Although out-of-the-box, mdsvex uses PrismJS for code highlighting, you can define a custom highlighter using Shiki (or even your own hand-rolled highlighter). To do this, just pass a highlighter function to the mdsvex configuration. The highlighter function takes three arguments, the code itself, the coding language of the code and some optional meta. The meta will be helpful if, for example, you want to add extra highlighting to certain lines.