Claude Haiku 5.5 vs DeepSeek V4.1 Flash
Pricing, context window and real answers (October 2026)
Claude Haiku 5.5 (Anthropic) and DeepSeek V4.1 Flash (DeepSeek), 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 Haiku 5.5 |  DeepSeek V4.1 Flash | |
|---|---|---|
| Provider | Anthropic | DeepSeek |
| Input (per 1M tokens) | $0.1055 | $0.211 |
| Output (per 1M tokens) | $0.5275 | $0.633 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | $0.3693 | $0.5275 |
| Context window | 1,000,000 tokens | 1,048,576 tokens |
| Release date | 10/7/2026 | 9/10/2026 |
| Input modalities | text, image, file | text, image |
| Throughput (p50) | — | 140 tokens/s (n=19) |
| Arena · overall | Unranked | #38 · ELO 1,474 |
| Arena · Japanese | Unranked | Unranked |
| Arena · coding | Unranked | #26 · ELO 1,528 |
Prices are FastMetal's rates, before tax.
Rankings: LMArena leaderboard dataset (lmarena-ai/leaderboard-dataset), CC BY 4.0, snapshot 2026-10-02; category names mapped and ratings rounded by FastMetal.
Which should you pick?
- On price, Claude Haiku 5.5: $0.5275 per 1M output tokens, 17% less than DeepSeek V4.1 Flash.
- For long documents, DeepSeek V4.1 Flash: a 1,048,576-token context window against 1,000,000 for Claude Haiku 5.5.
- 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 Haiku 5.5
There are **3** r's in "strawberry."
1. **Spell out the word:** s, t, r, a, w, b, e, r, r, y
2. **Go through each letter and count the r's:**
- Position 3: **r** (count = 1)
- Position 8: **r** (count = 2)
- Position 9: **r** (count = 3)
3. **Check the rest:** s, t, a, w, b, e, and y are not r's.
Total: **3**
2.4s200 output tokens
DeepSeek V4.1 Flash
The word **“strawberry”** has **3** letter **“r”**s.
Step-by-step:
1. Spell it out: **s t r a w b e r r y**
2. Find each **r**:
- Position 3: **r** in “str”
- Position 8: first **r** in “berry”
- Position 9: second **r** in “berry”
3. Total: **3**
**Answer: 3**
7.5s226 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 Haiku 5.5
The error means `users` is `undefined` when `UserList` renders, so `.map` is called on nothing. The component destructures the `users` prop, but the parent didn't pass it, or passed `undefined`.
## Common causes
**1. The parent doesn't pass the prop, or uses a different name**
```jsx
<UserList /> // users is undefined
<UserList user={users} /> // wrong name: "user" instead of "users"
```
**2. The data hasn't loaded yet (most common with fetched data)**
```jsx
function App() {
const [users, setUsers] = useState(); // undefined initially
useEffect(() => {
fetch('/api/users').then(r => r.json()).then(setUsers);
}, []);
return <UserList users={users} />;…
5.1s888 output tokens
DeepSeek V4.1 Flash
The error means that `users` is `undefined` when `UserList` renders, so JavaScript cannot call `.map()` on it.
Your component expects a `users` prop:
```jsx
function UserList({ users }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
But it is being rendered without `users`, or `users` has not loaded yet.
Common causes:
1. Parent renders it without the prop:
```jsx
<UserList />
```
instead of:
```jsx
<UserList users={users} />
```
2. The prop name is different:
```jsx
<UserList userList={users} />
```
3. The data is fetched asynchronously and is initially `undefined`:
```jsx
const [users, setUsers] = useState();
useEffect(…
16.0s945 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 Haiku 5.5
## Issues
**Correctness and robustness**
1. **Bare `except:`** catches everything, including `KeyboardInterrupt` and `SystemExit`, so Ctrl+C may not stop the program. Catch specific exceptions: `requests.RequestException` for network problems and `ValueError` for invalid JSON.
2. **Retries non-retryable errors.** A 404 or 401 won't succeed on retry, so retrying wastes time. Only retry transient failures such as 429, 5xx, timeouts, and connection errors.
3. **Sleeps after the final attempt.** The loop sleeps even when no retry follows.
4. **Fixed sleep with no backoff.** Exponential backoff is the standard approach for retries.
5. **Silent failure.** Every failure returns `[]` with no loggin…
18.1s4096 output tokens
DeepSeek V4.1 Flash
Here are the main improvements:
- Move imports to module level.
- Avoid bare `except`; catch specific exceptions.
- Use a `requests.Session` for connection reuse.
- Retry only transient network/HTTP failures, not all errors.
- Use exponential backoff and don’t sleep after the final attempt.
- Use a list comprehension for readability/performance.
- Add type hints, logging, constants, and basic JSON validation.
- Avoid `== True`; use `is True` or a truthy check depending on API contract.
Example refactor:
```python
from __future__ import annotations
import logging
import time
from typing import Any
import requests
logger = logging.getLogger(__name__)
TIMEOUT = (3.05, 10) # connect time…
31.5s5142 output tokens
Frequently asked questions
- Which is cheaper, Claude Haiku 5.5 or DeepSeek V4.1 Flash?
- Per 1M output tokens, Claude Haiku 5.5 is $0.5275 and DeepSeek V4.1 Flash is $0.633 on FastMetal (US dollars, before tax), so Claude Haiku 5.5 is cheaper.
- How do the context windows of Claude Haiku 5.5 and DeepSeek V4.1 Flash compare?
- Claude Haiku 5.5 takes 1,000,000 tokens; DeepSeek V4.1 Flash takes 1,048,576.
- Can I use Claude Haiku 5.5 and DeepSeek V4.1 Flash with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-haiku-5-5" or "deepseek-v4.1-flash" 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 Haiku 5.5 and DeepSeek V4.1 Flash from the browser chat and the API. No monthly fee.