diff --git a/braintrust/templates/api-configmap.yaml b/braintrust/templates/api-configmap.yaml
index 8063473..1bd41c2 100644
--- a/braintrust/templates/api-configmap.yaml
+++ b/braintrust/templates/api-configmap.yaml
@@ -27,6 +27,8 @@ metadata:
 data:
   ORG_NAME: {{ $orgName | quote }}
   PRIMARY_ORG_NAME: {{ $primaryOrgName | quote }}
+  # emit v3 spans in py+ts sdks. remove this setting when v4 migration is complete
+  BRAINTRUST_LEGACY_IDS: "true"
   {{- with $allowedOrgIds }}
   ALLOWED_ORG_IDS: {{ . | quote }}
   {{- end }}
diff --git a/braintrust/tests/api-configmap_test.yaml b/braintrust/tests/api-configmap_test.yaml
index 062b466..04854ef 100644
--- a/braintrust/tests/api-configmap_test.yaml
+++ b/braintrust/tests/api-configmap_test.yaml
@@ -19,6 +19,9 @@ tests:
       - equal:
           path: data.PRIMARY_ORG_NAME
           value: ""
+      - equal:
+          path: data.BRAINTRUST_LEGACY_IDS
+          value: "true"
       - equal:
           path: data.BRAINSTORE_ENABLED
           value: "true"