How GPT-5.6 Fuses Frontier Intelligence with Frontier Efficiency
We designed the GPT‑5.6 model family to balance capability and cost across the spectrum of tasks people use our models for. Our flagship model, GPT‑5.6 Sol, with max reasoning outperforms Claude Fable 5 on the Artificial Analysis Coding Agent Index at less than half of the cost. Terra performs as well as GPT‑5.5 on intelligence benchmarks at half the price, and Luna is our fastest and most affordable model, priced 80% less than the cost of Sol. To deliver these efficiencies, our research and technical teams have made significant optimizations at every major layer of our stack. These improvements span our models, inference (how we run models to generate output), and our agentic harness, which is used by both Codex and ChatGPT Work.
