Claude Opus 4.6 vs Gemini 3.5 Flash
Pricing, context window and real answers (August 2026)
Claude Opus 4.6 (Anthropic) and Gemini 3.5 Flash (Google), 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
 Claude Opus 4.6 |  Gemini 3.5 Flash | |
|---|---|---|
| Provider | Anthropic | |
| Input (per 1M tokens) | ¥850 | ¥268.05 |
| Output (per 1M tokens) | ¥4,200 | ¥1,608.3 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥2,950 | ¥1,072 |
| Context window | 1,000,000 tokens | 1,048,576 tokens |
| Release date | 2/4/2026 | 5/19/2026 |
| Input modalities | text, image | text, image, video, file, audio |
| Arena · overall | #5 · ELO 1,497 | #21 · ELO 1,479 |
| Arena · Japanese | #16 · ELO 1,482 | #17 · ELO 1,479 |
| Arena · coding | #5 · ELO 1,546 | #51 · ELO 1,508 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Gemini 3.5 Flash: ¥1,608.3 per 1M output tokens, 62% less than Claude Opus 4.6.
- On the Overall arena board, Claude Opus 4.6 ranks higher (#5; Gemini 3.5 Flash is #21).
- On the Japanese arena board, Claude Opus 4.6 ranks higher (#16; Gemini 3.5 Flash is #17).
- On the Coding arena board, Claude Opus 4.6 ranks higher (#5; Gemini 3.5 Flash is #51).
- For long documents, Gemini 3.5 Flash: a 1,048,576-token context window against 1,000,000 for Claude Opus 4.6.
- 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.
Claude Opus 4.6
I need to count the number of 'r's in the word 'strawberry'. Let me go through it letter by letter.
**s** - not an r
**t** - not an r
**r** - this is an r ✓ (count: 1)
**a** - not an r
**w** - not an r
**b** - not an r
**e** - not an r
**r** - this is an r ✓ (count: 2)
**r** - this is an r ✓ (count: 3)
**y** - not an r
There are **3** r's in 'strawberry'.
3.2s158 output tokens
Gemini 3.5 Flash
There are **3** 'r's in the word "strawberry".
Here is the step-by-step breakdown of how to count them:
1. **Break the word down into its individual letters:**
* 1st letter: **s**
* 2nd letter: **t**
* 3rd letter: **r** (First 'r')
* 4th letter: **a**
* 5th letter: **w**
* 6th letter: **b**
* 7th letter: **e**
* 8th letter: **r** (Second 'r')
* 9th letter: **r** (Third 'r')
* 10th letter: **y**
2. **Identify and count only the 'r's:**
* s - t - **r** (1) - a - w - b - e - **r** (2) - **r** (3) - y
By counting them as we go through the word, we find a total of **3** 'r's.
4.8s601 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…
Claude Opus 4.6
# Understanding the Error
The error `Cannot read properties of undefined (reading 'map')` means that **`users` is `undefined`** when the component renders. You're trying to call `.map()` on a value that doesn't exist yet.
This typically happens when:
- The parent component doesn't pass the `users` prop
- The data is being fetched asynchronously and hasn't loaded yet
- The prop name is misspelled
## Solutions
### 1. Add a Default Parameter Value (Simplest Fix)
```javascript
function UserList({ users = [] }) {
return (
<ul>
{users.map(user => <li key={user.id}>{user.name}</li>)}
</ul>
);
}
```
### 2. Add a Guard with Optional Chaining
```javascript
function UserList({…
10.5s599 output tokens
Gemini 3.5 Flash
### What is causing this error?
The error `TypeError: Cannot read properties of undefined (reading 'map')` means that your `UserList` component is trying to call `.map()` on the `users` variable, but **`users` is currently `undefined`**.
This usually happens for one of two reasons:
1. **The parent component forgot to pass the prop:** `<UserList />` was rendered without the `users` attribute.
2. **Asynchronous data fetching:** The parent component fetches the users from an API, but the API request hasn't finished yet when the component first renders, so `users` starts as `undefined`.
---
### How to fix it
Here are the three best ways to fix this, depending on how you want your UI to beh…
11.2s1524 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):…
Claude Opus 4.6
# Code Review: `get_data` Function
## Original Issues Identified
1. **Imports inside function** – reduces clarity and adds per-call overhead
2. **Bare `except`** – catches everything including `KeyboardInterrupt` and `SystemExit`
3. **`== True` comparison** – non-Pythonic
4. **Manual list building** – could use a list comprehension
5. **No logging** – failures happen silently
6. **No response validation** – assumes JSON is always a list of dicts with specific keys
7. **Magic numbers** – `timeout=10`, `sleep(2)` unexplained
8. **Vague function/variable names** – `r`, `data`, `get_data`
---
## Improved Version
```python
import logging
import time
from typing import Any
import requests
fr…
19.9s1223 output tokens
Gemini 3.5 Flash
Here is a review of your function, followed by two improved versions (one that keeps your structure but makes it Pythonic, and one production-ready version that uses industry best practices).
---
### Key Areas for Improvement
1. **Imports inside the function:** `import requests` and `import time` should be at the top of the file (PEP 8). Keeping them inside the function slows down execution if the function is called repeatedly.
2. **Bare `except:` clause:** Using `except:` without specifying an exception type is a major anti-pattern. It catches things you don't want to catch, like `KeyboardInterrupt` (Ctrl+C) or `SystemExit`. It should target `requests.RequestException`.
3. **Implicit `Tr…
19.7s2975 output tokens
Frequently asked questions
- Which is cheaper, Claude Opus 4.6 or Gemini 3.5 Flash?
- Per 1M output tokens, Claude Opus 4.6 is ¥4,200 and Gemini 3.5 Flash is ¥1,608.3 on FastMetal (yen, before tax), so Gemini 3.5 Flash is cheaper.
- How do the context windows of Claude Opus 4.6 and Gemini 3.5 Flash compare?
- Claude Opus 4.6 takes 1,000,000 tokens; Gemini 3.5 Flash takes 1,048,576.
- Which ranks higher, Claude Opus 4.6 or Gemini 3.5 Flash?
- Claude Opus 4.6 ranks higher on the public arena (Claude Opus 4.6 #16, Gemini 3.5 Flash #17). Ranks move as the leaderboard updates.
- Can I use Claude Opus 4.6 and Gemini 3.5 Flash with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-opus-4-6" or "gemini-3.5-flash" 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 Claude Opus 4.6 and Gemini 3.5 Flash from the browser chat and the API. No monthly fee.