Qwen3.8 2.4T A95B vs Solar Pro 4
Pricing, context window and real answers (August 2026)
Qwen3.8 2.4T A95B (Qwen) and Solar Pro 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
 Qwen3.8 2.4T A95B | Solar Pro 4 | |
|---|---|---|
| Provider | Qwen | Upstage |
| Input (per 1M tokens) | ¥351.83 | ¥5.28 |
| Output (per 1M tokens) | ¥1,055.5 | ¥21.11 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥880 | ¥16 |
| Context window | 1,048,576 tokens | 524,288 tokens |
| Release date | 8/12/2026 | 8/10/2026 |
| Input modalities | text | text |
| Arena · overall | Unranked | #173 · ELO 1,376 |
| Arena · Japanese | Unranked | Unranked |
| Arena · coding | Unranked | #140 · ELO 1,448 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Solar Pro 4: ¥21.11 per 1M output tokens, 98% less than Qwen3.8 2.4T A95B.
- For long documents, Qwen3.8 2.4T A95B: a 1,048,576-token context window against 524,288 for Solar Pro 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.
Qwen3.8 2.4T A95B
To count the number of **“r”**s in **“strawberry”**, spell it out letter by letter:
**s t r a w b e r r y**
Now check each letter:
1. s — not r
2. t — not r
3. r — yes, count 1
4. a — not r
5. w — not r
6. b — not r
7. e — not r
8. r — yes, count 2
9. r — yes, count 3
10. y — not r
So there are **3** “r”s in **strawberry**.
1.3s203 output tokens
Solar Pro 4
The word "strawberry" contains **3** 'r's. Here's the step-by-step breakdown:
1. **Spell out the word explicitly** to isolate each letter:
`s - t - r - a - w - b - e - r - r - y`
2. **Scan through the letters in order** and count every instance of the lowercase letter `r`:
- `s` → 0
- `t` → 0
- `r` → **1**
- `a` → 0
- `w` → 0
- `b` → 0
- `e` → 0
- `r` → **2**
- `r` → **3**
- `y` → 0
3. **Total the count**: The three `r`s appear at positions 3, 8, and 9 in the 10-letter word.
**Final count: 3**
11.4s215 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…
Qwen3.8 2.4T A95B
The error happens because `users` is `undefined` when React tries to render this line:
```js
{users.map(user => <li key={user.id}>{user.name}</li>)}
```
JavaScript cannot call `.map()` on `undefined`.
In your component:
```js
function UserList({ users }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
React expects `users` to be an array, but something is rendering `<UserList />` without providing a valid `users` prop.
---
## Common causes
### 1. The parent component is not passing `users`
For example:
```js
<UserList />
```
Instead of:
```js
<UserList users={users} />
```
---
### 2. The data has not loaded yet
If `users…
10.9s1318 output tokens
Solar Pro 4
### What's Causing the Error
The error `TypeError: Cannot read properties of undefined (reading 'map')` means that the `users` prop being passed to your `UserList` component is `undefined`. Since you're calling `.map()` directly on it, JavaScript throws an error because `undefined` doesn't have a `map` method.
This typically happens when:
- The parent component hasn't passed the `users` prop
- The prop is still loading (e.g., from an API call)
- The prop is conditionally undefined
---
### How to Fix It
You have a few options to handle this safely:
#### ✅ Option 1: Add a Default Prop Value (Recommended)
Provide a fallback empty array so `.map()` always has something to work with:
```j…
24.7s539 output tokens
Professional Email
Write a professional email to a client explaining that the project delivery will be delayed by two weeks due to unexpected technical challenges discovered during integration testing. The tone should be apologetic but con…
Qwen3.8 2.4T A95B
Subject: Updated Project Timeline – Revised Delivery Date
Dear [Client Name],
I hope this message finds you well.
I’m writing to provide an important update regarding the delivery timeline for [Project Name]. During our recent integration testing phase, we identified several unexpected technical challenges that require additional resolution to ensure the final deliverable meets the quality and performance standards we committed to.
After carefully reviewing the scope of these items with our technical team, we have determined that the project delivery will need to be extended by two weeks. I sincerely apologize for any inconvenience this may cause. Please be assured that we are taking imm…
4.6s449 output tokens
Solar Pro 4
**Subject:** Important Update: Project Timeline Adjustment for [Project Name]
Dear [Client Name],
I am writing to provide you with a transparent update regarding the delivery schedule for [Project Name].
During our final integration testing phase, our engineering team identified unexpected technical complexities that require additional attention to ensure the system's long-term stability and performance. While our initial goal was to deliver by [Original Date], we have determined that we need two additional weeks to resolve these issues thoroughly.
**Revised Delivery Date:**
We now anticipate delivering the final solution by **[New Date, e.g., Friday, October 27th]**.
**Why This Matters…
5.2s382 output tokens
Frequently asked questions
- Which is cheaper, Qwen3.8 2.4T A95B or Solar Pro 4?
- Per 1M output tokens, Qwen3.8 2.4T A95B is ¥1,055.5 and Solar Pro 4 is ¥21.11 on FastMetal (yen, before tax), so Solar Pro 4 is cheaper.
- How do the context windows of Qwen3.8 2.4T A95B and Solar Pro 4 compare?
- Qwen3.8 2.4T A95B takes 1,048,576 tokens; Solar Pro 4 takes 524,288.
- Can I use Qwen3.8 2.4T A95B and Solar Pro 4 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "qwen3.8-2.4t-a95b" or "solar-pro4" 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 Qwen3.8 2.4T A95B and Solar Pro 4 from the browser chat and the API. No monthly fee.