Claude Code Hooks Training Document

Overview

Claude Code Hooks is a groundbreaking feature released by Anthropic that allows developers to inject custom shell commands at specific lifecycle events within Claude Code's operation. This feature addresses the fundamental challenge of probabilistic AI behavior by providing deterministic control over critical development workflows[1][2].

What Are Claude Code Hooks?

Definition and Purpose

Claude Code Hooks are user-defined shell commands that execute automatically at predetermined points in Claude Code's workflow[2]. Unlike traditional prompting approaches that rely on the LLM to remember and execute commands, hooks guarantee that specific operations occur consistently without additional user intervention[1][2].

The core purpose of hooks is to bridge the gap between AI-driven assistance and rule-based automation, providing developers with:

• Deterministic Control: Ensures critical tasks always run, avoiding scenarios where the model might "forget" or choose not to execute an action[2][3]
• Workflow Automation: Eliminates repetitive manual steps by embedding them into the AI coding lifecycle[2]
• Integration: Seamlessly connects Claude Code with existing development tools and processes[2]

The Problem Hooks Solve

Large Language Models are inherently probabilistic, which means they might inconsistently execute requested actions. For instance, you might ask Claude to "always run prettier after editing a file," but the AI might not remember to do this in every instance. Hooks solve this by making such actions deterministic and automatic[1][3].

Hook Event Types

Claude Code supports four primary hook events that correspond to different stages of the AI's operation lifecycle:

1. PreToolUse

When: Runs after Claude creates tool parameters and before processing the tool call[2]

Use Cases:

• Validate code changes before they're applied
• Check for optimization principles before code generation
• Block operations that violate coding standards
• Perform pre-execution security checks

Common Tool Matchers:

• Write - File creation/overwriting
• Edit, MultiEdit - File editing operations
• Bash - Shell command execution
• Read - File reading operations
• Task - Agent task execution[2]

2. PostToolUse

When: Runs immediately after a tool completes successfully[2]

Use Cases:

• Automatic code formatting (e.g., running Prettier on TypeScript files)
• Code quality analysis and metrics calculation
• Logging of executed operations
• Backup or version control operations

3. Notification

When: Runs when Claude Code sends notifications to the user[2]

Use Cases:

• Custom notification systems (push notifications, emails, Slack messages)
• Pop-up windows for important alerts
• Integration with external monitoring systems

4. Stop

When: Runs when the main Claude Code agent has finished responding[2]

Use Cases:

• Final linting and formatting passes
• Comprehensive logging and reporting
• Cleanup operations
• Integration with CI/CD pipelines

5. SubagentStop

When: Runs when a Claude Code subagent (Task tool call) has finished responding[2]

Use Cases:

• Subagent-specific cleanup
• Hierarchical logging of nested operations

Configuration and Setup

Configuration Files

Hooks are configured through JSON settings files with the following priority order:

1. User Settings: ~/.claude/settings.json
2. Project Settings: .claude/settings.json
3. Local Project Settings: .claude/settings.local.json (not committed to version control)
4. Enterprise Managed Policy Settings[2]

Configuration Structure

{
  "hooks": {
    "EventName": [
      {
        "matcher": "ToolPattern",
        "hooks": [
          {
            "type": "command",
            "command": "your-command-here",
            "timeout": 30
          }
        ]
      }
    ]
  }
}

Key Configuration Elements:

• matcher: Pattern to match tool names (supports regex patterns like Edit|Write or Notebook.*)
• hooks: Array of commands to execute when the pattern matches
• type: Currently only "command" is supported
• command: The bash command to execute
• timeout: Optional timeout in seconds before canceling the hook[2]

Example Configuration

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write",
        "hooks": [
          {
            "type": "command",
            "command": "prettier --write ."
          }
        ]
      }
    ],
    "PreToolUse": [
      {
        "matcher": "Edit|MultiEdit",
        "hooks": [
          {
            "type": "command",
            "command": "./scripts/check-optimization.sh"
          }
        ]
      }
    ]
  }
}

Advanced Use Cases and Implementation Examples

1. Optimization Gatekeeper System

Ray Fernando's livestream demonstrates creating an "optimization gatekeeper" that enforces coding principles before code generation[1]. This system:

• Blocks operations that violate predefined optimization principles
• Analyzes code against existing patterns using a "lever framework"
• Provides specific feedback to Claude when violations occur
• Forces adherence to coding standards through exit codes

Implementation Approach:

#!/bin/bash
# optimization-check.sh
input=$(cat)
if [[ "$input" =~ "creating new file" ]]; then
    echo "BLOCKED: Creating new files when similar ones exist violates optimization principles"
    exit 2
fi

2. Automated Code Quality Pipeline

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit|MultiEdit",
        "hooks": [
          {
            "type": "command",
            "command": "eslint --fix .",
            "timeout": 60
          },
          {
            "type": "command", 
            "command": "npm test",
            "timeout": 300
          }
        ]
      }
    ]
  }
}

3. Notification Integration

{
  "hooks": {
    "Notification": [
      {
        "matcher": "",
        "hooks": [
          {
            "type": "command",
            "command": "notify-send 'Claude Code' 'Requires your attention'"
          }
        ]
      }
    ]
  }
}

4. Automatic Version Control

{
  "hooks": {
    "Stop": [
      {
        "matcher": "",
        "hooks": [
          {
            "type": "command",
            "command": "jj commit -m 'automatic commit'"
          }
        ]
      }
    ]
  }
}

Integration with Development Workflows

Cursor IDE Integration

Claude Code integrates seamlessly with Cursor IDE through several mechanisms:

• /IDE command: Integrates Claude Code directly with the IDE interface
• File selection: Claude Code automatically picks up selected files and lines
• New window mode: Pop out Claude Code into a separate window for multi-monitor workflows[1]

Command Line Interface

Essential Commands:

• claude - Start Claude Code session
• claude --resume or claude -r - Resume previous chat sessions
• bunXCC usage - Check Claude Code usage and costs (requires Bun)[1]

Ultra Think Mode

Ultra Think is a special keyword that provides Claude with a larger thinking window (up to 32,000 tokens) for complex analysis tasks. This is particularly useful when:

• Analyzing extensive documentation
• Following complex optimization principles
• Performing deep code reviews
• Working with large rule sets[1]

Security Considerations

Permissions and Safety

⚠️ Critical Security Note: Hooks execute with full user permissions without confirmation. Users are responsible for ensuring hooks are safe and secure. Anthropic is not liable for any data loss or system damage resulting from hook usage[2].

Best Practices:

• Always validate hook scripts before deployment
• Use least-privilege principles in hook commands
• Implement proper error handling and logging
• Test hooks in isolated environments first
• Review hook configurations regularly

Blocking Operations

Hooks can block operations by:

• Returning exit code 2: Prevents the operation from proceeding
• Providing feedback: Explaining why the operation was blocked
• Suggesting alternatives: Guiding Claude toward compliant solutions[1]

Advanced Features and Capabilities

Context Access

Hooks receive the full context of operations through standard input, enabling sophisticated analysis and decision-making based on:

• File paths and content being modified
• Tool parameters and arguments
• Operation metadata and context[1]

Pattern Matching

Hook matchers support:

• Exact matching: "Write" matches only the Write tool
• Regex patterns: "Edit|Write" or "Notebook.*"
• Wildcard matching: Empty string matches all events[2]

Timeout Management

Configure timeouts to prevent runaway hook processes:

{
  "type": "command",
  "command": "long-running-analysis.sh",
  "timeout": 300
}

Performance and Cost Considerations

Token Usage Management

When using "Ultra Think" mode with hooks:

• High token consumption: 5-10x more tokens than regular operations
• Strategic usage: Reserve for complex analysis tasks
• Cost awareness: Monitor usage with tools like bunXCC usage[1]

Claude Max Subscription Benefits

Ray Fernando's experience shows that the Claude Max $200/month plan provides:

• Unlimited Opus usage: No more hitting daily limits
• Consistent performance: Ability to use advanced features without constraints
• Better ROI: Pays for itself through increased productivity[1]

Real-World Applications

Convex Database Integration

The livestream demonstrates integrating hooks with Convex, a real-time reactive database system:

• Real-time updates: Frontend automatically refreshes when backend data changes
• Reduced boilerplate: Less state management code needed
• TypeScript integration: Strong typing prevents errors
• Cost-effective: Generous free tier for development[1]

Documentation Automation

Hooks can automate documentation updates:

• Auto-generate: Documentation from code changes
• Maintain consistency: Ensure docs stay in sync with code
• Organize content: Self-organize documentation into logical folders[1]

Troubleshooting and Best Practices

Common Issues

1. Hook not executing: Check matcher patterns and file permissions
2. Timeout errors: Increase timeout values for long-running operations
3. Permission errors: Ensure hooks have necessary file system access
4. Infinite loops: Avoid hooks that trigger themselves recursively[4]

Development Workflow Tips

1. Start simple: Begin with basic hooks before building complex systems
2. Test thoroughly: Use development environments to validate hook behavior
3. Monitor performance: Track hook execution times and resource usage
4. Document extensively: Maintain clear documentation of hook purposes and behaviors
5. Version control: Keep hook configurations in version control systems

Future Considerations

Emerging Patterns

The community is developing innovative hook patterns:

• Cognitive hooks: Using hooks to guide AI reasoning processes
• Workflow orchestration: Chaining multiple hooks for complex pipelines
• External integrations: Connecting with cloud services and APIs[1]

Ecosystem Development

The hooks ecosystem is rapidly expanding with:

• Community scripts: Shared hook configurations for common tasks
• Tool integrations: Plugins for popular development tools
• Template libraries: Reusable hook patterns for different use cases[5][6]

Conclusion

Claude Code Hooks represent a significant advancement in AI-assisted development, providing the deterministic control necessary for professional software development workflows. By understanding and implementing hooks effectively, developers can create robust, automated development environments that combine the creativity of AI with the reliability of traditional tooling.

The feature's power lies not just in its technical capabilities, but in its ability to ensure consistent, repeatable behaviors that can be trusted in production environments. As the ecosystem continues to evolve, hooks will likely become an essential component of modern AI-assisted development workflows.

[1] https://www.youtube.com/watch?v=fkQrySWqUa0
[2] https://js.langchain.com/docs/integrations/chat/anthropic/
[3] https://js.langchain.com/v0.2/docs/integrations/platforms/anthropic/
[4] https://www.anthropic.com/news/prompt-generator
[5] https://apidog.com/blog/claude-code-hooks/
[6] https://www.claudelog.com/faqs/what-is-hooks-in-claude-code
[7] https://docs.anthropic.com/en/docs/claude-code/hooks
[8] https://github.com/hikarubw/claude-commands
[9] https://docs.anthropic.com/en/docs/claude-code/slash-commands
[10] https://www.reddit.com/r/ClaudeAI/comments/1loodjn/claude_code_now_supports_hooks/
[11] https://docs.anthropic.com/en/docs/agents-and-tools/tool-use/bash-tool
[12] https://docs.anthropic.com/en/docs/claude-code/settings
[13] https://www.aibase.com/news/19442
[14] https://danielcorin.com/til/anthropic/claude-code/
[15] https://matthewsanabria.dev/posts/running-jujutsu-with-claude-code-hooks/
[16] https://www.reddit.com/r/ClaudeAI/comments/1lqs8rh/found_this_wild_livestream_about_claude_codes/
[17] https://www.reddit.com/r/ClaudeAI/comments/1loxkgj/how_to_run_terminal_command_inside_claude_code/
[18] https://www.cometapi.com/claude-code-hooks-what-is-and-how-to-use-it/
[19] https://news.ycombinator.com/item?id=44429225
[20] https://github.com/qdhenry/Claude-Command-Suite
[21] https://x.com/rohanpaul_ai/status/1939910693106639061