Hook

Their other posts in the index, biggest breakout first.
Fable 5 just came back and somebody's already leaked the entire system prompt on the internet. And this isn't just some basic prompt. It's 120,000 characters long and over 1,500 lines. And it covers the exact set of instructions Anthropic used to control how their most powerful model thinks, plans, and gets things done. And what's amazing is you can take these exact instructions and inject them into cheaper open source models like GLM 5.2 or Kimi 2.7. That way they follow the same playbook that Anthropic built for the world's fastest AI models. And this will significantly improve your output and lower your bills. So if you want it for yourselves, just comment FABLE 5 and I'll send you guys the link directly.