Available hook events with timing:

1. SessionStart
   • When it fires: Claude Code starts a new session or resumes existing one
   • Why useful: Load development context, set environment variables, check git status
   • Payload: Source type (startup/resume/clear), session information
   • Example use: Auto-load recent issues, check git status, prime development context
2. UserPromptSubmit
   • When it fires: Immediately when user submits a prompt (before Claude processes it)
   • Why useful: Validate prompts, inject context, add security filtering, enhance requests
   • Payload: Prompt text, session_id, timestamp
   • Example use: Add automatic context injection, validate dangerous requests, log all prompts
3. PreToolUse
   • When it fires: Before any tool execution (can block dangerous commands)
   • Why useful: Security validation, permission checking, command filtering
   • Payload: Tool name, tool input parameters
   • Example use: Block rm -rf commands, prevent .env file access, validate file paths
4. PostToolUse
   • When it fires: After successful tool completion
   • Why useful: Automatic formatting, testing, logging, notification sending
   • Payload: Tool name, input parameters, tool response with results
   • Example use: Auto-format code after editing, run tests after changes, update docs
5. Stop
   • When it fires: When conversation stops or user disconnects
   • Why useful: Cleanup tasks, final commits, summary generation
   • Payload: Session summary, final state
   • Example use: Auto-commit changes, send summary reports, cleanup temp files
6. Notification
   • When it fires: When Claude Code sends notifications (waiting for input, etc.)
   • Why useful: Custom alerts, text-to-speech, external notifications
   • Payload: Message content, notification type
   • Example use: Desktop notifications, TTS alerts, Slack messages