Message Scroller

Use the headless MessageScroller behavior with your own markup and styles.

MessageScroller ships as a headless primitive in the @shadcn/react package. The package owns all of the scroll behavior, anchoring turns, following streamed output, preserving the reader's place as history loads, and tracking visibility, and renders no styles of its own.

The message-scroller.tsx component in the registry is a thin wrapper that adds Tailwind classes on top. Use the package directly when you want full control over the markup and styles, or when you are not using the registry.

For the behavior guide and live examples, see the Message Scroller component.

Installation


pnpm add @shadcn/react

Usage

import {
  MessageScroller,
  useMessageScroller,
} from "@shadcn/react/message-scroller"

The package exports a namespace object instead of flat components. The parts and behavior are the same as the styled component, just unstyled.

<MessageScroller.Provider>
  <MessageScroller.Root>
    <MessageScroller.Viewport>
      <MessageScroller.Content>
        {messages.map((message) => (
          <MessageScroller.Item
            key={message.id}
            messageId={message.id}
            scrollAnchor={message.role === "user"}
          >
            {/* your message UI */}
          </MessageScroller.Item>
        ))}
      </MessageScroller.Content>
    </MessageScroller.Viewport>
    <MessageScroller.Button />
  </MessageScroller.Root>
</MessageScroller.Provider>

Parts

If you are coming from the styled component, the flat parts map to the namespace object like this.

Styled component	Unstyled part
`MessageScrollerProvider`	`MessageScroller.Provider`
`MessageScroller`	`MessageScroller.Root`
`MessageScrollerViewport`	`MessageScroller.Viewport`
`MessageScrollerContent`	`MessageScroller.Content`
`MessageScrollerItem`	`MessageScroller.Item`
`MessageScrollerButton`	`MessageScroller.Button`

The hooks are imported the same way and behave identically, since they read from MessageScroller.Provider.

import {
  useMessageScroller,
  useMessageScrollerScrollable,
  useMessageScrollerVisibility,
} from "@shadcn/react/message-scroller"

Example

Here is a complete example that brings its own styles and wires the scroller to the AI SDK.

"use client"
 
import { useChat } from "@ai-sdk/react"
import { MessageScroller } from "@shadcn/react/message-scroller"
import { DefaultChatTransport } from "ai"
 
import { ChatInput } from "@/components/chat-input"
 
export function Chat() {
  const { messages, sendMessage, status } = useChat({
    transport: new DefaultChatTransport({ api: "/api/chat" }),
  })
 
  return (
    <div className="flex h-svh w-full flex-col">
      <MessageScroller.Provider>
        <MessageScroller.Root className="relative flex flex-1 flex-col overflow-hidden">
          <MessageScroller.Viewport className="flex flex-1 flex-col overflow-y-auto">
            <MessageScroller.Content className="flex flex-col gap-4 p-6 text-base">
              {messages.map((message, index) => (
                <MessageScroller.Item
                  key={message.id}
                  messageId={`message-${index}`}
                  scrollAnchor={message.role === "user"}
                >
                  <div className="rounded-lg bg-muted p-4">
                    {message.parts.map((part, i) =>
                      part.type === "text" ? (
                        <span key={i}>{part.text}</span>
                      ) : null
                    )}
                  </div>
                </MessageScroller.Item>
              ))}
            </MessageScroller.Content>
          </MessageScroller.Viewport>
          <MessageScroller.Button className="absolute bottom-2 left-1/2 z-10 -translate-x-1/2 rounded-full border bg-background px-3 py-1 text-sm font-medium inert:opacity-0">
            Jump to latest
          </MessageScroller.Button>
        </MessageScroller.Root>
      </MessageScroller.Provider>
      <ChatInput onSend={sendMessage} disabled={status !== "ready"} />
    </div>
  )
}

Avoiding a Flash on Reload

A scroll container always opens at the top. HTML has no way to set scrollTop, so a server-rendered transcript shows the oldest messages first. After JavaScript runs, defaultScrollPosition moves the view, and you see a jump.

When defaultScrollPosition is "end" or "last-anchor", the viewport has data-pending-scroll until that position is applied. Give the viewport an id and hide it while the attribute is present. Scope the rule to that id so you do not hide the root.

#messages[data-pending-scroll] {
  visibility: hidden;
}

If you want "end" visible on first paint, add an inline script right after the viewport. Using the same id, scroll it to the bottom and remove data-pending-scroll.

const scrollToEndScript = `(function () {
  var viewport = document.getElementById("messages")
  if (!viewport) {
    return
  }
  viewport.scrollTop = viewport.scrollHeight
  viewport.removeAttribute("data-pending-scroll")
})()`
 
<MessageScroller.Root>
  <MessageScroller.Viewport id="messages" suppressHydrationWarning>
    <MessageScroller.Content>{/* transcript */}</MessageScroller.Content>
  </MessageScroller.Viewport>
  <script dangerouslySetInnerHTML={{ __html: scrollToEndScript }} />
  <MessageScroller.Button />
</MessageScroller.Root>

Put the script in your page, not in the primitive. It only works for "end", and only when the messages are already in the HTML. Add suppressHydrationWarning on the viewport. If you use a Content Security Policy, pass a nonce.

Do not use this script with "last-anchor". Skip it when messages load on the client.

API Reference

MessageScroller.Provider

The headless root. It owns scroll state and the behavior props, and provides them to the parts and the hooks. It renders no DOM of its own.

Prop	Type	Default	Description
`autoScroll`	`boolean`	`false`	Follow new content only while the reader is already at the live edge. Wheel, touch, keyboard scroll, and explicit jumps release it.
`defaultScrollPosition`	`"start" \| "end" \| "last-anchor"`	`"end"`	Opening position on the first non-empty render, applied once. `"last-anchor"` opens at the last `scrollAnchor` row and falls back to `"end"` when the turn fits or no anchor exists. For `"end"` and `"last-anchor"`, the viewport has `data-pending-scroll` until the position is applied. See Avoiding a Flash on Reload.
`scrollEdgeThreshold`	`number`	`8`	Distance from either edge that still counts as being at the start or end. Controls state attributes and scroll button visibility.
`scrollMargin`	`number`	`0`	Margin applied to the aligned edge for `scrollToMessage`, visibility, and programmatic targets.
`scrollPreviousItemPeek`	`number`	`64`	Extra margin added to `scrollMargin` when a newly appended `scrollAnchor` item is positioned so part of the previous item stays visible.

MessageScroller.Root

The frame and layout container. It fills its parent, so use it inside a height-constrained layout, within a MessageScroller.Provider.

Prop	Type	Default	Description
`...props`	`React.ComponentProps<"div">`	-	Props spread to the frame element.

The root mirrors the scroll-state attributes below (the viewport carries them too), so you can style the container by scroll state, such as edge fades on the frame. Headless usage should hide the viewport while data-pending-scroll is present, using visibility: hidden so layout still exists for the opening scroll.

Data attribute	Value	Description
`data-scrollable`	`"start"` \| `"end"` \| `"start end"` \| absent	Edges the viewport can scroll toward. Query one with `[data-scrollable~="end"]`; absent means it fits.
`data-autoscrolling`	present	Present while the viewport is programmatically scrolling to the latest message.
`data-pending-scroll`	present	Present until `defaultScrollPosition` (`"end"` or `"last-anchor"`) is applied, or skipped for an empty transcript. Hide the viewport while it is set. See Avoiding a Flash on Reload.

MessageScroller.Viewport

The scrollable viewport.

Prop	Type	Default	Description
`preserveScrollOnPrepend`	`boolean`	`true`	Keep the first visible message item stable when older rows are prepended.
`role`	`string`	`"region"`	Landmark role for the labelled scrollable transcript viewport.
`aria-label`	`string`	`"Messages"`	Accessible name for the scrollable chat transcript.
`tabIndex`	`number`	`0`	Makes the transcript viewport keyboard-scrollable.
`...props`	`React.ComponentProps<"div">`	-	Props spread to the viewport element.

Data attribute	Value	Description
`data-scrollable`	`"start"` \| `"end"` \| `"start end"` \| absent	Edges the viewport can scroll toward. Query one with `[data-scrollable~="end"]`; absent means it fits.
`data-autoscrolling`	present	Present while the viewport is programmatically scrolling to the latest message.
`data-pending-scroll`	present	Present until `defaultScrollPosition` (`"end"` or `"last-anchor"`) is applied, or skipped for an empty transcript. Hide the viewport while it is set. See Avoiding a Flash on Reload.

MessageScroller.Content

The transcript content element. Every direct child should be a MessageScroller.Item.

Prop	Type	Default	Description
`role`	`string`	`"log"`	ARIA role applied to the message list for live announcements.
`aria-relevant`	`string`	`"additions"`	Live-region updates to announce. Defaults to new transcript rows only.
`aria-busy`	`boolean`	-	Marks the live region busy while a turn streams, if needed.
`spacerClassName`	`string`	-	Class name for the internal spacer used to make room for anchored rows.
`...props`	`React.ComponentProps<"div">`	-	Props spread to the content element.

MessageScroller.Item

One transcript row: a message, marker, typing row, separator, or load-more row.

Prop	Type	Default	Description
`messageId`	`string`	-	Stable row id used by `scrollToMessage`, visibility, and prepend preservation.
`scrollAnchor`	`boolean`	`false`	Marks this row as a turn boundary that can anchor newly appended turns.
`...props`	`React.ComponentProps<"div">`	-	Props spread to the item element.

Data attribute	Value	Description
`data-message-id`	`string`	Mirrors `messageId` when provided.
`data-scroll-anchor`	`"true"` \| `"false"`	Mirrors `scrollAnchor`.

MessageScroller.Button

A button that scrolls to the start or end of the transcript. It is inert and removed from the tab order when there is nothing to scroll toward.

Prop	Type	Default	Description
`behavior`	`ScrollBehavior`	`"smooth"`	Native scroll behavior used when the button scrolls to its target edge.
`direction`	`"start" \| "end"`	`"end"`	Transcript edge the button scrolls toward.
`children`	`React.ReactNode`	-	Custom button content. Defaults to the scroll icon and accessible label.
`render`	`React.ReactElement \| render function`	-	Custom render target.
`...props`	`React.ComponentProps<"button">`	-	Props spread to the button.

Data attribute	Value	Description
`data-direction`	`"start"` \| `"end"`	Mirrors `direction`.
`data-active`	`"true"` \| `"false"`	Whether this button can currently scroll.

useMessageScroller

Imperative transcript controls.

Method	Type	Description
`scrollToMessage`	`(messageId: string, options?) => boolean`	Scroll to a mounted message id.
`scrollToEnd`	`(options?) => boolean`	Scroll to the latest message.
`scrollToStart`	`(options?) => boolean`	Scroll to the top.

All commands return false when the command could not be applied. scrollToStart and scrollToEnd return false only when the viewport is not mounted yet. scrollToMessage returns false when the target is not mounted and cannot be queued.

Command options:

Option	Type	Default	Description
`align`	`"start"` \| `"center"` \| `"end"` \| `"nearest"`	`"start"`	How a message target aligns in the viewport.
`behavior`	`ScrollBehavior`	`"auto"`	Native scroll behavior for the command.
`scrollMargin`	`number`	provider `scrollMargin`	Margin applied to the aligned edge for this command.

useMessageScrollerScrollable

Which edges the viewport can scroll toward, for sibling UI that needs the values in JavaScript. Prefer the data-scrollable attribute for styling the scroller itself.

Value	Type	Description
`start`	`boolean`	Whether the viewport can scroll toward the start. Content is hidden above (`!start` means at the top).
`end`	`boolean`	Whether the viewport can scroll toward the end. Content is hidden below (`!end` means at the bottom). Stays `false` while follow-output is keeping the reader at the live edge.

useMessageScrollerVisibility

Visibility state for outline, search, and active-turn UI. It subscribes separately from useMessageScrollerScrollable, so visibility work is only paid for when a consumer needs it.

Value	Type	Description
`currentAnchorId`	`string \| null`	The current anchored turn, based on the last `scrollAnchor` item at or above the reading line.
`visibleMessageIds`	`string[]`	Message ids intersecting the viewport, in document order.

Filter visibleMessageIds in your app when you need a narrower outline, such as user messages, anchored turns, or search hits.

llms.txt Questionnaire

On This Page

Installation Usage Parts Example Avoiding a Flash on Reload API Reference MessageScroller.Provider MessageScroller.Root MessageScroller.Viewport MessageScroller.Content MessageScroller.Item MessageScroller.Button useMessageScroller useMessageScrollerScrollable useMessageScrollerVisibility