diff --git a/docs/CURRENT-STATE.md b/docs/CURRENT-STATE.md
index f9637b600..c41e24ade 100644
--- a/docs/CURRENT-STATE.md
+++ b/docs/CURRENT-STATE.md
@@ -178,9 +178,20 @@ one application, and only the globe-bound parts move to the next engine.
 
 - **The engine contract** is `src/globe/contract.js`. `src/globe/cesium/*` and
   `src/globe/navara/*` implement it, `src/globe/testing/fakeEngine.js` stands
-  in for tests, and `src/globe/testing/contractSuite.mjs` runs the same checks
-  on every engine. `movers` and `lines` are optional capabilities: only
+  in for tests, and `src/globe/testing/contractSuite.mjs` holds the checks
+  every engine must pass. `npm test` runs them on the fake engine;
+  `node scripts/qa-contract-suite.mjs <origin>` runs them in headless Chrome
+  on the real Cesium and Navara of a keyless dev server. On November 7, 2026
+  Cesium passed 57 of 57 and Navara 64 of 67: a resting move raised no
+  `moveEnd`, a click payload never came, and contact sonar lost an angle-only
+  change inside the app. `movers` and `lines` are optional capabilities: only
   Navara has them, and the suite skips their checks elsewhere.
+- **Engine coupling.** `node scripts/report-engine-coupling.mjs` counts the
+  engine-specific code outside the engines: renderer lines per engine, Cesium
+  imports, `viewer` mentions, engine-name checks, raw Navara reads, Navara
+  ground passes, Cesium SDK loads and `ScreenSpaceEventHandler` users.
+  `scripts/engineCoupling.test.mjs` (in `npm test`) fails when a count grows
+  past `scripts/engine-coupling-baseline.json`.
 - **The session owns the state.** Catalog, layer models, sources, selection,
   camera mode and URL state outlive a switch. A layer that is a session model
   gets `attachRenderer(engine)` / `detachRenderer()` instead of being rebuilt,
diff --git a/scripts/engine-coupling-baseline.json b/scripts/engine-coupling-baseline.json
new file mode 100644
index 000000000..71e03a271
--- /dev/null
+++ b/scripts/engine-coupling-baseline.json
@@ -0,0 +1,16 @@
+{
+  "metrics": {
+    "cesiumLayerRendererLines": 5239,
+    "navaraLayerRendererLines": 12331,
+    "cesiumImportFiles": 69,
+    "viewerLines": 2424,
+    "navaraKindChecks": 17,
+    "engineSniffCalls": 51,
+    "navaraViewsReads": 27,
+    "groundEffectPasses": 9,
+    "cesiumSdkLoads": 6,
+    "screenSpaceHandlerFiles": 20,
+    "engineNameLines": 175
+  },
+  "measuredAt": "german/navara merged with origin/main 8da8c05e, 2026-11-07"
+}
diff --git a/scripts/engineCoupling.test.mjs b/scripts/engineCoupling.test.mjs
new file mode 100644
index 000000000..7830b26fb
--- /dev/null
+++ b/scripts/engineCoupling.test.mjs
@@ -0,0 +1,41 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import {
+  ENGINE_COUPLING_METRICS,
+  couplingGrowth,
+  measureEngineCoupling,
+  readBaseline,
+} from './report-engine-coupling.mjs';
+
+test('engine coupling does not grow past the baseline', () => {
+  const growth = couplingGrowth(
+    measureEngineCoupling(),
+    readBaseline().metrics,
+  );
+  assert.deepEqual(
+    growth,
+    [],
+    'Code outside the globe engines grew more engine-specific. Draw through ' +
+      'the globe contract instead; only a deliberate exception may raise ' +
+      'scripts/engine-coupling-baseline.json (--write-baseline).',
+  );
+});
+
+test('the baseline names every metric', () => {
+  const { metrics } = readBaseline();
+  assert.deepEqual(
+    Object.keys(metrics).sort(),
+    ENGINE_COUPLING_METRICS.map(({ id }) => id).sort(),
+  );
+});
+
+test('a metric that grows is reported, one that falls is not', () => {
+  const baseline = Object.fromEntries(
+    ENGINE_COUPLING_METRICS.map(({ id }) => [id, 10]),
+  );
+  const measured = { ...baseline, viewerLines: 11, navaraKindChecks: 3 };
+  assert.deepEqual(
+    couplingGrowth(measured, baseline).map(({ id }) => id),
+    ['viewerLines'],
+  );
+});
diff --git a/scripts/format-scope.json b/scripts/format-scope.json
index 6f7704712..d30a2cf57 100644
--- a/scripts/format-scope.json
+++ b/scripts/format-scope.json
@@ -1616,5 +1616,9 @@
   "src/layers/wildlifeSightings/density.test.mjs",
   "src/layers/wildlifeSightings/selection.test.mjs",
   "server/providers/inaturalist/proxy.fixture.mjs",
-  "src/globe/cesium/doubleClick.js"
+  "scripts/report-engine-coupling.mjs",
+  "scripts/engineCoupling.test.mjs",
+  "scripts/qa-contract-suite.mjs",
+  "src/globe/cesium/doubleClick.js",
+  "scripts/engine-coupling-baseline.json"
 ]
diff --git a/scripts/qa-contract-suite.mjs b/scripts/qa-contract-suite.mjs
new file mode 100644
index 000000000..643a49e43
--- /dev/null
+++ b/scripts/qa-contract-suite.mjs
@@ -0,0 +1,141 @@
+#!/usr/bin/env node
+/**
+ * Run the globe contract suite (src/globe/testing/contractSuite.mjs) in
+ * headless Chrome against the real engines of a running app, the way
+ * contract.test.mjs runs it against the fake engine.
+ *
+ *   GOOGLE_MAPS_API_KEY= CESIUM_ION_TOKEN= npm run dev -- --port 4241
+ *   node scripts/qa-contract-suite.mjs http://localhost:4241 [--engine=cesium,navara] [--json=FILE]
+ *
+ * Serve the app keyless from the dev server: Google and Cesium ion requests
+ * are refused here anyway, so neither engine draws photoreal tiles. The page
+ * imports the suite from the dev server, so it shares the app's modules (an
+ * engine event is recognised by the module that made it). It gets a real
+ * pointer (the pick checks) and no map sources (the maps checks would ask for
+ * photoreal tiles). Exits 1 when any check fails on any engine.
+ */
+import fs from 'node:fs';
+import puppeteer from 'puppeteer';
+
+const BLOCKED_HOSTS =
+  /(^|\.)(googleapis\.com|google\.com|gstatic\.com|cesium\.com)$/;
+
+const args = process.argv.slice(2);
+const origin = args.find((arg) => !arg.startsWith('--'));
+const option = (name) =>
+  args.find((arg) => arg.startsWith(`--${name}=`))?.slice(name.length + 3);
+if (!origin) {
+  console.error(
+    'Usage: node scripts/qa-contract-suite.mjs <origin> [--engine=cesium,navara] [--json=FILE]',
+  );
+  process.exit(2);
+}
+const engines = (option('engine') ?? 'cesium,navara').split(',');
+
+async function runOn(browser, kind) {
+  const page = await browser.newPage();
+  await page.setViewport({ width: 1280, height: 800 });
+  const pageErrors = [];
+  page.on('pageerror', (error) => pageErrors.push(error.message));
+  await page.setRequestInterception(true);
+  page.on('request', (request) => {
+    const { hostname } = new URL(request.url());
+    if (BLOCKED_HOSTS.test(hostname)) request.abort();
+    else request.continue();
+  });
+  // A view in the link: the app starts there instead of flying to a city.
+  await page.goto(
+    `${origin}/?welcome=0&engine=${kind}#v=2&lat=10&lon=20&alt=1000000&heading=0&pitch=-90&map=osm&l=`,
+  );
+  await page.waitForFunction(
+    (expected) =>
+      window.__godsEyeView?.engine?.kind === expected &&
+      document.getElementById('loading-screen')?.classList.contains('hidden'),
+    // A cold dev server compiles Navara's modules on the first visit.
+    { timeout: 300_000, polling: 250 },
+    kind,
+  );
+  // The suite owns the globe: no camera flight running, and the app's panels
+  // let the pointer through to the canvas.
+  await page.waitForFunction(
+    () => !window.__godsEyeView.engine.camera.flightActive(),
+    { timeout: 60_000, polling: 250 },
+  );
+  await page.addStyleTag({
+    content:
+      '* { pointer-events: none !important; } canvas { pointer-events: auto !important; }',
+  });
+  // A real left click and pointer move at a canvas position.
+  await page.exposeFunction('__contractPointer', async (type, x, y) => {
+    const box = await page.evaluate(() => {
+      const rect =
+        window.__godsEyeView.engine.host.canvas.getBoundingClientRect();
+      return { left: rect.left, top: rect.top };
+    });
+    const at = [box.left + x, box.top + y];
+    if (type === 'click') await page.mouse.click(...at);
+    else {
+      await page.mouse.move(at[0] - 1, at[1]);
+      await page.mouse.move(...at);
+    }
+  });
+  const results = await page.evaluate(async () => {
+    const { engine } = window.__godsEyeView;
+    const waitFrames = (count) =>
+      new Promise((resolve) => {
+        let left = count;
+        const remove = engine.frames.postRender.addEventListener(() => {
+          if (--left > 0) return;
+          remove();
+          resolve();
+        });
+        engine.render.request('contract-suite');
+      });
+    const pointer = {
+      click: (x, y) => window.__contractPointer('click', x, y),
+      move: (x, y) => window.__contractPointer('move', x, y),
+    };
+    const { runContractSuite } =
+      await import('/src/globe/testing/contractSuite.mjs');
+    const outcome = await runContractSuite(engine, {
+      waitFrames,
+      pointer,
+    });
+    return outcome.map(({ name, ok, error }) => ({
+      name,
+      ok,
+      error: error ? String(error.message ?? error) : undefined,
+    }));
+  });
+  await page.close();
+  return { engine: kind, results, pageErrors };
+}
+
+const browser = await puppeteer.launch({
+  headless: true,
+  // A Navara page can hold its main thread for minutes while it starts.
+  protocolTimeout: 600_000,
+  args: ['--use-angle=metal', '--enable-gpu', '--no-sandbox'],
+});
+const report = [];
+try {
+  for (const kind of engines) {
+    const run = await runOn(browser, kind);
+    report.push(run);
+    const failed = run.results.filter(({ ok }) => !ok);
+    console.log(
+      `${kind}: ${run.results.length - failed.length}/${run.results.length} checks pass`,
+    );
+    for (const { name, error } of failed)
+      console.log(`  FAIL ${name}: ${error}`);
+    for (const message of run.pageErrors)
+      console.log(`  page error: ${message}`);
+  }
+} finally {
+  await browser.close();
+}
+const json = option('json');
+if (json) fs.writeFileSync(json, `${JSON.stringify(report, null, 2)}\n`);
+process.exit(
+  report.every(({ results }) => results.every(({ ok }) => ok)) ? 0 : 1,
+);
diff --git a/scripts/report-engine-coupling.mjs b/scripts/report-engine-coupling.mjs
new file mode 100644
index 000000000..35e600164
--- /dev/null
+++ b/scripts/report-engine-coupling.mjs
@@ -0,0 +1,232 @@
+#!/usr/bin/env node
+/**
+ * How tightly the application is still tied to one globe engine: counts of
+ * engine-specific code outside the engines (src/globe/cesium, src/globe/navara).
+ * The renderer-abstraction work drives every number down; none may grow.
+ * engineCoupling.test.mjs (npm test) compares a fresh count with
+ * scripts/engine-coupling-baseline.json.
+ *
+ * Only production sources count: `.js` and `.vue` under src. Tests, fixtures
+ * and test doubles are `.mjs`.
+ *
+ *   node scripts/report-engine-coupling.mjs            # table
+ *   node scripts/report-engine-coupling.mjs --json
+ *   node scripts/report-engine-coupling.mjs --write-baseline
+ */
+import fs from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath, pathToFileURL } from 'node:url';
+
+const ROOT = fileURLToPath(new URL('..', import.meta.url));
+export const BASELINE_PATH = path.join(
+  ROOT,
+  'scripts',
+  'engine-coupling-baseline.json',
+);
+
+const inEngine = (file) =>
+  file.startsWith('src/globe/cesium/') || file.startsWith('src/globe/navara/');
+const inGlobe = (file) => file.startsWith('src/globe/');
+const isLayerRenderer = (engine) => (file) =>
+  file.startsWith('src/layers/') &&
+  new RegExp(`/render/${engine}([^/]*\\.js|/.+\\.js)$`).test(file);
+const isRenderer = (file) => /\/render\//.test(file);
+
+const lines = (text) => text.split('\n');
+const countLines = (text, pattern) =>
+  lines(text).filter((line) => pattern.test(line)).length;
+const countMatches = (text, pattern) =>
+  (text.match(new RegExp(pattern.source, 'g')) ?? []).length;
+
+/**
+ * The metrics, in report order. `measure(files)` gets every production
+ * source as `{ file, text }` (file relative to the repository, with `/`).
+ */
+export const ENGINE_COUPLING_METRICS = Object.freeze([
+  {
+    id: 'cesiumLayerRendererLines',
+    label: 'Lines in src/layers/**/render/cesium*',
+    measure: (files) =>
+      files
+        .filter(({ file }) => isLayerRenderer('cesium')(file))
+        .reduce((sum, { text }) => sum + lines(text).length, 0),
+  },
+  {
+    id: 'navaraLayerRendererLines',
+    label: 'Lines in src/layers/**/render/navara*',
+    measure: (files) =>
+      files
+        .filter(({ file }) => isLayerRenderer('navara')(file))
+        .reduce((sum, { text }) => sum + lines(text).length, 0),
+  },
+  {
+    id: 'cesiumImportFiles',
+    label: "Files importing 'cesium' outside src/globe/cesium and render/",
+    measure: (files) =>
+      files.filter(
+        ({ file, text }) =>
+          !file.startsWith('src/globe/cesium/') &&
+          !isRenderer(file) &&
+          /from\s+['"]cesium['"]|import\(\s*['"]cesium['"]\s*\)/.test(text),
+      ).length,
+  },
+  {
+    id: 'viewerLines',
+    label: 'Lines naming `viewer` outside src/globe/cesium',
+    measure: (files) =>
+      files
+        .filter(({ file }) => !file.startsWith('src/globe/cesium/'))
+        .reduce((sum, { text }) => sum + countLines(text, /\bviewer\b/), 0),
+  },
+  {
+    id: 'navaraKindChecks',
+    label: "`kind === 'navara'` checks outside src/globe",
+    measure: (files) =>
+      files
+        .filter(({ file }) => !inGlobe(file))
+        .reduce(
+          (sum, { text }) =>
+            sum + countMatches(text, /kind\s*[!=]==?\s*['"]navara['"]/),
+          0,
+        ),
+  },
+  {
+    id: 'engineSniffCalls',
+    label: 'isGlobeEngine / engineFromViewer calls outside src/globe',
+    measure: (files) =>
+      files
+        .filter(({ file }) => !inGlobe(file))
+        .reduce(
+          (sum, { text }) =>
+            sum + countMatches(text, /\b(?:isGlobeEngine|engineFromViewer)\(/),
+          0,
+        ),
+  },
+  {
+    id: 'navaraViewsReads',
+    label: 'Raw Navara reads through navaraViews',
+    measure: (files) =>
+      files
+        .filter(({ file }) => !inEngine(file))
+        .reduce(
+          (sum, { text }) => sum + countMatches(text, /\bnavaraViews\.get\(/),
+          0,
+        ),
+  },
+  {
+    id: 'groundEffectPasses',
+    label: 'Navara ground passes (defineGroundEffect calls)',
+    measure: (files) =>
+      files.reduce(
+        (sum, { text }) =>
+          sum + countMatches(text, /\bdefineGroundEffect\(\s*\{/),
+        0,
+      ),
+  },
+  {
+    id: 'cesiumSdkLoads',
+    label: 'Cesium SDK loads outside the engines and loadCesium.js',
+    measure: (files) =>
+      files
+        .filter(
+          ({ file }) => !inEngine(file) && file !== 'src/app/loadCesium.js',
+        )
+        .reduce(
+          (sum, { text }) =>
+            sum + countMatches(text, /\b(?:loadCesiumSdk|whenCesiumSdk)\(/),
+          0,
+        ),
+  },
+  {
+    id: 'screenSpaceHandlerFiles',
+    label: 'Files in src/layers and src/data using ScreenSpaceEventHandler',
+    measure: (files) =>
+      files.filter(
+        ({ file, text }) =>
+          (file.startsWith('src/layers/') || file.startsWith('src/data/')) &&
+          /ScreenSpaceEventHandler/.test(text),
+      ).length,
+  },
+  {
+    id: 'engineNameLines',
+    label:
+      "Lines with an engine name literal ('navara', 'cesium') outside src/globe",
+    measure: (files) =>
+      files
+        .filter(({ file }) => !inGlobe(file))
+        .reduce(
+          (sum, { text }) =>
+            sum + countLines(text, /['"](?:navara|cesium)['"]/),
+          0,
+        ),
+  },
+]);
+
+/** Production sources under `root`/src: `.js` and `.vue`. */
+export function readProductionSources(root = ROOT) {
+  const files = [];
+  const visit = (directory) => {
+    for (const entry of fs.readdirSync(directory, { withFileTypes: true })) {
+      const absolute = path.join(directory, entry.name);
+      if (entry.isDirectory()) visit(absolute);
+      else if (entry.isFile() && /\.(?:js|vue)$/.test(entry.name))
+        files.push({
+          file: path.relative(root, absolute).split(path.sep).join('/'),
+          text: fs.readFileSync(absolute, 'utf8'),
+        });
+    }
+  };
+  visit(path.join(root, 'src'));
+  return files.sort((a, b) => a.file.localeCompare(b.file));
+}
+
+/** Every metric's value for the sources under `root`. */
+export function measureEngineCoupling(root = ROOT) {
+  const files = readProductionSources(root);
+  return Object.fromEntries(
+    ENGINE_COUPLING_METRICS.map(({ id, measure }) => [id, measure(files)]),
+  );
+}
+
+/** The metrics that grew past `baseline`, with both values. */
+export function couplingGrowth(measured, baseline) {
+  return ENGINE_COUPLING_METRICS.filter(
+    ({ id }) => !(measured[id] <= (baseline[id] ?? -Infinity)),
+  ).map(({ id, label }) => ({
+    id,
+    label,
+    measured: measured[id],
+    baseline: baseline[id],
+  }));
+}
+
+export function readBaseline(file = BASELINE_PATH) {
+  return JSON.parse(fs.readFileSync(file, 'utf8'));
+}
+
+function main(args) {
+  const measured = measureEngineCoupling();
+  if (args.includes('--write-baseline')) {
+    const note = args.find((arg) => arg.startsWith('--note='))?.slice(7);
+    fs.writeFileSync(
+      BASELINE_PATH,
+      `${JSON.stringify({ metrics: measured, ...(note ? { measuredAt: note } : {}) }, null, 2)}\n`,
+    );
+  }
+  if (args.includes('--json')) {
+    console.log(JSON.stringify(measured, null, 2));
+    return;
+  }
+  const baseline = fs.existsSync(BASELINE_PATH) ? readBaseline().metrics : {};
+  for (const { id, label } of ENGINE_COUPLING_METRICS) {
+    const was = baseline[id];
+    const change =
+      was === undefined
+        ? ''
+        : ` (baseline ${was}, ${measured[id] - was >= 0 ? '+' : ''}${measured[id] - was})`;
+    console.log(`${String(measured[id]).padStart(7)}  ${label}${change}`);
+  }
+}
+
+if (import.meta.url === pathToFileURL(process.argv[1] ?? '').href)
+  main(process.argv.slice(2));