openapi-fetch

openapi-fetch does have parseAs blob. The friction is binary-format typing and the DOM download flow.

TL;DR: I assumed openapi-fetch couldn't handle binary downloads, but checking the source showed it supports blobs just fine. The real hurdles were typing that masks blobs as strings and the manual DOM work to trigger downloads. On the backend, the Go export validates module filters and always returns a valid file via excelize, even when empty.