diff --git a/src/app/globals.css b/src/app/globals.css
index da61632..907d1c4 100644
--- a/src/app/globals.css
+++ b/src/app/globals.css
@@ -1001,14 +1001,30 @@
   }
 }
 
-/* Unified scrollbar style for scrollable containers.
-   Thin overlay scrollbar — no gutter reserved, no layout shift. */
-.scrollbar-thin,
-.scrollbar-thin-edge {
+/* Native fallback for containers that cannot use OverlayScrollbars (e.g. virtua) */
+.scrollbar-thin {
   scrollbar-width: thin;
   scrollbar-color: var(--border) transparent;
 }
 
+/* OverlayScrollbars custom theme — 6px track, grows to 8px on hover.
+   Use compound selector to beat the base `.os-scrollbar` defaults
+   (--os-size:0, --os-handle-bg:none) regardless of CSS load order. */
+.os-scrollbar.os-theme-codeg {
+  --os-size: 6px;
+  --os-handle-bg: var(--border);
+  --os-handle-bg-hover: var(--muted-foreground);
+  --os-handle-bg-active: var(--muted-foreground);
+  --os-handle-border-radius: 999px;
+  --os-handle-perpendicular-size: 100%;
+  --os-handle-perpendicular-size-hover: 100%;
+  --os-handle-perpendicular-size-active: 100%;
+}
+
+.os-scrollbar.os-theme-codeg:hover {
+  --os-size: 8px;
+}
+
 /* Streamdown code blocks: dark mode via shiki dual-theme CSS variables */
 .dark [data-streamdown="code-block-body"] {
   background-color: var(--shiki-dark-bg, var(--sdm-bg, transparent)) !important;