This val exposes and endpoint that you can post code to and get back syntax highlighted html via Shiki. Shiki does server side highlighting, so it's perfect for val.town. You can switch themes by providing ?theme=<theme> and specify the language via ?lang=<language>

You can play with a working example here.

Create val
const res = await fetch(`https://just_be-highlight.web.val.run?lang=${lang}&theme=${theme}`, {
  method: "POST",
  body: code,
});

console.log(await res.text())

I want to add syntax highlighting to my blog soon and I'm experimenting with what it mean to offload parts of my rendering to val.town (behind a content-addressible cache, of course).