Claude Haiku 4.5 vs Claude Opus 4.6
Pricing, context window and real answers (August 2026)
Claude Haiku 4.5 (Anthropic) and Claude Opus 4.6 (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 Haiku 4.5 | Claude Opus 4.6 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Input (per 1M tokens) | ¥184.8 | ¥850 |
| Output (per 1M tokens) | ¥924 | ¥4,200 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥647 | ¥2,950 |
| Context window | 200,000 tokens | 1,000,000 tokens |
| Release date | 10/15/2025 | 2/4/2026 |
| Input modalities | image, text | text, image |
| Arena · overall | #129 · ELO 1,413 | #5 · ELO 1,497 |
| Arena · Japanese | #112 · ELO 1,357 | #16 · ELO 1,482 |
| Arena · coding | #95 · ELO 1,480 | #5 · ELO 1,546 |
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, 78% less than Claude Opus 4.6.
- On the Overall arena board, Claude Opus 4.6 ranks higher (#5; Claude Haiku 4.5 is #129).
- On the Japanese arena board, Claude Opus 4.6 ranks higher (#16; Claude Haiku 4.5 is #112).
- On the Coding arena board, Claude Opus 4.6 ranks higher (#5; Claude Haiku 4.5 is #95).
- For long documents, Claude Opus 4.6: a 1,000,000-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
Claude Opus 4.6
I need to count the number of 'r's in the word 'strawberry'. Let me go through it letter by letter.
**s** - not an r
**t** - not an r
**r** - this is an r ✓ (count: 1)
**a** - not an r
**w** - not an r
**b** - not an r
**e** - not an r
**r** - this is an r ✓ (count: 2)
**r** - this is an r ✓ (count: 3)
**y** - not an r
There are **3** r's in 'strawberry'.
3.2s158 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
Claude Opus 4.6
# Understanding the Error
The error `Cannot read properties of undefined (reading 'map')` means that **`users` is `undefined`** when the component renders. You're trying to call `.map()` on a value that doesn't exist yet.
This typically happens when:
- The parent component doesn't pass the `users` prop
- The data is being fetched asynchronously and hasn't loaded yet
- The prop name is misspelled
## Solutions
### 1. Add a Default Parameter Value (Simplest Fix)
```javascript
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
### 2. Add a Guard with Optional Chaining
```javascript
function UserList({…
10.5s599 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
Claude Opus 4.6
# Code Review: `get_data` Function
## Original Issues Identified
1. **Imports inside function** – reduces clarity and adds per-call overhead
2. **Bare `except`** – catches everything including `KeyboardInterrupt` and `SystemExit`
3. **`== True` comparison** – non-Pythonic
4. **Manual list building** – could use a list comprehension
5. **No logging** – failures happen silently
6. **No response validation** – assumes JSON is always a list of dicts with specific keys
7. **Magic numbers** – `timeout=10`, `sleep(2)` unexplained
8. **Vague function/variable names** – `r`, `data`, `get_data`
---
## Improved Version
```python
import logging
import time
from typing import Any
import requests
fr…
19.9s1223 output tokens
Frequently asked questions
- Which is cheaper, Claude Haiku 4.5 or Claude Opus 4.6?
- Per 1M output tokens, Claude Haiku 4.5 is ¥924 and Claude Opus 4.6 is ¥4,200 on FastMetal (yen, before tax), so Claude Haiku 4.5 is cheaper.
- How do the context windows of Claude Haiku 4.5 and Claude Opus 4.6 compare?
- Claude Haiku 4.5 takes 200,000 tokens; Claude Opus 4.6 takes 1,000,000.
- Which ranks higher, Claude Haiku 4.5 or Claude Opus 4.6?
- Claude Opus 4.6 ranks higher on the public arena (Claude Haiku 4.5 #112, Claude Opus 4.6 #16). Ranks move as the leaderboard updates.
- Can I use Claude Haiku 4.5 and Claude Opus 4.6 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-haiku-4-5" or "anthropic-claude-opus-4-6" 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 Claude Opus 4.6 from the browser chat and the API. No monthly fee.