AI Model APIs
AI Model APIsProviders
AI Model APIs

The complete platform for comparing AI models. Find pricing, capabilities, and the perfect model for your use case.

contact@aimodelapis.com

Resources

  • AI Models APIs
  • Providers

About

  • About
  • Contact
  • Privacy Policy
  • Terms of Service

© 2026 AI Model APIs. All rights reserved.

Back to Models
ZenMux

Step 3.5 Flash (Free) API

ZenMux
About

Build advanced reasoning agents with Step 3.5 Flash (Free), a specialized AI model optimized for complex logic and chain-of-thought tasks. This model delivers available completely free of charge, native tool calling support. Access Step 3.5 Flash (Free) via the ZenMux API with up to 64K output tokens.

Capabilities

Input Modalities

text

Output Modalities

text
Reasoning
Yes
Structured Output
No
Tool Use
Yes
WeightsClosed
Temperature
Adjustable
Attachment
Not Supported
Limits
Context Window
256K

Tokens

Input Limit
256K

Tokens

Max Output
64K

Tokens

Pricing

Standard (per 1M tokens)

Input
Free
Output
Free
Frequently Asked Questions

Step 3.5 Flash (Free) by ZenMux costs Free per 1M input tokens and Free per 1M output tokens.

Model Details
ID
stepfun/step-3.5-flash-free
Provider
ZenMux
Family
Release Date
Feb 2, 2026
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