GPT-5.5 Instant vs GPT-5.6 Terra
GPT-5.5 Instant Verdict
- GPT-5.6 Terra (xhigh) leads on quality: 64.4 vs 60.5.
- GPT-5.5 Instant is stronger in agents & tools, human preference, instruction following, knowledge, reasoning.
- GPT-5.6 Terra (xhigh) is stronger in coding, composite, long context, maths, multimodal.
- GPT-5.6 Terra (xhigh) is 2.5× cheaper ($4.50 vs $11.25 per 1M blended).
- GPT-5.5 Instant streams 1.6× faster (129 vs 79 tokens per second).
| Metric | GPT-5.5 Instant | GPT-5.6 Terra (xhigh) |
|---|---|---|
| BenchLeader Index | 60.5 | 64.4 |
| Agents & tools score | 70.7 | 69.8 |
| Coding score | 61.1 | 63.7 |
| Composite score | 62.9 | 77.3 |
| Human preference score | 67.5 | 66.7 |
| Instruction following score | 69.8 | 65.3 |
| Knowledge score | 69.4 | 61.0 |
| Long context score | 61.4 | 66.0 |
| Maths score | 42.5 | 71.0 |
| Multimodal score | 59.7 | 63.0 |
| Reasoning score | 62.6 | 58.6 |
| Blended price $/M | $11.25 | $4.50 |
| Output speed | 129 tok/s | 79 tok/s |
| Time to first answer | 16.8 s | 33.6 s |
| Context window | 400k | 1M |
| GPQA Diamond | 82.5% | – |
| FrontierMath Tiers 1–3 | 26.3% | – |
| FrontierMath Tier 4 | 2.4% | – |
| OTIS Mock AIME | 68.1% | – |
| SimpleBench | – | 48.9% |
| SciCode | 48.6% | 51.6% |
| ProofBench | – | 74.0% |
| Epoch Capabilities Index | 142.5 | – |
| LMArena Text | 1474 | 1466 |
| LMArena Hard Prompts | 1491 | 1491 |
| LMArena Coding | 1514 | 1519 |
| LMArena WebDev | – | 1521 |
| LMArena Vision | 1251 | 1269 |
| LMArena Agent | – | 1.5 |
| AA Intelligence Index | 26.8 | 38.2 |
| IFBench | 71.5% | 66.3% |
| AA-LCR | 70.0% | 79.0% |
| MMMU-Pro | – | 79.5% |
| AA-Omniscience | 11.2 | -3.0 |
| Terminal-Bench Hard | 42.4% | 62.9% |
| GPQA Diamond (AA) | 84.7% | 90.8% |
| Humanity's Last Exam (AA) | 21.6% | 41.9% |
| SciCode (AA) | 52.5% | 52.3% |
| τ²-Bench Telecom (AA) | 49.4% | 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% |
| 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-5.5 Instant vs GPT-5.6 Terra: questions
- Is GPT-5.5 Instant better than GPT-5.6 Terra?
- GPT-5.6 Terra (xhigh) leads on quality: 64.4 vs 60.5. 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-5.5 Instant better than GPT-5.6 Terra for coding?
- GPT-5.6 Terra scores higher in coding (64 vs 61 on the category index, where 50 is average).
- Is GPT-5.5 Instant better than GPT-5.6 Terra for agentic tasks?
- GPT-5.5 Instant scores higher in agentic tasks (71 vs 70 on the category index, where 50 is average).
- Which is cheaper, GPT-5.5 Instant or GPT-5.6 Terra?
- GPT-5.6 Terra is cheaper: $4.50 against $11.25 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.5 Instant or GPT-5.6 Terra?
- GPT-5.5 Instant streams faster: 129 against 79 output tokens per second.
- Which has the larger context window?
- GPT-5.6 Terra accepts more context: 1M against 400k tokens.