feat(core) Add preferred transport changed event

app/CMakeLists.txt

@@ -73,6 +73,7 @@ if ((NOT CONFIG_ZMK_SPLIT) OR CONFIG_ZMK_SPLIT_ROLE_CENTRAL)
   target_sources(app PRIVATE src/conditional_layer.c)
   target_sources(app PRIVATE src/endpoints.c)
   target_sources(app PRIVATE src/events/endpoint_changed.c)
+  target_sources(app PRIVATE src/events/preferred_transport_changed.c)
   target_sources(app PRIVATE src/hid_listener.c)
   target_sources(app PRIVATE src/keymap.c)
   target_sources(app PRIVATE src/events/layer_state_changed.c)

app/include/zmk/events/preferred_transport_changed.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2026 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <zephyr/kernel.h>
+
+#include <zmk/endpoints_types.h>
+#include <zmk/event_manager.h>
+
+struct zmk_preferred_transport_changed {
+    enum zmk_transport transport;
+};
+
+ZMK_EVENT_DECLARE(zmk_preferred_transport_changed);

app/src/endpoints.c

@@ -20,6 +20,7 @@
 #include <zmk/events/ble_active_profile_changed.h>
 #include <zmk/events/usb_conn_state_changed.h>
 #include <zmk/events/endpoint_changed.h>
+#include <zmk/events/preferred_transport_changed.h>
 
 #include <zephyr/logging/log.h>
 
@@ -135,7 +136,8 @@ int zmk_endpoint_set_preferred_transport(enum zmk_transport transport) {
 
     endpoints_save_preferred();
 
-    update_current_endpoint();
+    raise_zmk_preferred_transport_changed(
+        (struct zmk_preferred_transport_changed){.transport = preferred_transport});
 
     return 0;
 }
@@ -502,6 +504,7 @@ static int endpoint_listener(const zmk_event_t *eh) {
 }
 
 ZMK_LISTENER(endpoint_listener, endpoint_listener);
+ZMK_SUBSCRIPTION(endpoint_listener, zmk_preferred_transport_changed);
 #if IS_ENABLED(CONFIG_ZMK_USB)
 ZMK_SUBSCRIPTION(endpoint_listener, zmk_usb_conn_state_changed);
 #endif

app/src/events/preferred_transport_changed.c

@@ -0,0 +1,10 @@
+/*
+ * Copyright (c) 2026 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/kernel.h>
+#include <zmk/events/preferred_transport_changed.h>
+
+ZMK_EVENT_IMPL(zmk_preferred_transport_changed);