fix: fetch and activate the new service worker on Refresh UI when none is waiting yet

frontend/sw-update.test.js

@@ -93,6 +93,76 @@ test('falls back to a plain reload when there is no waiting worker', async () =>
   assert.strictEqual(reloadCount, 1);
 });
 
+test('with no waiting worker, fetches the SW update and activates the newly installed worker (buildTag-poll path)', async () => {
+  // Simulates: server redeployed (banner shown by the /api/version poll) but
+  // the browser hasn't fetched the new sw.js yet — reg.waiting is null until
+  // reg.update() is called and the new worker finishes installing.
+  const messages = [];
+  const container = fakeContainer();
+  let reloadCount = 0;
+
+  const stateListeners = [];
+  const installing = {
+    state: 'installing',
+    addEventListener: (type, fn) => { if (type === 'statechange') stateListeners.push(fn); },
+    postMessage: (m) => messages.push(m),
+  };
+  const reg = {
+    waiting: null,
+    installing: null,
+    update() {
+      // Browser found a byte-different sw.js → a new worker starts installing.
+      this.installing = installing;
+      return Promise.resolve();
+    },
+  };
+
+  const done = applyUpdate({
+    reg,
+    container,
+    reload: () => { reloadCount++; },
+    setTimeout: () => {}, // no-op — we drive state transitions manually
+  });
+
+  // Let applyUpdate reach the waitForInstalled stage, then finish the install.
+  await Promise.resolve(); await Promise.resolve();
+  installing.state = 'installed';
+  reg.waiting = installing;
+  stateListeners.forEach((fn) => fn());
+  await Promise.resolve(); await Promise.resolve();
+
+  assert.deepStrictEqual(messages, [{ type: 'SKIP_WAITING' }], 'skip-waiting sent to the freshly installed worker');
+  assert.strictEqual(reloadCount, 0, 'must not reload before the new SW takes control');
+
+  container.fireControllerChange();
+  await done;
+  assert.strictEqual(reloadCount, 1);
+});
+
+test('with no waiting worker and no update found, reloads once after the bounded wait', async () => {
+  const container = fakeContainer();
+  let reloadCount = 0;
+  const timeouts = [];
+
+  const reg = {
+    waiting: null,
+    installing: null,
+    update: () => Promise.resolve(), // update check ran; nothing new
+  };
+
+  const done = applyUpdate({
+    reg,
+    container,
+    reload: () => { reloadCount++; },
+    setTimeout: (fn) => { timeouts.push(fn); },
+  });
+
+  await Promise.resolve(); await Promise.resolve();
+  // reg.installing is null → waitForInstalled resolves immediately with null.
+  await done;
+  assert.strictEqual(reloadCount, 1, 'plain reload when the update check finds nothing');
+});
+
 test('falls back to a plain reload when there is no registration at all', async () => {
   const container = fakeContainer();
   let reloadCount = 0;