Module constants 

Wire-contract constants shared across every A2UI toolkit.

These values are a cross-language wire contract

Every shipping A2UI toolkit (TypeScript, .NET, Python) hard-codes the same strings, and the .NET constants file declares them a “cross-language wire contract” that “must not diverge”. A renderer written against the TypeScript toolkit will silently fail to see this crate’s output if any of them change.

Do not change these to match a newer spec revision on its own. The A2UI specification is at v1.0, but the interoperable toolkits still stamp PROTOCOL_VERSION "v0.9" — so this crate does too. Changing a value here is a breaking protocol change that has to land in every language at once.

Constants

A2UI_CLOSE_TAG

Closing tag an LLM wraps a raw A2UI JSON block in.

A2UI_OPEN_TAG

Opening tag an LLM wraps a raw A2UI JSON block in.

A2UI_OPERATIONS_KEY

Envelope key carrying a batch of A2UI operations over the transport.

A2UI_RECOVERY_ACTIVITY_TYPE

Activity type used to report recovery-loop progress to the caller.

BASIC_CATALOG_ID

catalogId for the standard basic component catalog.

DEFAULT_SURFACE_ID

surfaceId used when the caller does not supply one.

GENERATE_A2UI_TOOL_NAME

Planner-facing tool name: “build me a surface for this request”.

MAX_A2UI_ATTEMPTS

Total generation attempts before the recovery loop gives up.

MIME_TYPE

MIME type for a standalone A2UI payload (A2A parts, MCP resources, HTTP bodies).

PROTOCOL_VERSION

Value stamped into the version field of every message this crate emits.

RENDER_A2UI_TOOL_NAME

Inner structured-output tool name the generating model calls to emit a surface.

ROOT_ID

The id the root of a surface’s component tree must have.

SURFACE_COMPONENT

Component type name reserved for the implicit surface container.