Claude Code's Leaked Source: A Real-World...

Earlier this year, Mitchell Hashimoto coined the term "harness engineering" — the discipline of building everything around the model that makes an AI agent actually work in production. OpenAI wrote about it. Anthropic published guides. Martin Fowler analyzed it. Then Claude Code's source leaked. 512K lines of TypeScript. And suddenly we have the first real look at what production harness engineering looks like at scale. The Evolution: From Prompt to Harness The AI engineering discipline has shif