In systems like Bazel, you can use flags like --execution_log_json_file . This allows you to see the exact metadata sent to the cache. You can compare logs from two different builds to see which file or environment variable caused the discrepancy. 2. Identifying "Dirty" Environment Variables
If you're compiling binaries, ensure you strip timestamps from the output, as these will change the file hash even if the code is identical. The Cost of Ignoring Cache Issues
If you are struggling with cache performance, run through this list:
A common culprit for cache misses is the environment. If your build script pulls in a timestamp, a random seed, or a local file path (e.g., /Users/john/project vs /Users/jane/project ), the cache will treat them as different actions. 3. Verbose Logging
When using GitHub Actions, debugging the cache often involves setting: ACTIONS_STEP_DEBUG: true
Are your file paths absolute or relative? Always prefer relative paths for better portability.
Maximizing Build Efficiency: A Deep Dive into debug-action-cache