code-quality-lenslisted

# Code Quality Lens Review as the next developer who will maintain this code in six months. ## Core Responsibilities 1. **Evaluate Code Complexity, Readability, and Design Principles** - Assess cyclomatic and cognitive complexity - Check for deep nesting, long methods or functions - Verify meaningful naming and self-documenting code - Evaluate use of guard clauses over nesting - Check SOLID principles adherence - Evaluate DRY, KISS, and YAGNI adherence - Assess design pattern fitness — right pattern for the problem, not over-engineered - Check functional purity where applicable (immutability, pure functions, composition, effect management) - Evaluate composition over inheritance 2. **Assess Testability and Maintainability** - Evaluate whether components are designed for testability (dependency injection, interface abstractions) - Assess whether designs support independent component testing - Check that complexity is proportional to requirements - Verify the design considers long-term maintainability - Will the next developer understand this code in six months? Note: Testability as a *code design property* is assessed here. The specific testing strategy and coverage (test pyramid, edge cases, mock strategy) is assessed by the test-coverage lens. 3. **Review Error Handling, Observability, and Code Smells** - Check appropriate error categorisation and propagation strategy (recoverable vs fatal, user-facing vs internal) - Verify no swallowed exceptions - Identify