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fix(agent): complete stream when result is empty #1508

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91d7335
fix(agent): complete stream for empty results
JGoP-L May 27, 2026
fa417a0
Merge branch 'main' into fix/issue-1503-empty-stream-completion
JGoP-L May 27, 2026
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6 changes: 2 additions & 4 deletions agentscope-core/src/main/java/io/agentscope/core/agent/AgentBase.java
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Original file line number Diff line number Diff line change
Expand Up @@ -936,11 +936,9 @@ private Flux<Event> createEventStream(StreamOptions options, Supplier<Mono<Msg>>
finalMsg,
true));
}

// Complete the stream
sink.complete();
},
sink::error);
sink::error,
sink::complete);
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@AgentScopeJavaBot AgentScopeJavaBot May 28, 2026

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[minor] Consider also emitting a synthetic AGENT_RESULT (or at least a placeholder empty assistant Msg) when the upstream Mono completes empty, so downstream SSE / AG-UI adapters that key off AGENT_RESULT as the terminal event still receive a final marker. The current fix correctly unblocks completion, but consumers that loop until they observe an AGENT_RESULT will now silently terminate without one. If keeping the current behavior intentionally, please document it in the Javadoc of createEventStream (e.g. "if the agent call produces no final message, the stream completes without emitting an AGENT_RESULT event").

},
FluxSink.OverflowStrategy.BUFFER)
.publishOn(Schedulers.boundedElastic()));
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37 changes: 37 additions & 0 deletions agentscope-core/src/test/java/io/agentscope/core/agent/AgentStreamingTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,10 +20,13 @@
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertTrue;

import io.agentscope.core.ReActAgent;
import io.agentscope.core.agent.test.MockModel;
import io.agentscope.core.interruption.InterruptContext;
import io.agentscope.core.message.Msg;
import io.agentscope.core.message.MsgRole;
import io.agentscope.core.message.TextBlock;
import io.agentscope.core.model.ChatResponse;
import java.time.Duration;
import java.util.ArrayList;
import java.util.List;
Expand Down Expand Up @@ -248,4 +251,38 @@ void testStreamEventCount() {
// Should have at least one event (the agent result)
assertTrue(eventCount.get() >= 1);
}

@Test
void testReActAgentStreamCompletesWhenModelReturnsEmptyText() {
MockModel model =
new MockModel(
messages ->
List.of(
ChatResponse.builder()
.id("empty-msg")
.content(
List.of(
TextBlock.builder()
.text("")
.build()))
.build()));
ReActAgent agent = ReActAgent.builder().name("test-agent").model(model).build();

Msg inputMsg =
Msg.builder()
.name("user")
.role(MsgRole.USER)
.content(List.of(TextBlock.builder().text("hello").build()))
.build();

StepVerifier.create(agent.stream(List.of(inputMsg)))
.expectNextMatches(
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[nit] The test relies on at least one REASONING event being emitted by StreamingHook before completion. Per the issue analysis, an empty TextBlock does not satisfy TextAccumulator.hasContent(), so this assumption depends on hook implementation details (e.g. the start-of-reasoning event still firing). Consider making the assertion more defensive, e.g. .thenConsumeWhile(event -> true).expectComplete() without the upfront expectNextMatches, since the fix's contract is purely about completion, not about which events fire. As written the test couples the regression assertion to the StreamingHook event sequence and may become flaky if hook emission semantics change.

event ->
event.getType() == EventType.REASONING
&& !event.isLast()
&& event.getMessage() != null)
.thenConsumeWhile(event -> true)
.expectComplete()
.verify(Duration.ofSeconds(2));
}
}
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