diff --git a/config/initializers/active_storage.rb b/config/initializers/active_storage.rb
index d00bd74bf..4a4a0343d 100644
--- a/config/initializers/active_storage.rb
+++ b/config/initializers/active_storage.rb
@@ -4,9 +4,17 @@ ActiveSupport.on_load(:active_storage_blob) do
   end
 end
 
-ActiveSupport.on_load(:active_storage_record) do
-  configure_replica_connections
-end
+# Don't configure replica connections for ActiveStorage::Record.
+# When ActiveStorage uses `connects_to`, it creates a separate connection pool
+# from ApplicationRecord. This causes after_commit callbacks to fire in
+# non-deterministic order - the Attachment's create_variants callback can fire
+# before the User model's upload callback, causing FileNotFoundError when
+# using `process: :immediately` for variants.
+# See: https://github.com/rails/rails/issues/53694
+#
+# ActiveSupport.on_load(:active_storage_record) do
+#   configure_replica_connections
+# end
 
 module ActiveStorageControllerExtensions
   extend ActiveSupport::Concern
diff --git a/test/controllers/users/avatars_controller_test.rb b/test/controllers/users/avatars_controller_test.rb
index be4532448..3ded884b8 100644
--- a/test/controllers/users/avatars_controller_test.rb
+++ b/test/controllers/users/avatars_controller_test.rb
@@ -27,9 +27,7 @@ class Users::AvatarsControllerTest < ActionDispatch::IntegrationTest
   end
 
   test "show own image redirects to the blob url" do
-    # Create blob separately to ensure file is uploaded before variant processing
-    blob = ActiveStorage::Blob.create_and_upload!(io: File.open(file_fixture("moon.jpg")), filename: "moon.jpg", content_type: "image/jpeg")
-    users(:david).avatar.attach(blob)
+    users(:david).avatar.attach(io: File.open(file_fixture("moon.jpg")), filename: "moon.jpg", content_type: "image/jpeg")
     assert users(:david).avatar.attached?
 
     get user_avatar_path(users(:david))
@@ -38,9 +36,7 @@ class Users::AvatarsControllerTest < ActionDispatch::IntegrationTest
   end
 
   test "show other image redirects to the blob url" do
-    # Create blob separately to ensure file is uploaded before variant processing
-    blob = ActiveStorage::Blob.create_and_upload!(io: File.open(file_fixture("moon.jpg")), filename: "moon.jpg", content_type: "image/jpeg")
-    users(:kevin).avatar.attach(blob)
+    users(:kevin).avatar.attach(io: File.open(file_fixture("moon.jpg")), filename: "moon.jpg", content_type: "image/jpeg")
     assert users(:kevin).avatar.attached?
 
     get user_avatar_path(users(:kevin))
diff --git a/test/controllers/users_controller_test.rb b/test/controllers/users_controller_test.rb
index d8441d033..385bacaf3 100644
--- a/test/controllers/users_controller_test.rb
+++ b/test/controllers/users_controller_test.rb
@@ -79,10 +79,9 @@ class UsersControllerTest < ActionDispatch::IntegrationTest
   test "update with valid avatar" do
     sign_in_as :kevin
 
-    # Create blob separately to ensure file is uploaded before variant processing
-    blob = ActiveStorage::Blob.create_and_upload!(io: File.open(file_fixture("avatar.png")), filename: "avatar.png", content_type: "image/png")
+    png_file = fixture_file_upload("avatar.png", "image/png")
 
-    put user_path(users(:kevin)), params: { user: { avatar: blob.signed_id } }
+    put user_path(users(:kevin)), params: { user: { avatar: png_file } }
     assert_redirected_to user_path(users(:kevin))
     assert users(:kevin).reload.avatar.attached?
     assert_equal "image/png", users(:kevin).avatar.content_type
diff --git a/test/mailers/notification/bundle_mailer_test.rb b/test/mailers/notification/bundle_mailer_test.rb
index 63647e68a..fbc4274c9 100644
--- a/test/mailers/notification/bundle_mailer_test.rb
+++ b/test/mailers/notification/bundle_mailer_test.rb
@@ -22,12 +22,11 @@ class Notification::BundleMailerTest < ActionMailer::TestCase
   end
 
   test "renders avatar with external image URL when avatar is attached" do
-    blob = ActiveStorage::Blob.create_and_upload!(
+    @user.avatar.attach(
       io: File.open(Rails.root.join("test", "fixtures", "files", "avatar.png")),
       filename: "avatar.png",
       content_type: "image/png"
     )
-    @user.avatar.attach(blob)
 
     create_notification(@user)
 
diff --git a/test/models/user/avatar_test.rb b/test/models/user/avatar_test.rb
index 58b78969c..ed502d7ab 100644
--- a/test/models/user/avatar_test.rb
+++ b/test/models/user/avatar_test.rb
@@ -2,8 +2,7 @@ require "test_helper"
 
 class User::AvatarTest < ActiveSupport::TestCase
   test "avatar_thumbnail returns variant for variable images" do
-    blob = ActiveStorage::Blob.create_and_upload!(io: File.open(file_fixture("moon.jpg")), filename: "moon.jpg", content_type: "image/jpeg")
-    users(:david).avatar.attach(blob)
+    users(:david).avatar.attach(io: File.open(file_fixture("moon.jpg")), filename: "moon.jpg", content_type: "image/jpeg")
 
     assert users(:david).avatar.variable?
     assert_equal users(:david).avatar.variant(:thumb).blob, users(:david).avatar_thumbnail.blob
@@ -17,8 +16,7 @@ class User::AvatarTest < ActiveSupport::TestCase
   end
 
   test "allows valid image content types" do
-    blob = ActiveStorage::Blob.create_and_upload!(io: File.open(file_fixture("moon.jpg")), filename: "test.jpg", content_type: "image/jpeg")
-    users(:david).avatar.attach(blob)
+    users(:david).avatar.attach(io: File.open(file_fixture("moon.jpg")), filename: "test.jpg", content_type: "image/jpeg")
 
     assert users(:david).valid?
   end
@@ -31,19 +29,7 @@ class User::AvatarTest < ActiveSupport::TestCase
   end
 
   test "thumb variant is processed immediately on attachment" do
-    # Create blob separately to ensure file is uploaded before variant processing.
-    #
-    # Root cause: When ActiveStorage::Record uses `connects_to` for read replica support
-    # (as in SAAS mode), it creates a separate connection pool from application models.
-    # Since after_commit callbacks are tracked per connection pool, the callback order
-    # between User's pool (upload) and Attachment's pool (create_variants) isn't guaranteed.
-    # In MySQL/SAAS mode, the Attachment callback fires before the file is uploaded.
-    blob = ActiveStorage::Blob.create_and_upload!(
-      io: File.open(file_fixture("avatar.png")),
-      filename: "avatar.png",
-      content_type: "image/png"
-    )
-    users(:david).avatar.attach(blob)
+    users(:david).avatar.attach(io: File.open(file_fixture("avatar.png")), filename: "avatar.png", content_type: "image/png")
 
     assert users(:david).avatar.variant(:thumb).processed?
   end