> For the complete documentation index, see [llms.txt](https://docs.rootcause.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rootcause.ai/more-details/applications/application-modules/box.md).

# Box

> Drop a published box — a saved fragment of flow — in as one node.

One instance of a published box: a saved fragment of flow, dropped in as a single node.

A linked instance pins `boxId:version` and keeps no body of its own — the definition is fetched and the ports and tier follow it, stamped by the box sync on save. Unlinking copies the body in and the instance stops tracking the library. The palette builds a tile per library entry rather than one for `Box` itself, which is why this page is named from here.

## At a glance

|                          |                        |
| ------------------------ | ---------------------- |
| Module type              | `Box`                  |
| Category                 | Library                |
| Default tier             | `durable`              |
| Runs on                  | `reactive`, `durable`  |
| Starts a flow            | no                     |
| Holds a body             | yes                    |
| Keeps state between runs | no                     |
| Available in             | every application type |

## Parameters

### `version`

`string` · required · defaults to `""`

Which published version it is pinned to.

### `boxId`

`string` · required · defaults to `""`

The box in the library this instance is of.

### `linked`

`boolean` · required · defaults to `true`

Track the library version. Unlink to copy the body in and stop following it.

### `parameterValues`

`Record<string, unknown>` · required · defaults to `{}`

This instance's values for the box's declared parameters.

### `body`

`object` · required · defaults to `null`

The copied flow — its `modules` and `edges` — for an unlinked instance; null while it is still linked.

## Inputs

| Port | Kind    | Required | Description                                                                                                                           |
| ---- | ------- | -------- | ------------------------------------------------------------------------------------------------------------------------------------- |
| `on` | `event` | no       | Implicit on every module that does not itself start a flow: wire an event here to make this module the start of what that event runs. |

## Outputs

*Derived, not fixed: this module takes the ports of whatever it resolves to, so a freshly dropped one has none yet.*

***

[← All application modules](/more-details/applications/application-modules.md)