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Implement control protocol support for Python SDK (#139)
## Summary

This PR implements control protocol support in the Python SDK, aligning
it with the TypeScript implementation pattern. The refactor introduces a
Query + Transport separation to enable bidirectional communication
between the SDK and CLI.

## Motivation

The previous Python SDK implementation used a high-level abstraction in
the Transport ABC (`send_request`/`receive_messages`) that couldn't
handle bidirectional communication. This prevented support for:
- Control messages from CLI to SDK that need responses
- Hooks implementation  
- Dynamic permission mode changes
- SDK MCP servers

## Changes

### Core Architecture Refactor

1. **New Query Class** (`src/claude_code_sdk/_internal/query.py`)
   - Manages control protocol on top of Transport
   - Handles control request/response routing
   - Manages initialization handshake with timeout
   - Supports hook callbacks and tool permission callbacks
   - Implements message streaming

2. **Refactored Transport ABC**
(`src/claude_code_sdk/_internal/transport/__init__.py`)
- Changed from high-level (`send_request`/`receive_messages`) to
low-level (`write`/`read_messages`) interface
   - Now handles raw I/O instead of protocol logic
   - Aligns with TypeScript ProcessTransport pattern

3. **Updated SubprocessCLITransport**
(`src/claude_code_sdk/_internal/transport/subprocess_cli.py`)
   - Simplified to focus on raw message streaming
   - Removed protocol logic (moved to Query)
   - Improved cleanup and error handling

4. **Enhanced ClaudeSDKClient** (`src/claude_code_sdk/client.py`)
   - Now uses Query for control protocol
   - Supports initialization messages
   - Better error handling for control protocol failures

### Control Protocol Features

- **Initialization handshake**: SDK sends initialize request, CLI
responds with supported commands
- **Control message types**: 
  - `initialize`: Establish bidirectional connection
  - `interrupt`: Cancel ongoing operations  
  - `set_permission_mode`: Change permission mode dynamically
- **Timeout handling**: 60-second timeout for initialization to handle
CLI versions without control support

### Examples

Updated `examples/streaming_mode.py` to demonstrate control protocol
initialization and error handling.

## Testing

- Tested with current CLI (no control protocol support yet) - gracefully
falls back
- Verified backward compatibility with existing `query()` function
- Tested initialization timeout handling
- Verified proper cleanup on errors

## Design Alignment

This implementation closely follows the TypeScript reference:
- `src/core/Query.ts` → `src/claude_code_sdk/_internal/query.py`
- `src/transport/ProcessTransport.ts` →
`src/claude_code_sdk/_internal/transport/subprocess_cli.py`
- `src/entrypoints/sdk.ts` → `src/claude_code_sdk/client.py`

## Next Steps

Once the CLI implements the control protocol handler, this will enable:
- Hooks support
- Dynamic permission mode changes
- SDK MCP servers
- Improved error recovery

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Ashwin Bhat <ashwin@anthropic.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Kashyap Murali <kashyap@anthropic.com>
2025-09-01 23:04:22 -07:00
.github/workflows fix pytest allowed tool (#117) 2025-08-06 16:03:30 -07:00
examples Implement control protocol support for Python SDK (#139) 2025-09-01 23:04:22 -07:00
scripts Fix "Publish to PyPI" workflow: Add commit signing and improve diff (#82) 2025-07-21 09:53:24 -07:00
src/claude_code_sdk Implement control protocol support for Python SDK (#139) 2025-09-01 23:04:22 -07:00
tests Implement control protocol support for Python SDK (#139) 2025-09-01 23:04:22 -07:00
.gitignore Implement control protocol support for Python SDK (#139) 2025-09-01 23:04:22 -07:00
CHANGELOG.md Support --add-dir flag (#104) 2025-07-31 20:52:30 -07:00
CLAUDE.md Fix lint and test 2025-07-19 20:04:58 -07:00
LICENSE Initial Python SDK import 2025-06-12 00:16:19 -07:00
pyproject.toml chore: bump version to 0.0.20 (#121) 2025-08-14 08:45:28 -07:00
README.md fix: update the tool list in README.md 2025-06-27 06:30:54 +10:00

Claude Code SDK for Python

Python SDK for Claude Code. See the Claude Code SDK documentation for more information.

Installation

pip install claude-code-sdk

Prerequisites:

  • Python 3.10+
  • Node.js
  • Claude Code: npm install -g @anthropic-ai/claude-code

Quick Start

import anyio
from claude_code_sdk import query

async def main():
    async for message in query(prompt="What is 2 + 2?"):
        print(message)

anyio.run(main)

Usage

Basic Query

from claude_code_sdk import query, ClaudeCodeOptions, AssistantMessage, TextBlock

# Simple query
async for message in query(prompt="Hello Claude"):
    if isinstance(message, AssistantMessage):
        for block in message.content:
            if isinstance(block, TextBlock):
                print(block.text)

# With options
options = ClaudeCodeOptions(
    system_prompt="You are a helpful assistant",
    max_turns=1
)

async for message in query(prompt="Tell me a joke", options=options):
    print(message)

Using Tools

options = ClaudeCodeOptions(
    allowed_tools=["Read", "Write", "Bash"],
    permission_mode='acceptEdits'  # auto-accept file edits
)

async for message in query(
    prompt="Create a hello.py file", 
    options=options
):
    # Process tool use and results
    pass

Working Directory

from pathlib import Path

options = ClaudeCodeOptions(
    cwd="/path/to/project"  # or Path("/path/to/project")
)

API Reference

query(prompt, options=None)

Main async function for querying Claude.

Parameters:

  • prompt (str): The prompt to send to Claude
  • options (ClaudeCodeOptions): Optional configuration

Returns: AsyncIterator[Message] - Stream of response messages

Types

See src/claude_code_sdk/types.py for complete type definitions:

  • ClaudeCodeOptions - Configuration options
  • AssistantMessage, UserMessage, SystemMessage, ResultMessage - Message types
  • TextBlock, ToolUseBlock, ToolResultBlock - Content blocks

Error Handling

from claude_code_sdk import (
    ClaudeSDKError,      # Base error
    CLINotFoundError,    # Claude Code not installed
    CLIConnectionError,  # Connection issues
    ProcessError,        # Process failed
    CLIJSONDecodeError,  # JSON parsing issues
)

try:
    async for message in query(prompt="Hello"):
        pass
except CLINotFoundError:
    print("Please install 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}")

See src/claude_code_sdk/_errors.py for all error types.

Available Tools

See the Claude Code documentation for a complete list of available tools.

Examples

See examples/quick_start.py for a complete working example.

License

MIT