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Claude Fable 5.1 vs GPT-6 Luna

Updated October 21, 2026. 97 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 GPT-6 Luna
Claude Fable 5.1Anthropic
Coding
89.1
Overall
53.4
Output $/M
$50.00
96
GPT-6 LunaOpenAI
Coding
71.4
Overall
38.1
Output $/M
$0.50
1
vs boards won of 97 shared

Decision reading

Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 71.4 for GPT-6 Luna.

Pick GPT-6 Luna when output tokens cost 100.0x less, or when the context window is larger, 1.05M against 1M tokens.

Model AClaude Fable 5.1Anthropic89.1/1002 independent benchmarksNo cost per solved taskModel BGPT-6 LunaOpenAI71.4/1002 independent benchmarksNo cost per solved task
Shared results
97
Claude Fable 5.1 only
27
GPT-6 Luna 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, GPT-6 Luna 71.4 from 2 benchmarks.
Widest category
Agentic work, 21.9 points apart on average over 14 shared benchmarks.
Widest single gap
Mystery game puzzles: Claude Fable 5.1 58.0% against GPT-6 Luna 7.0%, 51.0 points apart on a 0 to 100 scale.
Output price
Claude Fable 5.1 $50.00 against GPT-6 Luna $0.50 per million output tokens, 100.0x apart.
Context window
Claude Fable 5.1 takes 1M tokens, GPT-6 Luna 1.05M.

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 5.1BarsGPT-6 LunaTies
Coding171
Intelligence20
Agentic work140
Reasoning120
Math60
Knowledge60
Web design90
General300
All shared boards961
CodingLike-for-likeFour of these boards feed the Vibe Coding Index171
Coding benchmarks for Claude Fable 5.1 and GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
LiveBench coding97.7%84.5%Claude Fable 5.1
LMArena WebDev17431578Claude Fable 5.1
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%13.6%Claude Fable 5.1
Vibe Code Bench (Vals AI)90.3%81.7%Claude Fable 5.1
Code migration (Vals AI)54.6%42.5%Claude Fable 5.1
ProgramBench (Vals AI)7.0%0.5%Claude Fable 5.1
IOI (Vals AI)90.8%55.6%Claude Fable 5.1
Terminal-Bench 2.1 (Vals AI)85.0%73.0%Claude Fable 5.1
SWE-bench Multimodal (Vals AI)61.3%37.5%Claude Fable 5.1
Vibe Code Bench 1-100 (Vals AI)28.0%Not measuredOnly Claude Fable 5.1 measured
SkillsBench (Vals AI)61.5%Not measuredOnly Claude Fable 5.1 measured
CyberBench (Vals AI)70.4%76.3%GPT-6 Luna
SciCode63.1%54.6%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%Not measuredOnly Claude Fable 5.1 measured
MirrorCode73.3%Not measuredOnly Claude Fable 5.1 measured
ALE-Bench2143.21576.9Claude Fable 5.1
LMArena Text: coding15321437Claude Fable 5.1
LMArena Text: software and IT15301423Claude Fable 5.1
LMArena WebDev: React17921573Claude Fable 5.1
LMArena WebDev: HTML16841595Claude Fable 5.1
LMArena WebDev: from an image17221571Claude Fable 5.1
Neither model has a result on the other 12 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Fable 5.1 and GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
AA Intelligence Index53.438.1Claude Fable 5.1
Epoch Capabilities Index166.5156.8Claude Fable 5.1
Agentic workLike-for-likePublic boards, shown as published, kept out of the index140
Agentic work benchmarks for Claude Fable 5.1 and GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
AA Agentic Index57.9Not measuredOnly Claude Fable 5.1 measured
Design Arena: agents building web apps13181189Claude Fable 5.1
Design Arena: agents building full-stack apps13261158Claude Fable 5.1
Design Arena: agents building mobile apps12671133Claude Fable 5.1
Design Arena: agents building Godot games1327Not measuredOnly Claude Fable 5.1 measured
Design Arena: PowerPoint slides1328Not measuredOnly Claude Fable 5.1 measured
Design Arena: spreadsheets1374Not measuredOnly Claude Fable 5.1 measured
LiveBench research82.0%43.5%Claude Fable 5.1
LiveBench browser100.0%72.0%Claude Fable 5.1
LiveBench long agentic80.8%48.1%Claude Fable 5.1
SREBench (Vals AI)22.9%2.7%Claude Fable 5.1
Finance Agent (Vals AI)58.9%49.9%Claude Fable 5.1
Tax Agent Bench (Vals AI)49.2%19.9%Claude Fable 5.1
Legal Research Bench (Vals AI)55.3%30.3%Claude Fable 5.1
Harvey's Legal Agent Benchmark (Vals AI)Not measured4.2%Only GPT-6 Luna measured
Excel Modeling Benchmark (Vals AI)76.7%68.5%Claude Fable 5.1
BioMysteryBench (Vals AI)Not measured61.5%Only GPT-6 Luna measured
Terminal-Bench-Science (Vals AI)40.0%4.3%Claude Fable 5.1
Vals Science IndexNot measured28.4%Only GPT-6 Luna measured
Time Horizon Index (Vals AI)63.3%Not measuredOnly Claude Fable 5.1 measured
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%44.3%Claude Fable 5.1
Remote Labor Index17.9%Not measuredOnly Claude Fable 5.1 measured
SpireClimb2.0%0.0%Claude Fable 5.1
Vending-Bench 2$5,422Not measuredOnly Claude Fable 5.1 measured
LMArena Search1246Not measuredOnly Claude Fable 5.1 measured
Neither model has a result on the other 12 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index120
Reasoning benchmarks for Claude Fable 5.1 and GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
GPQA Diamond93.4%Not measuredOnly Claude Fable 5.1 measured
LiveBench reasoning91.7%81.8%Claude Fable 5.1
MysteryMechanism (Vals AI)47.8%19.4%Claude Fable 5.1
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%38.5%Claude Fable 5.1
GPQA Diamond (Epoch AI run)Not measured90.5%Only GPT-6 Luna measured
ARC-AGI97.5%86.7%Claude Fable 5.1
ARC-AGI-290.0%59.3%Claude Fable 5.1
Chess puzzles48.0%36.0%Claude Fable 5.1
Mystery game puzzles58.0%7.0%Claude Fable 5.1
EBR-bench57.1%Not measuredOnly Claude Fable 5.1 measured
LMArena Text: hard prompts15281410Claude Fable 5.1
LMArena Text: expert15441442Claude Fable 5.1
LMArena Text: hard prompts in English15221410Claude Fable 5.1
LMArena Vision: diagrams13431245Claude Fable 5.1
LMArena Vision: homework13451261Claude Fable 5.1
Neither model has a result on the other 4 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index60
Math benchmarks for Claude Fable 5.1 and GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
OTIS Mock AIME100.0%98.9%Claude Fable 5.1
FrontierMath, tiers 1 to 390.2%78.9%Claude Fable 5.1
FrontierMath, tier 487.8%56.1%Claude Fable 5.1
ProofBench100.0%64.0%Claude Fable 5.1
LMArena Text: math15311409Claude Fable 5.1
LMArena Text: mathematical work15411427Claude 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 index60
Knowledge benchmarks for Claude Fable 5.1 and GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
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%44.7%Claude Fable 5.1
SimpleQA Verified70.8%41.4%Claude Fable 5.1
LMArena Text: science15321386Claude Fable 5.1
LMArena Text: medicine and healthcare15311352Claude Fable 5.1
LMArena Text: legal and government15141400Claude Fable 5.1
LMArena Text: business and finance14931388Claude 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 index90
Web design benchmarks for Claude Fable 5.1 and GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
Design Arena: websites13131272Claude Fable 5.1
Design Arena: UI components13381297Claude Fable 5.1
Design Arena: game dev13821259Claude Fable 5.1
Design Arena: data viz13441215Claude Fable 5.1
Design Arena: 3D13931217Claude Fable 5.1
Design Arena: all code categories13361271Claude Fable 5.1
Design Arena: SVG13011253Claude Fable 5.1
Design Arena: ASCII art13241156Claude Fable 5.1
LiveBench design83.4%82.5%Claude Fable 5.1
GeneralLike-for-likePublic boards, shown as published, kept out of the index300
General benchmarks for Claude Fable 5.1 and GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
Vals IndexNot measured52.3%Only GPT-6 Luna measured
LiveBench data analysis80.3%73.4%Claude Fable 5.1
Public Benefits Bench (Vals AI)74.9%57.6%Claude Fable 5.1
SAGE (Vals AI)48.5%48.1%Claude Fable 5.1
MedScribe (Vals AI)91.3%83.7%Claude Fable 5.1
Long context reasoning (AA-LCR)85.3%83.3%Claude Fable 5.1
DTBench97.6%90.1%Claude Fable 5.1
LMCA65.5%44.5%Claude Fable 5.1
Furniture assembly70.0%44.2%Claude Fable 5.1
LMArena Text15121389Claude Fable 5.1
LMArena Text: instruction following15181408Claude Fable 5.1
LMArena Text: creative writing15091363Claude Fable 5.1
LMArena Vision13191216Claude Fable 5.1
LMArena Text: English15061393Claude Fable 5.1
LMArena Text: non-English15081381Claude Fable 5.1
LMArena Text: Chinese15841427Claude Fable 5.1
LMArena Text: German14991376Claude Fable 5.1
LMArena Text: Japanese15621369Claude Fable 5.1
LMArena Text: Korean15171359Claude Fable 5.1
LMArena Text: French15231408Claude Fable 5.1
LMArena Text: Spanish15201391Claude Fable 5.1
LMArena Text: Russian15201392Claude Fable 5.1
LMArena Text: Polish15251383Claude Fable 5.1
LMArena Text: multi-turn14931392Claude Fable 5.1
LMArena Text: longer queries15241408Claude Fable 5.1
LMArena Text: writing and language15101384Claude Fable 5.1
LMArena Text: entertainment and media14971364Claude Fable 5.1
LMArena Vision: English13131204Claude Fable 5.1
LMArena Vision: Chinese13911266Claude Fable 5.1
LMArena Vision: reading text13271225Claude Fable 5.1
LMArena Vision: humor1318Not measuredOnly Claude Fable 5.1 measured
LMArena Vision: creative writing13301205Claude 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 GPT-6 Luna
BenchmarkClaude Fable 5.1GPT-6 LunaLeader
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
GPT-6 Luna$0.0003Fits in one request

GPT-6 Luna costs less

Repository review

50K input + 3K output tokens

Claude Fable 5.1$0.650Fits in one request
GPT-6 Luna$0.0065Fits in one request

GPT-6 Luna costs less

Agent loop

200K input + 10K output tokens

Claude Fable 5.1$2.50Fits in one request
GPT-6 Luna$0.025Fits in one request

GPT-6 Luna 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 GPT-6 Luna
SpecificationAnthropic Claude Fable 5.1OpenAI GPT-6 Luna
MakerAnthropicOpenAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 1, 2026September 22, 2026
Context window1M1.05M
Input $/Mtok$10.00$0.10
Output $/Mtok$50.00$0.50
Coding index89.171.4
Independent measurements behind it22
Cost per solved taskNot computableNot computable
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Fable 5.1 better than GPT-6 Luna for coding?

Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 71.4 for GPT-6 Luna. Pick GPT-6 Luna when output tokens cost 100.0x less, or when the context window is larger, 1.05M against 1M tokens.

Which is cheaper, Claude Fable 5.1 or GPT-6 Luna?

Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; GPT-6 Luna costs $0.10 and $0.50. Cost per solved task is known for neither of them.

Which has the bigger context window, Claude Fable 5.1 or GPT-6 Luna?

GPT-6 Luna, with 1.05M tokens against 1M.

How many benchmarks is the Claude Fable 5.1 vs GPT-6 Luna comparison based on?

97 benchmarks have a result for both models as of October 21, 2026. Claude Fable 5.1's coding index rests on 2 independent benchmarks and GPT-6 Luna's on 2. Where only one model has a result, the page says so instead of naming a winner.

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