diff --git a/server-common/src/main/java/io/a2a/server/requesthandlers/DefaultRequestHandler.java b/server-common/src/main/java/io/a2a/server/requesthandlers/DefaultRequestHandler.java
index 577e571c9..67c474a9c 100644
--- a/server-common/src/main/java/io/a2a/server/requesthandlers/DefaultRequestHandler.java
+++ b/server-common/src/main/java/io/a2a/server/requesthandlers/DefaultRequestHandler.java
@@ -326,8 +326,13 @@ public EventKind onMessageSend(MessageSendParams params, ServerCallContext conte
                     }
                 }
             }
-            if (kind instanceof Task taskResult && !taskId.equals(taskResult.getId())) {
-                throw new InternalError("Task ID mismatch in agent response");
+            if (kind instanceof Task taskResult) {
+                if (shouldAddPushInfo(params)) {
+                    pushConfigStore.setInfo(taskResult.getId(), params.configuration().pushNotificationConfig());
+                }
+                if (taskId != null && !taskId.equals(taskResult.getId())) {
+                    throw new InternalError("Task ID mismatch in agent response");
+                }
             }
 
             // Send push notification after initial return (for both blocking and non-blocking)
diff --git a/spec/src/main/java/io/a2a/spec/AgentCapabilities.java b/spec/src/main/java/io/a2a/spec/AgentCapabilities.java
index 2b4fbcee5..3abacf733 100644
--- a/spec/src/main/java/io/a2a/spec/AgentCapabilities.java
+++ b/spec/src/main/java/io/a2a/spec/AgentCapabilities.java
@@ -13,6 +13,10 @@
 public record AgentCapabilities(boolean streaming, boolean pushNotifications, boolean stateTransitionHistory,
                                 List<AgentExtension> extensions) {
 
+    public AgentCapabilities {
+        extensions = extensions == null ? List.of() : extensions;
+    }
+
     public static class Builder {
 
         private boolean streaming;