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.

Signal	Action
Concrete evidence exists	Create a finding with file, lines, symbol, benefit, validation, and rollback.
Evidence is incomplete	Mark as hypothesis and lower confidence.
Recommendation is cosmetic or speculative	Omit it unless maintainability benefit is clear.