OpenAI's GPT-5.5 Cyber AI beats Anthropic's banned Mythos model

GPT-5.5-Cyber scored 85.6% on the CyberGym benchmark, surpassing Anthropic's Mythos 5 at 83.8%. Mythos was pulled offline on June 12 after a U.S. government export ban citing national security. OpenAI is releasing the model to trusted defenders with safety controls.