A field guide to the practice that's reshaping how software gets built with AI agents.
TL;DR — Spec-Driven Development (SDD) makes a precise, executable specification the source of truth and treats code as a generated, verifiable artifact. The spec declares intent; the code realizes it. In 2026 it went mainstream because AI agents are great at writing code and terrible at guessing what you meant.
Jump to: Why now · Specs vs. executable specs · Maturity model · Workflow · Tooling · EARS · Worked example · Caveats · Bottom line
Why now? The "vibe coding" backlash
The movement defines itself against "vibe coding" — the term Andrej Karpathy popularized in early 2025 for loosely prompting an AI and shipping whatever comes back. Vibe coding is great for throwaway prototypes and miserable for anything that has to be maintained.
