A rehosted UI whose API requests land on its own static host (or a reverse proxy with no API route) got that host's 404 page back, and we echoed it verbatim — the reporter saw 'NOT_FOUND bom1::...' and had no way to know their requests were reaching the wrong server.
The backend now stamps x-omnivoice-backend on every response, exposed through CORS, so the client can tell 'the backend answered 404' from 'something else answered 404' without guessing at body shape. A 404 in any other voice is reported as a routing problem, naming the URL that answered and where to fix it. The message goes through the same i18n helper as the other backend-diagnosis copy, in all 21 locales.
Palash Debnath
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