GPT-5.5 Pro vs GPT-5.6 Terra
GPT-5.5 Pro Verdict
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 65.0.
- GPT-5.5 Pro (xhigh) is stronger in maths, reasoning.
- GPT-5.6 Terra (max) is stronger in agents & tools, coding, composite, instruction following, knowledge, long context, multimodal.
- GPT-5.6 Terra (max) is 15× cheaper ($4.50 vs $67.50 per 1M blended).
- GPT-5.6 Terra (max) streams 21.1× faster (84 vs 4 tokens per second).
| Metric | GPT-5.5 Pro (xhigh) | GPT-5.6 Terra (max) |
|---|---|---|
| BenchLeader Index | 67.1 | 65.0 |
| Maths score | 74.5 | 71.5 |
| Reasoning score | 80.1 | 72.3 |
| Agents & tools score | – | 59.0 |
| Coding score | – | 67.2 |
| Composite score | – | 71.5 |
| Instruction following score | – | 69.8 |
| Knowledge score | – | 58.8 |
| Long context score | – | 68.0 |
| Multimodal score | – | 65.3 |
| Blended price $/M | $67.50 | $4.50 |
| Output speed | 4 tok/s | 84 tok/s |
| Time to first answer | 3.5 s | 220.9 s |
| Context window | 1.1M | 1.1M |
| GPQA Diamond | – | 93.3% |
| FrontierMath Tiers 1–3 | 87.7% | 86.0% |
| FrontierMath Tier 4 | 78.0% | 70.7% |
| OTIS Mock AIME | – | 99.7% |
| SimpleQA Verified | – | 43.2% |
| Terminal-Bench | – | 21.5% |
| SciCode | – | 53.9% |
| LiveBench | – | 77.9% |
| LiveBench Reasoning | – | 90.6% |
| LiveBench Coding | – | 78.3% |
| LiveBench Agentic Coding | – | 55.0% |
| LiveBench Mathematics | – | 94.9% |
| LiveBench Data Analysis | – | 79.3% |
| LiveBench Language | – | 82.9% |
| LiveBench Instruction Following | – | 64.6% |
| AA Intelligence Index | – | 42.3 |
| IFBench | – | 71.2% |
| AA-LCR | – | 83.0% |
| MMMU-Pro | – | 80.7% |
| AA-Omniscience | – | 0.1 |
| Terminal-Bench Hard | – | 57.6% |
| GPQA Diamond (AA) | – | 92.5% |
| Humanity's Last Exam (AA) | – | 42.9% |
| SciCode (AA) | – | 55.0% |
| τ²-Bench Telecom (AA) | – | 86.3% |
| IOI | – | 87.6% |
| LegalBench | – | 85.1% |
| Terminal-Bench 2.1 (Vals) | – | 77.5% |
| SWE-bench (Vals) | – | 95.4% |
| Vals Index | – | 59.6 |
| ARC-AGI-1 | 95.0% | 96.5% |
| ARC-AGI-2 | 84.2% | 83.9% |
| ARC-AGI-3 | – | 0.8% |
| CritPt | 30.6% | 30.0% |
| GDPval (AA) | – | 48.9% |
| τ²-Bench Banking (AA) | – | 40.2% |
| ITBench SRE (AA) | – | 51.0% |
| APEX-Agents (AA) | – | 38.9% |
| Code Migration | – | 47.8% |
| Excel Modeling Benchmark | – | 66.2% |
| Finance Agent v2 | – | 54.4% |
| Harvey's Legal Agent Benchmark | – | 0.8% |
| Legal Research Bench | – | 41.4% |
| MMMU-Pro (Vals) | – | 86.5% |
| ProgramBench | – | 0.5% |
| SAGE | – | 47.0% |
| SkillsBench | – | 58.9% |
| Tax Agent Bench | – | 65.2% |
| Terminal-Bench 4.0 (Vals) | – | 26.3% |
| Terminal-Bench Science | – | 10.0% |
| Vibe Code Bench 1-100 | – | 14.8% |
| Vibe Code Bench v1.1 | – | 74.6% |
| Chess Puzzles | – | 54.0% |
| Mystery Game Puzzles | – | 35.0% |
| DeepSWE | – | 69.6% |
| LMCA | 53.9% | 52.2% |
| DTBench | 96.0% | 92.5% |
| CursorBench | – | 64.9% |
| ALE-Bench | – | 1951.4 |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
GPT-5.5 Pro vs GPT-5.6 Terra: questions
- Is GPT-5.5 Pro better than GPT-5.6 Terra?
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 65.0. The BenchLeader Index combines every independent quality benchmark; GPT-5.5 Pro (xhigh) is ahead overall as of 2026-09-19, but check the category scores for your use.
- Which is cheaper, GPT-5.5 Pro or GPT-5.6 Terra?
- GPT-5.6 Terra is cheaper: $4.50 against $67.50 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.5 Pro or GPT-5.6 Terra?
- GPT-5.6 Terra streams faster: 84 against 4 output tokens per second.
- Which has the larger context window?
- Both accept 1.1M tokens of context.