zeitwerk: Uninitialized constant with nested models Rails 6 upgrade

The issue

I’m almost certain I’m doing something simple wrong here, but I’ve been stuck on this for a few days now without success after much searching and experimentation.

I’m upgrading a Rails project from Rails 5 to Rails 6.0.4.1 (Ruby 2.7.3), and trying to get various models and classes loading using zeitwerk 2.4.2.

Some of my nested classes within an app/models/api folder seemingly aren’t discovered or aren’t loaded by zeitwerk. For example:

models/user.rb                -> User (loads)
models/api/base.rb            -> Api::Base (does not load)
models/api/person.rb          -> Api::Person (does not load)
models/api/person/address.rb  -> Api::Person::Address (does not load)

Some observations

1 - My Api::Base class loads when defined within a explicit module like so:

module Api
  class Base
  end
end

But the more succinct class Api::Base does not…

2 - I’ve also noticed that if I delete the /models/api/person directory, I can get the Api::Person class to load using the same explicit module approach above.

3 - Lastly, when I call Api.constants, I can see both Base and Person in the result:

> Api.constants
=> [
 :Base,
 :Person]

…but calling const_get on either of them gives me the uninitialized constant error.

To test all this, I’ve been firing up a rails console and just trying to use the models like so:

rails c
Loading development environment (Rails 6.0.4.1)
> Api::Person
NameError: uninitialized constant Api::Person
from (pry):1:in `__pry__'

---

I feel like I should apologize in advance for what’s likely to be a complete misunderstanding on my end. I keep coming back to the explicit namespaces section of the documentation and wondering why this isn’t working.

Any assistance anyone could offer would be much appreciated.