Hook Development

Claude Code plugin hooks are event-driven triggers enabling automation and prompt-based validation. They execute bash commands or leverage LLM reasoning during events like PreToolUse, PostToolUse, and SessionStart to validate file operations or load project context dynamically.

To create a PreToolUse hook for validating file write operations, configure a prompt-based or command hook in your hooks.json file. Use matchers to target specific tool calls, allowing the hook to intercept and validate file paths before Claude executes the write action.

Prompt-based hooks leverage LLM reasoning for context-aware validation and complex decision-making, while command hooks execute deterministic bash commands for straightforward file operations and external integrations without requiring language model processing.

Yes, you can use SessionStart hooks to load project context and environment variables automatically. Configuring this hook event ensures required variables are initialized and available before executing subsequent automation tasks within your Claude Code session.

Implementing Claude Code hooks requires following security best practices to prevent unauthorized path modifications and considering performance impacts of prompt-based validation. Apply proper matchers and debug techniques to ensure hooks execute efficiently without stalling processes.