diff --git a/app/workers/chunk_worker.py b/app/workers/chunk_worker.py
index d7e49ed..bd5fd94 100644
--- a/app/workers/chunk_worker.py
+++ b/app/workers/chunk_worker.py
@@ -282,6 +282,10 @@ async def _lookup_news_source(
         ):
             return src.country, src.name, src.language
 
+    logger.warning(
+        f"[chunk] news_source 매핑 실패: doc_id={doc.id} ai_sub_group={source_name!r} "
+        f"→ country NULL (news_sources prefix 미일치). 신규 source 또는 RSS category 오염 가능."
+    )
     return None, source_name, None