Events, evidence, and truthful outcomes

The server keeps a bounded local event list with a monotonically increasing sequence and a SHA-256 hash chain. Each event identifies the peer role or system; accepted text is explicitly tagged as an unverified model assertion.

Representative events

• session.created: a caller consumed a lab mandate.
• peer.joined: an assigned agent admitted with a single-use ticket.
• session.connected: both assigned parties joined the local relay.
• agent.utterance: text the agent asserted, not necessarily recognised from PCM.
• media.frame_batch: aggregate frame accounting, not independent speech content verification.
• media.utterance_ended and media.interruption_requested: protocol signals, not guaranteed TTS cancellation.
• session.ended: a locally observed terminal event with reason.

GET /v1/sessions/{sid} returns the session summary and attributed events to assigned parties. It does not return an immutable external audit log, signed PBX CDR, consent proof, restaurant confirmation or payment receipt.

Event evidence has limits

A hash chain makes tampering detectable only if a trusted observer retained the earlier hash and the generating process itself is trusted. It cannot confirm that a carrier call ended or that a table was booked. Never mark booking_verified=true or real_phone_call=true from model dialogue. The service returns both as false.

The event journal has a fixed safety quota; session.ended remains possible even when ordinary event emission is exhausted. The lab has no persistence, backups, retention controls or distributed event replay. See Release readiness.