Simplify stdio cleanup: unified stream cleanup across platforms

Copy of #555

Testing shows PR #559 stream cleanup alone prevents hanging,
even with servers that ignore SIGTERM and keep streams open.

Removes all timeout logic and Windows-specific termination
function in favor of unified `process.terminate()`.

Author: felixweinberger

src/mcp/client/stdio/__init__.py

@@ -16,7 +16,6 @@
 from .win32 import (
     create_windows_process,
     get_windows_executable_command,
-    terminate_windows_process,
 )
 
 # Environment variables to inherit by default
@@ -180,10 +179,12 @@ async def stdin_writer():
         finally:
             # Clean up process to prevent any dangling orphaned processes
             try:
-                if sys.platform == "win32":
-                    await terminate_windows_process(process)
-                else:
-                    process.terminate()
+                process.terminate()
+                with anyio.fail_after(2.0):
+                    await process.wait()
+            except TimeoutError:
+                # If process doesn't terminate in time, force kill it
+                process.kill()
             except ProcessLookupError:
                 # Process already exited, which is fine
                 pass

src/mcp/client/stdio/win32.py

@@ -8,9 +8,7 @@
 from pathlib import Path
 from typing import BinaryIO, TextIO, cast
 
-import anyio
 from anyio import to_thread
-from anyio.abc import Process
 from anyio.streams.file import FileReadStream, FileWriteStream
 
 
@@ -159,24 +157,3 @@ async def create_windows_process(
             bufsize=0,
         )
         return FallbackProcess(popen_obj)
-
-
-async def terminate_windows_process(process: Process | FallbackProcess):
-    """
-    Terminate a Windows process.
-
-    Note: On Windows, terminating a process with process.terminate() doesn't
-    always guarantee immediate process termination.
-    So we give it 2s to exit, or we call process.kill()
-    which sends a SIGKILL equivalent signal.
-
-    Args:
-        process: The process to terminate
-    """
-    try:
-        process.terminate()
-        with anyio.fail_after(2.0):
-            await process.wait()
-    except TimeoutError:
-        # Force kill if it doesn't terminate
-        process.kill()