fix: can't create chat app when get tenant default model schema error (#39266)

api/services/app_service.py

@@ -408,6 +408,7 @@ class AppService:
         default_model_config = app_template.get("model_config")
         default_model_config = default_model_config.copy() if default_model_config else None
         if default_model_config and "model" in default_model_config:
+            default_model_dict = default_model_config["model"]
             # get model provider
             model_manager = ModelManager.for_tenant(tenant_id=account.current_tenant_id or "")
 
@@ -422,7 +423,7 @@ class AppService:
                 logger.exception("Get default model instance failed, tenant_id: %s", tenant_id)
                 model_instance = None
 
-            if model_instance:
+            if model_instance is not None:
                 if (
                     model_instance.model_name == default_model_config["model"]["name"]
                     and model_instance.provider == default_model_config["model"]["provider"]
@@ -430,17 +431,28 @@ class AppService:
                     default_model_dict = default_model_config["model"]
                 else:
                     llm_model = cast(LargeLanguageModel, model_instance.model_type_instance)
-                    model_schema = llm_model.get_model_schema(model_instance.model_name, model_instance.credentials)
-                    if model_schema is None:
-                        raise ValueError(f"model schema not found for model {model_instance.model_name}")
-
-                    default_model_dict = {
-                        "provider": model_instance.provider,
-                        "name": model_instance.model_name,
-                        "mode": model_schema.model_properties.get(ModelPropertyKey.MODE),
-                        "completion_params": {},
-                    }
-            else:
+                    try:
+                        model_schema = llm_model.get_model_schema(model_instance.model_name, model_instance.credentials)
+                        if model_schema is None:
+                            raise ValueError(f"model schema not found for model {model_instance.model_name}")
+                    except Exception:
+                        # A removed provider model must not prevent creating an app.
+                        logger.warning(
+                            "Default model schema is unavailable, tenant_id: %s, provider: %s, model: %s",
+                            tenant_id,
+                            model_instance.provider,
+                            model_instance.model_name,
+                            exc_info=True,
+                        )
+                        model_instance = None
+                    else:
+                        default_model_dict = {
+                            "provider": model_instance.provider,
+                            "name": model_instance.model_name,
+                            "mode": model_schema.model_properties.get(ModelPropertyKey.MODE),
+                            "completion_params": {},
+                        }
+            if model_instance is None:
                 try:
                     provider, model = model_manager.get_default_provider_model_name(
                         tenant_id=account.current_tenant_id or "", model_type=ModelType.LLM

api/tests/unit_tests/services/test_app_service.py

@@ -8,6 +8,7 @@ from unittest.mock import MagicMock, patch
 import pytest
 from sqlalchemy.exc import IntegrityError
 
+from graphon.model_runtime.entities.model_entities import ModelType
 from models import Account
 from models.model import App, AppMode, AppModelConfig
 from models.workflow import Workflow
@@ -46,6 +47,52 @@ class TestCreateAppTransactionBoundary:
 
         assert phase_events == ["commit", "signal", "commit", "external"]
 
+    def test_falls_back_when_default_model_schema_is_unavailable(self) -> None:
+        session = MagicMock()
+        account = MagicMock(spec=Account, id="account-1", current_tenant_id="tenant-1")
+        model_type_instance = MagicMock()
+        model_type_instance.get_model_schema.side_effect = ValueError("Base model unknown-model not found")
+        model_instance = SimpleNamespace(
+            model_name="unknown-model",
+            provider="langgenius/openai/openai",
+            credentials={},
+            model_type_instance=model_type_instance,
+        )
+        model_manager = MagicMock()
+        model_manager.get_default_model_instance.return_value = model_instance
+        model_manager.get_default_provider_model_name.return_value = ("openai", "gpt-4o")
+        added_objects: list[object] = []
+        session.add.side_effect = added_objects.append
+
+        with (
+            patch("services.app_service.ModelManager.for_tenant", return_value=model_manager),
+            patch("services.app_service.app_was_created.send"),
+            patch("services.app_service.enterprise_rbac_service.try_sync_creator_access_policy_member_bindings"),
+            patch(
+                "services.app_service.FeatureService.get_system_features",
+                return_value=SimpleNamespace(webapp_auth=SimpleNamespace(enabled=False)),
+            ),
+            patch("services.app_service.dify_config.BILLING_ENABLED", False),
+        ):
+            app = AppService().create_app(
+                "tenant-1",
+                CreateAppParams(name="Chat", mode=AppMode.CHAT.value),
+                account,
+                session=session,
+            )
+
+        app_model_config = next(obj for obj in added_objects if isinstance(obj, AppModelConfig))
+        assert app.mode == AppMode.CHAT
+        assert app_model_config.model_dict == {
+            "provider": "openai",
+            "name": "gpt-4o",
+            "mode": "chat",
+            "completion_params": {},
+        }
+        model_manager.get_default_provider_model_name.assert_called_once_with(
+            tenant_id="tenant-1", model_type=ModelType.LLM
+        )
+
 
 @pytest.mark.parametrize(
     "update_status",