diff --git a/admin/.env.example b/admin/.env.example
new file mode 100644
index 0000000..706fd43
--- /dev/null
+++ b/admin/.env.example
@@ -0,0 +1,13 @@
+# NestQuest Admin PWA — runtime configuration (Vite env).
+# Copy to .env (or .env.local) and fill in real values. NEVER commit .env.
+
+# Authentik OIDC provider. Defaults to the issuer below when unset.
+VITE_AUTHENTIK_ISSUER=https://auth.cubecraftlabs.com/application/o/nestquest/
+
+# REQUIRED. OAuth2/OIDC client id of the PUBLIC (PKCE) Authentik application.
+# No default: the app shows a configuration error screen when this is missing.
+# Never set a client_secret — this is a browser SPA using PKCE only.
+VITE_AUTHENTIK_CLIENT_ID=
+
+# NestQuest API base URL.
+VITE_API_BASE_URL=https://nestquest.cubecraftlabs.com
diff --git a/admin/src/App.css b/admin/src/App.css
index fb95e11..590a28f 100644
--- a/admin/src/App.css
+++ b/admin/src/App.css
@@ -67,4 +67,51 @@
 .admin-tab.active {
   font-weight: 700;
   color: var(--nq-brand-blue);
-}
\ No newline at end of file
+}
+/* Auth screens (login, errors, refusal). */
+
+.admin-login,
+.admin-error,
+.admin-refusal,
+.admin-loading {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 10px;
+  min-height: 100%;
+  padding: 32px 16px;
+  text-align: center;
+}
+
+.admin-login-button {
+  margin-top: 8px;
+  padding: 12px 24px;
+  border: none;
+  border-radius: 8px;
+  background: var(--nq-a-accent, #2563eb);
+  color: #fff;
+  font-size: 15px;
+  font-weight: 700;
+  cursor: pointer;
+}
+
+.admin-error,
+.admin-refusal {
+  color: var(--nq-a-ink, inherit);
+}
+
+.admin-refusal h1,
+.admin-error h1 {
+  margin: 0;
+  font-size: 20px;
+}
+
+.admin-refusal p,
+.admin-error p {
+  margin: 0;
+  max-width: 34em;
+  font-size: 14px;
+  font-weight: 600;
+  color: var(--nq-a-ink-secondary);
+}
diff --git a/admin/src/AppRoutes.test.tsx b/admin/src/AppRoutes.test.tsx
new file mode 100644
index 0000000..abb0fc4
--- /dev/null
+++ b/admin/src/AppRoutes.test.tsx
@@ -0,0 +1,73 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { cleanup, render, screen, waitFor } from "@testing-library/react";
+import AppRoutes from "./AppRoutes";
+import { storeTokens } from "./auth/oidc";
+import { config } from "./config";
+
+// The bundled config reads real env at import time; seed the shared module's
+// clientId directly so AppRoutes sees a configured app in these tests.
+(config as { clientId: string | undefined }).clientId = "test-client-id";
+
+function jsonResponse(body: unknown, status = 200): Response {
+  return new Response(JSON.stringify(body), {
+    status,
+    headers: { "Content-Type": "application/json" },
+  });
+}
+
+describe("AppRoutes auth gating", () => {
+  afterEach(() => {
+    cleanup();
+    sessionStorage.clear();
+    vi.restoreAllMocks();
+    vi.unstubAllGlobals();
+    window.history.replaceState({}, "", "/");
+  });
+
+  it("renders the login screen when unauthenticated at /", () => {
+    render(<AppRoutes />);
+    expect(screen.getByTestId("login-screen")).toBeTruthy();
+    expect(
+      screen.getByRole("button", { name: /sign in with authentik/i }),
+    ).toBeTruthy();
+  });
+
+  it("renders the four-tab shell after a successful authenticated probe", async () => {
+    storeTokens({ access_token: "at-123", expires_in: 600 });
+    const fetchMock = vi.fn().mockResolvedValue(jsonResponse([]));
+    vi.stubGlobal("fetch", fetchMock);
+
+    render(<AppRoutes />);
+
+    await waitFor(() => {
+      expect(screen.getByRole("heading", { name: "NestQuest Admin" })).toBeTruthy();
+    });
+    for (const label of ["Today", "Tasks", "Schedule", "History"]) {
+      expect(screen.getByRole("tab", { name: label })).toBeTruthy();
+    }
+  });
+
+  it("renders the explicit refusal when the API answers 403", async () => {
+    storeTokens({ access_token: "at-123", expires_in: 600 });
+    const fetchMock = vi.fn().mockResolvedValue(new Response("", { status: 403 }));
+    vi.stubGlobal("fetch", fetchMock);
+
+    render(<AppRoutes />);
+
+    await waitFor(() => {
+      expect(screen.getByTestId("refusal-screen")).toBeTruthy();
+    });
+    expect(screen.getByText(/not in the nestquest-admins group/i)).toBeTruthy();
+  });
+
+  it("shows the configuration error screen when the client id is missing", () => {
+    const original = config.clientId;
+    (config as { clientId: string | undefined }).clientId = undefined;
+    try {
+      render(<AppRoutes />);
+      expect(screen.getByTestId("config-error-screen")).toBeTruthy();
+    } finally {
+      (config as { clientId: string | undefined }).clientId = original;
+    }
+  });
+});
diff --git a/admin/src/AppRoutes.tsx b/admin/src/AppRoutes.tsx
new file mode 100644
index 0000000..5a251b2
--- /dev/null
+++ b/admin/src/AppRoutes.tsx
@@ -0,0 +1,179 @@
+/**
+ * Minimal path-based routing without react-router-dom: the app only needs two
+ * paths (`/` shell and `/auth/callback`), so a tiny window.location switch is
+ * enough and keeps the bundle small. Change screens listen to popstate.
+ */
+import { useEffect, useState } from "react";
+import { config } from "./config";
+import {
+  AuthError,
+  buildAuthorizeUrl,
+  clearAuth,
+  handleCallback,
+  isAuthenticated,
+} from "./auth/oidc";
+import { ApiForbiddenError, apiFetch } from "./api/client";
+import AdminShell from "./App";
+
+type Screen =
+  | { kind: "loading" }
+  | { kind: "login" }
+  | { kind: "config-error"; message: string }
+  | { kind: "auth-error"; message: string }
+  | { kind: "refusal"; message: string }
+  | { kind: "app" };
+
+function currentPath(): string {
+  return window.location.pathname.replace(/\/+$/, "") || "/";
+}
+
+async function probeApi(setScreen: (screen: Screen) => void) {
+  // A cheap authenticated probe so a 403 surfaces as an explicit refusal
+  // right after login instead of a silent empty shell.
+  try {
+    const response = await apiFetch("/api/v1/children", {}, config);
+    if (response.status === 403) {
+      setScreen({
+        kind: "refusal",
+        message: "Your account is not in the nestquest-admins group.",
+      });
+      return;
+    }
+    setScreen({ kind: "app" });
+  } catch (error) {
+    if (error instanceof ApiForbiddenError) {
+      setScreen({ kind: "refusal", message: error.message });
+      return;
+    }
+    // Network or other failures still allow the shell to render; API screens
+    // handle their own errors in later tasks.
+    setScreen({ kind: "app" });
+  }
+}
+
+function LoginScreen({ onLogin }: { onLogin: () => void }) {
+  return (
+    <div className="admin-login" data-testid="login-screen">
+      <h1 className="admin-title">NestQuest Admin</h1>
+      <p className="admin-subline">Sign in to continue</p>
+      <button type="button" className="admin-login-button" onClick={onLogin}>
+        Sign in with Authentik
+      </button>
+    </div>
+  );
+}
+
+export default function AppRoutes() {
+  const [screen, setScreen] = useState<Screen>({ kind: "loading" });
+
+  useEffect(() => {
+    // Re-evaluate on navigation (popstate) — routing is path based.
+    const onPop = () => setScreen({ kind: "loading" });
+    window.addEventListener("popstate", onPop);
+    return () => window.removeEventListener("popstate", onPop);
+  }, []);
+
+  useEffect(() => {
+    let cancelled = false;
+    const path = currentPath();
+
+    if (!config.clientId) {
+      setScreen({
+        kind: "config-error",
+        message:
+          "Missing VITE_AUTHENTIK_CLIENT_ID configuration. Set it in your .env before building the admin PWA.",
+      });
+      return;
+    }
+
+    if (path === "/auth/callback") {
+      (async () => {
+        try {
+          await handleCallback(window.location.search, config);
+          if (cancelled) return;
+          window.history.replaceState({}, "", "/");
+          await probeApi((next) => !cancelled && setScreen(next));
+        } catch (error) {
+          if (cancelled) return;
+          const message =
+            error instanceof AuthError || error instanceof Error
+              ? error.message
+              : "Authentication failed.";
+          setScreen({ kind: "auth-error", message });
+        }
+      })();
+      return () => {
+        cancelled = true;
+      };
+    }
+
+    if (isAuthenticated()) {
+      void probeApi((next) => !cancelled && setScreen(next));
+    } else {
+      setScreen({ kind: "login" });
+    }
+    return () => {
+      cancelled = true;
+    };
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  const startLogin = async () => {
+    try {
+      const url = await buildAuthorizeUrl(config);
+      window.location.assign(url);
+    } catch (error) {
+      setScreen({
+        kind: "config-error",
+        message: error instanceof Error ? error.message : "Login failed.",
+      });
+    }
+  };
+
+  switch (screen.kind) {
+    case "loading":
+      return (
+        <div className="admin-loading" role="status" data-testid="loading-screen">
+          Loading…
+        </div>
+      );
+    case "login":
+      return <LoginScreen onLogin={startLogin} />;
+    case "config-error":
+      return (
+        <div className="admin-error" role="alert" data-testid="config-error-screen">
+          <h1>Configuration error</h1>
+          <p>{screen.message}</p>
+        </div>
+      );
+    case "auth-error":
+      return (
+        <div className="admin-error" role="alert" data-testid="auth-error-screen">
+          <h1>Sign-in failed</h1>
+          <p>{screen.message}</p>
+          <button
+            type="button"
+            onClick={() => {
+              clearAuth();
+              window.history.replaceState({}, "", "/");
+              setScreen({ kind: "loading" });
+            }}
+          >
+            Try again
+          </button>
+        </div>
+      );
+    case "refusal":
+      return (
+        <div className="admin-refusal" role="alert" data-testid="refusal-screen">
+          <h1>Access refused</h1>
+          <p>{screen.message}</p>
+          <button type="button" onClick={() => { clearAuth(); window.history.replaceState({}, "", "/"); setScreen({ kind: "login" }); }}>
+            Sign out
+          </button>
+        </div>
+      );
+    case "app":
+      return <AdminShell />;
+  }
+}
diff --git a/admin/src/api/client.test.ts b/admin/src/api/client.test.ts
new file mode 100644
index 0000000..4d62824
--- /dev/null
+++ b/admin/src/api/client.test.ts
@@ -0,0 +1,75 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import {
+  ApiForbiddenError,
+  ApiUnauthorizedError,
+  apiFetch,
+} from "./client";
+import { storeTokens } from "../auth/oidc";
+import type { AppConfig } from "../config";
+
+const app: AppConfig = {
+  issuer: "https://auth.example.com/application/o/nestquest",
+  clientId: "test-client-id",
+  apiBaseUrl: "https://api.example.com",
+  authorizeEndpoint: "https://auth.example.com/application/o/authorize/",
+  tokenEndpoint: "https://auth.example.com/application/o/token/",
+  userinfoEndpoint: "https://auth.example.com/application/o/userinfo/",
+  endSessionEndpoint: "https://auth.example.com/application/o/nestquest/end-session/",
+  redirectUri: "http://localhost:5173/auth/callback",
+};
+
+function jsonResponse(body: unknown, status = 200): Response {
+  return new Response(JSON.stringify(body), {
+    status,
+    headers: { "Content-Type": "application/json" },
+  });
+}
+
+describe("API client", () => {
+  beforeEach(() => {
+    sessionStorage.clear();
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    vi.unstubAllGlobals();
+  });
+
+  it("attaches the Bearer token to API calls", async () => {
+    storeTokens({ access_token: "at-123", expires_in: 600 });
+    const fetchMock = vi.fn().mockResolvedValue(jsonResponse([]));
+
+    await apiFetch("/api/v1/children", {}, app, fetchMock as any);
+
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+    const [url, init] = fetchMock.mock.calls[0];
+    expect(url).toBe("https://api.example.com/api/v1/children");
+    expect(init.headers.Authorization).toBe("Bearer at-123");
+  });
+
+  it("throws ApiForbiddenError on 403 (authenticated but refused)", async () => {
+    storeTokens({ access_token: "at-123", expires_in: 600 });
+    const fetchMock = vi.fn().mockResolvedValue(new Response("", { status: 403 }));
+
+    await expect(
+      apiFetch("/api/v1/children", {}, app, fetchMock as any),
+    ).rejects.toBeInstanceOf(ApiForbiddenError);
+  });
+
+  it("triggers a login redirect on 401 with no refresh token", async () => {
+    storeTokens({ access_token: "stale", expires_in: 600 });
+    const assign = vi.fn();
+    vi.stubGlobal("location", { ...window.location, assign });
+    const fetchMock = vi.fn().mockResolvedValue(new Response("", { status: 401 }));
+
+    await expect(
+      apiFetch("/api/v1/children", {}, app, fetchMock as any),
+    ).rejects.toBeInstanceOf(ApiUnauthorizedError);
+    expect(assign).toHaveBeenCalledTimes(1);
+    const url = new URL(assign.mock.calls[0][0] as string);
+    expect(url.origin + url.pathname).toBe(
+      "https://auth.example.com/application/o/authorize/",
+    );
+    expect(url.searchParams.get("code_challenge_method")).toBe("S256");
+  });
+});
diff --git a/admin/src/api/client.ts b/admin/src/api/client.ts
new file mode 100644
index 0000000..f65bfd3
--- /dev/null
+++ b/admin/src/api/client.ts
@@ -0,0 +1,90 @@
+/**
+ * Minimal fetch wrapper for the NestQuest API.
+ *
+ * - Attaches `Authorization: Bearer <access_token>` when a token is stored.
+ * - 401: not authenticated (or token expired) -> trigger a new login.
+ * - 403: authenticated but refused -> throws ApiForbiddenError so the UI can
+ *   render an explicit refusal message.
+ */
+import { config, type AppConfig } from "../config";
+import {
+  buildAuthorizeUrl,
+  getToken,
+  isExpired,
+  refreshAccessToken,
+} from "../auth/oidc";
+
+export class ApiForbiddenError extends Error {
+  constructor(message = "Your account is not in the nestquest-admins group.") {
+    super(message);
+    this.name = "ApiForbiddenError";
+  }
+}
+
+export class ApiUnauthorizedError extends Error {
+  constructor(message = "Not authenticated.") {
+    super(message);
+    this.name = "ApiUnauthorizedError";
+  }
+}
+
+export interface ApiRequestOptions extends Omit<RequestInit, "headers"> {
+  headers?: Record<string, string>;
+}
+
+/**
+ * Redirect the browser to Authentik to start a new login.
+ * Exported for testing injection.
+ */
+export async function triggerLogin(app: AppConfig = config): Promise<void> {
+  const url = await buildAuthorizeUrl(app);
+  window.location.assign(url);
+}
+
+export async function apiFetch(
+  path: string,
+  options: ApiRequestOptions = {},
+  app: AppConfig = config,
+  fetchImpl: typeof fetch = fetch,
+): Promise<Response> {
+  if (isExpired() && (await refreshAccessToken(app, fetchImpl))) {
+    // token renewed; fall through and use the fresh one
+  }
+
+  const token = getToken();
+  const headers = {
+    ...(options.headers ?? {}),
+    ...(token ? { Authorization: `Bearer ${token}` } : {}),
+  };
+
+  const response = await fetchImpl(`${app.apiBaseUrl}${path}`, {
+    ...options,
+    headers,
+  });
+
+  if (response.status === 401) {
+    // Not authenticated: either no token or an unusable one.
+    if (await refreshAccessToken(app, fetchImpl)) {
+      const retryToken = getToken();
+      const retryResponse = await fetchImpl(`${app.apiBaseUrl}${path}`, {
+        ...options,
+        headers: {
+          ...(options.headers ?? {}),
+          ...(retryToken ? { Authorization: `Bearer ${retryToken}` } : {}),
+        },
+      });
+      if (retryResponse.status === 403) throw new ApiForbiddenError();
+      if (retryResponse.ok) return retryResponse;
+      throw new ApiUnauthorizedError();
+    }
+    await triggerLogin(app);
+    throw new ApiUnauthorizedError();
+  }
+
+  if (response.status === 403) {
+    // Authenticated, but Authentik's token does not belong to nestquest-admins.
+    throw new ApiForbiddenError();
+  }
+
+  return response;
+}
diff --git a/admin/src/auth/oidc.test.ts b/admin/src/auth/oidc.test.ts
new file mode 100644
index 0000000..3175367
--- /dev/null
+++ b/admin/src/auth/oidc.test.ts
@@ -0,0 +1,136 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import {
+  buildAuthorizeUrl,
+  clearAuth,
+  getToken,
+  handleCallback,
+  logout,
+  storeTokens,
+} from "./oidc";
+import type { AppConfig } from "../config";
+
+function testApp(): AppConfig {
+  return {
+    issuer: "https://auth.example.com/application/o/nestquest",
+    clientId: "test-client-id",
+    apiBaseUrl: "https://api.example.com",
+    authorizeEndpoint: "https://auth.example.com/application/o/authorize/",
+    tokenEndpoint: "https://auth.example.com/application/o/token/",
+    userinfoEndpoint: "https://auth.example.com/application/o/userinfo/",
+    endSessionEndpoint: "https://auth.example.com/application/o/nestquest/end-session/",
+    redirectUri: "http://localhost:5173/auth/callback",
+  };
+}
+
+function jsonResponse(body: unknown, status = 200): Response {
+  return new Response(JSON.stringify(body), {
+    status,
+    headers: { "Content-Type": "application/json" },
+  });
+}
+
+describe("OIDC flow", () => {
+  beforeEach(() => {
+    sessionStorage.clear();
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("buildAuthorizeUrl carries all required params and stores state/verifier", async () => {
+    const app = testApp();
+    const url = new URL(await buildAuthorizeUrl(app));
+
+    expect(url.origin + url.pathname).toBe(app.authorizeEndpoint);
+    expect(url.searchParams.get("response_type")).toBe("code");
+    expect(url.searchParams.get("client_id")).toBe("test-client-id");
+    expect(url.searchParams.get("redirect_uri")).toBe(app.redirectUri);
+    expect(url.searchParams.get("scope")).toBe("openid email profile");
+    expect(url.searchParams.get("code_challenge_method")).toBe("S256");
+    expect(url.searchParams.get("code_challenge")).toMatch(/^[A-Za-z0-9_-]{43}$/);
+    expect(url.searchParams.get("state")).toMatch(/^[A-Za-z0-9_-]+$/);
+
+    expect(sessionStorage.getItem("nestquest.oidc_state")).toBe(
+      url.searchParams.get("state"),
+    );
+    expect(sessionStorage.getItem("nestquest.code_verifier")).toMatch(/^[A-Za-z0-9-._~]{43,128}$/);
+  });
+
+  it("handleCallback rejects a mismatched state", async () => {
+    await buildAuthorizeUrl(testApp());
+    sessionStorage.setItem("nestquest.oidc_state", "different-state");
+
+    const fetchMock = vi.fn();
+    await expect(
+      handleCallback("?code=abc&state=tampered", testApp(), fetchMock as any),
+    ).rejects.toThrow(/state mismatch/i);
+    expect(fetchMock).not.toHaveBeenCalled();
+    expect(getToken()).toBeUndefined();
+  });
+
+  it("handleCallback exchanges the code with the correct form body and stores the token", async () => {
+    await buildAuthorizeUrl(testApp());
+    const verifier = sessionStorage.getItem("nestquest.code_verifier")!;
+    const state = sessionStorage.getItem("nestquest.oidc_state")!;
+
+    const fetchMock = vi.fn().mockResolvedValue(
+      jsonResponse({
+        access_token: "at-123",
+        refresh_token: "rt-456",
+        id_token: "id-789",
+        expires_in: 300,
+      }),
+    );
+    await handleCallback(`?code=abc&state=${state}`, testApp(), fetchMock as any);
+
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+    const [url, init] = fetchMock.mock.calls[0];
+    expect(url).toBe("https://auth.example.com/application/o/token/");
+    expect(init.method).toBe("POST");
+    expect(init.headers["Content-Type"]).toBe("application/x-www-form-urlencoded");
+
+    const body = new URLSearchParams(init.body);
+    expect(body.get("grant_type")).toBe("authorization_code");
+    expect(body.get("code")).toBe("abc");
+    expect(body.get("redirect_uri")).toBe(testApp().redirectUri);
+    expect(body.get("client_id")).toBe("test-client-id");
+    expect(body.get("code_verifier")).toBe(verifier);
+    expect(body.has("client_secret")).toBe(false);
+
+    expect(getToken()).toBe("at-123");
+    // one-time values consumed
+    expect(sessionStorage.getItem("nestquest.oidc_state")).toBeNull();
+    expect(sessionStorage.getItem("nestquest.code_verifier")).toBeNull();
+  });
+
+  it("handleCallback surfaces provider errors", async () => {
+    await expect(
+      handleCallback("?error=access_denied&error_description=nope", testApp(), vi.fn() as any),
+    ).rejects.toThrow(/nope|access_denied/);
+  });
+
+  it("clearAuth removes all stored auth data", () => {
+    storeTokens({ access_token: "a", refresh_token: "r", expires_in: 60 });
+    clearAuth();
+    expect(getToken()).toBeUndefined();
+    expect(sessionStorage.length).toBe(0);
+  });
+
+  it("logout clears auth and redirects to the end-session endpoint", () => {
+    storeTokens({ access_token: "a", id_token: "idt", expires_in: 60 });
+    const assign = vi.fn();
+    const original = window.location;
+    vi.stubGlobal("location", { ...original, assign, origin: "http://localhost:5173" });
+
+    logout(testApp());
+
+    expect(assign).toHaveBeenCalledTimes(1);
+    const url = new URL(assign.mock.calls[0][0] as string);
+    expect(url.toString()).toBe(
+      "https://auth.example.com/application/o/nestquest/end-session/?id_token_hint=idt&client_id=test-client-id&post_logout_redirect_uri=http%3A%2F%2Flocalhost%3A5173",
+    );
+    expect(getToken()).toBeUndefined();
+    vi.unstubAllGlobals();
+  });
+});
diff --git a/admin/src/auth/oidc.ts b/admin/src/auth/oidc.ts
new file mode 100644
index 0000000..76330d1
--- /dev/null
+++ b/admin/src/auth/oidc.ts
@@ -0,0 +1,212 @@
+/**
+ * OIDC authorization-code + PKCE flow for a PUBLIC client.
+ *
+ * Never sends a client_secret anywhere. Tokens are stored in sessionStorage
+ * (per-tab, cleared on tab close) — never localStorage.
+ */
+import { config, type AppConfig } from "../config";
+import {
+  computeCodeChallenge,
+  generateCodeVerifier,
+  generateState,
+} from "./pkce";
+
+const STORAGE_KEYS = {
+  accessToken: "nestquest.access_token",
+  refreshToken: "nestquest.refresh_token",
+  expiresAt: "nestquest.expires_at",
+  idToken: "nestquest.id_token",
+  state: "nestquest.oidc_state",
+  codeVerifier: "nestquest.code_verifier",
+} as const;
+
+export class AuthError extends Error {}
+
+export interface TokenResponse {
+  access_token?: string;
+  refresh_token?: string;
+  id_token?: string;
+  expires_in?: number;
+  token_type?: string;
+}
+
+function makeScopes(): string {
+  return "openid email profile";
+}
+
+/**
+ * Build the Authentik authorization redirect URL, storing state + verifier in
+ * sessionStorage so the callback can validate them.
+ */
+export async function buildAuthorizeUrl(app: AppConfig = config): Promise<string> {
+  if (!app.clientId) {
+    throw new AuthError(
+      "Missing VITE_AUTHENTIK_CLIENT_ID configuration. Set it in your .env before building the admin PWA.",
+    );
+  }
+  const state = generateState();
+  const codeVerifier = generateCodeVerifier();
+  const codeChallenge = await computeCodeChallenge(codeVerifier);
+
+  sessionStorage.setItem(STORAGE_KEYS.state, state);
+  sessionStorage.setItem(STORAGE_KEYS.codeVerifier, codeVerifier);
+
+  const url = new URL(app.authorizeEndpoint);
+  url.searchParams.set("response_type", "code");
+  url.searchParams.set("client_id", app.clientId);
+  url.searchParams.set("redirect_uri", app.redirectUri);
+  url.searchParams.set("scope", makeScopes());
+  url.searchParams.set("state", state);
+  url.searchParams.set("code_challenge", codeChallenge);
+  url.searchParams.set("code_challenge_method", "S256");
+  return url.toString();
+}
+
+/**
+ * Handle the OAuth callback: validate state, exchange the code at the token
+ * endpoint (PKCE, form-urlencoded, no client_secret), store tokens.
+ */
+export async function handleCallback(
+  query: URLSearchParams | string = window.location.search,
+  app: AppConfig = config,
+  fetchImpl: typeof fetch = fetch,
+): Promise<void> {
+  const params =
+    typeof query === "string" ? new URLSearchParams(query) : query;
+
+  const providerError = params.get("error");
+  if (providerError) {
+    throw new AuthError(
+      params.get("error_description") || `Provider returned error: ${providerError}`,
+    );
+  }
+
+  const code = params.get("code");
+  const state = params.get("state");
+  if (!code || !state) {
+    throw new AuthError("Callback is missing the code or state parameter.");
+  }
+
+  const storedState = sessionStorage.getItem(STORAGE_KEYS.state);
+  const codeVerifier = sessionStorage.getItem(STORAGE_KEYS.codeVerifier);
+  if (!storedState || storedState !== state || !codeVerifier) {
+    throw new AuthError("State mismatch — possible CSRF; refusing to log in.");
+  }
+
+  if (!app.clientId) {
+    throw new AuthError(
+      "Missing VITE_AUTHENTIK_CLIENT_ID configuration. Set it in your .env before building the admin PWA.",
+    );
+  }
+
+  const body = new URLSearchParams({
+    grant_type: "authorization_code",
+    code,
+    redirect_uri: app.redirectUri,
+    client_id: app.clientId,
+    code_verifier: codeVerifier,
+  });
+
+  const response = await fetchImpl(app.tokenEndpoint, {
+    method: "POST",
+    headers: { "Content-Type": "application/x-www-form-urlencoded" },
+    body: body.toString(),
+  });
+  if (!response.ok) {
+    throw new AuthError(`Token exchange failed with HTTP ${response.status}`);
+  }
+  const tokens = (await response.json()) as TokenResponse;
+  if (!tokens.access_token) {
+    throw new AuthError("Token response did not include an access token.");
+  }
+
+  storeTokens(tokens);
+  // One-time use values are consumed on success.
+  sessionStorage.removeItem(STORAGE_KEYS.state);
+  sessionStorage.removeItem(STORAGE_KEYS.codeVerifier);
+}
+
+export function storeTokens(tokens: TokenResponse): void {
+  sessionStorage.setItem(STORAGE_KEYS.accessToken, tokens.access_token!);
+  if (tokens.refresh_token) {
+    sessionStorage.setItem(STORAGE_KEYS.refreshToken, tokens.refresh_token);
+  }
+  if (tokens.id_token) {
+    sessionStorage.setItem(STORAGE_KEYS.idToken, tokens.id_token);
+  }
+  if (typeof tokens.expires_in === "number") {
+    sessionStorage.setItem(
+      STORAGE_KEYS.expiresAt,
+      String(Date.now() + tokens.expires_in * 1000),
+    );
+  }
+}
+
+export function getToken(): string | undefined {
+  return sessionStorage.getItem(STORAGE_KEYS.accessToken) ?? undefined;
+}
+
+export function getRefreshToken(): string | undefined {
+  return sessionStorage.getItem(STORAGE_KEYS.refreshToken) ?? undefined;
+}
+
+export function getIdToken(): string | undefined {
+  return sessionStorage.getItem(STORAGE_KEYS.idToken) ?? undefined;
+}
+
+export function isAuthenticated(): boolean {
+  return Boolean(getToken());
+}
+
+/** True once the stored access token has passed its (approximate) expiry. */
+export function isExpired(): boolean {
+  const expiresAt = sessionStorage.getItem(STORAGE_KEYS.expiresAt);
+  if (!expiresAt) return false;
+  return Date.now() >= Number(expiresAt);
+}
+
+/**
+ * Refresh the access token with the refresh token grant. Returns false when
+ * no refresh token is stored or the grant fails (caller should re-login).
+ */
+export async function refreshAccessToken(
+  app: AppConfig = config,
+  fetchImpl: typeof fetch = fetch,
+): Promise<boolean> {
+  const refreshToken = getRefreshToken();
+  if (!refreshToken || !app.clientId) return false;
+
+  const body = new URLSearchParams({
+    grant_type: "refresh_token",
+    refresh_token: refreshToken,
+    client_id: app.clientId,
+  });
+
+  const response = await fetchImpl(app.tokenEndpoint, {
+    method: "POST",
+    headers: { "Content-Type": "application/x-www-form-urlencoded" },
+    body: body.toString(),
+  });
+  if (!response.ok) return false;
+  const tokens = (await response.json()) as TokenResponse;
+  if (!tokens.access_token) return false;
+  storeTokens(tokens);
+  return true;
+}
+
+export function clearAuth(): void {
+  for (const key of Object.values(STORAGE_KEYS)) {
+    sessionStorage.removeItem(key);
+  }
+}
+
+/** Sign out: clear local auth, then send the browser to the end-session endpoint. */
+export function logout(app: AppConfig = config): void {
+  const idTokenHint = getIdToken();
+  clearAuth();
+  const params = new URLSearchParams();
+  if (idTokenHint) params.set("id_token_hint", idTokenHint);
+  if (app.clientId) params.set("client_id", app.clientId);
+  params.set("post_logout_redirect_uri", window.location.origin);
+  window.location.assign(`${app.endSessionEndpoint}?${params.toString()}`);
+}
diff --git a/admin/src/auth/pkce.test.ts b/admin/src/auth/pkce.test.ts
new file mode 100644
index 0000000..7b7f686
--- /dev/null
+++ b/admin/src/auth/pkce.test.ts
@@ -0,0 +1,41 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import {
+  base64UrlEncode,
+  computeCodeChallenge,
+  generateCodeVerifier,
+  generateState,
+  isLikelyValidVerifier,
+} from "./pkce";
+
+describe("PKCE helpers", () => {
+  it("base64UrlEncode has no padding and url-safe characters", () => {
+    // bytes chosen to force "+" and "/" and padding in plain base64
+    const bytes = new Uint8Array([0xfb, 0xff, 0xbf, 0xff]);
+    const encoded = base64UrlEncode(bytes);
+    expect(encoded).not.toMatch(/[+/=]/);
+  });
+
+  it("computes the RFC 7636 appendix-B S256 vector", async () => {
+    const verifier =
+      "dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk";
+    const challenge = await computeCodeChallenge(verifier);
+    expect(challenge).toBe("E9Melhoa2OwvFrEMTJguCHaoeK1t8URWbuGJSstw-cM");
+  });
+
+  it("generates verifiers with valid charset and length", () => {
+    for (let i = 0; i < 20; i++) {
+      const verifier = generateCodeVerifier();
+      expect(isLikelyValidVerifier(verifier)).toBe(true);
+    }
+  });
+
+  it("rejects verifiers outside 43-128 chars or with reserved chars", () => {
+    expect(isLikelyValidVerifier("short")).toBe(false);
+    expect(isLikelyValidVerifier("a".repeat(129))).toBe(false);
+    expect(isLikelyValidVerifier("a".repeat(43) + "+")).toBe(false);
+  });
+
+  it("generates distinct random states", () => {
+    expect(generateState()).not.toBe(generateState());
+  });
+});
diff --git a/admin/src/auth/pkce.ts b/admin/src/auth/pkce.ts
new file mode 100644
index 0000000..de04c5f
--- /dev/null
+++ b/admin/src/auth/pkce.ts
@@ -0,0 +1,55 @@
+/**
+ * PKCE (RFC 7636) helpers for a public SPA client.
+ *
+ * Uses the Web Crypto API, which requires a SECURE CONTEXT: the app must be
+ * served over https or http://localhost, otherwise crypto.subtle is
+ * unavailable and login cannot work.
+ */
+
+const VERIFIER_CHARSET =
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~";
+
+/** base64url-encode bytes with NO padding. */
+export function base64UrlEncode(bytes: Uint8Array): string {
+  let binary = "";
+  for (const byte of bytes) {
+    binary += String.fromCharCode(byte);
+  }
+  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
+}
+
+function randomBase64Url(byteLength: number): string {
+  const bytes = new Uint8Array(byteLength);
+  crypto.getRandomValues(bytes);
+  return base64UrlEncode(bytes);
+}
+
+/**
+ * Random code_verifier: 43-128 chars, unreserved charset only.
+ * 32 random bytes -> 43 base64url chars, which is the minimum allowed length.
+ */
+export function generateCodeVerifier(): string {
+  return randomBase64Url(32);
+}
+
+/** S256 code_challenge = base64url(SHA-256(verifier)), no padding. */
+export async function computeCodeChallenge(verifier: string): Promise<string> {
+  const digest = await crypto.subtle.digest(
+    "SHA-256",
+    new TextEncoder().encode(verifier),
+  );
+  return base64UrlEncode(new Uint8Array(digest));
+}
+
+/** Random opaque state value for CSRF protection. */
+export function generateState(): string {
+  return randomBase64Url(16);
+}
+
+export function isLikelyValidVerifier(verifier: string): boolean {
+  return (
+    verifier.length >= 43 &&
+    verifier.length <= 128 &&
+    [...verifier].every((char) => VERIFIER_CHARSET.includes(char))
+  );
+}
diff --git a/admin/src/config.ts b/admin/src/config.ts
new file mode 100644
index 0000000..5e9309c
--- /dev/null
+++ b/admin/src/config.ts
@@ -0,0 +1,38 @@
+/**
+ * Runtime configuration, read from Vite env (import.meta.env).
+ * See .env.example for the variables and their defaults.
+ */
+
+export interface AppConfig {
+  issuer: string;
+  clientId: string | undefined;
+  apiBaseUrl: string;
+  authorizeEndpoint: string;
+  tokenEndpoint: string;
+  userinfoEndpoint: string;
+  endSessionEndpoint: string;
+  redirectUri: string;
+}
+
+export function readConfig(env: Record<string, string | undefined> = import.meta.env as any): AppConfig {
+  const issuer = (
+    env.VITE_AUTHENTIK_ISSUER || "https://auth.cubecraftlabs.com/application/o/nestquest/"
+  ).replace(/\/$/, "");
+  const clientId = env.VITE_AUTHENTIK_CLIENT_ID;
+  const apiBaseUrl = env.VITE_API_BASE_URL || "https://nestquest.cubecraftlabs.com";
+
+  return {
+    issuer,
+    // No default: a missing client id must surface as a configuration error
+    // screen, not a broken redirect to Authentik.
+    clientId: clientId || undefined,
+    apiBaseUrl,
+    authorizeEndpoint: "https://auth.cubecraftlabs.com/application/o/authorize/",
+    tokenEndpoint: "https://auth.cubecraftlabs.com/application/o/token/",
+    userinfoEndpoint: "https://auth.cubecraftlabs.com/application/o/userinfo/",
+    endSessionEndpoint: `${issuer}/end-session/`,
+    redirectUri: `${window.location.origin}/auth/callback`,
+  };
+}
+
+export const config: AppConfig = readConfig();
diff --git a/admin/src/main.tsx b/admin/src/main.tsx
index e9c7e64..35e1ff7 100644
--- a/admin/src/main.tsx
+++ b/admin/src/main.tsx
@@ -1,10 +1,10 @@
 import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";
-import App from "./App";
+import AppRoutes from "./AppRoutes";
 import "./index.css";
 
 createRoot(document.getElementById("root")!).render(
   <StrictMode>
-    <App />
+    <AppRoutes />
   </StrictMode>,
 );
\ No newline at end of file