--- a/src/luan/modules/ThreadLuan.java	Fri May 26 10:29:55 2023 -0600
+++ b/src/luan/modules/ThreadLuan.java	Tue Jun 06 14:33:24 2023 -0600
@@ -1,7 +1,6 @@
 package luan.modules;
 
 import java.io.Closeable;
-import java.util.Arrays;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.HashMap;
@@ -26,6 +25,11 @@
 public final class ThreadLuan {
 	private static final Logger logger = LoggerFactory.getLogger(ThreadLuan.class);
 
+	public static final String CLOSEABLES = "Luan.closeables";
+	public interface Closeables {
+		public void addCloseable(Closeable c) throws LuanException;
+	}
+
 	private static final Executor exec = Executors.newCachedThreadPool();
 	public static final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
 
@@ -50,8 +54,6 @@
 		exec.execute(runnable(luan,fn));
 	}
 
-	private static final Map<String,ScheduledFuture> scheduleds = new WeakCacheMap<String,ScheduledFuture>();
-
 	private static void cancel(ScheduledFuture sf,String src) {
 		boolean b = sf.cancel(false);
 		if( !sf.isCancelled() )
@@ -82,17 +84,13 @@
 		Number delay = Utils.removeNumber(options,"delay");
 		Number repeatingDelay = Utils.removeNumber(options,"repeating_delay");
 		Number repeatingRate = Utils.removeNumber(options,"repeating_rate");
-		Boolean dontGc = Utils.removeBoolean(options,"dont_gc");
 		String id = Utils.removeString(options,"id");
+		if( id != null )
+			logger.error("thread option 'id' is obsolete: "+id);
 		if( repeatingDelay!=null && repeatingRate!=null )
 			throw new LuanException("can't define both repeating_delay and repeating_rate");
 		boolean repeating = repeatingDelay!=null || repeatingRate!=null;
 		Utils.checkEmpty(options);
-		if( id != null ) {
-			ScheduledFuture sf = scheduleds.remove(id);
-			if( sf != null )
-				cancel(sf,"id "+id);
-		}
 		final Runnable r = runnable(newLuan,fn);
 		final ScheduledFuture sf;
 		if( repeatingDelay != null ) {
@@ -109,16 +107,18 @@
 			scheduler.schedule(r,0L,TimeUnit.MILLISECONDS);
 			return;
 		}
-		if( !Boolean.TRUE.equals(dontGc) ) {
-			Object c = new Object() {
+		Closeables cs = (Closeables)luan.registry().get(CLOSEABLES);
+		if( cs != null ) {
+			Closeable cl = new Closeable() {
+				public void close() {
+					cancel(sf,"close");
+				}
 				protected void finalize() throws Throwable {
-					cancel(sf,"gc");
+					cancel(sf,"gc");  // cancel on gc
 				}
 			};
-			luan.registry().put(c,c);  // cancel on gc
+			cs.addCloseable(cl);
 		}
-		if( id != null )
-			scheduleds.put(id,sf);
 	}