🐛 TanStack Start + Cloudflare + Paraglide JS == HELL

[luthfi-hh]

Which project does this relate to?

Start

Describe the bug

Locale redirect bug: navigating to /de immediately redirects to /en (cannot switch language)

Description

Repro repo

• https://github.com/luthfi-hh/tanstack-start-hell

Problem
When I try to switch the app language to German (/de), it immediately redirects back to English (/en). Even if I manually type /de in the URL, it redirects to /en, so I can’t use the de locale at all.

Steps to reproduce

1. Start the app (e.g. pnpm dev).
2. Open http://localhost:3000/de (or click a language switcher button that navigates/sets locale to de).
3. Observe the URL changes back to /en immediately.

Expected behavior

• Visiting /de stays on /de.
• The UI renders German messages and getLocale() (or equivalent) resolves to de.

Actual behavior

• /de always redirects to /en immediately.
• Language cannot be changed to German.

Relevant code / suspicion

• Suspicion: when running with Cloudflare + Vite dev, src/server.ts does not seem to be executed, so the Paraglide middleware (paraglideMiddleware) never runs.

Environment

• OS: macOS
• Date: 2026-01-02
• Package manager: pnpm
• Dev server: Vite / TanStack Start + Cloudflare
• Locales configured: en, de

Extra notes

• This happens even when the URL already includes /de, so it’s not just missing-locale auto-redirect from / → /en.

Your Example Website or App

https://github.com/luthfi-hh/tanstack-start-hell

Steps to Reproduce the Bug or Issue

1. Start the app (e.g. pnpm dev).
2. Open http://localhost:3000/de (or click a language switcher button that navigates/sets locale to de).
3. Observe the URL changes back to /en immediately.

Expected behavior

Visiting /de stays on /de.
The UI renders German messages and getLocale() (or equivalent) resolves to de.

Screenshots or Videos

No response

Platform

• Router / Start Version: 1.132.0
• OS: macOS
• Browser: Brave
• Brave 1.85.118 (Official Build) (arm64)
• Chromium: 143.0.7499.169
• Bundler: vite + cloudflare
• Bundler Version: 7.1.7

Additional context

No response

[juliomuhlbauer]

Your server.ts should be:

import handler from '@tanstack/react-start/server-entry'
import { paraglideMiddleware } from './paraglide/server'

export default {
  fetch(req: Request): Promise<Response> {
    return paraglideMiddleware(req, () => handler.fetch(req))
  },
}

If you are using the rewrite in createRouter, you should not use the request from Paraglide. We changed the example too.

Do not know if it will resolve the issue you are facing, but this is the correct implementation in server.ts (in your example, it will cause a infinite loop).

Please, test this. If it does not resolve it, let me know. And also update all dependencies of TS Router/Start.
Also, in dev works fine?

[luthfi-hh]

Hi, thanks for the suggestion! @juliomuhlbauer

I've changed my server.ts to match the recommended implementation fix: correct request handling in paraglide middleware for server fetch.
Unfortunately, the issue still persists.

[luthfi-hh]

It works fine when using Nitro example:

import { paraglideVitePlugin } from '@inlang/paraglide-js'
import { defineConfig } from 'vite'
import { devtools } from '@tanstack/devtools-vite'
import { tanstackStart } from '@tanstack/react-start/plugin/vite'
import viteReact from '@vitejs/plugin-react'
import viteTsConfigPaths from 'vite-tsconfig-paths'
import tailwindcss from '@tailwindcss/vite'
import { nitro } from 'nitro/vite'

const config = defineConfig({
  plugins: [
    paraglideVitePlugin({ 
      project: './project.inlang', 
      outdir: './src/paraglide',
      outputStructure: 'message-modules',
      cookieName: 'PARAGLIDE_LOCALE',
      strategy: ['url', 'cookie', 'preferredLanguage', 'baseLocale'],
      urlPatterns: [
        {
          pattern: '/',
          localized: [
            ['en', '/en'],
            ['de', '/de'],
          ],
        },
        {
          pattern: '/:path(.*)?',
          localized: [
            ['en', '/en/:path(.*)?'],
            ['de', '/de/:path(.*)?'],
          ],
        },
      ],
    }),
    devtools(),
    nitro(),
    // this is the plugin that enables path aliases
    viteTsConfigPaths({
      projects: ['./tsconfig.json'],
    }),
    tailwindcss(),
    tanstackStart(),
    viteReact(),
  ],
})

export default config

But it doesn't work when using @cloudflare/vite-plugin:

import { paraglideVitePlugin } from '@inlang/paraglide-js'
import { defineConfig } from 'vite'
import { devtools } from '@tanstack/devtools-vite'
import { tanstackStart } from '@tanstack/react-start/plugin/vite'
import viteReact from '@vitejs/plugin-react'
import viteTsConfigPaths from 'vite-tsconfig-paths'
import tailwindcss from '@tailwindcss/vite'
import { cloudflare } from '@cloudflare/vite-plugin'
import path from 'path'

const config = defineConfig({
  resolve: {
    alias: {
      '@': path.resolve(__dirname, './src'),
    },
  },
  plugins: [
    paraglideVitePlugin({ 
      project: './project.inlang', 
      outdir: './src/paraglide',
      outputStructure: 'message-modules',
      cookieName: 'PARAGLIDE_LOCALE',
      strategy: ['url', 'cookie', 'preferredLanguage', 'baseLocale'],
      urlPatterns: [
        {
          pattern: '/',
          localized: [
            ['en', '/en'],
            ['de', '/de'],
          ],
        },
        {
          pattern: '/:path(.*)?',
          localized: [
            ['en', '/en/:path(.*)?'],
            ['de', '/de/:path(.*)?'],
          ],
        },
      ],
    }),
    devtools(),
    cloudflare({ viteEnvironment: { name: 'ssr' } }),
    // this is the plugin that enables path aliases
    viteTsConfigPaths({
      projects: ['./tsconfig.json'],
    }),
    tailwindcss(),
    tanstackStart(),
    viteReact(),
  ],
})

export default config

[luthfi-hh]

I suspect @cloudflare/vite-plugin isn’t executing server.ts.
I added a console.log, but it never fired.

With Nitro, server.ts is executed as expected.

[SamuelAlev]

I suspect @cloudflare/vite-plugin isn’t executing server.ts.

When modifying the entrypoint aka custom server.ts and use the Cloudflare plugin, you need to go to the wrangler.jsonc / wrangler.toml, and update the main to point to the server.ts => "main": "./src/server.ts", in your case.

[luthfi-hh]

It seems to work when using "main": "./src/server.ts", but why do both the TanStack and Cloudflare docs recommend "main": "@tanstack/react-start/server-entry"? Are there any trade-offs?

TanStack Docs

Cloudflare Docs

[SamuelAlev]

Yup both docs are explaining the "basic" setup flow.
If you need to customize the server entrypoint, you need to replace @tanstack/react-start/server-entry with your actual server entrypoint (with TanStack Start, it will be ./src/server.ts).

Are there any trade-offs?

Nope, just make sure the handler.fetch(request) is called and you are good to go.

[luthfi-hh]

I think it should be documented as well so that anyone customizing their server entrypoint knows they must update main in wrangler.json to point to ./src/server.ts instead of @tanstack/react-start/server-entry.

Thanks @SamuelAlev for the clarification! I'll close this for now.