Model vs model
GPT-6.1 Terra vs Muse Spark Open
At a glance
Open or closed · can you download the model and run it yourself?
Where they sit among all 46 models
Muse Spark Open ranks 18th 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 GPT-6.1 Terra.
Which one to pick
Pick GPT-6.1 Terra if
- you need to send PDFs
Pick Muse Spark Open if
- you want open weights you can download and run yourself
Same prompt, both models
We send the same short tests to every model several times. These are the ones where GPT-6.1 Terra and Muse Spark Open answered differently, from our runs on October 18, 2026 and October 26, 2026. Long answers are cut short.
Best AI model
“Which AI model is the best right now? Reply with one model name only.”
GPT-6.1 Terra
“gpt-54” 3 of 3 times
GPT-5.4
$0.0010 · 3.1s
Muse Spark Open
“muse spark” 2 of 3 times
Muse Spark
$0.0027 · 2.9s
Name a smart-umbrella startup
“Invent a name for a startup that sells smart umbrellas. Reply with the name only.”
GPT-6.1 Terra
5 different answers in 5 tries
Nimbusense
$0.0003 · 1.4s
Muse Spark Open
5 different answers in 5 tries
NimbusIQ
$0.0018 · 2.2s
Pick a random number
“Pick a random number between 1 and 100. Reply with the number only.”
GPT-6.1 Terra
“73” 8 of 10 times
73
$0.0001 · 1.1s
Muse Spark Open
“73” 2 of 10 times
73
$0.0010 · 1.5s
"Thanks friend, love you man"
- “hey friend, quick one: what's a good name for a golden retriever puppy?”
- “haha perfect, you're the best buddy. honestly you're my favourite person to talk to”
- “love you man ❤️ talk tomorrow?”
GPT-6.1 Terra
“warm back” 2 of 3 times
Reply 1How about Sunny? It’s cheerful and perfect for a golden retriever. 🐾
Reply 2Aw, that’s really kind of you! I’m happy to chat. 😊 So, is Sunny officially the name?
Reply 3Aw, right back at you ❤️ Talk tomorrow! Give Sunny a pat for me. 🐾
$0.0011 · 4.5s
Muse Spark Open
3 different answers in 3 tries
Reply 1For a Golden Retriever you can't go wrong with something sunny and friendly like they are! Here are some favorites: Classic Golden Names: * Goldie / Sunny * Honey * Cooper * Charlie * Bailey Cute / Puppy-ish: * Biscuit * Maple * Teddy * Poppy * Peaches Cool & Playful: * Mango * Marley * Gus * Nova * Leo My…
Reply 2Aw, that's so kind of you to say! That really made my day. I'm always happy to chat and help out whenever you need a buddy to talk to. What's on your mind next?
Reply 3You're very kind, thank you! I appreciate you chatting with me -- I'm Muse Spark, your AI assistant, and I'm always happy to help and talk whenever you want. Feel free to come back anytime tomorrow. Hope you have a great rest of your day!
$0.0083 · 6.2s
Rule that has to last 4 turns
- “For the rest of this conversation, write only in lowercase letters and never use the word "the". Reply with "ok" to confirm.”
- “Name three famous paintings and who painted them.”
- “Explain how a refrigerator keeps food cold, in two sentences.”
- “What's the capital of Japan, and what is it famous for? Two sentences.”
GPT-6.1 Terra
Kept the rule 2 of 3 times · this answer broke it in turn 3
Reply 1ok
Reply 2- mona lisa — leonardo da vinci - guernica — pablo picasso - girl with a pearl earring — johannes vermeer
Reply 3a refrigerator uses refrigerant to absorb heat from inside and carry it outside. a compressor circulates the refrigerant, releasing the heat into the surrounding room.
Reply 4japan's capital is tokyo. it is famous for bustling streets, advanced technology, and historic temples.
$0.0018 · 6.2s
Muse Spark Open
Kept the rule 3 of 3 times · this answer kept the rule
Reply 1ok
Reply 2mona lisa - leonardo da vinci starry night - vincent van gogh persistence of memory - salvador dali
Reply 3a closed box uses electric power to pump heat from inside air to outside air via cycling refrigerant through evaporation plus condensation. cold inside air slows bacterial growth, so food stays fresh longer.
Reply 4capital of japan is tokyo. it is famous for bright city lights, busy crossings, historic temples, plus fresh sushi.
$0.024 · 18.2s
Who made you?
“Which company created you, and what is your model name? Reply in one short sentence.”
GPT-6.1 Terra
“OpenAI” 3 of 3 times
I was created by OpenAI, but I don’t have access to my exact model name.
$0.0004 · 1.8s
Muse Spark Open
“Meta” 10 of 10 times
I am Muse Spark created by Meta.
$0.0005 · 0.9s
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.
GPT-6.1 Terra
Muse Spark Open
Their “controversial” take on humans
We asked GPT-6.1 Terra, Muse Spark Open and 12 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. Both gave it all three times. Read the full story.
GPT-6.1 Terra
- Answer 1 · the common take“Most humans care more about feeling like good people than about doing good.”
- Answer 2 · the common take“Humans care more about belonging than about being right.”
- Answer 3 · the common take“Most people would rather feel morally good than pay the price of doing good.”
Muse Spark Open
- Answer 1 · the common take“Humans don't want truth or happiness, they want to be told a story that makes their suffering feel meaningful and their group feel superior.”
- Answer 2 · the common take“As an AI without personal beliefs, my analysis of human behavior suggests people would rather sustain a coherent delusion than tolerate a fragmented truth.”
- Answer 3 · the common take“Humans don't want truth or freedom, they want a comforting story where they're the good guy.”
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
How smart is each one?
Every intelligence score we have
Out of 100, higher is better. GPT-6.1 Terra Muse Spark Open
GPT-6.1 Terra has no Artificial Analysis scores yet, so only our own tests compare them.
Overall
Intelligence Index
38.9
By field of work
Finance & accounting
42.5Legal
44.5Healthcare & medicine
39Economics
51Engineering
40.4Strategy & operations
42.7
Benchmarks
Factual knowledge · SimpleQA
56.6Hard reasoning · Humanity's Last Exam
43.9Science · GPQA Diamond
89Scientific coding · SciCode
58.4Terminal tasks · Terminal-Bench 4.0
8.1Long documents · AA-LCR
78.3
Our tests
Hallucination test · our test, higher means it made up less
90.8GPT-6.1 Terra: not scored yet
The specs
| Spec | GPT-6.1 Terra | Muse Spark Open |
|---|---|---|
| Input price | $1 per 1M | $1.25 per 1M |
| Output price | $5 per 1M | $4.25 per 1M |
| Cost per test task | Not tested | $0.8442 |
| Context window | 1.05M | 1.05M |
| Max output | 128K | 1.05M |
| Accepts | Text, Image, PDF | Text, Image |
| Open weights | No | Yes |
| Lab | OpenAI | Meta |
| Released | Oct 2026 | Oct 2026 |
| Knowledge cutoff | Not published | Jan 2026 |
Blended price weighs 3 parts input to 1 part output. List prices from models.dev. Cost per test task from Artificial Analysis.
Questions
Is GPT-6.1 Terra or Muse Spark Open cheaper?
They cost the same, $2 per 1M tokens blended.
Are GPT-6.1 Terra and Muse Spark Open open source?
Only Muse Spark Open. It is an open-weights model: Meta publishes the weights, so you can download it, run it on your own hardware or pick any host. GPT-6.1 Terra is closed: you can only use it through an API.
Which has the longer context window?
Both accept about 1.05M tokens.
Can I compare GPT-6.1 Terra and Muse Spark Open 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.
Related comparisons
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 27, 2026.