diff --git a/public/viewer.js b/public/viewer.js
index d2f28e6..64828f4 100644
--- a/public/viewer.js
+++ b/public/viewer.js
@@ -351,19 +351,80 @@ function showNotice() {
   bar.style.display = 'flex';
 }
 
-// ── Snapshot aller Kameras ───────────────────────────────────────────────────
-function snapshotAll() {
-  const ts = Date.now();
-  const ids = cameras.map(c => c.id);
-  log('snap', `Snapshot alle: ${ids.join(', ')}`);
-  ids.forEach(id => {
-    const a = document.createElement('a');
-    a.href = `/api/snapshot/${id}`;
-    a.download = `${id}_${ts}.jpg`;
-    document.body.appendChild(a);
-    a.click();
-    a.remove();
-  });
+// ── HD-Snapshot aller Kameras (parallel) ─────────────────────────────────────
+// cam0 und cam1 liegen auf getrennten Geräten → gleichzeitiger Grab sicher.
+// Alle Live-Streams werden synchron eingefroren und losgelassen, dann beide
+// /hires-Requests parallel gefeuert. finally stellt immer alle zurück.
+async function snapshotAllHires() {
+  if (cameras.some(c => c.testing)) return;
+
+  const snapBtn = document.getElementById('snapAllBtn');
+  if (snapBtn) snapBtn.disabled = true;
+  cameras.forEach(c => { c.testing = true; c.hdBtn.disabled = true; });
+  log('snap', `HD-Grab alle: ${cameras.map(c => c.id).join(', ')}`);
+
+  try {
+    // 1. Alle Freeze-Canvases gleichzeitig aufbauen (je ein /api/snapshot-Fetch)
+    await Promise.all(cameras.map(c => showFreezeCanvas(c, 'Capturing HD…')));
+
+    // 2. Alle Live-Streams synchron loslassen → alle Consumer fallen gleichzeitig auf 0
+    cameras.forEach(c => stopStream(c));
+
+    const ts = Date.now();
+
+    // 3. Alle /hires-Grabs parallel – Fehler einer Kamera blockieren die andere nicht
+    await Promise.allSettled(cameras.map(async c => {
+      try {
+        const r = await fetch(
+          `/api/snapshot/${encodeURIComponent(c.id)}/hires`,
+          { signal: AbortSignal.timeout(20000) }
+        );
+        if (!r.ok) {
+          const body = await r.json().catch(() => ({}));
+          throw new Error(body.error ?? `HTTP ${r.status}`);
+        }
+        const blob   = await r.blob();
+        const blobUrl = URL.createObjectURL(blob);
+
+        if (c.freezeCanvas) {
+          const ctx = c.freezeCanvas.getContext('2d');
+          await new Promise(resolve => {
+            const img = new Image();
+            img.onload = () => { ctx.drawImage(img, 0, 0, 640, 480); resolve(); };
+            img.onerror = resolve;
+            img.src = blobUrl;
+          });
+          updateBadge(c, 'HD ✓', '#8f8');
+        }
+
+        const a = document.createElement('a');
+        a.href     = blobUrl;
+        a.download = `${c.id}_hires_${ts}.jpg`;
+        document.body.appendChild(a);
+        a.click();
+        a.remove();
+        URL.revokeObjectURL(blobUrl);
+
+        setInfo(c, 'HD gespeichert', 'ok');
+        log(c.id, `HD-Grab OK – ${blob.size} bytes`);
+      } catch (e) {
+        logErr(c.id, 'HD-Grab fehlgeschlagen', e);
+        setInfo(c, `HD Fehler: ${e.message}`, 'crit');
+      }
+    }));
+
+  } finally {
+    // 4. Immer: alle zurück auf Live
+    await sleep(600);
+    cameras.forEach(c => {
+      removeFreezeCanvas(c);
+      startStream(c);
+      c.testing = false;
+      c.hdBtn.disabled = false;
+    });
+    if (snapBtn) snapBtn.disabled = false;
+    log('snap', '── HD-Grab alle beendet, alle zurück auf Live ──');
+  }
 }
 
 // ── Kamera-View aufbauen ─────────────────────────────────────────────────────
@@ -443,7 +504,7 @@ async function init() {
   if (camIds.length === 0) { warn('init', 'Fallback cam0, cam1'); camIds = ['cam0', 'cam1']; }
 
   const snapBtn = document.getElementById('snapAllBtn');
-  if (snapBtn) { snapBtn.onclick = snapshotAll; snapBtn.disabled = false; }
+  if (snapBtn) { snapBtn.onclick = snapshotAllHires; snapBtn.disabled = false; }
 
   camIds.forEach(id => buildCamera(id, container));
   statusText.textContent = `${camIds.length} Kamera${camIds.length !== 1 ? 's' : ''} · WebRTC`;
diff --git a/src/snapshotService.js b/src/snapshotService.js
index dc80254..4d7a7a6 100644
--- a/src/snapshotService.js
+++ b/src/snapshotService.js
@@ -29,7 +29,7 @@ function readJpegWidth(buf) {
 //   GET /api/snapshot/cam0/hires   → 1280×960 JPEG via cam0_hires (Phase 2)
 function createSnapshotRouter(go2rtcUrl) {
   const router = express.Router();
-  let hiresLock = false;   // Mutex: nie zwei Hi-Res-Grabs gleichzeitig
+  const hiresLocks = {};   // Mutex pro Kamera: { cam0: false, cam1: false, … }
 
   // ── PHASE 1: Geräte-Freigabe messen (rein LESEND, kein Grab) ────────────────
   // Linchpin-Test aus doc/05_screenShot_roadmap.md: Gibt go2rtc das Gerät frei,
@@ -118,10 +118,10 @@ function createSnapshotRouter(go2rtcUrl) {
     const { id } = req.params;
     const hiresId = `${id}_hires`;
 
-    if (hiresLock) {
-      return res.status(429).json({ error: 'Hi-Res-Grab läuft bereits – bitte warten' });
+    if (hiresLocks[id]) {
+      return res.status(429).json({ error: `Hi-Res-Grab für ${id} läuft bereits – bitte warten` });
     }
-    hiresLock = true;
+    hiresLocks[id] = true;
     const t0 = Date.now();
 
     try {
@@ -206,7 +206,7 @@ function createSnapshotRouter(go2rtcUrl) {
     } catch (err) {
       if (!res.headersSent) res.status(503).json({ error: `hires: ${err.message}` });
     } finally {
-      hiresLock = false;
+      hiresLocks[id] = false;
     }
   });