OpenAI's model lineup changed twice in September 2026, and the result confuses even regular users. Here's the simple version: pick Sol when judgment matters, pick Luna when volume matters. The short answer GPT-6.1 Sol is the near-flagship workhorse: complex coding, multi-step agents, documents, computer use, research — at one-fifth of Astra's API price. GPT-6 Luna is the efficiency model: classification, extraction, routing, summaries, bulk transforms — at one-twentieth of...