Block's Dessa Is a Full-Duplex Speech Model Trained on Natural Conversation

Block (Jack Dorsey's fintech and technology company) has unveiled Dessa, a full-duplex speech model designed to handle simultaneous speaking and listening in real-time conversation, trained specifically on natural conversational data rather than scripted speech. Unlike half-duplex voice models that take turns speaking, full-duplex models can interrupt, respond to backchannels, and handle the overlapping audio that characterizes real human dialogue. Dessa is described as producing speech that sounds like an early-stage social interaction — natural but slightly awkward — which Block frames as a deliberate design choice to avoid the uncanny valley of overly polished AI voice. For developers building voice-first AI applications, Dessa represents a technically meaningful step toward AI voice that behaves more like a real conversation partner than a voice assistant reading from a script. The release adds to a growing field of conversational speech models and raises the bar for what developers should expect from voice AI infrastructure.