[19.10] When using uv projects, dependencies are not added to pyproject.toml

[MathiasBuus]

Describe the bug

When installing packages via marimo with uv configured as the package manager - the packages are not added to the uv project, but only installed inside the .venv.

Reproduce:

1. uv init marimo-test
2. cd marimo-test
3. uv add "marimo[recommended]"
4. uv run marimo edit
5. Create new notebook
6. Create import statement using a package not in environment. eg. "import pyproj"
7. Run cell and install package using uv
8. Notice that pyproj dependency is not in pyproject.toml or uv.lock
9. Notice that pyproj is insidde .venv/Lib folder

Will you submit a PR?

• Yes

Environment

Details

{
  "marimo": "0.19.10",
  "editable": false,
  "location": "C:/Users/MathiasBrochdorffBuu/Documents/Github/sensordata/marimo-test/.venv/Lib/site-packages/marimo",
  "OS": "Windows",
  "OS Version": "11",
  "Processor": "Intel64 Family 6 Model 186 Stepping 3, GenuineIntel",
  "Python Version": "3.13.0",
  "Locale": "--",
  "Binaries": {
    "Browser": "142.0.7444.135",
    "Node": "v22.14.0",
    "uv": "0.10.2 (a788db7e5 2026-02-10)"
  },
  "Dependencies": {
    "click": "8.3.1",
    "docutils": "0.22.4",
    "itsdangerous": "2.2.0",
    "jedi": "0.19.2",
    "markdown": "3.10.2",
    "narwhals": "2.16.0",
    "packaging": "26.0",
    "psutil": "7.2.2",
    "pygments": "2.19.2",
    "pymdown-extensions": "10.20.1",
    "pyyaml": "6.0.3",
    "starlette": "0.52.1",
    "tomlkit": "0.14.0",
    "typing-extensions": "4.15.0",
    "uvicorn": "0.40.0",
    "websockets": "16.0"
  },
  "Optional Dependencies": {
    "altair": "6.0.0",
    "duckdb": "1.4.4",
    "loro": "1.10.3",
    "nbformat": "5.10.4",
    "openai": "2.20.0",
    "polars": "1.38.1",
    "pyarrow": "23.0.0",
    "ruff": "0.15.0",
    "sqlglot": "28.6.0"
  },
  "Experimental Flags": {}
}

Code to reproduce

No response

[dmadisetti]

Hi @MathiasBuus. Are you using the --sandbox flag? I can't seem to reproduce this otherwise.

• Just to confirm, you're using WSL?
• Is this for all packages or just a specific one?

[MathiasBuus]

I am not using the --sandbox flag - as I understand this adds the dependencies inline on each script. What I want is to add the packages to my pyproject.toml file that I have from initializing a uv project.

• I am not using WSL - I am using normal windows
• every package I tried had the problem. Matplotlib aswell

Is it because it runs uv pip install instead of uv add when installing packages?

[MathiasBuus]

I have been reading more into the docs and I can see that it is specifically stated that it should be added to pyproject.toml.
Is there an issue on windows that it does not detect that it is an uv project and therefore uses uv pip install?
Relevant docs:
Installing packages
Using uv