Preserve provider changes before sending

web/src/lib/chat-model-selection.ts

@@ -0,0 +1,24 @@
+import type { Provider } from "./api";
+
+type PersistedChatModel = {
+  lastUsedProvider: Provider | null;
+  lastUsedModel: string | null;
+};
+
+export type ChatModelSelection = {
+  provider: Provider;
+  model: string;
+};
+
+export function getChatModelSelection(chat: PersistedChatModel | null): ChatModelSelection | null {
+  if (!chat?.lastUsedProvider || !chat.lastUsedModel?.trim()) return null;
+  return {
+    provider: chat.lastUsedProvider,
+    model: chat.lastUsedModel.trim(),
+  };
+}
+
+export function getChatModelSelectionSyncKey(chatId: string | null, selection: ChatModelSelection | null) {
+  if (!chatId || !selection) return null;
+  return JSON.stringify([chatId, selection.provider, selection.model]);
+}