Anthropic said Friday evening that the U.S. issued an export control directive suspending access to Fable 5 and Mythos 5 by any foreign national, including foreign nationals inside the United States and foreign national employees of the company. Anthropic said the order effectively forces it to abruptly disable both models for all customers while it works to comply, though the directive will not affect access to its other models.

The order marks one of the administration’s most aggressive steps yet to control access to frontier AI models, and increases tensions with Anthropic, which has become a darling in Washington policy circles for its often-public commitments to AI safety.

The move appears to stem from concerns about a possible jailbreak of Anthropic’s systems. Axios reported Friday evening that the Commerce Department acted after another company claimed it had jailbroken Mythos, alarming officials about potential national security risks. Anthropic in a blog post pushed back on the government’s rationale, saying the concern involved a narrow potential issue and did not justify pulling access to the models broadly.

“To date, the government has only given us verbal evidence of a potential narrow, non-universal jailbreak, which essentially consists of asking the model to read a specific codebase and fix any software flaws,” Anthropic wrote in a statement on the order. “Our understanding is that one potential jailbreak was shared with the government. We have reviewed a report that we believe is the basis of the government's directive and validated that the level of capability displayed there is widely available from other models (including OpenAI’s GPT-5.5), and is used every day by the defenders who keep systems safe.”

The Trump administration’s order does not make mention of GPT-5.5 Cyber, another advanced vulnerability-focused model currently available to cyber defenders.

The decision came just days after Anthropic released Fable 5 and Mythos 5, the former of which was made available to the public with restrictions on sensitive uses. Mythos 5 was offered through a more limited trusted-access program known as Project Glasswing for cyber defenders and critical infrastructure operators. The company has described Mythos as a highly capable cybersecurity model that could be leveraged for significant cyber intrusions.

That dual-use potential has placed Anthropic at the center of a broader policy fight over how the government should treat advanced AI systems that can help defenders find flaws but could also assist in offensive cyber operations. 

The government’s move to set export restrictions on the tools has drawn public support from senior defense technology officials. 

Kirsten Davies, the Department of Defense’s chief information officer, wrote on X that the department “fully support[s] @POTUS and @SecWar in prioritizing national security and the security of our warfighters, [Defense Industry Base] partners, critical infrastructure, international partners and allies,” she said, crediting President Donald Trump and Defense Secretary Pete Hegseth. 

“Some things are simply more important than revenue cycles, clickbait, and pre-IPO valuation. America First. Always,” she added.

The shutdown would likely complicate any near-term plans to test or deploy Anthropic’s most capable cyber-focused systems, especially for federal agencies and critical infrastructure partners. It also raises unresolved questions about how the government plans to balance trusted access for U.S. agencies and allies with fears that adversaries or unauthorized users could misuse the same systems.

The administration passed a sweeping AI executive order earlier this month, and has been discussing giving its main civilian cyberdefense agency full access to Mythos to aid in federal cyberdefense. Meanwhile, agency tech leaders have been struggling to both access and understand how to implement Mythos, citing lack of transparency from the White House’s cyber office. 

Anthropic has had a contentious relationship with the federal government in recent months, after the company refused to allow its products to be used for instances of domestic surveillance or autonomous lethal weaponry. The Pentagon subsequently designated the company as a supply chain risk, and Trump ordered that federal agencies stop all use of its products. A federal judge on March 27 issued a temporary injunction on both actions.

“AI regulation will be some of the most serious and consequential work the U.S. government does over the next generation, and it is imperative that this work be done consistently across industry, without favor, and according to a clear, rules-based process,” said Brad Carson, president of Americans for Responsible Innovation. “Based on what we know thus far, the decision to block Anthropic’s latest AI model fails that test, and as a result, risks America’s edge in AI innovation. While the federal government must have the capacity to evaluate and even block the deployment of advanced AI models in extraordinary situations, the utmost care is required to insulate these decisions from impulse and political favoritism.”