Align user chat with agent model flow

ai_knowledge_base_v2/apps/backend/app/services/model_service.py

@@ -10,7 +10,7 @@ from sqlalchemy import select
 from sqlalchemy.orm import Session
 
 from app.core.config import get_settings
-from app.models.ai_config import ModelConfig
+from app.models.ai_config import ModelConfig, SystemConfig
 from app.services.external_errors import ExternalServiceError
 from app.services.rag_service import NO_HIT_ANSWER, RagResult
 
@@ -27,17 +27,19 @@ class ModelCompletion:
 class ModelClientService:
     @staticmethod
     def complete(db: Session, rag_result: RagResult) -> ModelCompletion:
+        mock_model_enabled = _system_config_bool(db, "mock_model_enabled", get_settings().mock_model_enabled)
         model = db.scalar(
             select(ModelConfig)
             .where(ModelConfig.enabled == 1)
             .order_by(ModelConfig.id.desc())
             .limit(1)
         )
-        settings = get_settings()
-        if settings.mock_model_enabled or model is None:
+        if mock_model_enabled:
             model_name = model.model_name if model is not None else "mock-model"
             answer = _mock_answer(rag_result)
         else:
+            if model is None:
+                raise ExternalServiceError("未启用可用模型，请先在模型管理中启用一个模型。", provider="model")
             model_name = model.model_name
             answer = _call_configured_model(model, rag_result)
 
@@ -92,6 +94,13 @@ def _mock_answer(rag_result: RagResult) -> str:
     )
 
 
+def _system_config_bool(db: Session, key: str, default: bool) -> bool:
+    config = db.scalar(select(SystemConfig).where(SystemConfig.config_key == key))
+    if config is None or not config.config_value.strip():
+        return default
+    return config.config_value.strip().lower() in {"1", "true", "yes", "on", "启用"}
+
+
 def _copy_model_with_overrides(model: ModelConfig, overrides: dict[str, Any]) -> ModelConfig:
     debug_model = ModelConfig(
         provider=model.provider,