Expose the StdioServerParameters.cwd param (#1514)

Author: timesler

pydantic_ai_slim/pydantic_ai/mcp.py

@@ -4,6 +4,7 @@
 from collections.abc import AsyncIterator, Sequence
 from contextlib import AsyncExitStack, asynccontextmanager
 from dataclasses import dataclass
+from pathlib import Path
 from types import TracebackType
 from typing import Any
 
@@ -150,13 +151,16 @@ async def main():
     If you want to inherit the environment variables from the parent process, use `env=os.environ`.
     """
 
+    cwd: str | Path | None = None
+    """The working directory to use when spawning the process."""
+
     @asynccontextmanager
     async def client_streams(
         self,
     ) -> AsyncIterator[
         tuple[MemoryObjectReceiveStream[JSONRPCMessage | Exception], MemoryObjectSendStream[JSONRPCMessage]]
     ]:
-        server = StdioServerParameters(command=self.command, args=list(self.args), env=self.env)
+        server = StdioServerParameters(command=self.command, args=list(self.args), env=self.env, cwd=self.cwd)
         async with stdio_client(server=server) as (read_stream, write_stream):
             yield read_stream, write_stream
 

pydantic_ai_slim/pyproject.toml

@@ -69,7 +69,7 @@ tavily = ["tavily-python>=0.5.0"]
 # CLI
 cli = ["rich>=13", "prompt-toolkit>=3", "argcomplete>=3.5.0"]
 # MCP
-mcp = ["mcp>=1.4.1; python_version >= '3.10'"]
+mcp = ["mcp>=1.5.0; python_version >= '3.10'"]
 # Evals
 evals = ["pydantic-evals=={{ version }}"]
 

tests/test_mcp.py

@@ -1,5 +1,7 @@
 """Tests for the MCP (Model Context Protocol) server implementation."""
 
+from pathlib import Path
+
 import pytest
 from dirty_equals import IsInstance
 from inline_snapshot import snapshot
@@ -38,6 +40,14 @@ async def test_stdio_server():
         assert result.content == snapshot([TextContent(type='text', text='32.0')])
 
 
+async def test_stdio_server_with_cwd():
+    test_dir = Path(__file__).parent
+    server = MCPServerStdio('python', ['mcp_server.py'], cwd=test_dir)
+    async with server:
+        tools = await server.list_tools()
+        assert len(tools) == 1
+
+
 def test_sse_server():
     sse_server = MCPServerHTTP(url='http://localhost:8000/sse')
     assert sse_server.url == 'http://localhost:8000/sse'