[BUG] Hook stderr not visible in verbose mode when agent is blocked (v2.1.34)

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?

In v2.1.34 with verbose mode enabled, when a hook blocks an agent action, the stderr
output is not displayed. This makes it impossible to see why the hook blocked the action.

2.1.19

<img width="877" height="65" alt="Image" src="https://github.com/user-attachments/assets/136e362f-ab76-4089-b6cb-0ae5b343c470" />

2.1.34
<img width="282" height="82" alt="Image" src="https://github.com/user-attachments/assets/236ba6ea-3ec2-41fc-96bb-de14dfd944a3" />

What Should Happen?

The stderr from the hook should be visible, as it was in v2.1.19. This is critical for debugging hook configurations.

Error Messages/Logs

Steps to Reproduce

1. Configure a hook that blocks certain agent actions
2. Enable verbose mode
3. Trigger the hook block
4. stderr output is not shown

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.19

Claude Code Version

2.1.34

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_