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Model comparison

Hy4 vs Kimi K3.1 Pro

Pricing, context window and real answers (November 2026)

Hy4 (Tencent) 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

tencent logoHy4moonshotai logoKimi K3.1 Pro
ProviderTencentMoonshot
Input (per 1M tokens)$0.8799$2.11
Output (per 1M tokens)$2.64$10.55
Typical cost (1,000 in + 500 out tokens × 1,000 calls)$2.20$7.39
Context window1,000,000 tokens1,048,576 tokens
Release date11/4/202610/23/2026
Input modalitiestexttext, image, video
Throughput (p50)——
Arena · overallUnrankedUnranked
Arena · JapaneseUnrankedUnranked
Arena · codingUnrankedUnranked

Prices are FastMetal's rates, before tax.

Rankings: LMArena leaderboard dataset (lmarena-ai/leaderboard-dataset), CC BY 4.0, snapshot 2026-10-28; category names mapped and ratings rounded by FastMetal.

Which should you pick?

  • On price, Hy4: $2.64 per 1M output tokens, 75% less than Kimi K3.1 Pro.
  • For long documents, Kimi K3.1 Pro: a 1,048,576-token context window against 1,000,000 for Hy4.
  • 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.

Hy4

The word **“strawberry”** is spelled: **s t r a w b e r r y** Step by step: 1. Check each letter: s, t, **r**, a, w, b, e, **r**, **r**, y 2. Mark the **r**’s: one after **t**, and two near the end before **y**. 3. Count them: 1 + 1 + 1 = **3** So, there are **3** ‘r’s in **“strawberry”**.
4.2s343 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…

Hy4

The error is caused by this line: ```js {users.map(user => <li key={user.id}>{user.name}</li>)} ``` At render time, `users` is `undefined`. Since `.map()` only exists on arrays, JavaScript tries to read `map` from `undefined` and throws: ```txt Cannot read properties of undefined (reading 'map') ``` Even though this is in a Node.js app, this specific error is happening during React rendering, likely server-side rendering or a Node-based build/render process. Common causes: 1. The parent component is not passing `users`. 2. The prop name is misspelled. 3. `users` comes from async data and is `undefined` on the first render. 4. Your API returns something like `{ users: [...] }`, but you…
20.3s1951 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):…

Hy4

Here are the main improvement areas, followed by a possible rewrite. ## Key issues ### Readability / style - Move imports to the top of the module. - Use descriptive names: `response` instead of `r`, `attempt` instead of `i`. - `if item["active"] == True:` should be `if item.get("active") is True:` or simply `if item.get("active"):`, depending on intent. - The filtering loop can be a list comprehension. - Add type hints and a docstring. ### Performance - Repeated imports are cached by Python, so not a major cost, but top-level imports are cleaner. - Avoid sleeping after the final failed attempt. - Use `requests.Session` for connection pooling if this function may be called repeatedly or i…
110.2s10761 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 →

Our write-up on this matchup

Hy4 vs Kimi K3.1 Pro: 3x faster, and it explains itself

Frequently asked questions

Which is cheaper, Hy4 or Kimi K3.1 Pro?
Per 1M output tokens, Hy4 is $2.64 and Kimi K3.1 Pro is $10.55 on FastMetal (US dollars, before tax), so Hy4 is cheaper.
How do the context windows of Hy4 and Kimi K3.1 Pro compare?
Hy4 takes 1,000,000 tokens; Kimi K3.1 Pro takes 1,048,576.
Can I use Hy4 and Kimi K3.1 Pro with the same API key?
Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "hy4" 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 Hy4 and Kimi K3.1 Pro from the browser chat and the API. No monthly fee.

Create a free accountTry Hy4 in chatTry Kimi K3.1 Pro in chat

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