diff --git a/stylesheets/_modules.scss b/stylesheets/_modules.scss
index e8cd42dc7c..b2fdfedea9 100644
--- a/stylesheets/_modules.scss
+++ b/stylesheets/_modules.scss
@@ -2143,6 +2143,7 @@ $timer-icons:
 
 .module-inline-notification-wrapper {
   outline: none;
+  position: relative;
 
   &:focus {
     @include mixins.keyboard-mode {
diff --git a/ts/components/conversation/CollapseSet.dom.stories.tsx b/ts/components/conversation/CollapseSet.dom.stories.tsx
index 8b1368ffd0..f48e9af1ad 100644
--- a/ts/components/conversation/CollapseSet.dom.stories.tsx
+++ b/ts/components/conversation/CollapseSet.dom.stories.tsx
@@ -40,9 +40,11 @@ const defaultProps: Props = {
   isBlocked: false,
   isGroup: true,
   isSelectMode: false,
+  isSelected: false,
   renderItem,
   targetedMessage: undefined,
   toggleDeleteMessagesModal: action('toggleDeleteMessagesModal'),
+  toggleSelectMessage: action('toggleSelectMessage'),
 };
 
 export function GroupWithTwo(): React.JSX.Element {
@@ -57,6 +59,19 @@ export function GroupWithTwo(): React.JSX.Element {
   return <CollapseSetViewer {...props} />;
 }
 
+export function GroupWithTwoSelectedCannotCollapse(): React.JSX.Element {
+  const props: Props = {
+    ...defaultProps,
+    type: 'group-updates',
+    isSelected: true,
+    messages: [
+      { id: 'id1', isUnseen: false },
+      { id: 'id2', isUnseen: false },
+    ],
+  };
+  return <CollapseSetViewer {...props} />;
+}
+
 export function AutoexpandIfTargeted(): React.JSX.Element {
   const props: Props = {
     ...defaultProps,
diff --git a/ts/components/conversation/CollapseSet.dom.tsx b/ts/components/conversation/CollapseSet.dom.tsx
index ba6543281f..18e4132193 100644
--- a/ts/components/conversation/CollapseSet.dom.tsx
+++ b/ts/components/conversation/CollapseSet.dom.tsx
@@ -34,9 +34,16 @@ export type Props = CollapseSet & {
   isBlocked: boolean;
   isGroup: boolean;
   isSelectMode: boolean;
+  isSelected: boolean;
   renderItem: (props: RenderItemProps) => React.JSX.Element;
   targetedMessage: TargetedMessageType | undefined;
   toggleDeleteMessagesModal: (props: DeleteMessagesPropsType) => void;
+  toggleSelectMessage: (
+    conversationId: string,
+    messageId: string,
+    shift: boolean,
+    selected: boolean
+  ) => void;
 };
 
 export function CollapseSetViewer(props: Props): React.JSX.Element {
@@ -51,10 +58,12 @@ export function CollapseSetViewer(props: Props): React.JSX.Element {
     conversationId,
     isBlocked,
     isGroup,
+    isSelected,
     messages,
     renderItem,
     targetedMessage,
     toggleDeleteMessagesModal,
+    toggleSelectMessage,
   } = props;
   const [isExpanded, setIsExpanded] = useState(false);
   const [messageCache, setMessageCache] = useState<
@@ -151,6 +160,10 @@ export function CollapseSetViewer(props: Props): React.JSX.Element {
             dayCount={collapsedDayCount}
             isExpanded={isExpanded}
             onClick={() => {
+              if (isSelected) {
+                return;
+              }
+
               setIsAnimating(true);
               setIsExpanded(value => !value);
             }}
@@ -160,13 +173,20 @@ export function CollapseSetViewer(props: Props): React.JSX.Element {
                 messageIds: collapsedMessages.map(item => item.id),
               });
             }}
+            onSelect={() => {
+              collapsedMessages.forEach(message => {
+                toggleSelectMessage(conversationId, message.id, false, true);
+              });
+            }}
           />
         </div>
       ) : undefined}
       <div
         className={classNames(
           'CollapseSet__height-container',
-          isExpanded ? 'CollapseSet__height-container--expanded' : undefined
+          isSelected || isExpanded
+            ? 'CollapseSet__height-container--expanded'
+            : undefined
         )}
         onTransitionEnd={event => {
           if (event.propertyName === 'height') {
@@ -177,12 +197,12 @@ export function CollapseSetViewer(props: Props): React.JSX.Element {
         <div
           className={classNames(
             'CollapseSet__transparency-container',
-            isExpanded
+            isSelected || isExpanded
               ? 'CollapseSet__transparency-container--expanded'
               : undefined
           )}
         >
-          {shouldShowButton && (isExpanded || isAnimating) ? (
+          {shouldShowButton && (isSelected || isExpanded || isAnimating) ? (
             <>
               {collapsedMessages.map((child, index) => {
                 const previousMessage = messages[index - 1];
@@ -204,9 +224,10 @@ export function CollapseSetViewer(props: Props): React.JSX.Element {
                       containerElementRef,
                       containerWidthBreakpoint,
                       conversationId,
-                      interactivity: isExpanded
-                        ? MessageInteractivity.Normal
-                        : MessageInteractivity.Hidden,
+                      interactivity:
+                        isSelected || isExpanded
+                          ? MessageInteractivity.Normal
+                          : MessageInteractivity.Hidden,
                       isBlocked,
                       isGroup,
                       isOldestTimelineItem,
@@ -263,12 +284,23 @@ function CollapseSetButton(
     isExpanded: boolean;
     isGroup: boolean;
     isSelectMode: boolean;
+    isSelected: boolean;
     i18n: LocalizerType;
     onClick: () => unknown;
     onDelete: () => unknown;
+    onSelect: () => unknown;
   }
 ): React.JSX.Element {
-  const { count, dayCount, i18n, isExpanded, onClick, onDelete, type } = props;
+  const {
+    count,
+    dayCount,
+    i18n,
+    isExpanded,
+    isSelected,
+    onClick,
+    onDelete,
+    type,
+  } = props;
 
   strictAssert(
     type !== 'none',
@@ -317,7 +349,7 @@ function CollapseSetButton(
     });
   }
 
-  const trailingIcon = isExpanded ? (
+  let trailingIcon = isExpanded ? (
     <AxoSymbol.InlineGlyph
       symbol="chevron-up"
       label={i18n('icu:collapsedItems--expanded')}
@@ -328,6 +360,9 @@ function CollapseSetButton(
       label={i18n('icu:collapsedItems--collapsed')}
     />
   );
+  if (isSelected) {
+    trailingIcon = <span />;
+  }
 
   return (
     <MessageContextMenu
@@ -345,7 +380,7 @@ function CollapseSetButton(
       onRetryMessageSend={null}
       onRetryDeleteForEveryone={null}
       onCopy={null}
-      onSelect={null}
+      onSelect={props.onSelect}
       onForward={null}
       onMoreInfo={null}
       onPinMessage={null}
diff --git a/ts/components/conversation/ContactName.dom.tsx b/ts/components/conversation/ContactName.dom.tsx
index f1baff834f..aa78f399f9 100644
--- a/ts/components/conversation/ContactName.dom.tsx
+++ b/ts/components/conversation/ContactName.dom.tsx
@@ -89,7 +89,13 @@ export function ContactName({
         contactNameColor ? getClassName(`--${contactNameColor}`) : null
       )}
       dir="auto"
-      onClick={onClick}
+      onClick={(event: React.MouseEvent<HTMLButtonElement, MouseEvent>) => {
+        if (onClick) {
+          onClick();
+          event.stopPropagation();
+          event.preventDefault();
+        }
+      }}
     >
       <UserText text={text} />
       {(isSignalConversation || isMe) && (
diff --git a/ts/components/conversation/InlineNotificationWrapper.dom.stories.tsx b/ts/components/conversation/InlineNotificationWrapper.dom.stories.tsx
new file mode 100644
index 0000000000..55069df1a7
--- /dev/null
+++ b/ts/components/conversation/InlineNotificationWrapper.dom.stories.tsx
@@ -0,0 +1,40 @@
+// Copyright 2026 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as React from 'react';
+
+import type { Meta } from '@storybook/react';
+
+import { InlineNotificationWrapper } from './InlineNotificationWrapper.dom.js';
+import { action } from '@storybook/addon-actions';
+import { tw } from '../../axo/tw.dom.js';
+
+import type { Props } from './InlineNotificationWrapper.dom.js';
+
+export default {
+  title: 'Components/Conversation/InlineNotificationWrapper',
+  args: {
+    conversationId: 'cId1',
+    isTargeted: false,
+    isSelected: false,
+    targetMessage: action('targetMessage'),
+    toggleSelectMessage: action('toggleSelectMessage'),
+    children: (
+      <div className={tw('p-2.5 text-center')}>
+        This is the default contents
+      </div>
+    ),
+  },
+} satisfies Meta<Props>;
+
+export function Default(args: Props): React.JSX.Element {
+  return <InlineNotificationWrapper {...args} />;
+}
+
+export function SelectMode(args: Props): React.JSX.Element {
+  return <InlineNotificationWrapper {...args} isSelectMode />;
+}
+
+export function SelectModeAndSelected(args: Props): React.JSX.Element {
+  return <InlineNotificationWrapper {...args} isSelectMode isSelected />;
+}
diff --git a/ts/components/conversation/InlineNotificationWrapper.dom.tsx b/ts/components/conversation/InlineNotificationWrapper.dom.tsx
index ab376880ff..368d20a5f4 100644
--- a/ts/components/conversation/InlineNotificationWrapper.dom.tsx
+++ b/ts/components/conversation/InlineNotificationWrapper.dom.tsx
@@ -1,15 +1,26 @@
 // Copyright 2019 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-import type { ReactNode } from 'react';
 import React, { useCallback, useEffect, useRef } from 'react';
+import classNames from 'classnames';
+
+import type { ReactNode } from 'react';
+
 import { getInteractionMode } from '../../services/InteractionMode.dom.ts';
 
-type PropsType = {
+export type Props = {
   id: string;
   conversationId: string;
   isTargeted: boolean;
+  isSelectMode: boolean;
+  isSelected: boolean;
   targetMessage: (messageId: string, conversationId: string) => unknown;
+  toggleSelectMessage: (
+    conversationId: string,
+    messageId: string,
+    shift: boolean,
+    selected: boolean
+  ) => void;
   children: ReactNode;
 };
 
@@ -17,9 +28,12 @@ export function InlineNotificationWrapper({
   id,
   conversationId,
   isTargeted,
+  isSelectMode,
+  isSelected,
   targetMessage,
+  toggleSelectMessage,
   children,
-}: PropsType): React.JSX.Element {
+}: Props): React.JSX.Element {
   const focusRef = useRef<HTMLDivElement>(null);
 
   useEffect(() => {
@@ -37,6 +51,45 @@ export function InlineNotificationWrapper({
     }
   }, [id, conversationId, targetMessage]);
 
+  if (isSelectMode) {
+    return (
+      <div
+        className={classNames(
+          'module-inline-notification-wrapper',
+          isSelected ? 'module-message__wrapper--selected' : undefined
+        )}
+        role="checkbox"
+        tabIndex={0}
+        ref={focusRef}
+        onFocus={handleFocus}
+        onClick={(event: React.MouseEvent<HTMLSpanElement>) => {
+          toggleSelectMessage(conversationId, id, event.shiftKey, !isSelected);
+          event.stopPropagation();
+          event.preventDefault();
+        }}
+        onKeyDown={(event: React.KeyboardEvent<HTMLSpanElement>) => {
+          if (event.code === 'Space') {
+            toggleSelectMessage(
+              conversationId,
+              id,
+              event.shiftKey,
+              !isSelected
+            );
+            event.stopPropagation();
+            event.preventDefault();
+          }
+        }}
+      >
+        <span
+          aria-label="Select"
+          className="module-message__select-checkbox"
+          aria-checked={isSelected}
+        />
+        {children}
+      </div>
+    );
+  }
+
   return (
     <div
       className="module-inline-notification-wrapper"
diff --git a/ts/components/conversation/Message.dom.tsx b/ts/components/conversation/Message.dom.tsx
index c9ca65e357..224b11ec7d 100644
--- a/ts/components/conversation/Message.dom.tsx
+++ b/ts/components/conversation/Message.dom.tsx
@@ -2326,6 +2326,7 @@ export class Message extends React.PureComponent<Props, State> {
       direction,
       getPreferredBadge,
       i18n,
+      isSelectMode,
       shouldCollapseBelow,
       showContactModal,
       theme,
@@ -2341,6 +2342,7 @@ export class Message extends React.PureComponent<Props, State> {
           'module-message__author-avatar-container--with-reactions':
             this.#hasReactions(),
         })}
+        inert={isSelectMode ? true : undefined}
       >
         {shouldCollapseBelow ? (
           <AvatarSpacer size={GROUP_AVATAR_SIZE} />
@@ -3313,6 +3315,7 @@ export class Message extends React.PureComponent<Props, State> {
       deletedForEveryone,
       direction,
       id,
+      isSelectMode,
       isSticker,
       isTapToView,
       renderMessageContextMenu,
@@ -3375,7 +3378,7 @@ export class Message extends React.PureComponent<Props, State> {
     }
 
     function maybeWrapWithContextMenu(children: ReactNode): ReactNode {
-      if (renderMessageContextMenu) {
+      if (renderMessageContextMenu && !isSelectMode) {
         return renderMessageContextMenu('AxoContextMenu', children);
       }
       return children;
@@ -3397,6 +3400,7 @@ export class Message extends React.PureComponent<Props, State> {
               ev.stopPropagation();
             }}
             tabIndex={-1}
+            inert={isSelectMode ? true : undefined}
           >
             {this.#renderAuthor()}
             <div dir={TextDirectionToDirAttribute[textDirection]}>
@@ -3561,7 +3565,6 @@ export class Message extends React.PureComponent<Props, State> {
           role="row"
           onFocus={this.handleFocus}
           ref={this.focusRef}
-          inert={isSelectMode}
         >
           {this.#renderError()}
           {this.#renderAvatar()}
diff --git a/ts/components/conversation/Timeline.dom.stories.tsx b/ts/components/conversation/Timeline.dom.stories.tsx
index e2eb011710..8ce6481fc7 100644
--- a/ts/components/conversation/Timeline.dom.stories.tsx
+++ b/ts/components/conversation/Timeline.dom.stories.tsx
@@ -362,6 +362,7 @@ const renderItem = ({
     isBlocked={false}
     isGroup={false}
     isSelectMode={false}
+    isSelected={false}
     i18n={i18n}
     interactivity={MessageInteractivity.Normal}
     interactionMode="keyboard"
diff --git a/ts/components/conversation/TimelineItem.dom.stories.tsx b/ts/components/conversation/TimelineItem.dom.stories.tsx
index e8e8e817d7..69707c85b7 100644
--- a/ts/components/conversation/TimelineItem.dom.stories.tsx
+++ b/ts/components/conversation/TimelineItem.dom.stories.tsx
@@ -44,6 +44,7 @@ const getDefaultProps = () => ({
   isNextItemCallingNotification: false,
   isPinned: false,
   isSelectMode: false,
+  isSelected: false,
   isTargeted: false,
   isBlocked: false,
   isGroup: false,
diff --git a/ts/components/conversation/TimelineItem.dom.tsx b/ts/components/conversation/TimelineItem.dom.tsx
index cdad4133c3..c4b5cc134f 100644
--- a/ts/components/conversation/TimelineItem.dom.tsx
+++ b/ts/components/conversation/TimelineItem.dom.tsx
@@ -216,6 +216,7 @@ type PropsLocalType = {
   isGroup: boolean;
   isNextItemCallingNotification: boolean;
   isSelectMode: boolean;
+  isSelected: boolean;
   isTargeted: boolean;
   scrollToPinnedMessage: (pinMessage: PinMessageData) => void;
   scrollToPollMessage: (
@@ -224,6 +225,12 @@ type PropsLocalType = {
     conversationId: string
   ) => unknown;
   targetMessage: (messageId: string, conversationId: string) => unknown;
+  toggleSelectMessage: (
+    conversationId: string,
+    messageId: string,
+    shift: boolean,
+    selected: boolean
+  ) => void;
   shouldRenderDateHeader: boolean;
   onOpenEditNicknameAndNoteModal: (contactId: string) => void;
   onOpenMessageRequestActionsConfirmation: (state: MessageRequestState) => void;
@@ -267,6 +274,7 @@ export const TimelineItem = memo(function TimelineItem({
   isGroup,
   isNextItemCallingNotification,
   isSelectMode,
+  isSelected,
   isTargeted,
   item,
   onOpenEditNicknameAndNoteModal,
@@ -287,6 +295,7 @@ export const TimelineItem = memo(function TimelineItem({
   shouldRenderDateHeader,
   targetedMessage,
   theme,
+  toggleSelectMessage,
   ...reducedProps
 }: PropsType): React.JSX.Element | null {
   if (!item) {
@@ -317,6 +326,7 @@ export const TimelineItem = memo(function TimelineItem({
         platform={platform}
         i18n={i18n}
         theme={theme}
+        toggleSelectMessage={toggleSelectMessage}
       />
     );
   } else if (item.type === 'collapseSet') {
@@ -329,9 +339,11 @@ export const TimelineItem = memo(function TimelineItem({
         isBlocked={isBlocked}
         isGroup={isGroup}
         isSelectMode={isSelectMode}
+        isSelected={isSelected}
         renderItem={renderItem}
         targetedMessage={targetedMessage}
         toggleDeleteMessagesModal={reducedProps.toggleDeleteMessagesModal}
+        toggleSelectMessage={toggleSelectMessage}
         i18n={i18n}
       />
     );
@@ -518,7 +530,10 @@ export const TimelineItem = memo(function TimelineItem({
         id={id}
         conversationId={conversationId}
         isTargeted={isTargeted}
+        isSelectMode={isSelectMode}
+        isSelected={isSelected}
         targetMessage={targetMessage}
+        toggleSelectMessage={toggleSelectMessage}
       >
         {notification}
       </InlineNotificationWrapper>
diff --git a/ts/state/smart/TimelineItem.preload.tsx b/ts/state/smart/TimelineItem.preload.tsx
index 4fbdb97e82..879e07c6b7 100644
--- a/ts/state/smart/TimelineItem.preload.tsx
+++ b/ts/state/smart/TimelineItem.preload.tsx
@@ -151,6 +151,11 @@ export const SmartTimelineItem = memo(function SmartTimelineItem(
         }
       : itemFromSelector;
 
+  const isSelected =
+    selectedMessageIds?.includes(messageId) ||
+    (item.type !== 'none' &&
+      item.messages.some(message => selectedMessageIds?.includes(message.id)));
+
   const {
     blockGroupLinkRequests,
     cancelAttachmentDownload,
@@ -247,6 +252,7 @@ export const SmartTimelineItem = memo(function SmartTimelineItem(
       isNextItemCallingNotification={isNextItemCallingNotification}
       isTargeted={isTargeted}
       isSelectMode={selectedMessageIds != null}
+      isSelected={isSelected}
       renderAudioAttachment={renderAudioAttachment}
       renderContact={renderContact}
       renderReactionPicker={renderReactionPicker}