diff --git a/web/src/components/AuthGuard.test.tsx b/web/src/components/AuthGuard.test.tsx
new file mode 100644
index 0000000..79a2fdb
--- /dev/null
+++ b/web/src/components/AuthGuard.test.tsx
@@ -0,0 +1,73 @@
+import { render, screen, waitFor } from "@testing-library/react";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const { checkKillSwitchMock, logoutMock, refreshStoredAuthSessionMock, replaceMock, useAuthMock } = vi.hoisted(() => ({
+  checkKillSwitchMock: vi.fn(async () => ({ disabled: false, message: "" })),
+  logoutMock: vi.fn(),
+  refreshStoredAuthSessionMock: vi.fn(async () => true),
+  replaceMock: vi.fn(),
+  useAuthMock: vi.fn(() => ({ isAuthenticated: true, isLoading: false, logout: logoutMock })),
+}));
+
+vi.mock("next/navigation", () => ({
+  useRouter: () => ({ replace: replaceMock }),
+}));
+
+vi.mock("@/lib/auth", () => ({
+  useAuth: useAuthMock,
+}));
+
+vi.mock("@/lib/auth-session", () => ({
+  refreshStoredAuthSession: refreshStoredAuthSessionMock,
+}));
+
+vi.mock("@/lib/kill-switch", () => ({
+  checkKillSwitch: checkKillSwitchMock,
+}));
+
+import { AuthGuard } from "./AuthGuard";
+
+describe("AuthGuard", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    useAuthMock.mockReturnValue({ isAuthenticated: true, isLoading: false, logout: logoutMock });
+    refreshStoredAuthSessionMock.mockResolvedValue(true);
+    checkKillSwitchMock.mockResolvedValue({ disabled: false, message: "" });
+  });
+
+  it("redirects unauthenticated users to login", async () => {
+    useAuthMock.mockReturnValue({ isAuthenticated: false, isLoading: false, logout: logoutMock });
+
+    render(<AuthGuard><div>Private app</div></AuthGuard>);
+
+    await waitFor(() => expect(replaceMock).toHaveBeenCalledWith("/login"));
+    expect(screen.queryByText("Private app")).not.toBeInTheDocument();
+  });
+
+  it("refreshes an expired stored session before showing protected content", async () => {
+    render(<AuthGuard><div>Private app</div></AuthGuard>);
+
+    await waitFor(() => expect(refreshStoredAuthSessionMock).toHaveBeenCalledOnce());
+    expect(await screen.findByText("Private app")).toBeInTheDocument();
+    expect(logoutMock).not.toHaveBeenCalled();
+  });
+
+  it("logs out and redirects when session refresh fails", async () => {
+    refreshStoredAuthSessionMock.mockResolvedValue(false);
+
+    render(<AuthGuard><div>Private app</div></AuthGuard>);
+
+    await waitFor(() => expect(logoutMock).toHaveBeenCalledOnce());
+    expect(replaceMock).toHaveBeenCalledWith("/login");
+    expect(screen.queryByText("Private app")).not.toBeInTheDocument();
+  });
+
+  it("keeps protected content hidden when the kill switch is active", async () => {
+    checkKillSwitchMock.mockResolvedValue({ disabled: true, message: "Maintenance window" });
+
+    render(<AuthGuard><div>Private app</div></AuthGuard>);
+
+    expect(await screen.findByText("Maintenance window")).toBeInTheDocument();
+    expect(screen.queryByText("Private app")).not.toBeInTheDocument();
+  });
+});
diff --git a/web/src/components/AuthGuard.tsx b/web/src/components/AuthGuard.tsx
index a1aef2b..bcb01d8 100644
--- a/web/src/components/AuthGuard.tsx
+++ b/web/src/components/AuthGuard.tsx
@@ -3,34 +3,52 @@
 import { useEffect, useState, type ReactNode } from "react";
 import { useRouter } from "next/navigation";
 import { useAuth } from "@/lib/auth";
+import { refreshStoredAuthSession } from "@/lib/auth-session";
 import { checkKillSwitch } from "@/lib/kill-switch";
 
 export function AuthGuard({ children }: { children: ReactNode }) {
-  const { isAuthenticated, isLoading: authLoading } = useAuth();
+  const { isAuthenticated, isLoading: authLoading, logout } = useAuth();
   const router = useRouter();
   const [killSwitchMsg, setKillSwitchMsg] = useState<string | null>(null);
   const [ready, setReady] = useState(false);
 
   useEffect(() => {
     if (authLoading) return;
+    let active = true;
 
     if (!isAuthenticated) {
       router.replace("/login");
-      return;
+      return () => { active = false; };
     }
 
-    checkKillSwitch()
-      .then(({ disabled, message }) => {
+    async function verifySessionAndReadiness() {
+      const refreshed = await refreshStoredAuthSession();
+      if (!active) return;
+
+      if (!refreshed) {
+        logout();
+        router.replace("/login");
+        return;
+      }
+
+      try {
+        const { disabled, message } = await checkKillSwitch();
+        if (!active) return;
         if (disabled) {
           setKillSwitchMsg(message || "This application is currently unavailable.");
         } else {
           setReady(true);
         }
-      })
-      .catch(() => {
+      } catch {
+        if (!active) return;
         setReady(true);
-      });
-  }, [isAuthenticated, authLoading, router]);
+      }
+    }
+
+    void verifySessionAndReadiness();
+
+    return () => { active = false; };
+  }, [isAuthenticated, authLoading, logout, router]);
 
   if (killSwitchMsg) {
     return (
diff --git a/web/src/lib/api-helpers.ts b/web/src/lib/api-helpers.ts
index 55b0f10..ab56beb 100644
--- a/web/src/lib/api-helpers.ts
+++ b/web/src/lib/api-helpers.ts
@@ -1,12 +1,18 @@
 import { createApiClient } from "@bytelyst/api-client";
 import { NOTES_API_URL, PRODUCT_ID } from "@/lib/product-config";
+import { clearAuthSession, isAccessTokenExpired } from "@/lib/auth-session";
 
 export function getAccessToken(): string | null {
   if (typeof window === "undefined") {
     return null;
   }
 
-  return localStorage.getItem(`${PRODUCT_ID}_access_token`);
+  const token = localStorage.getItem(`${PRODUCT_ID}_access_token`);
+  if (isAccessTokenExpired(token)) {
+    clearAuthSession();
+    return null;
+  }
+  return token;
 }
 
 export function createNotesApiClient() {
diff --git a/web/src/lib/auth-session.test.ts b/web/src/lib/auth-session.test.ts
new file mode 100644
index 0000000..8796a23
--- /dev/null
+++ b/web/src/lib/auth-session.test.ts
@@ -0,0 +1,116 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import {
+  ACCESS_TOKEN_KEY,
+  AUTH_USER_KEY,
+  REFRESH_TOKEN_KEY,
+  clearAuthSession,
+  isAccessTokenExpired,
+  refreshStoredAuthSession,
+  restoreAuthSession,
+} from "@/lib/auth-session";
+import { PLATFORM_SERVICE_URL, PRODUCT_ID } from "@/lib/product-config";
+
+const storage = new Map<string, string>();
+const localStorageMock = {
+  getItem: vi.fn((key: string) => storage.get(key) ?? null),
+  setItem: vi.fn((key: string, value: string) => {
+    storage.set(key, value);
+  }),
+  removeItem: vi.fn((key: string) => {
+    storage.delete(key);
+  }),
+};
+
+function tokenWithExp(exp: number): string {
+  const payload = btoa(JSON.stringify({ exp })).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
+  return `header.${payload}.sig`;
+}
+
+function jsonResponse(data: unknown, status = 200) {
+  return {
+    ok: status >= 200 && status < 300,
+    status,
+    json: () => Promise.resolve(data),
+  };
+}
+
+describe("auth-session", () => {
+  beforeEach(() => {
+    storage.clear();
+    vi.clearAllMocks();
+    Object.defineProperty(window, "localStorage", {
+      configurable: true,
+      value: localStorageMock,
+    });
+    vi.stubGlobal("localStorage", localStorageMock);
+    vi.stubGlobal("fetch", vi.fn());
+  });
+
+  it("detects expired JWT access tokens with skew", () => {
+    expect(isAccessTokenExpired(tokenWithExp(100), 101_000, 0)).toBe(true);
+    expect(isAccessTokenExpired(tokenWithExp(200), 101_000, 0)).toBe(false);
+  });
+
+  it("restores a valid product-scoped session from localStorage", () => {
+    const accessToken = tokenWithExp(Math.floor(Date.now() / 1000) + 3600);
+    localStorage.setItem(AUTH_USER_KEY, JSON.stringify({ email: "a@b.com", name: "A", role: "editor", workspaceId: "ws-1" }));
+    localStorage.setItem(ACCESS_TOKEN_KEY, accessToken);
+    localStorage.setItem(REFRESH_TOKEN_KEY, "refresh-token");
+
+    expect(restoreAuthSession()).toMatchObject({
+      user: { email: "a@b.com" },
+      accessToken,
+      refreshToken: "refresh-token",
+    });
+  });
+
+  it("clears an expired session when no refresh token exists", () => {
+    localStorage.setItem(AUTH_USER_KEY, JSON.stringify({ email: "a@b.com" }));
+    localStorage.setItem(ACCESS_TOKEN_KEY, tokenWithExp(1));
+
+    expect(restoreAuthSession()).toBeNull();
+    expect(localStorageMock.removeItem).toHaveBeenCalledWith(AUTH_USER_KEY);
+    expect(localStorageMock.removeItem).toHaveBeenCalledWith(ACCESS_TOKEN_KEY);
+    expect(localStorageMock.removeItem).toHaveBeenCalledWith(REFRESH_TOKEN_KEY);
+  });
+
+  it("refreshes an expired access token through platform-service", async () => {
+    const fetchMock = vi.fn(async () => jsonResponse({ accessToken: "new-access", refreshToken: "new-refresh" }));
+    vi.stubGlobal("fetch", fetchMock);
+    localStorage.setItem(ACCESS_TOKEN_KEY, tokenWithExp(1));
+    localStorage.setItem(REFRESH_TOKEN_KEY, "old-refresh");
+
+    await expect(refreshStoredAuthSession()).resolves.toBe(true);
+    expect(fetchMock).toHaveBeenCalledWith(`${PLATFORM_SERVICE_URL}/auth/refresh`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json", "x-product-id": PRODUCT_ID },
+      body: JSON.stringify({ refreshToken: "old-refresh" }),
+    });
+    expect(localStorage.getItem(ACCESS_TOKEN_KEY)).toBe("new-access");
+    expect(localStorage.getItem(REFRESH_TOKEN_KEY)).toBe("new-refresh");
+  });
+
+  it("clears the session when refresh fails", async () => {
+    vi.stubGlobal("fetch", vi.fn(async () => jsonResponse({ error: "expired" }, 401)));
+    localStorage.setItem(AUTH_USER_KEY, JSON.stringify({ email: "a@b.com" }));
+    localStorage.setItem(ACCESS_TOKEN_KEY, tokenWithExp(1));
+    localStorage.setItem(REFRESH_TOKEN_KEY, "bad-refresh");
+
+    await expect(refreshStoredAuthSession()).resolves.toBe(false);
+    expect(localStorage.getItem(AUTH_USER_KEY)).toBeNull();
+    expect(localStorage.getItem(ACCESS_TOKEN_KEY)).toBeNull();
+    expect(localStorage.getItem(REFRESH_TOKEN_KEY)).toBeNull();
+  });
+
+  it("clears all product-scoped auth keys on logout cleanup", () => {
+    localStorage.setItem(AUTH_USER_KEY, "u");
+    localStorage.setItem(ACCESS_TOKEN_KEY, "a");
+    localStorage.setItem(REFRESH_TOKEN_KEY, "r");
+
+    clearAuthSession();
+
+    expect(localStorage.getItem(AUTH_USER_KEY)).toBeNull();
+    expect(localStorage.getItem(ACCESS_TOKEN_KEY)).toBeNull();
+    expect(localStorage.getItem(REFRESH_TOKEN_KEY)).toBeNull();
+  });
+});
diff --git a/web/src/lib/auth-session.ts b/web/src/lib/auth-session.ts
new file mode 100644
index 0000000..6c6b592
--- /dev/null
+++ b/web/src/lib/auth-session.ts
@@ -0,0 +1,127 @@
+import type { ProductUser } from "@/lib/types";
+import { PLATFORM_SERVICE_URL, PRODUCT_ID } from "@/lib/product-config";
+
+export const AUTH_USER_KEY = `${PRODUCT_ID}_auth_user`;
+export const ACCESS_TOKEN_KEY = `${PRODUCT_ID}_access_token`;
+export const REFRESH_TOKEN_KEY = `${PRODUCT_ID}_refresh_token`;
+
+interface JwtPayload {
+  exp?: number;
+}
+
+interface RefreshResponse {
+  accessToken?: string;
+  refreshToken?: string;
+}
+
+function getStorage(): Storage | null {
+  if (typeof window === "undefined") return null;
+  return window.localStorage;
+}
+
+function decodeBase64Url(value: string): string {
+  const padded = value.padEnd(value.length + ((4 - (value.length % 4)) % 4), "=");
+  return atob(padded.replace(/-/g, "+").replace(/_/g, "/"));
+}
+
+export function readJwtPayload(token: string): JwtPayload | null {
+  const [, payload] = token.split(".");
+  if (!payload) return null;
+
+  try {
+    return JSON.parse(decodeBase64Url(payload)) as JwtPayload;
+  } catch {
+    return null;
+  }
+}
+
+export function isAccessTokenExpired(token: string | null, nowMs = Date.now(), skewSeconds = 30): boolean {
+  if (!token) return true;
+  const payload = readJwtPayload(token);
+  if (!payload?.exp) return false;
+  return payload.exp * 1000 <= nowMs + skewSeconds * 1000;
+}
+
+export function clearAuthSession(): void {
+  const storage = getStorage();
+  if (!storage) return;
+  storage.removeItem(AUTH_USER_KEY);
+  storage.removeItem(ACCESS_TOKEN_KEY);
+  storage.removeItem(REFRESH_TOKEN_KEY);
+}
+
+export function getStoredAccessToken(): string | null {
+  return getStorage()?.getItem(ACCESS_TOKEN_KEY) ?? null;
+}
+
+export function getStoredRefreshToken(): string | null {
+  return getStorage()?.getItem(REFRESH_TOKEN_KEY) ?? null;
+}
+
+export function restoreAuthSession():
+  | { user: ProductUser; accessToken: string; refreshToken: string }
+  | null {
+  const storage = getStorage();
+  if (!storage) return null;
+
+  const rawUser = storage.getItem(AUTH_USER_KEY);
+  const accessToken = storage.getItem(ACCESS_TOKEN_KEY);
+  const refreshToken = storage.getItem(REFRESH_TOKEN_KEY);
+  if (!rawUser || !accessToken) return null;
+
+  if (isAccessTokenExpired(accessToken) && !refreshToken) {
+    clearAuthSession();
+    return null;
+  }
+
+  try {
+    return {
+      user: JSON.parse(rawUser) as ProductUser,
+      accessToken,
+      refreshToken: refreshToken ?? "",
+    };
+  } catch {
+    clearAuthSession();
+    return null;
+  }
+}
+
+export async function refreshStoredAuthSession(): Promise<boolean> {
+  const storage = getStorage();
+  if (!storage) return false;
+
+  const accessToken = storage.getItem(ACCESS_TOKEN_KEY);
+  if (!isAccessTokenExpired(accessToken)) return true;
+
+  const refreshToken = storage.getItem(REFRESH_TOKEN_KEY);
+  if (!refreshToken) {
+    clearAuthSession();
+    return false;
+  }
+
+  try {
+    const response = await fetch(`${PLATFORM_SERVICE_URL}/auth/refresh`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json", "x-product-id": PRODUCT_ID },
+      body: JSON.stringify({ refreshToken }),
+    });
+
+    if (!response.ok) {
+      clearAuthSession();
+      return false;
+    }
+
+    const data = (await response.json()) as RefreshResponse;
+    if (!data.accessToken || !data.refreshToken) {
+      clearAuthSession();
+      return false;
+    }
+
+    storage.setItem(ACCESS_TOKEN_KEY, data.accessToken);
+    storage.setItem(REFRESH_TOKEN_KEY, data.refreshToken);
+    return true;
+  } catch {
+    clearAuthSession();
+    return false;
+  }
+}
diff --git a/web/src/lib/auth.ts b/web/src/lib/auth.ts
index cd30e8d..5ce07b6 100644
--- a/web/src/lib/auth.ts
+++ b/web/src/lib/auth.ts
@@ -3,6 +3,7 @@
 import { createAuthProvider } from "@bytelyst/react-auth";
 import type { ProductUser } from "@/lib/types";
 import { PLATFORM_SERVICE_URL, PRODUCT_ID } from "@/lib/product-config";
+import { restoreAuthSession } from "@/lib/auth-session";
 
 interface LoginResponse {
   user?: ProductUser;
@@ -19,6 +20,8 @@ export const { AuthProvider, useAuth } = createAuthProvider<ProductUser>({
   changePasswordEndpoint: "/auth/change-password",
   deleteAccountEndpoint: "/auth/delete-account",
   refreshEndpoint: "/auth/refresh",
+  productId: PRODUCT_ID,
+  onInit: restoreAuthSession,
   mapLoginResponse: (data: unknown) => {
     const result = data as LoginResponse;
     return {