Anthropic: access to Fable 5 and Mythos 5 suspended by US government directive

Anthropic has reported that the US government issued an export control directive, citing national security authorities, requiring it to suspend all access to the Fable 5 and Mythos 5 models for foreign nationals everywhere, including foreign-national staff. To ensure compliance, both models were disabled for all customers, while other Anthropic models remain unaffected.

The directive was received at 5:21pm ET. The government raised concerns about a potential jailbreak technique, demonstrating a method that revealed only minor, previously-known vulnerabilities — relatively straightforward issues that comparable models can also surface without any bypass technique.

Anthropic stresses that its safeguard approach included extensive red-teaming with government agencies, third-party organizations, and internal teams, and that testing showed safeguards significantly outperforming previous models. The company nonetheless acknowledges that perfect jailbreak resistance does not appear achievable today, adopting instead a “defense in depth” strategy that combines narrow jailbreak difficulty with monitoring capabilities.

Having reviewed the disclosed potential jailbreak — essentially asking the model to analyze specific codebases for software flaws — Anthropic confirmed this capability is widely available among competing models. The company disagrees that discovering a narrow jailbreak warrants recalling a commercially-deployed model serving hundreds of millions of users, arguing such a standard would halt frontier model deployment across the entire industry.

While complying with the directive, Anthropic states it disagrees with the decision and believes the government should employ transparent, fair, and technically-grounded statutory processes to block unsafe deployments. The company apologizes for the disruption to customers and is working to restore access.