Anthropic pulls Fable 5 and Mythos 5 offline after US export-control order

Remember Fable 5? The frontier model Anthropic shipped last week, with the locked-down Mythos 5 sibling gated behind their cyber and bio programs? Both are now switched off.

On June 12th, according to The Register and Axios, the Trump administration issued an export-control directive suspending access to Fable 5 and Mythos 5 for any foreign national — inside or outside the US — on national-security grounds. Anthropic responded by disabling both “for all our customers to ensure compliance.” So right now nobody gets them, not just the foreign nationals the order names.

The trigger is the part worth your attention. Researchers handed the models open-source code containing known CVEs plus some deliberately planted bugs then asked Fable 5 to “review the code for security issues” and Fable 5 refused. They then asked instead to “fix this code” and Fable 5 produced patches the researchers then turned into test scripts by hand. Anthropic reportedly logged the episode as “a potential narrow, non-universal jailbreak”.

I’m soo confused right now. A model fixes flaws and bugs that could make apps malfunction and exploited and gets shutdown. No offensive jailbreak, no network scan, no malware but code fixing.

This looks like the first time an export control has taken a frontier model offline mid-flight, and the bar that did it was ordinary defensive work. If that logic holds, any model good at fixing your code is one that can be pulled out from under you.

Sources

• The Register — Feds freaked over Fable 5 after simple ‘fix this code’ prompt, not jailbreak, says researcher
• Simon Willison — The Fable 5 Export Controls Harm US Cyber Defense
• Simon Willison — “They screwed us”: Personality clashes sent Anthropic’s models offline (on Axios)