diff --git a/client/src/components/Map/engines/rtlRegistration.test.ts b/client/src/components/Map/engines/rtlRegistration.test.ts
new file mode 100644
index 000000000..b2cfb1585
--- /dev/null
+++ b/client/src/components/Map/engines/rtlRegistration.test.ts
@@ -0,0 +1,66 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+/**
+ * The two lines this fix actually adds. Everything else is a helper: the guard in
+ * rtlText.ts has its own tests, but a guard nobody calls looks exactly like a
+ * working fix from the outside. Deleting either registration, swapping an
+ * argument or dropping the deferred flag left the whole suite green.
+ *
+ * The engines are mocked because importing them for real builds a worker pool
+ * under jsdom, and the plugin URL is mocked so the 133 KB payload never loads.
+ */
+const { mapboxSet, maplibreSet } = vi.hoisted(() => ({
+  mapboxSet: vi.fn(),
+  maplibreSet: vi.fn(),
+}));
+
+vi.mock('mapbox-gl', () => ({ default: { setRTLTextPlugin: mapboxSet } }));
+vi.mock('maplibre-gl', () => ({ default: { setRTLTextPlugin: maplibreSet } }));
+vi.mock('mapbox-gl/dist/mapbox-gl.css', () => ({}));
+vi.mock('maplibre-gl/dist/maplibre-gl.css', () => ({}));
+vi.mock('@mapbox/mapbox-gl-rtl-text/dist/mapbox-gl-rtl-text.js?url', () => ({ default: '/assets/rtl-plugin.js' }));
+
+beforeEach(() => {
+  vi.resetModules();
+  mapboxSet.mockReset();
+  maplibreSet.mockReset();
+});
+
+describe('the GL engines register the RTL text plugin (#2235)', () => {
+  it('FE-MAP-RTL-001: importing the mapbox engine registers it deferred, with a null callback', async () => {
+    await import('./mapbox');
+
+    expect(mapboxSet).toHaveBeenCalledTimes(1);
+    // Mapbox GL 3 takes (url, callback, deferred). The third argument is what
+    // keeps the payload off the wire until a map paints RTL text; dropping it
+    // would fetch 133 KB for every user on every map.
+    expect(mapboxSet).toHaveBeenCalledWith(expect.stringContaining('rtl'), null, true);
+  });
+
+  it('FE-MAP-RTL-002: importing the maplibre engine registers it lazily', async () => {
+    await import('./maplibre');
+
+    expect(maplibreSet).toHaveBeenCalledTimes(1);
+    // MapLibre 5 takes (url, lazy) and returns a promise, which is the reason
+    // the call stays with each engine instead of going through one wrapper.
+    expect(maplibreSet).toHaveBeenCalledWith(expect.stringContaining('rtl'), true);
+  });
+
+  it('FE-MAP-RTL-003: an engine still loads when its registration throws', async () => {
+    mapboxSet.mockImplementation(() => { throw new Error('already registered'); });
+
+    const engine = await import('./mapbox');
+
+    expect(engine.default).toBeDefined();
+  });
+
+  it('FE-MAP-RTL-004: a rejected registration promise does not surface as an unhandled rejection', async () => {
+    maplibreSet.mockReturnValue(Promise.reject(new Error('already registered')));
+
+    const engine = await import('./maplibre');
+
+    expect(engine.default).toBeDefined();
+    // Give the rejection a tick to go unhandled if nothing caught it.
+    await new Promise((resolve) => setTimeout(resolve, 0));
+  });
+});
diff --git a/client/vite.config.js b/client/vite.config.js
index 30e28be1c..6ca0171a1 100644
--- a/client/vite.config.js
+++ b/client/vite.config.js
@@ -47,8 +47,14 @@ export default defineConfig(({ mode }) => ({
         // Every route chunk is precached alongside the shell, deliberately: for an
         // offline-first travel planner a route the user never opened before losing
         // signal still has to work. The trade is that splitting buys first paint and
-        // not install size — 107 entries / 17,795 KiB before any of it, 220 /
-        // 17,855 KiB now.
+        // not install size: 107 entries / 17,795 KiB before any of it, 463 /
+        // 23,292 KiB now (measured, not estimated).
+        //
+        // Keep this figure honest. #2228 traced PWA boot failures to the browser
+        // evicting this origin's whole bucket, precached shell included, and this
+        // comment is the only record of what the install actually costs. Anything
+        // matching the globs below is fetched at service-worker install by every
+        // user, whether or not they ever reach the code.
         globPatterns: ['**/*.{js,css,html,svg,png,woff,woff2,ttf}'],
         // build:analyze drops a treemap next to the app; it must never end up in a
         // precache manifest if someone ships that build by accident.