diff --git a/src/layers/bikeshare/edgeCases.test.mjs b/src/layers/bikeshare/edgeCases.test.mjs
new file mode 100644
index 000000000..74c94e48e
--- /dev/null
+++ b/src/layers/bikeshare/edgeCases.test.mjs
@@ -0,0 +1,144 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { createFakeEngine } from '../../globe/testing/fakeEngine.js';
+import { createBikeshareLayer } from './index.js';
+import { createBikeshareNavaraRenderer } from './render/navara.js';
+import { CITY_BY_ID } from './registry.js';
+
+// Two systems that cover one view and both number a station "1".
+const BICING = 'barcelona-bicing';
+const AMBICI = 'barcelona-ambici';
+const STATION = '1';
+const settle = () => new Promise((resolve) => setImmediate(resolve));
+
+const information = (name, lat, lon) => ({
+  data: {
+    stations: [{ station_id: STATION, name, lat, lon, capacity: 20 }],
+  },
+});
+const status = (bikes) => ({
+  data: {
+    stations: [
+      {
+        station_id: STATION,
+        num_bikes_available: bikes,
+        num_docks_available: 20 - bikes,
+        is_installed: true,
+        is_renting: true,
+        is_returning: true,
+      },
+    ],
+  },
+});
+
+function fixture() {
+  const bicing = CITY_BY_ID.get(BICING);
+  const ambici = CITY_BY_ID.get(AMBICI);
+  const feeds = new Map([
+    [bicing.stationInformationUrl, () => information('Bicing 1', 41.39, 2.16)],
+    [ambici.stationInformationUrl, () => information('AMBici 1', 41.37, 2.07)],
+    [bicing.stationStatusUrl, () => status(5)],
+    [ambici.stationStatusUrl, () => status(11)],
+  ]);
+  const makeEngine = () => {
+    const engine = createFakeEngine({ kind: 'navara' });
+    engine.fake.setPose({
+      longitude: (2.12 * Math.PI) / 180,
+      latitude: (41.38 * Math.PI) / 180,
+      height: 10000,
+    });
+    engine.fake.script('viewRectangle', null);
+    return engine;
+  };
+  let engine = makeEngine();
+  const entries = new Map();
+  const layer = createBikeshareLayer({
+    source: {
+      async getStations(url) {
+        const feed = feeds.get(url);
+        if (!feed) throw new Error(`unexpected ${url}`);
+        return feed();
+      },
+    },
+    services: {
+      render: { governorRequestRender() {} },
+      overlays: {
+        setOverlayEntries: (id, value) => entries.set(id, value),
+        setOverlaySourceVisible() {},
+        clearOverlaySource: (id) => entries.delete(id),
+      },
+    },
+    rendererFactory: (context) =>
+      createBikeshareNavaraRenderer(engine, context),
+  });
+  layer.init(null, { engine });
+  return {
+    layer,
+    entries,
+    feeds,
+    get engine() {
+      return engine;
+    },
+    switchEngine() {
+      layer.detachRenderer();
+      engine = makeEngine();
+      layer.attachRenderer(null, { engine });
+    },
+    card: () => entries.get('bikeshare-selected')?.[0] ?? null,
+    click(key) {
+      engine.fake.script('pick', { id: key });
+      engine.fake.input('click', { position: { x: 100, y: 100 } });
+    },
+  };
+}
+
+test('edge:bikeshare: two systems with the same station ID stay two stations', async () => {
+  const f = fixture();
+  try {
+    f.layer.enable();
+    await settle();
+    const pickIds = f.engine.fake.moverSet('bikeshare').store.pickIds;
+    const keys = [...pickIds].slice(0, f.layer.getStats().count).sort();
+    assert.deepEqual(keys, [`${AMBICI}:${STATION}`, `${BICING}:${STATION}`]);
+    f.click(`${BICING}:${STATION}`);
+    assert.equal(f.card().title, 'Bicing 1');
+    assert.match(f.card().details[0], /5 avail/);
+    f.click(`${AMBICI}:${STATION}`);
+    assert.equal(f.card().title, 'AMBici 1');
+    assert.match(f.card().details[0], /11 avail/);
+    // A status poll of one system never rewrites the other's station.
+    f.feeds.set(CITY_BY_ID.get(BICING).stationStatusUrl, () => status(0));
+    await f.layer.update();
+    assert.match(f.card().details[0], /11 avail/);
+  } finally {
+    f.layer.destroy();
+  }
+});
+
+test('edge:bikeshare: during a source outage the card keeps the last status, across an engine switch', async (t) => {
+  t.mock.method(console, 'warn', () => {});
+  const f = fixture();
+  try {
+    f.layer.enable();
+    await settle();
+    const key = `${AMBICI}:${STATION}`;
+    f.click(key);
+    assert.match(f.card().details[0], /11 avail/);
+    f.feeds.set(CITY_BY_ID.get(AMBICI).stationStatusUrl, () => {
+      throw new Error('HTTP 503');
+    });
+    await f.layer.update();
+    assert.equal(f.card().title, 'AMBici 1');
+    assert.match(f.card().details[0], /11 avail/);
+    // The other system still draws, so the layer is not reported as failed.
+    assert.equal(f.layer.getStats().error, undefined);
+
+    f.switchEngine();
+    await settle();
+    assert.equal(f.card()?.title, 'AMBici 1');
+    assert.match(f.card().details[0], /11 avail/);
+    assert.equal(f.layer.getStats().count, 2);
+  } finally {
+    f.layer.destroy();
+  }
+});