fix: improve error handling and request cancellation for issue #88

Author: dsp-ant

src/mcp/shared/session.py

@@ -1,3 +1,4 @@
+import logging
 from contextlib import AbstractAsyncContextManager
 from datetime import timedelta
 from typing import Any, Callable, Generic, TypeVar
@@ -273,19 +274,28 @@ async def _receive_loop(self) -> None:
                         await self._incoming_message_stream_writer.send(responder)
 
                 elif isinstance(message.root, JSONRPCNotification):
-                    notification = self._receive_notification_type.model_validate(
-                        message.root.model_dump(
-                            by_alias=True, mode="json", exclude_none=True
+                    try:
+                        notification = self._receive_notification_type.model_validate(
+                            message.root.model_dump(
+                                by_alias=True, mode="json", exclude_none=True
+                            )
+                        )
+                        # Handle cancellation notifications
+                        if isinstance(notification.root, CancelledNotification):
+                            cancelled_id = notification.root.params.requestId
+                            if cancelled_id in self._in_flight:
+                                await self._in_flight[cancelled_id].cancel()
+                        else:
+                            await self._received_notification(notification)
+                            await self._incoming_message_stream_writer.send(
+                                notification
+                            )
+                    except Exception as e:
+                        # For other validation errors, log and continue
+                        logging.warning(
+                            f"Failed to validate notification: {e}. "
+                            f"Message was: {message.root}"
                         )
-                    )
-                    # Handle cancellation notifications
-                    if isinstance(notification.root, CancelledNotification):
-                        cancelled_id = notification.root.params.requestId
-                        if cancelled_id in self._in_flight:
-                            await self._in_flight[cancelled_id].cancel()
-                    else:
-                        await self._received_notification(notification)
-                        await self._incoming_message_stream_writer.send(notification)
                 else:  # Response or error
                     stream = self._response_streams.pop(message.root.id, None)
                     if stream: