Chat history support

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/AppSettings.kt

@@ -12,5 +12,6 @@ package com.example.executorchllamademo
  * Holds app-wide settings that are independent of the current module/model.
  */
 data class AppSettings(
-    val appearanceMode: AppearanceMode = AppearanceMode.SYSTEM
+    val appearanceMode: AppearanceMode = AppearanceMode.SYSTEM,
+    val saveChatHistory: Boolean = false
 )

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/ui/screens/AppSettingsScreen.kt

@@ -30,6 +30,8 @@ import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.RadioButton
+import androidx.compose.material3.Switch
+import androidx.compose.material3.SwitchDefaults
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
@@ -141,6 +143,42 @@ fun AppSettingsScreen(
 
             Spacer(modifier = Modifier.height(8.dp))
 
+            // Save Chat History toggle
+            Row(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .background(appColors.settingsRowBackground, RoundedCornerShape(8.dp))
+                    .padding(horizontal = 16.dp, vertical = 12.dp),
+                verticalAlignment = Alignment.CenterVertically
+            ) {
+                Column(modifier = Modifier.weight(1f)) {
+                    Text(
+                        text = "Save Chat History",
+                        fontSize = 14.sp,
+                        color = appColors.settingsText
+                    )
+                    Text(
+                        text = "Persist conversations between sessions",
+                        fontSize = 12.sp,
+                        color = appColors.settingsText.copy(alpha = 0.6f)
+                    )
+                }
+                Switch(
+                    checked = appSettings.saveChatHistory,
+                    onCheckedChange = { enabled ->
+                        appSettings = appSettings.copy(saveChatHistory = enabled)
+                        val prefs = DemoSharedPreferences(context)
+                        prefs.saveAppSettings(appSettings)
+                    },
+                    colors = SwitchDefaults.colors(
+                        checkedThumbColor = Color.White,
+                        checkedTrackColor = BtnEnabled
+                    )
+                )
+            }
+
+            Spacer(modifier = Modifier.height(12.dp))
+
             // Clear Chat button
             Button(
                 onClick = { showClearChatDialog = true },
@@ -188,6 +226,8 @@ fun AppSettingsScreen(
                         val prefs = DemoSharedPreferences(context)
                         moduleSettings = moduleSettings.copy(isClearChatHistory = true)
                         prefs.saveModuleSettings(moduleSettings)
+                        // Also clear the saved messages immediately
+                        prefs.removeExistingMessages()
                         showClearChatDialog = false
                     }
                 ) {

llm/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/ui/viewmodel/ChatViewModel.kt

@@ -82,10 +82,29 @@ class ChatViewModel(application: Application) : AndroidViewModel(application), L
     private val contentResolver = application.contentResolver
 
     init {
-        loadSavedMessages()
+        // Check for clear chat history flag BEFORE loading saved messages
+        val moduleSettings = demoSharedPreferences.getModuleSettings()
+        if (moduleSettings.isClearChatHistory) {
+            // Clear the flag and don't load messages
+            // Keep isLoadModel flag so model still loads in checkAndLoadSettings()
+            demoSharedPreferences.removeExistingMessages()
+            demoSharedPreferences.saveModuleSettings(moduleSettings.copy(isClearChatHistory = false))
+            // Don't update currentSettingsFields here - let checkAndLoadSettings() handle it
+            // so it detects the change and loads the model if needed
+        } else {
+            loadSavedMessages()
+        }
     }
 
     private fun loadSavedMessages() {
+        val appSettings = demoSharedPreferences.getAppSettings()
+        // Only load saved messages if saveChatHistory is enabled
+        if (!appSettings.saveChatHistory) {
+            // Clear any existing saved messages since saving is disabled
+            demoSharedPreferences.removeExistingMessages()
+            return
+        }
+
         val existingMsgJSON = demoSharedPreferences.getSavedMessages()
         if (existingMsgJSON.isNotEmpty()) {
             val gson = Gson()
@@ -99,7 +118,14 @@ class ChatViewModel(application: Application) : AndroidViewModel(application), L
     }
 
     fun saveMessages() {
-        demoSharedPreferences.addMessages(_messages.toList())
+        val appSettings = demoSharedPreferences.getAppSettings()
+        // Only save messages if saveChatHistory is enabled
+        if (appSettings.saveChatHistory) {
+            demoSharedPreferences.addMessages(_messages.toList())
+        } else {
+            // Make sure no messages are persisted
+            demoSharedPreferences.removeExistingMessages()
+        }
     }
 
     private val systemPromptMessage = "To get started, select your desired model and tokenizer from the top right corner"
@@ -109,27 +135,27 @@ class ChatViewModel(application: Application) : AndroidViewModel(application), L
         val isUpdated = currentSettingsFields != updatedSettingsFields
         val isLoadModel = updatedSettingsFields.isLoadModel
         if (isUpdated) {
-            checkForClearChatHistory(updatedSettingsFields)
+            val settingsAfterClear = checkForClearChatHistory(updatedSettingsFields)
 
             if (isLoadModel) {
                 // Update local copy BEFORE checking media capabilities
-                val settingsWithLoadFlagCleared = updatedSettingsFields.copy(isLoadModel = false)
+                val settingsWithLoadFlagCleared = settingsAfterClear.copy(isLoadModel = false)
                 currentSettingsFields = settingsWithLoadFlagCleared
                 demoSharedPreferences.saveModuleSettings(settingsWithLoadFlagCleared)
 
                 // Update media capabilities after settings are updated
-                setBackendMode(updatedSettingsFields.backendType)
+                setBackendMode(settingsAfterClear.backendType)
 
                 loadLocalModelAndParameters(
-                    updatedSettingsFields.modelFilePath,
-                    updatedSettingsFields.tokenizerFilePath,
-                    updatedSettingsFields.dataPath,
-                    updatedSettingsFields.temperature.toFloat()
+                    settingsAfterClear.modelFilePath,
+                    settingsAfterClear.tokenizerFilePath,
+                    settingsAfterClear.dataPath,
+                    settingsAfterClear.temperature.toFloat()
                 )
             } else {
-                currentSettingsFields = updatedSettingsFields.copy()
+                currentSettingsFields = settingsAfterClear.copy()
                 // Update media capabilities after settings are updated
-                setBackendMode(updatedSettingsFields.backendType)
+                setBackendMode(settingsAfterClear.backendType)
                 if (module == null) {
                     addSystemMessage(systemPromptMessage)
                 }
@@ -175,13 +201,18 @@ class ChatViewModel(application: Application) : AndroidViewModel(application), L
         }
     }
 
-    private fun checkForClearChatHistory(updatedSettingsFields: ModuleSettings) {
+    private fun checkForClearChatHistory(updatedSettingsFields: ModuleSettings): ModuleSettings {
         if (updatedSettingsFields.isClearChatHistory) {
             _messages.clear()
             demoSharedPreferences.removeExistingMessages()
-            demoSharedPreferences.saveModuleSettings(updatedSettingsFields.copy(isClearChatHistory = false))
+            val clearedSettings = updatedSettingsFields.copy(isClearChatHistory = false)
+            demoSharedPreferences.saveModuleSettings(clearedSettings)
             module?.resetContext()
+            shouldAddSystemPrompt = true
+            promptID = 0
+            return clearedSettings
         }
+        return updatedSettingsFields
     }
 
     private fun loadLocalModelAndParameters(