Claude Opus 4.8 vs Gemini 3.8 Flash
Pricing, context window and real answers (September 2026)
Claude Opus 4.8 (Anthropic) and Gemini 3.8 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 4.8 |  Gemini 3.8 Flash | |
|---|---|---|
| Provider | Anthropic | |
| Input (per 1M tokens) | ¥893.5 | ¥128.83 |
| Output (per 1M tokens) | ¥4,467.5 | ¥644.15 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | ¥3,127 | ¥451 |
| Context window | 1,000,000 tokens | 1,048,576 tokens |
| Release date | 5/27/2026 | 9/2/2026 |
| Input modalities | text, image, file | text, image, video, file, audio |
| Arena · overall | #33 · ELO 1,473 | #8 · ELO 1,494 |
| Arena · Japanese | #31 · ELO 1,448 | Unranked |
| Arena · coding | #17 · ELO 1,527 | #7 · ELO 1,537 |
Prices are FastMetal's yen rates before tax. Arena ranks are as of the latest leaderboard scrape.
Which should you pick?
- On price, Gemini 3.8 Flash: ¥644.15 per 1M output tokens, 86% less than Claude Opus 4.8.
- On the Overall arena board, Gemini 3.8 Flash ranks higher (#8; Claude Opus 4.8 is #33).
- On the Coding arena board, Gemini 3.8 Flash ranks higher (#7; Claude Opus 4.8 is #17).
- For long documents, Gemini 3.8 Flash: a 1,048,576-token context window against 1,000,000 for Claude Opus 4.8.
- 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 4.8
# 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
Gemini 3.8 Flash
There are **3** 'r's in the word "strawberry".
Here is the step-by-step breakdown:
1. **Break the word into its individual letters:**
* **s** (1st letter)
* **t** (2nd letter)
* **r** (3rd letter) — **1st 'r'**
* **a** (4th letter)
* **w** (5th letter)
* **b** (6th letter)
* **e** (7th letter)
* **r** (8th letter) — **2nd 'r'**
* **r** (9th letter) — **3rd 'r'**
* **y** (10th letter)
2. **Count the occurrences:**
* One 'r' is in the first syllable: "st**r**aw"
* Two 'r's are in the second syllable: "be**rr**y"
Total: **3**
3.9s562 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 4.8
# 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
Gemini 3.8 Flash
### The Cause
This error occurs because the `users` prop is `undefined` when the component renders, and JavaScript cannot call `.map()` on `undefined`.
This typically happens in two common scenarios:
1. **Asynchronous data fetching:** The parent component fetches `users` from an API. On the initial render, the data hasn't arrived yet, so `users` defaults to `undefined`.
2. **Missing prop:** The parent component forgot to pass `users` (e.g., `<UserList />` instead of `<UserList users={data} />`).
---
### How to Fix It
Here are the most common ways to resolve this:
#### Option 1: Provide a default parameter (Recommended)
Set a default value of an empty array (`[]`) for `users`. If `users…
7.1s1003 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 4.8
# 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
Gemini 3.8 Flash
Here is a code review of your function, broken down by issue category, followed by refactored versions.
---
### Key Issues & Areas for Improvement
#### 1. Correctness & Error Handling
* **Bare `except:` clause:** Catching all exceptions with a bare `except:` is dangerous. It suppresses system exits (`KeyboardInterrupt`, `SystemExit`) and masks programming bugs (like `KeyError` or `NameError`). You should catch specific exceptions, primarily `requests.RequestException`.
* **Silent failure returning `[]`:** If all retries fail, returning an empty list makes it impossible for the caller to distinguish between *"the API returned 0 active items"* and *"the network is completely down"*. It is u…
15.1s2139 output tokens
Frequently asked questions
- Which is cheaper, Claude Opus 4.8 or Gemini 3.8 Flash?
- Per 1M output tokens, Claude Opus 4.8 is ¥4,467.5 and Gemini 3.8 Flash is ¥644.15 on FastMetal (yen, before tax), so Gemini 3.8 Flash is cheaper.
- How do the context windows of Claude Opus 4.8 and Gemini 3.8 Flash compare?
- Claude Opus 4.8 takes 1,000,000 tokens; Gemini 3.8 Flash takes 1,048,576.
- Which ranks higher, Claude Opus 4.8 or Gemini 3.8 Flash?
- Gemini 3.8 Flash ranks higher on the public arena (Claude Opus 4.8 #31, Gemini 3.8 Flash #8). Ranks move as the leaderboard updates.
- Can I use Claude Opus 4.8 and Gemini 3.8 Flash with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "anthropic-claude-opus-4-8" or "gemini-3.8-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 4.8 and Gemini 3.8 Flash from the browser chat and the API. No monthly fee.