Submitting tasks from codex cloud CLI fail with “Provided git ref main does not exist” on repos without main branch

What version of Codex is running?

0.45.0

Which model were you using?

_No response_

What platform is your computer?

Darwin 23.6.0 arm64 arm

What steps can reproduce the bug?

1. Have repo where the default branch is not named main (e.g. master).
2. Submit new task from codex cloud CLI.

What is the expected behavior?

The submitted task would run against the default branch, regardless of it's name.

What do you see instead?

Error in the codex cloud CLI:
Error

<img width="596" height="102" alt="Image" src="https://github.com/user-attachments/assets/023a97a1-b3f5-4fab-a2a3-5fdbd4b3276f" />

And in the codex cloud web UI:
Provided git ref main does not exist

<img width="809" height="123" alt="Image" src="https://github.com/user-attachments/assets/bcefafa0-9866-4210-98c3-632d8a1aaf02" />

Additional information

_No response_