Attempt to make modifier key changes take affect when the dialogue closes. This means you don't have to restart Fenrir to apply them.

internal/terminal/keyboard_linux.go

@@ -72,6 +72,36 @@ func (k *Keyboard) Close() error {
 	return nil
 }
 
+// Update_modifiers applies only between complete chords and outside modal capture.
+// The native transaction retains the previous grabs if any new grab is refused.
+func (k *Keyboard) Update_modifiers(fenrirKeys, scriptKeys []string) (bool, error) {
+	s := k.session
+	if s.router.Captured() || s.grabbed || s.captureBlocked || len(s.held) != 0 || len(s.replayed) != 0 {
+		return false, nil
+	}
+	candidate := s.router
+	if err := candidate.Configure_modifiers(fenrirKeys, scriptKeys); err != nil {
+		return false, err
+	}
+	var keys []C.int
+	for _, key := range append(candidate.Reader_keys(), candidate.Script_keys()...) {
+		keys = append(keys, C.int(key))
+	}
+	var keyPointer *C.int
+	if len(keys) > 0 {
+		keyPointer = &keys[0]
+	}
+	status := C.terminal_x_update_keys(s.x, keyPointer, C.int(len(keys)))
+	if err := native_error(status); err != nil {
+		return false, fmt.Errorf("update X11 modifier keys: %w", err)
+	}
+	if status != 0 {
+		return false, nil
+	}
+	s.router = candidate
+	return true, nil
+}
+
 // capture_keyboard treats desktop/focus contention as a refused chord, not a
 // terminal-session failure. Keep modal intent while discarding stale key state.
 func (s *Session) capture_keyboard() (int, error) {