Thanks for testing! Unfortunately I won't be able to review this until after EMF2026 and then work, next Monday at the very earliest. I hope that's fine since you don't use code-input.js.

Thanks! I've looked through your code and it makes a lot of sense (though I have a few suggestions I'll commit, and questions I'll put here).

One problem is that changing the template via DevTools of a dark mode code-input element (for example prism-dark.css rather than prism.css, or dark.css rather than default.css for highlight.js) to an unregistered name keeps the text white. If you want to manually test or fix this that would be great; I'll also look into it (it's to do with the colours set in internalStyle).