Merge upstream/main: air-quality layer (AQHI) meets i18n

Upstream's #568 adds the Air quality layer to the Weather group (ECCC
AQHI, Canada only) with a band legend, worst-first list and voice
support.

- package-boundaries: both sides' entries unioned.
- layerPanel/weatherPanel tests: both sides' new tests kept; the
  weatherPanel fixture follows upstream (legendCategorical: true, the
  'list' block id) while our localized-history (K-6) test stays.
- air-quality strings marked: band labels and the provider label as
  msg() data, the readings-list aria-label through t(); es/ru entries
  added (+6 keys each).
- The synthetic air-quality allocation-benchmark titles follow the
  file's own convention (// i18n-ignore) like TRK/VESSEL/CAMERA.

Also verified the auto-merged weatherPanel.js against upstream: ORDER
gains 'air-quality', OBSERVED stays slice(2, 5), and the data-driven
legendCategorical path is upstream's.

npm run i18n: complete (2559), no unmarked strings. npm test: only the
pre-existing environmental OPENAI_API_KEY leak fails. Build passes.

src/app/constructCatalog.js

@@ -24,6 +24,7 @@ import { createApplicationLocalAdsb } from './layers/localAdsb.js';
 import { createApplicationAwareness } from './layers/militaryAwareness.js';
 import { createApplicationFirms } from './layers/firms.js';
 import { createApplicationEarthquakes } from './layers/earthquakes.js';
+import { createApplicationAirQuality } from './layers/airQuality.js';
 import { createApplicationFirePerimeters } from './layers/perimeters.js';
 import { createApplicationGnssIntegrity } from './layers/gnss.js';
 import { createApplicationCables } from './layers/submarineCables.js';
@@ -118,6 +119,7 @@ export function createApplicationCatalog({
           ...(resolveAsset ? { resolveAsset } : {}),
         }),
         createApplicationEarthquakes({ source: sources.earthquakes }),
+        createApplicationAirQuality({ source: sources['air-quality'] }),
         createApplicationFirePerimeters({
           source: sources['fire-perimeters'],
         }),

src/app/constructCatalog.test.mjs

@@ -40,7 +40,7 @@ test('catalogs construct distinct layers and classification from their supplied
     signal: b.signal,
     surface: fixtureSurface(b.signal),
   });
-  assert.equal(first.layers.length, 31);
+  assert.equal(first.layers.length, 32);
   assert.ok(first.get('local-adsb'), 'Local ADS-B is registered');
   assert.deepEqual(
     first.metadata.find(({ id }) => id === 'local-adsb'),
@@ -154,7 +154,7 @@ test('Mapillary can be omitted or replaced without changing catalog membership',
     surface: fixtureSurface(lifetime.signal),
   };
   const catalog = createApplicationCatalog(options);
-  assert.equal(catalog.layers.length, 31);
+  assert.equal(catalog.layers.length, 32);
   assert.deepEqual(catalog.get('street-level').providerIds, []);
   assert.equal(
     catalogControlServices(catalog).streetLevelLayer,

src/app/layers/airQuality.js

@@ -0,0 +1,6 @@
+import { createAirQualityLayer } from '../../layers/airQuality/index.js';
+import { overlayHost } from './overlayHost.js';
+/** Wire air-quality readings to the application overlay host. */
+export function createApplicationAirQuality(options) {
+  return createAirQualityLayer({ overlayHost, ...options });
+}

src/app/sourceComposition.js

@@ -46,6 +46,7 @@ export const CATALOG_SOURCE_CONTRACTS = Object.freeze({
   cyclones: contract(['weather-cyclones'], ['getSnapshot']),
   earthquakes: contract(['earthquakes'], ['getSnapshot']),
   'fire-perimeters': contract(['fire-perimeters'], ['getSnapshot']),
+  'air-quality': contract(['air-quality'], ['getSnapshot']),
   'gnss-integrity': contract(['gnss-integrity'], ['getSnapshot']),
   cables: contract(['telegeography-submarine-cables'], ['fetch']),
   transit: contract(['transit'], ['requestSnapshot', 'getHistory']),

src/app/sourceComposition.test.mjs

@@ -37,7 +37,7 @@ test('every acquisition source can be omitted without losing catalog membership'
 
 test('all acquisition sources may be absent, and enable fails before initializing or fetching', async (t) => {
   const actual = catalog({}, t);
-  assert.equal(actual.layers.length, 31);
+  assert.equal(actual.layers.length, 32);
   const manager = new LayerLifecycle(
     {},
     { getSourceAvailability: actual.getSourceAvailability },

src/data/dataCredits.js

@@ -169,6 +169,13 @@ export const DATA_CREDITS = [
   },
   OSM_CREDIT,
   OPENMAPTILES_CREDIT,
+  {
+    key: 'eccc-aqhi',
+    html:
+      'Air quality (AQHI): Environment and Climate Change Canada — MSC GeoMet ' +
+      '(<a href="https://eccc-msc.github.io/open-data/" target="_blank" rel="noopener">eccc-msc.github.io/open-data</a>) ' +
+      '· <a href="https://eccc-msc.github.io/open-data/licence/readme_en/" target="_blank" rel="noopener">ECCC Data Servers End-use Licence</a>',
+  },
   {
     key: 'overture-military-names',
     html: 'Military area names: <a href="https://overturemaps.org" target="_blank" rel="noopener">Overture Maps Foundation</a> (ODbL)',

src/data/layerState.js

@@ -585,6 +585,11 @@ export const LAYER_STATE_TOKEN_RESERVATIONS =
  * owns stable URL ordering.
  */
 export const LAYER_STATE_REGISTRY = Object.freeze([
+  Object.freeze({
+    id: 'air-quality',
+    token: '4',
+    disposition: 'enabled-only',
+  }),
   Object.freeze({
     id: 'ais-live-vessels',
     token: 'a',

src/data/layerState.test.mjs

@@ -202,8 +202,8 @@ function encode(state) {
 
 test('production registry is exact, canonical, and rejects incomplete contracts', async () => {
   assert.equal(validateLayerStateRegistry(), true);
-  assert.equal(REGISTERED_LAYER_IDS.length, 30);
-  assert.equal(new Set(REGISTERED_LAYER_IDS).size, 30);
+  assert.equal(REGISTERED_LAYER_IDS.length, 31);
+  assert.equal(new Set(REGISTERED_LAYER_IDS).size, 31);
   assert.ok(REGISTERED_LAYER_IDS.includes('transit'));
   assert.deepEqual(REGISTERED_LAYER_IDS, [...REGISTERED_LAYER_IDS].sort());
   assert.deepEqual(LEGACY_LAYER_STATE_TOKENS, {
@@ -242,19 +242,19 @@ test('production registry is exact, canonical, and rejects incomplete contracts'
   for (const [id, token] of Object.entries(LEGACY_LAYER_STATE_TOKENS)) {
     assert.equal(LAYER_STATE_TOKEN_RESERVATIONS[id], token);
   }
-  assert.equal(nextLayerStateToken(), '4');
+  assert.equal(nextLayerStateToken(), '5');
   assert.equal(
     nextLayerStateToken({
       ...LAYER_STATE_TOKEN_RESERVATIONS,
-      alpha: '4',
-      bravo: '5',
+      alpha: '5',
+      bravo: '6',
     }),
-    '6',
+    '7',
   );
   const digitsExhausted = {
     ...LAYER_STATE_TOKEN_RESERVATIONS,
     ...Object.fromEntries(
-      [...'456789'].map((digit) => [`prior-${digit}`, digit]),
+      [...'56789'].map((digit) => [`prior-${digit}`, digit]),
     ),
   };
   assert.equal(nextLayerStateToken(digitsExhausted), '00');
@@ -307,8 +307,8 @@ test('production registry is exact, canonical, and rejects incomplete contracts'
   assert.equal(
     validateLayerStateAllocations(LAYER_STATE_TOKEN_RESERVATIONS, {
       ...LAYER_STATE_TOKEN_RESERVATIONS,
-      future: '4',
-      next: '5',
+      future: '5',
+      next: '6',
     }),
     true,
   );
@@ -318,7 +318,7 @@ test('production registry is exact, canonical, and rejects incomplete contracts'
         ...LAYER_STATE_TOKEN_RESERVATIONS,
         future: '00',
       }),
-    /next free token 4/,
+    /next free token 5/,
   );
   const beforeLastDigit = { ...digitsExhausted };
   delete beforeLastDigit['prior-9'];
@@ -341,10 +341,10 @@ test('production registry is exact, canonical, and rejects incomplete contracts'
   assert.throws(
     () =>
       validateLayerStateAllocations(
-        { ...LAYER_STATE_TOKEN_RESERVATIONS, merged: '4' },
-        { ...LAYER_STATE_TOKEN_RESERVATIONS, merged: '4', competing: '4' },
+        { ...LAYER_STATE_TOKEN_RESERVATIONS, merged: '5' },
+        { ...LAYER_STATE_TOKEN_RESERVATIONS, merged: '5', competing: '5' },
       ),
-    /next free token 5/,
+    /next free token 6/,
   );
   assert.throws(
     () => validateLayerStateAllocations({ future: '00' }, { future: '01' }),

src/data/layerStateTokenLedger.test.mjs

@@ -128,17 +128,23 @@ test('reservation ledger is complete, pinned, and rejects duplicate or malformed
     { ...parseLayerStateTokenReservations(reservationRows) },
     { ...LAYER_STATE_TOKEN_RESERVATIONS },
   );
-  assert.equal(Object.keys(LAYER_STATE_TOKEN_RESERVATIONS).length, 30);
+  assert.equal(Object.keys(LAYER_STATE_TOKEN_RESERVATIONS).length, 31);
   assert.deepEqual(
     { ...LAYER_STATE_TOKEN_RESERVATIONS },
     {
       ...LEGACY_LAYER_STATE_TOKENS,
       'street-level': '0',
       'gnss-integrity': '3',
+      'air-quality': '4',
     },
   );
   assert.throws(
-    () => parseLayerStateTokenReservations(reservationRows.slice(1)),
+    () =>
+      parseLayerStateTokenReservations(
+        // Drop a legacy row by id; the first row sorts as air-quality, which
+        // is not a legacy reservation.
+        reservationRows.filter(([id]) => id !== 'ais-live-vessels'),
+      ),
     /Missing or changed legacy/,
   );
   assert.throws(
@@ -155,9 +161,9 @@ test('reservation ledger is complete, pinned, and rejects duplicate or malformed
     /Duplicate layer-state token reservation/,
   );
   assert.equal(
-    parseLayerStateTokenReservations([...reservationRows, ['future', '4']])
+    parseLayerStateTokenReservations([...reservationRows, ['future', '5']])
       .future,
-    '4',
+    '5',
   );
   assert.throws(
     () =>
@@ -175,14 +181,14 @@ test('reservation ledger is complete, pinned, and rejects duplicate or malformed
 
 test('published retired digits and competing PRs advance the merge-time allocation', () => {
   withPublishedBase(
-    { rows: [...reservationRows, ['retired-layer', '4']] },
+    { rows: [...reservationRows, ['retired-layer', '5']] },
     (cwd) => {
       const published = readPublishedLayerStateReservations('HEAD', cwd);
-      assert.equal(nextLayerStateToken(published), '5');
+      assert.equal(nextLayerStateToken(published), '6');
       assert.equal(
         validateLayerStateAllocations(published, {
           ...published,
-          newcomer: '5',
+          newcomer: '6',
         }),
         true,
       );
@@ -190,15 +196,15 @@ test('published retired digits and competing PRs advance the merge-time allocati
         () =>
           validateLayerStateAllocations(published, {
             ...published,
-            competing: '4',
+            competing: '5',
           }),
-        /next free token 5/,
+        /next free token 6/,
       );
       assert.throws(
         () =>
           validateLayerStateAllocations(published, {
             ...LAYER_STATE_TOKEN_RESERVATIONS,
-            newcomer: '4',
+            newcomer: '5',
           }),
         /changed or removed: retired-layer/,
       );
@@ -206,8 +212,8 @@ test('published retired digits and competing PRs advance the merge-time allocati
   );
 });
 
-test('PR B manually replaces provisional 4 with 5 after PR A publishes 4', () => {
-  withPublishedBase({ rows: [...reservationRows, ['pr-a', '4']] }, (cwd) => {
+test('PR B manually replaces provisional 5 with 6 after PR A publishes 5', () => {
+  withPublishedBase({ rows: [...reservationRows, ['pr-a', '5']] }, (cwd) => {
     mkdirSync(path.join(cwd, 'scripts'));
     const fixtureChecker = path.join(
       cwd,
@@ -228,8 +234,8 @@ test('PR B manually replaces provisional 4 with 5 after PR A publishes 4', () =>
 
     writeCodecFixture(
       cwd,
-      [...reservationRows, ['pr-b', '4']],
-      [{ id: 'pr-b', token: '4' }],
+      [...reservationRows, ['pr-b', '5']],
+      [{ id: 'pr-b', token: '5' }],
     );
     const beforeRebase = runCheck();
     assert.equal(beforeRebase.status, 1);
@@ -237,10 +243,10 @@ test('PR B manually replaces provisional 4 with 5 after PR A publishes 4', () =>
 
     writeCodecFixture(
       cwd,
-      [...reservationRows, ['pr-a', '4'], ['pr-b', '4']],
+      [...reservationRows, ['pr-a', '5'], ['pr-b', '5']],
       [
-        { id: 'pr-a', token: '4' },
-        { id: 'pr-b', token: '4' },
+        { id: 'pr-a', token: '5' },
+        { id: 'pr-b', token: '5' },
       ],
     );
     const staleRebase = runCheck();
@@ -248,16 +254,16 @@ test('PR B manually replaces provisional 4 with 5 after PR A publishes 4', () =>
     assert.match(staleRebase.stderr, /Duplicate layer-state token reservation/);
 
     const published = readPublishedLayerStateReservations('HEAD', cwd);
-    assert.equal(nextLayerStateToken(published), '5');
-    const validBaselineRows = [...reservationRows, ['pr-a', '4']];
-    writeCodecFixture(cwd, validBaselineRows, [{ id: 'pr-a', token: '4' }]);
+    assert.equal(nextLayerStateToken(published), '6');
+    const validBaselineRows = [...reservationRows, ['pr-a', '5']];
+    writeCodecFixture(cwd, validBaselineRows, [{ id: 'pr-a', token: '5' }]);
     const helper = spawnSync(
       process.execPath,
       [realpathSync(fixtureNext), 'pr-b'],
       { cwd, encoding: 'utf8' },
     );
     assert.equal(helper.status, 0, helper.stderr);
-    assert.match(helper.stdout, /pr-b: 5/);
+    assert.match(helper.stdout, /pr-b: 6/);
     assert.deepEqual(
       JSON.parse(readFileSync(path.join(cwd, LEDGER_PATH), 'utf8')),
       validBaselineRows,
@@ -265,20 +271,20 @@ test('PR B manually replaces provisional 4 with 5 after PR A publishes 4', () =>
     );
     writeCodecFixture(
       cwd,
-      [...reservationRows, ['pr-a', '4'], ['pr-b', '5']],
+      [...reservationRows, ['pr-a', '5'], ['pr-b', '6']],
       [
-        { id: 'pr-a', token: '4' },
-        { id: 'pr-b', token: '5' },
+        { id: 'pr-a', token: '5' },
+        { id: 'pr-b', token: '6' },
       ],
     );
     const corrected = runCheck();
     assert.equal(corrected.status, 0, corrected.stderr);
-    assert.match(corrected.stdout, /31 published, 1 new/);
+    assert.match(corrected.stdout, /32 published, 1 new/);
   });
 });
 
 test('allocation batches cross the last digit and base-36 pair boundaries in order', () => {
-  const digitRows = [...'456789'].map((digit) => [`retired-${digit}`, digit]);
+  const digitRows = [...'56789'].map((digit) => [`retired-${digit}`, digit]);
   const allDigits = parseLayerStateTokenReservations([
     ...reservationRows,
     ...digitRows,
@@ -330,7 +336,7 @@ test('allocation batches cross the last digit and base-36 pair boundaries in ord
 test('an isolated valid two-character fixture round-trips an l field beyond the old 64-character cap', async () => {
   const cwd = mkdtempSync(path.join(tmpdir(), 'gev-layer-token-width-'));
   try {
-    const priorDigits = [...'456789'].map((digit) => [
+    const priorDigits = [...'56789'].map((digit) => [
       `qa-prior-digit-${digit}`,
       digit,
     ]);
@@ -367,7 +373,7 @@ test('an isolated valid two-character fixture round-trips an l field beyond the
     const params = new URLSearchParams([['v', '2']]);
     codec.encodeLayerStateParams(params, state);
     assert.ok(params.get('l').length > 64, 'fixture must cross the old cap');
-    assert.equal(params.get('l').length, 71);
+    assert.equal(params.get('l').length, 73);
     const restored = codec.decodeLayerStateParams(params);
     assert.deepEqual(restored?.enabledLayerIds, expectedLayerIds);
     assert.deepEqual(restored?.options, state.options);
@@ -385,7 +391,7 @@ test('checker reads a complete future base ledger and rejects retired-token reus
     },
     (cwd) => {
       const published = readPublishedLayerStateReservations('HEAD', cwd);
-      assert.equal(Object.keys(published).length, 31);
+      assert.equal(Object.keys(published).length, 32);
       assert.equal(published['retired-layer'], '00');
       assert.throws(
         () =>

src/data/layerStateTokenReservations.json

@@ -1,4 +1,5 @@
 [
+  ["air-quality", "4"],
   ["ais-live-vessels", "a"],
   ["alpr-cameras", "p"],
   ["bhote-koshi-2026", "h"],

src/firstRunExperience.test.mjs

@@ -994,10 +994,11 @@ test('the voice TOOL SCHEMA matches the pinned contract — the mission mapping
   // schema, which may not carry top-level anyOf), and Contacts requested-radius
   // list descriptions; the missions still ride existing tools.
   // Street Level and GNSS extend the manifest; broadcast caveats describe tracked and analyst aircraft.
-  assert.equal(block.length, 30511, 'serialized tool schema length drifted');
+  // Air quality (ECCC AQHI) extends the manifest.
+  assert.equal(block.length, 30655, 'serialized tool schema length drifted');
   assert.equal(
     crypto.createHash('sha256').update(block).digest('hex'),
-    '62d5df9cedf413403e4fd0a7cbe94bb2cd13736c3d8fedc84bcccd63ad253eb6',
+    '3b1d5e77c10a92f6543a4f9d1ff1870101a0306b65e5b8a6113111c81eda371e',
     'the first-run missions must ride EXISTING tools: no schema edit, no cache bust',
   );
   const instructions = fs.readFileSync(

src/i18n/locales/es.json

@@ -2779,6 +2779,12 @@
   "FILTER": "FILTRO",
   "Cloud filter strength": "Intensidad del filtro de nubes",
   "Panoramax answered HTTP {status}": "Panoramax respondió HTTP {status}",
+  "Highest air-quality readings in view": "Lecturas de calidad del aire más altas a la vista",
+  "Low": "Baja",
+  "Moderate": "Moderada",
+  "High": "Alta",
+  "Very High": "Muy alta",
+  "Air quality": "Calidad del aire",
   "{n} sequences in view · click a line for its nearest photo": {
     "one": "{n} secuencia a la vista · haz clic en una línea para su foto más cercana",
     "many": "{n} secuencias a la vista · haz clic en una línea para su foto más cercana",

src/i18n/locales/ru.json

@@ -2836,6 +2836,12 @@
   "FILTER": "ФИЛЬТР",
   "Cloud filter strength": "Сила фильтра облаков",
   "Panoramax answered HTTP {status}": "Panoramax ответил: HTTP {status}",
+  "Highest air-quality readings in view": "Наивысшие показатели качества воздуха в поле зрения",
+  "Low": "Низкий",
+  "Moderate": "Умеренный",
+  "High": "Высокий",
+  "Very High": "Очень высокий",
+  "Air quality": "Качество воздуха",
   "{n} sequences in view · click a line for its nearest photo": {
     "one": "{n} съёмка в кадре · щёлкните линию, чтобы открыть ближайшую фотографию",
     "few": "{n} съёмки в кадре · щёлкните линию, чтобы открыть ближайшую фотографию",

src/layers/airQuality/index.js

@@ -0,0 +1,287 @@
+import * as Cesium from 'cesium';
+import { t } from '../../i18n/index.js';
+import {
+  AIR_QUALITY_BANDS,
+  AIR_QUALITY_OVERLAY_SOURCE_ID,
+  AIR_QUALITY_OVERLAY_COHORT_LIMIT,
+  AIR_QUALITY_OVERLAY_COLLISION_CAPACITY,
+  AIR_QUALITY_PROVIDERS,
+  createAirQualityOverlayEntry,
+  mapAnalystRecord,
+  newestObservation,
+  readingsAreStale,
+  readingsInView,
+  selectAirQualityOverlayCohort,
+} from './model.js';
+export * from './model.js';
+export { createEcccAirQualitySource } from './source.js';
+
+/** Station markers are a point reading, not an extent. */
+const STATION_MARKER_RADIUS_M = 6_000;
+/** Readings listed in the readout card. */
+const READOUT_LIMIT = 5;
+
+/** Own one air-quality display, its refresh lifecycle, and its readout card. */
+export function createAirQualityLayer({ source, overlayHost } = {}) {
+  if (typeof source?.getSnapshot !== 'function')
+    throw new TypeError('Air quality requires a snapshot source');
+  if (!overlayHost) throw new TypeError('Air quality requires an overlay host');
+  let _viewer = null;
+  let _request = null;
+  let _dataSource = null;
+  let _readings = [];
+  let _count = 0;
+  let _lastUpdate = null;
+  let _lastError = null;
+  let _enabled = false;
+  let rowControlsListener = null;
+
+  const notify = () => rowControlsListener?.();
+
+  /** The camera's lon/lat rectangle in degrees, or null when unresolvable. */
+  const viewRectangle = () => {
+    const rectangle = _viewer?.camera?.computeViewRectangle?.();
+    if (!rectangle) return null;
+    const toDeg = Cesium.Math.toDegrees;
+    return {
+      west: toDeg(rectangle.west),
+      south: toDeg(rectangle.south),
+      east: toDeg(rectangle.east),
+      north: toDeg(rectangle.north),
+    };
+  };
+
+  const layer = {
+    id: 'air-quality',
+    name: 'Air quality',
+    icon: '◍',
+    source: 'ECCC MSC GeoMet',
+    updateInterval: 1_200_000,
+
+    init(viewer) {
+      if (_viewer) throw new Error('Air quality layer is already initialized');
+      _viewer = viewer;
+      _dataSource = new Cesium.CustomDataSource('air-quality');
+      _dataSource.show = false;
+      viewer.dataSources.add(_dataSource);
+      _readings = [];
+      _count = 0;
+      _lastUpdate = null;
+      _lastError = null;
+      _enabled = false;
+      overlayHost.setVisible(AIR_QUALITY_OVERLAY_SOURCE_ID, false);
+    },
+
+    enable() {
+      _enabled = true;
+      if (_dataSource) _dataSource.show = true;
+      overlayHost.setVisible(AIR_QUALITY_OVERLAY_SOURCE_ID, true);
+      notify();
+    },
+
+    disable() {
+      // Abort in flight: a response arriving after disable must not redraw.
+      _request?.abort();
+      _request = null;
+      _enabled = false;
+      if (_dataSource) _dataSource.show = false;
+      overlayHost.clearSource(AIR_QUALITY_OVERLAY_SOURCE_ID);
+      overlayHost.setVisible(AIR_QUALITY_OVERLAY_SOURCE_ID, false);
+      notify();
+    },
+
+    async update() {
+      if (!_enabled || !_dataSource) return false;
+      _request?.abort();
+      const request = new AbortController();
+      _request = request;
+      try {
+        const readings = await source.getSnapshot({ signal: request.signal });
+        // A superseded or aborted request must not touch the scene, and neither
+        // must one that lands after the layer was switched off.
+        if (request.signal.aborted || _request !== request || !_enabled)
+          return false;
+        _readings = readings;
+        this._render();
+        _count = _readings.length;
+        _lastUpdate = Date.now();
+        _lastError = null;
+        notify();
+        return true;
+      } catch (error) {
+        if (request.signal.aborted || _request !== request) return false;
+        _lastError = error?.message || 'Air quality request failed';
+        console.warn('[Data:AirQuality] Refresh failed:', _lastError);
+        notify();
+        return false;
+      } finally {
+        if (_request === request) _request = null;
+      }
+    },
+
+    /** Rebuild entities and overlay labels from the current readings. */
+    _render() {
+      if (!_dataSource) return;
+      _dataSource.entities.removeAll();
+      const overlayEntries = [];
+      for (const reading of _readings) {
+        const position = Cesium.Cartesian3.fromDegrees(
+          reading.lon,
+          reading.lat,
+        );
+        const color = Cesium.Color.fromCssColorString(reading.color);
+        _dataSource.entities.add(
+          new Cesium.Entity({
+            id: `air-quality:${reading.id}`,
+            position,
+            ellipse: {
+              // Static axes, as in the earthquake layer: a per-frame axis
+              // re-tessellates the clamped ground primitive every frame.
+              semiMajorAxis: STATION_MARKER_RADIUS_M,
+              semiMinorAxis: STATION_MARKER_RADIUS_M,
+              material: new Cesium.ColorMaterialProperty(color.withAlpha(0.35)),
+              outline: true,
+              outlineColor: color.withAlpha(0.9),
+              outlineWidth: 2,
+              heightReference: Cesium.HeightReference.CLAMP_TO_GROUND,
+            },
+            properties: {
+              provider: reading.provider,
+              scale: reading.scale,
+              value: reading.value,
+              band: reading.band,
+              name: reading.name,
+              zone: reading.zone,
+              risk: reading.risk,
+              observedMs: reading.observedMs,
+              note: reading.note,
+              lat: reading.lat,
+              lon: reading.lon,
+            },
+          }),
+        );
+        overlayEntries.push(
+          createAirQualityOverlayEntry({
+            id: reading.id,
+            position,
+            title: `${reading.name} ${reading.label}`,
+            accent: reading.color,
+            value: reading.value,
+          }),
+        );
+      }
+      if (_enabled) {
+        overlayHost.setEntries(
+          AIR_QUALITY_OVERLAY_SOURCE_ID,
+          selectAirQualityOverlayCohort(overlayEntries),
+          {
+            cohortLimit: AIR_QUALITY_OVERLAY_COHORT_LIMIT,
+            collisionCapacity: AIR_QUALITY_OVERLAY_COLLISION_CAPACITY,
+            moving: false,
+          },
+        );
+      }
+    },
+
+    destroy(viewer = _viewer) {
+      _request?.abort();
+      _request = null;
+      _enabled = false;
+      overlayHost.clearSource(AIR_QUALITY_OVERLAY_SOURCE_ID);
+      overlayHost.setVisible(AIR_QUALITY_OVERLAY_SOURCE_ID, false);
+      if (_dataSource) {
+        viewer?.dataSources?.remove(_dataSource, true);
+        _dataSource = null;
+      }
+      _viewer = null;
+      _readings = [];
+      _count = 0;
+      _lastUpdate = null;
+      _lastError = null;
+      rowControlsListener = null;
+    },
+
+    /**
+     * Readout descriptor for the Weather panel: the band legend, and the worst
+     * readings currently in view.
+     *
+     * `readout: true` renders the toggle and source line only; the card owns
+     * the rest. Coverage is stated plainly because this layer is not global.
+     */
+    getRowControls() {
+      const provider = AIR_QUALITY_PROVIDERS.eccc;
+      const inView = readingsInView(_readings, viewRectangle(), READOUT_LIMIT);
+      const newest = _readings.reduce(
+        (max, reading) => Math.max(max, reading.observedMs || 0),
+        0,
+      );
+      return {
+        readout: true,
+        summary: {
+          label: provider.label,
+          coverage: provider.coverage,
+          validTime: newest ? new Date(newest).toISOString() : undefined,
+          detail: `${provider.network} · ${provider.scale}`,
+          status: _lastError
+            ? _lastError
+            : _count === 0
+              ? _lastUpdate === null
+                ? 'No readings available'
+                : 'No current readings'
+              : `${_count} stations reporting`,
+          units: provider.scale,
+        },
+        legend: AIR_QUALITY_BANDS.map((band) => ({
+          color: band.color,
+          label: band.label,
+        })),
+        legendCategorical: true,
+        list: {
+          ariaLabel: t('Highest air-quality readings in view'),
+          items: inView.map((reading, index) => ({
+            id: reading.id,
+            ordinal: index + 1,
+            lead: `${reading.scale} ${reading.label}`,
+            text: `${reading.name} · ${reading.risk}`,
+            accent: reading.color,
+          })),
+        },
+      };
+    },
+
+    setRowControlsListener(listener) {
+      rowControlsListener = typeof listener === 'function' ? listener : null;
+    },
+
+    /**
+     * Snapshot readings as JSON-safe records for the analyst query engine.
+     * @param {number} [maxCount=500]
+     * @returns {Array<object>}
+     */
+    getAnalystRecords(maxCount = 500) {
+      if (!_enabled || !_readings.length) return [];
+      const limit = Number.isFinite(maxCount)
+        ? Math.max(1, Math.floor(maxCount))
+        : 500;
+      return _readings
+        .slice(0, limit)
+        .map((reading, index) => mapAnalystRecord(reading, index));
+    },
+
+    getStats() {
+      // `lastUpdate` is when a response was received; `observedAt` is when the
+      // network actually measured. Freshness is judged on the latter, so a feed
+      // that keeps answering with hours-old observations reports STALE rather
+      // than being narrated as live by the HUD and voice provenance envelope.
+      return {
+        count: _count,
+        lastUpdate: _lastUpdate,
+        error: _lastError,
+        observedAt: newestObservation(_readings),
+        // Only a completed refresh can be stale; before one there is no feed.
+        stale: _lastUpdate !== null && readingsAreStale(_readings),
+      };
+    },
+  };
+  return layer;
+}

src/layers/airQuality/model.js

@@ -0,0 +1,378 @@
+/**
+ * @module layers/airQuality/model
+ *
+ * Air-quality readings, normalized across networks. Pure — no Cesium, no
+ * network.
+ *
+ * Air-quality indices are not interchangeable numbers. Canada's AQHI runs 1 to
+ * 10+ on health risk; the US AQI runs 0 to 500 on concentration breakpoints;
+ * Europe's EAQI is a five-step category. A reading is therefore carried as
+ * `{ provider, scale, value, band }` — who measured it, which index it is, the
+ * value on that index's own terms, and the band it falls in — so a second
+ * network can be added without retrofitting a shared numeric meaning that does
+ * not exist.
+ *
+ * Only ECCC's AQHI is implemented here; `AIR_QUALITY_PROVIDERS` is the seam a
+ * later provider registers against.
+ */
+import { msg } from '../../i18n/index.js';
+
+/** Band identifiers shared across providers, in ascending severity. */
+export const AIR_QUALITY_BANDS = Object.freeze([
+  Object.freeze({ id: 'low', label: msg('Low'), color: '#4cc9f0' }),
+  Object.freeze({ id: 'moderate', label: msg('Moderate'), color: '#ffd43b' }),
+  Object.freeze({ id: 'high', label: msg('High'), color: '#ff6b35' }),
+  Object.freeze({ id: 'very-high', label: msg('Very High'), color: '#c1121f' }),
+]);
+
+const BAND_BY_ID = new Map(AIR_QUALITY_BANDS.map((band) => [band.id, band]));
+
+/** Colour used when a station reports no usable reading. */
+export const AIR_QUALITY_UNKNOWN_COLOR = '#6b7785';
+
+export const AIR_QUALITY_OVERLAY_SOURCE_ID = 'air-quality';
+export const AIR_QUALITY_OVERLAY_COHORT_LIMIT = 48;
+export const AIR_QUALITY_OVERLAY_COLLISION_CAPACITY = 32;
+
+/**
+ * A reading this old is stale enough that displaying it would misinform.
+ * AQHI publishes hourly, so six hours is five missed publications.
+ */
+export const OBSERVATION_MAX_AGE_MS = 6 * 60 * 60 * 1000;
+
+/**
+ * How old the newest observation may be before the layer reports itself stale.
+ *
+ * This is deliberately separate from the age at which a reading is dropped.
+ * `lastUpdate` records when we last *received* a response, which stays current
+ * even when the network publishes nothing new; freshness has to be judged on
+ * the source's own observation time instead. AQHI publishes hourly, so a newest
+ * reading beyond two hours means at least one publication was missed and the
+ * feed should not be described as live.
+ */
+export const STALE_AFTER_MS = 2 * 60 * 60 * 1000;
+
+/**
+ * The newest observation time across a set of readings, or null when empty.
+ * @param {Array<object>} readings
+ * @returns {number|null} Epoch ms.
+ */
+export function newestObservation(readings) {
+  if (!Array.isArray(readings) || readings.length === 0) return null;
+  let newest = null;
+  for (const reading of readings) {
+    const at = Number(reading?.observedMs);
+    if (Number.isFinite(at) && (newest === null || at > newest)) newest = at;
+  }
+  return newest;
+}
+
+/**
+ * Is a set of readings stale, judged on source observation time? An empty
+ * set is stale: a refresh that kept no current observation has nothing live.
+ * @param {Array<object>} readings
+ * @param {number} [now=Date.now()]
+ * @returns {boolean}
+ */
+export function readingsAreStale(readings, now = Date.now()) {
+  const newest = newestObservation(readings);
+  // No current observation at all — every row was dropped as too old or
+  // unusable — is the stalest a feed can be, not a nominal one.
+  if (newest === null) return true;
+  return now - newest > STALE_AFTER_MS;
+}
+
+/**
+ * Registered provider descriptors. `coverage` is stated plainly because the
+ * layer is not global and the row must say so.
+ */
+export const AIR_QUALITY_PROVIDERS = Object.freeze({
+  eccc: Object.freeze({
+    id: 'eccc',
+    scale: 'AQHI',
+    label: msg('Air quality'),
+    network: 'Environment and Climate Change Canada',
+    coverage: 'Canada only · ECCC AQHI network',
+    /** ECCC's published band thresholds, evaluated in order. */
+    bands: Object.freeze([
+      Object.freeze({ id: 'low', max: 3 }),
+      Object.freeze({ id: 'moderate', max: 6 }),
+      Object.freeze({ id: 'high', max: 10 }),
+      Object.freeze({ id: 'very-high', max: Infinity }),
+    ]),
+  }),
+});
+
+/** Band descriptor for an id, or null. */
+export function airQualityBandById(bandId) {
+  return BAND_BY_ID.get(String(bandId ?? '')) || null;
+}
+
+/** Accent colour for a band id, falling back to neutral grey. */
+export function airQualityColor(bandId) {
+  return airQualityBandById(bandId)?.color || AIR_QUALITY_UNKNOWN_COLOR;
+}
+
+/**
+ * The published AQHI value for a raw ECCC reading: an integer from 1 up.
+ *
+ * ECCC reports whole numbers with a floor of 1 — there is no "AQHI 0" and no
+ * "AQHI 1.08". A raw value below 1 is a legitimate low reading, not an error,
+ * and is published as 1.
+ *
+ * @param {number|string|null|undefined} raw - Raw `aqhi` value from the API.
+ * @returns {number|null} Published integer AQHI, or null when unusable.
+ */
+export function aqhiDisplayValue(raw) {
+  // Guard the empty forms BEFORE coercing: Number(null) and Number('') are both
+  // 0, which would otherwise floor to a confident "AQHI 1" for a station that
+  // reported nothing at all.
+  if (raw === null || raw === undefined || raw === '') return null;
+  if (typeof raw !== 'number' && typeof raw !== 'string') return null;
+  if (typeof raw === 'string' && raw.trim() === '') return null;
+  const value = Number(raw);
+  if (!Number.isFinite(value) || value < 0) return null;
+  return Math.max(1, Math.round(value));
+}
+
+/**
+ * The band id for a value on a provider's scale.
+ * @param {string} providerId
+ * @param {number|null} value - Already in the provider's published form.
+ * @returns {string|null}
+ */
+export function bandForValue(providerId, value) {
+  const provider = AIR_QUALITY_PROVIDERS[String(providerId ?? '')];
+  if (!provider || !Number.isFinite(value)) return null;
+  return provider.bands.find((band) => value <= band.max)?.id ?? null;
+}
+
+/**
+ * Display text for a value on a provider's scale.
+ * AQHI collapses everything above ten into the open-ended "10+".
+ * @param {string} providerId
+ * @param {number|null} value
+ * @returns {string}
+ */
+export function valueLabel(providerId, value) {
+  if (!Number.isFinite(value)) return '--';
+  if (providerId === 'eccc') return value > 10 ? '10+' : String(value);
+  return String(value);
+}
+
+/** Plain-language risk phrase for a band id. */
+export function bandRiskText(bandId) {
+  const band = airQualityBandById(bandId);
+  return band ? `${band.label} health risk` : null;
+}
+
+/**
+ * Validate a station FeatureCollection into an id-keyed catalog.
+ *
+ * Atomic: a structurally broken response returns null so the caller keeps its
+ * last good catalog. A station missing coordinates is skipped, since one
+ * unusable station is not evidence the catalog is broken.
+ *
+ * @param {object} geojson - GeoJSON FeatureCollection from `aqhi-stations`.
+ * @returns {Map<string, object>|null} Stations by location_id, or null.
+ */
+export function normalizeAqhiStations(geojson) {
+  if (!Array.isArray(geojson?.features)) return null;
+  const stations = new Map();
+  for (const feature of geojson.features) {
+    const properties = feature?.properties;
+    if (
+      !properties ||
+      typeof properties !== 'object' ||
+      Array.isArray(properties)
+    )
+      return null;
+    const coordinates = feature?.geometry?.coordinates;
+    if (!Array.isArray(coordinates) || coordinates.length < 2) continue;
+    const [lon, lat] = coordinates.map(Number);
+    if (!Number.isFinite(lon) || !Number.isFinite(lat)) continue;
+    if (Math.abs(lat) > 90 || Math.abs(lon) > 180) return null;
+    const id = String(properties.location_id ?? feature.id ?? '').trim();
+    if (!id) continue;
+    stations.set(id, {
+      id,
+      name: String(properties.location_name_en || id).trim(),
+      // ECCC's administrative zone: atl, que, ont, pnr, pyr.
+      zone: String(properties['eccc_administrative-zone'] || '').trim(),
+      lat,
+      lon,
+    });
+  }
+  return stations;
+}
+
+/**
+ * Join latest ECCC observations onto known stations into provider-shaped rows.
+ *
+ * The catalog is the only thing that supplies a reading its coordinates, so an
+ * observation without a matching station cannot be placed and is dropped.
+ * Readings older than OBSERVATION_MAX_AGE_MS are dropped too — a six-hour-old
+ * air-quality number presented as current is worse than no number.
+ *
+ * @param {object} geojson - FeatureCollection from `aqhi-observations-realtime`.
+ * @param {Map<string, object>} stations - Known stations by location_id.
+ * @param {number} [now=Date.now()] - Clock seam for tests.
+ * @returns {Array<object>|null} Normalized readings, or null when malformed.
+ */
+export function normalizeAqhiObservations(geojson, stations, now = Date.now()) {
+  if (!Array.isArray(geojson?.features)) return null;
+  if (!(stations instanceof Map)) return null;
+  const provider = AIR_QUALITY_PROVIDERS.eccc;
+  const newest = new Map();
+  for (const feature of geojson.features) {
+    const properties = feature?.properties;
+    if (
+      !properties ||
+      typeof properties !== 'object' ||
+      Array.isArray(properties)
+    )
+      return null;
+    const stationId = String(properties.location_id ?? '').trim();
+    const station = stations.get(stationId);
+    if (!station) continue;
+
+    const value = aqhiDisplayValue(properties.aqhi);
+    if (value === null) continue;
+    const observedMs = Date.parse(properties.observation_datetime);
+    if (!Number.isFinite(observedMs)) continue;
+    if (now - observedMs > OBSERVATION_MAX_AGE_MS) continue;
+
+    const previous = newest.get(stationId);
+    if (previous && previous.observedMs >= observedMs) continue;
+    const band = bandForValue(provider.id, value);
+    newest.set(stationId, {
+      id: `${provider.id}:${stationId}`,
+      provider: provider.id,
+      scale: provider.scale,
+      value,
+      band,
+      stationId,
+      name: station.name,
+      zone: station.zone,
+      lat: station.lat,
+      lon: station.lon,
+      observedMs,
+      color: airQualityColor(band),
+      label: valueLabel(provider.id, value),
+      risk: bandRiskText(band),
+      note: String(properties.special_notes_en || '').trim() || null,
+    });
+  }
+  return [...newest.values()].sort(
+    (a, b) => b.value - a.value || a.stationId.localeCompare(b.stationId),
+  );
+}
+
+/**
+ * Build the source-owned presentation for one station label.
+ * @param {object} input
+ * @returns {object}
+ */
+export function createAirQualityOverlayEntry({
+  id,
+  position,
+  title,
+  accent,
+  value,
+}) {
+  return {
+    id: String(id),
+    position,
+    variant: 'label',
+    title,
+    accent,
+    // Worse air wins the label budget — the reading people need to see first.
+    priority: Math.round(Number(value) || 0) * 1000,
+    collisionGroup: 'ambient-label',
+    paintLane: 'ambient-label',
+    interactive: false,
+    edgeFade: 'keyhole',
+    horizonCull: true,
+    terrainOcclusion: false,
+    gapPx: 14,
+    verticalOnly: true,
+    placement: 'above',
+  };
+}
+
+/** Keep the worst readings, with stable identity as the tie-break. */
+export function selectAirQualityOverlayCohort(
+  entries,
+  limit = AIR_QUALITY_OVERLAY_COHORT_LIMIT,
+) {
+  const cap = Math.max(
+    0,
+    Math.min(AIR_QUALITY_OVERLAY_COHORT_LIMIT, Math.floor(Number(limit) || 0)),
+  );
+  if (!Array.isArray(entries) || cap === 0) return [];
+  return entries
+    .slice()
+    .sort(
+      (a, b) =>
+        b.priority - a.priority || String(a.id).localeCompare(String(b.id)),
+    )
+    .slice(0, cap);
+}
+
+/**
+ * The worst readings inside a lon/lat rectangle, for the readout card.
+ *
+ * A null rectangle means the camera could not resolve one (a fully oblique or
+ * space-level view); everything is then in scope rather than nothing, so the
+ * card degrades to the worst readings overall instead of going blank.
+ *
+ * @param {Array<object>} readings
+ * @param {?{west:number, south:number, east:number, north:number}} rect - Degrees.
+ * @param {number} [limit=5]
+ * @returns {Array<object>}
+ */
+export function readingsInView(readings, rect, limit = 5) {
+  if (!Array.isArray(readings)) return [];
+  const cap = Math.max(0, Math.floor(Number(limit) || 0));
+  if (cap === 0) return [];
+  const inside = !rect
+    ? readings
+    : readings.filter((reading) => {
+        if (reading.lat < rect.south || reading.lat > rect.north) return false;
+        // A rectangle crossing the antimeridian has west > east.
+        return rect.west <= rect.east
+          ? reading.lon >= rect.west && reading.lon <= rect.east
+          : reading.lon >= rect.west || reading.lon <= rect.east;
+      });
+  return inside
+    .slice()
+    .sort((a, b) => b.value - a.value || a.stationId.localeCompare(b.stationId))
+    .slice(0, cap);
+}
+
+/**
+ * Map one reading to a JSON-safe analyst record. Pure — no Cesium types.
+ * @param {object|null|undefined} raw
+ * @param {number} [index=0]
+ * @returns {object}
+ */
+export function mapAnalystRecord(raw, index = 0) {
+  const num = (v) => (Number.isFinite(v) ? v : null);
+  const text = (v) => {
+    const t = String(v ?? '').trim();
+    return t || null;
+  };
+  return {
+    id: text(raw?.id) || `AIR-${String(index).padStart(4, '0')}`,
+    provider: text(raw?.provider),
+    scale: text(raw?.scale),
+    value: num(raw?.value),
+    band: text(raw?.band),
+    name: text(raw?.name),
+    zone: text(raw?.zone),
+    risk: text(raw?.risk),
+    lat: num(raw?.lat),
+    lon: num(raw?.lon),
+    observedMs: num(raw?.observedMs),
+  };
+}

src/layers/airQuality/model.test.mjs

@@ -0,0 +1,269 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  AIR_QUALITY_BANDS,
+  AIR_QUALITY_PROVIDERS,
+  AIR_QUALITY_UNKNOWN_COLOR,
+  OBSERVATION_MAX_AGE_MS,
+  STALE_AFTER_MS,
+  airQualityColor,
+  aqhiDisplayValue,
+  bandForValue,
+  bandRiskText,
+  mapAnalystRecord,
+  normalizeAqhiObservations,
+  normalizeAqhiStations,
+  readingsAreStale,
+  readingsInView,
+  selectAirQualityOverlayCohort,
+  valueLabel,
+} from './model.js';
+
+const NOW = Date.parse('2026-09-24T18:30:00Z');
+const RECENT = '2026-09-24T18:00:00Z';
+const collection = (features) => ({ type: 'FeatureCollection', features });
+const station = (id, name, zone, lon, lat) => ({
+  type: 'Feature',
+  geometry: { type: 'Point', coordinates: [lon, lat] },
+  properties: {
+    location_id: id,
+    location_name_en: name,
+    'eccc_administrative-zone': zone,
+  },
+});
+const observation = (id, aqhi, when = RECENT) => ({
+  type: 'Feature',
+  properties: { location_id: id, aqhi, observation_datetime: when },
+});
+
+const STATIONS = collection([
+  station('IAKID', 'Calgary', 'pnr', -114.0575, 51.0458),
+  station('OAAAA', 'Toronto', 'ont', -79.3832, 43.6532),
+  station('AAAAA', 'Halifax', 'atl', -63.5752, 44.6488),
+]);
+
+// ── provider-shaped records ────────────────────────────────────────────────
+
+test('readings carry the provider-neutral {provider, scale, value, band} shape', () => {
+  // Indices are not interchangeable numbers: AQHI is 1-10+ on health risk,
+  // US AQI is 0-500 on concentration. The shape names which index a value is on
+  // so a second network can be added without inventing a shared meaning.
+  const stations = normalizeAqhiStations(STATIONS);
+  const [row] = normalizeAqhiObservations(
+    collection([observation('IAKID', 2.32)]),
+    stations,
+    NOW,
+  );
+  assert.equal(row.provider, 'eccc');
+  assert.equal(row.scale, 'AQHI');
+  assert.equal(row.value, 2);
+  assert.equal(row.band, 'low');
+});
+
+test('bands map from a value on a named provider scale', () => {
+  assert.equal(bandForValue('eccc', 1), 'low');
+  assert.equal(bandForValue('eccc', 3), 'low');
+  assert.equal(bandForValue('eccc', 4), 'moderate');
+  assert.equal(bandForValue('eccc', 7), 'high');
+  assert.equal(bandForValue('eccc', 11), 'very-high');
+  // An unregistered provider cannot be banded rather than being guessed at.
+  assert.equal(bandForValue('unknown-network', 5), null);
+  assert.equal(bandForValue('eccc', null), null);
+});
+
+test('the provider states its coverage plainly', () => {
+  assert.match(AIR_QUALITY_PROVIDERS.eccc.coverage, /Canada only/);
+  assert.equal(AIR_QUALITY_PROVIDERS.eccc.scale, 'AQHI');
+});
+
+test("values above ten collapse to the scale's open-ended label", () => {
+  assert.equal(valueLabel('eccc', 10), '10');
+  assert.equal(valueLabel('eccc', 11), '10+');
+  assert.equal(valueLabel('eccc', null), '--');
+});
+
+test('every band has a distinct colour, and an unknown band is neutral', () => {
+  const colors = AIR_QUALITY_BANDS.map((b) => b.color);
+  assert.equal(new Set(colors).size, colors.length);
+  assert.equal(airQualityColor('nonsense'), AIR_QUALITY_UNKNOWN_COLOR);
+  assert.equal(bandRiskText('high'), 'High health risk');
+  assert.equal(bandRiskText(null), null);
+});
+
+// ── published form ─────────────────────────────────────────────────────────
+
+test('AQHI rounds to the published integer form and floors at 1', () => {
+  assert.equal(aqhiDisplayValue(1.08), 1);
+  assert.equal(aqhiDisplayValue(3.5), 4);
+  assert.equal(aqhiDisplayValue(0), 1);
+  assert.equal(aqhiDisplayValue('3'), 3);
+});
+
+test('an absent reading never becomes a confident AQHI 1', () => {
+  // Number(null) and Number('') are both 0, which would floor to 1.
+  for (const empty of [null, undefined, '', '   ', NaN, true, {}, [], -1]) {
+    assert.equal(aqhiDisplayValue(empty), null, `${JSON.stringify(empty)}`);
+  }
+});
+
+// ── snapshot validation ────────────────────────────────────────────────────
+
+test('stations normalize into an id-keyed catalog carrying their zone', () => {
+  const stations = normalizeAqhiStations(STATIONS);
+  assert.equal(stations.size, 3);
+  assert.equal(stations.get('OAAAA').zone, 'ont');
+});
+
+test('malformed payloads are rejected atomically', () => {
+  assert.equal(normalizeAqhiStations(null), null);
+  assert.equal(normalizeAqhiStations(collection([{ properties: null }])), null);
+  const stations = normalizeAqhiStations(STATIONS);
+  assert.equal(normalizeAqhiObservations(null, stations, NOW), null);
+  assert.equal(
+    normalizeAqhiObservations(collection([]), 'not a map', NOW),
+    null,
+  );
+});
+
+test('an observation with no matching station is dropped', () => {
+  const stations = normalizeAqhiStations(STATIONS);
+  const rows = normalizeAqhiObservations(
+    collection([observation('IAKID', 2), observation('ZZZZZ', 9)]),
+    stations,
+    NOW,
+  );
+  assert.equal(rows.length, 1);
+});
+
+test('a stale reading is dropped rather than shown as current', () => {
+  const stations = normalizeAqhiStations(STATIONS);
+  const old = new Date(NOW - OBSERVATION_MAX_AGE_MS - 60_000).toISOString();
+  const rows = normalizeAqhiObservations(
+    collection([observation('IAKID', 3, old), observation('OAAAA', 4)]),
+    stations,
+    NOW,
+  );
+  assert.deepEqual(
+    rows.map((r) => r.stationId),
+    ['OAAAA'],
+  );
+});
+
+test('a snapshot whose every observation was too old is stale, not nominal', () => {
+  const stations = normalizeAqhiStations(STATIONS);
+  const old = new Date(NOW - OBSERVATION_MAX_AGE_MS - 60_000).toISOString();
+  const rows = normalizeAqhiObservations(
+    collection([observation('IAKID', 3, old), observation('OAAAA', 4, old)]),
+    stations,
+    NOW,
+  );
+  assert.deepEqual(rows, []);
+  assert.equal(readingsAreStale(rows, NOW), true);
+  assert.equal(readingsAreStale([{ observedMs: NOW - 60_000 }], NOW), false);
+  assert.equal(
+    readingsAreStale([{ observedMs: NOW - STALE_AFTER_MS - 1 }], NOW),
+    true,
+  );
+});
+
+test('the newest reading per station wins and worst air sorts first', () => {
+  const stations = normalizeAqhiStations(STATIONS);
+  const rows = normalizeAqhiObservations(
+    collection([
+      observation('IAKID', 3, '2026-09-24T16:00:00Z'),
+      observation('IAKID', 7, '2026-09-24T18:00:00Z'),
+      observation('OAAAA', 5),
+    ]),
+    stations,
+    NOW,
+  );
+  assert.deepEqual(
+    rows.map((r) => r.value),
+    [7, 5],
+  );
+});
+
+// ── readout selection ──────────────────────────────────────────────────────
+
+const reading = (id, value, lat, lon) => ({
+  id,
+  stationId: id,
+  value,
+  lat,
+  lon,
+  name: id,
+});
+
+test('the readout lists the worst readings inside the view rectangle', () => {
+  const rows = [
+    reading('west', 9, 51.0, -114.0),
+    reading('east', 4, 43.6, -79.3),
+    reading('mild', 2, 51.1, -114.1),
+  ];
+  const inView = readingsInView(
+    rows,
+    { west: -115, south: 50, east: -113, north: 52 },
+    5,
+  );
+  assert.deepEqual(
+    inView.map((r) => r.id),
+    ['west', 'mild'],
+  );
+});
+
+test('an unresolvable view rectangle degrades to the worst overall, not to blank', () => {
+  // A space-level or fully oblique camera cannot produce a rectangle; the card
+  // should still say something useful.
+  const rows = [reading('a', 3, 0, 0), reading('b', 8, 10, 10)];
+  assert.deepEqual(
+    readingsInView(rows, null, 5).map((r) => r.id),
+    ['b', 'a'],
+  );
+  assert.deepEqual(readingsInView(rows, null, 0), []);
+  assert.deepEqual(readingsInView(null, null, 5), []);
+});
+
+test('a view rectangle crossing the antimeridian still selects correctly', () => {
+  // west > east is how a dateline-crossing rectangle is expressed.
+  const rows = [reading('near', 5, 0, 179), reading('far', 9, 0, 100)];
+  const inView = readingsInView(
+    rows,
+    { west: 170, south: -10, east: -170, north: 10 },
+    5,
+  );
+  assert.deepEqual(
+    inView.map((r) => r.id),
+    ['near'],
+  );
+});
+
+test('the overlay cohort is capped and deterministic', () => {
+  const entries = Array.from({ length: 120 }, (_, i) => ({
+    id: `s${i}`,
+    priority: i % 11,
+  }));
+  const cohort = selectAirQualityOverlayCohort(entries);
+  assert.ok(cohort.length <= 48);
+  assert.deepEqual(
+    cohort.map((e) => e.id),
+    selectAirQualityOverlayCohort(entries).map((e) => e.id),
+  );
+});
+
+test('analyst records are JSON-safe and name the provider and scale', () => {
+  const stations = normalizeAqhiStations(STATIONS);
+  const [row] = normalizeAqhiObservations(
+    collection([observation('IAKID', 2)]),
+    stations,
+    NOW,
+  );
+  const record = mapAnalystRecord(row, 0);
+  assert.deepEqual(JSON.parse(JSON.stringify(record)), record);
+  assert.equal(record.provider, 'eccc');
+  assert.equal(record.scale, 'AQHI');
+  const empty = mapAnalystRecord(undefined, 7);
+  assert.equal(empty.id, 'AIR-0007');
+  for (const [key, value] of Object.entries(empty)) {
+    assert.notEqual(value, undefined, `${key} must not be undefined`);
+  }
+});

src/layers/airQuality/ownership.test.mjs

@@ -0,0 +1,275 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { createAirQualityLayer } from './index.js';
+import { layerFeedState } from '../../data/feedState.js';
+import { STALE_AFTER_MS } from './model.js';
+
+function harness(source) {
+  const sources = [];
+  const events = [];
+  const viewer = {
+    dataSources: {
+      add(value) {
+        sources.push(value);
+      },
+      remove(value) {
+        sources.splice(sources.indexOf(value), 1);
+      },
+    },
+  };
+  const layer = createAirQualityLayer({
+    source,
+    overlayHost: {
+      setEntries(...args) {
+        events.push(args);
+      },
+      setVisible() {},
+      clearSource() {},
+    },
+  });
+  layer.init(viewer);
+  layer.enable(viewer);
+  return { layer, viewer, sources, events };
+}
+
+const reading = (id, value, overrides = {}) => ({
+  id: `eccc:${id}`,
+  provider: 'eccc',
+  scale: 'AQHI',
+  value,
+  band: 'low',
+  stationId: id,
+  name: id,
+  zone: 'ont',
+  lat: 43.65,
+  lon: -79.38,
+  observedMs: 1_700_000_000_000,
+  color: '#4cc9f0',
+  label: String(value),
+  risk: 'Low health risk',
+  note: null,
+  ...overrides,
+});
+
+const staticSource = (rows) => ({ getSnapshot: async () => rows });
+
+test('a layer requires both a snapshot source and an overlay host', () => {
+  assert.throws(() => createAirQualityLayer(), /snapshot source/);
+  assert.throws(
+    () => createAirQualityLayer({ source: staticSource([]) }),
+    /overlay host/,
+  );
+});
+
+test('initialization is single-use and owns exactly one data source', () => {
+  const { layer, viewer, sources } = harness(staticSource([]));
+  assert.equal(sources.length, 1);
+  assert.throws(() => layer.init(viewer), /already initialized/);
+  layer.destroy(viewer);
+  assert.equal(sources.length, 0);
+});
+
+test('a refresh renders readings and publishes an overlay cohort', async () => {
+  const { layer, events } = harness(
+    staticSource([reading('A', 2), reading('B', 7)]),
+  );
+  assert.equal(await layer.update(), true);
+  assert.equal(layer.getStats().count, 2);
+  assert.equal(layer.getStats().error, null);
+  assert.equal(events.at(-1)[0], 'air-quality');
+});
+
+// ── the abort + enabled guard ──────────────────────────────────────────────
+
+test('a response landing after disable cannot redraw the scene', async () => {
+  // The failure this prevents: disable() clears the overlay, then an in-flight
+  // response resolves and repopulates it behind the user's back.
+  let release;
+  const gate = new Promise((resolve) => {
+    release = resolve;
+  });
+  const { layer, events } = harness({
+    getSnapshot: async ({ signal } = {}) => {
+      await gate;
+      signal?.throwIfAborted();
+      return [reading('A', 5)];
+    },
+  });
+  const pending = layer.update();
+  layer.disable();
+  const publishedBefore = events.length;
+  release();
+  assert.equal(await pending, false, 'a late response must not be applied');
+  assert.equal(
+    events.length,
+    publishedBefore,
+    'no overlay write after disable',
+  );
+  assert.equal(layer.getStats().count, 0);
+});
+
+test('disable aborts the request in flight', async () => {
+  let seenSignal = null;
+  const { layer } = harness({
+    getSnapshot: async ({ signal } = {}) => {
+      seenSignal = signal;
+      await new Promise((resolve) => setTimeout(resolve, 40));
+      signal?.throwIfAborted();
+      return [];
+    },
+  });
+  const pending = layer.update();
+  layer.disable();
+  await pending;
+  assert.ok(seenSignal, 'a signal was passed through to the source');
+  assert.equal(seenSignal.aborted, true);
+});
+
+test('a superseded refresh does not clobber the newer one', async () => {
+  let call = 0;
+  const { layer } = harness({
+    getSnapshot: async ({ signal } = {}) => {
+      call += 1;
+      const mine = call;
+      await new Promise((resolve) => setTimeout(resolve, mine === 1 ? 40 : 1));
+      signal?.throwIfAborted();
+      return [reading(`call-${mine}`, mine)];
+    },
+  });
+  const first = layer.update();
+  const second = layer.update();
+  const [firstResult, secondResult] = await Promise.all([first, second]);
+  assert.equal(firstResult, false, 'the superseded call reports no update');
+  assert.equal(secondResult, true);
+  assert.equal(layer.getAnalystRecords()[0].name, 'call-2');
+});
+
+test('update is a no-op while the layer is disabled', async () => {
+  const { layer } = harness(staticSource([reading('A', 2)]));
+  layer.disable();
+  assert.equal(await layer.update(), false);
+  assert.equal(layer.getStats().count, 0);
+});
+
+// ── readout descriptor ─────────────────────────────────────────────────────
+
+test('the readout descriptor carries the band legend and coverage', async () => {
+  const { layer } = harness(staticSource([reading('A', 2), reading('B', 9)]));
+  await layer.update();
+  const controls = layer.getRowControls();
+  assert.equal(controls.readout, true);
+  assert.match(controls.summary.coverage, /Canada only/);
+  // The Weather panel's legend shape: one {color, label} per band.
+  assert.equal(controls.legendCategorical, true);
+  assert.deepEqual(
+    controls.legend.map((entry) => entry.label),
+    ['Low', 'Moderate', 'High', 'Very High'],
+  );
+  assert.ok(
+    controls.legend.every((entry) => /^#[0-9a-f]{6}$/i.test(entry.color)),
+  );
+  // Worst first, and every item keyed.
+  assert.deepEqual(
+    controls.list.items.map((i) => i.text),
+    ['B · Low health risk', 'A · Low health risk'],
+  );
+  assert.ok(controls.list.items.every((i) => i.id));
+  assert.match(controls.summary.status, /2 stations reporting/);
+});
+
+test('the readout reports an error rather than a silent empty card', async () => {
+  const { layer } = harness({
+    getSnapshot: async () => {
+      throw new Error('ECCC HTTP 503');
+    },
+  });
+  await layer.update();
+  assert.match(layer.getRowControls().summary.status, /503/);
+});
+
+test('row-control listeners are notified on refresh and teardown-safe', async () => {
+  const { layer, viewer } = harness(staticSource([reading('A', 2)]));
+  let calls = 0;
+  layer.setRowControlsListener(() => {
+    calls += 1;
+  });
+  await layer.update();
+  assert.ok(calls >= 1, 'a refresh notifies the card');
+  layer.destroy(viewer);
+  const after = calls;
+  layer.setRowControlsListener(() => {
+    calls += 1;
+  });
+  assert.equal(calls, after);
+});
+
+// ── feed-state honesty ─────────────────────────────────────────────────────
+
+test('freshness is judged on observation time, not on when we last fetched', async () => {
+  // lastUpdate stays current every time the network answers, even when it
+  // answers with nothing new. Judging freshness on it would let the HUD and
+  // voice describe hours-old air quality as live.
+  const aged = Date.now() - STALE_AFTER_MS - 60_000;
+  const { layer } = harness(
+    staticSource([reading('A', 2, { observedMs: aged })]),
+  );
+  await layer.update();
+  const stats = layer.getStats();
+  assert.ok(
+    stats.lastUpdate >= Date.now() - 5_000,
+    'we did just receive a response',
+  );
+  assert.equal(stats.observedAt, aged, 'but the observation itself is old');
+  assert.equal(stats.stale, true);
+  assert.equal(
+    layerFeedState(stats),
+    'stale',
+    'provenance must not read this as nominal',
+  );
+});
+
+test('a current reading reports nominal', async () => {
+  const { layer } = harness(
+    staticSource([reading('A', 2, { observedMs: Date.now() - 10 * 60_000 })]),
+  );
+  await layer.update();
+  const stats = layer.getStats();
+  assert.equal(stats.stale, false);
+  assert.equal(layerFeedState(stats), 'nominal');
+});
+
+test('a refresh that kept no current observation reports stale, not nominal', async () => {
+  // Every observation older than OBSERVATION_MAX_AGE_MS is dropped, so a feed
+  // that only has hours-old rows yields an empty snapshot. That is the
+  // stalest a feed can be; it must not read as a healthy empty layer.
+  const { layer } = harness(staticSource([]));
+  assert.equal(layer.getStats().stale, false, 'no refresh yet, no verdict');
+  await layer.update();
+  const stats = layer.getStats();
+  assert.equal(stats.count, 0);
+  assert.equal(stats.observedAt, null);
+  assert.equal(stats.stale, true);
+  assert.equal(layerFeedState(stats), 'stale');
+  assert.equal(layer.getRowControls().summary.status, 'No current readings');
+});
+
+test('a failed refresh over good readings reports degraded, not nominal', async () => {
+  let fail = false;
+  const { layer } = harness({
+    getSnapshot: async () => {
+      if (fail) throw new Error('ECCC HTTP 503');
+      return [reading('A', 2, { observedMs: Date.now() - 10 * 60_000 })];
+    },
+  });
+  await layer.update();
+  assert.equal(layerFeedState(layer.getStats()), 'nominal');
+  fail = true;
+  await layer.update();
+  const stats = layer.getStats();
+  assert.ok(stats.count > 0, 'the previous readings are still displayed');
+  assert.equal(
+    layerFeedState(stats),
+    'degraded',
+    'showing old data after a failure is degraded',
+  );
+});

src/layers/airQuality/source.js

@@ -0,0 +1,104 @@
+import { readResponseJsonCapped } from '../../sources/httpBody.js';
+import { normalizeAqhiStations, normalizeAqhiObservations } from './model.js';
+
+const COLLECTIONS_ROOT = 'https://api.weather.gc.ca/collections';
+const STATIONS_URL = `${COLLECTIONS_ROOT}/aqhi-stations/items`;
+const OBSERVATIONS_URL = `${COLLECTIONS_ROOT}/aqhi-observations-realtime/items`;
+
+/** Comfortably above Canada's ~134 stations without inviting a huge page. */
+const STATION_LIMIT = 500;
+const OBSERVATION_LIMIT = 500;
+/** Station geometry is near-static — a few changes a year. Refetch twice a day. */
+const STATION_TTL_MS = 12 * 60 * 60 * 1000;
+/** A full 500-row GeoJSON page is a few hundred KB; anything past this is not a page. */
+const MAX_RESPONSE_BYTES = 4 * 1024 * 1024;
+
+/**
+ * Request and validate a complete ECCC AQHI snapshot before it can replace
+ * displayed readings. The first registered air-quality provider.
+ *
+ * Two collections are involved. `aqhi-stations` is the catalog — it supplies
+ * every reading its coordinates and is cached for twelve hours because it
+ * barely changes. `aqhi-observations-realtime` is the hourly reading feed,
+ * requested with `latest=true` so the response is current values rather than
+ * the full observation history, which is roughly 2,000 rows nationally.
+ *
+ * The station catalog is only replaced when a refresh actually returns
+ * stations, so a transient empty response cannot blank the layer.
+ *
+ * @param {object} [options]
+ * @param {Function} [options.fetchImpl] - Injected fetch, for tests.
+ * @param {() => number} [options.now] - Clock seam, for tests.
+ * @param {number} [options.timeoutMs=15000] - Deadline for each request.
+ * @returns {{getSnapshot: Function}}
+ */
+export function createEcccAirQualitySource({
+  fetchImpl = (...args) => globalThis.fetch(...args),
+  now = () => Date.now(),
+  timeoutMs = 15_000,
+} = {}) {
+  /** @type {Map<string, object>} */
+  let stations = new Map();
+  let stationsFetchedAt = 0;
+
+  /** One bounded GeoJSON page: deadline, caller abort, byte cap, row cap. */
+  const getJson = async (url, limit, signal) => {
+    const controller = new AbortController();
+    const abort = () => controller.abort(signal.reason);
+    signal?.addEventListener('abort', abort, { once: true });
+    const timer = setTimeout(
+      () => controller.abort(new Error('ECCC request timed out')),
+      timeoutMs,
+    );
+    try {
+      signal?.throwIfAborted();
+      const response = await fetchImpl(url, {
+        headers: { Accept: 'application/json' },
+        signal: controller.signal,
+      });
+      if (!response.ok) throw new Error(`ECCC HTTP ${response.status}`);
+      const payload = await readResponseJsonCapped(
+        response,
+        MAX_RESPONSE_BYTES,
+        controller.signal,
+      );
+      // The server's `limit` is a request, not a guarantee.
+      if (Array.isArray(payload?.features) && payload.features.length > limit)
+        return { ...payload, features: payload.features.slice(0, limit) };
+      return payload;
+    } finally {
+      clearTimeout(timer);
+      signal?.removeEventListener('abort', abort);
+    }
+  };
+
+  return {
+    async getSnapshot({ signal } = {}) {
+      const clock = now();
+      if (stations.size === 0 || clock - stationsFetchedAt > STATION_TTL_MS) {
+        const payload = await getJson(
+          `${STATIONS_URL}?f=json&limit=${STATION_LIMIT}`,
+          STATION_LIMIT,
+          signal,
+        );
+        const next = normalizeAqhiStations(payload);
+        if (!next) throw new Error('Malformed AQHI station response');
+        // An empty refresh must not wipe a good catalog.
+        if (next.size > 0) {
+          stations = next;
+          stationsFetchedAt = clock;
+        }
+      }
+      if (stations.size === 0) throw new Error('No AQHI stations available');
+
+      const payload = await getJson(
+        `${OBSERVATIONS_URL}?f=json&latest=true&limit=${OBSERVATION_LIMIT}`,
+        OBSERVATION_LIMIT,
+        signal,
+      );
+      const readings = normalizeAqhiObservations(payload, stations, clock);
+      if (!readings) throw new Error('Malformed AQHI observation response');
+      return readings;
+    },
+  };
+}

src/layers/airQuality/source.test.mjs

@@ -0,0 +1,197 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { createEcccAirQualitySource } from './source.js';
+
+const NOW = Date.parse('2026-09-24T18:30:00Z');
+const HOUR = 60 * 60 * 1000;
+const station = (id) => ({
+  type: 'Feature',
+  geometry: { type: 'Point', coordinates: [-79.38, 43.65] },
+  properties: { location_id: id, location_name_en: id },
+});
+const observation = (id, at = NOW, aqhi = 3) => ({
+  type: 'Feature',
+  properties: {
+    location_id: id,
+    aqhi,
+    observation_datetime: new Date(at - 10 * 60_000).toISOString(),
+  },
+});
+const json = (body, init) =>
+  new Response(JSON.stringify(body), {
+    headers: { 'content-type': 'application/json' },
+    ...init,
+  });
+
+/** A fetch that serves the station catalog and observations from mutable state. */
+function feed() {
+  const state = {
+    clock: NOW,
+    stations: [station('A')],
+    stationIds: null,
+    urls: [],
+  };
+  state.source = createEcccAirQualitySource({
+    now: () => state.clock,
+    fetchImpl: async (url) => {
+      state.urls.push(url);
+      return json({
+        type: 'FeatureCollection',
+        // Every known station reports ten minutes before the current clock.
+        features: url.includes('aqhi-stations')
+          ? state.stations
+          : (state.stationIds || ['A']).map((id) =>
+              observation(id, state.clock),
+            ),
+      });
+    },
+  });
+  state.stationRequests = () =>
+    state.urls.filter((url) => url.includes('aqhi-stations')).length;
+  return state;
+}
+
+test('the station catalog is cached for twelve hours, then refetched', async () => {
+  const state = feed();
+  await state.source.getSnapshot();
+  state.clock = NOW + 12 * HOUR;
+  await state.source.getSnapshot();
+  assert.equal(state.stationRequests(), 1, 'within the TTL the cache serves');
+  state.clock = NOW + 12 * HOUR + 1;
+  await state.source.getSnapshot();
+  assert.equal(
+    state.stationRequests(),
+    2,
+    'past the TTL the catalog refreshes',
+  );
+});
+
+test('an empty catalog refresh keeps the previous catalog', async () => {
+  const state = feed();
+  await state.source.getSnapshot();
+  state.stations = [];
+  state.clock = NOW + 13 * HOUR;
+  const readings = await state.source.getSnapshot();
+  assert.deepEqual(
+    readings.map((reading) => reading.stationId),
+    ['A'],
+  );
+  // The empty refresh did not count as fresh, so the next call retries it.
+  await state.source.getSnapshot();
+  assert.equal(state.stationRequests(), 3);
+});
+
+test('an empty first catalog is an error, not an empty layer', async () => {
+  const state = feed();
+  state.stations = [];
+  await assert.rejects(state.source.getSnapshot(), /No AQHI stations/);
+});
+
+test('requests ask for JSON, the latest observations only, and a bounded page', async () => {
+  const state = feed();
+  await state.source.getSnapshot();
+  const [stations, observations] = state.urls.map((url) => new URL(url));
+  assert.equal(stations.pathname, '/collections/aqhi-stations/items');
+  assert.equal(stations.searchParams.get('f'), 'json');
+  assert.equal(stations.searchParams.get('limit'), '500');
+  assert.equal(
+    observations.pathname,
+    '/collections/aqhi-observations-realtime/items',
+  );
+  // Without latest=true the collection returns the full history (~2,000 rows).
+  assert.equal(observations.searchParams.get('latest'), 'true');
+  assert.equal(observations.searchParams.get('limit'), '500');
+});
+
+test('rows past the requested limit are ignored', async () => {
+  const state = feed();
+  state.stations = Array.from({ length: 600 }, (_, index) =>
+    station(`S${String(index).padStart(3, '0')}`),
+  );
+  state.stationIds = state.stations.map((row) => row.properties.location_id);
+  const readings = await state.source.getSnapshot();
+  assert.equal(readings.length, 500);
+});
+
+test('a malformed catalog and HTTP errors reject', async () => {
+  await assert.rejects(
+    createEcccAirQualitySource({
+      fetchImpl: async () => json({ features: 'no' }),
+    }).getSnapshot(),
+    /Malformed AQHI station/,
+  );
+  await assert.rejects(
+    createEcccAirQualitySource({
+      fetchImpl: async () => json({}, { status: 503 }),
+    }).getSnapshot(),
+    /ECCC HTTP 503/,
+  );
+});
+
+test('an oversized response is refused before it is parsed', async () => {
+  const big = 'x'.repeat(4 * 1024 * 1024 + 1);
+  await assert.rejects(
+    createEcccAirQualitySource({
+      fetchImpl: async () =>
+        new Response(new Blob([big]).stream(), {
+          headers: { 'content-type': 'application/json' },
+        }),
+    }).getSnapshot(),
+    (error) => error.code === 'RESPONSE_TOO_LARGE',
+  );
+  await assert.rejects(
+    createEcccAirQualitySource({
+      fetchImpl: async () =>
+        json({}, { headers: { 'content-length': String(5 * 1024 * 1024) } }),
+    }).getSnapshot(),
+    (error) => error.code === 'RESPONSE_TOO_LARGE',
+  );
+});
+
+test('a caller abort cancels the request and detaches its listener', async () => {
+  const caller = new AbortController();
+  let requestSignal = null;
+  const source = createEcccAirQualitySource({
+    fetchImpl: (_url, { signal }) => {
+      requestSignal = signal;
+      return new Promise((_resolve, reject) =>
+        signal.addEventListener('abort', () => reject(signal.reason), {
+          once: true,
+        }),
+      );
+    },
+  });
+  const pending = source.getSnapshot({ signal: caller.signal });
+  caller.abort(new Error('layer disabled'));
+  await assert.rejects(pending, /layer disabled/);
+  assert.equal(requestSignal.aborted, true);
+  const already = new AbortController();
+  already.abort(new Error('before start'));
+  let calls = 0;
+  await assert.rejects(
+    createEcccAirQualitySource({
+      fetchImpl: async () => {
+        calls += 1;
+        return json({ features: [] });
+      },
+    }).getSnapshot({ signal: already.signal }),
+    /before start/,
+  );
+  assert.equal(calls, 0);
+});
+
+test('a request that outlives its deadline is aborted', async (t) => {
+  t.mock.timers.enable({ apis: ['setTimeout'] });
+  const source = createEcccAirQualitySource({
+    timeoutMs: 1_000,
+    fetchImpl: (_url, { signal }) =>
+      new Promise((_resolve, reject) =>
+        signal.addEventListener('abort', () => reject(signal.reason), {
+          once: true,
+        }),
+      ),
+  });
+  const pending = source.getSnapshot();
+  t.mock.timers.tick(1_000);
+  await assert.rejects(pending, /ECCC request timed out/);
+});

src/layers/cyclones/index.js

@@ -437,6 +437,7 @@ export function createCyclonesLayer({
           })),
         },
         chips: [],
+        legendCategorical: true,
         legend: storm
           ? [
               {

src/overlays/worldOverlayAllocation.test.mjs

@@ -11,6 +11,7 @@ import { EARTHQUAKE_OVERLAY_COHORT_LIMIT } from '../data/earthquakes.js';
 import { ROCKET_MISSION_AMBIENT_OVERLAY_COHORT_LIMIT } from '../data/rocketLaunches.js';
 import { RADIO_OVERLAY_COHORT_LIMIT } from '../data/radio.js';
 import { CABLE_REFERENCE_LABEL_WINNER_CAP } from '../data/telegeographySubmarineCables.js';
+import { AIR_QUALITY_OVERLAY_COHORT_LIMIT } from '../layers/airQuality/model.js';
 import { isCalibratedAllocationRuntime } from '../../scripts/run-unit-tests.mjs';
 
 /**
@@ -34,6 +35,7 @@ import { isCalibratedAllocationRuntime } from '../../scripts/run-unit-tests.mjs'
  *   ---------------------+---------+------------+---------+----------------+-------------+-------------
  *   generic below cap    |      60 |         60 |      60 |           3182 |        53.0 |       4,100
  *   generic above cap    |     250 |        250 |      96 |          10022 |        40.1 |      13,000
+ *   air quality          |      48 |         48 |      32 |           3900 |        81.3 |       5,200
  *   local infrastructure |     320 |        320 |     192 |          39478 |       123.4 |      49,000
  *   Phase 3 + FIRMS      |     338 |        338 |     210 |          41220 |       122.0 |      53,600
  *   Phase 3 + vessels    |     451 |        451 |     311 |          67252 |       149.1 |      87,500
@@ -259,6 +261,23 @@ const WORKLOADS = [
     maxBytesPerFrame: 19_000,
     saturated: true,
   },
+  {
+    // The air-quality station cohort on its own. Measured standalone rather
+    // than stacked on the Phase-5 host (the submarine-cable precedent): these
+    // stations are sparse and, with the single registered provider,
+    // continental, so what matters is its own cohort cost.
+    //
+    // Re-measured against the current worker: median 3,900 B/frame, max 4,114,
+    // and 85.7 B/candidate at the ceiling — inside the shared 154 B/candidate
+    // bound, so no per-source exception is taken. The 5,200 frame budget
+    // carries 26.4% headroom over the measured maximum.
+    name: 'with the air-quality station cohort live',
+    profile: 'air-quality',
+    entries: AIR_QUALITY_OVERLAY_COHORT_LIMIT,
+    candidates: AIR_QUALITY_OVERLAY_COHORT_LIMIT,
+    maxBytesPerFrame: 5_200,
+    saturated: true,
+  },
   {
     name: 'with the Dense detection lane active over 5,000 observations',
     profile: 'phase6-detection',

src/overlays/worldOverlayAllocation.worker.mjs

@@ -26,6 +26,12 @@ import {
   TRACKED_OVERLAY_SOURCE_OPTIONS,
 } from '../data/trackedReadout.js';
 import { CCTV_AMBIENT_CARD_MAX } from '../data/cctvLod.js';
+import {
+  AIR_QUALITY_OVERLAY_COHORT_LIMIT,
+  AIR_QUALITY_OVERLAY_COLLISION_CAPACITY,
+  AIR_QUALITY_OVERLAY_SOURCE_ID,
+  createAirQualityOverlayEntry,
+} from '../layers/airQuality/model.js';
 import {
   CCTV_OVERLAY_SOURCE_ID,
   createCctvThumbnailOverlayEntry,
@@ -1110,6 +1116,69 @@ function buildSubmarineCablesWorkload(count) {
   );
 }
 
+/**
+ * The air-quality station cohort at full size.
+ *
+ * Measured standalone (the submarine-cable precedent) rather than stacked on
+ * the Phase-5 host: air-quality stations are sparse and, with the single
+ * currently-registered provider, continental — so the question a budget has to
+ * answer is what its own cohort costs, not what it adds to a worldwide worst
+ * case it never shares a viewport with. The entry shape is the same static
+ * `ambient-label` the earthquake layer publishes, so the per-candidate ceiling
+ * is the meaningful gate.
+ */
+function buildAirQualityWorkload(count) {
+  if (count !== AIR_QUALITY_OVERLAY_COHORT_LIMIT) {
+    throw new Error(
+      `air-quality requires ${AIR_QUALITY_OVERLAY_COHORT_LIMIT} entries`,
+    );
+  }
+  const workload = {
+    entries: [],
+    positions: [],
+    drifts: [],
+    registrations: [],
+  };
+  const columns = Math.max(1, Math.ceil(Math.sqrt((count * 16) / 9)));
+  const rows = Math.max(1, Math.ceil(count / columns));
+  const spanX = columns > 1 ? 1.68 / (columns - 1) : 0;
+  const spanY = rows > 1 ? 1.56 / (rows - 1) : 0;
+  const stations = [];
+  for (let index = 0; index < count; index++) {
+    const column = index % columns;
+    const row = Math.floor(index / columns);
+    const baseX = -0.84 + column * spanX;
+    const baseY = -0.78 + row * spanY;
+    const position = new Cesium.Cartesian3(baseX, baseY, 0);
+    workload.positions.push(position);
+    workload.drifts.push({
+      baseX,
+      baseY,
+      phase: index * 0.27,
+      rate: 0.32 + (index % 6) * 0.04,
+    });
+    const entry = createAirQualityOverlayEntry({
+      id: `air-${index}`,
+      position,
+      // i18n-ignore: synthetic allocation-benchmark fixture, not shown as UI
+      title: `Station ${index} ${1 + (index % 10)}`,
+      accent: '#4cc9f0',
+      value: 1 + (index % 10),
+    });
+    entry.horizonCull = false;
+    stations.push(entry);
+  }
+  workload.registrations.push({
+    sourceId: AIR_QUALITY_OVERLAY_SOURCE_ID,
+    entries: stations,
+    options: {
+      cohortLimit: AIR_QUALITY_OVERLAY_COHORT_LIMIT,
+      collisionCapacity: AIR_QUALITY_OVERLAY_COLLISION_CAPACITY,
+    },
+  });
+  return workload;
+}
+
 function buildPhase6DetectionWorkload(count) {
   const random = makeRandom(0xd37ec710);
   const positions = [];
@@ -1215,9 +1284,13 @@ function main() {
                                 ? buildPhase5RocketMissionWorkload(ENTRY_COUNT)
                                 : PROFILE === 'all-live-radio'
                                   ? buildAllLiveRadioWorkload(ENTRY_COUNT)
-                                  : PROFILE === 'submarine-cables'
-                                    ? buildSubmarineCablesWorkload(ENTRY_COUNT)
-                                    : buildWorkload(ENTRY_COUNT);
+                                  : PROFILE === 'air-quality'
+                                    ? buildAirQualityWorkload(ENTRY_COUNT)
+                                    : PROFILE === 'submarine-cables'
+                                      ? buildSubmarineCablesWorkload(
+                                          ENTRY_COUNT,
+                                        )
+                                      : buildWorkload(ENTRY_COUNT);
   const { entries, positions, drifts } = workload;
   const solveIntervalMs = Number(process.env.GEV_ALLOC_SOLVE_MS) || 125;
   const detectionActive = !!workload.detectionLayer;

src/sources/reference.js

@@ -1,4 +1,5 @@
 import { createUsgsEarthquakeSource } from '../layers/earthquakes/source.js';
+import { createEcccAirQualitySource } from '../layers/airQuality/source.js';
 import { createWfigsPerimeterSource } from '../layers/perimeters/source.js';
 import { createBundledCableSource } from '../layers/submarineCables/bundledSource.js';
 import { createAdsbGnssSource } from '../layers/gnss/source.js';
@@ -7,6 +8,7 @@ import { createAdsbGnssSource } from '../layers/gnss/source.js';
 export function createReferenceSources() {
   return {
     earthquakes: createUsgsEarthquakeSource(),
+    'air-quality': createEcccAirQualitySource(),
     'fire-perimeters': createWfigsPerimeterSource(),
     cables: createBundledCableSource(),
     'gnss-integrity': createAdsbGnssSource(),

src/sources/reference.test.mjs

@@ -14,15 +14,18 @@ test('reference factories retain compatibility without starting acquisition or s
   const second = createReferenceSources();
   assert.deepEqual(Object.keys(first), [
     'earthquakes',
+    'air-quality',
     'fire-perimeters',
     'cables',
     'gnss-integrity',
   ]);
   assert.notEqual(first.earthquakes, second.earthquakes);
+  assert.notEqual(first['air-quality'], second['air-quality']);
   assert.notEqual(first['fire-perimeters'], second['fire-perimeters']);
   assert.notEqual(first.cables, second.cables);
   assert.notEqual(first['gnss-integrity'], second['gnss-integrity']);
   assert.equal(typeof first.earthquakes.getSnapshot, 'function');
+  assert.equal(typeof first['air-quality'].getSnapshot, 'function');
   assert.equal(typeof first['fire-perimeters'].getSnapshot, 'function');
   assert.equal(typeof first.cables.fetch, 'function');
   assert.equal(typeof first['gnss-integrity'].getSnapshot, 'function');

src/ui/layerPanel.js

@@ -90,6 +90,7 @@ const PANEL_GROUPS = [
   {
     label: msg('Weather'),
     ids: [
+      'air-quality',
       'wind',
       'weather-radar',
       'weather-satellite',
@@ -569,6 +570,7 @@ export class LayerPanel {
               'weather-satellite',
               'weather-lightning',
               'weather-cyclones',
+              'air-quality',
             ].includes(layer.id),
         )
         .map((layer) => ({

src/ui/layerPanel.test.mjs

@@ -329,3 +329,31 @@ test('the unavailable chip may abbreviate, but its accessible name keeps the ful
   assert.equal(button.dataset.feedState, 'unavailable');
   assert.match(attrs.get('aria-label'), /^Active Fires: UNAVAILABLE\./);
 });
+
+test('the Weather readout receives enabled air-quality alongside weather layers', async () => {
+  const { LayerPanel } = await import('./layerPanel.js');
+  const layers = ['wind', 'air-quality', 'other'].map((id) => ({
+    id,
+    icon: '*',
+    enabled: true,
+  }));
+  layers.push({ id: 'weather-radar', icon: '*', enabled: false });
+  const panel = new LayerPanel({
+    getLayers: () => layers,
+    getRowControls: (id) => ({ readout: true, summary: { label: id } }),
+  });
+  let entries = null;
+  panel._weatherPanel = {
+    update: (next) => {
+      entries = next;
+    },
+  };
+  panel._refreshWeatherPanel();
+  assert.deepEqual(
+    entries.map(({ id, summary }) => [id, summary.label]),
+    [
+      ['wind', 'wind'],
+      ['air-quality', 'air-quality'],
+    ],
+  );
+});

src/ui/weatherPanel.js

@@ -11,8 +11,9 @@ const ORDER = [
   'weather-radar',
   'weather-satellite',
   'weather-lightning',
+  'air-quality',
 ];
-const OBSERVED = new Set(ORDER.slice(2));
+const OBSERVED = new Set(ORDER.slice(2, 5));
 const utc = (time) =>
   Number.isFinite(Date.parse(time))
     ? `${formatUtcDayMonth(time)} ${utcClock(time)}`
@@ -166,7 +167,10 @@ export function createWeatherPanel({
           ? t('LATEST · newest per product')
           : historyTime(state.target),
     });
-    const models = active.map(({ id, icon, summary, legend = [], list }) => {
+    const models = active.map((entry) => {
+      const { id, icon, summary, legend = [], list } = entry;
+      // Discrete classes (storm geometry, AQHI bands) list swatches, not a ramp.
+      const categorical = entry.legendCategorical === true;
       let detail = summary.detail;
       const product = state.products.find((item) => item.id === id);
       if (OBSERVED.has(id)) {
@@ -207,17 +211,15 @@ export function createWeatherPanel({
         id: 'legend',
         type: 'legend',
         legend: {
-          categorical: id === 'weather-cyclones',
+          categorical,
           colors: legend.map(({ color }) => color),
           labels: legend.map(({ label }) => label),
-          units: id === 'weather-cyclones' ? '' : summary.units,
+          units: categorical ? '' : summary.units,
           zeroIndex: legend.findIndex(({ label }) => label === '0'),
         },
       };
       const blocks = [
-        ...(id === 'weather-cyclones' && list?.items?.length
-          ? [{ id: 'storms', type: 'list', list }]
-          : []),
+        ...(list?.items?.length ? [{ id: 'list', type: 'list', list }] : []),
         { id: 'details', type: 'lines', lines },
         ...(legend.length ? [legendBlock] : []),
         ...(summary.settings?.length

src/ui/weatherPanel.test.mjs

@@ -3,6 +3,7 @@ import assert from 'node:assert/strict';
 import { setLocale } from '../i18n/index.js';
 import { createWeatherPanel } from './weatherPanel.js';
 import { railFixture } from './railTestFixture.mjs';
+import { createAirQualityLayer } from '../layers/airQuality/index.js';
 const ticks = ['2026-09-22T01:00:00Z', '2026-09-22T01:05:00Z'];
 const wind = {
   id: 'wind',
@@ -167,6 +168,7 @@ test('cyclone readout retains advisory, position, intensity, geometry, coverage,
         },
       ],
     },
+    legendCategorical: true,
     legend: [
       { label: 'Advisory center / forecast track', color: '#7fe6ed' },
       { label: 'Center-track uncertainty cone', color: '#7fe6ed44' },
@@ -411,7 +413,7 @@ test('cyclones lead, and observed history owns one bordered group with only acti
   assert.deepEqual(opened(f), ['weather-cyclones']);
   assert.equal(
     card(f, cyclone.id).children[1].children[0].dataset.blockId,
-    'storms',
+    'list',
   );
   view.update([wind, satellite]);
   assert.equal(group.children[1].textContent, 'Satellite clouds');
@@ -686,3 +688,68 @@ test('history time keeps the hour whatever the length of the localized date (K-6
     }
   }
 });
+
+
+test('air-quality readout renders its band legend, Canada coverage and worst-first list', async () => {
+  const observedMs = Date.now() - 10 * 60_000;
+  const reading = (stationId, value, band, name) => ({
+    id: `eccc:${stationId}`,
+    provider: 'eccc',
+    scale: 'AQHI',
+    value,
+    band,
+    stationId,
+    name,
+    zone: 'on',
+    lat: 43.65,
+    lon: -79.38,
+    observedMs,
+    color: '#4cc9f0',
+    label: String(value),
+    risk: `${band} risk`,
+    note: null,
+  });
+  const layer = createAirQualityLayer({
+    source: {
+      getSnapshot: async () => [
+        reading('B', 8, 'high', 'Hamilton'),
+        reading('A', 2, 'low', 'Toronto'),
+      ],
+    },
+    overlayHost: { setEntries() {}, setVisible() {}, clearSource() {} },
+  });
+  layer.init({ dataSources: { add() {}, remove() {} } });
+  layer.enable();
+  await layer.update();
+  const f = fixture();
+  const view = createWeatherPanel(f);
+  view.update([{ id: layer.id, icon: layer.icon, ...layer.getRowControls() }]);
+  const aq = card(f, 'air-quality');
+  assert.ok(aq, 'the air-quality card is shown');
+  assert.equal(aq.dataset.open, 'true');
+  assert.match(
+    f.find((n) => n.classList?.contains?.('rail-card-badge'), aq).textContent,
+    /Canada only/,
+  );
+  assert.match(line(f, 'air-quality', 'status').textContent, /2 stations/);
+  const entries = f.find((n) => n.className === 'rail-card-legend-entries', aq);
+  assert.equal(entries.hidden, false);
+  assert.deepEqual(
+    entries.children.map((entry) => entry.children[1].textContent),
+    ['Low', 'Moderate', 'High', 'Very High'],
+  );
+  assert.equal(
+    f.find((n) => n.className === 'rail-card-ramp', aq).hidden,
+    true,
+  );
+  const list = f.find((n) => n.dataset.blockId === 'list', aq);
+  assert.equal(list.hidden, false);
+  assert.deepEqual(
+    list.children.map((item) =>
+      item.children[0].children.map((part) => part.textContent).join(' '),
+    ),
+    ['AQHI 8 Hamilton · high risk', 'AQHI 2 Toronto · low risk'],
+  );
+  view.destroy();
+  layer.destroy();
+});

src/voice/actionSchemas.test.mjs

@@ -37,7 +37,8 @@ test('the complete Realtime tool payload pins the manifest-generated layer relea
     // omit top-level anyOf (OpenAI rejects it). Contacts list routing preserves
     // requested radius and center authority in descriptions only.
     // Street Level and GNSS extend the manifest; tracked and analyst aircraft describe broadcasts.
-    '9398815a573ab29ecc3ce527f6e1a2ad883804e7696e0444aebb11f973700d4b',
+    // Air quality (ECCC AQHI) extends the manifest.
+    '775ba323384b4c1b62fb8415bac52aecc3fc668e20bedcfa57e426dcd1da3969',
   );
 });
 

src/voice/layerManifest.js

@@ -250,6 +250,24 @@ const layers = [
     context: false,
     noQuery: 'map overlay; no countable records',
   },
+  {
+    id: 'air-quality',
+    aliases: ['air quality', 'aqhi', 'smog', 'air pollution'],
+    context: false,
+    query: {
+      fields: {
+        value: ['n', 'AQHI'],
+        band: ['t'],
+        scale: ['t'],
+        provider: ['t'],
+        name: ['t'],
+        zone: ['t'],
+        risk: ['t'],
+        observedMs: ['ms'],
+      },
+      timeField: 'observedMs',
+    },
+  },
   {
     id: 'traffic',
     aliases: ['street traffic', 'road traffic', 'congestion'],