diff --git a/web/service/__tests__/request-error-toast.spec.ts b/web/service/__tests__/request-error-toast.spec.ts
new file mode 100644
index 00000000000..c76780b4c29
--- /dev/null
+++ b/web/service/__tests__/request-error-toast.spec.ts
@@ -0,0 +1,204 @@
+import { toast } from '@langgenius/dify-ui/toast'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vite-plus/test'
+// oxlint-disable-next-line no-restricted-imports -- Exercise the shared request transport and its notification behavior.
+import { base } from '../fetch'
+import { clearRequestErrorToasts, notifyRequestError } from '../request-error-toast'
+
+vi.mock('@langgenius/dify-ui/toast', () => ({
+  toast: { error: vi.fn() },
+}))
+
+describe('request error toast timer lifecycle', () => {
+  const request = { method: 'GET', url: 'https://example.com/apps' }
+
+  beforeEach(() => {
+    vi.useFakeTimers()
+    vi.clearAllMocks()
+  })
+
+  afterEach(() => {
+    vi.runOnlyPendingTimers()
+    vi.useRealTimers()
+  })
+
+  it('expires by wall clock even when the timer callback has not run', () => {
+    notifyRequestError(request, 'A')
+
+    vi.setSystemTime(Date.now() + 10000)
+    notifyRequestError(request, 'A')
+
+    expect(vi.mocked(toast.error).mock.calls).toEqual([['A'], ['A']])
+  })
+
+  it('keeps a reopened window active past the cleared window’s old deadline', async () => {
+    notifyRequestError(request, 'A')
+    await vi.advanceTimersByTimeAsync(2000)
+    clearRequestErrorToasts(request)
+    notifyRequestError(request, 'A')
+
+    await vi.advanceTimersByTimeAsync(8000)
+    notifyRequestError(request, 'A')
+    expect(toast.error).toHaveBeenCalledTimes(2)
+
+    await vi.advanceTimersByTimeAsync(2000)
+    notifyRequestError(request, 'A')
+    expect(toast.error).toHaveBeenCalledTimes(3)
+  })
+
+  it('expires staggered messages independently', async () => {
+    notifyRequestError(request, 'A')
+    await vi.advanceTimersByTimeAsync(2000)
+    notifyRequestError(request, 'B')
+
+    await vi.advanceTimersByTimeAsync(8000)
+    notifyRequestError(request, 'A')
+    notifyRequestError(request, 'B')
+    expect(vi.mocked(toast.error).mock.calls).toEqual([['A'], ['B'], ['A']])
+
+    await vi.advanceTimersByTimeAsync(2000)
+    notifyRequestError(request, 'A')
+    notifyRequestError(request, 'B')
+    expect(vi.mocked(toast.error).mock.calls).toEqual([['A'], ['B'], ['A'], ['B']])
+  })
+})
+
+const errorResponse = (message = 'Unavailable', status = 500) =>
+  new Response(JSON.stringify({ message, status }), {
+    status,
+    headers: { 'Content-Type': 'application/json' },
+  })
+
+const expectError = async (...args: Parameters<typeof base>) => {
+  await expect(base(...args)).rejects.toMatchObject({ status: 500 })
+}
+
+describe('request error toast deduplication', () => {
+  const network = vi.fn<typeof fetch>()
+
+  beforeEach(() => {
+    vi.useFakeTimers()
+    vi.clearAllMocks()
+    network.mockReset()
+    network.mockImplementation(async () => errorResponse())
+    vi.stubGlobal('fetch', network)
+  })
+
+  afterEach(() => {
+    vi.runOnlyPendingTimers()
+    vi.useRealTimers()
+    vi.unstubAllGlobals()
+  })
+
+  it('shows immediately and again at 10000ms without extending the window for suppressed errors', async () => {
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledExactlyOnceWith('Unavailable')
+
+    await vi.advanceTimersByTimeAsync(5000)
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledTimes(1)
+
+    // Reach 9999ms from the last displayed toast.
+    await vi.advanceTimersByTimeAsync(4999)
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledTimes(1)
+
+    await vi.advanceTimersByTimeAsync(1)
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledTimes(2)
+
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledTimes(2)
+    expect(network).toHaveBeenCalledTimes(5)
+  })
+
+  it('shows each distinct message while suppressing a previously shown message', async () => {
+    network
+      .mockResolvedValueOnce(errorResponse('A'))
+      .mockResolvedValueOnce(errorResponse('B'))
+      .mockResolvedValueOnce(errorResponse('A'))
+
+    await expectError('/apps')
+    await expectError('/apps')
+    await expectError('/apps')
+
+    expect(toast.error).toHaveBeenCalledTimes(2)
+    expect(toast.error).toHaveBeenNthCalledWith(1, 'A')
+    expect(toast.error).toHaveBeenNthCalledWith(2, 'B')
+  })
+
+  it.each([
+    ['URL', '/datasets', {}],
+    ['query params', '/apps', { params: { page: 2 } }],
+  ] as const)(
+    'shows the same message independently for a different %s',
+    async (_, url, options) => {
+      await expectError('/apps')
+      await expectError(url, options)
+      await expectError('/apps')
+      await expectError(url, options)
+
+      expect(toast.error).toHaveBeenCalledTimes(2)
+      expect(toast.error).toHaveBeenNthCalledWith(1, 'Unavailable')
+      expect(toast.error).toHaveBeenNthCalledWith(2, 'Unavailable')
+    },
+  )
+
+  it('shows every POST, PUT, PATCH, and DELETE error even while the same GET error is suppressed', async () => {
+    await expectError('/apps')
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledExactlyOnceWith('Unavailable')
+
+    for (const method of ['POST', 'PUT', 'PATCH', 'DELETE']) {
+      const previousCount = vi.mocked(toast.error).mock.calls.length
+      await expectError('/apps', { method })
+      await expectError('/apps', { method })
+      expect(toast.error).toHaveBeenCalledTimes(previousCount + 2)
+      expect(toast.error).toHaveBeenNthCalledWith(previousCount + 1, 'Unavailable')
+      expect(toast.error).toHaveBeenNthCalledWith(previousCount + 2, 'Unavailable')
+    }
+
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledTimes(9)
+  })
+
+  it('clears all messages after success only for the successful request', async () => {
+    await expectError('/datasets')
+    network
+      .mockResolvedValueOnce(errorResponse('A'))
+      .mockResolvedValueOnce(errorResponse('B'))
+      .mockResolvedValueOnce(
+        new Response(JSON.stringify({ result: 'success' }), {
+          headers: { 'Content-Type': 'application/json' },
+        }),
+      )
+      .mockResolvedValueOnce(errorResponse('A'))
+      .mockResolvedValueOnce(errorResponse('B'))
+
+    await expectError('/apps')
+    await expectError('/apps')
+    await expect(base('/apps')).resolves.toEqual({ result: 'success' })
+    await expectError('/apps')
+    await expectError('/apps')
+    await expectError('/datasets')
+
+    expect(vi.mocked(toast.error).mock.calls).toEqual([['Unavailable'], ['A'], ['B'], ['A'], ['B']])
+  })
+
+  it('keeps silent errors silent without suppressing the next visible error', async () => {
+    await expectError('/apps', {}, { silent: true })
+    expect(toast.error).not.toHaveBeenCalled()
+
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledExactlyOnceWith('Unavailable')
+  })
+
+  it('suppresses 401 toasts without suppressing a subsequent non-401 error with the same message', async () => {
+    network.mockResolvedValueOnce(errorResponse('Unavailable', 401))
+
+    await expect(base('/apps')).rejects.toMatchObject({ status: 401 })
+    expect(toast.error).not.toHaveBeenCalled()
+
+    await expectError('/apps')
+    expect(toast.error).toHaveBeenCalledExactlyOnceWith('Unavailable')
+  })
+})
diff --git a/web/service/fetch.ts b/web/service/fetch.ts
index 7dfd5453da7..c6dc9b0f519 100644
--- a/web/service/fetch.ts
+++ b/web/service/fetch.ts
@@ -1,6 +1,5 @@
 import type { AfterResponseHook, BeforeRequestHook, Hooks } from 'ky'
 import type { IOtherOptions } from './base'
-import { toast } from '@langgenius/dify-ui/toast'
 import Cookies from 'js-cookie'
 import ky, { HTTPError } from 'ky'
 import {
@@ -15,6 +14,7 @@ import {
   WEB_APP_SHARE_CODE_HEADER_NAME,
 } from '@/config'
 import { shouldSuppressAppDeletionErrorToast } from './app-deletion'
+import { clearRequestErrorToasts, notifyRequestError } from './request-error-toast'
 import { getWebAppPublicApiPath, resolveWebAppAddress } from './webapp-address'
 import { getWebAppAccessToken, getWebAppPassport } from './webapp-auth'
 
@@ -84,10 +84,12 @@ const afterResponseErrorCode = (otherOptions: IOtherOptions): AfterResponseHook
         !shouldSuppressAppDeletionErrorToast(request.url, response.status)
 
       const errorMessage = errorData?.message || errorData?.error
-      if (shouldNotifyError && errorMessage) toast.error(errorMessage)
+      if (shouldNotifyError && errorMessage) notifyRequestError(request, errorMessage)
 
       if (response.status === 403 && errorData?.code === 'already_setup')
         globalThis.location.href = `${globalThis.location.origin}/signin`
+    } else {
+      clearRequestErrorToasts(request)
     }
   }
 }
diff --git a/web/service/request-error-toast.ts b/web/service/request-error-toast.ts
new file mode 100644
index 00000000000..5588e0753c1
--- /dev/null
+++ b/web/service/request-error-toast.ts
@@ -0,0 +1,44 @@
+import { toast } from '@langgenius/dify-ui/toast'
+
+const DEDUPE_WINDOW_MS = 10000
+
+type RequestIdentity = Pick<Request, 'method' | 'url'>
+type ErrorNotification = {
+  expiresAt: number
+  timer: ReturnType<typeof setTimeout>
+}
+
+const notifications = new Map<string, Map<string, ErrorNotification>>()
+const requestKey = (request: RequestIdentity) => JSON.stringify([request.method, request.url])
+
+export function clearRequestErrorToasts(request: RequestIdentity) {
+  const key = requestKey(request)
+  const messages = notifications.get(key)
+  if (!messages) return
+  for (const notification of messages.values()) clearTimeout(notification.timer)
+  notifications.delete(key)
+}
+
+export function notifyRequestError(request: RequestIdentity, message: string) {
+  // Writes can be separate user actions even when their errors are identical.
+  if (request.method !== 'GET') {
+    toast.error(message)
+    return
+  }
+
+  const key = requestKey(request)
+  const messages = notifications.get(key) ?? new Map<string, ErrorNotification>()
+  notifications.set(key, messages)
+  const previous = messages.get(message)
+  const now = Date.now()
+  if (previous && now < previous.expiresAt) return
+  if (previous) clearTimeout(previous.timer)
+
+  // Only a displayed toast starts the window; suppressed retries do not extend it.
+  const timer = setTimeout(() => {
+    messages.delete(message)
+    if (messages.size === 0) notifications.delete(key)
+  }, DEDUPE_WINDOW_MS)
+  messages.set(message, { expiresAt: now + DEDUPE_WINDOW_MS, timer })
+  toast.error(message)
+}