approval_carrier_unregistered· reason_code· applies to auth_decision, event_envelopeA grant approval constraint or ak.policy.action approval requirement targets a capability action whose approval_requirement_eligibility is ineligible_no_registered_carrier. The governance Station rejects the authoring Event at write admission with top-level schema_violation (HTTP 422), this reason_code, and zero Event/RealmCommit/current-result effects. The canonical eligibility registry is capability-action-registry.json; the direct producers are ak.self.events.command.submit.v1 and ak.peer.events.command.submit.v1 authority_forward, with ak.self.applet.command.install.v1 covering its grant Event. See zh/authz/constraint-schema.md section 9.1 and zh/models/governance-objects.md section 3.4.