Support separate asset base (CDN) vs app base in TanStack Start (Vite)

[Nandan1996]

Problem
We need the application to live at /app-base-path (e.g., https://www.example.com/app-base-path) while all built assets (JS/CSS) are served from a CDN like https://edge.example.com/asset-path. With TanStack Start today, Vite’s base config is used as a single source of truth (TSS_APP_BASE) for both routing and asset URLs, so we can’t configure a separate asset base without affecting the app base.

What we’ve tried

• Setting Vite base: '/app-base-path' + router basepath: '/app-base-path' → routes work, but assets resolve under /app-base-path on the origin.
• Using an absolute CDN base in Vite base makes the server/app base follow the CDN URL, which breaks routing/server paths.
• We didn’t find a built-in env or option to override only the asset URLs.

What we’re asking

• A supported way to keep the app/document base at /app-base-path while emitting SSR asset URLs that point to a different base (CDN), e.g. https://edge.example.com/asset-path. the idea is similar to what nextjs provides via assetPrefix config.

Possible approaches (examples)

• Env var only for SSR asset URLs:
  • TSS_ASSET_BASE=https://edge.example.com/asset-path
  • Falls back to app base if unset. Router base and server function paths remain derived from Vite base.
• Plugin option:

  // vite.config.ts
  import { defineConfig } from 'vite'
  import { tanstackStart } from '@tanstack/react-start/plugin/vite'
  
  export default defineConfig({
    base: '/app-base-path', // app/document base
    plugins: [
      tanstackStart({
        client: {
          assetsBase: 'https://edge.example.com/asset-path', // CDN asset base
        },
      }),
    ],
  })

Why this helps

• Lets teams use a CDN origin for assets without changing the document/app base or rewriting HTML at the edge.
• Keeps router behavior predictable while enabling flexible asset hosting strategies.

Is there an undocumented way to do this today? If not, would you consider adding support for a split asset base?