Nearly 150 cybersecurity leaders called on the Trump administration Tuesday to reverse the export directive that forced Anthropic to disable its Fable 5 and Mythos 5 models, recasting a five-day-old export fight as a question about U.S. cyber defenses and complicating the artificial-intelligence company's path to an initial public offering. The open letter was organized by Alex Stamos, Axios reported, and landed as Anthropic executives continued to press the White House to lift Friday's order.
The protest shifts the Anthropic dispute from a narrow export question into a broader fight over whether Washington is writing unwritten rules for AI security research. Anthropic's Monday meeting with administration officials, first reported by CNBC, has not produced a reversal, and the company's two most capable models remain dark for every customer worldwide while it works to comply.
What the letter says
The Stamos letter argues that the Fable and Mythos takedown could discourage American AI companies from building tools that defenders use to find and fix software vulnerabilities, Axios reported. Cyber experts told Axios that frontier labs fearing punishment for models that can identify vulnerabilities may now strip out the very capabilities defenders rely on. Anthropic has said it worked with internal teams and outside researchers to test Fable 5 for jailbreaks and other flaws before release.
The administration is separately standing up a vulnerability clearinghouse under a recent AI security executive order, Axios reported, a body that would triage reports of jailbreaks, prompt injections and other model threats. Researchers argued in the letter that the response to Mythos 5 risks giving adversaries an edge before that clearinghouse is operating.
The IPO overhang
The shutdown also lands at a delicate moment for Anthropic, which is preparing a public offering alongside OpenAI. Microsoft Chief Executive Satya Nadella, whose company is the principal backer of OpenAI and put billions into Anthropic last year, wrote Monday on X that companies need to "build agentic systems that improve over time, while still retaining control over their IP."
"The last thing any of us want is a world where every company across every sector is ceding value to a few models that eat everything they see," Nadella wrote.
Investors took the cue. Shares of MiniMax and Zhipu, the Chinese open-source AI labs, surged Monday as the Anthropic fight put a spotlight on downloadable models companies can run on their own servers. Yash Patel, chief executive of Applied Compute, told CNBC the episode "highlighted the significance of owning your own model," and said the conversation had moved into the mainstream in the past month.
The open-source pull
Open-source models from DeepSeek, Tencent, Xiaomi and MiniMax all rank among OpenRouter's most-used this month, CNBC reported, even against closed competitors. Zhipu framed its latest release as a rebuttal to Washington, arguing cutting-edge AI should not belong to a handful of players or be withdrawn at will. Patel said cost is accelerating the shift as well, with customers reacting to what he called a "token-pocalypse" by routing routine work to cheaper models.
The national-security case
The administration has not detailed its rationale on the record, but the directive Anthropic received Friday cited "national security authorities," CNBC reported. Weekend reporting from Axios, Semafor and the Washington Examiner described a call from Amazon Chief Executive Andy Jassy to the White House Thursday night flagging a Mythos 5 jailbreak, and Semafor separately reported the export order was driven in part by suspicions that a China-linked group had accessed Mythos 5. Cyber experts who signed the Stamos letter do not dispute that those risks exist; they argue, Axios reported, that punishing a frontier lab for shipping vulnerability-finding capabilities will push the industry to strip out exactly the tools defenders rely on.
The vulnerability clearinghouse described in the AI security executive order is not yet operating, and Anthropic has given no public timetable for restoring Fable 5 and Mythos 5. The company's next move is expected in the coming days as White House meetings continue.