style: shadow adjustments

[m-rgba]

📝 Summary

Before	After

cell-styling.mov

• Adds hover state (darker border) to default / has-error / needs-run cells.
• Uses 2px border for inactive state for emphasized cells (has-error / needs-run) - instead of 1px / solid shadow.
  • Reverts to 1px when focused.
• Adds tabIndex to error output (so that clicking outputs triggers focus-within vs our outline).

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Project	Deployment	Review	Updated (UTC)
marimo-docs	Ready	Preview, Comment	Jan 7, 2026 1:29am

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[m-rgba]

I have read the CLA Document and I hereby sign the CLA

[mscolnick]

@m-rgba 1px to 2px border swapping is going to cause a layout shift, which we would like to avoid

[m-rgba]

@m-rgba 1px to 2px border swapping is going to cause a layout shift, which we would like to avoid

@mscolnick gotcha, that's fair - we could look at something like an outline pattern to have a similar effect without the shift on focus. Updated with an example of that.

outline-pattern.mov

[manzt]

Thanks for iterating on this! The outline approach looks good and addresses the layout shift concern.

We're aligned with the direction here. The hover state improvement and cleaner shadow treatment are nice additions. We had some parallel work happening on our side (#7692) which unfortunately led to some wasted effort. These changes are definitely in the direction we want, but in the future it would be great to align on goals before diving into implementation so we can avoid stepping on each other's toes. Thanks again for the great contribution!

[github-actions]

🚀 Development release published. You may be able to view the changes at https://marimo.app?v=0.18.5-dev157