Every Android engineer consumes SDKs in their app. Far fewer devs had to build an SDK by tearing apart an app that was never designed to be one. Expect war stories with the receipts from our journey of abstracting an app to an SDK. A type definition in the public API that silently collided with the consumer's types. A manifest entry that quietly blocked Play Store installs. A service locator that failed unpredictably in the host app.

Building an Android SDK is not just extracting a feature module—it is a fundamental shift in constraints. We'll dissect the failures we encountered while turning an app into a reusable Android SDK, why they happened, and how to prevent them from happening again. Whether you plan to ship an AAR or considering it in the future or just want to stop guessing why a third-party SDK is misbehaving, you'll leave able to understand SDKs from both sides of the boundary.