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Testing A2UI with Composer and Theater

A verified workflow for generating, inspecting, and comparing A2UI interfaces with the official Composer tools.

Updated: 8/24/2026 Reviewed by: HIA2UI editorial team

Testing A2UI with Composer and Theater

The official A2UI Composer provides a browser-based environment for generating and inspecting A2UI interfaces. Its Theater displays examples across supported renderers, which is useful for comparing behavior without inventing a separate playground workflow.

  1. Open Composer and describe a small interface with explicit data and actions.
  2. Inspect the generated message stream rather than judging only the visual preview.
  3. Confirm that message names and component fields match the protocol version used by your application.
  4. Compare supported renderer output in Theater when cross-framework consistency matters.
  5. Copy only validated payloads into test fixtures; do not treat generated output as automatically production-safe.

What to inspect

Check that the stream creates a surface before updating it, uses only components from the selected catalog, binds data to expected paths, and requests only host-supported actions. Test empty values, long text, malformed input, repeated updates, narrow screens, keyboard navigation, and deletion cleanup.

Composer helps with authoring and visual inspection, but your application remains responsible for schema validation, catalog allowlisting, authorization, resource limits, accessibility, and safe fallback behavior. Review the official Composer documentation and message reference before integrating generated payloads.

For production launch criteria, use the renderer production-readiness guide.