[BUG] AskUserQuestion tool not available to subagents regardless of configuration

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 AskUserQuestion tool is never passed to subagents, even when explicitly listed in the agent's tools: configuration using the documented comma-separated format.

What Should Happen?

Agent should have access to AskUserQuestion when listed in the agent's tools: configuration.

Error Messages/Logs

Steps to Reproduce

1. Create a custom agent with:

``yaml
---
name: test-agent
tools: Bash, BashOutput, Read, AskUserQuestion
---
``

1. Spawn the agent and ask it to list available tools
2. Result: Agent reports Bash, BashOutput, Read - all configured tools EXCEPT AskUserQuestion

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.0.55

Claude Code Version

2.0.56

Platform

Other

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

AskUserQuestion appears to be explicitly filtered out when spawning subagents at the system level, regardless of configuration.