Code

Open source & tooling.

A small set of libraries and experiments — mostly around mobile payments, subscription state, and Android developer experience. Built in the gaps between shipping at billion-install scale.

Featured

renew-kt

v0.1 · Apache 2.0

A deterministic Kotlin state machine for the Google Play Billing subscription lifecycle. Models 7 canonical states (Active, InGracePeriod, OnHold, Paused, Cancelled, Expired…) and 11 events, rejecting invalid transitions with descriptive reasons instead of silently leaving your app in an inconsistent state.

Stack Kotlin / JVM, no Android deps
Tests 21 unit tests, CI on every push
Why The Play Billing docs answer "what should happen" across many pages; this library encodes the answer in one place.

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In progress

renew-play-billing — adapter that converts Play Billing real-time developer notifications and client-side Purchase payloads directly into renew-kt events.
subscription-store — a Coroutine StateFlow-backed wrapper over the state machine for reactive observation in MVI / MVVM apps.
Writeups — long-form posts on subscription state modelling, the hidden complexity of cross-grade architectures, and the things the Play Billing SDK doesn’t tell you. See /blog.

Reach me

Spot something off, or have a real-world Play Billing edge case that should be modelled? Open an issue, or email me.