feat: 补全模型能力选项(11种) + 按能力指定默认模型 + Auto自动模式

backend/python/app/api/chat.py

@@ -27,6 +27,7 @@ from ..models import (
 )
 from ..auth import get_current_user
 from ..middleware.log_service import LogService
+from ..capability_registry import resolve_auto_model
 
 router = APIRouter()
 
@@ -981,9 +982,14 @@ async def send_message(
     ai_model = None
     skills = []  # 初始化避免UnboundLocalError
     agents = []  # 初始化避免UnboundLocalError
-    if model_id:
+    # 解析模型：支持 Auto 模式（model_id='auto' 或未指定时，按能力自动匹配平台默认模型）
+    if model_id and model_id != "auto":
         ai_model = db.query(AIModel).filter(AIModel.id == model_id).first()
+    if not ai_model:
+        # Auto / 未指定 → 使用平台默认对话模型（文本能力默认）
+        ai_model = resolve_auto_model("text", db)
 
+    if ai_model:
         # ====== 图像/视频生成模型分支 ======
         caps = [c.lower() for c in (ai_model.capabilities or [])] if ai_model else []
         if ai_model and ("image" in caps or "video" in caps):
@@ -1137,7 +1143,7 @@ async def send_message(
         else:
             ai_content = "请选择一个已配置的AI模型进行对话。"
     else:
-        ai_content = "请先在聊天设置中选择一个AI模型。"
+        ai_content = "请先在后台管理-大模型库配置默认对话模型（或聊天中选择模型），Auto 模式下将自动使用平台默认模型。"
 
     ai_token_count = len(ai_content) // 2
     ai_msg = Message(
@@ -1146,7 +1152,7 @@ async def send_message(
         role="assistant",
         content=ai_content,
         token_used=ai_token_count,
-        model_id=req.model_id or conv.model_id,
+        model_id=ai_model.id if ai_model else (req.model_id or conv.model_id),
         skill_ids=req.skill_ids if req.skill_ids else None,
         agent_ids=req.agent_ids if req.agent_ids else None,
         knowledge_ids=req.knowledge_base_ids if req.knowledge_base_ids else None,
@@ -1168,8 +1174,8 @@ async def send_message(
     token_usage = TokenUsageLog(
         id=gen_uuid(),
         user_id=current_user.id,
-        model_id=req.model_id or conv.model_id,
-        model_name=ai_model.name if model_id and ai_model else None,
+        model_id=ai_model.id if ai_model else (req.model_id or conv.model_id),
+        model_name=ai_model.name if ai_model else None,
         conversation_id=conv_id,
         prompt_tokens=prompt_tokens or len(req.content) // 2,
         completion_tokens=completion_tokens or ai_token_count,
@@ -1454,3 +1460,4 @@ def get_models(db: Session = Depends(get_db)):
         })
     result.sort(key=lambda x: (0 if x["is_default"] else 1, x["name"]))
     return {"code": 0, "data": result, "message": "ok"}
+