diff --git a/tests/ci-gating-jobs.test.mjs b/tests/ci-gating-jobs.test.mjs
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+// Guards the one property that makes every other gate in this repository
+// worth running: that a failing gate actually fails its job.
+//
+// `.github/workflows/ci.yml` is the only `pull_request`-triggered workflow, so
+// its `validate`, `lint` and `e2e` jobs are the entire pre-merge gate. Adding
+// `continue-on-error: true` to any of them leaves every step running and every
+// step reporting, and makes the job report success regardless. The same line on
+// the `Run unit tests with coverage` step discards the unit suite and all four
+// coverage thresholds on its own.
+//
+// Nothing else in the suite sees that. tests/coverage-gate-thresholds.test.mjs
+// pins the threshold values and that ci.yml runs the gate command; both survive
+// the exit code being ignored. tests/workflow-scripts.test.mjs asks whether a
+// command is *run* by some workflow, and `continue-on-error` does not stop it
+// being run. Its `browser coverage is isolated in a visible non-gating job`
+// test asserts the relationship in one direction only — that `e2e-coverage`
+// *is* opted out — and says nothing about the jobs that must not be.
+//
+// The allowlist below follows the FLOORS convention in
+// coverage-gate-thresholds.test.mjs: a legitimate future non-gating job stays
+// possible, but it has to be argued for here rather than slipped in as one line
+// of YAML. The staleness guard forces an entry to be deleted once its job stops
+// opting out, so the allowlist cannot quietly outlive the exemption.
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { readFileSync, readdirSync } from 'node:fs';
+import { join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { parse } from 'yaml';
+
+const repoRoot = fileURLToPath(new URL('..', import.meta.url));
+const workflowDir = join(repoRoot, '.github', 'workflows');
+
+// `<workflow>#<job>` → why that job is allowed to swallow its own failure.
+const NON_GATING_JOBS = new Map([
+  [
+    'ci.yml#e2e-coverage',
+    'Browser coverage is published for information only; the required signal ' +
+      'is the separate e2e job. Pinned from the other side by the "browser ' +
+      'coverage is isolated in a visible non-gating job" test in ' +
+      'tests/workflow-scripts.test.mjs.',
+  ],
+]);
+
+// Jobs of ci.yml that are the pull_request gate. Named rather than derived so
+// that deleting one fails as loudly as disarming one.
+const REQUIRED_CI_JOBS = ['validate', 'lint', 'e2e'];
+
+const workflowFiles = readdirSync(workflowDir)
+  .filter((name) => name.endsWith('.yml') || name.endsWith('.yaml'))
+  .sort();
+
+const workflows = new Map(
+  workflowFiles.map((file) => [
+    file,
+    parse(readFileSync(join(workflowDir, file), 'utf8')),
+  ]),
+);
+
+// A `continue-on-error` is "declared" unless it is pinned off. The field
+// accepts an expression, so anything that is not literally false — including
+// `${{ ... }}`, which can evaluate to true at run time — counts as opting out.
+function optsOutOfFailure(value) {
+  if (value === undefined || value === null) return false;
+  if (typeof value === 'boolean') return value;
+  return String(value).trim().toLowerCase() !== 'false';
+}
+
+// The three scanners below take the parsed workflows as an argument rather
+// than closing over the repository's own, so the violation each one exists to
+// report can be exercised against a fixture. A guard whose failure path never
+// runs is a guard nobody has checked.
+function jobEntries(parsedWorkflows) {
+  const entries = [];
+  for (const [file, workflow] of parsedWorkflows) {
+    for (const [name, job] of Object.entries(workflow?.jobs ?? {})) {
+      entries.push({ key: `${file}#${name}`, file, name, job });
+    }
+  }
+  return entries;
+}
+
+function optedOutJobs(parsedWorkflows) {
+  return jobEntries(parsedWorkflows)
+    .filter(({ job }) => optsOutOfFailure(job?.['continue-on-error']))
+    .map(({ key }) => key)
+    .sort();
+}
+
+function suppressingSteps(parsedWorkflows, allowlist) {
+  const offenders = [];
+  for (const { key, job } of jobEntries(parsedWorkflows)) {
+    if (allowlist.has(key)) continue;
+    for (const step of job?.steps ?? []) {
+      if (!optsOutOfFailure(step?.['continue-on-error'])) continue;
+      offenders.push(`${key} → ${step.name ?? step.uses ?? step.run ?? '?'}`);
+    }
+  }
+  return offenders;
+}
+
+function staleAllowlistEntries(parsedWorkflows, allowlist) {
+  const stale = [];
+  for (const key of allowlist.keys()) {
+    const [file, name] = key.split('#');
+    const job = parsedWorkflows.get(file)?.jobs?.[name];
+    if (!job) {
+      stale.push(`${key} (no such job)`);
+      continue;
+    }
+    if (!optsOutOfFailure(job['continue-on-error'])) {
+      stale.push(`${key} (no longer opts out — delete this entry)`);
+    }
+  }
+  return stale;
+}
+
+// Smallest shape the scanners read: one workflow, one job, optional steps.
+function fixture(jobs) {
+  return new Map([['fixture.yml', { jobs }]]);
+}
+
+test('every workflow parses and ci.yml still defines its gating jobs', () => {
+  assert.ok(
+    workflowFiles.length > 0,
+    'no workflows found under .github/workflows',
+  );
+
+  const ci = workflows.get('ci.yml');
+  assert.ok(ci, 'ci.yml is missing; it is the only pull_request gate');
+  assert.deepEqual(
+    Object.keys(ci.on ?? ci.true ?? {}).includes('pull_request'),
+    true,
+    'ci.yml must stay triggered by pull_request',
+  );
+
+  const missing = REQUIRED_CI_JOBS.filter((name) => !ci.jobs?.[name]);
+  assert.deepEqual(missing, [], 'gating jobs removed from ci.yml');
+});
+
+test('only allowlisted jobs opt out of failing', () => {
+  assert.deepEqual(
+    optedOutJobs(workflows),
+    [...NON_GATING_JOBS.keys()].sort(),
+    'a job gained or lost continue-on-error; a gating job that swallows its ' +
+      'own failure reports success no matter what its steps do',
+  );
+});
+
+test("ci.yml's gating jobs are gating", () => {
+  // Redundant with the allowlist comparison by construction, but it names the
+  // three jobs explicitly so the failure message points straight at the gate
+  // that was disarmed rather than at a set difference.
+  const ci = workflows.get('ci.yml');
+  for (const name of REQUIRED_CI_JOBS) {
+    assert.equal(
+      optsOutOfFailure(ci.jobs[name]?.['continue-on-error']),
+      false,
+      `ci.yml job "${name}" must fail the run when it fails`,
+    );
+  }
+});
+
+test('no step inside a gating job suppresses its own failure', () => {
+  // A step-level opt-out is the narrower version of the same hole: one line on
+  // "Run unit tests with coverage" discards the unit suite and all four
+  // coverage thresholds while the job still reports success.
+  assert.deepEqual(
+    suppressingSteps(workflows, NON_GATING_JOBS),
+    [],
+    'steps of gating jobs that ignore failure',
+  );
+});
+
+test('the non-gating allowlist does not outlive its jobs', () => {
+  for (const [key, reason] of NON_GATING_JOBS) {
+    assert.ok(
+      typeof reason === 'string' && reason.length > 0,
+      `allowlist entry ${key} must record why the job is exempt`,
+    );
+  }
+  assert.deepEqual(
+    staleAllowlistEntries(workflows, NON_GATING_JOBS),
+    [],
+    'stale entries in NON_GATING_JOBS',
+  );
+});
+
+test('optsOutOfFailure reads an absent, pinned-off and expression value', () => {
+  // `continue-on-error` accepts an expression, so only a literal false is a
+  // guarantee. Anything else can evaluate to true at run time and has to count
+  // as opting out, or the guard is bypassed by writing `${{ true }}`.
+  assert.equal(optsOutOfFailure(undefined), false);
+  assert.equal(optsOutOfFailure(null), false);
+  assert.equal(optsOutOfFailure(false), false);
+  assert.equal(optsOutOfFailure('false'), false);
+  assert.equal(optsOutOfFailure(' FALSE '), false);
+  assert.equal(optsOutOfFailure(true), true);
+  assert.equal(optsOutOfFailure("${{ github.event_name == 'push' }}"), true);
+});
+
+test('optedOutJobs reports a job that gained continue-on-error', () => {
+  assert.deepEqual(optedOutJobs(fixture({ gate: {} })), []);
+  assert.deepEqual(
+    optedOutJobs(fixture({ gate: { 'continue-on-error': true }, other: {} })),
+    ['fixture.yml#gate'],
+  );
+});
+
+test('suppressingSteps names the step, and skips allowlisted jobs', () => {
+  const jobs = {
+    gate: {
+      steps: [
+        { name: 'Install dependencies' },
+        { name: 'Run unit tests with coverage', 'continue-on-error': true },
+        { uses: 'actions/upload-artifact@v7', 'continue-on-error': 'true' },
+        { run: 'npm run build', 'continue-on-error': true },
+        { 'continue-on-error': true },
+      ],
+    },
+  };
+  assert.deepEqual(suppressingSteps(fixture(jobs), new Map()), [
+    'fixture.yml#gate → Run unit tests with coverage',
+    'fixture.yml#gate → actions/upload-artifact@v7',
+    'fixture.yml#gate → npm run build',
+    'fixture.yml#gate → ?',
+  ]);
+
+  // An allowlisted job is non-gating as a whole, so its steps are its own
+  // business; scanning them would force an exemption to be written twice.
+  assert.deepEqual(
+    suppressingSteps(fixture(jobs), new Map([['fixture.yml#gate', 'why']])),
+    [],
+  );
+
+  // A job with no steps at all must not throw.
+  assert.deepEqual(suppressingSteps(fixture({ gate: {} }), new Map()), []);
+});
+
+test('staleAllowlistEntries catches a deleted job and a revoked opt-out', () => {
+  const allowlist = new Map([['fixture.yml#advisory', 'why']]);
+  assert.deepEqual(
+    staleAllowlistEntries(
+      fixture({ advisory: { 'continue-on-error': true } }),
+      allowlist,
+    ),
+    [],
+  );
+  assert.deepEqual(
+    staleAllowlistEntries(fixture({ advisory: {} }), allowlist),
+    ['fixture.yml#advisory (no longer opts out — delete this entry)'],
+  );
+  assert.deepEqual(staleAllowlistEntries(fixture({}), allowlist), [
+    'fixture.yml#advisory (no such job)',
+  ]);
+});