Does spec-driven development really work?

Spec-driven development is examined with skepticism: the methodology requires frontloading all thinking into a machine-readable spec before writing code, which contradicts how real-world complexity is discovered during implementation. Tools like GitHub Spec Kit and BMAD (AI agent orchestration via markdown files) are pushing this approach. While AI coding gives an 80% speed boost for simple apps, studies including the 2026 DORA AI report show a U-shaped productivity curve where real-world complexity causes productivity to drop below baseline. Over-reliance on AI also correlates with more software instability and weakened developer skills. The conclusion: the last 20% of real engineering — edge cases, debugging, abstraction — remains irreducibly human.