## The helper

```ruby
hotwire_native_app?          # true in either shell
hotwire_native_android?      # true in the Android shell specifically
```

Both are declared as `helper_method` in `app/controllers/application_controller.rb`, so views can
call them directly. The Android-specific one exists because the two platforms differ on what has to
be hidden, not because the code needs to know which phone it is talking to in general. The shells
that set the user agent are in `mobile/ios` and `mobile/android`.

## The case that actually matters

```erb
<% if hotwire_native_app? %>
  <%= link_to "Subscribe", iap_subscribe_path %>
<% else %>
  <%= button_to "Subscribe", checkout_path %>
<% end %>
```

Showing a Stripe checkout button inside the iOS app is the most common reason an app of this shape is
rejected. Apple requires digital subscriptions to go through StoreKit, and a link out to an external
payment page is what reviewers look for.

## Do not use it for authentication

A user agent is a string the client sends and anyone can set. It is fine for deciding which button to
render and wrong for deciding who someone is or what they may do. Entitlement still goes through
`Entitlement.for(Current.account)` and record access still goes through Pundit, regardless of the
client.

## Use it sparingly

Every branch on this helper is a second version of a page that has to be kept working. Two or three
in an app is normal: the purchase trigger, the subscription management link, and perhaps hiding a
footer. A dozen means the app and the site have quietly become different products.

## Check it while developing

```bash
bin/dev
```

Then load a page in the shell and one in a browser side by side. If you want to test the branch
without building, override the user agent in your browser's devtools to include "Hotwire Native" and
reload. That is faster than a rebuild for checking which button renders.