diff --git a/frontend/src/api/index.js b/frontend/src/api/index.js
new file mode 100644
index 0000000..6931bcc
--- /dev/null
+++ b/frontend/src/api/index.js
@@ -0,0 +1,46 @@
+const BASE_URL = '/api'
+
+async function request(path, options = {}) {
+  const url = `${BASE_URL}${path}`
+  const config = {
+    headers: {
+      'Content-Type': 'application/json',
+      ...options.headers,
+    },
+    ...options,
+  }
+  if (config.body && typeof config.body === 'object') {
+    config.body = JSON.stringify(config.body)
+  }
+  const res = await fetch(url, config)
+  if (!res.ok) {
+    const error = new Error(`API error: ${res.status}`)
+    error.status = res.status
+    try {
+      error.data = await res.json()
+    } catch {
+      error.data = await res.text()
+    }
+    throw error
+  }
+  if (res.status === 204) return null
+  return res.json()
+}
+
+// Devices
+export const getDevices = () => request('/devices')
+export const createDevice = (data) => request('/devices', { method: 'POST', body: data })
+export const getDevice = (id) => request(`/devices/${id}`)
+export const updateDevice = (id, data) => request(`/devices/${id}`, { method: 'PUT', body: data })
+export const deleteDevice = (id) => request(`/devices/${id}`, { method: 'DELETE' })
+export const sendCommand = (id, payload) =>
+  request(`/devices/${id}/command`, { method: 'POST', body: { payload } })
+export const getDeviceLogs = (id, limit = 20) => request(`/devices/${id}/logs?limit=${limit}`)
+
+// Broker
+export const getBrokerStatus = () => request('/broker/status')
+export const getBrokerClients = () => request('/broker/clients')
+export const getBrokerTopics = () => request('/broker/topics')
+
+// Dashboard
+export const getDashboardStats = () => request('/dashboard')
diff --git a/frontend/src/composables/useWebSocket.js b/frontend/src/composables/useWebSocket.js
new file mode 100644
index 0000000..f6f72d3
--- /dev/null
+++ b/frontend/src/composables/useWebSocket.js
@@ -0,0 +1,48 @@
+import { ref, onMounted, onUnmounted } from 'vue'
+
+export function useWebSocket(url, onMessage) {
+  const connected = ref(false)
+  let ws = null
+  let reconnectTimer = null
+  let retryDelay = 1000
+
+  function connect() {
+    const protocol = window.location.protocol === 'https:' ? 'wss:' : 'ws:'
+    const fullUrl = `${protocol}//${window.location.host}${url}`
+
+    ws = new WebSocket(fullUrl)
+
+    ws.onopen = () => {
+      connected.value = true
+      retryDelay = 1000
+    }
+
+    ws.onmessage = (event) => {
+      try {
+        const data = JSON.parse(event.data)
+        onMessage(data)
+      } catch {
+        // ignore non-JSON messages
+      }
+    }
+
+    ws.onclose = () => {
+      connected.value = false
+      reconnectTimer = setTimeout(connect, retryDelay)
+      retryDelay = Math.min(retryDelay * 2, 30000)
+    }
+
+    ws.onerror = () => {
+      ws.close()
+    }
+  }
+
+  onMounted(() => connect())
+
+  onUnmounted(() => {
+    clearTimeout(reconnectTimer)
+    if (ws) ws.close()
+  })
+
+  return { connected }
+}
diff --git a/frontend/src/stores/devices.js b/frontend/src/stores/devices.js
new file mode 100644
index 0000000..8ab1a0b
--- /dev/null
+++ b/frontend/src/stores/devices.js
@@ -0,0 +1,60 @@
+import { defineStore } from 'pinia'
+import { ref } from 'vue'
+import { getDevices, createDevice, deleteDevice, sendCommand as apiSendCommand } from '../api'
+import { useWebSocket } from '../composables/useWebSocket'
+
+export const useDeviceStore = defineStore('devices', () => {
+  const devices = ref([])
+  const loading = ref(false)
+  const wsConnected = ref(false)
+
+  async function fetchDevices() {
+    loading.value = true
+    try {
+      devices.value = await getDevices()
+    } finally {
+      loading.value = false
+    }
+  }
+
+  async function addDevice(data) {
+    const device = await createDevice(data)
+    devices.value.unshift(device)
+    return device
+  }
+
+  async function removeDevice(id) {
+    await deleteDevice(id)
+    devices.value = devices.value.filter((d) => d.id !== id)
+  }
+
+  async function sendCommand(id, payload) {
+    return await apiSendCommand(id, payload)
+  }
+
+  function handleWsMessage(data) {
+    if (data.type !== 'device_update') return
+    const idx = devices.value.findIndex((d) => d.id === data.device_id)
+    if (idx === -1) return
+    const device = devices.value[idx]
+    devices.value.splice(idx, 1, {
+      ...device,
+      state: data.state,
+      is_online: data.is_online,
+      last_seen: data.last_seen,
+    })
+  }
+
+  // Initialize WebSocket
+  const { connected } = useWebSocket('/ws/devices', handleWsMessage)
+
+  return {
+    devices,
+    loading,
+    wsConnected,
+    fetchDevices,
+    addDevice,
+    removeDevice,
+    sendCommand,
+  }
+})