diff --git a/browse/js/tree.js b/browse/js/tree.js
index 31183fd..918fc07 100644
--- a/browse/js/tree.js
+++ b/browse/js/tree.js
@@ -280,18 +280,43 @@
     // table); the tree.setSort() method still works but only via
     // programmatic callers — there's no UI for changing sort yet.
 
+    // True when this zip node lives inside another zip (so its bytes
+    // can't be fetched as a standalone server resource — we go through
+    // the parent JSZip / inner-zip download path instead). In server
+    // mode the URL of a zip-member-inside-a-zip contains ".zip/"; in
+    // FS-API mode zipParentId is set.
+    function zipNestedInsideZip(node) {
+        if (node.zipParentId != null) return true;
+        if (state.source === 'server') {
+            return pathFor(node).toLowerCase().indexOf('.zip/') !== -1;
+        }
+        return false;
+    }
+
     // Load a folder's children (lazy; idempotent re-loads). Dispatches
     // by node kind:
-    //   - regular folder → server JSON listing OR FS-API enumeration
-    //   - zip file       → fetch+JSZip; entries become virtual children
-    //   - zip child dir  → already-listed entries from the parent zip
-    //                       (zips are enumerated whole, so child dirs
-    //                       are pre-populated when the zip expands)
+    //   - regular folder      → server JSON listing OR FS-API enumeration
+    //   - top-level zip, server mode → server's virtual-directory listing
+    //                            of the zip's members (no whole-zip
+    //                            download — zddc-server extracts on demand)
+    //   - zip otherwise       → fetch+JSZip; entries become virtual children
+    //   - zip child dir       → already-listed entries from the parent zip
+    //                            (the whole zip was enumerated when it
+    //                            expanded, so child dirs are pre-seeded)
     async function loadChildren(node) {
         if (node.loaded) return;
         try {
             if (node.isZip) {
-                await loadZipChildren(node);
+                if (state.source === 'server' && !zipNestedInsideZip(node)) {
+                    // zddc-server serves "<…>.zip/" as a virtual
+                    // directory: GET it as a listing, GET a member URL
+                    // to extract just that file. Same shape as any
+                    // server directory, so no JSZip on the client.
+                    setChildren(node.id,
+                        await loader.fetchServerChildren(pathFor(node) + '/'));
+                } else {
+                    await loadZipChildren(node);
+                }
             } else if (node._zipSyntheticDir) {
                 // Synthetic dir node materialized when a zip's entry
                 // list referenced "a/b/file" but had no "a/" entry.