The U.S. government has ordered Anthropic to suspend access to its most advanced artificial intelligence models, Fable 5 and Mythos 5, citing national security risks related to potential system jailbreaks. The directive requires an immediate halt to all foreign national access and triggered a complete service shutdown for customers.
Financial markets reacted swiftly to the regulatory intervention. Anthropic perpetual contracts on Hyperliquid dropped approximately 3.7 percent to $1,627, retreating from recent highs above $1,800 established after the Fable 5 launch. This sell-off signals growing investor uncertainty regarding the company’s pre-IPO valuation and public listing timeline.
Anthropic is formally challenging the federal order. The company asserts that government officials provided only verbal evidence of a narrow vulnerability that competitors like OpenAI’s GPT-5.5 can also identify without bypassing safety protocols. Executives argue that enforcing this standard industry-wide would effectively halt all new frontier model deployments.
Known for its safety-first development philosophy, Anthropic contends the alleged jailbreak involves standard codebase review tasks rather than a universal security failure. The firm plans to publish a technical rebuttal within 24 hours. Market participants are now watching closely to see if regulators will reverse, narrow, or expand the restriction based on this forthcoming evidence.