Simpler dev server proxy fallback

[ThibautMarechal]

After migrating to Vite, I'm trying to replicate the same dev server proxy experience I had with my previous bundler.

Before Vite, I only needed to configure a single proxy rule, and any request that wasn’t handled by the bundler (e.g., static assets or SPA routes) was automatically forwarded to my backend. It was a simple and convenient fallback behavior.

With Vite, I find myself needing to explicitly list out all the path prefixes I want to proxy:

Using Vite proxy solution:

{
  server: {
    proxy: {
      '/api': 'https://example.com',
      '/auth': 'https://example.com',
      '/metrics': 'https://example.com'
    }
  }
}

This approach is a bit cumbersome when many endpoints need to be forwarded, and it becomes even trickier when some of those endpoints include WebSocket connections (especially if they share a common prefix with HTTP endpoints).

To work around this, I created a plugin:
👉 https://gist.github.com/ThibautMarechal/d8e27b9d665e29903791f36f4ad05da7

{
  plugins: [
    proxyEverything('https://example.com')
  ]
}

It basically proxies everything Vite doesn’t serve directly to a backend target. That way, I don’t have to manage a long list of prefixes or handle mismatched behavior for websockets.

I’m wondering:

Am I missing something in the Vite documentation?

Is there a built-in way to achieve this kind of fallback proxying?

Would this be a reasonable feature to support in core or via an official plugin?

It seems like a valid and common use case to forward all unmatched requests to a backend during development.