[BUG] Unexpected value(s) `effort-2025-11-24` for the `anthropic-beta` header. Please consult our documentation at docs.anthropic.com or try again without the header.

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 I upgraded ClaudeCode to the latest version, I encountered this error when using the Claude 4.5 model. Versions 4.6 and 4.7 do not have this error. Currently, version 2.1.114 is known to work correctly, while versions 2.1.116 and above do not and will report this error: Unexpected value(s) effort-2025-11-24 for the anthropic-beta header. Please consult our documentation at docs.anthropic.com or try again without the header.

What Should Happen?

This occurred during the upgrade to version 2.1.119. Setting CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS="1" is invalid.

Error Messages/Logs

Unexpected value(s) `effort-2025-11-24` for the `anthropic-beta` header. Please consult our documentation at docs.anthropic.com or try again without the header.

Steps to Reproduce

claudecode 2.1.119
model: claude_sonnet4_5

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.114

Claude Code Version

2.1.119

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Non-interactive/CI environment

Additional Information

_No response_