diff --git a/.github/workflows/psalm.yml b/.github/workflows/psalm.yml
new file mode 100644
index 0000000..5011311
--- /dev/null
+++ b/.github/workflows/psalm.yml
@@ -0,0 +1,49 @@
+# This workflow is provided via the organization template repository
+#
+# https://github.com/nextcloud/.github
+# https://docs.github.com/en/actions/learn-github-actions/sharing-workflows-with-your-organization
+#
+# SPDX-FileCopyrightText: 2022-2024 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: MIT
+
+name: Static analysis
+
+on: pull_request
+
+concurrency:
+  group: psalm-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  static-analysis:
+    runs-on: ubuntu-latest
+
+    name: static-psalm-analysis
+    steps:
+      - name: Checkout
+        uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
+
+      - name: Get php version
+        id: versions
+        uses: icewind1991/nextcloud-version-matrix@58becf3b4bb6dc6cef677b15e2fd8e7d48c0908f # v1.3.1
+
+      - name: Set up php${{ steps.versions.outputs.php-available }}
+        uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2.31.1
+        with:
+          php-version: ${{ steps.versions.outputs.php-available }}
+          extensions: bz2, ctype, curl, dom, fileinfo, gd, iconv, intl, json, libxml, mbstring, openssl, pcntl, posix, session, simplexml, xmlreader, xmlwriter, zip, zlib, sqlite, pdo_sqlite
+          coverage: none
+          ini-file: development
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Install dependencies
+        run: |
+          composer remove nextcloud/ocp --dev
+          composer i
+
+      - name: Install nextcloud/ocp
+        run: composer require --dev nextcloud/ocp:dev-${{ steps.versions.outputs.branches-max }} --ignore-platform-reqs --with-dependencies
+
+      - name: Run coding standards check
+        run: composer run psalm
diff --git a/composer.json b/composer.json
index 28148c2..6802fe1 100644
--- a/composer.json
+++ b/composer.json
@@ -22,6 +22,10 @@
 		"cs:fix": "php-cs-fixer fix",
 		"lint": "find . -name \\*.php -not -path './vendor/*' -not -path './build/*' -print0 | xargs -0 -n1 php -l",
 		"test:unit": "phpunit -c phpunit.xml --fail-on-warning  --fail-on-risky --color",
+		"psalm": "./vendor/bin/psalm.phar --show-info=false --no-cache",
+                "psalm:update-baseline": "./vendor/bin/psalm.phar --update-baseline",
+                "psalm:fix": "./vendor/bin/psalm.phar --no-cache --alter --issues=InvalidReturnType,InvalidNullableReturnType,MismatchingDocblockParamType,MismatchingDocblockReturnType,MissingParamType,InvalidFalsableReturnType",
+                "psalm:fix:dry": "./vendor/bin/psalm.phar --no-cache --alter --issues=InvalidReturnType,InvalidNullableReturnType,MismatchingDocblockParamType,MismatchingDocblockReturnType,MissingParamType,InvalidFalsableReturnType --dry-run",
 		"post-install-cmd": [
 			"@composer bin all install --ignore-platform-reqs # unfortunately the flag is required for 8.0",
 			"vendor/bin/php-scoper add-prefix --force # Scope our dependencies",
@@ -41,6 +45,8 @@
 	},
 	"require-dev": {
 		"phpunit/phpunit": "^9.5",
-		"nextcloud/coding-standard": "^1.0"
+		"nextcloud/coding-standard": "^1.0",
+		"psalm/phar": "^5.26",
+		"nextcloud/ocp": "dev-master"
 	}
 }
diff --git a/composer.lock b/composer.lock
index 76e6ca2..9b94435 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "5634452d94bc38893b6cda6a113cd5d1",
+    "content-hash": "67ede0e2200d678cc39965c1ea587455",
     "packages": [
         {
             "name": "bamarni/composer-bin-plugin",
@@ -354,6 +354,51 @@
             },
             "time": "2023-06-01T12:05:01+00:00"
         },
+        {
+            "name": "nextcloud/ocp",
+            "version": "dev-master",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/nextcloud-deps/ocp.git",
+                "reference": "6b2abc6f31dbfb3d21ee1d19453dc687fd46ae0d"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/nextcloud-deps/ocp/zipball/6b2abc6f31dbfb3d21ee1d19453dc687fd46ae0d",
+                "reference": "6b2abc6f31dbfb3d21ee1d19453dc687fd46ae0d",
+                "shasum": ""
+            },
+            "require": {
+                "php": "~8.0 || ~8.1 || ~8.2 || ~8.3",
+                "psr/clock": "^1.0",
+                "psr/container": "^2.0.2",
+                "psr/event-dispatcher": "^1.0",
+                "psr/log": "^3.0.2"
+            },
+            "default-branch": true,
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "31.0.0-dev"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "AGPL-3.0-or-later"
+            ],
+            "authors": [
+                {
+                    "name": "Christoph Wurst",
+                    "email": "christoph@winzerhof-wurst.at"
+                }
+            ],
+            "description": "Composer package containing Nextcloud's public API (classes, interfaces)",
+            "support": {
+                "issues": "https://github.com/nextcloud-deps/ocp/issues",
+                "source": "https://github.com/nextcloud-deps/ocp/tree/master"
+            },
+            "time": "2024-10-16T00:43:10+00:00"
+        },
         {
             "name": "nikic/php-parser",
             "version": "v5.0.0",
@@ -997,6 +1042,242 @@
             ],
             "time": "2023-12-01T16:55:19+00:00"
         },
+        {
+            "name": "psalm/phar",
+            "version": "5.26.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/psalm/phar.git",
+                "reference": "8a38e7ad04499a0ccd2c506fd1da6fc01fff4547"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/psalm/phar/zipball/8a38e7ad04499a0ccd2c506fd1da6fc01fff4547",
+                "reference": "8a38e7ad04499a0ccd2c506fd1da6fc01fff4547",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.1 || ^8.0"
+            },
+            "conflict": {
+                "vimeo/psalm": "*"
+            },
+            "bin": [
+                "psalm.phar"
+            ],
+            "type": "library",
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "Composer-based Psalm Phar",
+            "support": {
+                "issues": "https://github.com/psalm/phar/issues",
+                "source": "https://github.com/psalm/phar/tree/5.26.1"
+            },
+            "time": "2024-09-09T16:22:43+00:00"
+        },
+        {
+            "name": "psr/clock",
+            "version": "1.0.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-fig/clock.git",
+                "reference": "e41a24703d4560fd0acb709162f73b8adfc3aa0d"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-fig/clock/zipball/e41a24703d4560fd0acb709162f73b8adfc3aa0d",
+                "reference": "e41a24703d4560fd0acb709162f73b8adfc3aa0d",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.0 || ^8.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Psr\\Clock\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "PHP-FIG",
+                    "homepage": "https://www.php-fig.org/"
+                }
+            ],
+            "description": "Common interface for reading the clock.",
+            "homepage": "https://github.com/php-fig/clock",
+            "keywords": [
+                "clock",
+                "now",
+                "psr",
+                "psr-20",
+                "time"
+            ],
+            "support": {
+                "issues": "https://github.com/php-fig/clock/issues",
+                "source": "https://github.com/php-fig/clock/tree/1.0.0"
+            },
+            "time": "2022-11-25T14:36:26+00:00"
+        },
+        {
+            "name": "psr/container",
+            "version": "2.0.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-fig/container.git",
+                "reference": "c71ecc56dfe541dbd90c5360474fbc405f8d5963"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-fig/container/zipball/c71ecc56dfe541dbd90c5360474fbc405f8d5963",
+                "reference": "c71ecc56dfe541dbd90c5360474fbc405f8d5963",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.4.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psr\\Container\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "PHP-FIG",
+                    "homepage": "https://www.php-fig.org/"
+                }
+            ],
+            "description": "Common Container Interface (PHP FIG PSR-11)",
+            "homepage": "https://github.com/php-fig/container",
+            "keywords": [
+                "PSR-11",
+                "container",
+                "container-interface",
+                "container-interop",
+                "psr"
+            ],
+            "support": {
+                "issues": "https://github.com/php-fig/container/issues",
+                "source": "https://github.com/php-fig/container/tree/2.0.2"
+            },
+            "time": "2021-11-05T16:47:00+00:00"
+        },
+        {
+            "name": "psr/event-dispatcher",
+            "version": "1.0.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-fig/event-dispatcher.git",
+                "reference": "dbefd12671e8a14ec7f180cab83036ed26714bb0"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-fig/event-dispatcher/zipball/dbefd12671e8a14ec7f180cab83036ed26714bb0",
+                "reference": "dbefd12671e8a14ec7f180cab83036ed26714bb0",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.2.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psr\\EventDispatcher\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "PHP-FIG",
+                    "homepage": "http://www.php-fig.org/"
+                }
+            ],
+            "description": "Standard interfaces for event handling.",
+            "keywords": [
+                "events",
+                "psr",
+                "psr-14"
+            ],
+            "support": {
+                "issues": "https://github.com/php-fig/event-dispatcher/issues",
+                "source": "https://github.com/php-fig/event-dispatcher/tree/1.0.0"
+            },
+            "time": "2019-01-08T18:20:26+00:00"
+        },
+        {
+            "name": "psr/log",
+            "version": "3.0.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-fig/log.git",
+                "reference": "f16e1d5863e37f8d8c2a01719f5b34baa2b714d3"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-fig/log/zipball/f16e1d5863e37f8d8c2a01719f5b34baa2b714d3",
+                "reference": "f16e1d5863e37f8d8c2a01719f5b34baa2b714d3",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.0.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "3.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psr\\Log\\": "src"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "PHP-FIG",
+                    "homepage": "https://www.php-fig.org/"
+                }
+            ],
+            "description": "Common interface for logging libraries",
+            "homepage": "https://github.com/php-fig/log",
+            "keywords": [
+                "log",
+                "psr",
+                "psr-3"
+            ],
+            "support": {
+                "source": "https://github.com/php-fig/log/tree/3.0.2"
+            },
+            "time": "2024-09-11T13:17:53+00:00"
+        },
         {
             "name": "sebastian/cli-parser",
             "version": "1.0.1",
@@ -2014,11 +2295,13 @@
     ],
     "aliases": [],
     "minimum-stability": "stable",
-    "stability-flags": [],
+    "stability-flags": {
+        "nextcloud/ocp": 20
+    },
     "prefer-stable": false,
     "prefer-lowest": false,
-    "platform": [],
-    "platform-dev": [],
+    "platform": {},
+    "platform-dev": {},
     "platform-overrides": {
         "php": "8.0.2"
     },
diff --git a/lib/Client.php b/lib/Client.php
index 7902804..4782a26 100644
--- a/lib/Client.php
+++ b/lib/Client.php
@@ -41,6 +41,7 @@
 use Psr\Log\LoggerInterface;
 use function explode;
 use function json_decode;
+use function OCP\Log\logger;
 
 class Client {
 	public const DEFAULT_PROPERTIES = [
@@ -66,8 +67,6 @@ class Client {
 	/** @var string[] */
 	private $knownSP2013SystemFolders = ['Forms', 'Item', 'Attachments'];
 
-	/** @var array */
-	protected $lastResponse;
 	private LoggerInterface $logger;
 	// as there is one client per storage it is a 1:1 Client<->DocumentLibrary relation (lazy-loading)
 	private ?SPList $documentLibrary = null;
@@ -232,7 +231,7 @@ public function overwriteFileViaStream($relativeServerPath, $fp, $localPath): vo
 		$request->ensureHeader('X-HTTP-Method', 'PUT'); // yes, PUT
 		$this->context->ensureFormDigest($request);
 		$request->StreamHandle = $fp;
-		$request->ensureHeader("Content-Length", filesize($localPath));
+		$request->ensureHeader("Content-Length", (string)filesize($localPath));
 
 		$this->context->executeQueryDirect($request);
 	}
@@ -455,10 +454,6 @@ public function getDocumentLibrariesRootFolder(string $documentLibrary): Folder
 	 */
 	public function loadAndExecute(ClientObject $object, array $properties = null) {
 		$this->context->load($object, $properties);
-		$r = $this->context->getPendingRequest();
-		$r->afterExecuteRequest(function (Response $response) {
-			$this->lastResponse = $response->getContent();
-		});
 		$this->context->executeQuery();
 	}
 
@@ -485,9 +480,7 @@ private function ensureConnection() {
 			}
 			$this->context = $this->contextsFactory->getClientContext($this->sharePointUrl, $this->credentials['user'], $this->credentials['password']);
 		} catch (Exception $e) {
-			/** @var LoggerInterface $logger */
-			$logger = \OC::$server->get(LoggerInterface::class); // FIXME: DI
-			$logger->debug(
+			logger('sharepoint')->debug(
 				'Failed to acquire token for user, fall back to NTLM auth',
 				[
 					'app' => 'sharepoint',
diff --git a/lib/Listener/ExternalStoragesRegistrationListener.php b/lib/Listener/ExternalStoragesRegistrationListener.php
index bf25d7b..85ed6c3 100644
--- a/lib/Listener/ExternalStoragesRegistrationListener.php
+++ b/lib/Listener/ExternalStoragesRegistrationListener.php
@@ -30,18 +30,15 @@
 use OCP\EventDispatcher\Event;
 use OCP\EventDispatcher\IEventListener;
 
+/**
+ * @template-implements IEventListener<Event>
+ */
 class ExternalStoragesRegistrationListener implements IEventListener {
-	/** @var BackendService */
-	private $backendService;
-	/** @var BackendProvider */
-	private $backendProvider;
 
 	public function __construct(
-		BackendService $backendService,
-		BackendProvider $backendProvider
+		private BackendService $backendService,
+		private BackendProvider $backendProvider
 	) {
-		$this->backendService = $backendService;
-		$this->backendProvider = $backendProvider;
 	}
 
 	public function handle(Event $event): void {
diff --git a/psalm.xml b/psalm.xml
new file mode 100644
index 0000000..6bf76f8
--- /dev/null
+++ b/psalm.xml
@@ -0,0 +1,26 @@
+<?xml version="1.0"?>
+<!--
+  - SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+  - SPDX-License-Identifier: AGPL-3.0-or-later
+-->
+<psalm
+	errorLevel="4"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns="https://getpsalm.org/schema/config"
+	xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+>
+	<stubs>
+		<file name="tests/stub.phpstub" preloadClasses="true"/>
+	</stubs>
+	<projectFiles xmlns="https://getpsalm.org/schema/config">
+		<directory name="lib"/>
+		<ignoreFiles>
+			<directory name="lib/Vendor"/>
+			<directory name="vendor"/>
+		</ignoreFiles>
+	</projectFiles>
+	<extraFiles>
+		<directory name="lib/Vendor"/>
+		<directory name="vendor"/>
+	</extraFiles>
+</psalm>
diff --git a/tests/stub.phpstub b/tests/stub.phpstub
new file mode 100644
index 0000000..98f4f6d
--- /dev/null
+++ b/tests/stub.phpstub
@@ -0,0 +1,163 @@
+<?php
+
+namespace OC\Core\Command {
+	use Symfony\Component\Console\Output\OutputInterface;
+
+	class Base extends \Symfony\Component\Console\Command\Command {
+	}
+}
+
+namespace OC\Files\Storage {
+	class Common implements \OCP\Files\Storage\IStorage, \OCP\Files\Storage\ILockingStorage, \OCP\Files\Storage\IWriteStreamStorage, \OCP\Files\Storage\IConstructableStorage {
+		abstract public function isReadable($path): bool;
+		abstract public function isDeletable($path): bool;
+		abstract public function is_dir($path): bool;
+		abstract public function is_file($path): bool;
+		abstract public function filesize($path): int|float|false;
+		abstract public function isSharable($path): bool;
+		abstract public function getPermissions($path): int;
+		abstract public function filemtime($path): int|false;
+		abstract public function file_get_contents($path): string|false;
+		abstract public function file_put_contents($path, $data): int|float|false;
+		abstract public function copy($source, $target): bool;
+		abstract public function getMimeType($path): string|false;
+		abstract public function hash($type, $path, $raw = false): string|false;
+		abstract public function free_space($path): int|float|false;
+		abstract public function getLocalFile($path): string|false;
+		abstract public function hasUpdated($path, $time): bool;
+		abstract public function getETag($path): string|false;
+		abstract public function isLocal(): bool;
+		abstract public function instanceOfStorage($class): bool;
+		abstract public function getDirectDownload($path): array|false;
+		abstract public function verifyPath($path, $fileName): void;
+		abstract public function copyFromStorage(IStorage $sourceStorage, $sourceInternalPath, $targetInternalPath, $preserveMtime = false): bool;
+		abstract public function moveFromStorage(IStorage $sourceStorage, $sourceInternalPath, $targetInternalPath): bool;
+		abstract public function test(): bool;
+		abstract public function getAvailability(): array;
+		abstract public function setAvailability($isAvailable): void;
+		abstract public function needsPartFile(): bool;
+		abstract public function getOwner($path): string|false;
+		abstract public function setOwner(?string $user): void;
+		abstract public function getCache($path = '', $storage = null): ICache;
+		abstract public function getPropagator($storage = null): IPropagator;
+		abstract public function getScanner($path = '', $storage = null): IScanner;
+		abstract public function getUpdater($storage = null): IUpdater;
+		abstract public function getWatcher($path = '', $storage = null): IWatcher;
+		abstract public function acquireLock($path, $type, ILockingProvider $provider): void;
+		abstract public function releaseLock($path, $type, ILockingProvider $provider): void;
+		abstract public function changeLock($path, $type, ILockingProvider $provider): void;
+		abstract public function writeStream(string $path, $stream, ?int $size = null): int;
+	}
+}
+
+namespace OCA\Files_External\Service {
+	use OCA\Files_External\Lib\Config\IBackendProvider;
+
+	class BackendService {
+		abstract public function registerBackendProvider(IBackendProvider $provider);
+	}
+}
+
+namespace OCA\Files_External\Lib {
+	class DefinitionParameter {
+		public const VALUE_BOOLEAN = 1;
+		public function __construct(string $name, string $text, $defaultValue = null);
+		public function setTooltip(string $tooltip);
+		public function setType(int $type);
+	}
+}
+
+namespace OCA\Files_External\Lib\Auth\ {
+	class AuthMechanism {
+		public const SCHEME_PASSWORD = 'password';
+	}
+}
+
+namespace OCA\Files_External\Lib\Auth\Password {
+	use OCP\IL10N;
+
+	class Password {
+		public function __construct(IL10N $l);
+	}
+}
+
+namespace OCA\Files_External\Lib\Backend {
+	class Backend {
+		public function setIdentifier(string $identifier): self;
+		public function setStorageClass($class);
+	}
+}
+
+namespace OCA\Files_External\Lib\Config {
+	interface IBackendProvider {
+		abstract public function getBackends();
+	}
+}
+
+namespace Symfony\Component\Console\Input {
+	class InputInterface {
+		public function getOption(string $key) {}
+		public function setOption(string $key, $value) {}
+		public function getArgument(string $key) {}
+	}
+	class InputArgument {
+		const REQUIRED = 0;
+		const OPTIONAL = 1;
+		const IS_ARRAY = 1;
+	}
+	class InputOption {
+		const VALUE_NONE = 1;
+		const VALUE_REQUIRED = 1;
+		const VALUE_OPTIONAL = 1;
+	}
+}
+
+namespace Symfony\Component\Console\Question {
+	class ConfirmationQuestion {
+		public function __construct(string $text, bool $default) {}
+	}
+
+	class Question {
+		abstract public function __construct(string $question, $default = null);
+		abstract public function setHidden(bool $hidden);
+	}
+}
+
+namespace Symfony\Component\Console\Output {
+	class OutputInterface {
+		public const VERBOSITY_VERBOSE = 1;
+		public function writeln($text, int $flat = 0) {}
+		public function isVerbose(): bool {}
+		public function isVeryVerbose(): bool {}
+	}
+}
+
+namespace Symfony\Component\Console\Command {
+    abstract class Command {
+        public function __construct();
+        public function setName(string $name);
+        public function getHelper(string $name);
+    }
+}
+
+namespace Symfony\Component\Console\Helper {
+	use Symfony\Component\Console\Input\InputInterface;
+	use Symfony\Component\Console\Output\OutputInterface;
+	use Symfony\Component\Console\Question\Question;
+
+	class QuestionHelper {
+		abstract public function ask(InputInterface $input, OutputInterface $output, Question $question);
+	}
+
+	class Table {
+		public function __construct(OutputInterface $output);
+		public function render();
+		public function addRow($row);
+		public function setHeaders(array $headers);
+		public function setRows(array $rows);
+	}
+}
+
+namespace OCP\Log {
+        public function logger(?string $appId = null): \Psr\Log\LoggerInterface;
+}