StepFun: Step 3.5 Flash

Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token....

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$0.10/1M input tokens†

Context Window

262,144 tokens

Max Output

65,536 tokens

Input Modalities

text

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Real-World Usage

Real-world usage statistics from the Kilo Code community

Weekly Token Usage

Apr 13Apr 14Apr 15Apr 16Apr 17Apr 18Apr 19020.0M40.0M60.0M80.0M

Mode Rankings (Last Week)

Where this model ranks for each built-in mode

Architect

Plan and design before implementation

No data

Code

Write, modify, and refactor code

No data

Ask

Get answers and explanations

No data

Debug

Diagnose and fix software issues

#17

Orchestrator

Coordinate tasks across multiple modes

No data

Pricing

Cost per 1 million tokens

Input Tokens

$0.10

per 1M tokens

Output Tokens

$0.30

per 1M tokens

Example Cost

Analyzing a 10,000 line codebase (≈40k input tokens, 10k output tokens) costs approximately $0.0070

Coding Capabilities

Features and parameters relevant to coding tasks

Coding Features

  • Function Calling
  • Can call external functions/APIs
  • Tool Choice
  • Control over function selection
  • Structured Outputs
  • JSON schema validation
  • Reasoning Tokens
  • Extended thinking for complex problems

Technical Details

Architecture and implementation specifications

Model ID

stepfun/step-3.5-flash

Created

January 29, 2026

Tokenizer

Other

Input Modalities

text

Context Window

262,144 tokens

Max Completion Tokens

65,536 tokens

Input Price

$0.10 per 1M tokens

Output Price

$0.30 per 1M tokens

Content Moderation

Disabled

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