mimi_observer_write_forbidden· reason_code· applies to service_call, authzThe current accepted MIMI room binding has local_provider_role=observer during ak.open.mimi.command.submit_message.v1. The registered observer_role_guard rejects the whole request before Event construction, persistence, receipt or fanout, with zero write effect. Producer path: contract-registry.json operation_registry admission_guards. See zh/extensions/mimi-interop.md §7.