Marimo fails to create new notebooks with uvicorn 0.36.0 (works with 0.35.0) #6453
Description
Hi,
since today I am unable to create new Marimo notebooks on my system. When I try, I get the following error:
ERROR: Exception in ASGI application
Interestingly, existing notebooks still run fine. After some testing, I found that the issue is caused by uvicorn 0.36.0.
If I downgrade to uvicorn==0.35.0, the problem disappears and I can create new notebooks again.
Environment:
OS: Windows 11
Python: 3.13 (but i also tested older ones)
marimo: 0.16.0, 0.15.0 (installed using uv)
uvicorn: 0.36.0 (broken), 0.35.0 (works)
Steps to reproduce:
Install marimo with uv in an .venv. This automatically installs uvicorn==0.36.0
Run "uv run marimo edit new.py" or "uv run marimo edit" and create a new notebook in the web UI
Observe: ERROR: Exception in ASGI application
Downgrade to uvicorn 0.35.0 by "uv add uvicorn==0.35.0" → issue gone
Expected behavior:
Creating new notebooks should work with uvicorn 0.36.0 as it does with 0.35.0.
Will you submit a PR?
- Yes
Environment
{
"marimo": "0.16.0",
"editable": false,
"location": "C:/Users/Andreas Rott/AppData/Roaming/uv/tools/marimo/Lib/site-packages/marimo",
"OS": "Windows",
"OS Version": "11",
"Processor": "AMD64 Family 25 Model 80 Stepping 0, AuthenticAMD",
"Python Version": "3.13.7",
"Binaries": {
"Browser": "140.0.7339.128",
"Node": "--"
},
"Dependencies": {
"click": "8.3.0",
"docutils": "0.22.1",
"itsdangerous": "2.2.0",
"jedi": "0.19.2",
"markdown": "3.9",
"narwhals": "2.5.0",
"packaging": "25.0",
"psutil": "7.1.0",
"pygments": "2.19.2",
"pymdown-extensions": "10.16.1",
"pyyaml": "6.0.2",
"starlette": "0.48.0",
"tomlkit": "0.13.3",
"typing-extensions": "missing",
"uvicorn": "0.36.0",
"websockets": "15.0.1"
},
"Optional Dependencies": {
"loro": "1.6.0"
},
"Experimental Flags": {}
}
Code to reproduce
No response