fix: preserve first-turn sidebar row during refresh

static/sessions.js

@@ -1450,6 +1450,53 @@ window.addEventListener('resize',()=>{
 // with stale data, causing sessions to vanish from the sidebar.
 let _renderSessionListGen = 0;
 
+function _isOptimisticFirstTurnSessionRow(s){
+  if(!s||!s.session_id||s.archived) return false;
+  const messageCount=Number(s.message_count||0);
+  if(messageCount<=0&&!s.pending_user_message) return false;
+  return Boolean(
+    s.is_streaming||
+    s.active_stream_id||
+    s.pending_user_message||
+    s.pending_started_at||
+    _isSessionLocallyStreaming(s)||
+    _sessionStreamingById.get(s.session_id)===true
+  );
+}
+
+function _mergeOptimisticFirstTurnSessions(fetchedSessions){
+  const merged=Array.isArray(fetchedSessions)?[...fetchedSessions]:[];
+  const bySid=new Map();
+  merged.forEach((s,idx)=>{if(s&&s.session_id) bySid.set(s.session_id,idx);});
+  for(const local of Array.isArray(_allSessions)?_allSessions:[]){
+    if(!_isOptimisticFirstTurnSessionRow(local)) continue;
+    const sid=local.session_id;
+    const idx=bySid.has(sid)?bySid.get(sid):-1;
+    if(idx>=0){
+      const fetched=merged[idx]||{};
+      const localCount=Number(local.message_count||0);
+      const fetchedCount=Number(fetched.message_count||0);
+      const localTs=Number(local.last_message_at||local.updated_at||0);
+      const fetchedTs=Number(fetched.last_message_at||fetched.updated_at||0);
+      merged[idx]={
+        ...local,
+        ...fetched,
+        message_count:Math.max(localCount,fetchedCount),
+        last_message_at:Math.max(localTs,fetchedTs),
+        updated_at:Math.max(Number(local.updated_at||0),Number(fetched.updated_at||0),localTs,fetchedTs),
+        active_stream_id:fetched.active_stream_id||local.active_stream_id||null,
+        pending_user_message:fetched.pending_user_message||local.pending_user_message||null,
+        pending_started_at:fetched.pending_started_at||local.pending_started_at||null,
+        is_streaming:Boolean(fetched.is_streaming||local.is_streaming||_isSessionLocallyStreaming(local)),
+      };
+    }else{
+      merged.push({...local,is_streaming:true});
+      bySid.set(sid,merged.length-1);
+    }
+  }
+  return merged;
+}
+
 async function renderSessionList(){
   const _gen = ++_renderSessionListGen;
   try{
@@ -1465,7 +1512,7 @@ async function renderSessionList(){
     // active profile so the "Show N from other profiles" toggle can render
     // without a second round-trip. Stashed on the module for renderSessionListFromCache.
     _otherProfileCount = sessData.other_profile_count || 0;
-    _allSessions = sessData.sessions||[];
+    _allSessions = _mergeOptimisticFirstTurnSessions(sessData.sessions||[]);
     _allProjects = projData.projects||[];
     // Capture server clock for clock-skew compensation (issue #1144).
     // server_time is epoch seconds from the server's time.time().

tests/test_sidebar_first_turn_visibility.py

@@ -97,3 +97,20 @@ class TestSidebarFirstTurnVisibility:
             "The index-path empty-session filter must exempt pending first-turn sessions, "
             "matching the full-scan fallback."
         )
+
+    def test_session_refresh_preserves_optimistic_first_turn_rows_when_server_lags(self):
+        src = read("static/sessions.js")
+        assert "function _mergeOptimisticFirstTurnSessions" in src, (
+            "renderSessionList() must merge locally optimistically inserted first-turn rows "
+            "back into the fetched /api/sessions result. A session switch can re-fetch before "
+            "the server has saved pending state, and replacing _allSessions would hide the "
+            "new in-flight chat until the stream finishes."
+        )
+        render_start = src.index("async function renderSessionList")
+        render_end = src.index("// ── Gateway session SSE", render_start)
+        render_body = src[render_start:render_end]
+        assign_idx = render_body.index("_allSessions =")
+        assert "_mergeOptimisticFirstTurnSessions" in render_body[:assign_idx + 160], (
+            "The fetched session list should be merged with optimistic rows at the assignment "
+            "site, before completion transitions or renderSessionListFromCache() run."
+        )