[BUG] "classifyHandoffIfNeeded is not defined" error when sub-agent returns result to main agent

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When a sub-agent (launched via the Task tool with subagent_type=general-purpose) completes its task and attempts to return its final response to the main agent, the handoff fails with the following error:

classifyHandoffIfNeeded is not defined

The sub-agent itself executes successfully — it runs a bash command (docker run --rm with a Python script), produces correct output, and generates a final summary. The error only occurs at the point where the result is handed back to the main agent.

This appears to be a bug in the sub-agent → main agent handoff logic, where the classifyHandoffIfNeeded function is referenced but not defined.

What Should Happen?

The sub-agent's final response should be returned to the main agent without errors. Since the sub-agent's task completes successfully and the result is ready, the handoff should proceed normally.

Error Messages/Logs

Steps to Reproduce

1. Launch a sub-agent using the Task tool with subagent_type=general-purpose in the background
2. Have the sub-agent execute a Bash command (e.g., docker run --rm running a Python script) — this completes successfully
3. Have the sub-agent generate a final response (e.g., a data summary) — this also completes successfully
4. When the sub-agent attempts to return its response to the main agent, the error classifyHandoffIfNeeded is not defined is thrown

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.42

Platform

Anthropic API

Operating System

Other

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

• Agent ID: abadd71
• The sub-agent's actual work (data extraction, bash execution, result aggregation) all completed without issues. Only the final handoff step fails.
• This suggests the classifyHandoffIfNeeded function is missing from the handoff processing code path in v2.1.42, possibly a regression or an incomplete deployment of a new feature.