fix: only scroll active sidebar items into view when not already visible

frontend/src/hooks/useScrollActiveItemIntoView.js

@@ -1,5 +1,18 @@
 import { useEffect, useRef } from "react";
 
+/**
+ * Walks up the DOM tree from `el` to find the nearest ancestor
+ * that is actually scrollable (i.e. its content overflows).
+ */
+function findScrollableParent(el) {
+  let node = el.parentElement;
+  while (node && node !== document.body) {
+    if (node.scrollHeight > node.clientHeight) return node;
+    node = node.parentElement;
+  }
+  return null;
+}
+
 /**
  * Hook that scrolls an element into view when it becomes active.
  * @param {Object} options - The options for the hook.
@@ -16,8 +29,25 @@ export default function useScrollActiveItemIntoView({
   const ref = useRef(null);
 
   useEffect(() => {
-    if (isActive) {
-      ref.current.scrollIntoView({
+    if (isActive && ref.current) {
+      const el = ref.current;
+
+      // Skip scrolling if the element is already fully visible within its
+      // scrollable container. This prevents the sidebar from jumping when
+      // the active item is already in view.
+      // Walk up the DOM to find the nearest ancestor that actually scrolls
+      // (scrollHeight > clientHeight), rather than matching by class name,
+      // so this works regardless of how the scroll container is styled.
+      const scrollParent = findScrollableParent(el);
+      if (scrollParent) {
+        const parentRect = scrollParent.getBoundingClientRect();
+        const elRect = el.getBoundingClientRect();
+        const isVisible =
+          elRect.top >= parentRect.top && elRect.bottom <= parentRect.bottom;
+        if (isVisible) return;
+      }
+
+      el.scrollIntoView({
         behavior,
         block,
       });