fix: Model Selector choice sync (#21628)

tools/server/webui/src/lib/components/app/chat/ChatForm/ChatFormActions/ChatFormActions.svelte

@@ -62,10 +62,14 @@
 		chatStore.getConversationModel(activeMessages() as DatabaseMessage[])
 	);
 
+	let lastSyncedConversationModel: string | null = null;
+
 	$effect(() => {
-		if (conversationModel) {
+		if (conversationModel && conversationModel !== lastSyncedConversationModel) {
+			lastSyncedConversationModel = conversationModel;
 			modelsStore.selectModelByName(conversationModel);
 		} else if (isRouter && !modelsStore.selectedModelId && modelsStore.loadedModelIds.length > 0) {
+			lastSyncedConversationModel = null;
 			// auto-select the first loaded model only when nothing is selected yet
 			const first = modelOptions().find((m) => modelsStore.loadedModelIds.includes(m.model));
 			if (first) modelsStore.selectModelById(first.id);

tools/server/webui/src/routes/+page.svelte

@@ -77,6 +77,11 @@
 			!modelsStore.isModelLoaded(modelsStore.selectedModelName)
 		) {
 			modelsStore.clearSelection();
+
+			const first = modelOptions().find((m) => modelsStore.loadedModelIds.includes(m.model));
+			if (first) {
+				await modelsStore.selectModelById(first.id);
+			}
 		}
 
 		// Handle URL params only if we have ?q= or ?model= or ?new_chat=true