diff --git a/apps/dav/lib/CardDAV/CardDavBackend.php b/apps/dav/lib/CardDAV/CardDavBackend.php
index 98a50ed5d0df2..e19119eb672a0 100644
--- a/apps/dav/lib/CardDAV/CardDavBackend.php
+++ b/apps/dav/lib/CardDAV/CardDavBackend.php
@@ -723,6 +723,8 @@ public function updateCard($addressBookId, $cardUri, $cardData) {
 				return '"' . $etag . '"';
 			}
 
+			$storedEtag = $this->getCardEtag($addressBookId, $cardUri);
+
 			$query->update($this->dbCardsTable)
 				->set('carddata', $query->createNamedParameter($cardData, IQueryBuilder::PARAM_LOB))
 				->set('lastmodified', $query->createNamedParameter(time()))
@@ -735,9 +737,14 @@ public function updateCard($addressBookId, $cardUri, $cardData) {
 
 			$this->etagCache[$etagCacheKey] = $etag;
 
-			$this->addChange($addressBookId, $cardUri, 2);
 			$this->updateProperties($addressBookId, $cardUri, $cardData);
 
+			if ($storedEtag === $etag) {
+				return '"' . $etag . '"';
+			}
+
+			$this->addChange($addressBookId, $cardUri, 2);
+
 			$addressBookData = $this->getAddressBookById($addressBookId);
 			$shares = $this->getShares($addressBookId);
 			$objectRow = $this->getCard($addressBookId, $cardUri);
@@ -820,9 +827,9 @@ public function deleteCard($addressBookId, $cardUri) {
 				->andWhere($query->expr()->eq('uri', $query->createNamedParameter($cardUri)))
 				->executeStatement();
 
-			$this->addChange($addressBookId, $cardUri, 3);
-
 			if ($ret === 1) {
+				$this->addChange($addressBookId, $cardUri, 3);
+
 				if ($cardId !== null) {
 					$this->dispatcher->dispatchTyped(new CardDeletedEvent($addressBookId, $addressBookData, $shares, $objectRow));
 					$this->purgeProperties($addressBookId, $cardId);
@@ -1486,6 +1493,22 @@ protected function getCardId(int $addressBookId, string $uri): int {
 		return (int)$cardIds['id'];
 	}
 
+	/**
+	 * Get the etag currently stored for a contact, or null if there is none
+	 */
+	protected function getCardEtag(int $addressBookId, string $uri): ?string {
+		$query = $this->db->getQueryBuilder();
+		$query->select('etag')->from($this->dbCardsTable)
+			->where($query->expr()->eq('uri', $query->createNamedParameter($uri)))
+			->andWhere($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)));
+
+		$result = $query->executeQuery();
+		$etag = $result->fetchOne();
+		$result->closeCursor();
+
+		return $etag === false ? null : (string)$etag;
+	}
+
 	/**
 	 * For shared address books the sharee is set in the ACL of the address book
 	 *
diff --git a/apps/dav/tests/unit/CardDAV/CardDavBackendTest.php b/apps/dav/tests/unit/CardDAV/CardDavBackendTest.php
index 8b6b9fccd13fb..eb5dfa105ea24 100644
--- a/apps/dav/tests/unit/CardDAV/CardDavBackendTest.php
+++ b/apps/dav/tests/unit/CardDAV/CardDavBackendTest.php
@@ -141,13 +141,7 @@ protected function setUp(): void {
 			$this->createMock(LoggerInterface::class)
 		);
 
-		$this->backend = new CardDavBackend($this->db,
-			$this->principal,
-			$this->userManager,
-			$this->dispatcher,
-			$this->sharingBackend,
-			$this->config,
-		);
+		$this->backend = $this->createBackend();
 		// start every test with a empty cards_properties and cards table
 		$query = $this->db->getQueryBuilder();
 		$query->delete('cards_properties')->executeStatement();
@@ -163,6 +157,44 @@ protected function setUp(): void {
 		}
 	}
 
+	/**
+	 * A fresh instance starts with an empty in-memory etag cache, like a
+	 * subsequent request or background job would.
+	 */
+	private function createBackend(): CardDavBackend {
+		return new CardDavBackend($this->db,
+			$this->principal,
+			$this->userManager,
+			$this->dispatcher,
+			$this->sharingBackend,
+			$this->config,
+		);
+	}
+
+	private function countChanges(int $addressBookId): int {
+		$query = $this->db->getQueryBuilder();
+		$query->select($query->func()->count('*'))
+			->from('addressbookchanges')
+			->where($query->expr()->eq('addressbookid', $query->createNamedParameter($addressBookId)));
+		$result = $query->executeQuery();
+		$count = (int)$result->fetchOne();
+		$result->closeCursor();
+
+		return $count;
+	}
+
+	private function getSyncToken(int $addressBookId): int {
+		$query = $this->db->getQueryBuilder();
+		$query->select('synctoken')
+			->from('addressbooks')
+			->where($query->expr()->eq('id', $query->createNamedParameter($addressBookId)));
+		$result = $query->executeQuery();
+		$syncToken = (int)$result->fetchOne();
+		$result->closeCursor();
+
+		return $syncToken;
+	}
+
 	protected function tearDown(): void {
 		if (is_null($this->backend)) {
 			return;
@@ -486,6 +518,69 @@ public function testDeleteWithoutCard(): void {
 		$this->assertTrue($this->backend->deleteCard($bookId, $uri));
 	}
 
+	public function testDeleteCardWithoutMatchingRowRecordsNoChange(): void {
+		$this->backend->createAddressBook(self::UNIT_TEST_USER, 'Example', []);
+		$books = $this->backend->getUsersOwnAddressBooks(self::UNIT_TEST_USER);
+		$bookId = (int)$books[0]['id'];
+
+		$this->assertFalse($this->backend->deleteCard($bookId, 'does-not-exist.vcf'));
+
+		$this->assertSame(0, $this->countChanges($bookId));
+		$this->assertSame(1, $this->getSyncToken($bookId));
+	}
+
+	public function testUpdateCardWithUnchangedDataRecordsNoChange(): void {
+		$this->backend->createAddressBook(self::UNIT_TEST_USER, 'Example', []);
+		$books = $this->backend->getUsersOwnAddressBooks(self::UNIT_TEST_USER);
+		$bookId = (int)$books[0]['id'];
+
+		$uri = $this->getUniqueID('card');
+		$this->backend->createCard($bookId, $uri, $this->vcardTest0);
+		$changesAfterCreate = $this->countChanges($bookId);
+		$syncTokenAfterCreate = $this->getSyncToken($bookId);
+
+		$etag = $this->createBackend()->updateCard($bookId, $uri, $this->vcardTest0);
+
+		$this->assertEquals('"' . md5($this->vcardTest0) . '"', $etag);
+		$this->assertSame($changesAfterCreate, $this->countChanges($bookId));
+		$this->assertSame($syncTokenAfterCreate, $this->getSyncToken($bookId));
+	}
+
+	public function testUpdateCardWithChangedDataRecordsChange(): void {
+		$this->backend->createAddressBook(self::UNIT_TEST_USER, 'Example', []);
+		$books = $this->backend->getUsersOwnAddressBooks(self::UNIT_TEST_USER);
+		$bookId = (int)$books[0]['id'];
+
+		$uri = $this->getUniqueID('card');
+		$this->backend->createCard($bookId, $uri, $this->vcardTest0);
+		$changesAfterCreate = $this->countChanges($bookId);
+		$syncTokenAfterCreate = $this->getSyncToken($bookId);
+
+		$this->createBackend()->updateCard($bookId, $uri, $this->vcardTest1);
+
+		$this->assertSame($changesAfterCreate + 1, $this->countChanges($bookId));
+		$this->assertSame($syncTokenAfterCreate + 1, $this->getSyncToken($bookId));
+	}
+
+	/**
+	 * Federated full syncs null `lastmodified` up front and delete whatever is
+	 * still null afterwards, so an unchanged card must still refresh the column.
+	 */
+	public function testUpdateCardWithUnchangedDataClearsPendingState(): void {
+		$this->backend->createAddressBook(self::UNIT_TEST_USER, 'Example', []);
+		$books = $this->backend->getUsersOwnAddressBooks(self::UNIT_TEST_USER);
+		$bookId = (int)$books[0]['id'];
+
+		$uri = $this->getUniqueID('card');
+		$this->backend->createCard($bookId, $uri, $this->vcardTest0);
+		$this->backend->markCardsAsPending($bookId);
+		$this->assertCount(1, $this->backend->getPendingCards($bookId));
+
+		$this->createBackend()->updateCard($bookId, $uri, $this->vcardTest0);
+
+		$this->assertEmpty($this->backend->getPendingCards($bookId));
+	}
+
 	public function testSyncSupport(): void {
 		$this->backend = $this->getMockBuilder(CardDavBackend::class)
 			->setConstructorArgs([$this->db, $this->principal, $this->userManager, $this->dispatcher, $this->sharingBackend, $this->config])