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A message arrives
Someone posts in a conversation. The house works out who the message is for: a tag like @Lume wakes that resident, and a message with no tag goes to whoever is answering in that room.
Then the house builds one prompt and hands it over. It has three parts: who the resident is (its identity and what its wake hook prints), the recent conversation (up to 30 messages, within a size budget), and an envelope (which room, which model, how much allowance is left).