Block Unveils Dessa, a Full-Duplex Speech Model Trained on Conversation

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Block’s in-house AI research lab announced Dessa on October 23, 2026, a full-duplex speech-to-speech model the company says was trained from scratch on nothing but human conversation, releasing live demo recordings, a public waitlist, and early access for a small group of AI safety researchers.

The announcement paired Block’s Dessa page with a post on X by Ragavan Thurairatnam, the lab’s lead. Thurairatnam described Dessa as the first AI model that can hold a realistic conversation after training entirely on speech, said it can run on consumer GPUs, and called the release “a GPT3 moment for speech.” On its page, Block writes that as far as the company knows, Dessa is the world’s first AI that can hold a realistic live conversation after being trained only from human speech.

Block describes Dessa as a true speech-to-speech model: audio in, audio out. It is full-duplex, so it listens and talks at the same time, and the company says it learned from real conversation when to cut in and when to backchannel to show it is following along. Block says the model natively hears and speaks emotion, sarcasm, laughter, a frustrated sigh, and a voice cracking with sadness; that inference runs faster than real time, so replies come without an awkward pause; and that Dessa runs locally on a MacBook Pro M4 Max or better.

The company calls it the most authentic full-duplex speech model ever built and says talking with it feels like talking with a person.

According to the page, Dessa was trained from scratch on sounds alone, without any text or pretrained models, and learned to converse in real time purely by listening. Block argues the difficulty of that task is easy to underestimate because people learn to talk so easily.