Session not found under a green health check

MCP Session and the DataSignals Lab Standby/FastMCP operator note describe a deceptively healthy failure: the health check is green while the session the operator needs cannot be found. Liveness of the service is not proof that the session registry, routing key, or resumable state is present.

Treat health and session existence as separate checks. Record the session identifier, lookup scope, and last-seen evidence, then make “green but missing” an explicit state instead of sending an operator into retries that cannot recover a session the control plane has already lost.