fix: log the exception of graph execution (#577)

* fix: log the exeption of graph execution

* Update src/server/app.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/server/app.py

@@ -4,7 +4,7 @@
 import base64
 import json
 import logging
-from typing import Annotated, List, cast
+from typing import Annotated, Any, List, cast
 from uuid import uuid4
 
 from fastapi import FastAPI, HTTPException, Query
@@ -244,6 +244,7 @@ async def _stream_graph_events(
     graph_instance, workflow_input, workflow_config, thread_id
 ):
     """Stream events from the graph and process them."""
+    try:
         async for agent, _, event_data in graph_instance.astream(
             workflow_input,
             config=workflow_config,
@@ -256,13 +257,23 @@ async def _stream_graph_events(
                 continue
 
             message_chunk, message_metadata = cast(
-            tuple[BaseMessage, dict[str, any]], event_data
+                tuple[BaseMessage, dict[str, Any]], event_data
             )
 
             async for event in _process_message_chunk(
                 message_chunk, message_metadata, thread_id, agent
             ):
                 yield event
+    except Exception as e:
+        logger.exception("Error during graph execution")
+        yield _make_event(
+            "error",
+            {
+                "thread_id": thread_id,
+                "error": str(e),
+            },
+        )
+
 
 
 async def _astream_workflow_generator(