OpenAI announced price reductions for two of its GPT-5.6 models starting today, reflecting efficiency gains from improvements to model architecture, inference systems, and agent infrastructure.
According to the announcement, GPT-5.6 Luna, described as the fastest and most affordable model, will cost 80% less, while GPT-5.6 Terra, the balanced model for everyday work, will cost 20% less. These lower prices apply to API usage as well as subscriptions when using Codex and ChatGPT Work. Luna can use tools and complete multi-step workflows, making broader AI applications practical to run at scale.
OpenAI also introduced Fast mode in the API, which replaces its Priority Processing offering. For GPT-5.6 Sol, Fast mode delivers up to 2.5× faster speeds than Standard processing at twice the price, with no change in intelligence.
OpenAI states that Luna delivers performance comparable to frontier-class models from a year ago at roughly 6 cents per task, and at nearly nine times the speed. On professional work as measured by Agents’ Last Exam, Luna outperforms Fable 5 at an estimated cost per task nearly 99% lower.
The efficiency improvements came from multiple sources. GPT-5.6 models take a more direct path through work, better routing keeps hardware productive, optimized production software generates tokens more efficiently, and smarter context management helps agents avoid repeating completed work. According to the announcement, GPT-5.6 Sol helped identify further optimizations: within a human-led process, Sol autonomously rewrote and optimized production kernels and designed experiments to improve token generation. This kernel work reduced end-to-end serving costs by 20%, while experiments increased token-generation efficiency by more than 15%.
OpenAI emphasized that businesses can define their needed outcome and quality standards, then use evaluations to determine where additional intelligence materially improves results and where faster, lower-cost processing delivers the same quality. The GPT-5.6 family expands choices for different workflow stages.
Effective July 30, API pricing is $2 per million input tokens and $12 per million output tokens for Terra, and $0.20 per million input tokens and $1.20 per million output tokens for Luna. Sol pricing remains unchanged. In ChatGPT Work and Codex, Free and Go users can access Terra, while Plus, Pro, Business, and Enterprise users can choose between Terra and Luna.
Key facts
- GPT-5.6 Luna pricing drops 80%, Terra drops 20% starting today
- Luna delivers frontier-class performance from a year ago at 6 cents per task, nearly 9x faster
- Fast mode for Sol offers 2.5× faster speeds at twice the price with no intelligence change
- GPT-5.6 Sol helped optimize production kernels, reducing serving costs by 20% and improving token efficiency 15%