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Claude Fable 5.1 vs Claude Opus 5.5

Updated October 20, 2026. 100 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace Claude Fable 5.1 Replace Claude Opus 5.5
Claude Fable 5.1Anthropic
Coding
89.1
Overall
53.4
Output $/M
$50.00
23
Claude Opus 5.5Anthropic
Coding
92.2
Overall
57.6
Output $/M
$20.00
73
vs boards won of 100 shared, 4 tied

Decision reading

Pick Claude Opus 5.5 for coding: it scores 92.2 on the Vibe Coding Index against 89.1 for Claude Fable 5.1.

Pick Claude Fable 5.1 when what matters is LiveBench coding or LiveBench browser, where it leads.

Model AClaude Fable 5.1Anthropic89.1/1002 independent benchmarksNo cost per solved taskModel BClaude Opus 5.5Anthropic92.2/1002 independent benchmarksNo cost per solved task
Shared results
100
Claude Fable 5.1 only
24
Claude Opus 5.5 only
5
Like-for-like categories
8 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

At a glance

Coding index
Claude Fable 5.1 89.1 from 2 benchmarks, Claude Opus 5.5 92.2 from 2 benchmarks.
Widest category
Agentic work, 7.3 points apart on average over 19 shared benchmarks.
Widest single gap
Time Horizon Index (Vals AI): Claude Fable 5.1 63.3% against Claude Opus 5.5 91.3%, 28.0 points apart on a 0 to 100 scale.
Output price
Claude Fable 5.1 $50.00 against Claude Opus 5.5 $20.00 per million output tokens, 2.5x apart.
Context window
Both take 1M tokens.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
CategoryClaude Fable 5.1BarsClaude Opus 5.5Ties
Coding120
Intelligence02
Agentic work6121 tie
Reasoning013
Math222 ties
Knowledge51
Web design08
General9151 tie
All shared boards23734 ties
CodingLike-for-likeFour of these boards feed the Vibe Coding Index120
Coding benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
LiveBench coding97.7%96.3%Claude Fable 5.1
LMArena WebDev17431807Claude Opus 5.5
AA Coding Index81.6Not measuredOnly Claude Fable 5.1 measured
LiveCodeBench (Vals AI)90.5%Not measuredOnly Claude Fable 5.1 measured
Terminal-Bench 4 (Vals AI)58.1%65.2%Claude Opus 5.5
Vibe Code Bench (Vals AI)90.3%90.3%Claude Opus 5.5
Code migration (Vals AI)54.6%66.7%Claude Opus 5.5
ProgramBench (Vals AI)7.0%18.5%Claude Opus 5.5
IOI (Vals AI)90.8%95.1%Claude Opus 5.5
Terminal-Bench 2.1 (Vals AI)85.0%87.6%Claude Opus 5.5
SWE-bench Multimodal (Vals AI)61.3%70.2%Claude Opus 5.5
Vibe Code Bench 1-100 (Vals AI)28.0%30.4%Claude Opus 5.5
SkillsBench (Vals AI)61.5%Not measuredOnly Claude Fable 5.1 measured
CyberBench (Vals AI)70.4%74.6%Claude Opus 5.5
SciCode63.1%66.9%Claude Opus 5.5
FrontierCode50.9%54.6%Claude Opus 5.5
FrontierSWE56.3%62.3%Claude Opus 5.5
GSO-Bench88.2%Not measuredOnly Claude Fable 5.1 measured
WeirdML92.9%Not measuredOnly Claude Fable 5.1 measured
MirrorCode73.3%77.4%Claude Opus 5.5
ALE-Bench2143.22147.4Claude Opus 5.5
LMArena Text: coding15311545Claude Opus 5.5
LMArena Text: software and IT15291538Claude Opus 5.5
LMArena WebDev: React17921855Claude Opus 5.5
LMArena WebDev: HTML16841753Claude Opus 5.5
LMArena WebDev: from an image17221753Claude Opus 5.5
Neither model has a result on the other 12 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index02
Intelligence benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
AA Intelligence Index53.457.6Claude Opus 5.5
Epoch Capabilities Index164.7166.8Claude Opus 5.5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index612
Agentic work benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
AA Agentic Index57.9Not measuredOnly Claude Fable 5.1 measured
Design Arena: agents building web apps13181318Tie
Design Arena: agents building full-stack apps1326Not measuredOnly Claude Fable 5.1 measured
Design Arena: agents building mobile apps12661323Claude Opus 5.5
Design Arena: agents building Godot games1327Not measuredOnly Claude Fable 5.1 measured
Design Arena: PowerPoint slides1328Not measuredOnly Claude Fable 5.1 measured
LiveBench research82.0%85.0%Claude Opus 5.5
LiveBench browser100.0%80.0%Claude Fable 5.1
LiveBench long agentic80.8%85.0%Claude Opus 5.5
SREBench (Vals AI)22.9%33.6%Claude Opus 5.5
Finance Agent (Vals AI)58.9%58.6%Claude Fable 5.1
Tax Agent Bench (Vals AI)49.2%45.6%Claude Fable 5.1
Legal Research Bench (Vals AI)55.3%50.5%Claude Fable 5.1
Harvey's Legal Agent Benchmark (Vals AI)Not measured9.2%Only Claude Opus 5.5 measured
Excel Modeling Benchmark (Vals AI)76.7%75.9%Claude Fable 5.1
BioMysteryBench (Vals AI)Not measured79.3%Only Claude Opus 5.5 measured
Terminal-Bench-Science (Vals AI)40.0%47.1%Claude Opus 5.5
Vals Science IndexNot measured58.7%Only Claude Opus 5.5 measured
Time Horizon Index (Vals AI)63.3%91.3%Claude Opus 5.5
CUA-bench (Vals AI)13.2%14.0%Claude Opus 5.5
Robo-bench (Vals AI)5.8%14.6%Claude Opus 5.5
APEX-Agents68.6%73.5%Claude Opus 5.5
Remote Labor Index17.9%21.3%Claude Opus 5.5
SpireClimb2.0%3.3%Claude Opus 5.5
Vending-Bench 2$5,422$9,235Claude Opus 5.5
LMArena Search12461213Claude Fable 5.1
Neither model has a result on the other 13 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index013
Reasoning benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
GPQA Diamond93.4%Not measuredOnly Claude Fable 5.1 measured
LiveBench reasoning91.7%92.2%Claude Opus 5.5
MysteryMechanism (Vals AI)47.8%49.5%Claude Opus 5.5
MMMU Pro (Vals AI)90.6%Not measuredOnly Claude Fable 5.1 measured
GPQA Diamond (Artificial Analysis run)93.7%Not measuredOnly Claude Fable 5.1 measured
Humanity's Last Exam (Artificial Analysis run)59.1%61.4%Claude Opus 5.5
GPQA Diamond (Epoch AI run)Not measured90.6%Only Claude Opus 5.5 measured
ARC-AGI97.5%98.5%Claude Opus 5.5
ARC-AGI-290.0%93.3%Claude Opus 5.5
Humanity's Last Exam46.5%Not measuredOnly Claude Fable 5.1 measured
Chess puzzles48.0%67.0%Claude Opus 5.5
Mystery game puzzles58.0%71.0%Claude Opus 5.5
EBR-bench57.1%71.4%Claude Opus 5.5
LMArena Text: hard prompts15261535Claude Opus 5.5
LMArena Text: expert15401550Claude Opus 5.5
LMArena Text: hard prompts in English15211533Claude Opus 5.5
LMArena Vision: diagrams13431345Claude Opus 5.5
LMArena Vision: homework13451362Claude Opus 5.5
Neither model has a result on the other 3 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index22
Math benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
OTIS Mock AIME100.0%100.0%Tie
FrontierMath, tiers 1 to 390.2%91.2%Claude Opus 5.5
FrontierMath, tier 487.8%95.0%Claude Opus 5.5
ProofBench100.0%100.0%Tie
LMArena Text: math15281508Claude Fable 5.1
LMArena Text: mathematical work15371506Claude Fable 5.1
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index51
Knowledge benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
MMLU Pro92.4%Not measuredOnly Claude Fable 5.1 measured
LegalBench (Vals AI)88.5%Not measuredOnly Claude Fable 5.1 measured
TaxEval (Vals AI)76.0%Not measuredOnly Claude Fable 5.1 measured
MortgageTax (Vals AI)70.8%Not measuredOnly Claude Fable 5.1 measured
MedCode (Vals AI)53.5%49.8%Claude Fable 5.1
SimpleQA Verified70.8%72.2%Claude Opus 5.5
LMArena Text: science15321522Claude Fable 5.1
LMArena Text: medicine and healthcare15301513Claude Fable 5.1
LMArena Text: legal and government15111510Claude Fable 5.1
LMArena Text: business and finance14931492Claude Fable 5.1
Neither model has a result on the other 7 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index08
Web design benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
Design Arena: websites13131336Claude Opus 5.5
Design Arena: UI components13391386Claude Opus 5.5
Design Arena: game dev13811458Claude Opus 5.5
Design Arena: data viz13441397Claude Opus 5.5
Design Arena: 3D13931477Claude Opus 5.5
Design Arena: all code categories13361390Claude Opus 5.5
Design Arena: SVG13001332Claude Opus 5.5
Design Arena: ASCII art1323Not measuredOnly Claude Fable 5.1 measured
LiveBench design83.4%86.9%Claude Opus 5.5
GeneralLike-for-likePublic boards, shown as published, kept out of the index915
General benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
Vals IndexNot measured70.2%Only Claude Opus 5.5 measured
LiveBench data analysis80.3%80.3%Tie
Public Benefits Bench (Vals AI)74.9%70.6%Claude Fable 5.1
SAGE (Vals AI)48.5%45.8%Claude Fable 5.1
MedScribe (Vals AI)91.3%91.4%Claude Opus 5.5
Long context reasoning (AA-LCR)85.3%84.7%Claude Fable 5.1
DTBench97.6%98.9%Claude Opus 5.5
LMCA65.5%68.2%Claude Opus 5.5
Furniture assembly70.0%83.3%Claude Opus 5.5
LMArena Text15121516Claude Opus 5.5
LMArena Text: instruction following15171536Claude Opus 5.5
LMArena Text: creative writing15081534Claude Opus 5.5
LMArena Vision13191321Claude Opus 5.5
LMArena Text: English15051517Claude Opus 5.5
LMArena Text: non-English15071507Claude Fable 5.1
LMArena Text: Chinese15861584Claude Fable 5.1
LMArena Text: German1502Not measuredOnly Claude Fable 5.1 measured
LMArena Text: Japanese1560Not measuredOnly Claude Fable 5.1 measured
LMArena Text: Korean1521Not measuredOnly Claude Fable 5.1 measured
LMArena Text: French15271505Claude Fable 5.1
LMArena Text: Spanish15211519Claude Fable 5.1
LMArena Text: Russian15191519Claude Opus 5.5
LMArena Text: Polish1524Not measuredOnly Claude Fable 5.1 measured
LMArena Text: multi-turn14931502Claude Opus 5.5
LMArena Text: longer queries15231531Claude Opus 5.5
LMArena Text: writing and language15091534Claude Opus 5.5
LMArena Text: entertainment and media14951511Claude Opus 5.5
LMArena Vision: English13131317Claude Opus 5.5
LMArena Vision: Chinese1391Not measuredOnly Claude Fable 5.1 measured
LMArena Vision: reading text13271326Claude Fable 5.1
LMArena Vision: humor1318Not measuredOnly Claude Fable 5.1 measured
LMArena Vision: creative writing13301320Claude Fable 5.1
Neither model has a result on the other 14 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for Claude Fable 5.1 and Claude Opus 5.5
BenchmarkClaude Fable 5.1Claude Opus 5.5Leader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

Claude Fable 5.1$0.035Fits in one request
Claude Opus 5.5$0.014Fits in one request

Claude Opus 5.5 costs less

Repository review

50K input + 3K output tokens

Claude Fable 5.1$0.650Fits in one request
Claude Opus 5.5$0.260Fits in one request

Claude Opus 5.5 costs less

Agent loop

200K input + 10K output tokens

Claude Fable 5.1$2.50Fits in one request
Claude Opus 5.5$1.00Fits in one request

Claude Opus 5.5 costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of Claude Fable 5.1 and Claude Opus 5.5
SpecificationAnthropic Claude Fable 5.1Anthropic Claude Opus 5.5
MakerAnthropicAnthropic
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 1, 2026September 22, 2026
Context window1M1M
Input $/Mtok$10.00$4.00
Output $/Mtok$50.00$20.00
Coding index89.192.2
Independent measurements behind it22
Cost per solved taskNot computableNot computable
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Fable 5.1 better than Claude Opus 5.5 for coding?

Pick Claude Opus 5.5 for coding: it scores 92.2 on the Vibe Coding Index against 89.1 for Claude Fable 5.1. Pick Claude Fable 5.1 when what matters is LiveBench coding or LiveBench browser, where it leads.

Which is cheaper, Claude Fable 5.1 or Claude Opus 5.5?

Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; Claude Opus 5.5 costs $4.00 and $20.00. Cost per solved task is known for neither of them.

Which has the bigger context window, Claude Fable 5.1 or Claude Opus 5.5?

Neither: both take 1M tokens.

How many benchmarks is the Claude Fable 5.1 vs Claude Opus 5.5 comparison based on?

100 benchmarks have a result for both models as of October 20, 2026. Claude Fable 5.1's coding index rests on 2 independent benchmarks and Claude Opus 5.5's on 2. Where only one model has a result, the page says so instead of naming a winner.

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<p style="font:13px/1.4 sans-serif;margin:6px 0 0">Source: <a href="https://llmbenchmark.ai/compare/claude-fable-5-1-vs-claude-opus-5-5">LLMBenchmark.ai, Claude Fable 5.1 vs Claude Opus 5.5</a></p>