keypackage_welcome_envelope_mismatch· reason_code· applies to event_envelope, auth_decisionAn MLS Welcome arrived with a `claim_envelope` whose canonical signing input does not match the Welcome's actual intended_realm_id / claim_id / requester_actor_id, or the envelope signature does not chain to the requester's PCR current accepted device signing key and authorization Event. See zh/crypto-media/encryption-and-audit.md §2.6.