Commerce Department forces Anthropic to pull Fable 5 and Mythos 5 over claimed jailbreak

An export-control directive citing national security wiped Anthropic's two most advanced models off the market three days after Fable 5 launched.

At 5:21pm ET on Friday, Anthropic received a Commerce Department export-control directive that, by the end of the evening, had taken Claude Fable 5 and Claude Mythos 5 fully offline worldwide. Fable 5 had launched three days earlier. Vals AI had benchmarked it as the most capable publicly available model at release.

Anthropic says the letter cited national security authorities but “did not provide specific details.” From verbal briefings, the company’s understanding is that the government was shown a jailbreak that “essentially consists of asking the model to read a specific codebase and fix any software flaws,” a technique that surfaced “a small number of previously known, minor vulnerabilities” reproducible on OpenAI’s GPT-5.5. In a blog post, Anthropic argued that “If this standard was applied across the industry, we believe it would essentially halt all new model deployments for all frontier model providers.”

The Mythos restriction is less of a shock than the framing suggests. Since April, the model had been confined to roughly 50 vetted partners under Project Glasswing, including Amazon, Apple, Google, Microsoft and CrowdStrike. Fable 5 was the consumer-facing flagship. Now both are dark, and Claude Opus 4.8 is what’s left.

The directive doesn’t arrive in a vacuum. In February, Trump ordered federal agencies to stop using Claude. The Pentagon labeled Anthropic a supply-chain risk after the company refused contract language permitting model use “for any lawful purpose,” and Anthropic is suing to reverse the designation. Earlier this month, it filed confidentially for an IPO.

That sequencing is the story. AI critic Gary Marcus told Fortune the action is likely to push Chinese-born researchers back to China and spook investors. Anthropic built its brand on safety warnings loud enough to reach Washington. Washington heard them, then used a separate jailbreak demo, contested on the merits, to switch the company’s frontier products off three days into a launch cycle and weeks into a pre-IPO quiet period.