DeepSeek V4 Pro vs Gemini 3.8 Flash
Pricing, context window and real answers (September 2026)
DeepSeek V4 Pro (DeepSeek) and Gemini 3.8 Flash (Google), 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 |  Gemini 3.8 Flash | |
|---|---|---|
| Provider | DeepSeek | |
| Input (per 1M tokens) | ¥341.32 | ¥128.83 |
| Output (per 1M tokens) | ¥684.42 | ¥644.15 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥684 | ¥451 |
| Context window | 1,048,576 tokens | 1,048,576 tokens |
| Release date | 4/24/2026 | 9/2/2026 |
| Input modalities | text | text, image, video, file, audio |
| Arena · overall | #55 · ELO 1,458 | #8 · ELO 1,494 |
| Arena · Japanese | #21 · ELO 1,462 | Unranked |
| Arena · coding | #63 · ELO 1,502 | #7 · ELO 1,537 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Gemini 3.8 Flash: ¥644.15 per 1M output tokens, 6% less than DeepSeek V4 Pro.
- On the Overall arena board, Gemini 3.8 Flash ranks higher (#8; DeepSeek V4 Pro is #55).
- On the Coding arena board, Gemini 3.8 Flash ranks higher (#7; DeepSeek V4 Pro is #63).
- 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
Gemini 3.8 Flash
There are **3** 'r's in the word "strawberry".
Here is the step-by-step breakdown:
1. **Break the word into its individual letters:**
* **s** (1st letter)
* **t** (2nd letter)
* **r** (3rd letter) — **1st 'r'**
* **a** (4th letter)
* **w** (5th letter)
* **b** (6th letter)
* **e** (7th letter)
* **r** (8th letter) — **2nd 'r'**
* **r** (9th letter) — **3rd 'r'**
* **y** (10th letter)
2. **Count the occurrences:**
* One 'r' is in the first syllable: "st**r**aw"
* Two 'r's are in the second syllable: "be**rr**y"
Total: **3**
3.9s562 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
Gemini 3.8 Flash
### The Cause
This error occurs because the `users` prop is `undefined` when the component renders, and JavaScript cannot call `.map()` on `undefined`.
This typically happens in two common scenarios:
1. **Asynchronous data fetching:** The parent component fetches `users` from an API. On the initial render, the data hasn't arrived yet, so `users` defaults to `undefined`.
2. **Missing prop:** The parent component forgot to pass `users` (e.g., `<UserList />` instead of `<UserList users={data} />`).
---
### How to Fix It
Here are the most common ways to resolve this:
#### Option 1: Provide a default parameter (Recommended)
Set a default value of an empty array (`[]`) for `users`. If `users…
7.1s1003 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):…
DeepSeek V4 Pro
Here’s a review of your `get_data` function, highlighting issues and suggesting improvements.
## Overall Observations
- The function works but has several readability, robustness, and maintainability issues.
- Imports are inside the function, bare `except` hides errors, and the filtering logic is not Pythonic.
- No type hints or docstring, making it harder to use and understand.
## Specific Improvements
### 1. Move Imports to the Top of the Module
**Why:** Imports inside a function are executed every time the function is called, which is slightly slower and violates PEP 8 style guidelines.
**Before:**
```python
def get_data(url, retries=3):
import requests
import time
# ...
`…
40.5s2277 output tokens
Gemini 3.8 Flash
Here is a code review of your function, broken down by issue category, followed by refactored versions.
---
### Key Issues & Areas for Improvement
#### 1. Correctness & Error Handling
* **Bare `except:` clause:** Catching all exceptions with a bare `except:` is dangerous. It suppresses system exits (`KeyboardInterrupt`, `SystemExit`) and masks programming bugs (like `KeyError` or `NameError`). You should catch specific exceptions, primarily `requests.RequestException`.
* **Silent failure returning `[]`:** If all retries fail, returning an empty list makes it impossible for the caller to distinguish between *"the API returned 0 active items"* and *"the network is completely down"*. It is u…
15.1s2139 output tokens
Frequently asked questions
- Which is cheaper, DeepSeek V4 Pro or Gemini 3.8 Flash?
- Per 1M output tokens, DeepSeek V4 Pro is ¥684.42 and Gemini 3.8 Flash is ¥644.15 on FastMetal (yen, before tax), so Gemini 3.8 Flash is cheaper.
- How do the context windows of DeepSeek V4 Pro and Gemini 3.8 Flash compare?
- DeepSeek V4 Pro takes 1,048,576 tokens; Gemini 3.8 Flash takes 1,048,576.
- Which ranks higher, DeepSeek V4 Pro or Gemini 3.8 Flash?
- Gemini 3.8 Flash ranks higher on the public arena (DeepSeek V4 Pro #21, Gemini 3.8 Flash #8). Ranks move as the leaderboard updates.
- Can I use DeepSeek V4 Pro and Gemini 3.8 Flash with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "deepseek-v4-pro" or "gemini-3.8-flash" 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 Gemini 3.8 Flash from the browser chat and the API. No monthly fee.