Anthropic

Access 14 Anthropic models through Mastra's model router. Authentication is handled automatically using the ANTHROPIC_API_KEY environment variable.

Learn more in the Anthropic documentation.

.env

ANTHROPIC_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: "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);
}

Models

14 available models

Model	Context	Tools	Reasoning	Image	Audio	Video	Input $/1M	Output $/1M
anthropic/claude-fable-5	1.0M						$10	$50
anthropic/claude-fable-5-1	1.0M						$10	$50
anthropic/claude-haiku-4-5	200K						$1	$5
anthropic/claude-haiku-4-5-20251001	200K						$1	$5
anthropic/claude-opus-4-5	200K						$5	$25
anthropic/claude-opus-4-5-20251101	200K						$5	$25
anthropic/claude-opus-4-6	1.0M						$5	$25
anthropic/claude-opus-4-7	1.0M						$5	$25
anthropic/claude-opus-4-8	1.0M						$5	$25
anthropic/claude-opus-5	1.0M						$5	$25
anthropic/claude-sonnet-4-5	1.0M						$3	$15
anthropic/claude-sonnet-4-5-20250929	1.0M						$3	$15
anthropic/claude-sonnet-4-6	1.0M						$3	$15
anthropic/claude-sonnet-5	1.0M						$2	$10

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: {
    id: "anthropic/claude-fable-5",
    apiKey: process.env.ANTHROPIC_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
      ? "anthropic/claude-sonnet-5"
      : "anthropic/claude-fable-5";
  }
});

Provider Options

Anthropic supports the following provider-specific options via the providerOptions parameter:

const response = await agent.generate("Hello!", {
  providerOptions: {
    anthropic: {
      // See available options in the table below
    }
  }
});

Available Options

sendReasoning?:

boolean | undefined

structuredOutputMode?:

"outputFormat" | "jsonTool" | "auto" | undefined

thinking?:

{ type: "adaptive"; display?: "omitted" | "summarized" | undefined; } | { type: "enabled"; budgetTokens?: number | undefined; } | { type: "disabled"; } | undefined

disableParallelToolUse?:

boolean | undefined

cacheControl?:

{ type: "ephemeral"; ttl?: "5m" | "1h" | undefined; } | undefined

metadata?:

{ userId?: string | undefined; } | undefined

mcpServers?:

{ type: "url"; name: string; url: string; authorizationToken?: string | null | undefined; toolConfiguration?: { enabled?: boolean | null | undefined; allowedTools?: string[] | null | undefined; } | null | undefined; }[] | undefined

container?:

{ id?: string | undefined; skills?: { type: "anthropic" | "custom"; skillId: string; version?: string | undefined; }[] | undefined; } | undefined

toolStreaming?:

boolean | undefined

effort?:

"low" | "medium" | "high" | "xhigh" | "max" | undefined

taskBudget?:

{ type: "tokens"; total: number; remaining?: number | undefined; } | undefined

speed?:

"fast" | "standard" | undefined

inferenceGeo?:

"us" | "global" | undefined

fallbacks?:

"default" | { model: string; max_tokens?: number | undefined; thinking?: Record<string, unknown> | undefined; output_config?: Record<string, unknown> | undefined; speed?: "fast" | "standard" | undefined; }[] | undefined

anthropicBeta?:

string[] | undefined

contextManagement?:

{ edits: ({ type: "clear_tool_uses_20250919"; trigger?: { type: "input_tokens"; value: number; } | { type: "tool_uses"; value: number; } | undefined; keep?: { type: "tool_uses"; value: number; } | undefined; clearAtLeast?: { ...; } | undefined; clearToolInputs?: boolean | undefined; excludeTools?: string[] | undefin...