@@ -0,0 +1,60 @@
+name: Check supported Python versions
+
+on:
+  schedule:
+    - cron: '0 12 * * 1'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  issues: write
+
+concurrency:
+  group: check-supported-python-versions
+  cancel-in-progress: false
+
+jobs:
+  check:
+    if: github.repository_owner == 'microsoft'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+        with:
+          python-version: '3.15'
+      - name: Check for a new Python version
+        id: check
+        shell: bash
+        run: |
+          version="$(python build/update_python_versions.py)"
+          echo "version=$version" >> "$GITHUB_OUTPUT"
+      - name: Create issue
+        if: steps.check.outputs.version != ''
+        env:
+          GH_TOKEN: ${{ github.token }}
+          VERSION: ${{ steps.check.outputs.version }}
+        shell: bash
+        run: |
+          title="CI Python Versions: Update to Python $VERSION"
+          issue_number="$(
+            gh api --paginate \
+              -H "X-GitHub-Api-Version: 2022-11-28" \
+              "/repos/$GITHUB_REPOSITORY/issues?state=all&per_page=100" \
+              --jq ".[] | select(has(\"pull_request\") | not) | select(.title == \"$title\") | .number"
+          )"
+          if [[ -z "$issue_number" ]]; then
+            gh issue create \
+              --title "$title" \
+              --label debt \
+              --label python-version \
+              --body "Python $VERSION has a published release candidate according to the [Python.org downloads API](https://www.python.org/api/v2/downloads/release/?is_published=true&pre_release=true&version=3), but is missing from at least one CI test matrix.
+
+          ### Requested changes
+          - [ ] Ensure every explicit-version \`python\` matrix in \`.github/workflows/pr-check.yml\` includes Python $VERSION.
+          - [ ] Ensure every explicit-version \`python\` matrix in \`.github/workflows/build.yml\` includes Python $VERSION.
+          - [ ] Run the tests on Python $VERSION and resolve any compatibility failures.
+
+          Compare matrix entries by major.minor; patch and prerelease/dev variants of $VERSION already count as coverage. Add the version only where missing and preserve existing entries. Floating \`3.x\` entries do not declare release-candidate coverage.
+
+          Keep minimum-supported-version and build-runtime Python pins unchanged; adding CI coverage does not require raising the minimum supported Python version."
+          fi
@@ -0,0 +1,143 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
+
+import datetime
+
+import pytest
+import update_python_versions
+
+NOW = datetime.datetime(2026, 8, 2, tzinfo=datetime.timezone.utc)
+WORKFLOWS = ("pr-check.yml", "build.yml")
+
+
+def release(name="Python 3.15.0rc1", release_date="2026-08-01T00:00:00Z", **overrides):
+    result = {
+        "name": name,
+        "release_date": release_date,
+        "is_published": True,
+        "pre_release": True,
+        "version": 3,
+    }
+    result.update(overrides)
+    return result
+
+
+def test_latest_release_candidate_filters_and_orders_releases():
+    releases = [
+        release("Python 3.9.0rc10"),
+        release("Python 3.10.0rc2"),
+        release("Python 3.11.0b1"),
+        release("Python 3.11.0rc1", "2027-08-01T00:00:00Z"),
+        release("Python 3.12.0rc1", is_published=False),
+        release("Python 3.13.0rc1", pre_release=False),
+        None,
+    ]
+
+    assert update_python_versions.latest_release_candidate(releases, NOW) == "3.10"
+
+
+@pytest.mark.parametrize("release_date", [None, "invalid", "2026-08-01"])
+def test_latest_release_candidate_rejects_malformed_dates(release_date):
+    with pytest.raises(ValueError, match="release_date"):
+        update_python_versions.latest_release_candidate(
+            [release(release_date=release_date)], NOW
+        )
+
+
+def test_latest_release_candidate_requires_a_published_rc():
+    with pytest.raises(ValueError, match="released Python RC"):
+        update_python_versions.latest_release_candidate(
+            [release("Python 3.15.0"), release("Python 3.16.0a1")], NOW
+        )
+
+
+@pytest.mark.parametrize("key", ["python", "python-version"])
+def test_configured_versions_normalizes_explicit_series(tmp_path, key):
+    workflow = tmp_path / "workflow.yml"
+    workflow.write_text(
+        f"{key}: ['3.10.9', '3.11-dev', '3.12.0rc1', '3.x']\n", encoding="utf-8"
+    )
+
+    assert update_python_versions.configured_versions(workflow) == {
+        "3.10",
+        "3.11",
+        "3.12",
+    }
+
+
+@pytest.mark.parametrize("text", ["matrix: {}\n", "python: ['3.x']\n"])
+def test_configured_versions_requires_explicit_matrices(tmp_path, text):
+    workflow = tmp_path / "workflow.yml"
+    workflow.write_text(text, encoding="utf-8")
+
+    with pytest.raises(RuntimeError, match="Python version"):
+        update_python_versions.configured_versions(workflow)
+
+
+@pytest.mark.parametrize("key", ["python", "python-version"])
+@pytest.mark.parametrize(
+    "first, second, expected",
+    [
+        ("3.15", "3.14", set()),
+        ("3.14", "3.15", set()),
+        ("3.15.1", "3.15-dev", {"3.15"}),
+    ],
+)
+def test_configured_versions_requires_coverage_in_each_matrix(
+    tmp_path, key, first, second, expected
+):
+    workflow = tmp_path / "workflow.yml"
+    workflow.write_text(
+        f"{key}: ['{first}']\n{key}: ['{second}']\n{key}: ['3.x']\n",
+        encoding="utf-8",
+    )
+
+    assert update_python_versions.configured_versions(workflow) == expected
+
+
+@pytest.mark.parametrize(
+    "pr_version, push_version, expected",
+    [
+        ("3.14", "3.14", "3.15"),
+        ("3.15", "3.14", "3.15"),
+        ("3.14", "3.15", "3.15"),
+        ("3.15", "3.15", None),
+        ("3.15.1", "3.15.0-rc.2", None),
+        ("3.150", "3.15", "3.15"),
+    ],
+)
+def test_unconfigured_version(tmp_path, pr_version, push_version, expected):
+    workflows = [tmp_path / name for name in WORKFLOWS]
+    for workflow, version in zip(workflows, (pr_version, push_version)):
+        workflow.write_text(f"python: ['{version}']\n", encoding="utf-8")
+
+    assert (
+        update_python_versions.unconfigured_version([release()], workflows, NOW)
+        == expected
+    )
+
+
+@pytest.mark.parametrize(
+    "push_version, expected", [("3.14", "3.15\n"), ("3.15-dev", "")]
+)
+def test_main_checks_both_workflows(
+    tmp_path, monkeypatch, capsys, push_version, expected
+):
+    workflow_dir = tmp_path / ".github" / "workflows"
+    workflow_dir.mkdir(parents=True)
+    for name, version in zip(WORKFLOWS, ("3.15.1", push_version)):
+        (workflow_dir / name).write_text(f"python: ['{version}']\n", encoding="utf-8")
+    monkeypatch.setattr(
+        update_python_versions,
+        "__file__",
+        str(tmp_path / "build" / "update_python_versions.py"),
+    )
+    monkeypatch.setattr(
+        update_python_versions,
+        "fetch_releases",
+        lambda: [release(release_date="2020-08-01T00:00:00Z")],
+    )
+
+    update_python_versions.main()
+
+    assert capsys.readouterr().out == expected
@@ -0,0 +1,101 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
+
+import datetime
+import json
+import pathlib
+import re
+import urllib.request
+
+DOWNLOADS_URL = (
+    "https://www.python.org/api/v2/downloads/release/"
+    "?is_published=true&pre_release=true&version=3"
+)
+RC_NAME = re.compile(r"Python (?P<series>3\.\d+)\.0rc(?P<candidate>\d+)")
+VERSION_MATRIX = re.compile(
+    r"^\s*python(?:-version)?:\s*\[(?P<versions>[^\]\n]+)\]\s*$", re.MULTILINE
+)
+
+
+def fetch_releases():
+    """Fetch published Python prereleases from Python.org."""
+    request = urllib.request.Request(
+        DOWNLOADS_URL, headers={"User-Agent": "vscode-python-tools-version-check"}
+    )
+    with urllib.request.urlopen(request, timeout=30) as response:
+        return json.load(response)
+
+
+def latest_release_candidate(releases, now=None):
+    """Return the newest Python 3 series with a published release candidate."""
+    now = now or datetime.datetime.now(datetime.timezone.utc)
+    candidates = []
+    for release in releases:
+        if (
+            not isinstance(release, dict)
+            or release.get("is_published") is not True
+            or release.get("pre_release") is not True
+            or release.get("version") != 3
+            or not isinstance(release.get("name"), str)
+        ):
+            continue
+        match = RC_NAME.fullmatch(release["name"])
+        if not match:
+            continue
+        try:
+            release_date = datetime.datetime.fromisoformat(
+                release["release_date"].replace("Z", "+00:00")
+            )
+        except (AttributeError, KeyError, TypeError, ValueError) as exc:
+            raise ValueError(f"Invalid release_date for {release['name']}") from exc
+        if release_date.tzinfo is None:
+            raise ValueError(f"Missing timezone in release_date for {release['name']}")
+        if release_date <= now:
+            series = match.group("series")
+            candidates.append(
+                (
+                    tuple(map(int, series.split("."))),
+                    int(match.group("candidate")),
+                    series,
+                )
+            )
+    if not candidates:
+        raise ValueError("The downloads API did not contain a released Python RC")
+    return max(candidates)[2]
+
+
+def configured_versions(workflow):
+    """Return major.minor versions covered by every explicit Python matrix."""
+    matches = VERSION_MATRIX.findall(workflow.read_text(encoding="utf-8"))
+    if not matches:
+        raise RuntimeError(f"Expected a Python version matrix in {workflow}")
+    matrices = [
+        set(re.findall(r"['\"](\d+\.\d+)[^'\"]*['\"]", match)) for match in matches
+    ]
+    # Floating-only matrices such as ['3.x'] do not declare RC-series coverage.
+    explicit_matrices = [versions for versions in matrices if versions]
+    if not explicit_matrices:
+        raise RuntimeError(f"No explicit Python versions found in {workflow}")
+    return set.intersection(*explicit_matrices)
+
+
+def unconfigured_version(releases, workflows, now=None):
+    """Return the newest RC series when any explicit test matrix lacks it."""
+    latest = latest_release_candidate(releases, now)
+    for workflow in workflows:
+        if latest not in configured_versions(workflow):
+            return latest
+    return None
+
+
+def main():
+    """Print the newest RC series if it is missing from the CI test matrices."""
+    workflow_dir = pathlib.Path(__file__).parent.parent / ".github" / "workflows"
+    workflows = [workflow_dir / name for name in ("pr-check.yml", "build.yml")]
+    version = unconfigured_version(fetch_releases(), workflows)
+    if version:
+        print(version)
+
+
+if __name__ == "__main__":
+    main()