diff --git a/messages/en.json b/messages/en.json
index 7e4a072..d7cb273 100644
--- a/messages/en.json
+++ b/messages/en.json
@@ -98,6 +98,7 @@
   "admin_tasks_card_updated": "Updated:",
   "admin_tasks_card_user_prefix": "User #",
   "admin_tasks_card_view_details": "View Task",
+  "admin_tasks_card_visible_to_users": "Visible to Users",
   "admin_tasks_dialog_description": "Upload a task archive to the FileStorage service. The archive should contain all necessary files for the task.",
   "admin_tasks_dialog_title": "Upload Task",
   "admin_tasks_form_archive_label": "Task Archive",
@@ -106,6 +107,24 @@
   "admin_tasks_form_title_label": "Task Title",
   "admin_tasks_form_title_placeholder": "Enter task title",
   "admin_tasks_form_upload": "Upload",
+  "admin_tasks_form_update": "Update",
+  "admin_tasks_form_updating": "Updating...",
+  "admin_tasks_form_visible_label": "Make task visible to all users",
+  "admin_tasks_form_visible_description": "When checked, this task will be visible to all users immediately",
+  "admin_tasks_visibility_confirm_title": "Confirm Visibility Change",
+  "admin_tasks_visibility_confirm_enable": "Are you sure you want to make \"{taskTitle}\" visible to all users?",
+  "admin_tasks_visibility_confirm_disable": "Are you sure you want to hide \"{taskTitle}\" from users?",
+  "admin_tasks_visibility_confirm": "Confirm",
+  "admin_tasks_visibility_enabled": "Task is now visible to users",
+  "admin_tasks_visibility_disabled": "Task is now hidden from users",
+  "admin_tasks_visibility_error": "Failed to update task visibility",
+  "admin_tasks_card_edit": "Edit Task",
+  "admin_tasks_edit_dialog_title": "Edit Task",
+  "admin_tasks_edit_dialog_description": "Update the task details. Leave fields empty to keep current values.",
+  "admin_tasks_edit_form_title_note": "Leave empty to keep the current title",
+  "admin_tasks_edit_form_archive_note": "Optional - only upload if you want to replace the task archive",
+  "admin_tasks_edit_success": "Task updated successfully!",
+  "admin_tasks_edit_error": "Failed to update task. Please try again.",
   "admin_tasks_load_error_title": "Failed to load tasks",
   "admin_tasks_loading": "Loading tasks...",
   "admin_tasks_no_tasks_description": "Upload your first task to get started",
diff --git a/messages/pl.json b/messages/pl.json
index ef78b41..696772d 100644
--- a/messages/pl.json
+++ b/messages/pl.json
@@ -98,6 +98,7 @@
   "admin_tasks_card_updated": "Zaktualizowano:",
   "admin_tasks_card_user_prefix": "Użytkownik #",
   "admin_tasks_card_view_details": "Zobacz Zadanie",
+  "admin_tasks_card_visible_to_users": "Widoczne dla użytkowników",
   "admin_tasks_dialog_description": "Prześlij archiwum zadania do serwisu FileStorage. Archiwum powinno zawierać wszystkie niezbędne pliki zadania.",
   "admin_tasks_dialog_title": "Prześlij zadanie",
   "admin_tasks_form_archive_label": "Archiwum Zadania",
@@ -106,6 +107,24 @@
   "admin_tasks_form_title_label": "Tytuł Zadania",
   "admin_tasks_form_title_placeholder": "Wprowadź tytuł zadania",
   "admin_tasks_form_upload": "Prześlij",
+  "admin_tasks_form_update": "Aktualizuj",
+  "admin_tasks_form_updating": "Aktualizowanie...",
+  "admin_tasks_form_visible_label": "Udostępnij zadanie wszystkim użytkownikom",
+  "admin_tasks_form_visible_description": "Kiedy zaznaczone, to zadanie będzie natychmiast widoczne dla wszystkich użytkowników",
+  "admin_tasks_visibility_confirm_title": "Potwierdź zmianę widoczności",
+  "admin_tasks_visibility_confirm_enable": "Czy na pewno chcesz udostępnić zadanie \"{taskTitle}\" wszystkim użytkownikom?",
+  "admin_tasks_visibility_confirm_disable": "Czy na pewno chcesz ukryć zadanie \"{taskTitle}\" przed użytkownikami?",
+  "admin_tasks_visibility_confirm": "Potwierdź",
+  "admin_tasks_visibility_enabled": "Zadanie jest teraz widoczne dla użytkowników",
+  "admin_tasks_visibility_disabled": "Zadanie jest teraz ukryte przed użytkownikami",
+  "admin_tasks_visibility_error": "Nie udało się zaktualizować widoczności zadania",
+  "admin_tasks_card_edit": "Edytuj Zadanie",
+  "admin_tasks_edit_dialog_title": "Edytuj Zadanie",
+  "admin_tasks_edit_dialog_description": "Zaktualizuj szczegóły zadania. Pozostaw pola puste, aby zachować obecne wartości.",
+  "admin_tasks_edit_form_title_note": "Pozostaw puste, aby zachować obecny tytuł",
+  "admin_tasks_edit_form_archive_note": "Opcjonalne - prześlij tylko jeśli chcesz zastąpić archiwum zadania",
+  "admin_tasks_edit_success": "Zadanie zostało pomyślnie zaktualizowane!",
+  "admin_tasks_edit_error": "Nie udało się zaktualizować zadania. Spróbuj ponownie.",
   "admin_tasks_load_error_title": "Nie udało się załadować zadań",
   "admin_tasks_loading": "Ładowanie zadań...",
   "admin_tasks_no_tasks_description": "Prześlij swoje pierwsze zadanie, aby zacząć",
diff --git a/src/lib/components/dashboard/admin/contests/AddContestCollaboratorButton.svelte b/src/lib/components/dashboard/admin/contests/AddContestCollaboratorButton.svelte
index 1c1f4f7..fe97ec3 100644
--- a/src/lib/components/dashboard/admin/contests/AddContestCollaboratorButton.svelte
+++ b/src/lib/components/dashboard/admin/contests/AddContestCollaboratorButton.svelte
@@ -11,10 +11,8 @@
   import * as m from '$lib/paraglide/messages';
   import { Permission } from '$lib/dto/accessControl';
   import type { User } from '$lib/dto/user';
-  import type { Collaborator } from '$lib/dto/accessControl';
   import type { AddCollaboratorForm } from '$routes/dashboard/teacher/contests/[contestId]/collaborators/collaborators.remote';
   import { LoadingSpinner } from '$lib/components/common';
-  import { UserRole } from '$lib/dto/jwt';
   import type { PaginatedData } from '$lib/dto/response';
 
   interface Props {
@@ -23,31 +21,17 @@
     users: PaginatedData<User> | undefined;
     usersLoading: boolean;
     usersError: Error | null;
-    existingCollaborators: Collaborator[] | undefined;
   }
 
-  let {
-    contestId,
-    addCollaborator,
-    users,
-    usersLoading,
-    usersError,
-    existingCollaborators
-  }: Props = $props();
+  let { contestId, addCollaborator, users, usersLoading, usersError }: Props = $props();
 
   let dialogOpen = $state(false);
   let searchQuery = $state('');
   let selectedUserId = $state<number | null>(null);
   let selectedPermission = $state<Permission | null>(null);
 
-  // Filter out users who are already collaborators and users with student role
-  let availableUsers = $derived.by(() => {
-    if (!users) return [];
-    const collaboratorIds = new Set(existingCollaborators?.map((c) => c.userId) ?? []);
-    return users.items.filter(
-      (user) => !collaboratorIds.has(user.id) && user.role !== UserRole.Student
-    );
-  });
+  // Backend returns only assignable users (teachers who aren't already collaborators)
+  let availableUsers = $derived(users?.items ?? []);
 
   // Filter users by search query
   let filteredUsers = $derived.by(() => {
diff --git a/src/lib/components/dashboard/admin/contests/EditContestDialog.svelte b/src/lib/components/dashboard/admin/contests/EditContestDialog.svelte
index 5ac4f66..26fd5e6 100644
--- a/src/lib/components/dashboard/admin/contests/EditContestDialog.svelte
+++ b/src/lib/components/dashboard/admin/contests/EditContestDialog.svelte
@@ -252,7 +252,6 @@
 
         <div class="flex items-center gap-3">
           <Checkbox
-            id="isRegistrationOpen"
             {...updateContest.fields.isRegistrationOpen.as('checkbox')}
             checked={contest.isRegistrationOpen}
           />
@@ -263,7 +262,6 @@
 
         <div class="flex items-center gap-3">
           <Checkbox
-            id="isSubmissionOpen"
             {...updateContest.fields.isSubmissionOpen.as('checkbox')}
             checked={contest.isSubmissionOpen}
           />
@@ -274,7 +272,6 @@
 
         <div class="flex items-center gap-3">
           <Checkbox
-            id="isVisible"
             {...updateContest.fields.isVisible.as('checkbox')}
             checked={contest.isVisible}
           />
diff --git a/src/lib/components/dashboard/admin/tasks/AddCollaboratorButton.svelte b/src/lib/components/dashboard/admin/tasks/AddCollaboratorButton.svelte
index ca8c357..6aa88a2 100644
--- a/src/lib/components/dashboard/admin/tasks/AddCollaboratorButton.svelte
+++ b/src/lib/components/dashboard/admin/tasks/AddCollaboratorButton.svelte
@@ -11,10 +11,8 @@
   import * as m from '$lib/paraglide/messages';
   import { Permission } from '$lib/dto/accessControl';
   import type { User } from '$lib/dto/user';
-  import type { Collaborator } from '$lib/dto/accessControl';
   import type { AddCollaboratorForm } from '$routes/dashboard/teacher/tasks/[taskId]/collaborators/collaborators.remote';
   import { LoadingSpinner } from '$lib/components/common';
-  import { UserRole } from '$lib/dto/jwt';
   import type { PaginatedData } from '$lib/dto/response';
 
   interface Props {
@@ -23,25 +21,17 @@
     users: PaginatedData<User> | undefined;
     usersLoading: boolean;
     usersError: Error | null;
-    existingCollaborators: Collaborator[] | undefined;
   }
 
-  let { taskId, addCollaborator, users, usersLoading, usersError, existingCollaborators }: Props =
-    $props();
+  let { taskId, addCollaborator, users, usersLoading, usersError }: Props = $props();
 
   let dialogOpen = $state(false);
   let searchQuery = $state('');
   let selectedUserId = $state<number | null>(null);
   let selectedPermission = $state<Permission | null>(null);
 
-  // Filter out users who are already collaborators and users with student role
-  let availableUsers = $derived.by(() => {
-    if (!users) return [];
-    const collaboratorIds = new Set(existingCollaborators?.map((c) => c.userId) ?? []);
-    return users.items.filter(
-      (user) => !collaboratorIds.has(user.id) && user.role !== UserRole.Student
-    );
-  });
+  // Backend returns only assignable users (teachers who aren't already collaborators)
+  let availableUsers = $derived(users?.items ?? []);
 
   // Filter users by search query
   let filteredUsers = $derived.by(() => {
diff --git a/src/lib/components/dashboard/admin/tasks/TaskVisibilityToggle.svelte b/src/lib/components/dashboard/admin/tasks/TaskVisibilityToggle.svelte
new file mode 100644
index 0000000..58be366
--- /dev/null
+++ b/src/lib/components/dashboard/admin/tasks/TaskVisibilityToggle.svelte
@@ -0,0 +1,86 @@
+<script lang="ts">
+  import { toggleTaskVisibility } from '$routes/dashboard/teacher/tasks/tasks.remote';
+  import { Checkbox } from '$lib/components/ui/checkbox';
+  import { Label } from '$lib/components/ui/label';
+  import { Button } from '$lib/components/ui/button';
+  import * as Dialog from '$lib/components/ui/dialog';
+  import { toast } from 'svelte-sonner';
+  import * as m from '$lib/paraglide/messages';
+
+  interface TaskVisibilityToggleProps {
+    taskId: number;
+    taskTitle: string;
+    initialVisibility: boolean;
+    onToggled: () => void;
+  }
+
+  let { taskId, taskTitle, initialVisibility, onToggled }: TaskVisibilityToggleProps = $props();
+
+  let isVisible = $state(initialVisibility);
+  let showConfirmDialog = $state(false);
+  let pendingVisibility = $state(false);
+  let checkboxKey = $state(0);
+
+  function handleCheckboxChange(checked: boolean) {
+    pendingVisibility = checked;
+    showConfirmDialog = true;
+  }
+
+  async function confirmToggle() {
+    try {
+      await toggleTaskVisibility({ taskId, isVisible: pendingVisibility });
+      isVisible = pendingVisibility;
+      showConfirmDialog = false;
+      toast.success(
+        pendingVisibility ? m.admin_tasks_visibility_enabled() : m.admin_tasks_visibility_disabled()
+      );
+      onToggled();
+    } catch (error) {
+      toast.error(m.admin_tasks_visibility_error());
+      console.error('Failed to toggle visibility:', error);
+    }
+  }
+
+  function cancelToggle() {
+    showConfirmDialog = false;
+    checkboxKey++; // Force checkbox to re-render with current isVisible value
+  }
+</script>
+
+<div class="flex items-center space-x-2">
+  {#key checkboxKey}
+    <Checkbox
+      id="visibility-{taskId}"
+      checked={isVisible}
+      onCheckedChange={handleCheckboxChange}
+      class={isVisible ? '' : 'bg-card'}
+    />
+  {/key}
+  <Label
+    for="visibility-{taskId}"
+    class="cursor-pointer text-sm leading-none font-medium peer-disabled:cursor-not-allowed peer-disabled:opacity-70"
+  >
+    {m.admin_tasks_card_visible_to_users()}
+  </Label>
+</div>
+
+<Dialog.Root bind:open={showConfirmDialog}>
+  <Dialog.Content>
+    <Dialog.Header>
+      <Dialog.Title>{m.admin_tasks_visibility_confirm_title()}</Dialog.Title>
+      <Dialog.Description>
+        {pendingVisibility
+          ? m.admin_tasks_visibility_confirm_enable({ taskTitle })
+          : m.admin_tasks_visibility_confirm_disable({ taskTitle })}
+      </Dialog.Description>
+    </Dialog.Header>
+    <Dialog.Footer>
+      <Button type="button" variant="outline" onclick={cancelToggle}>
+        {m.admin_tasks_form_cancel()}
+      </Button>
+      <Button type="button" onclick={confirmToggle}>
+        {m.admin_tasks_visibility_confirm()}
+      </Button>
+    </Dialog.Footer>
+  </Dialog.Content>
+</Dialog.Root>
diff --git a/src/lib/components/dashboard/admin/tasks/TasksUploadDialog.svelte b/src/lib/components/dashboard/admin/tasks/TasksUploadDialog.svelte
index 2435f3a..4a2ffdb 100644
--- a/src/lib/components/dashboard/admin/tasks/TasksUploadDialog.svelte
+++ b/src/lib/components/dashboard/admin/tasks/TasksUploadDialog.svelte
@@ -3,6 +3,7 @@
   import { Button } from '$lib/components/ui/button';
   import { Input } from '$lib/components/ui/input';
   import { Label } from '$lib/components/ui/label';
+  import { Checkbox } from '$lib/components/ui/checkbox';
   import * as Dialog from '$lib/components/ui/dialog';
   import { toast } from 'svelte-sonner';
   import { isHttpError } from '@sveltejs/kit';
@@ -123,6 +124,21 @@
         {/if}
       </div>
 
+      <div class="flex items-start space-x-2">
+        <Checkbox {...uploadTask.fields.isVisible.as('checkbox')} />
+        <div class="grid gap-1.5 leading-none">
+          <Label
+            for="isVisible"
+            class="cursor-pointer text-sm leading-none font-medium peer-disabled:cursor-not-allowed peer-disabled:opacity-70"
+          >
+            {m.admin_tasks_form_visible_label()}
+          </Label>
+          <p class="text-sm text-muted-foreground">
+            {m.admin_tasks_form_visible_description()}
+          </p>
+        </div>
+      </div>
+
       <Dialog.Footer>
         <Button type="button" variant="outline" onclick={handleCancel}>
           {m.admin_tasks_form_cancel()}
diff --git a/src/lib/components/dashboard/tasks/AdminTaskCard.svelte b/src/lib/components/dashboard/tasks/AdminTaskCard.svelte
index 421308e..61633c0 100644
--- a/src/lib/components/dashboard/tasks/AdminTaskCard.svelte
+++ b/src/lib/components/dashboard/tasks/AdminTaskCard.svelte
@@ -12,6 +12,7 @@
   import { localizeHref } from '$lib/paraglide/runtime';
   import { AppRoutes } from '$lib/routes';
   import ManageTestCasesLimitsDialog from '$lib/components/dashboard/admin/tasks/ManageTestCasesLimitsDialog.svelte';
+  import TaskVisibilityToggle from '$lib/components/dashboard/admin/tasks/TaskVisibilityToggle.svelte';
   import RemoveTaskButton from '$lib/components/dashboard/admin/tasks/RemoveTaskButton.svelte';
   import type { DeleteTaskForm } from '$routes/dashboard/teacher/tasks/tasks.remote';
 
@@ -74,6 +75,16 @@
       </div>
     </div>
 
+    <!-- Visibility Toggle -->
+    <div class="rounded-lg border border-border bg-muted/30 p-3">
+      <TaskVisibilityToggle
+        taskId={task.id}
+        taskTitle={task.title}
+        initialVisibility={task.isVisible}
+        onToggled={() => {}}
+      />
+    </div>
+
     <!-- Action Buttons -->
     <div class="flex flex-col gap-2">
       <Button
diff --git a/src/lib/dto/accessControl.ts b/src/lib/dto/accessControl.ts
index 49b5e68..c021d10 100644
--- a/src/lib/dto/accessControl.ts
+++ b/src/lib/dto/accessControl.ts
@@ -7,6 +7,14 @@ export enum Permission {
   Owner = 'owner'
 }
 
+/**
+ * Resource types for access control.
+ */
+export enum ResourceType {
+  Tasks = 'tasks',
+  Contests = 'contests'
+}
+
 /**
  * Represents a collaborator on a task or contest.
  */
@@ -19,3 +27,18 @@ export interface Collaborator {
   permission: Permission;
   addedAt: string;
 }
+
+/**
+ * Request body for adding a collaborator.
+ */
+export interface AddCollaboratorRequest {
+  user_id: number;
+  permission: Permission.Edit | Permission.Manage;
+}
+
+/**
+ * Request body for updating a collaborator.
+ */
+export interface UpdateCollaboratorRequest {
+  permission: Permission.Edit | Permission.Manage;
+}
diff --git a/src/lib/dto/task.ts b/src/lib/dto/task.ts
index 039dc40..eabc625 100644
--- a/src/lib/dto/task.ts
+++ b/src/lib/dto/task.ts
@@ -4,6 +4,7 @@ export interface Task {
   createdAt: string;
   updatedAt: string;
   createdBy: number;
+  isVisible: boolean;
 }
 
 export interface TaskDetail {
@@ -37,6 +38,7 @@ export interface UploadTaskResponse {
 export interface UploadTaskDto {
   title: string;
   archive: File;
+  isVisible: boolean;
 }
 
 export interface UserContestTask {
diff --git a/src/lib/services/AccessControlService.ts b/src/lib/services/AccessControlService.ts
index 2673115..718f6c6 100644
--- a/src/lib/services/AccessControlService.ts
+++ b/src/lib/services/AccessControlService.ts
@@ -1,125 +1,49 @@
 import { ApiError, type ApiService } from './ApiService';
-import type { ApiResponse } from '../dto/response';
-import type { Collaborator, Permission } from '../dto/accessControl';
-
-export interface AddCollaboratorRequest {
-  user_id: number;
-  permission: Permission;
-}
-
-export interface UpdateCollaboratorRequest {
-  permission: Permission;
-}
+import type { ApiResponse, PaginatedData } from '../dto/response';
+import type {
+  Collaborator,
+  AddCollaboratorRequest,
+  UpdateCollaboratorRequest
+} from '../dto/accessControl';
+import { ResourceType } from '../dto/accessControl';
+import type { User } from '../dto/user';
 
 export class AccessControlService {
   constructor(private apiClient: ApiService) {}
 
   /**
-   * Get collaborators for a specific task.
-   * Only users with edit permission or higher can see collaborators.
+   * Get assignable users for a resource.
+   * Returns users (teachers) who can be granted access to the resource.
+   * Only users with manage permission can view assignable users.
+   * Returned users do not currently have any access entry for the resource.
    */
-  async getTaskCollaborators(taskId: number): Promise<{
-    success: boolean;
-    status: number;
-    data?: Collaborator[];
-    error?: string;
-  }> {
-    try {
-      const response = await this.apiClient.get<ApiResponse<Collaborator[]>>({
-        url: `/access-control/resources/tasks/${taskId}/collaborators`
-      });
-      return { success: true, data: response.data, status: 200 };
-    } catch (error) {
-      if (error instanceof ApiError) {
-        return {
-          success: false,
-          error: error.getApiMessage(),
-          status: error.getStatus()
-        };
-      }
-      throw error;
-    }
-  }
-
-  /**
-   * Add a collaborator to a specific task.
-   * Only users with manage permission can add collaborators.
-   */
-  async addTaskCollaborator(
-    taskId: number,
-    data: AddCollaboratorRequest
+  async getAssignableUsers(
+    resourceType: ResourceType,
+    resourceId: number,
+    params?: { limit?: number; offset?: number; sort?: string }
   ): Promise<{
     success: boolean;
     status: number;
+    data?: PaginatedData<User>;
     error?: string;
   }> {
     try {
-      await this.apiClient.post<ApiResponse<void>>({
-        url: `/access-control/resources/tasks/${taskId}/collaborators`,
-        body: JSON.stringify(data)
-      });
-      return { success: true, status: 201 };
-    } catch (error) {
-      if (error instanceof ApiError) {
-        return {
-          success: false,
-          error: error.getApiMessage(),
-          status: error.getStatus()
-        };
+      const queryParams = new URLSearchParams();
+      if (params?.limit !== undefined) {
+        queryParams.append('limit', params.limit.toString());
       }
-      throw error;
-    }
-  }
-
-  /**
-   * Update a collaborator's permission on a specific task.
-   * Only users with manage permission can update collaborators.
-   */
-  async updateTaskCollaborator(
-    taskId: number,
-    userId: number,
-    data: UpdateCollaboratorRequest
-  ): Promise<{
-    success: boolean;
-    status: number;
-    error?: string;
-  }> {
-    try {
-      await this.apiClient.put<ApiResponse<void>>({
-        url: `/access-control/resources/tasks/${taskId}/collaborators/${userId}`,
-        body: JSON.stringify(data)
-      });
-      return { success: true, status: 200 };
-    } catch (error) {
-      if (error instanceof ApiError) {
-        return {
-          success: false,
-          error: error.getApiMessage(),
-          status: error.getStatus()
-        };
+      if (params?.offset !== undefined) {
+        queryParams.append('offset', params.offset.toString());
+      }
+      if (params?.sort) {
+        queryParams.append('sort', params.sort);
       }
-      throw error;
-    }
-  }
 
-  /**
-   * Remove a collaborator from a specific task.
-   * Only users with manage or owner permission can remove collaborators.
-   * Managers can only remove editors and managers, owners can remove everyone except other owners.
-   */
-  async deleteTaskCollaborator(
-    taskId: number,
-    userId: number
-  ): Promise<{
-    success: boolean;
-    status: number;
-    error?: string;
-  }> {
-    try {
-      await this.apiClient.delete<ApiResponse<void>>({
-        url: `/access-control/resources/tasks/${taskId}/collaborators/${userId}`
+      const url = `/access-control/resources/${resourceType}/${resourceId}/assignable${queryParams.toString() ? `?${queryParams.toString()}` : ''}`;
+      const response = await this.apiClient.get<ApiResponse<PaginatedData<User>>>({
+        url
       });
-      return { success: true, status: 200 };
+      return { success: true, data: response.data, status: 200 };
     } catch (error) {
       if (error instanceof ApiError) {
         return {
@@ -133,10 +57,13 @@ export class AccessControlService {
   }
 
   /**
-   * Get collaborators for a specific contest.
+   * Get collaborators for a resource.
    * Only users with edit permission or higher can see collaborators.
    */
-  async getContestCollaborators(contestId: number): Promise<{
+  async getCollaborators(
+    resourceType: ResourceType,
+    resourceId: number
+  ): Promise<{
     success: boolean;
     status: number;
     data?: Collaborator[];
@@ -144,7 +71,7 @@ export class AccessControlService {
   }> {
     try {
       const response = await this.apiClient.get<ApiResponse<Collaborator[]>>({
-        url: `/access-control/resources/contests/${contestId}/collaborators`
+        url: `/access-control/resources/${resourceType}/${resourceId}/collaborators`
       });
       return { success: true, data: response.data, status: 200 };
     } catch (error) {
@@ -160,11 +87,12 @@ export class AccessControlService {
   }
 
   /**
-   * Add a collaborator to a specific contest.
+   * Add a collaborator to a resource.
    * Only users with manage permission can add collaborators.
    */
-  async addContestCollaborator(
-    contestId: number,
+  async addCollaborator(
+    resourceType: ResourceType,
+    resourceId: number,
     data: AddCollaboratorRequest
   ): Promise<{
     success: boolean;
@@ -173,7 +101,7 @@ export class AccessControlService {
   }> {
     try {
       await this.apiClient.post<ApiResponse<void>>({
-        url: `/access-control/resources/contests/${contestId}/collaborators`,
+        url: `/access-control/resources/${resourceType}/${resourceId}/collaborators`,
         body: JSON.stringify(data)
       });
       return { success: true, status: 201 };
@@ -190,11 +118,12 @@ export class AccessControlService {
   }
 
   /**
-   * Update a collaborator's permission on a specific contest.
+   * Update a collaborator's permission on a resource.
    * Only users with manage permission can update collaborators.
    */
-  async updateContestCollaborator(
-    contestId: number,
+  async updateCollaborator(
+    resourceType: ResourceType,
+    resourceId: number,
     userId: number,
     data: UpdateCollaboratorRequest
   ): Promise<{
@@ -204,7 +133,7 @@ export class AccessControlService {
   }> {
     try {
       await this.apiClient.put<ApiResponse<void>>({
-        url: `/access-control/resources/contests/${contestId}/collaborators/${userId}`,
+        url: `/access-control/resources/${resourceType}/${resourceId}/collaborators/${userId}`,
         body: JSON.stringify(data)
       });
       return { success: true, status: 200 };
@@ -221,12 +150,13 @@ export class AccessControlService {
   }
 
   /**
-   * Remove a collaborator from a specific contest.
+   * Remove a collaborator from a resource.
    * Only users with manage or owner permission can remove collaborators.
    * Managers can only remove editors and managers, owners can remove everyone except other owners.
    */
-  async deleteContestCollaborator(
-    contestId: number,
+  async deleteCollaborator(
+    resourceType: ResourceType,
+    resourceId: number,
     userId: number
   ): Promise<{
     success: boolean;
@@ -235,7 +165,7 @@ export class AccessControlService {
   }> {
     try {
       await this.apiClient.delete<ApiResponse<void>>({
-        url: `/access-control/resources/contests/${contestId}/collaborators/${userId}`
+        url: `/access-control/resources/${resourceType}/${resourceId}/collaborators/${userId}`
       });
       return { success: true, status: 200 };
     } catch (error) {
diff --git a/src/lib/services/TasksManagementService.ts b/src/lib/services/TasksManagementService.ts
index 6aa3a8d..e61eda5 100644
--- a/src/lib/services/TasksManagementService.ts
+++ b/src/lib/services/TasksManagementService.ts
@@ -18,6 +18,7 @@ export class TasksManagementService {
     const formData = new FormData();
     formData.append('title', body.title);
     formData.append('archive', body.archive);
+    formData.append('isVisible', body.isVisible.toString());
 
     try {
       const response = await this.apiClient.post<ApiResponse<UploadTaskResponse>>({
@@ -111,6 +112,31 @@ export class TasksManagementService {
     }
   }
 
+  async toggleTaskVisibility(
+    taskId: number,
+    isVisible: boolean
+  ): Promise<{ success: boolean; status: number; error?: string }> {
+    const formData = new FormData();
+    formData.append('isVisible', isVisible.toString());
+
+    try {
+      await this.apiClient.patch<ApiResponse<void>>({
+        url: `/tasks-management/tasks/${taskId}`,
+        body: formData
+      });
+      return { success: true, status: 200 };
+    } catch (error) {
+      if (error instanceof ApiError) {
+        return {
+          success: false,
+          error: error.getApiMessage(),
+          status: error.getStatus()
+        };
+      }
+      throw error;
+    }
+  }
+
   async deleteTask(taskId: number): Promise<{
     success: boolean;
     status: number;
diff --git a/src/routes/dashboard/teacher/contests/[contestId]/+layout.server.ts b/src/routes/dashboard/teacher/contests/[contestId]/+layout.server.ts
index 10196a9..25aa502 100644
--- a/src/routes/dashboard/teacher/contests/[contestId]/+layout.server.ts
+++ b/src/routes/dashboard/teacher/contests/[contestId]/+layout.server.ts
@@ -1,6 +1,7 @@
 import { error } from '@sveltejs/kit';
 import { createApiClient } from '$lib/services/ApiService';
 import { AccessControlService } from '$lib/services/AccessControlService';
+import { ResourceType } from '$lib/dto/accessControl';
 
 export const load = async ({
   params,
@@ -22,7 +23,7 @@ export const load = async ({
   // Verify contest exists by checking if we can access collaborators
   const apiClient = createApiClient(cookies);
   const accessControlService = new AccessControlService(apiClient);
-  const result = await accessControlService.getContestCollaborators(contestId);
+  const result = await accessControlService.getCollaborators(ResourceType.Contests, contestId);
 
   if (!result.success) {
     if (result.status === 404) {
diff --git a/src/routes/dashboard/teacher/contests/[contestId]/collaborators/+page.svelte b/src/routes/dashboard/teacher/contests/[contestId]/collaborators/+page.svelte
index db2ea35..cfe1040 100644
--- a/src/routes/dashboard/teacher/contests/[contestId]/collaborators/+page.svelte
+++ b/src/routes/dashboard/teacher/contests/[contestId]/collaborators/+page.svelte
@@ -1,7 +1,7 @@
 <script lang="ts">
   import {
     getContestCollaborators,
-    getAllUsers,
+    getAssignableUsers,
     addCollaborator,
     updateCollaborator,
     removeCollaborator
@@ -36,7 +36,7 @@
   let { data }: Props = $props();
 
   const collaboratorsQuery = getContestCollaborators(data.contestId);
-  const usersQuery = getAllUsers();
+  const assignableUsersQuery = getAssignableUsers(data.contestId);
 
   // Get current user's permission level
   const currentUserPermission = $derived.by(() => {
@@ -68,10 +68,9 @@
       <AddContestCollaboratorButton
         contestId={data.contestId}
         {addCollaborator}
-        users={usersQuery.current}
-        usersLoading={usersQuery.loading}
-        usersError={usersQuery.error}
-        existingCollaborators={collaboratorsQuery.current}
+        users={assignableUsersQuery.current}
+        usersLoading={assignableUsersQuery.loading}
+        usersError={assignableUsersQuery.error}
       />
     </div>
   </div>
diff --git a/src/routes/dashboard/teacher/contests/[contestId]/collaborators/collaborators.remote.ts b/src/routes/dashboard/teacher/contests/[contestId]/collaborators/collaborators.remote.ts
index a8a9b05..06ebadb 100644
--- a/src/routes/dashboard/teacher/contests/[contestId]/collaborators/collaborators.remote.ts
+++ b/src/routes/dashboard/teacher/contests/[contestId]/collaborators/collaborators.remote.ts
@@ -1,8 +1,7 @@
 import { query, form, getRequestEvent } from '$app/server';
 import { createApiClient } from '$lib/services/ApiService';
 import { AccessControlService } from '$lib/services/AccessControlService';
-import { UserService } from '$lib/services/UserService';
-import { Permission } from '$lib/dto/accessControl';
+import { Permission, ResourceType } from '$lib/dto/accessControl';
 import { error } from '@sveltejs/kit';
 import * as v from 'valibot';
 
@@ -12,7 +11,7 @@ export const getContestCollaborators = query(v.number(), async (contestId: numbe
   const apiClient = createApiClient(cookies);
   const accessControlService = new AccessControlService(apiClient);
 
-  const result = await accessControlService.getContestCollaborators(contestId);
+  const result = await accessControlService.getCollaborators(ResourceType.Contests, contestId);
 
   if (!result.success || !result.data) {
     error(result.status, { message: result.error || 'Failed to load collaborators' });
@@ -21,18 +20,18 @@ export const getContestCollaborators = query(v.number(), async (contestId: numbe
   return result.data;
 });
 
-export const getAllUsers = query(async () => {
+export const getAssignableUsers = query(v.number(), async (contestId: number) => {
   const { cookies } = getRequestEvent();
 
   const apiClient = createApiClient(cookies);
-  const userService = new UserService(apiClient);
+  const accessControlService = new AccessControlService(apiClient);
 
-  // Fetch users with a high limit for client-side filtering.
-  // Client-side filtering is performed in the AddContestCollaboratorButton component.
-  const result = await userService.listUsers({ limit: 1000 });
+  const result = await accessControlService.getAssignableUsers(ResourceType.Contests, contestId, {
+    limit: 1000
+  });
 
   if (!result.success || !result.data) {
-    error(result.status, { message: result.error || 'Failed to load users' });
+    error(result.status, { message: result.error || 'Failed to load assignable users' });
   }
 
   return result.data;
@@ -50,10 +49,14 @@ export const addCollaborator = form(
     const apiClient = createApiClient(cookies);
     const accessControlService = new AccessControlService(apiClient);
 
-    const result = await accessControlService.addContestCollaborator(data.contestId, {
-      user_id: data.userId,
-      permission: data.permission
-    });
+    const result = await accessControlService.addCollaborator(
+      ResourceType.Contests,
+      data.contestId,
+      {
+        user_id: data.userId,
+        permission: data.permission
+      }
+    );
 
     if (!result.success) {
       error(result.status, { message: result.error || 'Failed to add collaborator' });
@@ -80,7 +83,8 @@ export const updateCollaborator = form(
     const apiClient = createApiClient(cookies);
     const accessControlService = new AccessControlService(apiClient);
 
-    const result = await accessControlService.updateContestCollaborator(
+    const result = await accessControlService.updateCollaborator(
+      ResourceType.Contests,
       data.contestId,
       data.userId,
       {
@@ -112,7 +116,8 @@ export const removeCollaborator = form(
     const apiClient = createApiClient(cookies);
     const accessControlService = new AccessControlService(apiClient);
 
-    const result = await accessControlService.deleteContestCollaborator(
+    const result = await accessControlService.deleteCollaborator(
+      ResourceType.Contests,
       data.contestId,
       data.userId
     );
diff --git a/src/routes/dashboard/teacher/tasks/[taskId]/+layout.server.ts b/src/routes/dashboard/teacher/tasks/[taskId]/+layout.server.ts
index 7e1f779..db5d1df 100644
--- a/src/routes/dashboard/teacher/tasks/[taskId]/+layout.server.ts
+++ b/src/routes/dashboard/teacher/tasks/[taskId]/+layout.server.ts
@@ -1,6 +1,7 @@
 import { error } from '@sveltejs/kit';
 import { createApiClient } from '$lib/services/ApiService';
 import { AccessControlService } from '$lib/services/AccessControlService';
+import { ResourceType } from '$lib/dto/accessControl';
 
 export const load = async ({
   params,
@@ -22,7 +23,7 @@ export const load = async ({
   // Verify task exists by checking if we can access collaborators
   const apiClient = createApiClient(cookies);
   const accessControlService = new AccessControlService(apiClient);
-  const result = await accessControlService.getTaskCollaborators(taskId);
+  const result = await accessControlService.getCollaborators(ResourceType.Tasks, taskId);
 
   if (!result.success) {
     if (result.status === 404) {
diff --git a/src/routes/dashboard/teacher/tasks/[taskId]/collaborators/+page.svelte b/src/routes/dashboard/teacher/tasks/[taskId]/collaborators/+page.svelte
index b118578..de28d4a 100644
--- a/src/routes/dashboard/teacher/tasks/[taskId]/collaborators/+page.svelte
+++ b/src/routes/dashboard/teacher/tasks/[taskId]/collaborators/+page.svelte
@@ -1,7 +1,7 @@
 <script lang="ts">
   import {
     getTaskCollaborators,
-    getAllUsers,
+    getAssignableUsers,
     addCollaborator,
     updateCollaborator,
     removeCollaborator
@@ -36,7 +36,7 @@
   let { data }: Props = $props();
 
   const collaboratorsQuery = getTaskCollaborators(data.taskId);
-  const usersQuery = getAllUsers();
+  const assignableUsersQuery = getAssignableUsers(data.taskId);
 
   // Get current user's permission level
   const currentUserPermission = $derived.by(() => {
@@ -68,10 +68,9 @@
       <AddCollaboratorButton
         taskId={data.taskId}
         {addCollaborator}
-        users={usersQuery.current}
-        usersLoading={usersQuery.loading}
-        usersError={usersQuery.error}
-        existingCollaborators={collaboratorsQuery.current}
+        users={assignableUsersQuery.current}
+        usersLoading={assignableUsersQuery.loading}
+        usersError={assignableUsersQuery.error}
       />
     </div>
   </div>
diff --git a/src/routes/dashboard/teacher/tasks/[taskId]/collaborators/collaborators.remote.ts b/src/routes/dashboard/teacher/tasks/[taskId]/collaborators/collaborators.remote.ts
index 639e2b7..7347b06 100644
--- a/src/routes/dashboard/teacher/tasks/[taskId]/collaborators/collaborators.remote.ts
+++ b/src/routes/dashboard/teacher/tasks/[taskId]/collaborators/collaborators.remote.ts
@@ -1,8 +1,7 @@
 import { query, form, getRequestEvent } from '$app/server';
 import { createApiClient } from '$lib/services/ApiService';
 import { AccessControlService } from '$lib/services/AccessControlService';
-import { UserService } from '$lib/services/UserService';
-import { Permission } from '$lib/dto/accessControl';
+import { Permission, ResourceType } from '$lib/dto/accessControl';
 import { error } from '@sveltejs/kit';
 import * as v from 'valibot';
 
@@ -12,7 +11,7 @@ export const getTaskCollaborators = query(v.number(), async (taskId: number) =>
   const apiClient = createApiClient(cookies);
   const accessControlService = new AccessControlService(apiClient);
 
-  const result = await accessControlService.getTaskCollaborators(taskId);
+  const result = await accessControlService.getCollaborators(ResourceType.Tasks, taskId);
 
   if (!result.success || !result.data) {
     error(result.status, { message: result.error || 'Failed to load collaborators' });
@@ -21,18 +20,18 @@ export const getTaskCollaborators = query(v.number(), async (taskId: number) =>
   return result.data;
 });
 
-export const getAllUsers = query(async () => {
+export const getAssignableUsers = query(v.number(), async (taskId: number) => {
   const { cookies } = getRequestEvent();
 
   const apiClient = createApiClient(cookies);
-  const userService = new UserService(apiClient);
+  const accessControlService = new AccessControlService(apiClient);
 
-  // Fetch users with a high limit for client-side filtering.
-  // Client-side filtering is performed in the AddCollaboratorButton component.
-  const result = await userService.listUsers({ limit: 1000 });
+  const result = await accessControlService.getAssignableUsers(ResourceType.Tasks, taskId, {
+    limit: 1000
+  });
 
   if (!result.success || !result.data) {
-    error(result.status, { message: result.error || 'Failed to load users' });
+    error(result.status, { message: result.error || 'Failed to load assignable users' });
   }
 
   return result.data;
@@ -50,7 +49,7 @@ export const addCollaborator = form(
     const apiClient = createApiClient(cookies);
     const accessControlService = new AccessControlService(apiClient);
 
-    const result = await accessControlService.addTaskCollaborator(data.taskId, {
+    const result = await accessControlService.addCollaborator(ResourceType.Tasks, data.taskId, {
       user_id: data.userId,
       permission: data.permission
     });
@@ -80,9 +79,14 @@ export const updateCollaborator = form(
     const apiClient = createApiClient(cookies);
     const accessControlService = new AccessControlService(apiClient);
 
-    const result = await accessControlService.updateTaskCollaborator(data.taskId, data.userId, {
-      permission: data.permission
-    });
+    const result = await accessControlService.updateCollaborator(
+      ResourceType.Tasks,
+      data.taskId,
+      data.userId,
+      {
+        permission: data.permission
+      }
+    );
 
     if (!result.success) {
       error(result.status, { message: result.error || 'Failed to update collaborator' });
@@ -108,7 +112,11 @@ export const removeCollaborator = form(
     const apiClient = createApiClient(cookies);
     const accessControlService = new AccessControlService(apiClient);
 
-    const result = await accessControlService.deleteTaskCollaborator(data.taskId, data.userId);
+    const result = await accessControlService.deleteCollaborator(
+      ResourceType.Tasks,
+      data.taskId,
+      data.userId
+    );
 
     if (!result.success) {
       error(result.status, { message: result.error || 'Failed to remove collaborator' });
diff --git a/src/routes/dashboard/teacher/tasks/tasks.remote.ts b/src/routes/dashboard/teacher/tasks/tasks.remote.ts
index 1538a65..2d968e2 100644
--- a/src/routes/dashboard/teacher/tasks/tasks.remote.ts
+++ b/src/routes/dashboard/teacher/tasks/tasks.remote.ts
@@ -1,4 +1,4 @@
-import { query, form, getRequestEvent } from '$app/server';
+import { query, form, command, getRequestEvent } from '$app/server';
 import { createApiClient } from '$lib/services/ApiService';
 import { TasksManagementService } from '$lib/services/TasksManagementService';
 import { error } from '@sveltejs/kit';
@@ -17,6 +17,30 @@ export const getTasks = query(async () => {
   return result.data;
 });
 
+export const toggleTaskVisibility = command(
+  v.object({
+    taskId: v.pipe(v.number(), v.integer(), v.minValue(1)),
+    isVisible: v.boolean()
+  }),
+  async (data) => {
+    const { cookies } = getRequestEvent();
+
+    const apiClient = createApiClient(cookies);
+    const tasksManagementService = new TasksManagementService(apiClient);
+
+    const result = await tasksManagementService.toggleTaskVisibility(data.taskId, data.isVisible);
+
+    if (!result.success) {
+      error(result.status, { message: result.error || 'Failed to toggle task visibility' });
+    }
+
+    // Refresh tasks list
+    await getTasks().refresh();
+
+    return { success: true };
+  }
+);
+
 export const deleteTask = form(
   v.object({
     taskId: v.pipe(v.string(), v.transform(Number), v.integer(), v.minValue(1))
diff --git a/src/routes/dashboard/teacher/tasks/upload.remote.ts b/src/routes/dashboard/teacher/tasks/upload.remote.ts
index 3b6138d..9e673c8 100644
--- a/src/routes/dashboard/teacher/tasks/upload.remote.ts
+++ b/src/routes/dashboard/teacher/tasks/upload.remote.ts
@@ -7,7 +7,8 @@ import { getTasks } from './tasks.remote';
 
 const UploadTaskSchema = v.object({
   title: v.pipe(v.string('Title is required'), v.nonEmpty('Title cannot be empty')),
-  archive: v.instance(File, 'Task archive is required')
+  archive: v.instance(File, 'Task archive is required'),
+  isVisible: v.optional(v.boolean(), false)
 });
 
 type UploadTaskData = v.InferOutput<typeof UploadTaskSchema>;
@@ -19,7 +20,8 @@ export const uploadTask = form(UploadTaskSchema, async (data: UploadTaskData) =>
 
   const result = await tasksManagementService.uploadTask({
     title: data.title,
-    archive: data.archive
+    archive: data.archive,
+    isVisible: data.isVisible ?? false
   });
   if (!result.success) {
     error(result.status, { message: result.error || 'Failed to upload task.' });
diff --git a/src/routes/dashboard/user/contests/[contestId]/results/+layout.server.ts b/src/routes/dashboard/user/contests/[contestId]/results/+layout.server.ts
index b10e728..8b2ed10 100644
--- a/src/routes/dashboard/user/contests/[contestId]/results/+layout.server.ts
+++ b/src/routes/dashboard/user/contests/[contestId]/results/+layout.server.ts
@@ -2,6 +2,7 @@ import { error } from '@sveltejs/kit';
 import { createContestService } from '$lib/services/ContestService';
 import { createApiClient } from '$lib/services/ApiService';
 import { AccessControlService } from '$lib/services/AccessControlService';
+import { ResourceType } from '$lib/dto/accessControl';
 import { UserRole } from '$lib/dto/jwt';
 import { ContestStatus } from '$lib/dto/contest';
 import * as m from '$lib/paraglide/messages';
@@ -43,7 +44,7 @@ export const load = async ({
     if (isTeacher) {
       const apiClient = createApiClient(cookies);
       const accessControlService = new AccessControlService(apiClient);
-      const result = await accessControlService.getContestCollaborators(contestId);
+      const result = await accessControlService.getCollaborators(ResourceType.Contests, contestId);
 
       if (!result.success) {
         throw error(403, m.contest_results_access_denied());