TutorialFeb 14, 2026·Code Velocity Academy

Automate Your Dev Workflow with Claude Code Hooks

Hooks let you run custom shell commands when Claude Code takes specific actions. Auto-format on save, block dangerous edits, or inject context automatically.

Claude Code Hooks are shell commands that execute automatically in response to events. When Claude Code edits a file, runs a command, or starts a session, your hooks fire. This lets you build guardrails, enforce standards, and automate repetitive setup without manual intervention.

What hook events are available?

Event	When it fires	Common use case
PreToolUse	Before Claude executes a tool	Block dangerous operations, validate inputs
PostToolUse	After Claude executes a tool	Auto-format edited files, run linters
Notification	When Claude sends a notification	Log to file, send to Slack
SessionStart	When a new session begins	Inject context, check environment
ConfigChange	When settings change	Validate configuration

How do you create a hook?

Use the interactive menu or edit settings.json directly:

bash

# Interactive hook setup
claude /hooks

# Or edit settings.json directly
# Project: .claude/settings.json
# Global: ~/.claude/settings.json

Here's a settings.json with hooks configured:

json

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Edit|Write",
        "command": "npx prettier --write "$CLAUDE_FILE_PATH"",
        "description": "Auto-format edited files with Prettier"
      }
    ],
    "PreToolUse": [
      {
        "matcher": "Edit|Write",
        "command": "echo $CLAUDE_FILE_PATH | grep -q \.env && echo 'BLOCKED: Cannot edit .env files' && exit 1 || exit 0",
        "description": "Block edits to .env files"
      }
    ],
    "SessionStart": [
      {
        "command": "cat .claude/context-injection.md",
        "description": "Inject additional context at session start"
      }
    ]
  }
}

What are the most useful hooks?

1. Auto-format on edit

Run Prettier, Black, or gofmt every time Claude Code edits a file:

json

// PostToolUse hook
{
  "matcher": "Edit|Write",
  "command": "npx prettier --write \"$CLAUDE_FILE_PATH\""
}

2. Block sensitive file edits

Prevent Claude Code from modifying environment files, secrets, or critical configs:

json

// PreToolUse hook
{
  "matcher": "Edit|Write",
  "command": "echo $CLAUDE_FILE_PATH | grep -qE \"\.env|\.secret|credentials\" && exit 1 || exit 0"
}

3. Re-inject context after compaction

When Claude Code compacts its context window, important details can be lost. A hook can re-inject critical information:

json

// PostToolUse hook for compaction
{
  "matcher": "Compact",
  "command": "cat .claude/critical-context.md"
}

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Start with the auto-format hook. It's the highest-value hook with the lowest risk. Once you're comfortable, add file protection and context injection.

Frequently asked questions

Can a hook block Claude Code from doing something?+

Yes. PreToolUse hooks can exit with code 1 to block the action. Claude Code will see the block message and try a different approach. This is how you create guardrails for sensitive operations.

Do hooks work in headless mode?+

Yes. Hooks execute in all modes including headless (CI/CD). This makes them useful for enforcing standards in automated pipelines where no human is reviewing each action.

What environment variables are available in hooks?+

Hooks receive context through environment variables like $CLAUDE_FILE_PATH (the file being edited), $CLAUDE_TOOL_NAME (the tool being used), and $CLAUDE_SESSION_ID. The exact variables depend on the event type.

Can hooks slow down Claude Code?+

Yes, if the hook command is slow. Keep hooks fast (under 1 second). Avoid hooks that make network requests or run heavy builds. Use async logging if you need to track actions without blocking.