diff --git a/tools/update_from_main.sh b/tools/update_from_main.sh
index d1a9726..ef1acf4 100755
--- a/tools/update_from_main.sh
+++ b/tools/update_from_main.sh
@@ -35,16 +35,35 @@ REMOTE_HEAD="$(g rev-parse origin/main)"
 if [ "$LOCAL_HEAD" != "$REMOTE_HEAD" ]; then
   g merge-base --is-ancestor "$LOCAL_HEAD" "$REMOTE_HEAD" \
     || refuse "本地 main 与 origin/main 历史分叉，停止（未改写工作目录）"
-  TOP_AD="$(g diff --name-status HEAD origin/main | grep -E "^[AD][[:space:]]+[^/]+$" || true)"
+  CHANGES="$(g diff --no-renames --name-status HEAD origin/main)"
+  TOP_AD="$(printf '%s\n' "$CHANGES" | grep -E "^[AD][[:space:]]+[^/]+$" || true)"
   [ -z "$TOP_AD" ] || refuse "main 相比本地新增/删除了顶层文件，目录顶层归 root，需管理员执行：
 $TOP_AD"
-  TOP_MOD="$(g diff --name-status HEAD origin/main | grep -E "^M[[:space:]]+[^/]+$" | awk '{print $2}' || true)"
-  if [ -n "$TOP_MOD" ]; then
-    echo "==> 预写入顶层改动文件（顶层目录无删除权限，改为截断写入）"
-    while IFS= read -r f; do g show "origin/main:$f" > "$WORK_TREE/$f"; done <<< "$TOP_MOD"
-  fi
-  echo "==> 快进合并到 origin/main"
-  g merge --ff-only origin/main >/dev/null 2>&1 || refuse "无法快进合并 origin/main（历史分叉），停止"
+  echo "==> 同步 origin/main 文件（顶层文件保留原 inode，避免目录权限限制）"
+  while IFS=$'\t' read -r status path; do
+    [ -n "$path" ] || continue
+    case "$status" in
+      D)
+        case "$path" in
+          */*) rm -f -- "$WORK_TREE/$path" ;;
+          *) refuse "main 删除了顶层文件 $path，需管理员处理" ;;
+        esac
+        ;;
+      A|M)
+        MODE_BITS="$(g ls-tree origin/main -- "$path" | awk '{print $1}')"
+        case "$MODE_BITS" in
+          100644|100755) ;;
+          *) refuse "文件 ${path} 的 Git 类型 ${MODE_BITS} 不支持自动同步，需管理员处理" ;;
+        esac
+        mkdir -p -- "$(dirname "$WORK_TREE/$path")"
+        g show "origin/main:$path" > "$WORK_TREE/$path"
+        [ "$MODE_BITS" = "100755" ] && chmod 755 "$WORK_TREE/$path" || chmod 644 "$WORK_TREE/$path"
+        ;;
+      *) refuse "遇到未支持的 Git 变更类型 ${status}：${path}" ;;
+    esac
+  done <<< "$CHANGES"
+  g read-tree origin/main
+  g update-ref refs/heads/main "$REMOTE_HEAD" "$LOCAL_HEAD"
   DIRTY="$(g status --porcelain)"
   [ -z "$DIRTY" ] || refuse "快进后工作区仍不一致，停止：
 $DIRTY"