Claude Fable 5 vs Claude Fable 5.1
Pricing, context window and real answers (September 2026)
Claude Fable 5 (Anthropic) and Claude Fable 5.1 (Anthropic), 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 | Claude Fable 5.1 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Input (per 1M tokens) | ¥1,787 | ¥1,787 |
| Output (per 1M tokens) | ¥8,935 | ¥8,935 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥6,255 | ¥6,255 |
| Context window | 1,000,000 tokens | 1,000,000 tokens |
| Release date | 6/9/2026 | 9/1/2026 |
| Input modalities | text, image, file | text, image, file |
| Arena · overall | #1 · ELO 1,507 | #3 · ELO 1,504 |
| Arena · Japanese | #1 · ELO 1,526 | Unranked |
| Arena · coding | #3 · ELO 1,551 | #34 · ELO 1,517 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- Output pricing is identical (¥8,935 per 1M tokens).
- On the Overall arena board, Claude Fable 5 ranks higher (#1; Claude Fable 5.1 is #3).
- On the Coding arena board, Claude Fable 5 ranks higher (#3; Claude Fable 5.1 is #34).
- 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
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
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
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
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
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
Frequently asked questions
- Which is cheaper, Claude Fable 5 or Claude Fable 5.1?
- Both are ¥8,935 per 1M output tokens on FastMetal (yen, before tax).
- How do the context windows of Claude Fable 5 and Claude Fable 5.1 compare?
- Claude Fable 5 takes 1,000,000 tokens; Claude Fable 5.1 takes 1,000,000.
- Which ranks higher, Claude Fable 5 or Claude Fable 5.1?
- Claude Fable 5 ranks higher on the public arena (Claude Fable 5 #1, Claude Fable 5.1 #3). Ranks move as the leaderboard updates.
- Can I use Claude Fable 5 and Claude Fable 5.1 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-fable-5" or "anthropic-claude-fable-5-1" 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 Claude Fable 5.1 from the browser chat and the API. No monthly fee.