diff --git a/web/src/app.css b/web/src/app.css
index 8b8b692..23665ab 100644
--- a/web/src/app.css
+++ b/web/src/app.css
@@ -3,6 +3,12 @@
   themes: dark --default;
 }
 
+/* Reserve space for the vertical scrollbar even when the page doesn't scroll,
+   so switching to a taller tab (e.g. Services) doesn't shift the layout. */
+html {
+  scrollbar-gutter: stable;
+}
+
 /* Markdown reader: tables scroll sideways instead of overflowing the card. */
 .prose table {
   display: block;