StepFun: Gelab Zero 4b Preview
Gelab Zero 4b Preview is a language model from StepFun released on Dec 23, 2025. It reads text and images and writes text, with a 8K token context window and up to 4K tokens per reply.
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It supports tool calling.
- Modalities
- In / out price
- n/a
- Context
- 8K
- Max output
- 4K
- Released
- Dec 23, 2025
- Knowledge cutoff
- n/a
- Tool calling
- Structured output
- Reasoning
- Prompt caching
- Open weights
- Free to use
Supported request parameters
What you can set when you call Gelab Zero 4b Preview through an OpenAI compatible API.
- Tools
tools - Temperature
temperature
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Gelab Zero 4b Preview questions
What is the context window of Gelab Zero 4b Preview?
8,192 tokens of input, and it can write up to 4,096 tokens in one reply. As a rough guide, a million tokens is around 750,000 English words.
Does Gelab Zero 4b Preview support tool calling?
Yes. It accepts tool definitions, which is what an agent needs to call your APIs.
Is Gelab Zero 4b Preview open source?
No. StepFun serves it through an API only, so you cannot download the weights or host it yourself.
When was Gelab Zero 4b Preview released?
Dec 23, 2025.
Catalog data from models.dev (MIT licensed), refreshed daily, last on Oct 15, 2026. The summary is written from these facts.