The U.S. government ordered Anthropic to shut down its two most advanced AI models, Fable 5 and Mythos 5, citing national security concerns over a potential jailbreak vulnerability. Anthropic complied but challenged the directive, arguing the government's evidence is verbal and the vulnerability is narrow and previously known, similar to flaws in OpenAI's GPT-5.5. The company warned that applying such standards would halt all new model deployments in the industry. Traders reacted negatively: Anthropic's perpetual contract on Hyperliquid dropped 3.7% to around $1,627, from near all-time highs above $1,800 after Fable 5's launch. The open interest is about $8.6 million. The shutdown raises questions about Anthropic's pre-IPO valuation and listing prospects. Anthropic stated it will release technical details of the jailbreak within 24 hours. The crypto market views the shutdown as a negative for the IPO, and the company's public listing ambitions hinge on whether the order is reversed, narrowed, or extended.

Key facts

• US government ordered Anthropic to shut down Fable 5 and Mythos 5 citing national security.
• Anthropic challenged the directive, calling the vulnerability narrow and previously known.
• Hyperliquid perpetual contract dropped 3.7% to ~$1,627, from highs above $1,800.
• Open interest on the contract is about $8.6 million, small but meaningful for pre-IPO.
• Anthropic will release technical details of the jailbreak within 24 hours.