fix(win32): ensure proper termination of child processes

- Refactor process termination logic to handle both parent and child processes
- Increase timeout for graceful termination from 1s to 2s
- Consolidate process termination functions to avoid zombie processes
- Add proper type hints for process list handling

This change ensures that all child processes are properly terminated
when killing a parent process on Windows, preventing zombie processes
from being left behind.

Author: jingx8885

pyproject.toml

@@ -31,6 +31,7 @@ dependencies = [
     "sse-starlette>=1.6.1",
     "pydantic-settings>=2.5.2",
     "uvicorn>=0.23.1; sys_platform != 'emscripten'",
+    "psutil>=5.9.0"
 ]
 
 [project.optional-dependencies]

src/mcp/client/stdio/win32.py

@@ -6,8 +6,8 @@
 import subprocess
 import sys
 from pathlib import Path
-from typing import TextIO
-
+from typing import List, TextIO
+import psutil
 import anyio
 from anyio.abc import Process
 
@@ -87,8 +87,17 @@ async def create_windows_process(
         )
         return process
 
-
 async def terminate_windows_process(process: Process):
+    """
+    Terminate a process and subprocesses.
+    """
+    parent = psutil.Process(process.pid)
+    children = parent.children(recursive=True)
+    await terminate_psutil_process(children)
+    await terminate_psutil_process([parent])
+    
+
+async def terminate_psutil_process(processes: List[psutil.Process]):
     """
     Terminate a Windows process.
 
@@ -100,10 +109,20 @@ async def terminate_windows_process(process: Process):
     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()
+    for process in processes:
+        try:
+            process.terminate()  # Send SIGTERM (or equivalent on Windows)
+        except psutil.NoSuchProcess:
+            pass
+        except Exception:
+            pass
+    # Allow some time for children to terminate gracefully
+    _, alive = psutil.wait_procs(processes, timeout=2.0)
+    for child in alive:
+        try:
+            child.kill()  # Force kill if still alive
+        except psutil.NoSuchProcess:
+            pass  # Already gone
+        except Exception:
+            pass
+