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fastmcp.run() runtimeerror: task group is not initialized. make sure to use run(). #1372
Closed as not planned
Description
Initial Checks
- I confirm that I'm using the latest version of MCP Python SDK
- I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue
Description
following error sometime occur.
fastmcp.run() runtimeerror: task group is not initialized. make sure to use run().
Example Code
from mcp.server.fastmcp import FastMCP
# FastMCP instance
mcp = FastMCP(
name=setting.server["name"],
host=setting.server["host"],
port=setting.server["port"],
streamable_http_path=setting.server["streamable_http_path"],
api_route="/mcp/",
debug=True,
)
try:
mcp.run(transport="streamable-http")
except KeyboardInterrupt:
logger.info("Service shut down")Python & MCP Python SDK
mcp version (1.13.1)
Reacted by Patrick Decat
Activity
ChenyangLi4288 commentedon Oct 10, 2025
I can't reproduce this one.
felixweinberger commentedon Oct 13, 2025
I was also unable to reproduce this - could you provide any more information about your setup? Are you running into this issue with just the example code given and running
python -m main.py?tugbayatilla commentedon Oct 29, 2025
i just copy and paste this code block, and got the same result.
https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/snippets/servers/streamable_http_multiple_servers.py
python: 3.12
`Package Version
ally-ai-core 0.7.0
annotated-types 0.7.0
anyio 4.11.0
attrs 25.4.0
certifi 2025.10.5
click 8.3.0
h11 0.16.0
httpcore 1.0.9
httpx 0.28.1
httpx-sse 0.4.3
idna 3.11
jsonschema 4.25.1
jsonschema-specifications 2025.9.1
markdown-it-py 4.0.0
mcp 1.19.0
mdurl 0.1.2
pip 25.3
pydantic 2.12.3
pydantic_core 2.41.4
pydantic-settings 2.11.0
Pygments 2.19.2
python-dotenv 1.2.1
python-multipart 0.0.20
PyYAML 6.0.3
referencing 0.37.0
rich 14.2.0
rpds-py 0.28.0
shellingham 1.5.4
sniffio 1.3.1
sse-starlette 3.0.2
starlette 0.49.1
typer 0.20.0
typing_extensions 4.15.0
typing-inspection 0.4.2
uvicorn 0.38.0
`
maxisbey commentedon Aug 10, 2026
Thanks for the report. I'm closing this out as part of a backlog cleanup now that v2 is out. Feel free to reopen if this is still relevant.