ResearchLLM Verifications Leaderboard

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

Head to head · tested 27 Oct 2026

Claude Opus 5.5 vs Claude Sonnet 5.5: accuracy, speed and price

Similar accuracy; Claude Sonnet 5.5 costs less per question.

AnthropicClaude Opus 5.585.0% score · #1$0.015 per question129 tok/sAnthropicClaude Sonnet 5.578.8% score · #7$0.0054 per question126 tok/s

Verdict

Built from the measurements below

  • Accuracy is too close to call: Claude Opus 5.5 scored 85.0% and Claude Sonnet 5.5 78.8% on the same 80 questions, a gap within what chance alone could produce.
  • Claude Sonnet 5.5 is 2.7× cheaper per question as billed ($0.0054 vs $0.015), reasoning tokens included.
  • Output speed is similar (129 vs 126 tokens per second).
  • Claude Sonnet 5.5 starts answering sooner: 0.7 s to the first token, against 2.3 s for Claude Opus 5.5.

Which should you choose?

Choose Claude Sonnet 5.5 for the lower cost per correct answer ($0.0069 against $0.017) and a quicker first token. The widest subject gap is in law: Claude Opus 5.5 answered 5 of 6 correctly, Claude Sonnet 5.5 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 +6.3 points (z = 1.03). 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 Opus 5.5Claude Sonnet 5.5Edge
Verification scoreHigher is better85.0%78.8%Too close to call
Cost per questionLower is better$0.015$0.0054Claude Sonnet 5.5
Output speedHigher is better129126Similar
Time to first tokenLower is better2.3 s0.7 sClaude Sonnet 5.5
End-to-end response timeLower is better7.6 s6.2 sClaude Sonnet 5.5
Tokens per questionLower is better645456Claude Sonnet 5.5
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 Opus 5.5 first, Claude Sonnet 5.5 second

Verification scorehigher is better
Claude Opus 5.585.0%
Claude Sonnet 5.578.8%
Cost per questionlower is better
Claude Opus 5.5$0.015
Claude Sonnet 5.5$0.0054
Output speedhigher is better
Claude Opus 5.5129
Claude Sonnet 5.5126
Time to first tokenlower is better
Claude Opus 5.52.3 s
Claude Sonnet 5.50.7 s
End-to-end response timelower is better
Claude Opus 5.57.6 s
Claude Sonnet 5.56.2 s
Tokens per questionlower is better
Claude Opus 5.5645
Claude Sonnet 5.5456
Context windowhigher is better
Claude Opus 5.51M
Claude Sonnet 5.51M

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 405BMuse WonderGrok 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 SolGemini 4 ArgonGPT-5.4GPT-6 Lunagpt-oss-120bLlama 4 Maverick

Specifications and pricing

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

SpecificationClaude Opus 5.5Claude Sonnet 5.5
CreatorAnthropicAnthropic
Released22 Sept 202628 Sept 2026
Weights——
ReasoningYesYes
Inputtext, image, filetext, image, file
Outputtexttext
Context window1M tokens1M tokens
Knowledge cutoff——
List price in / out per 1M$4 / $20$2 / $10
Blended price per 1M (3:1)$8.00$4.00
Cheapest hostAmazon Bedrock · $4 / $20Google · $2 / $10
Hosts on OpenRouter55
Last tested25 Oct 202625 Oct 2026

Compare any two models →

Claude Opus 5.5 vs Claude Sonnet 5.5: frequently asked questions

Is Claude Opus 5.5 better than Claude Sonnet 5.5?
On accuracy they are statistically tied: Claude Opus 5.5 scored 85.0% and Claude Sonnet 5.5 78.8% on the same 80 questions from open datasets. Similar accuracy; Claude Sonnet 5.5 costs less per question.
Which is cheaper, Claude Opus 5.5 or Claude Sonnet 5.5?
Claude Sonnet 5.5 is cheaper: $0.0054 per question as billed, against $0.015. List prices: Claude Opus 5.5 $4 in / $20 out, Claude Sonnet 5.5 $2 in / $10 out per million tokens.
Which is faster, Claude Opus 5.5 or Claude Sonnet 5.5?
Their output speed is similar: 129 and 126 tokens per second.
Which has the larger context window, Claude Opus 5.5 or Claude Sonnet 5.5?
Both accept about the same amount of context: 1M and 1M tokens.