How much does the gpt-oss-120b API cost?

On FastMetal, gpt-oss-120b is billed per token in yen: ¥16 per 1M input tokens and ¥79 per 1M output tokens, before tax. Usage is drawn from a prepaid balance; there is no subscription or monthly fee.

Can I call gpt-oss-120b with the OpenAI SDK?

Yes. Point base_url at https://api.fastmetal.ai/v1 and pass "gpt-oss-120b" as the model; existing OpenAI-style code works unchanged, including streaming, tool calls and structured output.

What is the context window of gpt-oss-120b?

131,072 tokens, shared between the prompt and the response.

How does gpt-oss-120b rank?

#132 on the public arena's Japanese board (ELO 1,328). Ranks move as the leaderboard is updated.

What do I need to try gpt-oss-120b?

Create an account and add credit; the model is then available both in the browser chat and over the API. There is no contract or minimum spend.

Back to Models

openai/gpt-oss-120b

gpt-oss-120b

gpt-oss-120b is an open-weight, 117B-parameter Mixture-of-Experts (MoE) language model from OpenAI designed for high-reasoning, agentic, and general-purpose production use cases. It activates 5.1B parameters per forward pass and is optimized to run on a single H100 GPU with native MXFP4 quantization. The model supports configurable reasoning depth, full chain-of-thought access, and native tool use, including function calling, browsing, and structured output generation.

8/5/2025

131,072 tokens

#132 Text (Japanese)

Input: ¥16/M

Output: ¥79/M

Try in Chat Get API Key

Specifications

Modalities

Input

text

Output

text

Supported Parameters

frequency_penalty

include_reasoning

logit_bias

logprobs

max_tokens

min_p

presence_penalty

reasoning

reasoning_effort

repetition_penalty

response_format

seed

stop

structured_outputs

temperature

tool_choice

tools

top_k

top_logprobs

top_p

Code Examples

curl https://api.fastmetal.ai/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gpt-oss-120b",
    "messages": [{"role": "user", "content": "Hello!"}]
  }'

How gpt-oss-120b actually answers

Real responses to our standard prompts, recorded on FastMetal.

Count the number of 'r's in 'strawberry'

Count the number of 'r's in 'strawberry'. Explain your reasoning step by step.

**Step‑by‑step count of the letter “r” in the word “strawberry”** 1. Write out the word with each letter in order, labeling its position: | Position | Letter | |----------|--------| | 1 | s | | 2 | t | | 3 | **r** | | 4 | a | | 5 | w | | 6 | b | | 7 | e | | 8 | **r** | | 9 | **r** | |10 | y | 2. Scan the list and mark every occurrence of the letter **r**. - Position 3 → r (first occurrence) - Position 8 → r (second occurrence) - Position 9 → r (third occurrence) 3. Count the marked entries: there are **3** marked positions. **Result:** The word “strawberry” contains **3** occurrences of the letter **r**…

1.7s response332 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…

### Why the `map` can’t be called `Array.prototype.map` is a method that exists only on **arrays** (or array‑like objects). When you see ``` TypeError: Cannot read properties of undefined (reading 'map') at UserList (...) ``` it means that the variable you think is an array – `users` in this case – is actually **`undefined`** (or `null`). React is trying to evaluate this line: ```jsx {users.map(user => <li key={user.id}>{user.name}</li>)} ``` and it crashes because you can’t read `.map` from `undefined`. --- ## Common reasons `users` ends up undefined | Reason | Typical scenario | How it shows up | |--------|------------------|-----------------| | **Prop not passed** | `<Use…

7.3s response1610 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):…

Below is a **step‑by‑step review** of the original `get_data` implementation followed by a **refactored version** that addresses readability, performance, and modern Python best‑practice concerns. --- ## 1. What the original function does ```python def get_data(url, retries=3): import requests import time for i in range(retries): try: r = requests.get(url, timeout=10) if r.status_code == 200: data = r.json() result = [] for item in data: if item["active"] == True: result.append({"name": item["name"], "id": item["id"]}) return result…

14.4s response3132 output tokens

Compare these answers side by side with other models →

Frequently asked questions

How much does the gpt-oss-120b API cost?: On FastMetal, gpt-oss-120b is billed per token in yen: ¥16 per 1M input tokens and ¥79 per 1M output tokens, before tax. Usage is drawn from a prepaid balance; there is no subscription or monthly fee.
Can I call gpt-oss-120b with the OpenAI SDK?: Yes. Point base_url at https://api.fastmetal.ai/v1 and pass "gpt-oss-120b" as the model; existing OpenAI-style code works unchanged, including streaming, tool calls and structured output.
What is the context window of gpt-oss-120b?: 131,072 tokens, shared between the prompt and the response.
How does gpt-oss-120b rank?: #132 on the public arena's Japanese board (ELO 1,328). Ranks move as the leaderboard is updated.
What do I need to try gpt-oss-120b?: Create an account and add credit; the model is then available both in the browser chat and over the API. There is no contract or minimum spend.