fix: UI element interaction should respect overridden defs in embedded apps

[akshayka]

fix: UI element interactions when defs are overridden

This change fixes a bug in which cells run as a consequence of UI
element interactions did not respect overridden definitions in
embedded apps.

This fix adds internal APIs:

• check if the current runtime is embedded
• get overrides of an app

This fix also fixes a bug in which nested contexts had isolated
AppKernelRunner registries. With this change, contexts now share
their parent's registry to make sure runner retrieval can happen at runtime,
in a nested context. The registries are still isolated across run sessions.

Finally, it fixes a bug in App.clone, in which CellImpls were shallow copied even though they have mutable state.

Fixes #7685

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Review	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Jan 19, 2026 3:27pm

[akshayka]

@yairchu I believe this change fixes your minimal example, thank you for debugging and brainstorming with me. Could you try this change out and see if it feels correct? I am not sure if it fixes the "locking" in your original app, I haven't tried that out

[yairchu]

@akshayka this does solve the problem of overridden defs!

However a problem of strangely resetting sliders does remain in this example:

embed_test_a.py:

import marimo

__generated_with = "0.19.4"
app = marimo.App(width="full")


@app.cell
def _():
    import marimo as mo
    return


@app.cell
def _():
    import embed_test_b
    return (embed_test_b,)


@app.cell
def _(embed_test_b):
    clone_a = embed_test_b.app.clone()
    return (clone_a,)


@app.cell
async def _(clone_a):
    embed_a = await clone_a.embed()
    embed_a.output
    return (embed_a,)


@app.cell
def _(embed_test_b):
    clone_b = embed_test_b.app.clone()
    return (clone_b,)


@app.cell
async def _(clone_b, embed_a):
    (
        await clone_b.embed(
            defs={
                "slider": None,
                "value": embed_a.defs["value"],
                "label": "their",
                "kind": "warn",
            }
        )
    ).output
    return


@app.cell
def _():
    return


if __name__ == "__main__":
    app.run()

embed_test_b.py:

import marimo

__generated_with = "0.19.2"
app = marimo.App(width="full")


@app.cell
def _():
    import marimo as mo
    import time
    return (mo,)


@app.cell
def _():
    state = None
    return (state,)


@app.cell
def _(mo):
    slider = mo.ui.slider(0, 10, 1, 3, label="A slider")
    return (slider,)


@app.cell
def _(slider):
    slider
    return


@app.cell
def _(slider, state):
    value = slider.value if state is None else state()
    label = "our"
    return label, value


@app.cell
def _():
    kind = "info"
    return (kind,)


@app.cell
def _(kind, label, mo, value):
    mo.callout(
        mo.md(f"""
        The value of *{label}* slider is **{value}**!
        """), kind
    )
    return


@app.cell
def _():
    return


if __name__ == "__main__":
    app.run()

The slider seems to be "reseting" or recreating constantly when moved. Try to move the slider and notice how the value jumps between the dragging value and the initial value of 3.

[akshayka]

Thanks so much @yairchu for trying it out, and for sharing this example — it's very helpful.

I can see the incorrect behavior in the underlying code (slider in embed_test_a is recreated when it's interacted with, causing it to reset) but I'm not sure why it's happening. If I comment out the slider overriding in the second embed call, it's not recreated. Hopefully the bug unravels as I pull on this thread.

[yairchu]

@akshayka, if it helps, I think that it is somehow related to the undisplayed slider being recreated in the second instance of embed_test_b.

What leads me to think this:

• If I cp embed_test_b.py embed_test_c.py and change the second instance to be an embed of embed_test_c rather than a second instance of embed_test_b, then the problem vanishes
• The workaround I previously found, which makes the cell not run at all, still appears to solve the issue

[akshayka]

@yairchu, thanks so much! I pushed up additional changes, and the slider no longer resets. Want to give it one more try?

cloned_embed.mp4

[yairchu]

@akshayka works great now!

[github-actions]

🚀 Development release published. You may be able to view the changes at https://marimo.app?v=0.19.5-dev18