Claude Opus 5.5, GPT-6 Sol, GPT-6 Luna, and a new price war

22nd September 2026

Yesterday was Grok 4.7 (pelicans) and MiMo v2.6 Flash/Pro (more pelicans). Today Anthropic released Claude Opus 5.5, and around an hour later OpenAI released GPT-6 Sol and GPT-6 Luna. It’s going to take a while to get a good read on all of these new models, but here are my impressions so far.

GPT-6 Sol and Luna are half the price of their GPT-5.6 equivalents

GPT-5.6 Luna was already my favorite model for building applications against, because it combined excellent performance with being really cheap. Somehow GPT-6 Luna is half the price of that again—and GPT-6 Sol had a similar reduction compared to GPT-5.6 Sol.