diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 6c16b1906..dc70236ef 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -7,4 +7,6 @@ class ApplicationController < ActionController::Base
 
   stale_when_importmap_changes
   allow_browser versions: :modern
+
+  etag { "v1" } # 2025-11-05 @todo: To invalidate HTTP cache after big renaming. To remove after a few days.
 end