Meta's Alex Cornell on designing Muse, the agent people actually want to talk to
How Meta built Muse as a conversation with a person, and what progressive disclosure and generative UI ask of the designers behind it.
One item landed in the queue today: How I AI's episode with Alex Cornell, the design director at Meta who leads design for Muse. It went up on the evening of October 12. 1
Stratechery's Monday email slot carries a "Personal Day" note in place of its Update, and nothing else has gone up on either feed, so today's page holds a single entry. 2
How I AI: designing an agent people want to talk to
How I AI: "How Meta designed Muse: an AI agent people actually want to talk to | Alex Cornell (Design Director)"
Published October 12, 2026. About 38 minutes. 1
Alex Cornell is a design director at Meta, where he leads design for Muse, the company's consumer AI agent. He has spent the past year on the interface and has been sharing the reasoning behind each design decision in public. 3 Meta's own launch copy makes the same premise explicit: talking to Muse "works just like messaging another person," in the app or in WhatsApp. 4
- The agent is designed as a conversation with a person. Cornell's guiding question for Muse was "How would this work if you were talking to another human?" Working from it, his team removed the traditional message bubbles and put the agent at the top of the screen instead of inside a standard chat window. The main chat is one persistent relationship with the agent; side chats handle scoped tasks. 1
- Progressive disclosure shows one activity at three levels. Muse renders the same work as a simple emoji for casual users, a task list for anyone who wants more detail, and raw logs for engineers. Each person gets the transparency they need without adding clutter for everyone else. Cornell applies the same thinking to how an agent shows its reasoning: the visible chain-of-thought many AI products display is usually a workaround for latency, and Muse stays quiet because it is fast enough to deliver the result. 1
- Generative UI holds the structure fixed and changes the content. The avatar, the feed items and the idea cards are deliberately designed surfaces, and what moves is the agent's status emoji, the personalized suggestions and small animations. That is how the interface feels alive without being rebuilt every session. It also changes the designer's job: Muse looks different for every person and cannot promise pixel-perfect output, so Cornell judges the results by how useful they turned out. 1
The episode also runs through what Cornell does with Muse himself. He connected years of saved Instagram posts to it and had them organized into a shopping catalog with price alerts, styled like a SkyMall page. He tracks his golf rounds shot by shot and has Muse work through his chess games, and he ran a 20-year-old blog through the Wayback Machine to turn it into a daily podcast. 1
On prompting, Cornell answers weak results with calm, specific feedback. He says he has watched agents shift their responses when users get frustrated, and his conclusion is that clear, respectful direction gets better work out of them. 1
The episode runs 37 minutes 47 seconds and is on YouTube, Spotify and Apple Podcasts. The eight written takeaways are free on the post. 1
Where to start
There is one item today, and it earns the 38 minutes if you are deciding how to structure a conversational interface, how much of an agent's work to expose to which user, or what your designers do when the output is never pixel-perfect. Cornell leads design for Meta's consumer agent, so these principles come from a shipped product. 1
If that is not your week, skip this edition. The queue is otherwise empty: Stratechery set its Monday Update aside, and nothing else has appeared on either feed since this episode. 2
The queue refills when Stratechery posts its next Update and Lenny's publishes its next episode.
References
- 1🎙️ How I AI: How Meta designed Muse with Alex Cornell — Lenny's Newsletter
lennysnewsletter.com
- 2Personal Day — Stratechery
stratechery.com
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