diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2137eff6d..a7a9cafa6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -111,7 +111,23 @@ jobs:
 
   test-sqlite:
     needs: [changes, lint]
-    if: github.event_name != 'schedule' && (github.event_name != 'pull_request' || needs.changes.outputs.code == 'true' || needs.changes.outputs.deps == 'true' || needs.changes.outputs.workflows == 'true')
+    # `docs` is in this condition and NOT in the other test jobs' on purpose.
+    # Part of the suite this job runs takes documentation as its INPUT and
+    # asserts on its content — tests_py/scripts/test_codex_plugin_contract.py
+    # reads README.md and checks the canonical published identities (the
+    # hypermnesia-mcp-viz anchor, the viz/spec migration strings). Excluding
+    # '*.md' from the `code` filter therefore switched those guards OFF exactly
+    # when their subject changed: PR #509 was a README-only diff, every test job
+    # was skipped, it merged green, and the push to main went red on that test
+    # across five jobs (run 34238410970, 2026-09-08 — 7663 passed, 1 failed;
+    # fixed by #510).
+    #
+    # This job, not the 3.10-3.13 matrix, because it already runs THE FULL SUITE
+    # (see the "Scope" note on its pytest step) in one ~5-minute job, so it
+    # covers the doc-contract tests at the smallest cost that still closes the
+    # gap. Waking the whole matrix on every prose edit would undo the CI work in
+    # #475-#481.
+    if: github.event_name != 'schedule' && (github.event_name != 'pull_request' || needs.changes.outputs.code == 'true' || needs.changes.outputs.deps == 'true' || needs.changes.outputs.workflows == 'true' || needs.changes.outputs.docs == 'true')
     name: Test (SQLite backend)
     runs-on: ubuntu-latest
     # source: run 33806380625 (2026-09-03), max 292s; ceil(2 * 292 / 60).
diff --git a/scripts/check_ci_gate_results.py b/scripts/check_ci_gate_results.py
index 180c6c267..dad2d1440 100644
--- a/scripts/check_ci_gate_results.py
+++ b/scripts/check_ci_gate_results.py
@@ -82,6 +82,18 @@ def _required_jobs(flags: dict[str, bool], event_name: str, fork: bool) -> set[s
         required.add("docker-smoke")
     if flags["docker"] or event_name in ("schedule", "workflow_dispatch"):
         required.update(DOCKER_BUILD_JOBS)
+    # A docs-only PR must still run the one full-suite job. Part of that
+    # suite takes documentation as its INPUT — tests_py/scripts/
+    # test_codex_plugin_contract.py asserts on README.md's canonical published
+    # identities — so excluding '*.md' from `code` switched those guards off
+    # exactly when their subject changed. PR #509 was a README-only diff, every
+    # test job skipped, it merged green, and the push to main went red on that
+    # test across five jobs (run 34238410970, 2026-09-08; fixed by #510).
+    # Mirrors ci.yml's test-sqlite predicate, which carries the same note; this
+    # module and that predicate must stay in exact agreement (see the docstring
+    # on check_policy).
+    if not full and event_name == "pull_request" and flags["docs"]:
+        required.add("test-sqlite")
     if fork:
         required.discard("mcp-host-config")
     return required
diff --git a/tests_py/scripts/test_check_ci_gate_results.py b/tests_py/scripts/test_check_ci_gate_results.py
index ca72e265b..291da84ef 100644
--- a/tests_py/scripts/test_check_ci_gate_results.py
+++ b/tests_py/scripts/test_check_ci_gate_results.py
@@ -32,10 +32,25 @@ def _skip(needs: dict, jobs: frozenset[str]) -> dict:
 
 
 class JustifiedSkips(unittest.TestCase):
-    def test_docs_only_runs_only_changes_and_lint(self) -> None:
-        needs = _skip(_needs("docs"), gate.CONDITIONAL_JOBS)
+    def test_docs_only_still_requires_the_full_suite_job(self) -> None:
+        """A docs-only PR may skip every conditional job except test-sqlite.
+
+        Regression for the #509 -> #510 incident: README.md is the INPUT of
+        tests_py/scripts/test_codex_plugin_contract.py, so skipping every test
+        job on a docs-only diff switched that guard off exactly when its subject
+        changed. #509 merged green and main went red on the push (run
+        34238410970). test-sqlite is the one job that runs the full suite.
+        """
+        allowed = gate.CONDITIONAL_JOBS - {"test-sqlite"}
+        needs = _skip(_needs("docs"), allowed)
         self.assertEqual(gate.check(needs, "pull_request", _event()), [])
 
+        needs["test-sqlite"]["result"] = "skipped"
+        self.assertTrue(
+            gate.check(needs, "pull_request", _event()),
+            "skipping test-sqlite on a docs-only PR must not be justified",
+        )
+
     def test_docker_only_requires_docker_jobs(self) -> None:
         needs = _skip(_needs("docker"), gate.CODE_JOBS)
         self.assertEqual(gate.check(needs, "pull_request", _event()), [])
@@ -193,7 +208,10 @@ def _run(self, needs: str) -> subprocess.CompletedProcess:
             )
 
     def test_docs_only_cli_succeeds(self) -> None:
-        result = self._run(json.dumps(_skip(_needs("docs"), gate.CONDITIONAL_JOBS)))
+        # test-sqlite runs on a docs-only PR (it carries the doc-contract
+        # guards); every other conditional job may skip.
+        allowed = gate.CONDITIONAL_JOBS - {"test-sqlite"}
+        result = self._run(json.dumps(_skip(_needs("docs"), allowed)))
         self.assertEqual(result.returncode, 0, result.stderr)
 
     def test_malformed_json_cli_fails_with_diagnostic(self) -> None: