[BUG] Claude Code Oauth issues

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [x] Other: Claude Code
• Claude CLI version: 1.0.51 (Claude Code)
• Operating System: Windows 11 (Regardless of architecture, same thing for x64 and for arm64)
• Terminal: Powershell, but also when in WSL

Bug Description

When trying to run /install-github-app, it always throws an Oauth error. There's also an Oauth error when authenticating with claude for the first time as well, but at least in that case you can still copy and manually go to the URL directly, then paste back in the code. However, when running it as /install-github-app, it also fails the initial Oauth browser redirect and lets you copy the URL to go to as a backup...but provides no way to paste the resulting code in to continue the process.

Steps to Reproduce

1. Run claude
2. In the Claude code terminal, run /install-github-app, choose the repository, and install the Github app. Choose API Key > Create a long-lived token with your Claude subscription.
3. A browser opens with a truncated URL. We get an error page that says Invalid OAuth Request: Missing client_id parameter
4. Manually copy the URL in the terminal. Fix the URL (e.g. remove the extra | and spaces from copying)
5. Successfully authenticate and receive a code to enter back in.
6. ....There is no place to paste the code in the terminal. Can only cancel and is unable to proceed with the authentication flow.

Expected Behavior

• The URL we are redirected to initially in the browser should just work.
• If that fails, we should be able to copy the URL from the terminal without having to fix the formatting errors (e.g. the extra | and spaces that divide up the url)
• We should also be able to paste in the resulting code after successful authentication to continue the flow/process.

Actual Behavior

• The initial redirected page in the browser fails/shows an oauth error.
• When copying the URL we are told to go to in the terminal, it includes extra spaces and | symbols that mess up/cause an invalid URL.
• When a correct Oauth URL is used, we get an authentication code, but have no where to paste it to continue the authentication in the terminal.

Additional Context

<img width="939" height="682" alt="Image" src="https://github.com/user-attachments/assets/cc715a73-3146-4735-b6d9-c6f3532486e1" />

<img width="843" height="434" alt="Image" src="https://github.com/user-attachments/assets/ff739e6f-4512-4548-b03d-99c11ff3391c" />