#1189 ties up almost all the loose ends around defining entry and incumbent, as part of a series of work (most of which can be found by following links from #473). However, in the course of working on it, @bzbarsky and I discovered that figuring out how to preserve the entry concept correctly while executing EnqueueJob (i.e., promise jobs) is tricky. It looks like doing so would either require some strange contortions, or some more invasive changes to JS's promise mechanisms. See #1189 (comment) onward for details. In the meantime, #1189 adds a warning:

Let job settings be some appropriate environment settings object.

Warning: It is not yet clear how to specify the environment settings object that should be used here. In practice, this means that the entry concept is not correctly specified while executing a job. See discussion in issue #1189.