diff --git a/.github/workflows/community-ci.yml b/.github/workflows/community-ci.yml
index fe65ca0adc..b5d2d0ec17 100644
--- a/.github/workflows/community-ci.yml
+++ b/.github/workflows/community-ci.yml
@@ -817,6 +817,32 @@ jobs:
         with:
           python-version: "3.12"
 
+      - name: Use the official NVIDIA source for the pinned CUDA base
+        run: |
+          set -euo pipefail
+          docker buildx version
+          python3 -I - <<'PY'
+          import json
+          import os
+          from pathlib import Path
+
+          # Both registries serve the same immutable NVIDIA manifest. Keep the
+          # PR Dockerfile and test commands intact while avoiding Hub's shared
+          # anonymous pull quota on hosted runners. Only this exact pin matches.
+          reference = "nvidia/cuda:13.3.0-base-ubuntu24.04@sha256:bcf7d05f0b13b9bbb86d9a4cd039d331894b8f1145ad009d1af75023bcd1dc5c"
+          policy = Path(os.environ["RUNNER_TEMP"]) / "community-cpu-source-policy.json"
+          policy.write_text(json.dumps({
+              "rules": [{
+                  "action": "CONVERT",
+                  "selector": {"identifier": "docker-image://docker.io/" + reference, "matchType": "EXACT"},
+                  "updates": {"identifier": "docker-image://nvcr.io/" + reference},
+              }],
+          }) + "\n")
+          with Path(os.environ["GITHUB_ENV"]).open("a") as environment:
+              environment.write("DOCKER_BUILDKIT=1\n")
+              environment.write("EXPERIMENTAL_BUILDKIT_SOURCE_POLICY=" + str(policy) + "\n")
+          PY
+
       - name: Run hardened source-only units
         run: python3 -m tools.community_ci unit
 
diff --git a/tools/tests/test_community_ci.py b/tools/tests/test_community_ci.py
index 25f3e21d8f..a6c3fd7b03 100644
--- a/tools/tests/test_community_ci.py
+++ b/tools/tests/test_community_ci.py
@@ -714,6 +714,47 @@ def run(command: list[str], **_kwargs: object) -> subprocess.CompletedProcess[st
     assert calls[0][-1] == "requirements"
 
 
+def test_cpu_source_policy_changes_only_the_registry_for_one_immutable_pin(tmp_path):
+    script = _workflow_step_script(
+        "community-ci.yml", "unit", "Use the official NVIDIA source for the pinned CUDA base"
+    )
+    runner = tmp_path / "runner"
+    runner.mkdir()
+    source = tmp_path / "Dockerfile.community-cpu"
+    source.write_text("FROM example.invalid/unrelated:unchanged\n")
+    environment = tmp_path / "environment"
+    # No Docker operation is needed to check the workflow's generated policy;
+    # a separate real BuildKit experiment verifies conversion and DENY controls.
+    result = subprocess.run(
+        ["bash", "-c", 'docker() { test "$*" = "buildx version"; };\n' + script],
+        cwd=tmp_path,
+        env={**os.environ, "RUNNER_TEMP": str(runner), "GITHUB_ENV": str(environment)},
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+    assert result.stdout == ""
+    values = dict(line.split("=", 1) for line in environment.read_text().splitlines())
+    assert values["DOCKER_BUILDKIT"] == "1"
+    policy = json.loads(Path(values["EXPERIMENTAL_BUILDKIT_SOURCE_POLICY"]).read_text())
+    assert len(policy["rules"]) == 1
+    rule = policy["rules"][0]
+    assert rule["action"] == "CONVERT" and rule["selector"]["matchType"] == "EXACT"
+    original, mirrored = rule["selector"]["identifier"], rule["updates"]["identifier"]
+    assert original.startswith("docker-image://docker.io/nvidia/cuda:")
+    assert mirrored == original.replace("docker-image://docker.io/", "docker-image://nvcr.io/", 1)
+    assert (
+        original.split("@", 1)[1]
+        == "sha256:bcf7d05f0b13b9bbb86d9a4cd039d331894b8f1145ad009d1af75023bcd1dc5c"
+    )
+    assert "*" not in original
+    assert source.read_text() == "FROM example.invalid/unrelated:unchanged\n"
+    workflow = yaml.safe_load((REPO_ROOT / ".github/workflows/community-ci.yml").read_text())
+    steps = workflow["jobs"]["unit"]["steps"]
+    assert steps[-2]["run"] == script
+    assert steps[-1]["run"] == "python3 -m tools.community_ci unit"
+
+
 @pytest.mark.parametrize(
     ("job_status", "test_outcome", "test_conclusion", "expected"),
     [