Anthropic's Fable 5 Gets Three Days of Fame, Then the US Pulls the Plug 🪓

Anthropic suspended access to its Fable 5 and Mythos 5 artificial intelligence models on June 12 after receiving a US government export control directive citing national security authorities, the company said Friday. The order, delivered at 5:21 p.m. ET, required Anthropic to halt all access to the two models for any foreign national, whether inside or outside the United States, including foreign national Anthropic employees. To ensure full compliance, Anthropic abruptly disabled the models for all customers, while leaving its other products, including Opus 4.8, unaffected.

The directive came days after Anthropic released Fable 5 to the general public on Tuesday and Mythos 5 to approved cybersecurity partners, both built on top of Mythos Preview, a general-purpose language model the company previously said had identified thousands of vulnerabilities in critical software. Anthropic said the government did not detail the specific national security concern, but told the company it had become aware of a method to bypass, or jailbreak, Fable 5's safeguards. After reviewing a demonstration, Anthropic characterized the finding as minor and said it consisted essentially of asking the model to read a specific codebase and fix software flaws.

Anthropic pushed back on the order, saying that across thousands of hours of pre-release testing with the US government, the UK AISI, and multiple third-party red teams, no tester had discovered a universal jailbreak for Fable 5. The company added that other publicly available models, including OpenAI's GPT-5.5, can identify the same class of vulnerabilities without any bypass. "To date, the government has only given us verbal evidence of a potential narrow, non-universal jailbreak," Anthropic said, warning that applying such a standard across the industry "would essentially halt all new model deployments for all frontier model providers."

The suspension rippled into private markets. The Anthropic perpetual contract on Hyperliquid, a cash-settled contract that tracks where traders expect the company's equity to price, fell about 3.7% on Saturday to roughly $1,627, according to data cited in coverage. The contract had traded near all-time highs above $1,800 in the days following Fable 5's launch, with open interest near $8.6 million. Anthropic has not yet filed for an IPO, and the company said it would share more information about the directive and its next steps as details become available.