The UK AI Security Institute, or AISI, has put independent cyber-capability testing at the center of the debate over how frontier AI systems should be governed. Its work on Anthropic's Claude Mythos models and OpenAI's GPT-5.6 Sol examines how advanced systems perform on controlled cyber tasks when evaluators have access beyond the safeguards normally applied in public deployment. The most important takeaway is not that a single model has crossed a clearly defined threshold. It is that ext...