diff --git a/apps/files/tests/Sharing/Source/NodeShareSourceTypeTest.php b/apps/files/tests/Sharing/Source/NodeShareSourceTypeTest.php
index 3311775b4cc7d..31d699361cfd0 100644
--- a/apps/files/tests/Sharing/Source/NodeShareSourceTypeTest.php
+++ b/apps/files/tests/Sharing/Source/NodeShareSourceTypeTest.php
@@ -14,7 +14,6 @@
 use OC\Files\Filesystem;
 use OC\User\Database;
 use OCA\Files\Sharing\Source\NodeShareSourceType;
-use OCA\Sharing\SharingBackend;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\Files\IRootFolder;
 use OCP\Files\Node;
@@ -95,7 +94,6 @@ public function testGetSourceIcon(): void {
 	public function testDelete(): void {
 		$registry = Server::get(ISharingRegistry::class);
 		$registry->clear();
-		$registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$registry->registerSourceType($this->sourceType);
 
 		$accessContext = new ShareAccessContext(currentUser: $this->user1);
diff --git a/apps/sharebymail/lib/ShareByMailProvider.php b/apps/sharebymail/lib/ShareByMailProvider.php
index 1f9ee46ebc7ec..2aa239b0b241d 100644
--- a/apps/sharebymail/lib/ShareByMailProvider.php
+++ b/apps/sharebymail/lib/ShareByMailProvider.php
@@ -224,7 +224,9 @@ protected function publishActivity(string $subject, array $parameters, string $a
 	 * @throws \Exception
 	 */
 	protected function createMailShare(IShare $share): string {
-		$share->setToken($this->generateToken());
+		if ($share->getToken() === '') {
+			$share->setToken($this->generateToken());
+		}
 		return $this->addShareToDB(
 			$share->getNodeId(),
 			$share->getNodeType(),
diff --git a/apps/sharebymail/tests/ShareByMailProviderTest.php b/apps/sharebymail/tests/ShareByMailProviderTest.php
index 300bf7c94d0ec..2369aa544c9cd 100644
--- a/apps/sharebymail/tests/ShareByMailProviderTest.php
+++ b/apps/sharebymail/tests/ShareByMailProviderTest.php
@@ -670,7 +670,7 @@ public function testCreateFailed(): void {
 	}
 
 	public function testCreateMailShare(): void {
-		$this->share->expects($this->any())->method('getToken')->willReturn('token');
+		$this->share->expects($this->any())->method('getToken')->willReturn('');
 		$this->share->expects($this->once())->method('setToken')->with('token');
 		$this->share->expects($this->any())->method('getSharedBy')->willReturn('validby@valid.com');
 		$this->share->expects($this->any())->method('getSharedWith')->willReturn('validwith@valid.com');
diff --git a/apps/sharing/composer/composer/autoload_classmap.php b/apps/sharing/composer/composer/autoload_classmap.php
index 163ae995691ba..0d6e87b5cfd0d 100644
--- a/apps/sharing/composer/composer/autoload_classmap.php
+++ b/apps/sharing/composer/composer/autoload_classmap.php
@@ -27,5 +27,4 @@
     'OCA\\Sharing\\Middleware\\ShareApiEnabledMiddleware' => $baseDir . '/../lib/Middleware/ShareApiEnabledMiddleware.php',
     'OCA\\Sharing\\Migration\\Version1000Date20250929161325' => $baseDir . '/../lib/Migration/Version1000Date20250929161325.php',
     'OCA\\Sharing\\ResponseDefinitions' => $baseDir . '/../lib/ResponseDefinitions.php',
-    'OCA\\Sharing\\SharingBackend' => $baseDir . '/../lib/SharingBackend.php',
 );
diff --git a/apps/sharing/composer/composer/autoload_static.php b/apps/sharing/composer/composer/autoload_static.php
index 00ae4e33b5d40..22a3d83d9e4d0 100644
--- a/apps/sharing/composer/composer/autoload_static.php
+++ b/apps/sharing/composer/composer/autoload_static.php
@@ -42,7 +42,6 @@ class ComposerStaticInitSharing
         'OCA\\Sharing\\Middleware\\ShareApiEnabledMiddleware' => __DIR__ . '/..' . '/../lib/Middleware/ShareApiEnabledMiddleware.php',
         'OCA\\Sharing\\Migration\\Version1000Date20250929161325' => __DIR__ . '/..' . '/../lib/Migration/Version1000Date20250929161325.php',
         'OCA\\Sharing\\ResponseDefinitions' => __DIR__ . '/..' . '/../lib/ResponseDefinitions.php',
-        'OCA\\Sharing\\SharingBackend' => __DIR__ . '/..' . '/../lib/SharingBackend.php',
     );
 
     public static function getInitializer(ClassLoader $loader)
diff --git a/apps/sharing/lib/AppInfo/Application.php b/apps/sharing/lib/AppInfo/Application.php
index 0eec114787d09..680e125b05bcc 100644
--- a/apps/sharing/lib/AppInfo/Application.php
+++ b/apps/sharing/lib/AppInfo/Application.php
@@ -9,15 +9,12 @@
 
 namespace OCA\Sharing\AppInfo;
 
-use NCU\Sharing\ISharingRegistry;
 use OCA\Sharing\Capabilities;
 use OCA\Sharing\Middleware\ShareApiEnabledMiddleware;
-use OCA\Sharing\SharingBackend;
 use OCP\AppFramework\App;
 use OCP\AppFramework\Bootstrap\IBootContext;
 use OCP\AppFramework\Bootstrap\IBootstrap;
 use OCP\AppFramework\Bootstrap\IRegistrationContext;
-use OCP\Server;
 
 final class Application extends App implements IBootstrap {
 	public const string APP_ID = 'sharing';
@@ -30,9 +27,6 @@ public function __construct(array $urlParams = []) {
 	public function register(IRegistrationContext $context): void {
 		$context->registerCapability(Capabilities::class);
 		$context->registerMiddleware(ShareApiEnabledMiddleware::class);
-
-		$registry = Server::get(ISharingRegistry::class);
-		$registry->registerSharingBackend(Server::get(SharingBackend::class));
 	}
 
 	#[\Override]
diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index c58f6a0ed305d..79825014fdffc 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -2296,6 +2296,8 @@
     'OC\\Share20\\UserDeletedListener' => $baseDir . '/lib/private/Share20/UserDeletedListener.php',
     'OC\\Share20\\UserRemovedListener' => $baseDir . '/lib/private/Share20/UserRemovedListener.php',
     'OC\\Share\\Constants' => $baseDir . '/lib/private/Share/Constants.php',
+    'OC\\Sharing\\ISharingLegacyBackend' => $baseDir . '/lib/private/Sharing/ISharingLegacyBackend.php',
+    'OC\\Sharing\\SharingBackend' => $baseDir . '/lib/private/Sharing/SharingBackend.php',
     'OC\\Sharing\\SharingManager' => $baseDir . '/lib/private/Sharing/SharingManager.php',
     'OC\\Sharing\\SharingRegistry' => $baseDir . '/lib/private/Sharing/SharingRegistry.php',
     'OC\\Snowflake\\APCuSequence' => $baseDir . '/lib/private/Snowflake/APCuSequence.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index 32e4ffee59a32..260349ab1fdac 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -2337,6 +2337,8 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OC\\Share20\\UserDeletedListener' => __DIR__ . '/../../..' . '/lib/private/Share20/UserDeletedListener.php',
         'OC\\Share20\\UserRemovedListener' => __DIR__ . '/../../..' . '/lib/private/Share20/UserRemovedListener.php',
         'OC\\Share\\Constants' => __DIR__ . '/../../..' . '/lib/private/Share/Constants.php',
+        'OC\\Sharing\\ISharingLegacyBackend' => __DIR__ . '/../../..' . '/lib/private/Sharing/ISharingLegacyBackend.php',
+        'OC\\Sharing\\SharingBackend' => __DIR__ . '/../../..' . '/lib/private/Sharing/SharingBackend.php',
         'OC\\Sharing\\SharingManager' => __DIR__ . '/../../..' . '/lib/private/Sharing/SharingManager.php',
         'OC\\Sharing\\SharingRegistry' => __DIR__ . '/../../..' . '/lib/private/Sharing/SharingRegistry.php',
         'OC\\Snowflake\\APCuSequence' => __DIR__ . '/../../..' . '/lib/private/Snowflake/APCuSequence.php',
diff --git a/lib/private/Share20/Manager.php b/lib/private/Share20/Manager.php
index 74199ff5ca362..f1b8dbc4ce97e 100644
--- a/lib/private/Share20/Manager.php
+++ b/lib/private/Share20/Manager.php
@@ -268,7 +268,7 @@ protected function generalChecks(IShare $share): void {
 					throw new GenericShareException($isRestricted, code: 403);
 				}
 			} catch (\Exception $exception) {
-				throw new GenericShareException($exception->getMessage(), $exception instanceof HintException ? $exception->getHint() : '', code: 403);
+				throw new GenericShareException($exception->getMessage(), $exception instanceof HintException ? $exception->getHint() : '', code: 403, previous: $exception);
 			}
 		}
 	}
@@ -567,9 +567,11 @@ public function createShare(IShare $share): IShare {
 				|| $share->getShareType() === IShare::TYPE_EMAIL) {
 				$this->setLinkParent($share);
 
-				$token = $this->generateToken();
-				// Set the unique token
-				$share->setToken($token);
+				if ($share->getToken() === '') {
+					$token = $this->generateToken();
+					// Set the unique token
+					$share->setToken($token);
+				}
 
 				// Verify the expiration date
 				$share = $this->validateExpirationDateLink($share);
diff --git a/lib/private/Share20/Share.php b/lib/private/Share20/Share.php
index 3f8d3d97b21ef..d88710e4e191f 100644
--- a/lib/private/Share20/Share.php
+++ b/lib/private/Share20/Share.php
@@ -31,7 +31,7 @@ class Share implements IShare {
 	private $fileId;
 	/** @var string */
 	private $nodeType;
-	/** @var int */
+	/** @var IShare::TYPE_* */
 	private $shareType;
 	/** @var string */
 	private $sharedWith;
@@ -44,11 +44,11 @@ class Share implements IShare {
 	private $sharedBy;
 	/** @var string */
 	private $shareOwner;
-	/** @var int */
+	/** @var int-mask-of<Constants::PERMISSION_*> */
 	private $permissions;
 	/** @var IAttributes */
 	private $attributes;
-	/** @var int */
+	/** @var self::STATUS_* */
 	private $status;
 	/** @var string */
 	private $note = '';
@@ -60,7 +60,7 @@ class Share implements IShare {
 	/** @var bool */
 	private $sendPasswordByTalk = false;
 	/** @var string */
-	private $token;
+	private $token = '';
 	private ?int $parent = null;
 	/** @var string */
 	private $target;
@@ -358,7 +358,7 @@ public function setStatus(int $status): IShare {
 	 * @inheritdoc
 	 */
 	#[\Override]
-	public function getStatus(): int {
+	public function getStatus(): ?int {
 		return $this->status;
 	}
 
diff --git a/lib/private/Sharing/ISharingLegacyBackend.php b/lib/private/Sharing/ISharingLegacyBackend.php
new file mode 100644
index 0000000000000..5aa9f45271e75
--- /dev/null
+++ b/lib/private/Sharing/ISharingLegacyBackend.php
@@ -0,0 +1,59 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+declare(strict_types=1);
+
+namespace OC\Sharing;
+
+use NCU\Sharing\Exception\ShareNotFoundException;
+use NCU\Sharing\Recipient\IShareRecipientType;
+use NCU\Sharing\Share;
+use NCU\Sharing\ShareAccessContext;
+use NCU\Sharing\Source\IShareSourceType;
+
+/**
+ * This interface is only temporary and implemented in the files_sharing app.
+ */
+interface ISharingLegacyBackend {
+	/**
+	 * @return list<class-string<IShareSourceType>>
+	 */
+	public function getCompatibleSourceTypes(): array;
+
+	/**
+	 * @return list<class-string<IShareRecipientType>>
+	 */
+	public function getCompatibleRecipientTypes(): array;
+
+	/**
+	 * Update a share.
+	 */
+	public function updateShare(Share $share): void;
+
+	/**
+	 * Delete a share.
+	 *
+	 * @throws ShareNotFoundException
+	 */
+	public function deleteShare(string $id): void;
+
+	/**
+	 * Get a share.
+	 *
+	 * @throws ShareNotFoundException
+	 */
+	public function getShare(ShareAccessContext $accessContext, string $id): Share;
+
+	/**
+	 * Get multiple shares.
+	 *
+	 * @param ?class-string<IShareSourceType> $filterSourceTypeClass
+	 * @param ?positive-int $limit
+	 * @return list<Share>
+	 */
+	public function getShares(ShareAccessContext $accessContext, ?string $filterSourceTypeClass, ?string $filterSourceTypeValue, ?string $lastShareID, ?int $limit): array;
+}
diff --git a/apps/sharing/lib/SharingBackend.php b/lib/private/Sharing/SharingBackend.php
similarity index 91%
rename from apps/sharing/lib/SharingBackend.php
rename to lib/private/Sharing/SharingBackend.php
index aa196bc00ac50..5d6cb5d4017d2 100644
--- a/apps/sharing/lib/SharingBackend.php
+++ b/lib/private/Sharing/SharingBackend.php
@@ -7,7 +7,7 @@
 
 declare(strict_types=1);
 
-namespace OCA\Sharing;
+namespace OC\Sharing;
 
 use Exception;
 use NCU\Sharing\Exception\ShareInvalidException;
@@ -36,7 +36,6 @@
 use OCP\IUser;
 use OCP\IUserManager;
 use OCP\L10N\IFactory;
-use OCP\Snowflake\ISnowflakeGenerator;
 use RuntimeException;
 
 // TODO: Add mapping table for class names in sources, recipients, permissions and properties
@@ -51,7 +50,6 @@ public function __construct(
 		IFactory $factory,
 		private IDBConnection $connection,
 		private IUserManager $userManager,
-		private ISnowflakeGenerator $snowflakeGenerator,
 		private IAppConfig $appConfig,
 		private ISharingRegistry $registry,
 		private ISharingManager $manager,
@@ -60,10 +58,7 @@ public function __construct(
 	}
 
 	#[\Override]
-	public function createShare(ShareUser $owner): string {
-		$id = $this->snowflakeGenerator->nextId();
-		$lastUpdated = $this->manager->generateTimestamp();
-
+	public function createShare(string $id, ShareUser $owner, int $lastUpdated): void {
 		$qb = $this->connection->getQueryBuilder();
 		$qb
 			->insert('sharing_share')
@@ -75,15 +70,14 @@ public function createShare(ShareUser $owner): string {
 				'state' => $qb->createNamedParameter(ShareState::Draft->value),
 			])
 			->executeStatement();
-
-		return $id;
 	}
 
 	#[\Override]
-	public function onOwnerDeleted(ShareUser $owner): void {
+	public function onOwnerDeleted(ShareUser $owner): array {
 		$qb = $this->connection->getQueryBuilder();
 		$qb
-			->delete('sharing_share')
+			->selectDistinct('id')
+			->from('sharing_share')
 			->where($qb->expr()->eq('owner_user_id', $qb->createNamedParameter($owner->userId)));
 		if ($owner->instance === null) {
 			$qb->andWhere($qb->expr()->isNull('owner_instance'));
@@ -91,7 +85,25 @@ public function onOwnerDeleted(ShareUser $owner): void {
 			$qb->andWhere($qb->expr()->eq('owner_instance', $qb->createNamedParameter($owner->instance)));
 		}
 
-		$qb->executeStatement();
+		$result = $qb->executeQuery();
+
+		/** @var list<string|int> $ids */
+		$ids = $result->fetchFirstColumn();
+		if ($ids === []) {
+			return [];
+		}
+
+		$ids = array_map(static fn (string|int $id): string => (string)$id, $ids);
+
+		foreach (array_chunk($ids, 1000) as $chunk) {
+			$qb = $this->connection->getQueryBuilder();
+			$qb
+				->delete('sharing_share')
+				->where($qb->expr()->in('id', $qb->createNamedParameter($chunk, IQueryBuilder::PARAM_STR_ARRAY)))
+				->executeStatement();
+		}
+
+		return $ids;
 	}
 
 	#[\Override]
@@ -172,6 +184,10 @@ public function onSourceDeleted(ShareSource $source): array {
 
 	#[\Override]
 	public function addShareRecipient(string $id, ShareRecipient $recipient): void {
+		if ($recipient->secret === null) {
+			throw new RuntimeException('The secret must not be null.');
+		}
+
 		if (!$recipient->initiator instanceof ShareUser) {
 			throw new RuntimeException('The initiator must not be null.');
 		}
@@ -184,7 +200,7 @@ public function addShareRecipient(string $id, ShareRecipient $recipient): void {
 				'recipient_class' => $qb->createNamedParameter($recipient->class),
 				'recipient_value' => $qb->createNamedParameter($recipient->value),
 				'recipient_instance' => $qb->createNamedParameter($recipient->instance),
-				'recipient_secret' => $qb->createNamedParameter($this->manager->generateSecret()),
+				'recipient_secret' => $qb->createNamedParameter($recipient->secret),
 				'initiator_user_id' => $qb->createNamedParameter($recipient->initiator->userId),
 				'initiator_instance' => $qb->createNamedParameter($recipient->initiator->instance),
 			];
@@ -324,6 +340,35 @@ public function updateShareRecipientSecret(string $id, ShareRecipient $recipient
 		}
 	}
 
+	#[\Override]
+	public function createShareProperty(string $id, ShareProperty $property): void {
+		$value = $property->value;
+
+		$propertyType = $this->registry->getPropertyTypes()[$property->class];
+
+		if ($propertyType instanceof ISharePropertyTypeModifyValue) {
+			$value = $propertyType->modifyValueOnSave(null, $property->value);
+		}
+
+		try {
+			$qb = $this->connection->getQueryBuilder();
+			$qb
+				->insert('sharing_share_properties')
+				->values([
+					'share_id' => $qb->createNamedParameter($id),
+					'property_class' => $qb->createNamedParameter($property->class),
+					'property_value' => $qb->createNamedParameter($value),
+				])
+				->executeStatement();
+		} catch (\OCP\DB\Exception $exception) {
+			if ($exception->getReason() === \OCP\DB\Exception::REASON_UNIQUE_CONSTRAINT_VIOLATION) {
+				throw new RuntimeException('The property already exists: ' . $property->class, $exception->getCode(), $exception);
+			}
+
+			throw $exception;
+		}
+	}
+
 	#[\Override]
 	public function updateShareProperty(string $id, ShareProperty $property): void {
 		$value = $property->value;
@@ -359,6 +404,27 @@ public function updateShareProperty(string $id, ShareProperty $property): void {
 		}
 	}
 
+	#[\Override]
+	public function createSharePermission(string $id, SharePermission $permission): void {
+		try {
+			$qb = $this->connection->getQueryBuilder();
+			$qb
+				->insert('sharing_share_permissions')
+				->values([
+					'share_id' => $qb->createNamedParameter($id),
+					'permission_class' => $qb->createNamedParameter($permission->class),
+					'permission_enabled' => $qb->createNamedParameter($permission->enabled, IQueryBuilder::PARAM_BOOL),
+				])
+				->executeStatement();
+		} catch (\OCP\DB\Exception $exception) {
+			if ($exception->getReason() === \OCP\DB\Exception::REASON_UNIQUE_CONSTRAINT_VIOLATION) {
+				throw new RuntimeException('The permission already exists: ' . $permission->class, $exception->getCode(), $exception);
+			}
+
+			throw $exception;
+		}
+	}
+
 	#[\Override]
 	public function updateSharePermission(string $id, SharePermission $permission): void {
 		$qb = $this->connection->getQueryBuilder();
@@ -589,8 +655,6 @@ private function list(ShareAccessContext $accessContext, ?string $filterShareID,
 			$result = $qb->executeQuery();
 			$rows = $result->fetchAll();
 			foreach ($rows as $row) {
-				/** @var non-empty-string $id */
-				$id = (string)$row['id'];
 				/** @var non-empty-string $ownerUserId */
 				$ownerUserId = $row['owner_user_id'];
 				/** @var ?non-empty-string $ownerInstance */
@@ -601,6 +665,8 @@ private function list(ShareAccessContext $accessContext, ?string $filterShareID,
 					continue;
 				}
 
+				/** @var non-empty-string $id */
+				$id = (string)$row['id'];
 				/** @var non-negative-int $lastUpdated */
 				$lastUpdated = (int)$row['last_updated'];
 				/** @var string $state */
@@ -916,79 +982,23 @@ private function list(ShareAccessContext $accessContext, ?string $filterShareID,
 		}
 
 		foreach (array_keys($shares) as $id) {
-			foreach ($registryPropertyTypes as $propertyTypeClass => $propertyType) {
+			foreach (array_keys($registryPropertyTypes) as $propertyTypeClass) {
 				$share = $shares[$id];
 				if (
 					!isset($share->properties[$propertyTypeClass])
 					&& isset($shareSourceTypeClasses[$id], $shareRecipientTypeClasses[$id])
 					&& array_intersect($registryPropertyTypeCompatibleSourceTypeClasses[$propertyTypeClass], array_keys($shareSourceTypeClasses[$id])) !== []
 					&& array_intersect($registryPropertyTypeCompatibleRecipientTypeClasses[$propertyTypeClass], array_keys($shareRecipientTypeClasses[$id])) !== []) {
-					$value = $propertyType->getDefaultValue($share);
-
-					$timestamp = $this->manager->generateTimestamp();
-					$this->setLastUpdated([(string)$id], $timestamp);
-
-					$qb = $this->connection->getQueryBuilder();
-					$qb
-						->insert('sharing_share_properties')
-						->values([
-							'share_id' => $qb->createNamedParameter($id),
-							'property_class' => $qb->createNamedParameter($propertyTypeClass),
-							'property_value' => $qb->createNamedParameter($propertyType instanceof ISharePropertyTypeModifyValue ? $propertyType->modifyValueOnSave(null, $value) : $value),
-						])
-						->executeStatement();
-
-					$properties = $share->properties;
-					$properties[$propertyTypeClass] = new ShareProperty($propertyTypeClass, $value);
-
-					$shares[$id] = new Share(
-						$share->id,
-						$share->owner,
-						$timestamp,
-						$share->state,
-						$share->sources,
-						$share->recipients,
-						$properties,
-						$share->permissions,
-					);
+					$shares[$id] = $this->manager->createSharePropertyDefaultValue($shares[$id], $propertyTypeClass);
 				}
 			}
 		}
 
-		$permissionTypes = $this->registry->getPermissionTypes();
 		foreach (array_keys($shares) as $id) {
 			foreach (array_keys($shareCompatiblePermissionTypeClasses[$id]) as $permissionTypeClass) {
 				$share = $shares[$id];
 				if (!isset($share->permissions[$permissionTypeClass])) {
-					$permissionType = $permissionTypes[$permissionTypeClass];
-					$enabled = $permissionType->isEnabledByDefault();
-
-					$timestamp = $this->manager->generateTimestamp();
-					$this->setLastUpdated([(string)$id], $timestamp);
-
-					$qb = $this->connection->getQueryBuilder();
-					$qb
-						->insert('sharing_share_permissions')
-						->values([
-							'share_id' => $qb->createNamedParameter($id),
-							'permission_class' => $qb->createNamedParameter($permissionTypeClass),
-							'permission_enabled' => $qb->createNamedParameter($enabled, IQueryBuilder::PARAM_BOOL),
-						])
-						->executeStatement();
-
-					$permissions = $share->permissions;
-					$permissions[$permissionTypeClass] = new SharePermission($permissionTypeClass, $enabled);
-
-					$shares[$id] = new Share(
-						$share->id,
-						$share->owner,
-						$timestamp,
-						$share->state,
-						$share->sources,
-						$share->recipients,
-						$share->properties,
-						$permissions,
-					);
+					$shares[$id] = $this->manager->createSharePermissionDefaultValue($shares[$id], $permissionTypeClass);
 				}
 			}
 		}
diff --git a/lib/private/Sharing/SharingManager.php b/lib/private/Sharing/SharingManager.php
index e4d77626b2075..76593a8f4bc0b 100644
--- a/lib/private/Sharing/SharingManager.php
+++ b/lib/private/Sharing/SharingManager.php
@@ -28,12 +28,10 @@
 use NCU\Sharing\ShareUser;
 use NCU\Sharing\Source\ShareSource;
 use OC\Core\Sharing\Permission\ReshareSharePermissionType;
-use OCA\Sharing\SharingBackend;
 use OCP\EventDispatcher\Event;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\EventDispatcher\IEventListener;
-use OCP\ICache;
-use OCP\ICacheFactory;
+use OCP\IAppConfig;
 use OCP\IDBConnection;
 use OCP\IL10N;
 use OCP\Interaction\Actions\ShareAction;
@@ -42,6 +40,7 @@
 use OCP\IUserManager;
 use OCP\L10N\IFactory;
 use OCP\Security\ISecureRandom;
+use OCP\Snowflake\ISnowflakeGenerator;
 use OCP\User\Events\BeforeUserDeletedEvent;
 use Random\Randomizer;
 use RuntimeException;
@@ -59,31 +58,31 @@
 final readonly class SharingManager implements ISharingManager, IEventListener {
 	private Randomizer $randomizer;
 
-	private ICache $backendCache;
-
 	private IL10N $l10n;
 
+	private ISharingBackend $backend;
+
 	public function __construct(
-		ICacheFactory $cacheFactory,
 		IEventDispatcher $eventDispatcher,
 		private IUserManager $userManager,
 		private IFactory $l10nFactory,
+		private ISnowflakeGenerator $snowflakeGenerator,
 		private IDBConnection $dbConnection,
 		private ISharingRegistry $registry,
+		IAppConfig $appConfig,
 	) {
 		$this->randomizer = new Randomizer();
-
-		if ($cacheFactory->isAvailable()) {
-			$this->backendCache = $cacheFactory->createDistributed('sharing');
-		} elseif ($cacheFactory->isLocalCacheAvailable()) {
-			$this->backendCache = $cacheFactory->createLocal('sharing');
-		} else {
-			$this->backendCache = $cacheFactory->createInMemory();
-		}
+		$this->l10n = $l10nFactory->get('sharing');
+		$this->backend = new SharingBackend(
+			$l10nFactory,
+			$dbConnection,
+			$userManager,
+			$appConfig,
+			$registry,
+			$this,
+		);
 
 		$eventDispatcher->addServiceListener(BeforeUserDeletedEvent::class, self::class);
-
-		$this->l10n = $this->l10nFactory->get('sharing');
 	}
 
 	#[\Override]
@@ -158,9 +157,11 @@ public function createShare(ShareAccessContext $accessContext): string {
 
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend(null);
-		$id = $backend->createShare(new ShareUser($currentUser->getUID(), null));
-		$this->backendCache->set($id, $backend::class);
+		$id = $this->snowflakeGenerator->nextId();
+		$lastUpdated = $this->generateTimestamp();
+		$this->backend->createShare($id, new ShareUser($currentUser->getUID(), null), $lastUpdated);
+
+		$this->processShareUpdates([$id]);
 
 		return $id;
 	}
@@ -175,8 +176,13 @@ public function onOwnerDeleted(ShareAccessContext $accessContext, ShareUser $own
 
 		// No need to update the last updated timestamp, because the share will be deleted anyway.
 
-		foreach ($this->registry->getSharingBackends() as $backend) {
-			$backend->onOwnerDeleted($owner);
+		$ids = $this->backend->onOwnerDeleted($owner);
+
+		$legacyBackend = $this->registry->getLegacyBackend();
+		if ($legacyBackend instanceof ISharingLegacyBackend) {
+			foreach ($ids as $id) {
+				$legacyBackend->deleteShare($id);
+			}
 		}
 	}
 
@@ -184,28 +190,28 @@ public function onOwnerDeleted(ShareAccessContext $accessContext, ShareUser $own
 	public function updateShareState(ShareAccessContext $accessContext, string $id, ShareState $state): void {
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 		$this->validateShareOwnerOperation($accessContext, $owner);
 
 		if ($state === ShareState::Active) {
-			$share = $this->getShare($accessContext, $id, $backend);
+			$share = $this->getShare($accessContext, $id);
 			$this->assertShareCanBeActive($share);
 		}
 
-		$backend->updateShareState($id, $state);
+		$this->backend->updateShareState($id, $state);
+
+		$this->processShareUpdates([$id]);
 	}
 
 	#[\Override]
 	public function addShareSource(ShareAccessContext $accessContext, string $id, ShareSource $source): void {
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 		$this->validateShareOwnerOperation($accessContext, $owner);
 
 		if (($sourceType = $this->registry->getSourceTypes()[$source->class] ?? null) === null) {
@@ -216,29 +222,42 @@ public function addShareSource(ShareAccessContext $accessContext, string $id, Sh
 			throw new ShareInvalidException('Invalid source: ' . $source->value . ' ' . $source->class, $this->l10n->t('The source does not exist.'));
 		}
 
+		$share = $this->getShare($accessContext, $id);
+		$sources = $share->sources;
+		$sources[] = $source;
+		$share = new Share(
+			$share->id,
+			$share->owner,
+			$share->lastUpdated,
+			$share->state,
+			$sources,
+			$share->recipients,
+			$share->properties,
+			$share->permissions,
+		);
+
 		if (!$accessContext->overrideChecks) {
-			$share = $this->getShare($accessContext, $id, $backend);
-			$sources = $share->sources;
-			$sources[] = $source;
-			$this->validateInteraction($accessContext, $owner, $sources, $share->getEnabledPermissions(), $share->recipients);
+			$this->validateInteraction($accessContext, $share);
 		}
 
-		$backend->addShareSource($id, $source);
+		$this->backend->addShareSource($id, $source);
+
+		// The modified share object has to be used instead of fetching the share again, because it would trigger the insertion of default values prematurely.
+		$this->processShareUpdates([$share]);
 	}
 
 	#[\Override]
 	public function removeShareSource(ShareAccessContext $accessContext, string $id, ShareSource $source): void {
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 		$this->validateShareOwnerOperation($accessContext, $owner);
 
-		$backend->removeShareSource($id, $source);
+		$this->backend->removeShareSource($id, $source);
 
-		$this->makeSharesDraftIfNeeded([$id]);
+		$this->processShareUpdates([$id]);
 	}
 
 	#[\Override]
@@ -251,18 +270,14 @@ public function onSourceDeleted(ShareAccessContext $accessContext, ShareSource $
 
 		$timestamp = $this->generateTimestamp();
 
-		$ids = [];
-		foreach ($this->registry->getSharingBackends() as $backend) {
-			$updatedIds = $backend->onSourceDeleted($source);
-			if ($updatedIds === []) {
-				continue;
-			}
-
-			$backend->setLastUpdated($updatedIds, $timestamp);
-			$ids[] = $updatedIds;
+		$updatedIds = $this->backend->onSourceDeleted($source);
+		if ($updatedIds === []) {
+			return;
 		}
 
-		$this->makeSharesDraftIfNeeded(array_merge(...$ids));
+		$this->backend->setLastUpdated($updatedIds, $timestamp);
+
+		$this->processShareUpdates($updatedIds);
 	}
 
 	#[\Override]
@@ -273,16 +288,15 @@ public function addShareRecipient(ShareAccessContext $accessContext, string $id,
 
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 
 		try {
 			$this->validateShareOwnerOperation($accessContext, $owner);
 			$share = null;
 		} catch (ShareOperationForbiddenException) {
-			$share = $this->getShare($accessContext, $id, $backend);
+			$share = $this->getShare($accessContext, $id);
 			$this->validatePermission($share, ReshareSharePermissionType::class);
 		}
 
@@ -294,22 +308,41 @@ public function addShareRecipient(ShareAccessContext $accessContext, string $id,
 			throw new ShareInvalidException('Invalid recipient: ' . $recipient->value . ' ' . $recipient->class . ' ' . ($recipient->instance ?? 'local'), $this->l10n->t('The recipient does not exist.'));
 		}
 
-		if (!$accessContext->overrideChecks) {
-			$share ??= $this->getShare($accessContext, $id, $backend);
-			$recipients = $share->recipients;
-			$recipients[] = $recipient;
-			$this->validateInteraction($accessContext, $owner, $share->sources, $share->getEnabledPermissions(), $recipients);
-		}
-
-		$recipient = new ShareRecipient(
-			$recipient->class,
-			$recipient->value,
-			$recipient->instance,
-			$recipient->secret,
-			new ShareUser($currentUser->getUID(), null),
+		$share ??= $this->getShare($accessContext, $id);
+		$recipients = $share->recipients;
+		$recipients[] = $recipient;
+		$share = new Share(
+			$share->id,
+			$share->owner,
+			$share->lastUpdated,
+			$share->state,
+			$share->sources,
+			$recipients,
+			$share->properties,
+			$share->permissions,
 		);
 
-		$backend->addShareRecipient($id, $recipient);
+		if (!$accessContext->overrideChecks) {
+			$this->validateInteraction($accessContext, $share);
+		}
+
+		if ($recipient->secret === null || !$recipient->initiator instanceof ShareUser) {
+			$secret = $recipient->secret ?? $this->generateSecret();
+			$initiator = $recipient->initiator ?? new ShareUser($currentUser->getUID(), null);
+
+			$recipient = new ShareRecipient(
+				$recipient->class,
+				$recipient->value,
+				$recipient->instance,
+				$secret,
+				$initiator,
+			);
+		}
+
+		$this->backend->addShareRecipient($id, $recipient);
+
+		// The modified share object has to be used instead of fetching the share again, because it would trigger the insertion of default values prematurely.
+		$this->processShareUpdates([$share]);
 	}
 
 	#[\Override]
@@ -318,22 +351,21 @@ public function removeShareRecipient(ShareAccessContext $accessContext, string $
 
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 
 		try {
 			$this->validateShareOwnerOperation($accessContext, $owner);
 		} catch (ShareOperationForbiddenException) {
-			$share = $this->getShare($accessContext, $id, $backend);
+			$share = $this->getShare($accessContext, $id);
 			// This does not allow removing own recipients. A user can only reject a share, but not remove it for the recipient.
 			$this->validateReshareOperation($accessContext, $share, $recipient);
 		}
 
-		$backend->removeShareRecipient($id, $recipient);
+		$this->backend->removeShareRecipient($id, $recipient);
 
-		$this->makeSharesDraftIfNeeded([$id]);
+		$this->processShareUpdates([$id]);
 	}
 
 	#[\Override]
@@ -346,18 +378,14 @@ public function onRecipientDeleted(ShareAccessContext $accessContext, ShareRecip
 
 		$timestamp = $this->generateTimestamp();
 
-		$ids = [];
-		foreach ($this->registry->getSharingBackends() as $backend) {
-			$updatedIds = $backend->onRecipientDeleted($recipient);
-			if ($updatedIds === []) {
-				continue;
-			}
-
-			$backend->setLastUpdated($updatedIds, $timestamp);
-			$ids[] = $updatedIds;
+		$updatedIds = $this->backend->onRecipientDeleted($recipient);
+		if ($updatedIds === []) {
+			return;
 		}
 
-		$this->makeSharesDraftIfNeeded(array_merge(...$ids));
+		$this->backend->setLastUpdated($updatedIds, $timestamp);
+
+		$this->processShareUpdates($updatedIds);
 	}
 
 	#[\Override]
@@ -370,31 +398,28 @@ public function onInitiatorDeleted(ShareAccessContext $accessContext, ShareUser
 
 		$timestamp = $this->generateTimestamp();
 
-		foreach ($this->registry->getSharingBackends() as $backend) {
-			$updatedIds = $backend->onInitiatorDeleted($initiator);
-			if ($updatedIds === []) {
-				continue;
-			}
-
-			$backend->setLastUpdated($updatedIds, $timestamp);
+		$updatedIds = $this->backend->onInitiatorDeleted($initiator);
+		if ($updatedIds === []) {
+			return;
 		}
 
-		// No need to make shares draft, because promoting a reshare to the owner doesn't remove recipients.
+		$this->backend->setLastUpdated($updatedIds, $timestamp);
+
+		$this->processShareUpdates($updatedIds);
 	}
 
 	#[\Override]
 	public function updateShareRecipientSecret(ShareAccessContext $accessContext, string $id, ShareRecipient $recipient, string $secret): void {
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 
 		try {
 			$this->validateShareOwnerOperation($accessContext, $owner);
 		} catch (ShareOperationForbiddenException) {
-			$share = $this->getShare($accessContext, $id, $backend);
+			$share = $this->getShare($accessContext, $id);
 			$this->validateReshareOperation($accessContext, $share, $recipient);
 		}
 
@@ -410,17 +435,52 @@ public function updateShareRecipientSecret(ShareAccessContext $accessContext, st
 			throw new ShareInvalidException('Invalid secret: ' . $secret, $this->l10n->t('The value must be alphanumeric, 1 to 32 characters long and may contain dashes.'));
 		}
 
-		$backend->updateShareRecipientSecret($id, $recipient, $secret);
+		$this->backend->updateShareRecipientSecret($id, $recipient, $secret);
+
+		$this->processShareUpdates([$id]);
+	}
+
+	#[\Override]
+	public function createSharePropertyDefaultValue(Share $share, string $propertyTypeClass): Share {
+		$this->assertInTransaction();
+
+		$timestamp = $this->generateTimestamp();
+		$this->backend->setLastUpdated([$share->id], $timestamp);
+
+		if (($propertyType = $this->registry->getPropertyTypes()[$propertyTypeClass] ?? null) === null) {
+			throw new RuntimeException('The property is not registered: ' . $propertyTypeClass);
+		}
+
+		$property = new ShareProperty($propertyTypeClass, $propertyType->getDefaultValue($share));
+
+		$this->backend->createShareProperty($share->id, $property);
+
+		$properties = $share->properties;
+		$properties[$propertyTypeClass] = $property;
+
+		$share = new Share(
+			$share->id,
+			$share->owner,
+			$timestamp,
+			$share->state,
+			$share->sources,
+			$share->recipients,
+			$properties,
+			$share->permissions,
+		);
+
+		[$share] = $this->processShareUpdates([$share]);
+
+		return $share;
 	}
 
 	#[\Override]
 	public function updateShareProperty(ShareAccessContext $accessContext, string $id, ShareProperty $property): void {
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 		$this->validateShareOwnerOperation($accessContext, $owner);
 
 		if (($propertyType = $this->registry->getPropertyTypes()[$property->class] ?? null) === null) {
@@ -434,94 +494,130 @@ public function updateShareProperty(ShareAccessContext $accessContext, string $i
 			}
 		}
 
-		$backend->updateShareProperty($id, $property);
+		$this->backend->updateShareProperty($id, $property);
+
+		$this->processShareUpdates([$id]);
+	}
+
+	#[\Override]
+	public function createSharePermissionDefaultValue(Share $share, string $permissionTypeClass): Share {
+		$this->assertInTransaction();
+
+		$timestamp = $this->generateTimestamp();
+		$this->backend->setLastUpdated([$share->id], $timestamp);
+
+		if (($permissionType = $this->registry->getPermissionTypes()[$permissionTypeClass] ?? null) === null) {
+			throw new RuntimeException('The permission is not registered: ' . $permissionTypeClass);
+		}
+
+		$permission = new SharePermission($permissionTypeClass, $permissionType->isEnabledByDefault());
+
+		$this->backend->createSharePermission($share->id, $permission);
+
+		$permissions = $share->permissions;
+		$permissions[$permissionTypeClass] = $permission;
+
+		$share = new Share(
+			$share->id,
+			$share->owner,
+			$timestamp,
+			$share->state,
+			$share->sources,
+			$share->recipients,
+			$share->properties,
+			$permissions,
+		);
+
+		[$share] = $this->processShareUpdates([$share]);
 
-		$this->makeSharesDraftIfNeeded([$id]);
+		return $share;
 	}
 
 	#[\Override]
 	public function updateSharePermission(ShareAccessContext $accessContext, string $id, SharePermission $permission): void {
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 		$this->validateShareOwnerOperation($accessContext, $owner);
 
 		if (!isset($this->registry->getPermissionTypes()[$permission->class])) {
 			throw new RuntimeException('The permission type is not registered: ' . $permission->class);
 		}
 
+		$share = $this->getShare($accessContext, $id);
+		$permissions = $share->permissions;
+		$permissions[$permission->class] = $permission;
+		$share = new Share(
+			$share->id,
+			$share->owner,
+			$share->lastUpdated,
+			$share->state,
+			$share->sources,
+			$share->recipients,
+			$share->properties,
+			$permissions,
+		);
+
 		if (!$accessContext->overrideChecks) {
-			$share = $this->getShare($accessContext, $id, $backend);
-			$permissions = $share->permissions;
-			$permissions[$permission->class] = $permission;
-			$this->validateInteraction($accessContext, $owner, $share->sources, array_filter($permissions, static fn (SharePermission $permission): bool => $permission->enabled), $share->recipients);
+			$this->validateInteraction($accessContext, $share);
 		}
 
-		$backend->updateSharePermission($id, $permission);
+		$this->backend->updateSharePermission($id, $permission);
 
-		$this->makeSharesDraftIfNeeded([$id]);
+		// The modified share object has to be used instead of fetching the share again, because it would trigger the insertion of default values prematurely.
+		$this->processShareUpdates([$share]);
 	}
 
 	#[\Override]
 	public function selectSharePermissionPreset(ShareAccessContext $accessContext, string $id, string $permissionPresetClass): void {
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$backend->setLastUpdated([$id], $this->generateTimestamp());
+		$this->backend->setLastUpdated([$id], $this->generateTimestamp());
 
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 		$this->validateShareOwnerOperation($accessContext, $owner);
 
 		if (($this->registry->getPermissionPresetCompatiblePermissionTypeClasses()[$permissionPresetClass] ?? null) === null) {
 			throw new RuntimeException('The permission preset is not registered: ' . $permissionPresetClass);
 		}
 
-		$backend->selectSharePermissionPreset($id, $permissionPresetClass);
+		$this->backend->selectSharePermissionPreset($id, $permissionPresetClass);
+
+		$this->processShareUpdates([$id]);
 	}
 
 	#[\Override]
 	public function deleteShare(ShareAccessContext $accessContext, string $id): void {
 		$this->assertInTransaction();
 
-		$backend = $this->getBackend($id);
-		$owner = $backend->getShareOwner($id);
+		$owner = $this->backend->getShareOwner($id);
 
 		// No need to update the last updated timestamp, because the share will be deleted anyway.
 
 		$this->validateShareOwnerOperation($accessContext, $owner);
 
-		$backend->deleteShare($id);
+		$this->backend->deleteShare($id);
+
+		$legacyBackend = $this->registry->getLegacyBackend();
+		if ($legacyBackend instanceof ISharingLegacyBackend) {
+			$legacyBackend->deleteShare($id);
+		}
 	}
 
 	#[\Override]
-	public function getShare(ShareAccessContext $accessContext, string $id, ?ISharingBackend $backend = null): Share {
+	public function getShare(ShareAccessContext $accessContext, string $id): Share {
 		$this->assertInTransaction();
 
-		return ($backend ?? $this->getBackend($id))->getShare($accessContext, $id);
+		return $this->backend->getShare($accessContext, $id);
 	}
 
 	#[\Override]
 	public function getShares(ShareAccessContext $accessContext, ?string $filterSourceTypeClass, ?string $filterSourceTypeValue, ?string $lastShareID, ?int $limit): array {
 		$this->assertInTransaction();
 
-		$shares = [];
-
-		// TODO: Deal with more results than limit?
-		foreach ($this->registry->getSharingBackends() as $backend) {
-			$backendShares = $backend->getShares($accessContext, $filterSourceTypeClass, $filterSourceTypeValue, $lastShareID, $limit);
-			$shares[] = $backendShares;
-
-			foreach ($backendShares as $share) {
-				if ($this->backendCache->get($share->id) === null) {
-					$this->backendCache->set($share->id, $backend::class);
-				}
-			}
-		}
-
-		return array_merge(...$shares);
+		return $this->backend->getShares($accessContext, $filterSourceTypeClass, $filterSourceTypeValue, $lastShareID, $limit);
 	}
 
 	#[\Override]
@@ -545,39 +641,6 @@ private function assertInTransaction(): void {
 		}
 	}
 
-	private function getBackend(?string $id): ISharingBackend {
-		$availableBackends = $this->registry->getSharingBackends();
-		if ($availableBackends === []) {
-			throw new RuntimeException('No sharing backends registered');
-		}
-
-		$selectedBackend = null;
-		if ($id === null) {
-			// For new shares we only use the backend from the sharing app.
-			$selectedBackend = $availableBackends[SharingBackend::class] ?? null;
-		} else {
-			/** @var ?class-string<ISharingBackend> $cachedBackendClass */
-			$cachedBackendClass = $this->backendCache->get($id);
-			if ($cachedBackendClass !== null) {
-				$selectedBackend = $availableBackends[$cachedBackendClass] ?? null;
-			} else {
-				foreach ($availableBackends as $backend) {
-					if ($backend->hasShare($id)) {
-						$selectedBackend = $backend;
-						$this->backendCache->set($id, $backend::class);
-						break;
-					}
-				}
-			}
-		}
-
-		if ($selectedBackend === null) {
-			throw new RuntimeException('No sharing backend selected');
-		}
-
-		return $selectedBackend;
-	}
-
 	// TODO: Support IShareOwnerlessMount
 
 	/**
@@ -598,6 +661,7 @@ private function validateShareOwnerOperation(ShareAccessContext $accessContext,
 	 * @throws ShareOperationForbiddenException
 	 */
 	private function validatePermission(Share $share, string $permissionTypeClass): void {
+		// TODO: Only fetch permisions
 		if ((($permission = $share->permissions[$permissionTypeClass] ?? null) !== null) && $permission->enabled) {
 			return;
 		}
@@ -611,6 +675,7 @@ private function validatePermission(Share $share, string $permissionTypeClass):
 	private function validateReshareOperation(ShareAccessContext $accessContext, Share $share, ShareRecipient $recipient): void {
 		$this->validatePermission($share, ReshareSharePermissionType::class);
 
+		// TODO: Only fetch recipients
 		foreach ($share->recipients as $shareRecipient) {
 			if (
 				$recipient->class === $shareRecipient->class
@@ -627,20 +692,17 @@ private function validateReshareOperation(ShareAccessContext $accessContext, Sha
 	}
 
 	/**
-	 * @param list<ShareSource> $sources
-	 * @param array<class-string<ISharePermissionType>, SharePermission> $enabledPermissions
-	 * @param list<ShareRecipient> $recipients
 	 * @throws ShareInvalidException
 	 */
-	private function validateInteraction(ShareAccessContext $accessContext, ShareUser $owner, array $sources, array $enabledPermissions, array $recipients): void {
-		$action = new ShareAction(null, array_values(array_map(static fn (SharePermission $permission): string => $permission->class, $enabledPermissions)));
+	private function validateInteraction(ShareAccessContext $accessContext, Share $share): void {
+		$action = new ShareAction(null, array_values(array_map(static fn (SharePermission $permission): string => $permission->class, $share->getEnabledPermissions())));
 
 		$usersToCheck = [];
-		if ($owner->instance === null && ($ownerUser = $this->userManager->get($owner->userId)) !== null) {
+		if ($share->owner->instance === null && ($ownerUser = $this->userManager->get($share->owner->userId)) !== null) {
 			$usersToCheck[] = $ownerUser;
 		}
 
-		if ($accessContext->currentUser instanceof IUser && !$owner->isCurrentUser($accessContext)) {
+		if ($accessContext->currentUser instanceof IUser && !$share->owner->isCurrentUser($accessContext)) {
 			$usersToCheck[] = $accessContext->currentUser;
 		}
 
@@ -648,7 +710,7 @@ private function validateInteraction(ShareAccessContext $accessContext, ShareUse
 		$sourceTypes = $this->registry->getSourceTypes();
 
 		$receivers = [];
-		foreach ($recipients as $recipient) {
+		foreach ($share->recipients as $recipient) {
 			if (($recipientType = $recipientTypes[$recipient->class] ?? null) === null) {
 				throw new RuntimeException('The recipient type is not registered: ' . $recipient->class);
 			}
@@ -662,7 +724,7 @@ private function validateInteraction(ShareAccessContext $accessContext, ShareUse
 
 		foreach ($usersToCheck as $userToCheck) {
 			$resources = [];
-			foreach ($sources as $source) {
+			foreach ($share->sources as $source) {
 				if (($sourceType = $sourceTypes[$source->class] ?? null) === null) {
 					throw new RuntimeException('The source type is not registered: ' . $source->class);
 				}
@@ -708,21 +770,60 @@ private function assertShareCanBeActive(Share $share): void {
 	}
 
 	/**
-	 * @param list<string> $ids
+	 * @param non-empty-list<Share|string> $sharesOrIds
+	 * @return non-empty-list<Share>
 	 */
-	private function makeSharesDraftIfNeeded(array $ids): void {
-		foreach ($ids as $id) {
-			$backend = $this->getBackend($id);
-			$share = $backend->getShare(new ShareAccessContext(overrideChecks: true), $id);
-			if ($share->state !== ShareState::Active) {
-				continue;
+	private function processShareUpdates(array $sharesOrIds): array {
+		$shares = [];
+
+		foreach ($sharesOrIds as $shareOrId) {
+			if ($shareOrId instanceof Share) {
+				$share = $shareOrId;
+			} else {
+				$share = $this->backend->getShare(new ShareAccessContext(overrideChecks: true), $shareOrId);
 			}
 
-			try {
-				$this->assertShareCanBeActive($share);
-			} catch (ShareInvalidException) {
-				$backend->updateShareState($id, ShareState::Draft);
+			if ($share->state === ShareState::Active) {
+				try {
+					$this->assertShareCanBeActive($share);
+				} catch (ShareInvalidException) {
+					$this->backend->updateShareState($share->id, ShareState::Draft);
+
+					$share = new Share(
+						$share->id,
+						$share->owner,
+						$share->lastUpdated,
+						ShareState::Draft,
+						$share->sources,
+						$share->recipients,
+						$share->properties,
+						$share->permissions,
+					);
+				}
+			}
+
+			$legacyBackend = $this->registry->getLegacyBackend();
+			if ($legacyBackend instanceof ISharingLegacyBackend) {
+				$compatibleSourceTypes = array_fill_keys($legacyBackend->getCompatibleSourceTypes(), true);
+				foreach ($share->sources as $source) {
+					if (!isset($compatibleSourceTypes[$source->class])) {
+						throw new RuntimeException('The legacy backend ' . $legacyBackend::class . ' does not support this source type: ' . $source->class);
+					}
+				}
+
+				$compatibleRecipientTypes = array_fill_keys($legacyBackend->getCompatibleRecipientTypes(), true);
+				foreach ($share->recipients as $recipient) {
+					if (!isset($compatibleRecipientTypes[$recipient->class])) {
+						throw new RuntimeException('The legacy backend ' . $legacyBackend::class . ' does not support this recipient type: ' . $recipient->class);
+					}
+				}
+
+				$legacyBackend->updateShare($share);
 			}
+
+			$shares[] = $share;
 		}
+
+		return $shares;
 	}
 }
diff --git a/lib/private/Sharing/SharingRegistry.php b/lib/private/Sharing/SharingRegistry.php
index 92d415270f884..85647e18f2452 100644
--- a/lib/private/Sharing/SharingRegistry.php
+++ b/lib/private/Sharing/SharingRegistry.php
@@ -9,7 +9,6 @@
 
 namespace OC\Sharing;
 
-use NCU\Sharing\ISharingBackend;
 use NCU\Sharing\ISharingRegistry;
 use NCU\Sharing\Permission\ISharePermissionPreset;
 use NCU\Sharing\Permission\ISharePermissionType;
@@ -20,10 +19,7 @@
 
 // TODO: Maybe add validate method to run all checks before using the manager
 final class SharingRegistry implements ISharingRegistry {
-	/**
-	 * @var array<class-string<ISharingBackend>, ISharingBackend>
-	 */
-	private array $backends = [];
+	private ?ISharingLegacyBackend $legacyBackend = null;
 
 	/** @var array<class-string<IShareSourceType>, IShareSourceType> */
 	private array $sourceTypes = [];
@@ -63,7 +59,7 @@ final class SharingRegistry implements ISharingRegistry {
 
 	#[\Override]
 	public function clear(): void {
-		$this->backends = [];
+		$this->legacyBackend = null;
 		$this->sourceTypes = [];
 		$this->recipientTypes = [];
 		$this->propertyTypes = [];
@@ -79,22 +75,17 @@ public function clear(): void {
 	}
 
 	#[\Override]
-	public function registerSharingBackend(ISharingBackend $backend): void {
-		$class = $backend::class;
-
-		if (isset($this->backends[$class])) {
-			throw new RuntimeException('Sharing backend ' . $class . ' is already registered');
+	public function registerLegacyBackend(ISharingLegacyBackend $legacyBackend): void {
+		if ($this->legacyBackend instanceof ISharingLegacyBackend) {
+			throw new RuntimeException('A sharing legacy backend is already registered');
 		}
 
-		$this->backends[$class] = $backend;
+		$this->legacyBackend = $legacyBackend;
 	}
 
-	/**
-	 * @return array<class-string<ISharingBackend>, ISharingBackend>
-	 */
 	#[\Override]
-	public function getSharingBackends(): array {
-		return $this->backends;
+	public function getLegacyBackend(): ?ISharingLegacyBackend {
+		return $this->legacyBackend;
 	}
 
 	#[\Override]
diff --git a/lib/public/Share/IShare.php b/lib/public/Share/IShare.php
index 1323299bc5137..5e5647f52aa10 100644
--- a/lib/public/Share/IShare.php
+++ b/lib/public/Share/IShare.php
@@ -9,9 +9,8 @@
 namespace OCP\Share;
 
 use OCP\AppFramework\Attribute\Consumable;
+use OCP\Constants;
 use OCP\Files\Cache\ICacheEntry;
-use OCP\Files\File;
-use OCP\Files\Folder;
 use OCP\Files\Node;
 use OCP\Files\NotFoundException;
 use OCP\Share\Exceptions\IllegalIDChangeException;
@@ -209,7 +208,7 @@ public function getNodeType();
 	/**
 	 * Set the shareType
 	 *
-	 * @param int $shareType
+	 * @param self::TYPE_* $shareType
 	 * @return \OCP\Share\IShare The modified object
 	 * @since 9.0.0
 	 */
@@ -218,7 +217,7 @@ public function setShareType($shareType);
 	/**
 	 * Get the shareType
 	 *
-	 * @return int
+	 * @return self::TYPE_*
 	 * @since 9.0.0
 	 */
 	public function getShareType();
@@ -276,9 +275,8 @@ public function getSharedWithAvatar();
 
 	/**
 	 * Set the permissions.
-	 * See \OCP\Constants::PERMISSION_*
 	 *
-	 * @param int $permissions
+	 * @param int-mask-of<Constants::PERMISSION_*> $permissions
 	 * @return IShare The modified object
 	 * @since 9.0.0
 	 */
@@ -286,9 +284,8 @@ public function setPermissions($permissions);
 
 	/**
 	 * Get the share permissions
-	 * See \OCP\Constants::PERMISSION_*
 	 *
-	 * @return int
+	 * @return int-mask-of<Constants::PERMISSION_*>
 	 * @since 9.0.0
 	 */
 	public function getPermissions();
@@ -320,9 +317,8 @@ public function getAttributes(): ?IAttributes;
 
 	/**
 	 * Set the accepted status
-	 * See self::STATUS_*
 	 *
-	 * @param int $status
+	 * @param self::STATUS_* $status
 	 * @return IShare The modified object
 	 * @since 18.0.0
 	 */
@@ -330,12 +326,11 @@ public function setStatus(int $status): IShare;
 
 	/**
 	 * Get the accepted status
-	 * See self::STATUS_*
 	 *
-	 * @return int
+	 * @return ?self::STATUS_*
 	 * @since 18.0.0
 	 */
-	public function getStatus(): int;
+	public function getStatus(): ?int;
 
 	/**
 	 * Attach a note to a share
diff --git a/lib/unstable/Sharing/ISharingBackend.php b/lib/unstable/Sharing/ISharingBackend.php
index 2ae085b8e6233..a4cb1401dd9cc 100644
--- a/lib/unstable/Sharing/ISharingBackend.php
+++ b/lib/unstable/Sharing/ISharingBackend.php
@@ -17,27 +17,27 @@
 use NCU\Sharing\Recipient\ShareRecipient;
 use NCU\Sharing\Source\IShareSourceType;
 use NCU\Sharing\Source\ShareSource;
-use OCP\AppFramework\Attribute\Implementable;
+use OCP\AppFramework\Attribute\Consumable;
 
-// TODO: Add ability to start and commit a transaction
 /**
  * @experimental 35.0.0
  */
-#[Implementable(since: '35.0.0')]
+#[Consumable(since: '35.0.0')]
 interface ISharingBackend {
 	/**
 	 * Create a new share.
 	 *
 	 * @experimental 35.0.0
 	 */
-	public function createShare(ShareUser $owner): string;
+	public function createShare(string $id, ShareUser $owner, int $lastUpdated): void;
 
 	/**
 	 * Perform all updates when the owner was deleted.
 	 *
+	 * @return list<string>
 	 * @experimental 35.0.0
 	 */
-	public function onOwnerDeleted(ShareUser $owner): void;
+	public function onOwnerDeleted(ShareUser $owner): array;
 
 	/**
 	 * Update the state of a share.
@@ -113,6 +113,14 @@ public function onInitiatorDeleted(ShareUser $initiator): array;
 	 */
 	public function updateShareRecipientSecret(string $id, ShareRecipient $recipient, string $secret): void;
 
+	/**
+	 * Insert a property for a share.
+	 *
+	 * @throws ShareNotFoundException
+	 * @experimental 35.0.0
+	 */
+	public function createShareProperty(string $id, ShareProperty $property): void;
+
 	/**
 	 * Update a property of a share.
 	 *
@@ -121,6 +129,14 @@ public function updateShareRecipientSecret(string $id, ShareRecipient $recipient
 	 */
 	public function updateShareProperty(string $id, ShareProperty $property): void;
 
+	/**
+	 * Insert a permission for a share.
+	 *
+	 * @throws ShareNotFoundException
+	 * @experimental 35.0.0
+	 */
+	public function createSharePermission(string $id, SharePermission $permission): void;
+
 	/**
 	 * Update a permission of a share.
 	 *
diff --git a/lib/unstable/Sharing/ISharingManager.php b/lib/unstable/Sharing/ISharingManager.php
index ebbe7b6059c4f..21128680aaefc 100644
--- a/lib/unstable/Sharing/ISharingManager.php
+++ b/lib/unstable/Sharing/ISharingManager.php
@@ -13,7 +13,9 @@
 use NCU\Sharing\Exception\ShareNotFoundException;
 use NCU\Sharing\Exception\ShareOperationForbiddenException;
 use NCU\Sharing\Permission\ISharePermissionPreset;
+use NCU\Sharing\Permission\ISharePermissionType;
 use NCU\Sharing\Permission\SharePermission;
+use NCU\Sharing\Property\ISharePropertyType;
 use NCU\Sharing\Property\ShareProperty;
 use NCU\Sharing\Recipient\IShareRecipientType;
 use NCU\Sharing\Recipient\ShareRecipient;
@@ -148,6 +150,13 @@ public function onInitiatorDeleted(ShareAccessContext $accessContext, ShareUser
 	 */
 	public function updateShareRecipientSecret(ShareAccessContext $accessContext, string $id, ShareRecipient $recipient, string $secret): void;
 
+	/**
+	 * @param class-string<ISharePropertyType> $propertyTypeClass
+	 * @throws ShareNotFoundException
+	 * @experimental 35.0.0
+	 */
+	public function createSharePropertyDefaultValue(Share $share, string $propertyTypeClass): Share;
+
 	/**
 	 * Update a property of a share.
 	 *
@@ -158,6 +167,13 @@ public function updateShareRecipientSecret(ShareAccessContext $accessContext, st
 	 */
 	public function updateShareProperty(ShareAccessContext $accessContext, string $id, ShareProperty $property): void;
 
+	/**
+	 * @param class-string<ISharePermissionType> $permissionTypeClass
+	 * @throws ShareNotFoundException
+	 * @experimental 35.0.0
+	 */
+	public function createSharePermissionDefaultValue(Share $share, string $permissionTypeClass): Share;
+
 	/**
 	 * Update a permission of a share.
 	 *
diff --git a/lib/unstable/Sharing/ISharingRegistry.php b/lib/unstable/Sharing/ISharingRegistry.php
index 81fda046e17e2..a1a352da84582 100644
--- a/lib/unstable/Sharing/ISharingRegistry.php
+++ b/lib/unstable/Sharing/ISharingRegistry.php
@@ -14,6 +14,7 @@
 use NCU\Sharing\Property\ISharePropertyType;
 use NCU\Sharing\Recipient\IShareRecipientType;
 use NCU\Sharing\Source\IShareSourceType;
+use OC\Sharing\ISharingLegacyBackend;
 use OCP\AppFramework\Attribute\Consumable;
 
 /**
@@ -29,13 +30,12 @@ public function clear(): void;
 	/**
 	 * @experimental 35.0.0
 	 */
-	public function registerSharingBackend(ISharingBackend $backend): void;
+	public function registerLegacyBackend(ISharingLegacyBackend $legacyBackend): void;
 
 	/**
-	 * @return array<class-string<ISharingBackend>, ISharingBackend>
 	 * @experimental 35.0.0
 	 */
-	public function getSharingBackends(): array;
+	public function getLegacyBackend(): ?ISharingLegacyBackend;
 
 	/**
 	 * @experimental 35.0.0
diff --git a/tests/Core/Sharing/Recipient/GroupShareRecipientTypeTest.php b/tests/Core/Sharing/Recipient/GroupShareRecipientTypeTest.php
index 954e5835359a6..abfd54bc2a847 100644
--- a/tests/Core/Sharing/Recipient/GroupShareRecipientTypeTest.php
+++ b/tests/Core/Sharing/Recipient/GroupShareRecipientTypeTest.php
@@ -15,7 +15,6 @@
 use NCU\Sharing\ShareAccessContext;
 use OC\Core\Sharing\Recipient\GroupShareRecipientType;
 use OC\Group\Database;
-use OCA\Sharing\SharingBackend;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\IDBConnection;
 use OCP\IGroup;
@@ -132,7 +131,6 @@ public function testSearchRecipients(): void {
 	public function testDelete(): void {
 		$registry = Server::get(ISharingRegistry::class);
 		$registry->clear();
-		$registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$registry->registerRecipientType($this->recipientType);
 
 		$accessContext = new ShareAccessContext(currentUser: $this->user1);
diff --git a/tests/Core/Sharing/Recipient/UserShareRecipientTypeTest.php b/tests/Core/Sharing/Recipient/UserShareRecipientTypeTest.php
index 4cc6f232ea7c9..453c0ecd12ac4 100644
--- a/tests/Core/Sharing/Recipient/UserShareRecipientTypeTest.php
+++ b/tests/Core/Sharing/Recipient/UserShareRecipientTypeTest.php
@@ -15,7 +15,6 @@
 use NCU\Sharing\ShareAccessContext;
 use OC\Core\Sharing\Recipient\UserShareRecipientType;
 use OC\User\Database;
-use OCA\Sharing\SharingBackend;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\IDBConnection;
 use OCP\IUser;
@@ -136,7 +135,6 @@ public function testSearchRecipients(): void {
 	public function testDelete(): void {
 		$registry = Server::get(ISharingRegistry::class);
 		$registry->clear();
-		$registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$registry->registerRecipientType($this->recipientType);
 
 		$accessContext = new ShareAccessContext(currentUser: $this->user1);
diff --git a/tests/lib/Sharing/AbstractSharingManagerTests.php b/tests/lib/Sharing/AbstractSharingManagerTests.php
index dddd33f6ed008..8f4522dc86ff2 100644
--- a/tests/lib/Sharing/AbstractSharingManagerTests.php
+++ b/tests/lib/Sharing/AbstractSharingManagerTests.php
@@ -19,7 +19,6 @@
 use NCU\Sharing\ShareState;
 use NCU\Sharing\Source\ShareSource;
 use OC\Core\Sharing\Permission\ReshareSharePermissionType;
-use OCA\Sharing\SharingBackend;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\HintException;
 use OCP\IDBConnection;
@@ -113,7 +112,6 @@ public function setUp(): void {
 
 		$this->registry = Server::get(ISharingRegistry::class);
 		$this->registry->clear();
-		$this->registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$this->registry->registerSourceType(new TestShareSourceType1(['source1' => 'Source 1']));
 		$this->registry->registerSourceType(new TestShareSourceType2(['source2' => 'Source 2']));
 		$this->registry->registerRecipientType(new TestShareRecipientType1(
@@ -1718,7 +1716,6 @@ public function testUpdateSharePermissionInteractionRestricted(): void {
 
 	public function testSelectSharePermissionPreset(): void {
 		$this->registry->clear();
-		$this->registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$this->registry->registerPermissionPreset(new TestSharePermissionPreset1());
 		$this->registry->registerPermissionPreset(new TestSharePermissionPreset2());
 		$this->registry->registerPermissionType(null, new TestSharePermissionType1());
@@ -1918,7 +1915,6 @@ public function testSelectSharePermissionPreset(): void {
 
 	public function testSelectSharePermissionPresetCompatible(): void {
 		$this->registry->clear();
-		$this->registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$this->registry->registerSourceType(new TestShareSourceType1(['source1' => 'Source 1']));
 		$this->registry->registerPermissionPreset(new TestSharePermissionPreset1());
 		$this->registry->registerPermissionPreset(new TestSharePermissionPreset2());
@@ -2990,7 +2986,6 @@ public static function dataGetShareWithPublicSecret(): array {
 	#[DataProvider('dataGetShareWithPublicSecret')]
 	public function testGetShareWithPublicSecret(bool $isSecretPublic): void {
 		$this->registry->clear();
-		$this->registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$this->registry->registerRecipientType(new TestShareRecipientType1(
 			[
 				'recipient1' => 'Recipient 1',
@@ -3067,7 +3062,6 @@ public function testGetShareWithPublicSecret(bool $isSecretPublic): void {
 
 	public function testGetShareWithSecret(): void {
 		$this->registry->clear();
-		$this->registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$this->registry->registerSourceType(new TestShareSourceType1(['source1' => 'Source']));
 		$this->registry->registerRecipientType(new TestShareRecipientTypePublicSecret(
 			[
@@ -3146,7 +3140,6 @@ public function testGetShareWithSecret(): void {
 
 	public function testGetShareUniqueDisplayNames(): void {
 		$this->registry->clear();
-		$this->registry->registerSharingBackend(Server::get(SharingBackend::class));
 		$this->registry->registerSourceType(new TestShareSourceType1(['source1' => 'Source']));
 		$this->registry->registerSourceType(new TestShareSourceType2(['source2' => 'Source', 'source3' => 'Other']));
 		$this->registry->registerRecipientType(new TestShareRecipientType1(['recipient1' => 'Recipient'], [], []));