GPT-5.3-Codex vs GPT-5.6 Sol
GPT-5.3-Codex Verdict
- GPT-5.6 Sol (high) leads on quality: 68.2 vs 62.5.
- GPT-5.3-Codex is stronger in instruction following, long context.
- GPT-5.6 Sol (high) is stronger in agents & tools, coding, composite, knowledge, multimodal, reasoning.
- GPT-5.3-Codex is 1.7× cheaper ($4.81 vs $8.00 per 1M blended).
- GPT-5.3-Codex streams 2.1× faster (121 vs 59 tokens per second).
| Metric | GPT-5.3-Codex | GPT-5.6 Sol (high) |
|---|---|---|
| BenchLeader Index | 62.5 | 68.2 |
| Agents & tools score | 62.7 | 87.9 |
| Coding score | 54.8 | 72.4 |
| Composite score | 70.1 | 82.7 |
| Instruction following score | 73.2 | 67.8 |
| Knowledge score | 69.3 | 73.8 |
| Long context score | 68.3 | 67.4 |
| Multimodal score | 63.0 | 66.4 |
| Reasoning score | – | 63.3 |
| Blended price $/M | $4.81 | $8.00 |
| Output speed | 121 tok/s | 59 tok/s |
| Time to first answer | 58.2 s | 31.0 s |
| Context window | 400k | 1M |
| Terminal-Bench | 78.4% | – |
| SciCode | – | 56.9% |
| WeirdML | 79.3% | 88.8% |
| APEX-Agents | 31.8% | – |
| Epoch Capabilities Index | 156.6 | – |
| LMArena WebDev | 1409 | – |
| AA Intelligence Index | 32.5 | 42.5 |
| IFBench | 75.4% | 69.2% |
| AA-LCR | 83.3% | 81.7% |
| MMMU-Pro | 78.5% | 81.8% |
| AA-Omniscience | 10.9 | 20.4 |
| Terminal-Bench Hard | 53.0% | 62.1% |
| GPQA Diamond (AA) | 91.5% | 92.8% |
| Humanity's Last Exam (AA) | 42.5% | 46.0% |
| SciCode (AA) | – | 57.8% |
| τ²-Bench Telecom (AA) | 86.0% | 83.3% |
| EnigmaEval | – | 37.1% |
| HiL-Bench | 4.3% | – |
| ARC-AGI-1 | – | 97.0% |
| ARC-AGI-2 | – | 85.4% |
| ARC-AGI-3 | – | 2.2% |
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 GPT-5.6 Sol: questions
- Is GPT-5.3-Codex better than GPT-5.6 Sol?
- GPT-5.6 Sol (high) leads on quality: 68.2 vs 62.5. The BenchLeader Index combines every independent quality benchmark; GPT-5.6 Sol (high) is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GPT-5.3-Codex better than GPT-5.6 Sol for coding?
- GPT-5.6 Sol scores higher in coding (72 vs 55 on the category index, where 50 is average).
- Is GPT-5.3-Codex better than GPT-5.6 Sol for agentic tasks?
- GPT-5.6 Sol scores higher in agentic tasks (88 vs 63 on the category index, where 50 is average).
- Which is cheaper, GPT-5.3-Codex or GPT-5.6 Sol?
- GPT-5.3-Codex is cheaper: $4.81 against $8.00 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.3-Codex or GPT-5.6 Sol?
- GPT-5.3-Codex streams faster: 121 against 59 output tokens per second.
- Which has the larger context window?
- GPT-5.6 Sol accepts more context: 1M against 400k tokens.