When using sessions like they are used in this code, if the server's buildInfo indicates it does not support sessions, in my case 0.0.0 in a development build, the driver will silently fail. As a consequence, the driver accepted my configuration for sessions with causal consistency, but did not provide me causally consistent reads.

Using buildInfo to check for features appears to contradict the specification for How to Check Whether a Deployment Supports Sessions. The driver should either report an error in this case or not depend on buildInfo for feature support.