The US government has issued a directive to suspend access to Fable 5 and Mythos 5 for all foreign nationals, including foreign employees of Anthropic. As a result, Anthropic is required to disable these services for all customers to ensure compliance with the directive.

Claude 5 Fable is the first publicly released model in the Mythos class. It demonstrates significant advancements over previous AI models, although its guardrails restrict its use in cybersecurity applications.

Mythos, an AI model developed by Anthropic, has demonstrated exceptional ability in identifying security vulnerabilities in source code. Due to its effectiveness, Anthropic has opted to limit access to Mythos, providing it only to selected companies for initial testing and remediation of critical issues.

Anthropic's Mythos project utilized a budget of under $20,000 for a comprehensive search process involving approximately a thousand scaffolded runs and several dozen findings. The initial impression of Mythos being able to find a devastating bug for that price is misleading, as the findings were part of a larger testing effort.