mls_governance_anchor_unreachable· code· HTTP 409· scope endpoint· applies to endpointThe exact canonical proof_target_basis does not dominate the exact caller-supplied, locally trusted canonical proof_base_basis: at least one base leaf is neither retained as a target leaf nor an ancestor of a target leaf. Concurrent or otherwise unreachable cuts produce this error; byte-identical base and target antichains are a valid zero-transition query and MUST NOT produce it. Missing required RealmCommit/Event/witness material that prevents the service from deciding dominance is revision_unavailable instead. The service MUST NOT substitute a single head, common descendant, target, or untrusted base. The caller MAY retry only with another complete locally trusted basis or another authorized proof service.