UK AI Security Institute regains access to frontier AI models after 17-day US freeze

Britain’s AI Security Institute is back in the testing room. The UK body has regained access to pre-release versions of the latest frontier AI models from leading American developers, ending a 17-day stretch in which that access was cut off. Access was restored on October 11, 2026, and the institute announced the news on October 12. The models now under review include Google’s Gemini 4 Argon. What changed, and what didn’t The freeze began around September 24, 2026. It followed a request from the Office of the National Cyber Director, which wanted US safety reviews to come first. Companies did not all respond the same way. Anthropic chose to withhold its Claude Mythos 5.1 model from non-US entities while the freeze was in place. UK AI Minister Kanishka Narayan is credited with helping secure the renewed access. Both Narayan and Henry de Zoete have backed continued relationships with developers, despite the recent interruption. AISI officials have stressed that their ties with AI companies remain strong. They have also pointed to future collaboration focused on using advanced AI to strengthen cyber defenses. How a safety institute got locked out AISI was set up in 2023, following the...