1. Anthropic's 'Critical Threat' Mythos Preview Matches Public GPT-5.5 in UK AI Security Tests
The UK's AI Security Institute has delivered a pointed rebuttal to Anthropic's framing of its Mythos Preview model as an outsized cybersecurity risk. In head-to-head evaluations across 95 Capture the Flag challenges, OpenAI's GPT-5.5—released publicly last week—matched or slightly exceeded the performance of Anthropic'...