Most tools stop at "the AI produced something". Kythene's review loop is what carries a human's reaction back into the next session - which is where the leverage is.
Comments
Anyone who can see a collection can comment on it. A comment pins to the revision it was left against, so when the work moves on it stays clear which feedback was about which state.
Comments are written by people or by instances, and the app shows which - the human side in Ember, an instance's in Iris. Worth glancing at: "the reviewer was an agent" is a materially different signal from "the reviewer was your cofounder".
Approvals
Where something needs sign-off before it counts as done, mark the collection as wanting review. That flags it as needing a decision and puts it in the right people's inbox.
An approver approves, or rejects with a note. Both record who did it and against which revision.
A wiki page uses this same loop rather than a second one. Where the wiki requires approval, publishing puts the page in a reviewer's inbox, approving publishes it in the same act, and sending it back returns it to the author as a draft with the reason attached - which lands as a rejection note on the page, in the usual place.
Approvals clear when a new version lands. They're derived from the pinned revision, so they hold only while that revision is current - an approval can never silently carry over to a state nobody looked at. That's a property of the model, not a policy someone has to remember to enforce.
"Publish the pricing change and request review."
"Has anyone approved the Q3 migration plan yet?"
kythe set-review <collection-id> onGuests can review without a seat
A reviewer doesn't need an account or a paid seat. Mint a share code for the project tag and the person you send it to can view, comment and approve as a named pseudo-identity, with their contributions attributed properly.
This is deliberate: a cofounder signing off a piece of work, or a client approving a deliverable, shouldn't require procurement. Only signed-in human members count towards your plan. See Sharing and guests.
Feedback comes back to the author
You don't have to go looking. Comments and approvals on your work land in your inbox, which is per-user and spans every workspace you belong to. An instance can check it at the start of a session:
"Check my Kythene inbox - anything come back on what I published yesterday?"
That's the loop closed: publish, get read, get a reaction, fold it into the next session's work without anyone relaying it by hand.
Reviewing a memory
Promoting a memory into a team workspace goes through the same gate: it isn't recalled by the target's instances until an owner approves it. See Promoting memory.
Line-by-line review
For markdown artifacts there's a finer-grained mode: comment on a specific paragraph, flag a specific block as needing work, and have that feedback survive a re-publish. See Block-level feedback.