diff --git a/ui/src/e2e/chat-sidebar-panel-contract.e2e.test.ts b/ui/src/e2e/chat-sidebar-panel-contract.e2e.test.ts
index 7a019e996fec..14c92f064472 100644
--- a/ui/src/e2e/chat-sidebar-panel-contract.e2e.test.ts
+++ b/ui/src/e2e/chat-sidebar-panel-contract.e2e.test.ts
@@ -3,6 +3,7 @@ import type { Page } from "playwright";
 import { expect, it } from "vitest";
 import { waitForControlUiGatewayReady } from "../test-helpers/control-ui-e2e-readiness.ts";
 import {
+  controlUiBundledSettingsStorageKey,
   installMockGateway,
   type ControlUiMockGatewayScenario,
 } from "../test-helpers/control-ui-e2e.ts";
@@ -13,6 +14,8 @@ const suite = createControlUiE2eSuite({
   startServerBeforeBrowser: true,
 });
 
+const HIDDEN_BOARD_SESSION_KEY = "agent:main:hidden-board-slot";
+
 const ONE_PIXEL_PNG = Buffer.from(
   "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8/x8AAusB9Wl2nPcAAAAASUVORK5CYII=",
   "base64",
@@ -232,6 +235,38 @@ async function openColdSidebar(page: Page, scenario = coldOpenScenario()) {
   return choices;
 }
 
+async function seedHiddenBoardSlot(page: Page) {
+  const settingsKey = controlUiBundledSettingsStorageKey(suite.server.baseUrl);
+  await page.addInitScript(
+    ({ key, sessionKey }) => {
+      localStorage.setItem(
+        key,
+        JSON.stringify({
+          sessionKey,
+          sidebarSessionLayouts: {
+            [sessionKey]: {
+              columns: [
+                {
+                  id: "side-panel-column",
+                  side: "right",
+                  panels: [{ id: "chat", slot: "chat" }],
+                  activePanelId: "chat",
+                  height: 360,
+                  width: 480,
+                },
+              ],
+              dock: "right",
+              open: true,
+              expanded: false,
+            },
+          },
+        }),
+      );
+    },
+    { key: settingsKey, sessionKey: HIDDEN_BOARD_SESSION_KEY },
+  );
+}
+
 async function readColdOpenOutcome(page: Page): Promise<ColdOpenOutcome> {
   const activePanel = page.locator(".side-panel__panel:not([hidden])");
   await activePanel.waitFor();
@@ -280,6 +315,29 @@ async function readSlotColdOpenOutcome(
 }
 
 suite.define(() => {
+  it("closes a projected-empty side panel when a hidden board tab remains persisted", async () => {
+    const context = await suite.newBrowserContext({ serviceWorkers: "block" });
+    try {
+      const page = await context.newPage();
+      await seedHiddenBoardSlot(page);
+      await installMockGateway(page, {
+        ...coldOpenScenario(),
+        sessionKey: HIDDEN_BOARD_SESSION_KEY,
+      });
+      await page.goto(`${suite.server.baseUrl}chat`);
+      await waitForControlUiGatewayReady(page);
+
+      const panel = page.locator(".sidebar-region__right-runtime .side-panel");
+      await panel.locator(".side-panel-empty--selector").waitFor();
+      expect(await panel.locator("wa-tab").count()).toBe(0);
+
+      await panel.getByRole("button", { name: "Close", exact: true }).click();
+      await expect.poll(() => panel.count()).toBe(0);
+    } finally {
+      await suite.closeBrowserContext(context);
+    }
+  });
+
   it("preserves the production header-action shapes for Side chat and Discussion", async () => {
     const context = await suite.newBrowserContext({ serviceWorkers: "block" });
     const page = await context.newPage();
diff --git a/ui/src/pages/chat/sidebar-layout.ts b/ui/src/pages/chat/sidebar-layout.ts
index d3af78623f69..222562fa069f 100644
--- a/ui/src/pages/chat/sidebar-layout.ts
+++ b/ui/src/pages/chat/sidebar-layout.ts
@@ -121,7 +121,6 @@ export function closeSlot(layout: SidebarLayout, slot: SidebarSlotId): SidebarLa
     .find((entry) => entry.slot === slot);
   if (panel) {
     removePanel(next, panel.id);
-    next.open = true;
   }
   return next;
 }