diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2537419..b70f855 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,6 +23,7 @@ jobs:
       - run: sudo apt-get install -y ffmpeg
       - run: node scripts/fixtures.mjs
       - run: npm test
+      - run: node --expose-gc scripts/benchmark.mjs
       - run: npm run build
       - uses: actions/upload-artifact@v4
         with:
@@ -36,7 +37,7 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version-file: .nvmrc
-      - run: npm install --no-save --package-lock=false playwright@1.63.0
+      - run: npm install --no-save --package-lock=false playwright@1.63.0 axe-core@4.10.3
       - run: npx playwright install --with-deps chromium firefox webkit
       - name: Start virtual audio device
         run: |
@@ -47,3 +48,15 @@ jobs:
       - run: sudo apt-get install -y ffmpeg
       - run: node scripts/fixtures.mjs
       - run: npm run test:browser
+  safari:
+    runs-on: macos-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version-file: .nvmrc
+      - run: brew install ffmpeg
+      - run: node scripts/fixtures.mjs
+      - run: sudo safaridriver --enable
+      - run: python3 tests/safari.py
diff --git a/scripts/benchmark.mjs b/scripts/benchmark.mjs
new file mode 100644
index 0000000..0c28412
--- /dev/null
+++ b/scripts/benchmark.mjs
@@ -0,0 +1,22 @@
+import { cpus, totalmem, platform, release } from 'node:os';
+import { performance } from 'node:perf_hooks';
+import { project, voice, preset } from '../src/model.js';
+import { analyze, resolveStrokes } from '../src/signal.js';
+import { render } from '../src/render.js';
+const report={node:process.version,platform:platform(),os:release(),cpu:cpus()[0]?.model,cores:cpus().length,ramMiB:Math.round(totalmem()/1024**2),runs:[]};
+const p=project();p.duration=10;p.mode='envelope';
+p.voices=Array.from({length:4},(_,i)=>{const v=voice(i);v.hz=220+i*43;v.pitch=[[0,v.hz],[.4,v.hz*2],[1,v.hz*.7]];v.waveform.strokes=preset('saw');v.waveform.resolution=16384;v.harmonics=1024;v.gain=[[0,0],[.01,.7],[.8,.5],[1,0]];return v;});
+p.selectedId=p.modulation.oscillatorId=p.voices[0].id;p.assets=['clip'];
+p.modulation={...p.modulation,enabled:true,mode:'pitch',target:'mix',sourceId:'clip',semitones:24,sourceLoop:true,carrierLoop:true};
+const assets={clip:{sampleRate:48000,samples:Float32Array.from({length:480000},(_,i)=>.8*Math.sin(2*Math.PI*7*i/48000))}};
+const analysisTimes=[];
+for(let i=0;i<20;i++){const t=performance.now();analyze(resolveStrokes(p.voices[0].waveform.strokes,16384),220,1024);analysisTimes.push(performance.now()-t);}
+report.analysisP95Ms=analysisTimes.sort((a,b)=>a-b)[18];
+for(let i=0;i<10;i++){
+  global.gc?.();const before=process.memoryUsage(),start=performance.now(),result=await render(p,assets),ms=performance.now()-start,after=process.memoryUsage();
+  report.runs.push({ms,frames:result.samples.length,peak:result.peak,arrayBuffersMiB:after.arrayBuffers/1024**2,heapMiB:after.heapUsed/1024**2,rssMiB:after.rss/1024**2,arrayBufferIncreaseMiB:(after.arrayBuffers-before.arrayBuffers)/1024**2});
+}
+report.renderWorstMs=Math.max(...report.runs.map(r=>r.ms));report.renderP95Ms=report.runs.map(r=>r.ms).sort((a,b)=>a-b)[Math.ceil(report.runs.length*.95)-1];report.proposedTargets={analysisP95Ms:150,renderMs:2000,appOwnedBufferMiB:128};
+console.log('BENCHMARK:'+JSON.stringify(report));
+if(report.runs.some(r=>r.frames!==480000||r.peak>.950001||r.arrayBuffersMiB>128))throw new Error('Resource or output invariant failed');
+// Performance is reported explicitly; any missed release target must be addressed or documented.
diff --git a/src/app.js b/src/app.js
index bea392b..8c46cf2 100644
--- a/src/app.js
+++ b/src/app.js
@@ -1,6 +1,6 @@
 import { project, voice, id, clone, COLORS, duration, preset } from './model.js';
 import { History } from './history.js';
-import { resolveStrokes, analyze, sample, envelope, spectrum } from './signal.js';
+import { resolveStrokes, analyze, reconstruct, sample, envelope, spectrum } from './signal.js';
 import { DrawingCanvas, editEnvelope, drawSignal } from './canvas.js';
 import { Renderer, Transport } from './audio.js';
 const $=selector=>document.querySelector(selector);
@@ -19,10 +19,11 @@ export function element(tag,attrs={},...children){
 }
 const history=new History(project()),renderer=new Renderer(),changes=new Set(),cache=new Map();
 let playing=false,playingTag='editor',intent=0,lastRender=null,bypass=false,renderQueue=Promise.resolve();
-const view={tool:'pencil',zoom:1,pan:0,snap:false,only:false,hidden:new Set()};
+const view={modelOverlay:false,tool:'pencil',zoom:1,pan:0,snap:false,only:false,hidden:new Set()};
 const transport=new Transport((state,tag)=>{playing=state==='playing';playingTag=tag||playingTag;$('#play').textContent=playing?'↻ Restart':'▶ Play';$('#play').setAttribute('aria-label',playing?'Restart playback':'Play sound');$('#transport-state').textContent=playing?'Playing '+(tag==='editor'?'current sound':tag):'Stopped';});
 export const app={
-  get project(){return history.current;},get lastRender(){return lastRender;},assets:{},
+  get project(){return history.current;},
+  retainedAssetIds(){return [...new Set([history.current,...history.past,...history.future].flatMap(p=>p.assets))];},get lastRender(){return lastRender;},get playbackRevision(){return intent;},assets:{},
   element,transport,renderer,
   status(message,error=false){$('#status').textContent=message;$('#status').classList.toggle('error',error);},
   onChange(fn){changes.add(fn);return()=>changes.delete(fn);},
@@ -60,12 +61,13 @@ export const app={
   }
 };
 
-$('#app').innerHTML="<header class=\"topbar\"><a class=\"brand\" href=\"./\" aria-label=\"SIGINT home\">◒ SIGINT<span>Signal sketchpad</span></a><div class=\"transport\"><button id=\"play\" class=\"primary\" aria-label=\"Play sound\">▶ Play</button><button id=\"stop\">■ Stop</button><label class=\"monitor\">Monitor <input id=\"monitor\" type=\"range\" min=\"0\" max=\"1\" step=\".01\" value=\".1\" aria-label=\"Monitor volume\"><output id=\"monitor-value\">10%</output></label><span id=\"transport-state\">Stopped</span></div><div id=\"file-actions\" class=\"actions\"></div></header>\n<main id=\"workspace\">\n<div class=\"workspace-heading\"><div><p class=\"eyebrow\">DRAW → UNDERSTAND → HEAR</p><h1>Your next sound starts with a line.</h1></div><label class=\"project-name\">Sound name<input id=\"project-name\" maxlength=\"80\" value=\"Untitled sound\"></label></div>\n<div class=\"workspace-grid\">\n<aside class=\"panel voices-panel\"><div class=\"section-heading\"><h2>Oscillators</h2><button id=\"add-voice\" aria-label=\"Add oscillator\">＋</button></div><p class=\"hint\">One color. One voice. Your mix.</p><div id=\"voices\"></div><label class=\"check\"><input id=\"only\" type=\"checkbox\">Show selected voice only</label></aside>\n<section class=\"panel editor-panel\">\n<div class=\"tabs\" role=\"tablist\" aria-label=\"Workspace mode\"><button data-mode=\"waveform\" role=\"tab\">Waveform</button><button data-mode=\"envelope\" role=\"tab\">Envelopes</button><button data-mode=\"timeline\" role=\"tab\">Timeline</button></div>\n<div class=\"tool-row\"><div class=\"segmented\" aria-label=\"Drawing tools\"><button data-tool=\"pencil\">Pencil</button><button data-tool=\"line\">Line</button><button data-tool=\"eraser\">Eraser</button></div><button id=\"undo\" aria-label=\"Undo last edit\">↶ Undo</button><button id=\"redo\" aria-label=\"Redo last edit\">↷ Redo</button><button id=\"clear\">Clear</button><label class=\"check\"><input id=\"snap\" type=\"checkbox\">Snap</label></div>\n<div class=\"plot-heading\"><span id=\"canvas-title\">Waveform · signed amplitude</span><span id=\"time-extent\"></span></div>\n<div class=\"canvas-wrap\"><span class=\"axis-label\">+1<br><span>0</span><br>−1</span><canvas id=\"wave-canvas\" tabindex=\"0\" aria-label=\"Waveform drawing canvas. Numeric point controls are below.\"></canvas></div>\n<div class=\"axis-footer\"><span>Time →</span><span id=\"drawing-note\"></span></div>\n<div id=\"envelopes\" hidden><div class=\"plot-heading\"><span>Pitch · 20–20,000 Hz · logarithmic</span><span class=\"envelope-extent\"></span></div><canvas id=\"pitch-canvas\" class=\"lane\" tabindex=\"0\" aria-label=\"Pitch envelope drawing canvas\"></canvas><div class=\"plot-heading\"><span>Volume · linear gain 0–1</span><span class=\"envelope-extent\"></span></div><canvas id=\"gain-canvas\" class=\"lane\" tabindex=\"0\" aria-label=\"Volume envelope drawing canvas\"></canvas><p class=\"hint\">Pitch changes cycle spacing. Volume scales both sides of zero. Moving a waveform vertically adds DC.</p></div>\n<div class=\"viewport\"><label>Zoom<input id=\"zoom\" type=\"range\" min=\"1\" max=\"16\" step=\".5\" value=\"1\"></label><label>Position<input id=\"pan\" type=\"range\" min=\"0\" max=\"0\" step=\".001\" value=\"0\"></label><output id=\"zoom-value\">1×</output></div>\n<div id=\"voice-controls\" class=\"control-grid\"></div>\n<details class=\"numeric\"><summary>Edit exact points without drawing</summary><form id=\"point-form\" class=\"control-grid\"><label>Lane<select id=\"point-lane\"><option value=\"waveform\">Waveform</option><option value=\"pitch\">Pitch</option><option value=\"gain\">Volume</option></select></label><label>Time (seconds)<input id=\"point-time\" type=\"number\" min=\"0\" step=\"any\" value=\"0\" required></label><label>Value<input id=\"point-value\" type=\"number\" step=\"any\" value=\"0\" required></label><button type=\"submit\">Set point</button></form><p class=\"hint\">Waveform: −1…1. Pitch: 20…20,000 Hz. Volume: 0…1. Undo restores every edit.</p></details>\n</section>\n<aside class=\"panel inspector\"><p class=\"eyebrow\">THE MATH BEHIND THE SOUND</p><h2>Signal inspector</h2><div id=\"formula\" class=\"formula\"></div><div id=\"metrics\" class=\"metrics\"></div><h3>What you hear</h3><p id=\"hearing\" class=\"hint\">Press Play to render the selected source.</p><canvas id=\"output-canvas\" class=\"preview\" aria-label=\"Rendered output waveform\"></canvas><p class=\"plot-caption\">Rendered time → · signed amplitude</p><canvas id=\"spectrum-canvas\" class=\"preview\" aria-label=\"Rendered frequency spectrum\"></canvas><p class=\"plot-caption\" id=\"spectrum-caption\">Frequency → Hz · linear component magnitude<br>Hann window · up to 8192 samples</p><label class=\"check\"><input id=\"bypass\" type=\"checkbox\">Compare without clip modulation</label><p class=\"hint\">Comparison restarts from the same initial phase and clip position.</p></aside>\n</div>\n<div class=\"status-bar\"><span id=\"status\" role=\"status\" aria-live=\"polite\">Draw on the canvas, then press Play. Sound stays on this device.</span><progress id=\"render-progress\" value=\"0\" max=\"1\" hidden aria-label=\"Audio render progress\"></progress></div>\n<div id=\"extensions\"></div>\n</main><footer>Built for curiosity. Made to stay local. <a href=\"https://github.com/CurtisTechSolutions/SIGINTTool\">Source & documentation</a></footer>";
+$('#app').innerHTML="<header class=\"topbar\"><a class=\"brand\" href=\"./\" aria-label=\"SIGINT home\">◒ SIGINT<span>Signal sketchpad</span></a><div class=\"transport\"><button id=\"play\" class=\"primary\" aria-label=\"Play sound\">▶ Play</button><button id=\"stop\">■ Stop</button><label class=\"monitor\">Monitor <input id=\"monitor\" type=\"range\" min=\"0\" max=\"1\" step=\".01\" value=\".1\" aria-label=\"Monitor volume\"><output id=\"monitor-value\">10%</output></label><span id=\"transport-state\">Stopped</span></div><div id=\"file-actions\" class=\"actions\"></div></header>\n<main id=\"workspace\">\n<div class=\"workspace-heading\"><div><p class=\"eyebrow\">DRAW → UNDERSTAND → HEAR</p><h1>Your next sound starts with a line.</h1></div><label class=\"project-name\">Sound name<input id=\"project-name\" maxlength=\"80\" value=\"Untitled sound\"></label></div>\n<div class=\"workspace-grid\">\n<aside class=\"panel voices-panel\"><div class=\"section-heading\"><h2>Oscillators</h2><button id=\"add-voice\" aria-label=\"Add oscillator\">＋</button></div><p class=\"hint\">One color. One voice. Your mix.</p><div id=\"voices\"></div><label class=\"check\"><input id=\"only\" type=\"checkbox\">Show selected voice only</label></aside>\n<section class=\"panel editor-panel\">\n<div class=\"tabs\" role=\"tablist\" aria-label=\"Workspace mode\"><button data-mode=\"waveform\" role=\"tab\">Waveform</button><button data-mode=\"envelope\" role=\"tab\">Envelopes</button><button data-mode=\"timeline\" role=\"tab\">Timeline</button></div>\n<div class=\"tool-row\"><div class=\"segmented\" aria-label=\"Drawing tools\"><button data-tool=\"pencil\">Pencil</button><button data-tool=\"line\">Line</button><button data-tool=\"eraser\">Eraser</button></div><button id=\"undo\" aria-label=\"Undo last edit\">↶ Undo</button><button id=\"redo\" aria-label=\"Redo last edit\">↷ Redo</button><button id=\"clear\">Clear</button><label class=\"check\"><input id=\"snap\" type=\"checkbox\">Snap</label></div>\n<div class=\"plot-heading\"><span id=\"canvas-title\">Waveform · signed amplitude</span><span id=\"time-extent\"></span></div>\n<div class=\"canvas-wrap\"><span class=\"axis-label\">+1<br><span>0</span><br>−1</span><canvas id=\"wave-canvas\" tabindex=\"0\" aria-label=\"Waveform drawing canvas. Numeric point controls are below.\"></canvas></div>\n<div class=\"axis-footer\"><span>Time →</span><span id=\"drawing-note\"></span></div>\n<div id=\"envelopes\" hidden><div class=\"plot-heading\"><span>Pitch · 20–20,000 Hz · logarithmic</span><span class=\"envelope-extent\"></span></div><canvas id=\"pitch-canvas\" class=\"lane\" tabindex=\"0\" aria-label=\"Pitch envelope drawing canvas\"></canvas><div class=\"plot-heading\"><span>Volume · linear gain 0–1</span><span class=\"envelope-extent\"></span></div><canvas id=\"gain-canvas\" class=\"lane\" tabindex=\"0\" aria-label=\"Volume envelope drawing canvas\"></canvas><p class=\"hint\">Pitch changes cycle spacing. Volume scales both sides of zero. Moving a waveform vertically adds DC.</p></div>\n<div class=\"viewport\"><label>Zoom<input id=\"zoom\" type=\"range\" min=\"1\" max=\"16\" step=\".5\" value=\"1\"></label><label>Position<input id=\"pan\" type=\"range\" min=\"0\" max=\"0\" step=\".001\" value=\"0\"></label><output id=\"zoom-value\">1×</output></div>\n<div id=\"voice-controls\" class=\"control-grid\"></div>\n<details class=\"numeric\"><summary>Edit exact points without drawing</summary><form id=\"point-form\" class=\"control-grid\"><label>Lane<select id=\"point-lane\"><option value=\"waveform\">Waveform</option><option value=\"pitch\">Pitch</option><option value=\"gain\">Volume</option></select></label><label>Time (seconds)<input id=\"point-time\" type=\"number\" min=\"0\" step=\"any\" value=\"0\" required></label><label>Value<input id=\"point-value\" type=\"number\" step=\"any\" value=\"0\" required></label><button type=\"submit\">Set point</button></form><p class=\"hint\">Waveform: −1…1. Pitch: 20…20,000 Hz. Volume: 0…1. Undo restores every edit.</p></details>\n</section>\n<aside class=\"panel inspector\"><p class=\"eyebrow\">THE MATH BEHIND THE SOUND</p><h2>Signal inspector</h2><div id=\"formula\" class=\"formula\"></div><label class=\"check\"><input id=\"model-overlay\" type=\"checkbox\">Overlay selected model · white dotted line</label><div id=\"metrics\" class=\"metrics\"></div><h3>What you hear</h3><p id=\"hearing\" class=\"hint\">Press Play to render the selected source.</p><canvas id=\"output-canvas\" class=\"preview\" aria-label=\"Rendered output waveform\"></canvas><p class=\"plot-caption\">Rendered time → · signed amplitude</p><canvas id=\"spectrum-canvas\" class=\"preview\" aria-label=\"Rendered frequency spectrum\"></canvas><p class=\"plot-caption\" id=\"spectrum-caption\">Frequency → Hz · linear component magnitude<br>Hann window · up to 8192 samples</p><label class=\"check\"><input id=\"bypass\" type=\"checkbox\">Compare without clip modulation</label><p class=\"hint\">Comparison restarts from the same initial phase and clip position.</p></aside>\n</div>\n<div class=\"status-bar\"><span id=\"status\" role=\"status\" aria-live=\"polite\">Draw on the canvas, then press Play. Sound stays on this device.</span><progress id=\"render-progress\" value=\"0\" max=\"1\" hidden aria-label=\"Audio render progress\"></progress></div>\n<div id=\"extensions\"></div>\n</main><footer>Built for curiosity. Made to stay local. <a href=\"https://github.com/CurtisTechSolutions/SIGINTTool\">Source & documentation</a></footer>";
 function selected(){return app.project.voices.find(v=>v.id===app.project.selectedId);}
 function data(v){
   const old=cache.get(v.id);if(old?.voice===v)return old;
   const samples=resolveStrokes(v.waveform.strokes,v.waveform.resolution,v.waveform.smooth);
-  const next={voice:v,samples,analysis:analyze(samples,v.hz,v.harmonics)};cache.set(v.id,next);return next;
+  const analysis=analyze(samples,v.hz,v.harmonics),model=v.source==='sine'?Float64Array.from({length:samples.length},(_,i)=>analysis.sine.offset+analysis.sine.amplitude*Math.sin(2*Math.PI*analysis.sine.harmonic*i/samples.length+analysis.sine.phase)):reconstruct(analysis.coefficients,samples.length,v.harmonics);
+  const next={voice:v,samples,analysis,model};cache.set(v.id,next);return next;
 }
 function changed(){
   const wasPlaying=playing&&playingTag==='editor';intent++;renderer.cancel();
@@ -124,6 +126,7 @@ function curveSettings(lane){
   }else curves=p.voices.filter(o=>(!view.only||o.id===v.id)&&!view.hidden.has(o.id)).map(o=>({
     color:o.color,selected:o.id===v.id,value:u=>actual==='waveform'?sample(data(o).samples,u*o.hz/v.hz):envelope(o[actual],u,actual==='pitch',actual==='pitch'?o.hz:1)
   }));
+  if(actual==='waveform'&&view.modelOverlay)curves.push({color:v.color,strokeColor:'#e8edf5',pattern:[3,5],selected:false,value:u=>sample(data(v).model,u)});
   return {...view,lane:actual,color:v.color,curves};
 }
 function stroke(points,s){
@@ -197,6 +200,7 @@ $('#clear').onclick=()=>app.edit(p=>{if(p.mode==='timeline')p.timeline.strokes=[
 $('#only').onchange=e=>{view.only=e.target.checked;draw();};$('#snap').onchange=e=>{view.snap=e.target.checked;};
 $('#zoom').oninput=e=>{view.zoom=Number(e.target.value);view.pan=Math.min(view.pan,1-1/view.zoom);$('#pan').max=1-1/view.zoom;$('#pan').value=view.pan;$('#zoom-value').textContent=view.zoom+'×';refresh();};
 $('#pan').oninput=e=>{view.pan=Number(e.target.value);refresh();};
+$('#model-overlay').onchange=e=>{view.modelOverlay=e.target.checked;draw();};
 $('#bypass').onchange=e=>{bypass=e.target.checked;if(playing)app.play();};
 $('#point-lane').onchange=e=>{$('#point-value').value=e.target.value==='pitch'?440:e.target.value==='gain'?1:0;};
 $('#point-form').onsubmit=e=>{
diff --git a/src/canvas.js b/src/canvas.js
index 8b1fde5..cc0630f 100644
--- a/src/canvas.js
+++ b/src/canvas.js
@@ -50,7 +50,7 @@ export class DrawingCanvas {
     for(let i=0;i<=4;i++){ctx.beginPath();ctx.moveTo(0,h*i/4);ctx.lineTo(w,h*i/4);ctx.stroke();}
     if(s.lane==='waveform'||s.lane==='timeline'){ctx.strokeStyle='#586882';ctx.beginPath();ctx.moveTo(0,h/2);ctx.lineTo(w,h/2);ctx.stroke();}
     for(const curve of s.curves){
-      ctx.beginPath();ctx.strokeStyle=COLORS[curve.color]||'#b4c8df';ctx.lineWidth=curve.selected?2.5:1.5;ctx.globalAlpha=curve.selected?1:.55;ctx.setLineDash(curve.selected?[]:[5+curve.color*2,4]);
+      ctx.beginPath();ctx.strokeStyle=curve.strokeColor||COLORS[curve.color]||'#b4c8df';ctx.lineWidth=curve.selected?2.5:1.5;ctx.globalAlpha=curve.selected?1:.55;ctx.setLineDash(curve.pattern||(curve.selected?[]:[5+curve.color*2,4]));
       for(let x=0;x<=w;x++){const u=s.pan+x/w/s.zoom,v=curve.value(u),y=mapY(v);if(!x)ctx.moveTo(x,y);else ctx.lineTo(x,y);}
       ctx.stroke();
     }
diff --git a/src/format.js b/src/format.js
index 943fe50..762020d 100644
--- a/src/format.js
+++ b/src/format.js
@@ -28,17 +28,17 @@ export function unzip(bytes){
   const v=new DataView(bytes.buffer,bytes.byteOffset,bytes.byteLength),end=bytes.length-22;
   if(v.getUint32(end,true)!==0x06054b50||v.getUint16(end+20,true)!==0)throw new Error('Unsupported bundle directory');
   const count=v.getUint16(end+10,true),central=v.getUint32(end+16,true),centralSize=v.getUint32(end+12,true);
-  if(count>32||v.getUint16(end+8,true)!==count||central+centralSize!==end)throw new Error('Invalid bundle entry limit or directory');
+  if(v.getUint16(end+4,true)!==0||v.getUint16(end+6,true)!==0||count>32||v.getUint16(end+8,true)!==count||central+centralSize!==end)throw new Error('Invalid bundle entry limit or directory');
   const entries=Object.create(null);let pos=central,total=0;
   for(let i=0;i<count;i++){
     if(pos+46>end||v.getUint32(pos,true)!==0x02014b50)throw new Error('Invalid bundle entry');
     const flags=v.getUint16(pos+8,true),method=v.getUint16(pos+10,true),crc=v.getUint32(pos+16,true),size=v.getUint32(pos+20,true),expanded=v.getUint32(pos+24,true),length=v.getUint16(pos+28,true),extra=v.getUint16(pos+30,true),comment=v.getUint16(pos+32,true),local=v.getUint32(pos+42,true);
-    if(method!==0||flags!==0x800||size!==expanded)throw new Error('Use a SIGINT bundle with stored PCM entries');
+    if(v.getUint16(pos+34,true)!==0||method!==0||flags!==0x800||size!==expanded)throw new Error('Use a SIGINT bundle with stored PCM entries');
     if(pos+46+length+extra+comment>end||local+30>=central)throw new Error('Truncated bundle');
     const name=decoder.decode(bytes.subarray(pos+46,pos+46+length));
     if(!/^(project\.json|manifest\.json|audio\/[a-zA-Z0-9_-]+\.f32)$/.test(name)||Object.hasOwn(entries,name))throw new Error('Unsafe or duplicate bundle path');
     total+=expanded;if(total>64*1024**2)throw new Error('Bundle exceeds extracted byte limit');
-    if(v.getUint32(local,true)!==0x04034b50||v.getUint16(local+8,true)!==0||v.getUint32(local+18,true)!==size||v.getUint32(local+22,true)!==size)throw new Error('Mismatched bundle header');
+    if(v.getUint16(local+6,true)!==flags||v.getUint32(local,true)!==0x04034b50||v.getUint16(local+8,true)!==0||v.getUint32(local+18,true)!==size||v.getUint32(local+22,true)!==size)throw new Error('Mismatched bundle header');
     const n=v.getUint16(local+26,true),x=v.getUint16(local+28,true),start=local+30+n+x;
     if(start+size>central||decoder.decode(bytes.subarray(local+30,local+30+n))!==name)throw new Error('Invalid bundle data extent');
     const data=bytes.subarray(start,start+size);if(crc32(data)!==crc||v.getUint32(local+14,true)!==crc)throw new Error('Corrupt bundle checksum');
diff --git a/src/library.js b/src/library.js
index e8efcc8..2de0dc0 100644
--- a/src/library.js
+++ b/src/library.js
@@ -92,6 +92,7 @@ export async function installLibrary(app){
     }catch(e){app.status('Project was not opened: '+e.message,true);}finally{file.value='';}
   };
   app.onChange(p=>{
+    for(const key of Object.keys(app.assets))if(!p.assets.includes(key))delete app.assets[key];
     const revision=++saveRevision;clearTimeout(saveTimer);state.textContent='Draft has unsaved changes';
     saveTimer=setTimeout(async()=>{try{await store.saveProject('current',p,Object.values(await app.prepareAssets(p)));if(revision===saveRevision)state.textContent='Draft saved locally';}catch(e){if(revision===saveRevision)state.textContent='Draft not saved · '+e.message;}},350);
   });
diff --git a/src/modulation-ui.js b/src/modulation-ui.js
index 7624079..5f77a70 100644
--- a/src/modulation-ui.js
+++ b/src/modulation-ui.js
@@ -1,10 +1,22 @@
 import { COLORS } from './model.js';
+import { drawSignal } from './canvas.js';
 export function installModulation(app){
   const el=app.element,panel=app.addPanel('Shape one sound with another');
   const heading=el('p',{class:'hint'},'Choose a frozen audio clip as the modulator. It can follow volume, multiply the waveform, or bend pitch. Saved sounds are copied by content, so later edits to a pad do not change this sound.');
   const grid=el('div',{class:'control-grid',id:'modulation-controls'}),formula=el('code',{class:'route-formula',id:'modulation-formula'});
-  panel.append(heading,grid,formula);
-  let refreshToken=0;
+  const preview=el('canvas',{class:'preview','aria-label':'Modulator clip waveform'}),summary=el('p',{class:'hint',id:'mod-source-summary'}),audition=el('button',{id:'audition-source'},'Audition modulator');
+  panel.append(heading,grid,formula,preview,summary,audition);
+  let refreshToken=0,auditioning=false;
+  audition.onclick=async()=>{
+    app.stop();const token=app.playbackRevision,sourceId=app.project.modulation.sourceId;
+    try{
+      await app.transport.enable();const a=app.assets[sourceId]||await app.store.get('audio',sourceId);
+      if(token!==app.playbackRevision)return;if(!a)throw new Error('Choose a modulator clip first');
+      const samples=Float32Array.from(a.samples),edge=Math.min(Math.round(.005*a.sampleRate),Math.floor(samples.length/2));
+      for(let i=0;i<samples.length;i++)samples[i]*=.95*(edge?Math.min(1,i/edge,(samples.length-1-i)/edge):1);
+      app.transport.setVolume(app.project.monitor);app.transport.play({samples,sampleRate:a.sampleRate,duration:samples.length/a.sampleRate},{tag:'modulator · '+a.name});auditioning=true;app.status('Auditioning modulator '+a.name);
+    }catch(e){app.status(e.message,true);}
+  };
   function field(label,node){return el('label',{},label,node);}
   function select(id,values,value,change){
     const node=el('select',{id,'data-mod-key':id,onchange:e=>change(e.target.value)},...values.map(([value,text])=>el('option',{value},text)));node.value=value;return node;
@@ -52,9 +64,16 @@ export function installModulation(app){
       :m.target==='oscillator'?'f(t) = basePitch(t) × 2^(D(t) × modulator(t) / 12); phase = integral of frequency'
       :'readhead(t) = integral of 2^(D(t) × modulator(t) / 12); y(t) = carrier(readhead(t)). Pitch and timing change together.';
     if(!m.sourceLoop)formula.textContent+=' Outside the modulator clip: unchanged carrier.';
+    audition.disabled=!m.sourceId;
+    if(m.sourceId){
+      const a=app.assets[m.sourceId]||await app.store.get('audio',m.sourceId);if(token!==refreshToken)return;
+      if(a){let low=0,high=0,sum=0;for(const x of a.samples){low=Math.min(low,x);high=Math.max(high,x);sum+=x*x;}
+        drawSignal(preview,a.samples,{color:'#e8edf5'});summary.textContent=a.name+' · '+(a.samples.length/a.sampleRate).toFixed(3)+' s · min '+low.toFixed(3)+' · max '+high.toFixed(3)+' · RMS '+Math.sqrt(sum/a.samples.length).toFixed(3)+(m.mode==='pitch'?' · rate range '+(2**(m.semitones*low/12)).toFixed(2)+'–'+(2**(m.semitones*high/12)).toFixed(2)+'× before oscillator limits':'');
+      }
+    }else{drawSignal(preview,new Float32Array(1));summary.textContent='Choose an imported or saved clip. Preview above shows signed sample amplitude.';}
     if(focus)grid.querySelector('[data-mod-key="'+CSS.escape(focus)+'"]')?.focus();
   }
-  app.onChange(()=>refresh().catch(e=>app.status(e.message,true)));app.onAssetsChanged=()=>refresh().catch(e=>app.status(e.message,true));
+  app.onChange(()=>{if(auditioning){auditioning=false;app.stop();}refresh().catch(e=>app.status(e.message,true));});app.onAssetsChanged=()=>refresh().catch(e=>app.status(e.message,true));
   const oldRefresh=app.library.refresh;app.library.refresh=async()=>{await oldRefresh();await refresh();};
   // Soundboard operations publish a local event after their atomic transaction.
   window.addEventListener('sigint-library-change',()=>refresh().catch(e=>app.status(e.message,true)));
diff --git a/src/render.js b/src/render.js
index 642035e..03c2eeb 100644
--- a/src/render.js
+++ b/src/render.js
@@ -15,7 +15,7 @@ export function waveform(v) {
   for(let h=1;h<=source.length/2;h*=2)tables.push(reconstruct(c,source.length,Math.min(h,limit),true));
   return {source,data,tables,limit,selected:c,dc:c.a[0]};
 }
-function pitchCurve(points,length,fallback) {
+function pitchCurve(points,length,fallback,rate) {
   const nodes=points.length?points:[[0,fallback],[1,fallback]];
   const knots=nodes.map(([x,f])=>[x*length,f]);
   if(knots[0][0]>0)knots.unshift([0,knots[0][1]]);
@@ -25,11 +25,15 @@ function pitchCurve(points,length,fallback) {
     const dt=knots[i+1][0]-knots[i][0],q=Math.log(knots[i+1][1]/knots[i][1])/dt;
     slopes[i]=q;prefix[i+1]=prefix[i]+(Math.abs(q)<1e-12?knots[i][1]*dt:knots[i][1]*Math.expm1(q*dt)/q);
   }
-  let cursor=0;
+  let cursor=0,count=0;const state={hz:0,phase:0},steps=slopes.map(q=>({ratio:Math.exp(q/rate),cycles:Math.abs(q)<1e-12?1/rate:Math.expm1(q/rate)/q}));
   return t=>{
-    while(cursor<knots.length-2&&knots[cursor+1][0]<=t)cursor++;
-    const tau=t-knots[cursor][0],f=knots[cursor][1],q=slopes[cursor]||0;
-    return {hz:f*Math.exp(q*tau),phase:prefix[cursor]+(Math.abs(q)<1e-12?f*tau:f*Math.expm1(q*tau)/q)};
+    const old=cursor;while(cursor<knots.length-2&&knots[cursor+1][0]<=t)cursor++;
+    // Exact geometric increments between knots; periodic analytical resets bound round-off.
+    if(old!==cursor||(count++&1023)===0){
+      const tau=t-knots[cursor][0],f=knots[cursor][1],q=slopes[cursor]||0;
+      state.hz=f*Math.exp(q*tau);state.phase=prefix[cursor]+(Math.abs(q)<1e-12?f*tau:f*Math.expm1(q*tau)/q);
+    }else{state.phase+=state.hz*steps[cursor].cycles;state.hz*=steps[cursor].ratio;}
+    return state;
   };
 }
 function sourceState(asset,t,m) {
@@ -51,9 +55,10 @@ export async function render(input,assets={},options={}) {
   const source=enabled?assetAt(assets,m.sourceId):null;
   const carrier=route&&m.target==='asset'?assetAt(assets,m.carrierId):null;
   const needsCopy=enabled&&m.mode==='pitch'&&m.target==='mix';
-  if(n*OVERSAMPLE*8*(needsCopy?2:1)+n*4+Object.values(assets).reduce((s,a)=>s+(a.samples?.byteLength||0),0)>96*1024**2)throw new Error('Render exceeds the 128 MiB working-buffer budget');
-  const raw=new Float64Array(n*OVERSAMPLE),voices=p.mode==='timeline'?[]:includedVoices(p).map(v=>({v,...waveform(v),curve:pitchCurve(v.pitch,T,v.hz),phase:v.phase}));
-  const warnings=new Set();
+  if(n*OVERSAMPLE*8*(needsCopy?2:1)+n*(options.includeSource?12:4)+Object.values(assets).reduce((s,a)=>s+(a.samples?.byteLength||0),0)>96*1024**2)throw new Error('Render exceeds the 128 MiB working-buffer budget');
+  const raw=new Float64Array(n*OVERSAMPLE),voices=p.mode==='timeline'?[]:includedVoices(p).map(v=>({v,...waveform(v),curve:pitchCurve(v.pitch,T,v.hz,internal),phase:v.phase}));
+  const warnings=new Set(),inactive={value:0,availability:0};
+  if(voices.some(item=>Math.abs(item.dc)>1e-6))warnings.add('Oscillator DC removed before drawn gain');
   if(p.mode==='timeline'){
     raw.set(resolveStrokes(p.timeline.strokes,raw.length,false,false));
     const dc=metrics(raw).dc;for(let i=0;i<raw.length;i++)raw[i]-=dc;
@@ -64,9 +69,9 @@ export async function render(input,assets={},options={}) {
   for(let block=0;block<raw.length;block+=16384){
     if(options.signal?.aborted)throw new DOMException('Canceled','AbortError');
     for(let i=block;i<Math.min(raw.length,block+16384);i++){
-      const t=i/internal,state=enabled?sourceState(source,t,m):{value:0,availability:0};
+      const t=i/internal,state=enabled&&m.target==='oscillator'?sourceState(source,t,m):inactive;
       const amount=m.depth*state.availability,depth=m.semitones*state.availability;
-      const abs=Math.abs(state.value),a=abs>follower?attack:release;follower=a*follower+(1-a)*abs;
+      if(enabled&&m.target==='oscillator'&&m.mode==='volume'){const abs=Math.abs(state.value),a=abs>follower?attack:release;follower=a*follower+(1-a)*abs;}
       let sum=raw[i];
       for(const item of voices){
         const v=item.v,base=p.mode==='envelope'?item.curve(t):{hz:v.hz,phase:v.hz*t};
@@ -76,13 +81,12 @@ export async function render(input,assets={},options={}) {
           const requested=base.hz*2**(depth*state.value/12);
           hz=clamp(requested,20,Math.min(20000,rate/2-1));
           if(hz!==requested)warnings.add('Effective pitch limited to supported frequency range');
-          phase=item.phase;item.phase+=hz/internal;
+          if(i>0)item.phase+=(item.previousHz+hz)/(2*internal);phase=item.phase;item.previousHz=hz;
         }
         const h=Math.floor((rate/2-1)/hz);
-        const index=h<1?-1:v.source==='sine'?(h<item.data.sine.harmonic?-1:Math.ceil(Math.log2(item.data.sine.harmonic))):Math.min(item.tables.length-1,Math.floor(Math.log2(h)));
+        const index=h<1?-1:v.source==='sine'?(h<item.data.sine.harmonic?-1:Math.ceil(Math.log2(item.data.sine.harmonic))):Math.min(item.tables.length-1,31-Math.clz32(h));
         let value=index<0?0:sample(item.tables[index],phase);
-        if(h<item.limit)warnings.add('Harmonics above the playable bandwidth omitted');
-        if(Math.abs(item.dc)>1e-6)warnings.add('Oscillator DC removed before drawn gain');
+        if(h<item.limit&&!item.warned){warnings.add('Harmonics above the playable bandwidth omitted');item.warned=true;}
         value*=p.mode==='envelope'?envelope(v.gain,t/T,false,1):1;
         if(target&&m.mode==='ring')value*=1-amount+amount*state.value;
         if(target&&m.mode==='volume')value*=1-amount+amount*follower;
@@ -91,24 +95,27 @@ export async function render(input,assets={},options={}) {
       raw[i]=sum;
     }
     options.progress?.(.5*Math.min(1,(block+16384)/raw.length));
-    await new Promise(r=>setTimeout(r,0));
+    // Worker termination is immediate; only direct callers with an AbortSignal need event-loop yields.
+    if(options.signal)await new Promise(r=>setTimeout(r,0));
   }
   if(route&&m.target!=='oscillator'){
     const dry=needsCopy?raw.slice():raw;
-    let position=0;follower=0;
+    let position=0,previousRatio=1;follower=0;
     for(let block=0;block<raw.length;block+=16384){
       if(options.signal?.aborted)throw new DOMException('Canceled','AbortError');
       for(let i=block;i<Math.min(raw.length,block+16384);i++){
         const t=i/internal,state=sourceState(source,t,m),amount=m.depth*state.availability;
-        const abs=Math.abs(state.value),a=abs>follower?attack:release;follower=a*follower+(1-a)*abs;
+        if(m.mode==='volume'){const abs=Math.abs(state.value),a=abs>follower?attack:release;follower=a*follower+(1-a)*abs;}
         const ratio=m.mode==='pitch'?2**(m.semitones*state.availability*state.value/12):1;
+        if(i>0)position+=(previousRatio+ratio)/(2*internal);previousRatio=ratio;
         let value=carrier?readClip(carrier.samples,position,carrier.sampleRate,m.carrierLoop):needsCopy?readClip(dry,position,internal,m.carrierLoop):dry[i];
         if(m.mode==='ring')value*=1-amount+amount*state.value;
         if(m.mode==='volume')value*=1-amount+amount*follower;
-        raw[i]=value;position+=ratio/internal;
+        raw[i]=value;
       }
       options.progress?.(.5+.3*Math.min(1,(block+16384)/raw.length));
-      await new Promise(r=>setTimeout(r,0));
+      // Worker termination is immediate; only direct callers with an AbortSignal need event-loop yields.
+    if(options.signal)await new Promise(r=>setTimeout(r,0));
     }
   }
   if(enabled&&m.mode==='pitch'&&m.target!=='oscillator')warnings.add('Varispeed changes clip pitch and timing together');
diff --git a/src/resample.js b/src/resample.js
index 3c5edc8..06a6d1f 100644
--- a/src/resample.js
+++ b/src/resample.js
@@ -15,10 +15,16 @@ for(let p=0;p<=PHASES;p++){
 export function readClip(values, seconds, rate, loop=false) {
   if(!values.length || !Number.isFinite(seconds))return 0;
   let position=seconds*rate;
-  if(loop)position=((position%values.length)+values.length)%values.length;
+  if(loop&&(position<0||position>=values.length))position=((position%values.length)+values.length)%values.length;
   else if(position<0||position>=values.length)return 0;
   const index=Math.floor(position),fraction=(position-index)*PHASES,p=Math.floor(fraction),blend=fraction-p;
-  let out=0;
+  let out=0;const start=index-(HALF-1),left=p*TAPS,right=(p+1)*TAPS,inverse=1-blend;
+  if(start>=0&&start+TAPS<=values.length){
+    // Uniform 4× grids land on exact kernel phases; tolerate only floating-point round-off.
+    if(blend<1e-7||blend>1-1e-7){const base=blend<.5?left:right;for(let k=0;k<TAPS;k++)out+=values[start+k]*kernel[base+k];return out;}
+    for(let k=0;k<TAPS;k++)out+=values[start+k]*(kernel[left+k]*inverse+kernel[right+k]*blend);
+    return out;
+  }
   for(let k=0;k<TAPS;k++){
     let i=index+k-(HALF-1);
     if(loop)i=((i%values.length)+values.length)%values.length;
@@ -39,8 +45,9 @@ export function decimationFilter(factor=4,taps=257) {
 export function downsample(input,factor=4) {
   const h=decimationFilter(factor),half=(h.length-1)/2,out=new Float32Array(Math.round(input.length/factor));
   for(let n=0;n<out.length;n++){
-    const start=n*factor-half;let sum=0;
-    for(let k=Math.max(0,-start);k<h.length&&start+k<input.length;k++)sum+=input[start+k]*h[k];
+    const center=n*factor,start=center-half;let sum=0;
+    if(start>=0&&center+half<input.length){sum=input[center]*h[half];for(let j=1;j<=half;j++)sum+=(input[center-j]+input[center+j])*h[half+j];}
+    else {const end=Math.min(h.length,input.length-start);for(let k=Math.max(0,-start);k<end;k++)sum+=input[start+k]*h[k];}
     out[n]=sum;
   }
   return out;
diff --git a/src/signal.js b/src/signal.js
index a76b84d..89bba5a 100644
--- a/src/signal.js
+++ b/src/signal.js
@@ -20,7 +20,7 @@ export function resolveStrokes(strokes, size, smooth = false, periodic = true) {
 }
 export function sample(values, position, periodic = true) {
   if (!values.length || !Number.isFinite(position)) return 0;
-  if (periodic) position = ((position % 1) + 1) % 1;
+  if (periodic) position = position-Math.floor(position);
   else if (position < 0 || position >= 1) return 0;
   const x = position * values.length, i = Math.floor(x), f = x-i;
   return values[i]*(1-f) + values[i+1<values.length ? i+1 : periodic ? 0 : i]*f;
diff --git a/src/style.css b/src/style.css
index f6997ee..5665f52 100644
--- a/src/style.css
+++ b/src/style.css
@@ -8,3 +8,7 @@
 .trim-editor{margin:1rem 0;max-width:900px}.trim-editor canvas{width:100%;height:120px}.asset-list{display:grid;gap:.5rem;margin-top:1rem}.asset-row{display:flex;gap:1rem;align-items:center;padding:.75rem;background:var(--surface);border:1px solid var(--border);border-radius:8px}.asset-row strong{flex:1;overflow-wrap:anywhere}.asset-row button{margin-left:auto}
 
 .route-formula{display:block;white-space:normal;line-height:1.8;margin-top:1.25rem;color:#c9b5ff}.asset-row{flex-wrap:wrap}.asset-row .hint{white-space:nowrap}
+
+:root{--surface:#101925;--border:#2c384c}.mix-legend{color:#dce4f2}a:focus-visible,summary:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,canvas:focus-visible{outline:3px solid #8ee9ff;outline-offset:3px}
+
+.control-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.control-grid>label,.voice{min-width:0}.route-formula{overflow-wrap:anywhere}@media(max-width:700px){.control-grid,.voices-panel #voices{grid-template-columns:repeat(2,minmax(0,1fr))}.control-grid{padding:12px 0}.asset-row .hint{white-space:normal}.extra-panel h2{overflow-wrap:anywhere}}
diff --git a/tests/browser.mjs b/tests/browser.mjs
index 8ab38ec..b10d103 100644
--- a/tests/browser.mjs
+++ b/tests/browser.mjs
@@ -65,6 +65,21 @@ try {
       const route=await page.evaluate(()=>({target:window.testApp.project.modulation.oscillatorId,selected:window.testApp.project.selectedId}));
       assert.notEqual(route.target,route.selected);
       await page.getByRole('button',{name:'Play sound',exact:true}).click();await page.waitForFunction(()=>!!window.testApp.lastRender);await page.locator('#stop').click();
+      const unchanged=await page.evaluate(()=>JSON.stringify(window.testApp.project));
+      await page.getByLabel('Open project file').setInputFiles({name:'broken.json',mimeType:'application/json',buffer:Buffer.from('{}')});
+      await page.waitForFunction(()=>document.querySelector('#status').textContent.startsWith('Project was not opened:'));
+      assert.equal(await page.evaluate(()=>JSON.stringify(window.testApp.project)),unchanged);
+      const recovery=await page.evaluate(async()=>{
+        const app=window.testApp,before=app.library.entries.length,save=app.store.saveSound;
+        app.store.saveSound=async()=>{throw new DOMException('Quota fixture','QuotaExceededError');};
+        try{await app.library.save(null);}finally{app.store.saveSound=save;}
+        const {Importer}=await import('/src/importer.js'),importer=new Importer();
+        const file=new File([await(await fetch('/.fixtures/tone.wav')).arrayBuffer()],'tone.wav');
+        await importer.load(file);const pending=importer.trim({start:0,end:.1});importer.cancel();
+        let aborted=false;try{await pending;}catch(e){aborted=e.name==='AbortError';}
+        return {before,after:app.library.entries.length,status:document.querySelector('#status').textContent,aborted,worker:importer.worker};
+      });
+      assert.equal(recovery.before,recovery.after);assert.match(recovery.status,/not saved/);assert.equal(recovery.aborted,true);assert.equal(recovery.worker,null);
       const frozenId=await page.evaluate(()=>window.testApp.library.entries[0].audioId);
       await page.locator('#mod-source').selectOption(frozenId);
       await page.waitForFunction(id=>window.testApp.project.modulation.sourceId===id,frozenId);
@@ -91,8 +106,34 @@ try {
       await fresh.getByRole('button',{name:'Play sound',exact:true}).click();
       await fresh.waitForFunction(()=>!!window.testApp.lastRender);assert.ok(await fresh.evaluate(()=>window.testApp.lastRender.peak>0));
       await portable.close();
+      if(name==='chromium'){
+        await page.addScriptTag({path:'node_modules/axe-core/axe.min.js'});
+        const violations=await page.evaluate(async()=>{const r=await axe.run(document,{runOnly:{type:'tag',values:['wcag2a','wcag2aa','wcag21aa']}});return r.violations.map(v=>({id:v.id,impact:v.impact,nodes:v.nodes.map(n=>n.target)}));});
+        assert.deepEqual(violations,[]);
+        const stress=await page.evaluate(async()=>{
+          const app=window.testApp,{project}=await import('/src/model.js');
+          for(let k=0;k<31;k++){
+            const p=project();p.duration=10;p.name='Capacity '+k;p.voices[0].hz=220+k;
+            const samples=Float32Array.from({length:480000},(_,i)=>.3*Math.sin(2*Math.PI*p.voices[0].hz*i/48000));
+            await app.store.saveSound(p,{samples,sampleRate:48000,duration:10},[]);
+          }
+          let pcmReads=0;const get=app.store.get.bind(app.store);app.store.get=(name,...args)=>{if(name==='audio')pcmReads++;return get(name,...args);};
+          await app.library.refresh();const listingReads=pcmReads;app.store.get=get;
+          const entry=app.library.entries.find(e=>e.duration<1),times=[];
+          await app.library.play(entry);app.stop();
+          for(let i=0;i<100;i++){const t=performance.now();await app.library.play(entry);times.push(performance.now()-t);app.stop();}
+          await new Promise(r=>setTimeout(r,100));
+          const nodes=app.transport.nodes.size;
+          const pending=app.play();app.stop();await pending;
+          await new Promise(r=>setTimeout(r,100));
+          return {count:app.library.entries.length,listingReads,nodes,afterCancel:app.transport.nodes.size,padP95Ms:times.sort((a,b)=>a-b)[94]};
+        });
+        assert.equal(stress.count,32);assert.equal(stress.listingReads,0);assert.equal(stress.nodes,0);assert.equal(stress.afterCancel,0);console.log('BROWSER_STRESS:'+JSON.stringify(stress));
+        await page.setViewportSize({width:390,height:844});
+        const overflow=await page.evaluate(()=>({width:innerWidth,scroll:document.documentElement.scrollWidth,items:[...document.querySelectorAll('body *')].filter(n=>n.getBoundingClientRect().right>innerWidth+1).map(n=>n.tagName+'.'+n.className).slice(0,12)}));assert.ok(overflow.scroll<=overflow.width+1,JSON.stringify(overflow));
+      }
       assert.deepEqual(errors,[]);
-      if(name==='chromium')console.log('VISUAL:'+((await page.screenshot({type:'jpeg',quality:55,fullPage:true})).toString('base64')));
+      if(name==='chromium'){await page.setViewportSize({width:1440,height:1000});await page.evaluate(()=>scrollTo(0,0));console.log('VISUAL:'+((await page.screenshot({type:'jpeg',quality:60})).toString('base64')));}
       console.log(name+': draw, voices, envelopes, undo/redo, worker audio, and Stop passed');
     }catch(error){if(page){console.log('APP_STATE:'+await page.evaluate(()=>JSON.stringify({status:document.querySelector('#status')?.textContent,transport:document.querySelector('#transport-state')?.textContent,hasRender:!!window.testApp?.lastRender,audioState:window.testApp?.transport.context?.state,sampleRate:window.testApp?.transport.context?.sampleRate})));console.log('VISUAL:'+((await page.screenshot({type:'jpeg',quality:50,fullPage:true})).toString('base64')));}throw error;}finally{await browser.close();}
   }
diff --git a/tests/quality.test.mjs b/tests/quality.test.mjs
new file mode 100644
index 0000000..07b6a5b
--- /dev/null
+++ b/tests/quality.test.mjs
@@ -0,0 +1,29 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { project, voice, preset } from '../src/model.js';
+import { render } from '../src/render.js';
+import { downsample, decimationFilter } from '../src/resample.js';
+test('independent oscillator phases cancel and muted/solo selections remain silent',async()=>{
+  const p=project();p.duration=.04;const other=voice(1);other.phase=.5;p.voices.push(other);
+  let out=await render(p);assert.ok(out.peak<1e-6);
+  p.voices.forEach(v=>{v.muted=true;v.solo=true;});out=await render(p);assert.ok(out.samples.every(x=>x===0));
+});
+test('low-pass rejects ring sum above Nyquist and retains difference tone',async()=>{
+  const p=project();p.duration=.12;p.voices[0].hz=14000;p.voices[0].source='sine';p.assets=['mod'];p.modulation={...p.modulation,enabled:true,mode:'ring',depth:1,sourceId:'mod'};
+  const assets={mod:{sampleRate:48000,samples:Float32Array.from({length:9600},(_,i)=>Math.sin(2*Math.PI*13000*i/48000))}};
+  const result=await render(p,assets);
+  const mag=hz=>{let a=0,b=0;for(let i=960;i<4800;i++){a+=result.samples[i]*Math.cos(2*Math.PI*hz*i/48000);b+=result.samples[i]*Math.sin(2*Math.PI*hz*i/48000);}return 2*Math.hypot(a,b)/3840;};
+  assert.ok(mag(1000)>.30);assert.ok(mag(21000)<.002);
+});
+test('maximum numerical source stays finite and preserves one global attenuation',async()=>{
+  const p=project();p.duration=.02;p.voices=Array.from({length:4},(_,i)=>{const v=voice(i);v.waveform.resolution=16384;v.waveform.strokes=preset('square');v.hz=200+i*11;return v;});p.selectedId=p.modulation.oscillatorId=p.voices[0].id;
+  const out=await render(p);assert.ok(out.attenuation<1);assert.ok(out.peak<=.950001);assert.ok(out.samples.every(Number.isFinite));
+});
+
+test('geometric pitch stepping tracks an independent logarithmic sweep phase',async()=>{
+  const p=project();p.mode='envelope';p.duration=.15;p.voices[0].source='sine';p.voices[0].pitch=[[0,200],[1,1000]];
+  const r=await render(p),q=Math.log(5)/p.duration;
+  let squared=0,count=0;
+  for(let i=960;i<6000;i++){const t=i/48000,expected=.7*Math.sin(2*Math.PI*200*Math.expm1(q*t)/q);squared+=(r.samples[i]-expected)**2;count++;}
+  assert.ok(Math.sqrt(squared/count)<.001);
+});
diff --git a/tests/safari.py b/tests/safari.py
new file mode 100644
index 0000000..91f7ceb
--- /dev/null
+++ b/tests/safari.py
@@ -0,0 +1,85 @@
+"""Real Safari smoke test using Apple's bundled WebDriver; no Selenium dependency."""
+import json, subprocess, time, urllib.request, urllib.error, platform
+
+server = subprocess.Popen(["node", "scripts/serve.mjs"])
+driver = subprocess.Popen(["/usr/bin/safaridriver", "--port", "4444"])
+session = None
+
+def request(method, path, body=None):
+    payload = None if body is None else json.dumps(body).encode()
+    req = urllib.request.Request("http://127.0.0.1:4444"+path, data=payload, method=method, headers={"Content-Type":"application/json"})
+    try:
+        with urllib.request.urlopen(req, timeout=130) as result:
+            data=json.load(result)
+    except urllib.error.HTTPError as error:
+        raise RuntimeError(error.read().decode()) from error
+    value=data.get("value")
+    if isinstance(value, dict) and value.get("error"): raise RuntimeError(value)
+    return value
+
+def script(source, args=None, asynchronous=False):
+    return request("POST", "/session/"+session+"/execute/"+("async" if asynchronous else "sync"), {"script":source,"args":args or []})
+
+def async_script(source):
+    value=script("const done=arguments[arguments.length-1];(async()=>{"+source+"})().then(done,e=>done({error:e.stack||e.message}));", asynchronous=True)
+    if isinstance(value, dict) and value.get("error"): raise RuntimeError(value["error"])
+    return value
+
+def click(selector):
+    result=request("POST","/session/"+session+"/element",{"using":"css selector","value":selector})
+    key=result.get("element-6066-11e4-a52e-4f735466cecf") or result.get("ELEMENT")
+    request("POST","/session/"+session+"/element/"+key+"/click",{})
+
+try:
+    for _ in range(100):
+        try:
+            request("GET","/status")
+            urllib.request.urlopen("http://127.0.0.1:4173",timeout=1).close()
+            break
+        except Exception: time.sleep(.2)
+    result=request("POST","/session",{"capabilities":{"alwaysMatch":{"browserName":"Safari"}}})
+    session=result["sessionId"]
+    print("SAFARI_CAPABILITIES:"+json.dumps({"macOS":platform.mac_ver()[0],"machine":platform.machine(),"capabilities":result["capabilities"]}),flush=True)
+    request("POST","/session/"+session+"/timeouts",{"script":120000,"pageLoad":30000,"implicit":0})
+    request("POST","/session/"+session+"/url",{"url":"http://127.0.0.1:4173"})
+    async_script("window.testApp=(await import('/src/app.js')).app;await testApp.ready;testApp.edit(p=>{p.duration=.08;p.name='Safari fixture';});return true;")
+    codecs=async_script("""
+      const {Importer}=await import('/src/importer.js'),{makeAsset}=await import('/src/storage.js');
+      const results=[];
+      for(const type of ['wav','mp3']){
+        const bytes=await (await fetch('/.fixtures/tone.'+type)).arrayBuffer(),importer=new Importer();
+        const info=await importer.load(new File([bytes],'tone.'+type));
+        const trimmed=await importer.trim({start:0,end:.1,channel:'mix',sampleRate:48000});importer.cancel();
+        const asset=await makeAsset(trimmed.samples,48000,'Safari '+type,trimmed.provenance);
+        await testApp.store.transaction(['audio','audioMeta'],'readwrite',tx=>testApp.store.putAsset(tx,asset));
+        testApp.assets[asset.id]=asset;testApp.edit(p=>{p.assets.push(asset.id);p.modulation.sourceId=asset.id;});
+        results.push({type,rate:info.sampleRate,channels:info.channels,frames:asset.frames});
+      }
+      testApp.edit(p=>{p.modulation.enabled=true;p.modulation.mode='ring';p.modulation.depth=1;});
+      return results;
+    """)
+    assert all(c["rate"]==44100 and c["channels"]==2 and c["frames"]==4800 for c in codecs),codecs
+    click("#play")
+    for _ in range(150):
+        state=script("return {render:!!testApp.lastRender,status:document.querySelector('#status').textContent};")
+        if state["render"]: break
+        time.sleep(.1)
+    assert state["render"],state
+    audio=script("return {peak:testApp.lastRender.peak,rate:testApp.lastRender.sampleRate,state:testApp.transport.context.state};")
+    assert 0<audio["peak"]<=.950001 and audio["state"]=="running",audio
+    click("#stop")
+    saved=async_script("""
+      await testApp.library.save(null);
+      const entry=testApp.library.entries[0];if(!entry)throw Error('No saved sound');
+      testApp.edit(p=>{p.voices[0].hz=880;});
+      const snapshot=await testApp.store.get('projects',entry.projectId);
+      return {saved:snapshot.project.voices[0].hz,current:testApp.project.voices[0].hz};
+    """)
+    assert saved=={"saved":440,"current":880},saved
+    print("SAFARI_RESULT:"+json.dumps({"codecs":codecs,"audio":audio,"snapshotIsolation":saved}),flush=True)
+finally:
+    if session:
+        try: request("DELETE","/session/"+session)
+        except Exception: pass
+    driver.terminate()
+    server.terminate()