Google published A2UI v0.9, an Apache 2.0 standard enabling AI agents to declare UI intent in real-time using a client's existing component catalog — no new widgets or UI framework required. The release ships a Python Agent SDK (pip install a2ui-agent-sdk), a shared web-core renderer library, and official support for React, Flutter, Lit, and Angular, with Go and Kotlin bindings coming later. Because A2UI is a declarative data format rather than executable code, agents can only request components pre-approved by the application developer, limiting injection risk. The spec has attracted early integration from AG2, Vercel's json-renderer, and Oracle's Agent Spec.