We're now past C++ bootstrap.

Layers in the 1xx series are in bare SubX, without any syntax sugar. They are
intended to be used by the phases of the self-hosted translator to replicate
the functionality of the C++ bootstrap:
  hex.subx
  survey_elf.subx
  pack.subx
  dquotes.subx
  assort.subx
  tests.subx
