Google A2UI 1.0, Express Method Cuts Input Tokens by 45.4%

• The Google A2UI team released A2UI 1.0, the open protocol for generative UI, on November 11, 2026.
• Using A2UI Express reduces input tokens by 45.4% and generated code tokens by 63.2% compared to direct JSON generation (based on Google's internal evaluation).
• Support for bidirectional function calls (bidirectional RPC) and mixed multiple catalogs expands interaction between agents and renderers.
• When integrated with MCP Apps, A2UI screens can be provided to host apps via a web renderer inside an iframe.

Technical Changes

• Maintains a declarative data (JSON)-based UI description method; apps render only using a pre-registered native component catalog.
• Introduces @ prefix reserved keys (@path, @call, etc.) and removes theme to separate layout and branding.
• Adds WAI-ARIA accessibility attributes and defines the return structure for input validation results (ValidationResult).

Support Status and Roadmap

• React, Angular, Lit, Flutter, and SwiftUI renderers support 1.0; Jetpack Compose is scheduled to transition to 1.0.
• Provides Python, TypeScript, and Dart Agent SDKs; Macro functionality is supported exclusively in the Python SDK.
• Distributed under the Apache License 2.0, allowing free use for research and commercial purposes.