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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Client tool call hangs forever if server crashes or connection dies when using streamable-http","articleBody":"### Initial Checks\n\n- [x] I confirm that I'm using the latest version of MCP Python SDK\n- [x] I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue\n\n### Description\n\nIf the server dies during a tool call before it sends a response the client will get stuck forever.\n\n### Example Code\n\n```Python\n# server.py\n\nfrom mcp.server.fastmcp import FastMCP\nimport sys\n\nmcp = FastMCP(\"StatefulServer\")\n\n@mcp.tool()\ndef greet(name: str = \"World\") -\u003e str:\n    \"\"\"Greet someone by name.\"\"\"\n    sys.exit(0)\n    return f\"Hello, {name}!\"\n\n\nif __name__ == \"__main__\":\n    mcp.run(transport=\"streamable-http\")\n\n\n# client.py\n\nimport asyncio\n\nfrom mcp import ClientSession\nfrom mcp.client.streamable_http import streamablehttp_client\n\n\nasync def main():\n    # Connect to a streamable HTTP server\n    async with streamablehttp_client(\"http://localhost:8000/mcp\") as (\n        read_stream,\n        write_stream,\n        _,\n    ):\n        # Create a session using the client streams\n        async with ClientSession(read_stream, write_stream) as session:\n            # Initialize the connection\n            await session.initialize()\n\n            res = await session.call_tool(\"greet\", {\"name\": \"World\"})\n            print(res)\n\n\nif __name__ == \"__main__\":\n    asyncio.run(main())\n\n\n\n# Run server.py then client.py\n\n\n# client.py will hang forever in the tool call and never complete. I would expect it to throw an error since the connection died and it will never get a response.\n```\n\n### Python \u0026 MCP Python SDK\n\n```Text\nPython 3.13.7\nmcp 1.20.0\n```","author":{"url":"https://github.com/gyang-xai","@type":"Person","name":"gyang-xai"},"datePublished":"2025-11-05T02:57:42.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/1577/python-sdk/issues/1577"}