GPT-5 Mini vs Solar Pro 4
Pricing, context window and real answers (September 2026)
GPT-5 Mini (OpenAI) and Solar Pro 4 (Upstage), 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 Mini | Solar Pro 4 | |
|---|---|---|
| Provider | OpenAI | Upstage |
| Input (per 1M tokens) | ¥44.68 | ¥16.08 |
| Output (per 1M tokens) | ¥357.4 | ¥64.33 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥223 | ¥48 |
| Context window | 400,000 tokens | 524,288 tokens |
| Release date | 8/7/2025 | 8/10/2026 |
| Input modalities | text, image, file | text |
| Throughput (p50) | — | — |
| Arena · overall | #163 · ELO 1,390 | #177 · ELO 1,376 |
| Arena · Japanese | #109 · ELO 1,365 | Unranked |
| Arena · coding | #172 · ELO 1,431 | #144 · ELO 1,449 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Solar Pro 4: ¥64.33 per 1M output tokens, 82% less than GPT-5 Mini.
- On the Overall arena board, GPT-5 Mini ranks higher (#163; Solar Pro 4 is #177).
- On the Coding arena board, Solar Pro 4 ranks higher (#144; GPT-5 Mini is #172).
- For long documents, Solar Pro 4: a 524,288-token context window against 400,000 for GPT-5 Mini.
- 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 Mini
We examine the word "strawberry" letter by letter:
1. s — not an r (count = 0)
2. t — not an r (count = 0)
3. r — an r (count = 1)
4. a — not an r (count = 1)
5. w — not an r (count = 1)
6. b — not an r (count = 1)
7. e — not an r (count = 1)
8. r — an r (count = 2)
9. r — an r (count = 3)
10. y — not an r (count = 3)
Total number of 'r's = 3.
5.2s382 output tokens
Solar Pro 4
The word "strawberry" contains **3** 'r's. Here's the step-by-step breakdown:
1. **Spell out the word explicitly** to isolate each letter:
`s - t - r - a - w - b - e - r - r - y`
2. **Scan through the letters in order** and count every instance of the lowercase letter `r`:
- `s` → 0
- `t` → 0
- `r` → **1**
- `a` → 0
- `w` → 0
- `b` → 0
- `e` → 0
- `r` → **2**
- `r` → **3**
- `y` → 0
3. **Total the count**: The three `r`s appear at positions 3, 8, and 9 in the 10-letter word.
**Final count: 3**
11.4s215 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 Mini
That error means users is undefined when you call users.map(...). map is an Array method, so calling it on undefined throws "Cannot read properties of undefined (reading 'map')".
Common causes
- The parent component didn't pass a users prop.
- users is still loading (e.g. fetched asynchronously) and is null/undefined until the fetch completes.
- The parent initialized users to null instead of an empty array.
How to fix
Choose one or more of these approaches depending on your app:
1) Initialize the parent state as an array
If users is state in the parent, initialize it to [] so the child always receives an array:
const [users, setUsers] = useState([]);
// fetch and setUsers(data)
2) Give…
8.0s966 output tokens
Solar Pro 4
### What's Causing the Error
The error `TypeError: Cannot read properties of undefined (reading 'map')` means that the `users` prop being passed to your `UserList` component is `undefined`. Since you're calling `.map()` directly on it, JavaScript throws an error because `undefined` doesn't have a `map` method.
This typically happens when:
- The parent component hasn't passed the `users` prop
- The prop is still loading (e.g., from an API call)
- The prop is conditionally undefined
---
### How to Fix It
You have a few options to handle this safely:
#### ✅ Option 1: Add a Default Prop Value (Recommended)
Provide a fallback empty array so `.map()` always has something to work with:
```j…
24.7s539 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 Mini
Thanks — this is a nice simple function, but it can be improved in several ways: move imports to module scope, avoid broad except:, use connection pooling (Session) for performance, use specific exception types, add logging and docstring, avoid comparing to True, use list comprehensions, validate JSON shape, and implement backoff (or use urllib3 Retry).
Below are two improved alternatives and a short rationale for the changes.
1) A simple, clear improvement (small changes, explicit errors, backoff + jitter)
- Moves imports to top-level
- Uses requests.Session for connection pooling
- Catches specific exceptions (requests.RequestException, ValueError)
- Uses list comprehension and item.get(…
13.6s1702 output tokens
Solar Pro 4
Here’s a breakdown of the issues in the original function, followed by a refactored version and a detailed explanation of the improvements.
### 🔍 Key Issues in the Original Code
| Area | Problem |
|------|---------|
| **Import organization** | `import` inside the function is evaluated on every call. Imports should live at the top of the module. |
| **Exception handling** | Bare `except:` catches `SystemExit`, `KeyboardInterrupt`, and other fatal errors. Always catch specific exceptions (`requests.RequestException`). |
| **Loose equality** | `== True` is redundant and can cause subtle bugs. Use `if item["active"]:` or `.get()`. |
| **HTTP status handling** | Calling `.json()` only on `200`…
17.5s1172 output tokens
Frequently asked questions
- Which is cheaper, GPT-5 Mini or Solar Pro 4?
- Per 1M output tokens, GPT-5 Mini is ¥357.4 and Solar Pro 4 is ¥64.33 on FastMetal (yen, before tax), so Solar Pro 4 is cheaper.
- How do the context windows of GPT-5 Mini and Solar Pro 4 compare?
- GPT-5 Mini takes 400,000 tokens; Solar Pro 4 takes 524,288.
- Which ranks higher, GPT-5 Mini or Solar Pro 4?
- GPT-5 Mini ranks higher on the public arena (GPT-5 Mini #109, Solar Pro 4 #177). Ranks move as the leaderboard updates.
- Can I use GPT-5 Mini and Solar Pro 4 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-5-mini" or "solar-pro4" 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 Mini and Solar Pro 4 from the browser chat and the API. No monthly fee.