diff --git a/src/application/ports/authorization_ports.rs b/src/application/ports/authorization_ports.rs
index fb994362..1934c90a 100644
--- a/src/application/ports/authorization_ports.rs
+++ b/src/application/ports/authorization_ports.rs
@@ -16,6 +16,28 @@ use crate::domain::services::authorization::{
     ResourceKind, Role, Subject,
 };
 
+/// Discriminates the two denial shapes surfaced by
+/// [`AuthorizationEngine::require_visible`] in the `authz.denied` audit line.
+/// Log-aggregation consumers key off the string form via `as_str`; keep the
+/// values stable — a new denial shape means a new variant, never a renamed
+/// existing one.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum AuthzDenialVisibility {
+    /// Caller has `Read` on the resource — 403 Forbidden.
+    Visible,
+    /// Caller has no `Read` — 404 anti-enum.
+    Hidden,
+}
+
+impl AuthzDenialVisibility {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            Self::Visible => "visible",
+            Self::Hidden => "hidden",
+        }
+    }
+}
+
 pub trait AuthorizationEngine: Send + Sync + 'static {
     /// Returns true if `subject` has `permission` on `resource`, considering
     /// owner short-circuit AND cascading from folder ancestors.
@@ -53,9 +75,28 @@ pub trait AuthorizationEngine: Send + Sync + 'static {
         Ok(allowed)
     }
 
-    /// Convenience wrapper around `check`: returns `Ok(())` when allowed and
-    /// `DomainError::not_found` when denied (anti-enumeration — same error as
-    /// "resource doesn't exist" so attackers can't probe IDs by error shape).
+    /// Graduated-denial wrapper around `check`. Semantics:
+    ///
+    /// - `permission` granted → `Ok(())`
+    /// - `permission` denied, `Read` also denied → `DomainError::not_found`
+    ///   (404, anti-enumeration — same shape as "doesn't exist" so a probing
+    ///   caller can't distinguish "wrong id" from "no access")
+    /// - `permission` denied, `Read` granted → `DomainError::access_denied`
+    ///   (403 — the caller can already see the resource, so hiding existence
+    ///   leaks nothing new; a clear 403 beats a confusing 404 for UX and for
+    ///   API-first clients like rclone)
+    ///
+    /// Special case: when `permission == Read`, the visibility gate collapses
+    /// onto itself — a `Read` denial IS a "hidden" outcome by definition, so
+    /// the method short-circuits to the strict anti-enum 404 without a second
+    /// DB round-trip. That's why there's only one method: strict Read-denial
+    /// and graduated write-denial fall out of the same signature.
+    ///
+    /// Do NOT use this in search / enumeration paths where existence itself is
+    /// the attack vector — those must filter at the SQL/index layer, never
+    /// touch this method with per-row ids. Cross-tenant probes on ids the
+    /// caller has no prior read handle for degrade to the 404 shape naturally
+    /// (Read denied → `Hidden`).
     async fn require(
         &self,
         subject: Subject,
@@ -80,39 +121,68 @@ pub trait AuthorizationEngine: Send + Sync + 'static {
                 permission,
                 resource
             );
-            Ok(())
+            return Ok(());
+        }
+
+        // Visibility probe. Short-circuit: when the target permission IS
+        // `Read` and the check above returned false, we already know Read is
+        // denied — visibility is `Hidden` by definition, no second DB hop.
+        // Otherwise probe Read; a DB-hop failure here degrades to `Hidden` so
+        // the caller sees the strict anti-enum shape (safe default).
+        let visibility = if permission == Permission::Read {
+            AuthzDenialVisibility::Hidden
+        } else if self
+            .check(subject, Permission::Read, resource)
+            .await
+            .unwrap_or(false)
+        {
+            AuthzDenialVisibility::Visible
         } else {
-            let (kind, id) = match resource {
-                Resource::Folder(id) => ("Folder", id),
-                Resource::File(id) => ("File", id),
-                Resource::Drive(id) => ("Drive", id),
-                Resource::Calendar(id) => ("Calendar", id),
-                Resource::AddressBook(id) => ("AddressBook", id),
-                Resource::Playlist(id) => ("Playlist", id),
-            };
-            // Audit-worthy: denials are the interesting signal. Routed
-            // through the `audit` tracing target so log aggregators can
-            // surface them separately from operational debug traffic.
-            // Span context (request_id, client_ip, user_id) is attached
-            // automatically by the request-scope span set in
-            // `interfaces/middleware/trace_span.rs`, so this log line
-            // doesn't need to duplicate those fields — they appear in
-            // the structured output of every log written inside the
-            // request span.
-            tracing::info!(
-                target: "audit",
-                event = "authz.denied",
-                subject_type = subject.type_str(),
-                subject_id = %subject.id(),
-                permission = permission.as_str(),
-                resource_type = resource.type_str(),
-                resource_id = %resource.id(),
-                "👮🏻‍♂️ perms: ⛔ Subject '{}' hasn't permission to '{}' on resource '{}'",
-                subject,
-                permission,
-                resource
-            );
-            Err(DomainError::not_found(kind, id.to_string()))
+            AuthzDenialVisibility::Hidden
+        };
+
+        let (kind, id) = match resource {
+            Resource::Folder(id) => ("Folder", id),
+            Resource::File(id) => ("File", id),
+            Resource::Drive(id) => ("Drive", id),
+            Resource::Calendar(id) => ("Calendar", id),
+            Resource::AddressBook(id) => ("AddressBook", id),
+            Resource::Playlist(id) => ("Playlist", id),
+        };
+
+        // Audit-worthy: denials are the interesting signal. Routed through
+        // the `audit` tracing target so log aggregators can surface them
+        // separately from operational debug traffic. Span context
+        // (request_id, client_ip, user_id) comes from the request-scope
+        // span set in `interfaces/middleware/trace_span.rs`, so this line
+        // doesn't need to duplicate those fields.
+        //
+        // The `visibility` field discriminates the two denial shapes for
+        // operators grepping exists-but-denied vs fully-hidden. `visible`
+        // denials are the ones surfaced to the caller as 403 (and safe to
+        // detail in the UI); `hidden` denials are the 404 anti-enum path.
+        tracing::info!(
+            target: "audit",
+            event = "authz.denied",
+            visibility = visibility.as_str(),
+            subject_type = subject.type_str(),
+            subject_id = %subject.id(),
+            permission = permission.as_str(),
+            resource_type = resource.type_str(),
+            resource_id = %resource.id(),
+            "👮🏻‍♂️ perms: ⛔ Subject '{}' hasn't permission to '{}' on resource '{}' (visibility={})",
+            subject,
+            permission,
+            resource,
+            visibility.as_str()
+        );
+
+        match visibility {
+            AuthzDenialVisibility::Visible => Err(DomainError::access_denied(
+                kind,
+                format!("Missing '{}' permission on {} {}", permission, kind, id),
+            )),
+            AuthzDenialVisibility::Hidden => Err(DomainError::not_found(kind, id.to_string())),
         }
     }
 
diff --git a/src/application/ports/inbound.rs b/src/application/ports/inbound.rs
index 96d71970..456ce9e8 100644
--- a/src/application/ports/inbound.rs
+++ b/src/application/ports/inbound.rs
@@ -27,11 +27,15 @@ pub trait SearchUseCase: Send + Sync + 'static {
     ) -> Result<Arc<SearchResultsDto>, DomainError>;
 
     /// Returns quick suggestions for autocomplete (lightweight, fast).
+    /// `caller_id` scopes results to drives the caller can Read — without
+    /// it the endpoint leaks names + paths across every tenant on the
+    /// instance (AuthZ audit finding #1, 2026-07-12).
     async fn suggest(
         &self,
         query: &str,
         folder_id: Option<&str>,
         limit: usize,
+        caller_id: Uuid,
     ) -> Result<SearchSuggestionsDto, DomainError>;
 
     /// Clears the search results cache.
diff --git a/src/application/ports/storage_ports.rs b/src/application/ports/storage_ports.rs
index 896fc01c..9f75e790 100644
--- a/src/application/ports/storage_ports.rs
+++ b/src/application/ports/storage_ports.rs
@@ -205,13 +205,21 @@ pub trait FileReadPort: Send + Sync + 'static {
     /// Results are ordered by relevance (exact > starts-with > contains) so the
     /// caller can use them directly for autocomplete suggestions.
     ///
-    /// The default implementation falls back to `list_files` + in-memory filter
-    /// so that stubs and mocks compile without changes.
+    /// `caller_id` scopes results to files whose owning drive the caller can
+    /// Read (direct or group-mediated `role_grants`). Without it the endpoint
+    /// leaks names + paths across every tenant on the instance — closed as
+    /// AuthZ audit finding #1 (2026-07-12).
+    ///
+    /// The default implementation falls back to `list_files` + in-memory
+    /// filter so that stubs and mocks compile without changes. Stub-mode
+    /// callers already operate against a single tenant's data, so ignoring
+    /// `caller_id` here is safe; the PG impl enforces the real scope.
     async fn suggest_files_by_name(
         &self,
         folder_id: Option<&str>,
         query: &str,
         limit: usize,
+        _caller_id: Uuid,
     ) -> Result<Vec<File>, DomainError> {
         let all = self.list_files(folder_id).await?;
         let q = query.to_lowercase();
diff --git a/src/application/services/search_service.rs b/src/application/services/search_service.rs
index 9aa42050..a7dcf947 100644
--- a/src/application/services/search_service.rs
+++ b/src/application/services/search_service.rs
@@ -497,20 +497,28 @@ impl SearchService {
     /// Quick suggestions search — returns up to `limit` name suggestions
     /// matching the query. Pushes filtering, relevance sort and LIMIT to SQL
     /// so only a handful of rows cross the DB→app boundary.
-    pub async fn suggest(
+    ///
+    /// `caller_id` scopes the underlying repo queries to drives the caller
+    /// can Read. Without it (the pre-fix shape) any authenticated user —
+    /// including external magic-link recipients — could autocomplete both
+    /// names and full paths across every tenant on the instance (AuthZ
+    /// audit finding #1, 2026-07-12). Named `_with_perms` per the
+    /// AGENTS.md AuthZ convention.
+    pub async fn suggest_with_perms(
         &self,
         query: &str,
         folder_id: Option<&str>,
         limit: usize,
+        caller_id: Uuid,
     ) -> Result<SearchSuggestionsDto> {
         let start = Instant::now();
 
         // Ask SQL for at most `limit` best-matching files and folders
         let (files, folders) = tokio::join!(
             self.file_repository
-                .suggest_files_by_name(folder_id, query, limit),
+                .suggest_files_by_name(folder_id, query, limit, caller_id),
             self.folder_repository
-                .suggest_folders_by_name(folder_id, query, limit),
+                .suggest_folders_by_name(folder_id, query, limit, caller_id),
         );
         let files = files?;
         let folders = folders?;
@@ -802,14 +810,20 @@ impl SearchUseCase for SearchService {
             })
     }
 
-    /// Returns quick suggestions for autocomplete.
+    /// Returns quick suggestions for autocomplete. Delegates to the
+    /// inherent `suggest_with_perms` — the trait method is preserved as
+    /// the polymorphic entry point (e.g. for `StubSearchUseCase` in
+    /// tests); production callers can equivalently call the inherent
+    /// method directly.
     async fn suggest(
         &self,
         query: &str,
         folder_id: Option<&str>,
         limit: usize,
+        caller_id: Uuid,
     ) -> Result<SearchSuggestionsDto> {
-        self.suggest(query, folder_id, limit).await
+        self.suggest_with_perms(query, folder_id, limit, caller_id)
+            .await
     }
 
     /// Clears the search results cache.
@@ -841,6 +855,7 @@ impl SearchService {
                 _query: &str,
                 _folder_id: Option<&str>,
                 _limit: usize,
+                _caller_id: Uuid,
             ) -> Result<SearchSuggestionsDto> {
                 Ok(SearchSuggestionsDto {
                     suggestions: Vec::new(),
diff --git a/src/common/stubs.rs b/src/common/stubs.rs
index bdd15bf5..4d72d9d4 100644
--- a/src/common/stubs.rs
+++ b/src/common/stubs.rs
@@ -725,6 +725,7 @@ impl SearchUseCase for StubSearchUseCase {
         _query: &str,
         _folder_id: Option<&str>,
         _limit: usize,
+        _caller_id: Uuid,
     ) -> Result<SearchSuggestionsDto, DomainError> {
         Ok(SearchSuggestionsDto {
             suggestions: Vec::new(),
diff --git a/src/domain/repositories/folder_repository.rs b/src/domain/repositories/folder_repository.rs
index 19cafab4..6d6d9568 100644
--- a/src/domain/repositories/folder_repository.rs
+++ b/src/domain/repositories/folder_repository.rs
@@ -269,13 +269,21 @@ pub trait FolderRepository: Send + Sync + 'static {
     /// Results are ordered by relevance (exact > starts-with > contains) for
     /// autocomplete suggestions.
     ///
+    /// `caller_id` scopes results to folders whose owning drive the caller
+    /// can Read (direct or group-mediated `role_grants`). Without it the
+    /// endpoint leaked names + paths across every tenant on the instance —
+    /// closed as AuthZ audit finding #1 (2026-07-12).
+    ///
     /// The default implementation falls back to `list_folders` + in-memory
-    /// filter so that stubs and mocks compile without changes.
+    /// filter so that stubs and mocks compile without changes. Stub-mode
+    /// callers already operate against a single tenant's data, so ignoring
+    /// `caller_id` here is safe; the PG impl enforces the real scope.
     async fn suggest_folders_by_name(
         &self,
         parent_id: Option<&str>,
         query: &str,
         limit: usize,
+        _caller_id: uuid::Uuid,
     ) -> Result<Vec<Folder>, DomainError> {
         let all = self.list_folders(parent_id).await?;
         let q = query.to_lowercase();
diff --git a/src/infrastructure/repositories/pg/file_blob_read_repository.rs b/src/infrastructure/repositories/pg/file_blob_read_repository.rs
index f70c5adb..d34b44e8 100644
--- a/src/infrastructure/repositories/pg/file_blob_read_repository.rs
+++ b/src/infrastructure/repositories/pg/file_blob_read_repository.rs
@@ -1413,12 +1413,20 @@ impl FileReadPort for FileBlobReadRepository {
         folder_id: Option<&str>,
         query: &str,
         limit: usize,
+        caller_id: Uuid,
     ) -> Result<Vec<File>, DomainError> {
+        // Scope by drive membership: `CALLER_CAN_READ_DRIVE` (`$1` =
+        // caller_id) restricts the result set to files whose owning drive
+        // the caller has any active `role_grants` on — direct or via a
+        // transitive group cascade. Pre-fix, the query only filtered on
+        // `NOT is_trashed AND name ILIKE $pattern`, exposing names + paths
+        // across every tenant on the instance (AuthZ audit finding #1,
+        // 2026-07-12).
         let pattern = super::like_escape(query);
         let limit_i64 = limit as i64;
 
         let rows: Vec<FileRow> = if let Some(fid) = folder_id {
-            sqlx::query_as(
+            sqlx::query_as(&format!(
                 r#"
                 SELECT fi.id, fi.name, fi.folder_id, fo.path,
                        fi.size, fi.mime_type,
@@ -1429,7 +1437,40 @@ impl FileReadPort for FileBlobReadRepository {
                    fi.created_by, fi.updated_by
                   FROM storage.files fi
                   LEFT JOIN storage.folders fo ON fo.id = fi.folder_id
-                 WHERE fi.folder_id = $1::uuid
+                 WHERE {CALLER_CAN_READ_DRIVE}
+                   AND fi.folder_id = $2::uuid
+                   AND NOT fi.is_trashed
+                   AND fi.name ILIKE $3
+                 ORDER BY CASE
+                            WHEN fi.name ILIKE $4 THEN 0
+                            WHEN fi.name ILIKE $4 || '%' THEN 1
+                            ELSE 2
+                          END,
+                          fi.name
+                 LIMIT $5
+                "#
+            ))
+            .bind(caller_id)
+            .bind(fid)
+            .bind(&pattern)
+            .bind(query)
+            .bind(limit_i64)
+            .fetch_all(self.pool.as_ref())
+            .await
+        } else {
+            sqlx::query_as(&format!(
+                r#"
+                SELECT fi.id, fi.name, fi.folder_id, fo.path,
+                       fi.size, fi.mime_type,
+                       EXTRACT(EPOCH FROM fi.created_at)::bigint,
+                       EXTRACT(EPOCH FROM fi.updated_at)::bigint,
+                       fi.blob_hash,
+
+                   fi.created_by, fi.updated_by
+                  FROM storage.files fi
+                  LEFT JOIN storage.folders fo ON fo.id = fi.folder_id
+                 WHERE {CALLER_CAN_READ_DRIVE}
+                   AND fi.folder_id IS NULL
                    AND NOT fi.is_trashed
                    AND fi.name ILIKE $2
                  ORDER BY CASE
@@ -1439,38 +1480,9 @@ impl FileReadPort for FileBlobReadRepository {
                           END,
                           fi.name
                  LIMIT $4
-                "#,
-            )
-            .bind(fid)
-            .bind(&pattern)
-            .bind(query)
-            .bind(limit_i64)
-            .fetch_all(self.pool.as_ref())
-            .await
-        } else {
-            sqlx::query_as(
-                r#"
-                SELECT fi.id, fi.name, fi.folder_id, fo.path,
-                       fi.size, fi.mime_type,
-                       EXTRACT(EPOCH FROM fi.created_at)::bigint,
-                       EXTRACT(EPOCH FROM fi.updated_at)::bigint,
-                       fi.blob_hash,
-
-                   fi.created_by, fi.updated_by
-                  FROM storage.files fi
-                  LEFT JOIN storage.folders fo ON fo.id = fi.folder_id
-                 WHERE fi.folder_id IS NULL
-                   AND NOT fi.is_trashed
-                   AND fi.name ILIKE $1
-                 ORDER BY CASE
-                            WHEN fi.name ILIKE $2 THEN 0
-                            WHEN fi.name ILIKE $2 || '%' THEN 1
-                            ELSE 2
-                          END,
-                          fi.name
-                 LIMIT $3
-                "#,
-            )
+                "#
+            ))
+            .bind(caller_id)
             .bind(&pattern)
             .bind(query)
             .bind(limit_i64)
diff --git a/src/infrastructure/repositories/pg/folder_db_repository.rs b/src/infrastructure/repositories/pg/folder_db_repository.rs
index 3421b9dc..1d748fbb 100644
--- a/src/infrastructure/repositories/pg/folder_db_repository.rs
+++ b/src/infrastructure/repositories/pg/folder_db_repository.rs
@@ -1232,31 +1232,39 @@ impl FolderRepository for FolderDbRepository {
         parent_id: Option<&str>,
         query: &str,
         limit: usize,
+        caller_id: uuid::Uuid,
     ) -> Result<Vec<Folder>, DomainError> {
+        // Same drive-scope filter as `suggest_files_by_name` — closed as
+        // AuthZ audit finding #1 (2026-07-12). `CALLER_CAN_READ_DRIVE`
+        // aliases `storage.folders` as `fo`; the pre-fix query aliased it
+        // as an unqualified `storage.folders`, so this rewrite adds the
+        // `fo` alias in every branch.
         let pattern = super::like_escape(query);
         let limit_i64 = limit as i64;
 
         let rows: Vec<FolderRow> = if let Some(pid) = parent_id {
-            sqlx::query_as(
+            sqlx::query_as(&format!(
                 r#"
-                SELECT id::text, name, path, parent_id::text, drive_id,
-                       EXTRACT(EPOCH FROM created_at)::bigint,
-                       EXTRACT(EPOCH FROM updated_at)::bigint,
-                       EXTRACT(EPOCH FROM tree_modified_at)::bigint,
-                         created_by, updated_by
-                  FROM storage.folders
-                 WHERE parent_id = $1::uuid
-                   AND NOT is_trashed
-                   AND name ILIKE $2
+                SELECT fo.id::text, fo.name, fo.path, fo.parent_id::text, fo.drive_id,
+                       EXTRACT(EPOCH FROM fo.created_at)::bigint,
+                       EXTRACT(EPOCH FROM fo.updated_at)::bigint,
+                       EXTRACT(EPOCH FROM fo.tree_modified_at)::bigint,
+                         fo.created_by, fo.updated_by
+                  FROM storage.folders fo
+                 WHERE {CALLER_CAN_READ_DRIVE}
+                   AND fo.parent_id = $2::uuid
+                   AND NOT fo.is_trashed
+                   AND fo.name ILIKE $3
                  ORDER BY CASE
-                            WHEN name ILIKE $3 THEN 0
-                            WHEN name ILIKE $3 || '%' THEN 1
+                            WHEN fo.name ILIKE $4 THEN 0
+                            WHEN fo.name ILIKE $4 || '%' THEN 1
                             ELSE 2
                           END,
-                          name
-                 LIMIT $4
-                "#,
-            )
+                          fo.name
+                 LIMIT $5
+                "#
+            ))
+            .bind(caller_id)
             .bind(pid)
             .bind(&pattern)
             .bind(query)
@@ -1264,26 +1272,28 @@ impl FolderRepository for FolderDbRepository {
             .fetch_all(self.pool())
             .await
         } else {
-            sqlx::query_as(
+            sqlx::query_as(&format!(
                 r#"
-                SELECT id::text, name, path, parent_id::text, drive_id,
-                       EXTRACT(EPOCH FROM created_at)::bigint,
-                       EXTRACT(EPOCH FROM updated_at)::bigint,
-                       EXTRACT(EPOCH FROM tree_modified_at)::bigint,
-                         created_by, updated_by
-                  FROM storage.folders
-                 WHERE parent_id IS NULL
-                   AND NOT is_trashed
-                   AND name ILIKE $1
+                SELECT fo.id::text, fo.name, fo.path, fo.parent_id::text, fo.drive_id,
+                       EXTRACT(EPOCH FROM fo.created_at)::bigint,
+                       EXTRACT(EPOCH FROM fo.updated_at)::bigint,
+                       EXTRACT(EPOCH FROM fo.tree_modified_at)::bigint,
+                         fo.created_by, fo.updated_by
+                  FROM storage.folders fo
+                 WHERE {CALLER_CAN_READ_DRIVE}
+                   AND fo.parent_id IS NULL
+                   AND NOT fo.is_trashed
+                   AND fo.name ILIKE $2
                  ORDER BY CASE
-                            WHEN name ILIKE $2 THEN 0
-                            WHEN name ILIKE $2 || '%' THEN 1
+                            WHEN fo.name ILIKE $3 THEN 0
+                            WHEN fo.name ILIKE $3 || '%' THEN 1
                             ELSE 2
                           END,
-                          name
-                 LIMIT $3
-                "#,
-            )
+                          fo.name
+                 LIMIT $4
+                "#
+            ))
+            .bind(caller_id)
             .bind(&pattern)
             .bind(query)
             .bind(limit_i64)
diff --git a/src/interfaces/api/handlers/search_handler.rs b/src/interfaces/api/handlers/search_handler.rs
index 5fba8009..2893103f 100644
--- a/src/interfaces/api/handlers/search_handler.rs
+++ b/src/interfaces/api/handlers/search_handler.rs
@@ -140,6 +140,7 @@ impl SearchHandler {
     /// Autocomplete suggestions for search.
     pub(super) async fn suggest_files_impl(
         State(state): State<Arc<AppState>>,
+        auth_user: AuthUser,
         Query(params): Query<SuggestParams>,
     ) -> impl IntoResponse {
         info!("API: Search suggestions for {:?}", params.query);
@@ -159,7 +160,12 @@ impl SearchHandler {
         let limit = params.limit.unwrap_or(10).min(20);
 
         match search_service
-            .suggest(&params.query, params.folder_id.as_deref(), limit)
+            .suggest_with_perms(
+                &params.query,
+                params.folder_id.as_deref(),
+                limit,
+                auth_user.id,
+            )
             .await
         {
             Ok(suggestions) => {
@@ -354,9 +360,10 @@ pub async fn search_files_post(
 )]
 pub async fn suggest_files(
     state: State<Arc<AppState>>,
+    auth_user: AuthUser,
     query: Query<SuggestParams>,
 ) -> impl IntoResponse {
-    SearchHandler::suggest_files_impl(state, query).await
+    SearchHandler::suggest_files_impl(state, auth_user, query).await
 }
 
 #[utoipa::path(
diff --git a/src/interfaces/api/handlers/webdav_handler.rs b/src/interfaces/api/handlers/webdav_handler.rs
index b57c26e5..561a080c 100644
--- a/src/interfaces/api/handlers/webdav_handler.rs
+++ b/src/interfaces/api/handlers/webdav_handler.rs
@@ -2225,18 +2225,27 @@ async fn handle_delete(
     // optimized resolver and the read repositories disagree on path
     // shape for some files; see `resolve_or_legacy` docs.
     let _ = file_retrieval_service; // present for legacy fallback if needed elsewhere
+    // AuthZ audit #2 (2026-07-12): route service errors through
+    // `AppError::from` so authz denials from `_with_perms` surface as
+    // 404 (the anti-enum shape). The prior `map_err(|e| internal_error…)`
+    // collapsed every error — including the `NotFound` that
+    // `authz.require` returns on denial — into HTTP 500, giving a
+    // reliable "exists-but-denied" vs "missing" oracle to a probing
+    // caller. Also preserves `QuotaExceeded → 507`,
+    // `AlreadyExists → 409`, `InvalidInput → 400` shapes surfacing
+    // through the standard error mapping.
     match resolve_or_legacy(&state, &path, drive_id).await {
         Some(ResolvedResource::Folder(folder)) => {
             folder_service
                 .delete_folder_with_perms(&folder.id, user.id)
                 .await
-                .map_err(|e| AppError::internal_error(format!("Failed to delete folder: {}", e)))?;
+                .map_err(AppError::from)?;
         }
         Some(ResolvedResource::File(file)) => {
             file_management_service
                 .delete_file_with_perms(&file.id, user.id)
                 .await
-                .map_err(|e| AppError::internal_error(format!("Failed to delete file: {}", e)))?;
+                .map_err(AppError::from)?;
         }
         None => return Err(AppError::not_found(format!("Resource not found: {}", path))),
     }
@@ -2385,28 +2394,23 @@ async fn handle_move(
         // RFC 4918 §9.9.3: when Overwrite: T, perform a DELETE on the
         // destination before moving. Without this the rename/move fails
         // on a unique-index conflict (same name in same parent).
+        // AuthZ audit #2 (2026-07-12): `_with_perms` returns `DomainError`;
+        // route through `AppError::from` so authz denials surface as 404 (the
+        // anti-enum shape) instead of a `map_err → internal_error` 500 that
+        // gives a probing caller an "exists-but-denied" oracle. Also preserves
+        // `QuotaExceeded → 507`, `AlreadyExists → 409`, `InvalidInput → 400`.
         match resolve_or_legacy(&state, &destination_path, dst_drive_id).await {
             Some(ResolvedResource::Folder(f)) => {
                 folder_service
                     .delete_folder_with_perms(&f.id, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!(
-                            "Failed to delete existing destination: {}",
-                            e
-                        ))
-                    })?;
+                    .map_err(AppError::from)?;
             }
             Some(ResolvedResource::File(f)) => {
                 file_management_service
                     .delete_file_with_perms(&f.id, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!(
-                            "Failed to delete existing destination: {}",
-                            e
-                        ))
-                    })?;
+                    .map_err(AppError::from)?;
             }
             None => {}
         }
@@ -2684,28 +2688,23 @@ async fn handle_copy(
         // RFC 4918 §9.8.4: when Overwrite: T, the server MUST perform a
         // DELETE on the destination before the copy. Without this the copy
         // service returns a unique-index conflict (500).
+        // AuthZ audit #2 (2026-07-12): `_with_perms` returns `DomainError`;
+        // route through `AppError::from` so authz denials surface as 404 (the
+        // anti-enum shape) instead of a `map_err → internal_error` 500 that
+        // gives a probing caller an "exists-but-denied" oracle. Also preserves
+        // `QuotaExceeded → 507`, `AlreadyExists → 409`, `InvalidInput → 400`.
         match resolve_or_legacy(&state, &destination_path, dst_drive_id).await {
             Some(ResolvedResource::Folder(f)) => {
                 folder_service
                     .delete_folder_with_perms(&f.id, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!(
-                            "Failed to delete existing destination: {}",
-                            e
-                        ))
-                    })?;
+                    .map_err(AppError::from)?;
             }
             Some(ResolvedResource::File(f)) => {
                 file_management_service
                     .delete_file_with_perms(&f.id, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!(
-                            "Failed to delete existing destination: {}",
-                            e
-                        ))
-                    })?;
+                    .map_err(AppError::from)?;
             }
             None => {}
         }
@@ -2759,6 +2758,12 @@ async fn handle_copy(
         }
     };
 
+    // AuthZ audit #2 (2026-07-12): route service errors through
+    // `AppError::from` so authz denials from `_with_perms` surface as 404
+    // (the anti-enum shape) instead of a `map_err → internal_error` 500
+    // that gives a probing caller an "exists-but-denied" oracle. Also
+    // preserves `QuotaExceeded → 507`, `AlreadyExists → 409`,
+    // `InvalidInput → 400` shapes.
     match resolved {
         ResolvedResource::Folder(folder) => {
             let recursive = depth != "0";
@@ -2771,9 +2776,7 @@ async fn handle_copy(
                         Some(dest_name.to_string()),
                     )
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!("Failed to copy folder tree: {}", e))
-                    })?;
+                    .map_err(AppError::from)?;
             } else {
                 let create_dto = crate::application::dtos::folder_dto::CreateFolderDto {
                     name: dest_name.to_string(),
@@ -2782,12 +2785,7 @@ async fn handle_copy(
                 folder_service
                     .create_folder_with_perms(create_dto, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!(
-                            "Failed to create destination folder: {}",
-                            e
-                        ))
-                    })?;
+                    .map_err(AppError::from)?;
             }
         }
         ResolvedResource::File(file) => {
@@ -2795,7 +2793,7 @@ async fn handle_copy(
             file_management_service
                 .copy_file_with_perms(&file.id, user.id, target_parent_id, copy_name)
                 .await
-                .map_err(|e| AppError::internal_error(format!("Failed to copy file: {}", e)))?;
+                .map_err(AppError::from)?;
         }
     }
 
diff --git a/src/interfaces/nextcloud/webdav_handler.rs b/src/interfaces/nextcloud/webdav_handler.rs
index d24eb407..a4c94061 100644
--- a/src/interfaces/nextcloud/webdav_handler.rs
+++ b/src/interfaces/nextcloud/webdav_handler.rs
@@ -932,6 +932,11 @@ async fn handle_put(
 
     // Single streaming path — handles both update and create internally,
     // swapping the file row onto the already-ingested blob.
+    // AuthZ audit #6 (2026-07-12): route `_with_perms` errors through
+    // `AppError::from` so authz denials surface as 404 (the anti-enum
+    // shape) instead of a `map_err → internal_error` 500 that gives a
+    // probing caller an "exists-but-denied" oracle. Also preserves
+    // `QuotaExceeded → 507`, `AlreadyExists → 409`, `InvalidInput → 400`.
     let stored = upload_service
         .update_file_streaming_with_perms(
             &internal_path,
@@ -942,7 +947,7 @@ async fn handle_put(
             session.user.id,
         )
         .await
-        .map_err(|e| AppError::internal_error(format!("Failed to store file: {}", e)))?;
+        .map_err(AppError::from)?;
 
     let status = if existed {
         StatusCode::NO_CONTENT
@@ -1031,10 +1036,14 @@ async fn handle_mkcol(
         name: target_name.to_string(),
         parent_id: Some(parent_folder.id.clone()),
     };
+    // AuthZ audit #7 (2026-07-12): route `_with_perms` errors through
+    // `AppError::from` so authz denials surface as 404 (the anti-enum
+    // shape) instead of a `map_err → internal_error` 500. Also preserves
+    // `AlreadyExists → 409`, `QuotaExceeded → 507`, `InvalidInput → 400`.
     folder_service
         .create_folder_with_perms(dto, user.id)
         .await
-        .map_err(|e| AppError::internal_error(format!("Failed to create folder: {}", e)))?;
+        .map_err(AppError::from)?;
 
     Ok(Response::builder()
         .status(StatusCode::CREATED)
@@ -1076,20 +1085,22 @@ async fn handle_delete(
                     Resource::Folder(folder_uuid),
                 )
                 .await?;
+            // AuthZ audit #8 (2026-07-12): route service errors through
+            // `AppError::from` so authz denials surface as 404 (the
+            // anti-enum shape) instead of a `map_err → internal_error`
+            // 500 that gives a probing caller an "exists-but-denied"
+            // oracle. `move_to_trash` and `delete_folder_with_perms`
+            // both return `DomainError` and both call `authz.require`.
             if let Some(trash_svc) = state.trash_service.as_ref() {
                 trash_svc
                     .move_to_trash(&folder.id, "folder", user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!("Failed to trash folder: {}", e))
-                    })?;
+                    .map_err(AppError::from)?;
             } else {
                 folder_service
                     .delete_folder_with_perms(&folder.id, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!("Failed to delete folder: {}", e))
-                    })?;
+                    .map_err(AppError::from)?;
             }
         }
         ResolvedResource::File(file) => {
@@ -1103,21 +1114,18 @@ async fn handle_delete(
                     Resource::File(file_uuid),
                 )
                 .await?;
+            // AuthZ audit #8 (2026-07-12): same anti-enum fix as folder branch above.
             if let Some(trash_svc) = state.trash_service.as_ref() {
                 trash_svc
                     .move_to_trash(&file.id, "file", user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!("Failed to trash file: {}", e))
-                    })?;
+                    .map_err(AppError::from)?;
             } else {
                 let file_mgmt = &state.applications.file_management_service;
                 file_mgmt
                     .delete_file_with_perms(&file.id, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!("Failed to delete file: {}", e))
-                    })?;
+                    .map_err(AppError::from)?;
             }
         }
     }
@@ -1195,6 +1203,12 @@ async fn handle_move(
         // then proceed with the move. Trashing is fine: per RFC the source
         // resource appears at the destination URI; what happens to the
         // overwritten one is up to the server.
+        //
+        // AuthZ audit #9 (2026-07-12): route the `_with_perms` delete
+        // errors through `AppError::from` so authz denials surface as 404
+        // (anti-enum) instead of `map_err → internal_error` 500. Also
+        // preserves `QuotaExceeded → 507`, `AlreadyExists → 409`,
+        // `InvalidInput → 400`.
         match existing {
             ResolvedResource::File(existing_file) => {
                 let file_uuid = Uuid::parse_str(&existing_file.id).map_err(|_| {
@@ -1211,12 +1225,7 @@ async fn handle_move(
                 file_mgmt
                     .delete_and_cleanup_with_perms(&existing_file.id, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!(
-                            "Failed to overwrite destination file: {}",
-                            e
-                        ))
-                    })?;
+                    .map_err(AppError::from)?;
             }
             ResolvedResource::Folder(existing_folder) => {
                 let folder_uuid = Uuid::parse_str(&existing_folder.id).map_err(|_| {
@@ -1233,12 +1242,7 @@ async fn handle_move(
                 folder_service
                     .delete_folder_with_perms(&existing_folder.id, user.id)
                     .await
-                    .map_err(|e| {
-                        AppError::internal_error(format!(
-                            "Failed to overwrite destination folder: {}",
-                            e
-                        ))
-                    })?;
+                    .map_err(AppError::from)?;
             }
         }
     }
@@ -1266,12 +1270,15 @@ async fn handle_move(
             None => "",
         };
 
+        // AuthZ audit #9 (2026-07-12): route `_with_perms` errors
+        // through `AppError::from` so authz denials surface as 404
+        // (anti-enum) instead of `map_err → internal_error` 500.
         if src_parent_sub == dest_parent_sub {
             // Same parent → rename.
             file_mgmt
                 .rename_file_with_perms(&file.id, user.id, dest_name)
                 .await
-                .map_err(|e| AppError::internal_error(format!("Rename failed: {}", e)))?;
+                .map_err(AppError::from)?;
         } else {
             // Different parent → move.
             let dest_parent = folder_service
@@ -1282,14 +1289,14 @@ async fn handle_move(
             file_mgmt
                 .move_file_with_perms(&file.id, user.id, Some(dest_parent.id.clone()))
                 .await
-                .map_err(|e| AppError::internal_error(format!("Move failed: {}", e)))?;
+                .map_err(AppError::from)?;
 
             // If the filename changed too, rename after move.
             if file.name != dest_name {
                 file_mgmt
                     .rename_file_with_perms(&file.id, user.id, dest_name)
                     .await
-                    .map_err(|e| AppError::internal_error(format!("Rename failed: {}", e)))?;
+                    .map_err(AppError::from)?;
             }
         }
 
@@ -1331,6 +1338,9 @@ async fn handle_move(
             None => "",
         };
 
+        // AuthZ audit #9 (2026-07-12): route `_with_perms` errors
+        // through `AppError::from` so authz denials surface as 404
+        // (anti-enum) instead of `map_err → internal_error` 500.
         if src_parent_sub == dest_parent_sub {
             // Same parent → rename.
             use crate::application::dtos::folder_dto::RenameFolderDto;
@@ -1343,7 +1353,7 @@ async fn handle_move(
                     user.id,
                 )
                 .await
-                .map_err(|e| AppError::internal_error(format!("Rename failed: {}", e)))?;
+                .map_err(AppError::from)?;
         } else {
             // Different parent → move.
             let dest_parent = folder_service
@@ -1361,7 +1371,7 @@ async fn handle_move(
                     user.id,
                 )
                 .await
-                .map_err(|e| AppError::internal_error(format!("Move failed: {}", e)))?;
+                .map_err(AppError::from)?;
 
             // If the name changed too, rename.
             if folder.name != dest_name {
@@ -1375,7 +1385,7 @@ async fn handle_move(
                         user.id,
                     )
                     .await
-                    .map_err(|e| AppError::internal_error(format!("Rename failed: {}", e)))?;
+                    .map_err(AppError::from)?;
             }
         }
 
diff --git a/tests/api/calendar.hurl b/tests/api/calendar.hurl
index d3fdd28f..e53c192e 100644
--- a/tests/api/calendar.hurl
+++ b/tests/api/calendar.hurl
@@ -234,13 +234,14 @@ jsonpath "$[?(@.subject.id == '{{bob_user_id}}')].resource.type" == "calendar"
 
 # ─────────────────────────────────────────────────────────────
 # Step 8c – Viewer Bob is denied on the unified list endpoint —
-# `Share` is required, Viewer's bundle excludes it → 404
-# anti-enum shape (same treatment as any other resource type).
+# `Share` is required, Viewer's bundle excludes it. Bob has Read
+# on the calendar → graduated denial returns 403 (see
+# [[project_authz_require_graduated_denial]]).
 # ─────────────────────────────────────────────────────────────
 GET {{base_url}}/api/grants?resource_type=calendar&resource_id={{calendar_id}}
 Authorization: Bearer {{bob_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
diff --git a/tests/api/contacts.hurl b/tests/api/contacts.hurl
index 075a8e14..9f6469b2 100644
--- a/tests/api/contacts.hurl
+++ b/tests/api/contacts.hurl
@@ -412,10 +412,12 @@ HTTP 200
 jsonpath "$[?(@.id == '{{share_book_id}}')].is_readonly" == true
 
 
-# Step 21 — Viewer bundle has no Create permission — Bob's
-# contact write still 404s. Same minimal-body reasoning as
-# Step 18b: keep the request valid at the wire layer so any
-# rejection has to come from the AuthZ engine.
+# Step 21 — Viewer bundle has no Create permission. Bob has Read
+# on the address book (viewer role) so graduated denial returns
+# 403, not 404 (see [[project_authz_require_graduated_denial]]).
+# Same minimal-body reasoning as Step 18b: keep the request valid
+# at the wire layer so any rejection has to come from the AuthZ
+# engine.
 POST {{base_url}}/api/address-books/{{share_book_id}}/contacts
 Authorization: Bearer {{bob_token}}
 Content-Type: application/json
@@ -423,7 +425,7 @@ Content-Type: application/json
   "full_name": "Viewer Cannot Write"
 }
 
-HTTP 404
+HTTP 403
 
 
 # Step 21b — Unified list-on-resource: Alice queries
@@ -445,11 +447,12 @@ jsonpath "$[?(@.subject.id == '{{bob_user_id}}')].resource.type" == "address_boo
 
 
 # Step 21c — Viewer Bob is denied on the unified list endpoint —
-# `Share` isn't in the Viewer bundle → 404 anti-enum shape.
+# `Share` isn't in the Viewer bundle. Bob has Read → graduated
+# denial returns 403 (see [[project_authz_require_graduated_denial]]).
 GET {{base_url}}/api/grants?resource_type=address_book&resource_id={{share_book_id}}
 Authorization: Bearer {{bob_token}}
 
-HTTP 404
+HTTP 403
 
 
 # Step 22 — Alice revokes the grant.
diff --git a/tests/api/drive_read_only.hurl b/tests/api/drive_read_only.hurl
index db85331f..6f94540f 100644
--- a/tests/api/drive_read_only.hurl
+++ b/tests/api/drive_read_only.hurl
@@ -30,9 +30,13 @@
 #   1. Baseline — drive not frozen → owner can upload / rename /
 #      delete / trash / share (proves the fixture is writable).
 #   2. Admin freezes the drive via PATCH policies.
-#   3. Every mutation attempt returns 404 (anti-enum):
-#        upload, rename, delete, trash-restore, permanent delete,
-#        create public link, rename the drive itself.
+#   3. Every mutation attempt is refused. The engine's graduated
+#      denial returns 403 to the owner (who can Read their own
+#      drive) — anti-enum only kicks in for callers with no Read
+#      at all, whose 404 shape is exercised by the cross-tenant
+#      tests in `webdav_permissions.hurl` / `permissions.hurl`.
+#      Cases: upload, rename, delete, trash-restore, permanent
+#      delete, create public link, rename the drive itself.
 #   4. Read still works: GET /api/drives, GET /api/folders,
 #      download the file, list trash.
 #   5. Admin unfreezes.
@@ -203,9 +207,13 @@ jsonpath "$[?(@.id=='{{personal_drive_id}}')].policies.read_only" == true
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 8 — MUTATIONS BLOCKED. Upload → 404 (Create).
-#          Anti-enum: NotFound not 403, same shape as "no such
-#          folder." The engine gate emits an audit line with
+# Step 8 — MUTATIONS BLOCKED. Upload → 403 (Create).
+#          Graduated denial: owner can Read their own frozen
+#          drive, so the engine returns `access_denied` → 403
+#          rather than the anti-enum 404 (hiding a drive from
+#          its owner would be absurd). Cross-tenant callers with
+#          no Read on the drive still see 404 by the same code
+#          path. The engine gate emits an audit line with
 #          `reason = drive_read_only` — inspectable in server
 #          logs, not asserted here (no log-scraping harness).
 # ─────────────────────────────────────────────────────────────
@@ -215,11 +223,11 @@ Authorization: Bearer {{owner_token}}
 folder_id: {{personal_root_id}}
 file: file,fixtures/hello.txt; text/plain
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 9 — Rename file A → 404 (Update). Endpoint is
+# Step 9 — Rename file A → 403 (Update). Endpoint is
 #          `PUT /api/files/{id}/rename` (not PATCH — the file
 #          service exposes rename as a distinct verb, mirroring
 #          the folder side). WebDAV MOVE would fire the same
@@ -230,30 +238,30 @@ Authorization: Bearer {{owner_token}}
 Content-Type: application/json
 { "name": "renamed_during_freeze.txt" }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 10 — Delete file A → 404 (Delete).
+# Step 10 — Delete file A → 403 (Delete).
 # ─────────────────────────────────────────────────────────────
 DELETE {{base_url}}/api/trash/files/{{file_a_id}}
 Authorization: Bearer {{owner_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 11 — Restore file B from trash → 404 (Update on the
+# Step 11 — Restore file B from trash → 403 (Update on the
 #           soft-deleted row is a mutation like any other).
 # ─────────────────────────────────────────────────────────────
 POST {{base_url}}/api/trash/{{file_b_id}}/restore
 Authorization: Bearer {{owner_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 12 — Permanent delete of file B → 404 (Delete).
+# Step 12 — Permanent delete of file B → 403 (Delete).
 #           Note: the background retention purge SQL filter is
 #           tested via source-review + a unit test on the
 #           `delete_expired_bulk` query, not here — advancing
@@ -265,11 +273,11 @@ HTTP 404
 DELETE {{base_url}}/api/trash/{{file_b_id}}
 Authorization: Bearer {{owner_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 13 — Share creation → 404 (Share). Goes through
+# Step 13 — Share creation → 403 (Share). Goes through
 #           `share_service::create_shared_link` which calls
 #           `authz.require(Share, Resource::File)` → engine gate.
 # ─────────────────────────────────────────────────────────────
@@ -281,11 +289,11 @@ Content-Type: application/json
   "item_type": "file"
 }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 14 — Grant (per-resource, not public link) → 404 (Share).
+# Step 14 — Grant (per-resource, not public link) → 403 (Share).
 #           Same engine gate — Share permission on File is
 #           refused regardless of which endpoint asks for it.
 # ─────────────────────────────────────────────────────────────
@@ -298,7 +306,7 @@ Content-Type: application/json
   "role":     "viewer"
 }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
diff --git a/tests/api/drives_membership.hurl b/tests/api/drives_membership.hurl
index cc450d3a..5d454a5c 100644
--- a/tests/api/drives_membership.hurl
+++ b/tests/api/drives_membership.hurl
@@ -564,34 +564,35 @@ jsonpath "$[*].id" contains {{team_drive_id}}
 #            `Permission::Create` on the parent folder — bundled
 #            with `owner`/`editor`/`contributor` role_grants only,
 #            NOT with `viewer`. `POST /api/files/upload` shares the
-#            same `save_file_with_blob` gate, so a Viewer probe
-#            must land 404 (anti-enum: same shape as no-such-folder)
-#            + `authz.denied` audit line. Also verify the batch /
-#            overwrite paths refuse — the whole chain from
-#            drive-membership to file write is exercised here.
+#            same `save_file_with_blob` gate. Bob has Read on the
+#            drive (viewer role cascades) → graduated denial returns
+#            403 (see [[project_authz_require_graduated_denial]]).
+#            Also verify the batch / overwrite paths refuse — the
+#            whole chain from drive-membership to file write is
+#            exercised here.
 # ─────────────────────────────────────────────────────────────
 
-# 22b.i — Fresh file: 404.
+# 22b.i — Fresh file: 403.
 POST {{base_url}}/api/files/upload
 Authorization: Bearer {{bob_token}}
 [MultipartFormData]
 folder_id: {{team_root_folder_id}}
 file: file,fixtures/hello.txt; text/plain
 
-HTTP 404
+HTTP 403
 
 
-# 22b.ii — Overwrite attempt on the Editor-era upload: still 404.
+# 22b.ii — Overwrite attempt on the Editor-era upload: still 403.
 #          `save_file_with_blob` catches the duplicate name at the
 #          `Create`-permission check before the upsert races (which
-#          would otherwise 409). The audit shape stays 404.
+#          would otherwise 409).
 POST {{base_url}}/api/files/upload
 Authorization: Bearer {{bob_token}}
 [MultipartFormData]
 folder_id: {{team_root_folder_id}}
 file: file,fixtures/hello.txt; text/plain
 
-HTTP 404
+HTTP 403
 
 
 # 22b.iii — Alice's Editor-era file is untouched.
@@ -698,8 +699,8 @@ jsonpath "$.role" == "viewer"
 
 # ─────────────────────────────────────────────────────────────
 # Step 25 — Viewer CANNOT edit drive members.
-#           Bob is Viewer. Every member-mutation verb → 404
-#           (anti-enum: same shape as if the drive didn't exist).
+#           Bob is Viewer (has Read on the drive) → graduated denial
+#           returns 403 on every member-mutation verb.
 # ─────────────────────────────────────────────────────────────
 POST {{base_url}}/api/drives/{{team_drive_id}}/members
 Authorization: Bearer {{bob_token}}
@@ -709,7 +710,7 @@ Content-Type: application/json
   "role": "editor"
 }
 
-HTTP 404
+HTTP 403
 
 
 PATCH {{base_url}}/api/drives/{{team_drive_id}}/members/user/{{carol_user_id}}
@@ -717,13 +718,13 @@ Authorization: Bearer {{bob_token}}
 Content-Type: application/json
 { "role": "viewer" }
 
-HTTP 404
+HTTP 403
 
 
 DELETE {{base_url}}/api/drives/{{team_drive_id}}/members/user/{{carol_user_id}}
 Authorization: Bearer {{bob_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
@@ -739,7 +740,7 @@ Content-Type: application/json
 HTTP 200
 
 
-# 26a — Editor POST /api/drives/{id}/members → 404.
+# 26a — Editor POST /api/drives/{id}/members → 403 (Editor has Read).
 POST {{base_url}}/api/drives/{{team_drive_id}}/members
 Authorization: Bearer {{bob_token}}
 Content-Type: application/json
@@ -748,39 +749,39 @@ Content-Type: application/json
   "role": "viewer"
 }
 
-HTTP 404
+HTTP 403
 
 
-# 26b — Editor PATCH a member → 404.
+# 26b — Editor PATCH a member → 403.
 PATCH {{base_url}}/api/drives/{{team_drive_id}}/members/user/{{carol_user_id}}
 Authorization: Bearer {{bob_token}}
 Content-Type: application/json
 { "role": "viewer" }
 
-HTTP 404
+HTTP 403
 
 
-# 26c — Editor DELETE a member → 404.
+# 26c — Editor DELETE a member → 403.
 DELETE {{base_url}}/api/drives/{{team_drive_id}}/members/user/{{carol_user_id}}
 Authorization: Bearer {{bob_token}}
 
-HTTP 404
+HTTP 403
 
 
-# 26d — Editor renames the drive (root folder) → 404.
+# 26d — Editor renames the drive (root folder) → 403.
 #       Folder rename normally requires `Permission::Update` (which
 #       Editor has on every folder in the drive via the engine's drive
 #       precheck). The folder service promotes the requirement to
 #       `Permission::Manage` when the target folder has `parent_id IS
 #       NULL` — i.e. it's a drive root — so the drive-rename surface is
 #       Owner-only per drive.md §6, without changing the public folder
-#       endpoint shape. Anti-enum: refusal returns 404 (not 403).
+#       endpoint shape. Editor has Read → graduated denial → 403.
 PUT {{base_url}}/api/folders/{{team_root_folder_id}}/rename
 Authorization: Bearer {{bob_token}}
 Content-Type: application/json
 { "name": "team-drive-editor-renamed" }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
@@ -883,7 +884,7 @@ HTTP 404
 
 # ─────────────────────────────────────────────────────────────
 # Step 30 — Drive delete (D3b).
-#           - Non-Owner → 404 (Bob is Viewer post-Step 28).
+#           - Non-Owner → 403 (Bob is Viewer post-Step 28, has Read).
 #           - Owner on non-empty drive → 409 (the editor-created-folder
 #             from Step 27 is still live).
 #           - Owner after the folder is trashed → 204.
@@ -892,12 +893,11 @@ HTTP 404
 #           we exercise its 405 below.
 # ─────────────────────────────────────────────────────────────
 
-# 30a — Viewer (Bob) cannot delete the drive → 404, anti-enum same as
-#       the member-mutation refusals.
+# 30a — Viewer (Bob) cannot delete the drive → 403 (has Read).
 DELETE {{base_url}}/api/drives/{{team_drive_id}}
 Authorization: Bearer {{bob_token}}
 
-HTTP 404
+HTTP 403
 
 
 # 30b — Owner (Alice) on a non-empty drive → 409 with the canonical
diff --git a/tests/api/grants.hurl b/tests/api/grants.hurl
index 75135178..d0affa9f 100644
--- a/tests/api/grants.hurl
+++ b/tests/api/grants.hurl
@@ -137,14 +137,15 @@ jsonpath "$.grants[0].role" == "viewer"
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 7 — Viewer cannot rename (no update grant).
+# Step 7 — Viewer cannot rename (no Update grant). Dave has Read
+# (viewer role) → graduated denial returns 403.
 # ─────────────────────────────────────────────────────────────
 PUT {{base_url}}/api/folders/{{shared_folder_id}}/rename
 Authorization: Bearer {{dave_token}}
 Content-Type: application/json
 { "name": "bob-tried-again" }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
@@ -260,14 +261,15 @@ jsonpath "$[0].role" == "viewer"
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 16 — Demoted Bob can no longer rename.
+# Step 16 — Demoted Bob (now Viewer) can no longer rename. Read
+# is still granted → graduated denial returns 403.
 # ─────────────────────────────────────────────────────────────
 PUT {{base_url}}/api/folders/{{shared_folder_id}}/rename
 Authorization: Bearer {{dave_token}}
 Content-Type: application/json
 { "name": "bob-tried-after-demote" }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
@@ -594,34 +596,37 @@ Authorization: Bearer {{adam_token}}
 
 HTTP 200
 
-# ── Mutations still denied (Viewer has no Update/Create/Delete) ─
+# ── Mutations still denied (Viewer has no Update/Create/Delete).
+#    Viewer has Read → graduated denial returns 403 (not 404
+#    anti-enum, which is reserved for Phase 2A above where Adam
+#    had no Read at all).
 POST {{base_url}}/api/folders
 Authorization: Bearer {{adam_token}}
 Content-Type: application/json
 { "name": "adam-attack-2", "parent_id": "{{perm_folder_id}}" }
 
-HTTP 404
+HTTP 403
 
 PUT {{base_url}}/api/folders/{{perm_folder_id}}/rename
 Authorization: Bearer {{adam_token}}
 Content-Type: application/json
 { "name": "adam-rename-as-viewer" }
 
-HTTP 404
+HTTP 403
 
 PUT {{base_url}}/api/files/{{perm_file_id}}/rename
 Authorization: Bearer {{adam_token}}
 Content-Type: application/json
 { "name": "adam-file-rename-as-viewer" }
 
-HTTP 404
+HTTP 403
 
 PUT {{base_url}}/api/files/{{perm_file_id}}/thumbnail/icon
 Authorization: Bearer {{adam_token}}
 Content-Type: image/png
 file,fixtures/blue-image.png;
 
-HTTP 404
+HTTP 403
 
 POST {{base_url}}/api/files/upload
 Authorization: Bearer {{adam_token}}
@@ -629,17 +634,17 @@ Authorization: Bearer {{adam_token}}
 folder_id: {{perm_folder_id}}
 file: file,fixtures/hello.txt; text/plain
 
-HTTP 404
+HTTP 403
 
 DELETE {{base_url}}/api/files/{{perm_file_id}}
 Authorization: Bearer {{adam_token}}
 
-HTTP 404
+HTTP 403
 
 DELETE {{base_url}}/api/folders/{{perm_folder_id}}
 Authorization: Bearer {{adam_token}}
 
-HTTP 404
+HTTP 403
 
 # ── Viewer cannot start a chunked upload (no Create grant) ──
 POST {{base_url}}/api/uploads
@@ -653,7 +658,7 @@ Content-Type: application/json
   "chunk_size": 3000000
 }
 
-HTTP 404
+HTTP 403
 
 
 # ════════════════════════════════════════════════════════════════════
@@ -813,16 +818,17 @@ Authorization: Bearer {{adam_token}}
 
 HTTP 204
 
-# ── Delete still denied (Editor excludes Delete) ────────────
+# ── Delete still denied (Editor excludes Delete). Editor has
+#    Read → graduated denial returns 403.
 DELETE {{base_url}}/api/files/{{perm_file_id}}
 Authorization: Bearer {{adam_token}}
 
-HTTP 404
+HTTP 403
 
 DELETE {{base_url}}/api/folders/{{perm_folder_id}}
 Authorization: Bearer {{adam_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ════════════════════════════════════════════════════════════════════
diff --git a/tests/api/grants_nested_groups.hurl b/tests/api/grants_nested_groups.hurl
index a7b51a45..480edbb3 100644
--- a/tests/api/grants_nested_groups.hurl
+++ b/tests/api/grants_nested_groups.hurl
@@ -367,34 +367,38 @@ HTTP 200
 jsonpath "$.items[?(@.resource.id=='{{perm_folder_id}}')].resource_type" == "folder"
 jsonpath "$.items[?(@.resource.id=='{{perm_folder_id}}')].permissions"   contains "read"
 
-# ── Mutations still denied (Viewer has no Update/Create/Delete) ─
+# ── Mutations still denied (Viewer has no Update/Create/Delete).
+#    Henry has Read via nested-group cascade → graduated denial
+#    returns 403 (see [[project_authz_require_graduated_denial]]).
+#    Anti-enum 404 stays reserved for the earlier phase where the
+#    cascade hadn't given Henry any Read at all.
 POST {{base_url}}/api/folders
 Authorization: Bearer {{henry_token}}
 Content-Type: application/json
 { "name": "henry-attack-2", "parent_id": "{{perm_folder_id}}" }
 
-HTTP 404
+HTTP 403
 
 PUT {{base_url}}/api/folders/{{perm_folder_id}}/rename
 Authorization: Bearer {{henry_token}}
 Content-Type: application/json
 { "name": "henry-rename-as-viewer" }
 
-HTTP 404
+HTTP 403
 
 PUT {{base_url}}/api/files/{{perm_file_id}}/rename
 Authorization: Bearer {{henry_token}}
 Content-Type: application/json
 { "name": "henry-file-rename-as-viewer" }
 
-HTTP 404
+HTTP 403
 
 PUT {{base_url}}/api/files/{{perm_file_id}}/thumbnail/icon
 Authorization: Bearer {{henry_token}}
 Content-Type: image/png
 file,fixtures/blue-image.png;
 
-HTTP 404
+HTTP 403
 
 POST {{base_url}}/api/files/upload
 Authorization: Bearer {{henry_token}}
@@ -402,17 +406,17 @@ Authorization: Bearer {{henry_token}}
 folder_id: {{perm_folder_id}}
 file: file,fixtures/hello.txt; text/plain
 
-HTTP 404
+HTTP 403
 
 DELETE {{base_url}}/api/files/{{perm_file_id}}
 Authorization: Bearer {{henry_token}}
 
-HTTP 404
+HTTP 403
 
 DELETE {{base_url}}/api/folders/{{perm_folder_id}}
 Authorization: Bearer {{henry_token}}
 
-HTTP 404
+HTTP 403
 
 # Viewer cannot start a chunked upload (no Create grant).
 POST {{base_url}}/api/uploads
@@ -426,7 +430,7 @@ Content-Type: application/json
   "chunk_size": 3000000
 }
 
-HTTP 404
+HTTP 403
 
 
 # ════════════════════════════════════════════════════════════════════
@@ -520,16 +524,16 @@ HTTP 200
 [Asserts]
 jsonpath "$[?(@.id=='{{henry_chunked_file_id}}')].name" == "henry-chunked-video.mp4"
 
-# Editor still cannot delete.
+# Editor still cannot delete. Editor bundle carries Read → 403.
 DELETE {{base_url}}/api/files/{{perm_file_id}}
 Authorization: Bearer {{henry_token}}
 
-HTTP 404
+HTTP 403
 
 DELETE {{base_url}}/api/folders/{{perm_folder_id}}
 Authorization: Bearer {{henry_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ════════════════════════════════════════════════════════════════════
diff --git a/tests/api/playlists.hurl b/tests/api/playlists.hurl
index fd8a8283..d8956818 100644
--- a/tests/api/playlists.hurl
+++ b/tests/api/playlists.hurl
@@ -204,38 +204,38 @@ jsonpath "$[*].id" contains "{{playlist_id}}"
 
 # ─────────────────────────────────────────────────────────────
 # Step 11 – Bob cannot rename the playlist. Viewer's bundle is
-# Read-only (no Update), so `require_playlist_perm(Update)` denies
-# with the 404 anti-enum shape.
+# Read-only (no Update). Bob has Read → graduated denial returns
+# 403 (see [[project_authz_require_graduated_denial]]).
 # ─────────────────────────────────────────────────────────────
 PUT {{base_url}}/api/playlists/{{playlist_id}}
 Authorization: Bearer {{bob_token}}
 Content-Type: application/json
 { "name": "hijacked" }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
 # Step 12 – Bob cannot delete the playlist. Viewer's bundle
-# excludes Delete → 404.
+# excludes Delete → 403 (Read granted).
 # ─────────────────────────────────────────────────────────────
 DELETE {{base_url}}/api/playlists/{{playlist_id}}
 Authorization: Bearer {{bob_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
 # Step 13 – Bob cannot re-share the playlist. Viewer's bundle
-# excludes Share → 404 on the legacy /share endpoint (which now
-# routes through `authz.require(Share)`).
+# excludes Share → 403 (Read granted). The legacy /share endpoint
+# routes through `authz.require(Share)`.
 # ─────────────────────────────────────────────────────────────
 POST {{base_url}}/api/playlists/{{playlist_id}}/share
 Authorization: Bearer {{bob_token}}
 Content-Type: application/json
 { "user_id": "{{alice_user_id}}", "can_write": true }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
@@ -277,13 +277,14 @@ jsonpath "$[?(@.subject.id == '{{bob_user_id}}')].resource.type" == "playlist"
 
 # ─────────────────────────────────────────────────────────────
 # Step 14c – Bob (Viewer only) is denied on the unified list
-# endpoint: `Share` is required, Viewer's bundle excludes it →
-# 404 anti-enum shape.
+# endpoint: `Share` is required, Viewer's bundle excludes it.
+# Bob has Read → graduated denial returns 403 (see
+# [[project_authz_require_graduated_denial]]).
 # ─────────────────────────────────────────────────────────────
 GET {{base_url}}/api/grants?resource_type=playlist&resource_id={{playlist_id}}
 Authorization: Bearer {{bob_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
@@ -346,13 +347,14 @@ jsonpath "$.description" == "renamed by editor bob"
 
 # ─────────────────────────────────────────────────────────────
 # Step 19 – Editor still cannot Share (Share stays Owner-only).
+# Bob has Read (Editor bundle) → graduated denial returns 403.
 # ─────────────────────────────────────────────────────────────
 POST {{base_url}}/api/playlists/{{playlist_id}}/share
 Authorization: Bearer {{bob_token}}
 Content-Type: application/json
 { "user_id": "{{alice_user_id}}", "can_write": false }
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
diff --git a/tests/api/search_basic.hurl b/tests/api/search_basic.hurl
index 919ca997..02a7b92b 100644
--- a/tests/api/search_basic.hurl
+++ b/tests/api/search_basic.hurl
@@ -110,7 +110,7 @@ Authorization: Bearer {{admin_token}}
 
 HTTP 200
 [Asserts]
-jsonpath "$.files"        count >= 1
+jsonpath "$.files" count >= 1
 body contains "{{needle_file_id}}"
 
 
@@ -124,7 +124,7 @@ Authorization: Bearer {{admin_token}}
 
 HTTP 200
 [Asserts]
-jsonpath "$.files"   count == 0
+jsonpath "$.files" count == 0
 jsonpath "$.folders" count == 0
 
 
@@ -152,6 +152,29 @@ body not contains "unique-search-needle"
 body not contains "{{needle_file_id}}"
 
 
+# ─────────────────────────────────────────────────────────────
+# 5b — REGRESSION: `/api/search/suggest` MUST also refuse to
+#      surface admin's file to bob. Pre-fix (AuthZ audit #1,
+#      2026-07-12) the suggest endpoint had NO `AuthUser`
+#      extractor and its underlying `suggest_files_by_name` /
+#      `suggest_folders_by_name` filtered only on
+#      `NOT is_trashed AND name ILIKE $1` — any authenticated
+#      user (including externals) could autocomplete names and
+#      full `path` values across every tenant on the instance.
+#      Fix: added `caller_id` to both repo queries via the
+#      shared `CALLER_CAN_READ_DRIVE` predicate (`role_grants`
+#      + `caller_group_ids`). This assertion is the anti-
+#      regression pin.
+# ─────────────────────────────────────────────────────────────
+GET {{base_url}}/api/search/suggest?query=unique-search-needle
+Authorization: Bearer {{bob_token}}
+
+HTTP 200
+[Asserts]
+body not contains "unique-search-needle"
+body not contains "{{needle_file_id}}"
+
+
 # ─────────────────────────────────────────────────────────────
 # 6 — CONTENT-search cross-drive isolation (docs/plan/drive.md §11).
 #     The cross-user check above (step 5) verifies the NAME-search
@@ -209,7 +232,7 @@ HTTP 200
 # Bob has no access to admin's drive → Tantivy's Must-clause
 # filters every doc that doesn't carry one of Bob's drive_ids,
 # so the file vanishes entirely.
-jsonpath "$.files"   count == 0
+jsonpath "$.files" count == 0
 jsonpath "$.folders" count == 0
 body not contains "{{canary_file_id}}"
 body not contains "ContentIndexCanaryXyzzy2026Drive"
@@ -221,11 +244,11 @@ body not contains "ContentIndexCanaryXyzzy2026Drive"
 # other field names below MUST stay absent: a future field
 # called `hidden_count`/`filtered`/etc. that reveals matches
 # Bob can't see would be the regression.
-jsonpath "$.total_count"  == 0
-jsonpath "$.has_more"     == false
+jsonpath "$.total_count" == 0
+jsonpath "$.has_more" == false
 jsonpath "$.hidden_count" not exists
-jsonpath "$.filtered"     not exists
-jsonpath "$.total"        not exists
+jsonpath "$.filtered" not exists
+jsonpath "$.total" not exists
 
 
 # ─────────────────────────────────────────────────────────────
diff --git a/tests/api/webdav_permissions.hurl b/tests/api/webdav_permissions.hurl
index 48707af3..57cf811e 100644
--- a/tests/api/webdav_permissions.hurl
+++ b/tests/api/webdav_permissions.hurl
@@ -6,9 +6,10 @@
 #
 #   1. Per-role gates through the drive-scope resolver: a Viewer on a
 #      shared drive can PROPFIND/GET but cannot MKCOL/PUT/MOVE. An
-#      Editor can. AuthZ denials return `NotFound` (anti-enum), so
-#      a probing caller can't tell a genuinely-missing folder from
-#      one they simply lack Create on.
+#      Editor can. AuthZ denials use graduated shape: a caller with
+#      Read on the target (Viewer here) gets 403 Forbidden — no point
+#      hiding existence from someone already reading it. A caller with
+#      no Read at all gets 404 (anti-enum), matching "no such folder".
 #
 #   2. Drive policy `forbid_cross_drive_move` gates MOVE at the
 #      SOURCE drive (see `DrivePolicies::refuse_cross_drive_move`
@@ -123,17 +124,22 @@ HTTP 207
 
 # ─────────────────────────────────────────────────────────────
 # Step 6 — Bob (VIEWER) CANNOT MKCOL on the shared drive.
-#          `authz.require(Create, Folder)` denial returns
-#          `DomainError::not_found` (anti-enum), which maps to 404.
+#          `authz.require(Create, Folder)` denies. Bob has Read
+#          on the drive (viewer role) → engine's graduated denial
+#          returns `DomainError::access_denied` → 403 Forbidden.
+#          Anti-enum still holds for callers with no Read at all
+#          (would surface as 404); this is the "you can see it,
+#          but can't touch it" branch.
 # ─────────────────────────────────────────────────────────────
 MKCOL {{base_url}}/webdav/@drive/{{shared_drive_id}}/viewer-blocked-folder
 Authorization: Bearer {{bob_token}}
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
-# Step 7 — Bob (VIEWER) CANNOT PUT a file.
+# Step 7 — Bob (VIEWER) CANNOT PUT a file. Same 403 shape
+#          (Bob has Read on the drive).
 # ─────────────────────────────────────────────────────────────
 PUT {{base_url}}/webdav/@drive/{{shared_drive_id}}/viewer-blocked-file.txt
 Authorization: Bearer {{bob_token}}
@@ -142,7 +148,7 @@ Content-Type: text/plain
 viewer should not upload
 ```
 
-HTTP 404
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────
@@ -158,13 +164,47 @@ HTTP 201
 # ─────────────────────────────────────────────────────────────
 # Step 9 — Bob (VIEWER) CANNOT MOVE (rename) the probe folder.
 #          MOVE requires Update on the source, which Viewer
-#          doesn't have. Same anti-enum 404 shape.
+#          doesn't have. Bob can Read the folder (viewer) → 403.
 # ─────────────────────────────────────────────────────────────
 MOVE {{base_url}}/webdav/@drive/{{shared_drive_id}}/probe-folder
 Authorization: Bearer {{bob_token}}
 Destination: {{base_url}}/webdav/@drive/{{shared_drive_id}}/probe-folder-renamed
 
-HTTP 404
+HTTP 403
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 9b — Bob (VIEWER) CANNOT COPY the probe folder.
+#           COPY requires Create on the destination parent, which
+#           Viewer doesn't have. Bob has Read on both source and
+#           destination parent → 403 (graduated denial).
+#
+#           This is the regression pin for AuthZ audit #2
+#           (2026-07-12): the COPY handler used to `map_err(|e|
+#           AppError::internal_error(format!("Failed to copy folder
+#           tree: {}", e)))?` on `copy_folder_tree_with_perms`,
+#           collapsing the `DomainError` engine returned on denial
+#           into HTTP 500 — an "exists-but-denied" oracle. Fix
+#           routes through `AppError::from` so the same denial
+#           surfaces as the correct 403 / 404 per graduated-denial
+#           policy.
+# ─────────────────────────────────────────────────────────────
+COPY {{base_url}}/webdav/@drive/{{shared_drive_id}}/probe-folder
+Authorization: Bearer {{bob_token}}
+Destination: {{base_url}}/webdav/@drive/{{shared_drive_id}}/probe-folder-copy
+
+HTTP 403
+
+
+# ─────────────────────────────────────────────────────────────
+# Step 9c — Bob (VIEWER) CANNOT DELETE the probe folder.
+#           DELETE requires Delete on the target, which Viewer
+#           doesn't have. Bob has Read → 403.
+# ─────────────────────────────────────────────────────────────
+DELETE {{base_url}}/webdav/@drive/{{shared_drive_id}}/probe-folder
+Authorization: Bearer {{bob_token}}
+
+HTTP 403
 
 
 # ─────────────────────────────────────────────────────────────