diff --git a/docs/testing-notes/mutation-browser-guards.md b/docs/testing-notes/mutation-browser-guards.md
index 47850ee6..79454956 100644
--- a/docs/testing-notes/mutation-browser-guards.md
+++ b/docs/testing-notes/mutation-browser-guards.md
@@ -7,18 +7,25 @@ must be added deliberately under one reason below, and its mutant `because` must
 the concrete browser-only invariant.
 
 Converted witnesses are not listed here: their registry guard names an explicit `node --test`
-suite plus `test/mutation-browser-offload.test.mjs`, and every converted mutant is run once
-to prove that the Node witness actually kills it.
+suite. The original #659 conversions also use `test/mutation-browser-offload.test.mjs`;
+new behavioral witnesses execute the consumer directly where possible. Catching the mutant
+is verified by the nightly run under PROCESS §2.7, not by a development-time mutation run.
+
+`led-unbound-in-view` moved to `test/led-strip-runtime.test.mjs` in #791: its guard
+requires a non-null marker absent from runtime devices, whereas the browser's
+`marker: null` fixture exits before the mutated guard. The Node witness checks the
+exact surviving strip/owner and its live light; the browser smoke still covers
+unbound-strip visibility and cold loading.
 
 | Category | Count | Why a browser is still required |
 | --- | ---: | --- |
 | Performance threshold | 4 | The witness measures real browser wall-time or frame work; a pure assertion cannot prove the budget. |
 | Browser harness integrity | 4 | The mutation breaks page-error, round-trip or page-registration observation in the browser harness itself. |
-| Paint, cascade and layer composition | 38 | The invariant depends on computed CSS, SVG paint, clipping, stacking or pixels produced by Chromium. |
+| Paint, cascade and layer composition | 37 | The invariant depends on computed CSS, SVG paint, clipping, stacking or pixels produced by Chromium. |
 | Pointer geometry and trusted interaction | 49 | The invariant depends on hit testing, pointer capture, touch/keyboard dispatch or live DOM geometry. |
 | Responsive DOM layout | 38 | The invariant depends on measured element boxes, responsive breakpoints, native/HA dialog shells or focusable target size. |
 | Custom-element and HA browser lifecycle | 104 | The invariant crosses Lit/custom-element lifecycle, browser storage/events, lazy loading or a complete HA-card state transition. |
-| **Total** | **237 / 200** | Above the guideline `mutation-gate --check` warns rather than fails (#699); each guard above it is held by its own reason in this inventory and its `because`. |
+| **Total** | **236 / 200** | Above the guideline `mutation-gate --check` warns rather than fails (#699); each guard above it is held by its own reason in this inventory and its `because`. |
 
 ## Measured effect
 
@@ -102,7 +109,6 @@ The invariant depends on computed CSS, SVG paint, clipping, stacking or pixels p
 - `led-icon-not-suppressed`
 - `led-source-stays-round-at-anchor`
 - `led-static-live-ignored`
-- `led-unbound-in-view`
 - `stage3-w4-device-target-loses-44px-floor`
 - `stage3-w5-runtime-nudge-writes-storage`
 - `stage3-w6-no-borders-keeps-raised-plates`
diff --git a/scripts/mutation-registry.mjs b/scripts/mutation-registry.mjs
index 387c5d76..fe4de263 100644
--- a/scripts/mutation-registry.mjs
+++ b/scripts/mutation-registry.mjs
@@ -14506,8 +14506,10 @@ const MUTANT_DEFINITIONS = [
   },
   {
     id: 'led-unbound-in-view',
-    guard: 'node demo/smoke_led_strip_glow.mjs',
-    because: "#780 ТЗ §5: an unbound strip has no View representation, light or target",
+    guard: 'npx tsc -p tsconfig.test.json && node scripts/fix-test-build.mjs '
+      + '&& node --test test/led-strip-runtime.test.mjs',
+    because: '#780 ТЗ §5 / #791: ledFrame skips a non-null marker absent from runtime devices '
+      + 'without losing a valid neighbouring strip; the executable frame boundary needs no browser',
     patches: [{
       file: 'src/led-strip-runtime.ts',
       find: "    if (!device || device.space !== input.space.id) continue;",
diff --git a/test/led-strip-runtime.test.mjs b/test/led-strip-runtime.test.mjs
index a323ef6b..ceac333d 100644
--- a/test/led-strip-runtime.test.mjs
+++ b/test/led-strip-runtime.test.mjs
@@ -444,6 +444,35 @@ test('#784/AC9: the frame gives every strip the 30 cm default, not the shared ra
   assert.ok(Math.abs(frame.views[0].radius - (30 / 5) * (1000 / 240)) < 1e-9, `radius ${frame.views[0].radius}`);
 });
 
+test('#791: the frame skips missing runtime owners without dropping a valid neighbouring strip', () => {
+  const lamp = device({ entities: ['light.led'], marker: { id: 'm1', binding: 'device:m1' } });
+  const points = [[0.1, 0.1], [0.4, 0.1]];
+  const strips = [
+    // A non-null reference reaches the runtime-owner guard; marker:null alone
+    // is rejected earlier and never exercised the escaped nightly mutant.
+    { id: 'missing-owner', points, marker: 'absent-from-runtime' },
+    { id: 'unbound', points, marker: null },
+    { id: 'other-space', points, marker: 'm2' },
+    { id: 'inactive', points, marker: 'm1', active: false },
+    { id: 'valid', points, marker: 'm1' },
+  ];
+  const before = structuredClone(strips);
+  const frame = ledFrame({
+    space: { id: 's', vb: [0, 0, 1000, 1000], rooms: [{ id: 'room' }], led_strips: strips },
+    devices: [lamp, device({ id: 'm2', space: 'other', primary: 'light.other', entities: ['light.other'],
+      marker: { id: 'm2', binding: 'device:m2' } })],
+    hass: { states: { 'light.led': { state: 'on', attributes: { rgb_color: [128, 213, 255] } } } },
+    defaultColor: '#ffd27b', paletteAlpha: 0.7, cellCm: 5, gridPitch: 1000 / 240, iconPct: 3.4,
+    scene: null, polygons: [], glowFor: () => true, inRoom: () => true, showHidden: false,
+  });
+  assert.deepEqual(frame.views.map(view => [view.strip.id, view.device.id]), [['valid', 'm1']],
+    'only the same-space bound strip may reach stripe, light and hit rendering');
+  assert.equal(frame.views[0].state, 'on');
+  assert.equal(frame.views[0].glow, true);
+  assert.equal(frame.views[0].appearance?.c, '#80d5ff', 'the valid neighbour retains its live light');
+  assert.deepEqual(strips, before, 'runtime filtering must not rewrite stored strips');
+});
+
 test('AC2/r1 M2: an explicit valid room_id wins over the anchor room; a stale one falls back', () => {
   const rooms = [{ id: 'A' }, { id: 'B' }];
   const inA = (point, room) => room.id === 'A' && point[0] < 500;