The ThreadLocal Serialization.currentTransportInformation is used for serializing local actor refs, but it's also useful when a serializer library e.g. custom serializer/deserializer in Jackson need access to the current ActorSystem.

We set this in a rather ad-hoc way from remoting and in some persistence plugins, but it's only set for serialization and not deserialization, and it's easy for Persistence plugins or other libraries to forget this when using Akka serialization directly.