Claude Fable 5 and Claude Mythos 5
Security

Claude Fable 5 Hit by Jailbreak Claims and 'Secret Sabotage' Backlash Days After Launch

Anthropic's most powerful public model is having a rough first week. Days after the June 9, 2026 launch of Claude Fable 5, the company is fighting on two fronts: a prominent red-teamer claims to have defeated the model's safety system, while a separate and better-documented backlash accuses Anthropic of silently degrading the model for the researchers and developers who rely on it.
by Richard L. Wells
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