---
title: "Automate workflows with hooks"
source: "https://code.claude.com/docs/en/hooks-guide"
author:
published:
created: 2026-04-17
description: "Run shell commands automatically when Claude Code edits files, finishes tasks, or needs input. Format code, send notifications, validate commands, and enforce project rules."
tags:
  - "clippings"
---
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](https://code.claude.com/docs/en/skills) for giving Claude additional instructions and executable commands, [subagents](https://code.claude.com/docs/en/sub-agents) for running tasks in isolated contexts, and [plugins](https://code.claude.com/docs/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 .

## Set up your first hook

To create a hook, add a `hooks` block to a [settings file](#configure-hook-location). This walkthrough creates a desktop notification hook, so you get alerted whenever Claude is waiting for your input instead of watching the terminal.

The `/hooks` menu is read-only. To add, modify, or remove hooks, edit your settings JSON directly or ask Claude to make the change.

## 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](https://code.claude.com/docs/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 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`:

- macOS
- Linux
- Windows (PowerShell)

```json
{
  "hooks": {
    "Notification": [
      {
        "matcher": "",
        "hooks": [
          {
            "type": "command",
            "command": "osascript -e 'display notification \"Claude Code needs your attention\" with title \"Claude Code\"'"
          }
        ]
      }
    ]
  }
}
```

If no notification appears

`osascript` routes notifications through the built-in Script Editor app. If Script Editor doesn’t have notification permission, the command fails silently, and macOS won’t prompt you to grant it. Run this in Terminal once to make Script Editor appear in your notification settings:

```shellscript
osascript -e 'display notification "test"'
```

Nothing will appear yet. Open **System Settings > Notifications**, find **Script Editor** in the list, and turn on **Allow Notifications**. Run the command again to confirm the test notification appears.

### 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
{
  "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.

### 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
{
  "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](https://code.claude.com/docs/en/memory) instead. For environment variables, see [`CLAUDE_ENV_FILE`](https://code.claude.com/docs/en/hooks#persist-environment-variables) in the reference.

### Audit configuration changes

Track when settings or skills files change during a session. The `ConfigChange` event fires when an external process or editor modifies a configuration file, so you can log changes for compliance or block unauthorized modifications.

This example appends each change to an audit log. Add this to `~/.claude/settings.json`:

```json
{
  "hooks": {
    "ConfigChange": [
      {
        "matcher": "",
        "hooks": [
          {
            "type": "command",
            "command": "jq -c '{timestamp: now | todate, source: .source, file: .file_path}' >> ~/claude-config-audit.log"
          }
        ]
      }
    ]
  }
}
```

The matcher filters by configuration type: `user_settings`, `project_settings`, `local_settings`, `policy_settings`, or `skills`. To block a change from taking effect, exit with code 2 or return `{"decision": "block"}`. See the [ConfigChange reference](https://code.claude.com/docs/en/hooks#configchange) for the full input schema.

### Reload environment when directory or files change

Some projects set different environment variables depending on which directory you are in. Tools like [direnv](https://direnv.net/) do this automatically in your shell, but Claude’s Bash tool does not pick up those changes on its own.

A `CwdChanged` hook fixes this: it runs each time Claude changes directory, so you can reload the correct variables for the new location. The hook writes the updated values to `CLAUDE_ENV_FILE`, which Claude Code applies before each Bash command. Add this to `~/.claude/settings.json`:

```json
{
  "hooks": {
    "CwdChanged": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "direnv export bash >> \"$CLAUDE_ENV_FILE\""
          }
        ]
      }
    ]
  }
}
```

To react to specific files instead of every directory change, use `FileChanged` with a `matcher` listing the filenames to watch, separated by `|`. To build the watch list, this value is split into literal filenames rather than evaluated as a regex. See [FileChanged](https://code.claude.com/docs/en/hooks#filechanged) for how the same value also filters which hook groups run when a file changes. This example watches `.envrc` and `.env` in the working directory:

```json
{
  "hooks": {
    "FileChanged": [
      {
        "matcher": ".envrc|.env",
        "hooks": [
          {
            "type": "command",
            "command": "direnv export bash >> \"$CLAUDE_ENV_FILE\""
          }
        ]
      }
    ]
  }
}
```

See the [CwdChanged](https://code.claude.com/docs/en/hooks#cwdchanged) and [FileChanged](https://code.claude.com/docs/en/hooks#filechanged) reference entries for input schemas, `watchPaths` output, and `CLAUDE_ENV_FILE` details.

### Auto-approve specific permission prompts

Skip the approval dialog for tool calls you always allow. This example auto-approves `ExitPlanMode`, the tool Claude calls when it finishes presenting a plan and asks to proceed, so you aren’t prompted every time a plan is ready.

Unlike the exit-code examples above, auto-approval requires your hook to write a JSON decision to stdout. A `PermissionRequest` hook fires when Claude Code is about to show a permission dialog, and returning `"behavior": "allow"` answers it on your behalf.

The matcher scopes the hook to `ExitPlanMode` only, so no other prompts are affected. Add this to `~/.claude/settings.json`:

```json
{
  "hooks": {
    "PermissionRequest": [
      {
        "matcher": "ExitPlanMode",
        "hooks": [
          {
            "type": "command",
            "command": "echo '{\"hookSpecificOutput\": {\"hookEventName\": \"PermissionRequest\", \"decision\": {\"behavior\": \"allow\"}}}'"
          }
        ]
      }
    ]
  }
}
```

When the hook approves, Claude Code exits plan mode and restores whatever permission mode was active before you entered plan mode. The transcript shows “Allowed by PermissionRequest hook” where the dialog would have appeared. The hook path always keeps the current conversation: it cannot clear context and start a fresh implementation session the way the dialog can.

To set a specific permission mode instead, your hook’s output can include an `updatedPermissions` array with a `setMode` entry. The `mode` value is any permission mode like `default`, `acceptEdits`, or `bypassPermissions`, and `destination: "session"` applies it for the current session only.

`bypassPermissions` only applies if the session was launched with bypass mode already available: `--dangerously-skip-permissions`, `--permission-mode bypassPermissions`, `--allow-dangerously-skip-permissions`, or `permissions.defaultMode: "bypassPermissions"` in settings, and not disabled by [`permissions.disableBypassPermissionsMode`](https://code.claude.com/docs/en/permissions#managed-settings). It is never persisted as `defaultMode`.

To switch the session to `acceptEdits`, your hook writes this JSON to stdout:

```json
{
  "hookSpecificOutput": {
    "hookEventName": "PermissionRequest",
    "decision": {
      "behavior": "allow",
      "updatedPermissions": [
        { "type": "setMode", "mode": "acceptEdits", "destination": "session" }
      ]
    }
  }
}
```

Keep the matcher as narrow as possible. Matching on `.*` or leaving the matcher empty would auto-approve every permission prompt, including file writes and shell commands. See the [PermissionRequest reference](https://code.claude.com/docs/en/hooks#permissionrequest-decision-control) for the full set of decision fields.

## 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 |
| `PermissionDenied` | When a tool call is denied by the auto mode classifier. Return `{retry: true}` to tell the model it may retry the denied tool call |
| `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 |
| `TaskCreated` | When a task is being created via `TaskCreate` |
| `TaskCompleted` | When a task is being marked as completed |
| `Stop` | When Claude finishes responding |
| `StopFailure` | When the turn ends due to an API error. Output and exit code are ignored |
| `TeammateIdle` | When an [agent team](https://code.claude.com/docs/en/agent-teams) teammate is about to go idle |
| `InstructionsLoaded` | When a CLAUDE.md or `.claude/rules/*.md` file is loaded into context. Fires at session start and when files are lazily loaded during a session |
| `ConfigChange` | When a configuration file changes during a session |
| `CwdChanged` | When the working directory changes, for example when Claude executes a `cd` command. Useful for reactive environment management with tools like direnv |
| `FileChanged` | When a watched file changes on disk. The `matcher` field specifies which filenames to watch |
| `WorktreeCreate` | When a worktree is being created via `--worktree` or `isolation: "worktree"`. Replaces default git behavior |
| `WorktreeRemove` | When a worktree is being removed, either at session exit or when a subagent finishes |
| `PreCompact` | Before context compaction |
| `PostCompact` | After context compaction completes |
| `Elicitation` | When an MCP server requests user input during a tool call |
| `ElicitationResult` | After a user responds to an MCP elicitation, before the response is sent back to the server |
| `SessionEnd` | When a session terminates |

When multiple hooks match, each one returns its own result. For decisions, Claude Code picks the most restrictive answer. A `PreToolUse` hook returning `deny` cancels the tool call no matter what the others return. One hook returning `ask` forces the permission prompt even if the rest return `allow`. Text from `additionalContext` is kept from every hook and passed to Claude together.

Each hook has a `type` that determines how it runs. Most hooks use `"type": "command"`, which runs a shell command. Three other types are available:

- `"type": "http"`: POST event data to a URL. See [HTTP hooks](#http-hooks).
- `"type": "prompt"`: single-turn LLM evaluation. See [Prompt-based hooks](#prompt-based-hooks).
- `"type": "agent"`: multi-turn verification with tool access. See [Agent-based hooks](#agent-based-hooks).

### 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
{
  "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, clear, compact), and so on. See [Common input fields](https://code.claude.com/docs/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:

```shellscript
#!/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. The transcript shows a `<hook name> hook error` notice followed by the first line of stderr; the full stderr goes to the [debug log](https://code.claude.com/docs/en/hooks#debug-hooks).

#### 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
{
  "hookSpecificOutput": {
    "hookEventName": "PreToolUse",
    "permissionDecision": "deny",
    "permissionDecisionReason": "Use rg instead of grep for better performance"
  }
}
```

With `"deny"`, Claude Code cancels the tool call and feeds `permissionDecisionReason` back to Claude. These `permissionDecision` values are specific to `PreToolUse`:

- `"allow"`: skip the interactive permission prompt. Deny and ask rules, including enterprise managed deny lists, still apply
- `"deny"`: cancel the tool call and send the reason to Claude
- `"ask"`: show the permission prompt to the user as normal

A fourth value, `"defer"`, is available in [non-interactive mode](https://code.claude.com/docs/en/headless) with the `-p` flag. It exits the process with the tool call preserved so an Agent SDK wrapper can collect input and resume. See [Defer a tool call for later](https://code.claude.com/docs/en/hooks#defer-a-tool-call-for-later) in the reference.

Returning `"allow"` skips the interactive prompt but does not override [permission rules](https://code.claude.com/docs/en/permissions#manage-permissions). If a deny rule matches the tool call, the call is blocked even when your hook returns `"allow"`. If an ask rule matches, the user is still prompted. This means deny rules from any settings scope, including [managed settings](https://code.claude.com/docs/en/settings#settings-files), always take precedence over hook approvals.

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](https://code.claude.com/docs/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
{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Edit|Write",
        "hooks": [
          { "type": "command", "command": "prettier --write ..." }
        ]
      }
    ]
  }
}
```

The `"Edit|Write"` matcher fires only when Claude uses the `Edit` or `Write` tool, not when it uses `Bash`, `Read`, or any other tool. See [Matcher patterns](https://code.claude.com/docs/en/hooks#matcher-patterns) for how plain names and regular expressions are evaluated.

Each event type matches on a specific field:

| Event | What the matcher filters | Example matcher values |
| --- | --- | --- |
| `PreToolUse`, `PostToolUse`, `PostToolUseFailure`, `PermissionRequest`, `PermissionDenied` | tool name | `Bash`, `Edit\|Write`, `mcp__.*` |
| `SessionStart` | how the session started | `startup`, `resume`, `clear`, `compact` |
| `SessionEnd` | why the session ended | `clear`, `resume`, `logout`, `prompt_input_exit`, `bypass_permissions_disabled`, `other` |
| `Notification` | notification type | `permission_prompt`, `idle_prompt`, `auth_success`, `elicitation_dialog` |
| `SubagentStart` | agent type | `Bash`, `Explore`, `Plan`, or custom agent names |
| `PreCompact`, `PostCompact` | what triggered compaction | `manual`, `auto` |
| `SubagentStop` | agent type | same values as `SubagentStart` |
| `ConfigChange` | configuration source | `user_settings`, `project_settings`, `local_settings`, `policy_settings`, `skills` |
| `StopFailure` | error type | `rate_limit`, `authentication_failed`, `billing_error`, `invalid_request`, `server_error`, `max_output_tokens`, `unknown` |
| `InstructionsLoaded` | load reason | `session_start`, `nested_traversal`, `path_glob_match`, `include`, `compact` |
| `Elicitation` | MCP server name | your configured MCP server names |
| `ElicitationResult` | MCP server name | same values as `Elicitation` |
| `FileChanged` | literal filenames to watch (see [FileChanged](https://code.claude.com/docs/en/hooks#filechanged)) | `.envrc\|.env` |
| `UserPromptSubmit`, `Stop`, `TeammateIdle`, `TaskCreated`, `TaskCompleted`, `WorktreeCreate`, `WorktreeRemove`, `CwdChanged` | no matcher support | always fires on every occurrence |

A few more examples showing matchers on different event types:

- Log every Bash command
- Match MCP tools
- Clean up on session end

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
{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "jq -r '.tool_input.command' >> ~/.claude/command-log.txt"
          }
        ]
      }
    ]
  }
}
```

#### Filter by tool name and arguments with the if field

The `if` field requires Claude Code v2.1.85 or later. Earlier versions ignore it and run the hook on every matched call.

The `if` field uses [permission rule syntax](https://code.claude.com/docs/en/permissions) to filter hooks by tool name and arguments together, so the hook process only spawns when the tool call matches. This goes beyond `matcher`, which filters at the group level by tool name only.

For example, to run a hook only when Claude uses `git` commands rather than all Bash commands:

```json
{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "if": "Bash(git *)",
            "command": "\"$CLAUDE_PROJECT_DIR\"/.claude/hooks/check-git-policy.sh"
          }
        ]
      }
    ]
  }
}
```

The hook process only spawns when the Bash command starts with `git`. Other Bash commands skip this handler entirely. The `if` field accepts the same patterns as permission rules: `"Bash(git *)"`, `"Edit(*.ts)"`, and so on. To match multiple tool names, use separate handlers each with its own `if` value, or match at the `matcher` level where pipe alternation is supported.

`if` only works on tool events: `PreToolUse`, `PostToolUse`, `PostToolUseFailure`, `PermissionRequest`, and `PermissionDenied`. Adding it to any other event prevents the hook from running.

### 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](https://code.claude.com/docs/en/plugins) `hooks/hooks.json` | When plugin is enabled | Yes, bundled with the plugin |
| [Skill](https://code.claude.com/docs/en/skills) or [agent](https://code.claude.com/docs/en/sub-agents) frontmatter | While the skill or agent is active | Yes, defined in the component file |

Run [`/hooks`](https://code.claude.com/docs/en/hooks#the-hooks-menu) in Claude Code to browse all configured hooks grouped by event. To disable all hooks at once, set `"disableAllHooks": true` in your settings file.

If you edit settings files directly while Claude Code is running, the file watcher normally picks up hook changes automatically.

## 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
{
  "hooks": {
    "Stop": [
      {
        "hooks": [
          {
            "type": "prompt",
            "prompt": "Check if all tasks are complete. If not, respond with {\"ok\": false, \"reason\": \"what remains to be done\"}."
          }
        ]
      }
    ]
  }
}
```

## 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
{
  "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.

## HTTP hooks

Use `type: "http"` hooks to POST event data to an HTTP endpoint instead of running a shell command. The endpoint receives the same JSON that a command hook would receive on stdin, and returns results through the HTTP response body using the same JSON format.

HTTP hooks are useful when you want a web server, cloud function, or external service to handle hook logic: for example, a shared audit service that logs tool use events across a team.

This example posts every tool use to a local logging service:

```json
{
  "hooks": {
    "PostToolUse": [
      {
        "hooks": [
          {
            "type": "http",
            "url": "http://localhost:8080/hooks/tool-use",
            "headers": {
              "Authorization": "Bearer $MY_TOKEN"
            },
            "allowedEnvVars": ["MY_TOKEN"]
          }
        ]
      }
    ]
  }
}
```

The endpoint should return a JSON response body using the same [output format](https://code.claude.com/docs/en/hooks#json-output) as command hooks. To block a tool call, return a 2xx response with the appropriate `hookSpecificOutput` fields. HTTP status codes alone cannot block actions.

Header values support environment variable interpolation using `$VAR_NAME` or `${VAR_NAME}` syntax. Only variables listed in the `allowedEnvVars` array are resolved; all other `$VAR` references remain empty.

For full configuration options and response handling, see [HTTP hooks](https://code.claude.com/docs/en/hooks#http-hook-fields) in the reference.

## Limitations and troubleshooting

### Limitations

- Command hooks communicate through stdout, stderr, and exit codes only. They cannot trigger `/` commands or tool calls. Text returned via `additionalContext` is injected as a system reminder that Claude reads as plain text. HTTP hooks communicate through the response body instead.
- 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](https://code.claude.com/docs/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. API errors fire [StopFailure](https://code.claude.com/docs/en/hooks#stopfailure) instead.
- When multiple PreToolUse hooks return [`updatedInput`](https://code.claude.com/docs/en/hooks#pretooluse) to rewrite a tool’s arguments, the last one to finish wins. Since hooks run in parallel, the order is non-deterministic. Avoid having more than one hook modify the same tool’s input.

### Hooks and permission modes

PreToolUse hooks fire before any permission-mode check. A hook that returns `permissionDecision: "deny"` blocks the tool even in `bypassPermissions` mode or with `--dangerously-skip-permissions`. This lets you enforce policy that users cannot bypass by changing their permission mode.

The reverse is not true: a hook returning `"allow"` does not bypass deny rules from settings. Hooks can tighten restrictions but not loosen them past what permission rules allow.

### 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:
	```shellscript
	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.

- File edits are normally picked up automatically. If they haven’t appeared after a few seconds, the file watcher may have missed the change: restart your session to force 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`:

```shellscript
#!/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:

```text
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:

```shellscript
# 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

The transcript view, toggled with `Ctrl+O`, shows a one-line summary for each hook that fired: success is silent, blocking errors show stderr, and non-blocking errors show a `<hook name> hook error` notice followed by the first line of stderr.

For full execution details including which hooks matched, their exit codes, stdout, and stderr, read the debug log. Start Claude Code with `claude --debug-file /tmp/claude.log` to write to a known path, then `tail -f /tmp/claude.log` in another terminal. If you started without that flag, run `/debug` mid-session to enable logging and find the log path.

## Learn more

- [Hooks reference](https://code.claude.com/docs/en/hooks): full event schemas, JSON output format, async hooks, and MCP tool hooks
- [Security considerations](https://code.claude.com/docs/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