FAQ for Kotlin SDK

Why are there two subscribe methods?

The Kotlin SDK supports a modern, entity-based flow and retains a legacy subscribe() for backward compatibility.

Use the modern flow documented in Subscribe. It creates a Subscription or a SubscriptionSet, uses an event listener, and can resume from a timetoken with SubscriptionCursor. The legacy builder pubnub.subscribe(...) is documented in Subscribe (old) and remains for existing applications.

Why does my Android release build crash on startup but my debug build works fine?

Release builds enable ProGuard or R8 code shrinking by default, which debug builds typically skip. The PubNub Kotlin SDK has a transitive dependency on org.json — a library that is also bundled with the Android framework. When R8/ProGuard shrinks your APK, it renames org.json methods (for example, nextValue() → e()), but at runtime Android loads its own original version from the framework, causing a NoSuchMethodError crash.

The fix is to add a -keepnames rule for org.json in your ProGuard configuration. See Android crashes with org.json classes for the full details and rule.

Why does encryption use AES-128 when cryptoModule is configured?

If a call supplies a cipherKey (for encrypt/decrypt or stream helpers), that argument overrides the configured cryptoModule for that operation and uses legacy Advanced Encryption Standard (AES) with 128-bit keys. Remove the cipherKey argument to use the cryptoModule configuration (AES‑256‑CBC), or configure a separate cryptoModule instance for partial encryption scenarios.

For details, refer to CryptoModule configuration.