Model comparison

GPT-5.5 vs GPT-5.6 Terra

Data verified July 23, 2026

Head-to-head evidence from 39 shared benchmark results across 7 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

GPT-5.5

OpenAI

73.51/100

Margin

0.9pts

← winning

GPT-5.6 Terra

OpenAI

72.57/100

0 category wins5 category wins

Public leaderboard positions: GPT-5.5 #9 (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 and GPT-5.6 Terra share 39 comparable benchmark results. 5 of 8 categories are comparable. 18 results are unique to GPT-5.5; 5 to GPT-5.6 Terra.

Updated July 23, 2026

Shared results: 39
GPT-5.5 only: 18
GPT-5.6 Terra only: 5
Comparable categories: 5 / 8

Pick GPT-5.5 if you want the stronger benchmark profile. GPT-5.6 Terra only becomes the better choice if knowledge is the priority or you want the cheaper token bill.

Confidence note. This is a partial-evidence comparison with 39 shared benchmark results across 7 evidence categories; 5 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.

Why this result

GPT-5.5 has the cleaner BenchAlign overall profile here, landing at 73.51 versus 72.57. It is a real lead, but still close enough that category-level strengths matter more than the headline number.

GPT-5.5 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $2.50 input / $15.00 output per 1M tokens for GPT-5.6 Terra. That is roughly 2.0x 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 scores and score margins for GPT-5.5 and GPT-5.6 Terra
Category	GPT-5.5	Δ	GPT-5.6 Terra
Knowledge	GPT-5.557.8	Margin→ 35.1	GPT-5.6 Terra92.9
Math	GPT-5.547.6	Margin→ 33.2	GPT-5.6 Terra80.8
Multimodal	GPT-5.570.4	Margin→ 10.3	GPT-5.6 Terra80.7
Agentic	GPT-5.581.6	Margin→ 5.8	GPT-5.6 Terra87.4
Coding	GPT-5.558.6	Margin→ 4.8	GPT-5.6 Terra63.4
Reasoning	GPT-5.585.0	MarginNo overlap	GPT-5.6 TerraNot measured

Decisive benchmark drivers

The largest measured benchmark gaps in this matchup, with exact reported values.

A · GPT-5.5B · GPT-5.6 Terra

FrontierMath v2 (Tiers 1-3)
Math
Source ↗
A 51.700%B 84.900%
Winner: GPT-5.6 TerraΔ 33.2
FrontierMath v2 (Tiers 1-3): GPT-5.5 scored 51.700%; GPT-5.6 Terra scored 84.900%. GPT-5.6 Terra wins this benchmark.
FrontierMath v2 (Tier 4)
Math
Source ↗
A 35.400%B 68.300%
Winner: GPT-5.6 TerraΔ 32.9
FrontierMath v2 (Tier 4): GPT-5.5 scored 35.400%; GPT-5.6 Terra scored 68.300%. GPT-5.6 Terra wins this benchmark.
Terminal-Bench 2.0
Agentic
Source ↗
A 82%B 87.4%
Winner: GPT-5.6 TerraΔ 5.4
Terminal-Bench 2.0: GPT-5.5 scored 82%; GPT-5.6 Terra scored 87.4%. GPT-5.6 Terra wins this benchmark.
SWE-bench Pro
Coding
Source ↗
A 58.6%B 63.4%
Winner: GPT-5.6 TerraΔ 4.8
SWE-bench Pro: GPT-5.5 scored 58.6%; GPT-5.6 Terra scored 63.4%. GPT-5.6 Terra wins this benchmark.
BrowseComp
Agentic
Source ↗
A 84.4%B 87.5%
Winner: GPT-5.6 TerraΔ 3.1
BrowseComp: GPT-5.5 scored 84.4%; GPT-5.6 Terra scored 87.5%. GPT-5.6 Terra wins this benchmark.

Operational comparison

Runtime and commercial metrics are compared only when both models have a complete sourced value.

Metric	GPT-5.5	GPT-5.6 Terra	Comparison
Input / output priceUSD per 1M tokens	GPT-5.5$5 input / $30 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-5.5Not available	GPT-5.6 TerraNot available	A complete speed comparison is not available.
First-answer latencyseconds to first token	GPT-5.5Not available	GPT-5.6 TerraNot available	A complete latency comparison is not available.
Context windowmaximum listed tokens	GPT-5.51M	GPT-5.6 Terra1M	Listed context windows are equal.

Benchmark Deep Dive

AgenticGPT-5.6 Terra wins

24 benchmarks

Benchmark	GPT-5.5	GPT-5.6 Terra	Result
Terminal-Bench 2.0Source	82%	87.4%	GPT-5.6 Terra leads
CyberGymSource	81.8%	81.8%	Tie
BrowseCompSource	84.4%	87.5%	GPT-5.6 Terra leads
OSWorld-VerifiedSource	78.7%	—	Not comparable
MCP AtlasSource	75.3%	—	Not comparable
ToolathlonSource	55.6%	53.1%	GPT-5.5 leads
τ²-bench resultsSource	93.9%	86.3%	GPT-5.5 leads
AA Agentic IndexSource	44.9%	47.4%	GPT-5.6 Terra leads
APEX-Agents-AASource	37.7%	38.9%	GPT-5.6 Terra leads
GDPval-AASource	49.5%	54.1%	GPT-5.6 Terra leads
GDPval-AASource	1490	1581	GPT-5.6 Terra leads
Gert LabsSource	72.93%	—	Not comparable
ResearchClawBenchSource	17.0%	—	Not comparable
OSWorld 2.0Source	13.0%	50.2%	GPT-5.6 Terra leads
JobBenchSource	42.7%	—	Not comparable
ExploitGymSource	13.4%	23.2%	GPT-5.6 Terra leads
AA BriefcaseSource	1154	—	Not comparable
AA AutomationBenchSource	42.1%	45.6%	GPT-5.6 Terra leads
AA EnterpriseOps-GymSource	46.6%	—	Not comparable
AA Harvey LABSource	86.3%	85.2%	GPT-5.5 leads
AA ITBenchSource	45.8%	51.0%	GPT-5.6 Terra leads
AA Tau3 BankingSource	31.3%	31.8%	GPT-5.6 Terra leads
terminalBenchHardSource	60.6%	57.6%	GPT-5.5 leads
aaTerminalBench21Source	84.3%	88%	GPT-5.6 Terra leads

CodingGPT-5.6 Terra wins

11 benchmarks

Benchmark	GPT-5.5	GPT-5.6 Terra	Result
SWE-bench ProSource	58.6%	63.4%	GPT-5.6 Terra leads
Terminal-Bench 2.0Source	82.0%	87.4%	GPT-5.6 Terra leads
Vibe Code BenchSource	69.85%	—	Not comparable
React Native EvalsSource	84.7%	—	Not comparable
cursorBench31Source	59.2%	—	Not comparable
cursorBench32Source	58.4%	64.9%	GPT-5.6 Terra leads
AA Coding IndexSource	74.9%	76.7%	GPT-5.6 Terra leads
AA-SciCodeSource	56.1%	53.9%	GPT-5.5 leads
FrontierCode 1.1 MainSource	43.0%	—	Not comparable
deepSweSource	—	69.6%	Not comparable
FrontierCode 1.1 ExtendedSource	—	55.8%	Not comparable

Reasoning

6 benchmarks

Benchmark	GPT-5.5	GPT-5.6 Terra	Result
MRCR v2 64K-128KSource	83.1%	—	Not comparable
MRCR v2 128K-256KSource	87.5%	—	Not comparable
ARC-AGI-2Source	85%	—	Not comparable
AA-LCRSource	74.3%	74.0%	GPT-5.5 leads
CritPtSource	27.1%	30.0%	GPT-5.6 Terra leads
ARC-AGI-3Source	—	0.8%	Not comparable

KnowledgeGPT-5.6 Terra wins

12 benchmarks

Benchmark	GPT-5.5	GPT-5.6 Terra	Result
GPQASource	93.6%	92.9%	GPT-5.5 leads
GPQA-DSource	93.6%	92.9%	GPT-5.5 leads
HLESource	52.2%	—	Not comparable
HLE w/o toolsSource	41.4%	—	Not comparable
Artificial Analysis Intelligence IndexSource	54.8%	55.0%	GPT-5.6 Terra leads
AA-GPQA DiamondSource	93.5%	92.5%	GPT-5.5 leads
AA-HLESource	44.3%	41.8%	GPT-5.5 leads
AA-Omniscience IndexSource	20.1%	-0.2%	GPT-5.5 leads
AA-Omniscience AccuracySource	56.9%	45.9%	GPT-5.5 leads
AA-Omniscience Hallucination RateSource	85.5%	85.2%	GPT-5.6 Terra leads
HealthBench ProfessionalSource	—	57.7%	Not comparable
HealthBench HardSource	—	32.7%	Not comparable

MathGPT-5.6 Terra wins

3 benchmarks

Benchmark	GPT-5.5	GPT-5.6 Terra	Result
FrontierMath (legacy)Source	51.7%	84.9%	GPT-5.6 Terra leads
FrontierMath v2 (Tiers 1-3)Source	51.700%	84.900%	GPT-5.6 Terra leads
FrontierMath v2 (Tier 4)Source	35.400%	68.300%	GPT-5.6 Terra leads

MultimodalGPT-5.6 Terra wins

5 benchmarks

Benchmark	GPT-5.5	GPT-5.6 Terra	Result
MMMU-ProSource	81.2%	80.7%	GPT-5.5 leads
MMMU-Pro w/ PythonSource	83.2%	82%	GPT-5.5 leads
OfficeQA ProSource	54.1%	—	Not comparable
AA-MMMU-ProSource	79.9%	80.7%	GPT-5.6 Terra leads
Design Arena WebsiteSource	1282	—	Not comparable

Inst. Following

1 benchmarks

Benchmark	GPT-5.5	GPT-5.6 Terra	Result
AA-IFBenchSource	75.9%	71.2%	GPT-5.5 leads

Frequently Asked Questions (6)

Which is better, GPT-5.5 or GPT-5.6 Terra?

GPT-5.5 is ahead on BenchLM's BenchAlign leaderboard, 73.51 to 72.57. The biggest single separator in this matchup is FrontierMath v2 (Tiers 1-3), where the scores are 51.700% and 84.900%.

Which is better for knowledge tasks, GPT-5.5 or GPT-5.6 Terra?

GPT-5.6 Terra has the edge for knowledge tasks in this comparison, averaging 92.9 versus 57.8. Inside this category, AA-Omniscience Index is the benchmark that creates the most daylight between them.

Which is better for coding, GPT-5.5 or GPT-5.6 Terra?

GPT-5.6 Terra has the edge for coding in this comparison, averaging 63.4 versus 58.6. Inside this category, cursorBench32 is the benchmark that creates the most daylight between them.

Which is better for math, GPT-5.5 or GPT-5.6 Terra?

GPT-5.6 Terra has the edge for math in this comparison, averaging 80.8 versus 47.6. Inside this category, FrontierMath (legacy) is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, GPT-5.5 or GPT-5.6 Terra?

GPT-5.6 Terra has the edge for agentic tasks in this comparison, averaging 87.4 versus 81.6. Inside this category, GDPval-AA is the benchmark that creates the most daylight between them.

Which is better for multimodal and grounded tasks, GPT-5.5 or GPT-5.6 Terra?

GPT-5.6 Terra has the edge for multimodal and grounded tasks in this comparison, averaging 80.7 versus 70.4. Inside this category, MMMU-Pro w/ Python is the benchmark that creates the most daylight between them.

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