diff --git a/userscript/manga-bookmark.user.js b/userscript/manga-bookmark.user.js
index 5be6f6c..d598fcb 100644
--- a/userscript/manga-bookmark.user.js
+++ b/userscript/manga-bookmark.user.js
@@ -795,8 +795,8 @@
   }
 
   // Dwell timer: don't advance progress the instant a newer chapter opens (guards
-  // against a misclick on "latest chapter"). Arm a 25s timer instead; the countdown
-  // ring around the FAB shows it running. The manual "Update to X" button still fires
+  // against a misclick on "latest chapter"). Arm a 25s timer instead; the tab fills
+  // bottom-up to show it counting down. The manual "Update to X" button still fires
   // immediately. Timer is keyed to the chapter, not the URL, so turning pages within
   // the same chapter (Demonic /chapter/N/<page>) keeps it counting rather than resetting.
   const DWELL_MS = 25000;
@@ -1419,12 +1419,12 @@
   // ============================================================
   // Test hook
   //
-  // Node's require() defines `module`; Bromite's native engine, Tampermonkey,
-  // and Violentmonkey do not, so this is inert everywhere the script actually
-  // ships. Exposes pure logic only — see userscript/test/logic.test.js, which
-  // loads this file with document.body undefined so the UI never boots.
+  // Fires only in Node, where window is undefined. The typeof window check keeps it
+  // inert on pages whose own scripts define a UMD module shim — under @grant none
+  // the userscript shares page globals, so we must not clobber the page's exports.
+  // Exposes pure logic only — see userscript/test/logic.test.js.
   // ============================================================
-  if (typeof module === "object" && module.exports) {
+  if (typeof window === "undefined" && typeof module === "object" && module.exports) {
     module.exports = { stripBuildHash, asura, demonic, anchorsFromHTML, statusOf };
   }