/resources/shared_set.proto 

--- v22/resources/shared_set.proto  2026-01-23 15:36:23.000000000 +0000
+++ v23/resources/shared_set.proto  2026-01-23 15:36:31.000000000 +0000
@@ -78,4 +79,12 @@
   // only.
   optional int64 reference_count = 11
       [(google.api.field_behavior) = OUTPUT_ONLY];
+
+  // Immutable. Shared sets of type VERTICAL_ADS_ITEM_GROUP_RULE_LIST are
+  // associated with a particular vertical (e.g. hotels, things to do, flights,
+  // etc.). This field is required for shared sets of type
+  // VERTICAL_ADS_ITEM_GROUP_RULE_LIST.
+  optional google.ads.googleads.v23.enums.VerticalAdsItemVerticalTypeEnum
+      .VerticalAdsItemVerticalType vertical_ads_item_vertical_type = 12
+      [(google.api.field_behavior) = IMMUTABLE];
 }