fix(openai): retain capabilities when model listing is unavailable

backend/internal/service/upstream_models.go

@@ -208,6 +208,7 @@ func (s *AccountTestService) FetchUpstreamSupportedModels(ctx context.Context, a
 // untouched.
 func (s *AccountTestService) SyncUpstreamModelCatalog(ctx context.Context, account *Account) (*UpstreamModelCatalog, error) {
 	models, body, err := s.fetchUpstreamModelList(ctx, account)
+	liveListAvailable := err == nil
 	if err != nil {
 		configuredModels := configuredUpstreamModelsForCapabilitySync(account)
 		if !upstreamModelListEndpointUnsupported(err) || len(configuredModels) == 0 {
@@ -264,7 +265,14 @@ func (s *AccountTestService) SyncUpstreamModelCatalog(ctx context.Context, accou
 	if len(completeMetadata) > 0 && account != nil && account.ID > 0 && s.accountRepo != nil {
 		// Retain known metadata only for models still listed or explicitly mapped.
 		if previous := account.GetUpstreamModelMetadataSnapshot(); previous != nil {
-			for _, modelID := range capabilityIDs {
+			retainedModels := capabilityIDs
+			if !liveListAvailable {
+				retainedModels = append([]string(nil), capabilityIDs...)
+				for modelID := range previous.Models {
+					retainedModels = append(retainedModels, modelID)
+				}
+			}
+			for _, modelID := range retainedModels {
 				old, exists := previous.Models[modelID]
 				if !exists {
 					continue

backend/internal/service/upstream_models_test.go

@@ -545,8 +545,12 @@ func TestSyncUpstreamModelCatalogUsesConfiguredModelsWhenListEndpointUnsupported
 		},
 	}
 
+	account.SetUpstreamModelMetadataSnapshot(UpstreamModelMetadataSnapshot{Models: map[string]UpstreamModelMetadata{
+		"old-live-model": {ID: "old-live-model", ContextWindow: 256000},
+	}})
 	catalog, err := svc.SyncUpstreamModelCatalog(context.Background(), account)
 	require.NoError(t, err)
+	require.Contains(t, account.GetUpstreamModelMetadataSnapshot().Models, "old-live-model", "an unavailable model-list endpoint is not evidence of removal")
 	require.Equal(t, []string{"glm-5.3"}, catalog.Models)
 	require.Empty(t, catalog.Warnings)
 	require.Len(t, upstream.requests, 2)