# Agent SDK reference - Python

> Complete API reference for the Python Agent SDK, including all functions, types, and classes.

## Installation

```bash  theme={null}
pip install claude-agent-sdk
```

## Choosing Between `query()` and `ClaudeSDKClient`

The Python SDK provides two ways to interact with Claude Code:

### Quick Comparison

| Feature             | `query()`                     | `ClaudeSDKClient`                  |
| :------------------ | :---------------------------- | :--------------------------------- |
| **Session**         | Creates new session each time | Reuses same session                |
| **Conversation**    | Single exchange               | Multiple exchanges in same context |
| **Connection**      | Managed automatically         | Manual control                     |
| **Streaming Input** | ✅ Supported                   | ✅ Supported                        |
| **Interrupts**      | ❌ Not supported               | ✅ Supported                        |
| **Hooks**           | ❌ Not supported               | ✅ Supported                        |
| **Custom Tools**    | ❌ Not supported               | ✅ Supported                        |
| **Continue Chat**   | ❌ New session each time       | ✅ Maintains conversation           |
| **Use Case**        | One-off tasks                 | Continuous conversations           |

### When to Use `query()` (New Session Each Time)

**Best for:**

* One-off questions where you don't need conversation history
* Independent tasks that don't require context from previous exchanges
* Simple automation scripts
* When you want a fresh start each time

### When to Use `ClaudeSDKClient` (Continuous Conversation)

**Best for:**

* **Continuing conversations** - When you need Claude to remember context
* **Follow-up questions** - Building on previous responses
* **Interactive applications** - Chat interfaces, REPLs
* **Response-driven logic** - When next action depends on Claude's response
* **Session control** - Managing conversation lifecycle explicitly

## Functions

### `query()`

Creates a new session for each interaction with Claude Code. Returns an async iterator that yields messages as they arrive. Each call to `query()` starts fresh with no memory of previous interactions.

```python  theme={null}
async def query(
    *,
    prompt: str | AsyncIterable[dict[str, Any]],
    options: ClaudeAgentOptions | None = None
) -> AsyncIterator[Message]
```

#### Parameters

| Parameter | Type                         | Description                                                                |
| :-------- | :--------------------------- | :------------------------------------------------------------------------- |
| `prompt`  | `str \| AsyncIterable[dict]` | The input prompt as a string or async iterable for streaming mode          |
| `options` | `ClaudeAgentOptions \| None` | Optional configuration object (defaults to `ClaudeAgentOptions()` if None) |

#### Returns

Returns an `AsyncIterator[Message]` that yields messages from the conversation.

#### Example - With options

```python  theme={null}

import asyncio
from claude_agent_sdk import query, ClaudeAgentOptions

async def main():
    options = ClaudeAgentOptions(
        system_prompt="You are an expert Python developer",
        permission_mode='acceptEdits',
        cwd="/home/user/project"
    )

    async for message in query(
        prompt="Create a Python web server",
        options=options
    ):
        print(message)


asyncio.run(main())
```

### `tool()`

Decorator for defining MCP tools with type safety.

```python  theme={null}
def tool(
    name: str,
    description: str,
    input_schema: type | dict[str, Any]
) -> Callable[[Callable[[Any], Awaitable[dict[str, Any]]]], SdkMcpTool[Any]]
```

#### Parameters

| Parameter      | Type                     | Description                                             |
| :------------- | :----------------------- | :------------------------------------------------------ |
| `name`         | `str`                    | Unique identifier for the tool                          |
| `description`  | `str`                    | Human-readable description of what the tool does        |
| `input_schema` | `type \| dict[str, Any]` | Schema defining the tool's input parameters (see below) |

#### Input Schema Options

1. **Simple type mapping** (recommended):

   ```python  theme={null}
   {"text": str, "count": int, "enabled": bool}
   ```

2. **JSON Schema format** (for complex validation):

   ```python  theme={null}
   {
       "type": "object",
       "properties": {
           "text": {"type": "string"},
           "count": {"type": "integer", "minimum": 0}
       },
       "required": ["text"]
   }
   ```

#### Returns

A decorator function that wraps the tool implementation and returns an `SdkMcpTool` instance.

#### Example

```python  theme={null}
from claude_agent_sdk import tool
from typing import Any

@tool("greet", "Greet a user", {"name": str})
async def greet(args: dict[str, Any]) -> dict[str, Any]:
    return {
        "content": [{
            "type": "text",
            "text": f"Hello, {args['name']}!"
        }]
    }
```

### `create_sdk_mcp_server()`

Create an in-process MCP server that runs within your Python application.

```python  theme={null}
def create_sdk_mcp_server(
    name: str,
    version: str = "1.0.0",
    tools: list[SdkMcpTool[Any]] | None = None
) -> McpSdkServerConfig
```

#### Parameters

| Parameter | Type                            | Default   | Description                                           |
| :-------- | :------------------------------ | :-------- | :---------------------------------------------------- |
| `name`    | `str`                           | -         | Unique identifier for the server                      |
| `version` | `str`                           | `"1.0.0"` | Server version string                                 |
| `tools`   | `list[SdkMcpTool[Any]] \| None` | `None`    | List of tool functions created with `@tool` decorator |

#### Returns

Returns an `McpSdkServerConfig` object that can be passed to `ClaudeAgentOptions.mcp_servers`.

#### Example

```python  theme={null}
from claude_agent_sdk import tool, create_sdk_mcp_server

@tool("add", "Add two numbers", {"a": float, "b": float})
async def add(args):
    return {
        "content": [{
            "type": "text",
            "text": f"Sum: {args['a'] + args['b']}"
        }]
    }

@tool("multiply", "Multiply two numbers", {"a": float, "b": float})
async def multiply(args):
    return {
        "content": [{
            "type": "text",
            "text": f"Product: {args['a'] * args['b']}"
        }]
    }

calculator = create_sdk_mcp_server(
    name="calculator",
    version="2.0.0",
    tools=[add, multiply]  # Pass decorated functions
)

# Use with Claude
options = ClaudeAgentOptions(
    mcp_servers={"calc": calculator},
    allowed_tools=["mcp__calc__add", "mcp__calc__multiply"]
)
```

## Classes

### `ClaudeSDKClient`

**Maintains a conversation session across multiple exchanges.** This is the Python equivalent of how the TypeScript SDK's `query()` function works internally - it creates a client object that can continue conversations.

#### Key Features

* **Session Continuity**: Maintains conversation context across multiple `query()` calls
* **Same Conversation**: Claude remembers previous messages in the session
* **Interrupt Support**: Can stop Claude mid-execution
* **Explicit Lifecycle**: You control when the session starts and ends
* **Response-driven Flow**: Can react to responses and send follow-ups
* **Custom Tools & Hooks**: Supports custom tools (created with `@tool` decorator) and hooks

```python  theme={null}
class ClaudeSDKClient:
    def __init__(self, options: ClaudeAgentOptions | None = None)
    async def connect(self, prompt: str | AsyncIterable[dict] | None = None) -> None
    async def query(self, prompt: str | AsyncIterable[dict], session_id: str = "default") -> None
    async def receive_messages(self) -> AsyncIterator[Message]
    async def receive_response(self) -> AsyncIterator[Message]
    async def interrupt(self) -> None
    async def disconnect(self) -> None
```

#### Methods

| Method                      | Description                                                         |
| :-------------------------- | :------------------------------------------------------------------ |
| `__init__(options)`         | Initialize the client with optional configuration                   |
| `connect(prompt)`           | Connect to Claude with an optional initial prompt or message stream |
| `query(prompt, session_id)` | Send a new request in streaming mode                                |
| `receive_messages()`        | Receive all messages from Claude as an async iterator               |
| `receive_response()`        | Receive messages until and including a ResultMessage                |
| `interrupt()`               | Send interrupt signal (only works in streaming mode)                |
| `disconnect()`              | Disconnect from Claude                                              |

#### Context Manager Support

The client can be used as an async context manager for automatic connection management:

```python  theme={null}
async with ClaudeSDKClient() as client:
    await client.query("Hello Claude")
    async for message in client.receive_response():
        print(message)
```

> **Important:** When iterating over messages, avoid using `break` to exit early as this can cause asyncio cleanup issues. Instead, let the iteration complete naturally or use flags to track when you've found what you need.

#### Example - Continuing a conversation

```python  theme={null}
import asyncio
from claude_agent_sdk import ClaudeSDKClient, AssistantMessage, TextBlock, ResultMessage

async def main():
    async with ClaudeSDKClient() as client:
        # First question
        await client.query("What's the capital of France?")

        # Process response
        async for message in client.receive_response():
            if isinstance(message, AssistantMessage):
                for block in message.content:
                    if isinstance(block, TextBlock):
                        print(f"Claude: {block.text}")

        # Follow-up question - Claude remembers the previous context
        await client.query("What's the population of that city?")

        async for message in client.receive_response():
            if isinstance(message, AssistantMessage):
                for block in message.content:
                    if isinstance(block, TextBlock):
                        print(f"Claude: {block.text}")

        # Another follow-up - still in the same conversation
        await client.query("What are some famous landmarks there?")

        async for message in client.receive_response():
            if isinstance(message, AssistantMessage):
                for block in message.content:
                    if isinstance(block, TextBlock):
                        print(f"Claude: {block.text}")

asyncio.run(main())
```

#### Example - Streaming input with ClaudeSDKClient

```python  theme={null}
import asyncio
from claude_agent_sdk import ClaudeSDKClient

async def message_stream():
    """Generate messages dynamically."""
    yield {"type": "text", "text": "Analyze the following data:"}
    await asyncio.sleep(0.5)
    yield {"type": "text", "text": "Temperature: 25°C"}
    await asyncio.sleep(0.5)
    yield {"type": "text", "text": "Humidity: 60%"}
    await asyncio.sleep(0.5)
    yield {"type": "text", "text": "What patterns do you see?"}

async def main():
    async with ClaudeSDKClient() as client:
        # Stream input to Claude
        await client.query(message_stream())

        # Process response
        async for message in client.receive_response():
            print(message)

        # Follow-up in same session
        await client.query("Should we be concerned about these readings?")

        async for message in client.receive_response():
            print(message)

asyncio.run(main())
```

#### Example - Using interrupts

```python  theme={null}
import asyncio
from claude_agent_sdk import ClaudeSDKClient, ClaudeAgentOptions

async def interruptible_task():
    options = ClaudeAgentOptions(
        allowed_tools=["Bash"],
        permission_mode="acceptEdits"
    )

    async with ClaudeSDKClient(options=options) as client:
        # Start a long-running task
        await client.query("Count from 1 to 100 slowly")

        # Let it run for a bit
        await asyncio.sleep(2)

        # Interrupt the task
        await client.interrupt()
        print("Task interrupted!")

        # Send a new command
        await client.query("Just say hello instead")

        async for message in client.receive_response():
            # Process the new response
            pass

asyncio.run(interruptible_task())
```

#### Example - Advanced permission control

```python  theme={null}
from claude_agent_sdk import (
    ClaudeSDKClient,
    ClaudeAgentOptions
)

async def custom_permission_handler(
    tool_name: str,
    input_data: dict,
    context: dict
):
    """Custom logic for tool permissions."""

    # Block writes to system directories
    if tool_name == "Write" and input_data.get("file_path", "").startswith("/system/"):
        return {
            "behavior": "deny",
            "message": "System directory write not allowed",
            "interrupt": True
        }

    # Redirect sensitive file operations
    if tool_name in ["Write", "Edit"] and "config" in input_data.get("file_path", ""):
        safe_path = f"./sandbox/{input_data['file_path']}"
        return {
            "behavior": "allow",
            "updatedInput": {**input_data, "file_path": safe_path}
        }

    # Allow everything else
    return {
        "behavior": "allow",
        "updatedInput": input_data
    }

async def main():
    options = ClaudeAgentOptions(
        can_use_tool=custom_permission_handler,
        allowed_tools=["Read", "Write", "Edit"]
    )

    async with ClaudeSDKClient(options=options) as client:
        await client.query("Update the system config file")

        async for message in client.receive_response():
            # Will use sandbox path instead
            print(message)

asyncio.run(main())
```

## Types

### `SdkMcpTool`

Definition for an SDK MCP tool created with the `@tool` decorator.

```python  theme={null}
@dataclass
class SdkMcpTool(Generic[T]):
    name: str
    description: str
    input_schema: type[T] | dict[str, Any]
    handler: Callable[[T], Awaitable[dict[str, Any]]]
```

| Property       | Type                                       | Description                                |
| :------------- | :----------------------------------------- | :----------------------------------------- |
| `name`         | `str`                                      | Unique identifier for the tool             |
| `description`  | `str`                                      | Human-readable description                 |
| `input_schema` | `type[T] \| dict[str, Any]`                | Schema for input validation                |
| `handler`      | `Callable[[T], Awaitable[dict[str, Any]]]` | Async function that handles tool execution |

### `ClaudeAgentOptions`

Configuration dataclass for Claude Code queries.

```python  theme={null}
@dataclass
class ClaudeAgentOptions:
    allowed_tools: list[str] = field(default_factory=list)
    system_prompt: str | SystemPromptPreset | None = None
    mcp_servers: dict[str, McpServerConfig] | str | Path = field(default_factory=dict)
    permission_mode: PermissionMode | None = None
    continue_conversation: bool = False
    resume: str | None = None
    max_turns: int | None = None
    disallowed_tools: list[str] = field(default_factory=list)
    model: str | None = None
    permission_prompt_tool_name: str | None = None
    cwd: str | Path | None = None
    settings: str | None = None
    add_dirs: list[str | Path] = field(default_factory=list)
    env: dict[str, str] = field(default_factory=dict)
    extra_args: dict[str, str | None] = field(default_factory=dict)
    max_buffer_size: int | None = None
    debug_stderr: Any = sys.stderr  # Deprecated
    stderr: Callable[[str], None] | None = None
    can_use_tool: CanUseTool | None = None
    hooks: dict[HookEvent, list[HookMatcher]] | None = None
    user: str | None = None
    include_partial_messages: bool = False
    fork_session: bool = False
    agents: dict[str, AgentDefinition] | None = None
    setting_sources: list[SettingSource] | None = None
```

| Property                      | Type                                         | Default              | Description                                                                                                                                                                             |
| :---------------------------- | :------------------------------------------- | :------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `allowed_tools`               | `list[str]`                                  | `[]`                 | List of allowed tool names                                                                                                                                                              |
| `system_prompt`               | `str \| SystemPromptPreset \| None`          | `None`               | System prompt configuration. Pass a string for custom prompt, or use `{"type": "preset", "preset": "claude_code"}` for Claude Code's system prompt. Add `"append"` to extend the preset |
| `mcp_servers`                 | `dict[str, McpServerConfig] \| str \| Path`  | `{}`                 | MCP server configurations or path to config file                                                                                                                                        |
| `permission_mode`             | `PermissionMode \| None`                     | `None`               | Permission mode for tool usage                                                                                                                                                          |
| `continue_conversation`       | `bool`                                       | `False`              | Continue the most recent conversation                                                                                                                                                   |
| `resume`                      | `str \| None`                                | `None`               | Session ID to resume                                                                                                                                                                    |
| `max_turns`                   | `int \| None`                                | `None`               | Maximum conversation turns                                                                                                                                                              |
| `disallowed_tools`            | `list[str]`                                  | `[]`                 | List of disallowed tool names                                                                                                                                                           |
| `model`                       | `str \| None`                                | `None`               | Claude model to use                                                                                                                                                                     |
| `permission_prompt_tool_name` | `str \| None`                                | `None`               | MCP tool name for permission prompts                                                                                                                                                    |
| `cwd`                         | `str \| Path \| None`                        | `None`               | Current working directory                                                                                                                                                               |
| `settings`                    | `str \| None`                                | `None`               | Path to settings file                                                                                                                                                                   |
| `add_dirs`                    | `list[str \| Path]`                          | `[]`                 | Additional directories Claude can access                                                                                                                                                |
| `env`                         | `dict[str, str]`                             | `{}`                 | Environment variables                                                                                                                                                                   |
| `extra_args`                  | `dict[str, str \| None]`                     | `{}`                 | Additional CLI arguments to pass directly to the CLI                                                                                                                                    |
| `max_buffer_size`             | `int \| None`                                | `None`               | Maximum bytes when buffering CLI stdout                                                                                                                                                 |
| `debug_stderr`                | `Any`                                        | `sys.stderr`         | *Deprecated* - File-like object for debug output. Use `stderr` callback instead                                                                                                         |
| `stderr`                      | `Callable[[str], None] \| None`              | `None`               | Callback function for stderr output from CLI                                                                                                                                            |
| `can_use_tool`                | `CanUseTool \| None`                         | `None`               | Tool permission callback function                                                                                                                                                       |
| `hooks`                       | `dict[HookEvent, list[HookMatcher]] \| None` | `None`               | Hook configurations for intercepting events                                                                                                                                             |
| `user`                        | `str \| None`                                | `None`               | User identifier                                                                                                                                                                         |
| `include_partial_messages`    | `bool`                                       | `False`              | Include partial message streaming events                                                                                                                                                |
| `fork_session`                | `bool`                                       | `False`              | When resuming with `resume`, fork to a new session ID instead of continuing the original session                                                                                        |
| `agents`                      | `dict[str, AgentDefinition] \| None`         | `None`               | Programmatically defined subagents                                                                                                                                                      |
| `plugins`                     | `list[SdkPluginConfig]`                      | `[]`                 | Load custom plugins from local paths. See [Plugins](/en/api/agent-sdk/plugins) for details                                                                                              |
| `setting_sources`             | `list[SettingSource] \| None`                | `None` (no settings) | Control which filesystem settings to load. When omitted, no settings are loaded. **Note:** Must include `"project"` to load CLAUDE.md files                                             |

### `SystemPromptPreset`

Configuration for using Claude Code's preset system prompt with optional additions.

```python  theme={null}
class SystemPromptPreset(TypedDict):
    type: Literal["preset"]
    preset: Literal["claude_code"]
    append: NotRequired[str]
```

| Field    | Required | Description                                                   |
| :------- | :------- | :------------------------------------------------------------ |
| `type`   | Yes      | Must be `"preset"` to use a preset system prompt              |
| `preset` | Yes      | Must be `"claude_code"` to use Claude Code's system prompt    |
| `append` | No       | Additional instructions to append to the preset system prompt |

### `SettingSource`

Controls which filesystem-based configuration sources the SDK loads settings from.

```python  theme={null}
SettingSource = Literal["user", "project", "local"]
```

| Value       | Description                                  | Location                      |
| :---------- | :------------------------------------------- | :---------------------------- |
| `"user"`    | Global user settings                         | `~/.claude/settings.json`     |
| `"project"` | Shared project settings (version controlled) | `.claude/settings.json`       |
| `"local"`   | Local project settings (gitignored)          | `.claude/settings.local.json` |

#### Default behavior

When `setting_sources` is **omitted** or **`None`**, the SDK does **not** load any filesystem settings. This provides isolation for SDK applications.

#### Why use setting\_sources?

**Load all filesystem settings (legacy behavior):**

```python  theme={null}
# Load all settings like SDK v0.0.x did
from claude_agent_sdk import query, ClaudeAgentOptions

async for message in query(
    prompt="Analyze this code",
    options=ClaudeAgentOptions(
        setting_sources=["user", "project", "local"]  # Load all settings
    )
):
    print(message)
```

**Load only specific setting sources:**

```python  theme={null}
# Load only project settings, ignore user and local
async for message in query(
    prompt="Run CI checks",
    options=ClaudeAgentOptions(
        setting_sources=["project"]  # Only .claude/settings.json
    )
):
    print(message)
```

**Testing and CI environments:**

```python  theme={null}
# Ensure consistent behavior in CI by excluding local settings
async for message in query(
    prompt="Run tests",
    options=ClaudeAgentOptions(
        setting_sources=["project"],  # Only team-shared settings
        permission_mode="bypassPermissions"
    )
):
    print(message)
```

**SDK-only applications:**

```python  theme={null}
# Define everything programmatically (default behavior)
# No filesystem dependencies - setting_sources defaults to None
async for message in query(
    prompt="Review this PR",
    options=ClaudeAgentOptions(
        # setting_sources=None is the default, no need to specify
        agents={ /* ... */ },
        mcp_servers={ /* ... */ },
        allowed_tools=["Read", "Grep", "Glob"]
    )
):
    print(message)
```

**Loading CLAUDE.md project instructions:**

```python  theme={null}
# Load project settings to include CLAUDE.md files
async for message in query(
    prompt="Add a new feature following project conventions",
    options=ClaudeAgentOptions(
        system_prompt={
            "type": "preset",
            "preset": "claude_code"  # Use Claude Code's system prompt
        },
        setting_sources=["project"],  # Required to load CLAUDE.md from project
        allowed_tools=["Read", "Write", "Edit"]
    )
):
    print(message)
```

#### Settings precedence

When multiple sources are loaded, settings are merged with this precedence (highest to lowest):

1. Local settings (`.claude/settings.local.json`)
2. Project settings (`.claude/settings.json`)
3. User settings (`~/.claude/settings.json`)

Programmatic options (like `agents`, `allowed_tools`) always override filesystem settings.

### `AgentDefinition`

Configuration for a subagent defined programmatically.

```python  theme={null}
@dataclass
class AgentDefinition:
    description: str
    prompt: str
    tools: list[str] | None = None
    model: Literal["sonnet", "opus", "haiku", "inherit"] | None = None
```

| Field         | Required | Description                                                    |
| :------------ | :------- | :------------------------------------------------------------- |
| `description` | Yes      | Natural language description of when to use this agent         |
| `tools`       | No       | Array of allowed tool names. If omitted, inherits all tools    |
| `prompt`      | Yes      | The agent's system prompt                                      |
| `model`       | No       | Model override for this agent. If omitted, uses the main model |

### `PermissionMode`

Permission modes for controlling tool execution.

```python  theme={null}
PermissionMode = Literal[
    "default",           # Standard permission behavior
    "acceptEdits",       # Auto-accept file edits
    "plan",              # Planning mode - no execution
    "bypassPermissions"  # Bypass all permission checks (use with caution)
]
```

### `McpSdkServerConfig`

Configuration for SDK MCP servers created with `create_sdk_mcp_server()`.

```python  theme={null}
class McpSdkServerConfig(TypedDict):
    type: Literal["sdk"]
    name: str
    instance: Any  # MCP Server instance
```

### `McpServerConfig`

Union type for MCP server configurations.

```python  theme={null}
McpServerConfig = McpStdioServerConfig | McpSSEServerConfig | McpHttpServerConfig | McpSdkServerConfig
```

#### `McpStdioServerConfig`

```python  theme={null}
class McpStdioServerConfig(TypedDict):
    type: NotRequired[Literal["stdio"]]  # Optional for backwards compatibility
    command: str
    args: NotRequired[list[str]]
    env: NotRequired[dict[str, str]]
```

#### `McpSSEServerConfig`

```python  theme={null}
class McpSSEServerConfig(TypedDict):
    type: Literal["sse"]
    url: str
    headers: NotRequired[dict[str, str]]
```

#### `McpHttpServerConfig`

```python  theme={null}
class McpHttpServerConfig(TypedDict):
    type: Literal["http"]
    url: str
    headers: NotRequired[dict[str, str]]
```

### `SdkPluginConfig`

Configuration for loading plugins in the SDK.

```python  theme={null}
class SdkPluginConfig(TypedDict):
    type: Literal["local"]
    path: str
```

| Field  | Type               | Description                                                |
| :----- | :----------------- | :--------------------------------------------------------- |
| `type` | `Literal["local"]` | Must be `"local"` (only local plugins currently supported) |
| `path` | `str`              | Absolute or relative path to the plugin directory          |

**Example:**

```python  theme={null}
plugins=[
    {"type": "local", "path": "./my-plugin"},
    {"type": "local", "path": "/absolute/path/to/plugin"}
]
```

For complete information on creating and using plugins, see [Plugins](/en/api/agent-sdk/plugins).

## Message Types

### `Message`

Union type of all possible messages.

```python  theme={null}
Message = UserMessage | AssistantMessage | SystemMessage | ResultMessage
```

### `UserMessage`

User input message.

```python  theme={null}
@dataclass
class UserMessage:
    content: str | list[ContentBlock]
```

### `AssistantMessage`

Assistant response message with content blocks.

```python  theme={null}
@dataclass
class AssistantMessage:
    content: list[ContentBlock]
    model: str
```

### `SystemMessage`

System message with metadata.

```python  theme={null}
@dataclass
class SystemMessage:
    subtype: str
    data: dict[str, Any]
```

### `ResultMessage`

Final result message with cost and usage information.

```python  theme={null}
@dataclass
class ResultMessage:
    subtype: str
    duration_ms: int
    duration_api_ms: int
    is_error: bool
    num_turns: int
    session_id: str
    total_cost_usd: float | None = None
    usage: dict[str, Any] | None = None
    result: str | None = None
```

## Content Block Types

### `ContentBlock`

Union type of all content blocks.

```python  theme={null}
ContentBlock = TextBlock | ThinkingBlock | ToolUseBlock | ToolResultBlock
```

### `TextBlock`

Text content block.

```python  theme={null}
@dataclass
class TextBlock:
    text: str
```

### `ThinkingBlock`

Thinking content block (for models with thinking capability).

```python  theme={null}
@dataclass
class ThinkingBlock:
    thinking: str
    signature: str
```

### `ToolUseBlock`

Tool use request block.

```python  theme={null}
@dataclass
class ToolUseBlock:
    id: str
    name: str
    input: dict[str, Any]
```

### `ToolResultBlock`

Tool execution result block.

```python  theme={null}
@dataclass
class ToolResultBlock:
    tool_use_id: str
    content: str | list[dict[str, Any]] | None = None
    is_error: bool | None = None
```

## Error Types

### `ClaudeSDKError`

Base exception class for all SDK errors.

```python  theme={null}
class ClaudeSDKError(Exception):
    """Base error for Claude SDK."""
```

### `CLINotFoundError`

Raised when Claude Code CLI is not installed or not found.

```python  theme={null}
class CLINotFoundError(CLIConnectionError):
    def __init__(self, message: str = "Claude Code not found", cli_path: str | None = None):
        """
        Args:
            message: Error message (default: "Claude Code not found")
            cli_path: Optional path to the CLI that was not found
        """
```

### `CLIConnectionError`

Raised when connection to Claude Code fails.

```python  theme={null}
class CLIConnectionError(ClaudeSDKError):
    """Failed to connect to Claude Code."""
```

### `ProcessError`

Raised when the Claude Code process fails.

```python  theme={null}
class ProcessError(ClaudeSDKError):
    def __init__(self, message: str, exit_code: int | None = None, stderr: str | None = None):
        self.exit_code = exit_code
        self.stderr = stderr
```

### `CLIJSONDecodeError`

Raised when JSON parsing fails.

```python  theme={null}
class CLIJSONDecodeError(ClaudeSDKError):
    def __init__(self, line: str, original_error: Exception):
        """
        Args:
            line: The line that failed to parse
            original_error: The original JSON decode exception
        """
        self.line = line
        self.original_error = original_error
```

## Hook Types

### `HookEvent`

Supported hook event types. Note that due to setup limitations, the Python SDK does not support SessionStart, SessionEnd, and Notification hooks.

```python  theme={null}
HookEvent = Literal[
    "PreToolUse",      # Called before tool execution
    "PostToolUse",     # Called after tool execution
    "UserPromptSubmit", # Called when user submits a prompt
    "Stop",            # Called when stopping execution
    "SubagentStop",    # Called when a subagent stops
    "PreCompact"       # Called before message compaction
]
```

### `HookCallback`

Type definition for hook callback functions.

```python  theme={null}
HookCallback = Callable[
    [dict[str, Any], str | None, HookContext],
    Awaitable[dict[str, Any]]
]
```

Parameters:

* `input_data`: Hook-specific input data (see [hook documentation](https://docs.claude.com/en/docs/claude-code/hooks#hook-input))
* `tool_use_id`: Optional tool use identifier (for tool-related hooks)
* `context`: Hook context with additional information

Returns a dictionary that may contain:

* `decision`: `"block"` to block the action
* `systemMessage`: System message to add to the transcript
* `hookSpecificOutput`: Hook-specific output data

### `HookContext`

Context information passed to hook callbacks.

```python  theme={null}
@dataclass
class HookContext:
    signal: Any | None = None  # Future: abort signal support
```

### `HookMatcher`

Configuration for matching hooks to specific events or tools.

```python  theme={null}
@dataclass
class HookMatcher:
    matcher: str | None = None        # Tool name or pattern to match (e.g., "Bash", "Write|Edit")
    hooks: list[HookCallback] = field(default_factory=list)  # List of callbacks to execute
```

### Hook Usage Example

```python  theme={null}
from claude_agent_sdk import query, ClaudeAgentOptions, HookMatcher, HookContext
from typing import Any

async def validate_bash_command(
    input_data: dict[str, Any],
    tool_use_id: str | None,
    context: HookContext
) -> dict[str, Any]:
    """Validate and potentially block dangerous bash commands."""
    if input_data['tool_name'] == 'Bash':
        command = input_data['tool_input'].get('command', '')
        if 'rm -rf /' in command:
            return {
                'hookSpecificOutput': {
                    'hookEventName': 'PreToolUse',
                    'permissionDecision': 'deny',
                    'permissionDecisionReason': 'Dangerous command blocked'
                }
            }
    return {}

async def log_tool_use(
    input_data: dict[str, Any],
    tool_use_id: str | None,
    context: HookContext
) -> dict[str, Any]:
    """Log all tool usage for auditing."""
    print(f"Tool used: {input_data.get('tool_name')}")
    return {}

options = ClaudeAgentOptions(
    hooks={
        'PreToolUse': [
            HookMatcher(matcher='Bash', hooks=[validate_bash_command]),
            HookMatcher(hooks=[log_tool_use])  # Applies to all tools
        ],
        'PostToolUse': [
            HookMatcher(hooks=[log_tool_use])
        ]
    }
)

async for message in query(
    prompt="Analyze this codebase",
    options=options
):
    print(message)
```

## Tool Input/Output Types

Documentation of input/output schemas for all built-in Claude Code tools. While the Python SDK doesn't export these as types, they represent the structure of tool inputs and outputs in messages.

### Task

**Tool name:** `Task`

**Input:**

```python  theme={null}
{
    "description": str,      # A short (3-5 word) description of the task
    "prompt": str,           # The task for the agent to perform
    "subagent_type": str     # The type of specialized agent to use
}
```

**Output:**

```python  theme={null}
{
    "result": str,                    # Final result from the subagent
    "usage": dict | None,             # Token usage statistics
    "total_cost_usd": float | None,  # Total cost in USD
    "duration_ms": int | None         # Execution duration in milliseconds
}
```

### Bash

**Tool name:** `Bash`

**Input:**

```python  theme={null}
{
    "command": str,                  # The command to execute
    "timeout": int | None,           # Optional timeout in milliseconds (max 600000)
    "description": str | None,       # Clear, concise description (5-10 words)
    "run_in_background": bool | None # Set to true to run in background
}
```

**Output:**

```python  theme={null}
{
    "output": str,              # Combined stdout and stderr output
    "exitCode": int,            # Exit code of the command
    "killed": bool | None,      # Whether command was killed due to timeout
    "shellId": str | None       # Shell ID for background processes
}
```

### Edit

**Tool name:** `Edit`

**Input:**

```python  theme={null}
{
    "file_path": str,           # The absolute path to the file to modify
    "old_string": str,          # The text to replace
    "new_string": str,          # The text to replace it with
    "replace_all": bool | None  # Replace all occurrences (default False)
}
```

**Output:**

```python  theme={null}
{
    "message": str,      # Confirmation message
    "replacements": int, # Number of replacements made
    "file_path": str     # File path that was edited
}
```

### Read

**Tool name:** `Read`

**Input:**

```python  theme={null}
{
    "file_path": str,       # The absolute path to the file to read
    "offset": int | None,   # The line number to start reading from
    "limit": int | None     # The number of lines to read
}
```

**Output (Text files):**

```python  theme={null}
{
    "content": str,         # File contents with line numbers
    "total_lines": int,     # Total number of lines in file
    "lines_returned": int   # Lines actually returned
}
```

**Output (Images):**

```python  theme={null}
{
    "image": str,       # Base64 encoded image data
    "mime_type": str,   # Image MIME type
    "file_size": int    # File size in bytes
}
```

### Write

**Tool name:** `Write`

**Input:**

```python  theme={null}
{
    "file_path": str,  # The absolute path to the file to write
    "content": str     # The content to write to the file
}
```

**Output:**

```python  theme={null}
{
    "message": str,        # Success message
    "bytes_written": int,  # Number of bytes written
    "file_path": str       # File path that was written
}
```

### Glob

**Tool name:** `Glob`

**Input:**

```python  theme={null}
{
    "pattern": str,       # The glob pattern to match files against
    "path": str | None    # The directory to search in (defaults to cwd)
}
```

**Output:**

```python  theme={null}
{
    "matches": list[str],  # Array of matching file paths
    "count": int,          # Number of matches found
    "search_path": str     # Search directory used
}
```

### Grep

**Tool name:** `Grep`

**Input:**

```python  theme={null}
{
    "pattern": str,                    # The regular expression pattern
    "path": str | None,                # File or directory to search in
    "glob": str | None,                # Glob pattern to filter files
    "type": str | None,                # File type to search
    "output_mode": str | None,         # "content", "files_with_matches", or "count"
    "-i": bool | None,                 # Case insensitive search
    "-n": bool | None,                 # Show line numbers
    "-B": int | None,                  # Lines to show before each match
    "-A": int | None,                  # Lines to show after each match
    "-C": int | None,                  # Lines to show before and after
    "head_limit": int | None,          # Limit output to first N lines/entries
    "multiline": bool | None           # Enable multiline mode
}
```

**Output (content mode):**

```python  theme={null}
{
    "matches": [
        {
            "file": str,
            "line_number": int | None,
            "line": str,
            "before_context": list[str] | None,
            "after_context": list[str] | None
        }
    ],
    "total_matches": int
}
```

**Output (files\_with\_matches mode):**

```python  theme={null}
{
    "files": list[str],  # Files containing matches
    "count": int         # Number of files with matches
}
```

### NotebookEdit

**Tool name:** `NotebookEdit`

**Input:**

```python  theme={null}
{
    "notebook_path": str,                     # Absolute path to the Jupyter notebook
    "cell_id": str | None,                    # The ID of the cell to edit
    "new_source": str,                        # The new source for the cell
    "cell_type": "code" | "markdown" | None,  # The type of the cell
    "edit_mode": "replace" | "insert" | "delete" | None  # Edit operation type
}
```

**Output:**

```python  theme={null}
{
    "message": str,                              # Success message
    "edit_type": "replaced" | "inserted" | "deleted",  # Type of edit performed
    "cell_id": str | None,                       # Cell ID that was affected
    "total_cells": int                           # Total cells in notebook after edit
}
```

### WebFetch

**Tool name:** `WebFetch`

**Input:**

```python  theme={null}
{
    "url": str,     # The URL to fetch content from
    "prompt": str   # The prompt to run on the fetched content
}
```

**Output:**

```python  theme={null}
{
    "response": str,           # AI model's response to the prompt
    "url": str,                # URL that was fetched
    "final_url": str | None,   # Final URL after redirects
    "status_code": int | None  # HTTP status code
}
```

### WebSearch

**Tool name:** `WebSearch`

**Input:**

```python  theme={null}
{
    "query": str,                        # The search query to use
    "allowed_domains": list[str] | None, # Only include results from these domains
    "blocked_domains": list[str] | None  # Never include results from these domains
}
```

**Output:**

```python  theme={null}
{
    "results": [
        {
            "title": str,
            "url": str,
            "snippet": str,
            "metadata": dict | None
        }
    ],
    "total_results": int,
    "query": str
}
```

### TodoWrite

**Tool name:** `TodoWrite`

**Input:**

```python  theme={null}
{
    "todos": [
        {
            "content": str,                              # The task description
            "status": "pending" | "in_progress" | "completed",  # Task status
            "activeForm": str                            # Active form of the description
        }
    ]
}
```

**Output:**

```python  theme={null}
{
    "message": str,  # Success message
    "stats": {
        "total": int,
        "pending": int,
        "in_progress": int,
        "completed": int
    }
}
```

### BashOutput

**Tool name:** `BashOutput`

**Input:**

```python  theme={null}
{
    "bash_id": str,       # The ID of the background shell
    "filter": str | None  # Optional regex to filter output lines
}
```

**Output:**

```python  theme={null}
{
    "output": str,                                      # New output since last check
    "status": "running" | "completed" | "failed",       # Current shell status
    "exitCode": int | None                              # Exit code when completed
}
```

### KillBash

**Tool name:** `KillBash`

**Input:**

```python  theme={null}
{
    "shell_id": str  # The ID of the background shell to kill
}
```

**Output:**

```python  theme={null}
{
    "message": str,  # Success message
    "shell_id": str  # ID of the killed shell
}
```

### ExitPlanMode

**Tool name:** `ExitPlanMode`

**Input:**

```python  theme={null}
{
    "plan": str  # The plan to run by the user for approval
}
```

**Output:**

```python  theme={null}
{
    "message": str,          # Confirmation message
    "approved": bool | None  # Whether user approved the plan
}
```

### ListMcpResources

**Tool name:** `ListMcpResources`

**Input:**

```python  theme={null}
{
    "server": str | None  # Optional server name to filter resources by
}
```

**Output:**

```python  theme={null}
{
    "resources": [
        {
            "uri": str,
            "name": str,
            "description": str | None,
            "mimeType": str | None,
            "server": str
        }
    ],
    "total": int
}
```

### ReadMcpResource

**Tool name:** `ReadMcpResource`

**Input:**

```python  theme={null}
{
    "server": str,  # The MCP server name
    "uri": str      # The resource URI to read
}
```

**Output:**

```python  theme={null}
{
    "contents": [
        {
            "uri": str,
            "mimeType": str | None,
            "text": str | None,
            "blob": str | None
        }
    ],
    "server": str
}
```

## Advanced Features with ClaudeSDKClient

### Building a Continuous Conversation Interface

```python  theme={null}
from claude_agent_sdk import ClaudeSDKClient, ClaudeAgentOptions, AssistantMessage, TextBlock
import asyncio

class ConversationSession:
    """Maintains a single conversation session with Claude."""

    def __init__(self, options: ClaudeAgentOptions = None):
        self.client = ClaudeSDKClient(options)
        self.turn_count = 0

    async def start(self):
        await self.client.connect()
        print("Starting conversation session. Claude will remember context.")
        print("Commands: 'exit' to quit, 'interrupt' to stop current task, 'new' for new session")

        while True:
            user_input = input(f"\n[Turn {self.turn_count + 1}] You: ")

            if user_input.lower() == 'exit':
                break
            elif user_input.lower() == 'interrupt':
                await self.client.interrupt()
                print("Task interrupted!")
                continue
            elif user_input.lower() == 'new':
                # Disconnect and reconnect for a fresh session
                await self.client.disconnect()
                await self.client.connect()
                self.turn_count = 0
                print("Started new conversation session (previous context cleared)")
                continue

            # Send message - Claude remembers all previous messages in this session
            await self.client.query(user_input)
            self.turn_count += 1

            # Process response
            print(f"[Turn {self.turn_count}] Claude: ", end="")
            async for message in self.client.receive_response():
                if isinstance(message, AssistantMessage):
                    for block in message.content:
                        if isinstance(block, TextBlock):
                            print(block.text, end="")
            print()  # New line after response

        await self.client.disconnect()
        print(f"Conversation ended after {self.turn_count} turns.")

async def main():
    options = ClaudeAgentOptions(
        allowed_tools=["Read", "Write", "Bash"],
        permission_mode="acceptEdits"
    )
    session = ConversationSession(options)
    await session.start()

# Example conversation:
# Turn 1 - You: "Create a file called hello.py"
# Turn 1 - Claude: "I'll create a hello.py file for you..."
# Turn 2 - You: "What's in that file?"
# Turn 2 - Claude: "The hello.py file I just created contains..." (remembers!)
# Turn 3 - You: "Add a main function to it"
# Turn 3 - Claude: "I'll add a main function to hello.py..." (knows which file!)

asyncio.run(main())
```

### Using Hooks for Behavior Modification

```python  theme={null}
from claude_agent_sdk import (
    ClaudeSDKClient,
    ClaudeAgentOptions,
    HookMatcher,
    HookContext
)
import asyncio
from typing import Any

async def pre_tool_logger(
    input_data: dict[str, Any],
    tool_use_id: str | None,
    context: HookContext
) -> dict[str, Any]:
    """Log all tool usage before execution."""
    tool_name = input_data.get('tool_name', 'unknown')
    print(f"[PRE-TOOL] About to use: {tool_name}")

    # You can modify or block the tool execution here
    if tool_name == "Bash" and "rm -rf" in str(input_data.get('tool_input', {})):
        return {
            'hookSpecificOutput': {
                'hookEventName': 'PreToolUse',
                'permissionDecision': 'deny',
                'permissionDecisionReason': 'Dangerous command blocked'
            }
        }
    return {}

async def post_tool_logger(
    input_data: dict[str, Any],
    tool_use_id: str | None,
    context: HookContext
) -> dict[str, Any]:
    """Log results after tool execution."""
    tool_name = input_data.get('tool_name', 'unknown')
    print(f"[POST-TOOL] Completed: {tool_name}")
    return {}

async def user_prompt_modifier(
    input_data: dict[str, Any],
    tool_use_id: str | None,
    context: HookContext
) -> dict[str, Any]:
    """Add context to user prompts."""
    original_prompt = input_data.get('prompt', '')

    # Add timestamp to all prompts
    from datetime import datetime
    timestamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S")

    return {
        'hookSpecificOutput': {
            'hookEventName': 'UserPromptSubmit',
            'updatedPrompt': f"[{timestamp}] {original_prompt}"
        }
    }

async def main():
    options = ClaudeAgentOptions(
        hooks={
            'PreToolUse': [
                HookMatcher(hooks=[pre_tool_logger]),
                HookMatcher(matcher='Bash', hooks=[pre_tool_logger])
            ],
            'PostToolUse': [
                HookMatcher(hooks=[post_tool_logger])
            ],
            'UserPromptSubmit': [
                HookMatcher(hooks=[user_prompt_modifier])
            ]
        },
        allowed_tools=["Read", "Write", "Bash"]
    )

    async with ClaudeSDKClient(options=options) as client:
        await client.query("List files in current directory")

        async for message in client.receive_response():
            # Hooks will automatically log tool usage
            pass

asyncio.run(main())
```

### Real-time Progress Monitoring

```python  theme={null}
from claude_agent_sdk import (
    ClaudeSDKClient,
    ClaudeAgentOptions,
    AssistantMessage,
    ToolUseBlock,
    ToolResultBlock,
    TextBlock
)
import asyncio

async def monitor_progress():
    options = ClaudeAgentOptions(
        allowed_tools=["Write", "Bash"],
        permission_mode="acceptEdits"
    )

    async with ClaudeSDKClient(options=options) as client:
        await client.query(
            "Create 5 Python files with different sorting algorithms"
        )

        # Monitor progress in real-time
        files_created = []
        async for message in client.receive_messages():
            if isinstance(message, AssistantMessage):
                for block in message.content:
                    if isinstance(block, ToolUseBlock):
                        if block.name == "Write":
                            file_path = block.input.get("file_path", "")
                            print(f"🔨 Creating: {file_path}")
                    elif isinstance(block, ToolResultBlock):
                        print(f"✅ Completed tool execution")
                    elif isinstance(block, TextBlock):
                        print(f"💭 Claude says: {block.text[:100]}...")

            # Check if we've received the final result
            if hasattr(message, 'subtype') and message.subtype in ['success', 'error']:
                print(f"\n🎯 Task completed!")
                break

asyncio.run(monitor_progress())
```

## Example Usage

### Basic file operations (using query)

```python  theme={null}
from claude_agent_sdk import query, ClaudeAgentOptions, AssistantMessage, ToolUseBlock
import asyncio

async def create_project():
    options = ClaudeAgentOptions(
        allowed_tools=["Read", "Write", "Bash"],
        permission_mode='acceptEdits',
        cwd="/home/user/project"
    )

    async for message in query(
        prompt="Create a Python project structure with setup.py",
        options=options
    ):
        if isinstance(message, AssistantMessage):
            for block in message.content:
                if isinstance(block, ToolUseBlock):
                    print(f"Using tool: {block.name}")

asyncio.run(create_project())
```

### Error handling

```python  theme={null}
from claude_agent_sdk import (
    query,
    CLINotFoundError,
    ProcessError,
    CLIJSONDecodeError
)

try:
    async for message in query(prompt="Hello"):
        print(message)
except CLINotFoundError:
    print("Please install Claude Code: npm install -g @anthropic-ai/claude-code")
except ProcessError as e:
    print(f"Process failed with exit code: {e.exit_code}")
except CLIJSONDecodeError as e:
    print(f"Failed to parse response: {e}")
```

### Streaming mode with client

```python  theme={null}
from claude_agent_sdk import ClaudeSDKClient
import asyncio

async def interactive_session():
    async with ClaudeSDKClient() as client:
        # Send initial message
        await client.query("What's the weather like?")

        # Process responses
        async for msg in client.receive_response():
            print(msg)

        # Send follow-up
        await client.query("Tell me more about that")

        # Process follow-up response
        async for msg in client.receive_response():
            print(msg)

asyncio.run(interactive_session())
```

### Using custom tools with ClaudeSDKClient

```python  theme={null}
from claude_agent_sdk import (
    ClaudeSDKClient,
    ClaudeAgentOptions,
    tool,
    create_sdk_mcp_server,
    AssistantMessage,
    TextBlock
)
import asyncio
from typing import Any

# Define custom tools with @tool decorator
@tool("calculate", "Perform mathematical calculations", {"expression": str})
async def calculate(args: dict[str, Any]) -> dict[str, Any]:
    try:
        result = eval(args["expression"], {"__builtins__": {}})
        return {
            "content": [{
                "type": "text",
                "text": f"Result: {result}"
            }]
        }
    except Exception as e:
        return {
            "content": [{
                "type": "text",
                "text": f"Error: {str(e)}"
            }],
            "is_error": True
        }

@tool("get_time", "Get current time", {})
async def get_time(args: dict[str, Any]) -> dict[str, Any]:
    from datetime import datetime
    current_time = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    return {
        "content": [{
            "type": "text",
            "text": f"Current time: {current_time}"
        }]
    }

async def main():
    # Create SDK MCP server with custom tools
    my_server = create_sdk_mcp_server(
        name="utilities",
        version="1.0.0",
        tools=[calculate, get_time]
    )

    # Configure options with the server
    options = ClaudeAgentOptions(
        mcp_servers={"utils": my_server},
        allowed_tools=[
            "mcp__utils__calculate",
            "mcp__utils__get_time"
        ]
    )

    # Use ClaudeSDKClient for interactive tool usage
    async with ClaudeSDKClient(options=options) as client:
        await client.query("What's 123 * 456?")

        # Process calculation response
        async for message in client.receive_response():
            if isinstance(message, AssistantMessage):
                for block in message.content:
                    if isinstance(block, TextBlock):
                        print(f"Calculation: {block.text}")

        # Follow up with time query
        await client.query("What time is it now?")

        async for message in client.receive_response():
            if isinstance(message, AssistantMessage):
                for block in message.content:
                    if isinstance(block, TextBlock):
                        print(f"Time: {block.text}")

asyncio.run(main())
```

## See also

* [Python SDK guide](/en/api/agent-sdk/python) - Tutorial and examples
* [SDK overview](/en/api/agent-sdk/overview) - General SDK concepts
* [TypeScript SDK reference](/en/docs/claude-code/typescript-sdk-reference) - TypeScript SDK documentation
* [CLI reference](/en/docs/claude-code/cli-reference) - Command-line interface
* [Common workflows](/en/docs/claude-code/common-workflows) - Step-by-step guides