What problem does it solve? Teams often declare work done based on a passing unit test or a green diff, only to discover the bug still exists in production. This Skill enforces running-system verification: reproduce the failure where it lived, then prove it passes where the code will actually run. ## Core Features & Use Cases - Red-before-green proof: Reproduce the original defect before the fix and confirm it is gone after, so a green check actually means something. - Boundary and failure-path checks: Drive worst-case inputs (oversized, malformed, hostile, wrong auth) and exercise timeouts, dependency outages, and fallback paths. - Concurrency, scale, and prod-like validation: Run stateful operations twice, concurrently, and interrupted; verify cost-bearing paths at reachable scale in staging or canary environments. - Use Case: After fixing a race condition in a job queue, use this Skill to structure proof: replay the failing scenario, run the job concurrently, watch production-like signals, and pin a permanent regression test. ## Quick Start Ask the agent to verify that your recent fix actually works in a running system using the structural-verifying checklist.
