OpenCode Zen

Access 14 OpenCode Zen models through Mastra's model router. Authentication is handled automatically using the OPENCODE_API_KEY environment variable.

Learn more in the OpenCode Zen documentation.

OPENCODE_API_KEY=your-api-key

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

const agent = new Agent({
  name: "my-agent",
  instructions: "You are a helpful assistant",
  model: "opencode/an-gbt"
});

// 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 OpenCode Zen documentation for details.

Models

Model	Image	Audio	Video	Tools	Streaming	Context Window
opencode/an-gbt	✗	✗	✗	✓	✗	200,000
opencode/big-pickle	✗	✗	✗	✓	✗	200,000
opencode/claude-3-5-haiku	✓	✗	✗	✓	✗	200,000
opencode/claude-haiku-4-5	✓	✗	✗	✓	✗	200,000
opencode/claude-opus-4-1	✓	✗	✗	✓	✗	200,000
opencode/claude-sonnet-4	✓	✗	✗	✓	✗	1,000,000
opencode/claude-sonnet-4-5	✓	✗	✗	✓	✗	1,000,000
opencode/glm-4.6	✗	✗	✗	✓	✗	204,800
opencode/gpt-5	✓	✗	✗	✓	✗	400,000
opencode/gpt-5-codex	✓	✗	✗	✓	✗	400,000
opencode/grok-code	✗	✗	✗	✓	✗	256,000
opencode/kimi-k2	✗	✗	✗	✓	✗	262,144
opencode/minimax-m2	✗	✗	✗	✓	✗	200,000
opencode/qwen3-coder	✗	✗	✗	✓	✗	262,144

Advanced Configuration

Custom Headers

const agent = new Agent({
  name: "custom-agent",
  model: {
    url: "https://opencode.ai/zen/v1",
    id: "opencode/an-gbt",
    apiKey: process.env.OPENCODE_API_KEY,
    headers: {
      "X-Custom-Header": "value"
    }
  }
});

Dynamic Model Selection

const agent = new Agent({
  name: "dynamic-agent",
  model: ({ runtimeContext }) => {
    const useAdvanced = runtimeContext.task === "complex";
    return useAdvanced
      ? "opencode/qwen3-coder"
      : "opencode/an-gbt";
  }
});