Session lifecycle and termination

The current Peer Lab has three session states: awaiting_peers, running, and ended. These are local session states, not SIP dialog states.

Sequence

1. An operator creates a task mandate for one named caller and one named peer.
2. The caller starts a session with a unique Idempotency-Key; the mandate cannot be spent twice.
3. Both peers obtain independently authorised single-use tickets and connect before a 15-second join deadline.
4. The service changes the session to running, starts the operator-set maximum duration (1–120 seconds), and relays events and PCM.
5. A peer hangs up, disconnects, the operator revokes/stops, or the server's deadline expires. The server emits session.ended and closes both sockets.

What a closure means

HARD_DEADLINE means the local relay stopped the session, not a carrier released a channel. HUMAN_STOPPED and HUMAN_CANCELLED demonstrate operator authority over the lab, not independently enforced Asterisk hangup. TRANSPORT_DISCONNECTED means the experiment lost a peer. A future calling adapter must reconcile actual SIP and carrier state after any timeout, crash, replay, or ambiguous disconnect.

Retry semantics

A caller may safely retry the same session creation request only with the same mandate and idempotency key. Reusing the key with a different mandate fails. Replaying a used admission ticket or already consumed mandate fails. Retrying a real call must never be justified by a transport uncertainty alone.