[BUG] API Error 400

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?

When using the latest version of Claude Code for VS Code, I am getting the error:
API Error: 400 {"errorMessage":"{"message":"thinking: Input tag 'adaptive' found using 'type' does not match any of the expected tags: 'disabled', 'enabled'"}\n","errorCode":"UPSTREAM_LLM_ERROR","date":"2026-04-02T23:08:02.074304649Z","statusCode":400,"errorArgs":{"provider":"anthropic"}}
I do not get the error in the old version 2.1.81 and in the terminal. I was looking for a way to resolve the errors, but could not solve it. Could you please help, what should I do?

What Should Happen?

When trying 1*1 I expect 1

Error Messages/Logs

API Error: 400 {"errorMessage":"{"message":"thinking: Input tag 'adaptive' found using 'type' does not match any of the expected tags: 'disabled', 'enabled'"}\n","errorCode":"UPSTREAM_LLM_ERROR","date":"2026-04-02T23:08:02.074304649Z","statusCode":400,"errorArgs":{"provider":"anthropic"}}

Steps to Reproduce

I wrote 1*1 and got the message; in terminal I am getting 1

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.90

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_