accounts are strings in the client side2

common/proto/tables_data.proto

@@ -102,7 +102,8 @@ message PostTableDataRequest {
   // - System/FK columns:
   //    • "deleted" (BOOLEAN), optional; default FALSE if not provided
   //    • one BIGINT per link, named by whoever declared it
-  //    • "account" (slash-delimited account string) on ACCOUNTING-enabled tables
+  //    • "account" (required, non-null slash-delimited account string) on
+  //      ACCOUNTING-enabled tables
   //
   // Type expectations by SQL type:
   // - TEXT: string value; empty string is treated as NULL
@@ -182,6 +183,7 @@ message PutTableDataRequest {
   int64 id = 3;
 
   // Required. Columns to update (same typing rules as PostTableDataRequest.data).
+  // "account" may be omitted, but cannot be null when supplied.
   //
   // Special script rules:
   // - If a script targets column X and X is included here, the value for X must