Claude Code Leak: Anti-Distillation Fake Tools System Poisons Competitor Training Data via ANTI_DISTILLATION_CC Flag

Alex Kim's Blog·high signal

The source leak revealed Claude Code includes a flag called ANTI_DISTILLATION_CC that injects fake tool definitions into API requests. If competitors intercept and record Claude Code's API traffic to train their own models, the fake tools corrupt the training data. This is the first confirmed production deployment of anti-distillation as a competitive defense mechanism — a technique Anthropic disclosed theoretically but never confirmed using in shipping products.