FastMetal

Model comparison

GPT-6.1 Sol vs Kimi K3.1 Pro

Pricing, context window and real answers (October 2026)

GPT-6.1 Sol (OpenAI) and Kimi K3.1 Pro (Moonshot), 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

openai logoGPT-6.1 Solmoonshotai logoKimi K3.1 Pro
ProviderOpenAIMoonshot
Input (per 1M tokens)$2.11$2.11
Output (per 1M tokens)$10.55$10.55
Typical cost (1,000 in + 500 out tokens × 1,000 calls)$7.39$7.39
Context window1,050,000 tokens1,048,576 tokens
Release date9/29/202610/23/2026
Input modalitiesfile, image, texttext, image, video
Throughput (p50)93 tokens/s (n=24)—
Arena · overall#27 · ELO 1,480Unranked
Arena · JapaneseUnrankedUnranked
Arena · coding#14 · ELO 1,537Unranked

Prices are FastMetal's rates, before tax.

Rankings: LMArena leaderboard dataset (lmarena-ai/leaderboard-dataset), CC BY 4.0, snapshot 2026-10-22; category names mapped and ratings rounded by FastMetal.

Which should you pick?

  • Output pricing is identical ($10.55 per 1M tokens).
  • For long documents, GPT-6.1 Sol: a 1,050,000-token context window against 1,048,576 for Kimi K3.1 Pro.
  • 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-6.1 Sol

“strawberry” is spelled **s-t-r-a-w-b-e-r-r-y**. The letter **r** appears at positions **3, 8, and 9**. So, there are **3 r’s** in “strawberry.”
2.8s88 output tokens

Kimi K3.1 Pro

There are **3** ‘r’s in **“strawberry.”** 1. Write out each letter: **s – t – r – a – w – b – e – r – r – y** 2. Locate the ‘r’s: positions **3, 8, and 9**. 3. Count them: **1 + 1 + 1 = 3**.
11.3s

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-6.1 Sol

The error means **`users` is `undefined` when `UserList` renders**. Calling `.map()` on `undefined` throws this error. This commonly happens when the parent doesn’t pass the `users` prop, or when data hasn’t finished loading yet. ### Fix: provide a default empty array ```jsx function UserList({ users = [] }) { return ( <ul> {users.map(user => ( <li key={user.id}>{user.name}</li> ))} </ul> ); } ``` This renders an empty list if `users` is omitted or `undefined`. It does **not** handle `null`. ### Check the parent component too Make sure it passes an array: ```jsx <UserList users={users} /> ``` If you’re fetching users asynchronously, initialize the stat…
5.8s306 output tokens

Kimi K3.1 Pro

## What's causing the error The error means `users` is `undefined` when the component renders, and you can't call `.map()` on `undefined`. The component itself is fine — the problem is that whatever renders `<UserList />` either isn't passing the prop, or is passing a value that isn't an array yet. The most common cause is **async data fetching**: the parent renders `UserList` before the data has loaded. ```jsx function App() { const [users, setUsers] = useState(); // ❌ undefined on first render useEffect(() => { fetch('/api/users') .then(res => res.json()) .then(setUsers); }, []); return <UserList users={users} />; // users is undefined here initially } ``` On…
36.3s

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-6.1 Sol

The function is short, but its main weakness is that it hides failures: a network error, invalid JSON, and a genuinely empty result all return `[]`. ### Suggested improvements - **Move imports to module scope.** This is conventional and makes dependencies visible. Repeated imports are cached, so the performance benefit is minor. - **Avoid bare `except:`.** It catches everything, including `KeyboardInterrupt` and `SystemExit`, and can hide programming errors. - **Handle HTTP errors explicitly.** `raise_for_status()` provides useful exceptions. Retry transient failures such as timeouts, connection errors, HTTP 429, and HTTP 5xx—not permanent errors such as HTTP 404. - **Don’t sleep after the…
19.0s1094 output tokens

Kimi K3.1 Pro

The timeout and bounded retry loop are good starting points. The biggest issue is that failures—and even programming errors—are silently converted into retries and then `[]`. ### Suggested improvements - **Avoid bare `except:`**. It catches `KeyboardInterrupt`, `KeyError`, JSON/schema errors, and other bugs. Retry only expected transient network failures; let malformed responses fail visibly. - **Use a deliberate retry policy**. Retrying `401`, `403`, or `404` usually wastes time. Retry only transient statuses, use exponential backoff, and avoid sleeping after the final attempt. - **Do not use `[]` for both failure and no results**. Prefer raising the final exception so callers can disting…
560.2s

Compare on more prompts →

Frequently asked questions

Which is cheaper, GPT-6.1 Sol or Kimi K3.1 Pro?
Both are $10.55 per 1M output tokens on FastMetal (US dollars, before tax).
How do the context windows of GPT-6.1 Sol and Kimi K3.1 Pro compare?
GPT-6.1 Sol takes 1,050,000 tokens; Kimi K3.1 Pro takes 1,048,576.
Can I use GPT-6.1 Sol and Kimi K3.1 Pro with the same API key?
Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-6.1-sol" or "kimi-k3.1-pro" 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-6.1 Sol and Kimi K3.1 Pro from the browser chat and the API. No monthly fee.

Create a free accountTry GPT-6.1 Sol in chatTry Kimi K3.1 Pro in chat

More comparisons with GPT-6.1 Sol

More comparisons with Kimi K3.1 Pro