diff --git a/lib/Controller/AttachmentController.php b/lib/Controller/AttachmentController.php
index 28898655d88..68d2f50a38f 100644
--- a/lib/Controller/AttachmentController.php
+++ b/lib/Controller/AttachmentController.php
@@ -161,13 +161,17 @@ private function getUploadedFile(string $key): array {
 
 	/**
 	 * Serve the image files in the editor
+	 *
+	 * @return DataDownloadResponse|DataResponse
+	 *
+	 * @psalm-return DataDownloadResponse<200, string, array<never, never>>|DataResponse<404, '', array<never, never>>
 	 */
 	#[NoAdminRequired]
 	#[PublicPage]
 	#[NoCSRFRequired]
 	#[RequireDocumentSession]
 	public function getImageFile(string $imageFileName, ?string $shareToken = null,
-		int $preferRawImage = 0) {
+		int $preferRawImage = 0): DataResponse|DataDownloadResponse {
 		$documentId = $this->getSession()->getDocumentId();
 
 		try {
@@ -192,12 +196,16 @@ public function getImageFile(string $imageFileName, ?string $shareToken = null,
 
 	/**
 	 * Serve the media files in the editor
+	 *
+	 * @return DataDownloadResponse|DataResponse
+	 *
+	 * @psalm-return DataDownloadResponse<200, string, array<never, never>>|DataResponse<404, '', array<never, never>>
 	 */
 	#[NoAdminRequired]
 	#[PublicPage]
 	#[NoCSRFRequired]
 	#[RequireDocumentSession]
-	public function getMediaFile(string $mediaFileName, ?string $shareToken = null) {
+	public function getMediaFile(string $mediaFileName, ?string $shareToken = null): DataResponse|DataDownloadResponse {
 		$documentId = $this->getSession()->getDocumentId();
 
 		try {
diff --git a/lib/Controller/PublicSessionController.php b/lib/Controller/PublicSessionController.php
index a18735e1cce..a1cc09a07cd 100644
--- a/lib/Controller/PublicSessionController.php
+++ b/lib/Controller/PublicSessionController.php
@@ -40,7 +40,7 @@
 class PublicSessionController extends PublicShareController implements ISessionAwareController {
 	use TSessionAwareController;
 
-	private IShare $share;
+	private ?IShare $share = null;
 
 	public function __construct(
 		string $appName,
@@ -52,8 +52,16 @@ public function __construct(
 		parent::__construct($appName, $request, $session);
 	}
 
+	private function getShare(): IShare {
+		if ($this->share === null) {
+			throw new \Exception('Share has not been set yet');
+		}
+
+		return $this->share;
+	}
+
 	protected function getPasswordHash(): string {
-		return $this->share->getPassword();
+		return $this->getShare()->getPassword();
 	}
 
 	public function isValidToken(): bool {
@@ -66,12 +74,13 @@ public function isValidToken(): bool {
 	}
 
 	protected function isPasswordProtected(): bool {
-		return $this->share->getPassword() !== null;
+		/** @psalm-suppress RedundantConditionGivenDocblockType */
+		return $this->getShare()->getPassword() !== null;
 	}
 
 	#[NoAdminRequired]
 	#[PublicPage]
-	public function create(string $token, string $file = null, $guestName = null): DataResponse {
+	public function create(string $token, string $file = null, ?string $guestName = null): DataResponse {
 		return $this->apiService->create(null, $file, $token, $guestName);
 	}
 
@@ -95,10 +104,13 @@ public function sync(string $token, int $documentId, int $sessionId, string $ses
 		return $this->apiService->sync($this->getSession(), $this->getDocument(), $version, $autosaveContent, $documentState, $force, $manualSave, $token);
 	}
 
+	/**
+	 * @psalm-return DataResponse<int, array|null|object|scalar, array<string, mixed>>
+	 */
 	#[NoAdminRequired]
 	#[PublicPage]
 	#[RequireDocumentSession]
-	public function updateSession(string $guestName) {
+	public function updateSession(string $guestName): DataResponse {
 		return $this->apiService->updateSession($this->getSession(), $guestName);
 	}
 }
diff --git a/lib/Controller/SessionController.php b/lib/Controller/SessionController.php
index 66622e4a685..88fcd21754a 100644
--- a/lib/Controller/SessionController.php
+++ b/lib/Controller/SessionController.php
@@ -103,7 +103,7 @@ public function mention(string $mention): DataResponse {
 		return new DataResponse($this->notificationService->mention($this->getDocument()->getId(), $mention));
 	}
 
-	private function loginSessionUser() {
+	private function loginSessionUser(): void {
 		$currentSession = $this->getSession();
 		if (!$this->userSession->isLoggedIn()) {
 			$user = $this->userManager->get($currentSession->getUserId());
diff --git a/lib/Controller/SettingsController.php b/lib/Controller/SettingsController.php
index a901bc611e9..b1214cb5d59 100644
--- a/lib/Controller/SettingsController.php
+++ b/lib/Controller/SettingsController.php
@@ -32,25 +32,21 @@
 use OCP\IRequest;
 
 class SettingsController extends Controller {
-	private IConfig $config;
-	private ?string $userId;
-
 	public const ACCEPTED_KEYS = [
 		'workspace_enabled'
 	];
 
-	public function __construct($appName, IRequest $request, IConfig $config, $userId) {
+	public function __construct(string $appName, IRequest $request, private IConfig $config, private ?string $userId) {
 		parent::__construct($appName, $request);
-
-		$this->config = $config;
-		$this->userId = $userId;
 	}
 
 	/**
 	 * @throws \OCP\PreConditionNotMetException
+	 *
+	 * @psalm-return DataResponse<200|400, array{workspace_enabled?: mixed, message?: 'Invalid config key'}, array<never, never>>
 	 */
 	#[NoAdminRequired]
-	public function updateConfig(string $key, $value) {
+	public function updateConfig(string $key, string $value): DataResponse {
 		if (!in_array($key, self::ACCEPTED_KEYS, true)) {
 			return new DataResponse(['message' => 'Invalid config key'], Http::STATUS_BAD_REQUEST);
 		}
diff --git a/lib/Controller/WorkspaceController.php b/lib/Controller/WorkspaceController.php
index dd76762e639..b55d8613597 100644
--- a/lib/Controller/WorkspaceController.php
+++ b/lib/Controller/WorkspaceController.php
@@ -145,6 +145,7 @@ public function publicFolder(string $shareToken, string $path = '/'): DataRespon
 			if (!($share->getPermissions() & Constants::PERMISSION_READ)) {
 				throw new ShareNotFound();
 			}
+			/** @psalm-suppress RedundantConditionGivenDocblockType */
 			if ($share->getPassword() !== null) {
 				$shareId = $this->session->get('public_link_authenticated');
 				if ($share->getId() !== $shareId) {
diff --git a/lib/Cron/Cleanup.php b/lib/Cron/Cleanup.php
index 0ee0776f5b9..19933cfc17c 100644
--- a/lib/Cron/Cleanup.php
+++ b/lib/Cron/Cleanup.php
@@ -54,6 +54,10 @@ public function __construct(ITimeFactory $time,
 		$this->setInterval(SessionService::SESSION_VALID_TIME);
 	}
 
+	/**
+	 * @param array $argument
+	 * @return void
+	 */
 	protected function run($argument) {
 		$this->logger->debug('Run cleanup job for text documents');
 		$documents = $this->documentService->getAll();
diff --git a/lib/Db/Document.php b/lib/Db/Document.php
index bf3d0430ec5..69f89fabe59 100644
--- a/lib/Db/Document.php
+++ b/lib/Db/Document.php
@@ -41,7 +41,7 @@
  * @method setBaseVersionEtag(string $etag): void
  */
 class Document extends Entity implements \JsonSerializable {
-	public $id;
+	public $id = null;
 	// TODO: Remove obsolete field `currentVersion`
 	protected int $currentVersion = 0;
 	protected int $lastSavedVersion = 0;
diff --git a/lib/Db/DocumentMapper.php b/lib/Db/DocumentMapper.php
index ec30cf37016..13b878b7de2 100644
--- a/lib/Db/DocumentMapper.php
+++ b/lib/Db/DocumentMapper.php
@@ -39,7 +39,7 @@ public function __construct(IDBConnection $db) {
 	 * @return Document
 	 * @throws DoesNotExistException
 	 */
-	public function find($documentId): Document {
+	public function find(int $documentId): Document {
 		/* @var $qb IQueryBuilder */
 		$qb = $this->db->getQueryBuilder();
 		$result = $qb->select('*')
diff --git a/lib/Db/SessionMapper.php b/lib/Db/SessionMapper.php
index 03ca252f65a..8465d1bf5d6 100644
--- a/lib/Db/SessionMapper.php
+++ b/lib/Db/SessionMapper.php
@@ -53,7 +53,7 @@ public function findAllDocuments(): array {
 	 * @return Session
 	 * @throws DoesNotExistException
 	 */
-	public function find($documentId, $sessionId, $token): Session {
+	public function find(int $documentId, int $sessionId, string $token): Session {
 		/* @var $qb IQueryBuilder */
 		$qb = $this->db->getQueryBuilder();
 		$result = $qb->select('*')
@@ -71,7 +71,12 @@ public function find($documentId, $sessionId, $token): Session {
 		return Session::fromRow($data);
 	}
 
-	public function findAll($documentId) {
+	/**
+	 * @return Session[]
+	 *
+	 * @psalm-return array<Session>
+	 */
+	public function findAll(int $documentId): array {
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('id', 'color', 'document_id', 'last_awareness_message', 'last_contact', 'user_id', 'guest_name')
 			->from($this->getTableName())
@@ -80,7 +85,12 @@ public function findAll($documentId) {
 		return $this->findEntities($qb);
 	}
 
-	public function findAllActive($documentId) {
+	/**
+	 * @return Session[]
+	 *
+	 * @psalm-return array<Session>
+	 */
+	public function findAllActive(int $documentId): array {
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('id', 'color', 'document_id', 'last_awareness_message', 'last_contact', 'user_id', 'guest_name')
 			->from($this->getTableName())
@@ -90,7 +100,12 @@ public function findAllActive($documentId) {
 		return $this->findEntities($qb);
 	}
 
-	public function findAllInactive() {
+	/**
+	 * @return Session[]
+	 *
+	 * @psalm-return array<Session>
+	 */
+	public function findAllInactive(): array {
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('id', 'color', 'document_id', 'last_awareness_message', 'last_contact', 'user_id', 'guest_name')
 			->from($this->getTableName())
@@ -132,14 +147,14 @@ public function deleteInactiveWithoutSteps(?int $documentId = null): int {
 		return $deletedCount;
 	}
 
-	public function deleteByDocumentId($documentId): int {
+	public function deleteByDocumentId(int $documentId): int {
 		$qb = $this->db->getQueryBuilder();
 		$qb->delete($this->getTableName())
 			->where($qb->expr()->eq('document_id', $qb->createNamedParameter($documentId)));
 		return $qb->executeStatement();
 	}
 
-	public function isUserInDocument($documentId, $userId): bool {
+	public function isUserInDocument(int $documentId, string $userId): bool {
 		$qb = $this->db->getQueryBuilder();
 		$result = $qb->select('*')
 			->from($this->getTableName())
diff --git a/lib/Db/Step.php b/lib/Db/Step.php
index 92ae39d2d08..b2c1ff1aa63 100644
--- a/lib/Db/Step.php
+++ b/lib/Db/Step.php
@@ -37,6 +37,7 @@
  * @method setDocumentId(int $documentId): void
  */
 class Step extends Entity implements JsonSerializable {
+	public $id = null;
 	protected string $data = '';
 	protected int $version = 0;
 	protected int $sessionId = 0;
@@ -55,10 +56,10 @@ public function jsonSerialize(): array {
 			throw new \InvalidArgumentException('Failed to parse step data');
 		}
 		return [
-			'id' => $this->id,
+			'id' => $this->getId(),
 			'data' => $jsonData,
-			'version' => $this->version,
-			'sessionId' => $this->sessionId
+			'version' => $this->getVersion(),
+			'sessionId' => $this->getSessionId()
 		];
 	}
 }
diff --git a/lib/Db/StepMapper.php b/lib/Db/StepMapper.php
index ae4c7d9c88d..11b7d59f894 100644
--- a/lib/Db/StepMapper.php
+++ b/lib/Db/StepMapper.php
@@ -33,7 +33,10 @@ public function __construct(IDBConnection $db) {
 		parent::__construct($db, 'text_steps', Step::class);
 	}
 
-	public function find($documentId, $fromVersion, $lastAckedVersion = null) {
+	/**
+	 * @return Step[]
+	 */
+	public function find(int $documentId, int $fromVersion, int $lastAckedVersion = null): array {
 		/* @var $qb IQueryBuilder */
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('*')
@@ -51,7 +54,7 @@ public function find($documentId, $fromVersion, $lastAckedVersion = null) {
 		return $this->findEntities($qb);
 	}
 
-	public function getLatestVersion($documentId): ?int {
+	public function getLatestVersion(int $documentId): ?int {
 		/* @var $qb IQueryBuilder */
 		$qb = $this->db->getQueryBuilder();
 		$result = $qb->select('version')
@@ -69,22 +72,22 @@ public function getLatestVersion($documentId): ?int {
 		return $data['version'];
 	}
 
-	public function deleteAll($documentId): void {
+	public function deleteAll(int $documentId): void {
 		$qb = $this->db->getQueryBuilder();
 		$qb->delete($this->getTableName())
 			->where($qb->expr()->eq('document_id', $qb->createNamedParameter($documentId)))
 			->executeStatement();
 	}
 
-	public function deleteBeforeVersion($documentId, $version): void {
+	public function deleteBeforeVersion(int $documentId, int $version): int {
 		$qb = $this->db->getQueryBuilder();
-		$qb->delete($this->getTableName())
+		return $qb->delete($this->getTableName())
 			->where($qb->expr()->eq('document_id', $qb->createNamedParameter($documentId)))
 			->andWhere($qb->expr()->lte('version', $qb->createNamedParameter($version)))
 			->executeStatement();
 	}
 
-	public function deleteAfterVersion($documentId, $version): int {
+	public function deleteAfterVersion(int $documentId, int $version): int {
 		$qb = $this->db->getQueryBuilder();
 		return $qb->delete($this->getTableName())
 			->where($qb->expr()->eq('document_id', $qb->createNamedParameter($documentId)))
diff --git a/lib/Migration/Version010000Date20190617184535.php b/lib/Migration/Version010000Date20190617184535.php
index eb1e5dd1705..ee52e9d02fe 100644
--- a/lib/Migration/Version010000Date20190617184535.php
+++ b/lib/Migration/Version010000Date20190617184535.php
@@ -19,6 +19,8 @@ class Version010000Date20190617184535 extends SimpleMigrationStep {
 	 * @param IOutput $output
 	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
 	 * @param array $options
+	 *
+	 * @return void
 	 */
 	public function preSchemaChange(IOutput $output, Closure $schemaClosure, array $options) {
 	}
@@ -139,6 +141,8 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 	 * @param IOutput $output
 	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
 	 * @param array $options
+	 *
+	 * @return void
 	 */
 	public function postSchemaChange(IOutput $output, Closure $schemaClosure, array $options) {
 	}
diff --git a/lib/Service/ApiService.php b/lib/Service/ApiService.php
index c7cecb5420e..609f848b7cf 100644
--- a/lib/Service/ApiService.php
+++ b/lib/Service/ApiService.php
@@ -69,7 +69,7 @@ public function __construct(IRequest $request,
 		$this->l10n = $l10n;
 	}
 
-	public function create($fileId = null, $filePath = null, ?string $token = null, $guestName = null): DataResponse {
+	public function create(?int $fileId = null, ?string $filePath = null, ?string $token = null, ?string $guestName = null): DataResponse {
 		try {
 			if ($token) {
 				$file = $this->documentService->getFileByShareToken($token, $this->request->getParam('filePath'));
@@ -170,7 +170,7 @@ public function create($fileId = null, $filePath = null, ?string $token = null,
 		]);
 	}
 
-	public function close($documentId, $sessionId, $sessionToken): DataResponse {
+	public function close(int $documentId, int $sessionId, string $sessionToken): DataResponse {
 		$this->sessionService->closeSession($documentId, $sessionId, $sessionToken);
 		$this->sessionService->removeInactiveSessionsWithoutSteps($documentId);
 		$activeSessions = $this->sessionService->getActiveSessions($documentId);
@@ -183,8 +183,10 @@ public function close($documentId, $sessionId, $sessionToken): DataResponse {
 	/**
 	 * @throws NotFoundException
 	 * @throws DoesNotExistException
+	 *
+	 * @param null|string $token
 	 */
-	public function push(Session $session, Document $document, $version, $steps, $awareness, $token = null): DataResponse {
+	public function push(Session $session, Document $document, int $version, array $steps, string $awareness, string|null $token = null): DataResponse {
 		try {
 			$session = $this->sessionService->updateSessionAwareness($session, $awareness);
 		} catch (DoesNotExistException $e) {
@@ -209,7 +211,12 @@ public function push(Session $session, Document $document, $version, $steps, $aw
 		return new DataResponse($result);
 	}
 
-	public function sync(Session $session, Document $document, $version = 0, $autosaveContent = null, $documentState = null, bool $force = false, bool $manualSave = false, $token = null): DataResponse {
+	/**
+	 * @param null|string $autosaveContent
+	 * @param null|string $documentState
+	 * @param null|string $token
+	 */
+	public function sync(Session $session, Document $document, int $version = 0, string|null $autosaveContent = null, string|null $documentState = null, bool $force = false, bool $manualSave = false, string|null $token = null): DataResponse {
 		$documentId = $session->getDocumentId();
 		try {
 			$result = [
diff --git a/lib/Service/AttachmentService.php b/lib/Service/AttachmentService.php
index eccae278aea..459e9981cfe 100644
--- a/lib/Service/AttachmentService.php
+++ b/lib/Service/AttachmentService.php
@@ -272,7 +272,10 @@ private function getMediaFileMetadata(string $mediaFileName, File $textFile): ?a
 	 * @param string $newFileName
 	 * @param string $newFileContent
 	 * @param string $userId
+	 * @param resource $newFileResource
+	 *
 	 * @return array
+	 *
 	 * @throws NotFoundException
 	 * @throws NotPermittedException
 	 * @throws \OCP\Files\InvalidPathException
@@ -301,7 +304,10 @@ public function uploadAttachment(int $documentId, string $newFileName, $newFileR
 	 * @param string $newFileName
 	 * @param string $newFileContent
 	 * @param string $shareToken
+	 * @param resource $newFileResource
+	 *
 	 * @return array
+	 *
 	 * @throws NotFoundException
 	 * @throws NotPermittedException
 	 * @throws \OCP\Files\InvalidPathException
diff --git a/lib/Service/DocumentService.php b/lib/Service/DocumentService.php
index ae475628ece..ce6de82c132 100644
--- a/lib/Service/DocumentService.php
+++ b/lib/Service/DocumentService.php
@@ -86,7 +86,7 @@ class DocumentService {
 	private ILockManager $lockManager;
 	private IUserMountCache $userMountCache;
 
-	public function __construct(DocumentMapper $documentMapper, StepMapper $stepMapper, SessionMapper $sessionMapper, IAppData $appData, $userId, IRootFolder $rootFolder, ICacheFactory $cacheFactory, LoggerInterface $logger, ShareManager $shareManager, IRequest $request, IManager $directManager, ILockingProvider $lockingProvider, ILockManager $lockManager, IUserMountCache $userMountCache) {
+	public function __construct(DocumentMapper $documentMapper, StepMapper $stepMapper, SessionMapper $sessionMapper, IAppData $appData, ?string $userId, IRootFolder $rootFolder, ICacheFactory $cacheFactory, LoggerInterface $logger, ShareManager $shareManager, IRequest $request, IManager $directManager, ILockingProvider $lockingProvider, ILockManager $lockManager, IUserMountCache $userMountCache) {
 		$this->documentMapper = $documentMapper;
 		$this->stepMapper = $stepMapper;
 		$this->sessionMapper = $sessionMapper;
@@ -206,15 +206,10 @@ public function writeDocumentState(int $documentId, string $content): void {
 	}
 
 	/**
-	 * @param $documentId
-	 * @param $sessionId
-	 * @param $steps
-	 * @param $version
-	 * @return array
 	 * @throws DoesNotExistException
 	 * @throws InvalidArgumentException
 	 */
-	public function addStep(Document $document, Session $session, $steps, $version): array {
+	public function addStep(Document $document, Session $session, array $steps, int $version): array {
 		$sessionId = $session->getId();
 		$documentId = $session->getDocumentId();
 		$stepsToInsert = [];
@@ -255,17 +250,18 @@ public function addStep(Document $document, Session $session, $steps, $version):
 	 * @param $sessionId
 	 * @param $steps
 	 * @param $version
+	 *
 	 * @return int
+	 *
 	 * @throws DoesNotExistException
 	 * @throws InvalidArgumentException
+	 *
+	 * @psalm-param non-empty-list<mixed> $steps
 	 */
-	private function insertSteps(Document $document, Session $session, $steps, $version): int {
+	private function insertSteps(Document $document, Session $session, array $steps, ?int $version): int {
 		$stepsVersion = null;
 		try {
-			$stepsJson = json_encode($steps);
-			if (!is_array($steps) || $stepsJson === null) {
-				throw new InvalidArgumentException('Failed to encode steps');
-			}
+			$stepsJson = json_encode($steps, JSON_THROW_ON_ERROR);
 			$stepsVersion = $this->stepMapper->getLatestVersion($document->getId());
 			$newVersion = $stepsVersion + count($steps);
 			$this->logger->debug("Adding steps to " . $document->getId() . ": bumping version from $stepsVersion to $newVersion");
@@ -288,7 +284,7 @@ private function insertSteps(Document $document, Session $session, $steps, $vers
 		}
 	}
 
-	public function getSteps($documentId, $lastVersion): array {
+	public function getSteps(int $documentId, int $lastVersion): array {
 		if ($lastVersion === $this->cache->get('document-version-' . $documentId)) {
 			return [];
 		}
@@ -422,7 +418,7 @@ public function resetDocument(int $documentId, bool $force = false): void {
 		}
 	}
 
-	public function getAll() {
+	public function getAll(): array {
 		return $this->documentMapper->findAll();
 	}
 
@@ -519,7 +515,7 @@ public function getFileByShareToken(string $shareToken, ?string $path = null): F
 	}
 
 
-	public function isReadOnly($file, $token) {
+	public function isReadOnly(File $file, string|null $token): bool {
 		$readOnly = true;
 		if ($token) {
 			try {
@@ -543,7 +539,7 @@ public function isReadOnly($file, $token) {
 		return $readOnly || $lockInfo !== null;
 	}
 
-	public function getLockInfo($file): ?ILock {
+	public function getLockInfo(File $file): ?ILock {
 		try {
 			$locks = $this->lockManager->getLocks($file->getId());
 		} catch (NoLockProviderException|PreConditionNotMetException $e) {
@@ -554,10 +550,14 @@ public function getLockInfo($file): ?ILock {
 
 	/**
 	 * @param $shareToken
+	 *
 	 * @return void
+	 *
 	 * @throws NotFoundException|NotPermittedException
+	 *
+	 * @psalm-param 1|2 $permission
 	 */
-	public function checkSharePermissions(string $shareToken, $permission = Constants::PERMISSION_READ): void {
+	public function checkSharePermissions(string $shareToken, int $permission = Constants::PERMISSION_READ): void {
 		try {
 			$share = $this->shareManager->getShareByToken($shareToken);
 		} catch (ShareNotFound $e) {
@@ -569,7 +569,7 @@ public function checkSharePermissions(string $shareToken, $permission = Constant
 		}
 	}
 
-	public function hasUnsavedChanges(Document $document) {
+	public function hasUnsavedChanges(Document $document): bool {
 		$stepsVersion = $this->stepMapper->getLatestVersion($document->getId()) ?: 0;
 		$docVersion = $document->getLastSavedVersion();
 		return $stepsVersion !== $docVersion;
diff --git a/lib/Service/SessionService.php b/lib/Service/SessionService.php
index 480677b7357..569991b2c7e 100644
--- a/lib/Service/SessionService.php
+++ b/lib/Service/SessionService.php
@@ -60,7 +60,7 @@ public function __construct(
 		IAvatarManager $avatarManager,
 		IRequest $request,
 		IManager $directManager,
-		$userId,
+		?string $userId,
 		ICacheFactory $cacheFactory
 	) {
 		$this->sessionMapper = $sessionMapper;
@@ -84,7 +84,7 @@ public function __construct(
 		$this->cache = $cacheFactory->createDistributed('text_sessions');
 	}
 
-	public function initSession($documentId, $guestName = null): Session {
+	public function initSession(int $documentId, string $guestName = null): Session {
 		$session = new Session();
 		$session->setDocumentId($documentId);
 		$userName = $this->userId ? $this->userId : $guestName;
@@ -92,7 +92,7 @@ public function initSession($documentId, $guestName = null): Session {
 		$session->setToken($this->secureRandom->generate(64));
 		$session->setColor($this->getColorForGuestName($guestName));
 		if ($this->userId === null) {
-			$session->setGuestName($guestName);
+			$session->setGuestName($guestName ?? '');
 		}
 		$session->setLastContact($this->timeFactory->now()->getTimestamp());
 
@@ -141,11 +141,12 @@ public function getNameForSession(Session $session): ?string {
 		return $session->getGuestName();
 	}
 
-	public function findAllInactive() {
+	/** @return Session[] */
+	public function findAllInactive(): array {
 		return $this->sessionMapper->findAllInactive();
 	}
 
-	public function removeInactiveSessionsWithoutSteps(?int $documentId = null) {
+	public function removeInactiveSessionsWithoutSteps(?int $documentId = null): int {
 		// No need to clear the cache here as we already set a TTL
 		return $this->sessionMapper->deleteInactiveWithoutSteps($documentId);
 	}
@@ -205,16 +206,7 @@ public function getValidSession(int $documentId, int $sessionId, string $token):
 		return $session;
 	}
 
-	public function isValidSession($documentId, $sessionId, $token): bool {
-		return $this->getValidSession($documentId, $sessionId, $token) !== null;
-	}
-
 	/**
-	 * @param $documentId
-	 * @param $sessionId
-	 * @param $sessionToken
-	 * @param $guestName
-	 * @return Session
 	 * @throws DoesNotExistException
 	 */
 	public function updateSession(Session $session, string $guestName): Session {
@@ -227,11 +219,6 @@ public function updateSession(Session $session, string $guestName): Session {
 	}
 
 	/**
-	 * @param $documentId
-	 * @param $sessionId
-	 * @param $sessionToken
-	 * @param $message
-	 * @return Session
 	 * @throws DoesNotExistException
 	 */
 	public function updateSessionAwareness(Session $session, string $message): Session {
diff --git a/psalm.xml b/psalm.xml
index ff84f35c427..62b01cf6352 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <psalm
-    errorLevel="3"
+    errorLevel="2"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
     xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"