Start a generation. Manual trigger only — nothing calls this automatically.

one_opus is the default: it is the engine the reference documents were written by, which is checkable rather than assumed — it titles a document the way a writer would ("GameStop"), and the staged engine cannot, because extract deliberately keeps the platform label out of the persona and the title comes from the persona ("The assistant"). Its coverage headers are written per document for the same reason.

Both engines now face check_structure, so neither can report a clean run on a document with no sample conversation in it. engine=question still selects the staged engine: it asks one question per capability and repairs what the checks reject, which is the better shape when a config is thin enough that a single call has little to go on.