Can’t wait to build something quick and maybe a real reason to update some older apps to Meteor 3.
While this is still in beta you could rename meteor: { modern: true } to something like meteor: { rspack: true }. That way a future build flag wouldn’t have to named moreModern.
meteor: { modern: true } relates to Meteor’s bundler optimizations, not Rspack. Rspack integration depends on adding the rspack package, not modern setting. The modern option was created only for the Meteor perspective, to speed up its own bundler when processing apps, packages and other CLI processing.
Let me know how your experiments with Meteor-Rspack go, and if you get any feedback to improve it for the official version.
Some initial observations:
Something wrong with the certificate of this website.
It seems that I can no longer import /from/folder when I want to assume the index.js inside the folder and also I need to add .js extensions for all imports in the project.
The certificate issue is out of my action scope. For betas, we can live with it for now.
@paulishca: Regarding strict extension usage, I tried to reproduce it in a small app and couldn’t. I set "type": "module" in package.json but ran into other errors. I’d like a consistent repoduce it so I can provide a direct fix.
Also, can you try this in your rspack.config.js?
export default defineConfig(Meteor => {
return {
module: {
rules: [
{
test: /\.m?js$/,
resolve: { fullySpecified: false }, // allow extensionless ESM imports
},
],
},
};
});
If that turns out to fix your setup, I’ll make it the default. It would help to know how to configure my app to make this error appear. Could you provide a minimal repository?
First try. I have this error. @sw/helpers is installed.
[Transpiler] Used SWC for socket-stream-client/node.js (package) 🟢 Cache hit (os.linux.x86_64)
[Transpiler] Used SWC for socket-stream-client/common.js (package) 🟢 Cache hit (os.linux.x86_64)
[Transpiler] Used SWC for socket-stream-client/urls.js (package) 🟢 Cache hit (os.linux.x86_64)
[Transpiler] Used SWC for ecmascript/ecmascript.js (package) 🟢 Cache hit (os.linux.x86_64)
=> Linted your app. No linting errors.
W20250909-12:05:38.530(2)? (STDERR) packages/core-runtime.js:189
W20250909-12:05:38.530(2)? (STDERR) throw error;
W20250909-12:05:38.530(2)? (STDERR) ^
W20250909-12:05:38.530(2)? (STDERR)
W20250909-12:05:38.531(2)? (STDERR) Error: Cannot find module '@swc/helpers/_/_async_generator_delegate'
W20250909-12:05:38.531(2)? (STDERR) at makeMissingError (packages/modules-runtime.js:221:12)
W20250909-12:05:38.531(2)? (STDERR) at Module.require (packages/modules-runtime.js:240:17)
W20250909-12:05:38.531(2)? (STDERR) at Module.mod.require (/home/harry/.meteor/packages/modules/.0.20.3.13guc6xon0l++os+web.browser+web.browser.legacy+web.cordova/npm/node_modules/@meteorjs/reify/lib/runtime/index.js:30:33)
W20250909-12:05:38.531(2)? (STDERR) at Module.moduleLink [as link] (/home/harry/.meteor/packages/modules/.0.20.3.13guc6xon0l++os+web.browser+web.browser.legacy+web.cordova/npm/node_modules/@meteorjs/reify/lib/runtime/index.js:102:22)
W20250909-12:05:38.532(2)? (STDERR) at module.wrapAsync.self (/home/harry/Dev/VueGPX/.meteor/local/build/programs/server/app/app.js:121:144)
W20250909-12:05:38.532(2)? (STDERR) at Module.wrapAsync (/home/harry/.meteor/packages/modules/.0.20.3.13guc6xon0l++os+web.browser+web.browser.legacy+web.cordova/npm/node_modules/@meteorjs/reify/lib/runtime/index.js:252:8)
W20250909-12:05:38.532(2)? (STDERR) at module (/home/harry/Dev/VueGPX/.meteor/local/build/programs/server/app/app.js:121:9)
W20250909-12:05:38.532(2)? (STDERR) at fileEvaluate (packages/modules-runtime.js:335:7)
W20250909-12:05:38.532(2)? (STDERR) at Module.require (packages/modules-runtime.js:237:14)
W20250909-12:05:38.532(2)? (STDERR) at Module.mod.require (/home/harry/.meteor/packages/modules/.0.20.3.13guc6xon0l++os+web.browser+web.browser.legacy+web.cordova/npm/node_modules/@meteorjs/reify/lib/runtime/index.js:30:33)
W20250909-12:05:38.533(2)? (STDERR) at Module.moduleLink [as link] (/home/harry/.meteor/packages/modules/.0.20.3.13guc6xon0l++os+web.browser+web.browser.legacy+web.cordova/npm/node_modules/@meteorjs/reify/lib/runtime/index.js:102:22)
W20250909-12:05:38.533(2)? (STDERR) at module.wrapAsync.self (_build/main-dev/server-meteor.js:1:1)
W20250909-12:05:38.533(2)? (STDERR) at Module.wrapAsync (/home/harry/.meteor/packages/modules/.0.20.3.13guc6xon0l++os+web.browser+web.browser.legacy+web.cordova/npm/node_modules/@meteorjs/reify/lib/runtime/index.js:252:8)
W20250909-12:05:38.533(2)? (STDERR) at module (_build/main-dev/server-meteor.js:1:1)
W20250909-12:05:38.533(2)? (STDERR) at fileEvaluate (packages/modules-runtime.js:335:7)
W20250909-12:05:38.533(2)? (STDERR) at Module.require (packages/modules-runtime.js:237:14)
W20250909-12:05:38.533(2)? (STDERR)
W20250909-12:05:38.533(2)? (STDERR) Node.js v22.18.0
Could you check if this solves it for you? Adding "externalHelpers": false at .swcrc as showed in the other post.
I am trying to debug this problem, but it’s hard to get the same problem on Meteor checkout, I will need to debug on published versions.
Sorry, I missed this post. Thanks, it fixes it.
my project starts. Now, will look at vue support (Vue - Rspack)
I’ve deployed a few stability betas, the latest is 3.4-beta.6. This release fixes an issue where the published and checkout versions of Meteor 3.4 behaved differently, including how project files were handled for compilation. That mismatch caused problems like the @swc/helpers reports and others, and likely RAM-related instability.
@pmogollon, @harry73, @schlaegerz: the errors with '@swc/helpers/_/_async_generator_delegate' and related should be gone. You no longer need to set "externalHelpers": false in .swcrc. Can you confirm?
I’ll move on to other issues as soon as I have reproductions. As I test existing repos and apps, I’ll ship more fixes as well.
Perfect. I can confirm beta.6 fixes the issue when removing the externalHelpers setting.
Thanks.
beta.6 fixes it
Thanks.
I have the following error:
[Rspack Client] [client-rspack]:package ... /
ERROR in ./node_modules/@firebase/database-compat/dist/index.standalone.js 5:25-32
× Module not found: Can't resolve 'util' in '/home/Dev/VueGPX/node_modules/@firebase/database-compat/dist'
╭─[5:17]
3 │ Object.defineProperty(exports, '__esModule', { value: true });
4 │
5 │ var require$$2 = require('util');
· ───────────────
6 │ var require$$0 = require('buffer');
7 │ var require$$1 = require('events');
╰────
My original rspack.config.js is:
import { defineConfig } from '@meteorjs/rspack';
import { VueLoaderPlugin } from 'vue-loader';
export default defineConfig(Meteor => {
return {
...(Meteor.isClient && {
module: {
rules: [
{
test: /\.vue$/,
loader: 'vue-loader',
options: {
// Note, for the majority of features to be available, make sure this option is `true`
experimentalInlineMatchResource: true,
},
},
{
test: /\.(sass|scss)$/,
use: [
{
loader: 'sass-loader',
options: {
// using `modern-compiler` and `sass-embedded` together significantly improve build performance,
// requires `sass-loader >= 14.2.1`
api: 'modern-compiler',
implementation: 'sass-embedded',
},
},
],
// set to 'css/auto' if you want to support '*.module.(scss|sass)' as CSS Modules, otherwise set type to 'css'
type: 'css/auto',
},
{ test: /\.css$/, use: ['postcss-loader'], type: 'css' },
],
},
plugins: [new VueLoaderPlugin()],
}),
resolve: {
alias: {
'@ui': '/imports/ui',
'@api': '/imports/api',
'@plugins': '/imports/plugins',
'@server': '/server',
'@client': '/client',
'@packages': '/packages',
'@tests': '/tests',
'@public': '/public',
'@private': '/private',
},
},
};
});
and the one built by Meteor:
[Rspack Client] Config: {
name: '[client-rspack]',
target: 'web',
mode: 'development',
entry: '/home/Dev/VueGPX/_build/main-dev/client-entry.js',
output: {
path: '/home/Dev/VueGPX/public',
filename: [Function: filename],
libraryTarget: 'commonjs',
publicPath: '/',
chunkFilename: 'build-chunks/[id].js',
assetModuleFilename: 'build-assets/[hash][ext][query]',
cssFilename: 'build-chunks/[name].css',
cssChunkFilename: 'build-chunks/[id].css'
},
optimization: { usedExports: true, splitChunks: { chunks: 'async' } },
module: {
rules: [
{
test: /\.(?:[mc]?js|jsx|[mc]?ts|tsx)$/i,
exclude: /node_modules|\.meteor\/local/,
loader: 'builtin:swc-loader',
options: {
jsc: {
baseUrl: '/home/Dev/VueGPX',
paths: {
'/*': [ '*', '*' ],
'@api/*': [ 'imports/api/*' ],
'@ui/*': [ 'imports/ui/*' ],
'@plugins/*': [ 'imports/plugins/*' ],
'@server/*': [ 'server/*' ],
'@client/*': [ 'client/*' ],
'@packages/*': [ 'packages/*' ],
'@tests/*': [ 'tests/*' ],
'@public/*': [ 'public/*' ],
'@private/*': [ 'private/*' ]
},
parser: { syntax: 'ecmascript' },
target: 'es2015',
transform: { react: { development: true, refresh: true } },
externalHelpers: true
}
}
},
{
test: /\.vue$/,
loader: 'vue-loader',
options: { experimentalInlineMatchResource: true }
},
{
test: /\.(sass|scss)$/,
use: [
{
loader: 'sass-loader',
options: { api: 'modern-compiler', implementation: 'sass-embedded' }
}
],
type: 'css/auto'
},
{ test: /\.css$/, use: [ 'postcss-loader' ], type: 'css' }
]
},
resolve: {
extensions: [
'.ts', '.tsx',
'.mts', '.cts',
'.js', '.jsx',
'.mjs', '.cjs',
'.json', '.wasm'
],
alias: {
'/': '/home/Dev/VueGPX',
'@ui': '/imports/ui',
'@api': '/imports/api',
'@plugins': '/imports/plugins',
'@server': '/server',
'@client': '/client',
'@packages': '/packages',
'@tests': '/tests',
'@public': '/public',
'@private': '/private'
}
},
externals: [ /^meteor.*/ ],
plugins: [
RequireExternalsPlugin {
pluginName: 'RequireExternalsPlugin',
_externals: null,
_externalMap: null,
_enableGlobalPolyfill: true,
_isEagerImport: null,
_lastImports: null,
_defaultExternalPrefix: 'external ',
filePath: '/home/Dev/VueGPX/_build/main-dev/client-meteor.js',
backRoot: '../../',
_funcCount: 1
},
DefinePlugin {
affectedHooks: 'compilation',
name: 'DefinePlugin',
_args: [
{
'Meteor.isClient': 'true',
'Meteor.isServer': 'false',
'Meteor.isTest': 'false',
'Meteor.isAppTest': 'false',
'Meteor.isDevelopment': 'true',
'Meteor.isProduction': 'false'
}
]
},
BannerPlugin {
affectedHooks: undefined,
name: 'BannerPlugin',
_args: [
{
banner: '/**\n' +
'* @file client-rspack.js\n' +
'* @description Bundled output generated by Rspack\n' +
'* --------------------------------------------------------------------------\n' +
'* ⚡ Rspack Client App (Development)\n' +
'* --------------------------------------------------------------------------\n' +
'* • [ client-entry.js ] ──▶ [■ client-rspack.js ] ──▶ [ client-meteor.js ]\n' +
'*\n' +
'* This file is the bundled output generated by Rspack.\n' +
'* It contains all application code and assets combined into one build.\n' +
'* It is not used directly, but will be imported by the Meteor main module\n' +
'* file (`client-meteor.js`) so that Meteor runs the Rspack bundle.\n' +
'*\n' +
'* ⚠️ Note: This file is autogenerated. It is not meant to be modified manually.\n' +
'* These files also act as a cache: they can be safely removed and will be\n' +
'* regenerated on the next build. They should be ignored in IDE suggestions\n' +
'* and version control.\n' +
'*/\n' +
'\n' +
'/* No code generated as served by HMR server */\n',
entryOnly: true
}
]
},
HtmlRspackPlugin {
options: {
inject: false,
cache: true,
filename: '../_build/main-dev/index.html',
templateContent: '\n' +
' <head>\n' +
' <% for tag in htmlRspackPlugin.tags.headTags { %>\n' +
' <%= toHtml(tag) %>\n' +
' <% } %>\n' +
' </head>\n' +
' <body>\n' +
' <% for tag in htmlRspackPlugin.tags.bodyTags { %>\n' +
' <%= toHtml(tag) %>\n' +
' <% } %>\n' +
' </body>\n' +
' '
}
},
Plugin {}
],
watchOptions: { ignored: [ '**/.meteor/local/**', '**/dist/**' ] },
devtool: 'source-map',
devServer: {
static: {
directory: '/home/Dev/VueGPX/public',
publicPath: '/__rspack__/'
},
hot: true,
liveReload: true,
port: '8080',
devMiddleware: { writeToDisk: [Function: writeToDisk] }
},
experiments: { css: true }
}
[Rspack Server] [server-rspack]:package ... -
[server-rspack] compiled successfully in 686 ms
[Rspack Client] <i> [webpack-dev-server] Project is running at:
[Rspack Client] <i> [webpack-dev-server] Loopback: http://localhost:8080/, http://[::1]:8080/
<i> [webpack-dev-server] On Your Network (IPv4): http://192.168.1.45:8080/
<i> [webpack-dev-server] Content not from webpack is served from '/home/Dev/VueGPX/public' directory
This looks like you are trying to use node stuff on the client, you can either pull that stuff out of the client or use the node polyfill
Thanks. It was that.
With meteor-vite, this issue did not occur.
In a method code, a server code was included by this conditional statement if(!this.isSimulation). I replace it by if(Meteor.isServer)
Actually maybe this is something I can improve. If this.isSimulation is like Meteor.isClient, I will define that rule and will wipe out the contents and dependencies related where used. I can try that to see if it solves the issue.
wreiske@Wills-MacBook-Pro-M2 meteor-react-tailwind-prettier-starter % meteor npm run start
> start
> meteor run
[[[[[ ~/Documents/GitHub/meteor-react-tailwind-prettier-starter ]]]]]
=> Started proxy.
Error starting Mongo (2 tries left): Cannot run replSetReconfig because the node is currently updating its configuration
=> Started MongoDB.
[Rspack Client Error] npm error could not determine executable to run
[Rspack Client Error] npm error A complete log of this run can be found in: /Users/wreiske/.npm/_logs/2025-09-09T22_17_50_886Z-debug-0.log
[Rspack Server Error] npm error could not determine executable to run
[Rspack Server Error] npm error A complete log of this run can be found in: /Users/wreiske/.npm/_logs/2025-09-09T22_17_50_886Z-debug-0.log
Loading plugin `rspack` from package ... -
After upgrading to .6 from .3, this is now occurring.
13 silly packumentCache heap:4345298944 maxSize:1086324736 maxEntrySize:543162368
13 silly packumentCache heap:4345298944 maxSize:1086324736 maxEntrySize:543162368
14 http fetch GET 200 https://registry.npmjs.org/rspack 167ms (cache revalidated)
15 verbose stack Error: could not determine executable to run
15 verbose stack at getBinFromManifest (/Users/wreiske/.meteor/packages/meteor-tool/.3.4.0-beta.6.6mldn4xztdp++os.osx.arm64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.arm64/dev_bundle/lib/node_modules/npm/node_modules/libnpmexec/lib/get-bin-from-manifest.js:17:23)
15 verbose stack at exec (/Users/wreiske/.meteor/packages/meteor-tool/.3.4.0-beta.6.6mldn4xztdp++os.osx.arm64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.arm64/dev_bundle/lib/node_modules/npm/node_modules/libnpmexec/lib/index.js:202:15)
15 verbose stack at async Npm.exec (/Users/wreiske/.meteor/packages/meteor-tool/.3.4.0-beta.6.6mldn4xztdp++os.osx.arm64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.arm64/dev_bundle/lib/node_modules/npm/lib/npm.js:207:9)
15 verbose stack at async module.exports (/Users/wreiske/.meteor/packages/meteor-tool/.3.4.0-beta.6.6mldn4xztdp++os.osx.arm64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.arm64/dev_bundle/lib/node_modules/npm/lib/cli/entry.js:74:5)
16 verbose pkgid rspack@0.1.1
17 error could not determine executable to run
18 verbose cwd /Users/wreiske/Documents/GitHub/meteor-react-tailwind-prettier-starter
19 verbose os Darwin 24.5.0
20 verbose node v22.18.0
21 verbose npm v10.9.3
22 verbose exit 1
23 verbose code 1
24 error A complete log of this run can be found in: /Users/wreiske/.npm/_logs/2025-09-09T22_20_19_163Z-debug-0.log
14 http fetch GET 200 https://registry.npmjs.org/rspack 196ms (cache revalidated)
15 verbose stack Error: could not determine executable to run
15 verbose stack at getBinFromManifest (/Users/wreiske/.meteor/packages/meteor-tool/.3.4.0-beta.6.6mldn4xztdp++os.osx.arm64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.arm64/dev_bundle/lib/node_modules/npm/node_modules/libnpmexec/lib/get-bin-from-manifest.js:17:23)
15 verbose stack at exec (/Users/wreiske/.meteor/packages/meteor-tool/.3.4.0-beta.6.6mldn4xztdp++os.osx.arm64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.arm64/dev_bundle/lib/node_modules/npm/node_modules/libnpmexec/lib/index.js:202:15)
15 verbose stack at async Npm.exec (/Users/wreiske/.meteor/packages/meteor-tool/.3.4.0-beta.6.6mldn4xztdp++os.osx.arm64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.arm64/dev_bundle/lib/node_modules/npm/lib/npm.js:207:9)
15 verbose stack at async module.exports (/Users/wreiske/.meteor/packages/meteor-tool/.3.4.0-beta.6.6mldn4xztdp++os.osx.arm64+web.browser+web.browser.legacy+web.cordova/mt-os.osx.arm64/dev_bundle/lib/node_modules/npm/lib/cli/entry.js:74:5)
16 verbose pkgid rspack@0.1.1
17 error could not determine executable to run
18 verbose cwd /Users/wreiske/Documents/GitHub/meteor-react-tailwind-prettier-starter
19 verbose os Darwin 24.5.0
20 verbose node v22.18.0
21 verbose npm v10.9.3
22 verbose exit 1
23 verbose code 1
24 error A complete log of this run can be found in: /Users/wreiske/.npm/_logs/2025-09-09T22_20_19_163Z-debug-0.log
Did you do npm install? I think the reason is this. I’d like to improve the logs to warn about that, basically meaning that it can’t find the rspack .bin within node_modules, likely missing it due to need for its installation.
If it still happens, does this happens to you even after doing a meteor reset?
All of this looks great @nachocodoner ! I’m sure this will make Meteor 3 get more traction 
btw, I think that code inside isSimulation isn’t restricted to the client code, since it could also be run on the server when you connect a server to another meteor instance to calls remote methods
Thanks @tcastelli! Meteor needs modernization and a fresh view these days. 
btw, I think that code inside isSimulation isn’t restricted to the client code, since it could also be run on the server when you connect a server to another meteor instance to calls remote methods
You’re right. I probably won’t use this.isSimulation the way I was thinking and strip from server, since it’s a runtime check, not a build-time one like Meteor.isClient and Meteor.isServer. Safer not to assume based on that.
What I don’t understand is why meteor-vite didn’t mix the client code with the server-only code, did it inject a Node polyfill?
New stability release available: 3.4-beta.8. This includes fixes on Windows and improvements in the integration.
With this, and unless a critical issue appears in the Meteor-Rspack flow, I consider the first phase of the official 3.4 release complete. This phase focused on stability and was key to deliver the work done over the last months around Meteor-Rspack integration. We now have a working published version supporting all Meteor skeletons and allowing migration of existing projects. Meteor apps can now run with Rspack in dev mode, bundle visualizer mode, Cordova mode, build mode, testing with all options, and deploy to production. Detailed docs are also available to explain the approach and guide the migration process. A new modern test suite also ensures configs remain compatible and regressions are avoided in future updates.
The second phase will focus on extensibility. While stability is ready for you to start migrating your apps, we know projects may need special configs or customizations. This phase is about your feedback. As you adapt your apps, share your needs. We’ll suggest configs, packages, alternatives, or considerations to cover edge cases. This will help us expand the integration and improve the docs.
This phase is also about experimenting with new setups and customizations. We’ll provide ways to customize the new build contexts (_build, build-chunks, etc). I’d also like to experiment with Angular support in Meteor, since Rspack already supports Angular with its own config approach similarly as ours with Meteor. The idea is to complement Meteor’s config with it. Other customizations will be added as we understand needs and explore new ideas.
A call to action for every Meteor developer who believes in a new era of tools and a modern dev experience. The way we deliver ideas and products with Meteor is shifting, and your support is key. Every bit of feedback helps shape and expand this work. Please take a moment to contribute and support these improvements.