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Comparison · 2 models · Updated Oct 4, 2026

Claude Fable 5.1 vs Gemini 3.8 Flash

Gemini 3.8 Flash comes out ahead, 75 to 66 on our weighted score, and it is the cheaper option too.

  1. Anthropic

    Claude Fable 5.1

    Released Sep 1, 2026

    66/100
    • ECI164.8
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Fable 5.1
  2. Our pick

    Google

    Gemini 3.8 Flash

    Released Sep 2, 2026

    75/100
    • ECI156.9
    • Price$0.75 / $3.75
    • Context1.05M
    Full specs Remove Gemini 3.8 Flash

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Gemini 3.8 Flash is our pick

Gemini 3.8 Flash is the better all-round choice, scoring 75/100 against Claude Fable 5.1 (66). It leads on price and inputs & features. Claude Fable 5.1 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Fable 5.1Capabilities Index (ECI): Claude Fable 5.1 164.8 · Gemini 3.8 Flash 156.9
  • Lowest priceGemini 3.8 FlashGemini 3.8 Flash $1.50 · Claude Fable 5.1 $20.00 per 1M tokens (3:1 blend)
  • Longest contextGemini 3.8 FlashGemini 3.8 Flash 1,048,576 · Claude Fable 5.1 1,000,000 tokens
  • Widest inputsGemini 3.8 FlashClaude Fable 5.1: Text, Images, PDFs · Gemini 3.8 Flash: Text, Images, PDFs, Audio, Video
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightClaude Fable 5.1Gemini 3.8 Flash
CapabilityCapabilities Index (ECI)50%9787
Price25%042
Inputs & features15%80100
Context window10%6061
Overall100%66/10075/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Claude Fable 5.1 vs Gemini 3.8 Flash specifications side by side
SpecificationClaude Fable 5.1AnthropicGemini 3.8 FlashGoogle
Capability
Capabilities Index (ECI)164.8 (best)156.9
ECI rank#4 of 148 (best)#15 of 148
GPQA DiamondGraduate-level science questions—95.4%
FrontierMath Tiers 1–3Research-level mathematics90.2% (best)68.4%
OTIS Mock AIME 2024–2025Competition mathematics100% (best)98.9%
SimpleQA VerifiedShort factual questions70.8% (best)69.7%
Price per million tokens
Input$10.00$0.75 (best)
Output$50.00$3.75 (best)
Cached input$0.25$0.075 (best)
Blended (3:1)$20.00$1.50 (best)
Long-context rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial Google API
Limits
Context window1,000,000 tokens1,048,576 tokens (best)
Max output128,000 tokens (best)65,536 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoYes
VideoNoYes
ReasoningYeslow · medium · high · xhigh · maxYeslow · medium · high
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDclaude-fable-5-1gemini-3.8-flash
API providers29 (best)21
ReleasedSep 1, 2026Sep 2, 2026
Knowledge cutoffJun 2026—
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • Claude Fable 5.1$200.00
  • Gemini 3.8 Flash$15.00
04 — Questions

Which should you choose?

Which is better: Claude Fable 5.1 or Gemini 3.8 Flash?

Gemini 3.8 Flash is the better all-round choice, scoring 75/100 against Claude Fable 5.1 (66). It leads on price and inputs & features. Claude Fable 5.1 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Fable 5.1 or Gemini 3.8 Flash?

Gemini 3.8 Flash is cheaper at $0.75 input / $3.75 output per million tokens (official Google API price). Claude Fable 5.1 costs $10.00 input / $50.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $1.50 per million tokens for Gemini 3.8 Flash versus $20.00 for Claude Fable 5.1 (13× as much).

Which scores higher on benchmarks?

Claude Fable 5.1 scores higher on the Capabilities Index (ECI): Claude Fable 5.1 164.8 (#4 of 148) and Gemini 3.8 Flash 156.9 (#15 of 148). Their confidence ranges do not overlap (161.8–169.1 vs 154.6–160.4), so the gap is a real one. On individual benchmarks: FrontierMath Tiers 1–3 — Claude Fable 5.1 90.2%, Gemini 3.8 Flash 68.4%; OTIS Mock AIME 2024–2025 — Claude Fable 5.1 100%, Gemini 3.8 Flash 98.9%; SimpleQA Verified — Claude Fable 5.1 70.8%, Gemini 3.8 Flash 69.7%.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Fable 5.1 and Gemini 3.8 Flash yet, so there is no like-for-like coding score. On overall capability, Claude Fable 5.1 leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Gemini 3.8 Flash has the largest context window at 1,048,576 tokens, against 1,000,000 for Claude Fable 5.1. Maximum output per response: Claude Fable 5.1 up to 128,000, Gemini 3.8 Flash up to 65,536 tokens.

Which can read images, PDFs, audio or video?

Claude Fable 5.1 accepts text, images and PDFs; Gemini 3.8 Flash accepts text, images, PDFs, audio and video. Gemini 3.8 Flash handles the widest range of inputs.

Are any of these open source?

No. Claude Fable 5.1 and Gemini 3.8 Flash are proprietary and only available through APIs and apps.

Which is newer?

Gemini 3.8 Flash is the newest, released Sep 2, 2026. Claude Fable 5.1 came out Sep 1, 2026. Knowledge cutoff: Claude Fable 5.1 Jun 2026.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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