diff --git a/app-k9mail/src/main/kotlin/app/k9mail/K9KoinModule.kt b/app-k9mail/src/main/kotlin/app/k9mail/K9KoinModule.kt
index 1e50d35f93..fca597faa8 100644
--- a/app-k9mail/src/main/kotlin/app/k9mail/K9KoinModule.kt
+++ b/app-k9mail/src/main/kotlin/app/k9mail/K9KoinModule.kt
@@ -4,9 +4,9 @@ import app.k9mail.auth.K9OAuthConfigurationFactory
 import app.k9mail.core.common.oauth.OAuthConfigurationFactory
 import app.k9mail.core.common.provider.AppNameProvider
 import app.k9mail.core.featureflag.FeatureFlagFactory
+import app.k9mail.core.ui.theme.api.FeatureThemeProvider
 import app.k9mail.core.ui.theme.api.ThemeProvider
 import app.k9mail.dev.developmentModuleAdditions
-import app.k9mail.feature.launcher.FeatureLauncherExternalContract.FeatureThemeProvider
 import app.k9mail.feature.widget.shortcut.LauncherShortcutActivity
 import app.k9mail.featureflag.K9FeatureFlagFactory
 import app.k9mail.provider.K9AppNameProvider
diff --git a/app-k9mail/src/main/kotlin/app/k9mail/provider/K9FeatureThemeProvider.kt b/app-k9mail/src/main/kotlin/app/k9mail/provider/K9FeatureThemeProvider.kt
index b02abc2373..2a10add64f 100644
--- a/app-k9mail/src/main/kotlin/app/k9mail/provider/K9FeatureThemeProvider.kt
+++ b/app-k9mail/src/main/kotlin/app/k9mail/provider/K9FeatureThemeProvider.kt
@@ -2,9 +2,9 @@ package app.k9mail.provider
 
 import androidx.compose.runtime.Composable
 import app.k9mail.core.ui.compose.theme2.k9mail.K9MailTheme2
-import app.k9mail.feature.launcher.FeatureLauncherExternalContract
+import app.k9mail.core.ui.theme.api.FeatureThemeProvider
 
-class K9FeatureThemeProvider : FeatureLauncherExternalContract.FeatureThemeProvider {
+class K9FeatureThemeProvider : FeatureThemeProvider {
     @Composable
     override fun WithTheme(content: @Composable () -> Unit) {
         K9MailTheme2 {
diff --git a/app-thunderbird/src/main/kotlin/net/thunderbird/android/ThunderbirdKoinModule.kt b/app-thunderbird/src/main/kotlin/net/thunderbird/android/ThunderbirdKoinModule.kt
index 12f180d87e..92b41e1890 100644
--- a/app-thunderbird/src/main/kotlin/net/thunderbird/android/ThunderbirdKoinModule.kt
+++ b/app-thunderbird/src/main/kotlin/net/thunderbird/android/ThunderbirdKoinModule.kt
@@ -3,8 +3,8 @@ package net.thunderbird.android
 import app.k9mail.core.common.oauth.OAuthConfigurationFactory
 import app.k9mail.core.common.provider.AppNameProvider
 import app.k9mail.core.featureflag.FeatureFlagFactory
+import app.k9mail.core.ui.theme.api.FeatureThemeProvider
 import app.k9mail.core.ui.theme.api.ThemeProvider
-import app.k9mail.feature.launcher.FeatureLauncherExternalContract.FeatureThemeProvider
 import app.k9mail.feature.widget.shortcut.LauncherShortcutActivity
 import com.fsck.k9.AppConfig
 import com.fsck.k9.activity.MessageCompose
diff --git a/app-thunderbird/src/main/kotlin/net/thunderbird/android/provider/TbFeatureThemeProvider.kt b/app-thunderbird/src/main/kotlin/net/thunderbird/android/provider/TbFeatureThemeProvider.kt
index 436ee57057..115fa21bfe 100644
--- a/app-thunderbird/src/main/kotlin/net/thunderbird/android/provider/TbFeatureThemeProvider.kt
+++ b/app-thunderbird/src/main/kotlin/net/thunderbird/android/provider/TbFeatureThemeProvider.kt
@@ -2,9 +2,9 @@ package net.thunderbird.android.provider
 
 import androidx.compose.runtime.Composable
 import app.k9mail.core.ui.compose.theme2.thunderbird.ThunderbirdTheme2
-import app.k9mail.feature.launcher.FeatureLauncherExternalContract
+import app.k9mail.core.ui.theme.api.FeatureThemeProvider
 
-class TbFeatureThemeProvider : FeatureLauncherExternalContract.FeatureThemeProvider {
+class TbFeatureThemeProvider : FeatureThemeProvider {
     @Composable
     override fun WithTheme(content: @Composable () -> Unit) {
         ThunderbirdTheme2 {
diff --git a/core/ui/theme/README.md b/core/ui/theme/README.md
new file mode 100644
index 0000000000..9e4e205c38
--- /dev/null
+++ b/core/ui/theme/README.md
@@ -0,0 +1,3 @@
+## Theme
+
+The app theme is provided by the `ThemeProvider` found in the `api` module and should be implemented in the app modules with the required app themes from the `core:compose` and `core:legacy` modules.
diff --git a/core/ui/theme/api/build.gradle.kts b/core/ui/theme/api/build.gradle.kts
index ada1396c97..b1f8504e42 100644
--- a/core/ui/theme/api/build.gradle.kts
+++ b/core/ui/theme/api/build.gradle.kts
@@ -1,5 +1,5 @@
 plugins {
-    id(ThunderbirdPlugins.Library.android)
+    id(ThunderbirdPlugins.Library.androidCompose)
 }
 
 android {
diff --git a/core/ui/theme/api/src/main/kotlin/app/k9mail/core/ui/theme/api/FeatureThemeProvider.kt b/core/ui/theme/api/src/main/kotlin/app/k9mail/core/ui/theme/api/FeatureThemeProvider.kt
new file mode 100644
index 0000000000..70a3f53c44
--- /dev/null
+++ b/core/ui/theme/api/src/main/kotlin/app/k9mail/core/ui/theme/api/FeatureThemeProvider.kt
@@ -0,0 +1,13 @@
+package app.k9mail.core.ui.theme.api
+
+import androidx.compose.runtime.Composable
+
+/**
+ * Provides the compose theme for a feature.
+ */
+fun interface FeatureThemeProvider {
+    @Composable
+    fun WithTheme(
+        content: @Composable () -> Unit,
+    )
+}
diff --git a/feature/launcher/src/main/kotlin/app/k9mail/feature/launcher/FeatureLauncherExternalContract.kt b/feature/launcher/src/main/kotlin/app/k9mail/feature/launcher/FeatureLauncherExternalContract.kt
index aedf3178fe..589a6dfd48 100644
--- a/feature/launcher/src/main/kotlin/app/k9mail/feature/launcher/FeatureLauncherExternalContract.kt
+++ b/feature/launcher/src/main/kotlin/app/k9mail/feature/launcher/FeatureLauncherExternalContract.kt
@@ -1,22 +1,10 @@
 package app.k9mail.feature.launcher
 
-import androidx.compose.runtime.Composable
-
 /**
  * Contract defining the external functionality of the feature launcher to be provided by the host application.
  */
 interface FeatureLauncherExternalContract {
 
-    /**
-     * Provides the theme for the feature.
-     */
-    fun interface FeatureThemeProvider {
-        @Composable
-        fun WithTheme(
-            content: @Composable () -> Unit,
-        )
-    }
-
     fun interface AccountSetupFinishedLauncher {
         fun launch(accountUuid: String?)
     }
diff --git a/feature/launcher/src/main/kotlin/app/k9mail/feature/launcher/ui/FeatureLauncherApp.kt b/feature/launcher/src/main/kotlin/app/k9mail/feature/launcher/ui/FeatureLauncherApp.kt
index 927c778a47..dfaa5f9424 100644
--- a/feature/launcher/src/main/kotlin/app/k9mail/feature/launcher/ui/FeatureLauncherApp.kt
+++ b/feature/launcher/src/main/kotlin/app/k9mail/feature/launcher/ui/FeatureLauncherApp.kt
@@ -7,7 +7,7 @@ import androidx.compose.ui.Modifier
 import androidx.navigation.compose.rememberNavController
 import app.k9mail.core.ui.compose.common.activity.LocalActivity
 import app.k9mail.core.ui.compose.designsystem.atom.Surface
-import app.k9mail.feature.launcher.FeatureLauncherExternalContract.FeatureThemeProvider
+import app.k9mail.core.ui.theme.api.FeatureThemeProvider
 import app.k9mail.feature.launcher.navigation.FeatureLauncherNavHost
 import org.koin.compose.koinInject