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Head-to-head comparison

Claude Fable 5.1 vs Gemini 3.8 Flash

Claude Fable 5.1 (Anthropic) and Gemini 3.8 Flash (Google) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 3 September 2026

As of 3 September 2026, Claude Fable 5.1 holds the stronger ModelCap Index position (#2 vs #11); and Gemini 3.8 Flash is 13.3× cheaper per output token ($3.75/1M vs $50.00/1M).

Which should you choose?

Choose Claude Fable 5.1 if…

  • you want the stronger overall ModelCap Index position — #2 against #11 (84.1 vs 76.4 points).
  • you want provider choice — 4 listed API providers against 2.
  • AA Intelligence Index is your yardstick — 65.7 against 58.7.
  • AA Terminal-Bench 2.1 is your yardstick — 91.4% against 87.6%.
  • AA Humanity's Last Exam is your yardstick — 59.1% against 47.8%.

Choose Gemini 3.8 Flash if…

  • API cost matters — $3.75/1M output tokens against $50.00/1M, about 13.3× cheaper.
  • your workload is prompt-heavy — input tokens cost $0.75/1M against $10.00/1M.
  • you want the more recently listed model — Gemini 3.8 Flash was listed 2 September 2026, Claude Fable 5.1 1 September 2026.

Claude Fable 5.1 vs Gemini 3.8 Flash: specs, pricing and context

Specification comparison of Claude Fable 5.1 and Gemini 3.8 Flash
FieldClaude Fable 5.1AnthropicGemini 3.8 FlashGoogle
ModelCap Index position#2#11
Index score84.176.4
EvidenceMeasuredMeasured
Input price / 1M tokens$10.00$0.75
Output price / 1M tokens$50.00$3.75
Context window1M tokens1M tokens
Max output tokens128K66K
API providers listed42
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileText, Image, Video, File, Audio
First listed1 September 20262 September 2026
PublisherAnthropicGoogle

Evidence: 2 public benchmark observations across 2 boards · 1 public benchmark observation across 1 board. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Fable 5.1 vs Gemini 3.8 Flash

Public benchmark boards where Claude Fable 5.1 or Gemini 3.8 Flash has a published result
BoardClaude Fable 5.1Gemini 3.8 FlashLeads
ARC-AGI-2ARC Prize Foundation90.0%Max—Only one result
AA Intelligence IndexArtificial Analysis65.7intelligence-index58.7intelligence-indexClaude Fable 5.1
AA Terminal-Bench 2.1Artificial Analysis91.4%terminal-bench-2.187.6%terminal-bench-2.1Claude Fable 5.1
AA Humanity's Last ExamArtificial Analysis59.1%humanitys-last-exam47.8%humanitys-last-examClaude Fable 5.1

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Claude Fable 5.1 vs Gemini 3.8 Flash: common questions

Is Claude Fable 5.1 better than Gemini 3.8 Flash?

Claude Fable 5.1 ranks higher on the ModelCap Index as of 3 September 2026: #2 against #11. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it.

Is Claude Fable 5.1 cheaper than Gemini 3.8 Flash?

Gemini 3.8 Flash is cheaper on output tokens: $3.75/1M against $50.00/1M. Input tokens are $10.00/1M for Claude Fable 5.1 and $0.75/1M for Gemini 3.8 Flash. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

Which has the bigger context window, Claude Fable 5.1 or Gemini 3.8 Flash?

Both publish a 1M-token context window.

Which is better for coding, Claude Fable 5.1 or Gemini 3.8 Flash?

AA Terminal-Bench 2.1: Claude Fable 5.1 91.4%, Gemini 3.8 Flash 87.6% — Claude Fable 5.1 leads.

Are Claude Fable 5.1 and Gemini 3.8 Flash open-weight models?

Claude Fable 5.1: API only. Gemini 3.8 Flash: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Claude Fable 5.1 and Gemini 3.8 Flash?

ModelCap currently lists 4 API providers for Claude Fable 5.1 and 2 for Gemini 3.8 Flash, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Fable 5.1 vs Gemini 3.8 Flash comparison?

Every figure comes from the sealed ModelCap dataset published 3 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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