Keyweave is a web page, so the server that sent it is part of what you are trusting: a tampered copy of this app could show both of you matching words that mean nothing. Say the words out loud, face to face, and stop if they differ.
Your keys live in this browser, wrapped with this passphrase. There is no account and no recovery: if you forget it, the vault stays shut.
Keyweave pairs two devices that are in the same room, by showing a moving code on one screen and reading it with the other camera.
That is the whole authentication: a camera pointed at a screen has no network path for anyone else to sit in the middle of. Pairing over a call or a photo does not give you this, so do not do it.
Decide out loud who goes first. You will each take three turns.
Both screens should show the same six words in the same order. Read them to each other. This comparison is the trust decision: everything Keyweave does later rests on it.
If even one word differs, someone may be sitting between you. Say no.