diff --git a/sfm/waveform_viewer.html b/sfm/waveform_viewer.html
index f0da66b..a68f929 100644
--- a/sfm/waveform_viewer.html
+++ b/sfm/waveform_viewer.html
@@ -175,6 +175,27 @@
     }
     #connect-btn:hover { background: #2ea043; }
     #connect-btn:disabled { background: #21262d; color: #484f58; }
+
+    #debug-panel {
+      display: none;
+      background: #0d1117;
+      border-bottom: 1px solid #21262d;
+      padding: 6px 20px;
+      font-family: monospace;
+      font-size: 11px;
+      color: #6e7681;
+      line-height: 1.7;
+    }
+    #debug-panel.visible { display: block; }
+    #debug-panel .dp-row { display: flex; gap: 24px; flex-wrap: wrap; }
+    #debug-panel .dp-ch  { color: #8b949e; }
+    #debug-panel .dp-ch span { color: #c9d1d9; }
+    #debug-panel .dp-warn { color: #e3b341; }
+    #debug-toggle {
+      background: none; border: none; color: #484f58; font-size: 11px;
+      cursor: pointer; padding: 0; float: right; text-decoration: underline;
+    }
+    #debug-toggle:hover { color: #8b949e; }
   </style>
 </head>
 <body>
@@ -193,8 +214,10 @@
   </div>
   <button id="connect-btn" onclick="connectUnit()">Connect</button>
   <button id="load-btn" onclick="loadWaveform()" disabled>Load Waveform</button>
-  <label style="display:flex;align-items:center;gap:4px;color:#8b949e;font-size:12px;cursor:pointer">
-    <input type="checkbox" id="force-reload" style="accent-color:#1f6feb" />
+  <label style="display:flex;align-items:center;gap:4px;color:#8b949e;font-size:12px;cursor:pointer"
+         title="Re-download from device, bypassing server cache. Check this then click Load Waveform (or checking it will auto-reload if a waveform is already shown).">
+    <input type="checkbox" id="force-reload" style="accent-color:#1f6feb"
+           onchange="if(this.checked && lastData !== null) loadWaveform()" />
     Force&nbsp;reload
   </label>
   <button id="prev-btn" onclick="stepEvent(-1)" disabled>◀ Prev</button>
@@ -223,6 +246,10 @@
 </div>
 
 <div id="status-bar">Ready — enter device host and click Connect.</div>
+<div id="debug-panel">
+  <button id="debug-toggle" onclick="document.getElementById('debug-panel').classList.remove('visible')">hide</button>
+  <div id="debug-content"></div>
+</div>
 
 <div id="empty-state">
   <svg width="48" height="48" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5">
@@ -478,6 +505,7 @@
           ? 'Waveform decode returned no samples — check server logs'
           : `Record type "${recType}" — waveform decode not yet supported for this mode`;
       document.getElementById('charts').style.display = 'none';
+      document.getElementById('debug-panel').classList.remove('visible');
       Object.values(charts).forEach(c => c.destroy());
       charts = {};
       return;
@@ -687,6 +715,41 @@
 
       if (chart) charts[ch] = chart;
     }
+
+    // ── Debug panel: raw ADC counts + decode diagnostics ────────────────────
+    // Shows the first 8 decoded ADC counts per channel and whether peak values
+    // came from the 0C record (authoritative) or from Math.max fallback.
+    // Useful for diagnosing channel misalignment without touching server logs.
+    const dbg = document.getElementById('debug-panel');
+    const dbgContent = document.getElementById('debug-content');
+    const geoChans = ['Tran', 'Vert', 'Long'];
+    const rawChans = channels;
+    const scale = geoRange / 32767;
+
+    let dbgHtml = '<div class="dp-row">';
+
+    // per-channel first-8 raw counts
+    for (const ch of [...geoChans, 'Mic']) {
+      const raw = (rawChans[ch] || []).slice(0, 8);
+      if (raw.length === 0) continue;
+      const maxAbs = Math.max(...raw.map(Math.abs));
+      const p0c = peakValues0C?.[ch] ?? null;
+      const src = (ch !== 'Mic' && p0c !== null) ? `0C=${p0c.toFixed(4)}` : `Math.max=${(maxAbs*scale).toFixed(4)}`;
+      dbgHtml += `<div class="dp-ch">${ch} raw[0:8]: <span>${raw.join(', ')}</span>  peak src: <span>${src}</span></div>`;
+    }
+    dbgHtml += '</div>';
+
+    // warn if peak0C was null for any geo channel
+    const nullPeaks = geoChans.filter(ch => (peakValues0C?.[ch] ?? null) === null);
+    if (nullPeaks.length > 0) {
+      dbgHtml += `<div class="dp-warn">⚠ peak0C null for: ${nullPeaks.join(', ')} — using Math.max fallback (check Force reload + Load Waveform)</div>`;
+    }
+
+    // summary line
+    dbgHtml += `<div>decoded=${data.samples_decoded}  total=${data.total_samples}  pretrig=${data.pretrig_samples}  sr=${data.sample_rate}  geoRange=${geoRange}</div>`;
+
+    dbgContent.innerHTML = dbgHtml;
+    dbg.classList.add('visible');
   }
 
   // Auto-detect API base from wherever this page was served from
