diff --git a/wwwroot/api/import_category_products.dspy b/wwwroot/api/import_category_products.dspy
index 9c1f846..a5bc607 100644
--- a/wwwroot/api/import_category_products.dspy
+++ b/wwwroot/api/import_category_products.dspy
@@ -4,8 +4,11 @@ try:
     category_id = params_kw.get('category_id', '')
     # Debug: log incoming params to help diagnose tree selection issue
     from appPublic.log import debug
+    body_preview = 'none'
     raw_body = getattr(request, 'body', b'')
-    debug(f'[import_category] params_kw={dict(params_kw)}, category_id={category_id}, body={raw_body[:200] if raw_body else \"none\"}')
+    if raw_body:
+        body_preview = str(raw_body[:200])
+    debug('[import_category] params_kw=%s, category_id=%s, body=%s' % (dict(params_kw), category_id, body_preview))
 
     if not category_id:
         raise ValueError('请先选择一个产品类别')