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Claude Fable 5.1 vs Claude Opus 4.8

Claude Fable 5.1 leads Claude Opus 4.8 on coding, 84.2 to 65.0 on the Vibe Coding Index, and Claude Opus 4.8 costs 2.0x less per output token ($25.00 vs $50.00 per million). Updated October 22, 2026; 111 benchmarks have a result for both.

Replace Claude Fable 5.1 Replace Claude Opus 4.8
Claude Fable 5.1Anthropic
Coding
84.2
Overall
84.7
Output $/M
$50.00
108
Claude Opus 4.8Anthropic
Coding
65.0
Overall
69.8
Output $/M
$25.00
3
vs boards won of 111 shared

Claude Fable 5.1 or Claude Opus 4.8: which to pick

Pick Claude Fable 5.1 for coding: it scores 84.2 on the Vibe Coding Index against 65.0 for Claude Opus 4.8, though on 5 benchmarks against 6.

Pick Claude Opus 4.8 for output tokens 2.0x cheaper ($25.00 vs $50.00 per million) and work measured by Vending-Bench 2 or Chess puzzles, where it leads.

Model AClaude Fable 5.1Anthropic84.2/1005 independent benchmarksNo cost per solved taskModel BClaude Opus 4.8Anthropic65.0/1006 independent benchmarks$2.17 per solved task
Shared results
111
Claude Fable 5.1 only
13
Claude Opus 4.8 only
19
Like-for-like categories
8 of 9

Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.

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 84.2 from 5 benchmarks, Claude Opus 4.8 65.0 from 6 benchmarks.
Widest category
Math, 14.9 points apart on average over 6 shared benchmarks.
Widest single gap
Time Horizon Index (Vals AI): Claude Fable 5.1 63.3% against Claude Opus 4.8 11.8%, 51.5 points apart on a 0 to 100 scale.
Output price
Claude Fable 5.1 $50.00 against Claude Opus 4.8 $25.00 per million output tokens, 2.0x 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 4.8Ties
Coding180
Intelligence20
Agentic work191
Reasoning141
Math60
Knowledge100
Web design90
General301
All shared boards1083
CodingLike-for-likeSix of these boards feed the Vibe Coding Index180
Coding benchmarks for Claude Fable 5.1 and Claude Opus 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
LiveBench coding97.7%77.3%Claude Fable 5.1
LMArena WebDev17431556Claude Fable 5.1
AA Coding Index81.674.3Claude Fable 5.1
LiveCodeBench (Vals AI)90.5%87.8%Claude Fable 5.1
SWE-bench Verified (Vals AI)Not measured88.6%Only Claude Opus 4.8 measured
Terminal-Bench 4 (Vals AI)58.1%23.2%Claude Fable 5.1
Vibe Code Bench (Vals AI)90.3%82.7%Claude Fable 5.1
Code migration (Vals AI)54.6%47.3%Claude Fable 5.1
ProgramBench (Vals AI)7.0%1.0%Claude Fable 5.1
IOI (Vals AI)90.8%Not measuredOnly Claude Fable 5.1 measured
Terminal-Bench 2.1 (Vals AI)85.0%71.9%Claude Fable 5.1
SWE-bench Multimodal (Vals AI)61.3%Not measuredOnly Claude Fable 5.1 measured
Vibe Code Bench 1-100 (Vals AI)28.0%Not measuredOnly Claude Fable 5.1 measured
SkillsBench (Vals AI)61.5%59.2%Claude Fable 5.1
CyberBench (Vals AI)70.4%Not measuredOnly Claude Fable 5.1 measured
SciCode63.1%54.4%Claude Fable 5.1
Terminal-Bench Hard (Artificial Analysis run)Not measured58.3%Only Claude Opus 4.8 measured
FrontierCode50.9%46.5%Claude Fable 5.1
FrontierSWE56.3%Not measuredOnly Claude Fable 5.1 measured
GSO-Bench88.2%47.1%Claude Fable 5.1
WeirdML92.9%82.9%Claude Fable 5.1
MirrorCode73.3%Not measuredOnly Claude Fable 5.1 measured
ALE-Bench2143.2Not measuredOnly Claude Fable 5.1 measured
LMArena Text: coding15321490Claude Fable 5.1
LMArena Text: software and IT15301488Claude Fable 5.1
LMArena WebDev: React17921557Claude Fable 5.1
LMArena WebDev: HTML16841543Claude Fable 5.1
LMArena WebDev: from an image1722Not measuredOnly Claude Fable 5.1 measured
SciCodeNot measured12.3%Only Claude Opus 4.8 measured
Neither model has a result on the other 10 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Fable 5.1 and Claude Opus 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
AA Intelligence Index53.441.8Claude Fable 5.1
Epoch Capabilities Index166.5159.0Claude Fable 5.1
Agentic workLike-for-likePublic boards, shown as published, kept out of the index191
Agentic work benchmarks for Claude Fable 5.1 and Claude Opus 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
AA Agentic Index57.941.9Claude Fable 5.1
Design Arena: agents building web apps13181233Claude Fable 5.1
Design Arena: agents building full-stack apps13261249Claude Fable 5.1
Design Arena: agents building mobile apps12671223Claude Fable 5.1
Design Arena: agents building Android appsNot measured1233Only Claude Opus 4.8 measured
Design Arena: agents building Godot games13271231Claude Fable 5.1
Design Arena: agents building gamesNot measured1239Only Claude Opus 4.8 measured
Design Arena: HTML slidesNot measured1171Only Claude Opus 4.8 measured
Design Arena: PowerPoint slides13061204Claude Fable 5.1
Design Arena: spreadsheets13961311Claude Fable 5.1
LiveBench research82.0%81.8%Claude Fable 5.1
LiveBench browser100.0%96.0%Claude Fable 5.1
LiveBench long agentic80.8%48.3%Claude Fable 5.1
SREBench (Vals AI)22.9%Not measuredOnly Claude Fable 5.1 measured
Finance Agent (Vals AI)58.9%53.9%Claude Fable 5.1
Tax Agent Bench (Vals AI)49.2%30.0%Claude Fable 5.1
Legal Research Bench (Vals AI)55.3%43.8%Claude Fable 5.1
Excel Modeling Benchmark (Vals AI)76.7%69.4%Claude Fable 5.1
Terminal-Bench-Science (Vals AI)40.0%4.3%Claude Fable 5.1
Time Horizon Index (Vals AI)63.3%11.8%Claude Fable 5.1
CUA-bench (Vals AI)13.2%Not measuredOnly Claude Fable 5.1 measured
Robo-bench (Vals AI)5.8%Not measuredOnly Claude Fable 5.1 measured
τ²-Bench TelecomNot measured94.4%Only Claude Opus 4.8 measured
APEX-Agents68.6%48.9%Claude Fable 5.1
Remote Labor Index17.9%8.3%Claude Fable 5.1
OSWorld 2.0Not measured20.6%Only Claude Opus 4.8 measured
DeepResearch BenchNot measured50.2%Only Claude Opus 4.8 measured
PostTrainBenchNot measured33.8%Only Claude Opus 4.8 measured
SpireClimb2.0%Not measuredOnly Claude Fable 5.1 measured
Vending-Bench 2$5,422$5,787Claude Opus 4.8
LMArena Search12461204Claude Fable 5.1
Neither model has a result on the other 10 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index141
Reasoning benchmarks for Claude Fable 5.1 and Claude Opus 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
GPQA Diamond93.4%92.4%Claude Fable 5.1
LiveBench reasoning91.7%89.2%Claude Fable 5.1
MysteryMechanism (Vals AI)47.8%Not measuredOnly Claude Fable 5.1 measured
MMMU Pro (Vals AI)90.6%86.6%Claude Fable 5.1
GPQA Diamond (Artificial Analysis run)93.7%92.0%Claude Fable 5.1
Humanity's Last Exam (Artificial Analysis run)59.1%48.7%Claude Fable 5.1
GPQA Diamond (Epoch AI run)Not measured91.0%Only Claude Opus 4.8 measured
ARC-AGI97.5%92.5%Claude Fable 5.1
ARC-AGI-290.0%72.1%Claude Fable 5.1
SimpleBenchNot measured64.8%Only Claude Opus 4.8 measured
Chess puzzles48.0%52.0%Claude Opus 4.8
Mystery game puzzles58.0%36.0%Claude Fable 5.1
EBR-bench57.1%28.6%Claude Fable 5.1
LMArena Text: hard prompts15281482Claude Fable 5.1
LMArena Text: expert15441503Claude Fable 5.1
LMArena Text: hard prompts in English15221487Claude Fable 5.1
LMArena Vision: diagrams13431315Claude Fable 5.1
LMArena Vision: homework13451337Claude Fable 5.1
Kagi LLM BenchmarkNot measured88.8%Only Claude Opus 4.8 measured
Neither model has a result on the other 3 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index60
Math benchmarks for Claude Fable 5.1 and Claude Opus 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
OTIS Mock AIME100.0%98.3%Claude Fable 5.1
FrontierMath, tiers 1 to 390.2%80.0%Claude Fable 5.1
FrontierMath, tier 487.8%56.1%Claude Fable 5.1
ProofBench100.0%69.0%Claude Fable 5.1
LMArena Text: math15311486Claude Fable 5.1
LMArena Text: mathematical work15411497Claude 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 index100
Knowledge benchmarks for Claude Fable 5.1 and Claude Opus 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
MMLU Pro92.4%89.6%Claude Fable 5.1
LegalBench (Vals AI)88.5%83.6%Claude Fable 5.1
CorpFin (Vals AI)Not measured66.7%Only Claude Opus 4.8 measured
TaxEval (Vals AI)76.0%75.6%Claude Fable 5.1
MortgageTax (Vals AI)70.8%69.9%Claude Fable 5.1
MedCode (Vals AI)53.5%53.2%Claude Fable 5.1
SimpleQA Verified70.8%53.0%Claude Fable 5.1
LMArena Text: science15321477Claude Fable 5.1
LMArena Text: medicine and healthcare15311464Claude Fable 5.1
LMArena Text: legal and government15141477Claude Fable 5.1
LMArena Text: business and finance14931458Claude Fable 5.1
FACTS Benchmark SuiteNot measured53.5%Only Claude Opus 4.8 measured
Neither model has a result on the other 6 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index90
Web design benchmarks for Claude Fable 5.1 and Claude Opus 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
Design Arena: websites13121258Claude Fable 5.1
Design Arena: UI components13361255Claude Fable 5.1
Design Arena: game dev13811264Claude Fable 5.1
Design Arena: data viz13451240Claude Fable 5.1
Design Arena: 3D13921222Claude Fable 5.1
Design Arena: all code categories13351255Claude Fable 5.1
Design Arena: SVG13001194Claude Fable 5.1
Design Arena: ASCII art13231277Claude Fable 5.1
LiveBench design83.4%78.8%Claude Fable 5.1
GeneralLike-for-likePublic boards, shown as published, kept out of the index301
General benchmarks for Claude Fable 5.1 and Claude Opus 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
LiveBench data analysis80.3%66.0%Claude Fable 5.1
Public Benefits Bench (Vals AI)74.9%68.1%Claude Fable 5.1
SAGE (Vals AI)48.5%54.8%Claude Opus 4.8
MedScribe (Vals AI)91.3%85.8%Claude Fable 5.1
Vals Multimodal IndexNot measured70.9%Only Claude Opus 4.8 measured
IFBenchNot measured62.2%Only Claude Opus 4.8 measured
Long context reasoning (AA-LCR)85.3%77.7%Claude Fable 5.1
DTBench97.6%94.9%Claude Fable 5.1
LMCA65.5%57.5%Claude Fable 5.1
Surface Evolver BenchNot measured87.5%Only Claude Opus 4.8 measured
Furniture assembly70.0%42.5%Claude Fable 5.1
LMArena Text15121461Claude Fable 5.1
LMArena Text: instruction following15181476Claude Fable 5.1
LMArena Text: creative writing15091454Claude Fable 5.1
LMArena Vision13191294Claude Fable 5.1
LMArena Text: English15061468Claude Fable 5.1
LMArena Text: non-English15081450Claude Fable 5.1
LMArena Text: Chinese15841506Claude Fable 5.1
LMArena Text: German14991472Claude Fable 5.1
LMArena Text: Japanese15621442Claude Fable 5.1
LMArena Text: Korean15171431Claude Fable 5.1
LMArena Text: French15231481Claude Fable 5.1
LMArena Text: Spanish15201465Claude Fable 5.1
LMArena Text: Russian15201474Claude Fable 5.1
LMArena Text: Polish15251459Claude Fable 5.1
LMArena Text: multi-turn14931476Claude Fable 5.1
LMArena Text: longer queries15241483Claude Fable 5.1
LMArena Text: writing and language15101461Claude Fable 5.1
LMArena Text: entertainment and media14971440Claude Fable 5.1
LMArena Vision: English13131293Claude Fable 5.1
LMArena Vision: Chinese13911346Claude Fable 5.1
LMArena Vision: reading text13271303Claude Fable 5.1
LMArena Vision: humor13181282Claude Fable 5.1
LMArena Vision: creative writing13301301Claude Fable 5.1
LMArena DocumentNot measured1475Only Claude Opus 4.8 measured
Neither model has a result on the other 11 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 4.8
BenchmarkClaude Fable 5.1Claude Opus 4.8Leader
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 4.8$0.018Fits in one request

Claude Opus 4.8 costs less

Repository review

50K input + 3K output tokens

Claude Fable 5.1$0.650Fits in one request
Claude Opus 4.8$0.325Fits in one request

Claude Opus 4.8 costs less

Agent loop

200K input + 10K output tokens

Claude Fable 5.1$2.50Fits in one request
Claude Opus 4.8$1.25Fits in one request

Claude Opus 4.8 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 4.8
SpecificationAnthropic Claude Fable 5.1Anthropic Claude Opus 4.8
MakerAnthropicAnthropic
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 1, 2026May 27, 2026
Context window1M1M
Input $/Mtok$10.00$5.00
Output $/Mtok$50.00$25.00
Coding index84.265.0
Independent measurements behind it56
Cost per solved taskNot computable$2.17
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Fable 5.1 better than Claude Opus 4.8 for coding?

Pick Claude Fable 5.1 for coding: it scores 84.2 on the Vibe Coding Index against 65.0 for Claude Opus 4.8, though on 5 benchmarks against 6. Pick Claude Opus 4.8 for output tokens 2.0x cheaper ($25.00 vs $50.00 per million) and work measured by Vending-Bench 2 or Chess puzzles, where it leads.

Which is cheaper, Claude Fable 5.1 or Claude Opus 4.8?

Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; Claude Opus 4.8 costs $5.00 and $25.00. Cost per solved task is known for Claude Opus 4.8 only.

Which has the bigger context window, Claude Fable 5.1 or Claude Opus 4.8?

Neither: both take 1M tokens.

How many benchmarks is the Claude Fable 5.1 vs Claude Opus 4.8 comparison based on?

111 benchmarks have a result for both models as of October 22, 2026. Claude Fable 5.1's coding index rests on 5 independent benchmarks and Claude Opus 4.8's on 6. Where only one model has a result, the page says so instead of naming a winner.

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