Anthropic’s newest AI model got grounded by the US government, and the company is now showing its homework on how it plans to keep things locked down going forward.
Following a security incident in June 2026 that led the US Commerce Department to temporarily suspend global access to both Claude Fable 5 and its more powerful sibling Mythos 5, Anthropic has detailed a suite of cybersecurity safeguards and proposed an early framework for assessing how bad AI jailbreaks actually are.
What happened, and what Anthropic built in response
Fable 5 and Mythos 5 launched in early June 2026. Amazon researchers subsequently identified a narrow jailbreak vulnerability in Fable 5, one that allowed limited exploitation of known vulnerabilities. The jailbreak was characterized as non-universal, meaning it wasn’t some skeleton key that unlocked everything.
The US Commerce Department enforced export controls and temporarily yanked global access to both models. Access was restored on July 1, 2026, after Anthropic deployed a new safety classifier that blocks over 99% of attempts replicating the reported jailbreak.
