Builds become faster with dependency caching, but a reused cache sometimes introduces incompatible libraries after dependency changes. Which cache strategy should be used?

1. Key and invalidate caches according to relevant dependency and build-tool inputs, and validate restored content.
2. Treat a cache hit as proof that tests can be skipped.
3. Use one permanent cache key for all languages, branches, and dependency versions.
4. Allow untrusted builds to overwrite all privileged release caches without isolation.