diff --git a/frontend/js/pane-manager.js b/frontend/js/pane-manager.js
index a7de1c8..0be3343 100644
--- a/frontend/js/pane-manager.js
+++ b/frontend/js/pane-manager.js
@@ -156,6 +156,12 @@ function createPaneTabManager(paneId) {
       this._dirtyTabs.delete(tabId);
       if (this._tabs.length === 0) {
         this._activeTabId = null;
+        // If this pane has no more tabs and isn't the last pane, close it
+        if (window.PaneManager && window.PaneManager.isSplit() && window.PaneManager.panes.length > 1) {
+          this._renderTabs();
+          window.PaneManager.closePane(this.paneId);
+          return;
+        }
         this._showDashboard();
         if (this._tabBar) this._tabBar.hidden = true;
       } else if (this._activeTabId === tabId) {
@@ -216,9 +222,14 @@ function createPaneTabManager(paneId) {
       // Add to target
       targetTm._tabs.push({ ...tab, preview: false });
       targetTm._tabCache[tabId] = cache || { vault: tab.vault, path: tab.path, title: tab.name, data: null, rawSource: null, sourceView: false, scrollTop: 0, icon: tab.icon };
-      // Activate in source what's left, or show dashboard
+      // If source is now empty and not the last pane, close it
       if (this._tabs.length === 0) {
         this._activeTabId = null;
+        if (window.PaneManager && window.PaneManager.isSplit() && window.PaneManager.panes.length > 1) {
+          this._renderTabs();
+          window.PaneManager.closePane(this.paneId);
+          return true;
+        }
         this._showDashboard();
         if (this._tabBar) this._tabBar.hidden = true;
       } else if (this._activeTabId === tabId) {
@@ -236,15 +247,13 @@ function createPaneTabManager(paneId) {
       // Set temporary override so getContentArea() returns this pane's area
       const prev = window._activePaneContentArea;
       window._activePaneContentArea = area;
-      try {
-        // Dynamic import to avoid circular dep — renderFile is in viewer.js
-        import('./viewer.js').then(m => {
-          m.renderFile(data);
-          window._activePaneContentArea = prev;
-        });
-      } catch (e) {
+      // Use dynamic import to call viewer.js renderFile in the right context
+      import('./viewer.js').then(m => {
+        m.renderFile(data);
         window._activePaneContentArea = prev;
-      }
+      }).catch(() => {
+        window._activePaneContentArea = prev;
+      });
     },
 
     _saveCurrentTabState() {
@@ -910,9 +919,9 @@ if (typeof window !== 'undefined') {
     });
     // Init — wait for DOM + singleton TabManager to be ready
     setTimeout(() => {
-      // Store singleton TabManager reference
-      if (typeof TabManager !== 'undefined')
-        window._singletonTabManager = TabManager;
+      // Use window.TabManager (set by ui.js init) as the singleton fallback
+      if (!window._singletonTabManager && window.TabManager)
+        window._singletonTabManager = window.TabManager;
       PaneManager.init();
     }, 150);
   });
diff --git a/frontend/js/ui.js b/frontend/js/ui.js
index b30262f..bd3ba34 100644
--- a/frontend/js/ui.js
+++ b/frontend/js/ui.js
@@ -1880,6 +1880,9 @@ export const TabManager = {
   init() {
     this._tabBar = document.getElementById("tab-bar");
     this._tabList = document.getElementById("tab-list");
+    // Expose on window so pane-manager.js can reference the singleton
+    window.TabManager = this;
+    window._singletonTabManager = this;
   },
 
   /** Open a file as a preview tab (single-click).