# Customaize Agent:create Hook > Create and configure git hooks with intelligent project analysis, suggestions, and automated testing - Skill: `gabrielmoreira/customaize-agent-create-hook` (Agent Skill) - Install (CLI): `npx skillmds@latest add gabrielmoreira/customaize-agent-create-hook` - Raw SKILL.md: https://api.skillmd.com/api/skills/gabrielmoreira/customaize-agent-create-hook/raw - Safety review: pending (external: skill-scanner PASS, skillspector FAIL) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: gabrielmoreira (https://skillmd.com/u/gabrielmoreira) - Updated: 2026-09-21 - Page: https://skillmd.com/skills/gabrielmoreira/customaize-agent-create-hook --- # Create Hook Command Analyze the project, suggest practical hooks, and create them with proper testing. ## Your Task (/create-hook) 1. **Analyze environment** - Detect tooling and existing hooks 2. **Suggest hooks** - Based on your project configuration 3. **Configure hook** - Ask targeted questions and create the script 4. **Test & validate** - Ensure the hook works correctly ## Your Workflow ### 1. Environment Analysis & Suggestions Automatically detect the project tooling and suggest relevant hooks: **When TypeScript is detected (`tsconfig.json`):** - PostToolUse hook: "Type-check files after editing" - PreToolUse hook: "Block edits with type errors" **When Prettier is detected (`.prettierrc`, `prettier.config.js`):** - PostToolUse hook: "Auto-format files after editing" - PreToolUse hook: "Require formatted code" **When ESLint is detected (`.eslintrc.*`):** - PostToolUse hook: "Lint and auto-fix after editing" - PreToolUse hook: "Block commits with linting errors" **When package.json has scripts:** - `test` script → "Run tests before commits" - `build` script → "Validate build before commits" **When a git repository is detected:** - PreToolUse/Bash hook: "Prevent commits with secrets" - PostToolUse hook: "Security scan on file changes" **Decision Tree:** ``` Project has TypeScript? → Suggest type checking hooks Project has formatter? → Suggest formatting hooks Project has tests? → Suggest test validation hooks Security sensitive? → Suggest security hooks + Scan for additional patterns and suggest custom hooks based on: - Custom scripts in package.json - Unique file patterns or extensions - Development workflow indicators - Project-specific tooling configurations ``` ### 2. Hook Configuration Start by asking: **"What should this hook do?"** and offer relevant suggestions from your analysis. Then understand the context from the user's description and **only ask about details you're unsure about**: 1. **Trigger timing**: When should it run? - `PreToolUse`: Before file operations (can block) - `PostToolUse`: After file operations (feedback/fixes) - `UserPromptSubmit`: Before processing requests - Other event types as needed 2. **Tool matcher**: Which tools should trigger it? (`Write`, `Edit`, `Bash`, `*` etc) 3. **Scope**: `global`, `project`, or `project-local` 4. **Response approach**: - **Exit codes only**: Simple (exit 0 = success, exit 2 = block in PreToolUse) - **JSON response**: Advanced control (blocking, context, decisions) - Guide based on complexity: simple pass/fail → exit codes, rich feedback → JSON 5. **Blocking behavior** (if relevant): "Should this stop operations when issues are found?" - PreToolUse: Can block operations (security, validation) - PostToolUse: Usually provide feedback only 6. **Claude integration** (CRITICAL): "Should Claude Code automatically see and fix issues this hook detects?" - If YES: Use `additionalContext` for error communication - If NO: Use `suppressOutput: true` for silent operation 7. **Context pollution**: "Should successful operations be silent to avoid noise?" - Recommend YES for formatting, routine checks - Recommend NO for security alerts, critical errors 8. **File filtering**: "What file types should this hook process?" ### 3. Hook Creation You should: - **Create hooks directory**: `~/.claude/hooks/` or `.claude/hooks/` based on scope - **Generate script**: Create hook script with: - Proper shebang and executable permissions - Project-specific commands (use detected config paths) - Comments explaining the hook's purpose - **Update settings**: Add hook configuration to appropriate settings.json - **Use absolute paths**: Avoid relative paths to scripts and executables. Use `$CLAUDE_PROJECT_DIR` to reference project root - **Offer validation**: Ask if the user wants you to test the hook **Key Implementation Standards:** - Read JSON from stdin (never use argv) - Use top-level `additionalContext`/`systemMessage` for Claude communication - Include `suppressOutput: true` for successful operations - Provide specific error counts and actionable feedback - Focus on changed files rather than entire codebase - Support common development workflows **⚠️ CRITICAL: Input/Output Format** This is where most hook implementations fail. Pay extra attention to: - **Input**: Reading JSON from stdin correctly (not argv) - **Output**: Using correct top-level JSON structure for Claude communication - **Documentation**: Consulting official docs for exact schemas when in doubt ### 4. Testing & Validation **CRITICAL: Test both happy and sad paths:** **Happy Path Testing:** 1. **Test expected success scenario** - Create conditions where hook should pass - _Examples_: TypeScript (valid code), Linting (formatted code), Security (safe commands) **Sad Path Testing:** 2. **Test expected failure scenario** - Create conditions where hook should fail/warn - _Examples_: TypeScript (type errors), Linting (unformatted code), Security (dangerous operations) **Verification Steps:** 3. **Verify expected behavior**: Check if it blocks/warns/provides context as intended **Example Testing Process:** - For a hook preventing file deletion: Create a test file, attempt the protected action, and verify the hook prevents it **If Issues Occur, you should:** - Check hook registration in settings - Verify script permissions (`chmod +x`) - Test with simplified version first - Debug with detailed hook execution analysis ## Hook Templates ### Type Checking (PostToolUse) ``` #!/usr/bin/env node // Read stdin JSON, check .ts/.tsx files only // Run: npx tsc --noEmit --pretty // Output: JSON with additionalContext for errors ``` ### Auto-formatting (PostToolUse) ``` #!/usr/bin/env node // Read stdin JSON, check supported file types // Run: npx prettier --write [file] // Output: JSON with suppressOutput: true ``` ### Security Scanning (PreToolUse) ```bash #!/bin/bash # Read stdin JSON, check for secrets/keys # Block if dangerous patterns found # Exit 2 to block, 0 to continue ``` _Complete templates available at: _ ## Quick Reference **📖 Official Docs**: **Common Patterns:** - **stdin input**: `JSON.parse(process.stdin.read())` - **File filtering**: Check extensions before processing - **Success response**: `{continue: true, suppressOutput: true}` - **Error response**: `{continue: true, additionalContext: "error details"}` - **Block operation**: `exit(2)` in PreToolUse hooks **Hook Types by Use Case:** - **Code Quality**: PostToolUse for feedback and fixes - **Security**: PreToolUse to block dangerous operations - **CI/CD**: PreToolUse to validate before commits - **Development**: PostToolUse for automated improvements **Hook Execution Best Practices:** - **Hooks run in parallel** according to official documentation - **Design for independence** since execution order isn't guaranteed - **Plan hook interactions carefully** when multiple hooks affect the same files ## Success Criteria ✅ **Hook created successfully when:** - Script has executable permissions - Registered in correct settings.json - Responds correctly to test scenarios - Integrates properly with Claude for automated fixes - Follows project conventions and detected tooling **Result**: The user gets a working hook that enhances their development workflow with intelligent automation and quality checks. --- > ## Documentation Index > > Fetch the complete documentation index at: > Use this file to discover all available pages before exploring further. # Automate workflows with hooks > Run shell commands automatically when Claude Code edits files, finishes tasks, or needs input. Format code, send notifications, validate commands, and enforce project rules. Hooks are user-defined shell commands that execute at specific points in Claude Code's lifecycle. They provide deterministic control over Claude Code's behavior, ensuring certain actions always happen rather than relying on the LLM to choose to run them. Use hooks to enforce project rules, automate repetitive tasks, and integrate Claude Code with your existing tools. For decisions that require judgment rather than deterministic rules, you can also use [prompt-based hooks](#prompt-based-hooks) or [agent-based hooks](#agent-based-hooks) that use a Claude model to evaluate conditions. For other ways to extend Claude Code, see [skills](/en/skills) for giving Claude additional instructions and executable commands, [subagents](/en/sub-agents) for running tasks in isolated contexts, and [plugins](/en/plugins) for packaging extensions to share across projects. This guide covers common use cases and how to get started. For full event schemas, JSON input/output formats, and advanced features like async hooks and MCP tool hooks, see the [Hooks reference](/en/hooks). ## Set up your first hook The fastest way to create a hook is through the `/hooks` interactive menu in Claude Code. This walkthrough creates a desktop notification hook, so you get alerted whenever Claude is waiting for your input instead of watching the terminal. Type `/hooks` in the Claude Code CLI. You'll see a list of all available hook events, plus an option to disable all hooks. Each event corresponds to a point in Claude's lifecycle where you can run custom code. Select `Notification` to create a hook that fires when Claude needs your attention. The menu shows a list of matchers, which filter when the hook fires. Set the matcher to `*` to fire on all notification types. You can narrow it later by changing the matcher to a specific value like `permission_prompt` or `idle_prompt`. Select `+ Add new hook…`. The menu prompts you for a shell command to run when the event fires. Hooks run any shell command you provide, so you can use your platform's built-in notification tool. Copy the command for your OS: Uses [`osascript`](https://ss64.com/mac/osascript.html) to trigger a native macOS notification through AppleScript: ``` osascript -e 'display notification "Claude Code needs your attention" with title "Claude Code"' ``` Uses `notify-send`, which is pre-installed on most Linux desktops with a notification daemon: ``` notify-send 'Claude Code' 'Claude Code needs your attention' ``` Uses PowerShell to show a native message box through .NET's Windows Forms: ``` powershell.exe -Command "[System.Reflection.Assembly]::LoadWithPartialName('System.Windows.Forms'); [System.Windows.Forms.MessageBox]::Show('Claude Code needs your attention', 'Claude Code')" ``` The menu asks where to save the hook configuration. Select `User settings` to store it in `~/.claude/settings.json`, which applies the hook to all your projects. You could also choose `Project settings` to scope it to the current project. See [Configure hook location](#configure-hook-location) for all available scopes. Press `Esc` to return to the CLI. Ask Claude to do something that requires permission, then switch away from the terminal. You should receive a desktop notification. ## What you can automate Hooks let you run code at key points in Claude Code's lifecycle: format files after edits, block commands before they execute, send notifications when Claude needs input, inject context at session start, and more. For the full list of hook events, see the [Hooks reference](/en/hooks#hook-lifecycle). Each example includes a ready-to-use configuration block that you add to a [settings file](#configure-hook-location). The most common patterns: - [Get notified when Claude needs input](#get-notified-when-claude-needs-input) - [Auto-format code after edits](#auto-format-code-after-edits) - [Block edits to protected files](#block-edits-to-protected-files) - [Re-inject context after compaction](#re-inject-context-after-compaction) ### Get notified when Claude needs input Get a desktop notification whenever Claude finishes working and needs your input, so you can switch to other tasks without checking the terminal. This hook uses the `Notification` event, which fires when Claude is waiting for input or permission. Each tab below uses the platform's native notification command. Add this to `~/.claude/settings.json`, or use the [interactive walkthrough](#set-up-your-first-hook) above to configure it with `/hooks`: ```json theme={null} { "hooks": { "Notification": [ { "matcher": "", "hooks": [ { "type": "command", "command": "osascript -e 'display notification \"Claude Code needs your attention\" with title \"Claude Code\"'" } ] } ] } } ``` ```json theme={null} { "hooks": { "Notification": [ { "matcher": "", "hooks": [ { "type": "command", "command": "notify-send 'Claude Code' 'Claude Code needs your attention'" } ] } ] } } ``` ```json theme={null} { "hooks": { "Notification": [ { "matcher": "", "hooks": [ { "type": "command", "command": "powershell.exe -Command \"[System.Reflection.Assembly]::LoadWithPartialName('System.Windows.Forms'); [System.Windows.Forms.MessageBox]::Show('Claude Code needs your attention', 'Claude Code')\"" } ] } ] } } ``` ### Auto-format code after edits Automatically run [Prettier](https://prettier.io/) on every file Claude edits, so formatting stays consistent without manual intervention. This hook uses the `PostToolUse` event with an `Edit|Write` matcher, so it runs only after file-editing tools. The command extracts the edited file path with [`jq`](https://jqlang.github.io/jq/) and passes it to Prettier. Add this to `.claude/settings.json` in your project root: ```json theme={null} { "hooks": { "PostToolUse": [ { "matcher": "Edit|Write", "hooks": [ { "type": "command", "command": "jq -r '.tool_input.file_path' | xargs npx prettier --write" } ] } ] } } ``` The Bash examples on this page use `jq` for JSON parsing. Install it with `brew install jq` (macOS), `apt-get install jq` (Debian/Ubuntu), or see [`jq` downloads](https://jqlang.github.io/jq/download/). ### Block edits to protected files Prevent Claude from modifying sensitive files like `.env`, `package-lock.json`, or anything in `.git/`. Claude receives feedback explaining why the edit was blocked, so it can adjust its approach. This example uses a separate script file that the hook calls. The script checks the target file path against a list of protected patterns and exits with code 2 to block the edit. Save this to `.claude/hooks/protect-files.sh`: ```bash theme={null} #!/bin/bash # protect-files.sh INPUT=$(cat) FILE_PATH=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty') PROTECTED_PATTERNS=(".env" "package-lock.json" ".git/") for pattern in "${PROTECTED_PATTERNS[@]}"; do if [[ "$FILE_PATH" == *"$pattern"* ]]; then echo "Blocked: $FILE_PATH matches protected pattern '$pattern'" >&2 exit 2 fi done exit 0 ``` Hook scripts must be executable for Claude Code to run them: ```bash theme={null} chmod +x .claude/hooks/protect-files.sh ``` Add a `PreToolUse` hook to `.claude/settings.json` that runs the script before any `Edit` or `Write` tool call: ```json theme={null} { "hooks": { "PreToolUse": [ { "matcher": "Edit|Write", "hooks": [ { "type": "command", "command": "\"$CLAUDE_PROJECT_DIR\"/.claude/hooks/protect-files.sh" } ] } ] } } ``` ### Re-inject context after compaction When Claude's context window fills up, compaction summarizes the conversation to free space. This can lose important details. Use a `SessionStart` hook with a `compact` matcher to re-inject critical context after every compaction. Any text your command writes to stdout is added to Claude's context. This example reminds Claude of project conventions and recent work. Add this to `.claude/settings.json` in your project root: ```json theme={null} { "hooks": { "SessionStart": [ { "matcher": "compact", "hooks": [ { "type": "command", "command": "echo 'Reminder: use Bun, not npm. Run bun test before committing. Current sprint: auth refactor.'" } ] } ] } } ``` You can replace the `echo` with any command that produces dynamic output, like `git log --oneline -5` to show recent commits. For injecting context on every session start, consider using [CLAUDE.md](/en/memory) instead. For environment variables, see [`CLAUDE_ENV_FILE`](/en/hooks#persist-environment-variables) in the reference. ## How hooks work Hook events fire at specific lifecycle points in Claude Code. When an event fires, all matching hooks run in parallel, and identical hook commands are automatically deduplicated. The table below shows each event and when it triggers: | Event | When it fires | | :------------------- | :--------------------------------------------------- | | `SessionStart` | When a session begins or resumes | | `UserPromptSubmit` | When you submit a prompt, before Claude processes it | | `PreToolUse` | Before a tool call executes. Can block it | | `PermissionRequest` | When a permission dialog appears | | `PostToolUse` | After a tool call succeeds | | `PostToolUseFailure` | After a tool call fails | | `Notification` | When Claude Code sends a notification | | `SubagentStart` | When a subagent is spawned | | `SubagentStop` | When a subagent finishes | | `Stop` | When Claude finishes responding | | `PreCompact` | Before context compaction | | `SessionEnd` | When a session terminates | Each hook has a `type` that determines how it runs. Most hooks use `"type": "command"`, which runs a shell command. Two other options use a Claude model to make decisions: `"type": "prompt"` for single-turn evaluation and `"type": "agent"` for multi-turn verification with tool access. See [Prompt-based hooks](#prompt-based-hooks) and [Agent-based hooks](#agent-based-hooks) for details. ### Read input and return output Hooks communicate with Claude Code through stdin, stdout, stderr, and exit codes. When an event fires, Claude Code passes event-specific data as JSON to your script's stdin. Your script reads that data, does its work, and tells Claude Code what to do next via the exit code. #### Hook input Every event includes common fields like `session_id` and `cwd`, but each event type adds different data. For example, when Claude runs a Bash command, a `PreToolUse` hook receives something like this on stdin: ```json theme={null} { "session_id": "abc123", // unique ID for this session "cwd": "/Users/sarah/myproject", // working directory when the event fired "hook_event_name": "PreToolUse", // which event triggered this hook "tool_name": "Bash", // the tool Claude is about to use "tool_input": { // the arguments Claude passed to the tool "command": "npm test" // for Bash, this is the shell command } } ``` Your script can parse that JSON and act on any of those fields. `UserPromptSubmit` hooks get the `prompt` text instead, `SessionStart` hooks get the `source` (startup, resume, compact), and so on. See [Common input fields](/en/hooks#common-input-fields) in the reference for shared fields, and each event's section for event-specific schemas. #### Hook output Your script tells Claude Code what to do next by writing to stdout or stderr and exiting with a specific code. For example, a `PreToolUse` hook that wants to block a command: ```bash theme={null} #!/bin/bash INPUT=$(cat) COMMAND=$(echo "$INPUT" | jq -r '.tool_input.command') if echo "$COMMAND" | grep -q "drop table"; then echo "Blocked: dropping tables is not allowed" >&2 # stderr becomes Claude's feedback exit 2 # exit 2 = block the action fi exit 0 # exit 0 = let it proceed ``` The exit code determines what happens next: - **Exit 0**: the action proceeds. For `UserPromptSubmit` and `SessionStart` hooks, anything you write to stdout is added to Claude's context. - **Exit 2**: the action is blocked. Write a reason to stderr, and Claude receives it as feedback so it can adjust. - **Any other exit code**: the action proceeds. Stderr is logged but not shown to Claude. Toggle verbose mode with `Ctrl+O` to see these messages in the transcript. #### Structured JSON output Exit codes give you two options: allow or block. For more control, exit 0 and print a JSON object to stdout instead. Use exit 2 to block with a stderr message, or exit 0 with JSON for structured control. Don't mix them: Claude Code ignores JSON when you exit 2. For example, a `PreToolUse` hook can deny a tool call and tell Claude why, or escalate it to the user for approval: ```json theme={null} { "hookSpecificOutput": { "hookEventName": "PreToolUse", "permissionDecision": "deny", "permissionDecisionReason": "Use rg instead of grep for better performance" } } ``` Claude Code reads `permissionDecision` and cancels the tool call, then feeds `permissionDecisionReason` back to Claude as feedback. These three options are specific to `PreToolUse`: - `"allow"`: proceed without showing a permission prompt - `"deny"`: cancel the tool call and send the reason to Claude - `"ask"`: show the permission prompt to the user as normal Other events use different decision patterns. For example, `PostToolUse` and `Stop` hooks use a top-level `decision: "block"` field, while `PermissionRequest` uses `hookSpecificOutput.decision.behavior`. See the [summary table](/en/hooks#decision-control) in the reference for a full breakdown by event. For `UserPromptSubmit` hooks, use `additionalContext` instead to inject text into Claude's context. Prompt-based hooks (`type: "prompt"`) handle output differently: see [Prompt-based hooks](#prompt-based-hooks). ### Filter hooks with matchers Without a matcher, a hook fires on every occurrence of its event. Matchers let you narrow that down. For example, if you want to run a formatter only after file edits (not after every tool call), add a matcher to your `PostToolUse` hook: ```json theme={null} { "hooks": { "PostToolUse": [ { "matcher": "Edit|Write", "hooks": [ { "type": "command", "command": "prettier --write ..." } ] } ] } } ``` The `"Edit|Write"` matcher is a regex pattern that matches the tool name. The hook only fires when Claude uses the `Edit` or `Write` tool, not when it uses `Bash`, `Read`, or any other tool. Each event type matches on a specific field. Matchers support exact strings and regex patterns: | Event | What the matcher filters | Example matcher values | | :--------------------------------------------------------------------- | :------------------------ | :----------------------------------------------------------------------- | | `PreToolUse`, `PostToolUse`, `PostToolUseFailure`, `PermissionRequest` | tool name | `Bash`, `Edit\|Write`, `mcp__.*` | | `SessionStart` | how the session started | `startup`, `resume`, `clear`, `compact` | | `SessionEnd` | why the session ended | `clear`, `logout`, `prompt_input_exit`, `other` | | `Notification` | notification type | `permission_prompt`, `idle_prompt`, `auth_success`, `elicitation_dialog` | | `SubagentStart` | agent type | `Bash`, `Explore`, `Plan`, or custom agent names | | `PreCompact` | what triggered compaction | `manual`, `auto` | | `UserPromptSubmit`, `Stop` | no matcher support | always fires on every occurrence | | `SubagentStop` | agent type | same values as `SubagentStart` | A few more examples showing matchers on different event types: Match only `Bash` tool calls and log each command to a file. The `PostToolUse` event fires after the command completes, so `tool_input.command` contains what ran. The hook receives the event data as JSON on stdin, and `jq -r '.tool_input.command'` extracts just the command string, which `>>` appends to the log file: ```json theme={null} { "hooks": { "PostToolUse": [ { "matcher": "Bash", "hooks": [ { "type": "command", "command": "jq -r '.tool_input.command' >> ~/.claude/command-log.txt" } ] } ] } } ``` MCP tools use a different naming convention than built-in tools: `mcp____`, where `` is the MCP server name and `` is the tool it provides. For example, `mcp__github__search_repositories` or `mcp__filesystem__read_file`. Use a regex matcher to target all tools from a specific server, or match across servers with a pattern like `mcp__.*__write.*`. See [Match MCP tools](/en/hooks#match-mcp-tools) in the reference for the full list of examples. The command below extracts the tool name from the hook's JSON input with `jq` and writes it to stderr, where it shows up in verbose mode (`Ctrl+O`): ```json theme={null} { "hooks": { "PreToolUse": [ { "matcher": "mcp__github__.*", "hooks": [ { "type": "command", "command": "echo \"GitHub tool called: $(jq -r '.tool_name')\" >&2" } ] } ] } } ``` The `SessionEnd` event supports matchers on the reason the session ended. This hook only fires on `clear` (when you run `/clear`), not on normal exits: ```json theme={null} { "hooks": { "SessionEnd": [ { "matcher": "clear", "hooks": [ { "type": "command", "command": "rm -f /tmp/claude-scratch-*.txt" } ] } ] } } ``` For full matcher syntax, see the [Hooks reference](/en/hooks#configuration). ### Configure hook location Where you add a hook determines its scope: | Location | Scope | Shareable | | :--------------------------------------------------------- | :--------------------------------- | :--------------------------------- | | `~/.claude/settings.json` | All your projects | No, local to your machine | | `.claude/settings.json` | Single project | Yes, can be committed to the repo | | `.claude/settings.local.json` | Single project | No, gitignored | | Managed policy settings | Organization-wide | Yes, admin-controlled | | [Plugin](/en/plugins) `hooks/hooks.json` | When plugin is enabled | Yes, bundled with the plugin | | [Skill](/en/skills) or [agent](/en/sub-agents) frontmatter | While the skill or agent is active | Yes, defined in the component file | You can also use the [`/hooks` menu](/en/hooks#the-hooks-menu) in Claude Code to add, delete, and view hooks interactively. To disable all hooks at once, use the toggle at the bottom of the `/hooks` menu or set `"disableAllHooks": true` in your settings file. Hooks added through the `/hooks` menu take effect immediately. If you edit settings files directly while Claude Code is running, the changes won't take effect until you review them in the `/hooks` menu or restart your session. ## Prompt-based hooks For decisions that require judgment rather than deterministic rules, use `type: "prompt"` hooks. Instead of running a shell command, Claude Code sends your prompt and the hook's input data to a Claude model (Haiku by default) to make the decision. You can specify a different model with the `model` field if you need more capability. The model's only job is to return a yes/no decision as JSON: - `"ok": true`: the action proceeds - `"ok": false`: the action is blocked. The model's `"reason"` is fed back to Claude so it can adjust. This example uses a `Stop` hook to ask the model whether all requested tasks are complete. If the model returns `"ok": false`, Claude keeps working and uses the `reason` as its next instruction: ```json theme={null} { "hooks": { "Stop": [ { "hooks": [ { "type": "prompt", "prompt": "Check if all tasks are complete. If not, respond with {\"ok\": false, \"reason\": \"what remains to be done\"}." } ] } ] } } ``` For full configuration options, see [Prompt-based hooks](/en/hooks#prompt-based-hooks) in the reference. ## Agent-based hooks When verification requires inspecting files or running commands, use `type: "agent"` hooks. Unlike prompt hooks which make a single LLM call, agent hooks spawn a subagent that can read files, search code, and use other tools to verify conditions before returning a decision. Agent hooks use the same `"ok"` / `"reason"` response format as prompt hooks, but with a longer default timeout of 60 seconds and up to 50 tool-use turns. This example verifies that tests pass before allowing Claude to stop: ```json theme={null} { "hooks": { "Stop": [ { "hooks": [ { "type": "agent", "prompt": "Verify that all unit tests pass. Run the test suite and check the results. $ARGUMENTS", "timeout": 120 } ] } ] } } ``` Use prompt hooks when the hook input data alone is enough to make a decision. Use agent hooks when you need to verify something against the actual state of the codebase. For full configuration options, see [Agent-based hooks](/en/hooks#agent-based-hooks) in the reference. ## Limitations and troubleshooting ### Limitations - Hooks communicate through stdout, stderr, and exit codes only. They cannot trigger slash commands or tool calls directly. - Hook timeout is 10 minutes by default, configurable per hook with the `timeout` field (in seconds). - `PostToolUse` hooks cannot undo actions since the tool has already executed. - `PermissionRequest` hooks do not fire in [non-interactive mode](/en/headless) (`-p`). Use `PreToolUse` hooks for automated permission decisions. - `Stop` hooks fire whenever Claude finishes responding, not only at task completion. They do not fire on user interrupts. ### Hook not firing The hook is configured but never executes. - Run `/hooks` and confirm the hook appears under the correct event - Check that the matcher pattern matches the tool name exactly (matchers are case-sensitive) - Verify you're triggering the right event type (e.g., `PreToolUse` fires before tool execution, `PostToolUse` fires after) - If using `PermissionRequest` hooks in non-interactive mode (`-p`), switch to `PreToolUse` instead ### Hook error in output You see a message like "PreToolUse hook error: ..." in the transcript. - Your script exited with a non-zero code unexpectedly. Test it manually by piping sample JSON: ```bash theme={null} echo '{"tool_name":"Bash","tool_input":{"command":"ls"}}' | ./my-hook.sh echo $? # Check the exit code ``` * If you see "command not found", use absolute paths or `$CLAUDE_PROJECT_DIR` to reference scripts - If you see "jq: command not found", install `jq` or use Python/Node.js for JSON parsing - If the script isn't running at all, make it executable: `chmod +x ./my-hook.sh` ### `/hooks` shows no hooks configured You edited a settings file but the hooks don't appear in the menu. - Restart your session or open `/hooks` to reload. Hooks added through the `/hooks` menu take effect immediately, but manual file edits require a reload. - Verify your JSON is valid (trailing commas and comments are not allowed) - Confirm the settings file is in the correct location: `.claude/settings.json` for project hooks, `~/.claude/settings.json` for global hooks ### Stop hook runs forever Claude keeps working in an infinite loop instead of stopping. Your Stop hook script needs to check whether it already triggered a continuation. Parse the `stop_hook_active` field from the JSON input and exit early if it's `true`: ```bash theme={null} #!/bin/bash INPUT=$(cat) if [ "$(echo "$INPUT" | jq -r '.stop_hook_active')" = "true" ]; then exit 0 # Allow Claude to stop fi # ... rest of your hook logic ``` ### JSON validation failed Claude Code shows a JSON parsing error even though your hook script outputs valid JSON. When Claude Code runs a hook, it spawns a shell that sources your profile (`~/.zshrc` or `~/.bashrc`). If your profile contains unconditional `echo` statements, that output gets prepended to your hook's JSON: ``` Shell ready on arm64 {"decision": "block", "reason": "Not allowed"} ``` Claude Code tries to parse this as JSON and fails. To fix this, wrap echo statements in your shell profile so they only run in interactive shells: ```bash theme={null} # In ~/.zshrc or ~/.bashrc if [[ $- == *i* ]]; then echo "Shell ready" fi ``` The `$-` variable contains shell flags, and `i` means interactive. Hooks run in non-interactive shells, so the echo is skipped. ### Debug techniques Toggle verbose mode with `Ctrl+O` to see hook output in the transcript, or run `claude --debug` for full execution details including which hooks matched and their exit codes. ## Learn more - [Hooks reference](/en/hooks): full event schemas, JSON output format, async hooks, and MCP tool hooks - [Security considerations](/en/hooks#security-considerations): review before deploying hooks in shared or production environments - [Bash command validator example](https://github.com/anthropics/claude-code/blob/main/examples/hooks/bash_command_validator_example.py): complete reference implementation --- > ## Documentation Index > > Fetch the complete documentation index at: > Use this file to discover all available pages before exploring further. # Hooks reference > Reference for Claude Code hook events, configuration schema, JSON input/output formats, exit codes, async hooks, prompt hooks, and MCP tool hooks. For a quickstart guide with examples, see [Automate workflows with hooks](/en/hooks-guide). Hooks are user-defined shell commands or LLM prompts that execute automatically at specific points in Claude Code's lifecycle. Use this reference to look up event schemas, configuration options, JSON input/output formats, and advanced features like async hooks and MCP tool hooks. If you're setting up hooks for the first time, start with the [guide](/en/hooks-guide) instead. ## Hook lifecycle Hooks fire at specific points during a Claude Code session. When an event fires and a matcher matches, Claude Code passes JSON context about the event to your hook handler. For command hooks, this arrives on stdin. Your handler can then inspect the input, take action, and optionally return a decision. Some events fire once per session, while others fire repeatedly inside the agentic loop:
Hook lifecycle diagram showing the sequence of hooks from SessionStart through the agentic loop to SessionEnd
The table below summarizes when each event fires. The [Hook events](#hook-events) section documents the full input schema and decision control options for each one. | Event | When it fires | | :------------------- | :--------------------------------------------------- | | `SessionStart` | When a session begins or resumes | | `UserPromptSubmit` | When you submit a p …(truncated)