Key Takeaways
- Federal authorities mandated that Anthropic disable Fable 5 and Mythos 5, its most sophisticated AI systems, due to national security considerations.
- A purported jailbreak vulnerability prompted the action, though Anthropic characterizes it as limited in scope and non-universal.
- While Anthropic executed the shutdown directive, the company has publicly challenged its validity, asserting inadequate supporting evidence.
- Trading of Anthropic’s pre-IPO contracts on Hyperliquid declined 3.7% to approximately $1,627 after the announcement.
- The AI firm committed to publishing comprehensive technical documentation regarding the alleged vulnerability within one day, maintaining the directive results from miscommunication.
Federal authorities commanded Anthropic to disable its most advanced artificial intelligence systems on Friday. The decision sent shockwaves through pre-IPO trading platforms and positioned the AI developer in direct confrontation with U.S. regulators.
Details of the Federal Directive
The mandate reached Anthropic at 5:21 p.m. Eastern Time on Friday evening. Issued through national security channels, the directive demanded immediate suspension of Fable 5 and Mythos 5 access for any individual holding foreign nationality, regardless of their physical location.
The restrictions extended even to foreign nationals employed within Anthropic‘s own workforce.
For complete compliance assurance, the company terminated access to both systems for its entire user base. Alternative models in Anthropic’s portfolio, such as Opus 4.8, continued operating without interruption.
Fable 5 and Mythos 5 had only recently become available to users. Both systems were developed using Mythos Preview as their foundation, a versatile model that Anthropic credited with identifying thousands of security flaws in essential software infrastructure.
Federal officials informed Anthropic they had discovered a technique capable of jailbreaking Fable 5. Jailbreaking refers to methods that circumvent the protective safeguards built into AI models.
Following internal analysis, Anthropic contested the government’s characterization. Company representatives described the technique as limited in application, not a widespread jailbreak, and dependent on a handful of previously documented, relatively minor security weaknesses.
The firm further noted that alternative publicly accessible models, including OpenAI’s GPT-5.5, can identify identical vulnerabilities without requiring any workaround techniques.
“To date, the government has only given us verbal evidence of a potential narrow, non-universal jailbreak, which essentially consists of asking the model to read a specific codebase and fix any software flaws,” Anthropic said.
The organization emphasized that cybersecurity professionals routinely perform this identical function.
Market Reaction to the Shutdown
Financial markets reacted swiftly to the development. Anthropic’s perpetual contract on Hyperliquid, which functions as a proxy for anticipated equity valuations, decreased 3.7% on Saturday to settle near $1,627.
Prior to the announcement, the contract had been changing hands above $1,800 following Fable 5’s market introduction. Current open interest totals approximately $8.6 million, considerably smaller than the SpaceX perpetual contract but still significant for a firm that has not yet initiated its public offering process.
Anthropic maintains that the directive stems from miscommunication and is actively working toward reinstating access at the earliest opportunity.
The organization has pledged to release exhaustive technical analysis of the purported jailbreak method within the next 24 hours.
Anthropic warned that applying this standard broadly “would essentially halt all new model deployments for all frontier model providers.”
The organization, which established its market position emphasizing safety-oriented AI development, now finds itself openly contesting a federal directive based on its assessment that the supporting evidence fails to satisfy established thresholds.
The ultimate resolution—whether authorities rescind, modify, or expand the order—will significantly influence Anthropic’s trajectory toward becoming a publicly traded entity.