Methodology

For most of software history the spec was a temporary planning artifact and the code was ground truth. Spec-driven development inverts that: the versioned specification becomes the primary artifact, and code is generated or verified against it. The idea is old — formal methods, design-by-contract, BDD all contain versions. What’s new is the motive: AI agents need explicit, durable intent because prompts evaporate and sessions reset.

Spec-driven development entered 2026 as the serious developer’s answer to vibe coding drift: implement against a reviewed specification, not an ad-hoc prompt. Hacker News called it “Waterfall Strikes Back.” Both sides have a point — and the practical question was never which side wins, but how much spec a specific task needs.