Complete tasks in background thread

Author: kabir

server-common/src/main/java/io/a2a/server/requesthandlers/DefaultRequestHandler.java

@@ -217,12 +217,8 @@ public EventKind onMessageSend(MessageSendParams params, ServerCallContext conte
             // Send push notification after initial return (for both blocking and non-blocking)
             pushNotificationCallback.run();
         } finally {
-            if (interruptedOrNonBlocking) {
-                trackBackgroundTask(cleanupProducer(taskId, queue, false));
-            } else {
-                // For blocking requests, wait for cleanup to complete to ensure agent is removed from map
-                cleanupProducer(taskId, queue, false).join();
-            }
+            // Always track cleanup as background task to avoid blocking Vert.x threads
+            trackBackgroundTask(cleanupProducer(taskId, queue, false));
         }
 
         LOGGER.debug("Returning: {}", etai.eventType());
@@ -527,7 +523,13 @@ private void trackBackgroundTask(CompletableFuture<Void> task) {
         task.whenComplete((result, throwable) -> {
             try {
                 if (throwable != null) {
-                    if (throwable instanceof java.util.concurrent.CancellationException) {
+                    // Unwrap CompletionException to check for CancellationException
+                    Throwable cause = throwable;
+                    if (throwable instanceof java.util.concurrent.CompletionException && throwable.getCause() != null) {
+                        cause = throwable.getCause();
+                    }
+
+                    if (cause instanceof java.util.concurrent.CancellationException) {
                         LOGGER.debug("Background task cancelled: {}", task);
                     } else {
                         LOGGER.error("Background task failed", throwable);