Model Details
GPT-6 Luna
Quick answer: GPT-6 Luna is OpenAI's smallest, cheapest GPT-6-family model, released alongside GPT-6 Sol on September 22, 2026. It's priced 50% lower than GPT-5.6 Luna ($0.10/$0.50 per Mtok) while matching larger predecessor-tier models on agentic coding at a fraction of the cost.
What GPT-6 Luna Is
GPT-6 Luna is the small/cheap sibling in OpenAI's GPT-6 family, alongside GPT-6 Sol (mid) and GPT-6 Astra (flagship), available via ChatGPT and Codex. OpenAI positions it as comparable to prior mid-tier models on agentic coding tasks at a large cost reduction.
Specifications
| Organization | OpenAI |
| License | Proprietary (API only) |
| Release date | September 22, 2026 |
| Modality | Text |
| Knowledge cutoff | Not disclosed |
Public Benchmark Scores
| Benchmark | Score | Source | Date |
|---|---|---|---|
| DeepSWE v1.1 | 66.6% (max effort) | OpenAI | Sep 2026 |
Scores as reported in OpenAI's own GPT-6 Sol and Luna announcement (openai.com/index/introducing-gpt-6-sol-and-luna, September 2026); not independently verified by Benchgen.