[BUG] classifyHandoffIfNeeded error occurred in the framework layer

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?

The string classifyHandoffIfNeeded doesn't appear anywhere in the
agent's output — meaning the agent itself never tried to call
it. This is an internal Claude Code runtime error, not something
our agent definition caused.

★ Insight ─────────────────────────────────────

• classifyHandoffIfNeeded is an internal function in Claude

Code's agent orchestration system — it runs after the agent
finishes to determine if the output should trigger another agent
(like our bug-fixer-pro handoff).

• The agent completed all 5 phases successfully (login, testing,

evidence collection, report, handoff recommendation). The error
occurred in the framework layer during post-completion processing
— after the agent had already returned its full results.

• This is a Claude Code bug, not something we can fix in our

agent definition. The agent's actual output was complete and
usable.

What Should Happen?

agent 1 should handoff to agent 2

Error Messages/Logs

The string classifyHandoffIfNeeded doesn't appear anywhere in the
   agent's output — meaning the agent itself never tried to call   
  it. This is an internal Claude Code runtime error, not something
  our agent definition caused.                                     
                                                                   
  ★ Insight ─────────────────────────────────────                  
  - classifyHandoffIfNeeded is an internal function in Claude      
  Code's agent orchestration system — it runs after the agent
  finishes to determine if the output should trigger another agent
  (like our bug-fixer-pro handoff).
  - The agent completed all 5 phases successfully (login, testing,
  evidence collection, report, handoff recommendation). The error
  occurred in the framework layer during post-completion processing
   — after the agent had already returned its full results.
  - This is a Claude Code bug, not something we can fix in our
  agent definition. The agent's actual output was complete and
  usable.

Steps to Reproduce

trying to call a handoff function.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.39

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_