Constants: BULK_DISAPPEARANCE_RATIO = 0.5 and BULK_DISAPPEARANCE_MIN_COUNT = 3. Both must be met. The minimum count exists because a ratio alone jams small feeds permanently: a feed with exactly one booking that vanishes is "100% missing", the guard trips forever, and the booking can never be flagged, never accrue absence, and never cancel — the host is never told. Lemon found this in production in September 2026 (10 of 18 feeds carried two or fewer active bookings) and added the floor.
When the guard trips, the decision bulk_guard_triggered is logged and nothing else happens that cycle.