U.S. Government Directs Anthropic to Shut Down Fable 5 and Mythos 5 Models on National Security Grounds

Anthropic:

The US government, citing national security authorities, has issued an export control directive to suspend all access to Fable 5 and Mythos 5 by any foreign national, whether inside or outside the United States, including foreign national Anthropic employees. The net effect of this order is that we must abruptly disable Fable 5 and Mythos 5 for all our customers to ensure compliance. Access to all other Anthropic models will not be affected.

We received the directive from the government today at 5:21pm (ET). The letter did not provide specific details of its national security concern. Our understanding is that the government believes it has become aware of a method of bypassing, or “jailbreaking” Fable 5. We reviewed a demonstration of this specific technique being used to identify a small number of previously known, minor vulnerabilities. These vulnerabilities all appear relatively simple, and we have found that other publicly-available models are able to discover them as well without requiring a bypass.

Fable 5 and Mythos 5 were announced on Tuesday — that post has detailed comparisons, from Anthropic, on the models’ capabilities.

Having the access ban extend all the way to “foreign national Anthropic employees” is, to say the least, aggressive. Whether that degree of restriction is truly warranted, I don’t think we, on the outside, can say. The Trump administration lacks credibility, to say the least, when it comes to foreign nationals. But it’s Anthropic itself that repeatedly compares the power of frontier models to nuclear weapons. Here’s CEO Dario Amodei, in an essay published just this month:

There may come a time, perhaps relatively soon, when we need to go beyond this, when the most powerful AI systems look less like airplanes or automobiles and more like weaponizable nuclear materials — a threat to humanity rather than “just” a threat to public safety. If that occurs, we may need more aggressive regulatory measures than those I have laid out.

If that occurs — or if it already has occurred — it’s obviously not the place of Anthropic (or OpenAI or Google) to render that judgment. Ben Thompson wrote about this presciently back in March, and linking to his post, I wrote:

Nilay Patel, quoting the same section of Thompson’s column I quoted above, sees it as “Ben Thompson making a full-throated case for fascism”. I see it as the case against corporatocracy. Who sets our defense policies? Our democratically elected leaders, or the CEOs of corporate defense contractors?

★ Saturday, 13 June 2026