fix(webui): preserve named pane groups

webui/src/App.tsx

@@ -2154,9 +2154,16 @@ function Shell({
     const hasAutomations = (pendingDelete.automations?.length ?? 0) > 0;
     const deletingActive = activeKey !== null && deletingKeys.has(activeKey);
     const currentIndex = topicSessions.findIndex((s) => s.key === activeKey);
+    const availableKeys = new Set(topicSessions.map((session) => session.key));
+    const siblingFallbackKey = deletingActive
+      ? activeTabState?.paneKeys.find((key) => (
+          !deletingKeys.has(key) && availableKeys.has(key)
+        )) ?? null
+      : null;
     const fallbackKey = deletingActive
       ? (
-          topicSessions.slice(currentIndex + 1).find((session) => (
+          siblingFallbackKey
+          ?? topicSessions.slice(currentIndex + 1).find((session) => (
             !deletingKeys.has(session.key)
           ))?.key
           ?? topicSessions.slice(0, Math.max(0, currentIndex)).reverse().find((session) => (
@@ -2191,7 +2198,7 @@ function Shell({
     } catch (e) {
       console.error("Failed to delete session", e);
     }
-  }, [pendingDelete, deleteChat, activeKey, navigate, topicSessions]);
+  }, [pendingDelete, deleteChat, activeKey, activeTabState, navigate, topicSessions]);
 
   const onRequestDeleteMany = useCallback(async (items: SidebarDeleteItem[]) => {
     const uniqueItems = Array.from(new Map(items.map((item) => [item.key, item])).values());

webui/src/components/workbench/workbench-model.ts

@@ -72,9 +72,10 @@ function normalizeTab(value: unknown): WorkbenchTabState {
     ...requestedLayoutPaneKeys,
     ...paneKeys.filter((key) => !requestedLayoutPaneKeys.includes(key)),
   ];
+  const title = normalizeTitle(candidate.title);
   return {
-    explicit: candidate.explicit === true,
-    title: normalizeTitle(candidate.title),
+    explicit: candidate.explicit === true || title !== null,
+    title,
     paneKeys,
     layoutPaneKeys,
     layout: isLayout(candidate.layout) ? candidate.layout : "columns",
@@ -309,7 +310,9 @@ export function renameWorkbenchTab(
   const normalized = normalizeTitle(title);
   if (!normalized) return state;
   return updateTab(state, tabKey, (tab) => (
-    tab.title === normalized ? tab : { ...tab, title: normalized }
+    tab.title === normalized && tab.explicit
+      ? tab
+      : { ...tab, explicit: true, title: normalized }
   ));
 }
 

webui/src/tests/app-layout.test.tsx

@@ -3414,6 +3414,23 @@ describe("App layout", () => {
       expect(restoredGrid).toHaveAttribute("data-layout", "rows");
     });
 
+    const alphaGroupButton = within(sidebar).getByRole("button", {
+      name: "Group: Alpha",
+    });
+    const alphaGroup = alphaGroupButton.closest("[data-sidebar-tab-group]") as HTMLElement;
+    fireEvent.pointerDown(within(alphaGroup).getByLabelText("Topic actions for Alpha"), {
+      button: 0,
+      ctrlKey: false,
+    });
+    fireEvent.click(await screen.findByRole("menuitem", { name: "Rename" }));
+    const renameDialog = await screen.findByRole("dialog", { name: "Rename group" });
+    fireEvent.change(within(renameDialog).getByPlaceholderText("Group name"), {
+      target: { value: "Research" },
+    });
+    fireEvent.click(within(renameDialog).getByRole("button", { name: "Save" }));
+    expect(await within(sidebar).findByRole("button", { name: "Group: Research" }))
+      .toBeInTheDocument();
+
     fireEvent.pointerDown(within(sidebar).getByRole("button", {
       name: "New topic pane actions",
     }), { button: 0, ctrlKey: false });
@@ -3421,9 +3438,93 @@ describe("App layout", () => {
       name: "Remove",
     }));
     await waitFor(() => expect(screen.getByTestId("pane-grid").children).toHaveLength(1));
+    const researchGroup = within(sidebar).getByRole("button", {
+      name: "Group: Research",
+    }).closest("[data-sidebar-tab-group]") as HTMLElement;
+    expect(within(researchGroup).getByRole("list", { name: "Panes in Research" }))
+      .toBeInTheDocument();
+    expect(within(researchGroup).getByRole("button", { name: "Alpha" }))
+      .toBeInTheDocument();
     expect(within(sidebar).getAllByRole("button", { name: "New topic" })).toHaveLength(2);
   });
 
+  it("keeps a named group and its remaining pane active after deleting a pane", async () => {
+    mockSessions = [
+      {
+        key: "websocket:new-pane",
+        channel: "websocket",
+        chatId: "new-pane",
+        createdAt: "2026-08-05T12:00:00Z",
+        updatedAt: "2026-08-05T12:00:00Z",
+        title: "New topic",
+        preview: "",
+      },
+      {
+        key: "websocket:unrelated",
+        channel: "websocket",
+        chatId: "unrelated",
+        createdAt: "2026-08-05T11:00:00Z",
+        updatedAt: "2026-08-05T11:00:00Z",
+        title: "Unrelated",
+        preview: "",
+      },
+      {
+        key: "websocket:alpha",
+        channel: "websocket",
+        chatId: "alpha",
+        createdAt: "2026-08-05T10:00:00Z",
+        updatedAt: "2026-08-05T10:00:00Z",
+        title: "Alpha",
+        preview: "",
+      },
+    ];
+    window.history.replaceState(null, "", "/#/chat/websocket%3Anew-pane");
+    vi.stubGlobal("fetch", vi.fn().mockImplementation(async (url: string | URL | Request) => {
+      if (String(url) === "/api/webui/sidebar-state") {
+        return {
+          ok: true,
+          json: async () => ({
+            workbench: {
+              version: 1,
+              tabs: {
+                "tab:websocket:alpha": {
+                  explicit: false,
+                  title: "Research",
+                  paneKeys: ["websocket:alpha", "websocket:new-pane"],
+                  layoutPaneKeys: ["websocket:alpha", "websocket:new-pane"],
+                  layout: "columns",
+                  splitRatios: [],
+                },
+              },
+            },
+          }),
+        };
+      }
+      return { ok: false, status: 404 };
+    }));
+
+    render(<App />);
+
+    await waitFor(() => expect(connectSpy).toHaveBeenCalled());
+    const sidebar = screen.getByRole("navigation", { name: "Sidebar navigation" });
+    expect(await within(sidebar).findByRole("button", { name: "Group: Research" }))
+      .toBeInTheDocument();
+    fireEvent.pointerDown(within(sidebar).getByRole("button", {
+      name: "New topic pane actions",
+    }), { button: 0, ctrlKey: false });
+    fireEvent.click(await screen.findByRole("menuitem", { name: "Delete" }));
+    expect(await screen.findByText("Delete this topic?")).toBeInTheDocument();
+    fireEvent.click(screen.getByRole("button", { name: "Delete" }));
+
+    await waitFor(() => expect(deleteChatSpy).toHaveBeenCalledWith("websocket:new-pane"));
+    await waitFor(() => expect(window.location.hash).toBe("#/chat/websocket%3Aalpha"));
+    expect(within(sidebar).getByRole("button", { name: "Group: Research" }))
+      .toBeInTheDocument();
+    expect(screen.getByTestId("pane-grid").children).toHaveLength(1);
+    expect(screen.getByTestId("pane-grid").firstElementChild)
+      .toHaveAttribute("aria-label", "Alpha");
+  }, 15_000);
+
   it("opens search from the keyboard shortcut", async () => {
     mockSessions = [
       {

webui/src/tests/workbench-model.test.ts

@@ -53,7 +53,7 @@ describe("workbench model", () => {
     state = renameWorkbenchTab(state, tabKey, "Research");
 
     expect(workbenchTab(state, tabKey)).toEqual({
-      explicit: false,
+      explicit: true,
       title: "Research",
       paneKeys: ["pane-a", "pane-b"],
       layoutPaneKeys: ["pane-a", "pane-b"],
@@ -62,6 +62,24 @@ describe("workbench model", () => {
     });
   });
 
+  it("preserves a named group when a pane is detached", () => {
+    let state = addWorkbenchPane(EMPTY_WORKBENCH_STATE, "pane-a", "pane-b");
+    const tabKey = workbenchTabForPane(state, "pane-a").tabKey;
+    state = renameWorkbenchTab(state, tabKey, "Research");
+    state = detachWorkbenchPane(state, tabKey, "pane-b");
+
+    expect(workbenchTab(state, tabKey)).toEqual({
+      explicit: true,
+      title: "Research",
+      paneKeys: ["pane-a"],
+      layoutPaneKeys: ["pane-a"],
+      layout: "columns",
+      splitRatios: [],
+    });
+    expect(normalizeWorkbenchState(state)).toEqual(state);
+    expect(reconcileWorkbench(state, new Set(["pane-a"]))).toEqual(state);
+  });
+
   it("detaches a pane without persisting its standalone projection", () => {
     let state = addWorkbenchPane(EMPTY_WORKBENCH_STATE, "pane-a", "pane-b");
     const tabKey = workbenchTabForPane(state, "pane-a").tabKey;
@@ -198,7 +216,7 @@ describe("workbench model", () => {
     );
 
     expect(workbenchTab(reconciled, "alpha")).toEqual({
-      explicit: false,
+      explicit: true,
       title: "Alpha",
       paneKeys: ["pane-a", "pane-b"],
       layoutPaneKeys: ["pane-a", "pane-b"],