Claude Sonnet 4.6 vs GPT-6 Astra
Pricing, context window and real answers (September 2026)
Claude Sonnet 4.6 (Anthropic) and GPT-6 Astra (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
 Claude Sonnet 4.6 |  GPT-6 Astra | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥554.4 | ¥1,717.72 |
| Output (per 1M tokens) | ¥2,772 | ¥8,588.62 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥1,940 | ¥6,012 |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Release date | 2/17/2026 | 9/4/2026 |
| Input modalities | text, image | file, image, text |
| Arena · overall | #35 · ELO 1,472 | Unranked |
| Arena · Japanese | #42 · ELO 1,439 | Unranked |
| Arena · coding | #15 · ELO 1,528 | Unranked |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Claude Sonnet 4.6: ¥2,772 per 1M output tokens, 68% less than GPT-6 Astra.
- For long documents, GPT-6 Astra: a 1,050,000-token context window against 1,000,000 for Claude Sonnet 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 4.6
## Counting the letter 'r' in 'strawberry'
Let me go through the word letter by letter:
| Position | Letter | Is it 'r'? |
|----------|--------|------------|
| 1 | s | No |
| 2 | t | No |
| 3 | r | ✅ Yes |
| 4 | a | No |
| 5 | w | No |
| 6 | b | No |
| 7 | e | No |
| 8 | r | ✅ Yes |
| 9 | r | ✅ Yes |
| 10 | y | No |
## Result
There are **3 r's** in 'strawberry'.
2.2s181 output tokens
GPT-6 Astra
“strawberry” is spelled **s-t-r-a-w-b-e-r-r-y**.
The letter **r** appears in positions **3, 8, and 9**, so there are **3 r’s**.
3.8s85 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 4.6
## Problem Analysis
The error occurs because `users` is `undefined` when the component renders. You're calling `.map()` on `undefined`, which throws a `TypeError`.
**Common causes:**
- The prop isn't passed by the parent component
- Data is still loading asynchronously when the component first renders
- The parent passes `undefined` or a misspelled prop name
---
## Solutions
### Option 1: Default Parameter Value (Simplest Fix)
```javascript
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
This assigns an empty array if `users` is `undefined`, so `.map()` always has an array to work with.
---
###…
9.4s798 output tokens
GPT-6 Astra
The error means **`users` is `undefined` when React renders `UserList`**, so calling `users.map(...)` fails. This commonly happens when the parent doesn’t pass the prop or when data hasn’t finished loading.
### 1. Default `users` to an empty array
If an absent prop should mean “no users,” use a default value:
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => (
<li key={user.id}>{user.name}</li>
))}
</ul>
);
}
```
This handles a missing or `undefined` prop, but **not `null` or other non-array values**.
### 2. Check where the prop comes from
Make sure the parent passes an array. For data loaded asynchronously, initialize state to…
6.7s380 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 4.6
## Code Review and Improvements
### Issues Identified
1. **Imports inside function** – should be at module level
2. **Bare `except`** – catches everything including `KeyboardInterrupt`, `SystemExit`
3. **`== True` comparison** – not Pythonic
4. **No logging/error visibility** – silent failures make debugging hard
5. **Magic numbers** – hardcoded `2`, `10` with no explanation
6. **No distinction between retriable/non-retriable errors** – e.g., 404 should not be retried
7. **Inefficient list building** – list comprehension is cleaner
8. **No exponential backoff** – fixed sleep is naive for real-world retry logic
9. **Missing type hints and docstring**
---
### Improved Version
```python
im…
14.4s1099 output tokens
GPT-6 Astra
The function is compact, but its biggest issue is that **all failures silently become `[]`**, making an unavailable API indistinguishable from a successful response with no active items.
### Suggested improvements
- **Move imports to module scope** for clarity and conventional organization.
- **Avoid bare `except:`.** It catches everything, including `KeyboardInterrupt`, and hides bugs such as missing dictionary keys.
- **Retry only transient failures**, such as connection errors, timeouts, rate limiting, and selected server errors. Retrying a `401` or `404` usually won’t help.
- **Don’t sleep after the final failed attempt.** Use exponential backoff rather than a fixed delay.
- **Use desc…
19.2s965 output tokens
Frequently asked questions
- Which is cheaper, Claude Sonnet 4.6 or GPT-6 Astra?
- Per 1M output tokens, Claude Sonnet 4.6 is ¥2,772 and GPT-6 Astra is ¥8,588.62 on FastMetal (yen, before tax), so Claude Sonnet 4.6 is cheaper.
- How do the context windows of Claude Sonnet 4.6 and GPT-6 Astra compare?
- Claude Sonnet 4.6 takes 1,000,000 tokens; GPT-6 Astra takes 1,050,000.
- Can I use Claude Sonnet 4.6 and GPT-6 Astra with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-sonnet-4-6" or "gpt-6-astra" 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 4.6 and GPT-6 Astra from the browser chat and the API. No monthly fee.