GPT-5.6 Sol vs Grok 4.5
Pricing, context window and real answers (August 2026)
GPT-5.6 Sol (OpenAI) and Grok 4.5 (xAI), 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 |  Grok 4.5 | |
|---|---|---|
| Provider | OpenAI | xAI |
| Input (per 1M tokens) | ¥893.5 | ¥357.4 |
| Output (per 1M tokens) | ¥5,361 | ¥1,072.2 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥3,574 | ¥894 |
| Context window | 1,050,000 tokens | 500,000 tokens |
| Release date | 7/9/2026 | 7/8/2026 |
| Input modalities | file, image, text | text, image, file |
| Arena · overall | #13 · ELO 1,485 | #35 · ELO 1,468 |
| Arena · Japanese | Unranked | Unranked |
| Arena · coding | #16 · ELO 1,524 | #28 · ELO 1,516 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Grok 4.5: ¥1,072.2 per 1M output tokens, 80% less than GPT-5.6 Sol.
- On the Overall arena board, GPT-5.6 Sol ranks higher (#13; Grok 4.5 is #35).
- On the Coding arena board, GPT-5.6 Sol ranks higher (#16; Grok 4.5 is #28).
- For long documents, GPT-5.6 Sol: a 1,050,000-token context window against 500,000 for Grok 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.
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
Grok 4.5
The word "strawberry" is spelled as follows:
**s-t-r-a-w-b-e-r-r-y**
- Position 1: **s**
- Position 2: **t**
- Position 3: **r** ← (1st "r")
- Position 4: **a**
- Position 5: **w**
- Position 6: **b**
- Position 7: **e**
- Position 8: **r** ← (2nd "r")
- Position 9: **r** ← (3rd "r")
- Position 10: **y**
There are **3** occurrences of the letter "r".
6.5s350 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
Grok 4.5
The error occurs because `users` is `undefined` when the component renders, so calling `.map()` on it fails.
This commonly happens when:
- The parent component doesn’t pass a `users` prop at all
- The data is loaded asynchronously and is still `undefined` on the first render
- The prop is accidentally set to `undefined`/`null` instead of an array
### Fixes
**1. Default to an empty array (simplest)**
```js
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => (
<li key={user.id}>{user.name}</li>
))}
</ul>
);
}
```
**2. Optional chaining (also fine)**
```js
function UserList({ users }) {
return (
<ul>
{users?.map(user => (…
7.9s507 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
Grok 4.5
## Code Review: `get_data`
### Issues
| Area | Problem |
|------|---------|
| **Imports** | `requests` / `time` inside the function — re-imported on every call; belong at module level |
| **Exceptions** | Bare `except:` swallows `KeyboardInterrupt`, `SystemExit`, and hides bugs |
| **Boolean check** | `item["active"] == True` is unidiomatic; truthiness is enough |
| **Loop** | Manual `for` + `append` can be a list comprehension |
| **Retries** | Sleeps on non-200 but never logs or distinguishes failure modes; unused loop variable `i` |
| **Robustness** | No guard for non-list JSON, missing keys (`KeyError`), or invalid JSON |
| **API** | Magic numbers (`timeout=10`, `sleep=2`); no docstrin…
25.3s1363 output tokens
Frequently asked questions
- Which is cheaper, GPT-5.6 Sol or Grok 4.5?
- Per 1M output tokens, GPT-5.6 Sol is ¥5,361 and Grok 4.5 is ¥1,072.2 on FastMetal (yen, before tax), so Grok 4.5 is cheaper.
- How do the context windows of GPT-5.6 Sol and Grok 4.5 compare?
- GPT-5.6 Sol takes 1,050,000 tokens; Grok 4.5 takes 500,000.
- Which ranks higher, GPT-5.6 Sol or Grok 4.5?
- GPT-5.6 Sol ranks higher on the public arena (GPT-5.6 Sol #13, Grok 4.5 #35). Ranks move as the leaderboard updates.
- Can I use GPT-5.6 Sol and Grok 4.5 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-5.6-sol" or "grok-4.5" 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 Grok 4.5 from the browser chat and the API. No monthly fee.