This changes the default behavior of how mongosh connects to MongoDB nodes. The new behavior now is in line with the old shell (with 1 exception outlined below). The default behavior now is to add the directConnection=true query parameter to the connection string automatically except if at least one of the following is true: the replicaSet query parameter is present in the connection string the connection string uses the mongodb+srv:// scheme the connection string contains a seed list with multiple hosts Only the last case (multiple hosts) is a breaking change compared to the old shell behavior. The old shell would connect directly to the first host if no replicaSet / SRV were given. mongosh will treat the seed lists now as the nodes of a replica set and try to connect to the primary.