Deep Dive into AI Coding: Three Implementation Tiers of Spec-Driven Development
mattpocockuk · x · 2026-08-01
Birgitta Böckeler, Distinguished Engineer at Thoughtworks, explores the trending AI coding concept of Spec-Driven Development (SDD) on Martin Fowler's site.
The article explains that the core philosophy of SDD is writing a 'spec' before AI generates code, making it the single source of truth for both humans and AI. Based on tools like Kiro, spec-kit, and Tessl, the author categorizes SDD into three progressive implementation levels:
- Spec-first: A well-thought-out spec is written first and used in the AI-assisted workflow.
- Spec-anchored: The spec is retained after task completion for continuous feature evolution and maintenance.
- Spec-as-source: The spec becomes the primary source file over time, edited only by humans, while AI generates and updates the actual code.
Related event: Experts Rethink AI Coding: Spec Docs Should Be Ephemeral(2 posts)→
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