
OpenAI unveiled GPT-5.4-Cyber on Tuesday, a specialized variant designed for defensive cybersecurity work. The release follows Anthropic's April 7 announcement of Mythos model, deployed under Project Glasswing for cybersecurity purposes. Mythos has identified thousands of vulnerabilities in operating systems and browsers. OpenAI will initially distribute GPT-5.4-Cyber to vetted security vendors, organizations, and researchers. The company is expanding its Trusted Access for Cyber program launched in February, adding verification tiers that unlock increased capabilities.