Fugu Ultra v2 vs GPT-5.6 Sol
Pricing, context window and real answers (September 2026)
Fugu Ultra v2 (Sakana AI) and GPT-5.6 Sol (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
| Fugu Ultra v2 |  GPT-5.6 Sol | |
|---|---|---|
| Provider | Sakana AI | OpenAI |
| Input (per 1M tokens) | ¥893.5 | ¥893.5 |
| Output (per 1M tokens) | ¥5,361 | ¥5,361 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥3,574 | ¥3,574 |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Release date | 9/11/2026 | 7/9/2026 |
| Input modalities | text, image, file | file, image, text |
| Throughput (p50) | — | — |
| Arena · overall | Unranked | #18 · ELO 1,483 |
| Arena · Japanese | Unranked | #5 · ELO 1,503 |
| Arena · coding | Unranked | #17 · ELO 1,528 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- Output pricing is identical (¥5,361 per 1M tokens).
- For long documents, GPT-5.6 Sol: a 1,050,000-token context window against 1,000,000 for Fugu Ultra v2.
- 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.
Fugu Ultra v2
**Answer: 3**
**Step-by-step reasoning:**
1. **Write out the word letter by letter**, assigning each a position:
| Position | Letter | Is it 'r'? |
|---|---|---|
| 1 | s | no |
| 2 | t | no |
| 3 | **r** | ✅ yes |
| 4 | a | no |
| 5 | w | no |
| 6 | b | no |
| 7 | e | no |
| 8 | **r** | ✅ yes |
| 9 | **r** | ✅ yes |
| 10 | y | no |
2. **Tally the matches:** positions 3, 8, and 9 are 'r'.
3. **Sanity check by chunks:** "straw" contains one 'r' (str**a**w → the r in "str"), and "berry" contains two 'r's (be**rr**y). 1 + 2 = 3.
4. **Verify length:** the letters counted total 10, which matches the length of "strawberry" — so no letter was skipped or double-counted.
**Conclusion:** There a…
10.2s435 output tokens
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
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…
Fugu Ultra v2
## What the error means
`TypeError: Cannot read properties of undefined (reading 'map')` means that when `UserList` rendered, `users` was `undefined`, and JavaScript can't read the `.map` property off `undefined`.
The important detail: **the bug isn't really in `UserList`** — that's just where it surfaces. Destructuring `function UserList({ users })` does *not* throw when the prop is missing; it silently gives you `undefined`. The crash is deferred to the first property access, which is `.map` on line 12.
So the real question is: why is `props.users` not an array?
## Why `users` is undefined
**1. Async data hasn't arrived yet — by far the most common cause.**
```jsx
const [users, setUs…
70.8s5286 output tokens
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
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):…
Fugu Ultra v2
# Final Code Review: `get_data`
The function is compact and its intent is clear, but as written it will **fail silently in production**. Two defects dominate everything else:
1. The bare `except:` swallows every error — including `KeyboardInterrupt` and genuine logic bugs.
2. A total failure and a legitimately empty dataset both return `[]`, so callers cannot tell "the service is down" from "there are no active records."
Together these mean an outage looks exactly like a successful empty response. Everything else below is meaningful improvement; those two are the difference between code that fails loudly and code that fails invisibly.
---
## 1. Correctness and error handling
### 1.1 `e…
281.1s23317 output tokens
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
Frequently asked questions
- Which is cheaper, Fugu Ultra v2 or GPT-5.6 Sol?
- Both are ¥5,361 per 1M output tokens on FastMetal (yen, before tax).
- How do the context windows of Fugu Ultra v2 and GPT-5.6 Sol compare?
- Fugu Ultra v2 takes 1,000,000 tokens; GPT-5.6 Sol takes 1,050,000.
- Can I use Fugu Ultra v2 and GPT-5.6 Sol with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "fugu-ultra-v2" or "gpt-5.6-sol" 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 Fugu Ultra v2 and GPT-5.6 Sol from the browser chat and the API. No monthly fee.