Pi

Pi is built around tone rather than tasks. The interface is stripped to a single warm conversation with no sidebar of saved threads, no document panel, no model picker, which signals that it wants to be talked with, not operated. Its standout feature is voice: replies are spoken aloud in one of several distinct synthesized voices you can choose, and the writing is tuned short and conversational so the audio doesn't drone. Responses arrive in small, gentle paragraphs that ask questions back, pacing the exchange like a chat with a patient friend. The deliberate minimalism is also its ceiling. With little persistent structure or retrieval, Pi is poor at reference work and shines mainly as an unhurried, emotionally attuned back-and-forth.