Jack Dorsey introduces Dessa from Block, which Block calls the first live conversation AI trained only on human speech, with no text and no pretrained models
We believe voice is the most natural way to interact with intelligence, so we created Dessa, the most authentic full-duplex speech model ever built. Talking with it feels like talking with a person…full of emotion, nuance, pauses, and a natural cadence.
Context
Most voice assistants turn speech into text and lose tone, timing and emotion. Block says Dessa skips text entirely and listens and talks at once, a different route to voice AI. Every capability claim so far comes from Block itself.
Dessa comes from a small research lab at Block founded by former members of Dessa, the Toronto deep learning startup, and the lab says it reports directly to Jack Dorsey. Block's page describes a full duplex speech to speech model that listens and talks at the same time and was trained from scratch on human conversation audio. The post was published at 2:23 PM Eastern on October 23.
Deep dive
Jack Dorsey posted at 2:23 PM Eastern on October 23 that Block created Dessa, which he called the most authentic full duplex speech model ever built. That superlative is the company's own claim, and no independent benchmark has been published.
Block's launch page gives the details. Dessa is audio in, audio out: it hears speech and answers in speech, with no text step in between. It is full duplex, so it listens while it talks, and Block says it learned from real conversation when to cut in and when to make small listening sounds such as yeah or got it. Block says inference runs faster than real time and that the model runs locally on a MacBook Pro with an M4 Max chip or better.
The training claims are the unusual part. Block says Dessa was trained from scratch on nothing but human conversation, with no text and no pretrained models, and that it learned language from hundreds of times fewer words than large language models need. Block also says it trained the model on a single NVIDIA GB200 NVL72 system. As far as Block knows, it is the first AI that holds a realistic live conversation after training only on speech; that is Block's framing.
The page shares recorded clips, including one where Dessa talks with GPT Live 1, and notes that the developer of that model is not affiliated with Block and has not endorsed Dessa. Press coverage describes it as a research preview with no public API, weights or model specifications. Block is offering early access to a small group of AI safety researchers.
What to expect next
The open questions are access and measurement. Block has not published weights, an API, a model size or benchmark results, so outside testing is limited to the recordings Block chose to share. The early access program for safety researchers is the first route for independent evaluation, and Block says more recordings will be posted on X. Watch for a technical report, any developer access, and comparisons with speech systems such as ChatGPT's live voice mode, which would show whether training on speech alone holds up beyond curated demos.