diff --git a/src/Module/ProjectManagement/Domain/Entity/Task.php b/src/Module/ProjectManagement/Domain/Entity/Task.php
index 3d9daf8..28b0b72 100644
--- a/src/Module/ProjectManagement/Domain/Entity/Task.php
+++ b/src/Module/ProjectManagement/Domain/Entity/Task.php
@@ -111,6 +111,7 @@ class Task implements TaskInterface, TimestampableInterface, BlamableInterface
     #[ORM\ManyToOne(targetEntity: Project::class, inversedBy: 'tasks')]
     #[ORM\JoinColumn(nullable: false, onDelete: 'CASCADE')]
     #[Groups(['task:read', 'task:write'])]
+    #[Assert\NotNull]
     private ?Project $project = null;
 
     /** @var Collection<int, TaskTag> */
diff --git a/src/Module/ProjectManagement/Infrastructure/Service/CalDavService.php b/src/Module/ProjectManagement/Infrastructure/Service/CalDavService.php
index 8be1017..a35ef38 100644
--- a/src/Module/ProjectManagement/Infrastructure/Service/CalDavService.php
+++ b/src/Module/ProjectManagement/Infrastructure/Service/CalDavService.php
@@ -134,6 +134,12 @@ final class CalDavService
 
     public function syncTask(Task $task): void
     {
+        // No CalDAV server configured/enabled: skip all remote interaction so a
+        // task save never triggers a doomed HTTP request nor stores a sync error.
+        if (!$this->isConfigured()) {
+            return;
+        }
+
         if (!$task->isSyncToCalendar()) {
             $this->deleteEvent($task->getCalendarEventUid());
             $this->deleteTodo($task->getCalendarTodoUid());