OpenAI has released two new models, GPT-6 Sol and GPT-6 Luna, intended to provide high-level intelligence with improved cost efficiency. These models were trained using similar methods to the flagship GPT-6 Astra, but are optimized for faster and more affordable deployment.
Model ReleasesPricing & LimitsOpenAIGPT-6 SolGPT-6 Luna
OpenAI Launches GPT-6 Sol and Luna with 50% Lower API Prices
The new models have been made available starting September 22 in ChatGPT via the Work and Codex interfaces for Plus, Pro, Business, Enterprise, and Edu plans. Free and Go users can access Luna through the desktop application, though these models will be rolled out gradually to the standard chat interface. On GitHub, both models are being made available via GitHub Copilot.
API pricing for the new models has been reduced by 50% compared to the previous GPT-5.6 generation's promotional rates. GPT-6 Sol is priced at $2 per 1 million input tokens and $10 per 1 million output tokens, while GPT-6 Luna is priced at $0.1 per 1 million input tokens and $0.5 per 1 million output tokens. OpenAI stated that these savings result from improvements in caching and inference efficiency.
The models also introduce enhanced prompt caching capabilities, which allow developers to specify which parts of a prompt should be cached and help maintain cache even when changing reasoning effort or tool availability. Additionally, the models exhibit improved factual reliability; internal evaluations showed that GPT-6 Sol makes approximately half as many mistakes as its predecessor.
While Sol and Luna offer significant performance-to-cost improvements—with Sol outperforming Claude Opus 5 on certain business workflows at a fraction of the cost—the company noted that they have not reached the "Critical" safety level of the Astra model. Both models are classified as "High" capability in the areas of cybersecurity and biological/chemical risks under OpenAI's Preparedness Framework.
Sources
- OpenAI、「GPT-6 Sol」と「GPT-6 Luna」公開 API料金は前世代の半額に （ITmedia AI+, 2026-09-23）
- OpenAIの公式ブログ