fix(v2): a phone first login lands in the workspace thread

frontend/src/v2/__tests__/V2LayoutSelection.test.tsx

@@ -2,7 +2,7 @@
 import React from 'react';
 import { fireEvent, render, screen, waitFor } from '@testing-library/react';
 import {
-  MemoryRouter, Route, Routes, useLocation,
+  MemoryRouter, Route, Routes, useLocation, useNavigate,
 } from 'react-router-dom';
 import V2Layout from '../components/V2Layout';
 import type { V2Pod } from '../hooks/useV2Pods';
@@ -52,6 +52,31 @@ const CurrentPath = () => {
   return <span data-testid="current-path">{location.pathname}</span>;
 };
 
+// A path probe that can also step back through the router's own history, which
+// is the only way jsdom can tell a `replace` from a `push`.
+const CurrentPathWithBack = () => {
+  const location = useLocation();
+  const navigate = useNavigate();
+  return (
+    <>
+      <span data-testid="current-path">{location.pathname}</span>
+      <button type="button" onClick={() => navigate(-1)}>back</button>
+    </>
+  );
+};
+
+const usePhoneViewport = () => {
+  Object.defineProperty(window, 'matchMedia', {
+    configurable: true,
+    writable: true,
+    value: jest.fn((query: string) => ({
+      matches: query === '(max-width: 760px)',
+      addEventListener: jest.fn(),
+      removeEventListener: jest.fn(),
+    })),
+  });
+};
+
 const hqPod: V2Pod = {
   _id: 'hq',
   name: 'Commonly HQ',
@@ -86,6 +111,21 @@ const renderAutoLayout = () => render(
   </MemoryRouter>,
 );
 
+// The app's real shell: `/v2` mounts the auto selector, and the pod route mounts
+// the param shell (V2App.tsx:127 / :165), which is the instance that records the
+// visit. A test that only mounts the auto layout cannot see LAST_POD_KEY at all.
+const renderAutoIntoParamShell = () => render(
+  <MemoryRouter initialEntries={['/v2']}>
+    <Routes>
+      <Route path="/v2" element={<V2Layout selectionMode="auto" />} />
+      <Route
+        path="/v2/pods/:podId"
+        element={<><V2Layout selectionMode="param" /><CurrentPath /></>}
+      />
+    </Routes>
+  </MemoryRouter>,
+);
+
 describe('V2Layout default pod selection', () => {
   beforeEach(() => {
     jest.clearAllMocks();
@@ -119,6 +159,54 @@ describe('V2Layout default pod selection', () => {
     expect(screen.queryByRole('button', { name: 'toggle inspector' })).not.toBeInTheDocument();
   });
 
+  test('a phone first login lands in the workspace thread, and the list is where you come back to', async () => {
+    // TASK-144. The list is the right landing for a phone that has a pod to
+    // return to; a device that has never opened one has nothing to list, so the
+    // welcome thread is the first screen. The same redirect is what records the
+    // pod — which is why the back arrow lands on a list that then stays put.
+    usePhoneViewport();
+    expect(localStorage.getItem('v2:lastPodId')).toBeNull();
+
+    const first = renderAutoIntoParamShell();
+    await waitFor(() => {
+      expect(screen.getByTestId('current-path')).toHaveTextContent('/v2/pods/workspace');
+    });
+    // Written by the param shell that the redirect lands on — the same effect
+    // that runs when a returning user taps a pod.
+    await waitFor(() => expect(localStorage.getItem('v2:lastPodId')).toBe('workspace'));
+    first.unmount();
+
+    // ...and the next /v2 on this device is the list, with no second redirect.
+    renderAutoLayout();
+    await waitFor(() => {
+      expect(screen.getByTestId('pods-sidebar')).toHaveAttribute('data-variant', 'page');
+    });
+    expect(screen.queryByTestId('current-path')).not.toBeInTheDocument();
+  });
+
+  test('a phone first login replaces, so back does not bounce through the list', async () => {
+    usePhoneViewport();
+    render(
+      <MemoryRouter initialEntries={['/v2']}>
+        <Routes>
+          <Route path="/v2" element={<V2Layout selectionMode="auto" />} />
+          <Route
+            path="/v2/pods/:podId"
+            element={<><V2Layout selectionMode="param" /><CurrentPathWithBack /></>}
+          />
+        </Routes>
+      </MemoryRouter>,
+    );
+
+    await waitFor(() => {
+      expect(screen.getByTestId('current-path')).toHaveTextContent('/v2/pods/workspace');
+    });
+    fireEvent.click(screen.getByRole('button', { name: 'back' }));
+    // A push would leave /v2 underneath, so one step back would re-resolve the
+    // landing; a replace leaves nothing to step back into.
+    expect(screen.getByTestId('current-path')).toHaveTextContent('/v2/pods/workspace');
+  });
+
   test('keeps the create-pod query on /v2 until the sidebar finishes the round trip', async () => {
     render(
       <MemoryRouter initialEntries={['/v2?newPod=1']}>

frontend/src/v2/components/V2Layout.tsx

@@ -147,11 +147,21 @@ const V2Layout: React.FC<V2LayoutProps> = ({ selectionMode = 'auto' }) => {
     recordPodVisit(paramPodId);
   }, [paramPodId]);
 
-  // Desktop only: resume the last valid pod. A new user without history lands
-  // in their self-created invite-only workspace rather than the auto-joined HQ.
-  // The phone never redirects: `/v2` is the pods list page there.
+  // Resume the last valid pod; a new user without history lands in their
+  // self-created invite-only workspace rather than the auto-joined HQ.
+  //
+  // The phone normally stays on the list — `/v2` IS the pods list page there
+  // (#1578 direction C) — and that stays true for anyone who has opened a pod on
+  // this device. The exception is a device that has never opened one, which is
+  // every first login: the list has nothing to return to, and the workspace
+  // thread with its welcome and composer is the actual first screen. So the same
+  // resolution runs there too, exactly once. The redirect is self-limiting: it
+  // sets LAST_POD_KEY (the paramPodId effect above), so the next `/v2` — the
+  // thread's back arrow — finds the key set and stays on the list, and the
+  // redirect is a `replace`, so browser-back does not bounce through it either.
   useEffect(() => {
-    if (selectionMode !== 'auto' || paramPodId || loading || phone || createFromConnectors) return;
+    if (selectionMode !== 'auto' || paramPodId || loading || createFromConnectors) return;
+    if (phone && readLastPodId()) return;
     if (pods.length === 0) return;
 
     const lastPodId = readLastPodId();