Build with an agent

Tell your agent: “build me an app in helder.build”. It writes the files, you open its link, and the app is live in your browser, where you can keep editing it.

With MCP

Add helder.build to your agent once. Claude Code:

claude mcp add --transport http helder https://helder.build/mcp

Other agents: a remote MCP server at https://helder.build/mcp. The agent makes a draft and gives you a link; with it open, its edits show as they happen and it sees what you see: the checks, each screen's layout and a picture of it. Your own edits go back to it.

Without MCP

An agent can put the files in a link itself: https://helder.build/studio/#import=…. It opens as a new project in your browser; nothing is uploaded.

For the agent

llms.txt says how to write a Helder app that works: design files first, then code with stories, the elements and attributes, the tools and the limits.

What stays where

The studio runs, checks and draws everything in your browser.
An agent's draft is kept by helder.build as text, under an id only the link has, at most 1 MB, for 30 days after its last change.
No account. A link from #import= never reaches a server.

Agents in your browser

Where the browser has WebMCP, the studio registers the same tools for an agent running in it: read, patch, check, snapshot and the screens' trees of the project open.