diff --git a/nativelink-util/src/action_messages.rs b/nativelink-util/src/action_messages.rs
index 780e83eb997..c27a06dff63 100644
--- a/nativelink-util/src/action_messages.rs
+++ b/nativelink-util/src/action_messages.rs
@@ -1302,3 +1302,5 @@ impl ActionState {
         }
     }
 }
+
+// x2 code-only probe vs x2-base