Anthropic removes Claude Fable 5 and Mythos 5 after U.S. export-control order

• Anthropic's statement says a U.S. export-control directive forced it to suspend Claude Fable 5 and Claude Mythos 5 for all customers, even though the order targeted access by foreign nationals.
• ClaudeDevs' product notice says new sessions now fall back to a user's default model or Opus 4.8, while existing Fable 5 sessions and direct platform calls return errors.
• Simon Willison's minute-by-minute test caught the cutoff in real time, with the API switching from normal responses to a 404-style not-found error that explicitly told users to use Opus 4.8.
• According to Yahoo's summary of Axios reporting, Amazon and at least five other companies pressed the administration after a reported jailbreak demonstration.
• ClaudeDevs' follow-up reset 5-hour and weekly rate limits the same night, which turned an export-control event into an immediate product-operations event for active Claude users.

Anthropic's full statement says the government sent the directive at 5:21 p.m. ET and did not provide specific details of the national-security concern. You can read the original Fable 5 and Mythos 5 launch post, see Simon Willison's API cutoff log, and check Yahoo's summary of Axios reporting for the Amazon and White House timeline.

Anthropic said the order required it to suspend access to Fable 5 and Mythos 5 by any foreign national, including foreign national employees, whether they were inside or outside the United States. In its statement, the company said that requirement effectively forced a full shutdown for all customers.

Anthropic also said the government's evidence was a demonstration of a narrow, non-universal jailbreak against Fable 5, not a broad break of the model's safeguards. The company argued in the same statement that similar narrow jailbreaks exist across other publicly available frontier models.

The user-visible behavior was abrupt. ClaudeDevs' notice said existing Fable 5 sessions would terminate with an error, and Simon Willison's attached screenshot shows the API returning not_found_error with the message: "Claude Fable 5 is not available. Please use Opus 4.8."

The fallback path split across surfaces:

• In Claude apps, ClaudeDevs said new sessions would run on the user's selected default model or Opus 4.8.
• On the Claude Platform, the same notice said requests to Fable 5 would return an error until integrations switched models.
• In Claude Code, bridgemindai reported that Fable 5 disappeared from model selection entirely.
• In Devin, Cognition said it removed Fable 5 but kept other models, including Opus 4.8 and GPT-5.5, available.

Anthropic's official explanation is that the government believed it had become aware of a jailbreak method for Fable 5. Anthropic said it reviewed the demonstration and did not think the reported behavior justified recalling a model already deployed commercially.

Yahoo's summary of Axios reporting adds the missing politics: Amazon reportedly called administration officials on Thursday night with a report claiming access to dangerous parts of Mythos, and at least five other companies also contacted senior officials before the shutdown order landed. Theo's post pointed to that reporting, and deredleritt3r's thread separately cited follow-on reporting that Amazon CEO Andy Jassy was among the tech leaders raising concerns.

One detail from the original launch post makes the reversal stranger. Anthropic had introduced Mythos 5 as the same underlying model as Fable 5, with some safeguards lifted, and said it was being deployed through Project Glasswing in collaboration with the U.S. government.

The sharpest operational clause was not the model takedown itself, but who the order named. Anthropic said the restriction applied to any foreign national, including its own employees, which immediately raised questions about how a frontier lab staffed by international researchers is supposed to operate under an access rule like that.

The same clause also changed how non-U.S. customers read vendor risk. Gergely Orosz framed it as a live demonstration that access to a top U.S. model can disappear overnight for non-U.S. companies, while his follow-up argued that what had been a theoretical dependency risk had become a real one.

Anthropic reset 5-hour and weekly rate limits for all users less than two hours after the suspension notice. That did not restore Fable 5, but it did compensate for interrupted sessions and changed the immediate experience for paid users who were suddenly back on Opus 4.8.

The benchmarks and product charts moved backward too. Artificial Analysis said it was the first time its Intelligence Frontier chart had ever moved backward, a neat way to describe what happens when a frontier model disappears after three public days.

Anthropic had already scheduled a San Francisco "Claude Fable 5 Build Day" for June 13, with the original event post promising Claude Code access and a $150,000 prize pool in Claude credits across three finalists. Hours after the suspension, ClaudeDevs said the event would still happen, just on Opus 4.8 instead.