diff --git a/.github/workflows/cloud_build_failure_reporter.yml b/.github/workflows/cloud_build_failure_reporter.yml
index a07e3a676..493ddecd2 100644
--- a/.github/workflows/cloud_build_failure_reporter.yml
+++ b/.github/workflows/cloud_build_failure_reporter.yml
@@ -38,7 +38,7 @@ jobs:
     runs-on: 'ubuntu-latest'
 
     steps:
-      - uses: 'actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea' # v7
+      - uses: 'actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd' # v8
         with:
           script: |-
                   // parse test names
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 2b01fa803..301fb0204 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -46,16 +46,16 @@ jobs:
 
       # Initializes the CodeQL tools for scanning.
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@df559355d593797519d70b90fc8edd5db049e7a2 # v3.29.9
+        uses: github/codeql-action/init@e296a935590eb16afc0c0108289f68c87e2a89a5 # v4.30.7
         with:
           languages: ${{ matrix.language }}
 
       # Autobuild attempts to build any compiled languages  (C/C++, C#, Go, or Java).
       # If this step fails, then you should remove it and run the build manually
       - name: Autobuild
-        uses: github/codeql-action/autobuild@df559355d593797519d70b90fc8edd5db049e7a2 # v3.29.9
+        uses: github/codeql-action/autobuild@e296a935590eb16afc0c0108289f68c87e2a89a5 # v4.30.7
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@df559355d593797519d70b90fc8edd5db049e7a2 # v3.29.9
+        uses: github/codeql-action/analyze@e296a935590eb16afc0c0108289f68c87e2a89a5 # v4.30.7
         with:
           category: "/language:${{matrix.language}}"
diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index ecb188869..df109d873 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Setup Python
-        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c # v6.0.0
         with:
           python-version: "3.13"
 
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 481cd39ef..f82d503a0 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Setup Python
-        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c # v6.0.0
         with:
           python-version: "3.13"
 
diff --git a/.github/workflows/scorecard.yml b/.github/workflows/scorecard.yml
index 62dd7a387..3e8c8687f 100644
--- a/.github/workflows/scorecard.yml
+++ b/.github/workflows/scorecard.yml
@@ -65,6 +65,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@df559355d593797519d70b90fc8edd5db049e7a2 # v3.29.9
+        uses: github/codeql-action/upload-sarif@e296a935590eb16afc0c0108289f68c87e2a89a5 # v4.30.7
         with:
           sarif_file: resultsFiltered.sarif
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 63dc9a2be..b600742bf 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -47,7 +47,7 @@ jobs:
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
       - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c # v6.0.0
         with:
           python-version: ${{ matrix.python-version }}
 
@@ -56,7 +56,7 @@ jobs:
 
       - id: auth
         name: Authenticate to Google Cloud
-        uses: google-github-actions/auth@b7593ed2efd1c1617e1b0254da33b86225adb2a5 # v2.1.12
+        uses: google-github-actions/auth@7c6bc770dae815cd3e89ee6cdf493a5fab2cc093 # v3.0.0
         with:
           workload_identity_provider: ${{ vars.PROVIDER_NAME }}
           service_account: ${{ vars.SERVICE_ACCOUNT }}
@@ -64,7 +64,7 @@ jobs:
 
       - id: secrets
         name: Get secrets
-        uses: google-github-actions/get-secretmanager-secrets@50ec04d56ddf2740b0bde82926cc742f90e06d2b # v2.2.4
+        uses: google-github-actions/get-secretmanager-secrets@bc9c54b29fdffb8a47776820a7d26e77b379d262 # v3.0.0
         with:
           secrets: |-
             MYSQL_CONNECTION_NAME:${{ vars.GOOGLE_CLOUD_PROJECT }}/MYSQL_CONNECTION_NAME
@@ -156,7 +156,7 @@ jobs:
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
       - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c # v6.0.0
         with:
           python-version: ${{ matrix.python-version }}
 
@@ -167,7 +167,7 @@ jobs:
         name: Authenticate to Google Cloud
         # only needed for Flakybot on periodic (schedule) and continuous (push) events
         if: ${{ github.event_name == 'schedule' || github.event_name == 'push' }}
-        uses: google-github-actions/auth@b7593ed2efd1c1617e1b0254da33b86225adb2a5 # v2.1.12
+        uses: google-github-actions/auth@7c6bc770dae815cd3e89ee6cdf493a5fab2cc093 # v3.0.0
         with:
           workload_identity_provider: ${{ vars.PROVIDER_NAME }}
           service_account: ${{ vars.SERVICE_ACCOUNT }}
diff --git a/.gitignore b/.gitignore
index 9f449ce4a..06827b584 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,5 @@ dist/
 .idea
 .coverage
 sponge_log.xml
+.envrc
+*.iml
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 677c7d5a2..1347a4f8c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+## [1.18.5](https://github.com/GoogleCloudPlatform/cloud-sql-python-connector/compare/v1.18.4...v1.18.5) (2025-10-09)
+
+
+### Bug Fixes
+
+* error on connect_async() event loop mismatch ([#1113](https://github.com/GoogleCloudPlatform/cloud-sql-python-connector/issues/1113)) ([3030b82](https://github.com/GoogleCloudPlatform/cloud-sql-python-connector/commit/3030b824c899c56861832c0254df3c87585d3fcb))
+
 ## [1.18.4](https://github.com/GoogleCloudPlatform/cloud-sql-python-connector/compare/v1.18.3...v1.18.4) (2025-08-12)
 
 
diff --git a/README.md b/README.md
index 1c5489e04..9bea3d6d6 100644
--- a/README.md
+++ b/README.md
@@ -566,7 +566,7 @@ from google.cloud.sql.connector import Connector, create_async_connector
 
 async def main():
     # initialize Connector object for connections to Cloud SQL
-    connector = create_async_connector()
+    connector = await create_async_connector()
 
     # creation function to generate asyncpg connections as the 'connect' arg
     async def getconn(instance_connection_name, **kwargs) -> asyncpg.Connection:
diff --git a/build.sh b/build.sh
new file mode 100755
index 000000000..fc85edff9
--- /dev/null
+++ b/build.sh
@@ -0,0 +1,168 @@
+#!/usr/bin/env bash
+
+# Copyright 2025 Google LLC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http=//www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Set SCRIPT_DIR to the current directory of this file.
+SCRIPT_DIR=$(cd -P "$(dirname "$0")" >/dev/null 2>&1 && pwd)
+SCRIPT_FILE="${SCRIPT_DIR}/$(basename "$0")"
+
+##
+## Local Development
+##
+## These functions should be used to run the local development process
+##
+
+if [[ ! -d venv ]] ; then
+  echo "./venv not found. Setting up venv"
+  python3 -m venv "$PWD/venv"
+fi
+source "$PWD/venv/bin/activate"
+
+if which pip3 ; then
+  PIP_CMD=pip3
+elif which pip ; then
+  PIP_CMD=pip
+else
+  echo "pip not found. Please add pip to your path."
+  exit 1
+fi
+if ! which nox ; then
+  $PIP_CMD install nox
+fi
+
+
+
+## clean - Cleans the build output
+function clean() {
+  if [[ -d '.tools' ]] ; then
+    rm -rf .tools
+  fi
+}
+
+## build - Builds the project without running tests.
+function build() {
+  nox --sessions build
+}
+
+## test - Runs local unit tests.
+function test() {
+  nox --sessions unit --python=3.13
+}
+
+## e2e - Runs end-to-end integration tests.
+function e2e() {
+  if [[ ! -f .envrc ]] ; then
+    write_e2e_env .envrc
+  fi
+  source .envrc
+  nox --sessions system  --python=3.13
+}
+
+## fix - Fixes code format.
+function fix() {
+  nox --sessions format
+}
+
+## lint - runs the linters
+function lint() {
+  # Check the commit includes a go.mod that is fully
+  # up to date.
+  nox --sessions lint
+}
+
+## deps - updates project dependencies to latest
+function deps() {
+  echo "Todo: deps"
+  exit 1
+}
+
+# write_e2e_env - Loads secrets from the gcloud project and writes
+#     them to target/e2e.env to run e2e tests.
+function write_e2e_env(){
+  # All secrets used by the e2e tests in the form <env_name>=<secret_name>
+  secret_vars=(
+    MYSQL_CONNECTION_NAME=MYSQL_CONNECTION_NAME
+    MYSQL_USER=MYSQL_USER
+    MYSQL_USER_IAM=MYSQL_USER_IAM_GO
+    MYSQL_PASS=MYSQL_PASS
+    MYSQL_DB=MYSQL_DB
+    MYSQL_MCP_CONNECTION_NAME=MYSQL_MCP_CONNECTION_NAME
+    MYSQL_MCP_PASS=MYSQL_MCP_PASS
+    POSTGRES_CONNECTION_NAME=POSTGRES_CONNECTION_NAME
+    POSTGRES_USER=POSTGRES_USER
+    POSTGRES_USER_IAM=POSTGRES_USER_IAM_GO
+    POSTGRES_PASS=POSTGRES_PASS
+    POSTGRES_DB=POSTGRES_DB
+    POSTGRES_CAS_CONNECTION_NAME=POSTGRES_CAS_CONNECTION_NAME
+    POSTGRES_CAS_PASS=POSTGRES_CAS_PASS
+    POSTGRES_CUSTOMER_CAS_CONNECTION_NAME=POSTGRES_CUSTOMER_CAS_CONNECTION_NAME
+    POSTGRES_CUSTOMER_CAS_PASS=POSTGRES_CUSTOMER_CAS_PASS
+    POSTGRES_CUSTOMER_CAS_DOMAIN_NAME=POSTGRES_CUSTOMER_CAS_DOMAIN_NAME
+    POSTGRES_CUSTOMER_CAS_INVALID_DOMAIN_NAME=POSTGRES_CUSTOMER_CAS_INVALID_DOMAIN_NAME
+    POSTGRES_MCP_CONNECTION_NAME=POSTGRES_MCP_CONNECTION_NAME
+    POSTGRES_MCP_PASS=POSTGRES_MCP_PASS
+    SQLSERVER_CONNECTION_NAME=SQLSERVER_CONNECTION_NAME
+    SQLSERVER_USER=SQLSERVER_USER
+    SQLSERVER_PASS=SQLSERVER_PASS
+    SQLSERVER_DB=SQLSERVER_DB
+    QUOTA_PROJECT=QUOTA_PROJECT
+  )
+
+  if [[ -z "$TEST_PROJECT" ]] ; then
+    echo "Set TEST_PROJECT environment variable to the project containing"
+    echo "the e2e test suite secrets."
+    exit 1
+  fi
+
+  echo "Getting test secrets from $TEST_PROJECT into $1"
+  {
+  for env_name in "${secret_vars[@]}" ; do
+    env_var_name="${env_name%%=*}"
+    secret_name="${env_name##*=}"
+    set -x
+    val=$(gcloud secrets versions access latest --project "$TEST_PROJECT" --secret="$secret_name")
+    echo "export $env_var_name='$val'"
+  done
+  } > "$1"
+
+}
+
+## help - prints the help details
+##
+function help() {
+   # This will print the comments beginning with ## above each function
+   # in this file.
+
+   echo "build.sh <command> <arguments>"
+   echo
+   echo "Commands to assist with local development and CI builds."
+   echo
+   echo "Commands:"
+   echo
+   grep -e '^##' "$SCRIPT_FILE" | sed -e 's/##/ /'
+}
+
+set -euo pipefail
+
+# Check CLI Arguments
+if [[ "$#" -lt 1 ]] ; then
+  help
+  exit 1
+fi
+
+cd "$SCRIPT_DIR"
+
+"$@"
+
diff --git a/google/cloud/sql/connector/client.py b/google/cloud/sql/connector/client.py
index 2e1fbc20d..11508ce17 100644
--- a/google/cloud/sql/connector/client.py
+++ b/google/cloud/sql/connector/client.py
@@ -22,9 +22,9 @@
 import aiohttp
 from cryptography.hazmat.backends import default_backend
 from cryptography.x509 import load_pem_x509_certificate
-
 from google.auth.credentials import TokenState
 from google.auth.transport import requests
+
 from google.cloud.sql.connector.connection_info import ConnectionInfo
 from google.cloud.sql.connector.connection_name import ConnectionName
 from google.cloud.sql.connector.exceptions import AutoIAMAuthNotSupported
diff --git a/google/cloud/sql/connector/connector.py b/google/cloud/sql/connector/connector.py
index 05eaa51df..0229b7283 100755
--- a/google/cloud/sql/connector/connector.py
+++ b/google/cloud/sql/connector/connector.py
@@ -28,11 +28,13 @@
 import google.auth
 from google.auth.credentials import Credentials
 from google.auth.credentials import with_scopes_if_required
+
 import google.cloud.sql.connector.asyncpg as asyncpg
 from google.cloud.sql.connector.client import CloudSQLClient
 from google.cloud.sql.connector.enums import DriverMapping
 from google.cloud.sql.connector.enums import IPTypes
 from google.cloud.sql.connector.enums import RefreshStrategy
+from google.cloud.sql.connector.exceptions import ConnectorLoopError
 from google.cloud.sql.connector.instance import RefreshAheadCache
 from google.cloud.sql.connector.lazy import LazyRefreshCache
 from google.cloud.sql.connector.monitored_cache import MonitoredCache
@@ -280,6 +282,15 @@ async def connect_async(
             KeyError: Unsupported database driver Must be one of pymysql, asyncpg,
                 pg8000, and pytds.
         """
+        # check if event loop is running in current thread
+        if self._loop != asyncio.get_running_loop():
+            raise ConnectorLoopError(
+                "Running event loop does not match 'connector._loop'. "
+                "Connector.connect_async() must be called from the event loop "
+                "the Connector was initialized with. If you need to connect "
+                "across event loops, please use a new Connector object."
+            )
+
         if self._keys is None:
             self._keys = asyncio.create_task(generate_keys())
         if self._client is None:
diff --git a/google/cloud/sql/connector/refresh_utils.py b/google/cloud/sql/connector/refresh_utils.py
index 0ef7fcbf7..898f0f7a9 100644
--- a/google/cloud/sql/connector/refresh_utils.py
+++ b/google/cloud/sql/connector/refresh_utils.py
@@ -24,7 +24,6 @@
 from typing import Any, Callable
 
 import aiohttp
-
 from google.auth.credentials import Credentials
 from google.auth.credentials import Scoped
 import google.auth.transport.requests
diff --git a/google/cloud/sql/connector/version.py b/google/cloud/sql/connector/version.py
index 776c409a2..c42d7c855 100644
--- a/google/cloud/sql/connector/version.py
+++ b/google/cloud/sql/connector/version.py
@@ -12,4 +12,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-__version__ = "1.18.4"
+__version__ = "1.18.5"
diff --git a/noxfile.py b/noxfile.py
index f04756241..b0220f474 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -69,6 +69,15 @@ def format(session):
         *LINT_PATHS,
     )
 
+@nox.session()
+def build(session):
+    """
+    Just run the default tools to install requirements.
+    """
+    # Install all test dependencies, then install this package in-place.
+    session.install("-r", "requirements-test.txt")
+    session.install("-e", ".")
+    session.install("-r", "requirements.txt")
 
 def default(session, path):
     # Install all test dependencies, then install this package in-place.
diff --git a/requirements-test.txt b/requirements-test.txt
index 8f690bfc5..9cba5a851 100644
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -1,6 +1,6 @@
 pytest==8.4.1
 mock==5.2.0
-pytest-cov==6.2.1
+pytest-cov==7.0.0
 pytest-asyncio==1.1.0
 SQLAlchemy[asyncio]==2.0.43
 sqlalchemy-pytds==1.0.2
diff --git a/requirements.txt b/requirements.txt
index 5892a9341..766d62dc5 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
 aiofiles==24.1.0
 aiohttp==3.12.15
-cryptography==45.0.6
+cryptography==46.0.2
 dnspython==2.7.0
 Requests==2.32.4
 google-auth==2.40.3
diff --git a/tests/unit/mocks.py b/tests/unit/mocks.py
index 28c2fc307..66bf64a32 100644
--- a/tests/unit/mocks.py
+++ b/tests/unit/mocks.py
@@ -31,10 +31,10 @@
 from cryptography.hazmat.primitives import serialization
 from cryptography.hazmat.primitives.asymmetric import rsa
 from cryptography.x509.oid import NameOID
-
 from google.auth import _helpers
 from google.auth.credentials import Credentials
 from google.auth.credentials import TokenState
+
 from google.cloud.sql.connector.connector import _DEFAULT_UNIVERSE_DOMAIN
 from google.cloud.sql.connector.utils import generate_keys
 from google.cloud.sql.connector.utils import write_to_file
diff --git a/tests/unit/test_client.py b/tests/unit/test_client.py
index 2ecefe220..cfe509470 100644
--- a/tests/unit/test_client.py
+++ b/tests/unit/test_client.py
@@ -17,10 +17,10 @@
 
 from aiohttp import ClientResponseError
 from aioresponses import aioresponses
+from google.auth.credentials import Credentials
 from mocks import FakeCredentials
 import pytest
 
-from google.auth.credentials import Credentials
 from google.cloud.sql.connector.client import CloudSQLClient
 from google.cloud.sql.connector.utils import generate_keys
 from google.cloud.sql.connector.version import __version__ as version
diff --git a/tests/unit/test_connector.py b/tests/unit/test_connector.py
index 157697723..1bcb42616 100644
--- a/tests/unit/test_connector.py
+++ b/tests/unit/test_connector.py
@@ -16,19 +16,21 @@
 
 import asyncio
 import os
+from threading import Thread
 from typing import Union
 
 from aiohttp import ClientResponseError
+from google.auth.credentials import Credentials
 from mock import patch
 import pytest  # noqa F401 Needed to run the tests
 
-from google.auth.credentials import Credentials
 from google.cloud.sql.connector import Connector
 from google.cloud.sql.connector import create_async_connector
 from google.cloud.sql.connector import IPTypes
 from google.cloud.sql.connector.client import CloudSQLClient
 from google.cloud.sql.connector.connection_name import ConnectionName
 from google.cloud.sql.connector.exceptions import CloudSQLIPTypeError
+from google.cloud.sql.connector.exceptions import ConnectorLoopError
 from google.cloud.sql.connector.exceptions import IncompatibleDriverError
 from google.cloud.sql.connector.instance import RefreshAheadCache
 
@@ -280,6 +282,38 @@ async def test_Connector_connect_async(
             assert connection is True
 
 
+@pytest.mark.asyncio
+async def test_Connector_connect_async_multiple_event_loops(
+    fake_credentials: Credentials, fake_client: CloudSQLClient
+) -> None:
+    """Test that Connector.connect_async errors when run on wrong event loop."""
+
+    new_loop = asyncio.new_event_loop()
+    thread = Thread(target=new_loop.run_forever, daemon=True)
+    thread.start()
+
+    async with Connector(
+        credentials=fake_credentials, loop=asyncio.get_running_loop()
+    ) as connector:
+        connector._client = fake_client
+        with pytest.raises(ConnectorLoopError) as exc_info:
+            future = asyncio.run_coroutine_threadsafe(
+                connector.connect_async(
+                    "test-project:test-region:test-instance", "asyncpg"
+                ),
+                loop=new_loop,
+            )
+            future.result()
+        assert (
+            exc_info.value.args[0] == "Running event loop does not match "
+            "'connector._loop'. Connector.connect_async() must be called from "
+            "the event loop the Connector was initialized with. If you need to "
+            "connect across event loops, please use a new Connector object."
+        )
+    new_loop.call_soon_threadsafe(new_loop.stop)
+    thread.join()
+
+
 @pytest.mark.asyncio
 async def test_create_async_connector(fake_credentials: Credentials) -> None:
     """Test that create_async_connector properly initializes connector
diff --git a/tests/unit/test_refresh_utils.py b/tests/unit/test_refresh_utils.py
index 2d4cdb853..119e92c7a 100644
--- a/tests/unit/test_refresh_utils.py
+++ b/tests/unit/test_refresh_utils.py
@@ -20,19 +20,19 @@
 import datetime
 
 from conftest import SCOPES  # type: ignore
+import google.auth
+from google.auth.credentials import Credentials
+from google.auth.credentials import TokenState
+import google.oauth2.credentials
 from mock import Mock
 from mock import patch
 import pytest  # noqa F401 Needed to run the tests
 
-import google.auth
-from google.auth.credentials import Credentials
-from google.auth.credentials import TokenState
 from google.cloud.sql.connector.refresh_utils import _downscope_credentials
 from google.cloud.sql.connector.refresh_utils import _exponential_backoff
 from google.cloud.sql.connector.refresh_utils import _is_valid
 from google.cloud.sql.connector.refresh_utils import _seconds_until_refresh
 from google.cloud.sql.connector.refresh_utils import retry_50x
-import google.oauth2.credentials
 
 
 @pytest.fixture