The U.S. government issued an order on Friday directing Anthropic to immediately disable access to two of its most advanced AI models—Claude Fable 5 and Claude Mythos 5—citing national security concerns. Anthropic announced on X that it has complied with the directive, though it made clear that it believes the government’s decision is misguided. According to Anthropic, the order arrived at 5:21 pm ET on Friday and requires the company to block both models for all users worldwide, not just the foreign nationals the export control action was ostensibly targeting. Access to Anthropic’s other models remains unaffected.

Why does this matter? Mythos is Anthropic’s most capable AI model, which the company previewed in early April and has kept tightly restricted ever since due to what it described as an exceptional ability to identify security vulnerabilities in software. Anthropic reports that Mythos found flaws in every major operating system and web browser it tested. Rather than releasing it broadly, the company launched a controlled program called Project Glasswing, sharing Mythos with roughly 50 vetted organizations—including Amazon, Apple, Google, Microsoft, and CrowdStrike—for defensive cybersecurity work. Fable 5, released just three days ago, was Anthropic’s response to commercial pressure: a version of Mythos equipped with guardrails that block responses in high-risk areas like cybersecurity and biology, making it safe enough for public release, the company argued. According to benchmark tests from Vals AI, a firm that tracks AI performance, Fable 5 immediately became the most capable AI model available to the public.

The government’s directive is framed as an export control measure, aimed at restricting foreign nationals’ access to the models. However, in a lengthy blog post, Anthropic says it understands that the underlying concern involves a claimed jailbreak of Fable 5. So far, the company notes, the government has provided only verbal evidence of a “potential narrow, non-universal jailbreak”—which, as Anthropic describes it, essentially involves prompting the model to read a specific codebase and identify software flaws. Moreover, Anthropic adds that this “level of capability” is already widely available in other publicly accessible models, including OpenAI’s GPT-5.5. It is also a technique routinely used by cybersecurity professionals for defensive purposes, the company observes.

Anthropic’s broader argument is that its strongest safeguards operate through independent classifier systems that function separately from the model itself. This means that even if someone convinces Fable to keep talking past a refusal, the underlying protections against the most dangerous outputs remain in place. The company also notes in its post that a review of recent usage found no evidence of those safeguards being successfully bypassed to produce genuinely harmful content. Clearly, none of that was enough to stop the government from acting, and Anthropic isn’t hiding its frustration. “We disagree that the finding of a narrow potential jailbreak should be cause for recalling a commercial model deployed to hundreds of millions of people,” the company wrote. “If this standard was applied across the industry, we believe it would essentially halt all new model deployments for all frontier model providers.”

Anthropic is widely expected to pursue an IPO this year and has staked much of its public identity on being the safety-conscious alternative to its rivals. The irony isn’t lost on observers: the very caution Anthropic displayed in restricting Mythos—which it promoted as a model so dangerous it couldn’t be released publicly—has now apparently attracted exactly the kind of government scrutiny that could disrupt its business most. OpenAI’s Sam Altman must be enjoying this, at least. In April, he told podcaster Ashlee Vance that Anthropic’s handling of Mythos amounted to “fear-based marketing.” “It is clearly incredible marketing to say, ‘We have built a bomb. We were about to drop it on your head. We will sell you a bomb shelter for $100 million,’” Altman said. Altman, whose company is also widely expected to pursue an IPO as soon as possible, didn’t predict a government shutdown, but he identified something that has come back to bite Anthropic for now: when you spend months telling the world your AI is uniquely dangerous, the world—including the U.S. government—tends to listen.