diff --git a/lightsync/frontend/app.js b/lightsync/frontend/app.js
index 40b9a8e..49579f4 100644
--- a/lightsync/frontend/app.js
+++ b/lightsync/frontend/app.js
@@ -1,6 +1,6 @@
-// LightSync frontend — Phase 1 shell
-// WebSocket stub + device list loader
-// Phase 2 expands audio, transport, and WS protocol
+// LightSync frontend — Phase 02-03 browser-audio architecture
+// Browser <audio> element plays audio; server does beat detection via librosa
+// 10Hz position ticks sent to server; server sends beat notifications back
 
 const WS_URL = `${location.protocol === 'https:' ? 'wss' : 'ws'}://${location.host}/ws`;
 
@@ -19,6 +19,12 @@ async function apiDelete(path) {
     if (!res.ok && res.status !== 204) throw new Error(`DELETE ${path}: HTTP ${res.status}`);
 }
 
+// --- Beat markers state ---
+let beatTimestamps = [];   // sorted list of beat times in seconds
+let audioDuration = 0;
+let currentFilePath = "";  // absolute server path for beat/waveform fetches
+
+// --- WebSocket client ---
 class LightSyncClient {
     constructor() {
         this.ws = null;
@@ -56,9 +62,8 @@ class LightSyncClient {
     }
 
     handleMessage(msg) {
-        if (msg.type === 'tick') {
-            updatePosition(msg.position, msg.duration, msg.paused);
-            audioLoaded = msg.loaded;
+        if (msg.type === 'beat') {
+            flashBeatIndicator();
         } else {
             console.debug('[ws]', msg);
         }
@@ -71,12 +76,19 @@ class LightSyncClient {
     }
 }
 
-// --- Waveform rendering ---
-let waveformPeaks = [];
-let audioDuration = 0;
-let audioLoaded = false;
+// --- Beat indicator flash ---
+function flashBeatIndicator() {
+    const dot = document.getElementById('beat-indicator');
+    if (!dot) return;
+    dot.classList.add('beat-flash');
+    // Remove class after animation completes (200ms)
+    setTimeout(() => dot.classList.remove('beat-flash'), 200);
+}
 
-function drawWaveform(canvas, peaks) {
+// --- Waveform + beat marker rendering ---
+let waveformPeaks = [];
+
+function drawWaveform(canvas, peaks, beats, duration) {
     const ctx = canvas.getContext('2d');
     const dpr = window.devicePixelRatio || 1;
     const rect = canvas.getBoundingClientRect();
@@ -87,74 +99,230 @@ function drawWaveform(canvas, peaks) {
     const w = rect.width;
     const h = rect.height;
     const mid = h / 2;
-    const barWidth = w / peaks.length;
 
     ctx.clearRect(0, 0, w, h);
 
     // Draw waveform bars using --accent color
-    ctx.fillStyle = getComputedStyle(document.documentElement).getPropertyValue('--accent').trim() || '#0ff';
-    for (let i = 0; i < peaks.length; i++) {
-        const amp = peaks[i] * mid * 0.9;
-        const x = i * barWidth;
-        ctx.fillRect(x, mid - amp, Math.max(barWidth - 0.5, 0.5), amp * 2);
+    if (peaks.length > 0) {
+        const barWidth = w / peaks.length;
+        ctx.fillStyle = getComputedStyle(document.documentElement).getPropertyValue('--accent').trim() || '#0ff';
+        for (let i = 0; i < peaks.length; i++) {
+            const amp = peaks[i] * mid * 0.9;
+            const x = i * barWidth;
+            ctx.fillRect(x, mid - amp, Math.max(barWidth - 0.5, 0.5), amp * 2);
+        }
+    }
+
+    // Draw beat markers as thin vertical lines
+    if (beats.length > 0 && duration > 0) {
+        ctx.strokeStyle = 'rgba(255, 200, 0, 0.6)';
+        ctx.lineWidth = 1;
+        for (const t of beats) {
+            const x = (t / duration) * w;
+            ctx.beginPath();
+            ctx.moveTo(x, 0);
+            ctx.lineTo(x, h);
+            ctx.stroke();
+        }
     }
 }
 
-async function loadWaveform() {
+async function loadWaveformAndBeats(filePath) {
     try {
-        const res = await fetch('/api/audio/waveform?peaks=2000');
-        if (!res.ok) return;
-        const data = await res.json();
-        waveformPeaks = data.peaks;
-        const canvas = document.getElementById('waveform-canvas');
-        if (canvas) drawWaveform(canvas, waveformPeaks);
+        const encodedPath = encodeURIComponent(filePath);
+        const [waveRes, beatRes] = await Promise.allSettled([
+            fetch(`/api/audio/waveform?path=${encodedPath}&peaks=2000`),
+            fetch(`/api/audio/beats?path=${encodedPath}`),
+        ]);
+
+        if (waveRes.status === 'fulfilled' && waveRes.value.ok) {
+            const data = await waveRes.value.json();
+            waveformPeaks = data.peaks;
+        }
+
+        if (beatRes.status === 'fulfilled' && beatRes.value.ok) {
+            const data = await beatRes.value.json();
+            beatTimestamps = data.beats || [];
+            audioDuration = document.getElementById('player')?.duration || audioDuration;
+        }
+
+        redrawCanvas();
     } catch (err) {
-        console.error('[waveform]', err);
+        console.error('[waveform/beats]', err);
     }
 }
 
-// --- Time formatting ---
-function formatTime(seconds) {
-    if (seconds == null || isNaN(seconds)) return '0:00.0';
-    const m = Math.floor(seconds / 60);
-    const s = seconds % 60;
-    return `${m}:${s < 10 ? '0' : ''}${s.toFixed(1)}`;
+function redrawCanvas() {
+    const canvas = document.getElementById('waveform-canvas');
+    if (canvas) {
+        const audio = document.getElementById('player');
+        const dur = (audio && isFinite(audio.duration)) ? audio.duration : audioDuration;
+        drawWaveform(canvas, waveformPeaks, beatTimestamps, dur);
+    }
 }
 
-// --- Position update from WebSocket tick ---
-function updatePosition(position, duration, paused) {
-    audioDuration = duration || 0;
+// --- 10Hz position tick loop ---
+let _tickInterval = null;
 
-    document.getElementById('time-current').textContent = formatTime(position);
-    document.getElementById('time-duration').textContent = formatTime(duration);
+function startTickLoop() {
+    if (_tickInterval) return;
+    _tickInterval = setInterval(() => {
+        const audio = document.getElementById('player');
+        if (audio && !audio.paused && !audio.ended) {
+            client.send({ type: 'tick', position: audio.currentTime });
+        }
+    }, 100);
+}
 
-    // Update seek bar
-    const seekBar = document.getElementById('seek-bar');
-    if (duration > 0 && !seekBar._dragging) {
-        seekBar.value = (position / duration) * 100;
+function stopTickLoop() {
+    if (_tickInterval) {
+        clearInterval(_tickInterval);
+        _tickInterval = null;
     }
+}
 
-    // Update playback cursor position
+// --- Audio element event wiring ---
+function wireAudioElement() {
+    const audio = document.getElementById('player');
+    if (!audio) return;
+
+    // Also send ticks on native timeupdate (~4Hz) as a fallback bridge
+    audio.addEventListener('timeupdate', () => {
+        if (!audio.paused) {
+            client.send({ type: 'tick', position: audio.currentTime });
+            updateCursor(audio.currentTime, audio.duration);
+        }
+    });
+
+    audio.addEventListener('play', () => {
+        client.send({ type: 'play', position: audio.currentTime });
+        startTickLoop();
+        document.getElementById('show-name').textContent = currentFilePath
+            ? currentFilePath.split('/').pop()
+            : '— playing —';
+    });
+
+    audio.addEventListener('pause', () => {
+        client.send({ type: 'pause', position: audio.currentTime });
+        stopTickLoop();
+    });
+
+    audio.addEventListener('ended', () => {
+        stopTickLoop();
+        client.send({ type: 'pause', position: audio.currentTime });
+    });
+
+    audio.addEventListener('seeked', () => {
+        client.send({ type: 'seek', position: audio.currentTime });
+        updateCursor(audio.currentTime, audio.duration);
+    });
+
+    audio.addEventListener('loadedmetadata', () => {
+        audioDuration = audio.duration;
+        redrawCanvas();
+    });
+}
+
+function updateCursor(position, duration) {
     const cursor = document.getElementById('playback-cursor');
     const container = document.querySelector('.waveform-container');
     if (cursor && container && duration > 0) {
         const pct = (position / duration) * 100;
         cursor.style.left = pct + '%';
     }
+}
 
-    // Toggle play/pause button visibility
-    const btnPlay = document.getElementById('btn-play');
-    const btnPause = document.getElementById('btn-pause');
-    if (btnPlay && btnPause) {
-        btnPlay.style.display = paused ? '' : 'none';
-        btnPause.style.display = paused ? 'none' : '';
+// --- File selector ---
+async function refreshFileList(selectValue) {
+    const sel = document.getElementById('audio-select');
+    if (!sel) return;
+    try {
+        const res = await fetch('/api/audio/files');
+        if (!res.ok) return;
+        const { files } = await res.json();
+        const prev = selectValue ?? sel.value;
+        sel.innerHTML = '<option value="">&#8212; select file &#8212;</option>';
+        files.forEach(name => {
+            const opt = document.createElement('option');
+            opt.value = `/app/shows/${name}`;
+            opt.textContent = name;
+            if (opt.value === prev) opt.selected = true;
+            sel.appendChild(opt);
+        });
+    } catch (e) {
+        console.error('[audio] file list error:', e);
     }
 }
 
-const client = new LightSyncClient();
-client.connect();
+// --- Upload handler ---
+document.getElementById('audio-upload')?.addEventListener('change', async (e) => {
+    const file = e.target.files?.[0];
+    if (!file) return;
+    const form = new FormData();
+    form.append('file', file);
+    try {
+        const res = await fetch('/api/audio/upload', { method: 'POST', body: form });
+        if (!res.ok) {
+            const err = await res.json();
+            console.error('[audio] upload failed:', err.detail);
+            return;
+        }
+        const { path, beats } = await res.json();
+        // Cache beat timestamps returned from upload response
+        if (beats && beats.beats) {
+            beatTimestamps = beats.beats;
+        }
+        await refreshFileList(`/shows/${path.split('/').pop()}`);
+        // Auto-select and load the just-uploaded file
+        const sel = document.getElementById('audio-select');
+        const serverPath = `/shows/${path.split('/').pop()}`;
+        if (sel) {
+            // find matching option and select it
+            for (const opt of sel.options) {
+                if (opt.value === serverPath || opt.value === path) {
+                    opt.selected = true;
+                    break;
+                }
+            }
+        }
+        loadSelectedFile(path);
+    } catch (err) {
+        console.error('[audio] upload error:', err);
+    }
+    e.target.value = '';
+});
 
-// Load device list on startup
+// --- Load button handler ---
+document.getElementById('btn-load')?.addEventListener('click', () => {
+    const sel = document.getElementById('audio-select');
+    const path = sel?.value;
+    if (!path) return;
+    // Convert /shows/filename to /app/shows/filename for absolute path
+    const absPath = path.startsWith('/app/') ? path : `/app${path}`;
+    loadSelectedFile(absPath);
+});
+
+function loadSelectedFile(absPath) {
+    const audio = document.getElementById('player');
+    if (!audio) return;
+
+    // Derive the URL path from the absolute server path
+    // /app/shows/song.mp3 -> /shows/song.mp3
+    const urlPath = absPath.replace(/^\/app/, '');
+    audio.src = urlPath;
+    audio.load();
+
+    currentFilePath = absPath;
+    document.getElementById('show-name').textContent = absPath.split('/').pop();
+
+    // Tell WebSocket which file is loaded for beat lookup
+    client.send({ type: 'load', path: absPath });
+
+    // Fetch waveform + beat markers
+    loadWaveformAndBeats(absPath);
+}
+
+// --- Device management ---
 async function loadDevices() {
     try {
         const res = await fetch("/api/devices");
@@ -197,116 +365,24 @@ function escapeHtml(str) {
     return div.innerHTML;
 }
 
-loadDevices();
-
-// --- Transport controls ---
-document.getElementById('btn-play')?.addEventListener('click', () => {
-    client.send({ type: 'play' });
-});
-
-document.getElementById('btn-pause')?.addEventListener('click', () => {
-    client.send({ type: 'pause' });
-});
-
-document.getElementById('btn-stop')?.addEventListener('click', () => {
-    client.send({ type: 'pause' });
-    client.send({ type: 'seek', position: 0 });
-});
-
-// Seek bar interaction
-const seekBar = document.getElementById('seek-bar');
-if (seekBar) {
-    seekBar.addEventListener('mousedown', () => { seekBar._dragging = true; });
-    seekBar.addEventListener('mouseup', () => {
-        seekBar._dragging = false;
-        const pos = (parseFloat(seekBar.value) / 100) * audioDuration;
-        client.send({ type: 'seek', position: pos });
-    });
-}
-
-// Populate file selector
-async function refreshFileList(selectValue) {
-    const sel = document.getElementById('audio-select');
-    if (!sel) return;
-    try {
-        const res = await fetch('/api/audio/files');
-        if (!res.ok) return;
-        const { files } = await res.json();
-        const prev = selectValue ?? sel.value;
-        sel.innerHTML = '<option value="">— select file —</option>';
-        files.forEach(name => {
-            const opt = document.createElement('option');
-            opt.value = `/app/shows/${name}`;
-            opt.textContent = name;
-            if (opt.value === prev) opt.selected = true;
-            sel.appendChild(opt);
-        });
-    } catch (e) {
-        console.error('[audio] file list error:', e);
-    }
-}
-refreshFileList();
-
-// Upload audio file
-document.getElementById('audio-upload')?.addEventListener('change', async (e) => {
-    const file = e.target.files?.[0];
-    if (!file) return;
-    const form = new FormData();
-    form.append('file', file);
-    try {
-        const res = await fetch('/api/audio/upload', { method: 'POST', body: form });
-        if (!res.ok) {
-            const err = await res.json();
-            console.error('[audio] upload failed:', err.detail);
-            return;
-        }
-        const { path } = await res.json();
-        await refreshFileList(path);
-        setTimeout(loadWaveform, 500);
-    } catch (err) {
-        console.error('[audio] upload error:', err);
-    }
-    e.target.value = '';
-});
-
-// Load selected audio file
-document.getElementById('btn-load')?.addEventListener('click', async () => {
-    const sel = document.getElementById('audio-select');
-    const path = sel?.value;
-    if (!path) return;
-    try {
-        const res = await fetch('/api/audio/load', {
-            method: 'POST',
-            headers: { 'Content-Type': 'application/json' },
-            body: JSON.stringify({ path }),
-        });
-        if (!res.ok) {
-            const err = await res.json();
-            console.error('[audio] load failed:', err.detail);
-            return;
-        }
-        setTimeout(loadWaveform, 500);
-    } catch (err) {
-        console.error('[audio] load error:', err);
-    }
-});
-
-// Click on waveform to seek
+// --- Waveform click-to-seek ---
 document.querySelector('.waveform-container')?.addEventListener('click', (e) => {
-    if (audioDuration <= 0) return;
+    const audio = document.getElementById('player');
+    if (!audio || !isFinite(audio.duration) || audio.duration <= 0) return;
     const rect = e.currentTarget.getBoundingClientRect();
     const pct = (e.clientX - rect.left) / rect.width;
-    const pos = pct * audioDuration;
-    client.send({ type: 'seek', position: pos });
+    audio.currentTime = pct * audio.duration;
 });
 
-// Resize waveform on window resize
-window.addEventListener('resize', () => {
-    if (waveformPeaks.length > 0) {
-        const canvas = document.getElementById('waveform-canvas');
-        if (canvas) drawWaveform(canvas, waveformPeaks);
-    }
-});
+// --- Resize redraws ---
+window.addEventListener('resize', redrawCanvas);
+
+// --- Init ---
+const client = new LightSyncClient();
+client.connect();
+wireAudioElement();
+loadDevices();
+refreshFileList();
 
 document.getElementById("add-device-form").addEventListener("submit", async (e) => {
     e.preventDefault();
diff --git a/lightsync/frontend/index.html b/lightsync/frontend/index.html
index b56755d..57829d1 100644
--- a/lightsync/frontend/index.html
+++ b/lightsync/frontend/index.html
@@ -17,6 +17,7 @@
             <div class="status-dot" id="status-dot"></div>
             <span id="status-text" class="text-dim">OFFLINE</span>
             <span id="show-name" class="text-dim">&#8212; no show loaded &#8212;</span>
+            <div id="beat-indicator" class="beat-indicator" title="Beat pulse"></div>
         </header>
 
         <aside class="sidebar">
@@ -26,7 +27,7 @@
                     <span class="text-dim">loading...</span>
                 </div>
                 <details class="device-manage-section">
-                    <summary>⚙ MANAGE DEVICES</summary>
+                    <summary>&#9881; MANAGE DEVICES</summary>
                     <form id="add-device-form" class="device-form">
                         <input type="text" name="name" placeholder="Device name" required>
                         <select name="strip_type" required>
@@ -43,7 +44,14 @@
             </div>
             <div class="panel" id="animations-panel" style="flex: 1; min-height: 0;">
                 <div class="panel-header">ANIMATIONS</div>
-                <div class="panel-content text-dim">[ PHASE 3+ ]</div>
+                <div class="panel-content">
+                    <select id="animation-select" class="animation-select-input">
+                        <option value="beat_pulse">Beat Pulse</option>
+                        <option value="strobe">Strobe</option>
+                        <option value="color_wave">Color Wave</option>
+                        <option value="rainbow">Rainbow</option>
+                    </select>
+                </div>
             </div>
         </aside>
 
@@ -58,26 +66,16 @@
         </main>
 
         <footer class="transport-bar" id="transport-panel">
-            <div class="transport-controls">
-                <button id="btn-play" class="transport-btn" title="Play">&#9654;</button>
-                <button id="btn-pause" class="transport-btn" title="Pause" style="display:none">&#9646;&#9646;</button>
-                <button id="btn-stop" class="transport-btn" title="Stop">&#9632;</button>
-            </div>
-            <div class="transport-time">
-                <span id="time-current">0:00.0</span>
-                <span class="text-dim">/</span>
-                <span id="time-duration">0:00.0</span>
-            </div>
-            <div class="transport-seek">
-                <input type="range" id="seek-bar" min="0" max="100" value="0" step="0.1" class="seek-slider">
-            </div>
+            <!-- Hidden native audio element — browser handles playback -->
+            <audio id="player" style="display:none;"></audio>
+
             <div class="transport-file">
                 <label class="transport-btn" title="Upload MP3/WAV/FLAC/OGG from your computer" style="cursor:pointer;">
                     + UPLOAD
                     <input type="file" id="audio-upload" accept=".mp3,.wav,.flac,.ogg" style="display:none;">
                 </label>
                 <select id="audio-select" class="audio-path-input">
-                    <option value="">— no files yet, upload first —</option>
+                    <option value="">&#8212; no files yet, upload first &#8212;</option>
                 </select>
                 <button id="btn-load" class="transport-btn" title="Load selected file">LOAD</button>
             </div>
diff --git a/lightsync/frontend/style.css b/lightsync/frontend/style.css
index 0f73b8d..0538885 100644
--- a/lightsync/frontend/style.css
+++ b/lightsync/frontend/style.css
@@ -337,3 +337,35 @@ button:hover {
     transition: left 0.1s linear;
     z-index: 10;
 }
+
+/* Beat indicator in header */
+.beat-indicator {
+    width: 10px;
+    height: 10px;
+    border-radius: 50%;
+    background: var(--text-dim);
+    flex-shrink: 0;
+    transition: background 0.05s ease;
+}
+
+.beat-indicator.beat-flash {
+    background: #ffcc00;
+    box-shadow: 0 0 8px #ffcc00;
+}
+
+/* Animation selector */
+.animation-select-input {
+    background: var(--bg-primary);
+    color: var(--text-primary);
+    border: 1px solid var(--border-dim);
+    padding: 4px 8px;
+    font-family: var(--font-mono);
+    font-size: var(--font-size);
+    width: 100%;
+    cursor: pointer;
+}
+
+.animation-select-input:focus {
+    border-color: var(--border-bright);
+    outline: none;
+}