Anthropic Blocks Foreign Access To Fable 5, Mythos 5 After U.S. National Security Order

About four days after Anthropic released Claude Fable 5, a next-generation "Mythos-class" AI model, the frontier AI lab led by Dario Amodei revealed late Friday that it was disabling foreign customers' access to these cutting-edge models, citing an export-control directive from the federal government.

"The US government, citing national security authorities, has issued an export control directive to suspend all access to Fable 5 and Mythos 5 by any foreign national, whether inside or outside the United States, including foreign national Anthropic employees," Anthropic wrote on X around 9 p.m. ET.

The AI lab's website stated that the federal directive was received around 5:21 p.m. ET. To ensure compliance, the lab was forced to shut off Fable 5 and Mythos 5 for all customers.

Anthropic continued, "The net effect of this order is that we must abruptly disable Fable 5 and Mythos 5 for all our customers to ensure compliance. Access to all other Claude models is not affected."

The US government, citing national security authorities, has issued an export control directive to suspend all access to Fable 5 and Mythos 5 by any foreign national, whether inside or outside the United States, including foreign national Anthropic employees.

The net effect of…

— Anthropic (@AnthropicAI) June 13, 2026

Anthropic pointed out that it understands the government's concern centers on a potential method of bypassing, or "jailbreaking," Fable 5.

Dario's company laid out some of Fable's safeguards:

• We have instituted strong safeguards that greatly reduce the likelihood that Fable is misused for tasks related to cybersecurity (among others). In fact, our safeguards are so strong that many users have complained that they are overly broad.

• In the weeks leading up to the launch of Fable, Anthropic worked with the US government, the UK AISI, multiple private third-party organizations and internal teams to red-team Fable's safeguards for thousands of hours in total.

• These tests showed that Fable's safeguards are substantially more effective than those of any previously deployed model.

• No testers have yet been able to find a universal jailbreak—a jailbreak method that can very broadly bypass the model's safeguards, unblocking a wide range of cyber capabilities.

• We suspect that perfect jailbreak resistance is not currently possible for any model provider. Every safeguard used in the industry is vulnerable to non-universal jailbreaks (which can elicit some cyber information in specific circumstances), and it is likely that universal jailbreaks will eventually be found in the future. We stated this clearly when we released Fable 5.

• Given that perfect jailbreak resistance does not appear to be possible today, Anthropic adopted a defense in depth strategy with Fable 5. We aimed to make jailbreaks either narrow (in the case of non-universal jailbreaks) or very expensive to produce (in the case of universal jailbreaks), and to combine this with thorough monitoring to quickly detect and shut down any successful attacks. This is also why Anthropic has required 30-day retention of customer data with Fable—a policy change that carries real costs for us with customers, but that allows us to research and mitigate jailbreaks.

• We stand by this defense in depth strategy. It reduces the risks posed by Fable, making them comparable to the risks of existing models already deployed across the industry.

• We have not even received a disclosure of a concerning non-universal potential jailbreak that led to a harmful result. The potential jailbreaks that have been disclosed to us are either entirely benign responses or are minor findings that provide no Mythos-specific uplift.

Jailbreak concerns already out in the X universe? 

this is definitely what got fable banned https://t.co/3b0rmIIdLe

— Wes Winder (@weswinder) June 13, 2026

Last week, shortly after Tuesday's Fable release, BMO analyst Brian Pitz told clients, "We maintain that Anthropic is the leading pure-play AI lab, combining best-in-class model intelligence with its cutting-edge, benchmark-leading Claude Fable 5 frontier model released June 9, 2026; with clear commercial traction and momentum in its enterprise offerings."

Pitz said, "Anthropic's strengths are particularly evident in coding, agents, and enterprise, where Claude has emerged as a leading model powering tools such as Claude Code and Cowork, both of which have scaled rapidly. This reinforces the company's advantage in translating model intelligence beyond benchmark performance into viable, real-world applications—what we view as the next key battleground in AI."

The release of Claude Fable 5 prompted Pitz's team to declare, "While it is too early to crown a winner among foundation models, we see Anthropic and OpenAI as the leading pure-play AI labs today."

Read Pitz's note here.