A US official told AP that Anthropic’s Mythos model identified vulnerabilities in classified government systems within hours during Project Glasswing tests with intelligence agencies. The Trump administration then barred foreign access to Mythos and its limited Fable 5 model under a security directive, prompting cybersecurity experts to warn that restricting these tools could weaken US defenses.

A private online forum obtained Mythos the day Anthropic began limited company testing. According to a source with screenshots and a live demo, the group has kept using the model regularly without permission.