After GPT-6 Astra, OpenAI Expands GPT-6 Lineup with Lower-cost Sol and Luna Models
GPT-6 Sol and Luna bring capabilities from OpenAI’s GPT-6 Astra to lower-cost model tiers
API pricing starts at $2 per million input tokens for Sol and $0.10 for Luna
The models are available across the API, Codex, and ChatGPT, with access varying by plan.
Sep 22, 2026 - OpenAI has expanded its GPT-6 model family with GPT-6 Sol and GPT-6 Luna, adding two lower-cost models aimed at different workloads. Sol is positioned for more complex coding and agentic tasks. Luna targets faster, high-volume work where cost and speed are priorities.
The two ChatGPT models follow the launch of GPT-6 Astra earlier this month, which OpenAI describes as its flagship model for demanding reasoning and coding work. OpenAI said Sol and Luna incorporate advances from Astra while using more efficient inference and caching to reduce operating costs.
GPT-6 Sol is priced at $2 per million input tokens and $10 per million output tokens through the API. GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens. OpenAI said these prices are 50% lower than the promotional pricing of their GPT-5.6 counterparts.
OpenAI is positioning Sol as the middle option in the GPT-6 family for complex coding and agentic workflows. Luna sits at the lower-cost end and is intended for focused, high-volume tasks.
Both models accept text and image inputs and can generate text through OpenAI’s Responses and Chat Completions APIs. The models have a context window of up to 1.05 million tokens and support tools including web search, file search, and computer use.
OpenAI also reported improvements in factual reliability and coding compared with the GPT-5.6 generation. The company said an internal factuality evaluation based on real-world conversations where users had flagged mistakes showed GPT-6 Sol making about half as many mistakes as its predecessor.
The release gives developers another way to balance model capability against operating costs. With Sol aimed at more demanding workflows and Luna targeting high-volume workloads, OpenAI is expanding the GPT-6 family beyond a single flagship model and putting greater emphasis on price-performance across different types of AI work.
Sources:
https://openai.com/index/introducing-gpt-6-sol-and-luna/
https://github.blog/changelog/2026-09-22-openais-gpt-6-sol-and-gpt-6-luna-now-available/
