ServerlessBackend 401 on openai>=2.x: `auth_headers` override ignored, `_auth_headers` not overridden

[ryanyen2]

Bug Description

ServerlessBackend raises openai.AuthenticationError: 401 - Not authenticated when using openai>=2.x locally, even with a valid
WANDB_API_KEY. The same code and key work in Google Colab (where openai 1.x may be installed).

Root Cause

In openai 2.x, the base client (BaseClient) injects auth via _auth_headers(security) (method with underscore), not the
auth_headers property. The relevant line in openai/_base_client.py:

headers_dict = _merge_mappings({**self._auth_headers(options.security), **self.default_headers}, custom_headers)

art/serverless/client.py overrides auth_headers (the 1.x property), but _auth_headers is never overridden and returns {} by default
— so the Authorization header is never sent.

Steps to Reproduce

1. Create a fresh venv with openpipe-art==0.5.9 and openai>=2.14.0 (as required by the package)
2. Run any script that calls model.register(ServerlessBackend())
3. Observe 401 - Not authenticated despite a valid WANDB_API_KEY

Environment

• openpipe-art: 0.5.9
• openai: 2.37.0
• Python: 3.12.12

[falcondai]

I recently went into this as well. A change in openai version 2.34.0 broke the auth headers behavior. The simplest fix is to pip install -U openai<2.34.0.

[falcondai]

Note also that bc7e14c already fixed this issue in main.