Anthropic Restores Claude Fable 5 After U.S. Lifts Jailbreak-Linked Export Controls

Anthropic temporarily shut down Fable 5 after a reported jailbreak enabled the model to bypass safeguards and surface code demonstrating software flaws; the U.S. Commerce Department imposed export controls which were later lifted after Anthropic implemented a classifier to block the reported technique. Mythos 5 remains tightly restricted with limited access, and Anthropic is coordinating with the government, launching a HackerOne program, and proposing a shared severity scoring system for jailbreaks, while the report highlights broader risks that frontier models can discover and weaponize zero-day vulnerabilities.