The U.S. Commerce Department sent Anthropic a letter on Friday afternoon invoking an export control directive that bars non-Americans from accessing Fable 5 and Mythos 5, citing an unspecified national security concern [TechCrunch]. Anthropic, believing the letter relates to a guardrail bypass, shut down both models to all customers [TechCrunch]. The letter has not been made public and provides no specific details [TechCrunch].