Claude Code 2.1.265 fails with `Invalid schema for function 'Artifact'`

[FelixLisczyk]

After upgrading Claude Code from 2.1.263 to 2.1.265, every request sent through claude-code-proxy fails with the following error:

⏺ API Error: 400 Invalid schema for function 'Artifact':
  '^(?!__.*__$)[^\\p{Cc}\\p{Cf}\\p{Zl}\\p{Zp}"\\\\./[\\]]{1,200}$' is not a 'regex'.

This happens even for a trivial prompt such as:

Hello

Downgrading Claude Code back to 2.1.263 immediately fixes the problem with no other configuration changes.

Environment

• claude-code-proxy: 0.1.36

• Claude Code working version: 2.1.263

• Claude Code failing version: 2.1.265

• API provider: official OpenAI endpoint

• Models tested:

  • gpt-5.6-luna
  • gpt-6-astra

The issue occurs with both models.

Steps to reproduce

1. Run claude-code-proxy 0.1.36 against the official OpenAI API.
2. Use Claude Code 2.1.265.
3. Send a simple prompt such as Hello.
4. The request fails with:

API Error: 400 Invalid schema for function 'Artifact':
'^(?!__.*__$)[^\\p{Cc}\\p{Cf}\\p{Zl}\\p{Zp}"\\\\./[\\]]{1,200}$' is not a 'regex'.

5. Downgrade Claude Code to 2.1.263.
6. Send the same prompt with the same proxy configuration and model.
7. The request succeeds normally.

[raine]

Might be fixed in latest but untested.

[FelixLisczyk]

Looking good. Thank you!