WTF is Spec-driven Development?
Writing a structured spec before asking an AI to code, so the spec becomes the source of truth for both human and agent.
Also called: sdd, spec-first, spec-anchored, spec-as-source
TL;DR
Instead of prompting "build me X" and iterating on code, you first write a behaviour-focused spec in plain language, then let the agent implement from it. Variants range from throwaway specs per task to specs that are the only thing humans edit.
How it works
Birgitta Böckeler distinguishes three levels: spec-first (a spec precedes the task, then is discarded), spec-anchored (specs persist and evolve with the feature) and spec-as-source (specs are the primary artefact and humans never edit generated code). Her caveats: one-size-fits-all workflows, review burden from many Markdown files, agents still ignoring specs, blurred lines between functional and technical detail, and echoes of model-driven development's failures.
Origin
- Coined / introduced by
- AI coding tool makers; analysed by Birgitta Böckeler (Thoughtworks)
- When
- 2025
- Story
- Spread in 2025 through spec-centric coding tools; Böckeler's Oct 2025 memo on martinfowler.com gave the field its main taxonomy.