Side-by-side technical and economic comparison between OpenAI's GPT-5.6 Luna and Mistral AI's Mistral Small 4.
| Metric | GPT-5.6 Luna | Mistral Small 4 | Advantage |
|---|---|---|---|
| Provider Organization | OpenAI | Mistral AI | — |
| Standard Input / 1M | $0.20 | $0.15 | Mistral Small 4 (25% lower) |
| Cached Input / 1M | $0.02 | $0.015 | Mistral Small 4 lower |
| Output / 1M | $1.20 | $0.60 | Mistral Small 4 lower |
| Context Window | 1.05M | 256k | GPT-5.6 Luna (1.05M) |
| Max Generation Tokens | 16.4k | 8.2k | GPT-5.6 Luna |
| Tokenizer Family | OpenAI o200k_base (200k vocabulary) | Mistral Tekken Tokenizer (131k vocabulary) | — |
Opt for GPT-5.6 Luna when your engineering requirements prioritize OpenAI's ecosystem, specific tokenizer efficiencies (Exact BPE (o200k_base)), or when your expected prompt-to-completion ratios favor its $0.2/M input rate.
Opt for Mistral Small 4 when looking for Mistral AI's tooling integration, specific context window depth (256k tokens), or when output generation volume favors its $0.6/M rate.