GPT-5.3-Codex vs GPT-5.6 Terra
GPT-5.3-Codex Verdict
- GPT-5.6 Terra (xhigh) leads on quality: 64.4 vs 62.5.
- GPT-5.3-Codex is stronger in instruction following, knowledge, long context.
- GPT-5.6 Terra (xhigh) is stronger in agents & tools, coding, composite, human preference, maths, reasoning.
- They cost about the same ($4.50 per 1M blended).
- GPT-5.3-Codex streams 1.5× faster (121 vs 79 tokens per second).
| Metric | GPT-5.3-Codex | GPT-5.6 Terra (xhigh) |
|---|---|---|
| BenchLeader Index | 62.5 | 64.4 |
| Agents & tools score | 62.7 | 69.8 |
| Coding score | 54.8 | 63.7 |
| Composite score | 70.1 | 77.3 |
| Instruction following score | 73.2 | 65.3 |
| Knowledge score | 69.3 | 61.0 |
| Long context score | 68.3 | 66.0 |
| Multimodal score | 63.0 | 63.0 |
| Human preference score | – | 66.7 |
| Maths score | – | 71.0 |
| Reasoning score | – | 58.6 |
| Blended price $/M | $4.81 | $4.50 |
| Output speed | 121 tok/s | 79 tok/s |
| Time to first answer | 58.2 s | 33.6 s |
| Context window | 400k | 1M |
| Terminal-Bench | 78.4% | – |
| SimpleBench | – | 48.9% |
| SciCode | – | 51.6% |
| WeirdML | 79.3% | – |
| APEX-Agents | 31.8% | – |
| ProofBench | – | 74.0% |
| Epoch Capabilities Index | 156.6 | – |
| LMArena Text | – | 1466 |
| LMArena Hard Prompts | – | 1491 |
| LMArena Coding | – | 1519 |
| LMArena WebDev | 1409 | 1521 |
| LMArena Vision | – | 1269 |
| LMArena Agent | – | 1.5 |
| AA Intelligence Index | 32.5 | 38.2 |
| IFBench | 75.4% | 66.3% |
| AA-LCR | 83.3% | 79.0% |
| MMMU-Pro | 78.5% | 79.5% |
| AA-Omniscience | 10.9 | -3.0 |
| Terminal-Bench Hard | 53.0% | 62.9% |
| GPQA Diamond (AA) | 91.5% | 90.8% |
| Humanity's Last Exam (AA) | 42.5% | 41.9% |
| SciCode (AA) | – | 52.3% |
| τ²-Bench Telecom (AA) | 86.0% | 80.4% |
| LiveCodeBench | – | 85.9% |
| MMLU-Pro | – | 86.7% |
| IOI | – | 65.3% |
| CorpFin | – | 65.3% |
| TaxEval | – | 76.2% |
| GPQA Diamond (Vals) | – | 90.9% |
| HiL-Bench | 4.3% | – |
| ARC-AGI-1 | – | 94.0% |
| ARC-AGI-2 | – | 74.2% |
| ARC-AGI-3 | – | 0.7% |
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 Terra: questions
- Is GPT-5.3-Codex better than GPT-5.6 Terra?
- GPT-5.6 Terra (xhigh) leads on quality: 64.4 vs 62.5. The BenchLeader Index combines every independent quality benchmark; GPT-5.6 Terra (xhigh) 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 Terra for coding?
- GPT-5.6 Terra scores higher in coding (64 vs 55 on the category index, where 50 is average).
- Is GPT-5.3-Codex better than GPT-5.6 Terra for agentic tasks?
- GPT-5.6 Terra scores higher in agentic tasks (70 vs 63 on the category index, where 50 is average).
- Which is cheaper, GPT-5.3-Codex or GPT-5.6 Terra?
- GPT-5.6 Terra is cheaper: $4.50 against $4.81 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.3-Codex or GPT-5.6 Terra?
- GPT-5.3-Codex streams faster: 121 against 79 output tokens per second.
- Which has the larger context window?
- GPT-5.6 Terra accepts more context: 1M against 400k tokens.