More than 100 companies and institutions will now have access to Mythos 5, including many Fortune 500 companies, a source familiar with the new directive said, declining to be identified due to the sensitivity of the matter.
Concern that powerful AI systems could be misused by military intelligence users in China, Russia or other countries of concern has prompted President Donald Trump's administration to take an aggressive approach to oversight of releases of Anthropic's and rival OpenAI's frontier models.
Anthropic had abruptly disabled its most advanced AI models - Mythos 5 and Fable 5 - for all users after the government's June 12 export control order.
"Today, the government notified us that Mythos 5, our strongest cybersecurity model, can be redeployed to a set of US organisations that operate and defend critical infrastructure," Anthropic said in a statement.
"We're restoring access for these organisations quickly, and we're continuing to work with the government to expand access to Mythos 5 and make Fable 5 available for general use again," it added.
The government's vetting of which companies can gain access to Mythos has drawn much criticism.
"No one knows how these companies are picked and why everyone else is excluded," said John Coleman, legislative counsel for the Philadelphia-based nonpartisan free speech organisation, the Foundation for Individual Rights and Expression.
"This is putting too much power in the hands of the government. There's little transparency and it raises questions about the rule of law."
OpenAI boss Sam Altman echoed concerns about the government's choosing of who gets access to top models in a post on X.
Extensive safety testing "is not a bad idea. I just don't like the idea of the government picking the customers," he wrote.
Experts say Mythos models, in the wrong hands, could dramatically accelerate sophisticated cyberattacks, particularly in sectors such as banking that rely on complex, interconnected, and often decades-old technology systems.
A letter from US Commerce Secretary Howard Lutnick to Anthropic said there had been "significant progress" in work done by the company with the government to address "risks associated with the Covered Models."
It was not immediately clear what safeguards had been adopted.
Lutnick said in the letter that an export licence will no longer be needed for Mythos 5 to trusted companies and their employees who are not US citizens, or to Anthropic's employees who are not US citizens, but licensing restrictions will remain in place for companies that are not on the approved list.
The source said many of the approved companies are part of Anthropic's Project Glasswing, which includes about 100 well-known tech companies and institutions.
The government is also moving towards allowing Anthropic to release Fable soon, although a timeline is unclear, the source said.
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