feature(PayPal): collect and send device_info to determine app switch eligibility

[santugowda]

Summary of changes

Sends device information as a nested app_switch_context object in PayPal Hermes requests when enablePayPalAppSwitch is enabled. This data allows the PayPal server to determine app switch eligibility.

Background

The PayPal App Switch flow launches the PayPal native app directly, bypassing browser checkout. On low-RAM devices, running two apps simultaneously (the merchant app + PayPal app) can cause the OS to kill the merchant app in the background due to memory pressure — leading to a broken checkout experience when the user tries to return.

The PayPal server uses memory_available_mb and memory_total_mb to gate app switch eligibility — if the device doesn't have enough free RAM, the server skips app switch and falls back to browser checkout (Chrome Custom Tab), which is lighter on memory.

Currently the BT Android SDK sends app_switch_context (OS type, OS version, app link URL) but not device memory info. Without device_info, the server cannot make the eligibility decision and defaults to browser checkout.

This PR adds collection and injection of:

• model — device model (e.g. SM-A166U) for any device-specific overrides the server may have
• memory_available_mb — free RAM at request time
• memory_total_mb — total device RAM

These are injected into the request body under app_switch_context.device_info, giving the server everything it needs to decide whether to serve an app switch URL or a browser URL in the response.

JSON structure sent to BTGW:

{
  "launch_paypal_app": true,
  "app_switch_context": {
    "device_info": {
      "model": "SM-A166U",
      "memory_available_mb": 350,
      "memory_total_mb": 4096
    },
    "native_app": {
      "app_url": "https://...",
      "os_type": "ANDROID",
      "os_version": "35"
    }
  }
}

Changes:

• PayPalVaultRequest / PayPalCheckoutRequest: replaced flat os_type, os_version, merchant_app_return_url keys with nested app_switch_context.native_app object
• PayPalInternalClient: injectDeviceInfo() adds device_info (model, memory_available_mb, memory_total_mb) into app_switch_context
• PayPalRequest: updated constants for new nested key structure
• Updated unit and instrumentation tests to verify nested structure

Steps to Test

1. Set enablePayPalAppSwitch = true on PayPalCheckoutRequest or PayPalVaultRequest
2. Ensure the merchant app is configured with an App Link return URL
3. Trigger a PayPal checkout or vault flow
4. Intercept the request to paypal_hermes/create_payment_resource or paypal_hermes/setup_billing_agreement
5. Confirm app_switch_context.device_info is present in the request body with model, memory_available_mb, and memory_total_mb
6. On a device with sufficient RAM, confirm the server returns an app switch URL (PayPal app launches)
7. On a low-RAM device, confirm the server falls back to browser checkout (Chrome Custom Tab launches)

AI Usage

Which AI Agent Was Used?

• Claude

How was AI used?
Code generation, cross-codebase analysis (Android SDK, BTGW, backend), refactoring from flat to nested JSON structure, and writing tests.

Estimated AI Code Contribution

• less than 30%
• 30 - 60%
• 60 - 100%

Checklist

• Added a changelog entry
• Tested and confirmed payment flows affected by this change are functioning as expected

Authors

• @santugowda

---

Inner Source Process

Internal to PayPal contributors should fill out this section. All others can delete.

PR should follow these steps before codeowners review will begin:

1. Comment /inner source on this PR — this will automatically add the inner source and tech lead review required labels. Open the PR in a draft state.
2. PR should be reviewed by and approved by your team's technical lead, we do not allow LGTM reviews, there should be comments and feedback provided on all PR reviews
3. Once the above steps are completed, comment /ready on this PR — this will automatically remove the tech lead review required label. Move the PR to ready to review.
4. PR comments must be addressed within 24 hours, if you are unable to address within this timeframe, move the PR back to a draft state so our team knows not to review

Demo

Request body sent (key fields):

  {
    "launch_paypal_app": true,
    "app_switch_context": {
      "native_app": {
        "app_url": "https://mobile-sdk-demo-site-838cead5d3ab.herokuapp.com/braintree-payments",
        "os_type": "ANDROID",
        "os_version": "36"
      },
      "device_info": {
        "model": "SM-A166U",
        "memory_available_mb": 900,
        "memory_total_mb": 10000
      } 
    }   
  }

token=232345522J779231L

EC flow

paypal_appswitch_test.mp4

Billing Successful app-switch

BillingWithSupportedDevice.mp4

Billing on Low Ram device not app-switching

BillingWithLowRamDevice.mp4

Inner Source Checklist

• Added all labels to the PR
• Provide steps to test the flows changed, if applicable in the summary
• Demo video of the functionality, if applicable
• All upstream dependencies are merged in and this PR can be released at any time; PRs should not be opened until this is true
• Unit tests and builds have been run locally and pass/compile as expected

[jaxdesmarais]

@santugowda please follow the Inner Source Process in the PR description.

[santugowda]

/inner source

[santugowda]

@anbojorquez @ayer-ribeiro could you please review this PR? Thanks!

[ayer-ribeiro]

LGTM

[santugowda]

/ready