Codex cli OSS not working with openwebUI

What version of Codex is running?

codex-cli 0.23.0

Which model were you using?

gpt-oss:20b

What platform is your computer?

Macos

What steps can reproduce the bug?

Hello,
I was trying to run codex-cli with OSS flag and use openwebUI APIs(hosted in a server).
i set the following in environment variable
export OPENAI_API_KEY="openwebui key"
export OPENAI_API_BASE="https://url_of_openwebUI/v1"
export CODEX_OSS_BASE_URL="https://url_of_openwebUI/v1"

when i ran codex --oss -m gpt-oss:20b
and then i enter a prompt it gives me unexpected status 405 Method Not Allowed: {"detail":"Method Not Allowed"}

What is the expected behavior?

OpenWebUI should be supported

What do you see instead?

_No response_

Additional information

_No response_