diff --git a/src/layers/ghostMaps/edgeCases.test.mjs b/src/layers/ghostMaps/edgeCases.test.mjs
new file mode 100644
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+++ b/src/layers/ghostMaps/edgeCases.test.mjs
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+// Edge cases from docs/migration/planet-separation/layers.md (s2-ghostmaps):
+// change the KMZ edition and the engine before parsing finishes; only the
+// selected edition is shown, and a bad archive does not erase the working one.
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { createGhostMapsLayer } from './index.js';
+
+function element(localName, children = [], value = '') {
+  const node = {
+    localName,
+    children,
+    get textContent() {
+      return value + children.map((child) => child.textContent).join('');
+    },
+    getAttribute: () => null,
+    getElementsByTagName(name) {
+      return children.flatMap((child) => [
+        ...(name === '*' || name === child.localName ? [child] : []),
+        ...child.getElementsByTagName(name),
+      ]);
+    },
+  };
+  for (const child of children) child.parentElement = node;
+  return node;
+}
+
+// The XML double turns `<kml>NAME</kml>` into one placemark called NAME.
+function documentFor(xml) {
+  const name = /<kml>(.*)<\/kml>/.exec(xml)?.[1] ?? 'unnamed';
+  return element('document', [
+    element('kml', [
+      element('Document', [
+        element('Placemark', [
+          element('name', [], name),
+          element('Point', [element('coordinates', [], '12,34')]),
+        ]),
+      ]),
+    ]),
+  ]);
+}
+
+/** A stored (uncompressed) KMZ holding doc.kml only. */
+function kmz(name) {
+  const key = Buffer.from('doc.kml');
+  const bytes = Buffer.from(`<kml>${name}</kml>`);
+  const header = Buffer.alloc(30);
+  header.writeUInt32LE(0x04034b50);
+  header.writeUInt32LE(bytes.length, 18);
+  header.writeUInt32LE(bytes.length, 22);
+  header.writeUInt16LE(key.length, 26);
+  const directory = Buffer.alloc(46);
+  directory.writeUInt32LE(0x02014b50);
+  directory.writeUInt32LE(bytes.length, 20);
+  directory.writeUInt32LE(bytes.length, 24);
+  directory.writeUInt16LE(key.length, 28);
+  directory.writeUInt32LE(0, 42);
+  const central = Buffer.concat([directory, key]);
+  const end = Buffer.alloc(22);
+  end.writeUInt32LE(0x06054b50);
+  end.writeUInt16LE(1, 8);
+  end.writeUInt16LE(1, 10);
+  end.writeUInt32LE(central.length, 12);
+  end.writeUInt32LE(header.length + key.length + bytes.length, 16);
+  return new Uint8Array(Buffer.concat([header, key, bytes, central, end]));
+}
+
+function deferred() {
+  let resolve;
+  const promise = new Promise((done) => (resolve = done));
+  return { promise, resolve };
+}
+
+const catalog = (version) => ({
+  products: [{ id: 'cip', version, defaultOn: true }],
+});
+
+/** A scene-less renderer double that records live paints per engine. */
+function fakeRenderer(name, live) {
+  return {
+    name,
+    requestRender() {},
+    onClick: () => () => {},
+    draw(id, features) {
+      const paint = {
+        engine: name,
+        id,
+        names: features.map((feature) => feature.name),
+        ready: Promise.resolve(),
+        destroy() {
+          live.delete(paint);
+        },
+      };
+      live.add(paint);
+      return paint;
+    },
+    destroy() {},
+  };
+}
+
+function harness(t) {
+  const previous = Object.getOwnPropertyDescriptor(globalThis, 'DOMParser');
+  globalThis.DOMParser = class {
+    parseFromString(xml) {
+      return documentFor(xml);
+    }
+  };
+  t.after(() => {
+    if (previous) Object.defineProperty(globalThis, 'DOMParser', previous);
+    else delete globalThis.DOMParser;
+  });
+  t.mock.method(console, 'warn', () => {});
+  const files = new Map();
+  const live = new Set();
+  let listener = null;
+  const layer = createGhostMapsLayer({
+    storage: null,
+    createRenderer: (engine) => fakeRenderer(engine.name, live),
+    source: {
+      getCatalog: async () => catalog('v1'),
+      getFile: (_id, version) => files.get(version).promise,
+      subscribe(onCatalog) {
+        listener = onCatalog;
+        return () => {};
+      },
+    },
+  });
+  layer.init(null, { engine: { name: 'cesium' } });
+  layer.enable();
+  t.after(() => layer.destroy());
+  const file = (version) => {
+    const pending = deferred();
+    files.set(version, pending);
+    return pending;
+  };
+  const push = (next) => listener(next);
+  return { layer, live, file, push };
+}
+
+const names = (layer) => layer.getAnalystRecords().map((record) => record.name);
+const painted = (live) =>
+  [...live].map((paint) => `${paint.engine}:${paint.names.join(',')}`);
+
+test('edge:s2-ghostmaps: an edition and engine change mid-parse shows only the selected edition', async (t) => {
+  const { layer, live, file, push } = harness(t);
+  file('v1').resolve(kmz('edition one'));
+  await layer.update();
+  assert.deepEqual(names(layer), ['edition one']);
+
+  // v2 is still downloading when v3 is published and the engine is swapped.
+  const v2 = file('v2');
+  const v3 = file('v3');
+  push(catalog('v2'));
+  await new Promise(setImmediate);
+  push(catalog('v3'));
+  layer.detachRenderer();
+  await layer.attachRenderer(null, { engine: { name: 'navara' } });
+  v2.resolve(kmz('edition two'));
+  v3.resolve(kmz('edition three'));
+  // Let the queued syncs settle.
+  for (let i = 0; i < 20; i += 1) await new Promise(setImmediate);
+
+  assert.deepEqual(names(layer), ['edition three']);
+  assert.deepEqual(painted(live), ['navara:edition three']);
+  assert.equal(layer.getStats().loading, false);
+  assert.equal(layer.getStats().error, null);
+});
+
+test('edge:s2-ghostmaps: a bad archive keeps the working edition on the globe', async (t) => {
+  const { layer, live, file, push } = harness(t);
+  file('v1').resolve(kmz('working edition'));
+  await layer.update();
+  assert.deepEqual(painted(live), ['cesium:working edition']);
+
+  const broken = file('v2');
+  push(catalog('v2'));
+  // The engine changes while the broken file is still on its way.
+  layer.detachRenderer();
+  await layer.attachRenderer(null, { engine: { name: 'navara' } });
+  broken.resolve(new Uint8Array([1, 2, 3, 4]));
+  for (let i = 0; i < 20; i += 1) await new Promise(setImmediate);
+
+  assert.deepEqual(names(layer), ['working edition']);
+  assert.deepEqual(painted(live), ['navara:working edition']);
+  assert.ok(layer.getStats().error, 'the failed edition is reported');
+  const chip = layer.getRowControls().chips[0];
+  assert.equal(chip.state, 'error');
+});