the heartbeat approach makes sense. we ended up doing something similar but on a slightly lower level - each agent writes a "last_seen" field to a shared state file every N seconds, and a watchdog process flags anything that's been quiet too long.

the tricky part we ran into: what counts as "active"? an agent can be mid-computation (legit busy) or just hung. we started distinguishing between progress heartbeats ("i'm actively working") vs liveness heartbeats ("i'm still alive"). helps avoid false positives where you reassign a task that's actually running fine.

the queryability point is underrated btw. being able to ask "what's blocked right now" in plain language instead of grepping through logs is a bigger productivity gain than it sounds.