diff --git a/js/src/logger.ts b/js/src/logger.ts
index 8d834951a..eeca34846 100644
--- a/js/src/logger.ts
+++ b/js/src/logger.ts
@@ -1893,7 +1893,7 @@ function castLogger<ToB extends boolean, FromB extends boolean>(
 }
 
 function constructLogs3Data(items: string[]) {
-  return `{"rows": ${constructJsonArray(items)}, "api_version": 2}`;
+  return `{"rows": ${constructJsonArray(items)}, "api_version": 2, "async": true}`;
 }
 
 function now() {
diff --git a/py/src/braintrust/logger.py b/py/src/braintrust/logger.py
index f5490d6bd..57069ecb4 100644
--- a/py/src/braintrust/logger.py
+++ b/py/src/braintrust/logger.py
@@ -593,7 +593,7 @@ def construct_json_array(items: Sequence[str]):
 
 def construct_logs3_data(items: Sequence[str]):
     rowsS = construct_json_array(items)
-    return '{"rows": ' + rowsS + ', "api_version": ' + str(DATA_API_VERSION) + "}"
+    return '{"rows": ' + rowsS + ', "api_version": ' + str(DATA_API_VERSION) + ', "async": true}'
 
 
 def _check_json_serializable(event):