Clarification on updateComponents semantics in v0.9 — full tree vs. incremental?

[stimw]

Hi A2UI team,

We are implementing our own renderer based on the v0.9 spec (server-to-client JSON + standard catalog). We have a question about the intended semantics of updateComponents.

The spec allows sending multiple updateComponents messages, and it describes components as “a list containing all UI components for the surface,” with a required root component. In practice, does this imply:

• Each updateComponents message should contain the full component tree (full replacement),
  or
• It is valid to send incremental updates (only changed/new components), where the client merges them into existing state?

We’re trying to support progressive rendering (splitting large component trees into multiple messages), and want to align with the official intent.

Any guidance would be greatly appreciated. We’re happy to share our implementation details if helpful.

Thanks!