Rule 5 of Lemon's sync. The justification is a cost asymmetry: a false cancel the night before a turnover cannot be recovered in time (cleaner stood down, guest arrives to a dirty flat, review lost), while a false keep costs one visit to an empty apartment. When in doubt inside the window, keep and ask the host.
The constant is IMMINENT_CANCEL_PROTECTION_MS = 24h. In the 30 days to 2026-09-10 it produced 11 imminent_protected decisions — more than the 10 automatic cancellations in the same period.