Presence

Presence is the platform's real-time view of whether a device is currently connected: online, offline, or unknown.

• A presence boundary is an online/offline transition event (connect, disconnect, session eviction).
• Connection state is derived from the latest boundary; unknown means the device has never produced one.
• Last activity is the newer of the latest telemetry and the latest presence boundary, shown when hovering the connection badge.

Presence answers "is it connected now"; lifecycle state answers "what operational status is it in" (active, quarantined, decommissioned). The two are independent.

For a passive sub-device, presence does not prove field-bus reachability: it can stay online after the device itself drops off. An on-demand probe verifies that end-to-end.