OpenAI unveils GPT-5.4-Cyber a week after Anthropic's announcement of AI model

OpenAI on Tuesday unveiled GPT-5.4-Cyber, a variant of its latest flagship model fine-tuned specifically for defensive cybersecurity work, following rival Anthropic's announcement of frontier AI ⁠model Mythos.

Mythos, announced on April 7, is being deployed as part of Anthropic's "Project Glasswing", a controlled initiative under which select organisations are permitted to use the unreleased Claude ⁠Mythos Preview model for ⁠defensive cybersecurity purposes. It has found "thousands" of major vulnerabilities in operating systems, web browsers and other software.