Step 3.5 Flash API
About
Build advanced reasoning agents with Step 3.5 Flash, a specialized AI model optimized for complex logic and chain-of-thought tasks. This model delivers cost-effective pricing at $0.10/1M input and $0.30/1M output tokens, native tool calling support, open weights architecture. Access Step 3.5 Flash via the OpenRouter API with up to 66K output tokens.
Capabilities
Input Modalities
text
Output Modalities
text
Reasoning
Yes
Structured Output
No
Tool Use
Yes
WeightsOpen
Limits
Context Window
262K
Tokens
Input Limit
262K
Tokens
Max Output
66K
Tokens
Pricing
Standard (per 1M tokens)
Input
$0.10
Output
$0.30
Frequently Asked Questions
Step 3.5 Flash by OpenRouter costs $0.10 per 1M input tokens and $0.30 per 1M output tokens.
Model Details
ID
stepfun/step-3.5-flash
Provider
OpenRouterFamily
step
Release Date
Jan 29, 2026
Knowledge Cutoff
Jan 1, 2025
API Integration
NPM Package
@openrouter/ai-sdk-provider
Environment Variables
OPENROUTER_API_KEY
API Base URL
https://openrouter.ai/api/v1