diff --git a/static/sessions.js b/static/sessions.js
index 73560c49..bf82d935 100644
--- a/static/sessions.js
+++ b/static/sessions.js
@@ -4346,6 +4346,44 @@ function _syncSessionAttentionSoundState(sessions){
   next.forEach((sig,sid)=>_sessionAttentionSoundState.set(sid,sig));
 }
 
+// Signature of everything the sidebar render reads from the applied payload +
+// the coarse display state. Used to skip the full DOM rebuild when a poll
+// returns data identical to what is already on screen (the common idle case).
+// A streaming row's fields advance each poll so its signature changes and it
+// still renders; client-only display toggles (search, active, density, select,
+// lineage expansion) render through their own paths and are intentionally light
+// here. Serialization failure returns null → never skip. (#5455 WS2.4)
+let _lastSessionListRenderSig = null;
+function _sessionListRenderSignature(){
+  try{
+    const search=($('sessionSearch')&&$('sessionSearch').value)||'';
+    const sessionKeys = [
+      'session_id','id','display_name','title','created_at','started_at',
+      'updated_at','last_message_at','last_activity','message_count',
+      'actual_message_count','is_streaming','streaming','status','pinned',
+      'archived','project_id','source','session_source','generation',
+      '_lineage_root_id','_lineage_tip_id','_compression_segment_count',
+    ];
+    const sessionsSlim = Array.isArray(_allSessions) ? _allSessions.map(s => {
+      if(!s || typeof s !== 'object') return s;
+      const out={};
+      sessionKeys.forEach(k=>{ if(Object.prototype.hasOwnProperty.call(s,k)) out[k]=s[k]; });
+      return out;
+    }) : _allSessions;
+    return JSON.stringify([
+      sessionsSlim,
+      _allProjects,
+      _activeSessionIdForSidebar(),
+      search,
+      _sessionSourceFilter,
+      !!_sessionSelectMode,
+      (window._sidebarDensity==='detailed'?'d':'c'),
+      !!_showAllProfiles,
+      _otherProfileCount,_archivedWebuiCount,_archivedCliCount,
+      _serverWebuiSessionCount,_serverCliSessionCount,
+    ]);
+  }catch(_){ return null; }
+}
 function _applySessionListPayload(sessData, projData){
   // Server's other_profile_count tells us how many sessions exist outside the
   // active profile so the "Show N from other profiles" toggle can render
@@ -4428,6 +4466,22 @@ function _applySessionListPayload(sessData, projData){
   // authoritative render replaces the profile-switch skeleton — while unrelated renders that
   // fire before this point stay blocked by the guard in renderSessionListFromCache().
   _sessionListSkeletonActive = false;
+  // No-op fast path: if this payload renders identically to what is already on
+  // screen (the common case for idle polls) and no entrance animation is
+  // pending, skip the full DOM rebuild. Only applies here in the fetch/apply
+  // path; the 60s relative-time refresh and every other render trigger call
+  // renderSessionListFromCache directly and are unaffected. Guarded by the same
+  // conditions renderSessionListFromCache bails on, so a bailed render never
+  // caches a signature that would suppress the next real repaint. (#5455 WS2.4)
+  const _canRenderNow = !_renamingSid && !_sessionActionMenu;
+  const _renderSig = _sessionListRenderSignature();
+  if(_canRenderNow && !_sessionListRefreshAnimationPending && _renderSig && _renderSig===_lastSessionListRenderSig){
+    // Preserve the per-refresh INFLIGHT cleanup that renderSessionListFromCache
+    // would otherwise perform, then skip only the DOM rebuild.
+    if(typeof _purgeStaleInflightEntries==='function') _purgeStaleInflightEntries();
+    return;
+  }
+  if(_canRenderNow) _lastSessionListRenderSig = _renderSig;
   renderSessionListFromCache();  // no-ops if rename is in progress
 }
 
diff --git a/tests/test_issue4766_sidebar_source_pushdown.py b/tests/test_issue4766_sidebar_source_pushdown.py
index abbfb972..c1031174 100644
--- a/tests/test_issue4766_sidebar_source_pushdown.py
+++ b/tests/test_issue4766_sidebar_source_pushdown.py
@@ -472,13 +472,19 @@ global._sessionListLoadError = null;
 global._sessionListHasLoadedOnce = false;
 global._sessionListFirstRenderAnimated = true;
 global._sessionListSkeletonActive = true;
+global._sessionListRefreshAnimationPending = false;
+global._lastSessionListRenderSig = null;
 global._activeProject = null;
 global.NO_PROJECT_FILTER = '__none__';
 global._showAllProfiles = false;
 global._sessionSourceFilter = 'webui';
+global._renamingSid = null;
+global._sessionActionMenu = null;
 global.S = {{ activeProfile: 'default' }};
 global._reconcileActiveSessionIdleStateFromList = rows => rows;
 global._mergeOptimisticFirstTurnSessions = rows => rows;
+global._sessionListRenderSignature = () => '';
+global._purgeStaleInflightEntries = () => {{}};
 global._syncSessionAttentionSoundState = () => {{}};
 global._pruneLineageReportCacheToVisibleSessions = () => {{}};
 global._markPollingCompletionUnreadTransitions = () => {{}};
diff --git a/tests/test_webui_external_refresh_frontend.py b/tests/test_webui_external_refresh_frontend.py
index 395c5737..d37f253c 100644
--- a/tests/test_webui_external_refresh_frontend.py
+++ b/tests/test_webui_external_refresh_frontend.py
@@ -133,6 +133,19 @@ def test_session_event_profile_filter_tolerates_default_root_aliases():
     assert "S.activeProfileIsDefault = !!data.is_default;" in PANELS_JS
 
 
+def test_session_list_render_signature_ignores_non_display_session_fields():
+    start = SESSIONS_JS.find("function _sessionListRenderSignature()")
+    assert start != -1
+    block = SESSIONS_JS[start:start + 1500]
+    assert "const sessionKeys = [" in block
+    assert "const sessionsSlim = Array.isArray(_allSessions)" in block
+    assert "sessionKeys.forEach" in block
+    assert "_allSessions," not in block
+    assert "message_count" in block
+    assert "last_message_at" in block
+    assert "_compression_segment_count" in block
+
+
 def test_pwa_pull_to_refresh_refreshes_session_list_not_page_when_available():
     assert "window.refreshSessionList('pull', {force:true, refreshActive:true})" in UI_JS
     assert "Promise.resolve(window.refreshSessionList('pull', {force:true, refreshActive:true})).catch(()=>{}).finally(_ptrReset)" in UI_JS