Vivarium is a long-form AI roleplay and world-simulation app. You play a character inside a living world. The AI narrates and gives everyone a voice, but it never gets to decide what is true. The application holds the world’s state and rolls the dice; the model only describes what happened.

This blog is where I will write about building it: design decisions, what worked, what did not, and what is coming next. Posts will be short and honest. Expect a mix of product notes, engineering write-ups, and the occasional look at how the worlds themselves are authored.

If you want to follow along, the RSS feed is at /rss.xml.