fix(infrastructure): declutter stems and correct close-up sizing

src/data/localGeojson.js

@@ -10,6 +10,11 @@ import {
   setOverlayEntries,
   setOverlaySourceVisible,
 } from '../overlays/worldOverlay.js';
+import {
+  selectInfraLod,
+  applyInfraEvictionGrace,
+  shouldRecomputeInfraLod,
+} from './localGeojsonLod.js';
 
 const DEFAULT_LABEL_MAX = 900;
 const DEFAULT_LABEL_GRID_PX = 132;
@@ -305,6 +310,37 @@ export function createLocalGeoJsonLayer({
   let _stemGeometryDirty = true;
   let _lastVisibilityUpdate = 0;
   let _destroyed = false;
+  /**
+   * Globe-LOD active set: the record ids allowed to carry a live stem right
+   * now. This bounds geometry refreshes and ground-sample work to the
+   * camera-height budget in localGeojsonLod.js. Recomputed only
+   * when the camera moves (`_stemGeometryDirty`, raised by moveEnd and by the
+   * motion fallback below). Empty means "not computed yet" — the first
+   * post-enable walk fills it.
+   * @type {Set<string>}
+   */
+  let _activeLodIds = new Set();
+  /** Eviction-grace bookkeeping for `_activeLodIds` (id -> {misses, since}). */
+  let _lodGraceState = new Map();
+  /** Budget cap the most recent camera-height band produced (0 until computed). */
+  let _lastLodBudgetLimit = 0;
+  /**
+   * False until the first post-enable preRender walk has run the LOD
+   * selection. While false the walk treats every record as active (old
+   * behavior); once true, an EMPTY `_activeLodIds` legitimately means "nothing
+   * should carry a stem right now" (e.g. every feature occluded), not "not
+   * computed yet".
+   */
+  let _lodComputed = false;
+  /**
+   * Camera position the last LOD selection ran from — the reference the motion
+   * fallback measures travel against. Preallocated: the walk clones into it,
+   * so a moving camera allocates nothing per pass. Only meaningful while
+   * `_lodComputed` is true.
+   */
+  const _lastLodCameraPos = new Cesium.Cartesian3();
+  /** Last time the motion-fallback probe window opened (or a selection ran). */
+  let _lastLodProbeMs = Number.NEGATIVE_INFINITY;
   let _groundRetryTimer = null;
   /** Consecutive self-armed retries since the last grounding/camera motion. */
   let _groundRetryArms = 0;
@@ -355,6 +391,11 @@ export function createLocalGeoJsonLayer({
   const disableLayer = (viewer) => {
     _enabled = false;
     clearGroundRetryRender();
+    _activeLodIds = new Set();
+    _lodGraceState = new Map();
+    _lastLodBudgetLimit = 0;
+    _lodComputed = false;
+    _lastLodProbeMs = Number.NEGATIVE_INFINITY;
     if (_dataSource) _dataSource.show = false;
     _overlayPublisher.hide();
     clearSelectedEntityContextForLayer(id);
@@ -397,6 +438,21 @@ export function createLocalGeoJsonLayer({
       return { count: _count, lastUpdate: _lastUpdate, error: _error };
     },
 
+    /**
+     * Globe-LOD state for QA harnesses (scripts/qa-infra-lod.mjs) and tests.
+     * `active` is how many records currently carry a live stem; `total` is the
+     * full materialized set. `active < total` means the declutter is engaged.
+     * `budgetLimit` is the cap the last camera-height band produced; `computed`
+     * is false until the first post-enable walk has run the selection.
+     * @returns {{total:number, active:number, budgetLimit:number, computed:boolean}}
+     */
+    getLodDiagnostics: () => ({
+      total: _stemRecords.length,
+      active: _activeLodIds.size,
+      budgetLimit: _lastLodBudgetLimit,
+      computed: _lodComputed,
+    }),
+
     enable: async (viewer) => {
       if (_destroyed) return;
       _enabled = true;
@@ -404,6 +460,11 @@ export function createLocalGeoJsonLayer({
       _lastVisibilityUpdate = Number.NEGATIVE_INFINITY;
       _groundRetryArms = 0; // fresh give-up budget per enable-cycle
       _lastGroundSampleCapability = null;
+      _activeLodIds = new Set(); // fresh globe-LOD selection per enable-cycle
+      _lodGraceState = new Map();
+      _lastLodBudgetLimit = 0;
+      _lodComputed = false;
+      _lastLodProbeMs = Number.NEGATIVE_INFINITY;
       _overlayPublisher.show();
 
       // 1. Initialize data source
@@ -632,7 +693,29 @@ export function createLocalGeoJsonLayer({
 
           const cameraPos = viewer.camera.positionWC;
           if (!cameraPos) return;
-          
+
+          // --- Globe-LOD motion fallback. ---
+          // `_stemGeometryDirty` is otherwise raised only by moveEnd, which a
+          // tracked-entity follow, Cockpit, route flight, or continuous orbit
+          // never emits. Left alone the selection stays pinned to the region
+          // the camera left: the walk below hides those records one by one as
+          // they pass behind the globe and admits nothing newly visible, so
+          // the layer bleeds down to sparse-or-empty until motion stops.
+          // Bounded: rate-limited to a probe window, and only when the camera
+          // has actually travelled since the last selection.
+          if (!_stemGeometryDirty && _lodComputed && _stemRecords.length > 0) {
+            const probe = shouldRecomputeInfraLod({
+              nowMs: now,
+              lastProbeMs: _lastLodProbeMs,
+              movedSqM: Cesium.Cartesian3.distanceSquared(cameraPos, _lastLodCameraPos),
+              cameraHeightM: viewer.camera.positionCartographic?.height,
+            });
+            _lastLodProbeMs = probe.lastProbeMs;
+            // Re-selecting demands fresh stem geometry: a record admitted
+            // mid-motion has never had its tip sized for this camera.
+            if (probe.recompute) _stemGeometryDirty = true;
+          }
+
           const occluder = new Cesium.EllipsoidalOccluder(Cesium.Ellipsoid.WGS84, cameraPos);
           const visibleOverlayRecords = [];
           const refreshStemGeometry = _stemGeometryDirty;
@@ -649,8 +732,62 @@ export function createLocalGeoJsonLayer({
           _lastGroundSampleCapability = canSampleGround;
           let groundRetryPending = false;
           let groundSampleProgress = false;
+
+          // --- Globe-LOD: recompute the active-stem set on camera moves. ---
+          // `_stemGeometryDirty` is set by moveEnd, the first enable, and the
+          // motion fallback above — exactly when the camera-height budget and
+          // per-record distances can have changed. Without this, all local
+          // infrastructure features run stem trig + Cesium property writes on
+          // every move; with it, only the ~80 (global) to ~420 (regional)
+          // budgeted records do.
+          // The occluder test is the same cheap dot product used below.
+          if (refreshStemGeometry && _stemRecords.length > 0) {
+            const cameraHeightM = viewer.camera.positionCartographic?.height;
+            const candidates = new Array(_stemRecords.length);
+            for (let i = 0; i < _stemRecords.length; i++) {
+              const record = _stemRecords[i];
+              candidates[i] = {
+                id: record.id,
+                priority: record.priority,
+                distanceM: Cesium.Cartesian3.distance(cameraPos, record.base),
+                inView: occluder.isPointVisible(record.base),
+              };
+            }
+            const selection = selectInfraLod(candidates, {
+              cameraHeightM,
+              incumbentIds: _activeLodIds,
+            });
+            const grace = applyInfraEvictionGrace({
+              selectedIds: selection.activeIds,
+              builtIds: [..._activeLodIds],
+              graceState: _lodGraceState,
+              nowMs: now,
+              activeLimit: selection.budget.activeLimit,
+            });
+            _activeLodIds = new Set(grace.keepIds);
+            _lodGraceState = grace.graceState;
+            _lastLodBudgetLimit = selection.budget.activeLimit;
+            _lodComputed = true;
+            // Adopt this pass as the motion-fallback reference. Travel is
+            // measured from the last SELECTION, never the previous walk, so
+            // jitter around a parked camera never accumulates into a
+            // recompute while genuine slow travel eventually does.
+            Cesium.Cartesian3.clone(cameraPos, _lastLodCameraPos);
+            _lastLodProbeMs = now;
+          }
+
           for (let i = 0; i < _stemRecords.length; i++) {
             const record = _stemRecords[i];
+            const isActive = !_lodComputed || _activeLodIds.has(record.id);
+            const isVisible = isActive && occluder.isPointVisible(record.base);
+            if (record.entity.show !== isVisible) record.entity.show = isVisible;
+
+            // Records outside the globe-LOD active set carry no visible stem,
+            // so skip every per-frame cost for them — geometry trig, the
+            // ground-sample GPU readback, overlay-label candidacy. They rejoin
+            // on the next camera move if the budget has room.
+            if (!isActive) continue;
+
             const wasGroundSampled = record.groundSampled;
             if (refreshStemGeometry) {
               updateLocalStemGeometry(viewer, record, now);
@@ -678,8 +815,6 @@ export function createLocalGeoJsonLayer({
                 < GROUND_SAMPLE_MAX_DISTANCE_M) {
               groundRetryPending = true;
             }
-            const isVisible = occluder.isPointVisible(record.base);
-            if (record.entity.show !== isVisible) record.entity.show = isVisible;
             if (isVisible && record.entry) visibleOverlayRecords.push(record);
           }
           _stemGeometryDirty = false;
@@ -787,7 +922,9 @@ function updateLocalStemGeometry(viewer, record, now, knownDistance = null) {
     ? knownDistance
     : Cesium.Cartesian3.distance(viewer.camera.positionWC, record.base);
   if (distance < GROUND_SAMPLE_MAX_DISTANCE_M) sampleLocalGroundHeight(viewer, record, now);
-  const effectiveDistance = Math.max(distance, 5000);
+  // Keep the intended screen-size scaling in close-up views too. A 5 km
+  // minimum made a marker hundreds of metres tall beside a nearby building.
+  const effectiveDistance = Math.max(distance, 1);
   const canvasHeight = viewer.scene.canvas.clientHeight || 1080;
   const fov = viewer.camera.frustum.fov || (Math.PI / 3);
   const targetPx = 65;

src/data/localGeojson.test.mjs

@@ -14,6 +14,7 @@ import {
   selectLocalInfrastructureOverlayCohort,
 } from './localGeojson.js';
 import { layerFeedState } from './manager.js';
+import { INFRA_LOD_ACTIVE_MIN, INFRA_LOD_ACTIVE_MAX } from './localGeojsonLod.js';
 import {
   installRenderGovernor,
   getRenderGovernorDiagnostics,
@@ -445,6 +446,21 @@ test('a real enabled local layer has no native label graphics at runtime', async
   env.cleanup();
 });
 
+for (const [heightM, minStemM, maxStemM] of [[500, 45, 90], [10000, 1100, 1400]]) {
+  test(`local infrastructure keeps stems proportional at ${heightM} m`, async (t) => {
+    const env = await createRealLocalLayerHarness();
+    t.after(() => { env.layer.destroy(env.viewer); env.cleanup(); });
+    const entity = env.dataSources[0].entities.values[0];
+    const carto = entity.__localBaseCarto;
+    env.viewer.camera.positionWC = Cesium.Cartesian3.fromRadians(carto.longitude, carto.latitude, heightM);
+    env.preRender.raise(env.viewer.scene, Cesium.JulianDate.now());
+    const positions = entity.polyline.positions.getValue(Cesium.JulianDate.now());
+    const stemM = Cesium.Cartesian3.distance(positions[0], positions[1]);
+    assert.ok(stemM >= minStemM && stemM <= maxStemM,
+      `a ${heightM} m close-up must not inherit a globe-sized stem: ${stemM.toFixed(1)} m`);
+  });
+}
+
 test('local infrastructure creates no native labels or per-frame geometry callbacks', () => {
   const source = readFileSync(new URL('./localGeojson.js', import.meta.url), 'utf8');
   assert.doesNotMatch(source, /new Cesium\.LabelGraphics/);
@@ -963,3 +979,260 @@ test('after the cap a camera-motion frame still samples, and re-opens the budget
     'a grounded record asks for no further frames',
   );
 });
+
+// ── Globe-LOD: bound the active-stem set by camera height ────────────────────
+//
+// createLocalGeoJsonLayer used to give every feature a live stem and walk all
+// of them (geometry trig + Cesium property writes) on every camera move. With
+// three bundled-infra layers that is ~5,700 records on a full-earth view — the
+// frame-rate cliff that got the INFRASTRUCTURE first-run tile cut. The walk
+// now asks src/data/localGeojsonLod.js which records may carry a stem, sized to
+// the camera-height budget, and skips all per-frame cost for the rest.
+
+/**
+ * Harness with N in-view point features and a controllable camera height.
+ * Even-indexed features are named (high label priority), odd ones anonymous.
+ */
+async function createMultiFeatureLodHarness({ featureCount = 150, cameraHeightM = 9_000_000 } = {}) {
+  const originalFetch = globalThis.fetch;
+  const originalWindow = globalThis.window;
+  const preRender = new MockLayerEvent();
+  const moveEnd = new MockLayerEvent();
+  const dataSources = [];
+  const centerLon = -97.7;
+  const centerLat = 30.2;
+  // Polygons, not Points: Cesium's GeoJsonDataSource builds a PinBuilder
+  // billboard for a Point, which needs a DOM canvas the node test env lacks.
+  // The layer takes the polygon's bounding-sphere centre as the stem anchor.
+  const lines = Array.from({ length: featureCount }, (_, i) => {
+    const lon = centerLon + (i % 12) * 0.02;
+    const lat = centerLat + Math.floor(i / 12) * 0.02;
+    return JSON.stringify({
+      type: 'Feature',
+      id: `dc-${i}`,
+      properties: i % 2 === 0
+        ? { name: `Datacenter ${i}`, tags: { name: `Datacenter ${i}`, operator: 'Example Cloud' } }
+        : { tags: {} },
+      geometry: {
+        type: 'Polygon',
+        coordinates: [[
+          [lon, lat],
+          [lon + 0.004, lat],
+          [lon + 0.004, lat + 0.004],
+          [lon, lat],
+        ]],
+      },
+    });
+  });
+  globalThis.fetch = async () => ({ ok: true, status: 200, text: async () => lines.join('\n') });
+  globalThis.window = { dispatchEvent() {} };
+
+  const setPos = (m) => {
+    const p = Cesium.Cartesian3.fromDegrees(centerLon, centerLat, m);
+    viewer.camera.positionWC = p;
+    viewer.camera.positionCartographic = Cesium.Cartographic.fromCartesian(p);
+  };
+  const viewer = {
+    selectedEntity: undefined,
+    dataSources: {
+      add(ds) { dataSources.push(ds); return ds; },
+      remove(ds) {
+        const i = dataSources.indexOf(ds);
+        if (i >= 0) dataSources.splice(i, 1);
+        return i >= 0;
+      },
+    },
+    camera: {
+      positionWC: null,
+      positionCartographic: null,
+      frustum: { fov: Math.PI / 3 },
+      moveEnd,
+      flyTo() {},
+    },
+    scene: {
+      canvas: { clientWidth: 1440, clientHeight: 900 },
+      preRender,
+      sampleHeightSupported: false,
+      screenSpaceCameraController: { enableInputs: true },
+      pick() { return null; },
+      requestRender() {},
+    },
+  };
+  setPos(cameraHeightM);
+  const layer = createLocalGeoJsonLayer({
+    id: 'local-datacenters',
+    url: '/lod-fixture.geojsonl',
+    name: 'LOD Datacenters',
+    color: '#00ffff',
+    overlayHost: { setVisible() {}, setEntries() {}, clearSource() {} },
+    projectToWindow: () => ({ x: 700, y: 450 }),
+    screenSpaceEventHandlerFactory: () => ({ setInputAction() {}, destroy() {} }),
+  });
+  try {
+    await layer.enable(viewer);
+  } finally {
+    globalThis.fetch = originalFetch;
+  }
+  return {
+    layer,
+    viewer,
+    dataSources,
+    preRender,
+    moveEnd,
+    setCameraHeight: setPos,
+    shownCount() {
+      return dataSources[0].entities.values.filter((entity) => entity.show === true).length;
+    },
+    cleanup() {
+      if (originalWindow === undefined) delete globalThis.window;
+      else globalThis.window = originalWindow;
+    },
+  };
+}
+
+test('globe-LOD caps live stems at the camera-height budget and widens as you zoom in', async (t) => {
+  const env = await createMultiFeatureLodHarness({ featureCount: 150, cameraHeightM: 9_000_000 });
+  const clock = installFakeClock(t);
+  t.after(() => {
+    env.layer.destroy(env.viewer);
+    env.cleanup();
+  });
+
+  // Full-earth framing: 150 in-view features, but the global band allows 80.
+  env.preRender.raise();
+  assert.equal(env.dataSources[0].entities.values.length, 150, 'all features are materialized');
+  assert.equal(env.shownCount(), INFRA_LOD_ACTIVE_MIN, 'only the global-band budget carries a stem');
+
+  // Named features (label priority ~1240) outrank anonymous nodes (~60), so
+  // every one of the 75 named features keeps a stem; the 5 remaining budget
+  // slots go to unnamed ones.
+  const shownIds = new Set(
+    env.dataSources[0].entities.values.filter((entity) => entity.show === true).map((entity) => entity.id),
+  );
+  const namedIds = Array.from({ length: 150 }, (_, i) => i).filter((i) => i % 2 === 0).map((i) => `dc-${i}`);
+  assert.ok(namedIds.every((id) => shownIds.has(id)), 'every named feature wins a stem before any unnamed one');
+
+  // Zoom to continental framing: the budget opens to MID (200), so all 150
+  // in-view features now get a stem.
+  env.setCameraHeight(1_000_000);
+  env.moveEnd.raise();
+  clock.advance(500); // clear the 450 ms visibility gate
+  env.preRender.raise();
+  assert.equal(env.shownCount(), 150, 'a closer camera lifts the cap above the in-view count');
+});
+
+test('globe-LOD selection is stable between camera moves (no per-frame churn)', async (t) => {
+  const env = await createMultiFeatureLodHarness({ featureCount: 150, cameraHeightM: 9_000_000 });
+  const clock = installFakeClock(t);
+  t.after(() => {
+    env.layer.destroy(env.viewer);
+    env.cleanup();
+  });
+
+  env.preRender.raise();
+  const firstSet = env.dataSources[0].entities.values
+    .filter((entity) => entity.show === true)
+    .map((entity) => entity.id)
+    .sort();
+  assert.equal(firstSet.length, INFRA_LOD_ACTIVE_MIN);
+
+  // A second walk with no intervening moveEnd must not re-select.
+  clock.advance(500);
+  env.preRender.raise();
+  const secondSet = env.dataSources[0].entities.values
+    .filter((entity) => entity.show === true)
+    .map((entity) => entity.id)
+    .sort();
+  assert.deepEqual(secondSet, firstSet, 'the active set only changes on camera moves');
+});
+
+test('getLodDiagnostics reports the active/total split and the band budget', async (t) => {
+  const env = await createMultiFeatureLodHarness({ featureCount: 150, cameraHeightM: 9_000_000 });
+  const clock = installFakeClock(t);
+  t.after(() => {
+    env.layer.destroy(env.viewer);
+    env.cleanup();
+  });
+
+  assert.deepEqual(env.layer.getLodDiagnostics(), {
+    total: 150, active: 0, budgetLimit: 0, computed: false,
+  }, 'before the first walk: materialized but not yet selected');
+
+  env.preRender.raise();
+  const global = env.layer.getLodDiagnostics();
+  assert.equal(global.total, 150);
+  assert.equal(global.active, INFRA_LOD_ACTIVE_MIN);
+  assert.equal(global.budgetLimit, INFRA_LOD_ACTIVE_MIN);
+  assert.equal(global.computed, true);
+  assert.ok(global.active < global.total, 'active < total means the declutter is engaged');
+
+  env.setCameraHeight(60_000);
+  env.moveEnd.raise();
+  clock.advance(500);
+  env.preRender.raise();
+  const regional = env.layer.getLodDiagnostics();
+  assert.equal(regional.active, 150, 'regional band lifts the cap above the in-view count');
+  assert.ok(regional.budgetLimit >= 150, `regional budget widened (${regional.budgetLimit})`);
+});
+
+test('globe-LOD releases every stem when the layer is disabled', async (t) => {
+  const env = await createMultiFeatureLodHarness({ featureCount: 40, cameraHeightM: 9_000_000 });
+  t.after(() => {
+    env.layer.destroy(env.viewer);
+    env.cleanup();
+  });
+
+  env.preRender.raise();
+  assert.equal(env.shownCount(), 40, 'under-budget: all 40 show');
+
+  env.layer.disable(env.viewer);
+  // The data source is hidden wholesale on disable; re-enabling starts from a
+  // fresh (empty) LOD selection rather than inheriting the old active set.
+  await env.layer.enable(env.viewer);
+  env.preRender.raise();
+  assert.equal(env.shownCount(), 40, 're-enable rebuilds the selection cleanly');
+});
+
+test('globe-LOD re-selects during continuous motion, without ever seeing a moveEnd', async (t) => {
+  // A tracked-entity follow, Cockpit view, route flight, or continuous orbit
+  // moves the camera indefinitely without emitting moveEnd. Before the motion
+  // fallback the active set stayed pinned to the region the camera left, and
+  // the walk hid those records as they passed behind the globe while admitting
+  // nothing newly visible — the layer bled down to sparse-or-empty until the
+  // motion stopped.
+  const env = await createMultiFeatureLodHarness({ featureCount: 150, cameraHeightM: 9_000_000 });
+  const clock = installFakeClock(t);
+  t.after(() => {
+    env.layer.destroy(env.viewer);
+    env.cleanup();
+  });
+
+  env.preRender.raise();
+  assert.equal(env.layer.getLodDiagnostics().budgetLimit, INFRA_LOD_ACTIVE_MIN);
+  assert.equal(env.shownCount(), INFRA_LOD_ACTIVE_MIN, 'global band caps the first selection');
+
+  // The camera travels; NO moveEnd is raised, here or anywhere below.
+  env.setCameraHeight(60_000);
+
+  // Inside the probe window the selection deliberately stays put: the fallback
+  // is rate-limited so continuous motion cannot recompute on every walk.
+  clock.advance(500); // > the 450 ms visibility gate, < the 1 s probe window
+  env.preRender.raise();
+  assert.equal(env.layer.getLodDiagnostics().budgetLimit, INFRA_LOD_ACTIVE_MIN,
+    'the probe window rate-limits the recompute');
+
+  // Past the window, the travelled camera re-selects on its own.
+  clock.advance(600);
+  env.preRender.raise();
+  const moved = env.layer.getLodDiagnostics();
+  assert.equal(moved.budgetLimit, INFRA_LOD_ACTIVE_MAX, 'the new camera height re-banded the budget');
+  assert.equal(moved.active, 150, 'every in-view record is admitted again');
+  assert.equal(env.shownCount(), 150, 'and actually carries a stem');
+
+  // A parked camera past the same window costs nothing: travel is measured
+  // from the last selection, so there is none to report.
+  const parked = env.layer.getLodDiagnostics();
+  clock.advance(2_000);
+  env.preRender.raise();
+  assert.deepEqual(env.layer.getLodDiagnostics(), parked, 'a parked camera never re-selects');
+});

src/data/localGeojsonLod.js

@@ -0,0 +1,369 @@
+// src/data/localGeojsonLod.js
+/**
+ * @module localGeojsonLod
+ *
+ * Pure selection policy for the bundled local-infrastructure layers
+ * (`local-datacenters`, `local-dams`, and any future `createLocalGeoJsonLayer`
+ * dataset). Cesium-specific projection, occlusion, and stem geometry stay in
+ * `localGeojson.js`; this module turns the resulting in-view records into a
+ * bounded "active" set — the only records that layer should spend per-frame
+ * stem-geometry and ground-sample work on.
+ *
+ * The screen-space label overlay is already decluttered
+ * (LOCAL_OVERLAY_COHORT_LIMIT); this also bounds world-space stems and their
+ * geometry/ground-sampling work. It does not reduce the number of materialized
+ * entities. Submarine cables use their own renderer and are not changed here.
+ * Performance must be measured against the current renderer, not inferred
+ * from the number of hidden stems.
+ *
+ * Sense is INVERTED relative to `cctvLod.js`: a CCTV metro view earns MORE
+ * cards, but a zoomed-out infrastructure view must show FEWER stems — that is
+ * exactly the view where every feature piles onto the screen at once. Zoom in
+ * and the in-view count falls naturally, so the budget opens back up.
+ *
+ * The engine keeps three concerns, all pure and individually testable:
+ *   - BUDGET: camera height → how many stems may be active.
+ *   - RANK: importance (the existing label-priority score) blended with a
+ *     bounded proximity penalty, plus an incumbency bonus so the active set
+ *     does not batch-swap on small camera moves.
+ *   - EVICTION GRACE: a hysteresis planner (ported from cctvLod) so a stem at
+ *     the budget edge does not blink in and out while the camera orbits.
+ */
+
+/* ------------------------------------------------------------------ *
+ * BUDGET
+ * ------------------------------------------------------------------ */
+
+/** Active-stem budget at full-earth / global framing — the hot case. */
+export const INFRA_LOD_ACTIVE_MIN = 80;
+/** Active-stem budget at continental framing. */
+export const INFRA_LOD_ACTIVE_MID = 200;
+/** Active-stem budget at regional framing and closer (effectively "all in view"). */
+export const INFRA_LOD_ACTIVE_MAX = 420;
+
+/** At or above this camera height (m) the view is global: clamp hardest. */
+export const INFRA_LOD_GLOBAL_HEIGHT_M = 3_000_000;
+/** At or above this camera height (m) the view is continental. */
+export const INFRA_LOD_REGIONAL_HEIGHT_M = 200_000;
+
+/**
+ * Bounded active-stem budget for the current camera height. Non-finite input
+ * resolves to the GLOBAL band (fewest stems) — the safe default for a value we
+ * could not read is the cheapest one, not the most expensive.
+ *
+ * @param {number} cameraHeightM
+ * @returns {{activeLimit:number}}
+ */
+export function infraLodBudget(cameraHeightM) {
+  const height = Number.isFinite(cameraHeightM)
+    ? Math.max(0, cameraHeightM)
+    : INFRA_LOD_GLOBAL_HEIGHT_M;
+  if (height >= INFRA_LOD_GLOBAL_HEIGHT_M) return { activeLimit: INFRA_LOD_ACTIVE_MIN };
+  if (height >= INFRA_LOD_REGIONAL_HEIGHT_M) return { activeLimit: INFRA_LOD_ACTIVE_MID };
+  return { activeLimit: INFRA_LOD_ACTIVE_MAX };
+}
+
+/* ------------------------------------------------------------------ *
+ * RANK
+ * ------------------------------------------------------------------ */
+
+/**
+ * Priority points added for a record that currently holds an active stem, so a
+ * non-incumbent displaces it only when meaningfully better — not on sub-pixel
+ * camera jitter. Deliberately smaller than the label-priority "has a name"
+ * gap (≥700 in labelPriorityFromProperties), so incumbency reorders WITHIN a
+ * tier but never keeps an unnamed stem alive over a fresh named feature.
+ */
+export const INFRA_LOD_INCUMBENT_BONUS = 250;
+
+/**
+ * Distance at or beyond which the proximity penalty is fully applied (m).
+ * Matches LOCAL_OVERLAY_MAX_DISTANCE_M's order of magnitude in localGeojson.js.
+ */
+export const INFRA_LOD_FAR_M = 12_000_000;
+
+/**
+ * Maximum priority points subtracted for distance. Capped well below the
+ * label-priority name gap on purpose: proximity breaks ties among
+ * similarly-important features (show the near named dam before the far named
+ * dam) but can never promote an unnamed node over a named one.
+ */
+export const INFRA_LOD_MAX_DISTANCE_PENALTY = 200;
+
+/**
+ * Keep-score for one record. Higher wins. Pure; no clamping of the result
+ * (callers only compare it), but every input is normalized so the output is
+ * always a finite number.
+ *
+ * @param {number} priority Existing label-priority score (localGeojson.js).
+ * @param {number} distanceM Camera→feature distance in metres.
+ * @param {boolean} isIncumbent Record currently holds an active stem.
+ * @param {object} [options]
+ * @param {number} [options.incumbentBonus]
+ * @param {number} [options.farM]
+ * @param {number} [options.maxDistancePenalty]
+ * @returns {number}
+ */
+export function infraRankScore(priority, distanceM, isIncumbent, {
+  incumbentBonus = INFRA_LOD_INCUMBENT_BONUS,
+  farM = INFRA_LOD_FAR_M,
+  maxDistancePenalty = INFRA_LOD_MAX_DISTANCE_PENALTY,
+} = {}) {
+  const p = Number.isFinite(priority) ? priority : 0;
+  const far = Number.isFinite(farM) && farM > 0 ? farM : INFRA_LOD_FAR_M;
+  const d = Number.isFinite(distanceM) && distanceM >= 0 ? distanceM : far;
+  const penaltyCap = Number.isFinite(maxDistancePenalty) && maxDistancePenalty >= 0
+    ? maxDistancePenalty
+    : INFRA_LOD_MAX_DISTANCE_PENALTY;
+  const bonus = isIncumbent && Number.isFinite(incumbentBonus) ? incumbentBonus : 0;
+  return p + bonus - penaltyCap * Math.min(1, d / far);
+}
+
+/** Infinity-safe distance for a total sort order. */
+function sortableDistance(distanceM) {
+  return Number.isFinite(distanceM) && distanceM >= 0 ? distanceM : Number.MAX_VALUE;
+}
+
+/**
+ * Select the active-stem set from already projected in-view candidates.
+ *
+ * A candidate is `{ id, priority, distanceM, inView }`. Only `inView === true`
+ * candidates are eligible — the caller runs the (cheap) ellipsoidal-occluder
+ * test for every record and hands the result here; this module then decides
+ * which of those get the (expensive) stem geometry + ground-sample work.
+ *
+ * Ranking: `infraRankScore` descending, then nearer first, then id — a total
+ * order, so an under-budget cut is deterministic. Duplicate ids collapse to
+ * their best-scoring representative before the cut.
+ *
+ * @param {Array<{id:string,priority?:number,distanceM?:number,inView?:boolean}>} candidates
+ * @param {object} [options]
+ * @param {number} [options.cameraHeightM]
+ * @param {Iterable<string>|Set<string>} [options.incumbentIds] Ids that currently hold an active stem.
+ * @returns {{activeIds:string[], budget:{activeLimit:number}}}
+ */
+export function selectInfraLod(candidates, { cameraHeightM, incumbentIds } = {}) {
+  const budget = infraLodBudget(cameraHeightM);
+  const incumbents = incumbentIds instanceof Set ? incumbentIds : new Set(incumbentIds || []);
+
+  const byId = new Map();
+  for (const candidate of Array.isArray(candidates) ? candidates : []) {
+    if (!candidate || typeof candidate.id !== 'string' || !candidate.id) continue;
+    if (candidate.inView !== true) continue;
+    const distanceM = Number.isFinite(candidate.distanceM) && candidate.distanceM >= 0
+      ? candidate.distanceM
+      : Number.POSITIVE_INFINITY;
+    const normalized = {
+      id: candidate.id,
+      distanceM,
+      score: infraRankScore(candidate.priority, candidate.distanceM, incumbents.has(candidate.id)),
+    };
+    const current = byId.get(normalized.id);
+    if (!current
+      || normalized.score > current.score
+      || (normalized.score === current.score && normalized.distanceM < current.distanceM)) {
+      byId.set(normalized.id, normalized);
+    }
+  }
+
+  const ranked = [...byId.values()].sort((a, b) => (
+    b.score - a.score
+    || sortableDistance(a.distanceM) - sortableDistance(b.distanceM)
+    || a.id.localeCompare(b.id)
+  ));
+
+  return {
+    activeIds: ranked.slice(0, budget.activeLimit).map((entry) => entry.id),
+    budget,
+  };
+}
+
+/* ------------------------------------------------------------------ *
+ * EVICTION GRACE
+ * ------------------------------------------------------------------ */
+
+export const INFRA_LOD_GRACE_PASSES = 2;
+export const INFRA_LOD_GRACE_MS = 4_000;
+
+/**
+ * Eviction-grace hysteresis for the active-stem set. Ported from
+ * cctvLod.applyEvictionGrace — same algorithm, infra-tuned constants.
+ *
+ * Raw per-pass selection has no memory: a stem sitting at the budget edge
+ * churns in and out on every small camera move. This planner keeps an
+ * already-built stem alive for a short grace window after it falls out of the
+ * selection — dropped only once it STAYS unselected for `gracePasses`
+ * consecutive passes or `graceMs` of wall time, whichever comes first. A newly
+ * selected record enters immediately; the hard `activeLimit` cap is never
+ * exceeded (grace-period stems are evicted first under cap pressure,
+ * oldest-in-grace first).
+ *
+ * Pure: `graceState` is never mutated; the returned `graceState` replaces it.
+ *
+ * @param {object} [input]
+ * @param {string[]} [input.selectedIds] This pass's selection (already capped).
+ * @param {string[]} [input.builtIds] Ids that currently have a live stem.
+ * @param {Map<string,{misses:number,since:number}>} [input.graceState]
+ * @param {number} [input.nowMs]
+ * @param {number} [input.activeLimit] Hard cap on total kept stems.
+ * @param {number} [input.gracePasses]
+ * @param {number} [input.graceMs]
+ * @returns {{keepIds:string[], evictIds:string[], graceState:Map<string,{misses:number,since:number}>}}
+ */
+export function applyInfraEvictionGrace({
+  selectedIds = [],
+  builtIds = [],
+  graceState = new Map(),
+  nowMs = 0,
+  activeLimit = INFRA_LOD_ACTIVE_MAX,
+  gracePasses = INFRA_LOD_GRACE_PASSES,
+  graceMs = INFRA_LOD_GRACE_MS,
+} = {}) {
+  const selectedSet = new Set(
+    (Array.isArray(selectedIds) ? selectedIds : []).filter((id) => typeof id === 'string' && id),
+  );
+  const keepIds = [...selectedSet];
+  const evictIds = [];
+  const nextGrace = new Map();
+
+  const graced = [];
+  for (const id of Array.isArray(builtIds) ? builtIds : []) {
+    if (typeof id !== 'string' || !id || selectedSet.has(id)) continue;
+    const prior = graceState instanceof Map ? graceState.get(id) : undefined;
+    const misses = (prior?.misses || 0) + 1;
+    const since = Number.isFinite(prior?.since) ? prior.since : nowMs;
+    if (misses > gracePasses || nowMs - since >= graceMs) {
+      evictIds.push(id);
+    } else {
+      graced.push({ id, misses, since });
+    }
+  }
+
+  // Under cap pressure, grace-period stems go first: oldest-in-grace first
+  // (longest chance to return), then more misses, then id for determinism.
+  graced.sort((a, b) => a.since - b.since || b.misses - a.misses || a.id.localeCompare(b.id));
+  const cap = Number.isFinite(activeLimit) ? Math.max(0, Math.floor(activeLimit)) : INFRA_LOD_ACTIVE_MAX;
+  const capacity = Math.max(0, cap - keepIds.length);
+  const overflow = Math.max(0, graced.length - capacity);
+  for (let i = 0; i < graced.length; i++) {
+    if (i < overflow) {
+      evictIds.push(graced[i].id);
+      continue;
+    }
+    keepIds.push(graced[i].id);
+    nextGrace.set(graced[i].id, { misses: graced[i].misses, since: graced[i].since });
+  }
+
+  return { keepIds, evictIds, graceState: nextGrace };
+}
+
+/* ------------------------------------------------------------------ *
+ * MOTION FALLBACK
+ * ------------------------------------------------------------------ */
+
+/**
+ * Probe window for the motion fallback. `localGeojson.js` marks its selection
+ * dirty on `moveEnd`, which covers drags, one-shot `setView`, and voice
+ * `flyTo` — but a tracked-entity follow camera, a Cockpit view, a route
+ * flight, or a continuous orbit never emits one. Without a fallback the
+ * active set stays pinned to the region the camera left: the walk hides those
+ * records one by one as they rotate behind the globe and admits nothing newly
+ * visible, so the layer bleeds down to sparse-or-empty until motion stops.
+ *
+ * The fallback therefore samples camera travel at most this often. Shorter
+ * than the cable layer's 2 s window because the walk that consumes it already
+ * runs on a 450 ms cadence and the work it re-triggers is bounded by the
+ * budget above; longer than that cadence so continuous motion recomputes on a
+ * fixed clock rather than on every walk.
+ */
+export const INFRA_LOD_MOTION_PROBE_INTERVAL_MS = 1_000;
+
+/**
+ * Camera travel that counts as material motion, as a fraction of camera
+ * height. Scale-relative rather than absolute because the selection is a
+ * function of what the globe shows: 500 m of travel re-frames a city view
+ * completely and is invisible from 3,000 km up.
+ */
+export const INFRA_LOD_MOTION_EPSILON_RATIO = 0.02;
+
+/**
+ * Floor for that epsilon (m), so a camera near the surface still needs real
+ * travel to spend a recompute. Matches the cable layer's flat
+ * CABLE_SWEEP_MOTION_EPSILON_M.
+ */
+export const INFRA_LOD_MOTION_EPSILON_MIN_M = 250;
+
+/**
+ * Camera travel that counts as material motion at this camera height.
+ *
+ * An unreadable height resolves to the FLOOR — the most eager epsilon. That is
+ * the opposite polarity to `infraLodBudget`, deliberately: there, a height we
+ * could not read must not buy the most expensive band; here, a missed
+ * recompute empties the layer while a surplus one costs a single bounded pass.
+ *
+ * @param {number} cameraHeightM
+ * @param {object} [options]
+ * @param {number} [options.ratio]
+ * @param {number} [options.minM]
+ * @returns {number}
+ */
+export function infraLodMotionEpsilonM(cameraHeightM, {
+  ratio = INFRA_LOD_MOTION_EPSILON_RATIO,
+  minM = INFRA_LOD_MOTION_EPSILON_MIN_M,
+} = {}) {
+  const floor = Number.isFinite(minM) && minM >= 0 ? minM : INFRA_LOD_MOTION_EPSILON_MIN_M;
+  const scale = Number.isFinite(ratio) && ratio >= 0 ? ratio : INFRA_LOD_MOTION_EPSILON_RATIO;
+  const height = Number.isFinite(cameraHeightM) && cameraHeightM > 0 ? cameraHeightM : 0;
+  return Math.max(floor, height * scale);
+}
+
+/**
+ * Should the layer re-run its LOD selection on this pass? Pure: the caller
+ * owns `lastProbeMs` and the camera position the last selection ran from, and
+ * writes the returned `lastProbeMs` back.
+ *
+ * Two conditions, both required:
+ *   - the probe window has elapsed — the rate limit, so continuous motion
+ *     cannot recompute on every walk;
+ *   - the camera has travelled past the height-scaled epsilon SINCE THE LAST
+ *     SELECTION, not since the previous walk. A parked camera therefore costs
+ *     zero recomputes and sub-epsilon jitter never accumulates into one, while
+ *     genuine slow travel eventually does.
+ *
+ * The window re-arms whenever it opens, whether or not it recomputes, so a
+ * creeping camera probes on a fixed cadence instead of on every walk.
+ *
+ * Travel arrives SQUARED so the caller can hand over
+ * `Cesium.Cartesian3.distanceSquared` and spend no sqrt on a per-walk probe,
+ * the same trade `createCableReferenceSweepGate` makes.
+ *
+ * @param {object} [input]
+ * @param {number} [input.nowMs]
+ * @param {number} [input.lastProbeMs] When the window last opened, or the last selection ran.
+ * @param {number} [input.movedSqM] Squared camera travel (m²) since the last selection.
+ * @param {number} [input.cameraHeightM] Current height — a near camera earns a tighter epsilon.
+ * @param {number} [input.probeIntervalMs]
+ * @param {number} [input.motionEpsilonM] Explicit epsilon (m); overrides the height scale.
+ * @returns {{recompute:boolean, lastProbeMs:number}}
+ */
+export function shouldRecomputeInfraLod({
+  nowMs = 0,
+  lastProbeMs = Number.NEGATIVE_INFINITY,
+  movedSqM = 0,
+  cameraHeightM,
+  probeIntervalMs = INFRA_LOD_MOTION_PROBE_INTERVAL_MS,
+  motionEpsilonM,
+} = {}) {
+  const now = Number.isFinite(nowMs) ? nowMs : 0;
+  const last = Number.isFinite(lastProbeMs) ? lastProbeMs : Number.NEGATIVE_INFINITY;
+  const interval = Number.isFinite(probeIntervalMs) && probeIntervalMs >= 0
+    ? probeIntervalMs
+    : INFRA_LOD_MOTION_PROBE_INTERVAL_MS;
+  if (now - last < interval) return { recompute: false, lastProbeMs: last };
+
+  const movedSq = Number.isFinite(movedSqM) && movedSqM > 0 ? movedSqM : 0;
+  const epsilon = Number.isFinite(motionEpsilonM) && motionEpsilonM >= 0
+    ? motionEpsilonM
+    : infraLodMotionEpsilonM(cameraHeightM);
+  return { recompute: movedSq > epsilon * epsilon, lastProbeMs: now };
+}

src/data/localGeojsonLod.test.mjs

@@ -0,0 +1,379 @@
+// src/data/localGeojsonLod.test.mjs
+// Pure LOD-engine tests for the bundled local-infrastructure layers:
+// camera-height budget bands (inverted sense vs CCTV), importance+proximity
+// ranking with an incumbency bonus, in-view filtering, dedupe, and the
+// ported eviction-grace planner.
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import {
+  INFRA_LOD_ACTIVE_MIN,
+  INFRA_LOD_ACTIVE_MID,
+  INFRA_LOD_ACTIVE_MAX,
+  INFRA_LOD_GLOBAL_HEIGHT_M,
+  INFRA_LOD_REGIONAL_HEIGHT_M,
+  INFRA_LOD_INCUMBENT_BONUS,
+  INFRA_LOD_FAR_M,
+  INFRA_LOD_MAX_DISTANCE_PENALTY,
+  INFRA_LOD_GRACE_PASSES,
+  INFRA_LOD_GRACE_MS,
+  infraLodBudget,
+  infraRankScore,
+  selectInfraLod,
+  applyInfraEvictionGrace,
+  INFRA_LOD_MOTION_PROBE_INTERVAL_MS,
+  INFRA_LOD_MOTION_EPSILON_RATIO,
+  INFRA_LOD_MOTION_EPSILON_MIN_M,
+  infraLodMotionEpsilonM,
+  shouldRecomputeInfraLod,
+} from './localGeojsonLod.js';
+
+/**
+ * `count` in-view candidates. index 0 is the most important (highest priority)
+ * and the nearest; importance and distance both worsen with index.
+ */
+function candidates(count, options = {}) {
+  return Array.from({ length: count }, (_, index) => ({
+    id: `f-${String(index).padStart(3, '0')}`,
+    priority: 1000 - index,
+    distanceM: index * 1000,
+    inView: options.hiddenAt !== index,
+  }));
+}
+
+/* ----------------------------- budget ----------------------------- */
+
+test('infraLodBudget clamps hardest at global height and opens up as you zoom in', () => {
+  assert.equal(INFRA_LOD_ACTIVE_MIN, 80);
+  assert.equal(INFRA_LOD_ACTIVE_MID, 200);
+  assert.equal(INFRA_LOD_ACTIVE_MAX, 420);
+  assert.deepEqual(infraLodBudget(9_000_000), { activeLimit: INFRA_LOD_ACTIVE_MIN });
+  assert.deepEqual(infraLodBudget(1_000_000), { activeLimit: INFRA_LOD_ACTIVE_MID });
+  assert.deepEqual(infraLodBudget(50_000), { activeLimit: INFRA_LOD_ACTIVE_MAX });
+});
+
+test('infraLodBudget band boundaries are inclusive at the lower edge', () => {
+  assert.deepEqual(infraLodBudget(INFRA_LOD_GLOBAL_HEIGHT_M), { activeLimit: INFRA_LOD_ACTIVE_MIN });
+  assert.deepEqual(infraLodBudget(INFRA_LOD_GLOBAL_HEIGHT_M - 1), { activeLimit: INFRA_LOD_ACTIVE_MID });
+  assert.deepEqual(infraLodBudget(INFRA_LOD_REGIONAL_HEIGHT_M), { activeLimit: INFRA_LOD_ACTIVE_MID });
+  assert.deepEqual(infraLodBudget(INFRA_LOD_REGIONAL_HEIGHT_M - 1), { activeLimit: INFRA_LOD_ACTIVE_MAX });
+});
+
+test('infraLodBudget treats non-finite / negative height as the global (cheapest) band', () => {
+  assert.deepEqual(infraLodBudget(undefined), { activeLimit: INFRA_LOD_ACTIVE_MIN });
+  assert.deepEqual(infraLodBudget(NaN), { activeLimit: INFRA_LOD_ACTIVE_MIN });
+  assert.deepEqual(infraLodBudget(Number.POSITIVE_INFINITY), { activeLimit: INFRA_LOD_ACTIVE_MIN });
+  assert.deepEqual(infraLodBudget(-1), { activeLimit: INFRA_LOD_ACTIVE_MAX }); // max(0,-1) -> 0 -> closest band
+});
+
+/* ------------------------------ rank ----------------------------- */
+
+test('infraRankScore is priority minus a bounded distance penalty', () => {
+  assert.equal(infraRankScore(1000, 0, false), 1000);
+  assert.equal(infraRankScore(1000, INFRA_LOD_FAR_M, false), 1000 - INFRA_LOD_MAX_DISTANCE_PENALTY);
+  // half-way to FAR -> half the penalty
+  assert.equal(infraRankScore(1000, INFRA_LOD_FAR_M / 2, false), 1000 - INFRA_LOD_MAX_DISTANCE_PENALTY / 2);
+  // beyond FAR the penalty is capped, not extrapolated
+  assert.equal(infraRankScore(1000, INFRA_LOD_FAR_M * 10, false), 1000 - INFRA_LOD_MAX_DISTANCE_PENALTY);
+});
+
+test('infraRankScore incumbency bonus reorders within a tier but never beats a name gap', () => {
+  // Two similarly-important features: incumbency flips the order.
+  const freshNear = infraRankScore(900, 0, false);
+  const incumbentFar = infraRankScore(900, INFRA_LOD_FAR_M, true);
+  assert.ok(incumbentFar > freshNear);
+
+  // An unnamed incumbent (priority ~60) must NOT outrank a fresh named feature
+  // (priority ~1000): the incumbency bonus is smaller than that gap.
+  const unnamedIncumbent = infraRankScore(60, 0, true);
+  const namedFresh = infraRankScore(1000, INFRA_LOD_FAR_M, false);
+  assert.ok(namedFresh > unnamedIncumbent);
+  assert.ok(INFRA_LOD_INCUMBENT_BONUS < 700);
+});
+
+test('infraRankScore normalizes garbage inputs to a finite number', () => {
+  assert.equal(infraRankScore(NaN, NaN, false), 0 - INFRA_LOD_MAX_DISTANCE_PENALTY); // priority 0, distance -> FAR
+  assert.equal(Number.isFinite(infraRankScore('x', -5, true)), true);
+  assert.equal(infraRankScore(500, -5, false), 500 - INFRA_LOD_MAX_DISTANCE_PENALTY); // negative dist -> FAR
+});
+
+/* --------------------------- selectInfraLod ---------------------- */
+
+test('selectInfraLod returns everything in view when under budget', () => {
+  const { activeIds, budget } = selectInfraLod(candidates(10), { cameraHeightM: 9_000_000 });
+  assert.equal(budget.activeLimit, INFRA_LOD_ACTIVE_MIN);
+  assert.equal(activeIds.length, 10);
+  assert.deepEqual(activeIds.slice(0, 3), ['f-000', 'f-001', 'f-002']);
+});
+
+test('selectInfraLod caps at the global budget and keeps the most important', () => {
+  const { activeIds } = selectInfraLod(candidates(500), { cameraHeightM: 9_000_000 });
+  assert.equal(activeIds.length, INFRA_LOD_ACTIVE_MIN);
+  assert.equal(activeIds[0], 'f-000');
+  assert.equal(activeIds.at(-1), `f-${String(INFRA_LOD_ACTIVE_MIN - 1).padStart(3, '0')}`);
+});
+
+test('selectInfraLod cap follows the zoom band', () => {
+  assert.equal(selectInfraLod(candidates(600), { cameraHeightM: 9_000_000 }).activeIds.length, INFRA_LOD_ACTIVE_MIN);
+  assert.equal(selectInfraLod(candidates(600), { cameraHeightM: 1_000_000 }).activeIds.length, INFRA_LOD_ACTIVE_MID);
+  assert.equal(selectInfraLod(candidates(600), { cameraHeightM: 50_000 }).activeIds.length, INFRA_LOD_ACTIVE_MAX);
+});
+
+test('selectInfraLod excludes out-of-view records', () => {
+  const input = candidates(20, { hiddenAt: 0 });
+  const { activeIds } = selectInfraLod(input, { cameraHeightM: 50_000 });
+  assert.equal(activeIds.includes('f-000'), false);
+  assert.equal(activeIds.length, 19);
+});
+
+test('selectInfraLod orders by score: a near unnamed node never displaces a far named one', () => {
+  const input = [
+    { id: 'named-far', priority: 1000, distanceM: INFRA_LOD_FAR_M, inView: true },
+    { id: 'unnamed-near', priority: 60, distanceM: 0, inView: true },
+  ];
+  const { activeIds } = selectInfraLod(input, { cameraHeightM: 9_000_000 });
+  assert.deepEqual(activeIds, ['named-far', 'unnamed-near']);
+});
+
+test('selectInfraLod proximity breaks ties among equally important features', () => {
+  const input = [
+    { id: 'far', priority: 500, distanceM: 5_000_000, inView: true },
+    { id: 'near', priority: 500, distanceM: 1_000, inView: true },
+  ];
+  const { activeIds } = selectInfraLod(input, { cameraHeightM: 9_000_000 });
+  assert.deepEqual(activeIds, ['near', 'far']);
+});
+
+test('selectInfraLod incumbency keeps a budget-edge stem that would otherwise be cut', () => {
+  const base = candidates(INFRA_LOD_ACTIVE_MIN + 5, {});
+  // The record that sits just past the cap:
+  const edgeId = `f-${String(INFRA_LOD_ACTIVE_MIN).padStart(3, '0')}`;
+  const withoutIncumbency = selectInfraLod(base, { cameraHeightM: 9_000_000 });
+  assert.equal(withoutIncumbency.activeIds.includes(edgeId), false);
+
+  const withIncumbency = selectInfraLod(base, {
+    cameraHeightM: 9_000_000,
+    incumbentIds: new Set([edgeId]),
+  });
+  assert.equal(withIncumbency.activeIds.includes(edgeId), true);
+  assert.equal(withIncumbency.activeIds.length, INFRA_LOD_ACTIVE_MIN);
+});
+
+test('selectInfraLod accepts an array or a Set of incumbent ids', () => {
+  const base = candidates(INFRA_LOD_ACTIVE_MIN + 3, {});
+  const edgeId = `f-${String(INFRA_LOD_ACTIVE_MIN).padStart(3, '0')}`;
+  const viaArray = selectInfraLod(base, { cameraHeightM: 9_000_000, incumbentIds: [edgeId] });
+  assert.equal(viaArray.activeIds.includes(edgeId), true);
+});
+
+test('selectInfraLod collapses duplicate ids to their best-scoring representative', () => {
+  const input = [
+    { id: 'dup', priority: 100, distanceM: INFRA_LOD_FAR_M, inView: true },
+    { id: 'dup', priority: 900, distanceM: 0, inView: true },
+    { id: 'other', priority: 500, distanceM: 0, inView: true },
+  ];
+  const { activeIds } = selectInfraLod(input, { cameraHeightM: 9_000_000 });
+  assert.deepEqual(activeIds, ['dup', 'other']);
+  assert.equal(activeIds.filter((id) => id === 'dup').length, 1);
+});
+
+test('selectInfraLod is defensive about junk input', () => {
+  assert.deepEqual(selectInfraLod(null, {}).activeIds, []);
+  assert.deepEqual(selectInfraLod(undefined).activeIds, []);
+  assert.deepEqual(
+    selectInfraLod([null, {}, { id: '' }, { id: 'x', inView: false }], { cameraHeightM: 1000 }).activeIds,
+    [],
+  );
+});
+
+test('selectInfraLod produces a deterministic order for score+distance ties', () => {
+  const input = [
+    { id: 'b', priority: 500, distanceM: 1000, inView: true },
+    { id: 'a', priority: 500, distanceM: 1000, inView: true },
+    { id: 'c', priority: 500, distanceM: 1000, inView: true },
+  ];
+  const { activeIds } = selectInfraLod(input, { cameraHeightM: 50_000 });
+  assert.deepEqual(activeIds, ['a', 'b', 'c']);
+});
+
+/* ---------------------- applyInfraEvictionGrace ------------------ */
+
+test('applyInfraEvictionGrace keeps every selected id and starts no grace for them', () => {
+  const out = applyInfraEvictionGrace({
+    selectedIds: ['a', 'b'],
+    builtIds: ['a', 'b'],
+    nowMs: 1000,
+  });
+  assert.deepEqual(out.keepIds.sort(), ['a', 'b']);
+  assert.deepEqual(out.evictIds, []);
+  assert.equal(out.graceState.size, 0);
+});
+
+test('applyInfraEvictionGrace holds a dropped stem through the grace window then evicts it', () => {
+  let grace = new Map();
+  // pass 1: 'x' built but not selected -> graced (miss 1)
+  let out = applyInfraEvictionGrace({ selectedIds: ['a'], builtIds: ['a', 'x'], graceState: grace, nowMs: 0 });
+  assert.deepEqual(out.keepIds.sort(), ['a', 'x']);
+  assert.deepEqual(out.evictIds, []);
+  grace = out.graceState;
+
+  // pass 2: still missing -> miss 2, still within gracePasses (2)
+  out = applyInfraEvictionGrace({ selectedIds: ['a'], builtIds: ['a', 'x'], graceState: grace, nowMs: 10 });
+  assert.equal(out.keepIds.includes('x'), true);
+  grace = out.graceState;
+
+  // pass 3: miss 3 > gracePasses -> evicted
+  out = applyInfraEvictionGrace({ selectedIds: ['a'], builtIds: ['a', 'x'], graceState: grace, nowMs: 20 });
+  assert.deepEqual(out.evictIds, ['x']);
+  assert.equal(out.keepIds.includes('x'), false);
+  assert.equal(out.graceState.has('x'), false);
+});
+
+test('applyInfraEvictionGrace evicts on wall-clock even before the pass count', () => {
+  const grace = new Map([['x', { misses: 1, since: 0 }]]);
+  const out = applyInfraEvictionGrace({
+    selectedIds: [],
+    builtIds: ['x'],
+    graceState: grace,
+    nowMs: INFRA_LOD_GRACE_MS,
+    gracePasses: 99,
+  });
+  assert.deepEqual(out.evictIds, ['x']);
+});
+
+test('applyInfraEvictionGrace never exceeds the cap: oldest-in-grace evicted first', () => {
+  const grace = new Map([
+    ['old', { misses: 1, since: 0 }],
+    ['mid', { misses: 1, since: 5 }],
+    ['new', { misses: 1, since: 9 }],
+  ]);
+  const out = applyInfraEvictionGrace({
+    selectedIds: ['s1', 's2'],
+    builtIds: ['s1', 's2', 'old', 'mid', 'new'],
+    graceState: grace,
+    nowMs: 10,
+    activeLimit: 3, // room for only ONE graced stem on top of s1,s2
+  });
+  assert.deepEqual(out.keepIds.slice(0, 2).sort(), ['s1', 's2']);
+  assert.equal(out.keepIds.includes('new'), true);
+  assert.deepEqual(out.evictIds.sort(), ['mid', 'old']);
+});
+
+test('applyInfraEvictionGrace does not mutate the graceState it was given', () => {
+  const grace = new Map([['x', { misses: 1, since: 0 }]]);
+  const snapshot = JSON.stringify([...grace]);
+  applyInfraEvictionGrace({ selectedIds: [], builtIds: ['x'], graceState: grace, nowMs: 5 });
+  assert.equal(JSON.stringify([...grace]), snapshot);
+});
+
+test('applyInfraEvictionGrace tolerates missing / malformed input', () => {
+  const out = applyInfraEvictionGrace();
+  assert.deepEqual(out.keepIds, []);
+  assert.deepEqual(out.evictIds, []);
+  assert.equal(out.graceState instanceof Map, true);
+
+  const out2 = applyInfraEvictionGrace({ selectedIds: ['a', '', null], builtIds: [null, 'a', 3] });
+  assert.deepEqual(out2.keepIds, ['a']);
+});
+
+test('grace constants are the documented defaults', () => {
+  assert.equal(INFRA_LOD_GRACE_PASSES, 2);
+  assert.equal(INFRA_LOD_GRACE_MS, 4_000);
+});
+
+/* -------------------------- motion fallback ------------------------- */
+
+test('infraLodMotionEpsilonM scales with camera height above a fixed floor', () => {
+  assert.equal(INFRA_LOD_MOTION_EPSILON_RATIO, 0.02);
+  assert.equal(INFRA_LOD_MOTION_EPSILON_MIN_M, 250);
+  // Well above the floor: pure ratio.
+  assert.equal(infraLodMotionEpsilonM(3_000_000), 60_000);
+  assert.equal(infraLodMotionEpsilonM(1_000_000), 20_000);
+  // Near the surface the floor wins, so a low camera still needs real travel.
+  assert.equal(infraLodMotionEpsilonM(5_000), INFRA_LOD_MOTION_EPSILON_MIN_M);
+  assert.equal(infraLodMotionEpsilonM(0), INFRA_LOD_MOTION_EPSILON_MIN_M);
+});
+
+test('infraLodMotionEpsilonM falls back to the floor (most eager) on unreadable height', () => {
+  // Opposite polarity to infraLodBudget on purpose: a missed recompute empties
+  // the layer, a surplus one costs a single bounded pass.
+  assert.equal(infraLodMotionEpsilonM(undefined), INFRA_LOD_MOTION_EPSILON_MIN_M);
+  assert.equal(infraLodMotionEpsilonM(NaN), INFRA_LOD_MOTION_EPSILON_MIN_M);
+  assert.equal(infraLodMotionEpsilonM(Number.POSITIVE_INFINITY), INFRA_LOD_MOTION_EPSILON_MIN_M);
+  assert.equal(infraLodMotionEpsilonM(-9_000), INFRA_LOD_MOTION_EPSILON_MIN_M);
+});
+
+test('shouldRecomputeInfraLod recomputes once the camera has moved far enough', () => {
+  const out = shouldRecomputeInfraLod({
+    nowMs: 10_000,
+    lastProbeMs: 0,
+    movedSqM: 500_000 ** 2, // 500 km >> the 60 km epsilon at 3,000 km up
+    cameraHeightM: 3_000_000,
+  });
+  assert.equal(out.recompute, true);
+  assert.equal(out.lastProbeMs, 10_000, 'the window re-arms at this pass');
+});
+
+test('shouldRecomputeInfraLod holds the window shut inside the probe interval', () => {
+  const out = shouldRecomputeInfraLod({
+    nowMs: 500,
+    lastProbeMs: 0,
+    movedSqM: 9_000_000 ** 2, // enormous motion, but the rate limit comes first
+    cameraHeightM: 3_000_000,
+    probeIntervalMs: INFRA_LOD_MOTION_PROBE_INTERVAL_MS,
+  });
+  assert.equal(out.recompute, false);
+  assert.equal(out.lastProbeMs, 0, 'a shut window does not re-arm');
+});
+
+test('shouldRecomputeInfraLod spends nothing on a parked camera', () => {
+  const out = shouldRecomputeInfraLod({
+    nowMs: 60_000,
+    lastProbeMs: 0,
+    movedSqM: 0,
+    cameraHeightM: 3_000_000,
+  });
+  assert.equal(out.recompute, false);
+  assert.equal(out.lastProbeMs, 60_000, 'the window still re-arms, so the probe stays on a fixed cadence');
+});
+
+test('shouldRecomputeInfraLod ignores sub-epsilon jitter but accumulates real travel', () => {
+  const height = 1_000_000; // epsilon 20,000 m
+  const jitter = shouldRecomputeInfraLod({
+    nowMs: 5_000, lastProbeMs: 0, movedSqM: 19_999 ** 2, cameraHeightM: height,
+  });
+  assert.equal(jitter.recompute, false);
+  // Travel is measured from the last SELECTION, so a creeping camera keeps
+  // closing on the epsilon across windows instead of resetting every pass.
+  const crept = shouldRecomputeInfraLod({
+    nowMs: 10_000, lastProbeMs: 5_000, movedSqM: 20_001 ** 2, cameraHeightM: height,
+  });
+  assert.equal(crept.recompute, true);
+});
+
+test('shouldRecomputeInfraLod opens on first use and tolerates missing / malformed input', () => {
+  // No prior probe: the window is open immediately.
+  const first = shouldRecomputeInfraLod({ nowMs: 1_000, movedSqM: 5_000 ** 2, cameraHeightM: 50_000 });
+  assert.equal(first.recompute, true);
+  assert.equal(first.lastProbeMs, 1_000);
+
+  const empty = shouldRecomputeInfraLod();
+  assert.equal(empty.recompute, false, 'no motion reported means no recompute');
+  assert.equal(empty.lastProbeMs, 0);
+
+  const garbage = shouldRecomputeInfraLod({
+    nowMs: NaN, lastProbeMs: NaN, movedSqM: NaN, cameraHeightM: NaN, probeIntervalMs: NaN,
+  });
+  assert.equal(garbage.recompute, false);
+
+  // An explicit epsilon overrides the height scale.
+  const explicit = shouldRecomputeInfraLod({
+    nowMs: 2_000, lastProbeMs: 0, movedSqM: 300 ** 2, cameraHeightM: 9_000_000, motionEpsilonM: 100,
+  });
+  assert.equal(explicit.recompute, true);
+});
+
+test('motion-fallback constants are the documented defaults', () => {
+  assert.equal(INFRA_LOD_MOTION_PROBE_INTERVAL_MS, 1_000);
+  assert.equal(INFRA_LOD_MOTION_EPSILON_RATIO, 0.02);
+  assert.equal(INFRA_LOD_MOTION_EPSILON_MIN_M, 250);
+});