UK Regains Access to US Frontier AI Models After 17-Day Freeze

What Changed, and What Didn't

The freeze began around September 24, 2026, and 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.

How a Safety Institute Got Locked Out

AISI was set up in 2023, following the international AI Safety Summit held at Bletchley Park. Its mission was simple to describe and hard to execute: test the most capable AI systems before they reach the wider world.

The institute has more than 100 technical experts working on safety evaluations. It has also built a track record. AISI previously evaluated OpenAI's GPT-6 Astra, work that helped cement its role in shaping how frontier models get assessed globally.

What This Means for AI Developers and Governments

For the AI industry, the restored access may ease concerns that safety testing could fracture along national lines. The research findings suggest the move could reassure global researchers and tech investors who worried about isolation between the US and UK approaches.

A Look Ahead

Whether Anthropic's Claude Mythos 5.1 follows will be an early signal of how fully things have returned to normal. AISI officials have pointed to future collaborations on using advanced AI to bolster cyber defenses, which overlaps neatly with the concerns of the very office that triggered the freeze.

What to Watch Next

Whether the US formalizes any priority rules for domestic safety reviews, whether more developers resume sharing with non-US evaluators, and whether the voluntary framework from 2023 gets replaced with something sturdier.