governance_binding_mismatch· reason_code· applies to event_envelope, state_resolution, federation_transactionAn MLS Commit's mls_governance_binding GroupContext extension does not match the accepted key-access state, Event payload or active epoch chain: scope/base/epoch fields disagree, the unsigned monotonic key_access_revision counter differs from the Station's accepted key-access revision, or extension bytes differ from the Event payload. The receiver MUST reject the Commit - and, on a federation push, the batch - rather than advance an epoch under a forged or stale binding. See zh/crypto-media/encryption-and-audit.md §2.5.