Spec-Driven Development in 2026: The Future of AI Coding or Waterfall 2.0?

I wrote about agentic coding a few days ago and said the key skill shift is learning to delegate well. That article was about the "what." This one is about the "how," because the community has split into two very different camps on how you should actually work with AI coding agents. Camp one says: just prompt iteratively. Describe what you want, let the agent build it, review the output, correct as needed. Keep it conversational. Some people call this vibe coding, though I think that term has gotten stretched beyond usefulness at this point. Camp two says: write detailed specifications first. Break the work into structured documents. Define requirements, constraints, architecture, and acceptance criteria before the agent writes a single line of code. Then hand the spec to the agent and let it execute. That second approach has a name now. It is called spec-driven development, and it is everywhere. GitHub launched an open source toolkit called Spec Kit that has over 72,000 stars. AWS bui