Block unveils Dessa, a full-duplex speech model trained with zero text

Block’s AI research team, founded by former members of Toronto deep learning startup Dessa under lead researcher Ragavan Thurairatnam and reporting to Block cofounder and Chairman Jack Dorsey, has introduced Dessa, an end-to-end conversational speech model trained without a single word of text or any pretrained language model.

Conventional voice assistants rely on a three-stage pipeline that transcribes audio into text, processes it through a text language model and synthesises audio back out, discarding vocal timing and emotion at each boundary. Dessa instead models two synchronised audio speaker tracks directly from raw human conversation recordings. Because it processes both streams continuously in full duplex, the model listens while speaking, interjects natural backchannels such as “yeah” and “got it”, laughs mid-sentence, adjusts its speaking volume when asked and responds to paralinguistic cues including sighs, hesitation, sarcasm and regional accents.

Block trained the model on a single NVIDIA GB200 NVL72 system and kept the architecture compact enough to run faster than real time on a MacBook Pro equipped with an M4 Max chip or better. Block has published interactive multi-minute audio demos on its site, including an unscripted conversation between Dessa and GPT-Live-1, and opened an early-access waitlist for AI safety researchers. The company has not announced public weights or commercial API pricing.