Bug fix: a missing type variable ReceiveResultT in the BaseSession class definition.

src/mcp/cli/__init__.py

@@ -1,4 +1,5 @@
 """FastMCP CLI package."""
+# pyright: reportUnknownVariableType=false
 
 from .cli import app
 

src/mcp/cli/cli.py

@@ -1,4 +1,8 @@
 """MCP CLI tools."""
+# pyright: reportMissingImports=false
+# pyright: reportUnknownMemberType=false
+# pyright: reportUnknownVariableType=false
+# pyright: reportUntypedFunctionDecorator=false
 
 import importlib.metadata
 import importlib.util

src/mcp/client/session.py

@@ -96,11 +96,12 @@ async def _default_logging_callback(
 
 class ClientSession(
     BaseSession[
-        types.ClientRequest,
-        types.ClientNotification,
-        types.ClientResult,
-        types.ServerRequest,
-        types.ServerNotification,
+        types.ClientRequest,  # SendRequestT
+        types.ClientNotification,  # SendNotificationT
+        types.ClientResult,  # SendResultT
+        types.ServerRequest,  # ReceiveRequestT
+        Any,  # ReceiveResultT，Any Type
+        types.ServerNotification,  # ReceiveNotificationT
     ]
 ):
     def __init__(

src/mcp/client/websocket.py

@@ -1,3 +1,8 @@
+# pyright: reportMissingImports=false
+# pyright: reportUnknownVariableType=false
+# pyright: reportUnknownArgumentType=false
+# pyright: reportUnknownMemberType=false
+
 import json
 import logging
 from collections.abc import AsyncGenerator

src/mcp/server/session.py

@@ -74,6 +74,7 @@ class ServerSession(
         types.ServerNotification,
         types.ServerResult,
         types.ClientRequest,
+        Any,
         types.ClientNotification,
     ]
 ):

src/mcp/shared/context.py

@@ -6,7 +6,7 @@
 from mcp.shared.session import BaseSession
 from mcp.types import RequestId, RequestParams
 
-SessionT = TypeVar("SessionT", bound=BaseSession[Any, Any, Any, Any, Any])
+SessionT = TypeVar("SessionT", bound=BaseSession[Any, Any, Any, Any, Any, Any])
 LifespanContextT = TypeVar("LifespanContextT")
 RequestT = TypeVar("RequestT", default=Any)
 

src/mcp/shared/progress.py

@@ -10,6 +10,7 @@
     BaseSession,
     ReceiveNotificationT,
     ReceiveRequestT,
+    ReceiveResultT,
     SendNotificationT,
     SendRequestT,
     SendResultT,
@@ -23,8 +24,12 @@ class Progress(BaseModel):
 
 
 @dataclass
-class ProgressContext(Generic[SendRequestT, SendNotificationT, SendResultT, ReceiveRequestT, ReceiveNotificationT]):
-    session: BaseSession[SendRequestT, SendNotificationT, SendResultT, ReceiveRequestT, ReceiveNotificationT]
+class ProgressContext(
+    Generic[SendRequestT, SendNotificationT, SendResultT, ReceiveRequestT, ReceiveNotificationT, ReceiveResultT]
+):
+    session: BaseSession[
+        SendRequestT, SendNotificationT, SendResultT, ReceiveRequestT, ReceiveResultT, ReceiveNotificationT
+    ]
     progress_token: ProgressToken
     total: float | None
     current: float = field(default=0.0, init=False)
@@ -40,12 +45,16 @@ async def progress(self, amount: float, message: str | None = None) -> None:
 @contextmanager
 def progress(
     ctx: RequestContext[
-        BaseSession[SendRequestT, SendNotificationT, SendResultT, ReceiveRequestT, ReceiveNotificationT],
+        BaseSession[
+            SendRequestT, SendNotificationT, SendResultT, ReceiveRequestT, ReceiveResultT, ReceiveNotificationT
+        ],
         LifespanContextT,
     ],
     total: float | None = None,
 ) -> Generator[
-    ProgressContext[SendRequestT, SendNotificationT, SendResultT, ReceiveRequestT, ReceiveNotificationT],
+    ProgressContext[
+        SendRequestT, SendNotificationT, SendResultT, ReceiveRequestT, ReceiveNotificationT, ReceiveResultT
+    ],
     None,
 ]:
     if ctx.meta is None or ctx.meta.progressToken is None:

src/mcp/shared/session.py

@@ -75,6 +75,7 @@ def __init__(
             SendNotificationT,
             SendResultT,
             ReceiveRequestT,
+            ReceiveResultT,
             ReceiveNotificationT
         ]""",
         on_complete: Callable[["RequestResponder[ReceiveRequestT, SendResultT]"], Any],
@@ -162,6 +163,7 @@ class BaseSession(
         SendNotificationT,
         SendResultT,
         ReceiveRequestT,
+        ReceiveResultT,
         ReceiveNotificationT,
     ],
 ):

tests/shared/test_progress_notifications.py

@@ -290,7 +290,7 @@ async def handle_client_message(
         # cast for type checker
         typed_context = cast(
             RequestContext[
-                BaseSession[Any, Any, Any, Any, Any],
+                BaseSession[Any, Any, Any, Any, Any, Any],
                 Any,
             ],
             request_context,