Support for anywidget frontend hot-reload

[kolibril13]

Description

Marimo's mo.watch.file() works well for reloading widgets when their JS code changes:

# Cell 1
js_file = mo.watch.file("monkey.js")
css_file = mo.watch.file("monkey.css")

# Cell 2
class Widget(anywidget.AnyWidget):
    _esm = js_file.read_text()
    _css = css_file.read_text()
Widget()

However, the whole cell is now re-running, not only the frontend.

Here's a comparison screen recording, left JupyterLab with real hot reloading, and right the current marimo workaround.

Screen.Recording.2026-05-29.at.09.37.27.mp4

Would be great if Marimo could support real hot reloading as well!

Are you willing to submit a PR? (You must receive approval from the team before submitting a PR.)

• Yes

Alternatives

No response

Additional context

No response