Closed briefing sets stage for House hearing on Anthropic’s Mythos and cyber risks

The committee held a closed briefing Wednesday with company reps, and more oversight is in the works.

The House Homeland Security Committee is digging into Anthropic’s AI model Mythos in a series of briefings and hearings, as questions proliferate on whether and how the federal government will make use of the technology touted for its ability to autonomously uncover cyber vulnerabilities.

Wednesday brought a closed-door briefing for the House Homeland Security Committee from Anthropic. The chairman of the panel’s cybersecurity subcommittee said he is planning to hold a hearing on the topic. And committee Democrats are requesting a classified briefing with Anthropic.

A committee aide who attended the briefing said it included a live demonstration of Mythos, “allowing members to see firsthand how advanced AI can identify and reason through software vulnerabilities. What we saw reinforced the urgency of ensuring that federal agencies, including our civilian cyber defenders, can responsibly access and deploy the most advanced U.S. models to find and patch vulnerabilities before foreign adversaries or criminal actors exploit them.”

A number of key lawmakers, including top committee Democrat Bennie Thompson of Mississippi and GOP cyber subcommittee chair Andy Ogles of Tennessee, told CyberScoop they weren’t able to attend Wednesday’s briefing. A second source who attended said it was a “productive” meeting.

“Members on both sides were focused on preserving U.S. advantage in AI, which basically came down to preserving our edge on compute power,” the source said. “They were also asking questions about whether the federal government was using Mythos, including about where CISA is and the impact of the supply chain risk designation.”

The Hill reported that Wednesday’s briefing was led on the Anthropic side by Logan Graham, from the company’s frontier red team, and Josh Tilstra, from the firm’s national security programs and policy team. It follows another recent closed briefing with Anthropic and OpenAI for the House Homeland Security Committee.

Ogles told CyberScoop he plans to hold a hearing of his subcommittee related to Mythos, but wasn’t able to attend Wednesday’s briefing due to scheduling conflicts. The top Democrat on Ogle’s subcommittee, Delia Ramirez of Illinois, also was unable to join due to prior commitments, but she was set to receive a rundown from staff about Wednesday’s briefing, her office said.

There’s a divide on which federal agencies are using Mythos thus far. For example: CISA reportedly isn’t, but the National Security Agency is. 

The federal divide on its use follows a Department of Defense blacklist that labeled the company a “supply chain risk” after Anthropic resisted pressure from the Pentagon to use its Claude AI model in ways the company opposed. The department says it has been using Mythos to identify cyber vulnerabilities despite the blacklist.

A turf battle is brewing within the Trump administration over testing of AI models, The Washington Post reported this week. Connecticut Rep. Jim Himes, the top Democrat on the House Intelligence Committee, said this week that it would be ‘insane” for U.S. spy agencies not to have early access to advanced AI models.

The Mythos briefing came one day after OpenAI announced its own cybersecurity initiative.

The committee aide said that “as the PRC aggressively works to close the AI innovation gap with the United States, the committee remains focused on ensuring that America’s AI leadership translates into a durable national security advantage, not a temporary lead that adversaries can copy, steal, or rapidly commoditize.”

Updated 5/13/26: to include comment from a committee aide who attended the briefing.

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