reproduce_hook_bug.py

#!/usr/bin/env python3
"""
Minimal reproduction of PreToolUse hook not being called for non-existent file paths.

This script demonstrates that PreToolUse hooks are NOT invoked when Claude calls
the Read tool with a file path that doesn't exist, contradicting the documentation
which states hooks execute "before processing the tool call".
"""
import asyncio
import logging
from pathlib import Path
from typing import Optional

from claude_agent_sdk import ClaudeAgentOptions, ClaudeSDKClient
from claude_agent_sdk.types import (
    PreToolUseHookInput,
    PreToolUseHookSpecificOutput,
    HookContext,
    HookMatcher,
)

logging.basicConfig(level=logging.INFO, format='%(message)s')
logger = logging.getLogger(__name__)


async def test_hook(
    hook_input: PreToolUseHookInput,
    _subscription_id: Optional[str],
    _context: HookContext
) -> PreToolUseHookSpecificOutput:
    """Hook that logs ALL invocations."""
    tool_name = hook_input.get("tool_name", "")
    tool_input = hook_input.get("tool_input", {})

    logger.info("=" * 80)
    logger.info(f"[HOOK CALLED] Tool: {tool_name}")
    logger.info(f"[HOOK CALLED] Input: {tool_input}")
    logger.info("=" * 80)

    return {"hookSpecificOutput": {"hookEventName": "PreToolUse"}}


async def main():
    # Setup: Create test file in /tmp
    test_dir = Path("/tmp/hook_test")
    test_dir.mkdir(exist_ok=True)
    test_file = test_dir / "test.txt"
    test_file.write_text("Hello World")

    logger.info(f"Created test file: {test_file}")
    logger.info(f"File exists: {test_file.exists()}")

    # Configure SDK with hook
    options = ClaudeAgentOptions(
        permission_mode="bypassPermissions",
        cwd=str(test_dir),
        hooks={
            "PreToolUse": [
                HookMatcher(matcher="Read", hooks=[test_hook])
            ]
        },
    )

    # Test 1: Read non-existent file (hook should fire but doesn't)
    logger.info("\n" + "=" * 80)
    logger.info("TEST 1: Reading /workspace/test.txt (DOES NOT EXIST)")
    logger.info("=" * 80)

    async with ClaudeSDKClient(options=options) as client:
        await client.query("Read the file /workspace/test.txt")
        async for _ in client.receive_response():
            pass

    # Test 2: Read existing file (hook fires)
    logger.info("\n" + "=" * 80)
    logger.info(f"TEST 2: Reading {test_file} (EXISTS)")
    logger.info("=" * 80)

    async with ClaudeSDKClient(options=options) as client:
        await client.query(f"Read the file {test_file}")
        async for _ in client.receive_response():
            pass

    logger.info("\n" + "=" * 80)
    logger.info("EXPECTED: Hook called for BOTH tests")
    logger.info("ACTUAL: Hook only called for TEST 2 (existing file)")
    logger.info("=" * 80)


if __name__ == "__main__":
    asyncio.run(main())