Retain live flights and earthquake observations across globe switches

scripts/qa-engine-switch.mjs

@@ -67,6 +67,8 @@ try {
     await page.waitForSelector('#globe-engine', { visible: true });
     await page.evaluate(() => {
       window.__switchDocument = document;
+      window.__quakeEntry = window.__godsEyeView.dataManager.layers.get('earthquakes');
+      window.__quakeTimer = window.__quakeEntry.intervalId;
       window.__renderers ??= new Map();
       window.__renderers.set(
         window.__godsEyeView.engine.kind,
@@ -93,6 +95,8 @@ try {
         const previous = window.__renderers.get(engine.kind);
         return (
           !window.__switchSplash &&
+          window.__quakeEntry === window.__godsEyeView.dataManager.layers.get('earthquakes') &&
+          window.__quakeTimer === window.__quakeEntry.intervalId &&
           (!previous || previous === engine) &&
           !window.__outgoingEngine.isDestroyed() &&
           !window.__outgoingEngine.host.canvas.isConnected &&

scripts/qa-layer-handoff.mjs

@@ -0,0 +1,163 @@
+import assert from 'node:assert/strict';
+import puppeteer from 'puppeteer';
+import { blockPaidQaMaps } from './qa-map-policy.mjs';
+
+const url = new URL(process.argv[2]);
+if (
+  !['localhost', '127.0.0.1'].includes(url.hostname) ||
+  ['', '4173', '4185', '4186', '4187', '4188', '4189', '4194'].includes(
+    url.port,
+  )
+)
+  throw new Error('Supply an unreserved local keyless preview URL');
+url.search = '?engine=navara&welcome=0';
+url.hash =
+  'v=2&lat=40.2539&lon=-125.5779&alt=21130&heading=360&pitch=-35&map=sentinel2&l=f&lo=f.e.1_f.t.71be26';
+const browser = await puppeteer.launch({
+  headless: true,
+  args: ['--use-angle=metal', '--enable-gpu'],
+});
+try {
+  const page = await browser.newPage();
+  await blockPaidQaMaps(page);
+  const errors = [];
+  page.on('pageerror', (e) => errors.push(e.message));
+  await page.setViewport({ width: 1280, height: 720 });
+  await page.evaluateOnNewDocument(() => {
+    const fetch = window.fetch.bind(window);
+    window.__flightPolls = 0;
+    window.fetch = (input, options) => {
+      const path = new URL(input.url ?? input, document.baseURI).pathname;
+      const now = Math.floor(Date.now() / 1000);
+      if (path === '/api/flights') {
+        window.__flightPolls++;
+        return Promise.resolve(
+          Response.json({
+            time: now,
+            states: [
+              [
+                '71be26',
+                'GEV123',
+                'QA',
+                now,
+                now,
+                -125.5779,
+                40.2539,
+                9700,
+                false,
+                200,
+                45,
+                0,
+                null,
+                9700,
+                null,
+                false,
+                0,
+              ],
+            ],
+          }),
+        );
+      }
+      if (path === '/api/military')
+        return Promise.resolve(Response.json({ now: Date.now(), ac: [] }));
+      if (path === '/api/flights/track')
+        return Promise.resolve(Response.json({ path: [] }));
+      if (path.startsWith('/api/flights/') || path.startsWith('/api/openai/'))
+        return Promise.resolve(Response.json({}));
+      return fetch(input, options);
+    };
+  });
+  await page.goto(url.href, { waitUntil: 'domcontentloaded' });
+  const ready = (kind) =>
+    page.waitForFunction(
+      (engine) =>
+        window.__godsEyeView?.engine.kind === engine &&
+        !document.querySelector('#globe-engine')?.disabled &&
+        document.querySelector('#loading-screen.hidden') &&
+        !document.querySelector('.engine-switch-frame'),
+      { timeout: 90000 },
+      kind,
+    );
+  await ready('navara');
+  await page.evaluate(
+    () => window.__godsEyeView.styleManager.initialRestorePromise,
+  );
+  await page.waitForSelector('#cockpit-entry', { visible: true });
+  await page.click('#cockpit-entry');
+  await page.waitForFunction(
+    () => window.__godsEyeView.styleManager.getCockpitState().active,
+  );
+  await page.evaluate(() => {
+    const { dataManager, styleManager, tileset } = window.__godsEyeView;
+    if (window.__GOOGLE_MAPS_API_KEY__ || tileset)
+      throw Error('Keyless preview required');
+    styleManager.cockpitView.setVisionMode('thermal');
+    const entry = dataManager.layers.get('flights');
+    window.__handoff = {
+      dataManager,
+      entry,
+      timer: entry.intervalId,
+      model: entry.module,
+      pollCount: window.__flightPolls,
+      timestamp: entry.module.getStats().lastUpdate,
+      started: Date.now(),
+    };
+  });
+  for (const kind of ['cesium', 'navara']) {
+    await page.select('#globe-engine', kind);
+    await ready(kind);
+    const result = await page.evaluate(() => {
+      const { dataManager, engine, styleManager } = window.__godsEyeView;
+      const before = window.__handoff;
+      const entry = dataManager.layers.get('flights');
+      const cockpit = styleManager.getCockpitState();
+      return {
+        sameOwner:
+          before.dataManager === dataManager &&
+          before.entry === entry &&
+          before.model === entry.module,
+        sameTimer:
+          before.timer === entry.intervalId && entry.intervalId != null,
+        sourcePolls: window.__flightPolls - before.pollCount,
+        elapsed: Date.now() - before.started,
+        stamp: entry.module.getStats().lastUpdate,
+        initialStamp: before.timestamp,
+        id: cockpit.subject?.id,
+        active: cockpit.active,
+        mode: cockpit.visionMode,
+        hud: !document.querySelector('#cockpit-hud').hidden,
+        drawn: entry.module.qaDrawn().some((row) => row.id === '71be26'),
+        height: engine.camera.height(),
+      };
+    });
+    assert.ok(
+      result.sameOwner &&
+        result.sameTimer &&
+        result.active &&
+        result.hud &&
+        result.drawn,
+      JSON.stringify(result),
+    );
+    assert.equal(result.id, '71be26');
+    assert.equal(result.mode, 'thermal');
+    if (result.elapsed < 30000) {
+      assert.equal(result.sourcePolls, 0);
+      assert.equal(result.stamp, result.initialStamp);
+    }
+    await page.waitForFunction(
+      () => Math.abs(window.__godsEyeView.engine.camera.height() - 9700) < 1000,
+    );
+    console.log(
+      `PASS ${kind} cockpit, aircraft, HUD, manager and timer (${result.sourcePolls} polls since entry)`,
+    );
+  }
+  await page.evaluate(() =>
+    window.__godsEyeView.styleManager.controlCockpit('exit'),
+  );
+  await page.waitForFunction(
+    () => !window.__godsEyeView.styleManager.getCockpitState().active,
+  );
+  assert.deepEqual(errors, []);
+} finally {
+  await browser.close();
+}

src/app/constructCatalog.js

@@ -66,6 +66,7 @@ export function createApplicationCatalog({
   metadata = APPLICATION_LAYER_METADATA,
   vesselOptions,
   resolveAsset,
+  layerSession,
   nepalBoundaryResolver,
   streetLevelProviders,
   engineKind = 'cesium',
@@ -79,30 +80,48 @@ export function createApplicationCatalog({
 
   const sourceComposition = resolveCatalogSources(sources);
   sources = sourceComposition.sources;
-  const militaryRegistry = createMilitaryRegistry();
+  const militaryRegistry =
+    layerSession?.militaryRegistry ?? createMilitaryRegistry();
   const weatherClock = createWeatherClock();
   const dispose = () => {
     signal.removeEventListener('abort', dispose);
-    militaryRegistry.dispose();
+    if (!layerSession) militaryRegistry.dispose();
     weatherClock.destroy();
   };
   signal.addEventListener('abort', dispose, { once: true });
   try {
-    if (sourceComposition.isConfigured('military'))
+    if (!layerSession?.militaryRegistry) {
-      militaryRegistry.configureSource(sources.military, { signal });
+      const lifetime = layerSession?.lifetime.signal ?? signal;
+      if (sourceComposition.isConfigured('military'))
+        militaryRegistry.configureSource(sources.military, { signal: lifetime });
+      if (layerSession) {
+        layerSession.militaryRegistry = militaryRegistry;
+        lifetime.addEventListener('abort', militaryRegistry.dispose, {
+          once: true,
+        });
+      }
+    }
     // Shared instances (awareness and launches read others) are made once,
     // when the first layer that needs them is built.
     const once = (create) => {
       let value;
       return () => (value ??= create());
     };
+    const sessionModel = (id, create) => {
+      if (!layerSession) return create();
+      const models = (layerSession.models ??= new Map());
+      if (!models.has(id)) models.set(id, create());
+      return models.get(id);
+    };
     const flights = once(() =>
-      createApplicationFlights({
+      sessionModel('flights', () =>
-        surface,
+        createApplicationFlights({
-        source: sources.flights,
+          surface,
-        militaryRegistry,
+          source: sources.flights,
-        resolveAsset,
+          militaryRegistry,
-      }),
+          resolveAsset,
+        }),
+      ),
     );
     const military = once(() =>
       createApplicationMilitary({
@@ -158,7 +177,10 @@ export function createApplicationCatalog({
       ],
       [
         'earthquakes',
-        () => createApplicationEarthquakes({ source: sources.earthquakes }),
+        () =>
+          sessionModel('earthquakes', () =>
+            createApplicationEarthquakes({ source: sources.earthquakes }),
+          ),
       ],
       [
         'air-quality',

src/app/data.js

@@ -8,12 +8,13 @@ export function createApplicationData({
   controls: { styleManager },
   catalog,
   allowQaRegistration,
+  layerSession,
   onData,
   defer,
 }) {
   // Initialize data layer manager
   // The modules get { signal, engine } on every call (viewer null on Navara).
-  const dataManager = new LayerLifecycle(viewer, {
+  const dataManager = layerSession?.manager ?? new LayerLifecycle(viewer, {
     engine,
     allowQaRegistration,
     // A panel's host may report it hidden while it is on screen; its layers
@@ -21,7 +22,12 @@ export function createApplicationData({
     visibilityTarget: panelAwareVisibility(document),
     getSourceAvailability: catalog?.getSourceAvailability,
   });
+  if (layerSession) layerSession.manager = dataManager;
   defer(async () => {
+    if (layerSession && !layerSession.lifetime.signal.aborted) {
+      await dataManager.detachScene();
+      return;
+    }
     await dataManager.destroyAll();
     if (dataManager.layers.size)
       throw new Error(
@@ -35,12 +41,11 @@ export function createApplicationData({
   onData?.(dataManager);
   if (!catalog?.layers || !catalog?.metadata)
     throw new TypeError('An application layer catalog is required');
-  for (const layer of catalog.layers) dataManager.register(layer);
+  dataManager.bindCatalog(viewer, engine, catalog);
   for (const layer of catalog.layers) layer.attachDataManager?.(dataManager);
   for (const layer of catalog.layers)
     layer.attachMapStackController?.(mapStackController);
-  // Restoration starts only after the caller's complete registry is sealed.
+
-  dataManager.finalizeRegistrations(catalog.metadata);
   if (allowQaRegistration) {
     window.__gevQaRegisterLayer = (targetManager, layerModule) => {
       if (targetManager !== dataManager)

src/app/scene.js

@@ -29,12 +29,14 @@ export async function createApplicationScene({
   signal,
   defer,
   rendererCache,
+  layerSession,
   ...options
 }) {
-  const operations = createApplicationOperations({
+  const operations = layerSession?.operations ?? createApplicationOperations({
     requests: requestServices,
-    signal,
+    signal: layerSession?.lifetime.signal ?? signal,
   });
+  if (layerSession) layerSession.operations = operations;
   defer(initLogoGaze());
   const previousKey = window.__GOOGLE_MAPS_API_KEY__;
   if (googleApiKey) {
@@ -55,6 +57,14 @@ export async function createApplicationScene({
   const { viewer, engine, tileset, mapStackController } = rendererCache
     ? await rendererCache.acquire(options.engineKind, build, defer)
     : await build({ defer });
+  if (layerSession) {
+    // DEM cells belong to the session. Mesh samples came from the outgoing
+    // scene, including when the incoming canvas was warm in the cache.
+    operations.surface.groundFloor.clearMeshFloorCells();
+    operations.surface.groundFloor.setMeshFloorPreferred(
+      mapStackController.getActiveId() === 'photoreal',
+    );
+  }
   return { viewer, engine, tileset, mapStackController, operations };
 }
 

src/contextModePolicy.js

@@ -412,7 +412,7 @@ export function contextRestoreLayerIds(snapshot = {}) {
 }
 
 /**
- * Contacts mode requires both observed-flight feeds. Navara also supports
+ * Contacts mode requires both observed-flight feeds. Both globes support
  * first-person flight directly from a single selected aircraft layer.
  *
  * @param {object} input Current context and dependency visibility.

src/data/layerStateCoordinator.js

@@ -470,6 +470,36 @@ export class LayerStateCoordinator {
     return null;
   }
 
+  // On an in-page engine switch, an attached session model can already own
+  // this exact contact. Ordinary shared links must still verify the source.
+  retainedTrackingTarget() {
+    const selected = this._selectedShareTrackingTarget();
+    if (!selected || !this.dataManager.isEnabled(selected.layerId)) return null;
+    const model = this.dataManager.layers.get(selected.layerId)?.module;
+    if (
+      model?.attachRenderer &&
+      model.getParams?.()[selected.optionKey] === selected.targetId &&
+      model.hasContact?.(selected.targetId) === true
+    ) return selected;
+    return null;
+  }
+
+  resumeRetainedTracking(previous) {
+    const selected = this.retainedTrackingTarget();
+    if (
+      !selected || selected.layerId !== previous.layerId ||
+      selected.targetId !== previous.targetId
+    ) return null;
+    const model = this.dataManager.layers.get(selected.layerId).module;
+    const followed = model.trackById(selected.targetId, {
+      origin: LAYER_RESTORE_ORIGINS.share,
+    });
+    if (!followed) return null;
+    const result = { ...selected, status: 'found', classification: 'followed', cleared: false };
+    this._publishTrackingRestoreStatus(result);
+    return result;
+  }
+
   _passivelyClearTrackingSelection(selected) {
     const current =
       this._durableState.options?.[selected.optionOwner]?.[selected.optionKey];

src/data/lifecycle.js

@@ -121,6 +121,50 @@ export class LayerLifecycle {
     this._registerLayer(layerModule);
   }
 
+  /**
+   * Release the scene only. Models with an explicit renderer lifetime keep
+   * their entry, polling interval, visibility intents and in-flight source.
+   * Legacy modules use their ordinary teardown until they gain that contract.
+   */
+  async detachScene() {
+    for (const [id, entry] of [...this.layers]) {
+      await entry.toggleChain.catch(() => {});
+      if (entry.module.attachRenderer && entry.module.detachRenderer) {
+        if (entry.initialized) entry.module.detachRenderer(this.viewer);
+      } else if (!(await this.destroyLayer(id))) {
+        throw new Error(`Cannot detach layer ${id}`);
+      }
+    }
+    this.viewer = null;
+    this.engine = null;
+    this._registrationsFinalized = false;
+    this._registrationDispositions = null;
+  }
+
+  /** Bind the next catalog only after the preceding scene released its entries. */
+  bindCatalog(viewer, engine, catalog) {
+    if (this._registrationsFinalized) throw new Error('Scene already attached');
+    this.viewer = viewer;
+    this.engine = engine ?? engineFromViewer(viewer) ?? null;
+    this._catalogSourceAvailability = catalog.getSourceAvailability;
+    for (const layer of catalog.layers) {
+      const entry = this.layers.get(layer.id);
+      if (!entry) this.register(layer);
+      else {
+        if (entry.module !== layer) throw new Error(`Layer owner changed: ${layer.id}`);
+        if (entry.initialized) layer.attachRenderer(viewer, this._moduleContext());
+      }
+    }
+    // Retained entries may appear anywhere in the directory. Preserve both
+    // catalog order (panel/serialization) and each live entry's identity.
+    for (const { id } of catalog.layers) {
+      const entry = this.layers.get(id);
+      this.layers.delete(id);
+      this.layers.set(id, entry);
+    }
+    this.finalizeRegistrations(catalog.metadata);
+  }
+
   /** Register a synthetic layer after sealing in an explicitly dev-enabled manager. */
   registerForQa(layerModule) {
     if (!this._allowQaRegistration || !this._registrationsFinalized) {

src/layers/earthquakes/index.js

@@ -16,9 +16,9 @@ export { createUsgsEarthquakeSource } from './source.js';
 /**
  * Own one earthquake display and its refresh lifecycle.
  * renderer.create({viewer, engine}) owns drawing and returns:
- * setVisible(boolean), replace(discs), records(limit), destroy().
+ * setVisible(boolean), replace(discs), destroy().
  * Discs are plain ECEF anchors, metre radii and Rgba colours; renderers keep
- * source order and return plain raw analyst rows (model.mapAnalystRecord).
+ * source order. The layer retains observations for queries while detached.
  */
 export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
   if (typeof source?.getSnapshot !== 'function')
@@ -26,7 +26,10 @@ export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
   if (!overlayHost) throw new TypeError('Earthquakes require an overlay host');
   if (typeof renderer?.create !== 'function')
     throw new TypeError('Earthquakes require a renderer factory');
-  let _viewer = null;
+  let initialized = false;
+  let observations = [];
+  let discs = [];
+  let labels = [];
   let _request = null;
   let _renderer = null;
   let _count = 0;
@@ -34,6 +37,14 @@ export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
   let _lastError = null;
   let _enabled = false;
 
+  function publishLabels() {
+    overlayHost.setEntries(EARTHQUAKE_OVERLAY_SOURCE_ID, labels, {
+      cohortLimit: EARTHQUAKE_OVERLAY_COHORT_LIMIT,
+      collisionCapacity: EARTHQUAKE_OVERLAY_COLLISION_CAPACITY,
+      moving: false,
+    });
+  }
+
   const layer = {
     id: 'earthquakes',
     name: 'Earthquakes (24h)',
@@ -42,17 +53,32 @@ export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
     updateInterval: 60000,
 
     init(viewer, { engine = null } = {}) {
-      if (_renderer) throw new Error('Earthquake layer is already initialized');
+      if (initialized) throw new Error('Earthquake layer is already initialized');
-      _viewer = viewer;
+      initialized = true;
+      try {
+        if (viewer || engine) this.attachRenderer(viewer, { engine });
+      } catch (error) {
+        this.destroy();
+        throw error;
+      }
+      console.log('[Data:Earthquakes] Initialized');
+    },
+
+    attachRenderer(viewer, { engine = null } = {}) {
+      if (!initialized || _renderer) throw new Error('Invalid earthquake scene attachment');
       _renderer = renderer.create({ viewer, engine });
       if (!_renderer) throw new Error('Earthquake renderer unavailable');
-      _renderer.setVisible(false);
+      _renderer.setVisible(_enabled);
-      _count = 0;
+      if (discs.length) _renderer.replace(discs);
-      _lastUpdate = null;
+      overlayHost.setVisible(EARTHQUAKE_OVERLAY_SOURCE_ID, _enabled);
-      _lastError = null;
+      if (_enabled) publishLabels();
-      _enabled = false;
+    },
+
+    detachRenderer() {
+      overlayHost.clearSource(EARTHQUAKE_OVERLAY_SOURCE_ID);
       overlayHost.setVisible(EARTHQUAKE_OVERLAY_SOURCE_ID, false);
-      console.log('[Data:Earthquakes] Initialized');
+      _renderer?.destroy();
+      _renderer = null;
     },
 
     enable(viewer) {
@@ -60,7 +86,10 @@ export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
       // No continuous-render hold: the discs are static geometry now, so the
       // layer has no per-frame animator to keep the render loop alive for.
       _renderer?.setVisible(true);
-      overlayHost.setVisible(EARTHQUAKE_OVERLAY_SOURCE_ID, true);
+      if (_renderer) {
+        overlayHost.setVisible(EARTHQUAKE_OVERLAY_SOURCE_ID, true);
+        if (labels.length) publishLabels();
+      }
     },
 
     disable(viewer) {
@@ -73,7 +102,7 @@ export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
     },
 
     async update(viewer) {
-      if (!_enabled || !_renderer) return false;
+      if (!_enabled) return false;
       _request?.abort();
       const request = new AbortController();
       _request = request;
@@ -128,17 +157,12 @@ export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
           );
         }
 
-        _renderer.replace(nextDiscs);
+        observations = rows;
-        if (_enabled) {
+        discs = nextDiscs;
-          overlayHost.setEntries(
+        labels = selectEarthquakeOverlayCohort(overlayEntries);
-            EARTHQUAKE_OVERLAY_SOURCE_ID,
+        if (_renderer) {
-            selectEarthquakeOverlayCohort(overlayEntries),
+          _renderer.replace(discs);
-            {
+          publishLabels();
-              cohortLimit: EARTHQUAKE_OVERLAY_COHORT_LIMIT,
-              collisionCapacity: EARTHQUAKE_OVERLAY_COLLISION_CAPACITY,
-              moving: false,
-            },
-          );
         }
 
         _count = count;
@@ -157,15 +181,15 @@ export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
       }
     },
 
-    destroy(viewer = _viewer) {
+    destroy() {
       _request?.abort();
       _request = null;
-      _viewer = null;
+      initialized = false;
       _enabled = false;
-      overlayHost.clearSource(EARTHQUAKE_OVERLAY_SOURCE_ID);
+      this.detachRenderer();
-      overlayHost.setVisible(EARTHQUAKE_OVERLAY_SOURCE_ID, false);
+      observations = [];
-      _renderer?.destroy();
+      discs = [];
-      _renderer = null;
+      labels = [];
       _count = 0;
       _lastUpdate = null;
       _lastError = null;
@@ -180,11 +204,13 @@ export function createEarthquakesLayer({ source, overlayHost, renderer } = {}) {
      * @returns {Array<Object>} See mapAnalystRecord for the record shape.
      */
     getAnalystRecords(maxCount = 2000) {
-      if (!_enabled || !_renderer) return [];
+      if (!_enabled) return [];
       const limit = Number.isFinite(maxCount)
         ? Math.max(1, Math.floor(maxCount))
         : 2000;
-      return _renderer.records(limit).map(mapAnalystRecord);
+      return observations.slice(0, limit).map((row, index) =>
+        mapAnalystRecord({ ...row, id: row.usgsId, depth: row.depthKm }, index),
+      );
     },
 
     getStats() {

src/layers/earthquakes/ownership.test.mjs

@@ -92,3 +92,28 @@ test('USGS body completion honors cancellation even with an uncooperative transp
     name: 'AbortError',
   });
 });
+
+test('an observation received between scenes is queryable and draws without a second fetch', async () => {
+  let resolve, polls = 0;
+  const h = harness({ getSnapshot() {
+    polls++;
+    return new Promise(done => { resolve = done; });
+  } });
+  try {
+    const pending = h.layer.update();
+    h.layer.detachRenderer();
+    assert.equal(h.sources.length, 0);
+    resolve([row]);
+    assert.equal(await pending, true);
+    const [record] = h.layer.getAnalystRecords();
+    assert.equal(record.id, row.usgsId);
+    assert.equal(record.lat, row.lat);
+    assert.equal(h.events.length, 0);
+    h.layer.attachRenderer(h.viewer);
+    assert.equal(h.sources[0].entities.values.length, 1);
+    assert.equal(h.events.length, 1);
+    assert.equal(polls, 1);
+  } finally {
+    h.layer.destroy();
+  }
+});

src/main.js

@@ -15,11 +15,14 @@ let kind = pageEngineKind();
 let application;
 let busy = false;
 const renderers = createRendererCache();
+const layerSession = { lifetime: new AbortController() };
 window.addEventListener('pagehide', (event) => {
-  if (!event.persisted) renderers.clear();
+  if (event.persisted) return;
+  layerSession.lifetime.abort();
+  void application?.destroy().catch(report).finally(() => renderers.clear());
 });
 
-async function start(next, engineSwitch = false) {
+async function start(next, engineSwitch = false, cockpit = null) {
   kind = next;
   application = createStandaloneApplication({
     googleApiKey: import.meta.env.GOOGLE_MAPS_API_KEY,
@@ -27,11 +30,25 @@ async function start(next, engineSwitch = false) {
     allowQaRegistration: import.meta.env.DEV,
     engineKind: next,
     rendererCache: renderers,
+    layerSession,
     engineSwitch,
   });
   const { scene, controls } = await application.start();
   if (engineSwitch) {
-    await controls.styleManager.initialRestorePromise;
+    const style = controls.styleManager;
+    await style.initialRestorePromise;
+    // Only resume the aircraft that actually survived the handoff. A history
+    // entry may select a different subject, and a stale track may disappear.
+    const target = style.getAircraftTrackingTarget();
+    if (
+      cockpit?.active &&
+      target &&
+      target?.id === cockpit.subject?.id &&
+      target?.layerId === cockpit.subject?.layerId &&
+      style.controlCockpit('enter').ok
+    ) {
+      style.cockpitView.setVisionMode(cockpit.visionMode);
+    }
     await waitForGlobeFrame(scene.engine);
   }
 }
@@ -106,12 +123,16 @@ async function reconcile(remember = false) {
   present();
   const previous = kind;
   let cover;
+  let cockpit;
   try {
     while (pageEngineKind() !== kind) {
       cover ??= keepGlobeFrame(application.getComponents().scene.engine);
+      cockpit = application
+        .getComponents()
+        .controls.styleManager.getCockpitState();
       renderers.retain(kind);
       await application.destroy();
-      await start(pageEngineKind(), true);
+      await start(pageEngineKind(), true, cockpit);
     }
     if (remember) {
       try {
@@ -127,7 +148,7 @@ async function reconcile(remember = false) {
     history.replaceState(history.state, '', url);
     try {
       await application.destroy();
-      await start(previous, true);
+      await start(previous, true, cockpit);
       application
         .getComponents()
         .controls.styleManager._showToast(describeError(error));

src/services/groundFloor.js

@@ -500,7 +500,7 @@ export function createGroundFloor({ terrain, signal }) {
   }
 
   /** Test hook: clears mesh cells (never called at runtime — cells are valid all session). */
-  function _clearMeshFloorCellsForTest() {
+  function clearMeshFloorCells() {
     _meshCells.clear();
   }
 
@@ -663,7 +663,8 @@ export function createGroundFloor({ terrain, signal }) {
     meshFloorSampleWithinPrior,
     reportValidatedMeshFloorCell,
     cachedMeshFloor,
-    _clearMeshFloorCellsForTest,
+    clearMeshFloorCells,
+    _clearMeshFloorCellsForTest: clearMeshFloorCells,
     cachedGroundFloor,
     FLOOR_RESOLVE_DEADLINE_MS,
     resolveGroundFloorCellsBounded,

src/standalone/application.js

@@ -42,6 +42,7 @@ export function createStandaloneApplication({
   allowQaRegistration = false,
   engineKind = pageEngineKind(),
   rendererCache,
+  layerSession,
   engineSwitch = false,
 }) {
   if (owner)
@@ -89,6 +90,7 @@ export function createStandaloneApplication({
         loaderStatus,
         engineKind,
         rendererCache,
+        layerSession,
       });
       // The catalog of this engine: on Navara only the layers with a Navara
       // renderer (src/app/layers/renderers.js; none yet), the others' state
@@ -108,6 +110,7 @@ export function createStandaloneApplication({
           : {};
       catalog = createStandaloneCatalog({
         engineKind,
+        layerSession,
         sources: { ...sources, ...qaSources },
         streetLevelProviders,
         nepalBoundaryResolver: (signal) =>
@@ -132,7 +135,7 @@ export function createStandaloneApplication({
         catalog,
       }),
     createData: (context) =>
-      createStandaloneData({ ...context, allowQaRegistration, catalog }),
+      createStandaloneData({ ...context, allowQaRegistration, catalog, layerSession }),
     createTools: async (context) => {
       const tools = await createStandaloneTools({
         ...context,

src/standalone/catalog.js

@@ -8,6 +8,7 @@ export { createStandaloneReferenceSources } from './layerSources.js';
 export function createStandaloneCatalog({
   nepalBoundaryResolver,
   engineKind = 'cesium',
+  layerSession,
   sources = {},
   streetLevelProviders,
   signal = new AbortController().signal,
@@ -18,6 +19,7 @@ export function createStandaloneCatalog({
 } = {}) {
   return createApplicationCatalog({
     engineKind,
+    layerSession,
     nepalBoundaryResolver,
     surface,
     sources: createStandaloneLayerSources(sources),

src/ui/cockpitCoordinator.js

@@ -37,7 +37,7 @@ export class CockpitCoordinator {
       operations,
     );
     this._cockpitDisplayPortal = null;
-    this.cockpitView = viewer || engine?.kind === 'navara'
+    this.cockpitView = viewer || (engine?.frames?.preUpdate && engine?.camera?.followChanged)
       ? this._createCockpitView(viewer, services)
       : null;
   }
@@ -88,7 +88,7 @@ export class CockpitCoordinator {
         this._stampNavigation({ cancelPendingSelection: false }),
       isEntryAllowed: () =>
         cockpitEntryAllowed({
-          standaloneAircraft: this.engine?.kind === 'navara',
+          standaloneAircraft: true,
           contextMode: this._contextMode,
           contextModeChanging: this._contextModeChanging,
           flightsEnabled: !!this._dataManager?.isEnabled('flights'),
@@ -279,7 +279,7 @@ export class CockpitCoordinator {
           action: 'control_cockpit',
           error: this._contextModeChanging
             ? 'Contacts is still starting up — try Cockpit again in a moment'
-            : this.engine?.kind === 'navara'
+            : !this._contextMode
               ? 'Enable an aircraft layer and track a flight to enter Cockpit'
               : 'Contacts must be active to enter Cockpit — say "open contacts" first',
           state: this.getCockpitState(),

src/ui/navigationController.js

@@ -254,7 +254,7 @@ export class NavigationController {
     });
   }
 
-  _reassertNavigationHandoff(generation, { trackingOrigin = 'tool' } = {}) {
+  _reassertNavigationHandoff(generation, { trackingOrigin = 'tool', keepTracking = false } = {}) {
     return reassertNavigationHandoff({
       generation,
       currentGeneration: this._navigationGeneration,
@@ -266,7 +266,7 @@ export class NavigationController {
       // was refused by the cockpit leaves the old readout standing.
       release: () => {
         this.clearLocation();
-        return this._releaseFollowCamera({ trackingOrigin });
+        if (!keepTracking) return this._releaseFollowCamera({ trackingOrigin });
       },
     });
   }

src/ui/shareRestoration.js

@@ -174,12 +174,17 @@ export class ShareRestoration {
         this._initialShareRestoreTimeout = null;
         if (this._disposed) return;
         const generation = this._initialShareNavigationGeneration;
+        const retained = engineSwitch && this._layerStateCoordinator?.retainedTrackingTarget();
         const applyCamera =
           Number.isInteger(generation) &&
-          this.navigation._reassertNavigationHandoff(generation);
+          this.navigation._reassertNavigationHandoff(generation, {
+            trackingOrigin: engineSwitch ? 'share-restore' : 'tool',
+            keepTracking: Boolean(retained),
+          });
         void this._runShareRestore(savedState, {
           applyCamera,
           instant: engineSwitch,
+          retained,
           navigationToken: generation,
           layersPromise: this._layerStateRestorePromise,
           settle: (result) => this._settleInitialShareRestore(result),
@@ -238,7 +243,7 @@ export class ShareRestoration {
    */
   async _runShareRestore(
     state,
-    { applyCamera, instant = false, navigationToken, layersPromise, settle },
+    { applyCamera, instant = false, retained, navigationToken, layersPromise, settle },
   ) {
     const generation = this._shareRestoreGeneration;
     const current = () =>
@@ -253,7 +258,8 @@ export class ShareRestoration {
       if (!current()) return;
       const tracking =
         share.camera === 'applied'
-          ? await this._layerStateCoordinator?.restoreShareTrackingSelection?.()
+          ? (retained && this._layerStateCoordinator.resumeRetainedTracking(retained)) ||
+            await this._layerStateCoordinator?.restoreShareTrackingSelection?.()
           : {
               status: 'superseded',
               cleared: