/enums/third_party_viewability_integration_partner.proto 

--- v23/enums/third_party_viewability_integration_partner.proto 2026-05-08 16:34:06.000000000 +0000
+++ v24/enums/third_party_viewability_integration_partner.proto 2026-05-08 16:34:16.000000000 +0000
@@ -45,5 +45,8 @@

     // Integral Ad Science.
     INTEGRAL_AD_SCIENCE = 3;
+
+    // Zefr.
+    ZEFR = 4;
   }
 }