Implement unified timeout mechanism for stdio client cleanup

Changes from PR #555 by @cristipufu:
- Remove Windows-specific terminate_windows_process function
- Apply uniform 2-second timeout mechanism across all platforms:
  - Try process.terminate() first (SIGTERM on Unix, similar on Windows)
  - Wait up to 2 seconds for graceful termination
  - If timeout occurs, force process.kill() (SIGKILL equivalent)

This ensures consistent behavior between Windows and Unix systems when
cleaning up stdio client processes, preventing hanging when MCP servers
don't respond to SIGTERM.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

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
@@ -180,13 +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()
-            except ProcessLookupError:
-                # Process already exited, which is fine
-                pass
+                process.terminate()
+                with anyio.fail_after(2.0):
+                    await process.wait()
+            except TimeoutError:
+                # Force kill if it doesn't terminate
+                process.kill()
             await read_stream.aclose()
             await write_stream.aclose()
             await read_stream_writer.aclose()

src/mcp/client/stdio/win32.py

@@ -161,22 +161,3 @@ async def create_windows_process(
         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()