test_552_windows_hang.py•1.91 kB
"""Test for issue #552: stdio_client hangs on Windows."""
import sys
from textwrap import dedent
import anyio
import pytest
from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client
@pytest.mark.skipif(sys.platform != "win32", reason="Windows-specific test")
@pytest.mark.anyio
async def test_windows_stdio_client_with_session():
"""
Test the exact scenario from issue #552: Using ClientSession with stdio_client.
This reproduces the original bug report where stdio_client hangs on Windows 11
when used with ClientSession.
"""
# Create a minimal MCP server that responds to initialization
server_script = dedent(
"""
import json
import sys
# Read initialization request
line = sys.stdin.readline()
# Send initialization response
response = {
"jsonrpc": "2.0",
"id": 1,
"result": {
"protocolVersion": "1.0",
"capabilities": {},
"serverInfo": {"name": "test-server", "version": "1.0"}
}
}
print(json.dumps(response))
sys.stdout.flush()
# Exit after a short delay
import time
time.sleep(0.1)
sys.exit(0)
"""
).strip()
params = StdioServerParameters(
command=sys.executable,
args=["-c", server_script],
)
# This is the exact pattern from the bug report
with anyio.fail_after(10):
try:
async with stdio_client(params) as (read, write):
async with ClientSession(read, write) as session:
await session.initialize()
# Should exit ClientSession without hanging
# Should exit stdio_client without hanging
except Exception:
# Connection errors are expected when process exits
pass