assistant-ui logo/Docs
Runtimes

MessagePartRuntime

MessagePartRuntime state and helpers for inspecting assistant-ui text, tool calls, data parts, reasoning, and custom message content.

API Reference

EnrichedPartState

Enriched part state passed to children render functions.

For tool-call parts, adds toolUI, addResult, and resume. For data parts, adds dataRendererUI.

The render function is also invoked once with a synthetic empty text part ({ type: "text", text: "", status: { type: "running" } }) when the assistant message has no parts yet but is in the running state, so a loading indicator can render. Differentiate this from a real empty text via part.status?.type === "running" && part.text === "".

EnrichedPartState
type : "text"

Identifies this part as a tool call.

status : MessagePartStatus | ToolCallMessagePartStatus

type : "running"

The tool call is waiting for UI or human input before continuing.

MessagePartRuntime

MessagePartRuntime
addToolResult : (result: any | ToolResponse<any>) => void

resumeToolCall : (payload: unknown) => void

respondToToolApproval : (response: { approved: boolean; reason?: string; }) => void

path : MessagePartRuntimePath

ref : string

threadSelector : MessagePartRuntimePath["threadSelector"]

type : "main"

messageSelector : MessagePartRuntimePath["messageSelector"]

type : "messageId"

messagePartSelector : MessagePartRuntimePath["messagePartSelector"]

type : "index"

getState : () => MessagePartState

subscribe : (callback: () => void) => Unsubscribe

MessagePartState

MessagePartState
type : "text"

Identifies this part as a tool call.

status : MessagePartStatus | ToolCallMessagePartStatus

type : "running"

The tool call is waiting for UI or human input before continuing.

PartState

PartState
type : "text"

Identifies this part as a tool call.

status : MessagePartStatus | ToolCallMessagePartStatus

type : "running"

The tool call is waiting for UI or human input before continuing.