The Fable 5 ban has forced Anthropic to suspend access to both Claude Fable 5 and Claude Mythos 5 worldwide, only days after launching the new Mythos-class models. In an official statement, Anthropic said it received a US government export control directive on June 12 at 5:21 p.m. ET, citing national security authorities.
The directive blocks access to Fable 5 and Mythos 5 by any foreign national, whether inside or outside the United States, including Anthropic’s own foreign national employees. Anthropic says the practical result is broader than a country-by-country restriction: to comply, it is disabling both models for all customers. Access to other Anthropic models is not affected.
Why The Fable 5 Ban Matters
Anthropic says the government did not give detailed evidence for the national security concern, but the company believes the issue is tied to a possible narrow jailbreak for Fable 5. Anthropic says it reviewed a demonstration that used the model to identify a small number of already known and minor software vulnerabilities, adding that other publicly available AI models can find similar issues without a special bypass.
The company disputes the proportionality of the order. It says its teams, the US government, the UK AI Security Institute, outside organizations, and internal red teams spent thousands of hours testing Fable’s safeguards before launch. Anthropic also says no tester has found a universal jailbreak that broadly bypasses the model’s safety controls.
The shutdown comes after a very short launch window. Anthropic introduced Claude Fable 5 and Claude Mythos 5 on June 9, positioning Fable 5 as a Mythos-class model made safe for general use. Mythos 5 used the same underlying model but with some safeguards lifted for trusted cyberdefenders and infrastructure partners through Project Glasswing.
At launch, Anthropic said Fable 5 would fall back to Claude Opus 4.8 for some cybersecurity, biology, chemistry, and model-distillation requests. It also said more than 95 percent of Fable sessions involved no fallback, and priced both Fable 5 and Mythos 5 at $10 per million input tokens and $50 per million output tokens.
TechRadar framed the move as a sudden shutdown after a potential jailbreak, but Anthropic’s own statement is more specific: the company is complying with a legal directive while arguing that the technical basis appears narrow. Anthropic says it is working to restore access.
You can follow more developments in Technowatt’s Artificial Intelligence coverage.