Aggregate partials can be used to split large aggregate roots into separate classes. An aggregate partial belongs to an aggregate root, so from the outside you'd still interact with the aggregate root.
Just like aggregate roots, aggregate partials can record and apply events, these events are linked to the aggregate root a partial belongs to.
Here's an example of an aggregate partial, which manages cart items and is part of the cart aggregate root:
The package will determine automatically that CartItems is a partial, and will dispatch events to it without any other configuration.
As said before, you'd still interact with the aggregate root from the outside, so CartAggregateRoot still needs a method to add an item, though all functionality related to it is moved to a separate class: