diff --git a/src/zotero_kb/templates/index.html b/src/zotero_kb/templates/index.html
index ac59792..708d0cf 100644
--- a/src/zotero_kb/templates/index.html
+++ b/src/zotero_kb/templates/index.html
@@ -436,7 +436,6 @@
         selectDescendantsButton: document.getElementById("modal-select-descendants-button"),
         clearSelectionButton: document.getElementById("modal-clear-selection-button"),
         importSelectedItemsButton: document.getElementById("modal-import-selected-items-button"),
-        previewPopover: document.getElementById("item-preview-popover"),
         currentProjectLabel: document.getElementById("current-project-label"),
         cardList: document.getElementById("card-list"),
         cardDetail: document.getElementById("card-detail"),
@@ -613,6 +612,24 @@
         return lookup;
       }
 
+      function normalizeSelectedCollectionKey() {
+        if (!state.collectionTree.length) {
+          state.selectedCollectionKey = null;
+          state.expandedCollectionKeys.clear();
+          persistImportSessionState();
+          return null;
+        }
+        const parentLookup = collectCollectionParents(state.collectionTree);
+        if (!state.selectedCollectionKey || !parentLookup.has(state.selectedCollectionKey)) {
+          state.selectedCollectionKey = state.collectionTree[0].collection_key;
+        }
+        state.expandedCollectionKeys = new Set(
+          Array.from(state.expandedCollectionKeys).filter((key) => parentLookup.has(key))
+        );
+        persistImportSessionState();
+        return state.selectedCollectionKey;
+      }
+
       function ensureSelectedCollectionExpanded() {
         if (!state.selectedCollectionKey) {
           return;
@@ -733,9 +750,7 @@
         setStatus(elements.collectionStatus, "正在加载 collection...");
         const payload = await api("/api/zotero/collections/tree");
         state.collectionTree = Array.isArray(payload.collections) ? payload.collections : [];
-        if (!state.selectedCollectionKey && state.collectionTree.length) {
-          state.selectedCollectionKey = state.collectionTree[0].collection_key;
-        }
+        normalizeSelectedCollectionKey();
         ensureSelectedCollectionExpanded();
         persistImportSessionState();
         renderCollectionTree();
@@ -750,6 +765,16 @@
 
       async function loadCollectionItems(collectionKey) {
         state.selectedCollectionKey = collectionKey;
+        if (normalizeSelectedCollectionKey() !== collectionKey) {
+          state.visibleCollectionItems = [];
+          renderCollectionTree();
+          renderCollectionItems();
+          setStatus(elements.collectionStatus, state.selectedCollectionKey ? "已切换到可用 collection。" : "");
+          if (state.selectedCollectionKey) {
+            await loadCollectionItems(state.selectedCollectionKey);
+          }
+          return;
+        }
         ensureSelectedCollectionExpanded();
         persistImportSessionState();
         renderCollectionTree();
@@ -815,8 +840,6 @@
         elements.importModal.hidden = false;
         elements.importModal.setAttribute("aria-hidden", "false");
         document.body.classList.toggle("modal-open", true);
-        elements.previewPopover.hidden = true;
-        elements.previewPopover.textContent = "";
         updateImportActionState();
         if (!state.collectionTree.length) {
           try {
@@ -841,8 +864,6 @@
         elements.importModal.hidden = true;
         elements.importModal.setAttribute("aria-hidden", "true");
         document.body.classList.toggle("modal-open", false);
-        elements.previewPopover.hidden = true;
-        elements.previewPopover.textContent = "";
       }
 
       async function loadProjects() {
diff --git a/tests/test_ui.py b/tests/test_ui.py
index a576122..eae301e 100644
--- a/tests/test_ui.py
+++ b/tests/test_ui.py
@@ -45,5 +45,5 @@ def test_index_contains_import_modal_controls(tmp_path) -> None:
     assert "function openImportModal()" in html
     assert "function closeImportModal()" in html
     assert "function updateImportActionState()" in html
+    assert "function normalizeSelectedCollectionKey()" in html
     assert 'document.body.classList.toggle("modal-open"' in html
-    assert "${item.abstract" not in html