fix(react): continue after empty model responses

[Zbhbb]

AgentScope-Java Version

2.0.1-SNAPSHOT

Description

When a model returns an empty stream or only blank/whitespace text, the ReAct loop currently ends before it can produce a final response. Continue the existing bounded loop for those genuinely empty responses while preserving thinking-only completion, tool execution, middleware-stop, and max-iteration summary behavior.

This is distinct from #1508: that change made empty result streams complete; this change continues the existing bounded ReAct loop so the model can produce a usable response.

Changes

• Continue to the next iteration after a reasoning round accumulates no final message.
• Continue after blank or whitespace-only text, but keep thinking-only responses as a normal terminal result.
• Resume at the loop boundary so a recovered response passes through post-reasoning exactly once.
• Add regression coverage for empty stream, empty text, post-reasoning invocation count, and max-iteration summary behavior.

Test Plan

• mvn -q -T1 verify
• mvn -pl agentscope-core -am -Dtest=ReActAgentNewLoopReplyTest,ReActAgentThinkingCumulativeTest,ReActAgentHitlTest test

Checklist

• Code has been formatted with mvn spotless:apply
• Relevant tests are passing
• Javadoc comments are complete and follow project conventions
• Related documentation has been reviewed
• Code is ready for review

[Copilot]

Pull request overview

This PR adjusts the ReActAgent loop so that when the model produces an unusable response (empty stream / empty accumulated message / thinking-only / blank text), the agent continues the bounded ReAct loop to obtain a usable final assistant message, and adds regression tests for these edge cases.

Changes:

• Continue the ReAct iteration when a reasoning round accumulates no final message (e.g., empty stream / blank text that results in no accumulated content).
• Continue to the next iteration when the model returns thinking-only or blank/whitespace-only text (while persisting thinking context).
• Add regression tests covering empty stream, empty text, thinking-only, and max-iteration summary behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
agentscope-core/src/main/java/io/agentscope/core/ReActAgent.java	Updates the ReAct loop to continue iterations after unusable model responses and adds a helper to detect “no usable response” cases.
agentscope-core/src/test/java/io/agentscope/core/agent/ReActAgentNewLoopReplyTest.java	Adds regression tests for empty-stream, empty-text, thinking-only, and max-iteration summary paths.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!