name: markdown description: "Render and customize assistant message text as markdown in assistant-ui. Use when displaying model output as formatted markdown with MarkdownTextPrimitive from @assistant-ui/react-markdown wired into the MessagePrimitive.Parts text branch, configuring remarkPlugins (remark-gfm, remark-math) and rehypePlugins (rehype-katex), or memoizing components with unstable_memoizeMarkdownComponents. Covers code-block syntax highlighting via react-shiki or react-syntax-highlighter registered as SyntaxHighlighter in components/componentsByLanguage, LaTeX math rendering with KaTeX, Mermaid diagrams gated on stream completion, custom math delimiters via preprocess, and the StreamdownTextPrimitive alternative from @assistant-ui/react-streamdown with built-in Shiki/KaTeX/Mermaid and block streaming. For general chat UI composition route to primitives." license: MIT

assistant-ui Markdown

Always consult assistant-ui.com/llms.txt for the latest API.

Render and customize assistant message text as markdown with MarkdownTextPrimitive from @assistant-ui/react-markdown, wired into the MessagePrimitive.Parts text branch.

References

• ./references/markdown-text.md -- MarkdownTextPrimitive setup
• ./references/syntax-highlighting.md -- code highlighting (react-shiki / react-syntax-highlighter)
• ./references/latex-mermaid.md -- LaTeX and Mermaid
• ./references/streamdown.md -- StreamdownTextPrimitive alternative

Orientation

MarkdownTextPrimitive renders one text part as markdown. The registry component (npx assistant-ui@latest add markdown-text) generates components/assistant-ui/markdown-text.tsx, which exports a memoized MarkdownText built on the primitive plus a defaultComponents map from unstable_memoizeMarkdownComponents. Render MarkdownText from the text branch of MessagePrimitive.Parts.

import "@assistant-ui/react-markdown/styles/dot.css";
import { MarkdownTextPrimitive } from "@assistant-ui/react-markdown";
import { MessagePrimitive } from "@assistant-ui/react";
import remarkGfm from "remark-gfm";
import { memo } from "react";

const MarkdownTextImpl = () => (
  <MarkdownTextPrimitive
    remarkPlugins={[remarkGfm]}
    className="aui-md"
    components={defaultComponents}
  />
);

export const MarkdownText = memo(MarkdownTextImpl);

<MessagePrimitive.Parts>
  {({ part }) => (part.type === "text" ? <MarkdownText /> : null)}
</MessagePrimitive.Parts>;

Add highlighting, math, or diagrams by extending the same primitive: rehypePlugins for KaTeX, componentsByLanguage for a per-language SyntaxHighlighter (Mermaid, diff), and preprocess to normalize raw text before parsing. See the references for each. For a batteries-included alternative with built-in Shiki, KaTeX, Mermaid, and block streaming, swap in StreamdownTextPrimitive from @assistant-ui/react-streamdown.

Common Gotchas

• Nothing renders / plain text shows. The text branch must return MarkdownText; returning <p>{part.text}</p> bypasses markdown entirely.
• No syntax highlighting. Highlighting is not bundled. Register a SyntaxHighlighter in defaultComponents (react-shiki recommended) per the syntax-highlighting reference.
• KaTeX has no styling. Import katex/dist/katex.min.css once at the app root; rehypeKatex only emits markup.
• Mermaid parses partial diagrams while streaming. Gate rendering on stream completion (the reference uses useAuiState to detect the closing fence) instead of rendering every delta.
• Memoization export name. The package exports unstable_memoizeMarkdownComponents; the generated file aliases it to memoizeMarkdownComponents.
• Unstyled by default. The aui-md class and styles/dot.css provide base styling; add your own Tailwind/CSS otherwise.

Related Skills

• primitives -- general UI composition (ThreadPrimitive, ComposerPrimitive, MessagePrimitive.Parts) for assembling the message and the rest of the chat surface around the markdown text branch.