DeepSeek V4 Flash vs GPT-6 Sol
Pricing, context window and real answers (September 2026)
DeepSeek V4 Flash (DeepSeek) and GPT-6 Sol (OpenAI), 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 Flash |  GPT-6 Sol | |
|---|---|---|
| Provider | DeepSeek | OpenAI |
| Input (per 1M tokens) | ¥24.61 | ¥357.4 |
| Output (per 1M tokens) | ¥49.21 | ¥1,787 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥49 | ¥1,251 |
| Context window | 1,048,576 tokens | 1,050,000 tokens |
| Release date | 4/24/2026 | 9/22/2026 |
| Input modalities | text | file, image, text |
| Throughput (p50) | — | — |
| Arena · overall | #92 · ELO 1,436 | Unranked |
| Arena · Japanese | #78 · ELO 1,396 | Unranked |
| Arena · coding | #92 · ELO 1,483 | 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 Flash: ¥49.21 per 1M output tokens, 97% less than GPT-6 Sol.
- For long documents, GPT-6 Sol: a 1,050,000-token context window against 1,048,576 for DeepSeek V4 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 Flash
The word "strawberry" is spelled as s-t-r-a-w-b-e-r-r-y. I go through each letter: s (no), t (no), r (yes, first), a (no), w (no), b (no), e (no), r (yes, second), r (yes, third), y (no). Thus, there are three 'r's.
3.9s251 output tokens
GPT-6 Sol
“Strawberry” is spelled **s-t-r-a-w-b-e-r-r-y**. There’s one **r** near the beginning and two near the end, for a total of **3**.
2.7s76 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 Flash
The error occurs because `users` is `undefined` when the component tries to call `.map()` on it.
## Why this happens
Your component expects `users` to be an array, but it's receiving `undefined` as a prop. This typically happens when:
1. The parent component doesn't pass the `users` prop
2. The data fetching hasn't completed yet (async data loading)
3. The API response is missing the expected data structure
## How to fix it
### Option 1: Default prop value (Recommended for initial state)
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
### Option 2: Guard clause (More explicit)
```jsx
func…
6.3s422 output tokens
GPT-6 Sol
`users` is `undefined` when `UserList` renders, so calling `users.map(...)` throws the error. The component needs an array, but its parent may not be passing `users`, or the data may not have loaded yet.
You can default it to an empty array:
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
Also check the parent component to make sure it passes an array:
```jsx
<UserList users={users} />
```
If `users` comes from an API, initialize its state as `[]` or show a loading state until the data arrives.
2.2s161 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 Flash
Here's a comprehensive review with suggested improvements:
## Issues Identified:
1. **Import at wrong location** - Imports inside functions are inefficient and non-standard
2. **Bare `except:` clause** - Catches all exceptions including `KeyboardInterrupt`, `SystemExit`
3. **Missing error handling granularity** - Should distinguish between retryable and non-retryable errors
4. **Duplicate sleep logic** - Same sleep in `else` and `except` blocks
5. **Unnecessary variable** - `data` is only used once
6. **Inefficient list building** - Manual loop instead of list comprehension
7. **Hardcoded error message** - No logging or error context
8. **Missing type hints** - No type annotations
9. **Fun…
12.6s987 output tokens
GPT-6 Sol
The main issues are the bare `except`, which hides errors such as malformed JSON, and retrying every non-200 response, including client errors that usually won’t improve with another attempt. The function also sleeps after its final attempt.
```python
import time
import requests
def get_data(url, retries=3):
if retries < 1:
raise ValueError("retries must be at least 1")
for attempt in range(retries):
try:
response = requests.get(url, timeout=10)
except requests.RequestException:
if attempt == retries - 1:
raise
else:
# Retry rate limits and server errors, but not other client errors.…
10.3s814 output tokens
Frequently asked questions
- Which is cheaper, DeepSeek V4 Flash or GPT-6 Sol?
- Per 1M output tokens, DeepSeek V4 Flash is ¥49.21 and GPT-6 Sol is ¥1,787 on FastMetal (yen, before tax), so DeepSeek V4 Flash is cheaper.
- How do the context windows of DeepSeek V4 Flash and GPT-6 Sol compare?
- DeepSeek V4 Flash takes 1,048,576 tokens; GPT-6 Sol takes 1,050,000.
- Can I use DeepSeek V4 Flash and GPT-6 Sol with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "deepseek-v4-flash" or "gpt-6-sol" 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 Flash and GPT-6 Sol from the browser chat and the API. No monthly fee.