Skip to content

The Superfone Android app

Shipped to the Play Store

Android engineer · Superfone · 2021 – present

The original Superfone dialer — a business soft-phone that rings real SIP calls, built in Kotlin on the Linphone stack and maintained across thousands of commits since 2021.

Android · Kotlin · VoIP · SIP · Linphone

Google Play ↗

The Android app is the original Superfone — it shipped four years before the iOS one, and it’s where a lot of the platform’s hard call-handling logic was first worked out. A soft-phone is a deceptively deep thing to build: it has to behave like the user’s real phone while routing every call over SIP.

What I worked on

  • The SIP call engine. Embedded the Linphone SIP stack as the call engine and owned the parts that break in real life — codec negotiation, the inbound call state machine, and ANR/deadlock avoidance when the SIP layer and the UI thread fight.

  • Soft-phone correctness. Multi-call handling, proximity-sensor control during calls, call-end tone generation, and a proper taxonomy of call-end reasons (missed, declined, Do-Not-Disturb).

  • Push-to-ring and presence. Wired push notifications so an incoming call wakes the app reliably, and kept SIP registration state in sync with that wakeup path — the kind of bug that only shows up on someone’s locked phone.

  • Observability and AI features. Performance monitoring and product analytics, plus the in-app surfaces for the platform’s newer AI features.

Maintained across 2,000+ commits and four years of continuous product iteration — which is its own kind of engineering: keeping a calling app correct while it never stops shipping. It’s live on Google Play with a 4.3★ rating across 2,000+ reviews.