Tika merged the thumbnail catalog preset and ThumbnailUnpackSelector
(TIKA-4856): PUT /unpack/preset/thumbnail returns exactly the one raster
image a client would show for the document - a stored thumbnail, the
rendering of a metafile thumbnail, or the rendered first page. The
client-side selection over /unpack/all (embedded-resource-type marks,
metafile renderings, id-path matching) moves to the server; the preset
zip carries one image without metadata sidecars, so the entry's
extension names the type and the bytes break the tie. A 404 now points
at the preset activation the server config needs.
Dominik Schmidt