From 55484453a12efaa026e70b2e3c634269312db808 Mon Sep 17 00:00:00 2001
From: Linus Rath <139418639+rathlinus@users.noreply.github.com>
Date: Wed, 17 Jun 2026 09:39:20 +0200
Subject: [PATCH] fix: coalesce concurrent push setups to prevent subscription
 swarm

---
 src/lib/__tests__/push-notifications.test.ts | 18 +++++++++++++
 src/lib/push-notifications.ts                | 28 ++++++++++++++++++--
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/src/lib/__tests__/push-notifications.test.ts b/src/lib/__tests__/push-notifications.test.ts
index 2435e7bb..138a9da3 100644
--- a/src/lib/__tests__/push-notifications.test.ts
+++ b/src/lib/__tests__/push-notifications.test.ts
@@ -39,6 +39,7 @@ import AsyncStorage from '@react-native-async-storage/async-storage';
 import { setupPushNotifications, deviceClientIdKey } from '../push-notifications';
 import {
   listPushSubscriptions,
+  createPushSubscription,
   destroyPushSubscription,
 } from '../../api/push';
 import { generateAccountId } from '../account-utils';
@@ -74,6 +75,7 @@ function installFetch(states: Record<string, RelayState>): void {
 
 const destroyMock = destroyPushSubscription as ReturnType<typeof vi.fn>;
 const listMock = listPushSubscriptions as ReturnType<typeof vi.fn>;
+const createMock = createPushSubscription as ReturnType<typeof vi.fn>;
 
 function sub(id: string, deviceClientId: string) {
   return { id, deviceClientId, expires: new Date(Date.now() + 86400000).toISOString(), types: ['Email'] };
@@ -128,4 +130,20 @@ describe('setupPushNotifications leftover reaping', () => {
 
     expect(destroyMock.mock.calls.map((c) => c[0])).not.toContain('foreign-x');
   });
+
+  it('coalesces concurrent setups into a single flow (no subscription swarm)', async () => {
+    listMock.mockResolvedValue([]);
+    installFetch({});
+
+    // Fire several overlapping setups, as App.tsx does while auth settles and
+    // on FCM token refresh. Only one underlying JMAP subscription must be made.
+    const results = await Promise.all([
+      setupPushNotifications({ relayBaseUrl: RELAY }),
+      setupPushNotifications({ relayBaseUrl: RELAY }),
+      setupPushNotifications({ relayBaseUrl: RELAY }),
+    ]);
+
+    expect(createMock).toHaveBeenCalledTimes(1);
+    expect(new Set(results.map((r) => r.subscriptionId)).size).toBe(1);
+  });
 });
diff --git a/src/lib/push-notifications.ts b/src/lib/push-notifications.ts
index eaafec23..12850b8c 100644
--- a/src/lib/push-notifications.ts
+++ b/src/lib/push-notifications.ts
@@ -268,12 +268,36 @@ async function pollVerificationCode(
   throw new Error('Timed out waiting for PushVerification from JMAP server');
 }
 
+// Coalesce concurrent setup attempts per account. App.tsx re-runs its push
+// effect as auth state settles during startup and again on every FCM token
+// refresh; because a failing attempt blocks for up to 75s polling for the
+// verification code, those re-fires overlap. Without this guard each
+// overlapping run mints its OWN deviceClientId and JMAP subscription, and the
+// resulting swarm starves Stalwart's one-PushVerification-per-60s slot so none
+// of them ever verifies (the symptom is a perpetual "Timed out waiting for
+// PushVerification"). Callers share the first in-flight run instead.
+const inFlightSetups = new Map<string, Promise<PushSetupResult>>();
+
 /**
  * Full setup flow: ask permission, fetch the device's FCM token, register
  * with the relay, create a JMAP PushSubscription, poll for the verification
- * code, and finalise the subscription.
+ * code, and finalise the subscription. Concurrent calls for the same account
+ * are coalesced onto a single in-flight run.
  */
-export async function setupPushNotifications(
+export function setupPushNotifications(
+  params: PushSetupParams,
+): Promise<PushSetupResult> {
+  const key = `${jmapClient.username ?? ''}@${jmapClient.serverUrl ?? ''}`;
+  const existing = inFlightSetups.get(key);
+  if (existing) return existing;
+  const run = setupPushNotificationsInner(params).finally(() => {
+    inFlightSetups.delete(key);
+  });
+  inFlightSetups.set(key, run);
+  return run;
+}
+
+async function setupPushNotificationsInner(
   params: PushSetupParams,
 ): Promise<PushSetupResult> {
   const native = getNative();