diff --git a/sfm/waveform_viewer.html b/sfm/waveform_viewer.html
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+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8" />
+  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+  <title>SFM Waveform Viewer</title>
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/4.4.1/chart.umd.min.js"></script>
+  <style>
+    * { box-sizing: border-box; margin: 0; padding: 0; }
+
+    body {
+      background: #0d1117;
+      color: #c9d1d9;
+      font-family: 'Segoe UI', system-ui, sans-serif;
+      font-size: 13px;
+    }
+
+    header {
+      background: #161b22;
+      border-bottom: 1px solid #30363d;
+      padding: 12px 20px;
+      display: flex;
+      align-items: center;
+      gap: 16px;
+      flex-wrap: wrap;
+    }
+
+    header h1 {
+      font-size: 15px;
+      font-weight: 600;
+      color: #f0f6fc;
+      white-space: nowrap;
+      margin-right: 8px;
+    }
+
+    .conn-group {
+      display: flex;
+      align-items: center;
+      gap: 6px;
+      flex-wrap: wrap;
+    }
+
+    label { color: #8b949e; font-size: 12px; }
+
+    input[type="text"], input[type="number"] {
+      background: #0d1117;
+      border: 1px solid #30363d;
+      border-radius: 6px;
+      color: #c9d1d9;
+      padding: 5px 8px;
+      font-size: 13px;
+      width: 100px;
+    }
+    input[type="number"] { width: 70px; }
+    input:focus { outline: none; border-color: #388bfd; }
+
+    button {
+      background: #1f6feb;
+      border: none;
+      border-radius: 6px;
+      color: #fff;
+      cursor: pointer;
+      font-size: 13px;
+      font-weight: 500;
+      padding: 5px 14px;
+      transition: background 0.15s;
+    }
+    button:hover  { background: #388bfd; }
+    button:active { background: #1158c7; }
+    button:disabled { background: #21262d; color: #484f58; cursor: not-allowed; }
+
+    #status-bar {
+      background: #161b22;
+      border-bottom: 1px solid #21262d;
+      padding: 5px 20px;
+      font-size: 12px;
+      color: #8b949e;
+      min-height: 26px;
+      display: flex;
+      align-items: center;
+      gap: 20px;
+    }
+    #status-bar.error  { color: #f85149; }
+    #status-bar.ok     { color: #3fb950; }
+    #status-bar.loading { color: #d29922; }
+
+    .meta-pill {
+      background: #21262d;
+      border-radius: 4px;
+      padding: 2px 8px;
+      color: #c9d1d9;
+      font-family: monospace;
+    }
+
+    #charts {
+      padding: 12px 16px;
+      display: flex;
+      flex-direction: column;
+      gap: 10px;
+    }
+
+    .chart-wrap {
+      background: #161b22;
+      border: 1px solid #21262d;
+      border-radius: 8px;
+      padding: 10px 12px 8px;
+    }
+
+    .chart-label {
+      font-size: 11px;
+      font-weight: 600;
+      letter-spacing: 0.06em;
+      text-transform: uppercase;
+      margin-bottom: 4px;
+    }
+
+    .chart-canvas-wrap { position: relative; height: 130px; }
+
+    #empty-state {
+      display: flex;
+      flex-direction: column;
+      align-items: center;
+      justify-content: center;
+      height: 60vh;
+      color: #484f58;
+      gap: 8px;
+    }
+    #empty-state svg { opacity: 0.3; }
+    #empty-state p { font-size: 14px; }
+
+    .ch-tran { color: #58a6ff; }
+    .ch-vert { color: #3fb950; }
+    .ch-long { color: #d29922; }
+    .ch-mic  { color: #bc8cff; }
+  </style>
+</head>
+<body>
+
+<header>
+  <h1>SFM Waveform Viewer</h1>
+  <div class="conn-group">
+    <label>API</label>
+    <input type="text" id="api-base" value="http://localhost:8200" style="width:180px" />
+  </div>
+  <div class="conn-group">
+    <label>Device host</label>
+    <input type="text" id="dev-host" value="" placeholder="e.g. 10.0.0.5" />
+    <label>TCP port</label>
+    <input type="number" id="dev-tcp-port" value="9034" />
+    <label>Event #</label>
+    <input type="number" id="event-index" value="0" min="0" style="width:55px" />
+  </div>
+  <button id="load-btn" onclick="loadWaveform()">Load Waveform</button>
+  <button id="prev-btn" onclick="stepEvent(-1)" disabled>◀ Prev</button>
+  <button id="next-btn" onclick="stepEvent(+1)" disabled>Next ▶</button>
+</header>
+
+<div id="status-bar">Ready — enter device host and click Load Waveform.</div>
+
+<div id="empty-state">
+  <svg width="48" height="48" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5">
+    <polyline points="22 12 18 12 15 21 9 3 6 12 2 12"/>
+  </svg>
+  <p>No waveform loaded</p>
+</div>
+
+<div id="charts" style="display:none"></div>
+
+<script>
+  const CHANNEL_COLORS = {
+    Tran: '#58a6ff',
+    Vert: '#3fb950',
+    Long: '#d29922',
+    Mic:  '#bc8cff',
+  };
+
+  let charts = {};
+  let lastData = null;
+
+  function setStatus(msg, cls = '') {
+    const bar = document.getElementById('status-bar');
+    bar.textContent = msg;
+    bar.className = cls;
+  }
+
+  function appendMeta(label, value) {
+    const bar = document.getElementById('status-bar');
+    const pill = document.createElement('span');
+    pill.className = 'meta-pill';
+    pill.textContent = `${label}: ${value}`;
+    bar.appendChild(pill);
+  }
+
+  async function loadWaveform() {
+    const apiBase   = document.getElementById('api-base').value.replace(/\/$/, '');
+    const devHost   = document.getElementById('dev-host').value.trim();
+    const tcpPort   = document.getElementById('dev-tcp-port').value;
+    const evIndex   = parseInt(document.getElementById('event-index').value, 10);
+
+    if (!devHost) { setStatus('Enter a device host first.', 'error'); return; }
+
+    const btn = document.getElementById('load-btn');
+    btn.disabled = true;
+    setStatus('Fetching waveform…', 'loading');
+
+    const url = `${apiBase}/device/event/${evIndex}/waveform?host=${encodeURIComponent(devHost)}&tcp_port=${tcpPort}`;
+
+    let data;
+    try {
+      const resp = await fetch(url);
+      if (!resp.ok) {
+        const err = await resp.json().catch(() => ({ detail: resp.statusText }));
+        throw new Error(err.detail || resp.statusText);
+      }
+      data = await resp.json();
+    } catch (e) {
+      setStatus(`Error: ${e.message}`, 'error');
+      btn.disabled = false;
+      return;
+    }
+
+    lastData = data;
+    renderWaveform(data);
+    btn.disabled = false;
+    document.getElementById('prev-btn').disabled = evIndex <= 0;
+    document.getElementById('next-btn').disabled = false;
+  }
+
+  function stepEvent(delta) {
+    const el = document.getElementById('event-index');
+    const next = Math.max(0, parseInt(el.value, 10) + delta);
+    el.value = next;
+    loadWaveform();
+  }
+
+  function renderWaveform(data) {
+    const sr        = data.sample_rate  || 1024;
+    const pretrig   = data.pretrig_samples || 0;
+    const decoded   = data.samples_decoded || 0;
+    const total     = data.total_samples   || decoded;
+    const channels  = data.channels || {};
+
+    // Build time axis (ms)
+    const times = Array.from({ length: decoded }, (_, i) =>
+      ((i - pretrig) / sr * 1000).toFixed(2)
+    );
+
+    const triggerMs = 0;  // t=0 is trigger by construction
+
+    // Status bar
+    const bar = document.getElementById('status-bar');
+    bar.innerHTML = '';
+    bar.className = 'ok';
+    const ts = data.timestamp;
+    if (ts) {
+      bar.textContent = `Event #${data.index}  —  ${ts.display}    `;
+    } else {
+      bar.textContent = `Event #${data.index}    `;
+    }
+    appendMeta('sr', `${sr} sps`);
+    appendMeta('samples', `${decoded.toLocaleString()} / ${total.toLocaleString()}`);
+    appendMeta('pretrig', pretrig);
+    appendMeta('rectime', `${data.rectime_seconds ?? '?'}s`);
+
+    // Show charts area
+    document.getElementById('empty-state').style.display = 'none';
+    const chartsDiv = document.getElementById('charts');
+    chartsDiv.style.display = 'flex';
+    chartsDiv.innerHTML = '';
+
+    // Destroy old Chart instances
+    Object.values(charts).forEach(c => c.destroy());
+    charts = {};
+
+    for (const [ch, color] of Object.entries(CHANNEL_COLORS)) {
+      const samples = channels[ch];
+      if (!samples || samples.length === 0) continue;
+
+      const wrap = document.createElement('div');
+      wrap.className = 'chart-wrap';
+
+      const lbl = document.createElement('div');
+      lbl.className = `chart-label ch-${ch.toLowerCase()}`;
+
+      // Compute peak for label
+      const peak = Math.max(...samples.map(Math.abs));
+      lbl.textContent = `${ch}  —  peak ${peak.toLocaleString()} counts`;
+      wrap.appendChild(lbl);
+
+      const canvasWrap = document.createElement('div');
+      canvasWrap.className = 'chart-canvas-wrap';
+      const canvas = document.createElement('canvas');
+      canvasWrap.appendChild(canvas);
+      wrap.appendChild(canvasWrap);
+      chartsDiv.appendChild(wrap);
+
+      // Downsample for rendering if very long (keep chart responsive)
+      const MAX_POINTS = 4000;
+      let renderTimes = times;
+      let renderData  = samples;
+      if (samples.length > MAX_POINTS) {
+        const step = Math.ceil(samples.length / MAX_POINTS);
+        renderTimes = times.filter((_, i) => i % step === 0);
+        renderData  = samples.filter((_, i) => i % step === 0);
+      }
+
+      const chart = new Chart(canvas, {
+        type: 'line',
+        data: {
+          labels: renderTimes,
+          datasets: [{
+            data: renderData,
+            borderColor: color,
+            borderWidth: 1,
+            pointRadius: 0,
+            tension: 0,
+          }],
+        },
+        options: {
+          animation: false,
+          responsive: true,
+          maintainAspectRatio: false,
+          plugins: {
+            legend: { display: false },
+            tooltip: {
+              mode: 'index',
+              intersect: false,
+              callbacks: {
+                title: items => `t = ${items[0].label} ms`,
+                label: item => `${ch}: ${item.raw.toLocaleString()} counts`,
+              },
+            },
+            // Trigger line annotation (drawn manually via afterDraw)
+          },
+          scales: {
+            x: {
+              type: 'category',
+              ticks: {
+                color: '#484f58',
+                maxTicksLimit: 10,
+                maxRotation: 0,
+                callback: (val, i) => renderTimes[i] + ' ms',
+              },
+              grid: { color: '#21262d' },
+            },
+            y: {
+              ticks: { color: '#484f58', maxTicksLimit: 5 },
+              grid: { color: '#21262d' },
+            },
+          },
+        },
+        plugins: [{
+          // Draw trigger line at t=0
+          id: 'triggerLine',
+          afterDraw(chart) {
+            const ctx   = chart.ctx;
+            const xAxis = chart.scales.x;
+            const yAxis = chart.scales.y;
+
+            // Find index of t=0
+            const zeroIdx = renderTimes.findIndex(t => parseFloat(t) >= 0);
+            if (zeroIdx < 0) return;
+
+            const x = xAxis.getPixelForValue(zeroIdx);
+            ctx.save();
+            ctx.beginPath();
+            ctx.moveTo(x, yAxis.top);
+            ctx.lineTo(x, yAxis.bottom);
+            ctx.strokeStyle = 'rgba(248, 81, 73, 0.7)';
+            ctx.lineWidth = 1.5;
+            ctx.setLineDash([4, 3]);
+            ctx.stroke();
+            ctx.restore();
+          },
+        }],
+      });
+
+      charts[ch] = chart;
+    }
+  }
+
+  // Allow Enter key on inputs to trigger load
+  document.querySelectorAll('input').forEach(el => {
+    el.addEventListener('keydown', e => { if (e.key === 'Enter') loadWaveform(); });
+  });
+</script>
+</body>
+</html>
