- Introduce OnlineBackupValidator, while accepts serialized protobuf frames rather than processing an entire file at once. - Swift: SignalError.backupValidation was **removed** in favor of MessageBackupValidationError, which it was essentially redundant with. - ChatService will soon be replaced by ChatConnection, currently experimentally available in Node. (All of the networking-related APIs are still even more subject to change than the rest of libsignal. - The Node library now requires ES2021. - Methods issuing older AuthCredential formats were deprecated and will be removed in a future release. - Support for the CDSI option 'return_acis_without_uaks' was removed; it was already ignored by the service. - Further backup validator proto updates and performance improvements, including use of an extra worker thread for pipelining entire-file processing. ChatItem errors will now include the dateSent timestamp. - Further work on both key transparency and libsignal-net.