#GPT-6

GPT-6 Sol and Luna arrived at half the price of GPT-5.6, Claude Opus 5.5 delivers Fable 5.1 level at $4/$20 with four breaking changes in the API, and Google says Gemini 4 ships before the end of the year. What each one brings that's different, the catches (Luna regresses on agentic coding, Opus default effort dropped to medium), and which one to use now.

GPT-6 Astra is OpenAI's new top-of-the-line model, launched on September 3, 2026 at $10/$50 per million tokens, the same price as Claude Fable 5.1. Benchmark by benchmark against Fable 5.1 and GPT-5.6 Sol, the cache math that makes an agent session 54% more expensive on Astra, and the ARC-AGI-3 run where the same model scored 62.7% or 99.9% just by swapping the harness.

In July, Bloomberg reported Altman's briefing to the US government and the internet read it as an imminent GPT-6 launch. This tracker logged, with a date and a source, what was confirmed and what was speculation until the model shipped on September 3, 2026 as GPT-6 Astra. It stays up as a timeline; the numbers, the pricing and the comparison with Fable 5.1 and GPT-5.6 Sol are in the comparison post.