Head-to-head comparison

Claude Opus 4.8 vs. GPT-5.5

Compare published benchmark results from matching versions and cohorts, API pricing, and technical specifications. Any documented test setup differences remain visible.

shared result series: 260
distinct benchmarks: 30
latest retrieval: 2026-10-15

First modelSecond model

Specifications

General specifications

Release date, availability, context window, architecture, and published parameter counts at a glance. Undisclosed details remain marked as unavailable.

Specifications for Claude Opus 4.8 and GPT-5.5
Attribute	Claude Opus 4.8	GPT-5.5
Provider	Anthropic	OpenAI
Released	May 2026	Apr 23, 2026
Availability	Legacy	Active
Model type	Proprietary	Proprietary
Parameters	Not published	Not published
Architecture	Not published	Not published
Context window	1,000,000 tokens	1,050,000 tokens
Knowledge cutoff	January 2026	December 1, 2025
Technical sources	Model, Knowledge cutoff	Model

Pricing

API pricing compared

The table compares official standard API rates per 1M tokens, including published cache pricing. Batch, fast, priority, regional surcharges, tool calls, and cloud platform pricing are excluded.

API pricing for Claude Opus 4.8 and GPT-5.5
Price type	Claude Opus 4.8	GPT-5.5
API input	$5	$5 ≤272K / $10 >272K
API output	$25	$30 ≤272K / $45 >272K
Cache read	$0.5	$0.5 ≤272K / $1 >272K
Cache write (5 min.)	$6.25	Not listed
Cache write (1 hr.)	$10	Not listed
Price verified	09/22/2026 Source	09/22/2026 Source

Claude Opus 4.8GPT-5.5

API inputUSD per 1M tokens, base tier

Claude Opus 4.8$5

GPT-5.5$5

API outputUSD per 1M tokens, base tier

Claude Opus 4.8$25

GPT-5.5$30

Cache readUSD per 1M tokens, base tier

Claude Opus 4.8$0.5

GPT-5.5$0.5

Key to the marks:better valuebetter, but not conclusivetie

Pricing by provider

Direct developer pricing and provider endpoint tariffs routed through OpenRouter are listed separately. Prices are in USD per 1M tokens. Context-dependent direct tiers plus regional, Flex, Priority, and other OpenRouter tariffs remain individually identifiable.

No provider tariff for Claude Opus 4.8 is available in the stored OpenRouter snapshot. The official direct price is still shown.

Provider pricing for Claude Opus 4.8 and GPT-5.5
Model	Provider	Purchase route and tariff	Input per 1M tokens	Output per 1M tokens	Source
Claude Opus 4.8	Anthropic	Direct from developerStandard API	Lowest listed price: $5	Lowest listed price: $25	Source09/22/2026
GPT-5.5	OpenAI	Direct from developerUp to 272,000 context tokens	$5	$30	Source09/22/2026
	OpenAI	Direct from developerAbove 272,000 context tokens	$10	$45	Source09/22/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock/us-east-1	$5.5	$33	Source10/17/2026
	Azure	Via OpenRouterazure	$5	$30	Source10/17/2026
	Azure	Via OpenRouterazure/eu	$5.5	$33	Source10/17/2026
	Azure	Via OpenRouterazure/us	$5.5	$33	Source10/17/2026
	OpenAI	Via OpenRouteropenai	$5	$30	Source10/17/2026
	OpenAI	Via OpenRouteropenai/fast	$12.5	$75	Source10/17/2026
	OpenAI	Via OpenRouteropenai/flex	Lowest listed price: $2.5	Lowest listed price: $15	Source10/17/2026

Performance

Shared benchmarks

Only published results with the same benchmark version, task, metric, and comparison cohort are paired. Different reasoning levels, agents, harnesses, or output limits appear directly in the table.

Capability profile from matched benchmarks

Each axis averages directly matched benchmark families. A value of 100 means the stronger value within this pair, not a universal quality score.

Claude Opus 4.8

GPT-5.5

Coding: 100 / 98.9 (1 benchmark family)

Reasoning: 100 / 99.3 (1 benchmark family)

Mathematics: 99.4 / 100 (1 benchmark family)

Knowledge: 100 / 99.1 (1 benchmark family)

Finance: 100 / 100 (1 benchmark family)

Legal: 100 / 99.6 (1 benchmark family)

Multimodal: 99.7 / 99.8 (1 benchmark family)

Search: 98.2 / 100 (2 benchmark families)

77 matched rows from 5 benchmark families were considered. The radar shows 8 of 11 comparable categories.

Claude Opus 4.8GPT-5.5

BrowseCompOverall. Higher is better. No documented setup difference

Claude Opus 4.884.3 %

GPT-5.584.4 %

Code MigrationOverall. Higher is better. Test setup not documented as identical

Claude Opus 4.847.25 %

GPT-5.545.161 %

CorpFin v2Overall. Higher is better. Test setup not documented as identical

Claude Opus 4.866.706 %

GPT-5.568.415 %

EMBOverall. Higher is better. Test setup not documented as identical

Claude Opus 4.869.373 %

GPT-5.564.543 %

Finance Agent (v2)Overall. Higher is better. Test setup not documented as identical

Claude Opus 4.853.918 %

GPT-5.551.76 %

GPQA DiamondOverall. Higher is better. Test setup not documented as identical

Claude Opus 4.892.424 %

GPT-5.593.182 %

Harvey's Legal Agent BenchmarkOverall · Task fully resolved. Higher is better. Test setup not documented as identical

Claude Opus 4.89.583 %

GPT-5.53.75 %

Legal Research BenchOverall · All-pass. Higher is better. Test setup not documented as identical

Claude Opus 4.843.75 %

GPT-5.540.385 %

LegalBenchOverall. Higher is better. Test setup not documented as identical

Claude Opus 4.883.568 %

GPT-5.586.515 %

LiveCodeBench v6Overall. Higher is better. Test setup not documented as identical

Claude Opus 4.887.819 %

GPT-5.585.296 %

LMArena SearchOverall. Higher is better. No documented setup difference

Claude Opus 4.81,204.109

GPT-5.51,246.555

LMArena Text, Style ControlOverall. Higher is better. No documented setup difference

Claude Opus 4.81,474.25

GPT-5.51,476.692

Key to the marks:better valuebetter, but not conclusivetie

Benchmark scores for Claude Opus 4.8 and GPT-5.5
Benchmark and task	Claude Opus 4.8	GPT-5.5	Source
BrowseCompOverall Test details No documented difference in the test setupVersion: 1,266 tasksMetric: accuracyScoring: Higher is betterCross-vendor comparison table with browsing tools. Exact agent systems differ.	84.3 % Editorial selection from the vendor table, not a complete extract of the comparison cohort.	Winner84.4 % Editorial selection from the vendor table, not a complete extract of the comparison cohort.	OpenAI Source details Data as of: 07/09/2026
Code MigrationOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value47.25 %	45.161 %	Vals AI Source details Data as of: 10/12/2026
CorpFin v2Overall Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	66.706 %	Higher measured value68.415 %	Vals AI Source details Data as of: 08/12/2026
EMBOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value69.373 %	64.543 %	Vals AI Source details Data as of: 10/12/2026
Finance Agent (v2)Overall Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value53.918 %	51.76 %	Vals AI Source details Data as of: 10/12/2026
GPQA DiamondOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	92.424 %	Higher measured value93.182 %	Vals AI Source details Data as of: 09/01/2026
Harvey's Legal Agent BenchmarkOverall · Task fully resolved Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: task resolution rateScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value9.583 %	3.75 %	Vals AI Source details Data as of: 10/12/2026
Legal Research BenchOverall · All-pass Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: all-pass rateScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value43.75 %	40.385 %	Vals AI Source details Data as of: 10/12/2026
LegalBenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	83.568 %	Higher measured value86.515 %	Vals AI Source details Data as of: 10/13/2026
LiveCodeBench v6Overall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value87.819 %	85.296 %	Vals AI Source details Data as of: 09/01/2026
LMArena SearchOverall Test details No documented difference in the test setupVersion: searchMetric: Search Arena Bradley-Terry ratingScoring: Higher is betterClaude Opus 4.8: Snapshot: claude-opus-4-8, Harness: Arena Search GPT-5.5: Snapshot: gpt-5.5-search, Harness: Arena SearchClaude Opus 4.8: Arena rating from 106,304 published pairwise votes.GPT-5.5: Arena rating from 125,957 published pairwise votes.	1,204.109 95% confidence interval: ±5.622The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	Winner1,246.555 95% confidence interval: ±4.9The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	LMArena Source details Data as of: 10/13/2026
LMArena Text, Style ControlOverall Test details No documented difference in the test setupNo clear leadVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 4.8: Snapshot: claude-opus-4-8, Harness: Arena Text, style control GPT-5.5: Snapshot: gpt-5.5, Harness: Arena Text, style controlClaude Opus 4.8: Arena rating from 65,181 published pairwise votes.GPT-5.5: Arena rating from 70,990 published pairwise votes.	1,474.25 95% confidence interval: ±3.848The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	No clear lead1,476.692 95% confidence interval: ±3.689The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	LMArena Source details Data as of: 10/13/2026
LMArena Vision, Style ControlOverall Test details No documented difference in the test setupNo clear leadVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 4.8: Snapshot: claude-opus-4-8, Harness: Arena Vision, style control GPT-5.5: Snapshot: gpt-5.5, Harness: Arena Vision, style controlClaude Opus 4.8: Arena rating from 18,852 published pairwise votes.GPT-5.5: Arena rating from 27,993 published pairwise votes.	1,278.955 95% confidence interval: ±6.534The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	No clear lead1,285.781 95% confidence interval: ±5.856The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	LMArena Source details Data as of: 10/09/2026
MedCodeOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.5: Reasoning: xhigh, Temperature: 1, Output limit: 30,000 tokens	Higher measured value53.217 %	49.1 %	Vals AI Source details Data as of: 10/13/2026
MedScribeOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.5: Reasoning: xhigh, Temperature: 1, Output limit: 30,000 tokens	85.755 %	Higher measured value86.868 %	Vals AI Source details Data as of: 10/13/2026
MMLU-ProOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value89.585 %	88.144 %	Vals AI Source details Data as of: 09/01/2026
MMMU-ProOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	86.59 %	Higher measured value88.266 %	Vals AI Source details Data as of: 09/01/2026
MortgageTaxOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value69.912 %	68.76 %	Vals AI Source details Data as of: 09/01/2026
ProgramBenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: fully resolved rateScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value1 %	0.5 %	Vals AI Source details Data as of: 10/12/2026
Public Benefits Bench v1.1Overall Test details Test setup not documented as identicalNo direct winnerVersion: 1.1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value68.133 %	60.893 %	Vals AI Source details Data as of: 10/12/2026
SAGEOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.5: Reasoning: xhigh, Temperature: 1, Output limit: 30,000 tokens	Higher measured value54.788 %	51.532 %	Vals AI Source details Data as of: 10/08/2026
SkillsBenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Harness: OpenHands, Output limit: 128,000 tokens	59.227 %	Higher measured value62.209 %	Vals AI Source details Data as of: 09/27/2026
SWE-bench VerifiedOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value88.6 %	82.6 %	Vals AI Source details Data as of: 09/01/2026
Tax Agent BenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value29.999 %	21.762 %	Vals AI Source details Data as of: 10/12/2026
TaxEval v2Overall Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value75.634 %	74.98 %	Vals AI Source details Data as of: 09/01/2026
Terminal-Bench 2.0Overall Test details Test setup not documented as identicalNo direct winnerVersion: 2.0Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: high, Output limit: 128,000 tokens	70.037 %	Higher measured value73.202 %	Vals AI Source details Data as of: 06/04/2026
Terminal-Bench 2.1Overall Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: high, Output limit: 128,000 tokens	71.91 %	Higher measured value76.404 %	Vals AI Source details Data as of: 09/28/2026
Time Horizon Index: KSPOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: progressScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value11.833 %	8.333 %	Vals AI Source details Data as of: 10/07/2026
Vals Multimodal IndexOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1.2Metric: weighted index scoreScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value70.889 %	68.071 %	Vals AI Source details Data as of: 08/11/2026
Vibe Code Bench v1.1Overall Test details Test setup not documented as identicalNo direct winnerVersion: 1.1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Harness: OpenHands, Output limit: 128,000 tokens	Higher measured value82.725 %	69.847 %	Vals AI Source details Data as of: 10/12/2026
Code MigrationCLI Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value40.143 %	36.882 %	Vals AI Source details Data as of: 10/12/2026
CorpFin v2Exact Pages Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	64.336 %	Higher measured value65.618 %	Vals AI Source details Data as of: 08/12/2026
EMBComps Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value72.797 %	64.681 %	Vals AI Source details Data as of: 10/12/2026
Finance Agent (v2)Adjustments Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value48.387 %	45.74 %	Vals AI Source details Data as of: 10/12/2026
GPQA DiamondFew-Shot CoT Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	91.919 %	Higher measured value93.434 %	Vals AI Source details Data as of: 09/01/2026
Harvey's Legal Agent BenchmarkAntitrust Competition · Criteria passed Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: criteria pass rateScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value87.319 %	82.246 %	Vals AI Source details Data as of: 10/12/2026
Legal Research BenchAdministrative / Regulatory · All-pass Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: all-pass rateScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	43.939 %	Higher measured value53.03 %	Vals AI Source details Data as of: 10/12/2026
LegalBenchConclusion Tasks Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	88.937 %	Higher measured value89.644 %	Vals AI Source details Data as of: 10/13/2026
LiveCodeBench v6Easy Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value99.068 %	98.447 %	Vals AI Source details Data as of: 09/01/2026
LMArena Text, Style ControlOverall Test details No documented difference in the test setupNo clear leadVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 4.8: Snapshot: claude-opus-4-8-high, Reasoning: high, Harness: Arena Text, style control GPT-5.5: Snapshot: gpt-5.5-high, Reasoning: high, Harness: Arena Text, style controlClaude Opus 4.8: Arena rating from 64,112 published pairwise votes.GPT-5.5: Arena rating from 69,414 published pairwise votes.	No clear lead1,481.505 95% confidence interval: ±3.87The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,481.44 95% confidence interval: ±3.724The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	LMArena Source details Data as of: 10/13/2026
LMArena Vision, Style ControlOverall Test details No documented difference in the test setupNo clear leadVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 4.8: Snapshot: claude-opus-4-8-high, Reasoning: high, Harness: Arena Vision, style control GPT-5.5: Snapshot: gpt-5.5-high, Reasoning: high, Harness: Arena Vision, style controlClaude Opus 4.8: Arena rating from 18,341 published pairwise votes.GPT-5.5: Arena rating from 26,281 published pairwise votes.	No clear lead1,285.632 95% confidence interval: ±6.5The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,281.094 95% confidence interval: ±5.941The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	LMArena Source details Data as of: 10/09/2026
MMLU-ProBiology Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value94.7 %	94.003 %	Vals AI Source details Data as of: 09/01/2026
MortgageTaxNumerical Extraction Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value79.73 %	76.153 %	Vals AI Source details Data as of: 09/01/2026
ProgramBenchAlmost Resolved Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: almost-resolved rateScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value15.5 %	9.5 %	Vals AI Source details Data as of: 10/12/2026
SAGEAutomata Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.5: Reasoning: xhigh, Temperature: 1, Output limit: 30,000 tokens	Higher measured value41.666 %	40.476 %	Vals AI Source details Data as of: 10/08/2026
SkillsBenchNo Skills Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Harness: OpenHands, Output limit: 128,000 tokens	43.674 %	Higher measured value49.875 %	Vals AI Source details Data as of: 09/27/2026
SWE-bench Verified<15 min fix Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value92.784 %	91.753 %	Vals AI Source details Data as of: 09/01/2026
Tax Agent BenchControversy & Precedence Analysis Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value13.133 %	10 %	Vals AI Source details Data as of: 10/12/2026
TaxEval v2Correctness Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	64.513 %	Higher measured value65.495 %	Vals AI Source details Data as of: 09/01/2026
Terminal-Bench 2.0Easy Test details Test setup not documented as identicalNo direct winnerVersion: 2.0Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: high, Output limit: 128,000 tokens	Higher measured value91.667 %	85 %	Vals AI Source details Data as of: 06/04/2026
Terminal-Bench 2.1Easy Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: high, Output limit: 128,000 tokens	Higher measured value100 %	83.333 %	Vals AI Source details Data as of: 09/28/2026
Time Horizon Index: KSPProgress efficiency Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: progressScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value7.739 %	6.032 %	Vals AI Source details Data as of: 10/07/2026
Vals Multimodal IndexCorpFin v2 Test details Test setup not documented as identicalNo direct winnerVersion: 1.2Metric: benchmark scoreScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	65.967 %	Higher measured value69.58 %	Vals AI Source details Data as of: 08/11/2026
Code MigrationCOBOL Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	68.571 %	Higher measured value70 %	Vals AI Source details Data as of: 10/12/2026
CorpFin v2Max Fitting Context Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	69.814 %	Higher measured value70.047 %	Vals AI Source details Data as of: 08/12/2026
EMBDataroom Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value85.948 %	81.227 %	Vals AI Source details Data as of: 10/12/2026
Finance Agent (v2)All-Pass Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value43.517 %	39.562 %	Vals AI Source details Data as of: 10/12/2026
GPQA DiamondZero-Shot CoT Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	No direct winner92.929 %	No direct winner92.929 %	Vals AI Source details Data as of: 09/01/2026
Harvey's Legal Agent BenchmarkAntitrust Competition · Task fully resolved Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: task resolution rateScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	No direct winner0 %	No direct winner0 %	Vals AI Source details Data as of: 10/12/2026
Legal Research BenchAdministrative / Regulatory · Weighted partial credit Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: weighted partial-credit scoreScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value87.365 %	86.669 %	Vals AI Source details Data as of: 10/12/2026
LegalBenchInterpretation Tasks Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	82.703 %	Higher measured value83.836 %	Vals AI Source details Data as of: 10/13/2026
LiveCodeBench v6Hard Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.8: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.5: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value74.571 %	69.714 %	Vals AI Source details Data as of: 09/01/2026
LMArena Text, Style ControlBusiness, management and finance Test details No documented difference in the test setupNo clear leadVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 4.8: Snapshot: claude-opus-4-8, Harness: Arena Text, style control GPT-5.5: Snapshot: gpt-5.5, Harness: Arena Text, style controlClaude Opus 4.8: Arena rating from 12,774 published pairwise votes.GPT-5.5: Arena rating from 14,097 published pairwise votes.	No clear lead1,486.06 95% confidence interval: ±6.336The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,485.259 95% confidence interval: ±6.304The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	LMArena Source details Data as of: 10/13/2026
LMArena Vision, Style ControlChinese Test details No documented difference in the test setupNo clear leadVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 4.8: Snapshot: claude-opus-4-8, Harness: Arena Vision, style control GPT-5.5: Snapshot: gpt-5.5, Harness: Arena Vision, style controlClaude Opus 4.8: Arena rating from 1,131 published pairwise votes.GPT-5.5: Arena rating from 1,741 published pairwise votes.	No clear lead1,334.517 95% confidence interval: ±19.635The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,328.904 95% confidence interval: ±17.005The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	LMArena Source details Data as of: 10/09/2026
Key to the marks:better valuebetter, but not conclusivetie

Our model tests

Our tests

SVG short test

One SVG prompt and fixed output settings. Captures are shown only with 0 reported reasoning tokens or documented lack of reasoning controls. Identical test conditions do not make the models' internal compute identical.

Shared test round: 4ae5d8eeb9a9

Claude Opus 4.8

Unavailable in this round

GPT-5.5

Unavailable in this round

Earlier tests

Pelican on a bicycle

A community classic for free-form SVG drawing.

Claude Opus 4.8

Reasoning (requested): high

Current attempt

Run date: Oct 1, 2026
API provider: openrouter
Requested API model: anthropic/claude-opus-4.8
API model reported in response: anthropic/claude-opus-4.8
Reasoning setting: high
Pinned endpoint: Anthropic | anthropic/claude-4.8-opus-20260528
Temperature: Provider default
Token limit including reasoning: 8,192 tokens
Test protocol: community-visual-tests-v1
Technical checks: Passed, not a quality rating
Response time: 18 s

Visually reviewed. This individual test does not establish overall model quality.

GPT-5.5

Reasoning (requested): high

Current attempt

Run date: Oct 1, 2026
API provider: openrouter
Requested API model: openai/gpt-5.5
API model reported in response: openai/gpt-5.5
Reasoning setting: high
Pinned endpoint: OpenAI | openai/gpt-5.5-20260423
Temperature: Provider default
Token limit including reasoning: 8,192 tokens
Test protocol: community-visual-tests-v1
Technical checks: Passed, not a quality rating
Response time: 25.9 s

Visually reviewed. This individual test does not establish overall model quality.

Earlier attempts (1)

Sep 7, 2026API request failedReasoning setting: high

Prompt and test conditions

Generate an SVG of a pelican riding a bicycle

Token limit including reasoning: 8,192 tokens

Task origin (Simon Willison)

How to read this comparison

Winning one benchmark is not an overall verdict

Your workload, budget, and required context length matter most. A coding benchmark says little about visual understanding or agent performance.

The standard price table uses direct developer rates. The provider comparison labels OpenRouter endpoints, regions, and special tariffs separately.

Every result links to its measurement source and retrieval date. Labels distinguish vendor reports, official benchmark leaderboards, and independent evaluations. Disputed or archived results are excluded.

More matchups

Compare Claude Opus 4.8 and GPT-5.5 with other leading models using the same data and benchmark logic.

View the complete LLM comparison

Claude Opus 4.8 vs. GPT-5.5

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General specifications

API pricing compared

Shared benchmarks

Capability profile from matched benchmarks

Our tests

SVG short test

Claude Opus 4.8

GPT-5.5

Pelican on a bicycle

Winning one benchmark is not an overall verdict

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