/errors/multi_party_auth_review_error.proto 

--- v25/errors/multi_party_auth_review_error.proto  2026-07-21 22:09:38.000000000 +0000
+++ v26/errors/multi_party_auth_review_error.proto  2026-11-09 16:22:49.000000000 +0000
@@ -48,5 +48,9 @@

     // The user does not have permission to perform this action.
     PERMISSION_DENIED = 5;
+
+    // The Multi-Party Authorization review is stale because the target resource
+    // was modified or deleted after the review was created.
+    STALE_MULTI_PARTY_AUTH_REQUEST = 6;
   }
 }