OpenAI's GPT-5.5-Cyber beats Anthropic's banned Mythos on security

OpenAI's GPT-5.5-Cyber scored 85.6% on the CyberGym benchmark, surpassing Anthropic's Mythos (83.8%) and Claude Opus 4.7 (73.1%). The model is available to trusted defenders via OpenAI's Daybreak program, while Mythos was pulled offline on June 12 under a US export ban after a jailbreak.