After Steward or its database was down, every agent's age and every series' last sample were old, so all agent-offline rules fired and all rules went no-data at once, clearing a minute later. With per-account alert email that would have mailed everyone a dozen notices per restart. A periodic job now ticks a Watch (steward/core/watch.py) once it has reached the database; the Watch says since when runs have been unbroken (process start, or the end of a gap over 120 s). seconds_since_seen and the no-data sweep count silence from no earlier than that, so a source must stay quiet while Steward is watching before it counts as silent. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>