HUB: POST heartbeat every five minutes or Mission Control marks the seat offline and stops routing it work. SHAREPOINT: presence - a LastSeen column on the profile plus a view that reads stale as offline. STATUS: the OUTBOUND half is built and gated off; the INBOUND half does not exist, and it is the more interesting one. SPICE has no notion of whether its own agents are alive: the Watchdog health spine writes a rolling row whose freshness is a dead-man switch for the PLATFORM, but nothing says whether a given seat is available to receive work. Do the same trick per principal. The honesty rule matters more than the mechanism - a seat with no heartbeat must read UNKNOWN rather than offline, because never having beaten and having stopped beating are different facts.