Claude Fable 5.1 vs GPT-4o-mini
Pricing, context window and real answers (September 2026)
Claude Fable 5.1 (Anthropic) and GPT-4o-mini (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 Fable 5.1 |  GPT-4o-mini | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥1,787 | ¥26.81 |
| Output (per 1M tokens) | ¥8,935 | ¥107.22 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥6,255 | ¥80 |
| Context window | 1,000,000 tokens | 128,000 tokens |
| Release date | 9/1/2026 | 7/18/2024 |
| Input modalities | text, image, file | text, image, file |
| Throughput (p50) | — | — |
| Arena · overall | #5 · ELO 1,498 | #251 · ELO 1,318 |
| Arena · Japanese | Unranked | #187 · ELO 1,250 |
| Arena · coding | #32 · ELO 1,519 | #259 · ELO 1,348 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, GPT-4o-mini: ¥107.22 per 1M output tokens, 99% less than Claude Fable 5.1.
- On the Overall arena board, Claude Fable 5.1 ranks higher (#5; GPT-4o-mini is #251).
- On the Coding arena board, Claude Fable 5.1 ranks higher (#32; GPT-4o-mini is #259).
- For long documents, Claude Fable 5.1: a 1,000,000-token context window against 128,000 for GPT-4o-mini.
- 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 Fable 5.1
**Step 1: Write out the word letter by letter.**
s - t - r - a - w - b - e - r - r - y
**Step 2: Number each position.**
1. s
2. t
3. **r**
4. a
5. w
6. b
7. e
8. **r**
9. **r**
10. y
**Step 3: Identify which positions contain 'r'.**
- Position 3: r (in "str-")
- Position 8: r (in "-ber-")
- Position 9: r (in "-rry")
**Step 4: Count them.**
3 + 1 + 1 = **3**
**Answer: There are 3 'r's in "strawberry."**
A helpful way to check: split the word into its parts — "straw" (1 r) + "berry" (2 r's) = 3 r's total.
7.9s259 output tokens
GPT-4o-mini
To count the number of 'r's in the word "strawberry," we can follow these steps:
1. **Identify the word**: We have the word "strawberry."
2. **Break down the letters**: Let's write out the letters in the word:
- s
- t
- r
- a
- w
- b
- e
- r
- r
- y
3. **Locate the 'r's**: Now, we need to look for the letter 'r' among these letters.
- In the list of letters, we can see:
- The first 'r' is in the 3rd position.
- The second 'r' is in the 8th position.
- The third 'r' is in the 9th position.
4. **Count the occurrences**: We check each position we identified:
- There are three occurrences of 'r' in the word "strawberry."
5. **Conclusion**:…
2.1s239 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 Fable 5.1
The error means that when `UserList` rendered, the `users` prop was `undefined`, so calling `.map()` on it failed. This typically happens because:
1. **The parent isn't passing the prop** (or misspelled it, e.g. `<UserList user={...} />`), or
2. **The data hasn't loaded yet.** A common pattern is fetching users in a `useEffect` and storing them in state whose initial value is `undefined` (e.g. `useState()`), so the first render happens before the data arrives.
**Fixes**
Give the prop a default value so the component is safe to render with no data:
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}…
10.8s564 output tokens
GPT-4o-mini
The error you're encountering, `TypeError: Cannot read properties of undefined (reading 'map')`, indicates that the `users` prop is `undefined` when you try to call the `map` method on it.
In your `UserList` component, you're attempting to use `users.map(...)`, but if the `users` prop is not provided or is `undefined`, this will throw an error.
### Fixing the Error
1. **Default Props**: You can set a default value for the `users` prop to prevent the error when it is `undefined`.
```jsx
function UserList({ users = [] }) { // Default to an empty array
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```…
5.0s511 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 Fable 5.1
Here's a review of the function organized by category, followed by a refactored version.
## Issues
### Correctness / robustness
1. **Bare `except:`** — This catches *everything*, including `KeyboardInterrupt`, `SystemExit`, and bugs like `KeyError` from `item["active"]`. A malformed response would be silently retried three times and then swallowed. Catch `requests.RequestException` (and `ValueError` for bad JSON) specifically.
2. **Retrying non-retryable errors** — A 404 or 400 will never succeed on retry. Only retry on transient failures (timeouts, connection errors, 5xx, 429).
3. **Silent failure** — Returning `[]` after exhausting retries is indistinguishable from "the endpoint legitima…
27.7s2028 output tokens
GPT-4o-mini
Your Python function, `get_data`, essentially performs a GET request, handles retries on failure, and processes the response JSON to return a filtered list of dictionaries. Below, I've highlighted several improvements regarding readability, performance, and best practices:
1. **Avoid blanket exceptions**: It’s best practice to specify which exceptions you expect, allowing for better debugging and error handling.
2. **Use `requests` built-in exception handling**: Handle specific requests exceptions, such as `requests.exceptions.RequestException`.
3. **Improve condition checks**: Check for `item['active']` directly instead of comparing to `True`, which is more Pythonic.
4. **Use `time.sl…
8.8s628 output tokens
Frequently asked questions
- Which is cheaper, Claude Fable 5.1 or GPT-4o-mini?
- Per 1M output tokens, Claude Fable 5.1 is ¥8,935 and GPT-4o-mini is ¥107.22 on FastMetal (yen, before tax), so GPT-4o-mini is cheaper.
- How do the context windows of Claude Fable 5.1 and GPT-4o-mini compare?
- Claude Fable 5.1 takes 1,000,000 tokens; GPT-4o-mini takes 128,000.
- Which ranks higher, Claude Fable 5.1 or GPT-4o-mini?
- Claude Fable 5.1 ranks higher on the public arena (Claude Fable 5.1 #5, GPT-4o-mini #187). Ranks move as the leaderboard updates.
- Can I use Claude Fable 5.1 and GPT-4o-mini with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-fable-5-1" or "gpt-4o-mini" 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 Fable 5.1 and GPT-4o-mini from the browser chat and the API. No monthly fee.