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ADR-0011: Not the default SMS app in v1; minSdk 31

Status: Accepted (2026-09-30)

Context

Android delivers every incoming SMS to the default SMS app (SMS_DELIVER) and, as a notification, to every app holding RECEIVE_SMS (SMS_RECEIVED). The default app also skips the system's warning when an app sends more than 30 SMS a minute, and its messages do not appear in another app's inbox. Becoming the default means implementing a full messaging app: an inbox, MMS, a compose screen and a service for quick replies.

The only target device is a Galaxy S21 Ultra on Android 15.

Decision

  • The app holds RECEIVE_SMS and SEND_SMS and listens for SMS_RECEIVED. It is not the default SMS app.
  • The app's minimum SDK is 31 (Android 12), so SmsManager comes from getSystemService with no deprecated branches.

Why

  • A messaging app is a large product that has nothing to do with browsing.
  • The app sends one request per tap, far below the 30-a-minute prompt.

What it costs

  • The server's frames also appear in the phone's normal messaging app, as unreadable text from the server's number. The onboarding guide says to mute that conversation.
  • Android 15 treats SMS permissions for sideloaded apps as a "restricted setting", so the first install needs one extra toggle in App info. The onboarding guide shows it.

What would change our minds

The duplicated frames in the messaging app becoming a real problem in daily use. Then the app takes the SMS role and ships a minimal inbox (Phase 9 in the build plan).