Series: Spec-Driven Development with Claude Code — Part 1 · Part 2 · Part 3 66% of developers say their top AI frustration is code that's "almost right, but not quite" ( Stack Overflow Developer Survey 2025 ). A Cloud Security Alliance study found 45% of AI-generated code introduced OWASP Top 10 vulnerabilities. An METR randomized controlled trial showed developers were 19% slower using AI tools — despite predicting a 24% speedup. The model isn't the problem. Not knowing exactly what to ask for is the problem. Tell Claude Code "build me a login with Supabase" and you get functional code. But does it use your project patterns? Does it handle errors the way you expect? Does it protect routes correctly? Is the answer "almost"? Spec-Driven Development (SDD) fixes this with a simple principle: the specification is the primary artifact. Code is its compilation target. What Is Spec-Driven Development?…