diff --git a/src/__tests__/UpdateToast.test.tsx b/src/__tests__/UpdateToast.test.tsx
new file mode 100644
index 0000000..4ebff28
--- /dev/null
+++ b/src/__tests__/UpdateToast.test.tsx
@@ -0,0 +1,63 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { render, cleanup } from '@testing-library/react'
+
+// Track the onRegistered callback so we can invoke it after render
+let capturedOnRegistered: ((reg: unknown) => void) | undefined
+
+vi.mock('virtual:pwa-register/react', () => ({
+  useRegisterSW: (opts: { onRegistered?: (reg: unknown) => void }) => {
+    capturedOnRegistered = opts.onRegistered
+    return {
+      needRefresh: [false, vi.fn()],
+      updateServiceWorker: vi.fn(),
+    }
+  },
+}))
+
+// Import after mock is set up
+import UpdateToast from '../components/UpdateToast'
+
+describe('UpdateToast', () => {
+  beforeEach(() => {
+    vi.useFakeTimers()
+    capturedOnRegistered = undefined
+  })
+
+  afterEach(() => {
+    cleanup()
+    vi.useRealTimers()
+  })
+
+  it('clears the update-check interval on unmount', () => {
+    const fakeRegistration = { update: vi.fn() }
+
+    const { unmount } = render(<UpdateToast />)
+
+    // Simulate the service worker registration callback
+    capturedOnRegistered?.(fakeRegistration)
+
+    // Advance time to confirm the interval is active
+    vi.advanceTimersByTime(60 * 60 * 1000)
+    expect(fakeRegistration.update).toHaveBeenCalledTimes(1)
+
+    // Unmount and advance again — no additional calls should happen
+    unmount()
+    vi.advanceTimersByTime(60 * 60 * 1000)
+    expect(fakeRegistration.update).toHaveBeenCalledTimes(1)
+  })
+
+  it('does not leak intervals across multiple mount/unmount cycles', () => {
+    const fakeRegistration = { update: vi.fn() }
+
+    // Mount and unmount 3 times
+    for (let i = 0; i < 3; i++) {
+      const { unmount } = render(<UpdateToast />)
+      capturedOnRegistered?.(fakeRegistration)
+      unmount()
+    }
+
+    // After all unmounts, advancing time should trigger zero calls
+    vi.advanceTimersByTime(60 * 60 * 1000)
+    expect(fakeRegistration.update).toHaveBeenCalledTimes(0)
+  })
+})
diff --git a/src/components/UpdateToast.tsx b/src/components/UpdateToast.tsx
index 1696b9c..d943d65 100644
--- a/src/components/UpdateToast.tsx
+++ b/src/components/UpdateToast.tsx
@@ -1,3 +1,4 @@
+import { useEffect, useRef } from 'react'
 import { useRegisterSW } from 'virtual:pwa-register/react'
 import { XIcon } from './Icons'
 
@@ -32,16 +33,26 @@ export function UpdateToastView({ className = '', onReload, onDismiss }: UpdateT
 const UPDATE_CHECK_INTERVAL_MS = 60 * 60 * 1000 // 1 hour
 
 export default function UpdateToast() {
+  const intervalRef = useRef<ReturnType<typeof setInterval> | null>(null)
+
   const {
     needRefresh: [needRefresh, setNeedRefresh],
     updateServiceWorker,
   } = useRegisterSW({
     onRegistered(registration) {
       if (!registration) return
-      setInterval(() => registration.update(), UPDATE_CHECK_INTERVAL_MS)
+      intervalRef.current = setInterval(() => registration.update(), UPDATE_CHECK_INTERVAL_MS)
     },
   })
 
+  useEffect(() => {
+    return () => {
+      if (intervalRef.current !== null) {
+        clearInterval(intervalRef.current)
+      }
+    }
+  }, [])
+
   if (!needRefresh) return null
 
   return (