The splitVector command will scan a chunk for shard key values to split a chunk at and return an array of chosen points. Currently it is possible for the size of the chosen points to make the response exceed the max BSONObj size limit of 16MB, leading splitVector to fail with BSONObjectTooLarge. When the shard key size limit is removed in SERVER-42368, this will become more likely, so splitVector should be modified to stop selecting split points when they would push the response over the BSON size limit and return the already chosen points. If possible, splitVector should return at least one split point.