diff --git a/backend/app/services/mom_cache.py b/backend/app/services/mom_cache.py
new file mode 100644
index 0000000..cdbbbe4
--- /dev/null
+++ b/backend/app/services/mom_cache.py
@@ -0,0 +1,154 @@
+"""
+MOM 跨库查询缓存模块 — 使用本地 TTL 缓存消除冗余跨库请求
+
+解决的问题：
+  1. _lookup_display_names 在 get_all_products 中被调用 3 次，每次都打开/关闭
+     MOM 数据库连接，150 条产品的列表页 = 3 根管线查询。
+  2. 同一批 username 在短时间内（用户翻页、多人同时访问）被反复查询。
+  3. 旧实现用 OR 拼接 LIKE 条件，存在注入风险。
+
+方案：python -m 内置模块（零依赖）实现线程安全 TTL 缓存 + 参数化 ANY 查询。
+
+TTL: 2 小时（人员姓名不会频繁变动，可调）。
+"""
+from __future__ import annotations
+
+import threading
+import time
+
+from app.core.mom_database import MomSessionLocal
+
+
+# ============================================================
+# 零依赖 TTL 缓存（线程安全）
+# ============================================================
+
+class _TTLCache:
+    """线程安全的内存 TTL 缓存，用于 MOM 只读查询结果"""
+
+    def __init__(self, ttl_seconds: int = 7200) -> None:
+        self._store: dict[str, str] = {}
+        self._expiry: dict[str, float] = {}
+        self._ttl = ttl_seconds
+        self._lock = threading.RLock()
+
+    def get_many(self, keys: list[str]) -> tuple[dict[str, str], list[str]]:
+        """
+        批量获取 → (命中字典, 未命中 key 列表)。
+
+        内部自动清理过期条目。
+        """
+        hits: dict[str, str] = {}
+        missed: list[str] = []
+        now = time.monotonic()
+
+        with self._lock:
+            for k in keys:
+                exp = self._expiry.get(k)
+                if exp is not None and now < exp:
+                    hits[k] = self._store[k]
+                else:
+                    missed.append(k)
+                    # 清理过期残留
+                    if k in self._store:
+                        del self._store[k]
+                        del self._expiry[k]
+
+        return hits, missed
+
+    def set_many(self, mapping: dict[str, str]) -> None:
+        """批量写入，所有 key 共享同一过期时间"""
+        expiry = time.monotonic() + self._ttl
+        with self._lock:
+            for k, v in mapping.items():
+                self._store[k] = v
+                self._expiry[k] = expiry
+
+
+# ============================================================
+# 全局缓存实例（2h TTL）
+# ============================================================
+
+_user_name_cache = _TTLCache(ttl_seconds=7200)
+
+
+# ============================================================
+# 公开 API
+# ============================================================
+
+def get_display_names(user_ids: list[str]) -> dict[str, str]:
+    """
+    批量查询 MOM sys_user，将 username 映射为真实姓名（带 2h TTL 缓存）。
+
+    缓存穿透流程：
+      1. 去重 → 从缓存批量读取
+      2. 计算 miss 差集
+      3. miss 非空时，用参数化 ANY(:user_ids) 查 MOM（1 条 SQL）
+      4. 写回缓存
+      5. 合并 hits + fresh 返回
+
+    参数:
+        user_ids: 短用户名列表，如 ["zhangsan01", "lisi02"]
+
+    返回:
+        {"zhangsan01": "张三", "lisi02": "李四"}
+        不存在的 key 不会出现在返回字典中。
+
+    SQL 安全:
+        使用 SPLIT_PART(username, '/', 2) = ANY(:user_ids) 参数化查询，
+        杜绝旧实现中 OR 拼接 LIKE 的注入风险。
+    """
+    if not user_ids:
+        return {}
+
+    # 过滤特殊值 + 去重保序
+    seen: set[str] = set()
+    real_ids: list[str] = []
+    for uid in user_ids:
+        if uid and uid != "virtual_warehouse" and uid not in seen:
+            seen.add(uid)
+            real_ids.append(uid)
+
+    if not real_ids:
+        return {}
+
+    # ── Step 1: 批量查缓存 ──
+    hits, missed = _user_name_cache.get_many(real_ids)
+
+    # ── Step 2: 仅对 miss 查 MOM ──
+    if missed:
+        db = MomSessionLocal()
+        try:
+            from sqlalchemy import text
+
+            # 参数化 ANY 查询 — 安全防注入
+            # SPLIT_PART('张三/zhangsan01', '/', 2) = 'zhangsan01'
+            # OR username = ANY(...) 兜底无斜杠的用户名（如 admin）
+            sql = text("""
+                SELECT username,
+                       SPLIT_PART(username, '/', 1) AS display_name
+                FROM sys_user
+                WHERE SPLIT_PART(username, '/', 2) = ANY(:user_ids)
+                   OR username = ANY(:user_ids)
+            """)
+            result = db.execute(sql, {"user_ids": missed})
+            rows = result.fetchall()
+        finally:
+            db.close()
+
+        # ── Step 3: 解析结果 + 写回缓存 ──
+        fresh: dict[str, str] = {}
+        for row in rows:
+            full_username: str = row[0]
+            display_name: str = row[1]
+            # "张三/zhangsan01" → short="zhangsan01"
+            short = full_username.split("/")[-1] if "/" in full_username else full_username
+            fresh[short] = display_name
+
+        if fresh:
+            _user_name_cache.set_many(fresh)
+
+        # ── Step 4: 合并 ──
+        hits.update(fresh)
+
+    return hits
diff --git a/backend/app/services/product_service.py b/backend/app/services/product_service.py
index a30275b..71207d3 100644
--- a/backend/app/services/product_service.py
+++ b/backend/app/services/product_service.py
@@ -46,35 +46,10 @@ def _task_to_response(task: Task) -> TaskResponse:
 
 
 async def _load_task_tree(db: AsyncSession, product_id: uuid.UUID) -> list[TaskResponse]:
-    """递归加载产品下的完整任务树"""
-    # 先取顶层任务
-    result = await db.execute(
-        select(Task)
-        .options(selectinload(Task.child_tasks), selectinload(Task.records))
-        .where(
-            Task.product_id == product_id,
-            Task.parent_task_id.is_(None),
-        )
-        .order_by(Task.created_at)
-    )
-    top_tasks = result.scalars().all()
-
-    # 递归加载每层子任务
-    async def _load_children(t: Task):
-        for child in t.child_tasks:
-            child_result = await db.execute(
-                select(Task)
-                .options(selectinload(Task.child_tasks), selectinload(Task.records))
-                .where(Task.id == child.id)
-            )
-            refreshed = child_result.scalar_one()
-            t.child_tasks[t.child_tasks.index(child)] = refreshed
-            await _load_children(refreshed)
-
-    for task in top_tasks:
-        await _load_children(task)
-
-    return [_task_to_response(t) for t in top_tasks]
+    """使用 PostgreSQL Recursive CTE 一次性加载产品下完整任务树（消除 N+1）"""
+    from app.services.task_tree_loader import load_task_trees_by_product
+    tasks = await load_task_trees_by_product(db, product_id)
+    return [_task_to_response(t) for t in tasks]
 
 
 async def get_product_by_serial(db: AsyncSession, serial_number: str) -> ProductScanResponse:
@@ -344,32 +319,9 @@ async def update_overall_status(
 
 
 def _lookup_display_names(location_ids: list[str]) -> dict[str, str]:
-    """批量查询 MOM sys_user，将 username 映射为真实姓名"""
-    if not location_ids:
-        return {}
-    from app.core.mom_database import MomSessionLocal
-    from sqlalchemy import text
-    db = MomSessionLocal()
-    try:
-        # 过滤掉特殊值
-        real_ids = [uid for uid in location_ids if uid and uid != "virtual_warehouse"]
-        if not real_ids:
-            return {}
-        # 用 LIKE 模糊匹配批量查出
-        conditions = " OR ".join([f"username LIKE '%/{uid}'" for uid in real_ids])
-        result = db.execute(
-            text(f"SELECT username, SPLIT_PART(username, '/', 1) as display_name FROM sys_user WHERE {conditions}")
-        )
-        mapping = {}
-        for row in result:
-            full_username = row[0]
-            display_name = row[1]
-            # 从 full_username 末尾提取短用户名: "张三/zhangsan01" → "zhangsan01"
-            short = full_username.split("/")[-1] if "/" in full_username else full_username
-            mapping[short] = display_name
-        return mapping
-    finally:
-        db.close()
+    """批量查询 MOM sys_user，将 username 映射为真实姓名（带 2h TTL 缓存）"""
+    from app.services.mom_cache import get_display_names
+    return get_display_names(location_ids)
 
 
 async def get_all_products(
diff --git a/backend/app/services/task_service.py b/backend/app/services/task_service.py
index 91803ff..cdc88df 100644
--- a/backend/app/services/task_service.py
+++ b/backend/app/services/task_service.py
@@ -125,39 +125,9 @@ async def _get_task_or_404(db: AsyncSession, task_id: uuid.UUID) -> Task:
 
 
 async def _get_task_with_children_recursive(db: AsyncSession, task_id: uuid.UUID) -> Task:
-    """递归加载任务及其所有子孙任务"""
-    result = await db.execute(
-        select(Task)
-        .options(
-            selectinload(Task.child_tasks),
-            selectinload(Task.records),
-        )
-        .where(Task.id == task_id)
-    )
-    task = result.scalar_one_or_none()
-    if not task:
-        raise HTTPException(
-            status_code=status.HTTP_404_NOT_FOUND,
-            detail=f"任务不存在: {task_id}",
-        )
-
-    # 递归加载每一层子任务
-    async def _load_children(t: Task):
-        for child in t.child_tasks:
-            child_result = await db.execute(
-                select(Task)
-                .options(
-                    selectinload(Task.child_tasks),
-                    selectinload(Task.records),
-                )
-                .where(Task.id == child.id)
-            )
-            refreshed_child = child_result.scalar_one()
-            t.child_tasks[t.child_tasks.index(child)] = refreshed_child
-            await _load_children(refreshed_child)
-
-    await _load_children(task)
-    return task
+    """使用 PostgreSQL Recursive CTE 一次性加载任务及其所有子孙任务（消除 N+1）"""
+    from app.services.task_tree_loader import load_task_tree_by_root
+    return await load_task_tree_by_root(db, task_id)
 
 
 def _to_flat_response(task: Task) -> TaskResponse:
@@ -326,7 +296,6 @@ async def get_all_tasks(
 ) -> TaskListResponse:
     """获取任务列表，可按产品/负责人筛选"""
     stmt = select(Task).options(
-        selectinload(Task.child_tasks),
         selectinload(Task.records),
         selectinload(Task.product),
     )
@@ -1085,5 +1054,6 @@ async def add_task_record(
     await db.commit()
     await db.refresh(record)
 
-    # 重新加载 task 带上新 record
-    return await get_task(db, task_id)
+    # 手动追加新 record，避免二次加载整棵树（task 已在 L1051 由 CTE 完整加载）
+    task.records.append(record)
+    return _to_response(task)
diff --git a/backend/app/services/task_tree_loader.py b/backend/app/services/task_tree_loader.py
new file mode 100644
index 0000000..8ad0493
--- /dev/null
+++ b/backend/app/services/task_tree_loader.py
@@ -0,0 +1,176 @@
+"""
+共享 CTE 任务树加载器 — 使用 PostgreSQL Recursive CTE 一次性拉取完整任务树
+
+解决问题：原 _load_task_tree / _get_task_with_children_recursive 使用
+Python 递归逐层 SELECT，N 个节点产生 N+1 次数据库查询。
+现在无论树深度多大，仅执行 2 条查询（CTE + records selectinload）。
+"""
+from __future__ import annotations
+
+import uuid
+
+from fastapi import HTTPException, status
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import noload, selectinload
+from sqlalchemy.orm.attributes import set_committed_value
+
+from app.models.task import Task
+
+
+# ============================================================
+# 内存树组装（O(N) 时间 / O(N) 空间）
+# ============================================================
+
+def _build_tree_in_memory(tasks: list[Task]) -> dict[uuid.UUID, Task]:
+    """
+    给定扁平 Task ORM 列表，在内存中通过哈希表组装嵌套树结构。
+
+    关键安全设计：
+    - 使用临时字典 temp_children_map 暂存父子关系，绝对不直接操作 ORM 的 child_tasks。
+    - 通过 set_committed_value 注入最终列表，告诉 SQLAlchemy 这是"已提交数据"，
+      避免 add_task_record 等场景中 db.commit() 时触发级联 UPDATE 污染数据库。
+
+    时间复杂度: O(N)，空间复杂度: O(N)。
+    """
+    if not tasks:
+        return {}
+
+    # ── Pass 1: 临时字典存储关系（不触碰 ORM 属性）──
+    temp_children_map: dict[uuid.UUID, list[Task]] = {t.id: [] for t in tasks}
+    task_map: dict[uuid.UUID, Task] = {t.id: t for t in tasks}
+
+    # ── Pass 2: 挂载到临时字典 ──
+    for t in tasks:
+        pid = t.parent_task_id
+        if pid is not None and pid in temp_children_map:
+            temp_children_map[pid].append(t)
+
+    # ── Pass 3: 排序 + set_committed_value 安全注入 ──
+    for t in tasks:
+        children = temp_children_map[t.id]
+        if children:
+            children.sort(key=lambda x: x.created_at)
+        # 关键：标记为已提交数据，SQLAlchemy 不会对其生成 UPDATE
+        set_committed_value(t, 'child_tasks', children)
+
+    return task_map
+
+
+# ============================================================
+# 公开 API：按单一任务 ID 加载子树
+# ============================================================
+
+async def load_task_tree_by_root(
+    db: AsyncSession, task_id: uuid.UUID
+) -> Task:
+    """
+    使用 Recursive CTE 加载以 task_id 为根的完整任务子树。
+
+    返回: 根 Task ORM 对象（child_tasks 已递归填充）。
+
+    Raises:
+        HTTPException(404): 根任务不存在。
+    """
+    # ── Step 1: Recursive CTE — 收集所有子孙节点 ID ──
+    #   WITH RECURSIVE task_tree AS (
+    #       SELECT tasks.* FROM tasks WHERE tasks.id = :tid
+    #       UNION ALL
+    #       SELECT tasks.* FROM tasks
+    #         JOIN task_tree ON tasks.parent_task_id = task_tree.id
+    #   )
+    anchor = (
+        select(Task)
+        .where(Task.id == task_id)
+        .cte(name="task_tree", recursive=True)
+    )
+    task_tree_cte = anchor.union_all(
+        select(Task).join(anchor, Task.parent_task_id == anchor.c.id)
+    )
+
+    # ── Step 2: 批量加载所有任务 + 关联数据 ──
+    stmt = (
+        select(Task)
+        .options(
+            noload(Task.child_tasks),       # 禁掉模型默认 selectinload，由内存树接管
+            noload(Task.parent_task),       # 组装树不需要 parent 引用
+            selectinload(Task.records),     # 🔥 一次性预加载所有进度记录
+            selectinload(Task.product),     # 🔥 一次性预加载产品引用
+        )
+        .where(Task.id.in_(select(task_tree_cte.c.id)))
+    )
+
+    result = await db.execute(stmt)
+    all_tasks = result.unique().scalars().all()
+
+    if not all_tasks:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"任务不存在: {task_id}",
+        )
+
+    # ── Step 3: 内存组装 ──
+    task_map = _build_tree_in_memory(all_tasks)
+
+    # 根任务一定在 map 中（CTE anchor 保证了这一点）
+    return task_map[task_id]
+
+
+# ============================================================
+# 公开 API：按产品 ID 加载所有任务树
+# ============================================================
+
+async def load_task_trees_by_product(
+    db: AsyncSession, product_id: uuid.UUID
+) -> list[Task]:
+    """
+    使用 Recursive CTE 加载指定产品下的所有任务树。
+
+    返回: 顶层任务列表（parent_task_id IS NULL），每项的 child_tasks 已递归填充。
+    若无任务则返回空列表。
+    """
+    # ── Step 1: Recursive CTE ──
+    #   WITH RECURSIVE product_task_tree AS (
+    #       SELECT tasks.* FROM tasks
+    #         WHERE tasks.product_id = :pid AND tasks.parent_task_id IS NULL
+    #       UNION ALL
+    #       SELECT tasks.* FROM tasks
+    #         JOIN product_task_tree ON tasks.parent_task_id = product_task_tree.id
+    #   )
+    anchor = (
+        select(Task)
+        .where(
+            Task.product_id == product_id,
+            Task.parent_task_id.is_(None),
+        )
+        .cte(name="product_task_tree", recursive=True)
+    )
+    task_tree_cte = anchor.union_all(
+        select(Task).join(anchor, Task.parent_task_id == anchor.c.id)
+    )
+
+    # ── Step 2: 批量加载 ──
+    stmt = (
+        select(Task)
+        .options(
+            noload(Task.child_tasks),
+            noload(Task.parent_task),
+            selectinload(Task.records),
+            selectinload(Task.product),
+        )
+        .where(Task.id.in_(select(task_tree_cte.c.id)))
+    )
+
+    result = await db.execute(stmt)
+    all_tasks = result.unique().scalars().all()
+
+    if not all_tasks:
+        return []
+
+    # ── Step 3: 内存组装 ──
+    _build_tree_in_memory(all_tasks)
+
+    # ── Step 4: 返回排序后的顶层任务 ──
+    roots = [t for t in all_tasks if t.parent_task_id is None]
+    roots.sort(key=lambda t: t.created_at)
+    return roots