11 Minutes, $1.73, and GPT-5.5 Cybersecurity Simulation

The UK AI Security Institute says GPT-5.5 cybersecurity simulation results now look a lot less like a one-off milestone and a lot more like a repeatable frontier capability. In its latest evaluation, AISI found that an early checkpoint of OpenAI’s GPT-5.5 reached roughly the same level as Anthropic’s Mythos Preview on hard cyber tasks—and slightly beat it on one key benchmark. That matters because AISI was explicitly testing whether Mythos Preview’s earlier result was a weird outlier. Instead, a