diff --git a/lib/FilesHooks.php b/lib/FilesHooks.php
index 84d7ca8ee..57dd8f9cd 100644
--- a/lib/FilesHooks.php
+++ b/lib/FilesHooks.php
@@ -799,8 +799,8 @@ protected function shareWithTeam(string $shareWith, Node $fileSource, string $fi
 			return;
 		}
 
+		$this->teamManager->startSuperSession();
 		try {
-			$this->teamManager->startSuperSession();
 			$team = $this->teamManager->getCircle($shareWith);
 			$members = $team->getInheritedMembers();
 			$members = array_filter($members, fn ($member) => $member->getUserType() === Member::TYPE_USER);
@@ -809,6 +809,8 @@ protected function shareWithTeam(string $shareWith, Node $fileSource, string $fi
 			$this->logger->debug('Fetching team members for share activity failed', ['exception' => $e]);
 			// error in teams app - setting users list to empty
 			$userIds = [];
+		} finally {
+			$this->teamManager->stopSession();
 		}
 
 		// Activity for user performing the share
diff --git a/lib/NotificationGenerator.php b/lib/NotificationGenerator.php
index 59836ea07..6dd8fd1e9 100644
--- a/lib/NotificationGenerator.php
+++ b/lib/NotificationGenerator.php
@@ -124,8 +124,11 @@ public function prepare(INotification $notification, string $languageCode): INot
 			throw new AlreadyProcessedException();
 		}
 		$this->activityManager->setCurrentUserId($notification->getUser());
-		$event = $this->populateEvent($event, $languageCode);
-		$this->activityManager->setCurrentUserId(null);
+		try {
+			$event = $this->populateEvent($event, $languageCode);
+		} finally {
+			$this->activityManager->setCurrentUserId(null);
+		}
 
 		try {
 			return $this->getDisplayNotificationForEvent($event, $event->getObjectId());
diff --git a/tests/FilesHooksTest.php b/tests/FilesHooksTest.php
index 6939974bc..b992d3a0e 100644
--- a/tests/FilesHooksTest.php
+++ b/tests/FilesHooksTest.php
@@ -1039,6 +1039,31 @@ public static function dataAddNotificationsForUser(): array {
 		];
 	}
 
+	public function testAddNotificationsForUserSkipsInvalidEvent(): void {
+		$this->urlGenerator->method('linkToRouteAbsolute')
+			->willReturn('routeToFilesIndex');
+
+		$event = $this->createMock(IEvent::class);
+		$event->method('setApp')->willReturnSelf();
+		$event->method('setType')->willReturnSelf();
+		$event->method('setAffectedUser')->willReturnSelf();
+		$event->method('setTimestamp')->willReturnSelf();
+		$event->method('setSubject')
+			->willThrowException(new \InvalidArgumentException('invalid subject'));
+
+		$this->activityManager->expects($this->once())
+			->method('generateEvent')
+			->willReturn($event);
+
+		// A half-built event must never reach the stream or the mail queue
+		$this->data->expects($this->never())
+			->method('send');
+		$this->data->expects($this->never())
+			->method('storeMail');
+
+		self::invokePrivate($this->filesHooks, 'addNotificationsForUser', ['user1', 'subject', [], 42, '/file.txt', true, 3600, true, 'shared']);
+	}
+
 	#[DataProvider('dataAddNotificationsForUser')]
 	public function testAddNotificationsForUser(string $user, string $subject, array $parameter, int $fileId, string $path, string $urlPath, bool $isFile, bool $notification, bool $email, string $type, string $app, bool $sentEmail): void {
 		$this->urlGenerator->expects($this->once())
diff --git a/tests/NotificationGeneratorTest.php b/tests/NotificationGeneratorTest.php
new file mode 100644
index 000000000..98e329909
--- /dev/null
+++ b/tests/NotificationGeneratorTest.php
@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Activity\Tests;
+
+use OCA\Activity\Data;
+use OCA\Activity\NotificationGenerator;
+use OCA\Activity\UserSettings;
+use OCP\Activity\IEvent;
+use OCP\Activity\IManager as ActivityManager;
+use OCP\Activity\IProvider;
+use OCP\IL10N;
+use OCP\Notification\IManager as NotificationManager;
+use OCP\Notification\INotification;
+use PHPUnit\Framework\MockObject\MockObject;
+use Psr\Log\LoggerInterface;
+
+class NotificationGeneratorTest extends TestCase {
+	protected Data&MockObject $data;
+	protected ActivityManager&MockObject $activityManager;
+	protected NotificationGenerator $generator;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->data = $this->createMock(Data::class);
+		$this->activityManager = $this->createMock(ActivityManager::class);
+
+		$this->generator = new NotificationGenerator(
+			$this->data,
+			$this->activityManager,
+			$this->createMock(NotificationManager::class),
+			$this->createMock(UserSettings::class),
+			$this->createMock(IL10N::class),
+			$this->createMock(LoggerInterface::class),
+		);
+	}
+
+	public function testCurrentUserIsResetWhenAProviderThrows(): void {
+		$notification = $this->createMock(INotification::class);
+		$notification->method('getObjectType')->willReturn('activity_notification');
+		$notification->method('getObjectId')->willReturn('42');
+		$notification->method('getUser')->willReturn('affected');
+
+		$event = $this->createMock(IEvent::class);
+		$event->method('getAffectedUser')->willReturn('affected');
+		$this->data->method('getById')->willReturn($event);
+
+		$provider = $this->createMock(IProvider::class);
+		$provider->method('parse')
+			->willThrowException(new \RuntimeException('provider exploded'));
+		$this->activityManager->method('getProviders')
+			->willReturn([$provider]);
+
+		$seenUsers = [];
+		$this->activityManager->method('setCurrentUserId')
+			->willReturnCallback(static function (?string $uid) use (&$seenUsers): void {
+				$seenUsers[] = $uid;
+			});
+
+		try {
+			$this->generator->prepare($notification, 'en');
+			$this->fail('Expected the provider exception to propagate');
+		} catch (\RuntimeException) {
+		}
+
+		// The identity must not survive an exploding provider
+		$this->assertSame(['affected', null], $seenUsers);
+	}
+}
diff --git a/tests/psalm-baseline.xml b/tests/psalm-baseline.xml
index 2f435f189..25d3a3f89 100644
--- a/tests/psalm-baseline.xml
+++ b/tests/psalm-baseline.xml
@@ -23,6 +23,7 @@
   </file>
   <file src="lib/FilesHooks.php">
     <UndefinedClass>
+      <code><![CDATA[$this->teamManager]]></code>
       <code><![CDATA[$this->teamManager]]></code>
       <code><![CDATA[$this->teamManager]]></code>
       <code><![CDATA[Member]]></code>