[BUG] Official Greptile plugin fails with "Cannot POST /register" error

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?

Description

The official Greptile plugin shows as connected but all API calls fail with an authentication/registration error.

## Actual Behavior

MCP server shows as connected:
plugin:greptile:greptile: https://api.greptile.com/mcp (HTTP) - ✓ Connected

But API calls fail with:
HTTP 404: Invalid OAuth error response: SyntaxError: JSON Parse error: Unexpected identifier "Cannot". Raw body: Cannot POST /register

## Analysis

• The plugin attempts to call a /register endpoint that returns 404
• The response is plain text ("Cannot POST /register") but the plugin expects JSON
• This appears to be a backend OAuth integration issue, not a user configuration problem

What Should Happen?

Official plugins should handle authentication automatically without requiring user-provided credentials. The API call should succeed.

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code CLI in terminal 2. Verify the Greptile plugin is connected:

```bash
claude mcp list
Output shows:
plugin:greptile:greptile: https://api.greptile.com/mcp (HTTP) - ✓ Connected

1. Start a Claude Code session:

claude

1. Ask Claude to use any Greptile tool, for example:

• "List custom context from Greptile"
• "Search for patterns in Greptile"

1. Claude attempts to call a Greptile MCP tool (e.g., list_custom_context)
2. The call fails with the error:

HTTP 404: Invalid OAuth error response: SyntaxError: JSON Parse error: Unexpected identifier "Cannot". Raw body: Cannot POST /register

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.20

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

Since this is an official Claude plugin (not user-configured via claude mcp add), users should not need to provide separate Greptile API credentials. The authentication should be handled automatically by Anthropic's
integration.