diff --git a/frontend/src/components/cloud/CloudFolderTreeItem.vue b/frontend/src/components/cloud/CloudFolderTreeItem.vue
index 4f5d26d..ae1ca69 100644
--- a/frontend/src/components/cloud/CloudFolderTreeItem.vue
+++ b/frontend/src/components/cloud/CloudFolderTreeItem.vue
@@ -4,6 +4,7 @@
     :expandable="folder.is_dir"
     :load-children="loadChildren"
     :depth="depth"
+    :is-active="isActive"
     @select="navigate"
   >
     <template #icon>
@@ -15,7 +16,7 @@
         v-for="child in children"
         :key="child.id"
         :folder="child"
-        :provider="provider"
+        :connection-id="connectionId"
         :depth="depth + 1"
       />
     </template>
@@ -23,25 +24,33 @@
 </template>
 
 <script setup>
-import { useRouter } from 'vue-router'
+import { computed } from 'vue'
+import { useRouter, useRoute } from 'vue-router'
 import * as api from '../../api/client.js'
 import AppIcon from '../ui/AppIcon.vue'
 import TreeItem from '../ui/TreeItem.vue'
 
 const props = defineProps({
   folder: { type: Object, required: true },
-  provider: { type: String, required: true },
+  connectionId: { type: String, required: true },
   depth: { type: Number, default: 2 },
 })
 
 const router = useRouter()
+const route = useRoute()
+
+/** Active when the current route points to this exact folder. */
+const isActive = computed(() => {
+  return route.path === `/cloud/${props.connectionId}/${props.folder.id}`
+})
 
 async function loadChildren() {
-  const data = await api.getCloudFolders(props.provider, props.folder.id)
+  // Browse by connection UUID + provider item/path reference — never provider slug
+  const data = await api.getCloudFoldersByConnectionId(props.connectionId, props.folder.id)
   return (data.items ?? []).filter(i => i.is_dir)
 }
 
 function navigate() {
-  router.push(`/cloud/${props.provider}/${props.folder.id}`)
+  router.push(`/cloud/${props.connectionId}/${props.folder.id}`)
 }
 </script>
diff --git a/frontend/src/components/cloud/CloudProviderTreeItem.vue b/frontend/src/components/cloud/CloudProviderTreeItem.vue
index cb521c3..bfa0c16 100644
--- a/frontend/src/components/cloud/CloudProviderTreeItem.vue
+++ b/frontend/src/components/cloud/CloudProviderTreeItem.vue
@@ -1,8 +1,9 @@
 <template>
   <TreeItem
-    :label="connection.display_name"
+    :label="connectionName"
     :load-children="loadChildren"
     :depth="depth"
+    :is-active="isActive"
     @select="navigateToRoot"
   >
     <template #icon>
@@ -13,7 +14,7 @@
         v-for="folder in children"
         :key="folder.id"
         :folder="folder"
-        :provider="connection.provider"
+        :connection-id="connection.id"
         :depth="depth + 1"
       />
     </template>
@@ -22,7 +23,7 @@
 
 <script setup>
 import { computed } from 'vue'
-import { useRouter } from 'vue-router'
+import { useRouter, useRoute } from 'vue-router'
 import * as api from '../../api/client.js'
 import AppIcon from '../ui/AppIcon.vue'
 import TreeItem from '../ui/TreeItem.vue'
@@ -35,15 +36,30 @@ const props = defineProps({
 })
 
 const router = useRouter()
+const route = useRoute()
 
 const providerIconColor = computed(() => providerColor(props.connection.provider))
 
+const connectionName = computed(
+  () => props.connection.display_name || props.connection.provider
+)
+
+/** Active when the current route is this connection's root or any subfolder. */
+const isActive = computed(() => {
+  const path = route.path
+  return (
+    path === `/cloud/${props.connection.id}/root` ||
+    path.startsWith(`/cloud/${props.connection.id}/`)
+  )
+})
+
 async function loadChildren() {
-  const data = await api.getCloudFolders(props.connection.provider, 'root')
+  // Use connection UUID, never provider slug (UAT gap: 422 from UUID endpoint if slug passed)
+  const data = await api.getCloudFoldersByConnectionId(props.connection.id, '')
   return (data.items ?? []).filter(i => i.is_dir)
 }
 
 function navigateToRoot() {
-  router.push(`/cloud/${props.connection.provider}/root`)
+  router.push(`/cloud/${props.connection.id}/root`)
 }
 </script>
diff --git a/frontend/src/components/cloud/__tests__/CloudFolderTreeItem.test.js b/frontend/src/components/cloud/__tests__/CloudFolderTreeItem.test.js
new file mode 100644
index 0000000..f9e30ed
--- /dev/null
+++ b/frontend/src/components/cloud/__tests__/CloudFolderTreeItem.test.js
@@ -0,0 +1,82 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { mount } from '@vue/test-utils'
+import { createPinia, setActivePinia } from 'pinia'
+
+const mockPush = vi.fn()
+let mockRoutePath = '/cloud/uuid-conn-1/some-folder'
+
+vi.mock('vue-router', () => ({
+  useRouter: () => ({ push: mockPush }),
+  useRoute: () => ({ path: mockRoutePath }),
+}))
+
+vi.mock('../../../api/client.js', () => ({
+  getCloudFoldersByConnectionId: vi.fn().mockResolvedValue({ items: [] }),
+  getCloudFolders: vi.fn(), // deprecated — must NOT be called
+}))
+
+import * as api from '../../../api/client.js'
+import CloudFolderTreeItem from '../CloudFolderTreeItem.vue'
+
+const TreeItemStub = {
+  name: 'TreeItem',
+  template: `<div data-test="tree-item" @click="$emit('select')"><slot name="children" :children="[]" /></div>`,
+  props: ['label', 'loadChildren', 'depth', 'isActive', 'expandable'],
+  emits: ['select'],
+}
+
+const globalStubs = {
+  TreeItem: TreeItemStub,
+  AppIcon: true,
+}
+
+const folder = { id: 'some-folder', name: 'Documents', is_dir: true }
+
+beforeEach(() => {
+  setActivePinia(createPinia())
+  vi.clearAllMocks()
+  mockRoutePath = '/cloud/uuid-conn-1/some-folder'
+})
+
+describe('CloudFolderTreeItem', () => {
+  it('navigates to /cloud/{connectionId}/{folderId}, never /cloud/{provider}/{folderId}', async () => {
+    const wrapper = mount(CloudFolderTreeItem, {
+      props: { folder, connectionId: 'uuid-conn-1', depth: 2 },
+      global: { stubs: globalStubs },
+    })
+    await wrapper.find('[data-test="tree-item"]').trigger('click')
+    expect(mockPush).toHaveBeenCalledWith('/cloud/uuid-conn-1/some-folder')
+    expect(mockPush).not.toHaveBeenCalledWith(expect.stringContaining('nextcloud'))
+  })
+
+  it('browses children using getCloudFoldersByConnectionId with folder.id', async () => {
+    const wrapper = mount(CloudFolderTreeItem, {
+      props: { folder, connectionId: 'uuid-conn-1', depth: 2 },
+      global: { stubs: globalStubs },
+    })
+    const treeItemStub = wrapper.findComponent(TreeItemStub)
+    const loadChildren = treeItemStub.props('loadChildren')
+    if (loadChildren) {
+      await loadChildren()
+      expect(api.getCloudFoldersByConnectionId).toHaveBeenCalledWith('uuid-conn-1', 'some-folder')
+    }
+    expect(api.getCloudFolders).not.toHaveBeenCalled()
+  })
+
+  it('isActive=true when current route matches this folder', () => {
+    const wrapper = mount(CloudFolderTreeItem, {
+      props: { folder, connectionId: 'uuid-conn-1', depth: 2 },
+      global: { stubs: globalStubs },
+    })
+    expect(wrapper.findComponent(TreeItemStub).props('isActive')).toBe(true)
+  })
+
+  it('isActive=false when route does not match this folder', () => {
+    mockRoutePath = '/cloud/uuid-conn-1/other-folder'
+    const wrapper = mount(CloudFolderTreeItem, {
+      props: { folder, connectionId: 'uuid-conn-1', depth: 2 },
+      global: { stubs: globalStubs },
+    })
+    expect(wrapper.findComponent(TreeItemStub).props('isActive')).toBe(false)
+  })
+})
diff --git a/frontend/src/components/cloud/__tests__/CloudProviderTreeItem.test.js b/frontend/src/components/cloud/__tests__/CloudProviderTreeItem.test.js
new file mode 100644
index 0000000..227ae86
--- /dev/null
+++ b/frontend/src/components/cloud/__tests__/CloudProviderTreeItem.test.js
@@ -0,0 +1,92 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { mount } from '@vue/test-utils'
+import { createPinia, setActivePinia } from 'pinia'
+
+const mockPush = vi.fn()
+let mockRoutePath = '/cloud'
+
+vi.mock('vue-router', () => ({
+  useRouter: () => ({ push: mockPush }),
+  useRoute: () => ({ path: mockRoutePath }),
+}))
+
+vi.mock('../../../api/client.js', () => ({
+  getCloudFoldersByConnectionId: vi.fn().mockResolvedValue({ items: [] }),
+  getCloudFolders: vi.fn(), // deprecated — must NOT be called
+}))
+
+import * as api from '../../../api/client.js'
+import CloudProviderTreeItem from '../CloudProviderTreeItem.vue'
+
+const TreeItemStub = {
+  name: 'TreeItem',
+  template: `<div data-test="tree-item" @click="$emit('select')"><slot name="children" :children="[]" /></div>`,
+  props: ['label', 'loadChildren', 'depth', 'isActive'],
+  emits: ['select'],
+}
+
+const globalStubs = {
+  TreeItem: TreeItemStub,
+  CloudFolderTreeItem: true,
+  AppIcon: true,
+}
+
+const connection = {
+  id: 'uuid-conn-1',
+  provider: 'nextcloud',
+  display_name: 'My Nextcloud',
+  status: 'ACTIVE',
+}
+
+beforeEach(() => {
+  setActivePinia(createPinia())
+  vi.clearAllMocks()
+  mockRoutePath = '/cloud'
+})
+
+describe('CloudProviderTreeItem', () => {
+  it('uses connection.id (UUID) for browse, never provider slug', async () => {
+    const wrapper = mount(CloudProviderTreeItem, {
+      props: { connection },
+      global: { stubs: globalStubs },
+    })
+    // Call loadChildren from the stub's prop
+    const treeItemStub = wrapper.findComponent(TreeItemStub)
+    const loadChildren = treeItemStub.props('loadChildren')
+    if (loadChildren) {
+      await loadChildren()
+      expect(api.getCloudFoldersByConnectionId).toHaveBeenCalledWith('uuid-conn-1', '')
+      expect(api.getCloudFoldersByConnectionId).not.toHaveBeenCalledWith('nextcloud', expect.anything())
+    }
+    // getCloudFolders (deprecated) must never be called
+    expect(api.getCloudFolders).not.toHaveBeenCalled()
+  })
+
+  it('navigates to /cloud/{uuid}/root on select, never /cloud/{provider}', async () => {
+    const wrapper = mount(CloudProviderTreeItem, {
+      props: { connection },
+      global: { stubs: globalStubs },
+    })
+    await wrapper.find('[data-test="tree-item"]').trigger('click')
+    expect(mockPush).toHaveBeenCalledWith('/cloud/uuid-conn-1/root')
+    expect(mockPush).not.toHaveBeenCalledWith(expect.stringContaining('nextcloud'))
+  })
+
+  it('isActive=true when route matches connection root', () => {
+    mockRoutePath = '/cloud/uuid-conn-1/root'
+    const wrapper = mount(CloudProviderTreeItem, {
+      props: { connection },
+      global: { stubs: globalStubs },
+    })
+    expect(wrapper.findComponent(TreeItemStub).props('isActive')).toBe(true)
+  })
+
+  it('isActive=false when route is /cloud (overview)', () => {
+    mockRoutePath = '/cloud'
+    const wrapper = mount(CloudProviderTreeItem, {
+      props: { connection },
+      global: { stubs: globalStubs },
+    })
+    expect(wrapper.findComponent(TreeItemStub).props('isActive')).toBe(false)
+  })
+})
diff --git a/frontend/src/components/layout/AppSidebar.vue b/frontend/src/components/layout/AppSidebar.vue
index eeed7f0..0a79630 100644
--- a/frontend/src/components/layout/AppSidebar.vue
+++ b/frontend/src/components/layout/AppSidebar.vue
@@ -96,7 +96,7 @@
           <router-link
             to="/cloud"
             class="nav-link flex-1 min-w-0"
-            :class="{ 'nav-link-active': $route.path.startsWith('/cloud') }"
+            :class="{ 'nav-link-active': $route.path === '/cloud' }"
           >
             <AppIcon name="cloud" class="w-4 h-4 mr-2 shrink-0 text-sky-500" />
             Cloud Storage
diff --git a/frontend/src/components/layout/__tests__/AppSidebar.test.js b/frontend/src/components/layout/__tests__/AppSidebar.test.js
new file mode 100644
index 0000000..963489b
--- /dev/null
+++ b/frontend/src/components/layout/__tests__/AppSidebar.test.js
@@ -0,0 +1,76 @@
+/**
+ * AppSidebar cloud active-state tests.
+ *
+ * Verifies that the "Cloud Storage" nav link is active only when the route
+ * is exactly /cloud (the overview), NOT when a connection or folder is active.
+ */
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+import { mount, flushPromises } from '@vue/test-utils'
+import { setActivePinia, createPinia } from 'pinia'
+import { createRouter, createMemoryHistory } from 'vue-router'
+
+vi.mock('../../../api/client.js', () => ({
+  listFolders: vi.fn().mockResolvedValue({ items: [] }),
+  getSharedWithMe: vi.fn().mockResolvedValue([]),
+  listCloudConnections: vi.fn().mockResolvedValue({ items: [] }),
+  listTopics: vi.fn().mockResolvedValue({ topics: [] }),
+  getMyQuota: vi.fn().mockResolvedValue({ used_bytes: 0, limit_bytes: 104857600 }),
+}))
+
+const STUBS = {
+  FolderTreeItem: true,
+  CloudProviderTreeItem: true,
+  QuotaBar: true,
+  EmptyState: true,
+}
+
+function makeRouter(initialPath = '/cloud') {
+  const router = createRouter({
+    history: createMemoryHistory(),
+    routes: [
+      { path: '/', component: { template: '<div/>' } },
+      { path: '/settings', component: { template: '<div/>' } },
+      { path: '/topics', component: { template: '<div/>' } },
+      { path: '/shared', component: { template: '<div/>' } },
+      { path: '/cloud', component: { template: '<div/>' } },
+      { path: '/cloud/:connectionId/:folderId', component: { template: '<div/>' } },
+    ],
+  })
+  router.push(initialPath)
+  return router
+}
+
+import AppSidebar from '../AppSidebar.vue'
+
+beforeEach(() => {
+  setActivePinia(createPinia())
+  vi.clearAllMocks()
+})
+
+describe('AppSidebar cloud active state', () => {
+  it('Cloud Storage link has nav-link-active class at /cloud (exact)', async () => {
+    const router = makeRouter('/cloud')
+    await router.isReady()
+    const wrapper = mount(AppSidebar, {
+      global: { plugins: [router], stubs: STUBS },
+    })
+    await flushPromises()
+    // Find the Cloud Storage router-link — it should be active on /cloud
+    const cloudLink = wrapper.findAll('a').find(a => a.text().includes('Cloud Storage'))
+    expect(cloudLink).toBeTruthy()
+    expect(cloudLink.classes()).toContain('nav-link-active')
+  })
+
+  it('Cloud Storage link does NOT have nav-link-active when inside a connection folder', async () => {
+    const router = makeRouter('/cloud/uuid-conn-1/root')
+    await router.isReady()
+    const wrapper = mount(AppSidebar, {
+      global: { plugins: [router], stubs: STUBS },
+    })
+    await flushPromises()
+    const cloudLink = wrapper.findAll('a').find(a => a.text().includes('Cloud Storage'))
+    expect(cloudLink).toBeTruthy()
+    // Must NOT be active — only the connection/folder node is active
+    expect(cloudLink.classes()).not.toContain('nav-link-active')
+  })
+})