A2UI Schema v1.0

The A2UI protocol defines how the FERAL brain sends structured UI to any client renderer (iOS, web, Android, CLI).

Version

All A2UI messages include "a2ui_version": "1.0". Receivers should check compatibility before rendering.

Message Types

Type	Purpose
`beginRendering`	Initial surface with full component tree + data model
`surfaceUpdate`	Incremental component patches
`dataModelUpdate`	Data-only patches (re-render bound values)
`deleteSurface`	Remove a surface from the client

Message Envelope

{
  "a2ui_version": "1.0",
  "type": "beginRendering | surfaceUpdate | dataModelUpdate | deleteSurface",
  "surfaceId": "string",
  ...payload fields
}

Component Schema

Every component in the tree has:

Field	Type	Required	Description
`componentId`	string	yes	Unique ID within the surface
`type`	ComponentType	yes	One of the registered types below
`properties`	object	no	Type-specific props (value, label, color, etc.)
`children`	string[]	no	Ordered list of child componentIds

Core Component Types

Type	Category	Description
`Text`	Display	Text with style variants (headline, subtitle, body, caption)
`Image`	Display	Image from URL or data URI
`Icon`	Display	Named icon (Lucide set)
`Button`	Input	Interactive button with action_id
`Checkbox`	Input	Boolean toggle
`TextField`	Input	Text input
`Slider`	Input	Numeric range input
`Row`	Layout	Horizontal layout
`Column`	Layout	Vertical layout
`List`	Layout	Scrollable list
`Card`	Layout	Elevated card container
`Tabs`	Layout	Tabbed sections
`Divider`	Layout	Horizontal rule
`Modal`	Layout	Overlay dialog

FERAL Extensions

Type	Description
`MapView`	Interactive map with markers
`Chart`	Line/bar/pie chart
`MetricCard`	Numeric metric with icon + unit
`GraphView`	Knowledge graph (nodes + links)
`CodeBlock`	Syntax-highlighted code
`ProgressBar`	0-1 progress indicator
`Table`	Tabular data (headers + rows)
`WebView`	Embedded iframe

Data Binding

String values support data-model binding:

{ "literalString": "Hello" }
{ "path": "user/name" }

Paths are resolved against the surface’s dataModel using /-separated keys.

Compatibility

Clients that receive an unknown a2ui_version should render a fallback “update required” message.
Unknown component types should render as invisible placeholders, not crash.
Publisher-side contract bump policy is documented in Gen-UI contracts & versioning.

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A2UI Schema Reference

A2UI Schema v1.0

Version

Message Types

Message Envelope

Component Schema

Core Component Types

FERAL Extensions

Data Binding

Compatibility

​A2UI Schema v1.0

​Version

​Message Types

​Message Envelope

​Component Schema

​Core Component Types

​FERAL Extensions

​Data Binding

​Compatibility

A2UI Schema v1.0

Version

Message Types

Message Envelope

Component Schema

Core Component Types

FERAL Extensions

Data Binding

Compatibility