Spec-Driven Development: Why AI Is Bringing an Old Software Engineering Idea Back to Life

Spec-Driven Development is gaining renewed attention as AI coding tools make it practical to turn detailed specifications into working software. The core idea — describing what you want before generating how to build it — is rooted in decades-old concepts like executable specifications, BDD, TDD, and DDD. AI lowers the cost of producing useful specs by helping clarify thinking, identify gaps, and structure requirements. Key insights include: small batch delivery still outperforms large upfront design; context (architecture standards, security, testing strategies) is becoming as important as code itself; verification and validation matter more than generation speed; and spec ownership should rest with the tech lead and team. Four models are outlined — Spec-First, Spec-Driven, Spec-Source, and Spec-Aligned — with most teams likely adopting a hybrid. The future bottleneck in software engineering is shifting from implementation to clarity, intent, and organisational knowledge.