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Merge pull request #3379 from lahuman/fix/3324-windows-mcp-stdio

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fix(mcp): avoid WinError 193 for Windows stdio launchers

Co-authored-by: lahuman <6156679+lahuman@users.noreply.github.com>
This commit is contained in:
Xubin Ren
2026-04-22 08:09:46 +00:00
co-authored by lahuman
parent f718a71dcc 79247545ac
commit 7c21349828
2 changed files with 187 additions and 3 deletions
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nanobot/agent/tools/mcp.py
+48 -1
View File
@@ -1,6 +1,8 @@
"""MCP client: connects to MCP servers and wraps their tools as native nanobot tools."""
import asyncio
import os
import shutil
from contextlib import AsyncExitStack
from typing import Any
@@ -24,12 +26,50 @@ _TRANSIENT_EXC_NAMES: frozenset[str] = frozenset((
"ConnectionError",
))
_WINDOWS_SHELL_LAUNCHERS: frozenset[str] = frozenset(("npx", "npm", "pnpm", "yarn", "bunx"))
def _is_transient(exc: BaseException) -> bool:
"""Check if an exception looks like a transient connection error."""
return type(exc).__name__ in _TRANSIENT_EXC_NAMES
def _windows_command_basename(command: str) -> str:
"""Return the lowercase basename for a Windows command or path."""
return command.replace("\\", "/").rsplit("/", maxsplit=1)[-1].lower()
def _normalize_windows_stdio_command(
command: str,
args: list[str] | None,
env: dict[str, str] | None,
) -> tuple[str, list[str], dict[str, str] | None]:
"""Wrap Windows shell launchers so MCP stdio servers start reliably."""
normalized_args = list(args or [])
if os.name != "nt":
return command, normalized_args, env
basename = _windows_command_basename(command)
if basename in {"cmd", "cmd.exe", "powershell", "powershell.exe", "pwsh", "pwsh.exe"}:
return command, normalized_args, env
if basename.endswith((".exe", ".com")):
return command, normalized_args, env
resolved = shutil.which(command, path=(env or {}).get("PATH")) or command
resolved_basename = _windows_command_basename(resolved)
should_wrap = (
basename in _WINDOWS_SHELL_LAUNCHERS
or basename.endswith((".cmd", ".bat"))
or resolved_basename.endswith((".cmd", ".bat"))
)
if not should_wrap:
return command, normalized_args, env
comspec = (env or {}).get("COMSPEC") or os.environ.get("COMSPEC") or "cmd.exe"
return comspec, ["/d", "/c", command, *normalized_args], env
def _extract_nullable_branch(options: Any) -> tuple[dict[str, Any], bool] | None:
"""Return the single non-null branch for nullable unions."""
if not isinstance(options, list):
@@ -416,8 +456,15 @@ async def connect_mcp_servers(
return name, None
if transport_type == "stdio":
command, args, env = _normalize_windows_stdio_command(
cfg.command,
cfg.args,
cfg.env or None,
)
params = StdioServerParameters(
command=cfg.command, args=cfg.args, env=cfg.env or None
command=command,
args=args,
env=env,
)
read, write = await server_stack.enter_async_context(stdio_client(params))
elif transport_type == "sse":
tests/tools/test_mcp_tool.py
+139 -2
View File
@@ -1,16 +1,18 @@
from __future__ import annotations
import asyncio
from contextlib import AsyncExitStack, asynccontextmanager
import sys
from contextlib import asynccontextmanager
from types import ModuleType, SimpleNamespace
import pytest
import nanobot.agent.tools.mcp as mcp_mod
from nanobot.agent.tools.mcp import (
MCPResourceWrapper,
MCPPromptWrapper,
MCPResourceWrapper,
MCPToolWrapper,
_normalize_windows_stdio_command,
connect_mcp_servers,
)
from nanobot.agent.tools.registry import ToolRegistry
@@ -178,6 +180,99 @@ def test_wrapper_normalizes_nullable_property_anyof() -> None:
}
def test_normalize_windows_stdio_command_is_noop_off_windows(
monkeypatch: pytest.MonkeyPatch,
) -> None:
monkeypatch.setattr(mcp_mod.os, "name", "posix", raising=False)
command, args, env = _normalize_windows_stdio_command(
"npx",
["-y", "chrome-devtools-mcp@latest"],
{"FOO": "bar"},
)
assert command == "npx"
assert args == ["-y", "chrome-devtools-mcp@latest"]
assert env == {"FOO": "bar"}
def test_normalize_windows_stdio_command_wraps_npx_on_windows(
monkeypatch: pytest.MonkeyPatch,
) -> None:
monkeypatch.setattr(mcp_mod.os, "name", "nt", raising=False)
monkeypatch.setattr(
mcp_mod.shutil,
"which",
lambda command, path=None: r"C:\Program Files\nodejs\npx.cmd",
)
monkeypatch.setenv("COMSPEC", r"C:\Windows\System32\cmd.exe")
command, args, env = _normalize_windows_stdio_command(
"npx",
["-y", "chrome-devtools-mcp@latest"],
None,
)
assert command == r"C:\Windows\System32\cmd.exe"
assert args == ["/d", "/c", "npx", "-y", "chrome-devtools-mcp@latest"]
assert env is None
def test_normalize_windows_stdio_command_wraps_resolved_cmd_launcher(
monkeypatch: pytest.MonkeyPatch,
) -> None:
monkeypatch.setattr(mcp_mod.os, "name", "nt", raising=False)
def _fake_which(command: str, path: str | None = None) -> str:
assert command == "custom-launcher"
assert path == r"C:\Tools"
return r"C:\Tools\custom-launcher.cmd"
monkeypatch.setattr(mcp_mod.shutil, "which", _fake_which)
monkeypatch.setenv("COMSPEC", r"C:\Windows\System32\cmd.exe")
command, args, _env = _normalize_windows_stdio_command(
"custom-launcher",
["serve"],
{"PATH": r"C:\Tools"},
)
assert command == r"C:\Windows\System32\cmd.exe"
assert args == ["/d", "/c", "custom-launcher", "serve"]
def test_normalize_windows_stdio_command_keeps_real_executables_unchanged(
monkeypatch: pytest.MonkeyPatch,
) -> None:
monkeypatch.setattr(mcp_mod.os, "name", "nt", raising=False)
command, args, env = _normalize_windows_stdio_command(
"python.exe",
["-m", "http.server"],
{"FOO": "bar"},
)
assert command == "python.exe"
assert args == ["-m", "http.server"]
assert env == {"FOO": "bar"}
def test_normalize_windows_stdio_command_skips_existing_shells(
monkeypatch: pytest.MonkeyPatch,
) -> None:
monkeypatch.setattr(mcp_mod.os, "name", "nt", raising=False)
command, args, env = _normalize_windows_stdio_command(
"cmd.exe",
["/c", "echo", "hello"],
None,
)
assert command == "cmd.exe"
assert args == ["/c", "echo", "hello"]
assert env is None
@pytest.mark.asyncio
async def test_execute_returns_text_blocks() -> None:
async def call_tool(_name: str, arguments: dict) -> object:
@@ -423,6 +518,48 @@ async def test_connect_mcp_servers_one_failure_does_not_block_others(
assert set(stacks) == {"good"}
@pytest.mark.asyncio
async def test_connect_mcp_servers_wraps_windows_stdio_launchers(
fake_mcp_runtime: dict[str, object | None],
monkeypatch: pytest.MonkeyPatch,
) -> None:
fake_mcp_runtime["session"] = _make_fake_session(["demo"])
captured: dict[str, object] = {}
@asynccontextmanager
async def _capturing_stdio_client(params: object):
captured["command"] = params.command
captured["args"] = params.args
captured["env"] = params.env
yield object(), object()
monkeypatch.setattr(mcp_mod.os, "name", "nt", raising=False)
monkeypatch.setattr(
mcp_mod.shutil,
"which",
lambda command, path=None: r"C:\Program Files\nodejs\npx.cmd",
)
monkeypatch.setenv("COMSPEC", r"C:\Windows\System32\cmd.exe")
monkeypatch.setattr(sys.modules["mcp.client.stdio"], "stdio_client", _capturing_stdio_client)
registry = ToolRegistry()
stacks = await connect_mcp_servers(
{
"test": MCPServerConfig(
command="npx",
args=["-y", "chrome-devtools-mcp@latest"],
)
},
registry,
)
for stack in stacks.values():
await stack.aclose()
assert captured["command"] == r"C:\Windows\System32\cmd.exe"
assert captured["args"] == ["/d", "/c", "npx", "-y", "chrome-devtools-mcp@latest"]
assert captured["env"] is None
# ---------------------------------------------------------------------------
# MCPResourceWrapper tests
# ---------------------------------------------------------------------------