review(5 V2): flag stale rerun verdict race FAIL

machine-docs/BACKLOG-5.md

@@ -24,6 +24,34 @@ Single-writer: `## Build backlog` = Builder-only; `## Adversary findings` = Adve
 
 ## Adversary findings
 
+### [adversary] A5-3 — `POST=1 testme-on-pr.sh` can return a stale prior GREEN on re-runs
+**Status:** OPEN — found 2026-06-01T03:22:00Z.
+
+The helper currently posts a fresh `!testme`, then polls the recipe PR head's combined commit status.
+If that PR head SHA already has a previous successful `cc-ci/testme` status and the bridge has not yet
+processed the new comment, the helper exits immediately with the **old** GREEN/build URL instead of a
+fresh `PENDING` or the new run's URL.
+
+This is a real Phase-5/V2 correctness bug because re-commenting `!testme` on the same PR head is a
+supported path, and the helper is meant to report the verdict for the run it just triggered.
+
+**Cold repro:**
+1. Use an open PR whose current head SHA already has `cc-ci/testme: success` from an earlier run.
+2. Record the PR comment count.
+3. Run:
+   `POST=1 MAX_WAIT=40 INTERVAL=5 /srv/cc-ci/.claude/skills/recipe-upgrade/testme-on-pr.sh custom-html-tiny 5`
+4. Observe:
+   - the PR comment count increases by exactly one (`3 -> 4` in the reproducer), so one fresh `!testme`
+     was posted;
+   - the helper returns `VERDICT=GREEN` with the **old** build URL
+     `https://drone.ci.commoninternet.net/recipe-maintainers/cc-ci/37`;
+   - later, the live system shows a new run was actually triggered and reflected on the PR as build
+     `#41` (`cc-ci/testme pending -> success`, target URL `/41`).
+
+**Likely fix direction:** after `POST=1`, do not trust a pre-existing terminal status on the same SHA.
+Poll for evidence that belongs to the newly-triggered run (e.g. a newer status timestamp, a pending
+status after the new comment, or a changed build URL/context generation marker) before returning.
+
 ### [adversary] A5-2 — CRITICAL: testme-on-pr.sh cannot read verdicts (commit status vs comment mismatch)
 **Status:** CLOSED — re-tested 2026-05-31T19:41:12Z; see `REVIEW-5.md` follow-up entry.
 

machine-docs/BUILDER-INBOX.md

@@ -0,0 +1,15 @@
+## 2026-06-01T03:22:00Z — A5-3 heads-up
+
+Fresh adversary probe on `custom-html-tiny` PR `#5` found a V2 rerun bug and I recorded it formally in
+`REVIEW-5.md` / `BACKLOG-5.md` as **A5-3**.
+
+Summary:
+- `POST=1 MAX_WAIT=40 INTERVAL=5 /srv/cc-ci/.claude/skills/recipe-upgrade/testme-on-pr.sh custom-html-tiny 5`
+  posted exactly one new `!testme` comment.
+- The helper then returned the stale old GREEN/build URL for build `#37` immediately.
+- About 40s later, the live PR/statuses showed the newly-triggered run was actually build `#41`
+  (`pending -> success`, PR comment updated to `/41`).
+
+Interpretation: on a rerun against the same PR head SHA, the helper can read a pre-existing terminal
+`cc-ci/testme` status before the bridge posts the new pending status, so `POST=1` does not reliably
+report the run it just triggered.

machine-docs/REVIEW-5.md

@@ -149,3 +149,34 @@ I did **not** read `JOURNAL-5.md` before this verdict update.
   it that way posted a fresh `!testme` comment (`#13818`) and kicked off build `#35`.
 - This is a STATUS/HOW issue, not a new code defect. I notified the Builder via `BUILDER-INBOX.md` so
   the verification instructions can be corrected before the next claim.
+
+---
+
+## Cold-verify finding — 2026-06-01T03:22:00Z
+
+No `Gate: <Mn> CLAIMED` was pending in `STATUS-5.md`, so I used the idle slot for a fresh V2 rerun
+probe. I did **not** read `JOURNAL-5.md` before forming this verdict.
+
+### A5-3: `POST=1` can return a stale prior GREEN on a re-run of the same PR head
+- Probe target: `recipe-maintainers/custom-html-tiny` PR `#5`, head
+  `4bd8416a209f8521fdd804139c578156961633d3`.
+- Before invoking the helper, the PR had `BEFORE_COMMENTS=3` and the head SHA already carried an older
+  successful `cc-ci/testme` status pointing at build `#37`.
+- Cold-shell invocation:
+  `POST=1 MAX_WAIT=40 INTERVAL=5 /srv/cc-ci/.claude/skills/recipe-upgrade/testme-on-pr.sh custom-html-tiny 5`
+- Observed immediately from that single command:
+  - exactly one fresh trigger comment was posted (`AFTER_COMMENTS=4`);
+  - the helper returned:
+    `VERDICT=GREEN`
+    `BUILD=https://drone.ci.commoninternet.net/recipe-maintainers/cc-ci/37`
+  - That build URL was stale: it belonged to the previous successful run on the same SHA, not the run
+    just triggered by this new `!testme`.
+- Follow-up check ~40s later showed the live system had in fact started and reflected a new run for the
+  same SHA:
+  - `STATUS cc-ci/testme pending .../41 2026-06-01T03:21:30Z`
+  - `STATUS cc-ci/testme success .../41 2026-06-01T03:22:00Z`
+  - The PR result comment was updated to build `#41`.
+
+**Verdict:** FAIL for this V2 edge. Re-triggering `!testme` on an unchanged PR head can race against an
+older terminal commit status, causing `POST=1` to report the wrong run/result. Filed as
+`BACKLOG-5.md` item **A5-3**.