theTNai
Get the brief

Models · OpenAI · 22 Sep 2026

OpenAI released GPT-6 Sol and GPT-6 Luna, two lower-cost models in its GPT-6 family for coding, professional work and everyday use.

Sol is aimed at coding and professional work at USD 2 per million input tokens and USD 10 per million output tokens. Luna costs USD 0.10 and USD 0.50, and Free and Go users can use it in the ChatGPT desktop app.

What OpenAI released

GPT-6 Sol and GPT-6 Luna are new versions of OpenAI's smaller Sol and Luna models, which first came out earlier in 2026 with GPT-5.6. Both sit below GPT-6 Astra, which OpenAI released on 4 Sep 2026 and calls its most powerful model.

Sol is meant for harder work such as coding, agents and automating business tasks. Luna is a small, fast model for high-volume jobs with a clear goal, such as summarising documents, pulling out information or answering quick questions.

Price and limits

OpenAI says both cost about half as much as their GPT-5.6 versions, thanks to better caching and inference. Sol costs USD 2 per million input tokens and USD 10 per million output tokens. Luna costs USD 0.10 and USD 0.50. DataNorth reports that cached input is up to 90% cheaper when it is reused within 30 minutes.

Both models accept text and images and reply in text. Each can take in up to 1,050,000 tokens and write up to 128,000 tokens in one reply. A reasoning effort setting runs from none to max.

What OpenAI claims

On OpenAI's own factuality test, built from real conversations where users flagged mistakes, Sol makes about half as many errors as its predecessor, TechCrunch reports. OpenAI calls this "Astra-level reliability at much lower cost". In OpenAI's figures, Sol scores 68.8% on the DeepSWE v1.1 bug-fixing test at max effort, and Luna scores 66.6%.

These are OpenAI's own tests. DataNorth notes that the scores do not show how often a model fails in everyday use.

Who can use them

Plus, Pro, Business, Enterprise and Education users get both models in ChatGPT Work and Codex. Free and Go users can use Luna in the ChatGPT desktop app. Developers can use both through the API.

How to try it

  1. On ChatGPT Free or Go: use GPT-6 Luna in the ChatGPT desktop app.
  2. On a paid plan (Plus, Pro, Business, Enterprise or Education): both models are in ChatGPT Work and Codex.
  3. With the API: use the model name gpt-6-sol (USD 2 input / USD 10 output per million tokens) or gpt-6-luna (USD 0.10 / USD 0.50).
  4. Set the reasoning effort, from none to max, to suit the task.

How to get good results

Our practical advice, based on what the sources below say about it.

  1. Start with Luna for simple, repeated jobsOpenAI built Luna for clear, high-volume tasks: summarising documents, pulling out fields, quick answers. Its input price is one twentieth of Sol's, so test it first for work like this.
  2. Move up to Sol for code and agentsSol is meant for coding, agents and business automation. Use it when Luna's answers are not good enough.
  3. Raise the effort only when you need itThe headline bug-fixing scores were measured at max effort. The setting runs from none to max, so try lower levels for simple work and compare the results.
  4. Reuse long inputs to save moneyCached input is up to 90% cheaper when it is reused within 30 minutes. If you send the same long instructions or document many times, keep it the same between requests.
  5. Test on your own dataThe published scores come from OpenAI's own tests and do not show how often a model fails in everyday use. Try it on a sample of your real tasks before you switch.

Why it matters in Tamil Nadu

Luna's price is low enough for a student project or a small business chatbot to run on a tight budget, so it is worth testing before choosing a costlier model.

Where this comes from

  • SourceOpenAI
  • Also checkedTechCrunch Launch report: uses, factuality claim, availability
  • Also checkedDataNorth API prices, model names, context window, benchmark figures
  • Checked against the source11 Oct 2026
  • Written bytheTN.ai's AI agent, in its own words
  • Approved byPaul Jeevanesan, Founder and Chief EditorAlso founder and CEO of StudAI One, whose services wing is StudAI Works (related parties, see disclosures).

Spotted an error? Tell us: we fix confirmed errors within 24 hours and log them in public.

Cite this page

theTN.ai, "OpenAI released GPT-6 Sol and GPT-6 Luna, two lower-cost models in its GPT-6 family for coding, professional work and everyday use.", 22 Sep 2026. https://thetn.ai/tech/2026-09-22-openai-gpt-6-sol-luna/

More in Models