diff --git a/.github/codecov.yml b/.github/codecov.yml
new file mode 100644
index 00000000..21acaf76
--- /dev/null
+++ b/.github/codecov.yml
@@ -0,0 +1,6 @@
+# Inherits global settings from https://app.codecov.io/account/gh/python/yaml/
+# TODO: enable status checks to fail CI if coverage drops?
+# https://docs.codecov.com/docs/commit-status
+comment:
+  # https://docs.codecov.com/docs/pull-request-comments
+  layout: "condensed_header, diff, flags, files"
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 5c563144..2e4b9645 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -8,3 +8,5 @@ updates:
       actions:
         patterns:
           - "*"
+    cooldown:
+      default-days: 7
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1059f458..690f8c7c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -56,50 +56,33 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           persist-credentials: false
 
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python-version }}
           allow-prereleases: true
 
       - name: Install coverage
-        if: ${{ !startsWith(matrix.python-version, 'pypy') }}
         run: |
-          # Be wary that this does not install typing_extensions in the future
-          pip install coverage
+          # Be wary that this does not install typing_extensions in the future.
+          # 'toml' extra is needed to read settings from pyproject.toml on Python <3.11
+          pip install 'coverage[toml]'
 
       - name: Test typing_extensions with coverage
-        if: ${{ !startsWith(matrix.python-version, 'pypy') }}
         run: |
           # Be wary of running `pip install` here, since it becomes easy for us to
           # accidentally pick up typing_extensions as installed by a dependency
           cd src
           python --version  # just to make sure we're running the right one
           # Run tests under coverage
-          export COVERAGE_FILE=.coverage_${{ matrix.python-version }}
           python -m coverage run -m unittest test_typing_extensions.py
-      - name: Test typing_extensions no coverage on pypy
-        if: ${{ startsWith(matrix.python-version, 'pypy') }}
-        run: |
-          # Be wary of running `pip install` here, since it becomes easy for us to
-          # accidentally pick up typing_extensions as installed by a dependency
-          cd src
-          python --version  # just to make sure we're running the right one
-          python -m unittest test_typing_extensions.py
+          # Create xml file for Codecov
+          coverage xml --rcfile=../pyproject.toml --fail-under=0
 
-      - name: Archive code coverage results
-        id: archive-coverage
-        if: ${{ !startsWith(matrix.python-version, 'pypy') }}
-        uses: actions/upload-artifact@v4
-        with:
-          name: .coverage_${{ matrix.python-version }}
-          path: ./src/.coverage*
-          include-hidden-files: true
-          compression-level: 0 # no compression
       - name: Test CPython typing test suite
         # Test suite fails on PyPy even without typing_extensions
         if: ${{ !startsWith(matrix.python-version, 'pypy') }}
@@ -108,9 +91,18 @@ jobs:
           # Run the typing test suite from CPython with typing_extensions installed,
           # because we monkeypatch typing under some circumstances.
           python -c 'import typing_extensions; import test.__main__' test_typing -v
-    outputs:
-      # report if coverage was uploaded
-      cov_uploaded: ${{ steps.archive-coverage.outputs.artifact-id }}
+
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@671740ac38dd9b0130fbe1cec585b89eea48d3de
+        if: >-
+          github.repository == 'python/typing_extensions'
+          && (github.event_name == 'push' || github.event_name == 'pull_request')
+        with:
+          token: ${{ secrets.CODECOV_ORG_TOKEN }}
+          flags: ${{ matrix.python-version }}
+          directory: src
+          fail_ci_if_error: true
+          verbose: true
 
   create-issue-on-failure:
     name: Create an issue if daily tests failed
@@ -130,7 +122,7 @@ jobs:
       issues: write
 
     steps:
-      - uses: actions/github-script@v7
+      - uses: actions/github-script@v8
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           script: |
@@ -140,95 +132,3 @@ jobs:
               title: `Daily tests failed on ${new Date().toDateString()}`,
               body: "Runs listed here: https://github.com/python/typing_extensions/actions/workflows/ci.yml",
             })
-
-  report-coverage:
-    name: Report coverage
-
-    runs-on: ubuntu-latest
-
-    needs: [tests]
-
-    permissions:
-      pull-requests: write
-
-    # Job will run even if tests failed but only if at least one artifact was uploaded
-    if: ${{ always() && needs.tests.outputs.cov_uploaded != '' }}
-
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          persist-credentials: false
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3"
-      - name: Download coverage artifacts
-        uses: actions/download-artifact@v4
-        with:
-          pattern: .coverage_*
-          path: .
-          # merge only when files are named differently
-          merge-multiple: true
-      - name: Install dependencies
-        run: pip install coverage
-      - name: Combine coverage results
-        run: |
-          # List the files to see what we have
-          echo "Combining coverage files..."
-          ls -aR .coverage*
-          coverage combine .coverage*
-          echo "Creating coverage report..."
-          # Create xml file for further processing; Create even if below minimum
-          coverage xml --fail-under=0
-          # Write markdown report to job summary
-          coverage report --fail-under=0 --format=markdown -m >> "$GITHUB_STEP_SUMMARY"
-
-      # For future use in case we want to add a PR comment for 3rd party PRs which requires
-      # a workflow with elevated PR write permissions. Move below steps into a separate job.
-      - name: Archive code coverage report
-        id: cov_xml_upload
-        uses: actions/upload-artifact@v4
-        with:
-          name: coverage
-          path: coverage.xml
-      - name: Code Coverage Report (console)
-        run: |
-          # Create a coverage report (console), respects fail_under in pyproject.toml
-          coverage report
-
-      - name: Code Coverage Report
-        uses: irongut/CodeCoverageSummary@51cc3a756ddcd398d447c044c02cb6aa83fdae95 # v1.3.0
-        # Create markdown file even if coverage report fails due to fail_under
-        if: ${{ always() && steps.cov_xml_upload.outputs.artifact-id != '' }}
-        with:
-          filename: coverage.xml
-          badge: true
-          fail_below_min: true
-          format: markdown
-          hide_branch_rate: false
-          hide_complexity: true
-          indicators: true
-          output: both  # console, file or both
-          # Note: it appears fail below min is one off, use fail_under -1 here
-          thresholds: '95 98'
-
-      - name: Add link to report badge
-        if: ${{ always() && steps.cov_xml_upload.outputs.artifact-id != '' }}
-        run: |
-          run_url="${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}?pr=${{ github.event.pull_request.number }}"
-          sed -i "1s|^\(!.*\)$|[\1]($run_url)|" code-coverage-results.md
-
-      - name: Add Coverage PR Comment
-        uses: marocchino/sticky-pull-request-comment@52423e01640425a022ef5fd42c6fb5f633a02728  # v2.9.3
-        # Create PR comment when the branch is on the repo, otherwise we lack PR write permissions
-        # -> need another workflow with access to secret token
-        if: >-
-          ${{
-            always()
-            && github.event_name == 'pull_request'
-            && github.event.pull_request.head.repo.full_name == github.repository
-            && steps.cov_xml_upload.outputs.artifact-id != ''
-          }}
-        with:
-          hide_and_recreate: true
-          path: code-coverage-results.md
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index e078218f..3d5fdcef 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -23,11 +23,11 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           persist-credentials: false
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: "3.x"
       - name: Check package metadata
@@ -43,7 +43,7 @@ jobs:
       - name: Build a binary wheel and a source tarball
         run: python -m build
       - name: Store the distribution packages
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v7
         with:
           name: python-package-distributions
           path: dist/
@@ -55,15 +55,15 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           persist-credentials: false
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: "3.x"
       - name: Download all the dists
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           name: python-package-distributions
           path: dist/
@@ -84,15 +84,15 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           persist-credentials: false
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: "3.x"
       - name: Download all the dists
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           name: python-package-distributions
           path: dist/
@@ -112,15 +112,15 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           persist-credentials: false
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: "3.x"
       - name: Download all the dists
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           name: python-package-distributions
           path: dist/
@@ -152,11 +152,11 @@ jobs:
 
     steps:
       - name: Download all the dists
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           name: python-package-distributions
           path: dist/
       - name: Ensure exactly one sdist and one wheel have been downloaded
         run: test "$(find dist/*.tar.gz | wc -l | xargs)" = 1 && test "$(find dist/*.whl | wc -l | xargs)" = 1
       - name: Publish distribution to PyPI
-        uses: pypa/gh-action-pypi-publish@76f52bc884231f62b9a034ebfe128415bbaabdfc
+        uses: pypa/gh-action-pypi-publish@ed0c53931b1dc9bd32cbe73a98c7f6766f8a527e
diff --git a/.github/workflows/third_party.yml b/.github/workflows/third_party.yml
index 3a698bf7..0894c2d1 100644
--- a/.github/workflows/third_party.yml
+++ b/.github/workflows/third_party.yml
@@ -46,18 +46,19 @@ jobs:
         # PyPy is deliberately omitted here,
         # since pydantic's tests intermittently segfault on PyPy,
         # and it's nothing to do with typing_extensions
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        # Tests on 3.14 don't pass as of 2 November 2025
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Checkout pydantic
         run: git clone --depth=1 https://github.com/pydantic/pydantic.git || git clone --depth=1 https://github.com/pydantic/pydantic.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -65,7 +66,7 @@ jobs:
         working-directory: pydantic
         run: |
           uv add --editable ../typing-extensions-latest
-          uv sync --group dev
+          uv sync --all-packages --group testing-extra --all-extras
 
           printf "\n\nINSTALLED DEPENDENCIES ARE:\n\n"
           uv pip list
@@ -79,18 +80,18 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Checkout typing_inspect
         run: git clone --depth=1 https://github.com/ilevkivskyi/typing_inspect.git || git clone --depth=1 https://github.com/ilevkivskyi/typing_inspect.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -114,18 +115,18 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Check out pycroscope
         run: git clone --depth=1 https://github.com/JelleZijlstra/pycroscope.git || git clone --depth=1 https://github.com/JelleZijlstra/pycroscope.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -149,18 +150,18 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Check out typeguard
         run: git clone --depth=1 https://github.com/agronholm/typeguard.git || git clone --depth=1 https://github.com/agronholm/typeguard.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -186,18 +187,19 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        # 3.9 is no longer supported. 3.14 fails some tests as of 2 November 2025
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Check out typed-argument-parser
         run: git clone --depth=1 https://github.com/swansonk14/typed-argument-parser.git || git clone --depth=1 https://github.com/swansonk14/typed-argument-parser.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -228,18 +230,19 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        # 3.14 fails a test as of 2 November 2025
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Checkout mypy for stubtest and mypyc tests
         run: git clone --depth=1 https://github.com/python/mypy.git || git clone --depth=1 https://github.com/python/mypy.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -264,18 +267,18 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Checkout cattrs
         run: git clone --depth=1 https://github.com/python-attrs/cattrs.git || git clone --depth=1 https://github.com/python-attrs/cattrs.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -299,7 +302,7 @@ jobs:
       matrix:
         # PyPy is deliberately omitted here, since SQLAlchemy's tests
         # fail on PyPy for reasons unrelated to typing_extensions.
-        python-version: [ "3.9", "3.10", "3.11", "3.12", "3.13" ]
+        python-version: [ "3.10", "3.11", "3.12", "3.13", "3.14" ]
         checkout-ref: [ "main", "rel_2_0" ]
     # sqlalchemy tests fail when using the Ubuntu 24.04 runner
     # https://github.com/sqlalchemy/sqlalchemy/commit/8d73205f352e68c6603e90494494ef21027ec68f
@@ -307,13 +310,13 @@ jobs:
     timeout-minutes: 60
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Checkout sqlalchemy
         run: git clone -b ${{ matrix.checkout-ref }} --depth=1 https://github.com/sqlalchemy/sqlalchemy.git || git clone -b ${{ matrix.checkout-ref }} --depth=1 https://github.com/sqlalchemy/sqlalchemy.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -335,16 +338,17 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [ "3.9", "3.10", "3.11", "3.12", "3.13" ]
+        # As of 2 November 2025 a dependency is missing 3.14 wheels
+        python-version: [ "3.11", "3.12", "3.13" ]
     steps:
       - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@e92bafb6253dcd438e0484186d7669ea7a8ca1cc  # v6.4.3
+        uses: astral-sh/setup-uv@1e862dfacbd1d6d858c55d9b792c756523627244  # v7.1.4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Checkout litestar
         run: git clone --depth=1 https://github.com/litestar-org/litestar.git || git clone --depth=1 https://github.com/litestar-org/litestar.git
       - name: Checkout typing_extensions
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: typing-extensions-latest
           persist-credentials: false
@@ -353,7 +357,7 @@ jobs:
         run: |
           # litestar's python-requires means uv won't let us add typing-extensions-latest
           # as a requirement unless we do this
-          sed -i 's/^requires-python = ">=3.8/requires-python = ">=3.9/' pyproject.toml
+          sed -i 's/^requires-python = ">=3.8/requires-python = ">=3.10/' pyproject.toml
 
           uv add --editable ../typing-extensions-latest
           uv sync
@@ -377,6 +381,7 @@ jobs:
       - mypy
       - cattrs
       - sqlalchemy
+      - litestar
 
     if: >-
         ${{
@@ -392,6 +397,7 @@ jobs:
             || needs.mypy.result == 'failure'
             || needs.cattrs.result == 'failure'
             || needs.sqlalchemy.result == 'failure'
+            || needs.litestar.result == 'failure'
           )
         }}
 
@@ -399,7 +405,7 @@ jobs:
       issues: write
 
     steps:
-      - uses: actions/github-script@v7
+      - uses: actions/github-script@v8
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           script: |
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index bf8fd54d..2a3aedee 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,10 +1,10 @@
 repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.12.3
+    rev: v0.14.10
     hooks:
       - id: ruff
   - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v5.0.0
+    rev: v6.0.0
     hooks:
       - id: trailing-whitespace
       - id: end-of-file-fixer
@@ -17,11 +17,11 @@ repos:
       - id: mixed-line-ending
         args: [--fix=lf]
   - repo: https://github.com/sphinx-contrib/sphinx-lint
-    rev: v1.0.0
+    rev: v1.0.2
     hooks:
       - id: sphinx-lint
   - repo: https://github.com/python-jsonschema/check-jsonschema
-    rev: 0.33.2
+    rev: 0.36.0
     hooks:
       - id: check-dependabot
       - id: check-github-workflows
@@ -32,16 +32,16 @@ repos:
       - id: validate-pyproject
         additional_dependencies: ["validate-pyproject-schema-store[all]"]
   - repo: https://github.com/rhysd/actionlint
-    rev: v1.7.7
+    rev: v1.7.10
     hooks:
       - id: actionlint
         additional_dependencies:
           # actionlint has a shellcheck integration which extracts shell scripts in `run:` steps from GitHub Actions
           # and checks these with shellcheck. This is arguably its most useful feature,
           # but the integration only works if shellcheck is installed
-          - "github.com/wasilibs/go-shellcheck/cmd/shellcheck@v0.10.0"
+          - "github.com/wasilibs/go-shellcheck/cmd/shellcheck@v0.11.1"
   - repo: https://github.com/woodruffw/zizmor-pre-commit
-    rev: v1.11.0
+    rev: v1.19.0
     hooks:
       - id: zizmor
   - repo: meta
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f2e77c1f..733505a5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,19 @@
+# Unreleased
+
+- Fix incorrect behaviour on Python 3.9 and Python 3.10 that meant that
+  calling `isinstance` with `typing_extensions.Concatenate[...]` or
+  `typing_extensions.Unpack[...]` as the first argument could have a different
+  result in some situations depending on whether or not a profiling function had been
+  set using `sys.setprofile`. This affected both CPython and PyPy implementations.
+  Patch by Brian Schubert.
+- Fix `__init_subclass__()` behavior in the presence of multiple inheritance involving
+  an `@deprecated`-decorated base class. Backport of CPython PR
+  [#138210](https://github.com/python/cpython/pull/138210) by Brian Schubert.
+- Raise `TypeError` when attempting to subclass `typing_extensions.ParamSpec` on
+  Python 3.9. The `typing` implementation has always raised an error, and the
+  `typing_extensions` implementation has raised an error on Python 3.10+ since
+  `typing_extensions` v4.6.0. Patch by Brian Schubert.
+
 # Release 4.15.0 (August 25, 2025)
 
 No user-facing changes since 4.15.0rc1.
diff --git a/doc/conf.py b/doc/conf.py
index db9b5185..cef3215d 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -38,6 +38,27 @@
 
 html_theme = 'alabaster'
 
+html_theme_options = {
+    "description": "Backported and experimental type hints for Python",
+    # Make the sidebar "sticky" so that is stays visible when scrolling.
+    # Also makes the sidebar appear at the top of the page on mobile.
+    "fixed_sidebar": True,
+}
+
+html_sidebars = {
+    '**': [
+        'about.html',
+        'searchfield.html',
+        'localtoc.html',
+    ]
+}
+
+# Don't include object entries (e.g. functions, classes) in the table of contents.
+toc_object_entries = False
+
+# Warn about all references where the target cannot be found.
+nitpicky = True
+
 
 class MyTranslator(HTML5Translator):
     """Adds a link target to name without `typing_extensions.` prefix."""
diff --git a/doc/index.rst b/doc/index.rst
index 6aa95f5b..66577ef0 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -259,6 +259,13 @@ Special typing primitives
 
    .. versionadded:: 4.12.0
 
+.. data:: NoExtraItems
+
+   A sentinel used when the ``extra_items`` class argument to :class:`TypedDict` is not
+   provided. In ``typing`` since 3.15.
+
+   .. versionadded:: 4.13.0
+
 .. data:: NotRequired
 
    See :py:data:`typing.NotRequired` and :pep:`655`. In ``typing`` since 3.11.
@@ -296,7 +303,7 @@ Special typing primitives
       ``default=None`` is passed, and to :data:`NoDefault` if no value is passed.
 
       Previously, passing ``None`` would result in :attr:`!__default__` being set
-      to :py:class:`types.NoneType`, and passing no value for the parameter would
+      to :py:data:`types.NoneType`, and passing no value for the parameter would
       result in :attr:`!__default__` being set to ``None``.
 
    .. versionchanged:: 4.12.0
@@ -305,10 +312,9 @@ Special typing primitives
       with :py:class:`typing.ParamSpec` on Python 3.13+.
 
 .. class:: ParamSpecArgs
+           ParamSpecKwargs
 
-.. class:: ParamSpecKwargs
-
-   See :py:class:`typing.ParamSpecArgs` and :py:class:`typing.ParamSpecKwargs`.
+   See :py:data:`typing.ParamSpecArgs` and :py:data:`typing.ParamSpecKwargs`.
    In ``typing`` since 3.10.
 
 .. class:: Protocol
@@ -387,12 +393,13 @@ Special typing primitives
 
    .. versionadded:: 4.10.0
 
-.. class:: TypedDict(dict, total=True)
-
-   See :py:class:`typing.TypedDict` and :pep:`589`. In ``typing`` since 3.8.
+.. class:: TypedDict(dict, total=True, closed=False, extra_items=<no extra items>)
 
+   See :py:class:`typing.TypedDict` and :pep:`589`. In ``typing`` since 3.8, but
+   changed and enhanced in several ways since then.
    ``typing_extensions`` backports various bug fixes and improvements
-   to ``TypedDict`` on Python 3.11 and lower.
+   to ``TypedDict``.
+
    :py:class:`TypedDict` does not store runtime information
    about which (if any) keys are non-required in Python 3.8, and does not
    honor the ``total`` keyword with old-style ``TypedDict()`` in Python
@@ -426,35 +433,23 @@ Special typing primitives
 
       .. versionadded:: 4.9.0
 
-   The experimental ``closed`` keyword argument and the special key
-   ``__extra_items__`` proposed in :pep:`728` are supported.
-
-   When ``closed`` is unspecified or ``closed=False`` is given,
-   ``__extra_items__`` behaves like a regular key. Otherwise, this becomes a
-   special key that does not show up in ``__readonly_keys__``,
-   ``__mutable_keys__``, ``__required_keys__``, ``__optional_keys``, or
-   ``__annotations__``.
+   The ``closed`` and ``extra_items`` keyword arguments introduced by
+   :pep:`728` and supported in Python 3.15 and newer are supported.
 
    For runtime introspection, two attributes can be looked at:
 
    .. attribute:: __closed__
 
       A boolean flag indicating whether the current ``TypedDict`` is
-      considered closed. This is not inherited by the ``TypedDict``'s
-      subclasses.
+      considered closed. This reflects the ``closed`` class argument.
 
       .. versionadded:: 4.10.0
 
    .. attribute:: __extra_items__
 
-      The type annotation of the extra items allowed on the ``TypedDict``.
-      This attribute defaults to ``None`` on a TypedDict that has itself and
-      all its bases non-closed. This default is different from ``type(None)``
-      that represents ``__extra_items__: None`` defined on a closed
-      ``TypedDict``.
-
-      If ``__extra_items__`` is not defined or inherited on a closed
-      ``TypedDict``, this defaults to ``Never``.
+      The type of the extra items allowed on the ``TypedDict``.
+      This attribute defaults to :data:`NoExtraItems` if the ``extra_items``
+      class argument is not provided.
 
       .. versionadded:: 4.10.0
 
@@ -475,7 +470,7 @@ Special typing primitives
 
       ``TypedDict`` is now a function rather than a class.
       This brings ``typing_extensions.TypedDict`` closer to the implementation
-      of :py:mod:`typing.TypedDict` on Python 3.9 and higher.
+      of :py:class:`typing.TypedDict` on Python 3.9 and higher.
 
    .. versionchanged:: 4.7.0
 
@@ -495,6 +490,16 @@ Special typing primitives
       The keyword argument ``closed`` and the special key ``__extra_items__``
       when ``closed=True`` is given were supported.
 
+   .. versionchanged:: 4.13.0
+
+      :pep:`728` support was updated to a newer version. Extra items are now
+      indicated with an ``extra_items`` class argument, not a special key
+      ``__extra_items__``.
+
+      A value assigned to ``__total__`` in the class body of a
+      ``TypedDict`` will be overwritten by the ``total`` argument of the
+      ``TypedDict`` constructor.
+
 .. class:: TypeVar(name, *constraints, bound=None, covariant=False,
                    contravariant=False, infer_variance=False, default=NoDefault)
 
@@ -520,7 +525,7 @@ Special typing primitives
       ``default=None`` is passed, and to :data:`NoDefault` if no value is passed.
 
       Previously, passing ``None`` would result in :attr:`!__default__` being set
-      to :py:class:`types.NoneType`, and passing no value for the parameter would
+      to :py:data:`types.NoneType`, and passing no value for the parameter would
       result in :attr:`!__default__` being set to ``None``.
 
    .. versionchanged:: 4.12.0
@@ -551,7 +556,7 @@ Special typing primitives
       ``default=None`` is passed, and to :data:`NoDefault` if no value is passed.
 
       Previously, passing ``None`` would result in :attr:`!__default__` being set
-      to :py:class:`types.NoneType`, and passing no value for the parameter would
+      to :py:data:`types.NoneType`, and passing no value for the parameter would
       result in :attr:`!__default__` being set to ``None``.
 
    .. versionchanged:: 4.12.0
@@ -696,7 +701,8 @@ Decorators
 
 .. decorator:: deprecated(msg, *, category=DeprecationWarning, stacklevel=1)
 
-   See :pep:`702`. In the :mod:`warnings` module since Python 3.13.
+   See :py:func:`warnings.deprecated` and :pep:`702`. In the :mod:`warnings` module
+   since Python 3.13.
 
    .. versionadded:: 4.5.0
 
@@ -792,7 +798,7 @@ Functions
    * Raises :exc:`TypeError` when it encounters certain objects that are
      not valid type hints.
    * Replaces type hints that evaluate to :const:`!None` with
-     :class:`types.NoneType`.
+     :data:`types.NoneType`.
    * Supports the :attr:`Format.FORWARDREF` and
      :attr:`Format.STRING` formats.
 
@@ -809,6 +815,11 @@ Functions
    *format* specifies the format of the annotation and is a member of
    the :class:`Format` enum, defaulting to :attr:`Format.VALUE`.
 
+   .. caution::
+
+      This function may execute arbitrary code contained in annotations.
+      See :ref:`annotations-security` for more information.
+
    .. versionadded:: 4.13.0
 
 .. function:: get_annotations(obj, *, globals=None, locals=None, eval_str=False, format=Format.VALUE)
@@ -828,6 +839,11 @@ Functions
 
       typing_extensions.get_annotations(obj, format=Format.FORWARDREF)
 
+   .. caution::
+
+      This function may execute arbitrary code contained in annotations.
+      See :ref:`annotations-security` for more information.
+
    .. versionadded:: 4.13.0
 
 .. function:: get_args(tp)
@@ -895,6 +911,11 @@ Functions
    :py:data:`typing.Required` and :py:data:`typing.NotRequired`.
    ``typing_extensions`` backports these fixes.
 
+   .. caution::
+
+      This function may execute arbitrary code contained in annotations.
+      See :ref:`annotations-security` for more information.
+
    .. versionchanged:: 4.1.0
 
       Interaction with :data:`Required` and :data:`NotRequired`.
@@ -1362,7 +1383,7 @@ versions of Python, but all are listed here for completeness.
 
 .. data:: Union
 
-   See :py:data:`typing.Union`.
+   See :py:class:`typing.Union`.
 
    .. versionadded:: 4.7.0
 
@@ -1409,3 +1430,25 @@ If you have any feedback on our security process, please `open an issue
 <https://github.com/python/typing_extensions/issues/new>`__. To report
 an issue privately, use `GitHub's private reporting feature
 <https://github.com/python/typing_extensions/security>`__.
+
+.. _annotations-security:
+
+Introspection of annotations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Some functions in this module are designed to introspect annotations at
+runtime. These functions may therefore execute code contained in annotations,
+which can then perform arbitrary operations. For example,
+:func:`get_annotations` may call an arbitrary :term:`annotate function`, and
+:meth:`evaluate_forward_ref` may call :func:`eval` on an arbitrary string. Code contained
+in an annotation might make arbitrary system calls, enter an infinite loop, or perform any
+other operation. This is also true for any access of the :attr:`~object.__annotations__` attribute
+(as of Python 3.14),
+and for various functions in the :mod:`typing` module that work with annotations, such as
+:func:`typing.get_type_hints`.
+
+Any security issue arising from this also applies immediately after importing
+code that may contain untrusted annotations: importing code can always cause arbitrary operations
+to be performed. However, it is unsafe to accept strings or other input from an untrusted source and
+pass them to any of the APIs for introspecting annotations, for example by editing an
+``__annotations__`` dictionary or directly creating a :class:`ForwardRef` object.
diff --git a/pyproject.toml b/pyproject.toml
index adfed5d4..b024621d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -90,7 +90,6 @@ ignore = [
     "UP014",
     "UP019",
     "UP035",
-    "UP038",
     "UP045",  # X | None instead of Optional[X]
     # Not relevant here
     "RUF012",  # Use ClassVar for mutables
@@ -123,6 +122,7 @@ known-first-party = ["typing_extensions", "_typed_dict_test_helper"]
 
 [tool.coverage.report]
 fail_under = 96
+precision = 2
 show_missing = true
 # Omit files that are created in temporary directories during tests.
 # If not explicitly omitted they will result in warnings in the report.
diff --git a/src/test_typing_extensions.py b/src/test_typing_extensions.py
index 0986427c..f07e1eb0 100644
--- a/src/test_typing_extensions.py
+++ b/src/test_typing_extensions.py
@@ -531,6 +531,14 @@ def test_pickle(self):
             pickled = pickle.dumps(self.bottom_type, protocol=proto)
             self.assertIs(self.bottom_type, pickle.loads(pickled))
 
+    @skipUnless(TYPING_3_10_0, "PEP 604 has yet to be")
+    def test_or(self):
+        self.assertEqual(self.bottom_type | int, Union[self.bottom_type, int])
+        self.assertEqual(int | self.bottom_type, Union[int, self.bottom_type])
+
+        self.assertEqual(get_args(self.bottom_type | int), (self.bottom_type, int))
+        self.assertEqual(get_args(int | self.bottom_type), (int, self.bottom_type))
+
 
 class NoReturnTests(BottomTypeTestsMixin, BaseTestCase):
     bottom_type = NoReturn
@@ -805,6 +813,25 @@ class D(C, x=3):
 
         self.assertEqual(D.inited, 3)
 
+    def test_existing_init_subclass_in_sibling_base(self):
+        @deprecated("A will go away soon")
+        class A:
+            pass
+        class B:
+            def __init_subclass__(cls, x):
+                super().__init_subclass__()
+                cls.inited = x
+
+        with self.assertWarnsRegex(DeprecationWarning, "A will go away soon"):
+            class C(A, B, x=42):
+                pass
+        self.assertEqual(C.inited, 42)
+
+        with self.assertWarnsRegex(DeprecationWarning, "A will go away soon"):
+            class D(B, A, x=42):
+                pass
+        self.assertEqual(D.inited, 42)
+
     def test_init_subclass_has_correct_cls(self):
         init_subclass_saw = None
 
@@ -2210,6 +2237,39 @@ def test_or_and_ror(self):
             Union[typing_extensions.Generator, typing.Deque]
         )
 
+    def test_setattr(self):
+        origin = collections.abc.Generator
+        alias = typing_extensions.Generator
+        original_name = alias._name
+
+        def cleanup():
+            for obj in origin, alias:
+                for attr in 'foo', '__dunder__':
+                    try:
+                        delattr(obj, attr)
+                    except Exception:
+                        pass
+            try:
+                alias._name = original_name
+            except Exception:
+                pass
+
+        self.addCleanup(cleanup)
+
+        # Attribute assignment on generic alias sets attribute on origin
+        alias.foo = 1
+        self.assertEqual(alias.foo, 1)
+        self.assertEqual(origin.foo, 1)
+        # Except for dunders...
+        alias.__dunder__ = 2
+        self.assertEqual(alias.__dunder__, 2)
+        self.assertRaises(AttributeError, lambda: origin.__dunder__)
+
+        # ...and certain known attributes
+        alias._name = "NewName"
+        self.assertEqual(alias._name, "NewName")
+        self.assertRaises(AttributeError, lambda: origin._name)
+
 
 class OtherABCTests(BaseTestCase):
 
@@ -2379,6 +2439,16 @@ def test_error_message_when_subclassing(self):
             class ProUserId(UserId):
                 ...
 
+    def test_module_with_incomplete_sys(self):
+        def does_not_exist(*args):
+            raise AttributeError
+        with (
+            patch("sys._getframemodulename", does_not_exist, create=True),
+            patch("sys._getframe", does_not_exist, create=True),
+        ):
+            X = NewType("X", int)
+            self.assertEqual(X.__module__, None)
+
 
 class Coordinate(Protocol):
     x: int
@@ -4438,8 +4508,12 @@ def _make_td(future, class_name, annos, base, extra_names=None):
                     child = _make_td(
                         child_future, "Child", {"child": "int"}, "Base", {"Base": base}
                     )
-                    base_anno = typing.ForwardRef("int", module="builtins") if base_future else int
-                    child_anno = typing.ForwardRef("int", module="builtins") if child_future else int
+                    if sys.version_info >= (3, 14):
+                        base_anno = typing.ForwardRef("int", module="builtins", owner=base) if base_future else int
+                        child_anno = typing.ForwardRef("int", module="builtins", owner=child) if child_future else int
+                    else:
+                        base_anno = typing.ForwardRef("int", module="builtins") if base_future else int
+                        child_anno = typing.ForwardRef("int", module="builtins") if child_future else int
                     self.assertEqual(base.__annotations__, {'base': base_anno})
                     self.assertEqual(
                         child.__annotations__, {'child': child_anno, 'base': base_anno}
@@ -5297,6 +5371,17 @@ class A(TypedDict):
     def test_dunder_dict(self):
         self.assertIsInstance(TypedDict.__dict__, dict)
 
+    @skipUnless(TYPING_3_10_0, "PEP 604 has yet to be")
+    def test_or(self):
+        class TD(TypedDict):
+            a: int
+
+        self.assertEqual(TD | int, Union[TD, int])
+        self.assertEqual(int | TD, Union[int, TD])
+
+        self.assertEqual(get_args(TD | int), (TD, int))
+        self.assertEqual(get_args(int | TD), (int, TD))
+
 class AnnotatedTests(BaseTestCase):
 
     def test_repr(self):
@@ -5519,6 +5604,19 @@ def barfoo3(x: BA2): ...
             BA2
         )
 
+    @skipUnless(TYPING_3_11_0, "TODO: evaluate nested forward refs in Python < 3.11")
+    def test_get_type_hints_genericalias(self):
+        def foobar(x: list['X']): ...
+        X = Annotated[int, (1, 10)]
+        self.assertEqual(
+            get_type_hints(foobar, globals(), locals()),
+            {'x': list[int]}
+        )
+        self.assertEqual(
+            get_type_hints(foobar, globals(), locals(), include_extras=True),
+            {'x': list[Annotated[int, (1, 10)]]}
+        )
+
     def test_get_type_hints_refs(self):
 
         Const = Annotated[T, "Const"]
@@ -5973,6 +6071,11 @@ def run():
         # The actual test:
         self.assertEqual(result1, result2)
 
+    def test_subclass(self):
+        with self.assertRaises(TypeError):
+            class MyParamSpec(ParamSpec):
+                pass
+
 
 class ConcatenateTests(BaseTestCase):
     def test_basics(self):
@@ -6131,6 +6234,47 @@ def test_is_param_expr(self):
             self.assertTrue(typing._is_param_expr(concat))
             self.assertTrue(typing._is_param_expr(typing_concat))
 
+    def test_isinstance_results_unaffected_by_presence_of_tracing_function(self):
+        # See https://github.com/python/typing_extensions/issues/661
+
+        code = textwrap.dedent(
+            """\
+            import sys, typing
+
+            def trace_call(*args):
+                return trace_call
+
+            def run():
+                sys.modules.pop("typing_extensions", None)
+                from typing_extensions import Concatenate
+                return isinstance(Concatenate[...], typing._GenericAlias)
+            isinstance_result_1 = run()
+            sys.setprofile(trace_call)
+            isinstance_result_2 = run()
+            sys.stdout.write(f"{isinstance_result_1} {isinstance_result_2}")
+            """
+        )
+
+        # Run this in an isolated process or it pollutes the environment
+        # and makes other tests fail:
+        try:
+            proc = subprocess.run(
+                [sys.executable, "-c", code], check=True, capture_output=True, text=True,
+            )
+        except subprocess.CalledProcessError as exc:
+            print("stdout", exc.stdout, sep="\n")
+            print("stderr", exc.stderr, sep="\n")
+            raise
+
+        # Sanity checks that assert the test is working as expected
+        self.assertIsInstance(proc.stdout, str)
+        result1, result2 = proc.stdout.split(" ")
+        self.assertIn(result1, {"True", "False"})
+        self.assertIn(result2, {"True", "False"})
+
+        # The actual test:
+        self.assertEqual(result1, result2)
+
 class TypeGuardTests(BaseTestCase):
     def test_basics(self):
         TypeGuard[int]  # OK
@@ -6335,6 +6479,14 @@ def test_pickle(self):
             pickled = pickle.dumps(LiteralString, protocol=proto)
             self.assertIs(LiteralString, pickle.loads(pickled))
 
+    @skipUnless(TYPING_3_10_0, "PEP 604 has yet to be")
+    def test_or(self):
+        self.assertEqual(LiteralString | int, Union[LiteralString, int])
+        self.assertEqual(int | LiteralString, Union[int, LiteralString])
+
+        self.assertEqual(get_args(LiteralString | int), (LiteralString, int))
+        self.assertEqual(get_args(int | LiteralString), (int, LiteralString))
+
 
 class SelfTests(BaseTestCase):
     def test_basics(self):
@@ -6382,6 +6534,14 @@ def test_pickle(self):
             pickled = pickle.dumps(Self, protocol=proto)
             self.assertIs(Self, pickle.loads(pickled))
 
+    @skipUnless(TYPING_3_10_0, "PEP 604 has yet to be")
+    def test_or(self):
+        self.assertEqual(Self | int, Union[Self, int])
+        self.assertEqual(int | Self, Union[int, Self])
+
+        self.assertEqual(get_args(Self | int), (Self, int))
+        self.assertEqual(get_args(int | Self), (int, Self))
+
 
 class UnpackTests(BaseTestCase):
     def test_basic_plain(self):
@@ -6537,6 +6697,46 @@ def test_type_var_inheritance(self):
         self.assertFalse(isinstance(Unpack[Ts], TypeVar))
         self.assertFalse(isinstance(Unpack[Ts], typing.TypeVar))
 
+    def test_isinstance_results_unaffected_by_presence_of_tracing_function(self):
+        # See https://github.com/python/typing_extensions/issues/661
+
+        code = textwrap.dedent(
+            """\
+            import sys, typing
+
+            def trace_call(*args):
+                return trace_call
+
+            def run():
+                sys.modules.pop("typing_extensions", None)
+                from typing_extensions import TypeVarTuple, Unpack
+                return isinstance(Unpack[TypeVarTuple("Ts")], typing.TypeVar)
+            isinstance_result_1 = run()
+            sys.setprofile(trace_call)
+            isinstance_result_2 = run()
+            sys.stdout.write(f"{isinstance_result_1} {isinstance_result_2}")
+            """
+        )
+
+        # Run this in an isolated process or it pollutes the environment
+        # and makes other tests fail:
+        try:
+            proc = subprocess.run(
+                [sys.executable, "-c", code], check=True, capture_output=True, text=True,
+            )
+        except subprocess.CalledProcessError as exc:
+            print("stdout", exc.stdout, sep="\n")
+            print("stderr", exc.stderr, sep="\n")
+            raise
+
+        # Sanity checks that assert the test is working as expected
+        self.assertIsInstance(proc.stdout, str)
+        result1, result2 = proc.stdout.split(" ")
+        self.assertIn(result1, {"True", "False"})
+        self.assertIn(result2, {"True", "False"})
+
+        # The actual test:
+        self.assertEqual(result1, result2)
 
 class TypeVarTupleTests(BaseTestCase):
 
@@ -7711,42 +7911,61 @@ class A(Generic[T, P, U]): ...
         self.assertEqual(A[float, [range], int].__args__, (float, (range,), int))
 
 
-class NoDefaultTests(BaseTestCase):
+class SentinelTestsMixin:
     @skip_if_py313_beta_1
     def test_pickling(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
-            s = pickle.dumps(NoDefault, proto)
+            s = pickle.dumps(self.sentinel_type, proto)
             loaded = pickle.loads(s)
-            self.assertIs(NoDefault, loaded)
+            self.assertIs(self.sentinel_type, loaded)
 
     @skip_if_py313_beta_1
     def test_doc(self):
-        self.assertIsInstance(NoDefault.__doc__, str)
+        self.assertIsInstance(self.sentinel_type.__doc__, str)
 
     def test_constructor(self):
-        self.assertIs(NoDefault, type(NoDefault)())
+        self.assertIs(self.sentinel_type, type(self.sentinel_type)())
         with self.assertRaises(TypeError):
-            type(NoDefault)(1)
-
-    def test_repr(self):
-        self.assertRegex(repr(NoDefault), r'typing(_extensions)?\.NoDefault')
+            type(self.sentinel_type)(1)
 
     def test_no_call(self):
         with self.assertRaises(TypeError):
-            NoDefault()
+            self.sentinel_type()
 
     @skip_if_py313_beta_1
     def test_immutable(self):
         with self.assertRaises(AttributeError):
-            NoDefault.foo = 'bar'
+            self.sentinel_type.foo = 'bar'
         with self.assertRaises(AttributeError):
-            NoDefault.foo
+            self.sentinel_type.foo
 
         # TypeError is consistent with the behavior of NoneType
         with self.assertRaises(TypeError):
-            type(NoDefault).foo = 3
+            type(self.sentinel_type).foo = 3
         with self.assertRaises(AttributeError):
-            type(NoDefault).foo
+            type(self.sentinel_type).foo
+
+
+class NoDefaultTests(SentinelTestsMixin, BaseTestCase):
+    sentinel_type = NoDefault
+
+    def test_repr(self):
+        if hasattr(typing, 'NoDefault'):
+            mod_name = 'typing'
+        else:
+            mod_name = "typing_extensions"
+        self.assertEqual(repr(NoDefault), f"{mod_name}.NoDefault")
+
+
+class NoExtraItemsTests(SentinelTestsMixin, BaseTestCase):
+    sentinel_type = NoExtraItems
+
+    def test_repr(self):
+        if hasattr(typing, 'NoExtraItems'):
+            mod_name = 'typing'
+        else:
+            mod_name = "typing_extensions"
+        self.assertEqual(repr(NoExtraItems), f"{mod_name}.NoExtraItems")
 
 
 class TypeVarInferVarianceTests(BaseTestCase):
@@ -9359,6 +9578,10 @@ def test_sentinel_not_picklable(self):
         ):
             pickle.dumps(sentinel)
 
+def load_tests(loader, tests, pattern):
+    import doctest
+    tests.addTests(doctest.DocTestSuite(typing_extensions))
+    return tests
 
 if __name__ == '__main__':  # pragma: no cover
     main()
diff --git a/src/typing_extensions.py b/src/typing_extensions.py
index 77f33e16..20c331ee 100644
--- a/src/typing_extensions.py
+++ b/src/typing_extensions.py
@@ -148,7 +148,6 @@
     'ValuesView',
     'cast',
     'no_type_check',
-    'no_type_check_decorator',
 ]
 
 # for backward compatibility
@@ -160,17 +159,48 @@
 # Added with bpo-45166 to 3.10.1+ and some 3.9 versions
 _FORWARD_REF_HAS_CLASS = "__forward_is_class__" in typing.ForwardRef.__slots__
 
-# The functions below are modified copies of typing internal helpers.
-# They are needed by _ProtocolMeta and they provide support for PEP 646.
+class Sentinel:
+    """Create a unique sentinel object.
+
+    *name* should be the name of the variable to which the return value shall be assigned.
 
+    *repr*, if supplied, will be used for the repr of the sentinel object.
+    If not provided, "<name>" will be used.
+    """
+
+    def __init__(
+        self,
+        name: str,
+        repr: typing.Optional[str] = None,
+    ):
+        self._name = name
+        self._repr = repr if repr is not None else f'<{name}>'
 
-class _Sentinel:
     def __repr__(self):
-        return "<sentinel>"
+        return self._repr
+
+    if sys.version_info < (3, 11):
+        # The presence of this method convinces typing._type_check
+        # that Sentinels are types.
+        def __call__(self, *args, **kwargs):
+            raise TypeError(f"{type(self).__name__!r} object is not callable")
+
+    # Breakpoint: https://github.com/python/cpython/pull/21515
+    if sys.version_info >= (3, 10):
+        def __or__(self, other):
+            return typing.Union[self, other]
+
+        def __ror__(self, other):
+            return typing.Union[other, self]
+
+    def __getstate__(self):
+        raise TypeError(f"Cannot pickle {type(self).__name__!r} object")
 
 
-_marker = _Sentinel()
+_marker = Sentinel("sentinel")
 
+# The functions below are modified copies of typing internal helpers.
+# They are needed by _ProtocolMeta and they provide support for PEP 646.
 
 # Breakpoint: https://github.com/python/cpython/pull/27342
 if sys.version_info >= (3, 10):
@@ -524,7 +554,9 @@ def _is_dunder(attr):
 
 
     class _SpecialGenericAlias(typing._SpecialGenericAlias, _root=True):
-        def __init__(self, origin, nparams, *, inst=True, name=None, defaults=()):
+        def __init__(self, origin, nparams, *, defaults, inst=True, name=None):
+            assert nparams > 0, "`nparams` must be a positive integer"
+            assert defaults, "Must always specify a non-empty sequence for `defaults`"
             super().__init__(origin, nparams, inst=inst, name=name)
             self._defaults = defaults
 
@@ -542,20 +574,14 @@ def __getitem__(self, params):
             msg = "Parameters to generic types must be types."
             params = tuple(typing._type_check(p, msg) for p in params)
             if (
-                self._defaults
-                and len(params) < self._nparams
+                len(params) < self._nparams
                 and len(params) + len(self._defaults) >= self._nparams
             ):
                 params = (*params, *self._defaults[len(params) - self._nparams:])
             actual_len = len(params)
 
             if actual_len != self._nparams:
-                if self._defaults:
-                    expected = f"at least {self._nparams - len(self._defaults)}"
-                else:
-                    expected = str(self._nparams)
-                if not self._nparams:
-                    raise TypeError(f"{self} is not a generic class")
+                expected = f"at least {self._nparams - len(self._defaults)}"
                 raise TypeError(
                     f"Too {'many' if actual_len > self._nparams else 'few'}"
                     f" arguments for {self};"
@@ -1929,6 +1955,9 @@ def __reduce__(self):
         def __call__(self, *args, **kwargs):
             pass
 
+        def __init_subclass__(cls) -> None:
+            raise TypeError(f"type '{__name__}.ParamSpec' is not an acceptable base type")
+
 
 # 3.9
 if not hasattr(typing, 'Concatenate'):
@@ -1956,7 +1985,9 @@ class _ConcatenateGenericAlias(list):
         __class__ = typing._GenericAlias
 
         def __init__(self, origin, args):
-            super().__init__(args)
+            # Cannot use `super().__init__` here because of the `__class__` assignment
+            # in the class body (https://github.com/python/typing_extensions/issues/661)
+            list.__init__(self, args)
             self.__origin__ = origin
             self.__args__ = args
 
@@ -2259,10 +2290,10 @@ def f(val: Union[int, Awaitable[int]]) -> int:
         return typing._GenericAlias(self, (item,))
 
 
-# 3.14+?
+# 3.15+?
 if hasattr(typing, 'TypeForm'):
     TypeForm = typing.TypeForm
-# <=3.13
+# <=3.14
 else:
     class _TypeFormForm(_ExtensionsSpecialForm, _root=True):
         # TypeForm(X) is equivalent to X but indicates to the type checker
@@ -2515,7 +2546,10 @@ def __typing_is_unpacked_typevartuple__(self):
         def __getitem__(self, args):
             if self.__typing_is_unpacked_typevartuple__:
                 return args
-            return super().__getitem__(args)
+            # Cannot use `super().__getitem__` here because of the `__class__` assignment
+            # in the class body on Python <=3.11
+            # (https://github.com/python/typing_extensions/issues/661)
+            return typing._GenericAlias.__getitem__(self, args)
 
     @_UnpackSpecialForm
     def Unpack(self, parameters):
@@ -2873,9 +2907,9 @@ def method(self) -> None:
         return arg
 
 
-# Python 3.13.3+ contains a fix for the wrapped __new__
-# Breakpoint: https://github.com/python/cpython/pull/132160
-if sys.version_info >= (3, 13, 3):
+# Python 3.13.8+ and 3.14.1+ contain a fix for the wrapped __init_subclass__
+# Breakpoint: https://github.com/python/cpython/pull/138210
+if ((3, 13, 8) <= sys.version_info < (3, 14)) or sys.version_info >= (3, 14, 1):
     deprecated = warnings.deprecated
 else:
     _T = typing.TypeVar("_T")
@@ -2968,27 +3002,27 @@ def __new__(cls, /, *args, **kwargs):
 
                 arg.__new__ = staticmethod(__new__)
 
-                original_init_subclass = arg.__init_subclass__
-                # We need slightly different behavior if __init_subclass__
-                # is a bound method (likely if it was implemented in Python)
-                if isinstance(original_init_subclass, MethodType):
-                    original_init_subclass = original_init_subclass.__func__
+                if "__init_subclass__" in arg.__dict__:
+                    # __init_subclass__ is directly present on the decorated class.
+                    # Synthesize a wrapper that calls this method directly.
+                    original_init_subclass = arg.__init_subclass__
+                    # We need slightly different behavior if __init_subclass__
+                    # is a bound method (likely if it was implemented in Python).
+                    # Otherwise, it likely means it's a builtin such as
+                    # object's implementation of __init_subclass__.
+                    if isinstance(original_init_subclass, MethodType):
+                        original_init_subclass = original_init_subclass.__func__
 
                     @functools.wraps(original_init_subclass)
                     def __init_subclass__(*args, **kwargs):
                         warnings.warn(msg, category=category, stacklevel=stacklevel + 1)
                         return original_init_subclass(*args, **kwargs)
-
-                    arg.__init_subclass__ = classmethod(__init_subclass__)
-                # Or otherwise, which likely means it's a builtin such as
-                # object's implementation of __init_subclass__.
                 else:
-                    @functools.wraps(original_init_subclass)
-                    def __init_subclass__(*args, **kwargs):
+                    def __init_subclass__(cls, *args, **kwargs):
                         warnings.warn(msg, category=category, stacklevel=stacklevel + 1)
-                        return original_init_subclass(*args, **kwargs)
+                        return super(arg, cls).__init_subclass__(*args, **kwargs)
 
-                    arg.__init_subclass__ = __init_subclass__
+                arg.__init_subclass__ = classmethod(__init_subclass__)
 
                 arg.__deprecated__ = __new__.__deprecated__ = msg
                 __init_subclass__.__deprecated__ = msg
@@ -3829,8 +3863,8 @@ def get_protocol_members(tp: type, /) -> typing.FrozenSet[str]:
             >>> class P(Protocol):
             ...     def a(self) -> str: ...
             ...     b: int
-            >>> get_protocol_members(P)
-            frozenset({'a', 'b'})
+            >>> get_protocol_members(P) == frozenset({'a', 'b'})
+            True
 
         Raise a TypeError for arguments that are not Protocols.
         """
@@ -4207,44 +4241,6 @@ def evaluate_forward_ref(
             )
 
 
-class Sentinel:
-    """Create a unique sentinel object.
-
-    *name* should be the name of the variable to which the return value shall be assigned.
-
-    *repr*, if supplied, will be used for the repr of the sentinel object.
-    If not provided, "<name>" will be used.
-    """
-
-    def __init__(
-        self,
-        name: str,
-        repr: typing.Optional[str] = None,
-    ):
-        self._name = name
-        self._repr = repr if repr is not None else f'<{name}>'
-
-    def __repr__(self):
-        return self._repr
-
-    if sys.version_info < (3, 11):
-        # The presence of this method convinces typing._type_check
-        # that Sentinels are types.
-        def __call__(self, *args, **kwargs):
-            raise TypeError(f"{type(self).__name__!r} object is not callable")
-
-    # Breakpoint: https://github.com/python/cpython/pull/21515
-    if sys.version_info >= (3, 10):
-        def __or__(self, other):
-            return typing.Union[self, other]
-
-        def __ror__(self, other):
-            return typing.Union[other, self]
-
-    def __getstate__(self):
-        raise TypeError(f"Cannot pickle {type(self).__name__!r} object")
-
-
 if sys.version_info >= (3, 14, 0, "beta"):
     type_repr = annotationlib.type_repr
 else:
@@ -4302,11 +4298,16 @@ def type_repr(value):
     "ValuesView",
     "cast",
     "no_type_check",
-    "no_type_check_decorator",
     # This is private, but it was defined by typing_extensions for a long time
     # and some users rely on it.
     "_AnnotatedAlias",
 ]
+
+# Breakpoint: https://github.com/python/cpython/pull/133602
+if sys.version_info < (3, 15, 0):
+    _typing_names.append("no_type_check_decorator")
+    __all__.append("no_type_check_decorator")
+
 globals().update(
     {name: getattr(typing, name) for name in _typing_names if hasattr(typing, name)}
 )