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Metro babel transformer doesn't recognize .cjs config files (babel.config.cjs, .babelrc.cjs) #58525
Description
Description
The @react-native/metro-babel-transformer doesn't recognize .cjs babel config files, which causes silent failures when projects use "type": "module" in their package.json.
Problem
In @react-native/metro-babel-transformer/src/index.js (lines 74-88), the transformer only searches for:
- .babelrc
- .babelrc.js
- babel.config.js
When a project has "type": "module" in package.json:
- .js files are treated as ES modules by Node.js
- Babel config files that use module.exports = function(api) {...} (CommonJS) must use the .cjs extension
- Metro silently falls back to the default preset, ignoring custom plugins
This causes hard-to-debug issues. In my case, the react-native-worklets/plugin wasn't being applied, resulting in runtime errors like "Failed to create a worklet" with no indication that the babel config wasn't being loaded.
Expected behavior
Metro should also search for:
- .babelrc.cjs
- babel.config.cjs
This aligns with Babel's own configuration file resolution which supports .cjs extensions.
Workaround
Use extendsBabelConfigPath in Metro config:
// metro.config.cjs
const customConfig = {
transformer: {
extendsBabelConfigPath: path.resolve(__dirname, 'babel.config.cjs'),
},
};
Environment
React Native: 0.81.5
Node.js: 24.x
pnpm monorepo with "type": "module" in package.json
Activity
react-native-bot commentedon Sep 14, 2026
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Missing reproducer: We could not detect a reproducible example in your issue report. Reproducers are mandatory and we can accept only one of those as a valid reproducer:
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robhogan commentedon Sep 14, 2026
Transferred to
react/react-native, since the Babel config loading logic lives here, not in Metro itself.Thanks for the report - seems like a legitimate expectation that discovery should mirror Babel's - or at least support
.cjs.react-native-bot commentedon Sep 14, 2026
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Could not parse version: We could not find or parse the version number of React Native in your issue report. Please use the template, and report your version including major, minor, and patch numbers - e.g. 0.76.2.
react-native-bot commentedon Sep 14, 2026
Warning
Could not parse version: We could not find or parse the version number of React Native in your issue report. Please use the template, and report your version including major, minor, and patch numbers - e.g. 0.76.2.
react-native-bot commentedon Oct 9, 2026
This issue is waiting for author's feedback since 24 days. Please provide the requested feedback or this will be closed in 7 days.
react-native-bot commentedon Oct 9, 2026
This issue is waiting for author's feedback since 24 days. Please provide the requested feedback or this will be closed in 7 days.