feat: restore core chat and observability

backend-fastapi/ai_platform/services/chat_service.py

@@ -8,7 +8,7 @@ from typing import AsyncGenerator, Dict, List, Optional
 from sqlalchemy import select, func
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from ai_platform.models import AIApp, Conversation, Message, LLMModel
+from ai_platform.models import AIApp, Conversation, Message, LLMModel, LLMProvider
 from utils.context import get_current_user_id_from_context
 from .llm_service import LLMService
 
@@ -352,15 +352,33 @@ class ChatService:
     async def _get_effective_model(self, conversation: Conversation, app: AIApp) -> Optional[LLMModel]:
         """获取有效的模型"""
         model_id = conversation.model_override_id or app.model_id
-        if not model_id:
-            return None
-        
-        result = await self._db.execute(
-            select(LLMModel).where(
-                LLMModel.id == model_id,
-                LLMModel.is_active == True,
-                LLMModel.is_deleted == False
+        if model_id:
+            result = await self._db.execute(
+                select(LLMModel)
+                .join(LLMProvider, LLMProvider.id == LLMModel.provider_id)
+                .where(
+                    LLMModel.id == model_id,
+                    LLMModel.is_active == True,
+                    LLMModel.is_deleted == False,
+                    LLMProvider.is_active == True,
+                    LLMProvider.is_deleted == False,
+                )
             )
+            model = result.scalar_one_or_none()
+            if model:
+                return model
+
+        result = await self._db.execute(
+            select(LLMModel)
+            .join(LLMProvider, LLMProvider.id == LLMModel.provider_id)
+            .where(
+                LLMModel.is_active == True,
+                LLMModel.is_deleted == False,
+                LLMModel.model_type == "chat",
+                LLMProvider.is_active == True,
+                LLMProvider.is_deleted == False,
+            )
+            .order_by(LLMModel.sort.desc(), LLMModel.sys_create_datetime.desc())
         )
         return result.scalar_one_or_none()