JSystems

Plugin App: build your own desktop app by asking an AI agent

By JSystems2 min read

Short answer

Plugin App is a Windows desktop app made of plugins. You describe what you want, and an AI coding agent writes it as a TypeScript plugin that appears in the sidebar. Devin, Cursor, Codex, Claude Code, Gemini CLI, OpenCode, Kimi, Copilot, and Junie come preconfigured. It is not released yet.

Most apps give you the features someone else decided you need. Plugin App starts almost empty and grows the features you ask for. It is the second JSystems product and it is coming soon. This post explains what it does so you know what to expect.

How it works

  1. Describe a feature in the Build composer. For example: "a page that tracks my reading list and shows how many books I finished this month."
  2. An AI coding agent builds it as a plugin. A plugin can be a page (HTML, CSS, and TypeScript), a backend that runs in its own process, or both.
  3. The plugin shows up in the sidebar right away. Edits rebuild and reload as soon as they are saved.
  4. Ask again to change it. Describe what you want different, and the agent edits the same plugin.

What plugins can do

  • Save data with built-in storage, so a plugin keeps its state between launches.
  • Call web APIs, but only on hosts the plugin lists in its manifest.
  • Run backend code in its own process, which the page calls by name.

Each plugin is a folder you can read and change yourself. Nothing is hidden behind a service.

Which agents it works with

Plugin App talks to agents over the Agent Client Protocol (ACP). These come preconfigured:

  • Devin (the default)
  • Cursor
  • Codex
  • Claude Code
  • Gemini CLI
  • OpenCode
  • Kimi
  • Copilot
  • Junie

You can also add any other ACP agent as a custom command. A chat stays with the agent that answers it, and if you switch agents mid-chat, the new one gets the conversation so far.

Agents work with the app through a built-in MCP server, so they can create, build, reload, open, screenshot, and test plugins without you copying files around.

Who it is for

Plugin App is for people who already use an AI coding agent and want a place where its work becomes a real, running tool on their desktop, instead of a one-off script.

When it is coming

Plugin App is not released yet. It will be listed with a download on the JSystems products page when it is ready, and announced here on the blog.

Common questions

What is Plugin App?

A Windows desktop app made of plugins. You describe a feature and an AI coding agent writes it as a plugin that appears in the app's sidebar.

Which AI agents does Plugin App support?

Devin, Cursor, Codex, Claude Code, Gemini CLI, OpenCode, Kimi, Copilot, and Junie come preconfigured, and any other ACP agent can be added as a custom command.

Can I download Plugin App yet?

Not yet. It is coming soon for Windows 10 and 11.

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