diff --git a/static/sessions.js b/static/sessions.js
index a4b0ba20..c40d4829 100644
--- a/static/sessions.js
+++ b/static/sessions.js
@@ -6328,6 +6328,8 @@ function _attachChildSessionsToSidebarRows(collapsedRows, rawSessions, rawRefere
   };
   const orphans=[];
   const renderableChildIds=new Set((rawSessions||[]).map(s=>s&&s.session_id).filter(Boolean));
+  const childAttachOrderById=new Map();
+  let childAttachCursor=0;
   const attachQueueById=new Map();
   for(const candidate of [...(rawSessions||[]),...(referenceSessions||[])]){
     if(candidate&&candidate.session_id&&!attachQueueById.has(candidate.session_id)) attachQueueById.set(candidate.session_id,candidate);
@@ -6382,6 +6384,9 @@ function _attachChildSessionsToSidebarRows(collapsedRows, rawSessions, rawRefere
     }
     if(parentRow){
       const childCopy={...child};
+      if(!childAttachOrderById.has(childCopy.session_id)){
+        childAttachOrderById.set(childCopy.session_id, childAttachCursor++);
+      }
       if(parentSegment){
         childCopy._parent_segment_id=parentSegment.session_id;
         childCopy._parent_segment_title=_sessionDisplayTitle(parentSegment)||child.parent_title||'Untitled';
@@ -6410,6 +6415,23 @@ function _attachChildSessionsToSidebarRows(collapsedRows, rawSessions, rawRefere
       orphans.push({...child,_orphan_child_session:true});
     }
   }
+  const resolveReadOnlySession = typeof _isReadOnlySession === 'function'
+    ? _isReadOnlySession
+    : ((session) => !!(session && session.read_only));
+  for(const row of rows){
+    if(Array.isArray(row._child_sessions)&&row._child_sessions.length>1){
+      row._child_sessions.sort((a,b)=>{
+        const readOnlyCmp = Number(resolveReadOnlySession(a))-Number(resolveReadOnlySession(b));
+        if(readOnlyCmp!==0) return readOnlyCmp;
+        const aOrder = childAttachOrderById.get(a&&a.session_id) || 0;
+        const bOrder = childAttachOrderById.get(b&&b.session_id) || 0;
+        return aOrder-bOrder;
+      });
+    }
+    if(Array.isArray(row._child_sessions)){
+      row._child_session_count=row._child_sessions.length;
+    }
+  }
   return [...rows,...orphans];
 }
 
@@ -7523,7 +7545,7 @@ function renderSessionListFromCache(){
       const childList=document.createElement('div');
       childList.className='session-child-sessions';
       ['pointerdown','pointerup','click','touchstart','touchmove','touchend','touchcancel'].forEach(ev=>childList.addEventListener(ev,e=>e.stopPropagation()));
-      const sortedChildren=[...s._child_sessions].sort((a,b)=>_sessionTimestampMs(b)-_sessionTimestampMs(a));
+      const sortedChildren=[...s._child_sessions];
       const openChildSession=async(childSession)=>{
         // #5409: close mobile sidebar synchronously before navigation
         if(typeof closeMobileSidebar==='function')closeMobileSidebar();
diff --git a/tests/test_session_lineage_collapse.py b/tests/test_session_lineage_collapse.py
index 5a7ce5a6..65b262b3 100644
--- a/tests/test_session_lineage_collapse.py
+++ b/tests/test_session_lineage_collapse.py
@@ -554,6 +554,85 @@ console.log(JSON.stringify(rows));
     assert rows[0]["_child_sessions"][0]["session_id"] == "subagent_child"
 
 
+def test_read_only_child_sessions_are_stacked_after_writable_children():
+    """Read-only delegated children should render after fork/writable children."""
+    js = SESSIONS_JS_PATH.read_text(encoding="utf-8")
+    source = f"""
+const src = {js!r};
+function extractFunc(name) {{
+  const re = new RegExp('function\\\\s+' + name + '\\\\s*\\\\(');
+  const start = src.search(re);
+  if (start < 0) throw new Error(name + ' not found');
+  let i = src.indexOf('{{', start);
+  let depth = 1; i++;
+  while (depth > 0 && i < src.length) {{
+    if (src[i] === '{{') depth++;
+    else if (src[i] === '}}') depth--;
+    i++;
+  }}
+  return src.slice(start, i);
+}}
+eval(extractFunc('_isReadOnlySession'));
+eval(extractFunc('_isChildSession'));
+eval(extractFunc('_isForkWithResolvableParent'));
+eval(extractFunc('_sidebarLineageKeyForRow'));
+eval(extractFunc('_attachChildSessionsToSidebarRows'));
+const collapsed = [{{
+  session_id:'parent',
+  title:'Parent conversation',
+  message_count:3,
+  updated_at: 1700000010,
+  last_message_at: 1700000010,
+}}];
+const raw = [
+  collapsed[0],
+  {{
+    session_id:'read_only_subagent',
+    title:'Retained Subagent',
+    parent_session_id:'parent',
+    relationship_type:'child_session',
+    read_only: true,
+    raw_source:'subagent',
+    source_tag:'subagent',
+    session_source:'other',
+    source_label:'Subagent',
+    updated_at: 1700000030,
+    last_message_at: 1700000030,
+  }},
+  {{
+    session_id:'fork_child',
+    title:'Fork',
+    parent_session_id:'parent',
+    session_source:'fork',
+    raw_source:'webui',
+    source_tag:'webui',
+    source_label:'WebUI',
+    updated_at: 1700000040,
+    last_message_at: 1700000040,
+  }},
+  {{
+    session_id:'writable_subagent',
+    title:'Writable Subagent',
+    parent_session_id:'parent',
+    relationship_type:'child_session',
+    read_only: false,
+    raw_source:'subagent',
+    source_tag:'subagent',
+    session_source:'other',
+    source_label:'Subagent',
+    updated_at: 1700000020,
+    last_message_at: 1700000020,
+  }},
+];
+const rows = _attachChildSessionsToSidebarRows(collapsed, raw);
+console.log(JSON.stringify(rows[0]._child_sessions.map(row => row.session_id)));
+"""
+    rows = json.loads(_run_node(source))
+    assert rows == ["fork_child", "writable_subagent", "read_only_subagent"]
+    assert "const sortedChildren=[...s._child_sessions];" in js
+    assert "const sortedChildren=[...s._child_sessions].sort" not in js
+
+
 def test_parent_source_label_display_text_does_not_force_external_orphaning():
     """Display-only source labels must not drive machine source classification."""
     js = SESSIONS_JS_PATH.read_text(encoding="utf-8")