[Bug] statusline-setup agent causes excessive token usage via nested subagents on Windows

Summary

Using the statusline-setup agent for a simple file edit task caused 30% of the 5h rate limit to be consumed on a single session. The root cause was uncontrolled nested subagent spawning.

Environment

• OS: Windows 11 (Git Bash)
• Plan: Pro
• Claude Code version: latest

What happened

1. Asked to fix a statusline display issue (symbol rendering + missing fields)
2. Claude spawned statusline-setup agent (1st time) → agent asked for clarification, did nothing
3. Claude spawned statusline-setup agent (2nd time) → this agent spawned:

• Another statusline-setup subagent (3rd level nesting)
• A claude-code-guide subagent to ask about JSON schema
• Used sleep 15 while waiting for background winget install
• Repeatedly tried winget install stedolan.jq (wrong package name), then winget install jqlang.jq
• Suggested user manually run install commands even though it could have done it directly

1. Actual fix: copying jq.exe from WinGet cache to ~/bin/ — a single Bash command

Problems observed

1. Nested subagents (3 levels deep): statusline-setup agent spawned more statusline-setup and claude-code-guide agents internally with no guard against recursion
2. tool_uses count is unreliable: The agent reported tool_uses: 5 but actual log showed 14 tool calls (subagent-of-subagent calls not counted)
3. total_tokens likely underreported: Does not include tokens from nested subagents
4. Windows OS not considered: Agent kept pushing native install instructions instead of checking PATH and copying the existing binary
5. No value delivered: After all that token consumption, the agent failed to solve the problem

Expected behavior

• statusline-setup should not spawn further subagents
• Simple file edit tasks should not use subagents at all
• Token usage reported by subagents should include all nested consumption
• Agents should handle Windows environment differences

Impact

~30% of Pro plan 5h token limit consumed for a task that required one cp command.