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diff --git a/packages/cli/src/ui/hooks/useReverseSearchCompletion.test.tsx b/packages/cli/src/ui/hooks/useReverseSearchCompletion.test.tsx
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@@ -0,0 +1,260 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/** @vitest-environment jsdom */
+
+import { describe, it, expect } from 'vitest';
+import { renderHook, act } from '@testing-library/react';
+import { useReverseSearchCompletion } from './useReverseSearchCompletion.js';
+import { useTextBuffer } from '../components/shared/text-buffer.js';
+
+describe('useReverseSearchCompletion', () => {
+  function useTextBufferForTest(text: string) {
+    return useTextBuffer({
+      initialText: text,
+      initialCursorOffset: text.length,
+      viewport: { width: 80, height: 20 },
+      isValidPath: () => false,
+      onChange: () => {},
+    });
+  }
+
+  describe('Core Hook Behavior', () => {
+    describe('State Management', () => {
+      it('should initialize with default state', () => {
+        const mockShellHistory = ['echo hello'];
+
+        const { result } = renderHook(() =>
+          useReverseSearchCompletion(
+            useTextBufferForTest(''),
+            mockShellHistory,
+            false,
+          ),
+        );
+
+        expect(result.current.suggestions).toEqual([]);
+        expect(result.current.activeSuggestionIndex).toBe(-1);
+        expect(result.current.visibleStartIndex).toBe(0);
+        expect(result.current.showSuggestions).toBe(false);
+        expect(result.current.isLoadingSuggestions).toBe(false);
+      });
+
+      it('should reset state when reverseSearchActive becomes false', () => {
+        const mockShellHistory = ['echo hello'];
+        const { result, rerender } = renderHook(
+          ({ text, active }) => {
+            const textBuffer = useTextBufferForTest(text);
+            return useReverseSearchCompletion(
+              textBuffer,
+              mockShellHistory,
+              active,
+            );
+          },
+          { initialProps: { text: 'echo', active: true } },
+        );
+
+        // Simulate reverseSearchActive becoming false
+        rerender({ text: 'echo', active: false });
+
+        expect(result.current.suggestions).toEqual([]);
+        expect(result.current.activeSuggestionIndex).toBe(-1);
+        expect(result.current.visibleStartIndex).toBe(0);
+        expect(result.current.showSuggestions).toBe(false);
+      });
+
+      describe('Navigation', () => {
+        it('should handle navigateUp with no suggestions', () => {
+          const mockShellHistory = ['echo hello'];
+
+          const { result } = renderHook(() =>
+            useReverseSearchCompletion(
+              useTextBufferForTest('grep'),
+              mockShellHistory,
+              true,
+            ),
+          );
+
+          act(() => {
+            result.current.navigateUp();
+          });
+
+          expect(result.current.activeSuggestionIndex).toBe(-1);
+        });
+
+        it('should handle navigateDown with no suggestions', () => {
+          const mockShellHistory = ['echo hello'];
+          const { result } = renderHook(() =>
+            useReverseSearchCompletion(
+              useTextBufferForTest('grep'),
+              mockShellHistory,
+              true,
+            ),
+          );
+
+          act(() => {
+            result.current.navigateDown();
+          });
+
+          expect(result.current.activeSuggestionIndex).toBe(-1);
+        });
+
+        it('should navigate up through suggestions with wrap-around', () => {
+          const mockShellHistory = [
+            'ls -l',
+            'ls -la',
+            'cd /some/path',
+            'git status',
+            'echo "Hello, World!"',
+            'echo Hi',
+          ];
+
+          const { result } = renderHook(() =>
+            useReverseSearchCompletion(
+              useTextBufferForTest('echo'),
+              mockShellHistory,
+              true,
+            ),
+          );
+
+          expect(result.current.suggestions.length).toBe(2);
+          expect(result.current.activeSuggestionIndex).toBe(0);
+
+          act(() => {
+            result.current.navigateUp();
+          });
+
+          expect(result.current.activeSuggestionIndex).toBe(1);
+        });
+
+        it('should navigate down through suggestions with wrap-around', () => {
+          const mockShellHistory = [
+            'ls -l',
+            'ls -la',
+            'cd /some/path',
+            'git status',
+            'echo "Hello, World!"',
+            'echo Hi',
+          ];
+          const { result } = renderHook(() =>
+            useReverseSearchCompletion(
+              useTextBufferForTest('ls'),
+              mockShellHistory,
+              true,
+            ),
+          );
+
+          expect(result.current.suggestions.length).toBe(2);
+          expect(result.current.activeSuggestionIndex).toBe(0);
+
+          act(() => {
+            result.current.navigateDown();
+          });
+
+          expect(result.current.activeSuggestionIndex).toBe(1);
+        });
+
+        it('should handle navigation with multiple suggestions', () => {
+          const mockShellHistory = [
+            'ls -l',
+            'ls -la',
+            'cd /some/path/l',
+            'git status',
+            'echo "Hello, World!"',
+            'echo "Hi all"',
+          ];
+
+          const { result } = renderHook(() =>
+            useReverseSearchCompletion(
+              useTextBufferForTest('l'),
+              mockShellHistory,
+              true,
+            ),
+          );
+
+          expect(result.current.suggestions.length).toBe(5);
+          expect(result.current.activeSuggestionIndex).toBe(0);
+
+          act(() => {
+            result.current.navigateDown();
+          });
+          expect(result.current.activeSuggestionIndex).toBe(1);
+
+          act(() => {
+            result.current.navigateDown();
+          });
+          expect(result.current.activeSuggestionIndex).toBe(2);
+
+          act(() => {
+            result.current.navigateUp();
+          });
+          expect(result.current.activeSuggestionIndex).toBe(1);
+
+          act(() => {
+            result.current.navigateUp();
+          });
+          expect(result.current.activeSuggestionIndex).toBe(0);
+
+          act(() => {
+            result.current.navigateUp();
+          });
+          expect(result.current.activeSuggestionIndex).toBe(4);
+        });
+
+        it('should handle navigation with large suggestion lists and scrolling', () => {
+          const largeMockCommands = Array.from(
+            { length: 15 },
+            (_, i) => `echo ${i}`,
+          );
+
+          const { result } = renderHook(() =>
+            useReverseSearchCompletion(
+              useTextBufferForTest('echo'),
+              largeMockCommands,
+              true,
+            ),
+          );
+
+          expect(result.current.suggestions.length).toBe(15);
+          expect(result.current.activeSuggestionIndex).toBe(0);
+          expect(result.current.visibleStartIndex).toBe(0);
+
+          act(() => {
+            result.current.navigateUp();
+          });
+
+          expect(result.current.activeSuggestionIndex).toBe(14);
+          expect(result.current.visibleStartIndex).toBe(Math.max(0, 15 - 8));
+        });
+      });
+    });
+  });
+
+  describe('Filtering', () => {
+    it('filters history by buffer.text and sets showSuggestions', () => {
+      const history = ['foo', 'barfoo', 'baz'];
+      const { result } = renderHook(() =>
+        useReverseSearchCompletion(useTextBufferForTest('foo'), history, true),
+      );
+
+      // should only return the two entries containing "foo"
+      expect(result.current.suggestions.map((s) => s.value)).toEqual([
+        'foo',
+        'barfoo',
+      ]);
+      expect(result.current.showSuggestions).toBe(true);
+    });
+
+    it('hides suggestions when there are no matches', () => {
+      const history = ['alpha', 'beta'];
+      const { result } = renderHook(() =>
+        useReverseSearchCompletion(useTextBufferForTest('γ'), history, true),
+      );
+
+      expect(result.current.suggestions).toEqual([]);
+      expect(result.current.showSuggestions).toBe(false);
+    });
+  });
+});