Pages build ignoring configuration to use bun instead of node

sh 22:52:01.393    Executing user command: bun run build
22:52:01.612    $ astro build
22:52:01.896    Node.js v18.17.1 is not supported by Astro!
22:52:01.896    Please upgrade Node.js to a supported version: ">=18.20.8"
22:52:01.897    
22:52:01.899    Cloudflare Pages CI Environment Detected!
22:52:01.899    Additional steps may be needed to set your Node.js version:
22:52:01.899    Documentation: https://docs.astro.build/en/guides/deploy/
22:52:01.899    
22:52:01.903    error: script "build" exited with code 1