diff --git a/src/tests/backend/specs/settings_cjs_compat.ts b/src/tests/backend/specs/settings_cjs_compat.ts
new file mode 100644
index 000000000..c31fcebd3
--- /dev/null
+++ b/src/tests/backend/specs/settings_cjs_compat.ts
@@ -0,0 +1,41 @@
+'use strict';
+
+import {describe, it} from 'mocha';
+import assert from 'assert';
+
+describe('Settings CJS compatibility', function () {
+  it('CJS require can read settings properties directly', async function () {
+    // Simulate CJS require - the module.exports compatibility layer should
+    // expose settings properties directly (not under .default)
+    const settings = require('ep_etherpad-lite/node/utils/Settings');
+    assert(settings.root != null, 'settings.root should be accessible');
+    assert(typeof settings.port === 'number', 'settings.port should be a number');
+  });
+
+  it('CJS require can write settings properties', async function () {
+    // Regression test: the CJS compatibility layer must have setters,
+    // not just getters, so plugins can mutate settings (e.g. in tests).
+    const settings = require('ep_etherpad-lite/node/utils/Settings');
+    const original = settings.requireAuthentication;
+    try {
+      settings.requireAuthentication = !original;
+      assert.strictEqual(settings.requireAuthentication, !original,
+          'setting should be writable via CJS require');
+    } finally {
+      settings.requireAuthentication = original;
+    }
+  });
+
+  it('CJS writes are visible through ESM default import', async function () {
+    const settingsCjs = require('ep_etherpad-lite/node/utils/Settings');
+    const {default: settingsEsm} = await import('ep_etherpad-lite/node/utils/Settings');
+    const original = settingsCjs.title;
+    try {
+      settingsCjs.title = 'CJS_TEST_VALUE';
+      assert.strictEqual(settingsEsm.title, 'CJS_TEST_VALUE',
+          'CJS setter should update the same underlying object as ESM import');
+    } finally {
+      settingsCjs.title = original;
+    }
+  });
+});