Claude Haiku 4.5 vs GPT-5.4 Nano
Pricing, context window and real answers (September 2026)
Claude Haiku 4.5 (Anthropic) and GPT-5.4 Nano (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-5.4 Nano | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥184.8 | ¥35.74 |
| Output (per 1M tokens) | ¥924 | ¥223.38 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥647 | ¥147 |
| Context window | 200,000 tokens | 400,000 tokens |
| Release date | 10/15/2025 | 3/17/2026 |
| Input modalities | image, text | file, image, text |
| Throughput (p50) | — | — |
| Arena · overall | #129 · ELO 1,415 | #146 · ELO 1,402 |
| Arena · Japanese | #112 · ELO 1,361 | #107 · ELO 1,368 |
| Arena · coding | #96 · ELO 1,482 | #128 · ELO 1,460 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, GPT-5.4 Nano: ¥223.38 per 1M output tokens, 76% less than Claude Haiku 4.5.
- On the Overall arena board, Claude Haiku 4.5 ranks higher (#129; GPT-5.4 Nano is #146).
- On the Japanese arena board, GPT-5.4 Nano ranks higher (#107; Claude Haiku 4.5 is #112).
- On the Coding arena board, Claude Haiku 4.5 ranks higher (#96; GPT-5.4 Nano is #128).
- For long documents, GPT-5.4 Nano: a 400,000-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-5.4 Nano
**Step 1:** Write the word: **strawberry**
**Step 2:** Count each letter **r** in the word:
- s **t r** a w b e **r r** y
There are **3** **r**’s in total (**one** after the **t**, and **two** near the end).
✅ **Answer: 3**
1.5s86 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-5.4 Nano
This error means that **`users` is `undefined` (or otherwise not an array)** when your component renders, so calling `users.map(...)` throws:
```js
users.map(...)
^^^^ reading 'map' of undefined
```
### Why it happens
Common causes:
- You render `<UserList />` before data has loaded (e.g., `users` comes from an async fetch).
- The parent component passes the wrong prop name (e.g., `user` instead of `users`).
- The API/parent state initializes `users` as `undefined` rather than `[]`.
- You’re destructuring a prop incorrectly upstream.
### Fix options
#### 1) Ensure `users` is always an array (recommended)
Initialize/default it in the component:
```js
function UserList({ users = []…
3.3s383 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-5.4 Nano
Here are key improvements (readability, performance, robustness, best practices) and a revised version of your function.
## What to improve
1. **Avoid bare `except:`**
Catch specific exceptions from `requests` (e.g., `requests.exceptions.RequestException`) to avoid hiding bugs.
2. **Prefer `raise_for_status()` or check status codes clearly**
`r.raise_for_status()` is a common pattern.
3. **Use exponential backoff (or at least a clear retry delay)**
Instead of sleeping the same amount every time, consider increasing delay.
4. **Reuse a `requests.Session()` (optional but best practice)**
If this function is called repeatedly, passing a session or creating one outside i…
4.4s718 output tokens
Frequently asked questions
- Which is cheaper, Claude Haiku 4.5 or GPT-5.4 Nano?
- Per 1M output tokens, Claude Haiku 4.5 is ¥924 and GPT-5.4 Nano is ¥223.38 on FastMetal (yen, before tax), so GPT-5.4 Nano is cheaper.
- How do the context windows of Claude Haiku 4.5 and GPT-5.4 Nano compare?
- Claude Haiku 4.5 takes 200,000 tokens; GPT-5.4 Nano takes 400,000.
- Which ranks higher, Claude Haiku 4.5 or GPT-5.4 Nano?
- GPT-5.4 Nano ranks higher on the public arena (Claude Haiku 4.5 #112, GPT-5.4 Nano #107). Ranks move as the leaderboard updates.
- Can I use Claude Haiku 4.5 and GPT-5.4 Nano with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-haiku-4-5" or "gpt-5.4-nano" 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-5.4 Nano from the browser chat and the API. No monthly fee.