Model comparison
GPT-5.1-Codex vs Mistral Small 3.1
GPT-5.1-Codex is the stronger model overall, scoring 38.6 to 31.7 on the Noometry Index. Mistral Small 3.1 costs 8.6× less per token, which makes it the better buy when GPT-5.1-Codex's lead doesn't matter for your workload.
Last verified . 0 shared benchmarks.
Mistral AISummary
- The widest gap is in math, where GPT-5.1-Codex leads 30.3 to 14.7.
- Mistral Small 3.1 is cheaper at $0.35 / $0.56 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 128K.
- Mistral Small 3.1 has downloadable open weights; the other is API-only.
Side by side
| GPT-5.1-Codex | Mistral Small 3.1 | |
|---|---|---|
| Provider | OpenAI | Mistral AI |
| Noometry Index | 38.6 | 31.7 |
| Released | 2025-11-12 | 2025-03-17 |
| Weights | Proprietary | Open |
| Context window | 400K | 128K |
| Max output | 128K | 102K |
| Input $ / M tokens | $1.25 | $0.35 |
| Output $ / M tokens | $10 | $0.56 |
| Results tracked | 6 | 28 |
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Category by category
Coding GPT-5.1-Codex leads
GPT-5.1-Codex: 41.9 (#116), Mistral Small 3.1: 38.3 (#179)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| LMArena Coding | — | 1309 |
| ALE-Bench | 1,245 | — |
Agentic & Tool Use Not comparable
GPT-5.1-Codex: 38.0 (#33), Mistral Small 3.1: —
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |
Reasoning Not comparable
GPT-5.1-Codex: —, Mistral Small 3.1: 19.7 (#254)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| Chess Puzzles | — | 1% |
| LMArena Hard Prompts | — | 1278 |
| Epoch Capabilities Index | — | 127.48 |
Math GPT-5.1-Codex leads
GPT-5.1-Codex: 30.3 (#235), Mistral Small 3.1: 14.7 (#301)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| OTIS Mock AIME 2024-2025 | — | 3.9% |
| ProofBench | 9% | — |
| Omni-MATH | — | 24.8% |
| LMArena Math | — | 1262 |
Knowledge Not comparable
GPT-5.1-Codex: —, Mistral Small 3.1: 22.6 (#271)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| GPQA Diamond | — | 41.9% |
| MMLU-Pro | — | 61% |
| GPQA (HELM) | — | 39.2% |
| LMArena Expert | — | 1257 |
Multimodal Not comparable
GPT-5.1-Codex: —, Mistral Small 3.1: 33.2 (#99)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| LMArena Vision | — | 1136 |
Multilingual Not comparable
GPT-5.1-Codex: —, Mistral Small 3.1: 41.2 (#209)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| LMArena Non-English | — | 1255 |
| LMArena Chinese | — | 1253 |
| LMArena French | — | 1273 |
| LMArena German | — | 1266 |
| LMArena Japanese | — | 1208 |
| LMArena Korean | — | 1206 |
| LMArena Russian | — | 1263 |
| LMArena Spanish | — | 1283 |
Instruction Following Not comparable
GPT-5.1-Codex: —, Mistral Small 3.1: 63.6 (#230)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| IFEval | — | 75% |
| LMArena Instruction Following | — | 1264 |
Long Context Not comparable
GPT-5.1-Codex: —, Mistral Small 3.1: 39.5 (#178)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| LMArena Longer Query | — | 1299 |
Writing & Preference Not comparable
GPT-5.1-Codex: —, Mistral Small 3.1: 37.0 (#259)
| Benchmark | GPT-5.1-Codex | Mistral Small 3.1 |
|---|---|---|
| LMArena Text | — | 1277 |
| LMArena Creative Writing | — | 1253 |
| EQ-Bench Creative Writing | — | 761 |
| WildBench | — | 78.8% |
| LMArena Multi-Turn | — | 1270 |
Frequently asked questions
Is GPT-5.1-Codex better than Mistral Small 3.1?
GPT-5.1-Codex is the stronger model overall, scoring 38.6 to 31.7 on the Noometry Index. Mistral Small 3.1 costs 8.6× less per token, which makes it the better buy when GPT-5.1-Codex's lead doesn't matter for your workload.
Which is cheaper, GPT-5.1-Codex or Mistral Small 3.1?
Mistral Small 3.1 is cheaper. It lists at $0.35 per million input tokens and $0.56 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.
Is GPT-5.1-Codex or Mistral Small 3.1 better for coding?
GPT-5.1-Codex scores higher on coding benchmarks: 41.9 versus 38.3 in the Noometry coding category.
Which has the bigger context window?
GPT-5.1-Codex does, with 400K tokens against 128K.
How many benchmarks do GPT-5.1-Codex and Mistral Small 3.1 share?
0 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Mistral Small 3.1 has 28.