Claude Opus 5 vs GPT-5.3-Codex
Claude Opus 5 
GPT-5.3-Codex Verdict
- Claude Opus 5 leads on quality: 70.0 vs 62.5.
- Claude Opus 5 is stronger in agents & tools, coding, composite, human preference, knowledge, maths, multimodal, reasoning.
- GPT-5.3-Codex is stronger in long context, instruction following.
- GPT-5.3-Codex is 2.1× cheaper ($4.81 vs $10.00 per 1M blended).
- GPT-5.3-Codex streams 2.4× faster (121 vs 51 tokens per second).
| Metric | Claude Opus 5 | GPT-5.3-Codex |
|---|---|---|
| BenchLeader Index | 70.0 | 62.5 |
| Agents & tools score | 71.5 | 62.7 |
| Coding score | 74.5 | 54.8 |
| Composite score | 93.1 | 70.1 |
| Human preference score | 78.2 | – |
| Knowledge score | 70.6 | 69.3 |
| Long context score | 66.2 | 68.3 |
| Maths score | 67.1 | – |
| Multimodal score | 69.4 | 63.0 |
| Reasoning score | 71.5 | – |
| Instruction following score | – | 73.2 |
| Blended price $/M | $10.00 | $4.81 |
| Output speed | 51 tok/s | 121 tok/s |
| Time to first answer | 93.0 s | 58.2 s |
| Context window | 1M | 400k |
| GPQA Diamond | 92.9% | – |
| OTIS Mock AIME | 97.8% | – |
| Terminal-Bench | – | 78.4% |
| SimpleBench | 80.6% | – |
| WeirdML | 86.3% | 79.3% |
| APEX-Agents | – | 31.8% |
| Epoch Capabilities Index | 162.6 | 156.6 |
| LMArena WebDev | – | 1409 |
| AA Intelligence Index | 50.7 | 32.5 |
| IFBench | – | 75.4% |
| AA-LCR | 79.3% | 83.3% |
| MMMU-Pro | 84.7% | 78.5% |
| AA-Omniscience | 37.1 | 10.9 |
| Terminal-Bench Hard | – | 53.0% |
| GPQA Diamond (AA) | 93.2% | 91.5% |
| Humanity's Last Exam (AA) | 54.9% | 42.5% |
| SciCode (AA) | 56.4% | – |
| τ²-Bench Telecom (AA) | – | 86.0% |
| LiveCodeBench | 89.0% | – |
| MMLU-Pro | 91.6% | – |
| IOI | 91.7% | – |
| LegalBench | 87.0% | – |
| CorpFin | 73.2% | – |
| TaxEval | 75.1% | – |
| Terminal-Bench 2.1 (Vals) | 84.6% | – |
| SWE-bench (Vals) | 97.0% | – |
| GPQA Diamond (Vals) | 93.4% | – |
| Vals Index | 67.2 | – |
| HiL-Bench | 57.0% | 4.3% |
| EQ-Bench 4 | 1385 | – |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
Claude Opus 5 vs GPT-5.3-Codex: questions
- Is Claude Opus 5 better than GPT-5.3-Codex?
- Claude Opus 5 leads on quality: 70.0 vs 62.5. The BenchLeader Index combines every independent quality benchmark; Claude Opus 5 is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is Claude Opus 5 better than GPT-5.3-Codex for coding?
- Claude Opus 5 scores higher in coding (75 vs 55 on the category index, where 50 is average).
- Is Claude Opus 5 better than GPT-5.3-Codex for agentic tasks?
- Claude Opus 5 scores higher in agentic tasks (72 vs 63 on the category index, where 50 is average).
- Which is cheaper, Claude Opus 5 or GPT-5.3-Codex?
- GPT-5.3-Codex is cheaper: $4.81 against $10.00 per million tokens, blended at three input tokens per output token.
- Which is faster, Claude Opus 5 or GPT-5.3-Codex?
- GPT-5.3-Codex streams faster: 121 against 51 output tokens per second.
- Which has the larger context window?
- Claude Opus 5 accepts more context: 1M against 400k tokens.