diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index 5469aab..6eae0a2 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -1,13 +1,20 @@
 plugins {
     alias(libs.plugins.architecture.android.application)
     alias(libs.plugins.architecture.compose)
+    alias(libs.plugins.architecture.koin)
 }
 
 dependencies {
+    // :app is the only place modules are assembled and the dependency graph is wired.
+    implementation(project(":core:data"))
+    implementation(project(":core:design-system"))
+
     implementation(libs.androidx.core.ktx)
     implementation(libs.androidx.activity.compose)
     implementation(libs.androidx.lifecycle.runtime.ktx)
     implementation(libs.bundles.lifecycle.compose)
+    // Material Components — required for the Material3 XML Activity theme.
+    implementation(libs.material)
 
     androidTestImplementation(libs.androidx.compose.ui.test.junit4)
     debugImplementation(libs.androidx.compose.ui.test.manifest)
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 778f466..c10b0e4 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -2,6 +2,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
 
     <application
+        android:name=".ArchitectureApp"
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
diff --git a/app/src/main/kotlin/com/example/architecture/ArchitectureApp.kt b/app/src/main/kotlin/com/example/architecture/ArchitectureApp.kt
new file mode 100644
index 0000000..a7170fb
--- /dev/null
+++ b/app/src/main/kotlin/com/example/architecture/ArchitectureApp.kt
@@ -0,0 +1,24 @@
+package com.example.architecture
+
+import android.app.Application
+import com.example.architecture.core.data.di.coreDataModule
+import org.koin.android.ext.koin.androidContext
+import org.koin.android.ext.koin.androidLogger
+import org.koin.core.context.startKoin
+
+/**
+ * Single Koin entry point. Feature modules append their own `*DataModule` / `*PresentationModule`
+ * to the [modules] list — assembly happens only here, never inside feature modules.
+ */
+class ArchitectureApp : Application() {
+    override fun onCreate() {
+        super.onCreate()
+        startKoin {
+            androidLogger()
+            androidContext(this@ArchitectureApp)
+            modules(
+                coreDataModule,
+            )
+        }
+    }
+}
diff --git a/app/src/main/kotlin/com/example/architecture/MainActivity.kt b/app/src/main/kotlin/com/example/architecture/MainActivity.kt
index e3e00e9..abbb074 100644
--- a/app/src/main/kotlin/com/example/architecture/MainActivity.kt
+++ b/app/src/main/kotlin/com/example/architecture/MainActivity.kt
@@ -3,24 +3,24 @@ package com.example.architecture
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.padding
-import androidx.compose.material3.MaterialTheme
-import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
-import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import com.example.architecture.core.design.system.component.AppScaffold
+import com.example.architecture.core.design.system.theme.AppTheme
 
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
         setContent {
-            // Placeholder content. The real navigation host + AppTheme are wired in later
-            // milestones (design-system, characters graph, Koin bootstrap).
-            MaterialTheme {
-                Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
+            // Compose themes via AppTheme; the navigation host lands in a later milestone.
+            AppTheme {
+                AppScaffold { innerPadding ->
                     Box(
                         modifier = Modifier
                             .fillMaxSize()
diff --git a/app/src/main/res/values/themes.xml b/app/src/main/res/values/themes.xml
index 0376602..1a5fe7e 100644
--- a/app/src/main/res/values/themes.xml
+++ b/app/src/main/res/values/themes.xml
@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <!--
-      Compose drives the in-app theming via AppTheme (core:design-system). This XML theme only
-      styles the Activity window. It is upgraded to a Material3 (Theme.Material3.*) parent in the
-      Koin-bootstrap milestone so the later hosted Views renderer inherits Material3 styling.
+      Compose drives the in-app theming via AppTheme (core:design-system); this XML theme styles
+      the Activity window. It uses a Material3 parent so the Views renderer hosted later (via
+      Compose<->View interop) inherits Material3 styling.
     -->
-    <style name="Theme.AndroidArchitectureShowcase" parent="android:Theme.Material.Light.NoActionBar" />
+    <style name="Theme.AndroidArchitectureShowcase" parent="Theme.Material3.DayNight.NoActionBar" />
 </resources>