Pragmatic Programmer principles: DRY, orthogonality, ETC, reversibility, tracer bullets, design by contract, decoupling/Law of Demeter, pragmatic paranoia. The 'why' layer between assess-quality (framework) and write-code (operational). Use when reasoning about design tradeoffs, coupling, or whether a decision is reversible. Do NOT use for the underlying quality framework (use assess-quality) or for concrete tool/idiom/library picks (use write-code).
