CopilotKit releases A2UI Composer with AG-UI theater and JSON export

• CopilotKit shipped its A2UI Composer announcement as an interactive builder for A2UI widgets, with a hosted Composer app and source tied to Google's A2UI repo.
• According to CopilotKit's feature list, the tool centers on Theater for AG-UI event streams, a widget gallery, a 100-icon material set, component docs, and source-code inspection.
• CopilotKit's how-to post says the main loop is visual prototyping, prompt-to-JSON generation, live preview, then copying A2UI JSON into an agent app.
• The broader A2UI v0.9 push in CopilotKit's launch thread adds day-0 AG-UI support, bring-your-own components, live streaming, and a shared web-core spanning React, Angular, Flutter, and Lit.

You can open the Composer app, browse Google's A2UI spec, and jump straight to CopilotKit's A2UI docs. The launch thread also sneaks in the more interesting implementation bits: CopilotKit's v0.9 post lists incremental streaming and cross-framework web-core support, while its CLI example shows A2UI already wired into npx copilotkit@latest create my-app --framework a2ui.

CopilotKit is pitching Composer as the fastest way to stop hand-authoring every widget schema. CopilotKit's launch post says it lets developers build widgets interactively, inspect the AG-UI event stream as UI renders, and view the source and data behind each widget.

The feature inventory is easier to scan as a parts list:

• Theater, for live AG-UI event streams plus rendered UI
• Widget Gallery, for premade widgets you can modify
• Material Icons, with 100 common icons
• UI Components, with preview, usage, and props
• Source code and data inspectors for any widget, icon, or component

Those details line up with CopilotKit's longer blog post, which frames v0.9 as a more usable declarative UI layer rather than a raw spec drop.

The notable bit in this release is not just "agent outputs JSON." CopilotKit's repost of Atai's note says A2UI v0.9 now works over AG-UI out of the box, which makes the Composer's Theater view a debugging surface for agents that already speak the protocol.

In CopilotKit's own summary, the v0.9 upgrade adds:

• Day-0 AG-UI support
• Bring-your-own components
• Live streaming for incremental rendering
• A shared web-core for React, Angular, Flutter, and Lit
• Simpler transports, including AG-UI, MCP, WebSockets, REST, and A2A

That combination is what makes the demo feel useful instead of ornamental: the same declarative payload can be previewed in Composer, then rendered against an existing component catalog in an app, per the A2UI docs.

CopilotKit's getting-started post reduces the workflow to four steps: experiment visually, generate A2UI JSON by description, preview the result in real time, and copy the JSON into an agent. That is a much more practical pitch than "generative UI," because it turns the tool into a schema workbench.

CopilotKit also shipped the scaffolding path on day one. Its setup post points to npx copilotkit@latest create my-app --framework a2ui, while the main launch thread ties that starter flow to AG-UI support and custom component catalogs. For teams already evaluating A2UI, the interesting part is that Composer, docs, and app scaffolding all landed together instead of as separate ecosystem pieces.