diff --git a/apps/backend/scripts/check-sql-guard.ts b/apps/backend/scripts/check-sql-guard.ts
index 859fcb76..504bbb1c 100644
--- a/apps/backend/scripts/check-sql-guard.ts
+++ b/apps/backend/scripts/check-sql-guard.ts
@@ -4,6 +4,7 @@
  */
 import fs from 'node:fs'
 import path from 'node:path'
+import { execFileSync } from 'node:child_process'
 import { fileURLToPath } from 'node:url'

 const SCRIPT_DIR = path.dirname(fileURLToPath(import.meta.url))
@@ -57,6 +58,24 @@ const checks: Array<{ name: string; file: string; patterns: string[] }> = [
 ]

 const failures: string[] = []
+
+// 已应用的历史迁移必须保持字节不变，所有结构或数据修复都必须新增迁移文件。
+try {
+  const modifiedMigrations = execFileSync(
+    'git',
+    ['diff', '--name-only', '--diff-filter=M', 'HEAD', '--', 'src/db/migrations'],
+    { cwd: BACKEND_ROOT, encoding: 'utf8' },
+  )
+    .split('\n')
+    .map((file) => file.trim())
+    .filter((file) => file.endsWith('.sql'))
+  if (modifiedMigrations.length > 0) {
+    failures.push(`历史迁移文件不可修改: ${modifiedMigrations.join(', ')}`)
+  }
+} catch (error) {
+  failures.push(`历史迁移完整性检查失败: ${error instanceof Error ? error.message : String(error)}`)
+}
+
 for (const check of checks) {
   if (!fs.existsSync(check.file)) {
     failures.push(`${check.name}: 文件不存在 ${check.file}`)
diff --git a/apps/backend/src/db/migrations/069_worker_session_device_type.sql b/apps/backend/src/db/migrations/069_worker_session_device_type.sql
new file mode 100644
index 00000000..033b921e
--- /dev/null
+++ b/apps/backend/src/db/migrations/069_worker_session_device_type.sql
@@ -0,0 +1,8 @@
+-- 将历史平板会话归入手机设备桶，确保新旧数据使用同一套 PC/手机上限。
+UPDATE worker_sessions
+SET device_type = 'mobile', updated_at = NOW()
+WHERE device_type = 'tablet';
+
+UPDATE worker_sessions
+SET device_type = 'pc', updated_at = NOW()
+WHERE device_type IS NULL OR device_type NOT IN ('pc', 'mobile');
diff --git a/apps/backend/src/repositories/worker-platform/worker-session-repo.ts b/apps/backend/src/repositories/worker-platform/worker-session-repo.ts
index c59eb71d..fa1eaf1b 100644
--- a/apps/backend/src/repositories/worker-platform/worker-session-repo.ts
+++ b/apps/backend/src/repositories/worker-platform/worker-session-repo.ts
@@ -41,9 +41,9 @@ export async function createWorkerSessionRecord(
     )
     const activeResult = await client.query<WorkerSessionRow>(
       `SELECT * FROM worker_sessions
-       WHERE worker_id = $1 AND status = 'active' AND expires_at > $2
+       WHERE worker_id = $1 AND device_type = $2 AND status = 'active' AND expires_at > $3
        ORDER BY last_seen_at DESC, id DESC`,
-      [input.workerId, input.now],
+      [input.workerId, input.deviceType, input.now],
     )
     const activeSessions = activeResult.rows
     if (activeSessions.length >= input.maxDevices) {
diff --git a/apps/backend/src/services/worker-platform/worker-auth-policy.test.ts b/apps/backend/src/services/worker-platform/worker-auth-policy.test.ts
new file mode 100644
index 00000000..2da1ff5e
--- /dev/null
+++ b/apps/backend/src/services/worker-platform/worker-auth-policy.test.ts
@@ -0,0 +1,11 @@
+import assert from 'node:assert/strict'
+import test from 'node:test'
+
+import { normalizeWorkerDeviceType } from './worker-auth-policy.js'
+
+test('worker device types use separate PC and mobile buckets', () => {
+  assert.equal(normalizeWorkerDeviceType('pc'), 'pc')
+  assert.equal(normalizeWorkerDeviceType('desktop'), 'pc')
+  assert.equal(normalizeWorkerDeviceType('mobile'), 'mobile')
+  assert.equal(normalizeWorkerDeviceType('tablet'), 'mobile')
+})
diff --git a/apps/backend/src/services/worker-platform/worker-auth-policy.ts b/apps/backend/src/services/worker-platform/worker-auth-policy.ts
index 2698a7b4..11444cf5 100644
--- a/apps/backend/src/services/worker-platform/worker-auth-policy.ts
+++ b/apps/backend/src/services/worker-platform/worker-auth-policy.ts
@@ -28,7 +28,7 @@ export function normalizeWorkerDeviceType(value: unknown): string {
   const type = String(value || '')
     .trim()
     .toLowerCase()
-  return type === 'mobile' || type === 'tablet' ? type : 'pc'
+  return type === 'mobile' || type === 'tablet' ? 'mobile' : 'pc'
 }

 export function normalizeWorkerDeviceId(value: unknown, fallback: string): string {
diff --git a/apps/backend/src/services/worker-platform/worker-login-service.ts b/apps/backend/src/services/worker-platform/worker-login-service.ts
index c6de2243..36ec08fd 100644
--- a/apps/backend/src/services/worker-platform/worker-login-service.ts
+++ b/apps/backend/src/services/worker-platform/worker-login-service.ts
@@ -141,10 +141,14 @@ async function createWorkerLoginSession(
     maxDevices: WORKER_MAX_DEVICES,
   })
   if (!sessionRecord.created) {
-    throw createHttpError('在线设备已达到 3 台，请先删除旧的登录设备', {
-      statusCode: 409,
-      errorCode: 'worker_device_limit',
-    })
+    const deviceLabel = deviceType === 'pc' ? 'PC' : '手机'
+    throw createHttpError(
+      `${deviceLabel}设备已达到 ${WORKER_MAX_DEVICES} 台，请先删除旧的登录设备`,
+      {
+        statusCode: 409,
+        errorCode: 'worker_device_limit',
+      },
+    )
   }
   return { ...session, passwordWeak }
 }
diff --git a/apps/backend/src/services/worker-platform/worker-session-auth-service.ts b/apps/backend/src/services/worker-platform/worker-session-auth-service.ts
index f7e23119..7e69cbe1 100644
--- a/apps/backend/src/services/worker-platform/worker-session-auth-service.ts
+++ b/apps/backend/src/services/worker-platform/worker-session-auth-service.ts
@@ -135,8 +135,18 @@ export async function verifyWorkerSessionToken(token: unknown): Promise<WorkerSe

 export async function getWorkerSessions(session: WorkerSession) {
   const sessions = await listWorkerSessions(session.workerId, nowIso())
+  const deviceCounts = sessions.reduce(
+    (counts, item) => {
+      const deviceType = item.device_type === 'mobile' ? 'mobile' : 'pc'
+      counts[deviceType] += 1
+      return counts
+    },
+    { pc: 0, mobile: 0 },
+  )
   return {
     maxDevices: WORKER_MAX_DEVICES,
+    maxDevicesByType: { pc: WORKER_MAX_DEVICES, mobile: WORKER_MAX_DEVICES },
+    deviceCounts,
     items: sessions.map((item) => mapWorkerSession(item, session.sessionId)),
   }
 }
diff --git a/apps/frontend/src/pages/worker/WorkerLoginPage.tsx b/apps/frontend/src/pages/worker/WorkerLoginPage.tsx
index e525a32c..c9daceac 100644
--- a/apps/frontend/src/pages/worker/WorkerLoginPage.tsx
+++ b/apps/frontend/src/pages/worker/WorkerLoginPage.tsx
@@ -662,7 +662,7 @@ export default function WorkerLoginPage() {
         <Alert
           showIcon
           type="info"
-          message="验证账号密码后，可删除旧设备。所有 PC 和手机合计最多同时在线 3 台。"
+          message="验证账号密码后，可删除旧设备。PC 和手机分别最多同时在线 3 台。"
           style={{ marginBottom: 16 }}
         />
         <Table
diff --git a/apps/frontend/src/pages/worker/WorkerProfileAccountModals.tsx b/apps/frontend/src/pages/worker/WorkerProfileAccountModals.tsx
index e4330ba8..af9492ab 100644
--- a/apps/frontend/src/pages/worker/WorkerProfileAccountModals.tsx
+++ b/apps/frontend/src/pages/worker/WorkerProfileAccountModals.tsx
@@ -38,6 +38,7 @@ export function WorkerProfileAccountModals({
   setDevicesOpen,
   devices,
   maxDevices,
+  deviceCounts,
   devicesLoading,
   removeWorkerDevice,
   passwordOpen,
@@ -60,6 +61,7 @@ export function WorkerProfileAccountModals({
   setDevicesOpen: (open: boolean) => void
   devices: WorkerSessionDevice[]
   maxDevices: number
+  deviceCounts: { pc: number; mobile: number }
   devicesLoading: boolean
   removeWorkerDevice: (device: WorkerSessionDevice) => Promise<void>
   passwordOpen: boolean
@@ -88,7 +90,7 @@ export function WorkerProfileAccountModals({
         <Alert
           showIcon
           type="info"
-          message={`所有设备合计最多同时在线 ${maxDevices} 台，删除旧设备后才能在新设备登录。`}
+          message={`PC 和手机分别最多同时在线 ${maxDevices} 台（当前 PC ${deviceCounts.pc} 台、手机 ${deviceCounts.mobile} 台），删除对应旧设备后才能登录。`}
         />
         <Table<WorkerSessionDevice>
           size="small"
diff --git a/apps/frontend/src/pages/worker/WorkerProfilePage.tsx b/apps/frontend/src/pages/worker/WorkerProfilePage.tsx
index 5641b936..67231aa4 100644
--- a/apps/frontend/src/pages/worker/WorkerProfilePage.tsx
+++ b/apps/frontend/src/pages/worker/WorkerProfilePage.tsx
@@ -658,6 +658,7 @@ export default function WorkerProfilePage() {
         setDevicesOpen={setDevicesOpen}
         devices={devicesQuery.data?.data.items || []}
         maxDevices={devicesQuery.data?.data.maxDevices || 3}
+        deviceCounts={devicesQuery.data?.data.deviceCounts || { pc: 0, mobile: 0 }}
         devicesLoading={devicesQuery.isLoading || devicesQuery.isFetching}
         removeWorkerDevice={removeWorkerDevice}
         passwordOpen={passwordOpen}
diff --git a/apps/frontend/src/services/worker.ts b/apps/frontend/src/services/worker.ts
index 162ab6d1..1197a9ac 100644
--- a/apps/frontend/src/services/worker.ts
+++ b/apps/frontend/src/services/worker.ts
@@ -94,7 +94,7 @@ export function loginWorkerBySmsCode(payload: { phone: string; code: string }) {
 }

 export function fetchWorkerSessions() {
-  return apiGet<{ maxDevices: number; items: WorkerSessionDevice[] }>('/api/v1/worker/auth/devices')
+  return apiGet<WorkerDeviceLimitsResponse>('/api/v1/worker/auth/devices')
 }

 export function deleteWorkerSession(sessionId: string) {
@@ -102,10 +102,14 @@ export function deleteWorkerSession(sessionId: string) {
 }

 export function manageWorkerSessions(payload: { username: string; password: string }) {
-  return apiPost<{ maxDevices: number; items: WorkerSessionDevice[] }>(
-    '/api/v1/worker/auth/devices/manage/list',
-    payload,
-  )
+  return apiPost<WorkerDeviceLimitsResponse>('/api/v1/worker/auth/devices/manage/list', payload)
+}
+
+export type WorkerDeviceLimitsResponse = {
+  maxDevices: number
+  maxDevicesByType: { pc: number; mobile: number }
+  deviceCounts: { pc: number; mobile: number }
+  items: WorkerSessionDevice[]
 }

 export function deleteWorkerSessionWithCredentials(payload: {