fix: return empty data array instead of 500 when no models configured (#18556)

- /v2/model/info now returns {"data": []} when llm_router is None or model_list is empty
- /model_group/info now returns {"data": []} when llm_model_list is None or empty
- Fixes UI crash on fresh installs with STORE_MODEL_IN_DB=True
- Added 4 unit tests for empty model list scenarios

litellm/proxy/proxy_server.py

@@ -7322,13 +7322,9 @@ async def model_info_v2(
     """
     global llm_model_list, general_settings, user_config_file_path, proxy_config, llm_router
 
-    if llm_router is None:
-        raise HTTPException(
-            status_code=500,
-            detail={
-                "error": f"No model list passed, models router={llm_router}. You can add a model through the config.yaml or on the LiteLLM Admin UI."
-            },
-        )
+    # Return empty data array when no models are configured (graceful handling for fresh installs)
+    if llm_router is None or not llm_router.model_list:
+        return {"data": []}
 
     if prisma_client is None:
         raise HTTPException(
@@ -8228,14 +8224,9 @@ async def model_group_info(
     """
     global llm_model_list, general_settings, user_config_file_path, proxy_config, llm_router
 
-    if llm_model_list is None:
-        raise HTTPException(
-            status_code=500, detail={"error": "LLM Model List not loaded in"}
-        )
-    if llm_router is None:
-        raise HTTPException(
-            status_code=500, detail={"error": "LLM Router is not loaded in"}
-        )
+    # Return empty data array when no models are configured (graceful handling for fresh installs)
+    if llm_model_list is None or llm_router is None or not llm_model_list:
+        return {"data": []}
 
     from litellm.proxy.utils import get_available_models_for_user
 

tests/test_litellm/proxy/test_empty_model_list.py

@@ -0,0 +1,155 @@
+"""
+Tests for graceful handling of empty model list scenarios.
+
+These tests verify that /v2/model/info and /model_group/info endpoints
+return empty data arrays instead of 500 errors when no models are configured.
+"""
+
+import os
+import sys
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+from fastapi.testclient import TestClient
+
+sys.path.insert(
+    0, os.path.abspath("../../..")
+)  # Adds the parent directory to the system-path
+
+from litellm.proxy.proxy_server import app
+
+
+@pytest.fixture
+def client():
+    """Create a test client for the FastAPI app."""
+    return TestClient(app)
+
+
+class TestEmptyModelListHandling:
+    """Test suite for empty model list scenarios."""
+
+    def test_v2_model_info_returns_empty_data_when_router_is_none(
+        self, client, monkeypatch
+    ):
+        """
+        Test that /v2/model/info returns {"data": []} instead of 500
+        when llm_router is None.
+        """
+        monkeypatch.setattr("litellm.proxy.proxy_server.llm_router", None)
+        monkeypatch.setattr("litellm.proxy.proxy_server.llm_model_list", None)
+        monkeypatch.setattr("litellm.proxy.proxy_server.user_model", None)
+        monkeypatch.setattr("litellm.proxy.proxy_server.general_settings", {})
+
+        with patch(
+            "litellm.proxy.auth.user_api_key_auth.user_api_key_auth",
+            return_value=MagicMock(
+                user_id="test-user",
+                team_id=None,
+                team_models=[],
+                models=[],
+                user_role="proxy_admin",
+            ),
+        ):
+            response = client.get(
+                "/v2/model/info",
+                headers={"Authorization": "Bearer sk-test"},
+            )
+
+        assert response.status_code == 200
+        assert response.json() == {"data": []}
+
+    def test_v2_model_info_returns_empty_data_when_model_list_empty(
+        self, client, monkeypatch
+    ):
+        """
+        Test that /v2/model/info returns {"data": []} instead of 500
+        when llm_router exists but model_list is empty.
+        """
+        mock_router = MagicMock()
+        mock_router.model_list = []
+
+        monkeypatch.setattr("litellm.proxy.proxy_server.llm_router", mock_router)
+        monkeypatch.setattr("litellm.proxy.proxy_server.llm_model_list", [])
+        monkeypatch.setattr("litellm.proxy.proxy_server.user_model", None)
+        monkeypatch.setattr("litellm.proxy.proxy_server.general_settings", {})
+
+        with patch(
+            "litellm.proxy.auth.user_api_key_auth.user_api_key_auth",
+            return_value=MagicMock(
+                user_id="test-user",
+                team_id=None,
+                team_models=[],
+                models=[],
+                user_role="proxy_admin",
+            ),
+        ):
+            response = client.get(
+                "/v2/model/info",
+                headers={"Authorization": "Bearer sk-test"},
+            )
+
+        assert response.status_code == 200
+        assert response.json() == {"data": []}
+
+    def test_model_group_info_returns_empty_data_when_model_list_none(
+        self, client, monkeypatch
+    ):
+        """
+        Test that /model_group/info returns {"data": []} instead of 500
+        when llm_model_list is None.
+        """
+        monkeypatch.setattr("litellm.proxy.proxy_server.llm_router", None)
+        monkeypatch.setattr("litellm.proxy.proxy_server.llm_model_list", None)
+        monkeypatch.setattr("litellm.proxy.proxy_server.user_model", None)
+        monkeypatch.setattr("litellm.proxy.proxy_server.general_settings", {})
+
+        with patch(
+            "litellm.proxy.auth.user_api_key_auth.user_api_key_auth",
+            return_value=MagicMock(
+                user_id="test-user",
+                team_id=None,
+                team_models=[],
+                models=[],
+                user_role="proxy_admin",
+            ),
+        ):
+            response = client.get(
+                "/model_group/info",
+                headers={"Authorization": "Bearer sk-test"},
+            )
+
+        assert response.status_code == 200
+        assert response.json() == {"data": []}
+
+    def test_model_group_info_returns_empty_data_when_model_list_empty(
+        self, client, monkeypatch
+    ):
+        """
+        Test that /model_group/info returns {"data": []} instead of 500
+        when llm_model_list is empty.
+        """
+        mock_router = MagicMock()
+        mock_router.model_list = []
+
+        monkeypatch.setattr("litellm.proxy.proxy_server.llm_router", mock_router)
+        monkeypatch.setattr("litellm.proxy.proxy_server.llm_model_list", [])
+        monkeypatch.setattr("litellm.proxy.proxy_server.user_model", None)
+        monkeypatch.setattr("litellm.proxy.proxy_server.general_settings", {})
+
+        with patch(
+            "litellm.proxy.auth.user_api_key_auth.user_api_key_auth",
+            return_value=MagicMock(
+                user_id="test-user",
+                team_id=None,
+                team_models=[],
+                models=[],
+                user_role="proxy_admin",
+            ),
+        ):
+            response = client.get(
+                "/model_group/info",
+                headers={"Authorization": "Bearer sk-test"},
+            )
+
+        assert response.status_code == 200
+        assert response.json() == {"data": []}