U.S. Government Abruptly Halts Anthropic’s Most Advanced Model; “Pre-IPO Stock Price” Plummets 3.7% Overnight

Author: Claude, TechFlow

TechFlow Introduction: Citing national security concerns, the U.S. government abruptly ordered Anthropic on June 12 to shut down its two most advanced AI models—Fable 5 and Mythos 5. The move sent shockwaves through markets: Hyperliquid’s perpetual contract tracking Anthropic’s anticipated IPO valuation plunged 3.7% to approximately $1,627 on Saturday—down significantly from its post-launch peak of over $1,800. Anthropic publicly voiced strong opposition, stating the government demanded recall based solely on an oral notification regarding a single “narrow jailbreak vulnerability”; if applied industry-wide, such a standard “would effectively halt deployment of all frontier models.”

A company founded on the principle of “AI safety” is now forced to shut down its strongest products due to a government safety directive.

According to multiple reports—including from CoinDesk—the U.S. government issued an export control order to Anthropic on the afternoon of Friday, June 12, requiring the company to suspend all access to Claude Fable 5 and Claude Mythos 5 by foreign nationals—regardless of whether they are physically located inside or outside the United States, including Anthropic’s own non-U.S. employees. Unable to comply selectively without compromising regulatory compliance, Anthropic opted to disable both models globally for all users; other Claude models remain unaffected. In its statement, Anthropic explicitly rejected the government’s rationale, calling the incident “a misunderstanding” and pledging to restore access as soon as possible.

National Security Directive Triggers Full Shutdown—One Letter, Immediate Impact

According to The Wall Street Journal (cited by Quartz), U.S. Commerce Secretary Howard Lutnick sent a letter to Anthropic CEO Dario Amodei outlining the restrictions. Anthropic disclosed it received the directive at 5:21 p.m. ET that day—but the letter provided no specific details regarding the alleged national security concerns.

Anthropic stated it understood the government believed it possessed a method to bypass—or “jailbreak”—Fable 5. Company executives explained the cited vulnerability involved a narrow prompt-engineering technique designed to prompt the model to review existing minor software flaws in code—and emphasized similar outputs can be easily generated on competing models like OpenAI’s without any special circumvention techniques.

Anthropic’s statement used unusually direct language: “We are complying with the government’s legal directive and removing access to Fable 5 and Mythos 5 for all users. However, we do not agree that discovering one narrow potential jailbreak vulnerability justifies recalling a commercially deployed model serving hundreds of millions of users.” The company warned that if this standard were extended across the industry, “it would effectively halt all new model deployments by frontier model providers.”

The company further noted that, to date, the government has provided only oral evidence—no written documentation, no technical report, and no formal disclosure through established channels—and pledged to release further technical analysis within 24 hours to demonstrate the limited scope of the issue.

Market Reacts Instantly Ahead of IPO—Hyperliquid Perpetuals Plummet

This regulatory development became a financial event precisely because Anthropic remains unlisted—yet crypto markets have already created a “shadow pricing” mechanism for it.

As reported by CoinDesk, Anthropic’s perpetual contract on Hyperliquid dropped roughly 3.7% to ~$1,627 on Saturday—falling from its historical high near $1,800 reached in the days following Fable 5’s launch. The contract’s open interest stands at approximately $8.6 million—modest relative to larger private-market proxies, yet notable for a company that hasn’t even filed an IPO application.

The contract’s quoted price implies an implied valuation in the trillions of dollars—$1,638 corresponds to an implied valuation of ~$1.638 trillion. Within 24 hours of the news breaking, the contract’s 24-hour trading volume totaled ~$190,000, with a funding rate of 0.0056%.

The impact extended beyond the perpetuals market. According to Bitcoin.com, the ANTHROPIC token—issued on Solana by Prestocks and claiming to offer spot-like exposure via a Special Purpose Vehicle (SPV) structure—fell 9.11% to $655.32 within 24 hours; related liquidity pool volume contracted 18.09% to ~$126,000. It should be noted that Anthropic has previously warned publicly that any unauthorized tokenization or derivatives claiming equity exposure to the company may be deemed invalid; none of these products are endorsed or affiliated with Anthropic.

Shut Down Just Days After Launch—Fable 5 Was Meant to Be a Milestone

The two suspended models had launched only days earlier.

Multiple outlets reported Fable 5 and Mythos 5 debuted around June 9, representing major leaps in capabilities across software engineering, scientific reasoning, vision tasks, and long-context processing. Notably, Fable 5 marked Anthropic’s first public release of a Mythos-tier model—a tier positioned above its prior flagship Opus. Both models share the same underlying architecture, differing primarily in output control: Fable 5 incorporates a built-in classifier designed to intercept responses in high-risk domains such as cybersecurity, while Mythos 5 is accessible only to pre-vetted, trusted groups.

As summarized by MarkTechPost, Fable 5’s classifier is a standalone AI system tasked with identifying potential misuse; when queries touch on cybersecurity, biochemistry, or model distillation, the system falls back to Claude Opus 4.8—with users explicitly notified each time fallback occurs. The fallback rate is under 5%. Notably, Mythos 5 has also supported critical cybersecurity defense efforts via initiatives like Project Glasswing—prompting debate over whether the temporary suspension might actually impede infrastructure protection.

Blowback from the Safety Narrative—New Uncertainty for IPO Timeline

For Anthropic, the timing and logic of this incident are particularly awkward.

TechCrunch headlined its coverage: “Anthropic’s safety warnings may have just backfired”—a company whose entire identity rests on “responsible AI development” now finds itself compelled to shut down its most powerful model based on a verbal briefing alone. That’s a bitter pill to swallow—and Anthropic made its dissatisfaction public.

The episode coincides with a sensitive phase in Anthropic’s IPO preparations. The company recently filed registration documents confidentially, joining a cohort of leading AI firms actively planning public listings. Though instruments like Hyperliquid’s contract remain relatively illiquid, their price decline reflects investor caution regarding Anthropic’s near-term valuation and path to listing. Such sudden regulatory interventions add fresh uncertainty to an IPO process already fraught with unpredictability.

Anthropic stated it is actively engaging with authorities to resolve the matter and restore service as quickly as possible, characterizing the directive as “based on a misunderstanding.” The ultimate resolution of this incident may influence how regulators and innovators interact going forward—and shape how export controls and safety assessments apply to rapidly evolving AI technologies.