Custom feeds pick their format, and protected feeds stream directly
Custom Liquid feeds now choose XML, CSV or TXT output right in the Code panel, and password-protected feeds are served by streaming instead of a redirect.
A custom feed is your own Liquid template over your catalog, and it now picks its output format in the Code panel. XML, CSV and TXT each get their own escaping and layout rules, so a CSV column never breaks because a product title contains a comma.
Password-protected feeds changed how they are served. A protected feed used to answer with a redirect to a presigned storage URL, and some channels' fetchers drop the request or the credentials when a redirect appears. The file now streams through the same public URL, no redirect in between; the presigned URL remains available as an opt-in via ?redirect=1.
If a marketplace ever refused your protected feed with a mysterious fetch error, paste the same URL again. Picky fetchers now get the file on the first try.