How I Audited 250K Lines of Legacy Code with 11 AI Agents in One Week

I inherited a monolith. 250,000 lines of Python. 20+ years old. The framework was end-of-life since 2018. The language was end-of-life since 2020. Zero tests. Passwords stored in plain text. A proprietary library maintained by 2 people, embedded in 133 imports across 47 files. A database with 462 tables using exotic PostgreSQL inheritance instead of standard ORM patterns. And 900+ production websites depending on it. My job: audit the entire thing before a rebuild decision. Traditional approach: 2-3 senior consultants, 4-8 weeks, six figures. My approach: 11 AI agents, 2 adversarial teams, 7 iterations, 10 days. Here's what happened — including the mistakes that made it work. Iteration 1: The Naive Start (1 agent) I started where everyone starts. One Claude conversation. Upload the codebase. Ask questions. The results looked impressive: 1,100 paragraphs, 18 sections covering architecture, security, performance, business rules. My first thought was "this is amazing." My second thought,