The US government ordered Anthropic to suspend access to Claude Fable 5 and Mythos 5 over national security concerns tied to an alleged jailbreak vulnerability.
The US government issued an emergency export control directive on June 13 ordering Anthropic to suspend access to its two most advanced AI models, Claude Fable 5 and Claude Mythos 5, for all foreign nationals. The order cited national security concerns and took effect the same day it was received.
Anthropic said it received the directive at 5:21 pm ET. The order bars foreign nationals from accessing the models whether inside or outside the United States, including foreign nationals employed by Anthropic. To ensure compliance, the company disabled both models for its entire global user base. All other Anthropic models, including Opus 4.8, remain accessible.
The two models had been released just days before the directive arrived. Fable 5 and Mythos 5 were both built on Mythos Preview, a general-purpose language model that Anthropic previously described as capable of identifying thousands of vulnerabilities in critical software. Mythos 5 had been made available only to a limited group of partners before the shutdown.
What the Government Alleged
The government did not provide written details about the specific threat. Anthropic said it believes authorities identified a method of bypassing, or "jailbreaking," Fable 5's safeguards. "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 said in a statement.
Anthropic reviewed a demonstration of the reported technique and concluded the vulnerability is relatively basic. The company said the same level of capability is already accessible through competing models, including OpenAI's GPT-5.5, without any bypass required. It distinguished between a narrow, non-universal jailbreak and a universal one, arguing the latter would be a far more serious concern.
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"If this standard was applied across the industry, we believe it would essentially halt all new model deployments for all frontier model providers," Anthropic wrote.
David Sacks, co-chair of the President's Council of Advisers on Science and Technology, offered a different account on X on June 14. He said a trusted partner of both Anthropic and the US government had identified the jailbreak while testing Fable 5. Sacks said the administration asked Anthropic CEO Dario Amodei to either fix the issue or take the model offline, and that Amodei declined. "Anthropic prioritized the continued offering of the consumer model over safety," Sacks wrote. He added that the administration hopes Anthropic will resolve the issue and that Fable 5 can return to public release.
The episode follows a previous dispute between Anthropic and the federal government earlier in 2026, when Anthropic declined to sign an agreement that would have authorized mass domestic surveillance and fully autonomous lethal weapons systems. The Department of Defense subsequently labeled Anthropic a "supply chain risk," a designation the company has challenged in court. Anthropic said it believes the current directive stems from a misunderstanding and is working to restore access as quickly as possible.
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