diff --git a/static/sessions.js b/static/sessions.js
index 849ee30c..183342ef 100644
--- a/static/sessions.js
+++ b/static/sessions.js
@@ -392,6 +392,12 @@ async function loadSession(sid){
   S.session=data.session;
   S.session._modelResolutionDeferred=true;
   S.lastUsage={...(data.session.last_usage||{})};
+  // Reset scroll-direction tracker on session switch so the new chat's
+  // first scroll doesn't compare against the previous chat's scrollTop
+  // and false-trigger an unpin (#1731 follow-up — Opus stage-302 SHOULD-FIX).
+  if (typeof window !== 'undefined' && typeof window._resetScrollDirectionTracker === 'function') {
+    try { window._resetScrollDirectionTracker(); } catch (_) {}
+  }
   // Sync workspace display immediately so the chip label reflects the new session's workspace
   // before any async message-loading begins (mirrors how model is handled).
   if(typeof syncTopbar==='function') syncTopbar();
diff --git a/static/ui.js b/static/ui.js
index 2e226515..bef64a22 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -1401,6 +1401,11 @@ let _scrollPinned=true;
 let _programmaticScroll=false;
 let _nearBottomCount=0;
 let _lastScrollTop=null;
+// Reset hook for session-switch — called from sessions.js loadSession() to
+// prevent the new chat's first scroll comparing against the previous chat's
+// scrollTop (Opus stage-302 SHOULD-FIX, #1731 follow-up).
+function _resetScrollDirectionTracker(){ _lastScrollTop=null; }
+if (typeof window !== 'undefined') window._resetScrollDirectionTracker = _resetScrollDirectionTracker;
 (function(){
   const el=document.getElementById('messages');
   if(!el) return;