Sierra's agent protocol lets a visit start as a guest. Write the guest tier first.
Bret Taylor and Clay Bavor, Sierra's co-founders, laid it out in Sierra's Oct 9, 2026 post. They call it Poppy, and they named 35 more design partners.
bryn's /bin/ 2026/10
One take from 2026/10 on the AI, search and buyer news.