Anthropic Redeploys Claude Fable 5 on July 1 After US Export Controls Lift, Adds New Cybersecurity Classifier

Anthropic is redeploying Claude Fable 5 , its most capable generally available model. On June 30, it announced that US export controls had lifted. The controls had covered Claude Fable 5 and Claude Mythos 5 . Fable 5 returned to users globally on Wednesday, July 1. Mythos 5 access is restored to a set of US organizations.

The models were pulled on June 12. A US government directive restricted them to non-foreign-nationals. Anthropic could not verify nationality in real time. So it suspended both models for everyone.

This article explains what triggered the block. It covers the new safeguard and the proposed jailbreak framework. It also shows how Fable 5 compares to rivals like GLM-5.2.

Anthropic launched Fable 5 and Mythos 5 on June 9. Both share the same underlying model. Fable 5 ships with strong safeguards for general use. Mythos 5 has some safeguards lifted for defensive cybersecurity partners.

On June 12, the US government applied export controls. The order took effect immediately. Anthropic suspended access rather than risk non-compliance.

The trigger was a report from Amazon researchers. They found a method of bypassing Fable 5’s safeguards. The prompt made the model identify a number of software vulnerabilities. In one case, it produced code showing how to exploit one vulnerability.

By June 26, the government approved restoring Mythos 5 for some US organizations. On June 30, the controls were fully lifted.

Anthropic tested whether the finding was unique to Fable 5. It was not.

Less capable models identified the same vulnerabilities. That list includes Claude Opus 4.8, GPT-5.5, and Kimi K2.7.

For the single exploit demonstration, every tested model reproduced it. That set included Haiku 4.5, Sonnet 4.6, Opus 4.6, and Opus 4.7. It also covered Opus 4.8, GPT-5.4, GPT-5.5, and Kimi K2.7.

The Anthropic team states the technique exposed no unique Mythos-level cyber capabilities. It called the case a borderline one for Fable 5’s safeguards. The blocked behavior involved only routine defensive cybersecurity work.

Anthropic still moved to close the gap. It trained an improved safety classifier for the reported behavior.

The classifier blocks the specific technique in over 99% of cases. Blocked requests are not refused outright. They are routed to Claude Opus 4.8 instead. Users are notified when this fallback happens.