diff --git a/lib/react_on_rails/configuration.rb b/lib/react_on_rails/configuration.rb
index 3ef7332d2..7c51accfb 100644
--- a/lib/react_on_rails/configuration.rb
+++ b/lib/react_on_rails/configuration.rb
@@ -320,15 +320,20 @@ def configure_generated_assets_dirs_deprecation
     end
 
     def ensure_webpack_generated_files_exists
-      return unless webpack_generated_files.empty?
-
-      self.webpack_generated_files = [
+      all_required_files = [
         "manifest.json",
         server_bundle_js_file,
         rsc_bundle_js_file,
         react_client_manifest_file,
         react_server_client_manifest_file
       ].compact_blank
+
+      if webpack_generated_files.empty?
+        self.webpack_generated_files = all_required_files
+      else
+        missing_files = all_required_files.reject { |file| webpack_generated_files.include?(file) }
+        self.webpack_generated_files += missing_files if missing_files.any?
+      end
     end
 
     def configure_skip_display_none_deprecation
diff --git a/spec/react_on_rails/configuration_spec.rb b/spec/react_on_rails/configuration_spec.rb
index 4d79e0e6d..d4e25a29f 100644
--- a/spec/react_on_rails/configuration_spec.rb
+++ b/spec/react_on_rails/configuration_spec.rb
@@ -525,6 +525,152 @@ module ReactOnRails
         end
       end
     end
+
+    describe "#ensure_webpack_generated_files_exists" do
+      let(:config) { described_class.new }
+
+      before do
+        # Reset to test defaults
+        config.server_bundle_js_file = "server-bundle.js"
+        config.rsc_bundle_js_file = nil
+        config.react_client_manifest_file = "react-client-manifest.json"
+        config.react_server_client_manifest_file = "react-server-client-manifest.json"
+      end
+
+      context "when webpack_generated_files has default manifest.json only" do
+        it "automatically includes server bundle when configured" do
+          config.webpack_generated_files = %w[manifest.json]
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          expect(config.webpack_generated_files).to eq(%w[
+                                                         manifest.json
+                                                         server-bundle.js
+                                                         react-client-manifest.json
+                                                         react-server-client-manifest.json
+                                                       ])
+        end
+
+        it "does not duplicate manifest.json" do
+          config.webpack_generated_files = %w[manifest.json]
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          expect(config.webpack_generated_files.count("manifest.json")).to eq(1)
+        end
+      end
+
+      context "when webpack_generated_files is empty" do
+        it "populates with all required files" do
+          config.webpack_generated_files = []
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          expect(config.webpack_generated_files).to eq(%w[
+                                                         manifest.json
+                                                         server-bundle.js
+                                                         react-client-manifest.json
+                                                         react-server-client-manifest.json
+                                                       ])
+        end
+      end
+
+      context "when server bundle already included" do
+        it "does not duplicate entries" do
+          config.webpack_generated_files = %w[manifest.json server-bundle.js]
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          expect(config.webpack_generated_files).to eq(%w[
+                                                         manifest.json
+                                                         server-bundle.js
+                                                         react-client-manifest.json
+                                                         react-server-client-manifest.json
+                                                       ])
+          expect(config.webpack_generated_files.count("server-bundle.js")).to eq(1)
+        end
+      end
+
+      context "when custom files are configured" do
+        it "preserves custom files and adds missing critical files" do
+          config.webpack_generated_files = %w[manifest.json custom-bundle.js]
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          expect(config.webpack_generated_files).to include("manifest.json")
+          expect(config.webpack_generated_files).to include("custom-bundle.js")
+          expect(config.webpack_generated_files).to include("server-bundle.js")
+          expect(config.webpack_generated_files).to include("react-client-manifest.json")
+        end
+      end
+
+      context "when server bundle is not configured" do
+        it "does not add nil server bundle" do
+          config.server_bundle_js_file = nil
+          config.webpack_generated_files = %w[manifest.json]
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          expect(config.webpack_generated_files).not_to include(nil)
+          expect(config.webpack_generated_files).not_to include("server-bundle.js")
+          expect(config.webpack_generated_files).to include("manifest.json")
+        end
+      end
+
+      context "when RSC bundle is configured" do
+        it "includes RSC bundle in monitoring" do
+          config.rsc_bundle_js_file = "rsc-bundle.js"
+          config.webpack_generated_files = %w[manifest.json]
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          expect(config.webpack_generated_files).to include("rsc-bundle.js")
+          expect(config.webpack_generated_files).to include("server-bundle.js")
+          expect(config.webpack_generated_files).to include("manifest.json")
+        end
+      end
+
+      context "when React manifests are not configured" do
+        it "does not add nil React manifests" do
+          config.react_client_manifest_file = nil
+          config.react_server_client_manifest_file = nil
+          config.webpack_generated_files = %w[manifest.json]
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          expect(config.webpack_generated_files).not_to include(nil)
+          expect(config.webpack_generated_files).to eq(%w[manifest.json server-bundle.js])
+        end
+      end
+
+      context "when ensuring server bundle monitoring for RSpec optimization" do
+        it "ensures server bundle in private directory is monitored with default config" do
+          # Simulate default generator configuration
+          config.webpack_generated_files = %w[manifest.json]
+          config.server_bundle_js_file = "server-bundle.js"
+          config.server_bundle_output_path = "ssr-generated"
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          # Critical: server bundle must be included for RSpec helper optimization to work
+          expect(config.webpack_generated_files).to include("server-bundle.js")
+        end
+
+        it "handles all files being in different directories" do
+          # Simulate cross-directory scenario from PR #1798
+          config.webpack_generated_files = %w[manifest.json]
+          config.server_bundle_js_file = "server-bundle.js"
+          config.server_bundle_output_path = "ssr-generated"
+          config.generated_assets_dir = "public/packs"
+
+          config.send(:ensure_webpack_generated_files_exists)
+
+          # All critical files should be monitored regardless of directory
+          expect(config.webpack_generated_files).to include("manifest.json")
+          expect(config.webpack_generated_files).to include("server-bundle.js")
+        end
+      end
+    end
   end
 end