GPT-5.6 Luna vs Qwen3.8 27B
Pricing, context window and real answers (August 2026)
GPT-5.6 Luna (OpenAI) and Qwen3.8 27B (Qwen), 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
 GPT-5.6 Luna |  Qwen3.8 27B | |
|---|---|---|
| Provider | OpenAI | Qwen |
| Input (per 1M tokens) | ¥35.74 | ¥80.41 |
| Output (per 1M tokens) | ¥214.44 | ¥571.84 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥143 | ¥366 |
| Context window | 1,050,000 tokens | 1,000,000 tokens |
| Release date | 7/9/2026 | 8/14/2026 |
| Input modalities | file, image, text | text, image, video |
| Arena · overall | #63 · ELO 1,452 | #87 · ELO 1,436 |
| Arena · Japanese | #36 · ELO 1,444 | Unranked |
| Arena · coding | #69 · ELO 1,496 | #67 · ELO 1,498 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, GPT-5.6 Luna: ¥214.44 per 1M output tokens, 63% less than Qwen3.8 27B.
- On the Overall arena board, GPT-5.6 Luna ranks higher (#63; Qwen3.8 27B is #87).
- On the Coding arena board, Qwen3.8 27B ranks higher (#67; GPT-5.6 Luna is #69).
- For long documents, GPT-5.6 Luna: a 1,050,000-token context window against 1,000,000 for Qwen3.8 27B.
- 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.
GPT-5.6 Luna
The word **“strawberry”** is spelled:
**s – t – r – a – w – b – e – r – r – y**
The letter **“r”** appears at positions **3, 8, and 9**.
**Answer: 3**
3.0s120 output tokens
Qwen3.8 27B
The word is: **strawberry**
Break it into letters:
1. s
2. t
3. r
4. a
5. w
6. b
7. e
8. r
9. r
10. y
Now count the **r**’s:
- 3rd letter: **r**
- 8th letter: **r**
- 9th letter: **r**
So, there are **3** r’s in **strawberry**.
3.6s239 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…
GPT-5.6 Luna
`users` is `undefined` when `UserList` renders, so calling `.map()` on it fails. `.map()` only exists on arrays.
Common causes include:
- The parent does not pass a `users` prop.
- The prop name differs, such as `userList` instead of `users`.
- Users are loaded asynchronously and are initially undefined.
- The API response has a different shape, such as `{ data: [...] }`.
### Provide a default value
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => (
<li key={user.id}>{user.name}</li>
))}
</ul>
);
}
```
The parent should pass an array:
```jsx
<UserList users={users} />
```
If the list comes from state, initialize it as an empty…
4.8s507 output tokens
Qwen3.8 27B
The error means that `users` is `undefined` when `UserList` renders:
```jsx
{users.map(...)}
```
JavaScript cannot call `.map()` on `undefined`.
For example, this would cause the error:
```jsx
<UserList />
```
because `users` is not being passed in.
## Simple fix: give `users` a default value
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
Now if `users` is not passed in, it defaults to an empty array.
## Better fix: make sure the parent passes an array
Wherever you use `UserList`, pass `users`:
```jsx
<UserList users={users} />
```
If `users` comes from an API or state, make sure it…
9.5s601 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):…
GPT-5.6 Luna
### Main issues
- Imports should be at module level, not inside the function.
- A bare `except:` catches everything, including programming errors and `KeyboardInterrupt`.
- The function sleeps even after the final failed attempt.
- It retries all HTTP statuses, including permanent errors such as `404`.
- `status_code == 200` excludes other successful `2xx` responses.
- `if item["active"] == True` should generally be `if item.get("active") is True`.
- A `requests.Session` can reuse connections and improve performance.
- Returning `[]` for every failure makes it impossible to distinguish “no active items” from “request failed.”
- Retries should generally use backoff rather than a fixed delay.…
23.3s1978 output tokens
Qwen3.8 27B
The function works at a basic level, but it has several readability, reliability, and best-practice issues.
## Main issues
1. **Imports inside the function**
```python
import requests
import time
```
Imports should normally be at the top of the module unless there is a specific reason to lazy-load them.
2. **Bare `except` is too broad**
```python
except:
time.sleep(2)
```
This catches almost everything, including `KeyboardInterrupt`, `SystemExit`, `KeyError`, `TypeError`, and other programming errors. It makes debugging harder and can retry failures that should not be retried.
3. **It retries on every non-`200` status**
Retrying `401 Unauthorized`, `4…
205.9s13103 output tokens
Frequently asked questions
- Which is cheaper, GPT-5.6 Luna or Qwen3.8 27B?
- Per 1M output tokens, GPT-5.6 Luna is ¥214.44 and Qwen3.8 27B is ¥571.84 on FastMetal (yen, before tax), so GPT-5.6 Luna is cheaper.
- How do the context windows of GPT-5.6 Luna and Qwen3.8 27B compare?
- GPT-5.6 Luna takes 1,050,000 tokens; Qwen3.8 27B takes 1,000,000.
- Which ranks higher, GPT-5.6 Luna or Qwen3.8 27B?
- GPT-5.6 Luna ranks higher on the public arena (GPT-5.6 Luna #36, Qwen3.8 27B #87). Ranks move as the leaderboard updates.
- Can I use GPT-5.6 Luna and Qwen3.8 27B with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-5.6-luna" or "qwen3.8-27b" 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 GPT-5.6 Luna and Qwen3.8 27B from the browser chat and the API. No monthly fee.