yarn-cache-install

Install Yarn 4 dependencies after restoring the package cache

Apply the repository's mandatory agent tools and controlling instructions. This repair addresses Yarn 4 only.

The source action calls yarn cache dir, a Yarn Classic command rejected by Yarn 4. For Yarn 4, yarn config get cacheFolder reports the configured cache location. Select yarn.lock as the lockfile input to cache-key mechanisms, and follow the project's Yarn configuration. The source action defaults to a package-lock.json pattern, which is not a Yarn lockfile.

Ensure the project's declared, compatible Yarn version is available in the job before invoking it. Do not assume Corepack ships with every Node installation: Node stopped distributing it starting with Node 25. Provision the project's chosen package manager using its documented installation mechanism.

Run yarn install --immutable in the project directory even on a package-cache hit. Cached package archives are not the linked project state. This matters for both node_modules and Plug'n'Play projects. Keep an inconsistent lockfile as an installation failure. Respect project-specific zero-install and cache configuration; verify those arrangements before making broader assumptions.

The component review records the exact offline fixture and its limitations. It does not qualify Yarn Classic, pnpm, a real GitHub cache service, or agent performance.