diff --git a/app/static/js/app.jsx b/app/static/js/app.jsx
index 35dabe8..3b3ff89 100644
--- a/app/static/js/app.jsx
+++ b/app/static/js/app.jsx
@@ -13508,6 +13508,13 @@ const addMasterVst = (path) => { const fx = (masterFxList || []).find(f => f.pat
   const previewAudioRef = React.useRef(null);
   const [addMasterVstSel, setAddMasterVstSel] = React.useState('');
   const [masterVstPickerOpen, setMasterVstPickerOpen] = React.useState(false);
+  // FX RT telemetry (WebView2 không mở được devtools → hiển thị thẳng trên UI).
+  const [fxRtStats, setFxRtStats] = React.useState(null);
+  React.useEffect(() => {
+    if (!isOpen) return;
+    const iv = setInterval(() => { if (fxRt && fxRt.stats) setFxRtStats({ ...fxRt.stats }); }, 2000);
+    return () => clearInterval(iv);
+  }, [isOpen]);
 
   // Wave Observer Refs & States
   const woCanvasRef = React.useRef(null);
@@ -14223,6 +14230,17 @@ const addMasterVst = (path) => { const fx = (masterFxList || []).find(f => f.pat
           </button>
         </div>
 
+        {/* FX RT TELEMETRY — WebView2 không mở devtools, hiển thị thẳng trên UI */}
+        <div id="fxrt-stats-ui" className="h-6 bg-slate-950 border-b border-slate-800 px-4 flex items-center gap-3 text-[10px] oz-font-mono shrink-0">
+          <span className="text-slate-500 font-bold uppercase tracking-widest">FXRT</span>
+          {fxRtStats ? (
+            <span className={fxRtStats.underruns > 0 || fxRtStats.silences > 0 ? 'text-red-400' : 'text-emerald-400'}>
+              u={fxRtStats.underruns} h={fxRtStats.holds} f={fxRtStats.fades} s={fxRtStats.silences} q={fxRtStats.queueLen} cap={fxRtStats.capDrops} fadeIn={fxRtStats.fadeIns}
+            </span>
+          ) : <span className="text-slate-600">off</span>}
+          {fxRtStats && (fxRtStats.underruns > 0 || fxRtStats.silences > 0) && <span className="text-red-400">⚠ main-thread stall? Giảm tải UI / tăng FILL</span>}
+        </div>
+
         {/* MAIN WORKSPACE */}
         <main className="flex-1 flex overflow-hidden min-h-0">
 
diff --git a/app/static/js/app.precompiled.js b/app/static/js/app.precompiled.js
index a3fa88c..c99a93b 100644
--- a/app/static/js/app.precompiled.js
+++ b/app/static/js/app.precompiled.js
@@ -2296,4 +2296,19 @@ const tid=selectedTrackId||activeTracks&&activeTracks[0]&&activeTracks[0].id;if(
 instrumentSelectorData?.vst_instruments?.length>0&&/*#__PURE__*/React.createElement("div",{className:"mt-3 text-[10px] text-zinc-500 uppercase font-bold px-1 flex items-center gap-1"},/*#__PURE__*/React.createElement("i",{"data-lucide":"cpu",className:"w-3 h-3 text-violet-400"}),"VST Instruments"),(instrumentSelectorData?.vst_instruments||[]).map(v=>/*#__PURE__*/React.createElement("button",{key:'vst_modal_'+(v.id||v.name),onClick:()=>{setTrackInstrumentWithUndo(instrumentSelectorTrackId,v.id,v.name||v.id);closeInstrumentSelector();},className:"w-full text-left px-3 py-2 text-sm rounded bg-zinc-800 hover:bg-violet-800 text-zinc-300 flex items-center justify-between gap-2"},/*#__PURE__*/React.createElement("span",{className:"truncate"},v.name||v.id),/*#__PURE__*/React.createElement("span",{className:"text-[9px] text-cyan-400 shrink-0"},v.type||"VST")))),/*#__PURE__*/React.createElement("div",{className:"flex-1 overflow-y-auto space-y-0.5"},/*#__PURE__*/React.createElement("button",{onClick:()=>setTrackInstrumentWithUndo(instrumentSelectorTrackId,null),className:"w-full text-left px-3 py-2 text-sm rounded bg-zinc-800 hover:bg-zinc-700 text-zinc-400"},"None (Default Synth)"),sfPresets===null?(/*#__PURE__*/React.createElement("p",{className:"text-sm text-zinc-500 py-2"},"Loading instruments...")):sfPresets.length>0?sfPresets.filter(p=>!selectedSoundFontId||p._sfId===selectedSoundFontId).filter(p=>!sfPresetSearchQuery||(p.name||'').toLowerCase().includes(sfPresetSearchQuery.toLowerCase())||(p._sfName||'').toLowerCase().includes(sfPresetSearchQuery.toLowerCase())).map((p,i)=>/*#__PURE__*/React.createElement("button",{key:i,onClick:()=>setTrackInstrumentWithUndo(instrumentSelectorTrackId,p._sfId,p.name||'Preset '+p.program,p.bank,p.program),onDoubleClick:()=>{setTrackInstrumentWithUndo(instrumentSelectorTrackId,p._sfId,p.name||'Preset '+p.program,p.bank,p.program);closeInstrumentSelector();},className:"w-full text-left px-3 py-2 text-sm rounded bg-zinc-800/60 hover:bg-amber-800 text-zinc-300 truncate flex items-center gap-2"},/*#__PURE__*/React.createElement("span",{className:"text-xs text-zinc-500 shrink-0"},p._sfDisplay),p.bank===128?/*#__PURE__*/React.createElement("span",{className:"mr-1"},"🥁"):null,p.name||'Preset '+p.program)):(/*#__PURE__*/React.createElement("p",{className:"text-sm text-zinc-500 py-2"},sfPresetSearchQuery?"Kh\u00f4ng t\u00ecm th\u1ea5y nh\u1ea1c c\u1ee5 ph\u00f9 h\u1ee3p.":"No presets found.")))))),fxSelectorTrackId&&/*#__PURE__*/React.createElement("div",{className:"fixed inset-0 z-50 flex items-center justify-center bg-black/60 backdrop-blur-sm",onClick:()=>setFxSelectorTrackId(null)},/*#__PURE__*/React.createElement("div",{className:"bg-[#262626] border border-[#383838] rounded-xl shadow-2xl w-64 p-4 text-slate-200",onClick:e=>e.stopPropagation()},/*#__PURE__*/React.createElement("h3",{className:"text-sm font-bold text-purple-400 mb-3"},"Track FX"),/*#__PURE__*/React.createElement("div",{className:"space-y-1"},/*#__PURE__*/React.createElement("button",{onClick:()=>handleSetTrackFx(fxSelectorTrackId,null),className:"w-full text-left px-3 py-2 text-xs rounded bg-zinc-800 hover:bg-zinc-700 text-zinc-400"},"None"),/*#__PURE__*/React.createElement("button",{onClick:()=>handleSetTrackFx(fxSelectorTrackId,'chorus'),className:"w-full text-left px-3 py-2 text-xs rounded bg-zinc-800 hover:bg-cyan-800 text-cyan-300"},"Chorus"),/*#__PURE__*/React.createElement("button",{onClick:()=>handleSetTrackFx(fxSelectorTrackId,'reverb'),className:"w-full text-left px-3 py-2 text-xs rounded bg-zinc-800 hover:bg-purple-800 text-purple-300"},"Reverb")))),instrumentDropdownTrackId&&instrumentDropdownBtnRect&&/*#__PURE__*/React.createElement("div",{"data-instr-dropdown":"",className:"fixed z-[100] bg-[#1e1e1e] border border-zinc-700 rounded shadow-xl w-[220px] max-h-[300px] flex flex-col",style:{top:instrumentDropdownBtnRect.bottom+4,left:Math.max(4,Math.min(instrumentDropdownBtnRect.left,window.innerWidth-224))}},/*#__PURE__*/React.createElement("input",{type:"text",placeholder:"T\u00ecm nh\u1ea1c c\u1ee5...",value:instrumentSearchQuery,onChange:e=>setInstrumentSearchQuery(e.target.value),autoFocus:true,className:"w-full bg-black border-b border-zinc-700 px-2 py-1.5 text-xs outline-none"}),/*#__PURE__*/React.createElement("div",{className:"flex-1 overflow-y-auto"},/*#__PURE__*/React.createElement("button",{onClick:()=>setTrackInstrumentWithUndo(instrumentDropdownTrackId,null),className:"w-full text-left px-3 py-1.5 text-xs bg-zinc-800 hover:bg-zinc-700 text-zinc-400"},"None (Default Synth)"),filteredInstruments.soundfonts.length>0&&/*#__PURE__*/React.createElement("div",{className:"text-[10px] text-zinc-500 px-3 py-1 mt-1 uppercase font-bold"},"SoundFonts"),filteredInstruments.soundfonts.map((sf,i)=>/*#__PURE__*/React.createElement("button",{key:"sfd_"+i,onClick:()=>{setInstrumentDropdownTrackId(null);setInstrumentDropdownBtnRect(null);setTrackInstrumentWithUndo(instrumentDropdownTrackId,"sf_"+sf.id,sf.display||sf.name||sf.id,undefined,undefined);},className:"w-full text-left px-3 py-1.5 text-xs bg-zinc-800 hover:bg-amber-800 text-zinc-200 flex items-center justify-between"},/*#__PURE__*/React.createElement("span",{className:"truncate"},sf.display||sf.name||sf.id),/*#__PURE__*/React.createElement("span",{className:"text-[10px] text-amber-400 shrink-0 ml-1"},"SF"))),filteredInstruments.vst.length>0&&/*#__PURE__*/React.createElement("div",{className:"text-[10px] text-zinc-500 px-3 py-1 mt-1 uppercase font-bold"},"VST Instruments"),filteredInstruments.vst.map((v,i)=>/*#__PURE__*/React.createElement("div",{key:"vstd_"+i,className:"flex items-stretch"},/*#__PURE__*/React.createElement("button",{onClick:()=>{setInstrumentDropdownTrackId(null);setInstrumentDropdownBtnRect(null);setTrackInstrumentWithUndo(instrumentDropdownTrackId,v.id,v.name||v.id);},className:"flex-1 min-w-0 text-left px-3 py-1.5 text-xs bg-zinc-800 hover:bg-violet-800 text-zinc-200 flex items-center justify-between"},/*#__PURE__*/React.createElement("span",{className:"truncate"},v.name||v.id),/*#__PURE__*/React.createElement("span",{className:"text-[10px] text-cyan-400 shrink-0 ml-1"},v.type||"VST")))),filteredInstruments.vst.length>0&&/*#__PURE__*/React.createElement("div",{className:"text-[10px] text-zinc-500 px-3 py-1 mt-1 uppercase font-bold"},"VST Presets (.vstpreset)"),(window.SonicRuntime&&window.SonicRuntime.presets||[]).map((p,i)=>/*#__PURE__*/React.createElement("button",{key:"psd_"+i,onClick:()=>setTrackPreset(instrumentDropdownTrackId,p.id),className:"w-full text-left px-3 py-1 text-xs bg-zinc-800 hover:bg-emerald-800 text-zinc-300 flex items-center justify-between"},/*#__PURE__*/React.createElement("span",{className:"truncate"},p.name||p.id),/*#__PURE__*/React.createElement("span",{className:"text-[10px] text-emerald-400 shrink-0 ml-1"},"PRESET"))),/*#__PURE__*/React.createElement("button",{onClick:()=>{const inp=document.createElement('input');inp.type='file';inp.accept='.vstpreset,.fxp,.fxb,.dspreset';inp.onchange=()=>{const f=inp.files&&inp.files[0];if(!f)return;window.SonicAPI.uploadPreset(f).then(function(r){if(r&&r.success){if(window.SonicRuntime)window.SonicRuntime.refreshPresets();showToast('Đã upload preset: '+(r.original_name||r.name||''),'success');}else{showToast('Upload preset thất bại','error');}}).catch(function(err){showToast('Upload lỗi: '+(err.message||err),'error');});};inp.click();},className:"w-full text-left px-3 py-1 text-xs bg-zinc-800 hover:bg-teal-800 text-teal-300 border-t border-zinc-700",title:"Upload preset .vstpreset xuất từ native GUI"},"\u2B06 Upload preset (t\u1EEB native GUI...)"),!filteredInstruments.soundfonts.length&&!filteredInstruments.vst.length&&/*#__PURE__*/React.createElement("p",{className:"text-xs text-zinc-500 py-4 text-center"},"Kh\u00f4ng t\u00ecm th\u1ea5y nh\u1ea1c c\u1ee5 n\u00e0o"))));};// React onWheel is passive -> e.preventDefault() can't stop panel scroll, so the
 // ruler slips away from the cursor mid-scroll. Native capture listener (non-passive)
 // blocks scrolling whenever the wheel starts over a [data-sf-wheel] container.
-document.addEventListener('wheel',e=>{const t=e.target;if(t&&t.closest&&t.closest('[data-sf-wheel]'))e.preventDefault();},{passive:false,capture:true});const root=ReactDOM.createRoot(document.getElementById('root'));root.render(/*#__PURE__*/React.createElement(App,null));setTimeout(()=>lucide.createIcons(),300);
\ No newline at end of file
+document.addEventListener('wheel',e=>{const t=e.target;if(t&&t.closest&&t.closest('[data-sf-wheel]'))e.preventDefault();},{passive:false,capture:true});const root=ReactDOM.createRoot(document.getElementById('root'));root.render(/*#__PURE__*/React.createElement(App,null));setTimeout(()=>lucide.createIcons(),300);;
+(function(){
+  if (document.getElementById('fxrt-stats-ui')) return;
+  var iv = setInterval(function(){
+    if (document.getElementById('fxrt-stats-ui')) return;
+    var s = window.fxRt && window.fxRt.stats;
+    var el = document.getElementById('fxrt-stats-overlay');
+    if (!el) {
+      el = document.createElement('div');
+      el.id = 'fxrt-stats-overlay';
+      el.style.cssText = 'position:fixed;top:0;left:50%;transform:translateX(-50%);z-index:99999;font:10px Consolas,monospace;background:#0f172a;border:1px solid #334155;color:#34d399;padding:2px 10px;border-radius:0 0 8px 8px;white-space:nowrap;pointer-events:none;';
+      document.body.appendChild(el);
+    }
+    el.textContent = s ? ('FXRT u='+(s.underruns||0)+' h='+(s.holds||0)+' f='+(s.fades||0)+' s='+(s.silences||0)+' q='+(s.queueLen||0)+' cap='+(s.capDrops||0)+' fadeIn='+(s.fadeIns||0)+(((s.underruns||0)>0||(s.silences||0)>0)?'  WARN':'  ok')) : 'FXRT off';
+  }, 1000);
+})();
diff --git a/app/templates/index.html b/app/templates/index.html
index 78502db..d7f50de 100644
--- a/app/templates/index.html
+++ b/app/templates/index.html
@@ -51,7 +51,7 @@
     <script src="/static/js/services/promptTemplateManager.js?v=202607281039"></script>
     <script src="/static/js/services/undoRedoEngine.js?v=202607290941"></script>
     <script src="/static/js/services/chordTheory.js?v=202608211300"></script>
-    <script src="/static/js/app.precompiled.js?v=202608242100" defer></script>
+    <script src="/static/js/app.precompiled.js?v=202608242200" defer></script>
     <link rel="stylesheet" href="/static/css/styles.css?v=202607271016">
     <style>
         :root {