In a classified intelligence test under a program called Project Glasswing, Anthropic's Claude Mythos model exposed security flaws in highly sensitive U.S. government computer systems within hours, an official said. The official cautioned that identifying a weakness is not the same as exploiting it. Democratic Sen. Mark Warner of Virginia first referenced the tests on Jun. 11, attributing the account to Joshua Rudd, who leads the National Security Agency and U.S. Cyber Command. More than 100 cybersecurity leaders, including figures from Adobe and Nvidia, have pressed the government to reverse export curbs that pulled Mythos and Fable 5 offline, arguing the models are not uniquely capable. The pushback follows a Jun. 12 export directive that barred foreign nationals from Mythos 5 and Fable 5, leading Anthropic to disable both models for every customer. The directive followed an executive order from President Donald Trump that set up federal vetting of the most advanced AI systems for up to a month before release. Britain's AI Security Institute earlier cleared Mythos on expert-level capture-the-flag challenges that no system had solved before.