GPT-5 Nano vs GPT-6 Luna
| Benchmark | GPT-5 Nano | GPT-6 Luna |
|---|---|---|
| Humanity's Last Exam | 8.7 | 28.3 |
| Terminal-Bench 4.0 | — | 2.5 |
| AutomationBench-AA | — | 40.5 |
| MMMU-Pro (vision) | 58.2 | 77.9 |
Specs
| Spec | GPT-5 Nano | GPT-6 Luna |
|---|---|---|
| Input, per 1M | $0.05 | $0.10 |
| Output, per 1M | $0.40 | $0.50 |
| Cost per task? | — | $0.017 |
| Speed, tok/s | 158 | — |
| Context | 400K | 1.05M |
| Weights | Closed | Closed |
| Released | Aug 2025 | Sep 2026 |
| See images | ✓ | ✓ |
| Read PDFs | Partial | Partial |
| Hear audio | — | — |
| Watch video | — | — |
| Call tools | ✓ | ✓ |
| Force a tool call | Partial | Partial |
| Return strict JSON | ✓ | ✓ |
| Search the web | ? | ✓ |
| Run code | ? | ✓ |
| Use a computer | ? | ✓ |
What breaks when you switch
GPT-5 Nano → GPT-6 Luna
Function calling only with none · Chat Completions›
Chat Completions function calling requires reasoning_effort none; use Responses for reasoning with tools.
More than 272K input tokens›
Prompts above 272K input tokens charge 2× input and cache rates and 1.5× output rates for the entire request.
Remove unsupported sampling parameters›
When reasoning effort is not none, remove temperature, top_p and top_logprobs, plus Chat Completions logprobs or Responses output logprobs inclusion.
Cache writes billed at 1.25x›
Cache writes cost 1.25× the uncached input token rate.
GPT-6 Luna → GPT-5 Nano