US Orders Anthropic to Suspend Fable 5, Mythos 5

The U.S. government issued an export control directive late Friday requiring Anthropic to suspend all access to its Fable 5 and Mythos 5 AI models by any foreign national, whether inside or outside the United States, forcing the company to abruptly disable the models for all customers to ensure compliance. Anthropic had launched Claude Fable 5 and Claude Mythos 5 on June 9, 2026, making the government intervention just three days after release.

Claude Fable 5 and Claude 3 AI models launch announcement with fantasy fox and robot imagery for advanced AI accessibility.

Anthropic received the directive from the government at 5:21pm ET on Friday, marking one of the most aggressive actions the U.S. government has taken in response to advanced AI capabilities. The broad directive to Anthropic’s Mythos 5 and Fable 5 models is one of the furthest-reaching actions the government has taken in response to the advanced capabilities of an AI model.

National Security Concerns Drive Government Action

The government letter did not provide specific details of its national security concern, though Anthropic’s understanding is that the government believes it has become aware of a method of bypassing, or “jailbreaking” Fable 5. Commerce Secretary Howard Lutnick sent a letter to Anthropic CEO Dario Amodei saying that the Mythos 5 and Fable 5 models would be subject to export controls to any location outside of the U.S. and to all foreign persons within the country.

The company said the government didn’t provide specific details about the national security concerns, though it believed the government had “become aware” of a method of “jailbreaking” Fable 5, or getting around its internal safety guardrails. “We reviewed a demonstration of this specific technique being used to identify a small number of previously known, minor vulnerabilities,” Anthropic said in its statement.

Officials told Anthropic that the government made the decision after learning of a technique to bypass Fable 5’s safeguards, which were designed to prevent users from accessing the powerful cybersecurity abilities of Mythos, the underlying AI model on which Fable 5 is built.

Scope of the Ban and Compliance Challenges

The directive includes not just people located outside the U.S., but also any foreign national in the U.S., including Anthropic’s own non-citizen employees. The net effect of this order is that Anthropic must abruptly disable Fable 5 and Mythos 5 for all customers to ensure compliance, though access to all other Anthropic models will not be affected.

The company clarified that access to its less powerful Claude models, including its latest Claude Opus 4.8 model, was not affected. This means users can continue accessing older Claude versions while the two newest models remain offline.

What Made These Models So Powerful

Fable 5 was Anthropic’s first broadly available Mythos-class model, described as the most capable model it had ever released to the public, with large gains in software engineering, knowledge work, vision, scientific research, and long-running autonomous tasks. The model was particularly effective at identifying software vulnerabilities.

Both models stemmed from Claude Mythos Preview, a highly advanced model intended for security research, which was capable of finding security bugs and flaws. Access to Mythos Preview was initially limited to a small group of companies and research partners through Project Glasswing. In the weeks that followed, participants reported identifying and fixing numerous security issues with the model’s help. Mozilla alone said it resolved hundreds of vulnerabilities as a direct result of using Mythos Preview.

Mythos 5 was the same underlying model with some safeguards lifted for trusted cybersecurity and biology users.

Anthropic’s Response and Disagreement

While complying with the government’s legal directive and removing access to Fable 5 and Mythos 5 for all users, Anthropic disagrees 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 believes if this standard was applied across the industry, it would essentially halt all new model deployments for all frontier model providers.

Anthropic said it believed the jailbreak the government was citing was a narrow one that would unlock Mythos’s cybersecurity capabilities in only one specific instance and not a universal one that would defeat all of Fable 5’s safeguards. It also said it believed the same jailbreak could be used to elicit similar capabilities from other publicly available models, including OpenAI’s GPT-5.5, that are not subject to similar national security export controls.

Anthropic stated publicly that it believes the government should have the ability to block unsafe deployments, as part of a statutory process that is transparent, fair, clear, and grounded in technical facts, arguing this action does not adhere to those principles.

Working Toward Resolution

Anthropic apologized for the disruption to its customers and stated it believes this is a misunderstanding and is working to restore access as soon as possible. Axios reported that the Trump administration had previously tried to stop Anthropic from releasing the model, but failed.

Under the export control directive, a license would be required “for the export, re-export or domestic transfer of Anthropic’s models.” This suggests that Anthropic may need to work through a formal licensing process with the Commerce Department to restore access to the models.

Key Facts

Anthropic launched Claude Fable 5 and Claude Mythos 5 on June 9, 2026
The company received the government directive at 5:21pm ET on Friday, June 12
The export control directive suspends all access by any foreign national, forcing Anthropic to disable both models for all customers
Mozilla resolved hundreds of vulnerabilities using the earlier Mythos Preview model through Project Glasswing
Claude Opus 4.8 and other less powerful models remain accessible