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diff --git a/tooling/danger/multiversion.rb b/tooling/danger/multiversion.rb
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+++ b/tooling/danger/multiversion.rb
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+# frozen_string_literal: true
+
+module Tooling
+  module Danger
+    module Multiversion
+      FRONTEND_REGEX = %r{\A((ee|jh)/)?app/assets/.*(\.(vue|js|graphql))\z}
+      GRAPHQL_BACKEND_REGEX = %r{\A((ee|jh)/)?app/graphql/}
+
+      def check!
+        return unless helper.ci?
+        return unless frontend_changed? && backend_changed?
+
+        markdown <<~MARKDOWN
+        ## Multiversion compatibility
+
+        This merge request updates GraphQL backend and frontend code.
+
+        To prevent an incident, ensure the updated frontend code is backwards compatible.
+
+        For more information, see the [multiversion compatibility documentation](https://docs.gitlab.com/ee/development/graphql_guide/reviewing.html#multiversion-compatibility).
+        MARKDOWN
+      end
+
+      private
+
+      def frontend_changed?
+        !git.modified_files.grep(FRONTEND_REGEX).empty? || !git.added_files.grep(FRONTEND_REGEX).empty?
+      end
+
+      def backend_changed?
+        !git.added_files.grep(GRAPHQL_BACKEND_REGEX).empty? || !git.modified_files.grep(GRAPHQL_BACKEND_REGEX).empty?
+      end
+    end
+  end
+end