diff --git a/src/lib/unified-storage.test.ts b/src/lib/unified-storage.test.ts
new file mode 100644
index 0000000..276c9af
--- /dev/null
+++ b/src/lib/unified-storage.test.ts
@@ -0,0 +1,145 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+const {
+  callOrder,
+  mockFlaskGet,
+  mockIndexedGet,
+  mockSQLiteGet,
+  mockSparkGet,
+  MockFlaskBackendAdapter,
+  MockIndexedDBAdapter,
+  MockSQLiteAdapter,
+  MockSparkKVAdapter
+} = vi.hoisted(() => {
+  const callOrder: string[] = []
+  const mockFlaskGet = vi.fn<[], Promise<unknown>>()
+  const mockIndexedGet = vi.fn<[], Promise<unknown>>()
+  const mockSQLiteGet = vi.fn<[], Promise<unknown>>()
+  const mockSparkGet = vi.fn<[], Promise<unknown>>()
+
+  class MockFlaskBackendAdapter {
+    constructor() {
+      callOrder.push('flask')
+    }
+
+    get = mockFlaskGet
+  }
+
+  class MockIndexedDBAdapter {
+    constructor() {
+      callOrder.push('indexeddb')
+    }
+
+    get = mockIndexedGet
+  }
+
+  class MockSQLiteAdapter {
+    constructor() {
+      callOrder.push('sqlite')
+    }
+
+    get = mockSQLiteGet
+  }
+
+  class MockSparkKVAdapter {
+    constructor() {
+      callOrder.push('sparkkv')
+    }
+
+    get = mockSparkGet
+  }
+
+  return {
+    callOrder,
+    mockFlaskGet,
+    mockIndexedGet,
+    mockSQLiteGet,
+    mockSparkGet,
+    MockFlaskBackendAdapter,
+    MockIndexedDBAdapter,
+    MockSQLiteAdapter,
+    MockSparkKVAdapter
+  }
+})
+
+vi.mock('./unified-storage-adapters', () => ({
+  FlaskBackendAdapter: MockFlaskBackendAdapter,
+  IndexedDBAdapter: MockIndexedDBAdapter,
+  SQLiteAdapter: MockSQLiteAdapter,
+  SparkKVAdapter: MockSparkKVAdapter
+}))
+
+const createLocalStorageMock = () => {
+  const store = new Map<string, string>()
+
+  return {
+    getItem: vi.fn((key: string) => store.get(key) ?? null),
+    setItem: vi.fn((key: string, value: string) => {
+      store.set(key, value)
+    }),
+    removeItem: vi.fn((key: string) => {
+      store.delete(key)
+    }),
+    clear: vi.fn(() => {
+      store.clear()
+    })
+  }
+}
+
+describe('UnifiedStorage.detectAndInitialize', () => {
+  let localStorageMock: ReturnType<typeof createLocalStorageMock>
+
+  beforeEach(() => {
+    vi.resetModules()
+    callOrder.length = 0
+    mockFlaskGet.mockReset()
+    mockIndexedGet.mockReset()
+    mockSQLiteGet.mockReset()
+    mockSparkGet.mockReset()
+
+    localStorageMock = createLocalStorageMock()
+    vi.stubGlobal('localStorage', localStorageMock)
+    vi.stubGlobal('window', { spark: undefined })
+
+    if (!(import.meta as { env?: Record<string, string | undefined> }).env) {
+      ;(import.meta as { env?: Record<string, string | undefined> }).env = {}
+    }
+  })
+
+  it('tries Flask before IndexedDB when prefer-flask is set', async () => {
+    localStorageMock.setItem('codeforge-prefer-flask', 'true')
+    mockFlaskGet.mockRejectedValue(new Error('flask down'))
+    mockIndexedGet.mockResolvedValue(undefined)
+    vi.stubGlobal('indexedDB', {})
+
+    const { unifiedStorage } = await import('./unified-storage')
+    await unifiedStorage.getBackend()
+
+    expect(callOrder[0]).toBe('flask')
+    expect(callOrder).toContain('indexeddb')
+  })
+
+  it('falls back to IndexedDB when Flask initialization fails', async () => {
+    localStorageMock.setItem('codeforge-prefer-flask', 'true')
+    mockFlaskGet.mockRejectedValue(new Error('flask down'))
+    mockIndexedGet.mockResolvedValue(undefined)
+    vi.stubGlobal('indexedDB', {})
+
+    const { unifiedStorage } = await import('./unified-storage')
+    const backend = await unifiedStorage.getBackend()
+
+    expect(backend).toBe('indexeddb')
+  })
+
+  it('honors prefer-sqlite when configured', async () => {
+    localStorageMock.setItem('codeforge-prefer-sqlite', 'true')
+    mockSQLiteGet.mockResolvedValue(undefined)
+    delete (globalThis as { indexedDB?: unknown }).indexedDB
+
+    const { unifiedStorage } = await import('./unified-storage')
+    const backend = await unifiedStorage.getBackend()
+
+    expect(backend).toBe('sqlite')
+    expect(callOrder).toContain('sqlite')
+  })
+})
diff --git a/src/lib/unified-storage.ts b/src/lib/unified-storage.ts
index d430886..2ddd8a2 100644
--- a/src/lib/unified-storage.ts
+++ b/src/lib/unified-storage.ts
@@ -19,6 +19,23 @@ class UnifiedStorage {
       const flaskEnvUrl = import.meta.env.VITE_FLASK_BACKEND_URL
       const preferSQLite = localStorage.getItem('codeforge-prefer-sqlite') === 'true'
 
+      if (preferFlask || flaskEnvUrl) {
+        try {
+          console.log('[Storage] Flask backend explicitly configured, attempting to initialize...')
+          const flaskAdapter = new FlaskBackendAdapter(flaskEnvUrl)
+          await Promise.race([
+            flaskAdapter.get('_health_check'),
+            new Promise((_, reject) => setTimeout(() => reject(new Error('Flask connection timeout')), 2000))
+          ])
+          this.adapter = flaskAdapter
+          this.backend = 'flask'
+          console.log('[Storage] ✓ Using Flask backend')
+          return
+        } catch (error) {
+          console.warn('[Storage] Flask backend not available, falling back to IndexedDB:', error)
+        }
+      }
+
       if (typeof indexedDB !== 'undefined') {
         try {
           console.log('[Storage] Initializing default IndexedDB backend...')
@@ -33,26 +50,6 @@ class UnifiedStorage {
         }
       }
 
-      if (preferFlask || flaskEnvUrl) {
-        try {
-          console.log('[Storage] Flask backend explicitly configured, attempting to initialize...')
-          const flaskAdapter = new FlaskBackendAdapter(flaskEnvUrl)
-          const testResponse = await Promise.race([
-            flaskAdapter.get('_health_check'),
-            new Promise((_, reject) => setTimeout(() => reject(new Error('Flask connection timeout')), 2000))
-          ])
-          this.adapter = flaskAdapter
-          this.backend = 'flask'
-          console.log('[Storage] ✓ Using Flask backend')
-          return
-        } catch (error) {
-          console.warn('[Storage] Flask backend not available, already using IndexedDB:', error)
-          if (this.adapter && this.backend === 'indexeddb') {
-            return
-          }
-        }
-      }
-
       if (preferSQLite) {
         try {
           console.log('[Storage] SQLite fallback, attempting to initialize...')