GPT-5.5 vs GPT-5.6 Terra
Full profiles: GPT-5.5 (OpenAI) and GPT-5.6 Terra (OpenAI): every benchmark, price and rank.
Updated · Data from 12 sources
As of 25 Oct 2026, GPT-5.5 (xhigh) and GPT-5.6 Terra (max) are neck and neck on quality (66.1 vs 64.4 on the BenchLeader Index, inside the ±6.2 margin of error), and GPT-5.6 Terra (max) costs 2.5× less, which makes it the better buy for most workloads. Pick GPT-5.5 for knowledge (65 vs 57); pick GPT-5.6 Terra for coding (65 vs 61).
GPT-5.5 benchmarks Which to pick for…
The pick's numbers come first. Category scores on the BenchLeader scale (50 is the average model, 15 points one standard deviation). High confidence means a lead of half a standard deviation or more; under one point is called either.
| Use case | Pick | Why | Confidence |
|---|---|---|---|
| Coding | GPT-5.6 Terra | 65 vs 61 category score; SciCode 55.0% vs 55.8% | Medium |
| Agents & tool use | GPT-5.5 | 62 vs 59 category score; Terminal-Bench Hard 60.6% vs 57.6% | Medium |
| Maths | Either | 70 vs 69 category score; FrontierMath Tiers 1–3 85.3% vs 86.0% | Either |
| Reasoning | GPT-5.5 | 76 vs 70 category score; ARC-AGI-2 85.0% vs 83.9% | Medium |
| Knowledge | GPT-5.5 | 65 vs 57 category score; SimpleQA Verified 63.0% vs 43.2% | High |
| Long documents | Either | 67 vs 67 category score; AA-LCR 84.3% vs 83.0% | Either |
| Images and other media | Either | 63 vs 64 category score; MMMU-Pro 79.9% vs 80.7% | Either |
| Following instructions | GPT-5.5 | 74 vs 70 category score; IFBench 75.8% vs 71.2% | Medium |
| Lowest cost | GPT-5.6 Terra | $4.50 vs $11.25 per 1M blended; agentic coding session $0.168 vs $0.420 | – |
| Fastest first answer | GPT-5.5 | 39.1 s (GPT-5.5 (xhigh)) vs 101.0 s (GPT-5.6 Terra (max)) to the first answer token | – |
| High volume on a budget | Neither flagship | A smaller model is usually the better fit: Cheapest good LLMs, Fastest LLMs | – |
Key differences
- GPT-5.5 (xhigh) and GPT-5.6 Terra (max) are neck and neck on quality (66.1 vs 64.4, within the ±6.2 margin).
- GPT-5.5 (xhigh) is stronger in agents & tools, instruction following, knowledge, long context, maths, reasoning.
- GPT-5.6 Terra (max) is stronger in coding, composite, multimodal.
- GPT-5.6 Terra (max) is 2.5× cheaper ($4.50 vs $11.25 per 1M blended).
- GPT-5.6 Terra (max) streams 1.5× faster (126 vs 86 tokens per second).
At a glance
| Spec | GPT-5.5 | GPT-5.6 Terra |
|---|---|---|
| Developer | OpenAI | OpenAI |
| Released | 23 Apr 2026 | 9 Jul 2026 |
| Context window (tokens) | 1,050,000 | 1,050,000 |
| Compared at | GPT-5.5 (xhigh) | GPT-5.6 Terra (max) |
| Open weights | No | No |
| Price in / out / cached input per 1M | $5.00 / $30.00 / $0.500 | $2.00 / $12.00 / $0.200 |
Category by category
Category scores on the BenchLeader scale: 50 is the average evaluated model, 15 points is one standard deviation. A gap under one point is called level.
| Category | GPT-5.5 (xhigh) | GPT-5.6 Terra (max) | Leader |
|---|---|---|---|
| Reasoning | 75.5 | 70.1 | GPT-5.5 |
| Coding | 61.1 | 65.1 | GPT-5.6 Terra |
| Agents & tools | 62.3 | 58.9 | GPT-5.5 |
| Maths | 69.7 | 68.9 | level |
| Knowledge | 65.3 | 57.2 | GPT-5.5 |
| Instruction following | 73.9 | 69.9 | GPT-5.5 |
| Multimodal | 62.9 | 63.7 | level |
| Long context | 67.3 | 66.6 | level |
| Composite | 72.4 | 76.6 | GPT-5.6 Terra |
Where sources disagree
Across the 55 benchmarks both have, GPT-5.5 leads 28, GPT-5.6 Terra leads 26 and 1 is a tie. Independent sources split: GPT-5.5 leads on Arena Text; GPT-5.6 Terra leads on AA Intelligence Index v4.3.2.
| Overall index | GPT-5.5 (xhigh) | GPT-5.6 Terra (max) | Leader |
|---|---|---|---|
| BenchLeader Index | 66.1 | 64.4 | neck and neck |
| AA Intelligence Index v4.3.2 | 38.4 | 42.1 | GPT-5.6 Terra |
| Arena Text | 1482† | 1467 | GPT-5.5 |
Each publisher runs its own tasks, harnesses and effort settings, so their overall verdicts can differ; BenchLeader reconciles them on one scale. † measured at another effort setting of the same model (the publisher did not test the one compared here).
Price, speed and latency
List prices blended at three input tokens per output token. Per-task prices use the token counts on the methodology page; suite cost is what Artificial Analysis paid to run its whole Intelligence Index.
| Measure | GPT-5.5 (xhigh) | GPT-5.6 Terra (max) |
|---|---|---|
| Blended price per 1M tokens | $11.25 | $4.50 |
| Input / output per 1M | $5.00 / $30.00 | $2.00 / $12.00 |
| Cached input per 1M | $0.500 | $0.200 |
| Price per task: chat reply | $0.011 | $0.0044 |
| Price per task: summarize a 30-page report | $0.078 | $0.031 |
| Price per task: code edit | $0.075 | $0.030 |
| Price per task: agentic coding session | $0.420 | $0.168 |
| Price per task: structured extraction | $0.016 | $0.0064 |
| Cost to run a full benchmark suite | $2.63 | $1.40 |
| Output speed | 86 tok/s | 126 tok/s |
| Time to first answer | 39.1 s | 101.0 s |
| Time to a complete answer | 45.0 s | 105.0 s |
Per token is not per task: on Artificial Analysis' full suite GPT-5.5 (xhigh) cost $2.63 and GPT-5.6 Terra (max) $1.40, because GPT-5.6 Terra (max) used about 1.3× as many tokens for the same work, which a per-token price hides.
Each model is compared at its best-ranked reasoning-effort setting. GPT-5.5 (xhigh) scores 66.1 and takes 39 s to its first answer token; GPT-5.5 (high) scores 65.3 in 14 s, GPT-5.5 (medium) scores 62.9 in 3 s. GPT-5.6 Terra (max) scores 64.4 and takes 101 s to its first answer token; GPT-5.6 Terra (xhigh) scores 62.8 in 7 s, GPT-5.6 Terra (high) scores 61.3 in 2 s. Higher effort means more thinking before the answer: better scores, longer waits and more tokens billed. How reasoning effort changes scores and cost.
Every benchmark
143 benchmarks, grouped by category; each name links to the board and its leaders. † measured at another effort setting of the same model, shown for reference and not counted as a win.
| Metric | Publisher | GPT-5.5 (xhigh) | GPT-5.6 Terra (max) |
|---|---|---|---|
| BenchLeader Index | BenchLeader | 66.1 | 64.4 |
| Agents & tools score | BenchLeader | 62.3 | 58.9 |
| Coding score | BenchLeader | 61.1 | 65.1 |
| Composite score | BenchLeader | 72.4 | 76.6 |
| Instruction following score | BenchLeader | 73.9 | 69.9 |
| Knowledge score | BenchLeader | 65.3 | 57.2 |
| Long context score | BenchLeader | 67.3 | 66.6 |
| Maths score | BenchLeader | 69.7 | 68.9 |
| Multimodal score | BenchLeader | 62.9 | 63.7 |
| Reasoning score | BenchLeader | 75.5 | 70.1 |
| Blended price $/M | BenchLeader | $11.25 | $4.50 |
| Output speed | BenchLeader | 86 tok/s | 126 tok/s |
| Time to first answer | BenchLeader | 39.1 s | 101.0 s |
| Context window | BenchLeader | 1,050,000 tokens | 1,050,000 tokens |
| Reasoning | |||
| GPQA Diamond | Epoch AI Benchmarking Hub | 90.7%† | 93.3% |
| SimpleBench | SimpleBench | 69.0%† | 48.9%† |
| Arena Hard Prompts | Arena (LMArena) | 1499† | 1490† |
| LiveBench 2.0 Reasoning | LiveBench | 89.7%† | 90.6%† |
| LiveBench 1.0 Reasoning | LiveBench | 89.7% | 90.6% |
| GPQA Diamond (AA) | Artificial Analysis | 93.5% | 92.5% |
| Humanity's Last Exam (AA) | Artificial Analysis | 45.8% | 42.9% |
| GPQA Diamond (Vals) | Vals AI | 93.2% | 90.9%† |
| Kagi LLM Benchmark | Kagi LLM Benchmark | 88.8%† | 51.3%† |
| ARC-AGI-1 | ARC Prize | 95.0% | 96.5% |
| ARC-AGI-2 | ARC Prize | 85.0% | 83.9% |
| ARC-AGI-3 | ARC Prize | 0.4%† | 0.8% |
| CritPt | Artificial Analysis | 27.1% | 30.0% |
| Chess Puzzles | Epoch AI Benchmarking Hub | 63.0% | 47.0% |
| Mystery Game Puzzles | Epoch AI Benchmarking Hub | 56.0% | 35.0% |
| CL-bench Life | Epoch AI Benchmarking Hub | 22.2%† | – |
| LMCA | Epoch AI Benchmarking Hub | 54.3% | 55.0% |
| DTBench | Epoch AI Benchmarking Hub | 96.0% | 93.3% |
| ForecastBench | ForecastBench | 64.4%† | – |
| BTF-3 | Epoch AI Benchmarking Hub | 14.3%† | – |
| Coding | |||
| SciCode | SciCode | 55.8% | 55.0% |
| WeirdML | WeirdML | 84.9% | 78.3%† |
| FrontierCode | Cognition | 43.0%† | 41.3%† |
| GSO-Bench | GSO-Bench | 40.2% | – |
| Arena Coding | Arena (LMArena) | 1511† | 1518† |
Show all 143 benchmarks
| Metric | Publisher | GPT-5.5 (xhigh) | GPT-5.6 Terra (max) |
|---|---|---|---|
| Coding | |||
| Arena WebDev | Arena (LMArena) | 1513 | 1521† |
| LiveBench 2.0 Coding | LiveBench | 85.1%† | 86.2%† |
| LiveBench 1.0 Coding | LiveBench | 82.2% | 78.3% |
| LiveCodeBench | Vals AI | 85.3% | 85.9%† |
| IOI | Vals AI | – | 87.6% |
| SWE-bench (Vals) | Vals AI | 82.6% | 95.4% |
| Code Migration | Vals AI | 45.2% | 47.8% |
| ProgramBench | Vals AI | 0.5% | 0.5% |
| Vibe Code Bench 1-100 | Vals AI | – | 14.8% |
| Vibe Code Bench v1.1 | Vals AI | 69.8% | 74.6% |
| SWE Atlas: Codebase QnA | Scale AI SEAL | 45.4% | – |
| SWE Atlas: Refactoring | Scale AI SEAL | 44.8% | – |
| SWE Atlas: Test Writing | Scale AI SEAL | 42.6% | – |
| MirrorCode | Epoch AI Benchmarking Hub | 10.0%† | – |
| Surface Evolver Bench | Epoch AI Benchmarking Hub | 88.1%† | 83.8%† |
| DeepSWE v1.1 | Epoch AI Benchmarking Hub | 67.0% | 69.6% |
| CursorBench | Cursor | – | 41.3% |
| ALE-Bench | Epoch AI Benchmarking Hub | 1943.0 | 1951.4 |
| Terminal-Bench 4.0 (AA) | Artificial Analysis | 14.7% | 35.4% |
| Terminal-Bench 2.1 (AA) | Artificial Analysis | 84.3% | 88.0% |
| Startrise Frontend | Startrise | – | 66.9%† |
| Agents & tools | |||
| Terminal-Bench | Terminal-Bench | 84.7%† | 21.5% |
| OSWorld-Verified 2.0 | OSWorld | 13.0% | – |
| Remote Labor Index | Scale AI / CAIS | 6.3%† | – |
| APEX-Agents | Mercor | 55.1%† | 58.2% |
| Arena Agent | Arena (LMArena) | – | 0.2† |
| LiveBench Long Agentic | LiveBench | 44.6%† | 48.4%† |
| LiveBench Browser | LiveBench | 48.0%† | 84.0%† |
| LiveBench Agentic Coding | LiveBench | 54.0% | 55.0% |
| Terminal-Bench Hard | Artificial Analysis | 60.6% | 57.6% |
| τ²-Bench Telecom (AA) | Artificial Analysis | 93.9% | 86.3% |
| Terminal-Bench 2.1 (Vals) | Vals AI | 76.4%† | 77.5% |
| MCP Atlas | Scale AI SEAL | 75.3% | – |
| HiL-Bench | Scale AI SEAL | 39.7%† | – |
| τ³-bench Banking | τ²-bench | 44.6% | – |
| GDPval-AA v2.1 | Artificial Analysis | – | 47.6% |
| τ³-Banking (AA) | Artificial Analysis | 39.0% | 40.2% |
| ITBench SRE (AA) | Artificial Analysis | 45.8% | 51.0% |
| Analyst Agent (AA) | Artificial Analysis | 50.0% | – |
| APEX-Agents (AA) | Artificial Analysis | 37.7% | 38.9% |
| CyberBench | Vals AI | – | 72.1% |
| Finance Agent v2 | Vals AI | 51.8% | 54.4% |
| Harvey's Legal Agent Benchmark v1 | Vals AI | 3.8% | 0.8% |
| Legal Research Bench | Vals AI | 40.4% | 41.4% |
| SkillsBench | Vals AI | 62.2% | 58.9% |
| SREBench | Vals AI | 3.8% | 9.5% |
| Tax Agent Bench | Vals AI | 21.8% | 30.0% |
| Terminal-Bench 2.0 (Vals) | Vals AI | 73.2%† | – |
| Terminal-Bench 4.0 (Vals) | Vals AI | – | 22.7% |
| Terminal-Bench Science | Vals AI | – | 10.0% |
| Time Horizon Index: KSP | Vals AI | 8.3% | – |
| BALROG | BALROG | – | 53.2% |
| DeepResearch Bench | DeepResearch Bench | 54.0%† | – |
| PostTrainBench | Epoch AI Benchmarking Hub | 27.2% | – |
| ExploitBench | Epoch AI Benchmarking Hub | 47.4%† | – |
| GBAEval | Epoch AI Benchmarking Hub | 53.2%† | – |
| Vending-Bench 2 | Andon Labs | 7523.8† | 7343.2† |
| AutomationBench | Artificial Analysis | 47.3% | 59.6% |
| GDP.pdf (AA) | Artificial Analysis | 21.2% | 24.0% |
| EnterpriseOps-Gym | Artificial Analysis | 46.6% | 38.5% |
| AA-Briefcase v1.1 | Artificial Analysis | 1136 | – |
| Terminal-Bench-Science 0.1 (AA) | Artificial Analysis | – | 13.8% |
| FACTS Search | – | 81.7%† | |
| Maths | |||
| FrontierMath Tiers 1–3 | Epoch AI Benchmarking Hub | 85.3% | 86.0% |
| FrontierMath Tier 4 | Epoch AI Benchmarking Hub | 72.5% | 70.7% |
| OTIS Mock AIME | Epoch AI Benchmarking Hub | 84.4%† | 99.7% |
| ProofBench | Vals AI | 50.0% | 74.0%† |
| LiveBench Mathematics | LiveBench | 95.9% | 94.9% |
| AIME 2026 | MathArena | 100.0% | – |
| HMMT February 2026 | MathArena | 98.5% | – |
| USAMO 2026 | MathArena | 98.2% | – |
| MathArena Apex | MathArena | 80.2% | – |
| Arena Maths | Arena (LMArena) | 1501† | 1483† |
| Knowledge | |||
| SimpleQA Verified | Epoch AI Benchmarking Hub | 63.0% | 43.2% |
| LiveBench 2.0 Data Analysis | LiveBench | 81.6%† | 79.3%† |
| LiveBench Research | LiveBench | 61.6%† | 60.4%† |
| LiveBench 1.0 Data Analysis | LiveBench | 81.6% | 79.3% |
| AA-Omniscience | Artificial Analysis | 20.5 | 0.1 |
| MMLU-Pro | Vals AI | 88.1% | 86.7%† |
| LegalBench | Vals AI | 86.5% | 85.1% |
| CorpFin | Vals AI | 68.4% | 65.3%† |
| TaxEval | Vals AI | 75.0% | 76.2%† |
| CaseLaw v2 | Vals AI | 66.2% | – |
| Excel Modeling Benchmark | Vals AI | 64.5% | 66.2% |
| MedCode | Vals AI | 49.1% | 43.4%† |
| MedScribe | Vals AI | 86.9% | 82.9%† |
| Public Benefits Bench v1.1 | Vals AI | 60.9% | 62.4% |
| DrugDiscoveryBench | Scale AI SEAL | 51.6% | – |
| EBR-bench | Epoch AI Benchmarking Hub | 34.3% | – |
| GDP.pdf | Epoch AI Benchmarking Hub | 26.0% | 24.7%† |
| AA-Omniscience: accuracy | Artificial Analysis | 58.0% | 46.8% |
| AA-Omniscience: non-hallucination | Artificial Analysis | 11.0% | 12.1% |
| Instruction following | |||
| LiveBench Language | LiveBench | 87.4% | 82.9% |
| LiveBench Instruction Following | LiveBench | 70.7% | 64.6% |
| IFBench | Artificial Analysis | 75.8% | 71.2% |
| Arena Instruction Following | Arena (LMArena) | 1475† | 1464† |
| Human preference | |||
| Arena Text | Arena (LMArena) | 1477† | 1467† |
| EQ-Bench 4 | EQ-Bench | 1294† | 1224† |
| Arena Creative Writing | Arena (LMArena) | 1448† | 1429† |
| Arena Multi-turn | Arena (LMArena) | 1484† | 1472† |
| Arena Longer Queries | Arena (LMArena) | 1487† | 1468† |
| Multimodal | |||
| Arena Vision | Arena (LMArena) | 1297† | 1271† |
| LiveBench Design | LiveBench | 70.3%† | 76.0%† |
| MMMU-Pro | Artificial Analysis | 79.9% | 80.7% |
| MMMU-Pro (Vals) | Vals AI | 88.3% | 86.5% |
| MortgageTax | Vals AI | 68.8% | 67.3%† |
| SAGE | Vals AI | 51.5% | 47.0% |
| Blueprint-Bench 2 | Epoch AI Benchmarking Hub | 36.2%† | 30.8%† |
| Long context | |||
| AA-LCR | Artificial Analysis | 84.3% | 83.0% |
| Arena Document | Arena (LMArena) | 1483† | 1477† |
| MLCR | Artificial Analysis | 28.9% | 27.2% |
| Composite | |||
| Epoch Capabilities Index | Epoch AI Benchmarking Hub | 159.7† | 160.1† |
| LiveBench 2.0 | LiveBench | 68.7%† | 75.0%† |
| LiveBench 1.0 | LiveBench | 80.2% | 77.9% |
| AA Intelligence Index v4.3.2 | Artificial Analysis | 38.4 | 42.1 |
| Vals RSI Index | Vals AI | 16.5% | – |
| Vals Multimodal Index | Vals AI | 68.1% | 65.1%† |
| Safety & honesty | |||
| FORTRESS | Scale AI SEAL | 16.3% | – |
Data as of 2026-10-25. Best configuration of each model; every score links to its source on the model pages.
What changed
- GPT-5.5 (xhigh): 1 new result (AA-Briefcase v1.1).
- GPT-5.5 (xhigh): 2 new results (Harvey's Legal Agent Benchmark v1, Vals RSI Index).
- GPT-5.6 Terra (max): 1 new result (Harvey's Legal Agent Benchmark v1).
- GPT-5.5 (xhigh): 1 score revision.
- GPT-5.6 Terra (max): 1 score revision.
- GPT-5.6 Terra (max): BenchLeader Index 63.8 → 64.4.
- GPT-5.5 (xhigh): 6 new results (USAMO 2026, AutomationBench, GDP.pdf (AA)…).
- GPT-5.6 Terra (max): 5 new results (AutomationBench, GDP.pdf (AA), MLCR…).
- GPT-5.5 (xhigh): BenchLeader Index 66.2 → 65.7.
- GPT-5.5 (xhigh): 1 score revision.
Related comparisons
- GPT-5.5 vs Claude Opus 5.5
- GPT-5.5 vs Gemini 4 Argon
- GPT-5.5 vs Muse Wonder Full
- GPT-5.6 Terra vs Claude Opus 5.5
- GPT-5.6 Terra vs Gemini 4 Argon
- GPT-5.6 Terra vs Muse Wonder Full
- GPT-5.6 Terra vs Claude Fable 5.1
- GPT-5.4 vs GPT-5.6 Terra
Rankings: Best LLM overall · Best LLM for agents · Best cheap LLMs
GPT-5.5 vs GPT-5.6 Terra: questions
- Is GPT-5.5 better than GPT-5.6 Terra?
- GPT-5.5 (xhigh) and GPT-5.6 Terra (max) are neck and neck on quality (66.1 vs 64.4, within the ±6.2 margin). The BenchLeader Index combines every independent quality benchmark; the two are within the margin of error as of 2026-10-25, so check the category scores for your use.
- Which is cheaper, GPT-5.5 or GPT-5.6 Terra, and will that change?
- GPT-5.6 Terra is cheaper today: $4.50 against $11.25 per million tokens, blended at three input tokens per output token. No price change has been announced for either.
- Is GPT-5.5 better than GPT-5.6 Terra for coding?
- GPT-5.6 Terra scores higher in coding (65 vs 61 on the category index, where 50 is average). On SciCode, the top shared coding benchmark, it is 55.8% for GPT-5.5 against 55.0% for GPT-5.6 Terra.
- Is GPT-5.5 better than GPT-5.6 Terra for agents and tool use?
- GPT-5.5 scores higher in agentic tasks (62 vs 59 on the category index, where 50 is average). On τ³-Banking (AA), the top shared agents & tools benchmark, it is 39.0% for GPT-5.5 against 40.2% for GPT-5.6 Terra.
- Which is better for long documents?
- They are level on long-context benchmarks (67 vs 67). Both accept 1,050,000 tokens of context.
- Which has lower latency?
- GPT-5.5 (xhigh) answers first: 39.1 s against 101.0 s to the first answer token, as Artificial Analysis measures it. Reasoning effort drives most of this: a higher setting thinks longer before it answers.
- Which is faster, GPT-5.5 or GPT-5.6 Terra?
- GPT-5.6 Terra streams faster: 126 against 86 output tokens per second.
- Do independent benchmarks agree on GPT-5.5 vs GPT-5.6 Terra?
- Across the 55 benchmarks both have, GPT-5.5 leads 28, GPT-5.6 Terra leads 26 and 1 is a tie. Independent sources split: GPT-5.5 leads on Arena Text; GPT-5.6 Terra leads on AA Intelligence Index v4.3.2.
- When was GPT-5.6 Terra released?
- GPT-5.6 Terra was released on 9 Jul 2026.