Kimi K3.1 Pro vs Solar Mini 4
Pricing, context window and real answers (October 2026)
Kimi K3.1 Pro (Moonshot) and Solar Mini 4 (Upstage), compared as you can actually call them on FastMetal. Both are served from the same OpenAI-compatible endpoint and API key; switching is a change to the model string.
Specs and pricing
 Kimi K3.1 Pro | Solar Mini 4 | |
|---|---|---|
| Provider | Moonshot | Upstage |
| Input (per 1M tokens) | $2.11 | $0.055 |
| Output (per 1M tokens) | $10.55 | $0.22 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | $7.39 | $0.165 |
| Context window | 1,048,576 tokens | 524,288 tokens |
| Release date | 10/23/2026 | 9/23/2026 |
| Input modalities | text, image, video | text |
| Throughput (p50) | — | 95 tokens/s (n=27) |
| Arena · overall | Unranked | Unranked |
| Arena · Japanese | Unranked | Unranked |
| Arena · coding | Unranked | Unranked |
Prices are FastMetal's rates, before tax.
Rankings: LMArena leaderboard dataset (lmarena-ai/leaderboard-dataset), CC BY 4.0, snapshot 2026-10-22; category names mapped and ratings rounded by FastMetal.
Which should you pick?
- On price, Solar Mini 4: $0.22 per 1M output tokens, 98% less than Kimi K3.1 Pro.
- For long documents, Kimi K3.1 Pro: a 1,048,576-token context window against 524,288 for Solar Mini 4.
- If in doubt, try both on the same key. Switching is a change to the model string, and each is billed at its own rate.
Real answers to the same prompts
Exactly what the FastMetal gateway returned, side by side. Not benchmark scores: actual output.
Count the number of 'r's in 'strawberry'
Count the number of 'r's in 'strawberry'. Explain your reasoning step by step.
Kimi K3.1 Pro
There are **3** ‘r’s in **“strawberry.”**
1. Write out each letter: **s – t – r – a – w – b – e – r – r – y**
2. Locate the ‘r’s: positions **3, 8, and 9**.
3. Count them: **1 + 1 + 1 = 3**.
11.3s
Solar Mini 4
Sure! Let’s count the letter **'r'** in the word **'strawberry'** step by step.
**Step 1: Write out the word and its letters**
`s t r a w b e r r y`
**Step 2: Go through each letter one by one and check if it is 'r'**
1. `s` → not 'r'
2. `t` → not 'r'
3. `r` → **yes** (1st 'r')
4. `a` → not 'r'
5. `w` → not 'r'
6. `b` → not 'r'
7. `e` → not 'r'
8. `r` → **yes** (2nd 'r')
9. `r` → **yes** (3rd 'r')
10. `y` → not 'r'
**Step 3: Tally the total**
Total 'r' count = 3
**Final answer:** There are **3** letter 'r's in the word **'strawberry'**.
2.5s239 output tokens
Debug This Error
I'm getting the following error in my Node.js application: TypeError: Cannot read properties of undefined (reading 'map') at UserList (/app/components/UserList.js:12:25) at renderWithHooks (/app/node_modules/rea…
Kimi K3.1 Pro
## What's causing the error
The error means `users` is `undefined` when the component renders, and you can't call `.map()` on `undefined`. The component itself is fine — the problem is that whatever renders `<UserList />` either isn't passing the prop, or is passing a value that isn't an array yet.
The most common cause is **async data fetching**: the parent renders `UserList` before the data has loaded.
```jsx
function App() {
const [users, setUsers] = useState(); // ❌ undefined on first render
useEffect(() => {
fetch('/api/users')
.then(res => res.json())
.then(setUsers);
}, []);
return <UserList users={users} />; // users is undefined here initially
}
```
On…
36.3s
Solar Mini 4
This error occurs because the `users` prop being passed to your `UserList` component is `undefined` (or the component is rendered without that prop), and your code tries to call `.map()` on it.
### 🔍 Why this happens
In JavaScript, `undefined.map` is not a function, so calling it throws:
```
TypeError: Cannot read properties of undefined (reading 'map')
```
This commonly happens when:
- The parent component doesn't pass the `users` prop at all
- The parent passes `users` as `undefined`, `null`, or a non-array value (like a promise, object, or string)
- Data hasn't finished loading yet (e.g., fetched from an API asynchronously)
### ✅ How to fix it
The most robust solution is to provide a…
9.2s701 output tokens
Code Review
Please review the following Python function and suggest improvements for readability, performance, and best practices: def get_data(url, retries=3): import requests import time for i in range(retries):…
Kimi K3.1 Pro
The timeout and bounded retry loop are good starting points. The biggest issue is that failures—and even programming errors—are silently converted into retries and then `[]`.
### Suggested improvements
- **Avoid bare `except:`**. It catches `KeyboardInterrupt`, `KeyError`, JSON/schema errors, and other bugs. Retry only expected transient network failures; let malformed responses fail visibly.
- **Use a deliberate retry policy**. Retrying `401`, `403`, or `404` usually wastes time. Retry only transient statuses, use exponential backoff, and avoid sleeping after the final attempt.
- **Do not use `[]` for both failure and no results**. Prefer raising the final exception so callers can disting…
560.2s
Solar Mini 4
Here’s a reviewed version of your function, followed by a breakdown of the improvements:
```python
import time
import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry
def get_data(url: str, retries: int = 3) -> list[dict]:
"""
Fetch JSON from a URL and return a list of active items with name/id.
Args:
url: The endpoint to request.
retries: Number of retry attempts on failure.
Returns:
A list of dicts matching {'name': str, 'id': any} for active items.
"""
if retries < 1:
raise ValueError("retries must be at least 1")
session = requests.Session()
retry_strategy = Retry(
total=re…
10.8s1278 output tokens
Frequently asked questions
- Which is cheaper, Kimi K3.1 Pro or Solar Mini 4?
- Per 1M output tokens, Kimi K3.1 Pro is $10.55 and Solar Mini 4 is $0.22 on FastMetal (US dollars, before tax), so Solar Mini 4 is cheaper.
- How do the context windows of Kimi K3.1 Pro and Solar Mini 4 compare?
- Kimi K3.1 Pro takes 1,048,576 tokens; Solar Mini 4 takes 524,288.
- Can I use Kimi K3.1 Pro and Solar Mini 4 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "kimi-k3.1-pro" or "solar-mini4" as the model. Each is billed at its own rate from the same prepaid balance.
Try both on one API key
Create an account and add credit to call Kimi K3.1 Pro and Solar Mini 4 from the browser chat and the API. No monthly fee.