Anthropic suspends Fable and Mythos after US government jailbreak claim

Anthropic revoked Claude Fable 5 and Mythos 5 for all customers three days after release, following a US government directive citing a potential jailbreak as a national cybersecurity risk. Anthropic disputes the claim, stating it was based on a narrow, non-universal vulnerability and that similar capabilities exist in other models like GPT-5.5.