When I invoke a cancellation before the report processing starts, the expected behavior is that the report should really not even begin processing, but it runs to completion.

When I export to  XLSX, RTF, and CSV formats, and try to cancel the report a few seconds later, so that cancellation is signaled while report processing is already occurring, it doesn't stop. The expected behavior is that a TaskCanceledException should be raised, and the report processing should stop, but the report runs to completion. In PDF, DOCX, and PPTX, this works as expected.