/enums/conversion_action_category.proto 

--- v25/enums/conversion_action_category.proto  2026-10-09 20:58:00.000000000 +0000
+++ v26/enums/conversion_action_category.proto  2026-10-09 20:58:04.000000000 +0000
@@ -113,6 +113,10 @@
     // or a video from the same channel as the ad.
     YOUTUBE_FOLLOW_ON_VIEWS = 24;

+    // A message or chat interaction to indicate interest in an advertiser's
+    // offering.
+    MESSAGE_LEAD = 25;
+
     // An in-app ad revenue conversion.
     IN_APP_AD_REVENUE = 26;
   }