# Contract Testing

Fixtures cover HTTP responses, authenticated WebSocket events, errors, permissions,
version negotiation, reconnects, and server-owned state transitions. Fixtures are
deterministic, synthetic, and secret-free. Every new contract must include at
least one valid fixture and a negative case where validation rules are important.

The current realtime envelope is deliberately transport-neutral: the server may
deliver it over an authenticated WebSocket or a future compatible transport, but
the event identity and payload rules remain the same. `event_id` is the stable
deduplication key for at-least-once delivery.