Anthropic’s pre-IPO shares fall as US government shuts down its most powerful AI model
A jailbreak report prompted Washington to pull Fable 5 and Mythos 5 from all users. Anthropic complied but pushed back hard, saying the finding sets a standard that would halt the entire AI industry.
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Summary
- The U.S. government ordered Anthropic to shut down access to its two most advanced AI models, Fable 5 and Mythos 5, citing national security concerns over a potential jailbreak.
- Anthropic has challenged the directive, arguing that the government has only provided verbal evidence of a narrow, previously known vulnerability that similar models, including OpenAI’s GPT-5.5, can also identify.
- Traders reacted negatively to the shutdown, with the Anthropic perpetual contract on Hyperliquid falling about 3.7 percent and raising new questions about the company’s pre-IPO valuation and listing prospects.
