Claude Sonnet 5 vs Ember-1
Pricing, context window and real answers (September 2026)
Claude Sonnet 5 (Anthropic) and Ember-1 (Fireworks), 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 | Ember-1 | |
|---|---|---|
| Provider | Anthropic | Fireworks |
| Input (per 1M tokens) | ¥357.4 | ¥536.1 |
| Output (per 1M tokens) | ¥1,787 | ¥2,680.5 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥1,251 | ¥1,876 |
| Context window | 1,000,000 tokens | 1,048,576 tokens |
| Release date | 6/30/2026 | 9/24/2026 |
| Input modalities | text, image, file | text, image |
| Throughput (p50) | — | — |
| Arena · overall | #51 · ELO 1,461 | Unranked |
| Arena · Japanese | #30 · ELO 1,448 | Unranked |
| Arena · coding | #27 · ELO 1,520 | 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 5: ¥1,787 per 1M output tokens, 33% less than Ember-1.
- For long documents, Ember-1: a 1,048,576-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
Ember-1
# Counting the 'r's in "strawberry"
**Step 1: Write out the word letter by letter**
s - t - r - a - w - b - e - r - r - y
**Step 2: Examine each letter one at a time**
| Position | Letter | Is it 'r'? |
|----------|--------|------------|
| 1 | s | No |
| 2 | t | No |
| 3 | r | ✅ Yes (1) |
| 4 | a | No |
| 5 | w | No |
| 6 | b | No |
| 7 | e | No |
| 8 | r | ✅ Yes (2) |
| 9 | r | ✅ Yes (3) |
| 10 | y | No |
**Step 3: Verify by splitting the word into parts**
- "straw" → contains **1** r
- "berry" → contains **2** r's
- Total: 1 + 2 = **3**
## Answer
The word "strawberry" contains **3** r's.
8.2s482 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
Ember-1
## The Cause
The error means `users` is `undefined` when the component renders, so calling `.map()` on it fails. The component itself is fine — the problem is that the `users` prop isn't being provided (or isn't ready yet).
The most common reasons this happens:
1. **Async data hasn't loaded yet** — the parent fetches users from an API, and the component renders before the fetch completes:
```jsx
const [users, setUsers] = useState(); // undefined initially!
```
2. **The prop isn't passed or is misspelled** in the parent:
```jsx
<UserList user={users} /> // typo: should be "users"
```
3. **Wrong data shape** — e.g., passing the whole response object instead of `response…
18.2s960 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
Ember-1
# Code Review
## Bugs and correctness issues
- **Bare `except:`** catches *everything* — including `KeyboardInterrupt` and, critically, `KeyError` from `item["active"]`. A malformed item in the response would be misinterpreted as a network failure, wasting all your retries on a data problem that retrying can't fix.
- **Retrying all non-200 statuses** — a 404 or 401 will never succeed on retry. Only transient errors (connection failures, timeouts, 429, 5xx) are worth retrying.
- **Wasted sleep on the final attempt** — the loop sleeps 2 seconds even after the last failure, before returning `[]`.
- **Ambiguous return value** — `[]` means both "request failed" and "no active items." Callers ca…
95.0s5356 output tokens
Frequently asked questions
- Which is cheaper, Claude Sonnet 5 or Ember-1?
- Per 1M output tokens, Claude Sonnet 5 is ¥1,787 and Ember-1 is ¥2,680.5 on FastMetal (yen, before tax), so Claude Sonnet 5 is cheaper.
- How do the context windows of Claude Sonnet 5 and Ember-1 compare?
- Claude Sonnet 5 takes 1,000,000 tokens; Ember-1 takes 1,048,576.
- Can I use Claude Sonnet 5 and Ember-1 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-sonnet-5" or "ember-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 Sonnet 5 and Ember-1 from the browser chat and the API. No monthly fee.