GPT-5.5 is OpenAI's latest frontier model, released in April 2026 as the first fully retrained base model since GPT-4.5. It supports a 1M+ token context window with text and image inputs, delivering significantly improved token efficiency over GPT-5.4 to produce the same results at lower cost. With strengthened reasoning across coding, mathematics, research, and multi-step planning—offered at standard $5/$30 pricing—it suits a wide range of workflows.