DeepSeek V4 Pro vs Qwen3.8 Max
Pricing, context window and real answers (August 2026)
DeepSeek V4 Pro (DeepSeek) and Qwen3.8 Max (Qwen), 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
 DeepSeek V4 Pro |  Qwen3.8 Max | |
|---|---|---|
| Provider | DeepSeek | Qwen |
| Input (per 1M tokens) | ¥341.32 | ¥357.4 |
| Output (per 1M tokens) | ¥684.42 | ¥1,072.2 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥684 | ¥894 |
| Context window | 1,048,576 tokens | 1,000,000 tokens |
| Release date | 4/24/2026 | 8/3/2026 |
| Input modalities | text | text, image |
| Arena · overall | #49 · ELO 1,457 | Unranked |
| Arena · Japanese | #18 · ELO 1,462 | Unranked |
| Arena · coding | #54 · ELO 1,502 | Unranked |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, DeepSeek V4 Pro: ¥684.42 per 1M output tokens, 36% less than Qwen3.8 Max.
- For long documents, DeepSeek V4 Pro: a 1,048,576-token context window against 1,000,000 for Qwen3.8 Max.
- 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.
DeepSeek V4 Pro
The word is "strawberry". Let's count the occurrences of the letter 'r' step by step:
1. Write the word: s t r a w b e r r y
2. Examine each character:
- s: not an 'r'
- t: not an 'r'
- r: is an 'r' → count 1
- a: not an 'r'
- w: not an 'r'
- b: not an 'r'
- e: not an 'r'
- r: is an 'r' → count 2
- r: is an 'r' → count 3
- y: not an 'r'
3. Total number of 'r's = 3.
Therefore, there are **3** 'r's in "strawberry".
7.3s1136 output tokens
Qwen3.8 Max
The word **strawberry** is spelled:
**s t r a w b e r r y**
Now count the letter **r**:
1. s
2. t
3. **r** ← first r
4. a
5. w
6. b
7. e
8. **r** ← second r
9. **r** ← third r
10. y
There are **3** letters **r** in **strawberry**.
3.5s156 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…
DeepSeek V4 Pro
The error is occurring because `users` is `undefined` when the component renders, and you're trying to call `.map()` on it. This typically happens when the data hasn't been loaded yet or wasn't passed correctly to the component.
## Here are several ways to fix this:
### 1. **Add a default value with empty array (Simplest fix)**
```javascript
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
### 2. **Add a conditional check**
```javascript
function UserList({ users }) {
if (!users) {
return <div>No users found</div>;
}
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}<…
6.9s442 output tokens
Qwen3.8 Max
The error means `users` is `undefined` when `UserList` tries to render:
```js
{users.map(user => ...)}
```
JavaScript cannot call `.map()` on `undefined`, so React throws:
```text
Cannot read properties of undefined (reading 'map')
```
## Most likely cause
The parent component is rendering `UserList` without passing a valid `users` array, or it is passing `users` before the data has loaded.
For example:
```jsx
<UserList />
```
or:
```jsx
<UserList users={undefined} />
```
or:
```jsx
const [users, setUsers] = useState(); // undefined initially
```
Then later:
```jsx
<UserList users={users} />
```
On the first render, `users` is still `undefined`.
---
## Fix 1: Give `users` a d…
17.7s1020 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…
DeepSeek V4 Pro
Subject: Update on [Project Name] Delivery Timeline
Dear [Client Name],
I hope this message finds you well. I’m writing to share an important update on the delivery timeline for [Project Name].
During our integration testing phase, we encountered unexpected technical challenges that are more complex than initially anticipated. While we’ve already made significant progress in diagnosing the root causes, resolving them thoroughly and ensuring the solution meets the high standards we’ve set together will require additional time. As a result, we must adjust the delivery date by two weeks.
I want to sincerely apologize for this delay and any inconvenience it may cause. We fully unders…
28.3s1210 output tokens
Qwen3.8 Max
Subject: Revised Project Delivery Timeline – Updated Schedule and Next Steps
Dear [Client Name],
I hope this message finds you well.
I am writing to provide an update on the current status of the project and to inform you that, during our recent integration testing phase, we encountered several unexpected technical challenges that will impact the original delivery timeline. After careful review with the technical team, we now anticipate the revised delivery date will be [insert date – two weeks from original delivery date].
Please accept my sincere apologies for this delay. We understand the importance of this project and the expectations tied to the original schedule. While this situati…
11.9s547 output tokens
Frequently asked questions
- Which is cheaper, DeepSeek V4 Pro or Qwen3.8 Max?
- Per 1M output tokens, DeepSeek V4 Pro is ¥684.42 and Qwen3.8 Max is ¥1,072.2 on FastMetal (yen, before tax), so DeepSeek V4 Pro is cheaper.
- How do the context windows of DeepSeek V4 Pro and Qwen3.8 Max compare?
- DeepSeek V4 Pro takes 1,048,576 tokens; Qwen3.8 Max takes 1,000,000.
- Can I use DeepSeek V4 Pro and Qwen3.8 Max with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "deepseek-v4-pro" or "qwen3.8-max" 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 DeepSeek V4 Pro and Qwen3.8 Max from the browser chat and the API. No monthly fee.