diff --git a/appinfo/routes.php b/appinfo/routes.php
index 8a2b9be5fe..830ebbb153 100644
--- a/appinfo/routes.php
+++ b/appinfo/routes.php
@@ -140,17 +140,25 @@
 		['name' => 'board_ocs#index', 'url' => '/api/v{apiVersion}/boards', 'verb' => 'GET'],
 		['name' => 'board_ocs#read', 'url' => '/api/v{apiVersion}/board/{boardId}', 'verb' => 'GET'],
 		['name' => 'stack_ocs#index', 'url' => '/api/v{apiVersion}/stacks/{boardId}', 'verb' => 'GET'],
+		['name' => 'stack_ocs#getArchived', 'url' => '/api/v{apiVersion}/stacks/{boardId}/archived', 'verb' => 'GET'],
 		['name' => 'board_ocs#create', 'url' => '/api/v{apiVersion}/boards', 'verb' => 'POST'],
 		['name' => 'board_ocs#createForTeam', 'url' => '/api/v{apiVersion}/boards/team', 'verb' => 'POST'],
+		['name' => 'board_ocs#update', 'url' => '/api/v{apiVersion}/boards/{boardId}', 'verb' => 'PUT'],
 		['name' => 'board_ocs#addAcl', 'url' => '/api/v{apiVersion}/boards/{boardId}/acl', 'verb' => 'POST'],
+		['name' => 'board_ocs#leave', 'url' => '/api/v{apiVersion}/boards/{boardId}/leave', 'verb' => 'POST'],
 
 		['name' => 'card_ocs#create', 'url' => '/api/v{apiVersion}/cards', 'verb' => 'POST'],
 		['name' => 'card_ocs#update', 'url' => '/api/v{apiVersion}/cards/{cardId}', 'verb' => 'PUT'],
+		['name' => 'card_ocs#delete', 'url' => '/api/v{apiVersion}/cards/{cardId}', 'verb' => 'DELETE'],
 		['name' => 'card_ocs#assignLabel', 'url' => '/api/v{apiVersion}/cards/{cardId}/label/{labelId}', 'verb' => 'POST'],
 		['name' => 'card_ocs#assignUser', 'url' => '/api/v{apiVersion}/cards/{cardId}/assign', 'verb' => 'POST'],
 		['name' => 'card_ocs#unAssignUser', 'url' => '/api/v{apiVersion}/cards/{cardId}/unassign', 'verb' => 'PUT'],
 		['name' => 'card_ocs#removeLabel', 'url' => '/api/v{apiVersion}/cards/{cardId}/label/{labelId}', 'verb' => 'DELETE'],
 		['name' => 'card_ocs#reorder', 'url' => '/api/v{apiVersion}/cards/{cardId}/reorder', 'verb' => 'PUT'],
+		['name' => 'card_ocs#archive', 'url' => '/api/v{apiVersion}/cards/{cardId}/archive', 'verb' => 'PUT'],
+		['name' => 'card_ocs#unarchive', 'url' => '/api/v{apiVersion}/cards/{cardId}/unarchive', 'verb' => 'PUT'],
+		['name' => 'card_ocs#done', 'url' => '/api/v{apiVersion}/cards/{cardId}/done', 'verb' => 'PUT'],
+		['name' => 'card_ocs#undone', 'url' => '/api/v{apiVersion}/cards/{cardId}/undone', 'verb' => 'PUT'],
 		['name' => 'card_ocs#assignDependentCard', 'url' => '/api/v{apiVersion}/cards/{cardId}/dependentCards/{dependentCardId}', 'verb' => 'POST'],
 		['name' => 'card_ocs#removeDependentCard', 'url' => '/api/v{apiVersion}/cards/{cardId}/dependentCards/{dependentCardId}', 'verb' => 'DELETE'],
 
@@ -161,6 +169,8 @@
 
 		['name' => 'attachment_ocs#getAll', 'url' => '/api/v{apiVersion}/cards/{cardId}/attachments', 'verb' => 'GET'],
 		['name' => 'attachment_ocs#create', 'url' => '/api/v{apiVersion}/cards/{cardId}/attachment', 'verb' => 'POST'],
+		['name' => 'attachment_ocs#createRemote', 'url' => '/api/v{apiVersion}/cards/{cardId}/remote-attachment', 'verb' => 'POST'],
+		['name' => 'attachment_ocs#shareRemote', 'url' => '/api/v{apiVersion}/cards/{cardId}/share-attachment', 'verb' => 'POST'],
 		['name' => 'attachment_ocs#update', 'url' => '/api/v{apiVersion}/cards/{cardId}/attachments/{attachmentId}', 'verb' => 'PUT'],
 		['name' => 'attachment_ocs#delete', 'url' => '/api/v{apiVersion}/cards/{cardId}/attachments/{type}:{attachmentId}', 'verb' => 'DELETE'],
 		['name' => 'attachment_ocs#restore', 'url' => '/api/v{apiVersion}/cards/{cardId}/attachments/{attachmentId}/restore', 'verb' => 'PUT'],
diff --git a/lib/Controller/AttachmentOcsController.php b/lib/Controller/AttachmentOcsController.php
index 734daef49b..9f787499b9 100644
--- a/lib/Controller/AttachmentOcsController.php
+++ b/lib/Controller/AttachmentOcsController.php
@@ -9,10 +9,13 @@
 
 namespace OCA\Deck\Controller;
 
+use OCA\Deck\BadRequestException;
 use OCA\Deck\NotImplementedException;
 use OCA\Deck\Service\AttachmentService;
 use OCA\Deck\Service\BoardService;
+use OCA\Deck\Service\ExternalBoardService;
 use OCP\AppFramework\Http\Attribute\NoAdminRequired;
+use OCP\AppFramework\Http\Attribute\PublicPage;
 use OCP\AppFramework\Http\DataResponse;
 use OCP\AppFramework\OCSController;
 use OCP\IRequest;
@@ -23,6 +26,7 @@ public function __construct(
 		IRequest $request,
 		private AttachmentService $attachmentService,
 		private BoardService $boardService,
+		private ExternalBoardService $externalBoardService,
 	) {
 		parent::__construct($appName, $request);
 	}
@@ -37,19 +41,43 @@ private function ensureLocalBoard(?int $boardId): void {
 	}
 
 	#[NoAdminRequired]
+	#[PublicPage]
 	public function getAll(int $cardId, ?int $boardId = null): DataResponse {
-		$this->ensureLocalBoard($boardId);
+		$board = $this->boardService->find($boardId, false);
+		if ($board->getExternalId()) {
+			return new DataResponse($this->externalBoardService->getAttachmentsFromRemote($board, $cardId));
+		}
 		$attachment = $this->attachmentService->findAll($cardId, true);
 		return new DataResponse($attachment);
 	}
 
 	#[NoAdminRequired]
 	public function create(int $cardId, string $type, string $data = '', ?int $boardId = null): DataResponse {
-		$this->ensureLocalBoard($boardId);
+		$board = $this->boardService->find($boardId, false);
+		if ($board->getExternalId()) {
+			return new DataResponse($this->externalBoardService->createAttachmentForRemote($board, $cardId));
+		}
 		$attachment = $this->attachmentService->create($cardId, $type, $data);
 		return new DataResponse($attachment);
 	}
 
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function createRemote(int $cardId, string $token): DataResponse {
+		$this->attachmentService->acceptRemoteAttachment($cardId, $token);
+		return new DataResponse([]);
+	}
+
+	#[NoAdminRequired]
+	public function shareRemote(int $cardId, int $boardId, string $path): DataResponse {
+		$board = $this->boardService->find($boardId, false);
+		if (!$board->getExternalId()) {
+			throw new BadRequestException('board is not federated');
+		}
+		$token = $this->externalBoardService->shareAttachmentForRemote($board, $cardId, $path);
+		return new DataResponse(['token' => $token]);
+	}
+
 	#[NoAdminRequired]
 	public function update(int $cardId, int $attachmentId, string $data, string $type = 'file', ?int $boardId = null): DataResponse {
 		$this->ensureLocalBoard($boardId);
@@ -58,8 +86,12 @@ public function update(int $cardId, int $attachmentId, string $data, string $typ
 	}
 
 	#[NoAdminRequired]
+	#[PublicPage]
 	public function delete(int $cardId, int $attachmentId, string $type = 'file', ?int $boardId = null): DataResponse {
-		$this->ensureLocalBoard($boardId);
+		$board = $this->boardService->find($boardId, false);
+		if ($board->getExternalId()) {
+			return new DataResponse($this->externalBoardService->deleteAttachmentOnRemote($board, $cardId, $attachmentId, $type));
+		}
 		$attachment = $this->attachmentService->delete($cardId, $attachmentId, $type);
 		return new DataResponse($attachment);
 	}
diff --git a/lib/Controller/BoardController.php b/lib/Controller/BoardController.php
index 5c43ab7b12..5383e0adae 100644
--- a/lib/Controller/BoardController.php
+++ b/lib/Controller/BoardController.php
@@ -67,7 +67,12 @@ public function deleteUndo(int $boardId): Board {
 
 	#[NoAdminRequired]
 	public function leave(int $boardId) {
-		return $this->boardService->leave($boardId);
+		$localBoard = $this->boardService->find($boardId, true, true);
+		$result = $this->boardService->leave($boardId);
+		if ($localBoard->getExternalId() !== null) {
+			$this->externalBoardService->leaveBoardOnRemote($localBoard);
+		}
+		return $result;
 	}
 
 	#[NoAdminRequired]
diff --git a/lib/Controller/BoardOcsController.php b/lib/Controller/BoardOcsController.php
index fcfe09adbf..4d6d3f13b4 100644
--- a/lib/Controller/BoardOcsController.php
+++ b/lib/Controller/BoardOcsController.php
@@ -57,6 +57,18 @@ public function createForTeam(string $title, string $teamId, ?string $color = nu
 		return new DataResponse($this->boardService->createForTeam($title, $this->userId, $color, $teamId));
 	}
 
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function update(int $boardId, string $title, string $color, bool $archived): DataResponse {
+		$updatedBoard = $this->boardService->update($boardId, $title, $color, $archived);
+
+		if ($updatedBoard->getExternalId()) {
+			return $this->externalBoardService->updateBoardOnRemote($updatedBoard, $title, $color, $archived);
+		}
+
+		return new DataResponse($updatedBoard);
+	}
+
 	#[NoAdminRequired]
 	public function addAcl(int $boardId, int $type, string $participant, bool $permissionEdit, bool $permissionShare, bool $permissionManage, ?string $remote = null): DataResponse {
 		return new DataResponse($this->boardService->addAcl($boardId, $type, $participant, $permissionEdit, $permissionShare, $permissionManage));
@@ -66,4 +78,10 @@ public function addAcl(int $boardId, int $type, string $participant, bool $permi
 	public function updateAcl(int $id, bool $permissionEdit, bool $permissionShare, bool $permissionManage): DataResponse {
 		return new DataResponse($this->boardService->updateAcl($id, $permissionEdit, $permissionShare, $permissionManage));
 	}
+
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function leave(int $boardId): DataResponse {
+		return new DataResponse($this->boardService->leave($boardId));
+	}
 }
diff --git a/lib/Controller/CardOcsController.php b/lib/Controller/CardOcsController.php
index 6dbdb28138..02a5835856 100644
--- a/lib/Controller/CardOcsController.php
+++ b/lib/Controller/CardOcsController.php
@@ -120,7 +120,7 @@ public function removeLabel(?int $boardId, int $cardId, int $labelId): DataRespo
 
 	#[NoAdminRequired]
 	#[PublicPage]
-	public function update(int $id, string $title, int $stackId, string $type, int $order, string $description, $duedate, $deletedAt, ?int $boardId, array|string|null $owner = null, $archived = null, $startdate = null): DataResponse {
+	public function update(int $id, string $title, int $stackId, string $type, int $order, string $description, $duedate, $deletedAt, int $boardId, array|string|null $owner = null, $archived = null, $startdate = null): DataResponse {
 		$done = array_key_exists('done', $this->request->getParams())
 			? new OptionalNullableValue($this->request->getParam('done', null))
 			: null;
@@ -150,7 +150,9 @@ public function update(int $id, string $title, int $stackId, string $type, int $
 					$duedate,
 					$deletedAt,
 					$archived,
-					$done
+					$done,
+					$startdate,
+					$color,
 				));
 			}
 		}
@@ -171,6 +173,18 @@ public function update(int $id, string $title, int $stackId, string $type, int $
 		));
 	}
 
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function delete(int $cardId, ?int $boardId = null): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->deleteCardOnRemote($board, $cardId));
+			}
+		}
+		return new DataResponse($this->cardService->delete($cardId));
+	}
+
 	#[NoAdminRequired]
 	#[PublicPage]
 	public function reorder(int $cardId, int $stackId, int $order, ?int $boardId): DataResponse {
@@ -183,6 +197,30 @@ public function reorder(int $cardId, int $stackId, int $order, ?int $boardId): D
 		return new DataResponse($this->cardService->reorder($cardId, $stackId, $order));
 	}
 
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function archive(int $cardId, int $boardId): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->archiveCardOnRemote($board, $cardId));
+			}
+		}
+		return new DataResponse($this->cardService->archive($cardId));
+	}
+
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function unarchive(int $cardId, int $boardId): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->unarchiveCardOnRemote($board, $cardId));
+			}
+		}
+		return new DataResponse($this->cardService->unarchive($cardId));
+	}
+
 	#[NoAdminRequired]
 	#[PublicPage]
 	public function assignDependentCard(int $cardId, int $dependentCardId, ?int $boardId = null): DataResponse {
@@ -206,4 +244,28 @@ public function removeDependentCard(int $cardId, int $dependentCardId, ?int $boa
 		}
 		return new DataResponse($this->cardService->removeDependentCard($cardId, $dependentCardId));
 	}
+
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function done(int $cardId, ?int $boardId): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->setDoneCardOnRemote($board, $cardId));
+			}
+		}
+		return new DataResponse($this->cardService->done($cardId));
+	}
+
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function undone(int $cardId, ?int $boardId): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->setUndoneCardOnRemote($board, $cardId));
+			}
+		}
+		return new DataResponse($this->cardService->undone($cardId));
+	}
 }
diff --git a/lib/Controller/CommentsApiController.php b/lib/Controller/CommentsApiController.php
index 1794db5eae..8885660c2f 100644
--- a/lib/Controller/CommentsApiController.php
+++ b/lib/Controller/CommentsApiController.php
@@ -7,9 +7,12 @@
 
 namespace OCA\Deck\Controller;
 
+use OCA\Deck\Service\BoardService;
 use OCA\Deck\Service\CommentService;
+use OCA\Deck\Service\ExternalBoardService;
 use OCA\Deck\StatusException;
 use OCP\AppFramework\Http\Attribute\NoAdminRequired;
+use OCP\AppFramework\Http\Attribute\PublicPage;
 use OCP\AppFramework\Http\DataResponse;
 use OCP\AppFramework\OCSController;
 use OCP\IRequest;
@@ -22,6 +25,9 @@ public function __construct(
 		string $appName,
 		IRequest $request,
 		private CommentService $commentService,
+		private BoardService $boardService,
+		private ExternalBoardService $externalBoardService,
+		private ?string $userId,
 		string $corsMethods = 'PUT, POST, GET, DELETE, PATCH',
 		string $corsAllowedHeaders = 'Authorization, Content-Type, Accept',
 		int $corsMaxAge = 1728000,
@@ -33,7 +39,14 @@ public function __construct(
 	 * @throws StatusException
 	 */
 	#[NoAdminRequired]
-	public function list(int $cardId, int $limit = 20, int $offset = 0): DataResponse {
+	#[PublicPage]
+	public function list(int $cardId, int $limit = 20, int $offset = 0, ?int $boardId = null): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->getCardCommentsFromRemote($board, $cardId, $limit, $offset));
+			}
+		}
 		return $this->commentService->list($cardId, $limit, $offset);
 	}
 
@@ -41,7 +54,15 @@ public function list(int $cardId, int $limit = 20, int $offset = 0): DataRespons
 	 * @throws StatusException
 	 */
 	#[NoAdminRequired]
-	public function create(int $cardId, string $message, int $parentId = 0): DataResponse {
+	#[PublicPage]
+	public function create(int $cardId, string $message, int $parentId = 0, ?int $boardId = null): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->createCardCommentOnRemote($board, $cardId, $message, $parentId));
+			}
+		}
+
 		return $this->commentService->create($cardId, $message, $parentId);
 	}
 
@@ -49,7 +70,14 @@ public function create(int $cardId, string $message, int $parentId = 0): DataRes
 	 * @throws StatusException
 	 */
 	#[NoAdminRequired]
-	public function update(int $cardId, int $commentId, string $message): DataResponse {
+	#[PublicPage]
+	public function update(int $cardId, int $commentId, string $message, ?int $boardId = null): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->updateCardCommentOnRemote($board, $cardId, $commentId, $message));
+			}
+		}
 		return $this->commentService->update($cardId, $commentId, $message);
 	}
 
@@ -57,7 +85,14 @@ public function update(int $cardId, int $commentId, string $message): DataRespon
 	 * @throws StatusException
 	 */
 	#[NoAdminRequired]
-	public function delete(int $cardId, int $commentId): DataResponse {
+	#[PublicPage]
+	public function delete(int $cardId, int $commentId, ?int $boardId = null): DataResponse {
+		if ($boardId) {
+			$board = $this->boardService->find($boardId, false);
+			if ($board->getExternalId()) {
+				return new DataResponse($this->externalBoardService->deleteCardCommentOnRemote($board, $cardId, $commentId));
+			}
+		}
 		return $this->commentService->delete($cardId, $commentId);
 	}
 }
diff --git a/lib/Controller/StackOcsController.php b/lib/Controller/StackOcsController.php
index cada24f8e5..ecf73ae175 100644
--- a/lib/Controller/StackOcsController.php
+++ b/lib/Controller/StackOcsController.php
@@ -48,7 +48,7 @@ public function create(string $title, int $boardId, int $order = 0):DataResponse
 		} else {
 			$stack = $this->stackService->create($title, $boardId, $order);
 			return new DataResponse($stack);
-		};
+		}
 	}
 
 	#[NoAdminRequired]
@@ -91,4 +91,16 @@ public function reorder(int $stackId, int $order, ?int $boardId):DataResponse {
 		return new DataResponse($stacks);
 	}
 
+	#[NoAdminRequired]
+	#[PublicPage]
+	public function getArchived(int $boardId): DataResponse {
+		$board = $this->boardService->find($boardId, false);
+		if ($board->getExternalId()) {
+			$stacks = $this->externalBoardService->getArchivedStacksFromRemote($board);
+			return new DataResponse($stacks);
+		}
+		$stacks = $this->stackService->findAllArchived($boardId);
+		return new DataResponse($stacks);
+	}
+
 }
diff --git a/lib/Cron/ScanFederatedAttachment.php b/lib/Cron/ScanFederatedAttachment.php
new file mode 100644
index 0000000000..5cf3bae0e0
--- /dev/null
+++ b/lib/Cron/ScanFederatedAttachment.php
@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Deck\Cron;
+
+use OCA\Deck\Sharing\DeckShareProvider;
+use OCA\Files_Sharing\External\Manager as ExternalShareManager;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\BackgroundJob\IJobList;
+use OCP\BackgroundJob\QueuedJob;
+use OCP\Constants;
+use OCP\Files\IRootFolder;
+use OCP\IUserManager;
+use OCP\Share\IManager;
+use OCP\Share\IShare;
+
+class ScanFederatedAttachment extends QueuedJob {
+	public function __construct(
+		private readonly IJobList $jobList,
+		private readonly ExternalShareManager $externalShareManager,
+		private readonly IUserManager $userManager,
+		private readonly IRootFolder $rootFolder,
+		private readonly IManager $shareManager,
+		private readonly DeckShareProvider $deckShareProvider,
+		ITimeFactory $time,
+	) {
+		parent::__construct($time);
+	}
+
+	#[\Override]
+	protected function run($argument): void {
+		$cardId = $argument['cardId'];
+		$shareId = $argument['shareId'];
+		$userId = $argument['userId'];
+		$user = $this->userManager->get($userId);
+
+		if ($user === null) {
+			return;
+		}
+
+		$externalShare = $this->externalShareManager->getShare((string)$shareId, $user);
+
+		if ($externalShare === false) {
+			return;
+		}
+
+		$this->deckShareProvider->mountExternalShare($externalShare, $user);
+		$userFolder = $this->rootFolder->getUserFolder($user->getUID());
+
+		$node = $userFolder->get($externalShare->getMountpoint());
+		$files = $userFolder->getById($node->getId());
+
+		if (count($files) === 0) {
+			// Retry later, maybe the share is not yet mounted
+			$this->jobList->add(ScanFederatedAttachment::class, [
+				'cardId' => $cardId,
+				'shareId' => $shareId,
+				'userId' => $userId,
+			]);
+
+			// Scan the files to make sure the share is mounted and the files are available
+			exec('php ' . \OC::$SERVERROOT . '/occ files:scan --path="/' . $userId . '/files' . $externalShare->getMountpoint() . '"');
+			return;
+		}
+
+		$share = $this->shareManager->newShare();
+		$share->setNode($node);
+		$share->setShareType(ISHARE::TYPE_DECK);
+		$share->setSharedWith((string)$cardId);
+		$share->setPermissions(Constants::PERMISSION_READ);
+		$remote = substr($externalShare->getRemote(), 0, strrpos($externalShare->getRemote(), '/'));
+		$federatedId = $externalShare->getOwner() . '@' . $remote;
+		$share->setSharedBy($federatedId);
+		$share->setShareOwner($externalShare->getUser());
+		$this->shareManager->createShare($share);
+	}
+}
diff --git a/lib/Db/CardMapper.php b/lib/Db/CardMapper.php
index 47f3e58af3..f47c7a8b70 100644
--- a/lib/Db/CardMapper.php
+++ b/lib/Db/CardMapper.php
@@ -14,6 +14,7 @@
 use OCP\AppFramework\Db\Entity;
 use OCP\AppFramework\Db\QBMapper;
 use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\Federation\ICloudIdManager;
 use OCP\ICache;
 use OCP\ICacheFactory;
 use OCP\IDBConnection;
@@ -36,6 +37,8 @@ class CardMapper extends QBMapper implements IPermissionMapper {
 	private $notificationManager;
 	/** @var ICache */
 	private $cache;
+	/** @var ICloudIdManager */
+	private $cloudIdManager;
 	private $databaseType;
 	private $database4ByteSupport;
 
@@ -46,6 +49,7 @@ public function __construct(
 		IGroupManager $groupManager,
 		IManager $notificationManager,
 		ICacheFactory $cacheFactory,
+		ICloudIdManager $cloudIdManager,
 		$databaseType = 'sqlite3',
 		$database4ByteSupport = true,
 	) {
@@ -55,6 +59,7 @@ public function __construct(
 		$this->groupManager = $groupManager;
 		$this->notificationManager = $notificationManager;
 		$this->cache = $cacheFactory->createDistributed('deck-cardMapper');
+		$this->cloudIdManager = $cloudIdManager;
 		$this->databaseType = $databaseType;
 		$this->database4ByteSupport = $database4ByteSupport;
 	}
@@ -747,10 +752,15 @@ public function findBoardId(int $id): ?int {
 
 	public function mapOwner(Card &$card) {
 		$userManager = $this->userManager;
-		$card->resolveRelation('owner', function ($owner) use (&$userManager) {
+		$cloudIdManager = $this->cloudIdManager;
+		$card->resolveRelation('owner', function ($owner) use (&$userManager, &$cloudIdManager) {
 			if ($userManager->userExists($owner)) {
 				return new User($owner, $this->userManager);
 			}
+			if ($cloudIdManager->isValidCloudId($owner)) {
+				$cloudId = $cloudIdManager->resolveCloudId($owner);
+				return new FederatedUser($cloudId);
+			}
 			return null;
 		});
 	}
diff --git a/lib/Federation/DeckFederationProxy.php b/lib/Federation/DeckFederationProxy.php
index 2ab77fd515..8386b918ca 100644
--- a/lib/Federation/DeckFederationProxy.php
+++ b/lib/Federation/DeckFederationProxy.php
@@ -10,6 +10,10 @@
 use GuzzleHttp\Exception\ClientException;
 use GuzzleHttp\Exception\ServerException;
 use OC\Http\Client\Response;
+use OCA\Deck\BadRequestException;
+use OCA\Deck\NoPermissionException;
+use OCA\Deck\NotFoundException;
+use OCA\Deck\StatusException;
 use OCP\AppFramework\Http;
 use OCP\Http\Client\IClientService;
 use OCP\Http\Client\IResponse;
@@ -60,7 +64,7 @@ protected function prependProtocolIfNotAvailable(string $url): string {
 
 	/**
 	 * @param 'get'|'post'|'put'|'delete' $verb
-	 * @throws \Exception
+	 * @throws \Exception|StatusException
 	 */
 	protected function request(
 		string $verb,
@@ -96,7 +100,18 @@ protected function request(
 
 			$clientException = new \Exception($e->getMessage(), $status, $e);
 			$this->logger->debug('Client error from remote', ['exception' => $clientException]);
-			return new Response($e->getResponse(), false);
+
+			switch ($status) {
+				case 400:
+					throw new BadRequestException($data['ocs']['meta']['message'] ?? 'Bad request');
+				case 401:
+				case 403:
+					throw new NoPermissionException($data['ocs']['meta']['message'] ?? 'No permission');
+				case 404:
+					throw new NotFoundException($data['ocs']['meta']['message'] ?? 'Not found');
+				default:
+					return new Response($e->getResponse(), false);
+			}
 		} catch (ServerException|\Throwable $e) {
 			$serverException = new \Exception($e->getMessage(), $e->getCode(), $e);
 			$this->logger->error('Could not reach remote', ['exception' => $serverException]);
diff --git a/lib/Service/AttachmentService.php b/lib/Service/AttachmentService.php
index a871119f22..8aedb303db 100644
--- a/lib/Service/AttachmentService.php
+++ b/lib/Service/AttachmentService.php
@@ -11,6 +11,7 @@
 use OCA\Deck\AppInfo\Application;
 use OCA\Deck\BadRequestException;
 use OCA\Deck\Cache\AttachmentCacheHelper;
+use OCA\Deck\Cron\ScanFederatedAttachment;
 use OCA\Deck\Db\Acl;
 use OCA\Deck\Db\Attachment;
 use OCA\Deck\Db\AttachmentMapper;
@@ -19,10 +20,13 @@
 use OCA\Deck\InvalidAttachmentType;
 use OCA\Deck\NoPermissionException;
 use OCA\Deck\NotFoundException;
+use OCA\Deck\Sharing\DeckShareProvider;
 use OCA\Deck\StatusException;
 use OCA\Deck\Validators\AttachmentServiceValidator;
 use OCP\AppFramework\Db\IMapperException;
 use OCP\AppFramework\Http\Response;
+use OCP\BackgroundJob\IJobList;
+use OCP\Federation\ICloudIdManager;
 use OCP\IL10N;
 use OCP\IUserManager;
 use Psr\Container\ContainerExceptionInterface;
@@ -44,6 +48,9 @@ public function __construct(
 		private readonly IL10N $l10n,
 		private readonly ActivityManager $activityManager,
 		private readonly AttachmentServiceValidator $attachmentServiceValidator,
+		private readonly DeckShareProvider $deckShareProvider,
+		private readonly ICloudIdManager $cloudIdManager,
+		private readonly IJobList $jobList,
 	) {
 		// Register shipped attachment services
 		// TODO: move this to a plugin based approach once we have different types of attachments
@@ -205,6 +212,22 @@ public function create(int $cardId, string $type, string $data = '') {
 		return $attachment;
 	}
 
+	public function acceptRemoteAttachment(int $cardId, string $token): void {
+		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
+
+		$userId = $this->permissionService->getUserId();
+		if (!$this->cloudIdManager->isValidCloudId($userId)) {
+			throw new NoPermissionException('Only federated user is allowed');
+		}
+
+		$externalShare = $this->deckShareProvider->ensureAcceptRemoteShare($token, $this->cloudIdManager->resolveCloudId($userId)->getRemote());
+		$this->jobList->add(ScanFederatedAttachment::class, [
+			'cardId' => $cardId,
+			'shareId' => $externalShare->getId(),
+			'userId' => $externalShare->getUser(),
+		]);
+	}
+
 	/**
 	 * Apply import side effects to keep attachment behavior consistent with regular create flow.
 	 */
diff --git a/lib/Service/BoardService.php b/lib/Service/BoardService.php
index 2edb86a0b4..80864ca406 100644
--- a/lib/Service/BoardService.php
+++ b/lib/Service/BoardService.php
@@ -571,7 +571,8 @@ public function leave(int $boardId): ?Acl {
 			throw new BadRequestException('Board owner cannot leave board');
 		}
 
-		$acl = $this->aclMapper->findParticipantFromBoard($boardId, Acl::PERMISSION_TYPE_USER, $this->userId);
+		$userId = $this->userId ?? $this->permissionService->getUserId();
+		$acl = $this->aclMapper->findParticipantFromBoard($boardId, Acl::PERMISSION_TYPE_USER, $userId);
 
 		if (!$acl) {
 			throw new BadRequestException('Not a participant of this board');
diff --git a/lib/Service/CardService.php b/lib/Service/CardService.php
index 695a249d68..930a5eb0d0 100644
--- a/lib/Service/CardService.php
+++ b/lib/Service/CardService.php
@@ -87,7 +87,7 @@ public function enrichCards(array $cards): array {
 
 			// TODO We should find a better way just to get the comment count so we can save 1-3 queries per card here
 			$countComments = $this->commentsManager->getNumberOfCommentsForObject('deckCard', (string)$card->getId());
-			$lastRead = $countComments > 0 ? $this->commentsManager->getReadMark('deckCard', (string)$card->getId(), $user) : null;
+			$lastRead = $countComments > 0 && $user ? $this->commentsManager->getReadMark('deckCard', (string)$card->getId(), $user) : null;
 			$countUnreadComments = $lastRead ? $this->commentsManager->getNumberOfCommentsForObject('deckCard', (string)$card->getId(), $lastRead) : 0;
 			$card->setCommentsUnread($countUnreadComments);
 			$card->setCommentsCount($countComments);
diff --git a/lib/Service/CommentService.php b/lib/Service/CommentService.php
index e5d4bc140e..0cdd1e0dd7 100644
--- a/lib/Service/CommentService.php
+++ b/lib/Service/CommentService.php
@@ -18,6 +18,8 @@
 use OCP\Comments\ICommentsManager;
 use OCP\Comments\MessageTooLongException;
 use OCP\Comments\NotFoundException as CommentNotFoundException;
+use OCP\Federation\ICloudIdManager;
+use OCP\IURLGenerator;
 use OCP\IUserManager;
 use OutOfBoundsException;
 use Psr\Log\LoggerInterface;
@@ -30,6 +32,8 @@ public function __construct(
 		private CardMapper $cardMapper,
 		private IUserManager $userManager,
 		private LoggerInterface $logger,
+		private ICloudIdManager $cloudIdManager,
+		private IURLGenerator $urlGenerator,
 		private ?string $userId,
 	) {
 	}
@@ -110,7 +114,7 @@ public function create(int $cardId, string $message, int $replyTo = 0): DataResp
 		}
 
 		try {
-			$comment = $this->commentsManager->create('users', $this->userId, Application::COMMENT_ENTITY_TYPE, (string)$cardId);
+			$comment = $this->commentsManager->create('users', $this->userId ?? $this->permissionService->getUserId(), Application::COMMENT_ENTITY_TYPE, (string)$cardId);
 			$comment->setMessage($message);
 			$comment->setVerb('comment');
 			$comment->setParentId((string)$replyTo);
@@ -128,7 +132,8 @@ public function create(int $cardId, string $message, int $replyTo = 0): DataResp
 
 	public function update(int $cardId, int $commentId, string $message): DataResponse {
 		$comment = $this->get($cardId, $commentId);
-		if ($comment->getActorType() !== 'users' || $comment->getActorId() !== $this->userId) {
+		$userId = $this->userId ?? $this->permissionService->getUserId();
+		if ($comment->getActorType() !== 'users' || $comment->getActorId() !== $userId) {
 			throw new NoPermissionException('Only authors are allowed to edit their comment.');
 		}
 
@@ -148,7 +153,8 @@ public function delete(int $cardId, int $commentId): DataResponse {
 		} catch (CommentNotFoundException $e) {
 			throw new NotFoundException('No comment found.');
 		}
-		if ($comment->getActorType() !== 'users' || $comment->getActorId() !== $this->userId) {
+		$userId = $this->userId ?? $this->permissionService->getUserId();
+		if ($comment->getActorType() !== 'users' || $comment->getActorId() !== $userId) {
 			throw new NoPermissionException('Only authors are allowed to edit their comment.');
 		}
 		$this->commentsManager->delete((string)$commentId);
@@ -163,20 +169,28 @@ private function formatComment(IComment $comment, bool $addReplyTo = false): arr
 			'objectId' => (int)$comment->getObjectId(),
 			'message' => $comment->getMessage(),
 			'actorId' => $comment->getActorId(),
+			'actorRemote' => $this->cloudIdManager->isValidCloudId($comment->getActorId()) ? $this->cloudIdManager->resolveCloudId($comment->getActorId())->getRemote() : null,
 			'actorType' => $comment->getActorType(),
 			'actorDisplayName' => $actorDisplayName,
 			'creationDateTime' => $comment->getCreationDateTime()->format(\DateTime::ATOM),
 			'mentions' => array_map(function ($mention) {
+				$remote = $this->cloudIdManager->isValidCloudId($mention['id']) ? $this->cloudIdManager->resolveCloudId($mention['id'])->getRemote() : null;
+
 				try {
 					$displayName = $this->commentsManager->resolveDisplayName($mention['type'], $mention['id']);
 				} catch (OutOfBoundsException $e) {
 					$this->logger->warning('Mention type not registered, can not resolve display name.', ['exception' => $e, 'mention_type' => $mention['type']]);
 					// No display name, upon client's discretion what to display.
-					$displayName = '';
+					$displayName = $mention['id'] ?? '';
+					if ($remote === $this->urlGenerator->getBaseUrl()) {
+						$uid = $this->cloudIdManager->resolveCloudId($mention['id'])->getUser();
+						$displayName = $this->commentsManager->resolveDisplayName('user', $uid);
+					}
 				}
 
 				return [
 					'mentionId' => $mention['id'],
+					'mentionRemote' => $remote,
 					'mentionType' => $mention['type'],
 					'mentionDisplayName' => $displayName
 				];
diff --git a/lib/Service/ExternalBoardService.php b/lib/Service/ExternalBoardService.php
index fd48517ec1..734ec9fb33 100644
--- a/lib/Service/ExternalBoardService.php
+++ b/lib/Service/ExternalBoardService.php
@@ -16,6 +16,7 @@
 use OCA\Deck\Db\User;
 use OCA\Deck\Federation\DeckFederationProxy;
 use OCA\Deck\Model\OptionalNullableValue;
+use OCA\Deck\Sharing\DeckShareProvider;
 use OCP\AppFramework\Http\DataResponse;
 use OCP\Federation\ICloudIdManager;
 use OCP\IURLGenerator;
@@ -27,10 +28,11 @@ public function __construct(
 		private ICloudIdManager $cloudIdManager,
 		private DeckFederationProxy $proxy,
 		private ConfigService $configService,
-		private BoardService $boardService,
 		private PermissionService $permissionService,
 		private BoardMapper $boardMapper,
 		private IURLGenerator $urlGenerator,
+		private DeckShareProvider $deckShareProvider,
+		private FilesAppService $filesAppService,
 		private ?string $userId,
 	) {
 	}
@@ -43,6 +45,15 @@ public function getExternalBoardFromRemote(Board $localBoard):DataResponse {
 		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/board/' . $localBoard->getExternalId();
 		$resp = $this->proxy->get($participantCloudId->getId(), $shareToken, $url);
 		$ocs = $this->proxy->getOCSData($resp);
+
+		// Sync local board data with remote data
+		if ($ocs['title'] !== $localBoard->getTitle() || $ocs['color'] !== $localBoard->getColor() || $ocs['archived'] !== $localBoard->isArchived()) {
+			$localBoard->setTitle($ocs['title']);
+			$localBoard->setColor($ocs['color']);
+			$localBoard->setArchived($ocs['archived']);
+			$this->boardMapper->update($localBoard);
+		}
+
 		return new DataResponse($this->LocalizeRemoteBoard($ocs, $localBoard));
 	}
 	public function getExternalStacksFromRemote(Board $localBoard):DataResponse {
@@ -63,7 +74,8 @@ public function localizeRemoteUser(Board $localBoard, array $user): array|User|F
 		}
 		// if it's already a valid cloud id the user originates from a third instance and we pass it as is
 		if ($this->cloudIdManager->isValidCloudId($user['uid'])) {
-			if ($user['remote'] == $this->urlGenerator->getBaseUrl()) {
+			$cloudId = $this->cloudIdManager->resolveCloudId($user['uid']);
+			if ($cloudId->getRemote() == $this->urlGenerator->getBaseUrl()) {
 				// local user from remote: return as local user
 				$localuid = $this->cloudIdManager->resolveCloudId($user['uid'])->getUser();
 				return new User($localuid, $this->userManager);
@@ -85,7 +97,8 @@ public function LocalizeRemoteStacks(array $stacks, Board $localBoard) {
 				$stack['cards'][$j]['assignedUsers'] = array_map(function ($assignment) use ($localBoard) {
 					$assignment['participant'] = $this->localizeRemoteUser($localBoard, $assignment['participant']);
 					return $assignment;
-				}, $card['assignedUsers']);
+				}, $card['assignedUsers'] ?? []);
+				$stack['cards'][$j]['owner'] = $this->localizeRemoteUser($localBoard, $card['owner']);
 			}
 			$stacks[$i] = $stack;
 		}
@@ -98,6 +111,7 @@ public function LocalizeRemoteBoard(array $remoteBoard, Board $localBoard) {
 		$remoteBoard['acl'] = $localBoard->getAcl();
 		$remoteBoard['permissions'] = $localBoard->getPermissions();
 		$remoteBoard['users'] = $this->localizeRemoteUsers($remoteBoard['users'], $localBoard);
+		$remoteBoard['externalId'] = $localBoard->getExternalId();
 		return $remoteBoard;
 	}
 
@@ -110,6 +124,56 @@ public function localizeRemoteUsers(array $users, Board $localBoard) {
 		return $localizedUsers;
 	}
 
+	public function localizeRemoteComments(Board $localBoard, array $comments): array {
+		foreach ($comments as $i => $comment) {
+			// Localize actors
+			$localizedActor = $this->localizeRemoteUser($localBoard, ['uid' => $comment['actorId'], 'remote' => $comment['actorRemote']]);
+			if ($localizedActor instanceof FederatedUser) {
+				$comments[$i]['actorDisplayName'] = $localizedActor->getCloudId()->getId();
+				$comments[$i]['actorId'] = $localizedActor->getCloudId()->getId();
+				$comments[$i]['actorRemote'] = $localizedActor->getCloudId()->getRemote();
+			}
+			if ($localizedActor instanceof User) {
+				$comments[$i]['actorDisplayName'] = $localizedActor->getDisplayName();
+				$comments[$i]['actorId'] = $localizedActor->getUID();
+				$comments[$i]['actorRemote'] = null;
+			}
+			if ($comment['replyTo']) {
+				$localizedReplyActor = $this->localizeRemoteUser($localBoard, ['uid' => $comment['replyTo']['actorId'], 'remote' => $comment['replyTo']['actorRemote']]);
+				if ($localizedReplyActor instanceof FederatedUser) {
+					$comments[$i]['replyTo']['actorDisplayName'] = $localizedReplyActor->getCloudId()->getId();
+					$comments[$i]['replyTo']['actorId'] = $localizedReplyActor->getCloudId()->getId();
+					$comments[$i]['replyTo']['actorRemote'] = $localizedReplyActor->getCloudId()->getRemote();
+				}
+				if ($localizedReplyActor instanceof User) {
+					$comments[$i]['replyTo']['actorDisplayName'] = $localizedReplyActor->getDisplayName();
+					$comments[$i]['replyTo']['actorId'] = $localizedReplyActor->getUID();
+					$comments[$i]['replyTo']['actorRemote'] = null;
+				}
+			}
+
+			// Localize mentions
+			foreach ($comment['mentions'] as $j => $mention) {
+				$localizedMention = $this->localizeRemoteUser($localBoard, ['uid' => $mention['mentionId'], 'remote' => $mention['mentionRemote']]);
+				if ($localizedMention instanceof User) {
+					$comments[$i]['message'] = str_replace('@"federated_user/' . $mention['mentionId'], '@"' . $localizedMention->getUID(), $comment['message']);
+					$comments[$i]['mentions'][$j]['mentionDisplayName'] = $localizedMention->getDisplayName();
+					$comments[$i]['mentions'][$j]['mentionId'] = $localizedMention->getUID();
+					$comments[$i]['mentions'][$j]['mentionRemote'] = null;
+					$comments[$i]['mentions'][$j]['mentionType'] = 'user';
+				}
+				if ($localizedMention instanceof FederatedUser) {
+					$comments[$i]['message'] = str_replace('@' . $mention['mentionId'], '@federated_user/' . $localizedMention->getUID(), $comment['message']);
+					$comments[$i]['mentions'][$j]['mentionDisplayName'] = $localizedMention->getCloudId()->getId();
+					$comments[$i]['mentions'][$j]['mentionId'] = $localizedMention->getCloudId()->getId();
+					$comments[$i]['mentions'][$j]['mentionRemote'] = $localizedMention->getCloudId()->getRemote();
+					$comments[$i]['mentions'][$j]['mentionType'] = 'federated_user';
+				}
+			}
+		}
+		return $comments;
+	}
+
 	public function createCardOnRemote(
 		Board $localBoard,
 		string $title,
@@ -154,6 +218,8 @@ public function updateCardOnRemote(
 		?int $deletedAt = null,
 		?bool $archived = null,
 		?OptionalNullableValue $done = null,
+		?string $startdate = null,
+		?string $color = null,
 	): array {
 		$this->configService->ensureFederationEnabled();
 		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
@@ -173,12 +239,26 @@ public function updateCardOnRemote(
 			'deletedAt' => $deletedAt,
 			'archived' => $archived,
 			'done' => $done->getValue() ?? null,
+			'startdate' => $startdate,
+			'color' => $color,
 			'boardId' => $localBoard->getExternalId(),
 		];
 		$resp = $this->proxy->put($participantCloudId->getId(), $shareToken, $url, $params);
 		return $this->proxy->getOcsData($resp);
 	}
 
+	public function deleteCardOnRemote(Board $localBoard, int $cardId): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId;
+		$resp = $this->proxy->delete($ownerCloudId->getId(), $shareToken, $url, [
+			'boardId' => $localBoard->getExternalId(),
+		]);
+		return $this->proxy->getOcsData($resp);
+	}
+
 	public function assignLabelOnRemote(Board $localBoard, int $cardId, int $labelId): array {
 		$this->configService->ensureFederationEnabled();
 		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
@@ -351,4 +431,264 @@ public function reorderStackOnRemote(Board $localBoard, int $stackId, int $order
 		$resp = $this->proxy->put($participantCloudId->getId(), $shareToken, $url, $params);
 		return $this->proxy->getOcsData($resp);
 	}
+
+	public function getArchivedStacksFromRemote(Board $localBoard): array {
+		$this->configService->ensureFederationEnabled();
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/stacks/' . $localBoard->getExternalId() . '/archived';
+		$resp = $this->proxy->get($participantCloudId->getId(), $shareToken, $url);
+		$ocs = $this->proxy->getOCSData($resp);
+		return $this->LocalizeRemoteStacks($ocs, $localBoard);
+	}
+
+	public function archiveCardOnRemote(Board $localBoard, int $cardId): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/archive';
+		$params = [
+			'boardId' => $localBoard->getExternalId(),
+		];
+		$resp = $this->proxy->put($participantCloudId->getId(), $shareToken, $url, $params);
+		return $this->proxy->getOcsData($resp);
+	}
+
+	public function unarchiveCardOnRemote(Board $localBoard, int $cardId): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/unarchive';
+		$params = [
+			'boardId' => $localBoard->getExternalId(),
+		];
+		$resp = $this->proxy->put($participantCloudId->getId(), $shareToken, $url, $params);
+		return $this->proxy->getOcsData($resp);
+	}
+
+	public function setDoneCardOnRemote(Board $localBoard, int $cardId): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/done';
+		$params = [
+			'boardId' => $localBoard->getExternalId(),
+		];
+		$resp = $this->proxy->put($participantCloudId->getId(), $shareToken, $url, $params);
+		return $this->proxy->getOcsData($resp);
+	}
+
+	public function setUndoneCardOnRemote(Board $localBoard, int $cardId): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/undone';
+		$params = [
+			'boardId' => $localBoard->getExternalId(),
+		];
+		$resp = $this->proxy->put($participantCloudId->getId(), $shareToken, $url, $params);
+		return $this->proxy->getOcsData($resp);
+	}
+
+	public function getCardCommentsFromRemote(Board $localBoard, int $cardId, int $limit = 20, int $offset = 0): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_READ, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/comments';
+		$params = [
+			'boardId' => $localBoard->getExternalId(),
+			'limit' => $limit,
+			'offset' => $offset,
+		];
+		$resp = $this->proxy->get($participantCloudId->getId(), $shareToken, $url, $params);
+		$comments = $this->proxy->getOcsData($resp);
+		return $this->localizeRemoteComments($localBoard, $comments);
+	}
+
+	public function createCardCommentOnRemote(Board $localBoard, int $cardId, string $message, int $parentId = 0): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_READ, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/comments';
+
+		$params = [
+			'boardId' => $localBoard->getExternalId(),
+			'message' => $message,
+			'parentId' => $parentId,
+		];
+		$resp = $this->proxy->post($participantCloudId->getId(), $shareToken, $url, $params);
+		$newComment = $this->proxy->getOcsData($resp);
+		return $this->localizeRemoteComments($localBoard, [$newComment])[0];
+	}
+
+	public function updateCardCommentOnRemote(Board $localBoard, int $cardId, int $commentId, string $message): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_READ, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/comments/' . $commentId;
+		$params = [
+			'boardId' => $localBoard->getExternalId(),
+			'message' => $message,
+		];
+		$resp = $this->proxy->put($participantCloudId->getId(), $shareToken, $url, $params);
+		$updatedComment = $this->proxy->getOcsData($resp);
+		return $this->localizeRemoteComments($localBoard, [$updatedComment])[0];
+	}
+
+	public function deleteCardCommentOnRemote(Board $localBoard, int $cardId, int $commentId): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_READ, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/comments/' . $commentId;
+		$params = [
+			'boardId' => $localBoard->getExternalId(),
+		];
+		$resp = $this->proxy->delete($participantCloudId->getId(), $shareToken, $url, $params);
+		return $this->proxy->getOcsData($resp);
+	}
+
+	public function updateBoardOnRemote(Board $localBoard, string $title, string $color, bool $archived): DataResponse {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_MANAGE, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/boards/' . $localBoard->getExternalId();
+		$params = [
+			'title' => $title,
+			'color' => $color,
+			'archived' => $archived,
+		];
+		$resp = $this->proxy->put($participantCloudId->getId(), $shareToken, $url, $params);
+		$updatedBoard = $this->proxy->getOcsData($resp);
+		return new DataResponse($this->LocalizeRemoteBoard($updatedBoard, $localBoard));
+	}
+
+	public function leaveBoardOnRemote(Board $localBoard): void {
+		$this->configService->ensureFederationEnabled();
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/boards/' . $localBoard->getExternalId() . '/leave';
+		$this->proxy->post($participantCloudId->getId(), $shareToken, $url);
+	}
+
+	public function localizeRemoteAttachments(Board $localBoard, array $attachments): array {
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		foreach ($attachments as $i => $attachment) {
+			$createdByUser = $this->localizeRemoteUser($localBoard, ['uid' => $attachment['createdBy'], 'remote' => $attachment['extendedData']['createdByRemote']]);
+			if ($createdByUser instanceof FederatedUser) {
+				$attachments[$i]['createdBy'] = $createdByUser->getCloudId()->getId();
+				$attachments[$i]['createdByRemote'] = $createdByUser->getCloudId()->getRemote();
+				$attachments[$i]['extendedData']['attachmentCreator']['id'] = $createdByUser->getCloudId()->getId();
+				$attachments[$i]['extendedData']['attachmentCreator']['remote'] = $createdByUser->getCloudId()->getRemote();
+				$attachments[$i]['extendedData']['attachmentCreator']['displayName'] = $createdByUser->getCloudId()->getId();
+			}
+			if ($createdByUser instanceof User) {
+				$attachments[$i]['createdBy'] = $createdByUser->getUID();
+				$attachments[$i]['createdByRemote'] = null;
+				$attachments[$i]['extendedData']['attachmentCreator']['id'] = $createdByUser->getUID();
+				$attachments[$i]['extendedData']['attachmentCreator']['remote'] = null;
+				$attachments[$i]['extendedData']['attachmentCreator']['displayName'] = $createdByUser->getDisplayName();
+			}
+			if (!empty($attachment['extendedData']['shareToken'])) {
+				if ($createdByUser instanceof User) {
+					$file = $this->deckShareProvider->getLocalFile($attachment['extendedData']['shareToken']);
+				} else {
+					$file = $this->deckShareProvider->getRemoteFile($attachment['extendedData']['shareToken'], $ownerCloudId->getRemote());
+				}
+
+				if (empty($file)) {
+					unset($attachments[$i]);
+					continue;
+				}
+
+				$attachments[$i]['extendedData'] = array_merge($attachments[$i]['extendedData'], $file);
+				unset($attachments[$i]['extendedData']['shareToken']);
+			}
+		}
+		return $attachments;
+	}
+
+	public function getAttachmentsFromRemote(Board $localBoard, int $cardId): array {
+		$this->configService->ensureFederationEnabled();
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/attachments';
+		$resp = $this->proxy->get($participantCloudId->getId(), $shareToken, $url, [
+			'boardId' => $localBoard->getExternalId(),
+		]);
+		$attachments = $this->proxy->getOcsData($resp);
+		return $this->localizeRemoteAttachments($localBoard, $attachments);
+	}
+
+	public function createAttachmentForRemote(Board $localBoard, int $cardId): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+
+		// Upload and create remote share
+		$shareWithFederatedId = $ownerCloudId->getId();
+		$fileShareToken = $this->filesAppService->createForRemote($shareWithFederatedId);
+
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/remote-attachment';
+		$resp = $this->proxy->post($participantCloudId->getId(), $shareToken, $url, [
+			'boardId' => $localBoard->getExternalId(),
+			'cardId' => $cardId,
+			'token' => $fileShareToken,
+		]);
+		return $this->proxy->getOcsData($resp);
+	}
+
+	public function shareAttachmentForRemote(Board $localBoard, int $cardId, string $path): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$participantCloudId = $this->cloudIdManager->getCloudId($this->userId, null);
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+
+		// Create remote share
+		$shareWithFederatedId = $ownerCloudId->getId();
+		$fileShareToken = $this->filesAppService->createRemoteShareForPath($path, $shareWithFederatedId);
+
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/remote-attachment';
+		$resp = $this->proxy->post($participantCloudId->getId(), $shareToken, $url, [
+			'boardId' => $localBoard->getExternalId(),
+			'cardId' => $cardId,
+			'token' => $fileShareToken,
+		]);
+		return $this->proxy->getOcsData($resp);
+	}
+
+	public function deleteAttachmentOnRemote(Board $localBoard, int $cardId, int $attachmentId, string $type = 'file'): array {
+		$this->configService->ensureFederationEnabled();
+		$this->permissionService->checkPermission($this->boardMapper, $localBoard->getId(), Acl::PERMISSION_EDIT, $this->userId, false, false);
+		$shareToken = $localBoard->getShareToken();
+		$ownerCloudId = $this->cloudIdManager->resolveCloudId($localBoard->getOwner());
+		$url = $ownerCloudId->getRemote() . '/ocs/v2.php/apps/deck/api/v1.0/cards/' . $cardId . '/attachments/' . $type . ':' . $attachmentId;
+		$resp = $this->proxy->delete($ownerCloudId->getId(), $shareToken, $url, [
+			'boardId' => $localBoard->getExternalId(),
+		]);
+		return $this->proxy->getOcsData($resp);
+	}
 }
diff --git a/lib/Service/FilesAppService.php b/lib/Service/FilesAppService.php
index d6824c51b6..c331302c26 100644
--- a/lib/Service/FilesAppService.php
+++ b/lib/Service/FilesAppService.php
@@ -19,12 +19,14 @@
 use OCP\AppFramework\Http\StreamResponse;
 use OCP\Constants;
 use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\Federation\ICloudIdManager;
 use OCP\Files\File;
 use OCP\Files\Folder;
 use OCP\Files\IFilenameValidator;
 use OCP\Files\IMimeTypeDetector;
 use OCP\Files\InvalidPathException;
 use OCP\Files\IRootFolder;
+use OCP\Files\Node;
 use OCP\Files\NotFoundException;
 use OCP\IDBConnection;
 use OCP\IL10N;
@@ -43,6 +45,7 @@ class FilesAppService implements IAttachmentService, ICustomAttachmentService {
 	 * Reason is not having access to the original filename because of early sanitization in the request lifecycle.
 	 */
 	private const SANITIZED_CHAR_MAPPING = [':' => '/'];
+	private const FEDERATED_ATTACHMENT_TARGET_PREFIX = 'deck-card-attachment-';
 
 	private IRequest $request;
 	private IRootFolder $rootFolder;
@@ -58,6 +61,7 @@ class FilesAppService implements IAttachmentService, ICustomAttachmentService {
 	private LoggerInterface $logger;
 	private IDBConnection $connection;
 	private IFilenameValidator $filenameValidator;
+	private ICloudIdManager $cloudIdManager;
 
 	public function __construct(
 		IRequest $request,
@@ -73,6 +77,7 @@ public function __construct(
 		LoggerInterface $logger,
 		IDBConnection $connection,
 		IFilenameValidator $filenameValidator,
+		ICloudIdManager $cloudIdManager,
 		?string $userId,
 	) {
 		$this->request = $request;
@@ -89,10 +94,12 @@ public function __construct(
 		$this->logger = $logger;
 		$this->connection = $connection;
 		$this->filenameValidator = $filenameValidator;
+		$this->cloudIdManager = $cloudIdManager;
 	}
 
 	public function listAttachments(int $cardId): array {
-		$shares = $this->shareProvider->getSharedWithByType($cardId, IShare::TYPE_DECK, -1, 0);
+		$userId = $this->userId ?? $this->permissionService->getUserId();
+		$shares = $this->shareProvider->getSharedWithByType($cardId, IShare::TYPE_DECK, -1, 0, $userId);
 		return array_filter(array_map(function (IShare $share) use ($cardId) {
 			try {
 				$file = $share->getNode();
@@ -147,26 +154,91 @@ public function getAttachmentCountForCards(array $cardIds): array {
 	}
 
 	public function extendData(Attachment $attachment) {
-		$userFolder = $this->rootFolder->getUserFolder($this->userId);
 		$share = $this->getShareForAttachment($attachment);
-		$files = $userFolder->getById($share->getNode()->getId());
-		if (count($files) === 0) {
-			return $attachment;
+		$node = $share->getNode();
+
+		$requestUserId = $this->permissionService->getUserId();
+		if ($this->cloudIdManager->isValidCloudId($requestUserId)) {
+			if ($share->getSharedBy() === $requestUserId) {
+				$externalShare = $this->shareProvider->findRootExternalShare($share, $requestUserId);
+				$attachment->setExtendedData([
+					'data' => $node->getName(),
+					'shareToken' => $externalShare ? $externalShare->getRefreshToken() : null,
+				]);
+			} else {
+				$shareToken = $this->ensureFederatedAttachmentShare($share, $node, $requestUserId);
+				$attachment->setExtendedData([
+					'shareToken' => $shareToken,
+				]);
+			}
 		}
-		$file = array_shift($files);
-		$attachment->setExtendedData([
-			'path' => $userFolder->getRelativePath($file->getPath()),
-			'fileid' => $file->getId(),
-			'data' => $file->getName(),
-			'filesize' => $file->getSize(),
-			'mimetype' => $file->getMimeType(),
-			'info' => pathinfo($file->getName()),
-			'hasPreview' => $this->preview->isAvailable($file),
-			'permissions' => $share->getPermissions(),
-		]);
+
+		if ($this->userId !== null) {
+			$userFolder = $this->rootFolder->getUserFolder($this->userId);
+			$files = $userFolder->getById($node->getId());
+			if (count($files) === 0) {
+				return $attachment;
+			}
+			$file = array_shift($files);
+			$attachment->setExtendedData([
+				'path' => $userFolder->getRelativePath($file->getPath()),
+				'fileid' => $file->getId(),
+				'data' => $file->getName(),
+				'filesize' => $file->getSize(),
+				'mimetype' => $file->getMimeType(),
+				'info' => pathinfo($file->getName()),
+				'hasPreview' => $this->preview->isAvailable($file),
+				'permissions' => $share->getPermissions(),
+			]);
+		}
+
 		return $attachment;
 	}
 
+	private function ensureFederatedAttachmentShare(IShare $attachmentShare, Node $file, string $federatedCloudId): string {
+		if ($shareToken = $this->findFederatedAttachmentShareToken($file->getId(), $federatedCloudId)) {
+			return $shareToken;
+		}
+
+		$share = $this->shareManager->newShare();
+		$share->setNode($file);
+		$share->setShareType(IShare::TYPE_REMOTE);
+		$share->setSharedWith($federatedCloudId);
+		$share->setPermissions(Constants::PERMISSION_READ);
+		$share->setSharedBy($attachmentShare->getShareOwner());
+		$share->setShareOwner($attachmentShare->getShareOwner());
+
+		$createdShare = $this->shareManager->createShare($share);
+
+		$qb = $this->connection->getQueryBuilder();
+		$qb->update('share')
+			->set('parent', $qb->createNamedParameter($attachmentShare->getId(), IQueryBuilder::PARAM_INT))
+			->andWhere($qb->expr()->eq('id', $qb->createNamedParameter($createdShare->getId(), IQueryBuilder::PARAM_INT)))
+			->executeStatement();
+
+		return $createdShare->getToken();
+	}
+
+	private function findFederatedAttachmentShareToken(int $fileId, string $federatedCloudId): ?string {
+		$qb = $this->connection->getQueryBuilder();
+		$qb->select('id', 'token')
+			->from('share')
+			->andWhere($qb->expr()->eq('share_type', $qb->createNamedParameter(IShare::TYPE_REMOTE)))
+			->andWhere($qb->expr()->eq('share_with', $qb->createNamedParameter($federatedCloudId)))
+			->andWhere($qb->expr()->eq('file_source', $qb->createNamedParameter($fileId, IQueryBuilder::PARAM_INT)))
+			->setMaxResults(1);
+
+		$cursor = $qb->executeQuery();
+		$data = $cursor->fetch();
+		$cursor->closeCursor();
+
+		if ($data === false) {
+			return null;
+		}
+
+		return $data['token'] ?? null;
+	}
+
 	public function display(Attachment $attachment) {
 		// Problem: Folders
 		/** @psalm-suppress InvalidCatch */
@@ -234,11 +306,70 @@ public function create(Attachment $attachment) {
 		$share->setPermissions(Constants::PERMISSION_READ);
 		$share->setSharedBy($this->userId);
 		$share = $this->shareManager->createShare($share);
+
 		$attachment->setId((int)$share->getId());
 		$attachment->setData($target->getName());
 		return $attachment;
 	}
 
+	public function createForRemote(string $federatedCloudId): string {
+		$file = $this->getUploadedFile();
+		$fileName = $file['name'];
+		$this->validateFilename($fileName);
+
+		$userFolder = $this->rootFolder->getUserFolder($this->userId);
+		try {
+			$folder = $userFolder->get($this->configService->getAttachmentFolder());
+		} catch (NotFoundException) {
+			$folder = $userFolder->newFolder($this->configService->getAttachmentFolder());
+		}
+
+		if ($folder->isShared()) {
+			$folderName = $userFolder->getNonExistingName($this->configService->getAttachmentFolder());
+			$folder = $userFolder->newFolder($folderName);
+			$this->configService->setAttachmentFolder($this->userId, $folderName);
+		}
+
+		if (!$folder instanceof Folder || $folder->isShared()) {
+			throw new NotFoundException('No target folder found');
+		}
+
+		$fileName = $folder->getNonExistingName($fileName);
+		$target = $folder->newFile($fileName);
+		$content = fopen($file['tmp_name'], 'rb');
+		if ($content === false) {
+			throw new StatusException('Could not read file');
+		}
+		$target->putContent($content);
+		$createdShare = $this->createRemoteShareForNode($target, $federatedCloudId);
+
+		return $createdShare->getToken();
+	}
+
+	public function createRemoteShareForPath(string $path, string $federatedCloudId): string {
+		$userFolder = $this->rootFolder->getUserFolder($this->userId);
+		try {
+			$node = $userFolder->get($path);
+		} catch (NotFoundException) {
+			throw new NotFoundException('No target file found');
+		}
+		$createdShare = $this->createRemoteShareForNode($node, $federatedCloudId);
+
+		return $createdShare->getToken();
+	}
+
+	private function createRemoteShareForNode(Node $node, string $federatedCloudId): IShare {
+		$share = $this->shareManager->newShare();
+		$share->setNode($node);
+		$share->setShareType(IShare::TYPE_REMOTE);
+		$share->setSharedWith($federatedCloudId);
+		$share->setPermissions(Constants::PERMISSION_READ);
+		$share->setSharedBy($this->userId);
+		$share->setShareOwner($this->userId);
+
+		return $this->shareManager->createShare($share);
+	}
+
 	/**
 	 * Ensure the file exists in the owner’s Deck attachment folder, link it to the
 	 * Reuse file/share when already present
diff --git a/lib/Service/PermissionService.php b/lib/Service/PermissionService.php
index a22c6e12b4..a2dd5ba176 100644
--- a/lib/Service/PermissionService.php
+++ b/lib/Service/PermissionService.php
@@ -252,7 +252,7 @@ public function userCan(array $acls, $permission, $userId = null) {
 		}
 		// check for users
 		foreach ($acls as $acl) {
-			if ($acl->getType() === Acl::PERMISSION_TYPE_USER && $acl->getParticipant() === $userId) {
+			if (in_array($acl->getType(), [Acl::PERMISSION_TYPE_USER, Acl::PERMISSION_TYPE_REMOTE]) && $acl->getParticipant() === $userId) {
 				return $acl->getPermission($permission);
 			}
 
diff --git a/lib/Sharing/DeckShareProvider.php b/lib/Sharing/DeckShareProvider.php
index ef41e4301e..ad2b25cc48 100644
--- a/lib/Sharing/DeckShareProvider.php
+++ b/lib/Sharing/DeckShareProvider.php
@@ -9,26 +9,42 @@
 
 namespace OCA\Deck\Sharing;
 
+use OC\Federation\CloudId;
 use OC\Files\Cache\Cache;
 use OCA\Deck\Cache\AttachmentCacheHelper;
 use OCA\Deck\Db\Acl;
 use OCA\Deck\Db\BoardMapper;
 use OCA\Deck\Db\CardMapper;
+use OCA\Deck\Db\FederatedUser;
 use OCA\Deck\Db\User;
 use OCA\Deck\NoPermissionException;
 use OCA\Deck\Service\PermissionService;
+use OCA\Files_Sharing\External\ExternalShare;
+use OCA\Files_Sharing\External\Manager as ExternalShareManager;
+use OCA\Files_Sharing\External\Mount;
 use OCP\AppFramework\Db\DoesNotExistException;
 use OCP\AppFramework\Db\MultipleObjectsReturnedException;
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\Constants;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\EventDispatcher\IEventDispatcher;
-use OCP\Files\File;
+use OCP\Federation\ICloudIdManager;
+use OCP\Files\Config\IUserMountCache;
+use OCP\Files\Events\InvalidateMountCacheEvent;
 use OCP\Files\Folder;
 use OCP\Files\IMimeTypeLoader;
+use OCP\Files\IRootFolder;
 use OCP\Files\Node;
+use OCP\Http\Client\IClientService;
+use OCP\ICertificateManager;
+use OCP\IConfig;
 use OCP\IDBConnection;
 use OCP\IL10N;
+use OCP\IPreview;
+use OCP\IUser;
+use OCP\IUserManager;
+use OCP\OCM\IOCMDiscoveryService;
+use OCP\Server;
 use OCP\Share\Exceptions\GenericShareException;
 use OCP\Share\Exceptions\ShareNotFound;
 use OCP\Share\IAttributes;
@@ -62,6 +78,15 @@ public function __construct(
 		private IL10N $l,
 		private ITimeFactory $timeFactory,
 		private IMimeTypeLoader $mimeTypeLoader,
+		private ExternalShareManager $externalShareManager,
+		private IRootFolder $rootFolder,
+		private IPreview $preview,
+		private IConfig $config,
+		private \OC\Files\Mount\Manager $mountManager,
+		private IUserManager $userManager,
+		private IUserMountCache $userMountCache,
+		private IEventDispatcher $eventDispatcher,
+		private ICloudIdManager $cloudIdManager,
 		private ?string $userId = null,
 	) {
 	}
@@ -89,7 +114,7 @@ public function create(IShare $share) {
 		}
 
 		try {
-			$this->permissionService->checkPermission(null, $boardId, Acl::PERMISSION_EDIT);
+			$this->permissionService->checkPermission(null, $boardId, Acl::PERMISSION_EDIT, $share->getSharedBy());
 		} catch (NoPermissionException $e) {
 			$valid = false;
 		}
@@ -337,6 +362,7 @@ public function update(IShare $share) {
 	 * @inheritDoc
 	 */
 	public function delete(IShare $share) {
+		$this->deleteRemoteShares($share);
 		$qb = $this->dbConnection->getQueryBuilder();
 		$qb->delete('share')
 			->where($qb->expr()->eq('id', $qb->createNamedParameter($share->getId())));
@@ -345,9 +371,70 @@ public function delete(IShare $share) {
 
 		$qb->executeStatement();
 
+		$this->deleteExternalShare($share);
 		$this->attachmentCacheHelper->clearAttachmentCount((int)$share->getSharedWith());
 	}
 
+	private function deleteRemoteShares(IShare $share) {
+		$qb = $this->dbConnection->getQueryBuilder();
+		$qb->select('id', 'token')
+			->from('share')
+			->where($qb->expr()->eq('parent', $qb->createNamedParameter($share->getId())))
+			->andWhere($qb->expr()->eq('share_type', $qb->createNamedParameter(IShare::TYPE_REMOTE)));
+		$stmt = $qb->executeQuery();
+
+		while ($row = $stmt->fetchAssociative()) {
+			try {
+				$remoteShare = $this->shareManager->getShareByToken((string)$row['token']);
+				$this->shareManager->deleteShare($remoteShare);
+			} catch (\Exception $e) {
+				continue;
+			}
+		}
+	}
+
+	private function deleteExternalShare(IShare $share) {
+		$shareBy = $share->getSharedBy();
+
+		if (!$this->cloudIdManager->isValidCloudId($shareBy)) {
+			return;
+		}
+
+		$externalShare = $this->findRootExternalShare($share, $shareBy);
+
+		if (empty($externalShare)) {
+			return;
+		}
+
+		$user = $this->userManager->get($externalShare->getUser());
+		$this->externalShareManager->declineShare($externalShare, $user);
+	}
+
+	public function findRootExternalShare(IShare $share, string $ownerCloudId): ?ExternalShare {
+		$node = $share->getNode();
+		$cloudId = $this->cloudIdManager->resolveCloudId($ownerCloudId);
+		$mountPoint = str_replace('/' . $share->getShareOwner() . '/files', '', $node->getPath());
+
+		$qb = $this->dbConnection->getQueryBuilder();
+		$qb->select('id', 'refresh_token', 'mountpoint', 'user')
+			->from('share_external')
+			->andWhere($qb->expr()->eq('remote', $qb->createNamedParameter($cloudId->getRemote() . '/')))
+			->andWhere($qb->expr()->eq('owner', $qb->createNamedParameter($cloudId->getUser())))
+			->andWhere($qb->expr()->eq('mountpoint', $qb->createNamedParameter($mountPoint)))
+			->setMaxResults(1);
+
+		$cursor = $qb->executeQuery();
+		$data = $cursor->fetch();
+		$cursor->closeCursor();
+
+		if ($data === false) {
+			return null;
+		}
+
+		$user = $this->userManager->get($data['user']);
+		return $this->externalShareManager->getShare((string)$data['id'], $user);
+	}
+
 	/**
 	 * @inheritDoc
 	 */
@@ -870,7 +957,7 @@ private function _getSharedWith(
 	 * @param int $offset
 	 * @return IShare[]
 	 */
-	public function getSharedWithByType(int $cardId, int $shareType, $limit, $offset): array {
+	public function getSharedWithByType(int $cardId, int $shareType, $limit, $offset, ?string $userId = null): array {
 		/** @var IShare[] $shares */
 		$shares = [];
 
@@ -913,7 +1000,7 @@ public function getSharedWithByType(int $cardId, int $shareType, $limit, $offset
 		}
 		$cursor->closeCursor();
 
-		return $this->resolveSharesForRecipient($shares, $this->userId);
+		return $this->resolveSharesForRecipient($shares, $userId ?? $this->userId);
 	}
 
 	public function isAccessibleResult(array $data): bool {
@@ -1209,10 +1296,144 @@ public function getUsersForShare(IShare $share): iterable {
 			}
 
 			foreach ($this->permissionService->findUsers($boardId) as $user) {
+				if ($user instanceof FederatedUser) {
+					continue;
+				}
 				yield $user->getUserObject();
 			}
 		}
 
 		return [];
 	}
+
+	public function getRemoteFile(string $shareToken, string $remote): ?array {
+		$externalShare = $this->ensureAcceptRemoteShare($shareToken, $remote);
+		$user = $this->userManager->get($externalShare->getUser());
+		$userFolder = $this->rootFolder->getUserFolder($user->getUID());
+		$node = $userFolder->get($externalShare->getMountpoint());
+		$files = $userFolder->getById($node->getId());
+
+		if (count($files) === 0) {
+			return [
+				'path' => $externalShare->getMountpoint(),
+				'fileid' => $node->getId(),
+				'filesize' => $node->getSize(),
+				'mimetype' => $node->getMimetype(),
+				'info' => pathinfo($node->getName()),
+				'hasPreview' => false,
+			];
+		}
+
+		$file = array_shift($files);
+
+		return [
+			'path' => $userFolder->getRelativePath($file->getPath()),
+			'fileid' => $file->getId(),
+			'filesize' => $file->getSize(),
+			'mimetype' => $file->getMimeType(),
+			'info' => pathinfo($file->getName()),
+			'hasPreview' => $this->preview->isAvailable($file),
+		];
+	}
+
+	public function getLocalFile(string $shareToken): ?array {
+		try {
+			$share = $this->shareManager->getShareByToken($shareToken);
+		} catch (ShareNotFound $e) {
+			return null;
+		}
+
+		$userFolder = $this->rootFolder->getUserFolder($share->getSharedBy());
+		$node = $share->getNode();
+		$files = $userFolder->getById($node->getId());
+
+		if (count($files) === 0) {
+			return null;
+		}
+
+		$file = array_shift($files);
+
+		return [
+			'path' => $userFolder->getRelativePath($file->getPath()),
+			'fileid' => $file->getId(),
+			'filesize' => $file->getSize(),
+			'mimetype' => $file->getMimeType(),
+			'info' => pathinfo($file->getName()),
+			'hasPreview' => $this->preview->isAvailable($file),
+		];
+	}
+
+	public function ensureAcceptRemoteShare(string $shareToken, string $remote): ExternalShare {
+		$qb = $this->dbConnection->getQueryBuilder();
+		$qb->select('id', 'accepted', 'user')
+			->from('share_external')
+			->where($qb->expr()->eq('refresh_token', $qb->createNamedParameter($shareToken)))
+			->andWhere($qb->expr()->eq('remote', $qb->createNamedParameter($remote . '/')))
+			->setMaxResults(1);
+
+		$cursor = $qb->executeQuery();
+		$data = $cursor->fetch();
+		$cursor->closeCursor();
+
+		if ($data === false) {
+			throw new ShareNotFound();
+		}
+
+		$user = $this->userManager->get($data['user']);
+		$externalShare = $this->externalShareManager->getShare((string)$data['id'], $user);
+
+		if ($externalShare === false) {
+			throw new ShareNotFound();
+		}
+
+		if ((int)$data['accepted'] === 0 && !$this->externalShareManager->acceptShare($externalShare, $user)) {
+			throw new ShareNotFound();
+		}
+
+		$externalShare = $this->externalShareManager->getShare((string)$data['id'], $user);
+
+		// Update mount point to be under /Deck
+		if (strpos($externalShare->getMountpoint(), '/Deck') !== 0) {
+			$target = '/Deck' . $externalShare->getName();
+			$targetHash = md5($target);
+			$qb = $this->dbConnection->getQueryBuilder();
+			$qb->update('share_external')
+				->set('mountpoint', $qb->createNamedParameter($target))
+				->set('mountpoint_hash', $qb->createNamedParameter($targetHash))
+				->where($qb->expr()->eq('id', $qb->createNamedParameter($externalShare->getId())))
+				->executeStatement();
+			$this->eventDispatcher->dispatchTyped(new InvalidateMountCacheEvent($user));
+			$externalShare->setMountpoint('/Deck' . $externalShare->getName());
+		}
+
+		$this->mountExternalShare($externalShare, $user);
+
+		return $externalShare;
+	}
+
+	public function mountExternalShare(ExternalShare $externalShare, IUser $user): Mount {
+		$options = [
+			'remote' => $externalShare->getRemote(),
+			'token' => $externalShare->getRefreshToken(),
+			'password' => $externalShare->getPassword(),
+			'access_token' => $externalShare->getAccessToken(),
+			'access_token_expires' => $externalShare->getAccessTokenExpires(),
+			'mountpoint' => $externalShare->getMountpoint(),
+			'owner' => $externalShare->getOwner(),
+			'verify' => !$this->config->getSystemValueBool('sharing.federation.allowSelfSignedCertificates'),
+			'HttpClientService' => Server::get(IClientService::class),
+			'cloudId' => new CloudId($externalShare->getOwner() . '@' . $externalShare->getRemote(), $externalShare->getOwner(), $externalShare->getRemote()),
+			'manager' => $this->externalShareManager,
+			'certificateManager' => Server::get(ICertificateManager::class),
+			'discoveryService' => Server::get(IOCMDiscoveryService::class),
+		];
+		$mount = $this->externalShareManager->getMount($options, $user);
+		$this->mountManager->addMount($mount);
+
+		$userFolder = $this->rootFolder->getUserFolder($user->getUID());
+		$node = $userFolder->get($externalShare->getMountpoint());
+		$this->userMountCache->addMount($user, '/' . $user->getUID() . '/files' . $externalShare->getMountpoint() . '/', $node->getData(), $mount->getMountProvider(), $mount->getMountId());
+
+		return $mount;
+	}
 }
diff --git a/src/components/board/SharingTabSidebar.vue b/src/components/board/SharingTabSidebar.vue
index 02e0e67b81..5518de49bd 100644
--- a/src/components/board/SharingTabSidebar.vue
+++ b/src/components/board/SharingTabSidebar.vue
@@ -14,21 +14,20 @@
 			id="shareWithList"
 			class="shareWithList">
 			<li>
-				<NcAvatar :user="board.owner.uid" />
+				<NcAvatar :user="board.owner.uid" :isNoUser="board.owner.type !== 0" />
 				<span class="username">
-					{{ board.owner.displayname }}
-					<span class="board-owner-label">
+					{{ board.owner.type===6 ? board.owner.uid : board.owner.displayname }}
+					<span v-if="!isCurrentUser(board.owner.uid)" class="board-owner-label">
 						{{ t('deck', 'Board owner') }}
 					</span>
 				</span>
 			</li>
 			<li v-for="acl in board.acl" :key="acl.id" :data-cy="'acl-participant:' + acl.participant.uid">
-				<NcAvatar v-if="acl.type === 0" :user="acl.participant.uid" />
+				<NcAvatar v-if="acl.type === 0 || acl.type === 6" :user="acl.participant.uid" :isNoUser="acl.type !== 0" />
 				<div v-if="acl.type === 1" class="avatardiv icon icon-group" />
 				<div v-if="acl.type === 7" class="avatardiv icon icon-circles" />
-				<div v-if="acl.type === 6" class="avatardiv icon" />
 				<span class="username">
-					{{ acl.participant.displayname || acl.participant }}
+					{{ acl.type === 6 ? acl.participant.uid : acl.participant.displayname || acl.participant }}
 					<span v-if="acl.type === 1">{{ t('deck', '(Group)') }}</span>
 					<span v-if="acl.type === 7">{{ t('deck', '(Team)') }}</span>
 					<span v-if="acl.type === 6">{{ t('deck', '(remote)') }}</span>
@@ -314,6 +313,7 @@ export default {
 	.username {
 		padding: 12px 9px;
 		flex-grow: 1;
+		min-width: 0;
 	}
 
 	.board-owner-label {
diff --git a/src/components/card/AssignmentSelector.vue b/src/components/card/AssignmentSelector.vue
index 3f3b47f3fc..2bc2d1ff74 100644
--- a/src/components/card/AssignmentSelector.vue
+++ b/src/components/card/AssignmentSelector.vue
@@ -20,7 +20,7 @@
 			<NcUserBubble
 				v-for="option in assignedUsers"
 				:key="option.primaryKey"
-				:user="option.uid"
+				:user="option.isNoUser ? undefined : option.uid"
 				:displayName="option.displayname"
 				:isNoUser="option.isNoUser"
 				:size="32" />
@@ -72,7 +72,7 @@ export default defineComponent({
 					...item,
 					id: item.type + ':' + item.uid,
 					user: item.primaryKey,
-					displayName: item.displayname,
+					displayname: item.displayname,
 					icon: 'icon-user',
 					isNoUser: false,
 				}
@@ -85,6 +85,11 @@ export default defineComponent({
 					assignable.icon = 'icon-circles'
 					assignable.isNoUser = true
 				}
+				if (item.type === 6) {
+					assignable.isNoUser = true
+					assignable.icon = null
+					assignable.displayname = item.primaryKey
+				}
 
 				return assignable
 			})
@@ -111,9 +116,9 @@ export default defineComponent({
 				this.assignedUsers = this.card.assignedUsers.map((item) => ({
 					...item.participant,
 					id: item.participant.type + ':' + item.participant.uid,
-					displayName: item.participant.displayname,
 					isNoUser: item.participant.type !== 0,
 					user: item.participant.uid,
+					displayname: item.participant.type === 6 ? item.participant.uid : item.participant.displayname,
 				}))
 			} else {
 				this.assignedUsers = []
diff --git a/src/components/card/AttachmentList.vue b/src/components/card/AttachmentList.vue
index e0e8181f57..1bb6a19de6 100644
--- a/src/components/card/AttachmentList.vue
+++ b/src/components/card/AttachmentList.vue
@@ -36,19 +36,19 @@
 				v-for="attachment in attachments"
 				:key="attachment.id"
 				class="attachment"
-				:class="{ 'attachment--deleted': attachment.deletedAt > 0 }">
+				:class="{ 'attachment--deleted': attachment.deletedAt > 0, 'attachment--pending': attachment.deletedAt === 0 && !isAttachmentReady(attachment) }">
 				<a
 					class="fileicon"
 					:href="internalLink(attachment)"
 					:style="mimetypeForAttachment(attachment)"
-					@click.prevent="showViewer(attachment)" />
+					@click.prevent="handleAttachmentClick(attachment)" />
 				<div class="details">
-					<a :href="internalLink(attachment)" @click.prevent="showViewer(attachment)">
+					<a :href="internalLink(attachment)" @click.prevent="handleAttachmentClick(attachment)">
 						<div class="filename">
 							<span>{{ attachmentBasename(attachment) }}</span>
 							<span class="extension">.{{ attachmentExtension(attachment) }}</span>
 						</div>
-						<div v-if="attachment.deletedAt === 0">
+						<div v-if="attachment.deletedAt === 0 && isAttachmentReady(attachment)">
 							<span class="filesize">{{ formattedFileSize(attachment.extendedData.filesize) }}</span>
 							<span class="filedate">{{ relativeDate(attachment.createdAt * 1000) }}</span>
 							<span class="filedate">{{ attachment.extendedData.attachmentCreator.displayName }}</span>
@@ -58,12 +58,12 @@
 						</div>
 					</a>
 				</div>
-				<NcActions v-if="selectable">
+				<NcActions v-if="selectable && isAttachmentReady(attachment)">
 					<NcActionButton icon="icon-confirm" @click="$emit('selectAttachment', attachment)">
 						{{ t('deck', 'Add this attachment') }}
 					</NcActionButton>
 				</NcActions>
-				<NcActions v-if="removable && !isReadOnly" :forceMenu="true">
+				<NcActions v-if="removable && !isReadOnly && isAttachmentReady(attachment)" :forceMenu="true">
 					<NcActionLink v-if="attachment.extendedData.fileid" icon="icon-folder" :href="internalLink(attachment)">
 						{{ t('deck', 'Show in Files') }}
 					</NcActionLink>
@@ -151,6 +151,9 @@ export default {
 			overwriteAttachment: null,
 			isDraggingOver: false,
 			maxUploadSize: maxUploadSizeState,
+			attachmentReadyById: {},
+			attachmentsPollingIntervalId: null,
+			isRefreshingAttachments: false,
 		}
 	},
 
@@ -234,15 +237,22 @@ export default {
 		cardId: {
 			immediate: true,
 			handler() {
-				this.fetchAttachments(this.cardId)
+				this.stopAttachmentsPolling()
+				this.attachmentReadyById = {}
+				this.refreshAttachmentsAndReadiness()
 			},
 		},
 	},
 
+	beforeUnmount() {
+		this.stopAttachmentsPolling()
+	},
+
 	methods: {
 		...mapActions(useAttachmentStore, [
 			'fetchAttachments',
 			'unshareAttachment',
+			'shareFileToRemoteBoard',
 		]),
 
 		handleUploadFile(event) {
@@ -265,20 +275,116 @@ export default {
 						throw new Error(t('files', 'Invalid path selected'))
 					}
 
-					axios.post(generateOcsUrl('apps/files_sharing/api/v1/shares'), {
-						path,
-						shareType: 12,
-						shareWith: '' + this.cardId,
-					}).then(() => {
-						this.fetchAttachments(this.cardId)
-					})
+					if (!this.currentBoard.externalId) {
+						axios.post(generateOcsUrl('apps/files_sharing/api/v1/shares'), {
+							path,
+							shareType: 12,
+							shareWith: '' + this.cardId,
+						}).then(() => {
+							this.refreshAttachmentsAndReadiness()
+						})
+					} else {
+						const bodyFormData = new FormData()
+						bodyFormData.append('path', path)
+						await this.shareFileToRemoteBoard({ cardId: this.cardId, formData: bodyFormData })
+						await this.refreshAttachmentsAndReadiness()
+					}
+				})
+		},
+
+		isAttachmentReady(attachment) {
+			return this.attachmentReadyById[attachment.id] === true
+		},
+
+		async testAttachmentReadiness(attachment) {
+			if (attachment.deletedAt > 0 || !attachment.extendedData.fileid) {
+				return false
+			}
+
+			try {
+				const response = await axios.request({
+					method: 'HEAD',
+					url: this.downloadLink(attachment),
+					validateStatus: () => true,
 				})
+
+				return response.status >= 200 && response.status < 400
+			} catch (_error) {
+				return false
+			}
+		},
+
+		startAttachmentsPolling() {
+			if (this.attachmentsPollingIntervalId !== null) {
+				return
+			}
+
+			this.attachmentsPollingIntervalId = window.setInterval(() => {
+				this.refreshAttachmentsAndReadiness()
+			}, 5000)
+		},
+
+		stopAttachmentsPolling() {
+			if (this.attachmentsPollingIntervalId === null) {
+				return
+			}
+
+			window.clearInterval(this.attachmentsPollingIntervalId)
+			this.attachmentsPollingIntervalId = null
+		},
+
+		async checkAttachmentsReadiness() {
+			const attachments = this.attachments.filter(attachment => attachment.deletedAt === 0)
+			const readinessById = {}
+			const readinessChecks = await Promise.all(attachments.map(async (attachment) => {
+				if (!attachment.extendedData.fileid) {
+					return [attachment.id, false]
+				}
+
+				return [attachment.id, await this.testAttachmentReadiness(attachment)]
+			}))
+
+			for (const [id, isReady] of readinessChecks) {
+				readinessById[id] = isReady
+			}
+
+			this.attachmentReadyById = readinessById
+
+			const hasPendingAttachments = readinessChecks.some(([, isReady]) => !isReady)
+			if (hasPendingAttachments) {
+				this.startAttachmentsPolling()
+				return
+			}
+
+			this.stopAttachmentsPolling()
+		},
+
+		async refreshAttachmentsAndReadiness() {
+			if (this.isRefreshingAttachments) {
+				return
+			}
+
+			this.isRefreshingAttachments = true
+			try {
+				await this.fetchAttachments(this.cardId)
+				await this.checkAttachmentsReadiness()
+			} finally {
+				this.isRefreshingAttachments = false
+			}
 		},
 
 		clickAddNewAttachmment() {
 			this.$refs.localAttachments.click()
 		},
 
+		handleAttachmentClick(attachment) {
+			if (!this.isAttachmentReady(attachment)) {
+				return
+			}
+
+			this.showViewer(attachment)
+		},
+
 		showViewer(attachment) {
 			if (attachment.extendedData.fileid && window.OCA.Viewer.availableHandlers.map((handler) => handler.mimes).flat().includes(attachment.extendedData.mimetype)) {
 				// Hide the sidebar if opening card in modal to avoid wrong sidebar position calculating in Viewer app
@@ -361,6 +467,11 @@ export default {
 				opacity: .5;
 			}
 
+			&.attachment--pending {
+				opacity: .5;
+				pointer-events: none;
+			}
+
 			.fileicon {
 				display: inline-block;
 				min-width: 32px;
@@ -393,6 +504,7 @@ export default {
 			.filesize, .filedate {
 				font-size: 90%;
 				color: var(--color-text-maxcontrast);
+				padding-right: 3px;
 			}
 			.app-popover-menu-utils {
 				position: relative;
diff --git a/src/components/card/CardSidebar.vue b/src/components/card/CardSidebar.vue
index fd7f238672..207464f87c 100644
--- a/src/components/card/CardSidebar.vue
+++ b/src/components/card/CardSidebar.vue
@@ -21,7 +21,10 @@
 			<span>{{ subtitle }}</span>
 			<template v-if="cardOwner">
 				<span> ⸱ </span>
-				<NcUserBubble :user="cardOwner.uid" :displayName="cardOwner.displayName" />
+				<NcUserBubble
+					:user="cardOwner.isNoUser ? undefined : cardOwner.uid"
+					:displayName="cardOwner.displayName"
+					:isNoUser="cardOwner.isNoUser" />
 			</template>
 		</template>
 		<template #secondary-actions>
@@ -154,7 +157,8 @@ const cardOwner = computed(() => {
 	}
 	return {
 		uid: owner?.uid ?? (typeof owner === 'string' ? owner : null),
-		displayName: cardOwnerDisplayName.value,
+		displayName: owner?.type === 6 ? owner.uid : cardOwnerDisplayName.value,
+		isNoUser: owner?.type !== 0,
 	}
 })
 const modifiedTimestamp = computed(() => currentCard.value?.lastModified ? currentCard.value.lastModified * 1000 : null)
diff --git a/src/components/card/CardSidebarTabComments.vue b/src/components/card/CardSidebarTabComments.vue
index 7d72465c50..1469c5fadd 100644
--- a/src/components/card/CardSidebarTabComments.vue
+++ b/src/components/card/CardSidebarTabComments.vue
@@ -119,7 +119,7 @@ export default {
 			this.error = null
 			this.isLoading = true
 			try {
-				await this.commentStore.fetchComments({ cardId: this.card.id })
+				await this.commentStore.fetchComments({ cardId: this.card.id, boardId: this.currentBoard.id })
 				this.isLoading = false
 				if (this.card.commentsUnread > 0) {
 					await this.commentStore.markCommentsAsRead(this.card.id)
@@ -135,6 +135,7 @@ export default {
 			const commentObj = {
 				cardId: this.card.id,
 				comment,
+				boardId: this.currentBoard.id,
 			}
 			await this.commentStore.createComment(commentObj)
 			this.commentStore.setReplyTo(null)
@@ -144,7 +145,7 @@ export default {
 
 		async loadMore() {
 			this.isLoading = true
-			await this.commentStore.fetchMore({ cardId: this.card.id })
+			await this.commentStore.fetchMore({ cardId: this.card.id, boardId: this.currentBoard.id })
 			this.isLoading = false
 		},
 
diff --git a/src/components/card/CommentForm.vue b/src/components/card/CommentForm.vue
index b8874f0228..302116a1b7 100644
--- a/src/components/card/CommentForm.vue
+++ b/src/components/card/CommentForm.vue
@@ -75,10 +75,16 @@ export default {
 		members() {
 			const obj = {}
 			this.currentBoard.users.forEach((user) => {
-				obj[user.uid] = {
+				let uid = user.uid
+				if (user.remote) {
+					uid = `federated_user/${user.uid}`
+				} else if (this.currentBoard.externalId) {
+					uid = `federated_user/${user.uid}@${window.location.origin}`
+				}
+				obj[uid] = {
 					icon: 'icon-user',
-					id: user.uid,
-					label: user.displayname,
+					id: uid,
+					label: user.remote ? user.uid : user.displayname,
 					source: 'users',
 				}
 			})
diff --git a/src/components/card/CommentItem.vue b/src/components/card/CommentItem.vue
index f7a601e23a..9c9329e29d 100644
--- a/src/components/card/CommentItem.vue
+++ b/src/components/card/CommentItem.vue
@@ -8,7 +8,10 @@
 			<div class="reply--header">
 				<div class="reply--hint">
 					{{ t('deck', 'In reply to') }}
-					<NcUserBubble :user="comment.actorId" :displayName="comment.actorDisplayName" />
+					<NcUserBubble
+						:user="comment.actorRemote !== null ? undefined : comment.actorId"
+						:displayName="comment.actorDisplayName"
+						:isNoUser="comment.actorRemote !== null" />
 				</div>
 				<NcActions v-if="preview" class="reply--cancel">
 					<NcActionButton icon="icon-close" @click="$emit('cancel')">
@@ -27,7 +30,7 @@
 	</div>
 	<li v-else class="comment">
 		<div class="comment--header">
-			<NcAvatar :user="comment.actorId" />
+			<NcAvatar :user="comment.actorId" :isNoUser="comment.actorRemote !== null" />
 			<span class="username">
 				{{ comment.actorDisplayName }}
 			</span>
@@ -83,6 +86,8 @@
 </template>
 
 <script>
+import { useBoardStore } from '../../stores/board.js'
+import { mapState } from 'pinia'
 import { getCurrentUser } from '@nextcloud/auth'
 import { NcActionButton, NcActions, NcAvatar, NcRichText, NcUserBubble } from '@nextcloud/vue'
 import md5 from 'blueimp-md5'
@@ -160,6 +165,9 @@ export default {
 	},
 
 	computed: {
+		...mapState(useBoardStore, {
+			currentBoard: state => state.currentBoard,
+		}),
 		canEdit() {
 			return this.comment.actorId === getCurrentUser().uid
 		},
@@ -167,11 +175,17 @@ export default {
 		richText() {
 			return (comment) => {
 				let message = this.parsedMessage(comment.message)
+				message = message.replace('federated_user/', '')
 				comment.mentions.forEach((mention, index) => {
+					let mentionId = mention.mentionId
+					if (mention.mentionRemote === window.location.origin) {
+						mentionId = mention.mentionId.replace('@' + window.location.origin, '')
+						message = message.replace(mention.mentionId, mentionId)
+					}
 					// Currently only [a-z\-_0-9] are allowed inside of placeholders so we use a hash of the mention id as a unique identifier
-					const hash = md5(mention.mentionId)
-					message = message.split('@' + mention.mentionId + '').join(`{user-${hash}}`)
-					message = message.split('@"' + mention.mentionId + '"').join(`{user-${hash}}`)
+					const hash = md5(mentionId)
+					message = message.split('@' + mentionId + '').join(`{user-${hash}}`)
+					message = message.split('@"' + mentionId + '"').join(`{user-${hash}}`)
 				})
 				return message
 			}
@@ -181,11 +195,15 @@ export default {
 			return (comment) => {
 				const mentions = [...comment.mentions]
 				const result = mentions.reduce((result, item, index) => {
-					const itemKey = 'user-' + md5(item.mentionId)
+					let mentionId = item.mentionId
+					if (item.mentionRemote === window.location.origin) {
+						mentionId = item.mentionId.replace('@' + window.location.origin, '')
+					}
+					const itemKey = 'user-' + md5(mentionId)
 					result[itemKey] = {
 						component: AtMention,
 						props: {
-							user: item.mentionId,
+							user: mentionId,
 							displayName: item.mentionDisplayName,
 						},
 					}
@@ -227,6 +245,7 @@ export default {
 			const data = {
 				comment: { id: this.comment.id, message },
 				cardId: this.comment.objectId,
+				boardId: this.currentBoard.id,
 			}
 			await this.commentStore.updateComment(data)
 			this.hideUpdateForm()
@@ -236,6 +255,7 @@ export default {
 			const data = {
 				id: this.comment.id,
 				cardId: this.comment.objectId,
+				boardId: this.currentBoard.id,
 			}
 			this.commentStore.deleteComment(data)
 		},
diff --git a/src/components/cards/AvatarList.vue b/src/components/cards/AvatarList.vue
index 4dd20e7cf1..dc9f80c4d8 100644
--- a/src/components/cards/AvatarList.vue
+++ b/src/components/cards/AvatarList.vue
@@ -14,21 +14,23 @@
 						</div>
 						<div v-for="user in firstUsers" :key="user.id">
 							<NcAvatar
-								v-if="user.type === 0"
+								v-if="user.participant.type === 0"
 								:user="user.participant.uid"
 								:displayName="user.participant.displayname"
 								:disableMenu="true"
 								:hideStatus="true"
 								:size="32" />
 							<NcAvatar
-								v-if="user.type === 6"
+								v-if="user.participant.type === 6"
 								:user="user.participant.uid"
-								:displayName="user.participant.displayname"
+								:displayName="user.participant.uid"
+								:tooltipMessage="user.participant.uid + ' ' + t('deck', '(remote)')"
 								:disableMenu="true"
 								:hideStatus="true"
+								:isNoUser="true"
 								:size="32" />
 							<NcAvatar
-								v-if="user.type === 1"
+								v-if="user.participant.type === 1"
 								:user="user.participant.uid"
 								:displayName="user.participant.displayname"
 								:tooltipMessage="user.participant.displayname + ' ' + t('deck', '(Group)')"
@@ -36,7 +38,7 @@
 								:disableMenu="true"
 								:size="32" />
 							<NcAvatar
-								v-if="user.type === 7"
+								v-if="user.participant.type === 7"
 								:user="user.participant.uid"
 								:displayName="user.participant.displayname"
 								:tooltipMessage="user.participant.displayname + ' ' + t('deck', '(Team)')"
diff --git a/src/helpers/xml.js b/src/helpers/xml.js
index 04bf465df5..74ca4d78f1 100644
--- a/src/helpers/xml.js
+++ b/src/helpers/xml.js
@@ -57,6 +57,7 @@ function commentToObject(tag) {
 		id: tag['d:prop']['oc:id']['#text'],
 		actorId: tag['d:prop']['oc:actorId']['#text'],
 		actorDisplayName: tag['d:prop']['oc:actorDisplayName']['#text'],
+		actorRemote: tag['d:prop']['oc:actorRemote']['#text'],
 		creationDateTime: tag['d:prop']['oc:creationDateTime']['#text'],
 		message: tag['d:prop']['oc:message']['#text'],
 		isUnread: tag['d:prop']['oc:isUnread']['#text'] === 'true',
diff --git a/src/services/AttachmentApi.js b/src/services/AttachmentApi.js
index 117ed380df..c57d2c8b16 100644
--- a/src/services/AttachmentApi.js
+++ b/src/services/AttachmentApi.js
@@ -40,6 +40,19 @@ export class AttachmentApi {
 		return response.data.ocs.data
 	}
 
+	async shareFileToRemoteBoard({ cardId, formData, onUploadProgress, boardId }) {
+		const response = await axios({
+			method: 'POST',
+			url: this.ocsUrl(`/cards/${cardId}/share-attachment`),
+			params: {
+				boardId: boardId ?? null,
+			},
+			data: formData,
+			onUploadProgress,
+		})
+		return response.data.ocs.data
+	}
+
 	async updateAttachment({ cardId, attachment, formData, boardId }) {
 		const response = await axios({
 			method: 'POST',
diff --git a/src/services/BoardApi.js b/src/services/BoardApi.js
index b1e7e879d5..6cf3897848 100644
--- a/src/services/BoardApi.js
+++ b/src/services/BoardApi.js
@@ -29,10 +29,10 @@ export class BoardApi {
 	 * @return {Promise}
 	 */
 	updateBoard(board) {
-		return axios.put(this.url(`/boards/${board.id}`), board)
+		return axios.put(this.ocsUrl(`/boards/${board.id}`), board)
 			.then(
 				(response) => {
-					return Promise.resolve(response.data)
+					return Promise.resolve(response.data.ocs.data)
 				},
 				(err) => {
 					return Promise.reject(err)
diff --git a/src/services/CardApi.js b/src/services/CardApi.js
index 327b3dbffe..7407a0f71b 100644
--- a/src/services/CardApi.js
+++ b/src/services/CardApi.js
@@ -49,11 +49,11 @@ export class CardApi {
 			})
 	}
 
-	deleteCard(cardId) {
-		return axios.delete(this.url(`/cards/${cardId}`))
+	deleteCard(card, boardId) {
+		return axios.delete(this.ocsUrl(`/cards/${card.id}`), { params: { boardId } })
 			.then(
 				(response) => {
-					return Promise.resolve(response.data)
+					return Promise.resolve(response.data.ocs.data)
 				},
 				(err) => {
 					return Promise.reject(err)
@@ -139,11 +139,11 @@ export class CardApi {
 			})
 	}
 
-	archiveCard(card) {
-		return axios.put(this.url(`/cards/${card.id}/archive`))
+	archiveCard(card, boardId) {
+		return axios.put(this.ocsUrl(`/cards/${card.id}/archive`), { boardId })
 			.then(
 				(response) => {
-					return Promise.resolve(response.data)
+					return Promise.resolve(response.data.ocs.data)
 				},
 				(err) => {
 					return Promise.reject(err)
@@ -154,11 +154,11 @@ export class CardApi {
 			})
 	}
 
-	unArchiveCard(card) {
-		return axios.put(this.url(`/cards/${card.id}/unarchive`))
+	unArchiveCard(card, boardId) {
+		return axios.put(this.ocsUrl(`/cards/${card.id}/unarchive`), { boardId })
 			.then(
 				(response) => {
-					return Promise.resolve(response.data)
+					return Promise.resolve(response.data.ocs.data)
 				},
 				(err) => {
 					return Promise.reject(err)
@@ -169,11 +169,11 @@ export class CardApi {
 			})
 	}
 
-	markCardAsDone(card) {
-		return axios.put(this.url(`/cards/${card.id}/done`))
+	markCardAsDone(card, boardId) {
+		return axios.put(this.ocsUrl(`/cards/${card.id}/done`), { boardId })
 			.then(
 				(response) => {
-					return Promise.resolve(response.data)
+					return Promise.resolve(response.data.ocs.data)
 				},
 				(err) => {
 					return Promise.reject(err)
@@ -184,11 +184,11 @@ export class CardApi {
 			})
 	}
 
-	markCardAsUndone(card) {
-		return axios.put(this.url(`/cards/${card.id}/undone`))
+	markCardAsUndone(card, boardId) {
+		return axios.put(this.ocsUrl(`/cards/${card.id}/undone`), { boardId })
 			.then(
 				(response) => {
-					return Promise.resolve(response.data)
+					return Promise.resolve(response.data.ocs.data)
 				},
 				(err) => {
 					return Promise.reject(err)
diff --git a/src/services/CommentApi.js b/src/services/CommentApi.js
index 216d6bafec..3a4ac9f9fd 100644
--- a/src/services/CommentApi.js
+++ b/src/services/CommentApi.js
@@ -12,31 +12,35 @@ export class CommentApi {
 		return generateRemoteUrl(url)
 	}
 
-	async loadComments({ cardId, limit, offset }) {
+	async loadComments({ cardId, limit, offset, boardId }) {
 		const api = await axios.get(generateOcsUrl(`apps/deck/api/v1.0/cards/${cardId}/comments`), {
-			params: { limit, offset },
+			params: { limit, offset, boardId },
 			headers: { 'OCS-APIRequest': 'true' },
 		})
 		return api.data.ocs.data
 	}
 
-	async createComment({ cardId, comment, replyTo }) {
+	async createComment({ cardId, comment, replyTo, boardId }) {
 		const api = await axios.post(generateOcsUrl(`apps/deck/api/v1.0/cards/${cardId}/comments`), {
 			message: `${comment}`,
 			parentId: replyTo ? replyTo.id : null,
+			boardId,
 		})
 		return api.data.ocs.data
 	}
 
-	async updateComment({ cardId, id, comment }) {
+	async updateComment({ cardId, id, comment, boardId }) {
 		const api = await axios.put(generateOcsUrl(`apps/deck/api/v1.0/cards/${cardId}/comments/${id}`), {
 			message: `${comment}`,
+			boardId,
 		})
 		return api.data.ocs.data
 	}
 
-	async deleteComment({ cardId, id }) {
-		const api = await axios.delete(generateOcsUrl(`apps/deck/api/v1.0/cards/${cardId}/comments/${id}`))
+	async deleteComment({ cardId, id, boardId }) {
+		const api = await axios.delete(generateOcsUrl(`apps/deck/api/v1.0/cards/${cardId}/comments/${id}`), {
+			params: { boardId },
+		})
 		return api.data.ocs.data
 	}
 
diff --git a/src/services/StackApi.js b/src/services/StackApi.js
index 67b464d9c6..c5850009ed 100644
--- a/src/services/StackApi.js
+++ b/src/services/StackApi.js
@@ -47,10 +47,10 @@ export class StackApi {
 	}
 
 	loadArchivedStacks(boardId) {
-		return axios.get(this.url(`/stacks/${boardId}/archived`))
+		return axios.get(this.ocsUrl(`/stacks/${boardId}/archived`))
 			.then(
 				(response) => {
-					return Promise.resolve(response.data)
+					return Promise.resolve(response.data.ocs.data)
 				},
 				(err) => {
 					return Promise.reject(err)
diff --git a/src/stores/attachment.js b/src/stores/attachment.js
index 57c26152c0..a1c69be232 100644
--- a/src/stores/attachment.js
+++ b/src/stores/attachment.js
@@ -34,6 +34,17 @@ export const useAttachmentStore = defineStore('attachment', {
 			}
 			cardStore.cardIncreaseAttachmentCount(cardId)
 		},
+		async shareFileToRemoteBoard({ cardId, formData, onUploadProgress }) {
+			const cardStore = useCardStore()
+			const boardId = useBoardStore().currentBoard.id
+			const attachment = await apiClient.shareFileToRemoteBoard({ cardId, formData, onUploadProgress, boardId })
+			if (typeof this.attachments[cardId] === 'undefined') {
+				this.attachments[cardId] = [attachment]
+			} else {
+				this.attachments[cardId].push(attachment)
+			}
+			cardStore.cardIncreaseAttachmentCount(cardId)
+		},
 		async fetchAttachments(cardId) {
 			const cardStore = useCardStore()
 			const boardId = useBoardStore().currentBoard.id
diff --git a/src/stores/card.js b/src/stores/card.js
index 666b042a0e..5deed8e912 100644
--- a/src/stores/card.js
+++ b/src/stores/card.js
@@ -301,7 +301,8 @@ export const useCardStore = defineStore('card', {
 			this.deleteCardFromStore(updatedCard)
 		},
 		async deleteCard(card) {
-			await apiClient.deleteCard(card.id)
+			const stack = useStackStore().stackById(card.stackId)
+			await apiClient.deleteCard(card, stack.boardId)
 			this.deleteCardFromStore(card)
 			useTrashbinStore().moveCardToTrash(card)
 		},
@@ -329,7 +330,8 @@ export const useCardStore = defineStore('card', {
 				call = 'unArchiveCard'
 			}
 
-			const updatedCard = await apiClient[call](card)
+			const stack = useStackStore().stackById(card.stackId)
+			const updatedCard = await apiClient[call](card, stack.boardId)
 			this.updateCard(updatedCard)
 		},
 		async changeCardDoneStatus(card) {
@@ -338,7 +340,8 @@ export const useCardStore = defineStore('card', {
 				call = 'markCardAsUndone'
 			}
 
-			const updatedCard = await apiClient[call](card)
+			const stack = useStackStore().stackById(card.stackId)
+			const updatedCard = await apiClient[call](card, stack.boardId)
 			this.updateCardProperty({ property: 'done', card: updatedCard })
 
 			if (card.done !== false) {
diff --git a/src/stores/comment.js b/src/stores/comment.js
index 3ad0d3ae5a..02439ae05a 100644
--- a/src/stores/comment.js
+++ b/src/stores/comment.js
@@ -45,8 +45,8 @@ export const useCommentStore = defineStore('comment', {
 				this.comments[cardId].comments = [...this.comments[cardId].comments, ...newComments]
 			}
 		},
-		async updateComment({ cardId, comment }) {
-			const updatedComment = await apiClient.updateComment({ cardId, id: comment.id, comment: comment.message })
+		async updateComment({ cardId, comment, boardId }) {
+			const updatedComment = await apiClient.updateComment({ cardId, id: comment.id, comment: comment.message, boardId })
 			const existingIndex = this.comments[cardId].comments.findIndex((c) => c.id === updatedComment.id)
 			if (existingIndex !== -1) {
 				Object.assign(this.comments[cardId].comments[existingIndex], updatedComment)
@@ -68,11 +68,12 @@ export const useCommentStore = defineStore('comment', {
 		setReplyTo(comment) {
 			this.replyTo = comment
 		},
-		async fetchComments({ cardId, offset }) {
+		async fetchComments({ cardId, offset, boardId }) {
 			const comments = await apiClient.loadComments({
 				cardId,
 				limit: COMMENT_FETCH_LIMIT,
 				offset: offset || 0,
+				boardId,
 			})
 
 			this.addComments({ cardId, comments })
@@ -81,14 +82,14 @@ export const useCommentStore = defineStore('comment', {
 				this.endReached(cardId)
 			}
 		},
-		async fetchMore({ cardId }) {
+		async fetchMore({ cardId, boardId }) {
 			// fetch newer comments first
-			await this.fetchComments({ cardId })
-			await this.fetchComments({ cardId, offset: this.getCommentsForCard(cardId).length })
+			await this.fetchComments({ cardId, boardId })
+			await this.fetchComments({ cardId, offset: this.getCommentsForCard(cardId).length, boardId })
 		},
-		async createComment({ cardId, comment }) {
-			await apiClient.createComment({ cardId, comment, replyTo: this.replyTo })
-			await this.fetchComments({ cardId })
+		async createComment({ cardId, comment, boardId }) {
+			await apiClient.createComment({ cardId, comment, replyTo: this.replyTo, boardId })
+			await this.fetchComments({ cardId, boardId })
 		},
 	},
 })
diff --git a/tests/unit/Service/AttachmentServiceTest.php b/tests/unit/Service/AttachmentServiceTest.php
index c7c940c9bf..0c46f6eff7 100644
--- a/tests/unit/Service/AttachmentServiceTest.php
+++ b/tests/unit/Service/AttachmentServiceTest.php
@@ -37,8 +37,11 @@
 use OCA\Deck\InvalidAttachmentType;
 use OCA\Deck\NoPermissionException;
 use OCA\Deck\NotFoundException;
+use OCA\Deck\Sharing\DeckShareProvider;
 use OCA\Deck\Validators\AttachmentServiceValidator;
 use OCP\AppFramework\Http\Response;
+use OCP\BackgroundJob\IJobList;
+use OCP\Federation\ICloudIdManager;
 use OCP\IL10N;
 use OCP\IUserManager;
 use PHPUnit\Framework\MockObject\MockObject;
@@ -99,6 +102,18 @@ class AttachmentServiceTest extends TestCase {
 	 * @var AttachmentServiceValidator
 	 */
 	private $attachmentServiceValidator;
+	/**
+	 * @var DeckShareProvider
+	 */
+	private $deckShareProvider;
+	/**
+	 * @var ICloudIdManager|MockObject
+	 */
+	private $cloudIdManager;
+	/**
+	 * @var IJobList|MockObject
+	 */
+	private $jobList;
 
 	public function setUp(): void {
 		parent::setUp();
@@ -117,6 +132,9 @@ public function setUp(): void {
 		$this->application = $this->createMock(Application::class);
 		$this->attachmentCacheHelper = $this->createMock(AttachmentCacheHelper::class);
 		$this->activityManager = $this->createMock(ActivityManager::class);
+		$this->deckShareProvider = $this->createMock(DeckShareProvider::class);
+		$this->cloudIdManager = $this->createMock(ICloudIdManager::class);
+		$this->jobList = $this->createMock(IJobList::class);
 
 		$this->appContainer->expects($this->exactly(2))
 			->method('get')
@@ -145,7 +163,10 @@ public function setUp(): void {
 			$this->userId,
 			$this->l10n,
 			$this->activityManager,
-			$this->attachmentServiceValidator
+			$this->attachmentServiceValidator,
+			$this->deckShareProvider,
+			$this->cloudIdManager,
+			$this->jobList,
 		);
 	}
 
@@ -171,7 +192,23 @@ public function testRegisterAttachmentService() {
 		$application->expects($this->any())
 			->method('getContainer')
 			->willReturn($appContainer);
-		$attachmentService = new AttachmentService($this->configService, $this->attachmentMapper, $this->cardMapper, $this->userManager, $this->changeHelper, $this->permissionService, $application, $this->attachmentCacheHelper, $this->userId, $this->l10n, $this->activityManager, $this->attachmentServiceValidator);
+		$attachmentService = new AttachmentService(
+			$this->configService,
+			$this->attachmentMapper,
+			$this->cardMapper,
+			$this->userManager,
+			$this->changeHelper,
+			$this->permissionService,
+			$application,
+			$this->attachmentCacheHelper,
+			$this->userId,
+			$this->l10n,
+			$this->activityManager,
+			$this->attachmentServiceValidator,
+			$this->deckShareProvider,
+			$this->cloudIdManager,
+			$this->jobList,
+		);
 		$attachmentService->registerAttachmentService('custom', MyAttachmentService::class);
 		$this->assertEquals($fileServiceMock, $attachmentService->getService('deck_file'));
 		$this->assertEquals(MyAttachmentService::class, get_class($attachmentService->getService('custom')));
@@ -196,7 +233,23 @@ public function testRegisterAttachmentServiceNotExisting() {
 			->method('getContainer')
 			->willReturn($appContainer);
 
-		$attachmentService = new AttachmentService($this->configService, $this->attachmentMapper, $this->cardMapper, $this->userManager, $this->changeHelper, $this->permissionService, $application, $this->attachmentCacheHelper, $this->userId, $this->l10n, $this->activityManager, $this->attachmentServiceValidator);
+		$attachmentService = new AttachmentService(
+			$this->configService,
+			$this->attachmentMapper,
+			$this->cardMapper,
+			$this->userManager,
+			$this->changeHelper,
+			$this->permissionService,
+			$application,
+			$this->attachmentCacheHelper,
+			$this->userId,
+			$this->l10n,
+			$this->activityManager,
+			$this->attachmentServiceValidator,
+			$this->deckShareProvider,
+			$this->cloudIdManager,
+			$this->jobList,
+		);
 		$attachmentService->registerAttachmentService('custom', MyAttachmentService::class);
 		$attachmentService->getService('deck_file_invalid');
 	}
diff --git a/tests/unit/Service/BatchQueryPerformanceTest.php b/tests/unit/Service/BatchQueryPerformanceTest.php
index 76873614f8..00a72d2d60 100644
--- a/tests/unit/Service/BatchQueryPerformanceTest.php
+++ b/tests/unit/Service/BatchQueryPerformanceTest.php
@@ -37,11 +37,14 @@
 use OCA\Deck\Db\Stack;
 use OCA\Deck\Db\StackMapper;
 use OCA\Deck\Notification\NotificationHelper;
+use OCA\Deck\Sharing\DeckShareProvider;
 use OCA\Deck\Validators\AttachmentServiceValidator;
 use OCA\Deck\Validators\CardServiceValidator;
+use OCP\BackgroundJob\IJobList;
 use OCP\Collaboration\Reference\IReferenceManager;
 use OCP\Comments\ICommentsManager;
 use OCP\EventDispatcher\IEventDispatcher;
+use OCP\Federation\ICloudIdManager;
 use OCP\IDBConnection;
 use OCP\IL10N;
 use OCP\IRequest;
@@ -345,6 +348,9 @@ private function setUpAttachmentService(): void {
 			$this->createMock(IL10N::class),
 			$this->createMock(ActivityManager::class),
 			$this->createMock(AttachmentServiceValidator::class),
+			$this->createMock(DeckShareProvider::class),
+			$this->createMock(ICloudIdManager::class),
+			$this->createMock(IJobList::class),
 		);
 	}
 
diff --git a/tests/unit/Service/FilesAppServiceTest.php b/tests/unit/Service/FilesAppServiceTest.php
index 765c737c3c..071ab22d36 100644
--- a/tests/unit/Service/FilesAppServiceTest.php
+++ b/tests/unit/Service/FilesAppServiceTest.php
@@ -54,6 +54,7 @@ public function setUp(): void {
 			$this->createMock(\Psr\Log\LoggerInterface::class),
 			$this->createMock(\OCP\IDBConnection::class),
 			$this->filenameValidator,
+			$this->createMock(\OCP\Federation\ICloudIdManager::class),
 			'admin'
 		);
 	}