Head-to-head comparison

Claude Fable 5.1 vs. GPT-5.6 Terra

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

shared result series: 234
distinct benchmarks: 31
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 Fable 5.1 and GPT-5.6 Terra
Attribute	Claude Fable 5.1	GPT-5.6 Terra
Provider	Anthropic	OpenAI
Released	Sep 1, 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 Fable 5.1 and GPT-5.6 Terra
Price type	Claude Fable 5.1	GPT-5.6 Terra
API input	$10	$2 ≤272K / $4 >272K
API output	$50	$12 ≤272K / $18 >272K
Cache read	$0.25	$0.2 ≤272K / $0.4 >272K
Cache write (5 min.)	$12.5	$2.5 ≤272K / $5 >272K
Cache write (1 hr.)	$20	Not listed
Price verified	09/22/2026 Source	09/22/2026 Source

Claude Fable 5.1GPT-5.6 Terra

API inputUSD per 1M tokens, base tier

Claude Fable 5.1$10

GPT-5.6 Terra$2

API outputUSD per 1M tokens, base tier

Claude Fable 5.1$50

GPT-5.6 Terra$12

Cache readUSD per 1M tokens, base tier

Claude Fable 5.1$0.25

GPT-5.6 Terra$0.2

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 Fable 5.1 and GPT-5.6 Terra
Model	Provider	Purchase route and tariff	Input per 1M tokens	Output per 1M tokens	Source
Claude Fable 5.1	Anthropic	Direct from developerStandard API	Lowest listed price: $10	Lowest listed price: $50	Source09/22/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock	Lowest listed price: $10	Lowest listed price: $50	Source10/17/2026
	Anthropic	Via OpenRouteranthropic	Lowest listed price: $10	Lowest listed price: $50	Source10/17/2026
	Azure	Via OpenRouterazure	Lowest listed price: $10	Lowest listed price: $50	Source10/17/2026
	Google	Via OpenRoutergoogle-vertex/global	Lowest listed price: $10	Lowest listed price: $50	Source10/17/2026
GPT-5.6 Terra	OpenAI	Direct from developerUp to 272,000 context tokens	$2	$12	Source09/22/2026
	OpenAI	Direct from developerAbove 272,000 context tokens	$4	$18	Source09/22/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock/us-east-1	$2.2	$13.2	Source10/17/2026
	Azure	Via OpenRouterazure	$2	$12	Source10/17/2026
	Azure	Via OpenRouterazure/eu	$2.2	$13.2	Source10/17/2026
	Azure	Via OpenRouterazure/us	$2.2	$13.2	Source10/17/2026
	OpenAI	Via OpenRouteropenai	$2	$12	Source10/17/2026
	OpenAI	Via OpenRouteropenai/fast	$4	$24	Source10/17/2026
	OpenAI	Via OpenRouteropenai/flex	Lowest listed price: $1	Lowest listed price: $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 Fable 5.1GPT-5.6 Terra

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

Claude Fable 5.154.607 %

GPT-5.6 Terra47.804 %

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

Claude Fable 5.170.416 %

GPT-5.6 Terra72.084 %

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

Claude Fable 5.176.67 %

GPT-5.6 Terra66.205 %

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

Claude Fable 5.158.877 %

GPT-5.6 Terra54.436 %

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

Claude Fable 5.193.434 %

GPT-5.6 Terra90.909 %

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

Claude Fable 5.16.667 %

GPT-5.6 Terra0.833 %

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

Claude Fable 5.190.778 %

GPT-5.6 Terra87.611 %

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

Claude Fable 5.155.288 %

GPT-5.6 Terra41.346 %

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

Claude Fable 5.188.511 %

GPT-5.6 Terra85.105 %

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

Claude Fable 5.190.515 %

GPT-5.6 Terra85.93 %

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

Claude Fable 5.11,500.568

GPT-5.6 Terra1,465.897

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

Claude Fable 5.11,286.407

GPT-5.6 Terra1,268.044

Key to the marks:better valuebetter, but not conclusivetie

Benchmark scores for Claude Fable 5.1 and GPT-5.6 Terra
Benchmark and task	Claude Fable 5.1	GPT-5.6 Terra	Source
Code MigrationOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value54.607 %	47.804 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	70.416 %	Higher measured value72.084 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value76.67 %	66.205 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value58.877 %	54.436 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value93.434 %	90.909 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value6.667 %	0.833 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value90.778 %	87.611 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value55.288 %	41.346 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value88.511 %	85.105 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value90.515 %	85.93 %	Vals AI Source details Data as of: 09/01/2026
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 Fable 5.1: Snapshot: claude-fable-5.1-max, Reasoning: max, Harness: Arena Text, style control GPT-5.6 Terra: Snapshot: gpt-5.6-terra-xhigh, Reasoning: xhigh, Harness: Arena Text, style controlClaude Fable 5.1: Arena rating from 14,121 published pairwise votes.GPT-5.6 Terra: Arena rating from 42,358 published pairwise votes.	Higher measured value1,500.568 95% confidence interval: ±6.106The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,465.897 95% confidence interval: ±4.269The 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 Fable 5.1: Snapshot: claude-fable-5.1-max, Reasoning: max, Harness: Arena Vision, style control GPT-5.6 Terra: Snapshot: gpt-5.6-terra-xhigh, Reasoning: xhigh, Harness: Arena Vision, style controlClaude Fable 5.1: Arena rating from 4,648 published pairwise votes.GPT-5.6 Terra: Arena rating from 11,020 published pairwise votes.	Higher measured value1,286.407 95% confidence interval: ±9.66The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,268.044 95% confidence interval: ±7.452The 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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 30,000 tokens	Higher measured value53.509 %	43.414 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 30,000 tokens	Higher measured value91.294 %	82.869 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value92.375 %	86.659 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value90.636 %	86.474 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value70.786 %	67.329 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value7 %	0.5 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value100 %	74 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value74.899 %	62.382 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 30,000 tokens	Higher measured value48.526 %	47.003 %	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 Fable 5.1: Compute: max, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Harness: OpenHands, Output limit: 128,000 tokens	Higher measured value61.552 %	58.895 %	Vals AI Source details Data as of: 09/27/2026
SRE BenchOverall Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: fully solved rateScoring: Higher is betterClaude Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value22.901 %	9.542 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value49.194 %	30.035 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	75.961 %	Higher measured value76.166 %	Vals AI Source details Data as of: 09/01/2026
Terminal-Bench 2.1Overall Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: accuracyScoring: Higher is betterClaude Fable 5.1: Compute: high, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value85.019 %	77.528 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value58.081 %	22.727 %	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 Fable 5.1: Compute: max, Harness: Mini-SWE-agent, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Harness: Mini-SWE-agent, Output limit: 128,000 tokens	Higher measured value40 %	10 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value65.827 %	53.085 %	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 Fable 5.1: Compute: max, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Harness: OpenHands, Output limit: 128,000 tokens	Higher measured value28 %	14.822 %	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 Fable 5.1: Compute: max, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Harness: OpenHands, Output limit: 128,000 tokens	Higher measured value90.263 %	74.594 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value52.809 %	40.405 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	No direct winner87.5 %	No direct winner87.5 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value82.233 %	62.157 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value54.393 %	49.711 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value92.929 %	89.899 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value89.855 %	77.536 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: 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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value68.182 %	57.576 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value92.511 %	90.327 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value99.068 %	97.205 %	Vals AI Source details Data as of: 09/01/2026
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 Fable 5.1: Snapshot: claude-fable-5.1-max, Reasoning: max, Harness: Arena Text, style control GPT-5.6 Terra: Snapshot: gpt-5.6-terra-xhigh, Reasoning: xhigh, Harness: Arena Text, style controlClaude Fable 5.1: Arena rating from 2,589 published pairwise votes.GPT-5.6 Terra: Arena rating from 7,896 published pairwise votes.	Higher measured value1,485.231 95% confidence interval: ±11.847The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,466.115 95% confidence interval: ±7.508The 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 Test setup not documented as identicalNo direct winnerVersion: style-control-v1Metric: style-controlled Bradley-Terry ratingScoring: Higher is betterClaude Fable 5.1: Snapshot: claude-fable-5.1-max, Reasoning: max, Harness: Arena Vision, style control GPT-5.6 Terra: Snapshot: gpt-5.6-terra-xhigh, Reasoning: xhigh, Harness: Arena Vision, style controlClaude Fable 5.1: Arena rating from 260 published pairwise votes.GPT-5.6 Terra: Arena rating from 642 published pairwise votes.	Higher measured value1,340.8 95% confidence interval: ±36.169The Arena score measures human preference rather than a fixed capability test. The confidence interval, Arena category, and model configuration are part of the result.	1,313.871 95% confidence interval: ±24.287The 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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value96.095 %	93.026 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value77.583 %	74.324 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value53.5 %	15 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 30,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 30,000 tokens	34.524 %	Higher measured value38.889 %	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 Fable 5.1: Compute: max, Harness: OpenHands, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Harness: OpenHands, Output limit: 128,000 tokens	44.828 %	Higher measured value48.842 %	Vals AI Source details Data as of: 09/27/2026
SRE BenchCapability Score Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: capability scoreScoring: Higher is betterClaude Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value36.641 %	26.845 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value26.667 %	16.667 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	64.105 %	Higher measured value65.822 %	Vals AI Source details Data as of: 09/01/2026
Terminal-Bench 2.1Easy Test details Test setup not documented as identicalNo direct winnerVersion: 2.1Metric: accuracyScoring: Higher is betterClaude Fable 5.1: Compute: high, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	No direct winner100 %	No direct winner100 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: 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 Fable 5.1: Compute: max, Harness: Mini-SWE-agent, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Harness: Mini-SWE-agent, Output limit: 128,000 tokens	Higher measured value25 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value60.033 %	48.248 %	Vals AI Source details Data as of: 10/13/2026
Code MigrationCOBOL Test details Test setup not documented as identicalNo direct winnerVersion: 1Metric: accuracyScoring: Higher is betterClaude Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	60 %	Higher measured value70 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	53.333 %	Higher measured value56.667 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value86.736 %	82.161 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value47.773 %	42.756 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: xhigh, Output limit: 128,000 tokens	Higher measured value93.939 %	91.919 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: 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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value87.167 %	77.833 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value92.519 %	88.759 %	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 Fable 5.1: Compute: max, Temperature: 1, Output limit: 128,000 tokens GPT-5.6 Terra: Reasoning: max, Output limit: 128,000 tokens	Higher measured value86.902 %	83.178 %	Vals AI Source details Data as of: 10/13/2026
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 Fable 5.1

Unavailable in this round

GPT-5.6 Terra

Unavailable in this round

Earlier tests

Pelican on a bicycle

A community classic for free-form SVG drawing.

Claude Fable 5.1

Reasoning (requested): high

Current attempt

Run date: Sep 7, 2026
API provider: openrouter
Requested API model: anthropic/claude-fable-5.1
API model reported in response: anthropic/claude-fable-5.1
Reasoning setting: high
Pinned endpoint: Anthropic | anthropic/claude-fable-5.1-20260831
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: 27 s

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

GPT-5.6 Terra

Reasoning (requested): high

Current attempt

Run date: Sep 7, 2026
API provider: openrouter
Requested API model: openai/gpt-5.6-terra
API model reported in response: openai/gpt-5.6-terra
Reasoning setting: high
Pinned endpoint: OpenAI | openai/gpt-5.6-terra-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: 64.6 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 Fable 5.1 and GPT-5.6 Terra with other leading models using the same data and benchmark logic.

View the complete LLM comparison

Claude Fable 5.1 vs. GPT-5.6 Terra

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General specifications

API pricing compared

Shared benchmarks

Capability profile from matched benchmarks

Our tests

SVG short test

Claude Fable 5.1

GPT-5.6 Terra

Pelican on a bicycle

Winning one benchmark is not an overall verdict

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