email build fails on Vercel — installDependencies does not install package

[maximwas]

What versions are you using? (if relevant)

@react-email/components@x.y.z, react-email@x.y.z, etc.

Describe the Bug

Describe the bug

When deploying to Vercel using the official deployment guide, email build fails with:

✔ Successfully prepared `.react-email` for `next build`
sh: line 1: cross-env: command not found
Error: `npm run build` failed.

Note that .react-email is successfully prepared but then npm run build inside it fails because cross-env (and other packages) are not installed.
Root cause
In build.ts, installDependencies is called to install packages inside .react-email:

if (!isInReactEmailMonorepo) {
  await installDependencies({ cwd: builtPreviewAppPath })
}

On Vercel isInReactEmailMonorepo = false so installDependencies should run — and based on logs it does start — but Vercel cancels or ignores the nested npm install inside .react-email subfolder. As a result .react-email/node_modules is never created and packages like cross-env, next, etc. are missing when npm run build runs.

Steps to reproduce

1. Create a standard react-email-starter project
2. Follow the official Vercel deployment guide
3. Set Framework Preset → Next.js, Output Directory → .react-email/.next
4. Push to Vercel — build fails

Environment

react-email: 5.2.9
@react-email/preview-server: 5.2.9
Node: 20.x (Vercel default)

Expected Behavior

When following the official Vercel deployment guide, running email build on Vercel
should automatically install all required dependencies inside .react-email and
successfully complete next build without any manual workarounds.

[alexisdavalos]

@maximwas until this is patched, you can chain npm_config_production=false into your build command and the dev modules will install correctly