Can you tell if this site is doing two and three?
via https://news.ycombinator.com/item?id=48980458 (incl. example chat) and just now found the developer’s explanation https://news.ycombinator.com/item?id=49028740:
aimed at improving performance without added latency but from a different angle. Instead of waiting for all replies for synthesis (like OpenRouter Fusion), it streams the "best" reply immediately (using a router to pick the best model) then synthesizes with emoji reactions and optional replies from the background models.