Model comparison
GPT-5.5 Pro vs GPT-5.6 Terra
Head-to-head evidence from 5 shared benchmark results across 3 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.5 Pro #38 (Estimated); GPT-5.6 Terra #11 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.5 Pro and GPT-5.6 Terra share 5 comparable benchmark results. 3 of 8 categories are comparable. 2 results are unique to GPT-5.5 Pro; 39 to GPT-5.6 Terra.
Updated July 23, 2026- Shared results
- 5
- GPT-5.5 Pro only
- 2
- GPT-5.6 Terra only
- 39
- Comparable categories
- 3 / 8
Pick GPT-5.6 Terra if you want the stronger benchmark profile. GPT-5.5 Pro only becomes the better choice if agentic is the priority.
Confidence note. This is a partial-evidence comparison with 5 shared benchmark results across 3 evidence categories; 3 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
GPT-5.6 Terra is clearly ahead on the BenchAlign aggregate, 72.57 to 63.69. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.6 Terra's sharpest advantage is in knowledge, where it averages 92.9 against 57.2. The single biggest benchmark swing on the page is FrontierMath v2 (Tiers 1-3), 51.000% to 84.900%. GPT-5.5 Pro does hit back in agentic, so the answer changes if that is the part of the workload you care about most.
GPT-5.5 Pro is also the more expensive model on tokens at $30.00 input / $180.00 output per 1M tokens, versus $2.50 input / $15.00 output per 1M tokens for GPT-5.6 Terra. That is roughly 12.0x on output cost alone.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.5 Pro | Δ | GPT-5.6 Terra |
|---|---|---|---|
| Knowledge | GPT-5.5 Pro57.2 | Margin→ 35.7 | GPT-5.6 Terra92.9 |
| Math | GPT-5.5 Pro48.1 | Margin→ 32.7 | GPT-5.6 Terra80.8 |
| Agentic | GPT-5.5 Pro90.1 | Margin← 2.7 | GPT-5.6 Terra87.4 |
| Coding | GPT-5.5 ProNot measured | MarginNo overlap | GPT-5.6 Terra63.4 |
| Multimodal | GPT-5.5 ProNot measured | MarginNo overlap | GPT-5.6 Terra80.7 |
Decisive benchmark drivers
The largest measured benchmark gaps in this matchup, with exact reported values.
More
- Source ↗
FrontierMath v2 (Tiers 1-3)
MathA 51.000%B 84.900%Winner: GPT-5.6 TerraΔ 33.9FrontierMath v2 (Tiers 1-3): GPT-5.5 Pro scored 51.000%; GPT-5.6 Terra scored 84.900%. GPT-5.6 Terra wins this benchmark. - Source ↗
FrontierMath v2 (Tier 4)
MathA 39.600%B 68.300%Winner: GPT-5.6 TerraΔ 28.7FrontierMath v2 (Tier 4): GPT-5.5 Pro scored 39.600%; GPT-5.6 Terra scored 68.300%. GPT-5.6 Terra wins this benchmark. - Source ↗
BrowseComp
AgenticA 90.1%B 87.5%Winner: GPT-5.5 ProΔ 2.6BrowseComp: GPT-5.5 Pro scored 90.1%; GPT-5.6 Terra scored 87.5%. GPT-5.5 Pro wins this benchmark.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.5 Pro | GPT-5.6 Terra | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.5 Pro$30 input / $180 output | GPT-5.6 Terra$2.5 input / $15 output | GPT-5.6 Terra has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.5 ProNot available | GPT-5.6 TerraNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.5 ProNot available | GPT-5.6 TerraNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.5 Pro1M | GPT-5.6 Terra1M | Listed context windows are equal. |
Benchmark Deep Dive
AgenticGPT-5.5 Pro wins17 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-5.6 Terra | Result |
|---|---|---|---|
| BrowseCompSource | 90.1% | 87.5% | GPT-5.5 Pro leads |
| Terminal-Bench 2.0Source | — | 87.4% | Not comparable |
| OSWorld 2.0Source | — | 50.2% | Not comparable |
| CyberGymSource | — | 81.8% | Not comparable |
| ExploitGymSource | — | 23.2% | Not comparable |
| ToolathlonSource | — | 53.1% | Not comparable |
| AA Agentic IndexSource | — | 47.4% | Not comparable |
| τ²-bench resultsSource | — | 86.3% | Not comparable |
| GDPval-AASource | — | 54.1% | Not comparable |
| GDPval-AASource | — | 1581 | Not comparable |
| AA Harvey LABSource | — | 85.2% | Not comparable |
| AA ITBenchSource | — | 51.0% | Not comparable |
| AA Tau3 BankingSource | — | 31.8% | Not comparable |
| AA AutomationBenchSource | — | 45.6% | Not comparable |
| terminalBenchHardSource | — | 57.6% | Not comparable |
| aaTerminalBench21Source | — | 88% | Not comparable |
| APEX-Agents-AASource | — | 38.9% | Not comparable |
Coding7 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-5.6 Terra | Result |
|---|---|---|---|
| SWE-bench ProSource | — | 63.4% | Not comparable |
| Terminal-Bench 2.0Source | — | 87.4% | Not comparable |
| deepSweSource | — | 69.6% | Not comparable |
| FrontierCode 1.1 ExtendedSource | — | 55.8% | Not comparable |
| cursorBench32Source | — | 64.9% | Not comparable |
| AA Coding IndexSource | — | 76.7% | Not comparable |
| AA-SciCodeSource | — | 53.9% | Not comparable |
Reasoning3 benchmarks
KnowledgeGPT-5.6 Terra wins12 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-5.6 Terra | Result |
|---|---|---|---|
| HLESource | 57.2% | — | Not comparable |
| HLE w/o toolsSource | 43.1% | — | Not comparable |
| GPQASource | — | 92.9% | Not comparable |
| GPQA-DSource | — | 92.9% | Not comparable |
| HealthBench ProfessionalSource | — | 57.7% | Not comparable |
| HealthBench HardSource | — | 32.7% | Not comparable |
| Artificial Analysis Intelligence IndexSource | — | 55.0% | Not comparable |
| AA-GPQA DiamondSource | — | 92.5% | Not comparable |
| AA-HLESource | — | 41.8% | Not comparable |
| AA-Omniscience IndexSource | — | -0.2% | Not comparable |
| AA-Omniscience AccuracySource | — | 45.9% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 85.2% | Not comparable |
MathGPT-5.6 Terra wins3 benchmarks
Multimodal3 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-5.6 Terra | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 71.2% | Not comparable |
Frequently Asked Questions (4)
Which is better, GPT-5.5 Pro or GPT-5.6 Terra?
GPT-5.6 Terra is ahead on BenchLM's BenchAlign leaderboard, 72.57 to 63.69. The biggest single separator in this matchup is FrontierMath v2 (Tiers 1-3), where the scores are 51.000% and 84.900%.
Which is better for knowledge tasks, GPT-5.5 Pro or GPT-5.6 Terra?
GPT-5.6 Terra has the edge for knowledge tasks in this comparison, averaging 92.9 versus 57.2. GPT-5.5 Pro stays close enough that the answer can still flip depending on your workload.
Which is better for math, GPT-5.5 Pro or GPT-5.6 Terra?
GPT-5.6 Terra has the edge for math in this comparison, averaging 80.8 versus 48.1. Inside this category, FrontierMath v2 (Tiers 1-3) is the benchmark that creates the most daylight between them.
Which is better for agentic tasks, GPT-5.5 Pro or GPT-5.6 Terra?
GPT-5.5 Pro has the edge for agentic tasks in this comparison, averaging 90.1 versus 87.4. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.
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