diff --git a/internal/web/static/app.css b/internal/web/static/app.css
index 0262cc8..0983aa7 100644
--- a/internal/web/static/app.css
+++ b/internal/web/static/app.css
@@ -811,3 +811,20 @@ button[type="submit"]:focus-visible,
 .mt18 { margin-top: 18px; }
 .toggle-inline { display: inline-flex; }
 .wrap-normal { word-break: normal; overflow-wrap: break-word; }
+/* #169: persistent full-width divider between the editor head (dropdown
+   title area) and the editor body. Previously the perceived line was only
+   the two cards' own borders, which sat inside rounded corners and read as
+   a hover-dependent, flickering line. Draw one continuous separator that
+   spans the full card width and is always visible: border-bottom on the
+   head card, border-top on the editor card, square corners on the facing
+   edges so the two connect into a single unbroken line. */
+.pane-l-head {
+  border-bottom: 1px solid var(--border);
+  border-bottom-left-radius: 0;
+  border-bottom-right-radius: 0;
+}
+.pane-l-head + .editor-wrap {
+  border-top: 1px solid var(--border);
+  border-top-left-radius: 0;
+  border-top-right-radius: 0;
+}