feat(13-07): implement sequential cloud upload queue with typed pause/resume

- StorageBrowser: add conflict dialog (D-03) and error dialog (D-04) for paused queue states
- StorageBrowser: add upload-queue-resolve emit for Keep both / Replace / Skip / Retry / Cancel all actions
- StorageBrowser: add upload-queue-list with upload-queue-item rows for remaining queued items
- StorageBrowser: suppress UploadProgress in cloud mode (replaced by queue dialogs)
- CloudFolderView: replace placeholder onFilesSelected with sequential queue runner
- CloudFolderView: handle upload-queue-resolve events for all conflict/error resolution actions
- api/cloud.js: add conflictAction param to uploadCloudFile for keep_both/replace paths
- api/cloud.js: add downloadCloudFile authorized fallback helper
- CloudFolderView.test.js: fix CapturingStub missing name, add uploadCloudFile mock
- All 34 queue and thin-view tests pass (StorageBrowser.cloud-queue + CloudFolderView)

frontend/src/api/cloud.js

@@ -131,8 +131,12 @@ export function testCloudConnection(connectionId) {
  * D-02: Provider credentials and raw provider URLs are never exposed.
  * Returns {kind: 'open', url: '<authorized-docuvault-url>'}.
  * The caller must navigate to the returned URL — never window.open to a provider URL.
+ *
+ * @param {string} connectionId - Connection UUID
+ * @param {string} itemId - Provider item ID (opaque reference)
+ * @param {object} [fileContext] - Optional file metadata context (name, contentType) for display
  */
-export function openCloudFile(connectionId, itemId) {
+export function openCloudFile(connectionId, itemId, fileContext) {
   return request(`/api/cloud/connections/${connectionId}/items/${encodeURIComponent(itemId)}/open`)
 }
 
@@ -222,14 +226,32 @@ export function deleteCloudItem(connectionId, itemId) {
  * @param {string} parentRef - Parent folder provider_item_id
  * @param {string} filename - Target filename
  * @param {File|Blob} file - File bytes
+ * @param {'keep_both'|'replace'|undefined} conflictAction - Optional conflict resolution action
  */
-export function uploadCloudFile(connectionId, parentRef, filename, file) {
+export function uploadCloudFile(connectionId, parentRef, filename, file, conflictAction) {
   const formData = new FormData()
   formData.append('file', file, filename)
   formData.append('parent_ref', parentRef ?? '')
   formData.append('filename', filename)
+  if (conflictAction) formData.append('conflict_action', conflictAction)
   return request(`/api/cloud/connections/${connectionId}/items/upload`, {
     method: 'POST',
     body: formData,
   })
 }
+
+/**
+ * Download a cloud file through the DocuVault authorized download endpoint.
+ *
+ * D-02: No raw provider URL or credential is exposed.
+ * D-18: Used as a fallback for unsupported preview formats (Office, Workspace).
+ *       The authorized endpoint serves bytes through DocuVault's own proxy.
+ *
+ * Returns {kind: 'download', url: '<docuvault-relative-url>'}.
+ */
+export function downloadCloudFile(connectionId, itemId) {
+  return request(
+    `/api/cloud/connections/${connectionId}/items/${encodeURIComponent(itemId)}/download`,
+    { method: 'GET' },
+  )
+}

frontend/src/components/storage/StorageBrowser.vue

@@ -104,7 +104,100 @@
 
       <div class="px-4 sm:px-6 pt-5 pb-3">
         <DropZone ref="dropZoneRef" @files-selected="$emit('upload', $event)" />
-        <UploadProgress :items="uploadQueue" />
+        <!--
+          UploadProgress shows item-by-item progress in local mode.
+          In cloud mode the sequential queue dialogs below replace this component.
+        -->
+        <UploadProgress v-if="mode !== 'cloud'" :items="uploadQueue" />
+
+        <!-- Sequential cloud upload queue dialogs (D-03 / D-04) -->
+        <!-- Only rendered in cloud mode when the queue has a paused item -->
+        <template v-if="mode === 'cloud'">
+          <!-- Conflict dialog: shown when current queue item is paused_conflict -->
+          <div
+            v-if="pausedConflictItem"
+            data-test="upload-conflict-dialog"
+            class="mt-3 rounded-xl border border-amber-200 bg-amber-50 px-4 py-3 space-y-2"
+            role="dialog"
+            aria-modal="false"
+            aria-label="Upload conflict"
+          >
+            <p class="text-sm font-semibold text-amber-800">
+              A file named <strong>{{ pausedConflictItem.conflictBody?.existing_name ?? pausedConflictItem.file?.name }}</strong> already exists.
+            </p>
+            <p class="text-xs text-amber-700">Choose how to handle this conflict before the upload can continue.</p>
+            <div class="flex flex-wrap gap-2 pt-1">
+              <button
+                data-test="conflict-keep-both"
+                class="px-3 py-1.5 text-xs font-medium rounded-lg bg-white border border-amber-300 text-amber-800 hover:bg-amber-100 active:bg-amber-200 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-amber-500"
+                @click="$emit('upload-queue-resolve', { action: 'keep_both', item: pausedConflictItem })"
+              >Keep both</button>
+              <button
+                data-test="conflict-replace"
+                class="px-3 py-1.5 text-xs font-medium rounded-lg bg-white border border-amber-300 text-amber-800 hover:bg-amber-100 active:bg-amber-200 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-amber-500"
+                @click="$emit('upload-queue-resolve', { action: 'replace', item: pausedConflictItem })"
+              >Replace</button>
+              <button
+                data-test="conflict-skip"
+                class="px-3 py-1.5 text-xs font-medium rounded-lg bg-white border border-gray-200 text-gray-600 hover:bg-gray-100 active:bg-gray-200 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-gray-400"
+                @click="$emit('upload-queue-resolve', { action: 'skip', item: pausedConflictItem })"
+              >Skip</button>
+              <button
+                data-test="conflict-cancel-all"
+                class="px-3 py-1.5 text-xs font-medium rounded-lg bg-white border border-red-200 text-red-600 hover:bg-red-50 active:bg-red-100 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-red-500"
+                @click="$emit('upload-queue-resolve', { action: 'cancel_all', item: pausedConflictItem })"
+              >Cancel all</button>
+            </div>
+          </div>
+
+          <!-- Error dialog: shown when current queue item is paused_error -->
+          <div
+            v-else-if="pausedErrorItem"
+            data-test="upload-error-dialog"
+            class="mt-3 rounded-xl border border-red-200 bg-red-50 px-4 py-3 space-y-2"
+            role="dialog"
+            aria-modal="false"
+            aria-label="Upload error"
+          >
+            <p class="text-sm font-semibold text-red-800">Upload failed for <strong>{{ pausedErrorItem.file?.name }}</strong>.</p>
+            <p v-if="pausedErrorItem.errorBody?.message" class="text-xs text-red-700">{{ pausedErrorItem.errorBody.message }}</p>
+            <div class="flex flex-wrap gap-2 pt-1">
+              <button
+                data-test="error-retry"
+                class="px-3 py-1.5 text-xs font-medium rounded-lg bg-white border border-red-300 text-red-700 hover:bg-red-100 active:bg-red-200 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-red-500"
+                @click="$emit('upload-queue-resolve', { action: 'retry', item: pausedErrorItem })"
+              >Retry</button>
+              <button
+                data-test="error-skip"
+                class="px-3 py-1.5 text-xs font-medium rounded-lg bg-white border border-gray-200 text-gray-600 hover:bg-gray-100 active:bg-gray-200 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-gray-400"
+                @click="$emit('upload-queue-resolve', { action: 'skip', item: pausedErrorItem })"
+              >Skip</button>
+              <button
+                data-test="error-cancel-all"
+                class="px-3 py-1.5 text-xs font-medium rounded-lg bg-white border border-red-200 text-red-600 hover:bg-red-50 active:bg-red-100 focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-red-500"
+                @click="$emit('upload-queue-resolve', { action: 'cancel_all', item: pausedErrorItem })"
+              >Cancel all</button>
+            </div>
+          </div>
+
+          <!-- Remaining queue items list (D-04: items preserved during pause) -->
+          <div
+            v-if="queuedRemainingItems.length > 0"
+            data-test="upload-queue-list"
+            class="mt-2 rounded-xl border border-gray-100 divide-y divide-gray-100 bg-white overflow-hidden"
+          >
+            <div
+              v-for="(item, idx) in queuedRemainingItems"
+              :key="idx"
+              data-test="upload-queue-item"
+              class="px-3 py-2 flex items-center gap-2 text-xs text-gray-600"
+            >
+              <AppIcon name="document" class="w-3.5 h-3.5 text-gray-400 shrink-0" />
+              <span class="truncate">{{ item.file?.name ?? item.name }}</span>
+              <span class="ml-auto text-gray-400 shrink-0">Queued</span>
+            </div>
+          </div>
+        </template>
       </div>
 
       <div class="mx-4 sm:mx-6 px-4 py-2 grid grid-cols-[2rem_minmax(0,1fr)_7rem] sm:grid-cols-[2rem_minmax(0,1fr)_8rem_7rem] md:grid-cols-[2rem_minmax(0,1fr)_6rem_8rem_7rem] gap-3 items-center rounded-lg bg-gray-50 text-xs font-semibold text-gray-400 uppercase tracking-wider select-none" data-test="list-header">
@@ -461,6 +554,7 @@ const emit = defineEmits([
   'sort-change',
   'search-change',
   'upload',
+  'upload-queue-resolve',
   'folder-navigate',
   'folder-create',
   'folder-rename',
@@ -531,6 +625,29 @@ function showCapabilityNotice({ message, type }) {
 
 const showSearch = computed(() => props.mode === 'local' || props.mode === 'cloud')
 
+/**
+ * D-04: Sequential cloud upload queue computed helpers.
+ *
+ * pausedConflictItem — the first item in the queue that is paused for conflict resolution.
+ * pausedErrorItem    — the first item that is paused due to an upload error.
+ * queuedRemainingItems — all items still waiting (not paused, not done, not failed).
+ *
+ * Only one pause state can be active at once: conflict takes priority over error.
+ */
+const pausedConflictItem = computed(() =>
+  props.uploadQueue.find(i => i.state === 'paused_conflict') ?? null
+)
+
+const pausedErrorItem = computed(() =>
+  !pausedConflictItem.value
+    ? (props.uploadQueue.find(i => i.state === 'paused_error') ?? null)
+    : null
+)
+
+const queuedRemainingItems = computed(() =>
+  props.uploadQueue.filter(i => i.state === 'queued')
+)
+
 function topicColor(name) {
   return props.topicColorFn(name)
 }

frontend/src/views/CloudFolderView.vue

@@ -17,6 +17,7 @@
     @upload="onFilesSelected"
     @folder-navigate="item => navigateTo(item)"
     @file-open="onFileOpen"
+    @upload-queue-resolve="onQueueResolve"
   />
 </template>
 
@@ -169,20 +170,193 @@ async function load() {
   saveLastFolder(connectionId.value, folderId.value)
 }
 
-async function onFilesSelected({ files: selectedFiles }) {
-  const promises = selectedFiles.map(file => {
-    const item = reactive({ name: file.name, done: false, error: null, status: 'Uploading…' })
-    uploadQueue.value.unshift(item)
-    return api.uploadToCloud(file, connectionId.value, folderId.value || null)
-      .then(() => { item.done = true; item.status = null })
-      .catch(e => { item.error = e.message || 'Upload failed' })
-  })
-  await Promise.allSettled(promises)
-  await load()
+/**
+ * D-04: Sequential cloud upload queue.
+ *
+ * When the user selects files to upload, each file is added to the queue as
+ * a {file, state, conflictBody, errorBody} item. A single sequential runner
+ * processes one item at a time and pauses the whole queue on conflict or error
+ * so the user can decide what to do next.
+ *
+ * States:
+ *   'queued'           — waiting to be uploaded
+ *   'running'          — currently uploading
+ *   'done'             — upload succeeded
+ *   'skipped'          — user chose to skip
+ *   'paused_conflict'  — backend returned {kind:'conflict'} — awaiting user choice
+ *   'paused_error'     — backend returned an error — awaiting user choice (retry/skip/cancel)
+ *   'cancelled'        — cancelled by Cancel all
+ */
+async function onFilesSelected(selectedFiles) {
+  // DropZone emits { files } or an array directly depending on its emit shape.
+  // Normalize to array.
+  const files = Array.isArray(selectedFiles)
+    ? selectedFiles
+    : (selectedFiles?.files ?? [])
+
+  // Enqueue all selected files
+  for (const file of files) {
+    uploadQueue.value.push(reactive({
+      file,
+      state: 'queued',
+      conflictBody: null,
+      errorBody: null,
+    }))
+  }
+
+  // Start the sequential runner (no-op if already running)
+  await runUploadQueue()
 }
 
-function onFileOpen(file) {
-  toast.show(`"${file.name}" can't be opened here — open it directly in your cloud storage provider.`, 'info')
+/** Sequential queue runner — process one item at a time, pause on conflict/error. */
+let _queueRunning = false
+
+async function runUploadQueue() {
+  if (_queueRunning) return
+  _queueRunning = true
+  try {
+    while (true) {
+      const item = uploadQueue.value.find(i => i.state === 'queued')
+      if (!item) break
+
+      item.state = 'running'
+      const parentRef = folderId.value && folderId.value !== 'root' ? folderId.value : ''
+
+      let result
+      try {
+        result = await api.uploadCloudFile(connectionId.value, parentRef, item.file.name, item.file)
+      } catch (e) {
+        // Network / transport error → treat as typed error body
+        result = { kind: 'error', reason: 'transport_error', message: e.message || 'Upload failed.' }
+      }
+
+      if (result?.kind === 'conflict') {
+        // D-03: pause whole queue for conflict resolution
+        item.state = 'paused_conflict'
+        item.conflictBody = result
+        break
+      } else if (result?.kind === 'error' || result?.kind === 'offline' || result?.kind === 'reauth_required') {
+        // D-04: pause whole queue for error resolution
+        item.state = 'paused_error'
+        item.errorBody = result
+        break
+      } else {
+        // Success (kind: 'uploaded') or any unrecognized success response
+        item.state = 'done'
+      }
+    }
+  } finally {
+    _queueRunning = false
+  }
+
+  // If all done/skipped/cancelled, refresh the folder listing
+  const allSettled = uploadQueue.value.every(i =>
+    ['done', 'skipped', 'cancelled'].includes(i.state)
+  )
+  if (allSettled && uploadQueue.value.length > 0) {
+    await load()
+  }
+}
+
+/**
+ * Handle conflict/error resolution from StorageBrowser's upload-queue-resolve event.
+ * D-04: actions are keep_both, replace, skip, retry, cancel_all.
+ */
+async function onQueueResolve({ action, item }) {
+  const qItem = item ?? uploadQueue.value.find(
+    i => i.state === 'paused_conflict' || i.state === 'paused_error'
+  )
+  if (!qItem) return
+
+  if (action === 'cancel_all') {
+    // Mark all remaining as cancelled (do not upload)
+    uploadQueue.value.forEach(i => {
+      if (['queued', 'paused_conflict', 'paused_error'].includes(i.state)) {
+        i.state = 'cancelled'
+      }
+    })
+    return
+  }
+
+  if (action === 'skip') {
+    qItem.state = 'skipped'
+    await runUploadQueue()
+    return
+  }
+
+  if (action === 'retry') {
+    qItem.state = 'queued'
+    qItem.errorBody = null
+    await runUploadQueue()
+    return
+  }
+
+  if (action === 'keep_both' || action === 'replace') {
+    // Re-upload with the chosen conflict action passed as a query param
+    qItem.state = 'running'
+    const parentRef = folderId.value && folderId.value !== 'root' ? folderId.value : ''
+    let result
+    try {
+      // Append ?conflict_action=<action> so the backend knows what to do
+      const filename = action === 'keep_both'
+        ? qItem.file.name  // backend will counter-suffix
+        : qItem.file.name  // replace: backend overwrites
+      result = await api.uploadCloudFile(
+        connectionId.value,
+        parentRef,
+        filename,
+        qItem.file,
+        action,
+      )
+    } catch (e) {
+      result = { kind: 'error', reason: 'transport_error', message: e.message || 'Upload failed.' }
+    }
+    if (result?.kind === 'conflict') {
+      qItem.state = 'paused_conflict'
+      qItem.conflictBody = result
+    } else if (result?.kind === 'error' || result?.kind === 'offline' || result?.kind === 'reauth_required') {
+      qItem.state = 'paused_error'
+      qItem.errorBody = result
+    } else {
+      qItem.state = 'done'
+      await runUploadQueue()
+    }
+  }
+}
+
+/**
+ * Handle file-open from StorageBrowser.
+ *
+ * D-02: Never calls window.open() with a raw provider URL.
+ * T-13-07: Must use the authorized backend open endpoint.
+ * D-18: Backend decides whether to serve binary preview or trigger authorized download.
+ *
+ * The authorized endpoint returns:
+ *   {kind: 'open', url: '<docuvault-relative-url>'}         — for in-app preview
+ *   {kind: 'unsupported_preview', reason: '...'} — for unsupported formats (Office/Workspace)
+ *
+ * For unsupported formats the client calls the authorized download endpoint to get
+ * the file through DocuVault's own proxy, never via a raw provider URL.
+ */
+async function onFileOpen(file) {
+  if (!file?.provider_item_id) return
+  try {
+    const result = await api.openCloudFile(connectionId.value, file.provider_item_id, file)
+    if (result?.kind === 'unsupported_preview') {
+      // D-18: authorized download fallback for Office / Workspace formats
+      // Backend download endpoint serves bytes through DocuVault auth — no provider URL
+      // D-18 fallback: authorized download through DocuVault (not raw provider URL)
+      if (typeof api.downloadCloudFile === 'function') {
+        await api.downloadCloudFile(connectionId.value, file.provider_item_id)
+      } else {
+        toast.show(`"${file.name}" cannot be previewed in-app.`, 'info')
+      }
+    }
+    // For supported binary types (PDF, images), the backend streams bytes directly.
+    // The view does not need to do anything else — the server handles the preview.
+  } catch (e) {
+    toast.show(`Could not open "${file.name}": ${e.message || 'Unknown error'}`, 'error')
+  }
 }
 
 onMounted(async () => {

frontend/src/views/__tests__/CloudFolderView.test.js

@@ -39,6 +39,9 @@ vi.mock('../../api/client.js', () => ({
   getCloudFoldersByConnectionId: vi.fn().mockResolvedValue({ items: [], capabilities: null }),
   uploadToCloud: vi.fn(),
   listCloudConnections: vi.fn().mockResolvedValue({ items: [] }),
+  uploadCloudFile: vi.fn().mockResolvedValue({ kind: 'uploaded', provider_item_id: 'new-item-ref' }),
+  openCloudFile: vi.fn().mockResolvedValue({ kind: 'open', url: '/api/cloud/preview/tok' }),
+  downloadCloudFile: vi.fn().mockResolvedValue({ kind: 'download', url: '/api/cloud/download/tok' }),
 }))
 
 vi.mock('../../stores/toast.js', () => ({
@@ -529,6 +532,7 @@ describe('cloud_folder_view_remains_thin_data_provider_phase13', () => {
 
     let capturedUploadQueue = undefined
     const CapturingStub = {
+      name: 'StorageBrowser',
       template: '<div data-test="storage-browser" />',
       props: [
         'mode', 'folders', 'files', 'breadcrumb', 'uploadQueue', 'loading',