Claude Opus 4.6 vs Claude Opus 4.8
Pricing, context window and real answers (August 2026)
Claude Opus 4.6 (Anthropic) and Claude Opus 4.8 (Anthropic), 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 | Claude Opus 4.8 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Input (per 1M tokens) | ¥850 | ¥893.5 |
| Output (per 1M tokens) | ¥4,200 | ¥4,467.5 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥2,950 | ¥3,127 |
| Context window | 1,000,000 tokens | 1,000,000 tokens |
| Release date | 2/4/2026 | 5/27/2026 |
| Input modalities | text, image | text, image, file |
| Arena · overall | #5 · ELO 1,497 | #31 · ELO 1,473 |
| Arena · Japanese | #16 · ELO 1,482 | #30 · ELO 1,450 |
| Arena · coding | #5 · ELO 1,546 | #16 · ELO 1,527 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Claude Opus 4.6: ¥4,200 per 1M output tokens, 6% less than Claude Opus 4.8.
- On the Overall arena board, Claude Opus 4.6 ranks higher (#5; Claude Opus 4.8 is #31).
- On the Japanese arena board, Claude Opus 4.6 ranks higher (#16; Claude Opus 4.8 is #30).
- On the Coding arena board, Claude Opus 4.6 ranks higher (#5; Claude Opus 4.8 is #16).
- 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
Claude Opus 4.8
# Counting 'r's in "strawberry"
## Step-by-step process:
Let me go through each letter one at a time:
| Position | Letter | Is it 'r'? |
|----------|--------|-----------|
| 1 | s | No |
| 2 | t | No |
| 3 | r | ✓ Yes (1) |
| 4 | a | No |
| 5 | w | No |
| 6 | b | No |
| 7 | e | No |
| 8 | r | ✓ Yes (2) |
| 9 | r | ✓ Yes (3) |
| 10 | y | No |
## Answer:
There are **3** 'r's in "strawberry".
The three 'r's appear at positions 3, 8, and 9 — one after the "st" and two together in the "rry" ending.
4.5s262 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
Claude Opus 4.8
# What's Causing the Error
The error tells you exactly what's happening:
```
TypeError: Cannot read properties of undefined (reading 'map')
at UserList (/app/components/UserList.js:12:25)
```
At the moment `UserList` renders, the `users` prop is `undefined`, and you can't call `.map()` on `undefined`. This is extremely common when data is fetched asynchronously—the component renders **before** the data arrives.
Common reasons `users` is undefined:
- The parent hasn't passed the `users` prop at all
- Data is still loading from an API (initial state is `undefined`)
- The API response shape differs from what you expect (e.g. `data.users` vs `data`)
---
# How to Fix It
## Option 1: De…
11.3s761 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
Claude Opus 4.8
# Code Review
Here's a breakdown of issues and suggested improvements for your function.
## Key Issues
1. **Imports inside the function** — should be at module level (runs on every call, harder to see dependencies).
2. **Bare `except:`** — catches everything, including `KeyboardInterrupt` and `SystemExit`. Silently swallowing errors makes debugging hard.
3. **Magic numbers** — `10`, `2`, `200` scattered around; extract as parameters/constants.
4. **`== True` comparison** — non-Pythonic; use the value directly (or `is True` if strict).
5. **Blocking `time.sleep(2)`** — fixed delay; exponential backoff is a better practice.
6. **`r.status_code == 200`** — misses other success codes; use `ra…
16.9s1403 output tokens
Frequently asked questions
- Which is cheaper, Claude Opus 4.6 or Claude Opus 4.8?
- Per 1M output tokens, Claude Opus 4.6 is ¥4,200 and Claude Opus 4.8 is ¥4,467.5 on FastMetal (yen, before tax), so Claude Opus 4.6 is cheaper.
- How do the context windows of Claude Opus 4.6 and Claude Opus 4.8 compare?
- Claude Opus 4.6 takes 1,000,000 tokens; Claude Opus 4.8 takes 1,000,000.
- Which ranks higher, Claude Opus 4.6 or Claude Opus 4.8?
- Claude Opus 4.6 ranks higher on the public arena (Claude Opus 4.6 #16, Claude Opus 4.8 #30). Ranks move as the leaderboard updates.
- Can I use Claude Opus 4.6 and Claude Opus 4.8 with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-opus-4-6" or "anthropic-claude-opus-4-8" 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 Claude Opus 4.8 from the browser chat and the API. No monthly fee.