Anthropic confirmed tonight that it has disabled access to Claude Fable 5 and Claude Mythos 5 to all customers, following an export control directive from the US government. Here are the details.
Earlier this week, Anthropic launched Claude Mythos 5 and Claude Fable 5.
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.
When Anthropic unveiled Claude Mythos 5 and Claude Fable 5 this week, the company said the Mythos family would remain restricted to Project Glasswing participants, while Fable would be made publicly available.
Fable included several guardrails and restrictions intended to curb misuse, some of which drew heavy criticism. Since launch, Anthropic has been adjusting its safety measures to try to strike the right balance between safety and usability.
Earlier tonight, however, Axios reported that Commerce Secretary Howard Lutnick had “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.”
From Axios:
An administration official told Axios the Commerce Department decided to take the action after another company claimed it was able to jailbreak Mythos, alarming the administration about possible national security risks.
Axios added that the Trump administration had previously tried to stop Anthropic from releasing the model, but failed. The report also noted that, under the export control directive, a license would be required “for the export, re-export or domestic transfer of Anthropic’s models.”
In light of that, Anthropic announced that it has decided to disable Claude Mythos 5 and Claude Fable 5 for all customers, but stressed that access to all other models remains unaffected.
From 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.
The company listed the extensive safeguards it put in place when it released Fable 5, and added that while it intends to share more information over the next 24 hours, it believes the government’s directive is based on a narrow, non-universal jailbreak involving capabilities that are already available in other models, “including OpenAI’s GPT-5.5”.
Finally, Anthropic apologized for the disruption to customers, said it believes the government’s action is based on a misunderstanding, and pledged to work toward restoring access as soon as possible.
You can read Anthropic’s full statement here.
Update: Claude’s official account on X explained what users should expect as a result of tonight’s directive:
Across Claude products, new sessions will run on your selected default model or Opus 4.8, and existing Fable 5 sessions will end with an error.
On the Claude Platform, requests to Fable 5 will also return an error. Please update your integrations to other Claude models.
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