Vite middleware mode: cannot GET /

[xandris]

I'm using React Router as a...

framework

Reproduction

https://github.com/xandris/react-router-middleware-mode

in short, I

• npx create-react-router@latest my-react-router-app
• updated dependencies (vite 6, express 5)
• npm run build
• npm start (works)
• wrote a start.js that
  • creates an express app
  • creates a vite server in middleware mode
  • adds vite's middleware to the express app
  • starts the express app

the express app just gives 404s for any request

System Info

System:
    OS: macOS 15.3.1
    CPU: (16) arm64 Apple M3 Max
    Memory: 640.47 MB / 48.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.14.0 - /opt/homebrew/opt/node@22/bin/node
    npm: 11.2.0 - /opt/homebrew/bin/npm
    pnpm: 9.6.0 - ~/Library/pnpm/pnpm
  Browsers:
    Chrome: 134.0.6998.89
    Safari: 18.3
  npmPackages:
    @react-router/dev: ~7 => 7.3.0 
    @react-router/node: ~7 => 7.3.0 
    @react-router/serve: ~7 => 7.3.0 
    react-router: ~7 => 7.3.0 
    vite: ~6 => 6.2.2

Used Package Manager

npm

Expected Behavior

the same functionality as react-router dev

Actual Behavior

404s for any GET

[tclohm]

The issue is likely that Express is looking for files in the wrong directory.
Based on the build output, React Router 7 creates two separate directories:

./build/client - Contains the client-side files (JavaScript, CSS, assets)
./build/server - Contains the server-side rendering code

However, Express might be configured to look in Vite's default output directory (./dist) instead of the ./build/client directory that React Router actually uses.
You might need to update your Express server configuration to serve files from the correct location: the ./build/client directory where React Router places its build output.

I hope that helps.

[xandris]

oh sorry, this is for the dev server, not the built server. i was launching a backend server along with the vite dev server to save my developers the trouble of starting a separate server. as in attaching the vite middlewares to our existing backend server. but maybe i'll launch it in a child process instead