@lanodan Oh yeah, I forgot to document that ncdu doesn't support indefinite-length strings for the name field, they must be length-prefixed (That is such a CBOR misfeature).
The maximum length is actually a bit larger than that; the root item contains the full path of the scanned directory instead of just the name, and some filesystems apparently allow for 255 codepoints instead of bytes: https://en.wikipedia.org/wiki/Comparison_of_file_systems#Limits