Anthropic did not give Britain’s AI Security Institute (AISI) its Mythos 5.1 model to test before release, the Financial Times reported. Reporters Lucy Fisher and Madhumita Murgia said it is the first time a major model has been kept from the UK institute before launch. TNW has not independently verified the report.
The FT reported that Anthropic did give comparable US organisations access. According to the paper, UK officials fear a wider protectionist shift among American AI companies. They see it as falling into line with the Trump administration. Anthropic has not publicly explained the decision.
What the UK is missing
Anthropic released Mythos 5.1 on 1 September alongside Fable 5.1. Access is limited to approved partners in Project Glasswing. That is the industry group Anthropic formed around the original Mythos model.
AISI has tested Anthropic models before. In April it published an evaluation of the Mythos preview’s cyber capabilities. It found the model was the first to finish its 32-step simulated network attack. It did so in three of ten attempts.
