Content lost while editing with watch flag enabled

[fonnesbeck]

Describe the bug

When editing cells (markdown or python) in the editor interface with the --watch flag enabled, text is deleted shortly after being typed.

Here is an example, moving the cursor up and beginning to type a heading. The cell quickly reverts to its original state:

Screencast.From.2025-10-30.12-52-10.mp4

This happens even without the file open in a text editor.

Will you submit a PR?

• Yes

Environment

{
  "marimo": "0.17.3",
  "editable": false,
  "location": "/var/home/fonnesbeck/repos/xg_model/.pixi/envs/default/lib/python3.13/site-packages/marimo",
  "OS": "Linux",
  "OS Version": "6.16.10-200.fc42.x86_64",
  "Processor": "",
  "Python Version": "3.13.9",
  "Locale": "en_US",
  "Binaries": {
    "Browser": "142.0.7444.59",
    "Node": "v22.20.0"
  },
  "Dependencies": {
    "click": "8.3.0",
    "docutils": "0.22.2",
    "itsdangerous": "2.2.0",
    "jedi": "0.19.2",
    "markdown": "3.9",
    "narwhals": "2.10.0",
    "packaging": "25.0",
    "psutil": "7.1.2",
    "pygments": "2.19.2",
    "pymdown-extensions": "10.16.1",
    "pyyaml": "6.0.3",
    "starlette": "0.49.1",
    "tomlkit": "0.13.3",
    "typing-extensions": "4.15.0",
    "uvicorn": "0.38.0",
    "websockets": "15.0.1"
  },
  "Optional Dependencies": {
    "loro": "1.8.2",
    "mcp": "1.19.0",
    "nbformat": "5.10.4",
    "pandas": "2.3.3",
    "polars": "1.35.0",
    "pyarrow": "20.0.0",
    "pytest": "8.4.2",
    "ruff": "0.14.2"
  },
  "Experimental Flags": {}
}

Code to reproduce

No response

[mscolnick]

Sounds like it came up because we reverted this change #6534
We could either add this back, or have a smarter filewatcher (based on write times and who wrote it)

Do you have autosave enabled?