Model comparison
GPT-5.1-Codex vs Kimi K2.5
Kimi K2.5 is the stronger model overall, scoring 48.1 to 38.6 on the Noometry Index.
Last verified . 4 shared benchmarks.
Summary
- They share 4 benchmarks with published results for both. GPT-5.1-Codex scores higher in 1 category and Kimi K2.5 in 2 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where Kimi K2.5 leads 51.8 to 30.3.
- The biggest single-benchmark swing is Terminal-Bench: 60.4% for GPT-5.1-Codex and 43.2% for Kimi K2.5.
- Kimi K2.5 is cheaper at $0.45 / $2.25 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 262K.
- Kimi K2.5 has downloadable open weights; the other is API-only.
Side by side
| GPT-5.1-Codex | Kimi K2.5 | |
|---|---|---|
| Provider | OpenAI | Moonshot AI |
| Noometry Index | 38.6 | 48.1 |
| Released | 2025-11-12 | 2026-01-27 |
| Weights | Proprietary | Open |
| Context window | 400K | 262K |
| Max output | 128K | 262K |
| Input $ / M tokens | $1.25 | $0.45 |
| Output $ / M tokens | $10 | $2.25 |
| Results tracked | 6 | 51 |
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Category by category
Coding Kimi K2.5 leads
GPT-5.1-Codex: 41.9 (#116), Kimi K2.5: 48.8 (#53)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | 70.8% |
| LMArena WebDev | 1337 | 1437 |
| ALE-Bench | 1,245 | 821.65 |
| SWE-bench Verified | — | 73.8% |
| SWE-bench Multilingual | — | 67.3% |
| SciCode | — | 49% |
| WeirdML | — | 45.6% |
| LMArena Coding | — | 1474 |
Agentic & Tool Use GPT-5.1-Codex leads
GPT-5.1-Codex: 38.0 (#33), Kimi K2.5: 34.2 (#48)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| Terminal-Bench | 60.4% | 43.2% |
| OSWorld | — | 63.3% |
| METR Time Horizons | 70.8% | — |
| Vending-Bench 2 | — | 1,198 |
Reasoning Not comparable
GPT-5.1-Codex: —, Kimi K2.5: 31.2 (#80)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| ARC-AGI-2 | — | 11.8% |
| SimpleBench | — | 46.8% |
| Kagi LLM Benchmark | — | 78.5% |
| NYT Connections (extended) | — | 69.9% |
| ARC-AGI-1 | — | 65.3% |
| CritPt | — | 3.1% |
| Chess Puzzles | — | 12% |
| EnigmaEval | — | 3.4% |
| Thematic Generalization | — | 69.4% |
| LMArena Hard Prompts | — | 1453 |
| Epoch Capabilities Index | — | 148.03 |
Math Kimi K2.5 leads
GPT-5.1-Codex: 30.3 (#235), Kimi K2.5: 51.8 (#53)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| MathArena Final-Answer Competitions | — | 62.3% |
| OTIS Mock AIME 2024-2025 | — | 92.2% |
| ProofBench | 9% | — |
| LMArena Math | — | 1470 |
| FrontierMath (Feb 2025 set) | — | 27.9% |
| FrontierMath Tier 4 (v1) | — | 4.2% |
Knowledge Not comparable
GPT-5.1-Codex: —, Kimi K2.5: 53.6 (#56)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| GPQA Diamond | — | 87.6% |
| Humanity's Last Exam | — | 24.4% |
| SimpleQA Verified | — | 34.3% |
| Vectara Hallucination Rate | — | 14.2% |
| LMArena Expert | — | 1466 |
Multimodal Not comparable
GPT-5.1-Codex: —, Kimi K2.5: 41.1 (#39)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| LMArena Vision | — | 1269 |
| LMArena Document | — | 1430 |
Multilingual Not comparable
GPT-5.1-Codex: —, Kimi K2.5: 53.9 (#53)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| LMArena Non-English | — | 1433 |
| LMArena Chinese | — | 1495 |
| LMArena French | — | 1454 |
| LMArena German | — | 1441 |
| LMArena Japanese | — | 1421 |
| LMArena Korean | — | 1410 |
| LMArena Russian | — | 1435 |
| LMArena Spanish | — | 1450 |
Instruction Following Not comparable
GPT-5.1-Codex: —, Kimi K2.5: 75.3 (#64)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| LMArena Instruction Following | — | 1431 |
Long Context Not comparable
GPT-5.1-Codex: —, Kimi K2.5: 52.1 (#7)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| Fiction.LiveBench | — | 86.1% |
| CL-bench | — | 19.3% |
| CL-bench Life | — | 13.2% |
| LMArena Longer Query | — | 1445 |
Writing & Preference Not comparable
GPT-5.1-Codex: —, Kimi K2.5: 65.1 (#53)
| Benchmark | GPT-5.1-Codex | Kimi K2.5 |
|---|---|---|
| LMArena Text | — | 1445 |
| LMArena Creative Writing | — | 1423 |
| EQ-Bench Creative Writing | — | 1579 |
| LMArena Multi-Turn | — | 1444 |
Frequently asked questions
Is GPT-5.1-Codex better than Kimi K2.5?
Kimi K2.5 is the stronger model overall, scoring 48.1 to 38.6 on the Noometry Index.
Which is cheaper, GPT-5.1-Codex or Kimi K2.5?
Kimi K2.5 is cheaper. It lists at $0.45 per million input tokens and $2.25 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.
Is GPT-5.1-Codex or Kimi K2.5 better for coding?
Kimi K2.5 scores higher on coding benchmarks: 48.8 versus 41.9 in the Noometry coding category.
Which has the bigger context window?
GPT-5.1-Codex does, with 400K tokens against 262K.
How many benchmarks do GPT-5.1-Codex and Kimi K2.5 share?
4 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Kimi K2.5 has 51.