Soft Stack interface refresh
The biggest visual change since launch. The canvas moves to the Soft Stack system: depth communicates hierarchy, icon chips carry identity, and the whole surface is calmer to spend a day in.
- New node cards with provenance footers, so every card shows which model made it and when
- Sections for grouping related nodes and moving them as one
- Upgraded edges with endpoint dots and clearer labels
- Error recovery with retry: a failed response keeps its place on the canvas and can be re-run
- Light theme overhaul to match the new system