SPA mode configuration causes app to hang on loading skeleton with Bun + Vite 7

[Necmttn]

Description

When using TanStack Start with Bun runtime and Vite 7, having the spa configuration object present (even when commented out internally) causes the application to get stuck showing the loading skeleton and never hydrate properly.

Environment

• TanStack Start: Latest
• Vite: 7.1.6
• Runtime: Bun 1.2.23
• React: 19.1.1

Configuration that causes the issue

// vite.config.ts
tanstackStart({
    target: "bun",
    customViteReactPlugin: true,
    spa: {
        // enabled: true,
    },
}),

Working configuration

// vite.config.ts
tanstackStart({
    target: "bun",
    customViteReactPlugin: true,
    // spa: {
    //     // enabled: true,
    // },
}),

Symptoms

• Server starts successfully
• SSR returns loading skeleton HTML
• Client connects ("[vite] connected" in console)
• App remains in "pending" state and never hydrates
• No JavaScript errors in console
• Page shows only the animated loading skeleton

Expected behavior

The app should either:

1. Work correctly with an empty spa: {} configuration object, or
2. Throw a clear error if the configuration is invalid

Workaround

Completely commenting out the spa configuration object resolves the issue and allows the app to work normally in SSR mode.

[strickczq]

Same issue here. Did a binary search and found 1.131.47 works, but 1.131.48 and up are broken. Hope that helps!

[lhr0909]

Seems like disabling spa mode explicitly works. I feel like SPA mode does not work in vite dev server somehow.

// vite.config.ts
tanstackStart({
    spa: {
        enabled: false,
    },
}),

The best way I find is to disable SPA mode in dev in the vite config:

import { defineConfig } from 'vite';
import { tanstackStart } from '@tanstack/react-start/plugin/vite';

export default defineConfig(({ command }) => ({
  plugins: [
    tanstackStart({
      spa:
        command === 'serve'
          ? undefined
          : {
              enabled: true,
            },
    }),
  ],
}));

[schiller-manuel]

cc @nlynzaad

v1.131.48 contained #5169
don't see yet how this is related to SPA mode?

[nlynzaad]

Yeah I don't see how those can be related.

1.131.48 merely added tests and had one change in the parsing of paths, it came nowhere close to any of this.

I can confirm tonight.

[strickczq]

I patched @tanstack/router-core@1.131.48 by changing decodeURI(partToMatch) to (() => {console.log({ part, partToMatch }); return decodeURI(part)})().

It works now! For context, 1.131.47 uses decodeURI(part), while 1.131.48 uses decodeURI(partToMatch).

Console output shows:

[vite] connected.
{ part: '__root__', partToMatch: '__root_' }
{ part: '.', partToMatch: '.' }
{ part: '.well-known', partToMatch: '.well-known' }
{ part: 'appspecific', partToMatch: 'appspecific' }
{ part: 'com.chrome.devtools.json', partToMatch: 'com.chrome.devtools.json' }
{ part: '__root__', partToMatch: '__root_' }
{ part: '.', partToMatch: '.' }

Seems like the slicing logic (partToMatch = part.slice(-1) === '_' ? part.slice(0, -1) : part) is breaking the __root__ route in 1.131.48.