Claude Sonnet 5 vs Grok 4.6
Pricing, context window and real answers (August 2026)
Claude Sonnet 5 (Anthropic) 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
 Claude Sonnet 5 |  Grok 4.6 | |
|---|---|---|
| Provider | Anthropic | xAI |
| Input (per 1M tokens) | ¥357.4 | ¥357.4 |
| Output (per 1M tokens) | ¥1,787 | ¥1,072.2 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥1,251 | ¥894 |
| Context window | 1,000,000 tokens | 500,000 tokens |
| Release date | 6/30/2026 | 8/12/2026 |
| Input modalities | text, image, file | text, image, file |
| Arena · overall | #44 · ELO 1,460 | Unranked |
| Arena · Japanese | #14 · ELO 1,469 | Unranked |
| Arena · coding | #19 · ELO 1,522 | 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, 40% less than Claude Sonnet 5.
- For long documents, Claude Sonnet 5: a 1,000,000-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.
Claude Sonnet 5
# Counting 'r's in "strawberry"
**Step 1: Spell out the word letter by letter**
s - t - r - a - w - b - e - r - r - y
**Step 2: Number each letter position**
| Position | Letter |
|----------|--------|
| 1 | s |
| 2 | t |
| 3 | **r** |
| 4 | a |
| 5 | w |
| 6 | b |
| 7 | e |
| 8 | **r** |
| 9 | **r** |
| 10 | y |
**Step 3: Identify and count the 'r's**
- Position 3: **r** ✓ (1st r)
- Position 8: **r** ✓ (2nd r)
- Position 9: **r** ✓ (3rd r)
**Answer: There are 3 r's in "strawberry"**
5.9s405 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…
Claude Sonnet 5
# Root Cause
The `UserList` component receives `users` as a prop, but at the time it's rendered, `users` is `undefined` — not an empty array, but literally missing. When your code tries to call `.map()` on `undefined`, JavaScript throws that `TypeError`.
This typically happens when:
- The parent component hasn't fetched the data yet (e.g., an API call is still in progress)
- The prop name doesn't match what's being passed down (typo)
- The data source (API/state) genuinely returns `undefined` in some case
# Fixes
**1. Add a default prop value (quick fix)**
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</u…
8.8s750 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):…
Claude Sonnet 5
## Review of `get_data` Function
Here's an improved version followed by an explanation of the changes:
```python
import logging
import time
from typing import Any
import requests
logger = logging.getLogger(__name__)
def get_data(
url: str,
retries: int = 3,
timeout: float = 10.0,
backoff_factor: float = 2.0,
) -> list[dict[str, Any]]:
"""
Fetch active items from the given URL.
Args:
url: The endpoint to fetch data from.
retries: Number of attempts before giving up.
timeout: Request timeout in seconds.
backoff_factor: Multiplier for exponential backoff between retries.
Returns:
A list of dicts with "name" and "id"…
14.0s1299 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, Claude Sonnet 5 or Grok 4.6?
- Per 1M output tokens, Claude Sonnet 5 is ¥1,787 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 Claude Sonnet 5 and Grok 4.6 compare?
- Claude Sonnet 5 takes 1,000,000 tokens; Grok 4.6 takes 500,000.
- Can I use Claude Sonnet 5 and Grok 4.6 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-sonnet-5" 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 Claude Sonnet 5 and Grok 4.6 from the browser chat and the API. No monthly fee.