GPT-6 Luna
GPT-6 Luna is the lowest-cost model in OpenAI's GPT-6 family, built for focused, high-volume tasks. Released September 22, 2026, it keeps the family's 1.05M-token context window and supports reasoning effort from none to max.
Specifications
- Context window
- 1.05Mabout 788,000 words, or 1,580 pages
- Max output
- 125Ktokens per response
- Input price
- $0.10per 1M tokens
- Output price
- $0.50per 1M tokens
- Cached input
- $0.01per 1M tokens
- Weights
- ClosedProprietary
- Parameters
- Undisclosed
- Input types
- Text, Images
- Output types
- Text
- Reasoning mode
- Yes
- Tool calling
- Yes
- Released
- Sep 22, 2026Current
Standard rates for prompts up to 272K input tokens; a larger prompt costs $0.20 input, $0.02 cached and $0.75 output. Batch and Flex 50% off; Fast mode 2x. Regional processing adds 10%.
What it costs in practice
| Workload | Monthly cost at list price |
|---|---|
| Support chatbot30,000 conversations a month, 2,000 input and 400 output tokens each | $12 |
| Document summaries2,000 documents a month, 12,000 input and 800 output tokens each | $3.20 |
| Coding agent1,000 tasks a month, 60,000 input and 6,000 output tokens each | $9.00 |
Standard rates, no caching or batch discounts. Run your own numbers.
Strengths
- $0.10 input and $0.50 output per million tokens
- Reasoning can be set to none for quick, low-cost calls
- 1.05M-token context window and 128K-token output limit
Trade-offs to weigh
- Chat Completions supports function calling only with reasoning effort set to none
- Prompts over 272K input tokens cost 2x input and 1.5x output
Where it fits
OpenAI positions GPT-6 Luna for:
Where you can use it
- API
- ChatGPT
- Codex
- OpenRouter
Alternatives to consider
| Model | Tier | Context | Input / output per 1M | |
|---|---|---|---|---|
| Claude Haiku 5.5Anthropic | Efficient | 1M | $0.10 / $0.50 | Compare |
| Ministral 3 14BMistral AI | Efficient | 256K | $0.20 / $0.20 | Compare |
| GLM-5.3-FlashZ.ai (Zhipu AI) | Efficient | 1M | $0.15 / $0.50 | Compare |
| Gemma 4 31BGoogle | Efficient | 256K | $0.20 / $0.40 | Compare |
Frequently asked questions
How much does GPT-6 Luna cost?
GPT-6 Luna lists at $0.10 per million input tokens and $0.50 per million output tokens, with cached input at $0.01 (checked October 10, 2026). Standard rates for prompts up to 272K input tokens; a larger prompt costs $0.20 input, $0.02 cached and $0.75 output. Batch and Flex 50% off; Fast mode 2x. Regional processing adds 10%. Confirm current rates on the provider's pricing page before you commit.
What is the context window of GPT-6 Luna?
GPT-6 Luna accepts up to 1,050,000 tokens of context (about 788,000 words, or 1,580 pages), and it can write up to 125K tokens in a single response. Long prompts cost more and can be slower, so most apps send only what the task needs.
Is GPT-6 Luna open source?
No. GPT-6 Luna is a proprietary model from OpenAI; its weights aren't published. You can use it through the OpenAI API and through ChatGPT, Codex, OpenRouter.
What is GPT-6 Luna best for?
OpenAI positions GPT-6 Luna for high volume, low latency, data extraction, customer support. It accepts text, images as input, has a reasoning (thinking) mode and supports tool calling. Test it on a sample of your own tasks before you choose it for production.
Sources
- developers.openai.com/api/docs/models/gpt-6-luna
- developers.openai.com/api/docs/pricing
- developers.openai.com/api/docs/models/gpt-6-luna.md
- developers.openai.com/api/docs/pricing?no_head=1
- openai.com/index/introducing-gpt-6-sol-and-luna
- www.nocode.mba/ai-release-tracker/providers/openai
- openrouter.ai/~openai
- docs.perplexity.ai/docs/agent-api/models.md
Facts checked against these pages on October 10, 2026. Spot an error? Tell us.
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