diff --git a/apps/dav/lib/CardDAV/SyncService.php b/apps/dav/lib/CardDAV/SyncService.php
index 5ba0a1e529de7..78c02a9414e02 100644
--- a/apps/dav/lib/CardDAV/SyncService.php
+++ b/apps/dav/lib/CardDAV/SyncService.php
@@ -46,19 +46,26 @@ public function __construct(
 	 * @psalm-return list{0: ?string, 1: boolean}
 	 * @throws \Exception
 	 */
-	public function syncRemoteAddressBook(string $url, string $userName, string $addressBookUrl, string $sharedSecret, ?string $syncToken, string $targetBookHash, string $targetPrincipal, array $targetProperties): array {
+	public function syncRemoteAddressBook(string $url, string $userName, string $addressBookUrl, string $sharedSecret, ?string $syncToken, string $targetBookHash, string $targetPrincipal, array $targetProperties, bool $syncAddressBookData = true): array {
 		// 1. create addressbook
-		$book = $this->ensureSystemAddressBookExists($targetPrincipal, $targetBookHash, $targetProperties);
-		$addressBookId = $book['id'];
+		$addressBookId = null;
+		if ($syncAddressBookData) {
+			$book = $this->ensureSystemAddressBookExists($targetPrincipal, $targetBookHash, $targetProperties);
+			$addressBookId = $book['id'];
+		}
 
 		// 2. query changes
+		// This keeps validating the shared secret and advancing the sync token
+		// against the remote even when applying the changes locally is disabled.
 		try {
 			$absoluteUri = $this->prepareUri($url, $addressBookUrl);
 			$response = $this->requestSyncReport($absoluteUri, $userName, $sharedSecret, $syncToken);
 		} catch (ClientExceptionInterface $ex) {
 			if ($ex->getCode() === Http::STATUS_UNAUTHORIZED) {
 				// remote server revoked access to the address book, remove it
-				$this->backend->deleteAddressBook($addressBookId);
+				if ($addressBookId !== null) {
+					$this->backend->deleteAddressBook($addressBookId);
+				}
 				$this->logger->error('Authorization failed, remove address book: ' . $url, ['app' => 'dav']);
 				throw $ex;
 			}
@@ -68,21 +75,23 @@ public function syncRemoteAddressBook(string $url, string $userName, string $add
 
 		// 3. apply changes
 		// TODO: use multi-get for download
-		foreach ($response['response'] as $resource => $status) {
-			$cardUri = basename($resource);
-			if (isset($status[200])) {
-				$absoluteUrl = $this->prepareUri($url, $resource);
-				$vCard = $this->download($absoluteUrl, $userName, $sharedSecret);
-				$this->atomic(function () use ($addressBookId, $cardUri, $vCard): void {
-					$existingCard = $this->backend->getCard($addressBookId, $cardUri);
-					if ($existingCard === false) {
-						$this->backend->createCard($addressBookId, $cardUri, $vCard);
-					} else {
-						$this->backend->updateCard($addressBookId, $cardUri, $vCard);
-					}
-				}, $this->dbConnection);
-			} else {
-				$this->backend->deleteCard($addressBookId, $cardUri);
+		if ($syncAddressBookData) {
+			foreach ($response['response'] as $resource => $status) {
+				$cardUri = basename($resource);
+				if (isset($status[200])) {
+					$absoluteUrl = $this->prepareUri($url, $resource);
+					$vCard = $this->download($absoluteUrl, $userName, $sharedSecret);
+					$this->atomic(function () use ($addressBookId, $cardUri, $vCard): void {
+						$existingCard = $this->backend->getCard($addressBookId, $cardUri);
+						if ($existingCard === false) {
+							$this->backend->createCard($addressBookId, $cardUri, $vCard);
+						} else {
+							$this->backend->updateCard($addressBookId, $cardUri, $vCard);
+						}
+					}, $this->dbConnection);
+				} else {
+					$this->backend->deleteCard($addressBookId, $cardUri);
+				}
 			}
 		}
 
diff --git a/apps/federation/lib/SyncFederationAddressBooks.php b/apps/federation/lib/SyncFederationAddressBooks.php
index 5ad64708bb737..09960370ecbd3 100644
--- a/apps/federation/lib/SyncFederationAddressBooks.php
+++ b/apps/federation/lib/SyncFederationAddressBooks.php
@@ -9,6 +9,7 @@
 
 use OCA\DAV\CardDAV\SyncService;
 use OCP\AppFramework\Http;
+use OCP\IConfig;
 use OCP\OCS\IDiscoveryService;
 use Psr\Log\LoggerInterface;
 
@@ -18,6 +19,7 @@ public function __construct(
 		private SyncService $syncService,
 		private IDiscoveryService $ocsDiscoveryService,
 		private LoggerInterface $logger,
+		private IConfig $config,
 	) {
 	}
 
@@ -25,6 +27,10 @@ public function __construct(
 	 * @param \Closure $callback
 	 */
 	public function syncThemAll(\Closure $callback, bool $full = false) {
+		// When disabled, the sync-report request against the remote still runs
+		// each cycle (validating the shared secret and advancing the sync token),
+		// but the returned cards are not applied to the local address book.
+		$syncAddressBookData = $this->config->getSystemValueBool('federation_sync_addressbook_data', true);
 		$trustedServers = $this->dbHandler->getAllServer();
 		foreach ($trustedServers as $trustedServer) {
 			$url = $trustedServer['url'];
@@ -47,11 +53,19 @@ public function syncThemAll(\Closure $callback, bool $full = false) {
 			];
 
 			try {
+				// A full resync marks all existing cards as pending and then deletes
+				// whichever ones are not confirmed by the remote. That only makes
+				// sense if card data is actually being applied, otherwise it would
+				// just wipe out the local address book.
+				$full = $full && $syncAddressBookData;
 				$syncToken = $full ? null : $oldSyncToken;
 
-				$book = $this->syncService->ensureSystemAddressBookExists($targetPrincipal, $targetBookId, $targetBookProperties);
-				if ($full) {
-					$this->syncService->markCardsAsPending($book['id']);
+				$book = null;
+				if ($syncAddressBookData) {
+					$book = $this->syncService->ensureSystemAddressBookExists($targetPrincipal, $targetBookId, $targetBookProperties);
+					if ($full) {
+						$this->syncService->markCardsAsPending($book['id']);
+					}
 				}
 
 				do {
@@ -63,7 +77,8 @@ public function syncThemAll(\Closure $callback, bool $full = false) {
 						$syncToken,
 						$targetBookId,
 						$targetPrincipal,
-						$targetBookProperties
+						$targetBookProperties,
+						$syncAddressBookData
 					);
 				} while ($truncated);