diff --git a/packages/page-practice/lib/practice/Presenter.test.tsx b/packages/page-practice/lib/practice/Presenter.test.tsx
new file mode 100644
index 00000000..02564f1f
--- /dev/null
+++ b/packages/page-practice/lib/practice/Presenter.test.tsx
@@ -0,0 +1,62 @@
+import { test } from "node:test";
+import { FakeIntlProvider } from "@keybr/intl";
+import { lessonProps, LessonType } from "@keybr/lesson";
+import { FakePhoneticModel } from "@keybr/phonetic-model";
+import { PhoneticModelLoader } from "@keybr/phonetic-model-loader";
+import { FakeResultContext, ResultFaker } from "@keybr/result";
+import { FakeSettingsContext, Settings } from "@keybr/settings";
+import { act, render } from "@testing-library/react";
+import { includes, isNotNull } from "rich-assert";
+import { PracticeScreen } from "./PracticeScreen.tsx";
+
+// ---------------------------------------------------------------------------
+// Blur debounce — ad refresh regression tests
+// ---------------------------------------------------------------------------
+// Reproduces the bug reported in https://github.com/aradzie/keybr.com/issues/168:
+// third-party ad scripts steal focus briefly and then return it, which was
+// causing onResetLesson() to fire and interrupting the lesson mid-session.
+
+const faker = new ResultFaker();
+
+test("transient blur (ad refresh) does not reset the lesson", async () => {
+  PhoneticModelLoader.loader = FakePhoneticModel.loader;
+
+  const r = render(
+    <FakeIntlProvider>
+      <FakeSettingsContext
+        initialSettings={new Settings()
+          .set(lessonProps.type, LessonType.CUSTOM)
+          .set(lessonProps.customText.content, "abcdefghij")}
+      >
+        <FakeResultContext initialResults={faker.nextResultList(0)}>
+          <PracticeScreen />
+        </FakeResultContext>
+      </FakeSettingsContext>
+    </FakeIntlProvider>,
+  );
+
+  // Wait for the async practice screen to fully load.
+  isNotNull(await r.findByTitle("Change lesson settings", { exact: false }));
+
+  const textarea = r.container.querySelector("textarea");
+  isNotNull(textarea);
+
+  // Grab the lesson text before the blur cycle.
+  const textBefore = r.container.textContent!;
+  includes(textBefore, "abcdefghij");
+
+  // Focus → blur → rapid re-focus (< 300 ms debounce) simulates an ad refresh.
+  await act(async () => {
+    textarea!.focus();
+  });
+  await act(async () => {
+    textarea!.blur();
+    textarea!.focus();
+  });
+
+  // The lesson text should be unchanged — the transient blur must not have
+  // triggered a lesson reset.
+  includes(r.container.textContent!, "abcdefghij");
+
+  r.unmount();
+});
diff --git a/packages/page-practice/lib/practice/Presenter.tsx b/packages/page-practice/lib/practice/Presenter.tsx
index b1edb38d..26dee7e7 100644
--- a/packages/page-practice/lib/practice/Presenter.tsx
+++ b/packages/page-practice/lib/practice/Presenter.tsx
@@ -56,6 +56,7 @@ const propView = enumProp("prefs.practice.view", View, View.Normal);
 
 export class Presenter extends PureComponent<Props, State> {
   readonly focusRef = createRef<Focusable>();
+  #blurTimer: ReturnType<typeof setTimeout> | null = null;
 
   override state: State = {
     view: Preferences.get(propView),
@@ -72,6 +73,13 @@ export class Presenter extends PureComponent<Props, State> {
     }
   }
 
+  override componentWillUnmount() {
+    if (this.#blurTimer != null) {
+      clearTimeout(this.#blurTimer);
+      this.#blurTimer = null;
+    }
+  }
+
   override render() {
     const {
       props: { state, lines, depressedKeys },
@@ -218,6 +226,15 @@ export class Presenter extends PureComponent<Props, State> {
   };
 
   handleFocus = () => {
+    if (this.#blurTimer != null) {
+      // Focus returned before the debounce fired — this was a transient
+      // focus loss (e.g. an ad refresh). Cancel the reset and simply
+      // restore the focused state so the lesson continues uninterrupted.
+      clearTimeout(this.#blurTimer);
+      this.#blurTimer = null;
+      this.setState({ focus: true });
+      return;
+    }
     this.setState(
       {
         focus: true,
@@ -229,14 +246,18 @@ export class Presenter extends PureComponent<Props, State> {
   };
 
   handleBlur = () => {
-    this.setState(
-      {
-        focus: false,
-      },
-      () => {
-        this.props.onResetLesson();
-      },
-    );
+    this.setState({ focus: false });
+    // Delay the lesson reset to tolerate brief focus interruptions caused
+    // by third-party scripts (e.g. ad refreshes) that steal and quickly
+    // return focus. If focus comes back within the window the reset is
+    // cancelled; otherwise the lesson resets as normal.
+    if (this.#blurTimer != null) {
+      clearTimeout(this.#blurTimer);
+    }
+    this.#blurTimer = setTimeout(() => {
+      this.#blurTimer = null;
+      this.props.onResetLesson();
+    }, 300);
   };
 
   handleChangeView = () => {