GPT-5.5-Cyber

GPT-5.5-Cyber, announced June 22, 2026, was OpenAI's first cybersecurity-specialised model and the anchor of Daybreak, the vetted-access program for security defenders that OpenAI had introduced a month earlier. Trained to find, validate, and help patch software vulnerabilities across large codebases, it scored 85.6% on CyberGym at release, against the 81.8% posted by the general-purpose GPT-5.5.

The model never shipped to the public API — access ran through Daybreak's identity checks and monitoring, a template Google followed a month later with Gemini 3.5 Flash Cyber. Alongside the model, OpenAI and Trail of Bits launched Patch the Planet, which put the model to work on open-source projects including cURL and NATS Server. GPT-5.6-Cyber succeeded it in August 2026.