Question to the Cabinet Office:

To ask His Majesty's Government what assessment they have made of Anthropic’s decision not to provide its Claude Mythos 5.1 model to the UK AI Security Institute for pre-release testing; whether the Institute has subsequently been provided with access to that model; and what steps they are taking to ensure that the Institute has timely access to frontier AI models for independent safety evaluation.

AISI maintains strong relationships with all frontier AI developers, that whilst voluntary, are bound by memoranda of understanding, and continues to test the world’s most capable models prior to their deployment. Only this month, we tested OpenAI’s most powerful model, GPT-6 Astra, before it was released to the public. AISI has tested dozens of models from leading AI companies, including OpenAI, Google DeepMind and Anthropic.