diff --git a/app/models/library.py b/app/models/library.py
index ab722be..6f75e90 100644
--- a/app/models/library.py
+++ b/app/models/library.py
@@ -1,23 +1,41 @@
+from typing import TYPE_CHECKING
 from sqlalchemy import Column, DateTime, String, ForeignKey, BigInteger
 from sqlalchemy.sql import func
 from .base import AutoID, Base
 
+if TYPE_CHECKING:
+    from .user import User
+    from .workspace import Workspace
+
 class LibraryItem(Base, AutoID):
     """工作区共享媒体/文件资源库"""
     __tablename__ = "library_items"
 
-    workspace_id = Column(String(32), ForeignKey("workspaces.id", ondelete="CASCADE"), index=True)
+    workspace_id = Column(
+        String(Workspace.id_length()),
+        ForeignKey("workspaces.id", ondelete="CASCADE"),
+        index=True,
+    )
     # 自引用外键，支持无限级文件夹嵌套
-    parent_id = Column(String(32), ForeignKey("library_items.id", ondelete="CASCADE"), nullable=True, index=True)
-    
+    parent_id = Column(
+        String(AutoID.id_length()),
+        ForeignKey("library_items.id", ondelete="CASCADE"),
+        nullable=True,
+        index=True,
+    )
+
     name = Column(String, nullable=False)
     # 节点类型：'folder' (文件夹) 或 'file' (真实文件)
     item_type = Column(String, default="file", nullable=False)
 
     # --- 以下为真实文件（item_type='file'）的核心字段 ---
-    s3_key = Column(String, nullable=True)        # S3 中的 Object Key
+    s3_key = Column(String, nullable=True)         # S3 中的 Object Key
     file_size = Column(BigInteger, nullable=True)  # 文件大小（字节数 Bytes），用于统计容量占用
     mime_type = Column(String, nullable=True)      # 媒体类型，例如 'image/jpeg', 'video/mp4', 'application/pdf'
     
-    uploaded_by = Column(String(32), ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
+    uploaded_by = Column(
+        String(User.id_length()),
+        ForeignKey("users.id", ondelete="SET NULL"),
+        nullable=True,
+    )
     created_at = Column(DateTime(timezone=True), server_default=func.now())
\ No newline at end of file