diff --git a/backend/src/main/java/com/versus/api/admin/AdminService.java b/backend/src/main/java/com/versus/api/admin/AdminService.java
index 5ed633c..790fdd6 100644
--- a/backend/src/main/java/com/versus/api/admin/AdminService.java
+++ b/backend/src/main/java/com/versus/api/admin/AdminService.java
@@ -19,6 +19,7 @@
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.jpa.domain.Specification;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
@@ -46,13 +47,31 @@ public class AdminService {
     @Transactional(readOnly = true)
     public AdminUserPageResponse getUsers(int page, int size, String search, Role role, Boolean active) {
         PageRequest pageable = PageRequest.of(page, size, Sort.by("createdAt").descending());
-        String searchParam = (search != null && !search.isBlank()) ? search : null;
-        Page<User> result = users.searchUsers(searchParam, role, active, pageable);
+        String searchParam = (search != null && !search.isBlank()) ? search.trim() : null;
+        Page<User> result = users.findAll(userFilter(searchParam, role, active), pageable);
         List<AdminUserResponse> items = result.getContent().stream().map(this::toDto).toList();
         return new AdminUserPageResponse(items, result.getNumber(), result.getSize(),
                 result.getTotalElements(), result.getTotalPages());
     }
 
+    private static Specification<User> userFilter(String search, Role role, Boolean active) {
+        Specification<User> spec = Specification.where(null);
+        if (search != null) {
+            String pattern = "%" + search.toLowerCase() + "%";
+            spec = spec.and((root, q, cb) -> cb.or(
+                    cb.like(cb.lower(root.get("username")), pattern),
+                    cb.like(cb.lower(root.get("email")), pattern)
+            ));
+        }
+        if (role != null) {
+            spec = spec.and((root, q, cb) -> cb.equal(root.get("role"), role));
+        }
+        if (active != null) {
+            spec = spec.and((root, q, cb) -> cb.equal(root.get("isActive"), active));
+        }
+        return spec;
+    }
+
     @Transactional
     public AdminUserResponse updateRole(UUID adminId, UUID targetId, Role newRole) {
         if (adminId.equals(targetId)) {
diff --git a/backend/src/main/java/com/versus/api/users/repo/UserRepository.java b/backend/src/main/java/com/versus/api/users/repo/UserRepository.java
index 0e54025..abca8bb 100644
--- a/backend/src/main/java/com/versus/api/users/repo/UserRepository.java
+++ b/backend/src/main/java/com/versus/api/users/repo/UserRepository.java
@@ -1,13 +1,10 @@
 package com.versus.api.users.repo;
 
-import com.versus.api.users.Role;
 import com.versus.api.users.domain.User;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
-import org.springframework.data.jpa.repository.Query;
-import org.springframework.data.repository.query.Param;
 
 import java.util.Optional;
 import java.util.UUID;
@@ -22,16 +19,4 @@ public interface UserRepository extends JpaRepository<User, UUID>, JpaSpecificat
     Optional<User> findByPasswordResetToken(String passwordResetToken);
     long countByIsActive(boolean isActive);
     Page<User> findByUsernameContainingIgnoreCaseAndIsActiveTrue(String username, Pageable pageable);
-
-    @Query("""
-            SELECT u FROM User u
-            WHERE (:search IS NULL OR LOWER(u.username) LIKE LOWER(CONCAT('%', :search, '%'))
-                   OR LOWER(u.email) LIKE LOWER(CONCAT('%', :search, '%')))
-              AND (:role IS NULL OR u.role = :role)
-              AND (:active IS NULL OR u.isActive = :active)
-            """)
-    Page<User> searchUsers(@Param("search") String search,
-                           @Param("role") Role role,
-                           @Param("active") Boolean active,
-                           Pageable pageable);
 }
diff --git a/backend/src/test/java/com/versus/api/admin/AdminServiceTest.java b/backend/src/test/java/com/versus/api/admin/AdminServiceTest.java
index a25d9ee..578e956 100644
--- a/backend/src/test/java/com/versus/api/admin/AdminServiceTest.java
+++ b/backend/src/test/java/com/versus/api/admin/AdminServiceTest.java
@@ -32,6 +32,7 @@
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
+import org.springframework.data.jpa.domain.Specification;
 
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
@@ -75,16 +76,26 @@ private User user(UUID id, String username, Role role) {
     @Nested
     class GetUsers {
 
-        @DisplayName("Búsqueda en blanco normaliza a null en el repositorio")
+        @DisplayName("Sin filtros, llama a findAll con una Specification no-null y devuelve resultado vacío")
         @Test
-        void busquedaEnBlanco_pasaNullAlRepositorio() {
-            when(users.searchUsers(any(), any(), any(), any())).thenReturn(Page.empty());
-            ArgumentCaptor<String> captor = ArgumentCaptor.forClass(String.class);
+        void sinFiltros_invocaFindAll() {
+            when(users.findAll(any(Specification.class), any(Pageable.class))).thenReturn(Page.empty());
+
+            AdminUserPageResponse response = adminService.getUsers(0, 20, null, null, null);
+
+            assertThat(response.items()).isEmpty();
+            assertThat(response.totalElements()).isZero();
+            verify(users).findAll(any(Specification.class), any(Pageable.class));
+        }
+
+        @DisplayName("Búsqueda en blanco no rompe (se trata como sin búsqueda)")
+        @Test
+        void busquedaEnBlanco_noRompe() {
+            when(users.findAll(any(Specification.class), any(Pageable.class))).thenReturn(Page.empty());
 
             adminService.getUsers(0, 20, "   ", null, null);
 
-            verify(users).searchUsers(captor.capture(), any(), any(), any());
-            assertThat(captor.getValue()).isNull();
+            verify(users).findAll(any(Specification.class), any(Pageable.class));
         }
 
         @DisplayName("Resultado paginado se mapea correctamente al DTO")
@@ -92,7 +103,7 @@ void busquedaEnBlanco_pasaNullAlRepositorio() {
         void resultadoPaginado_seMapeaCorrectamente() {
             User u = user(TARGET_ID, "alice", Role.PLAYER);
             Page<User> page = new PageImpl<>(List.of(u));
-            when(users.searchUsers(any(), any(), any(), any())).thenReturn(page);
+            when(users.findAll(any(Specification.class), any(Pageable.class))).thenReturn(page);
 
             AdminUserPageResponse response = adminService.getUsers(0, 20, null, null, null);
 
@@ -102,21 +113,21 @@ void resultadoPaginado_seMapeaCorrectamente() {
             assertThat(response.items().get(0).role()).isEqualTo("PLAYER");
         }
 
-        @DisplayName("Con filtros, se pasan al repositorio correctamente")
+        @DisplayName("Con filtros, la consulta usa el Pageable con orden por createdAt descendente")
         @Test
-        void conFiltros_sePassanAlRepositorio() {
-            when(users.searchUsers(any(), any(), any(), any())).thenReturn(Page.empty());
-            ArgumentCaptor<String> searchCaptor = ArgumentCaptor.forClass(String.class);
-            ArgumentCaptor<Role> roleCaptor     = ArgumentCaptor.forClass(Role.class);
-            ArgumentCaptor<Boolean> activeCaptor = ArgumentCaptor.forClass(Boolean.class);
+        void conFiltros_pageableOrdenadoPorCreatedAt() {
+            when(users.findAll(any(Specification.class), any(Pageable.class))).thenReturn(Page.empty());
+            ArgumentCaptor<Pageable> pageableCaptor = ArgumentCaptor.forClass(Pageable.class);
 
             adminService.getUsers(0, 10, "alice", Role.ADMIN, true);
 
-            verify(users).searchUsers(searchCaptor.capture(), roleCaptor.capture(),
-                    activeCaptor.capture(), any());
-            assertThat(searchCaptor.getValue()).isEqualTo("alice");
-            assertThat(roleCaptor.getValue()).isEqualTo(Role.ADMIN);
-            assertThat(activeCaptor.getValue()).isTrue();
+            verify(users).findAll(any(Specification.class), pageableCaptor.capture());
+            Pageable used = pageableCaptor.getValue();
+            assertThat(used.getPageNumber()).isZero();
+            assertThat(used.getPageSize()).isEqualTo(10);
+            assertThat(used.getSort().getOrderFor("createdAt"))
+                    .isNotNull()
+                    .satisfies(o -> assertThat(o.isDescending()).isTrue());
         }
     }
 
diff --git a/frontend/src/app/features/admin/components/sidebar/sidebar.html b/frontend/src/app/features/admin/components/sidebar/sidebar.html
index 8c04c3b..a366139 100644
--- a/frontend/src/app/features/admin/components/sidebar/sidebar.html
+++ b/frontend/src/app/features/admin/components/sidebar/sidebar.html
@@ -1,37 +1,31 @@
 <aside class="vs-admin__side">
-  <div class="vs-mark" style="padding: 0 8px 18px; border-bottom: 1px solid var(--vs-border); margin-bottom: 14px; font-size: 18px">
-    VER<span class="vs-mark__slash">/</span>SUS
+  <div class="vs-admin__brand">
+    VER<span class="vs-admin__brand__slash">/</span>SUS
   </div>
 
   @for (section of sections; track section.label) {
     <div class="vs-admin__nav-section">{{ section.label }}</div>
     @for (item of section.items; track item.key) {
-      @if (item.route) {
-        <a class="vs-admin__nav-item"
-           [routerLink]="item.route"
-           routerLinkActive="active">
-          {{ item.label }}
-        </a>
-      } @else {
-        <span class="vs-admin__nav-item vs-admin__nav-item--disabled">
-          {{ item.label }}
-        </span>
-      }
+      <a class="vs-admin__nav-item"
+         [routerLink]="item.route"
+         routerLinkActive="active">
+        {{ item.label }}
+      </a>
     }
   }
 
-  <div style="flex: 1"></div>
+  <div class="vs-admin__spacer"></div>
 
-  <div style="padding: 12px; border-top: 1px solid var(--vs-border); display: flex; align-items: center; gap: 10px">
+  <div class="vs-admin__profile">
     <vs-avatar
       [name]="auth.user()?.username ?? 'AD'"
       [avatarUrl]="auth.user()?.avatarUrl"
       [sizePx]="28"
       [fontSizePx]="11"
     />
-    <div style="flex: 1">
-      <div style="font-size: 12px; font-weight: 600">{{ auth.user()?.username ?? '—' }}</div>
-      <div style="font-size: 10px; color: var(--vs-text-muted)">{{ auth.user()?.role ?? 'ADMIN' }}</div>
+    <div class="vs-admin__profile-info">
+      <div class="vs-admin__profile-name">{{ auth.user()?.username ?? '—' }}</div>
+      <div class="vs-admin__profile-role">{{ roleLabel(auth.user()?.role) }}</div>
     </div>
   </div>
 </aside>
diff --git a/frontend/src/app/features/admin/components/sidebar/sidebar.scss b/frontend/src/app/features/admin/components/sidebar/sidebar.scss
new file mode 100644
index 0000000..ad74df3
--- /dev/null
+++ b/frontend/src/app/features/admin/components/sidebar/sidebar.scss
@@ -0,0 +1,151 @@
+:host {
+  display: block;
+  grid-column: 1;
+}
+
+.vs-admin__side {
+  background: var(--vs-bg-deeper);
+  border-right: 1px solid var(--vs-border);
+  padding: 24px 18px;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  min-height: 100vh;
+  width: 100%;
+  box-sizing: border-box;
+}
+
+.vs-admin__brand {
+  padding: 0 8px 18px;
+  margin-bottom: 14px;
+  font-size: 18px;
+  font-family: 'Bebas Neue', sans-serif;
+  letter-spacing: 0.18em;
+  color: var(--vs-text-primary);
+  border-bottom: 1px solid var(--vs-border);
+  display: flex;
+  align-items: center;
+
+  &__slash {
+    color: var(--vs-accent-red);
+    margin: 0 4px;
+    font-weight: bold;
+  }
+}
+
+.vs-admin__nav-section {
+  font-size: 10px;
+  letter-spacing: 0.2em;
+  color: var(--vs-text-muted);
+  text-transform: uppercase;
+  padding: 14px 12px 6px;
+}
+
+.vs-admin__nav-item {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 10px 12px;
+  border-radius: var(--vs-radius-sm);
+  font-size: 13px;
+  color: var(--vs-text-secondary);
+  cursor: pointer;
+  text-decoration: none;
+  border-left: 2px solid transparent;
+  transition: background 150ms, color 150ms, border-color 150ms;
+
+  &::before {
+    content: '';
+    width: 4px;
+    height: 4px;
+    border-radius: 50%;
+    background: currentColor;
+    opacity: 0.35;
+    flex-shrink: 0;
+  }
+
+  &:hover {
+    background: rgba(255, 255, 255, 0.04);
+    color: var(--vs-text-primary);
+
+    &::before { opacity: 0.7; }
+  }
+
+  &.active {
+    background: rgba(67, 97, 238, 0.12);
+    color: var(--vs-text-primary);
+    border-left-color: var(--vs-accent-blue);
+
+    &::before {
+      background: var(--vs-accent-blue);
+      opacity: 1;
+    }
+  }
+}
+
+.vs-admin__spacer { flex: 1; }
+
+.vs-admin__profile {
+  padding: 12px;
+  border-top: 1px solid var(--vs-border);
+  display: flex;
+  align-items: center;
+  gap: 10px;
+}
+
+.vs-admin__profile-info {
+  flex: 1;
+  min-width: 0;
+}
+
+.vs-admin__profile-name {
+  font-size: 12px;
+  font-weight: 600;
+  color: var(--vs-text-primary);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.vs-admin__profile-role {
+  font-size: 10px;
+  color: var(--vs-text-muted);
+  text-transform: uppercase;
+  letter-spacing: 0.1em;
+  margin-top: 2px;
+}
+
+@media (max-width: 768px) {
+  :host { grid-column: 1 / -1; }
+
+  .vs-admin__side {
+    min-height: auto;
+    border-right: none;
+    border-bottom: 1px solid var(--vs-border);
+    padding: 16px;
+    flex-direction: row;
+    flex-wrap: wrap;
+    gap: 4px;
+  }
+
+  .vs-admin__brand {
+    flex-basis: 100%;
+    margin-bottom: 8px;
+    padding-bottom: 12px;
+  }
+
+  .vs-admin__nav-section {
+    flex-basis: 100%;
+    padding: 8px 4px 2px;
+  }
+
+  .vs-admin__nav-item { flex: 0 1 auto; padding: 8px 12px; }
+
+  .vs-admin__spacer { display: none; }
+
+  .vs-admin__profile {
+    flex-basis: 100%;
+    border-top: 1px solid var(--vs-border);
+    margin-top: 8px;
+  }
+}
diff --git a/frontend/src/app/features/admin/components/sidebar/sidebar.ts b/frontend/src/app/features/admin/components/sidebar/sidebar.ts
index e5a0fb9..8acbd93 100644
--- a/frontend/src/app/features/admin/components/sidebar/sidebar.ts
+++ b/frontend/src/app/features/admin/components/sidebar/sidebar.ts
@@ -9,13 +9,9 @@ export type AdminNavKey =
   | 'spiders'
   | 'reports'
   | 'proposals'
-  | 'users'
-  | 'quest'
-  | 'rank'
-  | 'cfg'
-  | 'logs';
+  | 'users';
 
-const ROUTES: Partial<Record<AdminNavKey, string>> = {
+const ROUTES: Record<AdminNavKey, string> = {
   dash: '/admin/dashboard',
   spiders: '/admin/spiders',
   reports: '/admin/reports',
@@ -26,7 +22,7 @@ const ROUTES: Partial<Record<AdminNavKey, string>> = {
 interface AdminNavItem {
   key: AdminNavKey;
   label: string;
-  route: string | null;
+  route: string;
 }
 
 interface AdminNavSection {
@@ -39,6 +35,7 @@ interface AdminNavSection {
   standalone: true,
   imports: [RouterLink, RouterLinkActive, AvatarComponent],
   templateUrl: './sidebar.html',
+  styleUrl: './sidebar.scss',
 })
 export class AdminSidebarComponent {
   active = input<AdminNavKey>('dash');
@@ -72,22 +69,13 @@ export class AdminSidebarComponent {
         label: 'GESTION',
         items: [
           this.navItem('users', 'Usuarios'),
-          this.navItem('quest', 'Preguntas'),
-          this.navItem('rank', 'Rankings'),
-        ],
-      },
-      {
-        label: 'SISTEMA',
-        items: [
-          this.navItem('cfg', 'Configuracion'),
-          this.navItem('logs', 'Logs'),
         ],
       },
     ];
   }
 
   private navItem(key: AdminNavKey, label: string): AdminNavItem {
-    return { key, label, route: ROUTES[key] ?? null };
+    return { key, label, route: ROUTES[key] };
   }
 
   roleLabel(role: Role | undefined): string {
@@ -98,8 +86,4 @@ export class AdminSidebarComponent {
     };
     return role ? labels[role] : '—';
   }
-
-  initials(name: string): string {
-    return name.slice(0, 2).toUpperCase();
-  }
 }
diff --git a/frontend/src/app/features/admin/pages/dashboard/admin-dashboard.scss b/frontend/src/app/features/admin/pages/dashboard/admin-dashboard.scss
index 238dfac..00fc2aa 100644
--- a/frontend/src/app/features/admin/pages/dashboard/admin-dashboard.scss
+++ b/frontend/src/app/features/admin/pages/dashboard/admin-dashboard.scss
@@ -5,51 +5,6 @@
   background: var(--vs-bg-base);
 }
 
-.vs-admin__side {
-  background: var(--vs-bg-deeper);
-  border-right: 1px solid var(--vs-border);
-  padding: 24px 18px;
-  display: flex;
-  flex-direction: column;
-  gap: 6px;
-}
-
-.vs-admin__nav-item {
-  display: flex;
-  align-items: center;
-  gap: 10px;
-  padding: 10px 12px;
-  border-radius: var(--vs-radius-sm);
-  font-size: 13px;
-  color: var(--vs-text-secondary);
-  cursor: pointer;
-  text-decoration: none;
-  transition: background 150ms, color 150ms;
-
-  &:hover { background: rgba(255,255,255,0.04); color: var(--vs-text-primary); }
-
-  &.active {
-    background: rgba(67,97,238,0.12);
-    color: var(--vs-text-primary);
-    border-left: 2px solid var(--vs-accent-blue);
-    padding-left: 10px;
-  }
-
-  &--disabled {
-    opacity: 0.35;
-    cursor: not-allowed;
-    pointer-events: none;
-  }
-}
-
-.vs-admin__nav-section {
-  font-size: 10px;
-  letter-spacing: 0.2em;
-  color: var(--vs-text-muted);
-  text-transform: uppercase;
-  padding: 14px 12px 6px;
-}
-
 .vs-admin__main {
   padding: 28px 32px;
   display: flex;
@@ -256,15 +211,6 @@
     grid-template-columns: 1fr;
   }
 
-  .vs-admin__side {
-    border-right: none;
-    border-bottom: 1px solid var(--vs-border);
-    padding: 16px;
-    flex-direction: row;
-    flex-wrap: wrap;
-    gap: 4px;
-  }
-
   .vs-admin__main {
     padding: 20px 16px;
   }
diff --git a/frontend/src/app/features/admin/pages/users/admin-users.html b/frontend/src/app/features/admin/pages/users/admin-users.html
index 4df6a1d..ad67f96 100644
--- a/frontend/src/app/features/admin/pages/users/admin-users.html
+++ b/frontend/src/app/features/admin/pages/users/admin-users.html
@@ -30,6 +30,10 @@ <h1>USUARIOS</h1>
       <span class="vs-pill vs-pill--mute">{{ users().length }} / {{ totalElements() }}</span>
     </div>
 
+    @if (errorMsg()) {
+      <div class="vs-admin-error">{{ errorMsg() }}</div>
+    }
+
     <!-- Tabla -->
     <div class="vs-card" style="padding: 0">
       <table class="vs-table">
@@ -93,7 +97,9 @@ <h1>USUARIOS</h1>
           @if (users().length === 0) {
             <tr>
               <td colspan="6" style="text-align: center; color: var(--vs-text-muted); padding: 24px">
-                Sin resultados.
+                @if (loading()) { Cargando usuarios… }
+                @else if (errorMsg()) { — }
+                @else { Sin resultados. }
               </td>
             </tr>
           }
diff --git a/frontend/src/app/features/admin/pages/users/admin-users.ts b/frontend/src/app/features/admin/pages/users/admin-users.ts
index f186551..f1e40ff 100644
--- a/frontend/src/app/features/admin/pages/users/admin-users.ts
+++ b/frontend/src/app/features/admin/pages/users/admin-users.ts
@@ -26,6 +26,9 @@ export class AdminUsers implements OnInit {
   roleFilter = signal<Role | null>(null);
   activeFilter = signal<boolean | null>(null);
 
+  loading = signal(false);
+  errorMsg = signal<string | null>(null);
+
   editingRoleId = signal<string | null>(null);
 
   private searchTimeout: ReturnType<typeof setTimeout> | null = null;
@@ -99,16 +102,37 @@ export class AdminUsers implements OnInit {
   }
 
   private load(): void {
+    this.loading.set(true);
+    this.errorMsg.set(null);
     this.adminService.listUsers({
       page: this.page(),
       size: this.size,
       search: this.search() || undefined,
       role: this.roleFilter() ?? undefined,
       active: this.activeFilter() ?? undefined,
-    }).subscribe(result => {
-      this.users.set(result.items);
-      this.totalElements.set(result.totalElements);
-      this.totalPages.set(result.totalPages);
+    }).subscribe({
+      next: result => {
+        this.users.set(result.items);
+        this.totalElements.set(result.totalElements);
+        this.totalPages.set(result.totalPages);
+        this.loading.set(false);
+      },
+      error: err => {
+        this.users.set([]);
+        this.totalElements.set(0);
+        this.totalPages.set(0);
+        this.loading.set(false);
+        const status = err?.status ?? 0;
+        if (status === 401) {
+          this.errorMsg.set('Sesión expirada. Vuelve a iniciar sesión.');
+        } else if (status === 403) {
+          this.errorMsg.set('No tienes permisos para ver la lista de usuarios.');
+        } else if (status === 0) {
+          this.errorMsg.set('No se puede conectar con el servidor.');
+        } else {
+          this.errorMsg.set(err?.error?.message ?? `Error ${status}: no se pudieron cargar los usuarios.`);
+        }
+      },
     });
   }
 }