diff --git a/server/public/home.html b/server/public/home.html
index 73c88dc..d250caa 100644
--- a/server/public/home.html
+++ b/server/public/home.html
@@ -1140,7 +1140,7 @@
 </head>
 <body>
 <script src="/icons.js?v=6"></script>
-<script>window.__BUILD='2026-07-18-batch121';console.log('%cBiz Connect','color:#1F3B73;font-weight:bold','build '+window.__BUILD);
+<script>window.__BUILD='2026-07-19-batch122';console.log('%cBiz Connect','color:#1F3B73;font-weight:bold','build '+window.__BUILD);
 // Emoji are rendered with the OS's own (colour) emoji font — instant, zero network.
 //
 // We used to run Twemoji over every emoji, which swapped each one for an <img> pulled INDIVIDUALLY from
@@ -1150,6 +1150,22 @@
 // existing call sites don't have to change.
 function twemojify(_el){ /* native emoji: nothing to do */ }</script>
 <script>
+// TEMP perf diagnostics → /api/dbg (server log). Remove once slide/scroll jank is fixed.
+window.bzDbg=function(tag,extra){ try{ var p={tag:tag,build:window.__BUILD}; if(extra) for(var k in extra) p[k]=extra[k]; fetch('/api/dbg',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify(p)}).catch(function(){}); }catch(e){} };
+// Measures frame gaps + long tasks over a window (the chat-open slide). Big maxGap / long tasks == the
+// main thread is blocked (jank); small gaps == the compositor is running the slide smoothly.
+window.__perfProbe=function(label){ try{
+  var frames=[], last=performance.now(), start=last, longtasks=[], po=null;
+  try{ po=new PerformanceObserver(function(l){ l.getEntries().forEach(function(e){ longtasks.push(Math.round(e.duration)); }); }); po.observe({entryTypes:['longtask']}); }catch(_){}
+  (function tick(now){ frames.push(Math.round(now-last)); last=now;
+    if(now-start<650){ requestAnimationFrame(tick); }
+    else { if(po) try{po.disconnect();}catch(_){}
+      var max=0; for(var i=1;i<frames.length;i++) if(frames[i]>max) max=frames[i];
+      var over=frames.filter(function(d){return d>24;}).length;
+      window.bzDbg('slidePerf',{label:label||'', frames:frames.length, maxGapMs:max, jankFrames:over, longtasks:longtasks, gaps:frames.slice(0,40)}); }
+  })(last);
+}catch(e){} };
+<script>
 // Native shell tag (iOS/Android). Safe-area insets are handled natively by the @capacitor-community/
 // safe-area plugin (it makes env(safe-area-inset-*) report real values), so there's no JS status-bar
 // juggling here — we only tag <html> so CSS can make small native-only tweaks if needed.
@@ -1498,8 +1514,11 @@ async function loadOlder(){
     const have=new Set(THREAD.map(m=>m.id)); const add=older.filter(m=>!have.has(m.id));
     if(add.length){ THREAD=add.concat(THREAD); THREAD_CACHE.set(kind+':'+id, THREAD.slice()); }
     if(older.length<PAGE) _hasMoreOlder=false;
+    if(window.__perfProbe) window.__perfProbe('older'); // TEMP: measure frame timing during the older-page render
+    const _beforeTop = box?box.scrollTop:0;
     renderThread(true);                                   // keep scroll (don't jump to bottom)
     _restore();                                           // put the anchor message back at its exact viewport position
+    if(window.bzDbg && box) window.bzDbg('older',{added:add.length, beforeScrollTop:Math.round(_beforeTop), afterScrollTop:Math.round(box.scrollTop), scrollH:Math.round(box.scrollHeight)}); // TEMP: did the anchor hold?
     if(box){ const imgs=[...box.querySelectorAll('.bubble img')].filter(im=>!im.complete); imgs.forEach(im=>im.addEventListener('load', _restore, {once:true})); setTimeout(()=>imgs.forEach(im=>{ try{ im.removeEventListener('load', _restore); }catch(_){} }), 3000); } // re-anchor as prepended images load (they'd shift it down)
   } else { _hasMoreOlder=false; }
   _loadingOlder=false; _olderCd=Date.now()+500; // brief cooldown so it can't re-fire and fight the scroll
@@ -2700,7 +2719,7 @@ function renderThread(keepScroll){
   if(!THREAD.length){ box.innerHTML='<div class="empty-thread">No messages yet — say hello 👋</div>'; return; }
   let html='';
   for(const m of THREAD){ const dk=dayKey(m.created_at); if(dk!==_lastDay){ html+='<div class="day-sep"><span>'+pEsc(dayLabel(m.created_at))+'</span></div>'; _lastDay=dk; } rendered.add(m.id); html+=bubbleHTML(m); }
-  box.innerHTML=html; twemojify(box);
+  var _rt0=performance.now(); box.innerHTML=html; twemojify(box); if(window.bzDbg && !keepScroll) window.bzDbg('render',{n:THREAD.length, innerHtmlKb:Math.round(html.length/1024), renderMs:Math.round(performance.now()-_rt0)}); // TEMP: how long the sync DOM build costs
   if(!keepScroll){
     if(_convoRevealed){
       // #7: a later render during the SAME open (network arriving after the cache render) — just stay at
@@ -2764,6 +2783,7 @@ function armOpenSlide(){
   if(c) c.addEventListener('transitionend', _slideEndHandler);
   requestAnimationFrame(()=>requestAnimationFrame(()=>{
     if(window.__slideTok!==token) return;
+    if(window.__perfProbe) window.__perfProbe('slide'); // TEMP: measure frame timing over the slide
     b.classList.add('chat-anim');                  // compositor now runs transform 100%->0
     window.__chatOpenT=setTimeout(done, 360);      // fallback if transitionend is missed (300ms + margin)
   }));
diff --git a/server/routes.js b/server/routes.js
index 1999fee..8b7f62a 100644
--- a/server/routes.js
+++ b/server/routes.js
@@ -1004,6 +1004,13 @@ try {
 } catch (_) {}
 route('GET', '/api/build', (req, res) => json(res, 200, { build: APP_BUILD }));
 
+// TEMP perf/debug sink — the app POSTs slide frame-timing + scroll state so we diagnose jank from the
+// server log (docker logs bizgaze-support) with real device numbers. Remove once the slide/scroll settle.
+route('POST', '/api/dbg', async (req, res) => {
+  try { const b = await readBody(req); console.log('[MDBG]', JSON.stringify(b)); } catch (_) {}
+  json(res, 200, { ok: true });
+});
+
 // Mint a LiveKit join token for the signed-in user + a specific room (the 6-digit meeting code).
 // The room-membership/host authorization already happens over the meeting WebSocket; this only
 // hands the client a media-plane credential scoped to that room and its own identity.
