StepFun

Access 3 StepFun models through Mastra's model router. Authentication is handled automatically using the STEPFUN_API_KEY environment variable.

Learn more in the StepFun documentation.

STEPFUN_API_KEY=your-api-key

import { Agent } from "@mastra/core/agent";

const agent = new Agent({
  id: "my-agent",
  name: "My Agent",
  instructions: "You are a helpful assistant",
  model: "stepfun/step-1-32k"
});

// Generate a response
const response = await agent.generate("Hello!");

// Stream a response
const stream = await agent.stream("Tell me a story");
for await (const chunk of stream) {
  console.log(chunk);
}

:::info

Mastra uses the OpenAI-compatible /chat/completions endpoint. Some provider-specific features may not be available. Check the StepFun documentation for details.

:::

Models

<ProviderModelsTable models={[ { "model": "stepfun/step-1-32k", "imageInput": false, "audioInput": false, "videoInput": false, "toolUsage": true, "reasoning": true, "contextWindow": 32768, "maxOutput": 32768, "inputCost": 2.05, "outputCost": 9.59 }, { "model": "stepfun/step-2-16k", "imageInput": false, "audioInput": false, "videoInput": false, "toolUsage": true, "reasoning": true, "contextWindow": 16384, "maxOutput": 8192, "inputCost": 5.21, "outputCost": 16.44 }, { "model": "stepfun/step-3.5-flash", "imageInput": false, "audioInput": false, "videoInput": false, "toolUsage": true, "reasoning": true, "contextWindow": 256000, "maxOutput": 256000, "inputCost": 0.096, "outputCost": 0.288 } ]} />

Advanced configuration

Custom headers

const agent = new Agent({
  id: "custom-agent",
  name: "custom-agent",
  model: {
    url: "https://api.stepfun.com/v1",
    id: "stepfun/step-1-32k",
    apiKey: process.env.STEPFUN_API_KEY,
    headers: {
      "X-Custom-Header": "value"
    }
  }
});

Dynamic model selection

const agent = new Agent({
  id: "dynamic-agent",
  name: "Dynamic Agent",
  model: ({ requestContext }) => {
    const useAdvanced = requestContext.task === "complex";
    return useAdvanced
      ? "stepfun/step-3.5-flash"
      : "stepfun/step-1-32k";
  }
});