feat: create @zag-js/lit (WIP)

[nikparo]

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📝 Description

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WIP work on creating a @zag-js/lit framework. Adds packages/frameworks/lit and examples/lit-ts, and adapts e2e/ testing suite to optionally work with shadow-dom.

This PR is only open for visibility and comments, it's not ready to be merged.

NOTE: Video is from my dev/lit branch that combines several other branches, including:
#2694
#2697
#2695

⛳️ Current behavior (updates)

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🚀 New behavior

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Screen.Recording.2025-09-09.at.12.46.26.mov

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📝 Additional Information

Related discussion threads:
#2681
#1210

Thank you @gperdomor for your work on #2608

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Project	Deployment	Preview	Updated (UTC)
zag-nextjs	Ready	Preview	Sep 9, 2025 9:57am
zag-solid	Ready	Preview	Sep 9, 2025 9:57am
zag-svelte	Ready	Preview	Sep 9, 2025 9:57am
zag-vue	Ready	Preview	Sep 9, 2025 9:57am
zag-website	Ready	Preview	Sep 9, 2025 9:57am

[gperdomor]

Amazing job @nikparo… I hope that this can be merged soon ❤️

[irontitan76]

This is awesome! Thank you, @nikparo, for putting this together. What is needed to push this across the line—reviews, more direct contributions, or something else altogether?

[gperdomor]

any progress with this?

[nikparo]

@gperdomor @irontitan76 Thanks for the interest. This did fall on the backburner for a while due to more pressing matters taking priority, though I've been working on it a bit here and there.

The main thing I've been working on is to verify that shadow-dom was working properly by refactoring the examples / e2e tests so that the shadow-dom boundaries are more realistically placed. It has been a bit challenging tbh - shadow-dom blocks things like document.getElementById, e2e targeting needs to work differently for shadow-dom and light-dom, but still work with all the frameworks, etc.

I'm still fairly optimistic that shadow-dom support is doable though - I've recently gotten the menu-nested example working pretty well using 3 separate menu-elements using both slots and cross-boundary querying, which is a pretty good proof-of-concept imo. It's been quite experimental, but will try and update my branches here once I've cleaned it up a bit.

One open question though is whether we should even try to support shadow-dom for the initial PR. It would certainly be much quicker to get the initial framework ready to be merged if we forgo that. Lit examples + e2e tests could then be updated on a component by component basis to use shadow-dom until all do.

Side note: Lit supports light-dom use, but doesn't recommend it, as slots and dom/style scoping isn't available.

[gperdomor]

@nikparo I'm not an expert and I don't know how can I help you but I think that having an initial framework in place, even without the shadow-dom support, would be great... Then all the missing things can be improved with other small MRs...