diff --git a/internal/http/backup_handler.go b/internal/http/backup_handler.go
index a5e10a3d..787829e4 100644
--- a/internal/http/backup_handler.go
+++ b/internal/http/backup_handler.go
@@ -85,6 +85,7 @@ func (h *BackupHandler) handleBackup(w http.ResponseWriter, r *http.Request) {
 	locale := extractLocale(r)
 
 	if !h.isOwnerUser(userID) {
+		slog.Warn("security.backup_owner_denied", "user_id", userID)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "system backup"))
 		return
diff --git a/internal/http/backup_s3_handler.go b/internal/http/backup_s3_handler.go
index b3971925..16b5cd55 100644
--- a/internal/http/backup_s3_handler.go
+++ b/internal/http/backup_s3_handler.go
@@ -52,6 +52,7 @@ func (h *BackupS3Handler) handleGetConfig(w http.ResponseWriter, r *http.Request
 	locale := extractLocale(r)
 
 	if !h.isOwnerUser(userID) {
+		slog.Warn("security.s3_owner_denied", "user_id", userID, "path", r.URL.Path)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "s3 config"))
 		return
@@ -83,6 +84,7 @@ func (h *BackupS3Handler) handleSaveConfig(w http.ResponseWriter, r *http.Reques
 	locale := extractLocale(r)
 
 	if !h.isOwnerUser(userID) {
+		slog.Warn("security.s3_owner_denied", "user_id", userID, "path", r.URL.Path)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "s3 config"))
 		return
@@ -136,6 +138,7 @@ func (h *BackupS3Handler) handleList(w http.ResponseWriter, r *http.Request) {
 	locale := extractLocale(r)
 
 	if !h.isOwnerUser(userID) {
+		slog.Warn("security.s3_owner_denied", "user_id", userID, "path", r.URL.Path)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "s3 list"))
 		return
@@ -167,6 +170,7 @@ func (h *BackupS3Handler) handleUpload(w http.ResponseWriter, r *http.Request) {
 	locale := extractLocale(r)
 
 	if !h.isOwnerUser(userID) {
+		slog.Warn("security.s3_owner_denied", "user_id", userID, "path", r.URL.Path)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "s3 upload"))
 		return
@@ -234,6 +238,7 @@ func (h *BackupS3Handler) handleBackupAndUpload(w http.ResponseWriter, r *http.R
 	locale := extractLocale(r)
 
 	if !h.isOwnerUser(userID) {
+		slog.Warn("security.s3_owner_denied", "user_id", userID, "path", r.URL.Path)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "s3 backup"))
 		return
diff --git a/internal/http/restore_handler.go b/internal/http/restore_handler.go
index f1e54dae..42ed8da7 100644
--- a/internal/http/restore_handler.go
+++ b/internal/http/restore_handler.go
@@ -44,6 +44,7 @@ func (h *RestoreHandler) handleRestore(w http.ResponseWriter, r *http.Request) {
 	locale := extractLocale(r)
 
 	if !h.isOwnerUser(userID) {
+		slog.Warn("security.restore_owner_denied", "user_id", userID)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "system restore"))
 		return
diff --git a/internal/http/tenant_backup_handler.go b/internal/http/tenant_backup_handler.go
index 4b045318..a3348ddc 100644
--- a/internal/http/tenant_backup_handler.go
+++ b/internal/http/tenant_backup_handler.go
@@ -73,6 +73,7 @@ func (h *TenantBackupHandler) handleBackup(w http.ResponseWriter, r *http.Reques
 	}
 
 	if !h.authorised(r, userID, tenantID) {
+		slog.Warn("security.tenant_backup_denied", "user_id", userID, "tenant_id", tenantID)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "tenant backup"))
 		return
diff --git a/internal/http/tenant_restore_handler.go b/internal/http/tenant_restore_handler.go
index 456727b1..20ec37b9 100644
--- a/internal/http/tenant_restore_handler.go
+++ b/internal/http/tenant_restore_handler.go
@@ -20,6 +20,7 @@ func (h *TenantBackupHandler) handleRestore(w http.ResponseWriter, r *http.Reque
 	locale := extractLocale(r)
 
 	if !h.isOwnerUser(userID) {
+		slog.Warn("security.tenant_restore_owner_denied", "user_id", userID)
 		writeError(w, http.StatusForbidden, protocol.ErrUnauthorized,
 			i18n.T(locale, i18n.MsgNoAccess, "tenant restore"))
 		return
diff --git a/internal/permissions/policy.go b/internal/permissions/policy.go
index 4f5cf7f8..d5227d8c 100644
--- a/internal/permissions/policy.go
+++ b/internal/permissions/policy.go
@@ -74,9 +74,16 @@ func NewPolicyEngine(ownerIDs []string) *PolicyEngine {
 }
 
 // IsOwner checks if a sender ID is an owner.
+// When no owner IDs are configured, "system" is treated as owner (fail-closed default).
 func (pe *PolicyEngine) IsOwner(senderID string) bool {
+	if senderID == "" {
+		return false
+	}
 	pe.mu.RLock()
 	defer pe.mu.RUnlock()
+	if len(pe.ownerIDs) == 0 {
+		return senderID == "system"
+	}
 	return pe.ownerIDs[senderID]
 }
 
diff --git a/ui/web/src/hooks/use-sse-progress.ts b/ui/web/src/hooks/use-sse-progress.ts
index 54164143..2d02cde2 100644
--- a/ui/web/src/hooks/use-sse-progress.ts
+++ b/ui/web/src/hooks/use-sse-progress.ts
@@ -166,7 +166,8 @@ export function useSseProgress(authHeaders: () => Record<string, string>): UseSs
         const res = await fetch(url, { ...init, signal: controller.signal });
         if (!res.ok) {
           const err = await res.json().catch(() => ({ error: res.statusText }));
-          setError({ phase: "request", detail: err.error ?? res.statusText, rolled_back: false });
+          const detail = typeof err.error === "string" ? err.error : err.error?.message ?? res.statusText;
+          setError({ phase: "request", detail, rolled_back: false });
           setStatus("error");
           cleanup();
           return;