diff --git a/src/testSupport/domAssert.mjs b/src/testSupport/domAssert.mjs
new file mode 100644
index 000000000..0c8de120f
--- /dev/null
+++ b/src/testSupport/domAssert.mjs
@@ -0,0 +1,19 @@
+import assert from 'node:assert/strict';
+
+const describe = (node) =>
+  node?.nodeType === 1
+    ? `<${node.tagName.toLowerCase()}${node.id ? `#${node.id}` : ''}>`
+    : String(node);
+
+/**
+ * Assert that two DOM nodes (or a node and null) are the same. Never hand
+ * happy-dom nodes to assert.equal or deepEqual: a failure prints both, and a
+ * node reaches the whole page and window, which runs the process out of
+ * memory.
+ */
+export function assertSameNode(actual, expected, message = '') {
+  assert.ok(
+    actual === expected,
+    `${message ? `${message}: ` : ''}${describe(actual)} is not ${describe(expected)}`,
+  );
+}
diff --git a/src/ui/panelNavigation.test.mjs b/src/ui/panelNavigation.test.mjs
index ec6cc8882..c253bb03d 100644
--- a/src/ui/panelNavigation.test.mjs
+++ b/src/ui/panelNavigation.test.mjs
@@ -1,5 +1,6 @@
 import { after, before, test } from 'node:test';
 import assert from 'node:assert/strict';
+import { assertSameNode } from '../testSupport/domAssert.mjs';
 import { installVueDom } from '../testSupport/vueDom.mjs';
 
 let PanelNavigation;
@@ -132,8 +133,8 @@ test('destroy removes the rails and stops following the stacks', async () => {
   const { left, right, calls, ui, navigation } = setup();
   navigation.destroy();
   navigation.destroy();
-  assert.equal(left.querySelector('.gev-panel-rail'), null);
-  assert.equal(right.querySelector('.gev-panel-rail'), null);
+  assertSameNode(left.querySelector('.gev-panel-rail'), null);
+  assertSameNode(right.querySelector('.gev-panel-rail'), null);
   navigation.select('data-panel');
   assert.deepEqual(calls, []);
   ui.destroy();
diff --git a/src/ui/railCards.test.mjs b/src/ui/railCards.test.mjs
index 7107fd093..d53b03831 100644
--- a/src/ui/railCards.test.mjs
+++ b/src/ui/railCards.test.mjs
@@ -1,6 +1,7 @@
 import '../testSupport/registerDom.mjs';
 import test from 'node:test';
 import assert from 'node:assert/strict';
+import { assertSameNode } from '../testSupport/domAssert.mjs';
 import { nextTick } from 'vue';
 import { createRailCards } from './railCards.js';
 import { railDocumentFixture as railFixture } from './railTestFixture.mjs';
@@ -94,7 +95,7 @@ test('footer buttons retain focus and current callbacks; links use safe new tabs
       },
     ]),
   ]);
-  assert.equal(f.document.activeElement, button);
+  assertSameNode(f.document.activeElement, button);
   assert.equal(button.parentElement.tagName, 'FOOTER');
   assert.equal(
     f.find((n) => n.className === 'rail-card-action-hint').textContent,
@@ -200,7 +201,7 @@ test('setting ranges stay below presets and commit expensive filters on release'
   assert.equal(slider.value, '53', 'release keeps the handle until the owner');
   view.update([model(53)]);
   assert.equal(slider.value, '53');
-  assert.equal(f.document.activeElement, slider);
+  assertSameNode(f.document.activeElement, slider);
   slider.value = '41';
   slider.dispatchEvent(new Event('input'));
   await nextTick();
@@ -334,7 +335,7 @@ test('labelled rows, lists and results retain focus and dispatch current params'
   const chip = f.find((n) => n.dataset.chipId === 'motion');
   chip.focus();
   view.update([model(true)]);
-  assert.equal(f.document.activeElement, chip);
+  assertSameNode(f.document.activeElement, chip);
   chip.click();
   assert.deepEqual(calls.at(-1), ['a', { paused: false }]);
   const storm = f.find(
diff --git a/src/ui/railTimeline.test.mjs b/src/ui/railTimeline.test.mjs
index fd9ced861..edbdbc7fe 100644
--- a/src/ui/railTimeline.test.mjs
+++ b/src/ui/railTimeline.test.mjs
@@ -1,6 +1,7 @@
 import '../testSupport/registerDom.mjs';
 import test from 'node:test';
 import assert from 'node:assert/strict';
+import { assertSameNode } from '../testSupport/domAssert.mjs';
 import { nextTick } from 'vue';
 import { createRailTimeline } from './railTimeline.js';
 import { railDocumentFixture as railFixture } from './railTestFixture.mjs';
@@ -46,8 +47,8 @@ test('preview is immediate, commits are coalesced and the drag DOM and tick mapp
     index: 1,
     readout: 'Refresh',
   });
-  assert.equal(slider.parentElement, row);
-  assert.equal(row.children[1], slider);
+  assertSameNode(slider.parentElement, row);
+  assertSameNode(row.children[1], slider);
   assert.equal(slider.value, '0');
   assert.equal(slider.max, '2');
   assert.equal(
diff --git a/src/ui/recentImagery.test.mjs b/src/ui/recentImagery.test.mjs
index 81d910e3a..5ed0b6bba 100644
--- a/src/ui/recentImagery.test.mjs
+++ b/src/ui/recentImagery.test.mjs
@@ -1,6 +1,7 @@
 import '../testSupport/registerDom.mjs';
 import test from 'node:test';
 import assert from 'node:assert/strict';
+import { assertSameNode } from '../testSupport/domAssert.mjs';
 import { readFileSync } from 'node:fs';
 import { createRecentImageryPanel } from './recentImagery.js';
 import { createRecentImageryLayer } from '../layers/recentImagery/index.js';
@@ -246,7 +247,7 @@ function part(f, id, name) {
 // ---- tests ---------------------------------------------------------------------
 test('the readout mounts in the rail body, hides while the layer is off and opens the panel once on first appearance', async () => {
   const f = fixture();
-  assert.equal(f.root.parentNode, f.body);
+  assertSameNode(f.root.parentNode, f.body);
   assert.equal(f.panel.hidden, true);
   assert.equal(f.count.textContent, '');
   await f.ready();
@@ -864,7 +865,7 @@ test('the divider exists only while a swipe is live, labelled A / B or IMAGE / B
   };
   assert.equal(swap.tagName, 'BUTTON');
   assert.equal(swap.textContent, 'SWAP');
-  assert.equal(swap.parentNode, f.byId('ri-controls'));
+  assertSameNode(swap.parentNode, f.byId('ri-controls'));
   await f.ready();
   await f.settleLease();
   assert.equal(f.splits.length, 0, 'one image, no divider');
@@ -993,7 +994,7 @@ test('opacity drives both images; EXPORT downloads the pin or the preview and EX
   f.readout.destroy();
   assert.equal(await f.readout.exportImage('a'), false);
   assert.equal(f.fetches.length, fetched);
-  assert.equal(container.querySelector('.recent-imagery-readout'), null);
+  assertSameNode(container.querySelector('.recent-imagery-readout'), null);
 });
 
 test('DETAILS is a collapsed rail card holding every note, and the empty-days toggle', async () => {
@@ -1077,7 +1078,7 @@ test('destroy returns every listener, the divider and the panel state', async ()
   assert.equal(split.destroyed, true);
   assert.equal(f.root.listenerCount(), 0);
   assert.equal(f.strip.listenerCount(), 0);
-  assert.equal(f.root.parentNode, null);
+  assertSameNode(f.root.parentNode, null);
   assert.equal(f.document.getElementById('recent-imagery-panel').hidden, true);
   f.layer.setMode('ab');
   assert.equal(f.splits.length, 1, 'no renders after destroy');
diff --git a/src/ui/sceneControls.test.mjs b/src/ui/sceneControls.test.mjs
index fdb9226ef..9ab9e6bd5 100644
--- a/src/ui/sceneControls.test.mjs
+++ b/src/ui/sceneControls.test.mjs
@@ -1,5 +1,6 @@
 import test, { after, before } from 'node:test';
 import assert from 'node:assert/strict';
+import { assertSameNode } from '../testSupport/domAssert.mjs';
 import { createStateChannel } from '../app/stateChannel.js';
 import { sceneElements } from './scenePresentation.js';
 import { mountSceneSharing } from './sceneSharing.js';
@@ -192,7 +193,7 @@ test('Scene controls dispatch panel and shot-row actions, and rows outlive repub
     ]);
     f.owner.renderShotList();
     await nextTick();
-    assert.equal(f.elements.shots.children[0], row);
+    assertSameNode(f.elements.shots.children[0], row);
     // An owner destroyed after a newer one attached leaves the newer list.
     const newer = new SceneControls({
       read: () => f.state,
@@ -391,7 +392,7 @@ test('inline shot names save on Enter, cancel on Escape, and reject blank names'
       label.dispatchEvent(new Event('dblclick'));
       await nextTick();
       const input = label.children[0];
-      assert.equal(document.activeElement, input);
+      assertSameNode(document.activeElement, input);
       input.value = value;
       input.dispatchEvent(key(commitKey));
       input.dispatchEvent(new Event('blur'));
@@ -482,7 +483,7 @@ test('Scene controls consume current state, preserve rows on progress, and unsub
     f.state.progress = 0.5;
     channel.publish({ type: 'progress-changed' });
     await nextTick();
-    assert.equal(f.elements.shots.children[0], row);
+    assertSameNode(f.elements.shots.children[0], row);
     f.state.status = 'Project exported';
     channel.publish({ type: 'project-exported' });
     assert.equal(f.elements.status.textContent, 'Project exported');
@@ -619,7 +620,7 @@ test('The sharing row sits under SAVE & SHARE, after the file row', () => {
     const dispose = mountSceneSharing({ edit() {}, share() {} }, panel);
     const bar = inner.children[1];
     assert.equal(bar.className, 'scene-controls');
-    assert.equal(inner.children[2], status);
+    assertSameNode(inner.children[2], status);
     assert.ok(bar.children.every((button) => button.title));
     dispose();
     assert.deepEqual(inner.children, [fileRow, status]);
diff --git a/src/ui/statusBadge.test.mjs b/src/ui/statusBadge.test.mjs
index 1ac67a385..c1c1b782b 100644
--- a/src/ui/statusBadge.test.mjs
+++ b/src/ui/statusBadge.test.mjs
@@ -1,6 +1,7 @@
 import '../testSupport/registerDom.mjs';
 import test from 'node:test';
 import assert from 'node:assert/strict';
+import { assertSameNode } from '../testSupport/domAssert.mjs';
 import { createStatusBadge, updateStatusBadge } from './statusBadge.js';
 import { createRailCards } from './railCards.js';
 import { railDocumentFixture as railFixture } from './railTestFixture.mjs';
@@ -51,7 +52,7 @@ test('painting preserves feature state, live regions and focus with zero identic
   assert.equal(badge.getAttribute('role'), 'status');
   assert.equal(badge.getAttribute('aria-live'), 'polite');
   assert.equal(badge.dataset.frameState, 'ready');
-  assert.equal(document.activeElement, focusOwner);
+  assertSameNode(document.activeElement, focusOwner);
 });
 
 test('coverage badges keep keyed identity, hide empty coverage and never claim feed health', () => {
@@ -74,7 +75,7 @@ test('coverage badges keep keyed identity, hide empty coverage and never claim f
     badge,
   );
   assert.deepEqual({ ...badge.dataset }, {});
-  assert.equal(f.document.activeElement, header);
+  assertSameNode(f.document.activeElement, header);
   view.destroy();
   view.update([card]);
   assert.equal(f.container.children.length, 0);
diff --git a/src/ui/weatherPanel.test.mjs b/src/ui/weatherPanel.test.mjs
index 921121fcc..60aa507ad 100644
--- a/src/ui/weatherPanel.test.mjs
+++ b/src/ui/weatherPanel.test.mjs
@@ -1,6 +1,7 @@
 import '../testSupport/registerDom.mjs';
 import test from 'node:test';
 import assert from 'node:assert/strict';
+import { assertSameNode } from '../testSupport/domAssert.mjs';
 import { setLocale } from '../i18n/index.js';
 import { createWeatherPanel } from './weatherPanel.js';
 import { railDocumentFixture as railFixture } from './railTestFixture.mjs';
@@ -115,7 +116,7 @@ test('ordered articles omit Controls and retain history labels, forecast dates a
   view.update([radar, wind]);
   const windCard = card(f, 'wind');
   assert.equal(windCard.tagName, 'ARTICLE');
-  assert.equal(windCard.parentElement.children[0], windCard);
+  assertSameNode(windCard.parentElement.children[0], windCard);
   assert.equal(
     f.find((n) => n.dataset.weatherOpen),
     null,
@@ -403,13 +404,13 @@ test('cyclones lead, and observed history owns one bordered group with only acti
     ['weather-cyclones', 'wind'],
   );
   const group = f.find((n) => n.className === 'weather-observed-group');
-  assert.equal(root.children[1], group);
+  assertSameNode(root.children[1], group);
   assert.equal(group.children[0].textContent, 'Observed history');
   assert.equal(
     group.children[1].textContent,
     'Rain radar · Satellite clouds · Lightning density',
   );
-  assert.equal(group.children[2], timelineHost(f));
+  assertSameNode(group.children[2], timelineHost(f));
   assert.deepEqual(
     [...group.children[3].children].map((n) => n.dataset.cardId),
     ['weather-radar', 'weather-satellite', 'weather-lightning'],