diff --git a/HellionChat/Plugin.cs b/HellionChat/Plugin.cs
index c8d4cd3..f7a4d42 100755
--- a/HellionChat/Plugin.cs
+++ b/HellionChat/Plugin.cs
@@ -349,6 +349,8 @@ public sealed class Plugin : IDalamudPlugin
                     }
                 }
 
+                // TEST-MIRROR: Hellion Build test/_Helpers/MigrationLogic.cs (local-only repo)
+                // If you change the formula here, change the mirror — tests assert the contract.
                 if (oldWindowAlpha != 100f
                     && Math.Abs(Config.WindowOpacity - 0.85f) < 0.001f)
                 {