In short
How they differ.
Worked out from the figures below. Prices and specs are the makers' own, read Oct 20, 2026.
- GPT-6 Luna is cheaper per output token: $0.50 against $7.50 per million tokens, so Mistral Medium 3.5 costs 15 times as much.
- GPT-6 Luna reads more at once: a context window of 1M tokens against 256K.
- Mistral Medium 3.5 can be downloaded and run on your own machine; GPT-6 Luna can't.
- No independent board we follow ranks both models yet.
Side by side
The specs.
| GPT-6 Luna | Mistral Medium 3.5 | |
|---|---|---|
| Made by | OpenAI · US | Mistral AI · France |
| Released | Sep 22, 2026 | Apr 28, 2026 |
| Price per 1M tokens | $0.10 in / $0.50 out | $1.50 in / $7.50 out |
| Context window | 1M | 256K |
| Takes in | text, image | text, image |
| Download and run it yourself | No | Yes (Modified MIT) |
| Size | Not published | 128B (dense) parameters |
| Maker says | “Our most efficient model for focused, high-volume tasks.” | “Our frontier-class multimodal model optimized for agentic and coding use cases.” |
| Sources | Prices, Oct 20, 2026 · Description | Prices, Oct 20, 2026 · Description |
Independent tests
Where they place.
Position on each board we follow (1 is best). Epoch AI's and Vectara's scores are shown; the other boards are linked for their own figures.
More comparisons