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Claude Fable 5 vs Gemini 3.8 Flash

Claude Fable 5 leads Gemini 3.8 Flash on coding, 79.3 to 61.6 on the Vibe Coding Index, and Gemini 3.8 Flash costs 13.3x less per output token ($3.75 vs $50.00 per million). Updated October 22, 2026; 112 benchmarks have a result for both.

Replace Claude Fable 5 Replace Gemini 3.8 Flash
Claude Fable 5Anthropic
Coding
79.3
Overall
79.0
Output $/M
$50.00
86
Gemini 3.8 FlashGoogle
Coding
61.6
Overall
69.0
Output $/M
$3.75
23
vs boards won of 112 shared, 3 tied

Claude Fable 5 or Gemini 3.8 Flash: which to pick

Pick Claude Fable 5 for coding: it scores 79.3 on the Vibe Coding Index against 61.6 for Gemini 3.8 Flash.

Pick Gemini 3.8 Flash for output tokens 13.3x cheaper ($3.75 vs $50.00 per million) and a larger context window (1.05M against 1M tokens).

Model AClaude Fable 5Anthropic79.3/1006 independent benchmarks$2.16 per solved taskModel BGemini 3.8 FlashGoogle61.6/1006 independent benchmarks$2.74 per solved task
Shared results
112
Claude Fable 5 only
15
Gemini 3.8 Flash only
16
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, Gemini 3.8 Flash 61.6 from 6 benchmarks.
Widest category
Math, 23.0 points apart on average over 6 shared benchmarks.
Widest single gap
FrontierMath, tier 4: Claude Fable 5 90.2% against Gemini 3.8 Flash 22.0%, 68.2 points apart on a 0 to 100 scale.
Output price
Claude Fable 5 $50.00 against Gemini 3.8 Flash $3.75 per million output tokens, 13.3x apart.
Context window
Claude Fable 5 takes 1M tokens, Gemini 3.8 Flash 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 5BarsGemini 3.8 FlashTies
Coding191
Intelligence20
Agentic work162
Reasoning852 ties
Math42
Knowledge82
Web design711 tie
General2210
All shared boards86233 ties
CodingLike-for-likeSix of these boards feed the Vibe Coding Index191
Coding benchmarks for Claude Fable 5 and Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
LiveBench coding98.3%82.2%Claude Fable 5
LMArena WebDev16241585Claude Fable 5
AA Coding Index76.576.3Claude Fable 5
LiveCodeBench (Vals AI)89.8%89.5%Claude Fable 5
SWE-bench Verified (Vals AI)95.0%80.0%Claude Fable 5
Terminal-Bench 4 (Vals AI)41.4%19.7%Claude Fable 5
Vibe Code Bench (Vals AI)90.3%78.7%Claude Fable 5
Code migration (Vals AI)55.1%36.5%Claude Fable 5
ProgramBench (Vals AI)2.0%1.0%Claude Fable 5
IOI (Vals AI)Not measured56.9%Only Gemini 3.8 Flash measured
Terminal-Bench 2.1 (Vals AI)80.5%81.3%Gemini 3.8 Flash
SWE-bench Multimodal (Vals AI)Not measured40.8%Only Gemini 3.8 Flash measured
Vibe Code Bench 1-100 (Vals AI)Not measured18.8%Only Gemini 3.8 Flash measured
SkillsBench (Vals AI)Not measured58.0%Only Gemini 3.8 Flash measured
CyberBench (Vals AI)Not measured43.8%Only Gemini 3.8 Flash measured
SciCode61.0%56.6%Claude Fable 5
Terminal-Bench Hard (Artificial Analysis run)62.9%Not measuredOnly Claude Fable 5 measured
FrontierCode53.5%41.2%Claude Fable 5
FrontierSWE47.0%19.6%Claude Fable 5
GSO-Bench78.4%Not measuredOnly Claude Fable 5 measured
WeirdML91.9%84.8%Claude Fable 5
MirrorCode63.9%Not measuredOnly Claude Fable 5 measured
ALE-Bench2041.31269.7Claude Fable 5
LMArena Text: coding15181508Claude Fable 5
LMArena Text: software and IT15131507Claude Fable 5
LMArena WebDev: React16311577Claude Fable 5
LMArena WebDev: HTML16511616Claude Fable 5
LMArena WebDev: from an image16231593Claude Fable 5
SciCodeNot measured12.3%Only Gemini 3.8 Flash 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 and Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
AA Intelligence Index49.640.9Claude Fable 5
Epoch Capabilities Index163.4157.4Claude Fable 5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index162
Agentic work benchmarks for Claude Fable 5 and Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
AA Agentic Index50.740.2Claude Fable 5
Design Arena: agents building web apps12611238Claude Fable 5
Design Arena: agents building full-stack apps12801244Claude Fable 5
Design Arena: agents building mobile apps12641236Claude Fable 5
Design Arena: agents building Android apps12841078Claude Fable 5
Design Arena: agents building Godot games12921273Claude Fable 5
Design Arena: agents building games1285Not measuredOnly Claude Fable 5 measured
Design Arena: HTML slides1227Not measuredOnly Claude Fable 5 measured
Design Arena: PowerPoint slides12701153Claude Fable 5
Design Arena: spreadsheetsNot measured1022Only Gemini 3.8 Flash measured
LiveBench research86.9%79.1%Claude Fable 5
LiveBench browser92.0%64.0%Claude Fable 5
LiveBench long agentic53.2%30.1%Claude Fable 5
SREBench (Vals AI)Not measured11.1%Only Gemini 3.8 Flash measured
Finance Agent (Vals AI)56.3%61.4%Gemini 3.8 Flash
Tax Agent Bench (Vals AI)38.3%32.1%Claude Fable 5
Legal Research Bench (Vals AI)49.5%38.9%Claude Fable 5
Harvey's Legal Agent Benchmark (Vals AI)Not measured12.1%Only Gemini 3.8 Flash measured
Excel Modeling Benchmark (Vals AI)73.7%72.2%Claude Fable 5
BioMysteryBench (Vals AI)Not measured62.2%Only Gemini 3.8 Flash measured
Terminal-Bench-Science (Vals AI)15.7%8.6%Claude Fable 5
Vals Science IndexNot measured35.8%Only Gemini 3.8 Flash measured
Time Horizon Index (Vals AI)Not measured18.8%Only Gemini 3.8 Flash measured
CUA-bench (Vals AI)Not measured4.2%Only Gemini 3.8 Flash measured
τ²-Bench Telecom98.5%Not measuredOnly Claude Fable 5 measured
APEX-Agents63.6%64.3%Gemini 3.8 Flash
Remote Labor Index16.1%5.8%Claude Fable 5
PostTrainBench41.8%Not measuredOnly Claude Fable 5 measured
Vending-Bench 2$5,680$5,094Claude Fable 5
LMArena Search1229Not measuredOnly Claude Fable 5 measured
Neither model has a result on the other 11 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index85
Reasoning benchmarks for Claude Fable 5 and Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
GPQA Diamond93.2%94.4%Gemini 3.8 Flash
LiveBench reasoning89.7%89.3%Claude Fable 5
MysteryMechanism (Vals AI)Not measured36.5%Only Gemini 3.8 Flash measured
MMMU Pro (Vals AI)89.3%89.1%Claude Fable 5
GPQA Diamond (Artificial Analysis run)92.6%95.3%Gemini 3.8 Flash
Humanity's Last Exam (Artificial Analysis run)55.5%47.8%Claude Fable 5
GPQA Diamond (Epoch AI run)85.9%95.4%Gemini 3.8 Flash
ARC-AGI98.5%98.5%Tie
ARC-AGI-289.2%89.2%Tie
SimpleBench81.9%Not measuredOnly Claude Fable 5 measured
Chess puzzles47.0%58.0%Gemini 3.8 Flash
Mystery game puzzles52.0%47.0%Claude Fable 5
EBR-bench39.5%Not measuredOnly Claude Fable 5 measured
LMArena Text: hard prompts15071509Gemini 3.8 Flash
LMArena Text: expert15341526Claude Fable 5
LMArena Text: hard prompts in English15091504Claude Fable 5
LMArena Vision: diagrams13571345Claude Fable 5
LMArena Vision: homework13611351Claude Fable 5
Kagi LLM Benchmark91.4%Not measuredOnly Claude Fable 5 measured
Neither model has a result on the other 3 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index42
Math benchmarks for Claude Fable 5 and Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
OTIS Mock AIME100.0%98.9%Claude Fable 5
FrontierMath, tiers 1 to 387.0%68.4%Claude Fable 5
FrontierMath, tier 490.2%22.0%Claude Fable 5
ProofBench95.0%48.0%Claude Fable 5
LMArena Text: math15161532Gemini 3.8 Flash
LMArena Text: mathematical work15151519Gemini 3.8 Flash
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index82
Knowledge benchmarks for Claude Fable 5 and Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
MMLU Pro91.5%90.2%Claude Fable 5
LegalBench (Vals AI)88.6%87.0%Claude Fable 5
CorpFin (Vals AI)71.8%Not measuredOnly Claude Fable 5 measured
TaxEval (Vals AI)76.9%74.5%Claude Fable 5
MortgageTax (Vals AI)68.9%65.3%Claude Fable 5
MedCode (Vals AI)56.1%48.1%Claude Fable 5
SimpleQA Verified70.7%69.7%Claude Fable 5
LMArena Text: science15061523Gemini 3.8 Flash
LMArena Text: medicine and healthcare14801508Gemini 3.8 Flash
LMArena Text: legal and government14981497Claude Fable 5
LMArena Text: business and finance14801479Claude Fable 5
FACTS Benchmark SuiteNot measured69.4%Only Gemini 3.8 Flash measured
Neither model has a result on the other 6 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index71
Web design benchmarks for Claude Fable 5 and Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
Design Arena: websites12951300Gemini 3.8 Flash
Design Arena: UI components13161316Tie
Design Arena: game dev13351304Claude Fable 5
Design Arena: data viz13041270Claude Fable 5
Design Arena: 3D13181294Claude Fable 5
Design Arena: all code categories13101303Claude Fable 5
Design Arena: SVG13021296Claude Fable 5
Design Arena: ASCII art13291262Claude Fable 5
LiveBench design84.7%72.7%Claude Fable 5
GeneralLike-for-likePublic boards, shown as published, kept out of the index2210
General benchmarks for Claude Fable 5 and Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
Vals IndexNot measured56.0%Only Gemini 3.8 Flash measured
LiveBench data analysis80.5%54.0%Claude Fable 5
Public Benefits Bench (Vals AI)70.4%65.3%Claude Fable 5
SAGE (Vals AI)51.9%35.1%Claude Fable 5
MedScribe (Vals AI)88.5%84.5%Claude Fable 5
Vals Multimodal Index74.2%Not measuredOnly Claude Fable 5 measured
IFBench63.5%Not measuredOnly Claude Fable 5 measured
Long context reasoning (AA-LCR)82.3%84.0%Gemini 3.8 Flash
DTBench98.4%95.7%Claude Fable 5
LMCA61.2%52.9%Claude Fable 5
Surface Evolver Bench95.0%76.9%Claude Fable 5
Furniture assembly35.8%31.7%Claude Fable 5
LMArena Text14911499Gemini 3.8 Flash
LMArena Text: instruction following15021492Claude Fable 5
LMArena Text: creative writing14941488Claude Fable 5
LMArena Vision13251315Claude Fable 5
LMArena Text: English14981498Gemini 3.8 Flash
LMArena Text: non-English14821491Gemini 3.8 Flash
LMArena Text: Chinese15431553Gemini 3.8 Flash
LMArena Text: German14861501Gemini 3.8 Flash
LMArena Text: Japanese15041507Gemini 3.8 Flash
LMArena Text: Korean14871464Claude Fable 5
LMArena Text: French15051496Claude Fable 5
LMArena Text: Spanish14981487Claude Fable 5
LMArena Text: Russian15031514Gemini 3.8 Flash
LMArena Text: Polish14941497Gemini 3.8 Flash
LMArena Text: multi-turn15041503Claude Fable 5
LMArena Text: longer queries15101507Claude Fable 5
LMArena Text: writing and language15011494Claude Fable 5
LMArena Text: entertainment and media14821480Claude Fable 5
LMArena Vision: English13231318Claude Fable 5
LMArena Vision: Chinese13731416Gemini 3.8 Flash
LMArena Vision: reading text13371333Claude Fable 5
LMArena Vision: humor13411321Claude Fable 5
LMArena Vision: creative writing13381299Claude Fable 5
LMArena Document1496Not measuredOnly Claude Fable 5 measured
Neither model has a result on the other 10 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 Gemini 3.8 Flash
BenchmarkClaude Fable 5Gemini 3.8 FlashLeader
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
Gemini 3.8 Flash$0.0026Fits in one request

Gemini 3.8 Flash costs less

Repository review

50K input + 3K output tokens

Claude Fable 5$0.650Fits in one request
Gemini 3.8 Flash$0.049Fits in one request

Gemini 3.8 Flash costs less

Agent loop

200K input + 10K output tokens

Claude Fable 5$2.50Fits in one request
Gemini 3.8 Flash$0.188Fits in one request

Gemini 3.8 Flash 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 Gemini 3.8 Flash
SpecificationAnthropic Claude Fable 5Google Gemini 3.8 Flash
MakerAnthropicGoogle
WeightsNo public weights listedNo public weights listed
ReleasedJune 9, 2026September 2, 2026
Context window1M1.05M
Input $/Mtok$10.00$0.75
Output $/Mtok$50.00$3.75
Coding index79.361.6
Independent measurements behind it66
Cost per solved task$2.16$2.74
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Fable 5 better than Gemini 3.8 Flash for coding?

Pick Claude Fable 5 for coding: it scores 79.3 on the Vibe Coding Index against 61.6 for Gemini 3.8 Flash. Pick Gemini 3.8 Flash for output tokens 13.3x cheaper ($3.75 vs $50.00 per million) and a larger context window (1.05M against 1M tokens).

Which is cheaper, Claude Fable 5 or Gemini 3.8 Flash?

Claude Fable 5 costs $10.00 per million input tokens and $50.00 per million output tokens; Gemini 3.8 Flash costs $0.75 and $3.75. Per solved SWE-bench Verified task, Claude Fable 5 costs $2.16 and Gemini 3.8 Flash $2.74.

Which has the bigger context window, Claude Fable 5 or Gemini 3.8 Flash?

Gemini 3.8 Flash, with 1.05M tokens against 1M.

How many benchmarks is the Claude Fable 5 vs Gemini 3.8 Flash comparison based on?

112 benchmarks have a result for both models as of October 22, 2026. Claude Fable 5's coding index rests on 6 independent benchmarks and Gemini 3.8 Flash's on 6. Where only one model has a result, the page says so instead of naming a winner.

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