270 lines
9.6 KiB
Markdown
270 lines
9.6 KiB
Markdown
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# Agent SDK — Python
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The Claude Agent SDK provides a higher-level interface for building AI agents with built-in tools, safety features, and agentic capabilities.
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## Installation
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```bash
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pip install claude-agent-sdk
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```
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---
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## Quick Start
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```python
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import anyio
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from claude_agent_sdk import query, ClaudeAgentOptions, ResultMessage
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async def main():
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async for message in query(
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prompt="Explain this codebase",
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options=ClaudeAgentOptions(allowed_tools=["Read", "Glob", "Grep"])
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):
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if isinstance(message, ResultMessage):
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print(message.result)
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anyio.run(main)
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```
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---
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## Built-in Tools
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| Tool | Description |
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| --------- | ------------------------------------ |
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| Read | Read files in the workspace |
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| Write | Create new files |
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| Edit | Make precise edits to existing files |
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| Bash | Execute shell commands |
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| Glob | Find files by pattern |
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| Grep | Search files by content |
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| WebSearch | Search the web for information |
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| WebFetch | Fetch and analyze web pages |
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| AskUserQuestion | Ask user clarifying questions |
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| Agent | Spawn subagents |
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---
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## Primary Interfaces
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### `query()` — Simple One-Shot Usage
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The `query()` function is the simplest way to run an agent. It returns an async iterator of messages.
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```python
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from claude_agent_sdk import query, ClaudeAgentOptions, ResultMessage
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async for message in query(
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prompt="Explain this codebase",
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options=ClaudeAgentOptions(allowed_tools=["Read", "Glob", "Grep"])
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):
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if isinstance(message, ResultMessage):
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print(message.result)
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```
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### `ClaudeSDKClient` — Full Control
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`ClaudeSDKClient` provides full control over the agent lifecycle. Use it when you need custom tools, hooks, streaming, or the ability to interrupt execution.
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```python
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import anyio
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from claude_agent_sdk import ClaudeSDKClient, ClaudeAgentOptions, AssistantMessage, TextBlock
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async def main():
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options = ClaudeAgentOptions(allowed_tools=["Read", "Glob", "Grep"])
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async with ClaudeSDKClient(options=options) as client:
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await client.query("Explain this codebase")
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async for message in client.receive_response():
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if isinstance(message, AssistantMessage):
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for block in message.content:
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if isinstance(block, TextBlock):
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print(block.text)
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anyio.run(main)
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```
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`ClaudeSDKClient` supports:
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- **Context manager** (`async with`) for automatic resource cleanup
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- **`client.query(prompt)`** to send a prompt to the agent
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- **`receive_response()`** for streaming messages until completion
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- **`interrupt()`** to stop agent execution mid-task
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- **Required for custom tools** (via SDK MCP servers)
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---
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## Permission System
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```python
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from claude_agent_sdk import query, ClaudeAgentOptions, ResultMessage
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async for message in query(
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prompt="Refactor the authentication module",
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options=ClaudeAgentOptions(
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allowed_tools=["Read", "Edit", "Write"],
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permission_mode="acceptEdits" # Auto-accept file edits
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)
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):
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if isinstance(message, ResultMessage):
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print(message.result)
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```
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Permission modes:
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- `"default"`: Prompt for dangerous operations
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- `"plan"`: Planning only, no execution
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- `"acceptEdits"`: Auto-accept file edits
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- `"dontAsk"`: Don't prompt (useful for CI/CD)
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- `"bypassPermissions"`: Skip all prompts (requires `allow_dangerously_skip_permissions=True` in options)
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---
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## MCP (Model Context Protocol) Support
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```python
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from claude_agent_sdk import query, ClaudeAgentOptions, ResultMessage
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async for message in query(
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prompt="Open example.com and describe what you see",
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options=ClaudeAgentOptions(
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mcp_servers={
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"playwright": {"command": "npx", "args": ["@playwright/mcp@latest"]}
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}
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)
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):
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if isinstance(message, ResultMessage):
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print(message.result)
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```
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---
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## Hooks
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Customize agent behavior with hooks using callback functions:
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```python
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from claude_agent_sdk import query, ClaudeAgentOptions, HookMatcher, ResultMessage
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async def log_file_change(input_data, tool_use_id, context):
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file_path = input_data.get('tool_input', {}).get('file_path', 'unknown')
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print(f"Modified: {file_path}")
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return {}
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async for message in query(
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prompt="Refactor utils.py",
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options=ClaudeAgentOptions(
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permission_mode="acceptEdits",
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hooks={
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"PostToolUse": [HookMatcher(matcher="Edit|Write", hooks=[log_file_change])]
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}
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)
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):
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if isinstance(message, ResultMessage):
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print(message.result)
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```
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Available hook events: `PreToolUse`, `PostToolUse`, `PostToolUseFailure`, `Notification`, `UserPromptSubmit`, `SessionStart`, `SessionEnd`, `Stop`, `SubagentStart`, `SubagentStop`, `PreCompact`, `PermissionRequest`, `Setup`, `TeammateIdle`, `TaskCompleted`, `ConfigChange`
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---
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## Common Options
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`query()` takes a top-level `prompt` (string) and an `options` object (`ClaudeAgentOptions`):
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```python
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async for message in query(prompt="...", options=ClaudeAgentOptions(...)):
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```
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| Option | Type | Description |
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| ----------------------------------- | ------ | -------------------------------------------------------------------------- |
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| `cwd` | string | Working directory for file operations |
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| `allowed_tools` | list | Tools the agent can use (e.g., `["Read", "Edit", "Bash"]`) |
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| `tools` | list | Built-in tools to make available (restricts the default set) |
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| `disallowed_tools` | list | Tools to explicitly disallow |
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| `permission_mode` | string | How to handle permission prompts |
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| `allow_dangerously_skip_permissions`| bool | Must be `True` to use `permission_mode="bypassPermissions"` |
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| `mcp_servers` | dict | MCP servers to connect to |
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| `hooks` | dict | Hooks for customizing behavior |
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| `system_prompt` | string | Custom system prompt |
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| `max_turns` | int | Maximum agent turns before stopping |
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| `max_budget_usd` | float | Maximum budget in USD for the query |
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| `model` | string | Model ID (default: determined by CLI) |
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| `agents` | dict | Subagent definitions (`dict[str, AgentDefinition]`) |
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| `output_format` | dict | Structured output schema |
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| `thinking` | dict | Thinking/reasoning control |
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| `betas` | list | Beta features to enable (e.g., `["context-1m-2025-08-07"]`) |
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| `setting_sources` | list | Settings to load (e.g., `["project"]`). Default: none (no CLAUDE.md files) |
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| `env` | dict | Environment variables to set for the session |
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---
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## Message Types
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```python
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from claude_agent_sdk import query, ClaudeAgentOptions, ResultMessage, SystemMessage
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async for message in query(
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prompt="Find TODO comments",
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options=ClaudeAgentOptions(allowed_tools=["Read", "Glob", "Grep"])
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):
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if isinstance(message, ResultMessage):
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print(message.result)
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elif isinstance(message, SystemMessage) and message.subtype == "init":
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session_id = message.session_id # Capture for resuming later
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```
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---
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## Subagents
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```python
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from claude_agent_sdk import query, ClaudeAgentOptions, AgentDefinition, ResultMessage
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async for message in query(
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prompt="Use the code-reviewer agent to review this codebase",
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options=ClaudeAgentOptions(
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allowed_tools=["Read", "Glob", "Grep", "Agent"],
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agents={
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"code-reviewer": AgentDefinition(
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description="Expert code reviewer for quality and security reviews.",
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prompt="Analyze code quality and suggest improvements.",
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tools=["Read", "Glob", "Grep"]
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)
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}
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)
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):
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if isinstance(message, ResultMessage):
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print(message.result)
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```
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---
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## Error Handling
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```python
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from claude_agent_sdk import query, ClaudeAgentOptions, CLINotFoundError, CLIConnectionError, ResultMessage
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try:
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async for message in query(
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prompt="...",
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options=ClaudeAgentOptions(allowed_tools=["Read"])
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):
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if isinstance(message, ResultMessage):
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print(message.result)
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except CLINotFoundError:
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print("Claude Code CLI not found. Install with: pip install claude-agent-sdk")
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except CLIConnectionError as e:
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print(f"Connection error: {e}")
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```
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---
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## Best Practices
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1. **Always specify allowed_tools** — Explicitly list which tools the agent can use
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2. **Set working directory** — Always specify `cwd` for file operations
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3. **Use appropriate permission modes** — Start with `"default"` and only escalate when needed
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4. **Handle all message types** — Check for `ResultMessage` to get agent output
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5. **Limit max_turns** — Prevent runaway agents with reasonable limits
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