OpenSpec (Spec-Driven Development) Failed My Experiment — Instructions.md Was Simpler and Faster

There’s a lot of discussion right now about how developers should work with AI coding tools. Over the past year we’ve seen the rise of two very different philosophies: 1. Vibe Coding — just prompt the AI and iterate quickly 2. Spec-Driven Development — enforce structure so AI understands requirements Frameworks like OpenSpec are trying to formalize the second approach. Instead of giving AI simple prompts, the workflow looks something like this: generate a proposal review specifications approve tasks allow the AI agent to execute the plan In theory, this should produce better and more reliable code. So I decided to test it on a real project. Watch Video The Experiment I’m building a car classifieds web application. The backend and basic functionality already exist, and the front-end is built using .NET Razor Pages. The problem is the UI. It works, but it looks very basic and a bit lifeless. My goal was simple: Use modern AI coding tools to generate a more premium looking front-end desig