With the BSONv4 upgrade options such as promoteValues and promoteLongs were lost as they were inherited properties of the initialized BSON class. Since BSONv4 is simplified to a namespace there is no longer the implicit inheritance of options. We need to ensure that the options the user passes in are respected in bson’s serialize and deserialize calls. This may require plumbing options into functions that previously did not have access to them. Additionally it may not be necessary to do this for every call, look for context around the call to see if it is bson that a user would get access to (e.g, auth code uses bson calls but it is entirely internal and doesn’t need to respect user options).