[BUG] All subagents fail to do anything

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?

After updating to latest version, all subagent tool invocations fail completely and never go through.

<img width="823" height="223" alt="Image" src="https://github.com/user-attachments/assets/a8326347-2708-419e-88a9-56cf6efd0fc3" />

<img width="843" height="406" alt="Image" src="https://github.com/user-attachments/assets/0effbebf-3684-4f8b-809a-f23783f40a39" />

What Should Happen?

Subagents should work without fail.

Error Messages/Logs

1. Tool Error: It was {"type":"error","error":{"type":"invalid_request_error","message":"tools: Tool names must be 
  unique."},"request_id":"req_..."}

  This means when I tried to use the Task tool with subagent_type, there were duplicate tool names being registered. 
  This is why all my attempts to use specialized agents (Explore, Plan, ultrathink-architect, etc.) failed.

Steps to Reproduce

Idk call subagents

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.30

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_