diff --git a/temporal/api/history/v1/message.proto b/temporal/api/history/v1/message.proto
index af7901fe..2f430755 100644
--- a/temporal/api/history/v1/message.proto
+++ b/temporal/api/history/v1/message.proto
@@ -842,6 +842,8 @@ message NexusOperationStartedEventAttributes {
 
     // The request ID allocated at schedule time.
     string request_id = 4;
+    // The Nexus handler reported operation start time.
+    google.protobuf.Timestamp start_time = 5;
 }
 
 // Nexus operation completed successfully.