castella

Build desktop, web, or terminal UIs with Castella. Create widgets, components, layouts, manage reactive state, handle events, and use the theme system.

Package Castella applications for distribution using ux, PyInstaller, or Nuitka. Create executables, macOS app bundles, and cross-compile for other platforms.

Connect to A2A protocol agents from Castella. Communicate with agents, display agent cards, send messages, handle responses, and stream results.

Render A2UI JSON as native Castella widgets. Parse A2UI messages, handle actions, progressive rendering, data binding, and connect to A2UI-enabled agents.

Build chat interfaces and agent management UIs with Castella. Create chat components, display tool calls, manage multiple agents, and build agent hubs.

Enable AI agents to introspect and control Castella UIs via MCP. Create MCP servers, expose UI resources, handle MCP tools, and use semantic IDs.