diff --git a/core/common/src/commonMain/kotlin/io/github/droidkaigi/confsched/compose/ComposeEffectErrorHandler.kt b/core/common/src/commonMain/kotlin/io/github/droidkaigi/confsched/compose/ComposeEffectErrorHandler.kt
index fe91110d5..c1b5a0a29 100644
--- a/core/common/src/commonMain/kotlin/io/github/droidkaigi/confsched/compose/ComposeEffectErrorHandler.kt
+++ b/core/common/src/commonMain/kotlin/io/github/droidkaigi/confsched/compose/ComposeEffectErrorHandler.kt
@@ -6,6 +6,7 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.ProvidedValue
 import androidx.compose.runtime.State
 import androidx.compose.runtime.currentComposer
+import androidx.compose.runtime.produceState
 import androidx.compose.runtime.staticCompositionLocalOf
 import io.github.takahirom.rin.produceRetainedState
 import kotlinx.coroutines.CancellationException
@@ -57,6 +58,28 @@ fun SafeLaunchedEffect(key: Any?, block: suspend CoroutineScope.() -> Unit) {
     }
 }
 
+@Composable
+fun <T : R, R> StateFlow<T>.safeCollectAsState(
+    context: CoroutineContext = EmptyCoroutineContext,
+): State<R> {
+    val composeEffectErrorHandler = LocalComposeEffectErrorHandler.current
+    return produceState(value, this, context) {
+        try {
+            if (context == EmptyCoroutineContext) {
+                collect { value = it }
+            } else {
+                withContext(context) {
+                    collect { value = it }
+                }
+            }
+        } catch (e: CancellationException) {
+            throw e
+        } catch (e: Throwable) {
+            composeEffectErrorHandler.emit(e)
+        }
+    }
+}
+
 @Composable
 fun <T : R, R> Flow<T>.safeCollectAsRetainedState(
     initial: R,
diff --git a/core/data/src/androidMain/kotlin/io/github/droidkaigi/confsched/data/user/UserDataStoreModule.kt b/core/data/src/androidMain/kotlin/io/github/droidkaigi/confsched/data/user/UserDataStoreModule.kt
index 60a6d7cf5..3e493a62f 100644
--- a/core/data/src/androidMain/kotlin/io/github/droidkaigi/confsched/data/user/UserDataStoreModule.kt
+++ b/core/data/src/androidMain/kotlin/io/github/droidkaigi/confsched/data/user/UserDataStoreModule.kt
@@ -6,6 +6,8 @@ import dagger.Module
 import dagger.Provides
 import dagger.hilt.InstallIn
 import dagger.hilt.components.SingletonComponent
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
 import javax.inject.Singleton
 
 @InstallIn(SingletonComponent::class)
@@ -18,6 +20,9 @@ public class UserDataStoreModule {
         @UserDataStoreQualifier
         dataStore: DataStore<Preferences>,
     ): UserDataStore {
-        return UserDataStore(dataStore)
+        return UserDataStore(
+            dataStore = dataStore,
+            coroutineScope = CoroutineScope(Job()),
+        )
     }
 }
diff --git a/core/data/src/commonMain/kotlin/io/github/droidkaigi/confsched/data/sessions/DefaultSessionsRepository.kt b/core/data/src/commonMain/kotlin/io/github/droidkaigi/confsched/data/sessions/DefaultSessionsRepository.kt
index 1e5ba29e4..cf4236e48 100644
--- a/core/data/src/commonMain/kotlin/io/github/droidkaigi/confsched/data/sessions/DefaultSessionsRepository.kt
+++ b/core/data/src/commonMain/kotlin/io/github/droidkaigi/confsched/data/sessions/DefaultSessionsRepository.kt
@@ -10,6 +10,7 @@ import androidx.compose.runtime.setValue
 import co.touchlab.kermit.Logger
 import io.github.droidkaigi.confsched.compose.SafeLaunchedEffect
 import io.github.droidkaigi.confsched.compose.safeCollectAsRetainedState
+import io.github.droidkaigi.confsched.compose.safeCollectAsState
 import io.github.droidkaigi.confsched.data.sessions.response.SessionsAllResponse
 import io.github.droidkaigi.confsched.data.user.UserDataStore
 import io.github.droidkaigi.confsched.model.DroidKaigi2024Day
@@ -17,7 +18,6 @@ import io.github.droidkaigi.confsched.model.SessionsRepository
 import io.github.droidkaigi.confsched.model.Timetable
 import io.github.droidkaigi.confsched.model.TimetableItem
 import io.github.droidkaigi.confsched.model.TimetableItemId
-import kotlinx.collections.immutable.persistentSetOf
 import kotlinx.coroutines.ensureActive
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.catch
@@ -44,7 +44,7 @@ public class DefaultSessionsRepository(
                 refreshSessionData()
                 emitAll(sessionCacheDataStore.getTimetableStream())
             },
-            userDataStore.getFavoriteSessionStream(),
+            userDataStore.getFavoriteSessionStream,
         ) { timetable, favorites ->
             timetable.copy(bookmarks = favorites)
         }
@@ -110,8 +110,8 @@ public class DefaultSessionsRepository(
             }
         }.safeCollectAsRetainedState(Timetable())
         val favoriteSessions by remember {
-            userDataStore.getFavoriteSessionStream()
-        }.safeCollectAsRetainedState(persistentSetOf())
+            userDataStore.getFavoriteSessionStream
+        }.safeCollectAsState()
 
         Logger.d { "DefaultSessionsRepository timetable() count=${timetable.timetableItems.size}" }
         return timetable.copy(bookmarks = favoriteSessions)
diff --git a/core/data/src/commonMain/kotlin/io/github/droidkaigi/confsched/data/user/UserDataStore.kt b/core/data/src/commonMain/kotlin/io/github/droidkaigi/confsched/data/user/UserDataStore.kt
index c2d5c84ef..36085452a 100644
--- a/core/data/src/commonMain/kotlin/io/github/droidkaigi/confsched/data/user/UserDataStore.kt
+++ b/core/data/src/commonMain/kotlin/io/github/droidkaigi/confsched/data/user/UserDataStore.kt
@@ -8,21 +8,28 @@ import androidx.datastore.preferences.core.emptyPreferences
 import androidx.datastore.preferences.core.stringPreferencesKey
 import io.github.droidkaigi.confsched.model.TimetableItemId
 import kotlinx.collections.immutable.PersistentSet
+import kotlinx.collections.immutable.persistentSetOf
 import kotlinx.collections.immutable.toPersistentSet
+import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
 
-public class UserDataStore(private val dataStore: DataStore<Preferences>) {
+public class UserDataStore(
+    private val dataStore: DataStore<Preferences>,
+    coroutineScope: CoroutineScope,
+) {
 
     private val mutableIdToken = MutableStateFlow<String?>(null)
     public val idToken: StateFlow<String?> = mutableIdToken
 
-    public fun getFavoriteSessionStream(): Flow<PersistentSet<TimetableItemId>> {
-        return dataStore.data
+    public val getFavoriteSessionStream: StateFlow<PersistentSet<TimetableItemId>> =
+        dataStore.data
             .catch { exception ->
                 if (exception is IOException) {
                     emit(emptyPreferences())
@@ -34,11 +41,14 @@ public class UserDataStore(private val dataStore: DataStore<Preferences>) {
                 (preferences[KEY_FAVORITE_SESSION_IDS]?.split(",") ?: listOf())
                     .map { TimetableItemId(it) }
                     .toPersistentSet()
-            }
-    }
+            }.stateIn(
+                scope = coroutineScope,
+                started = SharingStarted.WhileSubscribed(5_000),
+                initialValue = persistentSetOf(),
+            )
 
     public suspend fun toggleFavorite(id: TimetableItemId) {
-        val updatedFavorites = getFavoriteSessionStream().first().toMutableSet()
+        val updatedFavorites = getFavoriteSessionStream.first().toMutableSet()
 
         if (updatedFavorites.contains(id)) {
             updatedFavorites.remove(id)
diff --git a/core/data/src/iosMain/kotlin/io/github/droidkaigi/confsched/data/DataModule.kt b/core/data/src/iosMain/kotlin/io/github/droidkaigi/confsched/data/DataModule.kt
index eb86ed48b..f891beee5 100644
--- a/core/data/src/iosMain/kotlin/io/github/droidkaigi/confsched/data/DataModule.kt
+++ b/core/data/src/iosMain/kotlin/io/github/droidkaigi/confsched/data/DataModule.kt
@@ -46,6 +46,7 @@ import io.ktor.client.plugins.logging.Logging
 import kotlinx.cinterop.ExperimentalForeignApi
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
 import kotlinx.coroutines.SupervisorJob
 import org.koin.core.module.Module
 import org.koin.core.module.dsl.singleOf
@@ -109,7 +110,10 @@ public val dataModule: Module = module {
                 requireNotNull(documentDirectory).path + "/confsched2024.preferences_pb"
             },
         )
-        UserDataStore(dataStore)
+        UserDataStore(
+            dataStore = dataStore,
+            coroutineScope = CoroutineScope(Job()),
+        )
     }
     single {
         val dataStore = createDataStore(
diff --git a/core/testing/src/main/java/io/github/droidkaigi/confsched/testing/data/TestUserDataStoreModule.kt b/core/testing/src/main/java/io/github/droidkaigi/confsched/testing/data/TestUserDataStoreModule.kt
new file mode 100644
index 000000000..8e32d6bbe
--- /dev/null
+++ b/core/testing/src/main/java/io/github/droidkaigi/confsched/testing/data/TestUserDataStoreModule.kt
@@ -0,0 +1,33 @@
+package io.github.droidkaigi.confsched.testing.data
+
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.components.SingletonComponent
+import dagger.hilt.testing.TestInstallIn
+import io.github.droidkaigi.confsched.data.user.UserDataStore
+import io.github.droidkaigi.confsched.data.user.UserDataStoreModule
+import io.github.droidkaigi.confsched.data.user.UserDataStoreQualifier
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.test.TestDispatcher
+import javax.inject.Singleton
+
+@Module
+@TestInstallIn(components = [SingletonComponent::class], replaces = [UserDataStoreModule::class])
+class TestUserDataStoreModule {
+
+    @Provides
+    @Singleton
+    public fun provideUserDataStore(
+        @UserDataStoreQualifier
+        dataStore: DataStore<Preferences>,
+        testDispatcher: TestDispatcher,
+    ): UserDataStore {
+        return UserDataStore(
+            dataStore = dataStore,
+            coroutineScope = CoroutineScope(testDispatcher + Job()),
+        )
+    }
+}