[cixzhang]

Parked. Measured over a day of pull-request runs, pushes that only merge main are about 3% of PR CI, and none would have carried under this rule. Closed in favour of cheaper CI changes; reopen if merge-only pushes grow.

User impact

• Before: every push that only merges main into a pull request reruns all of its CI, though the pull request's own change is the same one that already passed. Long-lived pull requests merge main many times a day, and each merge pays the full suite again.
• After: when a push only merges main and the pull request's own diff is byte-identical to the previous head, whose run passed, the required checks (build, test, docsite-test, lint) pass at once and name the run they carry forward: "Carried forward from run N at ". Nothing is skipped silently.
• Unchanged: the pre-merge re-run (any later attempt) runs everything, so the run that gates the merge covers main's changes. A push that changes the pull request's diff, a file main also changed, an opened, reopened or ready pull request, a failed or cancelled previous run, and anything the step cannot read or compare all run normally. Merge-group entries, main, release checks and ci:heavy-lanes owners are unaffected.

Authority

Asked for by the CI owner, 2026-10-31: pull requests that receive hundreds of updates that only merge main. spec:AST-030 gains FR18 (and DEC-10, a Verification row and a CONTRIBUTING line). That needs an owner's /approve-spec at this head.

Changes

• .github/actions/test-scope/action.yml (loaded from the merge commit, as ci: the interaction job loads the heavy-suite caps from the merge commit, not the pull request head #9005 loads heavy-caps): a new carry-forward input. On the first attempt of a synchronize push it compares the pull request's own diff (each file's status, names, blob and patch against the merge base) at the push's previous head with this head's file list; when they are identical and the same workflow's last completed run on the previous head passed, it reports carried: true, carried_from: run N at <sha>, applies: false, and leaves a notice. A push that changes the diff makes one extra call; any error runs the job.
• ci.yml: docsite-test, test-ui, test-node, build-storybook, size-base, typecheck, test-build, pr-interaction, pr-interaction-webkit, native-swift-runner and the test join opt in and gain actions: read; every work step also requires carried != 'true' (the interaction and Swift jobs already gate on applies). build names the carried run from build-storybook.
• lint.yml: the scope step runs first with carry-forward, and every later step skips when it carries.
• Tests:
  • test-scope-action.test.mjs: carry cases (merge-only push after a pass; a failed, cancelled or unfinished previous run; a changed patch, blob, name or file set; truncated list; re-run; opened, reopened or ready; no previous head; another branch's run; a fork; unreadable runs or comparison).
  • ci-carry-forward.test.mjs (new): evaluates every step condition of every opted-in job with a carried result and fails if any work step would still run; checks actions: read, the build notice, and that the label opt-in owners do not carry. Mutation-checked: an unconditional step, or one condition without the carried check, fails it.
  • Six workflow contract tests updated for the added condition.

Evidence

• test-scope-action.test.mjs and ci-carry-forward.test.mjs: 79 pass. Dropping the carried check from one step, or adding an unconditional step, fails the contract test.
• The six updated workflow contract tests pass.
• Replay over the last day of pull-request runs: 22 of 699 CI runs followed a push that left the pull request's own diff unchanged. None of them was a merge-commit push after a passing run, so this rule would have carried none of them. Most merges of main changed the diff (main touched the same files), followed a failed run, or happened while the pull request was a draft.

Scope

• One change: a merge-only push carries the last passing result forward.
• Public text contains no internal Meta context.

Writing rubric results

• R1 narration: none. FR18 and DEC-10 are present tense.
• R2 research: none.
• R3 evidence: the FR18 Verification row names the new states (merge-only push after a pass, failure, cancelled run; changed diff; re-run; unreadable comparison) and failures (a carried job that runs work, a hidden carried run, a re-run or changed diff that carries).
• R4 rejected alternatives: DEC-10 records rerunning only what main's change reaches, and carrying across line-offset-only differences.

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Project	Deployment	Actions	Updated
astryx	Ready	Preview	Oct 31, 2026 6:03pm UTC

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Review status	Updated
🔄 In progress (for maintainers only)	Oct 31, 2026, 5:53 PM UTC

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