[BUG] session.initialize() hangs indefinitely with stdio_client setup

[Elijas]

Describe the bug
await session.initialize() runs forever (stopped it after >10 minutes)

For some reason all the other clients also run forever

To Reproduce

import asyncio
from mcp import ClientSession, StdioServerParameters, types
from mcp.client.stdio import stdio_client

# Create server parameters for stdio connection
server_params = StdioServerParameters(
    command="uvx",
    args=["mcp-timeserver"],
    env=None,
)


async def run():
    async with stdio_client(server_params) as (read, write):
        async with ClientSession(read, write) as session:
            # Initialize the connection
            await session.initialize()
            tools = await session.list_tools()
            print(tools)



if __name__ == "__main__":
    asyncio.run(run())

Expected behavior
Not get stuck

Additional context
Running from jupyter notebook opened in VSCode ipykernel==6.29.5 mcp==1.6.0 python=3.13 apple silicon

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• Python FastMCP stdio server doesn't initialize #395 (comment)