diff --git a/lib/__tests__/web-push.test.ts b/lib/__tests__/web-push.test.ts
index ea36d69ce..ec5434d5a 100644
--- a/lib/__tests__/web-push.test.ts
+++ b/lib/__tests__/web-push.test.ts
@@ -958,6 +958,50 @@ describe('a setup that gets stuck', () => {
   });
 });
 
+describe('a re-sync waiting its turn', () => {
+  afterEach(() => { delete (navigator as unknown as { locks?: unknown }).locks; });
+
+  it('does not bring back what another tab turned off meanwhile', async () => {
+    localStorage.setItem(DEVICE_KEY, THIS_DEVICE);
+    localStorage.setItem(SUB_KEY, 'push-mine');
+    localStorage.setItem(RELAY_BASE_KEY, RELAY);
+    const client = makeClient([sub('push-mine', THIS_DEVICE)]);
+    installFetch({ [THIS_DEVICE]: true });
+    let turn: Promise<unknown> = Promise.resolve();
+    let release = () => {};
+    turn = new Promise<void>((resolve) => { release = resolve; });
+    Object.defineProperty(navigator, 'locks', {
+      configurable: true,
+      value: { request: (_n: string, run: () => Promise<unknown>) => { const next = turn.then(run, run); turn = next.catch(() => undefined); return next; } },
+    });
+
+    const resync = resyncWebPush({ client, relayBaseUrl: RELAY, inboxOnly: false });
+    await vi.waitFor(() => expect((navigator as unknown as { locks: unknown }).locks).toBeTruthy());
+    await new Promise((resolve) => setTimeout(resolve, 0));
+    localStorage.removeItem(SUB_KEY); // The other tab, holding the lock.
+    release();
+    await resync;
+
+    expect(client.updatePushSubscription).not.toHaveBeenCalled();
+    expect(client.createPushSubscription).not.toHaveBeenCalled();
+    expect(localStorage.getItem(SUB_KEY)).toBeNull();
+  });
+});
+
+describe('a registration from before the relay was remembered', () => {
+  it('gets the relay noted when it is refreshed', async () => {
+    localStorage.setItem(DEVICE_KEY, THIS_DEVICE);
+    localStorage.setItem(SUB_KEY, 'push-mine');
+    const client = makeClient([sub('push-mine', THIS_DEVICE)]);
+    installFetch({ [THIS_DEVICE]: true });
+
+    await resyncWebPush({ client, relayBaseUrl: RELAY, inboxOnly: false });
+
+    expect(localStorage.getItem(RELAY_BASE_KEY)).toBe(RELAY);
+    expect(client.createPushSubscription).not.toHaveBeenCalled();
+  });
+});
+
 describe('resyncWebPush when the relay changed (#903)', () => {
   afterEach(() => setNoThirdPartyTraffic(false));
 
diff --git a/lib/web-push.ts b/lib/web-push.ts
index b399c6edf..d583ee993 100644
--- a/lib/web-push.ts
+++ b/lib/web-push.ts
@@ -428,6 +428,8 @@ export interface EnableWebPushParams {
   // that outlives a permission change keeps pushing for mailboxes the user can
   // no longer read - recreating is the only client-side remedy (#841).
   forceRecreate?: boolean;
+  // For a re-sync: stop if another tab turned push off while this waited its turn.
+  onlyIfStillOn?: boolean;
   // Scope OS push notifications to Inbox-only mail. Mirrors settings-store's
   // pushNotifyInboxOnly. Required, not optional: it changes the server-side
   // delivery filter, so every caller must decide explicitly.
@@ -813,6 +815,9 @@ async function enableWebPushForThisTab(
   params: EnableWebPushParams,
   relayBaseUrl: string,
 ): Promise<EnableWebPushResult> {
+  if (params.onlyIfStillOn && !localStorage.getItem(subscriptionIdKey(params.client.getAccountId()))) {
+    return { subscriptionId: '' };
+  }
   const registration = await ensureServiceWorker();
 
   const vapidPublicKey = await fetchVapidPublicKey(relayBaseUrl);
@@ -914,6 +919,8 @@ async function enableWebPushForThisTab(
         const refreshed = await refreshSubscriptionExpires(params.client, match, emailPush);
         if (refreshed) {
           rememberRefusedEmailPushAccounts(accountId, refusedBefore, emailPush, refreshed.emailPush);
+          // Unless it moved, which goes the other way, this is where it lives.
+          if (!localStorage.getItem(relayBaseKey(accountId))) localStorage.setItem(relayBaseKey(accountId), relayBaseUrl);
           return { subscriptionId: storedServerId };
         }
       }
@@ -1317,6 +1324,7 @@ async function runResync(accountId: string, params: ResyncWebPushParams): Promis
     if (!moved && !params.force && !(await resyncDue(accountId))) return false;
     await enableWebPush({
       client: params.client,
+      onlyIfStillOn: true,
       forceRecreate: moved,
       relayBaseUrl: params.relayBaseUrl,
       accountLabel: params.accountLabel,