Known Limitations

Encapsulated Plugin Registration

It's currently impossible to run @fastify/vite in an encapsulated Fastify plugin. You'll need to register @fastify/vite at the root context, or if you want to use it in a plugin, that plugin must be wrapped in fastify-plugin so it's also registered at the root context.

INFO

Investigation on this has started but is still pending — everything points to @fastify/middie, the Express compatibility layer needed to run the Vite development server middleware. It's just considered low-prio at the moment as in most setups, only a single instance is needed anyway.

Multiple Vite Instances

It's currently impossible to run multiple Vite development server middleware in your Fastify server, which means @fastify/vite can only be registered once. Configuration for this is somewhat tricky and there isn't documentation on how to do it. Once #108 is completed and merged, it will open the path to have a Vite development server factory that can create instances on-demand, but that approach still remains to be tested.

If you're looking into a microfrontend setup, consider this approach.

Using @fastify/middie Directly

@fastify/vite internally registers @fastify/middie in development mode to run Vite's dev server middleware. If you want to use middie yourself with different options:

In development mode: You can either register middie before @fastify/vite (it will detect this and skip its own registration), or simply use server.use() after calling server.vite.ready().

In production mode: @fastify/vite does not register middie since Vite's dev server isn't used. If you need middie in production, you must register it yourself.

import Fastify from 'fastify'
import middie from '@fastify/middie'
import FastifyVite from '@fastify/vite'

const server = Fastify()

// Register middie first - works in both dev and production
await server.register(middie, {
  /* options */
})

await server.register(FastifyVite, {
  /* options */
})