diff --git a/PROGRESS.md b/PROGRESS.md
index f856b48..72ac627 100644
--- a/PROGRESS.md
+++ b/PROGRESS.md
@@ -70,6 +70,7 @@
     - **`Escape`**: Instantly close any open modal (Task Detail, Add Task, Settings, or Audit Logs).
     - **`n`**: Open the "Add Task" modal from the main dashboard (disabled while typing in inputs).
 24. **Drag-and-Drop Stability:** Fixed a bug where tasks would "disappear" if dropped in an invalid area. Tasks now remain visible at their original position if a drop is cancelled.
+25. **User Deletion Safety:** Implemented a backend check to prevent deleting users who have assigned tasks or notes. Upgraded the frontend `ApiService` to correctly parse and display these descriptive error messages from the backend.
 
 ### Phase 3: Advanced Features
 - **Real-time Notifications:** Explore WebSockets for task assignments.
diff --git a/api.js b/api.js
index 1f2a97b..5883705 100644
--- a/api.js
+++ b/api.js
@@ -32,7 +32,12 @@ class ApiService {
       if (response.status === 401) {
         this.logout();
       }
-      throw new Error(`API Error: ${response.statusText}`);
+      let errorMsg = response.statusText;
+      try {
+        const data = await response.json();
+        if (data && data.detail) errorMsg = data.detail;
+      } catch (e) {}
+      throw new Error(`API Error: ${errorMsg}`);
     }
 
     return response.json();
diff --git a/app.jsx b/app.jsx
index 8d9a169..0784ad0 100644
--- a/app.jsx
+++ b/app.jsx
@@ -392,7 +392,7 @@ function App() {
               await api.addAudit({ actor: meId, action: 'user_deleted', summary: 'Removed ' + (u?u.name:id), target: null });
             } catch(e) {
               console.error(e);
-              alert("Failed to delete user");
+              alert("Failed to delete user: " + e.message);
             }
           }}
           onUpdateUserRole={async (id, edits) => {
@@ -401,7 +401,7 @@ function App() {
               await api.addAudit({ actor: meId, action: 'user_updated', summary: 'Updated ' + (userMap[id]?userMap[id].name:id) + ' permissions', target: null });
             } catch(e) {
               console.error(e);
-              alert("Failed to update user");
+              alert("Failed to update user: " + e.message);
             }
           }}
           onChangePassword={async (oldPwd, newPwd) => {
diff --git a/backend/main.py b/backend/main.py
index fac61fd..3d8e754 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -96,6 +96,19 @@ def delete_user(user_id: str, db: Session = Depends(get_db), current_user: model
     db_user = db.query(models.User).filter(models.User.id == user_id).first()
     if not db_user:
         raise HTTPException(status_code=404, detail="User not found")
+
+    # Check for OPEN assigned tasks (that are not in the trash)
+    open_tasks = db.query(models.Task).filter(
+        models.Task.assignee_id == user_id,
+        models.Task.status == "open",
+        models.Task.deleted_at == None
+    ).first()
+    if open_tasks:
+        raise HTTPException(status_code=400, detail="Cannot delete user: They still have OPEN tasks assigned to them. Reassign them first.")
+
+    # Nullify references in closed tasks and notes so we don't lose history
+    db.query(models.Task).filter(models.Task.assignee_id == user_id).update({"assignee_id": None})
+    db.query(models.TaskNote).filter(models.TaskNote.author_id == user_id).update({"author_id": None})
     
     db.delete(db_user)
     db.commit()
diff --git a/backend/models.py b/backend/models.py
index a6e1854..99bf66a 100644
--- a/backend/models.py
+++ b/backend/models.py
@@ -59,7 +59,7 @@ class TaskNote(Base):
 
     id = Column(Integer, primary_key=True, index=True)
     task_id = Column(String, ForeignKey("tasks.id", ondelete="CASCADE"), nullable=False)
-    author_id = Column(String, ForeignKey("users.id"), nullable=False)
+    author_id = Column(String, ForeignKey("users.id"), nullable=True)
     body = Column(String, nullable=False)
     created_at = Column(DateTime(timezone=True), server_default=func.now())
 
diff --git a/backend/schemas.py b/backend/schemas.py
index c28f98a..0ccd8c6 100644
--- a/backend/schemas.py
+++ b/backend/schemas.py
@@ -62,7 +62,7 @@ class Tag(TagBase):
 class TaskBase(BaseModel):
     title: str
     description: Optional[str] = None
-    assignee_id: str
+    assignee_id: Optional[str] = None
     added_by: str
     priority: str
     source: str
diff --git a/dashy.db b/dashy.db
index f7842e7..e2a6cab 100644
Binary files a/dashy.db and b/dashy.db differ