diff --git a/lib/hooks/useAISummarize.coverage.test.ts b/lib/hooks/useAISummarize.coverage.test.ts
new file mode 100644
index 0000000..2a918e8
--- /dev/null
+++ b/lib/hooks/useAISummarize.coverage.test.ts
@@ -0,0 +1,370 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { renderHook, act, waitFor } from '@testing-library/react';
+import { useAISummarize } from './useAISummarize';
+
+describe('useAISummarize Coverage', () => {
+    const mockSummarizer = {
+        summarize: vi.fn(),
+        summarizeStreaming: vi.fn(),
+        destroy: vi.fn(),
+    };
+
+    beforeEach(() => {
+        vi.stubGlobal('navigator', {
+            userActivation: { isActive: true },
+        });
+
+        const Summarizer = function() {};
+        Summarizer.availability = vi.fn().mockResolvedValue('readily');
+        Summarizer.create = vi.fn().mockResolvedValue(mockSummarizer);
+
+        vi.stubGlobal('Summarizer', Summarizer);
+
+        if (typeof window !== 'undefined') {
+            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            (window as any).Summarizer = Summarizer;
+        }
+    });
+
+    afterEach(() => {
+        vi.unstubAllGlobals();
+        vi.clearAllMocks();
+        if (typeof window !== 'undefined') {
+            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            delete (window as any).Summarizer;
+            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            delete (window as any).LanguageDetector;
+        }
+    });
+
+    it('should handle missing window.Summarizer', async () => {
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        delete (global as any).Summarizer;
+        if (typeof window !== 'undefined') {
+            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            delete (window as any).Summarizer;
+        }
+
+        const { result } = renderHook(() => useAISummarize());
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        expect(result.current.status).toBe('error');
+        expect(result.current.error?.message).toBe('Summarizer API not supported in this browser');
+    });
+
+    it('should handle Summarizer being a base constructor (Object)', async () => {
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        vi.stubGlobal('Summarizer', Object);
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        if (typeof window !== 'undefined') (window as any).Summarizer = Object;
+
+        const { result } = renderHook(() => useAISummarize());
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        expect(result.current.status).toBe('error');
+        expect(result.current.error?.message).toBe('Summarizer is not available');
+    });
+
+    it('should handle Summarizer availability "unavailable"', async () => {
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        (global as any).Summarizer.availability.mockResolvedValue('unavailable');
+
+        const { result } = renderHook(() => useAISummarize());
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        expect(result.current.status).toBe('error');
+        expect(result.current.error?.message).toBe('Summarizer is not available');
+    });
+
+    it('should set status to downloading if availability is "downloadable"', async () => {
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        (global as any).Summarizer.availability.mockResolvedValue('downloadable');
+        // Delay creation to capture downloading status
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        (global as any).Summarizer.create.mockImplementation(() => new Promise(resolve => setTimeout(() => resolve(mockSummarizer), 50)));
+
+        const { result } = renderHook(() => useAISummarize());
+
+        act(() => {
+            result.current.summarize('text');
+        });
+
+        await waitFor(() => expect(result.current.status).toBe('downloading'));
+        await waitFor(() => expect(result.current.status).toBe('success'));
+    });
+
+    it('should handle Summarizer.create being missing', async () => {
+        const Summarizer = function() {};
+        Summarizer.availability = vi.fn().mockResolvedValue('readily');
+
+        vi.stubGlobal('Summarizer', Summarizer);
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        if (typeof window !== 'undefined') (window as any).Summarizer = Summarizer;
+
+        const { result } = renderHook(() => useAISummarize());
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        expect(result.current.status).toBe('error');
+        expect(result.current.error?.message).toBe('Summarizer.create is not available');
+    });
+
+    it('should handle LanguageDetector being a base constructor (Array)', async () => {
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        vi.stubGlobal('LanguageDetector', Array);
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        if (typeof window !== 'undefined') (window as any).LanguageDetector = Array;
+
+        const { result } = renderHook(() => useAISummarize({ outputLanguage: 'auto' }));
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        // Should fallback to 'en'
+        expect(result.current.status).toBe('success');
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        expect((global as any).Summarizer.create).toHaveBeenCalledWith(
+            expect.objectContaining({ outputLanguage: 'en' })
+        );
+    });
+
+    it('should handle LanguageDetector availability "unavailable"', async () => {
+        const LanguageDetector = function() {};
+        LanguageDetector.availability = vi.fn().mockResolvedValue('unavailable');
+        LanguageDetector.create = vi.fn();
+
+        vi.stubGlobal('LanguageDetector', LanguageDetector);
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        if (typeof window !== 'undefined') (window as any).LanguageDetector = LanguageDetector;
+
+        const { result } = renderHook(() => useAISummarize({ outputLanguage: 'auto' }));
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        expect(result.current.status).toBe('success');
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        expect((global as any).Summarizer.create).toHaveBeenCalledWith(
+            expect.objectContaining({ outputLanguage: 'en' })
+        );
+    });
+
+    it('should handle LanguageDetector.create being missing', async () => {
+        const LanguageDetector = function() {};
+        LanguageDetector.availability = vi.fn().mockResolvedValue('readily');
+
+        vi.stubGlobal('LanguageDetector', LanguageDetector);
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        if (typeof window !== 'undefined') (window as any).LanguageDetector = LanguageDetector;
+
+        const { result } = renderHook(() => useAISummarize({ outputLanguage: 'auto' }));
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        expect(result.current.status).toBe('success');
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        expect((global as any).Summarizer.create).toHaveBeenCalledWith(
+            expect.objectContaining({ outputLanguage: 'en' })
+        );
+    });
+
+    it('should handle LanguageDetector returning empty results', async () => {
+        const mockDetector = {
+            detect: vi.fn().mockResolvedValue([]),
+            destroy: vi.fn(),
+        };
+        const LanguageDetector = function() {};
+        LanguageDetector.availability = vi.fn().mockResolvedValue('readily');
+        LanguageDetector.create = vi.fn().mockResolvedValue(mockDetector);
+
+        vi.stubGlobal('LanguageDetector', LanguageDetector);
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        if (typeof window !== 'undefined') (window as any).LanguageDetector = LanguageDetector;
+
+        const { result } = renderHook(() => useAISummarize({ outputLanguage: 'auto' }));
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        expect(result.current.status).toBe('success');
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        expect((global as any).Summarizer.create).toHaveBeenCalledWith(
+            expect.objectContaining({ outputLanguage: 'en' })
+        );
+    });
+
+    it('should reuse existing summarizer', async () => {
+        const { result } = renderHook(() => useAISummarize());
+
+        await act(async () => {
+            await result.current.summarize('first text');
+        });
+
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        expect((global as any).Summarizer.create).toHaveBeenCalledTimes(1);
+
+        await act(async () => {
+            await result.current.summarize('second text');
+        });
+
+        // Should not call create again
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        expect((global as any).Summarizer.create).toHaveBeenCalledTimes(1);
+    });
+
+    it('should use "en" as default outputLanguage during warmup if set to "auto"', async () => {
+        renderHook(() => useAISummarize({ warmup: true, outputLanguage: 'auto' }));
+
+        await waitFor(() => {
+            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            expect((global as any).Summarizer.create).toHaveBeenCalledWith(
+                expect.objectContaining({ outputLanguage: 'en' })
+            );
+        });
+    });
+
+    it('should use provided outputLanguage during warmup', async () => {
+        renderHook(() => useAISummarize({ warmup: true, outputLanguage: 'es' }));
+
+        await waitFor(() => {
+            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            expect((global as any).Summarizer.create).toHaveBeenCalledWith(
+                expect.objectContaining({ outputLanguage: 'es' })
+            );
+        });
+    });
+
+    it('should log error to console if warmup fails', async () => {
+        const consoleSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
+        const error = new Error('Warmup failed');
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        vi.mocked((global as any).Summarizer.create).mockRejectedValue(error);
+
+        renderHook(() => useAISummarize({ warmup: true }));
+
+        await waitFor(() => {
+            expect(consoleSpy).toHaveBeenCalledWith('Failed to warmup summarizer:', error);
+        });
+        consoleSpy.mockRestore();
+    });
+
+    it('should handle non-Error rejection in summarize', async () => {
+        mockSummarizer.summarize.mockRejectedValue('Something went wrong');
+
+        const { result } = renderHook(() => useAISummarize());
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        expect(result.current.status).toBe('error');
+        expect(result.current.error?.message).toBe('Unknown error during summarization');
+    });
+
+    it('should pass context to summarize', async () => {
+        mockSummarizer.summarize.mockResolvedValue('summary');
+
+        const { result } = renderHook(() => useAISummarize());
+
+        await act(async () => {
+            await result.current.summarize('text', 'some context');
+        });
+
+        expect(mockSummarizer.summarize).toHaveBeenCalledWith(
+            'text',
+            expect.objectContaining({ context: 'some context' })
+        );
+    });
+
+    it('should use provided outputLanguage when not "auto" or "user"', async () => {
+        const { result } = renderHook(() => useAISummarize({ outputLanguage: 'es' }));
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        expect((global as any).Summarizer.create).toHaveBeenCalledWith(
+            expect.objectContaining({ outputLanguage: 'es' })
+        );
+    });
+
+    it('should clear abortControllerRef on reset', async () => {
+        mockSummarizer.summarize.mockImplementation(() => new Promise(resolve => setTimeout(() => resolve('summary'), 100)));
+        const { result } = renderHook(() => useAISummarize());
+
+        act(() => {
+            result.current.summarize('text');
+        });
+
+        await waitFor(() => expect(result.current.status).toBe('summarizing'));
+
+        act(() => {
+            result.current.reset();
+        });
+
+        expect(result.current.status).toBe('idle');
+    });
+
+    it('should abort in-flight summarize on unmount', async () => {
+        const abortSpy = vi.fn();
+        const OriginalAbortController = global.AbortController;
+        vi.stubGlobal('AbortController', class extends OriginalAbortController {
+            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            abort(reason?: any) {
+                super.abort(reason);
+                abortSpy();
+            }
+        });
+
+        const { result, unmount } = renderHook(() => useAISummarize());
+
+        act(() => {
+            result.current.summarize('text');
+        });
+
+        await waitFor(() => expect(result.current.status).toBe('summarizing'));
+
+        unmount();
+        expect(abortSpy).toHaveBeenCalled();
+
+        vi.stubGlobal('AbortController', OriginalAbortController);
+    });
+
+    it('should fail if user activation is missing during language detection', async () => {
+        vi.stubGlobal('navigator', {
+            userActivation: { isActive: false },
+        });
+
+        const LanguageDetector = function() {};
+        vi.stubGlobal('LanguageDetector', LanguageDetector);
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        if (typeof window !== 'undefined') (window as any).LanguageDetector = LanguageDetector;
+
+        const { result } = renderHook(() => useAISummarize({ outputLanguage: 'auto' }));
+
+        await act(async () => {
+            await result.current.summarize('text');
+        });
+
+        // Even if detection falls back to 'en', creating the summarizer requires user activation
+        expect(result.current.status).toBe('error');
+        expect(result.current.error?.message).toContain('User activation required');
+    });
+});