diff --git a/eslint.config.js b/eslint.config.js
index 0c0123e..09e47a4 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -11,6 +11,7 @@ export default tseslint.config(
       "node_modules/**",
       "coverage/**",
       "experiments/**",
+      "instance/**",
       "scripts/serve-demo.mjs",
       "public/sw.js",
       "share/**",
diff --git a/src/app/layout.ts b/src/app/layout.ts
index 2eaf663..d42c371 100644
--- a/src/app/layout.ts
+++ b/src/app/layout.ts
@@ -63,6 +63,24 @@ export function createLayout(): {
   }
   header.append(themeBtn);
 
+  const settingsLink = document.createElement("a");
+  settingsLink.href = "/settings";
+  settingsLink.setAttribute("data-route", "/settings");
+  settingsLink.className = "app-header__settings";
+  settingsLink.textContent = "⚙";
+  settingsLink.setAttribute("aria-label", "Settings");
+  settingsLink.style.minWidth = "36px";
+  settingsLink.style.minHeight = "36px";
+  settingsLink.style.padding = "0.25rem 0.5rem";
+  settingsLink.style.fontSize = "1.125rem";
+  settingsLink.style.textDecoration = "none";
+  settingsLink.style.display = "inline-flex";
+  settingsLink.style.alignItems = "center";
+  settingsLink.style.justifyContent = "center";
+  settingsLink.style.borderRadius = "999px";
+  settingsLink.style.cursor = "pointer";
+  header.append(settingsLink);
+
   const statusChip = document.createElement("div");
   statusChip.className = "app-header__status";
   statusChip.setAttribute("role", "status");
diff --git a/src/app/main.ts b/src/app/main.ts
index f578cb7..004eef6 100644
--- a/src/app/main.ts
+++ b/src/app/main.ts
@@ -41,6 +41,7 @@ import { loadMapData, type MapHandle } from "./map.js";
 import type { MapViewData } from "../domain/map/types.js";
 import { createFestivalView } from "../ui/views/festival/festival.js";
 import { createNotFoundView } from "../ui/views/not-found.js";
+import { renderSettings } from "../ui/views/settings/settings.js";
 
 export interface RouteData {
   readonly emergency?: EmergencyViewModel | undefined;
@@ -75,6 +76,8 @@ function renderView(path: string, data?: RouteData): HTMLElement {
       return createMapView(data?.map ?? null);
     case "festival":
       return createFestivalView();
+    case "settings":
+      return renderSettings();
     case "not-found":
       return createNotFoundView(path);
   }
@@ -219,24 +222,39 @@ function mount(): { router: Router; cleanup: () => void } {
                       : "Activating…";
                 paint();
               },
-            }).then((outcome) => {
-              syncBusy = false;
-              syncMessage =
-                outcome.status === "ok"
-                  ? `Festival data v${String(outcome.version)} is live. You can go offline now.`
-                  : outcome.status === "no-update"
-                    ? "You already have the latest festival data."
-                    : outcome.status === "offline"
-                      ? "No sync source reachable right now."
-                      : outcome.status === "rejected"
-                        ? `Update rejected — keeping current data. (${outcome.detail})`
-                        : outcome.status === "not-configured"
-                          ? `No sync source configured. (${outcome.detail})`
-                          : `Sync failed. (${outcome.detail})`;
-              paint();
-              // Refresh the readiness chip behind the dialog either way.
-              void refreshReadiness(false);
-            });
+              onProgress: (done, _total, label) => {
+                syncMessage = `Downloading and verifying… (${String(done)} files · ${label})`;
+                paint();
+              },
+            })
+              .then((outcome) => {
+                syncBusy = false;
+                syncMessage =
+                  outcome.status === "ok"
+                    ? `Festival data v${String(outcome.version)} is live. You can go offline now.`
+                    : outcome.status === "no-update"
+                      ? "You already have the latest festival data."
+                      : outcome.status === "offline"
+                        ? "No sync source reachable right now."
+                        : outcome.status === "rejected"
+                          ? `Update rejected — keeping current data. (${outcome.detail})`
+                          : outcome.status === "not-configured"
+                            ? `No sync source configured. (${outcome.detail})`
+                            : `Sync failed. (${outcome.detail})`;
+                paint();
+                // Refresh the readiness chip behind the dialog either way.
+                void refreshReadiness(false);
+              })
+              .catch((error: unknown) => {
+                // Belt-and-braces: runSync is contracted to return outcomes, never
+                // throw — but a throw must never leave the button stuck on
+                // "Downloading…" forever with no message.
+                syncBusy = false;
+                syncMessage =
+                  error instanceof Error ? `Sync failed. (${error.message})` : "Sync failed.";
+                paint();
+                void refreshReadiness(false);
+              });
           },
         }),
       );
diff --git a/src/app/notifications.ts b/src/app/notifications.ts
new file mode 100644
index 0000000..085c02a
--- /dev/null
+++ b/src/app/notifications.ts
@@ -0,0 +1,106 @@
+export type NotifyMode = "banner" | "browser" | "sound";
+
+interface WindowWithLegacyAudio extends Window {
+  webkitAudioContext?: typeof AudioContext;
+}
+
+function getPrefs(): NotifyMode[] {
+  try {
+    const raw = localStorage.getItem("lumen-notify-modes");
+    return raw ? (JSON.parse(raw) as NotifyMode[]) : ["banner", "browser"];
+  } catch {
+    return ["banner", "browser"];
+  }
+}
+
+function setPrefs(modes: NotifyMode[]): void {
+  localStorage.setItem("lumen-notify-modes", JSON.stringify(modes));
+}
+
+export function getEnabledModes(): NotifyMode[] {
+  return getPrefs();
+}
+
+export function toggleMode(mode: NotifyMode): NotifyMode[] {
+  const current = getPrefs();
+  const next = current.includes(mode) ? current.filter((m) => m !== mode) : [...current, mode];
+  setPrefs(next);
+  return next;
+}
+
+function showToast(msg: string): void {
+  const existing = document.getElementById("lumen-notification-banner");
+  if (existing) {
+    existing.textContent = msg;
+    existing.classList.add("notify-banner--visible");
+    window.setTimeout(() => {
+      existing.classList.remove("notify-banner--visible");
+    }, 4000);
+    return;
+  }
+  const toast = document.createElement("div");
+  toast.id = "lumen-notification-banner";
+  toast.textContent = msg;
+  toast.className = "notify-banner notify-banner--visible";
+  document.body.appendChild(toast);
+  window.setTimeout(() => {
+    toast.remove();
+  }, 4000);
+}
+
+export function notify(msg: string, modes?: NotifyMode[]): void {
+  const active = modes ?? getPrefs();
+  if (active.includes("banner")) {
+    showToast(msg);
+  }
+  if (active.includes("browser") && typeof Notification !== "undefined") {
+    if (Notification.permission === "granted") {
+      new Notification(msg);
+    } else if (Notification.permission !== "denied") {
+      void Notification.requestPermission().then((p) => {
+        if (p === "granted") new Notification(msg);
+      });
+    }
+  }
+  if (active.includes("sound")) {
+    try {
+      const Ctor = window.AudioContext ?? (window as WindowWithLegacyAudio).webkitAudioContext;
+      if (Ctor) {
+        const ctx = new Ctor();
+        if (ctx.state === "suspended") {
+          void ctx.resume();
+        }
+        const osc = ctx.createOscillator();
+        const gain = ctx.createGain();
+        osc.connect(gain);
+        gain.connect(ctx.destination);
+        osc.frequency.value = 1200;
+        gain.gain.value = 0.5;
+        osc.start();
+        osc.stop(ctx.currentTime + 0.3);
+      }
+    } catch {
+      // audio is best-effort — a blocked AudioContext must not eat the notification
+    }
+    // Visual pulse fallback for mobile browsers that block Web Audio / vibration
+    const pulse = document.createElement("div");
+    pulse.className = "notify-pulse";
+    document.body.appendChild(pulse);
+    window.setTimeout(() => {
+      pulse.remove();
+    }, 600);
+    if (typeof navigator.vibrate === "function") {
+      try {
+        navigator.vibrate([300, 100, 300, 100, 300]);
+      } catch (e) {
+        console.warn("vibrate blocked", e);
+      }
+    }
+  }
+}
+
+export function requestBrowserPermission(): void {
+  if (typeof Notification !== "undefined" && Notification.permission !== "granted") {
+    void Notification.requestPermission();
+  }
+}
diff --git a/src/app/styles.css b/src/app/styles.css
index 0d35296..11c8c78 100644
--- a/src/app/styles.css
+++ b/src/app/styles.css
@@ -962,3 +962,149 @@ html.dark .app-main__icon {
   color: var(--muted);
   font-size: 0.875rem;
 }
+
+/* Notification banner that appears at top of app */
+.notify-banner {
+  position: fixed;
+  top: calc(var(--header-h, 56px) + 1rem);
+  left: 50%;
+  transform: translateX(-50%) translateY(-20px);
+  background: var(--accent, #c8473a);
+  color: #fff;
+  padding: 0.75rem 1.25rem;
+  border-radius: 999px;
+  font-weight: 600;
+  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.25);
+  opacity: 0;
+  visibility: hidden;
+  transition:
+    opacity 0.25s ease,
+    transform 0.25s ease,
+    visibility 0.25s;
+  z-index: 1000;
+  pointer-events: none;
+  font-size: 0.9rem;
+}
+
+.notify-banner--visible {
+  opacity: 1;
+  visibility: visible;
+  transform: translateX(-50%) translateY(0);
+}
+
+.settings-view {
+  padding: 1rem;
+  max-width: 42rem;
+  margin: 0 auto;
+}
+
+.settings-section {
+  margin-bottom: 2rem;
+}
+
+.settings-section h2 {
+  font-size: 1.1rem;
+  margin-bottom: 0.5rem;
+}
+
+.settings-section p {
+  color: var(--fg-muted, #888);
+  margin-bottom: 1rem;
+}
+
+.settings-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 1rem;
+  padding: 0.75rem 0;
+  border-bottom: 1px solid var(--border, #ddd);
+}
+
+.settings-row__label {
+  display: flex;
+  flex-direction: column;
+  gap: 0.15rem;
+}
+
+.settings-row__label strong {
+  font-size: 1rem;
+}
+
+.settings-row__label small {
+  color: var(--fg-muted, #888);
+  font-size: 0.8rem;
+}
+
+.toggle-btn {
+  min-width: 60px;
+  min-height: 36px;
+  padding: 0.5rem 1rem;
+  border: 1px solid var(--border, #ccc);
+  border-radius: 999px;
+  background: var(--surface, #f0f0f0);
+  color: var(--fg, #000);
+  font-weight: 700;
+  cursor: pointer;
+  transition:
+    background-color 0.2s ease,
+    color 0.2s ease;
+}
+
+.toggle-btn--on {
+  background: var(--accent, #c8473a);
+  color: #fff;
+  border-color: var(--accent, #c8473a);
+}
+
+.settings-test-btn {
+  display: block;
+  margin: 1.5rem auto 0;
+  padding: 0.75rem 1.5rem;
+  border: none;
+  border-radius: 999px;
+  background: var(--accent, #c8473a);
+  color: #fff;
+  font-weight: 600;
+  font-size: 1rem;
+  cursor: pointer;
+}
+
+.settings-test-btn:hover {
+  opacity: 0.9;
+}
+
+.notify-pulse {
+  position: fixed;
+  inset: 0;
+  background: rgba(200, 71, 58, 0.25);
+  pointer-events: none;
+  z-index: 9999;
+  animation: pulseFlash 0.6s ease-out forwards;
+}
+
+@keyframes pulseFlash {
+  0% {
+    opacity: 1;
+  }
+  100% {
+    opacity: 0;
+  }
+}
+.emergency-share-btn {
+  display: block;
+  margin: 0.75rem 0;
+  padding: 0.75rem 1.25rem;
+  width: 100%;
+  border: none;
+  border-radius: var(--radius);
+  background: var(--accent);
+  color: #fff;
+  font-weight: 700;
+  font-size: 1rem;
+  cursor: pointer;
+  text-align: center;
+}
+.emergency-share-btn:hover {
+  opacity: 0.9;
+}
diff --git a/src/ui/router/router.ts b/src/ui/router/router.ts
index 2658427..7b88ffd 100644
--- a/src/ui/router/router.ts
+++ b/src/ui/router/router.ts
@@ -4,7 +4,8 @@
  * Trace: IMPLEMENTATION-CONTRACT.md §7, ARCHITECTURE-DESIGN.md:207
  */
 
-export type RouteId = "home" | "emergency" | "schedule" | "map" | "festival" | "not-found";
+export type RouteId =
+  "home" | "emergency" | "schedule" | "map" | "festival" | "settings" | "not-found";
 
 export interface Route {
   id: RouteId;
@@ -21,6 +22,7 @@ export const ROUTES: readonly Route[] = [
   { id: "emergency", path: "/emergency", label: "Emergency", title: "Emergency" },
   { id: "schedule", path: "/schedule", label: "Schedule", title: "Schedule" },
   { id: "map", path: "/map", label: "Map", title: "Map" },
+  { id: "settings", path: "/settings", label: "Settings", title: "Settings" },
   { id: "festival", path: "/festival", label: "Information", title: "Information" },
 ] as const;
 
diff --git a/src/ui/views/home/home.ts b/src/ui/views/home/home.ts
index f9913eb..c90fa1f 100644
--- a/src/ui/views/home/home.ts
+++ b/src/ui/views/home/home.ts
@@ -25,6 +25,7 @@ export function createHomeView(): HTMLElement {
   grid.className = "home-grid";
 
   for (const r of ROUTES) {
+    if (r.id === "settings") continue;
     const a = document.createElement("a");
     a.className = `home-tile${r.id === "emergency" ? " home-tile--emergency" : ""}`;
     a.href = r.path;
diff --git a/src/ui/views/settings/settings.ts b/src/ui/views/settings/settings.ts
new file mode 100644
index 0000000..532472f
--- /dev/null
+++ b/src/ui/views/settings/settings.ts
@@ -0,0 +1,89 @@
+import {
+  getEnabledModes,
+  toggleMode,
+  requestBrowserPermission,
+  notify,
+  type NotifyMode,
+} from "../../../app/notifications.js";
+
+export function renderSettings(): HTMLElement {
+  const el = document.createElement("div");
+  el.className = "settings-view";
+  el.setAttribute("aria-labelledby", "settings-heading");
+
+  const h1 = document.createElement("h1");
+  h1.id = "settings-heading";
+  h1.textContent = "Settings";
+  el.appendChild(h1);
+
+  // Request browser notification permission on open
+  requestBrowserPermission();
+
+  // Notification section
+  const section = document.createElement("section");
+  section.className = "settings-section";
+  const sectionTitle = document.createElement("h2");
+  sectionTitle.textContent = "Notifications";
+  section.appendChild(sectionTitle);
+
+  const desc = document.createElement("p");
+  desc.textContent = "Choose how you want to be notified when things change.";
+  section.appendChild(desc);
+
+  const modes: { id: NotifyMode; label: string; hint: string }[] = [
+    { id: "banner", label: "On-screen banner", hint: "Shows a message inside the app" },
+    {
+      id: "browser",
+      label: "Browser notification",
+      hint: "Pops up even if the tab is in the background",
+    },
+    { id: "sound", label: "Sound", hint: "Plays a short beep" },
+  ];
+
+  const enabled = getEnabledModes();
+
+  for (const m of modes) {
+    const row = document.createElement("div");
+    row.className = "settings-row";
+
+    const label = document.createElement("div");
+    label.className = "settings-row__label";
+    const strong = document.createElement("strong");
+    strong.textContent = m.label;
+    const hint = document.createElement("small");
+    hint.textContent = m.hint;
+    label.append(strong, hint);
+    row.appendChild(label);
+
+    const toggle = document.createElement("button");
+    toggle.className = "toggle-btn" + (enabled.includes(m.id) ? " toggle-btn--on" : "");
+    toggle.setAttribute("role", "switch");
+    toggle.setAttribute("aria-checked", String(enabled.includes(m.id)));
+    toggle.textContent = enabled.includes(m.id) ? "ON" : "OFF";
+
+    toggle.addEventListener("click", () => {
+      const next = toggleMode(m.id);
+      const isOn = next.includes(m.id);
+      toggle.classList.toggle("toggle-btn--on", isOn);
+      toggle.setAttribute("aria-checked", String(isOn));
+      toggle.textContent = isOn ? "ON" : "OFF";
+      notify("Toggled " + m.label + " " + (isOn ? "ON" : "OFF"), [m.id]);
+    });
+
+    row.appendChild(toggle);
+    section.appendChild(row);
+  }
+
+  el.appendChild(section);
+
+  // Test notification button
+  const testBtn = document.createElement("button");
+  testBtn.className = "settings-test-btn";
+  testBtn.textContent = "Send a test notification";
+  testBtn.addEventListener("click", () => {
+    notify("Test notification — all enabled methods fired");
+  });
+  el.appendChild(testBtn);
+
+  return el;
+}
diff --git a/tests/unit/sw.test.ts b/tests/unit/sw.test.ts
index aac8514..4bba849 100644
--- a/tests/unit/sw.test.ts
+++ b/tests/unit/sw.test.ts
@@ -119,12 +119,20 @@ describe("SW registration — page bridge", () => {
   it("registers /sw.js with scope / when supported", async () => {
     const mockReg = { scope: "/", waiting: null } as unknown as ServiceWorkerRegistration;
     const mockRegister = vi.fn().mockResolvedValue(mockReg);
+    const mockUnregister = vi.fn().mockResolvedValue(true);
     Object.defineProperty(globalThis, "navigator", {
-      value: { serviceWorker: { register: mockRegister } },
+      value: {
+        serviceWorker: {
+          register: mockRegister,
+          getRegistrations: vi.fn().mockResolvedValue([{ unregister: mockUnregister }]),
+        },
+      },
       writable: true,
       configurable: true,
     });
     const res = await registerSW();
+    // clean-update: any pre-existing worker is unregistered before re-registering
+    expect(mockUnregister).toHaveBeenCalled();
     expect(mockRegister).toHaveBeenCalledWith("/sw.js", { scope: "/" });
     expect(res.status).toBe("registered");
   });
@@ -132,7 +140,12 @@ describe("SW registration — page bridge", () => {
   it("returns failed when register throws (offline or HTTPS issue)", async () => {
     const mockRegister = vi.fn().mockRejectedValue(new Error("HTTPS required"));
     Object.defineProperty(globalThis, "navigator", {
-      value: { serviceWorker: { register: mockRegister } },
+      value: {
+        serviceWorker: {
+          register: mockRegister,
+          getRegistrations: vi.fn().mockResolvedValue([]),
+        },
+      },
       writable: true,
       configurable: true,
     });
diff --git a/vite.config.ts b/vite.config.ts
index 8917292..e9ecf65 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -24,10 +24,11 @@ function lumenShellPlugin(): Plugin {
       const version = `${pkg.version}-${gitHash}`;
       const cacheName = `lumen-shell-${version}`;
 
-      // Collect hashed assets produced by this build
+      // Collect hashed assets produced by this build — sourcemaps excluded:
+      // they bloat the install (~580KB) and the SW would cache-first them.
       const assetsDir = join(dist, "assets");
       const assetFiles = existsSync(assetsDir) ? readdirSync(assetsDir) : [];
-      const hashedAssets = assetFiles.map((f) => `/assets/${f}`);
+      const hashedAssets = assetFiles.filter((f) => !f.endsWith(".map")).map((f) => `/assets/${f}`);
 
       // Core shell URLs that must be precached (deterministic list per build)
       const core = [