Unable to load plugin (yarn pnp issue?)

To reproduce:

import { execSync } from 'node:child_process';

execSync(
  'lessc --clean-css="--s1 --advanced --compatibility=ie8" index.less style.css',
  { stdio: 'inherit' },
);

Current behavior:

It seems that less cannot find clean-css.

Unable to load plugin clean-css please make sure that it is installed under or at the same level as less

Expected behavior:

Expected that less would find clean-css.

Environment information:

• less version: 4.4.1
• nodejs version: v22.15.0
• operating system: macos 14.6.1 (23G93)
• yarn version: 4.9.1
• less-plugin-clean-css version: 1.6.0
• clean-css version: 5.3.3

Additional context

• packages installed as dev deps (yarn add -D) in yarn workspace using pnp
• script is run with yarn dotenvx run tsx ./script.ts

Start by reproducing the command from script.ts with the listed Yarn Plug'n'Play environment, using index.less as the input and style.css as the output. Trace why less cannot load clean-css through less-plugin-clean-css, then verify that the command completes and produces the expected stylesheet without the plugin error.