Gemini 3.1 Pro Preview vs Grok 4.7
Pricing, context window and real answers (September 2026)
Gemini 3.1 Pro Preview (Google) and Grok 4.7 (xAI), 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
 Gemini 3.1 Pro Preview |  Grok 4.7 | |
|---|---|---|
| Provider | xAI | |
| Input (per 1M tokens) | ¥357.4 | ¥276.2 |
| Output (per 1M tokens) | ¥2,144.4 | ¥828.6 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥1,430 | ¥691 |
| Context window | 1,048,576 tokens | 500,000 tokens |
| Release date | 2/19/2026 | 9/21/2026 |
| Input modalities | audio, file, image, text, video | text, image, file |
| Throughput (p50) | — | — |
| Arena · overall | #15 · ELO 1,487 | Unranked |
| Arena · Japanese | #9 · ELO 1,494 | Unranked |
| Arena · coding | #28 · ELO 1,520 | Unranked |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Grok 4.7: ¥828.6 per 1M output tokens, 61% less than Gemini 3.1 Pro Preview.
- For long documents, Gemini 3.1 Pro Preview: a 1,048,576-token context window against 500,000 for Grok 4.7.
- 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.
Gemini 3.1 Pro Preview
There are **3** 'r's in the word 'strawberry'.
Here is the step-by-step breakdown of the spelling:
1. **s** - not an 'r'
2. **t** - not an 'r'
3. **r** - **1st 'r'**
4. **a** - not an 'r'
5. **w** - not an 'r'
6. **b** - not an 'r'
7. **e** - not an 'r'
8. **r** - **2nd 'r'**
9. **r** - **3rd 'r'**
10. **y** - not an 'r'
Therefore, the total count is 3.
5.3s503 output tokens
Grok 4.7
The word "strawberry" consists of the letters S-T-R-A-W-B-E-R-R-Y.
- The 3rd letter is R.
- The 8th letter is R.
- The 9th letter is R.
This gives a total of 3 R's.
4.7s299 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…
Gemini 3.1 Pro Preview
### The Cause
This error occurs because the `users` prop being passed to your `UserList` component is currently `undefined`.
In JavaScript, you can only use the `.map()` method on arrays. Because `users` is `undefined` (often due to data not finishing an API fetch yet, or the parent component forgetting to pass the prop), Node/React throws an error when it tries to read `.map`.
### How to Fix It
You can fix this in a few different ways, depending on how you want your application to behave.
#### Fix 1: Assign a Default Value (Recommended)
The cleanest way to handle this is to assign a default empty array to `users` in your component's parameters. If `users` is undefined, it defaults to…
13.2s1511 output tokens
Grok 4.7
The error happens because `users` is `undefined` when `UserList` renders, so calling `.map` on it fails.
That usually means the parent rendered `<UserList />` (or `<UserList users={undefined} />`) before data was loaded, or the prop name doesn’t match.
**Fix it in the component** so it tolerates a missing list:
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
Or guard the call:
```jsx
function UserList({ users }) {
return (
<ul>
{(users ?? []).map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
**Also check the parent** so you pass an array once data exists:
`…
12.8s393 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):…
Gemini 3.1 Pro Preview
Here is a review of your function. While the original code works, there are several areas where it can be improved regarding **best practices**, **readability**, and **performance**.
### 1. Refactored Code
Here is the improved version of your function. I will explain the specific changes below.
```python
import time
import requests
import logging
from typing import Any
# Optional: Set up a logger
logger = logging.getLogger(__name__)
def get_data(url: str, retries: int = 3, delay: int = 2, timeout: int = 10) -> list[dict[str, Any]]:
"""
Fetches JSON data from a URL and extracts active items.
Args:
url: The API endpoint to fetch data from.
retries: Number o…
23.6s3094 output tokens
Grok 4.7
## Review
The function works for the happy path, but it hides failures, retries the wrong errors, and is harder to read and debug than it needs to be.
### Issues
1. **Imports inside the function** — move them to module level unless you have a strong reason (circular imports, optional dependency).
2. **Bare `except`** — swallows `KeyboardInterrupt`, `SystemExit`, and programming bugs. Catch specific exceptions.
3. **Retries non-retryable failures** — 4xx (except maybe 429) will not succeed on retry. Network errors and 5xx are the usual candidates.
4. **Sleeps after the last attempt** — wastes up to 2 seconds before returning `[]`.
5. **Unused loop variable** and vague names (`r`, `i`).
6.…
22.3s1525 output tokens
Frequently asked questions
- Which is cheaper, Gemini 3.1 Pro Preview or Grok 4.7?
- Per 1M output tokens, Gemini 3.1 Pro Preview is ¥2,144.4 and Grok 4.7 is ¥828.6 on FastMetal (yen, before tax), so Grok 4.7 is cheaper.
- How do the context windows of Gemini 3.1 Pro Preview and Grok 4.7 compare?
- Gemini 3.1 Pro Preview takes 1,048,576 tokens; Grok 4.7 takes 500,000.
- Can I use Gemini 3.1 Pro Preview and Grok 4.7 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gemini-3.1-pro-preview" or "grok-4.7" 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 Gemini 3.1 Pro Preview and Grok 4.7 from the browser chat and the API. No monthly fee.