ResearchLLM Verifications Leaderboard

Data as of · 78 models, 80 questions · reviewed by Suhas Bhairav · methodology

Head to head · tested 27 Oct 2026

Claude Fable 5.1 vs Gemini 3.1 Pro Preview: accuracy, speed and price

Similar accuracy; Gemini 3.1 Pro Preview is faster.

AnthropicClaude Fable 5.181.2% score · #5$0.016 per question70 tok/sGoogleGemini 3.1 Pro Preview77.5% score · #9$0.017 per question124 tok/s

Verdict

Built from the measurements below

  • Accuracy is too close to call: Claude Fable 5.1 scored 81.2% and Gemini 3.1 Pro Preview 77.5% on the same 80 questions, a gap within what chance alone could produce.
  • They cost about the same per question ($0.016 vs $0.017).
  • Gemini 3.1 Pro Preview generates text 1.8× faster: 124 tokens per second against 70.
  • Claude Fable 5.1 starts answering sooner: 2.1 s to the first token, against 3.4 s for Gemini 3.1 Pro Preview.

Which should you choose?

Choose Claude Fable 5.1 for the lower cost per correct answer ($0.02 against $0.022), a quicker first token, shorter outputs (about 238 tokens per question against 1,382) and more hosts to choose from on OpenRouter (4 against 2). Choose Gemini 3.1 Pro Preview for faster streaming. The widest subject gap is in law: Claude Fable 5.1 answered 5 of 6 correctly, Gemini 3.1 Pro Preview 3 of 6. With so few questions per subject, treat this as a lead to test on your own prompts, not a result.

Accuracy gap +3.7 points (z = 0.59). A winner is called only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.

Head to head

Same questions, same prompt, same API

MeasureClaude Fable 5.1Gemini 3.1 Pro PreviewEdge
Verification scoreHigher is better81.2%77.5%Too close to call
Cost per questionLower is better$0.016$0.017Similar
Output speedHigher is better70124Gemini 3.1 Pro Preview
Time to first tokenLower is better2.1 s3.4 sClaude Fable 5.1
End-to-end response timeLower is better11.0 s8.9 sGemini 3.1 Pro Preview
Tokens per questionLower is better2381,382Claude Fable 5.1
Context windowHigher is better1M1MSimilar

Side by side

Bars are scaled to the larger of the two values. The winner on each measure is marked in bold.

Every measure

Claude Fable 5.1 first, Gemini 3.1 Pro Preview second

Verification scorehigher is better
Claude Fable 5.181.2%
Gemini 3.1 Pro Preview77.5%
Cost per questionlower is better
Claude Fable 5.1$0.016
Gemini 3.1 Pro Preview$0.017
Output speedhigher is better
Claude Fable 5.170
Gemini 3.1 Pro Preview124
Time to first tokenlower is better
Claude Fable 5.12.1 s
Gemini 3.1 Pro Preview3.4 s
End-to-end response timelower is better
Claude Fable 5.111.0 s
Gemini 3.1 Pro Preview8.9 s
Tokens per questionlower is better
Claude Fable 5.1238
Gemini 3.1 Pro Preview1,382
Context windowhigher is better
Claude Fable 5.11M
Gemini 3.1 Pro Preview1M

Score vs. cost per question

Both models in color, every other model in grey

Most attractive quadrant0255075100$0.00001$0.0001$0.001$0.01$0.10Cost per question (USD, log) →Verification score (%) →Qwen3.8 2.4T A95BCommand AReka Flash 3Gemma 4 26B A4BGemma 4 31BQwen3.5 397B A17BHermes 4 405BClaude Fable 5.1Grok 4.7o3gpt-oss-20bMinistral 3 3B 2512Nova Micro 1.0Phi 4Granite 4.2 8BHy3GLM 5.3 FlashSolar Pro 4Trinity Large ThinkingMiniMax M3Mistral Large 4Claude Opus 5.5GPT-6.1 SolGPT-6 Lunagpt-oss-120bLlama 4 MaverickQwen3.8 Max (0902)

Specifications and pricing

From OpenRouter's catalogue, plus the leaderboard's test dates

SpecificationClaude Fable 5.1Gemini 3.1 Pro Preview
CreatorAnthropicGoogle
Released1 Sept 202619 Feb 2026
Weights——
ReasoningYesYes
Inputtext, image, fileaudio, file, image, text, video
Outputtexttext
Context window1M tokens1M tokens
Knowledge cutoff——
List price in / out per 1M$10 / $50$2 / $12
Blended price per 1M (3:1)$20.00$4.50
Cheapest hostAzure · $10 / $50Google · $1 / $6
Hosts on OpenRouter42
Last tested27 Oct 202626 Oct 2026

Compare any two models →

Claude Fable 5.1 vs Gemini 3.1 Pro Preview: frequently asked questions

Is Claude Fable 5.1 better than Gemini 3.1 Pro Preview?
On accuracy they are statistically tied: Claude Fable 5.1 scored 81.2% and Gemini 3.1 Pro Preview 77.5% on the same 80 questions from open datasets. Similar accuracy; Gemini 3.1 Pro Preview is faster.
Which is cheaper, Claude Fable 5.1 or Gemini 3.1 Pro Preview?
They cost about the same per question as billed: $0.016 for Claude Fable 5.1 and $0.017 for Gemini 3.1 Pro Preview.
Which is faster, Claude Fable 5.1 or Gemini 3.1 Pro Preview?
Gemini 3.1 Pro Preview is faster at 124 output tokens per second, against 70. Time to first token: 2.1 s for Claude Fable 5.1, 3.4 s for Gemini 3.1 Pro Preview.
Which has the larger context window, Claude Fable 5.1 or Gemini 3.1 Pro Preview?
Both accept about the same amount of context: 1M and 1M tokens.