diff --git a/api/app/tasks/memoir_tasks.py b/api/app/tasks/memoir_tasks.py
index c70e895..f2b2a73 100644
--- a/api/app/tasks/memoir_tasks.py
+++ b/api/app/tasks/memoir_tasks.py
@@ -387,10 +387,13 @@ def _save_narrative_to_sections(db: Session, chapter, narrative: str, title: str
     def _placeholder_for_segment(seg: dict, order_idx: int) -> dict | None:
         ph = seg.get("placeholder_info")
         if ph and ph.get("placeholder") and ph.get("description"):
+            # 确保有 index，build_initial_image_assets 依赖此字段
+            if "index" not in ph:
+                ph = {**ph, "index": order_idx}
             return ph
         content = (seg.get("content") or "").strip()
         desc = (content[:50] + "…") if len(content) > 50 else (content or "章节配图")
-        return {"placeholder": f"{{{{{{{{IMAGE:{desc}}}}}}}}}", "description": desc}
+        return {"placeholder": f"{{{{{{{{IMAGE:{desc}}}}}}}}}", "description": desc, "index": order_idx}
 
     # 按顺序创建 section，每 3 个 section 对应 1 张配图
     for i, seg in enumerate(segments):