fix(import): share repeated KML styles before resource checks

CHANGELOG.md

@@ -172,7 +172,9 @@
   segments apart. Size limits are checked before anything is built. The import
   half of #890. Thanks to Chase Mills (@kapturner). Multipart geometry limits
   apply before loading, recorded KML tracks retain their original vertices,
-  and queued imports respect navigation made while waiting.
+  and queued imports respect navigation made while waiting. Repeated KML styles
+  are shared before the style limit is applied, allowing large files with many
+  copies of the same style to load without changing their graphics.
 
 ## [0.2.1] — 2026-10-02 — God's Eye View through Your Agent (with security fixes and other features)
 

docs/CURRENT-STATE.md

@@ -4331,9 +4331,9 @@ are omitted rather than framing the wrong part of the globe.
 - **An imported file cannot make the page fetch anything.** Before `KmlDataSource` reads a KML/KMZ document, `sanitizeKmlDocument` removes `NetworkLink`, `NetworkLinkControl`, `ScreenOverlay`, `PhotoOverlay`, `Model` and `Tour`, every `href` that is not an image packed in the same KMZ or a `data:image/` URL (an icon then falls back to Cesium's default pin, drawn locally, and a `GroundOverlay` left without an image is dropped), every `styleUrl` that is not a local `#id`, and placemark `description`/`BalloonStyle`/`Snippet` HTML and `ExtendedData` before metadata processing. GeoJSON `marker-symbol` (a maki icon asset) is dropped. KMZ images are served from blob URLs, one per packed image however many hrefs name it (`kmzImageResolver`). The hint says when something was left out. `scripts/qa-geo-import.mjs` imports files that name a trap host in each of those places and fails on any request that leaves the app's own origin.
 - **Imported metadata stays inert.** After loading, `scrubImportedEntities` removes every entity's description, native label, properties and KML extended data, and keeps the name only as plain text without control characters, at most 120 characters. GeoJSON is loaded with a `describe` that builds no HTML. The file name is shown with `textContent` only.
 - **KMZ** is read by a small zip reader (`readZipEntries`: stored and deflated entries through the platform `DecompressionStream`; no encryption, no ZIP64). The main document is `doc.kml`, else the shallowest `.kml`; relative hrefs resolve only to entries inside the archive.
-- **Bounds.** A file may be at most 50 MB (`MAX_IMPORT_BYTES`), a KMZ may inflate to at most 120 MB in total (`MAX_KMZ_INFLATED_BYTES`, the zip-bomb stop), one file may create at most 20,000 Cesium entities, including multipart geometries and KML parent containers (`MAX_IMPORT_ENTITIES`) and 250,000 vertices (`MAX_IMPORT_POSITIONS`), and a KML/KMZ at most 2,000 `<href>` and `<Style>` elements (`MAX_KML_LINKS`), counted before Cesium builds anything (`countGeoJsonGeometry`, `countKmlGeometry`, and while reading GPX), and the entity count is checked again after loading. At most 12 files are on the globe at once (`MAX_IMPORTED_FILES`): imports run one batch at a time, so two picks or drops in quick succession cannot pass the cap; files over it are not read. A refused file names its reason in the hint and does not stop the rest of the batch; a file with nothing to draw is refused.
+- **Bounds.** A file may be at most 50 MiB (`MAX_IMPORT_BYTES`), a KMZ may inflate to at most 120 MiB in total (`MAX_KMZ_INFLATED_BYTES`, the zip-bomb stop), one file may create at most 20,000 Cesium entities, including multipart geometries and KML parent containers (`MAX_IMPORT_ENTITIES`) and 250,000 vertices (`MAX_IMPORT_POSITIONS`), and a KML/KMZ at most 2,000 normalized style definitions (including named StyleMaps) and distinct surviving image links (`MAX_KML_LINKS`). Identical KML styles are shared after metadata and remote-reference cleanup, preserving inline overrides and local style references; repeated copies do not exhaust the style budget. Folder containers count toward the entity budget. Files of 20–30 MB fit within the byte limit; drawing complexity is bounded separately. Geometry is counted before Cesium builds anything (`countGeoJsonGeometry`, `countKmlGeometry`, and while reading GPX), and the entity count is checked again after loading. At most 12 files are on the globe at once (`MAX_IMPORTED_FILES`): imports run one batch at a time, so two picks or drops in quick succession cannot pass the cap; files over it are not read. A refused file names its reason in the hint and does not stop the rest of the batch; a file with nothing to draw is refused.
 - **Keyboard.** Hide, show and remove rebuild the list without losing focus: the same control on the same row keeps it, a removed row hands it to the next row (else the Import button).
-- Gate: `node scripts/qa-geo-import.mjs` (dev server up). Unit: `src/data/geoFileImport.test.mjs`, `src/ui/geoFileImport.test.mjs`, `src/ui/flyToDataSource.test.mjs`.
+- Gate: `node scripts/qa-geo-import.mjs` (dev server up). Large-file gate: `node scripts/qa-geo-import-large.mjs [--file /absolute/path/to/sample.kml]` tests a 27.6 MB repeated-style fixture, compares its graphics with an unshared Cesium control, and records matched frame times on the actual WebGL renderer. Unit: `src/data/geoFileImport.test.mjs`, `src/ui/geoFileImport.test.mjs`, `src/ui/flyToDataSource.test.mjs`.
 
 ### Recent Imagery (September 2026)
 

scripts/format-scope.json

@@ -202,6 +202,7 @@
   "scripts/qa-visual-effects.mjs",
   "scripts/qa-draw-tool.mjs",
   "scripts/qa-geo-import.mjs",
+  "scripts/qa-geo-import-large.mjs",
   "src/ui/mapSource.js",
   "src/ui/mapSourceControls.js",
   "src/ui/mapSourceControls.test.mjs",

scripts/qa-geo-import-large.mjs

@@ -0,0 +1,326 @@
+#!/usr/bin/env node
+/** Large KML acceptance: style equivalence, 25 MB import and optional real file.
+ * QA_BASE_URL defaults to http://localhost:4173. Optional --file /path/file.kml.
+ */
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import puppeteer from 'puppeteer';
+
+const base = process.env.QA_BASE_URL || 'http://localhost:4173';
+const supplied = process.argv.includes('--file')
+  ? path.resolve(process.argv[process.argv.indexOf('--file') + 1])
+  : null;
+const directory = fs.mkdtempSync(path.join(os.tmpdir(), 'gev-large-kml-'));
+const file = path.join(directory, 'metadata-rich-25mb.kml');
+const style =
+  '<Style><IconStyle><scale>0.6</scale><color>ff00dd66</color></IconStyle></Style>';
+const notes = 'A local observation with supporting detail. '.repeat(120);
+const placemarks = Array.from({ length: 5000 }, (_, i) => {
+  const lon = -122.6 + (i % 100) * 0.002;
+  const lat = 37.65 + Math.floor(i / 100) * 0.003;
+  return `<Placemark><name>Point ${i}</name><styleUrl>#base</styleUrl>${style}<description>${notes}</description><Point><coordinates>${lon},${lat},0</coordinates></Point></Placemark>`;
+});
+const wrap = (body) =>
+  `<kml xmlns="http://www.opengis.net/kml/2.2"><Document><Style id="base"><IconStyle><heading>25</heading><scale>1.2</scale></IconStyle><LineStyle><color>ffdd6600</color><width>7</width></LineStyle><PolyStyle><color>6600ddff</color><fill>1</fill><outline>0</outline></PolyStyle></Style>${body}</Document></kml>`;
+const large = wrap(placemarks.join(''));
+fs.writeFileSync(file, large);
+const bytes = fs.statSync(file).size;
+if (bytes < 20 * 1024 * 1024 || bytes > 30 * 1024 * 1024)
+  throw new Error(`Fixture must be 20–30 MiB, got ${bytes} bytes`);
+const small = wrap(
+  Array.from({ length: 6 }, (_, i) => {
+    const kind = i % 3;
+    const geometry =
+      kind === 0
+        ? '<Point><coordinates>-122.49,37.77,0</coordinates></Point>'
+        : kind === 1
+          ? '<LineString><coordinates>-122.50,37.77,0 -122.49,37.77,0</coordinates></LineString>'
+          : '<Polygon><outerBoundaryIs><LinearRing><coordinates>-122.50,37.77,0 -122.49,37.77,0 -122.49,37.78,0 -122.50,37.77,0</coordinates></LinearRing></outerBoundaryIs></Polygon>';
+    const override =
+      kind === 0
+        ? style
+        : kind === 1
+          ? '<Style><LineStyle><width>3</width></LineStyle></Style>'
+          : '<Style><PolyStyle><outline>1</outline></PolyStyle></Style>';
+    return `<Placemark><name>Small ${i}</name><styleUrl>#base</styleUrl>${override}${geometry}</Placemark>`;
+  }).join('') +
+    '<Style id="named-a"><IconStyle><scale>0.8</scale></IconStyle></Style>' +
+    '<Style id="named-b"><IconStyle><scale>0.8</scale></IconStyle></Style>' +
+    '<StyleMap id="paired"><Pair><key>normal</key><Style><IconStyle><scale>0.8</scale></IconStyle></Style></Pair></StyleMap>' +
+    ['named-a', 'named-b', 'paired']
+      .map(
+        (id) =>
+          `<Placemark><name>${id}</name><styleUrl>#${id}</styleUrl><Point><coordinates>-122.49,37.77,0</coordinates></Point></Placemark>`,
+      )
+      .join(''),
+);
+const browser = await puppeteer.launch({
+  headless: true,
+  args:
+    process.platform === 'darwin'
+      ? ['--use-gl=angle', '--use-angle=metal']
+      : ['--no-sandbox', '--use-gl=angle', '--use-angle=swiftshader'],
+});
+const page = await browser.newPage();
+const errors = [];
+const fileRequests = [];
+page.on('pageerror', (e) => errors.push(e.message));
+await page.setRequestInterception(true);
+page.on('request', (request) => {
+  if (new URL(request.url()).hostname === 'earthquake.usgs.gov') {
+    fileRequests.push(request.url());
+    void request.abort();
+  } else void request.continue();
+});
+let failures = 0;
+const check = (name, ok, detail) => {
+  console.log(`[${ok ? 'PASS' : 'FAIL'}] ${name}`, detail ?? '');
+  if (!ok) failures++;
+};
+try {
+  await page.setViewport({ width: 1440, height: 900 });
+  await page.goto(`${base}/?welcome=0`, { waitUntil: 'domcontentloaded' });
+  await page.waitForFunction(
+    () =>
+      window.__gevGeoImport &&
+      document.getElementById('loading-screen')?.classList.contains('hidden'),
+    { timeout: 60000 },
+  );
+  await page.evaluate(async () => {
+    const { viewer, dataManager } = window.__godsEyeView;
+    const C = window.__CESIUM__;
+    for (const id of dataManager.layers.keys())
+      await dataManager.setEnabled(id, false);
+    viewer.imageryLayers.removeAll();
+    viewer.terrainProvider = new C.EllipsoidTerrainProvider();
+    viewer.camera.cancelFlight();
+    viewer.camera.setView({
+      destination: C.Cartesian3.fromDegrees(-122.5, 37.72, 50000),
+      orientation: { heading: 0, pitch: -Math.PI / 2, roll: 0 },
+    });
+    window.__qaStyleSnapshot = (source) => {
+      const now = viewer.clock.currentTime;
+      const color = (p) => p?.getValue(now)?.toCssColorString();
+      const positions = (p) => p?.getValue(now)?.map((v) => [v.x, v.y, v.z]);
+      return source.entities.values
+        .map((e) => ({
+          name: e.name,
+          point: e.position?.getValue(now),
+          scale: e.billboard?.scale?.getValue(now),
+          rotation: e.billboard?.rotation?.getValue(now),
+          image: e.billboard?.image?.getValue(now),
+          color: color(e.billboard?.color),
+          width: e.polyline?.width?.getValue(now),
+          lineColor: color(e.polyline?.material?.color),
+          line: positions(e.polyline?.positions),
+          fill: e.polygon?.fill?.getValue(now),
+          outline: e.polygon?.outline?.getValue(now),
+          polygonColor: color(e.polygon?.material?.color),
+          polygon: e.polygon?.hierarchy
+            ?.getValue(now)
+            ?.positions?.map((v) => [v.x, v.y, v.z]),
+        }))
+        .sort((a, b) => a.name.localeCompare(b.name));
+    };
+    window.__qaUnsharedKml = async (text) => {
+      const doc = new DOMParser().parseFromString(text, 'application/xml');
+      for (const el of [...doc.getElementsByTagName('*')])
+        if (
+          ['description', 'ExtendedData', 'BalloonStyle'].includes(el.localName)
+        )
+          el.remove();
+      const source = await C.KmlDataSource.load(doc, {
+        camera: viewer.scene.camera,
+        canvas: viewer.scene.canvas,
+        clampToGround: true,
+      });
+      for (const e of source.entities.values) e.label = undefined;
+      return source;
+    };
+  });
+  const equivalent = await page.evaluate(async (text) => {
+    const { viewer } = window.__godsEyeView;
+    const control = await window.__qaUnsharedKml(text);
+    const outcomes = await window.__gevGeoImport.importFiles([
+      new File([text], 'style-equivalence.kml'),
+    ]);
+    const candidate = viewer.dataSources.get(viewer.dataSources.length - 1);
+    const result = {
+      ok: outcomes[0]?.ok,
+      same:
+        JSON.stringify(window.__qaStyleSnapshot(control)) ===
+        JSON.stringify(window.__qaStyleSnapshot(candidate)),
+      entities: candidate.entities.values.length,
+    };
+    await window.__gevGeoImport.remove(outcomes[0]?.id);
+    return result;
+  }, small);
+  check(
+    'shared inline and named styles preserve point, line and polygon overrides/inheritance',
+    equivalent.ok && equivalent.same && equivalent.entities === 9,
+    JSON.stringify(equivalent),
+  );
+
+  // The control bypasses the former style-count refusal solely in this test,
+  // to compare native unshared rendering against normalized rendering.
+  await page.evaluate(async (text) => {
+    const source = await window.__qaUnsharedKml(text);
+    window.__qaUnsharedSnapshot = JSON.stringify(
+      window.__qaStyleSnapshot(source),
+    );
+    window.__qaControl = source;
+    await window.__godsEyeView.viewer.dataSources.add(source);
+  }, large);
+  const measure = async () =>
+    page.evaluate(async () => {
+      const C = window.__CESIUM__,
+        { viewer } = window.__godsEyeView;
+      const scene = viewer.scene;
+      viewer.camera.cancelFlight();
+      viewer.camera.setView({
+        destination: C.Cartesian3.fromDegrees(-122.5, 37.72, 50000),
+        orientation: { heading: 0, pitch: -Math.PI / 2, roll: 0 },
+      });
+      const started = performance.now(),
+        samples = [];
+      let last,
+        frames = 0;
+      const remove = scene.postRender.addEventListener(() => {
+        const t = performance.now();
+        if (t - started < 2000) return;
+        frames++;
+        if (last !== undefined) samples.push(t - last);
+        last = t;
+      });
+      await new Promise((resolve) => {
+        let previous = performance.now();
+        function tick(t) {
+          viewer.camera.rotate(
+            C.Cartesian3.UNIT_Z,
+            Math.min(t - previous, 100) * 0.0000002,
+          );
+          previous = t;
+          scene.requestRender();
+          if (t - started < 7000) requestAnimationFrame(tick);
+          else resolve();
+        }
+        requestAnimationFrame(tick);
+      });
+      remove();
+      samples.sort((a, b) => a - b);
+      const gl = scene.context._gl,
+        debug = gl.getExtension('WEBGL_debug_renderer_info');
+      return {
+        fps: frames / 5,
+        p50Ms: samples[Math.floor(samples.length * 0.5)],
+        p95Ms: samples[Math.floor(samples.length * 0.95)],
+        renderer: debug ? gl.getParameter(debug.UNMASKED_RENDERER_WEBGL) : null,
+      };
+    });
+  console.log('UNSHARED CONTROL', JSON.stringify(await measure()));
+  await page.evaluate(() =>
+    window.__godsEyeView.viewer.dataSources.remove(window.__qaControl, true),
+  );
+
+  const loadPicked = async (filename, expected) => {
+    const before = await page.evaluate(
+      () => window.__godsEyeView.viewer.dataSources.length,
+    );
+    const started = performance.now();
+    await (await page.$('#geo-import-input')).uploadFile(filename);
+    const name = path.basename(filename);
+    const loaded = await page
+      .waitForFunction(
+        (name) =>
+          window.__gevGeoImport.list().some((f) => f.name === name) ||
+          document
+            .getElementById('geo-import-hint')
+            .textContent.startsWith(`${name}:`),
+        { timeout: 120000 },
+        name,
+      )
+      .then(
+        () => true,
+        () => false,
+      );
+    const state = await page.evaluate(() => ({
+      files: window.__gevGeoImport.list(),
+      hint: document.getElementById('geo-import-hint').textContent,
+      sources: window.__godsEyeView.viewer.dataSources.length,
+    }));
+    const item = state.files.find((f) => f.name === name);
+    check(
+      `picked ${name} loads`,
+      loaded &&
+        (expected === null
+          ? item?.entityCount > 0
+          : item?.entityCount === expected) &&
+        state.sources === before + 1,
+      JSON.stringify({
+        bytes: fs.statSync(filename).size,
+        loadMs: Math.round(performance.now() - started),
+        ...state,
+      }),
+    );
+    return item;
+  };
+  const item = await loadPicked(file, 5000);
+  if (item) {
+    const same = await page.evaluate(() => {
+      const viewer = window.__godsEyeView.viewer;
+      const source = viewer.dataSources.get(viewer.dataSources.length - 1);
+      return (
+        JSON.stringify(window.__qaStyleSnapshot(source)) ===
+        window.__qaUnsharedSnapshot
+      );
+    });
+    check('all 5,000 normalized graphics match their unshared control', same);
+    console.log('NORMALIZED CANDIDATE', JSON.stringify(await measure()));
+    await page.evaluate((id) => window.__gevGeoImport.remove(id), item.id);
+  }
+  if (supplied) {
+    const clockBefore = await page.evaluate(() => {
+      const v = window.__godsEyeView.viewer,
+        C = window.__CESIUM__;
+      return [
+        C.JulianDate.toIso8601(v.clock.startTime),
+        C.JulianDate.toIso8601(v.clock.stopTime),
+        v.clock.multiplier,
+      ];
+    });
+    const suppliedItem = await loadPicked(supplied, null);
+    const clockAfter = await page.evaluate(() => {
+      const v = window.__godsEyeView.viewer,
+        C = window.__CESIUM__;
+      return [
+        C.JulianDate.toIso8601(v.clock.startTime),
+        C.JulianDate.toIso8601(v.clock.stopTime),
+        v.clock.multiplier,
+      ];
+    });
+    check(
+      'real dated KML leaves the shared clock unchanged',
+      JSON.stringify(clockBefore) === JSON.stringify(clockAfter),
+    );
+    if (suppliedItem)
+      await page.evaluate(
+        (id) => window.__gevGeoImport.remove(id),
+        suppliedItem.id,
+      );
+  }
+  check(
+    'file-directed USGS icon/metadata requests never leave the page',
+    fileRequests.length === 0,
+    fileRequests.length,
+  );
+  check('no uncaught page errors', errors.length === 0, JSON.stringify(errors));
+  check(
+    'all imported sources are removed',
+    await page.evaluate(() => window.__gevGeoImport.list().length === 0),
+  );
+  console.log('Fixture retained at', file);
+} finally {
+  await browser.close();
+}
+process.exitCode = failures ? 1 : 0;

src/data/geoFileImport.js

@@ -42,7 +42,7 @@ export const MAX_IMPORTED_FILES = 12;
 export const MAX_IMPORT_ENTITIES = 20_000;
 /** Most vertices (points of every line, ring and marker) in one file. */
 export const MAX_IMPORT_POSITIONS = 250_000;
-/** Most `<href>` and `<Style>` elements in one KML/KMZ document. */
+/** Most normalized style definitions and local image links in one KML/KMZ. */
 export const MAX_KML_LINKS = 2_000;
 /** Longest plain-text name kept from a file's features. */
 export const MAX_IMPORT_NAME_LENGTH = 120;
@@ -225,11 +225,11 @@ export function countGeoJsonGeometry(
 function overLimitError({ over, features, positions }) {
   if (over === 'entities')
     return new GeoImportError(
-      `That file draws more than ${MAX_IMPORT_ENTITIES.toLocaleString()} objects (the limit).`,
+      `That file creates more than ${MAX_IMPORT_ENTITIES.toLocaleString()} map objects (the limit).`,
     );
   if (over === 'links')
     return new GeoImportError(
-      `That file has more than ${MAX_KML_LINKS.toLocaleString()} styles and icon links (the limit).`,
+      `That file has more than ${MAX_KML_LINKS.toLocaleString()} style definitions and image links after cleanup (the limit).`,
     );
   if (over === 'features')
     return new GeoImportError(
@@ -548,11 +548,118 @@ const childrenNamed = (el, localName) => {
 const childText = (el, localName) =>
   (childrenNamed(el, localName)[0]?.textContent || '').trim();
 
+/**
+ * Share identical styles before the loader builds their graphics. Inline
+ * overrides stay inline StyleMaps, so an existing styleUrl still supplies
+ * properties the override leaves unset. Named references are redirected.
+ * Random-color styles remain unchanged; duplicate IDs
+ * keep the loader's original precedence instead of being rewritten.
+ * @param {Document} doc Sanitized KML.
+ * @param {{serializeStyle?: Function, maxStyles?: number}} [options]
+ * @returns {number} Number of original style blocks replaced.
+ */
+export function deduplicateKmlStyles(
+  doc,
+  { serializeStyle, maxStyles = MAX_KML_LINKS } = {},
+) {
+  const serializer = serializeStyle ? null : new XMLSerializer();
+  const serialize =
+    serializeStyle || ((el) => serializer.serializeToString(el));
+  const groups = new Map();
+  const usedIds = new Set();
+  const duplicateIds = new Set();
+  for (const el of doc.getElementsByTagName('*')) {
+    const id = el.getAttribute('id');
+    if (id !== null) {
+      if (usedIds.has(id)) duplicateIds.add(id);
+      usedIds.add(id);
+    }
+  }
+  for (const style of elementsNamed(doc, 'Style')) {
+    if (
+      elementsNamed(style, 'colorMode').some(
+        (el) => el.textContent.trim() === 'random',
+      )
+    )
+      continue;
+    const template = style.cloneNode(true);
+    template.removeAttribute('id');
+    const key = serialize(template);
+    let group = groups.get(key);
+    if (!group) {
+      group = { template, nodes: [] };
+      groups.set(key, group);
+      if (groups.size > maxStyles) throw overLimitError({ over: 'links' });
+    }
+    group.nodes.push(style);
+  }
+  const redirects = new Map();
+  let replaced = 0;
+  let serial = 0;
+  let container;
+  for (const { template, nodes } of groups.values()) {
+    if (
+      nodes.length < 2 ||
+      nodes.some((el) => duplicateIds.has(el.getAttribute('id')))
+    )
+      continue;
+    const ns = template.namespaceURI || 'http://www.opengis.net/kml/2.2';
+    if (!container) {
+      const root = doc.documentElement;
+      container =
+        root.localName === 'Document'
+          ? root
+          : childrenNamed(root, 'Document')[0];
+      if (!container) {
+        container = doc.createElementNS(ns, 'Document');
+        while (root.firstChild) container.appendChild(root.firstChild);
+        root.appendChild(container);
+      }
+    }
+    let id;
+    do {
+      id = `gev-import-style-${++serial}`;
+    } while (usedIds.has(id));
+    usedIds.add(id);
+    template.setAttribute('id', id);
+    container.appendChild(template);
+    for (const style of nodes) {
+      const originalId = style.getAttribute('id');
+      if (originalId !== null) redirects.set(originalId, id);
+      let reference;
+      if (style.parentNode.localName === 'Pair') {
+        reference = doc.createElementNS(ns, 'styleUrl');
+        reference.textContent = `#${id}`;
+      } else {
+        reference = doc.createElementNS(ns, 'StyleMap');
+        for (const state of ['normal', 'highlight']) {
+          const pair = doc.createElementNS(ns, 'Pair');
+          const key = doc.createElementNS(ns, 'key');
+          key.textContent = state;
+          const url = doc.createElementNS(ns, 'styleUrl');
+          url.textContent = `#${id}`;
+          pair.appendChild(key);
+          pair.appendChild(url);
+          reference.appendChild(pair);
+        }
+      }
+      style.parentNode.replaceChild(reference, style);
+      replaced += 1;
+    }
+  }
+  for (const url of elementsNamed(doc, 'styleUrl')) {
+    const value = url.textContent.trim();
+    const id = value.startsWith('#') && redirects.get(value.slice(1));
+    if (id) url.textContent = `#${id}`;
+  }
+  return replaced;
+}
+
 /**
  * Count placemarks and vertices in a parsed KML document before Cesium reads
- * it: every `<coordinates>` tuple and every `gx:coord`, plus the `<href>`
- * and `<Style>` elements (`links`), each of which can make Cesium load and
- * decode an image.
+ * it: every `<coordinates>` tuple and every `gx:coord`, plus normalized
+ * style definitions and distinct image `<href>` values (`links`).
+ * Inline StyleMaps are references, not additional shared style definitions.
  * @param {Document} doc
  * @returns {{features: number, entities: number, positions: number, links: number,
  *   over: ''|'features'|'entities'|'positions'|'links'}}
@@ -570,6 +677,7 @@ export function countKmlGeometry(
   let entities = 0;
   let positions = 0;
   let links = 0;
+  const imageLinks = new Set();
   const result = (over) => ({ features, entities, positions, links, over });
   const geometryNames = new Set([
     'Point',
@@ -583,10 +691,11 @@ export function countKmlGeometry(
   ]);
   for (const el of doc.getElementsByTagName('*')) {
     const name = el.localName;
-    // Cesium creates a parent for every placemark and a child entity for
-    // each geometry in a MultiGeometry, including nested containers.
+    // Cesium creates entities for folders, a parent for every placemark, and
+    // a child for each geometry in a MultiGeometry, including nested containers.
     if (
       name === 'Placemark' ||
+      name === 'Folder' ||
       name === 'GroundOverlay' ||
       (geometryNames.has(name) &&
         ['MultiGeometry', 'MultiTrack'].includes(el.parentNode?.localName))
@@ -594,9 +703,19 @@ export function countKmlGeometry(
       entities += 1;
       if (entities > maxEntities) return result('entities');
     }
-    if (name === 'href' || name === 'Style') {
+    if (
+      name === 'Style' ||
+      (name === 'StyleMap' && el.getAttribute('id') !== null)
+    ) {
       links += 1;
       if (links > maxLinks) return result('links');
+    } else if (name === 'href') {
+      const href = el.textContent.trim();
+      if (!imageLinks.has(href)) {
+        imageLinks.add(href);
+        links += 1;
+        if (links > maxLinks) return result('links');
+      }
     } else if (name === 'Placemark') {
       features += 1;
       if (features > maxFeatures) return result('features');
@@ -888,9 +1007,14 @@ export async function loadGeoFile(file, { viewer, color = '#39d0ff' }) {
         text = new TextDecoder().decode(bytes);
       }
       const doc = parseXml(text, format.toUpperCase());
-      const size = countKmlGeometry(doc);
+      // Bound geometry before transformations, then count the styles and
+      // image links that survive sanitizing and sharing repeated styles.
+      const size = countKmlGeometry(doc, { maxLinks: Infinity });
       if (size.over) throw overLimitError(size);
       removed = sanitizeKmlDocument(doc, resolveLocal).removed;
+      deduplicateKmlStyles(doc);
+      const normalizedSize = countKmlGeometry(doc);
+      if (normalizedSize.over) throw overLimitError(normalizedSize);
       dataSource = await Cesium.KmlDataSource.load(doc, {
         camera: viewer.scene.camera,
         canvas: viewer.scene.canvas,
@@ -908,7 +1032,7 @@ export async function loadGeoFile(file, { viewer, color = '#39d0ff' }) {
   if (entityCount > MAX_IMPORT_ENTITIES) {
     revoke();
     throw new GeoImportError(
-      `That file has ${entityCount.toLocaleString()} features; the limit is ${MAX_IMPORT_ENTITIES.toLocaleString()}.`,
+      `That file has ${entityCount.toLocaleString()} map objects; the limit is ${MAX_IMPORT_ENTITIES.toLocaleString()}.`,
     );
   }
   if (entityCount === 0) {

src/data/geoFileImport.test.mjs

@@ -8,6 +8,7 @@ import {
   MAX_IMPORT_ENTITIES,
   countGeoJsonGeometry,
   countKmlGeometry,
+  deduplicateKmlStyles,
   detachImportedTime,
   gpxToGeoJson,
   importFeatureName,
@@ -231,8 +232,41 @@ function xmlEl(localName, attrs = {}, kids = []) {
   const el = {
     nodeType: 1,
     localName,
+    namespaceURI: 'http://www.opengis.net/kml/2.2',
     childNodes: [],
     getAttribute: (n) => (n in attrs ? String(attrs[n]) : null),
+    get attributes() {
+      return Object.entries(attrs);
+    },
+    setAttribute: (n, value) => {
+      attrs[n] = value;
+    },
+    removeAttribute: (n) => {
+      delete attrs[n];
+    },
+    cloneNode() {
+      return xmlEl(
+        localName,
+        { ...attrs },
+        text ?? el.childNodes.map((child) => child.cloneNode(true)),
+      );
+    },
+    getElementsByTagName(name) {
+      return xmlDoc(this).getElementsByTagName(name).slice(1);
+    },
+    appendChild(child) {
+      child.parentNode?.removeChild(child);
+      child.parentNode = this;
+      this.childNodes.push(child);
+    },
+    replaceChild(next, previous) {
+      const index = this.childNodes.indexOf(previous);
+      assert.ok(index >= 0);
+      next.parentNode?.removeChild(next);
+      this.childNodes[index] = next;
+      next.parentNode = this;
+      previous.parentNode = null;
+    },
     removeChild(child) {
       this.childNodes.splice(this.childNodes.indexOf(child), 1);
       child.parentNode = null;
@@ -242,14 +276,22 @@ function xmlEl(localName, attrs = {}, kids = []) {
     k.parentNode = el;
     el.childNodes.push(k);
   }
-  const text = typeof kids === 'string' ? kids : null;
+  let text = typeof kids === 'string' ? kids : null;
+  Object.defineProperty(el, 'firstChild', {
+    get: () => el.childNodes[0] || null,
+  });
   Object.defineProperty(el, 'textContent', {
     get: () => text ?? el.childNodes.map((c) => c.textContent).join(''),
+    set: (value) => {
+      text = value;
+      el.childNodes = [];
+    },
   });
   return el;
 }
 const xmlDoc = (root) => ({
   documentElement: root,
+  createElementNS: (_ns, name) => xmlEl(name),
   getElementsByTagName(name) {
     assert.equal(name, '*');
     const out = [];
@@ -261,6 +303,118 @@ const xmlDoc = (root) => ({
     return out;
   },
 });
+const serializeStyle = (el) =>
+  JSON.stringify({
+    name: el.localName,
+    attributes: el.attributes,
+    text: el.childNodes.length ? null : el.textContent,
+    children: el.childNodes.map(serializeStyle),
+  });
+
+test('repeated inline styles are shared without replacing their inherited styleUrl', () => {
+  const style = () =>
+    xmlEl('Style', {}, [xmlEl('IconStyle', {}, [xmlEl('scale', {}, '0.6')])]);
+  const placemarks = Array.from({ length: 2100 }, () =>
+    xmlEl('Placemark', {}, [xmlEl('styleUrl', {}, '#base'), style()]),
+  );
+  const doc = xmlDoc(
+    xmlEl('kml', {}, [
+      xmlEl('Document', {}, [
+        xmlEl('Style', { id: 'gev-import-style-1' }, [xmlEl('LineStyle')]),
+        ...placemarks,
+      ]),
+    ]),
+  );
+  assert.equal(countKmlGeometry(doc).over, 'links');
+  assert.equal(deduplicateKmlStyles(doc, { serializeStyle }), 2100);
+  assert.equal(countKmlGeometry(doc).over, '');
+  const styles = doc
+    .getElementsByTagName('*')
+    .filter((el) => el.localName === 'Style');
+  assert.equal(styles.length, 2);
+  assert.equal(styles[1].getAttribute('id'), 'gev-import-style-2');
+  for (const placemark of placemarks) {
+    assert.equal(placemark.childNodes[0].textContent, '#base');
+    assert.equal(placemark.childNodes[1].localName, 'StyleMap');
+    assert.deepEqual(
+      placemark.childNodes[1].childNodes.map((pair) =>
+        pair.childNodes.map((el) => el.textContent),
+      ),
+      [
+        ['normal', '#gev-import-style-2'],
+        ['highlight', '#gev-import-style-2'],
+      ],
+    );
+  }
+});
+
+test('identical named styles redirect existing references and Pair styles remain valid', () => {
+  const style = (id) =>
+    xmlEl('Style', id ? { id } : {}, [
+      xmlEl('LineStyle', {}, [xmlEl('width', {}, '3')]),
+    ]);
+  const reference = xmlEl('styleUrl', {}, '#b');
+  const pair = xmlEl('Pair', {}, [xmlEl('key', {}, 'normal'), style()]);
+  const doc = xmlDoc(
+    xmlEl('kml', {}, [
+      style('a'),
+      style('b'),
+      xmlEl('StyleMap', { id: 'map' }, [pair]),
+      xmlEl('Placemark', {}, [reference]),
+    ]),
+  );
+  assert.equal(deduplicateKmlStyles(doc, { serializeStyle }), 3);
+  assert.equal(doc.documentElement.firstChild.localName, 'Document');
+  assert.equal(reference.textContent, '#gev-import-style-1');
+  assert.equal(pair.childNodes[1].localName, 'styleUrl');
+  assert.equal(pair.childNodes[1].textContent, '#gev-import-style-1');
+  assert.equal(
+    doc.getElementsByTagName('*').filter((el) => el.localName === 'Style')
+      .length,
+    1,
+  );
+});
+
+test('random colors and ambiguous style IDs retain independent evaluations and precedence', () => {
+  const random = () =>
+    xmlEl('Style', {}, [
+      xmlEl('IconStyle', {}, [xmlEl('colorMode', {}, 'random')]),
+    ]);
+  const named = (width) =>
+    xmlEl('Style', { id: 'collision' }, [
+      xmlEl('LineStyle', {}, [xmlEl('width', {}, width)]),
+    ]);
+  const original = [random(), random(), named('1'), named('1'), named('2')];
+  const doc = xmlDoc(xmlEl('kml', {}, original));
+  assert.equal(deduplicateKmlStyles(doc, { serializeStyle }), 0);
+  assert.deepEqual(doc.documentElement.childNodes, original);
+});
+
+test('distinct style definitions and named StyleMaps still have a pre-loader budget', () => {
+  const doc = xmlDoc(
+    xmlEl(
+      'kml',
+      {},
+      ['1', '2', '3'].map((width) =>
+        xmlEl('Style', {}, [
+          xmlEl('LineStyle', {}, [xmlEl('width', {}, width)]),
+        ]),
+      ),
+    ),
+  );
+  assert.throws(
+    () => deduplicateKmlStyles(doc, { serializeStyle, maxStyles: 2 }),
+    GeoImportError,
+  );
+  const maps = xmlDoc(
+    xmlEl('kml', {}, [
+      xmlEl('StyleMap', { id: 'a' }),
+      xmlEl('StyleMap', { id: 'b' }),
+    ]),
+  );
+  assert.equal(countKmlGeometry(maps, { maxLinks: 1 }).over, 'links');
+});
+
 test('KML extended metadata is removed before the document reaches the loader', () => {
   const point = xmlEl('Point', {}, [xmlEl('coordinates', {}, '1,2,0')]);
   const metadata = xmlEl('ExtendedData', {}, [
@@ -495,14 +649,32 @@ test('KML multipart geometries count every Cesium entity before loading', () =>
   assert.equal(countKmlGeometry(oversized).over, 'entities');
 });
 
-test('KML styles and icon links are counted against their own limit', () => {
+test('KML folders contribute to the pre-loader entity budget', () => {
+  const doc = xmlDoc(
+    xmlEl('kml', {}, [
+      xmlEl('Folder', {}, [xmlEl('Folder', {}, [xmlEl('Placemark')])]),
+    ]),
+  );
+  assert.equal(countKmlGeometry(doc).entities, 3);
+  assert.equal(countKmlGeometry(doc, { maxEntities: 2 }).over, 'entities');
+});
+
+test('KML style definitions and distinct icon links have their own limit', () => {
   const style = () =>
     xmlEl('Style', {}, [
       xmlEl('IconStyle', {}, [xmlEl('Icon', {}, [xmlEl('href', {}, 'a.png')])]),
     ]);
   const doc = xmlDoc(xmlEl('kml', {}, [style(), style(), style()]));
-  assert.equal(countKmlGeometry(doc).links, 6);
-  assert.equal(countKmlGeometry(doc, { maxLinks: 5 }).over, 'links');
+  assert.equal(countKmlGeometry(doc).links, 4);
+  assert.equal(countKmlGeometry(doc, { maxLinks: 3 }).over, 'links');
+  const distinct = xmlDoc(
+    xmlEl(
+      'kml',
+      {},
+      ['a.png', 'b.png', 'c.png'].map((href) => xmlEl('href', {}, href)),
+    ),
+  );
+  assert.equal(countKmlGeometry(distinct, { maxLinks: 2 }).over, 'links');
 });
 
 test('a KMZ image gets one blob URL however many hrefs name it', () => {

src/ui/geoFileImport.js

@@ -409,6 +409,6 @@ export function summarize(outcomes) {
     0,
   );
   if (added && stripped)
-    parts.push('Network links and remote images in KML were left out.');
+    parts.push('KML descriptions and external references were left out.');
   return parts.join(' ');
 }

src/ui/geoFileImport.test.mjs

@@ -347,7 +347,7 @@ test('dropping files on the globe imports them; other drags are left alone', asy
 test('stripped KML content is mentioned once, for the batch that had it', () => {
   assert.equal(
     summarize([{ name: 'a.kml', ok: true, removed: 3 }]),
-    'Added 1 file. Network links and remote images in KML were left out.',
+    'Added 1 file. KML descriptions and external references were left out.',
   );
   assert.equal(
     summarize([{ name: 'b.geojson', ok: true, removed: 0 }]),