Anthropic Blocks Foreign Nationals From Using Its Mythos and Fable 5 A.I. Systems

Anthropic, a San Francisco-based AI company, announced on Friday night that the U.S. government had ordered it to suspend access to its Mythos and Fable 5 AI models for all foreign nationals, citing national security risks. The restriction also applies to foreign employees at Anthropic. The company confirmed the order in a social media post, stating it had to disable access to ensure compliance with government directives. The decision follows concerns that Mythos, unveiled in April, could be exploited by hackers to breach computer networks. Anthropic had previously shared the system with around 40 organizations managing critical infrastructure to help them identify and patch security vulnerabilities. The Commerce Department issued the order, though its duration remains unclear. Anthropic declined further comment, and the White House did not immediately respond to requests for clarification. The move comes as the White House, under President Trump, has shifted toward stricter AI oversight, including an executive order last week requiring companies to voluntarily submit new AI systems for government review before public release. Earlier this month, Anthropic had planned to expand access to Mythos to 150 additional organizations but later introduced Fable 5, a restricted version with guardrails blocking responses on cybersecurity, biology, and other sensitive topics. Fable 5 was designed to mitigate risks but may also limit its utility for cybersecurity experts defending against attacks. Queries deemed risky are redirected to an older model, Opus 4.8, which remains unaffected by the government’s order. Cybersecurity experts remain divided on whether Mythos should have been restricted, as its capabilities could be used for both offensive and defensive purposes. Anthropic expressed regret over the disruption, calling the government’s decision a misunderstanding and stating it was working to restore access as soon as possible. The suspension highlights growing tensions between AI innovation and national security concerns in the U.S.