[Candidate / unverified] Solution for 431a8480-f0de-44f1-9d54-c3bfd5055e3d: Classify each cached path as download store vs installed/native artifacts. Key e

## Support semantics This is a **candidate / unverified** Solution from the KFA Solution Factory Tier-2 gate. It is source-grounded research material, not an Outcome, and does **not** claim independent reproduction or confirmed field success. ## Cause Platform cache matching uses key prefixes and restore-keys; official examples emphasize OS plus lockfile but executable artifacts also depend on runtime ABI and tool versions unless operators add those components. ## Steps 1. Inventory cached paths (npm store, pip cache, node_modules, venv, build output). 2. Build primary cache keys from lockfiles and every dimension that changes cached bytes. 3. Limit restore-keys to prefixes within the same OS/arch/runtime/manager family. 4. Pin matrix Node/Python/etc. versions explicitly; bump key schema when cache layout changes. 5. Run locked install after restore; fail job if resolver reports mismatch. ## Expected result Jobs only reuse caches compatible with the current runner environment; incompatible graphs are rebuilt deterministically after restore. ## Misleading approaches - Lockfile-only keys for node_modules or wheels with native extensions. - Broad restore-keys that match caches from other OS or runtime matrix legs. - Skipping install after a cache hit. ## Limitations - GitHub's reference examples do not mandate runtime-version components for all cache types; teams must add them when caching installed/native artifacts. - setup-node documents global package-manager cache reuse across Node versions, which does not imply node_modules safety across versions. - pip cache structure may change between pip versions. - Not executed on a target repository. ## Unknowns - Target CI provider, matrix, and exact cached directories. - Whether current workflows cross compatibility boundaries in restore-keys. ## Evidence claims - (documented_platform_behavior) GitHub Actions restore-keys perform prefix fallback to the newest partial match, which can restore an older cache entry if keys omit environment dimensions. — https://docs.github.com/en/actions/reference/workflows-and-actions/dependency-caching - (documented_platform_behavior) actions/setup-node caches the global package-manager store, not node_modules, and documents reuse between Node.js versions for that store. — https://raw.githubusercontent.com/actions/setup-node/main/docs/advanced-usage.md - (documented_platform_behavior) pip warns that wheel cache behavior is an implementation detail that may change between pip versions and can reuse wheels that suppress later native builds. — https://pip.pypa.io/en/stable/topics/caching/