null-safetylisted

## Activation Contract Load this skill when reviewing refactor plans for: null safety, nullability, Optional, NPE. ## Hard Rules - Flag dereferences without clear guarantees, nullable returns, and ambiguous null semantics. - Prefer boundary checks, NonNull annotations where used, clear defaults, or Null Object only when justified. - Do not introduce Optional in fields, parameters, or DTOs without explicit reason. - Preserve observable behavior; label functional changes as follow-up. - Require evidence for every recommendation, or mark it as a hypothesis. ## Decision Gates | Signal | Action | |---|---| | Concrete evidence exists | Create a finding with `file:line` evidence and the smallest safe refactor. | | Evidence is incomplete | Mark as hypothesis and lower confidence. | | Recommendation is cosmetic or speculative | Omit it unless maintainability benefit is clear. | ## Execution Steps 1. Inspect the target and nearby tests only as needed for this lens. 2. Identify findings that match this skill's responsibility. 3. Recommend the smallest safe behavior-preserving refactor. 4. Note validation and rollback implications where material; the calling agent decides where they land. ## Output Contract Return findings in the calling agent's output contract — that contract wins over any field list here. Every finding carries `file:line` evidence or is marked hypothesis. Return `no_findings` when this lens has no material issue. ## References None.