The mongodb-driver artifact for version 3.8.0 has a pre-release Build-Version.
Because the ClientMetadata in the driver (sent to the server) is populated[1] using this manifest attribute, the server log and commands like currentOp show pre-release client versions.
[1] com.mongodb.internal.connection.ClientMetadataHelper#getDriverVersion
Reproduction:
$ mvn dependency:get -Dartifact=org.mongodb:mongodb-driver:3.8.0 > /dev/null $ unzip -p ~/.m2/repository/org/mongodb/mongodb-driver/3.8.0/mongodb-driver-3.8.0.jar META-INF/MANIFEST.MF | grep Build-Version Build-Version: 3.8.0-beta3-44-g1ff4ce53c-dirty