diff --git a/modules/resource_management/app/components/resource_allocations/list_item_component.rb b/modules/resource_management/app/components/resource_allocations/list_item_component.rb
index 21c5110e2d3..d92288cf1fd 100644
--- a/modules/resource_management/app/components/resource_allocations/list_item_component.rb
+++ b/modules/resource_management/app/components/resource_allocations/list_item_component.rb
@@ -115,12 +115,13 @@ module ResourceAllocations
     end
 
     # An allocation without a user yet (filter placeholder or lost principal)
-    # shows a person-add icon instead of an avatar.
+    # shows a person-add icon instead of an avatar. Sized to match the avatar so
+    # the leading column keeps the same width and the row stays aligned.
     def leading_visual
       if allocation.principal
         Primer::OpenProject::AvatarWithFallback.new(size: AVATAR_SIZE, **avatar_options)
       else
-        Primer::Beta::Octicon.new(icon: :"person-add", color: :muted, "aria-hidden": true)
+        Primer::Beta::Octicon.new(icon: :"person-add", size: :medium, color: :muted, "aria-hidden": true)
       end
     end
 
diff --git a/modules/resource_management/app/models/resource_allocation.rb b/modules/resource_management/app/models/resource_allocation.rb
index da15a7813cd..d7f07b163f6 100644
--- a/modules/resource_management/app/models/resource_allocation.rb
+++ b/modules/resource_management/app/models/resource_allocation.rb
@@ -31,6 +31,11 @@
 class ResourceAllocation < ApplicationRecord
   ALLOWED_ENTITY_TYPES = %w[WorkPackage].freeze
 
+  # `allocated_time` is stored in minutes in an integer column. Cap it at 5000
+  # hours so an absurdly large input is rejected with a validation error rather
+  # than overflowing the column and raising ActiveModel::RangeError on save.
+  MAX_ALLOCATED_TIME = (5000.hours / 1.minute).to_i
+
   belongs_to :entity, polymorphic: true, optional: false
   belongs_to :principal, class_name: "User", optional: true, inverse_of: :resource_allocations
   belongs_to :requested_by, class_name: "User", optional: true
@@ -119,6 +124,8 @@ class ResourceAllocation < ApplicationRecord
             presence: true,
             numericality: { only_integer: true, greater_than: 0 }
 
+  validate :allocated_time_within_limit
+
   validates :entity_type,
             inclusion: { in: ALLOWED_ENTITY_TYPES },
             allow_blank: true
@@ -207,6 +214,17 @@ class ResourceAllocation < ApplicationRecord
 
   private
 
+  # Capped above to keep `allocated_time` within the integer column. The field is
+  # entered in hours, so the message reports the limit in the same duration
+  # format rather than the raw minutes the column stores.
+  def allocated_time_within_limit
+    return if allocated_time.blank?
+    return if allocated_time <= MAX_ALLOCATED_TIME
+
+    errors.add(:allocated_time, :less_than_or_equal_to,
+               count: DurationConverter.output(MAX_ALLOCATED_TIME / 60.0))
+  end
+
   def starts_before_entity?
     entity_start_date.present? && start_date.present? && start_date < entity_start_date
   end
diff --git a/modules/resource_management/spec/models/resource_allocation_spec.rb b/modules/resource_management/spec/models/resource_allocation_spec.rb
index fd54dea341f..e5d47a6e826 100644
--- a/modules/resource_management/spec/models/resource_allocation_spec.rb
+++ b/modules/resource_management/spec/models/resource_allocation_spec.rb
@@ -401,6 +401,17 @@ RSpec.describe ResourceAllocation do
         allocation.allocated_time = 1
         expect(allocation).to be_valid
       end
+
+      it "is valid at the upper cap" do
+        allocation.allocated_time = described_class::MAX_ALLOCATED_TIME
+        expect(allocation).to be_valid
+      end
+
+      it "is invalid (rather than overflowing the column) above the cap" do
+        allocation.allocated_time = described_class::MAX_ALLOCATED_TIME + 1
+        expect(allocation).not_to be_valid
+        expect(allocation.errors.symbols_for(:allocated_time)).to include(:less_than_or_equal_to)
+      end
     end
 
     describe "date range" do
diff --git a/modules/resource_management/spec/requests/resource_allocations_spec.rb b/modules/resource_management/spec/requests/resource_allocations_spec.rb
index 1a8b1ac9717..41f4b15cfba 100644
--- a/modules/resource_management/spec/requests/resource_allocations_spec.rb
+++ b/modules/resource_management/spec/requests/resource_allocations_spec.rb
@@ -525,6 +525,18 @@ RSpec.describe "ResourceAllocations requests",
         expect(response).to have_http_status(:unprocessable_entity)
         expect(allocation.reload.allocated_time).to eq(600)
       end
+
+      # Regression: an absurdly large value used to overflow the integer column
+      # and raise ActiveModel::RangeError (500) instead of failing validation.
+      it "rejects a value above the maximum with an hours-formatted message" do
+        perform(allocated_hours: "999999999999h")
+
+        expect(response).to have_http_status(:unprocessable_entity)
+        expect(allocation.reload.allocated_time).to eq(600)
+        expect(response.body).to include(
+          DurationConverter.output(ResourceAllocation::MAX_ALLOCATED_TIME / 60.0)
+        )
+      end
     end
 
     context "when the update would overbook the assigned user" do