Pick this when
The OpenAI default. Everyday production work that should not hit Sol prices.
Skip when
You need the last few intelligence points, or you want open weights.
Same Responses API and tools as Sol. Most traffic should live here. Luna explores, Terra ships, Sol reviews.
Price
- Input / 1M
- $2.00
- Output / 1M
- $12
- Measured task
- $0.51
Same 272K long-context surcharge as Sol, scaled to this tier.
Shape
- Context
- 1.1M
- Max output
- 128K
- Released
- 2026-07
- Tools
- Yes
- Reasoning
- Yes
Scores
Intelligence index57
GPQA Diamond88
Terminal-Bench 2.179
Agentic index41
- Arena
- 1185
- Speed
- 117/s
- GPQA
- 88.1%
- Term.
- 79.4%
- AA Index. The single number most people mean by “how smart.” It is a blend, so a specialist can lose here and still win the job you care about.
- GPQA. A clean test of hard reasoning. PhD experts sit around 65%. It says little about writing, tools, or taste.
- Term.. Closest public proxy for coding agents that live in a terminal. A high index score with a weak terminal score is a warning.
- Arena. Captures taste and usefulness that unit tests miss. Sample size varies by model, so treat gaps under ~100 Elo as noise.
OpenAI · San Francisco. ChatGPT's parent. The GPT-5.6 line is a three-rung ladder: Sol for hard work, Terra for most production traffic, Luna for volume.