diff --git a/app/controllers/api/v1/grid_characters_controller.rb b/app/controllers/api/v1/grid_characters_controller.rb
index 6741719..a9df085 100644
--- a/app/controllers/api/v1/grid_characters_controller.rb
+++ b/app/controllers/api/v1/grid_characters_controller.rb
@@ -2,73 +2,117 @@
 
 module Api
   module V1
+    ##
+    # Controller handling API requests related to grid characters within a party.
+    #
+    # This controller provides endpoints for creating, updating, resolving conflicts,
+    # updating uncap levels, and deleting grid characters. It follows the structure of
+    # GridSummonsController and GridWeaponsController by using the new authorization method
+    # `authorize_party_edit!` and deprecating legacy methods such as `set` in favor of
+    # `find_party`, `find_grid_character`, and `find_incoming_character`.
+    #
+    # @see Api::V1::ApiController for shared API behavior.
     class GridCharactersController < Api::V1::ApiController
-      attr_reader :party, :incoming_character, :current_characters
-
-      before_action :find_party, only: :create
-      before_action :set, only: %i[update destroy]
-      before_action :authorize, only: %i[create update destroy]
+      before_action :find_grid_character, only: %i[update update_uncap_level destroy resolve]
+      before_action :find_party, only: %i[create resolve update update_uncap_level destroy]
       before_action :find_incoming_character, only: :create
-      before_action :find_current_characters, only: :create
+      before_action :authorize_party_edit!, only: %i[create resolve update update_uncap_level destroy]
 
+      ##
+      # Creates a new grid character.
+      #
+      # If a conflicting grid character is found (i.e. one with the same character_id already exists
+      # in the party), a conflict view is rendered so the user can decide on removal. Otherwise,
+      # any grid character occupying the desired position is removed and a new one is created.
+      #
+      # @return [void]
       def create
-        if !conflict_characters.nil? && conflict_characters.length.positive?
-          # Render a template with the conflicting and incoming characters,
-          # as well as the selected position, so the user can be presented with
-          # a decision.
+        processed_params = transform_character_params(character_params)
 
-          # Up to 3 characters can be removed at the same time
-          conflict_view = render_conflict_view(conflict_characters, incoming_character, character_params[:position])
-          render json: conflict_view
+        if conflict_characters.present?
+          render json: render_conflict_view(conflict_characters, @incoming_character, character_params[:position])
         else
-          # Destroy the grid character in the position if it is already filled
-          if GridCharacter.where(party_id: party.id, position: character_params[:position]).exists?
-            character = GridCharacter.where(party_id: party.id, position: character_params[:position]).limit(1)[0]
-            character.destroy
+          # Remove any existing grid character occupying the specified position.
+          if (existing = GridCharacter.find_by(party_id: @party.id, position: character_params[:position]))
+            existing.destroy
           end
 
-          # Then, create a new grid character
-          character = GridCharacter.create!(character_params.merge(party_id: party.id,
-                                                                   character_id: incoming_character.id))
+          # Build the new grid character
+          grid_character = build_new_grid_character(processed_params)
 
-          if character.save!
-            grid_character_view = render_grid_character_view(character)
-            render json: grid_character_view, status: :created
+          if grid_character.save
+            render json: GridCharacterBlueprint.render(grid_character,
+                                                       root: :grid_character,
+                                                       view: :nested), status: :created
+          else
+            render_validation_error_response(grid_character)
           end
         end
       end
 
+      ##
+      # Updates an existing grid character.
+      #
+      # Assigns new rings and awakening data to their respective virtual attributes and updates other
+      # permitted attributes. On success, the updated grid character view is rendered.
+      #
+      # @return [void]
       def update
-        permitted = character_params.to_h.deep_symbolize_keys
-        puts "Permitted:"
-        ap permitted
-
-        # For the new nested structure, assign them to the virtual attributes:
-        @character.new_rings = permitted[:rings] if permitted[:rings].present?
-        @character.new_awakening = permitted[:awakening] if permitted[:awakening].present?
-
-        # For the rest of the attributes, you can assign them normally.
-        @character.assign_attributes(permitted.except(:rings, :awakening))
-
-        if @character.save
-          render json: GridCharacterBlueprint.render(@character, view: :nested)
+        processed_params = transform_character_params(character_params)
+        assign_raw_attributes(@grid_character)
+        assign_transformed_attributes(@grid_character, processed_params)
+        
+        if @grid_character.save
+          render json: GridCharacterBlueprint.render(@grid_character,
+                                                     root: :grid_character,
+                                                     view: :nested)
         else
-          render_validation_error_response(@character)
+          ap "you are Here"
+          ap @grid_character.errors
+          render_validation_error_response(@grid_character)
         end
       end
 
+      ##
+      # Updates the uncap level and transcendence step of a grid character.
+      #
+      # The grid character's uncap level and transcendence step are updated based on the provided parameters.
+      # This action requires that the current user is authorized to modify the party.
+      #
+      # @return [void]
+      def update_uncap_level
+        @grid_character.uncap_level = character_params[:uncap_level]
+        @grid_character.transcendence_step = character_params[:transcendence_step]
+
+        if @grid_character.save
+          render json: GridCharacterBlueprint.render(@grid_character,
+                                                     root: :grid_character,
+                                                     view: :nested)
+        else
+          render_validation_error_response(@grid_character)
+        end
+      end
+
+      ##
+      # Resolves conflicts for grid characters.
+      #
+      # This action destroys any conflicting grid characters as well as any grid character occupying
+      # the target position, then creates a new grid character using a computed default uncap level.
+      # The default uncap level is determined by the incoming character's attributes.
+      #
+      # @return [void]
       def resolve
-        incoming = Character.find(resolve_params[:incoming])
-        conflicting = resolve_params[:conflicting].map { |id| GridCharacter.find(id) }
-        party = conflicting.first.party
+        incoming = Character.find_by(id: resolve_params[:incoming])
+        render_not_found_response('character') and return unless incoming
 
-        # Destroy each conflicting character
-        conflicting.each { |character| GridCharacter.destroy(character.id) }
+        conflicting = resolve_params[:conflicting].map { |id| GridCharacter.find_by(id: id) }.compact
+        conflicting.each(&:destroy)
 
-        # Destroy the character at the desired position if it exists
-        existing_character = GridCharacter.where(party: party.id, position: resolve_params[:position]).first
-        GridCharacter.destroy(existing_character.id) if existing_character
+        if (existing = GridCharacter.find_by(party_id: @party.id, position: resolve_params[:position]))
+          existing.destroy
+        end
 
+        # Compute the default uncap level based on the incoming character's flags.
         if incoming.special
           uncap_level = 3
           uncap_level = 5 if incoming.ulb
@@ -79,33 +123,146 @@ module Api
           uncap_level = 5 if incoming.flb
         end
 
-        character = GridCharacter.create!(party_id: party.id, character_id: incoming.id,
-                                          position: resolve_params[:position], uncap_level: uncap_level)
-        render json: GridCharacterBlueprint.render(character, view: :nested), status: :created if character.save!
+        grid_character = GridCharacter.create!(
+          party_id: @party.id,
+          character_id: incoming.id,
+          position: resolve_params[:position],
+          uncap_level: uncap_level
+        )
+        render json: GridCharacterBlueprint.render(grid_character,
+                                                   root: :grid_character,
+                                                   view: :nested), status: :created
       end
 
-      def update_uncap_level
-        character = GridCharacter.find(character_params[:id])
-
-        render_unauthorized_response if current_user && (character.party.user != current_user)
-
-        character.uncap_level = character_params[:uncap_level]
-        character.transcendence_step = character_params[:transcendence_step]
-        return unless character.save!
-
-        render json: GridCharacterBlueprint.render(character, view: :nested, root: :grid_character)
-      end
-
-      # TODO: Implement removing characters
+      ##
+      # Destroys a grid character.
+      #
+      # If the current user is not the owner of the party, an unauthorized response is rendered.
+      # On successful destruction, the destroyed grid character view is rendered.
+      #
+      # @return [void]
       def destroy
-        render_unauthorized_response if @character.party.user != current_user
-        return render json: GridCharacterBlueprint.render(@character, view: :destroyed) if @character.destroy
+        grid_character = GridCharacter.find_by('id = ?', params[:id])
+
+        return render_not_found_response('grid_character') if grid_character.nil?
+
+        render json: GridCharacterBlueprint.render(grid_character, view: :destroyed) if grid_character.destroy
       end
 
       private
 
+      ##
+      # Builds a new grid character using the transformed parameters.
+      #
+      # @param processed_params [Hash] the transformed parameters.
+      # @return [GridCharacter] the newly built grid character.
+      def build_new_grid_character(processed_params)
+        grid_character = GridCharacter.new(
+          character_params.except(:rings, :awakening).merge(
+            party_id: @party.id,
+            character_id: @incoming_character.id
+          )
+        )
+        assign_transformed_attributes(grid_character, processed_params)
+        assign_raw_attributes(grid_character)
+        grid_character
+      end
+
+      ##
+      # Assigns raw attributes from the original parameters to the grid character.
+      #
+      # These attributes (like new_rings and new_awakening) are used by model callbacks.
+      #
+      # @param grid_character [GridCharacter] the grid character instance.
+      # @return [void]
+      def assign_raw_attributes(grid_character)
+        grid_character.new_rings = character_params[:rings] if character_params[:rings].present?
+        grid_character.new_awakening = character_params[:awakening] if character_params[:awakening].present?
+        grid_character.assign_attributes(character_params.except(:rings, :awakening))
+      end
+
+      ##
+      # Assigns transformed attributes (such as uncap_level, transcendence_step, etc.) to the grid character.
+      #
+      # @param grid_character [GridCharacter] the grid character instance.
+      # @param processed_params [Hash] the transformed parameters.
+      # @return [void]
+      def assign_transformed_attributes(grid_character, processed_params)
+        grid_character.uncap_level = processed_params[:uncap_level] if processed_params[:uncap_level]
+        grid_character.transcendence_step = processed_params[:transcendence_step] if processed_params[:transcendence_step]
+        grid_character.perpetuity = processed_params[:perpetuity] if processed_params.key?(:perpetuity)
+        grid_character.earring = processed_params[:earring] if processed_params[:earring]
+
+        return unless processed_params[:awakening_id]
+
+        grid_character.awakening_id = processed_params[:awakening_id]
+        grid_character.awakening_level = processed_params[:awakening_level]
+      end
+
+      ##
+      # Transforms the incoming character parameters to the required format.
+      #
+      # The frontend sends parameters in a raw format that need to be processed (e.g., converting string
+      # values to integers, handling nested attributes for rings and awakening). This method extracts and
+      # converts only the keys that were provided.
+      #
+      # @param raw_params [ActionController::Parameters] the raw permitted parameters.
+      # @return [Hash] the transformed parameters.
+      def transform_character_params(raw_params)
+        # Convert to a symbolized hash for convenience.
+        raw = raw_params.to_h.deep_symbolize_keys
+
+        # Only update keys that were provided.
+        transformed = raw.slice(:uncap_level, :transcendence_step, :perpetuity)
+        transformed[:uncap_level] = raw[:uncap_level] if raw[:uncap_level].present?
+        transformed[:transcendence_step] = raw[:transcendence_step] if raw[:transcendence_step].present?
+
+        # Process rings if provided.
+        transformed.merge!(transform_rings(raw[:rings])) if raw[:rings].present?
+
+        # Process earring if provided.
+        transformed[:earring] = raw[:earring] if raw[:earring].present?
+
+        # Process awakening if provided.
+        if raw[:awakening].present?
+          transformed[:awakening_id] = raw[:awakening][:id]
+          # Default to 1 if level is missing (to satisfy validations)
+          transformed[:awakening_level] = raw[:awakening][:level].present? ? raw[:awakening][:level] : 1
+        end
+
+        transformed
+      end
+
+      ##
+      # Transforms the rings data to ensure exactly four rings are present.
+      #
+      # Pads the array with a default ring hash if necessary.
+      #
+      # @param rings [Array, Hash] the rings data from the frontend.
+      # @return [Hash] a hash with keys :ring1, :ring2, :ring3, :ring4.
+      def transform_rings(rings)
+        default_ring = { modifier: nil, strength: nil }
+        # Ensure rings is an array of hashes.
+        rings_array = Array(rings).map(&:to_h)
+        # Pad the array to exactly four rings if needed.
+        rings_array.fill(default_ring, rings_array.size...4)
+        {
+          ring1: rings_array[0],
+          ring2: rings_array[1],
+          ring3: rings_array[2],
+          ring4: rings_array[3]
+        }
+      end
+
+      ##
+      # Returns any grid characters in the party that conflict with the incoming character.
+      #
+      # Conflict is defined as any grid character already in the party with the same character_id as the
+      # incoming character. This method is used to prompt the user for conflict resolution.
+      #
+      # @return [Array<GridCharacter>]
       def conflict_characters
-        @conflict_characters ||= find_conflict_characters(incoming_character)
+        @party.characters.where(character_id: @incoming_character.id).to_a
       end
 
       def find_conflict_characters(incoming_character)
@@ -127,67 +284,102 @@ module Api
         end.flatten
       end
 
-      def set
-        @character = GridCharacter.includes(:awakening).find(params[:id])
-      end
-
-      def find_incoming_character
-        @incoming_character = Character.find(character_params[:character_id])
-      end
-
+      ##
+      # Finds and sets the party based on parameters.
+      #
+      # Checks for the party id in params[:character][:party_id], params[:party_id], or falls back to the party
+      # associated with the current grid character. Renders a not found response if the party is missing.
+      #
+      # @return [void]
       def find_party
-        @party = Party.find(character_params[:party_id])
-        render_unauthorized_response if current_user && (party.user != current_user)
+        @party = Party.find_by(id: params.dig(:character, :party_id)) ||
+          Party.find_by(id: params[:party_id]) ||
+          @grid_character&.party
+        render_not_found_response('party') unless @party
       end
 
-      def authorize
-        # Create
-        unauthorized_create = @party && (@party.user != current_user || @party.edit_key != edit_key)
-        unauthorized_update = @character && @character.party && (@character.party.user != current_user || @character.party.edit_key != edit_key)
-
-        render_unauthorized_response if unauthorized_create || unauthorized_update
+      ##
+      # Finds and sets the grid character based on the provided parameters.
+      #
+      # Searches for a grid character by its ID and renders a not found response if it is absent.
+      #
+      # @return [void]
+      def find_grid_character
+        grid_character_id = params[:id] || params.dig(:character, :id) || params.dig(:resolve, :conflicting)
+        @grid_character = GridCharacter.includes(:awakening).find_by(id: grid_character_id)
+        render_not_found_response('grid_character') unless @grid_character
       end
 
-      def transform_character_params(raw_params)
-        # Convert to a symbolized hash for convenience.
-        raw = raw_params.deep_symbolize_keys
+      ##
+      # Finds and sets the incoming character based on the provided parameters.
+      #
+      # Searches for a character using the :character_id parameter and renders a not found response if it is absent.
+      #
+      # @return [void]
+      def find_incoming_character
+        @incoming_character = Character.find_by(id: character_params[:character_id])
+        render_unprocessable_entity_response(Api::V1::NoCharacterProvidedError.new) unless @incoming_character
+      end
 
-        # Only update keys that were provided.
-        transformed = raw.slice(:uncap_level, :transcendence_step, :perpetuity)
-        transformed[:uncap_level] = raw[:uncap_level].to_i if raw[:uncap_level].present?
-        transformed[:transcendence_step] = raw[:transcendence_step].to_i if raw[:transcendence_step].present?
-
-        # Process rings if provided.
-        transformed.merge!(transform_rings(raw[:rings])) if raw[:rings].present?
-
-        # Process earring if provided.
-        transformed[:earring] = raw[:earring] if raw[:earring].present?
-
-        # Process awakening if provided.
-        if raw[:awakening].present?
-          transformed[:awakening_id] = raw[:awakening][:id]
-          # Default to 1 if level is missing (to satisfy validations)
-          transformed[:awakening_level] = raw[:awakening][:level].present? ? raw[:awakening][:level].to_i : 1
+      ##
+      # Authorizes the current action by ensuring that the current user or provided edit key
+      # matches the party's owner.
+      #
+      # For parties associated with a user, it verifies that the current user is the owner.
+      # For anonymous parties, it compares the provided edit key with the party's edit key.
+      #
+      # @return [void]
+      def authorize_party_edit!
+        if @party.user.present?
+          authorize_user_party
+        else
+          authorize_anonymous_party
         end
-
-        transformed
       end
 
-      def transform_rings(rings)
-        default_ring = { modifier: nil, strength: nil }
-        # Ensure rings is an array of hashes.
-        rings_array = Array(rings).map(&:to_h)
-        # Pad the array to exactly four rings if needed.
-        rings_array.fill(default_ring, rings_array.size...4)
-        {
-          ring1: rings_array[0],
-          ring2: rings_array[1],
-          ring3: rings_array[2],
-          ring4: rings_array[3]
-        }
+      ##
+      # Authorizes an action for a party that belongs to a user.
+      #
+      # Renders an unauthorized response unless the current user is present and matches the party's user.
+      #
+      # @return [void]
+      def authorize_user_party
+        return if current_user.present? && @party.user == current_user
+
+        render_unauthorized_response
       end
 
-      # Specify whitelisted properties that can be modified.
+      ##
+      # Authorizes an action for an anonymous party using an edit key.
+      #
+      # Compares the provided edit key with the party's edit key and renders an unauthorized response
+      # if they do not match.
+      #
+      # @return [void]
+      def authorize_anonymous_party
+        provided_edit_key = edit_key.to_s.strip.force_encoding('UTF-8')
+        party_edit_key = @party.edit_key.to_s.strip.force_encoding('UTF-8')
+        return if valid_edit_key?(provided_edit_key, party_edit_key)
+
+        render_unauthorized_response
+      end
+
+      ##
+      # Validates that the provided edit key matches the party's edit key.
+      #
+      # @param provided_edit_key [String] the edit key provided in the request.
+      # @param party_edit_key [String] the edit key associated with the party.
+      # @return [Boolean] true if the keys match; false otherwise.
+      def valid_edit_key?(provided_edit_key, party_edit_key)
+        provided_edit_key.present? &&
+          provided_edit_key.bytesize == party_edit_key.bytesize &&
+          ActiveSupport::SecurityUtils.secure_compare(provided_edit_key, party_edit_key)
+      end
+
+      ##
+      # Specifies and permits the allowed character parameters.
+      #
+      # @return [ActionController::Parameters] the permitted parameters.
       def character_params
         params.require(:character).permit(
           :id,
@@ -203,21 +395,13 @@ module Api
         )
       end
 
+      ##
+      # Specifies and permits the allowed resolve parameters.
+      #
+      # @return [ActionController::Parameters] the permitted parameters.
       def resolve_params
         params.require(:resolve).permit(:position, :incoming, conflicting: [])
       end
-
-      def render_conflict_view(conflict_characters, incoming_character, incoming_position)
-        ConflictBlueprint.render(nil,
-                                 view: :characters,
-                                 conflict_characters: conflict_characters,
-                                 incoming_character: incoming_character,
-                                 incoming_position: incoming_position)
-      end
-
-      def render_grid_character_view(grid_character)
-        GridCharacterBlueprint.render(grid_character, view: :nested)
-      end
     end
   end
 end
diff --git a/spec/requests/grid_characters_controller_spec.rb b/spec/requests/grid_characters_controller_spec.rb
index 25f2c33..459a984 100644
--- a/spec/requests/grid_characters_controller_spec.rb
+++ b/spec/requests/grid_characters_controller_spec.rb
@@ -1,13 +1,10 @@
 # frozen_string_literal: true
+
 require 'rails_helper'
 
 RSpec.describe 'GridCharacters API', type: :request do
   let(:user) { create(:user) }
   let(:party) { create(:party, user: user, edit_key: 'secret') }
-  # Use canonical records seeded into your DB.
-  # For example, assume Rosamia (granblue_id "3040087000") and Seofon (granblue_id "3040036000")
-  let(:rosamia) { Character.find_by(granblue_id: '3040087000') }
-  let(:seofon) { Character.find_by(granblue_id: '3040036000') }
   let(:access_token) do
     Doorkeeper::AccessToken.create!(
       resource_owner_id: user.id,
@@ -18,196 +15,370 @@ RSpec.describe 'GridCharacters API', type: :request do
   let(:headers) do
     {
       'Authorization' => "Bearer #{access_token.token}",
-      'Content-Type' => 'application/json',
-      'X-Edit-Key' => 'secret'
+      'Content-Type' => 'application/json'
     }
   end
 
-  describe 'POST /api/v1/characters (create)' do
-    context 'when creating a grid character with a unique canonical character (e.g. Seofon)' do
+  # Using canonical data from CSV for non-user-generated models.
+  let(:incoming_character) { Character.find_by(granblue_id: '3040036000') }
+
+  describe 'Authorization for editing grid characters' do
+    context 'when the party is owned by a logged in user' do
       let(:valid_params) do
         {
           character: {
             party_id: party.id,
-            character_id: seofon.id,
-            position: 0,
+            character_id: incoming_character.id,
+            position: 1,
             uncap_level: 3,
             transcendence_step: 0,
-            rings: [
-              { modifier: 'A', strength: 1 },
-              { modifier: 'B', strength: 2 }
-            ]
+            perpetuity: false,
+            rings: [{ modifier: '1', strength: '1500' }],
+            awakening: { id: 'character-balanced', level: 1 }
           }
         }
       end
 
-      it 'creates the grid character and returns status created' do
+      it 'allows the owner to create a grid character' do
         expect do
           post '/api/v1/characters', params: valid_params.to_json, headers: headers
         end.to change(GridCharacter, :count).by(1)
         expect(response).to have_http_status(:created)
-        json_response = JSON.parse(response.body)
-        expect(json_response).to include('position' => 0)
-      end
-    end
-
-    context 'when attempting to add a duplicate canonical character (e.g. Rosamia)' do
-      before do
-        # Create an initial grid character for Rosamia.
-        GridCharacter.create!(
-          party_id: party.id,
-          character_id: rosamia.id,
-          position: 1,
-          uncap_level: 3,
-          transcendence_step: 0
-        )
       end
 
-      let(:duplicate_params) do
-        {
+      it 'allows the owner to update a grid character' do
+        grid_character = create(:grid_character,
+                                party: party,
+                                character: incoming_character,
+                                position: 2,
+                                uncap_level: 3,
+                                transcendence_step: 0)
+        update_params = {
           character: {
+            id: grid_character.id,
             party_id: party.id,
-            character_id: rosamia.id, # same canonical character
+            character_id: incoming_character.id,
             position: 2,
-            uncap_level: 3,
-            transcendence_step: 0
+            uncap_level: 4,
+            transcendence_step: 1,
+            rings: [{ modifier: '1', strength: '1500' }, { modifier: '2', strength: '750' }],
+            awakening: { id: 'character-attack', level: 2 }
           }
         }
-      end
 
-      it 'detects the conflict and returns a conflict resolution view without adding a duplicate' do
-        # Here we simulate conflict resolution via the resolve endpoint.
-        expect do
-          post '/api/v1/characters/resolve',
-               params: { resolve: { position: 2, incoming: rosamia.id, conflicting: [GridCharacter.last.id] } }.to_json,
-               headers: headers
-        end.to change(GridCharacter, :count).by(0)
-        expect(response).to have_http_status(:created)
+        # Use the resource route for update (as defined by resources :grid_characters)
+        put "/api/v1/grid_characters/#{grid_character.id}", params: update_params.to_json, headers: headers
+        expect(response).to have_http_status(:ok)
         json_response = JSON.parse(response.body)
-        expect(json_response).to include('position' => 2)
-      end
-    end
-  end
-
-  describe 'PUT /api/v1/characters/:id (update)' do
-    before do
-      @grid_character = GridCharacter.create!(
-        party_id: party.id,
-        character_id: rosamia.id,
-        position: 1,
-        uncap_level: 3,
-        transcendence_step: 0
-      )
-    end
-
-    let(:update_params) do
-      {
-        character: {
-          id: @grid_character.id,
-          party_id: party.id,
-          character_id: rosamia.id,
-          position: 1,
-          uncap_level: 4,
-          transcendence_step: 0,
-          rings: [
-            { modifier: 'C', strength: 3 }
-          ]
-        }
-      }
-    end
-
-    it 'updates the grid character and returns the updated record' do
-      put "/api/v1/grid_characters/#{@grid_character.id}", params: update_params.to_json, headers: headers
-      expect(response).to have_http_status(:ok)
-
-      json_response = JSON.parse(response.body)
-      expect(json_response).to include('uncap_level' => 4)
-    end
-  end
-
-  describe 'POST /api/v1/characters/update_uncap (update uncap level)' do
-    context 'for a character that does NOT allow transcendence (e.g. Rosamia)' do
-      before do
-        @grid_character = GridCharacter.create!(
-          party_id: party.id,
-          character_id: rosamia.id,
-          position: 2,
-          uncap_level: 2,
-          transcendence_step: 0
-        )
+        expect(json_response['grid_character']).to include('uncap_level' => 4, 'transcendence_step' => 1)
       end
 
-      let(:update_uncap_params) do
-        {
+      it 'allows the owner to update the uncap level and transcendence step' do
+        grid_character = create(:grid_character,
+                                party: party,
+                                character: incoming_character,
+                                position: 3,
+                                uncap_level: 3,
+                                transcendence_step: 0)
+        update_uncap_params = {
           character: {
-            id: @grid_character.id,
+            id: grid_character.id,
             party_id: party.id,
-            character_id: rosamia.id,
-            uncap_level: 3,
-            transcendence_step: 0
+            character_id: incoming_character.id,
+            uncap_level: 5,
+            transcendence_step: 1
           }
         }
-      end
-
-      it 'caps the uncap level at 4 for a character with flb true' do
         post '/api/v1/characters/update_uncap', params: update_uncap_params.to_json, headers: headers
         expect(response).to have_http_status(:ok)
-
         json_response = JSON.parse(response.body)
-        expect(json_response['grid_character']).to include('uncap_level' => 3)
+        expect(json_response['grid_character']).to include('uncap_level' => 5, 'transcendence_step' => 1)
+      end
+
+      it 'allows the owner to resolve conflicts by replacing an existing grid character' do
+        # Create a conflicting grid character (same character_id) at the target position.
+        conflicting_character = create(:grid_character,
+                                       party: party,
+                                       character: incoming_character,
+                                       position: 4,
+                                       uncap_level: 3)
+        resolve_params = {
+          resolve: {
+            position: 4,
+            incoming: incoming_character.id,
+            conflicting: [conflicting_character.id]
+          }
+        }
+        expect do
+          post '/api/v1/characters/resolve', params: resolve_params.to_json, headers: headers
+        end.to change(GridCharacter, :count).by(0) # one record is destroyed and one is created
+        expect(response).to have_http_status(:created)
+        json_response = JSON.parse(response.body)
+        expect(json_response['grid_character']).to include('position' => 4)
+        expect { conflicting_character.reload }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'allows the owner to destroy a grid character' do
+        grid_character = create(:grid_character,
+                                party: party,
+                                character: incoming_character,
+                                position: 5,
+                                uncap_level: 3)
+        # Using the custom route for destroy: DELETE '/api/v1/characters'
+        expect do
+          delete '/api/v1/characters', params: { id: grid_character.id }.to_json, headers: headers
+        end.to change(GridCharacter, :count).by(-1)
+        expect(response).to have_http_status(:ok)
       end
     end
 
-    context 'for a character that allows transcendence (e.g. Seofon)' do
-      before do
-        # For Seofon, the "transcendence" behavior is enabled by its ulb flag.
-        @grid_character = GridCharacter.create!(
-          party_id: party.id,
-          character_id: seofon.id,
-          position: 2,
-          uncap_level: 5,
-          transcendence_step: 0
-        )
+    context 'when the party is anonymous (no user)' do
+      let(:anon_party) { create(:party, user: nil, edit_key: 'anonsecret') }
+      let(:headers) { { 'Content-Type' => 'application/json', 'X-Edit-Key' => 'anonsecret' } }
+      let(:valid_params) do
+        {
+          character: {
+            party_id: anon_party.id,
+            character_id: incoming_character.id,
+            position: 1,
+            uncap_level: 3,
+            transcendence_step: 0,
+            perpetuity: false,
+            rings: [{ modifier: '1', strength: '1500' }],
+            awakening: { id: 'character-balanced', level: 1 }
+          }
+        }
       end
 
+      it 'allows anonymous creation with correct edit_key' do
+        expect do
+          post '/api/v1/characters', params: valid_params.to_json, headers: headers
+        end.to change(GridCharacter, :count).by(1)
+        expect(response).to have_http_status(:created)
+      end
+
+      context 'when an incorrect edit_key is provided' do
+        let(:headers) { super().merge('X-Edit-Key' => 'wrong') }
+
+        it 'returns an unauthorized response' do
+          post '/api/v1/characters', params: valid_params.to_json, headers: headers
+          expect(response).to have_http_status(:unauthorized)
+        end
+      end
+    end
+  end
+
+  describe 'POST /api/v1/characters (create action) with invalid parameters' do
+    context 'with missing or invalid required fields' do
+      let(:invalid_params) do
+        {
+          character: {
+            party_id: party.id,
+            # Missing character_id
+            position: 1,
+            uncap_level: 2,
+            transcendence_step: 0
+          }
+        }
+      end
+
+      it 'returns unprocessable entity status with error messages' do
+        post '/api/v1/characters', params: invalid_params.to_json, headers: headers
+        expect(response).to have_http_status(:unprocessable_entity)
+        json_response = JSON.parse(response.body)
+        expect(json_response).to have_key('errors')
+        # Verify that the error message on uncap_level includes a specific phrase.
+        expect(json_response['errors']['code'].to_s).to eq('no_character_provided')
+      end
+    end
+  end
+
+  describe 'PUT /api/v1/grid_characters/:id (update action)' do
+    let!(:grid_character) do
+      create(:grid_character,
+             party: party,
+             character: incoming_character,
+             position: 2,
+             uncap_level: 3,
+             transcendence_step: 0)
+    end
+
+    context 'with valid parameters' do
+      let(:update_params) do
+        {
+          character: {
+            id: grid_character.id,
+            party_id: party.id,
+            character_id: incoming_character.id,
+            position: 2,
+            uncap_level: 4,
+            transcendence_step: 1,
+            rings: [{ modifier: '1', strength: '1500' }, { modifier: '2', strength: '750' }],
+            awakening: { id: 'character-balanced', level: 2 }
+          }
+        }
+      end
+
+      it 'updates the grid character and returns the updated record' do
+        put "/api/v1/grid_characters/#{grid_character.id}", params: update_params.to_json, headers: headers
+        expect(response).to have_http_status(:ok)
+        json_response = JSON.parse(response.body)
+        expect(json_response['grid_character']).to include('uncap_level' => 4, 'transcendence_step' => 1)
+      end
+    end
+
+    context 'with invalid parameters' do
+      let(:invalid_update_params) do
+        {
+          character: {
+            id: grid_character.id,
+            party_id: party.id,
+            character_id: incoming_character.id,
+            position: 2,
+            uncap_level: 'invalid',
+            transcendence_step: 1
+          }
+        }
+      end
+
+      it 'returns unprocessable entity status with error details' do
+        put "/api/v1/grid_characters/#{grid_character.id}", params: invalid_update_params.to_json, headers: headers
+        expect(response).to have_http_status(:unprocessable_entity)
+        json_response = JSON.parse(response.body)
+        expect(json_response).to have_key('errors')
+        expect(json_response['errors']['uncap_level'].to_s).to include('is not a number')
+      end
+    end
+  end
+
+  describe 'POST /api/v1/characters/update_uncap (update uncap level action)' do
+    let!(:grid_character) do
+      create(:grid_character,
+             party: party,
+             character: incoming_character,
+             position: 3,
+             uncap_level: 3,
+             transcendence_step: 0)
+    end
+
+    context 'with valid uncap level parameters' do
       let(:update_uncap_params) do
         {
           character: {
-            id: @grid_character.id,
+            id: grid_character.id,
             party_id: party.id,
-            character_id: seofon.id,
+            character_id: incoming_character.id,
             uncap_level: 5,
             transcendence_step: 1
           }
         }
       end
 
-      it 'updates the uncap level to 6 when the character supports transcendence via ulb' do
+      it 'updates the uncap level and transcendence step' do
         post '/api/v1/characters/update_uncap', params: update_uncap_params.to_json, headers: headers
         expect(response).to have_http_status(:ok)
-
         json_response = JSON.parse(response.body)
         expect(json_response['grid_character']).to include('uncap_level' => 5, 'transcendence_step' => 1)
       end
     end
   end
 
-  describe 'DELETE /api/v1/characters (destroy)' do
-    before do
-      @grid_character = GridCharacter.create!(
-        party_id: party.id,
-        character_id: rosamia.id,
-        position: 4,
-        uncap_level: 3,
-        transcendence_step: 0
-      )
+  describe 'POST /api/v1/characters/resolve (conflict resolution action)' do
+    let!(:conflicting_character) do
+      create(:grid_character,
+             party: party,
+             character: incoming_character,
+             position: 4,
+             uncap_level: 3)
     end
 
-    it 'destroys the grid character and returns a destroyed view' do
+    let(:resolve_params) do
+      {
+        resolve: {
+          position: 4,
+          incoming: incoming_character.id,
+          conflicting: [conflicting_character.id]
+        }
+      }
+    end
+
+    it 'resolves conflicts by replacing the existing grid character' do
+      expect(GridCharacter.exists?(conflicting_character.id)).to be true
       expect do
-        delete '/api/v1/characters', params: { id: @grid_character.id }.to_json, headers: headers
-      end.to change(GridCharacter, :count).by(-1)
-      expect(response).to have_http_status(:ok)
+        post '/api/v1/characters/resolve', params: resolve_params.to_json, headers: headers
+      end.to change(GridCharacter, :count).by(0) # one record deleted, one created
+      expect(response).to have_http_status(:created)
+      json_response = JSON.parse(response.body)
+      expect(json_response['grid_character']).to include('position' => 4)
+      expect { conflicting_character.reload }.to raise_error(ActiveRecord::RecordNotFound)
+    end
+  end
+
+  describe 'DELETE /api/v1/characters (destroy action)' do
+    context 'when the party is owned by a logged in user' do
+      let!(:grid_character) do
+        create(:grid_character,
+               party: party,
+               character: incoming_character,
+               position: 6,
+               uncap_level: 3)
+      end
+
+      it 'destroys the grid character and returns a success response' do
+        expect do
+          delete '/api/v1/characters', params: { id: grid_character.id }.to_json, headers: headers
+        end.to change(GridCharacter, :count).by(-1)
+        expect(response).to have_http_status(:ok)
+      end
+
+      it 'returns not found when trying to delete a non-existent grid character' do
+        delete '/api/v1/characters', params: { id: '00000000-0000-0000-0000-000000000000' }.to_json, headers: headers
+        expect(response).to have_http_status(:not_found)
+      end
+    end
+
+    context 'when the party is anonymous' do
+      let(:anon_party) { create(:party, user: nil, edit_key: 'anonsecret') }
+      let(:headers) { { 'Content-Type' => 'application/json', 'X-Edit-Key' => 'anonsecret' } }
+      let!(:grid_character) do
+        create(:grid_character,
+               party: anon_party,
+               character: incoming_character,
+               position: 6,
+               uncap_level: 3)
+      end
+
+      it 'allows anonymous user to destroy the grid character' do
+        expect do
+          delete '/api/v1/characters', params: { id: grid_character.id }.to_json, headers: headers
+        end.to change(GridCharacter, :count).by(-1)
+        expect(response).to have_http_status(:ok)
+      end
+
+      it 'prevents deletion when a logged in user attempts to delete an anonymous grid character' do
+        auth_headers = headers.except('X-Edit-Key')
+        expect do
+          delete '/api/v1/characters', params: { id: grid_character.id }.to_json, headers: auth_headers
+        end.not_to change(GridCharacter, :count)
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+  end
+
+  # Debug hook: if any example fails and a response exists, print the error message.
+  after(:each) do |example|
+    if example.exception && defined?(response) && response.present?
+      error_message = begin
+                        JSON.parse(response.body)['exception']
+                      rescue JSON::ParserError
+                        response.body
+                      end
+      puts "\nDEBUG: Error Message for '#{example.full_description}': #{error_message}"
+
+      # Parse once and grab the trace safely
+      parsed_body = JSON.parse(response.body)
+      trace = parsed_body.dig('traces', 'Application Trace')
+      ap trace if trace # Only print if trace is not nil
     end
   end
 end