diff --git a/backend/src/models/migrations/012_composite_avatar.sql b/backend/src/models/migrations/012_composite_avatar.sql
new file mode 100644
index 0000000..f4d4fa9
--- /dev/null
+++ b/backend/src/models/migrations/012_composite_avatar.sql
@@ -0,0 +1,5 @@
+-- Migration 012: Add composite_members to groups for private group avatar composites
+-- Stores up to 4 member previews (id, name, avatar) as a JSONB snapshot.
+-- Only set for non-managed, non-direct private groups with 3+ members.
+-- Updated only when a member is added and pre-add membership count was ≤3.
+ALTER TABLE groups ADD COLUMN IF NOT EXISTS composite_members JSONB;
diff --git a/backend/src/routes/groups.js b/backend/src/routes/groups.js
index ce877fb..f38f634 100644
--- a/backend/src/routes/groups.js
+++ b/backend/src/routes/groups.js
@@ -13,6 +13,21 @@ function deleteImageFile(imageUrl) {
 // Schema-aware room name helper
 const R = (schema, type, id) => `${schema}:${type}:${id}`;
 
+// Compute and store composite_members for a non-managed private group.
+// Captures up to 4 current members (excluding deleted users), ordered by name.
+async function computeAndStoreComposite(schema, groupId) {
+  const members = await query(schema,
+    `SELECT u.id, u.name, u.avatar FROM group_members gm
+     JOIN users u ON gm.user_id = u.id
+     WHERE gm.group_id = $1 AND u.name != 'Deleted User'
+     ORDER BY u.name LIMIT 4`,
+    [groupId]
+  );
+  await exec(schema, 'UPDATE groups SET composite_members=$1 WHERE id=$2',
+    [JSON.stringify(members), groupId]
+  );
+}
+
 module.exports = (io) => {
 
 async function emitGroupNew(schema, io, groupId) {
@@ -202,6 +217,11 @@ router.post('/', authMiddleware, async (req, res) => {
           await exec(req.schema, 'INSERT INTO group_members (group_id,user_id) VALUES ($1,$2) ON CONFLICT DO NOTHING', [groupId, uid]);
         }
       }
+      // Generate composite avatar for non-managed private groups with 3+ members
+      const totalCount = await queryOne(req.schema, 'SELECT COUNT(*) AS cnt FROM group_members WHERE group_id=$1', [groupId]);
+      if (parseInt(totalCount.cnt) >= 3) {
+        await computeAndStoreComposite(req.schema, groupId);
+      }
     }
     await emitGroupNew(req.schema, io, groupId);
     res.json({ group: await queryOne(req.schema, 'SELECT * FROM groups WHERE id=$1', [groupId]) });
@@ -246,6 +266,8 @@ router.post('/:id/members', authMiddleware, async (req, res) => {
     if (group.owner_id !== req.user.id && req.user.role !== 'admin') return res.status(403).json({ error: 'Only owner can add members' });
     const targetUser = await queryOne(req.schema, 'SELECT is_default_admin FROM users WHERE id=$1', [userId]);
     if (targetUser?.is_default_admin) return res.status(400).json({ error: 'Default admin cannot be added to private groups' });
+    // Capture pre-add count to decide if composite should regenerate
+    const preAddCount = await queryOne(req.schema, 'SELECT COUNT(*) AS cnt FROM group_members WHERE group_id=$1', [group.id]);
     await exec(req.schema, 'INSERT INTO group_members (group_id,user_id) VALUES ($1,$2) ON CONFLICT DO NOTHING', [group.id, userId]);
     const addedUser = await queryOne(req.schema, 'SELECT name,display_name FROM users WHERE id=$1', [userId]);
     const addedName = addedUser?.display_name || addedUser?.name || 'Unknown';
@@ -259,6 +281,14 @@ router.post('/:id/members', authMiddleware, async (req, res) => {
     );
     sysMsg.reactions = [];
     io.to(R(req.schema,'group',group.id)).emit('message:new', sysMsg);
+    // Regenerate composite if pre-add count was ≤3 and group is non-managed private
+    if (!group.is_managed && !group.is_direct && parseInt(preAddCount.cnt) <= 3) {
+      const newTotal = parseInt(preAddCount.cnt) + 1;
+      if (newTotal >= 3) {
+        await computeAndStoreComposite(req.schema, group.id);
+      }
+      await emitGroupUpdated(req.schema, io, group.id);
+    }
     io.in(R(req.schema,'user',userId)).socketsJoin(R(req.schema,'group',group.id));
     io.to(R(req.schema,'user',userId)).emit('group:new', { group });
     res.json({ success: true });
diff --git a/frontend/src/components/Sidebar.jsx b/frontend/src/components/Sidebar.jsx
index 63ef527..b074585 100644
--- a/frontend/src/components/Sidebar.jsx
+++ b/frontend/src/components/Sidebar.jsx
@@ -33,15 +33,15 @@ const COMPOSITE_LAYOUTS = {
   ],
 };
 
-function GroupAvatarComposite({ memberPreviews, fallbackLabel, fallbackColor }) {
+function GroupAvatarComposite({ memberPreviews }) {
   const members = (memberPreviews || []).slice(0, 4);
   const n = members.length;
   const positions = COMPOSITE_LAYOUTS[n];
 
   if (!positions) {
     return (
-      <div className="group-icon" style={{ background: fallbackColor, borderRadius: 8, fontSize: 11, fontWeight: 700 }}>
-        {fallbackLabel}
+      <div className="group-icon" style={{ background: '#a142f4', borderRadius: 8, fontSize: 11, fontWeight: 700 }}>
+        ?
       </div>
     );
   }
@@ -165,9 +165,11 @@ export default function Sidebar({ groups, activeGroupId, onSelectGroup, notifica
               {(group.peer_real_name || group.name)[0]?.toUpperCase()}
             </div>
           ) : group.is_managed && group.is_multi_group ? (
-            <GroupAvatarComposite memberPreviews={group.member_previews} fallbackLabel="MG" fallbackColor={settings.color_avatar_dm || '#a142f4'} />
+            <div className="group-icon" style={{ background: settings.color_avatar_dm || '#a142f4', borderRadius: 8, fontSize: 11, fontWeight: 700 }}>MG</div>
           ) : group.is_managed ? (
-            <GroupAvatarComposite memberPreviews={group.member_previews} fallbackLabel="UG" fallbackColor={settings.color_avatar_dm || '#a142f4'} />
+            <div className="group-icon" style={{ background: settings.color_avatar_dm || '#a142f4', borderRadius: 8, fontSize: 11, fontWeight: 700 }}>UG</div>
+          ) : group.composite_members?.length > 0 ? (
+            <GroupAvatarComposite memberPreviews={group.composite_members} />
           ) : (
             <div className="group-icon" style={{ background: group.type === 'public' ? (settings.color_avatar_public || '#1a73e8') : (settings.color_avatar_dm || '#a142f4') }}>
               {group.type === 'public' ? '#' : group.name[0]?.toUpperCase()}
@@ -231,7 +233,7 @@ export default function Sidebar({ groups, activeGroupId, onSelectGroup, notifica
         )}
         {groupMessagesMode && privateFiltered.length > 0 && (
           <div className="group-section">
-            <div className="section-label">PRIVATE GROUP MESSAGES</div>
+            <div className="section-label">USER GROUP MESSAGES</div>
             {privateFiltered.map(g => <GroupItem key={g.id} group={g} />)}
           </div>
         )}