fix(harness): emit subagent end before parent completion

[zouyx]

AgentScope-Java Version

2.0.1-SNAPSHOT

Description

Background

The Harness stream-event tests can intermittently miss the sourced child AGENT_END event. The child end event was emitted from doFinally, which runs after the terminal signal has propagated downstream. For a quickly completing child agent, the parent can therefore complete and close its event sink before the child end event is forwarded.

This race was exposed by the CI runs of #2532, but it is independent of that middleware-ordering change.

Changes

• Emit the child AGENT_END before success or error is propagated to the parent.
• Retain best-effort end signaling for cancellation.
• Guard emission with AtomicBoolean so completion and cancellation races cannot produce duplicate child end events.
• Strengthen the ordering test to require the sourced child AGENT_END before the parent AGENT_END.

The resulting order is:

parent AGENT_START
child  AGENT_START / events / AGENT_END
parent AGENT_END

Test

mvn -pl agentscope-harness -am \
  -Dtest=HarnessAgentSubagentStreamEventsTest \
  -Dsurefire.failIfNoSpecifiedTests=false \
  -Djacoco.skip=true \
  -DargLine=-javaagent:$HOME/.m2/repository/net/bytebuddy/byte-buddy-agent/1.17.7/byte-buddy-agent-1.17.7.jar \
  test

Result: 4 tests passed, 0 failures.

Checklist

• Code has been formatted with mvn spotless:apply
• All tests are passing (mvn test)
• Javadoc comments are complete and follow project conventions
• Related documentation has been updated (not applicable: no public API or documentation change)
• Code is ready for review

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[Copilot]

Pull request overview

This PR fixes an intermittent race in HarnessAgent.streamEvents() subagent forwarding where a quickly completing child agent could have its sourced AGENT_END emitted too late (after the parent stream’s terminal signal), allowing the parent to close its event sink before the child end event is forwarded.

Changes:

• Emit the sourced child AGENT_END on success/error before the terminal signal propagates downstream, while keeping best-effort cancel handling.
• Guard child-end emission with an AtomicBoolean to prevent duplicate end events across completion/cancellation races.
• Strengthen the ordering test to require the sourced child AGENT_END to occur before the parent AGENT_END.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
agentscope-harness/src/main/java/io/agentscope/harness/agent/tool/AgentSpawnTool.java	Moves sourced child AGENT_END emission earlier (success/error) and guards against duplicates; retains cancel best-effort signaling.
agentscope-harness/src/test/java/io/agentscope/harness/agent/HarnessAgentSubagentStreamEventsTest.java	Extends ordering assertions to require sourced child AGENT_END before parent AGENT_END.

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../agentscope/harness/agent/tool/AgentSpawnTool.java	90.90%	0 Missing and 1 partial ⚠️

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