Anthropic disabled Mythos 5 and Fable 5 after a US Commerce Department export-control order barred their use abroad. The administration asked for a pause amid reports of a narrow jailbreak letting Fable 5 analyze code for vulnerabilities. Anthropic says the issue produced only minor findings and that other models, like GPT-5.5, have similar capabilities.

• Anthropic disabled Mythos 5 and Fable 5 days after launch due to a Commerce Department export-control order barring their use outside the US.
• The trigger was a narrow jailbreak letting Fable 5 give cybersecurity/chemistry/biology advice on a specific codebase, but it only surfaced minor vulnerabilities.
• Anthropic claims other models like GPT-5.5 have similar capabilities, suggesting the singling-out of Fable 5 is inconsistent.
• The article's own account is internally contradictory: it names the Commerce Department order as Trump-administration action but then attributes the pause to "the Biden administration."

The US government issued an export control order to cut off all foreign-national access to Anthropic’s Fable 5 and Mythos 5, citing a potential jailbreak vulnerability. Anthropic says the reported exploit is narrow, already known across other models, and disagrees that it warrants a full suspension. The company plans to share more details within 24 hours and restore access if possible.

• The US government ordered Anthropic to cut off all foreign-national access to Fable 5 and Mythos 5 over a claimed jailbreak vulnerability, with only a "national security concerns" explanation given.
• Anthropic says the exploit is just a narrow codebase-scanning jailbreak trick that only surfaces minor, already-known vulnerabilities present in any public model, including OpenAI's GPT-5.5.
• Anthropic disabled both models entirely despite disputing the severity, arguing the shutdown is disproportionate and could chill AI releases industry-wide.
• The company is pushing for a transparent process with clear technical criteria instead of sudden verbal directives, and plans to release more details within 24 hours while seeking to restore access.