I said the same thing!

https://news.ycombinator.com/item?id=13605810

Worst case, make PFS without sync the default, but include a native feature for pasting into a shared document (Etherpad style, hosted by Keybase) for whatever your want to keep. Then you've got two spaces with different expectations, matching their capabilities.

And for attached files, they'd be displayed in a list while the chat is active, asking if you want to keep them in your keybase storage or let them vanish from the servers when you close the chat (delete their session keys).