Anthropic confirmed tonight that it has disabled access to Claude Fable 5 and Claude Mythos 5 for all customers, following an export control directive from the US government. Here are the details.
A little context
Earlier this week, Anthropic launched Claude Mythos 5 and Claude Fable 5.
Both models emerged from Claude Mythos Preview, a very advanced model intended for security research, which was capable of finding bugs and security flaws.
Access to Mythos Preview was initially limited to a small group of companies and research partners through Project Glasswing. In the following weeks, participants reported identifying and fixing numerous security issues with the help of the model. 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 publicly available.
Fable included several guardrails and restrictions intended to curb misuse, some of which attracted strong criticism. Since its launch, Anthropic has been adjusting its security measures to try to strike the right balance between security and usability.
Anthropic withdraws Fable 5 and Mythos 5
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 the U.S. and to all foreign persons within the country.”
Of axios:
An administration official told Axios that the Commerce Department decided to take the action after another company claimed it could jailbreak Mythos, alarming the administration about potential national security risks.
axios He added that the Trump administration had previously tried to stop Anthropic from launching 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 internal transfer of Anthropic models.”
In light of that, Anthropo announced which has decided to disable Claude Mythos 5 and Claude Fable 5 for all customers, but stressed that access to all other models will not be affected.
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 Anthropic’s foreign employees. The net effect of this order is that we must abruptly disable Fable 5 and Mythos 5 for all of our customers to ensure compliance. Access to all other Anthropic models will not be affected.
We received the government directive today at 5:21 pm (ET). The letter did not provide specific details of its national security concerns. It is our understanding that the government believes it has figured out a method to bypass or “jailbreak” Fable 5. We reviewed a demo of this specific technique that is used to identify a small number of previously known minor vulnerabilities. All of these vulnerabilities seem relatively simple, and we have found that other publicly available models can also discover them without needing to bypass them.
The company listed the extensive safeguards it put in place when it launched Fable 5, adding that while it intends to share more information over the next 24 hours, it believes the government directive is based on a limited, non-universal jailbreak that involves capabilities 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 to restore access as soon as possible.
You can read the full statement from Anthropic here.
Update: Claude’s official account on X explained What users should expect as a result of tonight’s directive:
In all Claude products, new sessions will run on the 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. Update your integrations with other Claude models.
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