US government ordered Anthropic to suspend all access to Fable 5 and Mythos 5 citing national security, citing discovery of a jailbreak method.
The government demonstrated a narrow, non-universal jailbreak involving asking the model to review code for flaws—a capability Anthropic says is widely available in other models like GPT-5.5.
Anthropic is complying but disagrees with the directive, arguing the jailbreak is minor and applying this standard would halt all frontier model deployments industry-wide.
Anthropic states Fable 5 underwent extensive red-teaming and has stronger safeguards than previous models, with no universal jailbreak discovered before the government's action.
All other Anthropic models remain unaffected; the company is working to restore access as soon as possible.