Fixed in http://github.com/sonatype/sisu/commit/4efc10f500dba7a4acfe91d782eebf71ff1f5d79
The problem was in container code that sets the TCCL for components with lifecycles (contextualizable, initializable, etc.). The TCCL should be set to whatever realm the component belongs to, in order for string-based lookups to work as expected from lifecycle methods.
Unfortunately this container code did not take into account the possibility of proxy classes, where the real component class (and the associated realm) is further up the class hierarchy. The fix is to search the hierarchy until we find a class which was loaded by a realm - and if we don't find one then we just leave the TCCL set to the last context realm.
[Note: the proxy class in this case was one generated by the container for situations where the same component implementation is used multiple times for different hints - we need a way to disambiguate between each use of the implementation when performing custom injection in Guice, and creating thin proxies was the easiest way to achieve this as the custom injection is performed per-type]