For all its convenience, chat has one structural flaw as a place where software gets made: it only has a past. Meaning a conversation ends up distributed by nothing more than recency — the decisions with the most force are the ones you made most recently.
A canvas is the opposite deal. The brief sits here, the agent cards run there, the diffs and checks collect around the work itself. Nothing scrolls away; anything that stops being true gets moved or removed.
Spatial memory is the feature
People navigate their own work by place, not by line number. You remember this as "the disputed diff near the top right," not "message two hundred and forty." That kind of spatial memory does more for shared understanding than any thread summary ever will.
Position is a message. A shared canvas keeps the message in place for everyone.
From the first sketches
That is why DNP is not a chat product with a visual skin. The canvas is where the work lives; the conversation is just one frame around it.