U.S. government orders Anthropic to disable Fable 5 and Mythos 5 access; perpetual contract slips 3.7%

CoinDesk reported that the U.S. government, citing national security, has instructed Anthropic to suspend access to its two most advanced models, Fable 5 and Mythos 5. After the news, the Anthropic perpetual contract on Hyperliquid's pre-IPO market fell about 3.7% as traders reassessed the company's listing outlook. Market data shows the cash-settled perpetual contract slid to around $1,627. The same contract had previously climbed above $1,800 following the release of Fable 5. These instruments primarily track market expectations for the firm's equity valuation. Open interest stands near $8.6 million—smaller than SpaceX-linked products, but meaningful given Anthropic has not filed for an IPO. Anthropic said it received a government directive at 5:21 p.m. Eastern Time on Friday. The order, issued under national security authority, required the company to block access to Fable 5 and Mythos 5 for all foreign citizens, whether located inside or outside the U.S. Anthropic later expanded the restriction to all customers and fully deactivated access. The government said it had identified a way to bypass the models' safeguards, described as a jailbreak. Anthropic has pushed back, saying officials have provided only verbal explanations and that the cited issues are not general-purpose jailbreaks, but a small number of known, minor vulnerabilities. The company added that other publicly available models, including OpenAI's GPT5.5, can surface similar issues without evading restrictions. Anthropic warned that applying this threshold to limit new model releases could disrupt deployment across the broader frontier AI sector. The episode has sharpened market focus on whether the government's order will be rescinded or narrowed, and whether similar constraints could spread to other model categories—both of which could influence Anthropic's valuation and IPO timeline.