Use the Vonage Client SDK

It’s time to complete Silent Authentication properly by having the Android app call the check_url using the mobile network, then sending the resulting code back to the backend via /check-code.

Rather than using OkHttp to call check_url, we’ll use the Vonage Client SDK because Silent Authentication depends on mobile network context (carrier routing, SIM/network identity), and the request may go over Wi-Fi, which breaks the purpose of Silent Auth.

The Vonage Client SDK exists to solve exactly this:

• It can force the request over cellular data (or use the correct network route)
• It handles redirects and request details in the way Silent Auth expects
• It gives you a structured response so you can extract the code cleanly

In this section we’re building the following:

1. If check_url exists, call it from the phone using the Vonage Client SDK.
2. Extract code from the response.
3. Send { request_id, code } to the backend via /check-code.
4. If Silent Auth fails, fall back to SMS:
   • call /next (best-effort, so we don’t wait ~20 seconds).
   • show the SMS code UI.

Add the Vonage Client SDK Dependency

Add the dependency to the current project. Open your build.gradle.kts and add:

After adding it, sync Gradle.

Initialize the SDK

Initialize the SDK once in MainActivity.onCreate():

This is safe to do at startup and avoids forgetting it later.

Implement checkSilentAuth(checkUrl) Using the SDK

Add this function to your MainActivity.kt.. It performs a cellular GET request to check_url, follows redirects, and extracts code from the JSON response.

The method returns a code string that your backend can validate with POST /check-code.

Update the “Start verification” Flow to Attempt Silent Auth

Now replace the “always force SMS fallback” logic from the previous section with:

• Try Silent Auth if check_url is present
• If it fails, trigger /next (best-effort) and show SMS UI

Conceptually:

1. POST /verification → (request_id, check_url?)

2. If check_url exists:

   • code = checkSilentAuth(check_url)
   • POST /check-code with (request_id, code)

3. If that fails:

   • call POST /next (optional UX optimization)
   • show SMS UI

Here’s the core part you should use inside your Compose button onClick (inside a coroutine):