GPT-5.6

GPT-5.6 closes OpenAI’s 5.x line as three tiers: Sol at the top, Terra as the fast and cheap middle, and Luna as the low-cost knowledge worker, cleared by Commerce after CAISI testing and launched in the second week of July 2026 (OpenAI). In this corpus its recursive significance is that Sol autonomously post-trained Luna, scoring 50.3% on PostTrainBench with Terra at 51.5%; the launch itself is recorded as a model clears review and ships globally, with the early verdict that one Fable turn does the work of ten from Sol.