astro/.changeset/large-zebras-sniff.md

astro
major

Updates internal Shiki rehype plugin to highlight code blocks as hast (using Shiki's codeToHast() API). This allows a more direct Markdown and MDX processing, and improves the performance when building the project, but may cause issues with existing Shiki transformers.

If you are using Shiki transformers passed to markdown.shikiConfig.transformers, you must make sure they do not use the postprocess hook as it no longer runs on code blocks in .md and .mdx files. (See the Shiki documentation on transformer hooks for more information).

Code blocks in .mdoc files and <Code /> component do not use the internal Shiki rehype plugin and are unaffected.