fix(auth): 'Sign in as a different user' performs full logout

The NoAccessPage button previously only called nav.push('/login'),
leaving the session cookie, React Query cache, and local auth state
intact. AuthInitializer then silently re-authenticates and bounces the
user right back to the workspace URL — the button appeared broken.

Extract the logout flow (clear per-workspace storage, clear cookies,
clear multica_tabs, queryClient.clear(), authStore.logout(), navigate
to /login) into a shared useLogout() hook in packages/views/auth/.
AppSidebar and NoAccessPage both use it now; any future logout entry
point can too.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/views/auth/index.ts

@@ -1 +1,2 @@
 export { LoginPage, validateCliCallback } from "./login-page";
+export { useLogout } from "./use-logout";

packages/views/auth/use-logout.ts

@@ -0,0 +1,63 @@
+"use client";
+
+import { useCallback } from "react";
+import { useQueryClient } from "@tanstack/react-query";
+import { useAuthStore } from "@multica/core/auth";
+import { workspaceKeys } from "@multica/core/workspace/queries";
+import { clearWorkspaceStorage, defaultStorage } from "@multica/core/platform";
+import { paths } from "@multica/core/paths";
+import type { Workspace } from "@multica/core/types";
+import { useNavigation } from "../navigation";
+
+/**
+ * Performs a complete logout: clears per-workspace client storage, legacy
+ * cookies, the desktop tab state, the entire React Query cache, the
+ * in-memory auth store, and finally navigates to /login. Wraps what was
+ * previously duplicated in app-sidebar's logout handler so NoAccessPage's
+ * "Sign in as a different user" and any future entry point can use the
+ * same flow.
+ *
+ * Without a unified logout, callers that only do `navigate('/login')`
+ * leave the auth cookie + React Query cache + local storage intact —
+ * AuthInitializer then silently re-authenticates the user on the login
+ * page and redirects them back where they came from.
+ */
+export function useLogout() {
+  const queryClient = useQueryClient();
+  const authLogout = useAuthStore((s) => s.logout);
+  const { push } = useNavigation();
+
+  return useCallback(() => {
+    // Clear workspace-scoped storage for every workspace this user has
+    // access to, BEFORE clearing the React Query cache (which holds the
+    // workspace list). Otherwise per-workspace drafts/chat/etc would leak
+    // to the next user on this device.
+    const cachedWorkspaces =
+      queryClient.getQueryData<Workspace[]>(workspaceKeys.list()) ?? [];
+    for (const ws of cachedWorkspaces) {
+      clearWorkspaceStorage(defaultStorage, ws.slug);
+    }
+
+    // Clear the last-workspace-slug cookie. Otherwise on a shared device
+    // the next user gets redirected by the proxy to the previous user's
+    // last workspace, then bounced to NoAccessPage — confusing.
+    if (typeof document !== "undefined") {
+      document.cookie =
+        "last_workspace_slug=; path=/; max-age=0; SameSite=Lax";
+    }
+
+    // Clear desktop tab state. Tab paths can contain workspace slugs and
+    // issue UUIDs that must not survive across user sessions on a shared
+    // machine. No-op on web (web doesn't write this key).
+    defaultStorage.removeItem("multica_tabs");
+
+    queryClient.clear();
+    authLogout();
+
+    // Navigate to /login explicitly. authLogout() clears state but doesn't
+    // move the URL — without this the caller might be on a workspace URL
+    // which renders null (layout gates on user) and leaves the user
+    // stuck on a blank page.
+    push(paths.login());
+  }, [queryClient, authLogout, push]);
+}

packages/views/layout/app-sidebar.tsx

@@ -75,8 +75,8 @@ import { useModalStore } from "@multica/core/modals";
 import { useMyRuntimesNeedUpdate } from "@multica/core/runtimes/hooks";
 import { pinListOptions } from "@multica/core/pins/queries";
 import { useDeletePin, useReorderPins } from "@multica/core/pins/mutations";
-import type { PinnedItem, Workspace } from "@multica/core/types";
-import { clearWorkspaceStorage, defaultStorage } from "@multica/core/platform";
+import type { PinnedItem } from "@multica/core/types";
+import { useLogout } from "../auth";
 
 // Nav items reference WorkspacePaths method names so they can be resolved
 // against the current workspace slug at render time (see AppSidebar body).
@@ -196,7 +196,7 @@ export function AppSidebar({ topSlot, searchSlot, headerClassName, headerStyle }
   const { pathname, push } = useNavigation();
   const user = useAuthStore((s) => s.user);
   const userId = useAuthStore((s) => s.user?.id);
-  const authLogout = useAuthStore((s) => s.logout);
+  const logout = useLogout();
   const workspace = useCurrentWorkspace();
   const p = useWorkspacePaths();
   const { data: workspaces = [] } = useQuery(workspaceListOptions());
@@ -262,33 +262,6 @@ export function AppSidebar({ topSlot, searchSlot, headerClassName, headerStyle }
       queryClient.invalidateQueries({ queryKey: workspaceKeys.myInvitations() });
     },
   });
-  const logout = () => {
-    // Clear workspace-scoped storage for every workspace this user has access to,
-    // before clearing the React Query cache (which holds the workspace list).
-    // Otherwise per-workspace drafts/chat/etc would leak to the next user on this device.
-    const cachedWorkspaces =
-      queryClient.getQueryData<Workspace[]>(workspaceKeys.list()) ?? [];
-    for (const ws of cachedWorkspaces) {
-      clearWorkspaceStorage(defaultStorage, ws.slug);
-    }
-    // Clear the last-workspace-slug cookie. Otherwise on a shared device the
-    // next user gets redirected by the proxy to the previous user's last
-    // workspace (then bounced to NoAccessPage by the layout — confusing).
-    if (typeof document !== "undefined") {
-      document.cookie = "last_workspace_slug=; path=/; max-age=0; SameSite=Lax";
-    }
-    // Clear desktop tab state. Tab paths can contain issue UUIDs which must
-    // not survive across user sessions on a shared machine. No-op on web
-    // (web doesn't write this key).
-    defaultStorage.removeItem("multica_tabs");
-    queryClient.clear();
-    authLogout();
-    // Navigate to /login explicitly. authLogout() clears state but doesn't
-    // move the URL, and the current URL is a workspace-scoped path that
-    // means nothing without auth — without this redirect the user stays on
-    // /{slug}/... and the layout renders null (blank screen).
-    push(paths.login());
-  };
 
   // Global "C" shortcut to open create-issue modal (like Linear)
   useEffect(() => {

packages/views/workspace/no-access-page.test.tsx

@@ -3,12 +3,21 @@ import { render, screen, fireEvent } from "@testing-library/react";
 import { NoAccessPage } from "./no-access-page";
 
 const navigate = vi.fn();
+const logout = vi.fn();
+
 vi.mock("../navigation", () => ({
   useNavigation: () => ({ push: navigate, replace: navigate }),
 }));
 
+vi.mock("../auth", () => ({
+  useLogout: () => logout,
+}));
+
 describe("NoAccessPage", () => {
-  beforeEach(() => navigate.mockReset());
+  beforeEach(() => {
+    navigate.mockReset();
+    logout.mockReset();
+  });
 
   it("renders generic message that doesn't leak existence", () => {
     render(<NoAccessPage />);
@@ -23,11 +32,14 @@ describe("NoAccessPage", () => {
     expect(navigate).toHaveBeenCalledWith("/");
   });
 
-  it("navigates to login on 'Sign in as a different user'", () => {
+  it("fully logs out on 'Sign in as a different user' instead of just navigating", () => {
     render(<NoAccessPage />);
     fireEvent.click(
       screen.getByRole("button", { name: /sign in as a different user/i }),
     );
-    expect(navigate).toHaveBeenCalledWith("/login");
+    expect(logout).toHaveBeenCalledTimes(1);
+    // Should NOT just navigate to /login — that would leave the session
+    // cookie + auth state intact and AuthInitializer would re-auth.
+    expect(navigate).not.toHaveBeenCalledWith("/login");
   });
 });

packages/views/workspace/no-access-page.tsx

@@ -3,6 +3,7 @@
 import { Button } from "@multica/ui/components/ui/button";
 import { paths } from "@multica/core/paths";
 import { useNavigation } from "../navigation";
+import { useLogout } from "../auth";
 
 /**
  * Rendered when the workspace slug in the URL does not resolve to a workspace
@@ -12,6 +13,7 @@ import { useNavigation } from "../navigation";
  */
 export function NoAccessPage() {
   const nav = useNavigation();
+  const logout = useLogout();
   return (
     <div className="flex min-h-svh flex-col items-center justify-center gap-6 px-6 text-center">
       <div className="space-y-2">
@@ -26,7 +28,7 @@ export function NoAccessPage() {
         <Button onClick={() => nav.push(paths.root())}>
           Go to my workspaces
         </Button>
-        <Button variant="outline" onClick={() => nav.push(paths.login())}>
+        <Button variant="outline" onClick={logout}>
           Sign in as a different user
         </Button>
       </div>