diff --git a/config/feature_flags/development/ci_value_change_for_processable_and_rules_entry.yml b/config/feature_flags/development/ci_value_change_for_processable_and_rules_entry.yml
new file mode 100644
index 0000000000000000000000000000000000000000..f7c2542cb22f8baf8a231b151bd68b855d3266b7
--- /dev/null
+++ b/config/feature_flags/development/ci_value_change_for_processable_and_rules_entry.yml
@@ -0,0 +1,8 @@
+---
+name: ci_value_change_for_processable_and_rules_entry
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/90238
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/365876
+milestone: '15.2'
+type: development
+group: group::pipeline authoring
+default_enabled: false
diff --git a/lib/gitlab/ci/config/entry/processable.rb b/lib/gitlab/ci/config/entry/processable.rb
index 46afedbcc3ad725e6d7ca98c4046bd0709f89052..d17c52a3ace6ea427005e14c8e871c1873b57d67 100644
--- a/lib/gitlab/ci/config/entry/processable.rb
+++ b/lib/gitlab/ci/config/entry/processable.rb
@@ -71,9 +71,9 @@ module Processable
           end
 
           def compose!(deps = nil)
-            super do
-              has_workflow_rules = deps&.workflow_entry&.has_rules?
+            has_workflow_rules = deps&.workflow_entry&.has_rules?
 
+            super do
               # If workflow:rules: or rules: are used
               # they are considered not compatible
               # with `only/except` defaults
@@ -86,12 +86,16 @@ def compose!(deps = nil)
                 @entries.delete(:except) unless except_defined? # rubocop:disable Gitlab/ModuleWithInstanceVariables
               end
 
-              unless has_workflow_rules
-                validate_against_warnings
+              unless ::Feature.enabled?(:ci_value_change_for_processable_and_rules_entry)
+                validate_against_warnings unless has_workflow_rules
               end
 
               yield if block_given?
             end
+
+            if ::Feature.enabled?(:ci_value_change_for_processable_and_rules_entry)
+              validate_against_warnings unless has_workflow_rules
+            end
           end
 
           def validate_against_warnings
diff --git a/lib/gitlab/ci/config/entry/rules.rb b/lib/gitlab/ci/config/entry/rules.rb
index 53e529814717185ecc5e3e1a019a39fbd8596615..4f2f08889a16ae0dfbed0afd50964128df33dc19 100644
--- a/lib/gitlab/ci/config/entry/rules.rb
+++ b/lib/gitlab/ci/config/entry/rules.rb
@@ -13,7 +13,12 @@ class Rules < ::Gitlab::Config::Entry::ComposableArray
           end
 
           def value
-            [@config].flatten
+            if ::Feature.enabled?(:ci_value_change_for_processable_and_rules_entry)
+              # `flatten` is needed to make it work with nested `!reference`
+              [super].flatten
+            else
+              [@config].flatten
+            end
           end
 
           def composable_class
diff --git a/spec/lib/gitlab/ci/config/entry/processable_spec.rb b/spec/lib/gitlab/ci/config/entry/processable_spec.rb
index 5b9337ede3437a09f151ee211051f9151e50c4b0..cc32c57e873f4313d088b1fde93393155f3a9244 100644
--- a/spec/lib/gitlab/ci/config/entry/processable_spec.rb
+++ b/spec/lib/gitlab/ci/config/entry/processable_spec.rb
@@ -278,8 +278,13 @@ def self.name
 
     context 'when workflow rules is not used' do
       let(:workflow) { double('workflow', 'has_rules?' => false) }
+      let(:ci_value_change_for_processable_and_rules_entry) { true }
 
       before do
+        stub_feature_flags(
+          ci_value_change_for_processable_and_rules_entry: ci_value_change_for_processable_and_rules_entry
+        )
+
         entry.compose!(deps)
       end
 
@@ -303,6 +308,14 @@ def self.name
             it 'raises a warning' do
               expect(entry.warnings).to contain_exactly(/may allow multiple pipelines/)
             end
+
+            context 'when the FF ci_value_change_for_processable_and_rules_entry is disabled' do
+              let(:ci_value_change_for_processable_and_rules_entry) { false }
+
+              it 'raises a warning' do
+                expect(entry.warnings).to contain_exactly(/may allow multiple pipelines/)
+              end
+            end
           end
 
           context 'and its value is `never`' do
diff --git a/spec/lib/gitlab/ci/config/entry/rules_spec.rb b/spec/lib/gitlab/ci/config/entry/rules_spec.rb
index cfec33003e4e6f220232252a9cdb84b26a8f018e..faae5aa121f12219833d51d6af83f2e79911ca99 100644
--- a/spec/lib/gitlab/ci/config/entry/rules_spec.rb
+++ b/spec/lib/gitlab/ci/config/entry/rules_spec.rb
@@ -1,10 +1,13 @@
 # frozen_string_literal: true
 
 require 'fast_spec_helper'
+require 'support/helpers/stubbed_feature'
 require 'support/helpers/stub_feature_flags'
 require_dependency 'active_model'
 
 RSpec.describe Gitlab::Ci::Config::Entry::Rules do
+  include StubFeatureFlags
+
   let(:factory) do
     Gitlab::Config::Entry::Factory.new(described_class)
       .metadata(metadata)
@@ -12,13 +15,12 @@
   end
 
   let(:metadata) { { allowed_when: %w[always never] } }
-  let(:entry)    { factory.create! }
 
-  describe '.new' do
-    subject { entry }
+  subject(:entry) { factory.create! }
 
+  describe '.new' do
     before do
-      subject.compose!
+      entry.compose!
     end
 
     context 'with a list of rule rule' do
@@ -73,7 +75,11 @@
   end
 
   describe '#value' do
-    subject { entry.value }
+    subject(:value) { entry.value }
+
+    before do
+      entry.compose!
+    end
 
     context 'with a list of rule rule' do
       let(:config) do
@@ -99,7 +105,15 @@
         { if: '$SKIP', when: 'never' }
       end
 
-      it { is_expected.to eq([config]) }
+      it { is_expected.to eq([]) }
+
+      context 'when the FF ci_value_change_for_processable_and_rules_entry is disabled' do
+        before do
+          stub_feature_flags(ci_value_change_for_processable_and_rules_entry: false)
+        end
+
+        it { is_expected.to eq([config]) }
+      end
     end
 
     context 'with nested rules' do