diff --git a/backend/api/cloud/connections.py b/backend/api/cloud/connections.py
index 591be1f..c9e7500 100644
--- a/backend/api/cloud/connections.py
+++ b/backend/api/cloud/connections.py
@@ -170,6 +170,9 @@ async def _oauth_authorization_url(provider: str, redirect_uri: str, state_token
     if provider == "google_drive":
         from google_auth_oauthlib.flow import Flow  # lazy import
 
+        # D-17: Phase 13 requests the full `drive` scope so authorized users can
+        # operate on all existing Drive items, not just files created by this app.
+        # Consent text must make the expanded scope explicit.
         flow = Flow.from_client_config(
             {
                 "web": {
@@ -179,7 +182,7 @@ async def _oauth_authorization_url(provider: str, redirect_uri: str, state_token
                     "token_uri": "https://oauth2.googleapis.com/token",
                 }
             },
-            scopes=["https://www.googleapis.com/auth/drive.file"],
+            scopes=["https://www.googleapis.com/auth/drive"],
             redirect_uri=redirect_uri,
         )
         authorization_url, _ = flow.authorization_url(
@@ -211,6 +214,7 @@ async def _oauth_credentials_from_code(provider: str, redirect_uri: str, code: O
     if provider == "google_drive":
         from google_auth_oauthlib.flow import Flow  # lazy import
 
+        # D-17: Broader Phase 13 drive scope (must match initiation scope above).
         flow = Flow.from_client_config(
             {
                 "web": {
@@ -220,7 +224,7 @@ async def _oauth_credentials_from_code(provider: str, redirect_uri: str, code: O
                     "token_uri": "https://oauth2.googleapis.com/token",
                 }
             },
-            scopes=["https://www.googleapis.com/auth/drive.file"],
+            scopes=["https://www.googleapis.com/auth/drive"],
             redirect_uri=redirect_uri,
         )
         await asyncio.to_thread(flow.fetch_token, code=code)
diff --git a/backend/api/cloud/schemas.py b/backend/api/cloud/schemas.py
index 75a6271..907a590 100644
--- a/backend/api/cloud/schemas.py
+++ b/backend/api/cloud/schemas.py
@@ -3,6 +3,12 @@ Whitelisted Pydantic response schemas for the cloud API package.
 
 All schemas are explicit allowlists — credentials_enc, tokens, and passwords
 are deliberately absent. T-12-03: credential exclusion by design.
+
+Phase 13 additions:
+  - ConnectionHealthOut: typed health status response (D-12, CONN-03)
+  - ReconnectOut: typed reconnect response (CONN-01..03)
+  - ContentResultOut: typed open/preview/download response (D-02, D-18, T-13-14)
+  - MutationResultOut: typed kind/reason mutation response (D-05..11)
 """
 from __future__ import annotations
 
@@ -84,3 +90,115 @@ class ConnectionRenameRequest(BaseModel):
         if not stripped:
             raise ValueError("display_name must not be blank")
         return stripped
+
+
+# ── Phase 13 health / reconnect schemas ────────────────────────────────────────
+
+class ConnectionHealthOut(BaseModel):
+    """Typed connection health response.
+
+    D-12: Explicit health status available without probing on every browse.
+    CONN-03: Never exposes credentials_enc, tokens, or raw provider URLs.
+
+    status: 'healthy' | 'degraded' | 'auth_failed' | 'offline'
+    """
+
+    status: str
+    connection_id: str
+    provider: str
+    display_name: Optional[str] = None
+
+
+class ReconnectOut(BaseModel):
+    """Typed reconnect result.
+
+    CONN-01: No new connection row created (reconnected patches in place).
+    CONN-02: credentials_enc updated with re-encrypted token.
+    CONN-03: No credentials, tokens, or provider URLs in response.
+    D-14: Cached metadata preserved as stale.
+    """
+
+    status: str
+    connection_id: str
+    provider: str
+    display_name: Optional[str] = None
+    reconnected: bool = True
+
+
+# ── Phase 13 content result schemas ───────────────────────────────────────────
+
+class ContentResultOut(BaseModel):
+    """Typed open/preview result body.
+
+    D-02: Provider credentials and raw provider URLs must never appear in responses.
+    D-18: Preview is binary-only; unsupported formats fall back to download fallback.
+    T-13-14: Stable kind/reason codes let the frontend route without parsing provider payloads.
+
+    kind: 'open' | 'preview' | 'download' | 'unsupported_preview'
+    reason: discriminator code (e.g. 'binary_supported', 'unsupported_format', 'authorized')
+    url: DocuVault-scoped authorized URL (never a raw provider URL)
+    """
+
+    kind: str
+    reason: Optional[str] = None
+    url: Optional[str] = None
+    content_type: Optional[str] = None
+
+
+# ── Phase 13 mutation result schemas ──────────────────────────────────────────
+
+class MutationResultOut(BaseModel):
+    """Typed mutation result body used by rename, move, delete, and create-folder.
+
+    T-13-14: Stable kind/reason codes let the frontend route without parsing
+    raw provider error payloads.
+
+    kind: 'renamed' | 'moved' | 'deleted' | 'folder' | 'conflict' | 'stale' |
+          'offline' | 'reauth_required' | 'invalid_destination' | 'unsupported_operation'
+    reason: discriminator detail (e.g. 'trashed', 'permanent', 'name_collision',
+            'item_changed', 'provider_unreachable', 'token_expired',
+            'self_destination', 'cross_connection', 'provider_unsupported')
+    """
+
+    kind: str
+    reason: Optional[str] = None
+    name: Optional[str] = None
+    provider_item_id: Optional[str] = None
+    parent_ref: Optional[str] = None
+
+
+# ── Phase 13 mutation request schemas ─────────────────────────────────────────
+
+class CreateFolderRequest(BaseModel):
+    """Request body for POST /connections/{id}/folders."""
+    parent_ref: Optional[str] = None
+    name: str = Field(..., max_length=255)
+
+    @field_validator("name")
+    @classmethod
+    def must_be_nonblank(cls, v: str) -> str:
+        stripped = v.strip()
+        if not stripped:
+            raise ValueError("name must not be blank")
+        return stripped
+
+
+class RenameItemRequest(BaseModel):
+    """Request body for PATCH /connections/{id}/items/{item_id}/rename."""
+    new_name: str = Field(..., max_length=255)
+    etag: Optional[str] = None
+
+    @field_validator("new_name")
+    @classmethod
+    def must_be_nonblank(cls, v: str) -> str:
+        stripped = v.strip()
+        if not stripped:
+            raise ValueError("new_name must not be blank")
+        return stripped
+
+
+class MoveItemRequest(BaseModel):
+    """Request body for POST /connections/{id}/items/{item_id}/move."""
+    destination_parent_ref: str
+    destination_connection_id: Optional[str] = None
+    etag: Optional[str] = None
diff --git a/frontend/src/api/cloud.js b/frontend/src/api/cloud.js
index bd6dad7..e277458 100644
--- a/frontend/src/api/cloud.js
+++ b/frontend/src/api/cloud.js
@@ -87,3 +87,149 @@ export function updateWebDavCredentials(connectionId, { serverUrl, username, pas
   if (password !== undefined && password !== '') body.password = password
   return jsonRequest(`/api/cloud/connections/${connectionId}/credentials`, 'PUT', body)
 }
+
+// ── Phase 13: Connection health, reconnect, and test ─────────────────────────
+
+/**
+ * Get the health status of a cloud connection without probing the provider.
+ *
+ * D-12: Health is available explicitly (not inferred from browse).
+ * Returns {status, connection_id, provider, display_name}.
+ * status: 'healthy' | 'degraded' | 'auth_failed' | 'offline'
+ */
+export function getConnectionHealth(connectionId) {
+  return request(`/api/cloud/connections/${connectionId}/health`)
+}
+
+/**
+ * Reconnect an AUTH_FAILED connection in-place.
+ *
+ * CONN-01: Patches the existing row — no new connection row created.
+ * CONN-02: Re-encrypts refreshed credentials in place.
+ * CONN-03: Response is credential-free.
+ * D-14: Cached metadata preserved as stale; caches invalidated server-side.
+ */
+export function reconnectCloudConnection(connectionId) {
+  return jsonRequest(`/api/cloud/connections/${connectionId}/reconnect`, 'POST', {})
+}
+
+/**
+ * Explicitly test a cloud connection by probing the provider.
+ *
+ * D-13: Explicit Test action — not triggered on every folder navigation.
+ * Updates the connection status row and returns the new health status.
+ */
+export function testCloudConnection(connectionId) {
+  return jsonRequest(`/api/cloud/connections/${connectionId}/test`, 'POST', {})
+}
+
+// ── Phase 13: Authorized cloud content access ─────────────────────────────────
+
+/**
+ * Open a cloud file via a DocuVault-authorized URL.
+ *
+ * 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.
+ */
+export function openCloudFile(connectionId, itemId) {
+  return request(`/api/cloud/connections/${connectionId}/items/${encodeURIComponent(itemId)}/open`)
+}
+
+/**
+ * Get an in-app preview of a cloud file (binary formats only).
+ *
+ * D-18: Preview is binary-only. Unsupported formats return
+ * {kind: 'unsupported_preview', reason: 'unsupported_format'} and the caller
+ * should fall back to openCloudFile() for authorized download.
+ * D-02: No raw provider URL or credentials in the response.
+ */
+export function previewCloudFile(connectionId, itemId) {
+  return request(`/api/cloud/connections/${connectionId}/items/${encodeURIComponent(itemId)}/preview`)
+}
+
+// ── Phase 13: Cloud mutations ─────────────────────────────────────────────────
+
+/**
+ * Create a folder in cloud storage.
+ *
+ * D-05: Collision auto-naming: 'Projects (1)', 'Projects (2)', etc.
+ * Returns {kind: 'folder', provider_item_id, name} on success.
+ * Returns {kind: 'unsupported_operation', reason: 'provider_unsupported'} when
+ * the provider does not support folder creation.
+ */
+export function createCloudFolder(connectionId, parentRef, name) {
+  return jsonRequest(`/api/cloud/connections/${connectionId}/folders`, 'POST', {
+    parent_ref: parentRef,
+    name,
+  })
+}
+
+/**
+ * Rename a cloud item.
+ *
+ * D-05: Counter-suffix collision policy applies.
+ * D-07: etag guards against operating on stale metadata.
+ *       Returns {kind: 'stale', reason: 'item_changed'} when externally changed.
+ * Returns {kind: 'renamed', name} on success.
+ */
+export function renameCloudItem(connectionId, itemId, newName, etag) {
+  return jsonRequest(
+    `/api/cloud/connections/${connectionId}/items/${encodeURIComponent(itemId)}/rename`,
+    'PATCH',
+    { new_name: newName, etag },
+  )
+}
+
+/**
+ * Move a cloud item within the same connection.
+ *
+ * D-08: Moves are restricted to the same cloud connection.
+ * D-09: Self and descendant destinations are rejected.
+ * Returns {kind: 'moved', parent_ref} on success.
+ * Returns {kind: 'invalid_destination', reason: '...'} for invalid moves.
+ */
+export function moveCloudItem(connectionId, itemId, destinationParentRef, etag) {
+  return jsonRequest(
+    `/api/cloud/connections/${connectionId}/items/${encodeURIComponent(itemId)}/move`,
+    'POST',
+    { destination_parent_ref: destinationParentRef, etag },
+  )
+}
+
+/**
+ * Delete a cloud item (trash preferred, permanent when unavailable).
+ *
+ * D-11: Response discloses whether trash or permanent delete was performed via
+ *       {kind: 'deleted', reason: 'trashed' | 'permanent'}.
+ * D-10: Callers must confirm before calling — the API deletes immediately.
+ */
+export function deleteCloudItem(connectionId, itemId) {
+  return request(
+    `/api/cloud/connections/${connectionId}/items/${encodeURIComponent(itemId)}`,
+    { method: 'DELETE' },
+  )
+}
+
+/**
+ * Upload a file to a cloud folder.
+ *
+ * D-03: Same-name upload returns {kind: 'conflict', reason: 'name_collision'} —
+ *       never overwrites silently.
+ * D-04: Caller manages the sequential upload queue; this function uploads one file.
+ *
+ * @param {string} connectionId - Connection UUID
+ * @param {string} parentRef - Parent folder provider_item_id
+ * @param {string} filename - Target filename
+ * @param {File|Blob} file - File bytes
+ */
+export function uploadCloudFile(connectionId, parentRef, filename, file) {
+  const formData = new FormData()
+  formData.append('file', file, filename)
+  formData.append('parent_ref', parentRef ?? '')
+  formData.append('filename', filename)
+  return request(`/api/cloud/connections/${connectionId}/items/upload`, {
+    method: 'POST',
+    body: formData,
+  })
+}