Hook Recipes: Format, Protect, Notify

##### ###### ##### ### # # ### # # ###### ## ## ## ## ## ## ## # # # # # ## ##### #### ##### # # # # # # # #### ## # ## ## ## ## # # # # # ## ## # ###### ## ### # ### # ######

Here are $5$ ready-to-use hook recipes. Drop them into your .claude/settings.json and adjust paths as needed.

Auto-format with Prettier after every file edit

This PostToolUse hook runs Prettier on whichever file Claude just edited.

{
  "hooks": {
    "PostToolUse": [{
      "matcher": "Edit|Write",
      "hooks": [{ "type": "command", "command": "jq -r '.tool_input.file_path' | xargs npx prettier --write" }]
    }]
  }
}

Block writes to protected files

This PreToolUse script exits with code $2$ when Claude tries to touch .env or package-lock.json. CLAUDE.md can suggest Claude avoid these files. This script makes it impossible.

#!/bin/bash
INPUT=$(cat)
FILE_PATH=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty')
PROTECTED=(".env" "package-lock.json")
for pattern in "${PROTECTED[@]}"; do
  if [[ "$FILE_PATH" == *"$pattern"* ]]; then
    echo "Blocked: $FILE_PATH is protected" >&2
    exit 2
  fi
done
exit 0

Desktop notification when Claude stops

When you're working in another window and Claude finishes, this Stop hook pings you.

# macOS
osascript -e 'display notification "Claude needs your attention" with title "Claude Code"'

# Linux
notify-send 'Claude Code' 'Needs your attention'

Always include this guard at the top of a Stop hook to prevent an infinite loop:

INPUT=$(cat)
if [ "$(echo "$INPUT" | jq -r '.stop_hook_active')" = "true" ]; then
  exit 0
fi

Run tests asynchronously after edits

async: true means Claude doesn't wait for the tests before continuing.

{
  "hooks": {
    "PostToolUse": [{
      "matcher": "Write|Edit",
      "hooks": [{ "type": "command", "command": ".claude/hooks/run-tests.sh", "async": true, "timeout": 300 }]
    }]
  }
}

Re-inject context after compaction

A SessionStart hook fires when the session opens and can echo constants back into context.

{
  "hooks": {
    "SessionStart": [{
      "matcher": "compact",
      "hooks": [{ "type": "command", "command": "echo 'Use Bun, not npm. Current sprint: auth refactor.'" }]
    }]
  }
}