Claude Code hooks are powerful configuration tools that allow you to customize and extend Claude’s behavior at various stages of interaction. They enable you to run shell commands automatically when certain events occur, making your development workflow more efficient and automated.

What are Claude Code hooks?

Hooks in Claude Code are shell commands or scripts that execute automatically in response to specific events during your interaction with Claude. They’re configured through JSON settings files and can help automate repetitive tasks, enforce code quality standards, or integrate Claude with your existing development tools.

Types of hooks

Claude Code supports several types of hooks that trigger at different stages:

PreToolUse

Runs before a specific tool is executed. Perfect for setup tasks or validation checks before Claude performs an action.

PostToolUse

Executes after a tool completes successfully. Ideal for cleanup tasks, code formatting, or running tests after file modifications.

UserPromptSubmit

Triggers when you submit a prompt to Claude. Useful for logging or preparing the environment before Claude processes your request.

SessionStart/SessionEnd

Run at the beginning or end of a Claude Code session. Great for environment setup or cleanup operations.

Configuration

Hooks are configured in your Claude Code settings JSON file. Here’s the basic structure:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit",
        "hooks": [
          {
            "type": "command",
            "command": "npm run lint"
          }
        ]
      }
    ]
  }
}

Matchers

You can specify which tools should trigger your hooks using matchers:

• Exact tool names: "Write" or "Edit"
• Multiple tools: "Write|Edit|MultiEdit"
• Regex patterns: For more complex matching scenarios

Practical examples

Automatic code formatting

Run your code formatter whenever Claude writes or edits files:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit|MultiEdit",
        "hooks": [
          {
            "type": "command",
            "command": "prettier --write ."
          }
        ]
      }
    ]
  }
}

Running tests after code changes

Automatically run your test suite when Claude modifies code files:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit",
        "hooks": [
          {
            "type": "command",
            "command": "npm test"
          }
        ]
      }
    ]
  }
}

Custom validation scripts

Execute custom scripts to validate changes:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit",
        "hooks": [
          {
            "type": "command",
            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/check-style.sh"
          }
        ]
      }
    ]
  }
}

Session logging

Log the start and end of Claude Code sessions:

{
  "hooks": {
    "SessionStart": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "echo \"Claude Code session started at $(date)\" >> .claude-sessions.log"
          }
        ]
      }
    ],
    "SessionEnd": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "echo \"Claude Code session ended at $(date)\" >> .claude-sessions.log"
          }
        ]
      }
    ]
  }
}

When to use hooks

Code quality enforcement

• Automatically format code after changes
• Run linters to catch style issues
• Execute static analysis tools

Testing automation

• Run relevant tests when code is modified
• Execute integration tests for critical changes
• Generate test coverage reports

Development workflow integration

• Commit changes to version control
• Deploy to staging environments
• Update documentation automatically
• Rebuild applications automatically with cloud solutions like AppIsUp that integrate hooks to trigger rebuilds on every code update

Environment management

• Set up development environment variables
• Clean up temporary files
• Sync dependencies

Best practices

Security considerations

Hooks execute shell commands with full system access, so always:

• Review hook commands carefully before adding them
• Use absolute paths when possible
• Avoid running untrusted commands
• Consider using dedicated hook scripts instead of inline commands

Performance tips

• Keep hook commands lightweight and fast
• Use conditional logic in scripts to avoid unnecessary work
• Consider running expensive operations in the background

Debugging

• Test your hooks thoroughly before relying on them
• Include error handling in custom scripts
• Use logging to track hook execution

Troubleshooting

If your hooks aren’t working as expected:

1. Check the JSON syntax - Invalid JSON will prevent hooks from loading
2. Verify matcher patterns - Ensure your matchers match the intended tools
3. Test commands manually - Run the hook commands directly to verify they work
4. Check permissions - Ensure Claude Code can execute the specified commands
5. Review logs - Look for error messages related to hook execution

Conclusion

Claude Code hooks provide a powerful way to integrate Claude into your existing development workflow. By automating repetitive tasks and enforcing consistency, hooks can significantly improve your productivity and code quality. Start with simple examples and gradually build more sophisticated automation as you become comfortable with the system.

Remember to always prioritize security when configuring hooks, and test thoroughly to ensure they work reliably in your development environment.