GPT-6 Luna is OpenAI’s cheapest GPT-6 model, released on September 22, 2026 with a 1.05-million-token context window and API pricing of $0.10 per million input tokens. This review covers the specs, what OpenAI’s benchmarks claim, and where independent testers disagree. It also explains why comparing GPT-6 Luna with ChatGPT mixes up a model and a product, how to reach it through the app and API, and what the evidence says about writing and content creation. Three prompt templates and a plain verdict on who should use it close the guide, with every figure linked back to its original source.