diff --git a/pkg/providers/factory.go b/pkg/providers/factory.go
index d82a623a2..5b3e42b9e 100644
--- a/pkg/providers/factory.go
+++ b/pkg/providers/factory.go
@@ -107,6 +107,9 @@ func resolveProviderSelection(cfg *config.Config) (providerSelection, error) {
 				sel.apiKey = cfg.Providers.LiteLLM.APIKey
 				sel.apiBase = cfg.Providers.LiteLLM.APIBase
 				sel.proxy = cfg.Providers.LiteLLM.Proxy
+				if sel.apiBase == "" {
+					sel.apiBase = "http://localhost:4000/v1"
+				}
 			}
 		case "zhipu", "glm":
 			if cfg.Providers.Zhipu.APIKey != "" {
diff --git a/pkg/providers/factory_test.go b/pkg/providers/factory_test.go
index 345b8631f..f7a916d9e 100644
--- a/pkg/providers/factory_test.go
+++ b/pkg/providers/factory_test.go
@@ -29,6 +29,15 @@ func TestResolveProviderSelection(t *testing.T) {
 			wantAPIBase: "http://localhost:4000/v1",
 			wantProxy:   "http://127.0.0.1:7890",
 		},
+		{
+			name: "explicit litellm provider defaults base when only key is configured",
+			setup: func(cfg *config.Config) {
+				cfg.Agents.Defaults.Provider = "litellm"
+				cfg.Providers.LiteLLM.APIKey = "litellm-key"
+			},
+			wantType:    providerTypeHTTPCompat,
+			wantAPIBase: "http://localhost:4000/v1",
+		},
 		{
 			name: "explicit claude-cli provider routes to cli provider type",
 			setup: func(cfg *config.Config) {