Claude Haiku 4.5 vs GPT-5.6 Sol
Pricing, context window and real answers (August 2026)
Claude Haiku 4.5 (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 Haiku 4.5 |  GPT-5.6 Sol | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥184.8 | ¥893.5 |
| Output (per 1M tokens) | ¥924 | ¥5,361 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥647 | ¥3,574 |
| Context window | 200,000 tokens | 1,050,000 tokens |
| Release date | 10/15/2025 | 7/9/2026 |
| Input modalities | image, text | file, image, text |
| Arena · overall | #120 · ELO 1,412 | #13 · ELO 1,485 |
| Arena · Japanese | #99 · ELO 1,355 | Unranked |
| Arena · coding | #86 · ELO 1,479 | #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, Claude Haiku 4.5: ¥924 per 1M output tokens, 83% less than GPT-5.6 Sol.
- On the Overall arena board, GPT-5.6 Sol ranks higher (#13; Claude Haiku 4.5 is #120).
- On the Coding arena board, GPT-5.6 Sol ranks higher (#16; Claude Haiku 4.5 is #86).
- For long documents, GPT-5.6 Sol: a 1,050,000-token context window against 200,000 for Claude Haiku 4.5.
- 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 4.5
# Counting the 'r's in "strawberry"
Let me go through each letter in the word "strawberry":
1. **s** - not an 'r'
2. **t** - not an 'r'
3. **r** - this is an 'r' ✓ (1st)
4. **a** - not an 'r'
5. **w** - not an 'r'
6. **b** - not an 'r'
7. **e** - not an 'r'
8. **r** - this is an 'r' ✓ (2nd)
9. **r** - this is an 'r' ✓ (3rd)
10. **y** - not an 'r'
**Answer: There are 3 'r's in "strawberry"**
The 'r's appear in positions 3, 8, and 9 of the word.
4.1s228 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 Haiku 4.5
# TypeError: Cannot read properties of undefined (reading 'map')
This error occurs because `users` is `undefined` when the component renders. You're trying to call `.map()` on `undefined`, which doesn't have that method.
## Common Causes
1. **Parent component didn't pass the `users` prop**
2. **Async data hasn't loaded yet**
3. **Props passed incorrectly**
## Solutions
### 1. **Provide a Default Value** (Recommended)
```javascript
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
### 2. **Add a Conditional Check**
```javascript
function UserList({ users }) {
if (!users) {
return <p>No users a…
3.9s671 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 Haiku 4.5
# Code Review and Improvements
## Issues Found
1. **Bare `except`** - Catches all exceptions, hiding bugs
2. **Imports inside function** - Should be at module level
3. **Redundant comparison** - `== True` is unnecessary
4. **No logging** - Hard to debug failures
5. **Magic numbers** - Hardcoded timeout and sleep values
6. **Inefficient retries** - Doesn't retry on 200 with parsing errors
7. **Poor variable names** - `r`, `i` are unclear
8. **No type hints** - Reduces code clarity
## Improved Version
```python
import logging
import requests
import time
from typing import Optional
from requests.exceptions import RequestException
logger = logging.getLogger(__name__)
def get_data(
url:…
5.7s988 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 Haiku 4.5 or GPT-5.6 Sol?
- Per 1M output tokens, Claude Haiku 4.5 is ¥924 and GPT-5.6 Sol is ¥5,361 on FastMetal (yen, before tax), so Claude Haiku 4.5 is cheaper.
- How do the context windows of Claude Haiku 4.5 and GPT-5.6 Sol compare?
- Claude Haiku 4.5 takes 200,000 tokens; GPT-5.6 Sol takes 1,050,000.
- Which ranks higher, Claude Haiku 4.5 or GPT-5.6 Sol?
- GPT-5.6 Sol ranks higher on the public arena (Claude Haiku 4.5 #99, GPT-5.6 Sol #13). Ranks move as the leaderboard updates.
- Can I use Claude Haiku 4.5 and GPT-5.6 Sol with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-haiku-4-5" 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 Haiku 4.5 and GPT-5.6 Sol from the browser chat and the API. No monthly fee.