The U.S. Just Put Anthropic’s Top Models Behind a National Security Wall

The Trump administration has taken an aggressive new step in AI governance, moving to block foreign governments, companies, and individuals from accessing Anthropic’s most advanced foundation models. Framed as a national security measure, the move effectively treats state‑of‑the‑art AI as dual‑use technology, comparable to sensitive semiconductor or cryptography exports.Practically, this means Anthropic has halted access to its frontier‑class models for a large swath of non‑U.S. users. International AI labs, robotics startups, and infrastructure providers that had begun standardizing on those models for control, perception, and planning now face an abrupt downgrade to weaker systems or a scramble to re‑platform onto alternative models. For any team building high‑autonomy agents, industrial robots, or cyber‑physical security tools, this is not a cosmetic change in API provider; it’s a hard constraint on the ceiling of model capability they can legally integrate.Note: Fable 5 and Mythos 5 are two configurations of the same base model, with Fable 5 adding stricter safety guardrails for general availability.Nicholas Thompson had a great post giving some background on Mythos in his most recent: “The Most Interesting Thing in Tech.”Statement from Anthropic:Statement on the US government directive to suspend access to Fable 5 and Mythos 5Jun 12, 2026The 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.Anthropic’s posture with respect to Fable’s safeguards, as laid out in our launch blog post, is the following:* We have instituted strong safeguards that greatly reduce the likelihood that Fable is misused for tasks related to cybersecurity (among others). In fact, our safeguards are so strong that many users have complained that they are overly broad.* In the weeks leading up to the launch of Fable, Anthropic worked with the US government, the UK AISI, multiple private third-party organizations and internal teams to red-team Fable’s safeguards for thousands of hours in total.* These tests showed that Fable’s safeguards are substantially more effective than those of any previously deployed model.* No testers have yet been able to find a universal jailbreak—a jailbreak method that can very broadly bypass the model’s safeguards, unblocking a wide range of cyber capabilities.* We suspect that perfect jailbreak resistance is not currently possible for any model provider. Every safeguard used in the industry is vulnerable to non-universal jailbreaks (which can elicit some cyber information in specific circumstances), and it is likely that universal jailbreaks will eventually be found in the future. We stated this clearly when we released Fable 5.* Given that perfect jailbreak resistance does not appear to be possible today, Anthropic adopted a defense in depth strategy with Fable 5. We aimed to make jailbreaks either narrow (in the case of non-universal jailbreaks) or very expensive to produce (in the case of universal jailbreaks), and to combine this with thorough monitoring to quickly detect and shut down any successful attacks. This is also why Anthropic has required 30-day retention of customer data with Fable—a policy change that carries real costs for us with customers, but that allows us to research and