Historically the shell has accepted a negative value for batchSize and passed this through to the server as a negative "ntoreturn" value. The query
means return up to 8 documents in the initial response batch, and then close the cursor.
When the shell is configured with --readMode commands, however, it currently passes the negative batchSize through to the server as a find command parameter. The server's find command implementation rejects negative batchSize:
This behavior is inconsistent with the drivers find command specification for the behavior of limit, skip, and batchSize. Instead, the shell should translate a batchSize of -n to a batchSize of +n with the singleBatch option set to true.