GPT-5.6 Terra vs Grok 4.6
Pricing, context window and real answers (August 2026)
GPT-5.6 Terra (OpenAI) and Grok 4.6 (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
 GPT-5.6 Terra |  Grok 4.6 | |
|---|---|---|
| Provider | OpenAI | xAI |
| Input (per 1M tokens) | ¥357.4 | ¥357.4 |
| Output (per 1M tokens) | ¥2,144.4 | ¥1,072.2 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥1,430 | ¥894 |
| Context window | 1,050,000 tokens | 500,000 tokens |
| Release date | 7/9/2026 | 8/12/2026 |
| Input modalities | file, image, text | text, image, file |
| Arena · overall | #34 · ELO 1,468 | Unranked |
| Arena · Japanese | Unranked | Unranked |
| Arena · coding | #22 · ELO 1,521 | 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 4.6: ¥1,072.2 per 1M output tokens, 50% less than GPT-5.6 Terra.
- For long documents, GPT-5.6 Terra: a 1,050,000-token context window against 500,000 for Grok 4.6.
- 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.
GPT-5.6 Terra
“strawberry” is spelled:
s t **r** a w b e **r** **r** y
There are **3** occurrences of the letter **r**.
3.6s71 output tokens
Grok 4.6
The word "strawberry" consists of the following letters in order:
s-t-r-a-w-b-e-r-r-y
Checking each one:
- s: not r
- t: not r
- r: yes (count = 1)
- a: not r
- w: not r
- b: not r
- e: not r
- r: yes (count = 2)
- r: yes (count = 3)
- y: not r
There are exactly 3 r's.
Final answer: 3
3.9s451 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…
GPT-5.6 Terra
The error means `users` is `undefined` when `UserList` renders, so React tries to evaluate:
```js
users.map(...)
```
But `.map()` only exists on arrays.
Common causes:
- The parent component does not pass a `users` prop.
- The user data is loaded asynchronously and has not arrived on the first render.
- The API response shape differs from what you expect, e.g. data is in `response.data.users` rather than `response.data`.
- The parent initializes its user state as `undefined` or `null`.
## Fix options
### 1. Initialize users as an empty array
In the parent component:
```jsx
const [users, setUsers] = useState([]);
```
Then pass it normally:
```jsx
<UserList users={users} />
```
An e…
5.8s559 output tokens
Grok 4.6
**The error happens because `users` is `undefined` when `.map()` is called.**
`UserList` destructures `{ users }` from its props. If the parent doesn't pass a `users` prop (or passes `undefined`/`null`), `users` is `undefined` and `undefined.map` throws.
This is extremely common when:
- Data is loaded asynchronously (initial render happens before the fetch finishes).
- The parent component forgets to pass the prop or uses a different name.
- The component is rendered before the data is ready (e.g. in a loading state).
### Quick fixes
**1. Default to an empty array (recommended)**
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => (
<li key={us…
20.3s598 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):…
GPT-5.6 Terra
Here are the main areas to improve:
### Issues in the original code
- **Imports inside the function**: Move `requests` and `time` imports to module scope.
- **Bare `except:`**: This catches everything, including `KeyboardInterrupt` and programming errors. Catch `requests.RequestException` (and possibly JSON decoding errors) instead.
- **Status code check**: Prefer `response.raise_for_status()` or `response.ok` over manually checking only for `200`. Successful responses can include other 2xx status codes.
- **`== True`**: Use `if item.get("active"):` instead.
- **Potential `KeyError`**: `item["name"]`, `item["id"]`, and `item["active"]` can fail if the API response is incomplete. Use `.get(…
10.6s939 output tokens
Grok 4.6
Here is a focused review of the function, followed by a cleaned-up version.
## Issues
**Imports inside the function**
`requests` and `time` should live at module level. Importing on every call is slower, hides dependencies, and is harder to mock in tests.
**Bare `except:`**
This swallows `KeyboardInterrupt`, `SystemExit`, and programming errors. Catch `requests.RequestException` (network/timeout/HTTP adapter errors) and JSON/`KeyError`/`TypeError` separately.
**Retrying the wrong things**
A 404 or 400 will never succeed on retry. Retry transient failures (timeouts, connection errors, 429, 5xx). Fail fast on most 4xx responses.
**Sleep after the last attempt**
On the final failur…
27.9s1770 output tokens
Frequently asked questions
- Which is cheaper, GPT-5.6 Terra or Grok 4.6?
- Per 1M output tokens, GPT-5.6 Terra is ¥2,144.4 and Grok 4.6 is ¥1,072.2 on FastMetal (yen, before tax), so Grok 4.6 is cheaper.
- How do the context windows of GPT-5.6 Terra and Grok 4.6 compare?
- GPT-5.6 Terra takes 1,050,000 tokens; Grok 4.6 takes 500,000.
- Can I use GPT-5.6 Terra and Grok 4.6 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-5.6-terra" or "grok-4.6" 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 GPT-5.6 Terra and Grok 4.6 from the browser chat and the API. No monthly fee.