Add timeout flush delay

Author: kabir

server-common/src/main/java/io/a2a/server/events/EventConsumer.java

@@ -259,6 +259,13 @@ public Flow.Publisher<EventQueueItem> consumeAll() {
                                     boolean writeCompleted = finalEventWriteLatch.await(2, TimeUnit.SECONDS);
                                     if (writeCompleted) {
                                         LOGGER.debug("Final event write confirmed via backpressure signal");
+                                        // CRITICAL: Even after backpressure confirms write to Vert.x buffer,
+                                        // TCP still needs time to transmit data to client socket.
+                                        // Brief delay ensures final event reaches client before stream closes.
+                                        // Without this, response.end() can close socket while TCP is still
+                                        // transmitting buffered data, causing "Stream cancelled" on client.
+                                        Thread.sleep(50);
+                                        LOGGER.debug("TCP flush delay completed");
                                     } else {
                                         LOGGER.warn("Timeout waiting for final event write confirmation - proceeding anyway");
                                     }