Remove unnecessary request_params from RequestResponder

Access task metadata directly from req.params instead of storing it
separately on RequestResponder. This simplifies the code and removes
an unnecessary indirection that was added during task refactoring.

Author: maxisbey

src/mcp/server/lowlevel/server.py

@@ -723,14 +723,18 @@ async def _handle_request(
                 # app.get_request_context()
                 client_capabilities = session.client_params.capabilities if session.client_params else None
                 task_support = self._experimental_handlers.task_support if self._experimental_handlers else None
+                # Get task metadata from request params if present
+                task_metadata = None
+                if hasattr(req, "params") and req.params is not None:
+                    task_metadata = getattr(req.params, "task", None)
                 token = request_ctx.set(
                     RequestContext(
                         message.request_id,
                         message.request_meta,
                         session,
                         lifespan_context,
                         Experimental(
-                            task_metadata=message.request_params.task if message.request_params else None,
+                            task_metadata=task_metadata,
                             _client_capabilities=client_capabilities,
                             _session=session,
                             _task_support=task_support,

src/mcp/shared/session.py

@@ -82,11 +82,9 @@ def __init__(
         ]""",
         on_complete: Callable[["RequestResponder[ReceiveRequestT, SendResultT]"], Any],
         message_metadata: MessageMetadata = None,
-        request_params: RequestParams | None = None,
     ) -> None:
         self.request_id = request_id
         self.request_meta = request_meta
-        self.request_params = request_params
         self.request = request
         self.message_metadata = message_metadata
         self._session = session
@@ -371,7 +369,6 @@ async def _receive_loop(self) -> None:
                                 session=self,
                                 on_complete=lambda r: self._in_flight.pop(r.request_id, None),
                                 message_metadata=message.metadata,
-                                request_params=validated_request.root.params,
                             )
                             self._in_flight[responder.request_id] = responder
                             await self._received_request(responder)