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Claude Fable 5.1 vs GPT-5.5

Updated October 21, 2026. 111 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-5.5
Claude Fable 5.1Anthropic
Coding
89.1
Overall
53.4
Output $/M
$50.00
106
GPT-5.5OpenAI
Coding
67.8
Overall
38.4
Output $/M
$30.00
5
vs boards won of 111 shared

Decision reading

Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 67.8 for GPT-5.5.

Pick GPT-5.5 when output tokens cost 1.7x 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-5.5OpenAI67.8/1002 independent benchmarks$1.65 per solved task
Shared results
111
Claude Fable 5.1 only
13
GPT-5.5 only
21
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-5.5 67.8 from 2 benchmarks.
Widest category
Agentic work, 23.4 points apart on average over 18 shared benchmarks.
Widest single gap
MirrorCode: Claude Fable 5.1 73.3% against GPT-5.5 10.0%, 63.3 points apart on a 0 to 100 scale.
Output price
Claude Fable 5.1 $50.00 against GPT-5.5 $30.00 per million output tokens, 1.7x apart.
Context window
Claude Fable 5.1 takes 1M tokens, GPT-5.5 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-5.5Ties
Coding191
Intelligence20
Agentic work171
Reasoning141
Math60
Knowledge100
Web design90
General292
All shared boards1065
CodingLike-for-likeFour of these boards feed the Vibe Coding Index191
Coding benchmarks for Claude Fable 5.1 and GPT-5.5
BenchmarkClaude Fable 5.1GPT-5.5Leader
LiveBench coding97.7%85.1%Claude Fable 5.1
LMArena WebDev17431513Claude Fable 5.1
AA Coding Index81.674.9Claude Fable 5.1
LiveCodeBench (Vals AI)90.5%85.3%Claude Fable 5.1
SWE-bench Verified (Vals AI)Not measured82.6%Only GPT-5.5 measured
Terminal-Bench 4 (Vals AI)58.1%Not measuredOnly Claude Fable 5.1 measured
Vibe Code Bench (Vals AI)90.3%69.8%Claude Fable 5.1
Code migration (Vals AI)54.6%45.2%Claude Fable 5.1
ProgramBench (Vals AI)7.0%0.5%Claude Fable 5.1
IOI (Vals AI)90.8%Not measuredOnly Claude Fable 5.1 measured
Terminal-Bench 2.1 (Vals AI)85.0%76.4%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%62.5%GPT-5.5
CyberBench (Vals AI)70.4%Not measuredOnly Claude Fable 5.1 measured
SciCode63.1%56.1%Claude Fable 5.1
Terminal-Bench Hard (Artificial Analysis run)Not measured60.6%Only GPT-5.5 measured
Terminal-BenchNot measured84.7%Only GPT-5.5 measured
FrontierCode50.9%43.0%Claude Fable 5.1
FrontierSWE56.3%Not measuredOnly Claude Fable 5.1 measured
GSO-Bench88.2%40.2%Claude Fable 5.1
WeirdML92.9%84.9%Claude Fable 5.1
MirrorCode73.3%10.0%Claude Fable 5.1
ALE-Bench2143.21943.0Claude Fable 5.1
LMArena Text: coding15321494Claude Fable 5.1
LMArena Text: software and IT15301493Claude Fable 5.1
LMArena WebDev: React17921506Claude Fable 5.1
LMArena WebDev: HTML16841543Claude Fable 5.1
LMArena WebDev: from an image17221532Claude Fable 5.1
Neither model has a result on the other 9 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Fable 5.1 and GPT-5.5
BenchmarkClaude Fable 5.1GPT-5.5Leader
AA Intelligence Index53.438.4Claude Fable 5.1
Epoch Capabilities Index166.5159.7Claude 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 GPT-5.5
BenchmarkClaude Fable 5.1GPT-5.5Leader
AA Agentic Index57.936.4Claude Fable 5.1
Design Arena: agents building web apps13181117Claude Fable 5.1
Design Arena: agents building full-stack apps13261089Claude Fable 5.1
Design Arena: agents building mobile apps12671143Claude Fable 5.1
Design Arena: agents building Android appsNot measured1169Only GPT-5.5 measured
Design Arena: agents building Godot games13271173Claude Fable 5.1
Design Arena: agents building gamesNot measured1179Only GPT-5.5 measured
Design Arena: HTML slidesNot measured1067Only GPT-5.5 measured
Design Arena: PowerPoint slides13281108Claude Fable 5.1
Design Arena: spreadsheets1374Not measuredOnly Claude Fable 5.1 measured
LiveBench research82.0%61.6%Claude Fable 5.1
LiveBench browser100.0%48.0%Claude Fable 5.1
LiveBench long agentic80.8%44.6%Claude Fable 5.1
SREBench (Vals AI)22.9%3.8%Claude Fable 5.1
Finance Agent (Vals AI)58.9%51.8%Claude Fable 5.1
Tax Agent Bench (Vals AI)49.2%21.8%Claude Fable 5.1
Legal Research Bench (Vals AI)55.3%40.4%Claude Fable 5.1
Excel Modeling Benchmark (Vals AI)76.7%64.5%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%8.3%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
τ²-Bench TelecomNot measured93.9%Only GPT-5.5 measured
APEX-Agents68.6%55.1%Claude Fable 5.1
Remote Labor Index17.9%6.3%Claude Fable 5.1
OSWorld 2.0Not measured13.0%Only GPT-5.5 measured
DeepResearch BenchNot measured54.0%Only GPT-5.5 measured
PostTrainBenchNot measured27.2%Only GPT-5.5 measured
SpireClimb2.0%Not measuredOnly Claude Fable 5.1 measured
Vending-Bench 2$5,422$7,524GPT-5.5
LMArena Search1246Not measuredOnly Claude Fable 5.1 measured
Neither model has a result on the other 8 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index141
Reasoning benchmarks for Claude Fable 5.1 and GPT-5.5
BenchmarkClaude Fable 5.1GPT-5.5Leader
GPQA Diamond93.4%93.2%Claude Fable 5.1
LiveBench reasoning91.7%89.7%Claude Fable 5.1
MysteryMechanism (Vals AI)47.8%Not measuredOnly Claude Fable 5.1 measured
MMMU Pro (Vals AI)90.6%88.3%Claude Fable 5.1
GPQA Diamond (Artificial Analysis run)93.7%93.5%Claude Fable 5.1
Humanity's Last Exam (Artificial Analysis run)59.1%45.8%Claude Fable 5.1
GPQA Diamond (Epoch AI run)Not measured90.7%Only GPT-5.5 measured
ARC-AGI97.5%95.0%Claude Fable 5.1
ARC-AGI-290.0%85.0%Claude Fable 5.1
SimpleBenchNot measured69.0%Only GPT-5.5 measured
Chess puzzles48.0%63.0%GPT-5.5
Mystery game puzzles58.0%56.0%Claude Fable 5.1
EBR-bench57.1%34.3%Claude Fable 5.1
LMArena Text: hard prompts15281489Claude Fable 5.1
LMArena Text: expert15441507Claude Fable 5.1
LMArena Text: hard prompts in English15221483Claude Fable 5.1
LMArena Vision: diagrams13431325Claude Fable 5.1
LMArena Vision: homework13451332Claude Fable 5.1
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 GPT-5.5
BenchmarkClaude Fable 5.1GPT-5.5Leader
OTIS Mock AIME100.0%84.4%Claude Fable 5.1
FrontierMath, tiers 1 to 390.2%85.3%Claude Fable 5.1
FrontierMath, tier 487.8%72.5%Claude Fable 5.1
ProofBench100.0%50.0%Claude Fable 5.1
LMArena Text: math15311487Claude Fable 5.1
LMArena Text: mathematical work15411496Claude 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 GPT-5.5
BenchmarkClaude Fable 5.1GPT-5.5Leader
MMLU Pro92.4%88.1%Claude Fable 5.1
LegalBench (Vals AI)88.5%86.5%Claude Fable 5.1
CaseLaw (Vals AI)Not measured66.2%Only GPT-5.5 measured
CorpFin (Vals AI)Not measured68.4%Only GPT-5.5 measured
TaxEval (Vals AI)76.0%75.0%Claude Fable 5.1
MortgageTax (Vals AI)70.8%68.8%Claude Fable 5.1
MedCode (Vals AI)53.5%49.1%Claude Fable 5.1
SimpleQA Verified70.8%63.0%Claude Fable 5.1
LMArena Text: science15321485Claude Fable 5.1
LMArena Text: medicine and healthcare15311465Claude Fable 5.1
LMArena Text: legal and government15141491Claude Fable 5.1
LMArena Text: business and finance14931478Claude Fable 5.1
Neither model has a result on the other 5 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-5.5
BenchmarkClaude Fable 5.1GPT-5.5Leader
Design Arena: websites13131256Claude Fable 5.1
Design Arena: UI components13381260Claude Fable 5.1
Design Arena: game dev13821294Claude Fable 5.1
Design Arena: data viz13441265Claude Fable 5.1
Design Arena: 3D13931198Claude Fable 5.1
Design Arena: all code categories13361260Claude Fable 5.1
Design Arena: SVG13011234Claude Fable 5.1
Design Arena: ASCII art13241254Claude Fable 5.1
LiveBench design83.4%70.3%Claude Fable 5.1
GeneralLike-for-likePublic boards, shown as published, kept out of the index292
General benchmarks for Claude Fable 5.1 and GPT-5.5
BenchmarkClaude Fable 5.1GPT-5.5Leader
LiveBench data analysis80.3%81.6%GPT-5.5
Public Benefits Bench (Vals AI)74.9%60.9%Claude Fable 5.1
SAGE (Vals AI)48.5%51.5%GPT-5.5
MedScribe (Vals AI)91.3%86.9%Claude Fable 5.1
Vals Multimodal IndexNot measured68.1%Only GPT-5.5 measured
IFBenchNot measured75.9%Only GPT-5.5 measured
Long context reasoning (AA-LCR)85.3%84.3%Claude Fable 5.1
DTBench97.6%96.0%Claude Fable 5.1
LMCA65.5%54.3%Claude Fable 5.1
Surface Evolver BenchNot measured88.1%Only GPT-5.5 measured
Furniture assembly70.0%44.2%Claude Fable 5.1
ExploitBenchNot measured47.4%Only GPT-5.5 measured
CL-bench LifeNot measured22.2%Only GPT-5.5 measured
LMArena Text15121471Claude Fable 5.1
LMArena Text: instruction following15181478Claude Fable 5.1
LMArena Text: creative writing15091455Claude Fable 5.1
LMArena Vision13191297Claude Fable 5.1
LMArena Text: English15061470Claude Fable 5.1
LMArena Text: non-English15081467Claude Fable 5.1
LMArena Text: Chinese15841534Claude Fable 5.1
LMArena Text: German14991480Claude Fable 5.1
LMArena Text: Japanese15621499Claude Fable 5.1
LMArena Text: Korean15171460Claude Fable 5.1
LMArena Text: French15231485Claude Fable 5.1
LMArena Text: Spanish15201468Claude Fable 5.1
LMArena Text: Russian15201473Claude Fable 5.1
LMArena Text: Polish15251465Claude Fable 5.1
LMArena Text: multi-turn14931476Claude Fable 5.1
LMArena Text: longer queries15241484Claude Fable 5.1
LMArena Text: writing and language15101466Claude Fable 5.1
LMArena Text: entertainment and media14971449Claude Fable 5.1
LMArena Vision: English13131292Claude Fable 5.1
LMArena Vision: Chinese13911360Claude Fable 5.1
LMArena Vision: reading text13271306Claude Fable 5.1
LMArena Vision: humor13181293Claude Fable 5.1
LMArena Vision: recognizing thingsNot measured1231Only GPT-5.5 measured
LMArena Vision: creative writing13301301Claude Fable 5.1
LMArena DocumentNot measured1486Only GPT-5.5 measured
Neither model has a result on the other 8 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-5.5
BenchmarkClaude Fable 5.1GPT-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
GPT-5.5$0.020Fits in one request

GPT-5.5 costs less

Repository review

50K input + 3K output tokens

Claude Fable 5.1$0.650Fits in one request
GPT-5.5$0.340Fits in one request

GPT-5.5 costs less

Agent loop

200K input + 10K output tokens

Claude Fable 5.1$2.50Fits in one request
GPT-5.5$1.30Fits in one request

GPT-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 GPT-5.5
SpecificationAnthropic Claude Fable 5.1OpenAI GPT-5.5
MakerAnthropicOpenAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 1, 2026April 24, 2026
Context window1M1.05M
Input $/Mtok$10.00$5.00
Output $/Mtok$50.00$30.00
Coding index89.167.8
Independent measurements behind it22
Cost per solved taskNot computable$1.65
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Fable 5.1 better than GPT-5.5 for coding?

Pick Claude Fable 5.1 for coding: it scores 89.1 on the Vibe Coding Index against 67.8 for GPT-5.5. Pick GPT-5.5 when output tokens cost 1.7x less, or when the context window is larger, 1.05M against 1M tokens.

Which is cheaper, Claude Fable 5.1 or GPT-5.5?

Claude Fable 5.1 costs $10.00 per million input tokens and $50.00 per million output tokens; GPT-5.5 costs $5.00 and $30.00. Cost per solved task is known for GPT-5.5 only.

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

GPT-5.5, with 1.05M tokens against 1M.

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

111 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-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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