Claude Fable 5 vs GPT-5.6 Sol
Pricing, context window and real answers (August 2026)
Claude Fable 5 (Anthropic) and GPT-5.6 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 Fable 5 |  GPT-5.6 Sol | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥1,787 | ¥893.5 |
| Output (per 1M tokens) | ¥8,935 | ¥5,361 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥6,255 | ¥3,574 |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Release date | 6/9/2026 | 7/9/2026 |
| Input modalities | text, image, file | file, image, text |
| Arena · overall | #1 · ELO 1,508 | #13 · ELO 1,485 |
| Arena · Japanese | #1 · ELO 1,529 | Unranked |
| Arena · coding | #2 · ELO 1,552 | #16 · ELO 1,524 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, GPT-5.6 Sol: ¥5,361 per 1M output tokens, 40% less than Claude Fable 5.
- On the Overall arena board, Claude Fable 5 ranks higher (#1; GPT-5.6 Sol is #13).
- On the Coding arena board, Claude Fable 5 ranks higher (#2; GPT-5.6 Sol is #16).
- For long documents, GPT-5.6 Sol: a 1,050,000-token context window against 1,000,000 for Claude Fable 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 Fable 5
# Counting 'r's in "strawberry"
Let me spell out the word letter by letter and check each one:
| Position | Letter | Is it 'r'? |
|----------|--------|------------|
| 1 | s | No |
| 2 | t | No |
| 3 | **r** | ✅ Yes (1st) |
| 4 | a | No |
| 5 | w | No |
| 6 | b | No |
| 7 | e | No |
| 8 | **r** | ✅ Yes (2nd) |
| 9 | **r** | ✅ Yes (3rd) |
| 10 | y | No |
## Reasoning breakdown:
- The word "strawberry" can be split into two parts: **straw** + **berry**
- "straw" contains one 'r': st**r**aw
- "berry" contains two 'r's: be**rr**y (a double-r)
## Answer: **3**
There are **three 'r's** in "strawberry."
39.6s354 output tokens
GPT-5.6 Sol
“strawberry” can be split into letters:
s, t, **r**, a, w, b, e, **r**, **r**, y
The letter **r** appears **3 times**.
3.0s78 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
## Cause
The error means that when `UserList` renders, the `users` prop is `undefined`, so calling `.map()` on it fails. This typically happens for one of these reasons:
1. **The parent isn't passing the prop** (or has a typo in the prop name):
```jsx
<UserList /> // users is undefined
<UserList user={users} /> // typo: "user" instead of "users"
```
2. **Data is fetched asynchronously** — the component renders before the API call finishes, and the initial state is `undefined`:
```jsx
const [users, setUsers] = useState(); // undefined initially!
```
## Fixes
**Option 1: Default parameter value** (quick fix)
```jsx
function UserList({ users = [] }) {
re…
51.3s686 output tokens
GPT-5.6 Sol
The error occurs because `users` is `undefined` when `UserList` renders, so JavaScript cannot call `.map()` on it. This often happens when data is loaded asynchronously or the parent does not pass the prop.
### Fix options
**1. Give `users` a default value:**
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => (
<li key={user.id}>{user.name}</li>
))}
</ul>
);
}
```
Note that this handles `undefined`, but not an explicitly passed `null`.
**2. Handle missing or invalid data explicitly:**
```jsx
function UserList({ users }) {
if (!Array.isArray(users)) {
return <p>No users available.</p>;
}
return (
<ul>
{users.m…
7.1s395 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
# Code Review
Your function works, but there are several issues worth addressing. Here's a breakdown by category:
## Issues Found
### 1. **Bare `except:` clause (critical)**
This catches *everything*, including `KeyboardInterrupt`, `SystemExit`, and bugs like `KeyError` or `TypeError` in your own parsing code. You'll silently retry on programming errors and mask real problems.
### 2. **Imports inside the function**
Imports belong at module level (PEP 8). Function-level imports add overhead on each call and hide dependencies.
### 3. **`== True` comparison**
Use truthiness directly: `if item["active"]:` (PEP 8 explicitly recommends this).
### 4. **Silent failures**
Returning `[]` on fail…
38.5s1528 output tokens
GPT-5.6 Sol
### Issues and suggested improvements
- Move imports to module scope.
- Avoid bare `except:`; it catches programming errors and interrupts such as `KeyboardInterrupt`.
- Use `response.raise_for_status()` instead of manually checking only for `200`; other 2xx responses may also be valid.
- Retry only transient failures, such as timeouts, connection errors, `429`, and selected `5xx` responses. Retrying most `4xx` errors is not useful.
- Use exponential backoff rather than a fixed delay.
- Avoid sleeping after the final failed attempt.
- Replace `item["active"] == True` with `item.get("active") is True`.
- Use a list comprehension for the transformation.
- Add type hints and validate arguments…
33.1s1646 output tokens
Frequently asked questions
- Which is cheaper, Claude Fable 5 or GPT-5.6 Sol?
- Per 1M output tokens, Claude Fable 5 is ¥8,935 and GPT-5.6 Sol is ¥5,361 on FastMetal (yen, before tax), so GPT-5.6 Sol is cheaper.
- How do the context windows of Claude Fable 5 and GPT-5.6 Sol compare?
- Claude Fable 5 takes 1,000,000 tokens; GPT-5.6 Sol takes 1,050,000.
- Which ranks higher, Claude Fable 5 or GPT-5.6 Sol?
- Claude Fable 5 ranks higher on the public arena (Claude Fable 5 #1, GPT-5.6 Sol #13). Ranks move as the leaderboard updates.
- Can I use Claude Fable 5 and GPT-5.6 Sol with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-fable-5" or "gpt-5.6-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 Fable 5 and GPT-5.6 Sol from the browser chat and the API. No monthly fee.