Restore cached outputs without touching unrelated files
A cached archive restored ../config.json during a local corruption test. Replace blind extraction with a validated manifest and staged restoration inside declared output roots.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Filesystem safety · Artifact integrity · Transactional writes · Threat modeling
Estimated field mix
- Security50%
- Developer tooling30%
- Storage systems20%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
A product team waits for every package to rebuild after small changes. An experimental cache is faster but occasionally returns success after a shared type changed. Build a small, auditable task runner around fixture packages.
Setup prerequisites
- Prepare four fixture packages with one shared library and two applications.
- Use only trusted fixture commands in local tests.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Every restored file has a normalized in-root path and verified content digest.
- Absolute paths, traversal paths, symlink escapes, and unexpected output entries are rejected.
- A rejected or interrupted restoration preserves the prior output set and reports a cache miss.
Implementation constraints
- Treat cache entries as untrusted even when the cache is local.
- Separate verification from replacement and avoid executing archive hooks.
Verification to include
- Restore a valid two-directory output manifest and compare every digest.
- Use traversal, digest mismatch, and interrupted replacement fixtures and verify unrelated files are unchanged.
Deliverables
- Validated cache restorer and corruption fixtures
Rollout and recovery
Enable restoration behind an opt-in flag; on any integrity error rebuild from source and quarantine that cache entry.
Value of the work
For the engineer: Practice incremental computation, dependency scheduling, cache correctness, and cancellation.
For the team: Inspect whether faster checks preserve the guarantees reviewers depend on.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.