On the evening of June 12, 2026 (U.S. Eastern Time) — the morning of the 13th in Korea — users lost access to a model that had been publicly released three days earlier. Anthropic said it had cut off access to Claude Fable 5 and Claude Mythos 5 for every customer worldwide. The move followed an export-control directive from the U.S. government.

What happened

The timeline runs as follows.

What the two models are

Fable 5 and Mythos 5 are what Anthropic calls Mythos-class models, a tier above its own Opus class. Anthropic said Fable 5 was "the most powerful model it has made publicly available." It works autonomously for longer than earlier Claude models, holds up to 1 million tokens of context, and refines its results using notes it leaves itself. At launch, Anthropic cited the payments company Stripe, saying the model completed work on a 50-million-line codebase in a single day (Anthropic's figure, not independently verified).

The two are in fact the same model. By Anthropic's account, "Mythos 5 is the same model as Fable 5, but with safeguards removed in certain areas," and those safeguards are exactly what separate them.

Why both models went down

The directive targeted foreign nationals. Anthropic blocked both models in full. The company said it could not screen millions of users by nationality in real time, so the only way to comply was to take both models down.

That said, Bloomberg reported that the non-public research version (Mythos Preview), which had been offered to a small number of partners before launch, remained with some companies, including Cisco Systems and Dragos, even after Anthropic blocked the public versions. Anthropic did not say on what basis it left those in place.

What Anthropic said

In an official statement, Anthropic said it views the move as stemming from a misunderstanding and that it would restore access as soon as possible.

According to Anthropic, the government did not give a specific reason in writing. The company said it understands the issue to be a "jailbreak" that bypasses Fable 5's safeguards, and described the method this way:

asking the model to read a specific codebase and fix any software flaws

The company said the vulnerabilities surfaced this way were already-known minor ones, at a level that other public models can find without any bypass.

What's a first here

As far as is known, this is the first time a deployed commercial AI model has been pulled from public use by government action. Until now, export controls aimed at AI have mostly targeted hardware such as chips. This time was different: the controls restricted access to the model itself.

Since then

The backlash was fast. About 150 security experts — among them Alex Stamos, the cybersecurity authority who led security at Yahoo and Facebook — signed an open letter within days demanding the government reverse the move. Stamos put it this way:

There was a speeding ticket, and they gave Fable the death penalty.

Fortune and others reported that in Europe, amid a sense of urgency that infrastructure held by another country can be cut off at any time, debate over "sovereign AI" — the idea that each country should have its own AI — had reignited.

Anthropic said it is in negotiations with the government, but as of June 22 there is no official announcement of a resumption date. We'll report more as there's news.

Sources