diff --git a/spec/models/grid_artifact_spec.rb b/spec/models/grid_artifact_spec.rb
index bb1d0c4..7d53a6d 100644
--- a/spec/models/grid_artifact_spec.rb
+++ b/spec/models/grid_artifact_spec.rb
@@ -6,6 +6,7 @@ RSpec.describe GridArtifact, type: :model do
   describe 'associations' do
     it { is_expected.to belong_to(:grid_character) }
     it { is_expected.to belong_to(:artifact) }
+    it { is_expected.to belong_to(:collection_artifact).optional }
   end
 
   describe 'validations' do
@@ -93,4 +94,99 @@ RSpec.describe GridArtifact, type: :model do
       expect(GridArtifact).to respond_to(:amoeba_block)
     end
   end
+
+  describe 'Collection Sync' do
+    let(:user) { create(:user) }
+    let(:grid_character) { create(:grid_character) }
+    let(:artifact) { create(:artifact) }
+    let(:collection_artifact) do
+      create(:collection_artifact,
+             user: user,
+             artifact: artifact,
+             element: 2,
+             level: 4,
+             skill1: { 'modifier' => 1, 'strength' => 10 },
+             skill2: { 'modifier' => 2, 'strength' => 5 },
+             skill3: {},
+             skill4: {},
+             reroll_slot: 3)
+    end
+
+    describe '#sync_from_collection!' do
+      context 'when collection_artifact is linked' do
+        let(:linked_grid_artifact) do
+          create(:grid_artifact,
+                 grid_character: grid_character,
+                 artifact: artifact,
+                 collection_artifact: collection_artifact,
+                 element: 1,
+                 level: 2,
+                 skill1: {}, skill2: {}, skill3: {}, skill4: {})
+        end
+
+        it 'copies customizations from collection' do
+          expect(linked_grid_artifact.sync_from_collection!).to be true
+          linked_grid_artifact.reload
+
+          expect(linked_grid_artifact.element).to eq(2)
+          expect(linked_grid_artifact.level).to eq(4)
+          expect(linked_grid_artifact.skill1).to eq({ 'modifier' => 1, 'strength' => 10 })
+          expect(linked_grid_artifact.reroll_slot).to eq(3)
+        end
+      end
+
+      context 'when no collection_artifact is linked' do
+        let(:unlinked_grid_artifact) do
+          create(:grid_artifact,
+                 grid_character: grid_character,
+                 artifact: artifact,
+                 element: 1,
+                 level: 2,
+                 skill1: {}, skill2: {}, skill3: {}, skill4: {})
+        end
+
+        it 'returns false' do
+          expect(unlinked_grid_artifact.sync_from_collection!).to be false
+        end
+      end
+    end
+
+    describe '#out_of_sync?' do
+      context 'when collection_artifact is linked' do
+        let(:linked_grid_artifact) do
+          create(:grid_artifact,
+                 grid_character: grid_character,
+                 artifact: artifact,
+                 collection_artifact: collection_artifact,
+                 element: 1,
+                 level: 2,
+                 skill1: {}, skill2: {}, skill3: {}, skill4: {})
+        end
+
+        it 'returns true when values differ' do
+          expect(linked_grid_artifact.out_of_sync?).to be true
+        end
+
+        it 'returns false after sync' do
+          linked_grid_artifact.sync_from_collection!
+          expect(linked_grid_artifact.out_of_sync?).to be false
+        end
+      end
+
+      context 'when no collection_artifact is linked' do
+        let(:unlinked_grid_artifact) do
+          create(:grid_artifact,
+                 grid_character: grid_character,
+                 artifact: artifact,
+                 element: 1,
+                 level: 2,
+                 skill1: {}, skill2: {}, skill3: {}, skill4: {})
+        end
+
+        it 'returns false' do
+          expect(unlinked_grid_artifact.out_of_sync?).to be false
+        end
+      end
+    end
+  end
 end
diff --git a/spec/models/grid_characters_spec.rb b/spec/models/grid_characters_spec.rb
index efbdf82..d535bee 100644
--- a/spec/models/grid_characters_spec.rb
+++ b/spec/models/grid_characters_spec.rb
@@ -16,6 +16,7 @@ RSpec.describe GridCharacter, type: :model do
   it { is_expected.to belong_to(:character) }
   it { is_expected.to belong_to(:party) }
   it { is_expected.to belong_to(:awakening).optional }
+  it { is_expected.to belong_to(:collection_character).optional }
 
   # Use the canonical "Balanced" awakening already loaded from CSV.
   before(:all) do
@@ -163,4 +164,101 @@ RSpec.describe GridCharacter, type: :model do
       end
     end
   end
+
+  describe 'Collection Sync' do
+    let(:user) { create(:user) }
+    let(:collection_character) do
+      create(:collection_character,
+             user: user,
+             character: character,
+             uncap_level: 5,
+             transcendence_step: 3,
+             perpetuity: true,
+             ring1: { 'modifier' => '1', 'strength' => 1500 },
+             ring2: { 'modifier' => '2', 'strength' => 750 },
+             ring3: { 'modifier' => nil, 'strength' => nil },
+             ring4: { 'modifier' => nil, 'strength' => nil },
+             earring: { 'modifier' => '3', 'strength' => 20 },
+             awakening: @balanced_awakening,
+             awakening_level: 7)
+    end
+
+    describe '#sync_from_collection!' do
+      context 'when collection_character is linked' do
+        before do
+          character.update!(ulb: true) # Enable transcendence
+          @grid_char = create(:grid_character,
+                              valid_attributes.merge(
+                                collection_character: collection_character,
+                                uncap_level: 3,
+                                transcendence_step: 0
+                              ))
+        end
+
+        it 'copies all customizations from collection' do
+          expect(@grid_char.sync_from_collection!).to be true
+          @grid_char.reload
+
+          expect(@grid_char.uncap_level).to eq(5)
+          expect(@grid_char.transcendence_step).to eq(3)
+          expect(@grid_char.perpetuity).to be true
+          expect(@grid_char.ring1).to eq({ 'modifier' => '1', 'strength' => 1500 })
+          expect(@grid_char.ring2).to eq({ 'modifier' => '2', 'strength' => 750 })
+          expect(@grid_char.awakening_level).to eq(7)
+        end
+      end
+
+      context 'when no collection_character is linked' do
+        before do
+          @grid_char = create(:grid_character, valid_attributes)
+        end
+
+        it 'returns false and does not change anything' do
+          original_uncap = @grid_char.uncap_level
+          expect(@grid_char.sync_from_collection!).to be false
+          expect(@grid_char.uncap_level).to eq(original_uncap)
+        end
+      end
+    end
+
+    describe '#out_of_sync?' do
+      context 'when collection_character is linked' do
+        before do
+          character.update!(ulb: true)
+          @grid_char = create(:grid_character,
+                              valid_attributes.merge(collection_character: collection_character))
+        end
+
+        it 'returns true when uncap_level differs' do
+          @grid_char.update!(uncap_level: 4)
+          expect(@grid_char.out_of_sync?).to be true
+        end
+
+        it 'returns true when transcendence_step differs' do
+          @grid_char.update!(transcendence_step: 1)
+          expect(@grid_char.out_of_sync?).to be true
+        end
+
+        it 'returns true when perpetuity differs' do
+          @grid_char.update!(perpetuity: false)
+          expect(@grid_char.out_of_sync?).to be true
+        end
+
+        it 'returns false when all values match' do
+          @grid_char.sync_from_collection!
+          expect(@grid_char.out_of_sync?).to be false
+        end
+      end
+
+      context 'when no collection_character is linked' do
+        before do
+          @grid_char = create(:grid_character, valid_attributes)
+        end
+
+        it 'returns false' do
+          expect(@grid_char.out_of_sync?).to be false
+        end
+      end
+    end
+  end
 end
diff --git a/spec/models/grid_summons_spec.rb b/spec/models/grid_summons_spec.rb
index a16a2cf..2a783f6 100644
--- a/spec/models/grid_summons_spec.rb
+++ b/spec/models/grid_summons_spec.rb
@@ -18,6 +18,13 @@ RSpec.describe GridSummon, type: :model do
       expect(association).not_to be_nil
       expect(association.macro).to eq(:belongs_to)
     end
+
+    it 'belongs to a collection_summon (optional)' do
+      association = described_class.reflect_on_association(:collection_summon)
+      expect(association).not_to be_nil
+      expect(association.macro).to eq(:belongs_to)
+      expect(association.options[:optional]).to be true
+    end
   end
 
   describe 'validations' do
@@ -232,4 +239,97 @@ RSpec.describe GridSummon, type: :model do
       expect(grid_summon.blueprint).to eq(GridSummonBlueprint)
     end
   end
+
+  describe 'Collection Sync' do
+    let(:party) { create(:party) }
+    let(:user) { create(:user) }
+    let(:summon) { Summon.find_by!(granblue_id: '2040433000') }
+    let(:collection_summon) do
+      create(:collection_summon,
+             user: user,
+             summon: summon,
+             uncap_level: 5,
+             transcendence_step: 2)
+    end
+
+    describe '#sync_from_collection!' do
+      context 'when collection_summon is linked' do
+        let(:linked_grid_summon) do
+          # Ensure summon has transcendence for valid transcendence_step
+          summon.update!(transcendence: true, ulb: true, flb: true)
+          create(:grid_summon,
+                 party: party,
+                 summon: summon,
+                 position: 1,
+                 collection_summon: collection_summon,
+                 uncap_level: 3,
+                 transcendence_step: 0)
+        end
+
+        it 'copies customizations from collection' do
+          expect(linked_grid_summon.sync_from_collection!).to be true
+          linked_grid_summon.reload
+
+          expect(linked_grid_summon.uncap_level).to eq(5)
+          expect(linked_grid_summon.transcendence_step).to eq(2)
+        end
+      end
+
+      context 'when no collection_summon is linked' do
+        let(:unlinked_grid_summon) do
+          build(:grid_summon,
+                party: party,
+                summon: summon,
+                position: 1,
+                uncap_level: 3,
+                transcendence_step: 0)
+        end
+
+        it 'returns false' do
+          unlinked_grid_summon.save!
+          expect(unlinked_grid_summon.sync_from_collection!).to be false
+        end
+      end
+    end
+
+    describe '#out_of_sync?' do
+      context 'when collection_summon is linked' do
+        let(:linked_grid_summon) do
+          summon.update!(transcendence: true, ulb: true, flb: true)
+          create(:grid_summon,
+                 party: party,
+                 summon: summon,
+                 position: 1,
+                 collection_summon: collection_summon,
+                 uncap_level: 3,
+                 transcendence_step: 0)
+        end
+
+        it 'returns true when values differ' do
+          expect(linked_grid_summon.out_of_sync?).to be true
+        end
+
+        it 'returns false after sync' do
+          linked_grid_summon.sync_from_collection!
+          expect(linked_grid_summon.out_of_sync?).to be false
+        end
+      end
+
+      context 'when no collection_summon is linked' do
+        let(:unlinked_grid_summon) do
+          build(:grid_summon,
+                party: party,
+                summon: summon,
+                position: 1,
+                uncap_level: 3,
+                transcendence_step: 0)
+        end
+
+        it 'returns false' do
+          unlinked_grid_summon.save!
+          expect(unlinked_grid_summon.out_of_sync?).to be false
+        end
+      end
+    end
+  end
 end
diff --git a/spec/models/grid_weapon_spec.rb b/spec/models/grid_weapon_spec.rb
index 9ccd74a..da9864c 100644
--- a/spec/models/grid_weapon_spec.rb
+++ b/spec/models/grid_weapon_spec.rb
@@ -13,6 +13,7 @@ RSpec.describe GridWeapon, type: :model do
   it { is_expected.to belong_to(:weapon_key3).optional }
   it { is_expected.to belong_to(:weapon_key4).optional }
   it { is_expected.to belong_to(:awakening).optional }
+  it { is_expected.to belong_to(:collection_weapon).optional }
 
   # Setup common test objects using FactoryBot.
   let(:party) { create(:party) }
@@ -134,4 +135,71 @@ RSpec.describe GridWeapon, type: :model do
       expect(grid_weapon.blueprint).to eq(GridWeaponBlueprint)
     end
   end
+
+  describe 'Collection Sync' do
+    let(:user) { create(:user) }
+    let(:collection_weapon) do
+      create(:collection_weapon,
+             user: user,
+             weapon: weapon,
+             uncap_level: 5,
+             transcendence_step: 0,
+             element: 2)
+    end
+
+    describe '#sync_from_collection!' do
+      context 'when collection_weapon is linked' do
+        let(:linked_grid_weapon) do
+          create(:grid_weapon,
+                 party: party,
+                 weapon: weapon,
+                 position: 0,
+                 collection_weapon: collection_weapon,
+                 uncap_level: 3)
+        end
+
+        it 'copies customizations from collection' do
+          expect(linked_grid_weapon.sync_from_collection!).to be true
+          linked_grid_weapon.reload
+
+          expect(linked_grid_weapon.uncap_level).to eq(5)
+          expect(linked_grid_weapon.element).to eq(2)
+        end
+      end
+
+      context 'when no collection_weapon is linked' do
+        it 'returns false' do
+          expect(grid_weapon.sync_from_collection!).to be false
+        end
+      end
+    end
+
+    describe '#out_of_sync?' do
+      context 'when collection_weapon is linked' do
+        let(:linked_grid_weapon) do
+          create(:grid_weapon,
+                 party: party,
+                 weapon: weapon,
+                 position: 0,
+                 collection_weapon: collection_weapon,
+                 uncap_level: 3)
+        end
+
+        it 'returns true when values differ' do
+          expect(linked_grid_weapon.out_of_sync?).to be true
+        end
+
+        it 'returns false after sync' do
+          linked_grid_weapon.sync_from_collection!
+          expect(linked_grid_weapon.out_of_sync?).to be false
+        end
+      end
+
+      context 'when no collection_weapon is linked' do
+        it 'returns false' do
+          expect(grid_weapon.out_of_sync?).to be false
+        end
+      end
+    end
+  end
 end