diff --git a/backend/api/admin.py b/backend/api/admin.py
index 7818db7..fc4032d 100644
--- a/backend/api/admin.py
+++ b/backend/api/admin.py
@@ -29,7 +29,7 @@ from datetime import datetime
 from typing import Optional
 
 from fastapi import APIRouter, Depends, HTTPException, Request, status
-from pydantic import BaseModel, EmailStr, field_validator
+from pydantic import BaseModel, EmailStr, Field, field_validator
 from sqlalchemy import func, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -141,7 +141,7 @@ class SystemTopicCreate(BaseModel):
 class UserDeleteConfirm(BaseModel):
     """Admin password confirmation required before hard-deleting a user (ADMIN-02, T-05-11-01)."""
 
-    admin_password: str
+    admin_password: str = Field(..., min_length=1)
 
 
 # ── SEC-08: Safe CloudConnection response model ───────────────────────────────
@@ -162,6 +162,8 @@ class CloudConnectionOut(BaseModel):
     display_name: str
     status: str
     connected_at: datetime
+    server_url: Optional[str] = None
+    connection_username: Optional[str] = None
     model_config = {"from_attributes": True}
 
     @field_validator("id", mode="before")
diff --git a/backend/api/documents.py b/backend/api/documents.py
index 491e980..b759065 100644
--- a/backend/api/documents.py
+++ b/backend/api/documents.py
@@ -27,12 +27,12 @@ from typing import Optional
 
 from fastapi import APIRouter, Depends, Form, HTTPException, Query, Request, UploadFile, File, status
 from fastapi.responses import StreamingResponse
-from pydantic import BaseModel
+from pydantic import BaseModel, Field, field_validator
 from sqlalchemy import select, text, func
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from config import settings
-from db.models import CloudConnection, Document, Quota, Share, User
+from db.models import CloudConnection, Document, Folder, Quota, Share, User
 from deps.auth import get_regular_user
 from deps.db import get_db
 from services import classifier, storage
@@ -78,9 +78,16 @@ class DocumentPatch(BaseModel):
     T-05-09-01: explicit field declaration prevents mass assignment.
     T-05-09-02: only filename and folder_id are accepted — no other fields can be set.
     """
-    filename: Optional[str] = None
+    filename: Optional[str] = Field(None, min_length=1, max_length=255)
     folder_id: Optional[uuid.UUID] = None
 
+    @field_validator("filename")
+    @classmethod
+    def filename_no_path_separators(cls, v: Optional[str]) -> Optional[str]:
+        if v is not None and ("/" in v or "\\" in v):
+            raise ValueError("filename must not contain path separators")
+        return v
+
 
 # ── POST /api/documents/upload-url ───────────────────────────────────────────
 
@@ -129,6 +136,7 @@ async def request_upload_url(
 async def upload_document(
     file: UploadFile = File(...),
     target_backend: str = Form("minio"),
+    cloud_folder_path: str = Form(None),
     request: Request = None,
     session: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_regular_user),
@@ -238,6 +246,8 @@ async def upload_document(
             file_bytes,
             extension,
             content_type,
+            cloud_folder=cloud_folder_path or None,
+            original_filename=filename if cloud_folder_path else None,
         )
     except CloudConnectionError as exc:
         raise HTTPException(
@@ -245,6 +255,11 @@ async def upload_document(
             detail="Cloud connection requires re-authentication. Please reconnect in Settings.",
         ) from exc
 
+    # Bust folder listing cache so the next GET /folders reflects the new file
+    if cloud_folder_path:
+        from services.cloud_cache import invalidate_provider_cache  # lazy import
+        invalidate_provider_cache(str(current_user.id), target_backend)
+
     doc = Document(
         id=doc_id,
         user_id=current_user.id,
@@ -570,6 +585,10 @@ async def patch_document(
 
     if "folder_id" in body.model_fields_set:
         # folder_id=null → move to root (no folder); folder_id=<uuid> → move to folder
+        if body.folder_id is not None:
+            target = await session.get(Folder, body.folder_id)
+            if target is None or target.user_id != current_user.id:
+                raise HTTPException(404, "Folder not found")
         doc.folder_id = body.folder_id
 
     await session.commit()
diff --git a/frontend/src/api/client.js b/frontend/src/api/client.js
index 0d9b5b8..80598e1 100644
--- a/frontend/src/api/client.js
+++ b/frontend/src/api/client.js
@@ -96,6 +96,14 @@ export function confirmUpload(documentId) {
   return request(`/api/documents/${documentId}/confirm`, { method: 'POST' })
 }
 
+export function uploadToCloud(file, provider, folderPath) {
+  const form = new FormData()
+  form.append('file', file)
+  form.append('target_backend', provider)
+  if (folderPath) form.append('cloud_folder_path', folderPath)
+  return request('/api/documents/upload', { method: 'POST', body: form })
+}
+
 // ── Topics ───────────────────────────────────────────────────────────────────
 
 export function listTopics() {
@@ -413,6 +421,9 @@ export async function fetchDocumentContent(docId, options = {}) {
     }
   }
 
+  if (!res.ok) {
+    throw new Error(`Failed to fetch document content: ${res.status}`)
+  }
   return res
 }
 
diff --git a/frontend/src/views/DocumentView.vue b/frontend/src/views/DocumentView.vue
index 8e1fe80..5eb594f 100644
--- a/frontend/src/views/DocumentView.vue
+++ b/frontend/src/views/DocumentView.vue
@@ -173,9 +173,15 @@ async function openPdf() {
       }
       const blob = await res.blob()
       const objectUrl = URL.createObjectURL(blob)
-      window.open(objectUrl, '_blank')
-      // Revoke after a delay to allow the new tab to load the content
-      setTimeout(() => URL.revokeObjectURL(objectUrl), 60000)
+      const tab = window.open(objectUrl, '_blank')
+      // Revoke once the new tab has loaded, or after 120s as a fallback.
+      // Also revoke if the user navigates away from this page before the tab loads.
+      const revoke = () => URL.revokeObjectURL(objectUrl)
+      const timer = setTimeout(revoke, 120000)
+      window.addEventListener('pagehide', revoke, { once: true })
+      if (tab) {
+        tab.addEventListener('load', () => { clearTimeout(timer); revoke() }, { once: true })
+      }
     } catch (err) {
       console.error('Failed to open document:', err)
     }