meteor-modern-build-stack

Modern build stack

The modern build stack is two independent tracks. Enable either or both.

1. Meteor Bundler Optimizations (Meteor 3.3+). One flag, SWC replaces Babel, SWC minifier replaces Terser, @parcel/watcher replaces the legacy watcher, development skips legacy archs.
2. Rspack Bundler Integration (Meteor 3.4+). Atmosphere package delegates app-code compilation to Rspack. Tree shaking, ESM, code splitting via HTTP, modern bundler plugins.

Standard current meteor create application skeletons ship both enabled. Purposefully small or compatibility-oriented skeletons, including minimal and legacy, may omit Rspack or the modern flag. Inspect the generated package.json and .meteor/packages instead of inferring features only from the Meteor version. For existing apps, enable optimizations first, then add Rspack once the app code is standards-clean.

Enable Meteor Bundler Optimizations

Add to package.json:

"meteor": {
  "modern": true
}

This enables SWC, the SWC minifier, the modern watcher, and dev-mode web arch skipping. Each falls back to legacy when something is incompatible, so this is backward compatible.

Opt out of pieces:

"meteor": {
  "modern": {
    "transpiler": false,
    "minifier": false,
    "watcher": false,
    "webArchOnly": false
  }
}

Or scope SWC: transpiler.excludeApp, transpiler.excludeNodeModules, transpiler.excludePackages, transpiler.excludeLegacy. Accept true or an array of paths/regexes.

Verbose transpiler logs to diagnose Babel fallbacks:

"meteor": {
  "modern": {
    "transpiler": { "verbose": true }
  }
}

Look for [Transpiler] Used Babel for <file> Fallback. The common cause is nested imports; see references/meteor-bundler-optimizations.md.

Enable Rspack integration

meteor add rspack

On first run the package installs the project-level Rspack setup. App code moves to Rspack; Meteor still handles Atmosphere packages and produces the final bundle. Requires entry points in package.json and no nested imports in app code. To migrate an existing app, use the migrate-to-rspack skill.