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URL: https://platform.claude.com/docs/en/managed-agents/quickstart

Quickstart

This guide walks you through creating an agent, setting up an environment, starting a session, and streaming agent responses.

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Prefer an interactive walkthrough? Run /claude-api managed-agents-onboard in the latest version of Claude Code for a guided setup and interactive question-answering.

Core concepts

Concept	Description
Agent	The model, system prompt, tools, MCP servers, and skills
Environment	Configuration for where sessions run: an Anthropic-managed cloud sandbox, or a self-hosted sandbox on your own infrastructure
Session	A running agent instance within an environment, performing a specific task and generating outputs
Events	Messages exchanged between your application and the agent (user turns, tool results, status updates)

Prerequisites

An Anthropic Console account
An API key

Install the CLI

Check the installation:

ant --version

Install the SDK

Set your API key as an environment variable:

export ANTHROPIC_API_KEY="your-api-key-here"

Create your first session

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All Managed Agents API requests require the managed-agents-2026-04-01 beta header. The SDK sets the beta header automatically.

What's happening

When you send a user event, Claude Managed Agents:

Provisions a sandbox: Your environment configuration determines how it's built.
Runs the agent loop: Claude determines which tools to use based on your message.
Executes tools: File writes, bash commands, and other tool calls run inside the sandbox.
Streams events: You receive real-time updates as the agent works.
Goes idle: The agent emits a session.status_idle event when it has nothing more to do.

Next steps

Define your agent

Create reusable, versioned agent configurations

Configure environments

Customize networking and sandbox settings

Agent tools

Enable specific tools for your agent

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Create an agent
Create an agent that defines the model, system prompt, and available tools.
ant beta:agents create \ --name "Coding Assistant" \ --model '{id: claude-opus-4-8}' \ --system "You are a helpful coding assistant. Write clean, well-documented code." \ --tool '{type: agent_toolset_20260401}'
The agent_toolset_20260401 tool type enables the full set of pre-built agent tools (bash, file operations, web search, and more). See Tools for the complete list and per-tool configuration options.
Save the returned agent.id. You'll reference it in every session you create.
Create an environment
An environment defines the sandbox where your agent runs.
ant beta:environments create \ --name "quickstart-env" \ --config '{type: cloud, networking: {type: unrestricted}}'
Save the returned environment.id. You'll reference it in every session you create.
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To run the sandbox on your own infrastructure instead of a cloud sandbox, see Self-hosted sandboxes.

Start a session

Create a session that references your agent and environment.

session = client.beta.sessions.create(
 agent=agent.id,
 environment_id=environment.id,
 title="Quickstart session",
)

print(f"Session ID: {session.id}")

Send a message and stream the response

Open a stream, send a user event, then process events as they arrive:

with client.beta.sessions.events.stream(session.id) as stream:
 # Send the user message after the stream opens
 client.beta.sessions.events.send(
 session.id,
 events=[
 {
 "type": "user.message",
 "content": [
 {
 "type": "text",
 "text": "Create a Python script that generates the first 20 Fibonacci numbers and saves them to fibonacci.txt",
 },
 ],
 },
 ],
 )

 # Process streaming events
 for event in stream:
 match event.type:
 case "agent.message":
 for block in event.content:
 print(block.text, end="")
 case "agent.tool_use":
 print(f"\n[Using tool: {event.name}]")
 case "session.status_idle":
 print("\n\nAgent finished.")
 break

The agent writes a Python script, executes it in the sandbox, and verifies the output file was created. Your output looks similar to this:

I'll create a Python script that generates the first 20 Fibonacci numbers and saves them to a file.
[Using tool: write]
[Using tool: bash]
The script ran successfully. Let me verify the output file.
[Using tool: bash]
fibonacci.txt contains the first 20 Fibonacci numbers (0 through 4181).

Agent finished.

Session event stream

Handle events and steer the agent mid-execution