OpenAI Debuts GPT-6 Sol and GPT-6 Luna at Half the API Price
OpenAI priced its two new mid-tier models below the GPT-5.6 line while keeping GPT-6 Astra as the ceiling, which leaves the previous generation without a clear price or capability role.
Key Facts
- OpenAI announced GPT-6 Sol and GPT-6 Luna on September 22, 2026.
- GPT-6 Sol costs $2 per million input tokens and $10 per million output tokens, while GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens.
- Both new models are priced at less than half the API cost of the GPT-5.6 series released in July 2026.
- GPT-6 Sol and GPT-6 Luna are available in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu subscribers.
- Free and Go plan users can use GPT-6 Luna on the desktop version of ChatGPT.
Reporting from 2 sources: ASCII.jp, GIGAZINE.
OpenAI announced GPT-6 Sol and GPT-6 Luna on September 22, 2026. Both models are trained with the same method as the top-tier GPT-6 Astra, and both cost less than half the API price of the GPT-5.6 series. GPT-6 Sol is built for complex work and coding, priced at $2 per million input tokens and $10 per million output tokens. GPT-6 Luna targets low-cost, high-volume use, at $0.10 per million input tokens and $0.50 per million output tokens. According to OpenAI, internal factuality evaluations put GPT-6 Sol at roughly half the error rate of GPT-5.6 Sol. Both models have rolled out to ChatGPT Plus, Pro, Business, Enterprise, and Edu subscribers in ChatGPT Work and Codex, but neither is available yet in regular Chat. Free and Go plan users can use GPT-6 Luna on the desktop version of ChatGPT.
GPT-6 Sol also had the tone of its output text adjusted. For the same prompt, the new model drops filler phrases such as "Absolutely" and "Done - open the live site" that appeared in GPT-5.6 Sol output, producing shorter replies. Both new models use the same alignment technology as GPT-6 Astra, which OpenAI says reduces misleading or dangerous outputs.
On the AutomationBench agent benchmark, GPT-6 Sol scored higher than Claude Fable 5.1 at one-tenth the cost, and GPT-6 Luna scored higher than GPT-5.6 Luna at a lower cost. On FrontierCode, which measures coding performance, GPT-6 Sol recorded a significantly higher score than GPT-5.6 Sol while keeping costs low. On a test of prompts designed to induce cheating, the cheating rate for both new models came in lower than for the previous generation. GIGAZINE lists the GPT-5.6 series, released in July 2026, as the three-model lineup of GPT-5.6 Sol, GPT-5.6 Terra, and GPT-5.6 Luna. It is unclear whether GPT-6 Sol and GPT-6 Luna will replace GPT-5.6, and OpenAI has not stated when that would happen. On Plus, the top-tier GPT-6 Astra is available only from Work and Codex, not as the top model in regular Chat.
- GPT-6 Sol: $2 per million input tokens and $10 per million output tokens; built for complex work and coding
- GPT-6 Luna: $0.10 per million input tokens and $0.50 per million output tokens; built for low-cost, high-volume use
Synthesized by Yomimono from the 2 cited sources below, including Japanese-language reporting where cited, then editorially reviewed before publishing.