diff --git a/modules/resource_management/app/models/resource_allocation.rb b/modules/resource_management/app/models/resource_allocation.rb
index f5174116280..12ff081a309 100644
--- a/modules/resource_management/app/models/resource_allocation.rb
+++ b/modules/resource_management/app/models/resource_allocation.rb
@@ -29,6 +29,8 @@
 #++
 
 class ResourceAllocation < ApplicationRecord
+  ALLOWED_ENTITY_TYPES = %w[WorkPackage].freeze
+
   belongs_to :entity, polymorphic: true, optional: false
   belongs_to :principal, class_name: "User", optional: true, inverse_of: :resource_allocations
 
@@ -46,6 +48,10 @@ class ResourceAllocation < ApplicationRecord
             presence: true,
             numericality: { only_integer: true, greater_than: 0 }
 
+  validates :entity_type,
+            inclusion: { in: ALLOWED_ENTITY_TYPES },
+            allow_blank: true
+
   validate :end_date_after_start_date
 
   # Resource allocations are scoped to whatever project their (polymorphic)
diff --git a/modules/resource_management/spec/contracts/resource_allocations/create_contract_spec.rb b/modules/resource_management/spec/contracts/resource_allocations/create_contract_spec.rb
index 72427bd9319..435a8cdb288 100644
--- a/modules/resource_management/spec/contracts/resource_allocations/create_contract_spec.rb
+++ b/modules/resource_management/spec/contracts/resource_allocations/create_contract_spec.rb
@@ -43,8 +43,8 @@ RSpec.describe ResourceAllocations::CreateContract do
     let(:current_user) do
       create(:user, member_with_permissions: { project => %i[view_resource_planners allocate_user_resources] })
     end
-    let(:planner) { create(:resource_planner, project:, principal: current_user) }
-    let(:resource_allocation) { build_stubbed(:resource_allocation, entity: planner, principal: current_user) }
+    let(:work_package) { create(:work_package, project:) }
+    let(:resource_allocation) { build_stubbed(:resource_allocation, entity: work_package, principal: current_user) }
     let(:contract) { described_class.new(resource_allocation, current_user) }
 
     it "allows entity to be set" do
diff --git a/modules/resource_management/spec/contracts/resource_allocations/delete_contract_spec.rb b/modules/resource_management/spec/contracts/resource_allocations/delete_contract_spec.rb
index a73a6ea38cd..319cc59bd94 100644
--- a/modules/resource_management/spec/contracts/resource_allocations/delete_contract_spec.rb
+++ b/modules/resource_management/spec/contracts/resource_allocations/delete_contract_spec.rb
@@ -36,9 +36,9 @@ RSpec.describe ResourceAllocations::DeleteContract do
 
   shared_let(:project) { create(:project, enabled_module_names: %w[resource_management]) }
   shared_let(:owner) { create(:user) }
-  shared_let(:planner) { create(:resource_planner, project:, principal: owner) }
+  shared_let(:work_package) { create(:work_package, project:) }
 
-  let(:resource_allocation) { build_stubbed(:resource_allocation, entity: planner, principal: owner) }
+  let(:resource_allocation) { build_stubbed(:resource_allocation, entity: work_package, principal: owner) }
   let(:contract) { described_class.new(resource_allocation, current_user) }
 
   context "when user has allocate_user_resources" do
diff --git a/modules/resource_management/spec/contracts/resource_allocations/shared_contract_examples.rb b/modules/resource_management/spec/contracts/resource_allocations/shared_contract_examples.rb
index 6dc00ed586e..107c7c1440c 100644
--- a/modules/resource_management/spec/contracts/resource_allocations/shared_contract_examples.rb
+++ b/modules/resource_management/spec/contracts/resource_allocations/shared_contract_examples.rb
@@ -34,10 +34,10 @@ require "contracts/shared/model_contract_shared_context"
 RSpec.shared_examples_for "resource allocation contract" do
   shared_let(:project) { create(:project, enabled_module_names: %w[resource_management]) }
   shared_let(:owner) { create(:user) }
-  shared_let(:planner) { create(:resource_planner, project:, principal: owner) }
+  shared_let(:work_package) { create(:work_package, project:) }
 
   let(:resource_allocation) do
-    build_stubbed(:resource_allocation, entity: planner, principal: owner)
+    build_stubbed(:resource_allocation, entity: work_package, principal: owner)
   end
 
   context "when user has the allocate_user_resources permission" do
diff --git a/modules/resource_management/spec/contracts/resource_allocations/update_contract_spec.rb b/modules/resource_management/spec/contracts/resource_allocations/update_contract_spec.rb
index e21158a8e33..ebbcae25b16 100644
--- a/modules/resource_management/spec/contracts/resource_allocations/update_contract_spec.rb
+++ b/modules/resource_management/spec/contracts/resource_allocations/update_contract_spec.rb
@@ -43,8 +43,8 @@ RSpec.describe ResourceAllocations::UpdateContract do
     let(:current_user) do
       create(:user, member_with_permissions: { project => %i[view_resource_planners allocate_user_resources] })
     end
-    let(:planner) { create(:resource_planner, project:, principal: current_user) }
-    let(:resource_allocation) { build_stubbed(:resource_allocation, entity: planner, principal: current_user) }
+    let(:work_package) { create(:work_package, project:) }
+    let(:resource_allocation) { build_stubbed(:resource_allocation, entity: work_package, principal: current_user) }
     let(:contract) { described_class.new(resource_allocation, current_user) }
 
     it "does not allow entity to be set" do
diff --git a/modules/resource_management/spec/factories/resource_allocation_factory.rb b/modules/resource_management/spec/factories/resource_allocation_factory.rb
index f277279473e..cbec2ab1045 100644
--- a/modules/resource_management/spec/factories/resource_allocation_factory.rb
+++ b/modules/resource_management/spec/factories/resource_allocation_factory.rb
@@ -30,7 +30,7 @@
 
 FactoryBot.define do
   factory :resource_allocation, class: "ResourceAllocation" do
-    entity factory: :resource_planner
+    entity factory: :work_package
     principal factory: :user
     state { "requested" }
     start_date { Date.new(2026, 1, 5) }
diff --git a/modules/resource_management/spec/models/resource_allocation_spec.rb b/modules/resource_management/spec/models/resource_allocation_spec.rb
index 233770a069e..1129790d56b 100644
--- a/modules/resource_management/spec/models/resource_allocation_spec.rb
+++ b/modules/resource_management/spec/models/resource_allocation_spec.rb
@@ -70,9 +70,9 @@ RSpec.describe ResourceAllocation do
   describe "validations" do
     shared_let(:project) { create(:project, enabled_module_names: %w[resource_management]) }
     shared_let(:owner) { create(:user, member_with_permissions: { project => %i[view_resource_planners] }) }
-    shared_let(:planner) { create(:resource_planner, project:, principal: owner) }
+    shared_let(:work_package) { create(:work_package, project:) }
 
-    let(:allocation) { build(:resource_allocation, entity: planner, principal: owner) }
+    let(:allocation) { build(:resource_allocation, entity: work_package, principal: owner) }
 
     it "is valid with the factory defaults" do
       expect(allocation).to be_valid
@@ -115,6 +115,23 @@ RSpec.describe ResourceAllocation do
       end
     end
 
+    describe "entity type" do
+      it "lists the supported entity types" do
+        expect(described_class::ALLOWED_ENTITY_TYPES).to eq(%w[WorkPackage])
+      end
+
+      it "is valid when the entity type is in the allowed list" do
+        allocation.entity = work_package
+        expect(allocation).to be_valid
+      end
+
+      it "is invalid when the entity type is outside the allowed list" do
+        allocation.entity = create(:resource_planner, project:, principal: owner)
+        expect(allocation).not_to be_valid
+        expect(allocation.errors.symbols_for(:entity_type)).to include(:inclusion)
+      end
+    end
+
     describe "allocated_time numericality" do
       it "is invalid when zero" do
         allocation.allocated_time = 0
@@ -175,7 +192,7 @@ RSpec.describe ResourceAllocation do
   describe "user_filter serialization" do
     shared_let(:project) { create(:project, enabled_module_names: %w[resource_management]) }
     shared_let(:owner) { create(:user, member_with_permissions: { project => %i[view_resource_planners] }) }
-    shared_let(:planner) { create(:resource_planner, project:, principal: owner) }
+    shared_let(:work_package) { create(:work_package, project:) }
 
     it "serializes filters using the same coder as UserQuery" do
       coder = described_class.type_for_attribute(:user_filter).coder
@@ -191,7 +208,7 @@ RSpec.describe ResourceAllocation do
       filter.operator = "~"
       filter.values = ["alice"]
 
-      allocation = create(:resource_allocation, entity: planner, principal: owner, user_filter: [filter])
+      allocation = create(:resource_allocation, entity: work_package, principal: owner, user_filter: [filter])
 
       reloaded = described_class.find(allocation.id)
       expect(reloaded.user_filter.size).to eq(1)
@@ -201,7 +218,7 @@ RSpec.describe ResourceAllocation do
     end
 
     it "defaults to an empty array" do
-      allocation = create(:resource_allocation, entity: planner, principal: owner)
+      allocation = create(:resource_allocation, entity: work_package, principal: owner)
       expect(allocation.reload.user_filter).to eq([])
     end
   end
diff --git a/modules/resource_management/spec/services/resource_allocations/create_service_spec.rb b/modules/resource_management/spec/services/resource_allocations/create_service_spec.rb
index 213d86df16d..9e1ca208f6a 100644
--- a/modules/resource_management/spec/services/resource_allocations/create_service_spec.rb
+++ b/modules/resource_management/spec/services/resource_allocations/create_service_spec.rb
@@ -35,12 +35,12 @@ RSpec.describe ResourceAllocations::CreateService, type: :model do
   shared_let(:owner) do
     create(:user, member_with_permissions: { project => %i[view_resource_planners allocate_user_resources] })
   end
-  shared_let(:planner) { create(:resource_planner, project:, principal: owner) }
+  shared_let(:work_package) { create(:work_package, project:) }
 
   let(:assignee) { create(:user, member_with_permissions: { project => %i[view_resource_planners] }) }
   let(:params) do
     {
-      entity: planner,
+      entity: work_package,
       principal: assignee,
       start_date: Date.new(2026, 1, 1),
       end_date: Date.new(2026, 1, 31),
@@ -53,7 +53,7 @@ RSpec.describe ResourceAllocations::CreateService, type: :model do
   it "creates a resource allocation" do
     result = service_call
     expect(result).to be_success, "expected success but got: #{result.errors.full_messages}"
-    expect(result.result.entity).to eq(planner)
+    expect(result.result.entity).to eq(work_package)
     expect(result.result.principal).to eq(assignee)
     expect(result.result.allocated_time).to eq(8)
   end
diff --git a/modules/resource_management/spec/services/resource_allocations/delete_service_spec.rb b/modules/resource_management/spec/services/resource_allocations/delete_service_spec.rb
index 2cd83d64c93..a25f95da2da 100644
--- a/modules/resource_management/spec/services/resource_allocations/delete_service_spec.rb
+++ b/modules/resource_management/spec/services/resource_allocations/delete_service_spec.rb
@@ -35,9 +35,9 @@ RSpec.describe ResourceAllocations::DeleteService, type: :model do
   shared_let(:owner) do
     create(:user, member_with_permissions: { project => %i[view_resource_planners allocate_user_resources] })
   end
-  shared_let(:planner) { create(:resource_planner, project:, principal: owner) }
+  shared_let(:work_package) { create(:work_package, project:) }
 
-  let!(:resource_allocation) { create(:resource_allocation, entity: planner, principal: owner) }
+  let!(:resource_allocation) { create(:resource_allocation, entity: work_package, principal: owner) }
 
   subject(:service_call) do
     described_class.new(user:, model: resource_allocation).call
diff --git a/modules/resource_management/spec/services/resource_allocations/update_service_spec.rb b/modules/resource_management/spec/services/resource_allocations/update_service_spec.rb
index 81ae0bd5e57..8eff1cfe6dc 100644
--- a/modules/resource_management/spec/services/resource_allocations/update_service_spec.rb
+++ b/modules/resource_management/spec/services/resource_allocations/update_service_spec.rb
@@ -35,10 +35,10 @@ RSpec.describe ResourceAllocations::UpdateService, type: :model do
   shared_let(:owner) do
     create(:user, member_with_permissions: { project => %i[view_resource_planners allocate_user_resources] })
   end
-  shared_let(:planner) { create(:resource_planner, project:, principal: owner) }
+  shared_let(:work_package) { create(:work_package, project:) }
 
   let!(:resource_allocation) do
-    create(:resource_allocation, entity: planner, principal: owner, state: "requested", allocated_time: 8)
+    create(:resource_allocation, entity: work_package, principal: owner, state: "requested", allocated_time: 8)
   end
 
   subject(:service_call) do
@@ -52,13 +52,13 @@ RSpec.describe ResourceAllocations::UpdateService, type: :model do
   end
 
   context "when attempting to change the entity" do
-    let(:other_planner) { create(:resource_planner, project:, principal: owner) }
+    let(:other_work_package) { create(:work_package, project:) }
 
     it "fails because entity is not writable" do
-      result = described_class.new(user: owner, model: resource_allocation).call(entity: other_planner)
+      result = described_class.new(user: owner, model: resource_allocation).call(entity: other_work_package)
       expect(result).not_to be_success
       expect(result.errors.symbols_for(:entity_id)).to include(:error_readonly)
-      expect(resource_allocation.reload.entity).to eq(planner)
+      expect(resource_allocation.reload.entity).to eq(work_package)
     end
   end