Claude Opus 4.8 vs GPT-5.3-Codex
Claude Opus 4.8 
GPT-5.3-Codex Verdict
- Claude Opus 4.8 leads on quality: 64.8 vs 62.5.
- Claude Opus 4.8 is stronger in agents & tools, coding, composite, human preference, multimodal, reasoning.
- GPT-5.3-Codex is stronger in instruction following, knowledge, long context.
- GPT-5.3-Codex is 2.1× cheaper ($4.81 vs $10.00 per 1M blended).
- GPT-5.3-Codex streams 2.2× faster (121 vs 56 tokens per second).
| Metric | Claude Opus 4.8 | GPT-5.3-Codex |
|---|---|---|
| BenchLeader Index | 64.8 | 62.5 |
| Agents & tools score | 65.0 | 62.7 |
| Coding score | 65.6 | 54.8 |
| Composite score | 82.1 | 70.1 |
| Human preference score | 65.8 | – |
| Instruction following score | 61.8 | 73.2 |
| Knowledge score | 66.5 | 69.3 |
| Long context score | 65.4 | 68.3 |
| Multimodal score | 64.5 | 63.0 |
| Reasoning score | 64.6 | – |
| Blended price $/M | $10.00 | $4.81 |
| Output speed | 56 tok/s | 121 tok/s |
| Time to first answer | 29.3 s | 58.2 s |
| Context window | 1M | 400k |
| Terminal-Bench | – | 78.4% |
| SimpleBench | 64.8% | – |
| Remote Labor Index | 8.3% | – |
| WeirdML | – | 79.3% |
| APEX-Agents | – | 31.8% |
| FrontierCode | 46.5% | – |
| GSO-Bench | 47.1% | – |
| Epoch Capabilities Index | 158.3 | 156.6 |
| LMArena Text | 1473 | – |
| LMArena Hard Prompts | 1503 | – |
| LMArena Coding | 1527 | – |
| LMArena WebDev | 1540 | 1409 |
| LMArena Vision | 1289 | – |
| AA Intelligence Index | 42.0 | 32.5 |
| IFBench | 62.2% | 75.4% |
| AA-LCR | 77.7% | 83.3% |
| MMMU-Pro | – | 78.5% |
| AA-Omniscience | 28.8 | 10.9 |
| Terminal-Bench Hard | 58.3% | 53.0% |
| GPQA Diamond (AA) | 92.0% | 91.5% |
| Humanity's Last Exam (AA) | 48.7% | 42.5% |
| SciCode (AA) | 54.4% | – |
| τ²-Bench Telecom (AA) | 94.4% | 86.0% |
| LiveCodeBench | 87.8% | – |
| MMLU-Pro | 89.6% | – |
| LegalBench | 83.6% | – |
| CorpFin | 66.7% | – |
| TaxEval | 75.6% | – |
| Terminal-Bench 2.1 (Vals) | 71.9% | – |
| SWE-bench (Vals) | 88.6% | – |
| GPQA Diamond (Vals) | 92.4% | – |
| Vals Index | 60.9 | – |
| HiL-Bench | 35.3% | 4.3% |
| EQ-Bench 4 | 1281 | – |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
Claude Opus 4.8 vs GPT-5.3-Codex: questions
- Is Claude Opus 4.8 better than GPT-5.3-Codex?
- Claude Opus 4.8 leads on quality: 64.8 vs 62.5. The BenchLeader Index combines every independent quality benchmark; Claude Opus 4.8 is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is Claude Opus 4.8 better than GPT-5.3-Codex for coding?
- Claude Opus 4.8 scores higher in coding (66 vs 55 on the category index, where 50 is average).
- Is Claude Opus 4.8 better than GPT-5.3-Codex for agentic tasks?
- Claude Opus 4.8 scores higher in agentic tasks (65 vs 63 on the category index, where 50 is average).
- Which is cheaper, Claude Opus 4.8 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 4.8 or GPT-5.3-Codex?
- GPT-5.3-Codex streams faster: 121 against 56 output tokens per second.
- Which has the larger context window?
- Claude Opus 4.8 accepts more context: 1M against 400k tokens.