Require confirmation and block deleting library actions still referenced by node groups.

service/internal/settings/node_action_groups.go

@@ -128,6 +128,23 @@ func GroupsForNode(store NodeActionGroupStore, nodeID string) []NodeActionGroup
 	return result
 }
 
+// LibraryActionInUse reports whether any group item still references actionID as a library source.
+// Local clones (source local) do not count even if they previously came from that action.
+func LibraryActionInUse(store NodeActionGroupStore, actionID string) bool {
+	actionID = strings.TrimSpace(actionID)
+	if actionID == "" {
+		return false
+	}
+	for _, group := range store.Groups {
+		for _, item := range group.Items {
+			if item.Source == ActionItemSourceLibrary && item.LibraryActionID == actionID {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 // UpdateGroupLastRunAt sets LastRunAt and UpdatedAt for a group and saves.
 func UpdateGroupLastRunAt(dir string, groupID string, at time.Time) error {
 	store, err := LoadNodeActionGroupsOrEmpty(dir)

service/internal/settings/node_action_groups_test.go

@@ -66,6 +66,48 @@ func TestNodeActionGroupsRoundTrip(t *testing.T) {
 	}
 }
 
+func TestLibraryActionInUse(t *testing.T) {
+	store := NodeActionGroupStore{
+		Groups: []NodeActionGroup{
+			{
+				ID:     "g1",
+				NodeID: "n1",
+				Name:   "Nightly",
+				Items: []NodeActionItem{
+					{
+						ID:              "lib-item",
+						Source:          ActionItemSourceLibrary,
+						LibraryActionID: "custom-1",
+					},
+					{
+						ID:     "local-item",
+						Source: ActionItemSourceLocal,
+						Name:   "Echo",
+						Kind:   ActionKindShell,
+						Body:   "echo hi",
+					},
+				},
+			},
+		},
+	}
+	if !LibraryActionInUse(store, "custom-1") {
+		t.Fatal("expected library action custom-1 to be in use")
+	}
+	if LibraryActionInUse(store, "other") {
+		t.Fatal("expected unrelated action not in use")
+	}
+	store.Groups[0].Items[0] = NodeActionItem{
+		ID:     "cloned",
+		Source: ActionItemSourceLocal,
+		Name:   "Echo host",
+		Kind:   ActionKindShell,
+		Body:   "echo",
+	}
+	if LibraryActionInUse(store, "custom-1") {
+		t.Fatal("expected cloned local item not to count as in use")
+	}
+}
+
 func TestIsScheduleDueInterval(t *testing.T) {
 	now := time.Date(2026, 7, 19, 12, 0, 0, 0, time.Local)
 	group := NodeActionGroup{