[BUG] Error: input_schema does not support oneOf, allOf, or anyOf at the top level

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?

Error: input_schema does not support oneOf, allOf, or anyOf at the top level
Happens in Code mode only
Persists with all plugins disabled and no MCP servers
macOS, Opus 4.6 model

<img width="1440" height="900" alt="Image" src="https://github.com/user-attachments/assets/3260ffec-7c82-4e3e-b848-39e88dacb341" />

What Should Happen?

unable to proceed with anything on Claude code.. errors out and keeps jumping on the tool number.

Error Messages/Logs

Steps to Reproduce

<img width="1440" height="900" alt="Image" src="https://github.com/user-attachments/assets/f9fde075-304e-4a32-8764-6b45c4c35f1c" />

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude 1.1.7203 (034f07) 2026-03-17T17:48:28.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_