Mods reference

Look up any event a mod can hook, mods API method it can call, or render site it can draw in, for the Claude Code CLI and the Desktop app as of v2.1.287. Each entry gives the name and a one-line description, and links to the guide section that explains it where there is one.

The complete reference is Claude Code’s TypeScript declarations for mods, which describe every event, method, and element, with examples. The copy on GitHub can be older than the Claude Code version you have installed. When the two disagree, trust the copy Claude Code writes for your version.

Files

A mod is a plugin directory with these files:

File	Required	Contents
`.claude-plugin/plugin.json`	Yes	The plugin manifest. Mods add no required fields.
`hooks/hooks.json`	Yes	`modules`: an array with one path, relative to this file, to the hooks module, as in `"modules": ["./register.js"]`. Can also hold settings hooks under `hooks`.
The hooks module, such as `hooks/register.js`	Yes	The mod’s entry point. Exports `register(on, options)`. Named `.js`, `.mjs`, `.cjs`, `.jsx`, `.ts`, `.mts`, `.cts`, or `.tsx`. An ES module.
`types/index.d.ts`, named by `types` in the manifest	When the mod uses `$.state` or adds a namespace to the mods API	Declares `PluginState` values and any namespace the mod adds
Files whose names end in `.test.ts` or `.test.tsx`	No	Tests that `claude plugin test` runs

register receives on and options. options holds the values of the userConfig fields the manifest declares, with defaults filled in.

The hook function

A mod registers each of its hooks, which are event handlers, by calling on inside register. on takes the event’s name, an optional matcher, which is a filter on the event’s fields, and the hook, as in on('tool.call', { tool: 'Bash' }, async ($, e, next) => next(e)). on returns a registration with one method, .catch(handler), which sets the hook’s error handler.

Argument	What it is
`$`	The mods API: every method in mods API methods. Write each call in full, namespace then method, as in `$.fs.read('notes.md')`.
`e`	The event’s input, as deeply frozen plain data. To change it, pass a copy to `next`.
`next(e)`	The next handler, as in middleware. Runs the hooks after this one, then Claude Code’s behavior. Resolves to the event’s result.
`next.signal`	An `AbortSignal` that fires when the event is abandoned
`next.origin`	`{ plugin, tier }` of whoever raised the event. Claude Code itself is `{ plugin: 'engine', tier: 'core' }`. A mod’s `tier` is its priority group in the order mods run in: `prepend`, `user`, `append`, or `builtin`.
`next.budget`	The hook’s time limit in milliseconds: `next.budget.ms` is the whole limit, and `next.budget.remainingMs` is what’s left now
`next.to(e, tier)`	Skips to a later tier, which is `append`, `builtin`, or `core`. `next.to(e, 'append')` skips the mods a user installed. Only a mod in `prependPlugins` or `appendPlugins` can call it.
`next.error`, `next.called`	In a `.catch` handler only. `next.error.kind` is `throw` or `timeout`, `next.error.message` is the error’s text, and `next.called` is `true` when the failed hook had called `next`.

Events

Every event a mod can hook is listed here, grouped by what it concerns, with when it fires and what a hook on it can return. Hooks on turn.step and process.spawn are async generators, and every other hook is an async function. The last column of each table uses shorthand. next(e) passes the event on unchanged. next({ ...e, text }) passes on a copy with the named field changed, as in next({ ...e, text: e.text.trim() }). An object answers the event without calling next, and a word such as reason stands for a string you write, as in { deny: 'Use the file tools.' }.

Tools

Tool events fire around each tool call Claude makes, from the description Claude reads to the decision on whether the call runs:

Event	Fires when	A hook can return
`tool.call`	A tool is about to run	`next(e)`, `{ deny: reason }`, or `{ result }`
`tool.check`	Claude Code decides whether a tool call may run, after the `tool.call` and `PreToolUse` hooks. `next(e)` resolves to the decision the rules, the permission mode, and those hooks reached.	`{ decision }`, which is `allow`, `ask`, or `deny`
`tool.describe`	Once for each tool, when its description is first sent to Claude	`{ description }`

Prompts and what Claude reads

Prompt events cover the text the user types and the text Claude Code sends to Claude on its own, such as the system prompt and reminders:

Event	Fires when	A hook can return
`prompt.submit`	A prompt is submitted	`next({ ...e, text })`, `next({ ...e, context })`, or `{ drop: reason }`
`prompt.fill`, `prompt.suggest`	Text is about to go into the prompt box as a draft, or as a dim suggestion	`next(e)` with changed text
`prompt.edit`	The user edits the prompt box	`next(e)`
`prompt.compose`	Claude Code renders a system prompt	`{ sections }`, a list of `{ id, text, scope }` in the order they’re sent
`prompt.section`	Once for each named section of the system prompt. `e.name` is the section’s `id` in `prompt.compose`.	`{ text }`, or `{ text: null }` to leave the section out
`prompt.context`	Once for each conversation, for the context sent with the first message	`{ blocks }`
`prompt.attachment`	Claude Code adds a message of its own for Claude, such as a reminder. `e.type` names the kind, and for the kinds the types declare, `e.detail` holds the facts the text was written from.	`{ text }`, or `{ text: null }` to leave it out
`skill.prompt`	A skill’s text is expanded for Claude	`{ text }`
`attribution.text`	Claude Code composes commit or pull request attribution text	`{ text }`

Commands and configuration

Command and configuration events fire when a command runs or is listed, and when a /config row is shown or changed:

Event	Fires when	A hook can return
`command.run`	A command is about to run	`{ text }`, `{}`, or `next(e)`
`command.describe`	Once for each command, for the command list	`{ description, argumentHint, isHidden }`
`config.set`	A `/config` row is about to change	`next({ ...e, value })` or `{ deny: reason }`
`config.describe`	Once for each `/config` row	`{ label, description, isHidden }`

Turns

Turn events follow one answer from start to finish, including each request to the model within it:

Event	Fires when	A hook can return
`turn.start`	A turn begins	`next(e)`
`turn.step`	One request is about to go to the model	`yield* next(e)`, or `next({ ...e, model })`, `next({ ...e, effort })`
`turn.complete`	A turn ended	`next(e)`, or `{ text }` to show a line under the answer

Session

Session events mark the session starting, ending, compacting, and exchanging messages with other sessions:

Event	Fires when	A hook can return
`session.start`	Once for each loaded mod, before the first prompt, and again after a reload of that mod. Not after `/clear`, `/resume`, or `/branch`.	`next(e)`
`session.end`	The session ends, or `/clear`, `/resume`, or `/branch` runs. `e.reason` is `clear`, `resume`, `logout`, `prompt_input_exit`, or `other`. `/branch` reports `resume`.	`next(e)`
`session.compact`	The conversation is about to be compacted	`{ skip: reason }`
`session.receive`, `session.send`	A message arrives from, or is about to go to, another agent or session. See Send and receive messages between sessions.	`{ consumed: reason }` for `receive`, `{ isDelivered: false, reason }` for `send`
`session.append`	Once for each row the conversation keeps, such as a prompt, a response block, a tool result, or a notice, before it’s stored	`next({ ...e, message })` to rewrite the row’s `content`
`session.attach`, `session.detach`	Another app connects to or disconnects from the session	`next(e)`
`session.measure`	After each turn, and when a plan limit’s percent used changes	`next(e)`

Subagents

Subagent events fire when a subagent type is offered to Claude and when one is about to start:

Event	Fires when	A hook can return
`agent.offer`	A subagent type is offered to Claude	`{ isOffered: false }` to withhold it
`agent.spawn`	A subagent is about to start	`{ model }` or `{ deny: reason }`

Interface

Interface events fire when Claude Code draws a render site and when the user uses a control a mod drew. Draw in the interface shows what a ui.render hook returns:

Event	Fires when
`ui.render`	A render site is about to be drawn
`ui.resolve`	Mods load, once for each app, render site, and mod. The result is the element table that `$.ui.resolve(e)` reads.
`ui.press`, `ui.input`, `ui.select`	A `Button`, `Input`, or `Select` a mod drew is used
`ui.focus`, `ui.scroll`	The focused control or the scroll position of a pane or the band is about to change
`ui.close`	A pane is about to close. `e.id` is the pane and `e.origin.kind` is `plugin`, `person`, or `unload`.
`ui.message`	A `Client` element posts data to its mod

Other mods

Two events let a mod act on other mods as they load, to refuse one or change the mods API it receives:

Event	Fires when	A hook can return
`plugin.register`	A hooks module is about to load. `e.uses` lists its events, mods API calls, environment variables, and state, as `claude plugin validate` prints them. Each call is spelled without the `$.` prefix, such as `fs.read`.	`{ refuse: reason }`
`engine.create`	The mods API is being built for this mod	A changed mods API, to add a namespace or withhold one

Telemetry

Telemetry events fire for the usage records Claude Code logs:

Event	Fires when	A hook can return
`telemetry.log`, `telemetry.mark`	A telemetry record is about to be logged, or one use of a feature is marked. Hook them by name or as `telemetry.`, because `` in a mod you install doesn’t select them.	`next(e)`, or `{ deny: reason }`

Settings hook events

Each settings hook event is an event named classic.<Event>, such as classic.Stop or classic.PostToolUse. e is the hook’s stdin JSON.

Mods API calls

Every mods API method is also an event, named for its namespace and method, such as fs.read, model.complete, or ui.open. A hook on one intercepts calls from the mods that run after it, and can return next(e), { deny: reason }, or { value }.

Mods API methods

The mods API is the $ argument every hook receives. Its methods are grouped in namespaces, such as $.ui. This table lists each namespace’s methods by name, so open in the $.ui row is the call $.ui.open(...). The guides show the common ones in use, and the types for your build document every method with an example.

Namespace	Methods
`$.plugin`	`name`, `root`: this plugin’s name and directory
`$.ui`	`resolve`, `invalidate`, `open`, `close`, `panes`, `focus`, `scroll`, `toast`, `status`, `log`, `notice`, `ask`, `copy`, `blit`
`$.command`	`register`, `run`, `list`
`$.tool`	`register`, `call`, `check`, `list`
`$.agent`	`register`, `spawn`, `list`
`$.model`	`complete`, `fork`, `classify`
`$.prompt`	`submit`, `read`, `fill`, `suggest`, `compose`. Claude reads text from `submit({ text })` after a sentence that names your mod as the sender. `submit({ text, asUser: true })` sends the text as the user’s own words, without that sentence.
`$.turn`	`abort`
`$.session`	`messages`, `cwd`, `root`, `model`, `turns`, `id`, `repo`, `surfaces`, `usage`, `version`, `compact`, `send`, `append`, `authorize`. `usage()` returns `{ startedAt, context, rateLimits, cost }`: `context` has `tokens`, `window`, and `percent`, and `rateLimits` is a list of `{ kind, percentUsed, resetsAt }`.
`$.config`	`list`, `set`
`$.settings`	`read`
`$.env`	`get`, `set`
`$.fs`	`read`, `write`, `list`, `exists`, `stat`, `ancestors`. `write` isn’t atomic: it replaces the file’s content in place, so another process can read a partly written file. Keep data that several sessions change in `$.store`.
`$.store`	`get`, `set`, `delete`, `keys`. A key-value store that every session on the machine shares. See Save from more than one session.
`$.state`	Reactive state: `get`, `set`, with the helpers `atom`, `read`, `update`, `derive`, and `memberOf` imported from `claude-code`
`$.clock`	`now`, `sleep`, `after`, `every`
`$.http`	`fetch`
`$.process`	`run`, `spawn`
`$.mcp`	`call`, `connect`. `connect(server)` connects an MCP server that your own plugin’s manifest lists.
`$.audio`	`play`, `speak`
`$.telemetry`	`log`, `mark`. A record is sent only when Claude Code or a built-in mod raised it.

Render sites

A render site is an extension point in Claude Code’s interface. Each row is a value of e.component in a ui.render hook, with the fields of e.props and the apps that raise it. e.surface is terminal or desktop. Change what Claude Code already draws shows what a hook can do at a site, with an example of each choice.

Site	`e.props`	`e.requestId`	Raised on
`Pane`	`title`, `isFocused`, `bodyColumns`, `placement`, `scroll`, `view`	The pane’s `id`	Terminal, Desktop
`AbovePrompt`	`hasSurvey`, `isWorking`, `maxRows`, `bodyColumns`, `scroll`, `view`	One instance	Terminal, Desktop
`UserMessage`	`text`, `origin`, `isExpanded`, and `task` or `from` by origin	The message id	Terminal, Desktop
`AssistantMessage`	The reply’s text	The message id	Terminal, Desktop
`ToolUse`, `ToolResult`, `ToolGroup`	The tool’s name, input, and result	The tool call id	Terminal, Desktop
`CommandOutput`	`command`, `text`	The message id	Terminal, Desktop
`AskUserQuestion`	The question and options	The tool call id	Terminal, Desktop
`ToolProgress`	`kind`	The tool call id	Terminal
`Spinner`	`word`, `message`, `suffix`, `mode`	The agent id	Terminal, Desktop
`TurnDuration`	`word`, `durationMs`	The message id	Terminal
`InfoNotice`	`text`, `command`	The message id	Terminal
`SessionMode`	`modes`	One instance	Terminal, Desktop
`PromptHint`	`isDraft`, `isWorking`, `hint`	One instance	Terminal, Desktop

e.viewport holds columns, rows, and isFullscreen. It’s absent until the app has measured its window. Its rows is the height of the whole window, not of your pane. To fit a tree to its site, read these props in the hook:

Width of a Pane or the band: draw to e.props.bodyColumns
Height of a Pane beside the transcript: where e.props.placement is 'dock', e.props.scroll.bodyRows is the number of rows the pane has
Height of a Pane above the prompt: where e.props.placement is 'inline', the pane grows with your tree up to a limit, and bodyRows counts only the rows showing now. The rows field of $.ui.open asks for a different limit.

A tree taller than the pane scrolls as a whole.

Elements

Elements are the building blocks of a tree a ui.render hook returns, and you get them from $.ui.resolve(e). Build a tree from elements shows the common ones with how the terminal draws them. A check mark means the app can draw the element.

Element	Main props	Terminal	Desktop
`Box`	`key`, flex layout, `gap`, `padding`, `margin`, `width`, `height`, `borderStyle`, `backgroundColor`, `position`, `hover`	✓	✓
`Text`	`color`, `backgroundColor`, `bold`, `italic`, `underline`, `dimColor`, `inverse`, `wrap`	✓	✓
`Button`	`key`, `label`, `onPress`, `hotkey`, `plain`, `dimColor`, `autoFocus`, `action`	✓	✓
`Link`	`href`, `label`	✓	✓
`Code`	The code, up to 10,000 characters	✓	✓
`Markdown`	`text`, up to 10,000 characters, `key`, `dimColor`, `onLinkPress`, `pressableLinks`	✓	✓
`Input`	`key`, `label`, `placeholder`, `value`, `submitLabel`, `onSubmit`, `onInput`, `autoFocus`	✓	✓
`Select`	`key`, `label`, `options`, `value`, `onSelect`, `autoFocus`	✓	✓
`Svg`	An SVG document, up to 131,072 characters		✓
`Client`	`module`, `key`	✓	✓
`Raster`	`key`, `columns` up to 512, `rows` up to 256, `cells`. See Draw a grid of colored cells.	✓
`Image`	PNG or RGBA bytes up to 2 MiB, or a file path	✓

Three more Button rules: action names one of Claude Code’s own keybinding actions, and the user’s binding for it presses the button when that binding is a chord or a modified key. A digit hotkey on a button in the band also fires when the user types that digit alone into an empty prompt and pauses. When two buttons in one drawing name the same hotkey, the later one gets it. Claude Code refuses autoFocus: false on any control, so leave the prop off instead.

Limits

Hooks and mods API calls run under time and size limits. Claude Code skips a hook that runs past a time limit and rejects a call that passes a size limit.

Limit	Value
A hook’s own running time for one event, not counting time inside `next` or a mods API call other than `$.clock.sleep`	10 seconds
A `.catch` handler’s running time	1 second
All `session.end` hooks together	1.5 seconds
`$.process.run` timeout	30 seconds by default, 10 minutes at most
`$.model.complete` `maxTokens`	1024 by default, up to 64,000 or the model’s output limit
`$.fs.read` and `$.fs.write`	4 MiB for one file
One string child of a `Text`	10,000 characters
`$.store`	4 MiB of JSON in total
`$.session.messages()`	The newest 4,096 entries
`$.ui.invalidate('ui.render')` redraws	Throttled to 10 a second, 30 for the visible pane and the band. Calls that come sooner are coalesced.
`$.ui.toast`	Shown for 4 seconds unless you pass `{ timeoutMs }`
A pane opened without the user asking	Placed from 144 terminal columns, 110 after they’ve opened it once
Command, tool, subagent type, and pane names	Letters, digits, `_`, and `-`, up to 64 characters
One `claude plugin test` test	5 seconds unless the test sets `timeoutMs`

Settings and environment variables

These are the settings and environment variables that affect mods. The Where column says which settings file or environment each one is read from:

Name	Where	What it does
`CLAUDE_CODE_PLUGIN_DIRS`	Environment, or `env` in `~/.claude/settings.json`	Plugin directories to load as `--plugin-dir` does, for apps you can’t pass a flag to. Absolute paths separated by `:`, or `;` on Windows.
`CLAUDE_CODE_PLUGIN_DIR_WATCH`	Environment	`1` makes a long-running non-interactive session reload `--plugin-dir` mods on save
`prependPlugins`, `appendPlugins`	Managed settings. User settings only on a machine with no managed settings, for a user who isn’t signed in with a Team or Enterprise plan.	Lists of plugin ids, such as `acme-guard@acme-tools`. Mods in `prependPlugins` run before every mod a user installs, and mods in `appendPlugins` run after, in the listed order. See The order mods run in.
`allowManagedModsOnly`	Managed settings, as an option on the built-in guard	Only mods that count as your organization’s, and mods built into Claude Code, load. Users’ settings hooks keep running.
`allowModsToOverrideDenyRules`	Managed settings, as an option on the built-in guard	Lets a mod a user installed approve a tool call that a `deny` rule refuses
`allowManagedHooksOnly`	Managed settings	Blocks hooks and installed mods that aren’t your organization’s. See what keeps running.
`disableAllHooks`	Any settings file	In managed settings, no mod or hook from an installed plugin runs. In your own settings, what your organization manages keeps running. See `disableAllHooks`.
`disableSideloadFlags`	Managed settings	Rejects `--plugin-dir` and `--plugin-url` at startup
`pluginConfigs`	User or managed settings	Holds `userConfig` values for a mod, keyed by the plugin’s id, such as `acme-guard@acme-tools`, or its name and `@inline`, such as `first-mod@inline`, for one loaded with `--plugin-dir`

sec-default@builtin is a guard built into Claude Code, listed as cc-plugin-sec-default in /plugin and the debug log. It loads ahead of every mod a person installs on a machine with managed settings, or for a user signed in with a Team or Enterprise plan. If managed prependPlugins is set, the guard loads only when that list names it, at the position listed. Its source is in the mods/sec-default directory of the Claude Code repository.

Commands

These commands and flags load, inspect, and test a mod. The claude commands run in your shell and the / commands at the Claude Code prompt. In the table, <directory> stands for a path you type, as in claude plugin validate ./first-mod. Square brackets mark an argument you can leave out.

Command	What it does
`/plugin`	Shows a line such as `1 mod active · first-mod` under its tabs when a mod that isn’t built in has loaded
`claude plugin validate <directory>`	Reads a plugin’s manifest and hooks module and reports errors, the events it hooks, and the mods API calls it makes. `--strict` treats warnings as errors and `--json` prints a machine-readable report.
`claude plugin test [directory]`	Runs every file under the directory, or the current directory when you give none, whose name ends in `.test.ts` or `.test.tsx`. Exits with status 1 when a test fails.
`claude --plugin-dir <directory>`	Loads a plugin directory for one session and reloads its hooks module when you save. Repeat the flag to load several.
`/reload-plugins`	Reloads plugins when you run it

Plugins

Use plugins

Create plugins

Mods

Run a marketplace

Manage plugins for your organization

Troubleshooting

Reference

Files

The hook function

Events

Tools

Prompts and what Claude reads

Commands and configuration

Turns

Session

Subagents

Interface

Other mods

Telemetry

Settings hook events

Mods API calls

Mods API methods

Render sites

Elements

Limits

Settings and environment variables

Commands

​Files

​The hook function

​Events

​Tools

​Prompts and what Claude reads

​Commands and configuration

​Turns

​Session

​Subagents

​Interface

​Other mods

​Telemetry

​Settings hook events

​Mods API calls

​Mods API methods

​Render sites

​Elements

​Limits

​Settings and environment variables

​Commands

Files

The hook function

Events

Tools

Prompts and what Claude reads

Commands and configuration

Turns

Session

Subagents

Interface

Other mods

Telemetry

Settings hook events

Mods API calls

Mods API methods

Render sites

Elements

Limits

Settings and environment variables

Commands