Unable to verify which customers are foreign nationals, Anthropic cut access for everyone.
On June 12, the US government ordered Anthropic to suspend access to Fable 5 and Mythos 5 for foreign nationals, citing national security concerns. To comply, Anthropic shut down access for all users, saying it has no mechanism to verify customer nationality.
The government says it has become aware of a jailbreak for Fable 5. Anthropic disputes the severity, calling it a non-universal jailbreak that works only in limited situations and only enables what other AI models already do freely.
Anthropic complied, but is pushing back. What the government shared, Anthropic says, constitutes a narrow, non-universal technique: one that works only under specific circumstances, not one that broadly defeats the model’s safeguards.
Anthropic said at the time of launch that no AI model can be made completely jailbreak-proof. Their stated strategy was to minimize the damage any jailbreak can cause, make them difficult to execute, and catch them quickly. The 30-day data retention requirement on Mythos-class models is part of that: it lets Anthropic review usage and shut down jailbreaks as they appear.
“If this standard was applied across the industry,” Anthropic said, “we believe it would essentially halt all new model deployments for all frontier model providers.”
Background
Mythos 5 and Fable 5 launched three days before the directive. Mythos 5 is available exclusively to vetted large tech companies, US and allied government organizations, and cybersecurity firms through Project Glasswing, Anthropic’s program for organizations that use AI to hunt for software vulnerabilities before attackers find them.
Fable 5 is the consumer version of the same underlying model, with filters that detect hacking-related requests and route them to a less capable model, Opus 4.8, rather than allowing Fable 5 to respond.
Glasswing launched in April 2026 with Claude Mythos Preview, the predecessor to Mythos 5. Partners in the project identified more than 10,000 vulnerabilities using Mythos Preview, including bugs that conventional security tools had missed.
The relationship between Anthropic and the US government is strained. The US government takes an active role in vetting which organizations can access Mythos 5 through Glasswing. This cooperation exists despite an ongoing lawsuit where Anthropic sued the Department of War after the DoW designated Anthropic a supply chain risk earlier this year.
Anthropic says it believes the suspension is a misunderstanding and is working to restore access as soon as possible.
