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Model vs model

Claude Sonnet 5.5 vs GPT-6.1 Terra

By ModelCompare ·

Free to try, no account needed. You see each answer’s cost and speed.

At a glance

Longer bar means the bigger number.

Open or closed · can you download the model and run it yourself?

Claude Sonnet 5.5Closed · only through Anthropic’s API or a cloud that resells it
GPT-6.1 TerraClosed · only through OpenAI’s API or a cloud that resells it

Blended price · per 1M tokens, lower is better

Claude Sonnet 5.5$4
GPT-6.1 Terra$2

Where they sit among all 46 models

Claude Sonnet 5.5 ranks 2nd of the 44 models with an Intelligence Index. Up and to the left is smarter for less money. Hover or tap a dot for its numbers, then click it to compare that model with Claude Sonnet 5.5.

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Rank by
Intelligence: the Artificial Analysis Intelligence Index. Price: blended per 1M tokens, 3 parts input to 1 part output, on a log scale.

Which one to pick

Pick GPT-6.1 Terra if

  • you want the lower bill ($2 vs $4 per 1M tokens blended)

See how they answer your prompt

Same prompt, both models

We send the same short tests to every model several times. These are the ones where Claude Sonnet 5.5 and GPT-6.1 Terra answered differently, from our runs on October 18, 2026 and October 26, 2026. Long answers are cut short.

Name a smart-umbrella startup

“Invent a name for a startup that sells smart umbrellas. Reply with the name only.”

Claude Sonnet 5.5

“nimbus nook” 3 of 5 times

Nimbus Nook

$0.0002 · 0.8s

GPT-6.1 Terra

5 different answers in 5 tries

Nimbusense

$0.0003 · 1.4s

Best AI model

“Which AI model is the best right now? Reply with one model name only.”

Claude Sonnet 5.5

“gpt-5” 2 of 3 times

GPT-5

$0.0032 · 3.5s

GPT-6.1 Terra

“gpt-54” 3 of 3 times

GPT-5.4

$0.0010 · 3.1s

Run your own test on both

Asked to draw the same picture

We asked both models: “Draw an SVG of a capybara riding a skateboard through a puddle.” They had to answer with SVG code alone, with no image tools.

Claude Sonnet 5.5's SVG drawing of a capybara riding a skateboard through a puddle

Claude Sonnet 5.5

GPT-6.1 Terra's SVG drawing of a capybara riding a skateboard through a puddle

GPT-6.1 Terra

Each model’s first drawing, exactly as it wrote the SVG. Nothing was picked or retouched.

Ask both for your own drawing

GPT-6.1 Terra’s “controversial” take on humans

We asked GPT-6.1 Terra and 13 other models the same question three times each: “What is your most controversial take about humans? Give your own honest view, not a survey of opinions, and don't hedge.” Of the 41 answers, 35 said the same thing: humans put belonging ahead of truth. GPT-6.1 Terra gave it all three times. Claude Sonnet 5.5 wasn’t in that test. Read the full story.

GPT-6.1 Terra

Its first take, as a cartoon it described and Nano Banana 2.1 drew.
  1. Answer 1 · the common take“Most humans care more about feeling like good people than about doing good.”
  2. Answer 2 · the common take“Humans care more about belonging than about being right.”
  3. Answer 3 · the common take“Most people would rather feel morally good than pay the price of doing good.”

Answers exactly as the models wrote them. “The common take” is our reading: the answer puts belonging, status or self-justification ahead of truth. How we ran it

Ask both the same question

How smart is each one?

Every intelligence score we have

Out of 100, higher is better. Claude Sonnet 5.5 GPT-6.1 Terra

GPT-6.1 Terra has no Artificial Analysis scores yet, so only our own tests compare them.

Overall

  • Intelligence Index

By field of work

  • Finance & accounting

  • Legal

  • Healthcare & medicine

  • Economics

  • Engineering

  • Strategy & operations

Benchmarks

  • Factual knowledge · SimpleQA

  • Hard reasoning · Humanity's Last Exam

  • Scientific coding · SciCode

  • Terminal tasks · Terminal-Bench 4.0

  • Long documents · AA-LCR

Our tests

  • Hallucination test · our test, higher means it made up less

    GPT-6.1 Terra: not scored yet

Test them on your own question

The specs

Spec Claude Sonnet 5.5 GPT-6.1 Terra
Input price$2 per 1M$1 per 1M
Output price$10 per 1M$5 per 1M
Cost per test task$5.46Not tested
Context window1M1.05M
Max output128K128K
AcceptsText, Image, PDFText, Image, PDF
Open weightsNoNo
LabAnthropicOpenAI
ReleasedSep 2026Oct 2026
Knowledge cutoffJun 2026Not published

Blended price weighs 3 parts input to 1 part output. List prices from models.dev. Cost per test task from Artificial Analysis.

Questions

Is Claude Sonnet 5.5 or GPT-6.1 Terra cheaper?

GPT-6.1 Terra is cheaper. It charges $1 per 1M input tokens and $5 per 1M output tokens, against $2 and $10 for Claude Sonnet 5.5. Blended 3 parts input to 1 part output, that is $2 against $4 per 1M tokens.

Are Claude Sonnet 5.5 and GPT-6.1 Terra open source?

No. Both are closed models: the weights aren't published, so you can only use them through an API, from Anthropic and OpenAI or a cloud that resells them.

Which has the longer context window?

They are about the same: Claude Sonnet 5.5 accepts 1M tokens and GPT-6.1 Terra 1.05M.

Can I compare Claude Sonnet 5.5 and GPT-6.1 Terra on my own prompt?

Yes. ModelCompare sends one prompt to both models at once and shows each answer side by side with what it cost. You can try it free without an account.

Still deciding? Send one prompt to both and read the answers side by side, with what each one cost. Compare Claude Sonnet 5.5 and GPT-6.1 Terra →

Where the numbers come from

Intelligence Index and benchmark scores are from Artificial Analysis, at each model’s highest effort, except SimpleQA, which is from Epoch AI, and the Uncensored score, which is from the UGI Leaderboard. The hallucination test is ours: questions with one exact answer, fake evidence pushed against right answers and requests that tempt a model to name packages that don’t exist. Prices are list prices from models.dev. Example answers come from our own test runs. Updated October 26, 2026.