TL;DR Spec-driven development replaces prompt-iterate-fix loops with a structured workflow: write a spec, generate a plan, break it into tasks, then implement each one. I used GitHub Spec Kit and Claude Code to build a Python CLI expense tracker from scratch in under 30 minutes. The first-pass code worked correctly because Claude Code had a complete requirements document to work from, not a moving target of conversational prompts. Here's the full walkthrough with every file and command. The Vibe Coding Problem I spent three weeks last month building a small internal tool with Claude Code using the normal vibe coding approach: prompt, review the code, prompt again, fix something, prompt a third time. The tool worked, but by the end I had 40+ conversation turns and a codebase that reflected every mid-stream change of mind. My input quality was the bottleneck. I was figuring out requirements while generating code, which meant the AI was chasing a moving target.…