Anthropic has blocked access to Cloud Fable 5 and Cloud Mythos 5 for all users following a US government directive to restrict access to foreign nationals. The company explained that they will have to completely disable both models to remain in compliance with the order.
What caused the suspension of the Fable 5 and Mythos 5, and what it means for users
Anthropic said US national security officials have not publicly identified specific concerns. The company claimed that the government is aware of a method to bypass or “jailbreak” Fable 5.
It also mentions reviewing the performance of this technology. According to Anthropic, the vulnerabilities exposed are “relatively simple” and other publicly available models can also find them without the need for bypass.
“We reviewed the performance of this specific technique used to identify a small number of previously known vulnerabilities,” Anthropic reported. “All of these vulnerabilities appear to be relatively simple, and we have found that other publicly available models can also find them without the need for bypasses.”
Customers using the Pro, Max, and Enterprise plans who accessed the Fable 5 during its free preview period can no longer use the model. The Mythos 5 Access program for verified partners is also affected.
Anthropic has not given any timeline for when Fable 5 or Mythos 5 might be available again or what conditions would need to be met for the suspension to be lifted. Other cloud models remain accessible, including Cloud Opus 4.8.
Widespread tensions between Anthropic and the Trump administration
The suspension comes amid the ongoing dispute between Anthropic and the Trump administration. President Donald Trump has publicly criticized the company, and former US Secretary of Defense Pete Hegseth has labeled Anthropic a “supply chain risk”.
This designation, usually reserved for hostile countries, is the first time a US company has received it, indicating that the equipment or service is not considered safe enough for government use.
Anthropic is suing the Pentagon over the designation, and a US judge has ruled that the Pentagon’s directive cannot be enforced while the lawsuit continues. As a result, government agencies and organizations working with the U.S. military may temporarily continue to use Anthropic products.
The BBC reported that it has contacted the US Commerce Department for comment on the Fable 5 suspension.
Anthropic previously stated that the Fable 5 surpasses the capabilities of any model made publicly available by the company, describing the Mythos architecture as “too powerful to release” without adequate safeguards.
Ahead of Fable 5’s wide release earlier this week, the Mythos program was limited to select trusted partners through Project Glasswing for cybersecurity research.
Anthropic has not announced any amendments to address the government’s concerns before restoring Fable 5 and Mythos 5.
Anthropic is suing the Pentagon over the designation. A US judge has ruled that the Pentagon’s directive cannot be implemented while the lawsuit continues, meaning government agencies and organizations working with the US military can still use Anthropic products in the interim.
The BBC reported that it has contacted the US Commerce Department for comment on the Fable 5 suspension.
Anthropic had previously described the Fable 5 as exceeding the capabilities of any model generally made available by the company, with the underlying Mythos architecture being described by Anthropic as “too powerful to release” without significant security measures.
The Mythos program was limited to a few trusted partners through Project Glasswing for cybersecurity research ahead of Fable 5’s wide release earlier this week.
Anthropic has not announced what changes, if any, will be made to address government concerns before Fable 5 and Mythos 5 return to availability.
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