fix: home tab, layout switch and missing layout fallbacks for looks

src/backend/database/routes/look.ts

@@ -13,6 +13,7 @@ import {
   LAYOUT_SETTING,
   LOOK_ID_PATTERN,
   THEME_SETTING,
+  installedLayoutIds,
   resolveDefaultLook,
   safeLayoutForced,
   unavailableLooks,
@@ -35,7 +36,7 @@ async function adminDefaults() {
  * /user-preferences/look:
  *   get:
  *     summary: Get the layout and theme to show the current user
- *     description: The user's own choice, the admin defaults, the default look of the bundled plugins, whether TERMIX_SAFE_LAYOUT forces the repair view, and installed layout or theme plugins that could not load. The browser resolves the final look from these.
+ *     description: The user's own choice, the admin defaults (a layout no installed plugin brings reads as null), the default look of the bundled plugins, whether TERMIX_SAFE_LAYOUT forces the repair view, and installed layout or theme plugins that could not load. The browser resolves the final look from these.
  *     tags:
  *       - User Preferences
  *     responses:
@@ -101,10 +102,14 @@ router.get("/", authenticateJWT, async (req: Request, res: Response) => {
     const preferences =
       await createCurrentUserPreferenceRepository().findByUserId(userId);
     const { loader } = getPluginRuntime();
+    const installed = installedLayoutIds(loader);
+    const known = (id: string | null | undefined) =>
+      id && installed.has(id) ? id : null;
+    const defaults = await adminDefaults();
     res.json({
-      layoutId: preferences?.layoutId ?? null,
+      layoutId: known(preferences?.layoutId),
       themeId: preferences?.themeId ?? null,
-      defaults: await adminDefaults(),
+      defaults: { ...defaults, layout: known(defaults.layout) },
       defaultLook: resolveDefaultLook(loader),
       safeLayout: safeLayoutForced(),
       unavailable: unavailableLooks(loader),

src/backend/plugins/looks.ts

@@ -14,6 +14,7 @@ export interface DefaultLook {
 
 interface LookLoader {
   get(pluginId: string): Pick<LoadedPlugin, "manifest"> | undefined;
+  list(): Array<Pick<LoadedPlugin, "manifest">>;
   skipped(): SkippedPlugin[];
 }
 
@@ -46,6 +47,24 @@ export function unavailableLooks(loader: LookLoader): SkippedPlugin[] {
     .filter((plugin) => plugin.layouts.length > 0 || plugin.themes.length > 0);
 }
 
+/**
+ * Layout ids some installed plugin brings, whether it runs, is turned off or
+ * failed to load. A choice outside this set was uninstalled, so the next
+ * choice down applies instead of the repair view.
+ */
+export function installedLayoutIds(loader: LookLoader): Set<string> {
+  const ids = new Set<string>();
+  for (const plugin of loader.list()) {
+    for (const layout of plugin.manifest.contributes?.layouts ?? []) {
+      ids.add(layout.id);
+    }
+  }
+  for (const plugin of loader.skipped()) {
+    for (const id of plugin.layouts) ids.add(id);
+  }
+  return ids;
+}
+
 /** TERMIX_SAFE_LAYOUT=1 starts everyone in the layout repair view. */
 export function safeLayoutForced(): boolean {
   const value = process.env.TERMIX_SAFE_LAYOUT?.trim().toLowerCase();

src/backend/tests/database/routes/look.test.ts

@@ -11,6 +11,7 @@ const state = vi.hoisted(() => ({
   audits: [] as unknown[],
   skipped: [] as unknown[],
   defaultLookIds: [] as string[],
+  installed: [] as string[],
 }));
 
 vi.mock("../../../utils/logger.js", () => ({
@@ -69,6 +70,15 @@ vi.mock("../../../plugins/index.js", () => ({
               },
             }
           : undefined,
+      list: () => [
+        {
+          manifest: {
+            contributes: {
+              layouts: state.installed.map((id) => ({ id, label: id })),
+            },
+          },
+        },
+      ],
       skipped: () => state.skipped,
     },
   }),
@@ -90,6 +100,7 @@ beforeEach(async () => {
   state.audits = [];
   state.skipped = [];
   state.defaultLookIds = [];
+  state.installed = [];
   delete process.env.TERMIX_SAFE_LAYOUT;
 
   const app = express();
@@ -133,6 +144,7 @@ describe("GET /user-preferences/look", () => {
 
   it("returns the user's pick, the admin defaults and the default look", async () => {
     state.prefs = { layoutId: "mine", themeId: "nord" };
+    state.installed = ["mine", "admin-layout"];
     state.settings.set("ui.layout", "admin-layout");
     state.settings.set("ui.theme", "gruvbox");
     state.defaultLookIds = ["shipped-look"];
@@ -162,6 +174,31 @@ describe("GET /user-preferences/look", () => {
   });
 });
 
+describe("GET /user-preferences/look with an uninstalled layout", () => {
+  it("drops a choice no installed plugin brings, so the next one applies", async () => {
+    state.prefs = { layoutId: "deleted", themeId: null };
+    state.settings.set("ui.layout", "also-deleted");
+    state.installed = ["kept"];
+    const { body } = await getLook();
+    expect(body.layoutId).toBeNull();
+    expect(body.defaults.layout).toBeNull();
+  });
+
+  it("keeps a choice whose plugin failed to load, for the repair view", async () => {
+    state.prefs = { layoutId: "b", themeId: null };
+    state.skipped = [
+      {
+        id: "broken",
+        version: "1.0.0",
+        layouts: ["b"],
+        themes: [],
+        error: "x",
+      },
+    ];
+    expect((await getLook()).body.layoutId).toBe("b");
+  });
+});
+
 describe("PUT /user-preferences/look/defaults", () => {
   it("is for admins only", async () => {
     const { status } = await putDefaults({ layout: "x" });

src/backend/tests/plugins/looks.test.ts

@@ -6,6 +6,7 @@ vi.mock("../../plugins/bundled-index.js", () => ({
 }));
 
 import {
+  installedLayoutIds,
   resolveDefaultLook,
   safeLayoutForced,
   unavailableLooks,
@@ -23,6 +24,10 @@ function loaderWith(
       plugins[id]
         ? ({ manifest: { contributes: plugins[id] } } as never)
         : undefined,
+    list: () =>
+      Object.values(plugins).map(
+        (contributes) => ({ manifest: { contributes } }) as never,
+      ),
     skipped: () => skipped,
   };
 }
@@ -103,3 +108,14 @@ describe("safeLayoutForced", () => {
     expect(safeLayoutForced()).toBe(false);
   });
 });
+
+describe("installedLayoutIds", () => {
+  it("lists layouts of loaded and skipped plugins", () => {
+    const ids = installedLayoutIds(
+      loaderWith({ a: { layouts: [{ id: "one" }], themes: [{ id: "t" }] } }, [
+        { id: "b", version: null, layouts: ["two"], themes: [], error: "x" },
+      ]),
+    );
+    expect([...ids].sort()).toEqual(["one", "two"]);
+  });
+});

src/ui/shell/controller/ShellControllerProvider.tsx

@@ -68,9 +68,10 @@ export function useTabStageStore(): TabStageStore {
  * renders it inside the scope its tab-close questions should show in.
  */
 export function ShellConfirmCapture(): null {
-  const { confirmRef } = useShellController();
+  // Optional, so the repair view still draws when the shell itself is broken.
+  const controller = useOptionalShellController();
   const confirm = useConfirm();
-  confirmRef.current = confirm;
+  if (controller) controller.confirmRef.current = confirm;
   return null;
 }
 

src/ui/shell/controller/plugin-shell.ts

@@ -51,13 +51,22 @@ export function usePluginShell(pluginId: string): PluginShellController | null {
     () => (hosts ?? []).map((host) => toPluginHostRecord(host, pluginId)),
     [hosts, pluginId],
   );
+  // The shell always keeps a home tab. A layout that registers no tab type
+  // for it never sees it, so it has no dead tab to draw.
+  const hasHome = useTabTypes().some((type) => type.id === "dashboard");
 
   if (!shell) return null;
   const { tabs, split, regions } = shell;
+  const shown = (list: typeof tabs.list) =>
+    (hasHome
+      ? list
+      : list.filter(
+          (tab) => tab.type !== "dashboard",
+        )) as unknown as ShellTabState[];
   return {
     tabs: {
-      list: tabs.list as unknown as ShellTabState[],
-      topLevel: tabs.topLevel as unknown as ShellTabState[],
+      list: shown(tabs.list),
+      topLevel: shown(tabs.topLevel),
       activeId: tabs.activeId,
       ready: tabs.ready,
       showNumbers: tabs.showNumbers,

src/ui/shell/layout/LayoutHost.tsx

@@ -1,4 +1,11 @@
-import { Component, useMemo, useState, type ReactNode } from "react";
+import {
+  Component,
+  useEffect,
+  useMemo,
+  useRef,
+  useState,
+  type ReactNode,
+} from "react";
 import { useIsMobile } from "@/hooks/use-mobile";
 import { isElectron } from "@/lib/electron";
 import { usePluginStore } from "@/plugin-host/plugin-store";
@@ -12,6 +19,7 @@ import { layoutStatus } from "@/look/layout-status";
 import { safeLayoutInUrl } from "@/look/resolve-look";
 import { useLookTheme } from "@/look/use-look-theme";
 import { RepairView } from "@/look/RepairView";
+import { useOptionalShellController } from "@/shell/controller/ShellControllerProvider";
 
 /** Catches a crash while a layout draws, so the repair view can take over. */
 class LayoutErrorBoundary extends Component<
@@ -34,6 +42,39 @@ class LayoutErrorBoundary extends Component<
   }
 }
 
+/**
+ * Only the chosen layout plugin runs, so the tabs the old one brought (its
+ * settings screen, say) cannot draw after a switch. Close them; the home tab
+ * stays, since core keeps it in every layout.
+ */
+function useCloseLeftoverTabs(layoutId: string, tabTypes: string[]) {
+  const shell = useOptionalShellController();
+  const previous = useRef<{ layoutId: string; tabTypes: string[] } | null>(
+    null,
+  );
+  const current = { layoutId, tabTypes };
+  const latest = useRef(current);
+  latest.current = current;
+  const shellRef = useRef(shell);
+  shellRef.current = shell;
+
+  useEffect(() => {
+    const before = previous.current;
+    previous.current = latest.current;
+    if (!before || before.layoutId === layoutId || !shellRef.current) return;
+    const kept = new Set(latest.current.tabTypes);
+    for (const tab of shellRef.current.tabs.list) {
+      if (
+        tab.id !== "dashboard" &&
+        before.tabTypes.includes(tab.type) &&
+        !kept.has(tab.type)
+      ) {
+        void shellRef.current.tabs.close(tab.id);
+      }
+    }
+  }, [layoutId]);
+}
+
 interface CrashState {
   layoutId: string | null;
   count: number;
@@ -64,6 +105,10 @@ export function LayoutHost() {
   const owner = [...store.records.values()].find((record) =>
     record.summary.contributes?.layouts?.some((l) => l.id === layoutId),
   );
+  useCloseLeftoverTabs(
+    layoutId,
+    owner?.summary.contributes?.tabs?.map((tab) => tab.id) ?? [],
+  );
   const status = layoutStatus({
     layoutId,
     safeFromUrl: safeLayoutInUrl(window.location.search),

src/ui/shell/tabUtils.tsx

@@ -206,6 +206,8 @@ export function renderTabContent(tab: Tab, context: TabRenderContext) {
 
     default: {
       const def = getTabType(tab.type);
+      // The home tab is empty until the layout gives it a tab type.
+      if (!def && tab.type === "dashboard") return null;
       if (!def) {
         const panel = getPanel(tab.type);
         if (panel) {

src/ui/tests/shell/controller/plugin-shell.test.tsx

@@ -30,8 +30,12 @@ vi.mock("@/hooks/use-permissions", () => ({
 
 import { ShellControllerProvider } from "@/shell/controller/ShellControllerProvider";
 import { usePluginShell } from "@/shell/controller/plugin-shell";
+import { registerTabType, resetTabTypes } from "@/shell/tab-registry";
 
-afterEach(cleanup);
+afterEach(() => {
+  cleanup();
+  resetTabTypes();
+});
 
 let shell: PluginShell | null = null;
 function Capture() {
@@ -67,4 +71,22 @@ describe("usePluginShell", () => {
     act(() => shell!.palette.open());
     expect(shell!.palette.isOpen).toBe(true);
   });
+
+  it("hides the home tab from a layout that gives it no tab type", async () => {
+    render(
+      <ShellControllerProvider username="ada" onLogout={() => {}}>
+        <Capture />
+      </ShellControllerProvider>,
+    );
+    await waitFor(() => expect(shell).not.toBeNull());
+    expect(shell!.tabs.list.map((tab) => tab.type)).not.toContain("dashboard");
+    expect(shell!.tabs.topLevel).toEqual([]);
+
+    act(() => {
+      registerTabType({ id: "dashboard", component: () => null });
+    });
+    await waitFor(() =>
+      expect(shell!.tabs.topLevel.map((tab) => tab.id)).toEqual(["dashboard"]),
+    );
+  });
 });

src/ui/tests/shell/layout/LayoutHost.repair.test.tsx

@@ -0,0 +1,292 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import {
+  act,
+  cleanup,
+  fireEvent,
+  render,
+  screen,
+  waitFor,
+} from "@testing-library/react";
+
+// The repair drill: a broken layout, the real repair view, the real look
+// store. Only the server, the plugin loader and the Plugins tab flows are fakes.
+
+vi.mock("react-i18next", () => ({
+  useTranslation: () => ({
+    t: (key: string, options?: Record<string, unknown>) =>
+      options && typeof options === "object" && !("defaultValue" in options)
+        ? `${key}:${JSON.stringify(options)}`
+        : ((options?.defaultValue as string | undefined) ?? key),
+    i18n: { language: "en" },
+  }),
+  initReactI18next: { type: "3rdParty", init: () => {} },
+}));
+
+const permissions = vi.hoisted(() => ({ isAdmin: true }));
+vi.mock("@/hooks/use-permissions", () => ({
+  usePermissions: () => ({
+    isAdmin: permissions.isAdmin,
+    permissions: [],
+    loaded: true,
+    has: () => permissions.isAdmin,
+  }),
+}));
+
+const lookApi = vi.hoisted(() => ({
+  getLook: vi.fn(),
+  saveUserLook: vi.fn(async (_patch: Record<string, unknown>) => {}),
+  saveDefaultLook: vi.fn(async (defaults: Record<string, unknown>) => ({
+    layout: null,
+    theme: null,
+    ...defaults,
+  })),
+}));
+vi.mock("@/api/look-api", () => lookApi);
+
+const loader = vi.hoisted(() => ({
+  retryPluginFrontend: vi.fn(async () => {}),
+  syncPlugins: vi.fn(async () => {}),
+}));
+vi.mock("@/plugin-host/loader", () => loader);
+vi.mock("@/hooks/use-mobile", () => ({ useIsMobile: () => false }));
+vi.mock("sonner", () => ({ toast: { error: vi.fn(), success: vi.fn() } }));
+
+const manager = vi.hoisted(() => ({
+  requestUpdate: vi.fn(),
+  requestInstall: vi.fn(),
+  toggle: vi.fn(),
+  setConsent: vi.fn(),
+  confirmConsent: vi.fn(),
+}));
+vi.mock("@/plugins/use-plugins-manager", () => ({
+  usePluginsManager: () => ({
+    ...manager,
+    loading: false,
+    registryError: null,
+    consent: null,
+    busy: new Set<string>(),
+    plugins: [
+      {
+        id: "fancy-layout",
+        name: "Fancy",
+        installed: true,
+        enabled: true,
+        updateAvailable: true,
+        latestVersion: "1.1.0",
+        managedByServer: false,
+        bundled: false,
+        versions: [],
+      },
+      {
+        id: "paper-themes",
+        name: "Paper themes",
+        description: "Light themes",
+        installed: false,
+        enabled: false,
+        updateAvailable: false,
+        latestVersion: "1.0.0",
+        versions: [{ version: "1.0.0", capabilities: ["ui:theme"] }],
+      },
+    ],
+  }),
+}));
+
+import { LayoutHost } from "@/shell/layout/LayoutHost";
+import {
+  registerLayout,
+  resetRegisteredLayouts,
+  setPluginLayouts,
+} from "@/look/layout-registry";
+import { loadLook, resetLook } from "@/look/look-store";
+import {
+  markPluginsSettled,
+  resetPluginStore,
+  setFrontendState,
+  setPluginSummaries,
+} from "@/plugin-host/plugin-store";
+import type { PluginSummary } from "@/api/plugins-api";
+
+const fancyPlugin: PluginSummary = {
+  id: "fancy-layout",
+  name: "Fancy",
+  version: "1.0.0",
+  enabled: true,
+  state: "active",
+  frontend: true,
+  contributes: { layouts: [{ id: "fancy", label: "Fancy" }] },
+};
+
+async function start(look: {
+  layoutId?: string | null;
+  defaultLayout?: string | null;
+  summaries?: PluginSummary[];
+}) {
+  lookApi.getLook.mockResolvedValue({
+    layoutId: look.layoutId ?? null,
+    themeId: null,
+    defaults: { layout: look.defaultLayout ?? null, theme: null },
+    defaultLook: { layout: "classic", theme: "dark" },
+    safeLayout: false,
+    unavailable: [],
+  });
+  await loadLook();
+  setPluginSummaries(look.summaries ?? []);
+  markPluginsSettled();
+}
+
+function Broken(): never {
+  throw new Error("draw exploded");
+}
+// React reports crashes it caught; these are expected here.
+const expectedCrash = (event: ErrorEvent) => event.preventDefault();
+
+beforeEach(() => {
+  permissions.isAdmin = true;
+  resetLook();
+  resetPluginStore();
+  resetRegisteredLayouts();
+  for (const fn of [
+    ...Object.values(manager),
+    lookApi.saveUserLook,
+    lookApi.saveDefaultLook,
+  ]) {
+    fn.mockClear();
+  }
+  setPluginLayouts([
+    { id: "fancy", label: "Fancy", pluginId: "fancy-layout" },
+    { id: "classic", label: "Classic", pluginId: "classic-layout" },
+  ]);
+  registerLayout({ id: "classic", component: () => <p>classic layout</p> });
+  vi.spyOn(console, "error").mockImplementation(() => {});
+  window.addEventListener("error", expectedCrash);
+});
+
+afterEach(() => {
+  cleanup();
+  window.removeEventListener("error", expectedCrash);
+  vi.restoreAllMocks();
+});
+
+describe("layout repair drill", () => {
+  it("a layout that throws while drawing ends in the repair view, and switching gets out", async () => {
+    registerLayout({ id: "fancy", component: Broken });
+    await start({ layoutId: "fancy", summaries: [fancyPlugin] });
+    render(<LayoutHost />);
+
+    expect(await screen.findByText("draw exploded")).toBeTruthy();
+    fireEvent.click(screen.getByText("Classic"));
+    await waitFor(() =>
+      expect(lookApi.saveUserLook).toHaveBeenCalledWith({
+        layoutId: "classic",
+      }),
+    );
+    expect(await screen.findByText("classic layout")).toBeTruthy();
+  });
+
+  it("a layout whose activate threw shows the error, and reset brings the default look back", async () => {
+    await start({ layoutId: "fancy", summaries: [fancyPlugin] });
+    setFrontendState("fancy-layout", "failed", "activate exploded");
+    render(<LayoutHost />);
+
+    expect(await screen.findByText("activate exploded")).toBeTruthy();
+    fireEvent.click(screen.getByText("looks.repair.reset"));
+    await waitFor(() =>
+      expect(lookApi.saveUserLook).toHaveBeenCalledWith({ layoutId: null }),
+    );
+    expect(lookApi.saveUserLook).toHaveBeenCalledWith({ themeId: null });
+    expect(await screen.findByText("classic layout")).toBeTruthy();
+  });
+
+  it("an admin updates the broken plugin when the registry has a newer one", async () => {
+    await start({ layoutId: "fancy", summaries: [fancyPlugin] });
+    setFrontendState("fancy-layout", "failed", "activate exploded");
+    render(<LayoutHost />);
+
+    fireEvent.click(await screen.findByText(/looks\.repair\.update/));
+    expect(manager.requestUpdate).toHaveBeenCalledWith(
+      expect.objectContaining({ id: "fancy-layout" }),
+    );
+  });
+
+  it("an admin installs a layout or theme from the registries", async () => {
+    await start({ layoutId: "fancy", summaries: [fancyPlugin] });
+    setFrontendState("fancy-layout", "failed", "activate exploded");
+    render(<LayoutHost />);
+
+    fireEvent.click(await screen.findByText("looks.repair.install"));
+    expect(await screen.findByText("Paper themes")).toBeTruthy();
+    fireEvent.click(screen.getByText("looks.repair.installButton"));
+    expect(manager.requestInstall).toHaveBeenCalledWith(
+      expect.objectContaining({ id: "paper-themes" }),
+    );
+  });
+
+  it("someone who is not an admin gets switch and reset, and a note to ask an admin", async () => {
+    permissions.isAdmin = false;
+    await start({ layoutId: "fancy", summaries: [fancyPlugin] });
+    setFrontendState("fancy-layout", "failed", "activate exploded");
+    render(<LayoutHost />);
+
+    expect(await screen.findByText("looks.repair.askAdmin")).toBeTruthy();
+    expect(screen.queryByText(/looks\.repair\.update/)).toBeNull();
+    expect(screen.queryByText("looks.repair.install")).toBeNull();
+    expect(screen.getByText("looks.repair.reset")).toBeTruthy();
+    expect(screen.getByText("Classic")).toBeTruthy();
+  });
+
+  it("the user's own layout wins over the admin default", async () => {
+    registerLayout({ id: "fancy", component: () => <p>fancy layout</p> });
+    await start({
+      layoutId: "fancy",
+      defaultLayout: "classic",
+      summaries: [fancyPlugin],
+    });
+    render(<LayoutHost />);
+    expect(await screen.findByText("fancy layout")).toBeTruthy();
+  });
+
+  it("a layout the server dropped as uninstalled falls back to the admin default", async () => {
+    // The server answers null for a choice no installed plugin brings.
+    registerLayout({ id: "fancy", component: () => <p>fancy layout</p> });
+    await start({ layoutId: null, defaultLayout: "fancy" });
+    render(<LayoutHost />);
+    expect(await screen.findByText("fancy layout")).toBeTruthy();
+
+    cleanup();
+    resetLook();
+    await start({ layoutId: null, defaultLayout: null });
+    render(<LayoutHost />);
+    expect(await screen.findByText("classic layout")).toBeTruthy();
+  });
+
+  it("?safe-layout=1 opens the repair view over a working layout, and leaving it draws the layout", async () => {
+    window.history.replaceState(null, "", "/?safe-layout=1");
+    await start({ layoutId: "classic" });
+    render(<LayoutHost />);
+    expect(await screen.findByText("looks.repair.safeTitle")).toBeTruthy();
+    expect(screen.queryByText("looks.repair.retry")).toBeNull();
+
+    cleanup();
+    window.history.replaceState(null, "", "/");
+    render(<LayoutHost />);
+    expect(await screen.findByText("classic layout")).toBeTruthy();
+  });
+
+  it("TERMIX_SAFE_LAYOUT on the server opens the repair view for everyone", async () => {
+    lookApi.getLook.mockResolvedValue({
+      layoutId: "classic",
+      themeId: null,
+      defaults: { layout: null, theme: null },
+      defaultLook: { layout: "classic", theme: "dark" },
+      safeLayout: true,
+      unavailable: [],
+    });
+    await act(async () => {
+      await loadLook();
+    });
+    setPluginSummaries([]);
+    markPluginsSettled();
+    render(<LayoutHost />);
+    expect(await screen.findByText("looks.repair.safeTitle")).toBeTruthy();
+  });
+});

src/ui/tests/shell/layout/LayoutHost.test.tsx

@@ -1,5 +1,23 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
-import { cleanup, render, screen, waitFor } from "@testing-library/react";
+import { act, cleanup, render, screen, waitFor } from "@testing-library/react";
+
+vi.mock("@/main-axios", () => ({
+  getUserInfo: vi.fn(async () => ({ is_admin: false })),
+  getUserPreferences: vi.fn(async () => ({ reopenTabsOnLogin: false })),
+  saveUserPreferences: vi.fn(async () => {}),
+  getSSHHosts: vi.fn(async () => []),
+  getSSHFolders: vi.fn(async () => []),
+  getOpenTabs: vi.fn(async () => []),
+  getActiveSessions: vi.fn(async () => []),
+  addOpenTab: vi.fn(async () => {}),
+  deleteOpenTab: vi.fn(async () => {}),
+  patchOpenTab: vi.fn(async () => {}),
+  createSSHHost: vi.fn(async () => ({})),
+}));
+vi.mock("@/hooks/use-sync-status", () => ({
+  useSyncStatus: () => undefined,
+  useSyncAttentionCount: () => 0,
+}));
 
 const lookApi = vi.hoisted(() => ({
   getLook: vi.fn(),
@@ -36,7 +54,13 @@ vi.mock("@/look/RepairView", () => ({
 
 import { LayoutHost } from "@/shell/layout/LayoutHost";
 import { registerLayout, resetRegisteredLayouts } from "@/look/layout-registry";
-import { loadLook, resetLook } from "@/look/look-store";
+import { chooseLayout, loadLook, resetLook } from "@/look/look-store";
+import {
+  ShellControllerProvider,
+  useShellController,
+} from "@/shell/controller/ShellControllerProvider";
+import type { ShellController } from "@/shell/controller/types";
+import { registerTabType, resetTabTypes } from "@/shell/tab-registry";
 import {
   markPluginsSettled,
   resetPluginStore,
@@ -196,4 +220,65 @@ describe("LayoutHost", () => {
       expect(loader.retryPluginFrontend).toHaveBeenCalledWith("fancy-layout"),
     );
   });
+
+  it("closes the tabs the old layout plugin brought when the layout changes", async () => {
+    registerLayout({ id: "fancy", component: () => <p>fancy layout</p> });
+    registerLayout({ id: "plain", component: () => <p>plain layout</p> });
+    registerTabType({
+      id: "fancy-settings",
+      component: () => null,
+      hostless: true,
+      singleton: true,
+    });
+    registerTabType({
+      id: "notes",
+      component: () => null,
+      hostless: true,
+      multiInstance: true,
+    });
+    await start("fancy", [
+      plugin({
+        contributes: {
+          layouts: [{ id: "fancy", label: "Fancy" }],
+          tabs: [
+            {
+              id: "fancy-settings",
+              titleKey: "x",
+              icon: "Settings",
+              openFrom: [],
+            },
+          ],
+        },
+      }),
+      plugin({
+        id: "plain-layout",
+        contributes: { layouts: [{ id: "plain", label: "Plain" }] },
+      }),
+    ]);
+    let shell: ShellController | null = null;
+    function Capture() {
+      shell = useShellController();
+      return null;
+    }
+    render(
+      <ShellControllerProvider username="ada" onLogout={() => {}}>
+        <Capture />
+        <LayoutHost />
+      </ShellControllerProvider>,
+    );
+    await screen.findByText("fancy layout");
+    act(() => {
+      shell!.tabs.openSingleton("fancy-settings");
+      shell!.tabs.openMultiInstance("notes");
+    });
+    const types = () => shell!.tabs.list.map((tab) => tab.type).sort();
+    await waitFor(() =>
+      expect(types()).toEqual(["dashboard", "fancy-settings", "notes"]),
+    );
+
+    await act(() => chooseLayout("plain"));
+    await screen.findByText("plain layout");
+    await waitFor(() => expect(types()).toEqual(["dashboard", "notes"]));
+    resetTabTypes();
+  });
 });

src/ui/tests/shell/stage/TabPortals.test.tsx

@@ -0,0 +1,211 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { act, cleanup, render, screen, waitFor } from "@testing-library/react";
+import { useEffect, useRef, useState } from "react";
+
+vi.mock("@/main-axios", () => ({
+  getUserInfo: vi.fn(async () => ({ is_admin: false })),
+  getUserPreferences: vi.fn(async () => ({ reopenTabsOnLogin: false })),
+  saveUserPreferences: vi.fn(async () => {}),
+  getSSHHosts: vi.fn(async () => []),
+  getSSHFolders: vi.fn(async () => []),
+  getOpenTabs: vi.fn(async () => []),
+  getActiveSessions: vi.fn(async () => []),
+  addOpenTab: vi.fn(async () => {}),
+  deleteOpenTab: vi.fn(async () => {}),
+  patchOpenTab: vi.fn(async () => {}),
+  createSSHHost: vi.fn(async () => ({})),
+}));
+vi.mock("@/hooks/use-sync-status", () => ({
+  useSyncStatus: () => undefined,
+  useSyncAttentionCount: () => 0,
+}));
+const lookApi = vi.hoisted(() => ({
+  getLook: vi.fn(),
+  saveUserLook: vi.fn(async () => {}),
+  saveDefaultLook: vi.fn(),
+}));
+vi.mock("@/api/look-api", () => lookApi);
+vi.mock("@/plugin-host/loader", () => ({
+  retryPluginFrontend: vi.fn(async () => {}),
+  syncPlugins: vi.fn(async () => {}),
+}));
+vi.mock("@/hooks/use-mobile", () => ({ useIsMobile: () => false }));
+
+import type { TabRenderProps } from "@/shell/tab-registry";
+import { registerTabType, resetTabTypes } from "@/shell/tab-registry";
+import {
+  ShellControllerProvider,
+  useShellController,
+} from "@/shell/controller/ShellControllerProvider";
+import type { ShellController } from "@/shell/controller/types";
+import { TabPortals } from "@/shell/stage/TabPortals";
+import { TabStage } from "@/shell/stage/TabStage";
+import { LayoutHost } from "@/shell/layout/LayoutHost";
+import { registerLayout, resetRegisteredLayouts } from "@/look/layout-registry";
+import { chooseLayout, loadLook, resetLook } from "@/look/look-store";
+import {
+  markPluginsSettled,
+  resetPluginStore,
+  setPluginSummaries,
+} from "@/plugin-host/plugin-store";
+
+const mounts = { count: 0 };
+
+/** Stands in for a terminal: a session id and scrollback that a remount would lose. */
+function FakeTerminal({ tab }: TabRenderProps) {
+  const session = useRef(`session-${Math.random().toString(36).slice(2)}`);
+  const [lines, setLines] = useState<string[]>([]);
+  useEffect(() => {
+    mounts.count += 1;
+  }, []);
+  return (
+    <div data-testid={`term-${tab.id}`} data-session={session.current}>
+      <button type="button" onClick={() => setLines((l) => [...l, "line"])}>
+        write {tab.id}
+      </button>
+      <pre>{lines.join("\n")}</pre>
+    </div>
+  );
+}
+
+let shell: ShellController | null = null;
+function Capture() {
+  shell = useShellController();
+  return null;
+}
+
+// Two layouts that put the stage in very different places.
+function RailLayout() {
+  return (
+    <div data-testid="rail-layout" className="flex">
+      <nav>rail</nav>
+      <main>
+        <TabStage />
+      </main>
+    </div>
+  );
+}
+function TopBarLayout() {
+  return (
+    <div data-testid="topbar-layout">
+      <header>bar</header>
+      <section>
+        <div>
+          <TabStage />
+        </div>
+      </section>
+    </div>
+  );
+}
+
+function App() {
+  return (
+    <ShellControllerProvider username="ada" onLogout={() => {}}>
+      <Capture />
+      <LayoutHost />
+      <TabPortals />
+    </ShellControllerProvider>
+  );
+}
+
+beforeEach(async () => {
+  mounts.count = 0;
+  shell = null;
+  resetLook();
+  resetPluginStore();
+  resetRegisteredLayouts();
+  registerTabType({
+    id: "fake-terminal",
+    component: FakeTerminal,
+    hostless: true,
+    multiInstance: true,
+  });
+  registerLayout({ id: "rail", component: RailLayout });
+  registerLayout({ id: "topbar", component: TopBarLayout });
+  lookApi.getLook.mockResolvedValue({
+    layoutId: "rail",
+    themeId: null,
+    defaults: { layout: null, theme: null },
+    defaultLook: { layout: null, theme: null },
+    safeLayout: false,
+    unavailable: [],
+  });
+  await loadLook();
+  setPluginSummaries([]);
+  markPluginsSettled();
+});
+
+afterEach(() => {
+  cleanup();
+  resetTabTypes();
+});
+
+describe("TabPortals", () => {
+  it("keeps three sessions and their scrollback through a split and a layout switch", async () => {
+    render(<App />);
+    await screen.findByTestId("rail-layout");
+    await waitFor(() => expect(shell).not.toBeNull());
+
+    const ids: string[] = [];
+    for (let i = 0; i < 3; i += 1) {
+      act(() => {
+        ids.push(shell!.tabs.openMultiInstance("fake-terminal"));
+      });
+    }
+    const terms = await Promise.all(
+      ids.map((id) => screen.findByTestId(`term-${id}`)),
+    );
+    const sessions = terms.map((el) => el.dataset.session);
+    expect(mounts.count).toBe(3);
+
+    // Some output in every terminal.
+    for (const id of ids) act(() => screen.getByText(`write ${id}`).click());
+    const scrollback = () =>
+      terms.map((el) => el.querySelector("pre")!.textContent);
+    expect(scrollback()).toEqual(["line", "line", "line"]);
+
+    const check = () => {
+      ids.forEach((id, index) => {
+        const el = screen.getByTestId(`term-${id}`);
+        expect(el).toBe(terms[index]);
+        expect(el.dataset.session).toBe(sessions[index]);
+      });
+      expect(scrollback()).toEqual(["line", "line", "line"]);
+      expect(mounts.count).toBe(3);
+    };
+
+    // The second one into a split, then back out.
+    const moved = ids[1];
+    act(() => {
+      shell!.split.handleAction({ kind: "split", tabId: moved, edge: "right" });
+    });
+    await waitFor(() =>
+      expect(terms[1].closest("[data-split-pane-id]")).not.toBeNull(),
+    );
+    check();
+    const splitId = shell!.split.active!.id;
+    act(() => {
+      shell!.split.handleAction({ kind: "unsplit", splitTabId: splitId });
+    });
+    await waitFor(() =>
+      expect(terms[1].closest("[data-split-pane-id]")).toBeNull(),
+    );
+    check();
+
+    // Switch layouts and back.
+    await act(() => chooseLayout("topbar"));
+    const topbar = await screen.findByTestId("topbar-layout");
+    await waitFor(() =>
+      terms.forEach((el) => expect(topbar.contains(el)).toBe(true)),
+    );
+    expect(screen.queryByTestId("rail-layout")).toBeNull();
+    check();
+
+    await act(() => chooseLayout("rail"));
+    const rail = await screen.findByTestId("rail-layout");
+    await waitFor(() =>
+      terms.forEach((el) => expect(rail.contains(el)).toBe(true)),
+    );
+    check();
+  });
+});

src/ui/tests/shell/tabUtils.test.tsx

@@ -49,6 +49,10 @@ describe("renderTabContent", () => {
     expect(screen.getByText("tab")).toBeInTheDocument();
     expect(screen.queryByText("panel")).toBeNull();
   });
+
+  it("draws nothing for the home tab when no layout gave it a type", () => {
+    expect(renderTabContent(tabOf("dashboard"), { shell })).toBeNull();
+  });
 });
 
 describe("promotableIds", () => {