includeAssetsImportedByServer

Default: true.

When includeAssetsImportedByServer is true, then static assets (CSS, images, ...) imported by server-only code are included in the client production build (/dist/client/assets/).

It's true by default and, in principle, there isn't any reason to disable it. You can however disable it:

// vite.config.js

import { ssr } from 'vite-plugin-ssr/plugin'

export default {
  plugins: [
    ssr({
      includeAssetsImportedByServer: false
    })
  ]
}