diff --git a/glfw/cocoa_window.m b/glfw/cocoa_window.m
index f3ef8b205..9496c0c40 100644
--- a/glfw/cocoa_window.m
+++ b/glfw/cocoa_window.m
@@ -3253,6 +3253,14 @@ bool _glfwPlatformToggleFullscreen(_GLFWwindow* w, unsigned int flags) {
             // As of Big Turd NSWindowStyleMaskFullScreen is no longer usable
             // Also no longer compatible after a minor release of macOS 10.15.7
             if (!w->ns.in_traditional_fullscreen) {
+                // Apple throws NSGenericException if setStyleMask: clears
+                // NSWindowStyleMaskFullScreen outside a transition (see #9572).
+                // Split View sets this flag via the system, so fall back to
+                // Cocoa fullscreen toggle instead of the traditional path.
+                if (sm & NSWindowStyleMaskFullScreen) {
+                    [window toggleFullScreen:nil];
+                    return false;
+                }
                 w->ns.pre_full_screen_style_mask = sm;
                 [window setStyleMask: NSWindowStyleMaskBorderless];
                 [[NSApplication sharedApplication] setPresentationOptions: NSApplicationPresentationAutoHideMenuBar | NSApplicationPresentationAutoHideDock];
@@ -3260,7 +3268,9 @@ bool _glfwPlatformToggleFullscreen(_GLFWwindow* w, unsigned int flags) {
                 w->ns.in_traditional_fullscreen = true;
             } else {
                 made_fullscreen = false;
-                [window setStyleMask: w->ns.pre_full_screen_style_mask];
+                // Same NSWindowStyleMaskFullScreen guard as glfwCocoaSetWindowChrome
+                NSWindowStyleMask fsmask = sm & NSWindowStyleMaskFullScreen;
+                [window setStyleMask: w->ns.pre_full_screen_style_mask | fsmask];
                 [[NSApplication sharedApplication] setPresentationOptions: NSApplicationPresentationDefault];
                 w->ns.in_traditional_fullscreen = false;
             }
diff --git a/kitty/glfw.c b/kitty/glfw.c
index 0741a3a48..5f842bc05 100644
--- a/kitty/glfw.c
+++ b/kitty/glfw.c
@@ -1291,6 +1291,14 @@ intercept_cocoa_fullscreen(GLFWwindow *w) {
                 global_state.callback_os_window);
         return false;
     }
+    // macOS Split View uses Cocoa fullscreen internally, so the window
+    // can end up with NSWindowStyleMaskFullScreen set even when
+    // macos_traditional_fullscreen is enabled. Redirecting to traditional
+    // fullscreen would crash in setStyleMask: (see #9572).
+    if (glfwIsFullscreen(w, 1)) {
+        global_state.callback_os_window->background_opacity.os_forces_opaque = false;
+        return false;
+    }
     toggle_fullscreen_for_os_window(global_state.callback_os_window);
     global_state.callback_os_window = NULL;
     return true;