diff --git a/src/store/middleware/__tests__/autoSyncManager.test.ts b/src/store/middleware/__tests__/autoSyncManager.test.ts
new file mode 100644
index 0000000..13018f7
--- /dev/null
+++ b/src/store/middleware/__tests__/autoSyncManager.test.ts
@@ -0,0 +1,112 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { AutoSyncManager } from '../autoSyncMiddleware'
+import { syncToFlaskBulk } from '../../slices/syncSlice'
+
+vi.mock('../../slices/syncSlice', () => ({
+  syncToFlaskBulk: vi.fn(() => ({ type: 'sync/syncToFlaskBulk' })),
+  checkFlaskConnection: vi.fn(() => ({ type: 'sync/checkConnection' })),
+}))
+
+type Deferred<T> = {
+  promise: Promise<T>
+  resolve: (value: T) => void
+  reject: (error?: unknown) => void
+}
+
+const createDeferred = <T,>(): Deferred<T> => {
+  let resolve!: (value: T) => void
+  let reject!: (error?: unknown) => void
+  const promise = new Promise<T>((res, rej) => {
+    resolve = res
+    reject = rej
+  })
+
+  return { promise, resolve, reject }
+}
+
+describe('AutoSyncManager', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('serializes syncs and runs one pending sync after completion', async () => {
+    const manager = new AutoSyncManager()
+    const deferreds = [createDeferred<void>(), createDeferred<void>()]
+    const dispatch = vi
+      .fn()
+      .mockImplementation(() => deferreds.shift()?.promise ?? Promise.resolve())
+
+    manager.setDispatch(dispatch)
+
+    const firstSync = manager.syncNow()
+    const secondSync = manager.syncNow()
+
+    expect(dispatch).toHaveBeenCalledTimes(1)
+
+    deferreds[0].resolve()
+    await Promise.resolve()
+
+    expect(dispatch).toHaveBeenCalledTimes(2)
+
+    deferreds[1].resolve()
+
+    await firstSync
+    await secondSync
+  })
+
+  it('resets changeCounter after a successful sync', async () => {
+    const manager = new AutoSyncManager()
+    const dispatch = vi.fn().mockResolvedValue(undefined)
+
+    manager.setDispatch(dispatch)
+    manager.trackChange()
+    manager.trackChange()
+
+    expect(manager.getStatus().changeCounter).toBe(2)
+
+    await manager.syncNow()
+
+    expect(manager.getStatus().changeCounter).toBe(0)
+    expect(dispatch).toHaveBeenCalledTimes(1)
+  })
+
+  it('coalesces multiple pending sync requests into one run', async () => {
+    const manager = new AutoSyncManager()
+    const deferreds = [createDeferred<void>(), createDeferred<void>()]
+    const dispatch = vi
+      .fn()
+      .mockImplementation(() => deferreds.shift()?.promise ?? Promise.resolve())
+
+    manager.setDispatch(dispatch)
+
+    const firstSync = manager.syncNow()
+    const secondSync = manager.syncNow()
+    const thirdSync = manager.syncNow()
+
+    expect(dispatch).toHaveBeenCalledTimes(1)
+
+    deferreds[0].resolve()
+    await Promise.resolve()
+
+    expect(dispatch).toHaveBeenCalledTimes(2)
+
+    deferreds[1].resolve()
+
+    await firstSync
+    await secondSync
+    await thirdSync
+
+    expect(dispatch).toHaveBeenCalledTimes(2)
+  })
+
+  it('dispatches the sync thunk when performing a sync', async () => {
+    const manager = new AutoSyncManager()
+    const dispatch = vi.fn().mockResolvedValue(undefined)
+
+    manager.setDispatch(dispatch)
+
+    await manager.syncNow()
+
+    expect(dispatch).toHaveBeenCalledWith(syncToFlaskBulk())
+  })
+})
diff --git a/src/store/middleware/autoSyncMiddleware.ts b/src/store/middleware/autoSyncMiddleware.ts
index 277769c..723a83a 100644
--- a/src/store/middleware/autoSyncMiddleware.ts
+++ b/src/store/middleware/autoSyncMiddleware.ts
@@ -9,7 +9,7 @@ interface AutoSyncConfig {
   maxQueueSize: number
 }
 
-class AutoSyncManager {
+export class AutoSyncManager {
   private config: AutoSyncConfig = {
     enabled: false,
     intervalMs: 30000,
@@ -21,6 +21,8 @@ class AutoSyncManager {
   private lastSyncTime = 0
   private changeCounter = 0
   private dispatch: any = null
+  private syncInFlight: Promise<void> | null = null
+  private pendingSync = false
 
   configure(config: Partial<AutoSyncConfig>) {
     this.config = { ...this.config, ...config }
@@ -69,12 +71,32 @@ class AutoSyncManager {
   private async performSync() {
     if (!this.dispatch) return
 
+    if (this.syncInFlight) {
+      this.pendingSync = true
+      return
+    }
+
+    const syncPromise = (async () => {
+      try {
+        await this.dispatch(syncToFlaskBulk())
+        this.lastSyncTime = Date.now()
+        this.changeCounter = 0
+      } catch (error) {
+        console.error('[AutoSync] Sync failed:', error)
+      }
+    })()
+
+    this.syncInFlight = syncPromise
+
     try {
-      await this.dispatch(syncToFlaskBulk())
-      this.lastSyncTime = Date.now()
-      this.changeCounter = 0
-    } catch (error) {
-      console.error('[AutoSync] Sync failed:', error)
+      await syncPromise
+    } finally {
+      this.syncInFlight = null
+    }
+
+    if (this.pendingSync) {
+      this.pendingSync = false
+      await this.performSync()
     }
   }