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Claude Fable 5 vs GPT-5.6 Luna

Claude Fable 5 leads GPT-5.6 Luna on coding, 79.3 to 58.0 on the Vibe Coding Index, and GPT-5.6 Luna costs 41.7x less per output token ($1.20 vs $50.00 per million). Updated October 23, 2026; 109 benchmarks have a result for both.

Replace Claude Fable 5 Replace GPT-5.6 Luna
Claude Fable 5Anthropic
Coding
79.3
Overall
79.0
Output $/M
$50.00
106
GPT-5.6 LunaOpenAI
Coding
58.0
Overall
61.6
Output $/M
$1.20
3
vs boards won of 109 shared

Claude Fable 5 or GPT-5.6 Luna: which to pick

Pick Claude Fable 5 for coding: it scores 79.3 on the Vibe Coding Index against 58.0 for GPT-5.6 Luna.

Pick GPT-5.6 Luna for output tokens 41.7x cheaper ($1.20 vs $50.00 per million) and a lower cost per solved task ($0.04 against $2.16).

Model AClaude Fable 5Anthropic79.3/1006 independent benchmarks$2.16 per solved taskModel BGPT-5.6 LunaOpenAI58.0/1006 independent benchmarks$0.04 per solved task
Shared results
109
Claude Fable 5 only
26
GPT-5.6 Luna only
11
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 79.3 from 6 benchmarks, GPT-5.6 Luna 58.0 from 6 benchmarks.
Widest category
Agentic work, 15.6 points apart on average over 11 shared benchmarks.
Widest single gap
Kagi LLM Benchmark: Claude Fable 5 91.4% against GPT-5.6 Luna 49.1%, 42.3 points apart on a 0 to 100 scale.
Output price
Claude Fable 5 $50.00 against GPT-5.6 Luna $1.20 per million output tokens, 41.7x apart.
Context window
Claude Fable 5 takes 1M tokens, GPT-5.6 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 5BarsGPT-5.6 LunaTies
Coding180
Intelligence20
Agentic work110
Reasoning161
Math60
Knowledge110
Web design90
General332
All shared boards1063
CodingLike-for-likeSix of these boards feed the Vibe Coding Index180
Coding benchmarks for Claude Fable 5 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 LunaLeader
LiveBench coding98.3%73.6%Claude Fable 5
LMArena WebDev16241519Claude Fable 5
AA Coding Index76.571.4Claude Fable 5
LiveCodeBench (Vals AI)89.8%Not measuredOnly Claude Fable 5 measured
SWE-bench Verified (Vals AI)95.0%93.0%Claude Fable 5
Terminal-Bench 4 (Vals AI)41.4%11.6%Claude Fable 5
Vibe Code Bench (Vals AI)90.3%77.1%Claude Fable 5
Code migration (Vals AI)55.1%44.5%Claude Fable 5
ProgramBench (Vals AI)2.0%0.0%Claude Fable 5
IOI (Vals AI)Not measured61.8%Only GPT-5.6 Luna measured
Terminal-Bench 2.1 (Vals AI)80.5%79.0%Claude Fable 5
Vibe Code Bench 1-100 (Vals AI)Not measured22.6%Only GPT-5.6 Luna measured
SkillsBench (Vals AI)Not measured60.5%Only GPT-5.6 Luna measured
CyberBench (Vals AI)Not measured73.6%Only GPT-5.6 Luna measured
SciCode61.0%53.6%Claude Fable 5
Terminal-Bench Hard (Artificial Analysis run)62.9%Not measuredOnly Claude Fable 5 measured
FrontierCode53.5%39.8%Claude Fable 5
FrontierSWE47.0%Not measuredOnly Claude Fable 5 measured
GSO-Bench78.4%Not measuredOnly Claude Fable 5 measured
WeirdML91.9%60.9%Claude Fable 5
MirrorCode63.9%Not measuredOnly Claude Fable 5 measured
ALE-Bench2041.31667.4Claude Fable 5
LMArena Text: coding15181467Claude Fable 5
LMArena Text: software and IT15121464Claude Fable 5
LMArena WebDev: React16311508Claude Fable 5
LMArena WebDev: HTML16501520Claude Fable 5
LMArena WebDev: from an image16231517Claude Fable 5
SciCodeNot measured6.2%Only GPT-5.6 Luna measured
SWE Atlas: Codebase QnA39.0%Not measuredOnly Claude Fable 5 measured
SWE Atlas: Refactoring54.8%Not measuredOnly Claude Fable 5 measured
SWE Atlas: Test Writing55.6%Not measuredOnly Claude Fable 5 measured
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 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 LunaLeader
AA Intelligence Index49.637.3Claude Fable 5
Epoch Capabilities Index163.4156.5Claude Fable 5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index110
Agentic work benchmarks for Claude Fable 5 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 LunaLeader
AA Agentic Index50.742.1Claude Fable 5
Design Arena: agents building web apps1261Not measuredOnly Claude Fable 5 measured
Design Arena: agents building full-stack apps1280Not measuredOnly Claude Fable 5 measured
Design Arena: agents building mobile apps1263Not measuredOnly Claude Fable 5 measured
Design Arena: agents building Android apps1285Not measuredOnly Claude Fable 5 measured
Design Arena: agents building Godot games1292Not measuredOnly Claude Fable 5 measured
Design Arena: agents building games1285Not measuredOnly Claude Fable 5 measured
Design Arena: HTML slides1183Not measuredOnly Claude Fable 5 measured
Design Arena: PowerPoint slides1260Not measuredOnly Claude Fable 5 measured
LiveBench research86.9%51.0%Claude Fable 5
LiveBench browser92.0%68.0%Claude Fable 5
LiveBench long agentic53.2%30.4%Claude Fable 5
SREBench (Vals AI)Not measured1.5%Only GPT-5.6 Luna measured
Finance Agent (Vals AI)56.3%55.0%Claude Fable 5
Tax Agent Bench (Vals AI)38.3%24.8%Claude Fable 5
Legal Research Bench (Vals AI)49.5%36.5%Claude Fable 5
Excel Modeling Benchmark (Vals AI)73.7%67.1%Claude Fable 5
BioMysteryBench (Vals AI)Not measured61.5%Only GPT-5.6 Luna measured
Terminal-Bench-Science (Vals AI)15.7%0.0%Claude Fable 5
Vals Science IndexNot measured25.3%Only GPT-5.6 Luna measured
τ²-Bench Telecom98.5%Not measuredOnly Claude Fable 5 measured
APEX-Agents63.6%43.0%Claude Fable 5
Remote Labor Index16.1%Not measuredOnly Claude Fable 5 measured
BALROGNot measured45.6%Only GPT-5.6 Luna measured
PostTrainBench41.8%Not measuredOnly Claude Fable 5 measured
Vending-Bench 2$5,680$4,095Claude Fable 5
LMArena Search1229Not measuredOnly Claude Fable 5 measured
MCP Atlas83.3%Not measuredOnly Claude Fable 5 measured
Neither model has a result on the other 14 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index161
Reasoning benchmarks for Claude Fable 5 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 LunaLeader
GPQA Diamond93.2%91.7%Claude Fable 5
LiveBench reasoning89.7%85.6%Claude Fable 5
MysteryMechanism (Vals AI)Not measured14.4%Only GPT-5.6 Luna measured
MMMU Pro (Vals AI)89.3%85.0%Claude Fable 5
GPQA Diamond (Artificial Analysis run)92.6%91.1%Claude Fable 5
Humanity's Last Exam (Artificial Analysis run)55.5%39.5%Claude Fable 5
GPQA Diamond (Epoch AI run)85.9%91.6%GPT-5.6 Luna
ARC-AGI98.5%88.0%Claude Fable 5
ARC-AGI-289.2%59.5%Claude Fable 5
SimpleBench81.9%46.8%Claude Fable 5
Chess puzzles47.0%43.0%Claude Fable 5
Mystery game puzzles52.0%21.0%Claude Fable 5
EBR-bench39.5%Not measuredOnly Claude Fable 5 measured
LMArena Text: hard prompts15071452Claude Fable 5
LMArena Text: expert15341478Claude Fable 5
LMArena Text: hard prompts in English15091460Claude Fable 5
LMArena Vision: diagrams13571273Claude Fable 5
LMArena Vision: homework13611282Claude Fable 5
Kagi LLM Benchmark91.4%49.1%Claude Fable 5
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 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 LunaLeader
OTIS Mock AIME100.0%98.3%Claude Fable 5
FrontierMath, tiers 1 to 387.0%82.1%Claude Fable 5
FrontierMath, tier 490.2%61.0%Claude Fable 5
ProofBench95.0%60.0%Claude Fable 5
LMArena Text: math15161459Claude Fable 5
LMArena Text: mathematical work15151470Claude Fable 5
MathArena51.5%Not measuredOnly Claude Fable 5 measured
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index110
Knowledge benchmarks for Claude Fable 5 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 LunaLeader
MMLU Pro91.5%86.0%Claude Fable 5
LegalBench (Vals AI)88.6%84.0%Claude Fable 5
CorpFin (Vals AI)71.8%64.2%Claude Fable 5
TaxEval (Vals AI)76.9%76.2%Claude Fable 5
MortgageTax (Vals AI)68.9%67.3%Claude Fable 5
MedCode (Vals AI)56.1%42.4%Claude Fable 5
SimpleQA Verified70.7%41.0%Claude Fable 5
LMArena Text: science15061433Claude Fable 5
LMArena Text: medicine and healthcare14801398Claude Fable 5
LMArena Text: legal and government14981446Claude Fable 5
LMArena Text: business and finance14791439Claude Fable 5
FACTS Benchmark SuiteNot measured35.0%Only GPT-5.6 Luna measured
PRBench Finance53.9%Not measuredOnly Claude Fable 5 measured
PRBench Legal52.6%Not measuredOnly Claude Fable 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 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 LunaLeader
Design Arena: websites12951255Claude Fable 5
Design Arena: UI components13161248Claude Fable 5
Design Arena: game dev13351194Claude Fable 5
Design Arena: data viz13051212Claude Fable 5
Design Arena: 3D13191122Claude Fable 5
Design Arena: all code categories13101230Claude Fable 5
Design Arena: SVG13021193Claude Fable 5
Design Arena: ASCII art13291142Claude Fable 5
LiveBench design84.7%76.0%Claude Fable 5
GeneralLike-for-likePublic boards, shown as published, kept out of the index332
General benchmarks for Claude Fable 5 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 LunaLeader
LiveBench data analysis80.5%78.0%Claude Fable 5
Public Benefits Bench (Vals AI)70.4%61.2%Claude Fable 5
SAGE (Vals AI)51.9%44.2%Claude Fable 5
MedScribe (Vals AI)88.5%84.4%Claude Fable 5
Vals Multimodal Index74.2%69.1%Claude Fable 5
IFBench63.5%Not measuredOnly Claude Fable 5 measured
Long context reasoning (AA-LCR)82.3%83.7%GPT-5.6 Luna
DTBench98.4%89.1%Claude Fable 5
LMCA61.2%48.5%Claude Fable 5
Surface Evolver Bench95.0%61.9%Claude Fable 5
Furniture assembly35.8%42.5%GPT-5.6 Luna
LMArena Text14911431Claude Fable 5
LMArena Text: instruction following15021438Claude Fable 5
LMArena Text: creative writing14931396Claude Fable 5
LMArena Vision13251257Claude Fable 5
LMArena Text: English14981441Claude Fable 5
LMArena Text: non-English14811417Claude Fable 5
LMArena Text: Chinese15441470Claude Fable 5
LMArena Text: German14851455Claude Fable 5
LMArena Text: Japanese15061416Claude Fable 5
LMArena Text: Korean14881415Claude Fable 5
LMArena Text: French15061457Claude Fable 5
LMArena Text: Spanish14951445Claude Fable 5
LMArena Text: Russian15031428Claude Fable 5
LMArena Text: Polish14901404Claude Fable 5
LMArena Text: multi-turn15041435Claude Fable 5
LMArena Text: longer queries15101436Claude Fable 5
LMArena Text: writing and language15011419Claude Fable 5
LMArena Text: entertainment and media14821402Claude Fable 5
LMArena Vision: English13231263Claude Fable 5
LMArena Vision: Chinese13731294Claude Fable 5
LMArena Vision: reading text13371264Claude Fable 5
LMArena Vision: humor13411190Claude Fable 5
LMArena Vision: creative writing13381257Claude Fable 5
LMArena Document14961457Claude Fable 5
EQ-Bench 413401156Claude Fable 5
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 and GPT-5.6 Luna
BenchmarkClaude Fable 5GPT-5.6 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$0.035Fits in one request
GPT-5.6 Luna$0.0008Fits in one request

GPT-5.6 Luna costs less

Repository review

50K input + 3K output tokens

Claude Fable 5$0.650Fits in one request
GPT-5.6 Luna$0.014Fits in one request

GPT-5.6 Luna costs less

Agent loop

200K input + 10K output tokens

Claude Fable 5$2.50Fits in one request
GPT-5.6 Luna$0.052Fits in one request

GPT-5.6 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 and GPT-5.6 Luna
SpecificationAnthropic Claude Fable 5OpenAI GPT-5.6 Luna
MakerAnthropicOpenAI
WeightsNo public weights listedNo public weights listed
ReleasedJune 9, 2026July 9, 2026
Context window1M1.05M
Input $/Mtok$10.00$0.20
Output $/Mtok$50.00$1.20
Coding index79.358.0
Independent measurements behind it66
Cost per solved task$2.16$0.04
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Fable 5 better than GPT-5.6 Luna for coding?

Pick Claude Fable 5 for coding: it scores 79.3 on the Vibe Coding Index against 58.0 for GPT-5.6 Luna. Pick GPT-5.6 Luna for output tokens 41.7x cheaper ($1.20 vs $50.00 per million) and a lower cost per solved task ($0.04 against $2.16).

Which is cheaper, Claude Fable 5 or GPT-5.6 Luna?

Claude Fable 5 costs $10.00 per million input tokens and $50.00 per million output tokens; GPT-5.6 Luna costs $0.20 and $1.20. Per solved SWE-bench Verified task, Claude Fable 5 costs $2.16 and GPT-5.6 Luna $0.04.

Which has the bigger context window, Claude Fable 5 or GPT-5.6 Luna?

GPT-5.6 Luna, with 1.05M tokens against 1M.

How many benchmarks is the Claude Fable 5 vs GPT-5.6 Luna comparison based on?

109 benchmarks have a result for both models as of October 23, 2026. Claude Fable 5's coding index rests on 6 independent benchmarks and GPT-5.6 Luna's on 6. Where only one model has a result, the page says so instead of naming a winner.

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