---
title: StepFun: Step 3.5 Flash API | Text Generation | ModelsLab
description: Open-source MoE LLM with 196B total/11B active params excels in reasoning, coding & agentic tasks; 256K context, 350 t/s speed, $0.1/$0.3 per 1M.
url: https://modelslab.com/models/stepfun/stepfun-step-3.5-flash.md
canonical: https://modelslab.com/models/stepfun/stepfun-step-3.5-flash.md
type: product
component: Playground/LLM/Index
generated_at: 2026-04-15T00:15:55.441067Z
---

StepFun: Step 3.5 Flash
---

 [LLMs.txt](https://modelslab.com/models/open_router/stepfun-step-3.5-flash/llms.txt) [.md](https://modelslab.com/models/stepfun/stepfun-step-3.5-flash.md)

stepfun-step-3.5-flash stepfun Closed Source Model $0.200000 / call

StepFun: Step 3.5 Flash
---

Choose a prompt below to get started or type your own message

 Explain quantum computing in simple terms

 Write a Python function to sort a list

 Create a marketing email for a SaaS product

 Compare REST vs GraphQL APIs

Send

### StepFun: Step 3.5 Flash

stepfun stepfun-step-3.5-flash

Copy model ID

PricingInput $0.10 / 1M tokens

Output $0.30 / 1M tokens

API EndpointsOpenAI Compatible

`https://modelslab.com/api/v7/llm/chat/completions`Endpoint

Anthropic Compatible

`https://modelslab.com/api/v7/llm/v1/messages`Messages

`https://modelslab.com/api/v7/llm/v1/messages/count_tokens`Count Tokens

`https://modelslab.com/api/v7/llm/v1/models`Models

Use with Claude Code

cURL Example

ParametersSystem MessageYou are a helpful AI assistant specialized in providing accurate and detailed responses.

Temperature0.7

Max Tokens1000

Top P0.9

Frequency Penalty0

Presence Penalty0

Model Info

Support

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About 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....

### Technical Specifications

Model IDstepfun-step-3.5-flashCategoryLLM ModelsTaskText GenerationPrice$0.200000 per million tokensAddedFebruary 20, 2026

### Key Features

- Chat completion and multi-turn conversation API
- Streaming response with token-by-token output
- Function calling and tool use support
- System prompts and role-based messaging
- JSON mode and structured output

### Quick Start

Integrate StepFun: Step 3.5 Flash into your application with a single API call. Get your API key from the [pricing page](https://modelslab.com/pricing) to get started.

PythonJavaScriptcURLPHP

```
<code>import requests
import json

url = "https://modelslab.com/api/v7/llm/chat/completions"

headers = {
    "Content-Type": "application/json"
}

data = {
        "model_id": "stepfun-step-3.5-flash",
        "messages": [
            {
                "role": "user",
                "content": "Hello!"
            }
        ],
        "max_tokens": 1000,
        "key": "YOUR_API_KEY"
    }

try:
    response = requests.post(url, headers=headers, json=data)
    response.raise_for_status()  # Raises an HTTPError for bad responses (4XX or 5XX)
    result = response.json()
    print("API Response:")
    print(json.dumps(result, indent=2))
except requests.exceptions.HTTPError as http_err:
    print(f"HTTP error occurred: {http_err} - {response.text}")
except Exception as err:
    print(f"Other error occurred: {err}")</code>
```

View the [full API documentation](https://modelslab.com/models/stepfun/stepfun-step-3.5-flash/api) for SDKs, code examples in Python, JavaScript, and more.

### Pricing

StepFun: Step 3.5 Flash API costs $0.200000 per million tokens. Pay only for what you use with no minimum commitments. [View pricing plans](https://modelslab.com/pricing)

### Use Cases

- AI chatbots and virtual assistants
- Code generation and developer tools
- Content writing and copywriting automation
- Data analysis, summarization, and extraction

[Learn more about StepFun: Step 3.5 Flash](https://modelslab.com/stepfun-step-35-flash) [Browse LLM Models](https://modelslab.com/models?feature=llmaster) [More from Stepfun](https://modelslab.com/models/open_router) [View Pricing](https://modelslab.com/pricing)

StepFun: Step 3.5 Flash FAQ
---

### What is 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....

### How do I use the StepFun: Step 3.5 Flash API?

You can integrate StepFun: Step 3.5 Flash into your application with a single API call. Sign up on ModelsLab to get your API key, then use the model ID "stepfun-step-3.5-flash" in your API requests. We provide SDKs for Python, JavaScript, and cURL examples in the API documentation.

### How much does StepFun: Step 3.5 Flash cost?

StepFun: Step 3.5 Flash costs $0.200000 per million tokens. ModelsLab uses pay-per-use pricing with no minimum commitments. A free tier is available to get started.

### What is the StepFun: Step 3.5 Flash model ID?

The model ID for StepFun: Step 3.5 Flash is "stepfun-step-3.5-flash". Use this ID in your API requests to specify this model.

### Does StepFun: Step 3.5 Flash have a free tier?

Yes, ModelsLab offers a free tier that lets you try StepFun: Step 3.5 Flash and other AI models. Sign up to get free API credits and start building immediately.

---

*This markdown version is optimized for AI agents and LLMs.*

**Links:**
- [Website](https://modelslab.com)
- [API Documentation](https://docs.modelslab.com)
- [Blog](https://modelslab.com/blog)

---
*Generated by ModelsLab - 2026-04-15*