Model comparison
GPT-5.1-Codex vs Kimi K2.5 Instant
Kimi K2.5 Instant is the stronger model overall, scoring 43.6 to 38.6 on the Noometry Index.
Last verified . 1 shared benchmarks.
Summary
- They share 1 benchmark with published results for both. GPT-5.1-Codex scores higher in 0 categories and Kimi K2.5 Instant in 2 categories; one gap is clear of the uncertainty.
- The widest gap is in math, where Kimi K2.5 Instant leads 39.4 to 30.3.
- Kimi K2.5 Instant has downloadable open weights; the other is API-only.
Side by side
| GPT-5.1-Codex | Kimi K2.5 Instant | |
|---|---|---|
| Provider | OpenAI | Moonshot AI |
| Noometry Index | 38.6 | 43.6 |
| Released | 2025-11-12 | — |
| Weights | Proprietary | Open |
| Context window | 400K | — |
| Max output | 128K | — |
| Input $ / M tokens | $1.25 | — |
| Output $ / M tokens | $10 | — |
| Results tracked | 6 | 18 |
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Category by category
Coding Too close to call
GPT-5.1-Codex: 41.9 (#116), Kimi K2.5 Instant: 42.6 (#97)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena WebDev | 1337 | 1404 |
| SWE-bench Verified (bash only) | 66% | — |
| LMArena Coding | — | 1484 |
| ALE-Bench | 1,245 | — |
Agentic & Tool Use Not comparable
GPT-5.1-Codex: 38.0 (#33), Kimi K2.5 Instant: —
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |
Reasoning Not comparable
GPT-5.1-Codex: —, Kimi K2.5 Instant: 29.7 (#90)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Hard Prompts | — | 1443 |
Math Kimi K2.5 Instant leads
GPT-5.1-Codex: 30.3 (#235), Kimi K2.5 Instant: 39.4 (#105)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| ProofBench | 9% | — |
| LMArena Math | — | 1442 |
Knowledge Not comparable
GPT-5.1-Codex: —, Kimi K2.5 Instant: 40.2 (#123)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Expert | — | 1440 |
Multimodal Not comparable
GPT-5.1-Codex: —, Kimi K2.5 Instant: 40.2 (#50)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Vision | — | 1254 |
Multilingual Not comparable
GPT-5.1-Codex: —, Kimi K2.5 Instant: 52.0 (#94)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Non-English | — | 1406 |
| LMArena Chinese | — | 1449 |
| LMArena French | — | 1403 |
| LMArena German | — | 1413 |
| LMArena Korean | — | 1378 |
| LMArena Russian | — | 1404 |
| LMArena Spanish | — | 1447 |
Instruction Following Not comparable
GPT-5.1-Codex: —, Kimi K2.5 Instant: 75.3 (#65)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Instruction Following | — | 1430 |
Long Context Not comparable
GPT-5.1-Codex: —, Kimi K2.5 Instant: 43.9 (#83)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Longer Query | — | 1435 |
Writing & Preference Not comparable
GPT-5.1-Codex: —, Kimi K2.5 Instant: 60.6 (#95)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Text | — | 1420 |
| LMArena Creative Writing | — | 1381 |
| LMArena Multi-Turn | — | 1427 |
Frequently asked questions
Is GPT-5.1-Codex better than Kimi K2.5 Instant?
Kimi K2.5 Instant is the stronger model overall, scoring 43.6 to 38.6 on the Noometry Index.
Is GPT-5.1-Codex or Kimi K2.5 Instant better for coding?
They score almost the same on coding (41.9 vs 42.6); test both on your own repository before choosing.
How many benchmarks do GPT-5.1-Codex and Kimi K2.5 Instant share?
1 benchmark has published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Kimi K2.5 Instant has 18.