GPT-5.6 Luna sits at the economical end of the GPT-5.6 family that OpenAI released for general availability on July 9, 2026, positioned alongside the flagship Sol tier and the balanced Terra tier. Within that lineup, Luna is described as the most cost-efficient option, built to deliver the same underlying improvements in useful work per token while keeping spend low for high-volume workloads. Its practical fit is teams that need capable reasoning, tool calling, and structured outputs on text, image, and PDF inputs at everyday price points, rather than the absolute ceiling of intelligence that Sol targets.

The Luna release was paired with a clear pricing trajectory rather than a static price tag: on July 30, 2026, OpenAI cut Luna's price by 80% (and Terra's by 20%) as part of a broader push to advance the price-performance frontier of the GPT-5.6 generation. That makes Luna a sensible default for production pipelines where throughput and unit economics matter more than pushing the upper bounds of coding or science benchmarks, with Sol available as an upgrade path for the hardest tasks that justify the higher spend.