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ZenMux

Step-3 API

ZenMux
About

Build advanced reasoning agents with Step-3, a specialized AI model optimized for complex logic and chain-of-thought tasks. This model delivers cost-effective pricing at $0.21/1M input and $0.57/1M output tokens, native tool calling support. Access Step-3 via the ZenMux API with up to 64K output tokens.

Capabilities

Input Modalities

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Output Modalities

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Reasoning
Yes
Structured Output
No
Tool Use
Yes
WeightsClosed
Temperature
Adjustable
Attachment
Supported
Limits
Context Window
66K

Tokens

Input Limit
66K

Tokens

Max Output
64K

Tokens

Pricing

Standard (per 1M tokens)

Input
$0.21
Output
$0.57
Frequently Asked Questions

Step-3 by ZenMux costs $0.21 per 1M input tokens and $0.57 per 1M output tokens.

Model Details
ID
stepfun/step-3
Provider
ZenMux
Family
Release Date
Jul 31, 2025
Knowledge Cutoff
Jan 1, 2025
API Integration
NPM Package
@ai-sdk/anthropic
Environment Variables
ZENMUX_API_KEY
API Base URL
https://zenmux.ai/api/anthropic/v1
Documentation