Claude Sonnet 5 vs GPT-6.1 Sol
Pricing, context window and real answers (September 2026)
Claude Sonnet 5 (Anthropic) and GPT-6.1 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
 Claude Sonnet 5 |  GPT-6.1 Sol | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥357.4 | ¥357.4 |
| Output (per 1M tokens) | ¥1,787 | ¥1,787 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥1,251 | ¥1,251 |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Release date | 6/30/2026 | 9/29/2026 |
| Input modalities | text, image, file | file, image, text |
| Throughput (p50) | 1170 tokens/s (n=17) | — |
| Arena · overall | #54 · ELO 1,462 | Unranked |
| Arena · Japanese | #39 · ELO 1,444 | Unranked |
| Arena · coding | #34 · ELO 1,519 | Unranked |
Prices are FastMetal's yen rates before tax.
Rankings: LMArena leaderboard dataset (lmarena-ai/leaderboard-dataset), CC BY 4.0, snapshot 2026-09-25; category names mapped and ratings rounded by FastMetal.
Which should you pick?
- Output pricing is identical (¥1,787 per 1M tokens).
- For long documents, GPT-6.1 Sol: a 1,050,000-token context window against 1,000,000 for Claude Sonnet 5.
- 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
GPT-6.1 Sol
“strawberry” is spelled **s-t-r-a-w-b-e-r-r-y**.
The letter **r** appears at positions **3, 8, and 9**.
So, there are **3 r’s** in “strawberry.”
2.8s88 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
GPT-6.1 Sol
The error means **`users` is `undefined` when `UserList` renders**. Calling `.map()` on `undefined` throws this error.
This commonly happens when the parent doesn’t pass the `users` prop, or when data hasn’t finished loading yet.
### Fix: provide a default empty array
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => (
<li key={user.id}>{user.name}</li>
))}
</ul>
);
}
```
This renders an empty list if `users` is omitted or `undefined`. It does **not** handle `null`.
### Check the parent component too
Make sure it passes an array:
```jsx
<UserList users={users} />
```
If you’re fetching users asynchronously, initialize the stat…
5.8s306 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
GPT-6.1 Sol
The function is short, but its main weakness is that it hides failures: a network error, invalid JSON, and a genuinely empty result all return `[]`.
### Suggested improvements
- **Move imports to module scope.** This is conventional and makes dependencies visible. Repeated imports are cached, so the performance benefit is minor.
- **Avoid bare `except:`.** It catches everything, including `KeyboardInterrupt` and `SystemExit`, and can hide programming errors.
- **Handle HTTP errors explicitly.** `raise_for_status()` provides useful exceptions. Retry transient failures such as timeouts, connection errors, HTTP 429, and HTTP 5xx—not permanent errors such as HTTP 404.
- **Don’t sleep after the…
19.0s1094 output tokens
Frequently asked questions
- Which is cheaper, Claude Sonnet 5 or GPT-6.1 Sol?
- Both are ¥1,787 per 1M output tokens on FastMetal (yen, before tax).
- How do the context windows of Claude Sonnet 5 and GPT-6.1 Sol compare?
- Claude Sonnet 5 takes 1,000,000 tokens; GPT-6.1 Sol takes 1,050,000.
- Can I use Claude Sonnet 5 and GPT-6.1 Sol with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-sonnet-5" or "gpt-6.1-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 Claude Sonnet 5 and GPT-6.1 Sol from the browser chat and the API. No monthly fee.