diff --git a/docker/frontend/src/Library.tsx b/docker/frontend/src/Library.tsx
index a6e61f1..5f7e698 100644
--- a/docker/frontend/src/Library.tsx
+++ b/docker/frontend/src/Library.tsx
@@ -519,7 +519,17 @@ function Catalogue() {
       if (pendingRows.length > 0) {
         const toAdd = pendingRows;
         pendingRows = [];
-        setPhotos((prev) => [...prev, ...toAdd]);
+        // A frame handed over the side is a frame the read-back that landed beside
+        // it already carries: a reading this window holds ends, the screen reads
+        // the catalogue back, and the rows it was handed are still waiting out
+        // their half second — so the same frame arrives twice and the header
+        // counts it twice. The id is the frame, so one of it in the strip is
+        // enough.
+        setPhotos((prev) => {
+          const have = new Set(prev.map((p) => p.id));
+          const landed = toAdd.filter((p) => !have.has(p.id));
+          return landed.length ? [...prev, ...landed] : prev;
+        });
       }
       updateTimer = null;
     };