lazerg · Oct 18, 2026 · Oct 18, 2026
@@ -265,6 +265,12 @@ def do(self) -> None:
                 r.error("start of buffer")
                 return
 
+            # Skip prompt-only rows, they hold no buffer positions
+            row = r.layout.rows[new_y]
+            while new_y > 0 and not row.char_widths and not row.buffer_advance:
+                new_y -= 1
+                row = r.layout.rows[new_y]
+
             if (
                 x
                 > (

@@ -215,7 +215,7 @@ def layout_content_lines(
                 index_to_wrap_before += 1
                 column += char_width
 
-            if index_to_wrap_before == 0 and start < total:
+            if index_to_wrap_before == 0 and not current_prompt_width:
                 index_to_wrap_before = 1  # force progress
 
             at_line_end = (start + index_to_wrap_before) >= total

@@ -229,17 +229,30 @@ def test_line_wraps(self):
 
     def test_wrapping_forces_progress(self):
         # When a single character is wider than available space, force 1 char
-        prompt = _prompt("P", 1)
-        body = (ContentFragment("W", 1),)
+        prompt = _prompt("", 0)
+        body = (ContentFragment("W", 2),)
         source = _source("W", has_newline=False)
         line = ContentLine(source, prompt, body)
-        # width=2 means prompt(1) + char(1) = 2, which fits (< width would be
-        # false for width=2 since 1+1 >= 2), so it wraps but forces progress
+        # width=2 means char(2) >= width, so it wraps but forces progress
         result = layout_content_lines((line,), 2, 0)
 
         self.assertEqual(len(result.wrapped_rows), 1)
         self.assertEqual(result.wrapped_rows[0].buffer_advance, 1)
 
+    def test_prompt_wider_than_terminal(self):
+        line = _content_line("Hello", prompt=_prompt("a" * 65, 65))
+        result = layout_content_lines((line,), 20, 0)
+
+        self.assertEqual(len(result.wrapped_rows), 2)
+        first, second = result.wrapped_rows
+        self.assertEqual(first.prompt_width, 65)
+        self.assertEqual(first.fragments, ())
+        self.assertEqual(first.suffix, "\\")
+        self.assertEqual(first.buffer_advance, 0)
+        self.assertEqual(second.prompt_width, 0)
+        self.assertEqual(second.buffer_advance, 6)
+        self.assertEqual(result.layout_map.pos_to_xy(0), (0, 1))
+
     def test_layout_map_matches_wrapped_rows(self):
         line = _content_line("abc")
         result = layout_content_lines((line,), 80, 0)

@@ -236,6 +236,22 @@ def test_up_arrow_after_ctrl_r(self):
         reader, _ = handle_all_events(events)
         self.assertIn(reader.screen, ([], [""]))
 
+    def test_up_arrow_with_prompt_wider_than_terminal(self):
+        events = itertools.chain(
+            code_to_events("x\nabc"),
+            [Event(evt="key", data="up", raw=bytearray(b"\x1bOA"))],
+        )
+        reader, _ = handle_all_events(
+            events,
+            prepare_console=functools.partial(prepare_console, width=20),
+            prepare_reader=functools.partial(
+                prepare_reader, get_prompt=lambda lineno, cursor_on_line: "a" * 30
+            ),
+        )
+        # the prompt-only row above "abc" is skipped, landing on "x"
+        self.assertEqual(reader.pos, 1)
+        self.assertEqual(reader.cxy, (1, 1))
+
     def test_newline_within_block_trailing_whitespace(self):
         # fmt: off
         code = (

diff --git a/Misc/NEWS.d/next/Library/2026-10-18-03-47-18.gh-issue-159658.7vC6hv.rst b/Misc/NEWS.d/next/Library/2026-10-18-03-47-18.gh-issue-159658.7vC6hv.rst
@@ -0,0 +1,2 @@
+Fix the :term:`REPL` mangling typed input when :data:`sys.ps1` is wider than
+the terminal.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix the :term:`REPL` mangling typed input when :data:`sys.ps1` is wider than
		the terminal.