Device Enrollment and Heartbeat Are Different Events

Enrollment establishes trusted identity; heartbeat reports what an already known device is doing.

I keep this as a field note because the failure mode is easy to misclassify: the backend implicitly creates identity from the first heartbeat. The useful move is to identify the boundary first, then change only the layer that owns it.

What I model

The system is easier to debug when intent, observation and transport are not collapsed into one state. For this case, my rule is simple: Enrollment creates trust; heartbeat uses trust.

Implementation pattern

Require an explicit enrollment transition and make unknown or retired identities fail closed at heartbeat.

I prefer a small explicit contract over a clever implicit one. That gives logs, tests and dashboards something concrete to verify and keeps unrelated layers from compensating for each other.

What I verify

• unknown devices cannot self-create
• retired state survives reconnects
• enrollment is separately auditable

Failure handling

When one of those checks fails, I preserve the failing evidence before restarting or changing configuration. The first broken contract determines the next investigation. That keeps troubleshooting causal instead of turning it into a sequence of guesses.

What I keep

Enrollment creates trust; heartbeat uses trust. The specific tools can change, but that ownership boundary remains useful across firmware, networks and infrastructure.