Hook Development Rules

When working with files in .claude/hooks/:

Pattern

Shell wrapper (.sh) → TypeScript (.ts) via npx tsx

Shell Wrapper Template

!/bin/bash

set -e cd "$CLAUDE_PROJECT_DIR/.claude/hooks" cat | npx tsx .ts

TypeScript Handler Pattern interface HookInput { // Event-specific fields }

async function main() { const input: HookInput = JSON.parse(await readStdin());

// Process input

const output = { result: 'continue', // or 'block' message: 'Optional system reminder' };

console.log(JSON.stringify(output)); }

Hook Events PreToolUse - Before tool execution (can block) PostToolUse - After tool execution UserPromptSubmit - Before processing user prompt PreCompact - Before context compaction SessionStart - On session start/resume/compact Stop - When agent finishes Testing

Test hooks manually:

echo '{"type": "resume"}' | .claude/hooks/session-start-continuity.sh

Registration

Add hooks to .claude/settings.json:

{ "hooks": { "EventName": [{ "matcher": ["pattern"], // Optional "hooks": [{ "type": "command", "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/hook.sh" }] }] } }