Claude Haiku 4.5 vs gpt-oss-20b
Pricing, context window and real answers (September 2026)
Claude Haiku 4.5 (Anthropic) and gpt-oss-20b (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-oss-20b | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input (per 1M tokens) | ¥184.8 | ¥5.36 |
| Output (per 1M tokens) | ¥924 | ¥25.02 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥647 | ¥18 |
| Context window | 200,000 tokens | 131,072 tokens |
| Release date | 10/15/2025 | 8/5/2025 |
| Input modalities | image, text | text |
| Throughput (p50) | — | — |
| Arena · overall | #129 · ELO 1,415 | #252 · ELO 1,317 |
| Arena · Japanese | #112 · ELO 1,361 | #179 · ELO 1,256 |
| Arena · coding | #96 · ELO 1,482 | #232 · ELO 1,369 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, gpt-oss-20b: ¥25.02 per 1M output tokens, 97% less than Claude Haiku 4.5.
- On the Overall arena board, Claude Haiku 4.5 ranks higher (#129; gpt-oss-20b is #252).
- On the Japanese arena board, Claude Haiku 4.5 ranks higher (#112; gpt-oss-20b is #179).
- On the Coding arena board, Claude Haiku 4.5 ranks higher (#96; gpt-oss-20b is #232).
- For long documents, Claude Haiku 4.5: a 200,000-token context window against 131,072 for gpt-oss-20b.
- 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-oss-20b
**Count of ‘r’ in “strawberry”: 3**
---
### Step‑by‑step reasoning
1. **Write out the word in individual letters**
```
s t r a w b e r r y
```
2. **Identify each ‘r’**
- The first ‘r’: appears after the “t” → **r**
- The second ‘r’: appears in the part “berry” → **r**
- The third ‘r’: the next letter after that → **r**
3. **Verify there are no more letters left**
The remaining letters are “b”, “e”, “y”, none of which are “r”.
4. **Count the identified ‘r’s**
1 (first) + 1 (second) + 1 (third) = **3**
---
### Quick recap
- Word: **strawberry**
- Letters containing “r”: positions 3, 8, and 9.
- Total count: **3**.
11.6s371 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-oss-20b
### Why does the error happen?
`users.map(...)` can only run when **`users` is an array**.
The stack trace shows that the crash happens on line 12 of `UserList.js`, which is the
exact spot where the code tries to call `.map`.
The value that is being passed to `UserList` (or the initial value that the parent
creates) is **`undefined`** (or it could be `null`/`{}`). When JavaScript tries to
read `users.map`, it throws:
```
TypeError: Cannot read properties of undefined (reading 'map')
```
Typical reasons for this are:
1. The parent component **didn’t pass the `users` prop** at all.
2. The parent passed it but the value was **`undefined` / `null`** because data
hasn’t been loaded ye…
11.4s1303 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-oss-20b
Below is a quick “code‑review” style list that touches the three axes you asked for – **readability**, **performance**, and **best practices**.
After the bullet‑list I’ll paste a refactored version that incorporates the most common fixes.
---
## 1. Readability
| Issue | Why it hurts | Quick fix |
|-------|--------------|-----------|
| **Imports inside the function** | Every call recompiles the import tables and makes the module’s top‑level slower. | Move `import requests` and `import time` to the module’s global header. |
| **Bare `except:`** | Catches *everything* (KeyboardInterrupt, SystemExit, MemoryError, etc.) and swallows useful tracebacks. | Catch only the expected network-relate…
24.6s2267 output tokens
Frequently asked questions
- Which is cheaper, Claude Haiku 4.5 or gpt-oss-20b?
- Per 1M output tokens, Claude Haiku 4.5 is ¥924 and gpt-oss-20b is ¥25.02 on FastMetal (yen, before tax), so gpt-oss-20b is cheaper.
- How do the context windows of Claude Haiku 4.5 and gpt-oss-20b compare?
- Claude Haiku 4.5 takes 200,000 tokens; gpt-oss-20b takes 131,072.
- Which ranks higher, Claude Haiku 4.5 or gpt-oss-20b?
- Claude Haiku 4.5 ranks higher on the public arena (Claude Haiku 4.5 #112, gpt-oss-20b #179). Ranks move as the leaderboard updates.
- Can I use Claude Haiku 4.5 and gpt-oss-20b with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-haiku-4-5" or "gpt-oss-20b" 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-oss-20b from the browser chat and the API. No monthly fee.