diff --git a/browser/components/sidebar/browser-sidebar.js b/browser/components/sidebar/browser-sidebar.js
index 197570702704..91db40dc0838 100644
--- a/browser/components/sidebar/browser-sidebar.js
+++ b/browser/components/sidebar/browser-sidebar.js
@@ -203,13 +203,15 @@ var SidebarController = {
       }
     );
 
-    this._sidebars.set("viewCustomizeSidebar", {
-      url: "chrome://browser/content/sidebar/sidebar-customize.html",
-      revampL10nId: "sidebar-menu-customize-label",
-      iconUrl: "chrome://global/skin/icons/settings.svg",
-      gleanEvent: Glean.sidebarCustomize.panelToggle,
-      visible: false,
-    });
+    if (this.sidebarRevampEnabled) {
+      this._sidebars.set("viewCustomizeSidebar", {
+        url: "chrome://browser/content/sidebar/sidebar-customize.html",
+        revampL10nId: "sidebar-menu-customize-label",
+        iconUrl: "chrome://global/skin/icons/settings.svg",
+        gleanEvent: Glean.sidebarCustomize.panelToggle,
+        visible: false,
+      });
+    }
 
     return this._sidebars;
   },
@@ -801,10 +803,16 @@ var SidebarController = {
     }
     if (!this._sidebars.get(this.lastOpenedId)) {
       this.lastOpenedId = this.DEFAULT_SIDEBAR_ID;
+      wasOpen = false;
     }
     this.updateToolbarButton();
     this._inited = false;
     this.init();
+
+    // Reopen the panel in the new or old sidebar now that we've inited
+    if (wasOpen) {
+      this.toggle();
+    }
   },
 
   /**
diff --git a/browser/components/sidebar/tests/browser/browser_sidebar_prefs.js b/browser/components/sidebar/tests/browser/browser_sidebar_prefs.js
index b276b49acd40..3c08888281be 100644
--- a/browser/components/sidebar/tests/browser/browser_sidebar_prefs.js
+++ b/browser/components/sidebar/tests/browser/browser_sidebar_prefs.js
@@ -230,6 +230,28 @@ add_task(async function test_flip_revamp_pref() {
   await BrowserTestUtils.closeWindow(win);
 });
 
+/**
+ * Check that panels can stay open when flipping sidebar.revamp
+ */
+add_task(async function test_flip_revamp_pref_with_panel() {
+  await toggleSidebarPanel(window, "viewGenaiChatSidebar");
+  ok(SidebarController.isOpen, "panel open with revamp");
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["sidebar.revamp", false]],
+  });
+
+  ok(SidebarController.isOpen, "panel still open after old");
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["sidebar.revamp", true]],
+  });
+
+  ok(SidebarController.isOpen, "panel still open after new");
+
+  await SidebarController.hide();
+});
+
 add_task(async function test_opening_panel_flips_has_used_pref() {
   Services.prefs.clearUserPref("sidebar.old-sidebar.has-used");
   Services.prefs.clearUserPref("sidebar.new-sidebar.has-used");