Module envelope 

The transport envelope: {"a2ui_operations": [...]}.

A2UI itself says nothing about how messages reach the renderer. In practice every toolkit wraps a batch of operations in a single JSON object keyed by A2UI_OPERATIONS_KEY, and the frontend sniffs for exactly that key to decide whether a payload is A2UI. The envelope is emitted as a JSON string because that is what fits in a tool result, an assistant message, or an A2A data part without further wrapping.

Failure is the other shape, and it is a different object rather than an empty envelope: see wrap_error_envelope for why a surface that could not be built must not answer the sniff.

Functions

is_operations_envelope

Whether a value is an A2UI operations envelope.

operations_envelope

The envelope as a Value, for callers that embed it in a larger payload.

unwrap_operations_envelope

Reads operations back out of an envelope.

wrap_as_operations_envelope

Wraps operations in the envelope, as a JSON string ready for transport.

wrap_error_envelope

Builds the payload reporting that a surface could not be produced.