astro/.changeset/neat-suns-search.md

astro
major

Implements a new scope style strategy called "attribute". When enabled, styles are applied using data-* attributes.

The default value of scopedStyleStrategy is "attribute".

If you want to use the previous behaviour, you have to use the "where" option:

import { defineConfig } from 'astro/config';

export default defineConfig({
+    scopedStyleStrategy: 'where',
});