fix(agui): migrate adapter to v2 streamEvents and bridge HITL confirmations (#2437)

agentscope-core/src/main/java/io/agentscope/core/ReActAgent.java

@@ -19,6 +19,7 @@
 import io.agentscope.core.agent.Agent;
 import io.agentscope.core.agent.AgentBase;
 import io.agentscope.core.agent.Event;
+import io.agentscope.core.agent.EventStreamingAgent;
 import io.agentscope.core.agent.RuntimeContext;
 import io.agentscope.core.agent.StreamOptions;
 import io.agentscope.core.agent.SubagentEventBus;
@@ -203,7 +204,7 @@
  * {@link io.agentscope.core.state.AgentStateStore} are all safe to share across instances.
  */
 @SuppressWarnings("deprecation")
-public class ReActAgent extends AgentBase implements AutoCloseable {
+public class ReActAgent extends AgentBase implements EventStreamingAgent, AutoCloseable {
 
     private static final Logger log = LoggerFactory.getLogger(ReActAgent.class);
     private static final GracefulShutdownManager shutdownManager =

agentscope-core/src/main/java/io/agentscope/core/agent/EventStreamingAgent.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2024-2026 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.agentscope.core.agent;
+
+import io.agentscope.core.event.AgentEvent;
+import io.agentscope.core.message.Msg;
+import java.util.List;
+import reactor.core.publisher.Flux;
+
+/**
+ * Capability interface for agents that can emit the fine-grained 2.0 {@link AgentEvent} stream.
+ *
+ * <p>This is the modern replacement for the deprecated v1 {@link StreamableAgent} {@code
+ * stream(...)} API, which only surfaced coarse {@code REASONING} / {@code SUMMARY} / {@code
+ * TOOL_RESULT} events and, critically, could not carry human-in-the-loop signals such as {@code
+ * RequireUserConfirmEvent} / {@code RequestStopEvent}.
+ *
+ * <p>Both {@code io.agentscope.core.ReActAgent} and {@code io.agentscope.harness.agent.HarnessAgent}
+ * (which wraps a {@code ReActAgent} delegate) implement this interface. Consumers such as the AG-UI
+ * adapter can branch on {@code agent instanceof EventStreamingAgent} to consume the v2 stream
+ * uniformly, regardless of the concrete agent type, while still falling back to the deprecated v1
+ * path for custom {@link Agent} implementations that do not support event streaming.
+ */
+public interface EventStreamingAgent {
+
+    /**
+     * Stream fine-grained {@link AgentEvent}s covering the full agent invocation lifecycle.
+     *
+     * @param msgs input messages
+     * @param context runtime context to propagate into the call
+     * @return event stream covering the full agent invocation lifecycle
+     */
+    Flux<AgentEvent> streamEvents(List<Msg> msgs, RuntimeContext context);
+}