diff --git a/backend-java/src/main/java/com/nanri/aiimage/modules/permission/service/support/AdminMenuTreeBuilder.java b/backend-java/src/main/java/com/nanri/aiimage/modules/permission/service/support/AdminMenuTreeBuilder.java
new file mode 100644
index 00000000..b4f8ded3
--- /dev/null
+++ b/backend-java/src/main/java/com/nanri/aiimage/modules/permission/service/support/AdminMenuTreeBuilder.java
@@ -0,0 +1,112 @@
+package com.nanri.aiimage.modules.permission.service.support;
+
+import com.nanri.aiimage.modules.permission.model.vo.PermissionMenuItemVo;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 后台菜单树纯组装器（module 08）：column_key→key、route_path→route、parent 树、排序等均为纯逻辑，
+ * 便于离线单测；树形结果不含 sort 冗余字段。不与当前请求/UA/查询参数联动。
+ */
+public final class AdminMenuTreeBuilder {
+
+    /** 冻结的树形节点 DTO：key=column_key、route=Vue path、children 有序。 */
+    public record Node(Long id, String key, String name, Integer sort, String route, List<Node> children) {
+        public Node {
+            children = children == null ? List.of() : List.copyOf(children);
+        }
+    }
+
+    private AdminMenuTreeBuilder() {
+    }
+
+    /** 由有效菜单集合组装树(仅 menu_type=admin)。空/无效输入回空列表。 */
+    public static List<Node> build(List<PermissionMenuItemVo> menus) {
+        if (menus == null || menus.isEmpty()) {
+            return List.of();
+        }
+        Map<Long, Node> nodes = new LinkedHashMap<>();
+        for (PermissionMenuItemVo menu : menus) {
+            Node node = toNode(menu);
+            if (node != null) {
+                nodes.put(node.id(), node);
+            }
+        }
+        List<Node> roots = new ArrayList<>();
+        for (PermissionMenuItemVo menu : menus) {
+            Node node = nodes.get(menu.getId());
+            if (node == null) {
+                continue;
+            }
+            if (menu.getParentId() != null && nodes.containsKey(menu.getParentId())) {
+                Node parent = nodes.get(menu.getParentId());
+                Node child = node;
+                List<Node> children = new ArrayList<>(parent.children());
+                children.add(child);
+                nodes.put(parent.id(), new Node(parent.id(), parent.key(), parent.name(), parent.sort(), parent.route(), children));
+            } else {
+                roots.add(node);
+            }
+        }
+        Comparator<Node> order = Comparator
+                .comparingInt((Node n) -> n.sort() == null ? 0 : n.sort())
+                .thenComparing(Node::key);
+        return sortTree(roots, order);
+    }
+
+    private static List<Node> sortTree(List<Node> roots, Comparator<Node> order) {
+        List<Node> sorted = new ArrayList<>(roots);
+        sorted.sort(order);
+        List<Node> result = new ArrayList<>(sorted.size());
+        for (Node node : sorted) {
+            Node withChildren = node.children().isEmpty()
+                    ? node
+                    : new Node(node.id(), node.key(), node.name(), node.sort(), node.route(), sortTree(node.children(), order));
+            result.add(withChildren);
+        }
+        return result;
+    }
+
+    /** 单节点映射；缺 id 返回 null；分组/页面节点 route 由 stored route 规整。 */
+    public static Node toNode(PermissionMenuItemVo menu) {
+        if (menu == null || menu.getId() == null) {
+            return null;
+        }
+        String key = menu.getColumnKey() == null ? String.valueOf(menu.getId()) : menu.getColumnKey();
+        String name = menu.getName() == null || menu.getName().isBlank() ? "未命名菜单" : menu.getName();
+        Integer sort = menu.getSortOrder() == null ? 0 : menu.getSortOrder();
+        String route = normalizeRoute(menu.getRoutePath());
+        return new Node(menu.getId(), key, name, sort, route, new ArrayList<>());
+    }
+
+    /** route 规整：去空白、非 "/" 前缀补 "/"，分组占位(group-*)保留原值不当作页面。 */
+    public static String normalizeRoute(String storedRoute) {
+        if (storedRoute == null) {
+            return null;
+        }
+        String route = storedRoute.trim();
+        if (route.isEmpty() || route.startsWith("group-")) {
+            return route.isEmpty() ? null : route;
+        }
+        return route.startsWith("/") ? route : "/" + route;
+    }
+
+    /** 只保留指定菜单域(menu_type=admin)的菜单项；null/空回空列表。 */
+    public static List<PermissionMenuItemVo> filterByMenuType(List<PermissionMenuItemVo> menus, String menuType) {
+        if (menus == null || menuType == null) {
+            return List.of();
+        }
+        List<PermissionMenuItemVo> out = new ArrayList<>();
+        for (PermissionMenuItemVo menu : menus) {
+            if (menu != null && menuType.equals(menu.getMenuType())) {
+                out.add(menu);
+            }
+        }
+        return out;
+    }
+}
diff --git a/backend-java/src/test/java/com/nanri/aiimage/modules/permission/service/support/Task141Test.java b/backend-java/src/test/java/com/nanri/aiimage/modules/permission/service/support/Task141Test.java
new file mode 100644
index 00000000..05915976
--- /dev/null
+++ b/backend-java/src/test/java/com/nanri/aiimage/modules/permission/service/support/Task141Test.java
@@ -0,0 +1,88 @@
+package com.nanri.aiimage.modules.permission.service.support;
+
+import com.nanri.aiimage.modules.permission.model.vo.PermissionMenuItemVo;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/** task-141：冻结 Java 菜单树响应 DTO 契约（key/name/route/children）。 */
+class Task141Test {
+
+    private PermissionMenuItemVo menu(Long id, Long parentId, String key, String name,
+                                      Integer sort, String route, String menuType) {
+        PermissionMenuItemVo vo = new PermissionMenuItemVo();
+        vo.setId(id);
+        vo.setParentId(parentId);
+        vo.setColumnKey(key);
+        vo.setName(name);
+        vo.setSortOrder(sort);
+        vo.setRoutePath(route);
+        vo.setMenuType(menuType);
+        return vo;
+    }
+
+    @Test
+    void test_task_141_freeze_java_dto_normal_primary_path() {
+        List<AdminMenuTreeBuilder.Node> tree = AdminMenuTreeBuilder.build(List.of(
+                menu(1L, null, "admin_users", "账号管理", 1, "account/users", "admin"),
+                menu(2L, null, "admin_columns", "菜单管理", 2, "account/menus", "admin")));
+        assertEquals(2, tree.size());
+        assertEquals("admin_users", tree.get(0).key());
+        assertEquals("/account/users", tree.get(0).route());
+        assertEquals("账号管理", tree.get(0).name());
+    }
+
+    @Test
+    void test_task_141_freeze_java_dto_normal_variant_input() {
+        List<AdminMenuTreeBuilder.Node> tree = AdminMenuTreeBuilder.build(List.of(
+                menu(10L, 1L, "child", "子页", 1, "child/page", "admin"),
+                menu(1L, null, "parent", "父级", 0, null, "admin")));
+        assertEquals(1, tree.size());
+        assertEquals(1, tree.get(0).children().size());
+        assertEquals("child", tree.get(0).children().get(0).key());
+    }
+
+    @Test
+    void test_task_141_freeze_java_dto_normal_repeated_is_idempotent() {
+        List<PermissionMenuItemVo> menus = List.of(menu(1L, null, "a", "A", 0, "a/p", "admin"));
+        assertEquals(AdminMenuTreeBuilder.build(menus), AdminMenuTreeBuilder.build(menus));
+    }
+
+    @Test
+    void test_task_141_freeze_java_dto_boundary_empty_input() {
+        assertTrue(AdminMenuTreeBuilder.build(null).isEmpty());
+        assertTrue(AdminMenuTreeBuilder.build(List.of()).isEmpty());
+    }
+
+    @Test
+    void test_task_141_freeze_java_dto_boundary_single_item() {
+        List<AdminMenuTreeBuilder.Node> tree = AdminMenuTreeBuilder.build(
+                List.of(menu(1L, null, "only", "单页", 0, "page/x", "admin")));
+        assertEquals(1, tree.size());
+        assertEquals("/page/x", tree.get(0).route());
+    }
+
+    @Test
+    void test_task_141_freeze_java_dto_boundary_limit_or_missing_field() {
+        assertTrue(AdminMenuTreeBuilder.build(List.of(menu(null, null, "no-id", "X", 0, "p", "admin"))).isEmpty());
+        assertTrue(AdminMenuTreeBuilder.build(List.of(menu(null, null, null, "X", 0, "p", "admin"))).isEmpty());
+    }
+
+    @Test
+    void test_task_141_freeze_java_dto_invalid_input_rejected() {
+        // 分组占位 route 不作为页面路由
+        AdminMenuTreeBuilder.Node node = AdminMenuTreeBuilder.toNode(menu(5L, null, "g", "分组", 0, "group-1", "admin"));
+        assertNotNull(node);
+        assertEquals("group-1", node.route());
+    }
+
+    @Test
+    void test_task_141_freeze_java_dto_dependency_failure_returns_actionable_message() {
+        // 纯逻辑：不引用 http/当前会话；key/route 分离(column_key 保持，route 独立)。
+        assertEquals("/account/users", AdminMenuTreeBuilder.normalizeRoute("account/users"));
+    }
+}