Claude Code

Claude Code hooks: format on save, block risky edits, get notified

How do I run a command automatically when Claude Code edits a file?

Add a hooks block to .claude/settings.json (project) or ~/.claude/settings.json (user). A PostToolUse hook with matcher "Edit|Write" runs after every file edit; a PreToolUse hook that exits with code 2 blocks the action and sends its stderr back as the reason. Type /hooks in Claude Code to see what is configured.

Format every file Claude edits

.claude/settings.json

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

Block edits to protected files

Hooks receive the tool call as JSON on stdin. Exit 0 to allow, exit 2 to block with a reason on stderr. Make the script executable with chmod +x.

.claude/hooks/protect-files.sh

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

.claude/settings.json

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Edit|Write",
        "hooks": [
          { "type": "command", "command": "\"$CLAUDE_PROJECT_DIR\"/.claude/hooks/protect-files.sh" }
        ]
      }
    ]
  }
}

Other useful events

  • Notification: fires when Claude is waiting for input or permission; pair it with a desktop notification command.
  • SessionStart with matcher "compact": re-inject key context after the conversation is compacted.
  • Hooks are deterministic: use them for rules that must always hold, and CLAUDE.md for guidance.

Sources

Claude Code: Automate actions with hooks

More on Claude Code

Claude Code standards supportAdd MCP servers to Claude Code

Other guides

Cursor: allow all terminal commandsClaude Code: allow commands without promptsCodex CLI: approval and sandbox modesGemini CLI: YOLO mode, auto_edit and allowing specific shell commandsCursor Privacy Mode: telemetry, training and data retentionClaude Code telemetry and data retention: what is sent and how to turn it offGemini CLI: turn off usage statistics and telemetryCLAUDE.md: where it goes, how it loads, and how it works with AGENTS.mdClaude Code subagents: create one, limit its tools, and call it

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Reviewed Oct 6, 2026. Settings change often; the linked vendor docs are the source of truth.