diff --git a/apps/web/src/service-worker.ts b/apps/web/src/service-worker.ts
new file mode 100644
index 0000000..565fecd
--- /dev/null
+++ b/apps/web/src/service-worker.ts
@@ -0,0 +1,77 @@
+/// <reference lib="webworker" />
+/// <reference types="@sveltejs/kit" />
+
+import { build, files, version } from '$service-worker';
+
+// Give `self` the correct type
+const selfRef = globalThis.self as unknown as ServiceWorkerGlobalScope;
+
+// Unique cache key per deployment
+const CACHE = `gt-cache-${version}`;
+
+// Precache application shell (built assets) and static files
+const ASSETS = [
+  ...build,
+  ...files
+];
+
+selfRef.addEventListener('install', (event) => {
+  event.waitUntil(
+    (async () => {
+      const cache = await caches.open(CACHE);
+      await cache.addAll(ASSETS);
+    })()
+  );
+});
+
+selfRef.addEventListener('activate', (event) => {
+  event.waitUntil(
+    (async () => {
+      const keys = await caches.keys();
+      await Promise.all(keys.map((k) => (k === CACHE ? undefined : caches.delete(k))));
+      // Claim clients so updated SW takes control immediately on refresh
+      await selfRef.clients.claim();
+    })()
+  );
+});
+
+selfRef.addEventListener('fetch', (event: FetchEvent) => {
+  // Only handle GET requests
+  if (event.request.method !== 'GET') return;
+
+  const url = new URL(event.request.url);
+
+  // Serve precached ASSETS from cache directly
+  if (ASSETS.includes(url.pathname)) {
+    event.respondWith(
+      (async () => {
+        const cache = await caches.open(CACHE);
+        const cached = await cache.match(url.pathname);
+        if (cached) return cached;
+        // Fallback to network if somehow missing
+        const res = await fetch(event.request);
+        if (res.ok) cache.put(url.pathname, res.clone());
+        return res;
+      })()
+    );
+    return;
+  }
+
+  // Runtime: network-first with cache fallback for other GETs
+  event.respondWith(
+    (async () => {
+      const cache = await caches.open(CACHE);
+      try {
+        const res = await fetch(event.request);
+        if (res instanceof Response && res.status === 200) {
+          cache.put(event.request, res.clone());
+        }
+        return res;
+      } catch (err) {
+        const cached = await cache.match(event.request);
+        if (cached) return cached;
+        throw err; // propagate if nothing cached
+      }
+    })()
+  );
+});
diff --git a/apps/web/svelte.config.js b/apps/web/svelte.config.js
index 5c6b098..1d0ff18 100644
--- a/apps/web/svelte.config.js
+++ b/apps/web/svelte.config.js
@@ -8,7 +8,10 @@ const config = {
     adapter: adapter({
       fallback: '200.html'
     }),
-    // Service worker wiring comes in T008
+    serviceWorker: {
+      // keep default auto-registration explicit
+      register: true
+    },
     paths: {
       // supports GitHub Pages-like hosting later; keep default for now
     }
diff --git a/specs/001-glowtrack-a-mood/tasks.md b/specs/001-glowtrack-a-mood/tasks.md
index e90df09..2c3aa41 100644
--- a/specs/001-glowtrack-a-mood/tasks.md
+++ b/specs/001-glowtrack-a-mood/tasks.md
@@ -60,7 +60,7 @@ Paths below are absolute to this repo.
   - Root CI scripts in tools/ci (stub) and package scripts wiring
   - Dependencies: T005
 
-- [ ] T008 PWA service worker wiring (SvelteKit)
+- [X] T008 PWA service worker wiring (SvelteKit)
   - Enable service worker in SvelteKit config and add minimal SW handler
   - Ensure static asset caching strategy is defined (runtime-minimal)
   - Dependencies: T005