fix: Refactor session retrieval fallback _streaming_agent_run_with_events.

PiperOrigin-RevId: 868781249

Author: Tongzhou-Jiang

vertexai/agent_engines/templates/adk.py

@@ -1190,6 +1190,8 @@ async def streaming_agent_run_with_events(self, request_json: str):
                     session_id=request.session_id,
                 )
             except ClientError:
+                session = None
+            if not session:
                 #  Fall back to create session if the session is not found.
                 #  Specifying session_id on creation is not supported,
                 #  so session id will be regenerated.

vertexai/preview/reasoning_engines/templates/adk.py

@@ -1024,7 +1024,11 @@ async def _invoke_agent_async():
                         session_id=request.session_id,
                     )
                 except ClientError:
+                    session = None
+                if not session:
                     #  Fall back to create session if the session is not found.
+                    #  Specifying session_id on creation is not supported,
+                    #  so session id will be regenerated.
                     session = await self._init_session(
                         session_service=session_service,
                         artifact_service=artifact_service,