diff --git a/src/contexts/AdminAssetsContext.jsx b/src/contexts/AdminAssetsContext.jsx
index b8b3c62..bba5c25 100644
--- a/src/contexts/AdminAssetsContext.jsx
+++ b/src/contexts/AdminAssetsContext.jsx
@@ -315,20 +315,26 @@ export function AssetsProvider({ children }) {
     );
 
     // ─── PATCH /api/admin/assets/:assetId ────────────────────────────────────
+    //
+    // A replacement file (video thumbnail, or an image/audio asset's main
+    // file) goes out the same presigned direct-to-storage path as
+    // uploadAsset() above — this backend never buffers it. The PATCH body
+    // itself is plain JSON either way (storage_key when a file was replaced).
     const updateAsset = useCallback(
         (assetId, fields, file = null) =>
             request(async () => {
-                const formData = new FormData();
-                Object.entries(fields).forEach(([key, value]) => {
-                    if (value !== undefined && value !== null) formData.append(key, value);
-                });
-                if (file) formData.append("file", file);
+                let filePayload = {};
+                if (file) {
+                    const presigned = await presignAssetUpload(file);
+                    await uploadPresigned(file, presigned);
+                    filePayload = {
+                        storage_key: presigned.key,
+                        original_name: file.name,
+                        mimetype: file.type || undefined,
+                    };
+                }
 
-                // No explicit Content-Type here — axios/the browser must set it
-                // itself so the multipart boundary is included. A hardcoded
-                // "multipart/form-data" header (no boundary) makes multer fail
-                // to parse the body, silently dropping the file and every field.
-                const res = await api.patch(`/admin/assets/${assetId}`, formData);
+                const res = await api.patch(`/admin/assets/${assetId}`, { ...fields, ...filePayload });
 
                 const asset = res.data?.data?.data ?? null;
                 if (asset) {