Block unveils Dessa, a full-duplex voice model trained from scratch only on recorded human conversation, with no text and no pretrained model

Block (the payments company co-founded by Jack Dorsey) published a page and an X post introducing Dessa, a voice model built by a small research lab inside Block that reports directly to Dorsey. Block says the model was trained “from scratch on nothing but human conversation”, with no text and no pretrained language model, and that it is full-duplex: it listens and speaks at the same time, decides when to interrupt, backchannels and laughs mid-sentence. It runs faster than real time on a high-end MacBook.

The page presents a dozen live recordings of people talking with Dessa (subtitles added afterward), including one in which Dessa talks with OpenAI’s GPT-Live-1; Block adds that OpenAI is not affiliated and has not reviewed or endorsed Dessa. Block frames the work partly as safety: voice assistants that go through text cannot hear emotion (“Imagine being in serious pain while a voice AI has no idea and just keeps going”), and it invites AI-safety researchers to test the model early.

Most voice assistants of 2026 convert speech to text or are built on text-trained models. A conversational model learned only from audio, small enough to run on a laptop, is a different design, with different behaviours to study (prosody, interruptions, emotion) and a new kind of safety question, which Block itself raises.

All claims come from Block’s own page and posts: there is no paper, no benchmark and no public model to test, and “the first AI … trained only from human speech” is qualified by Block itself with “as far as we know”. Textless speech models trained on audio alone existed before as research; the claim here is about holding a realistic live conversation.