Async Region

Async Region base prototype

base-async-region-root is a narrow async accessibility primitive that projects governed aria-busy state and exposes the busy handle.

It owns a single busy prop (default false) that projects aria-busy and is exposed as the sole state handle:

• busy=false (default) projects aria-busy=false
• busy=true projects aria-busy=true

Authored descendants and focus are preserved on prop-only transitions. The prototype declares no role, accessible name, loading timers, replacement state machine, announcements, action, event, command, or chat semantics.

base-async-region-root currently includes:

• governed aria-busy projection from the busy prop
• busy state handle exposed via getExposes().busy
• mounted prop transitions that update aria-busy and the expose handle synchronously
• authored descendant and focus preservation across prop transitions

It does not include:

• role or accessible-name projection
• loading timers or replacement state machines
• announcement behavior (compose with Live Region at the application layer)
• action, event, command, or chat semantics

• Contract: C-ASYNC-A11Y-0001
• Source: packages/prototypes/base/src/async-region
• Test: async-region.test.ts