[quality] lgtm removal no-op arms (onPrLgtm.ts:33 no-label synchronize, labels/lgtm.ts:106 /lgtm cancel without a commit binding) have 0 end-to-end hits #409

Finding

Two lgtm removal arms that have nothing to unbind run only under unit tests; the shipped bundle never reaches them:

Evidence (main @ 20d49e7, Node v26.10.0):

• Unit: npx vitest run --coverage → 100 % lines, 99.82 % branches (124 files / 1994 tests). Both arms are green; the only residual branches are approve.ts:417,505 and auth.ts:259.
• End-to-end: npm run test:coverage:e2e on a scratch branch = origin/main + the heads of all 15 open hold-gated bundle PRs (test(bundle): drive owners-label's early-return and failure arms through dist/index.js #298 … test(bundle): drive withdrawalReason's 'and N more' tail and no-withdrawer arm (approveReview.ts:105/120) through dist/index.js #408, all merge clean; 59 files / 425 tests pass) → 98.09 % lines of src/. Branch hits: onPrLgtm.ts:33 if = [2, 0], labels/lgtm.ts:106 if = [2, 0] — the then-arms (label present / binding on) run, the else-arms never do.
• No open PR claims them: __tests__/bundle/pullReqJobsArms.test.ts drives the lgtm job's failed labels read; __tests__/bundle/lgtmBindingArms.test.ts drives /lgtm cancel's failing reads and writes; bundle.test.ts:1374 drives bind_to_commit: false for the labeled event only.

Why it matters: these are the common no-op paths — every push to a pull request nobody has /lgtm'd goes through onPrLgtm.ts:33, and every repository running legacy label-only merging goes through lgtm.ts:106 on cancel. Only the unit suite (with labeling mocked) pins that they read the labels, remove nothing extra and never touch POST /statuses.

Recommendation

One deliverable — a bundle test (__tests__/bundle/lgtmRemovalNoopArms.test.ts) that drives through dist/index.js:

• pull_request synchronize + jobs: lgtm, pull request labelled kind/bug only → exit 0, no DELETE, calls = OWNERS reads, base probe, GET /issues/1
• /lgtm cancel on a pull request under lgtm:\n bind_to_commit: false → GET /issues/1, DELETE /issues/1/labels/lgtm, config reads, then tide's sweep; no POST /statuses/…
• /lgtm cancel on a plain issue carrying lgtm → root OWNERS probe + membership reads, GET /issues/1, DELETE …/labels/lgtm, config reads; no /pulls/ read, no POST

Priority

• Impact: medium (unit-covered, no end-to-end coverage)
• Effort: low

Filed by quality agent (hold-gated mode)

🐝 Hive Agent: quality | Instance: hosted-available-lke648397-260827-5q9t | SHA: 20d49e7

— hive: agent=quality backend=copilot model=claude-fable-5.1 copilot=1.0.88