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diff --git a/packages/cli/src/ui/hooks/useInputHistory.test.ts b/packages/cli/src/ui/hooks/useInputHistory.test.ts
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+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { act, renderHook } from '@testing-library/react';
+import { useInputHistory } from './useInputHistory.js';
+
+describe('useInputHistory', () => {
+  const mockOnSubmit = vi.fn();
+  const mockOnChange = vi.fn();
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  const userMessages = ['message 1', 'message 2', 'message 3'];
+
+  it('should initialize with historyIndex -1 and empty originalQueryBeforeNav', () => {
+    const { result } = renderHook(() =>
+      useInputHistory({
+        userMessages: [],
+        onSubmit: mockOnSubmit,
+        isActive: true,
+        currentQuery: '',
+        onChange: mockOnChange,
+      }),
+    );
+
+    // Internal state is not directly testable, but we can infer from behavior.
+    // Attempting to navigate down should do nothing if historyIndex is -1.
+    act(() => {
+      result.current.navigateDown();
+    });
+    expect(mockOnChange).not.toHaveBeenCalled();
+  });
+
+  describe('handleSubmit', () => {
+    it('should call onSubmit with trimmed value and reset history', () => {
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages,
+          onSubmit: mockOnSubmit,
+          isActive: true,
+          currentQuery: '  test query  ',
+          onChange: mockOnChange,
+        }),
+      );
+
+      act(() => {
+        result.current.handleSubmit('  submit value  ');
+      });
+
+      expect(mockOnSubmit).toHaveBeenCalledWith('submit value');
+      // Check if history is reset (e.g., by trying to navigate down)
+      act(() => {
+        result.current.navigateDown();
+      });
+      expect(mockOnChange).not.toHaveBeenCalled();
+    });
+
+    it('should not call onSubmit if value is empty after trimming', () => {
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages,
+          onSubmit: mockOnSubmit,
+          isActive: true,
+          currentQuery: '',
+          onChange: mockOnChange,
+        }),
+      );
+
+      act(() => {
+        result.current.handleSubmit('   ');
+      });
+
+      expect(mockOnSubmit).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('navigateUp', () => {
+    it('should not navigate if isActive is false', () => {
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages,
+          onSubmit: mockOnSubmit,
+          isActive: false,
+          currentQuery: 'current',
+          onChange: mockOnChange,
+        }),
+      );
+      act(() => {
+        const navigated = result.current.navigateUp();
+        expect(navigated).toBe(false);
+      });
+      expect(mockOnChange).not.toHaveBeenCalled();
+    });
+
+    it('should not navigate if userMessages is empty', () => {
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages: [],
+          onSubmit: mockOnSubmit,
+          isActive: true,
+          currentQuery: 'current',
+          onChange: mockOnChange,
+        }),
+      );
+      act(() => {
+        const navigated = result.current.navigateUp();
+        expect(navigated).toBe(false);
+      });
+      expect(mockOnChange).not.toHaveBeenCalled();
+    });
+
+    it('should call onChange with the last message when navigating up from initial state', () => {
+      const currentQuery = 'current query';
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages,
+          onSubmit: mockOnSubmit,
+          isActive: true,
+          currentQuery,
+          onChange: mockOnChange,
+        }),
+      );
+
+      act(() => {
+        result.current.navigateUp();
+      });
+
+      expect(mockOnChange).toHaveBeenCalledWith(userMessages[2]); // Last message
+    });
+
+    it('should store currentQuery as originalQueryBeforeNav on first navigateUp', () => {
+      const currentQuery = 'original user input';
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages,
+          onSubmit: mockOnSubmit,
+          isActive: true,
+          currentQuery,
+          onChange: mockOnChange,
+        }),
+      );
+
+      act(() => {
+        result.current.navigateUp(); // historyIndex becomes 0
+      });
+      expect(mockOnChange).toHaveBeenCalledWith(userMessages[2]);
+
+      // Navigate down to restore original query
+      act(() => {
+        result.current.navigateDown(); // historyIndex becomes -1
+      });
+      expect(mockOnChange).toHaveBeenCalledWith(currentQuery);
+    });
+
+    it('should navigate through history messages on subsequent navigateUp calls', () => {
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages,
+          onSubmit: mockOnSubmit,
+          isActive: true,
+          currentQuery: '',
+          onChange: mockOnChange,
+        }),
+      );
+
+      act(() => {
+        result.current.navigateUp(); // Navigates to 'message 3'
+      });
+      expect(mockOnChange).toHaveBeenCalledWith(userMessages[2]);
+
+      act(() => {
+        result.current.navigateUp(); // Navigates to 'message 2'
+      });
+      expect(mockOnChange).toHaveBeenCalledWith(userMessages[1]);
+
+      act(() => {
+        result.current.navigateUp(); // Navigates to 'message 1'
+      });
+      expect(mockOnChange).toHaveBeenCalledWith(userMessages[0]);
+    });
+  });
+
+  describe('navigateDown', () => {
+    it('should not navigate if isActive is false', () => {
+      const initialProps = {
+        userMessages,
+        onSubmit: mockOnSubmit,
+        isActive: true, // Start active to allow setup navigation
+        currentQuery: 'current',
+        onChange: mockOnChange,
+      };
+      const { result, rerender } = renderHook(
+        (props) => useInputHistory(props),
+        {
+          initialProps,
+        },
+      );
+
+      // First navigate up to have something in history
+      act(() => {
+        result.current.navigateUp();
+      });
+      mockOnChange.mockClear(); // Clear calls from setup
+
+      // Set isActive to false for the actual test
+      rerender({ ...initialProps, isActive: false });
+
+      act(() => {
+        const navigated = result.current.navigateDown();
+        expect(navigated).toBe(false);
+      });
+      expect(mockOnChange).not.toHaveBeenCalled();
+    });
+
+    it('should not navigate if historyIndex is -1 (not in history navigation)', () => {
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages,
+          onSubmit: mockOnSubmit,
+          isActive: true,
+          currentQuery: 'current',
+          onChange: mockOnChange,
+        }),
+      );
+      act(() => {
+        const navigated = result.current.navigateDown();
+        expect(navigated).toBe(false);
+      });
+      expect(mockOnChange).not.toHaveBeenCalled();
+    });
+
+    it('should restore originalQueryBeforeNav when navigating down to initial state', () => {
+      const originalQuery = 'my original input';
+      const { result } = renderHook(() =>
+        useInputHistory({
+          userMessages,
+          onSubmit: mockOnSubmit,
+          isActive: true,
+          currentQuery: originalQuery,
+          onChange: mockOnChange,
+        }),
+      );
+
+      act(() => {
+        result.current.navigateUp(); // Navigates to 'message 3', stores 'originalQuery'
+      });
+      expect(mockOnChange).toHaveBeenCalledWith(userMessages[2]);
+      mockOnChange.mockClear();
+
+      act(() => {
+        result.current.navigateDown(); // Navigates back to original query
+      });
+      expect(mockOnChange).toHaveBeenCalledWith(originalQuery);
+    });
+  });
+});