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Claude Fable 5.1 vs Grok 4.5

Claude Fable 5.1 leads Grok 4.5 on coding, 84.2 to 58.6 on the Vibe Coding Index, and Grok 4.5 costs 8.3x less per output token ($6.00 vs $50.00 per million). Updated October 22, 2026; 109 benchmarks have a result for both.

Replace Claude Fable 5.1 Replace Grok 4.5
Claude Fable 5.1Anthropic
Coding
84.2
Overall
84.7
Output $/M
$50.00
106
Grok 4.5xAI
Coding
58.6
Overall
62.1
Output $/M
$6.00
3
vs boards won of 109 shared

Claude Fable 5.1 or Grok 4.5: which to pick

Pick Claude Fable 5.1 for coding: it scores 84.2 on the Vibe Coding Index against 58.6 for Grok 4.5, though on 5 benchmarks against 6.

Pick Grok 4.5 for output tokens 8.3x cheaper ($6.00 vs $50.00 per million) and work measured by SkillsBench (Vals AI) or CyberBench (Vals AI), where it leads.

Model AClaude Fable 5.1Anthropic84.2/1005 independent benchmarksNo cost per solved taskModel BGrok 4.5xAI58.6/1006 independent benchmarks$0.62 per solved task
Shared results
109
Claude Fable 5.1 only
15
Grok 4.5 only
14
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, Grok 4.5 58.6 from 6 benchmarks.
Widest category
Math, 31.5 points apart on average over 6 shared benchmarks.
Widest single gap
ProofBench: Claude Fable 5.1 100.0% against Grok 4.5 31.0%, 69.0 points apart on a 0 to 100 scale.
Output price
Claude Fable 5.1 $50.00 against Grok 4.5 $6.00 per million output tokens, 8.3x apart.
Context window
Claude Fable 5.1 takes 1M tokens, Grok 4.5 500K.

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 5.1BarsGrok 4.5Ties
Coding192
Intelligence20
Agentic work171
Reasoning130
Math60
Knowledge100
Web design90
General300
All shared boards1063
CodingLike-for-likeSix of these boards feed the Vibe Coding Index192
Coding benchmarks for Claude Fable 5.1 and Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
LiveBench coding97.7%94.3%Claude Fable 5.1
LMArena WebDev17431553Claude Fable 5.1
AA Coding Index81.672.4Claude Fable 5.1
LiveCodeBench (Vals AI)90.5%87.3%Claude Fable 5.1
SWE-bench Verified (Vals AI)Not measured86.6%Only Grok 4.5 measured
Terminal-Bench 4 (Vals AI)58.1%8.6%Claude Fable 5.1
Vibe Code Bench (Vals AI)90.3%69.0%Claude Fable 5.1
Code migration (Vals AI)54.6%36.6%Claude Fable 5.1
ProgramBench (Vals AI)7.0%0.0%Claude Fable 5.1
IOI (Vals AI)90.8%40.6%Claude Fable 5.1
Terminal-Bench 2.1 (Vals AI)85.0%67.8%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%66.0%Grok 4.5
CyberBench (Vals AI)70.4%71.0%Grok 4.5
SciCode63.1%55.0%Claude Fable 5.1
FrontierCode50.9%42.4%Claude Fable 5.1
FrontierSWE56.3%Not measuredOnly Claude Fable 5.1 measured
GSO-Bench88.2%Not measuredOnly Claude Fable 5.1 measured
WeirdML92.9%46.4%Claude Fable 5.1
MirrorCode73.3%Not measuredOnly Claude Fable 5.1 measured
ALE-Bench2143.21309.3Claude Fable 5.1
LMArena Text: coding15321474Claude Fable 5.1
LMArena Text: software and IT15301471Claude Fable 5.1
LMArena WebDev: React17921556Claude Fable 5.1
LMArena WebDev: HTML16841567Claude Fable 5.1
LMArena WebDev: from an image17221562Claude Fable 5.1
SciCodeNot measured6.5%Only Grok 4.5 measured
Neither model has a result on the other 11 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Fable 5.1 and Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
AA Intelligence Index53.438.8Claude Fable 5.1
Epoch Capabilities Index166.5154.1Claude Fable 5.1
Agentic workLike-for-likePublic boards, shown as published, kept out of the index171
Agentic work benchmarks for Claude Fable 5.1 and Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
AA Agentic Index57.941.2Claude Fable 5.1
Design Arena: agents building web apps13181218Claude Fable 5.1
Design Arena: agents building full-stack apps13261249Claude Fable 5.1
Design Arena: agents building mobile apps12671220Claude Fable 5.1
Design Arena: agents building Android appsNot measured1236Only Grok 4.5 measured
Design Arena: agents building Godot games13271229Claude Fable 5.1
Design Arena: agents building gamesNot measured1236Only Grok 4.5 measured
Design Arena: HTML slidesNot measured1205Only Grok 4.5 measured
Design Arena: PowerPoint slides13051230Claude Fable 5.1
Design Arena: spreadsheets1380Not measuredOnly Claude Fable 5.1 measured
LiveBench research82.0%85.9%Grok 4.5
LiveBench browser100.0%44.0%Claude Fable 5.1
LiveBench long agentic80.8%27.9%Claude Fable 5.1
SREBench (Vals AI)22.9%0.8%Claude Fable 5.1
Finance Agent (Vals AI)58.9%48.4%Claude Fable 5.1
Tax Agent Bench (Vals AI)49.2%24.9%Claude Fable 5.1
Legal Research Bench (Vals AI)55.3%38.0%Claude Fable 5.1
Excel Modeling Benchmark (Vals AI)76.7%52.9%Claude Fable 5.1
Terminal-Bench-Science (Vals AI)40.0%Not measuredOnly Claude Fable 5.1 measured
Time Horizon Index (Vals AI)63.3%6.3%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
APEX-Agents68.6%56.2%Claude Fable 5.1
Remote Labor Index17.9%Not measuredOnly Claude Fable 5.1 measured
PostTrainBenchNot measured23.4%Only Grok 4.5 measured
SpireClimb2.0%Not measuredOnly Claude Fable 5.1 measured
Vending-Bench 2$5,422$3,887Claude Fable 5.1
LMArena Search12461216Claude 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 index130
Reasoning benchmarks for Claude Fable 5.1 and Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
GPQA Diamond93.4%92.9%Claude Fable 5.1
LiveBench reasoning91.7%87.2%Claude Fable 5.1
MysteryMechanism (Vals AI)47.8%Not measuredOnly Claude Fable 5.1 measured
MMMU Pro (Vals AI)90.6%61.8%Claude Fable 5.1
GPQA Diamond (Artificial Analysis run)93.7%93.1%Claude Fable 5.1
Humanity's Last Exam (Artificial Analysis run)59.1%42.7%Claude Fable 5.1
GPQA Diamond (Epoch AI run)Not measured93.4%Only Grok 4.5 measured
ARC-AGI97.5%87.2%Claude Fable 5.1
ARC-AGI-290.0%52.6%Claude Fable 5.1
SimpleBenchNot measured70.0%Only Grok 4.5 measured
Chess puzzles48.0%35.0%Claude Fable 5.1
Mystery game puzzles58.0%Not measuredOnly Claude Fable 5.1 measured
EBR-bench57.1%Not measuredOnly Claude Fable 5.1 measured
LMArena Text: hard prompts15281462Claude Fable 5.1
LMArena Text: expert15441465Claude Fable 5.1
LMArena Text: hard prompts in English15221464Claude Fable 5.1
LMArena Vision: diagrams13431304Claude Fable 5.1
LMArena Vision: homework13451295Claude Fable 5.1
Kagi LLM BenchmarkNot measured83.5%Only Grok 4.5 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 Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
OTIS Mock AIME100.0%97.8%Claude Fable 5.1
FrontierMath, tiers 1 to 390.2%57.2%Claude Fable 5.1
FrontierMath, tier 487.8%24.4%Claude Fable 5.1
ProofBench100.0%31.0%Claude Fable 5.1
LMArena Text: math15311460Claude Fable 5.1
LMArena Text: mathematical work15411482Claude 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 Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
MMLU Pro92.4%89.2%Claude Fable 5.1
LegalBench (Vals AI)88.5%86.0%Claude Fable 5.1
CorpFin (Vals AI)Not measured67.4%Only Grok 4.5 measured
TaxEval (Vals AI)76.0%71.7%Claude Fable 5.1
MortgageTax (Vals AI)70.8%61.8%Claude Fable 5.1
MedCode (Vals AI)53.5%43.3%Claude Fable 5.1
SimpleQA Verified70.8%48.3%Claude Fable 5.1
LMArena Text: science15321464Claude Fable 5.1
LMArena Text: medicine and healthcare15311440Claude Fable 5.1
LMArena Text: legal and government15141463Claude Fable 5.1
LMArena Text: business and finance14931441Claude Fable 5.1
FACTS Benchmark SuiteNot measured50.2%Only Grok 4.5 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 Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
Design Arena: websites13121281Claude Fable 5.1
Design Arena: UI components13361280Claude Fable 5.1
Design Arena: game dev13811264Claude Fable 5.1
Design Arena: data viz13441266Claude Fable 5.1
Design Arena: 3D13921257Claude Fable 5.1
Design Arena: all code categories13351275Claude Fable 5.1
Design Arena: SVG13001215Claude Fable 5.1
Design Arena: ASCII art13231256Claude Fable 5.1
LiveBench design83.4%78.1%Claude Fable 5.1
GeneralLike-for-likePublic boards, shown as published, kept out of the index300
General benchmarks for Claude Fable 5.1 and Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
LiveBench data analysis80.3%73.0%Claude Fable 5.1
Public Benefits Bench (Vals AI)74.9%Not measuredOnly Claude Fable 5.1 measured
SAGE (Vals AI)48.5%35.0%Claude Fable 5.1
MedScribe (Vals AI)91.3%86.9%Claude Fable 5.1
Vals Multimodal IndexNot measured63.4%Only Grok 4.5 measured
Long context reasoning (AA-LCR)85.3%79.3%Claude Fable 5.1
DTBench97.6%96.5%Claude Fable 5.1
LMCA65.5%45.2%Claude Fable 5.1
Surface Evolver BenchNot measured74.4%Only Grok 4.5 measured
Furniture assembly70.0%22.5%Claude Fable 5.1
LMArena Text15121448Claude Fable 5.1
LMArena Text: instruction following15181445Claude Fable 5.1
LMArena Text: creative writing15091442Claude Fable 5.1
LMArena Vision13191287Claude Fable 5.1
LMArena Text: English15061453Claude Fable 5.1
LMArena Text: non-English15081440Claude Fable 5.1
LMArena Text: Chinese15841495Claude Fable 5.1
LMArena Text: German14991448Claude Fable 5.1
LMArena Text: Japanese15621430Claude Fable 5.1
LMArena Text: Korean15171406Claude Fable 5.1
LMArena Text: French15231457Claude Fable 5.1
LMArena Text: Spanish15201451Claude Fable 5.1
LMArena Text: Russian15201449Claude Fable 5.1
LMArena Text: Polish15251432Claude Fable 5.1
LMArena Text: multi-turn14931456Claude Fable 5.1
LMArena Text: longer queries15241462Claude Fable 5.1
LMArena Text: writing and language15101445Claude Fable 5.1
LMArena Text: entertainment and media14971434Claude Fable 5.1
LMArena Vision: English13131285Claude Fable 5.1
LMArena Vision: Chinese13911345Claude Fable 5.1
LMArena Vision: reading text13271293Claude Fable 5.1
LMArena Vision: humor13181276Claude Fable 5.1
LMArena Vision: creative writing13301293Claude Fable 5.1
LMArena DocumentNot measured1452Only Grok 4.5 measured
Neither model has a result on the other 12 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 Grok 4.5
BenchmarkClaude Fable 5.1Grok 4.5Leader
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
Grok 4.5$0.0050Fits in one request

Grok 4.5 costs less

Repository review

50K input + 3K output tokens

Claude Fable 5.1$0.650Fits in one request
Grok 4.5$0.118Fits in one request

Grok 4.5 costs less

Agent loop

200K input + 10K output tokens

Claude Fable 5.1$2.50Fits in one request
Grok 4.5$0.460Fits in one request

Grok 4.5 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 Grok 4.5
SpecificationAnthropic Claude Fable 5.1SpaceXAI Grok 4.5
MakerAnthropicxAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 1, 2026July 8, 2026
Context window1M500K
Input $/Mtok$10.00$2.00
Output $/Mtok$50.00$6.00
Coding index84.258.6
Independent measurements behind it56
Cost per solved taskNot computable$0.62
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Fable 5.1 better than Grok 4.5 for coding?

Pick Claude Fable 5.1 for coding: it scores 84.2 on the Vibe Coding Index against 58.6 for Grok 4.5, though on 5 benchmarks against 6. Pick Grok 4.5 for output tokens 8.3x cheaper ($6.00 vs $50.00 per million) and work measured by SkillsBench (Vals AI) or CyberBench (Vals AI), where it leads.

Which is cheaper, Claude Fable 5.1 or Grok 4.5?

Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; Grok 4.5 costs $2.00 and $6.00. Cost per solved task is known for Grok 4.5 only.

Which has the bigger context window, Claude Fable 5.1 or Grok 4.5?

Claude Fable 5.1, with 1M tokens against 500K.

How many benchmarks is the Claude Fable 5.1 vs Grok 4.5 comparison based on?

109 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 Grok 4.5's on 6. Where only one model has a result, the page says so instead of naming a winner.

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