Debugging a cache requires understanding why it failed. GitHub Actions caches are immutable; once a cache is written to a specific key, it cannot be updated. Here are the most common root causes of cache issues: Issue A: The Cache Miss (False Negatives)

To follow along, ensure you have:

To get the most out of Debug Action Cache:

: Use the mxschmitt/action-tmate action to pause your workflow and SSH into the runner. This allows you to manually check if the files were actually restored to the directory you expected.

: Systems like Next.js and Ruby on Rails cache asset compilation and data fetching layer by layer.

provides a dedicated management interface to view and delete active caches. Navigation : Navigate to your repository on GitHub. Go to (left sidebar under "Management"). What to Look For

gh api --method DELETE -H "Accept: application/vnd.github+json" /repos/owner/repo/actions/caches/cache_id Use code with caution.

To help tailor this guide, what (e.g., GitHub Actions, GitLab, Bazel) are you using, and what specific programming language or framework is running inside your pipeline? Share public link

Enviroment variables are notorious for busting caches covertly. System updates might change your local PATH or add variables like USER or LANG .

When an action misses the cache, Bazel will print a message similar to this: Action cache miss:

The command line arguments for the tool (e.g., compiler flags). Environment variables. The toolchain configuration.