diff --git a/src/ui/railEdgeScroll.js b/src/ui/railEdgeScroll.js
index 548f79668..2a7a606c6 100644
--- a/src/ui/railEdgeScroll.js
+++ b/src/ui/railEdgeScroll.js
@@ -83,6 +83,11 @@ export function installRailEdgeScroll(doc = globalThis.document) {
     const railBox = rail.getBoundingClientRect();
     const box = on.getBoundingClientRect();
     const shown = gliding.has(rail);
+    // A rail opening its first panel folds its labelled pills to icons, the
+    // buttons shrinking over a few frames; the highlight waits until the open
+    // button is an icon again (square) rather than fading in at a pill's
+    // width and then shrinking.
+    if (!shown && (rail.classList.contains('ui-rail--expanded') || box.width > box.height + 2)) return;
     // Appearing from nothing: jump into place, then fade in.
     rail.classList.toggle('ui-rail--glide-jump', !shown);
     rail.style.setProperty('--rail-glide-x', `${box.left - railBox.left - rail.clientLeft}px`);
diff --git a/src/ui/styles/rail-edge.css b/src/ui/styles/rail-edge.css
index e1af40be4..cbcdb0eda 100644
--- a/src/ui/styles/rail-edge.css
+++ b/src/ui/styles/rail-edge.css
@@ -31,10 +31,11 @@
   opacity: 0;
   pointer-events: none;
   transform: translate(var(--rail-glide-x, 0), var(--rail-glide-y, 0));
+  /* Only the position slides. The size follows at once: it changes only
+     when the rail changes shape (its labelled pills folding to icons as a
+     panel opens), and a size easing there reads as a stretch. */
   transition:
     transform 380ms cubic-bezier(0.22, 1, 0.36, 1),
-    width 380ms cubic-bezier(0.22, 1, 0.36, 1),
-    height 380ms cubic-bezier(0.22, 1, 0.36, 1),
     border-radius var(--transition-fast),
     opacity 200ms ease;
 }
diff --git a/src/ui/styles/rail-split.css b/src/ui/styles/rail-split.css
index 22313cc7b..f974b0cbc 100644
--- a/src/ui/styles/rail-split.css
+++ b/src/ui/styles/rail-split.css
@@ -148,14 +148,16 @@
 }
 
 /* The open item takes the accent colour; its highlight is the rail's shared
-   one, which slides to it. Without that highlight the button carries its own. */
+   one, which slides to it. The button carries no fill of its own: as a rail
+   folds its labelled pills to icons, a fill on the shrinking button would
+   read as the highlight stretching. */
 :is(.gev-panel-rail--left, .gev-panel-rail--right) .ui-rail__item.ui-rail__item--on {
   color: #00d4ff !important;
 }
 
 :is(.gev-panel-rail--left, .gev-panel-rail--right) .ui-rail:not(.ui-rail--glide) .ui-rail__item.ui-rail__item--on {
-  background: rgba(0, 212, 255, 0.15);
-  border-color: rgba(0, 212, 255, 0.15);
+  background: none;
+  border-color: transparent;
 }
 
 :is(.gev-panel-rail--left, .gev-panel-rail--right) .ui-rail::before {