Retain observed settings through read failures and retry without default resets

tools/chatgui-android/app/src/main/java/com/utun/chat/data/SettingsOperations.kt

@@ -7,8 +7,11 @@ import kotlinx.coroutines.Deferred
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.async
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.retryWhen
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
 
@@ -37,4 +40,13 @@ class SettingsOperations(private val scope: CoroutineScope = CoroutineScope(Supe
     }
     fun dismissFailure() { _failed.value = false }
     suspend fun awaitIdle() { mutex.withLock { } }
+
+    /** Ошибка чтения не публикует defaults поверх последнего значения и не завершает подписку UI. */
+    fun <T> observe(name: String, values: Flow<T>): Flow<T> = values.retryWhen { error, attempt ->
+        if (error is CancellationException || error !is Exception) false else {
+            reportFailure(name, error)
+            delay((250L shl attempt.toInt().coerceIn(0, 7)).coerceAtMost(30_000))
+            true
+        }
+    }
 }

tools/chatgui-android/router-tests/src/test/kotlin/com/utun/chat/data/SettingsOperationsTest.kt

@@ -6,6 +6,9 @@ import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.async
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.take
+import kotlinx.coroutines.flow.toList
 import org.junit.Assert.*
 import org.junit.Test
 
@@ -39,4 +42,13 @@ class SettingsOperationsTest {
         val waiter = launch { owner.awaitIdle() }; waiter.cancel()
         gate.complete(Unit); change.await(); assertTrue(saved); assertFalse(change.isCancelled)
     }
+    @Test fun failedPreferenceObservationPreservesTheLastValueAndCanRecover() = runTest {
+        val owner = SettingsOperations(this) { _, _ -> }; var attempts = 0
+        val values = flow {
+            if (++attempts == 1) { emit(42); throw java.io.IOException("read failed") }
+            emit(43)
+        }
+        assertEquals(listOf(42, 43), owner.observe("preferences", values).take(2).toList())
+        assertTrue(owner.failed.value); assertEquals(2, attempts)
+    }
 }