How to export classes with Astro?

In the vite announcement post I saw that there's various ways to expose classes (for workflows and DO) — but I haven't found a way to do this in an Astro app. I think the issue is that the cloudflare adapter creates dist/_worker.js/index.js but there's no way to extend what is exported from this file. Has anyone else experimented with this and has more ideas to share? Otherwise I might try to open an issue on the Astro repo.