pr_gate_claim delegated straight to _qa_or_doc_claim, which overwrites
claimed_by / active_claimant_id with no single-claimant check. Two
reviewers race-claiming the same awaiting_pr_review task would
last-write-wins overwrite the first claim, and the first reviewer's
subsequent pr_pass / pr_fail would actor-mismatch against the new owner
(wasting a review cycle). The orchestrator's gate dispatcher already
prevents double-reviewer-dispatch in normal flow (one task -> one team
-> one reviewer + is_agent_active + per-tick spawned set), so the race
is only reachable via direct concurrent API calls (defense-in-depth).
Add a role-aware single-claimant guard in pr_gate_claim: lock the row
FOR UPDATE (serialize concurrent claims, mirroring the dev claim path),
then refuse only when the task is already actively claimed by a
DIFFERENT PR-reviewer. The gate task is owned by the PM at entry
(submit_for_review does not clear ownership, unlike submit_for_qa), so
the guard must distinguish a PM/dev owner — which the first reviewer
legitimately overclaims — from a competing reviewer claim; checking the
existing claimant's role (pr_reviewer) does exactly that. A re-claim by
the same reviewer is idempotent (skipped by the != check). The gateway
claim_gate_review handler already maps a None return to a clean
invalid_state envelope ('it may already be claimed; give_me_work for
the next'), so no gateway change is needed.
TDD: 3 integration tests in test_task_service_basics.py — reject a second
reviewer race-claim (returns None, first claim intact), allow the first
reviewer when the PM owns the root (regression guard for the
PM-owns-at-entry model), idempotent re-claim by the same reviewer.
Confirmed the reject test RED first (race-claim succeeded, overwriting
reviewer1).
Renn F
5a5e2b5fa0