1> ## Documentation Index
2> Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt
3> Use this file to discover all available pages before exploring further.
4
1# Hooks reference5# Hooks reference
2 6
3> This page provides reference documentation for implementing hooks in Claude Code.7> Reference for Claude Code hook events, configuration schema, JSON input/output formats, exit codes, async hooks, HTTP hooks, prompt hooks, and MCP tool hooks.
4 8
5<Tip>9<Tip>
6 For a quickstart guide with examples, see [Get started with Claude Code hooks](/en/hooks-guide).10 For a quickstart guide with examples, see [Automate workflows with hooks](/en/hooks-guide).
7</Tip>11</Tip>
8 12
9## Configuration13Hooks are user-defined shell commands, HTTP endpoints, 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, HTTP hooks, and MCP tool hooks. If you're setting up hooks for the first time, start with the [guide](/en/hooks-guide) instead.
10 14
11Claude Code hooks are configured in your [settings files](/en/settings):15## Hook lifecycle
12 16
13* `~/.claude/settings.json` - User settings17Hooks 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, input arrives on stdin. For HTTP hooks, it arrives as the POST request body. 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:
14* `.claude/settings.json` - Project settings18
15* `.claude/settings.local.json` - Local project settings (not committed)19<div style={{maxWidth: "500px", margin: "0 auto"}}>
16* Enterprise managed policy settings20 <Frame>
17 21 <img src="https://mintcdn.com/claude-code/JCMefyZyaJwkJgv-/images/hooks-lifecycle.svg?fit=max&auto=format&n=JCMefyZyaJwkJgv-&q=85&s=f004f3fc7324fa2a4630e8d6559cf6dd" alt="Hook lifecycle diagram showing the sequence of hooks from SessionStart through the agentic loop (PreToolUse, PermissionRequest, PostToolUse, SubagentStart/Stop, TaskCompleted) to Stop or StopFailure, TeammateIdle, PreCompact, PostCompact, and SessionEnd, with Elicitation and ElicitationResult nested inside MCP tool execution and WorktreeCreate, WorktreeRemove, Notification, ConfigChange, InstructionsLoaded, CwdChanged, and FileChanged as standalone async events" width="520" height="1100" data-path="images/hooks-lifecycle.svg" />
18### Structure22 </Frame>
19 23</div>
20Hooks are organized by matchers, where each matcher can have multiple hooks:24
25The 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.
26
27| Event | When it fires |
28| :------------------- | :----------------------------------------------------------------------------------------------------------------------------------------------------- |
29| `SessionStart` | When a session begins or resumes |
30| `UserPromptSubmit` | When you submit a prompt, before Claude processes it |
31| `PreToolUse` | Before a tool call executes. Can block it |
32| `PermissionRequest` | When a permission dialog appears |
33| `PostToolUse` | After a tool call succeeds |
34| `PostToolUseFailure` | After a tool call fails |
35| `Notification` | When Claude Code sends a notification |
36| `SubagentStart` | When a subagent is spawned |
37| `SubagentStop` | When a subagent finishes |
38| `Stop` | When Claude finishes responding |
39| `StopFailure` | When the turn ends due to an API error. Output and exit code are ignored |
40| `TeammateIdle` | When an [agent team](/en/agent-teams) teammate is about to go idle |
41| `TaskCompleted` | When a task is being marked as completed |
42| `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 |
43| `ConfigChange` | When a configuration file changes during a session |
44| `CwdChanged` | When the working directory changes, for example when Claude executes a `cd` command. Useful for reactive environment management with tools like direnv |
45| `FileChanged` | When a watched file changes on disk. The `matcher` field specifies which filenames to watch |
46| `WorktreeCreate` | When a worktree is being created via `--worktree` or `isolation: "worktree"`. Replaces default git behavior |
47| `WorktreeRemove` | When a worktree is being removed, either at session exit or when a subagent finishes |
48| `PreCompact` | Before context compaction |
49| `PostCompact` | After context compaction completes |
50| `Elicitation` | When an MCP server requests user input during a tool call |
51| `ElicitationResult` | After a user responds to an MCP elicitation, before the response is sent back to the server |
52| `SessionEnd` | When a session terminates |
53
54### How a hook resolves
55
56To see how these pieces fit together, consider this `PreToolUse` hook that blocks destructive shell commands. The hook runs `block-rm.sh` before every Bash tool call:
21 57
22```json theme={null}58```json theme={null}
23{59{
24 "hooks": {60 "hooks": {
25 "EventName": [61 "PreToolUse": [
26 {62 {
27 "matcher": "ToolPattern",63 "matcher": "Bash",
28 "hooks": [64 "hooks": [
29 {65 {
30 "type": "command",66 "type": "command",
31 "command": "your-command-here"67 "command": ".claude/hooks/block-rm.sh"
32 }68 }
33 ]69 ]
34 }70 }
37}73}
38```74```
39 75
40* **matcher**: Pattern to match tool names, case-sensitive (only applicable for76The script reads the JSON input from stdin, extracts the command, and returns a `permissionDecision` of `"deny"` if it contains `rm -rf`:
41 `PreToolUse`, `PermissionRequest`, and `PostToolUse`)
42 * Simple strings match exactly: `Write` matches only the Write tool
43 * Supports regex: `Edit|Write` or `Notebook.*`
44 * Use `*` to match all tools. You can also use empty string (`""`) or leave
45 `matcher` blank.
46* **hooks**: Array of hooks to execute when the pattern matches
47 * `type`: Hook execution type - `"command"` for bash commands or `"prompt"` for LLM-based evaluation
48 * `command`: (For `type: "command"`) The bash command to execute (can use `$CLAUDE_PROJECT_DIR` environment variable)
49 * `prompt`: (For `type: "prompt"`) The prompt to send to the LLM for evaluation
50 * `timeout`: (Optional) How long a hook should run, in seconds, before canceling that specific hook
51
52For events like `UserPromptSubmit`, `Stop`, and `SubagentStop`
53that don't use matchers, you can omit the matcher field:
54 77
55```json theme={null}78```bash theme={null}
56{79#!/bin/bash
57 "hooks": {80# .claude/hooks/block-rm.sh
58 "UserPromptSubmit": [81COMMAND=$(jq -r '.tool_input.command')
59 {82
60 "hooks": [83if echo "$COMMAND" | grep -q 'rm -rf'; then
61 {84 jq -n '{
62 "type": "command",85 hookSpecificOutput: {
63 "command": "/path/to/prompt-validator.py"86 hookEventName: "PreToolUse",
87 permissionDecision: "deny",
88 permissionDecisionReason: "Destructive command blocked by hook"
64 }89 }
65 ]90 }'
91else
92 exit 0 # allow the command
93fi
94```
95
96Now suppose Claude Code decides to run `Bash "rm -rf /tmp/build"`. Here's what happens:
97
98<Frame>
99 <img src="https://mintcdn.com/claude-code/c5r9_6tjPMzFdDDT/images/hook-resolution.svg?fit=max&auto=format&n=c5r9_6tjPMzFdDDT&q=85&s=ad667ee6d86ab2276aa48a4e73e220df" alt="Hook resolution flow: PreToolUse event fires, matcher checks for Bash match, hook handler runs, result returns to Claude Code" width="780" height="290" data-path="images/hook-resolution.svg" />
100</Frame>
101
102<Steps>
103 <Step title="Event fires">
104 The `PreToolUse` event fires. Claude Code sends the tool input as JSON on stdin to the hook:
105
106 ```json theme={null}
107 { "tool_name": "Bash", "tool_input": { "command": "rm -rf /tmp/build" }, ... }
108 ```
109 </Step>
110
111 <Step title="Matcher checks">
112 The matcher `"Bash"` matches the tool name, so `block-rm.sh` runs. If you omit the matcher or use `"*"`, the hook runs on every occurrence of the event. Hooks only skip when a matcher is defined and doesn't match.
113 </Step>
114
115 <Step title="Hook handler runs">
116 The script extracts `"rm -rf /tmp/build"` from the input and finds `rm -rf`, so it prints a decision to stdout:
117
118 ```json theme={null}
119 {
120 "hookSpecificOutput": {
121 "hookEventName": "PreToolUse",
122 "permissionDecision": "deny",
123 "permissionDecisionReason": "Destructive command blocked by hook"
66 }124 }
67 ]
68 }125 }
69}126 ```
70```
71 127
72### Project-Specific Hook Scripts128 If the command had been safe (like `npm test`), the script would hit `exit 0` instead, which tells Claude Code to allow the tool call with no further action.
129 </Step>
73 130
74You can use the environment variable `CLAUDE_PROJECT_DIR` (only available when131 <Step title="Claude Code acts on the result">
75Claude Code spawns the hook command) to reference scripts stored in your project,132 Claude Code reads the JSON decision, blocks the tool call, and shows Claude the reason.
76ensuring they work regardless of Claude's current directory:133 </Step>
134</Steps>
135
136The [Configuration](#configuration) section below documents the full schema, and each [hook event](#hook-events) section documents what input your command receives and what output it can return.
137
138## Configuration
139
140Hooks are defined in JSON settings files. The configuration has three levels of nesting:
141
1421. Choose a [hook event](#hook-events) to respond to, like `PreToolUse` or `Stop`
1432. Add a [matcher group](#matcher-patterns) to filter when it fires, like "only for the Bash tool"
1443. Define one or more [hook handlers](#hook-handler-fields) to run when matched
145
146See [How a hook resolves](#how-a-hook-resolves) above for a complete walkthrough with an annotated example.
147
148<Note>
149 This page uses specific terms for each level: **hook event** for the lifecycle point, **matcher group** for the filter, and **hook handler** for the shell command, HTTP endpoint, prompt, or agent that runs. "Hook" on its own refers to the general feature.
150</Note>
151
152### Hook locations
153
154Where you define a hook determines its scope:
155
156| Location | Scope | Shareable |
157| :--------------------------------------------------------- | :---------------------------- | :--------------------------------- |
158| `~/.claude/settings.json` | All your projects | No, local to your machine |
159| `.claude/settings.json` | Single project | Yes, can be committed to the repo |
160| `.claude/settings.local.json` | Single project | No, gitignored |
161| Managed policy settings | Organization-wide | Yes, admin-controlled |
162| [Plugin](/en/plugins) `hooks/hooks.json` | When plugin is enabled | Yes, bundled with the plugin |
163| [Skill](/en/skills) or [agent](/en/sub-agents) frontmatter | While the component is active | Yes, defined in the component file |
164
165For details on settings file resolution, see [settings](/en/settings). Enterprise administrators can use `allowManagedHooksOnly` to block user, project, and plugin hooks. See [Hook configuration](/en/settings#hook-configuration).
166
167### Matcher patterns
168
169The `matcher` field is a regex string that filters when hooks fire. Use `"*"`, `""`, or omit `matcher` entirely to match all occurrences. Each event type matches on a different field:
170
171| Event | What the matcher filters | Example matcher values |
172| :---------------------------------------------------------------------------------------------- | :-------------------------------------- | :------------------------------------------------------------------------------------------------------------------------ |
173| `PreToolUse`, `PostToolUse`, `PostToolUseFailure`, `PermissionRequest` | tool name | `Bash`, `Edit\|Write`, `mcp__.*` |
174| `SessionStart` | how the session started | `startup`, `resume`, `clear`, `compact` |
175| `SessionEnd` | why the session ended | `clear`, `resume`, `logout`, `prompt_input_exit`, `bypass_permissions_disabled`, `other` |
176| `Notification` | notification type | `permission_prompt`, `idle_prompt`, `auth_success`, `elicitation_dialog` |
177| `SubagentStart` | agent type | `Bash`, `Explore`, `Plan`, or custom agent names |
178| `PreCompact`, `PostCompact` | what triggered compaction | `manual`, `auto` |
179| `SubagentStop` | agent type | same values as `SubagentStart` |
180| `ConfigChange` | configuration source | `user_settings`, `project_settings`, `local_settings`, `policy_settings`, `skills` |
181| `CwdChanged` | no matcher support | always fires on every directory change |
182| `FileChanged` | filename (basename of the changed file) | `.envrc`, `.env`, any filename you want to watch |
183| `StopFailure` | error type | `rate_limit`, `authentication_failed`, `billing_error`, `invalid_request`, `server_error`, `max_output_tokens`, `unknown` |
184| `InstructionsLoaded` | load reason | `session_start`, `nested_traversal`, `path_glob_match`, `include`, `compact` |
185| `Elicitation` | MCP server name | your configured MCP server names |
186| `ElicitationResult` | MCP server name | same values as `Elicitation` |
187| `UserPromptSubmit`, `Stop`, `TeammateIdle`, `TaskCompleted`, `WorktreeCreate`, `WorktreeRemove` | no matcher support | always fires on every occurrence |
188
189The matcher is a regex, so `Edit|Write` matches either tool and `Notebook.*` matches any tool starting with Notebook. The matcher runs against a field from the [JSON input](#hook-input-and-output) that Claude Code sends to your hook on stdin. For tool events, that field is `tool_name`. Each [hook event](#hook-events) section lists the full set of matcher values and the input schema for that event.
190
191This example runs a linting script only when Claude writes or edits a file:
77 192
78```json theme={null}193```json theme={null}
79{194{
80 "hooks": {195 "hooks": {
81 "PostToolUse": [196 "PostToolUse": [
82 {197 {
83 "matcher": "Write|Edit",198 "matcher": "Edit|Write",
84 "hooks": [199 "hooks": [
85 {200 {
86 "type": "command",201 "type": "command",
87 "command": "\"$CLAUDE_PROJECT_DIR\"/.claude/hooks/check-style.sh"202 "command": "/path/to/lint-check.sh"
88 }203 }
89 ]204 ]
90 }205 }
93}208}
94```209```
95 210
96### Plugin hooks211`UserPromptSubmit`, `Stop`, `TeammateIdle`, `TaskCompleted`, `WorktreeCreate`, `WorktreeRemove`, and `CwdChanged` don't support matchers and always fire on every occurrence. If you add a `matcher` field to these events, it is silently ignored.
97 212
98[Plugins](/en/plugins) can provide hooks that integrate seamlessly with your user and project hooks. Plugin hooks are automatically merged with your configuration when plugins are enabled.213#### Match MCP tools
99 214
100**How plugin hooks work**:215[MCP](/en/mcp) server tools appear as regular tools in tool events (`PreToolUse`, `PostToolUse`, `PostToolUseFailure`, `PermissionRequest`), so you can match them the same way you match any other tool name.
101 216
102* Plugin hooks are defined in the plugin's `hooks/hooks.json` file or in a file given by a custom path to the `hooks` field.217MCP tools follow the naming pattern `mcp__<server>__<tool>`, for example:
103* When a plugin is enabled, its hooks are merged with user and project hooks
104* Multiple hooks from different sources can respond to the same event
105* Plugin hooks use the `${CLAUDE_PLUGIN_ROOT}` environment variable to reference plugin files
106 218
107**Example plugin hook configuration**:219* `mcp__memory__create_entities`: Memory server's create entities tool
220* `mcp__filesystem__read_file`: Filesystem server's read file tool
221* `mcp__github__search_repositories`: GitHub server's search tool
222
223Use regex patterns to target specific MCP tools or groups of tools:
224
225* `mcp__memory__.*` matches all tools from the `memory` server
226* `mcp__.*__write.*` matches any tool containing "write" from any server
227
228This example logs all memory server operations and validates write operations from any MCP server:
108 229
109```json theme={null}230```json theme={null}
110{231{
111 "description": "Automatic code formatting",
112 "hooks": {232 "hooks": {
113 "PostToolUse": [233 "PreToolUse": [
114 {234 {
115 "matcher": "Write|Edit",235 "matcher": "mcp__memory__.*",
116 "hooks": [236 "hooks": [
117 {237 {
118 "type": "command",238 "type": "command",
119 "command": "${CLAUDE_PLUGIN_ROOT}/scripts/format.sh",239 "command": "echo 'Memory operation initiated' >> ~/mcp-operations.log"
120 "timeout": 30240 }
241 ]
242 },
243 {
244 "matcher": "mcp__.*__write.*",
245 "hooks": [
246 {
247 "type": "command",
248 "command": "/home/user/scripts/validate-mcp-write.py"
121 }249 }
122 ]250 ]
123 }251 }
126}254}
127```255```
128 256
129<Note>257### Hook handler fields
130 Plugin hooks use the same format as regular hooks with an optional `description` field to explain the hook's purpose.
131</Note>
132 258
133<Note>259Each object in the inner `hooks` array is a hook handler: the shell command, HTTP endpoint, LLM prompt, or agent that runs when the matcher matches. There are four types:
134 Plugin hooks run alongside your custom hooks. If multiple hooks match an event, they all execute in parallel.
135</Note>
136 260
137**Environment variables for plugins**:261* **[Command hooks](#command-hook-fields)** (`type: "command"`): run a shell command. Your script receives the event's [JSON input](#hook-input-and-output) on stdin and communicates results back through exit codes and stdout.
262* **[HTTP hooks](#http-hook-fields)** (`type: "http"`): send the event's JSON input as an HTTP POST request to a URL. The endpoint communicates results back through the response body using the same [JSON output format](#json-output) as command hooks.
263* **[Prompt hooks](#prompt-and-agent-hook-fields)** (`type: "prompt"`): send a prompt to a Claude model for single-turn evaluation. The model returns a yes/no decision as JSON. See [Prompt-based hooks](#prompt-based-hooks).
264* **[Agent hooks](#prompt-and-agent-hook-fields)** (`type: "agent"`): spawn a subagent that can use tools like Read, Grep, and Glob to verify conditions before returning a decision. See [Agent-based hooks](#agent-based-hooks).
138 265
139* `${CLAUDE_PLUGIN_ROOT}`: Absolute path to the plugin directory266#### Common fields
140* `${CLAUDE_PROJECT_DIR}`: Project root directory (same as for project hooks)
141* All standard environment variables are available
142 267
143See the [plugin components reference](/en/plugins-reference#hooks) for details on creating plugin hooks.268These fields apply to all hook types:
144 269
145## Prompt-Based Hooks270| Field | Required | Description |
271| :-------------- | :------- | :-------------------------------------------------------------------------------------------------------------------------------------------- |
272| `type` | yes | `"command"`, `"http"`, `"prompt"`, or `"agent"` |
273| `timeout` | no | Seconds before canceling. Defaults: 600 for command, 30 for prompt, 60 for agent |
274| `statusMessage` | no | Custom spinner message displayed while the hook runs |
275| `once` | no | If `true`, runs only once per session then is removed. Skills only, not agents. See [Hooks in skills and agents](#hooks-in-skills-and-agents) |
146 276
147In addition to bash command hooks (`type: "command"`), Claude Code supports prompt-based hooks (`type: "prompt"`) that use an LLM to evaluate whether to allow or block an action. Prompt-based hooks are currently only supported for `Stop` and `SubagentStop` hooks, where they enable intelligent, context-aware decisions.277#### Command hook fields
148 278
149### How prompt-based hooks work279In addition to the [common fields](#common-fields), command hooks accept these fields:
150 280
151Instead of executing a bash command, prompt-based hooks:281| Field | Required | Description |
282| :-------- | :------- | :------------------------------------------------------------------------------------------------------------------ |
283| `command` | yes | Shell command to execute |
284| `async` | no | If `true`, runs in the background without blocking. See [Run hooks in the background](#run-hooks-in-the-background) |
152 285
1531. Send the hook input and your prompt to a fast LLM (Haiku)286#### HTTP hook fields
1542. The LLM responds with structured JSON containing a decision287
1553. Claude Code processes the decision automatically288In addition to the [common fields](#common-fields), HTTP hooks accept these fields:
156 289
157### Configuration290| Field | Required | Description |
291| :--------------- | :------- | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
292| `url` | yes | URL to send the POST request to |
293| `headers` | no | Additional HTTP headers as key-value pairs. Values support environment variable interpolation using `$VAR_NAME` or `${VAR_NAME}` syntax. Only variables listed in `allowedEnvVars` are resolved |
294| `allowedEnvVars` | no | List of environment variable names that may be interpolated into header values. References to unlisted variables are replaced with empty strings. Required for any env var interpolation to work |
295
296Claude Code sends the hook's [JSON input](#hook-input-and-output) as the POST request body with `Content-Type: application/json`. The response body uses the same [JSON output format](#json-output) as command hooks.
297
298Error handling differs from command hooks: non-2xx responses, connection failures, and timeouts all produce non-blocking errors that allow execution to continue. To block a tool call or deny a permission, return a 2xx response with a JSON body containing `decision: "block"` or a `hookSpecificOutput` with `permissionDecision: "deny"`.
299
300This example sends `PreToolUse` events to a local validation service, authenticating with a token from the `MY_TOKEN` environment variable:
158 301
159```json theme={null}302```json theme={null}
160{303{
161 "hooks": {304 "hooks": {
162 "Stop": [305 "PreToolUse": [
163 {306 {
307 "matcher": "Bash",
164 "hooks": [308 "hooks": [
165 {309 {
166 "type": "prompt",310 "type": "http",
167 "prompt": "Evaluate if Claude should stop: $ARGUMENTS. Check if all tasks are complete."311 "url": "http://localhost:8080/hooks/pre-tool-use",
312 "timeout": 30,
313 "headers": {
314 "Authorization": "Bearer $MY_TOKEN"
315 },
316 "allowedEnvVars": ["MY_TOKEN"]
168 }317 }
169 ]318 ]
170 }319 }
173}322}
174```323```
175 324
176**Fields:**325#### Prompt and agent hook fields
177 326
178* `type`: Must be `"prompt"`327In addition to the [common fields](#common-fields), prompt and agent hooks accept these fields:
179* `prompt`: The prompt text to send to the LLM
180 * Use `$ARGUMENTS` as a placeholder for the hook input JSON
181 * If `$ARGUMENTS` is not present, input JSON is appended to the prompt
182* `timeout`: (Optional) Timeout in seconds (default: 30 seconds)
183
184### Response schema
185
186The LLM must respond with JSON containing:
187
188```json theme={null}
189{
190 "decision": "approve" | "block",
191 "reason": "Explanation for the decision",
192 "continue": false, // Optional: stops Claude entirely
193 "stopReason": "Message shown to user", // Optional: custom stop message
194 "systemMessage": "Warning or context" // Optional: shown to user
195}
196```
197 328
198**Response fields:**329| Field | Required | Description |
330| :------- | :------- | :------------------------------------------------------------------------------------------ |
331| `prompt` | yes | Prompt text to send to the model. Use `$ARGUMENTS` as a placeholder for the hook input JSON |
332| `model` | no | Model to use for evaluation. Defaults to a fast model |
199 333
200* `decision`: `"approve"` allows the action, `"block"` prevents it334All matching hooks run in parallel, and identical handlers are deduplicated automatically. Command hooks are deduplicated by command string, and HTTP hooks are deduplicated by URL. Handlers run in the current directory with Claude Code's environment. The `$CLAUDE_CODE_REMOTE` environment variable is set to `"true"` in remote web environments and not set in the local CLI.
201* `reason`: Explanation shown to Claude when decision is `"block"`
202* `continue`: (Optional) If `false`, stops Claude's execution entirely
203* `stopReason`: (Optional) Message shown when `continue` is false
204* `systemMessage`: (Optional) Additional message shown to the user
205 335
206### Supported hook events336### Reference scripts by path
207 337
208Prompt-based hooks work with any hook event, but are most useful for:338Use environment variables to reference hook scripts relative to the project or plugin root, regardless of the working directory when the hook runs:
209 339
210* **Stop**: Intelligently decide if Claude should continue working340* `$CLAUDE_PROJECT_DIR`: the project root. Wrap in quotes to handle paths with spaces.
211* **SubagentStop**: Evaluate if a subagent has completed its task341* `${CLAUDE_PLUGIN_ROOT}`: the plugin's installation directory, for scripts bundled with a [plugin](/en/plugins). Changes on each plugin update.
212* **UserPromptSubmit**: Validate user prompts with LLM assistance342* `${CLAUDE_PLUGIN_DATA}`: the plugin's [persistent data directory](/en/plugins-reference#persistent-data-directory), for dependencies and state that should survive plugin updates.
213* **PreToolUse**: Make context-aware permission decisions
214* **PermissionRequest**: Intelligently allow or deny permission dialogs
215 343
216### Example: Intelligent Stop hook344<Tabs>
345 <Tab title="Project scripts">
346 This example uses `$CLAUDE_PROJECT_DIR` to run a style checker from the project's `.claude/hooks/` directory after any `Write` or `Edit` tool call:
217 347
218```json theme={null}348 ```json theme={null}
219{349 {
220 "hooks": {350 "hooks": {
221 "Stop": [351 "PostToolUse": [
222 {352 {
353 "matcher": "Write|Edit",
223 "hooks": [354 "hooks": [
224 {355 {
225 "type": "prompt",356 "type": "command",
226 "prompt": "You are evaluating whether Claude should stop working. Context: $ARGUMENTS\n\nAnalyze the conversation and determine if:\n1. All user-requested tasks are complete\n2. Any errors need to be addressed\n3. Follow-up work is needed\n\nRespond with JSON: {\"decision\": \"approve\" or \"block\", \"reason\": \"your explanation\"}",357 "command": "\"$CLAUDE_PROJECT_DIR\"/.claude/hooks/check-style.sh"
227 "timeout": 30
228 }358 }
229 ]359 ]
230 }360 }
231 ]361 ]
232 }362 }
233}363 }
234```364 ```
365 </Tab>
235 366
236### Example: SubagentStop with custom logic367 <Tab title="Plugin scripts">
368 Define plugin hooks in `hooks/hooks.json` with an optional top-level `description` field. When a plugin is enabled, its hooks merge with your user and project hooks.
237 369
238```json theme={null}370 This example runs a formatting script bundled with the plugin:
239{371
372 ```json theme={null}
373 {
374 "description": "Automatic code formatting",
240 "hooks": {375 "hooks": {
241 "SubagentStop": [376 "PostToolUse": [
242 {377 {
378 "matcher": "Write|Edit",
243 "hooks": [379 "hooks": [
244 {380 {
245 "type": "prompt",381 "type": "command",
246 "prompt": "Evaluate if this subagent should stop. Input: $ARGUMENTS\n\nCheck if:\n- The subagent completed its assigned task\n- Any errors occurred that need fixing\n- Additional context gathering is needed\n\nReturn: {\"decision\": \"approve\" or \"block\", \"reason\": \"explanation\"}"382 "command": "${CLAUDE_PLUGIN_ROOT}/scripts/format.sh",
383 "timeout": 30
247 }384 }
248 ]385 ]
249 }386 }
250 ]387 ]
251 }388 }
252}389 }
253```390 ```
254 391
255### Comparison with bash command hooks392 See the [plugin components reference](/en/plugins-reference#hooks) for details on creating plugin hooks.
393 </Tab>
394</Tabs>
256 395
257| Feature | Bash Command Hooks | Prompt-Based Hooks |396### Hooks in skills and agents
258| --------------------- | ----------------------- | ------------------------------ |
259| **Execution** | Runs bash script | Queries LLM |
260| **Decision logic** | You implement in code | LLM evaluates context |
261| **Setup complexity** | Requires script file | Just configure prompt |
262| **Context awareness** | Limited to script logic | Natural language understanding |
263| **Performance** | Fast (local execution) | Slower (API call) |
264| **Use case** | Deterministic rules | Context-aware decisions |
265 397
266### Best practices398In addition to settings files and plugins, hooks can be defined directly in [skills](/en/skills) and [subagents](/en/sub-agents) using frontmatter. These hooks are scoped to the component's lifecycle and only run when that component is active.
267 399
268* **Be specific in prompts**: Clearly state what you want the LLM to evaluate400All hook events are supported. For subagents, `Stop` hooks are automatically converted to `SubagentStop` since that is the event that fires when a subagent completes.
269* **Include decision criteria**: List the factors the LLM should consider
270* **Test your prompts**: Verify the LLM makes correct decisions for your use cases
271* **Set appropriate timeouts**: Default is 30 seconds, adjust if needed
272* **Use for complex decisions**: Bash hooks are better for simple, deterministic rules
273 401
274See the [plugin components reference](/en/plugins-reference#hooks) for details on creating plugin hooks.402Hooks use the same configuration format as settings-based hooks but are scoped to the component's lifetime and cleaned up when it finishes.
275 403
276## Hook Events404This skill defines a `PreToolUse` hook that runs a security validation script before each `Bash` command:
277 405
278### PreToolUse406```yaml theme={null}
407---
408name: secure-operations
409description: Perform operations with security checks
410hooks:
411 PreToolUse:
412 - matcher: "Bash"
413 hooks:
414 - type: command
415 command: "./scripts/security-check.sh"
416---
417```
279 418
280Runs after Claude creates tool parameters and before processing the tool call.419Agents use the same format in their YAML frontmatter.
281 420
282**Common matchers:**421### The `/hooks` menu
283 422
284* `Task` - Subagent tasks (see [subagents documentation](/en/sub-agents))423Type `/hooks` in Claude Code to open a read-only browser for your configured hooks. The menu shows every hook event with a count of configured hooks, lets you drill into matchers, and shows the full details of each hook handler. Use it to verify configuration, check which settings file a hook came from, or inspect a hook's command, prompt, or URL.
285* `Bash` - Shell commands
286* `Glob` - File pattern matching
287* `Grep` - Content search
288* `Read` - File reading
289* `Edit` - File editing
290* `Write` - File writing
291* `WebFetch`, `WebSearch` - Web operations
292 424
293Use [PreToolUse decision control](#pretooluse-decision-control) to allow, deny, or ask for permission to use the tool.425The menu displays all four hook types: `command`, `prompt`, `agent`, and `http`. Each hook is labeled with a `[type]` prefix and a source indicating where it was defined:
294 426
295### PermissionRequest427* `User`: from `~/.claude/settings.json`
428* `Project`: from `.claude/settings.json`
429* `Local`: from `.claude/settings.local.json`
430* `Plugin`: from a plugin's `hooks/hooks.json`
431* `Session`: registered in memory for the current session
432* `Built-in`: registered internally by Claude Code
296 433
297Runs when the user is shown a permission dialog.434Selecting a hook opens a detail view showing its event, matcher, type, source file, and the full command, prompt, or URL. The menu is read-only: to add, modify, or remove hooks, edit the settings JSON directly or ask Claude to make the change.
298Use [PermissionRequest decision control](#permissionrequest-decision-control) to allow or deny on behalf of the user.
299 435
300Recognizes the same matcher values as PreToolUse.436### Disable or remove hooks
301 437
302### PostToolUse438To remove a hook, delete its entry from the settings JSON file.
303 439
304Runs immediately after a tool completes successfully.440To temporarily disable all hooks without removing them, set `"disableAllHooks": true` in your settings file. There is no way to disable an individual hook while keeping it in the configuration.
305 441
306Recognizes the same matcher values as PreToolUse.442The `disableAllHooks` setting respects the managed settings hierarchy. If an administrator has configured hooks through managed policy settings, `disableAllHooks` set in user, project, or local settings cannot disable those managed hooks. Only `disableAllHooks` set at the managed settings level can disable managed hooks.
307 443
308### Notification444Direct edits to hooks in settings files are normally picked up automatically by the file watcher.
445
446## Hook input and output
447
448Command hooks receive JSON data via stdin and communicate results through exit codes, stdout, and stderr. HTTP hooks receive the same JSON as the POST request body and communicate results through the HTTP response body. This section covers fields and behavior common to all events. Each event's section under [Hook events](#hook-events) includes its specific input schema and decision control options.
449
450### Common input fields
309 451
310Runs when Claude Code sends notifications. Supports matchers to filter by notification type.452Hook events receive these fields as JSON, in addition to event-specific fields documented in each [hook event](#hook-events) section. For command hooks, this JSON arrives via stdin. For HTTP hooks, it arrives as the POST request body.
311 453
312**Common matchers:**454| Field | Description |
455| :---------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
456| `session_id` | Current session identifier |
457| `transcript_path` | Path to conversation JSON |
458| `cwd` | Current working directory when the hook is invoked |
459| `permission_mode` | Current [permission mode](/en/permissions#permission-modes): `"default"`, `"plan"`, `"acceptEdits"`, `"auto"`, `"dontAsk"`, or `"bypassPermissions"`. Not all events receive this field: see each event's JSON example below to check |
460| `hook_event_name` | Name of the event that fired |
313 461
314* `permission_prompt` - Permission requests from Claude Code462When running with `--agent` or inside a subagent, two additional fields are included:
315* `idle_prompt` - When Claude is waiting for user input (after 60+ seconds of idle time)
316* `auth_success` - Authentication success notifications
317* `elicitation_dialog` - When Claude Code needs input for MCP tool elicitation
318 463
319You can use matchers to run different hooks for different notification types, or omit the matcher to run hooks for all notifications.464| Field | Description |
465| :----------- | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
466| `agent_id` | Unique identifier for the subagent. Present only when the hook fires inside a subagent call. Use this to distinguish subagent hook calls from main-thread calls. |
467| `agent_type` | Agent name (for example, `"Explore"` or `"security-reviewer"`). Present when the session uses `--agent` or the hook fires inside a subagent. For subagents, the subagent's type takes precedence over the session's `--agent` value. |
320 468
321**Example: Different notifications for different types**469For example, a `PreToolUse` hook for a Bash command receives this on stdin:
322 470
323```json theme={null}471```json theme={null}
324{472{
325 "hooks": {473 "session_id": "abc123",
326 "Notification": [474 "transcript_path": "/home/user/.claude/projects/.../transcript.jsonl",
327 {475 "cwd": "/home/user/my-project",
328 "matcher": "permission_prompt",476 "permission_mode": "default",
329 "hooks": [477 "hook_event_name": "PreToolUse",
478 "tool_name": "Bash",
479 "tool_input": {
480 "command": "npm test"
481 }
482}
483```
484
485The `tool_name` and `tool_input` fields are event-specific. Each [hook event](#hook-events) section documents the additional fields for that event.
486
487### Exit code output
488
489The exit code from your hook command tells Claude Code whether the action should proceed, be blocked, or be ignored.
490
491**Exit 0** means success. Claude Code parses stdout for [JSON output fields](#json-output). JSON output is only processed on exit 0. For most events, stdout is only shown in verbose mode (`Ctrl+O`). The exceptions are `UserPromptSubmit` and `SessionStart`, where stdout is added as context that Claude can see and act on.
492
493**Exit 2** means a blocking error. Claude Code ignores stdout and any JSON in it. Instead, stderr text is fed back to Claude as an error message. The effect depends on the event: `PreToolUse` blocks the tool call, `UserPromptSubmit` rejects the prompt, and so on. See [exit code 2 behavior](#exit-code-2-behavior-per-event) for the full list.
494
495**Any other exit code** is a non-blocking error. stderr is shown in verbose mode (`Ctrl+O`) and execution continues.
496
497For example, a hook command script that blocks dangerous Bash commands:
498
499```bash theme={null}
500#!/bin/bash
501# Reads JSON input from stdin, checks the command
502command=$(jq -r '.tool_input.command' < /dev/stdin)
503
504if [[ "$command" == rm* ]]; then
505 echo "Blocked: rm commands are not allowed" >&2
506 exit 2 # Blocking error: tool call is prevented
507fi
508
509exit 0 # Success: tool call proceeds
510```
511
512#### Exit code 2 behavior per event
513
514Exit code 2 is the way a hook signals "stop, don't do this." The effect depends on the event, because some events represent actions that can be blocked (like a tool call that hasn't happened yet) and others represent things that already happened or can't be prevented.
515
516| Hook event | Can block? | What happens on exit 2 |
517| :------------------- | :--------- | :---------------------------------------------------------------------------- |
518| `PreToolUse` | Yes | Blocks the tool call |
519| `PermissionRequest` | Yes | Denies the permission |
520| `UserPromptSubmit` | Yes | Blocks prompt processing and erases the prompt |
521| `Stop` | Yes | Prevents Claude from stopping, continues the conversation |
522| `SubagentStop` | Yes | Prevents the subagent from stopping |
523| `TeammateIdle` | Yes | Prevents the teammate from going idle (teammate continues working) |
524| `TaskCompleted` | Yes | Prevents the task from being marked as completed |
525| `ConfigChange` | Yes | Blocks the configuration change from taking effect (except `policy_settings`) |
526| `StopFailure` | No | Output and exit code are ignored |
527| `PostToolUse` | No | Shows stderr to Claude (tool already ran) |
528| `PostToolUseFailure` | No | Shows stderr to Claude (tool already failed) |
529| `Notification` | No | Shows stderr to user only |
530| `SubagentStart` | No | Shows stderr to user only |
531| `SessionStart` | No | Shows stderr to user only |
532| `SessionEnd` | No | Shows stderr to user only |
533| `CwdChanged` | No | Shows stderr to user only |
534| `FileChanged` | No | Shows stderr to user only |
535| `PreCompact` | No | Shows stderr to user only |
536| `PostCompact` | No | Shows stderr to user only |
537| `Elicitation` | Yes | Denies the elicitation |
538| `ElicitationResult` | Yes | Blocks the response (action becomes decline) |
539| `WorktreeCreate` | Yes | Any non-zero exit code causes worktree creation to fail |
540| `WorktreeRemove` | No | Failures are logged in debug mode only |
541| `InstructionsLoaded` | No | Exit code is ignored |
542
543### HTTP response handling
544
545HTTP hooks use HTTP status codes and response bodies instead of exit codes and stdout:
546
547* **2xx with an empty body**: success, equivalent to exit code 0 with no output
548* **2xx with a plain text body**: success, the text is added as context
549* **2xx with a JSON body**: success, parsed using the same [JSON output](#json-output) schema as command hooks
550* **Non-2xx status**: non-blocking error, execution continues
551* **Connection failure or timeout**: non-blocking error, execution continues
552
553Unlike command hooks, HTTP hooks cannot signal a blocking error through status codes alone. To block a tool call or deny a permission, return a 2xx response with a JSON body containing the appropriate decision fields.
554
555### JSON output
556
557Exit codes let you allow or block, but JSON output gives you finer-grained control. Instead of exiting with code 2 to block, exit 0 and print a JSON object to stdout. Claude Code reads specific fields from that JSON to control behavior, including [decision control](#decision-control) for blocking, allowing, or escalating to the user.
558
559<Note>
560 You must choose one approach per hook, not both: either use exit codes alone for signaling, or exit 0 and print JSON for structured control. Claude Code only processes JSON on exit 0. If you exit 2, any JSON is ignored.
561</Note>
562
563Your hook's stdout must contain only the JSON object. If your shell profile prints text on startup, it can interfere with JSON parsing. See [JSON validation failed](/en/hooks-guide#json-validation-failed) in the troubleshooting guide.
564
565The JSON object supports three kinds of fields:
566
567* **Universal fields** like `continue` work across all events. These are listed in the table below.
568* **Top-level `decision` and `reason`** are used by some events to block or provide feedback.
569* **`hookSpecificOutput`** is a nested object for events that need richer control. It requires a `hookEventName` field set to the event name.
570
571| Field | Default | Description |
572| :--------------- | :------ | :------------------------------------------------------------------------------------------------------------------------- |
573| `continue` | `true` | If `false`, Claude stops processing entirely after the hook runs. Takes precedence over any event-specific decision fields |
574| `stopReason` | none | Message shown to the user when `continue` is `false`. Not shown to Claude |
575| `suppressOutput` | `false` | If `true`, hides stdout from verbose mode output |
576| `systemMessage` | none | Warning message shown to the user |
577
578To stop Claude entirely regardless of event type:
579
580```json theme={null}
581{ "continue": false, "stopReason": "Build failed, fix errors before continuing" }
582```
583
584#### Decision control
585
586Not every event supports blocking or controlling behavior through JSON. The events that do each use a different set of fields to express that decision. Use this table as a quick reference before writing a hook:
587
588| Events | Decision pattern | Key fields |
589| :-------------------------------------------------------------------------------------------------------------------------- | :----------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
590| UserPromptSubmit, PostToolUse, PostToolUseFailure, Stop, SubagentStop, ConfigChange | Top-level `decision` | `decision: "block"`, `reason` |
591| TeammateIdle, TaskCompleted | Exit code or `continue: false` | Exit code 2 blocks the action with stderr feedback. JSON `{"continue": false, "stopReason": "..."}` also stops the teammate entirely, matching `Stop` hook behavior |
592| PreToolUse | `hookSpecificOutput` | `permissionDecision` (allow/deny/ask), `permissionDecisionReason` |
593| PermissionRequest | `hookSpecificOutput` | `decision.behavior` (allow/deny) |
594| WorktreeCreate | stdout path | Hook prints absolute path to created worktree. Non-zero exit fails creation |
595| Elicitation | `hookSpecificOutput` | `action` (accept/decline/cancel), `content` (form field values for accept) |
596| ElicitationResult | `hookSpecificOutput` | `action` (accept/decline/cancel), `content` (form field values override) |
597| WorktreeRemove, Notification, SessionEnd, PreCompact, PostCompact, InstructionsLoaded, StopFailure, CwdChanged, FileChanged | None | No decision control. Used for side effects like logging or cleanup |
598
599Here are examples of each pattern in action:
600
601<Tabs>
602 <Tab title="Top-level decision">
603 Used by `UserPromptSubmit`, `PostToolUse`, `PostToolUseFailure`, `Stop`, `SubagentStop`, and `ConfigChange`. The only value is `"block"`. To allow the action to proceed, omit `decision` from your JSON, or exit 0 without any JSON at all:
604
605 ```json theme={null}
330 {606 {
331 "type": "command",607 "decision": "block",
332 "command": "/path/to/permission-alert.sh"608 "reason": "Test suite must pass before proceeding"
333 }609 }
334 ]610 ```
335 },611 </Tab>
612
613 <Tab title="PreToolUse">
614 Uses `hookSpecificOutput` for richer control: allow, deny, or escalate to the user. You can also modify tool input before it runs or inject additional context for Claude. See [PreToolUse decision control](#pretooluse-decision-control) for the full set of options.
615
616 ```json theme={null}
336 {617 {
337 "matcher": "idle_prompt",618 "hookSpecificOutput": {
338 "hooks": [619 "hookEventName": "PreToolUse",
620 "permissionDecision": "deny",
621 "permissionDecisionReason": "Database writes are not allowed"
622 }
623 }
624 ```
625 </Tab>
626
627 <Tab title="PermissionRequest">
628 Uses `hookSpecificOutput` to allow or deny a permission request on behalf of the user. When allowing, you can also modify the tool's input or apply permission rules so the user isn't prompted again. See [PermissionRequest decision control](#permissionrequest-decision-control) for the full set of options.
629
630 ```json theme={null}
339 {631 {
340 "type": "command",632 "hookSpecificOutput": {
341 "command": "/path/to/idle-notification.sh"633 "hookEventName": "PermissionRequest",
634 "decision": {
635 "behavior": "allow",
636 "updatedInput": {
637 "command": "npm run lint"
342 }638 }
343 ]
344 }639 }
345 ]
346 }640 }
347}641 }
348```642 ```
643 </Tab>
644</Tabs>
349 645
350### UserPromptSubmit646For extended examples including Bash command validation, prompt filtering, and auto-approval scripts, see [What you can automate](/en/hooks-guide#what-you-can-automate) in the guide and the [Bash command validator reference implementation](https://github.com/anthropics/claude-code/blob/main/examples/hooks/bash_command_validator_example.py).
351 647
352Runs when the user submits a prompt, before Claude processes it. This allows you648## Hook events
353to add additional context based on the prompt/conversation, validate prompts, or
354block certain types of prompts.
355 649
356### Stop650Each event corresponds to a point in Claude Code's lifecycle where hooks can run. The sections below are ordered to match the lifecycle: from session setup through the agentic loop to session end. Each section describes when the event fires, what matchers it supports, the JSON input it receives, and how to control behavior through output.
357 651
358Runs when the main Claude Code agent has finished responding. Does not run if652### SessionStart
359the stoppage occurred due to a user interrupt.
360 653
361### SubagentStop654Runs when Claude Code starts a new session or resumes an existing session. Useful for loading development context like existing issues or recent changes to your codebase, or setting up environment variables. For static context that does not require a script, use [CLAUDE.md](/en/memory) instead.
362 655
363Runs when a Claude Code subagent (Task tool call) has finished responding.656SessionStart runs on every session, so keep these hooks fast. Only `type: "command"` hooks are supported.
364 657
365### PreCompact658The matcher value corresponds to how the session was initiated:
366 659
367Runs before Claude Code is about to run a compact operation.660| Matcher | When it fires |
661| :-------- | :------------------------------------- |
662| `startup` | New session |
663| `resume` | `--resume`, `--continue`, or `/resume` |
664| `clear` | `/clear` |
665| `compact` | Auto or manual compaction |
368 666
369**Matchers:**667#### SessionStart input
370 668
371* `manual` - Invoked from `/compact`669In addition to the [common input fields](#common-input-fields), SessionStart hooks receive `source`, `model`, and optionally `agent_type`. The `source` field indicates how the session started: `"startup"` for new sessions, `"resume"` for resumed sessions, `"clear"` after `/clear`, or `"compact"` after compaction. The `model` field contains the model identifier. If you start Claude Code with `claude --agent <name>`, an `agent_type` field contains the agent name.
372* `auto` - Invoked from auto-compact (due to full context window)
373 670
374### SessionStart671```json theme={null}
672{
673 "session_id": "abc123",
674 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
675 "cwd": "/Users/...",
676 "hook_event_name": "SessionStart",
677 "source": "startup",
678 "model": "claude-sonnet-4-6"
679}
680```
681
682#### SessionStart decision control
375 683
376Runs when Claude Code starts a new session or resumes an existing session (which684Any text your hook script prints to stdout is added as context for Claude. In addition to the [JSON output fields](#json-output) available to all hooks, you can return these event-specific fields:
377currently does start a new session under the hood). Useful for loading in
378development context like existing issues or recent changes to your codebase, installing dependencies, or setting up environment variables.
379 685
380**Matchers:**686| Field | Description |
687| :------------------ | :------------------------------------------------------------------------ |
688| `additionalContext` | String added to Claude's context. Multiple hooks' values are concatenated |
381 689
382* `startup` - Invoked from startup690```json theme={null}
383* `resume` - Invoked from `--resume`, `--continue`, or `/resume`691{
384* `clear` - Invoked from `/clear`692 "hookSpecificOutput": {
385* `compact` - Invoked from auto or manual compact.693 "hookEventName": "SessionStart",
694 "additionalContext": "My additional context here"
695 }
696}
697```
386 698
387#### Persisting environment variables699#### Persist environment variables
388 700
389SessionStart hooks have access to the `CLAUDE_ENV_FILE` environment variable, which provides a file path where you can persist environment variables for subsequent bash commands.701SessionStart hooks have access to the `CLAUDE_ENV_FILE` environment variable, which provides a file path where you can persist environment variables for subsequent Bash commands.
390 702
391**Example: Setting individual environment variables**703To set individual environment variables, write `export` statements to `CLAUDE_ENV_FILE`. Use append (`>>`) to preserve variables set by other hooks:
392 704
393```bash theme={null}705```bash theme={null}
394#!/bin/bash706#!/bin/bash
395 707
396if [ -n "$CLAUDE_ENV_FILE" ]; then708if [ -n "$CLAUDE_ENV_FILE" ]; then
397 echo 'export NODE_ENV=production' >> "$CLAUDE_ENV_FILE"709 echo 'export NODE_ENV=production' >> "$CLAUDE_ENV_FILE"
398 echo 'export API_KEY=your-api-key' >> "$CLAUDE_ENV_FILE"710 echo 'export DEBUG_LOG=true' >> "$CLAUDE_ENV_FILE"
399 echo 'export PATH="$PATH:./node_modules/.bin"' >> "$CLAUDE_ENV_FILE"711 echo 'export PATH="$PATH:./node_modules/.bin"' >> "$CLAUDE_ENV_FILE"
400fi712fi
401 713
402exit 0714exit 0
403```715```
404 716
405**Example: Persisting all environment changes from the hook**717To capture all environment changes from setup commands, compare the exported variables before and after:
406
407When your setup modifies the environment (e.g., `nvm use`), capture and persist all changes by diffing the environment:
408 718
409```bash theme={null}719```bash theme={null}
410#!/bin/bash720#!/bin/bash
423exit 0733exit 0
424```734```
425 735
426Any variables written to this file will be available in all subsequent bash commands that Claude Code executes during the session.736Any variables written to this file will be available in all subsequent Bash commands that Claude Code executes during the session.
427 737
428<Note>738<Note>
429 `CLAUDE_ENV_FILE` is only available for SessionStart hooks. Other hook types do not have access to this variable.739 `CLAUDE_ENV_FILE` is available for SessionStart, [CwdChanged](#cwdchanged), and [FileChanged](#filechanged) hooks. Other hook types do not have access to this variable.
430</Note>740</Note>
431 741
432### SessionEnd742### InstructionsLoaded
433 743
434Runs when a Claude Code session ends. Useful for cleanup tasks, logging session744Fires when a `CLAUDE.md` or `.claude/rules/*.md` file is loaded into context. This event fires at session start for eagerly-loaded files and again later when files are lazily loaded, for example when Claude accesses a subdirectory that contains a nested `CLAUDE.md` or when conditional rules with `paths:` frontmatter match. The hook does not support blocking or decision control. It runs asynchronously for observability purposes.
435statistics, or saving session state.
436 745
437The `reason` field in the hook input will be one of:746The matcher runs against `load_reason`. For example, use `"matcher": "session_start"` to fire only for files loaded at session start, or `"matcher": "path_glob_match|nested_traversal"` to fire only for lazy loads.
438 747
439* `clear` - Session cleared with /clear command748#### InstructionsLoaded input
440* `logout` - User logged out
441* `prompt_input_exit` - User exited while prompt input was visible
442* `other` - Other exit reasons
443 749
444## Hook Input750In addition to the [common input fields](#common-input-fields), InstructionsLoaded hooks receive these fields:
445 751
446Hooks receive JSON data via stdin containing session information and752| Field | Description |
447event-specific data:753| :------------------ | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
754| `file_path` | Absolute path to the instruction file that was loaded |
755| `memory_type` | Scope of the file: `"User"`, `"Project"`, `"Local"`, or `"Managed"` |
756| `load_reason` | Why the file was loaded: `"session_start"`, `"nested_traversal"`, `"path_glob_match"`, `"include"`, or `"compact"`. The `"compact"` value fires when instruction files are re-loaded after a compaction event |
757| `globs` | Path glob patterns from the file's `paths:` frontmatter, if any. Present only for `path_glob_match` loads |
758| `trigger_file_path` | Path to the file whose access triggered this load, for lazy loads |
759| `parent_file_path` | Path to the parent instruction file that included this one, for `include` loads |
448 760
449```typescript theme={null}761```json theme={null}
450{762{
451 // Common fields763 "session_id": "abc123",
452 session_id: string764 "transcript_path": "/Users/.../.claude/projects/.../transcript.jsonl",
453 transcript_path: string // Path to conversation JSON765 "cwd": "/Users/my-project",
454 cwd: string // The current working directory when the hook is invoked766 "hook_event_name": "InstructionsLoaded",
455 permission_mode: string // Current permission mode: "default", "plan", "acceptEdits", or "bypassPermissions"767 "file_path": "/Users/my-project/CLAUDE.md",
456 768 "memory_type": "Project",
457 // Event-specific fields769 "load_reason": "session_start"
458 hook_event_name: string
459 ...
460}770}
461```771```
462 772
463### PreToolUse Input773#### InstructionsLoaded decision control
774
775InstructionsLoaded hooks have no decision control. They cannot block or modify instruction loading. Use this event for audit logging, compliance tracking, or observability.
776
777### UserPromptSubmit
778
779Runs when the user submits a prompt, before Claude processes it. This allows you
780to add additional context based on the prompt/conversation, validate prompts, or
781block certain types of prompts.
782
783#### UserPromptSubmit input
464 784
465The exact schema for `tool_input` depends on the tool.785In addition to the [common input fields](#common-input-fields), UserPromptSubmit hooks receive the `prompt` field containing the text the user submitted.
466 786
467```json theme={null}787```json theme={null}
468{788{
470 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",790 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
471 "cwd": "/Users/...",791 "cwd": "/Users/...",
472 "permission_mode": "default",792 "permission_mode": "default",
473 "hook_event_name": "PreToolUse",793 "hook_event_name": "UserPromptSubmit",
474 "tool_name": "Write",794 "prompt": "Write a function to calculate the factorial of a number"
475 "tool_input": {795}
476 "file_path": "/path/to/file.txt",796```
477 "content": "file content"797
478 },798#### UserPromptSubmit decision control
479 "tool_use_id": "toolu_01ABC123..."799
800`UserPromptSubmit` hooks can control whether a user prompt is processed and add context. All [JSON output fields](#json-output) are available.
801
802There are two ways to add context to the conversation on exit code 0:
803
804* **Plain text stdout**: any non-JSON text written to stdout is added as context
805* **JSON with `additionalContext`**: use the JSON format below for more control. The `additionalContext` field is added as context
806
807Plain stdout is shown as hook output in the transcript. The `additionalContext` field is added more discretely.
808
809To block a prompt, return a JSON object with `decision` set to `"block"`:
810
811| Field | Description |
812| :------------------ | :----------------------------------------------------------------------------------------------------------------- |
813| `decision` | `"block"` prevents the prompt from being processed and erases it from context. Omit to allow the prompt to proceed |
814| `reason` | Shown to the user when `decision` is `"block"`. Not added to context |
815| `additionalContext` | String added to Claude's context |
816
817```json theme={null}
818{
819 "decision": "block",
820 "reason": "Explanation for decision",
821 "hookSpecificOutput": {
822 "hookEventName": "UserPromptSubmit",
823 "additionalContext": "My additional context here"
824 }
825}
826```
827
828<Note>
829 The JSON format isn't required for simple use cases. To add context, you can print plain text to stdout with exit code 0. Use JSON when you need to
830 block prompts or want more structured control.
831</Note>
832
833### PreToolUse
834
835Runs after Claude creates tool parameters and before processing the tool call. Matches on tool name: `Bash`, `Edit`, `Write`, `Read`, `Glob`, `Grep`, `Agent`, `WebFetch`, `WebSearch`, and any [MCP tool names](#match-mcp-tools).
836
837Use [PreToolUse decision control](#pretooluse-decision-control) to allow, deny, or ask for permission to use the tool.
838
839#### PreToolUse input
840
841In addition to the [common input fields](#common-input-fields), PreToolUse hooks receive `tool_name`, `tool_input`, and `tool_use_id`. The `tool_input` fields depend on the tool:
842
843##### Bash
844
845Executes shell commands.
846
847| Field | Type | Example | Description |
848| :------------------ | :------ | :----------------- | :-------------------------------------------- |
849| `command` | string | `"npm test"` | The shell command to execute |
850| `description` | string | `"Run test suite"` | Optional description of what the command does |
851| `timeout` | number | `120000` | Optional timeout in milliseconds |
852| `run_in_background` | boolean | `false` | Whether to run the command in background |
853
854##### Write
855
856Creates or overwrites a file.
857
858| Field | Type | Example | Description |
859| :---------- | :----- | :-------------------- | :--------------------------------- |
860| `file_path` | string | `"/path/to/file.txt"` | Absolute path to the file to write |
861| `content` | string | `"file content"` | Content to write to the file |
862
863##### Edit
864
865Replaces a string in an existing file.
866
867| Field | Type | Example | Description |
868| :------------ | :------ | :-------------------- | :--------------------------------- |
869| `file_path` | string | `"/path/to/file.txt"` | Absolute path to the file to edit |
870| `old_string` | string | `"original text"` | Text to find and replace |
871| `new_string` | string | `"replacement text"` | Replacement text |
872| `replace_all` | boolean | `false` | Whether to replace all occurrences |
873
874##### Read
875
876Reads file contents.
877
878| Field | Type | Example | Description |
879| :---------- | :----- | :-------------------- | :----------------------------------------- |
880| `file_path` | string | `"/path/to/file.txt"` | Absolute path to the file to read |
881| `offset` | number | `10` | Optional line number to start reading from |
882| `limit` | number | `50` | Optional number of lines to read |
883
884##### Glob
885
886Finds files matching a glob pattern.
887
888| Field | Type | Example | Description |
889| :-------- | :----- | :--------------- | :--------------------------------------------------------------------- |
890| `pattern` | string | `"**/*.ts"` | Glob pattern to match files against |
891| `path` | string | `"/path/to/dir"` | Optional directory to search in. Defaults to current working directory |
892
893##### Grep
894
895Searches file contents with regular expressions.
896
897| Field | Type | Example | Description |
898| :------------ | :------ | :--------------- | :------------------------------------------------------------------------------------ |
899| `pattern` | string | `"TODO.*fix"` | Regular expression pattern to search for |
900| `path` | string | `"/path/to/dir"` | Optional file or directory to search in |
901| `glob` | string | `"*.ts"` | Optional glob pattern to filter files |
902| `output_mode` | string | `"content"` | `"content"`, `"files_with_matches"`, or `"count"`. Defaults to `"files_with_matches"` |
903| `-i` | boolean | `true` | Case insensitive search |
904| `multiline` | boolean | `false` | Enable multiline matching |
905
906##### WebFetch
907
908Fetches and processes web content.
909
910| Field | Type | Example | Description |
911| :------- | :----- | :---------------------------- | :----------------------------------- |
912| `url` | string | `"https://example.com/api"` | URL to fetch content from |
913| `prompt` | string | `"Extract the API endpoints"` | Prompt to run on the fetched content |
914
915##### WebSearch
916
917Searches the web.
918
919| Field | Type | Example | Description |
920| :---------------- | :----- | :----------------------------- | :------------------------------------------------ |
921| `query` | string | `"react hooks best practices"` | Search query |
922| `allowed_domains` | array | `["docs.example.com"]` | Optional: only include results from these domains |
923| `blocked_domains` | array | `["spam.example.com"]` | Optional: exclude results from these domains |
924
925##### Agent
926
927Spawns a [subagent](/en/sub-agents).
928
929| Field | Type | Example | Description |
930| :-------------- | :----- | :------------------------- | :------------------------------------------- |
931| `prompt` | string | `"Find all API endpoints"` | The task for the agent to perform |
932| `description` | string | `"Find API endpoints"` | Short description of the task |
933| `subagent_type` | string | `"Explore"` | Type of specialized agent to use |
934| `model` | string | `"sonnet"` | Optional model alias to override the default |
935
936#### PreToolUse decision control
937
938`PreToolUse` hooks can control whether a tool call proceeds. Unlike other hooks that use a top-level `decision` field, PreToolUse returns its decision inside a `hookSpecificOutput` object. This gives it richer control: three outcomes (allow, deny, or ask) plus the ability to modify tool input before execution.
939
940| Field | Description |
941| :------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
942| `permissionDecision` | `"allow"` skips the permission prompt. `"deny"` prevents the tool call. `"ask"` prompts the user to confirm. [Deny and ask rules](/en/permissions#manage-permissions) still apply when a hook returns `"allow"` |
943| `permissionDecisionReason` | For `"allow"` and `"ask"`, shown to the user but not Claude. For `"deny"`, shown to Claude |
944| `updatedInput` | Modifies the tool's input parameters before execution. Combine with `"allow"` to auto-approve, or `"ask"` to show the modified input to the user |
945| `additionalContext` | String added to Claude's context before the tool executes |
946
947When a hook returns `"ask"`, the permission prompt displayed to the user includes a label identifying where the hook came from: for example, `[User]`, `[Project]`, `[Plugin]`, or `[Local]`. This helps users understand which configuration source is requesting confirmation.
948
949```json theme={null}
950{
951 "hookSpecificOutput": {
952 "hookEventName": "PreToolUse",
953 "permissionDecision": "allow",
954 "permissionDecisionReason": "My reason here",
955 "updatedInput": {
956 "field_to_modify": "new value"
957 },
958 "additionalContext": "Current environment: production. Proceed with caution."
959 }
480}960}
481```961```
482 962
483### PostToolUse Input963<Note>
964 PreToolUse previously used top-level `decision` and `reason` fields, but these are deprecated for this event. Use `hookSpecificOutput.permissionDecision` and `hookSpecificOutput.permissionDecisionReason` instead. The deprecated values `"approve"` and `"block"` map to `"allow"` and `"deny"` respectively. Other events like PostToolUse and Stop continue to use top-level `decision` and `reason` as their current format.
965</Note>
966
967### PermissionRequest
968
969Runs when the user is shown a permission dialog.
970Use [PermissionRequest decision control](#permissionrequest-decision-control) to allow or deny on behalf of the user.
971
972Matches on tool name, same values as PreToolUse.
973
974#### PermissionRequest input
975
976PermissionRequest hooks receive `tool_name` and `tool_input` fields like PreToolUse hooks, but without `tool_use_id`. An optional `permission_suggestions` array contains the "always allow" options the user would normally see in the permission dialog. The difference is when the hook fires: PermissionRequest hooks run when a permission dialog is about to be shown to the user, while PreToolUse hooks run before tool execution regardless of permission status.
977
978```json theme={null}
979{
980 "session_id": "abc123",
981 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
982 "cwd": "/Users/...",
983 "permission_mode": "default",
984 "hook_event_name": "PermissionRequest",
985 "tool_name": "Bash",
986 "tool_input": {
987 "command": "rm -rf node_modules",
988 "description": "Remove node_modules directory"
989 },
990 "permission_suggestions": [
991 {
992 "type": "addRules",
993 "rules": [{ "toolName": "Bash", "ruleContent": "rm -rf node_modules" }],
994 "behavior": "allow",
995 "destination": "localSettings"
996 }
997 ]
998}
999```
1000
1001#### PermissionRequest decision control
1002
1003`PermissionRequest` hooks can allow or deny permission requests. In addition to the [JSON output fields](#json-output) available to all hooks, your hook script can return a `decision` object with these event-specific fields:
1004
1005| Field | Description |
1006| :------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
1007| `behavior` | `"allow"` grants the permission, `"deny"` denies it |
1008| `updatedInput` | For `"allow"` only: modifies the tool's input parameters before execution |
1009| `updatedPermissions` | For `"allow"` only: array of [permission update entries](#permission-update-entries) to apply, such as adding an allow rule or changing the session permission mode |
1010| `message` | For `"deny"` only: tells Claude why the permission was denied |
1011| `interrupt` | For `"deny"` only: if `true`, stops Claude |
1012
1013```json theme={null}
1014{
1015 "hookSpecificOutput": {
1016 "hookEventName": "PermissionRequest",
1017 "decision": {
1018 "behavior": "allow",
1019 "updatedInput": {
1020 "command": "npm run lint"
1021 }
1022 }
1023 }
1024}
1025```
1026
1027#### Permission update entries
1028
1029The `updatedPermissions` output field and the [`permission_suggestions` input field](#permissionrequest-input) both use the same array of entry objects. Each entry has a `type` that determines its other fields, and a `destination` that controls where the change is written.
1030
1031| `type` | Fields | Effect |
1032| :------------------ | :--------------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
1033| `addRules` | `rules`, `behavior`, `destination` | Adds permission rules. `rules` is an array of `{toolName, ruleContent?}` objects. Omit `ruleContent` to match the whole tool. `behavior` is `"allow"`, `"deny"`, or `"ask"` |
1034| `replaceRules` | `rules`, `behavior`, `destination` | Replaces all rules of the given `behavior` at the `destination` with the provided `rules` |
1035| `removeRules` | `rules`, `behavior`, `destination` | Removes matching rules of the given `behavior` |
1036| `setMode` | `mode`, `destination` | Changes the permission mode. Valid modes are `default`, `acceptEdits`, `dontAsk`, `bypassPermissions`, and `plan` |
1037| `addDirectories` | `directories`, `destination` | Adds working directories. `directories` is an array of path strings |
1038| `removeDirectories` | `directories`, `destination` | Removes working directories |
1039
1040The `destination` field on every entry determines whether the change stays in memory or persists to a settings file.
1041
1042| `destination` | Writes to |
1043| :---------------- | :---------------------------------------------- |
1044| `session` | in-memory only, discarded when the session ends |
1045| `localSettings` | `.claude/settings.local.json` |
1046| `projectSettings` | `.claude/settings.json` |
1047| `userSettings` | `~/.claude/settings.json` |
1048
1049A hook can echo one of the `permission_suggestions` it received as its own `updatedPermissions` output, which is equivalent to the user selecting that "always allow" option in the dialog.
1050
1051### PostToolUse
1052
1053Runs immediately after a tool completes successfully.
1054
1055Matches on tool name, same values as PreToolUse.
1056
1057#### PostToolUse input
1058
1059`PostToolUse` hooks fire after a tool has already executed successfully. The input includes both `tool_input`, the arguments sent to the tool, and `tool_response`, the result it returned. The exact schema for both depends on the tool.
1060
1061```json theme={null}
1062{
1063 "session_id": "abc123",
1064 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1065 "cwd": "/Users/...",
1066 "permission_mode": "default",
1067 "hook_event_name": "PostToolUse",
1068 "tool_name": "Write",
1069 "tool_input": {
1070 "file_path": "/path/to/file.txt",
1071 "content": "file content"
1072 },
1073 "tool_response": {
1074 "filePath": "/path/to/file.txt",
1075 "success": true
1076 },
1077 "tool_use_id": "toolu_01ABC123..."
1078}
1079```
1080
1081#### PostToolUse decision control
1082
1083`PostToolUse` hooks can provide feedback to Claude after tool execution. In addition to the [JSON output fields](#json-output) available to all hooks, your hook script can return these event-specific fields:
1084
1085| Field | Description |
1086| :--------------------- | :----------------------------------------------------------------------------------------- |
1087| `decision` | `"block"` prompts Claude with the `reason`. Omit to allow the action to proceed |
1088| `reason` | Explanation shown to Claude when `decision` is `"block"` |
1089| `additionalContext` | Additional context for Claude to consider |
1090| `updatedMCPToolOutput` | For [MCP tools](#match-mcp-tools) only: replaces the tool's output with the provided value |
1091
1092```json theme={null}
1093{
1094 "decision": "block",
1095 "reason": "Explanation for decision",
1096 "hookSpecificOutput": {
1097 "hookEventName": "PostToolUse",
1098 "additionalContext": "Additional information for Claude"
1099 }
1100}
1101```
1102
1103### PostToolUseFailure
1104
1105Runs when a tool execution fails. This event fires for tool calls that throw errors or return failure results. Use this to log failures, send alerts, or provide corrective feedback to Claude.
1106
1107Matches on tool name, same values as PreToolUse.
1108
1109#### PostToolUseFailure input
1110
1111PostToolUseFailure hooks receive the same `tool_name` and `tool_input` fields as PostToolUse, along with error information as top-level fields:
1112
1113```json theme={null}
1114{
1115 "session_id": "abc123",
1116 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1117 "cwd": "/Users/...",
1118 "permission_mode": "default",
1119 "hook_event_name": "PostToolUseFailure",
1120 "tool_name": "Bash",
1121 "tool_input": {
1122 "command": "npm test",
1123 "description": "Run test suite"
1124 },
1125 "tool_use_id": "toolu_01ABC123...",
1126 "error": "Command exited with non-zero status code 1",
1127 "is_interrupt": false
1128}
1129```
1130
1131| Field | Description |
1132| :------------- | :------------------------------------------------------------------------------ |
1133| `error` | String describing what went wrong |
1134| `is_interrupt` | Optional boolean indicating whether the failure was caused by user interruption |
1135
1136#### PostToolUseFailure decision control
1137
1138`PostToolUseFailure` hooks can provide context to Claude after a tool failure. In addition to the [JSON output fields](#json-output) available to all hooks, your hook script can return these event-specific fields:
1139
1140| Field | Description |
1141| :------------------ | :------------------------------------------------------------ |
1142| `additionalContext` | Additional context for Claude to consider alongside the error |
1143
1144```json theme={null}
1145{
1146 "hookSpecificOutput": {
1147 "hookEventName": "PostToolUseFailure",
1148 "additionalContext": "Additional information about the failure for Claude"
1149 }
1150}
1151```
1152
1153### Notification
1154
1155Runs when Claude Code sends notifications. Matches on notification type: `permission_prompt`, `idle_prompt`, `auth_success`, `elicitation_dialog`. Omit the matcher to run hooks for all notification types.
1156
1157Use separate matchers to run different handlers depending on the notification type. This configuration triggers a permission-specific alert script when Claude needs permission approval and a different notification when Claude has been idle:
1158
1159```json theme={null}
1160{
1161 "hooks": {
1162 "Notification": [
1163 {
1164 "matcher": "permission_prompt",
1165 "hooks": [
1166 {
1167 "type": "command",
1168 "command": "/path/to/permission-alert.sh"
1169 }
1170 ]
1171 },
1172 {
1173 "matcher": "idle_prompt",
1174 "hooks": [
1175 {
1176 "type": "command",
1177 "command": "/path/to/idle-notification.sh"
1178 }
1179 ]
1180 }
1181 ]
1182 }
1183}
1184```
1185
1186#### Notification input
1187
1188In addition to the [common input fields](#common-input-fields), Notification hooks receive `message` with the notification text, an optional `title`, and `notification_type` indicating which type fired.
1189
1190```json theme={null}
1191{
1192 "session_id": "abc123",
1193 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1194 "cwd": "/Users/...",
1195 "hook_event_name": "Notification",
1196 "message": "Claude needs your permission to use Bash",
1197 "title": "Permission needed",
1198 "notification_type": "permission_prompt"
1199}
1200```
1201
1202Notification hooks cannot block or modify notifications. In addition to the [JSON output fields](#json-output) available to all hooks, you can return `additionalContext` to add context to the conversation:
1203
1204| Field | Description |
1205| :------------------ | :------------------------------- |
1206| `additionalContext` | String added to Claude's context |
1207
1208### SubagentStart
1209
1210Runs when a Claude Code subagent is spawned via the Agent tool. Supports matchers to filter by agent type name (built-in agents like `Bash`, `Explore`, `Plan`, or custom agent names from `.claude/agents/`).
1211
1212#### SubagentStart input
1213
1214In addition to the [common input fields](#common-input-fields), SubagentStart hooks receive `agent_id` with the unique identifier for the subagent and `agent_type` with the agent name (built-in agents like `"Bash"`, `"Explore"`, `"Plan"`, or custom agent names).
1215
1216```json theme={null}
1217{
1218 "session_id": "abc123",
1219 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1220 "cwd": "/Users/...",
1221 "hook_event_name": "SubagentStart",
1222 "agent_id": "agent-abc123",
1223 "agent_type": "Explore"
1224}
1225```
1226
1227SubagentStart hooks cannot block subagent creation, but they can inject context into the subagent. In addition to the [JSON output fields](#json-output) available to all hooks, you can return:
1228
1229| Field | Description |
1230| :------------------ | :------------------------------------- |
1231| `additionalContext` | String added to the subagent's context |
1232
1233```json theme={null}
1234{
1235 "hookSpecificOutput": {
1236 "hookEventName": "SubagentStart",
1237 "additionalContext": "Follow security guidelines for this task"
1238 }
1239}
1240```
1241
1242### SubagentStop
1243
1244Runs when a Claude Code subagent has finished responding. Matches on agent type, same values as SubagentStart.
1245
1246#### SubagentStop input
1247
1248In addition to the [common input fields](#common-input-fields), SubagentStop hooks receive `stop_hook_active`, `agent_id`, `agent_type`, `agent_transcript_path`, and `last_assistant_message`. The `agent_type` field is the value used for matcher filtering. The `transcript_path` is the main session's transcript, while `agent_transcript_path` is the subagent's own transcript stored in a nested `subagents/` folder. The `last_assistant_message` field contains the text content of the subagent's final response, so hooks can access it without parsing the transcript file.
1249
1250```json theme={null}
1251{
1252 "session_id": "abc123",
1253 "transcript_path": "~/.claude/projects/.../abc123.jsonl",
1254 "cwd": "/Users/...",
1255 "permission_mode": "default",
1256 "hook_event_name": "SubagentStop",
1257 "stop_hook_active": false,
1258 "agent_id": "def456",
1259 "agent_type": "Explore",
1260 "agent_transcript_path": "~/.claude/projects/.../abc123/subagents/agent-def456.jsonl",
1261 "last_assistant_message": "Analysis complete. Found 3 potential issues..."
1262}
1263```
1264
1265SubagentStop hooks use the same decision control format as [Stop hooks](#stop-decision-control).
1266
1267### Stop
1268
1269Runs when the main Claude Code agent has finished responding. Does not run if
1270the stoppage occurred due to a user interrupt. API errors fire
1271[StopFailure](#stopfailure) instead.
1272
1273#### Stop input
1274
1275In addition to the [common input fields](#common-input-fields), Stop hooks receive `stop_hook_active` and `last_assistant_message`. The `stop_hook_active` field is `true` when Claude Code is already continuing as a result of a stop hook. Check this value or process the transcript to prevent Claude Code from running indefinitely. The `last_assistant_message` field contains the text content of Claude's final response, so hooks can access it without parsing the transcript file.
1276
1277```json theme={null}
1278{
1279 "session_id": "abc123",
1280 "transcript_path": "~/.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1281 "cwd": "/Users/...",
1282 "permission_mode": "default",
1283 "hook_event_name": "Stop",
1284 "stop_hook_active": true,
1285 "last_assistant_message": "I've completed the refactoring. Here's a summary..."
1286}
1287```
1288
1289#### Stop decision control
1290
1291`Stop` and `SubagentStop` hooks can control whether Claude continues. In addition to the [JSON output fields](#json-output) available to all hooks, your hook script can return these event-specific fields:
1292
1293| Field | Description |
1294| :--------- | :------------------------------------------------------------------------- |
1295| `decision` | `"block"` prevents Claude from stopping. Omit to allow Claude to stop |
1296| `reason` | Required when `decision` is `"block"`. Tells Claude why it should continue |
1297
1298```json theme={null}
1299{
1300 "decision": "block",
1301 "reason": "Must be provided when Claude is blocked from stopping"
1302}
1303```
1304
1305### StopFailure
1306
1307Runs instead of [Stop](#stop) when the turn ends due to an API error. Output and exit code are ignored. Use this to log failures, send alerts, or take recovery actions when Claude cannot complete a response due to rate limits, authentication problems, or other API errors.
1308
1309#### StopFailure input
1310
1311In addition to the [common input fields](#common-input-fields), StopFailure hooks receive `error`, optional `error_details`, and optional `last_assistant_message`. The `error` field identifies the error type and is used for matcher filtering.
1312
1313| Field | Description |
1314| :----------------------- | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
1315| `error` | Error type: `rate_limit`, `authentication_failed`, `billing_error`, `invalid_request`, `server_error`, `max_output_tokens`, or `unknown` |
1316| `error_details` | Additional details about the error, when available |
1317| `last_assistant_message` | The rendered error text shown in the conversation. Unlike `Stop` and `SubagentStop`, where this field holds Claude's conversational output, for `StopFailure` it contains the API error string itself, such as `"API Error: Rate limit reached"` |
1318
1319```json theme={null}
1320{
1321 "session_id": "abc123",
1322 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1323 "cwd": "/Users/...",
1324 "hook_event_name": "StopFailure",
1325 "error": "rate_limit",
1326 "error_details": "429 Too Many Requests",
1327 "last_assistant_message": "API Error: Rate limit reached"
1328}
1329```
1330
1331StopFailure hooks have no decision control. They run for notification and logging purposes only.
1332
1333### TeammateIdle
1334
1335Runs when an [agent team](/en/agent-teams) teammate is about to go idle after finishing its turn. Use this to enforce quality gates before a teammate stops working, such as requiring passing lint checks or verifying that output files exist.
1336
1337When a `TeammateIdle` hook exits with code 2, the teammate receives the stderr message as feedback and continues working instead of going idle. To stop the teammate entirely instead of re-running it, return JSON with `{"continue": false, "stopReason": "..."}`. TeammateIdle hooks do not support matchers and fire on every occurrence.
1338
1339#### TeammateIdle input
1340
1341In addition to the [common input fields](#common-input-fields), TeammateIdle hooks receive `teammate_name` and `team_name`.
1342
1343```json theme={null}
1344{
1345 "session_id": "abc123",
1346 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1347 "cwd": "/Users/...",
1348 "permission_mode": "default",
1349 "hook_event_name": "TeammateIdle",
1350 "teammate_name": "researcher",
1351 "team_name": "my-project"
1352}
1353```
1354
1355| Field | Description |
1356| :-------------- | :-------------------------------------------- |
1357| `teammate_name` | Name of the teammate that is about to go idle |
1358| `team_name` | Name of the team |
1359
1360#### TeammateIdle decision control
1361
1362TeammateIdle hooks support two ways to control teammate behavior:
1363
1364* **Exit code 2**: the teammate receives the stderr message as feedback and continues working instead of going idle.
1365* **JSON `{"continue": false, "stopReason": "..."}`**: stops the teammate entirely, matching `Stop` hook behavior. The `stopReason` is shown to the user.
1366
1367This example checks that a build artifact exists before allowing a teammate to go idle:
1368
1369```bash theme={null}
1370#!/bin/bash
1371
1372if [ ! -f "./dist/output.js" ]; then
1373 echo "Build artifact missing. Run the build before stopping." >&2
1374 exit 2
1375fi
1376
1377exit 0
1378```
1379
1380### TaskCompleted
1381
1382Runs when a task is being marked as completed. This fires in two situations: when any agent explicitly marks a task as completed through the TaskUpdate tool, or when an [agent team](/en/agent-teams) teammate finishes its turn with in-progress tasks. Use this to enforce completion criteria like passing tests or lint checks before a task can close.
1383
1384When a `TaskCompleted` hook exits with code 2, the task is not marked as completed and the stderr message is fed back to the model as feedback. To stop the teammate entirely instead of re-running it, return JSON with `{"continue": false, "stopReason": "..."}`. TaskCompleted hooks do not support matchers and fire on every occurrence.
1385
1386#### TaskCompleted input
1387
1388In addition to the [common input fields](#common-input-fields), TaskCompleted hooks receive `task_id`, `task_subject`, and optionally `task_description`, `teammate_name`, and `team_name`.
1389
1390```json theme={null}
1391{
1392 "session_id": "abc123",
1393 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1394 "cwd": "/Users/...",
1395 "permission_mode": "default",
1396 "hook_event_name": "TaskCompleted",
1397 "task_id": "task-001",
1398 "task_subject": "Implement user authentication",
1399 "task_description": "Add login and signup endpoints",
1400 "teammate_name": "implementer",
1401 "team_name": "my-project"
1402}
1403```
1404
1405| Field | Description |
1406| :----------------- | :------------------------------------------------------ |
1407| `task_id` | Identifier of the task being completed |
1408| `task_subject` | Title of the task |
1409| `task_description` | Detailed description of the task. May be absent |
1410| `teammate_name` | Name of the teammate completing the task. May be absent |
1411| `team_name` | Name of the team. May be absent |
1412
1413#### TaskCompleted decision control
1414
1415TaskCompleted hooks support two ways to control task completion:
1416
1417* **Exit code 2**: the task is not marked as completed and the stderr message is fed back to the model as feedback.
1418* **JSON `{"continue": false, "stopReason": "..."}`**: stops the teammate entirely, matching `Stop` hook behavior. The `stopReason` is shown to the user.
1419
1420This example runs tests and blocks task completion if they fail:
1421
1422```bash theme={null}
1423#!/bin/bash
1424INPUT=$(cat)
1425TASK_SUBJECT=$(echo "$INPUT" | jq -r '.task_subject')
1426
1427# Run the test suite
1428if ! npm test 2>&1; then
1429 echo "Tests not passing. Fix failing tests before completing: $TASK_SUBJECT" >&2
1430 exit 2
1431fi
1432
1433exit 0
1434```
1435
1436### ConfigChange
1437
1438Runs when a configuration file changes during a session. Use this to audit settings changes, enforce security policies, or block unauthorized modifications to configuration files.
1439
1440ConfigChange hooks fire for changes to settings files, managed policy settings, and skill files. The `source` field in the input tells you which type of configuration changed, and the optional `file_path` field provides the path to the changed file.
1441
1442The matcher filters on the configuration source:
1443
1444| Matcher | When it fires |
1445| :----------------- | :---------------------------------------- |
1446| `user_settings` | `~/.claude/settings.json` changes |
1447| `project_settings` | `.claude/settings.json` changes |
1448| `local_settings` | `.claude/settings.local.json` changes |
1449| `policy_settings` | Managed policy settings change |
1450| `skills` | A skill file in `.claude/skills/` changes |
1451
1452This example logs all configuration changes for security auditing:
1453
1454```json theme={null}
1455{
1456 "hooks": {
1457 "ConfigChange": [
1458 {
1459 "hooks": [
1460 {
1461 "type": "command",
1462 "command": "\"$CLAUDE_PROJECT_DIR\"/.claude/hooks/audit-config-change.sh"
1463 }
1464 ]
1465 }
1466 ]
1467 }
1468}
1469```
1470
1471#### ConfigChange input
1472
1473In addition to the [common input fields](#common-input-fields), ConfigChange hooks receive `source` and optionally `file_path`. The `source` field indicates which configuration type changed, and `file_path` provides the path to the specific file that was modified.
1474
1475```json theme={null}
1476{
1477 "session_id": "abc123",
1478 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
1479 "cwd": "/Users/...",
1480 "hook_event_name": "ConfigChange",
1481 "source": "project_settings",
1482 "file_path": "/Users/.../my-project/.claude/settings.json"
1483}
1484```
1485
1486#### ConfigChange decision control
1487
1488ConfigChange hooks can block configuration changes from taking effect. Use exit code 2 or a JSON `decision` to prevent the change. When blocked, the new settings are not applied to the running session.
1489
1490| Field | Description |
1491| :--------- | :--------------------------------------------------------------------------------------- |
1492| `decision` | `"block"` prevents the configuration change from being applied. Omit to allow the change |
1493| `reason` | Explanation shown to the user when `decision` is `"block"` |
1494
1495```json theme={null}
1496{
1497 "decision": "block",
1498 "reason": "Configuration changes to project settings require admin approval"
1499}
1500```
1501
1502`policy_settings` changes cannot be blocked. Hooks still fire for `policy_settings` sources, so you can use them for audit logging, but any blocking decision is ignored. This ensures enterprise-managed settings always take effect.
1503
1504### CwdChanged
1505
1506Runs when the working directory changes during a session, for example when Claude executes a `cd` command. Use this to react to directory changes: reload environment variables, activate project-specific toolchains, or run setup scripts automatically. Pairs with [FileChanged](#filechanged) for tools like [direnv](https://direnv.net/) that manage per-directory environment.
1507
1508CwdChanged hooks have access to `CLAUDE_ENV_FILE`. Variables written to that file persist into subsequent Bash commands for the session, just as in [SessionStart hooks](#persist-environment-variables). Only `type: "command"` hooks are supported.
1509
1510CwdChanged does not support matchers and fires on every directory change.
1511
1512#### CwdChanged input
1513
1514In addition to the [common input fields](#common-input-fields), CwdChanged hooks receive `old_cwd` and `new_cwd`.
1515
1516```json theme={null}
1517{
1518 "session_id": "abc123",
1519 "transcript_path": "/Users/.../.claude/projects/.../transcript.jsonl",
1520 "cwd": "/Users/my-project/src",
1521 "hook_event_name": "CwdChanged",
1522 "old_cwd": "/Users/my-project",
1523 "new_cwd": "/Users/my-project/src"
1524}
1525```
1526
1527#### CwdChanged output
1528
1529In addition to the [JSON output fields](#json-output) available to all hooks, CwdChanged hooks can return `watchPaths` to dynamically set which file paths [FileChanged](#filechanged) watches:
1530
1531| Field | Description |
1532| :----------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
1533| `watchPaths` | Array of absolute paths. Replaces the current dynamic watch list (paths from your `matcher` configuration are always watched). Returning an empty array clears the dynamic list, which is typical when entering a new directory |
1534
1535CwdChanged hooks have no decision control. They cannot block the directory change.
1536
1537### FileChanged
1538
1539Runs when a watched file changes on disk. The `matcher` field in your hook configuration controls which filenames to watch: it is a pipe-separated list of basenames (filenames without directory paths, for example `".envrc|.env"`). The same `matcher` value is also used to filter which hooks run when a file changes, matching against the basename of the changed file. Useful for reloading environment variables when project configuration files are modified.
1540
1541FileChanged hooks have access to `CLAUDE_ENV_FILE`. Variables written to that file persist into subsequent Bash commands for the session, just as in [SessionStart hooks](#persist-environment-variables). Only `type: "command"` hooks are supported.
1542
1543#### FileChanged input
1544
1545In addition to the [common input fields](#common-input-fields), FileChanged hooks receive `file_path` and `event`.
1546
1547| Field | Description |
1548| :---------- | :---------------------------------------------------------------------------------------------- |
1549| `file_path` | Absolute path to the file that changed |
1550| `event` | What happened: `"change"` (file modified), `"add"` (file created), or `"unlink"` (file deleted) |
1551
1552```json theme={null}
1553{
1554 "session_id": "abc123",
1555 "transcript_path": "/Users/.../.claude/projects/.../transcript.jsonl",
1556 "cwd": "/Users/my-project",
1557 "hook_event_name": "FileChanged",
1558 "file_path": "/Users/my-project/.envrc",
1559 "event": "change"
1560}
1561```
1562
1563#### FileChanged output
1564
1565In addition to the [JSON output fields](#json-output) available to all hooks, FileChanged hooks can return `watchPaths` to dynamically update which file paths are watched:
1566
1567| Field | Description |
1568| :----------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
1569| `watchPaths` | Array of absolute paths. Replaces the current dynamic watch list (paths from your `matcher` configuration are always watched). Use this when your hook script discovers additional files to watch based on the changed file |
484 1570
485The exact schema for `tool_input` and `tool_response` depends on the tool.1571FileChanged hooks have no decision control. They cannot block the file change from occurring.
1572
1573### WorktreeCreate
1574
1575When you run `claude --worktree` or a [subagent uses `isolation: "worktree"`](/en/sub-agents#choose-the-subagent-scope), Claude Code creates an isolated working copy using `git worktree`. If you configure a WorktreeCreate hook, it replaces the default git behavior, letting you use a different version control system like SVN, Perforce, or Mercurial.
1576
1577The hook must print the absolute path to the created worktree directory on stdout. Claude Code uses this path as the working directory for the isolated session.
1578
1579This example creates an SVN working copy and prints the path for Claude Code to use. Replace the repository URL with your own:
486 1580
487```json theme={null}1581```json theme={null}
488{1582{
489 "session_id": "abc123",1583 "hooks": {
490 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",1584 "WorktreeCreate": [
491 "cwd": "/Users/...",1585 {
492 "permission_mode": "default",1586 "hooks": [
493 "hook_event_name": "PostToolUse",1587 {
494 "tool_name": "Write",1588 "type": "command",
495 "tool_input": {1589 "command": "bash -c 'NAME=$(jq -r .name); DIR=\"$HOME/.claude/worktrees/$NAME\"; svn checkout https://svn.example.com/repo/trunk \"$DIR\" >&2 && echo \"$DIR\"'"
496 "file_path": "/path/to/file.txt",1590 }
497 "content": "file content"1591 ]
498 },1592 }
499 "tool_response": {1593 ]
500 "filePath": "/path/to/file.txt",1594 }
501 "success": true
502 },
503 "tool_use_id": "toolu_01ABC123..."
504}1595}
505```1596```
506 1597
507### Notification Input1598The hook reads the worktree `name` from the JSON input on stdin, checks out a fresh copy into a new directory, and prints the directory path. The `echo` on the last line is what Claude Code reads as the worktree path. Redirect any other output to stderr so it doesn't interfere with the path.
1599
1600#### WorktreeCreate input
1601
1602In addition to the [common input fields](#common-input-fields), WorktreeCreate hooks receive the `name` field. This is a slug identifier for the new worktree, either specified by the user or auto-generated (for example, `bold-oak-a3f2`).
508 1603
509```json theme={null}1604```json theme={null}
510{1605{
511 "session_id": "abc123",1606 "session_id": "abc123",
512 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",1607 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
513 "cwd": "/Users/...",1608 "cwd": "/Users/...",
514 "permission_mode": "default",1609 "hook_event_name": "WorktreeCreate",
515 "hook_event_name": "Notification",1610 "name": "feature-auth"
516 "message": "Claude needs your permission to use Bash",
517 "notification_type": "permission_prompt"
518}1611}
519```1612```
520 1613
521### UserPromptSubmit Input1614#### WorktreeCreate output
1615
1616The hook must print the absolute path to the created worktree directory on stdout. If the hook fails or produces no output, worktree creation fails with an error.
1617
1618WorktreeCreate hooks do not use the standard allow/block decision model. Instead, the hook's success or failure determines the outcome. Only `type: "command"` hooks are supported.
1619
1620### WorktreeRemove
1621
1622The cleanup counterpart to [WorktreeCreate](#worktreecreate). This hook fires when a worktree is being removed, either when you exit a `--worktree` session and choose to remove it, or when a subagent with `isolation: "worktree"` finishes. For git-based worktrees, Claude handles cleanup automatically with `git worktree remove`. If you configured a WorktreeCreate hook for a non-git version control system, pair it with a WorktreeRemove hook to handle cleanup. Without one, the worktree directory is left on disk.
1623
1624Claude Code passes the path that WorktreeCreate printed on stdout as `worktree_path` in the hook input. This example reads that path and removes the directory:
522 1625
523```json theme={null}1626```json theme={null}
524{1627{
525 "session_id": "abc123",1628 "hooks": {
526 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",1629 "WorktreeRemove": [
527 "cwd": "/Users/...",1630 {
528 "permission_mode": "default",1631 "hooks": [
529 "hook_event_name": "UserPromptSubmit",1632 {
530 "prompt": "Write a function to calculate the factorial of a number"1633 "type": "command",
1634 "command": "bash -c 'jq -r .worktree_path | xargs rm -rf'"
1635 }
1636 ]
1637 }
1638 ]
1639 }
531}1640}
532```1641```
533 1642
534### Stop and SubagentStop Input1643#### WorktreeRemove input
535 1644
536`stop_hook_active` is true when Claude Code is already continuing as a result of1645In addition to the [common input fields](#common-input-fields), WorktreeRemove hooks receive the `worktree_path` field, which is the absolute path to the worktree being removed.
537a stop hook. Check this value or process the transcript to prevent Claude Code
538from running indefinitely.
539 1646
540```json theme={null}1647```json theme={null}
541{1648{
542 "session_id": "abc123",1649 "session_id": "abc123",
543 "transcript_path": "~/.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",1650 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
544 "permission_mode": "default",1651 "cwd": "/Users/...",
545 "hook_event_name": "Stop",1652 "hook_event_name": "WorktreeRemove",
546 "stop_hook_active": true1653 "worktree_path": "/Users/.../my-project/.claude/worktrees/feature-auth"
547}1654}
548```1655```
549 1656
550### PreCompact Input1657WorktreeRemove hooks have no decision control. They cannot block worktree removal but can perform cleanup tasks like removing version control state or archiving changes. Hook failures are logged in debug mode only. Only `type: "command"` hooks are supported.
1658
1659### PreCompact
1660
1661Runs before Claude Code is about to run a compact operation.
1662
1663The matcher value indicates whether compaction was triggered manually or automatically:
1664
1665| Matcher | When it fires |
1666| :------- | :------------------------------------------- |
1667| `manual` | `/compact` |
1668| `auto` | Auto-compact when the context window is full |
1669
1670#### PreCompact input
551 1671
552For `manual`, `custom_instructions` comes from what the user passes into1672In addition to the [common input fields](#common-input-fields), PreCompact hooks receive `trigger` and `custom_instructions`. For `manual`, `custom_instructions` contains what the user passes into `/compact`. For `auto`, `custom_instructions` is empty.
553`/compact`. For `auto`, `custom_instructions` is empty.
554 1673
555```json theme={null}1674```json theme={null}
556{1675{
557 "session_id": "abc123",1676 "session_id": "abc123",
558 "transcript_path": "~/.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",1677 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
559 "permission_mode": "default",1678 "cwd": "/Users/...",
560 "hook_event_name": "PreCompact",1679 "hook_event_name": "PreCompact",
561 "trigger": "manual",1680 "trigger": "manual",
562 "custom_instructions": ""1681 "custom_instructions": ""
563}1682}
564```1683```
565 1684
566### SessionStart Input1685### PostCompact
1686
1687Runs after Claude Code completes a compact operation. Use this event to react to the new compacted state, for example to log the generated summary or update external state.
1688
1689The same matcher values apply as for `PreCompact`:
1690
1691| Matcher | When it fires |
1692| :------- | :------------------------------------------------- |
1693| `manual` | After `/compact` |
1694| `auto` | After auto-compact when the context window is full |
1695
1696#### PostCompact input
1697
1698In addition to the [common input fields](#common-input-fields), PostCompact hooks receive `trigger` and `compact_summary`. The `compact_summary` field contains the conversation summary generated by the compact operation.
567 1699
568```json theme={null}1700```json theme={null}
569{1701{
570 "session_id": "abc123",1702 "session_id": "abc123",
571 "transcript_path": "~/.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",1703 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
572 "permission_mode": "default",1704 "cwd": "/Users/...",
573 "hook_event_name": "SessionStart",1705 "hook_event_name": "PostCompact",
574 "source": "startup"1706 "trigger": "manual",
1707 "compact_summary": "Summary of the compacted conversation..."
575}1708}
576```1709```
577 1710
578### SessionEnd Input1711PostCompact hooks have no decision control. They cannot affect the compaction result but can perform follow-up tasks.
1712
1713### SessionEnd
1714
1715Runs when a Claude Code session ends. Useful for cleanup tasks, logging session
1716statistics, or saving session state. Supports matchers to filter by exit reason.
1717
1718The `reason` field in the hook input indicates why the session ended:
1719
1720| Reason | Description |
1721| :---------------------------- | :----------------------------------------- |
1722| `clear` | Session cleared with `/clear` command |
1723| `resume` | Session switched via interactive `/resume` |
1724| `logout` | User logged out |
1725| `prompt_input_exit` | User exited while prompt input was visible |
1726| `bypass_permissions_disabled` | Bypass permissions mode was disabled |
1727| `other` | Other exit reasons |
1728
1729#### SessionEnd input
1730
1731In addition to the [common input fields](#common-input-fields), SessionEnd hooks receive a `reason` field indicating why the session ended. See the [reason table](#sessionend) above for all values.
579 1732
580```json theme={null}1733```json theme={null}
581{1734{
582 "session_id": "abc123",1735 "session_id": "abc123",
583 "transcript_path": "~/.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",1736 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
584 "cwd": "/Users/...",1737 "cwd": "/Users/...",
585 "permission_mode": "default",
586 "hook_event_name": "SessionEnd",1738 "hook_event_name": "SessionEnd",
587 "reason": "exit"1739 "reason": "other"
588}1740}
589```1741```
590 1742
591## Hook Output1743SessionEnd hooks have no decision control. They cannot block session termination but can perform cleanup tasks.
592
593There are two mutually-exclusive ways for hooks to return output back to Claude Code. The output
594communicates whether to block and any feedback that should be shown to Claude
595and the user.
596
597### Simple: Exit Code
598 1744
599Hooks communicate status through exit codes, stdout, and stderr:1745SessionEnd hooks have a default timeout of 1.5 seconds. This applies to session exit, `/clear`, and switching sessions via interactive `/resume`. If your hooks need more time, set the `CLAUDE_CODE_SESSIONEND_HOOKS_TIMEOUT_MS` environment variable to a higher value in milliseconds. Any per-hook `timeout` setting is also capped by this value.
600 1746
601* **Exit code 0**: Success. `stdout` is shown to the user in verbose mode1747```bash theme={null}
602 (ctrl+o), except for `UserPromptSubmit` and `SessionStart`, where stdout is1748CLAUDE_CODE_SESSIONEND_HOOKS_TIMEOUT_MS=5000 claude
603 added to the context. JSON output in `stdout` is parsed for structured control1749```
604 (see [Advanced: JSON Output](#advanced-json-output)).
605* **Exit code 2**: Blocking error. Only `stderr` is used as the error message
606 and fed back to Claude. The format is `[command]: {stderr}`. JSON in `stdout`
607 is **not** processed for exit code 2. See per-hook-event behavior below.
608* **Other exit codes**: Non-blocking error. `stderr` is shown to the user in verbose mode (ctrl+o) with
609 format `Failed with non-blocking status code: {stderr}`. If `stderr` is empty,
610 it shows `No stderr output`. Execution continues.
611
612<Warning>
613 Reminder: Claude Code does not see stdout if the exit code is 0, except for
614 the `UserPromptSubmit` hook where stdout is injected as context.
615</Warning>
616
617#### Exit Code 2 Behavior
618 1750
619| Hook Event | Behavior |1751### Elicitation
620| ------------------- | ------------------------------------------------------------------ |
621| `PreToolUse` | Blocks the tool call, shows stderr to Claude |
622| `PermissionRequest` | Denies the permission, shows stderr to Claude |
623| `PostToolUse` | Shows stderr to Claude (tool already ran) |
624| `Notification` | N/A, shows stderr to user only |
625| `UserPromptSubmit` | Blocks prompt processing, erases prompt, shows stderr to user only |
626| `Stop` | Blocks stoppage, shows stderr to Claude |
627| `SubagentStop` | Blocks stoppage, shows stderr to Claude subagent |
628| `PreCompact` | N/A, shows stderr to user only |
629| `SessionStart` | N/A, shows stderr to user only |
630| `SessionEnd` | N/A, shows stderr to user only |
631 1752
632### Advanced: JSON Output1753Runs when an MCP server requests user input mid-task. By default, Claude Code shows an interactive dialog for the user to respond. Hooks can intercept this request and respond programmatically, skipping the dialog entirely.
633 1754
634Hooks can return structured JSON in `stdout` for more sophisticated control.1755The matcher field matches against the MCP server name.
635 1756
636<Warning>1757#### Elicitation input
637 JSON output is only processed when the hook exits with code 0. If your hook
638 exits with code 2 (blocking error), `stderr` text is used directly—any JSON in `stdout`
639 is ignored. For other non-zero exit codes, only `stderr` is shown to the user in verbose mode (ctrl+o).
640</Warning>
641 1758
642#### Common JSON Fields1759In addition to the [common input fields](#common-input-fields), Elicitation hooks receive `mcp_server_name`, `message`, and optional `mode`, `url`, `elicitation_id`, and `requested_schema` fields.
643 1760
644All hook types can include these optional fields:1761For form-mode elicitation (the most common case):
645 1762
646```json theme={null}1763```json theme={null}
647{1764{
648 "continue": true, // Whether Claude should continue after hook execution (default: true)1765 "session_id": "abc123",
649 "stopReason": "string", // Message shown when continue is false1766 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
650 1767 "cwd": "/Users/...",
651 "suppressOutput": true, // Hide stdout from transcript mode (default: false)1768 "permission_mode": "default",
652 "systemMessage": "string" // Optional warning message shown to the user1769 "hook_event_name": "Elicitation",
1770 "mcp_server_name": "my-mcp-server",
1771 "message": "Please provide your credentials",
1772 "mode": "form",
1773 "requested_schema": {
1774 "type": "object",
1775 "properties": {
1776 "username": { "type": "string", "title": "Username" }
1777 }
1778 }
653}1779}
654```1780```
655 1781
656If `continue` is false, Claude stops processing after the hooks run.1782For URL-mode elicitation (browser-based authentication):
657
658* For `PreToolUse`, this is different from `"permissionDecision": "deny"`, which
659 only blocks a specific tool call and provides automatic feedback to Claude.
660* For `PostToolUse`, this is different from `"decision": "block"`, which
661 provides automated feedback to Claude.
662* For `UserPromptSubmit`, this prevents the prompt from being processed.
663* For `Stop` and `SubagentStop`, this takes precedence over any
664 `"decision": "block"` output.
665* In all cases, `"continue" = false` takes precedence over any
666 `"decision": "block"` output.
667 1783
668`stopReason` accompanies `continue` with a reason shown to the user, not shown1784```json theme={null}
669to Claude.1785{
670 1786 "session_id": "abc123",
671#### `PreToolUse` Decision Control1787 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
672 1788 "cwd": "/Users/...",
673`PreToolUse` hooks can control whether a tool call proceeds.1789 "permission_mode": "default",
674 1790 "hook_event_name": "Elicitation",
675* `"allow"` bypasses the permission system. `permissionDecisionReason` is shown1791 "mcp_server_name": "my-mcp-server",
676 to the user but not to Claude.1792 "message": "Please authenticate",
677* `"deny"` prevents the tool call from executing. `permissionDecisionReason` is1793 "mode": "url",
678 shown to Claude.1794 "url": "https://auth.example.com/login"
679* `"ask"` asks the user to confirm the tool call in the UI.1795}
680 `permissionDecisionReason` is shown to the user but not to Claude.1796```
681 1797
682Additionally, hooks can modify tool inputs before execution using `updatedInput`:1798#### Elicitation output
683 1799
684* `updatedInput` allows you to modify the tool's input parameters before the tool executes.1800To respond programmatically without showing the dialog, return a JSON object with `hookSpecificOutput`:
685* This is most useful with `"permissionDecision": "allow"` to modify and approve tool calls.
686 1801
687```json theme={null}1802```json theme={null}
688{1803{
689 "hookSpecificOutput": {1804 "hookSpecificOutput": {
690 "hookEventName": "PreToolUse",1805 "hookEventName": "Elicitation",
691 "permissionDecision": "allow"1806 "action": "accept",
692 "permissionDecisionReason": "My reason here",1807 "content": {
693 "updatedInput": {1808 "username": "alice"
694 "field_to_modify": "new value"
695 }1809 }
696 }1810 }
697}1811}
698```1812```
699 1813
700<Note>1814| Field | Values | Description |
701 The `decision` and `reason` fields are deprecated for PreToolUse hooks.1815| :-------- | :---------------------------- | :--------------------------------------------------------------- |
702 Use `hookSpecificOutput.permissionDecision` and1816| `action` | `accept`, `decline`, `cancel` | Whether to accept, decline, or cancel the request |
703 `hookSpecificOutput.permissionDecisionReason` instead. The deprecated fields1817| `content` | object | Form field values to submit. Only used when `action` is `accept` |
704 `"approve"` and `"block"` map to `"allow"` and `"deny"` respectively.1818
705</Note>1819Exit code 2 denies the elicitation and shows stderr to the user.
1820
1821### ElicitationResult
1822
1823Runs after a user responds to an MCP elicitation. Hooks can observe, modify, or block the response before it is sent back to the MCP server.
706 1824
707#### `PermissionRequest` Decision Control1825The matcher field matches against the MCP server name.
708 1826
709`PermissionRequest` hooks can allow or deny permission requests shown to the user.1827#### ElicitationResult input
710 1828
711* For `"behavior": "allow"` you can also optionally pass in an `"updatedInput"` that modifies the tool's input parameters before the tool executes.1829In addition to the [common input fields](#common-input-fields), ElicitationResult hooks receive `mcp_server_name`, `action`, and optional `mode`, `elicitation_id`, and `content` fields.
712* For `"behavior": "deny"` you can also optionally pass in a `"message"` string that tells the model why the permission was denied, and a boolean `"interrupt"` which will stop Claude.
713 1830
714```json theme={null}1831```json theme={null}
715{1832{
716 "hookSpecificOutput": {1833 "session_id": "abc123",
717 "hookEventName": "PermissionRequest",1834 "transcript_path": "/Users/.../.claude/projects/.../00893aaf-19fa-41d2-8238-13269b9b3ca0.jsonl",
718 "decision": {1835 "cwd": "/Users/...",
719 "behavior": "allow",1836 "permission_mode": "default",
720 "updatedInput": {1837 "hook_event_name": "ElicitationResult",
721 "command": "npm run lint"1838 "mcp_server_name": "my-mcp-server",
722 }1839 "action": "accept",
723 }1840 "content": { "username": "alice" },
724 }1841 "mode": "form",
1842 "elicitation_id": "elicit-123"
725}1843}
726```1844```
727 1845
728#### `PostToolUse` Decision Control1846#### ElicitationResult output
729
730`PostToolUse` hooks can provide feedback to Claude after tool execution.
731 1847
732* `"block"` automatically prompts Claude with `reason`.1848To override the user's response, return a JSON object with `hookSpecificOutput`:
733* `undefined` does nothing. `reason` is ignored.
734* `"hookSpecificOutput.additionalContext"` adds context for Claude to consider.
735 1849
736```json theme={null}1850```json theme={null}
737{1851{
738 "decision": "block" | undefined,
739 "reason": "Explanation for decision",
740 "hookSpecificOutput": {1852 "hookSpecificOutput": {
741 "hookEventName": "PostToolUse",1853 "hookEventName": "ElicitationResult",
742 "additionalContext": "Additional information for Claude"1854 "action": "decline",
1855 "content": {}
743 }1856 }
744}1857}
745```1858```
746 1859
747#### `UserPromptSubmit` Decision Control1860| Field | Values | Description |
748 1861| :-------- | :---------------------------- | :--------------------------------------------------------------------- |
749`UserPromptSubmit` hooks can control whether a user prompt is processed and add context.1862| `action` | `accept`, `decline`, `cancel` | Overrides the user's action |
1863| `content` | object | Overrides form field values. Only meaningful when `action` is `accept` |
1864
1865Exit code 2 blocks the response, changing the effective action to `decline`.
1866
1867## Prompt-based hooks
1868
1869In addition to command and HTTP hooks, Claude Code supports prompt-based hooks (`type: "prompt"`) that use an LLM to evaluate whether to allow or block an action, and agent hooks (`type: "agent"`) that spawn an agentic verifier with tool access. Not all events support every hook type.
1870
1871Events that support all four hook types (`command`, `http`, `prompt`, and `agent`):
1872
1873* `PermissionRequest`
1874* `PostToolUse`
1875* `PostToolUseFailure`
1876* `PreToolUse`
1877* `Stop`
1878* `SubagentStop`
1879* `TaskCompleted`
1880* `UserPromptSubmit`
1881
1882Events that only support `type: "command"` hooks:
1883
1884* `ConfigChange`
1885* `CwdChanged`
1886* `Elicitation`
1887* `ElicitationResult`
1888* `FileChanged`
1889* `InstructionsLoaded`
1890* `Notification`
1891* `PostCompact`
1892* `PreCompact`
1893* `SessionEnd`
1894* `SessionStart`
1895* `StopFailure`
1896* `SubagentStart`
1897* `TeammateIdle`
1898* `WorktreeCreate`
1899* `WorktreeRemove`
750 1900
751**Adding context (exit code 0):**1901### How prompt-based hooks work
752There are two ways to add context to the conversation:
753 1902
7541. **Plain text stdout** (simpler): Any non-JSON text written to stdout is added1903Instead of executing a Bash command, prompt-based hooks:
755 as context. This is the easiest way to inject information.
756 1904
7572. **JSON with `additionalContext`** (structured): Use the JSON format below for19051. Send the hook input and your prompt to a Claude model, Haiku by default
758 more control. The `additionalContext` field is added as context.19062. The LLM responds with structured JSON containing a decision
19073. Claude Code processes the decision automatically
759 1908
760Both methods work with exit code 0. Plain stdout is shown as hook output in1909### Prompt hook configuration
761the transcript; `additionalContext` is added more discretely.
762 1910
763**Blocking prompts:**1911Set `type` to `"prompt"` and provide a `prompt` string instead of a `command`. Use the `$ARGUMENTS` placeholder to inject the hook's JSON input data into your prompt text. Claude Code sends the combined prompt and input to a fast Claude model, which returns a JSON decision.
764 1912
765* `"decision": "block"` prevents the prompt from being processed. The submitted1913This `Stop` hook asks the LLM to evaluate whether all tasks are complete before allowing Claude to finish:
766 prompt is erased from context. `"reason"` is shown to the user but not added
767 to context.
768* `"decision": undefined` (or omitted) allows the prompt to proceed normally.
769 1914
770```json theme={null}1915```json theme={null}
771{1916{
772 "decision": "block" | undefined,1917 "hooks": {
773 "reason": "Explanation for decision",1918 "Stop": [
774 "hookSpecificOutput": {1919 {
775 "hookEventName": "UserPromptSubmit",1920 "hooks": [
776 "additionalContext": "My additional context here"1921 {
1922 "type": "prompt",
1923 "prompt": "Evaluate if Claude should stop: $ARGUMENTS. Check if all tasks are complete."
1924 }
1925 ]
1926 }
1927 ]
777 }1928 }
778}1929}
779```1930```
780 1931
781<Note>1932| Field | Required | Description |
782 The JSON format is not required for simple use cases. To add context, you can1933| :-------- | :------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
783 just print plain text to stdout with exit code 0. Use JSON when you need to1934| `type` | yes | Must be `"prompt"` |
784 block prompts or want more structured control.1935| `prompt` | yes | The prompt text to send to the LLM. Use `$ARGUMENTS` as a placeholder for the hook input JSON. If `$ARGUMENTS` is not present, input JSON is appended to the prompt |
785</Note>1936| `model` | no | Model to use for evaluation. Defaults to a fast model |
786 1937| `timeout` | no | Timeout in seconds. Default: 30 |
787#### `Stop`/`SubagentStop` Decision Control
788 1938
789`Stop` and `SubagentStop` hooks can control whether Claude must continue.1939### Response schema
790 1940
791* `"block"` prevents Claude from stopping. You must populate `reason` for Claude1941The LLM must respond with JSON containing:
792 to know how to proceed.
793* `undefined` allows Claude to stop. `reason` is ignored.
794 1942
795```json theme={null}1943```json theme={null}
796{1944{
797 "decision": "block" | undefined,1945 "ok": true | false,
798 "reason": "Must be provided when Claude is blocked from stopping"1946 "reason": "Explanation for the decision"
799}1947}
800```1948```
801 1949
802#### `SessionStart` Decision Control1950| Field | Description |
1951| :------- | :--------------------------------------------------------- |
1952| `ok` | `true` allows the action, `false` prevents it |
1953| `reason` | Required when `ok` is `false`. Explanation shown to Claude |
803 1954
804`SessionStart` hooks allow you to load in context at the start of a session.1955### Example: Multi-criteria Stop hook
805 1956
806* `"hookSpecificOutput.additionalContext"` adds the string to the context.1957This `Stop` hook uses a detailed prompt to check three conditions before allowing Claude to stop. If `"ok"` is `false`, Claude continues working with the provided reason as its next instruction. `SubagentStop` hooks use the same format to evaluate whether a [subagent](/en/sub-agents) should stop:
807* Multiple hooks' `additionalContext` values are concatenated.
808 1958
809```json theme={null}1959```json theme={null}
810{1960{
811 "hookSpecificOutput": {1961 "hooks": {
812 "hookEventName": "SessionStart",1962 "Stop": [
813 "additionalContext": "My additional context here"1963 {
1964 "hooks": [
1965 {
1966 "type": "prompt",
1967 "prompt": "You are evaluating whether Claude should stop working. Context: $ARGUMENTS\n\nAnalyze the conversation and determine if:\n1. All user-requested tasks are complete\n2. Any errors need to be addressed\n3. Follow-up work is needed\n\nRespond with JSON: {\"ok\": true} to allow stopping, or {\"ok\": false, \"reason\": \"your explanation\"} to continue working.",
1968 "timeout": 30
1969 }
1970 ]
1971 }
1972 ]
814 }1973 }
815}1974}
816```1975```
817 1976
818#### `SessionEnd` Decision Control1977## Agent-based hooks
819
820`SessionEnd` hooks run when a session ends. They cannot block session termination
821but can perform cleanup tasks.
822
823#### Exit Code Example: Bash Command Validation
824
825```python theme={null}
826#!/usr/bin/env python3
827import json
828import re
829import sys
830
831# Define validation rules as a list of (regex pattern, message) tuples
832VALIDATION_RULES = [
833 (
834 r"\bgrep\b(?!.*\|)",
835 "Use 'rg' (ripgrep) instead of 'grep' for better performance and features",
836 ),
837 (
838 r"\bfind\s+\S+\s+-name\b",
839 "Use 'rg --files | rg pattern' or 'rg --files -g pattern' instead of 'find -name' for better performance",
840 ),
841]
842
843
844def validate_command(command: str) -> list[str]:
845 issues = []
846 for pattern, message in VALIDATION_RULES:
847 if re.search(pattern, command):
848 issues.append(message)
849 return issues
850
851
852try:
853 input_data = json.load(sys.stdin)
854except json.JSONDecodeError as e:
855 print(f"Error: Invalid JSON input: {e}", file=sys.stderr)
856 sys.exit(1)
857
858tool_name = input_data.get("tool_name", "")
859tool_input = input_data.get("tool_input", {})
860command = tool_input.get("command", "")
861
862if tool_name != "Bash" or not command:
863 sys.exit(1)
864
865# Validate the command
866issues = validate_command(command)
867
868if issues:
869 for message in issues:
870 print(f"• {message}", file=sys.stderr)
871 # Exit code 2 blocks tool call and shows stderr to Claude
872 sys.exit(2)
873```
874 1978
875#### JSON Output Example: UserPromptSubmit to Add Context and Validation1979Agent-based hooks (`type: "agent"`) are like prompt-based hooks but with multi-turn tool access. Instead of a single LLM call, an agent hook spawns a subagent that can read files, search code, and inspect the codebase to verify conditions. Agent hooks support the same events as prompt-based hooks.
876 1980
877<Note>1981### How agent hooks work
878 For `UserPromptSubmit` hooks, you can inject context using either method:
879 1982
880 * **Plain text stdout** with exit code 0: Simplest approach—just print text1983When an agent hook fires:
881 * **JSON output** with exit code 0: Use `"decision": "block"` to reject prompts,
882 or `additionalContext` for structured context injection
883 1984
884 Remember: Exit code 2 only uses `stderr` for the error message. To block using19851. Claude Code spawns a subagent with your prompt and the hook's JSON input
885 JSON (with a custom reason), use `"decision": "block"` with exit code 0.19862. The subagent can use tools like Read, Grep, and Glob to investigate
886</Note>19873. After up to 50 turns, the subagent returns a structured `{ "ok": true/false }` decision
19884. Claude Code processes the decision the same way as a prompt hook
887 1989
888```python theme={null}1990Agent hooks are useful when verification requires inspecting actual files or test output, not just evaluating the hook input data alone.
889#!/usr/bin/env python3
890import json
891import sys
892import re
893import datetime
894
895# Load input from stdin
896try:
897 input_data = json.load(sys.stdin)
898except json.JSONDecodeError as e:
899 print(f"Error: Invalid JSON input: {e}", file=sys.stderr)
900 sys.exit(1)
901
902prompt = input_data.get("prompt", "")
903
904# Check for sensitive patterns
905sensitive_patterns = [
906 (r"(?i)\b(password|secret|key|token)\s*[:=]", "Prompt contains potential secrets"),
907]
908
909for pattern, message in sensitive_patterns:
910 if re.search(pattern, prompt):
911 # Use JSON output to block with a specific reason
912 output = {
913 "decision": "block",
914 "reason": f"Security policy violation: {message}. Please rephrase your request without sensitive information."
915 }
916 print(json.dumps(output))
917 sys.exit(0)
918 1991
919# Add current time to context1992### Agent hook configuration
920context = f"Current time: {datetime.datetime.now()}"
921print(context)
922 1993
923"""1994Set `type` to `"agent"` and provide a `prompt` string. The configuration fields are the same as [prompt hooks](#prompt-hook-configuration), with a longer default timeout:
924The following is also equivalent:
925print(json.dumps({
926 "hookSpecificOutput": {
927 "hookEventName": "UserPromptSubmit",
928 "additionalContext": context,
929 },
930}))
931"""
932 1995
933# Allow the prompt to proceed with the additional context1996| Field | Required | Description |
934sys.exit(0)1997| :-------- | :------- | :------------------------------------------------------------------------------------------ |
935```1998| `type` | yes | Must be `"agent"` |
1999| `prompt` | yes | Prompt describing what to verify. Use `$ARGUMENTS` as a placeholder for the hook input JSON |
2000| `model` | no | Model to use. Defaults to a fast model |
2001| `timeout` | no | Timeout in seconds. Default: 60 |
936 2002
937#### JSON Output Example: PreToolUse with Approval2003The response schema is the same as prompt hooks: `{ "ok": true }` to allow or `{ "ok": false, "reason": "..." }` to block.
938
939```python theme={null}
940#!/usr/bin/env python3
941import json
942import sys
943
944# Load input from stdin
945try:
946 input_data = json.load(sys.stdin)
947except json.JSONDecodeError as e:
948 print(f"Error: Invalid JSON input: {e}", file=sys.stderr)
949 sys.exit(1)
950
951tool_name = input_data.get("tool_name", "")
952tool_input = input_data.get("tool_input", {})
953
954# Example: Auto-approve file reads for documentation files
955if tool_name == "Read":
956 file_path = tool_input.get("file_path", "")
957 if file_path.endswith((".md", ".mdx", ".txt", ".json")):
958 # Use JSON output to auto-approve the tool call
959 output = {
960 "decision": "approve",
961 "reason": "Documentation file auto-approved",
962 "suppressOutput": True # Don't show in verbose mode
963 }
964 print(json.dumps(output))
965 sys.exit(0)
966
967# For other cases, let the normal permission flow proceed
968sys.exit(0)
969```
970 2004
971## Working with MCP Tools2005This `Stop` hook verifies that all unit tests pass before allowing Claude to finish:
972 2006
973Claude Code hooks work seamlessly with2007```json theme={null}
974[Model Context Protocol (MCP) tools](/en/mcp). When MCP servers2008{
975provide tools, they appear with a special naming pattern that you can match in2009 "hooks": {
976your hooks.2010 "Stop": [
2011 {
2012 "hooks": [
2013 {
2014 "type": "agent",
2015 "prompt": "Verify that all unit tests pass. Run the test suite and check the results. $ARGUMENTS",
2016 "timeout": 120
2017 }
2018 ]
2019 }
2020 ]
2021 }
2022}
2023```
977 2024
978### MCP Tool Naming2025## Run hooks in the background
979 2026
980MCP tools follow the pattern `mcp__<server>__<tool>`, for example:2027By default, hooks block Claude's execution until they complete. For long-running tasks like deployments, test suites, or external API calls, set `"async": true` to run the hook in the background while Claude continues working. Async hooks cannot block or control Claude's behavior: response fields like `decision`, `permissionDecision`, and `continue` have no effect, because the action they would have controlled has already completed.
981 2028
982* `mcp__memory__create_entities` - Memory server's create entities tool2029### Configure an async hook
983* `mcp__filesystem__read_file` - Filesystem server's read file tool
984* `mcp__github__search_repositories` - GitHub server's search tool
985 2030
986### Configuring Hooks for MCP Tools2031Add `"async": true` to a command hook's configuration to run it in the background without blocking Claude. This field is only available on `type: "command"` hooks.
987 2032
988You can target specific MCP tools or entire MCP servers:2033This hook runs a test script after every `Write` tool call. Claude continues working immediately while `run-tests.sh` executes for up to 120 seconds. When the script finishes, its output is delivered on the next conversation turn:
989 2034
990```json theme={null}2035```json theme={null}
991{2036{
992 "hooks": {2037 "hooks": {
993 "PreToolUse": [2038 "PostToolUse": [
994 {
995 "matcher": "mcp__memory__.*",
996 "hooks": [
997 {
998 "type": "command",
999 "command": "echo 'Memory operation initiated' >> ~/mcp-operations.log"
1000 }
1001 ]
1002 },
1003 {2039 {
1004 "matcher": "mcp__.*__write.*",2040 "matcher": "Write",
1005 "hooks": [2041 "hooks": [
1006 {2042 {
1007 "type": "command",2043 "type": "command",
1008 "command": "/home/user/scripts/validate-mcp-write.py"2044 "command": "/path/to/run-tests.sh",
2045 "async": true,
2046 "timeout": 120
1009 }2047 }
1010 ]2048 ]
1011 }2049 }
1014}2052}
1015```2053```
1016 2054
1017## Examples2055The `timeout` field sets the maximum time in seconds for the background process. If not specified, async hooks use the same 10-minute default as sync hooks.
1018
1019<Tip>
1020 For practical examples including code formatting, notifications, and file protection, see [More Examples](/en/hooks-guide#more-examples) in the get started guide.
1021</Tip>
1022 2056
1023## Security Considerations2057### How async hooks execute
1024 2058
1025### Disclaimer2059When an async hook fires, Claude Code starts the hook process and immediately continues without waiting for it to finish. The hook receives the same JSON input via stdin as a synchronous hook.
1026 2060
1027**USE AT YOUR OWN RISK**: Claude Code hooks execute arbitrary shell commands on2061After the background process exits, if the hook produced a JSON response with a `systemMessage` or `additionalContext` field, that content is delivered to Claude as context on the next conversation turn.
1028your system automatically. By using hooks, you acknowledge that:
1029 2062
1030* You are solely responsible for the commands you configure2063Async hook completion notifications are suppressed by default. To see them, enable verbose mode with `Ctrl+O` or start Claude Code with `--verbose`.
1031* Hooks can modify, delete, or access any files your user account can access
1032* Malicious or poorly written hooks can cause data loss or system damage
1033* Anthropic provides no warranty and assumes no liability for any damages
1034 resulting from hook usage
1035* You should thoroughly test hooks in a safe environment before production use
1036 2064
1037Always review and understand any hook commands before adding them to your2065### Example: run tests after file changes
1038configuration.
1039 2066
1040### Security Best Practices2067This hook starts a test suite in the background whenever Claude writes a file, then reports the results back to Claude when the tests finish. Save this script to `.claude/hooks/run-tests-async.sh` in your project and make it executable with `chmod +x`:
1041 2068
1042Here are some key practices for writing more secure hooks:2069```bash theme={null}
2070#!/bin/bash
2071# run-tests-async.sh
1043 2072
10441. **Validate and sanitize inputs** - Never trust input data blindly2073# Read hook input from stdin
10452. **Always quote shell variables** - Use `"$VAR"` not `$VAR`2074INPUT=$(cat)
10463. **Block path traversal** - Check for `..` in file paths2075FILE_PATH=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty')
10474. **Use absolute paths** - Specify full paths for scripts (use
1048 "\$CLAUDE\_PROJECT\_DIR" for the project path)
10495. **Skip sensitive files** - Avoid `.env`, `.git/`, keys, etc.
1050 2076
1051### Configuration Safety2077# Only run tests for source files
2078if [[ "$FILE_PATH" != *.ts && "$FILE_PATH" != *.js ]]; then
2079 exit 0
2080fi
1052 2081
1053Direct edits to hooks in settings files don't take effect immediately. Claude2082# Run tests and report results via systemMessage
1054Code:2083RESULT=$(npm test 2>&1)
2084EXIT_CODE=$?
1055 2085
10561. Captures a snapshot of hooks at startup2086if [ $EXIT_CODE -eq 0 ]; then
10572. Uses this snapshot throughout the session2087 echo "{\"systemMessage\": \"Tests passed after editing $FILE_PATH\"}"
10583. Warns if hooks are modified externally2088else
10594. Requires review in `/hooks` menu for changes to apply2089 echo "{\"systemMessage\": \"Tests failed after editing $FILE_PATH: $RESULT\"}"
2090fi
2091```
1060 2092
1061This prevents malicious hook modifications from affecting your current session.2093Then add this configuration to `.claude/settings.json` in your project root. The `async: true` flag lets Claude keep working while tests run:
1062 2094
1063## Hook Execution Details2095```json theme={null}
2096{
2097 "hooks": {
2098 "PostToolUse": [
2099 {
2100 "matcher": "Write|Edit",
2101 "hooks": [
2102 {
2103 "type": "command",
2104 "command": "\"$CLAUDE_PROJECT_DIR\"/.claude/hooks/run-tests-async.sh",
2105 "async": true,
2106 "timeout": 300
2107 }
2108 ]
2109 }
2110 ]
2111 }
2112}
2113```
1064 2114
1065* **Timeout**: 60-second execution limit by default, configurable per command.2115### Limitations
1066 * A timeout for an individual command does not affect the other commands.
1067* **Parallelization**: All matching hooks run in parallel
1068* **Deduplication**: Multiple identical hook commands are deduplicated automatically
1069* **Environment**: Runs in current directory with Claude Code's environment
1070 * The `CLAUDE_PROJECT_DIR` environment variable is available and contains the
1071 absolute path to the project root directory (where Claude Code was started)
1072 * The `CLAUDE_CODE_REMOTE` environment variable indicates whether the hook is running in a remote (web) environment (`"true"`) or local CLI environment (not set or empty). Use this to run different logic based on execution context.
1073* **Input**: JSON via stdin
1074* **Output**:
1075 * PreToolUse/PermissionRequest/PostToolUse/Stop/SubagentStop: Progress shown in verbose mode (ctrl+o)
1076 * Notification/SessionEnd: Logged to debug only (`--debug`)
1077 * UserPromptSubmit/SessionStart: stdout added as context for Claude
1078 2116
1079## Debugging2117Async hooks have several constraints compared to synchronous hooks:
1080 2118
1081### Basic Troubleshooting2119* Only `type: "command"` hooks support `async`. Prompt-based hooks cannot run asynchronously.
2120* Async hooks cannot block tool calls or return decisions. By the time the hook completes, the triggering action has already proceeded.
2121* Hook output is delivered on the next conversation turn. If the session is idle, the response waits until the next user interaction.
2122* Each execution creates a separate background process. There is no deduplication across multiple firings of the same async hook.
1082 2123
1083If your hooks aren't working:2124## Security considerations
1084 2125
10851. **Check configuration** - Run `/hooks` to see if your hook is registered2126### Disclaimer
10862. **Verify syntax** - Ensure your JSON settings are valid
10873. **Test commands** - Run hook commands manually first
10884. **Check permissions** - Make sure scripts are executable
10895. **Review logs** - Use `claude --debug` to see hook execution details
1090 2127
1091Common issues:2128Command hooks run with your system user's full permissions.
1092 2129
1093* **Quotes not escaped** - Use `\"` inside JSON strings2130<Warning>
1094* **Wrong matcher** - Check tool names match exactly (case-sensitive)2131 Command hooks execute shell commands with your full user permissions. They can modify, delete, or access any files your user account can access. Review and test all hook commands before adding them to your configuration.
1095* **Command not found** - Use full paths for scripts2132</Warning>
1096 2133
1097### Advanced Debugging2134### Security best practices
1098 2135
1099For complex hook issues:2136Keep these practices in mind when writing hooks:
1100 2137
11011. **Inspect hook execution** - Use `claude --debug` to see detailed hook2138* **Validate and sanitize inputs**: never trust input data blindly
1102 execution2139* **Always quote shell variables**: use `"$VAR"` not `$VAR`
11032. **Validate JSON schemas** - Test hook input/output with external tools2140* **Block path traversal**: check for `..` in file paths
11043. **Check environment variables** - Verify Claude Code's environment is correct2141* **Use absolute paths**: specify full paths for scripts, using `"$CLAUDE_PROJECT_DIR"` for the project root
11054. **Test edge cases** - Try hooks with unusual file paths or inputs2142* **Skip sensitive files**: avoid `.env`, `.git/`, keys, etc.
11065. **Monitor system resources** - Check for resource exhaustion during hook
1107 execution
11086. **Use structured logging** - Implement logging in your hook scripts
1109 2143
1110### Debug Output Example2144## Debug hooks
1111 2145
1112Use `claude --debug` to see hook execution details:2146Run `claude --debug` to see hook execution details, including which hooks matched, their exit codes, and output. Toggle verbose mode with `Ctrl+O` to see hook progress in the transcript.
1113 2147
1114```2148```text theme={null}
1115[DEBUG] Executing hooks for PostToolUse:Write2149[DEBUG] Executing hooks for PostToolUse:Write
1116[DEBUG] Getting matching hook commands for PostToolUse with query: Write2150[DEBUG] Getting matching hook commands for PostToolUse with query: Write
1117[DEBUG] Found 1 hook matchers in settings2151[DEBUG] Found 1 hook matchers in settings
1118[DEBUG] Matched 1 hooks for query "Write"2152[DEBUG] Matched 1 hooks for query "Write"
1119[DEBUG] Found 1 hook commands to execute2153[DEBUG] Found 1 hook commands to execute
1120[DEBUG] Executing hook command: <Your command> with timeout 60000ms2154[DEBUG] Executing hook command: <Your command> with timeout 600000ms
1121[DEBUG] Hook command completed with status 0: <Your stdout>2155[DEBUG] Hook command completed with status 0: <Your stdout>
1122```2156```
1123 2157
1124Progress messages appear in verbose mode (ctrl+o) showing:2158For troubleshooting common issues like hooks not firing, infinite Stop hook loops, or configuration errors, see [Limitations and troubleshooting](/en/hooks-guide#limitations-and-troubleshooting) in the guide.
1125
1126* Which hook is running
1127* Command being executed
1128* Success/failure status
1129* Output or error messages