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Everything after since, plus whether the agent is mid-turn.

Cursor rather than page number: the thread only ever grows at the end, and a poll that asks for "what is new since 412" cannot skip or repeat a message the way an offset can when rows land between requests.

seen is the console saying the page is in front of someone. It is what holds back the "your agent wrote" email, and it is a separate flag rather than implied by the poll because a background tab keeps polling: a customer who left the tab open and walked away would otherwise never be told anything.