GPT-5.5-Cyber is here. What it means for defenders operating at the frontier.

Sophos describes its participation in OpenAI’s Trusted Access for Cyber (TAC) and the limited preview of GPT-5.5-Cyber, arguing that frontier AI should be given to verified defenders under strict controls. The document explains how Sophos Endpoint’s exploit mitigations and Sophos MDR’s human-on-the-loop operations are positioned to leverage TAC capabilities for faster vulnerability analysis, detection engineering, and automated response; it is a strategic/marketing explanation rather than a technical incident report.