fix: 去除LLM直接生成图片占位符逻辑

api/app/tasks/memoir_tasks.py

@@ -28,7 +28,7 @@ from app.core.dependencies import get_llm_provider
 from app.agents.state_schema import MemoirStateSchema, SlotData, default_state
 from app.agents.memoir.prompts import (
     STAGE_TO_ORDER,
-    get_narrative_prompt,
+    get_narrative_json_prompt,
     inject_image_placeholder_template,
 )
 from app.agents.memoir import MemoirOrchestrator
@@ -38,6 +38,7 @@ from app.agents.chat.prompts_profile import format_user_profile_context
 from app.features.memoir.memoir_images.parser import (
     build_initial_image_assets,
     parse_image_placeholders,
+    parse_narrative_to_sections,
     split_narrative_to_sections,
 )
 import hashlib
@@ -67,6 +68,14 @@ logger = get_logger(__name__)
 _REDIS_CLIENTS: dict[bool, redis.Redis] = {}
 
 
+def _is_json_narrative(text: str) -> bool:
+    """检测 narrative 是否为 JSON 格式（paragraphs 结构）"""
+    if not text or not text.strip():
+        return False
+    s = text.strip()
+    return s.startswith("{") and "paragraphs" in s
+
+
 def _get_llm():
     """Celery 任务内获取 LangChain LLM（通过 port）"""
     try:
@@ -328,7 +337,7 @@ def _save_narrative_to_sections(db: Session, chapter, narrative: str, title: str
     img_settings = MemoirImageSettings.from_env()
     prompt_service = MemoirImagePromptService(llm=None, settings=img_settings) if img_settings.enabled else None
 
-    segments = split_narrative_to_sections(narrative_to_parse)
+    segments = parse_narrative_to_sections(narrative_to_parse)
     if not segments:
         sec = ChapterSection(
             id=str(uuid.uuid4()),
@@ -368,8 +377,11 @@ def _save_narrative_to_sections(db: Session, chapter, narrative: str, title: str
         chapter.source_segments = list(set((chapter.source_segments or []) + (source_segments or [])))
         return chapter
 
-    # 每 3 个 section 对应 1 张图片，其他 section 的 image_id 为空
-    def _should_have_image(order_idx: int) -> bool:
+    def _should_have_image(seg: dict, order_idx: int) -> bool:
+        """有 placeholder_info 的段落配图；无则兼容旧格式（每 3 段 1 图）"""
+        ph = seg.get("placeholder_info")
+        if ph and ph.get("description"):
+            return True
         return (order_idx % 3) == 2
 
     def _placeholder_for_segment(seg: dict, order_idx: int) -> dict | None:
@@ -385,7 +397,7 @@ def _save_narrative_to_sections(db: Session, chapter, narrative: str, title: str
         order_idx = order_base + i
         content = (seg.get("content") or "").strip()
         image_asset = None
-        if img_settings.enabled and _should_have_image(order_idx):
+        if img_settings.enabled and _should_have_image(seg, order_idx):
             ph = _placeholder_for_segment(seg, order_idx)
             style = prompt_service.CATEGORY_STYLE_MAP.get(category, img_settings.default_style) if prompt_service else img_settings.default_style
             image_asset = build_initial_image_assets(
@@ -640,12 +652,14 @@ def process_memoir_segments(self, user_id: str, segment_ids: List[str]):
                     birth_year=birth_year,
                     llm=llm,
                 )
-                if existing_content:
+                if _is_json_narrative(new_narrative):
+                    narrative = new_narrative
+                elif existing_content:
                     narrative = f"{existing_content}\n\n{new_narrative}"
                 else:
                     narrative = new_narrative
 
-                if existing_content and len(narrative) < len(existing_content) * 0.8:
+                if existing_content and not _is_json_narrative(narrative) and len(narrative) < len(existing_content) * 0.8:
                     logger.warning(
                         "内容长度异常: existing=%d, new=%d, category=%s. 回退为追加模式",
                         len(existing_content),
@@ -654,7 +668,8 @@ def process_memoir_segments(self, user_id: str, segment_ids: List[str]):
                     )
                     narrative = f"{existing_content}\n\n{combined_text}"
 
-                narrative = inject_placeholders(narrative)
+                if not _is_json_narrative(narrative):
+                    narrative = inject_placeholders(narrative)
                 calculated_order_index = STAGE_TO_ORDER.get(chapter_category, 999)
 
                 chapter = _save_narrative_to_sections(
@@ -777,7 +792,7 @@ def generate_chapter_content(self, user_id: str, stage: str, new_content: str):
                 )
 
             if llm:
-                prompt = get_narrative_prompt(
+                prompt = get_narrative_json_prompt(
                     stage=stage,
                     slots={},
                     new_content=new_content,
@@ -785,24 +800,25 @@ def generate_chapter_content(self, user_id: str, stage: str, new_content: str):
                 )
                 response = llm.invoke(prompt)
                 new_narrative = response.content.strip()
-                # 追加而非替换
-                if existing_content:
+                if _is_json_narrative(new_narrative):
+                    narrative = new_narrative
+                elif existing_content:
                     narrative = f"{existing_content}\n\n{new_narrative}"
                 else:
                     narrative = new_narrative
             else:
                 narrative = f"{existing_content}\n\n{new_content}" if existing_content else new_content
 
-            # 安全检查：新内容不应比旧内容短
-            if existing_content and len(narrative) < len(existing_content) * 0.8:
+            # 安全检查：新内容不应比旧内容短（仅非 JSON 格式）
+            if existing_content and not _is_json_narrative(narrative) and len(narrative) < len(existing_content) * 0.8:
                 logger.warning(
                     f"内容长度异常: existing={len(existing_content)}, "
                     f"new={len(narrative)}, stage={stage}. 回退为追加模式"
                 )
                 narrative = f"{existing_content}\n\n{new_content}"
 
-            # 入库前：占位符位置用正则匹配后拼上固定模板
-            narrative = inject_image_placeholder_template(narrative)
+            if not _is_json_narrative(narrative):
+                narrative = inject_image_placeholder_template(narrative)
             calculated_order_index = STAGE_TO_ORDER.get(stage, 999)
             title = chapter.title if chapter else f"{stage} 回忆"
             chapter = _save_narrative_to_sections(