Opper

Access 40 Opper models through Mastra's model router. Authentication is handled automatically using the OPPER_API_KEY environment variable.

Learn more in the Opper documentation.

.env

OPPER_API_KEY=your-api-key

src/mastra/agents/my-agent.ts

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

const agent = new Agent({
  id: "my-agent",
  name: "My Agent",
  instructions: "You are a helpful assistant",
  model: "opper/anthropic/claude-fable-5"
});

// 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);
}

note

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

Models

40 available models

Model	Context	Tools	Reasoning	Image	Audio	Video	Input $/1M	Output $/1M
opper/anthropic/claude-fable-5	1.0M						$10	$50
opper/anthropic/claude-haiku-4-5	200K						$1	$5
opper/anthropic/claude-opus-4-5	200K						$5	$25
opper/anthropic/claude-opus-4-6	1.0M						$5	$25
opper/anthropic/claude-opus-4-7	1.0M						$5	$25
opper/anthropic/claude-opus-4-8	1.0M						$5	$25
opper/anthropic/claude-opus-5	1.0M						$5	$25
opper/anthropic/claude-sonnet-4-5	200K						$3	$15
opper/anthropic/claude-sonnet-4-6	1.0M						$3	$15
opper/anthropic/claude-sonnet-5	1.0M						$2	$10
opper/gemini/gemini-3-flash-preview	1.0M						$0.50	$3
opper/gemini/gemini-3.1-pro-preview	1.0M						$2	$12
opper/gemini/gemini-3.5-flash	1.0M						$2	$9
opper/gemini/gemini-3.5-flash-lite	1.0M						$0.30	$3
opper/meta/muse-spark-1.2	1.0M						$1	$4
opper/minimax/m3	1.0M						$0.60	$2
opper/mistral/devstral-2512	262K						$0.40	$2
opper/mistral/mistral-large-2512	262K						$0.50	$2
opper/mistral/mistral-small-2603	256K						$0.15	$0.60
opper/moonshot/kimi-k3	1.0M						$3	$15
opper/openai/gpt-5.3-chat-latest	128K						$2	$14
opper/openai/gpt-5.3-codex	400K						$2	$14
opper/openai/gpt-5.4	1.1M						$3	$15
opper/openai/gpt-5.4-mini	400K						$0.75	$5
opper/openai/gpt-5.4-nano	400K						$0.20	$1
opper/openai/gpt-5.4-pro	1.1M						$30	$180
opper/openai/gpt-5.5	1.1M						$5	$30
opper/openai/gpt-5.5-pro	1.1M						$30	$180
opper/openai/gpt-5.6-luna	1.1M						$0.20	$1
opper/openai/gpt-5.6-sol	1.1M						$5	$30
opper/openai/gpt-5.6-terra	1.1M						$2	$12
opper/perplexity/sonar	128K						$1	$1
opper/perplexity/sonar-pro	200K						$3	$15
opper/perplexity/sonar-reasoning-pro	128K						$2	$8
opper/vertexai/gemini-3.7-flash	1.0M						$0.75	$4
opper/vertexai/gemini-3.7-flash-eu	1.0M						$0.75	$4
opper/xai/grok-4.3	1.0M						$1	$3
opper/xai/grok-4.5	500K						$2	$6
opper/xai/grok-4.6	500K						$2	$6
opper/xai/grok-build-0.1	256K						$1	$2

Model availability, capabilities, context windows, and pricing are sourced from models.dev and may change.

Advanced configuration

Custom headers

src/mastra/agents/my-agent.ts

const agent = new Agent({
  id: "custom-agent",
  name: "custom-agent",
  model: {
    url: "https://api.opper.ai/v3/compat",
    id: "opper/anthropic/claude-fable-5",
    apiKey: process.env.OPPER_API_KEY,
    headers: {
      "X-Custom-Header": "value"
    }
  }
});

Dynamic model selection

src/mastra/agents/my-agent.ts

const agent = new Agent({
  id: "dynamic-agent",
  name: "Dynamic Agent",
  model: ({ requestContext }) => {
    const useAdvanced = requestContext.task === "complex";
    return useAdvanced
      ? "opper/xai/grok-build-0.1"
      : "opper/anthropic/claude-fable-5";
  }
});