Fable 5 and Mythos 5 are no longer available to Claude users due to a decision by the US government.

Anthropic has disabled its leading AI models due to US government requirements

The developer of AI models Fable 5 and Mythos 5, Anthropic, has suspended their operation in accordance with US government export restrictions that require the closure of access to the products for all foreigners.

The company announced the immediate suspension of access to these models after receiving a directive in which the US government referenced national security agencies. In the statement, Anthropic clarified that specific details of the national security threat were not disclosed in the government letter. As Anthropic noted, the authorities pointed to the potential circumvention of the model’s security system known as “jailbreaking,” which could expose minor vulnerabilities.

Fable 5 and Mythos 5 were introduced in June 2026 with the aim of high-efficiency programming, data processing, and document analysis. Fable 5, however, does not handle certain requests in the fields of cybersecurity, biology, and chemistry. In the event of a potential threat being identified, requests are handed over to the less powerful model Claude Opus 4.8. Mythos, in turn, is actively used in cybersecurity research despite controversies over the company being included in the list of risky providers.

Anthropic is concerned about the government’s decision, considering it excessive and unjustified for commercial products. Analysts predict that this restriction could impact Anthropic’s competitiveness in international markets and open up additional opportunities for competitors in AI technology development. The use of powerful models is subject to regulation, which may prompt other companies to receive increased attention from regulatory bodies. Governments may continue to develop rules for the use of artificial intelligence technologies that are becoming increasingly complex and require stricter control.