I Built a SaaS in 48 Hours Using Only AI Tools — Here's What Happened

Everyone talks about AI replacing developers. I decided to test it. I gave myself 48 hours to build a fully functional SaaS product using nothing but AI tools: Claude for architecture and code, Cursor as my IDE, v0 for the UI, and Supabase for the backend. The Rules No manual coding unless AI gets stuck Every decision goes through AI first Ship something real, not a toy project Hour 0-8: Architecture I described my product idea to Claude: a simple tool that helps freelancers track time and generate invoices automatically. Claude gave me: Database schema (PostgreSQL via Supabase) API routes structure Authentication flow Component hierarchy The architecture was solid. Better than what I'd sketch on a whiteboard in 2 hours. Hour 8-24: Building the Core This is where things got interesting. Cursor with Claude autocomplete was writing 80% of the code. But here's the thing nobody tells you: AI writes code fast, but you still need to understand what it's writing. I caught 3 security issues th