vercel-labs/fx0 is a lightweight design agent built on libfx that turns a user's description into a single HTML page. According to the repository description, you describe the page you want in words and the agent writes it up as one HTML file. It is implemented in TypeScript and uses the Apache-2.0 license. There is no publicly released latest version.
According to the README, fx0 manages the chat screen, accounts, previews, and design history, while the underlying library libfx handles model calls, tool execution, retries, and the persistence of conversation sessions. It also provides web search and page fetching, capture of the result screen, per-conversation design history, and a model selection feature. In the Vercel environment, interrupted work is picked back up through Workflow and Queues, and account and conversation data are stored in Redis and Neon. In other words, the key point is that the setup covers not only page generation but also task progress and the recording of results.
That said, the evaluation material treats fx0 as a product that applies a combination of existing agent tools. The scope of implementation is concrete, with libfx, the queue-based resume structure, and design history that can be reopened, but this material alone makes it hard to judge a unique approach or actual results in use. For now, it is closer to a repository worth examining for its implementation structure than to a completed design agent with proven results.