Anthropic said it would disable access to its latest top AI models, Fable 5 and Mythos 5, following a government export control that would bar foreign individuals and entities from using the products.
The company said in a blog post on Friday evening that it had received a letter from the US government at around 5:21 p.m. ET, citing national security concerns regarding Anthropic’s models.
Anthropic said the government’s order included any foreign national inside or outside the US, “including foreign national Anthropic employees,” and that the “net effect” of the order is to disable the models for everyone to ensure compliance.
The company added that the letter “did not provide specific details of its national security concern.”
Anthropic said it believes the government’s concern is a potential way to “jailbreak” Fable 5, but disputed the issue’s severity. The company said the technique appeared narrow, not universal, and involved known vulnerabilities that could be identified by other publicly available models.
The move marks the latest escalation in Anthropic’s clash with the Trump administration over AI safety, national security, and the extent of government control over frontier AI models.
In February, the Pentagon moved to designate Anthropic as a supply chain risk after the startup sought limits on its AI model for certain defense applications.
Anthropic sued the Defense Department over the designation. Two lawsuits related to the government’s supply-chain risk label remain pending.
A White House spokesperson did not immediately respond to a request for comment. The Pentagon’s chief information officer expressed support for the move in an X post, writing, “Some things are simply more important than revenue cycles, clickbait, and pre-IPO valuation.”
Anthropic said it was complying with the order but disagreed with the government’s finding. An Anthropic spokesperson did not say when exactly the company would disable access.
Access to Anthropic’s other models will not be affected, the company said.

Anthropic completely shut off access to its Mythos 5 and Fable 5 models Friday night, just days after they were launched.
The move comes after Anthropic’s receipt of a US Commerce Department directive Friday evening, subjecting the new models to export controls restricting their use anywhere outside the United States. In a message posted Friday night, Anthropic said the only way for it to ensure compliance with that government order in the immediate term “is that we must abruptly disable Fable 5 and Mythos 5 for all our customers.” Access to other Anthropic models is not affected.
An Axios report cited an administration official saying that the administration is concerned by reports of a jailbreak that reportedly gets around broad classifier-based safeguards meant to block Fable 5 prompts regarding cybersecurity, chemistry, and biology. The administration reportedly requested a pause in the release of these models to gain time for the “national security apparatus” to be “hardened” against this kind of threat. That hardening could be complete “in the next few weeks,” Axios’ source suggested.
In its Friday night announcement post, Anthropic said the government has only provided it with “verbal evidence of a potential narrow, non-universal jailbreak” that involves getting Fable 5 to review a specific codebase for software flaws. The company says it has only seen evidence of this kind of jailbreak being used to find “minor” and “relatively simple” software vulnerabilities, and that other publicly available models like GPT-5.5 has similar capabilities on this score.
“We are complying with the government’s legal directive and are removing access to Fable 5 and Mythos 5 for all users,” Anthropic writes. “However, we disagree that the finding of a narrow potential jailbreak should be cause for recalling a commercial model deployed to hundreds of millions of people. If this standard was applied across the industry, we believe it would essentially halt all new model deployments for all frontier model providers.”
Earlier this month, President Trump signed an executive order urging AI model makers to submit to voluntary government security testing. That order came after an initial signing ceremony planned for last month was abruptly postponed amid reported concerns of disagreements about it within the administration.
Anthropic apologized to customers for a “disruption” that it said is the result of a “misunderstanding,” and said it will release more details about the situation in the next 24 hours.

The U.S. government on Friday ordered Anthropic to immediately shut off access to two of its most powerful AI models — Claude Fable 5 and Claude Mythos 5 — citing national security concerns. Anthropic announced on X that it has complied, but it made clear it thinks the government got this one wrong.
The directive, which Anthropic said it received on Friday at 5:21 pm ET, forces the company to disable both models for all users worldwide — not just the foreign nationals the government’s export control order was nominally aimed at. Access to Anthropic’s other models isn’t affected.
Why does any of this matter? Mythos is Anthropic’s most capable AI model, one the company previewed in early April and has kept tightly restricted ever since because of what Anthropic described as its exceptional ability to find security vulnerabilities in software. According to Anthropic, Mythos identified flaws in every major operating system and web browser it tested, so rather than release it broadly, the company launched a controlled program called Project Glasswing, sharing it with roughly 50 vetted organizations, including Amazon, Apple, Google, Microsoft, and CrowdStrike, to use for defensive cybersecurity work.
Fable 5, released just three days ago, was Anthropic’s answer to the obvious commercial pressure: a version of Mythos fitted with guardrails that block responses in high-risk areas like cybersecurity and biology, making it safe enough for general release, the company argued. It was immediately the most capable AI model available to the public, according to benchmark tests from Vals AI, a company that tracks AI tech performance.
The government’s directive is framed as an export control action, restricting foreign national access to the models. But in a lengthy blog post, Anthropic says its understanding is that the underlying concern is a claimed jailbreak of Fable 5. So far, the company says, the government has provided only verbal evidence of a “potential narrow, non-universal jailbreak” — one that, as Anthropic describes it, amounts to prompting the model to read a specific codebase and identify software flaws. And by the way, adds the company, it’s a “level of capability” that’s already widely available in other publicly accessible models, including OpenAI’s GPT-5.5. It’s also used routinely by cybersecurity professionals for defensive purposes, says Anthropic.
Anthropic’s broader argument is that its strongest safeguards operate through independent classifier systems that function separately from the model itself, meaning that even if someone convinces Fable to keep talking past a refusal, the underlying protections against the most dangerous outputs remain in place.
Clearly, none of that was enough to stop the government from acting, and Anthropic isn’t hiding its frustration. “We disagree that the finding of a narrow potential jailbreak should be cause for recalling a commercial model deployed to hundreds of millions of people,” the company wrote. “If this standard was applied across the industry, we believe it would essentially halt all new model deployments for all frontier model providers.”
Anthropic is widely expected to pursue an IPO this year and has staked much of its public identity on being the safety-conscious alternative to its rivals. The irony isn’t lost on observers that the very caution Anthropic displayed in restricting Mythos — which it promoted as a model so dangerous it couldn’t be released publicly — has now apparently attracted exactly the kind of government scrutiny that could disrupt its business most.

The Justice Department on Friday approved Paramount’s proposed $111 billion takeover of Warner Bros. Discovery.
After concluding its antitrust investigation into the pending merger, the department said in a statement that it found that the deal posed no threat to competition or consumers of film, broadcast television or streaming.
The decision clears the way for a merger of two rival Hollywood studio titans: Paramount, the owner of CBS, including CBS News, will swallow the much larger Warner, which includes HBO and CNN.
The DOJ”s Antitrust Division concluded that a union of two studio giants isn’t anti-competitive because the streaming market has expanded the competition for conventional Hollywood studios, which includes Netflix, Apple and Amazon, as well as smaller streamers. The Justice Department’s view is that, for the same reason, consumers won’t lose out because there are plenty of other places to get entertainment.
Several states, including California, have raised antitrust concerns. The European Union is investigating as well.
California Attorney General Rob Bonta, who has been investigating the deal for antitrust violations, said in a post on social media following the Justice Department’s approval: “The merger of Warner Bros and Paramount is not a done deal and remains under investigation by my office.”
In a statement following the decision, Paramount described the deal as “pro-competitive,” and would result in “a stronger company better positioned to compete against dominant technology platforms in an industry increasingly defined by intense competition for audiences, talent, technology, and investment.”
The company said it planned to complete the merger as soon as possible, “delivering its benefits to consumers, creators, and the entertainment industry as a whole.”
The consolidation will put media mogul David Ellison — son of Oracle co-founder Larry Ellison — at the helm of Warner Bros. studio as well as its cable and streaming properties, including CNN and HBO. The Ellison family took over Paramount and CBS last summer.
In the months leading up to the regulatory approval, critics in Hollywood feared the deal would consolidate an already concentrated media landscape and lead to fewer jobs and less creative content.
In April, thousands of directors, actors, writers and other industry talent — including Kristen Stewart, Pedro Pascal and Javier Bardem — signed an open letter opposing the merger.
The elder Ellison is also a financial backer and adviser to President Trump on artificial intelligence. Critics of recent changes at CBS under the Ellisons’ control are concerned that, as they say has happened with CBS News, the acquisition would make CNN more friendly to Trump.
NPR’s Carrie Johnson and Mandalit del Barco contributed to this story.

The Justice Department will not challenge Paramount’s merger with Warner Bros. Discovery, clearing a major hurdle for the $111 billion deal, the agency said Friday.
The merger would consolidate the ownership of two major movie studios; two major streaming services, Paramount+ and HBO Max; and two television news networks, CNN and CBS News, under the leadership of the tech scion David Ellison.
The scale of that combination has raised concerns that it could reduce the number of buyers for TV and movie scripts and potential employers for actors and crew members, driving down wages and the prices paid for creative material. The Justice Department blocked a publishing deal in 2022 over similar claims.
In an unusual statement announcing its decision, the Department of Justice said its investigation of the deal had included hours of depositions, interviews and meetings that “all led to the same conclusion: The film and television industry is highly dynamic, and the proposed transaction is not likely to harm competition or American consumers.”
That statement could help Paramount fight any future challenges. Some state attorneys general have pledged to take a hard look at the deal, and could bring their own case. Also, an antitrust regulator in Britain said this week that it would launch its own investigation of the deal.
A spokeswoman for Paramount, Susan Friedman, said in a statement on Friday that the merger would result in a “stronger company” that could succeed “in an industry increasingly defined by intense competition for audiences, talent, technology and investment.”
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