diff --git a/tests/unit/i18n.vendor.spec.js b/tests/unit/i18n.vendor.spec.js
new file mode 100644
index 0000000..93049b9
--- /dev/null
+++ b/tests/unit/i18n.vendor.spec.js
@@ -0,0 +1,44 @@
+// How to run this test in isolation:
+//   npm run test:unit -- i18n.vendor.spec.js
+// This verifies vendor overlays (e.g., nvidia shared folder) and vendor-root fallback
+// without requiring component mounts or full app boot.
+describe('i18n vendor overlays', () => {
+  const ORIGINAL_ENV = process.env;
+  beforeEach(() => {
+    jest.resetModules();
+    process.env = { ...ORIGINAL_ENV };
+    // Ensure default locale is deterministic for the test
+    window.localStorage.setItem('storedLanguage', 'en-US');
+  });
+
+  afterEach(() => {
+    process.env = ORIGINAL_ENV;
+  });
+
+  test('falls back to vendor root overlays when env has hyphenated suffix', async () => {
+    // Simulate running in nvidia-gb but having overlays only in src/env/locales/nvidia
+    process.env.VUE_APP_ENV_NAME = 'nvidia-gb';
+
+    const { createI18nInstance } = await import('@/i18n');
+    const vendorEn = require('@/env/locales/nvidia/en-US.json');
+    const stubLoader = () => ({ 'en-US': vendorEn.default || vendorEn });
+    const i18nInstance = createI18nInstance('nvidia-gb', 'en-US', stubLoader);
+
+    // System HGX dump is NVIDIA-specific and defined in src/env/locales/nvidia/en-US.json
+    const translated = i18nInstance.global.t(
+      'pageDumps.dumpTypes.systemHgxDump',
+    );
+    expect(translated).toBe('System [HGX] dump (disruptive)');
+  });
+
+  test('base locales do not contain vendor-only keys', async () => {
+    process.env.VUE_APP_ENV_NAME = undefined;
+    const { createI18nInstance } = await import('@/i18n');
+    const i18nInstance = createI18nInstance(undefined, 'en-US');
+    const translated = i18nInstance.global.t(
+      'pageDumps.dumpTypes.systemHgxDump',
+    );
+    // When no env overlays are loaded, accessing vendor-only keys should return the key path
+    expect(translated).toBe('pageDumps.dumpTypes.systemHgxDump');
+  });
+});