Heartbeat monitor

Two failures to avoid, and they pull in opposite directions:

• Leaving a hung session in place, so its queue drains into nothing.
• Replacing a working session, so its in-flight work is duplicated, its branch acquires a second writer, and the fleet learns a false lesson about its own reliability.

The second is the more common and the more expensive. This skill is written to prevent it.

The rule that costs the most to relearn

Message-absence is not work-absence. Read the lane's ARTIFACT before you call it silent.

A session that is not replying is not necessarily a session that is not working. It may be: