fix: Simplify exception handling and refactor error messaging (#4496)

* Refactor `ExceptionWithMessageError` to remove redundant exception parameter

* Handle nested exceptions in message schema initialization

* fix: Simplify exception handling in LCAgentComponent

src/backend/base/langflow/base/agents/agent.py

@@ -160,7 +160,7 @@ class LCAgentComponent(Component):
             msg_id = e.agent_message.id
             await asyncio.to_thread(delete_message, id_=msg_id)
             self._send_message_event(e.agent_message, category="remove_message")
-            raise e.exception  # noqa: B904
+            raise
         except Exception:
             raise
 

src/backend/base/langflow/base/agents/events.py

@@ -14,9 +14,8 @@ from langflow.schema.message import Message
 
 
 class ExceptionWithMessageError(Exception):
-    def __init__(self, e: Exception, agent_message: Message):
+    def __init__(self, agent_message: Message):
         self.agent_message = agent_message
-        self.exception = e
         super().__init__()
 
 
@@ -253,5 +252,5 @@ async def process_agent_events(
                 start_time = start_time or perf_counter()
         agent_message.properties.state = "complete"
     except Exception as e:
-        raise ExceptionWithMessageError(e, agent_message) from e
+        raise ExceptionWithMessageError(agent_message) from e
     return Message(**agent_message.model_dump())

src/backend/base/langflow/schema/message.py

@@ -339,12 +339,15 @@ class ErrorMessage(Message):
 
     def __init__(
         self,
-        exception: Exception,
+        exception: BaseException,
         session_id: str,
         source: Source,
         trace_name: str | None = None,
         flow_id: str | None = None,
     ) -> None:
+        # This is done to avoid circular imports
+        if exception.__class__.__name__ == "ExceptionWithMessageError" and exception.__cause__ is not None:
+            exception = exception.__cause__
         # Get the error reason
         reason = f"**{exception.__class__.__name__}**\n"
         if hasattr(exception, "body") and "message" in exception.body: