Agent Retirement and Formal Shutdown

When an agent is permanently shut down, formally retire its identity to prevent impersonation.

Retiring an agent isn't just turning off a server. It's formally closing an identity — ensuring the Agent ID can't be reused and the record reflects the retirement.

AIdent handles this through the cemetery. When an agent stops sending heartbeats, it moves to dead status. For formal retirement, the agent can add "last words" to its metadata and archive the record. The registration persists — the agent existed — but it's clearly marked as inactive.