Seventh review found the claim-token fix incomplete, and its
reproduction is exact: the pre-POST check was READ-ONLY. A claimant
whose lease expired while suspended still passes it when it wakes
BEFORE anyone reclaims - its token is still in the row - and then a
second process legitimately reclaims while the first one's POST is in
flight. Both send. Reproduced at 60addb16e2: posts ['B', 'A'], both
reporting 'sent'. This is the check-to-POST expiry race, not the
documented mid-POST residual: A's lease was already dead before its
authority check passed.
The check is now an atomic RENEWAL (single CAS UPDATE): it requires the
token to match, the row to be pending, AND the current lease to be
unexpired, and only then extends next_attempt_at a fresh lease into the
future. rowcount == 1 is the only grant. A claimant that wakes past its
own lease fails the unexpired condition and yields even though its
token was never replaced - expiry alone means another process may
claim at any moment, so waking stale is disqualifying regardless of
whether anyone has taken the row yet. The renewed lease (300s) covers
the POST (30s timeout) with margin, and renewal runs before every
retry, not just the first attempt.
Regressions: the reviewer's exact ordering (expired wake before any
reclaim -> zero POSTs, row stays claimable), plus a healthy-claimant
renewal test. Mutation-checked: dropping the lease-unexpired condition
or the token condition each fails the suite.
The at-least-once scope note on _send_one stands: a suspension landing
mid-POST remains client-unfixable; the fixable window is now closed on
both sides (before the check, and between check and POST).
277 tests pass; ruff + footguns clean; staging E2E 202.
4bdabb21ed