US company Anthropic has been forced to immediately restrict access to its latest and most powerful artificial intelligence models. Under a direct order from the United States government, the company is prohibited from providing Fable 5 and Mythos 5 models to any foreign users, including foreign nationals who are themselves employees of the company. Due to the technical difficulty of selective blocking, Anthropic has decided to temporarily make the Fable 5 model unavailable to all users in the Claude application and web interface.
The ban is justified by officials as a threat to US national security. However, authorities did not specify the particular concerns. Anthropic nevertheless believes that the administration's move is driven by fear of security bypasses (so-called jailbreaks). While the Mythos 5 model is intended only for a narrow range of institutions due to its ability to detect software vulnerabilities, the Fable 5 version was intended to be a safer commercial variant with limited code analysis capabilities.
“We think the government believes it has learned of a way to 'jailbreak' or crack Fable 5. This is supposed to involve giving the model the task of reading specific code and fixing all software bugs in it.”
In its statement, Anthropic disputes the authorities' actions. According to the company's internal analysis, the techniques used to detect vulnerabilities are not unique, and similar results are shown by competing tools. The company argues that the same level of code analysis can now be performed, for example, by the ChatGPT 5.5 model from OpenAI, without users needing sophisticated protection circumvention.
Anthropic representatives also warn of a dangerous precedent that could affect the entire technology sector. If similar strict rules were applied across the board, it could, they say, paralyze the development and introduction of innovations by all major AI providers. Other publicly available Anthropic models are not yet affected by the restrictions, and the duration of the ban for the latest series is currently unknown.