chore: finalize backend feature scope

app/api/learning_assistant.py

@@ -5,33 +5,43 @@ from starlette.responses import StreamingResponse
 from app.core.response import ApiResponse, ok
 from app.core.user_context import UserContext, get_user_context
 from app.db.session import get_db
-from app.schemas.learning_assistant import LearningAssistantChatRequest, LearningAssistantChatResponse
+from app.schemas.learning_assistant import (
+    LearningAssistantChatRequest,
+    LearningAssistantSessionCreateRequest,
+    LearningAssistantSessionResponse,
+)
 from app.services.learning_assistant_service import LearningAssistantService
 
 router = APIRouter()
 
 
-@router.post("/chat", response_model=ApiResponse[LearningAssistantChatResponse], include_in_schema=False)
-async def learning_assistant_chat(
-    payload: LearningAssistantChatRequest,
+@router.post("/sessions", response_model=ApiResponse[LearningAssistantSessionResponse])
+async def create_learning_assistant_session(
+    payload: LearningAssistantSessionCreateRequest,
     ctx: UserContext = Depends(get_user_context),
     db: Session = Depends(get_db),
 ):
-    """AI 学习助手调试接口：非流式返回回答，正式前端联调使用流式接口。"""
-    result = await LearningAssistantService(db).chat(ctx, payload)
-    db.commit()
+    """学习助手会话创建：进入 AI 学习助手页面时生成短期会话 ID。"""
+    result = LearningAssistantService(db).create_session(ctx, payload)
     return ok(result)
 
 
-@router.post("/chat/stream", response_class=StreamingResponse)
-async def learning_assistant_stream_chat(
+@router.post("/sessions/{assistant_session_id}/chat/stream", response_class=StreamingResponse)
+async def stream_learning_assistant_session_chat(
+    assistant_session_id: str,
     payload: LearningAssistantChatRequest,
     ctx: UserContext = Depends(get_user_context),
     db: Session = Depends(get_db),
 ):
-    """AI 学习助手流式问答：返回 retrieval_done、answer_delta、answer_done 事件。"""
-    stream = LearningAssistantService(db).stream_chat(ctx, payload)
-    db.commit()
+    """学习助手会话式流式问答：绑定短期会话上下文，返回 SSE 增量回答。"""
+    service = LearningAssistantService(db)
+    assistant_session = service.validate_session(ctx, assistant_session_id)
+    stream = service.stream_session_chat(ctx, payload, assistant_session)
+    return _sse_response(stream)
+
+
+def _sse_response(stream) -> StreamingResponse:
+    """SSE 响应封装：关闭代理缓冲，避免前端长时间看不到增量内容。"""
     return StreamingResponse(
         stream,
         media_type="text/event-stream",