A periodic reconcile can synthesize a repair transition whose matching live
transition is still buffered in the alarm lease; both then broadcast as
indistinguishable duplicates on StreamAlarms and the dashboard hub. Nothing
serializes the two paths, and a correct serialization needs a worker-side
high-water mark on QueryActiveAlarms (proto + worker change + a stall path),
so this closes the common case with a local best-effort dedup instead: both
paths already carry the same worker-derived identity — the worker stamps
record.TransitionTimestampUtc into both OnAlarmTransitionEvent's
transition_timestamp and ActiveAlarmSnapshot.last_transition_timestamp — so
ApplyTransition suppresses a live transition whose (timestamp, resulting
state) the cache already carries from a repair. The Clear leg has no cache
entry left to compare, so ApplyReconcile tombstones each synthesized Clear by
the instance's original_raise_timestamp for one reconcile generation; a
matching live Clear consumes the tombstone, while a new raise/clear cycle
carries a newer raise timestamp and passes. Suppression fires only on a
positive marker match — unset timestamps keep today's behavior — so the
documented at-least-once consumer contract stands (gateway.md, Sessions.md
updated in the same change).
Tests: two new regressions drive the exact race through the GWC-26 harness
(repair-then-buffered-live for Raise and for Clear, each with a genuine
follow-up transition proving no over-suppression); GatewayAlarmMonitor
suites 18/18.
Joseph Doherty
2c03e0a684