app/controllers/guests_controller.rb

@@ -9,7 +9,7 @@ class GuestsController < ApplicationController
     render json: Guest.includes(:group)
                       .left_joins(:group)
                       .order('groups.name' => :asc, name: :asc)
-                      .as_json(only: %i[id name status], include: { group: { only: %i[id name] } })
+                      .as_json(only: %i[id name status invitation_id], include: { group: { only: %i[id name] } })
   end
 
   def create

app/controllers/invitations_controller.rb

@@ -1,5 +1,3 @@
-# frozen_string_literal: true
-
 # Copyright (C) 2024-2025 LibreWeddingPlanner contributors
 
 class InvitationsController < ApplicationController