snapshot_capacity_exceeded· reason_code· applies to event_envelope, auth_decisionThe candidate RealmCommit would make the maximal-disclosure, current governance Station-signed inline Realm State Snapshot exceed 8 MiB of complete RFC 8785 canonical signed bytes. Every operation branch that first admits an Event and signs a RealmCommit rechecks the final durable cut in the same transaction; overflow returns top-level failed_precondition (HTTP 409) with this reason_code and zero Event, RealmCommit, typed current, and snapshot writes. Exact 8 MiB is allowed. See zh/conformance/scalability-constraints.md section 4.1 and fixtures/scalability-limits-fixture.json.