ci(pm): refuse governed surfaces at the merge queue — the prevention half - #12102

Closes #11704

The prevention half of the governed-surface regime. check:pm-governed-merges is the detection half — report-only, post-merge, by design, and lint.yml's own comment calls it exactly that. This adds the refusal.

The card's first measurement was pre-answered in its grading comment (the queue refuses nothing today), so this starts past it.

The check

merge_group   → a governed diff with NO approving review is a REFUSAL (exit 3/4/5)
pull_request  → the same finding is an EARLY WARNING that exits 0

⭐ The one decision worth reviewing: the event split

The 2026-08-18 ruling retired ADR maintainer approval because it was red on every governed PR by design — 红灯常态化本身有毒. Rebuilding that is the obvious way to get this wrong, so the split is deliberate:

• A governed PR held as a draft for the maintainer to merge by hand is the regime's healthy end state. A check that reddens on it is red on the healthy case, forever — the retired gate with a new name. So the pull_request leg is green, and says out loud that it is deliberately green.
• The merge-queue build is a state a governed PR should never be in at all. Red there is red on the anomaly, and it is the last thing between a speculative merge and main. That is the prevention.

⚠️ Consequence, stated rather than discovered: this guard cannot stop a maintainer merging a governed PR by hand, and does not try — a direct merge produces no merge_group event. Under this regime that is not a hole; the human merge is the review record. What it closes is the seat path: flip ready → enqueue → the queue is the entire review.

What satisfies it — and one deliberate divergence from the dispatch

The dispatch said "no APPROVED review from the CODEOWNER/maintainer". I implemented "an APPROVED review exists", with no person named, because that is a standing ruling about this exact predicate (#8161, verbatim): 「门禁改成只要求「APPROVED review 存在」」/「不要指定具体的人」. The identity proxy was tried and became unsatisfiable — human and agent accounts are not stably partitioned, cloud sessions author under the maintainer's own account, and GitHub forbids self-approval, so an identity-keyed gate went permanently red exactly when the human was driving. Flagging the divergence rather than quietly picking one.

#11704's own retraction re-derives this from the other side: it built a three-instance case out of the GitHub actor field and had to withdraw a third of it. Its closing lesson — "attribution from the GitHub actor field is not a reading" — is why this guard keys on the diff's paths and needs no attribution at all.

The accepted cost is unchanged from #8161 and is printed on every clear verdict: no identity signal proves a review is human, so a seat can satisfy this by approving. What it can no longer do is the thing all three incidents actually were — a silent flip-and-enqueue with nothing recorded anywhere. An approval is a separate, deliberate, timestamped action. That is the whole delta, and it is real.

Restraint worth naming: an outstanding CHANGES_REQUESTED is reported loudly but does not flip the verdict, because the ruled predicate is "an APPROVED review exists" and widening a governance gate past its own ruling is how gates acquire policy nobody agreed to. One-line change if you want it.

Design choices, argued

A dedicated workflow, not a job in lint.yml. Three reasons: it needs pull-requests: read, which the lint job neither has nor should grow; a red here means "a governed surface is being merged unreviewed", which must not be mixed into a gate family whose red reads as "fix your lint"; and a standalone job yields one clean context name for branch protection. The retired gate was its own workflow for the same reasons.

No paths: filter, on either leg. A skipped job counts as SUCCESS in branch protection, so a filter would hand the queue a green Governed Surface Queue Guard for a PR it mis-scoped — the #4928 shape, on the one check whose entire job is to refuse. The path test lives inside the script.

Ordering, so fail-closed and fail-open never collide. Fail-open is wrong here specifically — this guard exists because everything else failed open — so an unreadable review list is a refusal with its own exit code. But a diff touching nothing governed must never be blocked by an API hiccup either. Reconciled by order, not tolerance: runGuard decomposes the diff and returns before constructing a single request. Pinned with a fetchReviews spy that throws if called at all — a mock returning [] would have passed against a broken version.

Multi-PR merge groups are decomposed per commit. merge_group.head_ref names only the last PR in a batch, so keying the group's diff to it would check the wrong PR's reviews — and in the direction that reads as compliance (PR B approved, PR A's governed diff rides in behind it). Each first-parent commit is attributed via the register's own pullNumberFromSubject; a governed commit naming no PR is UNATTRIBUTED with its own exit code, not dropped.

GOVERNED_SURFACES is read at runtime, never restated (#9840) — including the #9866/#10277 generated-artifact exception, applied through the register's own applyGeneratedExceptions with provenance recomputed byte-exact against this build's base sha. Without it every page-adding docs PR would be refused (measured 5-for-5 on #9866) — routine traffic reddening the guard is the same poison one level down.

Evidence

Self-test — node scripts/pm/check-governed-queue-guard.mjs --self-test:

✓ check-governed-queue-guard self-test: 80 cases pass (register-driven verdicts, the queue/PR
  event split, latest-decisive approval reduction, multi-PR group decomposition, three replayed
  incidents, the zero-API ordering guarantee measured with a throwing spy, and the workflow wiring pin).

Live end-to-end, real git + real GitHub API, replaying the merge of PR #11387 (docs/adr/0120-…md) as a merge group:

Governed Surface Queue Guard — merge_group — 1 governed pull request(s), 0 unattributed …, 1 review lookup(s).
  #11387 — governed:
        docs/adr/** ×1 — architecture decision records
          - docs/adr/0120-unique-scope-vocabulary-and-null-safe-tenant-uniqueness.md
        ⛔ NO approving review (0 review(s) read, none decisive-APPROVED)
  ⛔  REFUSED — this merge group must not land.

exit 3. The 0 reviews reading matches the card's own get_reviews → [].

⚠️ This is not a claim about #11387. That PR was the maintainer's own direct merge (「是我合并的」), it never entered a merge queue, and the card struck it as an instance. It is used here purely as a real governed diff with a real empty review list — the most honest fixture available. The same range on the pull_request leg exits 0 with the early warning, as designed.

Ablations — three mutations, each proven on disk by marker count and each restored (trap … EXIT INT TERM); no build/dist is involved, the script runs from source:

A first attempt at the second ablation injected q{APPROVED} and died on SyntaxError — red for the wrong reason. That reading was void and is recorded here rather than silently re-run; the table is the corrected run.

Gates — derived with node scripts/pm/dispatch-gates.mjs --repo objectstack-ai/objectstack (no hand-written path list), run at final commit 1080f6c24, all 26 green. The nine that first answered "a fresh worktree has no node_modules … nothing was measured" were re-run after pnpm install and are counted as measured, not as passes:

check:agent-test-spelling · check:cross-package-test-inputs · check:entry-guard · check:node-version · check:parse-guard · check:pnpm-acquisition · check:pnpm-filter-targets · check:required-contexts · check:shard-attestation · check:workflow-status-functions · check-aggregator-roster · check-ci-filter-parity · check-cross-package-test-inputs · check-required-contexts · check-self-test-wired · check-self-test-workflow-commands · check-shard-attestation · check-step-collectors · check-whole-set-label-write · check-drift-comment · check-governed-queue-guard --self-test · ci-failure --self-test · check:nul-bytes · check:pm-governed-merges · check:pm-governed-prose · check:pm-dispatch-gates

check-required-contexts prints its own verdict, which is the one that matters for a PR adding a workflow:

✓ check-required-contexts: 6 required context name(s) pinned across 2 workflow(s);
  5 instruction surface(s) scanned against 2 retired name(s) (#9491).

Lint, narrowed and declared. Repo-wide pnpm lint is CI's run. Locally: eslint --no-inline-config --format json over the diff. Population read from eslint's own config, not guessed — the .yml reports "File ignored because no matching configuration was supplied", so the real population for this diff is 1 file, scripts/pm/check-governed-queue-guard.mjs, with 0 errors, 0 warnings. --print-config shows languageOptions.parserOptions.project: null, i.e. type-aware linting is off, so this diff cannot move the verdict on any untouched file. The .yml is covered instead by the four workflow-scanning gates above, which parse it and pass.

⛔ Not done here — your step

Making this a required context is yours. Branch protection is the maintainer's, and #6865's two-step is a REQUIRED_CONTEXTS row in scripts/check-required-contexts.mjs plus the Settings → Rulesets entry, in one sitting. Adding the row alone would put it in direction A — registered here, NOT in the live required set, which that gate reports as a problem — so no row is added in this PR. The literal to pin, verbatim:

Governed Surface Queue Guard

The script's --self-test reads the workflow file and fails if that literal ever drifts, so the pin cannot later be taken against a name nothing publishes.

No token permission was widened. contents: read + pull-requests: read, both default read scopes; no write scope anywhere.

No changeset (skip-changeset): a CI workflow and a PM script publish nothing.

Until the context is required, this check is advisory — it will report on queue builds and go red, but nothing enforces it. That is #5617's own defect, and it is the reason the flip above is a real step rather than a formality.

Generated by Claude Code