> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fapost.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Flow node reference

> Type, version, and category for each node Core registers.

Nodes registered by Core. A handler is resolved by the pair `(type, version)`;
every Core node is currently at version 1.

| Category    | Type           | Label        |
| ----------- | -------------- | ------------ |
| Core        | `input`        | Input        |
| Core        | `send_message` | Send message |
| Logic       | `branch`       | Branch       |
| Logic       | `delay`        | Delay        |
| Logic       | `loop`         | Loop         |
| Logic       | `loop_end`     | Loop end     |
| Logic       | `subflow`      | Subflow      |
| Logic       | `emit_event`   | Emit event   |
| Logic       | `end`          | End          |
| Data        | `assign`       | Assign       |
| Data        | `set_tag`      | Set tag      |
| Contact     | `auth_request` | Auth request |
| Contact     | `notify`       | Notify       |
| Integration | `call`         | Call         |
| AI          | `rag_query`    | Rag query    |

`type` is what a flow definition stores and what the registry resolves against. It
is unique across every registered handler, Core and extension alike, so an
extension picking a name that Core might later want is a collision waiting to
happen — prefix yours.

## Nodes the engine treats specially

Most nodes execute and return a handle. Four alter the shape of execution itself:

| Type       | Effect                                                           |
| ---------- | ---------------------------------------------------------------- |
| `end`      | Sets the session status; the flow finishes                       |
| `loop_end` | Returns to the `loop` node named in its config                   |
| `subflow`  | Creates a child session and pauses the parent until it completes |
| `input`    | Returns `waiting`; the session pauses for the contact's reply    |

## Declaring a node

`type`, `version`, `label`, and `category` come from the handler. Core handlers
extend `AbstractVersionedHandler`, which derives them from a `TYPE` constant:

```php theme={"theme":"one-dark-pro"}
final class SendMessageNodeHandler extends AbstractVersionedHandler
{
    final public const string TYPE = 'send_message';

    public function version(): int
    {
        return 1;
    }
}
```

The base class defaults `label()` to a humanised form of the type and `category()`
to `Core`; override either to place a node elsewhere in the builder's palette.

See [Handler contract](/extending/flow-nodes/handler-contract) for the full
interface and [Versioning](/extending/flow-nodes/versioning) for when the version
must change.