ResearchLLM Verifications Leaderboard

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

Head to head · tested 27 Oct 2026

GPT-5.6 Terra vs GPT-6 Sol: accuracy, speed and price

Similar accuracy; GPT-6 Sol costs less per question.

OpenAIGPT-5.6 Terra75.0% score · #15$0.0063 per question101 tok/sOpenAIGPT-6 Sol73.8% score · #18$0.0024 per question92 tok/s

Verdict

Built from the measurements below

  • Accuracy is too close to call: GPT-5.6 Terra scored 75.0% and GPT-6 Sol 73.8% on the same 80 questions, a gap within what chance alone could produce.
  • GPT-6 Sol is 2.7× cheaper per question as billed ($0.0024 vs $0.0063), reasoning tokens included.
  • Output speed is similar (101 vs 92 tokens per second).
  • GPT-6 Sol starts answering sooner: 0.9 s to the first token, against 1.1 s for GPT-5.6 Terra.

Which should you choose?

Choose GPT-6 Sol for the lower cost per correct answer ($0.0032 against $0.0084), a quicker first token and shorter outputs (about 174 tokens per question against 472). The widest subject gap is in engineering: GPT-5.6 Terra answered 11 of 15 correctly, GPT-6 Sol 8 of 15. With so few questions per subject, treat this as a lead to test on your own prompts, not a result.

Accuracy gap +1.2 points (z = 0.18). 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

MeasureGPT-5.6 TerraGPT-6 SolEdge
Verification scoreHigher is better75.0%73.8%Too close to call
Cost per questionLower is better$0.0063$0.0024GPT-6 Sol
Output speedHigher is better10192Similar
Time to first tokenLower is better1.1 s0.9 sGPT-6 Sol
End-to-end response timeLower is better5.3 s4.4 sGPT-6 Sol
Tokens per questionLower is better472174GPT-6 Sol
Context windowHigher is better1.1M1.1MSimilar

Side by side

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

Every measure

GPT-5.6 Terra first, GPT-6 Sol second

Verification scorehigher is better
GPT-5.6 Terra75.0%
GPT-6 Sol73.8%
Cost per questionlower is better
GPT-5.6 Terra$0.0063
GPT-6 Sol$0.0024
Output speedhigher is better
GPT-5.6 Terra101
GPT-6 Sol92
Time to first tokenlower is better
GPT-5.6 Terra1.1 s
GPT-6 Sol0.9 s
End-to-end response timelower is better
GPT-5.6 Terra5.3 s
GPT-6 Sol4.4 s
Tokens per questionlower is better
GPT-5.6 Terra472
GPT-6 Sol174
Context windowhigher is better
GPT-5.6 Terra1.1M
GPT-6 Sol1.1M

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

SpecificationGPT-5.6 TerraGPT-6 Sol
CreatorOpenAIOpenAI
Released9 Jul 202622 Sept 2026
Weights——
ReasoningYesYes
Inputfile, image, textfile, image, text
Outputtexttext
Context window1.1M tokens1.1M tokens
Knowledge cutoff16 Feb 2026—
List price in / out per 1M$2 / $12$2 / $10
Blended price per 1M (3:1)$4.50$4.00
Cheapest hostOpenAI · $1 / $6OpenAI · $1 / $5
Hosts on OpenRouter33
Last tested27 Oct 202625 Oct 2026

Compare any two models →

GPT-5.6 Terra vs GPT-6 Sol: frequently asked questions

Is GPT-5.6 Terra better than GPT-6 Sol?
On accuracy they are statistically tied: GPT-5.6 Terra scored 75.0% and GPT-6 Sol 73.8% on the same 80 questions from open datasets. Similar accuracy; GPT-6 Sol costs less per question.
Which is cheaper, GPT-5.6 Terra or GPT-6 Sol?
GPT-6 Sol is cheaper: $0.0024 per question as billed, against $0.0063. List prices: GPT-5.6 Terra $2 in / $12 out, GPT-6 Sol $2 in / $10 out per million tokens.
Which is faster, GPT-5.6 Terra or GPT-6 Sol?
Their output speed is similar: 101 and 92 tokens per second.
Which has the larger context window, GPT-5.6 Terra or GPT-6 Sol?
Both accept about the same amount of context: 1.1M and 1.1M tokens.