GPT-5.3-Codex vs Kimi K3
GPT-5.3-Codex 
Kimi K3 Verdict
- Kimi K3 leads on quality: 66.5 vs 62.5.
- GPT-5.3-Codex is stronger in instruction following, knowledge.
- Kimi K3 is stronger in agents & tools, coding, composite, long context, multimodal, human preference, maths.
- GPT-5.3-Codex is 1.2× cheaper ($4.81 vs $6.00 per 1M blended).
- GPT-5.3-Codex streams 3.2× faster (121 vs 38 tokens per second).
| Metric | GPT-5.3-Codex | Kimi K3 |
|---|---|---|
| BenchLeader Index | 62.5 | 66.5 |
| Agents & tools score | 62.7 | 67.4 |
| Coding score | 54.8 | 65.0 |
| Composite score | 70.1 | 74.2 |
| Instruction following score | 73.2 | – |
| Knowledge score | 69.3 | 68.2 |
| Long context score | 68.3 | 71.1 |
| Multimodal score | 63.0 | 65.0 |
| Human preference score | – | 71.2 |
| Maths score | – | 78.1 |
| Blended price $/M | $4.81 | $6.00 |
| Output speed | 121 tok/s | 38 tok/s |
| Time to first answer | 58.2 s | 56.3 s |
| Context window | 400k | 1.0M |
| Terminal-Bench | 78.4% | – |
| SciCode | – | 58.7% |
| WeirdML | 79.3% | – |
| APEX-Agents | 31.8% | 39.3% |
| FrontierCode | – | 44.2% |
| ProofBench | – | 87.0% |
| Epoch Capabilities Index | 156.6 | 157.6 |
| LMArena WebDev | 1409 | – |
| LiveBench | – | 79.2% |
| LiveBench Reasoning | – | 90.7% |
| LiveBench Coding | – | 81.5% |
| LiveBench Agentic Coding | – | 62.2% |
| LiveBench Mathematics | – | 84.4% |
| LiveBench Data Analysis | – | 78.7% |
| LiveBench Language | – | 85.5% |
| AA Intelligence Index | 32.5 | 43.8 |
| IFBench | 75.4% | – |
| AA-LCR | 83.3% | 88.7% |
| MMMU-Pro | 78.5% | 80.5% |
| AA-Omniscience | 10.9 | 19.7 |
| Terminal-Bench Hard | 53.0% | – |
| GPQA Diamond (AA) | 91.5% | 93.5% |
| Humanity's Last Exam (AA) | 42.5% | 46.9% |
| SciCode (AA) | – | 59.5% |
| τ²-Bench Telecom (AA) | 86.0% | – |
| LegalBench | – | 86.0% |
| CorpFin | – | 71.6% |
| TaxEval | – | 75.7% |
| Terminal-Bench 2.1 (Vals) | – | 80.9% |
| SWE-bench (Vals) | – | 93.4% |
| GPQA Diamond (Vals) | – | 92.9% |
| Vals Index | – | 57.8 |
| HiL-Bench | 4.3% | – |
| EQ-Bench 4 | – | 1339 |
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 K3: questions
- Is GPT-5.3-Codex better than Kimi K3?
- Kimi K3 leads on quality: 66.5 vs 62.5. The BenchLeader Index combines every independent quality benchmark; Kimi K3 is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GPT-5.3-Codex better than Kimi K3 for coding?
- Kimi K3 scores higher in coding (65 vs 55 on the category index, where 50 is average).
- Is GPT-5.3-Codex better than Kimi K3 for agentic tasks?
- Kimi K3 scores higher in agentic tasks (67 vs 63 on the category index, where 50 is average).
- Which is cheaper, GPT-5.3-Codex or Kimi K3?
- GPT-5.3-Codex is cheaper: $4.81 against $6.00 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.3-Codex or Kimi K3?
- GPT-5.3-Codex streams faster: 121 against 38 output tokens per second.
- Which has the larger context window?
- Kimi K3 accepts more context: 1.0M against 400k tokens.