[BUG] GitHub App installation 404 error on install button

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?

Reference similar issues #3031, #3017, #251

<img width="1902" height="937" alt="Image" src="https://github.com/user-attachments/assets/b0db4b7e-3e0c-42e9-b943-f1b0060d1bb0" />
<img width="1923" height="792" alt="Image" src="https://github.com/user-attachments/assets/1c7e3b6b-9800-450a-80ab-b2646151ffc5" />

What Should Happen?

Claude should be able to read Github connection.

Error Messages/Logs

Steps to Reproduce

N/A

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.55

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_