Claude Agent SDK for Elixir

An Elixir SDK aiming for feature-complete parity with the official claude-agent-sdk-python. Build AI-powered applications with Claude using a production-ready interface for the Claude Code CLI, featuring streaming responses, lifecycle hooks, permission controls, and in-process tool execution via MCP.

Note: This SDK does not bundle the Claude Code CLI. You must install it separately (see Prerequisites).

What You Can Build

AI coding assistants with real-time streaming output
Automated code review pipelines with custom permission policies
Multi-agent workflows with specialized personas
Tool-augmented applications using the Model Context Protocol (MCP)
Interactive chat interfaces with typewriter-style output

Installation

Add to your mix.exs:

def deps do
  [
    {:claude_agent_sdk, "~> 0.11.0"}
  ]
end

Then fetch dependencies:

mix deps.get

Prerequisites

Install the Claude Code CLI (requires Node.js):

npm install -g @anthropic-ai/claude-code

Verify installation:

claude --version

Quick Start

1. Authenticate

Choose one method:

# Option A: Environment variable (recommended for CI/CD)
export ANTHROPIC_API_KEY="sk-ant-api03-..."

# Option B: OAuth token
export CLAUDE_AGENT_OAUTH_TOKEN="sk-ant-oat01-..."

# Option C: Interactive login
claude login

2. Run Your First Query

alias ClaudeAgentSDK.{ContentExtractor, Options}

# Simple query with streaming collection
ClaudeAgentSDK.query("Write a function that calculates factorial in Elixir")
|> Enum.each(fn msg ->
  case msg.type do
    :assistant -> IO.puts(ContentExtractor.extract_text(msg) || "")
    :result -> IO.puts("Done! Cost: $#{msg.data.total_cost_usd}")
    _ -> :ok
  end
end)

3. Real-Time Streaming

alias ClaudeAgentSDK.Streaming

{:ok, session} = Streaming.start_session()

Streaming.send_message(session, "Explain GenServers in one paragraph")
|> Stream.each(fn
  %{type: :text_delta, text: chunk} -> IO.write(chunk)
  %{type: :message_stop} -> IO.puts("")
  _ -> :ok
end)
|> Stream.run()

Streaming.close_session(session)

If session initialization or message send fails, the stream now emits an immediate %{type: :error, error: reason} event instead of waiting for the 5-minute stream timeout.

Authentication

The SDK supports three authentication methods, checked in this order:

Method	Environment Variable	Best For
OAuth Token	`CLAUDE_AGENT_OAUTH_TOKEN`	Production / CI
API Key	`ANTHROPIC_API_KEY`	Development
CLI Login	(uses `claude login` session)	Local development

Cloud Providers

AWS Bedrock:

export CLAUDE_AGENT_USE_BEDROCK=1
export AWS_ACCESS_KEY_ID=...
export AWS_SECRET_ACCESS_KEY=...
export AWS_REGION=us-west-2

Google Vertex AI:

export CLAUDE_AGENT_USE_VERTEX=1
export GOOGLE_APPLICATION_CREDENTIALS=/path/to/key.json
export GOOGLE_CLOUD_PROJECT=your-project-id

Token Setup (Local Development)

For persistent authentication without re-login:

mix claude.setup_token

AuthManager keeps running if token storage save/clear fails and returns {:error, reason}. Handle clear_auth/0 accordingly in your app code:

case ClaudeAgentSDK.AuthManager.clear_auth() do
  :ok -> :ok
  {:error, reason} -> IO.puts("Failed to clear auth: #{inspect(reason)}")
end

Check authentication status:

alias ClaudeAgentSDK.AuthChecker
diagnosis = AuthChecker.diagnose()
# => %{authenticated: true, auth_method: "Anthropic API", ...}

Core Concepts

Choosing the Right API

API	Use Case	When to Use
`query/2`	Simple queries	Batch processing, scripts
`Streaming`	Typewriter UX	Chat interfaces, real-time output
`Client`	Full control	Multi-turn agents, tools, hooks

Query API

The simplest way to interact with Claude:

# Basic query
messages = ClaudeAgentSDK.query("What is recursion?") |> Enum.to_list()

# With options
opts = %ClaudeAgentSDK.Options{
  model: "sonnet",
  max_turns: 5,
  output_format: :stream_json
}
messages = ClaudeAgentSDK.query("Explain OTP", opts) |> Enum.to_list()

# Streamed input prompts (unidirectional)
prompts = [
  %{"type" => "user", "message" => %{"role" => "user", "content" => "Hello"}},
  %{"type" => "user", "message" => %{"role" => "user", "content" => "How are you?"}}
]

ClaudeAgentSDK.query(prompts, opts) |> Enum.to_list()

# Custom transport injection
ClaudeAgentSDK.query("Hello", opts, {ClaudeAgentSDK.Transport.Port, []})
|> Enum.to_list()

# Lazy transport startup (defer subprocess spawn to handle_continue)
ClaudeAgentSDK.query(
  "Hello",
  opts,
  {ClaudeAgentSDK.Transport.Port, [startup_mode: :lazy]}
)
|> Enum.to_list()

# Continue a conversation
ClaudeAgentSDK.continue("Can you give an example?") |> Enum.to_list()

# Resume a specific session
ClaudeAgentSDK.resume("session-id", "What about supervision trees?") |> Enum.to_list()

Streaming API

For real-time, character-by-character output:

alias ClaudeAgentSDK.{Options, Streaming}

{:ok, session} = Streaming.start_session(%Options{model: "haiku"})

# Send messages and stream responses
Streaming.send_message(session, "Write a haiku about Elixir")
|> Enum.each(fn
  %{type: :text_delta, text: t} -> IO.write(t)
  %{type: :tool_use_start, name: n} -> IO.puts("\nUsing tool: #{n}")
  %{type: :message_stop} -> IO.puts("\n---")
  _ -> :ok
end)

# Multi-turn conversation (context preserved)
Streaming.send_message(session, "Now write one about Phoenix")
|> Enum.to_list()

Streaming.close_session(session)

Subagent Streaming: When Claude spawns subagents via the Task tool, events include a parent_tool_use_id field to identify the source. Main agent events have nil, subagent events have the Task tool call ID. Streaming events also include uuid, session_id, and raw_event metadata for parity with the Python SDK. Stream event wrappers require uuid and session_id (missing keys raise). See the Streaming Guide for details.

Hooks System

Intercept and control agent behavior at key lifecycle points:

alias ClaudeAgentSDK.{Client, Options}
alias ClaudeAgentSDK.Hooks.{Matcher, Output}

# Block dangerous commands
check_bash = fn input, _id, _ctx ->
  case input do
    %{"tool_name" => "Bash", "tool_input" => %{"command" => cmd}} ->
      if String.contains?(cmd, "rm -rf") do
        Output.deny("Dangerous command blocked")
      else
        Output.allow()
      end
    _ -> %{}
  end
end

opts = %Options{
  hooks: %{
    pre_tool_use: [Matcher.new("Bash", [check_bash])]
  }
}

{:ok, client} = Client.start_link(opts)

Available Hook Events (all 12 Python SDK events supported):

pre_tool_use / post_tool_use / post_tool_use_failure - Tool execution lifecycle
user_prompt_submit - Before sending user messages
stop / subagent_stop / subagent_start - Agent lifecycle
notification - CLI notifications
permission_request - Permission dialog interception
session_start / session_end - Session lifecycle
pre_compact - Before context compaction

See the Hooks Guide for comprehensive documentation.

Supervision

Hook and permission callbacks run in async tasks. For production, add the SDK task supervisor so callback processes are supervised:

children = [
  ClaudeAgentSDK.TaskSupervisor,
  {ClaudeAgentSDK.Client, options}
]

If you use a custom supervisor name, configure the SDK to match:

children = [
  {ClaudeAgentSDK.TaskSupervisor, name: MyApp.ClaudeTaskSupervisor}
]

config :claude_agent_sdk, task_supervisor: MyApp.ClaudeTaskSupervisor

If an explicitly configured supervisor is missing at runtime, the SDK logs a warning and falls back to Task.start/1. With default settings, missing ClaudeAgentSDK.TaskSupervisor falls back silently for backward compatibility. For stricter behavior in dev/test:

config :claude_agent_sdk, task_supervisor_strict: true

In strict mode, ClaudeAgentSDK.TaskSupervisor.start_child/2 returns {:error, {:task_supervisor_unavailable, supervisor}} instead of spawning an unsupervised fallback task.

Permission System

Fine-grained control over tool execution:

alias ClaudeAgentSDK.{Options, Permission.Result}

permission_callback = fn ctx ->
  case ctx.tool_name do
    "Write" ->
      # Redirect system file writes to safe location
      if String.starts_with?(ctx.tool_input["file_path"], "/etc/") do
        safe_path = "/tmp/sandbox/" <> Path.basename(ctx.tool_input["file_path"])
        Result.allow(updated_input: %{ctx.tool_input | "file_path" => safe_path})
      else
        Result.allow()
      end
    _ ->
      Result.allow()
  end
end

opts = %Options{
  can_use_tool: permission_callback,
  permission_mode: :default  # :default | :accept_edits | :plan | :bypass_permissions | :delegate | :dont_ask
}

Note: can_use_tool is mutually exclusive with permission_prompt_tool. The SDK routes can_use_tool through the control client (including string prompts), auto-enables include_partial_messages, and sets permission_prompt_tool to \"stdio\" internally so the CLI can emit permission callbacks. Use :default or :plan for built-in tool permissions; :delegate is intended for external tool execution. Hook-based fallback only applies in non-:delegate modes and ignores updated_permissions. If you do not see callbacks, your CLI build may not emit control callbacks (see examples/advanced_features/permissions_live.exs).

Stream a single client response until the final result:

Client.receive_response_stream(client)
|> Enum.to_list()

MCP Tools (In-Process)

Define custom tools that Claude can call directly in your application:

defmodule MyTools do
  use ClaudeAgentSDK.Tool

  deftool :calculate, "Perform a calculation", %{
    type: "object",
    properties: %{
      expression: %{type: "string", description: "Math expression to evaluate"}
    },
    required: ["expression"]
  } do
    def execute(%{"expression" => expr}) do
      # Your logic here
      result = eval_expression(expr)
      {:ok, %{"content" => [%{"type" => "text", "text" => "Result: #{result}"}]}}
    end
  end
end

# Create an MCP server with your tools
server = ClaudeAgentSDK.create_sdk_mcp_server(
  name: "calculator",
  version: "1.0.0",
  tools: [MyTools.Calculate]
)

# Optional: start tool registry under your DynamicSupervisor
{:ok, sup} = DynamicSupervisor.start_link(strategy: :one_for_one)

server = ClaudeAgentSDK.create_sdk_mcp_server(
  name: "calculator",
  version: "1.0.0",
  tools: [MyTools.Calculate],
  supervisor: sup
)

opts = %ClaudeAgentSDK.Options{
  mcp_servers: %{"calc" => server},
  allowed_tools: ["mcp__calc__calculate"]
}

Note: MCP server routing only supports initialize, tools/list, tools/call, and notifications/initialized. Calls to resources/list or prompts/list return JSON-RPC method-not-found errors to match the Python SDK. If version is omitted, it defaults to "1.0.0".

Configuration Options

Key options for ClaudeAgentSDK.Options:

Option	Type	Description
`model`	string	`"sonnet"`, `"opus"`, `"haiku"`
`max_turns`	integer	Maximum conversation turns
`system_prompt`	string	Custom system instructions
`output_format`	atom/map	`:text`, `:json`, `:stream_json`, or JSON schema (SDK enforces stream-json for transport; JSON schema still passed)
`allowed_tools`	list	Tools Claude can use
`permission_mode`	atom	`:default`, `:accept_edits`, `:plan`, `:bypass_permissions`, `:delegate`, `:dont_ask`
`hooks`	map	Lifecycle hook callbacks
`mcp_servers`	map or string	MCP server configurations (or JSON/path alias for `mcp_config`)
`cwd`	string	Working directory for file operations
`timeout_ms`	integer	Command timeout (default: 75 minutes)
`max_buffer_size`	integer	Maximum JSON buffer size (default: 1MB, overflow yields `CLIJSONDecodeError`)

CLI path override: set path_to_claude_code_executable or executable in Options (Python cli_path equivalent).

Runtime Application Config

config :claude_agent_sdk,
  # Timeout for in-process tool execution tasks in Tool.Registry
  tool_execution_timeout_ms: 30_000,
  # Query CLI stream backend module
  cli_stream_module: ClaudeAgentSDK.Query.CLIStream,
  # Fail fast when configured task supervisor is unavailable
  task_supervisor_strict: false

config :claude_agent_sdk, :process_module is still read as a fallback for query streaming, but it is deprecated and logs a warning once per legacy module.

SessionStore now hydrates on-disk cache in a handle_continue/2 step. Startup is faster, but list/search can be briefly incomplete immediately after boot while warmup finishes.

Transport.Port, Transport.Erlexec, and Streaming.Session support startup_mode: :lazy to defer subprocess startup to handle_continue/2. In lazy mode, start_link can succeed before the subprocess is spawned; startup failures then surface as process exit after init.

Query-side transport errors normalize equivalent reasons to stable atoms where possible: :port_closed is treated as :not_connected, and {:command_not_found, "claude"} is treated as :cli_not_found.

SDK Logging

The SDK uses its own log level filter (default: :warning) to keep output quiet in dev. Configure via application env:

config :claude_agent_sdk, log_level: :warning  # :debug | :info | :warning | :error | :off

Option Presets

alias ClaudeAgentSDK.OptionBuilder

# Environment-based presets
OptionBuilder.build_development_options()  # Permissive, verbose
OptionBuilder.build_production_options()   # Restrictive, safe
OptionBuilder.for_environment()            # Auto-detect from Mix.env()

# Use-case presets
OptionBuilder.build_analysis_options()     # Read-only code analysis
OptionBuilder.build_chat_options()         # Simple chat, no tools
OptionBuilder.quick()                      # Fast one-off queries

Examples

The examples/ directory contains runnable demonstrations.

Mix Task Example (Start Here)

If you want to integrate Claude into your own Mix project, see the mix_task_chat example — a complete working app with Mix tasks:

cd examples/mix_task_chat
mix deps.get
mix chat "Hello, Claude!"           # Streaming response
mix chat --interactive              # Multi-turn conversation
mix ask -q "What is 2+2?"           # Script-friendly output

Script Examples

# Run all examples
bash examples/run_all.sh

# Run a specific example
mix run examples/basic_example.exs
mix run examples/streaming_tools/quick_demo.exs
mix run examples/hooks/basic_bash_blocking.exs

Key Examples:

mix_task_chat/ - Full Mix task integration (streaming + interactive chat)
basic_example.exs - Minimal SDK usage
streaming_tools/quick_demo.exs - Real-time streaming
hooks/complete_workflow.exs - Full hooks integration
sdk_mcp_tools_live.exs - Custom MCP tools
advanced_features/agents_live.exs - Multi-agent workflows
advanced_features/subagent_spawning_live.exs - Parallel subagent coordination
advanced_features/web_tools_live.exs - WebSearch and WebFetch

Full Application Examples

Complete Mix applications demonstrating production-ready SDK integration patterns:

Example	Description	Key Features
`phoenix_chat/`	Real-time chat with Phoenix LiveView	LiveView, Channels, streaming responses, session management
`document_generation/`	AI-powered Excel document generation	elixlsx, natural language parsing, Mix tasks
`research_agent/`	Multi-agent research coordination	Task tool, subagent tracking via hooks, parallel execution
`skill_invocation/`	Skill tool usage and tracking	Skill definitions, hook-based tracking, GenServer state
`email_agent/`	AI-powered email assistant	SQLite storage, rule-based processing, natural language queries

# Run Phoenix Chat
cd examples/phoenix_chat && mix deps.get && mix phx.server
# Visit http://localhost:4000

# Run Document Generation
cd examples/document_generation && mix deps.get && mix generate.demo

# Run Research Agent
cd examples/research_agent && mix deps.get && mix research "quantum computing"

# Run Skill Invocation demo
cd examples/skill_invocation && mix deps.get && mix run -e "SkillInvocation.demo()"

# Run Email Agent
cd examples/email_agent && mix deps.get && mix email.assistant "find emails from last week"

Guides

Guide	Description
Getting Started	Installation, authentication, and first query
Streaming	Real-time streaming and typewriter effects
Hooks	Lifecycle hooks for tool control
MCP Tools	In-process tool definitions with MCP
Permissions	Fine-grained permission controls
Configuration	Complete options reference
Agents	Custom agent personas
Sessions	Session management and persistence
Testing	Mock system and testing patterns
Error Handling	Error types and recovery

Upgrading

For breaking changes and migration notes, see CHANGELOG.md.

0.11.0 breaking changes:

--print flag removed from all modules. All queries now use --output-format stream-json exclusively.
--agents CLI flag removed. Agents are now sent via the initialize control request. Use Options.agents_for_initialize/1.
AgentsFile module deleted. Remove any agents_temp_file_max_age_seconds config.
Client state is now a defstruct. Four deprecated fields removed: current_model, pending_model_change, current_permission_mode, pending_inbound_count.
All 12 hook events are now supported (6 new: post_tool_use_failure, notification, subagent_start, permission_request, session_start, session_end).

0.10.0 fix (resume turn persistence):

resume/3 no longer uses --print --resume (one-shot mode that dropped intermediate turns). It now uses --resume with --input-format stream-json, preserving the full conversation history across resume calls.
Updated default Opus model to claude-opus-4-6.

0.9.0 breaking change (streaming):

Stream event wrappers now require uuid and session_id. Missing keys raise and terminate the streaming client.
If you emit or mock stream_event wrappers, include both fields (custom transports, fixtures, tests).

Additional Resources:

CHANGELOG.md - Version history and release notes
HexDocs - API documentation
Claude Code SDK - Upstream documentation

License

MIT License - see LICENSE for details.

_{Built with Elixir and Claude}

Name		Name	Last commit message	Last commit date
Latest commit History 149 Commits
.github/workflows		.github/workflows
.kiro/specs/runtime-control-features		.kiro/specs/runtime-control-features
assets		assets
batch_output_analyze		batch_output_analyze
config		config
docs		docs
examples		examples
guides		guides
lib		lib
scripts		scripts
test		test
.credo.exs		.credo.exs
.dockerignore		.dockerignore
.formatter.exs		.formatter.exs
.gitignore		.gitignore
CHANGELOG.md		CHANGELOG.md
Dockerfile.test		Dockerfile.test
LICENSE		LICENSE
Makefile		Makefile
README.md		README.md
mix.exs		mix.exs
mix.lock		mix.lock
set_token_helper.sh		set_token_helper.sh
setup.sh		setup.sh
setup_erlexec.sh		setup_erlexec.sh

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nshkrdotcom/claude_agent_sdk

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Claude Agent SDK for Elixir

What You Can Build

Installation

Prerequisites

Quick Start

1. Authenticate

2. Run Your First Query

3. Real-Time Streaming

Authentication

Cloud Providers

Token Setup (Local Development)

Core Concepts

Choosing the Right API

Query API

Streaming API

Hooks System

Supervision

Permission System

MCP Tools (In-Process)

Configuration Options

Runtime Application Config

SDK Logging

Option Presets

Examples

Mix Task Example (Start Here)

Script Examples

Full Application Examples

Guides

Upgrading

License

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