Hi, @zetxek! Welcome to the Vercel Community

The most reliable solution would probably be to generate the critical CSS either locally or in a GitHub Action, where you have more control over the environment and can install the required system dependencies. This would avoid the limitations of the serverless environment while still allowing you to use Node.js 22 and the critical package. For example:

Run critical CSS generation locally:

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# Local script
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npm run critical-css
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git add assets/css/critical.css
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git commit -m "Update critical CSS"

Use GitHub Actions:

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name: Generate Critical CSS
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on: [push]
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jobs:
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  build:
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    runs-on: ubuntu-latest
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    steps:
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      - uses: actions/checkout@v2
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      - uses: actions/setup-node@v2
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        with:
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          node-version: '22'
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      - run: npm install
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      - run: npm run critical-css
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      - name: Commit changes
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        uses: EndBug/add-and-commit@v7
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        with:
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          message: 'Update critical CSS'
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          add: 'assets/css/critical.css'

Let us know how you get on!

This can work - I'll give it a try to the GitHub actions!

and coming back to say that it worked nicely :) I edited the idea a bit, but the inspiration was perfect: https://github.com/zetxek/adrianmoreno.info/blob/main/.github/workflows/generate-critical-css.yml

GitHub

adrianmoreno.info/.github/workflows/generate-critical-css.yml at main · zetxek/adrianmoreno.info

Static website generated with hugo CMS, hosted in vercel - zetxek/adrianmoreno.info

Perfect! Thanks for coming back and sharing that it worked.

Here if you have any more questions!