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diff --git a/packages/cli/src/ui/hooks/useLoadingIndicator.test.ts b/packages/cli/src/ui/hooks/useLoadingIndicator.test.ts
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+++ b/packages/cli/src/ui/hooks/useLoadingIndicator.test.ts
@@ -0,0 +1,164 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { renderHook, act } from '@testing-library/react';
+import { useLoadingIndicator } from './useLoadingIndicator.js';
+import { StreamingState } from '../types.js';
+import {
+  WITTY_LOADING_PHRASES,
+  PHRASE_CHANGE_INTERVAL_MS,
+} from '../constants.js';
+
+describe('useLoadingIndicator', () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('should initialize with default values when not responding', () => {
+    const { result } = renderHook(() =>
+      useLoadingIndicator(StreamingState.Idle, false),
+    );
+    expect(result.current.elapsedTime).toBe(0);
+    expect(result.current.currentLoadingPhrase).toBe(WITTY_LOADING_PHRASES[0]);
+    expect(result.current.shouldShowSpinner).toBe(true);
+  });
+
+  describe('when streamingState is Responding', () => {
+    it('should increment elapsedTime and cycle phrases when not paused', () => {
+      const { result } = renderHook(() =>
+        useLoadingIndicator(StreamingState.Responding, false),
+      );
+      expect(result.current.shouldShowSpinner).toBe(true);
+      expect(result.current.currentLoadingPhrase).toBe(
+        WITTY_LOADING_PHRASES[0],
+      );
+
+      act(() => {
+        vi.advanceTimersByTime(1000);
+      });
+      expect(result.current.elapsedTime).toBe(1);
+
+      act(() => {
+        vi.advanceTimersByTime(PHRASE_CHANGE_INTERVAL_MS);
+      });
+      expect(result.current.currentLoadingPhrase).toBe(
+        WITTY_LOADING_PHRASES[1],
+      );
+      expect(result.current.elapsedTime).toBe(
+        1 + PHRASE_CHANGE_INTERVAL_MS / 1000,
+      );
+    });
+
+    it('should pause elapsedTime, show specific phrase, and hide spinner when paused', () => {
+      const { result, rerender } = renderHook(
+        ({ isPaused }) =>
+          useLoadingIndicator(StreamingState.Responding, isPaused),
+        { initialProps: { isPaused: false } },
+      );
+
+      act(() => {
+        vi.advanceTimersByTime(2000);
+      });
+      expect(result.current.elapsedTime).toBe(2);
+      expect(result.current.shouldShowSpinner).toBe(true);
+
+      rerender({ isPaused: true });
+
+      expect(result.current.currentLoadingPhrase).toBe(
+        'Waiting for user confirmation...',
+      );
+      expect(result.current.shouldShowSpinner).toBe(false);
+
+      // Time should not advance while paused
+      const timeBeforePauseAdv = result.current.elapsedTime;
+      act(() => {
+        vi.advanceTimersByTime(3000);
+      });
+      expect(result.current.elapsedTime).toBe(timeBeforePauseAdv);
+
+      // Unpause
+      rerender({ isPaused: false });
+      expect(result.current.shouldShowSpinner).toBe(true);
+      // Phrase should reset to the beginning of witty phrases
+      expect(result.current.currentLoadingPhrase).toBe(
+        WITTY_LOADING_PHRASES[0],
+      );
+
+      act(() => {
+        vi.advanceTimersByTime(1000);
+      });
+      // Elapsed time should resume from where it left off
+      expect(result.current.elapsedTime).toBe(timeBeforePauseAdv + 1);
+    });
+
+    it('should reset timer and phrase when streamingState changes from Responding to Idle', () => {
+      const { result, rerender } = renderHook(
+        ({ streamingState }) => useLoadingIndicator(streamingState, false),
+        { initialProps: { streamingState: StreamingState.Responding } },
+      );
+
+      act(() => {
+        vi.advanceTimersByTime(PHRASE_CHANGE_INTERVAL_MS + 1000);
+      });
+      expect(result.current.elapsedTime).toBe(
+        PHRASE_CHANGE_INTERVAL_MS / 1000 + 1,
+      );
+      expect(result.current.currentLoadingPhrase).toBe(
+        WITTY_LOADING_PHRASES[1],
+      );
+
+      rerender({ streamingState: StreamingState.Idle });
+
+      expect(result.current.elapsedTime).toBe(0);
+      // When idle, the phrase interval should be cleared, but the last phrase might persist
+      // until the next "Responding" state. The important part is that the timer is reset.
+      // Depending on exact timing, it might be the last witty phrase or the first.
+      // For this test, we'll ensure it's one of them.
+      expect(WITTY_LOADING_PHRASES).toContain(
+        result.current.currentLoadingPhrase,
+      );
+    });
+  });
+
+  it('should clear intervals on unmount', () => {
+    const { unmount } = renderHook(() =>
+      useLoadingIndicator(StreamingState.Responding, false),
+    );
+    const clearIntervalSpy = vi.spyOn(global, 'clearInterval');
+    unmount();
+    // Expecting two intervals (elapsedTime and phraseInterval) to be cleared.
+    expect(clearIntervalSpy).toHaveBeenCalledTimes(2);
+  });
+
+  it('should reset to initial witty phrase when unpaused', () => {
+    const { result, rerender } = renderHook(
+      ({ isPaused }) =>
+        useLoadingIndicator(StreamingState.Responding, isPaused),
+      { initialProps: { isPaused: false } },
+    );
+
+    // Advance to the second witty phrase
+    act(() => {
+      vi.advanceTimersByTime(PHRASE_CHANGE_INTERVAL_MS);
+    });
+    expect(result.current.currentLoadingPhrase).toBe(WITTY_LOADING_PHRASES[1]);
+
+    // Pause
+    rerender({ isPaused: true });
+    expect(result.current.currentLoadingPhrase).toBe(
+      'Waiting for user confirmation...',
+    );
+
+    // Unpause
+    rerender({ isPaused: false });
+    expect(result.current.currentLoadingPhrase).toBe(WITTY_LOADING_PHRASES[0]);
+  });
+});