add agnostic message type

Author: sreenithi

src/mcp/client/base_client_session.py

@@ -10,6 +10,7 @@
 
 class BaseClientSession(
     CommonBaseSession[
+        Any,
         types.ClientRequest,
         types.ClientNotification,
         types.ClientResult,

src/mcp/shared/_context.py

@@ -8,7 +8,7 @@
 from mcp.shared.session import CommonBaseSession
 from mcp.types import RequestId, RequestParamsMeta
 
-SessionT_co = TypeVar("SessionT_co", bound=CommonBaseSession[Any, Any, Any, Any, Any], covariant=True)
+SessionT_co = TypeVar("SessionT_co", bound=CommonBaseSession[Any, Any, Any, Any, Any, Any], covariant=True)
 
 
 @dataclass(kw_only=True)

src/mcp/shared/message.py

@@ -6,6 +6,7 @@
 
 from collections.abc import Awaitable, Callable
 from dataclasses import dataclass
+from typing import TypeVar
 
 from mcp.types import JSONRPCMessage, RequestId
 
@@ -40,6 +41,8 @@ class ServerMessageMetadata:
 
 MessageMetadata = ClientMessageMetadata | ServerMessageMetadata | None
 
+WireMessageT = TypeVar("WireMessageT")
+
 
 @dataclass
 class SessionMessage:

src/mcp/shared/session.py

@@ -13,7 +13,7 @@
 from typing_extensions import Self
 
 from mcp.shared.exceptions import MCPError
-from mcp.shared.message import MessageMetadata, ServerMessageMetadata, SessionMessage
+from mcp.shared.message import MessageMetadata, ServerMessageMetadata, SessionMessage, WireMessageT
 from mcp.shared.response_router import ResponseRouter
 from mcp.types import (
     CONNECTION_CLOSED,
@@ -158,6 +158,7 @@ def cancelled(self) -> bool:
 class CommonBaseSession(
     ABC,
     Generic[
+        WireMessageT,
         SendRequestT,
         SendNotificationT,
         SendResultT,
@@ -176,8 +177,8 @@ class CommonBaseSession(
 
     def __init__(
         self,
-        read_stream: MemoryObjectReceiveStream[SessionMessage | Exception] | None = None,
-        write_stream: MemoryObjectSendStream[SessionMessage] | None = None,
+        read_stream: MemoryObjectReceiveStream[WireMessageT | Exception] | None = None,
+        write_stream: MemoryObjectSendStream[WireMessageT] | None = None,
         # If none, reading will never time out
         read_timeout_seconds: float | None = None,
     ) -> None:
@@ -228,6 +229,7 @@ async def send_progress_notification(
 
 class BaseSession(
     CommonBaseSession[
+        SessionMessage,
         SendRequestT,
         SendNotificationT,
         SendResultT,