GPT-5.3-Codex vs Kimi K2.6
GPT-5.3-Codex 
Kimi K2.6 Verdict
- GPT-5.3-Codex leads on quality: 62.5 vs 60.7.
- GPT-5.3-Codex is stronger in agents & tools, composite, knowledge, long context.
- Kimi K2.6 is stronger in coding, instruction following, multimodal, human preference, maths, reasoning.
- Kimi K2.6 is 2.8× cheaper ($1.71 vs $4.81 per 1M blended).
- GPT-5.3-Codex streams 2.7× faster (121 vs 44 tokens per second).
| Metric | GPT-5.3-Codex | Kimi K2.6 |
|---|---|---|
| BenchLeader Index | 62.5 | 60.7 |
| Agents & tools score | 62.7 | 45.1 |
| Coding score | 54.8 | 60.4 |
| Composite score | 70.1 | 68.6 |
| Instruction following score | 73.2 | 73.7 |
| Knowledge score | 69.3 | 58.6 |
| Long context score | 68.3 | 67.1 |
| Multimodal score | 63.0 | 63.7 |
| Human preference score | – | 60.8 |
| Maths score | – | 53.8 |
| Reasoning score | – | 66.0 |
| Blended price $/M | $4.81 | $1.71 |
| Output speed | 121 tok/s | 44 tok/s |
| Time to first answer | 58.2 s | 103.2 s |
| Context window | 400k | 262k |
| GPQA Diamond | – | 90.8% |
| FrontierMath Tiers 1–3 | – | 57.2% |
| FrontierMath Tier 4 | – | 25.6% |
| OTIS Mock AIME | – | 96.1% |
| SWE-bench Verified (Epoch) | – | 76.7% |
| SimpleQA Verified | – | 34.9% |
| Terminal-Bench | 78.4% | – |
| OSWorld-Verified 2.0 | – | 4.6% |
| SciCode | – | 53.5% |
| WeirdML | 79.3% | 55.9% |
| APEX-Agents | 31.8% | 18.9% |
| ProofBench | – | 16.0% |
| Epoch Capabilities Index | 156.6 | 151.0 |
| LMArena Text | – | 1461 |
| LMArena Hard Prompts | – | 1485 |
| LMArena Coding | – | 1514 |
| LMArena WebDev | 1409 | 1509 |
| LMArena Vision | – | 1281 |
| AA Intelligence Index | 32.5 | 31.3 |
| IFBench | 75.4% | 76.0% |
| AA-LCR | 83.3% | 81.0% |
| MMMU-Pro | 78.5% | 79.4% |
| AA-Omniscience | 10.9 | 5.3 |
| Terminal-Bench Hard | 53.0% | 43.9% |
| GPQA Diamond (AA) | 91.5% | 91.1% |
| Humanity's Last Exam (AA) | 42.5% | 37.5% |
| SciCode (AA) | – | 51.5% |
| τ²-Bench Telecom (AA) | 86.0% | 95.9% |
| LiveCodeBench | – | 86.8% |
| MMLU-Pro | – | 87.6% |
| LegalBench | – | 84.7% |
| CorpFin | – | 66.7% |
| TaxEval | – | 74.7% |
| Terminal-Bench 2.1 (Vals) | – | 53.6% |
| SWE-bench (Vals) | – | 76.2% |
| GPQA Diamond (Vals) | – | 89.1% |
| Vals Index | – | 43.5 |
| HiL-Bench | 4.3% | 18.7% |
| EQ-Bench 4 | – | 1202 |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
GPT-5.3-Codex vs Kimi K2.6: questions
- Is GPT-5.3-Codex better than Kimi K2.6?
- GPT-5.3-Codex leads on quality: 62.5 vs 60.7. The BenchLeader Index combines every independent quality benchmark; GPT-5.3-Codex is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GPT-5.3-Codex better than Kimi K2.6 for coding?
- Kimi K2.6 scores higher in coding (60 vs 55 on the category index, where 50 is average).
- Is GPT-5.3-Codex better than Kimi K2.6 for agentic tasks?
- GPT-5.3-Codex scores higher in agentic tasks (63 vs 45 on the category index, where 50 is average).
- Which is cheaper, GPT-5.3-Codex or Kimi K2.6?
- Kimi K2.6 is cheaper: $1.71 against $4.81 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.3-Codex or Kimi K2.6?
- GPT-5.3-Codex streams faster: 121 against 44 output tokens per second.
- Which has the larger context window?
- GPT-5.3-Codex accepts more context: 400k against 262k tokens.