Roots/List Request Hangs in Client-Server Communication #1097

from mcp.server.fastmcp import FastMCP, Context
from mcp.types import TextContent

mcp = FastMCP(
    name="mcp-roots-server",
    stateless_http=True
)

@mcp.tool()
async def analyze_project(ctx: Context) -> TextContent:
    print("-> Server: Requesting project roots from client...")
    roots = await ctx.session.list_roots()  # Hangs here
    
    if not roots or not roots.roots:
        return TextContent(text="No project roots found", type="text")
    
    # Never reaches this point
    return TextContent(text="Analysis complete", type="text")

mcp_app = mcp.streamable_http_app()

import asyncio
from pathlib import Path
from typing import Any
import mcp.types as types
from mcp.shared.context import RequestContext
from mcp import ClientSession
from mcp.client.streamable_http import streamablehttp_client

async def mock_roots_list(context: RequestContext["ClientSession", Any]) -> types.ListRootsResult | types.ErrorData:
    print(f"<- Client: Received roots/list request")
    root_uri = f"file://{Path.cwd().absolute()}"
    return types.ListRootsResult(roots=[types.Root(
        uri=types.FileUrl(root_uri),
        name="Current Project"
    )])

async def main():
    server_url = "http://localhost:8000/mcp/"
    async with streamablehttp_client(server_url) as (read_stream, write_stream, get_session_id):
        async with ClientSession(read_stream, write_stream, list_roots_callback=mock_roots_list) as session:
            await session.initialize()
            result = await session.call_tool("analyze_project")

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