Fix: Resolve CancelScope error in McpToolset session creation (issue #5729)

src/google/adk/tools/mcp_tool/session_context.py

@@ -1,4 +1,4 @@
-# Copyright 2025 Google LLC
+# Copyright 2026 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -9,7 +9,7 @@
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
+# See the License for the specific language governing permissions and:
 # limitations under the License.
 
 from __future__ import annotations
@@ -54,6 +54,9 @@ def __init__(
       timeout: Optional[float],
       sse_read_timeout: Optional[float],
       is_stdio: bool = False,
+      *,
+      sampling_callback: Optional[object] = None,
+      sampling_capabilities: Optional[object] = None,
   ):
     """
     Args:
@@ -63,6 +66,9 @@ def __init__(
         sse_read_timeout: Timeout in seconds for reading data from the MCP SSE
             server.
         is_stdio: Whether this is a stdio connection (affects read timeout).
+        sampling_callback: Optional callback to handle sampling requests from the
+            MCP server.
+        sampling_capabilities: Optional capabilities for sampling.
     """
     self._client = client
     self._timeout = timeout
@@ -140,7 +146,7 @@ async def close(self):
     except Exception as e:
       logger.warning(f'Failed to close MCP session: {e}')
 
-  async def __aenter__(self) -> ClientSession:
+  async def __a_enter__(self) -> ClientSession:
     return await self.start()
 
   async def __aexit__(self, exc_type, exc_val, exc_tb):
@@ -150,10 +156,7 @@ async def _run(self):
     """Run the complete session context within a single task."""
     try:
       async with AsyncExitStack() as exit_stack:
-        transports = await asyncio.wait_for(
-            exit_stack.enter_async_context(self._client),
-            timeout=self._timeout,
-        )
+        transports = await exit_stack.enter_async_context(self._client)
         # The streamable http client returns a GetSessionCallback in addition
         # to the read/write MemoryObjectStreams needed to build the
         # ClientSession. We limit to the first two values to be compatible