Fix deferred sections staying invisible after lazy mount.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/app/globals.css

@@ -1171,6 +1171,12 @@ img { max-width: 100%; display: block; }
   transform: translateY(0);
 }
 
+/* Deferred kits: once mounted, never stay invisible if JS timing races */
+[data-deferred="ready"] .reveal {
+  opacity: 1;
+  transform: translateY(0);
+}
+
 .deferred-skeleton {
   height: 120px;
   margin: 24px auto;

frontend/src/components/HomeClient.tsx

@@ -129,9 +129,13 @@ export default function HomeClient(props: Props) {
   }, []);
 
   useEffect(() => {
-    // Above-fold reveal only — deferred sections self-reveal via WhenVisible
-    const nodes = document.querySelectorAll(".reveal:not(.visible)");
-    if (!nodes.length) return;
+    // Above-fold reveal; keep watching briefly for late client mounts
+    const mark = (root: ParentNode = document) => {
+      root.querySelectorAll(".reveal:not(.visible)").forEach((el, i) => {
+        (el as HTMLElement).style.transitionDelay = `${(i % 6) * 0.08}s`;
+      });
+    };
+    mark();
     const observer = new IntersectionObserver(
       (entries) => entries.forEach((e) => {
         if (e.isIntersecting) {
@@ -139,13 +143,18 @@ export default function HomeClient(props: Props) {
           observer.unobserve(e.target);
         }
       }),
-      { threshold: 0.1, rootMargin: "0px 0px -40px 0px" }
+      { threshold: 0.08, rootMargin: "0px 0px -40px 0px" }
     );
-    nodes.forEach((el, i) => {
-      (el as HTMLElement).style.transitionDelay = `${(i % 6) * 0.08}s`;
-      observer.observe(el);
-    });
-    return () => observer.disconnect();
+    const observeAll = () => {
+      document.querySelectorAll(".reveal:not(.visible)").forEach((el) => observer.observe(el));
+    };
+    observeAll();
+    const mo = new MutationObserver(() => observeAll());
+    mo.observe(document.body, { childList: true, subtree: true });
+    return () => {
+      observer.disconnect();
+      mo.disconnect();
+    };
   }, []);
 
   const toggleCompare = (slug: string) => {

frontend/src/components/WhenVisible.tsx

@@ -29,7 +29,7 @@ export default function WhenVisible({
           io.disconnect();
         }
       },
-      { rootMargin, threshold: 0.01 }
+      { rootMargin, threshold: 0 }
     );
     io.observe(el);
     return () => io.disconnect();
@@ -37,10 +37,24 @@ export default function WhenVisible({
 
   useEffect(() => {
     if (!show || !ref.current) return;
-    // Reveal animations for deferred sections without a global MutationObserver
-    ref.current.querySelectorAll(".reveal:not(.visible)").forEach((node) => {
-      node.classList.add("visible");
-    });
+    const root = ref.current;
+
+    const markVisible = () => {
+      root.querySelectorAll(".reveal:not(.visible)").forEach((node) => {
+        node.classList.add("visible");
+      });
+    };
+
+    // Lazy chunks mount after show=true — watch subtree + retry briefly
+    markVisible();
+    const mo = new MutationObserver(markVisible);
+    mo.observe(root, { childList: true, subtree: true });
+    const timers = [50, 200, 600, 1500].map((ms) => window.setTimeout(markVisible, ms));
+
+    return () => {
+      mo.disconnect();
+      timers.forEach(clearTimeout);
+    };
   }, [show]);
 
   return (