DeepSeek V4.1 Flash vs Gemini 3.8 Flash
Pricing, context window and real answers (September 2026)
DeepSeek V4.1 Flash (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 V4.1 Flash |  Gemini 3.8 Flash | |
|---|---|---|
| Provider | DeepSeek | |
| Input (per 1M tokens) | ¥50.69 | ¥128.83 |
| Output (per 1M tokens) | ¥202.74 | ¥644.15 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥152 | ¥451 |
| Context window | 1,048,576 tokens | 1,048,576 tokens |
| Release date | 9/10/2026 | 9/2/2026 |
| Input modalities | text, image | text, image, video, file, audio |
| Arena · overall | Unranked | #8 · ELO 1,494 |
| Arena · Japanese | Unranked | Unranked |
| Arena · coding | Unranked | #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, DeepSeek V4.1 Flash: ¥202.74 per 1M output tokens, 69% less than Gemini 3.8 Flash.
- 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 V4.1 Flash
The word **“strawberry”** has **3** letter **“r”**s.
Step-by-step:
1. Spell it out: **s t r a w b e r r y**
2. Find each **r**:
- Position 3: **r** in “str”
- Position 8: first **r** in “berry”
- Position 9: second **r** in “berry”
3. Total: **3**
**Answer: 3**
7.5s226 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 V4.1 Flash
The error means that `users` is `undefined` when `UserList` renders, so JavaScript cannot call `.map()` on it.
Your component expects a `users` prop:
```jsx
function UserList({ users }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
But it is being rendered without `users`, or `users` has not loaded yet.
Common causes:
1. Parent renders it without the prop:
```jsx
<UserList />
```
instead of:
```jsx
<UserList users={users} />
```
2. The prop name is different:
```jsx
<UserList userList={users} />
```
3. The data is fetched asynchronously and is initially `undefined`:
```jsx
const [users, setUsers] = useState();
useEffect(…
16.0s945 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 V4.1 Flash
Here are the main improvements:
- Move imports to module level.
- Avoid bare `except`; catch specific exceptions.
- Use a `requests.Session` for connection reuse.
- Retry only transient network/HTTP failures, not all errors.
- Use exponential backoff and don’t sleep after the final attempt.
- Use a list comprehension for readability/performance.
- Add type hints, logging, constants, and basic JSON validation.
- Avoid `== True`; use `is True` or a truthy check depending on API contract.
Example refactor:
```python
from __future__ import annotations
import logging
import time
from typing import Any
import requests
logger = logging.getLogger(__name__)
TIMEOUT = (3.05, 10) # connect time…
31.5s5142 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 V4.1 Flash or Gemini 3.8 Flash?
- Per 1M output tokens, DeepSeek V4.1 Flash is ¥202.74 and Gemini 3.8 Flash is ¥644.15 on FastMetal (yen, before tax), so DeepSeek V4.1 Flash is cheaper.
- How do the context windows of DeepSeek V4.1 Flash and Gemini 3.8 Flash compare?
- DeepSeek V4.1 Flash takes 1,048,576 tokens; Gemini 3.8 Flash takes 1,048,576.
- Can I use DeepSeek V4.1 Flash and Gemini 3.8 Flash with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "deepseek-v4.1-flash" 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 V4.1 Flash and Gemini 3.8 Flash from the browser chat and the API. No monthly fee.