I was on the fence about unsetting _id or not. That's why I left this comment:

It makes it impossible to work with _id in result as it would be natively, while _id or id can both be used in a query.

Thanks for your feedback. It seems that we should unset _id indead.

I dont know if this an issue or anything that can be improved for now I made adjustment on my side by unsetting the _id field
Example

Address model
User with address field

$address = Address::find(objectIdhere);
 // unset($address ['_id']); Solution
$users = User::insert([
 'name' => $user->fullname,
 'username' => $user->username,
 'address' => $address->toArray()])

Cannot have both "id" and "_id" fields. {"exception":"[object] (InvalidArgumentException(code: 0): Cannot have both "id" and "_id" fields. at /app/vendor/mongodb/laravel-mongodb/src/Query/Builder.php:1620)
It seems good that it can detect also nested documents that has both id and _id, but is there a way it only returns id or do we just need to keep unsettting the _id field

We can also detect when _id === id in a query and unset(id). That would solve your issue.

I was on the fence about unsetting _id or not. That's why I left this comment:

laravel-mongodb/src/Query/Builder.php

Line 1662 in 7551f76

//unset($values['_id']);

It makes it impossible to work with _id in result as it would be natively, while _id or id can both be used in a query.

Thanks for your feedback. It seems that we should unset _id indeed.

Thanks for replying so fast, I edited my question now its below to the answer hahaha.

So the aliasIdForResult will just return the id field, but we cant access the native _id Objectid. This would be in line to Laravel behavior but probably needs to be documented. This is acceptable though just like prisma uses id for mongodb too.

We can also detect when _id === id in a query and unset(id). That would solve your issue.

When using v5 I always assume that _id is non existent so I always use id both for saving data and retrieving it.