feat: enhance message collapsing functionality in team activity components

- Added support for user-controlled message expansion in ActivityTimeline and LeadThoughtsGroup components.
- Integrated expand/collapse overrides to allow users to manually expand messages even in collapsed mode.
- Updated ActivityItem to trigger collapse toggle callbacks on click and key events for improved accessibility.
- Refactored related components to accommodate new expand/collapse logic, enhancing user experience in message handling.

src/renderer/components/team/TeamDetailView.tsx

@@ -17,6 +17,7 @@ import { getTeamColorSet } from '@renderer/constants/teamColors';
 import { useBranchSync } from '@renderer/hooks/useBranchSync';
 import { useTabUI } from '@renderer/hooks/useTabUI';
 import { useTeamMessagesRead } from '@renderer/hooks/useTeamMessagesRead';
+import { useTeamMessagesExpanded } from '@renderer/hooks/useTeamMessagesExpanded';
 import { cn } from '@renderer/lib/utils';
 import { useStore } from '@renderer/store';
 import { createChipFromSelection } from '@renderer/utils/chipUtils';
@@ -627,6 +628,7 @@ export const TeamDetailView = ({ teamName }: TeamDetailViewProps): React.JSX.Ele
   }, [data, timeWindow, messagesFilter, messagesSearchQuery, leadMemberName]);
 
   const { readSet, markRead, markAllRead } = useTeamMessagesRead(teamName ?? '');
+  const { expandedSet, toggle: toggleExpandOverride } = useTeamMessagesExpanded(teamName ?? '');
   const messagesUnreadCount = useMemo(
     () => filteredMessages.filter((m) => !m.read && !readSet.has(toMessageKey(m))).length,
     [filteredMessages, readSet]
@@ -1562,6 +1564,8 @@ export const TeamDetailView = ({ teamName }: TeamDetailViewProps): React.JSX.Ele
               members={data.members}
               readState={{ readSet, getMessageKey: toMessageKey }}
               allCollapsed={messagesCollapsed}
+              expandOverrides={expandedSet}
+              onToggleExpandOverride={toggleExpandOverride}
               onMemberClick={setSelectedMember}
               onCreateTaskFromMessage={(subject, description) => {
                 openCreateTaskDialog(subject, description);

src/renderer/components/team/activity/ActivityItem.tsx

@@ -340,13 +340,21 @@ export const ActivityItem = ({
           'flex items-center gap-2 px-3 py-2',
           isHeaderClickable ? 'cursor-pointer select-none' : '',
         ].join(' ')}
-        onClick={isHeaderClickable ? () => setIsExpanded((v) => !v) : undefined}
+        onClick={
+          isHeaderClickable
+            ? () => {
+                setIsExpanded((v) => !v);
+                onCollapseToggle?.();
+              }
+            : undefined
+        }
         onKeyDown={
           isHeaderClickable
             ? (e) => {
                 if (e.key === 'Enter' || e.key === ' ') {
                   e.preventDefault();
                   setIsExpanded((v) => !v);
+                  onCollapseToggle?.();
                 }
               }
             : undefined

src/renderer/components/team/activity/ActivityTimeline.tsx

@@ -1,6 +1,7 @@
-import React, { useEffect, useMemo, useRef, useState } from 'react';
+import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 
 import { buildMemberColorMap } from '@renderer/utils/memberHelpers';
+import { toMessageKey } from '@renderer/utils/teamMessageKey';
 
 import { ActivityItem, isNoiseMessage } from './ActivityItem';
 import { groupTimelineItems, isLeadThought, LeadThoughtsGroupRow } from './LeadThoughtsGroup';
@@ -28,6 +29,10 @@ interface ActivityTimelineProps {
   onRestartTeam?: () => void;
   /** When true, collapse all message bodies — show only headers with expand chevrons. */
   allCollapsed?: boolean;
+  /** Set of stable message keys that the user has manually expanded in collapsed mode. */
+  expandOverrides?: Set<string>;
+  /** Called when user toggles expand/collapse override on a specific message. */
+  onToggleExpandOverride?: (key: string) => void;
 }
 
 const VIEWPORT_THRESHOLD = 0.15;
@@ -50,6 +55,7 @@ const MessageRowWithObserver = ({
   onTaskIdClick,
   onRestartTeam,
   forceCollapsed,
+  onCollapseToggle,
 }: {
   message: InboxMessage;
   teamName: string;
@@ -67,6 +73,7 @@ const MessageRowWithObserver = ({
   onTaskIdClick?: (taskId: string) => void;
   onRestartTeam?: () => void;
   forceCollapsed?: boolean;
+  onCollapseToggle?: () => void;
 }): React.JSX.Element => {
   const ref = useRef<HTMLDivElement>(null);
   const reportedRef = useRef(false);
@@ -115,6 +122,7 @@ const MessageRowWithObserver = ({
         onTaskIdClick={onTaskIdClick}
         onRestartTeam={onRestartTeam}
         forceCollapsed={forceCollapsed}
+        onCollapseToggle={onCollapseToggle}
       />
     </div>
   );
@@ -132,6 +140,8 @@ export const ActivityTimeline = ({
   onTaskIdClick,
   onRestartTeam,
   allCollapsed,
+  expandOverrides,
+  onToggleExpandOverride,
 }: ActivityTimelineProps): React.JSX.Element => {
   const [visibleCount, setVisibleCount] = useState(MESSAGES_PAGE_SIZE);
 
@@ -297,6 +307,50 @@ export const ActivityTimeline = ({
   const pinnedThoughtGroup = timelineItems[0]?.type === 'lead-thoughts' ? timelineItems[0] : null;
   const startIndex = pinnedThoughtGroup ? 1 : 0;
 
+  // Determine the index of the "newest" non-thought timeline item (for auto-expand).
+  // Pinned thought group is always at index 0 when present, so newest message is the
+  // first non-thought item in the remaining list.
+  const newestMessageIndex = useMemo(() => {
+    for (let i = startIndex; i < timelineItems.length; i++) {
+      if (timelineItems[i].type !== 'lead-thoughts') return i;
+    }
+    return -1;
+  }, [timelineItems, startIndex]);
+
+  /**
+   * Compute per-item forceCollapsed + onCollapseToggle based on:
+   * - allCollapsed mode enabled/disabled
+   * - Whether this is the newest message (auto-expanded, no chevron)
+   * - Whether user has manually expanded this item (override in localStorage)
+   *
+   * | allCollapsed | isNewest | inOverrides | forceCollapsed | onCollapseToggle |
+   * |-------------|----------|-------------|----------------|------------------|
+   * | false       | any      | any         | undefined      | undefined        |
+   * | true        | yes      | any         | undefined      | undefined        |
+   * | true        | no       | yes         | false          | fn               |
+   * | true        | no       | no          | true           | fn               |
+   */
+  const getItemCollapseProps = useCallback(
+    (
+      stableKey: string,
+      itemIndex: number
+    ): { forceCollapsed?: boolean; onCollapseToggle?: () => void } => {
+      if (!allCollapsed) return {};
+      if (itemIndex === newestMessageIndex) return {};
+      // Pinned thought group (index 0) is always the newest thought → expanded
+      if (itemIndex === 0 && pinnedThoughtGroup) return {};
+
+      const isOverridden = expandOverrides?.has(stableKey) ?? false;
+      return {
+        forceCollapsed: !isOverridden,
+        onCollapseToggle: onToggleExpandOverride
+          ? () => onToggleExpandOverride(stableKey)
+          : undefined,
+      };
+    },
+    [allCollapsed, newestMessageIndex, pinnedThoughtGroup, expandOverrides, onToggleExpandOverride]
+  );
+
   return (
     <div className="space-y-1">
       {/* Pinned (newest) thought group — always at top */}
@@ -306,6 +360,8 @@ export const ActivityTimeline = ({
           const firstThought = group.thoughts[0];
           const info = memberInfo.get(firstThought.from);
           const itemKey = `thoughts-${firstThought.messageId ?? pinnedThoughtGroup.originalIndices[0]}`;
+          const stableKey = toMessageKey(firstThought);
+          const collapseProps = getItemCollapseProps(stableKey, 0);
           return (
             <LeadThoughtsGroupRow
               key={itemKey}
@@ -315,7 +371,8 @@ export const ActivityTimeline = ({
               isNew={newItemKeys.has(itemKey)}
               onVisible={onMessageVisible}
               zebraShade={zebraShadeSet.has(0)}
-              forceCollapsed={allCollapsed}
+              forceCollapsed={collapseProps.forceCollapsed}
+              onCollapseToggle={collapseProps.onCollapseToggle}
             />
           );
         })()}
@@ -348,6 +405,8 @@ export const ActivityTimeline = ({
           const firstThought = group.thoughts[0];
           const info = memberInfo.get(firstThought.from);
           const itemKey = `thoughts-${firstThought.messageId ?? item.originalIndices[0]}`;
+          const stableKey = toMessageKey(firstThought);
+          const collapseProps = getItemCollapseProps(stableKey, realIndex);
           return (
             <React.Fragment key={itemKey}>
               {sessionSeparator}
@@ -358,7 +417,8 @@ export const ActivityTimeline = ({
                 isNew={newItemKeys.has(itemKey)}
                 onVisible={onMessageVisible}
                 zebraShade={zebraShadeSet.has(realIndex)}
-                forceCollapsed={allCollapsed}
+                forceCollapsed={collapseProps.forceCollapsed}
+                onCollapseToggle={collapseProps.onCollapseToggle}
               />
             </React.Fragment>
           );
@@ -370,6 +430,8 @@ export const ActivityTimeline = ({
         const recipientColor =
           recipientInfo?.color ?? (message.to ? colorMap.get(message.to) : undefined);
         const messageKey = `${message.messageId ?? item.originalIndex}-${message.timestamp}-${message.from}`;
+        const stableKey = toMessageKey(message);
+        const collapseProps = getItemCollapseProps(stableKey, realIndex);
         const isUnread = readState
           ? !message.read && !readState.readSet.has(readState.getMessageKey(message))
           : !message.read;
@@ -392,7 +454,8 @@ export const ActivityTimeline = ({
               onVisible={onMessageVisible}
               onTaskIdClick={onTaskIdClick}
               onRestartTeam={onRestartTeam}
-              forceCollapsed={allCollapsed}
+              forceCollapsed={collapseProps.forceCollapsed}
+              onCollapseToggle={collapseProps.onCollapseToggle}
             />
           </React.Fragment>
         );

src/renderer/components/team/activity/LeadThoughtsGroup.tsx

@@ -88,6 +88,8 @@ interface LeadThoughtsGroupRowProps {
   zebraShade?: boolean;
   /** When true, collapse the thought body — show only the header with expand chevron. */
   forceCollapsed?: boolean;
+  /** Called when user toggles expand/collapse in collapsed mode. Presence enables chevron. */
+  onCollapseToggle?: () => void;
 }
 
 function formatTime(timestamp: string): string {
@@ -346,6 +348,7 @@ export const LeadThoughtsGroupRow = ({
   canBeLive,
   zebraShade,
   forceCollapsed,
+  onCollapseToggle,
 }: LeadThoughtsGroupRowProps): React.JSX.Element => {
   const ref = useRef<HTMLDivElement>(null);
   const scrollRef = useRef<HTMLDivElement>(null);
@@ -521,26 +524,34 @@ export const LeadThoughtsGroupRow = ({
         {/* Header */}
         {/* eslint-disable-next-line jsx-a11y/no-static-element-interactions -- role=button + tabIndex + onKeyDown below; nested tooltips prevent native button */}
         <div
-          role={forceCollapsed === true ? 'button' : undefined}
+          role={forceCollapsed === true || onCollapseToggle != null ? 'button' : undefined}
-          tabIndex={forceCollapsed === true ? 0 : undefined}
+          tabIndex={forceCollapsed === true || onCollapseToggle != null ? 0 : undefined}
           className={[
             'flex select-none items-center gap-2 px-3 py-1.5',
-            forceCollapsed === true ? 'cursor-pointer' : '',
+            forceCollapsed === true || onCollapseToggle != null ? 'cursor-pointer' : '',
           ].join(' ')}
-          onClick={forceCollapsed === true ? () => setIsBodyVisible((v) => !v) : undefined}
+          onClick={
+            forceCollapsed === true || onCollapseToggle != null
+              ? () => {
+                  setIsBodyVisible((v) => !v);
+                  onCollapseToggle?.();
+                }
+              : undefined
+          }
           onKeyDown={
-            forceCollapsed === true
+            forceCollapsed === true || onCollapseToggle != null
               ? (e) => {
                   if (e.key === 'Enter' || e.key === ' ') {
                     e.preventDefault();
                     setIsBodyVisible((v) => !v);
+                    onCollapseToggle?.();
                   }
                 }
               : undefined
           }
         >
           {/* Chevron for collapse mode */}
-          {forceCollapsed === true ? (
+          {forceCollapsed === true || onCollapseToggle != null ? (
             <ChevronRight
               className="size-3 shrink-0 transition-transform duration-150"
               style={{