fix: Refine the confusing error message.

DeanChensj · copybara-github · commit c39f24f07202 · 2025-05-12T11:20:54.000-07:00
PiperOrigin-RevId: 757841288
diff --git a/src/google/adk/sessions/database_session_service.py b/src/google/adk/sessions/database_session_service.py
@@ -484,11 +484,12 @@ def append_event(self, session: Session, event: Event) -> Event:
 
       if storage_session.update_time.timestamp() > session.last_update_time:
         raise ValueError(
-          f"Session last_update_time "
-          f"{datetime.fromtimestamp(session.last_update_time):%Y-%m-%d %H:%M:%S} "
-          f"is later than the update_time in storage "
-          f"{storage_session.update_time:%Y-%m-%d %H:%M:%S}"
-      )
+            "The last_update_time provided in the session object"
+            f" {datetime.fromtimestamp(session.last_update_time):'%Y-%m-%d %H:%M:%S'} is"
+            " earlier than the update_time in the storage_session"
+            f" {storage_session.update_time:'%Y-%m-%d %H:%M:%S'}. Please check"
+            " if it is a stale session."
+        )
 
       # Fetch states from storage
       storage_app_state = sessionFactory.get(
