Bug reproduction.

git clone [email protected]:brillout/vite3-prebundler-bug
cd vite3-prebundler-bug/
pnpm install
pnpm run dev:express

Same as single line (copy-paste me):

git clone [email protected]:brillout/vite3-prebundler-bug && cd vite3-prebundler-bug/ && pnpm install && pnpm run dev:express

Go to localhost:3000 and observe:

11:22:24 AM [vite] ✨ new dependencies optimized: react, react-dom/client
11:22:24 AM [vite] ✨ optimized dependencies changed. reloading

Interestingly, when using the Vite CLI $ vite, it only occasionally logs [vite] ✨ new dependencies optimized:

rm -rf node_modules/.vite/
pnpm run dev:vite

  VITE v3.0.0-beta.10  ready in 1166 ms

  ➜  Local:   http://localhost:3000/
  ➜  Network: use --host to expose

# Only sometimes:
3:48:53 PM [vite] ✨ new dependencies optimized: react, react-dom/client
3:48:54 PM [vite] ✨ optimized dependencies changed. reloading

Whereas the [vite] ✨ new dependencies optimized logs can be reliably reproduced when using the Express.js server:

rm -rf node_modules/.vite/
pnpm run dev:express