fix(chat): support confirmation dialog when switching to expensive or data-policy models (#1050)

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatScreen.kt

@@ -38,6 +38,7 @@ import androidx.compose.material.icons.filled.Add
 import androidx.compose.material.icons.filled.Close
 import androidx.compose.material.icons.filled.Search
 import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Button
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
@@ -911,6 +912,25 @@ fun ChatScreen(
             )
         }
 
+        // Expensive / Data-policy model confirmation dialog (issue #589 follow-up)
+        if (state.modelSwitchConfirmMessage != null) {
+            AlertDialog(
+                onDismissRequest = { viewModel.dismissModelSwitchConfirm() },
+                title = { Text(stringResource(R.string.model_expensive_title)) },
+                text = { Text(state.modelSwitchConfirmMessage!!) },
+                confirmButton = {
+                    Button(onClick = { viewModel.confirmModelSwitchExpensive() }) {
+                        Text(stringResource(R.string.model_confirm_continue))
+                    }
+                },
+                dismissButton = {
+                    TextButton(onClick = { viewModel.dismissModelSwitchConfirm() }) {
+                        Text(stringResource(R.string.common_cancel))
+                    }
+                },
+            )
+        }
+
         if (showContextSheet && state.contextBreakdown != null) {
             ContextDetailSheet(
                 breakdown = state.contextBreakdown!!,

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatViewModel.kt

@@ -327,6 +327,7 @@ data class ChatUiState(
     val modelPickerProviders: List<ModelProvider> = emptyList(),
     val modelPickerPinned: List<PinnedModel> = emptyList(),
     val modelPickerLoading: Boolean = false,
+    val modelSwitchConfirmMessage: String? = null,
     // Current session's active model label (provider/model), shown in the chip
     val currentSessionModel: String? = null,
     // Per-model reasoning capabilities for the current session's model
@@ -463,6 +464,15 @@ class ChatViewModel(
 
     private val sessionRequestById = ConcurrentHashMap<String, SessionRequest>()
     private var sessionGeneration = 0L
+
+    private data class ActiveModelSwitch(
+        val spec: String,
+        val previousModel: String?,
+    )
+
+    private val pendingModelSwitchRequests = ConcurrentHashMap<String, ActiveModelSwitch>()
+    private var activeModelSwitchConfirmation: ActiveModelSwitch? = null
+    private var optimisticPreviousModel: String? = null
     private var resumeRequestSequence = 0L
     private var activeResumeRequestSequence = 0L
     private var hydrationRequestSequence = 0L
@@ -1208,6 +1218,25 @@ class ChatViewModel(
                     addSystemMessage("Approval submitted")
                 }
             }
+
+            WsMethods.CONFIG_SET -> {
+                val pending = pendingModelSwitchRequests.remove(id)
+                val map = result as? Map<*, *> ?: return
+                val key = map["key"] as? String
+                if (key == "model") {
+                    val confirmRequired = map["confirm_required"] as? Boolean ?: false
+                    if (confirmRequired) {
+                        val confirmMessage =
+                            (map["confirm_message"] as? String)
+                                ?: (map["warning"] as? String)
+                                ?: "This model requires confirmation to switch. Continue?"
+                        activeModelSwitchConfirmation = pending
+                        _uiState.update {
+                            it.copy(modelSwitchConfirmMessage = confirmMessage)
+                        }
+                    }
+                }
+            }
         }
     }
 
@@ -1889,7 +1918,10 @@ class ChatViewModel(
      *   `<model> --provider <slug> --session`
      * (matching the TUI client's `modelValueForConfigSet`).
      */
-    private fun handleModelSwitch(command: String) {
+    private fun handleModelSwitch(
+        command: String,
+        confirmExpensive: Boolean = false,
+    ) {
         val sessionId = runtimeSessionId
         if (sessionId == null) {
             addAssistantMessage("No active session. Use `/new` to create one.")
@@ -1906,11 +1938,25 @@ class ChatViewModel(
             } else {
                 command.trim()
             }
+        val previousModel = optimisticPreviousModel ?: _uiState.value.currentSessionModel
+        optimisticPreviousModel = null
+        val params =
+            mutableMapOf<String, Any>(
+                "key" to "model",
+                "value" to spec,
+                "session_id" to sessionId,
+            )
+        if (confirmExpensive) {
+            params["confirm_expensive_model"] = true
+        }
         viewModelScope.launch(ioDispatcher) {
             wsClient.send(
                 WsMethods.CONFIG_SET,
-                mapOf("key" to "model", "value" to spec, "session_id" to sessionId),
-                onSent = { id -> trackRequest(id, WsMethods.CONFIG_SET) },
+                params,
+                onSent = { id ->
+                    trackRequest(id, WsMethods.CONFIG_SET)
+                    pendingModelSwitchRequests[id] = ActiveModelSwitch(spec, previousModel)
+                },
             )
         }
     }
@@ -2265,6 +2311,7 @@ class ChatViewModel(
         provider: String,
         model: String,
     ) {
+        optimisticPreviousModel = _uiState.value.currentSessionModel
         _uiState.update {
             it.copy(
                 showModelPicker = false,
@@ -2280,6 +2327,28 @@ class ChatViewModel(
         handleSlashCommand("/model $model --provider $provider --session")
     }
 
+    fun dismissModelSwitchConfirm() {
+        val pending = activeModelSwitchConfirmation
+        activeModelSwitchConfirmation = null
+        _uiState.update {
+            it.copy(
+                modelSwitchConfirmMessage = null,
+                currentSessionModel = pending?.previousModel ?: it.currentSessionModel,
+            )
+        }
+        syncCurrentModelCapabilities()
+        fetchContextUsage()
+    }
+
+    fun confirmModelSwitchExpensive() {
+        val pending = activeModelSwitchConfirmation
+        activeModelSwitchConfirmation = null
+        _uiState.update { it.copy(modelSwitchConfirmMessage = null) }
+        if (pending != null) {
+            handleModelSwitch(pending.spec, confirmExpensive = true)
+        }
+    }
+
     /**
      * Set the reasoning effort level for the current session.
      *
@@ -2575,6 +2644,7 @@ class ChatViewModel(
                 showSessionPicker = false,
                 showModelPicker = false,
                 modelPickerLoading = false,
+                modelSwitchConfirmMessage = null,
                 currentSessionModel = null,
                 currentModelCapabilities = null,
                 reasoningLevel = null,