fix: put unread separator above system messages and stop scrolling the host page on scroll to a message

examples/vite/src/App.tsx

@@ -44,6 +44,7 @@ import { appSettingsStore, useAppSettingsSelector } from './AppSettings';
 import { DESKTOP_LAYOUT_BREAKPOINT } from './ChatLayout/constants.ts';
 import { ChatSkipNavigation } from './AccessibilityNavigation/ChatSkipNavigation.tsx';
 import { ChannelsPanels, ThreadsPanels } from './ChatLayout/Panels.tsx';
+import { EmbeddedHostPage } from './ChatLayout/EmbeddedHostPage.tsx';
 import { SidebarProvider } from './ChatLayout/SidebarContext.tsx';
 import {
   ChatViewSelectorWidthSync,
@@ -508,39 +509,41 @@ const App = () => {
           <ChatSkipNavigation />
           {/* Publishes window.streamDebug — see src/Debug/StreamDebugHandles.tsx */}
           <StreamDebugHandles />
-          <div
-            className='app-chat-layout'
-            data-variant={messageUiVariant ?? undefined}
-            ref={appLayoutRef}
-            style={initialAppLayoutStyle}
-          >
-            <SystemNotification />
-            <div className='app-chat-layout__body'>
-              <PanelLayoutStyleSync layoutRef={appLayoutRef} />
-              <ChatViewSelectorWidthSync
-                iconOnly={chatView.iconOnly}
-                layoutRef={appLayoutRef}
-              />
-              <ChatView>
-                <DialogManagerProvider id={globalDialogManager}>
-                  <ChatStateSync initialChatView={initialChatView} />
-                  <SidebarLayoutSync />
-                  <ChannelsPanels
-                    filters={filters}
-                    iconOnly={chatView.iconOnly}
-                    initialChannelId={initialChannelId ?? undefined}
-                    itemSet={chatViewSelectorItemSet}
-                    options={options}
-                    sort={sort}
-                  />
-                  <ThreadsPanels
-                    iconOnly={chatView.iconOnly}
-                    itemSet={chatViewSelectorItemSet}
-                  />
-                </DialogManagerProvider>
-              </ChatView>
+          <EmbeddedHostPage>
+            <div
+              className='app-chat-layout'
+              data-variant={messageUiVariant ?? undefined}
+              ref={appLayoutRef}
+              style={initialAppLayoutStyle}
+            >
+              <SystemNotification />
+              <div className='app-chat-layout__body'>
+                <PanelLayoutStyleSync layoutRef={appLayoutRef} />
+                <ChatViewSelectorWidthSync
+                  iconOnly={chatView.iconOnly}
+                  layoutRef={appLayoutRef}
+                />
+                <ChatView>
+                  <DialogManagerProvider id={globalDialogManager}>
+                    <ChatStateSync initialChatView={initialChatView} />
+                    <SidebarLayoutSync />
+                    <ChannelsPanels
+                      filters={filters}
+                      iconOnly={chatView.iconOnly}
+                      initialChannelId={initialChannelId ?? undefined}
+                      itemSet={chatViewSelectorItemSet}
+                      options={options}
+                      sort={sort}
+                    />
+                    <ThreadsPanels
+                      iconOnly={chatView.iconOnly}
+                      itemSet={chatViewSelectorItemSet}
+                    />
+                  </DialogManagerProvider>
+                </ChatView>
+              </div>
             </div>
-          </div>
+          </EmbeddedHostPage>
         </Chat>
       </SidebarProvider>
     </WithComponents>

examples/vite/src/AppSettings/state.ts

@@ -72,6 +72,15 @@ export type MessageListSettingsState = {
   type: 'standard' | 'virtualized';
 };
 
+export type PageLayoutSettingsState = {
+  /**
+   * Dev harness: renders the chat as a fixed-height widget between host-page content that
+   * overflows the viewport, so the window itself scrolls. Reproduces integrations where
+   * scrolling inside the chat must not move the surrounding page.
+   */
+  embedded: boolean;
+};
+
 export type ComposerSettingsState = {
   /**
    * POC: allow sending a message while its attachments are still uploading.
@@ -102,6 +111,7 @@ export type AppSettingsState = {
   messageActions: MessageActionsSettingsState;
   messageList: MessageListSettingsState;
   notifications: NotificationsSettingsState;
+  pageLayout: PageLayoutSettingsState;
   panelLayout: PanelLayoutSettingsState;
   reactions: ReactionsSettingsState;
   theme: ThemeSettingsState;
@@ -165,6 +175,9 @@ const defaultAppSettingsState: AppSettingsState = {
   notifications: {
     verticalAlignment: 'bottom',
   },
+  pageLayout: {
+    embedded: false,
+  },
   panelLayout: {
     leftPanel: {
       collapsed: false,
@@ -300,6 +313,45 @@ const getSendMessagesWithPendingUploadsFromUrl = (): boolean | undefined => {
   return raw !== '0' && raw !== 'false';
 };
 
+const embeddedLayoutUrlParam = 'embedded_layout';
+
+/** Seeded from `?embedded_layout=1`; kept in the URL (not localStorage) so a reload keeps it. */
+const getEmbeddedLayoutFromUrl = (): boolean | undefined => {
+  if (typeof window === 'undefined') return;
+
+  const raw = new URLSearchParams(window.location.search).get(embeddedLayoutUrlParam);
+
+  if (raw === null) return;
+
+  return raw !== '0' && raw !== 'false';
+};
+
+const persistEmbeddedLayoutInUrl = (embedded: boolean) => {
+  if (typeof window === 'undefined') return;
+
+  const url = new URL(window.location.href);
+  const hasParam = url.searchParams.get(embeddedLayoutUrlParam) === '1';
+
+  if (hasParam === embedded) return;
+
+  if (embedded) url.searchParams.set(embeddedLayoutUrlParam, '1');
+  else url.searchParams.delete(embeddedLayoutUrlParam);
+
+  window.history.replaceState(
+    window.history.state,
+    '',
+    `${url.pathname}${url.search}${url.hash}`,
+  );
+};
+
+/** The root stylesheet switches #root from viewport height to page flow off this attribute. */
+const applyEmbeddedLayout = (embedded: boolean) => {
+  if (typeof document === 'undefined') return;
+
+  if (embedded) document.documentElement.setAttribute('data-embedded-layout', '');
+  else document.documentElement.removeAttribute('data-embedded-layout');
+};
+
 const getThemeModeFromUrl = (): ThemeSettingsState['mode'] | undefined => {
   if (typeof window === 'undefined') return;
 
@@ -373,6 +425,9 @@ const initialAppSettingsState: AppSettingsState = {
     // A delay in the URL means the harness is wanted, so it arms the switch too.
     slowUploads: (getSlowUploadMsFromUrl() ?? 0) > 0,
   },
+  pageLayout: {
+    embedded: getEmbeddedLayoutFromUrl() ?? defaultAppSettingsState.pageLayout.embedded,
+  },
   panelLayout: getStoredPanelLayoutSettings() ?? defaultAppSettingsState.panelLayout,
   theme: {
     ...defaultAppSettingsState.theme,
@@ -403,6 +458,14 @@ appSettingsStore.subscribeWithSelector(
 // Apply initial direction on load
 applyDirection(initialAppSettingsState.theme.direction);
 
+appSettingsStore.subscribeWithSelector(
+  ({ pageLayout }) => ({ embedded: pageLayout.embedded }),
+  ({ embedded }) => {
+    persistEmbeddedLayoutInUrl(embedded);
+    applyEmbeddedLayout(embedded);
+  },
+);
+
 appSettingsStore.subscribeWithSelector(
   ({ panelLayout }) => panelLayout,
   (panelLayout) => {

examples/vite/src/AppSettings/tabs/General/GeneralTab.tsx

@@ -12,6 +12,7 @@ type GeneralTabProps = {
 export const GeneralTab = ({ close }: GeneralTabProps) => {
   const {
     messageList,
+    pageLayout,
     theme,
     theme: { direction },
   } = useAppSettingsState();
@@ -79,6 +80,34 @@ export const GeneralTab = ({ close }: GeneralTabProps) => {
             </Button>
           </div>
         </div>
+        <div className='app__settings-modal__field'>
+          <div className='app__settings-modal__field-label'>Page layout</div>
+          <div className='app__settings-modal__options-row'>
+            <Button
+              aria-pressed={!pageLayout.embedded}
+              className='app__settings-modal__option-button str-chat__button--outline str-chat__button--secondary str-chat__button--size-sm'
+              onClick={() =>
+                appSettingsStore.partialNext({ pageLayout: { embedded: false } })
+              }
+            >
+              Full viewport
+            </Button>
+            <Button
+              aria-pressed={pageLayout.embedded}
+              className='app__settings-modal__option-button str-chat__button--outline str-chat__button--secondary str-chat__button--size-sm'
+              onClick={() =>
+                appSettingsStore.partialNext({ pageLayout: { embedded: true } })
+              }
+            >
+              Embedded in page
+            </Button>
+          </div>
+          <div className='app__settings-modal__field-comment'>
+            Embedded places the chat between host-page content taller than the viewport,
+            so the window scrolls too. Use it to check that scrolling inside the chat
+            (e.g. jumping to unread or quoted messages) leaves the page in place.
+          </div>
+        </div>
       </SettingsTabBody>
     </div>
   );

examples/vite/src/ChatLayout/EmbeddedHostPage.tsx

@@ -0,0 +1,42 @@
+import type { ReactNode } from 'react';
+
+import { type AppSettingsState, useAppSettingsSelector } from '../AppSettings';
+
+const pageLayoutSelector = ({ pageLayout }: AppSettingsState) => ({
+  embedded: pageLayout.embedded,
+});
+
+/**
+ * With the "Embedded in page" layout setting, renders the chat as a fixed-height widget
+ * between host-page content taller than the viewport, so the window scrolls as well.
+ * Any scroll the chat performs on an ancestor (e.g. Element.scrollIntoView) then shows up
+ * as the host page moving.
+ *
+ * The chat wrapper stays mounted in both layouts (it is `display: contents` in the full
+ * viewport one), so toggling the setting does not remount the chat.
+ */
+export const EmbeddedHostPage = ({ children }: { children: ReactNode }) => {
+  const { embedded } = useAppSettingsSelector(pageLayoutSelector);
+
+  return (
+    <>
+      {embedded && (
+        <header className='app-embedded-host__content'>
+          <strong>Host page header</strong>
+          <p>
+            The chat below is embedded in a page that scrolls. Scrolling inside the chat
+            should never move this page. Scroll the page so the chat is only partly in
+            view, then e.g. jump to the first unread message and check that the page stays
+            where it was.
+          </p>
+        </header>
+      )}
+      <div className='app-embedded-host__chat'>{children}</div>
+      {embedded && (
+        <footer className='app-embedded-host__content'>
+          <strong>Host page footer</strong>
+        </footer>
+      )}
+    </>
+  );
+};

examples/vite/src/index.scss

@@ -39,6 +39,41 @@ body {
   min-height: 0;
 }
 
+/* "Embedded in page" layout: #root flows with its content so the window scrolls. */
+html[data-embedded-layout] #root {
+  height: auto;
+}
+
+.app-embedded-host__content {
+  box-sizing: border-box;
+  min-height: 60vh;
+  padding: 24px;
+  font-family: system-ui, sans-serif;
+  color: #333;
+  background: repeating-linear-gradient(-45deg, #fdecec 0 16px, #fbe0e0 16px 32px);
+
+  p {
+    max-width: 60ch;
+  }
+}
+
+/* Layout-neutral in the full viewport layout; stays mounted so toggling keeps the chat. */
+.app-embedded-host__chat {
+  display: contents;
+}
+
+html[data-embedded-layout] .app-embedded-host__chat {
+  display: flex;
+  flex-direction: column;
+  flex: none;
+  /* Shorter than the viewport, so the page around the chat stays visible when scrolled to. */
+  height: 85vh;
+  height: 85dvh;
+  min-height: 0;
+  margin: 0 24px;
+  outline: 2px solid #e58a8a;
+}
+
 @layer stream-overrides {
   .app-chat-layout {
     --app-left-panel-width: 360px;

src/components/MessageComposer/__tests__/MessageInput.test.tsx

@@ -482,6 +482,23 @@ describe(`MessageInputFlat`, () => {
     expect(results).toHaveNoViolations();
   });
 
+  it('should not scroll ancestors when focusing the textarea because of the `focus` prop', async () => {
+    const focusSpy = vi.spyOn(HTMLTextAreaElement.prototype, 'focus');
+    await renderComponent({
+      messageInputProps: {
+        focus: true,
+      },
+    });
+    await waitFor(() => {
+      expect(screen.getByPlaceholderText(inputPlaceholder)).toHaveFocus();
+    });
+    expect(focusSpy).toHaveBeenCalled();
+    focusSpy.mock.calls.forEach(([options]) => {
+      expect(options).toEqual({ preventScroll: true });
+    });
+    focusSpy.mockRestore();
+  });
+
   it('should render default file upload icon', async () => {
     const { container } = await renderComponent();
     const fileUploadIcon = await screen.findByTestId('invoke-attachment-selector-button');

src/components/MessageComposer/hooks/useTextareaRef.ts

@@ -4,10 +4,10 @@ import type { MessageComposerProps } from '../MessageComposer';
 export const useTextareaRef = (props: MessageComposerProps) => {
   const { focus } = props;
   const textareaRef = useRef<HTMLTextAreaElement>(undefined);
-  // Focus
+  // Focus on mount without scrolling the host page to the composer
   useEffect(() => {
     if (focus && textareaRef.current) {
-      textareaRef.current.focus();
+      textareaRef.current.focus({ preventScroll: true });
     }
   }, [focus]);