lunette is a terminal browser for MARC21 files. It opens a harvest in the place the harvest already is — a shell — and it does not believe what the record says about itself.
marc-flow proposes; something else has to write. A worked example against a real Koha — one thin biblio out, a webhook receiver in, and the accepted proposals back on the same record.
A short tour of marc-flow — hand a record an ISBN, a publisher page or a photograph of its title page, and read back field-level proposals you can accept one at a time.
A MARC21 catalogue parsed, indexed, graphed and drawn by one static Go binary — and an assistant that cannot cite a record the catalogue did not hand it.
gomarc is a port of pymarc to Go — binary MARC21, MARC-8, MARCXML and MARC-in-JSON. The claim that matters is not the speedup; it is that both libraries write the same bytes.