diff --git a/app/models/notification/bundle.rb b/app/models/notification/bundle.rb
index 74a681888..84e1058cb 100644
--- a/app/models/notification/bundle.rb
+++ b/app/models/notification/bundle.rb
@@ -6,6 +6,7 @@ class Notification::Bundle < ApplicationRecord
   before_create :set_default_window
 
   scope :due, -> { pending.where("ends_at <= ?", Time.current) }
+  scope :containing, -> (notification) { where("starts_at <= ? AND ends_at >= ?", notification.created_at, notification.created_at) }
 
   class << self
     def deliver_all
@@ -19,10 +20,6 @@ class Notification::Bundle < ApplicationRecord
     end
   end
 
-  def add(notification)
-    update! ends_at: [ ends_at, notification.created_at ].max
-  end
-
   def notifications
     user.notifications.where(created_at: window)
   end
diff --git a/app/models/user/notifiable.rb b/app/models/user/notifiable.rb
index 0f6cf3b94..015186d15 100644
--- a/app/models/user/notifiable.rb
+++ b/app/models/user/notifiable.rb
@@ -8,12 +8,20 @@ module User::Notifiable
 
   def bundle(notification)
     transaction do
-      find_or_create_pending_bundle_for(notification).add(notification)
+      find_or_create_bundle_for(notification)
     end
   end
 
   private
-    def find_or_create_pending_bundle_for(notification)
-      notification_bundles.pending.last || notification_bundles.create!(starts_at: notification.created_at)
+    def find_or_create_bundle_for(notification)
+      find_bundle_for(notification) || create_bundle_for(notification)
+    end
+
+    def find_bundle_for(notification)
+      notification_bundles.pending.containing(notification).last
+    end
+
+    def create_bundle_for(notification)
+      notification_bundles.create!(starts_at: notification.created_at)
     end
 end
diff --git a/db/migrate/20250826131458_remove_unique_constraint_from_notification_bundles_user_id.rb b/db/migrate/20250826131458_remove_unique_constraint_from_notification_bundles_user_id.rb
new file mode 100644
index 000000000..d5c83236c
--- /dev/null
+++ b/db/migrate/20250826131458_remove_unique_constraint_from_notification_bundles_user_id.rb
@@ -0,0 +1,6 @@
+class RemoveUniqueConstraintFromNotificationBundlesUserId < ActiveRecord::Migration[8.1]
+  def change
+    remove_index :notification_bundles, :user_id, unique: true
+    add_index :notification_bundles, %i[ ends_at status ]
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index c27e4b231..234dc517a 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.1].define(version: 2025_08_26_084559) do
+ActiveRecord::Schema[8.1].define(version: 2025_08_26_131458) do
   create_table "accesses", force: :cascade do |t|
     t.datetime "accessed_at"
     t.integer "collection_id", null: false
@@ -302,9 +302,9 @@ ActiveRecord::Schema[8.1].define(version: 2025_08_26_084559) do
     t.integer "status", default: 0, null: false
     t.datetime "updated_at", null: false
     t.integer "user_id", null: false
+    t.index ["ends_at", "status"], name: "index_notification_bundles_on_ends_at_and_status"
     t.index ["user_id", "starts_at", "ends_at"], name: "idx_on_user_id_starts_at_ends_at_7eae5d3ac5"
     t.index ["user_id", "status"], name: "index_notification_bundles_on_user_id_and_status"
-    t.index ["user_id"], name: "index_notification_bundles_on_user_id", unique: true
   end
 
   create_table "notifications", force: :cascade do |t|
diff --git a/db/schema_cache.yml b/db/schema_cache.yml
index 811f78807..434e9ad75 100644
--- a/db/schema_cache.yml
+++ b/db/schema_cache.yml
@@ -2352,10 +2352,11 @@ indexes:
     valid: true
   - !ruby/object:ActiveRecord::ConnectionAdapters::IndexDefinition
     table: notification_bundles
-    name: index_notification_bundles_on_user_id
-    unique: true
+    name: index_notification_bundles_on_ends_at_and_status
+    unique: false
     columns:
-    - user_id
+    - ends_at
+    - status
     lengths: {}
     orders: {}
     opclasses: {}
@@ -2860,4 +2861,4 @@ indexes:
     comment:
     valid: true
   workflows: []
-version: 20250826084559
+version: 20250826131458