The Feature class (and its subclass HintForFindAndModifyFeature) in MongoDB.Driver.Core.Misc is currently public but serves no external use case. It is internal driver infrastructure for gating commands based on server wire version. The public constructor, public instance methods (ThrowIfNotSupported(IMongoClient), ThrowIfNotSupportedAsync), and public static feature constants are technically public API today, but have no meaningful external use case.

What to do

• Make Feature internal.
• Add InternalsVisibleTo for MongoDB.Driver.Encryption to cover cross-assembly usage (e.g. ClientEncryption calling Feature.Csfle2QEv2.ThrowIfNotSupported).