---
name: "reference-ai-sdk-uimessage"
title: "AI SDK UIMessage shape"
description: "UIMessage is id+role+parts; unknown part types render as null"
type: "reference"
category: "ai-sdk"
tags: ["reference", "ai-sdk", "web"]
related: ["[[tech-ai-sdk-history-dto-convert]]", "[[tech-ai-agent-stack]]"]
sources: ["https://ai-sdk.dev/docs/ai-sdk-ui/chatbot-message-persistence"]
---
Vercel AI SDK `UIMessage` = `{id, role, parts[], metadata?}`. Renderer switches on `part.type` and drops unknowns.

Native tool parts: `dynamic-tool` / `tool-${name}` with `{state, input, output}`.
See [[tech-ai-sdk-history-dto-convert]], [[tech-ai-agent-stack]].