GPT-5.6 Sol vs GPT-6 Astra
Pricing, context window and real answers (September 2026)
GPT-5.6 Sol (OpenAI) and GPT-6 Astra (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
 GPT-5.6 Sol | GPT-6 Astra | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Input (per 1M tokens) | ¥893.5 | ¥1,717.72 |
| Output (per 1M tokens) | ¥5,361 | ¥8,588.62 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥3,574 | ¥6,012 |
| Context window | 1,050,000 tokens | 1,050,000 tokens |
| Release date | 7/9/2026 | 9/4/2026 |
| Input modalities | file, image, text | file, image, text |
| Arena · overall | #17 · ELO 1,483 | Unranked |
| Arena · Japanese | #2 · ELO 1,522 | Unranked |
| Arena · coding | #14 · ELO 1,529 | Unranked |
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 Sol: ¥5,361 per 1M output tokens, 38% less than GPT-6 Astra.
- 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 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
GPT-6 Astra
“strawberry” is spelled **s-t-r-a-w-b-e-r-r-y**.
The letter **r** appears in positions **3, 8, and 9**, so there are **3 r’s**.
3.8s85 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 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
GPT-6 Astra
The error means **`users` is `undefined` when React renders `UserList`**, so calling `users.map(...)` fails. This commonly happens when the parent doesn’t pass the prop or when data hasn’t finished loading.
### 1. Default `users` to an empty array
If an absent prop should mean “no users,” use a default value:
```jsx
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => (
<li key={user.id}>{user.name}</li>
))}
</ul>
);
}
```
This handles a missing or `undefined` prop, but **not `null` or other non-array values**.
### 2. Check where the prop comes from
Make sure the parent passes an array. For data loaded asynchronously, initialize state to…
6.7s380 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 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
GPT-6 Astra
The function is compact, but its biggest issue is that **all failures silently become `[]`**, making an unavailable API indistinguishable from a successful response with no active items.
### Suggested improvements
- **Move imports to module scope** for clarity and conventional organization.
- **Avoid bare `except:`.** It catches everything, including `KeyboardInterrupt`, and hides bugs such as missing dictionary keys.
- **Retry only transient failures**, such as connection errors, timeouts, rate limiting, and selected server errors. Retrying a `401` or `404` usually won’t help.
- **Don’t sleep after the final failed attempt.** Use exponential backoff rather than a fixed delay.
- **Use desc…
19.2s965 output tokens
Frequently asked questions
- Which is cheaper, GPT-5.6 Sol or GPT-6 Astra?
- Per 1M output tokens, GPT-5.6 Sol is ¥5,361 and GPT-6 Astra is ¥8,588.62 on FastMetal (yen, before tax), so GPT-5.6 Sol is cheaper.
- How do the context windows of GPT-5.6 Sol and GPT-6 Astra compare?
- GPT-5.6 Sol takes 1,050,000 tokens; GPT-6 Astra takes 1,050,000.
- Can I use GPT-5.6 Sol and GPT-6 Astra with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-5.6-sol" or "gpt-6-astra" 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 Sol and GPT-6 Astra from the browser chat and the API. No monthly fee.