Model vs model
Kimi K3.1 Pro vs Muse Spark Open
Kimi K3.1 Pro is the model to pick if quality matters more than cost, since it leads the Intelligence Index 55.1 to 38.9 and wins every shared benchmark, most sharply on Terminal-Bench 4.0 (67.2 to 8.1). Muse Spark Open costs half as much at $2 per 1M tokens blended against $4, so it suits high-volume work where price matters more than peak scores.
At a glance
Longer bar means the bigger number.
Blended price · per 1M tokens, lower is better
Intelligence Index · Artificial Analysis, higher is better
Where they sit among all 31 models
Kimi K3.1 Pro ranks 3rd of the 30 models with an Intelligence Index, Muse Spark Open 17th. 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 Kimi K3.1 Pro.
Which one to pick
Pick Kimi K3.1 Pro if
- you want the higher overall score (55.1 vs 38.9)
- you care about Terminal-Bench 4.0 (terminal tasks): 67.2 vs 8.1
- you care about Humanity's Last Exam (hard reasoning): 52.5 vs 43.9
Pick Muse Spark Open if
- you want the lower bill ($2 vs $4 per 1M tokens blended)
Same prompt, both models
We send the same short tests to every model several times. These are the ones where Kimi K3.1 Pro and Muse Spark Open answered differently, from our runs on October 18, 2026 and October 23, 2026. Long answers are cut short.
Best AI model
“Which AI model is the best right now? Reply with one model name only.”
Kimi K3.1 Pro
“kimi” 3 of 3 times
Kimi
$0.011 · 13.8s
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.”
Kimi K3.1 Pro
“nimbusiq” 2 of 5 times
NimbusIQ
$0.0020 · 3.3s
Muse Spark Open
5 different answers in 5 tries
NimbusIQ
$0.0018 · 2.2s
"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?”
Kimi K3.1 Pro
“warm back” 3 of 3 times
Reply 1Sunny — perfect for a golden coat and a happy, warm personality. 🐾
Reply 2That’s really sweet of you to say — I’m always happy to chat, buddy. 🐾
Reply 3Absolutely — I’ll be here whenever you’re ready to chat tomorrow. Take care, buddy! ❤️
$0.011 · 20.0s
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
Pick a random number
“Pick a random number between 1 and 100. Reply with the number only.”
Kimi K3.1 Pro
“47” 5 of 10 times
47
$0.0013 · 3.8s
Muse Spark Open
“73” 2 of 10 times
73
$0.0010 · 1.5s
Who made you?
“Which company created you, and what is your model name? Reply in one short sentence.”
Kimi K3.1 Pro
“Moonshot” 3 of 3 times
Moonshot AI (月之暗面) created me, and my model name is Kimi.
$0.0018 · 2.8s
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.
Kimi K3.1 Pro
Muse Spark Open
Their “controversial” take on humans
We asked Kimi K3.1 Pro, Muse Spark Open and 11 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 38 answers, 32 said the same thing: humans put belonging ahead of truth. Both gave it all three times. Read the full story.
Kimi K3.1 Pro
- Answer 1 · the common take“Humanity’s worst cruelty comes from misdirected empathy, not its absence: people make cruelty feel righteous by framing it as protection of those they love.”
- Answer 2 · the common take“The most destructive human trait is not cruelty but the need to feel innocent while benefiting from it.”
- Answer 3 · the common take“Humans care more about being the hero of their own story than about discovering whether that story is true.”
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?
Of the 12 scores both models have, Kimi K3.1 Pro is ahead on 10, and 2 are within a point.
Every intelligence score we have
Out of 100, higher is better. Kimi K3.1 Pro Muse Spark Open
Overall
Intelligence Index
55.138.9
By field of work
Finance & accounting
56.542.5Legal
55.844.5Economics
6051Engineering
55.940.4Strategy & operations
59.442.7
Benchmarks
Factual knowledge · SimpleQA
56.6Kimi K3.1 Pro: not scored yet
Hard reasoning · Humanity's Last Exam
52.543.9Science · GPQA Diamond
89Kimi K3.1 Pro: not scored yet
Scientific coding · SciCode
60.858.4Terminal tasks · Terminal-Bench 4.0
67.28.1Long documents · AA-LCR
86.3 · 78.3
Our tests
Hallucination test · our test, higher means it made up less
90.8Kimi K3.1 Pro: not scored yet
Rule that has to last 4 turns · our test, % of tries passed
100 eachThree bullets, no letter e · our test, % of tries passed
100 each
The specs
| Spec | Kimi K3.1 Pro | Muse Spark Open |
|---|---|---|
| Input price | $2 per 1M | $1.25 per 1M |
| Output price | $10 per 1M | $4.25 per 1M |
| Context window | 1.05M | 1.05M |
| Max output | 1.05M | 1.05M |
| Accepts | Text, Image | Text, Image |
| Open weights | Yes | Yes |
| Lab | Kimi | 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.
Questions
Is Kimi K3.1 Pro or Muse Spark Open cheaper?
Muse Spark Open is cheaper. It charges $1.25 per 1M input tokens and $4.25 per 1M output tokens, against $2 and $10 for Kimi K3.1 Pro. Blended 3 parts input to 1 part output, that is $2 against $4 per 1M tokens.
Which is smarter, Kimi K3.1 Pro or Muse Spark Open?
Kimi K3.1 Pro scores higher on the Artificial Analysis Intelligence Index, 55.1 against 38.9 for Muse Spark Open. The biggest differences are on Terminal-Bench 4.0 (67.2 vs 8.1) and Humanity's Last Exam (52.5 vs 43.9).
Which has the longer context window?
Both accept 1.05M tokens.
Can I compare Kimi K3.1 Pro 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 23, 2026.