The new platform pairs GPT-5.5 variants with Codex Security and a roster of enterprise security partners, all aimed at defenders. OpenAI has unveiled Daybreak , a cybersecurity initiative aimed at finding software vulnerabilities, generating patches, and validating fixes inside enterprise codebases. The launch positions OpenAI directly against Anthropic’s Mythos , which has spent the past few months dominating the conversation about AI-powered defence. Daybreak rests on three model variants, according to OpenAI . GPT-5.5 covers general-purpose use under standard safeguards. GPT-5.5 with Trusted Access for Cyber is reserved for verified defenders performing tasks such as secure code review, vulnerability triage, malware analysis, and patch validation. A third model, GPT-5.5-Cyber, is a more permissive variant for authorised red teaming, penetration testing, and controlled validation.…