MessagePart

AI SDK v6 `UIMessage.parts[]` element. Loose shape for forward-compat — the runner emits whatever part types it uses; consumers render based on `type`. Known types: `text`, `reasoning`, `tool-{name}`, `dynamic-tool`, `file`, `source-url`, `source-document`, `data-{name}`, `step-start`. Extended thinking blocks must round-trip verbatim to preserve signatures.

Definition

interface MessagePart {
  [x: string]: unknown;
  type: string;
}

Fields