GPT-5.6 Luna

GPT-5.6 Luna is the budget tier of the GPT-5.6 family — fast, cheap, and still surprisingly capable. At $1/$6 per million tokens, it is roughly 5x cheaper than Sol and 2.5x cheaper than Terra, making it the natural choice for high-volume pipelines, classification, summarization, and interactive chat where latency matters. It shares the same 1M+ context window and 128K output limit as its siblings. Think of it as the successor to mini/nano tiers: good enough for most everyday tasks, with the option to escalate harder problems to Terra or Sol.