GPT-5.6 Terra vs Grok 4.6
GPT-5.6 Terra 
Grok 4.6 Verdict
- GPT-5.6 Terra (xhigh) and Grok 4.6 (medium) are level on quality (64.2 vs 63.8).
- GPT-5.6 Terra (xhigh) is stronger in agents & tools, human preference, instruction following, maths, multimodal.
- Grok 4.6 (medium) is stronger in coding, composite, knowledge, long context, reasoning.
- Grok 4.6 (medium) is 1.5× cheaper ($3.00 vs $4.50 per 1M blended).
- GPT-5.6 Terra (xhigh) streams 1.7× faster (93 vs 55 tokens per second).
| Metric | GPT-5.6 Terra (xhigh) | Grok 4.6 (medium) |
|---|---|---|
| BenchLeader Index | 64.2 | 63.8 |
| Agents & tools score | 69.6 | – |
| Coding score | 63.7 | 63.9 |
| Composite score | 77.1 | 83.2 |
| Human preference score | 66.3 | – |
| Instruction following score | 65.0 | – |
| Knowledge score | 60.9 | 77.3 |
| Long context score | 66.0 | 67.1 |
| Maths score | 71.0 | – |
| Multimodal score | 63.0 | – |
| Reasoning score | 58.2 | 62.1 |
| Blended price $/M | $4.50 | $3.00 |
| Output speed | 93 tok/s | 55 tok/s |
| Time to first answer | 32.5 s | 36.7 s |
| Context window | 1M | 500k |
| SimpleBench | 48.9% | – |
| SciCode | 51.6% | 54.6% |
| ProofBench | 74.0% | – |
| LMArena Text | 1466 | – |
| LMArena Hard Prompts | 1491 | – |
| LMArena Coding | 1519 | – |
| LMArena WebDev | 1521 | – |
| LMArena Vision | 1269 | – |
| LMArena Agent | 1.5 | – |
| AA Intelligence Index | 38.2 | 43.0 |
| IFBench | 66.3% | – |
| AA-LCR | 79.0% | 81.0% |
| MMMU-Pro | 79.5% | – |
| AA-Omniscience | -3.0 | 28 |
| Terminal-Bench Hard | 62.9% | – |
| GPQA Diamond (AA) | 90.8% | 93.5% |
| Humanity's Last Exam (AA) | 41.9% | 42.1% |
| SciCode (AA) | 52.3% | 55.9% |
| τ²-Bench Telecom (AA) | 80.4% | – |
| LiveCodeBench | 85.9% | – |
| MMLU-Pro | 86.7% | – |
| IOI | 65.3% | – |
| CorpFin | 65.3% | – |
| TaxEval | 76.2% | – |
| GPQA Diamond (Vals) | 90.9% | – |
| ARC-AGI-1 | 94.0% | 87.5% |
| ARC-AGI-2 | 74.2% | 61.3% |
| ARC-AGI-3 | 0.7% | – |
Data as of 2026-09-09. Best configuration of each model; every score links to its source on the model pages.