fix(openai): preserve manifest key validation

backend/internal/service/openai_codex_models_service.go

@@ -2461,18 +2461,21 @@ func mergeMissingCodexModelFields(current, defaults map[string]json.RawMessage)
 }
 
 func validateCodexModelsManifestEnvelope(body []byte) error {
-	var envelope *struct {
-		Models []json.RawMessage `json:"models"`
-	}
+	var envelope map[string]json.RawMessage
 	if err := json.Unmarshal(body, &envelope); err != nil {
 		return fmt.Errorf("decode JSON object: %w", err)
 	}
 	if envelope == nil {
 		return errors.New("expected a JSON object")
 	}
-	if envelope.Models == nil {
+	models, ok := envelope["models"]
+	if !ok {
 		return errors.New("missing top-level models array")
 	}
+	models = bytes.TrimSpace(models)
+	if len(models) == 0 || models[0] != '[' {
+		return errors.New("top-level models field is not an array")
+	}
 	return nil
 }
 

backend/internal/service/openai_codex_models_service_test.go

@@ -2562,6 +2562,11 @@ func TestFetchCodexModelsManifestRejectsInvalidEnvelope(t *testing.T) {
 	}
 }
 
+func TestValidateCodexModelsManifestEnvelopeRequiresExactModelsKey(t *testing.T) {
+	require.NoError(t, validateCodexModelsManifestEnvelope([]byte(`{"models":[]}`)))
+	require.Error(t, validateCodexModelsManifestEnvelope([]byte(`{"Models":[]}`)))
+}
+
 func TestFetchCodexModelsManifestAPIKeyDoesNotCacheInvalidEnvelope(t *testing.T) {
 	var calls atomic.Int32
 	upstream := &codexModelsHTTPUpstreamStub{do: func(_ *http.Request, _ string, _ int64, _ int) (*http.Response, error) {