Head-to-head comparison

Claude Opus 5.5 vs. GPT-5.6 Luna

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

shared result series: 194
distinct benchmarks: 25
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 5.5 and GPT-5.6 Luna
Attribute	Claude Opus 5.5	GPT-5.6 Luna
Provider	Anthropic	OpenAI
Released	Sep 22, 2026	Jul 9, 2026
Availability	Active	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	June 2026	February 16, 2026
Technical sources	Model	Model, Context, Knowledge cutoff

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 5.5 and GPT-5.6 Luna
Price type	Claude Opus 5.5	GPT-5.6 Luna
API input	$4	$0.2 ≤272K / $0.4 >272K
API output	$20	$1.2 ≤272K / $1.8 >272K
Cache read	$0.2	$0.02 ≤272K / $0.04 >272K
Cache write (5 min.)	$5	$0.25 ≤272K / $0.5 >272K
Cache write (1 hr.)	$8	Not listed
Price verified	09/22/2026 Source	09/22/2026 Source

Claude Opus 5.5GPT-5.6 Luna

API inputUSD per 1M tokens, base tier

Claude Opus 5.5$4

GPT-5.6 Luna$0.2

API outputUSD per 1M tokens, base tier

Claude Opus 5.5$20

GPT-5.6 Luna$1.2

Cache readUSD per 1M tokens, base tier

Claude Opus 5.5$0.2

GPT-5.6 Luna$0.02

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.

Provider pricing for Claude Opus 5.5 and GPT-5.6 Luna
Model	Provider	Purchase route and tariff	Input per 1M tokens	Output per 1M tokens	Source
Claude Opus 5.5	Anthropic	Direct from developerStandard API	Lowest listed price: $4	Lowest listed price: $20	Source09/22/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock	Lowest listed price: $4	Lowest listed price: $20	Source10/17/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock/eu-west-1	$4.4	$22	Source10/17/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock/us-east-1	$4.4	$22	Source10/17/2026
	Anthropic	Via OpenRouteranthropic	Lowest listed price: $4	Lowest listed price: $20	Source10/17/2026
	Anthropic	Via OpenRouteranthropic/fast	$8	$40	Source10/17/2026
	Azure	Via OpenRouterazure/global	Lowest listed price: $4	Lowest listed price: $20	Source10/17/2026
	Azure	Via OpenRouterazure/us	$4.4	$22	Source10/17/2026
	Claude Platform on AWS	Via OpenRouterclaude-on-aws	Lowest listed price: $4	Lowest listed price: $20	Source10/17/2026
	Google	Via OpenRoutergoogle-vertex/europe	$4.4	$22	Source10/17/2026
	Google	Via OpenRoutergoogle-vertex/global	Lowest listed price: $4	Lowest listed price: $20	Source10/17/2026
	Google	Via OpenRoutergoogle-vertex/us	$4.4	$22	Source10/17/2026
GPT-5.6 Luna	OpenAI	Direct from developerUp to 272,000 context tokens	$0.2	$1.2	Source09/22/2026
	OpenAI	Direct from developerAbove 272,000 context tokens	$0.4	$1.8	Source09/22/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock/us-east-1	$0.22	$1.32	Source10/17/2026
	Azure	Via OpenRouterazure	$0.2	$1.2	Source10/17/2026
	Azure	Via OpenRouterazure/eu	$0.22	$1.32	Source10/17/2026
	Azure	Via OpenRouterazure/us	$0.22	$1.32	Source10/17/2026
	OpenAI	Via OpenRouteropenai	$0.2	$1.2	Source10/17/2026
	OpenAI	Via OpenRouteropenai/fast	$0.4	$2.4	Source10/17/2026
	OpenAI	Via OpenRouteropenai/flex	Lowest listed price: $0.1	Lowest listed price: $0.6	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.

Not enough directly matched categories for a reliable radar

Only 0 of at least 5 categories have comparable, direct model measurements. The benchmark tables below show the available evidence without filling missing axes.

Claude Opus 5.5GPT-5.6 Luna

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

Claude Opus 5.579.259 %

GPT-5.6 Luna61.481 %

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

Claude Opus 5.566.646 %

GPT-5.6 Luna44.55 %

CyberBench v1.1Overall. Higher is better. Test setup not documented as identical

Claude Opus 5.555.357 %

GPT-5.6 Luna73.631 %

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

Claude Opus 5.575.938 %

GPT-5.6 Luna67.116 %

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

Claude Opus 5.558.587 %

GPT-5.6 Luna55.044 %

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

Claude Opus 5.53.75 %

GPT-5.6 Luna1.25 %

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

Claude Opus 5.595.056 %

GPT-5.6 Luna61.778 %

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

Claude Opus 5.550.481 %

GPT-5.6 Luna36.538 %

LMArena Text, Style ControlOverall. Higher is better. Test setup not documented as identical

Claude Opus 5.51,508.083

GPT-5.6 Luna1,452.509

LMArena Vision, Style ControlOverall. Higher is better. Test setup not documented as identical

Claude Opus 5.51,292.688

GPT-5.6 Luna1,257.662

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

Claude Opus 5.549.797 %

GPT-5.6 Luna42.391 %

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

Claude Opus 5.591.43 %

GPT-5.6 Luna84.391 %

Key to the marks:better valuebetter, but not conclusivetie

Benchmark scores for Claude Opus 5.5 and GPT-5.6 Luna
Benchmark and task	Claude Opus 5.5	GPT-5.6 Luna	Source
BioMysteryBenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Harness: Terminus 2, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Harness: Terminus 2, Output limit: 128,000 tokens	Higher measured value79.259 %	61.481 %	Vals AI Source details Data as of: 10/12/2026
Code MigrationOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value66.646 %	44.55 %	Vals AI Source details Data as of: 10/12/2026
CyberBench v1.1Overall Test details Test setup not documented as identicalNo direct winnerVersion: 1.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	55.357 %	Higher measured value73.631 %	Vals AI Source details Data as of: 10/12/2026
EMBOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value75.938 %	67.116 %	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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value58.587 %	55.044 %	Vals AI Source details Data as of: 10/12/2026
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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value3.75 %	1.25 %	Vals AI Source details Data as of: 10/12/2026
IOIOverall Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value95.056 %	61.778 %	Vals AI Source details Data as of: 10/14/2026
Legal Research BenchOverall · All-pass Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: all-pass rateScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value50.481 %	36.538 %	Vals AI Source details Data as of: 10/12/2026
LMArena Text, Style ControlOverall Test details Test setup not documented as identicalNo direct winnerVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 5.5: Snapshot: claude-opus-5.5-high, Reasoning: high, Harness: Arena Text, style control GPT-5.6 Luna: Snapshot: gpt-5.6-luna-xhigh, Reasoning: xhigh, Harness: Arena Text, style controlClaude Opus 5.5: Arena rating from 7,687 published pairwise votes.GPT-5.6 Luna: Arena rating from 41,103 published pairwise votes.	Higher measured value1,508.083 95% confidence interval: ±7.535The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,452.509 95% confidence interval: ±4.306The 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 Test setup not documented as identicalNo direct winnerVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 5.5: Snapshot: claude-opus-5.5-high, Reasoning: high, Harness: Arena Vision, style control GPT-5.6 Luna: Snapshot: gpt-5.6-luna-xhigh, Reasoning: xhigh, Harness: Arena Vision, style controlClaude Opus 5.5: Arena rating from 2,508 published pairwise votes.GPT-5.6 Luna: Arena rating from 11,086 published pairwise votes.	Higher measured value1,292.688 95% confidence interval: ±12.73The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,257.662 95% confidence interval: ±7.463The 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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 30,000 tokens	Higher measured value49.797 %	42.391 %	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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 30,000 tokens	Higher measured value91.43 %	84.391 %	Vals AI Source details Data as of: 10/13/2026
MysteryMechanismOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value49.55 %	14.414 %	Vals AI Source details Data as of: 10/12/2026
ProgramBenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: fully resolved rateScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value18.5 %	0 %	Vals AI Source details Data as of: 10/12/2026
ProofBenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value100 %	60 %	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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value70.636 %	61.164 %	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 5.5: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 30,000 tokens	Higher measured value45.831 %	44.22 %	Vals AI Source details Data as of: 10/08/2026
SRE BenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: fully solved rateScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value33.588 %	1.527 %	Vals AI Source details Data as of: 10/14/2026
Tax Agent BenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value45.573 %	24.815 %	Vals AI Source details Data as of: 10/12/2026
Terminal-Bench 2.1Overall Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: high, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value87.64 %	79.026 %	Vals AI Source details Data as of: 09/28/2026
Terminal-Bench 4.0Overall Test details Test setup not documented as identicalNo direct winnerVersion: 4.0Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value65.152 %	11.616 %	Vals AI Source details Data as of: 10/13/2026
Terminal-Bench ScienceOverall Test details Test setup not documented as identicalNo direct winnerVersion: 0.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Harness: Mini-SWE-agent, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Harness: Mini-SWE-agent, Output limit: 128,000 tokens	Higher measured value47.143 %	0 %	Vals AI Source details Data as of: 10/14/2026
Vals IndexOverall Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: weighted index scoreScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value66.972 %	51.687 %	Vals AI Source details Data as of: 10/13/2026
Vibe Code Bench 1-100Overall Test details Test setup not documented as identicalNo direct winnerVersion: 1.0Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: xhigh, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Harness: OpenHands, Output limit: 128,000 tokens	Higher measured value30.361 %	22.594 %	Vals AI Source details Data as of: 10/14/2026
Vibe Code Bench v1.1Overall Test details Test setup not documented as identicalNo direct winnerVersion: 1.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Harness: OpenHands, Output limit: 128,000 tokens	Higher measured value90.294 %	77.055 %	Vals AI Source details Data as of: 10/12/2026
BioMysteryBenchHard Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Harness: Terminus 2, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Harness: Terminus 2, Output limit: 128,000 tokens	Higher measured value47.059 %	27.451 %	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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value65.528 %	36.067 %	Vals AI Source details Data as of: 10/12/2026
CyberBench v1.1Patch Test details Test setup not documented as identicalNo direct winnerVersion: 1.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value85.714 %	83.929 %	Vals AI Source details Data as of: 10/12/2026
EMBComps Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value76.405 %	54.573 %	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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value54.528 %	52.027 %	Vals AI Source details Data as of: 10/12/2026
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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	82.246 %	Higher measured value85.145 %	Vals AI Source details Data as of: 10/12/2026
IOIIOI 2024 Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value100 %	85 %	Vals AI Source details Data as of: 10/14/2026
Legal Research BenchAdministrative / Regulatory · All-pass Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: all-pass rateScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value65.152 %	48.485 %	Vals AI Source details Data as of: 10/12/2026
LMArena Text, Style ControlBusiness, management and finance Test details Test setup not documented as identicalNo direct winnerVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 5.5: Snapshot: claude-opus-5.5-high, Reasoning: high, Harness: Arena Text, style control GPT-5.6 Luna: Snapshot: gpt-5.6-luna-xhigh, Reasoning: xhigh, Harness: Arena Text, style controlClaude Opus 5.5: Arena rating from 1,370 published pairwise votes.GPT-5.6 Luna: Arena rating from 7,709 published pairwise votes.	Higher measured value1,492.054 95% confidence interval: ±16.446The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,461.658 95% confidence interval: ±7.593The 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 ControlCreative writing vision Test details Test setup not documented as identicalNo direct winnerVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 5.5: Snapshot: claude-opus-5.5-high, Reasoning: high, Harness: Arena Vision, style control GPT-5.6 Luna: Snapshot: gpt-5.6-luna-xhigh, Reasoning: xhigh, Harness: Arena Vision, style controlClaude Opus 5.5: Arena rating from 219 published pairwise votes.GPT-5.6 Luna: Arena rating from 969 published pairwise votes.	Higher measured value1,301.035 95% confidence interval: ±42.823The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,258.178 95% confidence interval: ±20.085The 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
ProgramBenchAlmost Resolved Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: almost-resolved rateScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value65 %	9 %	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 5.5: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 30,000 tokens	Higher measured value32.54 %	31.35 %	Vals AI Source details Data as of: 10/08/2026
SRE BenchCapability Score Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: capability scoreScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value53.562 %	6.361 %	Vals AI Source details Data as of: 10/14/2026
Tax Agent BenchControversy & Precedence Analysis Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value30 %	10 %	Vals AI Source details Data as of: 10/12/2026
Terminal-Bench 2.1Easy Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: high, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value100 %	83.333 %	Vals AI Source details Data as of: 09/28/2026
Terminal-Bench 4.0Hardware Test details Test setup not documented as identicalNo direct winnerVersion: 4.0Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value60 %	0 %	Vals AI Source details Data as of: 10/13/2026
Terminal-Bench ScienceEarth Sciences Test details Test setup not documented as identicalNo direct winnerVersion: 0.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Harness: Mini-SWE-agent, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Harness: Mini-SWE-agent, Output limit: 128,000 tokens	Higher measured value37.5 %	0 %	Vals AI Source details Data as of: 10/14/2026
Vals IndexCode Migration Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: benchmark scoreScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value68.901 %	44.774 %	Vals AI Source details Data as of: 10/13/2026
BioMysteryBenchHuman-solvable Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Harness: Terminus 2, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Harness: Terminus 2, Output limit: 128,000 tokens	Higher measured value86.758 %	69.406 %	Vals AI Source details Data as of: 10/12/2026
Code MigrationCOBOL Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	No direct winner70 %	No direct winner70 %	Vals AI Source details Data as of: 10/12/2026
CyberBench v1.1PoC Test details Test setup not documented as identicalNo direct winnerVersion: 1.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	25 %	Higher measured value63.333 %	Vals AI Source details Data as of: 10/12/2026
EMBDataroom Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value84.873 %	83.009 %	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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value48.111 %	43.285 %	Vals AI Source details Data as of: 10/12/2026
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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	No direct winner0 %	No direct winner0 %	Vals AI Source details Data as of: 10/12/2026
IOIIOI 2025 Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value100 %	49.833 %	Vals AI Source details Data as of: 10/14/2026
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 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	85.427 %	Higher measured value87.513 %	Vals AI Source details Data as of: 10/12/2026
LMArena Text, Style ControlChinese Test details Test setup not documented as identicalNo direct winnerVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 5.5: Snapshot: claude-opus-5.5-high, Reasoning: high, Harness: Arena Text, style control GPT-5.6 Luna: Snapshot: gpt-5.6-luna-xhigh, Reasoning: xhigh, Harness: Arena Text, style controlClaude Opus 5.5: Arena rating from 704 published pairwise votes.GPT-5.6 Luna: Arena rating from 3,212 published pairwise votes.	Higher measured value1,574.432 95% confidence interval: ±22.751The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,476.812 95% confidence interval: ±11.28The 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 ControlDiagram Test details Test setup not documented as identicalNo direct winnerVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Opus 5.5: Snapshot: claude-opus-5.5-high, Reasoning: high, Harness: Arena Vision, style control GPT-5.6 Luna: Snapshot: gpt-5.6-luna-xhigh, Reasoning: xhigh, Harness: Arena Vision, style controlClaude Opus 5.5: Arena rating from 589 published pairwise votes.GPT-5.6 Luna: Arena rating from 2,783 published pairwise votes.	Higher measured value1,324.12 95% confidence interval: ±25.101The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,279.537 95% confidence interval: ±11.779The 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
ProgramBenchFully Resolved Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: fully resolved rateScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value18.5 %	0 %	Vals AI Source details Data as of: 10/12/2026
SAGECalculus Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 30,000 tokens	Higher measured value83.642 %	64.506 %	Vals AI Source details Data as of: 10/08/2026
SRE BenchFully Solved Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: fully solved rateScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value33.588 %	1.527 %	Vals AI Source details Data as of: 10/14/2026
Tax Agent BenchControversy & Precedence Analysis Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value66.871 %	61.219 %	Vals AI Source details Data as of: 10/12/2026
Terminal-Bench 2.1Hard Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: high, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value81.111 %	70 %	Vals AI Source details Data as of: 09/28/2026
Terminal-Bench 4.0Media Test details Test setup not documented as identicalNo direct winnerVersion: 4.0Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value75 %	0 %	Vals AI Source details Data as of: 10/13/2026
Terminal-Bench ScienceEngineering Sciences Test details Test setup not documented as identicalNo direct winnerVersion: 0.1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Harness: Mini-SWE-agent, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Harness: Mini-SWE-agent, Output limit: 128,000 tokens	Higher measured value22.222 %	0 %	Vals AI Source details Data as of: 10/14/2026
Vals IndexEMB Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: benchmark scoreScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value75.938 %	67.116 %	Vals AI Source details Data as of: 10/13/2026
Code MigrationCode Quality Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: mean reviewer code-quality ratingScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value4.541 / 5	3.195 / 5	Vals AI Source details Data as of: 10/12/2026
EMBDCF Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	Higher measured value70.139 %	60.482 %	Vals AI Source details Data as of: 10/12/2026
Finance Agent (v2)Comparables Test details Test setup not documented as identicalNo direct winnerVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 5.5: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Luna: Reasoning: max, Output limit: 128,000 tokens	45.756 %	Higher measured value48.285 %	Vals AI Source details Data as of: 10/12/2026
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 5.5

Unavailable in this round

GPT-5.6 Luna

Unavailable in this round

Earlier tests

Pelican on a bicycle

A community classic for free-form SVG drawing.

Claude Opus 5.5

Reasoning (requested): high

Current attempt

Run date: Oct 1, 2026
API provider: openrouter
Requested API model: anthropic/claude-opus-5.5
API model reported in response: anthropic/claude-opus-5.5
Reasoning setting: high
Pinned endpoint: Anthropic | anthropic/claude-opus-5.5-20260921
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: 33.2 s

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

GPT-5.6 Luna

Reasoning (requested): high

Current attempt

Run date: Sep 7, 2026
API provider: openrouter
Requested API model: openai/gpt-5.6-luna
API model reported in response: openai/gpt-5.6-luna
Reasoning setting: high
Pinned endpoint: OpenAI | openai/gpt-5.6-luna-20260709
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: 49.9 s

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

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 5.5 and GPT-5.6 Luna with other leading models using the same data and benchmark logic.

View the complete LLM comparison

Claude Opus 5.5 vs. GPT-5.6 Luna

Change model selection

General specifications

API pricing compared

Shared benchmarks

Capability profile from matched benchmarks

Our tests

SVG short test

Claude Opus 5.5

GPT-5.6 Luna

Pelican on a bicycle

Winning one benchmark is not an overall verdict

Related LLM comparisons