Subagent crash: classifyHandoffIfNeeded is not defined

Bug Report

Version

Claude Code 2.1.32, macOS Darwin 24.6.0

Description

Subagents launched via the Task tool consistently crash with error:

classifyHandoffIfNeeded is not defined

Reproduction

1. Launch a subagent using the Task tool (subagent_type: "Explore" or "general-purpose")
2. Agent runs successfully for 30-70+ tool calls
3. Agent crashes with classifyHandoffIfNeeded is not defined
4. Task status shows as "failed"

Frequency

• Happens on ~80% of long-running subagents (30+ tool uses)
• Shorter agents sometimes complete before the crash
• Observed across multiple sessions over 2 days (2026-02-05 to 2026-02-06)
• All agent types affected: Explore, general-purpose, Plan

Context

• Parent session is on claude-opus-4-6 model
• Subagents use claude-sonnet-4-5-20250929 (specified via model: "sonnet")
• Agents are doing read-only operations (Glob, Grep, Read, Bash for ls/which)
• No file writes or destructive operations
• Error appears to be in internal message classification/routing, not in tool execution

Workaround

Work directly in the parent session instead of delegating to subagents.

Example Agent IDs (from one session)

• a386763 - "Audit current skills organization" - failed after ~55 tools
• a71b4e5 - "Analyze EmailGolem current capabilities" - failed after ~32 tools
• a3c60c7 - "Analyze Zikaron as plugin candidate" - failed after ~50 tools
• ab3a02d - "Audit plan items already done" - failed earlier in session

All failed with identical error: classifyHandoffIfNeeded is not defined