Review round 2 (Codex gpt-5.6-terra) found both functions returned a
readback that a concurrent writer could overwrite between the UPDATE
and the SELECT, so the returned record could be the other caller's
values. Both now run existence-check, duplicate scan, UPDATE and
readback inside the DAOs' shared connection-scoped lock. Two gated
concurrency tests prove the contract deterministically: task A paused
at its UPDATE while task B queues, each returns its own values, final
stored state is the last writer's. Suite: 850 passed.
Joshua King
5578507ce8