[BUG] API Error: Unexpected value(s) `interleaved-thinking-2025-05-14` for the `anthropic-beta` header. when using via Vertex AI

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [x] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.0 (Claude Code)
• Operating System: Debian
• Terminal: VS Code Terminal

Bug Description

I cannot use Claude Code today because all requests fail 🥲

Steps to Reproduce

1. Configure Claude Code to use Vertex AI
2. Say something to Claude Code, e.g. hello world

Expected Behavior

It should greet me back.

Actual Behavior

> hello world
  ⎿ API Error: 400 
    {"type":"error","error":{"type":"invalid_request_error","message":"Unexpected value(s) 
    `interleaved-thinking-2025-05-14` for the `anthropic-beta` header. Please consult our 
    documentation at docs.anthropic.com or try again without the header."}}

Additional Context

Screenshot:
<img width="757" alt="Image" src="https://github.com/user-attachments/assets/8a83a591-5643-4601-ab7a-05e11c0c25f4" />