Review round 1 (Codex gpt-5.6-terra, LOW): the racing test completed
synchronously and proved nothing. The executor now gates task A's
INSERT — inside its open transaction, after its overlap probe — so
task B queues on the connection lock, re-runs the probe against A's
committed row, and is rejected; exactly one lands. Suite: 990 passed.
The matrix test's end-before-start probe (expecting the schema's
end>=start IntegrityError) hit the new overlap query first, since an
inverted range lexically 'overlaps' the seeded row. The overlap
check now runs only for well-ordered ranges; invalid ones fall
through to the INSERT and keep the IntegrityError contract. Suite:
990 passed.
PresenceOverridesDao.create now refuses an override that overlaps any
existing override of the SAME child (inclusive boundaries): the check
runs inside the same transaction as the INSERT under the connection
lock, so a racing create cannot slip a conflict between check and
write — a deterministic race test proves exactly one of two concurrent
overlapping creates lands. The ValueError names the conflicting
override's id, its range, and its flag. Round-trip, per-child scope,
and remove-then-recreate tests added. Suite: 990 passed.
Joshua King