTF-8", "UTF_8"),
+    ("  .UTF--8.  ", ".UTF_8."),
+    ("---", ""),
+    ("A__-- B", "A_B"),
+    ("AéB", "A_B"),
+    ("éUTF-8Ω", "UTF_8"),
+    ("A😀B", "A_B"),
+    ("UTF-8\x00ignored", "UTF_8"),
+    ("\x00UTF-8", ""),
+):
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        assert _codecs._normalize_encoding(encoding) == expected
+        assert _codecs._normalize_encoding(encoding=EncodingName(encoding)) == expected
+        assert not caught
+
+for encoding in (b"UTF-8", bytearray(b"UTF-8"), None, 1):
+    try:
+        _codecs._normalize_encoding(encoding)
+    except TypeError:
+        pass
+    else:
+        assert False, "non-string encoding was accepted"
+
+# UTF-8 validation precedes scanning, including a surrogate after NUL.
+for encoding in ("A\ud800B", "A\x00\ud800B"):
+    try:
+        _codecs._normalize_encoding(encoding)
+    except UnicodeEncodeError as error:
+        assert error.encoding == "utf-8"
+        assert error.object == encoding
+        assert error.start == encoding.index("\ud800")
+        assert error.end == error.start + 1
+    else:
+        assert False, "surrogate encoding was accepted"
+
+with warnings.catch_warnings(record=True) as caught:
+    warnings.simplefilter("always")
+    assert encodings.normalize_encoding(b"UTF-8") == "UTF_8"
+    assert not caught
+    assert encodings.normalize_encoding("AéB") == "A_B"
+    assert len(caught) == 1
+    assert caught[0].category is DeprecationWarning
+
+try:
+    encodings.normalize_encoding(b"UTF-\xff")
+except UnicodeDecodeError:
+    pass
+else:
+    assert False, "non-ASCII bytes encoding was accepted"
+
+for args, kwargs in (
+    ((), {}),
+    (("UTF-8", "ASCII"), {}),
+    (("UTF-8",), {"encoding": "ASCII"}),
+    ((), {"name": "UTF-8"}),
+):
+    try:
+        _codecs._normalize_encoding(*args, **kwargs)
+    except TypeError:
+        pass
+    else:
+        assert False, "invalid normalization arguments were accepted"
+
+
+# Registry removal and competing lookup results may run Python destructors.
+def test_registry_reentrant_cleanup():
+    released = []
+
+    class ErrorHandler:
+        def __call__(self, error):
+            raise AssertionError("handler should not be called")
+
+        def __del__(self):
+            codecs.lookup_error("strict")
+            released.append("handler")
+
+    codecs.register_error("test_registry_cleanup", ErrorHandler())
+    assert _codecs._unregister_error("test_registry_cleanup")
+    assert released == ["handler"]
+    released.clear()
+
+    class Codec(tuple):
+        def __new__(cls, label):
+            result = super().__new__(cls, (None, None, None, None))
+            result.label = label
+            return result
+
+        def __del__(self):
+            codecs.lookup_error("strict")
+            released.append(self.label)
+
+    def search(name):
+        if name == "test_registry_cleanup":
+            return Codec("cached")
+
+    codecs.register(search)
+    codecs.lookup("test_registry_cleanup")
+    codecs.unregister(search)
+    assert released == ["cached"]
+    released.clear()
+
+    entered = False
+
+    def reentrant_search(name):
+        nonlocal entered
+        if name == "test_registry_reentry":
+            if not entered:
+                entered = True
+                codecs.lookup(name)
+                return Codec("outer")
+            return Codec("inner")
+
+    codecs.register(reentrant_search)
+    try:
+        codecs.lookup("test_registry_reentry")
+        assert len(released) == 1
+    finally:
+        codecs.unregister(reentrant_search)
+    assert sorted(released) == ["inner", "outer"]
+
+
+test_registry_reentrant_cleanup()
diff --git a/extra_tests/snippets/stdlib_collections.py b/extra_tests/snippets/stdlib_collections.py
index e4602d1c9ce..be9e7a99cb2 100644
--- a/extra_tests/snippets/stdlib_collections.py
+++ b/extra_tests/snippets/stdlib_collections.py
@@ -91,6 +91,60 @@ def __repr__(self):
 ordered = OrderedDict()
 _count_elements(ordered, "bab")
 assert list(ordered.items()) == [("b", 2), ("a", 1)]
+
+
+# OrderedDict views show their contents in insertion order, including recursion.
+def check_ordered_dict_view_repr():
+    ordered = OrderedDict([("b", 2), ("a", 1)])
+    for method, contents in (
+        ("keys", "['b', 'a']"),
+        ("values", "[2, 1]"),
+        ("items", "[('b', 2), ('a', 1)]"),
+    ):
+        assert repr(getattr(OrderedDict(), method)()) == "odict_" + method + "([])"
+        assert (
+            repr(getattr(ordered, method)()) == "odict_" + method + "(" + contents + ")"
+        )
+
+    recursive = OrderedDict()
+    values = recursive.values()
+    items = recursive.items()
+    recursive["self"] = values
+    assert repr(values) == "odict_values([...])"
+    recursive["self"] = items
+    assert repr(items) == "odict_items([('self', ...)])"
+
+    # Repr must snapshot the contents before arbitrary repr code mutates them.
+    for method in ("keys", "values", "items"):
+
+        class MutatingRepr:
+            def __repr__(self):
+                ordered.clear()
+                return "mutated"
+
+        item = MutatingRepr()
+        ordered = OrderedDict([(item, item), ("tail", "last")])
+        expected = {
+            "keys": "odict_keys([mutated, 'tail'])",
+            "values": "odict_values([mutated, 'last'])",
+            "items": "odict_items([(mutated, mutated), ('tail', 'last')])",
+        }
+        assert repr(getattr(ordered, method)()) == expected[method]
+        assert not ordered
+
+    class BadRepr:
+        def __repr__(self):
+            raise ValueError("view repr")
+
+    ordered = OrderedDict([(BadRepr(), BadRepr())])
+    for method in ("keys", "values", "items"):
+        with assert_raises(ValueError) as caught:
+            repr(getattr(ordered, method)())
+        assert str(caught.exception) == "view repr"
+
+
+check_ordered_dict_view_repr()
+
 factory = defaultdict(lambda: 100)
 _count_elements(factory, "a")
 assert factory == {"a": 1}
@@ -116,3 +170,85 @@ def get(self, key, default=None):
 assert custom_get == {"a": 101, "b": 101}
 with assert_raises(AttributeError):
     _count_elements([], "a")
+
+
+# defaultdict union constructs the subclass with its factory and left operand.
+def check_defaultdict_subclass_union():
+    calls = []
+
+    class DefaultSubclass(defaultdict):
+        def __init__(self, factory=None, initial=()):
+            calls.append((factory, initial))
+            super().__init__(factory, initial)
+
+        def update(self, *args, **kwargs):
+            raise AssertionError("union must use native dict update")
+
+        def __setitem__(self, key, value):
+            raise AssertionError("union must not call overridden __setitem__")
+
+    for factory in (None, list):
+        left = DefaultSubclass(factory, {"shared": 1, "left": 2})
+        right = {"right": 3, "shared": 4}
+        calls.clear()
+        result = left | right
+        assert type(result) is DefaultSubclass
+        assert result.default_factory is factory
+        assert list(result.items()) == [("shared", 4), ("left", 2), ("right", 3)]
+        assert len(calls) == 1 and calls[0][0] is factory and calls[0][1] is left
+
+        calls.clear()
+        result = right | left
+        assert type(result) is DefaultSubclass
+        assert result.default_factory is factory
+        assert list(result.items()) == [("right", 3), ("shared", 1), ("left", 2)]
+        assert len(calls) == 1 and calls[0][0] is factory and calls[0][1] is right
+        assert left == {"shared": 1, "left": 2}
+        assert right == {"right": 3, "shared": 4}
+
+        calls.clear()
+        assert left.__or__([("x", 1)]) is NotImplemented
+        assert left.__ror__([("x", 1)]) is NotImplemented
+        assert calls == []
+
+    class FailingSubclass(defaultdict):
+        fail = False
+
+        def __init__(self, *args):
+            if self.fail:
+                raise ValueError("union constructor")
+            super().__init__(*args)
+
+    left = FailingSubclass(int, {"a": 1})
+    FailingSubclass.fail = True
+    with assert_raises(ValueError) as caught:
+        left | {}
+    assert str(caught.exception) == "union constructor"
+    with assert_raises(ValueError) as caught:
+        {} | left
+    assert str(caught.exception) == "union constructor"
+
+    class ReplacingSubclass(defaultdict):
+        replacement = None
+
+        def __new__(cls, *args):
+            if cls.replacement is not None:
+                return cls.replacement
+            return super().__new__(cls)
+
+    left = ReplacingSubclass(int, {"left": 1})
+    replacement = {"replacement": 2}
+    ReplacingSubclass.replacement = replacement
+    assert left | {"right": 3} is replacement
+    assert replacement == {"replacement": 2, "right": 3}
+    replacement.clear()
+    assert {"right": 3} | left is replacement
+    assert replacement == {"left": 1}
+    ReplacingSubclass.replacement = object()
+    with assert_raises(SystemError):
+        left | {}
+    with assert_raises(SystemError):
+        {} | left
+
+
+check_defaultdict_subclass_union()
diff --git a/extra_tests/snippets/stdlib_contextvars.py b/extra_tests/snippets/stdlib_contextvars.py
index 915f732d188..a54d6a3a618 100644
--- a/extra_tests/snippets/stdlib_contextvars.py
+++ b/extra_tests/snippets/stdlib_contextvars.py
@@ -84,3 +84,35 @@ def __eq__(self, other):
         for var, value in copy_context().items()
         if var.name == "child_marker"
     ] == []
+
+
+def context_cache_does_not_outlive_its_context():
+    import contextvars
+
+    for factory_name in ("new", "copy"):
+        for _ in range(100):
+            var = contextvars.ContextVar("var", default="default")
+            empty = contextvars.Context()
+            ctx = contextvars.Context() if factory_name == "new" else empty.copy()
+            ctx.run(var.set, "cached")
+            del ctx
+            ctx = contextvars.Context() if factory_name == "new" else empty.copy()
+            assert list(ctx.items()) == []
+            assert ctx.run(var.get) == "default"
+            assert ctx.run(var.get, "explicit default") == "explicit default"
+
+            missing = contextvars.ContextVar("missing")
+            ctx.run(missing.set, "cached")
+            del ctx
+            ctx = contextvars.Context() if factory_name == "new" else empty.copy()
+            try:
+                ctx.run(missing.get)
+            except LookupError:
+                pass
+            else:
+                raise AssertionError(
+                    "an empty context returned a destroyed context value"
+                )
+
+
+context_cache_does_not_outlive_its_context()
diff --git a/extra_tests/snippets/stdlib_csv.py b/extra_tests/snippets/stdlib_csv.py
index c80847bc741..6bf29a67c3f 100644
--- a/extra_tests/snippets/stdlib_csv.py
+++ b/extra_tests/snippets/stdlib_csv.py
@@ -361,3 +361,281 @@ def __str__(self):
 
 
 test_quote_nonnumeric_writer()
+
+
+def test_dialect_truth_conversion():
+    def registered(dialect, **kwargs):
+        name = "truth_conversion"
+        try:
+            csv.register_dialect(name, dialect, **kwargs)
+            return csv.get_dialect(name)
+        finally:
+            if name in csv.list_dialects():
+                csv.unregister_dialect(name)
+
+    constructors = (
+        lambda dialect, **kwargs: csv.reader([], dialect, **kwargs).dialect,
+        lambda dialect, **kwargs: csv.writer(io.StringIO(), dialect, **kwargs).dialect,
+        _csv.Dialect,
+        registered,
+    )
+
+    class TruthError:
+        def __init__(self, error):
+            self.error = error
+            self.calls = 0
+
+        def __bool__(self):
+            self.calls += 1
+            raise self.error
+
+    class InvalidTruth:
+        def __bool__(self):
+            return 1
+
+    for construct in constructors:
+        for field in ("strict", "doublequote", "skipinitialspace"):
+            for error_type in (RuntimeError, AttributeError, TypeError):
+                for use_class in (False, True):
+                    error = error_type("dialect truth conversion")
+                    value = TruthError(error)
+
+                    class Dialect(csv.excel):
+                        def __new__(cls):
+                            raise AssertionError(
+                                "dialect classes must not be instantiated"
+                            )
+
+                    dialect = Dialect if use_class else csv.excel()
+                    setattr(dialect, field, value)
+                    try:
+                        construct(dialect)
+                    except error_type as caught:
+                        assert caught is error
+                    else:
+                        raise AssertionError("dialect truth error was suppressed")
+                    assert value.calls == 1
+
+                    # An explicit option replaces the attribute before conversion.
+                    result = construct(dialect, **{field: True})
+                    assert getattr(result, field) is True
+                    assert value.calls == 1
+
+                value = TruthError(error)
+                try:
+                    construct(None, **{field: value})
+                except error_type as caught:
+                    assert caught is error
+                else:
+                    raise AssertionError("keyword truth error was replaced")
+                assert value.calls == 1
+
+            for value in (None, False, True, 0, 1, [], [1]):
+                dialect = csv.excel()
+                setattr(dialect, field, value)
+                assert getattr(construct(dialect), field) is bool(value)
+                assert getattr(construct(None, **{field: value}), field) is bool(value)
+
+            dialect = csv.excel()
+            setattr(dialect, field, InvalidTruth())
+            with assert_raises(TypeError):
+                construct(dialect)
+            with assert_raises(TypeError):
+                construct(None, **{field: InvalidTruth()})
+
+    # csv.Dialect's Python validation wrapper translates TypeError to csv.Error.
+    for error_type in (RuntimeError, AttributeError, TypeError):
+        error = error_type("direct Python dialect validation")
+        value = TruthError(error)
+
+        class Dialect(csv.excel):
+            strict = value
+
+        expected = csv.Error if error_type is TypeError else error_type
+        try:
+            Dialect()
+        except expected as caught:
+            assert str(caught) == str(error)
+            if error_type is not TypeError:
+                assert caught is error
+        else:
+            raise AssertionError("Python dialect validation swallowed the error")
+        assert value.calls == 1
+
+
+test_dialect_truth_conversion()
+
+
+def test_dialect_lookup_and_conversion_order():
+    fields = (
+        "delimiter",
+        "doublequote",
+        "escapechar",
+        "lineterminator",
+        "quotechar",
+        "quoting",
+        "skipinitialspace",
+        "strict",
+    )
+    defaults = (",", True, None, "\r\n", '"', csv.QUOTE_MINIMAL, False, False)
+    constructors = (
+        lambda dialect, **kwargs: csv.reader([], dialect, **kwargs).dialect,
+        lambda dialect, **kwargs: csv.writer(io.StringIO(), dialect, **kwargs).dialect,
+        _csv.Dialect,
+    )
+
+    for construct in constructors:
+        for error_type in (AttributeError, RuntimeError, KeyboardInterrupt):
+            events = []
+
+            class Missing:
+                def __getattribute__(self, name):
+                    events.append(name)
+                    raise error_type(name)
+
+            if error_type is AttributeError:
+                result = construct(Missing())
+                assert tuple(getattr(result, field) for field in fields) == defaults
+                assert events == list(fields)
+            else:
+                with assert_raises(error_type) as caught:
+                    construct(Missing())
+                assert caught.exception.args == ("delimiter",)
+                assert events == ["delimiter"]
+        for dialect in (None, object(), _csv.Dialect(csv.excel)):
+            result = construct(dialect)
+            assert tuple(getattr(result, field) for field in fields) == defaults
+
+        events = []
+
+        class Truth:
+            def __init__(self, name):
+                self.name = name
+
+            def __bool__(self):
+                events.append("bool:" + self.name)
+                return False
+
+        values = dict(zip(fields, defaults))
+        for field in ("doublequote", "skipinitialspace", "strict"):
+            values[field] = Truth(field)
+
+        class Dialect:
+            def __getattribute__(self, name):
+                events.append(name)
+                return values[name]
+
+        construct(Dialect())
+        assert events == list(fields) + [
+            "bool:doublequote",
+            "bool:skipinitialspace",
+            "bool:strict",
+        ]
+
+        events.clear()
+        construct(Dialect(), strict=True, doublequote=True)
+        assert events == [
+            field for field in fields if field not in ("strict", "doublequote")
+        ] + ["bool:skipinitialspace"]
+
+        events.clear()
+        construct(
+            None,
+            strict=Truth("strict"),
+            skipinitialspace=Truth("skipinitialspace"),
+            doublequote=Truth("doublequote"),
+        )
+        assert events == ["bool:doublequote", "bool:skipinitialspace", "bool:strict"]
+
+        # Collect every attribute before starting conversions, even on failure.
+        events.clear()
+        values["delimiter"] = "too long"
+        with assert_raises(TypeError):
+            construct(Dialect())
+        assert events == list(fields)
+
+        error = RuntimeError("truth conversion wins")
+
+        class BadTruth:
+            def __bool__(self):
+                raise error
+
+        # Conversion order differs from option-validation order.
+        for options in (
+            {"doublequote": BadTruth(), "escapechar": "too long"},
+            {"strict": BadTruth(), "quoting": 42},
+            {"strict": BadTruth(), "quotechar": None, "quoting": csv.QUOTE_ALL},
+            {"strict": BadTruth(), "delimiter": "\n"},
+        ):
+            try:
+                construct(None, **options)
+            except RuntimeError as caught:
+                assert caught is error
+            else:
+                raise AssertionError("conversion order did not preserve truth error")
+        for options in (
+            {"delimiter": "too long", "doublequote": BadTruth()},
+            {"lineterminator": None, "skipinitialspace": BadTruth()},
+            {"quoting": None, "strict": BadTruth()},
+            {"unknown_option": None, "strict": BadTruth()},
+        ):
+            with assert_raises(TypeError):
+                construct(None, **options)
+
+        class IntegerSubclass(int):
+            pass
+
+        class Index:
+            def __index__(self):
+                raise AssertionError("quoting must not call __index__")
+
+        for value in (True, IntegerSubclass(0), Index()):
+            with assert_raises(TypeError):
+                construct(None, quoting=value)
+        with assert_raises(OverflowError):
+            construct(None, quoting=2**40, strict=BadTruth())
+
+        # None quotechar disables quoting only when quoting was not supplied.
+        assert construct(None, quotechar=None).quoting == csv.QUOTE_NONE
+        with assert_raises(TypeError):
+            construct(csv.excel, quotechar=None)
+        with assert_raises(TypeError):
+            construct(None, quotechar=None, quoting=csv.QUOTE_MINIMAL)
+
+    assert _csv.Dialect().strict is False
+    assert _csv.Dialect(strict=True).strict is True
+    for constructor, arg in ((csv.reader, []), (csv.writer, io.StringIO())):
+        with assert_raises(TypeError):
+            constructor(arg, None, None, strict=BadTruth())
+
+
+test_dialect_lookup_and_conversion_order()
+
+
+def test_field_size_limit_types():
+    index_calls = []
+
+    class IntSubclass(int):
+        pass
+
+    class Index:
+        def __index__(self):
+            index_calls.append(True)
+            return 17
+
+    old_limit = csv.field_size_limit()
+    try:
+        assert csv.field_size_limit(23) == old_limit
+        for value in (True, IntSubclass(17), Index()):
+            with assert_raises(TypeError):
+                csv.field_size_limit(value)
+            assert csv.field_size_limit() == 23
+        assert index_calls == []
+        with assert_raises(OverflowError):
+            csv.field_size_limit(2**100)
+        assert csv.field_size_limit() == 23
+    finally:
+        csv.field_size_limit(old_limit)
+
+
+test_field_size_limit_types()
diff --git a/extra_tests/snippets/stdlib_ctypes.py b/extra_tests/snippets/stdlib_ctypes.py
index 827fc598826..c4bdf0d939a 100644
--- a/extra_tests/snippets/stdlib_ctypes.py
+++ b/extra_tests/snippets/stdlib_ctypes.py
@@ -1,4 +1,5 @@
 import ctypes
+import gc
 import itertools
 import os as _os
 import sys as _sys
@@ -458,4 +459,111 @@ def get_win_folder_via_ctypes(csidl_name: str) -> str:
 else:
     raise AssertionError("an unallocatable array was created")
 
+# A function-pointer cast retains the callback and its executable address.
+Unary = ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_int)
+callback = Unary(lambda value: value + 1)
+address = ctypes.cast(callback, ctypes.c_void_p)
+roundtrip = ctypes.cast(address, Unary)
+assert roundtrip._objects[id(callback)] is callback
+del callback, address
+gc.collect()
+assert roundtrip(41) == 42
+
+
+class ArrayField(ctypes.Structure):
+    _fields_ = [("prefix", ctypes.c_int), ("values", ctypes.c_int * 3)]
+
+
+owner = ArrayField(99, (1, 2, 3))
+view = owner.values
+assert view._b_base_ is owner
+assert ctypes.addressof(view) == ctypes.addressof(owner) + ArrayField.values.offset
+ctypes.resize(owner, ctypes.sizeof(owner))
+assert ctypes.addressof(view) == ctypes.addressof(owner) + ArrayField.values.offset
+pointer = ctypes.cast(view, ctypes.POINTER(ctypes.c_int))
+pointer[1] = 42
+assert list(owner.values) == [1, 42, 3]
+owner.values[0] = 7
+assert bytes(view) == bytes(owner.values)
+memoryview(view).cast("B")[:] = bytes((ctypes.c_int * 3)(7, 42, 9))
+assert list(owner.values) == [7, 42, 9]
+del owner
+assert list(view) == [7, 42, 9]
+
+
+class OverlappingFields(ctypes.Union):
+    _fields_ = [("a", ctypes.c_ubyte * 8), ("b", ctypes.c_ubyte * 8)]
+
+
+overlap = OverlappingFields()
+overlap.a[:] = range(8)
+memoryview(overlap.a).cast("B")[::2] = memoryview(overlap.b).cast("B")[:4]
+assert list(overlap.a) == [0, 1, 1, 3, 2, 5, 3, 7]
+
+backing = bytearray(range(8))
+view = (ctypes.c_ubyte * 7).from_buffer(backing, 1)
+view._objects.clear()  # Alias detection must not depend on mutable retention metadata.
+memoryview(view).cast("B")[::2] = memoryview(backing)[:4]
+assert list(backing) == [0, 0, 2, 1, 4, 2, 6, 3]
+
+raw_owner = (ctypes.c_ubyte * 8)()
+raw_views = [type(raw_owner).from_address(ctypes.addressof(raw_owner))]
+if _sys.version_info >= (3, 14):
+    raw_views.append(
+        ctypes.memoryview_at(ctypes.addressof(raw_owner), ctypes.sizeof(raw_owner))
+    )
+for raw_view in raw_views:
+    for source, dest in ((raw_owner, raw_view), (raw_view, raw_owner)):
+        raw_owner[:] = range(8)
+        memoryview(dest).cast("B")[::2] = memoryview(source).cast("B")[:4]
+        assert list(raw_owner) == [0, 1, 1, 3, 2, 5, 3, 7]
+
+# A snapshotted source's release hook must run after the destination write.
+raw_owner[:] = range(8)
+destination_buffer = bytearray(b"abcdefgh")
+destination_view = memoryview(destination_buffer)
+release_events = []
+
+
+class ReleasingBuffer:
+    def __buffer__(self, flags):
+        return memoryview(raw_views[0]).cast("B")
+
+    def __release_buffer__(self, view):
+        release_events.append(bytes(destination_buffer))
+        destination_view.release()
+        destination_buffer.clear()
+
+
+destination_view[:] = ReleasingBuffer()
+assert release_events == [bytes(raw_owner)]
+assert destination_buffer == b""
+
+
+# byref carries an address, including its byte offset, rather than the value
+# stored in the referenced object.
+pair = (ctypes.c_int * 2)(42, 99)
+for offset in (0, ctypes.sizeof(ctypes.c_int)):
+    ref = ctypes.byref(pair, offset)
+    assert ctypes.cast(ref, ctypes.c_void_p).value == ctypes.addressof(pair) + offset
+    assert (
+        ctypes.string_at(ref, ctypes.sizeof(ctypes.c_int))
+        == bytes(pair)[offset : offset + ctypes.sizeof(ctypes.c_int)]
+    )
+zero = ctypes.c_size_t(0)
+assert ctypes.string_at(ctypes.byref(zero), ctypes.sizeof(zero)) == bytes(zero)
+param = ctypes.c_void_p.from_param(ctypes.addressof(zero))
+assert ctypes.cast(param, ctypes.c_void_p).value == ctypes.addressof(zero)
+assert ctypes.string_at(param, ctypes.sizeof(zero)) == bytes(zero)
+for read in (
+    lambda p: ctypes.cast(p, ctypes.c_void_p),
+    lambda p: ctypes.string_at(p, 0),
+):
+    try:
+        read(ctypes.c_char_p.from_param(b"x"))
+    except (TypeError, ctypes.ArgumentError):
+        pass
+    else:
+        raise AssertionError("non-pointer argument wrapper accepted")
+
 print("done")
diff --git a/extra_tests/snippets/stdlib_datetime.py b/extra_tests/snippets/stdlib_datetime.py
index d6609528cca..62fd04f4d6b 100644
--- a/extra_tests/snippets/stdlib_datetime.py
+++ b/extra_tests/snippets/stdlib_datetime.py
@@ -3941,18 +3941,46 @@ class Name(str):
         assert reference() is None
 
 
+def test_windows_time64():
+    if sys.platform == "win32":
+        for timestamp in (2_208_988_800, 2_208_988_800.0):
+            assert datetime_module.datetime.fromtimestamp(
+                timestamp, datetime_module.timezone.utc
+            ) == datetime_module.datetime(
+                2040, 1, 1, tzinfo=datetime_module.timezone.utc
+            )
+
+
 def test_timestamp_errno():
     if sys.platform == "win32":
         try:
-            datetime_module.datetime.fromtimestamp(-1)
+            datetime_module.datetime.fromtimestamp(2**40)
         except OSError as error:
             assert error.errno == errno.EINVAL
         else:
-            raise AssertionError("Windows localtime accepted a negative timestamp")
+            raise AssertionError(
+                "Windows localtime accepted a timestamp beyond the CRT range"
+            )
+        assert datetime_module.datetime.fromtimestamp(
+            -86400, datetime_module.timezone.utc
+        ) == datetime_module.datetime(1969, 12, 31, tzinfo=datetime_module.timezone.utc)
+        assert datetime_module.datetime.fromtimestamp(
+            -11_644_473_600, datetime_module.timezone.utc
+        ) == datetime_module.datetime(1601, 1, 1, tzinfo=datetime_module.timezone.utc)
+        for zone in (None, datetime_module.timezone.utc):
+            try:
+                datetime_module.datetime.fromtimestamp(-11_644_473_601, zone)
+            except OverflowError as error:
+                assert str(error) == "timestamp out of range for Windows FILETIME"
+            else:
+                raise AssertionError(
+                    "pre-FILETIME datetime did not raise OverflowError"
+                )
 
 
 test_astimezone_subclass_state()
 test_timezone_cycles()
+test_windows_time64()
 test_timestamp_errno()
 
 
diff --git a/extra_tests/snippets/stdlib_functools.py b/extra_tests/snippets/stdlib_functools.py
index 355c3187616..2d5c8389d3e 100644
--- a/extra_tests/snippets/stdlib_functools.py
+++ b/extra_tests/snippets/stdlib_functools.py
@@ -1,9 +1,13 @@
 import gc
 import weakref
+from _functools import _lru_cache_wrapper
 from functools import cache, cmp_to_key, lru_cache, partial, reduce
 
 from testutils import assert_raises
 
+# Cached wrappers support method-descriptor lookup and binding.
+assert _lru_cache_wrapper.__flags__ & (1 << 17)
+
 
 class Squares:
     def __init__(self, max):
diff --git a/extra_tests/snippets/stdlib_genericalias.py b/extra_tests/snippets/stdlib_genericalias.py
new file mode 100644
index 00000000000..ddfb6d5587a
--- /dev/null
+++ b/extra_tests/snippets/stdlib_genericalias.py
@@ -0,0 +1,226 @@
+from types import GenericAlias
+
+from testutils import assert_raises
+
+
+class Parameter:
+    def __typing_subst__(self, value):
+        return value
+
+
+parameter = Parameter()
+
+
+# Construction does not inspect arguments. Both entry points populate the cache
+# using the attributes present at the first lookup, rather than construction.
+class LateParameter:
+    __parameters__ = (parameter,)
+
+    def __repr__(self):
+        return "late_parameter"
+
+
+for materialize in (False, True):
+    late = LateParameter()
+    alias = GenericAlias(list, late)
+    if materialize:
+        cached = alias.__parameters__
+        assert cached == (parameter,)
+    late.__typing_subst__ = lambda value: value
+    if materialize:
+        with assert_raises(TypeError) as caught:
+            alias[int]
+        assert str(caught.exception) == (
+            "argument late_parameter with __typing_subst__ was not found in __parameters__"
+        )
+        assert alias.__parameters__ is cached
+    else:
+        assert alias[int] == list[int]
+        cached = alias.__parameters__
+        assert cached == (late,)
+        assert alias.__parameters__ is cached
+
+late = LateParameter()
+alias = GenericAlias(list, late)
+late.__typing_subst__ = lambda value: value
+assert alias.__parameters__ == (late,)
+assert alias[int] == list[int]
+
+# Empty tuples are cached too, even if parameters appear later.
+empty = LateParameter()
+empty.__parameters__ = ()
+alias = GenericAlias(list, empty)
+cached = alias.__parameters__
+empty.__typing_subst__ = lambda value: value
+assert alias.__parameters__ is cached
+assert cached == ()
+with assert_raises(TypeError):
+    alias[int]
+
+
+# Lookup errors happen lazily and leave the cache uninitialized for a retry.
+class FailingParameter:
+    def __init__(self, failing_attribute):
+        self.failing_attribute = failing_attribute
+        self.fail = True
+        self.lookups = []
+
+    def __getattribute__(self, name):
+        if name in ("__typing_subst__", "__parameters__"):
+            self.lookups.append(name)
+            if name == self.failing_attribute and self.fail:
+                raise RuntimeError("parameter lookup failed")
+        return object.__getattribute__(self, name)
+
+    __parameters__ = (parameter,)
+
+
+for attribute in ("__typing_subst__", "__parameters__"):
+    for subscribe in (False, True):
+        failing = FailingParameter(attribute)
+        alias = GenericAlias(list, failing)
+        assert failing.lookups == []
+        with assert_raises(RuntimeError) as caught:
+            if subscribe:
+                alias[int]
+            else:
+                alias.__parameters__
+        assert str(caught.exception) == "parameter lookup failed"
+        failing.fail = False
+        cached = alias.__parameters__
+        assert cached == (parameter,)
+        count = len(failing.lookups)
+        assert alias.__parameters__ is cached
+        assert len(failing.lookups) == count
+
+
+# A nested lookup may populate the cache, but the outer calculation replaces it.
+inner_parameter = Parameter()
+outer_parameter = Parameter()
+
+
+class ReentrantParameter:
+    entered = False
+
+    @property
+    def __parameters__(self):
+        if not self.entered:
+            self.entered = True
+            self.inner = self.alias.__parameters__
+            return (outer_parameter,)
+        return (inner_parameter,)
+
+
+reentrant = ReentrantParameter()
+reentrant.alias = GenericAlias(list, reentrant)
+cached = reentrant.alias.__parameters__
+assert reentrant.inner == (inner_parameter,)
+assert cached == (outer_parameter,)
+assert cached is reentrant.alias.__parameters__
+assert cached is not reentrant.inner
+
+
+# A cyclic parameter lookup raises rather than deadlocking or overflowing Rust.
+class RecursiveParameter:
+    recurse = True
+
+    @property
+    def __parameters__(self):
+        if self.recurse:
+            return self.alias.__parameters__
+        return (parameter,)
+
+
+recursive = RecursiveParameter()
+recursive.alias = GenericAlias(list, recursive)
+with assert_raises(RecursionError):
+    recursive.alias.__parameters__
+recursive.recurse = False
+assert recursive.alias.__parameters__ == (parameter,)
+
+# Substitution and unpacking construct aliases with their own lazy caches.
+failing = FailingParameter("__parameters__")
+result = GenericAlias(list, parameter)[failing]
+assert failing.lookups == []
+with assert_raises(RuntimeError):
+    result.__parameters__
+
+failing = FailingParameter("__parameters__")
+original = GenericAlias(tuple, failing)
+starred = next(iter(original))
+assert failing.lookups == []
+with assert_raises(RuntimeError):
+    starred.__parameters__
+failing.fail = False
+assert starred.__parameters__ == (parameter,)
+failing.__parameters__ = ()
+assert original.__parameters__ == ()
+assert starred.__parameters__ == (parameter,)
+
+# Concurrent descriptor callbacks can overlap without holding the cache lock.
+import threading
+
+barrier = threading.Barrier(2)
+
+
+class ConcurrentParameter:
+    @property
+    def __parameters__(self):
+        barrier.wait(timeout=10)
+        return (parameter,)
+
+
+concurrent = GenericAlias(list, ConcurrentParameter())
+results = []
+errors = []
+
+
+def read_parameters():
+    try:
+        results.append(concurrent.__parameters__)
+    except BaseException as error:
+        errors.append(error)
+
+
+threads = [threading.Thread(target=read_parameters) for _ in range(2)]
+for thread in threads:
+    thread.start()
+for thread in threads:
+    thread.join(timeout=15)
+assert all(not thread.is_alive() for thread in threads)
+assert errors == []
+assert results == [(parameter,), (parameter,)]
+cached = concurrent.__parameters__
+assert any(cached is result for result in results)
+assert concurrent.__parameters__ is cached
+
+
+# Failure in the outer calculation clears an inner successful cache as well.
+class ReentrantFailure:
+    entered = False
+    fail = True
+
+    @property
+    def __parameters__(self):
+        if not self.entered:
+            self.entered = True
+            self.inner = self.alias.__parameters__
+            if self.fail:
+                raise RuntimeError("outer lookup failed")
+        return (inner_parameter,) if self.fail else (outer_parameter,)
+
+
+for subscribe in (False, True):
+    failure = ReentrantFailure()
+    failure.alias = GenericAlias(list, failure)
+    with assert_raises(RuntimeError) as caught:
+        if subscribe:
+            failure.alias[int]
+        else:
+            failure.alias.__parameters__
+    assert str(caught.exception) == "outer lookup failed"
+    assert failure.inner == (inner_parameter,)
+    failure.fail = False
+    cached = failure.alias.__parameters__
+    assert cached == (outer_parameter,)
+    assert failure.alias.__parameters__ is cached
diff --git a/extra_tests/snippets/stdlib_hashlib.py b/extra_tests/snippets/stdlib_hashlib.py
index f3400aed57d..9cbc6bffc7e 100644
--- a/extra_tests/snippets/stdlib_hashlib.py
+++ b/extra_tests/snippets/stdlib_hashlib.py
@@ -1,5 +1,7 @@
+import _hashlib
 import _md5
 import _sha1
+import array
 import hashlib
 
 from testutils import assert_raises
@@ -64,3 +66,17 @@
 # narrower than the length asked for, converting the argument fails first.
 with assert_raises(OverflowError):
     hashlib.pbkdf2_hmac("sha256", b"password", b"salt", 1, 2**62)
+
+
+# Invalid names use the native constructor's bounded type diagnostic.
+for value, name in (
+    (None, "None"),
+    (42, "int"),
+    (b"sha256", "bytes"),
+    (array.array("b"), "array.array"),
+    (type("x" * 60, (), {})(), "x" * 50),
+    (type("€" * 17, (), {})(), "€" * 16),
+):
+    with assert_raises(TypeError) as caught:
+        _hashlib.new(value)
+    assert str(caught.exception) == f"new() argument 'name' must be str, not {name}"
diff --git a/extra_tests/snippets/stdlib_imp.py b/extra_tests/snippets/stdlib_imp.py
index 9fd5f8a36fa..b5184e89a01 100644
--- a/extra_tests/snippets/stdlib_imp.py
+++ b/extra_tests/snippets/stdlib_imp.py
@@ -1,7 +1,7 @@
 import _imp
 import time as import_time
 
-from testutils import assert_raises
+from testutils import assert_raises, skip_if_unsupported
 
 assert _imp.is_builtin("time") == True
 assert _imp.is_builtin("os") == False
@@ -23,7 +23,8 @@ def __init__(self, name):
 # assert imp_time.sleep == import_time.sleep
 
 B = FakeSpec("not existing module")
-assert _imp.create_builtin(B) == None
+with assert_raises(ModuleNotFoundError):
+    _imp.create_builtin(B)
 
 _imp.exec_builtin(imp_time) == 0
 
@@ -42,3 +43,45 @@ def __init__(self, name):
 assert ispkg is False
 assert origname == "__hello__"
 assert _imp.get_frozen_object("__hello__", data).co_name == "<module>"
+
+
+def test_lazy_attributes_eager_registry():
+    # CPython accepts any first argument and a string name. In an eager-only
+    # interpreter there are no pending lazy module names to remove.
+    for modobj in (None, object(), {}, 42):
+        assert _imp._set_lazy_attributes(modobj, "package.module") is None
+        assert _imp._set_lazy_attributes(modobj, "\ud800") is None
+
+    for name in (None, 1, b"package.module", [], {}):
+        with assert_raises(TypeError):
+            _imp._set_lazy_attributes(None, name)
+
+    with assert_raises(TypeError):
+        _imp._set_lazy_attributes(modobj=None, name="package.module")
+
+    class ModuleName(str):
+        hashes = 0
+
+        def __hash__(self):
+            self.hashes += 1
+            return 42
+
+    name = ModuleName("package.module")
+    assert _imp._set_lazy_attributes(None, name) is None
+    assert name.hashes == 1
+
+    class UnhashableName(str):
+        __hash__ = None
+
+    with assert_raises(TypeError):
+        _imp._set_lazy_attributes(None, UnhashableName("package.module"))
+
+    class HashErrorName(str):
+        def __hash__(self):
+            raise RuntimeError("name hash failed")
+
+    with assert_raises(RuntimeError):
+        _imp._set_lazy_attributes(None, HashErrorName("package.module"))
+
+
+skip_if_unsupported(3, 15, test_lazy_attributes_eager_registry)
diff --git a/extra_tests/snippets/stdlib_io.py b/extra_tests/snippets/stdlib_io.py
index 8346ddbb62d..4aed3ebbffe 100644
--- a/extra_tests/snippets/stdlib_io.py
+++ b/extra_tests/snippets/stdlib_io.py
@@ -3,6 +3,39 @@
 
 from testutils import assert_raises
 
+# Overwriting replaces characters, even when their encoded widths differ.
+for initial, replacement in (
+    ("abc", "é"),
+    ("ébc", "a"),
+    ("а😀в", "XY"),
+    ("a\ud800c", "\udfffé"),
+):
+    stream = StringIO("prefix:" + initial)
+    stream.seek(7)
+    assert stream.write(replacement) == len(replacement)
+    assert stream.getvalue() == "prefix:" + replacement + initial[len(replacement) :]
+    assert stream.tell() == 7 + len(replacement)
+    assert stream.read() == initial[len(replacement) :]
+    assert stream.tell() == 7 + len(initial)
+
+# Truncation keeps the character position, then pads in characters on writing.
+stream = StringIO("é😀abc")
+stream.seek(4)
+stream.truncate(1)
+assert stream.tell() == 4
+assert stream.read() == ""
+assert stream.tell() == 4
+assert stream.write("") == 0
+assert stream.getvalue() == "é"
+state = stream.__getstate__()
+stream = StringIO()
+stream.__setstate__(state)
+assert stream.tell() == 4
+stream.write("Ж")
+assert stream.getvalue() == "é\0\0\0Ж"
+assert stream.tell() == 5
+
+
 fi = FileIO("README.md")
 assert fi.seekable()
 bb = BufferedReader(fi)
@@ -166,10 +199,23 @@ def __index__(self):
     "underlying buffer has been detached",
     lambda: setattr(detached_textio, "_CHUNK_SIZE", 16),
 )
-expect_value_error(
-    "underlying buffer has been detached",
-    lambda: delattr(detached_textio, "_CHUNK_SIZE"),
-)
+for wrapper, error_type, message in (
+    (textio, AttributeError, "cannot delete attribute"),
+    (uninitialized_textio, ValueError, "I/O operation on uninitialized object"),
+    (detached_textio, ValueError, "underlying buffer has been detached"),
+):
+    with assert_raises(error_type) as error:
+        del wrapper._CHUNK_SIZE
+    assert str(error.exception) == message
+
+
+for wrapper_name in ("ChunkWrapper", "€" * 34):
+    wrapper_type = type(wrapper_name, (TextIOWrapper,), {})
+    wrapper = wrapper_type(BytesIO())
+    with assert_raises(AttributeError) as error:
+        del wrapper._CHUNK_SIZE
+    assert str(error.exception) == "cannot delete attribute"
+    wrapper.close()
 
 
 long_type_name = "X" * 250
diff --git a/extra_tests/snippets/stdlib_itertools.py b/extra_tests/snippets/stdlib_itertools.py
index ef06ce52985..04917fe994b 100644
--- a/extra_tests/snippets/stdlib_itertools.py
+++ b/extra_tests/snippets/stdlib_itertools.py
@@ -569,3 +569,82 @@ def __iter__(self):
 with assert_raises(OverflowError):
     itertools.product(Watched(), repeat=2**62)
 assert ran == []
+
+
+# compress consumes data, then the selector, then tests the selector's truth.
+def check_compress_consumption():
+    events = []
+
+    def tracked(name, values):
+        for value in values:
+            events.append(name)
+            yield value
+        events.append(name + " exhausted")
+
+    class Selector:
+        def __init__(self, value):
+            self.value = value
+
+        def __bool__(self):
+            events.append("bool")
+            return self.value
+
+    assert list(
+        itertools.compress(
+            tracked("data", [1, 2]),
+            tracked("selectors", [Selector(False), Selector(True), Selector(True)]),
+        )
+    ) == [2]
+    assert events == [
+        "data",
+        "selectors",
+        "bool",
+        "data",
+        "selectors",
+        "bool",
+        "data exhausted",
+    ], events
+
+    events.clear()
+    data = tracked("data", [1, 2, 3])
+    assert list(itertools.compress(data, tracked("selectors", [True]))) == [1]
+    assert events == ["data", "selectors", "data", "selectors exhausted"], events
+    assert next(data) == 3
+
+    events.clear()
+    assert (
+        list(itertools.compress(tracked("data", []), tracked("selectors", [True])))
+        == []
+    )
+    assert events == ["data exhausted"], events
+
+    def failing(name):
+        events.append(name)
+        raise ValueError(name)
+        yield
+
+    events.clear()
+    with assert_raises(ValueError) as caught:
+        next(itertools.compress(failing("data"), tracked("selectors", [True])))
+    assert str(caught.exception) == "data"
+    assert events == ["data"], events
+
+    events.clear()
+    with assert_raises(ValueError) as caught:
+        next(itertools.compress(tracked("data", [1]), failing("selectors")))
+    assert str(caught.exception) == "selectors"
+    assert events == ["data", "selectors"], events
+
+    class BadSelector:
+        def __bool__(self):
+            events.append("bool")
+            raise ValueError("truth")
+
+    events.clear()
+    with assert_raises(ValueError) as caught:
+        next(itertools.compress(tracked("data", [1]), [BadSelector()]))
+    assert str(caught.exception) == "truth"
+    assert events == ["data", "bool"], events
+
+
+check_compress_consumption()
diff --git a/extra_tests/snippets/stdlib_json.py b/extra_tests/snippets/stdlib_json.py
index e55382c8223..8366a19cd66 100644
--- a/extra_tests/snippets/stdlib_json.py
+++ b/extra_tests/snippets/stdlib_json.py
@@ -67,6 +67,24 @@ def json_load(obj):
 assert "{}" == json_dump({})
 assert round_trip_test({"a": "b"})
 
+
+class EmptyDictWithItems(dict):
+    def items(self):
+        raise AssertionError("items() must not be called for an empty dictionary")
+
+
+for sort_keys in (False, True):
+    assert json.dumps(EmptyDictWithItems(), sort_keys=sort_keys) == "{}"
+    assert json.dumps([EmptyDictWithItems()], sort_keys=sort_keys) == "[{}]"
+
+
+class NonemptyDictWithItems(dict):
+    def items(self):
+        return [("replacement", 2)]
+
+
+assert json.dumps(NonemptyDictWithItems(original=1)) == '{"replacement": 2}'
+
 # should reject non-str keys in jsons
 assert_raises(json.JSONDecodeError, lambda: json.loads('{3: "abc"}'))
 assert_raises(json.JSONDecodeError, lambda: json_load('{3: "abc"}'))
diff --git a/extra_tests/snippets/stdlib_locale.py b/extra_tests/snippets/stdlib_locale.py
new file mode 100644
index 00000000000..3c6edbbbf7c
--- /dev/null
+++ b/extra_tests/snippets/stdlib_locale.py
@@ -0,0 +1,14 @@
+import locale
+import sys
+
+from testutils import assert_raises
+
+# Windows counts the modifier toward the code-page length before calling the CRT.
+if sys.platform == "win32":
+    for category, name in (
+        (locale.LC_CTYPE, "English.1252@" + "x" * 16),
+        (locale.LC_ALL, "LC_CTYPE=English.1252@" + "x" * 16),
+    ):
+        with assert_raises(locale.Error) as caught:
+            locale.setlocale(category, name)
+        assert caught.exception.args == ("unsupported locale setting",)
diff --git a/extra_tests/snippets/stdlib_math.py b/extra_tests/snippets/stdlib_math.py
index 00d6c5f3ab1..b06bf8446f6 100644
--- a/extra_tests/snippets/stdlib_math.py
+++ b/extra_tests/snippets/stdlib_math.py
@@ -7,6 +7,81 @@
 INF = float("inf")
 NINF = float("-inf")
 
+
+def test_math_315_apis():
+    import math.integer
+    import sys
+
+    import _math_integer
+
+    assert math.integer is _math_integer
+    assert sys.modules["math.integer"] is math.integer
+    assert math.integer.__name__ == "math.integer"
+    for name, args, expected in (
+        ("comb", (5, 2), 10),
+        ("factorial", (5,), 120),
+        ("gcd", (12, 18), 6),
+        ("isqrt", (17,), 4),
+        ("lcm", (4, 6), 12),
+        ("perm", (5, 2), 20),
+    ):
+        function = getattr(math, name)
+        assert function is getattr(math.integer, name)
+        assert function.__module__ == "math.integer"
+        assert function(*args) == expected
+
+    for value in (1.0, -1.0, sys.float_info.min, sys.float_info.max):
+        assert math.isnormal(value) is True
+        assert math.issubnormal(value) is False
+    for value in (sys.float_info.min / 2, -sys.float_info.min / 2):
+        assert math.isnormal(value) is False
+        assert math.issubnormal(value) is True
+    for value in (0.0, -0.0, INF, NINF, NAN):
+        assert math.isnormal(value) is False
+        assert math.issubnormal(value) is False
+    for value in (0.0, 1.0, INF, NAN):
+        assert math.signbit(math.copysign(value, 1.0)) is False
+        assert math.signbit(math.copysign(value, -1.0)) is True
+
+    class FloatArgument:
+        def __float__(self):
+            return -2.0
+
+    class IndexArgument:
+        def __index__(self):
+            return 2
+
+    for function in (math.isnormal, math.issubnormal, math.signbit):
+        assert function(FloatArgument()) == function(-2.0)
+        assert function(IndexArgument()) == function(2.0)
+        assert_raises(TypeError, function, object())
+        assert_raises(TypeError, function, x=1.0)
+        assert_raises(TypeError, function)
+        assert_raises(TypeError, function, 1.0, 2.0)
+
+    for function, expected in ((math.fmax, 2.0), (math.fmin, -2.0)):
+        assert function(-2.0, 2.0) == expected
+        assert function(2.0, -2.0) == expected
+        assert type(function(1, 2)) is float
+        assert function(FloatArgument(), IndexArgument()) == expected
+        assert math.isnan(function(NAN, NAN))
+        for value in (0.0, -0.0, 1.0, -1.0, INF, NINF):
+            for result in (function(NAN, value), function(value, NAN)):
+                assert result == value
+                assert math.signbit(result) == math.signbit(value)
+        assert function(0.0, -0.0) == 0.0
+        assert function(-0.0, 0.0) == 0.0
+        assert_raises(TypeError, function, object(), 1.0)
+        assert_raises(TypeError, function, 1.0, object())
+        assert_raises(TypeError, function, x=1.0, y=2.0)
+        assert_raises(TypeError, function, 1.0)
+        assert_raises(TypeError, function, 1.0, 2.0, 3.0)
+    assert math.fmax(NINF, INF) == INF
+    assert math.fmin(NINF, INF) == NINF
+
+
+test_math_315_apis()
+
 # assert(math.exp(2) == math.exp(2.0))
 # assert(math.exp(True) == math.exp(1.0))
 #
@@ -17,6 +92,114 @@
 #
 # assert math.log(1.1111) == math.log(Conversible())
 
+# A logarithm can fit in a float even when its integer base cannot.
+assert math.isclose(math.log(2**4000, 2**2000), 2.0)
+assert math.isclose(math.log(2.0, 2**2000), 1.0 / 2000)
+
+for value in (1, 8.0, INF, NAN):
+    assert_raises(ZeroDivisionError, math.log, value, 1)
+assert_raises(TypeError, math.log, object(), 1)
+assert_raises(ValueError, math.log, 8, -(2**2000))
+
+log_conversions = []
+
+
+class LogFloat:
+    def __init__(self, name, value):
+        self.name = name
+        self.value = value
+
+    def __float__(self):
+        log_conversions.append(self.name)
+        return self.value
+
+
+assert math.isclose(math.log(LogFloat("x", 8.0), LogFloat("base", 2.0)), 3.0)
+assert log_conversions == ["x", "base"]
+log_conversions.clear()
+assert_raises(ValueError, math.log, -1, LogFloat("base", 2.0))
+assert log_conversions == []
+
+
+class LogFloatOverflow:
+    def __float__(self):
+        log_conversions.append("float")
+        raise OverflowError("float conversion failed")
+
+    def __index__(self):
+        log_conversions.append("index")
+        return 2**2000
+
+
+class LogIndexOnly:
+    def __index__(self):
+        return 2**2000
+
+
+for logarithm in (math.log, math.log2, math.log10):
+    log_conversions.clear()
+    assert math.isclose(logarithm(LogFloatOverflow()), logarithm(2**2000))
+    assert log_conversions == ["float", "index"]
+    assert math.isclose(logarithm(LogIndexOnly()), logarithm(2**2000))
+
+    for error_type in (TypeError, ValueError, RuntimeError):
+        error = error_type("float conversion failed")
+
+        class FailedFloat(LogFloatOverflow):
+            def __float__(self):
+                raise error
+
+        with assert_raises(error_type) as caught:
+            logarithm(FailedFloat())
+        assert caught.exception is error
+
+    error = RuntimeError("index conversion failed")
+
+    class FailedIndex(LogFloatOverflow):
+        def __index__(self):
+            raise error
+
+    with assert_raises(RuntimeError) as caught:
+        logarithm(FailedIndex())
+    assert caught.exception is error
+
+    class NegativeIndex(LogFloatOverflow):
+        def __index__(self):
+            return -1
+
+    assert_raises(ValueError, logarithm, NegativeIndex())
+
+    class InvalidIndex(LogFloatOverflow):
+        def __index__(self):
+            return 1.0
+
+    assert_raises(TypeError, logarithm, InvalidIndex())
+
+    class NoIndex:
+        __float__ = LogFloatOverflow.__float__
+
+    assert_raises(OverflowError, logarithm, NoIndex())
+
+    class SuccessfulFloat:
+        def __float__(self):
+            return 8.0
+
+        def __index__(self):
+            raise AssertionError("successful float conversion must not retry index")
+
+    assert logarithm(SuccessfulFloat()) == logarithm(8.0)
+
+assert math.isclose(math.log(8, LogFloatOverflow()), 3 / 2000)
+assert math.isclose(math.log(8, LogIndexOnly()), 3 / 2000)
+
+
+class LogInt(int):
+    def __float__(self):
+        raise AssertionError("integer logarithms use the native integer value")
+
+
+assert math.isclose(math.log(LogInt(2**4000), LogInt(2**2000)), 2.0)
+
 # roundings
 assert int.__trunc__
 assert int.__floor__
diff --git a/extra_tests/snippets/stdlib_mmap.py b/extra_tests/snippets/stdlib_mmap.py
index 9d4414e5552..094c1aa9d74 100644
--- a/extra_tests/snippets/stdlib_mmap.py
+++ b/extra_tests/snippets/stdlib_mmap.py
@@ -25,9 +25,9 @@
 assert mapped.rfind(b"") == 3
 assert mapped.find(b"", 1, 2) == 1
 assert mapped.rfind(b"", 1, 2) == 2
-# offsets past the end are clamped and negative ones count from the end
-assert mapped.find(b"", 5) == 3
-assert mapped.rfind(b"", 5) == 3
+# starts past the end find nothing and negative offsets count from the end
+assert mapped.find(b"", 5) == -1
+assert mapped.rfind(b"", 5) == -1
 assert mapped.find(b"", -1) == 2
 assert mapped.rfind(b"", 0, -1) == 2
 # an inverted range holds nothing, not even the empty subsequence
@@ -39,3 +39,79 @@
     mapped.find(b"")
 with assert_raises(ValueError):
     mapped.rfind(b"")
+
+
+# Buffer acquisition must reject a closed mapping before returning a view.
+with assert_raises(ValueError):
+    memoryview(mapped)
+
+mapped = mmap.mmap(-1, 4)
+mapped[:] = b"data"
+view = memoryview(mapped)
+child = view[1:]
+view.release()
+with assert_raises(BufferError):
+    mapped.close()
+assert not mapped.closed
+assert child.tobytes() == b"ata"
+child.release()
+mapped.close()
+mapped.close()
+
+# On Windows resize must neither invalidate an export nor revive a closed map.
+import sys
+
+if sys.platform == "win32":
+    mapped = mmap.mmap(-1, 4)
+    mapped[:] = b"data"
+    with memoryview(mapped) as view:
+        with assert_raises(BufferError):
+            mapped.resize(8)
+        with assert_raises(BufferError):
+            mapped.resize(0)
+        assert view.tobytes() == b"data"
+    mapped.resize(8)
+    with memoryview(mapped) as view:
+        assert view.tobytes() == b"data" + b"\0" * 4
+    mapped.close()
+    with assert_raises(ValueError):
+        mapped.resize(4)
+    assert mapped.closed
+
+
+# Assignment validates current storage after argument conversion, even if empty.
+with mmap.mmap(-1, 4) as mapped:
+    with assert_raises(ValueError):
+        mapped[4] = 256
+    mapped[0:0] = b""
+with assert_raises(ValueError):
+    mapped[0:0] = b""
+
+with mmap.mmap(-1, 4, access=mmap.ACCESS_READ) as mapped:
+    with assert_raises(TypeError):
+        mapped[0:0] = b""
+
+
+class CloseOnIndex:
+    def __init__(self, mapped):
+        self.mapped = mapped
+
+    def __index__(self):
+        self.mapped.close()
+        return 0
+
+
+for close_from in ("key", "value", "slice"):
+    mapped = mmap.mmap(-1, 4)
+    closer = CloseOnIndex(mapped)
+    try:
+        with assert_raises(ValueError):
+            if close_from == "key":
+                mapped[closer] = 0
+            elif close_from == "value":
+                mapped[0] = closer
+            else:
+                mapped[closer:0] = b""
+        assert mapped.closed
+    finally:
+        mapped.close()
diff --git a/extra_tests/snippets/stdlib_multiprocessing_condition.py b/extra_tests/snippets/stdlib_multiprocessing_condition.py
index 6d38dc0db9b..2ab4e17b943 100644
--- a/extra_tests/snippets/stdlib_multiprocessing_condition.py
+++ b/extra_tests/snippets/stdlib_multiprocessing_condition.py
@@ -2,6 +2,7 @@
 
 import multiprocessing
 import threading
+from _multiprocessing import SemLock
 
 
 def wait_on_condition(cond, started, woken):
@@ -80,6 +81,17 @@ def notify_one_then_the_other(ctx):
 
 if __name__ == "__main__":
     multiprocessing.freeze_support()
+    # Low-level callers can supply every constructor parameter by name.
+    name = f"/rustpython_kw_{multiprocessing.current_process().pid}"
+    for args, kwargs in (
+        ((1, 1, 1), {"name": name, "unlink": True}),
+        ((), {"kind": 1, "value": 1, "maxvalue": 1, "name": name, "unlink": True}),
+    ):
+        sem = SemLock(*args, **kwargs)
+        assert sem.acquire(False)
+        assert not sem.acquire(False)
+        sem.release()
+        del sem
     methods = ["spawn"]
     if "forkserver" in multiprocessing.get_all_start_methods():
         methods.append("forkserver")
diff --git a/extra_tests/snippets/stdlib_operator.py b/extra_tests/snippets/stdlib_operator.py
index d0954b12261..1fa1b177023 100644
--- a/extra_tests/snippets/stdlib_operator.py
+++ b/extra_tests/snippets/stdlib_operator.py
@@ -3,3 +3,31 @@
 assert _operator._compare_digest("abcdef", "abcdef")
 assert not _operator._compare_digest("abcdef", "abc")
 assert not _operator._compare_digest("abc", "abcdef")
+
+
+def check_operator_reference_cycles():
+    import gc
+    import weakref
+
+    class Holder:
+        pass
+
+    class Name(str):
+        pass
+
+    for make, make_payload in (
+        (_operator.itemgetter, Holder),
+        (lambda value: _operator.methodcaller("method", value), Holder),
+        (lambda value: _operator.methodcaller("method", value=value), Holder),
+        (_operator.attrgetter, lambda: Name("attribute")),
+    ):
+        payload = make_payload()
+        wrapper = make(payload)
+        payload.wrapper = wrapper
+        reference = weakref.ref(payload)
+        del wrapper, payload
+        gc.collect()
+        assert reference() is None
+
+
+check_operator_reference_cycles()
diff --git a/extra_tests/snippets/stdlib_os.py b/extra_tests/snippets/stdlib_os.py
index a1f40ef4c45..cc845adafe0 100644
--- a/extra_tests/snippets/stdlib_os.py
+++ b/extra_tests/snippets/stdlib_os.py
@@ -8,6 +8,111 @@
 
 assert os.name == "posix" or os.name == "nt"
 
+
+def windows_stat_preserves_time64():
+    import tempfile
+
+    with tempfile.TemporaryDirectory() as directory:
+        filename = os.path.join(directory, "time64")
+        with open(filename, "wb"):
+            pass
+        timestamp = 2_208_988_800  # 2040-01-01, beyond signed 32-bit seconds.
+        os.utime(filename, (timestamp, timestamp))
+        with open(filename, "rb") as file:
+            results = [os.stat(filename), os.fstat(file.fileno())]
+        with os.scandir(directory) as entries:
+            results.append(next(entries).stat())
+        for result in results:
+            assert result.st_mtime == timestamp
+            assert result.st_mtime_ns == timestamp * 1_000_000_000
+
+
+if sys.platform == "win32":
+    windows_stat_preserves_time64()
+
+
+def stat_rejects_negative_file_descriptors():
+    import errno
+    import os
+
+    for stat in (os.stat, os.fstat):
+        for fd in (-1, -5, -9, -100, -(2**31)):
+            try:
+                stat(fd)
+            except OSError as exc:
+                assert exc.errno == errno.EBADF, (stat, fd, exc)
+            else:
+                raise AssertionError((stat, fd, "accepted a negative file descriptor"))
+
+
+# Keep the original RustPython-only coverage: CPython treats -1 as a path sentinel.
+if os.name == "posix" and sys.implementation.name == "rustpython":
+    stat_rejects_negative_file_descriptors()
+
+
+def chmod_supports_directory_descriptors():
+    import errno
+    import tempfile
+
+    assert os.chmod in os.supports_dir_fd
+    assert os.chmod in os.supports_fd
+    with tempfile.TemporaryDirectory() as directory:
+        filename = os.path.join(directory, "file")
+        with open(filename, "wb"):
+            pass
+        dir_fd = os.open(directory, os.O_RDONLY)
+        try:
+            os.chmod("file", 0o640, dir_fd=dir_fd)
+            assert stat.S_IMODE(os.stat(filename).st_mode) == 0o640
+
+            # Absolute paths ignore even an invalid directory descriptor.
+            os.chmod(path=filename, mode=0o600, dir_fd=-1)
+            assert stat.S_IMODE(os.stat(filename).st_mode) == 0o600
+
+            class DirectoryDescriptor:
+                def __index__(self):
+                    return dir_fd
+
+            os.chmod(b"file", 0o640, dir_fd=DirectoryDescriptor())
+            assert stat.S_IMODE(os.stat(filename).st_mode) == 0o640
+            with assert_raises(OSError) as error:
+                os.chmod("file", 0o600, dir_fd=-1)
+            assert error.exception.errno == errno.EBADF
+            assert error.exception.filename == "file"
+            for invalid, message in (
+                (-(2**31) - 1, "fd is less than minimum"),
+                (2**31, "fd is greater than maximum"),
+            ):
+                with assert_raises(OverflowError) as error:
+                    os.chmod(filename, 0o600, dir_fd=invalid)
+                assert str(error.exception) == message
+
+            link = os.path.join(directory, "link")
+            os.symlink("file", link)
+            os.chmod("link", 0o600, dir_fd=dir_fd)
+            assert stat.S_IMODE(os.stat(filename).st_mode) == 0o600
+            for path, options, error_type, message in (
+                (link, {}, NotImplementedError, "follow_symlinks unavailable"),
+                (
+                    "link",
+                    {"dir_fd": dir_fd},
+                    ValueError,
+                    "cannot use dir_fd and follow_symlinks together",
+                ),
+            ):
+                try:
+                    os.chmod(path, 0o640, follow_symlinks=False, **options)
+                except error_type as error:
+                    assert message in str(error)
+                assert stat.S_IMODE(os.stat(filename).st_mode) == 0o600
+        finally:
+            os.close(dir_fd)
+
+
+if os.name == "posix" and hasattr(os, "fchmod"):
+    chmod_supports_directory_descriptors()
+
+
 fd = os.open("README.md", os.O_RDONLY)
 assert fd > 0
 
@@ -125,6 +230,11 @@ def __exit__(self, exc_type, exc_val, exc_tb):
     assert os.write(fd, CONTENT2) == len(CONTENT2)
     os.close(fd)
 
+    # A valid negative access time must reach the invalid modification time.
+    for atime in (-1, -0.25):
+        assert_raises(TypeError, os.utime, fname, (atime, object()))
+    assert_raises(TypeError, os.utime, fname, ns=(-1, object()))
+
     fd = os.open(fname, os.O_WRONLY | os.O_APPEND)
     assert os.write(fd, CONTENT3) == len(CONTENT3)
     os.close(fd)
@@ -545,3 +655,159 @@ def __exit__(self, exc_type, exc_val, exc_tb):
 assert os.stat_result(tuple(range(10)), {"st_atime": 1.5}).st_atime == 1.5
 with assert_raises(TypeError):
     os.stat_result(tuple(range(10)), ["st_atime"])
+
+
+def mkfifo_paths_and_directory_descriptors():
+    import errno
+    import inspect
+    import tempfile
+    import warnings
+
+    assert str(inspect.signature(os.mkfifo)) == "(path, mode=438, *, dir_fd=None)"
+    assert os.mkfifo not in os.supports_fd
+    assert os.mkfifo not in os.supports_follow_symlinks
+    if sys.platform.startswith("linux"):
+        assert os.mkfifo in os.supports_dir_fd
+
+    class Path:
+        def __init__(self, value):
+            self.value = value
+
+        def __fspath__(self):
+            return self.value
+
+    class Index:
+        def __init__(self, value):
+            self.value = value
+
+        def __index__(self):
+            return self.value
+
+    class BadIndex:
+        def __index__(self):
+            raise RuntimeError("mkfifo index marker")
+
+    # Never open a FIFO: creating, inspecting and unlinking it cannot wait for
+    # another process to connect. All paths belong to this temporary directory.
+    with tempfile.TemporaryDirectory(prefix="rustpython-mkfifo-") as directory:
+        path = os.path.join(directory, "fifo")
+        for value in (path, os.fsencode(path), Path(path), Path(os.fsencode(path))):
+            assert os.mkfifo(path=value, mode=0) is None
+            info = os.stat(path)
+            assert stat.S_ISFIFO(info.st_mode)
+            assert stat.S_IMODE(info.st_mode) == 0
+            with assert_raises(FileExistsError) as error:
+                os.mkfifo(value)
+            assert error.exception.errno == errno.EEXIST
+            assert error.exception.filename is None
+            os.unlink(path)
+
+        assert os.mkfifo(path, dir_fd=None) is None
+        assert stat.S_ISFIFO(os.stat(path).st_mode)
+        assert stat.S_IMODE(os.stat(path).st_mode) & ~0o666 == 0
+        os.unlink(path)
+
+        for value in (None, 1.5):
+            assert_raises(TypeError, os.mkfifo, path, value)
+        for value in (2**31, -(2**31) - 1, 2**100, -(2**100)):
+            with assert_raises(OverflowError) as error:
+                os.mkfifo(path, value)
+            assert str(error.exception) == "Python int too large to convert to C int"
+            with assert_raises(OverflowError) as error:
+                os.mkfifo(path, dir_fd=value)
+            expected = (
+                "fd is greater than maximum" if value > 0 else "fd is less than minimum"
+            )
+            assert str(error.exception) == expected
+        for value in (1.5, "fd"):
+            assert_raises(TypeError, os.mkfifo, path, dir_fd=value)
+        for value in (None, 1):
+            with assert_raises(TypeError) as error:
+                os.mkfifo(value)
+            expected = "NoneType" if value is None else "int"
+            assert str(error.exception) == (
+                "mkfifo: path should be string, bytes or os.PathLike, not " + expected
+            )
+        assert_raises(TypeError, os.mkfifo, Path(None))
+        for value in (path + "\0", os.fsencode(path) + b"\0"):
+            with assert_raises(ValueError) as error:
+                os.mkfifo(value)
+            assert str(error.exception) == "mkfifo: embedded null character in path"
+        assert_raises(TypeError, os.mkfifo, path, 0o600, None)
+        for options in ({"mode": BadIndex()}, {"dir_fd": BadIndex()}):
+            with assert_raises(RuntimeError) as error:
+                os.mkfifo(path, **options)
+            assert str(error.exception) == "mkfifo index marker"
+        with assert_raises(FileNotFoundError) as error:
+            os.mkfifo(os.path.join(directory, "missing", "fifo"))
+        assert error.exception.errno == errno.ENOENT
+        assert error.exception.filename is None
+
+        directory_fd = os.open(directory, os.O_RDONLY)
+        try:
+            if os.mkfifo in os.supports_dir_fd:
+                assert (
+                    os.mkfifo(Path(b"fifo"), Index(0o600), dir_fd=Index(directory_fd))
+                    is None
+                )
+                assert stat.S_ISFIFO(os.stat(path).st_mode)
+                assert stat.S_IMODE(os.stat(path).st_mode) & ~0o600 == 0
+                os.unlink(path)
+                for value in (-1, -(2**31)):
+                    assert os.mkfifo(path, dir_fd=value) is None
+                    assert stat.S_ISFIFO(os.stat(path).st_mode)
+                    os.unlink(path)
+                with assert_raises(OSError) as error:
+                    os.mkfifo("fifo", dir_fd=-1)
+                assert error.exception.errno == errno.EBADF
+                assert error.exception.filename is None
+                with warnings.catch_warnings(record=True) as records:
+                    warnings.simplefilter("always")
+                    assert os.mkfifo(path, dir_fd=True) is None
+                assert len(records) == 1
+                assert records[0].category is RuntimeWarning
+                assert str(records[0].message) == "bool is used as a file descriptor"
+                os.unlink(path)
+            else:
+                with assert_raises(NotImplementedError) as error:
+                    os.mkfifo(path, dir_fd=directory_fd)
+                assert str(error.exception) == "dir_fd unavailable on this platform"
+        finally:
+            os.close(directory_fd)
+
+
+if sys.platform.startswith("linux"):
+    assert hasattr(os, "mkfifo")
+if hasattr(os, "mkfifo"):
+    mkfifo_paths_and_directory_descriptors()
+
+
+import errno
+
+
+def nonblocking_windows_pipe():
+    reader, writer = os.pipe()
+    try:
+        for fd in (reader, writer):
+            assert os.get_blocking(fd)
+            os.set_blocking(fd, False)
+            assert not os.get_blocking(fd)
+            os.set_blocking(fd, True)
+            assert os.get_blocking(fd)
+            os.set_blocking(fd, False)
+
+        assert os.read(reader, 0) == b""
+        assert os.write(writer, b"") == 0
+        try:
+            os.read(reader, 1)
+        except BlockingIOError as error:
+            assert error.errno == errno.EAGAIN
+        else:
+            raise AssertionError("empty nonblocking pipe did not raise")
+    finally:
+        os.close(reader)
+        os.close(writer)
+
+
+if os.name == "nt":
+    nonblocking_windows_pipe()
diff --git a/extra_tests/snippets/stdlib_pickle.py b/extra_tests/snippets/stdlib_pickle.py
new file mode 100644
index 00000000000..999106d4235
--- /dev/null
+++ b/extra_tests/snippets/stdlib_pickle.py
@@ -0,0 +1,118 @@
+import _pickle
+import io
+import sys
+from types import MappingProxyType, MethodType
+
+from testutils import assert_raises
+
+# BINPUT leaves holes; MEMOIZE uses the number of present entries.
+unpickler = _pickle.Unpickler(io.BytesIO(b"\x80\x04]q\x07\x94h\x01\x86."))
+left, right = unpickler.load()
+assert left is right
+memo = unpickler.memo.copy()
+assert list(memo) == [1, 7]
+assert memo[1] is left
+assert memo[7] is left
+
+# Slot wrapper descriptors reduce to lookup on their defining class.
+assert object.__str__.__reduce__() == (getattr, (object, "__str__"))
+assert _pickle.loads(_pickle.dumps(object.__str__)) is object.__str__
+
+# Oversized advertised lengths are rejected before trying to read or allocate.
+for opcode, name in (
+    (b"\x8e", "BINBYTES"),
+    (b"\x8d", "BINUNICODE"),
+    (b"\x95", "FRAME"),
+):
+    data = b"\x80\x04" + opcode + (sys.maxsize + 1).to_bytes(8, "little")
+    for load in (
+        _pickle.loads,
+        lambda data: _pickle.Unpickler(io.BytesIO(data)).load(),
+    ):
+        with assert_raises(OverflowError) as caught:
+            load(data)
+        if name == "FRAME":
+            expected = f"FRAME length exceeds system's maximum of {sys.maxsize} bytes"
+        else:
+            expected = f"{name} exceeds system's maximum size of {sys.maxsize} bytes"
+        assert str(caught.exception) == expected
+
+
+# Reduction returns getattr from the active frame's builtins without calling it.
+class ReductionOwner:
+    __slots__ = ("slot",)
+
+    def method(self):
+        pass
+
+
+owner = ReductionOwner()
+items = []
+replacement_getattr = object()
+for descriptor, receiver, name in (
+    (object.__str__, object, "__str__"),
+    (str.join, str, "join"),
+    (io.BytesIO.getvalue, io.BytesIO, "getvalue"),
+    (ReductionOwner.slot, ReductionOwner, "slot"),
+    (owner.__str__, owner, "__str__"),
+    (items.append, items, "append"),
+    (dict.fromkeys, dict, "fromkeys"),
+    (owner.method, owner, "method"),
+):
+    for builtins_type in (dict, MappingProxyType):
+        namespace = {
+            "__builtins__": builtins_type({"getattr": replacement_getattr}),
+            "descriptor": descriptor,
+        }
+        exec("reduced = descriptor.__reduce__()", namespace)
+        assert namespace["reduced"] == (replacement_getattr, (receiver, name))
+
+        namespace["__builtins__"] = builtins_type({})
+        with assert_raises(AttributeError) as caught:
+            exec("descriptor.__reduce__()", namespace)
+        assert caught.exception.args == ("getattr",)
+
+# Module-bound functions reduce to a name without looking up getattr.
+namespace = {"__builtins__": {}, "function": len}
+exec("reduced = function.__reduce__()", namespace)
+assert namespace["reduced"] == "len"
+
+
+class MissingBuiltin(dict):
+    def __getitem__(self, key):
+        raise KeyError(key)
+
+    def __missing__(self, key):
+        raise AssertionError("must not retry __missing__ after custom __getitem__")
+
+
+for descriptor, name in (
+    (object.__str__, "getattr"),
+    (iter([1]), "iter"),
+    (reversed([1]), "reversed"),
+):
+    namespace = {"__builtins__": MissingBuiltin(), "descriptor": descriptor}
+    with assert_raises(AttributeError) as caught:
+        exec("descriptor.__reduce__()", namespace)
+    assert caught.exception.args == (name,)
+
+
+name_error = RuntimeError("function name first")
+
+
+class NamedCallable:
+    def __call__(self, *args):
+        pass
+
+    @property
+    def __name__(self):
+        raise name_error
+
+
+namespace = {
+    "__builtins__": {},
+    "method": MethodType(NamedCallable(), owner),
+}
+with assert_raises(RuntimeError) as caught:
+    exec("method.__reduce__()", namespace)
+assert caught.exception is name_error
diff --git a/extra_tests/snippets/stdlib_pyexpat.py b/extra_tests/snippets/stdlib_pyexpat.py
new file mode 100644
index 00000000000..512a4a529d8
--- /dev/null
+++ b/extra_tests/snippets/stdlib_pyexpat.py
@@ -0,0 +1,50 @@
+from xml.parsers import expat
+
+# Without namespace expansion, element and attribute names retain prefixes.
+for separator, expected_name, expected_attribute in (
+    (None, "p:x", "p:a"),
+    ("!", "urn:p!x", "urn:p!a"),
+):
+    for ordered in (False, True):
+        parser = expat.ParserCreate(namespace_separator=separator)
+        parser.ordered_attributes = ordered
+        starts = []
+        ends = []
+        parser.StartElementHandler = lambda name, attrs: starts.append((name, attrs))
+        parser.EndElementHandler = ends.append
+        parser.Parse('<r xmlns:p="urn:p"><p:x p:a="v" a="u"></p:x></r>', True)
+        assert [name for name, attrs in starts] == ["r", expected_name]
+        assert ends == [expected_name, "r"]
+        expected_attributes = (
+            [expected_attribute, "v", "a", "u"]
+            if ordered
+            else {expected_attribute: "v", "a": "u"}
+        )
+        assert starts[1][1] == expected_attributes
+
+# Parse accepts contiguous buffer objects, including views of mutable input.
+for xml in (bytearray(b"<r>ok</r>"), memoryview(b"<r>ok</r>")):
+    parser = expat.ParserCreate()
+    text = []
+    parser.CharacterDataHandler = text.append
+    assert parser.Parse(xml, True) == 1
+    assert "".join(text) == "ok"
+
+try:
+    expat.ParserCreate().Parse(memoryview(b"<r/>")[::2], True)
+except BufferError:
+    pass
+else:
+    raise AssertionError("Parse accepted a non-contiguous buffer")
+
+# Keep the export alive through callbacks without retaining its read lock.
+xml = bytearray(b"<r/>")
+parser = expat.ParserCreate()
+parser.StartElementHandler = lambda *_: xml.extend(b" ")
+try:
+    parser.Parse(xml, True)
+except BufferError:
+    pass
+else:
+    raise AssertionError("Parse released its input buffer before the callback")
+xml.extend(b" ")
diff --git a/extra_tests/snippets/stdlib_select.py b/extra_tests/snippets/stdlib_select.py
index 6b214cfc374..733e8421ff4 100644
--- a/extra_tests/snippets/stdlib_select.py
+++ b/extra_tests/snippets/stdlib_select.py
@@ -83,6 +83,25 @@ def fileno(self):
 b.close()
 
 
+# Windows supports up to 512 entries, above the Windows SDK default of 64.
+for count in (65, 512) if sys.platform == "win32" else (65,):
+    pairs = []
+    try:
+        for _ in range(count):
+            pairs.append(socket.socketpair())
+        readers = [reader for reader, writer in pairs]
+        assert select.select(readers, [], [], 0) == ([], [], [])
+        for reader, writer in pairs:
+            writer.send(b"x")
+        assert select.select(readers, [], [], 0) == (readers, [], [])
+        if sys.platform == "win32":
+            assert_raises(ValueError, select.select, [readers[0]] * 513, [], [], 0)
+    finally:
+        for pair in pairs:
+            for sock in pair:
+                sock.close()
+
+
 # fileno() runs while the sequence is being read, and it can mutate the very
 # list it was handed.
 mutable_pair, other_end = socket.socketpair()
diff --git a/extra_tests/snippets/stdlib_signal.py b/extra_tests/snippets/stdlib_signal.py
index 50a025a0604..ba333f90032 100644
--- a/extra_tests/snippets/stdlib_signal.py
+++ b/extra_tests/snippets/stdlib_signal.py
@@ -21,8 +21,37 @@ def handler(signum, frame):
 assert signal.getsignal(signal.SIGILL) is signal.SIG_DFL
 
 
-# unix
-if "win" not in sys.platform:
+# Ignoring a synchronously raised signal must not invoke a callback, including
+# on WASI where libc uses a function pointer rather than integer 1 for SIG_IGN.
+synchronous_signals = []
+
+
+def synchronous_handler(signum, frame):
+    synchronous_signals.append(signum)
+
+
+previous = signal.signal(signal.SIGILL, synchronous_handler)
+try:
+    signal.raise_signal(signal.SIGILL)
+    assert synchronous_signals == [signal.SIGILL]
+    assert signal.signal(signal.SIGILL, signal.SIG_IGN) is synchronous_handler
+    signal.raise_signal(signal.SIGILL)
+    assert synchronous_signals == [signal.SIGILL]
+    assert signal.getsignal(signal.SIGILL) is signal.SIG_IGN
+finally:
+    signal.signal(signal.SIGILL, previous)
+
+if sys.platform == "wasi":
+    # wasi-libc rejects SIGKILL (9) and SIGSTOP (19), even though they are not
+    # exported by RustPython's minimal WASI signal module.
+    for uncatchable in (9, 19):
+        previous = signal.getsignal(uncatchable)
+        assert_raises(OSError, signal.signal, uncatchable, signal.SIG_IGN)
+        assert signal.getsignal(uncatchable) is previous
+
+
+# unix, and not WASI
+if "win" not in sys.platform and sys.platform != "wasi":
     signal.signal(signal.SIGALRM, handler)
     assert signal.getsignal(signal.SIGALRM) is handler
 
@@ -77,3 +106,243 @@ def arm_other(signum, frame):
     signal.signal(signal.SIGALRM, signal.SIG_DFL)
     signal.signal(signal.SIGUSR1, signal.SIG_DFL)
     signal.signal(signal.SIGUSR2, signal.SIG_DFL)
+
+
+def check_windows_wakeup_reporting():
+    if sys.platform != "win32":
+        return
+
+    import errno
+    import socket
+
+    def fill_socket(write):
+        # A nonblocking Windows send can briefly fail before TCP has filled
+        # the receiving socket. Require repeated one-byte failures to settle.
+        deadline = time.monotonic() + 5.0
+        written = 0
+        blocked = 0
+        for _ in range(4096):
+            assert time.monotonic() < deadline, "socket fill timed out"
+            assert written < 16 * 1024 * 1024, "socket fill exceeded byte bound"
+            try:
+                written += write.send(b"x" * 65536)
+            except BlockingIOError:
+                try:
+                    written += write.send(b"x")
+                except BlockingIOError:
+                    blocked += 1
+                    if blocked == 4:
+                        return
+                    time.sleep(0.050)
+                    continue
+            blocked = 0
+        raise AssertionError("socket did not fill within the attempt bound")
+
+    # Use numeric loopback addresses and bounded connection/receive calls.
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as listener:
+        listener.settimeout(5.0)
+        listener.bind(("127.0.0.1", 0))
+        listener.listen(1)
+        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as write:
+            write.settimeout(5.0)
+            write.connect(listener.getsockname())
+            read, _ = listener.accept()
+            with read:
+                read.settimeout(5.0)
+                read.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 4096)
+                write.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, 4096)
+                write.setblocking(False)
+                old_handler = signal.getsignal(signal.SIGINT)
+                old_hook = sys.unraisablehook
+                old_fd = signal.set_wakeup_fd(-1)
+                errors = []
+                delivered = []
+
+                def raise_wakeup_signal():
+                    delivered.clear()
+                    # Reinstall for each raise: Windows CRT handlers can reset.
+                    signal.signal(
+                        signal.SIGINT, lambda signum, frame: delivered.append(signum)
+                    )
+                    signal.raise_signal(signal.SIGINT)
+                    assert delivered == [signal.SIGINT]
+
+                try:
+                    sys.unraisablehook = errors.append
+                    signal.set_wakeup_fd(write.fileno())
+                    raise_wakeup_signal()
+                    assert read.recv(1) == bytes([signal.SIGINT])
+                    assert not errors
+
+                    for options in (
+                        {},
+                        {"warn_on_full_buffer": True},
+                        {"warn_on_full_buffer": False},
+                        {},
+                    ):
+                        fill_socket(write)
+                        signal.set_wakeup_fd(write.fileno(), **options)
+                        raise_wakeup_signal()
+                        if options.get("warn_on_full_buffer", True):
+                            assert len(errors) == 1, errors
+                            error = errors.pop()
+                            assert error.exc_type is BlockingIOError
+                            assert error.exc_value.winerror == errno.WSAEWOULDBLOCK
+                            assert error.exc_value.errno in (
+                                errno.EAGAIN,
+                                errno.EWOULDBLOCK,
+                            )
+                            assert error.object is None
+                            assert error.exc_traceback is error.exc_value.__traceback__
+                            assert error.err_msg == (
+                                "Exception ignored while trying to send "
+                                "to the signal wakeup fd"
+                            )
+                        else:
+                            assert not errors
+
+                    # False suppresses a full buffer, not other send failures.
+                    signal.set_wakeup_fd(write.fileno(), warn_on_full_buffer=False)
+                    write.close()
+                    raise_wakeup_signal()
+                    assert len(errors) == 1, errors
+                    assert errors[0].exc_type is OSError
+                    assert errors[0].exc_value.winerror == errno.WSAENOTSOCK
+                    assert errors[0].err_msg == (
+                        "Exception ignored while trying to send to the signal wakeup fd"
+                    )
+                finally:
+                    signal.set_wakeup_fd(old_fd)
+                    signal.signal(signal.SIGINT, old_handler)
+                    sys.unraisablehook = old_hook
+
+
+check_windows_wakeup_reporting()
+
+
+def check_native_stdin_eintr():
+    if sys.platform in ("win32", "wasi", "emscripten"):
+        return
+    if not sys.executable or not hasattr(sys, "_baserepl"):
+        return
+
+    import os
+    import select
+    import subprocess
+
+    if os.name != "posix":
+        return
+
+    prompt = b"__NATIVE_STDIN_PROMPT__"
+    handled = b"__NATIVE_STDIN_HANDLED__"
+    executed = b"__NATIVE_STDIN_EXECUTED__"
+
+    # This explicitly exercises the native adapter rather than an editor REPL.
+    # Lib/test/test_repl.py covers ordinary input, not a blocked native read
+    # interrupted while its pipe remains open and no complete line is supplied.
+    setup = (
+        "import signal, sys\n"
+        f"sys.ps1 = {prompt.decode()!r}\n"
+        "sys.ps2 = '__NATIVE_STDIN_CONTINUATION__'\n"
+    )
+    setup += (
+        "def handler(signum, frame):\n"
+        "    print('__NATIVE_' + 'STDIN_HANDLED__', flush=True)\n"
+        "signal.signal(signal.SIGINT, handler)\n"
+    )
+    setup += "sys._baserepl()\n"
+    process = subprocess.Popen(
+        [sys.executable, "-i", "-S", "-u", "-c", setup],
+        stdin=subprocess.PIPE,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+        bufsize=0,
+    )
+    output = bytearray()
+    output_eof = False
+    deadline = time.monotonic() + 10.0
+
+    def remaining():
+        timeout = deadline - time.monotonic()
+        assert timeout > 0, ("native stdin child timed out", output)
+        return timeout
+
+    def read_output(timeout):
+        nonlocal output_eof
+        ready, _, _ = select.select([process.stdout], [], [], min(timeout, remaining()))
+        if ready:
+            try:
+                chunk = os.read(process.stdout.fileno(), 4096)
+            except BlockingIOError:
+                return
+            if chunk:
+                output.extend(chunk)
+                assert len(output) <= 65536, ("child output limit", output)
+            else:
+                output_eof = True
+
+    def expect(marker, start=0, interrupt=False):
+        observed = len(output)
+        retry_at = time.monotonic()
+        attempts = 0
+        while marker not in output[start:]:
+            assert not output_eof, ("child exited before marker", marker, output)
+            timeout = remaining()
+            if interrupt and len(output) == observed and attempts < 10:
+                # Drain bytes already available before deciding to retry.
+                read_output(0)
+                if len(output) != observed or output_eof:
+                    continue
+                now = time.monotonic()
+                if now >= retry_at:
+                    # Prompt emission precedes read(). Retry only this child
+                    # to cover that race; never send input to wake the read.
+                    assert process.poll() is None, ("child exited", output)
+                    process.send_signal(signal.SIGINT)
+                    attempts += 1
+                    retry_at = now + 0.5
+                timeout = min(timeout, max(0, retry_at - time.monotonic()))
+            # Any response stops retries, including a partial traceback or
+            # marker, so another SIGINT does not interrupt its reporting.
+            read_output(timeout)
+
+    def write_input(data):
+        offset = 0
+        while offset < len(data):
+            _, ready, _ = select.select([], [process.stdin], [], remaining())
+            if ready:
+                try:
+                    written = os.write(process.stdin.fileno(), data[offset:])
+                except BlockingIOError:
+                    continue
+                assert written > 0
+                offset += written
+
+    try:
+        os.set_blocking(process.stdin.fileno(), False)
+        os.set_blocking(process.stdout.fileno(), False)
+        expect(prompt)
+        after_prompt = len(output)
+        source = b"print('__NATIVE_' + 'STDIN_EXECUTED__', flush=True)"
+        # Keep the pipe empty until the native reader dispatches the signal.
+        # Only then provide a complete line and EOF; this does not assert
+        # CPython's behavior for a partial libc fgets interrupted by a signal.
+        expect(handled, after_prompt, interrupt=True)
+        write_input(source + b"\n")
+        process.stdin.close()
+        expect(executed, after_prompt)
+        while not output_eof:
+            read_output(remaining())
+        returncode = process.wait(timeout=remaining())
+        assert returncode == 0, (returncode, output)
+        assert output.count(executed) == 1, output
+        assert b"KeyboardInterrupt" not in output, output
+    finally:
+        process.stdin.close()
+        process.stdout.close()
+        if process.poll() is None:
+            process.kill()
+        process.wait(timeout=5.0)
+
+
+check_native_stdin_eintr()
diff --git a/extra_tests/snippets/stdlib_socket.py b/extra_tests/snippets/stdlib_socket.py
index d9dadeb4a4b..a6a6b86ce6d 100644
--- a/extra_tests/snippets/stdlib_socket.py
+++ b/extra_tests/snippets/stdlib_socket.py
@@ -186,3 +186,89 @@
             pass
     with assert_raises(ValueError):
         sizes.recvfrom(-1)
+
+
+import sys
+
+
+def receive_sizes_and_truncation():
+    with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as receiver:
+        receiver.bind(("127.0.0.1", 0))
+        receiver.settimeout(2)
+        with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as sender:
+            for method in (receiver.recv_into, receiver.recvfrom_into):
+                for size in (-1, 5):
+                    try:
+                        method(bytearray(4), size)
+                    except ValueError:
+                        pass
+                    else:
+                        raise AssertionError("invalid receive size accepted")
+                sender.sendto(b"abc", receiver.getsockname())
+                destination = bytearray(b"------")
+                result = method(memoryview(destination)[1:5], 0)
+                assert (result[0] if isinstance(result, tuple) else result) == 3
+                assert destination == b"-abc--"
+
+            if sys.platform.startswith("linux"):
+                for method in (receiver.recv_into, receiver.recvfrom_into):
+                    sender.sendto(b"abcdefgh", receiver.getsockname())
+                    for flags in (socket.MSG_PEEK | socket.MSG_TRUNC, socket.MSG_TRUNC):
+                        destination = bytearray(b"------")
+                        result = method(memoryview(destination)[1:5], 3, flags)
+                        assert (result[0] if isinstance(result, tuple) else result) == 8
+                        assert destination == b"-abc--"
+                for method in (receiver.recv, receiver.recvfrom, receiver.recvmsg):
+                    sender.sendto(b"abcdefgh", receiver.getsockname())
+                    result = (
+                        method(3, 0, socket.MSG_TRUNC)
+                        if method == receiver.recvmsg
+                        else method(3, socket.MSG_TRUNC)
+                    )
+                    data = result[0] if isinstance(result, tuple) else result
+                    assert data[:3] == b"abc"
+                    if sys.implementation.name == "rustpython":
+                        # Some CPython recv paths enlarge the bytes result to the
+                        # reported datagram length, including an unwritten tail.
+                        assert data == b"abc"
+
+
+def tcp_truncation_preserves_buffer(protocol=0):
+    import signal
+
+    try:
+        listener = socket.socket(socket.AF_INET, socket.SOCK_STREAM, protocol)
+    except OSError:
+        if protocol:
+            return  # MPTCP is optional in the running kernel.
+        raise
+    with listener:
+        listener.bind(("127.0.0.1", 0))
+        listener.listen()
+        with socket.create_connection(listener.getsockname()) as sender:
+            receiver, _ = listener.accept()
+            with receiver:
+                receiver.settimeout(2)
+                for method in (receiver.recv_into, receiver.recvfrom_into):
+                    destination = bytearray(b"original")
+
+                    def send_after_mutation(signum, frame):
+                        destination[0] = ord("X")
+                        sender.sendall(b"abc")
+
+                    previous = signal.signal(signal.SIGALRM, send_after_mutation)
+                    try:
+                        signal.setitimer(signal.ITIMER_REAL, 0.05)
+                        result = method(destination, 0, socket.MSG_TRUNC)
+                        assert (result[0] if isinstance(result, tuple) else result) == 3
+                        assert destination == b"Xriginal"
+                    finally:
+                        signal.setitimer(signal.ITIMER_REAL, 0)
+                        signal.signal(signal.SIGALRM, previous)
+
+
+receive_sizes_and_truncation()
+if sys.platform.startswith("linux"):
+    tcp_truncation_preserves_buffer()
+    if hasattr(socket, "IPPROTO_MPTCP"):
+        tcp_truncation_preserves_buffer(socket.IPPROTO_MPTCP)
diff --git a/extra_tests/snippets/stdlib_sqlite.py b/extra_tests/snippets/stdlib_sqlite.py
index 83fc7db94f0..684a3765e2c 100644
--- a/extra_tests/snippets/stdlib_sqlite.py
+++ b/extra_tests/snippets/stdlib_sqlite.py
@@ -70,3 +70,975 @@ def finalize(self):
     expected = b"t5i4 3l2b1" + data[10:]
     assert actual == expected, f"got {actual!r}, expected {expected!r}"
     blob.close()
+
+
+# Aggregate instances belong to a query, including its error and cancellation paths.
+import gc
+import weakref
+
+from testutils import assert_raises
+
+
+def check_aggregate_lifetime(failure):
+    refs = []
+
+    class TrackedAggregate:
+        def __init__(self):
+            refs.append(weakref.ref(self))
+
+        def step(self, value):
+            if failure == "step":
+                raise ValueError("step")
+
+        def finalize(self):
+            if failure == "finalize":
+                raise ValueError("finalize")
+            return object() if failure == "result" else 1
+
+    cx.create_aggregate("tracked", 1, TrackedAggregate)
+    query = "SELECT tracked(key) FROM foo GROUP BY key % 2"
+    if failure:
+        with assert_raises(sqlite.OperationalError):
+            cx.execute(query).fetchall()
+    else:
+        assert cx.execute(query).fetchall() == [(1,), (1,)]
+    assert refs
+    gc.collect()
+    assert all(ref() is None for ref in refs), failure
+
+    # xFinal may run without any preceding xStep.
+    refs.clear()
+    assert cx.execute("SELECT tracked(key) FROM foo WHERE 0").fetchall() == [(None,)]
+    assert not refs
+
+
+for failure in (None, "step", "finalize", "result"):
+    check_aggregate_lifetime(failure)
+
+
+# Window functions share aggregate finalization, including an unfinished cursor.
+window_refs = []
+
+
+class TrackedWindow:
+    def __init__(self):
+        window_refs.append(weakref.ref(self))
+
+    def step(self, value):
+        pass
+
+    def inverse(self, value):
+        pass
+
+    def value(self):
+        return 1
+
+    def finalize(self):
+        return 1
+
+
+cx.create_window_function("tracked_window", 1, TrackedWindow)
+window_query = """
+    SELECT tracked_window(key) OVER (
+        ORDER BY key ROWS BETWEEN 1 PRECEDING AND CURRENT ROW
+    ) FROM foo
+"""
+assert cx.execute(window_query).fetchall() == [(1,)] * 4
+assert window_refs
+assert all(ref() is None for ref in window_refs)
+window_refs.clear()
+window_cursor = cx.execute(window_query)
+assert window_cursor.fetchone() == (1,)
+window_cursor.close()
+gc.collect()
+assert window_refs and all(ref() is None for ref in window_refs)
+
+
+# Releasing the last reference can run Python that reads the cursor/connection.
+def check_aggregate_destructor(operation):
+    connection = sqlite.connect(":memory:")
+    cursor = connection.cursor()
+    cursor_ref = weakref.ref(cursor)
+    released = []
+
+    class Aggregate:
+        def step(self, value):
+            pass
+
+        def value(self):
+            return 1
+
+        finalize = value
+
+        def __del__(self):
+            current = cursor_ref()
+            if current is not None:
+                try:
+                    current.description
+                except sqlite.ProgrammingError:
+                    pass  # The cursor may already have been closed.
+            released.append(connection.total_changes)
+
+    connection.create_aggregate("tracked", 1, Aggregate)
+    expected = 1
+    if operation == "execute":
+        cursor.execute("SELECT tracked(1)")
+    elif operation == "script":
+        cursor.executescript("SELECT tracked(1);")
+    elif operation == "many":
+        connection.execute("CREATE TABLE results(value)")
+        cursor.executemany("INSERT INTO results SELECT tracked(?)", [(1,), (2,)])
+        expected = 2
+    else:
+        connection.create_window_function("tracked_window", 1, Aggregate)
+        cursor.execute("""
+            SELECT tracked_window(x) OVER (ROWS UNBOUNDED PRECEDING)
+            FROM (SELECT 1 AS x UNION ALL SELECT 2 UNION ALL SELECT 3)
+        """)
+        assert not released
+        if operation == "fetch":
+            assert cursor.fetchall() == [(1,), (1,), (1,)]
+        elif operation == "close":
+            cursor.close()
+        elif operation == "replace":
+            cursor.execute("SELECT 2")
+        else:
+            del cursor
+            gc.collect()
+    assert len(released) == expected, (operation, released)
+    connection.close()
+
+
+for operation in ("execute", "script", "many", "fetch", "close", "replace", "drop"):
+    check_aggregate_destructor(operation)
+
+
+# A nested query must not release its aggregate while an outer callback holds locks.
+def check_nested_aggregate_destructor(operation):
+    outer = sqlite.connect(":memory:", autocommit=False)
+    nested = sqlite.connect(":memory:")
+    released = []
+    inspect = lambda: outer.total_changes
+
+    class Aggregate:
+        def step(self, value):
+            pass
+
+        def finalize(self):
+            return 1
+
+        def __del__(self):
+            try:
+                inspect()
+            except sqlite.ProgrammingError:
+                pass  # Closing the outer connection may finish before cleanup.
+            released.append(True)
+
+    nested.create_aggregate("tracked", 1, Aggregate)
+    outer.set_trace_callback(lambda sql: nested.execute("SELECT tracked(1)"))
+    if operation == "commit":
+        outer.commit()
+    elif operation == "rollback":
+        outer.rollback()
+    elif operation == "autocommit":
+        outer.autocommit = True
+    elif operation in ("blobopen", "blob_index"):
+        outer.execute("CREATE TABLE blobs(data BLOB)")
+        outer.execute("INSERT INTO blobs VALUES (zeroblob(1))")
+        released.clear()
+
+        def progress():
+            nested.execute("SELECT tracked(1)")
+            return 0
+
+        outer.set_progress_handler(progress, 1)
+        blob = outer.blobopen("blobs", "data", 1)
+        outer.set_progress_handler(None, 0)
+        if operation != "blobopen":
+            released.clear()
+            inspect = lambda: len(blob)
+
+            class Index:
+                def __index__(self):
+                    nested.execute("SELECT tracked(1)")
+                    return 0
+
+            index = Index()
+            assert blob[index] == 0
+            blob[index] = 1
+            assert len(released) == 2
+        blob.close()
+    elif operation == "replace_callback":
+
+        class Callback:
+            def __call__(self):
+                return 1
+
+            def __del__(self):
+                nested.execute("SELECT tracked(1)")
+
+        for register in (
+            lambda cb: outer.create_function("hook", 0, cb),
+            lambda cb: outer.create_aggregate("hook", 0, cb),
+            lambda cb: outer.create_window_function("hook", 0, cb),
+            lambda cb: outer.create_collation("hook", cb),
+        ):
+            released.clear()
+            register(Callback())
+            register(None)
+            assert released
+    else:
+        outer.close()
+    assert released, operation
+    if operation != "close":
+        outer.set_trace_callback(None)
+    outer.close()
+    nested.close()
+
+
+for operation in (
+    "commit",
+    "rollback",
+    "autocommit",
+    "close",
+    "blobopen",
+    "blob_index",
+    "replace_callback",
+):
+    check_nested_aggregate_destructor(operation)
+
+
+class BlobIndex:
+    def __init__(self, value):
+        self.value = value
+
+    def __index__(self):
+        return self.value
+
+
+class BlobInt(int):
+    pass
+
+
+class BrokenBlobIndex:
+    def __index__(self):
+        raise OverflowError("index conversion failed")
+
+
+cx.execute("CREATE TABLE blobindices(b BLOB)")
+cx.execute("INSERT INTO blobindices(b) VALUES (?)", (b"abc",))
+with cx.blobopen("blobindices", "b", 1) as blob:
+    assert blob[BlobIndex(-1)] == ord("c")
+    blob[BlobIndex(0)] = ord("A")
+    assert blob[0] == ord("A")
+
+    test = unittest.TestCase()
+    for index in (sys.maxsize, -sys.maxsize - 1):
+        with test.assertRaisesRegex(IndexError, "^Blob index out of range$"):
+            blob[index]
+        with test.assertRaisesRegex(IndexError, "^Blob index out of range$"):
+            blob[index] = 0
+
+    for value in (sys.maxsize + 1, -sys.maxsize - 2):
+        for index in (value, BlobInt(value), BlobIndex(value)):
+            message = (
+                f"^cannot fit '{type(index).__name__}' into an index-sized integer$"
+            )
+            with test.assertRaisesRegex(IndexError, message):
+                blob[index]
+            with test.assertRaisesRegex(IndexError, message):
+                blob[index] = 0
+
+    for name, bounded_name in (("X" * 250, "X" * 200), ("€" * 67, "€" * 66)):
+        long_index = type(name, (), {"__index__": lambda self: sys.maxsize + 1})()
+        message = f"^cannot fit '{bounded_name}' into an index-sized integer$"
+        with test.assertRaisesRegex(IndexError, message):
+            blob[long_index]
+        with test.assertRaisesRegex(IndexError, message):
+            blob[long_index] = 0
+
+    with test.assertRaisesRegex(OverflowError, "^index conversion failed$"):
+        blob[BrokenBlobIndex()]
+    with test.assertRaisesRegex(OverflowError, "^index conversion failed$"):
+        blob[BrokenBlobIndex()] = 0
+    assert blob[:] == b"Abc"
+
+
+import sqlite3
+
+
+def statement_cache_reuse():
+    for capacity, expected in ((0, 3), (-1, 3), (2, 1), (None, 1)):
+        options = {} if capacity is None else {"cached_statements": capacity}
+        with sqlite3.connect(":memory:", **options) as connection:
+            prepared = []
+
+            def authorizer(action, *args):
+                if action == sqlite3.SQLITE_SELECT:
+                    prepared.append(action)
+                return sqlite3.SQLITE_OK
+
+            connection.set_authorizer(authorizer)
+            for parameter in (1, 2, 3):
+                assert connection.execute("SELECT ?", (parameter,)).fetchall() == [
+                    (parameter,)
+                ]
+            assert len(prepared) == expected
+            if capacity == 2:
+                prepared.clear()
+                for value in (1, 2, 1, 3, 2):
+                    assert connection.execute(f"SELECT {value}").fetchall() == [
+                        (value,)
+                    ]
+                assert len(prepared) == 4
+        connection.close()
+
+
+statement_cache_reuse()
+
+
+def cache_reprepare_with_authorizer():
+    connection = sqlite3.connect(":memory:")
+    connection.execute("CREATE TABLE words(word TEXT COLLATE NOCASE)")
+    connection.execute("CREATE INDEX word_index ON words(word)")
+    connection.executemany("INSERT INTO words VALUES (?)", [("alpha",), ("beta",)])
+    sql = "SELECT word FROM words WHERE word LIKE ?"
+    assert connection.execute(sql, ("a%",)).fetchall() == [("alpha",)]
+    authorizations = []
+
+    def authorizer(action, *args):
+        if action == sqlite3.SQLITE_SELECT and not authorizations:
+            authorizations.append(True)
+        return sqlite3.SQLITE_OK
+
+    connection.set_authorizer(authorizer)
+    for prefix, result in (("b%", "beta"), ("a%", "alpha")):
+        authorizations.clear()
+        assert connection.execute(sql, (prefix,)).fetchall() == [(result,)]
+        assert authorizations == [True]
+    connection.execute("ALTER TABLE words ADD COLUMN extra")
+    authorizations.clear()
+    assert connection.execute(sql, ("b%",)).fetchall() == [("beta",)]
+    assert authorizations == [True]
+    connection.close()
+
+
+cache_reprepare_with_authorizer()
+
+
+def statement_cache_connection_lifetime():
+    # CPython 3.14 can crash when an adapter closes its connection.
+    if sys.implementation.name != "rustpython":
+        return
+    test = unittest.TestCase()
+    for phase in ("bind", "step", "fetch", "iterate"):
+        connection = sqlite3.connect(":memory:")
+        connection.execute("CREATE TABLE t(x)")
+
+        def change_connection():
+            connection.close()
+
+        class Parameter:
+            def __conform__(self, protocol):
+                change_connection()
+                return 1
+
+        def change_on(value):
+            if phase == "step" or value == 2:
+                change_connection()
+            return value
+
+        def parameters():
+            yield (1,)
+            change_connection()
+            yield (2,)
+
+        connection.create_function("change_on", 1, change_on)
+        with test.assertRaises(sqlite3.ProgrammingError):
+            if phase == "bind":
+                connection.execute("SELECT ?", (Parameter(),))
+            elif phase == "step":
+                connection.execute("SELECT change_on(1)")
+            elif phase == "fetch":
+                cursor = connection.execute(
+                    "SELECT change_on(1) UNION ALL SELECT change_on(2)"
+                )
+                cursor.fetchone()
+            else:
+                connection.executemany("INSERT INTO t VALUES (?)", parameters())
+        connection.close()
+
+
+statement_cache_connection_lifetime()
+
+
+def statement_cache_deferred_cleanup():
+    # CPython can block when closing a populated cache from a callback's thread.
+    if sys.implementation.name != "rustpython":
+        return
+    import threading
+
+    test = unittest.TestCase()
+    for action in ("close", "reinit"):
+        for autocommit in (sqlite3.LEGACY_TRANSACTION_CONTROL, False):
+            connection = sqlite3.connect(
+                ":memory:", check_same_thread=False, autocommit=autocommit
+            )
+            connection.execute("SELECT 123").fetchall()
+            traced = []
+            connection.set_trace_callback(traced.append)
+            completed = []
+            workers = []
+            failures = []
+
+            def change_connection():
+                try:
+                    if action == "close":
+                        connection.close()
+                    else:
+                        connection.__init__(":memory:", check_same_thread=False)
+                except Exception as error:
+                    failures.append(error)
+
+            def callback():
+                worker = threading.Thread(target=change_connection, daemon=True)
+                workers.append(worker)
+                worker.start()
+                worker.join(5)
+                completed.append(not worker.is_alive())
+                return 1
+
+            connection.create_function("callback", 0, callback)
+            if action == "close":
+                with test.assertRaises(sqlite3.ProgrammingError):
+                    connection.execute("SELECT callback()")
+            else:
+                assert connection.execute("SELECT callback()").fetchall() == [(1,)]
+                assert connection.execute("SELECT 456").fetchall() == [(456,)]
+            for worker in workers:
+                worker.join(5)
+                assert not worker.is_alive()
+            assert not failures, failures
+            assert completed == [True], (action, autocommit)
+            if autocommit is False:
+                assert "ROLLBACK" in traced, traced
+            connection.close()
+
+
+def concurrent_sqlite_error_snapshots():
+    # CPython also races when reading the connection's last error after a call.
+    if sys.implementation.name != "rustpython":
+        return
+    import threading
+
+    connection = sqlite3.connect(":memory:", check_same_thread=False, autocommit=True)
+    for index in range(4):
+        connection.execute(f"CREATE TABLE t{index}(x UNIQUE)")
+        connection.execute(f"INSERT INTO t{index} VALUES (1)")
+
+    for prepare in (True, False):
+        barrier = threading.Barrier(4)
+        failures = []
+        completed = [0] * 4
+
+        def worker(index):
+            if prepare:
+                sql = f"SELECT * FROM missing_table_{index}"
+                expected = (
+                    sqlite3.OperationalError,
+                    f"no such table: missing_table_{index}",
+                    sqlite3.SQLITE_ERROR,
+                )
+            else:
+                sql = f"INSERT INTO t{index} VALUES (1)"
+                expected = (
+                    sqlite3.IntegrityError,
+                    f"UNIQUE constraint failed: t{index}.x",
+                    sqlite3.SQLITE_CONSTRAINT_UNIQUE,
+                )
+            barrier.wait()
+            for _ in range(1000):
+                try:
+                    connection.execute(sql)
+                except sqlite3.Error as error:
+                    actual = (type(error), str(error), error.sqlite_errorcode)
+                    if actual == expected:
+                        completed[index] += 1
+                        continue
+                    failures.append((expected, actual))
+                else:
+                    failures.append((expected, "no error"))
+                break
+
+        workers = [
+            threading.Thread(target=worker, args=(i,), daemon=True) for i in range(4)
+        ]
+        for thread in workers:
+            thread.start()
+        for thread in workers:
+            thread.join(10)
+            assert not thread.is_alive(), "concurrent SQLite call blocked"
+        assert not failures, failures
+        assert completed == [1000] * 4, completed
+    connection.close()
+
+
+statement_cache_deferred_cleanup()
+concurrent_sqlite_error_snapshots()
+
+
+def script_stops_after_close():
+    # CPython can crash when its connection closes inside a callback.
+    if sys.implementation.name != "rustpython":
+        return
+    test = unittest.TestCase()
+    for phase in ("prepare", "step", "commit"):
+        connection = sqlite3.connect(":memory:")
+        continued = []
+        connection.create_function("tail", 0, lambda: continued.append(True))
+        connection.create_function("closeme", 0, connection.close)
+        if phase == "prepare":
+
+            def authorizer(*args):
+                connection.close()
+                return sqlite3.SQLITE_OK
+
+            connection.set_authorizer(authorizer)
+        elif phase == "commit":
+            connection.execute("CREATE TABLE t(x)")
+            connection.execute("INSERT INTO t VALUES (1)")
+            connection.set_trace_callback(lambda sql: connection.close())
+        script = (
+            "SELECT closeme(); SELECT tail();" if phase == "step" else "SELECT tail();"
+        )
+        with test.assertRaises(sqlite3.ProgrammingError):
+            connection.executescript(script)
+        assert not continued, phase
+
+
+def concurrent_sqlite_results():
+    # CPython also races when reading connection-wide result metadata/errors.
+    if sys.implementation.name != "rustpython":
+        return
+    import threading
+
+    connection = sqlite3.connect(":memory:", check_same_thread=False, autocommit=True)
+    connection.execute("CREATE TABLE t(id INTEGER PRIMARY KEY, value)")
+    connection.executemany("INSERT INTO t VALUES (?, 0)", [(i,) for i in range(4)])
+    for operation in ("insert", "update", "many", "returning", "backup"):
+        barrier = threading.Barrier(4, timeout=10)
+        failures = []
+        completed = [0] * 4
+
+        def worker(index):
+            source = sqlite3.connect(":memory:") if operation == "backup" else None
+            try:
+                barrier.wait()
+                for iteration in range(500):
+                    expected = index + 1
+                    if source is not None:
+                        try:
+                            source.backup(connection, name=f"missing_{index}")
+                        except sqlite3.OperationalError as error:
+                            assert str(error) == f"unknown database missing_{index}", (
+                                str(error)
+                            )
+                            assert error.sqlite_errorcode == sqlite3.SQLITE_ERROR
+                        else:
+                            raise AssertionError("backup accepted an unknown schema")
+                    elif operation == "insert":
+                        expected = 1000 + index * 10000 + iteration
+                        cursor = connection.execute(
+                            "INSERT INTO t VALUES (?, 0)", (expected,)
+                        )
+                        assert cursor.lastrowid == expected, (
+                            expected,
+                            cursor.lastrowid,
+                        )
+                        assert cursor.rowcount == 1
+                    else:
+                        sql = "UPDATE t SET value=value+1 WHERE id < ?"
+                        if operation == "many":
+                            cursor = connection.executemany(
+                                sql, [(expected,), (expected,)]
+                            )
+                            expected *= 2
+                        else:
+                            if operation == "returning":
+                                sql += " RETURNING id"
+                            cursor = connection.execute(sql, (expected,))
+                            cursor.fetchall()
+                        assert cursor.rowcount == expected, (
+                            operation,
+                            expected,
+                            cursor.rowcount,
+                        )
+                    assert not connection.in_transaction
+                    assert connection.total_changes >= 4
+                    completed[index] += 1
+            except Exception as error:
+                failures.append(error)
+            finally:
+                if source is not None:
+                    source.close()
+
+        workers = [
+            threading.Thread(target=worker, args=(i,), daemon=True) for i in range(4)
+        ]
+        for worker_thread in workers:
+            worker_thread.start()
+        for worker_thread in workers:
+            worker_thread.join(15)
+            assert not worker_thread.is_alive(), operation
+        assert not failures, failures
+        assert completed == [500] * 4, (operation, completed)
+    connection.close()
+
+
+def sqlite_callbacks_use_calling_thread():
+    import threading
+
+    connection = sqlite3.connect(":memory:", check_same_thread=False)
+    connection.create_function("exception", 0, lambda: str(sys.exception()))
+    traced = []
+    connection.set_trace_callback(lambda sql: traced.append(str(sys.exception())))
+    results = []
+
+    def worker():
+        try:
+            raise ValueError("worker")
+        except ValueError:
+            results.append(connection.execute("SELECT exception()").fetchone()[0])
+
+    try:
+        raise RuntimeError("main")
+    except RuntimeError:
+        thread = threading.Thread(target=worker, daemon=True)
+        thread.start()
+        thread.join(5)
+        assert not thread.is_alive()
+        assert str(sys.exception()) == "main"
+    assert results == ["worker"], results
+    assert traced == ["worker"], traced
+    connection.close()
+
+
+sqlite_callbacks_use_calling_thread()
+
+
+def concurrent_sqlite_transactions():
+    if sys.implementation.name != "rustpython":
+        return
+    import threading
+    import time
+
+    connection = sqlite3.connect(":memory:", check_same_thread=False)
+    connection.execute("CREATE TABLE t(x)")
+    queries = ("INSERT INTO t VALUES (1)", "INSERT INTO t VALUES (2)")
+    for query in queries:
+        connection.execute(query)
+    connection.rollback()
+    entered = threading.Event()
+    started = threading.Event()
+    failures = []
+
+    def trace(sql):
+        if sql.startswith("BEGIN") and not entered.is_set():
+            entered.set()
+            started.wait(5)
+            # Let the competing cached execute reach its implicit BEGIN check.
+            time.sleep(0.05)
+
+    def insert():
+        try:
+            assert entered.wait(5)
+            started.set()
+            connection.execute(queries[1])
+        except Exception as error:
+            failures.append(error)
+
+    connection.set_trace_callback(trace)
+    worker = threading.Thread(target=insert, daemon=True)
+    worker.start()
+    connection.execute(queries[0])
+    worker.join(5)
+    assert not worker.is_alive()
+    assert not failures, failures
+    assert connection.execute("SELECT count(*) FROM t").fetchone() == (2,)
+    connection.set_trace_callback(None)
+    connection.rollback()
+
+    # Either ordering of legacy DML and autocommit=False must be rollbackable.
+    barrier = threading.Barrier(3, timeout=10)
+    rounds = 500
+
+    def run(setter):
+        for _ in range(rounds):
+            barrier.wait()
+            try:
+                if setter:
+                    connection.autocommit = False
+                else:
+                    connection.execute(queries[0])
+            except Exception as error:
+                failures.append(error)
+            barrier.wait()
+
+    workers = [
+        threading.Thread(target=run, args=(setter,), daemon=True)
+        for setter in (False, True)
+    ]
+    for worker in workers:
+        worker.start()
+    remaining = []
+    for _ in range(rounds):
+        connection.autocommit = True
+        connection.autocommit = sqlite3.LEGACY_TRANSACTION_CONTROL
+        barrier.wait()
+        barrier.wait()
+        connection.rollback()
+        remaining.append(connection.execute("SELECT count(*) FROM t").fetchone()[0])
+    for worker in workers:
+        worker.join(5)
+        assert not worker.is_alive()
+    assert not failures, failures
+    assert not any(remaining), remaining
+    connection.close()
+
+
+script_stops_after_close()
+concurrent_sqlite_results()
+concurrent_sqlite_transactions()
+
+
+def callback_registration_lifetimes():
+    class Callback:
+        def __init__(self, connection):
+            self.connection = connection
+
+        def __call__(self, *args):
+            return sqlite.SQLITE_OK
+
+        def __del__(self):
+            if action in ("reinit", "reentrant_reinit"):
+                events.append("drop")
+                try:
+                    self.connection.close()
+                except sqlite.ProgrammingError:
+                    pass
+                if action == "reentrant_reinit" and len(events) == 1:
+                    self.connection.__init__(":memory:")
+                    register(Callback(self.connection), *args)
+
+    for method, args in (
+        ("set_trace_callback", ()),
+        ("set_authorizer", ()),
+        ("set_progress_handler", (1,)),
+        ("set_progress_handler", (0,)),
+    ):
+        for action in ("disable", "replace", "close", "reinit", "reentrant_reinit"):
+            if args == (0,) and action != "disable":
+                continue
+            events = []
+            connection = sqlite.connect(":memory:")
+            cursor = connection.execute("SELECT 1 UNION ALL SELECT 2")
+            register = getattr(connection, method)
+            callback = Callback(connection)
+            reference = weakref.ref(callback)
+            register(callback, *args)
+            del callback
+            assert reference() is not None
+            if action == "disable":
+                register(None, *args)
+            elif action == "replace":
+                register(lambda *args: 0, *args)
+            elif action == "close":
+                connection.close()
+            else:
+                connection.__init__(":memory:")
+                assert events == ["drop"] * (2 if action == "reentrant_reinit" else 1)
+                assert connection.execute("SELECT 1").fetchone() == (1,)
+            assert reference() is None, (method, args, action)
+            del cursor
+            connection.close()
+
+
+def callback_self_removal_lifetime():
+    for method, args in (
+        ("set_trace_callback", ()),
+        ("set_authorizer", ()),
+        ("set_progress_handler", (1,)),
+    ):
+        connection = sqlite.connect(":memory:")
+        register = getattr(connection, method)
+        events = []
+
+        class Result:
+            def __bool__(self):
+                assert events == ["call"]
+                return False
+
+        class Callback:
+            def __call__(self, *unused):
+                register(None, *args)
+                events.append("call")
+                return Result() if args else sqlite.SQLITE_OK
+
+            def __del__(self):
+                events.append(("drop", connection.execute("SELECT 2").fetchone()))
+
+        register(Callback(), *args)
+        # The callable connection also prepares statements and invokes authorizers.
+        if method == "set_authorizer":
+            connection("SELECT 1")
+        else:
+            connection.execute("SELECT 1").fetchall()
+        assert events == ["call", ("drop", (2,))], (method, events)
+        connection.close()
+
+
+callback_registration_lifetimes()
+callback_self_removal_lifetime()
+
+
+def blob_close_during_cursor_reset():
+    import tempfile
+    import threading
+
+    with tempfile.TemporaryDirectory() as directory:
+        path = directory + "/blob.db"
+        connection = sqlite.connect(path, isolation_level=None, check_same_thread=False)
+        connection.execute("CREATE TABLE t(value)")
+        connection.execute("INSERT INTO t VALUES (zeroblob(1)), (zeroblob(1))")
+        resetting = threading.Event()
+        release = threading.Event()
+        cursor_closed = threading.Event()
+        blob_closed = threading.Event()
+        failures = []
+
+        class Window:
+            def step(self, value):
+                pass
+
+            def value(self):
+                return 0
+
+            def finalize(self):
+                resetting.set()
+                if not release.wait(5):
+                    failures.append("cursor reset timed out")
+                return 0
+
+        connection.create_window_function("hold", 1, Window)
+        blob = connection.blobopen("t", "value", 1)
+        cursor = connection.execute(
+            "SELECT hold(rowid) OVER (ROWS UNBOUNDED PRECEDING) FROM t"
+        )
+
+        def close(resource, finished):
+            resource.close()
+            finished.set()
+
+        resetter = threading.Thread(
+            target=close, args=(cursor, cursor_closed), daemon=True
+        )
+        closer = threading.Thread(target=close, args=(blob, blob_closed), daemon=True)
+        resetter.start()
+        assert resetting.wait(5)
+        closer.start()
+        # CPython waits for reset; RustPython may queue the BLOB for later cleanup.
+        blob_closed.wait(0.2)
+        release.set()
+        resetter.join(5)
+        closer.join(5)
+        assert not resetter.is_alive() and not closer.is_alive()
+        assert cursor_closed.is_set() and blob_closed.is_set()
+        assert not failures, failures
+        other = sqlite.connect(path, timeout=0, isolation_level=None)
+        try:
+            # No intervening call on connection may be needed to release its lock.
+            other.execute("UPDATE t SET value=zeroblob(1)")
+        finally:
+            other.close()
+            connection.close()
+
+
+blob_close_during_cursor_reset()
+
+
+def reinit_during_isolation_cleanup():
+    import threading
+
+    failures = []
+    armed = False
+
+    class Callback:
+        def __call__(self, sql):
+            pass
+
+        def __del__(self):
+            try:
+                connection.close()
+            except Exception as exc:
+                failures.append(exc)
+
+    def replace():
+        try:
+            connection.__init__(":memory:", check_same_thread=False, autocommit=True)
+            connection.set_trace_callback(Callback())
+        except Exception as exc:
+            failures.append(exc)
+
+    class Level(str):
+        def __del__(self):
+            # CPython releases this subclass during argument conversion;
+            # RustPython retains it until the isolation level is replaced.
+            if armed:
+                worker = threading.Thread(target=replace, daemon=True)
+                worker.start()
+                worker.join(5)
+                if worker.is_alive():
+                    failures.append("reentrant initializer blocked")
+
+    connection = sqlite.connect(
+        ":memory:", isolation_level=Level(""), check_same_thread=False
+    )
+    armed = True
+    try:
+        connection.__init__(":memory:", check_same_thread=False, autocommit=False)
+        assert not failures, failures
+        assert connection.execute("SELECT 1").fetchone() == (1,)
+        assert connection.autocommit is False
+        assert connection.in_transaction
+    finally:
+        connection.close()
+
+
+reinit_during_isolation_cleanup()
+
+
+def reinit_restores_factories_after_callback_cleanup():
+    connection = sqlite.connect(":memory:")
+    events = []
+
+    class Callback:
+        def __call__(self, sql):
+            pass
+
+        def __del__(self):
+            connection.row_factory = sqlite.Row
+            connection.text_factory = bytes
+            events.append("factories changed")
+
+    connection.set_trace_callback(Callback())
+    try:
+        connection.__init__(":memory:")
+        assert events == ["factories changed"]
+        assert connection.row_factory is None
+        assert connection.text_factory is str
+        assert connection.execute("SELECT 'hello'").fetchone() == ("hello",)
+    finally:
+        connection.close()
+
+
+reinit_restores_factories_after_callback_cleanup()
diff --git a/extra_tests/snippets/stdlib_ssl.py b/extra_tests/snippets/stdlib_ssl.py
index cad505eebc1..7ad7427f152 100644
--- a/extra_tests/snippets/stdlib_ssl.py
+++ b/extra_tests/snippets/stdlib_ssl.py
@@ -1,5 +1,10 @@
 import pathlib
+import socket
 import ssl
+import threading
+import time
+
+from test.test_ssl import HOST, ThreadedEchoServer, testing_context
 
 CERT = (
     pathlib.Path(__file__).resolve().parent.parent.parent
@@ -23,6 +28,18 @@
 client = client_context.wrap_bio(client_in, client_out)
 server = server_context.wrap_bio(server_in, server_out, server_side=True)
 
+# A write that starts the handshake must release its caller's buffer on WANT.
+# Save the valid retry before resizing and changing the original exporter.
+exporter = bytearray(b"saved application bytes before WANT_READ")
+saved_write = bytes(exporter)
+try:
+    client.write(exporter)
+except ssl.SSLWantReadError:
+    exporter[:] = b"changed after WANT"
+    exporter.extend(b"; no outstanding buffer export")
+else:
+    raise AssertionError("write before the peer handshake did not need a read")
+
 for _ in range(5):
     try:
         client.do_handshake()
@@ -37,6 +54,12 @@
 client.do_handshake()
 server.do_handshake()
 
+# OpenSSL retries require the original content and length. Never retry with
+# the mutated exporter: behavior for an invalid retry is not a parity claim.
+assert client.write(saved_write) == len(saved_write)
+server_in.write(client_out.read())
+assert server.read(len(saved_write)) == saved_write
+
 try:
     server.unwrap()
 except ssl.SSLWantReadError:
@@ -44,3 +67,285 @@
 client_in.write(server_out.read() + TAIL)
 client.unwrap()
 assert client_in.read() == TAIL
+
+
+TIMEOUT = 10.0
+
+
+class BoundedEchoServer(ThreadedEchoServer):
+    # Keep the canonical accept, handshake and echo implementation. Its normal
+    # context manager and handler joins need bounds for a deadlock regression.
+    class ConnectionHandler(ThreadedEchoServer.ConnectionHandler):
+        def __init__(self, server, connsock, addr):
+            super().__init__(server, connsock, addr)
+            self.sock.settimeout(TIMEOUT)
+            server.handlers.append(self)
+
+        def run(self):
+            try:
+                try:
+                    super().run()
+                finally:
+                    self.close()
+            except BaseException as exc:
+                self.server.errors.append(exc)
+
+        def join(self, timeout=TIMEOUT * 10):
+            super().join(timeout)
+            if self.is_alive():
+                self.server.errors.append(
+                    AssertionError("echo connection handler did not stop")
+                )
+                self.server.stop()
+
+    def __init__(self, context):
+        self.errors = []
+        self.handlers = []
+        super().__init__(context=context, chatty=False)
+
+    def __enter__(self):
+        assert not self._in_context
+        self._in_context = True
+        self.start(threading.Event())
+        if not self.flag.wait(TIMEOUT):
+            self.__exit__()
+            raise AssertionError("echo server did not start")
+        return self
+
+    def run(self):
+        try:
+            try:
+                super().run()
+            finally:
+                self.close()
+        except BaseException as exc:
+            self.errors.append(exc)
+
+    def __exit__(self, *args):
+        self.stop()
+        self.join(TIMEOUT * 2)
+        self._in_context = False
+        assert not self.is_alive(), "echo server did not stop"
+        for handler in self.handlers:
+            handler.join(TIMEOUT)
+            assert not handler.is_alive(), "echo connection handler did not stop"
+        if self.errors:
+            raise self.errors[0]
+        assert not self.conn_errors, self.conn_errors
+
+
+def test_write_return_during_reader_callback():
+    client_context, server_context, hostname = testing_context()
+    client_context.maximum_version = ssl.TLSVersion.TLSv1_2
+    server_context.maximum_version = ssl.TLSVersion.TLSv1_2
+    writer_thread = threading.current_thread()
+    reader_thread = None
+    round_active = False
+
+    def message_callback(conn, direction, version, content_type, msg_type, data):
+        if (
+            not round_active
+            or conn is not connection
+            or content_type != ssl._TLSContentType.HEADER
+            or msg_type != ssl._TLSContentType.APPLICATION_DATA
+        ):
+            return
+        current_thread = threading.current_thread()
+        if (
+            direction == "write"
+            and current_thread is writer_thread
+            and not write_started.is_set()
+        ):
+            write_started.set()
+            assert reader_started.wait(TIMEOUT), "reader did not start"
+            # Encourage the reader to queue behind the native writer. Python
+            # cannot force its acquisition into the native cleanup window.
+            time.sleep(0.01)
+        elif (
+            direction == "read"
+            and current_thread is reader_thread
+            and not read_callback_seen.is_set()
+        ):
+            read_callback_seen.set()
+            assert write_returned.wait(TIMEOUT), (
+                "write did not return while another thread's read callback ran"
+            )
+
+    client_context._msg_callback = message_callback
+    with BoundedEchoServer(server_context) as echo_server:
+        with client_context.wrap_socket(
+            socket.socket(), server_hostname=hostname
+        ) as connection:
+            connection.settimeout(TIMEOUT)
+            connection.connect((HOST, echo_server.port))
+            try:
+                # This is a cleanup/callback race, not another generic duplex
+                # smoke test. The canonical duplex test remains authoritative.
+                for _ in range(20):
+                    payload = b"WRITE RETURN DURING READER CALLBACK\n"
+                    write_started = threading.Event()
+                    reader_started = threading.Event()
+                    write_returned = threading.Event()
+                    read_callback_seen = threading.Event()
+                    errors = []
+
+                    def read_echo():
+                        try:
+                            assert write_started.wait(TIMEOUT), (
+                                "writer did not enter its application-record callback"
+                            )
+                            reader_started.set()
+                            received = b""
+                            while len(received) < len(payload):
+                                chunk = connection.read(len(payload) - len(received))
+                                assert chunk, (
+                                    "unexpected EOF in echoed application data"
+                                )
+                                received += chunk
+                            assert received == payload.lower(), received
+                        except BaseException as exc:
+                            errors.append(exc)
+
+                    reader_thread = threading.Thread(target=read_echo, daemon=True)
+                    round_active = True
+                    reader_thread.start()
+                    try:
+                        assert connection.write(payload) == len(payload)
+                    finally:
+                        # Set only after the Python write call has returned or
+                        # raised. The reader callback never waits on itself.
+                        write_returned.set()
+                        reader_thread.join(TIMEOUT * 2)
+                        if reader_thread.is_alive():
+                            # Interrupt transport I/O without starting SSL I/O.
+                            try:
+                                socket.socket.shutdown(connection, socket.SHUT_RDWR)
+                            except OSError:
+                                pass
+                            reader_thread.join(TIMEOUT * 2)
+                        round_active = False
+                        assert not reader_thread.is_alive(), "reader did not stop"
+                    if errors:
+                        raise errors[0]
+                    assert write_started.is_set(), "write callback was not exercised"
+                    assert read_callback_seen.is_set(), (
+                        "read callback was not exercised"
+                    )
+                connection.write(b"over\n")
+            finally:
+                round_active = False
+                client_context._msg_callback = None
+
+
+test_write_return_during_reader_callback()
+
+
+# Limit initial nonblocking writes to 4 MiB. Small socket buffers plus a peer
+# paused after its handshake must actually produce WANT_WRITE on this platform.
+WRITE_SIZE = 64 * 1024
+MAX_INITIAL_WRITES = 64
+
+
+class PausedSinkServer(BoundedEchoServer):
+    class ConnectionHandler(BoundedEchoServer.ConnectionHandler):
+        def __init__(self, server, connsock, addr):
+            super().__init__(server, connsock, addr)
+            self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, 4096)
+
+        def read(self):
+            assert self.server.read_enabled.wait(TIMEOUT), "sink was not released"
+            data = super().read()
+            if not data:
+                self.server.reached_eof.set()
+            else:
+                assert data == b"x" * len(data), "pending write data changed"
+                self.server.received += len(data)
+                assert self.server.received <= (MAX_INITIAL_WRITES + 1) * WRITE_SIZE
+            return data
+
+        def write(self, data):
+            # Data was checked before canonical echo processing normalizes it.
+            # Send nothing back, avoiding two-peer application backpressure.
+            pass
+
+        def run(self):
+            try:
+                super().run()
+            finally:
+                self.server.finished.set()
+
+    def __init__(self, context):
+        self.read_enabled = threading.Event()
+        self.finished = threading.Event()
+        self.reached_eof = threading.Event()
+        self.received = 0
+        super().__init__(context)
+
+
+def test_exporter_release_after_application_want_write():
+    client_context, server_context, hostname = testing_context()
+    client_context.maximum_version = ssl.TLSVersion.TLSv1_2
+    server_context.maximum_version = ssl.TLSVersion.TLSv1_2
+    with PausedSinkServer(server_context) as sink:
+        try:
+            with client_context.wrap_socket(
+                socket.socket(), server_hostname=hostname
+            ) as connection:
+                connection.settimeout(TIMEOUT)
+                connection.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, 4096)
+                connection.connect((HOST, sink.port))
+                connection.setblocking(False)
+                exporter = bytearray(b"x" * WRITE_SIZE)
+                saved_write = bytes(exporter)
+                acknowledged = 0
+                for _ in range(MAX_INITIAL_WRITES):
+                    try:
+                        acknowledged += connection.write(exporter)
+                    except ssl.SSLWantWriteError:
+                        break
+                else:
+                    raise AssertionError(
+                        "bounded application writes never reached WANT_WRITE"
+                    )
+
+                # Returning WANT must release the export while native retries
+                # retain stable original bytes. Resize and mutate only the old
+                # exporter; the retry still uses identical saved bytes/length.
+                exporter[:] = b"changed after application WANT_WRITE"
+                exporter.extend(b"; exporter is no longer held")
+                sink.read_enabled.set()
+                # A successful write may accept a prefix. The first retry
+                # must still use identical bytes/length; advance only after a
+                # positive result, and keep the same pending slice on WANT.
+                retry_deadline = time.monotonic() + TIMEOUT
+                accepted = 0
+                pending = saved_write
+                for _ in range(64):
+                    remaining = retry_deadline - time.monotonic()
+                    assert remaining > 0, "saved-byte retry deadline expired"
+                    connection.settimeout(remaining)
+                    try:
+                        count = connection.write(pending)
+                    except (ssl.SSLWantReadError, ssl.SSLWantWriteError):
+                        continue
+                    assert 0 < count <= len(pending), count
+                    accepted += count
+                    if accepted == len(saved_write):
+                        break
+                    pending = saved_write[accepted:]
+                else:
+                    raise AssertionError("saved-byte retry exceeded 64 attempts")
+                assert accepted == len(saved_write)
+
+                # TCP EOF follows every sent TLS byte. Let the sink consume to
+                # EOF before checking the total, so extra replay is detected.
+                socket.socket.shutdown(connection, socket.SHUT_WR)
+                assert sink.finished.wait(TIMEOUT), "sink did not consume through EOF"
+                assert sink.reached_eof.is_set(), "sink stopped before observing EOF"
+                assert sink.received == acknowledged + len(saved_write), sink.received
+        finally:
+            # Setup or oracle failure must not strand the paused peer.
+            sink.read_enabled.set()
+
+
+test_exporter_release_after_application_want_write()
diff --git a/extra_tests/snippets/stdlib_struct.py b/extra_tests/snippets/stdlib_struct.py
index c80f5511713..5184493b14c 100644
--- a/extra_tests/snippets/stdlib_struct.py
+++ b/extra_tests/snippets/stdlib_struct.py
@@ -78,19 +78,18 @@ def __index__(self):
 assert struct.error.__name__ == "error"
 
 # Non-ASCII format string: error type matches CPython.
-# str → UnicodeEncodeError (encoding='ascii')
-# bytes → struct.error
+# str and bytes → ValueError
 try:
     struct.Struct("\udc00")
-except UnicodeEncodeError as e:
-    assert e.encoding == "ascii"
+except ValueError as e:
+    assert str(e) == "non-ASCII character in struct format"
 else:
-    raise AssertionError("expected UnicodeEncodeError")
+    raise AssertionError("expected ValueError")
 
-with assert_raises(UnicodeEncodeError):
+with assert_raises(ValueError):
     struct.Struct("한")
 
-with assert_raises(struct.error):
+with assert_raises(ValueError):
     struct.Struct(b"\xff")
 
 
@@ -128,7 +127,7 @@ def __index__(self):
 
 # A format that cannot be read leaves the Struct as it was.
 for bad in ("\udc00", "$"):
-    with assert_raises((UnicodeEncodeError, struct.error)):
+    with assert_raises((ValueError, struct.error)):
         s.__init__(bad)
     assert s.format == ">hh"
     assert s.pack(1, 2) == b"\x00\x01\x00\x02"
@@ -145,8 +144,9 @@ def __init__(self):
 # Until __init__ runs there is no format to answer with.
 blank = struct.Struct.__new__(struct.Struct)
 assert blank.size == -1
+with assert_raises(AttributeError):
+    blank.format
 for call in (
-    lambda: blank.format,
     lambda: blank.pack(1),
     lambda: blank.unpack(b"aa"),
     lambda: blank.unpack_from(b"aaaa"),
@@ -184,3 +184,21 @@ def __index__(self):
 buffer = bytearray(2)
 struct.pack_into("<H", buffer, 0, ClearFormats())
 assert buffer == b"\x2a\x00"
+
+
+# Struct's format is positional-or-keyword, including inherited initialization.
+class KeywordStruct(struct.Struct):
+    pass
+
+
+for cls in (struct.Struct, KeywordStruct):
+    for fmt in (">h", b">h"):
+        s = cls(format=fmt)
+        assert s.format == ">h"
+        assert s.pack(7) == b"\x00\x07"
+        s.__init__(format=">hh")
+        assert s.unpack(b"\x00\x01\x00\x02") == (1, 2)
+        with assert_raises(struct.error):
+            s.__init__(format="$")
+        assert s.format == ">hh"
+        assert s.pack(1, 2) == b"\x00\x01\x00\x02"
diff --git a/extra_tests/snippets/stdlib_subinterpreters.py b/extra_tests/snippets/stdlib_subinterpreters.py
index 3ca0be27411..e2ad9d76be9 100644
--- a/extra_tests/snippets/stdlib_subinterpreters.py
+++ b/extra_tests/snippets/stdlib_subinterpreters.py
@@ -117,3 +117,50 @@ def receive():
         encoding="utf-8",
     )
     subprocess.run([sys.executable, str(script)], check=True, timeout=30)
+
+
+# Releasing queued buffers can run a finalizer which reenters the channel API.
+subprocess.run(
+    [
+        sys.executable,
+        "-c",
+        """
+import _interpchannels as channels
+import _interpreters
+import sys
+
+released = []
+
+class Exporter(bytearray):
+    def __del__(self):
+        channels.list_all()
+        released.append(True)
+
+for operation in ("destroy", "close", "drop", "timeout"):
+    # CPython 3.14.6 also deadlocks when close/drop releases a reentrant exporter.
+    if sys.implementation.name == "cpython" and operation in ("close", "drop"):
+        continue
+    channel = channels.create(3)
+    released.clear()
+    if operation == "timeout":
+        try:
+            channels.send_buffer(channel, Exporter(b"data"), timeout=0)
+        except TimeoutError:
+            pass
+        else:
+            raise AssertionError("send must time out without a receiver")
+    else:
+        channels.send_buffer(channel, Exporter(b"data"), blocking=False)
+        assert not released
+        if operation == "destroy":
+            channels.destroy(channel)
+        elif operation == "close":
+            channels.close(channel, force=True)
+        else:
+            del channel
+    assert released == [True], operation
+""",
+    ],
+    check=True,
+    timeout=30,
+)
diff --git a/extra_tests/snippets/stdlib_sys.py b/extra_tests/snippets/stdlib_sys.py
index 9dba301fb01..40daf9530f9 100644
--- a/extra_tests/snippets/stdlib_sys.py
+++ b/extra_tests/snippets/stdlib_sys.py
@@ -1,7 +1,10 @@
 import os
+import shutil
 import subprocess
 import sys
+import tempfile
 import warnings
+from pathlib import Path
 
 from testutils import assert_raises
 
@@ -25,6 +28,13 @@
 assert isinstance(sys.implementation.name, str)
 assert isinstance(sys.implementation.cache_tag, str)
 
+assert sys.version_info[:3] == (3, 15, 0)
+assert sys.hexversion >> 8 == 0x030F00
+assert sys.version.startswith("3.15.0")
+assert sys.implementation.cache_tag == (
+    f"{sys.implementation.name}-{sys.version_info.major}{sys.version_info.minor}"
+)
+
 assert sys.getfilesystemencoding() == "utf-8"
 assert sys.getfilesystemencodeerrors().startswith("surrogate")
 
@@ -59,6 +69,92 @@ def demo(x):
 
 assert ("demo", "call", None) in events
 
+# The eager iterator prefix of a generator expression is not traced, but
+# monitoring still reports the error it raises.
+
+
+class GoodIterable:
+    def __iter__(self):
+        return iter([1])
+
+
+class BadIterable:
+    def __iter__(self):
+        raise ValueError("eager iterator")
+
+
+def create_genexpr(iterable):
+    return (value for value in iterable)
+
+
+events = []
+
+
+def trc(frame, event, arg):
+    if frame.f_code.co_name in ("create_genexpr", "<genexpr>", "__iter__"):
+        events.append((frame.f_code.co_name, event))
+    return trc
+
+
+sys.settrace(trc)
+try:
+    create_genexpr(GoodIterable()).close()
+    try:
+        create_genexpr(BadIterable())
+    except ValueError as error:
+        tb_names = []
+        tb = error.__traceback__
+        while tb is not None:
+            tb_names.append(tb.tb_frame.f_code.co_name)
+            tb = tb.tb_next
+    else:
+        raise AssertionError("expected eager iterator error")
+finally:
+    sys.settrace(None)
+assert events == [
+    ("create_genexpr", "call"),
+    ("create_genexpr", "line"),
+    ("__iter__", "call"),
+    ("__iter__", "line"),
+    ("__iter__", "return"),
+    ("create_genexpr", "return"),
+    ("create_genexpr", "call"),
+    ("create_genexpr", "line"),
+    ("__iter__", "call"),
+    ("__iter__", "line"),
+    ("__iter__", "exception"),
+    ("__iter__", "return"),
+    ("create_genexpr", "exception"),
+    ("create_genexpr", "return"),
+    ("create_genexpr", "exception"),
+    ("create_genexpr", "return"),
+], events
+assert tb_names == ["<module>", "create_genexpr", "__iter__"], tb_names
+
+monitoring = sys.monitoring
+event_names = ("PY_START", "PY_RESUME", "PY_UNWIND", "RAISE", "LINE", "INSTRUCTION")
+records = []
+monitoring.use_tool_id(2, "genexpr-prefix")
+try:
+    for name in event_names:
+
+        def callback(code, *args, name=name):
+            if code.co_name == "<genexpr>":
+                records.append(name)
+
+        monitoring.register_callback(2, getattr(monitoring.events, name), callback)
+    monitoring.set_events(
+        2, sum(getattr(monitoring.events, name) for name in event_names)
+    )
+    create_genexpr(GoodIterable()).close()
+    assert records == [], records
+    with assert_raises(ValueError):
+        create_genexpr(BadIterable())
+finally:
+    monitoring.set_events(2, 0)
+    monitoring.free_tool_id(2)
+assert records == ["RAISE", "PY_UNWIND"], records
+
 assert sys.exc_info() == (None, None, None)
 
 try:
@@ -149,6 +245,17 @@ def recursive_call(n):
 assert proc.stdout.rstrip() == "True"
 assert proc.returncode == 0, proc
 
+# -S must prevent the site import itself, not just its customizations.
+subprocess.run(
+    [
+        sys.executable,
+        "-S",
+        "-c",
+        "import sys; assert sys.flags.no_site; assert 'site' not in sys.modules",
+    ],
+    check=True,
+)
+
 assert sys._getframemodulename() == "__main__", sys._getframemodulename()
 
 
@@ -174,3 +281,132 @@ def test_getframemodulename():
         del os.environ["PYTHONBREAKPOINT"]
     else:
         os.environ["PYTHONBREAKPOINT"] = saved_breakpoint_env
+
+
+# A venv's symlink target takes precedence over home/<invoked name>.
+if os.name == "posix" and sys.platform not in ("wasi", "emscripten"):
+    with tempfile.TemporaryDirectory() as directory:
+        root = Path(directory).resolve()
+        interpreter = Path(sys.executable).resolve()
+        # A framework build can also run its embedded app directly. Match the
+        # installed launcher's file identity before applying launcher semantics.
+        framework_base = (
+            Path(sys.base_prefix)
+            / "bin"
+            / f"python{sys.version_info.major}.{sys.version_info.minor}"
+        )
+        framework_launcher = (
+            sys.platform == "darwin"
+            and bool(getattr(sys, "_framework", ""))
+            and framework_base.is_file()
+            and interpreter.samefile(framework_base)
+        )
+        home = root / "home"
+        home.mkdir()
+        venv_env = dict(os.environ)
+        for name in ("PYTHONHOME", "PYTHONEXECUTABLE", "__PYVENV_LAUNCHER__"):
+            venv_env.pop(name, None)
+        # Keep startup imports available even with the synthetic home directory.
+        venv_env["PYTHONPATH"] = os.pathsep.join(sys.path)
+        path_code = (
+            "import sys; print(sys.executable); "
+            "print(sys._base_executable); print(sys.prefix)"
+        )
+
+        def executable_paths(executable, *, cwd=None, env=venv_env):
+            result = subprocess.run(
+                [str(executable), "-B", "-S", "-c", path_code],
+                cwd=cwd,
+                env=env,
+                capture_output=True,
+                text=True,
+                timeout=10,
+            )
+            assert result.returncode == 0, result.stderr
+            return result.stdout.splitlines()
+
+        for kind in ("absolute", "relative", "chain"):
+            bin_dir = root / kind / "bin"
+            bin_dir.mkdir(parents=True)
+            # Exercise both parent and adjacent pyvenv.cfg discovery.
+            prefix = bin_dir if kind == "chain" else bin_dir.parent
+            (prefix / "pyvenv.cfg").write_text(f"home = {home}\n")
+            executable = bin_dir / kind
+            # This regular file must never be preferred to a symlink's target.
+            (home / kind).touch()
+            if kind == "absolute":
+                executable.symlink_to(interpreter)
+            elif kind == "relative":
+                executable.symlink_to(os.path.relpath(interpreter, bin_dir))
+            else:
+                (bin_dir / "target").symlink_to(interpreter)
+                executable.symlink_to("target")
+            invocation = f"./bin/{kind}" if kind == "relative" else executable
+            assert executable_paths(invocation, cwd=bin_dir.parent) == [
+                str(executable),
+                str(framework_base if framework_launcher else interpreter),
+                str(prefix),
+            ]
+
+        # Framework launchers preset their base; ordinary binaries keep argv[0].
+        plain = root / "plain" / "python"
+        plain.parent.mkdir()
+        plain.symlink_to(interpreter)
+        assert executable_paths(plain)[:2] == [
+            str(plain),
+            str(framework_base if framework_launcher else plain),
+        ]
+
+        # Without a launcher preset, copies fall back to home/<invoked name>.
+        copied = root / "copied" / "python"
+        copied.parent.mkdir()
+        shutil.copy2(interpreter, copied)
+        (home / copied.name).touch()
+        (copied.parent / "pyvenv.cfg").write_text(f"home = {home}\n")
+        assert executable_paths(copied) == [
+            str(copied),
+            str(framework_base if framework_launcher else home / copied.name),
+            str(copied.parent),
+        ]
+
+        # A directory alias does not turn a copied executable into a symlink.
+        directory_alias = root / "directory-alias"
+        directory_alias.symlink_to(copied.parent, target_is_directory=True)
+        aliased_copy = directory_alias / copied.name
+        # The framework launcher canonicalizes its directory before dispatch.
+        assert executable_paths(aliased_copy) == [
+            str(copied if framework_launcher else aliased_copy),
+            str(framework_base if framework_launcher else home / copied.name),
+            str(copied.parent if framework_launcher else directory_alias),
+        ]
+
+        # Without a launcher preset, final-link resolution preserves target aliases.
+        target_link = root / "linked" / "python"
+        target_link.parent.mkdir()
+        (target_link.parent / "pyvenv.cfg").write_text(f"home = {home}\n")
+        target_link.symlink_to("../directory-alias/python")
+        assert executable_paths(target_link) == [
+            str(target_link),
+            str(framework_base if framework_launcher else aliased_copy),
+            str(target_link.parent),
+        ]
+
+        # macOS framework builds use a framework-derived base for overrides.
+        if sys.platform == "linux":
+            # Relative targets also preserve a double-leading-slash directory.
+            double_target = root / "double-target"
+            double_target.symlink_to("directory-alias/python")
+            target_link.unlink()
+            target_link.symlink_to("/" + str(double_target))
+            assert executable_paths(target_link) == [
+                str(target_link),
+                "/" + str(aliased_copy),
+                str(target_link.parent),
+            ]
+
+            override_env = dict(venv_env, __PYVENV_LAUNCHER__=str(executable))
+            assert executable_paths(plain, env=override_env) == [
+                str(executable),
+                str(plain),
+                str(prefix),
+            ]
diff --git a/extra_tests/snippets/stdlib_sys_getframe.py b/extra_tests/snippets/stdlib_sys_getframe.py
index 50447ce8822..80b63187d67 100644
--- a/extra_tests/snippets/stdlib_sys_getframe.py
+++ b/extra_tests/snippets/stdlib_sys_getframe.py
@@ -23,3 +23,26 @@ def __init__(self):
 
 
 TestClass()
+
+
+# A frame entered from a generator expression's eager iterator prefix sees
+# the creating function as its caller.
+iterator_frames = []
+
+
+class Iterable:
+    def __iter__(self):
+        iterator_frames.append((sys._getframe(), sys._getframe(1)))
+        return iter([7])
+
+
+def create():
+    return (value for value in Iterable())
+
+
+generator = create()
+frame, caller = iterator_frames[0]
+assert caller.f_code.co_name == "create"
+assert frame.f_back is caller
+assert generator.gi_frame.f_back is None
+assert list(generator) == [7]
diff --git a/extra_tests/snippets/stdlib_threading_current_frames.py b/extra_tests/snippets/stdlib_threading_current_frames.py
index e93a222148e..332c29eb5e7 100644
--- a/extra_tests/snippets/stdlib_threading_current_frames.py
+++ b/extra_tests/snippets/stdlib_threading_current_frames.py
@@ -97,4 +97,48 @@ def f123():
     leave.set()
     t.join()
 
+
+def release_deep_snapshot():
+    # Detached snapshots can own a deep chain of untracked frames. Releasing
+    # one on a small native stack must not recurse through the entire chain.
+    depth = 5000
+    ready = threading.Event()
+    release = threading.Event()
+    disposed = threading.Event()
+
+    def recurse(n):
+        if n:
+            recurse(n - 1)
+        else:
+            ready.set()
+            release.wait()
+
+    def inspect():
+        frame = sys._current_frames()[worker.ident]
+        del frame
+        disposed.set()
+
+    old_limit = sys.getrecursionlimit()
+    old_stack = threading.stack_size()
+    worker = threading.Thread(target=recurse, args=(depth,), daemon=True)
+    try:
+        sys.setrecursionlimit(depth + 100)
+        worker.start()
+        assert ready.wait(30), "worker did not reach the bottom of its stack"
+        threading.stack_size(256 * 1024)
+        observer = threading.Thread(target=inspect, daemon=True)
+        observer.start()
+        observer.join(30)
+        assert not observer.is_alive(), "snapshot disposal did not finish"
+        assert disposed.is_set(), "snapshot disposal failed"
+    finally:
+        threading.stack_size(old_stack)
+        release.set()
+        worker.join(30)
+        sys.setrecursionlimit(old_limit)
+    assert not worker.is_alive(), "worker did not finish"
+
+
+release_deep_snapshot()
+
 print("ok")
diff --git a/extra_tests/snippets/stdlib_time.py b/extra_tests/snippets/stdlib_time.py
index b74d5bbc638..1aa2627ce42 100644
--- a/extra_tests/snippets/stdlib_time.py
+++ b/extra_tests/snippets/stdlib_time.py
@@ -1,6 +1,118 @@
 import sys
 import time
 
+from testutils import assert_raises
+
+if sys.platform == "win32":
+    # Record the native runtime before evaluating the range regression below.
+    print("Windows time runtime:", sys.version, sys.implementation, sys.flags)
+    print("Windows time word size:", sys.maxsize)
+    if hasattr(sys, "getwindowsversion"):
+        print("Windows version:", sys.getwindowsversion())
+    try:
+        import sysconfig
+
+        build_keys = (
+            "Py_DEBUG",
+            "Py_GIL_DISABLED",
+            "Py_ENABLE_SHARED",
+            "SIZEOF_TIME_T",
+            "CC",
+            "CFLAGS",
+        )
+        print(
+            "Windows time build:",
+            dict(zip(build_keys, sysconfig.get_config_vars(*build_keys))),
+        )
+    except Exception as error:
+        print("Windows time build unavailable:", type(error).__name__, str(error))
+    for converter in (time.gmtime, time.localtime, time.ctime):
+        for timestamp in (
+            0,
+            -1,
+            -43200,
+            -43201,
+            -86400,
+            2**40,
+            2**63 - 1,
+            -(2**63),
+            -float(2**63),
+            float(2**63),
+        ):
+            try:
+                result = converter(timestamp)
+            except Exception as error:
+                print(
+                    "Windows time result:",
+                    converter.__name__,
+                    repr(timestamp),
+                    type(error).__name__,
+                    str(error),
+                    getattr(error, "errno", None),
+                    getattr(error, "winerror", None),
+                )
+            else:
+                print(
+                    "Windows time result:",
+                    converter.__name__,
+                    repr(timestamp),
+                    "success",
+                    repr(result),
+                )
+
+if sys.platform != "wasi":
+    for converter in (time.gmtime, time.localtime, time.ctime):
+        # 2**63 is outside signed time_t even though its maximum rounds up to
+        # that value when represented as a float.
+        try:
+            converter(float(2**63))
+        except OverflowError:
+            pass
+        else:
+            raise AssertionError("out-of-range timestamp did not raise OverflowError")
+
+if sys.platform == "win32":
+    import errno
+
+    for converter in (time.gmtime, time.localtime, time.ctime):
+        # Non-negative timestamps still use UCRT and preserve errno.
+        for timestamp in (2**40, 2**63 - 1):
+            try:
+                converter(timestamp)
+            except OSError as error:
+                assert error.errno == errno.EINVAL, (converter, timestamp, error)
+            else:
+                raise AssertionError("UCRT timestamp failure did not raise OSError")
+
+        # Negative timestamps use FILETIME, whose epoch is 1601-01-01.
+        for timestamp in (-11_644_473_601, -(2**63), -float(2**63)):
+            try:
+                converter(timestamp)
+            except OverflowError as error:
+                assert str(error) == "timestamp out of range for Windows FILETIME"
+            else:
+                raise AssertionError(
+                    "pre-FILETIME timestamp did not raise OverflowError"
+                )
+
+    assert time.gmtime(-11_644_473_600) == (1601, 1, 1, 0, 0, 0, 0, 1, 0)
+    assert time.gmtime(-86400) == (1969, 12, 31, 0, 0, 0, 2, 365, 0)
+    assert time.gmtime(-1) == (1969, 12, 31, 23, 59, 59, 2, 365, 0)
+    # Leap-year accounting uses the historical date, including century rules.
+    assert time.gmtime(-2_203_891_200).tm_yday == 60  # 1900-03-01
+    assert time.gmtime(-2_330_035_200).tm_yday == 61  # 1896-03-01
+    for timestamp in (-15_897_600, -86400, -43201, -1):
+        local = time.localtime(timestamp)
+        assert local.tm_isdst == -1
+        assert local[:6] == time.gmtime(timestamp + local.tm_gmtoff)[:6]
+        assert time.ctime(timestamp) == time.asctime(local)
+
+if sys.platform == "win32":
+    # The explicit 64-bit CRT ABI must accept timestamps beyond 2038.
+    for timestamp in (2_208_988_800, 2_208_988_800.0):
+        assert time.gmtime(timestamp) == (2040, 1, 1, 0, 0, 0, 6, 1, 0)
+
+
 x = time.gmtime(1000)
 
 assert x.tm_year == 1970
@@ -12,6 +124,29 @@
 # print(s)
 assert s == "1970-01-01-00-16-40"
 
+if sys.platform in ("linux", "darwin"):
+    import locale
+
+    old_locale = locale.setlocale(locale.LC_ALL)
+    try:
+        # Locale output must be Unicode even when the locale is not UTF-8.
+        # Keep LC_CTYPE and LC_TIME consistent for wcsftime on macOS.
+        # These locales are optional on the host running the snippet.
+        for time_locale in ("fr_FR.ISO8859-1", "fr_FR.UTF-8"):
+            try:
+                locale.setlocale(locale.LC_ALL, time_locale)
+            except locale.Error:
+                continue
+            february = (2024, 2, 1, 12, 0, 0, 3, 32, 0)
+            assert time.strftime("%B", february) == "février"
+            assert (
+                time.strftime("[%B] 🐍 \ud800\0%Y", february)
+                == "[février] 🐍 \ud800\0" + "2024"
+            )
+            assert time.strftime("%B" * 300, february) == "février" * 300
+    finally:
+        locale.setlocale(locale.LC_ALL, old_locale)
+
 if sys.platform != "wasi":
     # _strptime depends on time.tzname, which is not available on WASI yet.
     x2 = time.strptime(s, "%Y-%m-%d-%H-%M-%S")
@@ -83,6 +218,62 @@
 assert monotonic_elapsed >= 0.01
 assert perf_elapsed >= 0.01
 
+# Sleep validates signed nanoseconds before rejecting negative durations.
+for duration in (
+    2**63,
+    -(2**63) - 1,
+    2**34,
+    -(2**34),
+    2**63 / 1_000_000_000,
+    -1e10,
+    float("inf"),
+    -float("inf"),
+):
+    with assert_raises(OverflowError) as error:
+        time.sleep(duration)
+    assert str(error.exception) == "timestamp out of range for C PyTime_t"
+assert_raises(ValueError, time.sleep, float("nan"))
+
+
+class SleepTypeNamespace:
+    class Invalid:
+        pass
+
+
+for module in ("__main__", "sleep_test"):
+    SleepTypeNamespace.Invalid.__module__ = module
+    with assert_raises(TypeError) as error:
+        time.sleep(SleepTypeNamespace.Invalid())
+    assert str(error.exception) == "must be real number, not Invalid"
+
+
+class FloatSleepDuration:
+    def __float__(self):
+        return -0.5
+
+
+class IndexedSleepDuration(FloatSleepDuration):
+    def __index__(self):
+        return -1
+
+    def __float__(self):
+        raise AssertionError("sleep must prefer __index__")
+
+
+class InvalidIndexedSleepDuration(FloatSleepDuration):
+    def __index__(self):
+        raise TypeError("index conversion failed")
+
+
+for duration in (FloatSleepDuration(), IndexedSleepDuration()):
+    with assert_raises(ValueError) as error:
+        time.sleep(duration)
+    assert str(error.exception) == "sleep length must be non-negative"
+
+with assert_raises(TypeError) as error:
+    time.sleep(InvalidIndexedSleepDuration())
+assert str(error.exception) == "index conversion failed"
+
 # The optional second argument fills the fields that are not part of the
 # sequence.
 fields = (2024, 1, 2, 3, 4, 5, 6, 7, 0)
diff --git a/extra_tests/snippets/stdlib_types.py b/extra_tests/snippets/stdlib_types.py
index d913095f2f9..bc9017b881b 100644
--- a/extra_tests/snippets/stdlib_types.py
+++ b/extra_tests/snippets/stdlib_types.py
@@ -43,25 +43,47 @@ def _run_missing_type_params_regression():
 
 _run_missing_type_params_regression()
 
-if sys.implementation.name == "rustpython":
-    # __parameters__ is computed when the alias is built, and the walk descends
-    # into every list and tuple argument, so a self-referential or deeply
-    # nested argument must be caught. CPython, which also runs this snippet,
-    # does not walk into plain lists at all.
-    self_referential = []
-    self_referential.append(self_referential)
-    with assert_raises(RecursionError):
-        list[self_referential]
+# GenericAlias construction is lazy. Python 3.15 walks nested lists and tuples
+# when parameters are first needed, including during subscription.
+self_referential = []
+self_referential.append(self_referential)
+alias = list[self_referential]
+with assert_raises(RecursionError):
+    alias.__parameters__
+with assert_raises(RecursionError):
+    alias[int]
 
+if sys.implementation.name == "rustpython":
+    # Finite-depth stack exhaustion depends on the interpreter build and OS stack.
+    # Keep this native stress case separate from the shared cyclic contract above.
     nested = [0]
     for _ in range(100_000):
         nested = [nested]
+    alias = list[nested]
     with assert_raises(RecursionError):
-        list[nested]
+        alias.__parameters__
+    with assert_raises(RecursionError):
+        alias[int]
 
-    # hashing an alias walks the same shape
+    # hashing an alias walks the same shape. Release inlining of the hash
+    # slot needs more depth than debug to trip the native stack guard.
     deep_alias = int
-    for _ in range(100_000):
+    for _ in range(500_000):
         deep_alias = list[deep_alias]
     with assert_raises(RecursionError):
         hash(deep_alias)
+
+
+# FunctionType preserves the code qualified name when a name is supplied.
+def outer():
+    def nested():
+        pass
+
+    return nested
+
+
+original = outer()
+for name in ("renamed", ""):
+    function = types.FunctionType(original.__code__, globals(), name)
+    assert function.__name__ == name
+    assert function.__qualname__ == "outer.<locals>.nested"
diff --git a/extra_tests/snippets/stdlib_typing.py b/extra_tests/snippets/stdlib_typing.py
index 4082d683f8d..d39f1392f46 100644
--- a/extra_tests/snippets/stdlib_typing.py
+++ b/extra_tests/snippets/stdlib_typing.py
@@ -63,3 +63,409 @@ def method(self, value: Union[int, float]) -> Union[str, bytes]:
     repr(nested)
 except RecursionError:
     pass
+
+
+# Python 3.14.8 retains ParamSpec bounds without converting or validating them.
+assert ParamSpec("Unbounded").__bound__ is None
+for bound in (None, "int", "not valid Python!", (int, str), object()):
+    assert ParamSpec("BoundSpec", bound=bound).__bound__ is bound
+
+# Eager aliases without a caller module never inspect their aliased value.
+alias_module_lookups = []
+
+
+class AliasModuleValue:
+    @property
+    def __module__(self):
+        alias_module_lookups.append(True)
+        return "unexpected_value_module"
+
+
+for alias_value in (int, AliasModuleValue()):
+    alias_namespace = {"value": alias_value}
+    exec(
+        "from typing import TypeAliasType; alias = TypeAliasType('Alias', value)",
+        alias_namespace,
+    )
+    assert alias_namespace["alias"].__module__ is None
+assert alias_module_lookups == []
+
+
+# GenericAlias rejects parameters added after its parameter tuple was cached.
+from types import GenericAlias
+
+
+class LateParameter:
+    def __repr__(self):
+        return "late_parameter"
+
+
+first = LateParameter()
+first.__typing_subst__ = lambda value: value
+late = LateParameter()
+alias = GenericAlias(dict, (first, late))
+assert alias.__parameters__ == (first,)
+late.__typing_subst__ = lambda value: value
+with assert_raises(TypeError) as caught:
+    alias[0]
+assert str(caught.exception) == (
+    "argument late_parameter with __typing_subst__ was not found in __parameters__"
+)
+
+
+def test_union_lazy_parameters():
+    import threading
+    from types import GenericAlias
+    from typing import Union
+
+    from testutils import assert_raises
+
+    class Parameter:
+        def __typing_subst__(self, value):
+            return value
+
+    parameter = Parameter()
+
+    class LateParameter:
+        __parameters__ = (parameter,)
+
+        def __repr__(self):
+            return "late_parameter"
+
+    # Building a union must not freeze the nested alias's parameter cache.
+    for materialize in (False, True):
+        for subscribe_first in (False, True):
+            late = LateParameter()
+            alias = GenericAlias(list, late)
+            union = alias | int
+            if materialize:
+                cached = union.__parameters__
+                assert cached == (parameter,)
+            late.__typing_subst__ = lambda value: value
+            if materialize:
+                with assert_raises(TypeError) as caught:
+                    union[str]
+                assert str(caught.exception) == (
+                    "argument late_parameter with __typing_subst__ was not found in __parameters__"
+                )
+                assert union.__parameters__ is cached
+            else:
+                if not subscribe_first:
+                    assert union.__parameters__ == (late,)
+                assert union[str] == (list[str] | int)
+                assert alias[str] == list[str]
+                cached = union.__parameters__
+                assert cached == (late,)
+                assert union.__parameters__ is cached
+
+    # typing.Union and flattening an existing union preserve the same lazy boundary.
+    for make_union in (
+        lambda alias: Union[alias, int],
+        lambda alias: (alias | bytes) | int,
+    ):
+        late = LateParameter()
+        alias = GenericAlias(list, late)
+        union = make_union(alias)
+        late.__typing_subst__ = lambda value: value
+        assert union[str] == make_union(list[str])
+        assert alias[str] == list[str]
+
+    # Nested descriptor failures occur on first use and do not poison either cache.
+    class FailingParameter:
+        fail = True
+        lookups = 0
+
+        @property
+        def __parameters__(self):
+            self.lookups += 1
+            if self.fail:
+                raise RuntimeError("lazy union failure")
+            return (parameter,)
+
+    for subscribe in (False, True):
+        failing = FailingParameter()
+        alias = GenericAlias(list, failing)
+        union = alias | int
+        assert failing.lookups == 0
+        with assert_raises(RuntimeError) as caught:
+            if subscribe:
+                union[str]
+            else:
+                union.__parameters__
+        assert str(caught.exception) == "lazy union failure"
+        failing.fail = False
+        cached = union.__parameters__
+        assert cached == (parameter,)
+        count = failing.lookups
+        assert union.__parameters__ is cached
+        assert failing.lookups == count
+
+    # Parameter collection uses identity, not union argument hash/equality rules.
+    parameter_comparisons = []
+
+    class EqualParameter(Parameter):
+        def __hash__(self):
+            parameter_comparisons.append("hash")
+            return 0
+
+        def __eq__(self, other):
+            parameter_comparisons.append("eq")
+            return True
+
+    first = EqualParameter()
+    second = EqualParameter()
+    union = GenericAlias(tuple, (first, second)) | int
+    parameter_comparisons.clear()
+    cached = union.__parameters__
+    assert len(cached) == 2
+    assert cached[0] is first and cached[1] is second
+    assert parameter_comparisons == []
+    assert union.__parameters__ is cached
+
+    # Empty caches are also stable when a nested alias's descriptor changes.
+    state = {"parameters": ()}
+
+    class ChangingAlias(GenericAlias):
+        @property
+        def __parameters__(self):
+            return state["parameters"]
+
+    union = ChangingAlias(list, int) | str
+    cached = union.__parameters__
+    assert cached == ()
+    state["parameters"] = (parameter,)
+    assert union.__parameters__ is cached
+    with assert_raises(TypeError):
+        union[bytes]
+
+    # Reentrant callbacks may populate the cache. The outer calculation replaces
+    # that cache on success and clears it on failure, allowing another attempt.
+    inner_parameter = Parameter()
+    outer_parameter = Parameter()
+
+    for fail in (False, True):
+        state = {"entered": False, "parameters": (inner_parameter,)}
+
+        class ReentrantAlias(GenericAlias):
+            @property
+            def __parameters__(self):
+                if not state["entered"]:
+                    state["entered"] = True
+                    state["inner"] = state["union"].__parameters__
+                    if fail:
+                        raise RuntimeError("outer union failure")
+                    return (outer_parameter,)
+                return state["parameters"]
+
+        state["union"] = ReentrantAlias(list, int) | str
+        union = state["union"]
+        if fail:
+            with assert_raises(RuntimeError) as caught:
+                union.__parameters__
+            assert str(caught.exception) == "outer union failure"
+            state["parameters"] = (outer_parameter,)
+        cached = union.__parameters__
+        assert state["inner"] == (inner_parameter,)
+        assert cached == (outer_parameter,)
+        assert cached is not state["inner"]
+        assert union.__parameters__ is cached
+
+    # Concurrent callbacks must run without holding the union's parameter lock.
+    barrier = threading.Barrier(2)
+
+    class ConcurrentAlias(GenericAlias):
+        @property
+        def __parameters__(self):
+            barrier.wait(timeout=10)
+            return (parameter,)
+
+    union = ConcurrentAlias(list, int) | str
+    results = []
+    errors = []
+
+    def read_parameters():
+        try:
+            results.append(union.__parameters__)
+        except BaseException as error:
+            errors.append(error)
+
+    threads = [threading.Thread(target=read_parameters) for _ in range(2)]
+    for thread in threads:
+        thread.start()
+    for thread in threads:
+        thread.join(timeout=15)
+    assert all(not thread.is_alive() for thread in threads)
+    assert errors == []
+    assert results == [(parameter,), (parameter,)]
+    cached = union.__parameters__
+    assert any(cached is result for result in results)
+    assert union.__parameters__ is cached
+
+
+test_union_lazy_parameters()
+
+
+# Python 3.15 type alias qualified names and writable module metadata.
+def test_type_alias_metadata():
+    from typing import TypeAliasType
+
+    class Name(str):
+        def __str__(self):
+            raise AssertionError("must use stored string contents")
+
+    name = Name("Alias\ud800")
+    qualname = Name("Scope.Alias\udfff")
+    for explicit in (None, qualname):
+        alias = TypeAliasType(name, int, qualname=explicit)
+        expected = name if explicit is None else qualname
+        assert alias.__name__ is name
+        assert alias.__qualname__ is expected
+        assert repr(alias) == expected
+        assert alias.__reduce__() is name
+        with assert_raises(AttributeError):
+            alias.__qualname__ = "Other"
+        with assert_raises(AttributeError):
+            del alias.__qualname__
+        for module in (object(), None, 42, "another_module"):
+            alias.__module__ = module
+            assert alias.__module__ is module
+        del alias.__module__
+        assert alias.__module__ is None
+        del alias.__module__
+        assert alias.__module__ is None
+
+    assert TypeAliasType(name="Alias", value=int).__qualname__ == "Alias"
+    with assert_raises(TypeError):
+        TypeAliasType("Alias", int, qualname=42)
+
+    type Local = int
+    assert Local.__qualname__ == "test_type_alias_metadata.<locals>.Local"
+    assert repr(Local) == Local.__qualname__
+    assert Local.__reduce__() == "Local"
+    original_module = Local.__module__
+    Local.__module__ = None
+    assert Local.__module__ is None
+    del Local.__module__
+    assert Local.__module__ == original_module
+
+    class Container:
+        type Nested = int
+
+    assert Container.Nested.__qualname__ == (
+        "test_type_alias_metadata.<locals>.Container.Nested"
+    )
+
+
+def test_typevartuple_bound_and_variance():
+    from typing import NoDefault, TypeVarTuple
+
+    class Name(str):
+        def __str__(self):
+            raise AssertionError("must use stored string contents")
+
+    name = Name("Ts\ud800")
+    for options, prefix, flags in (
+        ({}, "~", (False, False, False)),
+        ({"covariant": True}, "+", (True, False, False)),
+        ({"contravariant": True}, "-", (False, True, False)),
+        ({"infer_variance": True}, "", (False, False, True)),
+    ):
+        parameter = TypeVarTuple(name, **options)
+        assert parameter.__name__ is name
+        assert repr(parameter) == prefix + name
+        assert parameter.__bound__ is None
+        assert parameter.__default__ is NoDefault
+        assert not parameter.has_default()
+        assert (
+            parameter.__covariant__,
+            parameter.__contravariant__,
+            parameter.__infer_variance__,
+        ) == flags
+        for attr in (
+            "__bound__",
+            "__covariant__",
+            "__contravariant__",
+            "__infer_variance__",
+        ):
+            with assert_raises(AttributeError):
+                setattr(parameter, attr, None)
+            with assert_raises(AttributeError):
+                delattr(parameter, attr)
+
+    for bound in (None, "not valid Python!", (int, str), object()):
+        default = object()
+        parameter = TypeVarTuple(name="Ts", bound=bound, default=default)
+        assert parameter.__bound__ is bound
+        assert parameter.__default__ is default
+        assert parameter.has_default()
+
+    for options, message in (
+        (
+            {"covariant": True, "contravariant": True, "infer_variance": True},
+            "Bivariant types are not supported.",
+        ),
+        (
+            {"covariant": True, "infer_variance": True},
+            "Variance cannot be specified with infer_variance.",
+        ),
+        (
+            {"contravariant": True, "infer_variance": True},
+            "Variance cannot be specified with infer_variance.",
+        ),
+    ):
+        with assert_raises(ValueError) as caught:
+            TypeVarTuple("Ts", **options)
+        assert str(caught.exception) == message
+
+    calls = []
+
+    class Truth:
+        def __init__(self, label, fail=False):
+            self.label = label
+            self.fail = fail
+
+        def __bool__(self):
+            calls.append(self.label)
+            if self.fail:
+                raise RuntimeError(self.label)
+            return False
+
+    for positional, extra in (
+        (("Ts",), {"unexpected": None}),
+        (("Ts",), {"name": "Duplicate"}),
+        ((42,), {}),
+        (("Ts", "extra"), {}),
+        ((), {}),
+    ):
+        with assert_raises(TypeError):
+            TypeVarTuple(*positional, covariant=Truth("not called", fail=True), **extra)
+        assert calls == []
+
+    TypeVarTuple(
+        "Ts",
+        infer_variance=Truth("infer"),
+        contravariant=Truth("contra"),
+        covariant=Truth("co"),
+    )
+    assert calls == ["co", "contra", "infer"]
+    calls.clear()
+    with assert_raises(RuntimeError):
+        TypeVarTuple(
+            "Ts",
+            covariant=Truth("co", fail=True),
+            contravariant=Truth("contra"),
+            infer_variance=Truth("infer"),
+        )
+    assert calls == ["co"]
+
+    type Variadic[*Ts] = tuple[*Ts]
+    (parameter,) = Variadic.__type_params__
+    assert parameter.__infer_variance__ is True
+    assert parameter.__covariant__ is False
+    assert parameter.__contravariant__ is False
+    assert parameter.__bound__ is None
+    assert repr(parameter) == "Ts"
+
+
+test_type_alias_metadata()
+test_typevartuple_bound_and_variance()
diff --git a/extra_tests/snippets/stdlib_warnings.py b/extra_tests/snippets/stdlib_warnings.py
index 95092e50668..974899d8b9e 100644
--- a/extra_tests/snippets/stdlib_warnings.py
+++ b/extra_tests/snippets/stdlib_warnings.py
@@ -1,3 +1,67 @@
 import _warnings
 
 _warnings.warn("Test")
+
+
+import warnings
+
+
+class CustomWarning(UserWarning):
+    pass
+
+
+for category in (None, DeprecationWarning, int, 42):
+    message = CustomWarning("sentinel")
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        warnings.warn(message, category)
+    assert len(caught) == 1
+    assert caught[0].message is message
+    assert caught[0].category is CustomWarning
+
+
+from importlib.machinery import ModuleSpec
+
+events = []
+
+
+class WarningLoader:
+    def get_source(self, name):
+        events.append(("source", name))
+        return "source line\n"
+
+
+class WarningGlobals(dict):
+    def get(self, key, default=None):
+        events.append(("get", key))
+        return super().get(key, default)
+
+    def __getitem__(self, key):
+        raise AssertionError("module name must use stored dict lookup")
+
+    __missing__ = __getitem__
+
+
+loader = WarningLoader()
+module_globals = WarningGlobals(
+    __name__="stored_name",
+    __loader__=loader,
+    __spec__=ModuleSpec("stored_name", loader),
+)
+for has_name in (True, False):
+    events.clear()
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        warnings.warn_explicit(
+            "subclass globals",
+            UserWarning,
+            "fixed_ascii.py",
+            1,
+            module_globals=module_globals,
+        )
+    assert len(caught) == 1
+    expected = [("get", "__loader__"), ("get", "__spec__")]
+    if has_name:
+        expected.append(("source", "stored_name"))
+        del module_globals["__name__"]
+    assert events == expected
diff --git a/extra_tests/snippets/stdlib_winapi.py b/extra_tests/snippets/stdlib_winapi.py
new file mode 100644
index 00000000000..ef1cad44c37
--- /dev/null
+++ b/extra_tests/snippets/stdlib_winapi.py
@@ -0,0 +1,39 @@
+"""Check Windows event-log conversions without invoking host operations."""
+
+import sys
+
+from testutils import assert_raises
+
+if sys.platform == "win32":
+    import _winapi
+
+    # Every call fails before a host operation. ReportEvent overflow cases
+    # also retain an embedded NUL as an independent safety barrier.
+    assert _winapi.EVENTLOG_SUCCESS == 0
+    assert _winapi.EVENTLOG_ERROR_TYPE == 1
+    assert _winapi.EVENTLOG_WARNING_TYPE == 2
+    assert _winapi.EVENTLOG_INFORMATION_TYPE == 4
+    assert _winapi.EVENTLOG_AUDIT_SUCCESS == 8
+    assert _winapi.EVENTLOG_AUDIT_FAILURE == 16
+
+    assert_raises(TypeError, _winapi.RegisterEventSource, 1, "source\0")
+    assert_raises(TypeError, _winapi.RegisterEventSource, None, 1)
+    assert_raises(TypeError, _winapi.RegisterEventSource, None, None)
+    assert_raises(ValueError, _winapi.RegisterEventSource, None, "source\0")
+    assert_raises(ValueError, _winapi.RegisterEventSource, "server\0", "source\0")
+    assert_raises(ValueError, _winapi.RegisterEventSource, "", "source\0")
+    assert_raises(TypeError, _winapi.DeregisterEventSource, "invalid handle")
+    assert_raises(TypeError, _winapi.DeregisterEventSource, None)
+    assert_raises(
+        TypeError, _winapi.ReportEvent, "invalid handle", 0, 0, 0, "message\0"
+    )
+    assert_raises(ValueError, _winapi.ReportEvent, 0, 0, 0, 0, "message\0")
+    assert_raises(TypeError, _winapi.ReportEvent, 0, 0, 0, 0, None)
+    for index, bits in ((1, 16), (2, 16), (3, 32)):
+        for invalid, exception in ((-1, ValueError), (1 << bits, OverflowError)):
+            arguments = [0, 0, 0, 0, "message\0"]
+            arguments[index] = invalid
+            assert_raises(exception, _winapi.ReportEvent, *arguments)
+        arguments = [0, 0, 0, 0, "message\0"]
+        arguments[index] = "invalid integer"
+        assert_raises(TypeError, _winapi.ReportEvent, *arguments)
diff --git a/extra_tests/snippets/stdlib_xml.py b/extra_tests/snippets/stdlib_xml.py
index 34f1a726e4c..2540e5aa015 100644
--- a/extra_tests/snippets/stdlib_xml.py
+++ b/extra_tests/snippets/stdlib_xml.py
@@ -1,4 +1,6 @@
+import array
 import xml.sax
+from xml.etree.ElementTree import Element
 from xml.parsers import expat
 
 from testutils import assert_raises
@@ -66,3 +68,91 @@ def endElement(self, name):
     ("characters", "text"),
     ("end-cdata",),
 ]
+
+root = Element("root")
+for value, type_name in (
+    (None, "None"),
+    (1, "int"),
+    ("child", "str"),
+    (array.array("b"), "array.array"),
+    (type("A" * 60, (), {})(), "A" * 50),
+    (type("€" * 20, (), {})(), "€" * 16),
+):
+    with assert_raises(TypeError) as caught:
+        root.remove(value)
+    assert str(caught.exception) == (
+        "remove() argument must be xml.etree.ElementTree.Element, not " + type_name
+    )
+
+
+def test_element_frozen_attrib_identity_bounded():
+    class Frozen(frozendict):
+        def __getitem__(self, key):
+            raise AssertionError("Element.get must use the stored entries")
+
+        def keys(self):
+            raise AssertionError("Element.keys must use the stored entries")
+
+        def items(self):
+            raise AssertionError("Element.items must use the stored entries")
+
+    for mapping in (frozendict(), frozendict(a=1), Frozen(a=1)):
+        element = Element("root")
+        element.attrib = mapping
+        assert element.attrib is mapping
+        assert element.get("a", 7) == (1 if mapping else 7)
+        assert element.get("missing", 7) == 7
+        assert element.keys() == (["a"] if mapping else [])
+        assert element.items() == ([("a", 1)] if mapping else [])
+        with assert_raises(AttributeError):
+            del element.attrib
+        assert element.attrib is mapping
+        element.clear()
+        assert type(element.attrib) is dict and element.attrib == {}
+        element.set("new", 2)
+        assert element.attrib == {"new": 2}
+        assert dict(mapping) == ({"a": 1} if mapping else {})
+
+
+def test_element_frozen_attrib_mutation_bounded():
+    class Key:
+        def __hash__(self):
+            raise AssertionError("frozen assignment must fail before hashing")
+
+    element = Element("root")
+    mapping = frozendict(a=1)
+    element.attrib = mapping
+    for key in ("a", "new", Key()):
+        with assert_raises(TypeError) as caught:
+            element.set(key, 2)
+        assert str(caught.exception) == (
+            "frozendict object does not support item assignment"
+        )
+        assert element.attrib is mapping and mapping == {"a": 1}
+
+
+def test_element_frozen_attrib_copy_state_bounded():
+    import copy
+
+    for mapping in (frozendict(), frozendict(a=[1])):
+        element = Element("root")
+        element.attrib = mapping
+        shallow = copy.copy(element)
+        assert shallow is not element and shallow.attrib is mapping
+        deep = copy.deepcopy(element)
+        assert deep is not element
+        assert type(deep.attrib) is frozendict and deep.attrib == mapping
+        if mapping:
+            assert deep.attrib["a"] is not mapping["a"]
+            deep.attrib["a"].append(2)
+            assert mapping["a"] == [1]
+        state = element.__getstate__()
+        assert state["attrib"] is mapping
+        restored = Element("restored")
+        restored.__setstate__(state)
+        assert restored.attrib is mapping
+
+
+test_element_frozen_attrib_identity_bounded()
+test_element_frozen_attrib_mutation_bounded()
+test_element_frozen_attrib_copy_state_bounded()
diff --git a/extra_tests/snippets/stdlib_zoneinfo.py b/extra_tests/snippets/stdlib_zoneinfo.py
new file mode 100644
index 00000000000..c8004585f81
--- /dev/null
+++ b/extra_tests/snippets/stdlib_zoneinfo.py
@@ -0,0 +1,19 @@
+import io
+import struct
+from zoneinfo import ZoneInfo
+
+from testutils import assert_raises
+
+# Minimal TZif v3 data with no transitions and a POSIX rule in the footer.
+header = (b"TZif3" + b"\0" * 15 + struct.pack(">6l", 0, 0, 0, 0, 0, 0)) * 2
+
+
+def zone_from_rule(rule):
+    return ZoneInfo.from_file(io.BytesIO(header + b"\n" + rule + b"\n"))
+
+
+for rule in (b"<>5", b"AAA4<>,M3.2.0/2,M11.1.0/3"):
+    assert_raises(ValueError, zone_from_rule, rule)
+
+# Quoting still permits nonempty numeric abbreviations.
+assert zone_from_rule(b"<+05>-5").tzname(None) == "+05"
diff --git a/extra_tests/snippets/syntax_annotations.py b/extra_tests/snippets/syntax_annotations.py
index 0f78bdc2be1..b6859a89b3f 100644
--- a/extra_tests/snippets/syntax_annotations.py
+++ b/extra_tests/snippets/syntax_annotations.py
@@ -1,5 +1,18 @@
 from typing import get_type_hints
 
+# Future f-string annotations canonicalize fields, not their literal padding.
+for formatted, expected in (
+    ("f'{ value }'", "f'{value}'"),
+    ("f'{ value = }'", "f' value = {value!r}'"),
+    ("f'{ value : >8}'", "f'{value: >8}'"),
+    ("f'{ {1, 2} }'", "f'{ {1, 2}}'"),
+):
+    formatted_code = compile(
+        "from __future__ import annotations\nx: " + formatted, "<test>", "exec"
+    )
+    assert expected in formatted_code.co_consts
+
+
 def func(s: str) -> int:
     return int(s)
 
@@ -8,3 +21,15 @@ def func(s: str) -> int:
 # The order of type hints matters for certain functions
 # e.g. functools.singledispatch
 assert list(hints.items()) == [('s', str), ('return', int)]
+
+
+# Template format specs use canonical expression text inside future annotations.
+for template, expected in (
+    ("t'{value:04}'", "t'{value:04}'"),
+    ("t'{value:{(width)}}'", "t'{value:{width}}'"),
+    ("t'{(value):{(width)!r}}'", "t'{(value):{width!r}}'"),
+):
+    annotation_code = compile(
+        "from __future__ import annotations\nx: " + template, "<test>", "exec"
+    )
+    assert expected in annotation_code.co_consts
diff --git a/extra_tests/snippets/syntax_doc.py b/extra_tests/snippets/syntax_doc.py
index bdfc1fe7788..37aebb43dbd 100644
--- a/extra_tests/snippets/syntax_doc.py
+++ b/extra_tests/snippets/syntax_doc.py
@@ -13,3 +13,77 @@ def f2():
     """
 
 assert f2.__doc__ == '\nx\n    y\n'
+
+
+# Regression test: a module docstring must be stored through module name
+# resolution, so a nested `global __doc__` declaration makes the module body
+# emit STORE_GLOBAL (writing module globals) instead of STORE_NAME (writing
+# the provided locals mapping). Mirrors CPython codegen_nameop behavior.
+
+import dis
+
+
+def opnames(code):
+    return [instr.opname for instr in dis.get_instructions(code)]
+
+
+def run_split(src, optimize=0):
+    code = compile(src, "<test>", "exec", optimize=optimize)
+    g, loc = {}, {}
+    exec(code, g, loc)
+    return code, g, loc
+
+
+# A nested function declaring `global __doc__` makes the module docstring
+# store target module globals.
+src_global = '"module doc"\ndef f():\n    global __doc__\n'
+code, g, loc = run_split(src_global)
+ops = opnames(code)
+assert "STORE_GLOBAL" in ops, ops
+assert "STORE_NAME" not in ops or "__doc__" not in [
+    instr.argval for instr in dis.get_instructions(code) if instr.opname == "STORE_NAME"
+], ops
+assert g.get("__doc__") == "module doc", g
+assert "__doc__" not in loc, loc
+
+# The declaration may be nested more than one scope deep.
+src_deep = '"module doc"\ndef f():\n    def g():\n        global __doc__\n'
+code, g, loc = run_split(src_deep)
+assert "STORE_GLOBAL" in opnames(code), opnames(code)
+assert g.get("__doc__") == "module doc", g
+assert "__doc__" not in loc, loc
+
+# Control: without a nested global declaration the docstring stays a
+# STORE_NAME and lands in the provided locals mapping.
+src_plain = '"module doc"\nx = 1\n'
+code, g, loc = run_split(src_plain)
+doc_stores = [
+    instr.opname
+    for instr in dis.get_instructions(code)
+    if instr.argval == "__doc__" and instr.opname.startswith("STORE_")
+]
+assert doc_stores == ["STORE_NAME"], doc_stores
+assert loc.get("__doc__") == "module doc", loc
+assert "__doc__" not in g, g
+
+# optimize=1 keeps the docstring and the same global resolution.
+code, g, loc = run_split(src_global, optimize=1)
+assert "STORE_GLOBAL" in opnames(code), opnames(code)
+assert g.get("__doc__") == "module doc", g
+
+# optimize=2 strips the docstring entirely: no __doc__ store in either dict.
+code, g, loc = run_split(src_global, optimize=2)
+assert not any(
+    instr.argval == "__doc__" and instr.opname.startswith("STORE_")
+    for instr in dis.get_instructions(code)
+), opnames(code)
+assert "__doc__" not in g and "__doc__" not in loc, (g, loc)
+
+# A class docstring still belongs to the class namespace even when a nested
+# scope declares `global __doc__`.
+src_class = '"module doc"\ndef f():\n    global __doc__\nclass C:\n    "class doc"\n'
+g, loc = {}, {}
+exec(compile(src_class, "<test>", "exec"), g, loc)
+assert g.get("__doc__") == "module doc", g
+assert loc["C"].__doc__ == "class doc", loc["C"].__doc__
+assert "__doc__" not in loc, loc
diff --git a/extra_tests/snippets/syntax_function_args.py b/extra_tests/snippets/syntax_function_args.py
index eb4f94b8a36..6fd39c951e7 100644
--- a/extra_tests/snippets/syntax_function_args.py
+++ b/extra_tests/snippets/syntax_function_args.py
@@ -1,6 +1,90 @@
 from testutils import assert_raises
 
 
+def error(call, expected):
+    try:
+        call()
+    except TypeError as exc:
+        assert str(exc) == expected, (str(exc), expected)
+    else:
+        raise AssertionError("expected TypeError")
+
+
+error(lambda: id(obj=1), "id() takes no keyword arguments")
+error(lambda: id(**{"obj": 1}), "id() takes no keyword arguments")
+error(lambda: id(1, 2, obj=1), "id() takes no keyword arguments")
+error(lambda: list.append(x=1), "unbound method list.append() needs an argument")
+error(lambda: list.append(**{"x": 1}), "unbound method list.append() needs an argument")
+error(
+    lambda: list.append(1, x=1),
+    "descriptor 'append' for 'list' objects doesn't apply to a 'int' object",
+)
+error(lambda: list.append([], x=1), "list.append() takes no keyword arguments")
+error(lambda: list.append([], **{"x": 1}), "list.append() takes no keyword arguments")
+error(lambda: [].append(x=1), "list.append() takes no keyword arguments")
+error(lambda: [].clear(1, x=1), "list.clear() takes no keyword arguments")
+
+
+class Index:
+    def __index__(self):
+        raise AssertionError("conversion ran before keyword check")
+
+
+error(lambda: bin(Index(), x=1), "bin() takes no keyword arguments")
+assert id(1, **{}) == id(1)
+assert round(1.25, ndigits=1) == 1.2
+assert pow(2, exp=3) == 8
+assert sorted([2, 1], reverse=True) == [2, 1]
+assert sum([1, 2], start=4) == 7
+values = []
+list.append(values, 1)
+values.append(2)
+assert values == [1, 2]
+list.clear(values)
+assert values == []
+
+# Keyword metadata must forward raw arguments without changing body validation.
+for choose in (min, max):
+    assert choose([], default=42) == 42
+    assert choose([1, 2], key=lambda value: -value) == (2 if choose is min else 1)
+    try:
+        choose(bogus=1)
+    except TypeError as exc:
+        assert str(exc) == f"{choose.__name__} expected at least 1 argument, got 0"
+    else:
+        raise AssertionError("missing positional argument was accepted")
+    try:
+        choose(1, 2, default=0)
+    except TypeError as exc:
+        assert str(exc) == (
+            f"Cannot specify a default for {choose.__name__}() "
+            "with multiple positional arguments"
+        )
+    else:
+        raise AssertionError("default with multiple arguments was accepted")
+
+# Named fields in argument structs must override positional-only arguments.
+assert eval("value", globals={"value": 42}) == 42
+namespace = {}
+exec("value = 42", globals=namespace)
+assert namespace["value"] == 42
+assert compile(source="42", filename="<inference>", mode="eval")
+assert __import__(name="sys").__name__ == "sys"
+
+from io import StringIO
+
+output = StringIO()
+print(1, 2, sep=":", end="!", file=output)
+assert output.getvalue() == "1:2!"
+
+# Methods using a keyword-only argument struct must keep accepting keywords.
+values = [1, 2]
+values.sort(reverse=True)
+assert values == [2, 1]
+
+# Definitions built without the macros infer their calling convention too.
+assert int.__new__(int, "11", base=2) == 3
+
 def sum(x, y):
     return x+y
 
@@ -129,3 +213,50 @@ def f(a, b, /, c, d, *, e, f):
     f(1,2,3,4,5,f=6)
 with assert_raises(TypeError):
     f(1,2,3,4,5,6)
+
+
+def test_keyword_dict_stored_hashes():
+    class Keyword(str):
+        def __hash__(self):
+            assert not getattr(self, "hashed", False), "keyword was rehashed"
+            self.hashed = True
+            return str.__hash__(self)
+
+    def accept(*, value):
+        return value
+
+    source = {Keyword("value"): 42}
+    assert accept(**source) == 42
+    with assert_raises(TypeError) as raised:
+        accept(value=1, **source)
+    assert str(raised.exception).endswith(
+        "got multiple values for keyword argument 'value'"
+    )
+
+    class NonString:
+        def __hash__(self):
+            assert not getattr(self, "hashed", False), "non-string key was rehashed"
+            self.hashed = True
+            return 0
+
+    source = {NonString(): 42}
+    with assert_raises(TypeError) as raised:
+        accept(**source)
+    assert str(raised.exception) == "keywords must be strings"
+
+    failure = RuntimeError("keyword comparison failed")
+
+    class BadEquality(str):
+        __hash__ = str.__hash__
+
+        def __eq__(self, other):
+            raise failure
+
+    left = {BadEquality("value"): 1}
+    right = {BadEquality("value"): 2}
+    with assert_raises(RuntimeError) as raised:
+        accept(**left, **right)
+    assert raised.exception is failure
+
+
+test_keyword_dict_stored_hashes()
diff --git a/extra_tests/snippets/syntax_invalid.py b/extra_tests/snippets/syntax_invalid.py
index 37a3805a295..00acf6cfb16 100644
--- a/extra_tests/snippets/syntax_invalid.py
+++ b/extra_tests/snippets/syntax_invalid.py
@@ -77,3 +77,46 @@ def valid_func():
 from __future__ import print_function
 """
 compile(src, 'test.py', 'exec')
+
+
+# CPython reports the unparenthesized `except ... as` error with a range that starts at the
+# first exception type and stops just before the `:` closing the clause. `end_offset` is an
+# exclusive 1-based *character* column, so that end lands on the column the `:` sits on.
+#
+# The cases below pin the parts that are easy to get wrong: the column counts characters
+# rather than UTF-8 bytes, and an explicit line join may sit anywhere between the exception
+# types and the `:`. Values verified against CPython 3.14.
+except_as_ranges = [
+    # (clause, (lineno, offset), (end_lineno, end_offset))
+    ("except A, B as e:", (3, 8), (3, 17)),
+    ("except A, B as e :", (3, 8), (3, 18)),
+    ("except A, B as e   :", (3, 8), (3, 20)),
+    ("except A, B as e\t:", (3, 8), (3, 18)),
+    ("except A, B, C as blech:", (3, 8), (3, 24)),
+    ("except* A, B, C as e:", (3, 9), (3, 21)),
+    # A non-ASCII name must not push the column right by its extra UTF-8 bytes.
+    ("except Ä, B as e:", (3, 8), (3, 17)),
+    ("except 사과, B as e:", (3, 8), (3, 18)),
+    ("except A, B as 오:", (3, 8), (3, 17)),
+    # An explicit line join may precede or follow `as`, or close the clause on its own line.
+    ("except A, B as exc\\\n    :", (3, 8), (4, 5)),
+    ("except A, B \\\nas exc:", (3, 8), (4, 7)),
+    ("except A, \\\nB as exc:", (3, 8), (4, 9)),
+    ("except A, B as \\\nexc:", (3, 8), (4, 4)),
+]
+
+for clause, start, end in except_as_ranges:
+    src = "try:\n    pass\n%s\n    pass\n" % clause
+    with assert_raises(SyntaxError) as ae:
+        compile(src, "test.py", "exec")
+    exc = ae.exception
+    assert exc.msg == "multiple exception types must be parenthesized when using 'as'", (
+        clause,
+        exc.msg,
+    )
+    assert (exc.lineno, exc.offset) == start, (clause, (exc.lineno, exc.offset), start)
+    assert (exc.end_lineno, exc.end_offset) == end, (
+        clause,
+        (exc.end_lineno, exc.end_offset),
+        end,
+    )
diff --git a/extra_tests/snippets/vm_frame_locals.py b/extra_tests/snippets/vm_frame_locals.py
index 608167c2a17..4313b07dbda 100644
--- a/extra_tests/snippets/vm_frame_locals.py
+++ b/extra_tests/snippets/vm_frame_locals.py
@@ -230,6 +230,33 @@ def frame_with_overwritten_fast_local():
         frame.clear()
         self.assertEqual(len(events), 1)
 
+    def test_closed_coroutine_state_is_visible_to_frame_local_finalizers(self):
+        events = []
+
+        class ReentrantFinalizer:
+            def __del__(self):
+                events.append(getattr(owner, state_attribute))
+
+        async def coroutine(value):
+            return value
+
+        async def async_generator(value):
+            yield value
+
+        for factory, state_attribute, closed in (
+            (coroutine, "cr_state", "CORO_CLOSED"),
+            (async_generator, "ag_state", "AGEN_CLOSED"),
+        ):
+            with self.subTest(state_attribute=state_attribute):
+                events.clear()
+                owner = factory(ReentrantFinalizer())
+                if state_attribute == "cr_state":
+                    owner.close()
+                else:
+                    with self.assertRaises(StopIteration):
+                        owner.aclose().send(None)
+                self.assertEqual(events, [closed])
+
     def test_unoptimized_frame_locals_are_readable_from_another_thread(self):
         ready = threading.Event()
         release = threading.Event()
diff --git a/extra_tests/snippets/vm_specialization.py b/extra_tests/snippets/vm_specialization.py
index b1d201e8ac1..99b7af51780 100644
--- a/extra_tests/snippets/vm_specialization.py
+++ b/extra_tests/snippets/vm_specialization.py
@@ -342,3 +342,50 @@ def read():
 
 
 module_attribute_custom_dict_key()
+
+
+## STORE_SUBSCR_LIST_INT: the replaced element's finalizer can read the list
+
+
+def store_subscr_list_int_finalizer_reads_list():
+    target = [None]
+    seen = []
+
+    class Item:
+        def __init__(self, value):
+            self.value = value
+
+        def __del__(self):
+            seen.append((self.value, len(target), target[0] is self))
+
+    def store(value):
+        target[0] = value
+
+    for i in range(300):
+        store(Item(i))
+    assert any(
+        op.opname == "STORE_SUBSCR_LIST_INT"
+        for op in dis.get_instructions(store, adaptive=True)
+    )
+    store(None)
+    assert seen == [(i, 1, False) for i in range(300)]
+
+
+store_subscr_list_int_finalizer_reads_list()
+
+
+def store_attr_uses_setter_without_getter():
+    class IntegerField:
+        def __set__(self, obj, value):
+            obj.__dict__["value"] = int(value)
+
+    class Model:
+        value = IntegerField()
+
+    obj = Model()
+    for _ in range(300):
+        obj.value = "42"
+    assert obj.value == 42
+
+
+store_attr_uses_setter_without_getter()
diff --git a/scripts/libc_posix.py b/scripts/libc_posix.py
index 82f3eb96d83..1392352442f 100644
--- a/scripts/libc_posix.py
+++ b/scripts/libc_posix.py
@@ -8,7 +8,7 @@
 
 import tomllib
 
-CPYTHON_VERSION = "3.14"
+CPYTHON_VERSION = "3.15"
 
 CONSTS_PATTERN = re.compile(r"\b_*[A-Z]+(?:_+[A-Z]+)*_*\b")
 
diff --git a/scripts/update_lib/__main__.py b/scripts/update_lib/__main__.py
index 49399db6f43..7eb91970f2f 100644
--- a/scripts/update_lib/__main__.py
+++ b/scripts/update_lib/__main__.py
@@ -8,6 +8,7 @@
     python scripts/update_lib migrate cpython/Lib/test/test_foo.py
     python scripts/update_lib patches --from Lib/test/foo.py --to cpython/Lib/test/foo.py
     python scripts/update_lib auto-mark Lib/test/test_foo.py
+    python scripts/update_lib copy-test SOURCE DESTINATION --test ClassName.method_name --source-sha256 HASH --destination-sha256 HASH
 """
 
 import argparse
@@ -49,6 +50,11 @@ def main(argv: list[str] | None = None) -> int:
         help="Copy library file/directory from CPython (delete existing first)",
         add_help=False,
     )
+    subparsers.add_parser(
+        "copy-test",
+        help="Copy one complete canonical test from hash-pinned inputs",
+        add_help=False,
+    )
     subparsers.add_parser(
         "deps",
         help="Show dependency information for a module",
@@ -72,6 +78,11 @@ def main(argv: list[str] | None = None) -> int:
 
         return copy_lib_main(remaining)
 
+    if args.command == "copy-test":
+        from update_lib.cmd_copy_test import main as copy_test_main
+
+        return copy_test_main(remaining)
+
     if args.command == "migrate":
         from update_lib.cmd_migrate import main as migrate_main
 
diff --git a/scripts/update_lib/cmd_copy_lib.py b/scripts/update_lib/cmd_copy_lib.py
index 1b16497fc83..848ee9213c2 100644
--- a/scripts/update_lib/cmd_copy_lib.py
+++ b/scripts/update_lib/cmd_copy_lib.py
@@ -16,6 +16,14 @@
 import sys
 
 
+def _ignore_bytecode_caches(directory: str, names: list[str]) -> set[str]:
+    return {
+        name
+        for name in names
+        if name == "__pycache__" and (pathlib.Path(directory) / name).is_dir()
+    }
+
+
 def _copy_single(
     src_path: pathlib.Path,
     lib_path: pathlib.Path,
@@ -38,7 +46,7 @@ def _copy_single(
         if verbose:
             print(f"Copying directory: {src_path} -> {lib_path}")
         lib_path.parent.mkdir(parents=True, exist_ok=True)
-        shutil.copytree(src_path, lib_path)
+        shutil.copytree(src_path, lib_path, ignore=_ignore_bytecode_caches)
     else:
         if verbose:
             print(f"Copying file: {src_path} -> {lib_path}")
@@ -66,6 +74,14 @@ def copy_lib(
     path_str = str(src_path).replace("\\", "/")
     if "/Lib/" not in path_str:
         raise ValueError(f"Path must contain '/Lib/' (got: {src_path})")
+    if not src_path.exists():
+        raise FileNotFoundError(f"Source path does not exist: {src_path}")
+
+    # Data files name an exact asset, not the containing top-level module.
+    # Expanding Lib/test/data.txt as "test" would replace the entire test tree.
+    if src_path.is_file() and src_path.suffix != ".py":
+        _copy_single(src_path, parse_lib_path(src_path), verbose)
+        return
 
     cpython_prefix, after_lib = path_str.split("/Lib/", 1)
     # Get module name (first component, without .py)
diff --git a/scripts/update_lib/cmd_copy_test.py b/scripts/update_lib/cmd_copy_test.py
new file mode 100644
index 00000000000..5e14959bb02
--- /dev/null
+++ b/scripts/update_lib/cmd_copy_test.py
@@ -0,0 +1,134 @@
+"""Copy one complete canonical test definition without refreshing its module."""
+
+import argparse
+import ast
+import hashlib
+import json
+from pathlib import Path
+
+from update_lib.patch_spec import _iter_class_methods, _iter_module_classes
+
+
+def _definition(contents: str, qualified_name: str):
+    parts = qualified_name.split(".")
+    if len(parts) != 2 or not all(part.isidentifier() for part in parts):
+        raise ValueError("test name must be ClassName.method_name")
+    tree = ast.parse(contents)
+    classes = [node for node in _iter_module_classes(tree) if node.name == parts[0]]
+    if len(classes) != 1:
+        raise ValueError(f"Expected one class named {parts[0]}, found {len(classes)}")
+    methods = [
+        node for node in _iter_class_methods(classes[0]) if node.name == parts[1]
+    ]
+    if len(methods) != 1:
+        raise ValueError(
+            f"Expected one method named {qualified_name}, found {len(methods)}"
+        )
+    method = methods[0]
+    parents = {
+        child: parent
+        for parent in ast.walk(tree)
+        for child in ast.iter_child_nodes(parent)
+    }
+    guards = []
+    child = method
+    while child in parents:
+        parent = parents[child]
+        if isinstance(parent, ast.If):
+            branch = "body" if child in parent.body else "orelse"
+            guards.append((ast.dump(parent.test), branch))
+        elif not isinstance(parent, (ast.Module, ast.ClassDef)):
+            raise ValueError("Only module/class scopes and if guards are supported")
+        child = parent
+    start = min([method.lineno, *(node.lineno for node in method.decorator_list)]) - 1
+    return method, guards, start, method.end_lineno
+
+
+def copy_test(source: str, destination: str, qualified_name: str) -> str:
+    """Replace an unambiguous whole definition, preserving all surrounding bytes.
+
+    Guard, signature, decorator and indentation differences require a broader
+    migration rather than silently changing the selected test's execution context.
+    """
+    src, src_guards, src_start, src_end = _definition(source, qualified_name)
+    dst, dst_guards, dst_start, dst_end = _definition(destination, qualified_name)
+    if src_guards != dst_guards:
+        raise ValueError("Source and destination test guards differ")
+
+    def signature(node):
+        return (
+            ast.dump(node.args),
+            ast.dump(node.returns) if node.returns is not None else None,
+            [ast.dump(param) for param in getattr(node, "type_params", [])],
+        )
+
+    if type(src) is not type(dst) or signature(src) != signature(dst):
+        raise ValueError("Source and destination test signatures differ")
+    if [ast.dump(node) for node in src.decorator_list] != [
+        ast.dump(node) for node in dst.decorator_list
+    ]:
+        raise ValueError(
+            "Source and destination decorators differ; preserve markers explicitly"
+        )
+    if src.col_offset != dst.col_offset:
+        raise ValueError("Source and destination indentation differs")
+    source_lines = source.splitlines(keepends=True)
+    destination_lines = destination.splitlines(keepends=True)
+    # AST equality omits comments, including project marker rationales. Require
+    # the complete decorator block to match before replacing the definition.
+    if (
+        source_lines[src_start : src.lineno - 1]
+        != destination_lines[dst_start : dst.lineno - 1]
+    ):
+        raise ValueError(
+            "Source and destination decorator text differs; preserve markers explicitly"
+        )
+    definition = source_lines[src_start:src_end]
+    result = "".join(
+        destination_lines[:dst_start] + definition + destination_lines[dst_end:]
+    )
+    _, _, result_start, result_end = _definition(result, qualified_name)
+    if result.splitlines(keepends=True)[result_start:result_end] != definition:
+        raise ValueError("Copied definition is not byte-identical to the source")
+    return result
+
+
+def main(argv: list[str] | None = None) -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("source", type=Path)
+    parser.add_argument("destination", type=Path)
+    parser.add_argument("--test", required=True, help="Exact ClassName.method_name")
+    parser.add_argument("--source-sha256", required=True)
+    parser.add_argument("--destination-sha256", required=True)
+    args = parser.parse_args(argv)
+    try:
+        source = args.source.read_bytes()
+        destination = args.destination.read_bytes()
+        for label, contents, expected in (
+            ("source", source, args.source_sha256),
+            ("destination", destination, args.destination_sha256),
+        ):
+            if hashlib.sha256(contents).hexdigest() != expected:
+                raise ValueError(f"{label} SHA256 does not match the pinned input")
+        result = copy_test(
+            source.decode("utf-8"), destination.decode("utf-8"), args.test
+        ).encode("utf-8")
+        # Recheck the destination immediately before writing so stale invocations
+        # fail instead of overwriting an intervening edit.
+        if args.destination.read_bytes() != destination:
+            raise ValueError("Destination changed during test preparation")
+        args.destination.write_bytes(result)
+    except (OSError, UnicodeError, SyntaxError, ValueError) as exc:
+        parser.exit(1, f"Error: {exc}\n")
+    print(
+        json.dumps(
+            {
+                "test": args.test,
+                "source_sha256": args.source_sha256,
+                "destination_before_sha256": args.destination_sha256,
+                "destination_after_sha256": hashlib.sha256(result).hexdigest(),
+            },
+            sort_keys=True,
+        )
+    )
+    return 0
diff --git a/scripts/update_lib/cmd_migrate.py b/scripts/update_lib/cmd_migrate.py
index 97cdf7b141b..f2db1bf0cf3 100644
--- a/scripts/update_lib/cmd_migrate.py
+++ b/scripts/update_lib/cmd_migrate.py
@@ -4,6 +4,21 @@
 
 Usage:
     python scripts/update_lib migrate cpython/Lib/test/test_foo.py
+    python scripts/update_lib migrate cpython/Lib/test/test_foo.py --patches remaining.json
+    python scripts/update_lib migrate cpython/Lib/test/test_foo --canonical-removals removals.json --dry-run
+
+Remaining metadata names the exact repository-relative target and its existing
+decorator patches. An optional "doctests" object selects existing guarded inputs
+by exact source text, mapping each to a single-line reason. Guarded doctests need
+this explicit selection; an empty object retires all their guards. Canonical
+expected output is never copied from the old file.
+
+Canonical removals are a separate, explicit operation. JSON source metadata
+pins path (Lib/test/test_*), commit and tree; removals maps explicit relative
+filenames to sha256 and upstream_commit. The caller must first verify and
+review historical provenance, including release-branch evidence. This command
+checks pinned canonical absence and exact local bytes; it does not authenticate
+historical evidence. --dry-run performs all validation without deleting files.
 
 This will:
     1. Extract patches from Lib/test/test_foo.py (if exists)
@@ -12,18 +27,805 @@
 """
 
 import argparse
+import ast
+import builtins
+import collections
+import copy
+import hashlib
+import json
+import os
 import pathlib
+import re
 import shutil
+import subprocess
 import sys
+import textwrap
 
 sys.path.insert(0, str(pathlib.Path(__file__).parent.parent))
 
 from update_lib.file_utils import parse_lib_path
 
+SYSCONFIG_UPSTREAM = "def _get_implementation():\n    return 'Python'\n"
+SYSCONFIG_LOCAL = (
+    "def _get_implementation():\n"
+    "    return 'RustPython'  # XXX: RUSTPYTHON; For site-packages\n"
+)
+JIT_ERROR = """# NOTE: RUSTPYTHON exceptions
+try:
+    JitError
+except NameError:
+    pass
+else:
+    PYTHON2_EXCEPTIONS += ("JitError",)
+
+"""
+EXCEPTION_LOOP = """for excname in PYTHON2_EXCEPTIONS:
+    NAME_MAPPING[("exceptions", excname)] = ("builtins", excname)
+"""
+MULTIPHASE_UPSTREAM = (
+    "# gh-116303: Skip test module dependent tests if test modules are unavailable\n"
+    'import_helper.import_module("_testmultiphase")\n'
+)
+MULTIPHASE_LOCAL = """try: # TODO: RUSTPYTHON
+    import_helper.import_module("_testmultiphase")
+except unittest.SkipTest:
+    _testmultiphase = None
+"""
+LOCK_SPECIALIZATION = """(Frozen_LifetimeTests,
+ Source_LifetimeTests
+ ) = test_util.test_both(LifetimeTests, init=init)
+"""
+LOCK_SKIP = """# TODO: RUSTPYTHON; dead weakref module locks not cleaned up in frozen bootstrap
+Frozen_LifetimeTests.test_all_locks = unittest.skip("TODO: RUSTPYTHON")(
+    Frozen_LifetimeTests.test_all_locks
+)
+"""
+TYPES_DATETIME_GUARD = """# XXX: RUSTPYTHON
+try:
+    import _datetime
+except ImportError:
+    _datetime = None
+"""
+TYPES_UNITTEST_IMPORT = (
+    "import unittest  # XXX: RUSTPYTHON; importing to be able to skip tests\n"
+)
+BYTES_CAPI_UPSTREAM = (
+    "    _testlimitedcapi = import_helper.import_module('_testlimitedcapi')\n"
+)
+BYTES_CAPI_LOCAL = """    # TODO: RUSTPYTHON; import_helper.import_module here cause the entire test stopping
+    # _testlimitedcapi = import_helper.import_module('_testlimitedcapi')
+    try:
+        import _testlimitedcapi
+    except ImportError:
+        _testlimitedcapi = None
+"""
+BYTES_ALLOCATION_COMMENTS = {
+    "test_alloc": """    # NOTE: RUSTPYTHON:
+    #
+    # The second instance of self.assertGreater was replaced with
+    # self.assertGreaterEqual since, in RustPython, the underlying storage
+    # is a Vec which doesn't require trailing null byte.
+""",
+    "test_init_alloc": """    # NOTE: RUSTPYTHON:
+    #
+    # The usages of self.assertGreater were replaced with
+    # self.assertGreaterEqual since, in RustPython, the underlying storage
+    # is a Vec which doesn't require trailing null byte.
+""",
+}
+
+
+def _bytes_bindings(root, name):
+    """Find bindings conservatively, including nested or indirect shadows."""
+    for node in ast.walk(root):
+        if isinstance(node, ast.Name) and isinstance(node.ctx, (ast.Store, ast.Del)):
+            bound = node.id
+        elif isinstance(node, ast.alias):
+            bound = node.asname or node.name.split(".")[0]
+        elif isinstance(
+            node,
+            (
+                ast.FunctionDef,
+                ast.AsyncFunctionDef,
+                ast.ClassDef,
+                ast.ExceptHandler,
+                ast.MatchAs,
+                ast.MatchStar,
+            ),
+        ):
+            bound = node.name
+        elif isinstance(node, ast.MatchMapping):
+            bound = node.rest
+        elif isinstance(node, ast.arg):
+            bound = node.arg
+        elif isinstance(node, (ast.Global, ast.Nonlocal)):
+            bound = name if name in node.names else None
+        else:
+            continue
+        if bound == name:
+            yield node
+
+
+def _bytes_owner(contents):
+    tree = ast.parse(contents)
+    owner = _unique_anchor(
+        contents,
+        tree,
+        lambda node: isinstance(node, ast.ClassDef) and node.name == "ByteArrayTest",
+        direct=True,
+    )
+    if list(_bytes_bindings(tree, "ByteArrayTest")) != [owner]:
+        raise ValueError("Shadowed bytes test class")
+    return owner
+
+
+def _verify_bytes_capi(contents: str, block: str) -> ast.stmt:
+    owner = _bytes_owner(contents)
+    expected = ast.parse(textwrap.dedent(block)).body[0]
+    anchor = _unique_anchor(
+        contents, owner, lambda node: ast.dump(node) == ast.dump(expected), direct=True
+    )
+    allowed = set(ast.walk(anchor))
+    if any(node not in allowed for node in _bytes_bindings(owner, "_testlimitedcapi")):
+        raise ValueError("Shadowed optional bytes C API import")
+    start = anchor.lineno - 1 - (2 if block == BYTES_CAPI_LOCAL else 0)
+    anchored_text = "".join(
+        contents.splitlines(keepends=True)[start : anchor.end_lineno]
+    )
+    if start < 0 or anchored_text != block:
+        raise ValueError("Missing, changed, or ambiguous optional bytes C API import")
+    return anchor
+
+
+def _preserve_bytes_allocations(old: str, new: str) -> str:
+    """Keep only the existing three Vec allocation assertion adaptations."""
+    owners = [_bytes_owner(contents) for contents in (old, new)]
+    replacements = []
+    for name, count in (("test_alloc", 1), ("test_init_alloc", 2)):
+        methods = [
+            _unique_anchor(
+                contents,
+                owner,
+                lambda node: (
+                    isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+                    and node.name == name
+                ),
+                direct=True,
+            )
+            for contents, owner in zip((old, new), owners)
+        ]
+        if any(
+            list(_bytes_bindings(owner, name)) != [method]
+            for owner, method in zip(owners, methods)
+        ):
+            raise ValueError("Shadowed bytes allocation test")
+        if any(not isinstance(method, ast.FunctionDef) for method in methods):
+            raise ValueError("Changed bytes allocation test kind")
+        normalized = copy.deepcopy(methods[0])
+        expected = ast.parse("self.assertGreaterEqual(alloc, len(b))", mode="eval").body
+        matches = [
+            node
+            for node in ast.walk(normalized)
+            if isinstance(node, ast.Call) and ast.dump(node) == ast.dump(expected)
+        ]
+        if len(matches) != count:
+            raise ValueError("Changed local bytes allocation contract")
+        for node in matches:
+            node.func.attr = "assertGreater"
+        if ast.dump(normalized) != ast.dump(methods[1]):
+            raise ValueError("Changed canonical bytes allocation contract")
+        old_lines = old.splitlines(keepends=True)
+        comment = BYTES_ALLOCATION_COMMENTS[name]
+        start = methods[0].lineno - 1 - len(comment.splitlines())
+        if start < 0 or "".join(old_lines[start : methods[0].lineno - 1]) != comment:
+            raise ValueError("Changed local bytes allocation explanation")
+        local = "".join(old_lines[start : methods[0].end_lineno])
+        replacements.append((methods[1].lineno - 1, methods[1].end_lineno, local))
+    lines = new.splitlines(keepends=True)
+    for start, end, local in sorted(replacements, reverse=True):
+        lines[start:end] = [local]
+    result = "".join(lines)
+    ast.parse(result)
+    return result
+
+
+def _unique_anchor(contents, root, predicate, *, direct=False, exact=None):
+    """Select one real AST anchor, optionally in the immediate owner body."""
+    matches = [node for node in ast.walk(root) if predicate(node)]
+    if (
+        len(matches) != 1
+        or (direct and matches[0] not in root.body)
+        or (exact is not None and ast.get_source_segment(contents, matches[0]) != exact)
+    ):
+        raise ValueError("Missing, changed, or ambiguous migration anchor")
+    return matches[0]
+
+
+def _unique_function(contents: str, expected: str) -> bool:
+    tree = ast.parse(contents)
+    target = ast.parse(expected).body[0]
+    node = _unique_anchor(
+        contents,
+        tree,
+        lambda node: (
+            isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+            and node.name == target.name
+        ),
+        direct=True,
+    )
+    return ast.dump(node) == ast.dump(target) and not any(
+        (
+            isinstance(node, ast.Name)
+            and node.id == target.name
+            and isinstance(node.ctx, (ast.Store, ast.Del))
+        )
+        or (isinstance(node, ast.ClassDef) and node.name == target.name)
+        or (
+            isinstance(node, ast.alias)
+            and (node.asname or node.name.split(".")[0]) == target.name
+        )
+        for node in ast.walk(tree)
+    )
+
+
+def _exception_loop(contents: str) -> bool:
+    _unique_anchor(
+        contents,
+        ast.parse(contents),
+        lambda node: (
+            isinstance(node, ast.For)
+            and isinstance(node.iter, ast.Name)
+            and node.iter.id == "PYTHON2_EXCEPTIONS"
+        ),
+        direct=True,
+        exact=EXCEPTION_LOOP.rstrip(),
+    )
+    return True
+
+
+def _jit_block(contents: str) -> bool:
+    tree = ast.parse(contents)
+    expected = ast.dump(ast.parse(JIT_ERROR).body[0])
+    _unique_anchor(contents, tree, lambda node: ast.dump(node) == expected, direct=True)
+    return (
+        sum(
+            isinstance(node, ast.Name) and node.id == "JitError"
+            for node in ast.walk(tree)
+        )
+        == 1
+    )
+
+
+def _preserve_top_level_block(old, new, upstream, local):
+    """Require exact, consecutive top-level AST statements and comment bytes."""
+    for contents, fragment in ((old, local), (new, upstream)):
+        tree, expected = ast.parse(contents), ast.parse(fragment).body
+        nodes = [
+            _unique_anchor(
+                contents,
+                tree,
+                lambda node: ast.dump(node) == ast.dump(item),
+                direct=True,
+            )
+            for item in expected
+        ]
+        start = tree.body.index(nodes[0])
+        lines = contents.splitlines(keepends=True)
+        first = nodes[0].lineno - expected[0].lineno
+        if (
+            tree.body[start : start + len(nodes)] != nodes
+            or contents.count(fragment) != 1
+            or "".join(lines[first : nodes[-1].end_lineno]) != fragment
+        ):
+            raise ValueError("Changed or ambiguous migration customization anchor")
+    return new.replace(upstream, local, 1)
+
+
+def _preserve_multiphase_guard(old, new):
+    for contents, local in ((old, True), (new, False)):
+        tree = ast.parse(contents)
+        if sum(
+            isinstance(n, ast.Constant) and n.value == "_testmultiphase"
+            for n in ast.walk(tree)
+        ) != 1 or sum(
+            isinstance(n, ast.Name) and n.id == "_testmultiphase"
+            for n in ast.walk(tree)
+        ) != int(local):
+            raise ValueError("Ambiguous _testmultiphase anchor")
+    return _preserve_top_level_block(old, new, MULTIPHASE_UPSTREAM, MULTIPHASE_LOCAL)
+
+
+def _preserve_frozen_lock_skip(old, new):
+    methods = []
+    for contents, local in ((old, True), (new, False)):
+        tree = ast.parse(contents)
+        owner = _unique_anchor(
+            contents,
+            tree,
+            lambda n: isinstance(n, ast.ClassDef) and n.name == "LifetimeTests",
+            direct=True,
+        )
+        method = _unique_anchor(
+            contents,
+            owner,
+            lambda n: isinstance(n, ast.FunctionDef) and n.name == "test_all_locks",
+            direct=True,
+        )
+        methods.append(ast.dump(method))
+        if sum(
+            isinstance(n, ast.Name) and n.id == "Frozen_LifetimeTests"
+            for n in ast.walk(tree)
+        ) != (3 if local else 1):
+            raise ValueError("Ambiguous frozen lock specialization")
+    if methods[0] != methods[1]:
+        raise ValueError("Frozen lock test changed; review its customization")
+    setup = "def setUpModule():\n    thread_info = threading_helper.threading_setup()\n    unittest.addModuleCleanup(threading_helper.threading_cleanup, *thread_info)\n"
+    return _preserve_top_level_block(
+        old,
+        new,
+        LOCK_SPECIALIZATION + "\n\n" + setup,
+        LOCK_SPECIALIZATION + "\n" + LOCK_SKIP + "\n" + setup,
+    )
+
+
+def preserve_migration_customizations(path: pathlib.Path, old: str, new: str) -> str:
+    """Fail closed if either known local patch or its canonical anchor changes."""
+    parts = path.parts
+    if path.is_absolute():
+        raise ValueError("Runtime patch target must be repository-relative")
+    if parts == ("Lib", "sysconfig", "__init__.py"):
+        if old.count(SYSCONFIG_LOCAL) != 1 or not _unique_function(
+            old, SYSCONFIG_LOCAL
+        ):
+            raise ValueError("Unrecognized sysconfig implementation identity")
+        if (
+            new.count(SYSCONFIG_UPSTREAM) != 1
+            or not _unique_function(new, SYSCONFIG_UPSTREAM)
+            or "RustPython" in new
+        ):
+            raise ValueError("Unrecognized canonical sysconfig implementation anchor")
+        return new.replace(SYSCONFIG_UPSTREAM, SYSCONFIG_LOCAL, 1)
+    if parts == ("Lib", "_compat_pickle.py"):
+        if (
+            old.count(JIT_ERROR + EXCEPTION_LOOP) != 1
+            or not _jit_block(old)
+            or not _exception_loop(old)
+        ):
+            raise ValueError("Unrecognized local JitError compatibility mapping")
+        if (
+            new.count(EXCEPTION_LOOP) != 1
+            or not _exception_loop(new)
+            or "JitError" in new
+        ):
+            raise ValueError("Unrecognized canonical exception mapping anchor")
+        return new.replace(EXCEPTION_LOOP, JIT_ERROR + EXCEPTION_LOOP, 1)
+    if parts == ("Lib", "test", "test_cmd_line.py"):
+        _verify_call(old, LOCAL_CALL)
+        _verify_call(new, CANONICAL_CALL)
+        return new.replace(CANONICAL_CALL, LOCAL_CALL, 1)
+    if parts == ("Lib", "test", "test_bytes.py"):
+        _verify_bytes_capi(old, BYTES_CAPI_LOCAL)
+        anchor = _verify_bytes_capi(new, BYTES_CAPI_UPSTREAM)
+        lines = new.splitlines(keepends=True)
+        lines[anchor.lineno - 1 : anchor.end_lineno] = [BYTES_CAPI_LOCAL]
+        return _preserve_bytes_allocations(old, "".join(lines))
+    if parts == ("Lib", "test", "test_importlib", "util.py"):
+        return _preserve_multiphase_guard(old, new)
+    if parts == ("Lib", "test", "test_importlib", "test_locks.py"):
+        return _preserve_frozen_lock_skip(old, new)
+    if parts == ("Lib", "test", "test_types.py"):
+        for contents in (old, new):
+            if (
+                sum(
+                    isinstance(node, ast.alias) and node.name == "_datetime"
+                    for node in ast.walk(ast.parse(contents))
+                )
+                != 1
+            ):
+                raise ValueError("Ambiguous test_types _datetime import")
+        if any(
+            isinstance(node, ast.alias) and node.name == "unittest"
+            for node in ast.walk(ast.parse(new))
+        ):
+            raise ValueError("Canonical test_types already imports unittest directly")
+        new = _preserve_top_level_block(
+            old, new, "import _datetime\n", TYPES_DATETIME_GUARD
+        )
+        return _preserve_top_level_block(
+            old, new, "import typing\n", "import typing\n\n" + TYPES_UNITTEST_IMPORT
+        )
+    return new
+
+
+CANONICAL_CALL = """assert_python_ok('-c', code, PYTHONPATH="")"""
+LOCAL_CALL = """assert_python_ok('-c', code, PYTHONPATH="", RUSTPYTHONPATH="")"""
+
+
+def _verify_call(contents: str, expected: str) -> None:
+    tree = ast.parse(contents)
+    owner = _unique_anchor(
+        contents,
+        tree,
+        lambda node: isinstance(node, ast.ClassDef) and node.name == "CmdLineTest",
+        direct=True,
+    )
+    method = _unique_anchor(
+        contents,
+        owner,
+        lambda node: (
+            isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+            and node.name == "test_empty_PYTHONPATH_issue16309"
+        ),
+        direct=True,
+    )
+    target = ast.dump(ast.parse(expected, mode="eval").body)
+    _unique_anchor(
+        contents,
+        method,
+        lambda node: isinstance(node, ast.Call) and ast.dump(node) == target,
+        exact=expected,
+    )
+    if contents.count(expected) != 1:
+        raise ValueError("Ambiguous environment-reset call text")
+
+
+SYMLINK_UPSTREAM = """            home = os.path.dirname(self.real)
+            if sysconfig.is_python_build():
+                home = os.path.join(home, sysconfig.get_config_var('VPATH'))
+            self._env["PYTHONHOME"] = home
+"""
+SYMLINK_LEGACY = """            self._env["PYTHONHOME"] = os.path.dirname(self.real)
+            if sysconfig.is_python_build():
+                self._env["PYTHONPATH"] = STDLIB_DIR
+"""
+SYMLINK_LOCAL = (
+    SYMLINK_UPSTREAM
+    + """            # TODO: RUSTPYTHON; Cargo builds do not use CPython's Modules/Setup.
+            if sys.implementation.name == 'rustpython':
+                self._env["PYTHONPATH"] = STDLIB_DIR
+"""
+)
+
+
+def copy_support_python_symlink(source, destination):
+    """Adapt only the canonical Windows symlink helper's library environment."""
+    owners = []
+    for contents in (source, destination):
+        tree = ast.parse(contents)
+        owner = _unique_anchor(
+            contents,
+            tree,
+            lambda node: (
+                isinstance(node, ast.ClassDef) and node.name == "PythonSymlink"
+            ),
+            direct=True,
+        )
+        if list(_bytes_bindings(tree, "PythonSymlink")) != [owner]:
+            raise ValueError("Shadowed PythonSymlink class")
+        owners.append(owner)
+    canonical = ast.get_source_segment(source, owners[0]) + "\n"
+    current = ast.get_source_segment(destination, owners[1]) + "\n"
+    if canonical.count(SYMLINK_UPSTREAM) != 1 or SYMLINK_LOCAL in canonical:
+        raise ValueError("Changed canonical PythonSymlink environment anchor")
+    platform = _unique_anchor(
+        canonical,
+        ast.parse(canonical).body[0],
+        lambda node: (
+            isinstance(node, ast.If)
+            and ast.dump(node.test)
+            == ast.dump(ast.parse("sys.platform == 'win32'", mode="eval").body)
+        ),
+        direct=True,
+    )
+    method = _unique_anchor(
+        canonical,
+        ast.Module(body=platform.body, type_ignores=[]),
+        lambda node: (
+            isinstance(node, ast.FunctionDef) and node.name == "_platform_specific"
+        ),
+        direct=True,
+    )
+    condition = _unique_anchor(
+        canonical,
+        method,
+        lambda node: (
+            isinstance(node, ast.If)
+            and ast.dump(node.test)
+            == ast.dump(ast.parse("sysconfig.is_python_build()", mode="eval").body)
+        ),
+        direct=True,
+    )
+    lines = canonical.splitlines(keepends=True)
+    if (
+        "".join(lines[condition.lineno - 2 : condition.end_lineno + 1])
+        != SYMLINK_UPSTREAM
+    ):
+        raise ValueError("Changed canonical PythonSymlink environment body")
+    adapted = canonical.replace(SYMLINK_UPSTREAM, SYMLINK_LOCAL, 1)
+    legacy = canonical.replace(SYMLINK_UPSTREAM, SYMLINK_LEGACY, 1)
+    if current not in (canonical, legacy, adapted):
+        raise ValueError("Changed local PythonSymlink; review before migration")
+    lines = destination.splitlines(keepends=True)
+    lines[owners[1].lineno - 1 : owners[1].end_lineno] = [adapted]
+    result = "".join(lines)
+    ast.parse(result)
+    return result
+
+
+def migrate_support_python_symlink(path, source_hash, destination_hash):
+    target = parse_lib_path(path)
+    if target.parts != ("Lib", "test", "support", "__init__.py"):
+        raise ValueError(
+            "PythonSymlink migration requires Lib/test/support/__init__.py"
+        )
+    source, destination = path.read_bytes(), target.read_bytes()
+    for label, contents, expected in (
+        ("source", source, source_hash),
+        ("destination", destination, destination_hash),
+    ):
+        if hashlib.sha256(contents).hexdigest() != expected:
+            raise ValueError(f"{label} SHA256 does not match the pinned input")
+    result = copy_support_python_symlink(
+        source.decode("utf-8"), destination.decode("utf-8")
+    ).encode("utf-8")
+    if target.read_bytes() != destination:
+        raise ValueError("Destination changed during PythonSymlink preparation")
+    target.write_bytes(result)
+    print(
+        json.dumps(
+            {
+                "helper": "PythonSymlink",
+                "source_sha256": source_hash,
+                "destination_before_sha256": destination_hash,
+                "destination_after_sha256": hashlib.sha256(result).hexdigest(),
+            },
+            sort_keys=True,
+        )
+    )
+
+
+def copy_support_assignments(source, destination, names, exports):
+    """Copy contiguous canonical assignments and export lines, failing closed.
+
+    Only additions are supported. Dependencies must already be imported with the
+    same bindings, or be builtins/earlier selected assignments. The next unchanged
+    top-level statement is the insertion anchor; unrelated bytes stay untouched.
+    """
+    if (
+        not names
+        or len(set(names)) != len(names)
+        or not all(name.isidentifier() for name in names)
+    ):
+        raise ValueError("Assignment names must be unique identifiers")
+    if len(set(exports)) != len(exports) or not set(exports) <= set(names):
+        raise ValueError("Exports must be unique selected assignment names")
+    src, dst = ast.parse(source), ast.parse(destination)
+
+    def assignment(tree, name):
+        matches = [
+            node
+            for node in ast.walk(tree)
+            if isinstance(node, ast.Name)
+            and isinstance(node.ctx, ast.Store)
+            and node.id == name
+        ]
+        nodes = [
+            node
+            for node in tree.body
+            if isinstance(node, ast.Assign)
+            and len(node.targets) == 1
+            and isinstance(node.targets[0], ast.Name)
+            and node.targets[0].id == name
+        ]
+        rebound = any(
+            isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef, ast.ClassDef))
+            and node.name == name
+            or isinstance(node, ast.alias)
+            and (node.asname or node.name.split(".")[0]) == name
+            for node in ast.walk(tree)
+        )
+        if len(nodes) != 1 or matches != [nodes[0].targets[0]] or rebound:
+            raise ValueError(f"Expected one top-level assignment to {name}")
+        return nodes[0]
+
+    selected = [assignment(src, name) for name in names]
+    start = src.body.index(selected[0])
+    if src.body[start : start + len(names)] != selected or start + len(names) == len(
+        src.body
+    ):
+        raise ValueError("Assignments must be contiguous and followed by an anchor")
+    if (start and src.body[start - 1].end_lineno >= selected[0].lineno) or (
+        selected[-1].end_lineno >= src.body[start + len(names)].lineno
+    ):
+        raise ValueError("Selected assignments must occupy complete source lines")
+    for node in ast.walk(dst):
+        if (
+            isinstance(node, ast.Name)
+            and isinstance(node.ctx, ast.Store)
+            and node.id in names
+            or isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef, ast.ClassDef))
+            and node.name in names
+            or isinstance(node, ast.alias)
+            and (node.asname or node.name.split(".")[0]) in names
+        ):
+            raise ValueError("A selected assignment already exists in the destination")
+
+    anchor = src.body[start + len(names)]
+    matches = [node for node in dst.body if ast.dump(node) == ast.dump(anchor)]
+    if len(matches) != 1:
+        raise ValueError("Expected one unchanged destination anchor")
+    for tree, node in ((src, anchor), (dst, matches[0])):
+        index = tree.body.index(node)
+        if (
+            getattr(node, "decorator_list", ())
+            or node.col_offset
+            or index
+            and tree.body[index - 1].end_lineno >= node.lineno
+            or index + 1 < len(tree.body)
+            and tree.body[index + 1].lineno <= node.end_lineno
+        ):
+            raise ValueError(
+                "Anchor must be undecorated and occupy complete source lines"
+            )
+    available = set(vars(builtins))
+    imports = (set(), set())
+    for node in src.body:
+        matching = [
+            other
+            for other in dst.body
+            if ast.dump(node) == ast.dump(other) and other.lineno < matches[0].lineno
+        ]
+        if (
+            isinstance(node, (ast.Import, ast.ImportFrom))
+            and node.lineno < selected[0].lineno
+            and len(matching) == 1
+        ):
+            imports[0].update(node.names)
+            imports[1].update(matching[0].names)
+            available.update(
+                alias.asname or alias.name.split(".")[0] for alias in node.names
+            )
+    dependencies = set()
+    for name, node in zip(names, selected):
+        used = {
+            child.id
+            for child in ast.walk(node.value)
+            if isinstance(child, ast.Name) and isinstance(child.ctx, ast.Load)
+        }
+        missing = used - available
+        if missing:
+            raise ValueError(f"Missing dependencies for {name}: {sorted(missing)}")
+        dependencies.update(used - set(names))
+        available.add(name)
+    for tree, boundary, allowed in (
+        (src, selected[0].lineno, imports[0]),
+        (dst, matches[0].lineno, imports[1]),
+    ):
+        if dependencies and any(
+            isinstance(node, ast.ImportFrom)
+            and node.lineno < boundary
+            and any(alias.name == "*" for alias in node.names)
+            for node in ast.walk(tree)
+        ):
+            raise ValueError("Wildcard import makes dependency bindings ambiguous")
+        for dependency in dependencies:
+            bindings = []
+            for node in ast.walk(tree):
+                if getattr(node, "lineno", boundary) >= boundary:
+                    continue
+                if isinstance(node, ast.Name) and isinstance(
+                    node.ctx, (ast.Store, ast.Del)
+                ):
+                    name = node.id
+                elif isinstance(node, ast.alias):
+                    name = node.asname or node.name.split(".")[0]
+                elif isinstance(
+                    node,
+                    (
+                        ast.FunctionDef,
+                        ast.AsyncFunctionDef,
+                        ast.ClassDef,
+                        ast.ExceptHandler,
+                        ast.MatchAs,
+                        ast.MatchStar,
+                    ),
+                ):
+                    name = node.name
+                elif isinstance(node, ast.arg):
+                    name = node.arg
+                elif isinstance(node, ast.MatchMapping):
+                    name = node.rest
+                else:
+                    continue
+                if name == dependency:
+                    bindings.append(node)
+            if len(bindings) > 1 or any(node not in allowed for node in bindings):
+                raise ValueError(f"Ambiguous dependency binding: {dependency}")
+
+    source_lines, lines = source.splitlines(True), destination.splitlines(True)
+    additions = [
+        (
+            matches[0].lineno - 1,
+            source_lines[selected[0].lineno - 1 : anchor.lineno - 1],
+        )
+    ]
+    if exports:
+        src_all, dst_all = assignment(src, "__all__"), assignment(dst, "__all__")
+        if not isinstance(src_all.value, ast.List) or not isinstance(
+            dst_all.value, ast.List
+        ):
+            raise ValueError("__all__ must be a literal list")
+        if any(
+            not isinstance(node, ast.Constant) or not isinstance(node.value, str)
+            for node in src_all.value.elts + dst_all.value.elts
+        ):
+            raise ValueError("__all__ entries must be literal strings")
+        src_values, dst_values = (
+            ast.literal_eval(src_all.value),
+            ast.literal_eval(dst_all.value),
+        )
+        if any(src_values.count(name) != 1 or name in dst_values for name in exports):
+            raise ValueError(
+                "Exports must occur once in canonical __all__ and be absent locally"
+            )
+        export_nodes = [node for node in src_all.value.elts if node.value in exports]
+        export_lines = sorted({node.lineno - 1 for node in export_nodes})
+        fragment = "".join(source_lines[line] for line in export_lines)
+        if ast.literal_eval("[\n" + fragment + "]") != exports:
+            raise ValueError(
+                "Canonical export lines include unselected entries or differ in order"
+            )
+        if lines[dst_all.lineno - 1].strip() != "__all__ = [":
+            raise ValueError("Expected a multiline destination __all__ list")
+        additions.append((dst_all.lineno, [fragment]))
+    for offset, fragment in sorted(additions, reverse=True):
+        lines[offset:offset] = fragment
+    result = "".join(lines)
+    ast.parse(result)
+    return result
+
+
+def migrate_support_assignments(path, names, exports, source_hash, destination_hash):
+    target = parse_lib_path(path)
+    if (
+        target.parts[:3] != ("Lib", "test", "support")
+        or ".." in target.parts
+        or target.suffix != ".py"
+    ):
+        raise ValueError(
+            "Selective assignments are restricted to Lib/test/support Python files"
+        )
+    source, destination = path.read_bytes(), target.read_bytes()
+    for label, contents, expected in (
+        ("source", source, source_hash),
+        ("destination", destination, destination_hash),
+    ):
+        if hashlib.sha256(contents).hexdigest() != expected:
+            raise ValueError(f"{label} SHA256 does not match the pinned input")
+    result = copy_support_assignments(
+        source.decode("utf-8"), destination.decode("utf-8"), names, exports
+    ).encode("utf-8")
+    if target.read_bytes() != destination:
+        raise ValueError("Destination changed during assignment preparation")
+    target.write_bytes(result)
+    print(
+        json.dumps(
+            {
+                "assignments": names,
+                "exports": exports,
+                "source_sha256": source_hash,
+                "destination_before_sha256": destination_hash,
+                "destination_after_sha256": hashlib.sha256(result).hexdigest(),
+            },
+            sort_keys=True,
+        )
+    )
+
 
 def patch_single_content(
     src_path: pathlib.Path,
     lib_path: pathlib.Path,
+    patches_document: dict | None = None,
 ) -> str:
     """
     Patch content without writing to disk.
@@ -36,15 +838,47 @@ def patch_single_content(
         The patched content.
     """
     from update_lib import apply_patches, extract_patches
+    from update_lib.patch_spec import apply_doctest_metadata, extract_doctest_guards
 
     # Extract patches from existing file (if exists)
     if lib_path.exists():
-        patches = extract_patches(lib_path.read_text(encoding="utf-8"))
+        old_content = lib_path.read_text(encoding="utf-8")
+        patches = extract_patches(old_content)
     else:
         patches = {}
 
+    repository = pathlib.Path(__file__).resolve().parents[2]
+    try:
+        relative_path = lib_path.resolve().relative_to(repository)
+    except ValueError:
+        # Explicit output paths outside this repository are not its Lib.
+        relative_path = pathlib.Path("__external_output__")
+    if patches_document is not None:
+        from update_lib.patch_spec import select_remaining_patches
+
+        patches = select_remaining_patches(
+            patches,
+            patches_document,
+            relative_path,
+            old_content=old_content if lib_path.exists() else None,
+        )
+
     # Apply patches to source content
     src_content = src_path.read_text(encoding="utf-8")
+    if lib_path.exists():
+        src_content = preserve_migration_customizations(
+            relative_path, old_content, src_content
+        )
+        guards = extract_doctest_guards(old_content)
+        selection = patches_document.get("doctests") if patches_document else None
+        if guards and selection is None:
+            raise ValueError(
+                "Existing doctest guards require explicit doctests metadata"
+            )
+        if selection is not None:
+            src_content = apply_doctest_metadata(old_content, src_content, selection)
+    if not src_content and not patches:
+        return src_content
     return apply_patches(src_content, patches)
 
 
@@ -52,6 +886,7 @@ def patch_file(
     src_path: pathlib.Path,
     lib_path: pathlib.Path | None = None,
     verbose: bool = True,
+    patches_document: dict | None = None,
 ) -> None:
     """
     Patch a single file from source to lib.
@@ -67,10 +902,12 @@ def patch_file(
     if lib_path.exists():
         if verbose:
             print(f"Patching: {src_path} -> {lib_path}")
-        content = patch_single_content(src_path, lib_path)
+        content = patch_single_content(src_path, lib_path, patches_document)
     else:
         if verbose:
             print(f"Copying: {src_path} -> {lib_path}")
+        if patches_document is not None:
+            raise ValueError("Marker override requires an existing target")
         content = src_path.read_text(encoding="utf-8")
 
     lib_path.parent.mkdir(parents=True, exist_ok=True)
@@ -93,7 +930,11 @@ def patch_directory(
     if lib_dir is None:
         lib_dir = parse_lib_path(src_dir)
 
-    src_files = sorted(f for f in src_dir.glob("**/*") if f.is_file())
+    src_files = sorted(
+        f
+        for f in src_dir.glob("**/*")
+        if f.is_file() and "__pycache__" not in f.relative_to(src_dir).parts[:-1]
+    )
 
     for src_file in src_files:
         rel_path = src_file.relative_to(src_dir)
@@ -118,6 +959,306 @@ def patch_directory(
             shutil.copy2(src_file, lib_file)
 
 
+def migrate_package(
+    src_dir: pathlib.Path, lib_dir: pathlib.Path, mapping_path: pathlib.Path
+) -> None:
+    """Validate the complete migration before writing or removing legacy files.
+
+    The JSON map names legacy files beside lib_dir, mapping every marked class
+    to its canonical file relative to src_dir. Empty maps retire unmarked files.
+    No test modules are imported or executed.
+    """
+    from update_lib.patch_spec import (
+        _iter_class_methods,
+        _iter_module_classes,
+        apply_patches,
+        build_patch_dict,
+        extract_doctest_guards,
+        iter_patches,
+    )
+
+    mapping = json.loads(mapping_path.read_text(encoding="utf-8"))
+    if not isinstance(mapping, dict) or not mapping:
+        raise ValueError("Legacy mapping must be a nonempty object")
+    if lib_dir.exists():
+        raise ValueError(f"Destination already exists: {lib_dir}")
+    if (
+        src_dir.resolve() == lib_dir.resolve()
+        or src_dir.resolve() in lib_dir.resolve().parents
+    ):
+        raise ValueError("Source and destination overlap")
+    source_files = sorted(
+        p
+        for p in src_dir.rglob("*")
+        if p.is_file() and "__pycache__" not in p.relative_to(src_dir).parts[:-1]
+    )
+    if not (src_dir / "__init__.py").is_file():
+        raise ValueError("Source must be a Python package")
+    if any(
+        p.is_symlink() or src_dir.resolve() not in p.resolve().parents
+        for p in source_files
+    ):
+        raise ValueError("Source files must remain inside the canonical package")
+    contents = {p.relative_to(src_dir): p.read_bytes() for p in source_files}
+    entries = collections.defaultdict(list)
+    owners = {}
+    legacy_files = []
+    for name, class_map in mapping.items():
+        if pathlib.Path(name).name != name or not name.endswith(".py"):
+            raise ValueError(f"Legacy file must be a sibling .py file: {name}")
+        if not isinstance(class_map, dict):
+            raise ValueError(f"Class map must be an object: {name}")
+        legacy = lib_dir.parent / name
+        if legacy.is_symlink() or legacy.resolve().parent != lib_dir.parent.resolve():
+            raise ValueError(f"Legacy file escapes destination parent: {name}")
+        if (
+            legacy.resolve() == lib_dir.resolve()
+            or src_dir.resolve() in legacy.resolve().parents
+        ):
+            raise ValueError(f"Legacy file overlaps canonical package: {name}")
+        legacy_files.append(legacy)
+        legacy_content = legacy.read_text(encoding="utf-8")
+        if extract_doctest_guards(legacy_content):
+            raise ValueError("Legacy package migration cannot select doctest guards")
+        patches = list(iter_patches(legacy_content))
+        legacy_classes = collections.defaultdict(list)
+        for cls in _iter_module_classes(ast.parse(legacy_content)):
+            legacy_classes[cls.name].append(cls)
+        if set(class_map) != {p.parent_class for p in patches}:
+            raise ValueError(f"Missing or unused class mapping: {name}")
+        for entry in patches:
+            source_classes = legacy_classes[entry.parent_class]
+            if len(source_classes) != 1:
+                raise ValueError(f"Ambiguous legacy class: {entry.parent_class}")
+            if (
+                entry.test_name != "__self__"
+                and sum(
+                    method.name == entry.test_name
+                    for method in _iter_class_methods(source_classes[0])
+                )
+                != 1
+            ):
+                raise ValueError(
+                    f"Ambiguous legacy method: {entry.parent_class}.{entry.test_name}"
+                )
+            target = pathlib.Path(class_map[entry.parent_class])
+            if target.is_absolute() or ".." in target.parts or target not in contents:
+                raise ValueError(f"Invalid canonical destination: {target}")
+            if target.suffix != ".py":
+                raise ValueError(f"Marker destination is not Python: {target}")
+            tree = ast.parse(contents[target].decode("utf-8"))
+            classes = collections.defaultdict(list)
+            for cls in _iter_module_classes(tree):
+                classes[cls.name].append(cls)
+
+            def has_method(class_name, seen):
+                if class_name in seen:
+                    return False
+                seen = seen | {class_name}
+                nodes = classes.get(class_name, [])
+                if len(nodes) != 1:
+                    raise ValueError(f"Missing or ambiguous class: {class_name}")
+                cls = nodes[0]
+                methods = [
+                    m for m in _iter_class_methods(cls) if m.name == entry.test_name
+                ]
+                if len(methods) > 1:
+                    raise ValueError(
+                        f"Ambiguous method: {class_name}.{entry.test_name}"
+                    )
+                if methods or entry.test_name == "__self__":
+                    return True
+                return any(
+                    has_method(base.id, seen)
+                    for base in cls.bases
+                    if isinstance(base, ast.Name) and base.id in classes
+                )
+
+            if not has_method(entry.parent_class, set()):
+                raise ValueError(
+                    f"Missing method: {entry.parent_class}.{entry.test_name}"
+                )
+            owner_key = (target, entry.parent_class, entry.test_name)
+            if owner_key in owners and owners[owner_key] != legacy:
+                raise ValueError(
+                    f"Duplicate mapped marker: {entry.parent_class}.{entry.test_name}"
+                )
+            owners[owner_key] = legacy
+            entries[target].append(entry)
+    # Render and validate everything before changing the destination.
+    for target, patches in entries.items():
+        contents[target] = apply_patches(
+            contents[target].decode("utf-8"), build_patch_dict(iter(patches))
+        ).encode("utf-8")
+    for target, data in contents.items():
+        if target.suffix == ".py":
+            text = data.decode("utf-8")
+            ast.parse(text)
+            if collections.Counter(iter_patches(text)) != collections.Counter(
+                entries[target]
+            ):
+                raise ValueError(f"Marker roundtrip mismatch: {target}")
+    for target, data in contents.items():
+        destination = lib_dir / target
+        destination.parent.mkdir(parents=True, exist_ok=True)
+        destination.write_bytes(data)
+    for legacy in legacy_files:
+        legacy.unlink()
+
+
+def remove_canonical_files(src_dir, manifest_path, *, dry_run=False):
+    """Remove only explicitly reviewed files, validating the whole batch first."""
+
+    def unique_object(pairs):
+        result = {}
+        for key, value in pairs:
+            if key in result:
+                raise ValueError(f"Duplicate removal metadata key: {key}")
+            result[key] = value
+        return result
+
+    def relative(name):
+        path = pathlib.PurePosixPath(name) if isinstance(name, str) else None
+        if (
+            not path
+            or not path.parts
+            or path.is_absolute()
+            or ".." in path.parts
+            or "\\" in name
+            or path.as_posix() != name
+            or "\0" in name
+        ):
+            raise ValueError("Expected an exact relative POSIX filename")
+        return pathlib.Path(path)
+
+    def no_symlinks(path):
+        if any(p.is_symlink() or p.is_junction() for p in (path, *path.parents)):
+            raise ValueError(f"Symlink or junction in removal path: {path}")
+
+    def git(*args):
+        result = subprocess.run(
+            ["git", "-C", str(src_dir), *args],
+            env={
+                **os.environ,
+                "GIT_NO_LAZY_FETCH": "1",
+                "GIT_NO_REPLACE_OBJECTS": "1",
+                "GIT_TERMINAL_PROMPT": "0",
+            },
+            capture_output=True,
+            check=False,
+        )
+        if result.returncode:
+            raise ValueError("Cannot verify pinned canonical source")
+        return result.stdout.decode().strip()
+
+    document = json.loads(
+        manifest_path.read_text(encoding="utf-8"), object_pairs_hook=unique_object
+    )
+    if not isinstance(document, dict) or set(document) != {"source", "removals"}:
+        raise ValueError("Expected source and removals metadata")
+    source, removals = document["source"], document["removals"]
+    if not isinstance(source, dict) or set(source) != {"path", "commit", "tree"}:
+        raise ValueError("Expected source path, commit and tree")
+    package = relative(source["path"])
+    if (
+        len(package.parts) != 3
+        or package.parts[:2] != ("Lib", "test")
+        or not package.name.startswith("test_")
+        or not package.name.isidentifier()
+    ):
+        raise ValueError("Removals require an exact Lib/test/test_* package")
+    if any(
+        not isinstance(source[k], str) or not re.fullmatch(r"[0-9a-f]{40}", source[k])
+        for k in ("commit", "tree")
+    ):
+        raise ValueError("Source commit and tree must be full Git hashes")
+    if not isinstance(removals, dict) or not removals:
+        raise ValueError("Removals must be a nonempty filename map")
+    src_dir = src_dir.absolute()
+    destination = pathlib.Path.cwd() / package
+    for path in (src_dir, destination):
+        no_symlinks(path)
+        if not path.is_dir():
+            raise ValueError("Source and destination packages must exist")
+    if (
+        src_dir == destination
+        or src_dir in destination.parents
+        or destination in src_dir.parents
+    ):
+        raise ValueError("Source and destination overlap")
+    if (
+        src_dir != pathlib.Path(git("rev-parse", "--show-toplevel")) / package
+        or git("rev-parse", "HEAD") != source["commit"]
+        or git("rev-parse", f"HEAD:{package.as_posix()}") != source["tree"]
+    ):
+        raise ValueError("Canonical source identity differs from the pinned input")
+    canonical = set(
+        git(
+            "ls-tree",
+            "--full-tree",
+            "-r",
+            "--name-only",
+            "-z",
+            "HEAD",
+            "--",
+            package.as_posix(),
+        ).split("\0")
+    )
+    snapshots, receipt = {}, {"source": source, "dry_run": dry_run, "removals": {}}
+    for name, entry in sorted(removals.items()):
+        path = relative(name)
+        if (
+            not isinstance(entry, dict)
+            or set(entry) != {"sha256", "upstream_commit"}
+            or any(
+                not isinstance(entry[k], str)
+                or not re.fullmatch(f"[0-9a-f]{{{length}}}", entry[k])
+                for k, length in (("sha256", 64), ("upstream_commit", 40))
+            )
+        ):
+            raise ValueError(f"Missing or invalid hash/provenance pins: {name}")
+        target = destination / path
+        no_symlinks(target)
+        no_symlinks(src_dir / path)
+        if (package / path).as_posix() in canonical or (src_dir / path).exists():
+            raise ValueError(f"Selected file is still canonical: {name}")
+        if target.exists() and not target.is_file():
+            raise ValueError(f"Removal target is not a regular file: {name}")
+        data = target.read_bytes() if target.exists() else None
+        if data is not None and (
+            hashlib.sha256(data).hexdigest() != entry["sha256"]
+            or b"rustpython" in data.lower()
+        ):
+            raise ValueError(f"Changed bytes or RustPython customization: {name}")
+        snapshots[target] = data
+        receipt["removals"][name] = {
+            **entry,
+            "status": "already_absent"
+            if data is None
+            else "would_remove"
+            if dry_run
+            else "removed",
+        }
+    if git("rev-parse", "HEAD") != source["commit"]:
+        raise ValueError("Canonical source changed during validation")
+    for target, data in snapshots.items():
+        no_symlinks(target)
+        canonical_path = src_dir / target.relative_to(destination)
+        no_symlinks(canonical_path)
+        if canonical_path.exists():
+            raise ValueError("Canonical source changed during validation")
+        if (target.exists() and not target.is_file()) or (
+            target.read_bytes() if target.exists() else None
+        ) != data:
+            raise ValueError(f"Removal target changed during validation: {target}")
+    if not dry_run:
+        for target, data in snapshots.items():
+            if data is not None:
+                target.unlink()
+    print(json.dumps(receipt, sort_keys=True))
+    return receipt
+
+
 def main(argv: list[str] | None = None) -> int:
     parser = argparse.ArgumentParser(
         description=__doc__,
@@ -129,13 +1270,110 @@ def main(argv: list[str] | None = None) -> int:
         help="Source path containing /Lib/ (file or directory)",
     )
 
+    parser.add_argument(
+        "--legacy-map",
+        type=pathlib.Path,
+        help="Explicit legacy-file/class to package-file JSON mapping",
+    )
+    parser.add_argument(
+        "--canonical-removals",
+        type=pathlib.Path,
+        help="Remove only selected unchanged historical files absent from a pinned canonical tree",
+    )
+    parser.add_argument(
+        "--dry-run",
+        action="store_true",
+        help="Validate canonical removals without deleting",
+    )
+
+    parser.add_argument(
+        "--patches",
+        type=pathlib.Path,
+        help="Single-file target, remaining decorator patches, and optional doctests JSON",
+    )
+    parser.add_argument(
+        "--support-assignments",
+        nargs="+",
+        help="Add selected canonical test.support assignments",
+    )
+    parser.add_argument(
+        "--support-python-symlink",
+        action="store_true",
+        help="Adapt the canonical Windows PythonSymlink library environment",
+    )
+    parser.add_argument("--support-exports", nargs="+", default=[])
+    parser.add_argument("--source-sha256")
+    parser.add_argument("--destination-sha256")
     args = parser.parse_args(argv)
 
     try:
-        if args.path.is_dir():
+        if args.canonical_removals is not None:
+            if (
+                args.legacy_map is not None
+                or args.patches is not None
+                or args.support_assignments
+                or args.support_python_symlink
+                or args.support_exports
+                or args.source_sha256
+                or args.destination_sha256
+            ):
+                raise ValueError(
+                    "Canonical removals cannot combine with other migration modes"
+                )
+            try:
+                remove_canonical_files(
+                    args.path, args.canonical_removals, dry_run=args.dry_run
+                )
+            except (OSError, UnicodeError) as exc:
+                raise ValueError(str(exc)) from exc
+            return 0
+        if args.dry_run:
+            raise ValueError("--dry-run requires --canonical-removals")
+        if args.support_python_symlink:
+            if (
+                args.legacy_map is not None
+                or args.patches is not None
+                or args.support_assignments
+                or args.support_exports
+            ):
+                raise ValueError(
+                    "PythonSymlink migration cannot combine with other migration modes"
+                )
+            migrate_support_python_symlink(
+                args.path, args.source_sha256, args.destination_sha256
+            )
+            return 0
+        if args.support_assignments:
+            if args.legacy_map is not None or args.patches is not None:
+                raise ValueError(
+                    "Selective support imports cannot combine with --legacy-map or --patches"
+                )
+            try:
+                migrate_support_assignments(
+                    args.path,
+                    args.support_assignments,
+                    args.support_exports,
+                    args.source_sha256,
+                    args.destination_sha256,
+                )
+            except (SyntaxError, UnicodeError) as exc:
+                raise ValueError(str(exc)) from exc
+            return 0
+        if args.support_exports or args.source_sha256 or args.destination_sha256:
+            raise ValueError("Selective options require --support-assignments")
+        if args.patches is not None and (
+            args.path.is_dir() or args.legacy_map is not None
+        ):
+            raise ValueError("--patches requires a single file without --legacy-map")
+        document = (
+            json.loads(args.patches.read_text()) if args.patches is not None else None
+        )
+        if args.legacy_map is not None:
+            migrate_package(args.path, parse_lib_path(args.path), args.legacy_map)
+        elif args.path.is_dir():
             patch_directory(args.path)
         else:
-            patch_file(args.path)
+            patch_file(args.path, patches_document=document)
         return 0
     except ValueError as e:
         print(f"Error: {e}", file=sys.stderr)
diff --git a/scripts/update_lib/deps.py b/scripts/update_lib/deps.py
index da49490c7ec..129faf3dea6 100644
--- a/scripts/update_lib/deps.py
+++ b/scripts/update_lib/deps.py
@@ -570,10 +570,7 @@ def clear_import_graph_caches() -> None:
     "io": {
         "hard_deps": ["_pyio.py"],
         "test": [
-            "test_io.py",
-            "test_bufio.py",
-            "test_fileio.py",
-            "test_memoryio.py",
+            "test_io",
         ],
     },
     "dbm": {
@@ -607,8 +604,7 @@ def clear_import_graph_caches() -> None:
     "file": {
         "lib": [],
         "test": [
-            "test_file.py",
-            "test_largefile.py",
+            "test_io",
         ],
     },
     "fcntl": {
@@ -651,6 +647,7 @@ def clear_import_graph_caches() -> None:
         "lib": [],
         "test": [
             "test_math.py",
+            "test_math_integer.py",
             "test_math_property.py",
         ],
     },
diff --git a/scripts/update_lib/patch_spec.py b/scripts/update_lib/patch_spec.py
index 996b78bfa18..35828e685d8 100644
--- a/scripts/update_lib/patch_spec.py
+++ b/scripts/update_lib/patch_spec.py
@@ -11,10 +11,12 @@
 import ast
 import collections
 import contextlib
+import doctest
 import enum
 import re
 import textwrap
 import typing
+from pathlib import Path
 
 if typing.TYPE_CHECKING:
     from collections.abc import Iterator
@@ -121,7 +123,9 @@ def try_from_ast_node(
         # If our ut_method has args then,
         # we need to search for a constant that contains our `COMMENT`.
         # Otherwise we need to search it in the raw source code :/
-        if ut_method.has_args():
+        if ut_method.has_args() and not (
+            ut_method is UtMethod.Skip and isinstance(node, ast.Attribute)
+        ):
             reason = next(
                 (
                     inner_node.value
@@ -197,7 +201,10 @@ def visit_ClassDef(self, node: ast.ClassDef):
                 patch = patch._replace(test_name="__self__")
                 self.patches.append(patch)
 
-            self.generic_visit(node)
+            # Keep conditional methods in this namespace, but do not enter
+            # nested classes or the bodies of methods.
+            for item in _iter_class_methods(node):
+                self.visit(item)
 
 
 class PatchEntry(typing.NamedTuple):
@@ -228,22 +235,35 @@ def iter_patch_entries(
         yield from visitor.patches
 
 
-def iter_tests(
-    tree: ast.Module,
-) -> "Iterator[tuple[ast.ClassDef, ast.FunctionDef | ast.AsyncFunctionDef]]":
-    for key, nodes in ast.iter_fields(tree):
-        if key != "body":
-            continue
+def _iter_module_classes(node: ast.AST) -> "Iterator[ast.ClassDef]":
+    """Find module-scope classes, including conditional definitions.
 
-        for cls_node in nodes:
-            if not isinstance(cls_node, ast.ClassDef):
-                continue
+    Function-local and class-nested definitions have different namespaces and
+    cannot be addressed by the patch format's unqualified class names.
+    """
+    for child in ast.iter_child_nodes(node):
+        if isinstance(child, ast.ClassDef):
+            yield child
+        elif not isinstance(child, (ast.FunctionDef, ast.AsyncFunctionDef, ast.Lambda)):
+            yield from _iter_module_classes(child)
 
-            for fn_node in cls_node.body:
-                if not isinstance(fn_node, (ast.FunctionDef, ast.AsyncFunctionDef)):
-                    continue
 
-                yield (cls_node, fn_node)
+def _iter_class_methods(
+    node: ast.AST,
+) -> "Iterator[ast.FunctionDef | ast.AsyncFunctionDef]":
+    for child in ast.iter_child_nodes(node):
+        if isinstance(child, (ast.FunctionDef, ast.AsyncFunctionDef)):
+            yield child
+        elif not isinstance(child, (ast.ClassDef, ast.Lambda)):
+            yield from _iter_class_methods(child)
+
+
+def iter_tests(
+    tree: ast.Module,
+) -> "Iterator[tuple[ast.ClassDef, ast.FunctionDef | ast.AsyncFunctionDef]]":
+    for cls_node in _iter_module_classes(tree):
+        for fn_node in _iter_class_methods(cls_node):
+            yield (cls_node, fn_node)
 
 
 def iter_patches(contents: str) -> "Iterator[PatchEntry]":
@@ -286,24 +306,43 @@ def _iter_patch_lines(
     # Track class bases for inherited async method lookup
     class_bases: dict[str, list[str]] = {}
     all_classes = set()
-    all_class_nodes = []
-    for node in tree.body:
-        if not isinstance(node, ast.ClassDef):
-            continue
-
+    all_class_nodes = list(_iter_module_classes(tree))
+    # Only names used to place a patch (including inherited methods) need a
+    # unique definition. Conditional, unpatched helpers are common upstream.
+    relevant_classes = set(patches)
+    while True:
+        ancestors = {
+            base.id
+            for node in all_class_nodes
+            if node.name in relevant_classes
+            for base in node.bases
+            if isinstance(base, ast.Name)
+        }
+        expanded = relevant_classes | ancestors
+        if expanded == relevant_classes:
+            break
+        relevant_classes = expanded
+    for node in all_class_nodes:
+        if node.name in all_classes and node.name in relevant_classes:
+            raise ValueError(f"Ambiguous module-scope class name: {node.name}")
         all_classes.add(node.name)
-        all_class_nodes.append(node)
+        method_counts = collections.Counter(
+            item.name for item in _iter_class_methods(node)
+        )
+        for method in patches.get(node.name, {}):
+            if method_counts[method] > 1:
+                raise ValueError(f"Ambiguous method name: {node.name}.{method}")
 
-    for node in tree.body:
+    for node in all_class_nodes:
         if isinstance(node, ast.ClassDef):
-            cache[node.name] = node.end_lineno
+            cache[node.name] = (node.end_lineno, node.col_offset + len(DEFAULT_INDENT))
             class_bases[node.name] = [
                 base.id
                 for base in node.bases
                 if isinstance(base, ast.Name) and base.id in all_classes
             ]
             cls_async: set[str] = set()
-            for item in node.body:
+            for item in _iter_class_methods(node):
                 if isinstance(item, ast.AsyncFunctionDef):
                     cls_async.add(item.name)
             if cls_async:
@@ -319,10 +358,11 @@ def _iter_patch_lines(
 
     # Phase 2: Iterate and mark inherited tests
     for cls_name, tests in sorted(patches.items()):
-        lineno = cache.get(cls_name)
-        if not lineno:
+        location = cache.get(cls_name)
+        if not location:
             print(f"WARNING: {cls_name} does not exist in remote file", file=sys.stderr)
             continue
+        lineno, indent = location
 
         for test_name, specs in sorted(tests.items()):
             if test_name == "__self__":
@@ -356,7 +396,7 @@ async def {test_name}(self):
 def {test_name}(self):
 {DEFAULT_INDENT}return super().{test_name}()
 """.rstrip()
-            yield (lineno, textwrap.indent(patch_lines, DEFAULT_INDENT))
+            yield (lineno, textwrap.indent(patch_lines, " " * indent))
 
     # Phase 3: Mark the class itself
     for cls_node in all_class_nodes:
@@ -393,8 +433,36 @@ def _find_import_insert_line(tree: ast.Module) -> int:
     return 0
 
 
+def _expand_inline_class_suites(contents: str, patches: Patches) -> str:
+    """Make room for inherited overrides without changing existing class bodies."""
+    tree = ast.parse(contents)
+    lines = contents.splitlines()
+    replacements = []
+    for node in _iter_module_classes(tree):
+        methods = {method.name for method in _iter_class_methods(node)}
+        inherited = set(patches.get(node.name, {})) - methods - {"__self__"}
+        if not inherited:
+            continue
+        first = node.body[0]
+        line = lines[first.lineno - 1].encode("utf-8")
+        header = line[: first.col_offset].decode("utf-8")
+        if not header.strip():
+            continue
+        body = line[first.col_offset :].decode("utf-8")
+        replacements.append(
+            (
+                first.lineno - 1,
+                header.rstrip() + "\n" + " " * (node.col_offset + 4) + body,
+            )
+        )
+    for index, replacement in sorted(replacements, reverse=True):
+        lines[index] = replacement
+    return "\n".join(lines) + "\n"
+
+
 def apply_patches(contents: str, patches: Patches) -> str:
     """Apply patches to file contents and return modified contents."""
+    contents = _expand_inline_class_suites(contents, patches)
     tree = ast.parse(contents)
     lines = contents.splitlines()
 
@@ -415,6 +483,7 @@ def apply_patches(contents: str, patches: Patches) -> str:
         lines.insert(lineno, patch)
 
     joined = "\n".join(lines)
+    ast.parse(joined)
     return f"{joined}\n"
 
 
@@ -480,3 +549,209 @@ def temp_attr(obj: object, attr: str, value: object):
         yield obj
     finally:
         setattr(obj, attr, old)
+
+
+def _conditional_retirements(document, old_content):
+    entries = document.get("retire_conditional", [])
+    if not isinstance(entries, list):
+        raise ValueError("Conditional retirements must be a list")
+    if not entries:
+        return {}
+    if not isinstance(old_content, str):
+        raise ValueError("Conditional retirements require original source")
+    tree = ast.parse(old_content)
+    lines = old_content.splitlines(keepends=True)
+    result = {}
+    for entry in entries:
+        if not isinstance(entry, dict) or set(entry) != {
+            "class",
+            "method",
+            "decorator",
+        }:
+            raise ValueError("Invalid conditional retirement metadata")
+        if not all(isinstance(value, str) and value for value in entry.values()):
+            raise ValueError("Conditional retirement fields must be nonempty strings")
+        key = (entry["class"], entry["method"])
+        if key in result:
+            raise ValueError("Duplicate conditional retirement")
+        classes = [
+            node
+            for node in ast.walk(tree)
+            if isinstance(node, ast.ClassDef) and node.name == key[0]
+        ]
+        if len(classes) != 1:
+            raise ValueError("Missing or ambiguous conditional retirement class")
+        methods = [
+            node for node in _iter_class_methods(classes[0]) if node.name == key[1]
+        ]
+        if len(methods) != 1:
+            raise ValueError("Missing or ambiguous conditional retirement method")
+        matches = [
+            node
+            for node in methods[0].decorator_list
+            if "".join(lines[node.lineno - 1 : node.end_lineno]) == entry["decorator"]
+        ]
+        if len(matches) != 1:
+            raise ValueError(
+                "Original conditional decorator does not match exactly once"
+            )
+        marker = PatchSpec.try_from_ast_node(matches[0], old_content.splitlines())
+        if marker is None or marker.ut_method != UtMethod.ExpectedFailureIf:
+            raise ValueError(
+                "Only explicit expectedFailureIf retirements are supported"
+            )
+        result[key] = marker
+    return result
+
+
+def select_remaining_patches(
+    current, document, relative_path: Path, *, old_content=None
+):
+    if not isinstance(document, dict) or (
+        not {"target", "patches"} <= set(document)
+        or not set(document) <= {"target", "patches", "doctests", "retire_conditional"}
+    ):
+        raise ValueError("Expected target and patches metadata")
+    if (
+        relative_path.parts[:2] != ("Lib", "test")
+        or relative_path.suffix != ".py"
+        or document["target"] != relative_path.as_posix()
+    ):
+        raise ValueError("Marker override target does not match the test file")
+    if "doctests" in document and not isinstance(document["doctests"], dict):
+        raise ValueError("Doctests metadata must be an object")
+    try:
+        remaining = patches_from_json(document["patches"])
+    except (TypeError, KeyError, AttributeError, ValueError) as error:
+        raise ValueError("Invalid remaining marker metadata") from error
+    retirements = _conditional_retirements(document, old_content)
+    consumed = set()
+    for cls, methods in remaining.items():
+        if cls not in current or any(method not in current[cls] for method in methods):
+            raise ValueError("Marker override cannot add targets")
+    for cls, methods in current.items():
+        for method, existing in methods.items():
+            pending = list(existing)
+            omitted = []
+            for marker in remaining.get(cls, {}).get(method, []):
+                if marker not in pending:
+                    raise ValueError(
+                        "Marker override cannot add, change, or reorder markers"
+                    )
+                index = pending.index(marker)
+                omitted.extend(pending[:index])
+                pending = pending[index + 1 :]
+            omitted.extend(pending)
+            for marker in omitted:
+                if marker.ut_method == UtMethod.ExpectedFailure:
+                    continue
+                key = (cls, method)
+                if (
+                    key in consumed
+                    or retirements.get(key) != marker
+                    or existing.count(marker) != 1
+                ):
+                    raise ValueError(
+                        "Conditional removal requires an exact explicit retirement"
+                    )
+                consumed.add(key)
+    if consumed != set(retirements):
+        raise ValueError("Conditional retirement was not removed exactly once")
+    return remaining
+
+
+EXPECTED_FAILURE = doctest.register_optionflag("EXPECTED_FAILURE")
+CANONICAL_LOAD_TESTS = """def load_tests(loader, tests, pattern):
+    tests.addTest(doctest.DocTestSuite())
+    return tests"""
+PATCHED_LOAD_TESTS = """def load_tests(loader, tests, pattern):
+    from test.support.rustpython import DocTestChecker  # TODO: RUSTPYTHON
+    tests.addTest(doctest.DocTestSuite(checker=DocTestChecker()))  # TODO: RUSTPYTHON
+    return tests"""
+
+
+def _examples(contents):
+    tree = ast.parse(contents)
+    if not tree.body or not isinstance(tree.body[0], ast.Expr):
+        raise ValueError("Missing module doctest")
+    doc = tree.body[0].value
+    if not isinstance(doc, ast.Constant) or not isinstance(doc.value, str):
+        raise ValueError("Missing module doctest")
+    # Raw docstring offsets map directly to source lines, unlike cleaned docs.
+    return tree, doc, doctest.DocTestParser().get_examples(doc.value)
+
+
+def apply_doctest_metadata(old, canonical, metadata):
+    """Preserve only listed guards, without carrying old expected output."""
+    if not isinstance(metadata, dict) or any(
+        not isinstance(source, str)
+        or not isinstance(reason, str)
+        or "\n" in reason
+        or "\r" in reason
+        for source, reason in metadata.items()
+    ):
+        raise ValueError("Doctest metadata must map exact input to single-line reasons")
+    _, _, old_examples = _examples(old)
+    tree, doc, examples = _examples(canonical)
+    lines = canonical.splitlines(keepends=True)
+    for source in metadata:
+        old_matches = [
+            example
+            for example in old_examples
+            if re.sub(r"\s+# TODO: RUSTPYTHON[^\n]*", "", example.source) == source
+        ]
+        if len(old_matches) != 1 or not old_matches[0].options.get(EXPECTED_FAILURE):
+            raise ValueError("Missing or ambiguous existing doctest guard")
+        matches = [example for example in examples if example.source == source]
+        if len(matches) != 1 or matches[0].options:
+            raise ValueError("Missing, ambiguous, or already marked canonical doctest")
+        index = doc.lineno - 1 + matches[0].lineno
+        line = lines[index]
+        if (
+            ">>>" not in line
+            or line.split(">>>", 1)[1].strip() != source.splitlines()[0]
+        ):
+            raise ValueError("Unrecognized canonical doctest prompt")
+        lines[index] = (
+            line.rstrip("\n")
+            + "  # TODO: RUSTPYTHON; "
+            + metadata[source]
+            + " # doctest: +EXPECTED_FAILURE\n"
+        )
+
+    if not metadata:
+        return canonical
+
+    loaders = [
+        node
+        for node in ast.walk(tree)
+        if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+        and node.name == "load_tests"
+    ]
+    if len(loaders) != 1 or loaders[0] not in tree.body:
+        raise ValueError("Missing or ambiguous doctest loader")
+    if ast.get_source_segment(canonical, loaders[0]) != CANONICAL_LOAD_TESTS:
+        raise ValueError("Changed canonical doctest loader")
+    result = "".join(lines)
+    if result.count(CANONICAL_LOAD_TESTS) != 1:
+        raise ValueError("Ambiguous canonical doctest loader text")
+    return result.replace(CANONICAL_LOAD_TESTS, PATCHED_LOAD_TESTS, 1)
+
+
+def extract_doctest_guards(contents: str) -> dict[str, str]:
+    """Extract guarded module-docstring inputs without executing examples."""
+    tree = ast.parse(contents)
+    if not tree.body or not isinstance(tree.body[0], ast.Expr):
+        return {}
+    doc = tree.body[0].value
+    if not isinstance(doc, ast.Constant) or not isinstance(doc.value, str):
+        return {}
+    guards = {}
+    for example in doctest.DocTestParser().get_examples(doc.value):
+        if not example.options.get(EXPECTED_FAILURE):
+            continue
+        source = re.sub(r"\s+# TODO: RUSTPYTHON[^\n]*", "", example.source)
+        if source in guards:
+            raise ValueError("Ambiguous existing doctest guard")
+        guards[source] = example.source
+    return guards
diff --git a/scripts/update_lib/tests/test_copy_lib.py b/scripts/update_lib/tests/test_copy_lib.py
index aca00cb18f3..69b430af985 100644
--- a/scripts/update_lib/tests/test_copy_lib.py
+++ b/scripts/update_lib/tests/test_copy_lib.py
@@ -1,5 +1,6 @@
 """Tests for copy_lib.py - library copying with dependencies."""
 
+import contextlib
 import pathlib
 import tempfile
 import unittest
@@ -57,10 +58,114 @@ def test_removes_existing_before_copy(self):
 
             self.assertEqual(dst.read_text(), "new content")
 
+    def test_directory_copy_excludes_bytecode_cache_directories(self):
+        from update_lib.cmd_copy_lib import _copy_single
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = pathlib.Path(tmpdir)
+            src = root / "source"
+            dst = root / "destination"
+            for relative in ("__pycache__", "package/__pycache__", "assets"):
+                (src / relative).mkdir(parents=True)
+            files = {
+                "__init__.py": b"source\n",
+                "package/module.py": b"nested source\n",
+                "assets/data.bin": b"\x00\xffasset",
+                "assets/__pycache__": b"ordinary file, not a directory",
+                "assets/fixture.pyc": b"canonical bytecode fixture",
+                "__pycache__/module.cpython-315.pyc": b"stale cache",
+                "package/__pycache__/module.cpython-315.pyc": b"nested cache",
+            }
+            for relative, content in files.items():
+                (src / relative).write_bytes(content)
+
+            _copy_single(src, dst, verbose=False)
+
+            expected = {
+                relative: content
+                for relative, content in files.items()
+                if "__pycache__" not in pathlib.Path(relative).parts[:-1]
+            }
+            actual = {
+                path.relative_to(dst).as_posix(): path.read_bytes()
+                for path in dst.rglob("*")
+                if path.is_file()
+            }
+            self.assertEqual(actual, expected)
+            self.assertFalse((dst / "__pycache__").exists())
+            self.assertFalse((dst / "package/__pycache__").exists())
+            for relative, content in files.items():
+                self.assertEqual((src / relative).read_bytes(), content)
+
 
 class TestCopyLib(unittest.TestCase):
     """Tests for copy_lib function."""
 
+    def test_nested_data_file_preserves_siblings(self):
+        from update_lib.cmd_copy_lib import copy_lib
+
+        for name in ("hierarchy.txt", "fixture.bin", "README"):
+            with self.subTest(name=name), tempfile.TemporaryDirectory() as tmpdir:
+                root = pathlib.Path(tmpdir)
+                source = root / "cpython/Lib/test/data" / name
+                source.parent.mkdir(parents=True)
+                source.write_bytes(b"canonical\x00\xff\n")
+                (source.parent / "other.txt").write_bytes(b"unselected source")
+                target = root / "Lib/test/data" / name
+                target.parent.mkdir(parents=True)
+                target.write_bytes(b"old")
+                sibling = root / "Lib/test/test_local.py"
+                sibling.write_bytes(b"local guards\n")
+                with contextlib.chdir(root):
+                    copy_lib(source, verbose=False)
+                self.assertEqual(target.read_bytes(), source.read_bytes())
+                self.assertEqual(sibling.read_bytes(), b"local guards\n")
+                self.assertFalse((target.parent / "other.txt").exists())
+
+    def test_missing_data_file_does_not_copy_containing_package(self):
+        from update_lib.cmd_copy_lib import copy_lib
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = pathlib.Path(tmpdir)
+            source = root / "cpython/Lib/test/missing.txt"
+            source.parent.mkdir(parents=True)
+            (source.parent / "other.py").write_text("unselected source")
+            sibling = root / "Lib/test/test_local.py"
+            sibling.parent.mkdir(parents=True)
+            sibling.write_bytes(b"local guards\n")
+            with contextlib.chdir(root), self.assertRaises(FileNotFoundError):
+                copy_lib(source, verbose=False)
+            self.assertEqual(sibling.read_bytes(), b"local guards\n")
+            self.assertFalse((sibling.parent / "other.py").exists())
+
+    def test_python_module_still_copies_hard_dependencies(self):
+        from update_lib.cmd_copy_lib import copy_lib
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = pathlib.Path(tmpdir)
+            source = root / "cpython/Lib"
+            source.mkdir(parents=True)
+            for name in ("pickle.py", "_compat_pickle.py"):
+                (source / name).write_text(name)
+            with contextlib.chdir(root):
+                copy_lib(source / "pickle.py", verbose=False)
+            for name in ("pickle.py", "_compat_pickle.py"):
+                self.assertEqual((root / "Lib" / name).read_text(), name)
+
+    def test_package_still_copies_directory(self):
+        from update_lib.cmd_copy_lib import copy_lib
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            root = pathlib.Path(tmpdir)
+            source = root / "cpython/Lib/json"
+            source.mkdir(parents=True)
+            for name in ("__init__.py", "decoder.py"):
+                (source / name).write_text(name)
+            with contextlib.chdir(root):
+                copy_lib(source, verbose=False)
+            for name in ("__init__.py", "decoder.py"):
+                self.assertEqual((root / "Lib/json" / name).read_text(), name)
+
     def test_raises_on_path_without_lib(self):
         """Test that copy_lib raises ValueError when path doesn't contain /Lib/."""
         from update_lib.cmd_copy_lib import copy_lib
diff --git a/scripts/update_lib/tests/test_copy_test.py b/scripts/update_lib/tests/test_copy_test.py
new file mode 100644
index 00000000000..5dc61452c90
--- /dev/null
+++ b/scripts/update_lib/tests/test_copy_test.py
@@ -0,0 +1,206 @@
+"""Tests for bounded, hash-pinned canonical test copying."""
+
+import ast
+import contextlib
+import hashlib
+import io
+import tempfile
+import unittest
+from pathlib import Path
+
+from update_lib.cmd_copy_test import copy_test, main
+
+
+class TestCopyTest(unittest.TestCase):
+    destination = '''# Destination-only header
+class Finder:
+    if int.__doc__:
+        def example():
+            r"""Count is below 800. π\\n"""
+
+    def untouched(self):
+        return "destination"
+'''
+    source = '''# Canonical header must not be copied
+class Finder:
+    if int.__doc__:
+        def example():
+            r"""Count is below 850. π\\n"""
+
+    def untouched(self):
+        return "canonical"
+'''
+
+    def test_complete_definition_and_surroundings(self):
+        result = copy_test(self.source, self.destination, "Finder.example")
+        self.assertEqual(result, self.destination.replace("below 800", "below 850"))
+        self.assertIn('return "destination"', result)
+        source_method = ast.parse(self.source).body[0].body[0].body[0]
+        result_method = ast.parse(result).body[0].body[0].body[0]
+        self.assertEqual(
+            ast.get_source_segment(self.source, source_method),
+            ast.get_source_segment(result, result_method),
+        )
+
+    def test_guard_mismatch_is_rejected(self):
+        with self.assertRaisesRegex(ValueError, "guards differ"):
+            copy_test(
+                self.source.replace("if int.__doc__", "if enabled"),
+                self.destination,
+                "Finder.example",
+            )
+
+    def test_missing_or_ambiguous_definition_is_rejected(self):
+        for source in ("class Other: pass\n", self.source + self.source):
+            with self.subTest(source=source):
+                with self.assertRaisesRegex(ValueError, "Expected one class"):
+                    copy_test(source, self.destination, "Finder.example")
+        duplicate = self.source.replace(
+            "    def untouched(self):",
+            "    def example():\n        pass\n\n    def untouched(self):",
+        )
+        with self.assertRaisesRegex(ValueError, "Expected one method"):
+            copy_test(duplicate, self.destination, "Finder.example")
+
+    def test_decorator_and_signature_changes_are_rejected(self):
+        decorated = self.source.replace(
+            "        def example():", "        @decorator\n        def example():"
+        )
+        with self.assertRaisesRegex(ValueError, "decorators differ"):
+            copy_test(decorated, self.destination, "Finder.example")
+        with self.assertRaisesRegex(ValueError, "signatures differ"):
+            copy_test(
+                self.source.replace("def example():", "def example(arg):"),
+                self.destination,
+                "Finder.example",
+            )
+
+    def test_nested_local_scope_is_not_selected(self):
+        local = "def factory():\n" + "".join(
+            "    " + line for line in self.source.splitlines(True)
+        )
+        with self.assertRaisesRegex(ValueError, "Expected one class"):
+            copy_test(local, self.destination, "Finder.example")
+
+    def test_decorator_comments_must_match_exactly(self):
+        for source_marker, destination_marker in (
+            (
+                "@unittest.expectedFailure",
+                "@unittest.expectedFailure  # TODO: RUSTPYTHON; reason",
+            ),
+            (
+                "@unittest.expectedFailure  # original reason",
+                "@unittest.expectedFailure  # changed reason",
+            ),
+            (
+                "@unittest.expectedFailure\n        @other",
+                "@unittest.expectedFailure\n        # marker rationale\n        @other",
+            ),
+            (
+                "@unittest.expectedFailureIf(\n            condition,\n            'reason',\n        )",
+                "@unittest.expectedFailureIf(\n            condition,  # project limitation\n            'reason',\n        )",
+            ),
+        ):
+            with self.subTest(destination_marker=destination_marker):
+                source = self.source.replace(
+                    "        def example():",
+                    f"        {source_marker}\n        def example():",
+                )
+                destination = self.destination.replace(
+                    "        def example():",
+                    f"        {destination_marker}\n        def example():",
+                )
+                with self.assertRaisesRegex(ValueError, "decorator text differs"):
+                    copy_test(source, destination, "Finder.example")
+
+    def test_identical_decorator_comments_are_preserved(self):
+        prefix = (
+            "        @unittest.expectedFailure  # TODO: RUSTPYTHON; reason\n"
+            "        # Keep this rationale with the marker.\n"
+            "        def example():"
+        )
+        for declaration in ("def example():", "async def example():"):
+            with self.subTest(declaration=declaration):
+                source = self.source.replace("        def example():", prefix)
+                destination = self.destination.replace("        def example():", prefix)
+                source = source.replace("def example():", declaration)
+                destination = destination.replace("def example():", declaration)
+                self.assertEqual(
+                    copy_test(source, destination, "Finder.example"),
+                    destination.replace("below 800", "below 850"),
+                )
+
+    def test_cli_does_not_write_on_decorator_comment_mismatch(self):
+        with tempfile.TemporaryDirectory() as temp:
+            source = Path(temp) / "source.py"
+            destination = Path(temp) / "destination.py"
+            source.write_text(
+                self.source.replace(
+                    "        def example():",
+                    "        @unittest.expectedFailure\n        def example():",
+                )
+            )
+            destination.write_text(
+                self.destination.replace(
+                    "        def example():",
+                    "        @unittest.expectedFailure  # TODO: RUSTPYTHON; reason\n"
+                    "        def example():",
+                )
+            )
+            before = destination.read_bytes()
+            with (
+                contextlib.redirect_stderr(io.StringIO()) as errors,
+                self.assertRaises(SystemExit),
+            ):
+                main(
+                    [
+                        str(source),
+                        str(destination),
+                        "--test",
+                        "Finder.example",
+                        "--source-sha256",
+                        hashlib.sha256(source.read_bytes()).hexdigest(),
+                        "--destination-sha256",
+                        hashlib.sha256(before).hexdigest(),
+                    ]
+                )
+            self.assertIn("decorator text differs", errors.getvalue())
+            self.assertEqual(destination.read_bytes(), before)
+
+    def test_return_annotation_and_type_parameters_are_rejected(self):
+        for declaration in ("def example() -> int:", "def example[T]():"):
+            with self.subTest(declaration=declaration):
+                source = self.source.replace("def example():", declaration)
+                with self.assertRaisesRegex(ValueError, "signatures differ"):
+                    copy_test(source, self.destination, "Finder.example")
+
+    def test_cli_hashes_and_no_write_on_stale_input(self):
+        with tempfile.TemporaryDirectory() as temp:
+            source = Path(temp) / "source.py"
+            destination = Path(temp) / "destination.py"
+            source.write_bytes(self.source.encode())
+            destination.write_bytes(self.destination.encode())
+            args = [
+                str(source),
+                str(destination),
+                "--test",
+                "Finder.example",
+                "--source-sha256",
+                hashlib.sha256(source.read_bytes()).hexdigest(),
+                "--destination-sha256",
+                "0" * 64,
+            ]
+            with (
+                contextlib.redirect_stderr(io.StringIO()),
+                self.assertRaises(SystemExit),
+            ):
+                main(args)
+            self.assertEqual(destination.read_bytes(), self.destination.encode())
+            args[-1] = hashlib.sha256(destination.read_bytes()).hexdigest()
+            with contextlib.redirect_stdout(io.StringIO()) as output:
+                self.assertEqual(main(args), 0)
+            self.assertIn('"source_sha256"', output.getvalue())
+            self.assertEqual(
+                destination.read_text(),
+                self.destination.replace("below 800", "below 850"),
+            )
diff --git a/scripts/update_lib/tests/test_deps.py b/scripts/update_lib/tests/test_deps.py
index d97af2867aa..4d5d6c0a44e 100644
--- a/scripts/update_lib/tests/test_deps.py
+++ b/scripts/update_lib/tests/test_deps.py
@@ -110,6 +110,18 @@ def test_known_dependency(self):
         self.assertEqual(len(paths), 1)
         self.assertEqual(paths[0], pathlib.Path("cpython/Lib/test/test_regrtest"))
 
+    def test_io_package(self):
+        self.assertEqual(
+            get_test_paths("io", "cpython"),
+            (pathlib.Path("cpython/Lib/test/test_io"),),
+        )
+
+    def test_file_alias_uses_io_package(self):
+        self.assertEqual(
+            get_test_paths("file", "cpython"),
+            (pathlib.Path("cpython/Lib/test/test_io"),),
+        )
+
     def test_default_directory(self):
         """Test default to test_name/ directory."""
         with tempfile.TemporaryDirectory() as tmpdir:
diff --git a/scripts/update_lib/tests/test_migrate.py b/scripts/update_lib/tests/test_migrate.py
index 0cc247ba841..1a138742012 100644
--- a/scripts/update_lib/tests/test_migrate.py
+++ b/scripts/update_lib/tests/test_migrate.py
@@ -1,20 +1,751 @@
 """Tests for migrate.py - file migration operations."""
 
+import contextlib
+import hashlib
+import io
+import json
+import os
 import pathlib
+import subprocess
 import tempfile
 import unittest
+from pathlib import Path
+from unittest.mock import patch
 
 from update_lib.cmd_migrate import (
+    BYTES_ALLOCATION_COMMENTS,
+    BYTES_CAPI_LOCAL,
+    BYTES_CAPI_UPSTREAM,
+    CANONICAL_CALL,
+    EXCEPTION_LOOP,
+    JIT_ERROR,
+    LOCAL_CALL,
+    LOCK_SKIP,
+    LOCK_SPECIALIZATION,
+    MULTIPHASE_LOCAL,
+    MULTIPHASE_UPSTREAM,
+    SYMLINK_LEGACY,
+    SYMLINK_LOCAL,
+    SYMLINK_UPSTREAM,
+    SYSCONFIG_LOCAL,
+    SYSCONFIG_UPSTREAM,
+    TYPES_DATETIME_GUARD,
+    TYPES_UNITTEST_IMPORT,
+    copy_support_assignments,
+    copy_support_python_symlink,
+    main,
+    migrate_package,
     patch_directory,
     patch_file,
     patch_single_content,
+    preserve_migration_customizations,
+    remove_canonical_files,
 )
-from update_lib.patch_spec import COMMENT
+from update_lib.patch_spec import (
+    CANONICAL_LOAD_TESTS,
+    COMMENT,
+    PatchSpec,
+    UtMethod,
+    extract_patches,
+    iter_patches,
+    patches_to_json,
+    select_remaining_patches,
+)
+
+
+class TestPythonSymlinkMigration(unittest.TestCase):
+    prefix = """class PythonSymlink:
+    if sys.platform == "win32":
+        def _platform_specific(self):
+            self._env = {}
+"""
+    suffix = """    else:
+        def _platform_specific(self):
+            pass
+"""
+    canonical = prefix + SYMLINK_UPSTREAM + suffix
+    adapted = prefix + SYMLINK_LOCAL + suffix
+    legacy = prefix + SYMLINK_LEGACY + suffix
+
+    def test_canonical_and_legacy_import_are_idempotent(self):
+        for before in (self.canonical, self.legacy, self.adapted):
+            with self.subTest(before=before):
+                self.assertEqual(
+                    copy_support_python_symlink(self.canonical, before), self.adapted
+                )
+
+    def test_unrelated_support_content_is_preserved(self):
+        destination = "existing_guard = True\n" + self.legacy + "other_helper = 1\n"
+        self.assertEqual(
+            copy_support_python_symlink(
+                "new_upstream = 1\n" + self.canonical, destination
+            ),
+            "existing_guard = True\n" + self.adapted + "other_helper = 1\n",
+        )
+
+    def test_changed_missing_duplicate_or_nested_class_fails_closed(self):
+        for value in (self.canonical, self.legacy):
+            for changed in (
+                value.replace("PythonSymlink", "OtherHelper"),
+                value + value,
+                "if True:\n"
+                + "".join("    " + line for line in value.splitlines(True)),
+                value.replace("sys.platform", "other.platform"),
+                value.replace("self._env = {}", "self._env = None"),
+            ):
+                with self.subTest(changed=changed):
+                    with self.assertRaises(ValueError):
+                        copy_support_python_symlink(self.canonical, changed)
+
+    def test_source_anchor_drift_fails_closed(self):
+        for changed in (
+            self.canonical.replace("'VPATH'", "'OTHER'"),
+            self.canonical.replace("sys.platform", "other.platform"),
+            self.canonical.replace("sysconfig.is_python_build()", "True"),
+            self.canonical.replace(SYMLINK_UPSTREAM, SYMLINK_UPSTREAM * 2),
+            self.adapted,
+        ):
+            with self.subTest(changed=changed):
+                with self.assertRaises(ValueError):
+                    copy_support_python_symlink(changed, self.legacy)
+
+    def test_class_shadow_fails_closed(self):
+        for shadow in (
+            "PythonSymlink = None\n",
+            "del PythonSymlink\n",
+            "import other as PythonSymlink\n",
+        ):
+            with self.subTest(shadow=shadow):
+                for source, target in (
+                    (self.canonical + shadow, self.legacy),
+                    (self.canonical, self.legacy + shadow),
+                ):
+                    with self.assertRaises(ValueError):
+                        copy_support_python_symlink(source, target)
+
+    def test_cli_pins_inputs_rejects_conflicts_and_repeats(self):
+        with tempfile.TemporaryDirectory() as root, contextlib.chdir(root):
+            source = Path("canonical/Lib/test/support/__init__.py")
+            target = Path("Lib/test/support/__init__.py")
+            for path, contents in ((source, self.canonical), (target, self.legacy)):
+                path.parent.mkdir(parents=True)
+                path.write_text(contents)
+            base = [str(source), "--support-python-symlink"]
+            source_hash = hashlib.sha256(source.read_bytes()).hexdigest()
+            destination_hash = hashlib.sha256(target.read_bytes()).hexdigest()
+            pins = [
+                "--source-sha256",
+                source_hash,
+                "--destination-sha256",
+                destination_hash,
+            ]
+            for args in (
+                base,
+                base
+                + [
+                    "--source-sha256",
+                    "0" * 64,
+                    "--destination-sha256",
+                    destination_hash,
+                ],
+                base
+                + ["--source-sha256", source_hash, "--destination-sha256", "0" * 64],
+                base + pins + ["--support-assignments", "other"],
+                base + pins + ["--support-exports", "other"],
+                base + pins + ["--patches", "unused.json"],
+                base + pins + ["--dry-run"],
+            ):
+                with (
+                    self.subTest(args=args),
+                    contextlib.redirect_stdout(io.StringIO()),
+                    contextlib.redirect_stderr(io.StringIO()),
+                ):
+                    self.assertEqual(main(args), 1)
+                    self.assertEqual(target.read_text(), self.legacy)
+            with contextlib.redirect_stdout(io.StringIO()):
+                self.assertEqual(main(base + pins), 0)
+                self.assertEqual(target.read_text(), self.adapted)
+                pins[-1] = hashlib.sha256(target.read_bytes()).hexdigest()
+                self.assertEqual(main(base + pins), 0)
+                self.assertEqual(target.read_text(), self.adapted)
+
+    def test_adapted_environment_preserves_cpython_and_sets_rustpython_library(self):
+        import textwrap
+        from types import SimpleNamespace
+
+        for implementation, build, expected_home, expected_path in (
+            ("cpython", False, "/build", None),
+            ("cpython", True, os.path.join("/build", "source"), None),
+            ("rustpython", False, "/build", "/actual/Lib"),
+        ):
+            helper = SimpleNamespace(_env={"KEEP": "value"}, real="/build/python")
+            namespace = {
+                "self": helper,
+                "os": os,
+                "sys": SimpleNamespace(
+                    implementation=SimpleNamespace(name=implementation)
+                ),
+                "sysconfig": SimpleNamespace(
+                    is_python_build=lambda: build, get_config_var=lambda name: "source"
+                ),
+                "STDLIB_DIR": "/actual/Lib",
+            }
+            exec(textwrap.dedent(SYMLINK_LOCAL), namespace)
+            self.assertEqual(helper._env["PYTHONHOME"], expected_home)
+            self.assertEqual(helper._env.get("PYTHONPATH"), expected_path)
+            self.assertEqual(helper._env["KEEP"], "value")
+
+
+class TestBytesPreservation(unittest.TestCase):
+    path = Path("Lib/test/test_bytes.py")
+    prefix = "class ByteArrayTest(BaseBytesTest, unittest.TestCase):\n"
+    allocations = """
+    def test_alloc(self):
+        b = bytearray()
+        alloc = b.__alloc__()
+        self.assertGreaterEqual(alloc, 0)
+        # existing allocation adaptation
+        self.assertGreaterEqual(alloc, len(b))
+
+    def test_init_alloc(self):
+        b = bytearray()
+        def g():
+            alloc = b.__alloc__()
+            self.assertGreaterEqual(alloc, len(b))
+            yield 1
+        b.__init__(g())
+        alloc = b.__alloc__()
+        self.assertGreaterEqual(alloc, len(b))
+"""
+    canonical_allocations = allocations.replace(
+        "assertGreaterEqual(alloc, len(b))", "assertGreater(alloc, len(b))"
+    ).replace("        # existing allocation adaptation\n", "")
+    for name, comment in BYTES_ALLOCATION_COMMENTS.items():
+        allocations = allocations.replace(
+            f"    def {name}(", comment + f"    def {name}("
+        )
+    old = prefix + BYTES_CAPI_LOCAL + allocations
+    canonical = prefix + BYTES_CAPI_UPSTREAM + canonical_allocations
+
+    def assert_rejected(self, changed, *, local):
+        with self.assertRaises(ValueError):
+            preserve_migration_customizations(
+                self.path,
+                changed if local else self.old,
+                self.canonical if local else changed,
+            )
+
+    def test_preserves_existing_blocks_and_is_idempotent(self):
+        source = self.canonical + "\nnew_canonical_content = True\n"
+        expected = self.old + "\nnew_canonical_content = True\n"
+        result = preserve_migration_customizations(self.path, self.old, source)
+        self.assertEqual(result, expected)
+        self.assertEqual(
+            preserve_migration_customizations(self.path, result, source), result
+        )
+
+    def test_earlier_nested_import_and_decoy_text_are_untouched(self):
+        earlier = (
+            "class BaseBytesTest:\n    def test_sq_item(self):\n    "
+            + BYTES_CAPI_UPSTREAM
+        )
+        decoy = 'description = """\n' + BYTES_CAPI_UPSTREAM + '"""\n'
+        prefix = earlier + decoy
+        self.assertEqual(
+            preserve_migration_customizations(
+                self.path, prefix + self.old, prefix + self.canonical
+            ),
+            prefix + self.old,
+        )
+
+    def test_import_missing_duplicate_changed_and_moved_fail_closed(self):
+        for local, block, allocations in (
+            (True, BYTES_CAPI_LOCAL, self.allocations),
+            (False, BYTES_CAPI_UPSTREAM, self.canonical_allocations),
+        ):
+            source = self.prefix + block + allocations
+            for changed in (
+                self.prefix + "    pass\n" + allocations,
+                source + block,
+                source + source,
+                source.replace("ByteArrayTest", "OtherTest"),
+                source.replace("_testlimitedcapi", "_other"),
+                source.replace("ImportError", "Exception")
+                if local
+                else source.replace("import_module", "other"),
+                "if True:\n"
+                + "".join("    " + line for line in source.splitlines(True)),
+            ):
+                with self.subTest(local=local, changed=changed):
+                    self.assert_rejected(changed, local=local)
+
+    def test_import_and_owner_shadows_fail_closed(self):
+        shadows = (
+            "    _testlimitedcapi = None\n",
+            "    del _testlimitedcapi\n",
+            "    import other as _testlimitedcapi\n",
+            "    def _testlimitedcapi(self): pass\n",
+            "    async def _testlimitedcapi(self): pass\n",
+            "    class _testlimitedcapi: pass\n",
+            "    try:\n        pass\n"
+            "    except Exception as _testlimitedcapi:\n        pass\n",
+            "    match None:\n        case _testlimitedcapi: pass\n",
+            "    global _testlimitedcapi\n",
+            "ByteArrayTest = Other\n",
+            "del ByteArrayTest\n",
+            "from other import ByteArrayTest\n",
+            "def ByteArrayTest(): pass\n",
+            "async def ByteArrayTest(): pass\n",
+            "try:\n    pass\nexcept Exception as ByteArrayTest:\n    pass\n",
+            "match None:\n    case ByteArrayTest: pass\n",
+        )
+        for local, source in ((True, self.old), (False, self.canonical)):
+            for shadow in shadows:
+                with self.subTest(local=local, shadow=shadow):
+                    self.assert_rejected(source + shadow, local=local)
+
+    def test_decoy_cannot_validate_changed_real_import(self):
+        for local, block, allocations in (
+            (True, BYTES_CAPI_LOCAL, self.allocations),
+            (False, BYTES_CAPI_UPSTREAM, self.canonical_allocations),
+        ):
+            decoy = '    """\n' + block + '    """\n'
+            changed = (
+                self.prefix
+                + decoy
+                + block.replace("_testlimitedcapi =", "_testlimitedcapi  =")
+                + allocations
+            )
+            with self.subTest(local=local):
+                self.assert_rejected(changed, local=local)
+        self.assert_rejected(
+            self.canonical.replace(
+                BYTES_CAPI_UPSTREAM,
+                BYTES_CAPI_UPSTREAM.rstrip() + "; unrelated = 1\n",
+            ),
+            local=False,
+        )
+        self.assert_rejected(
+            self.old.replace("# TODO: RUSTPYTHON;", "# changed existing comment;"),
+            local=True,
+        )
+
+    def test_changed_allocation_methods_fail_closed(self):
+        for local, source in ((True, self.old), (False, self.canonical)):
+            for changed in (
+                source.replace("len(b)", "len(other)", 1),
+                source.replace(
+                    "def test_alloc(self):",
+                    "def test_alloc(self):\n        changed = True",
+                ),
+                source.replace("def test_alloc(self):", "def renamed(self):"),
+                source.replace("def test_alloc(self):", "async def test_alloc(self):"),
+                source + "\n    def test_alloc(self): pass\n",
+            ):
+                with self.subTest(local=local, changed=changed):
+                    self.assert_rejected(changed, local=local)
+        for changed in (
+            self.old.replace(
+                "assertGreaterEqual(alloc, len(b))", "assertEqual(alloc, len(b))", 1
+            ),
+            self.old.replace("self.assertGreaterEqual(alloc, len(b))", "pass", 1),
+            self.old.replace(
+                "self.assertGreaterEqual(alloc, len(b))",
+                "self.assertGreaterEqual(alloc, len(b)); "
+                "self.assertGreaterEqual(alloc, len(b))",
+                1,
+            ),
+        ):
+            self.assert_rejected(changed, local=True)
+
+    def test_allocation_method_shadows_fail_closed(self):
+        for name in ("test_alloc", "test_init_alloc"):
+            for local, source in ((True, self.old), (False, self.canonical)):
+                for shadow in (
+                    f"    {name} = None\n",
+                    f"    del {name}\n",
+                    f"    from other import {name}\n",
+                    f"    async def {name}(self): pass\n",
+                    f"    class {name}: pass\n",
+                    "    try:\n        pass\n"
+                    f"    except Exception as {name}:\n        pass\n",
+                    f"    match None:\n        case {name}: pass\n",
+                ):
+                    with self.subTest(name=name, local=local, shadow=shadow):
+                        self.assert_rejected(source + shadow, local=local)
+
+    def test_changed_allocation_explanation_fails_closed(self):
+        for comment in BYTES_ALLOCATION_COMMENTS.values():
+            for replacement in ("", comment.replace("RUSTPYTHON", "changed")):
+                with self.subTest(comment=comment, replacement=replacement):
+                    self.assert_rejected(
+                        self.old.replace(comment, replacement), local=True
+                    )
+
+    def test_other_paths_are_untouched(self):
+        for path in ("Lib/test/other.py", "Lib/other/test_bytes.py"):
+            self.assertEqual(
+                preserve_migration_customizations(Path(path), "old", "new"), "new"
+            )
+
+    def test_file_migration_preserves_guards_and_rejection_writes_nothing(self):
+        guard = (
+            "\n    @unittest.expectedFailure  # TODO: RUSTPYTHON\n"
+            "    def test_example(self):\n        pass\n"
+        )
+        canonical_test = "\n    def test_example(self):\n        pass\n"
+        with tempfile.TemporaryDirectory() as temporary:
+            root = Path(temporary)
+            output = root / self.path
+            output.parent.mkdir(parents=True)
+            output.write_text("import unittest\n" + self.old + guard, encoding="utf-8")
+            source = root / "canonical.py"
+            source.write_text(
+                "import unittest\n" + self.canonical + canonical_test, encoding="utf-8"
+            )
+            before_source = source.read_bytes()
+            before_guards = patches_to_json(extract_patches(output.read_text()))
+            module_file = root / "scripts/update_lib/cmd_migrate.py"
+            with patch("update_lib.cmd_migrate.__file__", str(module_file)):
+                patch_file(source, output, verbose=False)
+                self.assertEqual(
+                    output.read_text(), "import unittest\n" + self.old + guard
+                )
+                self.assertEqual(source.read_bytes(), before_source)
+                self.assertEqual(
+                    patches_to_json(extract_patches(output.read_text())), before_guards
+                )
+                self.assertEqual(
+                    patch_single_content(source, output), output.read_text()
+                )
+                before_output = output.read_bytes()
+                source.write_text(
+                    source.read_text().replace("ByteArrayTest", "OtherTest"),
+                    encoding="utf-8",
+                )
+                rejected_source = source.read_bytes()
+                with self.assertRaises(ValueError):
+                    patch_file(source, output, verbose=False)
+                self.assertEqual(output.read_bytes(), before_output)
+                self.assertEqual(source.read_bytes(), rejected_source)
+
+
+class TestSupportAssignments(unittest.TestCase):
+    names = ["_available", "requires_available", "requires_unavailable"]
+    exports = names[1:]
+    imports = "import os\nimport unittest\n\n"
+    export_line = '    "requires_available", "requires_unavailable",\n'
+    block = (
+        "_available = hasattr(os, 'geteuid') and os.geteuid() == 0\n"
+        'requires_available = unittest.skipUnless(_available, "needs privilege")\n'
+        'requires_unavailable = unittest.skipIf(_available, "needs no privilege")\n\n\n'
+    )
+    source = (
+        imports
+        + '__all__ = [\n    "existing",\n'
+        + export_line
+        + "]\n\n\n"
+        + block
+        + "STATUS = 1\n"
+    )
+    destination = (
+        imports
+        + '__all__ = [\n    "existing",\n]\n\n\ndef legacy():\n    return "keep π"\n\n\nSTATUS = 1\n'
+    )
+
+    def test_canonical_bytes_and_unrelated_helpers_are_preserved(self):
+        result = copy_support_assignments(
+            self.source, self.destination, self.names, self.exports
+        )
+        self.assertEqual(
+            result,
+            self.destination.replace(
+                "__all__ = [\n", "__all__ = [\n" + self.export_line
+            ).replace("STATUS = 1\n", self.block + "STATUS = 1\n"),
+        )
+
+    def test_missing_ambiguous_and_noncontiguous_assignments_are_rejected(self):
+        for source in (
+            self.source.replace("_available =", "_other ="),
+            self.source + "_available = False\n",
+            self.source + "def requires_available(): pass\n",
+            self.source + "import other as requires_unavailable\n",
+            self.source.replace(
+                "requires_available =", "unselected = 0\nrequires_available ="
+            ),
+            self.source.replace("_available =", "unselected = 0; _available =", 1),
+            self.source.replace("STATUS = 1", ""),
+        ):
+            with self.subTest(source=source), self.assertRaises(ValueError):
+                copy_support_assignments(
+                    source, self.destination, self.names, self.exports
+                )
+
+    def test_existing_bindings_dependencies_and_anchor_fail_closed(self):
+        for destination in (
+            self.destination + "_available = False\n",
+            self.destination + "def requires_available(): pass\n",
+            self.destination + "import other as requires_unavailable\n",
+            self.destination.replace("import os\n", ""),
+            self.destination.replace("import os\n", "import os as other\n"),
+            self.destination.replace("import os\n", "") + "import os\n",
+            self.destination.replace("STATUS = 1", "STATUS = 2"),
+            self.destination + "STATUS = 1\n",
+        ):
+            with self.subTest(destination=destination), self.assertRaises(ValueError):
+                copy_support_assignments(
+                    self.source, destination, self.names, self.exports
+                )
+
+    def test_invalid_exports_are_rejected(self):
+        for source, destination, exports in (
+            (self.source, self.destination, self.exports + self.exports),
+            (self.source, self.destination, ["unselected"]),
+            (self.source, self.destination, list(reversed(self.exports))),
+            (self.source, self.destination, self.exports[:1]),
+            (
+                self.source,
+                self.destination.replace('"existing"', '"requires_available"'),
+                self.exports,
+            ),
+            (self.source.replace(self.export_line, ""), self.destination, self.exports),
+            (
+                self.source,
+                self.destination.replace('[\n    "existing",\n]', '("existing",)'),
+                self.exports,
+            ),
+            (self.source.replace('"existing"', "3"), self.destination, self.exports),
+            (self.source, self.destination.replace('"existing"', "3"), self.exports),
+        ):
+            with self.subTest(exports=exports), self.assertRaises(ValueError):
+                copy_support_assignments(source, destination, self.names, exports)
+
+    def test_dependency_rebinding_deletion_and_builtin_shadowing_are_rejected(self):
+        for binding in (
+            "os = replacement",
+            "del os",
+            "import other as os",
+            "hasattr = replacement",
+            "del hasattr",
+            "if condition:\n    unittest = replacement",
+        ):
+            for source_side in (False, True):
+                source, destination = self.source, self.destination
+                if source_side:
+                    source = source.replace("__all__ = [", binding + "\n__all__ = [")
+                else:
+                    destination = destination.replace(
+                        "__all__ = [", binding + "\n__all__ = ["
+                    )
+                with (
+                    self.subTest(binding=binding, source_side=source_side),
+                    self.assertRaisesRegex(ValueError, "Ambiguous dependency binding"),
+                ):
+                    copy_support_assignments(
+                        source, destination, self.names, self.exports
+                    )
+
+    def test_decorated_and_partial_line_anchors_are_rejected(self):
+        for replacement in (
+            "@decorator\ndef anchor(): pass",
+            "STATUS = 1; other = 2",
+            "other = 2; STATUS = 1",
+        ):
+            with self.subTest(replacement=replacement), self.assertRaises(ValueError):
+                copy_support_assignments(
+                    self.source.replace("STATUS = 1", replacement),
+                    self.destination.replace("STATUS = 1", replacement),
+                    self.names,
+                    self.exports,
+                )
+
+    def test_wildcard_import_dependencies_are_rejected(self):
+        for source, destination in (
+            ("from other import *\n" + self.source, self.destination),
+            (self.source, "from other import *\n" + self.destination),
+        ):
+            with self.assertRaisesRegex(ValueError, "Wildcard import"):
+                copy_support_assignments(source, destination, self.names, self.exports)
+
+    def test_cli_hash_pins_scope_and_receipt(self):
+        with tempfile.TemporaryDirectory() as temp, contextlib.chdir(temp):
+            source = pathlib.Path("canonical/Lib/test/support/__init__.py")
+            target = pathlib.Path("Lib/test/support/__init__.py")
+            source.parent.mkdir(parents=True)
+            target.parent.mkdir(parents=True)
+            source.write_text(self.source)
+            target.write_text(self.destination)
+            args = [
+                str(source),
+                "--support-assignments",
+                *self.names,
+                "--support-exports",
+                *self.exports,
+                "--source-sha256",
+                hashlib.sha256(source.read_bytes()).hexdigest(),
+                "--destination-sha256",
+                "0" * 64,
+            ]
+            with contextlib.redirect_stderr(io.StringIO()):
+                self.assertEqual(main(args), 1)
+                self.assertEqual(
+                    main([str(source), "--support-assignments", *self.names]), 1
+                )
+            self.assertEqual(target.read_text(), self.destination)
+            args[-1] = hashlib.sha256(target.read_bytes()).hexdigest()
+            with contextlib.redirect_stdout(io.StringIO()) as output:
+                self.assertEqual(main(args), 0)
+            self.assertIn('"destination_after_sha256"', output.getvalue())
+            self.assertIn(self.block, target.read_text())
+            for path in (
+                "canonical/Lib/os.py",
+                "canonical/Lib/test/support/../../os.py",
+            ):
+                with contextlib.redirect_stderr(io.StringIO()):
+                    self.assertEqual(main([path, *args[1:]]), 1)
+
+    def test_selective_mode_rejects_existing_modes_before_reading_metadata(self):
+        for mode in ("--patches", "--legacy-map"):
+            with contextlib.redirect_stderr(io.StringIO()) as errors:
+                self.assertEqual(
+                    main(
+                        [
+                            "missing/Lib/test/support/example.py",
+                            "--support-assignments",
+                            *self.names,
+                            mode,
+                            "missing-metadata.json",
+                        ]
+                    ),
+                    1,
+                )
+            self.assertIn("cannot combine", errors.getvalue())
+            with contextlib.redirect_stderr(io.StringIO()) as errors:
+                self.assertEqual(
+                    main(
+                        [
+                            "missing/Lib/test/support/example.py",
+                            "--support-exports",
+                            *self.exports,
+                            mode,
+                            "missing-metadata.json",
+                        ]
+                    ),
+                    1,
+                )
+            self.assertIn("require --support-assignments", errors.getvalue())
+
+    def test_default_syntax_error_behavior_is_unchanged(self):
+        with patch(
+            "update_lib.cmd_migrate.patch_file", side_effect=SyntaxError("invalid")
+        ):
+            with self.assertRaises(SyntaxError):
+                main(["missing/Lib/test/support/example.py"])
+        with patch(
+            "update_lib.cmd_migrate.migrate_support_assignments",
+            side_effect=SyntaxError("invalid"),
+        ):
+            with contextlib.redirect_stderr(io.StringIO()) as errors:
+                self.assertEqual(
+                    main(
+                        [
+                            "missing/Lib/test/support/example.py",
+                            "--support-assignments",
+                            *self.names,
+                        ]
+                    ),
+                    1,
+                )
+            self.assertIn("invalid", errors.getvalue())
 
 
 class TestPatchSingleContent(unittest.TestCase):
     """Tests for patch_single_content function."""
 
+    def migrate_doctest(self, selection=None, explicit=False):
+        old = '''"""
+>>> raise X, Y  # TODO: RUSTPYTHON; old mismatch # doctest: +EXPECTED_FAILURE
+SyntaxError: old result
+>>> raise Z  # TODO: RUSTPYTHON; obsolete mismatch # doctest: +EXPECTED_FAILURE
+SyntaxError: obsolete result
+"""
+'''
+        canonical = (
+            '''"""
+>>> raise X, Y
+SyntaxError: canonical result
+>>> raise Z
+SyntaxError: canonical second result
+"""
+'''
+            + CANONICAL_LOAD_TESTS
+            + "\n"
+        )
+        with tempfile.TemporaryDirectory() as temporary:
+            root = Path(temporary) / "repository"
+            target = root / "Lib/test/test_example.py"
+            target.parent.mkdir(parents=True)
+            target.write_text(old)
+            source = Path(temporary) / "canonical/Lib/test/test_example.py"
+            source.parent.mkdir(parents=True)
+            source.write_text(canonical)
+            args = [str(source)]
+            if explicit:
+                metadata = Path(temporary) / "selection.json"
+                metadata.write_text(
+                    json.dumps(
+                        {
+                            "target": "Lib/test/test_example.py",
+                            "patches": {},
+                            "doctests": selection,
+                        }
+                    )
+                )
+                args += ["--patches", str(metadata)]
+            with (
+                contextlib.chdir(root),
+                patch(
+                    "update_lib.cmd_migrate.__file__",
+                    str(root / "scripts/update_lib/cmd_migrate.py"),
+                ),
+                contextlib.redirect_stdout(io.StringIO()),
+                contextlib.redirect_stderr(io.StringIO()),
+            ):
+                result = main(args)
+            return result, target.read_text(), old, canonical
+
+    def test_doctest_default_requires_explicit_selection(self):
+        status, result, old, _ = self.migrate_doctest()
+        self.assertEqual(status, 1)
+        self.assertEqual(result, old)
+
+    def test_doctest_cli_selection_keeps_only_reviewed_guard(self):
+        status, result, _, _ = self.migrate_doctest(
+            {"raise X, Y\n": "known mismatch"}, True
+        )
+        self.assertEqual(status, 0)
+        self.assertEqual(result.count("+EXPECTED_FAILURE"), 1)
+        self.assertIn("SyntaxError: canonical result", result)
+        self.assertIn("SyntaxError: canonical second result", result)
+        self.assertNotIn("obsolete mismatch", result)
+
+    def test_doctest_empty_selection_keeps_canonical_unchanged(self):
+        status, result, _, canonical = self.migrate_doctest({}, True)
+        self.assertEqual(status, 0)
+        self.assertEqual(result, canonical)
+
+    def test_doctest_invalid_selection_writes_nothing(self):
+        for selection in (
+            None,
+            [],
+            {"raise unknown\n": "unrecognized"},
+            {"raise X, Y\n": "line\nbreak"},
+        ):
+            with self.subTest(selection=selection):
+                status, result, old, _ = self.migrate_doctest(selection, True)
+                self.assertEqual(status, 1)
+                self.assertEqual(result, old)
+
     def test_patch_with_no_existing_file(self):
         """Test patching when lib file doesn't exist."""
         with tempfile.TemporaryDirectory() as tmpdir:
@@ -136,6 +867,48 @@ def test_one(self):
 class TestPatchDirectory(unittest.TestCase):
     """Tests for patch_directory function."""
 
+    def test_empty_canonical_fixture_stays_byte_empty(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            source, target = Path(temporary) / "canonical", Path(temporary) / "local"
+            source.mkdir()
+            target.mkdir()
+            (source / "empty.py").write_bytes(b"")
+            (target / "empty.py").write_bytes(b"\n")
+            for _ in range(2):
+                patch_directory(source, target, verbose=False)
+                self.assertEqual((target / "empty.py").read_bytes(), b"")
+
+    def test_excludes_cache_directories_but_preserves_canonical_assets(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            root = pathlib.Path(temporary)
+            source = root / "source"
+            destination = root / "destination"
+            for relative in ("__pycache__", "nested/__pycache__", "assets"):
+                (source / relative).mkdir(parents=True)
+            files = {
+                "module.py": b"# canonical source\n",
+                "__pycache__/module.cpython-315.pyc": b"stale cache",
+                "nested/__pycache__/module.cpython-315.pyc": b"nested cache",
+                "assets/__pycache__": b"ordinary canonical file",
+                "assets/fixture.pyc": b"canonical bytecode fixture",
+            }
+            for relative, content in files.items():
+                (source / relative).write_bytes(content)
+            patch_directory(source, destination, verbose=False)
+            expected = {
+                relative: content
+                for relative, content in files.items()
+                if "__pycache__" not in pathlib.Path(relative).parts[:-1]
+            }
+            actual = {
+                path.relative_to(destination).as_posix(): path.read_bytes()
+                for path in destination.rglob("*")
+                if path.is_file()
+            }
+            self.assertEqual(actual, expected)
+            for relative, content in files.items():
+                self.assertEqual((source / relative).read_bytes(), content)
+
     def test_patch_directory_all_files(self):
         """Test that patch_directory processes all .py files."""
         with tempfile.TemporaryDirectory() as tmpdir:
@@ -192,5 +965,954 @@ def test_one(self):
             self.assertIn("@unittest.expectedFailure", content)
 
 
+class RuntimePatchTests(unittest.TestCase):
+    def test_sysconfig_identity_and_new_content(self):
+        path = Path("Lib/sysconfig/__init__.py")
+        source = SYSCONFIG_UPSTREAM + "new_final_behavior = True\n"
+        result = preserve_migration_customizations(path, SYSCONFIG_LOCAL, source)
+        self.assertEqual(result, SYSCONFIG_LOCAL + "new_final_behavior = True\n")
+        self.assertEqual(
+            preserve_migration_customizations(path, result, source), result
+        )
+
+    def test_pickle_jit_mapping_and_new_content(self):
+        path = Path("Lib/_compat_pickle.py")
+        source = "final_mapping = 'ImportCycleError'\n" + EXCEPTION_LOOP
+        result = preserve_migration_customizations(
+            path, JIT_ERROR + EXCEPTION_LOOP, source
+        )
+        self.assertEqual(
+            result, "final_mapping = 'ImportCycleError'\n" + JIT_ERROR + EXCEPTION_LOOP
+        )
+        self.assertEqual(
+            preserve_migration_customizations(path, result, source), result
+        )
+
+    def test_changed_or_ambiguous_anchors_fail(self):
+        cases = [
+            (Path("Lib/sysconfig/__init__.py"), SYSCONFIG_LOCAL, SYSCONFIG_UPSTREAM),
+            (Path("Lib/_compat_pickle.py"), JIT_ERROR + EXCEPTION_LOOP, EXCEPTION_LOOP),
+        ]
+        for path, old, source in cases:
+            for bad_old in (
+                "",
+                old + old,
+                old.replace("RustPython", "Other").replace("JitError", "Other"),
+            ):
+                with (
+                    self.subTest(path=path, bad_old=bad_old),
+                    self.assertRaises(ValueError),
+                ):
+                    preserve_migration_customizations(path, bad_old, source)
+            for bad_source in (
+                "",
+                source + source,
+                source.replace("Python", "Other").replace("excname", "other"),
+            ):
+                with (
+                    self.subTest(path=path, bad_source=bad_source),
+                    self.assertRaises(ValueError),
+                ):
+                    preserve_migration_customizations(path, old, bad_source)
+
+    def test_unrelated_file_unchanged(self):
+        self.assertEqual(
+            preserve_migration_customizations(Path("Lib/other.py"), JIT_ERROR, "new\n"),
+            "new\n",
+        )
+
+    def test_decoy_and_shadowed_sysconfig_anchors_fail(self):
+        path = Path("Lib/sysconfig/__init__.py")
+        for source in (
+            'doc = """' + SYSCONFIG_UPSTREAM + '"""\n',
+            SYSCONFIG_UPSTREAM + "def _get_implementation():\n    return 'Other'\n",
+            SYSCONFIG_UPSTREAM + "_get_implementation = lambda: 'Other'\n",
+            SYSCONFIG_UPSTREAM + "from other import _get_implementation\n",
+            SYSCONFIG_UPSTREAM + "import other as _get_implementation\n",
+            SYSCONFIG_UPSTREAM + "class _get_implementation: pass\n",
+            SYSCONFIG_UPSTREAM + "del _get_implementation\n",
+        ):
+            with self.subTest(source=source), self.assertRaises(ValueError):
+                preserve_migration_customizations(path, SYSCONFIG_LOCAL, source)
+
+    def test_decoy_and_reordered_pickle_anchors_fail(self):
+        path = Path("Lib/_compat_pickle.py")
+        old = JIT_ERROR + EXCEPTION_LOOP
+        with self.assertRaises(ValueError):
+            preserve_migration_customizations(
+                path, old, 'doc = """' + EXCEPTION_LOOP + '"""\n'
+            )
+        with self.assertRaises(ValueError):
+            preserve_migration_customizations(
+                path, EXCEPTION_LOOP + JIT_ERROR, EXCEPTION_LOOP
+            )
+
+    def test_similarly_named_nested_files_are_untouched(self):
+        for path in (
+            "Lib/other/sysconfig/__init__.py",
+            "Lib/other/_compat_pickle.py",
+            "other/sysconfig/__init__.py",
+        ):
+            self.assertEqual(
+                preserve_migration_customizations(Path(path), "old", "new"), "new"
+            )
+
+    def test_absolute_target_requires_explicit_repository_resolution(self):
+        with self.assertRaises(ValueError):
+            preserve_migration_customizations(
+                Path("/parent/Lib/repository/Lib/sysconfig/__init__.py"),
+                SYSCONFIG_LOCAL,
+                SYSCONFIG_UPSTREAM,
+            )
+
+    def test_migrate_resolves_real_repository_under_lib_parent(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            root = Path(temporary) / "Lib" / "repository"
+            output = root / "Lib" / "sysconfig" / "__init__.py"
+            output.parent.mkdir(parents=True)
+            output.write_text(SYSCONFIG_LOCAL, encoding="utf-8")
+            source = Path(temporary) / "canonical.py"
+            source.write_text(SYSCONFIG_UPSTREAM, encoding="utf-8")
+            module_file = root / "scripts" / "update_lib" / "cmd_migrate.py"
+            with patch("update_lib.cmd_migrate.__file__", str(module_file)):
+                self.assertEqual(patch_single_content(source, output), SYSCONFIG_LOCAL)
+                outside = (
+                    Path(temporary) / "outside" / "Lib" / "sysconfig" / "__init__.py"
+                )
+                outside.parent.mkdir(parents=True)
+                outside.write_text(SYSCONFIG_LOCAL, encoding="utf-8")
+                self.assertEqual(
+                    patch_single_content(source, outside), SYSCONFIG_UPSTREAM
+                )
+
+
+CALL_PATH = Path("Lib/test/test_cmd_line.py")
+CALL_TEMPLATE = """class CmdLineTest:
+    def test_empty_PYTHONPATH_issue16309(self):
+        result = CALL
+        self.assertEqual(result, 'new final assertion')
+"""
+CALL_OLD = CALL_TEMPLATE.replace("CALL", LOCAL_CALL).replace(
+    "new final assertion", "old assertion"
+)
+CALL_CANONICAL = CALL_TEMPLATE.replace("CALL", CANONICAL_CALL)
+
+
+class CallPatchTests(unittest.TestCase):
+    def test_final_body_and_roundtrip(self):
+        result = preserve_migration_customizations(CALL_PATH, CALL_OLD, CALL_CANONICAL)
+        self.assertEqual(result, CALL_TEMPLATE.replace("CALL", LOCAL_CALL))
+        self.assertIn("new final assertion", result)
+        self.assertEqual(
+            preserve_migration_customizations(CALL_PATH, result, CALL_CANONICAL), result
+        )
+
+    def test_missing_duplicate_owners_and_calls_fail(self):
+        for source in (
+            CALL_CANONICAL.replace("CmdLineTest", "Other"),
+            CALL_CANONICAL + CALL_CANONICAL,
+            CALL_CANONICAL.replace(
+                "        result = ", "        " + CANONICAL_CALL + "\n        result = "
+            ),
+            CALL_CANONICAL.replace("test_empty_PYTHONPATH_issue16309", "other"),
+        ):
+            with self.subTest(source=source), self.assertRaises(ValueError):
+                preserve_migration_customizations(CALL_PATH, CALL_OLD, source)
+
+    def test_changed_keywords_and_decoy_fail(self):
+        for old in (
+            CALL_OLD.replace('RUSTPYTHONPATH=""', 'RUSTPYTHONPATH="changed"'),
+            CALL_CANONICAL,
+            'doc = """' + CALL_OLD + '"""\n',
+        ):
+            with self.subTest(old=old), self.assertRaises(ValueError):
+                preserve_migration_customizations(CALL_PATH, old, CALL_CANONICAL)
+        with self.assertRaises(ValueError):
+            preserve_migration_customizations(
+                CALL_PATH,
+                CALL_OLD,
+                CALL_CANONICAL.replace('PYTHONPATH=""', 'PYTHONPATH="changed"'),
+            )
+
+    def test_unrelated_file_unchanged(self):
+        self.assertEqual(
+            preserve_migration_customizations(Path("Lib/test/other.py"), "old", "new"),
+            "new",
+        )
+
+
+OVERRIDE_CLEAN = """import unittest
+class Example(unittest.TestCase):
+    def test_known(self):
+        self.assertEqual(1, 1)
+    def test_guarded(self):
+        self.assertEqual(2, 2)
+"""
+OVERRIDE_OLD = OVERRIDE_CLEAN.replace(
+    "    def test_known",
+    "    @unittest.expectedFailure  # TODO: RUSTPYTHON; old failure\n    def test_known",
+).replace(
+    "    def test_guarded",
+    '    @unittest.skip("TODO: RUSTPYTHON; retained guard")\n    def test_guarded',
+)
+
+
+class MarkerOverrideTests(unittest.TestCase):
+    def invoke(self, mutation=None, directory=False, override=True, legacy=False):
+        with tempfile.TemporaryDirectory() as temporary:
+            root = Path(temporary) / "repository"
+            output = root / "Lib" / "test" / "test_example.py"
+            output.parent.mkdir(parents=True)
+            output.write_text(OVERRIDE_OLD)
+            source = Path(temporary) / "cpython" / "Lib" / "test" / "test_example.py"
+            source.parent.mkdir(parents=True)
+            source.write_text(OVERRIDE_CLEAN)
+            markers = patches_to_json(extract_patches(OVERRIDE_OLD))
+            del markers["Example"]["test_known"]
+            document = {"target": "Lib/test/test_example.py", "patches": markers}
+            if mutation:
+                mutation(document)
+            metadata = Path(temporary) / "remaining.json"
+            metadata.write_text(json.dumps(document))
+            args = [str(source.parent if directory else source)]
+            if override:
+                args += ["--patches", str(metadata)]
+            if legacy:
+                args += ["--legacy-map", str(metadata)]
+            with (
+                contextlib.chdir(root),
+                patch(
+                    "update_lib.cmd_migrate.__file__",
+                    str(root / "scripts/update_lib/cmd_migrate.py"),
+                ),
+                contextlib.redirect_stdout(io.StringIO()),
+                contextlib.redirect_stderr(io.StringIO()),
+            ):
+                status = main(args)
+            return status, output.read_text()
+
+    def test_cli_override_removes_only_requested_expected_failure(self):
+        status, result = self.invoke()
+        self.assertEqual(status, 0)
+        self.assertNotIn("expectedFailure", result)
+        self.assertIn('unittest.skip("TODO: RUSTPYTHON; retained guard")', result)
+        self.assertIn("self.assertEqual(1, 1)", result)
+        self.assertIn("self.assertEqual(2, 2)", result)
+
+    def test_default_migration_preserves_all_markers(self):
+        status, result = self.invoke(override=False)
+        self.assertEqual(status, 0)
+        self.assertIn("expectedFailure", result)
+        self.assertIn("retained guard", result)
+
+    def test_invalid_target_does_not_write(self):
+        status, result = self.invoke(
+            lambda document: document.update(target="Lib/test/other.py")
+        )
+        self.assertEqual(status, 1)
+        self.assertEqual(result, OVERRIDE_OLD)
+
+    def test_removing_skip_does_not_write(self):
+        status, result = self.invoke(
+            lambda document: document["patches"]["Example"].clear()
+        )
+        self.assertEqual(status, 1)
+        self.assertEqual(result, OVERRIDE_OLD)
+
+    def test_directory_override_does_not_write(self):
+        status, result = self.invoke(directory=True)
+        self.assertEqual(status, 1)
+        self.assertEqual(result, OVERRIDE_OLD)
+
+    def test_legacy_combination_does_not_write(self):
+        status, result = self.invoke(legacy=True)
+        self.assertEqual(status, 1)
+        self.assertEqual(result, OVERRIDE_OLD)
+
+    def test_added_changed_or_reordered_markers_fail(self):
+        failure = PatchSpec(UtMethod.ExpectedFailure, reason="known failure")
+        success = PatchSpec(UtMethod.ExpectedSuccess, reason="known success")
+        current = {"Example": {"test_known": [failure, success]}}
+        for markers in (
+            [failure, success, failure],
+            [PatchSpec(UtMethod.ExpectedFailure, reason="changed"), success],
+            [success, failure],
+        ):
+            document = {
+                "target": "Lib/test/test_example.py",
+                "patches": patches_to_json({"Example": {"test_known": markers}}),
+            }
+            with self.subTest(markers=markers), self.assertRaises(ValueError):
+                select_remaining_patches(current, document, Path(document["target"]))
+
+
+class ConditionalMarkerOverrideTests(unittest.TestCase):
+    decorator = (
+        '    @unittest.expectedFailureIf(not support.is_android, "TODO: RUSTPYTHON")\n'
+    )
+
+    def fixture(self):
+        old = OVERRIDE_CLEAN.replace(
+            "    def test_known", self.decorator + "    def test_known"
+        )
+        current = extract_patches(old)
+        document = {
+            "target": "Lib/test/test_example.py",
+            "patches": {},
+            "retire_conditional": [
+                {
+                    "class": "Example",
+                    "method": "test_known",
+                    "decorator": self.decorator,
+                }
+            ],
+        }
+        return old, current, document
+
+    def select(self, old, current, document):
+        return select_remaining_patches(
+            current,
+            document,
+            Path(document["target"]),
+            old_content=old,
+        )
+
+    def test_explicit_conditional_retirement(self):
+        old, current, document = self.fixture()
+        self.assertEqual(self.select(old, current, document), {})
+
+    def test_omitted_conditional_without_authorization_fails(self):
+        old, current, document = self.fixture()
+        del document["retire_conditional"]
+        with self.assertRaises(ValueError):
+            self.select(old, current, document)
+
+    def test_absent_duplicate_modified_and_retained_fail_closed(self):
+        for change in (
+            "absent",
+            "duplicate",
+            "text",
+            "condition",
+            "retained",
+            "duplicate_source",
+        ):
+            old, current, document = self.fixture()
+            with self.subTest(change=change), self.assertRaises(ValueError):
+                if change == "absent":
+                    document["retire_conditional"][0]["method"] = "missing"
+                elif change == "duplicate":
+                    document["retire_conditional"] *= 2
+                elif change == "text":
+                    document["retire_conditional"][0]["decorator"] = (
+                        self.decorator.replace('"', "'")
+                    )
+                elif change == "condition":
+                    old = old.replace("not support.is_android", "support.is_android")
+                    current = extract_patches(old)
+                elif change == "retained":
+                    document["patches"] = patches_to_json(current)
+                elif change == "duplicate_source":
+                    old = old.replace(self.decorator, self.decorator * 2)
+                    current = extract_patches(old)
+                self.select(old, current, document)
+
+    def test_other_guards_and_original_source_required(self):
+        for replacement in ("skipIf", "expectedFailureIfWindows"):
+            old, current, document = self.fixture()
+            old = old.replace("expectedFailureIf", replacement)
+            document["retire_conditional"][0]["decorator"] = self.decorator.replace(
+                "expectedFailureIf", replacement
+            )
+            with self.subTest(replacement=replacement), self.assertRaises(ValueError):
+                self.select(old, extract_patches(old), document)
+        old, current, document = self.fixture()
+        with self.assertRaises(ValueError):
+            self.select(None, current, document)
+
+    def test_cli_conditional_retirement_preserves_remaining_markers(self):
+        old = OVERRIDE_OLD.replace(
+            "    @unittest.expectedFailure  # TODO: RUSTPYTHON; old failure\n",
+            self.decorator,
+        )
+
+        def authorize(document):
+            document["retire_conditional"] = [
+                {
+                    "class": "Example",
+                    "method": "test_known",
+                    "decorator": self.decorator,
+                }
+            ]
+
+        with patch(__name__ + ".OVERRIDE_OLD", old):
+            status, result = MarkerOverrideTests().invoke(authorize)
+            self.assertEqual(status, 0)
+            self.assertNotIn("expectedFailureIf", result)
+            self.assertIn('unittest.skip("TODO: RUSTPYTHON; retained guard")', result)
+            status, result = MarkerOverrideTests().invoke()
+            self.assertEqual(status, 1)
+            self.assertEqual(result, old)
+
+
+PACKAGE_MARKED = """import unittest
+class Example:
+    @unittest.expectedFailure  # TODO: RUSTPYTHON; retained reason
+    def test_one(self):
+        pass
+"""
+PACKAGE_CANONICAL = """import unittest
+class Example:
+    def test_one(self):
+        pass
+"""
+
+
+class TestMigratePackage(unittest.TestCase):
+    def setUp(self):
+        self.temp = tempfile.TemporaryDirectory()
+        self.addCleanup(self.temp.cleanup)
+        self.root = Path(self.temp.name)
+        self.src = self.root / "canonical" / "package"
+        self.src.mkdir(parents=True)
+        (self.src / "__init__.py").write_text("# canonical package\n")
+        (self.src / "test_part.py").write_text(PACKAGE_CANONICAL)
+        self.dest = self.root / "Lib" / "test" / "package"
+        self.dest.parent.mkdir(parents=True)
+        self.old = self.dest.parent / "old.py"
+        self.old.write_text(PACKAGE_MARKED)
+        self.manifest = self.root / "map.json"
+        self.mapping = {"old.py": {"Example": "test_part.py"}}
+
+    def run_migration(self):
+        self.manifest.write_text(json.dumps(self.mapping))
+        migrate_package(self.src, self.dest, self.manifest)
+
+    def assert_rejected(self):
+        before = self.old.read_bytes()
+        with self.assertRaises((ValueError, FileNotFoundError, SyntaxError)):
+            self.run_migration()
+        self.assertFalse(self.dest.exists())
+        self.assertEqual(self.old.read_bytes(), before)
+
+    def test_preserves_marker_and_canonical_asset(self):
+        (self.src / "asset.dat").write_bytes(b"\x00canonical")
+        self.run_migration()
+        self.assertFalse(self.old.exists())
+        self.assertEqual((self.dest / "asset.dat").read_bytes(), b"\x00canonical")
+        self.assertEqual(
+            list(iter_patches((self.dest / "test_part.py").read_text())),
+            list(iter_patches(PACKAGE_MARKED)),
+        )
+
+    def test_preserves_inherited_override(self):
+        (self.src / "test_part.py").write_text(
+            PACKAGE_CANONICAL.replace("class Example:", "class Base:")
+            + "\nclass Example(Base):\n    pass\n"
+        )
+        self.run_migration()
+        text = (self.dest / "test_part.py").read_text()
+        self.assertIn("return super().test_one()", text)
+        self.assertEqual(list(iter_patches(text)), list(iter_patches(PACKAGE_MARKED)))
+
+    def test_excludes_cache_directories_but_preserves_canonical_assets(self):
+        for relative in ("__pycache__", "nested/__pycache__", "assets"):
+            (self.src / relative).mkdir(parents=True)
+        files = {
+            "__pycache__/module.cpython-315.pyc": b"stale cache",
+            "nested/__pycache__/module.cpython-315.pyc": b"nested cache",
+            "assets/__pycache__": b"ordinary canonical file",
+            "assets/fixture.pyc": b"canonical bytecode fixture",
+        }
+        for relative, content in files.items():
+            (self.src / relative).write_bytes(content)
+        self.run_migration()
+        self.assertFalse((self.dest / "__pycache__").exists())
+        self.assertFalse((self.dest / "nested" / "__pycache__").exists())
+        for relative in ("assets/__pycache__", "assets/fixture.pyc"):
+            self.assertEqual((self.dest / relative).read_bytes(), files[relative])
+        for relative, content in files.items():
+            self.assertEqual((self.src / relative).read_bytes(), content)
+
+    def test_missing_method(self):
+        (self.src / "test_part.py").write_text(
+            PACKAGE_CANONICAL.replace("test_one", "test_other")
+        )
+        self.assert_rejected()
+
+    def test_missing_class(self):
+        (self.src / "test_part.py").write_text(
+            PACKAGE_CANONICAL.replace("Example", "Other")
+        )
+        self.assert_rejected()
+
+    def test_ambiguous_class(self):
+        (self.src / "test_part.py").write_text(PACKAGE_CANONICAL + PACKAGE_CANONICAL)
+        self.assert_rejected()
+
+    def test_ambiguous_method(self):
+        (self.src / "test_part.py").write_text(
+            PACKAGE_CANONICAL + "    def test_one(self):\n        pass\n"
+        )
+        self.assert_rejected()
+
+    def test_missing_destination(self):
+        self.mapping["old.py"]["Example"] = "missing.py"
+        self.assert_rejected()
+
+    def test_unused_mapping(self):
+        self.mapping["old.py"]["Unused"] = "test_part.py"
+        self.assert_rejected()
+
+    def test_unmapped_marker(self):
+        self.mapping["old.py"] = {}
+        self.assert_rejected()
+
+    def test_target_traversal(self):
+        self.mapping["old.py"]["Example"] = "../outside.py"
+        self.assert_rejected()
+
+    def test_legacy_traversal(self):
+        self.mapping["../old.py"] = self.mapping.pop("old.py")
+        self.assert_rejected()
+
+    def test_duplicate_marker(self):
+        (self.old.parent / "second.py").write_text(PACKAGE_MARKED)
+        self.mapping["second.py"] = self.mapping["old.py"]
+        self.assert_rejected()
+        self.assertEqual((self.old.parent / "second.py").read_text(), PACKAGE_MARKED)
+
+    def test_preserves_ordered_markers_from_one_legacy_method(self):
+        marked = PACKAGE_MARKED.replace(
+            "    def test_one",
+            '    @unittest.skip("TODO: RUSTPYTHON; retained skip")\n    def test_one',
+        )
+        self.old.write_text(marked)
+        self.run_migration()
+        result = (self.dest / "test_part.py").read_text()
+        self.assertEqual(list(iter_patches(result)), list(iter_patches(marked)))
+        self.assertLess(result.index("expectedFailure"), result.index("unittest.skip"))
+
+    def test_duplicate_legacy_owner_is_rejected(self):
+        for source in (
+            PACKAGE_MARKED + PACKAGE_MARKED,
+            PACKAGE_MARKED + "    def test_one(self):\n        pass\n",
+        ):
+            with self.subTest(source=source):
+                self.old.write_text(source)
+                self.assert_rejected()
+
+    def test_unmarked_legacy_retired(self):
+        self.old.write_text(PACKAGE_CANONICAL)
+        self.mapping["old.py"] = {}
+        self.run_migration()
+        self.assertFalse(self.old.exists())
+        self.assertEqual((self.dest / "test_part.py").read_text(), PACKAGE_CANONICAL)
+
+    def test_legacy_doctest_guards_prevent_all_writes(self):
+        self.old.write_text(
+            '"""\n'
+            ">>> raise ValueError  # TODO: RUSTPYTHON; mismatch # doctest: +EXPECTED_FAILURE\n"
+            "ValueError\n"
+            '"""\n' + PACKAGE_MARKED
+        )
+        self.assert_rejected()
+
+    def test_validation_failure_after_valid_entry_writes_nothing(self):
+        self.mapping["missing.py"] = {}
+        self.assert_rejected()
+
+    def test_existing_destination_is_not_overwritten(self):
+        self.dest.mkdir()
+        with self.assertRaises(ValueError):
+            self.run_migration()
+        self.assertTrue(self.old.exists())
+        self.assertEqual(list(self.dest.iterdir()), [])
+
+    def test_source_escape_rejected(self):
+        outside = self.root / "outside.py"
+        outside.write_text(PACKAGE_CANONICAL)
+        (self.src / "test_part.py").unlink()
+        (self.src / "test_part.py").symlink_to(outside)
+        self.assert_rejected()
+
+    def test_legacy_symlink_rejected(self):
+        outside = self.root / "outside.py"
+        outside.write_text(PACKAGE_MARKED)
+        self.old.unlink()
+        self.old.symlink_to(outside)
+        self.assert_rejected()
+
+    def test_inheritance_cycle_rejected(self):
+        (self.src / "test_part.py").write_text(
+            "class Example(Base):\n    pass\nclass Base(Example):\n    pass\n"
+        )
+        self.assert_rejected()
+
+    def test_canonical_marker_collision_rejected(self):
+        (self.src / "test_part.py").write_text(PACKAGE_MARKED)
+        self.assert_rejected()
+
+    def test_unmarked_syntax_error_prevents_all_writes(self):
+        (self.src / "broken.py").write_text("class :\n")
+        self.assert_rejected()
+
+
+class TestCanonicalRemovals(unittest.TestCase):
+    def setUp(self):
+        temporary = tempfile.TemporaryDirectory()
+        self.addCleanup(temporary.cleanup)
+        self.root = Path(temporary.name)
+        self.source = self.root / "canonical/Lib/test/test_example"
+        self.target = self.root / "local/Lib/test/test_example"
+        self.source.mkdir(parents=True)
+        self.target.mkdir(parents=True)
+        (self.source / "__init__.py").write_bytes(b"")
+        self.git("init", "-q")
+        self.git("add", ".")
+        self.git("commit", "-qm", "canonical test fixture")
+        self.document = {
+            "source": {
+                "path": "Lib/test/test_example",
+                "commit": self.git("rev-parse", "HEAD"),
+                "tree": self.git("rev-parse", "HEAD:Lib/test/test_example"),
+            },
+            "removals": {},
+        }
+        for name, data in (("a.py", b"old\n"), ("data/z.bin", b"\x00\xff")):
+            path = self.target / name
+            path.parent.mkdir(exist_ok=True)
+            path.write_bytes(data)
+            self.document["removals"][name] = {
+                "sha256": hashlib.sha256(data).hexdigest(),
+                "upstream_commit": "1" * 40,
+            }
+        self.manifest = self.root / "removals.json"
+
+    def git(self, *args):
+        return subprocess.check_output(
+            ["git", "-C", str(self.source.parents[2]), *args],
+            env={
+                **os.environ,
+                "GIT_AUTHOR_NAME": "Fixture",
+                "GIT_AUTHOR_EMAIL": "fixture@example.invalid",
+                "GIT_COMMITTER_NAME": "Fixture",
+                "GIT_COMMITTER_EMAIL": "fixture@example.invalid",
+            },
+            text=True,
+        ).strip()
+
+    def run_removal(self, dry_run=False):
+        self.manifest.write_text(json.dumps(self.document))
+        with (
+            contextlib.chdir(self.target.parents[2]),
+            contextlib.redirect_stdout(io.StringIO()),
+        ):
+            return remove_canonical_files(self.source, self.manifest, dry_run=dry_run)
+
+    def test_dry_run_explicit_scope_receipt_and_idempotence(self):
+        (self.target / "unselected").write_text("keep")
+        for dry_run, expected in (
+            (True, "would_remove"),
+            (False, "removed"),
+            (False, "already_absent"),
+        ):
+            receipt = self.run_removal(dry_run)
+            self.assertEqual(receipt["source"], self.document["source"])
+            self.assertEqual(
+                {v["status"] for v in receipt["removals"].values()}, {expected}
+            )
+            self.assertEqual((self.target / "a.py").exists(), dry_run)
+            self.assertEqual((self.target / "unselected").read_text(), "keep")
+
+    def test_junction_components_reject_the_whole_batch(self):
+        before = {
+            name: (self.target / name).read_bytes()
+            for name in self.document["removals"]
+        }
+        for junction in (
+            self.source,
+            self.source.parent,
+            self.source / "data",
+            self.target,
+            self.target.parent,
+            self.target / "data",
+        ):
+            for dry_run in (True, False):
+                with self.subTest(junction=junction, dry_run=dry_run):
+                    self.assertFalse(junction.is_symlink())
+                    with (
+                        patch.object(
+                            Path,
+                            "is_junction",
+                            autospec=True,
+                            side_effect=lambda path: path == junction,
+                        ),
+                        self.assertRaisesRegex(ValueError, "[Jj]unction"),
+                    ):
+                        self.run_removal(dry_run)
+                    self.assertEqual(
+                        {name: (self.target / name).read_bytes() for name in before},
+                        before,
+                    )
+
+    def test_junction_revalidation_prevents_partial_removal(self):
+        for junction in (self.target / "data", self.source / "data"):
+            checks = 0
+
+            def becomes_junction(path):
+                nonlocal checks
+                if path == junction:
+                    checks += 1
+                    return checks > 1
+                return False
+
+            with self.subTest(junction=junction):
+                with (
+                    patch.object(
+                        Path, "is_junction", autospec=True, side_effect=becomes_junction
+                    ),
+                    self.assertRaisesRegex(ValueError, "[Jj]unction"),
+                ):
+                    self.run_removal()
+                self.assertEqual(checks, 2)
+                self.assertEqual((self.target / "a.py").read_bytes(), b"old\n")
+                self.assertEqual((self.target / "data/z.bin").read_bytes(), b"\x00\xff")
+
+    def test_utf8_manifest_ignores_non_utf8_default_encoding(self):
+        name = "caf\u00e9.py"
+        target = self.target / name
+        target.write_bytes(b"old\n")
+        self.document["removals"][name] = dict(self.document["removals"]["a.py"])
+        self.manifest.write_bytes(
+            json.dumps(self.document, ensure_ascii=False).encode("utf-8")
+        )
+        with (
+            patch(
+                "pathlib.io.text_encoding",
+                side_effect=lambda encoding, *args: (
+                    "latin-1" if encoding is None else encoding
+                ),
+            ),
+            contextlib.chdir(self.target.parents[2]),
+            contextlib.redirect_stdout(io.StringIO()),
+        ):
+            self.assertNotEqual(
+                self.manifest.read_text(), self.manifest.read_text(encoding="utf-8")
+            )
+            for dry_run, expected in (
+                (True, "would_remove"),
+                (False, "removed"),
+                (False, "already_absent"),
+            ):
+                receipt = remove_canonical_files(
+                    self.source, self.manifest, dry_run=dry_run
+                )
+                self.assertEqual(
+                    set(receipt["removals"]), set(self.document["removals"])
+                )
+                self.assertEqual(receipt["removals"][name]["status"], expected)
+                self.assertEqual(target.exists(), dry_run)
+
+    def test_cli_dry_run_never_migrates_or_changes_destination_bytes(self):
+        def snapshot():
+            return {
+                p.relative_to(self.target): p.read_bytes()
+                for p in self.target.rglob("*")
+                if p.is_file()
+            }
+
+        before = snapshot()
+        self.manifest.write_text(json.dumps(self.document))
+        with contextlib.ExitStack() as stack:
+            stack.enter_context(contextlib.chdir(self.target.parents[2]))
+            stack.enter_context(contextlib.redirect_stdout(io.StringIO()))
+            for name in (
+                "patch_file",
+                "patch_directory",
+                "migrate_package",
+                "migrate_support_assignments",
+            ):
+                stack.enter_context(
+                    patch(
+                        f"update_lib.cmd_migrate.{name}",
+                        side_effect=AssertionError("Dry-run must not migrate"),
+                    )
+                )
+            self.assertEqual(
+                main(
+                    [
+                        str(self.source),
+                        "--canonical-removals",
+                        str(self.manifest),
+                        "--dry-run",
+                    ]
+                ),
+                0,
+            )
+        self.assertEqual(snapshot(), before)
+
+    def test_hash_customization_and_all_batch_preflight(self):
+        path = self.target / "data/z.bin"
+        for data, repin in ((b"changed", False), (b"# TODO: RUSTPYTHON", True)):
+            path.write_bytes(data)
+            if repin:
+                self.document["removals"]["data/z.bin"]["sha256"] = hashlib.sha256(
+                    data
+                ).hexdigest()
+            with self.assertRaises(ValueError):
+                self.run_removal()
+            self.assertEqual((self.target / "a.py").read_bytes(), b"old\n")
+
+    def test_canonical_source_identity_and_tracked_absence(self):
+        for key, value in (
+            ("commit", "0" * 40),
+            ("tree", "0" * 40),
+            ("path", "Lib/test/test_other"),
+        ):
+            old = self.document["source"][key]
+            self.document["source"][key] = value
+            with self.subTest(key=key), self.assertRaises(ValueError):
+                self.run_removal()
+            self.document["source"][key] = old
+        (self.source / "__init__.py").unlink()
+        self.document["removals"]["__init__.py"] = self.document["removals"]["a.py"]
+        with self.assertRaisesRegex(ValueError, "still canonical"):
+            self.run_removal()
+        self.assertTrue((self.target / "a.py").exists())
+
+    def test_invalid_paths_symlinks_directories_and_empty_selection(self):
+        original = self.document["removals"]
+        for name in ("../a.py", "/a.py", "./a.py", "data//z.bin", "data\\z.bin"):
+            self.document["removals"] = {name: original["a.py"]}
+            with self.subTest(name=name), self.assertRaises(ValueError):
+                self.run_removal()
+        self.document["removals"] = {}
+        with self.assertRaises(ValueError):
+            self.run_removal()
+        self.document["removals"] = original
+        target = self.target / "a.py"
+        target.unlink()
+        target.symlink_to(self.target / "data/z.bin")
+        with self.assertRaisesRegex(ValueError, "Symlink"):
+            self.run_removal()
+        target.unlink()
+        target.mkdir()
+        with self.assertRaisesRegex(ValueError, "regular file"):
+            self.run_removal()
+
+    def test_cli_refuses_combined_modes_and_duplicate_metadata(self):
+        for option in ("--patches", "--legacy-map", "--support-assignments"):
+            with contextlib.redirect_stderr(io.StringIO()):
+                self.assertEqual(
+                    main(
+                        [
+                            str(self.source),
+                            "--canonical-removals",
+                            "unused",
+                            option,
+                            "unused",
+                        ]
+                    ),
+                    1,
+                )
+        self.manifest.write_text('{"source": {}, "source": {}}')
+        with self.assertRaisesRegex(ValueError, "Duplicate"):
+            remove_canonical_files(self.source, self.manifest)
+
+
+class TestImportlibGuardMigration(unittest.TestCase):
+    def test_exact_guards_preserved_and_changed_ambiguous_anchors_refused(self):
+        setup = "def setUpModule():\n    thread_info = threading_helper.threading_setup()\n    unittest.addModuleCleanup(threading_helper.threading_cleanup, *thread_info)\n"
+        cases = (
+            ("util.py", MULTIPHASE_LOCAL, MULTIPHASE_UPSTREAM),
+            (
+                "test_locks.py",
+                "class LifetimeTests:\n    def test_all_locks(self): pass\n\n"
+                + LOCK_SPECIALIZATION
+                + "\n"
+                + LOCK_SKIP
+                + "\n"
+                + setup,
+                "class LifetimeTests:\n    def test_all_locks(self): pass\n\n"
+                + LOCK_SPECIALIZATION
+                + "\n\n"
+                + setup,
+            ),
+        )
+        for filename, old, new in cases:
+            path = Path("Lib/test/test_importlib") / filename
+            result = preserve_migration_customizations(path, old, new + "VALUE = 2\n")
+            self.assertEqual(result, old + "VALUE = 2\n")
+            self.assertEqual(
+                preserve_migration_customizations(path, result, new + "VALUE = 2\n"),
+                result,
+            )
+            for changed_old, changed_new in (
+                (old + old, new),
+                (old, new + new),
+                (old.replace("TODO: RUSTPYTHON", "changed"), new),
+                (
+                    old,
+                    "if True:\n"
+                    + "".join("    " + line for line in new.splitlines(keepends=True)),
+                ),
+            ):
+                with self.subTest(filename=filename), self.assertRaises(ValueError):
+                    preserve_migration_customizations(path, changed_old, changed_new)
+
+
+class TestTypesGuardMigration(unittest.TestCase):
+    path = Path("Lib/test/test_types.py")
+    old = (
+        "import copy\n"
+        + TYPES_DATETIME_GUARD
+        + "import gc\nimport unittest.mock\nimport typing\n\n"
+        + TYPES_UNITTEST_IMPORT
+        + "\nVALUE = 1\n"
+    )
+    new = (
+        "import copy\nimport _datetime\nimport gc\nimport unittest.mock\n"
+        "import typing\nimport re\n\nVALUE = 2\n"
+    )
+
+    def test_exact_guards_and_unrelated_canonical_changes_survive_idempotently(self):
+        expected = self.new.replace("import _datetime\n", TYPES_DATETIME_GUARD).replace(
+            "import typing\n", "import typing\n\n" + TYPES_UNITTEST_IMPORT
+        )
+        result = preserve_migration_customizations(self.path, self.old, self.new)
+        self.assertEqual(result, expected)
+        self.assertEqual(
+            preserve_migration_customizations(self.path, result, self.new), expected
+        )
+
+    def test_changed_ambiguous_or_misplaced_local_guards_are_refused(self):
+        for old in (
+            self.old.replace("except ImportError:", "except Exception:"),
+            self.old.replace("_datetime = None", "_datetime = False"),
+            self.old.replace("# XXX: RUSTPYTHON\n", "# changed\n"),
+            self.old.replace("importing to be able to skip tests", "changed reason"),
+            self.old + TYPES_DATETIME_GUARD,
+            self.old + "import _datetime\n",
+            self.old + TYPES_UNITTEST_IMPORT,
+            self.old.replace("import typing\n\n", "import typing\nVALUE = 3\n\n"),
+        ):
+            with self.subTest(old=old), self.assertRaises(ValueError):
+                preserve_migration_customizations(self.path, old, self.new)
+
+    def test_changed_ambiguous_or_nested_canonical_anchors_are_refused(self):
+        for new in (
+            self.new.replace("import _datetime", "import _datetime as other"),
+            self.new.replace("import _datetime\n", "if True:\n    import _datetime\n"),
+            self.new.replace("import _datetime\n", 'TEXT = "import _datetime\\n"\n'),
+            self.new.replace("import typing", "import typing as other"),
+            self.new.replace("import typing\n", "if True:\n    import typing\n"),
+            self.new + "import _datetime\n",
+            self.new + "import typing\n",
+            self.new + "import unittest\n",
+        ):
+            with self.subTest(new=new), self.assertRaises(ValueError):
+                preserve_migration_customizations(self.path, self.old, new)
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/scripts/update_lib/tests/test_patch_spec.py b/scripts/update_lib/tests/test_patch_spec.py
index 92a0a35a153..1a68ca10d26 100644
--- a/scripts/update_lib/tests/test_patch_spec.py
+++ b/scripts/update_lib/tests/test_patch_spec.py
@@ -4,11 +4,15 @@
 import unittest
 
 from update_lib.patch_spec import (
+    CANONICAL_LOAD_TESTS,
     COMMENT,
+    PATCHED_LOAD_TESTS,
     PatchSpec,
     UtMethod,
     _find_import_insert_line,
+    apply_doctest_metadata,
     apply_patches,
+    extract_doctest_guards,
     extract_patches,
     iter_tests,
 )
@@ -67,6 +71,73 @@ async def test_async(self):
 class TestExtractPatches(unittest.TestCase):
     """Tests for extract_patches function."""
 
+    def test_class_conditional_method_markers_are_preserved(self):
+        code = """class Owner:
+    if enabled:
+        @unittest.expectedFailure  # TODO: RUSTPYTHON
+        def test_value(self):
+            return 42
+"""
+        patches = extract_patches(code)
+        self.assertIn("test_value", patches["Owner"])
+        clean = code.replace(
+            "        @unittest.expectedFailure  # TODO: RUSTPYTHON\n", ""
+        )
+        result = apply_patches(clean, patches)
+        self.assertIn("        @unittest.expectedFailure", result)
+        method = list(iter_tests(ast.parse(result)))[0][1]
+        self.assertEqual(method.col_offset, 8)
+        self.assertEqual(ast.dump(method.body[0]), "Return(value=Constant(value=42))")
+
+    def test_nested_class_markers_do_not_target_module_names(self):
+        code = """class Container:
+    class Target:
+        @unittest.expectedFailure  # TODO: RUSTPYTHON
+        def test_value(self):
+            pass
+def factory():
+    class Target:
+        @unittest.expectedFailure  # TODO: RUSTPYTHON
+        def test_value(self):
+            pass
+"""
+        self.assertEqual(extract_patches(code), {})
+
+    def test_bare_marked_skip_roundtrip(self):
+        clean = """class Owner:
+    def test_value(self):
+        return 42
+"""
+        marked = clean.replace(
+            "    def test_value",
+            "    @unittest.skip  # TODO: RUSTPYTHON; original guard\n    def test_value",
+        )
+        patches = extract_patches(marked)
+        self.assertEqual(
+            patches["Owner"]["test_value"],
+            [PatchSpec(UtMethod.Skip, reason="original guard")],
+        )
+        result = apply_patches(clean, patches)
+        self.assertIn('@unittest.skip("TODO: RUSTPYTHON; original guard")', result)
+        self.assertEqual(apply_patches(clean, extract_patches(result)), result)
+        method = list(iter_tests(ast.parse(result)))[0][1]
+        self.assertEqual(ast.dump(method.body[0]), "Return(value=Constant(value=42))")
+
+    def test_unmarked_bare_skip_and_unrelated_decorators_are_not_patches(self):
+        code = """class Owner:
+    @unittest.skip
+    def test_unmarked(self):
+        pass
+    @other.skip  # TODO: RUSTPYTHON; unrelated
+    def test_other(self):
+        pass
+    @unittest.other  # TODO: RUSTPYTHON; unrelated
+    def test_unknown(self):
+        pass
+"""
+        self.assertEqual(extract_patches(code), {})
+        self.assertEqual(apply_patches(code, {}), code)
+
     def test_extract_expected_failure(self):
         """Test extracting @unittest.expectedFailure decorator."""
         code = f"""
@@ -177,6 +248,143 @@ def test_one(self):
 class TestApplyPatches(unittest.TestCase):
     """Tests for apply_patches function."""
 
+    def test_conditional_class_existing_method(self):
+        code = """import unittest
+if enabled:
+    class TestConditional:
+        def test_value(self):
+            assert 1 + 1 == 2
+"""
+        result = apply_patches(
+            code,
+            {
+                "TestConditional": {
+                    "test_value": [
+                        PatchSpec(
+                            UtMethod.ExpectedFailureIf, "condition", "known limitation"
+                        )
+                    ]
+                }
+            },
+        )
+        original = list(iter_tests(ast.parse(code)))[0][1]
+        updated = list(iter_tests(ast.parse(result)))[0][1]
+        self.assertEqual(ast.dump(original.body[0]), ast.dump(updated.body[0]))
+        self.assertEqual(updated.col_offset, 8)
+        self.assertIn("        @unittest.expectedFailureIf", result)
+
+    def test_conditional_class_inherited_override(self):
+        code = """import unittest
+class Parent:
+    async def test_value(self):
+        return 42
+if enabled:
+    class Child(Parent):
+        pass
+"""
+        result = apply_patches(
+            code, {"Child": {"test_value": [PatchSpec(UtMethod.ExpectedSuccess)]}}
+        )
+        methods = list(iter_tests(ast.parse(result)))
+        self.assertEqual([cls.name for cls, _ in methods], ["Parent", "Child"])
+        self.assertIsInstance(methods[1][1], ast.AsyncFunctionDef)
+        self.assertIn("        return await super().test_value()", result)
+        self.assertIn("        @unittest.expectedSuccess", result)
+
+    def test_duplicate_conditional_class_names_are_rejected(self):
+        code = """if enabled:
+    class Duplicate:
+        pass
+else:
+    class Duplicate:
+        pass
+"""
+        with self.assertRaisesRegex(ValueError, "Ambiguous.*Duplicate"):
+            apply_patches(
+                code,
+                {"Duplicate": {"test_value": [PatchSpec(UtMethod.ExpectedFailure)]}},
+            )
+
+    def test_unpatched_conditional_helpers_are_allowed(self):
+        code = """if enabled:
+    class Helper:
+        pass
+else:
+    class Helper:
+        pass
+class Target:
+    helper = Helper
+    def test_value(self):
+        return 1
+"""
+        result = apply_patches(
+            code, {"Target": {"test_value": [PatchSpec(UtMethod.ExpectedFailure)]}}
+        )
+        self.assertEqual(result.count("class Helper:"), 2)
+        self.assertEqual(result.count("@unittest.expectedFailure"), 1)
+
+    def test_ambiguous_transitive_ancestor_is_rejected(self):
+        code = """if enabled:
+    class Ancestor:
+        async def test_value(self):
+            pass
+else:
+    class Ancestor:
+        def test_value(self):
+            pass
+class Middle(Ancestor):
+    pass
+class Target(Middle):
+    pass
+"""
+        with self.assertRaisesRegex(ValueError, "Ambiguous.*Ancestor"):
+            apply_patches(
+                code, {"Target": {"test_value": [PatchSpec(UtMethod.ExpectedFailure)]}}
+            )
+
+    def test_local_class_names_do_not_shadow_module_class(self):
+        code = """import unittest
+class Target:
+    def test_value(self):
+        return 1
+class Container:
+    class Target:
+        def test_value(self):
+            return 2
+def factory():
+    class Target:
+        def test_value(self):
+            return 3
+"""
+        result = apply_patches(
+            code, {"Target": {"test_value": [PatchSpec(UtMethod.ExpectedFailure)]}}
+        )
+        tree = ast.parse(result)
+        targets = [
+            node
+            for node in ast.walk(tree)
+            if isinstance(node, ast.ClassDef) and node.name == "Target"
+        ]
+        self.assertEqual(
+            [len(node.body[0].decorator_list) for node in targets], [1, 0, 0]
+        )
+
+    def test_duplicate_conditional_method_names_are_rejected(self):
+        code = """class Owner:
+    if enabled:
+        def test_value(self):
+            return 1
+    else:
+        def test_value(self):
+            return 2
+"""
+        with self.assertRaisesRegex(
+            ValueError, "Ambiguous method name: Owner.test_value"
+        ):
+            apply_patches(
+                code, {"Owner": {"test_value": [PatchSpec(UtMethod.ExpectedFailure)]}}
+            )
+
     def test_apply_expected_failure(self):
         """Test applying @unittest.expectedFailure."""
         code = """import unittest
@@ -242,6 +450,39 @@ def test_one(self):
         self.assertIn("@some_decorator", result)
         self.assertIn("@unittest.expectedFailure", result)
 
+    def test_inherited_override_expands_inline_class(self):
+        for source in (
+            "class Child(Base): pass  # keep comment\n",
+            "class Child(Base): value = 1; other = 2\n",
+            "class Child(\n    Base\n): pass\n",
+            "if True:\n    class Child(Base): pass\n",
+            "class Café(Base): pass\n",
+        ):
+            with self.subTest(source=source):
+                name = "Café" if "Café" in source else "Child"
+                patches = {
+                    name: {
+                        "test_parent": [PatchSpec(UtMethod.ExpectedFailure, None, "")]
+                    }
+                }
+                before = ast.parse(source)
+                result = apply_patches(source, patches)
+                after = ast.parse(result)
+                old_class = next(
+                    node for node in ast.walk(before) if isinstance(node, ast.ClassDef)
+                )
+                new_class = next(
+                    node for node in ast.walk(after) if isinstance(node, ast.ClassDef)
+                )
+                self.assertEqual(
+                    [ast.dump(node) for node in old_class.body],
+                    [ast.dump(node) for node in new_class.body[:-1]],
+                )
+                self.assertEqual(new_class.body[-1].name, "test_parent")
+                self.assertIn("return super().test_parent()", result)
+                if "# keep comment" in source:
+                    self.assertIn("# keep comment", result)
+
     def test_apply_inherited_method(self):
         """Test applying patch to inherited method (creates override)."""
         code = """import unittest
@@ -408,5 +649,90 @@ def test_no_imports_no_docstring(self):
         self.assertEqual(line, 0)
 
 
+DOCTEST_SOURCE = "raise X, Y\n"
+DOCTEST_METADATA = {DOCTEST_SOURCE: "known mismatch"}
+DOCTEST_OLD = (
+    '''"""
+>>> raise X, Y  # TODO: RUSTPYTHON; old reason # doctest: +EXPECTED_FAILURE
+Traceback (most recent call last):
+SyntaxError: old message
+"""
+'''
+    + PATCHED_LOAD_TESTS
+    + "\n"
+)
+DOCTEST_CANONICAL = (
+    '''"""
+>>> raise X, Y
+Traceback (most recent call last):
+SyntaxError: final message
+"""
+'''
+    + CANONICAL_LOAD_TESTS
+    + "\n"
+)
+
+
+class ExactDoctestTests(unittest.TestCase):
+    def test_extracts_only_existing_guards(self):
+        self.assertEqual(set(extract_doctest_guards(DOCTEST_OLD)), {DOCTEST_SOURCE})
+        self.assertEqual(extract_doctest_guards(DOCTEST_CANONICAL), {})
+        self.assertEqual(extract_doctest_guards("value = 1\n"), {})
+
+    def test_duplicate_existing_guards_are_rejected(self):
+        duplicate = DOCTEST_OLD.replace(
+            ">>> raise X, Y  # TODO:",
+            ">>> raise X, Y  # TODO: RUSTPYTHON; duplicate # doctest: +EXPECTED_FAILURE\n"
+            ">>> raise X, Y  # TODO:",
+        )
+        with self.assertRaises(ValueError):
+            extract_doctest_guards(duplicate)
+
+    def test_preserves_final_output_and_roundtrips(self):
+        result = apply_doctest_metadata(
+            DOCTEST_OLD, DOCTEST_CANONICAL, DOCTEST_METADATA
+        )
+        self.assertIn("SyntaxError: final message", result)
+        self.assertNotIn("old message", result)
+        self.assertEqual(result.count("doctest: +EXPECTED_FAILURE"), 1)
+        self.assertIn(PATCHED_LOAD_TESTS, result)
+        self.assertEqual(
+            apply_doctest_metadata(result, DOCTEST_CANONICAL, DOCTEST_METADATA), result
+        )
+
+    def test_duplicate_input_is_rejected(self):
+        duplicate = DOCTEST_CANONICAL.replace(
+            ">>> raise X, Y\n", ">>> raise X, Y\n>>> raise X, Y\n"
+        )
+        with self.assertRaises(ValueError):
+            apply_doctest_metadata(DOCTEST_OLD, duplicate, DOCTEST_METADATA)
+
+    def test_missing_canonical_or_old_case_is_rejected(self):
+        with self.assertRaises(ValueError):
+            apply_doctest_metadata(
+                DOCTEST_OLD,
+                DOCTEST_CANONICAL.replace("raise X, Y", "raise X"),
+                DOCTEST_METADATA,
+            )
+        with self.assertRaises(ValueError):
+            apply_doctest_metadata(
+                DOCTEST_OLD.replace("raise X, Y", "raise X"),
+                DOCTEST_CANONICAL,
+                DOCTEST_METADATA,
+            )
+
+    def test_changed_loader_and_unmarked_old_case_are_rejected(self):
+        with self.assertRaises(ValueError):
+            apply_doctest_metadata(
+                DOCTEST_OLD,
+                DOCTEST_CANONICAL.replace("DocTestSuite()", "DocTestSuite(None)"),
+                DOCTEST_METADATA,
+            )
+        with self.assertRaises(ValueError):
+            apply_doctest_metadata(
+                DOCTEST_CANONICAL, DOCTEST_CANONICAL, DOCTEST_METADATA
+            )
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/scripts/whats_left.py b/scripts/whats_left.py
index 40b7b5be9d8..9adae4c9c86 100755
--- a/scripts/whats_left.py
+++ b/scripts/whats_left.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env -S python3 -I
 # /// script
-# requires-python = ">=3.14"
+# requires-python = ">=3.15.0"
 # ///
 
 # This script generates Lib/snippets/whats_left_data.py with these variables defined:
@@ -39,9 +39,9 @@
 implementation = platform.python_implementation()
 if implementation != "CPython":
     sys.exit(f"whats_left.py must be run under CPython, got {implementation} instead")
-if sys.version_info[:2] < (3, 14):
+if sys.version_info[:2] < (3, 15):
     sys.exit(
-        f"whats_left.py must be run under CPython 3.14 or newer, got {implementation} {sys.version} instead. If you have uv, try `uv run python -I scripts/whats_left.py` to select a proper Python interpreter easier."
+        f"whats_left.py must be run under CPython 3.15 or newer, got {implementation} {sys.version} instead. If you have uv, try `uv run python -I scripts/whats_left.py` to select a proper Python interpreter easier."
     )
 
 
diff --git a/src/interpreter.rs b/src/interpreter.rs
index a8b03cba0b0..c2ddf8cc5fa 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -19,11 +19,9 @@ impl InterpreterBuilderExt for InterpreterBuilder {
         let builder = builder.init_hook(install_default_tls_provider);
 
         cfg_select! {
-            feature = "freeze-stdlib" => {
-                builder
-                    .add_frozen_modules(rustpython_pylib::FROZEN_STDLIB)
-                    .init_hook(set_frozen_stdlib_dir)
-            }
+            feature = "freeze-stdlib" => builder
+                .add_frozen_modules(rustpython_pylib::FROZEN_STDLIB)
+                .init_hook(set_frozen_stdlib_dir),
             _ => builder.init_hook(setup_dynamic_stdlib),
         }
     }
@@ -57,8 +55,11 @@ fn install_default_tls_provider(_vm: &mut crate::VirtualMachine) {
 fn set_frozen_stdlib_dir(vm: &mut crate::VirtualMachine) {
     use rustpython_vm::common::rc::PyRc;
 
-    let state = PyRc::get_mut(&mut vm.state).unwrap();
-    state.config.paths.stdlib_dir = Some(rustpython_pylib::LIB_PATH.to_owned());
+    if use_build_stdlib(vm) {
+        let state = PyRc::get_mut(&mut vm.state).unwrap();
+        state.config.paths.stdlib_dir =
+            Some(canonical_stdlib_path(rustpython_pylib::LIB_PATH.to_owned()));
+    }
 }
 
 /// Setup dynamic standard library loading from filesystem
@@ -66,23 +67,13 @@ fn set_frozen_stdlib_dir(vm: &mut crate::VirtualMachine) {
 fn setup_dynamic_stdlib(vm: &mut crate::VirtualMachine) {
     use rustpython_vm::common::rc::PyRc;
 
+    if !use_build_stdlib(vm) {
+        return;
+    }
     let state = PyRc::get_mut(&mut vm.state).unwrap();
     let paths: Vec<String> = collect_stdlib_paths()
         .into_iter()
-        .map(|p| {
-            std::fs::canonicalize(&p)
-                .map(|canonical| {
-                    let s = canonical.to_string_lossy();
-                    #[cfg(windows)]
-                    {
-                        if let Some(stripped) = s.strip_prefix(r"\\?\") {
-                            return stripped.to_owned();
-                        }
-                    }
-                    s.into_owned()
-                })
-                .unwrap_or(p)
-        })
+        .map(canonical_stdlib_path)
         .collect();
 
     // Set stdlib_dir to the first stdlib path if available
@@ -90,10 +81,39 @@ fn setup_dynamic_stdlib(vm: &mut crate::VirtualMachine) {
         state.config.paths.stdlib_dir = Some(first_path.clone());
     }
 
-    // Insert at the beginning so stdlib comes before user paths
-    for path in paths.into_iter().rev() {
-        state.config.paths.module_search_paths.insert(0, path);
-    }
+    rustpython_vm::getpath::add_build_time_paths(
+        &state.config.settings,
+        &mut state.config.paths,
+        paths,
+    );
+}
+
+// Preserve a discovered library. Only an explicit nonempty prefix half of
+// PYTHONHOME forbids falling back to the build-tree pure-Python library.
+#[cfg(feature = "stdlib")]
+fn use_build_stdlib(vm: &crate::VirtualMachine) -> bool {
+    vm.state.config.paths.stdlib_dir.is_none()
+        && vm.state.config.settings.home.as_deref().is_none_or(|home| {
+            let (prefix, _) = home
+                .split_once(if cfg!(windows) { ';' } else { ':' })
+                .unwrap_or((home, home));
+            prefix.is_empty()
+        })
+}
+
+/// Resolve the build-tree library link consistently for both backends.
+#[cfg(feature = "stdlib")]
+fn canonical_stdlib_path(path: String) -> String {
+    std::fs::canonicalize(&path)
+        .map(|canonical| {
+            let value = canonical.to_string_lossy();
+            #[cfg(windows)]
+            if let Some(stripped) = value.strip_prefix(r"\\?\") {
+                return stripped.to_owned();
+            }
+            value.into_owned()
+        })
+        .unwrap_or(path)
 }
 
 /// Collect standard library paths from build-time configuration
diff --git a/src/lib.rs b/src/lib.rs
index e3798512602..2f6ee077f53 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -59,7 +59,9 @@ mod shell;
 #[cfg(feature = "rustpython-pylib")]
 pub use rustpython_pylib as pylib;
 
-use rustpython_vm::{AsObject, PyObjectRef, PyResult, VirtualMachine, scope::Scope};
+use rustpython_vm::{
+    AsObject, PyObjectRef, PyResult, VirtualMachine, builtins::PyBaseExceptionRef, scope::Scope,
+};
 use std::env;
 use std::io::IsTerminal;
 use std::process::ExitCode;
@@ -121,13 +123,8 @@ pub fn run(mut builder: InterpreterBuilder) -> ExitCode {
 
     let interp = builder.interpreter();
     let exitcode = cfg_select! {
-        feature = "capi" => {{
-            let local_vm = interp.enter(|vm| vm.new_thread());
-            rustpython_capi::init_main_interpreter(interp);
-            let result = local_vm.run(|vm| run_rustpython(vm, run_mode));
-            rustpython_capi::get_main_interpreter().take().unwrap().finalize(result.err())
-        }},
-        _ => interp.run(move |vm| run_rustpython(vm, run_mode)),
+        feature = "capi" => rustpython_capi::run_main_interpreter(interp, move |vm| run_rustpython(vm, run_mode)),
+        _ => interp.run_main(move |vm| run_rustpython(vm, run_mode)),
     };
 
     rustpython_vm::host_env::os::exit_code(exitcode)
@@ -218,7 +215,7 @@ fn script_sys_path0(argv0: &str) -> String {
 }
 
 // pymain_run_file_obj in Modules/main.c
-fn run_file(vm: &VirtualMachine, scope: Scope, argv0: &str) -> PyResult<()> {
+fn run_file(vm: &VirtualMachine, scope: Scope, argv0: &str) -> PyResult<u32> {
     // config_run_filename_abspath: __file__ and co_filename are absolute even
     // when the script was named relative to the working directory.
     let path = &abs_path(argv0);
@@ -229,7 +226,7 @@ fn run_file(vm: &VirtualMachine, scope: Scope, argv0: &str) -> PyResult<()> {
         let runpy = vm.import("runpy", 0)?;
         let run_module_as_main = runpy.get_attr("_run_module_as_main", vm)?;
         run_module_as_main.call((vm::identifier!(vm, __main__).to_owned(), false), vm)?;
-        return Ok(());
+        return Ok(0);
     }
 
     // Add script directory to sys.path[0]
@@ -238,30 +235,32 @@ fn run_file(vm: &VirtualMachine, scope: Scope, argv0: &str) -> PyResult<()> {
     }
 
     cfg_select! {
-        feature = "host_env" => {
-            match rustpython_vm::host_env::fs::metadata(path) {
-                Ok(_) => vm.run_any_file(scope, path),
-                Err(err) => cant_open_file(vm, path, &err),
-            }
-        }
+        feature = "host_env" => match rustpython_vm::host_env::fs::metadata(path) {
+            Ok(_) => vm.run_any_file(scope, path).map(|()| 0),
+            Err(err) => cant_open_file(vm, path, &err),
+        },
         _ => {
             // In sandbox mode, the binary reads the file and feeds source to the VM.
             // The VM itself has no filesystem access.
             let path = if path.is_empty() { "???" } else { path };
             match std::fs::read_to_string(path) {
-                Ok(source) => vm.run_string(scope, &source, path).map(drop),
+                Ok(source) => vm.run_string(scope, &source, path).map(|_| 0),
                 Err(err) => cant_open_file(vm, path, &err),
             }
         }
     }
 }
 
-fn cant_open_file(vm: &VirtualMachine, path: &str, err: &std::io::Error) -> PyResult<()> {
-    let program = &vm.state.config.paths.executable;
+fn cant_open_file(vm: &VirtualMachine, path: &str, err: &std::io::Error) -> PyResult<u32> {
+    let program_name = &vm.state.config.paths.program_name;
     let filename_repr = vm.ctx.new_str(path).as_object().repr(vm)?;
     let errno = err.raw_os_error().unwrap_or(2);
-    eprintln!("{program}: can't open file {filename_repr}: [Errno {errno}] {err}");
-    Err(vm.new_system_exit(vec![vm.ctx.new_int(2).into()].into()))
+    let strerror = vm::host_env::errno::strerror_string(errno).unwrap_or_default();
+    writeln!(
+        vm::stdlib::sys::PyStderr(vm),
+        "{program_name}: can't open file {filename_repr}: [Errno {errno}] {strerror}"
+    );
+    Ok(2)
 }
 
 fn get_importer(path: &str, vm: &VirtualMachine) -> PyResult<Option<PyObjectRef>> {
@@ -295,11 +294,26 @@ fn get_importer(path: &str, vm: &VirtualMachine) -> PyResult<Option<PyObjectRef>
     })
 }
 
-// pymain_run_python
-fn run_rustpython(vm: &VirtualMachine, run_mode: RunMode) -> PyResult<()> {
+fn run_rustpython(vm: &VirtualMachine, run_mode: RunMode) -> u32 {
     #[cfg(feature = "flame-it")]
     let main_guard = flame::start_guard("RustPython main");
 
+    let exitcode =
+        pymain_run_python(vm, run_mode).unwrap_or_else(|exc| vm.handle_exit_exception(exc));
+
+    #[cfg(feature = "flame-it")]
+    {
+        main_guard.end();
+        if let Err(e) = write_profile(&vm.state.as_ref().config.settings) {
+            error!("Error writing profile information: {}", e);
+        }
+    }
+
+    exitcode
+}
+
+// pymain_run_python
+fn pymain_run_python(vm: &VirtualMachine, run_mode: RunMode) -> PyResult<u32> {
     let scope = vm.new_scope_with_main()?;
 
     // Initialize warnings module to process sys.warnoptions
@@ -311,14 +325,16 @@ fn run_rustpython(vm: &VirtualMachine, run_mode: RunMode) -> PyResult<()> {
     // Import site first, before setting sys.path[0]
     // This matches CPython's behavior where site.removeduppaths() runs
     // before sys.path[0] is set, preventing '' from being converted to cwd
-    let site_result = vm.import("site", 0);
-    if site_result.is_err() {
+    if vm.state.config.settings.import_site && vm.import("site", 0).is_err() {
         warn!(
             "Failed to import site, consider adding the Lib directory to your RUSTPYTHONPATH \
              environment variable",
         );
     }
 
+    // CPython activates configured all-mode after site to avoid startup cycles.
+    vm.apply_startup_lazy_imports();
+
     // _PyPathConfig_ComputeSysPath0 - set sys.path[0] after site import
     if !vm.state.config.settings.safe_path {
         let path0: Option<String> = match &run_mode {
@@ -342,8 +358,9 @@ fn run_rustpython(vm: &VirtualMachine, run_mode: RunMode) -> PyResult<()> {
     }
 
     let is_repl = matches!(run_mode, RunMode::Repl);
+    // pymain_header
     if !vm.state.config.settings.quiet
-        && (vm.state.config.settings.verbose > 0 || (is_repl && std::io::stdin().is_terminal()))
+        && (vm.state.config.settings.verbose > 0 || (is_repl && vm.stdin_is_interactive()))
     {
         eprintln!(
             "Welcome to the magnificent Rust Python {} interpreter \u{1f631} \u{1f596}",
@@ -358,58 +375,220 @@ fn run_rustpython(vm: &VirtualMachine, run_mode: RunMode) -> PyResult<()> {
 
         eprintln!("Type \"help\", \"copyright\", \"credits\" or \"license\" for more information.");
     }
-    let res = match run_mode {
+
+    let set_running_main = vm.state.set_running_main();
+    let exitcode =
+        pymain_run_main(vm, scope, run_mode).unwrap_or_else(|exc| vm.handle_exit_exception(exc));
+    if set_running_main {
+        vm.state.set_not_running_main();
+    }
+    Ok(exitcode)
+}
+
+/// The part of pymain_run_python that runs while the main thread owns
+/// `__main__`.
+fn pymain_run_main(vm: &VirtualMachine, scope: Scope, run_mode: RunMode) -> PyResult<u32> {
+    let is_repl = matches!(run_mode, RunMode::Repl);
+    vm.check_signals()?;
+    let result = match run_mode {
         RunMode::Command(command) => {
             debug!("Running command {command}");
-            vm.run_string(scope.clone(), &command, "<string>").map(drop)
+            vm.run_string(scope, &command, "<string>").map(|_| 0)
         }
         RunMode::Module(module) => {
             debug!("Running module {module}");
-            vm.run_module(&module)
+            vm.run_module(&module).map(|()| 0)
         }
-        RunMode::InstallPip(installer) => install_pip(installer, scope.clone(), vm),
+        RunMode::InstallPip(installer) => install_pip(installer, scope, vm).map(|()| 0),
         RunMode::Script(script_path) => {
             // pymain_run_file_obj
             debug!("Running script {script_path}");
-            run_file(vm, scope.clone(), &script_path)
+            run_file(vm, scope, &script_path)
         }
-        RunMode::Repl => Ok(()),
+        RunMode::Repl => Ok(pymain_run_stdin(vm, scope)),
     };
-    let result = if is_repl || vm.state.config.settings.inspect {
-        if std::io::stdin().is_terminal() {
-            warn_if_pyrepl_unavailable(vm);
-        }
-        shell::run_shell(vm, scope)
-    } else {
-        res
+    let mut exitcode = result.unwrap_or_else(|exc| vm.handle_exit_exception(exc));
+    vm.check_signals()?;
+
+    pymain_repl(vm, !is_repl, &mut exitcode);
+    Ok(exitcode)
+}
+
+/// pymain_err_print
+///
+/// Report `exc` and return the exit code if it ends the process.
+fn pymain_err_print(vm: &VirtualMachine, exc: PyBaseExceptionRef) -> Option<u32> {
+    if let Some(exitcode) = vm.handle_system_exit_and_keyboard_interrupt(&exc) {
+        return Some(exitcode);
+    }
+    vm.print_uncaught_exception(&exc);
+    None
+}
+
+// pymain_set_inspect
+fn pymain_set_inspect(vm: &VirtualMachine, inspect: bool) {
+    if let Err(exc) = vm.config_set_inspect(inspect) {
+        eprintln!("Could not set the inspect flag");
+        vm.print_uncaught_exception(&exc);
+    }
+}
+
+// pymain_run_startup
+fn pymain_run_startup(vm: &VirtualMachine, scope: Scope) -> Option<u32> {
+    let exc = run_startup(vm, scope).err()?;
+    pymain_err_print(vm, exc)
+}
+
+fn run_startup(vm: &VirtualMachine, scope: Scope) -> PyResult<()> {
+    if vm.state.config.settings.ignore_environment {
+        return Ok(());
+    }
+    let Some(startup) = env::var_os("PYTHONSTARTUP").filter(|value| !value.is_empty()) else {
+        return Ok(());
     };
+    let startup = vm.fsdecode(startup);
+    vm.audit("cpython.run_startup", || (startup.clone(),))?;
+    let could_not_open = |err: std::io::Error| {
+        use vm::convert::ToPyException;
+        writeln!(
+            vm::stdlib::sys::PyStderr(vm),
+            "Could not open PYTHONSTARTUP"
+        );
+        let exc = err.to_pyexception(vm);
+        exc.as_object().set_attr("filename", startup.clone(), vm)?;
+        Err(exc)
+    };
+    let path = startup.expect_str();
+    cfg_select! {
+        feature = "host_env" => match vm::host_env::fs::open(path) {
+            Ok(_) => vm.run_any_file(scope, path),
+            Err(err) => could_not_open(err),
+        },
+        _ => match std::fs::read_to_string(path) {
+            Ok(source) => vm.run_string(scope, &source, path).map(drop),
+            Err(err) => could_not_open(err),
+        },
+    }
+}
 
-    #[cfg(feature = "flame-it")]
+// pymain_run_interactive_hook
+fn pymain_run_interactive_hook(vm: &VirtualMachine) -> Option<u32> {
+    let exc = run_interactive_hook(vm).err()?;
+    writeln!(
+        vm::stdlib::sys::PyStderr(vm),
+        "Failed calling sys.__interactivehook__"
+    );
+    pymain_err_print(vm, exc)
+}
+
+fn run_interactive_hook(vm: &VirtualMachine) -> PyResult<()> {
+    let Some(hook) = vm
+        .sys_module
+        .dict()
+        .get_item_opt("__interactivehook__", vm)?
+    else {
+        return Ok(());
+    };
+    vm.audit("cpython.run_interactivehook", || (hook.clone(),))?;
+    hook.call((), vm)?;
+    Ok(())
+}
+
+// pymain_run_stdin
+fn pymain_run_stdin(vm: &VirtualMachine, scope: Scope) -> u32 {
+    if vm.stdin_is_interactive() {
+        // do exit on SystemExit
+        pymain_set_inspect(vm, false);
+
+        if let Some(exitcode) = pymain_run_startup(vm, scope) {
+            return exitcode;
+        }
+        if let Some(exitcode) = pymain_run_interactive_hook(vm) {
+            return exitcode;
+        }
+    }
+    pymain_run_repl(vm, false)
+}
+
+// pymain_repl
+fn pymain_repl(vm: &VirtualMachine, run_code: bool, exitcode: &mut u32) {
+    // Check this environment variable at the end, to give programs the
+    // opportunity to set it from Python.
+    if !vm.config_inspect()
+        && !vm.state.config.settings.ignore_environment
+        && env::var_os("PYTHONINSPECT").is_some_and(|value| !value.is_empty())
     {
-        main_guard.end();
-        if let Err(e) = write_profile(&vm.state.as_ref().config.settings) {
-            error!("Error writing profile information: {}", e);
+        pymain_set_inspect(vm, true);
+    }
+
+    if !(vm.config_inspect() && vm.stdin_is_interactive() && run_code) {
+        return;
+    }
+
+    pymain_set_inspect(vm, false);
+    if let Some(code) = pymain_run_interactive_hook(vm) {
+        *exitcode = code;
+        return;
+    }
+
+    *exitcode = pymain_run_repl(vm, true);
+}
+
+// _pymain_run_repl
+fn pymain_run_repl(vm: &VirtualMachine, startup: bool) -> u32 {
+    run_repl(vm, startup).unwrap_or_else(|exc| vm.handle_exit_exception(exc))
+}
+
+fn run_repl(vm: &VirtualMachine, startup: bool) -> PyResult<u32> {
+    vm.check_signals()?;
+    vm.audit("cpython.run_stdin", || ())?;
+
+    let tty = std::io::stdin().is_terminal();
+    if tty
+        && (vm.state.config.settings.ignore_environment
+            || env::var_os("PYTHON_BASIC_REPL").is_none_or(|value| value.is_empty()))
+    {
+        match vm.import("_pyrepl", 0) {
+            Ok(_) => return Ok(pymain_run_pyrepl(vm, startup)),
+            Err(exc) if !exc.fast_isinstance(vm.ctx.exceptions.module_not_found_error) => {
+                eprintln!("Could not import _pyrepl.main");
+                return Err(exc);
+            }
+            Err(_) => {}
         }
     }
 
-    result
+    // _PyRun_AnyFile(stdin, "<stdin>")
+    vm.run_any_stdin()?;
+    Ok(0)
 }
 
-/// When the fancy REPL cannot start (for example `TERM=dumb`), print the same
-/// warning `_pyrepl.main` would have printed, then keep the rustyline shell.
-fn warn_if_pyrepl_unavailable(vm: &VirtualMachine) {
-    let _ = vm.run_simple_string(
-        r"
-import os, sys
-if not os.getenv('PYTHON_BASIC_REPL'):
-    try:
-        from _pyrepl.main import CAN_USE_PYREPL, FAIL_REASON
-        if not CAN_USE_PYREPL and FAIL_REASON:
-            print(FAIL_REASON, file=sys.stderr)
-    except Exception:
-        pass
-",
-    );
+// pymain_run_pyrepl
+fn pymain_run_pyrepl(vm: &VirtualMachine, pythonstartup: bool) -> u32 {
+    run_pyrepl(vm, pythonstartup).map_or_else(|exc| vm.handle_exit_exception(exc), |()| 0)
+}
+
+fn run_pyrepl(vm: &VirtualMachine, pythonstartup: bool) -> PyResult<()> {
+    let pyrepl = vm.import("_pyrepl.main", 0).inspect_err(|_| {
+        eprintln!("Could not import _pyrepl.main");
+    })?;
+    let console = pyrepl
+        .get_attr("main", vm)
+        .and_then(|main| main.get_attr("interactive_console", vm))
+        .inspect_err(|_| {
+            eprintln!("Could not access _pyrepl.main.interactive_console");
+        })?;
+    let kwargs: vm::function::KwArgs = [
+        ("mainmodule".to_owned(), vm.add_main_module()?.into()),
+        (
+            "pythonstartup".to_owned(),
+            vm.ctx.new_bool(pythonstartup).into(),
+        ),
+    ]
+    .into_iter()
+    .collect();
+    console.call(vm::function::FuncArgs::new(vec![], kwargs), vm)?;
+    Ok(())
 }
 
 #[cfg(feature = "flame-it")]
diff --git a/src/settings.rs b/src/settings.rs
index 975204c00e0..af9cf418876 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -95,6 +95,8 @@ Options (and corresponding environment variables):
          also PYTHONWARNINGS=arg
 -x     : skip first line of source, allowing use of non-Unix forms of #!cmd
 -X opt : set implementation-specific option
+-X lazy_imports=all|normal: control global lazy imports (default: normal);
+         also PYTHON_LAZY_IMPORTS
 --check-hash-based-pycs always|default|never:
          control how Python invalidates hash-based .pyc files
 --help-env: print help about Python environment variables and exit
@@ -231,6 +233,10 @@ pub fn parse_opts() -> Result<(Settings, RunMode), lexopt::Error> {
 
     let get_env = |env| (!ignore_environment).then(|| env::var_os(env)).flatten();
 
+    settings.home = get_env("PYTHONHOME")
+        .filter(|home| !home.is_empty())
+        .map(|home| home.to_string_lossy().into_owned());
+
     let env_count = |env| {
         get_env(env).filter(|v| !v.is_empty()).map_or(0, |val| {
             val.to_str().and_then(|v| v.parse::<u8>().ok()).unwrap_or(1)
@@ -299,6 +305,17 @@ pub fn parse_opts() -> Result<(Settings, RunMode), lexopt::Error> {
         };
     }
 
+    if let Some(val) = get_env("PYTHON_LAZY_IMPORTS").filter(|val| !val.is_empty()) {
+        settings.lazy_imports = parse_lazy_imports(val.to_str(), "PYTHON_LAZY_IMPORTS");
+    }
+
+    if let Some(value) = get_env("PYTHONPROFILEIMPORTTIME").filter(|value| !value.is_empty()) {
+        settings.import_time = parse_import_time(value.to_str(), "PYTHONPROFILEIMPORTTIME");
+    }
+
+    // CPython uses the first occurrence of these -X options.
+    let mut lazy_imports_option_seen = false;
+    let mut import_time_option_seen = false;
     let xopts = args.implementation_option.into_iter().map(|s| {
         let (name, value) = match s.split_once('=') {
             Some((name, value)) => (name.to_owned(), Some(value)),
@@ -306,6 +323,10 @@ pub fn parse_opts() -> Result<(Settings, RunMode), lexopt::Error> {
         };
         match &*name {
             "dev" => settings.dev_mode = true,
+            "importtime" if !import_time_option_seen => {
+                settings.import_time = parse_import_time(value, "-X importtime");
+                import_time_option_seen = true;
+            }
             "faulthandler" => settings.faulthandler = true,
             "warn_default_encoding" => settings.warn_default_encoding = true,
             "utf8" => {
@@ -325,6 +346,10 @@ pub fn parse_opts() -> Result<(Settings, RunMode), lexopt::Error> {
             }
             "no_sig_int" => settings.install_signal_handlers = false,
             "no_debug_ranges" => settings.code_debug_ranges = false,
+            "lazy_imports" if !lazy_imports_option_seen => {
+                settings.lazy_imports = parse_lazy_imports(value, "-X lazy_imports");
+                lazy_imports_option_seen = true;
+            }
             "cpu_count" => {
                 settings.cpu_count = match parse_cpu_count(value) {
                     Ok(cpu_count) => cpu_count,
@@ -488,6 +513,48 @@ fn parse_cpu_count(value: Option<&str>) -> Result<Option<NonZeroI32>, ()> {
     }
 }
 
+/// = config_init_import_time
+fn parse_import_time(value: Option<&str>, source: &str) -> u8 {
+    let value = value
+        .and_then(|value| {
+            value
+                .trim_start_matches([' ', '\t', '\n', '\r', '\x0b', '\x0c'])
+                .parse::<i32>()
+                .ok()
+        })
+        .unwrap_or(1);
+    if !(0..=2).contains(&value) {
+        let numeric = if source == "PYTHONPROFILEIMPORTTIME" {
+            "numeric "
+        } else {
+            ""
+        };
+        eprintln!(
+            "Fatal Python error: config_init_import_time: {source}: \
+             {numeric}values other than 1 and 2 are reserved for future use.\n\
+             Python runtime state: preinitialized\n"
+        );
+        std::process::exit(1);
+    }
+    value as u8
+}
+
+/// = config_init_lazy_imports
+fn parse_lazy_imports(value: Option<&str>, source: &str) -> i8 {
+    match value {
+        Some("normal") => -1,
+        Some("all") => 1,
+        _ => {
+            eprintln!(
+                "Fatal Python error: config_init_lazy_imports: \
+                 {source}: invalid value; expected 'all' or 'normal'\n\
+                 Python runtime state: preinitialized\n"
+            );
+            std::process::exit(1);
+        }
+    }
+}
+
 fn get_paths(env_variable_name: &str) -> impl Iterator<Item = String> + '_ {
     env::var_os(env_variable_name)
         .filter(|v| !v.is_empty())
diff --git a/src/shell.rs b/src/shell.rs
index d727003e6d6..7d206f28e9e 100644
--- a/src/shell.rs
+++ b/src/shell.rs
@@ -1,241 +1,41 @@
 mod helper;
 
-use rustpython_compiler::{
-    CompileError, ParseError, parser::InterpolatedStringErrorType, parser::LexicalErrorType,
-    parser::ParseErrorType,
-};
 use rustpython_vm::{
-    AsObject, PyResult, VirtualMachine,
-    builtins::PyBaseExceptionRef,
-    bytecode::CodeFlags,
-    compiler::{self},
+    PyResult, VirtualMachine,
     readline::{Readline, ReadlineResult},
     scope::Scope,
-    vm::VmCompileError,
+    vm::InteractiveLine,
 };
 
-enum ShellExecResult {
-    Ok,
-    PyErr(PyBaseExceptionRef),
-    ContinueBlock,
-    ContinueLine,
-}
-
-fn shell_exec(
-    vm: &VirtualMachine,
-    source: &str,
-    scope: Scope,
-    empty_line_given: bool,
-    continuing_block: bool,
-    future_features: &mut CodeFlags,
-) -> ShellExecResult {
-    // compiling expects only UNIX style line endings, and will replace windows line endings
-    // internally. Since we might need to analyze the source to determine if an error could be
-    // resolved by future input, we need the location from the error to match the source code that
-    // was actually compiled.
-    #[cfg(windows)]
-    let source = &source.replace("\r\n", "\n");
-    let opts = compiler::CompileOpts {
-        future_features: *future_features,
-        ..vm.compile_opts()
-    };
-    match vm.compile_with_opts(source, compiler::Mode::Single, "<stdin>", opts) {
-        Ok(code) => {
-            *future_features |= code.code.flags & CodeFlags::FUTURE_MASK;
-            let _ = vm.register_code_in_linecache(&code, source);
-            if empty_line_given || !continuing_block {
-                match vm.run_code_obj(code, scope) {
-                    Ok(_val) => ShellExecResult::Ok,
-                    Err(err) => ShellExecResult::PyErr(err),
-                }
-            } else {
-                // We can just return an ok result
-                ShellExecResult::Ok
-            }
-        }
-        Err(err) => {
-            if matches!(
-                &err,
-                VmCompileError::Compile(CompileError::Parse(ParseError {
-                    error: ParseErrorType::Lexical(
-                        LexicalErrorType::Eof
-                            | LexicalErrorType::FStringError(
-                                InterpolatedStringErrorType::UnterminatedTripleQuotedString,
-                            )
-                    ),
-                    ..
-                }))
-            ) {
-                return ShellExecResult::ContinueLine;
-            }
-            if let VmCompileError::Compile(CompileError::Parse(ParseError {
-                error: ParseErrorType::Lexical(LexicalErrorType::UnclosedStringError),
-                raw_location,
-                ..
-            })) = &err
-            {
-                let loc = raw_location.start().to_usize();
-                let mut iter = source.chars();
-                if let Some(quote) = iter.nth(loc)
-                    && iter.next() == Some(quote)
-                    && iter.next() == Some(quote)
-                {
-                    return ShellExecResult::ContinueLine;
-                }
-            }
-
-            // An unfinished suite is _IncompleteInputError, not IndentationError.
-            let exc = err.into_pyexception_maybe_incomplete(vm, Some(source), !empty_line_given);
-            if !empty_line_given && exc.fast_isinstance(vm.ctx.exceptions.incomplete_input_error) {
-                ShellExecResult::ContinueBlock
-            } else {
-                ShellExecResult::PyErr(exc)
-            }
-        }
-    }
-}
-
-fn flush_stdio(vm: &VirtualMachine) {
-    for name in ["stdout", "stderr"] {
-        if let Ok(stream) = vm.sys_module.get_attr(name, vm) {
-            let _ = vm.call_method(&stream, "flush", ());
-        }
-    }
-}
-
 /// Enter a repl loop
+///
+/// rustyline takes the role of `PyOS_Readline` with the readline module,
+/// adding line editing, completion and history.
 pub fn run_shell(vm: &VirtualMachine, scope: Scope) -> PyResult<()> {
-    let mut repl = Readline::new(helper::ShellHelper::new(vm, scope.globals.clone()));
-    let mut full_input = String::new();
-
-    // Retrieve a `history_path_str` dependent on the OS
-    let repl_history_path = match dirs::config_dir() {
-        Some(mut path) => {
+    let mut repl = Readline::new(helper::ShellHelper::new(vm, scope.globals));
+    let history = dirs::config_dir().map_or_else(
+        || ".repl_history.txt".into(),
+        |mut path| {
             path.push("rustpython");
             path.push("repl_history.txt");
             path
+        },
+    );
+    let _ = repl.load_history(&history);
+    let result = vm.run_interactive_loop(|prompt| match repl.readline(prompt) {
+        ReadlineResult::Line(line) => {
+            let _ = repl.add_history_entry(line.trim_end());
+            Ok(Some(InteractiveLine::Text(line)))
         }
-        None => ".repl_history.txt".into(),
-    };
-
-    let _ = repl.load_history(&repl_history_path);
-
-    // We might either be waiting to know if a block is complete, or waiting to know if a multiline
-    // statement is complete. In the former case, we need to ensure that we read one extra new line
-    // to know that the block is complete. In the latter, we can execute as soon as the statement is
-    // valid.
-    let mut continuing_block = false;
-    let mut continuing_line = false;
-    let mut future_features = CodeFlags::empty();
-
-    loop {
-        let prompt_name = if continuing_block || continuing_line {
-            "ps2"
-        } else {
-            "ps1"
-        };
-        let prompt = vm
-            .sys_module
-            .get_attr(prompt_name, vm)
-            .and_then(|prompt| prompt.str(vm));
-        let prompt = match prompt {
-            Ok(ref s) => s.expect_str(),
-            Err(_) => "",
-        };
-
-        continuing_line = false;
-        let result = match repl.readline(prompt) {
-            ReadlineResult::Line(line) => {
-                #[cfg(debug_assertions)]
-                debug!("You entered {line:?}");
-
-                repl.add_history_entry(line.trim_end()).unwrap();
-
-                let empty_line_given = line.is_empty();
-
-                if full_input.is_empty() {
-                    full_input = line;
-                } else {
-                    full_input.push_str(&line);
-                }
-                full_input.push('\n');
-
-                match shell_exec(
-                    vm,
-                    &full_input,
-                    scope.clone(),
-                    empty_line_given,
-                    continuing_block,
-                    &mut future_features,
-                ) {
-                    ShellExecResult::Ok => {
-                        if continuing_block {
-                            if empty_line_given {
-                                // We should exit continue mode since the block successfully executed
-                                continuing_block = false;
-                                full_input.clear();
-                            }
-                        } else {
-                            // We aren't in continue mode so proceed normally
-                            full_input.clear();
-                        }
-                        Ok(())
-                    }
-                    // Continue, but don't change the mode
-                    ShellExecResult::ContinueLine => {
-                        continuing_line = true;
-                        Ok(())
-                    }
-                    ShellExecResult::ContinueBlock => {
-                        continuing_block = true;
-                        Ok(())
-                    }
-                    ShellExecResult::PyErr(err) => {
-                        continuing_block = false;
-                        full_input.clear();
-                        Err(err)
-                    }
-                }
-            }
-            ReadlineResult::Interrupt => {
-                continuing_block = false;
-                full_input.clear();
-                let keyboard_interrupt =
-                    vm.new_exception_empty(vm.ctx.exceptions.keyboard_interrupt.to_owned());
-                Err(keyboard_interrupt)
-            }
-            ReadlineResult::Eof => {
-                break;
-            }
-            #[cfg(unix)]
-            ReadlineResult::OsError(num) => {
-                let os_error = vm.new_exception_msg(
-                    vm.ctx.exceptions.os_error.to_owned(),
-                    format!("{num:?}").into(),
-                );
-                vm.print_exception(&os_error);
-                break;
-            }
-            ReadlineResult::Other(err) => {
-                eprintln!("Readline error: {err:?}");
-                break;
-            }
-            ReadlineResult::Io(err) => {
-                eprintln!("IO error: {err:?}");
-                break;
-            }
-        };
-
-        if let Err(exc) = result {
-            if exc.fast_isinstance(vm.ctx.exceptions.system_exit) {
-                repl.save_history(&repl_history_path).unwrap();
-                return Err(exc);
-            }
-            vm.print_exception(&exc);
+        ReadlineResult::Eof => Ok(None),
+        ReadlineResult::Interrupt => {
+            Err(vm.new_exception_empty(vm.ctx.exceptions.keyboard_interrupt.to_owned()))
         }
-        flush_stdio(vm);
-    }
-    repl.save_history(&repl_history_path).unwrap();
-
-    Ok(())
+        ReadlineResult::Io(_) => Ok(None),
+        #[cfg(unix)]
+        ReadlineResult::OsError(_) => Ok(None),
+        ReadlineResult::Other(_) => Ok(None),
+    });
+    let _ = repl.save_history(&history);
+    result
 }
diff --git a/src/shell/helper.rs b/src/shell/helper.rs
index 15fc75563dc..a1c8c6301a2 100644
--- a/src/shell/helper.rs
+++ b/src/shell/helper.rs
@@ -1,14 +1,14 @@
 #![cfg_attr(target_arch = "wasm32", allow(dead_code))]
 use rustpython_vm::{
-    AsObject, PyResult, TryFromObject, VirtualMachine,
-    builtins::{PyDictRef, PyStrRef},
+    AsObject, PyRef, PyResult, TryFromObject, VirtualMachine,
+    builtins::{PyAnyDict, PyStrRef},
     function::ArgIterable,
     identifier,
 };
 
 pub(super) struct ShellHelper<'vm> {
     vm: &'vm VirtualMachine,
-    globals: PyDictRef,
+    globals: PyRef<PyAnyDict>,
 }
 
 fn reverse_string(s: &mut String) {
@@ -54,7 +54,7 @@ fn split_idents_on_dot(line: &str) -> Option<(usize, Vec<String>)> {
 }
 
 impl<'vm> ShellHelper<'vm> {
-    pub(super) const fn new(vm: &'vm VirtualMachine, globals: PyDictRef) -> Self {
+    pub(super) const fn new(vm: &'vm VirtualMachine, globals: PyRef<PyAnyDict>) -> Self {
         ShellHelper { vm, globals }
     }
 
@@ -149,8 +149,8 @@ impl<'vm> ShellHelper<'vm> {
 cfg_select! {
     not(target_arch = "wasm32") => {
         use rustyline::{
-            completion::Completer, highlight::Highlighter, hint::Hinter, validate::Validator, Context,
-            Helper,
+            Context, Helper, completion::Completer, highlight::Highlighter, hint::Hinter,
+            validate::Validator,
         };
         impl Completer for ShellHelper<'_> {
             type Candidate = String;
diff --git a/tools/opcode_metadata/conf.toml b/tools/opcode_metadata/conf.toml
index e69de29bb2d..765ecd1b45b 100644
--- a/tools/opcode_metadata/conf.toml
+++ b/tools/opcode_metadata/conf.toml
@@ -0,0 +1,2 @@
+[BuildListFromArg]
+stack_effect = { pushed = "2", popped = "1" }
diff --git a/tools/opcode_metadata/generate_py_opcode_metadata.py b/tools/opcode_metadata/generate_py_opcode_metadata.py
index 08f350e4b39..2341588cd5c 100644
--- a/tools/opcode_metadata/generate_py_opcode_metadata.py
+++ b/tools/opcode_metadata/generate_py_opcode_metadata.py
@@ -1,7 +1,5 @@
 """
 Generate Lib/_opcode_metadata.py for RustPython bytecode.
-
-This file generates opcode metadata that is compatible with CPython 3.14.
 """
 
 import functools
@@ -24,10 +22,10 @@
     "RESUME",
     "INSTRUMENTED_LINE",
     "ENTER_EXECUTOR",
+    "TRACE_RECORD",
 }
 
 INDENT = " " * 4
-INDENT2 = INDENT * 2
 
 
 def main():
@@ -43,52 +41,51 @@ def main():
     out.write(
         f"""
 # This file is generated by {script_path}
-# for RustPython bytecode format (CPython 3.14 compatible opcode numbers).
+# for RustPython bytecode format.
 # Do not edit!
 """.lstrip()
     )
 
     # _specializations
-    out.write("\n")
-    out.write("_specializations = {\n")
+    out.write("_specializations = frozendict(\n")
 
     deopts = functools.reduce(operator.ior, map(operator.attrgetter("deopts"), infos))
 
     for key, lst in deopts.items():
         key = to_upper_snake_case(key)
-        out.write(f'{INDENT}"{key}": [\n')
+        out.write(f"{INDENT}{key}=(\n")
 
-        for item in map(to_upper_snake_case, lst):
-            out.write(f'{INDENT2}"{item}",\n')
+        for item in map(to_upper_snake_case, dict.fromkeys(lst)):
+            out.write(f'{INDENT * 3}"{item}",\n')
 
-        out.write(f"{INDENT}],\n")
+        out.write(f"{INDENT}),\n")
 
-    out.write("}\n")
+    out.write(")\n")
 
     # _specialized_opmap
     out.write("\n")
-    out.write("_specialized_opmap = {\n")
+    out.write("_specialized_opmap = frozendict(\n")
 
     specialized = set(itertools.chain.from_iterable(deopts.values()))
     for opcode in sorted(opcodes, key=lambda op: op.cpython_name):
         if opcode.rust_name not in specialized:
             continue
-        out.write(f"{INDENT}'{opcode.cpython_name}': {opcode.id},\n")
+        out.write(f"{INDENT}{opcode.cpython_name}={opcode.id},\n")
 
-    out.write("}\n")
+    out.write(")\n")
 
     # opmap
     out.write("\n")
-    out.write("opmap = {\n")
+    out.write("opmap = frozendict(\n")
 
     key = lambda op: (op.cpython_name not in PRIORITY_OPMAP, op.id)
     for opcode in sorted(opcodes, key=key):
         if opcode.rust_name in specialized:
             continue
 
-        out.write(f"{INDENT}'{opcode.cpython_name}': {opcode.id},\n")
+        out.write(f"{INDENT}{opcode.cpython_name}={opcode.id},\n")
 
-    out.write("}\n")
+    out.write(")\n")
 
     # min
     out.write("\n")
diff --git a/wasm/demo/package-lock.json b/wasm/demo/package-lock.json
index 3860bd7bd44..6f85ed43ff2 100644
--- a/wasm/demo/package-lock.json
+++ b/wasm/demo/package-lock.json
@@ -4565,9 +4565,9 @@
             }
         },
         "node_modules/postcss-selector-parser": {
-            "version": "7.1.5",
-            "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-7.1.5.tgz",
-            "integrity": "sha512-KvvtD7SrlBP7dlgkBghEE3r84CABm5SmV2aNcG4oCA+qDnJ/tvKonFVvwWAyyWUEwxuNawdfEAZKP9zM3oZ2Uw==",
+            "version": "7.1.6",
+            "resolved": "https://registry.npmjs.org/postcss-selector-parser/-/postcss-selector-parser-7.1.6.tgz",
+            "integrity": "sha512-7qASPzhKF2l2KLboRZux8CCTRMdGiV08vWmyKzPz22qZ7ZjQBOeY7rNzNoCLSUiftJ7HUq0GERHmxw/t0dCdMw==",
             "dev": true,
             "license": "MIT",
             "dependencies": {
@@ -4604,9 +4604,9 @@
             "license": "MIT"
         },
         "node_modules/proxy-addr": {
-            "version": "2.0.7",
-            "resolved": "https://registry.npmjs.org/proxy-addr/-/proxy-addr-2.0.7.tgz",
-            "integrity": "sha512-llQsMLSUDUPT44jdrU/O37qlnifitDP+ZwrmmZcoSKyLKvtZxpyV0n2/bD/N4tBAAZ/gJEdZU7KMraoK1+XYAg==",
+            "version": "2.0.8",
+            "resolved": "https://registry.npmjs.org/proxy-addr/-/proxy-addr-2.0.8.tgz",
+            "integrity": "sha512-5nnx0yGyVUcY6t9RnWcARWtwT9F1D8O9rt08htPvnd49W1IgZtmLkhu9WfMzQj1cFxjHIO6connUNVW5k7AVyQ==",
             "dev": true,
             "license": "MIT",
             "dependencies": {
@@ -4615,6 +4615,10 @@
             },
             "engines": {
                 "node": ">= 0.10"
+            },
+            "funding": {
+                "type": "opencollective",
+                "url": "https://opencollective.com/express"
             }
         },
         "node_modules/proxy-addr/node_modules/ipaddr.js": {
@@ -5253,9 +5257,9 @@
             }
         },
         "node_modules/shell-quote": {
-            "version": "1.10.0",
-            "resolved": "https://registry.npmjs.org/shell-quote/-/shell-quote-1.10.0.tgz",
-            "integrity": "sha512-w1aiOKwKuRgtwAReIIj89puqg+I7GvX4IbLrvmhXbzQsj1+Zwi4VO3+fa6ZF91TWSjIxoEkKnMeHcLEODK5ZXA==",
+            "version": "1.12.0",
+            "resolved": "https://registry.npmjs.org/shell-quote/-/shell-quote-1.12.0.tgz",
+            "integrity": "sha512-PcByqNyT/38F2kDNi006HAMRJaULuBzq/FOsw3qdZvX/GA9W/jamDaRskgHjubHiftXK5sIFxLNkvrXUwcof6Q==",
             "dev": true,
             "license": "MIT",
             "engines": {
@@ -5371,9 +5375,9 @@
             }
         },
         "node_modules/source-map-js": {
-            "version": "1.2.1",
-            "resolved": "https://registry.npmjs.org/source-map-js/-/source-map-js-1.2.1.tgz",
-            "integrity": "sha512-UXWMKhLOwVKb728IUtQPXxfYU+usdybtUrK/8uGE8CQMvrhOpwvzDBwj0QhSL7MQc7vIsISBG8VQ8+IDQxpfQA==",
+            "version": "1.2.2",
+            "resolved": "https://registry.npmjs.org/source-map-js/-/source-map-js-1.2.2.tgz",
+            "integrity": "sha512-KGj/8Y43x35aZVDtt+J4mK1hoLGHULMYfSkODJNQjNDC3oW1PqPoxMwo0pLUsWM/UEGzON/NxeHywEfNXNP3Vw==",
             "dev": true,
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