Failure Depth and Recovery: Conditional Repair Across Evaluation Layers, Mechanisms, Reachability and Intervention Tests

RT8 distinguishes the location of a failure from the repair depth sufficient for a declared objective, intervention family, budget, and observation horizon. Constructed dynamics show that a position reset can yield durable functional recovery even when a distorted evaluator or faulty update generator remains. The earlier universal minimum-depth correspondence is withdrawn. A narrower conditional relation depends on whether unchanged mechanisms regenerate failure throughout states accessible to shallower interventions and whether repair reaches a stable acceptable region. The paper separates optional repair capabilities from compulsory bundles and temporal deterioration from treatment effects. Deployment diagnosis, broad recovery benefits, and universal repair-cost ordering remain unvalidated.