ChirpAppKMP

A Kotlin Multiplatform chat application that shares its entire UI and business logic across Android and iOS using Compose Multiplatform.

The app supports account registration and email verification, login and password reset, a chat list with an adaptive list/detail layout, one-to-one and group chats, chat management, and a user profile with avatar media picking.

Targets: Android (androidMain) and iOS (iosArm64, iosSimulatorArm64). The convention plugins do not currently configure a Desktop/JVM target.

Tech Stack

Concern	Library
UI	Compose Multiplatform, Material 3, Compose Navigation, Adaptive layouts
Dependency injection	Koin
Networking	Ktor client (OkHttp on Android, Darwin on iOS) + WebSockets
Local persistence	Room (KMP) + SQLite, DataStore
Serialization	kotlinx.serialization
Async	kotlinx.coroutines
Images	Coil 3
Logging	Kermit
Build config	BuildKonfig
Firebase	Firebase BOM (Android)

Versions are centralized in the version catalog at gradle/libs.versions.toml.

Architecture

The project is split into many small Gradle modules following a strict layered, per-feature structure. Module dependencies only point downward:

presentation → domain ← data → database
                  ↑
             core/* (shared by everything)

Modules

• composeApp — shared application code and entry point (App.kt, NavigationRoot.kt). Aggregates every feature/core module and starts Koin via initKoin().
• androidApp — the Android application module (Android manifest, launcher, Firebase / Google Services). Depends on composeApp.
• iosApp — the iOS application entry point (open in Xcode). Consumes the shared Kotlin code as a framework.
• core/
  • core/domain — shared domain models and interfaces (no platform deps).
  • core/data — shared data implementations and platform bindings.
  • core/presentation — shared presentation utilities.
  • core/designsystem — reusable Chirp* Compose components.
• feature/auth/ — presentation, domain (login, register, email verification, forgot/reset password).
• feature/chat/ — presentation, domain, data, database (chat list, chat detail, create/manage chat, profile). feature/chat/database is the Room KMP database; exported schemas live in feature/chat/database/schemas/.

Convention plugins (build-logic/)

Module build files are intentionally tiny because shared configuration lives in build-logic/convention/ as plugins applied by id:

• convention.kmp.library — base KMP library (Android + iOS targets; namespace/framework name derived from the module path).
• convention.cmp.library — KMP library + Compose Multiplatform.
• convention.cmp.feature — cmp.library + Koin, Compose navigation/viewmodel, and core:presentation/core:designsystem. Use for feature/*/presentation.
• convention.cmp.application — the composeApp itself.
• convention.android.application — the androidApp module.
• convention.room — applies KSP + Room; registers kspAndroid / kspIosSimulatorArm64 / kspIosArm64 and sets the schema dir.
• convention.buildkonfig — generates BuildKonfig with API_KEY (package derived from the module path).

Key patterns

• MVI presentation — each screen folder contains XxxViewModel, XxxState, XxxAction, and (when needed) XxxEvent.
• Koin DI — one module per layer (coreDataModule, chatDataModule, chatPresentationModule, corePresentationModule, authPresentationModule, …), all registered in composeApp/.../di/initKoin.kt. Platform bindings use expect/actual module declarations.
• expect/actual — common code in Platform.kt with Platform.android.kt / Platform.ios.kt actuals; the iOS data layer also uses a cinterop (network.def).
• Offline-first repositories — OfflineFirst*Repository read/write the Room cache and reconcile with Ktor/WebSocket services.

Prerequisites

• JDK 17+

• Android Studio (latest) with the Kotlin Multiplatform tooling

• Xcode (for building/running the iOS app)

• API_KEY in local.properties — BuildKonfigConventionPlugin reads it and fails the build if it is missing:

  API_KEY=your_api_key_here

Build & Run

Android

./gradlew :composeApp:assembleDebug   # build the Android APK

Or use the run configuration from the run widget in the IDE toolbar.

iOS

Open the iosApp/ directory in Xcode and run, or use the IDE run configuration. The shared Kotlin code is exposed as a framework whose baseName is derived from the module path (e.g. :core:domain → CoreDomain).

Everything

./gradlew build

Validating Room DAOs on iOS

For source sets targeting non-Android platforms, Room requires every @Query method to be either suspend or return an observable type (Flow). Always validate DAO changes with the iOS KSP task, not just the Android build:

./gradlew :feature:chat:database:kspKotlinIosSimulatorArm64

Learn more about Kotlin Multiplatform and Compose Multiplatform.