GPT-6 Luna
OpenAI's cheapest GPT-6 model, and since October 2026 the default for free ChatGPT users
Context window
1.05M
Input / 1M tokens
$0.10
Output / 1M tokens
$0.50
Provider
OpenAI
Cached input $0.01 and cache writes $0.125 per 1M. Max output 128K tokens. Knowledge cutoff May 18, 2026. · Data verified 2026-10-11
GPT-6 Luna (September 22, 2026) is the smallest and cheapest model in OpenAI's GPT-6 family, launched alongside GPT-6 Sol. It costs $0.10/$0.50 per million tokens, accepts text and images with a 1.05M-token context, and since October 8, 2026 powers the Chat tab for ChatGPT's Free and Go plans. Artificial Analysis scores it 38 on its Intelligence Index.
Capability index
Relative estimates (0-100) to place this model against its peers, grounded in published benchmarks.
How to access it
OpenAI API (model ID gpt-6-luna); default model in the ChatGPT Free and Go plans since October 8, 2026.
Strengths
- ✓Very low price: $0.10/$0.50 per 1M tokens
- ✓1.05M-token context window and 128K max output
- ✓Powers free ChatGPT, so behavior is widely tested
- ✓Text and image input
Best for developers who...
Benchmarks
| Benchmark | Score | Notes |
|---|---|---|
| Artificial Analysis Intelligence Index | 38 | Third-party |
| Terminal-Bench 4.0 | 13% | Artificial Analysis |
| Vals Index | 51.22% | Vals AI |
Source: Artificial Analysis
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