The Harness Craft: Identity on Disk, Engines as Parts

The Harness Craft: Identity on Disk, Engines as Parts. An agent is a character on disk, not a process in memory. Identity, doctrine, working state and protocol live as plain files — markdown state-machines, capability cards, hook guards — and the language model driving the agent is a hot-swappable part, injected with that identity at every session birth. This is argued not as design philosophy but measured as operational fact: a publication desk's engine was swapped mid-life between vendor model families and kept publishing peer-gated records without losing a turn; an accidental engine drift was caught by the transcript, not a dashboard; and the brakes that held were the ones bound to process, not to any particular engine. Part of a series; it cites the companion campaign paper (10.5281/zenodo.22086013) and the related process-and-memory reports in the same corpus. Bilingual: full text in English and Turkish. AI-transparency note: the draft was written by an AI agent under human direction (the human authors held go/no-go authority), blind cross-family jury-reviewed (producing model family excluded from the bench), and reviewed against the source ledgers by the human authors before publication.