anthropic's claude fable 5 and mythos 5 models were shut down by government order days after a system prompt leak revealed hidden safety rules, shared architecture between the two models, and performance throttles on suspected competitors. a government entity ordering a commercial ai model offline is structurally unprecedented in this industry's short history. the gap between what the leaked prompt disclosed — deliberate performance restrictions on rivals — and what anthropic had publicly presented about its models is itself a notable signal.