Head-to-head comparison

Claude Fable 5.1 vs. Claude Opus 4.5

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

shared result series: 10
distinct benchmarks: 10
latest retrieval: 2026-09-29

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 Claude Opus 4.5
Attribute	Claude Fable 5.1	Claude Opus 4.5
Provider	Anthropic	Anthropic
Released	Sep 1, 2026	Nov 2025
Availability	Active	Active
Model type	Proprietary	Proprietary
Parameters	Not published	Not published
Architecture	Not published	Not published
Context window	1,000,000 tokens	200,000 tokens
Knowledge cutoff	June 2026	May 2025
Technical sources	Model	Model, Context

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 Claude Opus 4.5
Price type	Claude Fable 5.1	Claude Opus 4.5
API input	$10	$5
API output	$50	$25
Cache read	$0.25	$0.5
Cache write (5 min.)	$12.5	$6.25
Cache write (1 hr.)	$20	$10
Price verified	09/22/2026 Source	09/22/2026 Source

Claude Fable 5.1Claude Opus 4.5

API inputUSD per 1M tokens, base tier

Claude Fable 5.1$10

Claude Opus 4.5$5

API outputUSD per 1M tokens, base tier

Claude Fable 5.1$50

Claude Opus 4.5$25

Cache readUSD per 1M tokens, base tier

Claude Fable 5.1$0.25

Claude Opus 4.5$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.

Provider pricing for Claude Fable 5.1 and Claude Opus 4.5
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	Source10/07/2026
	Anthropic	Via OpenRouteranthropic	Lowest listed price: $10	Lowest listed price: $50	Source10/07/2026
	Azure	Via OpenRouterazure	Lowest listed price: $10	Lowest listed price: $50	Source10/07/2026
	Google	Via OpenRoutergoogle-vertex/global	Lowest listed price: $10	Lowest listed price: $50	Source10/07/2026
Claude Opus 4.5	Anthropic	Direct from developerStandard API	Lowest listed price: $5	Lowest listed price: $25	Source09/22/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock	Lowest listed price: $5	Lowest listed price: $25	Source10/07/2026
	Amazon Bedrock	Via OpenRouteramazon-bedrock/eu-west-1	$5.5	$27.5	Source10/07/2026
	Anthropic	Via OpenRouteranthropic	Lowest listed price: $5	Lowest listed price: $25	Source10/07/2026
	Azure	Via OpenRouterazure/global	Lowest listed price: $5	Lowest listed price: $25	Source10/07/2026
	Claude Platform on AWS	Via OpenRouterclaude-on-aws	Lowest listed price: $5	Lowest listed price: $25	Source10/07/2026
	Google	Via OpenRoutergoogle-vertex/global	Lowest listed price: $5	Lowest listed price: $25	Source10/07/2026

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 Fable 5.1

Claude Opus 4.5

Coding: 100 / 82.9 (1 benchmark family)

Reasoning: 100 / 85.1 (1 benchmark family)

Knowledge: 100 / 92.7 (1 benchmark family)

Finance: 100 / 97.4 (2 benchmark families)

Legal: 100 / 93.6 (1 benchmark family)

Multimodal: 100 / 89.5 (1 benchmark family)

Health: 100 / 87.8 (2 benchmark families)

Education: 100 / 92.7 (1 benchmark family)

10 matched rows from 10 benchmark families were considered. The radar shows 8 of 8 comparable categories.

Claude Fable 5.1Claude Opus 4.5

GPQA DiamondOverall. Higher is better. No documented setup difference

Claude Fable 5.193.434 %

Claude Opus 4.579.546 %

LegalBenchOverall. Higher is better. No documented setup difference

Claude Fable 5.188.511 %

Claude Opus 4.582.837 %

LiveCodeBench v6Overall. Higher is better. No documented setup difference

Claude Fable 5.190.515 %

Claude Opus 4.575.034 %

MedCodeOverall. Higher is better. No documented setup difference

Claude Fable 5.153.509 %

Claude Opus 4.545.174 %

MedScribeOverall. Higher is better. No documented setup difference

Claude Fable 5.191.294 %

Claude Opus 4.583.246 %

MMLU-ProOverall. Higher is better. No documented setup difference

Claude Fable 5.192.375 %

Claude Opus 4.585.59 %

MMMU-ProOverall. Higher is better. No documented setup difference

Claude Fable 5.190.636 %

Claude Opus 4.581.098 %

MortgageTaxOverall. Higher is better. No documented setup difference

Claude Fable 5.170.786 %

Claude Opus 4.568.68 %

SAGEOverall. Higher is better. No documented setup difference

Claude Fable 5.148.526 %

Claude Opus 4.545.002 %

TaxEval v2Overall. Higher is better. No documented setup difference

Claude Fable 5.175.961 %

Claude Opus 4.574.325 %

Key to the marks:better valuebetter, but not conclusivetie

Benchmark scores for Claude Fable 5.1 and Claude Opus 4.5
Benchmark and task	Claude Fable 5.1	Claude Opus 4.5	Source
GPQA DiamondOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner93.434 %	79.546 %	Vals AI Source details Data as of: 09/01/2026
LegalBenchOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner88.511 %	82.837 %	Vals AI Source details Data as of: 09/27/2026
LiveCodeBench v6Overall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner90.515 %	75.034 %	Vals AI Source details Data as of: 09/01/2026
MedCodeOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner53.509 %	45.174 %	Vals AI Source details Data as of: 09/26/2026
MedScribeOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner91.294 %	83.246 %	Vals AI Source details Data as of: 09/26/2026
MMLU-ProOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner92.375 %	85.59 %	Vals AI Source details Data as of: 09/01/2026
MMMU-ProOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner90.636 %	81.098 %	Vals AI Source details Data as of: 09/01/2026
MortgageTaxOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner70.786 %	68.68 %	Vals AI Source details Data as of: 09/01/2026
SAGEOverall Test details No documented difference in the test setupVersion: 1Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner48.526 %	45.002 %	Vals AI Source details Data as of: 09/26/2026
TaxEval v2Overall Test details No documented difference in the test setupVersion: 2Metric: accuracyScoring: Higher is betterClaude Opus 4.5: Snapshot: claude-opus-4-5-20251101	Winner75.961 %	74.325 %	Vals AI Source details Data as of: 09/01/2026
Key to the marks:better valuebetter, but not conclusivetie

Our model tests

Our tests

Compare how the models respond to the same prompt. Each test shows the latest attempt, with no subsequent fixes to the generated code. Earlier runs remain available in the test details. These results do not contribute to an overall score.

Pelican on a bicycle

A community classic for free-form SVG drawing.

Claude Fable 5.1

Reasoning (requested): high

Current attempt

Run date: 7 Sept 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.

Claude Opus 4.5

Reasoning (requested): high

Current attempt

Run date: 1 Oct 2026
API provider: openrouter
Requested API model: anthropic/claude-opus-4.5
API model reported in response: anthropic/claude-opus-4.5
Reasoning setting: high
Pinned endpoint: Anthropic | anthropic/claude-4.5-opus-20251124
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: 21.6 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 Claude Opus 4.5 with other leading models using the same data and benchmark logic.

View the complete LLM comparison