--- a/ui/server/window.h	Mon Dec 08 18:11:54 2025 +0100
+++ b/ui/server/window.h	Wed Dec 10 19:04:46 2025 +0100
@@ -36,8 +36,21 @@
 extern "C" {
 #endif
 
+enum UiWindowType {
+    UI_WINDOW_MAIN = 0,
+    UI_WINDOW_SIMPLE,
+    UI_WINDOW_SIDEBAR,
+    UI_WINDOW_SPLITVIEW
+};
+typedef enum UiWindowType UiWindowType;
 
+typedef struct UiWindow {
+    UiWidget widget;
+    UiWindowType type;
+    cxmutstr title;
+} UiWindow;
 
+cxmutstr ui_window_serialize(UiWindow *w);
 
 #ifdef __cplusplus
 }