hooks-creator

Hooks Creator

Create Claude Code hooks - shell commands that execute automatically at specific lifecycle points.

Quick Reference: Hook Events

Workflow

Step 1: Determine Hook Requirements

Ask the user:

1. What should trigger the hook? (which event from table above)
2. What should the hook do? (the action to take)
3. Should it block/modify behavior? (for events that support blocking)

Step 2: Determine Installation Scope

Ask where to install the hook:

For user-level hooks, ask which profile or if using default ~/.claude/.

Step 3: Create the Hook

Configuration Format

{
  "hooks": {
    "EventName": [
      {
        "matcher": "ToolPattern",
        "hooks": [
          {
            "type": "command",
            "command": "path/to/script.py",
            "timeout": 60
          }
        ]
      }
    ]
  }
}

Matcher Patterns

• Exact match: "Write" - matches only Write tool
• Wildcard: "*" or "" - matches all tools
• Regex: "Edit|Write" - matches Edit OR Write
• MCP tools: "mcp__server__tool" pattern

Events WITHOUT matcher support: UserPromptSubmit, Stop, SubagentStop, SessionEnd

Hook Script Template

Create a Python script that:

1. Reads JSON from stdin
2. Processes the input
3. Outputs JSON for control (optional)
4. Exits with appropriate code

#!/usr/bin/env python3
import json
import sys

try:
    input_data = json.load(sys.stdin)
except json.JSONDecodeError:
    sys.exit(0)

# Process input_data based on hook event
# Common fields: session_id, transcript_path, cwd, permission_mode, hook_event_name

# Exit codes:
#   0 = Success (allow)
#   2 = Block (stderr used as error message)
#   other = Non-blocking error

sys.exit(0)

Step 4: Hook Input/Output Reference

See references/hook-events.md for detailed input/output fields per event.

See references/examples.md for complete working examples.

Environment Variables

Security Considerations

• Hooks run with your user credentials
• Always validate and sanitize inputs
• Quote shell variables: "$CLAUDE_PROJECT_DIR"
• Block path traversal: reject paths with ..
• Set reasonable timeouts (default 60s)
• Never access .env, credentials, private keys