Runs on pull_request_target against master. PR code is never checked out
or executed: metadata + a 120KB-capped diff come from the GitHub API only;
the base-repo checkout provides the rubric script. All interpolations are
env-bound; actions SHA-pinned; permissions limited to contents:read +
pull-requests:write + issues:write; per-PR concurrency with cancel.
scripts/pr-gate.mjs (no deps, fetch only) classifies via the strict
usefulness rubric (claude-sonnet-5, strict JSON schema, thinking disabled;
sampling params omitted — rejected on this model), posts one sticky
comment (<!-- gbrain-pr-gate -->), applies exactly one gate:* label, and
exits 1 only on close-lane. Missing ANTHROPIC_API_KEY or API failure after
2 retries NEUTRAL-skips loudly (comment + warning, exit 0). Mechanical
(no-LLM) checks: version-first title rule and diff red flags (>40 files,
node_modules, symlinks, workflow edits force needs-maintainer, new
package.json deps, deleted tests).
test/pr-gate-workflow.test.ts pins the security invariants and unit-tests
the exported title rule + red-flag detector (import side-effect guarded).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
