diff --git a/src/application/adapters/webdav_adapter.rs b/src/application/adapters/webdav_adapter.rs
index 47d33bbe..ce03ffc5 100644
--- a/src/application/adapters/webdav_adapter.rs
+++ b/src/application/adapters/webdav_adapter.rs
@@ -430,18 +430,27 @@ impl WebDavAdapter {
         Ok(PropFindRequest { prop_find_type })
     }
 
-    fn folder_prop_is_known(prop: &QualifiedName) -> bool {
-        prop.namespace == "DAV:"
-            && matches!(
-                prop.name.as_str(),
-                "resourcetype"
-                    | "displayname"
-                    | "creationdate"
-                    | "getlastmodified"
-                    | "getetag"
-                    | "getcontentlength"
-                    | "getcontenttype"
-            )
+    /// `quota` reflects whether the caller could resolve the account's
+    /// storage quota for this request (the quota service is optional —
+    /// `OXICLOUD_ENABLE_*` feature flags can disable it) and, independently,
+    /// whether the account has a finite available-bytes figure to report.
+    /// RFC 4331's `quota-used-bytes` / `quota-available-bytes` are each only
+    /// reported as known properties when a value actually exists —
+    /// otherwise they fall through to the standard 404 propstat like any
+    /// other property this server doesn't support. Unlimited accounts have
+    /// `quota-used-bytes` known but `quota-available-bytes` unknown (see
+    /// `resolve_quota` in `webdav_handler.rs`).
+    fn folder_prop_is_known(prop: &QualifiedName, quota: Option<(i64, Option<i64>)>) -> bool {
+        if prop.namespace != "DAV:" {
+            return false;
+        }
+        match prop.name.as_str() {
+            "resourcetype" | "displayname" | "creationdate" | "getlastmodified" | "getetag"
+            | "getcontentlength" | "getcontenttype" => true,
+            "quota-used-bytes" => quota.is_some(),
+            "quota-available-bytes" => quota.is_some_and(|(_, available)| available.is_some()),
+            _ => false,
+        }
     }
 
     fn file_prop_is_known(prop: &QualifiedName) -> bool {
@@ -550,16 +559,25 @@ impl WebDavAdapter {
         folder: &FolderDto,
         request: &PropFindRequest,
         href: &str,
+        quota: Option<(i64, Option<i64>)>,
     ) -> Result<()> {
-        Self::write_folder_response_with_dead_props(xml_writer, folder, request, href, &[])
+        Self::write_folder_response_with_dead_props(xml_writer, folder, request, href, &[], quota)
     }
 
+    /// `quota` is `Some((used_bytes, available_bytes))` for the caller's
+    /// account when the quota subsystem is enabled and reachable —
+    /// `available_bytes` is itself `None` for unlimited accounts, which
+    /// omits `quota-available-bytes` from the response entirely (see
+    /// [`Self::folder_prop_is_known`]). It's the same value regardless of
+    /// which folder is being described (quota is account-wide, not
+    /// per-folder), so callers resolve it once per PROPFIND request.
     fn write_folder_response_with_dead_props<W: Write>(
         xml_writer: &mut Writer<W>,
         folder: &FolderDto,
         request: &PropFindRequest,
         href: &str,
         dead_props: &[(QualifiedName, Option<String>)],
+        quota: Option<(i64, Option<i64>)>,
     ) -> Result<()> {
         xml_writer.write_event(Event::Start(BytesStart::new("D:response")))?;
 
@@ -585,8 +603,9 @@ impl WebDavAdapter {
                 // RFC 4918 §9.2: known props → 200 propstat; unknown → 404 propstat.
                 // Props found in the dead store are returned in the dead 200 propstat,
                 // so exclude them from the 404 propstat to avoid duplicate reporting.
-                let (known, unknown): (Vec<_>, Vec<_>) =
-                    props.iter().partition(|p| Self::folder_prop_is_known(p));
+                let (known, unknown): (Vec<_>, Vec<_>) = props
+                    .iter()
+                    .partition(|p| Self::folder_prop_is_known(p, quota));
                 let truly_unknown: Vec<_> = unknown
                     .into_iter()
                     .filter(|p| !dead_name_set.contains(*p))
@@ -594,7 +613,7 @@ impl WebDavAdapter {
 
                 xml_writer.write_event(Event::Start(BytesStart::new("D:propstat")))?;
                 xml_writer.write_event(Event::Start(BytesStart::new("D:prop")))?;
-                Self::write_folder_requested_props(xml_writer, folder, &known)?;
+                Self::write_folder_requested_props(xml_writer, folder, &known, quota)?;
                 xml_writer.write_event(Event::End(BytesEnd::new("D:prop")))?;
                 xml_writer.write_event(Event::Start(BytesStart::new("D:status")))?;
                 xml_writer.write_event(Event::Text(BytesText::new("HTTP/1.1 200 OK")))?;
@@ -608,10 +627,10 @@ impl WebDavAdapter {
                 xml_writer.write_event(Event::Start(BytesStart::new("D:prop")))?;
                 match other {
                     PropFindType::AllProp => {
-                        Self::write_folder_standard_props(xml_writer, folder)?;
+                        Self::write_folder_standard_props(xml_writer, folder, quota)?;
                     }
                     PropFindType::PropName => {
-                        Self::write_folder_prop_names(xml_writer)?;
+                        Self::write_folder_prop_names(xml_writer, quota)?;
                     }
                     PropFindType::Prop(_) => unreachable!(),
                 }
@@ -720,6 +739,7 @@ impl WebDavAdapter {
     fn write_folder_standard_props<W: Write>(
         xml_writer: &mut Writer<W>,
         folder: &FolderDto,
+        quota: Option<(i64, Option<i64>)>,
     ) -> Result<()> {
         // Resource type (collection)
         xml_writer.write_event(Event::Start(BytesStart::new("D:resourcetype")))?;
@@ -768,6 +788,33 @@ impl WebDavAdapter {
         xml_writer.write_event(Event::Text(BytesText::new("httpd/unix-directory")))?;
         xml_writer.write_event(Event::End(BytesEnd::new("D:getcontenttype")))?;
 
+        if let Some((used, available)) = quota {
+            Self::write_quota_props(xml_writer, used, available)?;
+        }
+
+        Ok(())
+    }
+
+    /// Write RFC 4331 `quota-used-bytes` / `quota-available-bytes`. Shared
+    /// by the allprop and named-prop paths so the element shape only
+    /// lives in one place. `available_bytes` is `None` for unlimited
+    /// accounts — RFC 4331 §3 lets a server omit `quota-available-bytes`
+    /// rather than disclose a made-up value, so the element is skipped.
+    fn write_quota_props<W: Write>(
+        xml_writer: &mut Writer<W>,
+        used_bytes: i64,
+        available_bytes: Option<i64>,
+    ) -> Result<()> {
+        xml_writer.write_event(Event::Start(BytesStart::new("D:quota-used-bytes")))?;
+        xml_writer.write_event(Event::Text(BytesText::new(&used_bytes.to_string())))?;
+        xml_writer.write_event(Event::End(BytesEnd::new("D:quota-used-bytes")))?;
+
+        if let Some(available_bytes) = available_bytes {
+            xml_writer.write_event(Event::Start(BytesStart::new("D:quota-available-bytes")))?;
+            xml_writer.write_event(Event::Text(BytesText::new(&available_bytes.to_string())))?;
+            xml_writer.write_event(Event::End(BytesEnd::new("D:quota-available-bytes")))?;
+        }
+
         Ok(())
     }
 
@@ -825,7 +872,10 @@ impl WebDavAdapter {
     }
 
     /// Write folder property names
-    fn write_folder_prop_names<W: Write>(xml_writer: &mut Writer<W>) -> Result<()> {
+    fn write_folder_prop_names<W: Write>(
+        xml_writer: &mut Writer<W>,
+        quota: Option<(i64, Option<i64>)>,
+    ) -> Result<()> {
         // Write empty property elements for folders
         xml_writer.write_event(Event::Empty(BytesStart::new("D:resourcetype")))?;
         xml_writer.write_event(Event::Empty(BytesStart::new("D:displayname")))?;
@@ -834,6 +884,12 @@ impl WebDavAdapter {
         xml_writer.write_event(Event::Empty(BytesStart::new("D:getetag")))?;
         xml_writer.write_event(Event::Empty(BytesStart::new("D:getcontentlength")))?;
         xml_writer.write_event(Event::Empty(BytesStart::new("D:getcontenttype")))?;
+        if let Some((_, available)) = quota {
+            xml_writer.write_event(Event::Empty(BytesStart::new("D:quota-used-bytes")))?;
+            if available.is_some() {
+                xml_writer.write_event(Event::Empty(BytesStart::new("D:quota-available-bytes")))?;
+            }
+        }
 
         Ok(())
     }
@@ -857,6 +913,7 @@ impl WebDavAdapter {
         xml_writer: &mut Writer<W>,
         folder: &FolderDto,
         props: &[&QualifiedName],
+        quota: Option<(i64, Option<i64>)>,
     ) -> Result<()> {
         for prop in props {
             if prop.namespace == "DAV:" {
@@ -917,6 +974,28 @@ impl WebDavAdapter {
                             .write_event(Event::Text(BytesText::new("httpd/unix-directory")))?;
                         xml_writer.write_event(Event::End(BytesEnd::new("D:getcontenttype")))?;
                     }
+                    "quota-used-bytes" => {
+                        if let Some((used, _)) = quota {
+                            xml_writer
+                                .write_event(Event::Start(BytesStart::new("D:quota-used-bytes")))?;
+                            xml_writer
+                                .write_event(Event::Text(BytesText::new(&used.to_string())))?;
+                            xml_writer
+                                .write_event(Event::End(BytesEnd::new("D:quota-used-bytes")))?;
+                        }
+                    }
+                    "quota-available-bytes" => {
+                        if let Some((_, Some(available))) = quota {
+                            xml_writer.write_event(Event::Start(BytesStart::new(
+                                "D:quota-available-bytes",
+                            )))?;
+                            xml_writer
+                                .write_event(Event::Text(BytesText::new(&available.to_string())))?;
+                            xml_writer.write_event(Event::End(BytesEnd::new(
+                                "D:quota-available-bytes",
+                            )))?;
+                        }
+                    }
                     _ => {
                         // Unknown prop — skipped here; caller writes 404 propstat.
                     }
@@ -1445,7 +1524,7 @@ impl WebDavAdapter {
         request: &PropFindRequest,
         href: &str,
     ) -> Result<()> {
-        Self::write_folder_response(writer, folder, request, href)
+        Self::write_folder_response(writer, folder, request, href, None)
     }
 
     /// Writes a single `<D:response>` element for a file, including dead properties.
@@ -1465,8 +1544,11 @@ impl WebDavAdapter {
         request: &PropFindRequest,
         href: &str,
         dead_props: &[(QualifiedName, Option<String>)],
+        quota: Option<(i64, Option<i64>)>,
     ) -> Result<()> {
-        Self::write_folder_response_with_dead_props(writer, folder, request, href, dead_props)
+        Self::write_folder_response_with_dead_props(
+            writer, folder, request, href, dead_props, quota,
+        )
     }
 
     /// Writes a file entry including dead (custom) properties.
diff --git a/src/application/services/drive_management_service.rs b/src/application/services/drive_management_service.rs
index b2b34537..3276ce87 100644
--- a/src/application/services/drive_management_service.rs
+++ b/src/application/services/drive_management_service.rs
@@ -24,6 +24,7 @@ use uuid::Uuid;
 
 use crate::application::ports::authorization_ports::AuthorizationEngine;
 use crate::common::errors::DomainError;
+use crate::domain::entities::drive::DriveKind;
 use crate::domain::repositories::drive_repository::{DriveRepository, DriveRepositoryError};
 use crate::domain::repositories::subject_group_repository::SubjectGroupRepository;
 use crate::domain::services::authorization::{Grant, Permission, Resource, Role, Subject};
@@ -556,7 +557,7 @@ impl DriveManagementService {
         let drive = self.drive_repo.get_by_id(drive_id).await.map_err(|e| {
             DomainError::internal_error("Drive", format!("Failed to fetch drive: {e:?}"))
         })?;
-        if drive.drive.is_personal() {
+        if matches!(drive.drive.kind, DriveKind::Personal) {
             tracing::info!(
                 target: "audit",
                 event = "drive_membership.rejected",
diff --git a/src/application/services/file_upload_service.rs b/src/application/services/file_upload_service.rs
index a6ac8209..f3eb48f7 100644
--- a/src/application/services/file_upload_service.rs
+++ b/src/application/services/file_upload_service.rs
@@ -353,16 +353,24 @@ impl FileUploadService {
     /// the target drive is `kind='personal'`, so a shared-drive upload
     /// still doesn't touch any user envelope.
     fn maybe_update_storage_usage(&self, file: &FileDto, caller_id: Uuid) {
+        self.apply_storage_usage_delta(file.size as i64, &file.folder_id, caller_id);
+    }
+
+    /// Same as [`Self::maybe_update_storage_usage`] but takes an explicit
+    /// `delta` instead of assuming "whole file size" — the overwrite path
+    /// (`update_file_streaming_with_perms`) needs `new_size - old_size`,
+    /// not the new size added a second time on top of what the old
+    /// content already contributed.
+    fn apply_storage_usage_delta(&self, delta: i64, folder_id: &Option<String>, caller_id: Uuid) {
         let Some(storage_service) = &self.storage_usage_service else {
             return;
         };
-        let delta = file.size as i64;
+        if delta == 0 {
+            return;
+        }
 
         let owner = Some(caller_id);
-        let folder = file
-            .folder_id
-            .as_deref()
-            .and_then(|s| Uuid::parse_str(s).ok());
+        let folder = folder_id.as_deref().and_then(|s| Uuid::parse_str(s).ok());
 
         // Per-user delta — only when the target drive is `kind='personal'`.
         // The user envelope (`auth.users.storage_quota_bytes`) caps the SUM
@@ -496,6 +504,7 @@ impl FileUploadUseCase for FileUploadService {
                 )
                 .await?;
 
+            let old_size = file.size();
             let file_id = file.id().to_string();
             let (new_hash, updated_at) = self
                 .file_write
@@ -531,6 +540,11 @@ impl FileUploadUseCase for FileUploadService {
                 DomainError::internal_error("FileUpload", format!("rebuild entity: {e}"))
             })?;
             let dto = FileDto::from(updated);
+            self.apply_storage_usage_delta(
+                blob.size as i64 - old_size as i64,
+                &dto.folder_id,
+                caller_id,
+            );
             if let Some(hook) = &self.file_lifecycle_hook {
                 hook.on_file_updated(&file_id, &dto.content_hash, content_type);
             }
@@ -603,6 +617,7 @@ impl FileUploadUseCase for FileUploadService {
             )
             .await?;
         let dto = FileDto::from(created);
+        self.maybe_update_storage_usage(&dto, caller_id);
         if let Some(hook) = &self.file_lifecycle_hook {
             hook.on_file_created(&dto.id, &dto.content_hash, content_type, is_new_blob);
         }
diff --git a/src/common/di.rs b/src/common/di.rs
index 5b78fbc5..be2f9c7a 100644
--- a/src/common/di.rs
+++ b/src/common/di.rs
@@ -1,9 +1,13 @@
 use sqlx::PgPool;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
+use uuid::Uuid;
 
 use crate::application::ports::blob_storage_ports::BlobStorageBackend;
+use crate::application::ports::storage_ports::StorageUsagePort;
 use crate::common::config::StorageBackendType;
+use crate::domain::entities::drive::DriveKind;
+use crate::domain::repositories::drive_repository::DriveRepository;
 use crate::infrastructure::db::DbPools;
 
 use crate::application::services::admin_settings_service::AdminSettingsService;
@@ -2165,6 +2169,51 @@ pub struct AppState {
 
 // All AppState construction is done via struct literal in build_app_state().
 
+impl AppState {
+    /// Drive-aware RFC 4331 quota resolution — shared by the native and
+    /// NextCloud-compatible WebDAV PROPFIND handlers so both surfaces
+    /// report the same numbers for the same drive.
+    ///
+    /// - `drive_id == Uuid::nil()`: synthetic drive-listing pseudo-root —
+    ///   no single drive, so the account envelope is the only defensible
+    ///   answer.
+    /// - Personal drives carry no quota of their own (`Drive::quota_bytes`
+    ///   is NULL post-migration) — the account envelope in `auth.users`
+    ///   caps them.
+    /// - Shared drives carry their own finite quota on `storage.drives` —
+    ///   report that, not the owner's unrelated personal envelope.
+    ///
+    /// `available` is `None` for unlimited accounts/drives (quota <= 0 or
+    /// unset) — RFC 4331 §3 lets a server omit `quota-available-bytes`
+    /// rather than disclose a made-up value. Any lookup failure (quota
+    /// subsystem disabled, drive gone) is treated the same way: quota is
+    /// silently omitted rather than failing the whole PROPFIND.
+    pub async fn resolve_webdav_quota(
+        &self,
+        user_id: Uuid,
+        drive_id: Uuid,
+    ) -> Option<(i64, Option<i64>)> {
+        let storage_svc = self.storage_usage_service.as_ref()?;
+
+        if drive_id.is_nil() {
+            let (used, quota) = storage_svc.get_user_storage_info(user_id).await.ok()?;
+            return Some((used, (quota > 0).then(|| (quota - used).max(0))));
+        }
+
+        let drive = self.drive_repo.get_by_id(drive_id).await.ok()?.drive;
+        match drive.kind {
+            DriveKind::Personal => {
+                let (used, quota) = storage_svc.get_user_storage_info(user_id).await.ok()?;
+                Some((used, (quota > 0).then(|| (quota - used).max(0))))
+            }
+            DriveKind::Shared => {
+                let used = drive.used_bytes;
+                Some((used, drive.quota_bytes.map(|q| (q - used).max(0))))
+            }
+        }
+    }
+}
+
 /// Builds the authorization engine. Today this only constructs `PgAclEngine`;
 /// the `OXICLOUD_AUTHZ_ENGINE` env var is reserved for future alternate
 /// implementations (e.g. `openfga`).
diff --git a/src/domain/entities/drive.rs b/src/domain/entities/drive.rs
index 7d1f562b..d2f2cb9b 100644
--- a/src/domain/entities/drive.rs
+++ b/src/domain/entities/drive.rs
@@ -131,12 +131,6 @@ impl Drive {
         self.default_for_user == Some(user_id)
     }
 
-    /// `true` if this drive is a personal drive of any kind (default or
-    /// secondary). Encapsulates the kind check at the call site.
-    pub fn is_personal(&self) -> bool {
-        matches!(self.kind, DriveKind::Personal)
-    }
-
     /// Typed view of `policies` for enforcement code. Lenient deserialise:
     /// unknown keys are preserved on disk (the column stays the canonical
     /// JSONB bag) but ignored here, missing keys default to `false`.
@@ -144,6 +138,12 @@ impl Drive {
     pub fn typed_policies(&self) -> DrivePolicies {
         DrivePolicies::from_value(&self.policies)
     }
+
+    /// `true` if this drive is a personal drive of any kind (default or
+    /// secondary). Encapsulates the kind check at the call site.
+    pub fn is_personal(&self) -> bool {
+        matches!(self.kind, DriveKind::Personal)
+    }
 }
 
 /// Typed mirror of the `policies` JSONB. Five known keys; the JSONB column
diff --git a/src/interfaces/api/handlers/webdav_handler.rs b/src/interfaces/api/handlers/webdav_handler.rs
index 0a29f029..6268ddd0 100644
--- a/src/interfaces/api/handlers/webdav_handler.rs
+++ b/src/interfaces/api/handlers/webdav_handler.rs
@@ -557,6 +557,7 @@ async fn handle_propfind(
                 created_by: None,
                 updated_by: None,
             };
+            let quota = state.resolve_webdav_quota(user.id, Uuid::nil()).await;
             return build_streaming_propfind_response(
                 root_folder,
                 None, // folder_id = None → root children (drive-root folders)
@@ -567,6 +568,7 @@ async fn handle_propfind(
                 file_retrieval_service,
                 user.id,
                 state.webdav_dead_props.clone(),
+                quota,
             )
             .await;
         }
@@ -595,6 +597,7 @@ async fn handle_propfind(
                     )
                     .await?;
                 let folder_id = folder.id.clone();
+                let quota = state.resolve_webdav_quota(user.id, drive_id).await;
                 return build_streaming_propfind_response(
                     folder,
                     Some(folder_id),
@@ -605,6 +608,7 @@ async fn handle_propfind(
                     file_retrieval_service,
                     user.id,
                     state.webdav_dead_props.clone(),
+                    quota,
                 )
                 .await;
             }
@@ -659,6 +663,7 @@ async fn handle_propfind(
                 )
                 .await?;
             let folder_id = folder.id.clone();
+            let quota = state.resolve_webdav_quota(user.id, drive_id).await;
             return build_streaming_propfind_response(
                 folder,
                 Some(folder_id),
@@ -669,6 +674,7 @@ async fn handle_propfind(
                 file_retrieval_service,
                 user.id,
                 state.webdav_dead_props.clone(),
+                quota,
             )
             .await;
         }
@@ -732,6 +738,7 @@ async fn build_streaming_propfind_response(
     file_retrieval_service: std::sync::Arc<FileRetrievalService>,
     user_id: Uuid,
     dead_props_store: Arc<DeadPropertyStore>,
+    quota: Option<(i64, Option<i64>)>,
 ) -> Result<Response<Body>, AppError> {
     let depth = depth.to_string();
     let base_href = base_href.to_string();
@@ -752,7 +759,7 @@ async fn build_streaming_propfind_response(
             let mut w = Writer::new(&mut buf);
             WebDavAdapter::write_multistatus_start(&mut w)
                 .map_err(|e| std::io::Error::other(e.to_string()))?;
-            WebDavAdapter::write_folder_entry_with_dead_props(&mut w, &folder, &propfind_request, &base_href, &folder_dead)
+            WebDavAdapter::write_folder_entry_with_dead_props(&mut w, &folder, &propfind_request, &base_href, &folder_dead, quota)
                 .map_err(|e| std::io::Error::other(e.to_string()))?;
         }
         yield Bytes::from(buf);
@@ -795,7 +802,7 @@ async fn build_streaming_propfind_response(
                     let mut w = Writer::new(&mut chunk);
                     for (subfolder, child_dead) in result.items.iter().zip(subfolder_deads.iter()) {
                         let href = format!("{}{}/", base_href, encode_path_segment(&subfolder.name));
-                        WebDavAdapter::write_folder_entry_with_dead_props(&mut w, subfolder, &propfind_request, &href, child_dead)
+                        WebDavAdapter::write_folder_entry_with_dead_props(&mut w, subfolder, &propfind_request, &href, child_dead, quota)
                             .map_err(|e| std::io::Error::other(e.to_string()))?;
                     }
                 }
diff --git a/src/interfaces/nextcloud/report_handler.rs b/src/interfaces/nextcloud/report_handler.rs
index 2078613c..609180ce 100644
--- a/src/interfaces/nextcloud/report_handler.rs
+++ b/src/interfaces/nextcloud/report_handler.rs
@@ -213,6 +213,10 @@ async fn handle_filter_files(
                 (fid, oc_id.as_deref()),
                 &user.username,
                 &favorite_ids,
+                // REPORT results are a flat filter/search listing, not a
+                // PROPFIND on a specific collection — quota isn't
+                // meaningful here (see `AppState::resolve_webdav_quota`).
+                None,
                 &dead,
             )
             .map_err(|e| AppError::internal_error(format!("XML write error: {}", e)))?;
@@ -346,6 +350,10 @@ async fn handle_search(
                 (fid, oc_id.as_deref()),
                 &user.username,
                 &favorite_ids,
+                // REPORT results are a flat filter/search listing, not a
+                // PROPFIND on a specific collection — quota isn't
+                // meaningful here (see `AppState::resolve_webdav_quota`).
+                None,
                 &dead,
             )
             .map_err(|e| AppError::internal_error(format!("XML write error: {}", e)))?;
diff --git a/src/interfaces/nextcloud/webdav_handler.rs b/src/interfaces/nextcloud/webdav_handler.rs
index 2468fa33..6ecace2e 100644
--- a/src/interfaces/nextcloud/webdav_handler.rs
+++ b/src/interfaces/nextcloud/webdav_handler.rs
@@ -341,6 +341,7 @@ async fn handle_propfind(
             // function's username arg. Refining the owner-id usages
             // back to the canonical username is deferred to the
             // NcSession commit.
+            let quota = state.resolve_webdav_quota(user.id, chroot.drive_id).await;
             Ok(build_nc_streaming_propfind(
                 state.clone(),
                 folder,
@@ -348,6 +349,7 @@ async fn handle_propfind(
                 user.id,
                 url_user.to_string(),
                 subpath.to_string(),
+                quota,
             ))
         }
         ResolvedResource::File(file) => {
@@ -1481,6 +1483,7 @@ fn build_nc_streaming_propfind(
     user_id: Uuid,
     username: String,
     subpath: String,
+    quota: Option<(i64, Option<i64>)>,
 ) -> Response<Body> {
     let stream = async_stream::try_stream! {
         let file_id_svc = state.nextcloud.as_ref().map(|n| &n.file_ids);
@@ -1509,7 +1512,7 @@ fn build_nc_streaming_propfind(
             let href = nc_collection_href(&username, &subpath);
             let fid = folder_id_map.get(&folder.id).copied();
             let oc_id = fid.map(|id| format_oc_id(id, file_id_svc));
-            write_folder_response(&mut xml, &folder, &href, (fid, oc_id.as_deref()), &username, &folder_favs, &folder_dead)
+            write_folder_response(&mut xml, &folder, &href, (fid, oc_id.as_deref()), &username, &folder_favs, quota, &folder_dead)
                 .map_err(std::io::Error::other)?;
         }
         yield Bytes::from(buf);
@@ -1608,7 +1611,7 @@ fn build_nc_streaming_propfind(
                         let href = nc_collection_href(&username, &child_sub);
                         let fid = sub_id_map.get(&sf.id).copied();
                         let oc_id = fid.map(|id| format_oc_id(id, file_id_svc));
-                        write_folder_response(&mut xml, sf, &href, (fid, oc_id.as_deref()), &username, &favs, dead)
+                        write_folder_response(&mut xml, sf, &href, (fid, oc_id.as_deref()), &username, &favs, quota, dead)
                             .map_err(std::io::Error::other)?;
                     }
                 }
@@ -1647,6 +1650,7 @@ fn build_nc_streaming_propfind(
 /// together (`oc_id` is derived from `file_id`) — to stay under
 /// clippy's argument-count lint now that `dead_props` is also threaded
 /// through.
+#[allow(clippy::too_many_arguments)]
 pub fn write_folder_response<W: std::io::Write>(
     xml: &mut Writer<W>,
     folder: &FolderDto,
@@ -1654,6 +1658,7 @@ pub fn write_folder_response<W: std::io::Write>(
     oc_ids: (Option<i64>, Option<&str>),
     owner: &str,
     favorite_ids: &HashSet<String>,
+    quota: Option<(i64, Option<i64>)>,
     dead_props: &[(QualifiedName, Option<String>)],
 ) -> Result<(), String> {
     let (file_id, oc_id) = oc_ids;
@@ -1705,6 +1710,16 @@ pub fn write_folder_response<W: std::io::Write>(
     // Numeric share-permissions bitmask: Read=1 + Update=2 + Create=4 + Delete=8 + Share=16 = 31
     write_text_element(xml, "ocs:share-permissions", "31")?;
     write_text_element(xml, "oc:size", "0")?;
+    // RFC 4331 — same account/drive-wide value regardless of which
+    // folder entry is being described, mirroring the native WebDAV
+    // surface's `write_folder_standard_props` (see
+    // `AppState::resolve_webdav_quota`).
+    if let Some((used, available)) = quota {
+        write_text_element(xml, "d:quota-used-bytes", &used.to_string())?;
+        if let Some(avail) = available {
+            write_text_element(xml, "d:quota-available-bytes", &avail.to_string())?;
+        }
+    }
     write_text_element(xml, "oc:owner-id", owner)?;
     write_text_element(xml, "oc:owner-display-name", owner)?;
     write_text_element(xml, "nc:has-preview", "false")?;
diff --git a/tests/api/nc_webdav_quota_properties.hurl b/tests/api/nc_webdav_quota_properties.hurl
new file mode 100644
index 00000000..99775a07
--- /dev/null
+++ b/tests/api/nc_webdav_quota_properties.hurl
@@ -0,0 +1,171 @@
+# =============================================================
+# OxiCloud — NC WebDAV quota properties (RFC 4331)
+# =============================================================
+# The NextCloud-compatible WebDAV surface
+# (`interfaces/nextcloud/webdav_handler.rs`) previously had NO
+# `d:quota-used-bytes`/`d:quota-available-bytes` support at all. This
+# pins the new coverage added alongside the native surface's
+# drive-awareness fix (`AppState::resolve_webdav_quota`):
+#
+#   1. Personal-drive PROPFIND (no drive marker in the Basic Auth
+#      username) reports the caller's account envelope.
+#   2. A SHARED drive with its own finite quota reports THAT quota —
+#      not the owner's personal envelope — when addressed via the
+#      multi-drive POC's `{user}~{root_folder_id}` Basic Auth marker
+#      (see `basic_auth_middleware.rs` — the marker is the drive's
+#      ROOT FOLDER id, not the drive's own id).
+#   3. quota-used-bytes on the shared drive increases after a PUT.
+#
+# This file always emits the full property set regardless of the
+# PROPFIND request body (see `handle_propfind`'s doc comment — "the
+# NC response always emits the full property set"), so no XML body
+# is needed to request the props; a bare PROPFIND suffices.
+# =============================================================
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 1 — Admin login + mint admin's own NC app password (for
+#          the personal-envelope case).
+# ─────────────────────────────────────────────────────────────
+POST {{base_url}}/api/auth/login
+Content-Type: application/json
+{ "username": "{{username}}", "password": "{{password}}" }
+
+HTTP 200
+[Captures]
+admin_token: jsonpath "$.access_token"
+
+POST {{base_url}}/api/auth/app-passwords
+Authorization: Bearer {{admin_token}}
+Content-Type: application/json
+{ "label": "nc_webdav_quota_properties personal" }
+
+HTTP 200
+[Captures]
+admin_nc_username: jsonpath "$.username"
+admin_nc_password: jsonpath "$.password"
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 2 — Personal-drive PROPFIND (no `~` marker) surfaces the
+#          account envelope. `>= 0` / `> 0` rather than exact
+#          numbers since admin's envelope already has content
+#          from earlier tests in the suite.
+# ─────────────────────────────────────────────────────────────
+PROPFIND {{base_url}}/remote.php/dav/files/{{username}}/
+Depth: 0
+[BasicAuth]
+{{admin_nc_username}}: {{admin_nc_password}}
+
+HTTP 207
+[Asserts]
+xpath "number(//*[local-name()='quota-used-bytes'])" >= 0
+xpath "number(//*[local-name()='quota-available-bytes'])" > 0
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 3 — Fresh user + a 500-byte shared drive owned by them.
+# ─────────────────────────────────────────────────────────────
+POST {{base_url}}/api/admin/users
+Authorization: Bearer {{admin_token}}
+Content-Type: application/json
+{
+  "username": "ncq_owner",
+  "password": "NcqOwnerPwd1!",
+  "email":    "ncq_owner@example.com",
+  "role":     "user"
+}
+
+HTTP 201
+
+POST {{base_url}}/api/auth/login
+Content-Type: application/json
+{ "username": "ncq_owner", "password": "NcqOwnerPwd1!" }
+
+HTTP 200
+[Captures]
+ncq_owner_jwt: jsonpath "$.access_token"
+ncq_owner_id: jsonpath "$.user.id"
+
+POST {{base_url}}/api/auth/app-passwords
+Authorization: Bearer {{ncq_owner_jwt}}
+Content-Type: application/json
+{ "label": "nc_webdav_quota_properties shared" }
+
+HTTP 200
+[Captures]
+ncq_nc_username: jsonpath "$.username"
+ncq_nc_password: jsonpath "$.password"
+
+
+POST {{base_url}}/api/drives
+Authorization: Bearer {{admin_token}}
+Content-Type: application/json
+{
+  "kind": "shared",
+  "name": "ncq-shared",
+  "owner": { "type": "user", "id": "{{ncq_owner_id}}" },
+  "quota_bytes": 500
+}
+
+HTTP 201
+[Captures]
+ncq_root_folder_id: jsonpath "$.root_folder_id"
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 4 — PROPFIND the shared drive via the multi-drive POC's
+#          `{user}~{root_folder_id}` Basic Auth marker. Brand-new
+#          drive → used == 0, available == quota exactly.
+# ─────────────────────────────────────────────────────────────
+PROPFIND {{base_url}}/remote.php/dav/files/{{ncq_nc_username}}~{{ncq_root_folder_id}}/
+Depth: 0
+[Options]
+variable: ncq_composite_user={{ncq_nc_username}}~{{ncq_root_folder_id}}
+[BasicAuth]
+{{ncq_composite_user}}: {{ncq_nc_password}}
+
+HTTP 207
+[Asserts]
+xpath "number(//*[local-name()='quota-used-bytes'])" == 0
+xpath "number(//*[local-name()='quota-available-bytes'])" == 500
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 5 — PUT a file into the shared drive; quota-used-bytes
+#          must reflect it, quota-available-bytes must shrink.
+# ─────────────────────────────────────────────────────────────
+PUT {{base_url}}/remote.php/dav/files/{{ncq_nc_username}}~{{ncq_root_folder_id}}/quota-probe.txt
+Content-Type: text/plain
+[Options]
+variable: ncq_composite_user={{ncq_nc_username}}~{{ncq_root_folder_id}}
+[BasicAuth]
+{{ncq_composite_user}}: {{ncq_nc_password}}
+```
+32-byte-ish payload for nc
+```
+
+HTTP 201
+
+
+# The drive-usage bump is fire-and-forget on a tokio task (see
+# `file_upload_service.rs::maybe_update_storage_usage`), so retry
+# until `used_bytes` catches up — same shape as `drive_quota.hurl`
+# Step 5.
+PROPFIND {{base_url}}/remote.php/dav/files/{{ncq_nc_username}}~{{ncq_root_folder_id}}/
+Depth: 0
+[Options]
+variable: ncq_composite_user={{ncq_nc_username}}~{{ncq_root_folder_id}}
+retry: 10
+retry-interval: 200ms
+[BasicAuth]
+{{ncq_composite_user}}: {{ncq_nc_password}}
+
+HTTP 207
+[Asserts]
+xpath "number(//*[local-name()='quota-used-bytes'])" > 0
+xpath "number(//*[local-name()='quota-available-bytes'])" < 500
+
+
+# No further cleanup needed — `tests/api/storage_cleanup_check.sh`
+# drains/deletes every non-admin-default drive at suite end.
diff --git a/tests/api/run.sh b/tests/api/run.sh
index 3288ae29..8613f11a 100755
--- a/tests/api/run.sh
+++ b/tests/api/run.sh
@@ -195,6 +195,8 @@ hurl --variables-file "$API_DIR/test.env" --file-root "$REPO_ROOT/tests" --test
   "$API_DIR/webdav_dead_properties.hurl" \
   "$API_DIR/nc_webdav_dead_properties.hurl" \
   "$API_DIR/webdav_protected_properties.hurl" \
+  "$API_DIR/webdav_quota_properties.hurl" \
+  "$API_DIR/nc_webdav_quota_properties.hurl" \
   "$API_DIR/webdav_drive_root.hurl" \
   "$API_DIR/webdav_permissions.hurl" \
   "$API_DIR/webdav_nested_move_cascade.hurl" \
diff --git a/tests/api/webdav_quota_properties.hurl b/tests/api/webdav_quota_properties.hurl
new file mode 100644
index 00000000..d092578f
--- /dev/null
+++ b/tests/api/webdav_quota_properties.hurl
@@ -0,0 +1,235 @@
+# =============================================================
+# OxiCloud — WebDAV quota properties (RFC 4331)
+# =============================================================
+# `DAV:quota-available-bytes` / `DAV:quota-used-bytes` are resolved once
+# per PROPFIND request via `AppState::resolve_webdav_quota` — see
+# webdav_handler.rs / webdav_adapter.rs::write_quota_props.
+# Unlimited accounts/drives (quota <= 0 or unset) omit
+# quota-available-bytes entirely per RFC 4331 §3, rather than reporting
+# a sentinel value.
+#
+# Coverage:
+#   1. Named-prop PROPFIND for both properties on the WebDAV root → 207,
+#      both present with numeric values.
+#   2. allprop PROPFIND also includes both properties.
+#   3. quota-used-bytes increases by (at least) the size of a file
+#      just uploaded through WebDAV.
+#   4. A SHARED drive with its own finite quota reports THAT quota on
+#      `/webdav/@drive/<id>/`, distinct from the caller's personal
+#      envelope — the drive-awareness fix (previously `resolve_quota`
+#      ignored `drive_id` entirely and always reported the envelope).
+# =============================================================
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 1 — Login, capture JWT
+# ─────────────────────────────────────────────────────────────
+POST {{base_url}}/api/auth/login
+Content-Type: application/json
+{ "username": "{{username}}", "password": "{{password}}" }
+
+HTTP 200
+[Captures]
+token: jsonpath "$.access_token"
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 2 — Named-prop PROPFIND for the two quota properties.
+# ─────────────────────────────────────────────────────────────
+PROPFIND {{base_url}}/webdav/
+Authorization: Bearer {{token}}
+Depth: 0
+Content-Type: application/xml; charset=utf-8
+```
+<?xml version="1.0" encoding="utf-8"?>
+<D:propfind xmlns:D="DAV:">
+  <D:prop>
+    <D:quota-available-bytes/>
+    <D:quota-used-bytes/>
+  </D:prop>
+</D:propfind>
+```
+
+HTTP 207
+[Asserts]
+xpath "string(//*[local-name()='propstat'][1]/*[local-name()='status'])" contains "200 OK"
+xpath "number(//*[local-name()='quota-used-bytes'])" >= 0
+xpath "number(//*[local-name()='quota-available-bytes'])" > 0
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 3 — allprop PROPFIND also surfaces both properties.
+# ─────────────────────────────────────────────────────────────
+PROPFIND {{base_url}}/webdav/
+Authorization: Bearer {{token}}
+Depth: 0
+Content-Type: application/xml; charset=utf-8
+```
+<?xml version="1.0" encoding="utf-8"?>
+<D:propfind xmlns:D="DAV:">
+  <D:allprop/>
+</D:propfind>
+```
+
+HTTP 207
+[Asserts]
+xpath "number(//*[local-name()='quota-used-bytes'])" >= 0
+xpath "number(//*[local-name()='quota-available-bytes'])" > 0
+[Captures]
+used_before: xpath "number(//*[local-name()='quota-used-bytes'])"
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 4 — Upload a file, then confirm quota-used-bytes reflects it.
+# ─────────────────────────────────────────────────────────────
+PUT {{base_url}}/webdav/quota-probe.txt
+Authorization: Bearer {{token}}
+Content-Type: text/plain
+```
+quota accounting probe payload
+```
+
+HTTP 201
+
+
+PROPFIND {{base_url}}/webdav/
+Authorization: Bearer {{token}}
+Depth: 0
+Content-Type: application/xml; charset=utf-8
+```
+<?xml version="1.0" encoding="utf-8"?>
+<D:propfind xmlns:D="DAV:">
+  <D:prop>
+    <D:quota-used-bytes/>
+  </D:prop>
+</D:propfind>
+```
+
+HTTP 207
+[Asserts]
+xpath "number(//*[local-name()='quota-used-bytes'])" >= {{used_before}}
+
+
+# ─────────────────────────────────────────────────────────────
+# Cleanup
+# ─────────────────────────────────────────────────────────────
+DELETE {{base_url}}/webdav/quota-probe.txt
+Authorization: Bearer {{token}}
+
+HTTP 204
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 5 — Shared drive with its own finite quota reports THAT
+#          quota, not the owner's personal envelope.
+#
+#          Provision a fresh user + a 500-byte shared drive owned
+#          by them, then PROPFIND `/webdav/@drive/<id>/` (see
+#          `webdav_drive_root.hurl` for the URL-scheme contract).
+#          A brand-new drive has `used_bytes == 0`, so
+#          quota-available-bytes must equal the quota exactly —
+#          a value that cannot coincide with the personal envelope
+#          asserted above (that account already had files on it
+#          from earlier steps).
+# ─────────────────────────────────────────────────────────────
+POST {{base_url}}/api/admin/users
+Authorization: Bearer {{token}}
+Content-Type: application/json
+{
+  "username": "wq_owner",
+  "password": "WqOwnerPwd1!",
+  "email":    "wq_owner@example.com",
+  "role":     "user"
+}
+
+HTTP 201
+
+POST {{base_url}}/api/auth/login
+Content-Type: application/json
+{ "username": "wq_owner", "password": "WqOwnerPwd1!" }
+
+HTTP 200
+[Captures]
+wq_owner_token: jsonpath "$.access_token"
+wq_owner_id: jsonpath "$.user.id"
+
+
+POST {{base_url}}/api/drives
+Authorization: Bearer {{token}}
+Content-Type: application/json
+{
+  "kind": "shared",
+  "name": "wq-shared",
+  "owner": { "type": "user", "id": "{{wq_owner_id}}" },
+  "quota_bytes": 500
+}
+
+HTTP 201
+[Captures]
+wq_drive_id: jsonpath "$.id"
+
+
+PROPFIND {{base_url}}/webdav/@drive/{{wq_drive_id}}/
+Authorization: Bearer {{wq_owner_token}}
+Depth: 0
+Content-Type: application/xml; charset=utf-8
+```
+<?xml version="1.0" encoding="utf-8"?>
+<D:propfind xmlns:D="DAV:">
+  <D:prop>
+    <D:quota-available-bytes/>
+    <D:quota-used-bytes/>
+  </D:prop>
+</D:propfind>
+```
+
+HTTP 207
+[Asserts]
+xpath "number(//*[local-name()='quota-used-bytes'])" == 0
+xpath "number(//*[local-name()='quota-available-bytes'])" == 500
+
+
+# Upload a 32-byte file into the shared drive; quota-used-bytes must
+# reflect it and quota-available-bytes must shrink accordingly —
+# confirms the shared-drive branch reads `storage.drives` live, not
+# a cached/stale value.
+PUT {{base_url}}/webdav/@drive/{{wq_drive_id}}/quota-probe.txt
+Authorization: Bearer {{wq_owner_token}}
+Content-Type: text/plain
+```
+32-byte-ish payload for drv
+```
+
+HTTP 201
+
+
+# The drive-usage bump is fire-and-forget on a tokio task (see
+# `file_upload_service.rs::maybe_update_storage_usage`), so the SQL
+# UPDATE may not have landed yet when the PUT above returned. Retry
+# the PROPFIND until `used_bytes` catches up — same shape as
+# `drive_quota.hurl` Step 5.
+PROPFIND {{base_url}}/webdav/@drive/{{wq_drive_id}}/
+Authorization: Bearer {{wq_owner_token}}
+Depth: 0
+Content-Type: application/xml; charset=utf-8
+[Options]
+retry: 10
+retry-interval: 200ms
+```
+<?xml version="1.0" encoding="utf-8"?>
+<D:propfind xmlns:D="DAV:">
+  <D:prop>
+    <D:quota-available-bytes/>
+    <D:quota-used-bytes/>
+  </D:prop>
+</D:propfind>
+```
+
+HTTP 207
+[Asserts]
+xpath "number(//*[local-name()='quota-used-bytes'])" > 0
+xpath "number(//*[local-name()='quota-available-bytes'])" < 500
+
+
+# No further cleanup needed — `tests/api/storage_cleanup_check.sh`
+# drains/deletes every non-admin-default drive at suite end.